i

ANALYZING THE SIGNAL FLOW AND

RF PLANNING IN GSM NETWORK

A PROJECT REPORT

Submitted by

GOKULAPRIYA P

Register No: 14MAE005

in partial fulfillment for the requirement of award of the degree

of

MASTER OF ENGINEERING

in

APPLIED ELECTRONICS

Department of Electronics and Communication Engineering

KUMARAGURU COLLEGEOF TECHNOLOGY

(An autonomous institution affiliated to Anna University, Chennai)

COIMBATORE-641 049

ANNA UNIVERSITY: CHENNAI 600 025

APRIL 2016

ii

BONAFIDE CERTIFICATE

Certified that this project report titled “ANALYZING THE SIGNAL FLOW AND RF

PLANNING IN GSM NETWORK” is the bonafide work of GOKULAPRIYA.P

[Reg. No. 14MAE005] who carried out the work under my supervision. Certified further

that to the best of my knowledge the work reported herein does not form part of any other

project or dissertation on the basis of which a degree or award was conferred on an earlier

occasion on this or any other candidate.

HHHH

The candidate with Register No.14MAE005 was examined by us in the project

viva-voice examination held on...............................

INTERNAL EXAMINER EXTERNAL EXAMINER

SIGNATURE

R.KARTHIKEYAN

ASSISTANT PROFESSOR II

PROJECT SUPERVISOR

Department of ECE

Kumaraguru College of Technology

Coimbatore-641 049

SIGNATURE

Dr. A.VASUKI

HEAD OF THE DEPARTMENT

Department of ECE

Kumaraguru College of Technology

Coimbatore-641 049

iii

ACKNOWLEDGEMENT

First, I would like to express my praise and gratitude to the Lord, who has

showered his grace and blessings enabling me to complete this project in an excellent

manner.

I express my sincere thanks to the management of Kumaraguru College of

Technology and Joint Correspondent Shri Shankar Vanavarayar for his kind support

and for providing necessary facilities to carry out the work.

I would like to express my sincere thanks to our beloved Principal

Dr.R.S.Kumar Ph.D., Kumaraguru College of Technology, who encouraged me with

his valuable thoughts.

I would like to thank Dr.A.Vasuki Ph.D., Head of the Department, Electronics

and Communication Engineering, for her kind support and for providing necessary

facilities to carry out the project work.

In particular, I wish to thank with everlasting gratitude to the project

coordinator Ms.S.Umamaheswari M.E.,(Ph.D) Associate Professor, Department of

Electronics and Communication Engineering, throughout the course of this project

work.

I am greatly privileged to express my heartfelt thanks to my project guide

Mr.R.Karthikeyan M.E., Assistant Professor-II, Department of Electronics and

Communication Engineering, for his expert counselling and guidance to make this

project to a great deal of success and I wish to convey my deep sense of gratitude to all

teaching and non-teaching staff of ECE department for their help and cooperation.

Finally, I thank my parents and my family members for giving me the moral

support and abundant blessings in all of my activities and my dear friends who helped

me to endure my difficult times with their unfailing support and warm wishes.

iv

ABSTRACT

In this fast moving electronic world, planning, building and optimisation

process of radio access network is a complex dynamical activity, which requires a lot

of planning effort and time. This project is proposed in the intention of planning a

network with reduced call drops, which seems to be a very big issue among the

subscribers as well as the service providers. It is found that call drops in conventional

networks is less than 0.01% and in mobile network it is greater than 0.1%. As per

TRAI (Telecom Regularity Authority of India), call drops have doubled in last one

year. Call drops jumped two-fold on 2G and 65% on 3G networks. Since continuation

of an active call is a prime importance in cellular system, a new approach has been

proposed to minimize the rate of call drops and increase the quality of the network

both related to customer satisfaction and performance of cellular operator which

enhances the revenue of the company. This approach deals with the design of

increasing the number of carriers in each sector of the BTS (Base Transceiver Station),

which reduces call drops to a greater extent even during peak hours. The optimization

in radio frequency planning is done by increasing the number of carriers in each sector

of the BTS. This planning process is done using a commercial tool called “ATOLL

(Acceptance Test Or Launch Language) TOOL”, which is a 64-bit multi-technology

wireless network design and optimization platform. This includes the coverage,

capacity and frequency planning of RF network, which in turn covers the vast area

effectively. Initially, an effective frequency planning is done for 900MHz BTS (Base

Transceiver Station) sites with a set of BSIC (Base station Identity Code), BCCH

(Broadcast channel), MAL frequency (Mobile Allocation List) and MAIO (Mobile

Allocation Index List).

v

TABLE OF CONTENTS

CHAPTER

NO.

TITLE PAGE NO.

ABSTRACT

iv

LIST OF TABLES viii

LIST OF FIGURES ix

LIST OF ABBREVIATIONS x

1 INTRODUCTION 1

1.1 INTRODUCTION TO MOBILE

COMMUNICATION

1

1.2 DUPLEXING

METHODOLOGY

2

1.2.1 Frequency Division Duplex 2

1.2.2 Time Division Duplex 2

1.3 MULTIPLE ACCESS

TECHNOLOGIES

2

1.3.1 Frequency Division Multiple

Access

3

1.3.2 Time Division Multiple Access 3

1.3.3 Code Division Multiple Access 4

1.4 OVERVIEW OF GSM

NETWORK

4

1.5 GSM ARCHITECTURE 5

1.5.1 Network and Switching

subsystem

6

1.5.1.1 Mobile Switching Centre 6

vi

1.5.1.2 Home Location Register 6

1.5.1.3 Visitor Location Register 6

1.5.1.4 Equipment Identity

Register

7

1.5.2 Operation and Maintenance

Centre

7

1.5.3 Base Station Subsystem 8

1.5.3.1 Base Transceiver Station 8

1.5.3.2 Base Station Controller 8

1.5.4 Mobile Station 8

1.5.4.1 The Terminal 9

1.5.4.2 The SIM 9

1.6 GEOGRAPHICAL AREAS OF

THE GSM NETWORK

9

1.7 CONTROL CHANNELS 10

1.7.1 Traffic channels 11

1.7.2 Broadcast channels 11

1.7.3 Common control channels 12

1.7.4 Dedicated control channels 13

1.8 CALL SETUP IN GSM

NETWORK

14

2 LITERATURE REVIEW 15

3 GSM NETWORK PLANNING 18

3.1 INTRODUCTION TO RF

NETWORK PLANNING

18

3.2 PLANNING PROCEDURE FOR

RF NETWORK

18

vii

3.3 CAPACITY PLANNING 19

3.3.1 Network Dimensioning 19

3.3.2 Capacity calculation 20

3.3.3 Structure of Erlang B table 21

3.3.4 Frequency reuse schemes 22

3.3.5 Power budget calculations 23

3.4 COVERAGE PLANNING 23

3.5 FREQUENCY PLANNING 24

3.5.1 Frequency reuse 24

3.5.2 Frequency hopping 25

3.5.3 Implementation of frequency

hopping

25

3.5.3.1 Hopping Sequence Number 26

3.5.3.3 Rules for using HSN and

MAIO

26

3.6 PLANNING MODELS 27

4 DESIGN AND

IMPLEMENTATION

28

4.1 SOFTWARE USED 28

4.1.1 ATOLL planning tool 28

4.2 SCENARIO DESCRIPTION 29

4.3 SAMPLE PROCESS OF

WORKING OF ATOLL TOOL

29

5 RESULTS AND DISCUSSION 35

6 CONCLUSION AND FUTURE

WORK

42

REFERENCES 43

LIST OF PUBLICATIONS 46

viii

LIST OF TABLES

TABLE NO. CAPTION PAGE NO.

3.1 Erlang B table 21

3.2 BCCH channel assignment 25

3.3 TDMA frame sequence for 2/2/2 sectors 26

5.1 OMCR report before planning 36

5.2 OMCR report after planning 38

5.3 Total traffic in Erlang 39

5.4 Total Call drops 40

ix

LIST OF FIGURES

FIGURE NO. CAPTION PAGE NO.

1.1 Access Network 1

1.2 FDMA Frame 3

1.3 TDMA Frame 4

1.4 GSM Architecture 5

1.5 GSM Network Areas 9

1.6 Channels of GSM Network 10

3.1 RF Planning Process 19

4.1 New document 29

4.2 Digital Map import 30

4.3 Clutter Properties 30

4.4 Vectors import 31

4.5 Importing places 31

4.6 BTS Properties configured 32

4.7 Propagation model

configured

32

4.8 BCCH Assignment 33

4.9 Signal strength for 4 BTS 33

4.10 C/I level of 4 BTS 34

5.1 Area under Test 35

5.2 Signal Level of Area Under

Test

37

5.3 C/I Level of Area under Test 38

x

LIST OF ABBREVIATIONS

AGCH Access Grant Channel

ARFCN Absolute Radio Frequency Channel Number

ATOOL Acceptance, Test Or Launch Language

AUC Authentication Centre

BCCH Broadcast Control Channel

BSC Base Station Controller

BSS Base Station Subsystem

BTS Base Transceiver Station

CBCH Cell Broadcast Channel

CDMA Code Division Multiple Access

EIR Equipment Identity Register

FCCH Frequency Correction Channel

FDMA Frequency Division Multiple Access

GSM Global System for Mobile

HLR Home Location Register

HSN Hopping Sequence Number

ISDN International Service Digital Network

LAI Location Area Identity

LU Location Updation

MAIO Mobile Allocation and Index Offset

MS Mobile Station

MSC Mobile Switching Centre

MSISDN Mobile Station International Service Digital Network

MSRN Mobile Station Roaming Number

xi

ND Network Dimensioning

NSS Network Switching and Subsystem

OMC Operation and Maintenance Centre

OMCR Operation Maintenance Control and Radio Network

PCH Paging Channel

PLMN Public Land Mobile Network

PSTN Public Switched Telephone Network

QOS Quality Of Service

RACH Random Access Channel

SCH Synchronization Channel

SIM Subscriber Identity Module

TCH Traffic Channel

TDMA Time Division Multiple Access

TMSI Temporary Mobile Subscriber Identity

VLR Visitor Location Register

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CHAPTER-1

INTRODUCTION

1.1Introduction to Mobile Communication:

In Telecom network conventionally each user is connected to the Telephone

exchange individually. This dedicated pair starts from MDF, where it is connected to

the appropriate Equipment point and ends at the customer premises Telephone. (With

flexibility at cabinet/pillar/ distribution points DPs)

Fig 1.1. Access network

The connectivity from exchange to customer premises is called “Access

Network or Local Loop”, and mostly comprises of underground cable from exchange

up to DP‟s and insulated copper wires (Drop Wires) later on This type of Access

Network does not require separate Authentication of customer before extending

services. Whenever the cable capacity has reached the maximum additional cable is

laid to augment the capacity. Even though there are advantages in introducing wireless

connectivity in Subscriber‟s loop, we have to tackle certain issues viz,

1. Duplexing methodology.

2. Multiple Access methods.

3. Cellular principle or reuse concept.

4. Techniques to cope with “mobile” environment.

2

1.2 Duplexing Methodology:

Duplexing is the technique by which the send and receive paths are separated

over the medium, since transmission entities (modulator, amplifiers, demodulators)

are involved.

There are two types of duplexing.

• Frequency Division Duplexing (FDD)

•Time Division Duplexing (TDD)

1.2.1 Frequency Division Duplexing (FDD):

Different Frequencies are used for send and receive paths and hence there will

be a forward band and reverse band. Duplexer is needed if simultaneous transmission

(send) and reception (receive) methodology is adopted .Frequency separation between

forward band and reverse band is constant

1.2.2 Time Division Duplexing (TDD):

TDD uses different time slots for transmission and reception paths. Single radio

frequency can be used in both the directions instead of two as in FDD. No duplexer is

required. Only a fast switching synthesizer, RF filter path and fast antenna switch are

needed. It increases the battery life of mobile phones.

GSM and CDMA systems use Frequency Division Duplexing and correct uses

Time Division Duplexing.

1.3 Multiple Access methodologies:

The technique of dynamically sharing the finite limited radio spectrum by

multiple users is called Multiple Access Technique. By adopting multiple access

techniques all users cannot get the services simultaneously and some amount of

blocking is introduced by the system. This is known as GOS (Grade of Service).

Generally there are three different types of multiple access technologies. They

are

• Frequency Division Multiple Access (FDMA)

• Time Division Multiple Access (TDMA)

• Code Division multiple Access (CDMA)

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1.3.1 Frequency Division Multiple Access (FDMA):

FDMA is a familiar method of allocating bandwidth, where a base station is

allowed to transmit on one or more number of preassigned carrier frequencies and a

mobile unit transmits on corresponding reverse channels. No other base station within

range of the mobile will be transmitting on the same forward channel, and no other

mobile within range of the base station should be transmitting on the same reverse

channel. Both the base and the mobile usually transmit continuously during a

conversation, and fully occupy their assigned forward and reverse channels. No other

conversation can take place on these channels until the first conversation is completed.

Fig 1.2. FDMA Frame

1.3.2 Time Division Multiple Access (TDMA):

TDMA is a more efficient, but more complicated way of using FDMA

channels. In a TDMA system each channel is split up into time segments, and a

transmitter is given exclusive use of one or more channels only during a particular

time period. A conversation, then, takes place during the time slots to which each

transmitter (base and mobile) is assigned. TDMA requires a master time reference to

synchronize all transmitters and receivers.

4

Fig 1.3. TDMA Frame

1.3.3 Code Division Multiple Access (CDMA):

CDMA is fundamentally different than TDMA and FDMA. Where FDMA and

TDMA transmit a strong signal in a narrow frequency band, CDMA transmits a

relatively weak signal across a wide frequency band. Using a technique called direct

sequence spread spectrum, the data to be transmitted are combined with a pseudo-

noise code (a pre-determined binary sequence that appears random) and transmitted

broadband. CDMA under Interim Standard 95 uses a bandwidth of 1.25 MHz The

pseudo-noise code (PN code) is a series of binary "chips" that are much shorter in

duration than the data bits. Since the chips appear to be in a random pattern, and there

are many chips per data bit (in IS-95 there are 128 chips for each data bit), the

modulated result appears to normal (FDMA) receivers as background noise.

1.4 Overview of GSM

Global System for Mobile Communication (GSM) is a globally accepted standard for

digital cellular communication. GSM is the name of a standardization group established

in 1982 to create a common European mobile telephone standard that would formulate

5

specifications for a pan-European mobile cellular radio system operating at 900 MHz.

GSM was devised as a cellular system specific to the 900 MHz band, called "The Primary

Band". The primary band includes two sub bands of 25 MHz each, 890 to 915 MHz and

935 MHz to 960 MHz. A GSM network is composed of several functional entities, whose

functions and interfaces are specified as,

Uplink frequency band: 890 to 915 MHz (MS transmits, BTS receives).

Downlink frequency band: 935 to 960 MHz (BTS transmits, MS receives).

1.5 GSM ARCHITECTURE

The GSM network is divided into four major systems

Network and switching subsystem(NSS)

Operation and maintenance centre(OMC)

Base station Subsystem(BSS)

Mobile station(MS)

Fig 1.4. GSM Architecture

6

1.5.1 Network and switching subsystem (NSS):

The NSS is responsible for performing call processing and subscriber-related

functions. The switching system includes the following functional units

Mobile Switching centre

Home location register

Visitor location register

Equipment identity register

Authentication centre

1.5.1.1 Mobile Switching Centre (MSC):

MSC performs all switching functions for all mobile stations, located in the

geographic area controlled by its assigned BSS‟s. Also it interfaces with PSTN, with

other MSC‟s and other system entities.

1.5.1.2 Home Location Registers (HLR):

It contains

The identity of mobile subscriber called IMSI

ISDN directory number of mobile station

Subscription information on services

Service restrictions.

1.5.1.3 Visitor Location Registers (VLR):

The VLR always integrated with the MSC. When a mobile station roams into a

new MSC area, the VLR connected to that MSC would request data about the mobile

station from the HLR. Later, if the mobile station makes a call, the VLR will have the

information needed for call setup without having to interrogate the HLR.

7

1.5.1.4 Equipment Identity Registers (EIR):

Equipment identity register consists of identity of mobile station equipment

called IMEI, which may be valid, suspect and prohibited. The information is available

in the form of three lists.

White list-The terminal which is allowed to connect to the network.

Black list-The terminal reported as stolen are not kept approved. They

are not allowed to connect to the network.

Grey list-The grey list consists of the IMEI numbers of the devices

which are outside of the white and black lists and of which electronic

communication connections are open.

1.5.1.5 Authentication Centre:

It is associated with the HLR. It stores an identity key called Ki for each

mobile subscriber. This key is used to generate the authentication

triplets.

It is authenticated using a RAND (random number).

It consists of SRES(signed response)-to authenticate IMSI.

Also, it has another key called Kc (Cipher key) to cipher

communication over the radio path between the MS and the network.

1.5.2 Operation and Maintenance Centre (OMC):

The OAM function allows the operator to monitor and control the system as

well as to modify the configuration of the elements of the system. Not only the OSS is

part of the OAM, also the BSS and NSS participate in its functions as it is shown in

the following examples:

• The components of the BSS and NSS provide the operator with all the

information it needs. This information is then passed to the OSS which is in charge of

analyzing it and control the network.

• The self-test tasks, usually incorporated in the components of the BSS and

NSS, also contribute to the OAM functions.

8

• The BSC, in charge of controlling several BTSs, is another example of an

OAM function performed outside the OSS.

1.5.3 Base Station Subsystem (BSS):

The BSS connects the Mobile Station and the NSS. It is in charge of the

transmission and reception. The BSS can be divided into two parts:

1.5.3.1 The Base Transceiver Station (BTS):

The BTS corresponds to the transceivers and antennas used in each cell of the

network. A BTS is usually placed in the centre of a cell. Its transmitting power defines

the size of a cell. Each BTS has between one and sixteen transceivers depending on

the density of users in the cell.

1.5.3.2 The Base Station Controller (BSC):

The BSC controls a group of BTS and manages their radio resources. A BSC is

principally in charge of handovers, frequency hopping, exchange functions and

control of the radio frequency power levels of the BTSs.

Characteristics of the Base Station System (BSS) are:

• The BSS is responsible for communicating with mobile stations in cell areas.

• One BSC controls one or more BTSs and can perform inter-BTS and intra-

BTS handovers.

• The BTS serves one or more cells in the cellular network and contains one or

more TRXs (Transceivers or radio units).

• The TRX serves full duplex communications to the MS.

1.5.4 Mobile Station (MS):

A Mobile Station consists of two main elements:

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1.5.4.1 The Terminal:

There are different types of terminals distinguished principally by their power

and application:

• The `fixed' terminals are the ones installed in cars. Their maximum allowed

output power is 20 W.

• The GSM portable terminals can also be installed in vehicles. Their maximum

allowed output power is 8W.

• The handheld terminals have experienced the biggest success thanks to the

weight and volume, which are continuously decreasing. These terminals can emit up

to 2 W. The evolution of technologies allows decreasing the maximum allowed power

to 0.8 W.

1.5.4.2 The SIM:

The SIM is a smart card that identifies the terminal. By inserting the SIM card

into the terminal, the user can have access to all the subscribed services. Without the

SIM card, the terminal is not operational. The SIM card is protected by a four-digit

Personal Identification Number (PIN). In order to identify the subscriber to the

system, the SIM card contains some parameters of the user such as its International

Mobile Subscriber Identity (IMSI). Another advantage of the SIM card is the mobility

of the users. In fact, the only element that personalizes a terminal is the SIM card.

Therefore, the user can have access to its subscribed services in any terminal using its

SIM card.

1.6 GEOGRAPHICAL AREAS OF THE GSM NETWORK

Fig 1.5. GSM network areas

10

The figure 1.5 represents the different areas that form a GSM network. As it

has already been explained a cell, identified by its Cell Global Identity number (CGI),

corresponds to the radio coverage of a base transceiver station. A Location Area (LA),

identified by its Location Area Identity (LAI) number, is a group of cells served by a

single MSC/VLR. A group of location areas under the control of the same MSC/VLR

defines the MSC/VLR area. A Public Land Mobile Network (PLMN) is the area

served by one network operator.

1.7 Control channels:

One or more logical channel scan be transmitted on a physical channel. There

are different types of logical channels. The type of logical channel is determined by

the function of the information transmitted over it.

The following types of logical channels exist:

Traffic channels

Broadcast channels

Common control channels

Dedicated control channels

Note that the first channel type carries speech and data, and the other types

control information (signalling).

Fig 1.6. Channels of GSM Network

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1.7.1 TRAFFIC CHANNELS

The traffic channels are used to send speech or data services. There are two

types of traffic channels. They are distinguished by their transmission rates.

The following traffic channels are provided:

TCH/F (Traffic Channel Full rate)

The TCH/F carries information at a gross bit rate of 22.8 kbit/s (after channel

coding). The net (or effective) bit rate at the TCH/F is for speech 13 kbit/s and for data

12, 6 or 3.6 kbit/s (before channel coding). The transmission rates of the data services

allow services which are compatible to the existing, respectively, 9.6, 4.8 and 2.4

kbit/s PSTN and ISDN services.

TCH/HR (Traffic Channel Half rate)

The TCH/H carries information at a gross bit rate of 11.4 kbit/s. The net bit rate

at the TCH/H is for speech 5.6 kbit/s and for data 6 or 3.6 kbit/s.

TCH/EFR (Enhanced Full rate)

The EFR provides a voice coding algorithm offering improved speech quality.

The algorithm is fully compatible with a BSM speech quality. The algorithm is fully

compatible with a GSM 13 kbit/s speech channel. The main benefit will be improved

voice quality which offers prospects to compete with PSTN networks.

1.7.2 BROADCAST CHANNELS

The information distributed over the broadcast channels helps the mobile

stations to orient themselves in the mobile radio network. The broadcast channels are

point-to-multipoint channels which are only defined for the downlink direction (BTS

to the mobile station). They are four types:

BCCH (Broadcast Control Channel)

The mobile station is informed about the system configuration parameters (for

example Local Area Identification, Cell Identity and Neighbour Cells). Using this

12

information the mobile stations can choose the best cell to attach to. The BCCH is also

known as beacon.

FCCH (Frequency Correction Channel)

To communicate with the BTS the mobile station must tune to the BTS. The

FCCH transmits a constant frequency shift of the radio frequency carrier that can be

used by the mobile station for frequency correction.

SCH (Synchronization Channel)

The SCH is used to time synchronize the mobile stations. The data on this

channel carries the TDMA frame number and the BSIC (Base Station Identity Code).

CBCH (Cell Broadcast Channel)

The CBCH is used for the transmission of generally accessible information

(Short Message Service messages) in a cell, which can be polled by the mobile station.

1.7.3 COMMON CONTROL CHANNELS

Common control channels are specified as point-to-multipoint channels which

only operate in one direction of transmission, either in the uplink or downlink

direction. There are three types:-

PCH (Paging Channel)

The PCH is used in the downlink direction for paging the mobile stations.

AGCH (Access Grant Channel)

The AGCH is also used in the downlink direction. A logical channel for a

connection is allocated via the AGCH if the mobile station has requested such a

channel via the RACH.

13

RACH (Random Access Channel)

The RACH is used in the uplink direction by the mobile stations for requesting

a channel for a connection. It is an access channel that uses the slotted Aloha access

scheme.

1.7.4 DEDICATED CONTROL CHANNELS

Dedicated control channels are full-duplex, point-to-point channels. They are

used for signaling between the BTS and a certain mobile station.

SACCH (Slow Associated Control Channel)

The SACCH is a duplex channel which is always allocated to a TCH or

SDCCH. The SACCH is used for transmission of signaling data, radio link

supervision measurements, transmit power control and timing advance data. Note that

the SACCH is only used for non-urgent procedures.

FACCH (Fast Associated Control Channel)

The FACCH is used as a main signalling link for the transmission of signalling

data (for example handover commands). It is also required for every call set-up and

release. During the call the FACCH data is transmitted over the allocated TCH instead

of traffic data; this is marked by a flag called a stealing flag. The process of stealing a

TCH for FACCH data is called pre-emption.

SDCCH (Stand-alone Dedicated Control Channel)

The SDCCH is a duplex, point-to-point channel which is used for signaling in

higher layers. It carries all signaling between the BTS and the mobile station when no

TCH is allocated. The SDCCHs are used for service requests (for example Short

Message Service), location updates, subscriber authentication, ciphering initiation,

equipment validation and assignment to a TCH. The net SDCCH bit rate is about 0.8 k

bit/s.

14

1.8 CALL SETUP IN GSM NETWORK

The successful call set up consists of two procedures. First procedure is

Immediate Assignment procedure which is used to create a signaling connection

between the Mobile station (MS) and the network. It can be initiated only by the MS

sending a CHANNEL REQUEST message on the Random Access channel (RACH)

to the BTS that it requires a signaling channel (SDCCH). This message contains the

information field establishment cause and random reference. The establishment cause

gives the reason why the MS is requesting a SDCCH. Possible reasons are emergency

call, call re-establishment, originating speech call and location updating. The

successful seizure of SDCCH is acknowledged by sending the Establish Indication

message from MS to BTS and then to BSC. Further coordination procedure

(authentication, ciphering etc.) are now performed on the SDCCH. Second procedure

is Assignment procedure which is used to occupy a radio resource (speech channel).

The MSC is initiator of this procedure. The MSC sends an ASSIGNMENT

REQUEST message to the BSC requesting the assignment of a radio resource (RR).

Then it comes next signalization between BTS and BSC in order to allocate and

activate a suitable traffic channel. If the TCH is successfully seizure by MS, the BSC

sends the ASSIGNMENT COMPLETE message.

The main reasons for unsuccessful call setups in mobile networks are lack of

radio coverage (either in the downlink or the uplink), radio interference between

different subscribers, imperfections in the functioning of the network (such as failed

call setup redirect procedures), overload of the different elements of the network (such

as cells), etc.

15

CHAPTER-2

LITERATURE REVIEW

[1] “Effective Frequency Planning to Achieve Improved KPI’S, TCH and

SDCCH Drops for a Real GSM Cellular Network”, The drastic development in the

field of wireless communications has resulted huge demand for voice and data

communication in public domain but spectrum is the major concern and scarce

resources which imposes a high cost on the data transmission. The objective is to

provide a quality communication to maximum number of users. The number of users

supported by system can be increased by using more Frequencies, hence efficient RF

(radio frequency) planning is required to maximize the limited spectrum resources.

One has to look for optimum compromise between dense reuse with least interference.

To establish the quality communication, we investigate KPI (key performance

indicators), TCH (traffic channel) and SDCCH (stand alone dedicated control

channel) drop on 93 GSM sites for a cellular operator in a city of India. An efficient

frequency planning approach practically with limited spectrum availability and

BCCH-BSIC (broad cast channel- Base station Identity code) set of frequencies, MAL

(mobile allocation list) and DCHNO (TCH) frequency with NCCPERM (national

color code permitted) parameter are used for least interference is designed. With the

help of Google Earth and simulation software to practically implement these change

values in field data. The significant improvements in KPl's, TCH drop and SDCCH

drop which outperform the previous frequency plan have been found.

[2] “A Practical Approach of Planning and Optimization for Efficient Usage of

GSM Network On the Performance of Largest-Deficit-First for Scheduling Real-

Time Traffic in Wireless Networks”, In this paper, the planning of wireless

networks is vital if operators wish to make full use of the existing investments. This

paper deals with a practical approach of radio network planning process for efficient

usage of GSM network. The key performance indicator (KPI) and drive test report of

16

a Bangladeshi operator “Teletalk Bangladesh Limited” are used to make proposals on

how operators can optimize radio resources as well as provide the required QoS to the

subscribers. This study would help to plan operators to enhance coverage, improve

quality and increase capacity in the days to come.

[3] “A Design Approach to Maximize Handover performance Success Rate and

Enhancement of voice Quality Samples for a GSM Cellular Network”,

Continuation of an active call is of prime importance in the cellular systems. In this

paper a new approach has been designed to maximize handover success rate (HOSR)

and voice quality for a GSM cellular network both related to customer satisfaction and

performance of cellular operator which enhances revenue of the company. Initially, an

effective frequency planning is done for GSM 1800 MHz BTS (base transreceiver

station) sites, where a set of BCCH frequency (broad cast channel) - BSIC (base

station identity code), MAL frequency (mobile allocation list) with MAIO (mobile

allocation index offset) and HSN (hopping sequence no) is used. Afterwards to

improve handover, neighbor list verification is done and unnecessary neighbors are

deleted. Neighbors define within the first tear of base cell with the help of commercial

tool. the help of Google Earth and simulation software to practically implement these

changed values in the mobile industry field.

[4]“Scheduling in Successive Interference Cancellation based Wireless Ad Hoc

Networks”, Successive Interference Cancellation (SIC) allows multiple transmissions

in the same neighbourhood by enabling both concurrent reception and interference

rejection via decoding and subtracting the signals successively from the composite

received signal. In this paper, they studied the scheduling problem for minimizing the

schedule length required to satisfy the traffic demands of the links in SIC based

wireless ad hoc networks. Upon proving the NP-hardness of the problem, they

proposed a novel efficient heuristic scheduling algorithm based on the greedy

assignment of the links to each time slot by using a novel metric called Interference

Effect (IE). The IE of a feasible link is defined as the total Signal-to-Interference-plus-

17

Noise Ratio (SINR) drop of the links in the scheduled set with the addition of that

link. They demonstrate via extensive simulations that the proposed algorithm

performs better than the previous algorithms, with lower computational complexity.

[5] “Throughput–Delay Trade off in Interference-Free Wireless Networks With

Guaranteed Energy Efficiency”, Existing works have addressed the tradeoffs

between any two of the three performance metrics: throughput, energy efficiency

(EE), and delay. In this paper, they unveil the intertwined relations among these three

metrics under a unifying framework and particularly investigate the problem of EE-

guaranteed throughput–delay trade-off in interference-free wireless networks. They

first propose two admission control schemes, referred to as the first-out and first-in

schemes. Then formulate it as two stochastic optimization problems, aiming at

throughput maximization (in the first-out scheme) or dropping rate minimization (in

the first-in scheme) subject to requirement of EE, stability, admission control, and

transmit power. To solve the problems, the EEGuaranteed algorithm for throughput-

delay trade off (eGuard), respectively called eGuard-I and eGuard-II in the first-out

and first-in schemes, is devised. Moreover, with guaranteed RoE, They theoretically

showed that the eGuard (I and II) can not only push the throughput arbitrarily close to

the optimal with tradeoffs in delay but also quantitatively control the throughput–

delay performance on demand. Simulation results consolidate the theoretical analysis

and particularly show the pros and cons of the two schemes.

[6] "Impact of mobility on call block, call drops and optimal cell size in small cell

networks", Assuming Poisson call arrivals at random positions with random

velocities, they have discussed about the characterization of handovers at the

boundaries. In this paper, the explicit expressions for call block and call drop

probabilities using tools from spatial queuing theory have been derived. These

expressions are used to derive optimal cell sizes for various profiles of velocities in

small cell networks via some numerical examples.

18

CHAPTER-3

GSM NETWORK PLANNING

3.1. Introduction to RF Network Planning

Achieving maximum capacity while maintaining an acceptable grade of service

and good speech quality is the main issue for the network planning. Planning an

immature network with a limited number of subscribers is not the real problem. The

difficulty is to plan a network that allows future growth.

3.2 Planning procedure for RF network

Planning means building a network able to provide service to the customers

wherever they are need. For a well-planned cell network a planner should meet the

following requirements

• Coverage as required and predicted.

• Co channel and adjacent channel interference levels as predicted for maintaining

good quality of service.

• Minimum antenna adjustments during the optimization process.

• Maximizing the network capacity (Erl/km2) with limited frequency band (MHz) by

reusing the same frequencies.

• Minimum changes to the BSS parameters/database during the optimization phase.

• Facilitate easy expansion of the network with minimal changes in the system.

In general the planning process starts with the inputs from the customer. The customer

inputs include customer requirements business plans system characteristics and any

other constraints. After the planned system is implemented the assumptions made

19

during the planning process to be validated and corrected wherever necessary through

an optimization process.

RF Planning is divided in to three parts:

• Capacity Planning

• Frequency Planning

• Coverage Planning

Fig 3.1. Radio Frequency planning process

3.3 Capacity Planning

3.3.1 Network dimensioning

Network Dimensioning (ND) is usually the first task to start the planning of a

given cellular network. The main result is an estimation of the equipment necessary to

meet the following requirements.

• Capacity

• Coverage

• Quality

ND gives an overall picture of the network and is used as a base for all further

planning activities.

20

Network dimensioning inputs are

• Capacity related

o Spectrum available.

o Subscriber growth forecast

o Traffic density map (Traffic per subs)

• Coverage related

o Coverage regions

o Area types information

• Quality related

o MS classes

o Blocking probability

o Location probability

o Redundancy

o Indoor coverage.

The operator normally supplies the input data, but use of defaults is also possible.

The technical parameter and characteristics of the equipment to be used are another

very important part of the input. This includes the basic network modules as well as

some additional elements.

3.3.2 Capacity calculation

The capacity of a given network is measured in terms of the subscribers or the

traffic load that it can handle. The former requires knowledge of subscriber calling

habits while the latter is more general.

The steps for calculating the network capacity are

• Find the maximum no of carriers per cell that can be reached for the different

regions based on the frequency reuse patterns and the available spectrum.

21

• Calculate the capacity of the given cell using blocking probability and the number of

carriers.

• Finally the sum of all cell capacities gives the network capacity.

Spectrum Efficiency= BAn

s

S - Total spectrum available

n - Reuse factor

A - Cell area

B - Channel bandwidth

3.3.3 Structure of Erlang B table

Fig 3.2. Erlang B table structure

Example:

At 2% blocking (0.02 GoS), 2 traffic channels can carry 0.2235 erlangs of traffic

Table 3.1 Erlang B table

22

To calculate the capacity, refer Fig 3.2 for the given cell using blocking

probability and the number of carriers we need the well-known Erlang B table or

formulas and the no of traffic channels for different number of carriers. The result we

get is the traffic capacity in Erlangs, which can easily be transferred into the number

of subscribers.

Each TDMA frame consists of 8time slots. One for signaling information

and Remaining 7 time slots for TCH (Traffic channel) For example: consider 1 carrier

for 3 sector 1|1|1

TCH = 7

Traffic per sector = 2.935E X 3 = 8.82E

Traffic generated per user:

Rural = 1.5/60 = 0.25E

Urban = 2.4/60 = 0.04E

Traffic per BTS (Rural) = 8.82/0.25 =352.8

Given , If the total traffic = 700E

1BTS traffic = 2.935E

No of BTS = 700/8.82 = 79.365

Total user = 79.365 X 352.8 = 28000

3.3.4 Frequency reuse schemes

A cellular network can easily be drawn as a combination of hexagons or circles

by the help of regular grids. One of the advantages is the possibility to try different

frequency reuse patterns and calculate the expected co-channel interference. This is

required to assign a frequency reuse no to any of the network regions area types. It is

clear that the high-density regions are the most problematic parts of the network.

23

3.3.5 Power budget calculations

To guarantee a good quality in both directions the power of BTS and MS

should be in balance at the edge of the cell. The main idea behind the power budget

calculations is to receive the maximum output power level of BTS transmitter as a

function of BTS and MS sensitivity levels, MS output power, antenna gain, diversity

reception, cable loss, combiner loss. The power budget calculations provides

following useful results:

BTS transmitted power: BTS transmitted power is adjusted to provide a

balanced radio link for given BTS and MS receiver performance, MS

transmitter performance, antenna and feeder cable characteristics.

Isotropic path loss: this is the maximum path loss between BTS and MS

according to given radio system performance requirements.

Coverage threshold: downlink signal strength at coverage area border for

given location probability.

Cell range for indoor and outdoor coverage: this is a rough indication about

cell range in different area types and can be used for network dimensioning. It

can also be used for comparing the effect of different equipment specification

and antenna heights for the cell range.

3.4 Coverage Planning

The objective of coverage planning phase in coverage limited network areas is

to find a minimum amount of cell sites with optimum locations for producing the

required coverage for the target area. Coverage planning is normally performed with

prediction modules on digital map database. The basic input information for coverage

planning includes:

• Coverage regions

• Coverage threshold values on per regions

24

• Antenna, Preferred antenna line system specifications

3.5 Frequency Planning

The main goal of the frequency-planning task is to increase the efficiency of

the spectrum usage, keeping the interference in the network below some predefined

level. Therefore it is always related to interference predictions.

There are two basic approaches to solve the frequency assignment problem.

• Frequency reuse patterns

• Automatic frequency allocation

Some software‟s are used with automatic frequency allocation algorithms for

finding the optimum solutions. The frequency allocation is generally guided by the

following information:

• Channel requirement on cell basis according to the capacity planning

• Channel spacing limitations according to BTS specification

• Quality of service requirement which is conserved to acceptable interference

probability

• Traffic density distribution over the service area

• Performance of advanced system features

The frequency allocation is based on cell-to-cell interference probability estimation

according to the network topology, field strength distribution and traffic load.

3.5.1 Frequency Reuse

A frequency used in one cell can be reused in another cell at a certain distance.

This distance is called reuse distance. The advantage of digital system is that they can

reuse frequencies more efficiently than the analogue ones, i.e. the reuse distance can

be shorter, and the capacity increased. A cellular system is based in reuse of

25

frequencies. All the available frequencies are divided into different frequency groups

so that a certain frequency always belongs to a certain frequency group. The

frequency groups together form a cluster.

3.5.2 Frequency hopping

Frequency hopping is a method of transmitting radio signals by rapidly

switching a carrier among many frequency channels, using a pseudorandom

sequence known to both transmitter and receiver.

3.5.3 Implementation of frequency hopping

Each call has its time slots transmitted in sequence across a defined set of

hopping frequencies. Frequency hopping occurs between time slots: a mobile station

transmits or receives on a fixed frequency during one time slot, then changes

frequency before the time slot on the next TDMA frame. The total number of

available hopping sequences is 64 multiplied by the number of hopping frequencies.

Hopping sequences are described per channel by two network parameters: HSN and

MAIO. GSM uses FDMA/TDMA techniques for frequency allocation. Totally 125

carriers used in GSM Absolute Radio Frequency Carrier Number (ARFCN) uses 124

carriers and remaining 1 carrier acts as guard band. As per Telecom Regulatory

Authority of India (TRAI), Maximum 4 operators can be served in 1Band.Therefore,

124/4 = 31 carriers .31 carries are spitted into : 15 carriers (BCCH) + 16carriers (Non-

BCCH) Maximum of 1 BCCH in one sector. For example: Consider ARFCN no. is

assigned from 1 to 15

Table 3.2 BCCH Chanel Assignment

1 2 3 4 5

6 7 8 9 10

11 12 13 14 15

26

3.5.3.1 HSN

HSN (Hopping Sequence Number) defines a number that is fed into the

frequency hopping algorithm to generate the hopping sequence. Values can be 0 to 63.

Value 0 defines cyclic hopping and all other values generate a random sequence.

3.5.3.2 MAIO

MAIO (Mobile Allocation Index Offset) defines the starting frequency, or

offset, the transmission will start on within a hopping sequence. The value can be 0 to

N-1 where N is the number of allocated frequencies.

3.5.3.3 Rules for using HSN and MAIO

To fight the interference with frequency hopping, use the following rules:

• Two channels with the same HSN but different MAIO never use the same frequency

at the same time.

• Channels in the same cell using the same hopping frequency set should have the

same HSN, and different MAIO, to avoid co-channel interference within the cell.

• If random hopping is used, each channel in distant cells using the same frequency set

should have a different HSN, this optimizes the benefits of interference diversity.

Table 3.3 TDMA Frame sequence for 2|2|2 sectors

SECTORS MAIO TDMA

FRAME

1 2 3 4

A1 _ 1 1 1 1

A2 0 16 17 18 19

B1 _ 6 6 6 6

B2 2 18 19 20 21

C1 _ 11 11 11 11

C2 4 20 21 22 23

Where, A1, B1, C1 – BCCH carriers and A2, B2, C2 –NON-BCCH carriers

27

• Between the sectors the difference should be 2 or more

• Each sector difference is 3 or more

3.6 Planning models

Propagation in land mobile service at frequencies from 300 to 1800MHz is

affected in varying degrees by topography, morphography, ground constants and

atmospheric conditions. A very common way of propagation loss presentation is the

usage of so called propagation curves, normally derived from some measurement

formulae are

• Okumara Y. and others, for field strength and its variability in VHF and UHF land

Mobile Radio Service

• Hata. M, Empirical formula for Propagation Loss in Land Mobile Radio Services.

• Cost –207, Digital Land Mobile Radio Communication.

• Cost-231, Urban Transmission Loss for Mobile Radio in the 900 and 1800MHz

bands.

.

28

CHAPTER- 4

DESIGN AND IMPLEMENTATION

4.1 SOFTWARE USED

Acceptance, Test or Launch Language (ATOLL version3.2.1)

4.1.1 ATOLL planning tool

Atoll is a scalable and flexible multi-technology network design and

optimization platform that supports wireless operators throughout the network

lifecycle, from initial design to densification and optimization.

Atoll is also an open technical information system that easily integrates with

other IT applications and increases productivity. It features advanced

development tools and open interfaces that enable the integration of customized

or commercially available complementary modules.

Atoll is designed to work in a wide range of implementation scenarios, from

standalone to enterprise-wide server-based configurations using distributed and

parallel computing.

Atoll includes advanced multi-technology network planning features and a

combined Single-RAN Multi-RAT GSM/ UMTS/LTE Monte-Carlo simulator

and traffic model. Atoll supports GSM/GPRS/EDGE, UMTS/HSPA, LTE,

CDMA2000 1xRTT/EV-DO, TD-SCDMA, WiMAX, and Microwave link

networks; it also includes a high- performance propagation calculation engine,

and state- of-the-art network planning and analysis features. It has a set of fully

integrated AFP (Automatic Frequency Planning) tools and ACP (Automatic

Cell Planning) tools, allowing operators to perform design and optimization

tasks from a single application using a single database and IT infrastructure.

Optimization tools are available for GSM, UMTS, LTE and WiMAX

29

4.2 Scenario Description

In second generation systems, detailed planning concentrated strongly on coverage

planning and capacity analysis than simple coverage optimization is needed. The tool should

aid the planner to optimize the base station configurations, the antenna selections and antenna

directions and even the site locations, in order to meet the quality of service and the capacity

and service requirements at minimum cost.

4.3 SAMPLE PROCESS OF WORKING OF ATOLL TOOL:

Creating a new document

Fig 4.1. New document

30

Importing Digital Map

Fig 4.2. Digital Map import

Importing Clutter Properties

Fig 4.3. Clutter Properties

31

Importing digital terrain model

Fig 4.4. Vectors import

Importing Places

Fig 4.5. Importing places

32

BTS Configuration

Fig4.6. BTS Properties configured

Propagation model configuration

Fig 4.7. Propagation model configured

33

BCCH Assignment

Fig 4.8. BCCH Assignment

Frequency planning for 4 BTS:

Fig 4.9. Signal strength for 4 BTS

34

Fig 4.10. C/I level of 4 BTS

The frequency planning of 4BTS covers in and around areas of guindy, which

covers about 2km radius approximately. In this area, signal strength and C/I level are

measured intentionally since they are the prime factors of reducing the number of call

drops which stands as a major issue in telecommunication network.

There are two types of tests are carried out for analysis.

1. Hotspot test

2. Drive test

Hotspot test:

The test made using setup, which includes 2 mobile phones, GPs, laptop is

carried out in a same place without mobility. Here, the handovers does not take

place.

35

Drive Test:

As the analysis of the network before planning is being carried out by

travelling/moving on the route, the testing equipments and tools are taken by a

vehicle, hence called as drive test. Here, handovers takes place.

There are 2 types of calls made in hotspot test and drive test. They are:

1. Long call

2. Short call

Long call:

The call is connected to the server without specifying any duration. The call is

being cut when the caller themselves cuts the call.

Short call:

The call is connected to the server by giving some stipulated duration. When

the call is being cut, it automatically reconnects to the server.

36

CHAPTER-5

RESULTS AND DISCUSSIONS

The main aim of this project is to reduce the number of call drops which occurs

due to traffic. On analysis from the OMCR (Operation Maintenance Control and

Radio Network) and also by the analysis made from ATOLL TOOL before planning,

it is found that call drops occur to a greater extent. Hence, planning is made for

consideration from the above analysis to reduce number of call drops. In addition to

this analysis, drive test has been made in the region under test, which is also one of the

survey report for planning the network.

The area chosen for the test is pallavaram area under Chennai zone. Here, it is

clear that signal strength level in the network is quite low, which is indicated using

yellow colour and is shown in fig 5.1.

Fig 5.1. Area under Test

37

Table 5.1 OMCR Report before Planning

By the use of ATOLL TOOL, the signal strength and Channel to

Interference(C/I) level is analysed in the pallavaram area. Signal Strength refers to

the transmitter power output as received by a reference antenna at a distance from the

transmitting antenna. The channel to interference refers to the interference occurs

between the carriers in a single sector or the interference occur between the carriers in

different sectors

The fig.5.2 depicts the signal strength of pre-planned network, where call drop

occurs.

38

Fig 5.2. Signal Level of Area under Test

The Signal strength of GSM network ranges from -43dbm to -110dbm. In the

fig 5.2, the gray colour depicts the best signal strength of the network that is around -

50dBm and green colour depicts the optimum signal obtained from BTS which is in

the range between -70dbm to -80dbm, whereas yellow colour depicts the poor quality

of signal strength received from BTS that is below -110 dBm.

39

Fig 5.3. C/I Level of Area under Test

The fig.5.3 depicts the C/I level of pre-planned network. Generally, a standard

value for best C/I level is ≥ 9 dB where as in practical it is found to be ≥ 12 dB as a

best result. Here, gray colour represents the lowest interference range. The dark green

depicts the optimum C/I level of the network. The light green colour depicts the area

where highest interference occurs.

Table 5.2 OMCR Report after Planning

40

The OMCR report shows the pallavaram area of Chennai zone after planning

process, which is represented in Table 5.2. Here, it shows that call drops have been

reduced great in number. Also, the total traffic, call drop ratio and call block ratio has

got reduced. The call drop is nothing but fraction of telephone calls which due to technical

reason were cut off before the speaking parties had finished their conversation tone and

before one of them had hang up. Call blocking allows a subscriber to block incoming calls

from specific telephone numbers. Also to be elaborated, call blocking occurs when the

channel is not available for call process

Table 5.3 Total Traffic in Erlang

41

Table 5.4 Total Call Drops

From the results above, it is inferred that the parameters like total traffic and

total call drop are reduced to a greater extent by planning the network, in which

carriers are increased from 3/3/3 to 5/5/5 in each sector. The analysis is made by the

OMCR report taken before (Mar-18) and after (Mar-24) planning of the network,

which is taken at different time intervals.

42

CHAPTER-6

CONCLUSION AND FUTURE WORK

As a result from OMCR report and viewing the existing scenario of area under

test using ATOLL TOOL, it is found that the call drops occur in the area of

Pallavaram in Chennai zone. Also, by the study and survey, it is clear that the reason

for call drop is that RF carriers are not sufficient in each sector. Hence, capacity

planning in RF medium is done to increase the capacity of the carriers. At present, the

sector consists of 3/3/3 carriers, which allows the entry of 63 subscribers in a second.

On analysing, 2 more carriers are added in each sector which is represented as 5/5/5 to

increase the capacity of carriers. This paves a path for the entry of 105 subscribers in a

second to get into the network, which reduces the call drop effectively even during

peak hours. On increasing the carriers, the network faces the issues such as low signal

strength from BTS to MS and high interference between the carriers and sectors.

Hence, by the use of ATOLL TOOL, it is planned such that the call drops are reduced

in number, which made the network effective with increased signal strength and

reduced interference.

In future, there is an opportunity to improve the network performance by

focusing on the following factors such as the missing neighbour relations, proposing

antenna tilt changes, adjusting handover margins (Power Budget, Level, Quality, and

Umbrella HOs).

43

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45

ACKNOWLEDGEMENT

I would like to thank Mr.K.RAMESH (SUB-DIVISIONAL ENGINEER) from

RGMTTC (Rajiv Gandhi Memorial Telecom Training Centre) of BSNL (Bharat Sanchar

Nigam Limited) at Chennai, for his support in completion of this research project

successfully.

46

LIST OF PUBLICATIONS

P. Gokulapriya, R.Karthikeyan, “ANALYZING THE SIGNAL FLOW AND

RF PLANNING IN GSM NETWORK”,IEEE sponsored International

Conference on Innovations in Information Embedded and Communication

Systems [ICIIECS‟16], Karpagam College of Engineering, Coimbatore.