CANCELLATION OF EXTERNAL AND MULTIPLE-ACCESS INTERFERENCE IN CDMA SYSTEMS USING ANTENNA-ARRAYS

This paper deals with the problem of multisensor-multiuser detection i n CDMA systems in the presence of interferences external to the system . The paper presents a new method able to estimate the spatial signatu re of all active users projected onto the subspace orthogonal to the e xternal interference. With this information a specific beamformer can be designed for each user in order to combat the external and multiple access interference. The method performs in frequency non-selective m ultipath scenarios as they arise from some CDMA satellite and indoor c ommunications systems. The estimation process does not require any tra ining signal nor any a priori spatial information. It exploits the tem poral structure of CDMA signals and extract the required information d irectly from the received signals. In addition, the method is independ ent of the nature of the external interference and it can cope with na rrow-band and wide-band interfering signals. (C) 1997 Elsevier Science B.V.