Frequency reuse

The ability of specific channels assigned to a single cell to be used again in another cell, when there is enough distance between the two cells to prevent co-channel interference from affecting service quality. The technique enables a cellular system to increase capacity with a limited number of channels. (Cingular)

Technology that allows frequencies to be re-used after they have been vacated by a mobile-phone user leaving a particular cell. One measure of a system's effectiveness is how far the initial user of a specific frequency must travel away from the cell site before the frequency may be re-used. (Motorola)

The increased capacity in a cellular network, comparing to a network with a single transmitter, comes from the fact that the same radio frequency can be reused in a different area for a completely different transmission. If there is a single plain transmitter, only one transmission can be used on any given frequency. Unfortunately, there is inevitably some level of interference from the signal from the other cells which use the same frequency. This means that, in a standard FDMA system, there must be at least a one cell gap between cells which reuse the same frequency.

The frequency reuse factor is the rate at which the same frequency can be used in the network. It is 1/n where n is the number of cells which cannot use a frequency for transmission.

Code division multiple access-based systems use a wider frequency band to achieve the same rate of transmission as FDMA, but this is compensated for by the ability to use a frequency reuse factor of 1. In other words, every cell uses the same frequency and the different systems are separated by codes rather than frequencies.

Depending on the size of the city, a taxi system may not have any frequency reuse in its own city, but certainly in other nearby cities, the same frequency can be used. In a big city, on the other hand, frequency reuse could certainly be in use.

(Wikipedia)