347
RADIO TRANSMISSION NETWORK AND FREQUENCY PLANNING LZB 111 0162 © Ericsson Radio Systems AB 1999 This book is a training document and contains simplifications. The contents are subject to revision without notice. Ericsson assumes no legal responsibility for any error or damage resulting from the usage of this document. All rights reserved. Regardless of the purpose, no parts of this publication may be reproduced or utilized in any form or by any means, whether electronic or mechanical, including photocopying and microfilm,without the expressed written permission of Ericsson Radio Systems AB. LZB 111 0162

TND Complete

Embed Size (px)

Citation preview

Page 1: TND Complete

RADIO TRANSMISSION NETWORK AND

FREQUENCY PLANNING

LZB 111 0162

© Ericsson Radio Systems AB 1999

This book is a training document and contains simplifications.The contents are subject to revision without notice.Ericsson assumes no legal responsibility for any error or damage resultingfrom the usage of this document.

All rights reserved. Regardless of the purpose, no parts of this publicationmay be reproduced or utilized in any form or by any means, whetherelectronic or mechanical, including photocopying and microfilm,withoutthe expressed written permission of Ericsson Radio Systems AB.

LZB 111 0162

Page 2: TND Complete

RUBRIKFÖRTECKNINGLIST OF HEADINGSDokumentnr - Document no.

001 51-LZB 111 0162

Datum - Date

1999-10-28Rev

A

INTRODUCTION 1

RADIO-RELAY TRANSMISSION OVERVIEW 2

RADIO COMMUNICATION SYSTEMCOMPONENTS

3

RADIOWAVE PROPAGATION 4

THE INTERNATIONAL TELECOMMUNICATIONUNION (ITU)

5

QUALITY AND AVAILABILITY TARGETS 6

RADIO REGULATIONS 7

THE RADIO SPECTRUM AND CHANNELARRANGEMENT

8

INTERFERENCE - BASIC CONCEPTS 9

NEAR INTERFERENCE 10

FAR INTERFERENCE 11

PATH AND FREQUENCY PLANNING 12

RADIO-RELAY TRANSMISSION - DISCUSSION 13

RADIO TRANSMISSION NETWORK PLANNING -APPLICATION

14

RADIO-METEOROLOGICAL PARAMETERS FORRL-DESIGN

15

Page 3: TND Complete

i

INTRODUCTION

This chapter provides a general presentation to thistraining document, its background and objective.

TABLE OF CONTENTS

Background ....................................................................................................................................................... 1Objective ........................................................................................................................................................... 1Scope of the book.............................................................................................................................................. 2Notes to the reader ............................................................................................................................................ 4Acknowledgments ............................................................................................................................................. 4

Page 4: TND Complete

INTRODUCTION

Ericsson Radio Systems AB

1/038 02-LZU 102 152, Rev A, November 1999

1

Background

Different applications of radio-relay transmission, in particular, line-of-sight links, have grown considerably since radio-link techniques werecommercially introduced just prior to World War II. The vast number ofapplications and implementations of radio-link systems since the 1950shave brought about severe frequency spectrum congestion, forcing theutilization of higher frequencies. In addition, sophisticated radioengineering solutions and the significant changes that have been maderequire a better understanding of radio engineering concepts and theirapplications.

This book is dedicated to improving the understanding of the radionetwork planning process. It includes a collection of the basicprinciples, methods, theory and guidelines for radio system planningand design that are often essential to the tasks performed by networkplanners and the designers of telecommunications operatingorganizations.

We have carefully organized and presented what we believe to beindispensable basic concepts of radiowave propagation, spectrummanagement and radio-system design in this ”RADIOTRANSMISSION NETWORK AND FREQUENCY PLANNING”.

Objective

The purpose of this book is to provide essential design techniques forradio-relay transmission, focusing on the general aspects of point-to-point services operating at frequencies above 1 GHz.

The book treats the basic principles of radiowave propagation, qualityand availability targets, frequency aspects, interference and generalinformation related to the ITU organization and its administrative tasks.

The book is intended in part or in its entirety, as training documentationfor courses in radio transmission network planning and related subjects.It is therefore our intention to provide customers with suggestions andadvisory support as to how one starts a network-planning project basedon concrete input data. We aim to describe how radio-links operate,how to use or dimension terminals and their equipment, and how toselect the necessary performance parameters and equipmentspecifications to meet the needs of specific customers.

Page 5: TND Complete

RADIO TRANSMISSION NETWORK AND FREQUENCY PLANNING

2 Ericsson Radio Systems AB

1/038 02-LZU 102 152, Rev A, November 1999

Scope of the book

This book is subdivided and structured into 14 independent chapters. Asa consequence, each chapter functions as a specific guideline.

Chapter 1 (this chapter), INTRODUCTION, provides a presentation ofthe book, its background and objectives.

Chapter 2, RADIO-RELAY TRANSMISSION - AN OVERVIEW,presents some general facts about the development of radio-relaytransmission since its first commercial application in 1934.

Chapter 3, RADIO COMMUNICATION SYSTEMCOMPONENTS, describes in some detail the components that makeup radio communication systems, different traffic setups and possibleinterference sources and how they can affect signal transmission.

Chapter 4, RADIOWAVE PROPAGATION, a presentation of thebasic principles and algorithms related to radiowave propagation usedin radio-relay transmission. Both loss and attenuation algorithms plusfade prediction models for different fading mechanisms are thoroughlydiscussed. The chapter also includes a presentation of the basic conceptsof main propagation mechanisms, Fresnel zone, equivalent and trueEarth radii and the decibel scale.

Chapter 5, INTERNATIONAL TELECOMMUNICATION UNION,describes in detail the ITU organization and its administrative tasks.This chapter provides valuable information on how to search and locateimportant ITU-R and ITU-T reports and recommendations on specificsubjects related to radio-relay transmission.

Chapter 6, QUALITY AND AVAILABILITY TARGETS, providesan extensive description of digital transmission network models used inerror performance analysis and quality and availability targets inaccordance with ITU-T Recommendations G.821 and G.826. Thechapter discusses quality and availability parameters, their calculationand their relationships to existing atmospheric fading mechanisms.

Chapter 7, RADIO REGULATIONS, describes the ITU-R publication”Radio Regulations”, its publisher, and the contents and the generalstructure of the publication. The primary objective of this chapter is tohandle the subject of Radio Regulations in connection with the use offrequencies for fixed terrestrial radio-links.

Page 6: TND Complete

INTRODUCTION

Ericsson Radio Systems AB

1/038 02-LZU 102 152, Rev A, November 1999

3

Chapter 8, FREQUENCY SPECTRUM AND CHANNELALLOCATION, provides an introduction to the radio spectrum bypointing out some of usual apprehensions concerning its limitations andcrowding. In addition, the chapter also presents an introduction to radio-frequency channel arrangements, frequency economy and finally, itprovides a complete list on channel arrangements for radio-relaysystems in the range 1.5 to 55 GHz.

Chapter 9, INTERFERENCE - BASIC CONCEPTS, provides adetailed discussion of the different types of interference sources andtheir effects on radio-relay equipment. The location of several radiosystems to the same site is also discussed in some detail.

In Chapter 10, NEAR INTERFERENCE, includes a discussion of thebasic principles and definitions used in the calculation of nearinterference; some algorithms are also provided. A presentation ofintermodulation at the receiver and transmitter includes some examplesof intermodulation products.

Chapter 11, FAR INTERFERENCE, provides basic concepts anddefinitions used in the calculation of far interference. A typicalperformance diagram and interference scenariois discussed. Thecalculation of the contributions of the individual interference signallevels, plus the resulting interference level at one receiver and thresholddegradation.

Chapter 12, PATH AND FREQUENCY PLANNING, covers some ofthe issues that may arise concerning path profile, line-of-sightrequirements, input signals and their variation, diversity, reflections andfrequency planning. In addition, surveying possible radio-link paths andsite requirements are discussed.

Chapter 13, RADIO-RELAY TRANSMISSION - DISCUSSION, theprimary objective of this chapter is to encourage a discussion onspecific and general subjects of interest in transmission networkplanning, for instance, practices versus theory, current trends in todayworlds market that affect radio-relay transmission, personal experienceand future prospects for radio-relay technology.

Chapter 14, NETWORK PLANNING - APPLICATION, is to becustomized and adjusted to specific applications. Instructions andguidelines are provided on how to select the necessary performanceparameters and equipment specifications to meet the needs of specificcustomers.

Page 7: TND Complete

RADIO TRANSMISSION NETWORK AND FREQUENCY PLANNING

4 Ericsson Radio Systems AB

1/038 02-LZU 102 152, Rev A, November 1999

Notes to the reader

The contents treated in this book are subject to changes due tocontinued development in methodology and design. Furthermore,network planning is in some aspects strongly dependent on ITUrecommendations, which are continuously the subject of corrections,additions and improvements. Therefore, it is strongly recommended thatreaders are aware of ongoing ITU Study Group activities.

References to some sources of the material used in each chapter aregiven in the last section of that chapter.

Acknowledgments

Thanks to Malin Ström and Christer Lehman who patiently drew mostof the figures in this book. Thanks to Inger Meltzer for her kindassistance with the layout of the front cover.

The authors are very grateful to any comments and suggestions that mayimprove the content of this book.

Page 8: TND Complete

i

RADIO-RELAY TRANSMISSION

OVERVIEW

This chapter contains an overview of radio-relaytransmission with a brief review. In addition, it provides asummary on suitable applications and describes thegeneral aspects and advantages of network planning. Theprediction cycle along its activity blocks employed in radiotransmission planning is presented.

TABLE OF CONTENTS

Transmission options......................................................................................................................................... 1Introduction......................................................................................................................................... 1Radio links versus cable links ............................................................................................................. 1Radio-relay transmission - advantages ................................................................................................ 2Transmission - capacity and covered distance..................................................................................... 2Radio-relay transmission - suitability .................................................................................................. 3

The beginning of the radio-relay transmission era ............................................................................................ 4The digitalization era......................................................................................................................................... 4Synchronous Digital Hierarchy (SDH).............................................................................................................. 4What is radio-network planning? ...................................................................................................................... 5The trinity principle of network planning.......................................................................................................... 6The prediction cycle .......................................................................................................................................... 7References ......................................................................................................................................................... 8

Page 9: TND Complete

RADIO-RELAY TRANSMISSION - AN OVERVIEW

Ericsson Radio Systems AB

2/038/ 02-LZU 102 158, Rev A, November 1999

1

Transmission options

IntroductionTransmission is generally made possible by employing the followingthree major media:

• optical-fiber cables

• copper coaxial cables

• radio-relay

Another available transmission option is the use of satellite links, whichare more appropriate, than the use of ordinary terrestrial radio-relay andcable, in such applications as long-haul routes in international networksthat do not require extremely high transmission capacity.

Radio links versus cable linksRadio-links exhibit many advantages in comparison to fiber-optic links,for example:

• cost-effective transmission links in inaccessible terrain and difficultenvironments

• the quick coverage of large areas by new operators

• higher security due to the fact that equipment can be physicallyconcentrated

Radio-relay transmission is therefore a very attractive alternative forapplications ranging from the coverage of the rural, sparsely populatedareas, of developing countries having ineffective or minimalinfrastructures to the well-developed industrial countries that requireexpansion of their telecommunications networks.

Page 10: TND Complete

RADIO TRANSMISSION NETWORK AND FREQUENCY PLANNING

2 Ericsson Radio Systems AB

02/038 02-LZU 102 152, Rev A, November 1999

Radio-relay transmission - advantagesConsidering the three transmission media mentioned above, radio-relaytransmission is the most suitable option for networks that are located inareas of difficult terrain topography or where other limitations areimposed on the use of optical fiber and/or copper coaxial cables.Generally speaking, radio-relay transmission is most suitable in thefollowing applications:

• long-haul routes for national and international networks coveringareas of difficult terrain topography

• national networks containing radio-relay in parallel with opticalfiber

• backbone routes

• urban access routes connecting interurban optical-fiber cable routesand in-town terminal stations

• rapid geographical changes of station location as a consequence ofcatastrophic or emergency situations

• short-term projects

• access links from cellular to public networks

• cellular transmission networks

• radio in the local loop

• point-to-multipoint operation

It is possible to combine the different applications presented above, thusmaking radio-relay transmission a very competitive option – bothtechnically and economically.

Transmission - capacity and covered distanceFigure 1 is a rough illustration of the possible transmission options as afunction of the different ranges of transmission capacity (Mbit/s) anddistance (km). Except for some overlapping, the figure clearly showsthat the transmission options are complementary, while at the sametime, each option exhibits its own domain of optimal cost effectiveness.

Page 11: TND Complete

RADIO-RELAY TRANSMISSION - AN OVERVIEW

Ericsson Radio Systems AB

2/038/ 02-LZU 102 158, Rev A, November 1999

3

Distance, km

thousands

tens

hundreds

Capacity, Mbit/s

tens hundreds thousands

Optical fiber

Satellites

Fib

er in

the

loop

Radio-relaypoint-to-point

point-to-multipoint

Figure 1: Transmission options for different capacities and covered distances.

Radio-relay transmission - suitabilityTable 1 illustrates the different aspects of radio-relay transmission andthe corresponding suitable conditions.

Subject Suitable conditionsfor radio-relay transmission

Transmission capacityRoutesTerrain topographyInfrastructureProject implementationInitial operationCoverageSpecial operationDamaging intentionAvailability

Low, medium and high (not very high)Short and medium (not very long)Inaccessible terrain (not over water)None or hardly existingShort timeHigh initial investmentContinental rural and urbanEmergency useEasy to protect important sites (nodes)Very high (if required)

Table 1: Suitable conditions for radio-relay transmission.

Page 12: TND Complete

RADIO TRANSMISSION NETWORK AND FREQUENCY PLANNING

4 Ericsson Radio Systems AB

02/038 02-LZU 102 152, Rev A, November 1999

The beginning of the radio-relay transmission era

The world’s first commercial radio-relay link was put into operation in1934 after intensive preliminary attempts that were started in 1931, inParis, at the Laboratories Central des Télécommunications, a subsidiaryof the former International Telephone and Telegraph Corporation, theformer IT&T. It consisted of a 56 km radio-relay path across the EnglishChannel between Calais (France) and Dover (England), amplitudemodulated (AM), using a klystron that generated 1 W RF output powerand operating at 1.7 GHz. The hardware technology was provided bytwo manufactures: the British company Standard Telephones andCables (now a part of Northern Telecom) and the French company LeMatériel Téléphonique (now integrated into Alcatel Telspace).

The digitalization era

Integrated semiconductor technology started a new era in radiotelecommunication. Optical fiber was not available for transmission latein 60’s and early 70’s. Digital transmission on coaxial cable was tooexpensive (repeaters at extremely short intervals) and slowlyimplemented for relatively long telecommunication routes. Thus, low-cost semiconductor technology in the beginning of the 70’s wastherefore the start of a new telecommunications era.

Digital transmission has several advantages compared to analogtransmission:

• Up to a certain threshold limit, the received signal can be restored toits original shape irrespective of the signal-to-noise ratio (SNR),thus enabling a large, almost unlimited number of repeaters.

• Radio-relay transmission at high frequencies (10 GHz)

The world’s first digital radio-relay link was a 17 Mbit/s unit that wasplaced into operation in Japan, in 1969. It provided 240 telephonechannels in the 2 GHz frequency band.

Synchronous Digital Hierarchy (SDH)

SDH links have become the international standard for the expansion oftelecommunication network infrastructures. Radio-relay transmission,and in particular microwave links have begun to be adapted to the SDHdata format and a good number of ITU-T recommendations are nowavailable. These recommendations represent general directives aimed atensuring that radio systems are designed so that they conform to SDHinterface specifications.

Page 13: TND Complete

RADIO-RELAY TRANSMISSION - AN OVERVIEW

Ericsson Radio Systems AB

2/038/ 02-LZU 102 158, Rev A, November 1999

5

SDH provides some key benefits in comparison with PlesiochronousDigital Hierarchy (PDH):

• Higher transmissions speeds are defined.

• Direct multiplexing is possible without intermediate multiplexingstages. This is accomplished through the use of pointers in themultiplexing overhead that directly identify the position of thepayload.

• The SDH overhead supports an effective network management,control over the traffic, network status etc.

• The SDH protocol is able to handle both the European standard andAmerican standard payloads.

SDH technology will, for the next 20-30 years, offer a standardizedmethod for the worldwide transmission of all types of data traffic forboth existing and future data transmission systems.

What is radio-network planning?

Network planning can be a quite complicated and time-consuming task.The degree of difficulty is a function of that which is to be included inthe task. For instance, the task may include initial planning plus anoverview of the entire network, frequency planning, site survey, pathanalysis, installation and tests. Network operational requirements mayalso constitute a crucial factor in the planning process. Regardless thedegree of difficulty, it will always be an iterative process!

Generally speaking, the initial design of a radio-link is performed infour steps:

• Initial planning and site selection

• Topographical analysis

• Preliminary path and frequency planning analysis

• Site survey

Network planning as a multi-task process is illustrated inFigure 2.

Page 14: TND Complete

RADIO TRANSMISSION NETWORK AND FREQUENCY PLANNING

6 Ericsson Radio Systems AB

02/038 02-LZU 102 152, Rev A, November 1999

NETWORK PLANNING

Quality and AvailabilityPrediction

Network Management

RadiowavePropagation

InterferenceAnalysis

Traffic Demand

Network Status

Figure 2: Overview of network planning.

The trinity principle of network planning

The iterative, multi-task, process of network planning is controlled bythree important factors:

• availability, currently expressed as a fraction of time

• quality, currently expressed in bit-error ratio (BER) for digital links

• cost, expressed in the actual currency

These three factors constitute the basic body of network planning. Themulti-task process, along with all of the possible items, is in some wayrelated to these three factors, seeFigure 3. In fact, they are theparametersthat are usually supplied by the customer. The answer isalready known before starting the network planning process!

Page 15: TND Complete

RADIO-RELAY TRANSMISSION - AN OVERVIEW

Ericsson Radio Systems AB

2/038/ 02-LZU 102 158, Rev A, November 1999

7

Costs

AVAILABILITYQUALITY

$

BER % of time

2

3 4 5

6 7

8

10

11

1213

141516

1

1

2

3

4

5

6

7

8

Coordination

Flight-path obstacle

Road requirements

Path length

Protective measures

Far interference

Interception risk

Frequency aspects

9

9

10

11

12

13

14

15

16

Site layout

Near interference

Equipment data

Power supply requirements

Capacity

Obstacles

Terrain

Interference risks

Figure 3: The trinity principle of network planning.

The prediction cycle

Figure 4 displays the four main actvity blocks which form the planningprocess: loss/attenuation, fading, frequency planning and quality andavailability. A preliminary fade margin is calculated in theloss/attenuation block which is used for preliminary fade predictions inthe fading block. If interference is present in the frequency planningblock, then the threshold degradation is included in the fade margin.The updated fade margin will become the effective fade margin andemployed in the fading predictions. The results in the loss/attenuationand fading blocks will form the necessary input to the quality andavailability block.

Page 16: TND Complete

RADIO TRANSMISSION NETWORK AND FREQUENCY PLANNING

8 Ericsson Radio Systems AB

02/038 02-LZU 102 152, Rev A, November 1999

Quality & Availability

Not always present butstatistically predictable

Fading prediction

Rain attenuationDiffraction-refraction loss

Fading

Multipath propagation

+

Always presentand predictable

Link budget

Predictableif present

Loss/attenuation

Predictableif present

Fre

qu

ency

Pla

nn

ing

Free-space andGas attenuation

Obstacle andReflections loss

Interference

Figure 4: The prediction cycle.

References

”Test av nya generationens SDH-radionät” (in Swedish), Elektronik iNorden, 46, vol. 6,1997.

”Radio-Relay Systems”, Huurdeman, A. A., Artech House, 1995.

“Radio-System Design for Telecommunications (1-100 GHz)”,Freeman, R. L., 1987.

Page 17: TND Complete

i

RADIO COMMUNICATION SYSTEMCOMPONENTS

This chapter deals with the components that make up radiocommunication systems, different traffic setups andpossible interference sources and how they can affectsignal transmission.

TABLE OF CONTENTS

Introduction....................................................................................................................................................... 1Radio communication systems .......................................................................................................................... 1

The transmitter .................................................................................................................................... 3The receiver......................................................................................................................................... 3The antenna ......................................................................................................................................... 4Feeder cabling ..................................................................................................................................... 4Antenna coupling unit ......................................................................................................................... 4Frequency and bandwidth.................................................................................................................... 4

Traffic setup ...................................................................................................................................................... 5Simplex ............................................................................................................................................... 5Two-frequency simplex....................................................................................................................... 5Duplex................................................................................................................................................. 6

Transmitter ........................................................................................................................................................ 8Receiver ............................................................................................................................................................ 12

Receiver characteristic data................................................................................................................. 13Sensitivity.............................................................................................................................. 13Sensitivity to co-channel Interference ................................................................................... 15Adjacent channel selection.................................................................................................... 16Blocking level ....................................................................................................................... 18Intermodulation level ............................................................................................................ 20

Feeder cabling ................................................................................................................................................... 21Coaxial cable....................................................................................................................................... 21Waveguides ......................................................................................................................................... 21

Duplex filters..................................................................................................................................................... 22Transmitter combiners....................................................................................................................................... 22Receivers multicouplers .................................................................................................................................... 25Antennas............................................................................................................................................................ 26

Antenna gain for parabolic antennas ................................................................................................... 27Antenna diagram ................................................................................................................................. 28

References ......................................................................................................................................................... 30

Page 18: TND Complete

RADIO COMMUNICATION SYSTEM COMPONENTS

Ericsson Radio Systems AB

3/038 02-LZU 102 152, Rev A, November 1999

1

Introduction

The term system is nowadays generally used rather broadly. What aresystems? One possible definition of a system is a set or arrangement ofitems, so related or connected, as to form an entire unit. Thus a radiosystem may range from encompassing a simple transceiver, a length ofcoaxial line and the antenna to which it is connected to, toencompassing a combination of many receivers, transmitters, controland coding apparatus, towers and antennas all assembled into acoordinated functioning complex.

An ordinary communication system can therefore consist of manysystem components whose primary task is the transmission ofinformation-conveying signals to a user. The actual transmission istransmitted via some sort of transmission medium. Commontransmission mediums are the atmosphere, coax cables or a fiber opticalcomponents. This implies that the signal carrying the information mustassume a suitable form that is fitted to the particular characteristics ofthe medium over which it is to be transmitted.

Radio communication systems

A radio communication system utilizes atmosphere as propagationmedium. The signal power of radio waves reduces as a function ofdistance as they propagate through space. Radio links transmitdirectional information from a transmitter to a receiver usingelectromagnetic waves. Radio link systems are important examples of aradio communication system.

Radio-link systems operate primarily in the frequency range between200 MHz and 60 GHz. Although Radio Regulations allocates servicesin the frequency range up to 275 GHz, it is unusual, for the present, tofind commercial radio-link systems that make use of frequencies higherthan 60 GHz.

The frequencies that are used for radio communications havesuccessively moved upwards from lower to higher frequencies (shorterwavelengths). Back in the early days of radio, it was easier to generatecarrier frequencies of sufficient power at the lower frequency spectrum.With the advent of new techniques, it became possible to successivelydevelop new components that have made it possible to use higher andhigher frequencies.

Page 19: TND Complete

RADIO TRANSMISSION NETWORK AND FREQUENCY PLANNING

2 Ericsson Radio Systems AB

3/038 02-LZU 102 152, Rev A, November 1999

An additional motive for the use of ever-increasing frequencies forradio communication is the increased frequency crowding that is takingplace in the used and relatively low frequency ranges. Frequencycrowding increases the risk of interference and presents limitations inthe possibility to transmit large amounts of bandwidth-demandinginformation. This presents a natural need for the utilization of frequencyranges that have not been utilized earlier (i.e., high frequencies).

At its outset, mobile communications utilized frequencies in the 30-40MHz range which then successively increased and passed 80, 160, 450MHz, reaching frequencies of around 900 MHz (which is, for example,used in mobile telephony applications). The range 1700-2500 MHz,used today by a number of communications systems, will in the nearfuture also be used to provide mobile personal telephone services.

An advantage of using higher frequencies for communication is theincrease in available bandwidth brought about by the utilization of thesefrequencies. For example, a speech channel depending on modulationscheme will typically require a bandwidth of 12.5 to 25 kHz meaningthat a 1 MHz interval can contain 40-80 speech channels. It is obviousthat there exists many more available 1 MHz intervals in, for example,the 900 or 1800 MHz ranges than in the 30 MHz range.

On the other hand, the use of higher frequencies introduces certaindifficulties resulting from the fact that a speech channel having abandwidth of 25 kHz takes up a smaller relative bandwidth at 1800MHz than it does at 30 MHz. This places much higher demands on theexactness of frequency generation and filtering, so that a channelmaintains one and the same bandwidth while at the same timemaintaining sufficient isolation (filtering) to its adjacent channels.

Today’s radio links employ frequencies ranging from approx. 200 MHzup to 60 GHz. Relatively few speech channels are transmitted over thelower band (below 2 GHz) while the higher bands (above 2 GHz) areused for the simultaneous transmission of up to 1920 speech channels.In these cases, the links are used for traffic having high capacityrequirements, the ”highways” of the telephony network. The higherfrequencies make it easier to direct radiation between the transmitterand the receiver using reasonably sized antennas, since the antenna’sdirectivity is a function of its size in relation to the wavelength used.This also contributes to the effective increase in the possibility to useavailable channels since they, for a geographical area, are easier toisolate from one another.

Radio equipment that is included in radio-link systems may besubdivided into two main groups:

• mounted on the ground

Page 20: TND Complete

RADIO COMMUNICATION SYSTEM COMPONENTS

Ericsson Radio Systems AB

3/038 02-LZU 102 152, Rev A, November 1999

3

• mounted on masts

Mast-mounted radio equipment comprises, together with an antenna, arelatively compact system that has short feeder cabling. Ground-mounted radio equipment, on the other hand, is generally connected toantennas via longer feeder cabling.

Figure 1 provides a schematic illustration of a block diagram for asimplified radio communication system. At each end, the systemconsists of a transmitter, a receiver and an antenna. Feeder cable(s) mayalso be required, depending on the application.

Rx2

Tx2Tx1

Rx1

Figure 1: Block diagram for a simplified radio communication system.

The transmitterThe purpose of the transmitter is to generate the carrier frequency that isto be used for the communication, to modulate this carrier frequencywith the desired information and finally, to amplify the signal so that itattains a sufficiently high power level so that it may traverse the desiredcommunication distance to the receiver.

The receiverThe receiver amplifies the received signal (which is at this point muchweaker than when it was transmitted), filters out any undesirable signals(interfering signals) that the receiver picked up and finally, detects theexistence of information in the carrier frequency.

Page 21: TND Complete

RADIO TRANSMISSION NETWORK AND FREQUENCY PLANNING

4 Ericsson Radio Systems AB

3/038 02-LZU 102 152, Rev A, November 1999

The antennaThe antenna adapts the generated signal to the surrounding environment(to the propagation medium) and directs the radio waves that are to betransmitted towards the receiving station. When receiving, the antennareceives the signal from the desired direction and transfers it to thereceiver. Antennas may be built having different directivities, frommore or less isotropic antennas (radiate equally in all directions) toantennas that exhibit extremely high directivities.

Feeder cablingThe purpose of the feeder cable is to interconnect the antenna with thetransmitter/receiver.

Antenna coupling unitThe antenna-coupling unit makes it possible to utilize a commonantenna for both the transmitter and receiver. The transmitter andreceiver can, for example, be connected to one and the same antennaeither via a duplex filter or a transmitter/receiver switch. The duplexfilter prevents the transmitter’s frequency from blocking the receiver ina T/R configuration. A transmitter/receiver switch disconnects thereceiver in a T/R configuration from the antenna when in transmittingmode and thereby prevents any blockage of the receiver.

Frequency and bandwidthA given radio connection is established at a specific frequency or radiochannel. The available frequency range is subdivided into a number ofsuch radio channels that are assigned bandwidths that reflect theselected modulation scheme as well as the amount and type ofinformation that is to be transmitted. For example, a speech channelrequires less bandwidth than a TV channel. In many cases, it may bedesirable to transmit many speech channels simultaneously(multiplexed together) which increases bandwidth requirements. A datachannel can assume different bandwidths as a function of thetransmission capacity.

Page 22: TND Complete

RADIO COMMUNICATION SYSTEM COMPONENTS

Ericsson Radio Systems AB

3/038 02-LZU 102 152, Rev A, November 1999

5

Traffic setup

SimplexEmploying the simplest form of radio connection setup, the transmitterand receiver operate at the same frequency (transmit and receive overthe same channel). In other words, simplex operation only permits thetransmission of signals in either direction alternately. This traffic setupis referred to as simplex, see Figure 2. Simplex traffic was the mostcommon setup back in the early days of radio. It is still often used, forexample, when communicating via walkie-talkies. Simplex trafficrequires good traffic discipline in order to avoid both ends transmittingat the same time.

T/R = Transmitter/Receiver switch

Tx2

Rx1

T/R T/R

f1

f1

f1

f1

f1

f1

Tx1

Rx2

Figure 2: Block diagram of simplex traffic setup.

Two-frequency simplexWhen employing two-frequency simplex, see Figure 3, the transmitterand receiver operate over different channels. However, this setup doesnot allow simultaneous reception and transmission since sufficientfiltering (usually performed by the duplex filter) does not exist as a rule,and reception may be disturbed by the transmitter in a T/Rconfiguration.

Page 23: TND Complete

RADIO TRANSMISSION NETWORK AND FREQUENCY PLANNING

6 Ericsson Radio Systems AB

3/038 02-LZU 102 152, Rev A, November 1999

T/R = Transmitter/Receiver switch

Tx2

Rx1

T/R T/R

f2

f2

f1

f1

f2

f1

Tx1

Rx2

Figure 3: Block diagram of two-frequency simplex setup.

Note that two types of stations have been introduced in the case of two-frequency simplex traffic: one having the transmitter frequency abovethe receiver frequency and one having the transmitter frequency beneaththe receiver frequency. Communication between such stations requiresthat the stations be of opposite types.

In comparison with ordinary simplex, two-frequency simplex has theadvantage that interference between two base stations is not present ifthe base station’s transmitters are operating in the same duplex band.Frequency re-using is, however, strongly dependent on the mobile’sgeographical position.

DuplexIn the case of duplex traffic, see Figure 4 and Figure 5, transmission andreception occur simultaneously and over separate frequencies (channels)which allows simultaneous communication in both directions, betweenthe called and the calling parties, to take place. On occasion, so-calledsemi-duplex is used, in which case one of the stations (usually the fixedstation, often referred to as the base station) operates in duplex and themobile station in simplex. Two channels are still used for thiscommunication setup.

Page 24: TND Complete

RADIO COMMUNICATION SYSTEM COMPONENTS

Ericsson Radio Systems AB

3/038 02-LZU 102 152, Rev A, November 1999

7

Tx2

Rx1

Duplexer

f2

f2

f1

f1

f2

f1

Tx1

Rx2

Duplexer

Figure 4: Duplex traffic with simultaneous transmission.

T/R = Transmitter/Receiver switch

Tx2

Rx1

Duplexer T/R

f2

f2

f1

f1

f2

f1

Tx1

Rx2

Base station Mobile terminal

Figure 5: Semi-duplex traffic.

The frequency plan for duplex, see Figure 6, illustrates a duplex bandseparation between the transmitting and receiving bands and the duplexspacing between the transmitted and the corresponding receivedfrequencies.

Page 25: TND Complete

RADIO TRANSMISSION NETWORK AND FREQUENCY PLANNING

8 Ericsson Radio Systems AB

3/038 02-LZU 102 152, Rev A, November 1999

Tx-band Rx-band f

Duplex bandseparation

Duplex spacing

Figure 6: Frequency plan for duplex.

In Figure 6, transmitter frequencies are shown as located in the lowerduplex-half and receiver frequencies in the upper duplex-half. This maybe reversed, for example, in the case of a radio link made up of severalhops.

Transmitter

Figure 7 illustrates a simplified block diagram of a transmitter. It hasbeen assumed that the transmitter is capable of transmitting digitalinformation, which is usually the case nowadays.

Frequencygenerator

Modulator

LP-filter BP-filter

To antenna

Crystal

Digitalinformation

~~ ~~~

Figure 7: Simplified block diagram of a transmitter.

The simplified transmitter consists of a frequency generator, amodulator that modulates the digital information over the transmitter’scarrier frequency and a power amplifier that amplifies the signal toattain a suitable power level before being sent to the antenna forradiation into the propagation medium.

Page 26: TND Complete

RADIO COMMUNICATION SYSTEM COMPONENTS

Ericsson Radio Systems AB

3/038 02-LZU 102 152, Rev A, November 1999

9

The digital information is characterized by the fact that it only containsdiscrete levels, for example, binary information (ones and zeroes). Ifspeech is to be transmitted, the analog information represented in thespeech must first be digitized by a so-called speech coder. A frequentlyused form of speech coding is Pulse Code Modulation (PCM). A speechchannel is then transmitted as a bit stream having a transmissioncapacity of 64 kbit/s. The transmission of speech, digitized to 64 kbit/s,requires a larger bandwidth than the equivalent analog speech channelwould require. PCM is commonly used in connection with radio linksand is used throughout the fixed telephone network (for digitalnetworks).

The special speech coders that are used today for mobilecommunication provide high quality even at lower bit speeds, forexample, around 10 kbit/s. This facilitates increased frequency economyin the propagation medium.

The digital data stream then modulates the carrier frequency that ispicked up from the frequency generator. A modern frequency generatoris synthesized, meaning that the desired frequency or channel is selecteddigitally, e.g., from a keypad. A component that is vital to the operationof the frequency generator is a stable frequency reference. This isachieved through the use of a crystal oscillator, where the crystal is thedetermining factor in frequency stability. Older equipment is often notfitted with frequency synthesizer functionality, which means that aparticular crystal is required for each individual channel, i.e., for theparticular frequency that is desired. As a rule, crystals for such olderequipment cannot be ordered until after the frequency planning phasehas been completed, i.e., not until after the channel has been assigned tothe equipment in question. This must be performed individually foreach unit of equipment in the network, and therefore results in longerimplementation lead times.

The transmitted signal is characterized by its center frequency and by agiven bandwidth around the center frequency. This bandwidth is afunction of the transmitted information (the transmission capacity of thedigital information) and the modulation, for example the 3 dBbandwidth, B3 dB. The signal is characterized by its frequency spectrum,i.e., by energy content as a function of frequency separation from thecenter frequency, see Figure 8.

Page 27: TND Complete

RADIO TRANSMISSION NETWORK AND FREQUENCY PLANNING

10 Ericsson Radio Systems AB

3/038 02-LZU 102 152, Rev A, November 1999

It is important that the transmitter spectrum is not unnecessarily wide inorder to achieve proper isolation to adjacent channels. In order to reduceovertone-like spectrum widening resulting from modulation, it iscommon to precede the modulator by a low pass filter that limitsspectrum widening in the vicinity of the center frequency. In the sameway, the power or output stage is followed by a band-pass filter to limitthe overtones and noise generated in the output power amplifier. Thelatter filter is often a part of the duplex filter that facilitatessimultaneous transmission and reception.

f0

3 dB

dB

B3dB

f

Figure 8: Transmitter spectrum of a modulated carrier.

In addition to being a function of the filter, the appearance of thespectrum depends also on the method of modulation. A commonmodulation method is the Phase Shift Keying (PSK). It results in aspectrum that falls off rather slowly. Quadrature Phase Shift Keying(QPSK) is a more effective modulation method. This method results ina spectrum having half the width of that generated by the PSK methodbut otherwise having the same form (it is scaled to half the bandwidth).More modern modulation methods such as Gaussian Filtered MinimumShift Keying (GMSK) have, in principle, the same effective bandwidth(the band in which the greater portion of the power is concentrated) asthat resulting from QPSK, but with the added property that the spectrumoutside of the effective bandwidth falls off significantly faster. Thismeans that this modulation method allows one to pack channels closertogether while still maintaining the same degree of isolation betweenchannels. Modern modulation methods are very involved in maintaininggood frequency economy (efficient channel packing).

Page 28: TND Complete

RADIO COMMUNICATION SYSTEM COMPONENTS

Ericsson Radio Systems AB

3/038 02-LZU 102 152, Rev A, November 1999

11

For larger separations from the carrier frequency, the spectrum ischaracterized by sideband noise and spurious signals (unwantedbyproducts produced by the transmitter), see Figure 9. The noisespectrum is quantitatively expressed by the power density w (W/Hz),that is, the power per unity of bandwidth, and normally decreases withlarger frequency separation from the unmodulated carrier. Thebandwidth B (Hz) in Figure 9 contains a power which is w⋅B (W).

FrequencyB

Sideband noise

Unmodulatedcarrier

Figure 9: Sideband noise.

The level of these spurious products is generally specified by EuropeanTelecommunications Standards Institute (ETSI) to max. -36 dBm forfrequencies below 1 GHz and -30 dBm above 1 GHz. For specialapplications there may be other specifications.

The sideband noise produced by the transmitter, which is also a limitingfactor for duplex operation as well as the localization of differentsystems to one and the same site, is typically 140 dB below the carrierfrequency per Hz of bandwidth (-140 dBc/Hz) within approximately 1%frequency separation from the carrier frequency and is -150 dBc/Hz forlarger separations, where the values apply without the use of a radiofrequency (RF) filter.

Page 29: TND Complete

RADIO TRANSMISSION NETWORK AND FREQUENCY PLANNING

12 Ericsson Radio Systems AB

3/038 02-LZU 102 152, Rev A, November 1999

Receiver

Frequencygenerator

Crystal

DemodulatorDetectorMixer

Amplifier IF-filter

~~~RF-filter

~~~

Figure 10: Simplified block diagram of a receiver.

The weak signal coming from the antenna is amplified initially in aradio-frequency amplifier (RF amplifier). The amplifier is normallypreceded by a RF-filter which filters out unwanted signals, i.e., those ofother frequencies than the one desired. Since we are dealing with ahigh-frequency signal, it is very difficult to effectively filter out signalsother than those that lie at a relatively great separation from themidpoint of the carrier.

A mixer follows the RF amplifier, which mixes the input signal with thesignal from a local oscillator, and gives as output an intermediatefrequency (IF). The local oscillator frequency is related to the wantedreceiver RF frequency in a way that always gives a fixed intermediatefrequency as a result. A common intermediate frequency is 70 MHz. Itis at this frequency, which is significantly lower than the frequency ofthe input signal that unwanted signals are filtered out. Generally acrystal filter is used for this purpose. The IF filter’s bandwidth isgenerally equivalent to the wanted signal’s effective bandwidth and itsattenuation often increases drastically with increasing separation fromthe center frequency. The IF filter is primarily responsible for thereceiver’s adjacent channel selection.

To enable the receiver to receive channels that cover a wider band, thelocal oscillator must be capable of being tuned in accordance with theincoming signal’s frequency in order to maintain a fixed IF frequency.The local oscillator is therefore, as in the transmitter, often constructedas a digital frequency generator. Such tunable local oscillators allowreceivers to be set to different receiver frequencies or channels.

A detector follows the IF amplifier and IF filter in which the wantedinformation is retrieved and a digital bit stream is generated. This maythen be converted to intelligible speech via a speech decoder.

Page 30: TND Complete

RADIO COMMUNICATION SYSTEM COMPONENTS

Ericsson Radio Systems AB

3/038 02-LZU 102 152, Rev A, November 1999

13

Receiver characteristic dataReceiver attributes are described in terms of its characteristic data:

• sensitivity

• sensitivity to co-channel interference

• adjacent channel selection

• blocking level

• resistance to intermodulation level

Sensitivity

The receiver’s sensitivity or threshold is generally defined in terms ofthe lowest input signal level that is required in order that the detectionof the received information attain a given level of minimum acceptablequality. The quality of a digital receiver is usually expressed in terms ofthe BER (Bit-Error Ratio), e.g., 10-3 or 10-6.

Receiver sensitivity is a function of:

• the receiver’s noise factor

• the noise bandwidth

• the modulation method

The greater the bandwidth of the transmitted information the greater isthe noise bandwidth. A broadband system is therefore less sensitivethan is a narrowband system. Noise bandwidth is generally determinedby the IF filter.

Sensitivity is limited, as described above, by the noise level of thereceiver input. It is estimated as

BTkFN ⋅⋅⋅= ......................................................................................... (1)

where

N = Receiver noise level

F = Receiver noise factor

k = Boltzman’s constant, 1.38·10-23, J/K

T = Absolute temperature at the receiver input, K

Page 31: TND Complete

RADIO TRANSMISSION NETWORK AND FREQUENCY PLANNING

14 Ericsson Radio Systems AB

3/038 02-LZU 102 152, Rev A, November 1999

B = Receiver effective bandwidth, normally the IF bandwidth, Hz

or expressed in decibels

BTkFN +++= .................................................................................... (2)

The receiver’s noise factor is a measure of how much noise the receivergenerates in relation to a noise-free amplifier. Typical values liebetween 5 and10 dB.

The value of the product k⋅T, (K+T) in decibels, at room temperature is -174 dBm/Hz. The effective bandwidth of the receiver is expressed indBHz.

Example - calculating receiver sensitivity

The following presents three example calculations of the theoreticalsensitivity of a receiver.

Example 1: To begin with, assume the receiver is being used formobile communication in the UHF band (450 MHz). The method ofmodulation is FM (frequency modulation) with a channel separation of25 kHz. The bandwidth of the receiver is then, typically, 12.5 kHz.Assume a receiver noise factor of 10 dB.

Since the receiver’s effective bandwidth in this case is 41 dBHz (12.5kHz = 12500 Hz converted to dBHz), equation (2) results in thefollowing value for receiver noise level

N = 10 dB -174 dBm/Hz + 41 dBHz = -123 dBm

A given signal-to-noise ratio, S/N, is required to attain a given level ofreception quality. In the case of FM, S/N= 10 dB is a typical value,which gives a receiver threshold of S= -123+10= -113 dBm.

In the case of mobile radio, sensitivity is also often specified as avoltage (in micro-volts) which represents the EMK required to impartthe necessary power to a 50-ohm receiver or one that corresponds to theterminal voltage, i.e., half of the EMK.

A sensitivity of -113 dBm corresponds to a terminal voltage of 0.5microvolts across 50 ohms.

Example 2: Assume a digital receiver, e.g., a radio link thatdemonstrates a transmission capacity of 2 Mbit/s. Assume that PhaseShift Keying (PSK) is the modulation method used. The bandwidth ofthe receiver is now typically 2 MHz. Assume a receiver noise factor of10 dB.

Page 32: TND Complete

RADIO COMMUNICATION SYSTEM COMPONENTS

Ericsson Radio Systems AB

3/038 02-LZU 102 152, Rev A, November 1999

15

Since the effective bandwidth of the receiver in this case is 63 dBHz (2MHz = 2 000 000 Hz converted to dBHz), equation (2) results in thefollowing value for receiver noise level

N = 10 dB -174 dBm/Hz + 63 dBHz = -101 dBm

A typical value for signal-to-noise ratio at a bit-error ratio of 10-3 andPSK modulation is S/N= 10 dB. The receiver threshold is therefore S= -101 dBm + 10 dB = -91 dBm.

If the receiver’s measure of quality is instead set to a bit-error ratio of10-6, then an S/N is required which is 3 dB higher, i.e., the receiverthreshold at BER=10-6 is now 3 dB higher than that at BER=10-3 whichmeans at -88 dBm.

Example 3: Assume that the link is to transfer 8 Mbit/s using QPSKmodulation, which requires a bandwidth equivalent to half of thetransmission capacity, or in this case, 4 MHz. Assume a receiver noisefactor of 10 dB.

Since the receiver’s effective bandwidth in this case is 66 dBHz (4 MHz= 4 000 000 Hz converted to dBHz), equation (2) results in thefollowing value for receiver noise level

N = 10 dB -174 dBm/Hz + 66 dBHz = -98 dBm

QPSK requires an additional 3 dB higher S/N than does PSK, i.e., 13dB. Receiver threshold for an 8 Mbit/s link is therefore S/N= -98 dBm +13 dB = -85 dBm for BER=10-3 and S/N= -82 dBm for BER=10-6.

Consequently, the receiver threshold is 6 dB higher for 8 Mbit/s ascompared to 2 Mbit/s which is equivalent to a transmission capacity thatis 4 times higher (6dB).

Sensitivity to co-channel Interference

This attribute is important when attempting to re-use a frequency orchannel several times over a geographical area. The amount of co-channel interference tolerated by a receiver is defined by its sensitivityto a given connection quality (expressed in BER) and it is a function ofthe method of modulation used. As a rule, a receiver is exposed to bothnoise and co-channel interference at the same time. Since the wantedsignal lies close to the noise threshold, less co-channel interference istolerated, seen from a relative point of view. When the level of thewanted signal is sufficiently high, the required relationship between thewanted signal level and the level of the co-channel interferer is aconstant (C/I, carrier to interference).

Page 33: TND Complete

RADIO TRANSMISSION NETWORK AND FREQUENCY PLANNING

16 Ericsson Radio Systems AB

3/038 02-LZU 102 152, Rev A, November 1999

A C/I of approximately 8 dB is typically required for mobilecommunications FM receivers if larger input signals are to be received.A digital radio link typically requires a C/I in the vicinity of 10-15 dBsince input signals are well in excess of the threshold.

Figure 11 illustrates a typical curve of required C/I, at a given BER, as afunction of input signal level. The figure illustrates a receiver thresholddegradation (3 dB) for a certain C/I ratio.

-80

17

10

20

30

-85 -75-90

C/I (dB)

C (dBm)

3 dB

-70

Figure 11: Typical curve of required C/I, at a given BER, as a functionof input signal level.

Adjacent channel selection

Adjacent channel selection describes the receiver’s sensitivity toadjacent channel interference.

This attribute is also important when considering frequency economy.The adjacent channel selection is determined, above all, by themodulation method, the frequency separation to the adjacent channeland the receiver’s IF filter. It is also dependent on the wanted signallevel in relation to the noise threshold. When the level of the wantedsignal is sufficiently high, the required relationship between the wantedsignal level and that of the interference level, is a constant (for a givenfrequency separation).

Figure 12 illustrates a typical curve of allowable interference signals ona link as a function of frequency separation at an input signal of 1 dBabove the threshold (1 dB threshold degradation) for 2, 8 and 34 Mbit/s.The curve principally illustrates the selection of the IF filter.

Page 34: TND Complete

RADIO COMMUNICATION SYSTEM COMPONENTS

Ericsson Radio Systems AB

3/038 02-LZU 102 152, Rev A, November 1999

17

0 50 100 150 200 250

100

50

0

50

34 Mbit/s8 Mbit/s2 Mbit/s

Frequency separation (MHz)

Max

imum

inte

rfer

ence

leve

l (dB

m)

y34i

y8j

y2k

,,x34i

x8j

x2k

Figure 12: Allowable interference signal for 1 dB threshold degradationfor 2, 8 and 34 Mbit/s.

Adjacent channel selection is often specified at 70 dB for mobilecommunications. This is a result of the desire to allow different users tooperate over adjacent channels without the necessity of having tocoordinate their individual selection of site locations for their basestations. In more modern mobile telephone systems, where an operatormakes use of an entire band for their system, it is common place thatadjacent channel selection requirements are significantly relaxed sincethe operator is able to perform frequency planning for the entire band inorder to avoid interference between adjacent channels. This leads to thefact that the channels are located closer to one another, i.e., a higherpacking density, which results in better frequency economy. For thecase that adjacent channels no longer fulfill the old requirement of 70dB selection (or adjacent channel selection), one often refers to thechannels as being interleaved, i.e., interleaved with one another.

In the case of radio links, one usually uses an adjacent channel selectionof 25-35 dB. The objective is that adjacent channels are to be usable inone and the same node, which is usually facilitated by antenna isolationbetween neighboring paths.

Page 35: TND Complete

RADIO TRANSMISSION NETWORK AND FREQUENCY PLANNING

18 Ericsson Radio Systems AB

3/038 02-LZU 102 152, Rev A, November 1999

It is common place that the different connections in a network havedifferent capacities. Interference characteristics between radio linksystems, having different capacities, can be described with the aid of aC/I matrix, see Table 1. This matrix allows one to find the C/I for agiven threshold degradation that is required when the interfering linkhas another specific capacity.

C/I [dB] and frequency separation for 3 dB degradation andBER=10-6

Capacity [Mbit/s] Frequency Separation [MHz]Carrier Interferer 0 7 14 21 28

2x2 2x28

2x82x(2x8)

21201717

-37-144

17

<-50<-50-194

<-50<-50<-50-19

<-50<-50<-50<-50

8 2x28

2x82x(2x8)

21212020

-10-11020

-40-37-1410

<-50<-50-45-14

<-50<-50<-50-45

2x8 2x28

2x82x(2x8)

21212121

19202121

-11-10-121

-30-29-23-1

-41-40-37-23

2x(2x8) 2x28

2x82x(2x8)

21212121

21212121

19202121

-11-10-121

-30-29-23-1

Table 1: C/I matrix.

Blocking level

The blocking level specifies the maximum strength of an interferingsignal that a receiver can withstand without its sensitivity degrading bymore than for example 3 dB. Blocking is a special case of adjacentchannel interference, namely for the case of large adjacent channelseparation, see Figure 13. It is usually specified in the case of mobileradio as being a frequency separation of 1 MHz. In the case of blockingin situations of larger frequency separations, both the IF and RF filterscontribute to suppressing interference.

Page 36: TND Complete

RADIO COMMUNICATION SYSTEM COMPONENTS

Ericsson Radio Systems AB

3/038 02-LZU 102 152, Rev A, November 1999

19

Signal level

FrequencyfRxfTx

Received signal

Receiver’s blockinglevel

Transmitter’sspectrum

Transmitter’snoise level

Receiver’snoise level

Transmitted signal

Figure 13: Interference with duplex setup.

The concept of blocking may be clarified as being the reception ofsignificantly large interference signals that exist at a frequency adjacentto the desired frequency. The result is that the input signal to thedetector will consist of, aside from the smaller signal carrying the actualinformation, a powerful interference signal (resulting from insufficientfiltering) which will literally block the smaller information signal at thedetector.

The blocking level is not to be confused with the maximum allowableinput signal level, which represents a degradation of the receiver’scharacteristics. This is a maximum level for the desired signal andspecifies a boundary value for the receiver’s dynamics at the desiredfrequency. Exceeding this boundary value will result in over-excitationand distortion in the detector.

Blocking is often specified for mobile communication receivers as lyingat least 80 dB above the receiver’s threshold at a 1MHz separation.With the threshold at -113 dBm, the blocking level will be -113+80= -33 dBm. At a 10 MHz frequency separation between a transmitter and areceiver, which is a typical duplex separation in the 450 MHz band, theIF filter will exhibit a typical 20 dB attenuation and the blocking levelwill be instead -33 dBm + 20 dB = -13 dBm.

Page 37: TND Complete

RADIO TRANSMISSION NETWORK AND FREQUENCY PLANNING

20 Ericsson Radio Systems AB

3/038 02-LZU 102 152, Rev A, November 1999

Intermodulation level

Intermodulation results from the fact that receivers exhibitcertainnonlinear behavior and are therefore sensitive to interferencesignals occurring at certain frequency combinations. These frequenciesmay combine, as a result of this nonlinear behavior in the receiver, intoone frequency that corresponds to the wanted received frequency.Intermodulation level is defined as the level assumed by theseinterference signals, to bring about a given degradation in receiversensitivity when the wanted signal is at the threshold level.Intermodulation level is a function of the ordinal number for theintermodulation. The higher the ordinal number, the higher is the levelof interference tolerated by the receiver.

The only protection against intermodulation is through filtering beforeapplying the signal to the RF amplifier, i.e., in the RF filter. Protectionmay also be achieved through frequency planning thereby avoiding thecreation of dangerous intermodulation frequencies. Instead of specifyingthe intermodulation level, one may, on occasion, specify receiverintermodulation attenuation - which is the difference (in dB) betweenthe level of the signals that cause the intermodulation product and thereceiver’s threshold level. These levels are measured at the receiver’santenna connector. A typical value of intermodulation attenuation for3rd-order intermodulation is 70 dB for mobile radio and in generalsomewhat worse for radio links. Then, the level of the interferingsignals at the input of the receiver’s antenna connector should be givenby

dB 370 =⇒+≤ DPP th ............................................................ (3)

where Pth is the threshold level of the receiver and D the thresholddegradation. Typical values for intermodulation attenuation for mobileand link are given in Table 2.

Intermodulation attenuation(dB)

Intermodulation order Mobile Link

3 70 50 (?)

5 90 70 (?)Table 2: Typical values for intermodulation attenuation for mobile radiosystems and radio link systems.

Page 38: TND Complete

RADIO COMMUNICATION SYSTEM COMPONENTS

Ericsson Radio Systems AB

3/038 02-LZU 102 152, Rev A, November 1999

21

The intermodulation signal will be suppressed when passing thereceiver’s IF, to a degree corresponding to the relationship between thebandwidth of the intermodulation signal and that of the receiver. Thesuppression factor of intermodulation is expressed as follows,

i

m

B

BR = ...................................................................................................... (4)

where Bi is given by

...+⋅+⋅+⋅= 332211 BnBnBnBi .......................................................... (5)

and the desired bandwidth of the receiver is Bm.

Feeder cabling

Feeder cabling between the radio equipment and the antenna mayconsist of coaxial cabling or a waveguide.

Coaxial cableCoaxial cabling is normally used for frequencies around 2 GHz andlower - cable attenuation would otherwise be unreasonably high athigher frequencies.

See the table below showing coaxial cable attenuation at differentfrequencies:

HF3/8 Cu2Y 6.1 dB/100 m 400 MHz

HF1 5/8 Cu2Y 6.35 dB/100 m 400 MHz

HF3/8 Cu2Y 14 dB/100 m 2000 MHz

HF1 5/8 Cu2Y 3.1 dB/100 m 2000 MHz

WaveguidesWaveguides are used for frequencies above 2 GHz. The most commonwaveguide forms are the rectangular, the elliptical and the circular.However, other forms also exist. Since the cross-section of a waveguidehas a given relationship to wavelength, the selection of a waveguide isdependent on the frequency band to be used.

The table below shows the attenuation for various waveguides atdifferent frequencies:

Page 39: TND Complete

RADIO TRANSMISSION NETWORK AND FREQUENCY PLANNING

22 Ericsson Radio Systems AB

3/038 02-LZU 102 152, Rev A, November 1999

E70 4.75 dB/100 m 7300 MHz

E130 11.2 dB/100 m 13000 MHz

EW220 30 dB/100 m 20000 MHz

Duplex filters

The purpose of duplex filtering is to protect the receiver from thedisturbing effects of the transmitter when transmission and reception areconcurrent (duplex operation).

The transmitter can interfere with the receiver in two ways: via thatportion of the transmitter’s sideband noise that lies within the receiver’spassband, or via receiver blocking caused by the transmitted power.

Assume, for example, a mobile communication base station having atransmission power of 20 W (43 dBm). Typical values for sidebandnoise lie approximately -140 dB/Hz below the carrier, which is in thiscase a level of -97 dBm/Hz (43 dBm -140 dB/Hz). For a bandwidthcorresponding to 12.5 kHz (41 dBHz), transmitter noise level would bewithin receiver bandwidth -56 dBm (-97 dBm/Hz + 41 dBHz).

The receiver’s own noise level was in the above example -123 dBm. Ifone accepts an increase of the total noise level of 1 dB, i.e., an increaseto -122 dBm, then the transmitter’s noise level to the receiver may notexceed -123-6=-129 dBm. Transmitter noise must then be attenuated byat least 129-56=73 dB before arriving at the receiver. This isaccomplished via a bandpass filter at the output of the transmitter thatattenuates the signal by at least 73 dB within the receiver’s passband.

We will now consider blocking requirements. A blocking level of -13dBm and a transmitter power of 43 dBm require a transmission signalattenuation of at least 56 dB. This can be accomplished through the useof a bandpass filter located at the receiver input that attenuates thetransmitted frequency by at least 56 dB.

A conclusion that may be drawn from the above example is thattransmitter noise places greater demands on filtering than it does onblocking.

Transmitter combiners

It is often desirable, for sites having more than one transmitter, to beable to utilize one common antenna for all transmitters. To this end, so-called combiners are often used. The job of these combiners is asfollows:

Page 40: TND Complete

RADIO COMMUNICATION SYSTEM COMPONENTS

Ericsson Radio Systems AB

3/038 02-LZU 102 152, Rev A, November 1999

23

• ensure that every transmitter delivers its power to the antennawithout any appreciable losses.

• to limit the occurrence of intermodulation between the varioustransmitters

A combiner may be either passive or active. The simplest form of apassive combiner may be constructed using hybrids as illustrated inFigure 14. In a hybrid, however, half (3 dB) of the transmitted power islost. The more transmitters combined to use one antenna, the greater isthe number of hybrids required and the greater is the loss. Using 4transmitters requires the use of 3 hybrids and the loss is 6 dB - using 8transmitters requires a tree-connection of 7 hybrids which results in aloss of 9 dB, and so on.

F F

HYBRID COUPLER

Tx1

INPUTTx2

INPUT

ISOLATORIN EACHPATH

BANDPASS, LOW OR2ND HARM, FILTERS

LOAD TERMINATION

Figure 14: Example of a hybrid.

An active combiner combines a number of low-power transmitters viathe use of hybrids or a resistive network into a common port where thecollective signal is amplified via a linear amplifier to attain the desiredoutput power. This technique is not very widely utilized due to the factthat it is difficult to achieve sufficient output power without introducingintermodulation.

Figure 15 illustrates a schematic block diagram of another transmissioncombiner, a multiple connector. Each transmitter is connected via a so-called isolator and a filter to a star network, in which the differenttransmitters are inputs to the network and the antenna is the output.

Page 41: TND Complete

RADIO TRANSMISSION NETWORK AND FREQUENCY PLANNING

24 Ericsson Radio Systems AB

3/038 02-LZU 102 152, Rev A, November 1999

Tx1

etc

f1

f2

≈ -10dBat ∆f

Star net

~~~

~~~Tx2

Figure 15: Schematic block diagram of a multiple connector.

The isolator, see Figure 16, normally a so-called circulator, is a non-reciprocal component that has negligible attenuation (at the most one ortwo dB) in its forward direction and a significantly high attenuation (25-30 dB) in its reverse direction. Its function being to prevent leakagefrom other transmitters into the transmitter that it is connected to andthereby avoiding intermodulation.

Figure 16: An isolator (circulator).

The job of the filter is to create an mismatch as seen from the othertransmitters so that their output power is primarily directed to theantenna and not inwards towards the network and the other transmitters.Since the frequencies of the different transmitters generally lie relativelyclose to one another, the filters must be of the cavity type so thatsufficient signal attenuation is achieved across the frequencyseparations for the particular transmitters in question.

Page 42: TND Complete

RADIO COMMUNICATION SYSTEM COMPONENTS

Ericsson Radio Systems AB

3/038 02-LZU 102 152, Rev A, November 1999

25

Typically, the lowest frequency separation between neighboringtransmitters is often around 500 kHz in both the 450 and 900 MHzranges, i.e., approximately an 0.1% frequency separation. Requiredattenuation for a neighboring transmitter for the achievement ofsufficient mismatch can be as low as 10 dB. This does not preventtransmitter power leakage through the filter into the neighboringtransmitter, which would cause damaging intermodulation. This iswhere the function of the isolator comes into play, providing additionalattenuation to reduce transmitter leakage.

Any intermodulation products are attenuated once again by the cavityfilter on their way out to the antenna. A typical combiner maintains anintermodulation level at the antenna output of 70 dB below each of thetransmitters’ power levels.

Receivers multicouplers

It is often desirable to use a single antenna even if more than onereceiver is located at one and the same site. To this end, multicouplersare utilized. Figure 17 illustrates a schematic block diagram of amulticoupler.

O

O

O

Powerdivider

connected toeach receiver

1

2

16

~~~........

Figure 17: Schematic block diagram of a multicoupler.

The signal from the antenna is first filtered by a highly selectivebandpass filter, then amplified and then separated in a signal powerdivider (occasionally called splitter).

Page 43: TND Complete

RADIO TRANSMISSION NETWORK AND FREQUENCY PLANNING

26 Ericsson Radio Systems AB

3/038 02-LZU 102 152, Rev A, November 1999

An effective filter located at the input to the multicoupler may oftenserve to reduce the requirement for a duplex filter. The followingamplifier is intended to compensate for the attenuation and the noiseresulting from the split and distribution of the signal to severalreceivers. The signal power divider is constructed to achieve a dualpurpose. Firstly to match to the individual receivers to the antenna andsecondly to isolate the receivers from one another. Multicouplerspresent a problem in maintaining satisfactory performance in preventingintermodulation and blocking at its input. A typical receivermulticoupler can connect up to 16 receivers. All of the outputs of themulticouplers should be terminated even if they are not used for theconnection of a receiver.

Antennas

The primary purpose of a radio system antenna is:

• when transmitting, to deliver to the surrounding environment thepower generated by the transmitter without incurring any losses inthe desired direction

• when receiving, to deliver the available radiation power to thereceiver

An antenna is characterized by the following attributes:

• impedance

• bandwidth

• directivity

• polarization

Directivity in a given direction is defined as the ratio of the intensity ofradiation (the power per unit solid angle), in that direction, to theradiation intensity averaged over all directions. It may in turn beexpressed by antenna gain and side lobe level.

The antenna gain specifies the degree to which the power radiated in thedesired direction as compared to the level of the power radiated equallyin all directions (i.e., an isotropic antenna). On occasion, antenna gain isspecified as above but relative a dipole antenna, which is 2.15 dB lowerthan the gain relative an isotropic antenna.

Page 44: TND Complete

RADIO COMMUNICATION SYSTEM COMPONENTS

Ericsson Radio Systems AB

3/038 02-LZU 102 152, Rev A, November 1999

27

Antenna gain is specified in units of dBd or dBi to specify whether thegain information for a given antenna is relative a dipole or an isotropicantenna. If the gain is specified in dB then the value given is relative anisotropic antenna.

To be effective, an antenna should be of the same magnitude of size asthe wavelength of the frequency in question.

Vertical rod antennas are normally used for mobile communications.Such antennas radiate omnidirectionally in the horizontal plane.Polarization is in this case vertical. The shortest antenna is often in suchcases a quarter wavelength, i.e., just under 20 cm at 450 MHz.

Base station antennas are often directional in the vertical plane, which isachieved by using a number of half-wave dipoles that are stacked oneabove the other. These antennas are referred to as being co-linear. Thegain is then essentially proportional to the number of elements.

Antenna gain for parabolic antennasParabolic antennas, which function as mirrors, are almost withoutexception used for radio links having frequencies from approximately 2GHz and upwards. The following relationship apply to these antennas:

22 0.30.3

2222

2

44 fdfAAG

⋅⋅=

⋅⋅⋅=

⋅⋅=

ππ

λ

π....................................................... (6)

where

G = Antenna gain

A = Effective antenna area, m2

d= Antenna diameter, m

λ = Wavelength, m

f= Frequency, GHz

The antenna gain as calculated by equation (3) is specified as a factor.The result of the equation (3) can be obtained in dB by applying thefollowing relationship:

Page 45: TND Complete

RADIO TRANSMISSION NETWORK AND FREQUENCY PLANNING

28 Ericsson Radio Systems AB

3/038 02-LZU 102 152, Rev A, November 1999

( ) ( )fdG log20log2020.4 ⋅+⋅+= ......................................................... (7)

The effective antenna surface is typically approximately 50-70% of theactual geometric surface, depending on the manner in which theaperture is illuminated. It is clearly evident that the gain, for a givenantenna size, increases with decreasing wavelength, i.e., as frequencyincreases.

Example: assume a parabolic antenna having a diameter of 2 m andoperating at a frequency of 5 GHz. This corresponds to an area of 3.14m2 and a wavelength of 0.06 m. Antenna gain can be calculated fromequation (3) as being a factor of 10,965 corresponding to 40.4 dB. Butthe measured gain of the antenna is only 37 dB, which seems to implythat there is a 3-dB loss in effectivity, an efficiency of only 50%.

Antenna diagramSide lobe level indicates how much lower the power is in a non-desireddirection (side lobe) than that radiated in the desirable direction (mainlobe), Figure 18.

αα

0G

GGS

αα

bg bg( )0

=

Main lobe

Side lobe

Figure 18: Main and side lobes.

The front-to-back ratio gives the relationship between the powerradiated in the forward direction vs. the power radiated in the reversedirection.

The lobe width that corresponds to a 3 dB lower gain in relation to themain lobe gain, see Figure 18, can be calculated as

fdk

⋅⋅=

0.3θ ............................................................................................... (8)

where

θ = Lobe width, degree

k= Constant, 75-85

Page 46: TND Complete

RADIO COMMUNICATION SYSTEM COMPONENTS

Ericsson Radio Systems AB

3/038 02-LZU 102 152, Rev A, November 1999

29

d= Antenna diameter, m

f= Frequency, GHz

Figure 19 illustrates a schematic antenna diagram for a 18 GHz antennawith a 44.5 dBi gain. The antenna has a diameter of 1.2 m. The figurealso shows the corresponding diagram for the cross-polarization field.

0 5 10 15

0

10

30

20

50

40

70

60

dB

degree20 40 60 80 100 120 140 160 180

copolar

crosspolar

Figure 19: Antenna diagram for an 18 GHz antenna.

Page 47: TND Complete

RADIO TRANSMISSION NETWORK AND FREQUENCY PLANNING

30 Ericsson Radio Systems AB

3/038 02-LZU 102 152, Rev A, November 1999

References

“Grundläggande Radioteknik” (in Swedish), Billström, O., EricssonRadio Systems AB, 1993.

“Radio System Design for Telecommunications (1-100 GHz)”,Freeman, R. L., 1987.

Page 48: TND Complete

i

RADIOWAVE PROPAGATION

This chapter provides a presentation of the basic principlesand algorithms related to radiowave propagation used inradio-relay transmission. Both loss and attenuationalgorithms plus fade prediction models for different fadingmechanisms are thoroughly discussed. The chapter alsoincludes a presentation of the basic concepts of mainpropagation mechanisms, Fresnel zone, equivalent andtrue Earth radii and the decibel scale.

TABLE OF CONTENTSThe decibel........................................................................................................................................................ 1

A relative comparison ......................................................................................................................... 1Some motivations for using decibels................................................................................................... 1Absolute comparisons ......................................................................................................................... 1The comparison of field quantities...................................................................................................... 2An overview........................................................................................................................................ 3

The main propagation mechanisms................................................................................................................... 3Propagation along the earth’s surface ................................................................................................. 4

Fading................................................................................................................................................................ 4Definition ............................................................................................................................................ 4Cause................................................................................................................................................... 4General classification .......................................................................................................................... 4Classification based on source ............................................................................................................ 5

The Fresnel zone ............................................................................................................................................... 5Definition ............................................................................................................................................ 5The Fresnel ellipsoid ........................................................................................................................... 6

Equivalent and true earth radii .......................................................................................................................... 7Earth-radius factor............................................................................................................................... 7Equivalent and true Earth surface - a comparison............................................................................... 8

Prediction models.............................................................................................................................................. 8Attenuation: free-space loss .............................................................................................................................. 9

Definition ............................................................................................................................................ 9Free-space loss between two isotropic antennas ................................................................................. 9

Diagram................................................................................................................................. 10Attenuation: gas ................................................................................................................................................ 10

Definition ............................................................................................................................................ 10The troposphere................................................................................................................................... 11Chemical composition......................................................................................................................... 11Absorption peaks................................................................................................................................. 11Calculating total gas attenuation ......................................................................................................... 12

Oxygen (dry air).................................................................................................................... 12Water vapor........................................................................................................................... 13Total gas attenuation ............................................................................................................. 14

Total specific gas attenuation - diagram............................................................................................................ 15Attenuation: reflection....................................................................................................................................... 15

Ground reflection interference ............................................................................................................ 16

Page 49: TND Complete

ii

The problems of handling reflection ................................................................................................... 16Reflection coefficient .......................................................................................................................... 17

The Fresnel reflection coefficient ......................................................................................... 17Divergence factor.................................................................................................................. 18Correction factor ................................................................................................................... 18

Example: rough estimation of the total reflection coefficient ............................................................. 19Calculation of the position of the reflection point............................................................................... 19

Attenuation: precipitation.................................................................................................................................. 21Types of precipitation ......................................................................................................................... 21Snow.................................................................................................................................................... 21Hail...................................................................................................................................................... 22Fog and haze ....................................................................................................................................... 22Rain ..................................................................................................................................................... 22Cumulative distribution of rain ........................................................................................................... 23Rain zones - diagram........................................................................................................................... 23The new ITU model for calculation of rain intensity .......................................................................... 24The calculation of the specific rain attenuation................................................................................... 26Table containing the frequency dependent coefficients ...................................................................... 27Calculating total rain attenuation ........................................................................................................ 32Calculating total rain attenuation for 0.01% ....................................................................................... 32

Attenuation: obstruction.................................................................................................................................... 33Knife-edge obstructions ...................................................................................................................... 33Knife-edge loss curve.......................................................................................................................... 34Typical knife-edge losses.................................................................................................................... 35Single-peak method............................................................................................................................. 36Triple-peak method ............................................................................................................................. 37Smoothly spherical earth..................................................................................................................... 39Typical losses resulting from smoothly spherical earth ...................................................................... 40Clearance and path geometry .............................................................................................................. 41

The Earth bulge..................................................................................................................... 41Path geometry ....................................................................................................................... 41The height of the line-of-sight............................................................................................... 42

Path losses ......................................................................................................................................................... 42Definition ............................................................................................................................................ 42Fade margin......................................................................................................................................... 43Power diagram .................................................................................................................................... 43Effective fade margin .......................................................................................................................... 44

Fading - prediction models................................................................................................................................ 45The concept of outage ......................................................................................................................... 45Rain fading.......................................................................................................................................... 45

Calculation of the fade margin based on a yearly basis ........................................................ 45Outage due to rain fading - annual basis ............................................................................... 46Transformation between yearly and worst month basis ........................................................ 46

From yearly to worst month.................................................................................... 46From worst month to yearly.................................................................................... 47

Climatic parameters .............................................................................................................. 47Presentation of the rain fading models in diagram form....................................................... 48

Multipath fading.................................................................................................................................. 49The occurrence of multipath propagation ............................................................................. 49Flat and frequency selective fading....................................................................................... 50The effects of multipath propagation .................................................................................... 51Measures taken against multipath fading .............................................................................. 51Outage due to flat fading....................................................................................................... 52

Introduction............................................................................................................. 52Fade occurrence factor ............................................................................................ 52

Flat fading and error performance......................................................................................... 53Method for small percentages of time................................................................................... 53

Estimation of the geoclimatic factor ....................................................................... 53Inland Links ............................................................................................................ 53Coastal Links .......................................................................................................... 55

Page 50: TND Complete

iii

Link and terrain parameters – overview................................................................................ 57Estimation of the path slope.................................................................................................. 58Outage due to flat fading....................................................................................................... 59Range of values for the climatic factor pL ............................................................................. 59Method for small percentage of time - conclusion................................................................ 60Method for various percentages of time................................................................................ 61Range of validity for the flat fading method ......................................................................... 63Main differences between Rec. ITU-R P.530-6 and Rec. ITU-R P.530-7 ............................ 64

Outage due to frequency selective fading ........................................................................................... 64ITU-R F.1093 model............................................................................................................. 66

Refraction fading................................................................................................................................. 68The total fading outage...................................................................................................................................... 68Basic radio-meteorological parameters for RL-design...................................................................................... 69

Earth-radius factor............................................................................................................................... 69Surface water vapor density ................................................................................................................ 69Relative humidity................................................................................................................................ 70pL factor (refractive factor).................................................................................................................. 70Refractive gradient .............................................................................................................................. 70Rain frequency-dependent coefficients ............................................................................................... 70Rain climate zones .............................................................................................................................. 70Rain intensity distribution ................................................................................................................... 71Annual and worst-month statistics ...................................................................................................... 71

Hardware failure................................................................................................................................................ 71The calculation of the radio-link system’s MTBF ............................................................................... 71Non-redundant systems....................................................................................................................... 72Redundant systems.............................................................................................................................. 73Hardware failure per path.................................................................................................................... 75

Diversity............................................................................................................................................................ 76The basic concepts .............................................................................................................................. 76The definition of the improvement factor ........................................................................................... 77The calculation of the improvement factor: space diversity................................................................ 78The calculation of the improvement factor: frequency diversity......................................................... 79

Analogue 1+1 system.............................................................................................. 79Digital 1+1 system .................................................................................................. 79

The calculation of the improvement factor: space-frequency diversity .............................................. 80The calculation of outage when employing diversity.......................................................................... 80

Passive repeaters ............................................................................................................................................... 80The basic concepts .............................................................................................................................. 80Path calculation when using passive repeaters.................................................................................... 81

References ......................................................................................................................................................... 83

Page 51: TND Complete

ii

Page 52: TND Complete

RADIO WAVE PROPAGATION

Ericsson Radio Systems AB 1

4/038 02-LZU 102 152, Rev A, November 1999

The decibel

A relative comparisonIt is often the case within the realm of radio technique, that twodifferent values or entities are compared with one another. For instance,two power levels can be compared by calculating their ratio. Thedecibel is a measure of the relationship between two power levels.Decibel is abbreviated as dB and is defined as follows

[ ]2

110log.10dB

P

PA = ..............................................................................(1)

where P1 and P2 are the power levels being compared.

Note that the decibel is a measure of a relationship and has no actualphysical significance. The decibel is therefore not a measure of aphysical entity.

One decibel corresponds approximately to the smallest variation insound volume that can be discerned by the human ear.

Some motivations for using decibelsSome of the motivations behind the widespread use of the decibel are:

• The decibel is convenient to use since the direct relationshipbetween radio-related power levels covers a wide range ofnumerical values. The logarithmic nature of the relationshipbetween two power-levels results in values that are easy to handle.

• Addition or subtraction operations can be easily performed onlogarithmic values, simplifying the handling of amplification andattenuation.

• The manner in which human sensory organs perceive differences inthe sensory impressions of varying intensity that they receive is infact logarithmic.

Absolute comparisons The decibel concept defined above is related to the quotient of twovalues, and provides no information as to the absolute value of theseentities. An absolute comparison between two power levels canhowever be performed if a reference value is employed, for example theW (Watt) or mW (milliWatt), referred to respectively as dBW anddBm.

Page 53: TND Complete

RADIO TRANSMISSION NETWORK AND FREQUENCY PLANNING

2 Ericsson Radio Systems AB

4/038 02-LZU 102 152, Rev A, November 1999

[ ] Watt1

log.10dBW 10

PA = ....................................................................(2)

where P is the power in Watt.

[ ]milliWatt 1

log.10dBm 10

PA = .............................................................(3)

where P is the power in milliWatt.

Since,

10

dBW

10 W1

=P

.........................................................................................(4)

and

10

dBm

10mW 1

=P

......................................................................................(5)

the result obtained following division is

= 10

dBm-dBW

10 W1mW 1

..............................................................................(6)

or

= 10

dBm-dBW3

10 W1 W1

..............................................................................(7)

giving

10dBm-dBW

3 =− ................................................................................(8)

or

30dBWdBm += .................................................................................(9)

The comparison of field quantities The decibel concept can be generalized to also include the comparisonbetween field magnitudes. The term field quantity refers to a quantitywhose square is proportional to power. Examples of field quantities areelectrical voltages, currents and field strengths.

Page 54: TND Complete

RADIO WAVE PROPAGATION

Ericsson Radio Systems AB 3

4/038 02-LZU 102 152, Rev A, November 1999

The application of the decibel concept results in

[ ] ( )( )

⋅=

2

110 quantity Field

quantity Fieldlog20dBA .................................................(10)

An overview Power and field quantities, lying between 103 and 10-3 are expressed intheir equivalent decibel values in Table 1.

Powerrelationship

dB Field quantityrelationship

dB

1 000=103

30

1 000=103

60

100=102

20

100=102

40 10=101

10

10=101

20

9

9.5

9

19 8

9

8

18

7

8.5

7

17 6

8

6

16

5

7

5

14 4

6

4

12

3

5

3

9.5 2

3

2

6

1

0 1 0

1/2 -3

1/2 -6

1/4 -6

1/4 -12

1/8 -9

1/8 -18

1/10=10-1 -10

1/10=10-1 -20

1/100=10-2 -20

1/100=10-2 -40

1/1000=10-3 -30

1/1000=10-3 -60 Table 1: Power and field relationship.

The main propagation mechanisms

Most of the propagation mechanisms are affected by climacticconditions. When calculating the transmission quality and availabilityof radio networks, the significance of the various mechanisms vary as afunction of the radio spectrum. The following propagation mechanismsmay however be considered as the most notable:

• free-space

• diffraction

Page 55: TND Complete

RADIO TRANSMISSION NETWORK AND FREQUENCY PLANNING

4 Ericsson Radio Systems AB

4/038 02-LZU 102 152, Rev A, November 1999

• refraction

• absorption

• scattering

• reflection

Propagation along the earth’s surface An electromagnetic wave traveling close to and along the surface of theearth is affected by the following factors:

• the electrical properties of the earth’s surface

• the earth’s curvature

• the atmosphere

• the earth’s topography

• vegetation

Fading

Definition Fading is often defined as a variation in signal strength over time, phaseor polarization. Fading is normally the result of changes in the physicalproperties of the atmosphere or due to ground or water reflections.

Cause Fading can be caused by the occurrence of an isolated phenomenon, onethat is solely responsible for its appearance. It is however morecommon that fading appears in one and the same hop as the result of acombination of various phenomenon that interact with one another,leading to the degradation of signal quality and availability. Climate,topography and surroundings can vary to such great degrees that fadingoften depends on the aggregate effects of numerous phenomenon.

General classification Fading can be classed as follows:

Page 56: TND Complete

RADIO WAVE PROPAGATION

Ericsson Radio Systems AB 5

4/038 02-LZU 102 152, Rev A, November 1999

• source

• propagation attributes

• time variation

• statistical distribution

Classification based on source The phenomenon of fading is often classified based on the source of thephenomenon. Source can be divided into four primary groups:

• atmospheric fading: absorption, refraction and turbulence.

• ground-based fading: geology, the roughness of the surroundingterrain, propagation path differences due to tides or variations insnow depth, obstructions due to variations in vegetation

• ”man-made” fading: obstruction or reflection caused by boats,aircraft and temporary constructions sites, antenna vibration.

• mixed fading: due to the occurrence of atmospheric inversion layersand the reflection they cause.

The Fresnel zone

Definition Fresnel zones are specified employing an ordinal number thatcorresponds to the number of half-wavelength multiples that representsthe difference in radio wave propagation path from the direct path. Thefirst Fresnel zone is therefore an ellipsoid whose surface corresponds toone half-wavelength path difference and represents the smallest volumeof all the other Fresnel zones.

The first Fresnel zone contains almost all the energy that is transmittedbetween the antennas and is therefore of great significance in thecalculation of the attenuation caused by obstructing bodies.

Page 57: TND Complete

RADIO TRANSMISSION NETWORK AND FREQUENCY PLANNING

6 Ericsson Radio Systems AB

4/038 02-LZU 102 152, Rev A, November 1999

The Fresnel ellipsoid The Fresnel zone is an ellipsoid having its focal points at the antennapoints A and B, see Figure 1. The radius of the first Fresnel zone, r1F, isa function of the distance between A and B, the distance between anypoint, M, on the ellipsoid and the frequency. The radius of the firstFresnel zone is indirectly proportional to frequency and the higher thefrequency the narrower the Fresnel zones.

Page 58: TND Complete

RADIO WAVE PROPAGATION

Ericsson Radio Systems AB 7

4/038 02-LZU 102 152, Rev A, November 1999

d1

A B

Fresnel zone

d

Equivalent earth surface

N

M

r1F Unobstructed line-of-sight

Figure 1: The Fresnel zone.

Equivalent and true earth radii

Earth-radius factor In simple terms, one can describe the ray beam between two antennasby employing an imagined propagation path that directly links the twoantennas. In free-space this path would describe a straight line, a so-called optical line-of-sight.

If instead, the antennas are placed on a spherical body surrounded by anatmosphere (as in the case for the earth), wave propagation will beaffected by variations in atmospheric refractive index as the wavetravels through the various atmospheric layers. The ray beam will nownot follow the optical line-of-sight, but will describe a curved linebetween the two antennas. The form of the curve will vary as a functionof variations in the refractive index of the atmosphere traversed by thewave.

To simplify the description of this curved ray beam, the concept ofequivalent earth surface having an equivalent earth radius, Re, has beenintroduced. Defined as follows:

RkRe ⋅= ............................................................................................(11)

where

k = Earth-radius factor

Page 59: TND Complete

RADIO TRANSMISSION NETWORK AND FREQUENCY PLANNING

8 Ericsson Radio Systems AB

4/038 02-LZU 102 152, Rev A, November 1999

R = True earth radius (6.37·106 m)

The earth-radius factor is a function of the refractive index gradient. Fornormal atmosphere (i.e., atmosphere in which the refractive indexgradient decreases linearly with altitude), the k-value is 4/3 if therefractive index gradient is -39 N-units/km.

Equivalent and true Earth surface - a comparison The equivalent earth surface is that earth surface that would be requiredfor the ray beam between the antennas to lie along a straight line, seeFigure 2. A beam that travels outside of the optical line-of-sight mustbend downwards in order to become a straight line, which is equivalentto enlarging the earth’s radius, i.e. reducing the curvature of the earth.The earth-radius factor, k, describes exactly the degree to which theearth’s radius would have to be changed in order that the ray beamdescribe a straight line.

True earth surface

Optical line-of-sightTrue ray beam

R

Equivalent ray beam

Equivalent earth surface

Optical line-of-sight

Re = k · R

Figure 2: The equivalent and the true earth surface.

Prediction models

Prediction models for the purpose of performing fading prognoses arealmost always empirical (comes from the Greek word empeiriameaning experience), i.e., they are not founded on theoreticalconsiderations but are only built upon observation and experience.

Empirical models are arrived as the result of the application ofmathematical regression techniques on measurement data and thereforeresult in a relationship that describes a variable’s dependency undercertain given conditions.

Page 60: TND Complete

RADIO WAVE PROPAGATION

Ericsson Radio Systems AB 9

4/038 02-LZU 102 152, Rev A, November 1999

Empirical prediction models often provide a fair description of thefading process for distances and frequencies that lie within the data-ranges for which measurements have actually been collected. Theirapplication to other distances and frequency ranges may, on the otherhand, result in significant error.

Attenuation: free-space loss

Definition Free-space wave propagation implies that the effects caused bydisturbing objects and other obstacles that are located at sufficientlylong distances are assumed to be negligible.

Free-space loss between two isotropic antennas The free-space loss between two isotropic antennas can be derived fromthe relationship between total output power and received power. Theresulting expression is

λπ d

Abf

⋅⋅⋅=

4log20 .........................................................................(12)

where

Abf = Free-space loss, dB

d = Distance from the transmitting antenna, km

λ = Wavelength, m

Following the transformation of wavelength into frequency(c=2.99792500 · 108 m/s) and entering of the actual units, the followingis attained

fdAbf log20log205.92 ⋅+⋅+= ......................................................(13)

where

Abf = Free-space loss, dB

d = Distance from the transmitting antenna, km

f = Frequency, GHz

If the distance is doubled while maintaining constant frequency, thefree-space loss is increased by 20·log 2= 6 dB. The same applies to adoubling of the frequency while maintaining a constant distance. Inother words, an additional attenuation of 6 dB will be caused for everydoubling of either the distance or the frequency.

Page 61: TND Complete

RADIO TRANSMISSION NETWORK AND FREQUENCY PLANNING

10 Ericsson Radio Systems AB

4/038 02-LZU 102 152, Rev A, November 1999

Diagram

The free-space loss (dB) as a function of distance (km) is illustrated inFigure 3 for eight different frequencies (GHz).

1 GHz

15

5

203040

10

50

0 10 20 30 40 50

Distance, km

-170

-160

-150

-140

-130

-120

-110

-100

-90

-80

Fre

e-s

pa

ce lo

ss, d

B

Figure 3: The free-space loss as a function of distance for eight differentfrequencies.

Note that the free-space loss in the GHz range is a minimum ofapproximately 92 dB.

Attenuation: gas

Definition The atmosphere, up to an altitude of 30-40 km, consists of two layers

• troposphere

• stratosphere

The two layers are separated by an often sharply demarcated transitionlayer referred to as the troposphere.

It is within this troposphere in which all weather-related processes(precipitation, cloud formation, electrical storms, etc.) arise.

Page 62: TND Complete

RADIO WAVE PROPAGATION

Ericsson Radio Systems AB 11

4/038 02-LZU 102 152, Rev A, November 1999

The troposphere lies at an altitude of 10 km over the earth’s mediumlatitudes and somewhat less over its poles. At the equator, thetroposphere lies at an altitude varying between 16 and 18 km above theearth’s surface.

The troposphere The troposphere consists of approximately 9/10 of the earth’satmospheric mass, and aside from variations in moisture content,density and temperature, its constitution is more or less constantthroughout its volume. This layer contains just a few notable elementsand their compounds, which are of significance in the propagation ofradio waves.

Chemical composition Nitrogen and oxygen molecules account for approximately 99% of thetotal volume. From the propagation point of view, it is suitable toconsider the atmosphere as being a mixture of two gases, dry air andwater vapor.

The chemical composition of the earth’s atmosphere is illustrated inTable 2.

CHEMICAL COMPOSITION OF THE EARTH´S ATMOSPHERE, % N2 O2 Ar CO2 Ne He Kr Xe H2

78.09 20.93 0.93 0.03 0.00018 5.2⋅10-4 1.0⋅10-4 8.0⋅0-6 <5⋅10-5

Table 2: The chemical composition of the earth’s atmosphere.

Absorption peaks Water and dry air (oxygen) result in the following absorption peaks:

• Water (H2O) displays absorption peaks at the following radiofrequencies: 22,235 GHz, 183,310 GHz and at 323.8 GHz. Inaddition, even greater absorption occurs at higher frequencies,where the propagation of IR and visible light transmission areprimarily affected.

• Oxygen molecules (O2) displays absorption peaks at the followingradio frequencies: 50-70 GHz (a complex system of absorptionpeaks lie in this frequency band), 118.75 GHz and at 367 GHz.

Page 63: TND Complete

RADIO TRANSMISSION NETWORK AND FREQUENCY PLANNING

12 Ericsson Radio Systems AB

4/038 02-LZU 102 152, Rev A, November 1999

Calculating total gas attenuationIn what follows, the algorithms for the calculation of the specificattenuation due to oxygen (dry air) and water vapor will be describedstep-by-step.

Oxygen (dry air)

Two atmospheric parameters are involved in the calculation of thespecific attenuation of oxygen: the atmospheric pressure and thetemperature.

The atmospheric pressure is normalized to the value at see level (1013hPa) by

1013p

rp = ...........................................................................................(14)

where rp is the normalization factor and p (hPa) the pressure of theatmosphere at a certain altitude. A “normal atmosphere” is theatmosphere where the pressure at the see level is 760 mmHg, whichcorresponds to 1 atm or 1013.25 hPa. The non-SI unity is bar (100kPa).

The temperature is normalized to a mean value of 15 °C by

( )trt +=

273288

......................................................................................(15)

where rt is the normalization factor and t is the temperature (°C).

The following parameters are determined:

( )[ ]115663.15106.05050.01 e7665.6 −−⋅− ⋅⋅⋅= tr

tp rrη ...........................................(16)

( )[ ]115496.08491.04908.02 e8843.27 −−⋅−− ⋅⋅⋅= tr

tp rrη .......................................(17)

( )5.3ln

ln1

2

=ηη

a ........................................................................................(18)

1

a

b = ................................................................................................(19)

Page 64: TND Complete

RADIO WAVE PROPAGATION

Ericsson Radio Systems AB 13

4/038 02-LZU 102 152, Rev A, November 1999

( ) ( )[ ]trtpO rr −⋅−− ⋅⋅⋅= 15280.26032.14954.1' e128.254γ ......................................(20)

Finally, the specific attenuation due to oxygen for frequencies equal orlower than 54 GHz is given by

( )( )

32222

32

1054

54'3429.0

36.0

34.7 −⋅⋅

+−⋅⋅

+⋅⋅+

⋅⋅= f

bf

b

rrf

rra

O

tp

tpO

γγ ................(21)

where f is the frequency and the other parameters are defined earlier.

Water vapor

In the calculation of the specific attenuation due to water vapor, onemore atmospheric parameter is required: water-vapor content (g/m3).This parameter can be selected from the charts included in [4].However, in combination with a given temperature, the water-vaporcontent selected from the charts might not be physically consistent withthe appropriate value correspondent to the vapor saturation pressure. Inother words, the water-vapor pressure can not exceed the vaporsaturation pressure at the temperature considered. To avoid thiscommon mistake, one more atmospheric parameter has been introducedin the step-by-step calculation: relative humidity (%).

The vapor saturation pressure, ps, is solely dependent on thetemperature and is given by

+⋅

⋅= 97.240

502.17

e1121.6 t

t

sp ........................................................................(22)

The relative humidity of the atmosphere, RH, is given as the ratiobetween the water vapor pressure in the atmosphere, pH2O, and thevapor saturation pressure, ps.

1002 ⋅=s

OH

p

pRH .............................................................................. (23)

Solving the above expression for the vapor pressure it is obtained

sOH pRH

p ⋅=1002 ................................................................................. (24)

The water vapor content (water-vapor density) can be derived from thegeneral gas equation. It is given by

15.2737.216

2

+=

t

p OHρ ........................................................................(25)

Page 65: TND Complete

RADIO TRANSMISSION NETWORK AND FREQUENCY PLANNING

14 Ericsson Radio Systems AB

4/038 02-LZU 102 152, Rev A, November 1999

The following parameters are determined

ρξ ⋅+⋅⋅= 0061.09544.0 69.01 tpw rr .................................................... (26)

ρξ ⋅+⋅⋅= 0067.095.0 64.02 tpw rr ....................................................... (27)

ρξ ⋅+⋅⋅= 0059.09561.0 67.03 tpw rr ................................................... (28)

ρξ ⋅+⋅⋅= 0061.09543.0 68.04 tpw rr ....................................................(29)

ρξ ⋅+⋅⋅= 006.0955.0 68.05 tpw rr ....................................................... (30)

( )( )2

2

22235.22

235.221

+−

+=f

fg ..................................................................... (31)

( )( )2

2

557557

5571

+−

+=f

fg ......................................................................... (32)

( )( )2

2

752752

7521

+−

+=f

fg ......................................................................... (33)

Finally, the specific attenuation of water vapor for frequencies equal orlower than 50 GHz is given by

( )( )

( )( )( )

( )

( )( )

( )( )( )

( )

( )( )

( )( )( )

( )

( )( )

( )( )( )

( )

42

2

141.07525

2

117.05575

2

146.15

2

109.15

24

2

16.14

23

2

14385.63

22

2

17.02

21

2

123.2221

5.25.8322 10

752

e6.302

557

e7.883

448

e87.17

380

e36.26

22.9153.325

e76.3

29.6226.321

e078.0

48.931.183

e48.10

42.9235.22

e84.3

1076.11013.3 −

−−

−−

−−

−− ⋅⋅⋅

⋅⋅⋅+

+−

⋅⋅⋅+

⋅⋅+

+−

⋅⋅+

⋅+−

⋅⋅+

+⋅+−

⋅⋅+

⋅+−

⋅⋅+

+⋅+−

⋅⋅⋅

⋅+⋅⋅⋅+⋅⋅⋅= ρ

ξ

ξξ

ξ

ξ

ξ

ξ

ξ

ξ

ξ

ξ

ξ

ργ f

f

g

f

g

f

ff

ff

f

g

rrrr

t

tt

tt

tt

t

rw

rw

rw

rw

w

rw

w

rw

w

rw

w

rw

tttpw

(34)

Total gas attenuation

Adding the oxygen (dry air) and water vapor contributions, the total gasattenuation is obtained as follows

Page 66: TND Complete

RADIO WAVE PROPAGATION

Ericsson Radio Systems AB 15

4/038 02-LZU 102 152, Rev A, November 1999

( ) dA wOG ⋅+= γγ ............................................................................. (35)

where

AG = Total gas attenuation, dB

γ w = Specific absorption due to the effects of water vapor,dB/km

γ o = Specific absorption due to the effects of oxygen (dry air), dB/km

d = Path length, km

Total specific gas attenuation - diagram

Figure 4 shows the total specific atmospheric attenuation as a functionof frequency up to 50 GHz for three different values of temperature andrelative humidity.

Figure 4: The total specific atmospheric attenuation as a function offrequency for different values of temperature and humidity.

Attenuation: reflection

Reflection loss is normally not considered in RL-applications since itsuncertain contribution in the link-budget may lead to heavy over orunder dimensioning. Rough estimations of reflection loss as a functionof the total reflection coefficient is described below.

Page 67: TND Complete

RADIO TRANSMISSION NETWORK AND FREQUENCY PLANNING

16 Ericsson Radio Systems AB

4/038 02-LZU 102 152, Rev A, November 1999

Ground reflection interference The respective field strength components of the direct and reflectedwaves interfere with one another at the receiver. Receiver interferencedue to ground reflection is the result of the reception of the resultantfield strength, i.e., the vector addition of the field components.

Signal strength is dependent on the total reflection coefficient (resultingfrom dielectric constant, conductivity and polarization) and the totalphase shift (resulting from antenna height, path length, earth-radiusfactor, frequency and the phase angle of the reflection coefficient).

Figure 5 illustrates two extreme cases:

1) how the highest value of signal strength, AMAX, varies with the totalreflection coefficient. This case illustrates amplification, i.e., the fieldstrength components have the exact same direction, a phase angle of 0°.

2) how the lowest value of signal strength, AMIN, varies with the totalreflection coefficient. This case illustrates a loss, i.e., the field strengthcomponents are directed opposite to one another, a phase angle of 180°.

Figure 5: The signal strength as a function of the total reflectioncoefficient. The highest value of signal strength is obtained for a phaseangle of 0° and the lowest value for a phase angle of 180°.

The problems of handling reflection The handling of reflection is a very difficult and intricate problemincluding the utilization of numerous parameters. For example:

Page 68: TND Complete

RADIO WAVE PROPAGATION

Ericsson Radio Systems AB 17

4/038 02-LZU 102 152, Rev A, November 1999

• high frequencies mean short wavelengths (at 23 GHz, thewavelength ≈ 1.3 cm)

• terrain data accuracy can affect the total reflection coefficient whichin effect, consists of three factors, of which one is directly coupledto the degree of irregularity of the terrain

• antenna height cannot be determined with sufficient accuracy sincethe height database has its limitations

• the earth-radius factor

Reflection coefficient The total reflection coefficient for a smooth spherical surface consistsof three elements: Fresnel reflection coefficient, divergence factor andcorrection factor.

The Fresnel reflection coefficient

The Fresnel reflection coefficient for a smooth flat surface isdependent on frequency, grazing angle, polarization and groundcharacteristics (from the dielectric and conductivity constant). Figure 6shows the Fresnel reflection coefficient’s absolute value for sea wateras a function of grazing angle, two different frequencies and bothhorizontal and vertical polarization.

Page 69: TND Complete

RADIO TRANSMISSION NETWORK AND FREQUENCY PLANNING

18 Ericsson Radio Systems AB

4/038 02-LZU 102 152, Rev A, November 1999

Figure 6: The Fresnel reflection coefficient as a function of the grazingangle for seawater.

Divergence factor

The divergence factor is applied to the Fresnel reflection coefficientwhen approximating the earth’s surface as being spherical. Its value isa function of antenna height, earth radius factor and the path length.

The divergence factor increases as both the difference in antennaheights, transmitter-receiver, and the value of the earth radius factorincrease - it decreases with hop length (longer distances along theearth’s surface must be considered as being an arc).

Correction factor

The correction factor accounts for the surface irregularities (roughness)in different types of ground formations. Table 3 illustrates theapproximate values of the correction factor for different groundsurfaces at two different frequencies, 1 and 10 GHz.

Ground-surface types ρs 1 GHz

ρs 10 GHz

Sea, lake, mirror-face ice field 0.95-1 0.90-1 Snow & ice field, frozen soil, naked dampground

0.85-0.95 0.80-0.90

Damp field, flat and large scale agriculturaland cattle breeding land

0.75-0.85 0.65-0.80

Flat grass land, flat field with thin bush,desert

0.55-0.75 0.45-0.65

Gently rolling terrain, savanna, partitionedplowed fields and pasture

0.35-0.55 0.25-0.45

Rolling terrain, forest, thick forest againstsandy wind, wind break, medium or smallcity area, area where a bank or a high waytransverses the radio path near the reflectionpoint

0.18-0.35 0.09-0.25

Terrain with outstanding undulation,undulated forest, medium or small city withhigh rise buildings, area with large factories,stadiums located to transverses the radiopath near the reflection point

0.08-0.18 0.04-0.09

Mountainous area, area with a deep ridge toshield the reflected area

0.04-0.18 <0.04

Page 70: TND Complete

RADIO WAVE PROPAGATION

Ericsson Radio Systems AB 19

4/038 02-LZU 102 152, Rev A, November 1999

Table 3: Approximate values of the correction factor for differentground-surface types.

Example: rough estimation of the total reflection coefficient The Fresnel reflection coefficient is very close to 1 for small grazingangles, regardless of frequency and polarization. Ordinarily, grazingangles, in connection with radio links, lie between 1 and 10 mrad whichis equivalent to 1/1000 and 1/100, respectively, of the relationshipbetween the antenna height and the hop length (both are to be specifiedin the same units). The Fresnel reflection coefficient for a surfacehaving good reflective characteristics may lie in the vicinity of 0.90.

The value of the divergence factor may also lie around 0.90. Forexample the divergence factor is 0.91, for a 30 kilometer hop and aheight difference of 30 m between the antennas and k=1.33. If theheight difference is increased to 330 m, the divergence factor increasesto 0.97 for the same k value. If the hop length is decreased to 15 km, thedivergence factor increases to 0.99 for a height difference of 30 m and ak value of 1.33.

The value of the correction factor varies with frequency and groundsurface type in accordance with the Table 3. For very smooth surfaces,e.g., the surface of a body of water, the correction factor isapproximately 0.90.

The total reflection coefficient for a spherical and very smooth surfacecan be approximated to 0.90 x 0.90 x 0.90 ≅ 0.73. From the diagram inFigure 5, the reflection loss is approximately 12 dB.

Estimations can be easily performed if one assumes that the values ofboth the Fresnel reflection coefficient and divergence factor lie close to0.90 and then apply the correction factor value given in the Table 3 forthe different ground surface types.

Calculation of the position of the reflection point The calculation of the position of the reflection point is primarily ageometric problem and the result is therefore presented in connectionwith the presentation of the path profile. The ground-reflected beampath and the reflection point’s position are clarified.

There are two different methods available for the calculation of thereflection point’s position. The simplest algorithm avoids the numericalsolution of third-degree equation and is therefore employed in here. Thefollowing intermediate parameters are calculated initially:

Page 71: TND Complete

RADIO TRANSMISSION NETWORK AND FREQUENCY PLANNING

20 Ericsson Radio Systems AB

4/038 02-LZU 102 152, Rev A, November 1999

Intermediate parameter c

BA

BA

hh

hhc

''

''

+−

= .......................................................................................(36)

where

c = Intermediate parameter m

h′A = Antenna height at station A, m

h′B = Antenna height at station B, m

Intermediate parameter m

( ) 3

2

10''4 −⋅+⋅⋅=

BAe hhR

dm .................................................................(37)

where

m = Intermediate parameter

d = Distance between stations A and B, km

Re = Equivalent earth radius, km

h′A = Antenna height at station A, m

h′B = Antenna height at station B, m

Intermediate parameter b

( )

+⋅

⋅⋅

⋅+⋅⋅+

⋅=31

32

3acos

31

3cos

31

2m

mcm

mb

π...........................(38)

The position of the reflection point is calculated from

( )bd

d A +⋅= 12

....................................................................................(39)

and

AB ddd −= ........................................................................................(40)

where

dA = The distance between station A and the reflection point, km

dB = The distance between station B and the reflection point, km

d = The distance between stations A and B, km

b = The intermediate parameter as above

Page 72: TND Complete

RADIO WAVE PROPAGATION

Ericsson Radio Systems AB 21

4/038 02-LZU 102 152, Rev A, November 1999

Attenuation: precipitation

Types of precipitation

Precipitation can take the form of:

• rain

• snow

• hail

• fog and haze

In common for all of the above forms of precipitation is the fact thatthey all consist of water particles (haze can also consist of small solidparticles). Their distinctions lie in the distribution of the size and formof their water drops.

Sharp demarcations between these forms of precipitation is however notalways apparent. ”Intermediate” states can very well occur.

Snow Attenuation is only caused by wet snow.

The attenuation caused by dry snow can be considered as negligible forfrequencies below 50 GHz.

Snow cover on antennas and radomes, so-called ice coatings, can resultin two problems:

• increased attenuation

• the deformation of the antenna’s field radiation diagram

Both cases result in the reduction of the input signal strength at thereceiving station.

Antenna ice coating can of course be alleviated by electrically heatingthe antennas, however the disadvantages are unfortunately greater thanthe advantages. Some of the disadvantages are:

• the antennas must be held warm constantly, there is otherwise therisk that melted snow forms to ice

Page 73: TND Complete

RADIO TRANSMISSION NETWORK AND FREQUENCY PLANNING

22 Ericsson Radio Systems AB

4/038 02-LZU 102 152, Rev A, November 1999

• electrical heating may be interrupted in the event of an electricalpower loss

• there is no knowledge as to the impact, or its degree, on anantenna’s field radiation diagram due to electrical heating

Hail The effects of hail on radio connections are first apparent when hailparticle sizes approach the size of radio waves, for example, 150 mm (2GHz), 9.6 mm (31 GHz) and 6 mm (50 GHz). Hail particle sizes greaterthan 10 mm are however quite rare.

Measurements made in Sweden show that the deepest fading lasted forjust under 5 minutes and was less than 10 dB.

Hail storms can not therefore be considered as availability limitingfactor, since they occur quite infrequently together with other forms ofprecipitation.

Fog and haze Measurements performed in Sweden show that the deepest fading thatcan be related to heavy fog and haze amounted to between 4 and 7 dB.

Fog and haze can not therefore be considered as availability limitingfactor, since both fog and haze occur quite infrequently together withother forms of precipitation.

Rain Attenuation due to rain is the generally responsible for two principalattenuation mechanisms: absorption and scattering caused by theraindrops.

The extent of the attenuation due to rain is primarily a function of

• the form of the rain drops

• the size distribution of the rain drops

The most common form of falling raindrops under the influence of airresistance is the oblate form (not exactly ellipsoidal). This causeshorizontally polarized waves to attenuate more than vertically polarizedwaves.

Page 74: TND Complete

RADIO WAVE PROPAGATION

Ericsson Radio Systems AB 23

4/038 02-LZU 102 152, Rev A, November 1999

Cumulative distribution of rain Due to the rapid time-variation of rain, the measured cumulativedistribution of rain intensity is heavily dependent of the integration timeselected for the measuring process. The rain intensity statisticaldistributions used in ITU-R reports are assumed to be the results ofmeasurements or transformations corresponding to an integration timeof 1 minute. The instantaneous rain intensity (which is extremelydifficult to measure) is however more suitable from a network-planningstandpoint.

For the purpose of availability calculations, one is however interested inthe cumulative distribution of rain intensity, i.e., that percentage of timeduring which a given level of rain intensity is attained or exceeded.

Normally, the reference level applied to rain intensity is the rainintensity that is exceeded during 0.01% of the time, which is oftendesignated as R0.01.

ITU-R subdivides the earth into 15 different rain zones. Rain intensity(mm/h) that is exceeded for different fractions of time (%) are shown inTable 4 for the different rain zones. The rain zones are defined in theRadiowave propagation appendix. Sweden is covered by three rainzones, C, E and G and Brazil by three rain zones, K, N and P.

RAIN ZONES Percentageof time (%)

A B C D E F G H J K L M N P Q

1.0 <0.1 0.5 0.7 2.1 0.6 1.7 3 2 8 1.5 2 4 5 12 24 0.3 0.8 2.0 2.8 4.5 2.4 4.5 7 4 13 4.2 7 11 15 34 49 0.1 2 3 5 8 6 8 12 10 20 12 15 22 35 65 72 0.03 5 6 9 13 12 15 20 18 28 23 33 40 65 105 96 0.01 8 12 15 19 22 28 30 32 35 42 60 63 95 145 115 0.003 14 21 26 29 41 54 45 55 45 70 105 95 140 200 142 0.001 22 32 42 42 70 78 65 83 55 100 150 120 180 250 170

Table 4: Rain zones. The values in the table represent a percentage oftime for which a given rain intensity is attained or exceeded.

Rain zones - diagram The cumulative distributions that are shown in the previous table areillustrated in diagram form, see Figure 7. The curves represent ITU-R’s15 different rain zones covering the entire earth. The distribution of rainintensity (mm/h) represents a percentage of time that is equivalent tothe attainment or exceeding of a given rain intensity. The Y-axis to theright shows the time percentage expressed in minutes per year.

Page 75: TND Complete

RADIO TRANSMISSION NETWORK AND FREQUENCY PLANNING

24 Ericsson Radio Systems AB

4/038 02-LZU 102 152, Rev A, November 1999

0 50 100 150 200 250

Rain intensity, mm/h

0.001

0.010

0.100

1.000

2

3

4

5

6

7

8

9

2

3

4

5

6

7

8

9

2

3

4

5

6

7

8

9

Pe

rce

nta

ge

of t

ime

ra

in in

ten

sity

is e

xce

ed

ed

, %

5.26

52.56

525.60

5256.00

Min

utes

/yr

P

N Q

LMKHFG

E

J

A B

CD

Per

cent

age

of ti

me

rain

inte

nsity

is e

xcee

ded,

%

Figure 7: The rain zones represented as cumulative distributions.

The new ITU model for calculation of rain intensityThe new ITU-R rainfall rate procedure, also known as Baptista-Salonen model, is conditioned to the following aspects:

1. High quality, long integration-time (few hours) and high spatialresolution (about one grid point per 100 km)

2. Models for transforming long integration-time rain data to shortintegration-time rain data

The new procedure does not demand any rain zone chart and the rainfallrates (rain intensity) are directly calculated as a function of thegeographical location of the site.

The basic of the new ITU-rainfall model is the rainfall rate data that isnow available from two different rain-data programs: 1) GlobalPrecipitation Climate Project (GPCP-data) and 2) European Center forMedium-Range Weather Forecast (ECMWF-data).

Page 76: TND Complete

RADIO WAVE PROPAGATION

Ericsson Radio Systems AB 25

4/038 02-LZU 102 152, Rev A, November 1999

The new model is derived in two steps. First, suitable functionsdescribing properly the rainfall rate distributions in tropical and mid-latitude climates are derived. This function is expressed as follows:

( )( )Rc

RbRa

ePp ⋅+⋅+

⋅⋅−

⋅= 1

1

0 ...............................................................................(41)

where p is the annual probability that the rainfall rate R (mm/h) isexceeded, P0 is the rain probability obtained from statistical data and a,b and c are parameters.

The next step is to optimize the above parameters by employingempirical functions. The difference between predicted and measuredrainfall rates is minimized. The rainfall rate data used in theoptimization is from ITU-R databases covering a large amount of sitesat different climates.

The probability of rain P0 is approximated by the following expression:

−⋅=

⋅6

0.0117-

60 e1 r

S

P

M

rPP .....................................................................(42)

where Ms (mm) is the annual rainfall amount of stratiform-type rainsand Pr6 (%) is the probability of rainy 6 hours periods.

The annual probability that the rainfall rate R (mm/h) is obtained fromthe previous expression

ACABB

R⋅

⋅⋅−+−=

242

.................................................................. (43)

where

baA ⋅= ............................................................................................. (44)

⋅+=

0

lnPp

caB .............................................................................. (45)

=

0

lnPp

C ........................................................................................ (46)

For p>P0, R(p)=0

The parameters a, b and c are empirically optimized and finally givenby the expressions:

1.1=a ............................................................................................... (47)

Page 77: TND Complete

RADIO TRANSMISSION NETWORK AND FREQUENCY PLANNING

26 Ericsson Radio Systems AB

4/038 02-LZU 102 152, Rev A, November 1999

( )022932 P

MMb sc

⋅+

= .................................................................................. (48)

where Mc (mm) is the annual rainfall amount of convective-type rains.

bc ⋅= 5.31 ......................................................................................... (49)

The users of the new ITU rainfall rate model are, however, not forced tocalculate the parameters Ms, Mc and Prg6 since they are calculated andstored in the following data files, see ??:

ESARAINPR6.TEXT è contains the numerical values of theparameter Pr6.

ESARAIN_MC.TXT è contains the numerical values of the parameterMc.

ESARAIN_MS.TXT è contains the numerical values of the parameterMs.

The values of the parameters Ms, Mc and Pr6 are stored as 121-rows and241-columns matrix (121x241) corresponding to each point in a gridsystem.

The values of the longitude and latitude for all grid points are alsostored as 121-rows and 241-columns matrix (121x241) and can beobtained from the following data files, see ??:

ESARAINLON.TXT è contains the longitude values for each gridpoint.

ESARAINLAT.TXT è contains the latitude values for each grid point.

For each specific grid point (LONi, LATj) there will be Msij, Mcij and Pr6ij

corresponding values.

Parameter values for other geographical locations than the grid pointsgiven in the above matrices are obtained by two-dimensionalinterpolation technique.

The calculation of the specific rain attenuation The calculation of specific rain attenuation is performed in two steps:

Page 78: TND Complete

RADIO WAVE PROPAGATION

Ericsson Radio Systems AB 27

4/038 02-LZU 102 152, Rev A, November 1999

• first, a calculation is performed of the values of the coefficientscorresponding to certain assumptions concerning the distribution ofrain-drop size, form, temperature and type of polarization(horizontal/vertical)

• then, a calculation is performed of the specific rain attenuation for agiven instantaneous rain intensity

Calculate the coefficients as follows

( ) ( )2

2coscos2 τθ ⋅⋅⋅−++= VHVH

f

kkkkk .......................................(50)

( ) ( )f

VVHHVVHHf k

kkkk

⋅⋅⋅⋅⋅−⋅+⋅+⋅

=2

2coscos2 τθααααα ..........(51)

where

kH,aH,kV,aV = Frequency dependent coefficients that are providedin Table 5

θ = The path’s elevation angle

τ = The polarization tilt angle relative to the horizontalplane

Table containing the frequency dependent coefficients The values of the frequency dependent coefficientsprovided in Table 5 are for frequencies between 1and 50 GHz (the symbol * implies values that havebeen interpolated).

Frequency GHz k H kV αH αV

1 0.0000387 0.0000352 0.912 0.880 2 0.000154 0.000138 0.963 0.923

3* 0.000358 0.000323 1.055 1.012 4 0.000650 0.000591 1.121 1.075

5* 0.001120 0.001000 1.224 1.180 6 0.00175 0.00155 1.308 1.265 7 0.00301 0.00265 1.332 1.312 8 0.00454 0.00395 1.327 1.310

9* 0.00692 0.00605 1.300 1.286 10 0.0101 0.00887 1.276 1.264

11* 0.0140 0.01240 1.245 1.231 12 0.0188 0.0168 1.217 1.200

Page 79: TND Complete

RADIO TRANSMISSION NETWORK AND FREQUENCY PLANNING

28 Ericsson Radio Systems AB

4/038 02-LZU 102 152, Rev A, November 1999

13* 0.0239 0.0215 1.194 1.174 14* 0.0298 0.0271 1.173 1.150 15 0.0367 0.0335 1.154 1.128

16* 0.0431 0.0394 1.142 1.114 17* 0.0501 0.0459 1.130 1.101 18* 0.0578 0.0530 1.119 1.088 19* 0.0661 0.0607 1.109 1.076 20 0.0751 0.0691 1.099 1.065

21* 0.0838 0.0769 1.091 1.057 22* 0.0930 0.0853 1.083 1.050

Page 80: TND Complete

RADIO WAVE PROPAGATION

Ericsson Radio Systems AB 29

4/038 02-LZU 102 152, Rev A, November 1999

Frequency GHz k H kV αH αV

23* 0.1030 0.0940 1.075 1.043 24* 0.1130 0.1030 1.068 1.036 25 0.124 0.113 1.061 1.030

26* 0.135 0.123 1.052 1.024 27* 0.147 0.133 1.044 1.017 28* 0.160 0.144 1.036 1.011 29* 0.173 0.155 1.028 1.006 30 0.187 0.167 1.021 1.000

31* 0.201 0.179 1.012 0.992 32* 0.216 0.192 1.003 0.985 33* 0.231 0.205 0.995 0.977 34* 0.247 0.219 0.987 0.970 35 0.263 0.233 0.979 0.963

36* 0.279 0.247 0.971 0.956 37* 0.296 0.262 0.962 0.949 38* 0.314 0.278 0.954 0.942 39* 0.332 0.294 0.947 0.935 40 0.350 0.310 0.939 0.929

41* 0.368 0.326 0.931 0.922 42* 0.386 0.342 0.924 0.916 43* 0.404 0.359 0.917 0.909 44* 0.423 0.376 0.910 0.903 45 0.442 0.393 0.903 0.897

46* 0.456 0.410 0.897 0.891 47* 0.479 0.426 0.891 0.885 48* 0.497 0.444 0.885 0.879 49* 0.517 0.461 0.879 0.874 50 0.536 0.479 0.873 0.868

Table 5: Frequency dependent coefficients for the calculation ofspecific rain attenuation.

The calculation of specific rain attenuation (dB/km) is performed asfollows

fRk fRαγ ⋅= ......................................................................................(52)

where

kf,af = Frequency dependent coefficients

R = Rain intensity, mm/h

The specific rain attenuation that is exceeded during 0.01% of the time,can be calculated by relating the rain intensity to the reference level0.01%, i.e.,

Page 81: TND Complete

RADIO TRANSMISSION NETWORK AND FREQUENCY PLANNING

30 Ericsson Radio Systems AB

4/038 02-LZU 102 152, Rev A, November 1999

fRk fRαγ 01.001.0

⋅= ...................................................................................(53)

Figure 8 illustrates specific rain attenuation (dB/km) that are exceededduring 0.01% of the time as a function of frequency (GHz) for threedifferent values of rain intensity, R0.01, for both horizontal and verticalpolarization.

Figure 8: Specific rain attenuation exceeded during 0.01% of the timeas a function of frequency.

Figure 9 illustrates the specific rain attenuation (dB/km) that areexceeded during 0.01% of the time as a function of rain intensity forfour different values of frequency (GHz), for both horizontal andvertical polarization.

Page 82: TND Complete

RADIO WAVE PROPAGATION

Ericsson Radio Systems AB 31

4/038 02-LZU 102 152, Rev A, November 1999

Figure 9: Specific rain attenuation exceeded during 0.01% of the timeas a function of rain intensity.

Figure 10 illustrates the specific rain attenuation (dB/km) that isexceeded during 0.01% of the time as a function of rain intensity forhorizontal (H) and vertical (V) polarization at 23 GHz.

At 23 GHz and horizontal polarization, the specific rain attenuation atR0.01=30 mm/h is almost twice the value at R0.01=12 mm/h.

Figure 10: Specific rain attenuation exceeded during 0.01% of the timeas a function of rain intensity for a frequency of 23 GHz.

Page 83: TND Complete

RADIO TRANSMISSION NETWORK AND FREQUENCY PLANNING

32 Ericsson Radio Systems AB

4/038 02-LZU 102 152, Rev A, November 1999

Calculating total rain attenuation The total rain attenuation for a radio link path can be calculated asfollows, if the statistical distribution of the rain cells along the path isknown

effRR dA ⋅= γ ......................................................................................(54)

where

AR = Total rain attenuation, dB

γ R = Specific rain attenuation, dB/km

deff = Effective path length, km

The effective path length is calculated as follows

rdd eff ⋅= ...........................................................................................(55)

where

d = Actual path length, km

r = Reduction factor

The reduction factor is arrived at as follows

0

1

1

dd

r+

= ...........................................................................................(56)

The factor 1/d0 is coupled to rain intensity for the 0.01% referencelevel. d0 is then

01.0015.00 e35 Rd ⋅−⋅= ...............................................................................(57)

The reduction factor accounts for the extensions of rain cells andtransforms actual path lengths to equivalent path lengths along whichthe rain can be regarded as having a uniform distribution.

Calculating total rain attenuation for 0.01% The total rain attenuation that is exceeded 0.01% of the time can becalculated if the rain intensity is related to the 0.01% reference level, asfollows

effRR dA ⋅=01.001.0

γ ................................................................................(58)

where

Page 84: TND Complete

RADIO WAVE PROPAGATION

Ericsson Radio Systems AB 33

4/038 02-LZU 102 152, Rev A, November 1999

AR0 01.= Total rain attenuation that is exceeded during 0.01% of thetime, dB

γ R0 01.= Specific rain attenuation that is exceeded during 0.01% ofthe time, dB/km

deff = Effective path length, km

The total rain attenuation that is exceeded during 0.01% of the time isused later in the calculation of unavailability caused by rain.

Attenuation: obstruction

Obstruction losses are calculated based on the path’s geometry and onthe actual frequency used.

The geometry is a function of:

• topography

• The antenna’s height above ground level

• The earth-radius factor, k

Different k-values result in different obstruction loss values. Small k-values result in the greatest obstruction loss due to the fact that thebeam tends to bend more towards the ground surface, or expresses inanother manner, the obstruction penetrates deeper into the Fresnel zone.

Knife-edge obstructions A knife-edge obstruction is one that consists of an individualobstruction having negligible length in the direction of the radio wave’spropagation path, see Figure 11. The loss contributed by such anobstruction is derived from the knife-edge loss curve, which is aphysically derived function.

Page 85: TND Complete

RADIO TRANSMISSION NETWORK AND FREQUENCY PLANNING

34 Ericsson Radio Systems AB

4/038 02-LZU 102 152, Rev A, November 1999

A B

Equivalent earth surface

r1F

hLOS

v < 0

v > 0

Figure 11: Knife-edge obstruction showing the obstruction’s heightrelative the free line-of-sight.

In the case of knife-edge obstructions, the obstruction loss value, AH isonly dependent on the parameter ν, which is defined as theobstruction’s relative penetration of the Fresnel zone:

F

LOS

r

h

1

=ν .............................................................................................(59)

where

hLOS = The obstruction’s height above the free line-of-sight

r1F = The Fresnel zone’s radius at the point of the obstruction

The parameter ν, as defined above, differs by a factor of 2 ≅ 1.41from the definition in Rep. 715-3, vol. 5, which means a difference ofapproximately 1-3 dB in obstruction loss for the particular value of ν.

The height of the obstruction over the free line-of-sight may be definedas

hLOS = (ground elevation + height of the tree line or building height) - the height of the free line-of-sight

Knife-edge loss curve The loss caused by an obstruction is arrived at from the knife-edge losscurve, which is a physically derived function. Knife-edge loss AH as afunction of the relative penetration ν, is shown in Figure 12.

Page 86: TND Complete

RADIO WAVE PROPAGATION

Ericsson Radio Systems AB 35

4/038 02-LZU 102 152, Rev A, November 1999

Figure 12: Knife-edge loss as a function of the relative penetrationparameter.

When performing path calculations, realistic degrees of Fresnel zonepenetration are often considered as lying in the interval from -0.5 to 2which means calculation of obstruction losses based on the diagraminsertion above.

For ν≥10, obstruction losses are calculated as follows:

( ) 10 log2016 ≥⋅+= ννHA .................................................(60)

where

AH = Obstruction loss, dB

v = The obstruction’s relative penetration of the Fresnel zone

Typical knife-edge losses Figure 13 illustrates a few typical examples of loss values (dB) for theknife-edge function.

Page 87: TND Complete

RADIO TRANSMISSION NETWORK AND FREQUENCY PLANNING

36 Ericsson Radio Systems AB

4/038 02-LZU 102 152, Rev A, November 1999

0 0 6 12 16 20

Figure 13: Typical loss values (dB) resulting from the knife-edgefunction.

Single-peak method The single-peak method calculates the value of the obstruction loss asthe greatest knife-edge obstruction loss attained as a result of anindividual obstruction lying along the path, see Figure 14.

The algorithm defines those peaks in the path profile between station Aand station B that penetrate the Fresnel zone. The penetration, ν, ofevery peak is calculated relative to the Fresnel zone along the free line-of-sight, AB . The corresponding knife-edge loss, AH, is calculated as ifonly one peak existed along the path. The greatest loss value that isfound along the path is returned as the sought obstruction loss value.

A B

Figure 14: In the single-peak method the obstruction loss is taken as thegreatest knife-edge obstruction loss lying along the path.

Page 88: TND Complete

RADIO WAVE PROPAGATION

Ericsson Radio Systems AB 37

4/038 02-LZU 102 152, Rev A, November 1999

The single-peak method is, as is obvious, a pure application of theknife-edge model. It works best for paths that have one dominant peak.The results of the model are less reliable for more realistic paths havinga number of significant peaks.

Triple-peak method Simply stated, the triple-peak method may be described as a calculationof the obstruction loss value along the propagation path, based on thesum of the three largest knife-edge losses.

The algorithm involves an initial calculation of the obstruction lossbased on the single-peak method, as described earlier. This firstcalculation of the single knife-edge loss represents the first contribution,A1, to the total obstruction loss.

The path profile is then split at that the point, M, which resulted in thelargest knife-edge loss, see Figure 15. The peak of point M is regardedas being a common antenna or termination point along the partial pathsAM and MB . If the peak consists of trees, then the mast height of thefictitious antenna is set to the height of the trees, otherwise the mastheight is set to zero. In the event that the fictitious antenna attains aheight beneath the original free line-of-sight, AB , then the mast heightis instead set so that the antenna exactly reaches the free line-of-sight.

A B

M

Figure 15: The path profile after the first split.

Page 89: TND Complete

RADIO TRANSMISSION NETWORK AND FREQUENCY PLANNING

38 Ericsson Radio Systems AB

4/038 02-LZU 102 152, Rev A, November 1999

The partial paths, AM and MB to the left and right of the located peak,M, are each searched for two new paths in the same manner as was theoriginal path. Note that the partial paths, as illustrated in the figureabove, generally have other free lines-of-sight and Fresnel zones thandoes the original path. Each partial path results in a separate knife-edgeloss value. The higher of the two values will represent the secondcontribution, A2, to the total obstruction loss.

The particular partial path is then subdivided at the peak, N, thatresulted in the highest knife-edge loss, see Figure 16. The resultantpartial paths are then each searched in the same manner as was theoriginal partial paths. The third and final contribution, A3, to the totalobstruction loss is the largest knife-edge loss resulting from one of thepartial paths AN, NM, and MB.

The total obstruction loss, AH, is obtained by summing the threecontributions described above, A1, A2 and A3.

321 AAAAObst ++= ............................................................................(61)

A B

N M

Figure 16: The path profile after the second split.

The triple-peak method is entirely empirical, but it has proven to workwell in actual applications. It works better than the single-peak methodfor practically all most occurring path profiles, since it accounts formore than only the highest peak along the path.

The difference between the triple-peak method and a hypotheticalrepetition (three times) of the single-peak method, lies in the fact thatsecondary peaks in the triple-peak method will contribute less than theprimary peak considering the peaks’ penetration of the original Fresnelzone. This is a function of two factors:

Page 90: TND Complete

RADIO WAVE PROPAGATION

Ericsson Radio Systems AB 39

4/038 02-LZU 102 152, Rev A, November 1999

• the partial paths are always shorter than the full path

• the partial paths’ free lines-of sight always lies higher than (or at thesame level as) the original full path

A shorter path results in a smaller Fresnel zone radius. Higher free line-of-sight results in a relatively lower peak free line-of-sight. Together,these factors result in a smaller relative penetration. The result is thatthe secondary peaks cause lower obstruction losses.

The triple-peak method, as it is applied here, is a further development ofthe original multiple-peak method introduced by Deygout, ”MultipleKnife-Edge Diffraction of Microwaves”, IEEE Trans. Ant. Prop. vol.AP-14, 1966.

Smoothly spherical earth In the case of smoothly spherical earth (flat-earth), the obstruction isrepresented by an smooth surface, such as a sea or lake, penetrating theFresnel zone. Losses are calculated using a simple function that may bederived from empirical considerations. The geometry of the smoothlyspherical earth is illustrated in Figure 17.

dr

d

dBdA

hB

hA B

A

Figure 17: The geometry of the smoothly spherical earth.

The loss calculation is performed in accordance with the Cheriexmethod. First the distances to the radio horizon from both antennas arecalculated as follows

AA hRkd ⋅⋅⋅⋅≅ −3102 .....................................................................(62)

BB hRkd ⋅⋅⋅⋅≅ −3102 .....................................................................(63)

where

dA = The distance from station A to the radio horizon, km

dB = The distance from station B to the radio horizon, km

Page 91: TND Complete

RADIO TRANSMISSION NETWORK AND FREQUENCY PLANNING

40 Ericsson Radio Systems AB

4/038 02-LZU 102 152, Rev A, November 1999

hA = The antenna height at station A, m

hB = The antenna height at station B, m

k = The earth-radius factor

R = True earth radius (≅ 6370 km)

The distance between both radio horizons may be easily calculated as

( )BAr dddd +−≅ .............................................................................(64)

where

d = Distance between station A and B, km

The obstruction loss for evenly curved earth is calculated as

rObst dkfA ⋅⋅⋅+≅−

3

2

3112.020 .........................................................(65)

where

AObst = Obstruction loss, dB

f = Frequency, MHz

Typical losses resulting from smoothly spherical earth Figure 18 illustrates typical loss values (dB) for smoothly sphericalearth for a path of 50 kilometers and a frequency of 2.2 GHz.

40

10

20

Figure 18: Typical loss values (dB) resulting from a smoothly sphericalearth.

For grazing lines-of-sight, i.e., the antennas have the same horizon (dA +dB = d), the loss is 20 dB, which applies regardless of frequency andpath length.

Page 92: TND Complete

RADIO WAVE PROPAGATION

Ericsson Radio Systems AB 41

4/038 02-LZU 102 152, Rev A, November 1999

Clearance and path geometry

The Earth bulge

The local height of the Earth bulge (h) is dependent of the k-value. Theparameter h is very important for clearance purposes. The shadowregion in Figure 19 covers its local value.

x

hmax

d2d1y

y=d/2y=-d/2

k·Rk·R k·R-hmax

h

O

AB

M

N

Figure 19: The local height of Earth bulge.

The local height of the Earth bulge is given by

k

ddh

⋅⋅

=74.12

21 ...................................................................................... (66)

where the distances d1 and d2 are normally expressed in km and h inmeters.

The local height of the Earth bulge is inversely proportional to theearth-radius factor. For high k-values, the Earth surface is close to aplane surface while for low k-values the Earth surface becomes morecurved and may penetrate the radio path.

Path geometry

Page 93: TND Complete

RADIO TRANSMISSION NETWORK AND FREQUENCY PLANNING

42 Ericsson Radio Systems AB

4/038 02-LZU 102 152, Rev A, November 1999

In what follows, clearance, obstacle penetration and antenna height willbe discussed. Figure 20 displays the path geometry for which the pathparameter clearance c is depicted. The height of the line-of-sight is x,the bulge of the Earth is h and the height of the obstacle above the earthsurface is h3. The other parameters have their habitual designation.Referring to the Earth surface, the height of the line-of-sight is x = c +h3. The antenna heights are represented as “total” heights, that is, boththe terrain and the actual antenna heights are included.

h1

d2

x

d1

h2

h

x-h1

θ

θ

d

h3

h

c

Figure 20: Path geometry.

The height of the line-of-sight

The height of the line-of-sight with respect to the Earth surface

1112 hd

d

hhx +⋅

−= .................................................................................... (67)

where h1and h2 are given in m and d and d1 in km.

Path losses

Definition The path loss is the sum of all losses and gains between thetransmitter’s and the receiver’s antenna contacts and is calculated asfollows:

Page 94: TND Complete

RADIO WAVE PROPAGATION

Ericsson Radio Systems AB 43

4/038 02-LZU 102 152, Rev A, November 1999

ARxATxFLObstGbfS GGAAAAAA −−++++= ∑ .............................(68)

where

AS = Path loss, dB

Abf = Free-space loss, dB

AG = Gas attenuation, dB

AObst = Obstruction loss, dB

AL = Additional loss, dB

AF = Antenna feeder loss, dB

GATx = Transmitter antenna gain, dBi

GARx = Receiver antenna gain, dBi

Fade margin Under interference-free conditions, the fade margin is defined as thedifference between the received signal level under ”normal” wavepropagation conditions (fade-free time) and the receiver’s thresholdlevel at a given bit-error level, i.e.,

TrR PPM −= ......................................................................................(69)

where

M = Fade margin, dB

PR = Receiver signal level, dBm

PTr = Receiver threshold level, dBm

Receiver signal level is calculated as the difference between thetransmitter’s output power and the path loss, i.e.,

STrR APP −= ......................................................................................(70)

where

PR = Receiver signal level, dB

PTr = Transmitter output power, dBm

AS = Path loss, dB

Power diagram A power diagram is a schematic approach to the illustration of theeffects on a transmitter’s radiated power as it propagates towards areceiving station, see Figure 21. Concepts such as fade margin andreceiver threshold value are also included in the definition.

Page 95: TND Complete

RADIO TRANSMISSION NETWORK AND FREQUENCY PLANNING

44 Ericsson Radio Systems AB

4/038 02-LZU 102 152, Rev A, November 1999

antenna gain

feeder lossreceived power

fade margin

receiver thresholdvalue

wave propagation losses

antennagain

outputpower

feeder loss

POWER

Figure 21: The power diagram.

Effective fade margin The receiver’s threshold value as defined earlier only applies undernegligible or interference-free conditions. In reality, this is however notthe case. A certain interference contribution is almost always presentwhen performing path calculations, which usually affects availabilityresults.

The interference contribution can be interpreted as degradation in thereceiver’s threshold value, i.e., threshold degradation. The effectivefade margin is therefore defined as the difference between the fademargin and the threshold degradation. The effective fade margin is usedlater in availability calculations.

Interference calculations provide the value of the threshold degradation.

Page 96: TND Complete

RADIO WAVE PROPAGATION

Ericsson Radio Systems AB 45

4/038 02-LZU 102 152, Rev A, November 1999

Fading - prediction models

The concept of outageOutage is generally defined as the probability that a pre-defined bit-error ratio is exceeded during a certain measured period of time.

Rain fading

Calculation of the fade margin based on a yearly basis

The fade margin that is exceeded during different periods of time basedon a yearly basis is calculated as follows

( )PRP PAM log043.0546.0

01.012.0 ⋅+−⋅⋅= ......................................................(71)

where

AR0 01.= Total rain attenuation that is exceeded 0.01% of the time,dB

MP = Fade margin that is exceeded p% of the time, dB

P = The percentage of the time during which 0.001 < P < 1%

The total attenuation for 0.01% of time, A0.01, is calculated as a functionof the rain intensity (rainfall rate) for 0.01% of time, R0.01, and theeffective path length by equation (??).

The attenuation exceeded for a certain percentage of time can bereferred to as the fade depth. If we adapt the fade margin, M, to be asmuch as the fade depth, then Ap can be replaced by M in bothexpressions above.

In the previous ITU-model, the above expression was valid for allvalues of latitude and longitude. In the new revision of the ITU-Rrecommendation [2], however, the above expression is modified to fitdifferent values of the latitude. Thus, for radio links located at latitudesequal or greater than 30° (North and South) the above expression is stillapplied. On the other side, for latitudes lower than 30°N and 30°S (60°belt along the equator), the valid expression is

( )pp pA

A log139.0855.0

01.0

07.0 ⋅+−⋅= ..............................................................(72)

with the parameters defined as previously.

Page 97: TND Complete

RADIO TRANSMISSION NETWORK AND FREQUENCY PLANNING

46 Ericsson Radio Systems AB

4/038 02-LZU 102 152, Rev A, November 1999

Compared to the previous model, the new model presented in [2] doesnot provide any remarkable improvement. In addition, it seems to bestatistically inconsistent since it gives higher p values than the modelused for latitudes equal to or greater than 30°N and 30°S.

When discussing both models for calculating the probability(percentage of time) that the fade margin will be exceeded, transmissionnetwork planners are encouraged to stress the inconsistency of the newmodel to be used in the 60° belt along the equator. Particularly, the factthe model does not provide any remarkable improvement.

Outage due to rain fading - annual basis

The prediction model for the rain fading across a particular area is acumulative distribution over fade margin. It calculates the probabilitythat a given fade margin will be exceeded.

The probability that a given fade margin M is exceeded, on an annualbasis, can be attained from the previous mathematical expression bysolving the equation for the fraction of time, P. The empiricalprediction model for rain fading becomes

⋅⋅++−

=M

AR

P

01.012.0log172.029812.0546.0628.11

10 ..............................................(73)

where

P = The time, expressed in percent of a year, during which agiven fade-depth M (fade margin) is exceeded, %

AR0 01.= Total rain attenuation that is exceeded 0.01% of the time,dB

M = Fade margin, dB

Transformation between yearly and worst month basis

From yearly to worst month

The transformation from an annual probability to one based on a worstmonth is achieved as follows

PQp ⋅=w ..........................................................................................(74)

where

Page 98: TND Complete

RADIO WAVE PROPAGATION

Ericsson Radio Systems AB 47

4/038 02-LZU 102 152, Rev A, November 1999

pw = The portion of time, expressed in percent of the worstmonth, during which a given fade-depth M (fade margin) isexceeded, %

P = The portion of time, expressed in percent of a year, duringwhich a given fade-depth M (fade margin) is exceeded, %

Q = Conversion factor (climatic constant), 12> Q >1

The probability pw and P are referred to the same threshold level. Theconversion factor Q is expressed as a function of P and the climaticparameters Q1 and β. In the range of interest for microwave planning, Qis given by following expression

% 3 12

for

1

11 <<

⋅= P

QPQQ -

ββ .............................(75)

Substituting (73) in (72), the transformation from yearly basis to worstmonth basis is given by

β−⋅= 11 PQpw .....................................................................................(76)

The values of the climatic constants, for ”global planning” purposes arespecified by ITU-R as

Q1 = 2.85

β = 0.13

From worst month to yearly

The transformation from a yearly probability to worst-monthprobability is obtained from expression (74)

ββ −−− ⋅= 1

1

1

1

1 wpQP ...............................................................................(77)

Climatic parameters

The values of the climatic parameters Q1 and β and the interval ofvalidity for pw are given in Table 6 for rain and multipath propagationfor different climatic regions.

Page 99: TND Complete

RADIO TRANSMISSION NETWORK AND FREQUENCY PLANNING

48 Ericsson Radio Systems AB

4/038 02-LZU 102 152, Rev A, November 1999

RegionGlobal planning

Europe (Nordic)Europe (North West)Europe (Mediterranean)Europe (Alpine)Europe (Poland)Europe (Russia)Canada (Prairie & North)Canada (Cost & Great Lake)Canada (Central & Mountain)Japan (Tokyo)CongoIndonesia

β Q1

0.13 2.85

pw interval1.9·10 -4 - 7.4

RAIN

β Q1

0.13 2.85

pw interval

1.9·10 -4 - 7.4

MULTIPATH

0.15 3.0 1.2·10 -3 - 7.6 0.12 5.0 8.1·10 -3 - 13.20.13 3.0 2.8·10 -4 - 7.8 0.13 4.0 2.6·10 -3 - 10.40.14 2.6 2.2·10 -4 - 6.7 - - -

0.15 3.0 1.2·10 -3 - 7.6 - - -0.18 2.6 2.5·10 -3 - 6.4 - - -0.14 3.6 2.2·10 -3 - 9.3 - - -

0.08 4.3 3.2·10 -5 -11.8 - - -

0.10 2.7 4.0·10 -6 - 7.3 - - -

0.13 3.0 1.2·10 -3 - 7.6 - - -

0.20 3.0 1.2·10 -2 - 7.2 - - -0.25 1.5 2.9·10 -3 - 3.4 - - -

0.22 1.7 1.7·10 -3 - 4.0 - - -

Table 6: Values of the climatic parameters Q1 and β for rain andmultipath fading for different regions. The range of validity is alsodisplayed.

The selection of the climatic parameters when transforming annualworst-month time percentage to average annual time percentages mayhave a conclusive impact when dimensioning microwave links. In anear future, when more climatic values become available, employingadequate values for the climatic parameters will increase in importance.

The range of validity of the conversion model is strongly dependent onthe climate and should be known by microwave designers.

Presentation of the rain fading models in diagram form

Figure 22 illustrates the rain fading models (worst month and on ayearly basis) for different values of the quotient between total rainattenuation exceeding 0.01% of the time (AR0.01) and the fade margin,M. When the quotient is equal to 0.155, outage is set to 8·10-7.

Page 100: TND Complete

RADIO WAVE PROPAGATION

Ericsson Radio Systems AB 49

4/038 02-LZU 102 152, Rev A, November 1999

0 1 102 3 4 5 6 7 8 9 2 3 4 5 6 7 8

AR0.01/M

10-8

10-7

10-6

10-5

10-4

10-3

10-2

10-1

100

Per

cent

age

of ti

me

the

fade

mar

gin

is e

xcee

ded,

%

Rain fading modelannual basis

Rain fading modelworst month

1

Figure 22: The rain fading models for worst month and on a yearlybasis.

Multipath fading

The occurrence of multipath propagation

Figure 23 illustrates a multipath scenario.

Atmospheric layer

Figure 23: Multipath propagation illustrated by three radio beams:

Page 101: TND Complete

RADIO TRANSMISSION NETWORK AND FREQUENCY PLANNING

50 Ericsson Radio Systems AB

4/038 02-LZU 102 152, Rev A, November 1999

Beams that are reflected by the atmosphere or the ground travel a longerdistance than do direct beams. Dependent on the size of the time delaysand the employed channel bandwidth, fading can either be

• flat, or• frequency selective

In general:

• Fading due to rain, for frequencies below 10 GHz, may beconsidered as negligible in comparison with fading due to multipathpropagation, which is often dominant below 10 GHz.

• Fading due to multipath propagation, for frequencies above 10 GHz,may be considered as negligible in comparison with fading due torain, which is often dominant above 10 GHz.

• A good rule of thumb is however, that there exists a cross-overregion between the frequencies of 10 and 18 GHz, and a point atwhich fading due to rain and multipath propagation are of about thesame order of magnitude.

Flat and frequency selective fading

Flat fading implies that there does not exist any noticeable localvariation within the transmitted frequency band, see Figure 24, i.e.,fading has the same degree throughout the band.

Frequency selective fading implies that there does exist a noticeablevariation within the transmitted frequency band (see the figure below).

fB

A

fB

A Flat fading Frequency selective fading

Figure 24: Flat and frequency selective fading.

Page 102: TND Complete

RADIO WAVE PROPAGATION

Ericsson Radio Systems AB 51

4/038 02-LZU 102 152, Rev A, November 1999

The extent of the influence of multipath propagation on a radio linksystem depends on whether the system is analog or digital and whetherthe fading is flat or frequency selective.

The effects of multipath propagation

The effect of flat fading for digital and analog connections is similar.Signal level decreases and quality degrades. Continued qualitydegradation will eventually lead to the breakdown of the connection.Digital systems usually exhibit a somewhat higher tolerance to flatfading than do analog systems.

In the case of base band, analog link connections utilize frequencymultiplexing in which each channel of N channels contains a small(B/N) frequency band.

For frequency selective fading, signal levels vary locally within thefrequency band, both in amplitude and phase. The result, in the case ofanalog connections, is that a number of channels may attain signallevels that are so low that connection within these channels is virtuallyimpossible. The connection can, however, be maintained at a lowercapacity.

In the case of base band, digital link connections utilize the entirefrequency band, B, of all channels in a time-multiplexed manner. Thismeans that every channel has a time slot and synchronism is thereforerequired for system management purposes.

In-band variations in the case of a time-duplexed digital connectionrepresents a loss of information, the connection loses synchronization,resulting in the fact that the connection can no longer be maintained.The disturbance affects all channels and is abated, only aftersynchronization is once again established.

Measures taken against multipath fading

Measures that are aimed at suppressing fading due to multipathpropagation can be divided into three categories:

• diversity

Diversity implies that a signal reaches the receiver via a number (atleast two) of different alternatives, the purpose being that the receivedsignals are to be uncorrelated. Examples of diversity are frequency,space, path, polarization and angle.

• adaptive equalizer

Page 103: TND Complete

RADIO TRANSMISSION NETWORK AND FREQUENCY PLANNING

52 Ericsson Radio Systems AB

4/038 02-LZU 102 152, Rev A, November 1999

The purpose of adaptive equalizer (in both the time and frequencydomains) is the equalization of signal amplitude and phase.

• system

By modifying system parameters or other system attributes, one canattain an improvement in system tolerance to multipath fading. Forexample, improvements can, in some cases, be achieved through themodification of path geometry or by simply changing the antenna.

Outage due to flat fading

Introduction

Flat fading, also known as single-frequency, frequency independent ornarrow-band fading, can generally be predicted for any part of theworld. The method relies on the prediction of the distribution at largefade depths in the average worst month. Unlike the former predictionmethod, the present method normally employed for large fade depthsdoes not take into account the path profile and, therefore, is suitable forinitial planning, licensing or design purposes.

In addition, there is a method applicable for all fade depths, in whichthe method for large fade depths and an interpolation procedure forsmall fade depths are employed

Fade occurrence factor

Worldwide measurements and statistical compilations of fading eventsindicate that the probability the received level fades F dB below thefree-space level is given by

100 10

F

flat pp−

⋅= ..................................................................................(78)

where the fade depth F is normally interpreted as the fade margin (M)and p0 is the fade occurrence factor.

The fade occurrence factor, p0, is usually given as a function of climaticand path parameters and is obtained as

( ) 4.189.06.30 1 −+⋅⋅⋅= εfdKp .............................................................(79)

where

K = Geoclimactic factor

Page 104: TND Complete

RADIO WAVE PROPAGATION

Ericsson Radio Systems AB 53

4/038 02-LZU 102 152, Rev A, November 1999

d = Path length, km

f = Frequency, GHz

ε = Path slope, mrad

M = Fade margin, dB

The estimations of the geoclimatic factor correspondent to differentclimates are discussed in the following sections.

Flat fading and error performance

Generally, multipath fading is considered as negligible for frequenciesabove 10 GHz for which rain is the dominating fading mechanism. Thesignificance of multipath fading in rain abundant regions may even benegligible for frequencies lower than 10 GHz.

Multipath fading (flat fading and frequency selective) is normally themain contributor to Severely Errored Seconds (SES). Comparing flatand frequency selective fading, the former is usually more frequent innarrow bandwidth systems.

Method for small percentages of time

Estimation of the geoclimatic factor

The geoclimatic factor is strongly dependent on the geographical pathlocation, antenna altitude and size of bodies of water in the vicinity ofthe path (refraction anomalies). The geoclimatic factor is calculated forknown terrain (inland and coastal links) or for unknown terrain.

Inland Links

Inland links are links for which

• The entire path profile is above 100 m altitude (with respect to meansea level) or beyond 50 km from the nearest coastline or

• part or all the entire path profile is below 100 m altitude (withrespect to mean sea level) and entirely within 50 km of thecoastline, but having an intervening height of land higher than 100m between the link and the coastline.

Links passing over a river or a small lake should normally be classed aspassing over land.

Normally, measured values of the geoclimatic factor Ki are notavailable, but it can be estimated according to

Page 105: TND Complete

RADIO TRANSMISSION NETWORK AND FREQUENCY PLANNING

54 Ericsson Radio Systems AB

4/038 02-LZU 102 152, Rev A, November 1999

( ) 5.11.07 010100.5 LCCC

i pK LonLat ⋅⋅⋅= −−⋅−− .................................................(80)

Where

C0 =Antenna altitude coefficient, dB

CLat =Latitude coefficient, dB

CLon =Longitude coefficient, dB

pL =Percentage of time the refractivity gradient in the lowest100 m of the atmosphere is lower than –100 N units/km in theestimated average worst month, %

Antenna altitude coefficient

The values of the antenna altitude coefficients are classified accordingto:

• Low altitude antenna: lower-antenna altitude less than 400 m abovemean sea level

• Medium altitude antenna: lower-antenna altitude in the range 400-700 m above mean sea level

• High altitude antenna: lower-antenna altitude higher than 700 mabove mean sea level

The terrain type is classified according to:

• Plains

• Hills

• Mountains

The C0 values are displayed in Table 7 for links located on knownterrain and in Table 8 for links located on unknown terrain.

Low altitudeantenna (0-400 m)

Medium altitudeantenna (400-700 m)

High altitude antenna(above 700 m)

Plains Hills Plains Hills Plains Hills Mountains

0 3.5 2.5 6 5.5 8 10.5

Table 7: Antenna altitude coefficient values for links located on knownterrain.

When the type of the terrain is not known, the following table gives theC0 values for planning purpose.

Page 106: TND Complete

RADIO WAVE PROPAGATION

Ericsson Radio Systems AB 55

4/038 02-LZU 102 152, Rev A, November 1999

Low altitudeantenna (0-400 m)

Medium altitudeantenna (400-700 m)

High altitude antenna(above 700 m)

1.7 4.2 8.0

Table 8: Antenna altitude coefficient values for links located onunknown terrain.

Latitude coefficient

The latitude coefficient is given for three latitude regions according to

CLat = 0 for 53 °S ≥ ξ ≤ 53 °N

CLat = -53 + ξ for 53 °N or °S < ξ < 53 °N or °S

CLat = 7 for ξ < 60 °N or °S......................................

Longitude coefficient

CLon = 3 for longitudes of Europe and Africa

CLon = -3 for longitudes of North and South America

CLon = 0 for all other longitudes

Climatic factor pL

The specific value of the refractivity gradient, pD = -157 N units/km,represents the boundary between super-refraction and ducting, thusbecoming the probability for the occurrence of a radio duct. Unlike pD,pL values are readily available in the literature. In addition, it has beenfound that pD and pL

1.5 are highly correlated. Therefore pL values arecurrently employed in the estimation of the geoclimatic factor.

The pL values for the entire world are obtained from the maps includedin Rec. ITU-R P.453-6 for four different seasons represented by themonths February, May, August and November. The highest value,expressed in %, obtained from the four maps should be used forplanning purposes. An exception is when planning for latitudes greaterthan 60 °N or 60 °S when the maps of May and August should be used.

Coastal Links

Coastal links are links having a fraction rc of the path profile

• Less than 100 m above a body of water

Page 107: TND Complete

RADIO TRANSMISSION NETWORK AND FREQUENCY PLANNING

56 Ericsson Radio Systems AB

4/038 02-LZU 102 152, Rev A, November 1999

• Within 50 km of its coastline

• No height of land above the 100 m altitude (relative to the meanaltitude of the body of water in question) between the fraction of thepath profile and the coastline.

Coastal links over/near large bodies of water

The size of large bodies of water is considered with respect to severalknown examples:

• English Channel

• North Sea

• Large reaches of the Baltic and Mediterranean Seas

• Hudson Strait

• Other bodies of water of similar size

Normally, measured values of the geoclimatic factor K are notavailable, but it can be estimated according to

( )icl

KrKrl KKK clcic ≥= ⋅+⋅− n whe10 loglog1 .................................(81)

Ki when Kcl < Ki

ξ⋅−⋅−− ⋅⋅= 011.01.04 010103.2 CclK ............................................................(82)

where Ki is given by expression (51) and C0 is obtained from Table 7.The condition Kcl < Ki occurs in a few regions at low and mid latitudes.

The parameter rc is the fraction of the path profile below 100 m altitudeabove the mean sea level of the body of water in question and within 50km of the coastline, without intervening height above 100 m altitude.

Coastal links over/near medium-sized bodies of water

The size of medium-sized bodies of water is considered with respect toseveral known examples

• Bay of Fundy (East Coast of Canada)

• Strait of Georgia (West Coast of Canada)

• Gulf of Finland and other bodies of water of similar size

Page 108: TND Complete

RADIO WAVE PROPAGATION

Ericsson Radio Systems AB 57

4/038 02-LZU 102 152, Rev A, November 1999

Normally, measured values of the geoclimatic factor K are notavailable, but it can be estimated according to

( )icm

KrKrm KKK cmcic ≥= ⋅+⋅− n whe10 loglog1 ...............................(83)

Ki when Kcm < Ki

( )cli KKcmK loglog5.010 +⋅= .........................................................................(84)

where Ki is given by expression (51) and C0 is given by Table 7. Thecondition Kcm < Ki occurs in a few regions at low and mid latitudes. Theparameter rc is as above.

When the size of the body of water classification (medium or large) inquestion is not easy applicable, then the geoclimatic factor should beestimated according to

( ) ( )clcmcic KKrKrK loglog5.0log110 +⋅⋅+⋅−= ...........................................................(85)

where the parameters are defined above.

Links at other regions

There are regions consisting of extensive area of lakes or “watersystems”. Typical example is the region of lakes in southern Finland.

Links not located in coastal areas but near vast area of lakes areconsidered as coastal areas and the geoclimatic factor should beestimated according to

( )[ ]cmcic KrKrK loglog25.010 ⋅+⋅−⋅= ...................................................................(86)

where the parameters are defined above.

Link and terrain parameters – overview

When topography databases are not available, the alternative “unknownterrain” and the corresponding three antenna altitude coefficientalternatives should be employed. When topography databases areavailable, the parameter input for the flat fading prediction cangenerally be structured according to Figure 25.

Page 109: TND Complete

RADIO TRANSMISSION NETWORK AND FREQUENCY PLANNING

58 Ericsson Radio Systems AB

4/038 02-LZU 102 152, Rev A, November 1999

Unknownterrain

Knownterrain

1) Low altitude antenna (0-400m)2) Medium altitude antenna (400-700m)3) High altitude antenna (above 700m)

Coastal Links

Inland Links

Links at otherregions

1) Over/near large bodies of water2) Over/near medium- sized bodies of water

1) Low altitude antenna (0-400m) a) Hills b) Plains2) Medium altitude antenna (400-700m) a) Hills b) Plains3) High altitude antenna (above 700m) a) Hills b) Plains c) Mountains

Figure 25: The structure of the parameter input in the flat fadingprediction function.

Estimation of the path slope

Path slope is calculated as follows

d

hh BA −=ε .......................................................................................(87)

where

ε =Path slope, mrad

hA =Antenna height + ground elevation at the transmitter, m

hB =Antenna height + ground elevation at the receiver, m

d =Path length, km

A general rule of thumb is that rays will penetrate a duct without beingsignificantly reflected when the path slope is approximately greater than0.4° (7 mrad). This would correspond approximately to a path length of7 km and an antenna height difference of 50 m or a path length of about3 km and an antenna height difference of 20 m.

Page 110: TND Complete

RADIO WAVE PROPAGATION

Ericsson Radio Systems AB 59

4/038 02-LZU 102 152, Rev A, November 1999

Outage due to flat fading

The percentage of time pw that the system’s fade margin, M, is exceededin the average worst month is calculated as follows,

( )

− ⋅+⋅⋅⋅= 104.189.06.3 101M

fdKp εω ...............................................(88)

where

K = Geoclimactic factor

d = Path length, km

f = Frequency, GHz

ε = Path slope, mrad

M = Fade margin, dB

Range of values for the climatic factor pL

The range of the climatic factor and its impact on the fading results isexamined. The probability to exceed fade margin as a function of pathlength is displayed for different pL settings, ranging from 1% (areas ofhigh latitudes) to approximately 40% (specific areas in the vicinity ofthe equator). Fade margin close to 30 dB and frequency 7 GHz arenormally frequent values in many link applications. The path isconsidered horizontal through all calculations, thus giving somewhatmore pessimistic probabilities to exceed fade margin.

Considering the actual parameter settings, the corresponding probabilityrange to exceed fade margin is extremely large, approximately threeorders of magnitude, see Figure 26.

Page 111: TND Complete

RADIO TRANSMISSION NETWORK AND FREQUENCY PLANNING

60 Ericsson Radio Systems AB

4/038 02-LZU 102 152, Rev A, November 1999

0 10 20 30 4010-6

10-5

10-4

10-3

10-2

10-1

Pro

ba

bil

ity

to e

xce

ed

fa

de

ma

rgin

, %

M = 30 dB

CLat = 0 dB

CLon = 3 dBf = 7 GHz

ε = 0 deg.

pL (%)

� 1

� 5

� 10

� 20

� 30

� 40

� 50

� 60

� 70

��

��

C0 = 0 dB

Path length, km

Figure 26: The probability range to exceed fade margin for climaticfactor in the range 1% and 40%.

Method for small percentage of time - conclusion

The wide range of the parameter values has considerable effects on theflat fading results. In fact, the influence of some parameters on themodel is rather noticeable.

Figure 27 displays two extreme planning alternatives: “easy” and“difficult”. Typical for the “easy” alternative are lower frequencies andlow pL values, high altitude antenna situated on mountains in thevicinity of the equator at longitude corresponding to North and SouthAmerica. Typical for the “difficult” alternative are higher frequenciesand high pL values, low altitude antenna situated on plains far from theequator at longitudes corresponding to Europe and Africa. The rangedisplayed in Figure 27 is approximately three orders of magnitude andit might be wider for regions with stronger refraction properties (high pL

values).

Since flat fading is one of the major contributors to severely erroredseconds (SES), the wide range of parameter values plays a decisive partwhen dimensioning the path length to fulfil the actual error performanceobjectives. The transmission network planners should therefore selectthe parameter values with caution.

Page 112: TND Complete

RADIO WAVE PROPAGATION

Ericsson Radio Systems AB 61

4/038 02-LZU 102 152, Rev A, November 1999

0 10 20 30 40

Path length, km

10-6

10-5

10-4

10-3

10-2

10-1

Pro

ba

bili

ty t

o e

xce

ed

fa

de

ma

rgin

, %

C0 = 10.5 dB

pL = 1% CLat = 0 dB

ε = 0 deg

M = 30 dB

CLon = -3 dB

pL =40%

f = 7 GHz

C0 = 0 dBM = 30 dB

CLat = 7 dB

ε = 0 deg CLon = 3 dB

f= 2 GHz

Figure 27: Two extreme planning alternatives: “easy” (the lowestcurve) and “difficult”.

Method for various percentages of time

The prediction method described below combines an empiricalinterpolation procedure between the deep fading region of thedistribution and 0 dB with the prediction method for small percentagesof time described in the previous section.

The interpolation procedure is performed in the following steps:

a) The percentage of time pw that the fade margin 35 dB is exceeded iscalculated according to (59)

b) The parameter q’a for fade margin 35 dB and the corresponding pw

value from step a is calculated as follows

M

p

q

w

a

−⋅−=

100

100lnlog20

' ........................................................(89)

c) The parameter qt is calculated according to

Page 113: TND Complete

RADIO TRANSMISSION NETWORK AND FREQUENCY PLANNING

62 Ericsson Radio Systems AB

4/038 02-LZU 102 152, Rev A, November 1999

( )

+−

⋅+

−=

⋅−− 800103.4

10103.01

220

016.020

' Mqq

M

MM

at .......................(90)

d) If qt > 0, repeat steps a) to c) for M = 25 dB to obtain the final qt

value.

e) Depending on the value of the fade margin, the percentage of time pw

can be calculated as follows:

• For M > 25 dB or M > 35 dB, as appropriate, calculate thepercentage of time pw that the fade margin M is exceeded using themethod given by (59)

• For M < 25 dB or M < 35 dB, as appropriate, calculate thepercentage of time pw that the fade margin M is exceeded

−⋅=

⋅−

− 2010e1100Maq

pω ......................................................................(91)

where the parameter qa is obtained as follows:

[ ]

+⋅+⋅⋅

⋅++=

−⋅−−

800103.410103.012 20016.020 M

qqM

tM

M

a ............(92)

The value of parameter qt is obtained in step c or d.

The prediction methods for small percentages of time and variouspercentages of time are compared in Figure 28 for a path length of 20km and with the previous parameter setting. For fade margin valuesnormally employed in most link applications, the output of bothmethods are comparable, then making the method for small percentagesof time more suitable since it is relatively straightforward.

Page 114: TND Complete

RADIO WAVE PROPAGATION

Ericsson Radio Systems AB 63

4/038 02-LZU 102 152, Rev A, November 1999

0 10 20 30 40 50

Fade margin, dB

10-5

10-4

10-3

10-2

10-1

100

101

102

Pro

ba

bil

ity

to e

xce

ed

fa

de

ma

rgin

, %

C0 = 0 dB

pL = 5%

f = 7 GHz

d = 20 km

ε = 0 deg

CLat = 0 dB

Small percentagesof time

Various percentagesof time

CLon = 0 dB

Figure 28: Comparison between the prediction methods for smallpercentages of time and various percentages of time

Range of validity for the flat fading method

The flat fading prediction models described above are valid within thefollowing ranges:

95 ≥ d ≥ 7 km

37 ≥ f ≥ 2 GHz

24 ≥ ε ≥ 0 mrad

Path lengths up to approximately 190 km have been checked forfrequencies as low as 500 MHz. The results indicate that the validityranges described above, can be extended for larger ranges of path lengthand frequency, and that the lower frequency limit of validity isinversely proportional to path length, given roughly by

df

15min = ............................................................................................(93)

Page 115: TND Complete

RADIO TRANSMISSION NETWORK AND FREQUENCY PLANNING

64 Ericsson Radio Systems AB

4/038 02-LZU 102 152, Rev A, November 1999

Main differences between Rec. ITU-R P.530-6 and Rec. ITU-R P.530-7

Comparing the methods for evaluation of flat fading depicted in Rec.ITU-R P.530-6 and in Rec. ITU-R P.530-7, the main differences are thefollowing:

a) Flat fading in the former method (Rec. ITU-R P.530-6) is predictedfor paths with and without profiles. This option of path profiles areincluded in the actual method (Rec. ITU-R P.530-7) via the parameters(terrain type and antenna altitude coefficients) used for the calculationof the geoclimatic factor

b) The classification of the antenna altitude comprises three classes (0-400, 400-700 and above 700 m above the mean sea level) in Rec. ITU-R P.530-7 while in Rec. ITU-R P.530-6 there are two classes (lowerthan 700 and higher than 700 m above the mean see level)

c) The calculation of the geoclimatic parameter

d) The dependence on the grazing angle has been removed

In several climates, however, ground reflections are rather morefrequent than atmospheric reflections, in some cases 70 to 80% morefrequent. For those specific climates, the absence of the grazing angledependence in the flat fading model is therefore surprising.

As mentioned before (see b), there are now three antenna altitudeclasses instead of two classes. Comparing inland links in ITU-R P.530-6 and ITU-R P.530-7, the latter gives probability to exceed fade marginabout 3 and 1.7 times more pessimistic, for low and medium altitudeantenna, respectively. For high altitude antennas, however, theprobability to exceed fade margin is comparable in bothrecommendations.

Outage due to frequency selective fading In the case of frequency selective fading, waves from different pathsinterfere with one another at the receiver. The different propagationwaves can often be the result of ground reflections, reflections in theducting layer or propagation in layers having highly positive refractiongradients. Layers having horizontal structures can also result infrequency selective fading.

Occasionally, the various constituents unite with one another so that afield-strength minimum arises in the case of certain frequencies.Atmospheric layer movement (changes in path geometry) causes theseminimums to shift across the frequency band. The speed of suchshifting can vary from tens to hundreds of MHz/sec.

Page 116: TND Complete

RADIO WAVE PROPAGATION

Ericsson Radio Systems AB 65

4/038 02-LZU 102 152, Rev A, November 1999

Frequency selective fading is often characterized with by specifying thedifference in propagation time between the direct and indirect waves.The propagation time differences are in turn a function of certain pathparameters (e.g., path length and path inclination) as well asmeteorological parameters.

The first cause of frequency selective fading is in-band distortion,which can be described with the aid of the transfer function’s slopewithin the frequency band.

Measurements performed in Sweden and simulations employing the 3-path model have shown that a slope of a minimum of 0.22 dB/MHz isattained within bandwidth B if the relative delay, τ, fulfills thefollowing relation

B50

≥τ ................................................................................................(94)

where

τ = Relative delay, ns

B = Bandwidth, MHz

The choice of the 0.22 dB/MHz threshold for the transfer function’sslope is directly related to the fact that in-band distortion has proven tocause system outage at values as low as 0.2 dB/MHz.

For a bandwidth B=50 MHz, the relative delay, τ, becomes ≥ 1 ns andmultipath fading is classified as being frequency selective. For systemshaving smaller bandwidths, the relative delay is longer for a given pathlength which means that the system becomes less sensitive to frequencyselective fading, since longer relative delays are less probable thanshorter relative delays.

A rule of thumb is that multipath fading, for radio links havingbandwidths less than 40 MHz and path lengths less than approximately30 km, is described as being flat instead of frequency selective.

The prediction of frequency selective fading is a very difficult task.There exist many different prediction models, the results of whichunfortunately deviate considerably from one another. With theexception of the fact that contributions from flat and frequency selectivefading are not weighted but are additive, the prediction modelsdescribed here is the model specified in the ITU-R F.1093recommendation.

Page 117: TND Complete

RADIO TRANSMISSION NETWORK AND FREQUENCY PLANNING

66 Ericsson Radio Systems AB

4/038 02-LZU 102 152, Rev A, November 1999

ITU-R F.1093 model

The probability of the occurrence of multipath fading, P, is calculatedas a function of the probabilities of the occurrence of selective fadingps and flat fading pf as follows

222

ααα

+= fls PPP ................................................................................(95)

The parameter α in the above expression determines how theprobability of the occurrence of fading may be weighted.. Theprobability of the occurrence of multipath fading is simply obtained bythe sum of the probabilities of the occurrence, ps and pfl .

The probability of the occurrence of flat fading, pf , is obtainedaccording to the previous section.

The probability of the occurrence of frequency selective fading isobtained by

mpss Pp /⋅= η ......................................................................................(96)

where

Ps/mp = Probability of the occurrence of fading caused byintersymbol interference during multipath fading

η = Probability of the occurrence of multipath fading

The propagation parameter η is empirically obtained by the followingexpression

⋅−

−=4

3

02.0

e1P

η ...................................................................................(97)

where P0 is the fade occurrence factor and is expressed by

100

10 10

0

=

M

p

................................................................................(98)

where

pw = Probability of the occurrence of flat fading during the worstmonth, %

M = Fade margin, dB

Page 118: TND Complete

RADIO WAVE PROPAGATION

Ericsson Radio Systems AB 67

4/038 02-LZU 102 152, Rev A, November 1999

Note, however, that P0 in the above expression is not expressed as apercentage.

The echo delay, τ, can be characterized by different types ofdistributions. This method employs an empirical relation, whichassumes exponentially distributed delays. Thus, it is expressed asfollows

n

mm

D

⋅=

500ττ .................................................................................(99)

where

τm = Mean value of the echo delay, ns

τm0 = Mean relative delay for a standard path of 50 km, ns

D = Path length, km

n = normalization exponent with values in the range of 1.3 and 1.5.

The mean relative delay for a standard path, τm0, is usually about 0.7seconds for exponentially distributed delays.

The probability of the occurrence of fading due to intersymbolinterference during multipath fading can be written as follows

( )r

m

B

bmps

WpCP

ττ 220

/

2101 ⋅⋅⋅⋅⋅=

....................................................(100)

where

Ps/mp = The probability of the occurrence of fading due tointersymbol interference during multipath fading

C = Constant factor

pb(1) = The value of pb when b=1

W = Signature width, GHz

B = Signature depth, dB

τr = Reference delay for λa (average of linear signature), ns

The value of the product C⋅pb(1) is usually 2.16 and the value of thereference delay τr is 6.3 ns.

Page 119: TND Complete

RADIO TRANSMISSION NETWORK AND FREQUENCY PLANNING

68 Ericsson Radio Systems AB

4/038 02-LZU 102 152, Rev A, November 1999

Refraction fading Refraction fading, also known as k-type fading, is characterized by thefact that a lower earth-radius factor, k, causes the effective earth radiusto be less (the curvature of the effective earth surface becomes larger).This, in turn, may cause earth surface irregularities (buildings,vegetation, mountains, etc.) to penetrate the first Fresnel zone and causeobstruction attenuation. The lower the values of the earth-radius factorthe smaller the effective earth radius and the greater the obstructionattenuation.

The probability of refraction fading is therefore coupled to obstructionattenuation for a given value of earth-radius factor. Since the earth-radius factor is not constant, the probability of refraction fading iscalculated based on the cumulative distribution of the earth-radiusfactor.

The probability of refraction fading is calculated in four steps:

1. A table is first constructed containing probabilities that the various k-values will not be exceeded. A k-value distribution table for anyspecific pL factor is employed, in order to interpolate the probabilitiesfor given k-values.

2. Obstruction attenuation values for the given k-values in the abovetable are calculated based on an algorithm selected by the user.

3. The calculated obstruction attenuation values then replace the k-values in the table. The earlier table is transformed into a new tablecontaining the probabilities in which the different obstructionattenuation values will be exceeded.

4. Finally, fade margin is coupled to obstruction attenuation byapplying the link budget and the probabilities are calculated thatdifferent fade margin values will be exceeded.

The total fading outage

The total outage is calculated by adding the contributions from thefrequency selective fading, flat fading, rain and refraction fading asfollows

krwstot ppppP +++= ...................................................................(101)

where

Page 120: TND Complete

RADIO WAVE PROPAGATION

Ericsson Radio Systems AB 69

4/038 02-LZU 102 152, Rev A, November 1999

ps = The portion of time, expressed as a percentage of the worstmonth, that the system’s fade margin, M , for BER = 10-3, isexceeded due to frequency selective fading, %

pw = The portion of time, expressed as a percentage of the worstmonth, that the system’s fade margin, M , for BER = 10-3, isexceeded due to flat fading, %

pr = The portion of time, expressed in percent of the worstmonth, during which a given fade-depth M (fade margin) isexceeded, due to rain fading, %

pk = The portion of time, expressed in percent of the worstmonth, during which a given fade-depth M (fade margin) isexceeded, due to refraction fading (k-type fading), %

The contribution from frequency selective fading is calculated inaccordance with equation (67), rain fading in accordance with equation(46), flat fading in accordance with equation (59) and refraction fadingin accordance with the method described in “Refraction fading”.

Basic radio-meteorological parameters for RL-design

Several prediction models previously described in this chapter demandradio-meteorological parameters. In what follows, the definition of theparameters is presented along with the references where they areencountered.

More accurate local radio-meteorological parameters are alwayspreferable.

Earth-radius factor Definition: the earth-radius factor accounts for the refractive propertiesof the atmosphere

Used: design of path profile, estimation obstacle loss and refraction-diffraction fading

Reference: estimated as a function of the refraction gradient

Surface water vapor density Definition: the annual surface water vapor density is the seasonalsurface water vapor density in the lowest part of the atmosphere.

Used: estimation of the gas attenuation

Page 121: TND Complete

RADIO TRANSMISSION NETWORK AND FREQUENCY PLANNING

70 Ericsson Radio Systems AB

4/038 02-LZU 102 152, Rev A, November 1999

Reference: Rec. ITU-R P.836-1

Relative humidity Definition: the ratio between the air’s vapor pressure and its saturationpressure

Used: estimation of the gas attenuation

Reference: estimated as a function of the temperature

pL factor (refractive factor) Definition: the pL factor is the percentage of time the refractivity in thelowest 100 m of the atmosphere is lower than –100 N-units/km duringthe estimated average worst month.

Used: estimation of flat fading.

Reference: Rec. ITU-R P.453-6.

Refractive gradient Definition: the refractive gradient in the lowest layer of the atmosphere,100 m from the surface of the Earth.

Used: estimation of the local Earth-radius factor

Reference: Rec. ITU-R P.453-6.

Rain frequency-dependent coefficients Definition: the rain frequency-dependent coefficients involve theassumptions concerning the distribution of rain-drop size, form,temperature and type of polarization.

Used: calculation of rain attenuation

Reference: Rec. ITU-R P.838

Rain climate zones Definition: 15 ITU-structured rain climate zones

Used: prediction of zone-wide precipitation effects

Page 122: TND Complete

RADIO WAVE PROPAGATION

Ericsson Radio Systems AB 71

4/038 02-LZU 102 152, Rev A, November 1999

Reference: Rec. ITU-R P.837-1

Rain intensity distribution Definition: cumulative distribution of rain intensity for thecorresponding rain climate zone

Used: prediction of zone-wide precipitation effects

Reference: Rec. ITU-R P.837-1

Annual and worst-month statistics Definition: conversion parameters for annual and worst-month statisticsfor different locations.

Used: conversion between annual and worst-month statistics inmultipath and rain fading.

Reference: Rec. ITU-R P.841

Hardware failure

Hardware failure is calculated for systems with and withoutredundancy. Passive redundancy applies to redundant systemsconfigurations including monitored hot standby.

The word standby, as used here, implies that a ”reserve” component isconnected when replacing one that has failed, i.e., passive redundancy.Hot refers to the fact that the ”reserve” component functions optimallyfrom the point at which it is introduced into the system, no ”warm-up/switch-over” is therefore required. Monitored implies electroniccontrol/supervision.

The calculation of the radio-link system’s MTBF

The MTBF (Mean Time Between Failure) for a particular equipmentcan be arrived at both theoretically and practically. Theoretical MTBFvalues are attained in accordance with certain reliability models that areapplied to the equipment. This is performed on a component level andis a highly complex operation since many different parameters may beinvolved. Practical MTBF is, on the other hand, somewhat simpler toestimate via life-cycle testing aided by the collection of reliability datafrom the equipment that is included in numerous systems. However, toarrive at reliable MTBF values, it is very important that the number ofinvestigated units (the population), from which reliability data iscollected, is sufficiently large.

Page 123: TND Complete

RADIO TRANSMISSION NETWORK AND FREQUENCY PLANNING

72 Ericsson Radio Systems AB

4/038 02-LZU 102 152, Rev A, November 1999

Modern radio-link equipment exhibits very high availability. MTBFvalues between 10 and 15 years are no longer unusual. Radio-linkmanufacturers often specify the total MTBF of their radio-links, wherethe MTBFs of the individual components (Mux, BB, MF and RF units,power supplies, etc.) are included. It is however important that onealways check which elements are included in the equipment’s MTBFbefore starting unavailability calculations.

The system’s total mean time between failures, MTBFS, can beexpressed as a function of the component’s mean time between failure,MTBFi, as follows

∑=

=n

i i

S

MTBF

MTBF

1

11

.......................................................................(102)

where

MTBFs = The system’s total mean time between failure, years

MTBFi = The component’s individual mean time between failure,years

n = The number of components in the system

Non-redundant systems The probability of hardware failure for non-redundant systems iscalculated as follows

100

8760

8760 ⋅+

=MTTR

MTBF

MTTR

p

S

s .............................................................(103)

where

ps = Probability of hardware failure for a non-redundantsystem, %

MTBFs = The system’s total mean time between failure, years

MTTR = The mean time to restore, hours

Page 124: TND Complete

RADIO WAVE PROPAGATION

Ericsson Radio Systems AB 73

4/038 02-LZU 102 152, Rev A, November 1999

The factor (1/8760) transforms MTTR from hours into years, therebyhaving the same units as MTBFS. Mean time to repair, MTTR (MeanTime To Restore), is defined as the duration of the interruption. As arule, this time consists of the travel time required between a mannedsupervising station and the station containing the failed equipment plusthe actual repair time. It is important to note that the waiting time thatalways arises in connection with the ordering and delivery of spareparts is often not included in MTTR. The mean time to restore conceptassumes that spare parts are always available when failure occur.

MTTR may be considered as a measure of a system’s maintainabilityand is always, for practical purposes, specified in hours.

Figure 29 illustrates, for four different values of MTTR, the probabilityof hardware failure of a non-redundant system as a function of MTBF.

0 3 6 9 12 15MTBF, years

0.00

0.02

0.04

0.06

0.08

0.10

Pro

babi

lity

of h

ardw

are

failu

re, %

MTTR= 6 hours

MTTR= 12 hours

MTTR= 24 hours

MTTR= 48 hours

0.10

Figure 29: Hardware failure of a non-redundant system as a function ofthe MTBF.

Redundant systems The probability of hardware failure for redundant systems is calculatedas follows

Page 125: TND Complete

RADIO TRANSMISSION NETWORK AND FREQUENCY PLANNING

74 Ericsson Radio Systems AB

4/038 02-LZU 102 152, Rev A, November 1999

1001

8760

87608760⋅

+

⋅+

⋅⋅

⋅=

u

u

u

SSs

MTTRMTTR

MTBF

MTTR

MTBF

MTTR

MTBF

MTTRp ..........(104)

where

pr = Probability of hardware failure of a redundant system, %

MTBFs = The system’s total mean time between failure of one theduplicated equipment, years

MTBFu = The mean time between failure of the non-doubled (non-redundant) equipment (base-band distributor + switch),years

MTTR = The mean time to restore of one of the doubled ................(redundant) units of a redundant system, hours

MTTRu = The mean time to restore of the non-doubled (non-redundant) equipment (base-band distributor + switch),hours

The function of the switch-unit is to automatically switch traffic fromfailed equipment to equipment that is in proper operating condition. Thecomments above therefore only apply under the premise that a switch-unit fault does not cause total system failure due to the fact that theswitch is required for system recovery. This means that traffic continuesvia the remaining operational equipment even if the switch-unit and oneof the doubled components are not operating.

The probability of hardware failure of a redundant system (monitoredhot standby-configuration) as a function of MTBF has been calculatedfor four different values of MTTR and is illustrated in the figure below.In the calculation, the values of MTBFu and MTTRu, for the non-doubled equipment (the base- band distributor + switch), have been setto 10 years and 12 hours, respectively.

Page 126: TND Complete

RADIO WAVE PROPAGATION

Ericsson Radio Systems AB 75

4/038 02-LZU 102 152, Rev A, November 1999

0 3 6 9 12 15

MTBF, years

10-6

10-4

10-4

Pro

babi

lity

of h

ardw

are

failu

re, %

MTTR= 6 hours

-5

MTTR= 12 hours

MTTR= 24 hours

MTTR= 48 hours

Figure 30: The probability of hardware failure of a redundant system asa function of the MTBF.

Hardware failure per path The probability of hardware failure is calculated per path. Theassumption is, however, that the input parameters apply to the entireradio-link system in question. This means, therefore, that the MTBF ofthe radio-link system includes all individual components, includingtheir respective MTBF values, for both the transmitter and the receiverin a duplex-setup configuration. The calculation of the probability ofhardware failure is performed separately for each station. The totalprobability of hardware failure for each direction of the path (go andreturn) is obtained by adding the hardware failure contributions of bothstations.

The calculated probability of hardware failure is given in percent peryear.

The following parameters are required:

• Configuration: redundant, non-redundant or no calculation ofunavailability due to hardware failure.

• The path’s mean time between failure for the doubled equipment,years

Page 127: TND Complete

RADIO TRANSMISSION NETWORK AND FREQUENCY PLANNING

76 Ericsson Radio Systems AB

4/038 02-LZU 102 152, Rev A, November 1999

• The path’s mean time between failure for the non-doubledequipment, years

• The mean time to restore for the doubled units of a redundantsystem, hours

• The mean time to restore for the non-doubled units, hours

Diversity

The basic concepts Systems that include doubled sets of equipment or systems that transmitthe same signal in parallel over two or more radio channels havingdifferent frequencies are referred to as being redundant systems. In thisrespect, redundancy and diversity have the same meaning.

Diversity receiving is an effective means of reducing the effects of,above all, multipath fading, where the received signal is the vectoraddition of multipath components that primarily vary in time, phase andangle of arrival.

Random signal variations often occur during very short periods of timeand may very well be described with the aid of the Rayleighdistribution. One utilizes the fact that deep fading in radio channels thattransmit the same information but are sufficiently separated in, forexample, frequency and/or space, have low correlation. The lower thecorrelation, the higher is the improvement gained by the use ofdiversity. In practice, good improvement can already be noticed at acorrelation of 0.6. Diversity is therefore a method that providesstatistically independent multipath components at the receiver.

Two fading depth statistical distributions are compared when measuringthe diversity improvement on a radio connection: one for the path withdiversity and one for the path without diversity. The measuredimprovement can be expressed in two different ways: diversity gain anddiversity improvement.

Page 128: TND Complete

RADIO WAVE PROPAGATION

Ericsson Radio Systems AB 77

4/038 02-LZU 102 152, Rev A, November 1999

Figure 31 illustrates two fade-depth statistical distributions, for one andthe same path. Points A (without diversity) and C (with diversity)correspond to two different fading levels having the same probability.The measured improvement is referred to as diversity gain and isexpressed in dB. Points A (without diversity) and B (with diversity)correspond to two different probabilities for the same level of fadingand is referred to as the improvement and is expressed as a factor.Diversity improvement can therefore be expressed as the ratio of twoprobabilities.

Probability of exceeding the fading depth, %

Fad

ing

dept

h, d

B

Without diversity

With diversity

improvementga

in

A

B

C

10-2 10-3 10-4 10-5 10-6 10-7

-10

-20

-30

-40

-50

0

Figure 31: Two fade-depth statistical distributions for one and the samepath, without and with diversity.

The definition of the improvement factor Diversity is primarily utilized to reduce the effects of multipath fading.The improvement factor can therefore be associated with the statisticalcumulative distribution of fading depth during the year’s worst monthin accordance with the prediction model for flat multipath fading.

In the calculation of the improvement factor for digital links, theexpression for analogue or narrow-band systems is adjusted in the caseof frequency diversity. For space diversity, however, it is used the sameexpression in the calculation of the improvement factor for both analogand digital or narrow-band systems.

As shown in Figure 26, the improvement factor can be defined as theratio of two probabilities: with the use of diversity and without the useof diversity. Note however, that the improvement implies that theprobability of a given event will be even less, i.e., outage will increase.

Page 129: TND Complete

RADIO TRANSMISSION NETWORK AND FREQUENCY PLANNING

78 Ericsson Radio Systems AB

4/038 02-LZU 102 152, Rev A, November 1999

( )( )MP

MPI

with

without= ..................................................................................(105)

where

I = Improvement factor

Pwithout(M) = Probability that the fading depth will be greater than orequal to M dB during the worst month for a path withoutdiversity, (%)

Pwith(M) = Probability that the fading depth will be greater than orequal to M dB during the worst month for a path with diversity,(%)

The calculation of the improvement factor: space diversity The improvement factor due to the use of space diversity is calculatedhere using the same algorithm for both analog and digital links

( )[ ] 101034.3 10e104.1

048.012.087.04

GMPdfsI

∆−⋅⋅⋅⋅⋅− ⋅−=

−−−

........................................(106)

where

I = The improvement factor for analog and digital links

s = Vertical separation between the antennas, m

f = Frequency, GHz

d = Path length, km

M = Fade margin, dB

∆G = The difference in antenna gain between the two antennas,dB

Parameter P0 is calculated as

( )100

10 10

0

M

without MPP

⋅= .......................................................................(107)

where

Pwithout (M) = The probability that fading depth is greater than orequal to M dB during the worst month for a pathwithout diversity, (%). Pwithout(M) is the outagedue to flat multipath fading for the worst month.

The prediction model is considered as giving valid results within thefollowing interval:

Page 130: TND Complete

RADIO WAVE PROPAGATION

Ericsson Radio Systems AB 79

4/038 02-LZU 102 152, Rev A, November 1999

3 ≤ s ≤ 23 m2 ≤ f ≤ 11 GHz43 ≤ d ≤ 243 km

The model’s validity for values outside of these boundaries is unknown.

The calculation of the improvement factor: frequency diversity

Analogue 1+1 system

The frequency-diversity improvement factor for a 1+1 analogue systemor path without strong surface reflections can be calculated as follows:

10108.0 M

a ff

dfI ⋅

⋅=

∆.....................................................................(108)

where

Ia = The improvement factor for analog or narrow-band systems

f = Band center frequency, GHz

∆f = Frequency spacing, GHz

d = Path length, km

M = Fade margin, dB

The prediction model is considered as giving valid results within thefollowing interval:

30 ≤ d ≤ 70 km2 ≤ f ≤ 11 GHz∆f /f ≤ 5 %

The model’s validity for values outside of these boundaries is unknown.

Digital 1+1 system

The improvement factor for digital 1+1 system is adjusted from theanalogue expression according to the following expression

ad II ⋅= 10 ........................................................................................(109)

where

Id = The improvement factor for digital or narrow-band systems

Page 131: TND Complete

RADIO TRANSMISSION NETWORK AND FREQUENCY PLANNING

80 Ericsson Radio Systems AB

4/038 02-LZU 102 152, Rev A, November 1999

Ia = The improvement factor for analog or narrow-band systems

The calculation of the improvement factor: space-frequencydiversity

The improvement factor for combined space-frequency diversity isgiven by

fssf III += .....................................................................................(110)

where

Isf = The improvement factor for combined space-frequency .....

diversity

Is = The improvement factor for space diversity

If = The improvement factor for frequency diversity

The calculation of outage when employing diversity When calculating the improvement brought about by the use ofdiversity, it is important to remember that the probability that is referredto above is the outage due to flat multipath fading for the worst month.

Following the calculation of the improvement factor, the outage inconjunction with the use of diversity can be attained from equation (80).

( ) ( )I

MPMP without

with = .......................................................................(111)

Passive repeaters

The basic concepts Passive repeaters generally consist of larger mirrored surfaces thanthose of reflectors and are often used either on mountain peaks as planereflectors or in conjunction with certain applications when they arereferred to as back-to-back reflectors.

Back-to-back reflectors are discussed here. These reflectors consist oftwo parabolic antennas, often mounted back-to-back on a low mast andare connected to one another by a short waveguide/cable. There existstherefore no direct connection from either a transmitter or receiver tothese parabolic antennas. They are primarily used in cities where line-of-sight transmission is not possible due to buildings and otherobstructions.

Page 132: TND Complete

RADIO WAVE PROPAGATION

Ericsson Radio Systems AB 81

4/038 02-LZU 102 152, Rev A, November 1999

Path calculation in connection with the use of back-to-back reflectorsrequires the calculation of

• the received and radiated power of the repeaters

• path attenuation

• fade margin

The intention behind the use of back-to-back reflectors is consequentlyto influence the final quality of the path.

Path calculation when using passive repeatersAn added attenuation arises when using passive repeaters between twostations due to the fact that the path between A and B is calculated astwo independent paths: from station A to the repeater R, see Figure 32,and from the repeater to station B.

The added attenuation consists of obstruction, gas attenuation and free-space loss and affects the total path attenuation between A and B.

AB

R

dAdB

Figure 32: A passive repeater consisting of two parabolic antennasmounted back-to-back.

Before calculating the added attenuation, one must first calculate thereceived and the radiated power of the repeater.

A repeater can be considered as being a directional antenna, both in thedirections of the transmitter and receiver antennas. The input signal atR, from station A, is calculated as being

ARbfRAAR L

GGPP,

1⋅⋅⋅= ..................................................................(112)

where

Page 133: TND Complete

RADIO TRANSMISSION NETWORK AND FREQUENCY PLANNING

82 Ericsson Radio Systems AB

4/038 02-LZU 102 152, Rev A, November 1999

PR = Power received by the receiving antenna at R (the repeater)

PA = Radiated power of the transmitting antenna atA

GA = Antenna gain of the transmitting antenna at A

GR = Antenna gain of the repeater R

Lbf,AR = Free-space loss between the transmitting antennaand the repeater

Free-space loss Lbf,SR between A and R can be written as

2

,

4

⋅⋅

π AARbf

dL ........................................................................(113)

where

λ = Wavelength, m

dA = Distance between the transmitter antenna and the repeater,m

If the repeater reflects the received power, PR, in the direction of thereceiver, B, the received power at B is

RBbfBRRR L

GGPP,

'

1⋅⋅⋅= ..................................................................(114)

where

PR’ = Power at the receiver antenna B

PR = Radiated power of the repeater

GR = Antenna gain of the repeater R

GB = Antenna gain of the receiver B

Lbf,RM = Free-space loss between the repeater and thereceiver antennas

Free-space loss Lbf,RM between R and B can be written as

2

,

4

⋅⋅

π BRBbf

dL .........................................................................(115)

where

dB = The distance between the repeater and the receiverantennas, m

λ = Wavelength, m

Page 134: TND Complete

RADIO WAVE PROPAGATION

Ericsson Radio Systems AB 83

4/038 02-LZU 102 152, Rev A, November 1999

Note that free-space loss, Lbf,AR and Lbf,RB are transformed to dBfollowing logarithmic conversion, see equation (13).

The total path loss is calculated as follows

RBARBAKBKA

RBGARGRBHARHRBbfARbfS

GGGGAA

AAAAAAA

−−−−−+

++++++= −−−−,, .................(116)

where

AS = Total path attenuation, dB

Abf,AR = Free-space loss for the partial path AR, dB

Abf,BR = Free-space loss for the partial path BR, dB

AH-AR = Obstruction loss for the partial path AR, dB

AH-BR = Obstruction loss for the partial path BR, dB

AG-AR = Gas attenuation for the partial path AR, dB

AG-BR = Gas attenuation for the partial path BR, dB

AKA = Feeder loss at station A, dB

AKB = Feeder loss at station B, dB

GA = Antenna gain at station A, dBi

GB = Antenna gain at station B, dBi

GAR = Antenna gain for the antenna at R facing station A, dBi

GBR = Antenna gain for the antenna at R facing station B, dBi

The fade margin for a path using back-to-back antennas is calculated asfollows

SthTr APPM −−= ............................................................................(117)

where

M = Fade margin, dB

PTr = The transmitter’s output power, dBm

Pth = The receiver’s threshold for a given bit-error ratio, dBm

AS = Total path loss, dB

References

Rec. ITU-R P.341-4

Rec. ITU-R P.453-6

Rec. ITU-R P.525-2

Page 135: TND Complete

RADIO TRANSMISSION NETWORK AND FREQUENCY PLANNING

84 Ericsson Radio Systems AB

4/038 02-LZU 102 152, Rev A, November 1999

Rec. ITU-R P.526-5

Rec. ITU-R P.530-7

Rec. ITU-R P.581-2

Rec. ITU-R P.676-3

Rec. ITU-R P.834-2

Rec. ITU-R P.836-1

Rec. ITU-R P.837-1

Rec. ITU-R P.838

Rec. ITU-R P.841

Rec. ITU-R P.1057

“Radiowave Propagation”, Boithias, L., North Oxford Academic, 1987.

“Low-Angle Microwave Propagation: Physics and Modeling”, Giger,A. J., Artech House, 1991.

Page 136: TND Complete

i

THE INTERNATIONALTELECOMMUNICATION UNION

(ITU)

This chapter deals with the ITU organization and itsadministrative tasks. The chapter provides valuableinformation on how to search and locate important ITU-Rand ITU-T reports and recommendations on specificsubjects related to radio-relay transmission.

TABLE OF CONTENTS

Introduction....................................................................................................................................................... 1The new ITU organization ................................................................................................................................ 2The administration of the ITU........................................................................................................................... 2

The Plenipotentiary Conference .......................................................................................................... 3The Council......................................................................................................................................... 4World Conferences on International Telecommunications ................................................................. 4The Radio communication Sector (ITU-R) ......................................................................................... 5

Radio Communication Study Group Structure...................................................................... 5The Telecommunication Standardization Sector (ITU-T)................................................................... 9The Telecommunication Development Sector (ITU-D)...................................................................... 9The General Secretariat....................................................................................................................... 10Advisory Groups ................................................................................................................................. 11

Financing of the ITU ......................................................................................................................................... 11ITU Member countries ........................................................................................................................ 11Other organizations (Sector members) ................................................................................................ 12

Publications and seminars ................................................................................................................................. 12Telecom Information Exchange Services (TIES).............................................................................................. 13References ......................................................................................................................................................... 13ITU-R Recommendations matrix ...................................................................................................................... 13Appendices........................................................................................................................................................ 14

Appendix A: ITU Top Management (1999-2002) .............................................................................. 14Appendix B: Radio Regulations Board (1999-2002) - Members........................................................ 14Appendix C: ITU Landmarks.............................................................................................................. 14Appendix D: ITU Secretary-Generals (1869 to present)..................................................................... 17Appendix E: Acronyms ....................................................................................................................... 18Appendix F: ITU-R Recommendations............................................................................................... 19Appendix G: P Series Recommendations - Radiowave Propagation................................................... 20Appendix H: F Series Recommendations - Fixed service ................................................................... 23

Page 137: TND Complete

THE INTERNATIONAL TELECOMMUNICATION UNION (ITU)

Ericsson Radio Systems AB

5/038 02-LZU 102 152, Rev A, November 1999

1

Introduction

The International Telecommunication Union (ITU) has been aspecialized agency of the United Nations since 1947. Founded in 1865in Paris, it was originally named the International Telegraph Union. Ithas been operating under its present name and since 1934. In addition tothe Member States (basically the same countries which are members ofthe United Nations), the ITU consists of about 575 members (byNovember 1999) from scientific and industrial companies, public andprivate operators, broadcasters and regional and internationalorganizations. There are 7 membership categories: 1) RecognizedOperating Agencies, 2) Scientific or Industrial Organizations, 3)Financial or Development Institutions, 4) Other Entities dealing withtelecommunication matters, 5) Regional and Other InternationalOrganizations, 6) Regional Telecommunication Organizations and 7)Intergovernmental Organizations Operating Satellite Systems.

Both the private and the public sectors cooperate in the development ofthe telecommunications area through several ITU activities, howeverthe primary purpose of the ITU is to adopt international regulations andagreements aimed at managing all terrestrial and space uses of thefrequency spectrum, including the use of the geostationary-satelliteorbit.

The ITU also develops standards for making the interconnection oftelecommunication systems possible, irrespective of the type oftechnology. Further, the ITU provides developing countries withspecialized technical assistance in the areas of telecommunicationpolicies, management, choice and transfer of technologies, financing ofinvestment projects, installation and maintenance of networks, researchand development.

Generally, the following issues are the responsibility of the ITU:

• Technical issues: improve the efficiency and usefulness oftelecommunication services and their general availability to thepublic by offering and promoting the development and efficientoperation of telecommunication applications.

• Development issues: promote and offer technical assistance todeveloping countries in the area of telecommunication through themobilization of human and financial resources.

• Policy issues: stimulate the adoption of a general approach onquestions concerning telecommunication and its connection toeconomy and society on a worldwide scale.

Page 138: TND Complete

RADIO TRANSMISSION NETWORK AND FREQUENCY PLANNING

2 Ericsson Radio Systems AB

5/038 02-LZU 102 152, Rev A, November 1999

The new ITU organization

Regulating the use of frequencies is an essential aspect of the work ofITU. To increase the efficiency of this effort, it was decided to separatethe standards-setting activities of the former International ConsultativeRadio Committee (CCIR) from its activities related to the efficientmanagement of the radio-frequency spectrum in terrestrial and spaceradiocommunication.

Following a three year study and review performed by the Membercountries as to the need for the ITU to meet the rapidly evolvingrequirements of modern telecommunications, the 1992 AdditionalPlenipotentiary Conference reaffirmed the basic purposes of the Unionand updated the ITU structures.

The Conference restructured the ITU into three Sectors in order toimprove coordination, to improve the user interface and othercooperating organizations and to provide for the continuous review ofstrategy and planning.

The standards-setting functions were then merged with those of theformer International Consultative Telegraph and Telephone Committee(CCITT) to form a telecommunication standardization sector; the othertechnical activities were integrated into a new radiocommunicationsector along with the regulatory activities formerly carried out by theInternational Frequency Registration Board (IFRB).

The administration of the ITU

The ITU administration body is composed of several departments andsectors. The Radiocommunication Sector was created on 1 March 1993.The other two Sectors are the Telecommunication Standardization andTelecommunication Development Sectors. This is illustrated in Figure 1below.

Page 139: TND Complete

THE INTERNATIONAL TELECOMMUNICATION UNION (ITU)

Ericsson Radio Systems AB

5/038 02-LZU 102 152, Rev A, November 1999

3

World Conferenceson International

Telecommunications

TS AG

StudyGroups

TelecommunicationStandardization Sector

World/RegionalTelecommunication

DevelopmentConferences

TD AB

StudyGroups

TelecommunicationDevelopment Sector

RadiocommunicationSector

RAG CPM SCStudyGroups

World/Regional

RadioConferences

RadioRegulation

Board

RadioAssembly

PlenipotentiaryConference

Council

Member States and Sector Members Member States

WorldTelecommunication

StandardizationConferences

Figure 1: The ITU governing bodies.

All ITU efforts in the field of radiocommunication have beenconsolidated into the Radiocommunication Sector. A two-year cycle ofconferences and meetings, accelerated publications and a new ITUmanagement system have been introduced to facilitate timely and cost-effective functions.

The following is a description of each unity.

The Plenipotentiary ConferenceThe Plenipotentiary Conference is the supreme authority of the ITU.This body meets every four years to adopt the fundamental policies ofthe organization and a strategic plan. It also makes decisions as to itsorganization and activities.

Page 140: TND Complete

RADIO TRANSMISSION NETWORK AND FREQUENCY PLANNING

4 Ericsson Radio Systems AB

5/038 02-LZU 102 152, Rev A, November 1999

The CouncilThe Council is represented by a number of members corresponding to25% of the ITU membership. Its responsibility is to act on behalf of thePlenipotentiary Conference by meeting annually to consider generaltelecommunication policy issues, the approval of budgets and thecoordination of the various ongoing tasks. The annual meetings alsoensure that the policies and strategies undertaken by the ITU are in linewith the frequent changes and developments arising intelecommunication issues.

The fifteenth Plenipotentiary Conference of the InternationalTelecommunication Union (ITU) was held in Minneapolis, USA, duringOctober 12 and November 6, 1998. The next ITU Council was electedfor the period 1999-2002 and is composed of forty-six Members of theUnion elected by the Plenipotentiary Conference with due regard as tothe need for the equitable distribution of Council seats among all fiveregions of the world:

Region A (Americas): Argentina, Brazil, Canada, Cuba, Mexico, SaintLucia, USA and Venezuela.

Region B (Western Europe): Denmark, France, Germany, Italy,Portugal, Spain, Switzerland and United Kingdom.

Region C (Eastern Europe): Bulgaria, Czech Republic, Poland,Romania and Russia.

Region D (Africa): Algeria, Burkina Faso, Cameroon, Côte d’Ivoire,Egypt, Gabon, Kenya, Mali, Morocco, Senegal, South Africa, Tanzaniaand Tunisia.

Region E (Asia & Australia): Australia, China, India, Japan, Korea(Rep), Kuwait, Malaysia, Pakistan, Philippines, Saudi Arabia, Thailandand Vietnam.

World Conferences on International TelecommunicationsThe World Conferences on International Telecommunications takeplace periodically to review and revise the internationaltelecommunication regulations applicable to administrations andoperators of international communications. The world conferencesestablish the general principles related to the provision and operation ofpublic international telecommunications services.

Page 141: TND Complete

THE INTERNATIONAL TELECOMMUNICATION UNION (ITU)

Ericsson Radio Systems AB

5/038 02-LZU 102 152, Rev A, November 1999

5

The Radio communication Sector (ITU-R)The Radiocommunication Sector is in particular responsible for theproviding of impartial, rational, efficient and economical use of theradio-frequency spectrum by all classes of radiocommunicationservices, including those services employing geostationary-satelliteorbits. It handles technical and operational questions specifically relatedto radiocommunication. It is also responsible for performing thenecessary studies on which the recommendations are then based andadopted. Its policy and legislative functions are exercised at world andregional telecommunication conferences and radiocommunicationassemblies supported by study groups.

Radio Communication Study Group Structure

More than 1,500 specialists, from telecommunication organizations andadministrations throughout the world, participate in the work of theRadiocommunication Study Groups.

The functions of the Study Groups are:

• draft the technical basis for Radiocommunication Conferences

• develop drafts for ITU-R Recommendations as to the technicalcharacteristics of, and operational procedures for,radiocommunication services and systems

• compile Handbooks on spectrum management and emergingradiocommunication services and systems.

Drafted ITU-R Recommendations may be approved either bycorrespondence or by the next Radiocommunication Assembly. Studiesof mutual interest to the Radiocommunication and TelecommunicationStandardization Study Groups are overseen by Inter-sector CoordinationGroups.

Conference Preparatory Meetings (CPMs) prepare a consolidated reportas to the technical, operational and regulatory/procedural bases for aWRC. The appropriate Study Groups undertake regulatory studies of atechnical or operational nature. Regulatory/procedural matters areaddressed in a Special Committee. The CPM updates and evaluates thematerial from the Study Groups and Special Committee, against anynew material submitted to it.

Page 142: TND Complete

RADIO TRANSMISSION NETWORK AND FREQUENCY PLANNING

6 Ericsson Radio Systems AB

5/038 02-LZU 102 152, Rev A, November 1999

Each group has a consular, a chairman and several vice chairmen. Theidentification number of each study group follows the earlier groupnumbering. After the reorganization of the ITU, some groups weremerged together forming a group with a specific number while someother numbers were suppressed.

The groups are subdivided into working parties according to specificfields, each working party having a chairman.

At present, there are 8 Study Groups (SGs), comprising 10 Task Groupsand 32 Working Parties, addressing the following topics:

SG 1: Spectrum management

Working Party 1A (Chairman: T. Jeacock): Engineering principles andtechniques, including computer-aided analysis for effective spectrummanagement

Working Party 1B (Chairman: A. Pavliouk): Principles and techniquesfor spectrum planning and sharing

Working Party 1C (Chairman: N. Kisrawi): Techniques for spectrummonitoring

Task Group 1/4 (Chairman for Phase 2: D. Bacon): Electronic exchangeof spectrum management information

Task Group 1/5 (Chairman: M. S. Dhamrait): Unwanted emissions andthe modification of Rec. SM.328-8 concerning out-of-band emissions

Task Group 1/6 (Chairman: G. Chan): Development of method(s) forthe determination of the coordination area around Earth stations

SG 3: Radiowave propagation

Working Party 3J (Chairman: G. Brussaard): Propagation fundamentals

Working Party 3K (Chairman: E. J. Haakinson): Point-to-areapropagation

Working Party 3L (Chairman: R. Hanbaba): HF propagation

Working Party 3M (Chairman: M. P. M. Hall): Point-to-Point andEarth-space propagation

Page 143: TND Complete

THE INTERNATIONAL TELECOMMUNICATION UNION (ITU)

Ericsson Radio Systems AB

5/038 02-LZU 102 152, Rev A, November 1999

7

SG 4: Fixed-satellite services

Working Party 4A (Chairman: A. G. Reed): Efficient orbit/spectrumutilization

Working Party 4B (Chairman: D. Weinreich): Systems, performance,availability and maintenance

Working Party 4-9S (Chairman: W. Rummler): Frequency sharingbetween the fixed-satellite service and fixed service

Working Party 4SNG (Chairman: A. Uyttendaele): Satellite newsgathering, outside broadcast via satellite

SG 7: Science services

Working Party 7A (Chairman: G. De Jong): Time signals and frequencystandard emissions

Working Party 7B (Chairman: R. Taylor): Space radio systems

Working Party 7C (Chairman: L. Ruiz): Earth exploration - satellitesystems and meteorological systems

Working Party 7D (Chairman: J. Whiteoak): Radio astronomy

SG 8: Mobile, radio-determination, amateur and related satelliteservices

Working Party 8A (Chairman: O. Villanyi): Land mobile servicesexcluding FPLMTS; amateur and amateur satellite services

Working Party 8B (Chairman: R. L. Swanson): Maritime mobileservices including the global maritime distress and safety system(GMDSS)and aeronautical mobile services excluding public telephoneservices to aircraft.

Working Party 8D (Chairman: T. Mizuike): All mobile satellite servicesexcept the amateur satellite service; radio-determination satelliteservices; public telephone services to aircraft

Task Group 8/1 (Chairman: M. H. Callendar): Future public landmobile telecommunication systems (FPLMTS)

Page 144: TND Complete

RADIO TRANSMISSION NETWORK AND FREQUENCY PLANNING

8 Ericsson Radio Systems AB

5/038 02-LZU 102 152, Rev A, November 1999

SG 9: Fixed services

Working Party 9A (Chairman: V. M. Minkin): Performance andavailability, interference objectives and analysis, effects of propagationand terminology

Working Party 9B (Acting Chairman: A. Hashimoto): Radio-frequencychannel arrangements, radio-system characteristics, interconnection,maintenance and applications

Working Party 9C (Chairman: N. M. Serinken): HF systems

Working Party 9D (Chairman: G. F. Hurt): Sharing with other services(except for the fixed-satellite service)

SG 10: Broadcasting services (sound)

Working Party 10A (Chairman: L. Olson): Sound broadcasting atfrequencies below 30 MHz and antennas for sound broadcasting

Working Party 10B (Chairman: F. Konway): Terrestrial soundbroadcasting at frequencies above 30 MHz

Working Party 10C (Chairman: C. Todd): Audio-frequencycharacteristics of sound broadcasting signals

Task Group 10-6 (Chairman: J. Chilton): Digital sound broadcasting atfrequencies below 30 MHz

SG 11: Broadcasting service (television)

Working Party 11A (Chairman: D. Wood): Television systems and databroadcasting

Working Party 11B (Chairman: J. Johann): Digital television (sourcecoding)

Working Party 11C (Chairman: S. Perpar): Terrestrial television(emission and planning parameters)

Working Party 10-11Q (Chairman: J.-P. Evain): Audio and videoquality evaluation (documents are posted under SG 11)

Working Party 10-11R (Chairman: P. Zaccarian): Recording forbroadcasting (documents are posted under SG 11)

Working Party 10-11S (Chairman: R. Zeitoun): Satellite broadcasting(documents are posted under SG 11)

Page 145: TND Complete

THE INTERNATIONAL TELECOMMUNICATION UNION (ITU)

Ericsson Radio Systems AB

5/038 02-LZU 102 152, Rev A, November 1999

9

Task Group 10/11 (Chairman: C. Weinzweig): Multimedia broadcastevolution and common content format (documents are posted under SG11)

Task Group 11/5 (Chairman: B. E. Aldous): Digital sound broadcastingat frequencies below 30 MHz

SG CCV: Coordination Committee for Vocabulary (Ms. D. Fabiani)

The Telecommunication Standardization Sector (ITU-T)The Telecommunication Standardization Sector is responsible for thestudy of technical, operational and tariff-related issues and to thenprovide worldwide recommendations that are to be used asdocumentation for telecommunications standardization. It is alsoresponsible for recommendations concerning the interconnection ofradio systems in public telecommunication networks and the necessaryperformance and availability required by such interconnections.Generally, ITU-T Recommendations are complied with since theyguarantee the worldwide interconnectivity of networks.

Supported by study groups, the policy-making and legislative functionsof the Telecommunication Standardization Sector present their findingsat World Telecommunication Standardization Conferences.

The Telecommunication Development Sector (ITU-D)The Telecommunication Development Sector is responsible forestablishing and highlighting telecommunication developments byoffering, organizing and coordinating technical cooperation andassistance activities. The policy functions are fulfilled by world andregional telecommunication development conferences, which aresupported by study groups.

Page 146: TND Complete

RADIO TRANSMISSION NETWORK AND FREQUENCY PLANNING

10 Ericsson Radio Systems AB

5/038 02-LZU 102 152, Rev A, November 1999

The General SecretariatThe General Secretariat is responsible for administrative and financialaspects, see Figure 2. In addition, it is also responsible for thepreparation, publication and distribution of reports dealing with changesin telecommunication issues, the organization and provision of logisticsupport to ITU conferences, the coordination of ITU efforts with theUnited Nations and other international organizations, that its Membersand users cooperate fully, the organization of worldwide and regionaltelecommunication exhibitions and discussion forums, to provide thepress, institutions, general public and telecommunications users withavailable information, and finally, to make electronic documents,publications and databases available and accessible.

DirectorBR

DirectorBDT

DirectorTSB

Secretary General

Deputy SecretaryGeneral

BureauBR

GeneralSecretariat

BureauBDT

BureauTSB

WTAC

Coordination Committee

Elected Officials Advisory BoardStaff

Figure 2: The ITU secretariats.

Page 147: TND Complete

THE INTERNATIONAL TELECOMMUNICATION UNION (ITU)

Ericsson Radio Systems AB

5/038 02-LZU 102 152, Rev A, November 1999

11

Advisory GroupsThe Director of each Bureau is assisted by a number of advisory groups(the Radiocommunication Advisory Group, RAG, theTelecommunication Standardization Advisory Group, TSAG, and theTelecommunication Development Advisory Board, TDAB) whose roleis to:

• review Sector activity priorities and strategies

• review the progress of work-program implementation

• provide guidelines for the undertakings of the Study Groups

• recommend measures that foster cooperation and coordination withother organizations as well as within the various constituents of theUnion.

The advisory groups are open to representatives of administrations, toorganizations authorized to participate in the work of the Union and toSector Study Group representatives.

The ordinary budget covers expenditures pertaining to theAdministrative Council, common Headquarters expenditures (staff,social security, premises, mission expenses, office expenses) andexpenditures pertaining to ITU conferences and meetings. TheTechnical Cooperation Special Accounts Budget covers administrativeexpenditures associated with projects that are related to technicalassistance grants to developing nations. Such projects are financed bythe United Nations Development Program and funds-in-trust. ThePublications Budget covers production costs for all publications, and isfinanced by the sale of these publications.

Financing of the ITU

ITU Member countriesAt each Plenipotentiary Conference, ITU Member countries choosetheir class of contribution, generally ranging from 1/16 to 40. Theclasses, 1/16 and 1/8, are reserved for those countries classified as LeastDeveloped Countries by the United Nations plus other countries, asselected by the ITU Council.

Page 148: TND Complete

RADIO TRANSMISSION NETWORK AND FREQUENCY PLANNING

12 Ericsson Radio Systems AB

5/038 02-LZU 102 152, Rev A, November 1999

The contribution of ITU Member countries covers their participation inall sectors and in all activities with the exception of regional radioconferences. The value of the contributory unit is calculated by dividingthe ordinary budget of the Union by the number of units contributed byMembers. Participation in regional radio conferences requires anadditional financial contribution, and is calculated by dividing the totalbudget for the conference by the number of units contributed by theMembers of that region.

Other organizations (Sector members)All other organizations that are permitted to participate in the work ofthe Union, may choose a class of contribution between 1/2 and 40 withthe exception of those classified as belonging to the Developmentsector, in which case classes of contributions may range from 1/16 to40. The class of contribution is multiplied by 1/5th of the value of thecontributory unit of Member countries.

The contribution covers participation in all Sector activities includingits conferences and/or assemblies, with the exception of radioconferences. A separate contribution is required for PlenipotentiaryConferences, World Conferences on International Telecommunications(which are not part of any Sector), radio conferences and Sectorconferences or assemblies in which the contributor is not a member. Insuch cases, the value of the contributory unit is calculated by dividingthe total budget for the conference/assembly by the number of unitscontributed by Members to the ordinary budget of the Union, multipliedby 1/5.

Each member, non-exempted international organization, operatingagency and scientific or industrial organization chooses the class ofcontribution in which it wishes to be included and then pays its annualcontributory share in advance, as calculated on the basis of the ordinarybudget.

Publications and seminars

The publications of the Sector are available for sale in three or more ofthe six official languages of the ITU. They are distributed in a variety offormats, including microfiche, CD-ROM, diskette and are also availableon-line.

The Bureau publishes the ITU-R Recommendations developed by theStudy Groups, as well as Radio Regulations, Frequency Assignment andAllotment Plans, HF Broadcasting Schedules plus a weekly circularcontaining notifications and findings.

Page 149: TND Complete

THE INTERNATIONAL TELECOMMUNICATION UNION (ITU)

Ericsson Radio Systems AB

5/038 02-LZU 102 152, Rev A, November 1999

13

Telecom Information Exchange Services (TIES)

TIES is a set of networked information services and resources for theglobal telecommunication community available via Internet. Someworking documents of Study Groups and other contributions related topre-working activities at conferences are only available via TIES. TIES-membership is not charged for the Ericsson community and registrationis available at the following address: http://www.itu.int/TIES/.

References

General information and ITU factual information were gathered fromInternet ”http//www.itu.int” during November 1999.

General information may also be obtained via Ericsson’s Intranet:http://standards.lme.ericsson.se. This is Ericsson’s source forinformation, documents and www-links in Telecom Standards andRegulations.

ITU-R Recommendations matrix

The ITU-R Recommendations currently used in the prediction cycle ofradio transmission planning are structured in Figure 3 according to themain four activity blocks.

Qu

alit

y &

Ava

ilab

ility ITU-T G.821 based

ITU-T G.826 based

ITU-T G.827 based

Att

enu

atio

nL

oss Atmospheric

Free-space

Reflection

Obstacle

Rain

Multipath - Flat

Multipath - Freq. Sel

Rain

Refraction - Diffract.

Fa

di

ng

Mec

hani

sms

ITU

-R P

.341

-4IT

U-R

P.4

53-6

ITU

-R P

.525

-2IT

U-R

P.5

26-5

ITU

-R P

.527

-3IT

U-R

P.5

30-7

ITU

-R P

.581

-2IT

U-R

P.6

76-3

ITU

-R P

.833

-1IT

U-R

P.8

34-2

ITU

-R P

.835

-2IT

U-R

P. 8

36-1

ITU

-R P

.837

-1IT

U-R

P.8

38IT

U-R

P.8

40-3

ITU

-R P

.841

ITU

-R P

.105

7IT

U-R

F.1

093-

1IT

U-R

F.5

56-1

ITU

-R F

.557

-4IT

U-R

F.5

94-4

ITU

-R F

.634

-4IT

U-R

F.6

95IT

U-R

F.6

96-2

ITU

-R F

.697

-2

ITU

-R F

.118

9-1

ITU

-R F

.124

1

ITU

-R F

.751

-2IT

U-R

F.1

092-

1

Interference assessment

Frequency arrangements

Fr

eque

ncy

Planning

ITU

-R F

.384

-7IT

U-R

F.3

87-8

ITU

-R F

.497

-6IT

U-R

F.5

95-6

ITU

-R F

.635

-5IT

U-R

F.7

46-4

ITU

-R F

.748

-3IT

U-R

F.1

098-

1IT

U-R

F.1

099-

3IT

U-R

F.6

99-4

ITU

-R F

.109

4-1

ITU

-R F

.110

8-2

ITU

-R F

.119

0IT

U-R

F.1

191-

1IT

U-R

SF

.358

-5IT

U-R

SF

.406

-8IT

U-R

SF

.100

4IT

U-R

SF

.100

5IT

U-R

SF

.100

6IT

U-R

SF

.100

8-1

Figure 3: The ITU-R Recommendations matrix.

Page 150: TND Complete

RADIO TRANSMISSION NETWORK AND FREQUENCY PLANNING

14 Ericsson Radio Systems AB

5/038 02-LZU 102 152, Rev A, November 1999

Appendices

Appendix A: ITU Top Management (1999-2002)Yoshio Utsumi (Japan): Secretary-General

Roberto Blois (Brazil): Deputy Secretary-General

Robert W. Jones (Canada) : Director, Radiocommunication Bureau(BR)

Hamadoun I. Touré (Mali): Director, Telecommunication DevelopmentBureau (BDT)

Houlin Zhao (China): Director, Telecommunication StandardizationBureau (TSB)

Appendix B: Radio Regulations Board (1999-2002) - MembersRadio Regulations Board (1999-2002) – Members:

Region A (Americas): Carlos Alejandro Merchán Escalante (Mexico)and James R. Carroll (USA).

Region B (West. Europe): Pierre Aboudarham (France) and GaborKovacs (Hungary).

Region C (East. Europe): Valery V. Timofeev (Russia) and Ryszard G.Struzak (Poland).

Region D (Africa): Jean-Baptiste Yao Kouakou (Côte d'Ivoire), JohnRay Kwabena Tandoh (Ghana) and Ahmed Toumi (Marocco).

Region E (Asia and Australasia): Ravindra N. Agarwal (India), MianMuhammad Javed (Pakistan) and George Hugh Railton (New Zealand).

Appendix C: ITU Landmarks1837 Invention of the first electric telegraph.

1865 17 May. Foundation of the International Telegraph Union bytwenty States with the adoption of the first Convention. First TelegraphRegulations.

1868 Vienna - Telegraph Conference. Decision to establish Unionheadquarters in Bern.

Page 151: TND Complete

THE INTERNATIONAL TELECOMMUNICATION UNION (ITU)

Ericsson Radio Systems AB

5/038 02-LZU 102 152, Rev A, November 1999

15

1869 Publication of Telegraph Journal.

1876 Alexander Graham Bell patents his invention of the telephone.

1885 Berlin - Telegraph Conference. First provisions for internationaltelephone service.

1895 First signals transmitted by radio-relay system.

1902 First radio transmissions of the human voice.

1906 Berlin - International Radiotelegraph Conference(Plenipotentiary). First Radiotelegraph Convention; ServiceRegulations. Adoption of SOS signal. First trials of broadcasting (voiceand music) using radiotelephony.

1920 Birth of sound-broadcasting.

1924 Paris - Creation of CCIF (international Telephone ConsultativeCommittee).

1925 Paris - Creation of CCIT (International Telegraph ConsultativeCommittee).

1927 Washington - Radiotelegraph Conference (Plenipotentiary).Creation of the CCIR (International Radio Consultative Committee).

1932 Madrid - Plenipotentiary Conference. Telegraph andRadiotelegraph Conventions merged into a single InternationalTelecommunication Convention. Telegraph Union changes name toInternational Telecommunication Union. Telegraph Journal becomesTelecommunication Journal.

1947 Atlantic City - Plenipotentiary Conference. Creation of IFRB(international Frequency Registration Board). Administrative Councilset up. ITU becomes a specialized agency of the United Nations.

1948 ITU headquarters transferred to Geneva.

1952 Buenos Aires - Plenipotentiary Conference. Start of ITU technicalcooperation activities.

1956 Geneva - CCIF and CCIT merged into new CCITT (InternationalTelegraph and Telephone Consultative Committee).

1957 Launching of Sputnik-1, the Earth's first artificial satellite.

1962 New building for ITU headquarters in Geneva.

Page 152: TND Complete

RADIO TRANSMISSION NETWORK AND FREQUENCY PLANNING

16 Ericsson Radio Systems AB

5/038 02-LZU 102 152, Rev A, November 1999

1963 Geneva - First World Space Radiocommunication Conference.

1965 Montreux - Plenipotentiary Conference. Centenary of the Union.Commemorative ceremony in Paris.

1971 First World Telecommunication Exhibition and FORUM -TELECOM 71.

1982 Nairobi - Plenipotentiary Conference. Independent Commissionfor World-Wide Telecommunications Development established

1983 World Communications Year (WCY).

1985 Asia TELECOM 85 - First regional telecommunication exhibitionin Asia and the Pacific region.

1986 Africa TELECOM 86 - First regional telecommunicationexhibition in Africa region.

1988 America TELECOM 88 - First regional telecommunicationexhibition in the Americas region.

1989 Nice - Plenipotentiary Conference, Creation of the High LevelCommittee to carry out an in-depth review of the structure andfunctioning of the Union, in order to recommend reforms enabling theorganization to respond to the challenges of the new internationaltelecommunications environment.

1990 125th anniversary of the ITU

1992 Torremolinos - World Administrative Radio Conference fordealing with frequency allocations in certain parts of the spectrum(WARC-92) Geneva - Plenipotentiary Conference to adopt anystructural reforms deemed necessary in light of the Recommendationsof the High Level Committee. Creation of three sectors(radiocommunications, telecommunication standardization anddevelopment) into which functions previously carried out by organs(IFRB, CCIR, CCITT, BDT) are integrated Europa TELECOM 92 -First regional telecommunication exhibition in Europe.

1993 Helsinki - First World Telecommunication StandardizationConference Geneva - First World Radiocommunication Conference andAssembly.

1994 Kyoto - Plenipotentiary Conference.

1995 130th anniversary of the ITU.

Page 153: TND Complete

THE INTERNATIONAL TELECOMMUNICATION UNION (ITU)

Ericsson Radio Systems AB

5/038 02-LZU 102 152, Rev A, November 1999

17

1998 Minneapolis - Plenipotentiary Conference.

Appendix D: ITU Secretary-Generals (1869 to present)Louis CURCHOD (Switzerland) Director 1 January 1869 to 24 May1872 and 23 February 1873 to 18 October 1889

Charles LENDI (Switzerland) Director from 24 May 1872 to 12 January1873

Auguste FREY (Switzerland) Director from 25 February 1890 to 28June 1890

Timothie ROTHEN (Switzerland) Director from 25 November 1890 to11 February 1897

Emile FREY (Swizerland) Director from 11 March 1897 to 1 August1921

Henri ETIENNE (Switzerland) Director from 2 August 1921 to 16December 1927

Joseph RABER (Switzerland) Director from 1 February 1928 to 30October 1934

Franz von ERNST (Switzerland) Director from 1 January 1935 to 31December 1949

Leon MULATIER (France) Secretary-General from 1 January 1950 to31 December 1953

Marco Aurelio ANDRADA (Argentina) Secretary-General from 1January 1954 to 18 June 1958

Gerald C. GROSS (United States) Secretary-General from 1 January1960 to 29 October 1965

Manohar Balaji SARWATE (India) Secretary-General from 30 October1965 to 19 February 1967

Mohamed Ezzedine MILI (Tunisia) Secretary-General 20-Feb-1967 to31-Dec-1973, 1-Jan-1974 to 31-Dec-1982

Richard E. BUTLER (Australia) Secretary-General from 1 January 1983to 31 October 1989

Pekka TARJANNE (Finland) Secretary-General from 1 November 1989to 31 December 1998.

Page 154: TND Complete

RADIO TRANSMISSION NETWORK AND FREQUENCY PLANNING

18 Ericsson Radio Systems AB

5/038 02-LZU 102 152, Rev A, November 1999

Yoshio UTSUMI (Japan) Secretary General from 1 January 1999.

Appendix E: AcronymsITU International Telecommunication Union

SG General Secretariat

WTAC World Telecommunication Advisory Council

ITU-R Radiocommunication Sector

BR Radiocommunication Bureau

ITU-R Recommendations

RRB Radio Regulations Board

SG Study Groups

RAG Radiocommunication Advisory Group

WRC World Radiocommunication Conference

RA Radiocommunication Assembly

RRC Regional Radiocommunication Conference

ITU-T Telecommunication Standardization Sector

TSB Telecommunication Standardization Bureau

ITU-T Recommendations

SG Study Groups

TSAG Telecommunication Standardization Advisory Group

WTSC World Telecommunication Standardization Conference

ITU-D Telecommunication Development Sector

BDT Telecommunication Development Bureau

ITU-D Recommendations

SG Study Groups

TDAB Telecommunication Development Advisory Board

Page 155: TND Complete

THE INTERNATIONAL TELECOMMUNICATION UNION (ITU)

Ericsson Radio Systems AB

5/038 02-LZU 102 152, Rev A, November 1999

19

WTDC World Telecommunication Development Conference

RTDC Regional Telecommunication Development Conference

WCIT World Conference on International Telecommunication

Appendix F: ITU-R RecommendationsBO Series Recommendations - Broadcasting satellite service (sound andtelevision) (20)

BR Series Recommendations - Sound and television recording (29)

BS Series Recommendations - Broadcasting service (sound) (46)

BT Series Recommendations - Broadcasting service (television) (63)

F Series Recommendations - Fixed service (123)

IS Series Recommendations - Inter-service sharing and compatibility(10)

M Series Recommendations - Mobile, radiodetermination, amateur andrelated satellite services (122)

P Series Recommendations - Radiowave Propagation (67)

RA Series Recommendations - Radioastronomy (6)

S Series Recommendations - Fixed satellite service (57)

SA Series Recommendations - Space applications and meteorology (45)

SF Series Recommendations - Frequency sharing between the fixedsatellite service and the fixed service (16)

SM Series Recommendations - Spectrum management (41)

SNG Series Recommendations - Satellite news gathering (7)

TF Series Recommendations - Time signals and frequency standardsemissions (21)

V Series Recommendations - Vocabulary and related subjects (12)

Page 156: TND Complete

RADIO TRANSMISSION NETWORK AND FREQUENCY PLANNING

20 Ericsson Radio Systems AB

5/038 02-LZU 102 152, Rev A, November 1999

Appendix G: P Series Recommendations - Radiowave Propagation[P.310-9] Definitions of terms relating to propagation in non-ionizedmedia

[P.311-8] Acquisition, presentation and analysis of data in studies oftropospheric propagation

[P.313-8] (REVISED) Exchange of information for short-term forecastsand transmission of ionospheric disturbance warnings

[P.341-4] (REVISED) The concept of transmission loss for radio links

[P.368-7a] Ground-wave propagation curves for frequencies between 10kHz and 30 MHz

[P.368-7b] Ground-wave propagation curves for frequencies between10 kHz and 30 MHz

[P.368-7c] Ground-wave propagation curves for frequencies between 10kHz and 30 MHz

[P.370-7] (REVISED) VHF and UHF propagation curves for thefrequency range from 30 MHz to 1000 MHz. Broadcasting services

[P.371-7] (REVISED) Choice of indices for long-term ionosphericpredictions

[P.372-6a] Radio noise

[P.372-6b] Radio noise

[P.372-6c] Radio noise

[P.372-6d] Radio noise

[P.372-6e] Radio noise

[P.373-7] (REVISED) Definitions of maximum and minimumtransmission frequencies

[P.452-8] Prediction procedure for the evaluation of microwaveinterference between stations on the surface of the Earth at frequenciesabove about 0.7 GHz

[P.453-6] The radio refractice index: its formula and refractivity data

[P.525-2] Calculation of free space attenuation

Page 157: TND Complete

THE INTERNATIONAL TELECOMMUNICATION UNION (ITU)

Ericsson Radio Systems AB

5/038 02-LZU 102 152, Rev A, November 1999

21

[P.526-5] Propagation by diffraction

[P.527-3] Electrical characteristics of the surface of the Earth

[P.528-2] Propagation curves for aeronautical mobile andradionavigation services using the VHF, UHF and SHF bands

[P.529-2] (REVISED) Prediction methods for the terrestrial land mobileservice in the VHF and UHF bands

[P.530-7] Propagation data and prediction methods required for thedesign of terrestrial line-of-sight systems

[P.531-4] Ionospheric propagation data and prediction methodsrequired for the design of satellite services and systems

[P.532-1] Ionospheric effects and operational considerations associatedwith artificial modification of the ionosphere and the radio-wavechannel

[P.533-5] (REVISED) HF propagation prediction method

[P.534-3] Method for calculating sporadic-E field strength

[P.581-2] The concept of ''worst month"

[P.616] Propagation data for terrestrial maritime mobile servicesoperating at frequencies above 30 MHz

[P.617-1] Propagation prediction techniques and data required for thedesign of trans-horizon radio-relay systems

[P.618-5] Datos de propagación y métodos de predicción necesariospara el diseño sistemas de telecomunicación Tierra-espacio

[P.619-1] Propagation data required for the evaluation of interferencebetween stations in space and those on the surface of the Earth

[P.620-3] Propagation data required for the evaluation of coordinationdistances in the frequency range 0.85-60 GHz

[P.676-3] Attenuation by atmospheric gases

[P.678-1] Characterization of the natural variability of propagationphenomena

[P.679-1] Propagation data required for the design of broadcasting-satellite systems

Page 158: TND Complete

RADIO TRANSMISSION NETWORK AND FREQUENCY PLANNING

22 Ericsson Radio Systems AB

5/038 02-LZU 102 152, Rev A, November 1999

[P.680-2] Propagation data required for the design of Earth-spacemaritime mobile telecommunication systems

[P.681-3] Propagation data required for the design of Earth-space landmobile telecommunication systems

[P.682-1] Propagation data required for the design of Earth-spaceaeronautical mobile telecommunication systems

[P.684-1] Prediction of field strength at frequencies below about 500kHz

[P.832-1a] World atlas of ground conductivities

[P.832-1b] World atlas of ground conductivities

[P.832-1c] World atlas of ground conductivities

[P.832-1d] World atlas of ground conductivities

[P.833-1] Attenuation in vegetation

[P.834-2] Effects of tropospheric refraction on radiowave propagation

[P.835-2] Reference standard atmospheres

[P.836-1] Water vapour: surface density and total columnar content

[P.837-1] Characteristics of precipitation for propagation modelling

[P.838] Specific attenuation model for rain for use in predictionmethods

[P.839-1] Rain height model for prediction methods

[P.840-2] Attenuation due to clouds and fog

[P.841] Conversion of annual statistics to worst-months statistics

[P.842-1] Computation of reliability and compatibility of HF radiosystems

[P.843-1] Communication by meteor-burst propagation

[P.844-1] Ionospheric factors affecting frequency sharing in the VHFand UHF bands (30 MHz - 3 GHz)

[P.845-3] HF field-strength measurement

Page 159: TND Complete

THE INTERNATIONAL TELECOMMUNICATION UNION (ITU)

Ericsson Radio Systems AB

5/038 02-LZU 102 152, Rev A, November 1999

23

[P.846-1] (REVISED) Measurements of ionospheric and relatedcharacteristics

[P.1057] Probability distributions relevant to radiowave propagationmodelling

[P.1058-1] Digital topographic databases for propagation studies

[P.1060] Propagation factors affecting frequency sharing in HFterrestrial systems

[P.1144] (NEW) Guide to the application of the propagation methods ofStudy Group 3

[P.1145] (NEW) Propagation data for the terrestrial land mobile servicein the VHF and UHF bands

[P.1146] (NEW) The prediction of field strength for land mobile andterrestrial broadcasting services in the frequency range from 1 to 3 GHz

[P.1147] (NEW) Prediction of sky-wave field strength at frequenciesbetween about and 1 700 kHz

[P.1148-1] Standardized procedure for comparing predicted andobserved HF sky-wave signal intensities and the presentation of suchcomparisons

[P.1238] Propagation data and prediction models for the planning ofindoor radiocommunication systems and radio local area networks inthe frequency range 900 MHz to 100 GHz

[P.1239] ITU-R Reference ionospheric characteristics

[P.1240] ITU-R Methods of basic MUF, operational MUF and ray-pathprediction

[P.1321] Propagation factors affecting systems using digital modulationtechniques at LF and MF

[P.1322] Radiometric estimation of atmospheric attenuation

Appendix H: F Series Recommendations - Fixed service[F.106-1] Voice-frequency telegraphy on radio circuits

[F.162-3] Use of directional transmitting antennas in the fixed serviceoperating in bands below about 30 MHz

Page 160: TND Complete

RADIO TRANSMISSION NETWORK AND FREQUENCY PLANNING

24 Ericsson Radio Systems AB

5/038 02-LZU 102 152, Rev A, November 1999

[F.240-6] Signal-to-interference protection ratios for various classes ofemission in the fixed service below about 30 MHz

[F.246-3] Frequency-shift keying

[F.268-1] Interconnection at audio frequencies of radio-relay systemsfor telephony

[F.270-2] Interconnection at video signal frequencies of radio-relaysystems for television

[F.275-3] Pre-emphasis characteristic for frequency modulation radio-relay systems for telephony using frequency-division multiplex

[F.276-2] Frequency deviation and the sense of modulation for analogueradio-relay systems for television

[F.283-5] Radio-frequency channel arrangements for low and mediumcapacity analogue or digital radio-relay systems operating in the 2 GHzband

[F.290-3] Maintenance measurements on radio-relay systems fortelephony using frequency-division multiplex

[F.302-3] Limitation of interference from trans-horizon radio-relaysystems

[F.305] Stand-by arrangements for radio-relay systems for televisionand telephony

[F.306] Procedure for the international connection of radio-relaysystems with different characteristics

[F.335-2] Use of radio links in international telephone circuits

[F.338-2] Bandwidth required at the output of a telegraph or telephonereceiver

[F.339-6] Bandwidths, signal-to-noise ratios and fading allowances incomplete systems

[F.342-2] Automatic error-correcting system for telegraph signalstransmitted over radio circuits

[F.345] Telegraph distortion

Page 161: TND Complete

THE INTERNATIONAL TELECOMMUNICATION UNION (ITU)

Ericsson Radio Systems AB

5/038 02-LZU 102 152, Rev A, November 1999

25

[F.347] Classification of multi-channel radiotelegraph systems for long-range circuits operating at frequencies below about 30 MHz and thedesignation of the channels in these systems

[F.348-4] Arrangements of channels in multi-channel single-sidebandand independent-sideband transmitters for long-range circuits operatingat frequencies below about 30 MHz

[F.349-4] Frequency stability required for systems operating in the HFfixed service to make the use of automatic frequency controlsuperfluous

[F.380-4] Interconnection at baseband frequencies of radio-relaysystems for telephony using frequency-division multiplex

[F.381-2] Conditions relating to line regulating and other pilots and tolimits for the residues of signals outside the baseband in theinterconnection of radio-relay and line systems for telephony

[F.382-6] Radio-frequency channel arrangements for radio-relaysystems operating in the 2 and 4 GHz bands

[F.383-5] Radio-frequency channel arrangements for high capacityradio-relay systems operating in the lower 6 GHz band

[F.384-6] (REVISED) Radio-frequency channel arrangements formedium and high capacity analogue or digital radio-relay systemsoperating in the upper 6 GHz band

[F.385-6] Radio-frequency channel arrangements for radio-relaysystems operating in the 7 GHz band

[F.386-4] Radio-frequency channel arrangements for radio-relaysystems operating in the 8 GHz band

[F.387-7] (REVISED) Radio-frequency channel arrangements for radio-relay systems operating in the 11 GHz band

[F.388] Radio-frequency channel arrangements for trans-horizon radio-relay systems

[F.389-2] Preferred characteristics of auxiliary radio-relay systemsoperating in the 2,4, 6 or 11 GHz bands

[F.390-4] Definitions of terms and references concerning hypotheticalreference circuits and hypothetical reference digital paths for radio-relaysystems

Page 162: TND Complete

RADIO TRANSMISSION NETWORK AND FREQUENCY PLANNING

26 Ericsson Radio Systems AB

5/038 02-LZU 102 152, Rev A, November 1999

[F.391] Hypothetical reference circuit for radio-relay systems fortelephony using frequency-division multiplex with a capacity of 12 to60 telephone channels

[F.392] Hypothetical reference circuit for radio-relay systems fortelephony using frequency-division multiplex with a capacity of morethan 60 telephone channels

[F.393-4] Allowable noise power in the hypothetical reference circuitfor radio-relay systems for telephony using frequency-divisionmultiplex

[F.395-2] Noise in the radio portion of circuits to be established overreal radio-relay links for FDM telephony

[F.396-1] Hypothetical reference circuit for trans-horizon radio-relaysystems for telephony using frequency-division multiplex

[F.397-3] Allowable noise power in the hypothetical reference circuit oftrans-horizon radio-relay systems for telephony using frequency-division multiplex

[F.398-3] Measurements of noise in actual traffic over radio-relaysystems for telephony using frequency-division multiplex

[F.399-3] Measurement of noise using a continuous uniform spectrumsignal on frequency-division multiplex telephony radio-relay systems

[F.400-2] Service channels to be provided for the operation andmaintenance of radio-relay systems

[F.401-2] Frequencies and deviations of continuity pilots for frequencymodulation radio-relay systems for television and telephony

[F.402-2] The preferred characteristics of a single sound channelsimultaneously transmitted with a television signal on an analogueradio-relay system

[F.403-3] Intermediate-frequency characteristics for the interconnectionof analogue radio-relay systems

[F.404-2] Frequency deviation for analogue radio-relay systems fortelephony using frequency-division multiplex

[F.405-1] Pre-emphasis characteristics for frequency modulation radio-relay systems for television

Page 163: TND Complete

THE INTERNATIONAL TELECOMMUNICATION UNION (ITU)

Ericsson Radio Systems AB

5/038 02-LZU 102 152, Rev A, November 1999

27

[F.436-4] (REVISED) Arrangement of voice-frequency , frequency-shift telegraph channels over HF radio circuits

[F.444-3] Preferred characteristics for multi-line switchingarrangements of analogue radio-relay systems

[F.454-1] Pilot carrier level for HF single-sideband and independent-sideband reduced-carrier systems

[F.455-2] Improved transmission system for HF radiotelephone circuits

[F.463-1] Limits for the residues of signals outside the baseband ofradio-relay systems for television

[F.480] Semi-automatic operation on HF radiotelephone circuits.Devices for remote connection to an automatic exchange byradiotelephone circuits

[F.497-5] (REVISED) Radio-frequency channel arrangements for radio-relay systems operating in the 13 GHz frequency band

[F.518-1] Single-channel simplex ARQ telegraph system

[F.519] Single-channel duplex ARQ telegraph system

[F.520-2] Use of high frequency ionospheric channel simulators

[F.555-1] Permissible noise in the hypothetical reference circuit ofradio-relay systems for television

[F.556-1] Hypothetical reference digital path for radio-relay systemswhich may form part of an integrated services digital network with acapacity above the second hierarchical level

[F.557-3] Availability objective for radio-relay systems over ahypothetical reference circuit and a hypothetical reference digital path

[F.592-2] Terminology used for radio-relay systems

[F.593] Noise in real circuits of multi-channel trans-horizon FM radio-relay systems of less than 2500 km

[F.594-3] Allowable bit error ratios at the output of the hypotheticalreference digital path for radio-relay systems which may form part of anintegrated services digital network

[F.595-4] (REVISED) Radio-frequency channel arrangements for radio-relay systems operating in the 18 GHz frequency band

Page 164: TND Complete

RADIO TRANSMISSION NETWORK AND FREQUENCY PLANNING

28 Ericsson Radio Systems AB

5/038 02-LZU 102 152, Rev A, November 1999

[F.596-1] Interconnection of digital radio-relay systems

[F.612] Measurement of reciprocal mixing in HF communicationreceivers in the fixed service

[F.613] The use of ionospheric channel sounding systems operating inthe fixed service at frequencies below about 30 MHz

[F.634-3] Error performance objectives for real digital radio-relay linksforming part of a high-grade circuit within an integrated services digitalnetwork

[F.635-3] (REVISED) Radio-frequency channel arrangements based ona homogeneous pattern for radio-relay systems operating in the 4 GHzband

[F.636-3] Radio-frequency channel arrangements for radio-relaysystems operating in the 15 GHz band

[F.637-2] Radio-frequency channel arrangements for radio-relaysystems operating in the 23 GHz band

[F.695] Availability objectives for real digital radio-relay links formingpart of a high-grade circuit within an integrated services digital network

[F.696-1] Error performance and availability objectives for hypotheticalreference digital sections utilizing digital radio-relay systems formingpart or all of the medium-grade portion of an ISDN connection

[F.697-1] Error performance and availabiltiy objectives for the local-grade portion at each end of an ISDN connection utilizing digital radio-relay systems

[F.698-2] Preferred frequency bands for trans-horizon radio-relaysystems

[F.699-4] Reference radiation patterns for line-of-sight radio-relaysystem antennas for use in coordination studies and interferenceassessment in the frequency range from 1 to about 40 GHz

[F.700-2] Error performance and availability measurement algorithmfor digital radio-relay links at the system bit-rate interface

[F.701-1] Radio-frequency channel arrangements for analogue anddigital point-to-multipoint radio systems operating in frequency bandsin the range 1.427 to 2.690 GHz

[F.745] CCIR Recommendations for analogue radio-relay systems

Page 165: TND Complete

THE INTERNATIONAL TELECOMMUNICATION UNION (ITU)

Ericsson Radio Systems AB

5/038 02-LZU 102 152, Rev A, November 1999

29

[F.746-3] Radio-frequency channel arrangements for radio-relaysystems

[F.747] Radio-frequency channel arrangements for radio-relay systemsoperating in the 10 GHz band

[F.748-2] (REVISED) Radio-frequency channel arrangements for radio-relay systems operating in the 25, 26 and 28 GHz bands

[F.749-1] Radio-frequency channel arrangements for radio-relaysystems operating in the 38 GHz band

[F.750-2] (REVISED) Architectures and functional aspects of radio-relay systems for SDH-based networks

[F.751-1] Transmission characteristics and performance requirements ofradio-relay systems for SDH-based networks

[F.752-1] Diversity techniques for radio-relay systems

[F.753] Preferred methods and characteristics for the supervision andprotection of digital radio-relay systems

[F.754] Radio-relay systems in bands 8 and 9 for the provision oftelephone trunk connections in rural areas

[F.755-1] Point-to-multipoint systems used in the fixed service

[F.756] TDMA point-to-multipoint systems used as radio concentrators

[F.757] Basic system requirements and performance objectives forcellular type mobile systems used as fixed systems

[F.758] Considerations in the development of criteria for sharingbetween the terrestrial fixed service and other services

[F.759] Use of frequencies in the band 500 to 3 000 MHz for radio-relay systems

[F.760-1] Protection of terrestrial line-of-sight radio-relay systemsagainst interference from the broadcasting-satellite service in the bandsnear 20 GHz

[F.761] Frequency sharing between the fixed service and passivesensors in the band 18.6-18.8 GHz

[F.762-2] (REVISED) Main characteristics of remote control andmonitoring systems for HF receiving and transmitting stations

Page 166: TND Complete

RADIO TRANSMISSION NETWORK AND FREQUENCY PLANNING

30 Ericsson Radio Systems AB

5/038 02-LZU 102 152, Rev A, November 1999

[F.763-2] (REVISED) Data transmission over HF circuits using phase-shift keying

[F.764-1] Minimum requirements for HF radio systems using a packettransmission protocol

[F.1092] Error performance objectives for constant bit rate digital pathat or above the primary rate carried by digital radio-relay systems whichmay form part of the international portion of a 27 500 KM hypotheticalreference path

[F.1093] Effects of multipath propagation on the design and operationof line-of-sight digital radio-relay systems

[F.1094-1] (REVISED) Maximum allowable error performance andavailability degradations to digital radio-relay systems arising frominterference from emissions and radiations from other sources

[F.1095] A procedure for determining coordination area between radio-relay stations of the fixed service

[F.1096] Methods of calculating line-of-sight interference into radio-relay systems to account for terrain scattering

[F.1097] Interference mitigation options to enhance compatibilitybetween radar systems and digital radio-relay systems

[F.1098-1] (REVISED) Radio-frequency channel arrangements forradio-relay systems in the 1 900-2 300 MHz band

[F.1099-1] (REVISED) Radio-frequency channel arrangements forhigh-capacity digital radio-relay systems in the 5 GHz (4 400-5 000MHz) band

[F.1100] Radio-frequency channel arrangements for radio-relay systemsoperating in the 55 GHz band

[F.1101] Characteristics of digital radio-relay systems below about 17GHz

[F.1102] Characteristics of radio-relay systems operating in frequencybands above about 17 GHz

[F.1103] Radio-relay systems operating in bands 8 and 9 for theprovision of subscriber telephone connections in rural areas

[F.1104] Requirements for point-to-multipoint radio systems used in thelocal grade portion of an ISDN connection

Page 167: TND Complete

THE INTERNATIONAL TELECOMMUNICATION UNION (ITU)

Ericsson Radio Systems AB

5/038 02-LZU 102 152, Rev A, November 1999

31

[F.1105] Transportable fixed radiocommunications equipment for reliefoperations

[F.1106] Effects of propagation on the design and operation of trans-horizon radio-relay systems

[F.1107] Probabilistic analysis for calculating interference into the fixedservice from satellites occupying the geostationary orbit

[F.1108-1] (REVISED) Determination of the criteria to protect fixedservice receivers from the emissions of space stations operating in non-geostationary orbits in shared frequency bands

[F.1109] ITU-R Recommendations relating to systems in the fixedservice service operating at frequencies below about 30 MHz which arenot reprinted

[F.1110-1] (REVISED) Adaptive radio systems for frequencies belowabout 30 MHz

[F.1111-1] (REVISED) Improved Lincompex system for HFradiotelephone circuits

[F.1112-1] (REVISED) Digitized speech transmissions for systemsoperating below about 30 MHz

[F.1113] Radio systems employing meteor-burst propagation

[F.1189] (NEW) Error-performance objectives for constant bit ratedigital paths at or above the primary rate carried by digital radio-relaysystems which may form part or all of the national portion of a 27 500km hypothetical reference path

[F.1190] (NEW) Protection criteria for digital radio-relay systems toensure compatibility with radar systems in the radiodeterminationservice

[F.1191] (NEW) Bandwidths and unwanted emissions of digital radio-relay systems

[F.1192] (NEW) Traffic capacity of automatically controlled radiosystems and networks in the HF fixed service

[F.1241] Performance degradation due to interf. from other servicessharing the same freq. bands on a primary basis with digital radio-relaysyst. oper. at or above the primary rate and which may form part of theintern. portion of a 27 500 km hypoth. ref. path

Page 168: TND Complete

RADIO TRANSMISSION NETWORK AND FREQUENCY PLANNING

32 Ericsson Radio Systems AB

5/038 02-LZU 102 152, Rev A, November 1999

[F.1242] Radio-frequency channel arrangements for digital radiosystems operating in the range 1 350 MHz to 1 530 MHz

[F.1243] Radio-frequency channel arrangements for digital radiosystems operating in the range 2 290-2 670 MHz

[F.1244] Radio local area networks (RLANs)

[F.1245] Mathematical model of average radiation patterns for line-of-sight point-to-point radio-relay system antennas for use in certaincoordination studies and interference assessment in the frequency rangefrom 1 to about 40 GHz

[F.1246] Reference bandwidth of receiving stations in the fixed serviceto be used in coordination of frequency assignments with transmittingspace stations in the mobile-satellite service in the 1-3 GHz range

[F.1247] Technical and operational characteristics of systems in thefixed service to facilitate sharing with the space research, spaceoperation and Earth exploration-satellite services operating in the bands2 025-2 110 MHz and 2 200-2 290 MHz

[F.1248] Limiting interference to satellites in the space science servicesfrom the emissions of trans-horizon radio-relay systems in the bands 2025-2 110 MHz and 2 200-2 290 MHz

[F.1249] Maximum equivalent isotropically radiated power oftransmitting stations in the fixed service operating in the frequency band25.25-27.5 GHz shared with the inter-satellite service

Page 169: TND Complete

i

QUALITY AND AVAILABILITYTARGETS

This chapter provides an extensive description of digitaltransmission network models used in error performanceanalysis and quality and availability targets in accordancewith ITU-T Recommendations G.821 and G.826. The chapterdiscusses quality and availability parameters, their calculationand their relationships to existing atmospheric fadingmechanisms.

TABLE OF CONTENTSPredicting quality .............................................................................................................................................. 1Quality and availability targets.......................................................................................................................... 1

Why and at what price? ....................................................................................................................... 1Recommendations - background ......................................................................................................... 1

ITU-T Recommendation G.821 ............................................................................................ 2ITU-T Recommendation G.826 ............................................................................................ 2

Digital transmission network models ................................................................................................................ 2Introduction......................................................................................................................................... 2Hypothetical Reference Connection (HRX)........................................................................................ 2

Definition .............................................................................................................................. 2Classification......................................................................................................................... 3Example ................................................................................................................................ 4

Other digital transmission network models ......................................................................................... 4Hypothetical Reference Digital Path (HRDP)..................................................................................... 5

Hypothetical Reference Digital Section (HRDS) .................................................................. 5Hypothetical Reference Path (HRP)...................................................................................... 6

The ITU-T Rec. G821 - basic concepts............................................................................................................. 7Bit error............................................................................................................................................... 7Bit rate................................................................................................................................................. 7Bit-error ratio ...................................................................................................................................... 7Expressing the quality targets.............................................................................................................. 7Bit-error ratio and time intervals ......................................................................................................... 7Available and unavailable time - definition......................................................................................... 8Available and unavailable time - example........................................................................................... 8Expressing available and unavailable time.......................................................................................... 8Definitions of events occurring during available time......................................................................... 9BER at bit rate 64 kbit/s ...................................................................................................................... 9Error performance objectives .............................................................................................................. 9Definition of availability parameters ................................................................................................... 9

Errored second ratio .............................................................................................................. 9Severely errored second ratio................................................................................................ 9

Page 170: TND Complete

ii

Quality and availability parameters ..................................................................................................... 10Performance parameters and objective allocation ............................................................................... 10Objective allocation for the three circuit classes ................................................................................. 11End-to-end quality allocation in the network model HRX .................................................................. 11The derivation of the quality parameters values.................................................................................. 12Quality allocation - summary .............................................................................................................. 13

Radio applications............................................................................................................................................. 14Local-grade portion of the HRX ......................................................................................................... 14

Quality objectives - ITU-R Rec. F.697-1 .............................................................................. 14Availability objectives - ITU-R Rec. F.697-1 ....................................................................... 15

Medium-grade portion of the HRX ..................................................................................................... 15Quality objectives - ITU-R Rec. F.696-1 (addresses to G.821) ............................................ 15Availability objectives........................................................................................................... 16

Digital section - medium grade ........................................................................................................... 16Quality classification and allocation - ITU-T Rec. 921......................................................... 16Quality objectives - ITU-R Rec. F.696-1 .............................................................................. 16The derivation of the quality parameters values - ITU-R Rec. F.696-1 ................................ 17Unavailability objectives - ITU-R Rec. F.696-1 ................................................................... 18

High-grade portion of the HRX........................................................................................................... 19Quality objectives - ITU-T Rec. G.821................................................................................. 19Availability objectives........................................................................................................... 19

Hypothetical Reference Digital Path - HRDP (high grade)................................................................. 19Quality objectives - ITU-R F.594.3 ...................................................................................... 19Availability objectives - ITU-R Rec. F.557-3 ....................................................................... 20

Real Digital Radio Link (high grade) .................................................................................................. 20Quality objectives - ITU-R Rec. F.634-3 .............................................................................. 20Availability objectives - ITU-R Rec. F.695 .......................................................................... 20

Summary of network models............................................................................................................................. 21G.821 - HRX....................................................................................................................................... 21G.821 - HRDS..................................................................................................................................... 22G.821 - HRDP..................................................................................................................................... 23G.821 - RDRL..................................................................................................................................... 23G.826 - HRP........................................................................................................................................ 24

Quality and availability targets - summary........................................................................................................ 24Quality targets ..................................................................................................................................... 24Availability targets .............................................................................................................................. 25

Reports and recommendations - summary......................................................................................................... 25Quality and availability parameters versus fading mechanisms......................................................................... 26

Fading occurrence ............................................................................................................................... 26Calculation of the unavailability parameters - Rec. G.821.................................................................. 27

Unavailable time ratio (UATR)............................................................................................. 27Available time ratio (UATR) ................................................................................................ 28Severely errored second ratio (SESR)................................................................................... 28Errored second ratio (ESR) ................................................................................................... 28

Planning unavailable time ................................................................................................................... 28The ITU-T Recommendation G.826 - basic concepts ....................................................................................... 29

Introduction......................................................................................................................................... 29Hypothetical Reference Path (HRP).................................................................................................... 29Available and unavailable time ........................................................................................................... 30Definition of block .............................................................................................................................. 30Events occurring during available time ............................................................................................... 30

Errored Block (EB) ............................................................................................................... 30Errored Second (ES) ............................................................................................................. 30Severely Errored Second (SES) ............................................................................................ 31Background Block Error (BBE)............................................................................................ 31

Definitions of quality parameters ........................................................................................................ 31

Page 171: TND Complete

iii

Errored Second Ratio (ESR) ................................................................................................. 31Severely Errored Second Ratio (SESR) ................................................................................ 31Background Block Error Ratio (BBER)................................................................................ 31

A comparison of SESR (G.826) and SESR (G.821) ........................................................................... 31End-to-end objectives apportionment in the HRP ............................................................................... 32Quality objectives allocation in the HRP ............................................................................................ 33

National portion .................................................................................................................... 33International portion.............................................................................................................. 34

Unavailability allocation in the HRP................................................................................................... 36Radio applications of the ITU-T´S Rec. G.826................................................................................................. 36

National portion of the HRP - basic sections ...................................................................................... 37Quality objectives allocation................................................................................................. 38

Long-haul section.................................................................................................... 38Short-haul section.................................................................................................... 38Access section ......................................................................................................... 39

Summary of quality objectives .............................................................................................. 39International portion of the HRP ......................................................................................................... 40Radio applications of the ITU-T Rec. G.826 ...................................................................................... 42

The ITU-T Recommendation G.827 ................................................................................................................. 42References ......................................................................................................................................................... 43

Page 172: TND Complete

ii

Page 173: TND Complete

QUALITY AND AVAILABILITY TARGETS

Ericsson Radio Systems AB 1

6/038 02-LZU 102 152, Rev A, November1999

Predicting quality

1. Is the connection available?

2. If yes, what are the values of the availability and quality parameters?

3. How good is the connection in comparison with the currentavailability and quality targets?

Quality and availability targets

Why and at what price?During the process of planning a radio connection, adequate quality andavailability targets are established following careful consideration ofthose parameters that affect these attributes. These targets then provide,to a certain degree, a ”built-in” confidence level that guard againstfading caused by interactions between the transmitted signals and theatmosphere, topography and the signals transmitted by other radiostations located in the vicinity.

Quality and availability targets are often a result of a compromise. Acompromise between, on the one hand, compliance with requirementsof the service, and on the other hand, current economic and technicallimitations.

Recommendations - backgroundThe recommendations in this book take into account that services arebased on the concept of an Integrated Services Digital Network (ISDN).The following ITU-T recommendations will be covered:

• Recommendation G.821

• Recommendation G.826

Page 174: TND Complete

RADIO TRANSMISSION NETWORK AND FREQUENCY PLANNING

2 Ericsson Radio Systems AB

6/038 02-LZU 102 152 Rev A, November 1999

ITU-T Recommendation G.821

Recommendation G.821 was developed during the late 70’s andadopted in 1980. It defined quality and availability parameters andobjectives applicable to international digital connections operating at 64kbit/s. An annex (Annex D) indicating how to derive error performancedata at higher bit rates was added to the former recommendation.

G.821 is now restricted to bit rates in the range between 64 kbit/s andbelow the primary rate of the digital hierarchy. Additional experimentalwork indicated in many cases, however, that the annex D turned out togive doubtful results making necessary a new recommendation.

ITU-T Recommendation G.826

Recommendation G.826 was developed during the late 80’s andadopted in 1993. It defines quality and availability parameters andobjectives applicable for constant bit-rate digital paths operating at bitrates at and above the primary rate of the digital hierarchy.

Digital transmission network models

IntroductionIn order to facilitate the study of the error performance of digitaltransmission systems (bit errors, jitter, transmission delays, availability,etc), it is occasionally necessary to define digital transmission networkmodels that comprise a combination of different types of transmissiondevices. These models are hypothetical in that they include entities of adefined length and composition corresponding to real digital radio-relaylinks present in international networks.

Transmission may be conducted via optical fiber, radio-relay systems,satellite systems or cable.

Hypothetical Reference Connection (HRX)

Definition

A digital HRX (Hypothetical Reference Connection) is a network modelin which studies relating to overall performance may be conducted,thereby facilitating the formulation of standards and objectives. TheHRX is the starting-point for the apportionment strategy found in ITU-T Recommendation G.821.

Page 175: TND Complete

QUALITY AND AVAILABILITY TARGETS

Ericsson Radio Systems AB 3

6/038 02-LZU 102 152, Rev A, November1999

The HRX is a 27,500 km connection operating at 64 kbit/s and issubdivided into circuit grades (classes) that represent the sections in areal end-to-end connection.

The grades may be local, medium and high and are illustrated in Figure1.

Highgrade

Mediumgrade

Mediumgrade

Localgrade

Localgrade

LE ISC LEISC

1250 km 25,000 km 1250 km

27,500 km

T=Terminal Point, LE= LocalISC=International Switching Center

TT

Figure 1: The Hypothetical Reference Connection and its grades.

A precise location of the boundary between the medium and the highgrade of the HRX is presently not available.

Classification

Local grade circuits are defined as those operating between thesubscribers and the local exchange at rates below 2 Mbit/s. Typically,they are metallic subscriber loop circuits.

Medium grade circuits are those operating between local exchangesand the national network. The combined length of the local and mediumgrade links must not exceed 1250 km.

High grade circuits are long-haul links, for example, satelliteconnections and international connections operating at primarily highbit-rates.

Page 176: TND Complete

RADIO TRANSMISSION NETWORK AND FREQUENCY PLANNING

4 Ericsson Radio Systems AB

6/038 02-LZU 102 152 Rev A, November 1999

Example

An example of a possible geographical location of grades is illustratedin Figure 2.

T

LETT

ISC

TT

T

T

T = TerminalLE = Local ExchangeISC = International Switching Center

Medium-grade

Local-grade

Fukuyama

Uunimannaq

CopacabanaHigh-grade

High-grade

High-grade

Figure 2: Possible geographical location of grades.

Other digital transmission network modelsThe following digital transmission network models will be studied:

Hypothetical Reference Digital Link (HRDL) employed by ITU-T indigital systems, the length of which is 2500 km.

Hypothetical Reference Digital Path (HRDP) employed by ITU-R andwhich is equivalent to HRDL. Designed for the performancespecification of transmission systems as radio systems.

Page 177: TND Complete

QUALITY AND AVAILABILITY TARGETS

Ericsson Radio Systems AB 5

6/038 02-LZU 102 152, Rev A, November1999

Hypothetical Reference Digital Section (HRDS) employed by ITU-Rand designed to accommodate the performance specification oftransmission systems as digital lines and radio systems.

Hypothetical Reference Digital Path (HRDP)An HRDP is built up of nine consecutive, equally long (approx. 280km), radiolink sections (HRDS), see Figure 3. HRDP also includes ninesets of digital multiplexing equipment in accordance with CCITT’s(currently ITU-T) recommended hierarchical levels. Each of the unitsmay consist of a number of linked multiplexing units. HRDP comprisesa portion of the entire HRX.

2500 km

64 kbit/s 64 kbit/s 64 kbit/s 64 kbit/s

First-order digital multiplexer

Other multiplexer eqipment located at the ITU-recommended hierarchical

Digital radio section

8 974 65321

Figure 3: The Hypothetical Reference Digital Path (HRDP).

Hypothetical Reference Digital Section (HRDS)

The path lengths have been chosen to be representative of digitalsections likely to be encountered in real operational networks, and aresufficiently long to permit a realistic performance specification fordigital radio systems, see Figure 4.

This model does not include digital equipment such as multiplexers andexchanges. An HRDS can form a constituent element of an HRDL.

Page 178: TND Complete

RADIO TRANSMISSION NETWORK AND FREQUENCY PLANNING

6 Ericsson Radio Systems AB

6/038 02-LZU 102 152 Rev A, November 1999

The appropriate value of the distance Y is dependent on the networkapplication. For now, the lengths of 50 km and 280 km have beenidentified as being necessary.

Y km

Terminalequipment

Terminalequipment

X kbit/s X kbit/s

Figure 4: The Hypothetical Reference Digital Section (HRDS).

Hypothetical Reference Path (HRP)

A digital HRP (Hypothetical Reference Path) is, like the HRX, anetwork model in which studies relating to overall performance may beconducted, thereby facilitating the formulation of standards andobjectives, see Figure 5. The HRP is the starting-point for theapportionment strategy found in ITU-T Recommendation G.826.

IGIGIGIGIG PEPPEP

JJJJJJJ

Nationalportion

Nationalportion

International portion

PEP=Path End Point IG=International Gateway

Hypothetical Reference Path (HRP)27,500 km

Terminatingcountry

Inter-countryIntermediate countries

Terminatingcountry

Figure 5: The Hypothetical Reference Path (HRP).

Page 179: TND Complete

QUALITY AND AVAILABILITY TARGETS

Ericsson Radio Systems AB 7

6/038 02-LZU 102 152, Rev A, November1999

The ITU-T Rec. G821 - basic concepts

Bit errorRecommendation G.821 quantifies the occurrence of transmissionimpairments (bit error) restricted to the bit rates in the range between 64kbit/s and below the primary rate, operating as a part of an ISDN-network, which is based on the control of bit impairment (bit error) ofeach bit position.

Bit rateBit rate is the amount of transmitted bits per time unity, usuallymeasured in seconds. For example: 64 kbit/s and 2 Mbit/s.

Bit-error ratioBit-error ratio is the amount of bit errors with respect to the totalamount of transmitted bits during a specified time interval.

Expressing the quality targetsThe quality targets are expressed as the ratio of average periods, each oftime interval T0, during which the bit-error ratio (BER) exceeds athreshold value. The ratio is assessed over a much longer time intervalTL, that is, TL>>T0.

Bit-error ratio and time intervalsThe following bit-error ratios and time intervals are used in qualitytarget statements, in accordance with Recommendation G.821:

• BER > 1 ⋅ 10-6 during T0 = 1 minute

• BER > 1 ⋅ 10-3 during T0 = 1 second

• zero bit errors under T0 = 1 second, which is equivalent to the conceptof EFS (Error Free Seconds).

Thus, the reference values for time intervals are 1 minute and 1 secondwhile the reference values for the bit-error ratios are 1⋅10-3 (one biterror per one thousand bits) and 1⋅10-6 (one bit error per one millionbits).

Page 180: TND Complete

RADIO TRANSMISSION NETWORK AND FREQUENCY PLANNING

8 Ericsson Radio Systems AB

6/038 02-LZU 102 152 Rev A, November 1999

Available and unavailable time - definition

A period of Unavailable Time (UAT) begins when, in at least one ofthe transmission directions, one or both of the following conditionsoccur for 10 consecutive seconds:

1. the digital signal is interrupted

2. the bit-error ratio (BER) in each second of the 10 consecutiveseconds is worse than 1⋅10-3. These 10 seconds are considered to beunavailable time.

A new period of Available Time (AT) begins with the first second of aperiod of ten consecutive seconds, of which each second displays a bit-error ratio (BER) better than 1⋅10-3.

Available and unavailable time - exampleConsider a measured period of 1 month divided into one-secondintervals, see Figure 6.

TIMETL =1 month

T0 =1 sAvailable Unavailable UnavailableUnavailable Available Available

No bit errorNo biterror

No bit error No bit error

BER=4·10-3

BER=2·10-4

BER=1·10-3

BER=2·10-4 BER=2·10-4

BER=6·10-3

BER=3·10-3

BER<6·10-5BER>3·10-3

1·10-8 1·10-7 1·10-6 1·10-5 1·10-4 1·10-3 1·10-2 1·10-1 1·100

Available time Unavailable time

BER

Figure 6: Available and unavailable time.

Expressing available and unavailable timeAVAILABLE TIME + UNAVAILABLE TIME = MEASURED TIME

AT + UAT = 100%

or

Page 181: TND Complete

QUALITY AND AVAILABILITY TARGETS

Ericsson Radio Systems AB 9

6/038 02-LZU 102 152, Rev A, November1999

AT + UAT = 1

Definitions of events occurring during available time

Errored second (ES) is defined as any second containing one or moreerrors.

Severely errored second (SES) is an errored second with a bit errorratio worse than 1⋅10-3.

BER at bit rate 64 kbit/s

UATand SES 101000 64

64BER 3−⋅== ......................(1)

Error performance objectivesThe error performance objectives are stated in terms of the eventsdiscussed earlier. These events constitute the error performanceparameters and should only be evaluated whilst the path is in theavailable state.

The quality parameters (also known as performance parameters) areusually defined with respect to the total available time during ameasured period, that is, generally as a ratio of the averaged measuredperiods.

The measured periods over which the ratios are to be assessed have stillnot been specified since the period may depend upon the application.

Definition of availability parameters

Errored second ratio

Errored Second Ratio (ESR) is the ratio of ES to total seconds inavailable time during a fixed measurement interval.

Severely errored second ratio

Severely Errored Second Ratio (SESR) is the ratio of SES to totalseconds in available time during a fixed measurement interval.

Page 182: TND Complete

RADIO TRANSMISSION NETWORK AND FREQUENCY PLANNING

10 Ericsson Radio Systems AB

6/038 02-LZU 102 152 Rev A, November 1999

Quality and availability parameters

PARAMETERS UNDER UNAVAILABLE TIME

PARAMETERS UNDER AVAILABLE TIME

ES

SES

UAT

1⋅10-21⋅10-3 1⋅10-11⋅10-41⋅10-51⋅10-61⋅10-71⋅10-8 1⋅100

BER

Figure 7: Parameters under available and unavailable time.

The parameters are divided in two parts: parameters under availabletime and parameters under unavailable time, see Figure 7.

Performance parameters and objective allocationThe performance parameters and objective allocation is illustrated inTable 1. The performance objectives illustrated in the table should bemet concurrently. In other words, the connection fails to satisfy theobjective if any of the requirements in the table are not met.

Performanceclassification

Performanceobjectives

Severely errored seconds < 0.002Errored seconds < 0.08

Table 1: Performance parameters and objective allocation.

Page 183: TND Complete

QUALITY AND AVAILABILITY TARGETS

Ericsson Radio Systems AB 11

6/038 02-LZU 102 152, Rev A, November1999

Objective allocation for the three circuit classesThe quality parameters errored seconds and severely errored seconds arerelated to the three classes a, b and c in an ISDN-connection. Theallocation is illustrated in Table 2.

CircuitClassification

Allocation of errored seconds and severely erroredseconds given in the previous table

Local grade(2 ends)

15% block allowance to each end

Medium grade(2 ends)

15% block allowance to each end

High grade 40% (equivalent to conceptual quality of 0.0016% per kmfor 25,000 km)

Table 2: Objective allocation for the three circuit classes.

Block allowance implies that the stated ratio of the overall end-to-end allowance is allocated to a local or medium grade portionregardless of its length.

The length of the circuit is considered when allocating the high-grade portion. The high-grade allotment is then divided on the basisof the length resulting from a hypothetical per-kilometer allocation,that is, 40%÷25,000 km yields 0.000016 /km.

The actual length covered by the medium grade part of theconnection will vary considerably from one country to another.Transmission systems in this classification exhibit a variation inquality falling between the other classification.

End-to-end quality allocation in the network model HRXThe end-to-end allocation of quality in the HRX network model isillustrated in Figure 8.

Page 184: TND Complete

RADIO TRANSMISSION NETWORK AND FREQUENCY PLANNING

12 Ericsson Radio Systems AB

6/038 02-LZU 102 152 Rev A, November 1999

Highgrade

Mediumgrade

Mediumgrade

Localgrade

Localgrade

LE ICS LEICS

1250 km 25,000 km 1250 km

TT

40% 15%15%15%15%

Figure 8: The end-to-end allocation of quality in the HRX networkmodel.

The derivation of the quality parameters valuesThe quality parameters values are derived in accordance with Table 1and Table 2, see Figure 9.

Page 185: TND Complete

QUALITY AND AVAILABILITY TARGETS

Ericsson Radio Systems AB 13

6/038 02-LZU 102 152, Rev A, November1999

AdditionalallowanceSES=0.1%

SES=0.2%

ES=8%

Medium gradeES=1.2%

Local gradeES=1.2%

High gradeES=3.2%

At one end

15%

At one end

15%

40%

Medium gradeSES=0.015%

Local gradeSES=0.015%

High gradeSES=0.040%

At one end

15%

At one end

15% 40%

50% 50%

? ?

SES

ES

SES=0.1%

Figure 9: The derivation of the values of the quality parameters.

Quality allocation - summaryThe allocation of the quality parameters errored seconds and severelyerrored seconds for the three different classes local, medium and highgrade is illustrated in Table 3.

Circuitclassification

Performance objective

ESR SESRNormal Adverse condition

Local grade 0.012 0.00015 ---------------------Medium grade 0.012 0.00015 0.001

High grade 0.032 0.0004

Table 3: A summary of quality allocation.

Page 186: TND Complete

RADIO TRANSMISSION NETWORK AND FREQUENCY PLANNING

14 Ericsson Radio Systems AB

6/038 02-LZU 102 152 Rev A, November 1999

The remaining 0.001 SESR is a block allowance to the medium andhigh grade classifications to accommodate the occurrence of adversenetwork conditions occasionally experienced (intended to mean theworst-month of the year) on transmission systems. The followingallowances are consistent with the total 0.001 SESR figure:

• 0.0005 SESR to a 2,500 km HRDP for radio-relay systems which canbe used in the high grade and the medium grade portion of theconnection

• 0.0001 SESR to a satellite HRDP

Whenever necessary, administrations may allocate the block allowancesfor the local and medium grade portions of the connection but withinthe total allowance of 30% for any one end of the connection.

The objectives presented above correspond to a very long connection.However, large portions of real international connections will beshorter, thus it is expected that a significant portion of real connectionswill offer a better performance than the limiting values discussed above.On the other hand, a small percentage of the connections will be longerand in this case may exceed the allowances outlined in therecommendation.

Radio applications

Local-grade portion of the HRX

Quality objectives - ITU-R Rec. F.697-1

The local grade is a portion in the HRX network model which togetherwith the medium-grade has a length of 1250 km. Local grade circuitsoperate between the subscribers (T) and the local exchange (LE).

The following quality objectives apply to each direction and to each 64kbit/s channel of a digital radio system when constituting the entirelocal-grade portion of an ISDN connection. These quality objectives areto take into consideration fading, short-term and long-term interferenceand all other sources of performance degradation during periods underwhich the system is considered to be available.

Page 187: TND Complete

QUALITY AND AVAILABILITY TARGETS

Ericsson Radio Systems AB 15

6/038 02-LZU 102 152, Rev A, November1999

• SESR: the bit error ratio should not exceed 1⋅10-3 for more than0.00015 of any month with an integration time of 1 second.

• ESR: the total errored seconds should not exceed 0.012 of any month.

The quality objectives correspond to the values in the first row of theTable 3.

Availability objectives - ITU-R Rec. F.697-1

So far, the ITU-T and ITU-R does not include availability objectives inthe local-grade portion of the HRX. For example, ITU-Rrecommendation 697 does not include availability objectives of anykind. There are, however, a number of values in ITU-T rep. 1053-1suggesting that unavailability objectives should range between 0.01%and 1%, averaged over one or more years for a bi-directional system.

For local-grade systems, unavailability is determined as a result of twoprincipal effects - equipment and adverse propagation.

Medium-grade portion of the HRX

Quality objectives - ITU-R Rec. F.696-1 (addresses to G.821)

The medium grade is a portion in the HRX network model whichtogether with the local-grade portion has a length of 1250 km. Mediumgrade circuits operate between the local exchange (LE) and theInternational Switching Center (ISC).

The following quality objectives apply to each direction and to each 64kbit/s channel of a digital radio system when constituting the entiremedium-grade portion at each end of an HRX, realized entirely withdigital radio-relay systems. These quality objectives are to take intoconsideration fading, short-term and long-term interference and all othersources of performance degradation during periods under which thesystem is considered to be available.

• SESR: the bit error ratio should not exceed 1⋅10-3 for more than0.0004 of any month with an integration time of 1 second.

• ESR: the total errored seconds should not exceed 0.012 of any month.

The quality values correspond to the values in the second row of theTable 3. Note that there is an additional allowance of 0.00025 over andabove the SESR value for adverse propagation conditions.

Page 188: TND Complete

RADIO TRANSMISSION NETWORK AND FREQUENCY PLANNING

16 Ericsson Radio Systems AB

6/038 02-LZU 102 152 Rev A, November 1999

Availability objectives

The ITU-T and ITU-R have not specified the availability objectives forthe medium-grade portion of the HRX.

Digital section - medium grade

Quality classification and allocation - ITU-T Rec. 921

The length of the local and medium-grade portion (1250 km) of aninternational connection is often far from the actual sizes employed bythe countries. This means that it is difficult to define just one generalquality allocation for the medium-grade portion of the HRDS, which isapplicable to all countries.

Depending on the different applications, four section types withdifferent quality classifications are introduced in the medium-gradeportion, see Table 4. These classes were introduced by ITU-T’srecommendation G.921 probably with the intention of allowing formore scope in future quality specifications.

Section qualityclassification

HRDS length(km)

Allocation(%)

Class

1 280 0.45 High grade2 280 2 Medium grade3 50 2 Medium grade4 50 5 Medium grade

Table 4: Digital section quality classifications for error performance.

The allocations in column 3 are the percentages of the performanceobjectives for ESR (0.08) and SESR (0.001), see Table 1 and Figure 9.

Example: The SESR corresponding to the class medium-grade class,section quality class 3, should be 2% (from column 3 of the above table)of 0.001, which gives 0.00002.

Quality objectives - ITU-R Rec. F.696-1

The path lengths in the HRDS have been chosen to be representative ofdigital sections likely to be encountered in real operational networks,and that are sufficiently long to permit a realistic performancespecification for digital radio systems. This model does not includedigital equipment such as multiplexers and exchanges.

Page 189: TND Complete

QUALITY AND AVAILABILITY TARGETS

Ericsson Radio Systems AB 17

6/038 02-LZU 102 152, Rev A, November1999

The values for the quality parameters ESR and SESR are assignedaccording to column 3, Table 5, for the four quality classes. The sameproportion is allocated as earlier, that is, 0.001 is allotted to SESR. Thetrue value is 0.002, however 0.001 is apportioned for errored secondsand the remaining 0.001 is a block allowance for the medium and high-grade classifications to accommodate for the occurrence of adversenetwork conditions. In addition it is allocated 0.08 for ESR of theavailable time.

The following quality objectives apply to each direction and to each 64kbit/s channel when constituting the HRDS portion, realized entirelywith digital radio-relay systems. These quality objectives are to takeinto consideration fading, short-term and long-term interference and allother sources of performance degradation during periods under whichthe system is considered to be available.

Classes 1 and 2 are allotted an additional allowance of 0.0005 for thetotal 2500 km length of the HRDS to accommodate for the occurrenceof adverse propagation conditions. This corresponds to 0.000055 of the280 km length representing the classes 1 and 2.

Performance parameters Ratio of any monthClass1280 km

Class2280 km

Class350 km

Class450 km

BER>1⋅10-3 (SESR) 0.00006 0.000075 0.00002 0.00005One or more errors (ESR) 0.00036 0.0016 0.0016 0.004

Table 5: Error performance objectives for a digital section in the HRDS.

The quality objectives are used for dimensioning radio-relay links. Ithas to be taken into consideration that the allocation in the table is ablock allowance and not a per kilometer allocation.

The derivation of the quality parameters values - ITU-R Rec. F.696-1

The derivation of the quality parameters values for a digital section inthe HRDS follows Table 4 and Table 5, and is illustrated in Figure 10.

Page 190: TND Complete

RADIO TRANSMISSION NETWORK AND FREQUENCY PLANNING

18 Ericsson Radio Systems AB

6/038 02-LZU 102 152 Rev A, November 1999

Additional allowance 0.000055

SESR=0.000060

ESR=0.000360.08

SESR=0.00000450.001

Additional allowance 0.000055

SESR=0.000075

ESR=0.00160.08

SESR=0.00002 0.001

ESR=0.00160.08

SESR=0.0000200.001

ESR=0.0040.08

SESR=0.0000500.001

Class 1: 280 km 0.0045

Class 2: 280 km 0.02

Class 3: 50 km 0.02

Class 4: 50 km 0.05

Figure 10: The derivation of the values of the quality parameters.

Unavailability objectives - ITU-R Rec. F.696-1

The following values are assigned to the four different classes of themedium-grade of an HRDS:

Class 1 (High grade): 0.00033 .......................... distance based allowance

Class 2 (Medium grade): 0.0005....................... block allowance

Class 3 (Medium grade): 0.0005....................... block allowance

Class 4 (Medium grade): 0.001......................... block allowance

The quality values are the same regardless of the length of a real HRDSsection. Then, there is no ”compensation” for the case when the lengthof a real section is shorter than that of the corresponding class length.

Page 191: TND Complete

QUALITY AND AVAILABILITY TARGETS

Ericsson Radio Systems AB 19

6/038 02-LZU 102 152, Rev A, November1999

High-grade portion of the HRX

Quality objectives - ITU-T Rec. G.821

The high-grade is a portion of the HRX network model situatedbetween the International Switching Centers (ISC) having a length of25,000 km.

The following quality objectives are employed:

• SESR: the bit error ratio should not exceed 1⋅10-3 for more than0.0004 of any month with an integration time of 1 second.

• ESR: the total errored seconds should not exceed 0.032 of any month.

The quality values correspond to the values in the third row of the Table3.

Availability objectives

The ITU-T and ITU-R have not specified availability objectives for thehigh-grade portion of the HRX.

Hypothetical Reference Digital Path - HRDP (high grade)

Quality objectives - ITU-R F.594.3

The HRDP network model is composed of digital radio-relay systemsand its length is 2500 km. The quality objectives for an HRDP is relatedto the quality objectives of the high-grade portion of an HRDP since,according to the ITU-T, the length of the HRDP (2500 km) is one tenthof the length of the HRX’s high grade (25,000 km).

The quality parameters SESR and ESR describing the quality objectivesof an HRDP are stated as for each direction of the 64 kbit/s channel ofthe HRDP. The effects of fading, interference and all other sources ofperformance degradation are taken into account. The following qualityobjectives are one tenth of the corresponding values for the high-gradeportion of the HRX:

SESR = 0.00004 + 0.0005 = 0.00054

ESR = 0.0032

Page 192: TND Complete

RADIO TRANSMISSION NETWORK AND FREQUENCY PLANNING

20 Ericsson Radio Systems AB

6/038 02-LZU 102 152 Rev A, November 1999

Note that the SESR value is allotted an additional 0.0005 for adversepropagation conditions.

Availability objectives - ITU-R Rec. F.557-3

The availability objective for digital radio-relay systems that constitutepart of an HRDP is 99.7% of the time, the percentage being consideredover a period of time sufficiently long to be statistically valid. Itincludes all causes that are statistically predictable, unintentional andresulting from radio equipment, power supplies, propagation,interference and from auxiliary equipment and human activity.

The value of 99.7% is a provisional one and it is recognized that, inreality, the selected objectives may fall into the range 99.5 to 99.9%.

Real Digital Radio Link (high grade)

Quality objectives - ITU-R Rec. F.634-3

Real digital radio-relay links with lengths shorter than 2500 km mayform part of the high-grade portion of an ISDN, and may occasionallydiffer in composition from the HRDP.

The following quality objectives are applied to real digital radio linksintended to form a part of a high-grade circuit within an ISDN for whichthe length of the link L is between 280 and 2500 km.

• SESR: the bit error ratio should not exceed 1⋅10-3 for more than(L/2500) ⋅ 0.00054 of any month with an integration time of 1 second.

• ESR: the total errored seconds should not exceed (L/2500) ⋅ 0.0032 ofany month.

The availability objectives are valid for link lengths in the range 280and 2500 km and include allowances for all performance degradationsover and above fading.

Availability objectives - ITU-R Rec. F.695

The following availability objective is appropriate for a real digitalradio link forming a part of a high-grade circuit within an ISDN

Page 193: TND Complete

QUALITY AND AVAILABILITY TARGETS

Ericsson Radio Systems AB 21

6/038 02-LZU 102 152, Rev A, November1999

500 2

3.0UATL

⋅= ..............................................................................(2)

where L is the length of a link in the range 280 to 2500 km.

The availability objective is valid in the range between 280 and 2500km. It includes all causes that are statistically predictable, unintentionaland resulting from radio equipment, power supplies, propagation,interference and from auxiliary equipment and human activity. Theestimate of unavailability should also include consideration of the meantime to restore.

The value of 0.3 is a provisional one and it is recognized that, in reality,the value selected may fall into the range 0.1 to 0.5. The choice of thespecific value is dependent on various aspects, such as propagation,geographical size, population distribution and the organization ofmaintenance.

Summary of network models

G.821 - HRX

High gradeMediumgrade

Mediumgrade

Localgrade

27,500 km

1250 km

Localgrade

25,000 km 1250 km

64kbit/s 64kbit/s

Page 194: TND Complete

RADIO TRANSMISSION NETWORK AND FREQUENCY PLANNING

22 Ericsson Radio Systems AB

6/038 02-LZU 102 152 Rev A, November 1999

G.821 - HRDS

50 km and 280 km

class1-4

X kbit/sX kbit/s

1250 km

PORTION OF HRX

One or more repeaters may occur.

HRDS

Medium grade

Page 195: TND Complete

QUALITY AND AVAILABILITY TARGETS

Ericsson Radio Systems AB 23

6/038 02-LZU 102 152, Rev A, November1999

G.821 - HRDP

2500 km64 kbit/s64 kbit/s

25,000 km

High grade PORTION OF HRX

Composed of nine consecutive identical radio sections of about 280 kmeach.

HRDP

G.821 - RDRL

280 < L ≤ 2500km64 kbit/s64 kbit/s

2500 km

HRDP

L = The length of the model

RDRL

Page 196: TND Complete

RADIO TRANSMISSION NETWORK AND FREQUENCY PLANNING

24 Ericsson Radio Systems AB

6/038 02-LZU 102 152 Rev A, November 1999

G.826 - HRP

27,500 km

International portion

Access

Nationalportion

Nationalportion

Short Haul Long Haul

LE

PCSCTC

LE = Local ExchangePC = Primary CenterSC = Secondary CenterTC = Tertiary Center

Quality and availability targets - summary

Quality targetsTable 6 furnishes a summary of the quality objectives for the studiednetwork models.

Networkmodel

Portion/Class SESR ESR

Local 0.00015 0.012HRX Medium 0.00040 0.012

High 0.00040 0.032Class 1 (280 km) 0.00006 0.00036

HRDS Class 2 (280 km) 0.000075 0.0016Class 3 (50 km) 0.00002 0.0016Class 4 (50 km) 0.00005 0.004

HRDP High grade 0.0032 0.0032RDRL High grade 0.00054 ·(L/2500) 0.0032 ·(L/2500)

Table 6: Summary of the quality and availability objectives for thestudied network models.

Page 197: TND Complete

QUALITY AND AVAILABILITY TARGETS

Ericsson Radio Systems AB 25

6/038 02-LZU 102 152, Rev A, November1999

Availability targetsTable 7 furnishes a summary of the availability objectives for thestudied network models.

Network model Portion/Class UATRLocal 0.0001-0.010

HRX Medium not definedHigh not defined

Class 1 (280 km) 0.00033HRDS Class 2 (280 km) 0.0005

Class 3 (50 km) 0.0005Class 4 (50 km) 0.001

HRDP High grade 0.003RDRL High grade 0.003 ·(L/2500)

Table 7: Summary of the availability objectives for the studied networkmodels.

Reports and recommendations - summary

Table 8 furnishes a summary of the reports and recommendationsdealing with quality and availability objectives for the studied networkmodels.

Local gradeNetwork model Quality objectives Availability objectives

HRX ITU-R Rec. F.697-1 ITU-R Rec. F.697-1

Medium gradeNetwork model Quality objectives Availability objectives

HRX ITU-R Rec. F.696-1 ---------------------HRDS ITU-T Rec. G.921

ITU-R Rec. F.696-1 ITU-R Rec. F.696-1

High gradeNetwork model Quality objectives Availability objectives

HRX ITU-T Rec. G.821 ---------------------HRDP ITU-R F.594.3 ITU-R Rec. F.557-3RDRL ITU-R Rec. F.634-3 ITU-R Rec. F.695

Table 8: Summary of the ITU-T and ITU-R reports andrecommendations.

Page 198: TND Complete

RADIO TRANSMISSION NETWORK AND FREQUENCY PLANNING

26 Ericsson Radio Systems AB

6/038 02-LZU 102 152 Rev A, November 1999

Quality and availability parameters versus fadingmechanisms

Fading occurrenceFigure 11 illustrates a fading occurrence. The received signal varies as afunction of time due to different types of fading mechanisms.

In this example, a simplified fading occurrence, the received signalcrosses the receiver’s threshold level for two different bit-error ratios,10-6 and 10-3, and the errored events are registered as qualityparameters SESR and ESR.

time<10 s time>10 s

UATR

ESR

ATR

ESRSESR

ESR

ATR

ESR ESR

Pr

Ptr

Ptr

≅≅3 dB

TIME

BER=10-6

BER=10-3

POWER

Figure 11: A simplified fading occurrence showing the received signalvarying as a function of time due to different types of fadingmechanisms.

The corresponding relationship between the quality and availabilityparameters and the fading mechanisms is illustrated in Figure 12.

Page 199: TND Complete

QUALITY AND AVAILABILITY TARGETS

Ericsson Radio Systems AB 27

6/038 02-LZU 102 152, Rev A, November1999

QUALITY AND AVAILABILITYPARAMETERS

UATR

ESR

SESR HARDWARE FAILURE No fading

Slow fadingRAIN

FADING MECHANISMS FADING EVENTS

REFRACTION-DIFFRACTION Slow fading

Rapid fadingMULTIPATH

FLAT

SELECTIVEPROPAGATION Rapid fading

Figure 12: Correspondence between the quality and availabilityparameters and the fading mechanisms.

The relationship between the quality and availability parameters and thefading mechanisms is not described in any ITU recommendation orreport!

Calculation of the unavailability parameters - Rec. G.821

Unavailable time ratio (UATR)

UATR is the ratio of a measured period for which the bit-error ratio isworse than 1⋅10-3 due to rain and refraction fading and hardwarefailure.

Unavailable time ratio is calculated as the probability P1 that BERexceeds 10-3 due to rain and refraction-diffraction fading:

UATR 1P= ........................................................................................(3)

Unavailability due to rain and refraction fading is obtained by using the3-dB criterion, that is, assuming that the fade margin at the threshold,BER = 10-3, is 3 dB greater than the fade margin used in the probabilitycalculation at the threshold for BER = 10-6.

Unavailability due to hardware failure causes interruption in the radioconnection and should therefore be included in the dimensioning of theunavailable time.

Page 200: TND Complete

RADIO TRANSMISSION NETWORK AND FREQUENCY PLANNING

28 Ericsson Radio Systems AB

6/038 02-LZU 102 152 Rev A, November 1999

Available time ratio (UATR)

ATR, expressed as a ratio, is calculated as

UATR1UATR −= ...........................................................................(4)

Severely errored second ratio (SESR)

SESR is the ratio of the total AT during a measured period for whichthe bit-error ratio is worse than 1⋅10-3 due multipath propagation (flatand frequency selective fading).

Severely errored second ratio is obtained by calculating the probability,P2, that BER exceeds 10-3 due to multipath propagation (flat andfrequency selective fading).

SESR 2P= .........................................................................................(5)

The fade margin, at BER = 10-3, is assumed to be 3 dB greater than thatat BER = 10-6.

Errored second ratio (ESR)

ESR is the ratio of the total AT in a measured period during which anyerror occurs, regardless of the type of fading mechanism, but notincluded in the unavailable time.

Seconds during which BER is worse than 10-6 appear both duringavailable and unavailable time. Thus, error seconds are obtained as aratio, by calculating the probability, P3, that BER exceeds 10-6 due tomultipath propagation (flat and frequency selective fading), rain andrefraction fading and then subtracting unavailable time, during which,seconds having a BER worse than 10-3 are included, that is,

UATR-ESR 3P= ..............................................................................(6)

Planning unavailable timeUnavailable time was discussed earlier and the conclusion was that itsprimary constituents resulted from the occurrence of two fadingmechanisms (rain and refraction) and radio equipment failure. But othereventual causes must be considered, such as,

• auxiliary equipment

• human activity

Page 201: TND Complete

QUALITY AND AVAILABILITY TARGETS

Ericsson Radio Systems AB 29

6/038 02-LZU 102 152, Rev A, November1999

• interference

• power supplies

The ITU-T Recommendation G.826 - basicconcepts

IntroductionRecommendation G.826 is applicable to international, constant bit-ratedigital path at or above the primary rate (2048 kbit/s).

Recommendation G.826 is based upon the measurement of block error-performance.

Hypothetical Reference Path (HRP)A digital HRP (Hypothetical Reference Path) is, as is the case for theHRX, a network model in which studies relating to overall performancemay be conducted, thereby facilitating the formulation of standards andobjectives. The HRP, see Figure 13, is the starting-point for theapportionment strategy in ITU-T Recommendation G.826.

IGIGIGIGIG PEPPEP

JJJJJJJ

Nationalportion

Nationalportion

International portion

PEP=Path End Point IG=International Gateway

Hypothetical Reference Path (HRP)27,500 km

Terminatingcountry

Inter-countryIntermediate countries

Terminatingcountry

Figure 13: The Hypothetical Reference Path (HRP).

Page 202: TND Complete

RADIO TRANSMISSION NETWORK AND FREQUENCY PLANNING

30 Ericsson Radio Systems AB

6/038 02-LZU 102 152 Rev A, November 1999

Available and unavailable time

A period of Unavailable Time (UAT) begins with the onset of 10consecutive SES events. These 10 seconds are considered to be part ofunavailable time.

A new period of Available Time (AT) begins with the onset of 10consecutive non-SES events. These 10 seconds are considered to be partof available time.

Definition of block

A block is a set of consecutive bits associated with the path and each bitbelongs to only one block. Table 9 specifies the recommended range ofthe number of bits within each block for different bit-rate ranges.

Bit rate (Mbit/s) 1.5-5 >5-15 >15-55 >55-160 160>3500 >3500Bits/block 800-

50002000-8000

4000-20000

6000-20000

15000-30000

for furtherstudy

Table 9: Recommended range of the number of bits within each blockfor different bit-rate ranges.

Because bit-error ratios are not expected to decrease dramatically as thebit rates of transmission systems increase, the block sizes used inevaluating very high bit rate paths should remain within the range of 15000 to 30 000 bits/block. Preserving a constant block size for very highbit-rate paths result in relatively constant BBER and SESR objectivesfor these paths.

Events occurring during available time

Errored Block (EB)

Errored Block is a block in which one or more bits are in error.

Errored Second (ES)

Errored Second is a one-second period containing one or more erroredblocks.

Page 203: TND Complete

QUALITY AND AVAILABILITY TARGETS

Ericsson Radio Systems AB 31

6/038 02-LZU 102 152, Rev A, November1999

Severely Errored Second (SES)

Severely Errored Second is a one-second period containing ≥ 30%errored blocks.

Background Block Error (BBE)

Background Block Error is an errored block not occurring as part of aSES.

Definitions of quality parametersThe quality objectives are defined based on the events defined earlier.These events constitute the quality parameters and should only beevaluated whilst the path is in the available state.

Errored Second Ratio (ESR)

Errored Second Ratio is the ratio of ES to the total seconds of availabletime during a fixed measurement interval. ESR is not expressed inpercentage.

Severely Errored Second Ratio (SESR)

Severely Errored Second Ratio (SESR) is the ratio of SES to the totalseconds of available time during a fixed measurement interval. SESR isnot expressed as a percentage.

Background Block Error Ratio (BBER)

Background Block Error Ratio (BBER) is the ratio of errored blocks tototal blocks during a fixed measurement interval, excluding all blocksduring SES and UAT.

A comparison of SESR (G.826) and SESR (G.821)Assume an equipment having block size of 2,048 bits/block and a blockrate of 1000 blocks/s. The number of transmitted/received bits during aperiod of one second is the following:

1000 blocks ⋅ 2,048 bits/block = 2.048 ⋅ 106 bits

One SES contains at least 30% errored blocks, that is, 30% of 1000blocks yields a minimum of 300 errored blocks.

Page 204: TND Complete

RADIO TRANSMISSION NETWORK AND FREQUENCY PLANNING

32 Ericsson Radio Systems AB

6/038 02-LZU 102 152 Rev A, November 1999

As a result of the fact that one errored block contains a minimum ofone bit error, then 300 errored blocks contain a minimum of 300 biterrors. The bit-error ratio is therefore a minimum of

46

1046.110048.2

300BER −⋅=

⋅= ............................................................(7)

The comparison between G.821 and G.826 yields:

G.821 SES 1.00 ⋅ 10-3

G.826 SESR 1.46 ⋅ 10-4

The value of SESR is then about 7 times lower than the value of SESprovided that the above requirements are valid.

If 300 errored blocks contain more than 300 bit errors, e.g. 2,048 biterrors, then BER= 10-3, which means that SESR and SES have thesame value.

Smaller block size also causes BER in recommendation G.826 to becomparable to BER in recommendation G.821. For instance, a blocksize of 300 bits/block yields BER=10-3 if just one bit error appears,thereby yielding the same value for both SESR and SES.

End-to-end objectives apportionment in the HRPThe quality parameters are allocated as ratios, which are related to thetotal available time. The quality parameters apportionment for differentbit rates are illustrated in Table 10.

Bit rate (Mbit/s)

Quality 1.5-5 >5-15 >15-55 >55-160 >160-3500 >3500

ESR 0.04 0.05 0.075 0.16 Not confirmed For further study

SESR 0.002 0.002 0.002 0.002 0.002 For further study

BBER 2⋅10-4

2⋅10-4

2⋅10-4

2⋅10-4

2⋅10-4

For further study

Table 10: The apportionment of quality parameters for different bitrates.

The values in the table are not expressed as percentages.

Page 205: TND Complete

QUALITY AND AVAILABILITY TARGETS

Ericsson Radio Systems AB 33

6/038 02-LZU 102 152, Rev A, November1999

Quality objectives allocation in the HRP

National portion

The total allocation to the national portion, see Figure 14, is composedof two components:

1. Each national portion is allocated a fixed block allowance of 17.5%of the end-to-end objective.

2. A distance-based allocation of 1% per 500 km is assigned to theportion between PEP and IG and is added to the current blockallowance. The actual route length (if it is known) and the air routebetween the PEP and the IG should first be calculated. Thecalculated air route should be multiplied by an appropriate routingfactor specified as follows:

• If the air route distance is shorter than 1000 km, the routing factor is1.5

• If the air route distance is greater or equal 1000 km but shorter than1200 km, the calculated route length is taken to be 1500 km

• If the air route distance is greater or equal 1200 km, the routing factoris 1.25

When both actual and calculated route lengths are known, the smallervalue is retained. This distance should be rounded up to the nearest 500km, that is, the two national portions comprise at least 500 km each.

Page 206: TND Complete

RADIO TRANSMISSION NETWORK AND FREQUENCY PLANNING

34 Ericsson Radio Systems AB

6/038 02-LZU 102 152 Rev A, November 1999

IGIGIGIGIG PEPPEP

JJJJJJJ

Nationalportion

Nationalportion

International portion

Hypothetical Reference Path27,500 km

Terminatingcountry

Inter-country

Intermediate countriesTerminating

country

17.5% Block allowance Block allowance 17.5%

1%/500 km Distance-based allocation

Distance-based 1%/500 kmallocation

Figure 14: The allocation in the national portion of the HRP.

When a national portion includes a satellite hop, a total allowance of42% of the end-to-end objectives in Table 10 is allocated to thisnational portion. This allowance completely replaces both the block andthe distance-based allowances otherwise allotted to the nationalportions.

International portion

The total allocation to the international portion, see Figure 15, iscomposed of two components:

1. The international portion is allocated a block allowance of 2% perintermediate country, plus 1% for each terminating country.

Page 207: TND Complete

QUALITY AND AVAILABILITY TARGETS

Ericsson Radio Systems AB 35

6/038 02-LZU 102 152, Rev A, November1999

2. A distance-based allocation of 1% per 500 km is assigned to the totalinternational portion that may pass through ”intermediate countries”.The actual route length between consecutive IGs (one or two for eachintermediate country) should be added in order to calculate theoverall length of the international portion. The air-route distancebetween consecutive IGs should also be used and multiplied by anappropriate routing factor specified as follows for each elementbetween IGs:

• If the air route distance between two IGs is shorter than 1000 km, therouting factor is 1.5

• If the air route distance is greater or equal 1000 km but shorter than1200 km, the calculated route length is taken to be 1500 km

• If the air route distance between two IGs is greater or equal 1200 km,the routing factor is 1.25

When both actual and calculated route lengths are known, the smallervalue is retained for each element between IGs. This distance should berounded up to the nearest 500 km, but shall not exceed 26 500 km.

In cases where the allocation to the international portion is less than 6%,then 6% shall be used as the allocation.

Independent of the distance spanned, any satellite hop in theinternational portion receives a 35% allocation of the objectives Table10. When allocating 35% to a satellite hop, employed in theinternational portion, the distance spanned by the satellite is notincluded in the distance-based allocation.

Page 208: TND Complete

RADIO TRANSMISSION NETWORK AND FREQUENCY PLANNING

36 Ericsson Radio Systems AB

6/038 02-LZU 102 152 Rev A, November 1999

IGIGIGIGIG PEPPEP

JJJJJJJ

Nationalportion

Nationalportion

International portion

Hypothetical Reference Path27,500 km

Terminatingcountry

Inter-country

Intermediate countriesTerminating

country

1% 1%

1%/500 kmDistance based

allocation

Block allowance

Figure 15: The allocation in the international portion of the HRP.

Unavailability allocation in the HRPThe allocation of unavailability in the national and internationalportions of the HRP is not defined in Rec. G.826.

Radio applications of the ITU-T´S Rec. G.826

The quality objectives defined in ITU-T’s Recommendation G.826furnish a more detailed guidance for network dimensioning thanRecommendation G.821. The revised quality objectives are applicableto both the national and the international portions of the HRP.

Page 209: TND Complete

QUALITY AND AVAILABILITY TARGETS

Ericsson Radio Systems AB 37

6/038 02-LZU 102 152, Rev A, November1999

National portion of the HRP - basic sectionsSince there is one LE and one PC (alternatively one SC or one TC,depending on the size of the country) between the PEP and the IG, thenational portion of the HRP (the portion between the PEP and the IG) isfurther divided in three portions. These portions, digital sections, arecalled ”Access”, ”Short Haul” and ”Long Haul” and are illustrated inFigure 16. The quality objectives for the national portion are thereforeassigned separately to the three portions.

Access Short Haul Long Haul

PEP

PEP

IG

IG

LE

PCSCTC

Figure 16: The national portion of the HRP (the portion between thePEP and the IG) is divided in three portions.

PEP=Path End Point, IG=International Gateway, LE=Local Exchange,PC=Primary Center, SC=Secondary Center, TC=Tertiary Center.

The three portions are defined as follows:

Access is the section including the connections between the Path EndPoint (PEP) and the Local Exchange (LE).

Short Haul is the section including the connections between the LocalExchange (LE) and Primary Center (PC) - alternatively the SecondaryCenter (SC) or Tertiary Center (TC), depending of the networkarchitecture.

Long haul is the section including the connections between the PrimaryCenter (PC) - alternatively Secondary Center (SC) or Tertiary Center(TC) - and the International Gate (IG).

Page 210: TND Complete

RADIO TRANSMISSION NETWORK AND FREQUENCY PLANNING

38 Ericsson Radio Systems AB

6/038 02-LZU 102 152 Rev A, November 1999

Quality objectives allocation

Long-haul section

For each transmission direction and for each of the different bit-rates,the quality objectives related to the long-haul section are to consist of adistance-based allocation and a block allocation as illustrated inTable 11.

Bit rate ( Mbit/s)Quality 1.5-5 >5-15 >15-55 >55-160 >160-3500

ESR 0.04⋅A 0.05⋅A 0.075⋅A 0.16⋅A for further studySESR 0.002⋅A 0.002⋅A 0.002⋅A 0.002⋅A 0.002⋅ABBER 2⋅A⋅10-4 2⋅A⋅10-4 2⋅A⋅10-4 2⋅A⋅10-4 1⋅A⋅10-4

Table 11: The allocation of the quality objectives in the long-haulsection.

The parameter A in the table is calculated as follows:

50001.01

LAA ⋅+= ...............................................................................(8)

where

A1 has provisionally been agreed to be in the range of 1 to 2%

L the nearest 500 km value rounded up from L.

Short-haul section

For each transmission direction and for each of the different bit-rates,the quality objectives related to the short-haul section are to consist of ablock allocation as illustrated in Table 12.

Bit rate ( Mbit/s)Quality 1.5-5 >5-15 >15-55 >55-160 >160-3500

ESR 0.04⋅B 0.05⋅B 0.075⋅B 0.16⋅B for further studySESR 0.002⋅B 0.002⋅B 0.002⋅B 0.002⋅B 0.002⋅BBBER 2⋅B⋅10-4 2⋅B⋅10-4 2⋅B⋅10-4 2⋅B⋅10-4 1⋅B⋅10-4

Table 12: The allocation of the quality objectives in the short-haulsection.

Page 211: TND Complete

QUALITY AND AVAILABILITY TARGETS

Ericsson Radio Systems AB 39

6/038 02-LZU 102 152, Rev A, November1999

The value of B has provisionally been agreed to be in the range of 7.5 to8.5%.

Access section

For each transmission direction and for each of the different bit-rates,the quality objectives related to the access section are to consist of ablock allocation as illustrated in Table 13.

Bit rate ( Mbit/s)Quality 1.5-5 >5-15 >15-55 >55-160 >160-3500

ESR 0.04⋅C 0.05⋅C 0.075⋅C 0.16⋅C for further studySESR 0.002⋅C 0.002⋅C 0.002⋅C 0.002⋅C 0.002⋅CBBER 2⋅C⋅10-4 2⋅C⋅10-4 2⋅C⋅10-4 2⋅C⋅10-4 1⋅C⋅10-4

Table 13: The allocation of the quality objectives in the access section.

The value of C has provisionally been agreed to be in the range of 7.5 to8.5%.

Summary of quality objectives

A summary of the allocation of the quality parameters in the threesections of the national portion of the HRP is illustrated in Table 14.

Bit rate(Mbit/s)

Qualityparameter

Long haul Short haul Access

ESR 0.04⋅A 0.04⋅B 0.04⋅C1.5-5 SESR 0.002⋅A 0.002⋅B 0.002⋅C

BBER 2⋅A⋅10-4 2⋅B⋅10-4 2⋅C⋅10-4

ESR 0.05⋅A 0.05⋅B 0.05⋅C>5-15 SESR 0.002⋅A 0.002⋅B 0.002⋅C

BBER 2⋅A⋅10-4 2⋅B⋅10-4 2⋅C⋅10-4

ESR 0.075⋅A 0.075⋅B 0.075⋅C>15-55 SESR 0.002⋅A 0.002⋅B 0.002⋅C

BBER 2⋅A⋅10-4 2⋅B⋅10-4 2⋅C⋅10-4

ESR 0.16⋅A 0.16⋅B 0.16⋅C>55-160 SESR 0.002⋅A 0.002⋅B 0.002⋅C

BBER 2⋅A⋅10-4 2⋅B⋅10-4 2⋅C⋅10-4

ESR For further study For further study For further study>160-3500 SESR 0.002⋅A 0.002⋅B 0.002⋅C

BBER 1⋅A⋅10-4 1⋅B⋅10-4 1⋅C⋅10-4

Page 212: TND Complete

RADIO TRANSMISSION NETWORK AND FREQUENCY PLANNING

40 Ericsson Radio Systems AB

6/038 02-LZU 102 152 Rev A, November 1999

Table 14: Allocation of the quality parameters in the three sections ofthe national portion of the HRP.

The following conditions are provisionally valid:

1) A% + B% + C% ≤ 17.5%

2) B% + C% are in the range 15.5 to 16.5%

3) The effects of interference and all other sources of performancedegradation are included in the above table.

4) The suggested evaluation period is one month for all of theparameters, and the quality objectives apply only when the system isconsidered to be available.

International portion of the HRPThe international portion of the HRP consists of the network betweenthe International Gateways (IG) of two countries. A connection in theinternational portion may, however, pass through several countries.

The ITU has assumed that the connection passes through four countries(each with two IGs) and that both terminating countries have one IGeach. This is illustrated in Figure 17.

IGIGIGIGIG

JJJJJ

International portion

Inter-countryIntermediate countries

Ter

min

atin

g co

untr

y

Ter

min

atin

g co

untr

y

Figure 17: The international portion of the HRP.

Page 213: TND Complete

QUALITY AND AVAILABILITY TARGETS

Ericsson Radio Systems AB 41

6/038 02-LZU 102 152, Rev A, November1999

The following quality objectives, see Table 15, for different bit rates,are allocated to the international portion of the HRP:

Bit rate ( Mbit/s)Quality 1.5-5 >5-15 >15-55 >55-160 >160-3500

ESR 0.04⋅(FL+BL) 0.05⋅(FL+BL) 0.075⋅(FL+BL) 0.16⋅(FL+BL) for further studySESR 0.002⋅(FL+BL)BBER 2⋅ 10-4⋅(FL+BL) 2⋅ 10-4⋅(FL+BL)

Table 15: Allocation of the quality parameters in the internationalportion of the HRP.

The values in the table are used with a distance allocation factor givenby

50001.0

LFL ⋅= .....................................................................................(9)

and a block allowance factor BL, which is applicable under the

following conditions:

Intermediate countries:

refref

RL LLLL

LBB ≤<⋅⋅= minfor 02.0 .........................................(10)

refRL LLBB >⋅= for 02.0 ....................................................(11)

Terminating countries:

refref

RL LLLL

LBB ≤<⋅⋅= minfor 01.0 .........................................(12)

refRL LLBB >⋅= for 01.0 ....................................................(13)

Block allowance factor: BR (0<B

R≤1)

Reference length: Lref

=1000 km (provisionally)

The following conditions are provisionally valid:

Page 214: TND Complete

RADIO TRANSMISSION NETWORK AND FREQUENCY PLANNING

42 Ericsson Radio Systems AB

6/038 02-LZU 102 152 Rev A, November 1999

1) The value of BR has provisionally been agreed to be 1. Furtherstudies are required to establish a final value for B

Rthat can be used for

different transmission components.

2) The effects of interference and all other sources of performancedegradation are included in the above table.

3) The suggested evaluation period is one month for all the parameters,and the quality objectives apply only when the system is considered tobe available.

4) The overall length of the international path passing through one ormore countries should be rounded up to the nearest multiple of 500km.

Radio applications of the ITU-T Rec. G.826The objective values presented in ITU-T Rec. G.826 for the nationalportion of the HRP are included in the ITU-R Rec. F.1189.

It is one of the prime objectives of ITU-T Rec. G.826 to define allperformance parameters in such a way that in-service estimation ispossible. Thus, parameter definitions based upon bit-error ratios are notchosen.

As mentioned before, the quality objectives for the national portion ofthe HDP are assigned separately to the three portions.

The ITU-T Recommendation G.827

The purpose of this recommendation is to specify the availabilityparameters and objectives for path elements of international constantbit-rate digital paths at or above the primary rate.

Two types of paths are considered: paths between the InternationalSwitching Centers (ISCs) consisting only of an international portion andpaths extending beyond the ISC consisting of both national andinternational portions. The ITU-T Rec. G.827 specifies objectives forthe availability performance of each of these paths.

Many of the subjects included in the ITU-T Rec. G.827 are, however,still for further study. For instance, the exact location of the Path EndPoint (PEP) in the international portion and the availability performanceobjectives

Page 215: TND Complete

QUALITY AND AVAILABILITY TARGETS

Ericsson Radio Systems AB 43

6/038 02-LZU 102 152, Rev A, November1999

References

ITU-T Recommendation G.102

ITU-T Recommendation G.801

ITU-T Recommendation G.821

ITU-T Recommendation G.826

ITU-T Recommendation G.921

ITU-I Recommendation I.120

ITU-R Recommendation F.556-1

ITU-R Recommendation F.557-3

ITU-R Recommendation F.594-4

ITU-R Recommendation F.634-3

ITU-R Recommendation F.695

ITU-R Recommendation F.696-1

ITU-R Recommendation F.697-1

ITU-R Recommendation F.1092

ITU-R Recommendation F.1189

ITU-R Report F-930-2

ITU-R Report F-1052-1

Page 216: TND Complete

i

RADIO REGULATIONS

This chapter briefly describes the ITU-R publication”Radio Regulations”, the publisher, the contents and thegeneral structure of the publication. The primary objectiveof this chapter is to deal with the subject of RadioRegulations in connection with the use of frequencies forfixed terrestrial radio-links.

TABLE OF CONTENTS

Introduction....................................................................................................................................................... 1What is meant by Radio Regulations?............................................................................................................... 1Who is the publisher?........................................................................................................................................ 2Content and structure......................................................................................................................................... 3

Volume 1, Radio Regulations.............................................................................................................. 3Volume 2, Appendices ........................................................................................................................ 4Volume 3, Resolutions and Recommendations ................................................................................... 4

The principle articles dealing with frequency allocation................................................................................... 4Article 1 (RR footnotes 2 - 207).......................................................................................................... 4Article 2 (RR footnotes 208- 234)....................................................................................................... 5Article 4 (RR footnotes 264 - 298)...................................................................................................... 5Article 6 (RR footnotes 339 - 373)...................................................................................................... 6Article 7 (RR footnotes 374 - 390)...................................................................................................... 7Article 8 (RR footnotes 391 - 952)...................................................................................................... 7Article 9 (RR footnotes 953 - 989)...................................................................................................... 8Article 10 (RR footnotes 990 -1040)................................................................................................... 9

Radio Regulations volume 4 ............................................................................................................................. 10References ......................................................................................................................................................... 10

Page 217: TND Complete

RADIO REGULATIONS

Ericsson Radio Systems AB

7/038 02-LZU 102 152, Rev A, November 1999

1

Introduction

The chapter does not consider all of the required provisions and, as aresult, is not to be construed as a substitute for the publication ”RadioRegulations”. Instead, it is meant as a guide when seeking importantinternational treatise in the area of radio frequency allocations and radiofrequency management.

What is meant by Radio Regulations?

Radio Regulations is a set of documents consisting of three mainvolumes and one additional volume containing updates. The volumesconstitutes an international radio communication treaty and deals withthe various radio communication services and their use of the radio-frequency spectrum. The regulations contain allocation rules andregulations relating to services using the radio spectrum up to 400 GHz.

The documents cover both worldwide and regional frequencyallocations as well as the priorities that are assigned to the differentservices when sharing the same frequency band. The combination ofworldwide frequency allocation regulations together with regionalallocation regulations (that may vary from one region to another) is thevery foundation upon which interference-free global radiocommunication services exist.

The objective of the regulations is to maintain efficient and economicaluse of the radio-frequency spectrum and to coordinate the efforts thatwill lead to the elimination of destructive interference between radiostations located in different countries.

As for terrestrial fixed radio-link transmission services, RadioRegulations controls the allocation of frequency bands both on a globaland on a regional basis, i.e., the allocation of worldwide frequencybands as well as the allocation of frequency bands employed within thedifferent geographical regions of the world. These frequency bands mayeither be exclusively allocated for fixed terrestrial radio or, undercertain conditions, may be shared with other services. Particularattention is paid to the coordination between terrestrial services andspace services, between satellites and earth stations, and between fixedand mobile services - all of which are strictly regulated.

Page 218: TND Complete

RADIO TRANSMISSION NETWORK AND FREQUENCY PLANNING

2 Ericsson Radio Systems AB

7/038 02-LZU 102 152, Rev A, November 1999

When attempting to establish frequencies for a radio-link hop or aradio-link network in a particular country, Radio Regulations willprovide available frequency bands for the country or region in question- frequency bands that are internationally approved for the service inquestion. Based on these frequency allocations, the allotment will thenbe made in accordance with the recommendations in the ITU-R series F(Fixed Services) publications. The allotments consist of one or morealternative radio-frequency channel arrangements. These arrangementsare then to be used as in accordance with the rules of the administrationin question. Based on the selected radio-frequency channel arrangementand the stipulations found in Radio Regulations, the planning andassignment of frequencies for the radio-link hop or radio-link networkcan take place.

A significant portion of Radio Regulations deals with the handling andassignment of frequencies in the areas of maritime and aeronauticalservices and in the areas of vital safety and distress services.

Who is the publisher?

Radio Regulations is published under the authority of the SecretaryGeneral of the International Telecommunication Union, ITU. As ITU isa part of the United Nations, the Radio Regulation document representsa treaty between most of the countries in the world.

Radio Communication Conferences are held every two years by the ITURadio Communication Sector, ITU-R, having their primary function asthe development and adoption of Radio Regulations.

Other bodies of the Radio communication sector that participate in theRadio Regulations effort are:

• Radio Communication Bureau, which provides administrative andtechnical support to Radio Communication Conferences

and the

• Radio Regulation Board, which among all its other activities alsoapproves the rules of procedure as used in the application of theRadio Regulations.

The Radio Communication Conferences are open to all ITU Members,Administrations, the United Nations, international organizations,regional telecommunication organizations and intergovernmentalorganizations.

Page 219: TND Complete

RADIO REGULATIONS

Ericsson Radio Systems AB

7/038 02-LZU 102 152, Rev A, November 1999

3

Content and structure

Radio Regulations is a consolidated document consisting of threevolumes which incorporate:

• Volume 1: Radio Regulations

• Volume 2 : Appendices

• Volume 3: Resolutions and Recommendations

• Volume 4: Articles, Appendix, WRC-95 Resolutions andRecommendations

Volume 1, Radio RegulationsVolume 1 consists, for the time being, of 5197 regulatory footnotes thatare divided in 69 articles (subdivided into sections), 13 chapters andtwo parts (A and B).

Volume 1 Parts A and B Chapter I - XIII Article 1 - 69 (subdivided into sections) Regulations, footnotes 1 - 5197

Furthermore, volume 1 contains sections that are aimed at helping thereader and at increasing the ease-of-use of the document. For the mostpart, these sections consist of:

• Table of contents for all three volumes

• Analytical tables - a list of key words in alphabetic order coveringboth the main body of the regulations as well as the Appendices tothe Radio Regulations.

• Analytical index - a set of eight tables containing the primarycontent of the Resolutions and the Recommendations.

• Notes by the General Secretary where, for example, note 3 (N-3)refers to ITU-R recommendations concerning the field of RadioRegulations. Most of the other notes consist of flowcharts coveringradio regulatory procedures.

Page 220: TND Complete

RADIO TRANSMISSION NETWORK AND FREQUENCY PLANNING

4 Ericsson Radio Systems AB

7/038 02-LZU 102 152, Rev A, November 1999

Volume 2, AppendicesThe appendices, referring to one or more articles or regulatoryfootnotes, contain additional information over and above that providedin RR volume 1. The information consists of more detailed andspecified texts, algorithms, tables and figures. Two examples areillustrated below:

1. Appendix 6, ”Determination of Necessary Bandwidths IncludingExamples for their Calculation and Associated Examples for theDesignation of Emissions”

2. Appendix 28, ”Methods for the Determination of Coordination AreaAround an Earth Station in Frequency Bands Between 1 GHz and 40GHz Shared Between Space and Terrestrial Radio CommunicationServices.

The Appendices are numbered in order, depending on the services theycover. An analytical table is provided in volume 1.

Volume 3, Resolutions and RecommendationsThe Resolutions and Recommendations contain administrativedecisions concerning principles, general procedures and cooperation.They also regulate how and when actions that have been decided upon,as well as future issues, are to be carried out.

The Resolutions and Recommendations are numbered in order,depending on the services they cover. An analytical index is provided involume 1.

The principle articles dealing with frequencyallocation

The examples below deal with fixed terrestrial radio and cover the mostimportant sections of Radio Regulations. The examples do notreproduce the entire text found in Radio Regulations, they only serve asa guide to the contents therein. For all the provisions and their terms,see Radio Regulations, Volume 1.

Article 1 (RR footnotes 2 - 207)“Terms and Definitions”.

This article contains Terms and Definitions that are important to theunderstanding of Radio Regulations.

Page 221: TND Complete

RADIO REGULATIONS

Ericsson Radio Systems AB

7/038 02-LZU 102 152, Rev A, November 1999

5

Three important definitions that relate to Frequency Management(footnotes 17, 18 and 19):

• Allocation (of a frequency band): Frequency distribution to services.Frequency allocation of a given frequency band for the purpose ofits use, i.e. the allocation of frequencies to specific services underspecified conditions.

• Allotment (of a radio frequency or radio frequency channel):Frequency distribution to areas or countries. The allotment of adesignated frequency channel, that is specified in an agreedfrequency plan, for use in a country or area.

• Assignment (of a radio frequency or a radio frequency channel):Frequency distribution to stations. The authorization granted by anadministration to a radio station allowing the use of a radiofrequency or radio frequency channel under specified conditions.

Article 2 (RR footnotes 208- 234)“Nomenclature related to the Frequency and Wavelength Bands Used inRadio Communication”.

The radio spectrum is subdivided into nine frequency bands that aredesignated by band numbers (consecutive whole numbers). At presentthe numbers cover the range four (4) to twelve (12). The frequencyrange covers the spectrum from 3 kHz up to 3000 GHz.

The frequency bands also have corresponding symbols (e.g., VHF,UHF), a metric band division (e.g., metric waves, decimetric waves)and metric abbreviations (e.g., B.m, B.dm)

Article 4 (RR footnotes 264 - 298)“Emission designations”.

Emissions are to be designated in accordance with their necessarybandwidth and their classification. The classification is a description ofthe type of modulation, nature of the signal and information to betransmitted. The purpose of the designation is to achieve a concise andstandardized emission description, i.e., to achieve a concise andstandardized terminology in the communication between operators,administrations and the ITU.

The designation describes:

Page 222: TND Complete

RADIO TRANSMISSION NETWORK AND FREQUENCY PLANNING

6 Ericsson Radio Systems AB

7/038 02-LZU 102 152, Rev A, November 1999

• Necessary bandwidth, by three numerals and one alphabeticcharacter. The alphabetic character is to be H (Hz), K (KHz), M(MHz) or G (GHz) and is to occupy the position of the decimalpoint and is to represent the unit of bandwidth. Example: Thebandwidth 28.0 MHz is designated as ”28M0”.

• The class of emission is to be designated by a set of alpha-numericcharacteristics. The basic characteristics are:

(1) first symbol - type of modulation of the main carrier. Example:”G”, Phase modulation(2) second symbol - nature of signal(s) modulating the main carrier.Example: ”7”, Two or more channels containing quantified ordigital information;(3) third symbol - type of information to be transmitted. Example:”E”, Telephony;

• Optional additional characteristics consisting of two symbols, thefourth and the fifth, are provided in Appendix 6, part A:

(4) fourth symbol - signal details. Example: ”D”, Four-conditioncode in which each condition represents a signal element, e.g., oneor more bits;(5) fifth symbol - nature of multiplexing. Example: ”T”, Timedivision multiplexing;

The examples above give the designation: 28M0G7EDT for a signalhaving a bandwidth of 28 MHz, that is phase modulated, that handlesdigital telephony, in which the signal is coded with a four-conditioncode and that is time division multiplexed.

Appendix 6, part B, provides a number of methods for thedetermination of the necessary bandwidth for different modulationmethods. The appendix also includes some examples of theircalculation.

Article 6 (RR footnotes 339 - 373)“General Rules for the Assignment and Use of Frequencies”.

Article 6 provides general rules relating to frequency economy, harmfulinterference and stations in distress. The salient points are:

• Frequency economy: The limitation of the number of frequenciesand the used spectrum to the minimum required for the satisfactoryoperation of the necessary services. Use the latest technicaladvances.

Page 223: TND Complete

RADIO REGULATIONS

Ericsson Radio Systems AB

7/038 02-LZU 102 152, Rev A, November 1999

7

• Harmful interference: In order to avoid harmful interference,frequencies are to be assigned to radio stations in accordance withthe Table of Frequency Allocations (Article 8). The frequenciesassigned near the limits of an allocated band may not cause harmfulinterference to services allocated to adjoining frequency bands.When allocating a band of frequencies to a variety of services inadjacent regions, the basic principle is the equality of the right tooperate. No harmful interference may affect the services in otherregions.

• Distress: The Radio Regulations makes no provision for theprevention of the use of a radio or any other means of radiocommunications in situations of distress.

Article 7 (RR footnotes 374 - 390)“Special Agreements”.

Two or more members (of the ITU) may, with some exceptions,conclude special agreements regarding the sub-allocation of bands ofservices or the assignment of frequencies to specific services. Thespecial agreements shall not be in conflict with any of the provisions ofthe Radio Regulations, i.e., no radio system may be affected by harmfulinterference resulting from such agreements.

Article 8 (RR footnotes 391 - 952)“Frequency Allocations”.

This important part of the Radio Regulations contains informationconcerning the allocation and regulation of frequency bands for allservices. This implies that the frequency spectrum from approximately9 kHz up to 400 GHz is allocated and regulated by these stipulations.

The following subjects are of interest:

Article 8, Section I: Regions and Areas

The world has been divided into three regions (footnotes 393 to 399) forthe purposes of frequency allocation. Notes often exist that regulate theuse of the different frequency bands used in the smaller areas of aregion (such as in countries). The regions are shown on a map anddescribed in detail in the text.

The three regions are roughly the following:

Region 1: Europe, Russia, Middle East and Africa.

Page 224: TND Complete

RADIO TRANSMISSION NETWORK AND FREQUENCY PLANNING

8 Ericsson Radio Systems AB

7/038 02-LZU 102 152, Rev A, November 1999

Region 2: America, North and South.

Region 3: The remainder of the world.

Article 8, Section II: Service and Allocation categories

The Tables of Frequency Allocations found in Section IV of Article 8indicate that some frequency bands are allocated to more than oneservice, either on a worldwide or on a regional basis. These services aredivided into different categories, where the main categories are(footnotes 413 - 425):

• Primary Service and Permitted Service which have equal rights,except that, in the preparation of frequency plans, the primaryservice as compared with the permitted service, shall have priorchoice of frequencies.

Secondary Servicea) shall not cause harmful interference to stations of primary orpermitted services to which frequencies already are assigned or to whichfrequencies may be assigned at a later Date.b) cannot claim protection from harmful interference from stations ofprimary or permitted service to which frequencies already are assignedor to which frequencies may be assigned at a later Date.c) can claim protection, however, from harmful interference fromstations of the same or other secondary services to which frequenciesmay be assigned at a later Date.

In addition, three more categories should be noted:

• Additional Allocations (footnotes 426 - 429)

• Alternative Allocations (footnotes 430 - 433)

• Miscellaneous Provisions (footnotes 434 - 436)

Article 9 (RR footnotes 953 - 989)“Special Rules for the Assignment and Use of Frequencies”.

Article 9 deals with rules concerning safety services, the use of lowfrequencies and the use of frequencies allocated to one service that areused by other services, e.g., aircraft earth stations are in some casesauthorized to use frequencies allocated to maritime mobile-satelliteservices.

Some examples of the contents are:

Page 225: TND Complete

RADIO REGULATIONS

Ericsson Radio Systems AB

7/038 02-LZU 102 152, Rev A, November 1999

9

Low frequencies that have long-distance characteristics, i.e., those in theband between 5 MHz and 30 MHz, are to be reserved for long distancecommunication as far as is possible.

Of special interest, from the radio-link transmission point of view, are:

Any emission capable of causing harmful interference to distress, alarm,urgency or safety communication over the international distress andemergency frequencies that have been established for these purposes byRadio Regulations is prohibited.

Any administration may assign a frequency in a band allocated to thefixed service to transmit from one specified fixed point to one or morespecified fixed points provided that such transmissions are not intendedto be received directly by the general public (i.e., point to multipointsystems are allowed in the fixed frequency bands).

Article 10 (RR footnotes 990 -1040)“International Frequency Registration Board”.

The International Frequency Registration Board (IFRB) formed prior to1993 is a part of the former ITU organization, equal in stature to CCITTand CCIR. Today, IFRB duties are carried out by the ITU-R RadioCommunication Bureau and Radio Regulations Board. Relevantprovisions in the present edition of the Radio Regulations (edition of1990, revised 1994) still refer to the IFRB.

The constitution and essential duties of the International FrequencyRegistration Board are defined in the ITU Convention. The Board hasfrequent meetings, at least once a week.

Examples of functions of the Board are the following:

• Processing and administration of the Master International FrequencyRegister. Compilation for publication of frequency lists reflectingthe data recorded in the Master International Frequency Register.

• The study, on a long-term basis, of the usage of the radio frequencyspectrum, with a view to making recommendations for its moreeffective use.

• Assistance to the ITU or administrations in the investigation ofharmful interference in order to achieve the efficient use of theradio-frequency spectrum. This is achieved through the use oftechnical standards and training in the fields of spectrummanagement and the utilization of frequencies.

Page 226: TND Complete

RADIO TRANSMISSION NETWORK AND FREQUENCY PLANNING

10 Ericsson Radio Systems AB

7/038 02-LZU 102 152, Rev A, November 1999

Radio Regulations volume 4

Radio regulation volume 4 is an update of Radio Regulations edition1994. This publication is complementary to the three earlier mentionedvolumes of the Radio Regulations.

Volume 4 of the Radio Regulations is a consolidated documentincorporating the decisions of the World Radio CommunicationConference 1995 (WRC-95) concerning the revised provisions of theRadio Regulationsthat came into force provisionally on 1 January 1997.

Revisions are made in:

• Article 8, Frequency Allocations.

• Article 28, Space Radio Communication Services Sharing FrequencyBands with Terrestrial Radio Communication Services above 1 GHz.

• Article 29, Special Rules Relating to Space Radio CommunicationServices.

• Appendices 1 and 2, concerning Notification and Recording in theMaster International Frequency Register of Frequency Assignmentsto Terrestrial Radio Communication Stations.

• Appendix 3, Notices Relating to Space Radio Communication andRadio Astronomy Stations.

• Appendix 4, Advance Publication Information to Be Furnished for aSatellite Network.

• Appendix 5, concerning the Frequency Allotment Plan for CoastRadiotelephone Stations.

References

”Radio Regulations” ITU publication, vol. 1-4, revised edition 1998.

General information and facts on ITU were gathered from Internet”http//www.itu.int” during November 1999.

Page 227: TND Complete

i

THE RADIO SPECTRUM

AND

CHANNEL ARRANGEMENT

The chapter deals with the principles that apply to thestructuring of frequency channel arrangements, necessarychannel separation as a function of modulation methodand transmission capacity plus a reference to currentlyapplicable ITU-R recommendations concerning frequencychannel arrangements in the frequency band 1.5 to 55GHz.

TABLE OF CONTENTS

Available frequency bands ................................................................................................................................ 1Available frequency-channel arrangements....................................................................................................... 1The spectrum..................................................................................................................................................... 1

The radio spectrum.............................................................................................................................. 2Channel width ..................................................................................................................................... 3

Modulation ........................................................................................................................................................ 5Analog systems.................................................................................................................................... 6Digital systems .................................................................................................................................... 6Modulation and spectral efficiency ..................................................................................................... 6

Two-state Phase-shift Keying (2 PSK) modulation............................................................... 6Four-state Phase-shift Keying (4 PSK) modulation .............................................................. 7Eight-state Phase-shift Keying (8 PSK) modulation ............................................................. 7Quadrature amplitude modulation......................................................................................... 7

Frequency-channel arrangements ...................................................................................................................... 8Construction of channel arrangements ................................................................................................ 8

Alternated Pattern ................................................................................................................. 11Co-channel band re-use......................................................................................................... 11Interleaved pattern................................................................................................................. 12

ITU-R defined radio-frequency channel arrangements ..................................................................................... 12References ......................................................................................................................................................... 14

Page 228: TND Complete

THE RADIO SPECTRUM AND CHANNEL ARRANGEMENT

Ericsson Telecom AB

8/038 02-LZU 102 152, Rev A, November 1999

1

Available frequency bands

When attempting to establish frequencies for a radio-link hop or aradio-link network in a particular country, Radio Regulations Article 8will provide available frequency bands for the country or region inquestion - frequency bands that are internationally approved for theservice in question.

Based on these frequency allocations, the allotment will then be made inaccordance with the recommendations in the ITU-R series F (FixedServices) publications. The allotments consist of one or morealternative radio-frequency channel arrangements. These arrangementsare then to be used in accordance with the rules of the administration inquestion.

Based on the selected radio-frequency channel arrangement and thestipulations found in Radio Regulations, the planning and assignment offrequencies for the radio-link hop or radio-link network can take place.

Available frequency-channel arrangements

Internationally recommended frequency channel arrangements exist tofacilitate the achievement of international coordination and a uniformstandard for the planning of spectrum utilization including standards forthe manufacturers of radio equipment. A number of frequency channelarrangements that lie in the range from 1.5 to 55 GHz have been workedout by ITU-R and may be found in the F series (Fixed Service)recommendations. The frequency channel arrangements have beenadapted to various bandwidth requirements through suitable channelspacing.

In ITU studies that have been carried out to date, a number of bandshave not been the subject of Recommendations for specificradio-frequency channel arrangements which might be fitted into aninternational pattern as has already been done in other parts of thefrequency spectrum. On a regional basis, one may find both otherfrequency bands and other frequency channel arrangements than thoserecommended by ITU.

The spectrum

Electromagnetic waves exist at all frequencies (or wavelengths). Thisendless scale is referred to as the electromagnetic spectrum. The speedof electromagnetic waves is constant (c ≅ 3⋅108 m/s in vacuum).

Page 229: TND Complete

RADIO TRANSMISSION NETWORK AND FREQUENCY PLANNING

2 Ericsson Telecom AB

8/038 02-LZU 102 152, Rev A, November 1999

The radio spectrum is a natural resource. It is limited, but to someextent recoverable. It can also be misused and can be exposed to”environmentally destructive forces” through laziness, unwise frugality,and ruthless exploitation. As a result, it may be difficult to effectivelyutilize portions of the spectrum that have been released and madeavailable for other usage.

It is necessary that one is aware of the consequences to other spectrumusers, when one is vigilant in accommodating one’s owncommunication requirements. A change can create an unpredictablechain reaction. A small-scale improvement may, from a more macropoint of view, prove to be a deterioration. The scarcity of the radiospectrum requires that it has to be rationed, sometimes heavily.

On occasion, more than one radio service may share the same spectralpotion - a proviso being that all users must show consideration for oneanother. It is often the case that one must forgo one’s own wishes sothat the collective capacity that available to the different services is asgreat as possible.

In today’s information society, one is dependent on the fact that allcommunications resources operate effectively. If a dominant services isallowed to expand at the cost of a number of small services, thedominant service may prove to be of little or no use - simply becausethe dominating service is dependent on the support of the smallerservices.

The radio spectrumThe radio spectrum consists of electromagnetic fluctuations that havethe same physical properties as visible light, but have lower frequencies(which is the same as greater wavelengths). Frequency is measured inHertz (Hz) and 1 Hz corresponds to one fluctuation (or cycle) persecond.

There is no physical limit, either upwards or downwards, for thefrequency of electromagnetic fluctuations, however, in accordance withinternational Radio Regulations, it has been more or less arbitrarilydecided that frequency limits exist at 9 kHz and 3,000 GHz (equivalentto wavelengths of 33 km and 0.1 mm respectively). These are theadministrative limits of the Radio Regulations, and it is within theselimits that the following traditional frequency ranges exist:

• HF, high frequencies (3...30 MHz)

• VHF, very high frequencies (30...300 MHz)

• UHF, ultra high frequencies (300...3000 MHz)

Page 230: TND Complete

THE RADIO SPECTRUM AND CHANNEL ARRANGEMENT

Ericsson Telecom AB

8/038 02-LZU 102 152, Rev A, November 1999

3

• SHF, super high frequencies (3...30 GHz)

• EHF, extremely high frequencies (30...300 GHz)

• Not labeled (300…3000GHz)

The different frequency bands have different characteristics with respectto range and the size of the antennas used.

Channel widthThe frequency raster is a fundamental concept in the performance offrequency planning activities. A raster is a subdivision of a frequencyrange or a portion of an available spectrum into segments (channels).

Channel arrangements may be determined both for analog and fordigital systems. When constructing a raster, and during thedetermination of channel assignment, consideration is given to themethod of modulation and the radio link’s capacity – both of whichaffect bandwidth and interference tolerance. For a digital signal, thecapacity is equal to the information data rate expressed in bits/s. Theconcept of modulation will be explained in the next section.

The method of modulation determines the required bandwidth for thetransmitted signal. The suitability of a given modulation method to aparticular application is determined by the following characteristics:

• Spectrum efficiencyA common definition of spectrum efficiency is transmitted quantityof information per used spectrum. The transmitted quantity ofinformation within a given spectrum is expressed in bits/s/Hz.Spectrum efficiency will increase with an increase in number ofmodulation levels.

• Interference toleranceDifferent modulation methods have different interference tolerancecharacteristics. The interference tolerance of digital systems ispresented as a minimum C/I quotient (carrier/interference ratio) fordifferent bit-error ratios. In general, interference tolerancedeteriorates as the number of modulation levels is increased.

Table 1 gives some examples of modulation schemes and theirrespective Nyquist bandwidths. The Nyquist bandwidth values are oneof the factors determining channel separation.

Page 231: TND Complete

RADIO TRANSMISSION NETWORK AND FREQUENCY PLANNING

4 Ericsson Telecom AB

8/038 02-LZU 102 152, Rev A, November 1999

Modulation Variant Nyquist bandwidth (bn)

TCM 16 TCM-2D32 TCM-2D128 TCM-2D512 TCM-2D64 TCM-4D128 TCM-4D512 TCM-4D

B/3B/4B/6B/8

B/5.5B/6.5B/8.5

Table 1:. Examples of different modulation schemes and their respectiveNyquist bandwidths.

bn = Nyquist bandwidthB = Bit rate, code redundancy is not includedPSK = Phase Shift KeyingQAM = Quadrature Amplitude ModulationTCM = Trellis Coded Modulation

The Nyquist bandwidth occupied by the modulated signal can be usedin comparing various modulation schemes. However, this does notgenerally indicate the radio-frequency channel bandwidth that must, inpractice, be allotted to a digitally modulated signal. This channelbandwidth is, in principle, a trade-off between the choice of modulation,inter-channel interference and network constraints and is, in practice,provided by the relevant ITU-R Recommendation on radio-frequencychannel arrangements. It is expected to vary in the range 1.2 bn to 2 bn

for various systems.

PSK 2-state PSK4-state PSK8-state PSK16-state PSK

BB/2B/3B/4

QAM 16-QAM32-QAM64-QAM128-QAM256-QAM512-QAM

B/4B/5B/6B/7B/8B/9

Page 232: TND Complete

THE RADIO SPECTRUM AND CHANNEL ARRANGEMENT

Ericsson Telecom AB

8/038 02-LZU 102 152, Rev A, November 1999

5

Modulation

Generally speaking, modulation is a physical operation related to themodification of certain wave characteristics in accordance with thecharacteristics of another wave. In radio-relay systems, the basebandsignal containing the information to be transmitted from one place toanother is used to modulate the radio-frequency carrier (RF carrier)during the transmission process. The reverse occurs during the receptionprocess in which the signal containing the information is extracted bydemodulating the received signal.

The RF carrier is a sine wave given by

f)ð(öAU ⋅⋅+⋅= 2cos ........................................................................(1)

where

U = RF carrier strength

A = amplitude

ϕ= phase

f = frequency

Modification of the RF carrier (i.e., modulation) is possible by using ofone of, or combinations of the following three modes:

• changing its amplitude A, that is, amplitude modulation (AM)

• changing its phase ϕ, that is, phase modulation (PM)

• changing its frequency f, that is, frequency modulation (FM)

Direct modulation of the baseband on the RF carrier is usuallyencountered in low-cost analog systems having low and mediumcapacities. A two-step procedure can also be used, where the basebandis modulated on an Intermediate Frequency (IF) in the first step, and thefrequency is up-converted to RF in the second step. Modern equipmenteliminates the IF stage by performing RF frequency generation andmodulation in one and the same circuit.

Page 233: TND Complete

RADIO TRANSMISSION NETWORK AND FREQUENCY PLANNING

6 Ericsson Telecom AB

8/038 02-LZU 102 152, Rev A, November 1999

Analog systemsFrequency modulation (FM) is usually employed in analog radio-systems because it is more ”resistant” to distortion than amplitudemodulation (AM). Using frequency modulation, the IF and RF carrierdeviate from their nominal values as a function of baseband frequency.The relation between frequency deviation and baseband frequency isreferred to as the modulation index. The higher the modulation index,the better the signal-to-noise ratio (SNR) but also the larger is thebandwidth required in the RF and IF frequency spectrums.

Digital systemsDigital modulation is generally much more complex than analogmodulation. The following will introduce some general digitalmodulation concepts.

A digital telephone channel requires 64 kbit/s as compared with 4 kHzfor an analog telephone channel. In addition, existing frequency planswere originally established for analog transmission. The result is thatthe transmission capacity of digital signals must be accommodated forin such frequency plans. Economizing on the usage of frequencyspectrum is therefore of great importance when applying digitalmodulation.

Bandwidth economy may otherwise be referred to as spectral efficiencyand is defined as the quotient between transmission capacity and RFcarrier bandwidth, that is, by bit/s/Hz. Spectral efficiency dependslargely on the modulation mode.

Modulation and spectral efficiencyThe main objective of digital modulation is to bring the baseband signalonto the RF carrier using a minimum of bandwidth. Basically, digitalsignals have two amplitude states, 0 or 1, corresponding to phases 0 and180 degrees.

Two-state Phase-shift Keying (2 PSK) modulation

The simplest modulation mode is two-state Phase-Shift Keying (2 PSK)and is obtained by keying the two state conditions 0 and 180 degreesonto the RF carrier by shifting the phase of the carrier. Shifting thecarrier phase by 180 degrees requires one hertz of the carrier frequencyfor each bit of the baseband, which gives a spectral efficiency of 1bit/s/Hz. Thus, a 2-Mbit/s baseband modulated with 2 PSK requires aRF carrier with a bandwidth of 2 MHz.

Page 234: TND Complete

THE RADIO SPECTRUM AND CHANNEL ARRANGEMENT

Ericsson Telecom AB

8/038 02-LZU 102 152, Rev A, November 1999

7

Four-state Phase-shift Keying (4 PSK) modulation

Four-state phase-shift keying modulation (4 PSK) is also calledquaternary PSK (QPSK) modulation because the binary signal isconverted into a quaternary signal and the four possible phases of thequaternary signal are keyed onto the RF carrier by shifting the carrierphase in steps of 90-degrees. The spectral efficiency is 2.0 bit/s/Hz.Thus a 2-Mbit/s baseband modulated with 4 PSK requires a RF carrierwith a bandwidth of 1 MHz.

Eight-state Phase-shift Keying (8 PSK) modulation

By shifting the carrier in steps of 45-degrees, eight possible phases ofthe signal are keyed onto the RF carrier. This is eight-state phase-shiftkeying modulation (8 PSK). The spectral efficiency is 3 bit/s/Hz. Thus a2-Mbit/s baseband modulated with 8 PSK requires a RF carrier with abandwidth of 0.67 MHz.

Quadrature amplitude modulation

Higher modulation mode, for instance 16 PSK, requires better signal-to-noise performance, which is practically difficult to accomplish. In suchcases, quadrature amplitude modulation (QAM) which is a combinationof phase-shifting and amplitude modulation of the carrier, may be used.In this case, two carriers that are 90 degrees out of phase (this is phasequadrature) are amplitude modulated (AM) by a digital signal(baseband) having a finite number, m, of amplitude levels - that aresubsequently added to one another. This is known by m-QAM.

For instance, 16 QAM gives 16 different signal states, which are bothamplitude and phase-shift modulated onto the RF carrier. This yields aspectral efficiency of 4 bit/s/Hz. Thus a 140 Mbit/s baseband requires aRF carrier that has a bandwidth of 140÷4 = 35 MHz. This fits the 40MHz RF channel spacing for the bands in the range 4 to 11 GHz. 16QAM modulation is however not applicable for the bands ranging from2 to 8 GHz, where RF channel spacing is 29/30 MHz.

64 QAM modulation yields a spectral efficiency of 6 bit/s/Hz. Thus a140 Mbit/s baseband requires an RF carrier that has a bandwidth of140÷6 ≈ 23 MHz, which fits the 29/30 MHz RF channel spacing in thefrequency range mentioned above.

Page 235: TND Complete

RADIO TRANSMISSION NETWORK AND FREQUENCY PLANNING

8 Ericsson Telecom AB

8/038 02-LZU 102 152, Rev A, November 1999

Frequency-channel arrangements

Construction of channel arrangementsFor radio systems that use Frequency Division Duplex (FDD) theavailable frequency band is subdivided into two equal halves, a lowerand an upper duplex half. The separation between the lowest frequencyin the lower half and that of the upper half is referred to as the duplexseparation. The duplex separation is always to be sufficiently large suchthat the intended radio equipment can operate interference-free underduplex operation, i.e., concurrent transmission over, for example, thelower duplex half and reception over the duplex separation of the upperhalf.

An additional problem arises when more than one link is located at thesame site, namely that a transmitter belonging to a radio system may notinterfere the receiver belonging to another radio system. To achieve this,a minimum frequency separation is required between the transmitter andreceiver in question. This minimum frequency separation is less thanthe duplex separation, and is (among other factors) dependent on theantenna isolation between the two systems. By selecting a separationbetween the upper and lower duplex bands that at least corresponds tothis minimum frequency separation, the conditions required forinterference-free transmission will be met as long as all of thetransmitters in a given node are localized to one duplex band and all ofthe receivers to the other.

Rec. ITU-R F.746-3 describes the construction of frequency channelarrangements having two duplex halves. The recommendation alsoincludes a table containing frequency channel arrangements defined byITU-R plus a reference to currently valid recommendations.

ITU-R recommends that the preferred radio-frequency channelarrangements should be developed from the homogeneous patternsgiven by:

• alternated, Figure 1a

• co-channel band re-use, Figure 1b

• interleaved band re-use, Figure 1c

The primary parameters affecting the choice of radio-frequency channelarrangements are:

Page 236: TND Complete

THE RADIO SPECTRUM AND CHANNEL ARRANGEMENT

Ericsson Telecom AB

8/038 02-LZU 102 152, Rev A, November 1999

9

• XS, carrier spacing, defined as the radio-frequency separationbetween the center frequencies of adjacent radio-frequency channelsof the same polarization and in the same direction of transmission;

• YS, defined as the radio-frequency separation between the centerfrequencies of the go and return radio-frequency channels which arenearest to each other. For the case where the go and return frequencysub-bands are not contiguous, such that there exists band(s)allocated for service(s) in the gap between them; then YS is to beconsidered as including the band separation (BS) equal to the totalwidth of the allocated band(s) used by such service(s).

• ZS, defined as the radio-frequency separation between the centerfrequencies of the outermost radio-frequency channels and the edgeof the frequency band. For the case where the lower and upperseparations differ in value, Z1S refers to the lower separation and Z2Srefers to the upper separation. For the case where go and returnfrequency sub-bands are not contiguous, such that there existsband(s) allocated for service(s) in the gap between them; then ZSi

will be defined for the innermost edges of both sub-bands and willbe included in YS.

• DS, Tx/Rx duplex spacing, defined as the radio-frequencyseparation between corresponding go and return channels, constantfor each couple of i-th and i'-th frequencies, within a given channelarrangement.

Page 237: TND Complete

RADIO TRANSMISSION NETWORK AND FREQUENCY PLANNING

10 Ericsson Telecom AB

8/038 02-LZU 102 152, Rev A, November 1999

A B

A B

A B

Alternated patternMain frequencies

FIGURE 1

Channel arrangements for the three possibleschemes considered in the text

Channel number

Main frequencypattern

Band re-use in theco-channel mode

Channel number

Main frequencypattern

Band re-use in theinterleaved modeChannel number

a)

b)

c)

Pola

riza

tion

sPo

lari

zati

ons

Pola

riza

tion

s

H(V)

V(H)

H(V)

V(H)

H(V)

V(H)

XS

XSXS2

1 3

2 4 N

D01

1′ 3′

2′ 4′ N′ZSYS

XS

YS

DS

DS

N1 2 3 4

1r 2r 3r 4r Nr

N′1′ 2′ 3′ 4′

1′r 2′r 3′r 4′r N′rZS

XS

YS

DS

N1 2 3 4

1r 2r 3r 4r Nr

N′1′ 2′ 3′ 4′

1′r 2′r 3′r 4′r N′rZS

XSXS2

A: “go” channels B: “return” channels

Figure 1: Channel arrangements for the three possible schemes.

The choice of radio-frequency channel arrangement depends on thevalues of cross-polar discrimination, XPD [see equation 2], and netfilter discrimination, NFD [see equation 3], where these parameters aredefined as:

RXV

RXH

P

PXPD = ........................................................................................(2)

where:

XPD = cross-polar discrimination

PRXH = power received on horizontal polarization transmitted onhorizontal polarization, mW.

PRXV = power received on vertical polarization transmitted onhorizontal polarization, mW.

Page 238: TND Complete

THE RADIO SPECTRUM AND CHANNEL ARRANGEMENT

Ericsson Telecom AB

8/038 02-LZU 102 152, Rev A, November 1999

11

Equation (2) also applies for the case where the polarization plan is thereverse.

filter)RX(ADJ

RX(ADJ)

+

=P

PNFD ..............................................................................(3)

where:

NFD = net filter discrimination

PRX(ADJ) = Adjacent channel received power, mW

PRX(ADJ+filter) = Adjacent channel received power by the main receiver,mW following the RF (radio frequency), IF (intermediate) and BB (baseband) filters.

The XPD and NFD parameters are usually expressed in dB andcontribute to the value of carrier-to-interference ratio. When the ratiobetween two received powers, expressed in mW is A, then the ratio indB becomes AdB=10⋅logA.

The XPD and NFD parameters (dB) contribute to the value of carrier-to-interference ratio.

If XPDmin is the minimum value reached for the percentage timerequired, the total amount of interfering power can be evaluated fromthis value of XPDmin and from the adjacent channel NFD. The resultmust be compared with the minimum value of carrier-to-interferenceratio (C / I)min that is acceptable to the modulation method adopted.

Alternated Pattern

Alternated channel arrangements can be used (neglecting the co-polaradjacent channel interference contribution) if:

( ) dB 3min

min

≥−+

IC

NFDXPD ......................................................(4)

Co-channel band re-use

Co-channel arrangements can be used if:

dB

10

1

10

11

log10min

10

3

10

+⋅

−+IC

aNFDXIFXPD

.........................................(5)

Page 239: TND Complete

RADIO TRANSMISSION NETWORK AND FREQUENCY PLANNING

12 Ericsson Telecom AB

8/038 02-LZU 102 152, Rev A, November 1999

where:

XIF = XPD improvement factor of any cross-polar interferencecountermeasures, if implemented in the receiver affected by theinterference.

NFDa = Net Filter Discrimination evaluated at XS frequency spacing.

The NFD value (NFD-3) takes into account double-sided like-modulated interference.

Interleaved pattern

Interleaved channel arrangements can be used if:

( )

dB

10

1

10

11

log10min

10

3

10

3

+⋅

−−+IC

aa NFDNFDXPD

...................................(6)

where:

NFDb = Net Filter Discrimination evaluated at XS / 2 frequency spacing.

ITU-R defined radio-frequency channelarrangements

Table 2 and Table 3 (from Rec. ITU-R F.746-3) present a summary ofthe currently ITU-R defined radio-frequency channel arrangementsincluding references to the relevant Recommendations.

Page 240: TND Complete

THE RADIO SPECTRUM AND CHANNEL ARRANGEMENT

Ericsson Telecom AB

8/038 02-LZU 102 152, Rev A, November 1999

13

Table 2: Radio-frequency channel arrangements for radio-relaysystems in frequency bands below about 17 GHz.

Band

(GHz)

Frequency range

(GHz)

Recommendation ITU-R

F-Series

Channel spacing

(MHz)

1.5 1.427-1.53 746, Annex 1 0.5; 1; 2; 3.5

2 1.427-2.69

1.7-2.1; 1.9-2.3

1.7-2.3

1.9-2.3

1.9-2.3

1.9-2.3

2.3-2.5

2.5-2.7

701

382

283

1098

1098, Annexes 1, 2

1098, Annex 3

746, Annex 2

283

0.5 (pattern)

29

14

3.5; 2.5 (patterns)

14

10

1; 2; 4; 14; 28

14

4 3.8-4.2

3.6-4.2

3.6-4.2

382

635

635, Annex 1

29

10 (pattern)

90; 80; 60; 40

5 4.4-5.0

4.4-5.0

4.4-5.0

4.54-4.9

746, Annex 3

1099

1099, Annex 1

1099, Annex 2

28

10 (pattern)

40; 60; 80

40; 20

L6 5.925-6.425

5.85-6.425

383

383, Annex 1

29.65

90; 80; 60

U6 6.425-7.11

6.425-7.11

384

384, Annex 1

40; 20

80

7 7.425-7.725

7.425-7.725

7.435-7.75

7.11-7.75

385

385, Annex 1

385, Annex 2

385, Annex 3

7

28

5

28

8 8.2-8.5

7.725-8.275

7.725-8.275

8.275-8.5

386

386, Annex 1

386, Annex 2

386, Annex 3

11.662

29.65

40.74

14; 7

10 10.3-10.68

10.5-10.68

10.55-10.68

746, Annex 4

747, Annex 1

747, Annex 2

20; 5; 2

7; 3.5 (patterns)

5; 2.5; 1.25 (patterns)

11 10.7-11.7

10.7-11.7

10.7-11.7

10.7-11.7

387, Annexes 1 and 2

387, Annex 3

387, Annex 4

387, Annex 5

40

67

60

80

12 11.7-12.5

12.2-12.7

746, Annex 5, § 3

746, Annex 5, § 2

19.18

20 (pattern)

13 12.75-13.25

12.75-13.25

12.7-13.25

497

497, Annex 1

746, Annex 5, § 1

28; 7; 3.5

35

25; 12.5

14 14.25-14.5

14.25-14.5

746, Annex 6

746, Annex 7

28; 14; 7; 3.5

20

15 14.4-15.35

14.5-15.35

14.5-15.35

636

636, Annex 1

636, Annex 2

28; 14; 7; 3.5

2.5 (pattern)

2.5

Page 241: TND Complete

RADIO TRANSMISSION NETWORK AND FREQUENCY PLANNING

14 Ericsson Telecom AB

8/038 02-LZU 102 152, Rev A, November 1999

Table 3: Radio-frequency channel arrangements for radio-relaysystems in frequency bands above about 17 GHz.

References

Rec. ITU-R F.746-3.

Rec. ITU-R F.1101.

“Ang planering av frekvensraster”, Billström, O., Privatecommunication, Ericsson Radio Systems, 1993.

“Frekvensplanering”, Hultgren, D., GT/RA 9344, 1989.

Band

(GHz)

Frequency range

(GHz)

Recommendation ITU-R

F-Series

Channel spacing

(MHz)

18 17.7-19.7

17.7-21.2

17.7-19.7

17.7-19.7

17.7-19.7

595

595, Annex 1

595, Annex 2

595, Annex 3

595, Annex 4

220; 110; 55; 27.5

160

220; 80; 40; 20; 10; 6

3.5

13.75; 27.5

23 21.2-23.6

21.2-23.6

21.2-23.6

21.2-23.6

21.2-23.6

21.2-23.6

22.0-23.6

637

637, Annex 1

637, Annex 2

637, Annex 3

637, Annex 4

637, Annex 5

637, Annex 1

3.5; 2.5 (patterns)

112 to 3.5

28; 3.5

28; 14; 7; 3.5

50

112 to 3.5

112 to 3.5

27 24.25-25.25

24.25-25.25

25.25-27.5

25.25-27.5

27.5-29.5

27.5-29.5

27.5-29.5

748

748, Annex 3

748

748, Annex 1

748

748, Annex 2

748, Annex 3

3.5; 2.5 (patterns)

56; 28

3.5; 2.5 (patterns)

112 to 3.5

3.5; 2.5 (patterns)

112 to 3.5

112; 56; 28

31 31.0-31.3 746, Annex 8 25; 50

38 36.0-40.5

36.0-37.0

37.0-39.5

38.6-40.0

39.5-40.5

749

749, Annex 3

749, Annex 1

749, Annex 2

749, Annex 3

3.5; 2.5 (patterns)

112 to 3.5

140; 56; 28; 14; 7; 3.5

50

112 to 3.5

55 54.25-58.2

54.25-57.2

57.2-58.2

1100

1100, Annex 1

1100, Annex 2

3.5; 2.5 (patterns)

140; 56; 28; 14

100

Page 242: TND Complete

i

INTERFERENCEBASIC CONCEPTS

The objective of this chapter is to introduce and describethe basic concepts that apply to the analysis of interferenceand, in particular, the origins and the possible sources ofinterference. The chapter provides a detailed discussion ofthe different types of interference sources and their effectson radio-relay equipment. The location of several radiosystems to the same site is also discussed in some detail.

TABLE OF CONTENTS

Introduction....................................................................................................................................................... 1Background ......................................................................................................................................... 1Interference sources and paths ............................................................................................................ 1Basic concepts..................................................................................................................................... 2

Interference ........................................................................................................................... 2Interference analysis.............................................................................................................. 2Telecommunication conflicts ................................................................................................ 3Nominal frequency................................................................................................................ 3Frequency coincidence.......................................................................................................... 3

The co-location of more than one radio station................................................................................................. 3Mutual interference ........................................................................................................................................... 4Types of interference......................................................................................................................................... 5Transmitter unwanted characteristics ................................................................................................................ 6

Transmitter harmonics......................................................................................................................... 6Noise spectrum.................................................................................................................................... 7The transmitter’s total spectrum.......................................................................................................... 8Transmitter false frequencies .............................................................................................................. 9

Receiver unwanted characteristics..................................................................................................................... 9Receiver intermodulation .................................................................................................................... 9Blocking .............................................................................................................................................. 9Secondary channels ............................................................................................................................. 9Adjacent signal interference ................................................................................................................ 10

Interference-free networks................................................................................................................................. 10How may interference be avoided? ................................................................................................................... 10References ......................................................................................................................................................... 11

Page 243: TND Complete

INTERFERENCE - BASIC CONCEPTS

Ericsson Radio Systems AB

9/038 02-LZU 102 152, Rev A, November 1999

1

Introduction

BackgroundThe increased use of radio communications has given rise to significantinterference risks. The number of radio stations located in denselypopulated areas is often, for example, so large that careful networkplanning is of decisive importance in maintaining the availability andquality of these radio connections. Every one of a network hops musttherefore exhibit such availability and quality that the entire connection,subscriber to subscriber, maintains the dimensioning standard that is tobe achieved. The correct execution of optimized frequency assignmentsshould give rise to interference levels that are sufficiently low so as notto affect radio connection availability and quality.

Interference sources and pathsThe risk of interference between radio installations has increased in stepwith the increased use of radio communications services for both publicand military applications. The increased demographic crowd has givenrise to a situation in which installations that transmit and receive radiosignals over adjacent frequencies are often placed so close to oneanother that the risk of unintentional interference is very great.

Many different types of interference sources exist that can affect thetransmitters and receivers of a radio communication system: cosmicradiation, radar and navigation systems, electrical power lines, sparkgenerating equipment, etc. This document only addresses interferencethat is caused by other radio systems.

Interference may reach a receiver via its antenna, its power supplysystem or via the equipment’s housing. In principle, numerousalternatives are possible, interference may propagate from:

• the equipment housing of one unit to that of another unit, betweenunits housed in the same cabinet or in the same telecommunicationroom

• the transmitter antenna to the receiver’s equipment housing

• the transmitter’s antenna to the receiver’s antenna

• the transmitter’s equipment housing to the receiver’s antenna

Page 244: TND Complete

RADIO TRANSMISSION NETWORK AND FREQUENCY PLANNING

2 Ericsson Radio Systems AB

9/038 02-LZU 102 152, Rev A, November 1999

• as a result of spurious signals in the power supply system

Figure 1 illustrates possible interference paths.

T R

Figure 1: Possible interference paths.

The complexity of large installations may be so significant that findinga solution that prevents or that ”neutralizes” the effects of interferencemay be very difficult. Regardless of an installation’s complexity, anumber of interference paths can be avoided by following certain rulesand regulations when placing equipment in the installation. This sectionwill however primarily address interference that is spread via antennasystems.

Basic concepts

Interference

The concept of interference can be interpreted in many different ways.In the context of radio links, one often encounters the concept ofinterference in connection with frequency planning, which generallyentails the optimization of frequency utilization based on givenprerequisites such that unintentional telecommunications conflicts maybe avoided.

Interference analysis

Interference analysis, i.e., the study of possible interference risks undergiven conditions. Interference analysis and frequency planning gotherefore hand-in-hand with one another.

Actually, interference includes many different concepts and embraces alarge number of applications. Knowledge in related areas is thereforeimportant, for example, knowledge of ITU-T and ITU-Rrecommendations as well as knowledge of country-wide regional andlocal frequency plans is of very great consequence.

Page 245: TND Complete

INTERFERENCE - BASIC CONCEPTS

Ericsson Radio Systems AB

9/038 02-LZU 102 152, Rev A, November 1999

3

Telecommunication conflicts

Interference that is the result of other radio transmitters is referred to asinterference or as telecommunication conflicts and arises due toimproper frequency planning or as the result of imperfections in theradio equipment. Such imperfections exist even in the latest generationradio equipment. A transmitter designed to radiate a given frequencymay therefore concurrently radiate other frequencies (generally of lowerpower).

Nominal frequency

An important concept is this context is nominal frequency which isdefined as the frequency to which a transmitter or receiver is tuned.

Frequency coincidence

Frequency coincidence refers to the fact that a radiated frequencycorresponds to the frequency of a receiver, such that

• a transmitter’s nominal frequency corresponds to the receiver’snominal frequency

• a transmitter’s nominal frequency corresponds to one of thesecondary channels of the receiver

• a false frequency or harmonic produced by a transmitter correspondsto a receiver’s nominal frequency

• an intermodulation product between two or more transmitterscorresponds to a receiver’s nominal frequency

This section will describe the various possible types of interference thatmay arise in both transmitters and receivers.

The co-location of more than one radio station

Co-location is a general concept that refers to a so-called multi-stationsite consisting of numerous transmitters and receivers installed within alimited geographical area. The site often consists of a number ofantennas that are all mounted on one and the same mast or distributedamong a small number of closely positioned masts.

The co-location of radio stations may give rise to significantinterference if not preceded by pre-studies and careful planning. In spiteof the risk of interference, the co-location of radio stations isoccasionally unavoidable for the following reasons:

Page 246: TND Complete

RADIO TRANSMISSION NETWORK AND FREQUENCY PLANNING

4 Ericsson Radio Systems AB

9/038 02-LZU 102 152, Rev A, November 1999

• for one reason or another, the licensing agency refuses to grantpermission for the new construction of a mast and refers theapplicant to use existing masts for the new radio users

• the characteristics of certain geographical locations are such thatthey are perceived as being attractive from a radio coverage point-of-view, for example locations that are situated high above thesurrounding areas that already have existing masts

• larger radio systems may often be made up of numerous stations thatmust be co-located – for reasons such as the achievement of optimalresource utilization, such as road networks, electrical power andmaintenance

Mutual interference

The co-location of more than one radio station may give rise tointerference between the transmitters and the receivers. The source ofthe interference experienced by one of the co-located receivers may beone or more of the other receivers or transmitters, which is mostcommon. Generally, the mutual interference that occurs between radiostations may be subdivided into two main groups:

• interference between different radio systems that utilize the sameradio frequency

• interference between different radio systems that utilize differentradio frequencies

Interference between different radio systems that utilize the same radiofrequency is usually corrected by the governmental agencies whose dutyit is to assign frequencies. The guiding principle for such frequencyassignment is the size of the geographical distance that should beapplied between the different radio systems having the same frequency.Interference between different radio systems that utilize the samefrequency is therefore not addressed here.

As mentioned earlier, interference between different radio systems thatutilize different radio frequencies is the result of imperfections in radioequipment or is due to the predominance of a high-power signal thatinterferes with a receiver that expects a signal of a comparatively lowerpower level. One condition for the occurrence of interference is theresult of, among many other factors, a sort of ”collaboration” betweenthe transmitter’s and the receiver’s secondary characteristics, i.e., otherattributes over and above the attributes that were designed into theequipment in order that they fulfill their intended function.

Page 247: TND Complete

INTERFERENCE - BASIC CONCEPTS

Ericsson Radio Systems AB

9/038 02-LZU 102 152, Rev A, November 1999

5

Stated simply, equipment imperfections always exist and may thereforelead to situations in which the transmitted power of frequencies that lieoutside of the transmitter’s nominal frequency may reach receivers thatare sensitive to frequencies that lie outside of their nominal receptionfrequencies. The collaboration mentioned above refers to a certainamount of correspondence between the ”other” frequencies of thetransmitter and the ”other” sensitivities of the receiver. This type ofinterference will be addressed in detail.

Types of interference

The cause of the aforementioned radio equipment imperfections is thenon-linearities that are inherent in transmitters and receivers plus thenoise generated by the various components used in these transmittersand receivers, e.g., those found in oscillators. Non-linearities areunavoidable and are therefore an ”innate” problem in practically allactive components found in radio equipment. A sinusoidal signal,sin (f0), that is applied to a non-linear amplifier stage will give rise toharmonics having frequencies n⋅f0, see Figure 2.

Vout

Vin

b f⋅sin 0b g

c f c f1 0 2 02⋅ + ⋅ +sin sin ...b g b g

Vin Vout

f0f0, 2f0, 3f0, 4f0 ...

Figure 2: A non-linear amplifier stage gives rise to harmonics.

This ”collaboration” between a transmitter and receiver results thereforein interference that makes its presence felt in different ways dependingon the secondary characteristics of the transmitter and receiver. Thesesecondary characteristics are primarily the result of the non-linearitiesinherent in high-frequency circuitry.

The following interference characteristics may possibly appear intransmitters:

Page 248: TND Complete

RADIO TRANSMISSION NETWORK AND FREQUENCY PLANNING

6 Ericsson Radio Systems AB

9/038 02-LZU 102 152, Rev A, November 1999

• transmitter harmonics

• transmitter false frequencies (spurious signals)

• transmitter noise

• transmitter intermodulation (more than one transmitter is involved)

The following interference characteristics may possibly appear in areceiver:

• receiver intermodulation (more than one transmitter frequency aremixed in one receiver)

• blocking

• receiver spurious signals

• secondary channels

• adjacent signal interference

Transmitter unwanted characteristics

The description that follows deals with the most important unwantedcharacteristics of a transmitter that may give rise to interference.

Transmitter harmonicsThe non-linearities mentioned above arise during signal amplification(non-linear amplification), in transmitters or receivers. In general,output signals are not completely proportional to the input signals whichmay result in an individual input frequency giving rise to harmonics,i.e., output frequencies that are integer multiples of the individualfrequency in question. These discrete harmonic frequencies areillustrated in Figure 3.

Page 249: TND Complete

INTERFERENCE - BASIC CONCEPTS

Ericsson Radio Systems AB

9/038 02-LZU 102 152, Rev A, November 1999

7

Power

Frequency

Carrier Harmonics

f 02 0f 3 0f 4 0f

P1

P2

P3

P4

Figure 3: The basic tone and its harmonics that arise as the result ofnon-linear amplification.

Harmonic generation occurs in the transmitters output stage. Atransmitter having a nominal frequency of f0 will exhibit all frequenciesn⋅f0. The power level of the harmonics diminish with increased n.Normally odd values of n represents higher power levels than even.

Noise spectrumAside from the discrete interference products described in the precedingsection, the transmitter’s carrier frequency oscillator also generates anoise spectrum around the carrier frequency that is of a continuouscharacter. This arises due to the oscillators’ inability to stably generateone and only one frequency thereby generating the aforementionednoise spectrum that is more or less centered around the transmitter’scarrier frequency. Figure 4 below illustrates the frequency spectrum ofan oscillator.

Page 250: TND Complete

RADIO TRANSMISSION NETWORK AND FREQUENCY PLANNING

8 Ericsson Radio Systems AB

9/038 02-LZU 102 152, Rev A, November 1999

FrequencyB

Sideband noise

Unmodulatedcarrier

Figure 4: The noise spectrum existing around the unmodulated carrierfrequency.

Noise spectrum interference is quantitatively expressed in terms of apower density w (W/Hz), i.e., interference power per unit of bandwidth,which normally diminishes with frequencies that lie further away fromthe carrier frequency. The frequency band B, in Figure 4, thereforecontains an interference power of P = w⋅B.

The transmitter’s total spectrumDiscrete interference frequencies and noise almost always exist at thesame time.This means that the total frequency spectrum consists of thebasic tone (the ”clean” carrier frequency), the harmonics and the noisespectrum, see Figure 5, where the levels of the basic tone and theharmonics are expressed in W while the noise level is expressed inW/Hz. Both levels may also be expressed in dBW (dB over 1 W) or dBover 1 W/Hz.

Unmodulated carrier

Sideband noise

Harmonics

Frequency

Power

3f02f0f0

Figure 5: The total frequency spectrum consisting of the basic tone (thecarrier frequency), the harmonics and the noise spectrum.

Page 251: TND Complete

INTERFERENCE - BASIC CONCEPTS

Ericsson Radio Systems AB

9/038 02-LZU 102 152, Rev A, November 1999

9

Transmitter false frequenciesSince no radio equipment is perfect (this applies even to the latestgeneration of radio equipment), a transmitter can transmit at otherfrequencies (usually having lower power levels) than at the frequency itwas designed for. These frequencies are often referred to as falsefrequencies.

In addition to harmonics, the frequency-generating portions (oscillatorsand frequency multipliers) of the majority of transmitters also generateother undesirable frequencies that do not give rise to frequencies thatare integer multiples of the transmitter’s nominal frequency. Theseundesirable frequencies (frequencies both below and above the carrierfrequency) are specific to each transmitter type, may lie rather close tothe carrier frequency and ordinarily display very complex patterns.

Receiver unwanted characteristics

The description that follows deals with the most important unwantedcharacteristics of a receiver that may give rise to interference.

Receiver intermodulationReceiver intermodulation means that signals arriving from two or moretransmitters are mixed with one another and give rise to a combinationproduct that falls within the receiver’s pass-band. The mixing processtakes place internal to the receiver.

BlockingThe concept of blocking may be illustrated by the fact that the inputsignal to the detector consists of two contributions – a situation thatarises when powerful interference signals exist alongside the desiredfrequency: a weak payload signal and a stronger interference signal(following insufficient filtering). The latter blocks the payload signal tothe detector.

Secondary channelsReceiver secondary channels arise when the receiver is sensitive toother frequencies than its nominal frequency.

Page 252: TND Complete

RADIO TRANSMISSION NETWORK AND FREQUENCY PLANNING

10 Ericsson Radio Systems AB

9/038 02-LZU 102 152, Rev A, November 1999

Adjacent signal interferenceAdjacent signal interference means that a signal, whose frequency liesclose to a receiver’s frequency, can interfere with the receiver. Theinterference is due to the fact that the signal mixes with the noise of thelocal oscillator plus the fact that the resultant noise mixture falls withinthe intermediate frequency.

Interference-free networks

Entirely interference-free radio networks do not exist! A radio networkmay, however, be considered as approximating an interference-freenetwork if some general rules and simplifications are applied, seeFigure 6.

Are the radio relayssufficiently frequencyseparated from each other?

yes

no

Trouble!Any appropriate antennadiscrimination, obstacleloss and/or geographicalseparation ?

Probably an “interference-free” network

Probably an “interference-free”network

yes

no

Figure 6: Interference-free networks.

How may interference be avoided?

Generally, interference may be avoided if the two following conditionsare met:

• interference signals are sufficiently weak

• receiver frequencies are sufficiently separated from interferencesignals, i.e., no frequency overlap

Page 253: TND Complete

INTERFERENCE - BASIC CONCEPTS

Ericsson Radio Systems AB

9/038 02-LZU 102 152, Rev A, November 1999

11

The first condition may be very difficult to meet, often as the result offrequent occurrence of co-located radio systems (occasionally forcedco-location) – while the second condition may be attained but requirescareful frequency planning.

Interference need not necessarily occur even if the aforementionedconditions are not met since all transmitters must be transmittingconcurrently if all possible intermodulation products are to have achance of arising. The probability that all, or even some, of thetransmitters are concurrently transmitting traffic, may however vary forthe different services – however, in the case of radio links, allequipment is transmitting on a continuous basis and frequency planningshould always consider the case of multiple concurrent transmission.

If interference is to be avoided, it is also imperative that an installation’santennas be separated so that sufficient attenuation is achieved betweenthe different stations. Vertical separation often gives better results thandoes horizontal separation.

References

”Telekonflikter i Radioanläggningar” (written in Swedish, Englishtranslation of the title is ”Telecommunication conflicts in radioinstallations”), written by Försvarets materielverk (The SwedishDepartment of Defense), M7773-400210,1975.

“Radio System Design for Telecommunications (1-100 GHz)”,Freeman, R. L., 1987.

Page 254: TND Complete

i

NEAR INTERFERENCE

This chapter provides a discussion of the basic principlesand definitions used in the calculation of near interference;some algorithms are also provided. The chapter contents apresentation of intermodulation at the receiver andtransmitter, including some examples of intermodulationproducts.

TABLE OF CONTENTS

Near interference ............................................................................................................................................... 1Intermodulation ................................................................................................................................................. 1

Intermodulation at the transmitter ....................................................................................................... 1Intermodulation at the receiver............................................................................................................ 2Intermodulation by corrosion of metallic joints .................................................................................. 2The frequency of intermodulated signal .............................................................................................. 2

Intermodulation order........................................................................................................................................ 3Third and fifth order products - example........................................................................................................... 3Near interference in receivers............................................................................................................................ 5

Receiver spurious signals and secondary channels.............................................................................. 6Spurious signal frequencies................................................................................................... 6Mirrored spurious signals...................................................................................................... 7Near spurious signals ............................................................................................................ 10

Receiver intermodulation .................................................................................................................... 11Intermodulation in the RF stage ............................................................................................ 11Intermodulation in the mixer stage........................................................................................ 13

Spurious signals caused by LO-signal distortion................................................................................. 14Near interference at the transmitter ................................................................................................................... 15

Introduction......................................................................................................................................... 15Transmitter spurious signals................................................................................................................ 17

References ......................................................................................................................................................... 17

Page 255: TND Complete

NEAR INTERFERENCE

Ericsson Radio Systems AB

10/038 02-LZU 102 152, Rev A, November 1999

1

Near interference

The signification of the expression ”near interference” is somewhatambiguous. In this book, however, ”near interference” means theinterference contributions arising from transmitters and receiverssituated at the ”same site” or at its immediate vicinity. For the purposeof interference analyses, other interference contributions will then beconsidered as ”far interference”.

Intermodulation

Intermodulation occurs because of different kinds of nonlinearprocesses taking place in the equipment forming the transmitter andreceiver. Furthermore, intermodulation may also occur at the peripheryof the transmitter, for instance, at antennas, towers and severe corrosionof metallic joints.

Three types of intermodulation may be present:

• intermodulation in the transmitter

• intermodulation in the receiver

• intermodulation caused by corrosion of metallic joints

Intermodulation disturbances are generally not expected to affect radiolinks (here considered as systems using wave-guides and parabolicantennas) and therefore they are normally excluded during the processof radio-link planning. The are two main reasons for excludingintermodulation from radio-relay planning: 1) the higher degree ofantenna isolation for typical radio-link antennas and 2) the cross sectionof waveguides (employed for frequencies higher than 2 GHz) normallydoes not fit the frequencies (wavelengths) of the intermodulationproducts and the frequencies of radio systems operating in otherfrequency bands.

Intermodulation at the transmitterIntermodulation at the transmitter occurs when external signals arrive atthe transmitter through the antenna and occasionally together with thetransmitter signal generate interfered signals in the nonlinearcomponents. This is illustrated in Figure 1.

Page 256: TND Complete

RADIO TRANSMISSION NETWORK AND FREQUENCY PLANNING

2 Ericsson Radio Systems AB

10/038 02-LZU 102 152, Rev A, November 1999

TX1

TX2

TX3

RX

Figure 1: Intermodulation at the transmitter.

Intermodulation at the receiverIntermodulation at the receiver is possible when external signals arriveat the receiver through its antenna. In this case the local oscillator at thereceiver may also contribute to the resultant intermodulated signal.Intermodulation at the receiver is illustrated in Figure 2.

TX1

TX2

TX3

RX

Figure 2: Intermodulation at the receiver.

Intermodulation by corrosion of metallic jointsIntermodulation caused by corrosion of towers, antennas and metallicjoints is strongly dependent on the environment conditions like climateand air pollution. It is, therefore, very difficult to know in advancewhether or not intermodulation will be formed.

The frequency of intermodulated signalAn intermodulated signal is formed by the addition of the interferencesignals and their integer products. The intermodulated signal is thenexpressed by

Page 257: TND Complete

NEAR INTERFERENCE

Ericsson Radio Systems AB

10/038 02-LZU 102 152, Rev A, November 1999

3

zzIM fafafaf ⋅±±⋅±⋅±= ...2211 ..................... ( 1 )

where

fIM = intermodulated signal

f1...fz = interferer’s frequencies

a1...az = positive integer coefficients

When the signals are formed at the receiver, the local oscillator isincluded as follows

lolozzIM fafafafaf ⋅±⋅±±⋅±⋅±= ...2211 ...... ( 2 )

where

flo = frequency of the local oscillator

alo = Positive integer coefficients of the local oscillator

Intermodulation order

The integer coefficients may assume all positive integer values and thisgives an infinitely number of possible combinations. In order tofacilitate the calculations, it is necessary to simplify the number ofcombinations. This is possible by defining an order term N as follows

∑=

=+++=z

nnz aaaaN

121 ... ............................... ( 3 )

The higher the order term the lower the strengths of the intermodulatedsignals. The coefficient alo is not included in the definition of the orderterm N.

Third and fifth order products - example

Table 1 illustrates the third and fifth intermodulation products obtainedwith two and three intermodulating transmitters (f1, f2 and f3).

Page 258: TND Complete

RADIO TRANSMISSION NETWORK AND FREQUENCY PLANNING

4 Ericsson Radio Systems AB

10/038 02-LZU 102 152, Rev A, November 1999

TWO TRANSMITTERS THREE TRANSMITTERS

THIRD ORDER FIFTH ORDER THIRD ORDER FIFTH ORDER

2⋅f1-f2 3⋅f1-2⋅f2 f1+f2- f3 3⋅f1-f2- f3

2⋅f2-f1 3⋅f2-2⋅f1 f1+f3- f2 3⋅f2-f1- f3

f2+f3- f1 3⋅f3-f1- f2

2⋅f1+f2-2⋅f3

2⋅f3+f2-2⋅f1

2⋅f2+f1-2⋅f3

2⋅f3+f1-2⋅f2

2⋅f1+f3-2⋅f2

2⋅f2+f3-2⋅f1

Table 1: Third and fifth order intermodulation products for two andthree transmitters.

Figure 3 illustrates the location of third order intermodulationfrequencies with respect to the center frequencies for two and threetransmitters.

2 1 2f f− f1

Two transmitters

Three transmitters

f f f1 2 3+ − f1 f f f1 3 2+ − f2 f3f f f2 3 1+ −

f

f

f2 2 2 1f f−

Figure 3: Location of third order intermodulation frequencies withrespect to the center frequencies for two and three transmitters.

Figure 4 illustrates the location of the fifth order intermodulationfrequencies with respect to the center frequencies for two and threetransmitters.

Page 259: TND Complete

NEAR INTERFERENCE

Ericsson Radio Systems AB

10/038 02-LZU 102 152, Rev A, November 1999

5

3 21 2f f− f1 f2 3 22 1f f−

3 1 2 3f f f− −2 21 2 3f f f+ −

2 22 1 3f f f+ −2 21 3 2f f f+ −

f1

2 23 1 2f f f+ −f2

f3

3 2 1 3f f f− −3 3 1 2f f f− −

2 22 3 1f f f+ −

2 23 2 1f f f+ −

Two transmitters

Three transmitters

f

f

Figure 4: Location of fifth order intermodulation frequencies withrespect to the center frequencies for two and three transmitters.

Near interference in receivers

Figure 5 illustrates a desired signal of level Pr (dBm) and a frequency offr that arrives at the RF stage. At the output of the IF filter, the level ofthe desired signal is Pd (dBm), which provides a certain level oftransmission quality. The level following the IF filter correspondstherefore to a certain value of C/N, where C is a function of Pr and N ofthe receiving system’s receiver noise factor F and the IF filter’sbandwidth (the receiver’s effective bandwidth) B (see Section 3).

Localoscillator

Crystal

Mixer ~~~

flo

Pr, frPd , fIF

Desired output signalfollowing the IF-filter

interfering signal

RF-amplifier

Psp, fsp Pm,n , fx

Desired input signal

Intermodulation productfollowing the IF-filter

Figure 5: Near interference in the receiver.

Page 260: TND Complete

RADIO TRANSMISSION NETWORK AND FREQUENCY PLANNING

6 Ericsson Radio Systems AB

10/038 02-LZU 102 152, Rev A, November 1999

Assume that a powerful interfering signal (e.g., a spurious signal)having a level of Psp and a frequency of fsp arrives at the input to RFstage. Spurious frequencies (the secondary channels) result in anundesirable intermodulation product having a level of Pm,n andfrequencies that are very close to the desired receiver frequency, therebyfalling into the pass-band of the IF filter. This interfering signal iscombined with the normal receiver noise N (following the IF amplifier)and C/N reduces, leading to reduced transmission quality.

The spurious attenuation, P (dB), for the frequency fsp is defined as thedifference in levels at the input to the receiver between the spurioussignal Psp and the desired signal Pr, i.e.,

rsp PPP −= ......................................................... ( 4 )

An allowable level of Pm,n, i.e., the level resulting in the maximumallowable increase in N, is a function of a number of factors, such astransmission quality requirements and type of modulation.

Receiver spurious signals and secondary channelsReceiver secondary channels arise as the result of receiver sensitivity tofrequencies other than the nominal frequency of the receiver. Non-linearities in the RF amplifier and mixer can result in receiver spurioussignals as in the case of the combination products arising in the RFstage that acquire frequencies close to the desired receiver frequency.

Spurious signal frequencies

Since the filtering out of spurious signals before the mixer is practicallyimpossible, spurious signals that fall close to the frequency of thereceiver can be a very difficult proposition. Figure 6 illustrates a mixer,an IF filter and a local oscillator.

Localoscillator

Crystal

Mixer ~~~

flo

fm

fsp fx

Desired signalf fm lo− fIF

m f n fsp lo⋅ − ⋅

Page 261: TND Complete

NEAR INTERFERENCE

Ericsson Radio Systems AB

10/038 02-LZU 102 152, Rev A, November 1999

7

Figure 6: Incoming spurious signals at the receiver’s mixer.

The desired input signal, having a frequency of fm, arrives at the mixerinput together with an unfiltered spurious signal of frequency fsp.Together with the local oscillator frequency flo, the spurious signal givesrise to an intermodulated signal having an intermediate frequency of fx

at the output of the IF filter. The combination product that arises can becalculated as

lospx fnfmf ⋅−⋅= .............................................. ( 5 )

where m and n are positive whole integers. The wanted combination iscalculated as

lomIF fff −= ...................................................... ( 6 )

Spurious frequencies are often described as a function of the desiredreceiver frequency fm and the intermediate frequency fx, which, whenapplying equations (5) and (6), gives

( )[ ]mxsp fnfnm

f ⋅+⋅+⋅= 11

............................... ( 7 )

Note that if n=-1 and m=-1 in the above equation, the result is fsp = fm,which is the desired combination.

Mirrored spurious signals

There exists two possible cases of undesirable output signals, namely fm

> f0 and fm < f0. Spurious signal frequencies for both cases, as shownabove, can be expressed by considering fx as positive (fx > 0 ⇒ f0 > fm)and negative (fx < 0 ⇒ f0 < fm).

Mirrored signals, m= n=1

If n=1 and m=1, equation (7) gives the following spurious signalfrequencies for the two cases mentioned above:

f0 > fm xmsp fff ⋅+= 2 .................................. ( 8 )

f0 < fm xmsp fff ⋅−= 2 ................................. ( 9 )

Page 262: TND Complete

RADIO TRANSMISSION NETWORK AND FREQUENCY PLANNING

8 Ericsson Radio Systems AB

10/038 02-LZU 102 152, Rev A, November 1999

From a frequency aspect, the mirrored signal falls into the opposite sideof the local oscillator frequency and the frequency separation betweenthe desired signal fm and the mirrored signal is therefore 2⋅ fx . Themirrored signal is illustrated by a whole line and the desired input signalby a dashed line, see Figure 7.

f0fmMirrored signal

2 ⋅ f x

f0 < fm

f0fm Mirrored signal

2 ⋅ f x

f0 > fm

fx < 0

fx > 0

Figure 7: Mirrored frequencies for fm > f0 and fm < f0 when m=n=1.

Mirrored signals, m= n>1

The most dangerous spurious signal frequencies, i.e., the smallestfrequency separation to the desired input signal for given values of mand n, results when m=n < 0 which when entered into equation (7)gives

( )[ ] xmxxsp fm

mffmfm

mf ⋅

−+=⋅−⋅+−⋅

−=

11

1( 10 )

If the above equation is applied to both cases, the results are

f0 > fm xmsp fm

mff ⋅

−+=

1......................... ( 11 )

f0 < fm xmsp fm

mff ⋅

−−=

1......................... ( 12 )

Page 263: TND Complete

NEAR INTERFERENCE

Ericsson Radio Systems AB

10/038 02-LZU 102 152, Rev A, November 1999

9

The most troublesome spurious signals (i.e., those closest to the desiredinput signal and that have the lowest ordinal numbers) occur whenm=n= 2. The spurious signal frequencies that are considered asdangerous in this case are illustrated in Figure 8 as having whole lines.

Spurious signal frequencies that are considered as not dangerous, i.e.,those having greater frequency separation to the desired input signal forgiven values of m and n, occur when m=n > 0 which when enteredinto equation (7) gives

xmsp fm

mff ⋅

++=

1........................................... ( 13 )

These non-hazardous spurious signal frequencies (high filter selectionrequirements aimed at eliminating mirrored signals, generally result insufficient filter attenuation for the elimination of these spurious signals)are illustrated in Figure 8 by dashed lines.

Page 264: TND Complete

RADIO TRANSMISSION NETWORK AND FREQUENCY PLANNING

10 Ericsson Radio Systems AB

10/038 02-LZU 102 152, Rev A, November 1999

f0fmMirrored signal

2 ⋅ f x

f0 < fm

f0 > fm

ff x / 2

2 3f x /

3 4f x /

fm Mirrored signal

2 ⋅ f x

ff0f x / 2

2 3f x /

3 4f x /

m (m-1)/ m

2 1/2

3 2/3

4 3/4

Figure 8: Mirrored signal frequencies for fm > f0 and fm < f0 whenm=n>1.

Near spurious signals

Certain combinations of m and n give rise to spurious signal frequenciesthat fall in the vicinity of the desired receiver frequency and thereforepass through the input filter without being subjected to any appreciableattenuation. Near spurious signals refers to spurious signals whosefrequencies are fsp ≅ fm. The most dangerous spurious signals, so-calledextremely near spurious signals, are naturally those spurious signals forwhich fsp = fm. Entering fsp = fm = f into equation (7) gives

Page 265: TND Complete

NEAR INTERFERENCE

Ericsson Radio Systems AB

10/038 02-LZU 102 152, Rev A, November 1999

11

( ) ( ) xfnfnm ⋅+=⋅− 1 ......................................... ( 14 )

which may be rewritten as

( )( )1+

−=

nnm

f

f x ....................................................... ( 15 )

Certain m, n combinations give rise to a critical value of fx / f, causingthe frequency of the undesired signal to correspond exactly to thereceiver frequency – the same situation as in the case of the frequencyof the combination product corresponding exactly to the frequency ofthe desired output signal from the mixer.

Receiver intermodulationThe RF stage is often well isolated from the local oscillator’s signal viathe mixer – which means that at least two powerful interference signalsmust be introduced if troublesome combination products(intermodulation) are to arise in the RF stage.

Intermodulation in the RF stage

Two powerful interfering signals having frequencies in the vicinity ofthe desired signal’s frequency, (fm + ∆1) and (fm + ∆2), give rise toreceiver intermodulation. The situation is illustrated in Figure 9. Thefigure deals with intermodulation generated in a RF stage. Thefrequency positions of the interfering input signals (that are the cause ofthe intermodulation), are to be adapted so that their combinationproduct corresponds to the desired receiver frequency (in the IFfollowing the mixer).

Page 266: TND Complete

RADIO TRANSMISSION NETWORK AND FREQUENCY PLANNING

12 Ericsson Radio Systems AB

10/038 02-LZU 102 152, Rev A, November 1999

~~~fm

fm

Desired signal

fm

m f n fm m⋅ + + ⋅ +∆ ∆1 2b g b gf m + ∆ 1b gf m + ∆ 2b g

Spurios signal pair

fm

f

f m + ∆ 2b gf m + ∆ 1b g

Spurious signals

Desired signal

Figure 9: Intermodulation at the RF stage.

The desired signal fm, is as shown in Figure 9,

( ) ( )21 ÄÄ +⋅++⋅= mmm fnfmf ........................ ( 16 )

which may be rewritten as

( ) 0ÄÄ1 21 =⋅+⋅+−+ nmfnm m ....................... ( 17 )

where ∆1 << fm and ∆2 << fm. The above equation is applicable when

( ) 01 =−+ nm ...................................................... ( 18 )

( ) 0ÄÄ 21 =⋅+⋅ nm .............................................. ( 19 )

The following applies in the case of third order intermodulation, m=2 and n= 1 which gives ∆2 = 2⋅ ∆1 and equation (16) may berewritten as

( ) ( ) ( )2121 ÄÄ2Ä1Ä2 −⋅+=+⋅−+⋅= mmmm ffff ( 20 )

Thus, third order intermodulation arises if the interfering frequenciesare located at each side of the desired receiver frequency – at aseparation of ∆1 and 2⋅∆1 respectively, see Figure 10.

Page 267: TND Complete

NEAR INTERFERENCE

Ericsson Radio Systems AB

10/038 02-LZU 102 152, Rev A, November 1999

13

fm f

∆ 2

∆1

Figure 10: Possible interference frequencies for third orderintermodulation are located at each side of the desired frequency at aseparation of ∆1 and 2⋅∆1 respectively.

The following applies in the case of fifth order intermodulation, m=3 and n= 2 which gives 3⋅ ∆1 = 2⋅ ∆1 and equation (16) may berewritten as

( ) ( ) ( )2121 Ä2Ä3Ä2Ä3 ⋅−⋅+=+⋅−+⋅= mmmm ffff ( 21 )

Thus, fifth order intermodulation arises if the interfering frequencies arelocated at each side of the desired receiver frequency – at a separationof ∆1 and 3/2⋅∆1 respectively, see Figure 11.

fm f

∆ 2

∆1

Figure 11: Possible interference frequencies for fifth orderintermodulation are located at each side of the desired frequency at aseparation of ∆1 and 2⋅∆1 respectively.

Intermodulation in the mixer stage

The occurrence of intermodulation in the mixer stage is very similar theearlier case (i.e., the occurrence of intermodulation in the RF stage).The signal from the local oscillator may even play a part in theformation of the combination product, see Figure 12.

Page 268: TND Complete

RADIO TRANSMISSION NETWORK AND FREQUENCY PLANNING

14 Ericsson Radio Systems AB

10/038 02-LZU 102 152, Rev A, November 1999

Localoscillator

Crystal

Mixer ~~~

flo

fm fIF

Desired signal

f f fm lo IF− =

f m + ∆ 1b gf m + ∆ 2b g

Spurioussignal pair

m f n f fm m lo⋅ + + ⋅ + −∆ ∆1 2b g b g

fx

Figure 12: Intermodulation in the mixer stage.

The desired signal is consequently

( ) ( ) lommlomx ffnfmfff −+⋅++⋅=−= 21 ÄÄ ( 22 )

Third and fourth order intermodulation products are the same as thosein the case of intermodulation in the RF stage (see above).

Spurious signals caused by LO-signal distortionAdditional combination products may arise if the signal generated bythe local oscillator contains numerous frequency components, seeFigure 13.

Localoscillator

Crystal

Mixer ~~~flo

fm

fsp fx

Desired signalf k fm − ⋅ 0

fIF

m f n fsp⋅ − ⋅'0

f0 k f f lo⋅ =0

Figure 13: Spurious signals caused by LO-signal distortion.

The desired signal is given by

0fkff mIF ⋅−= .................................................. ( 23 )

Page 269: TND Complete

NEAR INTERFERENCE

Ericsson Radio Systems AB

10/038 02-LZU 102 152, Rev A, November 1999

15

The combination product that arises may be expressed as

0' fnfmf spx ⋅−⋅= ............................................... ( 24 )

and the spurious signal frequencies may be expressed as

( )[ ]xmsp fknfnmk

f ⋅−−⋅⋅

= ''1

............................. ( 25 )

The relationship between the coefficients k and n’ may be expressed as

kn

n'

= .................................................................. ( 26 )

which when substituted into equation (25) gives

( )[ ]xmsp fnfnm

f ⋅−−⋅= 11

................................. ( 27 )

Providing that n is allowed to assume other values than just integervalues, the above expression corresponds to spurious signal frequenciesthat were studied earlier, see equation (7).

If the local oscillator’s third harmonic (k=3) is used to generate thedesired intermediate frequency, see Figure 13, at the same time as n’=1,2, 3, 4, … then he following will apply n=1/3, 2/3, 3/3, 4/3, …. whichimplies the occurrence of additional spurious signal frequencies.

Near interference at the transmitter

IntroductionTransmitter intermodulation may arise in the output-stage amplifiers ofthe transmitters if the mutual isolation between the transmitters isinsufficient. A mutual coupling may thereby exist between the output ofthe combiner that connects the transmitters to a common antenna orbetween separate but neighboring transmitter antennas. Both cases areillustrated in Figure 14.

Page 270: TND Complete

RADIO TRANSMISSION NETWORK AND FREQUENCY PLANNING

16 Ericsson Radio Systems AB

10/038 02-LZU 102 152, Rev A, November 1999

fI

fI

Tx2f2

Disturbingtransmitter

Disturbedtransmitter

Disturbedreceiver

Rx2f1-f22f2-f1

Tx1f1

f2

fI

fI

Tx2f2

Tx1f1

Combiner

f2

Rx2f1-f22f2-f1

fI

Disturbingtransmitter

Disturbedtransmitter

Disturbedreceiver

Figure 14: The effect of the transmitter intermodulation product onreceivers sharing a common antenna or mounted on separate butneighboring antennas.

An example of a typical near interference scenario is a large number oftransmitters that are concentrated to one and the same mast orconcentrated base station locations that transmit and receive numerousmodulated carrier waves. The transmitters described in this scenariomay generate interference signals in the form of intermodulationproducts that interfere with neighboring receivers.

Assume an interference signal having a frequency of f2 that lies in thevicinity of the transmission frequency f1, i.e.,

212 Äfor Ä fffff <<+= ........................ ( 28 )

The frequency of the resultant combination product having atransmission frequency ordinal number n and an interference frequencyordinal number m, may be expressed as

21 fmfnf I ⋅−⋅= ............................................. ( 29 )

Using equations (28) and (29) gives

( ) Ä1 fmfmnf I ⋅+⋅−= ................................... ( 30 )

Page 271: TND Complete

NEAR INTERFERENCE

Ericsson Radio Systems AB

10/038 02-LZU 102 152, Rev A, November 1999

17

which indicates that only combination products having |n-m| = 1 andwhere the size of m is moderate will fall in the vicinity of thetransmission frequency. The combination product’s ordinal number isdetermined, as indicated earlier, by |m| + |n| and the lowest ordinalnumber of interest are the third and fifth, i.e., |m| + |n| = 3 and |m| + |n| =5 respectively.

Transmitter intermodulation responds to the combination productsbetween the desired output signal from the transmitter and the generatedinterference signals. The desired output signal from a transmitter havinga frequency of f1, see above, often dominates the combination processand causes the level of the combination products fall off slowly withordinal number n of frequency f1 but fall off sharply with increasingordinal number m of frequency f2 of the interfering signal.

Transmitter spurious signalsThe occurrence of transmitter spurious signals may generally beaddressed in the same manner as are receiver spurious signals, see undersection 4.

Non-linearities in sections of the transmitter such as in the section thatgenerates the carrier frequency or in the RF amplifier, can give rise totransmitter spurious signals that of themselves or via generatedcombination products in the RF stage, attain frequencies that are closeto the desired receiver frequency.

References

TEMS LinkPlanner, User’s Guide, Rev. 5.0, 1999.

Page 272: TND Complete

i

FAR INTERFERENCE

This chapter presents general concepts considered in thefield of far interference and provides guidelines forinterference calculation. A typical performance diagramand interference scenario is discussed. The chapterprovides the algorithm for the calculation of thecontributions of the individual interference signal levels,plus the resulting interference level at one receiver andthreshold degradation.

TABLE OF CONTENTS

Introduction....................................................................................................................................................... 1Performance diagram ........................................................................................................................................ 1Interference-free signal...................................................................................................................................... 3Interfering scenario ........................................................................................................................................... 3Interference-free reception ................................................................................................................................ 4Reception with interference............................................................................................................................... 5Example............................................................................................................................................................. 6Interference tolerance........................................................................................................................................ 7Interference signal level .................................................................................................................................... 7Resulting interference level ............................................................................................................................... 8Threshold degradation method.......................................................................................................................... 9

Introduction......................................................................................................................................... 9Example .............................................................................................................................................. 9General comments............................................................................................................................... 10

References ......................................................................................................................................................... 10

Page 273: TND Complete

FAR INTERFERENCE

Ericsson Radio Systems AB

11/038 02-LZU 102 152, Rev A, November 1999

1

Introduction

For a particular bit-error ratio (BER), the presence of interfering signalswill degrade the receiver’s threshold level. In order to maintain theperformance, an increasing at the receiver input level during fading-freetime is necessary to an unchanged fade margin.

The influence of interfering signals is first noticeable during fadingconditions as a deterioration of the receiver threshold level, that is, as adecrease of the path’s fade margin.

Far interference is present when a received signal is disturbed by signalssent on the same or an adjacent channel and generated by a transmitterlocated far away from the receiver.

Performance diagram

Performance diagram is a diagram used for the purposes of planningdigital radio-relay equipment in a network. The performance diagram issome kind of radio-relay equipment “signature”, that is, each radioequipment type presents a specific performance diagram, basicallydependent on, among other properties, the equipment’s capacity andmodulation method.

The diagram illustrates the bit-error ratio (BER) as a function of thereceiver input level for different values of the carrier-to-interferenceratio (C/I), see Figure 1, and is for an equipment operating at 2 GHz andwith transmission capacity 2048 kbit/s.

Page 274: TND Complete

RADIO TRANSMISSION NETWORK AND FREQUENCY PLANNING

2 Ericsson Radio Systems AB

11/038 02-LZU 102 152, Rev A, November 1999

Received Signal Level (dBm)

Bit

-Err

or

Rat

io

-96 -95 -94 -93 -92 -91 -90 -89 -88 -87 -86 -85 -84 -83 -82 -811.E-8

1.E-7

1.E-6

1.E-5

1.E-4

.001

C/I "infinite" C/I=20 dB

C/I=15 dB

C/I=10 dB

Figure 1: Performance diagram for co-channel interference for anequipment operating at 2 GHz and with transmission capacity 2048kbit/s.

Manufactures of digital equipment normally provides set of curves (seeFigure 1) which display the BER dependence on co-channel andadjacent channel interference for different modulation schemes.

The two important conclusions on the performance diagram illustratedin Figure 1 may be drawn:

1. The received signal level becomes higher with decreasing carrier-to-interference ratio (C/I) if the bit-error ratio (BER) is maintained atthe same value. In practice, a higher fade margin is required in orderto sustain the same quality targets.

Page 275: TND Complete

FAR INTERFERENCE

Ericsson Radio Systems AB

11/038 02-LZU 102 152, Rev A, November 1999

3

2. The bit-error ratio (BER) gets worse for decreasing carrier-to-interference ratio (C/I) if the received signal level is retained at thesame value, which means decreased quality. In practice, theequipment threshold value gets lower and the fade margin increases,and as expected it is easier to fulfill low-quality requirements.

Performance diagram is normally used for analysis of co-channel andadjacent channel interference. It is not always presented as curves in theequipment data sheet, often as a C/I value corresponding to adegradation value, for instance, co-channel C/I=15 dB and adjacentC/I=-20 dB for 3 dB degradation.

Interference-free signal

A signal is theoretically interference free when the following conditionoccurs

∞≥IC

.................................................................................. ( 1 )

For most practical applications, however, a signal can be consideredinterference free when

dB 25≥IC

........................................................................... ( 2 )

which means that the carrier C is approximately 316 times higher thanthe interference signal I. The carrier and the interference signal areequal when C/I= 0 dB.

Interfering scenario

Figure 2 illustrates a simplified scenario containing two paths. Thereceiver located at site A is disturbed by the transmitter located at site Dgiving rise to an interfering path AD. In this specific case, the resultinginterference level at the disturbed receiver located at A consists of thecontribution arriving from the transmitter located at D, that is, its outputpower and other path and frequency dependent contributions.

Page 276: TND Complete

RADIO TRANSMISSION NETWORK AND FREQUENCY PLANNING

4 Ericsson Radio Systems AB

11/038 02-LZU 102 152, Rev A, November 1999

PR = Receiver input level of thewanted signal at the disturbed receiver, dBm

PI = Resulting interference level at thedisturbed receiver, dBm

PT = Disturbing transmitter’s outputpower, dBm

Disturbingtransmitter

DisturbedreceiverA

B

PR C

D

PT

PI

θ1 = Angle between the interference-freepath and the interfering path

θ 1

θ2 = Angle between the disturbingand the interference path

θ 2

Disturbingpath

Interferingpath

Figure 2: Simplified interfering scenario containing two paths.

Interference-free reception

In interference-free reception, see Figure 3, the path fade margin issolely dependent on the path parameters and it is written as

thR PPM −= ........................................................................ ( 3 )

where

M = path fade margin, dB

PR = received signal at the receiver, dBm

Pth = receiver’s threshold, dBm

It should be pointed out that the receiver’s threshold value is alwaysconnected to a given bit-error ratio.

Page 277: TND Complete

FAR INTERFERENCE

Ericsson Radio Systems AB

11/038 02-LZU 102 152, Rev A, November 1999

5

Interference-free reception means

The path fade margin is solelydependent on the path parameters

M = Fade margin for interference-freereception, dB

Pth = Receiver threshold level forundisturbed receiver, dBm

PR = Receiver input level duringfading-free time, dBm

PR

at given BER!!!Pth

M

Power (dBm)

Figure 3: Interference-free reception.

Reception with interference

In reception with interference, see Figure 4, the fade margin is changedbecause the receiver’s threshold is degraded for the same bit-error ratio.The degradation is generally the result of two level contributions: theresulting (total) interference level (I or PI) at the receiver and thereceiver noise level (N), that is, (N+I). Now, the actual fade margin(including interference), the effective fade margin, is as follows

thIReff PPM −= ................................................................... ( 4 )

where PthI is the receiver’s threshold value when affected by a resultinginterference level PI (dBm) and PR (dBm) as above.

The degradation is therefore given by

ththI PPD −= ....................................................................... ( 5 )

where D is the degradation (dB) and the other parameters as above. Itfollows that the effective fade margin as a function of the degradation isobtained as

DMM eff −= ..................................................................... ( 6 )

Page 278: TND Complete

RADIO TRANSMISSION NETWORK AND FREQUENCY PLANNING

6 Ericsson Radio Systems AB

11/038 02-LZU 102 152, Rev A, November 1999

Now, the carrier-to-interference ratio (C/I) symbolizes the interferencelevel arriving at the receiver, PI, thus imposing a new threshold valuePthI. If C is considered as PthI (valid during fade depths equal to thefade margin), this may be expressed as follows

IthI PPIC

−= ........................................................................ ( 7 )

or solving for the threshold PthI

IC

PP IthI += ....................................................................... ( 8 )

N

N+I

DPthI

M-D

PI (=I) = Resulting interference threshold level, dBm

N = Noise level at the receiver input, dB

N + I = Sum of the noise and interference levels, dBm

D = Threshold level degradation, dB

PR

Pth

Power (dBm)

at given BER!!!

M

PR = Receiver input level during fading-free time, dBm

Pth = Receiver threshold level for undisturbed receiver, dBm

M = Fade margin for interference-free reception, dB

PthI = Resulting interference threshold level , dBm

M - D = Effective fade margin for reception with interference, dB

I PI

C/I

D

Figure 4: Reception with interference.

Example

To operate correctly, a digital system normally requires a carrier-to-interference ratio (C/I) of 15-20 dB, depending on the used modulationscheme. In a complex network with many different interferenceconfigurations, a 15-20 dB C/I–value must be maintained, even underfading conditions. This means that the interfering level has to be 15-20dB below the receiver threshold.

Page 279: TND Complete

FAR INTERFERENCE

Ericsson Radio Systems AB

11/038 02-LZU 102 152, Rev A, November 1999

7

For instance, if the receiver threshold is –85 dBm for a specific bit-errorratio and the fade margin is 35 dB, then the interference level must be atleast 15-20 dB below the receiver threshold, that is, between –100 and -105 dBm [-85 dBm + (-15 to 20 dB)]. To make the fade margin of 35dB fully usable for covering fading, then a C/I–value of 15-20 dB muststill be available at the receiver threshold. Hence, the total requirementof ”isolation” (unfaded carrier to the inteference level) must be between50 and 55 dB (35 dB+15 to 20 dB).

Interference tolerance

The tolerance of digital channels to interference depends on themodulation scheme. In particular, a modulation scheme which requiresa low C/I for a certain bit-error ratio is more tolerant to interference.Robust modulation schemes are 2PSK and 4PSK, while more complexmodulation schemes as 128QAM require much larger C/I-values.

Interference signal level

Any interference signal level among j - individual interference signals isgenerally calculated as following:

AFRFTGbfTIj AAAGGAAPP −−−++−−=21 θθ ............... ( 9 )

where

PIj = The level of a single interference signal j, dBm

PT = The output level of the disturbing transmitter, dBm

Abf = The basic free-space loss between disturbing transmitter anddisturbed receiver, dB

AG = The gas attenuation, dB

Gθ1 = The antenna gain θ1 degrees from maximum gain, dBi

Gθ2 = The antenna gain θ2 degrees from maximum gain, dBi

AFT = The feeder attenuation at the transmitter station, dB

AFR = The feeder attenuation at the receiver station, dB

AA = The additional attenuation (obstacle loss, RF attenuators, etc), dB

Page 280: TND Complete

RADIO TRANSMISSION NETWORK AND FREQUENCY PLANNING

8 Ericsson Radio Systems AB

11/038 02-LZU 102 152, Rev A, November 1999

The antenna gains are calculated in the direction given by the anglesθ1 and θ2, defined as follows

θ1 = angle between the interference-free and the interference signal

θ2 = angle between the interfering signal and the interference path

Resulting interference level

The resulting interference level of the combined individual interferencelevels at the receiver is given by

( )

⋅= ∑

=

−n

j

AP

I

adIj

P1

1010log10 ................................................... ( 10 )

where:

PI = resulting interference level, dBm

PI j= level of an individual interference signal, dBm

Aad = adjacent-channel attenuation, dB

For co-channel Aad= 0.

The Aad attenuation depends basically on channel separation.

Applying the equation above for 1 interfering signal (n=1) the result is:

( )

⋅= ∑

=

−1

1

101

10log10j

AP

I

adI

P .................................................. ( 11 )

and performing the operations the final result is

( )

( ) adIadI

AP

I APAP

PadI

−=⋅−

⋅=

⋅=

1110 10log10

1010log101

( 12 )

This result is expected since the resulting interference level in dBm atthe receiver, considering only one interfering signal, can be obtained bysubtracting the adjacent-channel attenuation from the only individualinterfering participating in the interference scenario. Note, however, thatthe result will not be simply expressed by a subtraction whenconsidering more than one participating interferer.

Page 281: TND Complete

FAR INTERFERENCE

Ericsson Radio Systems AB

11/038 02-LZU 102 152, Rev A, November 1999

9

Threshold degradation method

IntroductionGenerally, the degradation imposed by interfering signals in a radionetwork is taken into account by considering the degradation value as afree parameter. Thus, the resulting interference level and finally the fademargin for the path can be obtained. This is performed in five steps:

Step 1: Assume a suitable degradation D for the receiver’s thresholdlevel

Step 2: Find the value for the receiver’s input level during interference-free condition for a given bit-error ratio according to equation (1) in theperformance diagram, see Figure 1.

Step 3: Calculate the degraded threshold level using equation (5)

Step 4: Determine, in the performance diagram, the C/I levelcorresponding to the degraded threshold level for the given bit-errorratio

Step 5: Calculate the resulting interference level by using equation (8)

ExampleThe performance diagram is for co-channel interference for anequipment operating at 2 GHz and with transmission capacity 2048kbit/s.

Step1: it is assumed a 2.5 dB degradation

D= 2.5 dB

Step 2: the receiver’s input level for interference-free reception forBER= 10-3 is read off on Figure 1, approximately.

Pth= -94.5 dBm

Step 3: the degraded threshold level is obtained by equation (5), that is,

PthI= -94.5 dBm + 2.5 dB= -92 dBm

Step 4: the corresponding C/I level for BER= 10-3 in the performancediagram is

C/I= 15 dB

Page 282: TND Complete

RADIO TRANSMISSION NETWORK AND FREQUENCY PLANNING

10 Ericsson Radio Systems AB

11/038 02-LZU 102 152, Rev A, November 1999

Step 5: finally, the resulting interference level is obtained by equation(8).

PI= PthI - C/I= -92 dBm - 15 dB= -107 dBm

General commentsAdvantage: the influence of the bit-error ratio (BER) on theperformance and availability is considered when starting the planning(the effective fade margin is known)

Disadvantage: the final extension of the network has to be estimatedwith some accuracy. For example, if the number of interfering paths isless than the estimated (the network never reaches the number ofplanned links), the performance will be overestimated. If the number ofinterfering paths is larger than the estimated, existing antennas mayhave to be changed or another frequency band has to be employed in thenetwork. In both cases the result is an unnecessary expensive network.

A certain economical risk is, however, normally present.

References

TEMS LinkPlanner, User’s Guide, Rev. 5.0, 1999.

Page 283: TND Complete

i

PATH AND FREQUENCY PLANNING

This chapter covers some of the issues that may ariseconcerning path profiles, line-of-sight requirements, inputsignals and their variation, diversity, reflections andfrequency planning. In addition, surveying possible radio-link paths and site requirements are discussed.

TABLE OF CONTENTS

Objective and scope .......................................................................................................................................... 1Initial planning .................................................................................................................................................. 1Network configurations ..................................................................................................................................... 2

Star network, alternative 1................................................................................................................... 2Star network, alternative 2................................................................................................................... 3Chain network ..................................................................................................................................... 4Loop network ...................................................................................................................................... 4

Line of sight ...................................................................................................................................................... 5Clearance........................................................................................................................................................... 5Path profiles ...................................................................................................................................................... 7Link budget ....................................................................................................................................................... 9Fading................................................................................................................................................................ 11

Fade margin......................................................................................................................................... 11Rain ..................................................................................................................................................... 11Multipath propagation......................................................................................................................... 11General ................................................................................................................................................ 12

Diversity............................................................................................................................................................ 12Space diversity .................................................................................................................................... 12Frequency diversity ............................................................................................................................. 13Improvement ....................................................................................................................................... 13

Reflection .......................................................................................................................................................... 14Path and site surveys ......................................................................................................................................... 17Frequency planning ........................................................................................................................................... 18

General ................................................................................................................................................ 18Far interference ................................................................................................................................... 19Near interference................................................................................................................................. 20Frequency economy ............................................................................................................................ 23

References ......................................................................................................................................................... 23

Page 284: TND Complete

PATH AND FREQUENCY PLANNING

Ericsson Radio Systems AB

12/038 02-LZU 102 152, Rev A, November 1999

1

Objective and scope

In preparation for the configuration of a radio link network, a number oftasks must be performed that will eventually supply input to thenecessary path calculations. These tasks are described herein and deal,for the most part, with terrain, climate, equipment data and siteconfiguration. Frequency planning is considered as one of the moreimportant tasks in the planning of a network.

This section will cover some of the issues that may arise concerningpath profiles, requirements regarding line-of-sight, input signal and theirvariation, diversity, reflections and frequency planning. A section isincluded which deals with the survey of possible radio-link paths andsite requirements.

Initial planning

Before starting the actual planning of a radio link path, one shouldacquire an overview of the construction of the entire network (of whichthe path in question is to be a part of), and of the network functionalitythat the proposed path is to provide. This background knowledge willenable decision as to the quality and availability standards that shouldbe conformed to when dimensioning the path.

Network planning is generally based upon the network’s operationalrequirements. These can be expressed in terms of:

• Quality

• Availability

• Traffic requirements and capacity

The manner in which one goes about determining the requirementspertaining to the dimensioning of individual radio-link paths is afunction of the configuration and the dimensioning of the local networkand, if such be the case, of other surrounding networks that may beinvolved. Every network component path is to exhibit a level ofavailability and quality such that the entire connection, subscriber-to-subscriber, maintains the overall standards that were selected.

Page 285: TND Complete

RADIO TRANSMISSION NETWORK AND FREQUENCY PLANNING

2 Ericsson Radio Systems AB

12/038 02-LZU 102 152, Rev A, November 1999

The International Telecommunication Union, ITU, publishesrecommendationsthat provide guidance as to the dimensioning ofnetworks intended for international connection. Practical examples ofthis type of network is found in the transmission to/from the radio basestations of a mobile telephone network or in the internal companynetworks that are connected to public communications networks. Seethe section ”QUALITY AND AVAILABILITY TARGETS”, for moreinformation.

Network configurations

A number of examples are included below including common networkconfigurations in which a number of radio base stations (RBS) are to beconnected to a mobile telephone exchange (MSC), see Figure 1.

MSC

Figure 1: RBS sites that are to be connected to an MSC.

Star network, alternative 1Figure 2 illustrates a usual pattern, in which all sites are connecteddirectly to the MSC in a star network. In principle, this configuration issimple and offers the following advantages:

• The RBS-sites may be established to expanding requirements in anarea instead of network configuration requirements.

• The network may gradually be taken into service in phase with theestablishment of new sites.

However a star network configuration represents some disadvantages:

• It involves a large number of incoming MSC routes and theirrespective antennas. This may cause both space and strengthproblems for antenna support structures.

• The high number of incoming routes may lead to problems infinding sufficient frequencies, i.e., bandwidth.

Page 286: TND Complete

PATH AND FREQUENCY PLANNING

Ericsson Radio Systems AB

12/038 02-LZU 102 152, Rev A, November 1999

3

• A number of the sites may be too remote, leading to range problems,i.e., distances are too great.

MSC

Figure 2: Star network, alternative 1.

Star network, alternative 2Figure 3 illustrates another version of the star network. Here,connections are made in two stages. The more distant sites areconnected first to a common node, which is then connected to the MSC.The link from the common node to the MSC must generally have highercapacity than the individual RBS connections. It may also be necessaryto assign a lower frequency band to the link between the common nodeand the MSC in order to handle the longer distance involved. A higherfrequency band may often be used for the connection of the individuallinks.

MSC

Figure 3: Star network, alternative 2.

Page 287: TND Complete

RADIO TRANSMISSION NETWORK AND FREQUENCY PLANNING

4 Ericsson Radio Systems AB

12/038 02-LZU 102 152, Rev A, November 1999

Chain networkFigure 4 illustrates another configuration in which the individual sitesare connected in chains , or in tandem, to the MSC. This often providesminimum length per link. Two disadvantages of the configuration arethe poorer reliability caused by hardware faults since the links arecoupled in sequence, and the increase in capacity requirement along thechain. Drop insert or DDC (Digital Cross Connect) may help tominimize capacity requirements.

MSC

Figure 4: Chain network.

Loop networkFigure 5 shows all sites connected in a loop. The advantage of thisconfiguration is that it is possible to achieve a redundant (duplicated)network. In the event of a breakdown in one link, traffic can be divertedin the other direction around the loop. If the loop has sufficient capacityto carry all the traffic from every site in both directions, then one hasachieved complete redundancy. The capacity requirement is then thetotal sum of the individual capacity requirements. Here again, dropinsert or DCC, would help to minimize capacity requirements.

Unavailable time caused by hardware faults is reduced in this type ofnetwork without the necessity of doubling the radio equipment. On theother hand, if network capacity is not increased, the ability to handletraffic decreases.

MSC

Figure 5: Loop network.

Page 288: TND Complete

PATH AND FREQUENCY PLANNING

Ericsson Radio Systems AB

12/038 02-LZU 102 152, Rev A, November 1999

5

It should be observed that a looped network may involve specialsynchronization problems. Under normal conditions, ratesynchronization is supplied from the transmission end, which passes therate to the receiving end. Using a loop to route traffic in the event ofhardware failure or long lasting fading requires that the base stationhandle traffic to/from two directions. In this case, the base stationrequires the capability of handling two connection routes, both from thetraffic and synchronization standpoints.

Line of sight

Frequencies above 7 GHz require free line-of-sight between thetransmitting and receiving antennas. Obstructions that penetrate intoand above the line-of-sight cause signal attenuation that may cause thepath to be unusable. Such obstructions may be composed of terrain,forests, buildings, chimneys, etc. If one uses maps to investigate freeline-of-sight conditions, one should be especially observant as toobstructions close to the sites (in the vicinity of 100-200 meters) thatmay not be indicated due to inaccuracies in the map due to insufficientresolution. Maps are not the besttool to judge the height of buildingsand other man-made obstructions. A line-of-sight investigation shouldalways be performed on site before finally selecting station sites.

Clearance

Even if one finds that a path exhibits proper line-of-sight characteristics,path obstacles may have attenuating effects on the signal if they aresituated sufficiently close to the path. Usually, one defines a Fresnelzone around the center line of the path, see Figure 6. The first Fresnelzone is defined as a zone that takes the form of an ellipsoidal shell,having its focal points at the antennas of both sites. The Fresnel zonediminishes with increasing frequency. (See the section ”RADIO WAVEPROPAGATION”).

Provided that there is no obstacle within the first Fresnel zone, obstacleattenuation can be ignored, and clearance demands are in most casessatisfied. If one has, for example, a backbone network operating at alower frequency than for example 7 GHz, the path length may requiremore clearance than that required by the first Fresnel zone. One may berequired to keep the first Fresnel zone free from obstacles at a smallereffective earth-radius than for k=4/3. For example, the requirement mayentail a free first Fresnel zone for k=0.5.

Page 289: TND Complete

RADIO TRANSMISSION NETWORK AND FREQUENCY PLANNING

6 Ericsson Radio Systems AB

12/038 02-LZU 102 152, Rev A, November 1999

On the other hand, at frequencies less than about 2 GHz, one may beable to tolerate some obstacle attenuation. The need for clearance forthese frequency bands must be calculated for each individual path.

The first Fresnel zone can be calculated as follows:

( )21

213.17ddf

ddr

+⋅⋅

⋅= (1)

where

r = The radius of the first Fresnel zone at a given point along apath, m

d1 = The distance from the first site to this point, km

d2 = The distance from the second site to the point, km

f = Frequency, GHz

d1

A B

d

Effective Earth

M

Rn Sight line

d2

Figure 6: Fresnel zone.

Some examples of how the radius of the Fresnel zone varies with pathlength for different frequency bands are shown in Table 1. The tableshows the Fresnel zone’s mid-path, which provides an indication of theclearance requirements that are demanded.

Page 290: TND Complete

PATH AND FREQUENCY PLANNING

Ericsson Radio Systems AB

12/038 02-LZU 102 152, Rev A, November 1999

7

Frequency (GHz)

Distance (km) 0.45 7 15 23 26 38

5 29 7.3 5.0 4.0 3.8 3.1

15 50 12.7 8.7 7.0 6.6 5.4

40 82 20.7 - - - -

Table 1: Radius (m) of the first Fresnel zone (mid-path) for somefrequencies. The distance of 40 km is not applicable in the frequencyrange 0.45 to 38 GHz as indicated by the table.

Path profiles

The intention of the path profile is to provide material for the decisionas to whether a free line-of-sight exists between the selected sites for thestations and whether sufficient clearance exists to avoid obstacleattenuation. The path profile is also useful when calculating variationsin received signals (fading).

The path profile is essentially a plot of the Earth’s elevation as afunction of distance along the path between the transmitting andreceiving sites. Data is derived by locating the two terminals on anelevation contour map, drawing a straight line between the two points,and then reading the elevation contours at suitable distance intervals.

Topographical information, used in the construction of path profiles,may also be derived from topographical databases. Such databases arerequired to include both altitude data and land-use data.

A path profile is plotted in a so-called path-profile chart. Path profilecharts are constructed by computing earth bulge, ∆h , see Figure 7:

Rk

ddh

⋅⋅⋅

=2

Ä 21 (2)

where:

∆h = The Earth bulge at a given point along the path, m

d1 = The distance from one site to the point, km

Page 291: TND Complete

RADIO TRANSMISSION NETWORK AND FREQUENCY PLANNING

8 Ericsson Radio Systems AB

12/038 02-LZU 102 152, Rev A, November 1999

d2 = The distance from the opposite site to the same point, km

k = Earth radius factor

R = The true earth radius, km

d2d1

∆h

Distance

Ear

th e

leva

ition

Figure 7: Earth bulge.

A radio ray beam may be shown as a straight line in a path profile that isconstructed having an earth radius factor that corresponds to theconditions defined by a normal atmosphere for the particulargeographical locations at which the sites are located.

A factor that may be used for the calculation of the particular k-value(∆N ) for different parts of the world can be found in Rec. ITU-R P.453-6 ”. The maps show ∆N from ground level and up to an altitude of onekm.

The transformation from ∆N to k-factor is performed in accordancewith section ”RADIO WAVE PROPAGATION”.

The path profile chart may now be completed. Antenna height and line-of-sight information are added to the chart. Adding the first Fresnelradius to the chart will allow the determination of free line-of-sight andwhether or not sufficient clearance exists along the path. The pathprofile is to clearly indicate any forest areas, buildings and other man-made obstructions, see Figure 8.

Page 292: TND Complete

PATH AND FREQUENCY PLANNING

Ericsson Radio Systems AB

12/038 02-LZU 102 152, Rev A, November 1999

9

Figure 8: Path profile.

Link budget

A link budget is established to enable calculations involving signalreception under fade-free conditions. The budget contains a summationof all losses and amplifications of the signal as it propagates from thetransmitter to the receiver. This is illustrated in Figure 9.

Transmitter ReceiverAF

PoutPin

AF

G

AL

AO

AGAbf

G

Figure 9: Losses and gains along a path.

The power received by the radio link terminal, as illustrated in Figure10, can be calculated as follows:

∑ ∑ −−−−+−= LGbfFoutin AAAAGAPP 0 (3)

Page 293: TND Complete

RADIO TRANSMISSION NETWORK AND FREQUENCY PLANNING

10 Ericsson Radio Systems AB

12/038 02-LZU 102 152, Rev A, November 1999

where

Pin = Received power, dBm

Pout = Transmitted power, dBm

AF = Antenna feeder loss, dB

G = Antenna gain, dBi

Abf = Free space loss between isotropic antennas, dB

AO = Obstacle loss, dB

AG = Gas attenuation, dB

AL = Additional loss, dB

antenna gain

feeder lossreceived power

fade margin

receiver thresholdvalue

wave propagation losses

antennagain

outputpower

feeder loss

POWER

Figure 10: Losses and gains.

Page 294: TND Complete

PATH AND FREQUENCY PLANNING

Ericsson Radio Systems AB

12/038 02-LZU 102 152, Rev A, November 1999

11

Fading

Fade marginThe incoming signal that is calculated with the help of the link budgetapplies to fade-free time. Actual incoming signals to the radio-linkreceiver vary over time due to fading. To allow for a sufficient powerrange in connection with incoming signal variations, paths aredimensioned so that a given margin is attained between fade-freeincoming signal levels and the receiver threshold value. This is referredto as the fade margin. The fade margin is to be sufficiently large so thatthe probability of it being exceeded due to fading is sufficiently small inorder to meet with the functional demands that are placed on the path.The requirements placed on fade-margin size are indirectly set as aresult of the norm used when dimensioning the path. Fade margins lyingin the range 25 to 40 dB are most common. Climate, terrain and pathlength are factors that affect the degree to which a radio-link path issensitive to fading.

RainThe most common types of fading are ordinarily the result ofprecipitation (rain), multipath propagation and refraction.

For frequencies greater than 10 GHz, rain is generally the determiningfactor. Rain intensity is a parameter that is required when calculatingfading due to rain. The algorithms that are generally employed require avalue for the rain intensity that is exceeded more than 0.01% of the time(based on an annual average). Actual values of the ”rain-intensity-at -0.01% value”, for different parts of the world, can be found in Rec.ITU-R PN.837-1.

Multipath propagationFor frequencies less than 10 GHz, multipath propagation and refractionare the dominant causes of fading. A climate dependent factor isinvolved in the calculation of fading caused by multipath propagation,which may be found in Rec. ITU-R PN.530-7.

It should be noted that more small-scale climactic variations may existthan those found in the ITU-R recommendation (also applies to rain).For example, for paths that for the most part traverse large bodies ofwater, the results of the algorithms are often too optimistic whenapplying large-scale ”normal” climactic factors in the calculation offading due to multipath propagation.

Page 295: TND Complete

RADIO TRANSMISSION NETWORK AND FREQUENCY PLANNING

12 Ericsson Radio Systems AB

12/038 02-LZU 102 152, Rev A, November 1999

The climate dependent portion of the algorithm should, in such cases,be adapted to ”local climactic conditions” in order to assure betterresults.

GeneralMore on fading, its causes and how it is calculated are described in thesection ”RADIO WAVE PROPAGATION”.

The calculated probability related to how the different types of fadingalong a radio-link path are expected to behave are then transformed intoquality and unavailability objectives that are defined in the norm that isapplied in the dimensioning of the path. The quantities that arecommonly applied are generally standardized by ITU. See the section”QUALITY AND AVAILABILITY TARGETS”.

Diversity

Diversity should be used when constructing paths that are heavilyexposed to fading caused by multipath propagation. Extreme cases offading due to multipath propagation are usually the result of long paths,atmospheric disturbances or reflections of the radio waves by large flatsurfaces. Radio-link paths over water, are examples of paths that oftenrequire diversity. Diversity techniques reduce the effects of fading butalso cause an increase in the amount of hardware required.

The basis for diversity lies in the fact that radio waves are given thepossibility of reaching the receiver via two or more paths. Incomingsignals arriving along different paths are assumed to have faded tovarying degrees, independent of one another, and are as a result,uncorrelated. The receiver then selects the signal that contains thegreatest amount of energy or in some applications, a combination ofboth of the received signals. The most commonplace forms of diversityare space diversity and frequency diversity.

Space diversityA transmitter antenna and two receiver antennas are used whenemploying space diversity. The two receiving antennas make it possibleto receive signals propagating along different paths. The approachrequires twice as many antennas at each end of the path, a unit thatselects the best signal and duplicated receiver equipment (either entirelyduplicated or partially duplicated).

Page 296: TND Complete

PATH AND FREQUENCY PLANNING

Ericsson Radio Systems AB

12/038 02-LZU 102 152, Rev A, November 1999

13

Frequency diversityOne and the same signal is transmitted via two different frequencies. Asa result of the difference in frequencies, there is no correlation betweenthe fading of the two signals. Only one antenna is required at each endof the path, but equipment for the selection of the better signal as wellas duplicated transmitters and receivers are required. The inferior levelof frequency economy generally causes space diversity to be chosenover frequency diversity.

Combinations of the two approaches are not unusual when solvingextremely difficult fading situations.

ImprovementImprovements that are achieved as the result of diversity are expressedas a factor, referred to as the improvement factor, which affects thecalculated probability of multipath fading, see Figure 11. Theimprovement varies for different fade depths. It is greatest for deepfading where improvements of up to 100 times can be achieved. Theimprovement factor is calculated using a number of algorithms,depending on the selected diversity method. The factor is affected, forthe most part, by antenna separation in the case of space diversity andby frequency difference in the case of frequency diversity.

Probability of exceeding the fading depth, %

Fad

ing

dept

h, d

B

Without diversity

With diversity

improvement

gain

A

B

C

10-2 10-3 10-4 10-5 10-6 10-7

-10

-20

-30

-40

-50

0

Figure 11: Diversity improvement.

Page 297: TND Complete

RADIO TRANSMISSION NETWORK AND FREQUENCY PLANNING

14 Ericsson Radio Systems AB

12/038 02-LZU 102 152, Rev A, November 1999

Reflection

Radio wave reflections from large plane surfaces, e.g., lakes and otherlarge bodies of water, can cause degradation of a connection’s qualityand availability. The reflected wave propagates along a different paththan that taken by the direct wave, and therefore traverses a differentdistance before arriving at the receiving station. This difference indistance causes the arriving waves to be phase-shifted with respect toone another. In addition to the phase-shift caused by the aforementioneddifference in path length, another source causing phase difference is thephase-shift produced at the moment of reflection.

The desired signal is attenuated as a result of phase differences in thedirect and reflected incoming waves. The decisive factors as to theseriousness of the effects of such reflections are the electricalcharacteristics of the ground, the grazing angle, the frequency, thesignal’s polarization, and any small-scale variations in elevation thatexist at the point of reflection.

Radio-link paths for which reflections are likely to occur should beconstructed employing space-diversity. The distance between theprimary and the diversity antennas should be adapted to the path’sgeometry so that one always achieves the best possible signal in one ofthe antennas.

To calculate the optimum height difference between the diversityantennas, one first calculates the height difference between two adjacentpoints along the mast, at which signal strength is a minimum (or amaximum). This calculation is naturally performed for both stations, Aand B. For example, assume that an antenna is mounted on a mast at agiven position, i.e., at a given height. As the antenna is moved from thisstarting position, the resultant signal strength, i.e. the sum of the signalstrengths of the direct and the phase-shifted reflected waves, will eitherincrease to a maximum or decrease to a minimum depending on thedirection of movement. The distance between the points in whichminimum (or maximum) signal strength is measured is the distancereferred to above.

32

'

' 10

74.12

123.0

⋅−

⋅⋅

=

k

dh

fd

hB

B

Aδ (4)

Page 298: TND Complete

PATH AND FREQUENCY PLANNING

Ericsson Radio Systems AB

12/038 02-LZU 102 152, Rev A, November 1999

15

32

'

' 10

74.12

123.0

⋅−

⋅⋅

=

k

dh

fd

hA

A

Bδ (5)

where

δh A' = The height difference between the two maximums/minimumsat station A, m

δh B' = The height difference between the two maximums/-minimums at station B, m

h A' = The antenna height above the point of reflection at stationA, m

h B' = The antenna height above the point of reflection at stationB, m

dA = The distance between station A and the point of reflection,km

dB = The distance between station B and the point of reflection,km

d = The distance between station A and B, km

f = Frequency, GHz

k = Earth-radius factor

The distance between the stations and the point of reflection iscalculated as described in section ”RADIO WAVE PROPAGATION”.

The distance required between the diversity antennas is then calculatedas follows:

2

'A

A

hh

δδ = (6)

and

2

'B

B

hh

δδ = (7)

where

δh A = The height difference between the antennas at station A, m

δh B = The height difference between the antennas at station B, m

Page 299: TND Complete

RADIO TRANSMISSION NETWORK AND FREQUENCY PLANNING

16 Ericsson Radio Systems AB

12/038 02-LZU 102 152, Rev A, November 1999

If possible, station locations should be selected so that the risk ofreflection is avoided, see Figure 12, or reduced, e.g., do not, if possible,select paths that cross large bodies of water. If, however, one is forcedto select paths that are likely to cause reflections, one should attempt toselect antenna heights and a wave propagation path such that reflectedwaves are, as far as is possible, attenuated by obstructions that aresituated along the path of reflection. The risk of interference is as aresult considerably reduced through planned attenuation.

A B

Figure 12: Obstacle attenuation in a reflected wave.

In addition to the reflection problems caused when radio wavespropagate across large bodies of water, these regions also cause othertransmission difficulties due to the propagation-impairing atmosphericconditions that often prevail in these areas. These factors sufficientlymotivate the use of space-diversity when constructing such paths, evenin the event that one feels fairly certain that the effects of reflectionshave been reduced through planned obstacle attenuation.

Page 300: TND Complete

PATH AND FREQUENCY PLANNING

Ericsson Radio Systems AB

12/038 02-LZU 102 152, Rev A, November 1999

17

Path and site surveys

Site and path surveys are often necessary in conjunction with theplanning of proposed radio-links. This process may be subdivided intotwo activities. The first of which is the actual inspection of the pathitself and the nature and positions of any obstacles along the path, thestudy of the reflective attributes of the path, the actual positions ofobstacles that are expected to attenuate reflections, etc. The secondrelates to the inspection of the station site, including activities such asthe physical inspection of the antenna masts, their height, theirstructural properties and their ability to carry the required antennaequipment, whether or not sufficient space has been allotted for themounting of antennas, the availability of secure and sufficient electricalpower, etc.

The checklist below includes a number of the essential points thatshould be investigated.

Find/verify:

• Geographical position of the site.

• Antenna carrier height above ground level.

• Antenna carrier type, strength and torsional strength.

• Ground level above mean sea level.

• Possibility to mount antennas at necessary heights.

• Obstacles in path directions, height and width.

• Potential reflecting surfaces.

• Radio environment, other radio equipment in the vicinity orpotential sources of signal interference.

• Distance between indoor and outdoor equipment.

• Floor/wall space for mounting indoor equipment. Power.

• Battery backup.

• Possibility of mounting antenna feeder or multi-cable between theindoor and outdoor equipment, considering space, wall entrance,bend radius, etc.

• New sites - proximity to roads and power transformer stations.

Page 301: TND Complete

RADIO TRANSMISSION NETWORK AND FREQUENCY PLANNING

18 Ericsson Radio Systems AB

12/038 02-LZU 102 152, Rev A, November 1999

Frequency planning

GeneralThe objective of frequency planning is to assign frequencies to anetwork using as few frequencies as is possible and in such a manner,that the quality and availability of the radio-link’s path is minimallyaffected by interference. It is not economically feasible to achievecompletely interference-free networks through the use of frequencyplanning techniques. Frequency planning is often performed based onthe acceptance of a given and calculated level of interference that resultsin acceptable threshold degradation, at the radio-link receiver, ofapproximately no more than 3 dB. This requires that the fade margin be3 dB higher than the demands made due to wave propagation andhardware. Equipment data describes maximum interference levels thatcan be tolerated by the particular radio-link equipment before the 3 dBthreshold degradation level is exceeded. The data describes theallowable level of the interfering signal, I, in relation to the radio signal,C, for a given frequency separation. The “3 dB threshold degradation”approach is, however, not recommended in a computer environment inwhich more sophisticated methodology is strongly recommended. Atthe end, the final limitations are provided by the quality and availabilityobjectives.

Both near and far interference contributions are considered whenperforming frequency planning.

The following are the basic considerations involved in the assignmentof radio frequencies:

• Prevention of mutual interference such as the interference betweenthe radio frequency channels in the actual path, interference to/fromother radio paths, interference to/from satellite communicationsystem, etc.

• Frequency economy of the available radio frequency spectrum.

• Proper selection of frequency band that conforms to the requiredtransmission capacity.

• Frequency band suitable to both path characteristics (path length,site location, terrain topography) and atmospheric effects

Page 302: TND Complete

PATH AND FREQUENCY PLANNING

Ericsson Radio Systems AB

12/038 02-LZU 102 152, Rev A, November 1999

19

Far interferenceBy far interference is meant unwanted disturbances between atransmitter and a receiver that are not co-located (i.e., located in veryclose proximity to one anther), see Figure 13. The distance between thedisturbing transmitter and the disturbed receiver may vary between afew kilometers, or perhaps a few hundred meters, up to many tens ofkilometers.

The most serious interference caused by interfering transmitters occurswhen they transmit at the same frequency at which the disturbedreceiver is tuned to. This type of interference is referred to as co-channel interference. A common requirement on signal-to-interferenceratio in the case of co-channel interference is C/I= 20 dB.

In some cases, serious disturbances may arise even though theinterfering signal lies in an adjacent and separate channel than thechannel containing the desired signal, so-called adjacent-channelinterference. C/I = -15 dB is a common require for the avoidance ofadjacent-channel interference. These requirements are equipmentdependent and vary for the adjacent-channel case as a function offrequency separation between the disturbing and the disturbed signal.The bandwidth of the interfering signal in relation to the bandwidth ofthe disturbed receiver also affects the demand placed on the C/I ratio.

Planning a network that is free from the effects of far interferencerequires knowledge of the geographic locations at which the sites arelocated, the layout and dimensioning of the radio-link paths (includingboth the paths and the transmitting and receiving sites and theirrespective equipment), equipment data, existing network frequencyassignment and a model allowing the study of wave propagationbetween the disturbed receiver and the interfering transmitter.

Far interference is often the primary factor that limits the number ofpaths that can be set up within a given geographical area. It also affectsthe possibility of realizing a variety of network solutions, for example,the number of possible paths within a node located in a star network.High quality antennas, which are often analogous with large antennas,are advantageous in the achievement of one’s planning objectives.

Page 303: TND Complete

RADIO TRANSMISSION NETWORK AND FREQUENCY PLANNING

20 Ericsson Radio Systems AB

12/038 02-LZU 102 152, Rev A, November 1999

Tx=f2

Rx=f1

Tx=f1

Rx=f2

Tx=f1

Rx=f2Tx=f2

Rx=f1

Figure 13: Far interference.

Near interferenceNear interference refers to receiver disturbances that are generated bytransmitters that are grouped at one and the same site. Disturbances maybe caused both by in-house and foreign equipment, either individuallyor as a result of their interaction.

Disturbances may appear in the form of intermodulation effects, i.e., themixture of two or more transmitter frequencies that may arise close to aparticular receiver frequency, see Figure 14.

Page 304: TND Complete

PATH AND FREQUENCY PLANNING

Ericsson Radio Systems AB

12/038 02-LZU 102 152, Rev A, November 1999

21

f2f1

frx ftx

3f2-2f12f2-f1

Figure 14: Near interference.

Disturbances arising from intermodulation effects in cases wherewaveguide-bound frequency bands are used (i.e., ≥ 6 GHz) arenegligible. Of course wave-guide-bound systems may contribute tointermodulation effects in systems working at lower frequency bandsand therefore using coaxial cables as antenna feeders. It should be notedthat this effect is due to the fact waveguides are more frequencydiscriminating (hi-pass filter characteristic) then antenna feeder cables.

Degraded performance can also be the result of transmitter frequenciesthat lie too close to a receiver’s frequency thereby directly degradingreception quality.

An additional cause of degraded reception quality is blocking. Blockingcan arise even if the disturbing transmitter frequency lies well separatedfrom the receiver frequency if the emitted field-strength by thetransmitter is sufficiently strong. Examples of situations in whichblocking can arise is when the radio-links are co-located with high-power transmitters such as radar stations and radio broadcastingstations.

Page 305: TND Complete

RADIO TRANSMISSION NETWORK AND FREQUENCY PLANNING

22 Ericsson Radio Systems AB

12/038 02-LZU 102 152, Rev A, November 1999

Another important characteristic, that should be considered whencalculating the effect of near interference, is the coupling loss betweentwo antennas located at the same site, see Figure 15. This identifies thatportion of the radiated power, from one of the antennas, that leaks overto the other antenna.

P1

A = Coupling loss

P2

A

P P A2 1= −

Figure 15: Coupling loss between two antennas.

The following isolation values may be used when performing roughestimates:

• approximately 40 dB between two antennas made up of dipoles

• approximately 80 dB between two parabolic antennas

These values are in reality, naturally dependent on the distance andangles between the two antennas.

The selection of proper duplex-bands for transmitter and receiverequipment, during the frequency-allocation process, is essential if one isto control the risk of disturbances that arise as a result of insufficienttransmitter-receiver frequency separation. Allocating all the transmittersto one of the duple-bands and all the receivers to the other alwaysattains maximum site frequency economy for a specific radio-frequencychannel arrangement. This often results in also satisfying therequirement of maintaining the necessary frequency separation betweentransmitter and receiver frequencies.

Making use of one of the ITU’s standardized radio-frequency channelarrangement generally facilitates the planning process. These standardsare internationally and widely accepted by numerous governmentfrequency regulating bodies.

Page 306: TND Complete

PATH AND FREQUENCY PLANNING

Ericsson Radio Systems AB

12/038 02-LZU 102 152, Rev A, November 1999

23

Frequency economySome general pointers that should be followed in the frequencyplanning process:

• Reuse frequencies, i.e., repeat the use of frequencies as often as ispossible.

• Use antennas having high front-to-back ratios and large side-lobesuppression. These result in both good frequency economy and, inthe final analysis, good overall network economy. High performanceantennas may be a suitable alternative.

• Do not use higher radio-link output power than necessary.

• If the choice is between higher transmitter output power and largerantennas, choose (if possible) a larger antenna. Power will beconcentrated along the intended path, i.e., towards the receiver.

References

Rec. ITU-R P.453-6

Rec. ITU-R P.530-7

Rec. ITU-R P.837-1

Page 307: TND Complete

i

RADIO-RELAY TRANSMISSION

DISCUSSION

The primary objective of this chapter is to encourage adiscussion on specific and general subjects of interest intransmission network planning, for instance, practicesversus theory, current trends in today’s world market thataffect radio-relay transmission, personal experience andfuture prospects for radio-relay technology.

TABLE OF CONTENTS

Introduction....................................................................................................................................................... 1World market trends.......................................................................................................................................... 1New technology................................................................................................................................................. 1Future outlook ................................................................................................................................................... 2References ......................................................................................................................................................... 3Question form.................................................................................................................................................... 4

Page 308: TND Complete

RADIO-RELAY TRANSMISSION - DISCUSSION

Ericsson Radio Systems AB

13/038 02-LZU 102 152, Rev A, November 1999

1

Introduction

Commercially operated radio-relay transmission facilities have been inexistence for some 60 years. Radio-relay technology has seen vastdevelopment during that period of time, progressing from the stages ofthe earlier, now antiquated, analog systems to systems based on moderndigital technology. Modern transmission technologies, such as optical-fiber transmission, were introduced during the last two-three decades.Despite the limited transmission capacity of radio-relay systems, incomparison to optical fiber, radio-relay transmission still seems to bethe best alternative for many applications. Future trends and theprospect of new applications seem to confirm the continued suitabilityof utilizing radio-relay in future networks.

World market trends

Radio-relay transmission will undoubtedly play a major role in thesocial-technical structure of the future - a structure upon which theenvisioned global information society is to rest. Nowadays, about tenmajor companies are competing in the area of radio-relay transmissionand for the past 20 years, an almost constant amount of radio-relayequipment has been manufactured per year on a worldwide basis (about50,000 transmitters and receivers). Furthermore, radio-relay equipmentis constantly getting better, smaller and less expensive.

Present world market trends in this area seem to indicate that thecoming years will see an increase in both the need for, and theproduction of, radio-relay transmitter and receiver equipment. Thisequipment will be utilized in responding to the demands for:

• high-capacity short-haul urban systems

• small and medium-capacity rural and urban access systems

• high-capacity long-haul systems applicable to the regional networksof developing and geographically inaccessible countries

New technology

In addition, worldwide business transformations that have beenimplemented during recent years, aimed at creating greater deregulationand reduced centralization, have also acted as catalysts in the creation ofnew business opportunities and markets.

Page 309: TND Complete

RADIO TRANSMISSION NETWORK AND FREQENCY PLANNING

2 Ericsson Radio Systems AB

13/038 02-LZU 102 152, Rev A, November 1999

The traditionally long-haul high-capacity systems installed in extremelylarge countries such as China, Russia, India and Brazil will certainly beextended to greater transmission capacities. The majority of systemsbased on older radio technologies and cable connections will certainlybe replaced by newer technologies, in many cases new radio-relaysystems will appear as the best and most cost-effective alternative. Inaddition, as installed radio-relay systems around the world grow olderand approach obsolescence, they will require continuous maintenanceand upgrading programs to maintain sufficient efficiency, flexibility andproductivity.

Short-haul systems will undoubtedly be highly integrated with compactcost-effective equipment operating at higher frequency bands. Thesesystems will be characterized by their short installation time, their easeof maintenance and will be used in the following applications:

• the interconnection of long-haul routes with urban exchange stations

• the interconnection of cellular base stations with one another andwith the Public Switched Telephone Network (PSTN)

• Radio in the Local Loop (RLL) for the final subscriber

Future outlook

New radio-relay technologies that are suited to the new market demandswill most certainly appear and advances will very likely appear in thefollowing areas:

• Frequency bands below 20 GHz will become more crowded andconsequently a shift will take place towards higher frequencies

• more sophisticated modulation methods will improve frequencyutilization

• higher transmission capacities will, in many situations, complementoptical-fiber cable transmission systems

• greater digitalization of the signal processing stages plus built-inintelligence

• increased equipment integration will produce more compact andmore cost-effective equipment

• adaptive equalization and automatic output power regulation

Page 310: TND Complete

RADIO-RELAY TRANSMISSION - DISCUSSION

Ericsson Radio Systems AB

13/038 02-LZU 102 152, Rev A, November 1999

3

Since the establishment of the first commercial link between Calais andDover some 60 years ago, the importance of radio-relay transmissionhas steadily increased - resulting in more reliable and cost-effectivetransmission systems. It is not at all unlikely that radio-relaytransmission will emerge as being the best transmission alternative formany future applications yet to come.

References

”Radio-Relay Systems”, Huurdeman, A. A., Artech House, 1995.

“Radio-System Design for Telecommunications (1-100 GHz)”,Freeman, R. L., 1987.

Page 311: TND Complete

RADIO TRANSMISSION NETWORK AND FREQENCY PLANNING

4 Ericsson Radio Systems AB

13/038 02-LZU 102 152, Rev A, November 1999

Question form

If you have any question or subject of general interest for discussion,please fill in this form and forward it to the course instructors. Issuesconcerning path and frequency planning, methods, trends or “countryspecific” matters such as access to frequencies/ frequency bands, errorperformance and availability, interference aspects, hardwarerequirements, climate effects on radio-relay transmission, etc. arewelcome. We believe the form will facilitate structuring your questionsand subjects and improve the outcome of our discussion.

________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________

Page 312: TND Complete

i

RADIO TRANSMISSION NETWORKPLANNING - APPLICATION

This chapter provides an extensive exercise in the subjectof radio-transmission network and frequency planning.

TABLE OF CONTENTS

Introduction....................................................................................................................................................... 1Assign values for the planning parameters and establish a network.................................................................. 1

Assign channel table............................................................................................................................ 1Assign Radio Systems ......................................................................................................................... 2Assign quality and availability targets................................................................................................. 3Assign default parameter values.......................................................................................................... 3Establish sites ...................................................................................................................................... 6Establish paths..................................................................................................................................... 6

Planning procedures .......................................................................................................................................... 7Path planning guidelines ..................................................................................................................... 7Frequency assignment guidelines ........................................................................................................ 8Final path calculation .......................................................................................................................... 8

Page 313: TND Complete

RADIO TRANSMISSION NETWORK PLANNING - APPLICATION

Ericsson Radio Systems AB

14/038 14-LZU 102 152, Rev A, November 1999

1

Introduction

The purpose of this exercise is to provide an introduction to radiotransmission network and frequency planning. Instructions and advisoryguidelines will facilitate the initialisation and the final analysis of aradio transmission network comprising 20 sites. One of the sites will beconsidered as the joint-point site for all connections.

The following will be considered:

• Assign values for the planning parameters

• Establish a network

• Perform planning procedures

Assign values for the planning parameters andestablish a network

Assign channel table

Select Define - Channel table. Create a new channel table according toTable 1, and give it the name “RTNFP practice”. Use channels B1, B2,C1, D1, D4 and D9. The channel configuration is illustrated in Figure 1.

Upper Band Lower Band

Frequency Frequency Channel spacing

MHz MHz 3.5 MHZ 7 MHz 14 MHz 28 MHz

14921.00 14501.0014924.50 14504.50 D114928.00 14508.00 D2 C114931.50 14511.50 D314935.00 14515.00 D4 C2 B1 A114938.50 14518.50 D514942.00 14522.00 D6 C414945.50 14525.50 D714949.00 14529.00 D8 C5 B214952.50 14532.50 D9

Table 1. Channel table.

Page 314: TND Complete

RADIO TRANSMISSION NETWORK AND FREQENCY PLANNING

2 Ericsson Radio Systems AB

14/038 14-LZU 102 152, Rev A, November 1999

Channel1 92 3 4 5 6 7 8 10 11 12 13 14 15 16 17 18 19 20

D1C1

D4

B2

D9

B1

D1

C1

D4

B1 B2

D9

3.5 MHz

Figure 1. ML channels RTNFP training network.

Assign Radio Systems

Select Define - Radio System. Define 4 different radio systems.

Radio System 1:

Copy E-CAP 2x2. Select the copy and rename it as “ML 15 E 2x2 HP”.

Select the following components:

Radio: ML 15 E 2x2 HP

Antenna type: ML 15 0.6 HP

Channel table: RTNFP practice

Configuration: Not doubled

MTTR: 8 hours

Radio System 2:

Copy E-CAP 4x2. Select the copy and rename it as “ML 15 E 4x2 HP”.

Select the following components:

Radio: ML 15 E 4x2/8 HP

Antenna type: ML 15 0.6 HP

Channel table: RTNFP practice

Page 315: TND Complete

RADIO TRANSMISSION NETWORK PLANNING - APPLICATION

Ericsson Radio Systems AB

14/038 14-LZU 102 152, Rev A, November 1999

3

Configuration: Not doubled

MTTR: 8 hours

Radio System 3:

Copy E-CAP 8x2. Select the copy and rename it as “ML 15 E 8x2 HP”.

Select the following components:

Radio: ML 15 E 8x2/2x8 HP

Antenna type: ML 15 0.6 HP

Channel table: RTNFP practice

Configuration: Not doubled

MTTR: 8 hours

Radio System 4:

Copy E-CAP 8x2. Select the copy and rename it as “ML 15 E 8x2HP1,2”.

Select the following components:

Radio: ML 15 E 8x2/2x8 HP

Antenna type: ML 15 1.2 HP

Channel table: RTNFP practice

Configuration: Not doubled

MTTR: 8 hours

Assign quality and availability targets

Select Define - Quality and Availability targets. Press the “New“button and assign the name “G821” to the existing table.

Assign default parameter values

Select Define - Default parameters. Create a new default table withthe name “RTNFP practice”.

Page 316: TND Complete

RADIO TRANSMISSION NETWORK AND FREQENCY PLANNING

4 Ericsson Radio Systems AB

14/038 14-LZU 102 152, Rev A, November 1999

Equipment default

Path Radio System: ML 15 E 2x2 HP

Antenna height: 36 m

Polarisation: Vertical

Algorithms

Obstacle attenuation: Smooth-spherical-earth method (Cheriex).

Multipath fading, flat: ITU-R Rec. P.530-7

Multipath fading, frequency selective: ITU-R Rec. F.1093

Parameters

• Earth-radius factor (k):k-value statistics use k-distribution related to the actual pL factor, seeChapter 15 [4. Refractive gradient and 1. Earth radius factor as afunction of the refraction gradient].k at normal atmosphere will automatically be set from k-valuestatistics.

• Gas attenuation:Temperature, 30°C.Relative humidity, the most unfavourable parameter value, seeChapter 15, [2. Relative humidity as a function of temperature].

• Rain fading:Use the 0.01 % value, see Chapter 15 [7. Rain climate zones and 8.Rain intensity distribution].SESR fraction, 0 %.

• Flat multipath fading:pL-factor, most unfavourable parameter value, see Chapter 15 [3.Refractive factor (pL factor)].Terrain class, Inland links.Terrain type, Plains.Coastal fraction, 0 %.

Page 317: TND Complete

RADIO TRANSMISSION NETWORK PLANNING - APPLICATION

Ericsson Radio Systems AB

14/038 14-LZU 102 152, Rev A, November 1999

5

• Interference, Far interferenceUse C/I matrix: YesAdjacent channel attenuation: 20 dBInterference radius: 200 km

Result presentation:Exclude interferes when threshold level/interference level is > 40 dB.Highlight interfered paths when threshold degradation is > 3.0 dB.

Presentation

Quality template: Final.rrt.Report title: e.g. name and date.

Time unit: Second

Do not forget to SAVE the default parameters!

Page 318: TND Complete

RADIO TRANSMISSION NETWORK AND FREQENCY PLANNING

6 Ericsson Radio Systems AB

14/038 14-LZU 102 152, Rev A, November 1999

Establish sites• Open the project “RTNFP practice” and select “RTNFP practice” as

default parameters (save).

• Open the version “RTNFP practice version 1” and assign new sitesaccording to Table 2. Label the sites 1, 2, 3,.....20.

Site La Lo Z

1 24 19 19.5 75 37 56.2 502 24 15 50.3 75 42 14.1 503 24 16 48.5 75 41 14.8 504 24 17 17.7 75 41 59.9 505 24 18 11.3 75 40 37.3 356 24 17 19.7 75 39 27.4 507 24 18 43.5 75 39 38.4 468 24 18 03.7 75 42 00.0 509 24 17 42.2 75 43 17.3 50

10 24 18 45.6 75 41 15.5 5011 24 18 37.1 75 43 22.7 5012 24 19 44.8 75 42 00.4 4713 24 18 17.0 75 37 31.5 5414 24 14 31.9 75 44 12.5 5015 24 21 39.9 75 41 06.5 5016 24 31 30.4 75 44 25.3 7417 24 24 53.0 75 44 30.1 6518 24 27 15.4 75 41 44.7 6519 24 29 21.5 75 45 08.8 6520 24 30 21.2 75 46 13.9 65

Table 2. Sites

The entire network is displayed at the end of this chapter.

Establish pathsAll paths are MINI-LINK 15-E, 0.6m HP antennas (except path 15 to 19in which 1.2m HP antennas are used).

For each path, select Q&A target, Rec. G.821, medium grade, class 3.

Check if the default radio system is valid. The radio system may have tobe changed according to Table 3.

Make each path active.

Page 319: TND Complete

RADIO TRANSMISSION NETWORK PLANNING - APPLICATION

Ericsson Radio Systems AB

14/038 14-LZU 102 152, Rev A, November 1999

7

Path Site Antenna Site Antenna Capacityno height no height Mb/s

1 to 7 1 36 7 41 2x22 to 4 2 27 4 26 2x22 to 14 2 35 14 32 2x23 to 4 3 24 4 27 2x24 to 6 4 26 6 36 4x25 to 7 5 36 7 40 8x25 to 10 5 36 10 40 8x25 to 12 5 36 12 38 8x26 to 7 6 32 7 40 8x27 to 13 7 41 13 37 2x28 to 10 8 19 10 36 2x29 to 11 9 26 11 28 2x210 to 15 10 40 15 28 8x211 to 12 11 30 12 30 2x212 to 17 12 30 17 30 8x215 to 19 19 33 15 28 8x2 (*)16 to 20 16 26 20 26 2x217 to 19 17 35 19 33 8x218 to 19 18 35 19 33 2x219 to 20 19 33 20 22 2x2

Table 3. Path and antenna heights. (*) Use radio system number 4.

Planning procedures

Path planning guidelines• Make a preliminary path calculation for each path in the network.

Use as low output power as possible. It is possible to vary the outputpower in the rage of 5 - 25 dBm.

• Considerthe receiver threshold degradation caused by interference.A ”normal” reference valuefor the threshold degradation is 3 dB,which means that the fade margin has to be 3 dB greater whencompared to interference-free conditions.

• Check that the quality and availability targets are fulfilled. Apply theITU-R Hypothetical Reference Connection (HRX) in a proper way toyour training network by defining Hypothetical Reference DigitalSections (HRDS) that consist of a proper number of paths.

Page 320: TND Complete

RADIO TRANSMISSION NETWORK AND FREQENCY PLANNING

8 Ericsson Radio Systems AB

14/038 14-LZU 102 152, Rev A, November 1999

• Consider site number 5, as the joint-point site for all connections (forinstance, the location of an exchange). In this training, it is possibleto make use of maximum two Hypothetical Reference DigitalSections (HRDS).

Frequency assignment guidelines• Start in the middle of the network, for example with site 5.

• Assign for the entire network, high or low duplex to each end of thepaths. Try to avoid transmitter frequencies and receiver frequenciesin the same duplex half at one and same site.

• Re-use frequencies and polarisation as often as possible. That is, ifone channel is assigned to a site, always try to assign the samechannel for the other paths on the same site and also for theneighbouring sites.

• In the occurrence of unacceptable threshold degradation(unacceptable C/I-values), first change the polarisation. If that doesnot help, then try an adjacent channel.

• Do not exceed the threshold degradation used in the path planning.

Final path calculation• When frequencies are assigned to the network, make a final path

calculation. For each path, use the actual threshold degradationachieved in the interference calculations.

• The degradation will automatically be transferred from the farinterference calculations to the path calculations.

Page 321: TND Complete

1. Earth-radius factor as a function ofthe refraction gradient

Page 322: TND Complete

-80 -70 -60 -50 -40 -30 -20 -10 0

Refraction gradient (dN/dh), N-units/km

1.00

1.10

1.20

1.30

1.40

1.50

1.60

1.70

1.80

1.90

2.00

2.10

Ea

rth

-ra

diu

s fa

cto

r (k

)

Refraction gradients are obtainedfrom Rec. ITU-R P.453-6.

Refraction gradients are obtainedfrom ITU-R Rec. P.453-6

Page 323: TND Complete

2. Surface water vapor densityRec. ITU.R P.836-1

Page 324: TND Complete

0836-01sc

Lat

itud

e (d

egre

es)

Longitude (degrees)

FIGURE 1

Annual surface water vapour density (g/m3)

Page 325: TND Complete

0836-02sc

Lat

itud

e (d

egre

es)

Longitude (degrees)

FIGURE 2

December, January, February: surface water vapour density (g/m3)

Page 326: TND Complete

0836-03sc

Lat

itud

e (d

egre

es)

Longitude (degrees)

FIGURE 3

March, April, May: surface water vapour density (g/m3)

Page 327: TND Complete

0836-04sc

Lat

itud

e (d

egre

es)

Longitude (degrees)

FIGURE 4

June, July, August: surface water vapour density (g/m3)

Page 328: TND Complete

0836-05sc

Lat

itude

(de

gree

s)

Longitude (degrees)

FIGURE 5

September, October, November: surface water vapour density (g/m3)

Page 329: TND Complete

3. Relative humidity as a function oftemperature

Page 330: TND Complete

0 10 20 30 40 50

Temperatur, °C

0

10

20

30

40

50

60

70

80

90

100

Re

lati

ve h

um

idity

, %

0.5 g/m3

1 g/m3

2 g/m3

5 g/m3

10 g/m3

15 g/m3

20 g/m3

Water vapor density is obtained

from Rec. ITU-R P.836-1.

Water vapor density are obtainedfrom ITU-R Rec. P.836-1

Page 331: TND Complete

4. Refractive factor (pL factor)Rec. ITU.R P.453

Page 332: TND Complete

0453-7-8

FIGURE 7Percentage of time gradient ≤≤ – 100 (N-units/km): February

FIGURE 8Percentage of time gradient ≤≤ – 100 (N-units/km): May

Page 333: TND Complete

453-9-10

FIGURE 9Percentage of time gradient ≤≤ – 100 N-units/km: August

FIGURE 10Percentage of time gradient ≤≤ – 100 N-units/km: November

Page 334: TND Complete

5. Refractive gradientRec. ITU.R P.453

Page 335: TND Complete

0453-3-4

Page 336: TND Complete

0453-5-6

Page 337: TND Complete

6. Rain frequency-dependentcoefficients

Rec. ITU.R P.838

Page 338: TND Complete

TABLE 1

Regression coefficients for estimating specific attenuation in equation (1)

Frequency(GHz)

kH kV αH αV

1 0.0000387 0.0000352 0.912 0.8802 0.000154 0.000138 0.963 0.9234 0.000650 0.000591 1.121 1.0756 0.00175 0.00155 1.308 1.2657 0.00301 0.00265 1.332 1.3128 0.00454 0.00395 1.327 1.310

10 0.0101 0.00887 1.276 1.26412 0.0188 0.0168 1.217 1.20015 0.0367 0.0335 1.154 1.12820 0.0751 0.0691 1.099 1.06525 0.124 0.113 1.061 1.03030 0.187 0.167 1.021 1.00035 0.263 0.233 0.979 0.96340 0.350 0.310 0.939 0.92945 0.442 0.393 0.903 0.89750 0.536 0.479 0.873 0.86860 0.707 0.642 0.826 0.82470 0.851 0.784 0.793 0.79380 0.975 0.906 0.769 0.76990 1.06 0.999 0.753 0.754

100 1.12 1.06 0.743 0.744120 1.18 1.13 0.731 0.732150 1.31 1.27 0.710 0.711200 1.45 1.42 0.689 0.690300 1.36 1.35 0.688 0.689400 1.32 1.31 0.683 0.684

Page 339: TND Complete

7. Rain climate zonesRec. ITU.R P.837

Page 340: TND Complete

RAIN ZONESPercentageof time (%)

A B C D E F G H J K L M N P Q

1.0 <0.1 0.5 0.7 2.1 0.6 1.7 3 2 8 1.5 2 4 5 12 240.3 0.8 2.0 2.8 4.5 2.4 4.5 7 4 13 4.2 7 11 15 34 490.1 2 3 5 8 6 8 12 10 20 12 15 22 35 65 720.03 5 6 9 13 12 15 20 18 28 23 33 40 65 105 960.01 8 12 15 19 22 28 30 32 35 42 60 63 95 145 115

0.003 14 21 26 29 41 54 45 55 45 70 105 95 140 200 1420.001 22 32 42 42 70 78 65 83 55 100 150 120 180 250 170

Page 341: TND Complete

8. Rain intensity distributionRec. ITU.R P.837-1

Page 342: TND Complete

D01-sc

Page 343: TND Complete

D02-sc

Page 344: TND Complete

D03-sc

Page 345: TND Complete

9. Annual and worst-month statisticsRec. ITU.R P.841

Page 346: TND Complete

ββ and Q1 values for various propagation effects and locationsP

Rain effectterrestrial

Rain effectslant path

Multipath Trans-horizonland

Trans-horizonsea

Global 0.13; 2.85 0.13; 2.85 0.13; 2.85 0.13; 2.85 0.13; 2.85

CANADAPrairie&North

0.08; 4.3

CANADACoast&G.Lake

0.10; 2.7

CANADACent.&Mount.

0.13; 3.0

USAVirginia

0.15; 2.7

JAPANTokyo

0.20; 3.0

JAPANYamaguchi

0.15; 4.0

JAPANKashima

0.15; 2.7

CONGO 0.25; 1.5

EUROPENorth West

0.13; 3.0 0.16; 3.1 0.13; 4.0 0.18; 3.3 0.11; 5.0

EUROPEMediterranean

0.14; 2.6 0.16; 3.1

EUROPENordic

0.15; 3.0 0.16; 3.8 0.12; 5.0

EUROPEAlpine

0.15; 3.0 0.16; 3.8

EUROPEPoland

0.18; 2.6

EUROPERussia

0.14; 3.6

INDONESIA 0.22; 1.7

Page 347: TND Complete

RA

DIO

TR

AN

SM

ISS

ION

NE

TW

OR

K A

ND

FR

EQ

UE

NC

Y P

LA

NN

ING

RA

DIO

TR

AN

SM

ISS

ION

NE

TW

OR

K A

ND

FR

EQ

UE

NC

Y P

LA

NN

ING

RA

DIO

TR

AN

SM

ISS

ION

NE

TW

OR

K A

ND

FR

EQ

UE

NC

Y P

LA

NN

ING

RA

DIO

TR

AN

SM

ISS

ION

NE

TW

OR

K A

ND

FR

EQ

UE

NC

Y P

LA

NN

ING

RA

DIO

TR

AN

SM

ISS

ION

NE

TW

OR

K A

ND

FR

EQ

UE

NC

Y P

LA

NN

ING

RA

DIO

TR

AN

SM

ISS

ION

NE

TW

OR

K A

ND

FR

EQ

UE

NC

Y P

LA

NN

ING

RA

DIO

TR

AN

SM

ISS

ION

NE

TW

OR

K A

ND

FR

EQ

UE

NC

Y P

LA

NN

ING

RA

DIO

TR

AN

SM

ISS

ION

NE

TW

OR

K A

ND

FR

EQ

UE

NC

Y P

LA

NN

ING

RA

DIO

TR

AN

SM

ISS

ION

NE

TW

OR

K A

ND

FR

EQ

UE

NC

Y P

LA

NN

ING

RA

DIO

TR

AN

SM

ISS

ION

NE

TW

OR

K A

ND

FR

EQ

UE

NC

Y P

LA

NN

ING

RA

DIO

TR

AN

SM

ISS

ION

NE

TW

OR

K A

ND

FR

EQ

UE

NC

Y P

LA

NN

ING

RA

DIO

TR

AN

SM

ISS

ION

NE

TW

OR

K A

ND

FR

EQ

UE

NC

Y P

LA

NN

ING

LZB 111 0162 LBZ 111 0162 LZB 111 0162 LZB 111 0162 LZB 111 0162 LZB 111 0162