Improved performance of MMSE multiuser receivers for asynchronous CDMA: preliminary results

The minimum mean square error (MMSE) multiuser detector has received great attention as the optimum linear solution for reducing the multiple access interference (MAI) in DS-CDMA systems. In asynchronous frequency selective channels the covariance matrix estimation errors may introduce BER performance degradation. The aim of this paper is to outline such degradation and to improve the MMSE receiver performance by convenient covariance matrix estimations. Two different approaches are introduced. Simulation results are shown in order to validate the effectiveness of the proposed techniques.