Cellular telephone systems are a way of providing portable telephone services. Each phone is connected by a radio link to a base station. In turn, this is linked to the telephone network, which is the largest machine on the planet.
There is nothing special about radio links - they've been used for scores of years. What is clever is that with a cellular system, each base station covers a limited area, and if a phone moves away, the connection is passed across to an adjacent base. This is called a hand-off, and allows mobility of phones, whilst permitting re-use of frequencies by base stations in nearby, but not adjacent, 'cells'.
The size of cells varies from system to system and place to place. They can be from over 50 miles across on the analogue 'TACS' systems from Vodafone and Cellnet, to less than 500 metres in busy areas on the 'GSM 1800' networks, One2one and Orange. The smaller the cell size, the more users that can be fitted onto the network, and the less power the mobile handset needs to reach the base, so it and its batteries can be smaller and lighter. Unfortunately, small cell sizes means more cells, so more expense to install, and more problems covering remote, low-population areas.
A cellular network is an expensive thing to build, and it costs well over £1,000,000,000 to get into this in a serious way. The four UK players in this game are all big, multi-national companies, who have big money to invest, or access to it from other sources.
cellular. v1.52 13 October 2000