Performance analysis of minimum variance CDMA receivers

Constrained optimization of the receiver's output variance has been proposed as a relatively simple method for designing blind multiuser detectors for DS-CDMA systems. A single constraint is sufficient to avoid signal cancellation in the AWGN case, while multiple constraints should be used in a multipath environment. A max/min approach for optimizing the constraint is proposed, resulting in blind solutions with improved performance. It is shown that the performance of the proposed method approaches that of the MMSE receiver at high SNR, while the constraint parameters converge to the multipath channel parameters. The proposed method does not require knowledge of the interfering users' codes and timing. Simulation results support those performance claims.