Forward link interference suppression using multiple element adaptive array at mobile terminals

The co-channel interference of the forward link of CDMA mobile systems results from two sources: the serving base station which also serves other users within the same cell and adjacent base stations. The former can be greatly reduced by using orthogonal spreading but the later has to be processed by other means. We study the application of multiple element arrays at mobile terminals for the purpose of suppressing interference from the other non-serving base stations. The adaptive array has the potential to enhance the SINR linearly proportional to the number of elements but other factors limit our choice of the maximal number of elements used. With such a limitation in mind we investigate the potential to process and cancel the effects of stronger interfering signals based on the knowledge of the spreading codes for all base stations and the estimates of the spatial signature vectors. We conclude that by processing the first two or three strangest interfering signals we achieve the substantial performance gain, hence we can reduce the total number of elements required by conventional adaptive beamforming techniques