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

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