Near-decorrelating multistage detector for asynchronous DS-CDMA -real-time decorrelation with multistage architecture

In cellular communications using asynchronous DS-CDMA, the capacity is restricted mainly by the interference in the reverse link. To improve the capacity by decreasing the interference, many techniques for canceling interference in DS-CDMA signals have been proposed and studied. We present a real-time decorrelation scheme for asynchronous DS-CDMA with multistage architecture. One difference from a conventional multistage interference canceler is that our scheme only makes use of users´ spreading codes and their timings. We state the principle of our proposed scheme theoretically, and prove that the performance approaches that of perfect decorrelation when the number of stages are increased. The computer simulation shows that the number of simultaneous users at BER=10^-2 is the same as the processing gain with four stages in AWGN channels. In the case of fast Rayleigh fading channels, it is about half of the processing gain when four stages are used, and increases to seventy percent when eight stages are used