SEMINAR REPORT ON GSM ARCHITECTURE

A

SEMINAR REPORT

ON

GSM ARCHITECTURE

Submitted in partial fulfilment of

The requirements for the award of the degree

Of

BACHELOR OF TECHNOLOGY

IN

ELECTRONICS & COMMUNICATION ENGINEERING

By

G.KOTESWARARAO

(15765A0415)

DEPARTMENT OF ELECTRONICS & COMMUNICATION ENGINEERING

LAKIREDDY BALI REDDY COLLEGE OF ENGINEERING(Autonomous &Affiliated to JNTUK, Kakinada & Approved by AICTE, New Delhi)

(Accredited by NBA of AICTE & Certified by ISO 9001:2000)

L B REDDY NAGAR, MYLAVARAM-521 230

Krishna District, Andhra Pradesh 2014-2015

Dept., of ECE, LBRCE 1

LAKIREDDY BALI REDDY COLLEGE OF ENGINEERING(Autonomous &Affiliated to JNTUK, Kakinada & Approved by AICTE, New Delhi)

(Accredited by NBA of AICTE & Certified by ISO 9001:2000)

L B REDDY NAGAR, MYLAVARAM-521 230

Krishna District, Andhra Pradesh

DEPARTMENT OF ELECTRONICS & COMMUNICATION ENGINEERING

CERTIFICATEThis is certify that G.KOTESWARARAO (15765A0415), student of B. tech, III semester (ELECTRONICS

AND COMMUNICATION ENGINEERING) have successfully completed his Seminar titled “GSM

ARCHITECTURE” at Lakireddy Bali Reddy College of Engineering during the academic year 2016-

2017. This seminar Report is submitted in partial fulfilment for the award of degree B. Tech (Electronics

And Communication Engineering).

Date:

Place:

SEMINAR CO-ORDINATOR HEAD OF THE DEPARTMENT

Prof. B. RAMESH REDDY


ACKNOWLEDGEMENTS

First and foremost we sincerely thank our institution Lakireddy Bali Reddy College of

Engineering for giving this opportunity for fulfilling our dreams of becoming engineers. We express

our special gratitude to our Director Dr. E.V.Prasad who made this endeavour possible.

We have the immense pleasure in expressing our thanks and deep sense of gratitude of Prof

B. Ramesh Reddy, Head of the Department of Electronics & Communication Engineering for

extending necessary facilities for the completion of project.

We are highly thankful to our seminar coordinators Mr. Ch. V. Naga Bhaskar, Asst. Prof of

ECE Smt.K. Lakshmi., and Asst. Prof of ECE for providing the knowledge to deal with the

problem at every phase of our seminar in a systematic manner.

We would like to extend our deepest gratitude to the support rendering by the Teaching and

Non-Teaching staff of Electronics and Communication Engineering department during the course of

this work. Finally we thank each and every one who indirectly contributed his or her help to

complete this project.

G.KOTESWARARAO

(15765A0415)


GSM ARCHITECTURE


TOPICSABSTRACT

1.INTRODUCTION2.History of GSM Technology3.SYSTEM ARCHITECTURE4.MOBILITY MANAGEMENT 5.ADVANTAGES & DISADVANTAGES

6.APPLICATIONS & FUTURE SCOPE

7.CONCLUSION


FIGURES & TABULATIONS

FIGURES:

FIGURE 1: SYSTEM ARCHITECTURE……………………………………………..11

FIGURE 2:STRUCTURE OF GSM NETWORK……………………………………..14


Abstract

GSM, the Global System for Mobile communications, is a digital cellular communications system which has rapidly gained acceptance and market share worldwide, although it was initially developed in a European context. In addition to digital transmission, GSM incorporates many advanced services and features, including ISDN compatibility and worldwide roaming in other GSM networks. The advanced services and architecture of GSM have made it a model for future third-generation cellular systems, such as UMTS. This paper will give an overview of the services offered by GSM, the system architecture, the radio transmission structure, and the signaling functional architecture.

Services provided by GSMGSM was designed having interoperability with ISDN in mind, and the services provided by GSM are a subset of the standard ISDN services. Speech is the most basic, and most important, teleservice provided by GSM.

In addition, various data services are supported, with user bit rates up to 9600 bps. Specially equipped GSM terminals can connect with PSTN, ISDN, Packet Switched and Circuit Switched Public Data Networks, through several possible methods, using synchronous or asynchronous transmission. Also supported are Group 3 facsimile service, videotext, and teletex. Other GSM services include a cell broadcast service, where messages such as traffic reports, are broadcast to users in particular cells


1 INTRODUCTION

The development of GSM started in 1982 when a study group „Group

Special Mobile‟ was formed during Conference of European Posts and

Telegraphs (CEPT) this group was to develop a Pan-European public cellular system in the 900 MHz

range. Some of the basic criteria for their proposed system were:

Good subjective speech quality

ISDN compatibility

Spectral efficiency

Support for international roaming

Support for range of new services and facilities

In 1989, GSM responsibility was transferred to European Telecommunication Standards Institute (ETSI)

and commercial service was started in mid 1991. Although GSM was standardized in Europe, now it is

operational in other continents also. The acronym GSM now aptly stands for Global System for Mobile

Communication.

CELLULAR CONCEPT

Cellular radio was devised in order to make better use of limited resource of Radio Spectrum. Each Megahertz of spectrum will only support a comparatively a small number of simultaneous conversations and the same frequency must be reused many times in order to meet the capacity needed for national or regional service. Cellular radio achieves this by creating a honeycomb of cells over the region and assigning frequencies


2.History of GSM Technology

Europeans quickly realized the disadvantages of each European country operating on their mobile network. It prevents cell phone use from country to country within Europe. With the emerging European Union and high travel volume between countries in Europe this was seen as a problem. Rectifying the situation the Conference of European Posts and Telegraphs (CEPT) assembled a research group with intentions of researching the mobile phone system in Europe. This group was called Group Special Mobile (GSM).

For the next ten years the GSM group outlined standards, researched technology and designed a way to implement a pan-European mobile phone network. In 1989 work done by the GSM group was transferred to the European Telecommunication Standards Institute (ETSI). The name GSM was transposed to name the type of service invented. The acronym GSM had been changed from Group Special Mobile to Global Systems Mobile Telecommunications.

By April of 1991 commercial service of the GSM network had begun. Just a year and half later in 1993 there were already 36 GSM networks in over 22 countries. Several other countries were on the rise to adopt this new mobile phone network and participate in what was becoming a worldwide standard. At the same time, GSM also became widely used in the Middle East, South Africa and Australia.

There are five major GSM frequencies that have become standard worldwide. They include GSM-900, GSM-1800, GSM-850, GSM-1900 and GSM-400.

GSM-900 and GSM-1800

GSM-900 and GSM-1800 are standards used mostly worldwide. It is the frequency European phones operate on as well as most of Asia and Australia.

GSM-850 and GSM-1900

GSM-850 and GSM-1900 are primarily United States frequencies. They are also the standard for Canada GSM service and countries in Latin and South America. Most of the Cingular network operates on GSM 850, while much of T-Mobile operates at GSM-1900. T-Mobile however, has roaming agreements with Cingular. Meaning in the case of no service at GSM-1900, the phone will switch to GSM-850 and operate on Cingular’s network.

GSM-400

GSM-400 is the least popular of the bunch and is rarely used. It is an older frequency that was used in Russia and Europe before GSM-900 and GSM-1800 became available. There is not many networks currently operating at this frequency.


3 SYSTEM ARCHITECTUREThe functional architecture of a GSM system can be broadly classified into

Mobile Station (MS)

Base Station Subsystem (BSS)

Network and Switching Subsystem (NSS)

Operation Subsystem (OSS)

The MS and the BSS communicate via the Um interface or radio link. The BSS communicates with Mobile Service Switching Center across the A interface.

MOBILE STATION

This may be a standalone piece of equipment for certain services or support the connection of

external terminals. The MS consists of the Mobile Equipment (ME) and a Subscriber Identity

Module (SIM).

The ME is uniquely identified by the International Mobile Equipment Identity (IMEI), but it need

not be personally assigned to one subscriber, The SIM which is a smart card provides personal

mobility and the user can access the subscriber services. The subscriber can operate on any

terminal just by inserting the SIM card in that GSM terminal. SIM card contains the International

Mobile Subscriber Identity (IMSI) used to identify the subscriber to the system, a secret key for

authentication and other security information’s. SIM card may be protected against unauthorized

use by a password.

BASE STATIONSUBSYSTEM

The BSS is composed of three parts, Base Transceiver Station (BTS) and U3ase Station

Controller (BSC). These two communicate across the standardized Abius interface. The third part

is Transcoder and Rate Adaptation Unit (TRAU).


Base Transceiver Station:

This provides the GSM radio coverage within a cell. It comprises of radio transmitting and

receiving equipment and associated signal processing units. This complements the radio features

of ME.

Base Station Controller

This manages the radio resources for one or more BTS‟s. It handles radio channel set-up,

Handovers and frequency hopping. Handovers between BTS‟s belonging to different BSC‟s

however can involve MSC‟s but are still managed by the original serving BSC. It controls the

transmission of information about Local Area Codes (LAC), signaling channel configuration and

information’s about neighboring cells.

FIGURE 1:SYSTEM ARCHITECTURE


Transcoder and Rate Adaptation Unit.

This is responsible for transcoding between GSM encoded speech at I 3KPS and fixed

network speech at 64KPS. Similarly it performs rate adaptation of GSM data services. Although

it is a part of BSS, it is located at MSC Sites. This is to benefit from the lower rate coding and

consequent saving in transmission costs.

NETWORK AND SWITCHING SUBSYSTEM

NSS in GSM uses an Intelligent Network (The central component of NSS is the Mobile Service Switching Center (MSC). It is supported by Interworking functions (JWF), Home Location Register (HLR), Visitor Location Register (VLR), Gateway MSC (GMSC) and Signal Transfer Point (STP).

Mobile Service Switching Center

It acts like a switching node and additionally provides all the functionality needed to handle a

mobile subscriber such as registration, authentication, location updating. Handovers and call

routing to a roaming subscribe. These functions are provided in conjunction with several functional

entities. An MSC controls several BSC‟s.

Inter Working Function, (IWF)

A gateway for MSC to interface with external networks for communications with users outside GSM. The role of IWF depends upon the type of user data and the network to which it interfaces. Home Location Register (HLR,)

It consists of a computer without switching capabilities. It is a database, which contains subscriber

information related to the subscriber’s current locations but not the actual location. HLR has two

divisions Authentication Center (AuC) and Equipment Identity Register (EIR). The AuC manages

the security data for subscriber authentication. The EIR database carrying information about

certain ME‟s. The security procedure is discussed later.

Visitor Location Register VLR,).


It links to one or more MSC‟s, temporarily storing subscription data currently served by its

corresponding MSC. VLR holds more current subscriber location than l—ILR. Although VLR is

an independent unit, it is always implemented together with the MSC.

Gateway MSC GMSC)

In order to set-up a requested call, the call is initially routed to a GMSC which finds the correct

HLR.GMSC has an interface with external network for gatewaying and the network operates the

full signaling system 7 (SS7) between NSS Machines.

Signaling Transfer Point

It acts as a standalone node to optimize the cost of the signaling transport among

MSC/VLR, GMSC and HLR>

OPERATING SUBSYSTEM

There are three area of OSS

Network operation and maintenance function. •

Subscription management including charging and billing.

Mobile Equipment and Management.

LAYER MODELLING

Transmission

Radio resource management

Mobility management

Communication management


FIG2:

ASPECTSThe International Telecommunication Union (ITU) which manages Allocation of radio

spectrum has allocated the bands 890-915MHz for the uplink (MS To BS) and 960MHz for the

downlink (BS To MS) for mobile networks.

MULTIPLE ACCESS AND CHANNEL STRUCTUREDue to the scarcity of radio spectrum, a method must be devised to divide bandwidth

among as many users as possible. GSM uses a combination of FDMA TDMA. FDMA part involves the division by frequency of the 25M1-lz bandwidth into carrier frequencies of 200KHz bandwidth. One or more carrier frequencies is then divided in time using TDMA scheme.


TRAFFIC CHANNELS

This is also called physical channel. This is used to carry speech and

data traffic: They are of Three kinds

TCH/F (full rate): Transmits the speech code of 13 KBPS or Three data mode 12,6 and 3.6 1KBPS.

TCIH/H(half rate):Transmits the speech code of 7 1KBPS or Two

data modes 6 3.6 1KBPS

TCI-118( 1/8th rate): Used for low rate signaling channels, Common channels and

channels. They are also called Stand Alone Dedicated Control Channel(SDCCH)

CELL SELECTIONUsing the best cell from an MS depends on three factors

The level of signal received by the MS.

The maximum transmission power of the MS.

Two parameters P1 and P2 specified by the cell

C1 = A-max (B, 0)

A = received level average-P 1

B = P2-Max RF power of the MS.

P1 = A value between —110 and —48dBm

P2 = A value between 13 and 43dBm


4 MOBILITY MANAGEMENTThis layer handles the functions that arise from the mobility of the subscribers as well as the

authentication and security aspects.

LOCATION UPDATING

The mobile phone receives constantly information send by the network. This information includes

identification of the area where the mobile is currently located. In order to keep track of its

location, the mobile stores the ID of the area in which it is currently registered. Every time the

network broadcasts the ID of the area, the mobile compares this, information to the area ID stored

in its memory. When the two ID‟s are no longer the same, the mobile sends the network a request,

i.e. Registration inquiry to the area it has entered. The network receives the request and registers

the mobile in the new area, a new VLR. Simultaneously, a subscriber HLR is informed about the

new location and the data of the subscriber is cleared from the previous VLR.

AUTHENTICATION AND SECURITY

Authentication involves two functional entities: -SIM and AuC.Each subscriber is given a secret

key, one copy of which is stored in SIM card and the other in AuC. During Authentication, the

AUC, a 128 bit random number RANI) thatxs is send o lie Mobile. Both mobile and the AuC then

uses the RAND in conjunction with the subscribers secret key and a ciphering algorithm call lcd

A3, to generate a 32 bit long signal response (SRES) that is send back to AuC.lf both numbers

match the subscriber is authenticated.

COMMUNICATION MANAGEMENT

This layer is responsible for call control, supplementary service management and short message

service management.

CALL CONTROL

Call control functions set up calls, maintain calls and release calls.


CALL ROUTING

The directory number dialed to reach a mobile subscriber is called the mobile subscriber

ISDN (MSISDN) which is defined by E.164 numbering plan. This number includes country code

and national destination code, which identifies the subscriber’s operator. The first few digits of

the remaining subscriber number may identify the subscriber’s HLR.

An incoming mobile terminating call is directed to the GMSC. GMSC contains table

linking MSISDN to their corresponding HLR. The GMSC queries the called subscriber’s HLR

for a Mobile Station Roaming

Number (MSRN). The HLR typically stores only the SS7 address of the subscriber’s current VLR and so HLR queries the current VLR, which will temporarily allocate an MSRN from its pool for the call. This MSRN is returned to the HLR and back to GMSE, which can then route the call to the new MSC. At the new MSC the IMISI corresponding to the MSRN is looked up and the mobile is paged in its current location area. SUPPLEMENTARY

SERVICE MANAGEMENT

GSM provides services like call waiting, call forwarding and automatic canceling. SSM is a

point to point management service.

SHORT MESSAGE SERVICE

SMS allows alphanumeric text messages to be sent to and from a mobile phone via a

service center using SACCH. The size of the single short message is limited to 160 characters.

The received short messages are normally stored in SIM.


STRENGTHS OF GSMCompatibility with ISDN using rate adaptation box.

Use of SIM cards.

Control of transmission power.

Frequency hopping.

Discontinuous transmission.

Mobile assisted handover.

GSM Services

GSM was designed to do 3 things:

– 1. Bearer data services: Faxes, text messages, web pages.

Basic GSM had a basic data rate that is limited to 9.6 kbps

– Extended by GMRS and EDGE to around 384 Kbps

– 2. Voice traffic

But, at a lower quality than analog.

– 3. Other features:

Call forwarding, caller id, etc.…

– Meaning, we need to connect to the SS7 network

–


5.ADVANTAGES & DISADVANTAGES

Advantages

• There are numerous handsets and service providers available in the market. Hence the buyers can choose from a variety of options.

• They come with a variety of plans with cheaper call rates, free messaging facility, and limited free calls and so on.

• The quality of calling in GSM is better and also better secured than CDMA.

• A number of value-added services such as GPRS are making GSM a perfect choice.

• The consumption of power is less in GSM mobiles.

• With the tri-band GSM, one can use the phone anywhere around the world.

Disadvantages

• The per-unit charge on roaming calls is higher in GSM than in CDMA.

• Calls made through GSM mobiles can be tampered.

• If the SIM gets lost, one can lose all the data, if the same is not saved in the phone.



FUTURE SCOPE

The market for mobiles communications has grown up explosively since the introduction of 2nd generation of digital system 3rd generation is the technology for the future the need for higher speed & capacity, much more services like multimedia internet is growing gsm has to upgrade for 3g the most imp steps involved in the evolution of gsm to increase the data


CONCLUSIONThis report has given a overview of GSM is the first approach at the true Personal Communication

„Systems (PCS). The SIM card is a novel approach that implements the personal and terminal

mobility. Together with international roaming and support for various services GSM comes close

to fulfilling the requirements of PCS. GSM is being used for the next generation of mobile

telecommunication technology the Universal Mobile Telecommunication Systems (UMTS). The

GSM network functions system architecture and protocols are spread over a large number of GSM

documents.


REFERENCES

William C.Y.Lee, “Mobile Cellular Telecommunications” 2nd Edition, Mc Graw Hill Publication

R.C.V.Macario, “Modern Personal Radio Systems” IEEE Telecommunication Series

John Scourious, “Overview of USM Cellular Systems” University of

Waterloo

Electronics and Communication Engineering Journal Jan/Feb 1989 Vol.1, No: 1, pp7-13

IEEE Communication Magazine April 1993 Vol.3 1, No: 4,

pp92-100
