==Cellular Communication==A cellular mobile communications system uses a large number of low-power wireless transmitters to create cells—the cells — the basic geographic service area of a wireless communications system. Variable power levels allow cells to be sized according to the subscriber density and demand within a particular region. As mobile users travel from cell to cell, their conversations are handed off between cells to maintain seamless service. Channels (frequencies) used in one cell can be reused in another cell some distance away. Cells can be added to accommodate growth, creating new cells in unserved areas or overlaying cells in existing areas.[http://www.IEC.org Source]<br>
There are three main entities in cellular communication
* Mobile station Station (MS)- : A mobile station consists of 2 entities- Equipment equipment and SIM card* Base Transceiver station(BTS) - : A base transceiver station consists of 2 entities- Base a base transceiver(transmitter and receiver) station and Base a base station controller. This The BTS is the antenna tower site.* Main Switching centre(MSC) - Heart : The main switching centre is the heart of the network, Central - the central switching office which controls all the base stations and provides connection with landline phones.Three It performs three main jobstasks. It:# connects calls from sender to receiver,# collects details of the calls made and received, and# supervises operation of the rest of the network components.
==Cellular System Architecture==