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Minimum Probability of Error Based Prefiltering for DS-CDMA Systems

In order to reduce the complexity of the mobile receiver, we develop two prefilter models using a linear FIR prefilter for minimizing the probability of error (MPOE) in multi-user transmission scenario. We consider downlink transmission. In the first system model we have single common prefilter for all users at the base station transmitter and in the second prefilter design model we consider individual prefilter for each and every user. We 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 also 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 and the mean square error (MMSE). Simulation results are provided to illustrate the performance of the system model