THE CELLULAR CONCEPT

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THE CELLULAR CONCEPT


      The cellular concept was developed and introduced by the Bell Laboratories in the early 1970s. One of the most successful initial implementation of the cellular concept was the advanced mobile phone system (AMPS), which has been available in the United States since 1983. A cellular system is a high capacity land mobile system. The available frequency spectrum is partitioned into discrete channels which are assigned in groups to geographic cells. Each cell covers a Geographic Service Area (GSA). The discrete channels are capable of being reused in different cells within the service area. Thus the principle of cellular systems is to divide a large geographic service area into cells with diameters from 2 to 50 km, each of which is allocated a number of radio frequency (RF) channels. Transmitters in each adjacent cell operate on different frequencies to avoid interference.

MULTIPLE ACCESS TECHNIQUES


           Multiple Access is a multiplexing technique in which the signals to be multiplexed originate at different at different locations. The simplest multiple access scheme is the one used by radio and television broadcasting stations. There are three types of multiple access:

§Frequency Division Multiple Access (FDMA)

§Time Division Multiple Access (TDMA)

§Code Division Multiple Access (CDMA)

 

  

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