Independent component analysis with code information utilization in DS-CDMA signal separation

We consider symbol estimation in a direct-sequence code division multiple access (DS-CDMA) communication system. Among the existing methods, some assume the chip timing and/or channel to be known, but in the most challenging approach neither is assumed to be known, and independent component analysis (ICA) can be used. A drawback of the ICA methods in CDMA is that they do not utilize the known code which is the only a prior information available. In this paper we remove this disadvantage and introduce a way to efficiently exploit the known code information in ICA methods. Experiments with DS-CDMA downlink data, and the previously reported linear ICA method show that the scheme gives the possibility to reach a performance which is competitive with the blind linear MMSE detector, and the traditional single user detector. The experiments speaks for the usefulness of the scheme especially in a severe multipath environment, where channel and chip timing estimation errors are more likely to occur, usually quite dramatically degrading the estimation performance.