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 2 Mbps 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 multipath 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 multipath 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 multipath propagation environment