Wireless Mobile Communication

Concept of cellular communication:

In a cellular communication system, a geographical area is subdivided into small regions where each small region is called as a CELL. All communications within a particular cell is done using a specific center frequency which is assigned to that particular cell.

A basic cellular system consists of three parts as listed below:

1. A mobile unit
2. A cell site
3. A mobile Telephone Switching Office (MTSO)

The mobile unit (Mobile Telephone) contains a control unit, a transceiver (combination of Transmitter and Receiver), and an antenna system. Whenever a mobile unit wants to setup a call, it contacts the cell site of the particular cell which it exists at that time. The cell site consists of control unit, antennas, power plant and data terminals. The cell site is in fact acting as an interface to the MTSO. After the mobile unit contacts the cell site, the cell site in turn contacts the MTSO which processes the call further depending  on whether it is a mobile to mobile call or mobile to fixed station call.

Another major situation, which arises frequently while considering the propagation of waves in a mobile environment is usually, called multi path. Multi path arises because of reflections of transmitted signals from man made structures such as buildings.

Long Distance Propagation:

The advantage of a high cell site is that it covers the signal in a large area, especially in a noise-limited system where usually different frequencies are repeatedly used in different areas. However, one has to be aware of the long distance propagation phenomena. A noise-limited system, gradually becomes an interference-limited system as the traffic increases.