AN ADAPTIVE ARRAY FOR MOBILE COMMUNICATION-SYSTEMS

The rapid increase in the number of users of mobile telephones places challenging demands on future communication systems. Frequency hopping and advanced coding techniques have already been implemented to reduce the unavoidable increase of co-channel interference. Despite these improvements, it has turned out that it still will be difficult to accommodate enough users. In this paper, the application of adaptive antenna techniques to additionally increase the channel capacity is discussed. Directional sensitivity is obtained by employing an antenna array at the base station, possibly both in receiving and transmitting mode. A scheme for separating several signals at the same frequency is proposed. The method is based on high-resolution direction finding followed by optimal combination of the antenna outputs. Comparisons to a method based on reference signals are made. Computer simulations are carried out, for testing the applicability of the technique to scattering scenarios that typically arise in urban areas. The proposed scheme is found to have great potential in rejecting co-channel interference, albeit at the expense of high computational requirements.