Multiuser detection in mismatched multiple-access channels

We consider an additive white Gaussian noise multiple-access channel and investigate the performance degradation of several multiuser detectors due to imperfect knowledge of the channel parameters, induced by either estimation errors or sampling/quantization of the receiver´s sufficient statistics. The symbol error rates and the asymptotic multiuser efficiencies (AMEs) of these detectors are examined as functions of both true and approximated channel parameters for 2 asynchronous users. The results quantify the loss of near-far resistance due to parameter estimation errors and demonstrate that detectors which are optimal for ideal conditions are often more sensitive to parameter mismatch. Examples are given which illustrate a reverse ordering of the symbol error rates for these detectors in the high signal-to-noise regime, and also illustrate cases when the conventional matched filter detector exhibits superior performance over multiuser detectors