Mobile Phones - the Technology Behind the Call

A recent study that deprived 300 volunteers of their mobile phones for two weeks found that one in six reported a loss of appetite and/or depression, a further quarter also found that without their mobile companions their confidence was stunted. With over 70% of Britain's population owing a mobile and the global figure recently tipping the billion mark, meaning that mobile phones now outnumber landlines, it's clear to see that mobiles have become a truly indispensable aspect of many people's lives. Perhaps one of the most interesting things about the mobile phone is that it is essentially just a radio, albeit an extremely sophisticated radio. In fact, all of the components and technology packed into today's handheld devices would have filled an entire office building floor some 30 years ago! Unlike traditional radio equipment (e.g. walkie-talkies, CB Radio's) which is known as half-duplex equipment, mobile phones are full-duplex. This means that they utilise two frequencies, one for talking and a second for listing. In order for a mobile to make and receive phone calls it must be in range of a base station. Base stations are a familiar site, generally comprised of an antenna mounted on a mast or building and below this is a small box house that contains the radio transmitters and receivers. Within a relatively large city there can be hundreds of these base stations, each one serving their own area (typically 10sq/m), known as 'cells'. Utilising cells enables the same RF to be used within a small area, meaning that hundreds of people in a relatively small area can all use their phones simultaneously. From the second a phone is powered up it is seeking out the nearest stations, which upon finding it exchanges various information with, some of which enables the station to keep track of exactly which cell you are in. This information is relayed to a Digital Switching Centre, which control all voice and data communications between wireless handsets and also patches calls onto the fixed public telephone network.