There are currently more than 50 million mobile phones in use in the UK. To support these phones a network of 35,000 base stations are required. It is projected that by 2007 there maybe as many as 48,000 base stations.
In mobile radio communications networks there are two way radio transmissions between mobile phones and nearby base stations.
As these communications occur at low power levels the phones must be close to the base stations.
Over large geographical areas a network of many base stations must be established with each base station providing coverage over a small area called a cell.
The communications between the phones and the base stations use radio signals which are transmitted between the aerials of the base stations and those of the mobile phones.
Radio signals are electromagnetic fields (EMF) which transfer energy and hence information between the base station and the phone. This energy can also be absorbed by the body.
In general absorption is related to the power level and distance from the emitter. Hence greater power levels are experienced from the phones than from the base station when both are operational.
The advent of 3G (generation) mobile phones will entail the construction of more base stations to service the network.