Cellular Telephony in Telecommunication
Cellular Telephony was developed by Martin Cooper, a Motorola researcher and executive, at Bell Laboratories in 1973, he discovered the first mobile telephone in the world. It establishes call, maintains it and terminates as the call is over.
It is a modern system that is designed to communicate between two moving units or moving telephone sets, which is called Mobile Station (MS). The basic difference of this system with a general wireless network is that in case of later the stations are static ones, they don’t move. But in the case of the former, the stations may travel from one place to another while in a call.
To make this tracking easy the service provider divides the area into small regions are called cells. Each cell contains a control office with a tower for transmission. The office is called the Base Station (BS). All base stations are connected to a central controlling office is called the Mobile Switching Centre (MSC). The MSC coordinates communication between the base stations and with the landline telephone exchange.
In Telecommunication, There are two types of methods of Cellular Telephony:
When a call is established a unique frequency channel is provided to the communication. It is not possible to provide a unique channel to all the users because of the limited band of frequency permitted for cellular telephony.
A frequency pattern is a configuration of N cells in which each cell uses a unique set of frequencies. Here N is called frequency re-use factor.
When the user of a mobile station dials a number, the MS searches for a strong signal for setting up a channel. Once the channel is set up it sends the destination phone number to the nearest BS. The BS relays the data to the MSC. The MSC sends the data to the telephone central office for searching the receiver. The receiver may be present under another MSC. The MSC searches for the mobile station by generating a query signal to each cell.
Once the destination mobile station is found, the MSC transmits the ringing signal to the receiver and the result is relayed back to the calling MSC and a connection is established between the two mobile stations.