Asymptotic analysis of optimum and sub-optimum CDMA downlink MMSE receivers

In this paper, we investigate the performance of linear receivers for CDMA downlink transmissions over frequency selective channels, the users having possibly different powers. For large spreading factors and under some technical conditions, signal to interference and noise ratios (SINR) at the output of these receivers have simple and easily interpretable expressions. Free probability, a theory which studies in particular the asymptotic behavior of some large random matrices, is used. Two linear receivers are considered and compared: the MMSE receiver and a chip equalizer.