GSM CELLS

There are two main types of cells:

Omni directional cell

An omni-directional cell (or omnicell) is served by a BTS with an antenna which transmits equally in all directions (360 degrees).

Sector cell

A sector cell is the area of coverage from an antenna, which transmits, in a given direction only. For example, this may be equal to 120 degrees or 180 degrees of an equivalent omni- directional cell. One BTS can serve one of these sector cells with a collection of BTS’s at a site serving more than one, leading to terms such as two-sectored sites and more commonly, three-sectored sites.

Typically, omni-directional cells are used to gain coverage, whereas sector cells are used to gain capacity.

  Cell types

Reuse of frequency is an important factor when planning a GSM network. The frequency re-use patterns recommended for GSM are the 4/12 and the 3/9 pattern. 4/12 means that there are four three-sector sites supporting twelve cells using twelve frequency groups.

   

 Frequency reuse patterns