Experiments on coherent adaptive antenna array diversity for wideband CDMA mobile radio

In wideband DS-CDMA (W-CDMA) in which mobile multimedia services up to 2Mbps will be provided, adaptive antenna array diversity can be applied to reduce multiple access interference (MAI), especially in cases of severe interference from high rate users. A pilot symbol-assisted coherent adaptive antenna array diversity (PSA-CAAAD) receiver is implemented for W-CDMA mobile radio and its performance in a multi-path fading environment is evaluated both in laboratory and field experiments. The PSA-CAAAD receiver comprises an adaptive antenna array based on a minimum mean square error (MMSE) criterion and Rake combiner. It is demonstrated from the experimental results that the nulls could be precisely directed toward the interfering signals under a real multi-path propagation environment. Compared to antenna diversity with the same number of antennas, the PSA-CAAAD receiver can significantly reduce the interference from high bit-rate users. For a two-user case (one interfering-user with high transmit power), the required signal-to-interference plus background noise ratio (SIR) for obtaining the average BER of 10(-3) is found to be reduced by about 4.5 dB with a 4-element PSA-CAAAD receiver compared to 4-branch antenna diversity in a real multi-path propagation environment.