Co-channel cells: Frequency reuse implies that in a given coverage area, there are several cells that use the same set of frequencies. These cells are called co-channel cells.

Causes:

1. Reduction of D/R ratio, which reduce distance between two co-channels.

2. Use of omnidirectional antennas at the base station.

3. Increasing the antenna height at the base station.

Effects of co-channel interference on system capacity:

The parameter Q, called the co-channel reuse ratio, is related to cluster size N,

$Q=D/R=\sqrt{3N}$

A small value of Q provides larger capacity since the cluster size N is small, whereas a large value of Q implies smaller level of co-channel interference. Thus with reduction in cp-channel interference there will reduction in system capacity.