Multiuser detection in mismatched multiple-access channels

In this paper we consider an additive white Gaussian noise multiple-access channel and investigate the performance degradation of several multiuser detectors due to imperfect knowledge of 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 (AME's) 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.