Performance of linear multiuser detectors in time-varying multipath fading CDMA channels

A class of linear multiuser detectors in which multiple-access interference is eliminated prior to combining is considered for application in rapidly fading multipath channels. Performance of an adaptive coherent receiver with maximum-ratio combining and that of a differentially coherent receiver with equal-gain combining are evaluated analytically, showing functional dependence on the fading rate of the channel and the number of active CDMA users. Fading-induced imperfect channel tracking leads to performance degradation, resulting in irreducible bit error rates.