Rno Principles - Interim Version

8/21/2019 Rno Principles - Interim Version

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Copyright ©2008 Telefocal Asia Pte Ltd. All rights reserved.1

Radio Network Optimisation

Principles

Instructor: Dr Tony Vernon


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Overview of entire five day courseWhat will be learned over the next five days

Why this is important in the context of radio networkoptimisation


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Overview of Day 1

First, Second and Third Generation Networks

Introduction to Generic Radio Access Networks

Radio Propagation Theory

Multiple Access Schemes

The GSM 2G Air Interface

UTRAN – The UMTS 3G Radio Access Network

The Upgrade Migration Path 2G > 2.5G > 2.75G > 3G


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Day 1 Section 1 – 1st, 2nd and 3rd Generation Networks

1st Generation Analog NetworksCoverage on Regional Basis

Out of Town High Sites

Cell Radii 5-20km

Mobile coverage targeted

No express indoor coverage

Later deployments reduced

cell size and emphasisedindoor reliability (1990-)

Town 1 Town 2

Town 3

Town 4


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2nd Generation Digital NetworksSmaller cell size

Sectorisation to reduceinterference

Tighter frequency reuse

More robust, digital modul-ation schemes

Advanced understanding of differing requirements for Urban,Suburban and Rural/Road coverage

Town 1


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2nd Generation Digital Networks (cont.)The ‘Air Interface Wars’

IS-95 CDMA advocated by Qualcomm + acolytes

GSM advocated by LM Ericsson + acolytes

Claim & counter-claim for spectral efficiency,immunity from interference, adaptability to differentcoverage scenarios etc.

GSM now by far the dominant 2G standard, 80.79%of all connections to cdmaOne (=IS95 CDMA) 0.22%*

*source: GSM Association http://www.gsmworld.com/news/statistics/pdf/gsma_stats_q2_08.pdf


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3rd Generation Mobile Networks3G rollout less driven by coverage scenario, moreoriented toward usage scenario

Source: Morawek, R and Özcelik, H “General UMTS Network Architecture” http://www.morawek.at/roman/papers/umts.pdf


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3rd Generation Mobile Networks (cont.)Development of 3G standards started in early ’90s, atlaunch of the first 2G GSM and cdmaOne networks

Another air interface ‘Holy War’ with wideband CDMA

prevailing for the air interface and GSM RAN behind this A number of multiple access schemes standardised bythe ITU, of which 3GSM (UMTS) and the CDMA 2000variants are most widespread

China, which adopted GSM in the 2G era, has mandatedTD-SCDMA as its preferred 3G standard, which may aidthe rollout of this air interface to other territories


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144kb/s

384kb/s


2G Standards offered a single (low) data rate everywhereThe ITU mandated “graceful degradation”, or graduallyfalling bit rate for 3G, with increasing distance from theRadio Base Station

Up to 2Mb/s close to site (~10m)Up to 768kb/s in vicinityof site (~100m)

Up to 384kb/s in general

area of site (~1km)Up to 144kb/s (2B+D ISDN)elsewhere

768kb/s

2Mb/s


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Day 1 Section 2 – Introduction to Radio Access Network

Section OverviewObjective of Radio Network Planning (RNP)

Operator Perspective of RNP

RNP Technology and Automation

Relationship between RNP and Frequency Planning

Radio Propagation Principles (Reflection, Refraction,Diffraction, Absorbtion, Multipath)


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The Radio Access Network governs one third of theusers’ overall experienceand 100% of users’ qualityof service

The operator inter-acts with the network and users via theOperations Subsystem

Both users and the operatorinteract with external networksvia the Network Subsystem

Operator

E x t e

r n a l

N e t w o r k s

S u b

s c r i b

e r s

OSS

N S S

B S S / R A N

M S / U E

Adapted from Mouly & Pautet, ‘The GSM System’


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Operator view of RNPBase Station Subsystem defines 100% of users’ technicalexperience with the operator (ignoring NSS faults)

Operator can differentiate itself from other mobile

networks in the territory by investing in the RANCAPEX sunk into RAN precedes operating profits with nodirect ‘return on investment’

Many 3G networks built on top of existing 2G properties

2G site topology not necessarily suitable for 3G

Operators in mature markets outsourcing their RNP


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RNP Technology – RudimentaryCalculate approximatecell radius for differing

‘clutter’ types

Clutter maps commonfor at least rural,suburban, urban anddense urban

Perform ‘best fit’ of cellcoverage areas to cluttermap, bearing in mindhandover overlap


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RNP Technology – SophisticatedSignal from each sectorcomputed from clutter typein which it is located

Not necessary to maintainsite raster or orientation

Software fits sites so thatentire region to be servedhas coverage at least tominimum field strength

Town 1 Town 2

Town 3

Town 4


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Simple (Omni) Frequency PlanningGSM900 = 124 ARFCNs

Operator allocation =e.g 45 ARFCNs

Divide up into 7 ‘reuse’ groups

6 ARFCNs per site= (6 x 7) + 3 spare

for special purposes A connection suffers inter-ference from up to 6 neighbours


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Simple (Sector) Frequency PlanningOperator allocation =e.g. 45 ARFCNs

Divide frequencies

per site by numberof sectors, e.g.(2 x 3 x 7) + 3

Connection is nowinterfered by only3 other neighbours

Sectorisation reduces capacity


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-14 -13 -12 -11 -10 -9 -8 -7 -6 -5 -4 -3 -2 -1 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14

Distance from Site (km)

S i g n a l S t r e n g t h

Serving SiteAdjacent Site Adjacent Site

+

+

=

Interferenceapproximatelyconstant over

service area of site

Reuse Site Reuse Site

Interference ‘wash’ from more distant reuse sites


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Direct Path

Diffraction

Reflections

Refrac-tionThe

signal arrivesat the mobileterminal via avariety of paths

Interferer

Man-madeand

NaturalInterference

Sourcesof inter-

ference areless welldefined.


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Day 1 Section 3 Radio Propagation Theory

IntroductionRadio Propagation Environment

Frequency Division

Fast and Slow Fading

Propagation Loss

Propagation Models

Doppler Effect

Fresnel Zone


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Introduction

SimpleDipole

Antenna

I

I

R

Rr

Current flow in the antennafor a given electrical stimulusis determined by the real and‘radiation’ resistance of the

antenna

H

EPower expended againstthe radiation resistance

flows away from theantenna in the form oflines of electric potential, Eand magnetic induction, H,

i.e. ElectromagneticRadiation

V ~

I

I


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Radio Propagation EnvironmentElectromagnetic energyis scattered from objectsin the area of the terminalknown as DominantSecondary Scatterers

Close to the terminal, e.g.30-40m, smaller objectsreflect signal, linking to the

terminal’s antenna. Theseare called Primary Scatterers

Base site

PrimaryscatterersWater

tower

Dominant secondaryscatterers

Othermast

Tallbuilding


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Frequency DivisionSecondary scatterers link signal from the base sitefar outside its main service area

Pool of frequencies used by the operator is subdivided sothat e.g. (f1,f2,f3) are not used within 3 cell radii etc.


Minimum distance at which ‘red’frequency can be reused

Coverage Zone

Interference Zone


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Fading Effects

0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0

Frame Number

-92

-90

-88

-86

-84

-82

-80

Power(dBm)

Acknowledgement: University of Bristol TSUNAMI II Testbed

Fast Fading

Slow FadingVerySlow

Fading


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Fading Effects (cont.)Fast Fading – due to primary scatterers near MS

Slow Fading – caused by secondary scatterers randomlybecoming obstructions that cause signal loss

Very Slow Fading – used to be relevant when cell sizeswere 20km+, caused by random losses when signaldiffracts over landscape.

Very Slow Fading now absorbed into ‘propagation model’

or factored out as small cell size in modern networksmeans that topography does not vary significantly withincell coverage area


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Fast Fading

Object within 30-40mof the terminal link

signal in to the antenna

Many random, smallE-field contributions

R e c e i v e d P

o w e r

Distance/Time

|| (rand[-1..1] + rand [-j..j]) ||

rand[-1..1]

rand[-j..j]


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Slow Fading

A large number of objects, either primary or secondaryscatterers, obstruct the path between base site and MS.Each has a random loss between 0dB and Lmax dB

‘Propagation’ LossLoss 1 Loss 2

Loss 3

Loss 4


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Slow Fading (cont.)

BS MSL1 L2 L3 L4 L5 L6 L7 L8 L9 L10

rand[0..Lmax] rand[0..Lmax] rand[0..Lmax] rand[0..Lmax] rand[0..Lmax] rand[0..Lmax] rand[0..Lmax] rand[0..Lmax] rand[0..Lmax] rand[0..Lmax]

Slow fading isthe outcome ofa large numberof linked fadingprocesses, andthe overall lossis Sum(L1..L10)

For L=5dB

and 10000

samples

0

100

200

300

400

500

600

700

800

900

1 3 5 7 9 1 1 1 3 15 1 7 19 21 2 3 25 27 2 9 31 33 3 5 37 3 9 41 43 4 5 47 4 9 51

Slow Fading Loss (dB)

N u

m b e r o f S a m p l e s

Classic‘Lognormal’distribution


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Propagation Model As terminal moves away from base station, an increasingaverage number of objects obstruct the signal

Total propagation loss = free space loss (≥ 1/r²) +obstruction loss (1/[r→r²])


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Propagation Model (cont.)Huygens Principle: each point on a wavefront can beregarded as a source of secondary ‘wavelets’

The envelope of these wavelets, at a later instant, gives

a divergent wave with the BS antenna at its centre.


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Propagation Model (cont.)The space between BS and MS antenna can be dividedup into a number of ‘Fresnel Zones’, the edges of whichcorrespond to a path length increment of half awavelength over the direct path between BS and MS

p+λ /2

p

p+2λ /2

p+3λ /2

Resultant

Huygens wavelets over oddnumber zones contribute to

an increasing resultantamplitude until their edge-to-edge phase difference is λ /2


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Propagation Model (cont.)

Obstruction

a

b

c

d

e

a

b

c

d

e

As an obstruction intrudes into the pathbetween BS and MS, the main Fresnel

Zones are obstructed and receivedamplitude at the MS reduces

Receivedamplitude


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Propagation Model (cont.)Overall progation loss = free space loss (1/r²) +obstruction loss (1/r) + Fresnel loss (1/[/[r→r²])

Free Space Loss A + Br²

Free Space + Obstruction LossC + Dr[2-3]

Free Space + Obstruction + Fresnel LossE + Fr[3.5-5]

Distance from Site

PowerReceivedat MS


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Doppler Effect

Primaryscatterers

Dominant secondaryscatterers

MS/UE Locus

f

Doppler effect increasesbit error rate and reduceshandover reliability

f f-f d f+f d

Frequency domainis spread by

Doppler

Time domain is‘smeared’ by

Doppler


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Day 1 Section 4 Multiple Access Schemes

A ‘multiple access scheme’ determines how mobileterminals and base stations share the transmissionresources to send and receive voice and packet data

Four multiple access schemes dominate (in order of increasing complexity

CSMA Carrier Sense Multiple Access

FDMA Frequency Division Multiple Access

TDMA Time Division Multiple Access

CDMA Code Division Multiple Access


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CSMA Carrier Sense Multiple AccessBase stations and mobiles shareall network resources in common

Before transmitting, a base station

scans and listens on F1-Fn for othersites transmitting on that frequency.If a ‘clash’ is detected, the BS waitsa random interval before trying again

Mobile Terminals do the same, possibly

on a different set of frequencies f 1-f n

Commonest example - Ethernet

F1-Fn

F1-Fn

F1-Fn

f 1-f m

f 1-f m

f 1-f m

f 1-f m


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Frequency Division Multiple Access

FDMA tries to solve the ‘distant clash’ problem of CSMA by setting a minimum

spacing at which a givenfrequency is used

The handset receiving on F1,F2,F3 should not be able to hear or be interfered bythe base stations where this frequency group is reused, as a number of cell spacings now intervene

F1,F2,F3

F4,F5,F6

F7,F8,F9

F10,F11,F12F13,F14,F15

F16,F17,F18F1,F2,F3

F1,F2,F3

F1,F2,F3f 1,f 2 ,f 3


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Time Division Multiple AccessFn+Fn+1+Fn+2 combined into a digital allocation

Where in FDMA each MSused F1, F2 or F3 100%of the time, in TDMA all

three MSs use F A 33.3%of the time.

FA

FB

FC

FDFE

FGFA

FA

FAf A

f A

f A


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Time Division Multiple Access (cont.)

Frequency

F1 F2 F3

Frequency

FA

In TDMA a numberof narrow FDMA allocations

are combined into a muchwider bandwidth TDMA channel

The wider frequency allocationpermits a higher digital modulationrate, and therefore a highercarrier bit rate. Each MS shares

the frequency resource for apercentage of the time, thereforea TDMA ‘channel’ is a combinationof frequency, start and stop times,known as a ‘timeslot’.

MS1 MS2 MS3 MS1 MS2 MS3

Time

T r a n s m

i t P o w e r


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Time Division Multiple Access (cont.) Advantages:

Reduced Base Station complexity – many FDMA trans-ceivers (TRXs) channels replaced by single TDMA TRX,

also reduced combiner complexityExtra data can be incorporated in each TDMA timeslotto permit ‘channel estimation’ on uplink and downlink

Digital modulation schemes much more robust against

interference, e.g. 8dB margin for GMSK vs 25dB for FM As all information streams are digital, circuit and packetswitched data can much more easily be incorporated


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Time Division Multiple Access (cont.)Disadvantages:

TDMA modulation schemes (usually a variant of MSK for2G systems) are much more complex than simple FM

modulation and demodulationCapacity can only be added in blocks corresponding tothe number of timeslots in a single TDMA carrier, or

Absolute Radio Frequency Channel Number (ARFCN).This may be inappropriate for low-traffic rural sites.


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Code Division Multiple AccessF A +FB+..+FG combined into one allocation, F

In CDMA all BSs sharea single frequencyallocation. Voice or packet

data in low bitrate digitalform is multiplied with amuch higher bitrate ‘spreadingcode’. At the receiver the incomingsignal is multiplied by a synchronised versionof the spreading code and the original information recovered.

F

F

F

FF

FF

F

F

f

f

f


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Code Division Multiple Access (cont.)

Frequency

FA FB FC FD FE FG

Frequency

FEntire Operator Allocation

UserData

-f f

SpreadingCode

-f f

TX

SpreadingCode

-f f

RX

fUserData

-f f


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Code Division Multiple Access (cont.) Advantages:

Simple BS design, need only one wideband TX and RX

Secure – in order to intercept the signal, an eavesdropper

needs to know not only the baseband encryption but alsothe ‘scrambling code’

Wide flexibility in matching user data rate to air interface

User data is spread over a wide range of RF frequencies,

which reduces vulnerability to frequency-dependentfading. Also allows possibility for use of ‘rake’ receiverto increase the recovered signal by channel matching


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Code Division Multiple Access (cont.)Disadvantages:

Increased complexity relative to FDMA and TDMA

Requires contiguous block of frequencies at least as

large as the baseband spectrum of the spreading code

High-power wideband RF amplifiers tend to be inefficient

All base stations and all MSs interfere with each other,there is no possibility of setting aside special frequencies

or groups of frequencies to manage difficult sites

IPR issues – Qualcomm holds many key CDMA patents


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Day 1 Section 5 The GSM Air Interface

GSM, developed in 1980’s by Groupe Spéciale Mobile GSM has a hybrid TDMA-with-FDMA air interface, withorigins in UK military comms

Aim of GSM was originally to develop a Europe -wide

mobile communications system using 900 MHz spectrumthat had recently (1982) been harmonised for EU use.The system was designed to access the ISDN.

System developed in tandem with the Digital CellularSystem, which was an upbanded version of GSM for

1800 MHz frequencies.

Systems were referred to as GSM900 and DCS1800


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GSM channel structureFirst generation systems tended to have FM channelsspaced at 25kHz. 8 of these are combined for a single200 kHz GSM channel

Gaussian Minimum Shift Keying (GMSK) modulation used,channel width is 260 kHz with 200 kHz channel spacing

Frequency

25 kHz

Frequency

200 kHz


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GSM Timeslot Structure8 timeslots of 15/26ms are grouped into 60/13ms frames

Time

TS0 TS1 TS2 TS3 TS4 TS5 TS6 TS7

15/26ms577µs

60/13ms4.615ms

Information57 bits

Information57 bits

TrainingSequence

26 bits

Signalling1 bit

T a i l 3 b i t s

T a i l 3 b i t s

GuardPeriod

8.25 bits


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GSM Physical and Logical ChannelsOne view is that a physical channel is a combination of frequency, start and stop time (i.e. timeslot) in the frame

In successive frames, a physical channel supports one ormore logical channels. For example, the TACH/F physical

channel ‘multiframe’ has 26 Traffic Channel (TCH) bursts,1 Slow Associated Channel (SACCH) burst and 1 idle burst

Time

Broad-

cast

TACH 1 TACH 2 TACH 3 TACH 4 TACH 5 TACH 6 TACH 7

T T T T T T T T T T T T T S T T T T T T T T T T T T T I


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GSM Broadcast and Common Control Channel At least one basic physical channel on the first GSMcarrier, the ‘C0’ carrier, must carry the Broadcast andCommon Control Channel

Extra BCCH+CCCH blocks are needed in cases of low,medium, high and very high signalling load

0 1 2 3 4 5 6 7 7 0

BCCH+

CCCHTCH TCH TCH TCH TCH TCH TCH

BCCH+CCCH TCH TCH TCH TCH

BCCH+CCCH

BCCH+CCCH

BCCH+CCCH

BCCH+CCCH TCH TCH TCH TCH TCH TCH

BCCH+CCCH

TCH TCH TCH TCH TCHBCCH+CCCH

BCCH+CCCH

BCCH+CCCH


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51 Frame Structure and Schedule for BCCH+CCCH

The Broadcast Control Channel, BCCH, transmits infor-mation about the cell

The Frequency Correction and Synchronisation ChannelsFCCH and SCH allow the MSs to find and lock to the cell

The Common Control Channel CCCH controls MS access

TCH FCCH SCH BCCH CCCH

time time/8


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Frame Structure and Schedule for TACH/F and /H

TACH/H, even timeslots

TACH/H, odd timeslots

time/8

time TACH/F

Traffic Burst Slow Associated Burst Idle


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Frame Structure and Schedule for TACH/8 (No.0 shown)

Traffic and Associated Channel/8, TACH/8 is also known

as Standalone Dedicated Control Channel, SDCCH

Normally used for call setup and Short Message Service

Traffic Burst Slow Associated Burst Idle


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Structure of GSM Common Control Channel, CCCHOn the downlink, the CCCH is shared between the PagingChannel, PCH, and the Access Grant Channel, AGCH

MSs listen to a pre-determined paging channel. When an

incoming call arrives the MS transfers to the AGCHIn low traffic cells, the AGCH ‘steals’ idle PCH blocks. Inhigh traffic cells, between 2 and 7 blocks are reserved

TCH FCCH SCH BCCH AGCHPCH

time time/8


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Structure of GSM Common Control Channel, CCCH (cont.)For low traffic cells, four TACH/8 channels and theirSACCHs can be combined onto the BCCH+CCCH BPC

This configuration avoids having to set aside a BPC ona single TRX site for 8 x TACH/8, leaving seven BPCsfor traffic

time time/8

TCH FCCH SCH BCCH TACH/8PAGCH


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Structure of GSM Common Control Channel, CCCH (cont.)The uplink portion of the BCCH+CCCH BPC is used bythe Random Access Channel, RACH. MSs send ‘AccessBursts’ on the uplink RACH in response to pages and torequest channels for outgoing calls. For the normal

configuration, all uplink timeslots are used by the RACH

In the low traffic configuration, the uplink timeslotscorresponding to the 4 x TACH/8 channels are not used

time time/8RACH/H


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Allowed GSM Channel Combination TypesLow Traffic Cell, 1 TRX:BPC 0: FCCH, SCH, BCCH, PAGCH/3, RACH/H, 4xTACH/8BPC 1-7: TACH/F

Medium Traffic Cell, 4 TRXs:C0: FCCH, SCH, BCCH, PAGCH/F, RACH/F, 7xTACH/FC1-3: 23xTACH/F, one BPC of 8xTACH/8

High Traffic Cell, 16 TRXs:C0 BPC 0: FCCH, SCH, BCCH, PAGCH/F, RACH/F

C0 BPC 2,4,6: BCCH, PAGC/F, RACH/FC1-15: 120xTACH/F,


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Day 1 Section 6 The UMTS Radio Access Network

UTRAN ArchitectureWCDMA Characteristics

Intra and Inter-System Handover in UMTS

UTRAN Channel Structure

UMTS coverage planning issues

UTRAN Evolution


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UTRAN Architecture

Iub Iub

Iub

Iub Iub

Iur

Core Network

Iu Iu

Serving RNC Drift RNC


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WCDMAcharacteristics

Flexible multiplexing of userdata, from low bitrate voiceto very high bitrate packet

Built-in capability tohandle multiple serviceswith different QoS andbitrate requirements

Many operating modes

available to the plannerto give high spectralefficiency from macrocellto pico and even femtocell

Support for IP packet data

handling, both instantaneouslyand explicitly through introduc-tion of HSPA extension modes

Robust interferenceaveraging to permithigh spectral efficiency

Designed in support for futuretransmit diversity, interferencecancellation, smart antennasand other advances


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Intra and Inter-System Handover in UMTS

F

F

F

FAF sector 1

F sector 2

F

FII

Intersite Soft Handover

IntersystemHandover

3G

3G

3G

2G

IntersiteHard

Handover

IntersectorSofter Handover


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UTRAN Channel Structure

Voice

FixedData

2G CN2G

BTS

Logical Channel

PhysicalChannel MS

3G CN3G

RBS

VoiceMusic

streamingVideo

StreamingDownloads

wwwetc.

+control

Logical Channel(s)

UE

Channel code 1

Channel code 2

Channel code 3

More physical channels

Transportchannel = f (logical

channel,transportformat)


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UTRAN Channel Structure (cont.)

Broadcast Control Channel (BCCH)Broadcast Control Channel (BCCH) Broadcast Channel (BCH)Broadcast Channel (BCH)

Forward Access Channel (FACH)Forward Access Channel (FACH)

Paging Control Channel (PCCH)Paging Control Channel (PCCH) Paging Channel (PCH)Paging Channel (PCH)

Common Control Channel (CCCH)Common Control Channel (CCCH)Random Access channel (RACH)Random Access channel (RACH)


Common Traffic Channel (CTCH)Common Traffic Channel (CTCH) Forward Access Channel (FACH)Forward Access Channel (FACH)

Dedicated Traffic Channel (DTCH)Dedicated Traffic Channel (DTCH)

&&

Dedicated Control Channel (DCCH)Dedicated Control Channel (DCCH)


Dedicated Channel (DCH)Dedicated Channel (DCH)Downlink Shared Channel (DSCH)Downlink Shared Channel (DSCH)

Random Access channel (RACH)Random Access channel (RACH)

Common Packet Channel (CPCH)Common Packet Channel (CPCH)

Logical Channel Transport Channel


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UMTS Coverage Planning Issues

2G networks could be plannedsite by site due to theirseparation in frequency

Mutual interference cannot be avoided

in 3G networks, so sites have to beidentified and planned as groups withbenign coverage/interference. These

groups are known as ‘clusters’.


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UTRAN EvolutionImproved throughput, RTT than existing legacy RAN

Seamless incorporation of future HSPA modes, LTE

IP network transport replaces ATM

Use of open specifications, i.e. IETF

Control and User planes allowed to scale independently,i.e. better flexibility and reliability

Better native handling of user data at intermediatenodes, e.g. MPLS, deep packet inspection etc


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UTRAN Evolution (cont.)

ATM-based transport betweenRNC and NodeB

Centralised ‘Radio Network Controller’

Radio-specific User Data handlingin RNC for Radio Link Control,Medium Access Control

IP based transport network management at Layer 3

Centralised termination of Iu_controlinterface in RAN server for RANAP

Radio independent control interface

SHO support on Iur between mergedNodeBs


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Day 1 Section 7 The Migration Path 2G > 2.5G > 2.75G > 3G

Review of 3G EvolutionGSM vs 3GSM

GSM Access and Core Network

Spreading and Modulation

Link Structures

High Data Rate Capabilities

Migration Scenarios

Packet Switched Networks


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Review of 3G Evolution

MSC/ VLR

BSC

BTS BTS BTS BTS

Abis Abis

A

A

PSTN

C7

Signalling

ATM

Data

IP

FrameRelay

SGSN

Internet

Gb

Gb

2.5G2.5G

BSC

2.75G2.75GEDGE EDGE EDGE EDGE

MSCserver

RNC

NodeB NodeB NodeB NodeB

Iubis Iubis

Iu-CS

Iu-CS

PSTN

ATM

SGSN

Internet

Iu-PS

Iu-PS

RNC

ATM

Iubis

3G >3G >


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GSM vs 3GSM

Voice:support for half

rate, AMR modesbeing retrofitted to BSS

Data capability up to ~400kb/s

via GPRS and E-GPRS

Some mobility, relocation

Spectral efficiency ~ 53 users/ 5MHz max.

Designed to access the ISDN

packet capability retro-fitted but neverfully exploited

Voice:native support

for half rate, AMR,DTX, DRX

Data capability up to 2Mb/s

(R99) and > 10MB/s (HSPA)

Enhanced radio resourcemanagement via 3G-SGSN

Spectral efficiency ~ 95 users/ 5MHz max.

Designed for advancedIP level access to

Internet

GSMGSM3GSM/ 3GSM/ UMTSUMTS


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GSM Access and Core Network

Abis

A

A

PSTN

Internet

Gb

Gb

Abis

MSC Server/ Visitor Location Register

Gateway GPRSSupport Node

Serving GPRSSupport Node

PacketControl

Unit

Media Gateway

HomeLocationRegister

Base StationController

Base StationController

Fixedmapping

links


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Spreading and Modulation

XWidebandModulator

CarrierGenerator

CodeGenerator

WidebandDemodulator

CarrierGenerator

De-spreading

CodeGenerator

Code Sync/ Tracking

Transmitter Receiver


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Spreading and Modulation (cont.)

Multiplication of symbol andchip information ‘spreads’ the spectrum over anextent equal to the base-

band chip rate

The ratio between chipand symbol rate is the

‘processing gain’

Processing Gain Gp =Chip rate/ Symbol rate

Chip rateChip rateSymbol rateSymbol rate

2 x Symbol rate2 x Symbol rate


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Spreading and Modulation (cont.)

0 1 0Symbol

De-Spread

Data

Chip

Local Code

ReceivedData


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Link Structures

Downlink

Acknowledgement: LM Ericsson


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Link Structure (cont.)

UplinkAcknowledgement:

LM Ericsson


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High Data Rate Capabilities

High Speed Downlink Packet Access

Uses all spare power to transmit two new channel types

MSs share the High Speed Downlink Shared Channel

Control is via the High Speed Shared Control Channel

The link is maintained over A-DCHs between sites

HS-DSCH

HS-SCCH

A-DCH A-DCH


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High Data Rate Capabilities (cont.)

Physical channels associated with HS-DSCH and HS-SCCHconsume whatever power is left after common anddedicated channel power has been allocated

HSDPA

Common channels (not power controlled)

Dedicated channels (power controlled)

T o t a

l a v a i l a b l e c e l l p o w e r


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Migration Scenarios

All operators have re-engineered for 2.5G GSM-GPRS

The main hassle is not hardware but software issues

MSC MGW SGSN3G- 3G- 3G-

C7/FR

3G Antennasand feeder

Aggregated Transmission

2G BTS 3G RBS/ NodeB BSC

ATM

RNC


79/358



Migration Scenarios (cont.)

2G→3G: Straight swap of BSS for hybrid 2G/3G kit

2.5G→3G: GPRS capability can be upgraded, MSC, SGSN,MGW→3G-SGSN, 3G-MSC, 3G-MGW, add RNCs and Iur,2G BTS unlikely to be upgradable so replace with newand upgrade transmission to site

2.75G→3G: Probably only need software upgrade in MSC,SGSN, and MGW, add RNCs and Iur, EDGE BTSs likelysoftware or easily hardware upgradable to 3G. Power

at each site may need upgraded due to extra loadingfrom 3G RBS. Transmission to sites can probably copebut again may need upgraded


80/358



Packet Switched Networks

Serving GPRSSupport Node

Gateway GPRSSupport Node

IP Domain

RNC

BSC

IP Mobility Management,RRM, tracks MSs and UEs at

cell level, terminates PacketData Protocol, performsMSC-like functions in packetdomain

Very large ATM switch,interfaces IP domain,VPNs and Internet to theSGSN(s) and BSS/UTRAN

Packet DataProtocol


81/358


Overview of Day 2

Basics of Radio Network Planning

Radio Network Pre-planning

Radio Network Parameter Planning

Antenna and Feeder Cable Design


82/358


Day 2 Section 8 Basics of Radio Network Planning

Scope of RNP

Cell Shape

Elements in a Radio Network

Radio Network Planning Process

Radio Cell and Wave Propagation

Wave Propagation Effects and Parameters


83/358



Scope of RNP Define Service Area

Select Sites based onlocal clutter criteria

Simulate coverageand quality

Optimisation

Coverage/ quality criteria

met?

No

Yes

Management & Strategy

Site Acquisition &Civils Construction

Radio Planning

Radio Planning

No

Yes

All sites acquired?RNP occupies the

stratum betweenservice area

definition and radionetwork optimisation


84/358



Cell Shape

Due to signal propagation limitations,

real-world cell shapes are fardifferent from the idea RNP scenario


85/358



Elements in a Radio Network

2G MS

TerminalEquipment

SubscriberIdentityModule

GSM Air Interface

3G UE

TerminalEquipment

USIM

Uu Interface

Mobile

Equipment

3G Air Interface

Cu Interface

Radio, channel

funtionalities

User applications


86/358



Elements in a Radio Network (cont.)

RF Filter

WidebandPower

Amplifier

InputCombiner

TRX

PowerSupply

ApplicationManager

andSignal

Processor

Summingand

Multiplexing

ATMMultiplexer

andInterface

Unit

Transmission

Baseband Unit

BTS Manager

TRXs

Power Supply

Combiner& Filter

Generic 2G BTS Nokia UltraSite 3G RBS

Singlesectorshown

For a 3G RBS, the term NodeB describesthe collection of radio equipment for allsectors. These must be grouped together asa functional unit to permit softer handover


87/358



Channel Configuration in GSM

Rural Configuration:Single TRX Site, OmniAntennas, Low Capacity

Suburban Configuration:2-4 TRX per sector,Sector Antennas, Low-Medium Capacity

Urban Configuration:2-4 TRX per sector Site, SectorAntennas, Medium Capacity

Dense Urban Configuration:8-16 TRX per sector Site, SectorAntennas, High Capacity


88/358


Town 1 Town 2

Town 3

Town 4


Radio Network Planning Process

Two key steps – siteidenfication/selectionand coverage simulation

Define ‘search radii’, withinwhich option sites are to beidentified

Simulate area coverage andquality using ‘hot option’ sites

(not necessarily best radioquality)


89/358



Radio Cell and Wave Propagation

F(bi,x)

b1

b2 b3

bnFor each location, calculate:

CoverageBest Server

Mutual Interference ProbabilityAssignment Probability


90/358



Lfs[db] = 10*log(F0 /F1)

= 32.4+ 20*log(d/km)

+ 20*log(f/MHz)

Half wave dipole

f

2 f

Antenna

EffectiveAperture

Wave Propagation Effects and Parameters

In free space, electromagnetic wave loss depends onlyon frequency and distance between transmitter andreceiver


91/358



Wave Propagation Effects and Parameters (cont.)

The propagation of radio waves is more complex, and depends onconditions within the first ‘Fresnel Zone’. This is an ellipsoid ofrevolution defined by all points where the summed distance betweenbase antenna and MS exceeds free space by half a wavelength

Free space loss can be assumed only if the first Fresnel Zone is unobstructed.This is almost never true. Instead, especially close to the MS there areobstructions due to a) mountains, hills and other terrain profile features and b)

buildings trees and other features of the morphostructure.

Shadowing and reflections from obstructions in the first Fresnel Zone causelosses that cannot be computed analytically, the planner must choose anappropriate empirical pathloss model


92/358




R e c

e i v e d P o w e r

Distance/Time

|| (rand[-1..1] + rand [-j..j]) ||

rand[-1..1]

rand[-j..j]

Incoming wavefrontfrom base station

Field Strength = Σ Ai cos (2πf+∆i)N

i=1

Rayleigh Fading

Many random, smallE-field contributionsfrom objects 30-40m

away from MS


93/358




[0..Lossmax] [0..Lossmax] [0..Lossmax] [0..Lossmax]

A number of objectsintervene between

base station and MS

with random lossesbetween 0 and Lossmax

N u m b e r

o f s a m p l e s

Loss (dB)

LognormalDistribution

2

2

2

))(ln(

2

1),;( σ

µ

π σ σ µ

−−

=

x

e x

xF


94/358




Lin-car ≈10 dB

Lindoor ≈3-15 dB

Lindoor ≈ 13-25 dB

The network operator may specify that thenetwork has to be engineered for operation

inside buildings and vehicles. This isaccounted for as an extra loss on top of that

computed from the pathloss model

Lindoor ≈ 17- ∞dB

Lindoor ≈7-18 dB

Flr 1-10- 2.7 dB/flr

Flr 11+- 0.3 dB/flr

gheight


95/358




Incoming wavefront

The interior of a building is illuminatedby only a subset of primary andsecondary scatterers

The fading statisticsof the surroundingenvironment aresuperceded by anaverage set of

statistics derived forbuildings in the areaor country of interest.

σindoor ≈ 5dB


96/358




For propagation over water, it is usual to remove an amountof pathloss corresponding to the ‘opening’ of the first

Fresnel Zone. The propagation loss is then roughly equal to

free space loss. The actual loss factor dependson the measured statistics for the area.

Lwater = -5 to -10 dB

D 2 S i 8 B i f R di N k Pl i


97/358




Summer

Winter

In summer, loss in decidous forest isapprox 10dB, in winter approx 5dB

For evergreen forests,there is very little difference

between summer and winterloss (approx. 6 and 5 dB)

D 2 S ti 8 B i f R di N t k Pl i


98/358


95% of signalsamples fall

within twostandarddeviations of

the mean value

2σ



Why are the fading statistics important?

Received Power (dBm)

Probability

ofReceived

Power

Computer toolscalculate averagereceived power

If we wish 95% probability of service, we must engineer everywhere for a mean power level 2 σ dBm greater than threshold



99/358




Received Power (dBm)

Interference Margin

S i g n a l S t r e n g t h Interference approximately

constant over service area of site

For normal frequency reuse ina GSM system, the background

noise level is raised by

approximately 2 dB due tosystem-wide cochannel

interference

Add an ‘interference margin tomove the entire received powerprobability distribution curve up

by the amount of theinterference introduced



100/358




Receiver sensitivity depends on required C/N ratio. Whenfrequencies are reused the the received carrier powermust be large enough to combat both noise and inter-ference, i.e. C/(N+I) must exceed the receiver threshold

In a normal GSM system, with frequency hopping,dynamic power control and DTC, an interference marginof 2dB is used.

Due to the mutual interference of 3G networks, a higher

interference margin of 3 dB is used. This varies withtraffic, and is called the ‘System Noise Rise’

D 2 S ti 9 R di N t k P Pl i


101/358


Day 2 Section 9 Radio Network Pre-Planning

Capacity and Quality

Site Survey and Site Selection

Result of Site Survey Process

Frequency Hopping

Equipment Enhancements

Power Control

Handover

D 2 S ti 9 R di N t k P Pl i


102/358



Capacity and Quality

CapacityCapacityLow bandwidth,Low bandwidth,

bitratebitrate perperbasic physicalbasic physicalchannelchannel

QualityQualityHigh bandwidth,High bandwidth,

bitratebitrate perperbasic physicalbasic physical

channelchannel

The requirements of capacity and quality

conflict in the network design

Da 2 Section 9 Radio Net ork Pre Planning


103/358



Capacity and Quality (cont.)

Introduce HalfRate Codec

Legacy GSM Network, 7 cell repeat

Full rate codec, 13kb/s,high quality

Half rate codec, 5.6kb/s,medium/low quality

No change to frequencymanagement structure

No extra investment in

Base Station TRXs etc

MSs must support HR

Day 2 Section 9 Radio Network Pre Planning


104/358




0

5

10

15

20

25

F R

A M R 1

2 . 2

A M R 1

0 . 2

A M R 7

. 9 5

A M R 7

. 4

A M R 6

. 7

A M R 5

. 9

A M R 5

. 1 5

A M R 4

. 7 5

B i t R a t e ( k b / s )

Increasing robustness

Channel Coding

Source Coding

8 dB 2.8 dBFull Rate C/(N+I) for 1% FER

0

2

4

6

8

10

12

H R

A M R 7

. 9 5

A M R 7

. 4

A M R 6

. 7

A M R 5

. 9

A M R 5

. 1 5

A M R 4

. 7 5

B i t

R a t e ( k b / s )

Increasing robustness

18 dB 8.5 dB

Half Rate C/(N+I) for 1% FER



105/358




7 cell repeat, 2 TRXs per cell

Full rate codec, 13kb/s,high quality

4 cell repeat, 3-4 TRXs per cell

AMR codecs, 12.2 – 4.75kb/s, high - low quality

Introduce AMRCodec

HigherCell Interference



106/358



Site Survey and Selection

First Choice Sites

● Site survey

● Verification measurements

● Negotiations with owners

Preliminary NetworkDesign and Analysis

Site proposals Preliminary site selections

Detailed network designand analysis



107/358



Site Survey and Selection (cont.)

The site acquisition process is costly and time consuming

Need to consider:

Site Access and Availability

Installation conditions (antenna mounting and cabling,availability of equipment rooms, possibility of aircon, etc)

Available and adequate mains power supply

In urban areas:

Check antennas can be installed significantly above roof

No ‘clipping’ from nearby higher buildings and towers



108/358



Results of the Site Survey Process

Ideal coverage scenario

Site too low

Site too high

Coverage hole

Poorhandover

zone

Sitemissing

Multiple streetfurniture sites

Real-World coverage scenario



109/358



Frequency Hopping

Baseband hopping on F1-F4 combatsRayleigh fading for slow moving MSs

Resultant after de-interleaving and error correction

Resultant after hopping on F1-F4



110/358



Frequency Hopping (cont.)

Need high reliability decoding of the Broadcast and Pagingchannels, so no frequency hopping on the BCCH/C0carrier. High quality 7 site or medium quality 4 site repeat

F1 F2

F3

F4 F5

F6

F7 F8

F9

F10 F11

F12

F13 F14

F15

F16 F17

F18

F19 F20

F21

21 x 200kHz= 4.2MHz

F1 F2

F3

F4 F5

F6

F7 F8

F9

F10 F11

F12

12 x 200kHz= 2.4MHz



111/358




For the frequencies carrying only traffic channels, theseare gathered together in three groups in a 1 x 3 config-uration or as a global ensemble in a 1 x 1 configurationand RF/synthesiser frequency hopping employed

1x3 TCHrepeat

1x1 TCHrepeat



112/358




Power reduction toMS close to the sitereduces its C/(N+I) tothe minimumacceptable, but alsoensured that little

interference spillsover to MSs inadjacent cells in thesame timeslot

Synthesiserfrequency hoppingworks by trying to

average out theC/(I+N) for each

MS to the minimumpossible



113/358



Equipment Enhancements

Two receive antennas are installed at thebase location to create RX diversity. With

sufficient antenna spacing, the fadingprocesses are uncorrelated between thetwo antennas. At the receiver, the two

received signals are combined bitwise.

Where space does not permit twohorizontally spaced antennas, a single

antenna with two separate cross-polarisedbrances may be used

For both configurations, GDIVERSITY ≈ 3.5dB in rural areas,and 4.5dB in suburban/urban areas



114/358



Equipment Enhancements (cont.)

‘Cell splitting’, where a singleexisting omnidirectional antennais changed out for three or moresector antennas, is the simplestform of capacity enhancement.

When cells are split, thefrequency reuse pattern must berevised.

1

2

3

4

4

2

1



115/358




If a particularly high site has tobe accepted in the planning, thesignal coverage may be much

larger than intended

The solution is to add a downtiltkit to the top of the antenna,tilting it forward and reducing

the coverage area



116/358




Downtilting can also be used to limitthe amount of traffic handled by acell. The traffic is given by theintegral over the area where the siteis ‘best server’, i.e. the area where a

new call will be assigned to the site,multiplied by the ‘offered traffic’ map

High Traffic Lower Traffic

Town 1 Town 2

Town 3

Town 4

Traffic Erlangs/km²

0.01 0.1 1 10



117/358




The nature of the constructed network depends on ‘average antenna height’.

For a high coverage, medium capacity GSM900 network, the desired antennaheight is approximately 30m. For a high capacity GSM1800 or W-CDMA

network, average antenna height is 20m

In the case of siteswhich are lower than

the specifiedminimum, a stubmast may have to beconstructed to raise

the antennas tomimimum height

If a particularly highsite is acquired, theantennas must bedropped down thesite of the structure 20-30m



118/358



Power Control

Frequency hopping,power control and DTX(DiscontinuousTransmission) areessential for goodquality with 1 x 3 or 1 x1 reuse on TCHfrequencies

MS distant, high power MS in middle of cell,medium power

User of MS talking,uplink active, downlink

inactive due to DTX

MS close to site, downlink power low



119/358



Handover

Normal Handover Zone

During voice calls or data sessions, the MS tries to attach itself to the basesite with the lowest pathloss. This ensures that the minimum power necessaryto maintain the link is used. This process is called handover. The handoverprocess may fail for a number of reasons, and if so the MS ‘drags’ coverageinto adjacent cells



120/358


y g

Handover (cont.)

Distance

R e c e i v e d P o

w e r

Site 1

Site 2

hysteresis

In the handover zone, shadowfading results in alternatingdominance of two base sites.

To reduce the number ofhandovers that would result, a

‘hysteresis’ level is set, which site2’s received power level mustexceed in order to initiatehandover.

High hysteresis reduces thenumber of handovers, but

increases the risk of coveragedragging. A good compromisevalue is 3 dB

Day 2 Section 10 Radio Network Parameter Planning


121/358


y g

Signalling

Radio Resource and Mobility Management

Basics of Radio Network Optimisation

Network Performance Monitoring

Network Performance Assessment



122/358


y g

Signalling

An GSM MS exchanges call setup and control messageswith BTS, BSC and MSC. In the same way a 3G UEexchanges similar messages with the RBS, RNC and 3G-MSC. These messages can be captured at the radio and

network interfaces and used as valuable diagnostic aids

BTS BSC MSC2G MS

RBS RNC 3G-MSC3G UE



123/358


y g

Radio Resource and Mobility Management

Location Area 1

Location Area 2

Location Area 3

For paging purposes, sites are groupedinto ‘Location Areas’. As the 2G MS or

3G UE moves around, it sends LocationUpdate messages to the MobilityManagement function of the network

LocationUpdate

Location Update



124/358


y g

Radio Resource and Mobility Management (cont.)

RNCUE detectsmismatchbetween storedand receivedLocation Areas

Home LocationRegister

Visitor LocationRegister

3G-MSC

RBS

RBS

Location Update Request

Radio Resources ReservedChannel Setup

Channel Setup complete

Location Update RequestAuthentication

Information ReqAuthentication Request

Authentication ResponseSubscriber

Information Req

Location Update SuccessfulRadio Resource Release

Release

Signalling

shown for 3Gcase, 2Gsimilar



125/358


y g


BA list

For 2G GSM the BTS sends a Base-station Allocation (BA) list to the MS.The MS uses the BA list as a

neighbour list and measures all thefrequencies, sending the strongest sixback to the BSC in a ‘measurementreport’, as potential handover targets.

Measurement Report



126/358


y g


In both idle and dedicated mode, the MS receives aBasestation Allocation (BA) List from the network

This is a list of frequencies and Base Station IdentificationCodes (BSICs) for neighbouring 2G scrambling codes for

3G base stations

In idle mode, the BA list is used by the MS for cellreselection

In 2G dedicated mode the MS sends a list of the strongest

six received ARFCNs+BSICs to the Radio ResourceManagement function in the network to permit handover



127/358



MeasurementControl

In 3G, the UE receives Measurement Controlmessages from the Radio Resource Managementfunction in the RNC, containing the scrambling codes(SCs) of neighbouring base sites. The UE replies withMeasurement Report messages for all decoded SCs,and also requests the RNC to add, drop or modify theserving scrambling codes in Soft Handover.

Add SHO Add SHO

MeasurementReport



128/358



In 3G dedicated mode, the UE receives a list ofneighbouring Scrambling Codes (SCs) via a MeasurementControl message from the RNC

The Measurement Control message modifies a register in

the UE containing SCs the RNC is targeting for handover

The UE replies with a Measurement Report message,containing all the validly decoded SCs

The UE requests the RNC to add SCs its Active Set, when

these would otherwise cause unacceptable interference.When their power level recedes, they can be removed



129/358



Iubis

RNC

Iur

Iu

3G-MSC

Nethawk

L 3

Analysis of the‘Layer 3’ Mobility

and RadioResource

Managementmessages

between UE andRNC is the

majority of RNO

Occasionally, higher layer messages on the Iu, Iur andIubis need to be analysed to solve difficult problems



130/358



Identify Site Clusters

Test Drive

Site Cluster

Analyse L3 andother signalling data

Identify problem sectors/sites

Change Antennas,Downtilts, pans,

RAN parameters

PrelaunchPrelaunchOptimisation Optimisation



131/358


Network Performance Monitoring

Gather Key Performance IndicatorsAnalyse and Report

Plan coverage / capacity / service /no. of sites enhancement

Implementation, logistics, fieldengineering, site construction and

preparation

Provision and upload radio networkparameter plan, dimension data

warehousing and storage

Engineering drivers:

performanceoptimisation andtroubleshooting

Business drivers:NW expansion andchange in offeredQoS

Schedule

Project setup

Progress

reports fromsiteimplemenation

Readyparameters,routing tablesetc



132/358


Network Performance Assessment

MS

PAIR_INTERFACE

BTS

PBTS

BSC

PBSC

MSC

PMSC

TransportNetwork

PTRANSPORT_NETWORK

In the 2G case, with only voice and simple data as services,the end-to-end performance is a simple function of the

performance of each network element

Poverall = f ( PAIR_INTERFACE + PBTS + PBSC + PMSC + PTRANSPORT_NETWORK )



133/358


Network Performance Assessment (cont.)

UE

RBS

RNC 3G-MSC

TransportNetwork

AMR12.2

AMR10.2

AMR7.95

AMR7.4

AMR6.7

AMR5.9

AMR5.15

AMR4.75

FR

HR

Voice

Video, Streaming, www, downloads etcSF8

SF16

SF32

SF64

SF128

HSDPA

It is impractical to optimise 3G at theindividual service level

3G Multiservice Environment



134/358



RBSRNC

3G-MSC Event Counters

RRC Releases, RAB Setup, DroppedCalls, SF16 Admission Control, etc etc

The performance of the network is

‘abstracted’ from the physical servicesby collecting and processing event

counters from RBS, RNC and 3G-MSC

Key Performance

Indicators (KPIs)

Call Setup Rate

Call Completion Rate

PDP Context Activation Rate



135/358



Town 1 Town 2

Town 3

Town 4

Operator needs ability to visualisecoverage

Internal counters for 2G can be e.g.commanded power level, received incall power levels

Internal counters for 3G iscommanded power level, percentageof calls in SHO, softer HO, handeddown to 2G etc

External counters for 2G and 3G are

scanner received power levelmeasurements and for 3G, differencebetween this and RSSI (i.e. Ec/Io)



136/358



Capacity only assessed wherecoverage exists

Most important counters onthe Uu (air) interface, as

capacity can be planned on Iuan Iubis

Capacitycan be assessed at

either network orcell (hotspot) level

RBS

RNC

3G-MSC

RBS

RBS

Uu blocking rate, Admission Control

Iubis blocking, configurationetc

Iubis blocking, configurationetc



137/358



Quality of Service (QoS) can be set either on the cell ornetwork level

QoS QoS

Blocked calls - hardware

‘Soft’ blocking - interference

Call setup failures

Dropped calls

Call quality target missedR99 data retransmissions

HSDPA MAC-d data retransmissions

Hard Handover Failures

Downlink overload

Uplink overload

Excess delay and RTT



138/358



Key Performance Indicators

Cost Function 1

Cost Function 2

Cost Function n S t a r t i n g P a r a

m e t e r S e t

RadioNetwork

SubsystemSimulator

ChangedParameterValues

We attempt to simplify the optimisation process as a set of‘cost’ functions that trade off sometimes conflicting parameters

Day 2 Section 11 Antenna and Feeder Network Design


139/358


Basics of Antennas

Antenna Gain

Directional Diagram

Polarisation

Antenna Diversity

Antenna New Technology

Shaped Beam Technology

Intelligent Antennas

Downtilt Planning

Downtilt Design

Antenna Selection

Current Antenna Use Problems

Urban Base Site Antennas

Rural Base Site Antennas

Highway Base Site Antennas

Combining and Distribution Unit

Combiner Principles

Outdoor Antenna FeederSystem

Tower Mounted Amplifiers

Feeder Cables



140/358


Basics of Antennas

Current

Voltage

Minimum Radiation

Maximum Radiation

An antenna matches the impedanceof the feeder cable, usually 50Ω tofree-space impedance of ~ 73Ω. An

electric field propagates away fromthe antenna parallel to the elementsand a magnetic field perpendicular



141/358


Antenna Gain When n dipole elements are fed by signals

in phase, the overall effect at a point in thefar field is that the electric field is multipliedby n and the power received by n².

The antenna ‘gain’ is definedrelative to the 2.2 dB ‘cardioid’ gainof an individual element, or relative

to a fictitious ‘isotropic’ radiator,where all of the power is distributed

evenly over 4π solid angle



142/358


Directional Diagram

From above, the lines of equalelectric field strength, or ‘radiat-ion pattern’ form a near perfect

circle in the horizontal plane

If a long reflector is added close tothe colinear, the radiation pattern is

biased away from the reflector,creating gain in the horizontal plane

Dipole elements are stacked end on end to form a colinear antenna

RF



143/358


Polarisation

Cellular antennas areusually vertically polarised,parallel to the verticalcolinear radiating structuresthey contain

When antenna diversitycannot be used, anantenna with two slantsenses of polarisation andseparate receive branches

may be used to obtain ‘polarisation diversity’

E

H

TX/RX

EH

45°

TX/RXTX/RX



144/358


Antenna Diversity

d+

=

By combining the signal fromtwo horizontally spacedantennas, deep fades in theRayleigh fading processescan be evened out.Combining can either be on asignal level basis or ‘bestdecoded bit’ at the receiver



145/358


Antenna New Technology

GSM and other 2G technologies not originally designed for ‘advanced’ antenna technologies

3G systems have built-in functionality to assist the lastestgeneration smart antennas

Antenna technology used either to extend coverage rangein rural areas or to give immunity to interference insuburban/urban areas

Interference reduction in 3G leads directly to capacity

gains, but space division multiple access (SDMA) may infuture be used to multiply base site capacity



146/358


Shaped Beam Technology

RX

RX

RX

RX D i g i t a l S i g n a l P r o c e s s i n g

Beam 2

Beam 3

Beam 4

Beam 1

Range

Receiving range ofindividual sector antenna

UE falls within extendedrange of shaped beam 2

Plan view of shaped beamantenna, four elements



147/358


Intelligent Antennas

RX

RX

RX

RX D i g i t a l S i g n a l P

r o c e s s i n gUE1

UE2

UEn

Intelligent beamformer createsdeep nulls to remove the two

interferers, while preserving gainin the direction of the wanted UE

Interferer 1

Interferer 2

Wanted UEtransmitsreference

information to aidthe beamformer



148/358


Downtilt Planning

The vertical radiationpattern of the antenna

may result insignificant overshootand thus interference

in urban areas

By vertically downtiltingthe antenna the

interference zone iscurtailed. Downtilts

between 6°and 10°areused in urb

Documents

Rno Principles - Interim Version