Smart antennas for multiuser DS/CDMA communications in multipath fading channels

Abstract

Smart antennas, with spatial processing, used in code division multiple access (CDMA) multiuser communications can enhance range, reliability and capacity. Moreover, adaptive beamforming techniques can remove unwanted noise and jamming from the received signal. We use a least mean squares algorithm and propose four adaptive antenna receiver structures for a direct-sequence (DS) CDMA multiuser environment with multipath fading channels. Narrowband and wideband adaptive array receiver structures are considered. LMS algorithms are employed in both narrowband and wideband receiver structures to adjust the spreading code coefficients. We call these new schemes Wiener code filters. The weights of the adaptive beamformer and the spreading code are updated every bit interval, so the computational complexity is very low. Simulation examples are given to compare the performances of the proposed receiver structures.