Adaptive antennas for frequency re-use in every cell of a GSM network

The capacity of cellular radio networks can be considerably increased if carriers are reused in every cell. The paper shows how a well-known technique (an adaptive antenna) can, together with other techniques, be used to combat the resulting co-channel interference to make this possible. Adaptive antennas have been employed in military systems for many years as a countermeasure for deliberate, high power jamming. Their use in civil applications such as cellular radio to counter co-channel interference has, it is believed, yet to be exploited in practical systems. The application of adaptive antennas to this environment is considered and an implementation suitable for GSM (also DCS1800, DCS1900) networks is developed. Some corresponding simulation results are presented. The elements of an adaptive antenna generally need to be separated by about half a wavelength. This means, for the frequency bands considered, that an adaptive antenna is only practically applicable at the base station and cannot be applied to a hand held mobile. Thus all the potential gains of an adaptive antenna can be achieved for the uplink but they can only be partially realised for the downlink. Other interference reduction techniques are required. This is also discussed