MPOE Based Prefiltering and MRT Beamforming for DS-CDMA Systems

In order to reduce the complexity of the mobile receiver, we propose a prefilter model using a linear FIR pre-filter for minimizing the probability of error (MPOE) in multiuser transmission scenario. We consider downlink transmission and assume complete knowledge of the channel at the base station. In order to fully utilise the knowledge available at the transmitter, the filter weights are computed conditioned on the transmitted bit vector sequence. This makes the computation of the optimal coefficients linear in the number of users as opposed to the exponential complexity otherwise. Weights of FIR prefilter are computed by minimizing the conditional probability of error (MPOE) and the mean square error (MMSE). To improve the performance further in multipath fading environment, we consider maximum ratio transmission (MRT) beamforming at the base station. Simulation results are provided to illustrate the performance of the proposed system model