VODAFONE MOBILE SERVICES LTD.

BELA MORE SHAYAMA REGENCY

DARBHANGA(BIHAR)

INDUSTRY ORIENTED PROJECT TRAINING REPORT

SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE AWARD

OF THE DEGREE OF

BACHELOR OF TECHNOLOGY

(Electronics & communication engineering)

SUBMITTED TO

PUNJAB TECHNICAL UNIVERSITY,JALANDHAR

SUBMITTED BY

Name of student University Roll No.

MUKESH PRASAD 1249522

06-01-2016 to 15-04-216

(Duration of Training period)

RIMT-INSTITUTE OF ENGINEERING & TECHNOLOGY,MANDI

GOBINDGARH PUNJAB

CERTIFICATE

I hereby certify that I have completed the Four months Industrial Training in partial fulfillment of the

requirements for the award of Bachelor of Technology in Electronics & Communication Engineering.

I did my training in Vodafone mobile services Limited , Darbhanga(Bihar) from 06-01-16 to 15-04-16.

The matter presented in this Report has not been submitted by me for the award of any other degree elsewhere.

Signature of Student

Mukesh Prasad (1249522)

Signatures

Examined by:

(Internal Examiner – 1) (Internal Examiner – 2)

HOD

Electronics & Communication Engineering

Examined by External Examiner

i

ACKNOWLEDGEMENT

I would like to place on record my deep sense of gratitude to Mr. Alok kumar srivastava DM &

Networking head of Vodafone(Darbhanga circle), Darbhanga(Bihar) for his generous guidance,

help and useful suggestions.

I express my sincere gratitude to Mr. Ashok kumar & shajid Networking Engineer of Vodafone

darbhanga for his stimulating guidance, and continuous encouragement.

I also wish to extend my thanks to other workers for guiding and providing the knowledge related

to machinery and processes.

I am extremely thankful to Associate Professor Ms.Monika Mehra ECE, HOD, RIMT IET, Mandi

Gobindgarh, for valuable suggestions and encouragement.

I am also thankful to Mr. Gurpreet singh, Training In-charge, ECE and Mr………….. Training and

placement officer, RIMT-IET, Mandi Gobindgarh for providing the opportunity to get the

knowledge .

Signature of Student

MUKESH PRASAD (1249522)

ii

ABOUT VODAFONE

Vodafone is a mobile communications company which provides services to mobile voice,

messaging, data and fixed line. The Company’s money transfer service M-Pesa enables people in

emerging markets, to send and receive money through a mobile phone. The Company also has

products such as international money transfer savings and loans salary disbursements and access to

insurance products in different markets. Vodafone Red offers consumers and businesses a package

with mobile data allowances unlimited calls and texts plus cloud and back-up services to secure

personal data. Vodafone Cloud allows customers to store their personal digital content, such as

contacts, photos and videos in the Vodafone network and to access it on the move from any

connected device.

In india Vodafone India Ltd is the second largest mobile network operator in India by subscriber

baseafter Airtel. It is headquartered inMumbai, Maharashtra. It has approximately 185 million

customers as of June 2015. It offers both prepaid and postpaid GSM cellular phone coverage

throughout India with better presence in the metros. Vodafone India provides services on basis of

900 MHz and 1800 MHz digital GSM technology. Vodafone India launched 3G services in the

country in the January–March quarter of 2011 and plans to spend up to $500 million within two

years on its 3G networks.It has already launched its 4G services in Mumbai from February,2016

and plans to expands its network to various cities from March 2016 .Vodafone is the second largest

player in telecom operator in India after Airtel, with a market share of 18.42% Vodafone is a

leading international mobile communications company with interests in 27 countries further 40

countries. It has over 71,000 employees throughout the world.

On 8 December 2015, Vodafone announced the roll out of its 4G network in India on 1800 MHz

band, starting from Kochi, Kerala. On 25th December 2015, Vodafone launced their 4G LTE

services in Kolkata. It had been reported that on the first speed test of 4G in Kolkata gave around

100 Mbps of Download and around 29 Mbps of Upload speed.The award & achievements by

Vodafone are Case study on Project Drishti awarded the Runner-up Trophy at the 6th AIMA

Business Responsibility Summit 2014 case study contest, Ogilvy One won DMAI Award for

Marketing Effectiveness for Vodafone Foundation's World of Difference campaign in the non-

profit category (Bronze).

Table of contents

Acknowledgement i

About company ii

List of table iii-vii

List of Figures viii-ix

Chapter 1: Introduction iii

1.0 Basic of Gsm 1

1.1 Advantages of Gsm 1

1.2 GSM network 2

1.3 The mobile network 2

1.4 The base station 2

1.5 Network switching subsystem 3

1.6 Operation support system 3

1.7 public switched telephone network 4

1.8 Integrated services digital network 4

1.9 Public switched data network 4

1.10 Public land mobile network 4-5

1.11 Home location register 5

1.12 Visitor location register 6

1.13 Equipment identity register 6

1.14 Authentication center 7

1.15 SMS serving center 7

1.16 Gateway Msc 8

1.17 Chargeback system 8

1.18 Transcoder & adaptation unit 8

1.19 Frequency spectrum 8-9

iii

Table of contents

1.20 .1 Introduction 8-9

1.20 Frequency reuse 9

1.21 Radio frequency carriers 9-10

1.22 Broadcast channels 10

1.22.1 Frequency correction channel 10

1.22.2 Synchronization channel 10

1.22.3 Broadcast control channel 10-11

1.23 Half rate channels 11

1.24 Base station identity code 11-12

1.25 Calls 12

1.25.1 Calls from ms 12-14

1.26 3G(THIRD GENERATION) 14

1.27 History 15

1.28 Wcdma 15

1.29 IMT-2000 15-16

1.30 Basic terminologies 17

1.30.1 Forward & reverse link 17

1.31 Channel access duplex methods 17

1.31.1 Time division duplex 17-18

1.31.2 Frequency division duplex 18-19

1.32 Spred spectrum technique 19-20

1.33 Cdma-2000 21

1.33.1 Technical summary for cdma-2000 21

1.34 channelization in cdma 2000 22-23

1.35 Forward link 23-24

iv

Table of contents

1.35.1 uplink 23

1.35.2 Downlink 23

1.36 Traffic channel 24

1.37 Reverse link 24

1.38 Access channel 24

1.39 Reverse traffic channel 25

1.40 Optical fiber communication 26

1.41 Construction of optical fiber 25-26

1.41.1 Core 26

1.41.2 Cladding 26

1.41.3 Coating 26

1.41.4 Strengthening fiber 26

1.41.5 Cable jacket 26

1.42 types of optical fiber 27-28

1.42.1 Single mode fiber 27

1.42.2 Multimode fiber 27

1.42.3 Step index multimode fiber 28

1.42.4 Graded index multimode fiber 28

1.43 Optical fiber color code 29

1.44 Advantages of optical fiber 30

1.45 Area of application 30

Chapter 2: Project work 31

2. project work 31

2.1 Optimization 32

2.2 Purpose & scope of optimization 32

v

Table of contents

2.3 Optimication process 33

2.3.1 Problem analysis 33

2.3.2 Checks prior to action 33

2.4 importance of optimization 34-35

2.5 Hardware optimization typical hardware problem 35

2.5.1 Path balance problem 35

2.5.2 Processor problem 35

2.6 Bsc/Transcoder problem 36

2.7 Physical optimization 37-38

2.8 Analysis & trouble shooting 38

2.9 Coverage issues 38

2.10 Poor coverage issue 38-39

2.11 Dropped calls 39

2.12 Handover problems 39

2.12.1 step to identify and solve handover issue 40

2.12.2 Handover failure problem 40

2.13 Steps to identify and solve handover issue 40-45

2.14 Handover 41-44

2.15 Handover problem 42

2.16 Antenna optimization & site survey 43

2.16.1 Site survey 43

2.16.2 Site survey team 43

2.16.3 Tools used for site survey 44

2.16.4 Site candidates reports 44

2.17 Installation planning 44-45

vi

Table of contents

2.18 Antenna 45

2.19 Types of Antenna 45

2.19.1 Rectangular antenna 45

2.19.2 Parabolic or omnidirectional antenna 46

2.20 Antenna installation 46-47

2.21 Vswr 47

3.0 Results & Discussion 48

4.0 Conclusion & future scope 49

References 50

vii

LIST OF FIGURE

Figure Title Page

1 Base station system 2

2 Network switching subsystem 3

3 Operation support system 3

4 Gsm network 4

5 Home location register 5

6 Visitor location register 6

7 Equipment identity register 6

8 Authentication center 7

9 Sms serving center 7

10 Base station identity code 12

11 Mobile originating call establishment 13

12 Call establishment 14

13 Architecture of 3G 14

14 imt 2000 16

15 Forward & reverse link 17

16 Time division duplex 18

17 Frequency division duplex 19

18 Spread spectrum technique 20

19 Cdma 2000 21

20 Cdma,Tdma,Fdma 23

viii

LIST OF FIGURE

21 Access channel 24

22 Construction of fiber 26

23 Single mode fiber 27

24 Multimode fiber 27

25 Step index multimode fiber 28

26 Graded index multimode fiber 28

27 Color code of optical fiber 29

28 optimization stage 33

29 Antennas 45

30 Rectangular antenna 45

31 Parabolic antenna 46

32 antenna connection with bts 47

ix

1

CHAPTER-1

1.0 BASIC OF GSM

Global system for mobile is a digital cellular technology used for transmitting mobile voices and

data services.The GSM system was designed as a second generation (2G) cellular phone

technology. One of the basic aims was to provide a system that would enable greater capacity to be

achieved than the previous first generation analogue systems. GSM achieved this by using a digital

tdma by adopting this technique more users could be accommodated within the available

bandwidth.

The Global System for Mobile communications (GSM) is a huge, rapidly expanding and

successful technology. Less than five years ago, there were a few 10's of companies working on

GSM. Each of these companies had a few GSM experts who brought knowledge back from the

European Telecommunications Standards Institute (ETSI) committees designing the GSM

specification. Now there are 100's of companies working on GSM and 1000's of GSM experts.

GSM is no longer state-of-the-art. It is everyday-technology, as likely to be understood by the

service technician as the ETSI committee member. In this presentation we will understand the

basic GSM network elements and some of the important features. Since this is a very complex

system, we have to develop the knowledge in a step by step approach.

1.1 Advantages of gsm

Due to the requirements set for the GSM system, many advantages will be achieved. These

advantages can be summarized as follows:

GSM uses radio frequencies efficiently, and due to the digital radio path, the system

tolerates more intercell disturbances.

The average quality of speech achieved is better than in analog cellular systems.

Data transmission is supported throughout the GSM system.

Speech is encrypted and subscriber information security is guaranteed.

International roaming is technically possible within all countries using the GSM system.

2

1.2 GSM Network

A GSM network comprises of many functional units. The diagram opposite shows a simplified

GSM network. Each network component is Illustrated only once, however, many of the

components will occur several times throughout a network Each network component is designed to

communicate over an interface specified by the GSM standards.

1.3 The Mobile Station (MS)

The MS consists of the physical equipment, such as the radio transceiver, display and digital

signal processors, and the SIM card. It provides the air interface to the user in GSM networks.

1.4 The Base Station System (BSS)

The BTS and the BSC communicate across the specified Abis interface, enabling operations

between components that are made by different suppliers. The radio components of a BSS may

consist of four to seven or nine cells. A BSS may have one or more base stations. The BSS uses

the Abis interface between the BTS and the BSC. A separate high-speed line (T1 or E1) is then

connected from the BSS to the Mobile MSC.

Fig 1.0 Base station system

3

1.5 Network switching subsystem

The Network switching system (NSS), the main part of which is the Mobile Switching

Center (MSC), performs the switching of calls between the mobile and other fixed or

mobile network users, as well as the management of mobile services such as

authentication.

Fig 2.0 Network switching subsystem

1.6 Operation support system

The operations and maintenance center (OMC) is connected to all equipment in the

switching system and to the BSC. The implementation of OMC is called the operation and

support system (OSS).

Fig 3.0 operation support system

4

1.7 Public switched telephone network

PSTN is the aggregate of the world's circuit-switched telephone networks that are operated by

national, regional, or local telephone operators. providing infrastructure and services for

public telecommunication The PSTN consists of telephone lines fiber optic cables microwave

transmission links cellular networks communications satellites.

1.8 Integrated Services Digital Network

The main differences that can be seen between the PSTN line are analogue and isdn are digital. the

PSTN lines are used for small companies and ISDL are used for bigger companies. the ISDN the

PSTN are mostly used as single lines for firms or companies that need ADSL. With Integrated

Services Digital Network, one can run as many as 2, 10, 20 or 30 channels that could be run with a

single line.

1.9 Public switched data network

PSDN is a publicly available packet-switched network, distinct from the PSTN. This term

referred only to Packet Switch Stream (PSS), an X.25-based packet-switched network, mostly used

to provide leased-line connections between local area networks and the Internet using permanent

virtual circuits.

1.10 Public land mobile network

A public land mobile network (PLMN) is any wireless communications system intended for use by

terrestrial subscribers in vehicles or on foot. Such a system can stand alone, but often it is

interconnected with a fixed system such as the public switched telephone network (PSTN).

The additional components of the GSM architecture comprise of databases and messaging systems

functions

Home Location Register (HLR)

Visitor Location Register (VLR)

Equipment Identity Register (EIR)

5

Authentication Center (AuC)

SMS Serving Center (SMS SC)

Gateway MSC (GMSC)

Chargeback Center (CBC)

Transcoder and Adaptation Unit (TRAU)

Fig 4.0 Gsm network

1.11 Home location register

The Home Location Register is a database from a mobile network in which information from

all mobile subscribers is stored. The HLR contains information about the subscribers identity,

his telephone number, the associated services and general information about the location of

the subscriber.

Fig 5.0 Home location register

6

1.12 Visitor location register

The Visitor Location Register (VLR) is a database in a mobile communications network associated

to a Mobile Switching Centre (MSC). The VLR contains the exact location of all mobile

subscribers currently present in the service area of the MSC. This information is necessary to route

a call to the right base station. The database entry of the subscriber is deleted when the subscriber

leaves the service area.

Fig 6.0 Home location register

1.13 Equipment Identity Register

The Equipment Identity Register (EIR) is a database that contains a record of the all the mobile

stations (MS) that are allowed in a network as well as an database of all equipment that is banned,

e.g. because it is lost or stolen.The identity of the mobile station is given by the International

Mobile Equipment Identity (IMEI). Each time a call is made, the MSC requests the IMEI of the

mobile station, which is then send to the EIR for 6uthorization.

Fig 7.0 Equipment identity register

7

1.14 Authentication Center

The Authentication Centre (AUC) is a function in a GSM network used for the authentication a

mobile subscriber that wants to be connected to the network. Authentication is done by

identification and verification of the validity of theSIM.

Once the subscriber is authenticated, the AUC is responsible for the generation of the parameters

used for the privacy and the ciphering of the radio link. To ensure the privacy of the mobile

subscriber a Temporary Mobile Subscriber Identity (TMSI) is assigned for the duration that the

subscriber is under control of the specific Mobile Switching Centre (MSC) associated with the

AUC.

Fig 8.0 Authentication centre

1.15 Sms serving center

The Short Message Service Centre (SMSC) is an element in a GSM network responsible for the

delivery of short messages (SMS). All messages are sent to the SMSC. The SMSC stores the

messages, extracts the destination from it and tries to deliver the message. If the message can not

be delivered, the SMSC will try again to deliver the message in a so-called retry-schedule. If the

mobile phone is turned on or comes within reach of the network, the SMSC will also retry to

deliver the message. If a mobile telephone received a message, it will send an acknowledgement

back. Usually the message will be discarded after two days if the destination can not be reached.

Fig 9.0 sms serving center

8

1.16 Gateway msc

The Gateway Mobile Switching Centre (GMSC) is a special kind of MSC that is used to route

calls outside the mobile network. Whenever a call for a mobile subscriber comes from outside the

mobile network, or the subscriber wants to make a call to somebody outside the mobile network

the call is routed through the GMSC.

1.17 Chargeback system

Chargeback is the return of funds to a consumer initiated by the issuing bank of the instrument

used by a consumer to settle a debt it is the reversal of a prior outbound transfer of funds from a

consumer's bank account, line of credit, or credit card.

1.18 Transcoder and Adaptation Unit

TRAU performs transcoding function for speech channels and RA (Rate Adaptation) for data

channels in the GSM network. The Transcoder/Rate Adaptation Unit (TRAU) is the data rate

conversion unit. The PSTN/ISDN switch is a switch for 64 kbit/s voice. Current technology

permits to decrease the bit-rate (in GSM radio interface it is 13 kbit/s for full rate and 6.5 kbit/s for

half rate). Since MSC is basically a PSTN/ISDN switch its bit-rate is still 64 kbit/s. That is why a

rate conversion is required in between the BSC and MSC.

1.19 Frequency Spectrum

1.19.1 Introduction

The frequency spectrum is very congested, with only narrow slots of bandwidth allocated for

cellular communications. The list opposite shows the number of frequencies and spectrum

allocated for GSM, Extended GSM 900 (EGSM), GSM 1800 (DCS1800) and PCS1900. A single

Absolute Radio Frequency Channel Number (ARFCN) or RF carrier is actually a pair of

frequencies, one used in each direction (transmit and receive). This allows information to be

passed in both directions. For GSM900 and EGSM900 the paired frequencies are separated by 45

MHz, for DCS1800 the separation is 95 MHz and for PCS1900 separation is 80 MHz. For each

cell in a GSM network at least one ARFCN must be allocated, and more may be allocated to

provide greater capacity.The RF carrier in GSM can support up to eight Time Division Multiple

9

Access (TDMA) timeslots. That is, in theory, each RF carrier is capable of supporting up to

eightsimultaneous telephone calls, but as we will see later in this course although this is possible

network signalling and messaging may reduce the overall number from eight timeslots per RF

carrier to six or seven timeslots per RF carrier, therefore reducing the number of mobiles that can

be supported.

Unlike a PSTN network, where every telephone is linked to the land network by a pair of fixed

wires, each MS only connects to the network over the radio interface when required. Therefore, it

is possible for a single RF carrier to support many more mobile stations than its eight TDMA

timeslots would lead us to believe. Using statistics, it has been found that a typical RF carrier can

support up to 15, 20 or even 25 MSs. Obviously, not all of these MS subscribers could make a call

at the same time, but it is also unlikely that all the MS subscribers would want to make a call at the

same time. Therefore without knowing it, MSs share the same physical resources, but at different

times.

1.20 Frequency reuse

Standard GSM has a total of 124 frequencies available for use in a network. Most network

providers are unlikely to be able to use all of these frequencies and are generally allocated a small

subset of the 124.

Example:

A network provider has been allocated 48 frequencies to provide coverage over a large area let us

take for example Great Britain. As we have already seen, the maximum cell size is approximately

70 km in diameter, thus our 48 frequencies would not be able to cover the whole of Britain. To

overcome this limitation the network provider must re-use the same frequencies over and over

again, in what is termed a “frequency re-use pattern”.

1.21 Radio frequency carriers

GSM 900 GSM 1800 GSM 1900

Uplink 890 - 915 MHz 1710 - 1785 MHz 1850 - 1910 MHz

10

Downlink 935 - 960 MHz 1805 - 1880 MHz 1930 - 1990 MHz

Carrier separation is 200 kHz, which provides:

124 pairs of carriers in the GSM 900 band

374 pairs of carriers in the GSM 1800 band

299 pairs of carriers in the GSM 1900 band

Using Time Division Multiple Access (TDMA) each of these carriers is divided into eight Time

Slots (TS). One TS on a TDMA frame is called a physical channel, i.e. on each duplex pair of

carriers there are eight physical channels. A variety of information is transmitted between the BTS

and the MS. The information is grouped into different logical channels. Each logical channel is

used for a specific purpose such As paging, call set-up and speech. For example, speech is sent on

the logical channel Traffic CHannel (TCH). The logical channels are mapped onto the physical

channels. The information in this chapter does not include channels specific for GPRS (General

Packet Radio Service).

1.22 Broadcast channels (BCH)

1.22.1 Frequency Correction Channel (FCCH)

On FCCH, bursts only containing zeroes are transmitted. This serves two purposes. First to make

sure that this is the BCCH carrier, and second to allow the MS to synchronize to the frequency.

FCCH is transmitted downlink only.

1.22.2 Synchronization Channel (SCH)

The MS needs to synchronize to the time-structure within this particular cell, and also ensure that

the chosen BTS is a GSM base station. By listening to the SCH, the MS receives information about

the frame number in this cell and about BSIC of the chosen BTS. BSIC can only be decoded if the

base station belongs to the GSM network. SCH is transmitted downlink only.

1.22.3 Broadcast Control Channel (BCCH)

The MS must receive some general information concerning the cell in order to start roaming,

waiting for calls to arrive or making calls. The needed information is broadcast on the Broadcast

Control CHannel (BCCH) and includes the Location Area Identity (LAI), maximum output power

11

allowed in the cell and the BCCH carriers for the neighboring cells on which the MS performs

measurements. BCCH is transmitted on the downlink only. Using FCCH, SCH, and BCCH the MS

tunes to a BTS and synchronized with the frame structure in that cell. The BTSs are not

synchronized to each other. Therefore, every time the MS camps on another cell, it must listen to

FCCH, SCH and BCCH in the new cell.

1.23 Half Rate channels

So far, this chapter has described full rate TCH and SACCH/T that uses all of the allocated

resources (all 26 timeslots in a multiframe). When half rate traffic channels are implemented in the

system, traffic capacity will double. Two users share the same physical channel when channel

combinations (ii) and (iii) are used. Using half rate channels, the Idle frame from the full rate

channel will be used for SACCH signaling for the second MS. Since the MSs only use every other

time slot for the call, the multiframe will contain 13 idle frames for each MS. Using channel

combination (iii) one mobile can also be allocated two traffic channels, for example, one for

speech and the other for data.

1.24 Base station identity code (BSIC)

BSIC allows a mobile station to distinguish between different neighboring base stations.

BSIC (see Figure) consists of:

BSIC = NCC + BCC

NCC = Network Color Code (3 bits), identifies the PLMN. Note that it does not uniquely identify

the operator. NCC is primarily used to distinguish between operators on each side of a border.

BCC = Base Station Color Code (3 bits), identifies the Base Station to help distinguish between

BTS using the same BCCH frequencies.

12

Fig 10. Base station identity code

1.25 Calls

1.25.1 Call from MS

Provided that the MS is listening to the system information in the cell and that it is registered in the

MSC/VLR handling this cell, the MS can attempt to make a call. The procedures are shown in

Figure.

1. a)The MS requests a dedicated channel using the RACH.

b)The MS gets information about the dedicated resource on the AGCH.

2. The MS indicates that it wants to set up a call. The identity of the MS, IMSI, is analyzed and the

MS is marked as busy in the VLR.

3. Authentication is performed as described for location updating.

4. Ciphering may be initiated.

5. The MSC receives a setup message from the MS. This information includes the kind of service

the MS wants and the number (called the B number) dialed by the mobile subscriber. MSC checks

that the MS does not have services like barring of outgoing calls activated. Barring can be

13

activated either by the subscriber or by the operator. If the MS is not barred, the setup of the call

proceeds.

6. Between the MSC and the BSC a link is established and a PCM TS is seized. The MSC sends a

request to the BSC to assign a TCH. The BSC checks if there is an idle TCH. assigns it to the call

and tells the BTS to activate the channel. The BTS sends an acknowledgment when the activation

is complete and then the BSC orders the MS to transfer to the TCH. The BSC informs the MSC

when the assignment is complete. The traffic control subsystem analyses the digits and sets up the

connection to the called subscriber. The call is connected through in the group switch.

7. An alert message is sent to the MS indicating that a ringing tone has been generated on the other

side. The ringing tone generated in the exchange on the B subscriber side is sent to the MS via the

group switch in MSC. The ringing tone is sent over the air, not generated in the MS.

8. When the B subscriber answers, the network sends a connect message to the MS indicating that

the call is accepted. The MS returns a connect acknowledgment, which completes the call setup.

Fig11. Mobile originating call establishment.

14

Fig 12. call establishment.

1.26 3G (THIRD GENERATION)

3G technology comes with better features than previous mobile network technologies. It has

transmission which is at high speed, better multimedia access as well as connection globally.3G

used with mobile phones a connects the phone with the internet and other IP connections which

allow voice as well as video calls to be accessed. Not only this but also helps to download and surf

the internet From lower mobile technologies, 3G technology has higher data speed, better audio

and video access, video calling support, Web use at quicker speeds and TV through the Internet.

In 3G networks the transfer speed is between 128 and 144 kbps for devices that are fast and 384

kbps for slower ones. Wireless fixed LAN's have a sped beyond 2Mbps. W-CDMA,TD-SCDMA,

WLAN and cellular radio, among others are some of the technologies that 3G includes. Third

generation (3G) is the generic term used for the next generation of mobile communications

systems. These have been created to support the effective delivery of a range of multimedia

services. In addition, they provide more efficient systems for the over-the-air transmission of

existing services, such as voice, text and data that are available today.

Fig 13 Architecture of 3G

15

1.27 HISTORY

3G technology is the result of research and development work carried out by the International

Telecommunication Union (ITU) in the early 1980s. 3G specifications and standards were

developed in fifteen years. The technical specifications were made available to the public under the

name IMT-2000. The communication spectrum between 400 MHz to 3 GHz was allocated for 3G.

Both the government and communication companies approved the 3G standard. The first pre

commercial 3G network was launched by NTT DoCoMo in Japan in 1998 branded as FOMA. It

was first available in May 2001 as a pre-release (test) of W-CDMA technology. The first

commercial launch of 3G was also by NTT Docomo in Japan on 1 October 2001, although it was

initially some what limited in scope broader availability of the system was delayed by apparent

concerns over its reliability.

1.28 WCDMA

The third-generation Universal Mobile Telecommunications System (UMTS) will be able to

deliver high data rates of up to 384 kb/s at wide area applications or even 2 Mb/s indoors . This is

achieved by using wide-bandwidth signals with Code-Division for Multiple Access (W-CDMA).

The user data are multiplied by a fast pseudorandom spreading sequence before phase modulating

the radio-frequency (RF) carrier. The resulting signals which are then broadcast have a bandwidth

of approximately 4.5 MHz.

1.29 IMT-2000

The main characteristics of 3G systems, known collectively as IMT–2000, are a single family

of compatible standards that have the following characteristics:

1. Used worldwide

2. Used for all mobile applications

3. Support both packet-switched (PS) and circuit-switched (CS) data transmission

4. Offer high data rates up to 2 Mbps (depending on mobility/velocity)

5. Offer high spectrum efficiency

16

IMT–2000 is a set of requirements defined by the International Telecommunications Union

(ITU). As previously mentioned, IMT stands for International Mobile Telecommunications, and

“2000” represents both the scheduled year for initial trial systems and the frequency range of

2000 MHz (WARC’92: 1885–2025 MHz and 2110– 2200 MHz). All 3G standards have been

developed by regional standards developing organizations (SDOs). In total, proposals for 17

different IMT–2000 standards were submitted by regional SDOs to ITU in 1998—11 proposals

for terrestrial systems and 6 for mobile satellite systems (MSSs). Evaluation of the proposals

was completed at the end of 1998, and negotiations to build a consensus among differing views

were completed in mid 1999. All 17 proposals have been accepted by ITU as IMT–2000

standards. The specification for the Radio Transmission Technology (RTT) was released at the

end of 1999.

The most important IMT–2000 proposals are the UMTS (W-CDMA) as the successor to GSM,

CDMA2000 as the interim standard ’95 (IS–95) successor, and time division– synchronous

CDMA (TD–SCDMA) (universal wireless communication–136 [UWC– 136]/EDGE) as

TDMA–based enhancements to D–AMPS/GSM—all of which are leading previous standards

toward the ultimate goal of IMT–2000.

Fig.14 IMT 2000

17

1.30 Basic terminologies

Some of the Concepts which should e considered in order to understand the further details

of the of CDMA2000 and WCDMA are discussed in the following section.

1.30.1 Forward and Reverse Link

The transmission from a base station to a mobile phone is considered as the forward link. The

reverse link is from the mobile phone to the base station. Reverse and forward links are shown

in figure 3.

Fig.15 Forward and reverse link

1.31 Channel Access Duplex Methods

Channel access methods are used in point to multipoint networks such as cellular networks for

dividing forward and reverse communication channels on the same physical communications

medium, they are known as duplexing methods.

1.31.1 Time Division Duplex

Time division duplex (TDD) is the application of time-division multiple access to separate

outward and return signals. Time division duplex has a strong advantage in the case where the

asymmetry of the uplink and downlink data speed is variable. As the amount of uplink data

increases, more bandwidth can be allocated to that and as it shrinks it can be taken away.

Another advantage is that the uplink and downlink radio paths are likely to be very similar in the

case of a slow moving system. This means that techniques such as beam forming work well with

TDD systems.

18

Fig 16 Time division duplex

1.31.2 Frequency Division Duplex

Frequency division duplex (FDD) is the application of frequency-division multiple access to

separate outward and return signals. The uplink and downlink sub-bands are said to be separated

by the "frequency offset". Frequency division duplex is much more efficient in the case of

symmetric traffic. In this case TDD tends to waste bandwidth during switchover from transmit to

receive, has greater inherent latency, and may require more complex, more power-hungry

circuitry.

Another advantage of FDD is that it makes radio planning easier and more efficient since base

stations do not "hear" each other (as they transmit and receive in different sub-

bands) and therefore will normally not interfere each other. With TDD systems, caremust be

taken to keep guard bands between neighboring base stations (which decreases spectral

19

efficiency) or to synchronize base stations so they will transmit and receive at the same time

(which increases network complexity and therefore cost, and reduces bandwidth allocation

flexibility as all base stations and sectors will be forced to use the same uplink/downlink.

Fig 17 Frequency division duplex

1.32 Spread Spectrum Techniques

There are major two type of spread spectrum techniques. Direct Sequence Spread spectrum

and Frequency hoping spread Spectrum. CDMA is a multiple-access scheme based on spread-

spectrum communication techniques. It spreads the message signal to a relatively wide

bandwidth by using a unique code that reduces interference, enhances system processing, and

differentiates users. CDMA does not require frequency or time- division for multiple access;

20

thus, it improves the capacity of the communication system. Spread-spectrum communications

is a secondary modulation technique. In a typical spread-spectrum communication system, the

message signal is first modulated by traditional amplitude, frequency, or phase techniques. A

pseudorandom noise (PN) signal is then applied to spread the modulated waveform over a

relatively wide bandwidth. The PN signal can amplitude modulate the message waveform to

generate direct-sequence spreading, or it can shift the carrier frequency of the message signal

to produce frequency-hopped spreading, as shown in Figure 3. The direct-sequence spread-

spectrum signal is generated by multiplying the message signal d(t) by a pseudorandom noise

signal pn (t).

Fig18 Spread Spectrum Techniques

21

1.33 CDMA 2000

Cdma2000 specification was developed by the Third Generation Partnership Project 2

(3GPP2), a partnership consisting of five telecommunications standards bodies: ARIB and

TTC in Japan, CWTS in China, TTA in Korea and TIA in North America.

Cdma2000 has already been implemented to several networks as an evolutionary step from

CDMAOne as cdma2000 provides full backward compatibility with IS-95B. Cdma2000 is not

constrained to only the IMT-2000 band, but operators can also overlay acdma2000 1x system,

which supports 144 kbps now and data rates up to 307 kbps in the future, on top of their existing

CDMAOne network.

The evolution of cdma2000 1x is labeled cdma2000 1xEV. 1xEV will be implemented in steps:

1xEV-DO and 1xEV-DV. 1xEV-DO stands for "1x Evolution Data Only". 1xEV- DV stands for

"1x Evolution Data and Voice". Both 1xEV cdma2000 evolution steps will use a standard 1.25

MHz carrier. 1xEV-DO probably will be available for cdma2000 operators during 2002 and

1xEV-DV solutions will be available approximately late 2003 or early 2004.

Cdma2000 1x EV-DO and cdma2000 3x are an ITU-approved, IMT-2000 (3G) standards.

Cdma2000 3x is part of what the ITU has termed IMT-2000 CDMA MC (Multi Carrier). It

uses less that 5 MHz spectrum (3x 1.25 MHz channels) to give speeds of over 2 Mbps.

Cdma2000 1x with lower data speed is considered to be a 2.5G technology.

1.33.1 Technical Summary for CDMA2000

Frequency band Any existing band.

Minimum frequency band required 1x: 2x1.25MHz, 3x: 2x3.75

Chip rate 1x: 1.2288, 3x: 3.6864 Mcps

Maximum user data rate: 1x: 144 kbps now, 307 kbps in the future

1xEV-DO: max 384 kbps - 2.4 Mbps,

1xEV-DV: 4.8 Mbps. Frame length 5ms, 10ms or 20ms

Power control rate 800 Hz

Spreading factors 4 ... 256 UL

Fig 19 Cdma 2000

22

1.34 Channelization in CDMA2000

CDMA is a scheme by which multiple users are assigned radio resources using DS-SS

techniques. Although all users are transmitting in the same RF band, individual users are

separated from each other via the use of orthogonal codes.

The North American CDMA standard, or IS-95, specifies that each user conveys base band

information at 9.6 Kbps (Rate Set 1), which is the rate of the vocoder output. The rate of the

final spread signal is 1.2288 Mcps, resulting in an RF bandwidth of approximately 1.25 MHz.

There can be many 1.25-MHz signals present in the same RF band. To a large degree, the

performance of a CDMA system is interference-limited. This means that the capacity and quality

of the system are limited by the amount of interference power present in the band. Capacity is

defined as the total number of simultaneous users the system can support, and quality is defined

as the perceived condition of a radio link assigned to a particular user; this perceived link quality

is directly related to the probability of bit error, or bit error rate (BER). This chapter presents

those characteristics of a CDMA system that need to be optimized in order to reduce interference

and increase quality.

The IS-95 CDMA and CDMA2000 system is unique in that its forward and reverse links have

different link structures. This is necessary to accommodate the requirements of a land-mobile

communication system. The forward link consists of four types of logical channels: pilot, sync,

paging, and traffic channels. There is one pilot channel, one sync channel, up to seven paging

channels, and several traffic channels. Each of these forward- link channels is first spread

orthogonally by its Walsh function, and then it is spread by a quadrature pair of short PN

sequences. All channels are added together to form the composite SS signal to be transmitted on

the forward link.

The reverse link consists of two types of logical channels: access and traffic channels. Each of

these reverse-link channels is spread orthogonally by a unique long PN sequence; hence, each

channel is identified using the distinct long PN code. The reason that a pilot channel is not used

on the reverse link is that it is impractical for each mobile to broadcast its own pilot sequence.

23

Fig 20 CDMA, TDMA, and FDMA

1.35 Forward Link

In radio communications, the link from a fixed location (e.g., a base station) to a mobile user. If the

link includes a communications relay satellite, the forward link will consist of both an uplink (base

station to satellite) and a downlink (satellite to mobile user).

1.35.1 Uplink

1. an electronic link by which signals are sent from a transmitter on the earth's surface to an orbiting

satellite, spacecraft, etc.

2. the site, facility etc. from which such signals are transmitted

to connect to a satellite spacecraft etc.

1.35.2 Downlink

1. an electronic link by which signals are received on the earth's surface from an orbiting satellite,

spacecraft, etc.

2. the site, facility, etc. which receives such signals

FDM

A

TDM

A

CDM

A

24

to connect to a satellite, spacecraft, etc. using such a link

to receive (signals, data, etc.

1.36 Traffic Channel

The forward traffic channel is used to transmit user data and voice; signaling messages are also

sent over the traffic channel. The structure of the forward traffic channel is similar to that of the

paging channel. The only difference is that the forward traffic channel contains multiplexed PCBs.

1.37 Reverse Link

The reverse link supports two types of logical channels: access channels and traffic channels.

Because of the non coherent nature of the reverse link, Walsh functions are not used for

channelization. Instead, long PN sequences are used to distinguish the users from one another.

1.38 Access Channel

The access channel is used by the mobile to communicate with the base station when the mobile

doesn’t have a traffic channel assigned. The mobile uses this channel to make call originations

and respond to pages and orders. The baseband data rate of the access channel is fixed at 4.8

Kbps. The baseband information is first error protected by an R = 1/3 convolutional encoder. The

lower encoding rate makes error protection more robust on the reverse link, which is often the

weaker of the two links. The symbol repetition function repeats the symbol once, yielding a code

symbol rate of 28.8 Ksps (Kilo- Samples per Second). The data is then interleaved to combat

fading.

Fig.21 Access channel

25

1.39 Reverse Traffic channel

The reverse traffic channel is used to transmit user data and voice signaling messages are also sent

over the traffic channel. The structure of the reverse traffic channel is similar to that of the access

channel. The major difference is that the reverse traffic channel contains a data burst randomizer.

The orthogonally modulated data is fed into the data burst randomizer. The function of the data

burst randomizer is to take advantage of the voice activity factor on the reverse link. Recall that the

forward link uses a different scheme to take advantage of the voice activity factor when the

vocoder is operating at a lower rate, the forward link transmits the repeated symbols at a reduced

energy per symbol and thereby reduces the forward- link power during any given period. At a

reduced rate, the receiver takes longer to detect each symbol. This scheme is fine for a forward link

where the speed requirement of forward-link power control is not stringent.

1.40 Optical fiber communication

Fiber-optic communication is a method of transmitting information from one place to another by

sending pulses of light through anoptical fiber. The light forms an electromagnetic carrier

wave that is modulated to carry information.[1]

First developed in the 1970s, fiber-optics have

revolutionized the telecommunications industry and have played a major role in the advent of

the Information Age. Because of its advantages over electrical transmission, optical fibers have

largely replaced copper wire communications in core networks in thedeveloped world. Optical

fiber is used by many telecommunications companies to transmit telephone signals, Internet

communication, and cable television signals.

1.41 Construction of optical fiber

The optical fiber mainly constract with

Core

Cladding

Coating

Strenghening fibers

Cable jacket

26

Fig 22 construction of fiber

1.41.1 Core

This is the physical medium that transports optical data signals from an attached light source to a

receiving device. The core is a single continuous strand of glass or plastic that measured in

microns (µ) by the size of its outer diameter. The larger the core more light the cable can carry.

All fibre optic cable is sized according to its core’s outer diameter. The three multimode sizes most

commonly available are 50, 62.5, and 100 microns. Single-mode cores are generally less than 9

microns.

1.41.2 Cladding

This is the thin layer that surrounds the fibre core and serves as a boundary that contains the light

waves and causes the refraction, enabling data to travel throughout the length of the fibre segment.

1.41.3 Coating

This is a layer of plastic that surrounds the core and cladding to reinforce and protect the fibre

core. Coatings are measured in microns and can range from 250 to 900 microns.

1.41.4 Strengthening fibres

These components help protect the core against crushing forces and excessive tension during

installation. The materials can range from Kevlar to wire strands to gel-filled sleeves.

1.41.5 Cable jacket

This is the outer layer of any cable. Most fibre optic cables have an orange jacket, although some

types can have black or yellow jackets.

27

1.42 Types of optical fiber

Single mode optical fiber

Multimode optical fiber

1. Step index multimode fiber

2. Graded index multimode fiber

1.42.1 Single mode fiber

Single mode fibre is optical fibre that is designed to carry a single signal at a time. It is used

mainly for long distance signal transmission.

Fig 23 single mode fiber

1.42.2 Multimode fiber

multimode fibre is optical fibre that is designed to carry more than one signal at a time. Each

carries multiple rays or modes concurrently, each at a slightly different reflection angle with the

optical fibre core. Multimode fibre transmission is used for relatively short distances because the

modes tend to disperse over longer lengths. Commonly used for hauling traffic over short

distances

Fig 24 Multimode fiber

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1.42.3 Step index multimode fiber

The refractive index of the core is uniform and step or abrupt change in refractive index takes

place at the interface of core and cladding in step index fibres.The light rays propagate in zig-zag

manner inside the core. The rays travel in the fibre as meridional rays and they cross the fibre axis

for every reflection.

Fig 25 Step index Multimode fiber

1.42.4 Graded index multimode fiber

The refractive index of core is non-uniform, the refractive index of core decreases parabolically

from the axis of the fibre to its surface.The light rays propagate in the form of skew rays or helical

rays. They will not cross the fibre axis.

Fig 26 Graded index multimode fiber

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1.43 Optical fiber colour code

Optical fiber has a color code designation for strands of fiber within the larger cable, as well as the

cable's jacket. These color codes are set by the EIA/TIA-598 standards guide identification for

fiber and fiber related units that determines which color codes are used in which applications. The

colors don't only apply for the application though, they also are meant to be of use in determining a

cables properties. The differences in colors are based upon different levels of OM and OS fiber

(Optical Multimode & Optical Singlemode).

Fig 27 color code of optical fiber

30

1.44 Advantages of optical fiber

Wide Bandwidth:- Optical fibers offer greater bandwidth due to the use of light as carrier. The

frequency range used for glass fiber communication extends from 2*e14Hz to 4*e14Hz. Hence

optical fibers are suitable for high speed, large capacity telecommunication lines.

Low Loss:- In a coaxial cable attenuation increases with frequency. The higher the frequency of

information signals the greater the loss, whereas in an optical fiber the attenuation is independent

of frequency. They offer a loss of0.2 dBm/km, allowing repeater separation upto 50Km or more.

Non conductivity:- Optical fibers are non-conductive and are not effective by strong

electromagnetic interference such as lighting. These are usable in explosive environment.

Small diameters and less weight:- Even multi fiber optical cables have a small diameter and are

light weight, and flexible optical fiber cables permit effective utilization of speech and can also be

applicable to long distance use are easier to handle and install than conventional cables.

Security:- Fiber optic is a highly source transmission medium. It does not radiate energy that can

be received by a nearby antenna, and it is extremely difficult to tap a fiber and virtually impossible

to make the tap undetected.

Safety:- Fibre is a dielectric and does not carry electricity. It presents no sparks or fire hazards. It

does not cause explosions, which occur due to faulty copper cable.

1.45 Areas of Application

Telecommunications:- Optical fibers are now the standard point to point cable link between

telephone substations.

Local Area Networks (LAN’s):- Multimode fiber is commonly used as the “backbone” to carry

signals between the hubs of LAN’s from where copper coaxial cable takes the data to the desktop.

Fiber links to the desktop, however, are also common.

Cable TV:- As mentioned before domestic cable TV networks use optical fiber because of its

very low power consumption.

CCTV:- Closed circuit television security systems use optical fiber because of its security,

31

CHAPTER-2

2.0 PROJECT WORK

During the Four months training, I had participated in various small projects, this help me a lot in

gaining and enhancing my knowledge in the field of Telecommunication. During this Four months

I have participated in many projects or targets, which I have completed successfully. I worked at

“Network Optimization” department under experts of the field. The following are those key skills

which I have learnt in these Four months.

BASIC OF GSM

3G (THIRD GENERATION)

OPTIMIZATION

BASIC OF OPTIAL COMMUNICATION & OPTICAL NETWORKING

Network KPIs and Quality

Daily Analysis of Statistics and Performance Reports

Alarm monitoring & solving

Neighbour Deletion

Co BCCH sites

DRIVE TEST

Frequency change

Swap

GPRS & Voice call check

Software upgrade

LAC change & BSC change

ANTENNA OPTIMIZATION & SITE SURVEY

Measurement of Angle of Sectors

Calculation of VSWR

Installing/Swapping Hardware

VARIOUS REPORT ANALYSIS

Daily Cell hourly & HOSR Report

Daily POP UP Report & GPRS Report

32

2.1 Optimization

Every alive Network needs to be under continuous control to maintain/improve the performance.

Optimization is basically the only way to keep track of the network bylooking deep into statistics

and collecting/analyzing drive test data. It is keeping an eye on its growth and modifying it for the

future capacity enhancements. It also helps operation and maintenance for troubleshooting

purposes.Successful Optimization requires:

• Recognition and understanding of common reasons for call failure

• Capture of RF and digital parameters of the call prior to drop

• Analysis of call flow, checking messages on both forward and reverse links to establish “what

happened”, where, and why. Optimization will be more effective and successful if you are aware

of what you are doing. The point is that you should know where to start, what to do and how to do.

2.2 Purpose and Scope of Optimization

The optimization is to intend providing the best network quality using available

spectrum as efficiently as possible. The scope will consist all below;

• Finding and correcting any existing problems after site implementation and

integration.

• Meeting the network quality criteria agreed in the contract.

• Optimization will be continuous and iterative process of improving overall

network quality.

• Optimization can not reduce the performance of the rest of the network.

• Area of interest is divided in smaller areas called clusters to make optimization

and follow up processes easier to handle.

33

2.3 Optimization Process

Optimization process can be explained by below step by step description

2.3.1 Problem Analysis

Analyzing performance retrieve tool reports and statistics for the worst performing BSCs and/or

Sites Viewing ARQ Reports for BSC/Site performance trends Examining Planning tool Coverage

predictions. Analyzing previous drive test data. Discussions with local engineers to prioritize

problems. Checking Customer Complaints reported to local engineers.

2.3.2 Checks Prior to Action

Cluster definitions by investigating BSC borders, main cities, freeways, major roads Investigating

customer distribution, customer habits (voice/data usage) Running specific traces on Network to

categorize problems. Checking trouble ticket history for previous problems. Checking any fault

reports to limit possible hardware problems prior to Test.The process of Optimization is explained

with a process a cycle known as Network Optimization Cycle.

Fig 28 optimization stage

34

2.4 Importance of Optimization

• RF Optimization is a continuous and iterative process.

• Main Goal – To achieve performance levels to a certain set standard.

• Network subscribers expect wire line/near wire line quality.

• Network subscribers also expect 100 % availability at all given times.

Network optimization is a process to try and meet the expectation of subscribers in terms of

coverage, QoS, network availability.

Optimization also aims to maximize the utility of the available network resources.

• Each operator has a certain set of decided KPIs (Key Performance Indicators) based on

which the operator gauges the performance of his network.

• RF/Access Network KPIs can be broadly classified into three types

– Access related KPI

– Traffic/Resource Usage related KPI

– Handover related KPI

• Examples of access KPI

a) SDCCH Drop rate b) Call setup success rate

c) SDCCH Blocking etc.

• Examples of Traffic KPI

a) TCH Drop Rate b) Call success rate

c) TCH Blocking, etc.

• Examples of handover performance KPI

a) Handover Success rate b) Handover failure rate.

c) Handover per cause, per neighbor, etc.

• Apart from the KPIs mentioned earlier the operator may have his own set of custom KPIs

which the operator feels is critical to gauge the performance of his network.

• RF optimization process drives the effort to achieve and maintain the network performance

KPI.

35

• Optimization can be broadly divided into 3 categories, as follows –

– Hardware Optimization

– Physical Optimization

– Database/Parameter Optimization

• Generally the activities mentioned above are done in parallel. In some cases one may

precede the Other.

2.5 Hardware Optimization - Typical Hardware Problems

2.5.1 Path balance problems

If the path balance is below 100 or above 120, it indicates that there could be a problem in either

downlink or uplink. PB value above 120 represents a weaker uplink and stronger downlink,

whereas PB value below 100 would represent a weaker downlink.

Path Balance – If the PB statistic indicates problem in the downlink/uplink – the RF path

should be traced for possible hardware faults. Possible things that could go wrong are –

a) High VSWR due to faulty feeder cable

b) Improper connectorisation

c) Faulty combiner

d) Faulty antenna – improper impedance matching between

antenna and feeder cable (rare case).

2.5.2 Processor problems

• The present BTS equipment architecture is quite robust and with the evolution of VLSI

techniques, the different hardware modules have been compacted into single units.

• The current TRXs/TRUs are having inbuilt processing abilities apart from also containing

the RF physical channels.

• However in places where older equipment are still in use, problems with processor, could

be encountered.

36

• These problems are easily identifiable by drive test and usually also show up degradation

on OMCR statistics. However in the current scenario these problems have rare occurences.

2.6 BSC/Transcoder Problems .

Although the occurrence is rare, there are instances where some part of Transcoder or

timeslot on the PCM link goes faulty. In such cases, the timeslot mapping needs to be

identified and appropriate troubleshooting steps need to be taken. These problems can

seldom be identified by drive testing.

• Steps for Hardware Optimization

a) Check from OMCR statistics for indications of hardware faults

b) Check event logs from OMCR to find out if any alarms were generated

c) Conduct call test on the site/cell in question – check for assignment

failures, handover failures, from layer 3 messages.

d) Isolate the problem to the specific TRX. This can be done by ‘locking’ the

suspicious TRX.

e) Check for downlink receive level on each TRX. In some cases the downlink

receive level on a particular TRX may be very low, due to faulty radio.

f) Request VSWR test to be performed if the problem appears to be related to poor

path balance.

g) Check for improper connectorization, improper antenna installation. One loose

connector could skew the performance of the entire cell!!!

f) If the problem is not isolated to a bad TRX/ other BTS hardware – further

investigations needed to check other possible faulty hardware in the BSC/XCDR.

37

2.7 Physical Optimization

• A well designed RF is key to good network performance.

• More often than not, the actual network built is deviated from the network designed from

the desktop. The variations are

a) Actual site locations are away from the nominal planned locations.

b) It is not practicable to build a grid-based network due to several constraints.

c) Antenna heights may differ from the planned antenna heights.

• Physical RF optimization may be done at several stages of network rollout.

• Physical RF Optimization is an essential requirement during the network build/pre

optimization stages. In most cases the OEM vendor is responsible for the network during

this phase and he carries out the process to ensure that the actual network is as near good as

the desktop designed one.

• The process comprises of conducting a drive test for the entire cluster, which may comprise

of one or several BSC areas.

• The drive test results are plotted on a GIS map and deficiencies in coverage/interference

problems are identified by plotting Rxlev/Rxqual values.

• Most of the coverage deficiencies are fixed by making changes to antenna heights (rare),

bore and tilts.

• At later stages parametric optimization is done to bring the network performance close to

desktop design.

• RF optimization is also carried out during network expansion phase, i.e when new site or

group of sites are added into the network.

• In many networks RF optimization is also done as a regular process to maintain good

network performance.

• RF optimization is helpful in resolving specific coverage problems or interference

problems, cell overreach, no dominant server issues, etc.

• Typical thumb rule to follow while carrying out physical RF optimization for resolving

coverage or interference issues -

• Step 1:- Try tilting the antennas.

• Step 2:- Try changing the orientation.

38

• Step 3:- Increase or reduce the height if tilt/reorientation does not solve the problem

• Step 4:- Change the antenna type as a last resort.

2.8 Analysis and troubleshooting

Things which normally subscribers normally experience(common problems)

• No coverage/poor coverage issues.

• Dropped calls.

• Failed handovers/Dominant server issues.

• Breaks in speech/crackling sound or bad voice quality.

• Access related problems – “Network Busy”. Often all the above problems are addressed to

the RF optimization team for resolution.

2.9 Coverage Issues

• Coverage problems are one of the most concerning issues.

• Subscribers experience a “No network” or “Network Search” scenarios on the fringe area

of the cells.

• Mostly these problems are experienced in suburban areas and also in many cases in

building coverage problems occur.

• Analysis is simple

• TEMS equipment/test phone displays Rxlev of serving cell and neighbour cells – Generally

problem occurs when Rxlev drops below –95 dBm. When the Rxlev drops to –100 dBm or

lower the subscriber experiences a “fluctuating single bar” or a “network search” scenario.

• When Rxlev (DL) drops below –95 dBm its very difficult to have successful call setup, as

typically the uplink Rxlev would be much lower.

2.10 Poor Coverage Issues (Steps to solve the problem)

• Analyze the extent of area which is experiencing a coverage problem

• Can this be solved by physical optimization??

• Possible steps would be to improve the existing serving cell strength by proper antenna

orientation or up-tilting the antenna.

39

• If it is an indoor coverage/limited area coverage issue, this could be resolved by deploying

a repeater/micro cell if the traffic requirement in the question area is high.

• In case of rural/suburban cells where the concern is a weak uplink – TMA could be

installed.

2.11 Dropped Calls

• Dropped calls may be attributed to several reasons.

• Usually categorized as –

– Drop during call setup – aka SDCCH Drop.

– Drop during call progress – aka TCH Drop.

– Drop due to failed handovers – with no recovery.

• Call drops may occur due to RF/non RF reasons.

• RF Reasons attributing to dropped calls

– Weak coverage – RL timer times out.

– Interference – low C/I – bad Rx Qual – RL timer times out.

– Faulty TRX – resulting in low C/I – call may drop during setup or after TCH

assignment – RL timer may/may not time out.

Non RF Reasons

– Switch related – MS experiences a “Downlink Disconnect” – abnormal release,

usually with a Cause Value.

– CV 47 is a common example – Layer 3 message “DL Disconnect”.

– Non RF related call drops need to be escalated to isolate the fault which could be

related to the switch/transcoder or at any point in the Abis/A Interface.

2.12 Handover Problems

• Handover failures may also be attributed to different reasons.

• Usually occur due to RF reasons.

• Common RF reasons for handover failures

• Interference – Co BCCH/Co BSIC issue.

• Faulty hardware on target cell.

40

• Improper neighbourlist definition. Steps to identify and solve Handover issues.

• Use TEMS (layer 3 messages) to identify the cell to which the MS attempts handover and

results in a failure.

2.12.1 Steps to identify and solve Handover issues.

• The sequence of layer 3 messages –

• Handover Command

• Handover Access

• Handover Complete

• Handover Failure

• Sometimes the sequence of messages would be

• Handover Command

• Handover Access

2.12.2 Handover Failures/Problems

• Handover failures may also be attributed to different reasons.

• Usually occur due to RF reasons.Common RF reasons for handover failures

• Interference – Co BCCH/Co BSIC issue.

• Faulty hardware on target cell.

• Improper neighbor list definition

2.13 Steps to identify and solve Handover issues

• Use TEMS (layer 3 messages) to identify the cell to which the MS attempts handover and

results in a failure.

• The “Handover Command” message contains information about the BCCH and BSIC of

the target cell to which the handover was attempted. Check for any possible Co BCCH/Co

BSIC interferers.

• Check for possible hardware faults on the target cell.

41

• Neighbour list problems

• Sometimes handover problems occur due to improper neighbour list definition.

• Neighbour Rxlevel are reported to be strong, but “Handover Command” does not get

initiated.

• Call drags on the source cell and in some situation drops.

• Most common cause is improper definition of “neighbour BSIC/BCCH”

2.14 Handover

Mobiles in communication with the network will continuously perform measurements on serving

and neighboring cells. The measurement results are sent to the BSC and used in the locating

procedure to make decisions about handover. There are different types of handovers:

Intra BSC handover: The new and old cells both belong to the same BSC. The BSC can

handle the handover on its own.

Inter BSC handover: The new and old cells belong to different BSC but the same

MSC/VLR. In this case the MSC/VLR must help the BSC to carry out the handover.

Inter MSC handover: The new and old cells belong to different MSC/VLR. The serving

MSC/VLR must get help from the new MSC/VLR to carry out the handover.

Intra cell handover: No change of cell but of connection within the cell.

During a call, the serving BSC decides that a handover is necessary. The handover

procedure happens in this way:

The serving BSC sends Handover Required, including the identity of the target cell, to the

MSC.

The old MSC asks the new MSC for help.

The new MSC allocates a handover number (ordinary telephone number) in order to

reroute the call. A handover request is sent to the new BSC.

The new BSC, in cases where there is an idle TCH in the target cell, tells the new BTS to

activate a TCH.

The new MSC receives the information about the new TCH and handover reference.

42

The TCH description and handover reference is passed on to the old MSC together with the

handover number.

A link is set up from the old MSC to the new MSC.

A Handover Command message is sent on a signaling channel (FACCH) to the MS with

information about which frequency and time slot to use in the new cell and what handover

reference to use in the HO access burst.

The MS tunes to the new frequency and sends HO access bursts on the FACCH. When the

new BTS detects the HO access burst it sends physical information containing timing

advance to the MS on the FACCH. The old MSC is informed (via, the new BSC and the

new MSC) about the detection of HO bursts. The new path through the group switch in the

old MSC is set–up.

A handover complete message is sent from the MS. The new BSC and MSC inform the old

MSC. The old MSC informs the old BSC and the old TCH is released. The originating

MSC retains the main control of the call until it is cleared. This MSC is called the anchor

MSC. Because the call entered a new LA the MS is required to perform a location updating

when the call is released. During the location updating, the HLR is updated and sends a

Cancel Location message to the old VLR telling it to delete all stored

information about the subscriber.

Handover decision is given following order of priority :

– RXQUAL

– RXLEV

– DISTANCE

2.15 Handover Problems

Always keep in mind that all power related parameters need to be correctly set. Otherwise the

handover (HO) attempts will be done in a wrong place. There will always be risk of a handover

loop if handover parameters between two neighbors are not correctly set.

43

2.16 Antenna optimization & site survey

2.16.1 Site Survey

• Taking our perfect network we generate a Site Survey Request for each nominal

• This is a request to the site survey engineer to go out and find candidates based on

specifications

• These specifications are:

– Location

– Height

– Area of interest

• It is a function in Network Planning for the identification of the best candidates for a new

site.

• To get all relevant information of the site

• In some cases, the Acquisition team also takes part in the site survey and helps in getting

civil and legal clarifications from site owners.

2.16.2 Site Survey Team

• The Site survey team should generally consists of;

• RF Site Survey Engineer :

– Responsibility :To decide on best location for the site,

– To decide the best location, height , type and orientation of Antenna

Transmission Survey Engineer

Responsibility – To check LOS with neighbouring sites and to decide on

connectivity

Site Acquisition Representative

Responsibility – To check for site survey permission and legal/civil

information.

and M engineer

Responsibility – To check for space and power requirements

44

2.16.3 Tools used for Site Survey

• GPS

• Digital Camera

• Magnetic Compass

• Measuring Tape

• RF/Transmission Site Survey Form

• Accessories

2.16.4 Site candidate reports

• The site survey engineer will return a candidate report for each nominal

• Each candidate will have:

– A location in co-ordinates

– An address

– Building height

– Site photos

– Panoramic photos taken from the roof

– Any structural information

– Potential BTS locations

2.17 Installation Planning

• Installation planning is based on the equipment requirements, observations and agreed

decisions during the site survey. Installation planning is used to achieve an efficient usage

of installation materials, and for fast and flexible installation for every network element and

site in the project. The task is to define drawings for the construction works and installation

purposes.

• Site specific documentation generated in installation planning include:

• Installation material list

• Floor layout drawing showing the location of network elements, other equipment and cable

ladder routes at the site

45

• Grounding, power, transmission and external cables related drawings

• Outdoor layout drawing for feeder, antenna and micro wave radio installations

2.18 Antenna

The antenna is a device which transforms guided electromagnetic signals into electromagnetic

waves propagating in free space. It can be used for reception and transmission

Fig 29 Antennas

2.19 Types of antenna

2.19.1 Rectangular antenna

Both 2G and 3G use similar type of rectangular antenna for communication between the user and

cell site of frequency band 700-900MHZ.

Fig 30 rectangular antenna

46

2.19.2 Parabolic or omnidirectional antenna

Parabolic antennas are used as high-gain antennas for point-to-point communications in

applications such as microwave relay links and suitable for LTE and 4G technology of frequency

band 800-2700 MHZ

Fig 31 parabolic antenna

2.20 Antenna Installation

• Check frequency range of used material

• Approved connector types have to be used

• Used connectors have to be suitable for used cable type

• All cables have to be labeled on both end of the cable

• Proper tools have to be used during antenna line installation

All cables have to be fixed properly

47

Fig 32 antenna connection with BTS

1. Verify that antenna support are installed and in right location.

2. Hoist the antenna up to the antenna support.

Note: when hoisting antenna in foul weather conditions, it is necessary to control antenna

movement to avoid damage. Use ropes etc. Install the antennas on the antenna support exactly

vertical or with a specified offset.

3. Use the data specified in the site installation documentation to set the antenna heading, height,

vertical and horizontal separation.

4. Connect one end of the antenna jumpers to the antennas, leaving the opposite ends

open.

5.Clamp the jumpers to the antenna support.

2.21 VSWR (Voltage Standing Wave Ratio):

“Voltage Standing Wave Ratio (VSWR) is another parameter used to describe an antenna

performance. It deals with the impedance match of the antenna feed point to the feed or

transmission line. The antenna input impedance establishes a load on the transmission line as

well as on the radio link transmitter and receiver. To have RF energy produced by the

transmitter radiated with minimum loss or the energy picked up by the antenna passed to the

receiver with minimum loss,the input or base impedance of the antenna must be matched to

the characteristics of the transmission line.”

VSWR = Vmax/Vmin

48

CHAPTER-3

3.0 RESULT & DISCUSSION

The Purpose of the industrial training is to provide an opportunity to undergraduates to identity. I

observe and practice how engineering is applicable in the industry also observe management

practices and to interact with fellow works.it is easy to work with sophisticated machines.

I feel I got maximum out of that experience also I learnt the way of work is an organization the

importance of being punctual the importance of maximum commitance and the importance of team

spirit.

The training program having three destination was a lot more useful than staying at one place

throughout the whole four month in my opinion.i have gained lot of knowledge and experience

needed to be successful in a great,as in my opinion engineering is after all a challenge and not a

job.

49

CHAPTER-4

4.0 CONCLUSION & FUTURE SCOPE

The main objective of the industrial training is to provide an opportunity to undergraduates to

identity.i have interest in telecom and I want to make carrier in telecom sector during training I

observe and practice how engineering is applicable in the industry.

It is not only to get experience on technical practices but also observe management practices and to

interact with fellow works.it is easy to work with sophisticated machines but not with people.the

only chance that an undergraduate has to this experience is the industrial training period.

I feel I got maximum out of that experience also I learnt the way of work is an organization the

importance of being punctual the importance of maximum commitance and the importance of team

spirit.

The training program having three destination was a lot more useful than staying at one place

throughout the whole four month in my opinion.i have gained lot of knowledge and experience

needed to be successful in a great,as in my opinion engineering is after all a challenge and not a

job.

50

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1. D. Hondros and P. Debye, ‘Electromagnetic waves along long cylinders of dielectric.

2. O. Schriever, ‘Electromagnetic waves in dielectric .

3. A. C. S. van Heel, ‘A new method of transporting optical images without aberrations’, Nature,

4. H. H. Hopkins and N. S. Kapany, ‘A flexible fibrescope, using static.

5. K. C. Kao and G. A. Hockham, ‘Dielectric-fibre surface waveguides for optical.

6. A. Werts, ‘Propagation de la lumière coherente dans les fibres.

7. S. Takahashi and T. Kawashima, ‘Preparation of low loss multi-component glass fiber’, Tech.

Dig. Int. Conf. on Integrated Optics and Optical Fiber Communication,

8. J. B. MacChesney, P. B. O’Connor, F. W. DiMarcello, J. R. Simpson and P. D. Lazay,

‘Preparation of low-loss optical fibres using simultaneous vapour phase deposition and fusion.

9.John M senior.

10.www.wikipedia.com