Near optimum low complexity MMSE multi-user detector

In this paper we propose a novel multiuser detector for the synchronous CDMA system. Its BER performance approaches the optimum MMSE multiuser detector while the complexity only polynomially increases to the number of active users. We also demonstrate its complexity and performance against the optimum MMSE multiuser detector and decorrelator. In addition to the synchronous AWGN channel case, we also provide the mechanism for the asynchronous case, Rayleigh fading channel case, and frequency selective channel case.