Global System for Mobile Communication

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Table of Contents
PAGE NO.
1 INTRODUCTION ……………………………………….…… 2 TRANSTION FROM ANALOG TO DIGITAL………………

1
2

2.1 Capacity of the system

3

2.2 Compatibility
2.3 Aspects of quality
CELLULAR SYSTEM ………………………………………

3

Cellular structure & Coverage

4 The GSM network

………………………………………

5

4.1 Architecture of the GSM network
4.2 The geographical areas of the GSM network
4.3 The GSM functions

5 The GSM radio interface …………………………………

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5.1 Frequency allocation
5.2 Multiple access scheme
5.3 From source information to radio waves
5.4 Discontinuous transmission (DTX)
5.5 Timing advance
5.6 Power control
5.7 Discontinuous reception
5.8 Multipath and equalisation

6 GSM services …………………………………………………

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6.1 Teleservices
6.2 Bearer services
6.3 Supplementary Services

7 Conclusion ……………………………………………………

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INTRODUCTION
The Global System for Mobile communications is a digital cellular communications system. It was developed in order to create a common European mobile telephone standard but it has been rapidly accepted worldwide. GSM was designed to be compatible with ISDN services.

HISTORY OF GSM :--The idea of cell-based mobile radio systems appeared at Bell Laboratories (in USA) in the early 1970s. However, mobile cellular systems were not introduced for commercial use until the 1980s. During the early 1980s, analog cellular telephone systems experienced a very rapid growth in Europe, particularly in Scandinavia and the United Kingdom. Today cellular systems still represent one of the fastest growing telecommunications systems.

But in the beginnings of cellular systems, each country developed its own system, which was an undesirable situation for the following reasons:



The equipment was limited to operate only within the boundaries of each country. The market for each mobile equipment was limited.

In order to overcome these problems, the Conference of European Posts and Telecommunications (CEPT) formed, in 1982, the Groupe Spécial Mobile (GSM) in order to develop a pan-European mobile cellular radio system (the GSM acronym became later the acronym for Global System for Mobile communications). The standardized system had to meet certain criteria:








Spectrum efficiency
International roaming
Low mobile and base stations costs
Good subjective voice quality
Compatibility with other systems such as ISDN , PSTN , PSPDN etc. Ability to support new services

GSM system is based on digital technology which has many
advantages over analog technology. It also provides the technology as ROAMING, SMS TELETEX , Fax mail.

1

TRANSITION FROM ANALOG TO DIGITAL
In the 1980s most mobile cellular systems were based on analog systems as AMPS. Second generation cellular digital systems like GSM , DAMPS, were implemented then. From 1984-86, GSM focused on to compare different technical possibilities for transmission. It was decided to compare several technical proposals on the basis of prototypes allowing actual radio transmission.

The capacity of the system
Cellular systems have experienced a very important growth. Analog systems were not able to cope with this increasing demand. In order to overcome this problem, new frequency bands and new technologies were proposed. But the possibility of using new frequency bands was rejected by a big number of countries because of the restricted spectrum. The new analog technologies proposed were able to overcome the problem to a certain degree but the costs were too important.

The digital radio was, therefore, the best option to handle the capacity needs in a costefficiency way.

Compatibility with other systems such as ISDN
The decision of adopting a digital technology for GSM was made in the course of developing the standard. During the development of GSM, the telecommunications industry converted to digital methods. The ISDN network is an example of this evolution. In order to make GSM compatible with...
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