Modern mobile phone networks are digital

Why a new system?

As analogue mobile phones were gaining in popularity, it became clear that the design of the system was going to put a hard limitation on the number of mobiles and the call volume the networks could manage. There were issues with security, celebrities' taped mobile conversations being published, and increasing numbers of mobile phones being illegally "cloned". People were wanting to use their mobile phones in other countries, which the analogue system did not really support.

GSM -- the committee

In 1982 the Conference of European Posts and Telecommunications (CEPT) formed a committee called the Groupe Spécial Mobile.

This committee was to develop a standard for mobile phones that would use radio spectrum efficiently, provide international roaming, give satisfactory voice quality, have low equipment costs, be compatible with other systems such as ISDN (Integrated Services Digital Network) and be ready to support new services as they were developed.

This committee worked together, designing a system which depended on technologies not available at the time, and following 1986 field tests of different radio techniques proposed for the air interface, in 1987 they produced a proposal for a TDMA system which was incorporated in an initial Memorandum of Understanding (MoU), signed by telecommunications operators from twelve countries.

GSM goes live

In 1989 CEPT's GSM passed the specifications to the European Telecommunications Standards Institute (ETSI). The following year (1990) phase 1 of the GSM specification was published. In 1991 the first commercial GSM mobile telephone system went into service.

In 1992 GSM coverage was restricted to large cities, and around airports. The networks rolled out, more countries signed up to the system, and by 1995 rural areas were seeing GSM coverage. In 1995 Phase 2 of the GSM (by now renamed to Global System for Mobiles) was published, adding additional features and services.

In retrospect, GSM was a wonderful idea, well defined, and able to incorporate new technologies as they became available. For the technical details of how GSM is designed, see the How It Works section.

GSM is the dominant digital mobile phone service, but there are other mobile phone systems in use across the world, as well as the Total Access Communication System (TACS) previously used in the UK: for details, see the Cellular page. A new generation of digital networks is now being brought into service, and no doubt more will follow in time.

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