The cellular concept

In the initial stages of this concept, researchers used analog frequency modulation for speech transmission and frequency shift keying for signaling. This is the basic concept of FDMA technology where individual calls use different frequency channels and the spectrum is treated as common which is shared based on frequency division multiple access. Nowadays cellular subscribers prefer AMPS system which was developed by Bell laboratories in 1976. The first implementation of this technique was by one C hicago firm in 1978. Two more systems in use are Nordic Mobile telephone (NMT) and the Total Access Communication system (TACS). TACS system was developed in the UK and NMT was developed by Denmark-Norway-Sweden-Finland collaboration