Linear multiuser detectors for synchronous CDMA communication over Rayleigh fading channels

We analyze a class of suboptimum linear multiuser detectors for synchronous code division multiple access (CDMA) transmission over Rayleigh fading channels. The general structure of the detectors consists of a bank of matched filters, whose output vector is then linearly processed, and then a set of threshold devices make the final decision. Based on the simple linear structure, the performance of linear minimum mean square error (LMMSE) estimator that has the minimum Bayesian MSE among linear estimators is analyzed. We then propose a modified LMMSE estimator to enhance the robustness in the near-far environment at the sacrifice of slightly larger average error probability compared to the earlier LMMSE estimator