Digital Cellular Systems (CDMA)

Several factors should be taken into account, in the cellular system design. A short review of the most important factors follows:

The designer has to put care in the minimum separation between two co-channel cells, based on the co-channel interference reduction factor, q.

The handoff is the necessary overhead in order to switch the call to a new frequency channel in a new cell site without either interrupting the call or alerting the user. Fortunately, based on its intrinsic characteristics, CDMA has a soft handoff problem.

In FDMA and TDMA, during a call process, different frequencies are assigned to different calls. The total allocated channels will be divided by k. There are k sets of frequencies; and each cell operates its own set of frecuencies.

The reverse-link power control is for reducing near-end to far-end interference. The interference occurs when a mobile unit close to the cell site can mask the received signal at the cell site so that the signal from a far-end mobile unit is unable to be received by the cell site at the same time.

The forward-link power control is used to reduce the neccessary interference outside its own cell boundary.

Last but not least, The capacity of cellular system can be increased by handling q (co-channel interference reduction factor) properly.