Mobile Network Infrastructure
The mobile communication system divides its service area into smaller geographical areas, or cells. Cells vary in sizes, depending on geographical features and physical obstacle to radio transmission. Usually, cells in urban areas are smaller and those in rural areas bigger. Radio frequency for call use in a cell can be used for other cells. Therefore, mobile phone technology can serve more subscribers with the same radio frequency.

Main components of our mobile phone system consists are:

Base station site, physical locations in each cell, one base station equipped at each base station site, containing transmitter, receiver and other devices, communicating with mobile phones in the cell coverage via the radio channel.

Base station controller links and controls a certain number of base stations.

Mobile switching center, used to control base station controller and call routing.

Transmission line, used to link mobile switching center, base station controller, base station and fixed line PSTN to enable mobile phone subscribers to be connected to public fixed line network, to call out and receive long-distance calls.

When a mobile subscriber makes a telephone call, the cellular phone transmits radio signals to the base station with best radio signals, then, the base station transfers the call to the base station controller (BSC) connected to it. The BSC then forwards the call to the mobile switching center. For calls between our mobile subscribers, signals are retransmitted to the cell base station where the called is via the mobile switching center, and this base station transmits the call to the called party. If the call needs to be connected with PSTN, the mobile switching center will retransmit the signal to PSTN.

The capacity of the mobile phone system depends on several factors, including:

Enough cells should usually be designed for a network system, and certain radio frequencies allocated to each cell to meet anticipated subscriber and network traffic needs in every service area. With the increase of cell capacity demands, radio frequencies increase for use in the cell until reaching the design capacity of the mobile system. Capacity increase needs can also be met through the procedure known as cell division, namely, one cell being divided into some smaller cells to enable frequency reuse.