Design of MMSE multiuser detectors using random matrix techniques

Reduced-rank MMSE receivers using asymptotic weights reduce receiver complexity while maintaining good performance in long-sequence DS-CDMA systems. In this paper, we analyze such receivers in multipath fading channels and extend their design to multicarrier CDMA (both uplink and downlink). An explicit expression is obtained for the asymptotic eigenvalue moments of the interference autocorrelation matrix and for the asymptotic weights derived there from and used in the reduced-rank receiver. The full-rank MMSE receiver is also considered for multicarrier CDMA and a fixed point of equation of the asymptotic maximum output SINR is derived, which particularizes to the Tse-Hanly fixed point equation for the special case of DS-CDMA. An explicit expression of the MMSE spectral efficiency is proposed for multicarrier CDMA.