Global System for Mobile Communicatin- Basics and History
GSM Standardization and Service Aspects
#The GSM standard was developed by the Groupe SpecialMobile, which was an initiative of the Conference of European Post and Telecommunications (CEPT) administrations.
#)The underlying aim was to design a uniform panEuropean mobile system to replace the existing incompatible analog systems.
#)Work on the standard was started in 1982, and the first full set of specifications (phase 1) became available in 1990.
#)The responsibility for GSM standardization now resides with the Special Mobile Group (SMG) under the European
#)Telecommunication Standards Institute (ETSI), and revisions/enhancements to various aspects of GSM standard are being carried out in SMG technical subcommittees.
#)Figure below shows the structure of SMG and the primary responsibilities of the various SMG subcommittees.
Characteristics of initial GSM Standards
#)The characteristics of the initial GSM standard include the following:
1)Fully digital system utilizing the 900 MHz frequency band
2)TDMA over radio carriers (200 kHz carrier spacing)
3)8 full-rate or 16 half-rate TDMA channels per carrier
4)User/terminal authentication for fraud control
5)Encryption of speech and data transmissions over the radio path
6)Full international roaming capability
7)Low speed data services (up to 9.6 kb/s)
8)Compatibility with ISDN for supplementary services
9)Support of short message service (SMS)
#)GSM supports a range of basic and supplementary services, and these services are defined in terms analogous to those for ISDN (i.e., bearer services, teleservices, and supplementary services).
#)The most important service supported by GSM is telephony.
#)Other services derived from telephony included in the GSM specification are emergency calling and voice messaging.
#)Emergency calling refers to such services as E.911 in North America and E112 in Europe.
#)Bearer services supported in GSM include various asynchronous and synchronous data services for information transfer between GSM and other networks (i.e., PSTN, ISDN, CSPDN, PSPDN) at rates from 300 to 9600 b/s.
#)Teleservices based on these bearer services include group 3 fax and short message service (SMS).
#)The data capabilities of GSM have now been enhanced to include high speed circuit-switched data (HSCSD) and general packet radio service (GPRS).
#)The common ISDN-like supplementary services supported by GSM include the following:
1)call offering services—call forwarding
2)call restriction services—call barring
3)call waiting service
4)call hold service
5)Multi party service—tele conferencing
6)calling line presentation restriction services
7)Advice of charge service
8)closed user group service
#)Whereas the first two categories of supplementary services (call offering and call restriction) are defined in the original GSM specification (phase 1), the remaining services were recently added as part of enhancements to GSM (phase2).
#)Many of these services are similar (at least in their description) to services currently available in fixed networks.
#)However, because of the mobile radio link, their implementation may impose special requirements.
#)The GSM standard has been undergoing continuous extensions and enhancements to support more services and capabilities like high speed circuitswitched data (HSCSD), general packet radio service (GPRS), and CAMEL (customized applications for mobile network-enhanced logic).
#)An 1800 MHz version of GSM, known as DCS1800, has also been standardized in Europe.
#)Further, Committee T1P1 and TIA TR46 are responsible for the PCS1900 standard in the United States, which is based on the GSM and DCS1800 European standards. A number of PCS1900 systems are now operational and they represent North American implementations of GSM.
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