Performance Analysis of an Improved MMSEMulti - user Receiver for Mismatched Delay

| Motivated by the fact that time delays in a practical Direct-Sequence Code-Division Multiple-Access system can never be perfectly estimated, an improved Minimum-Mean Squared-Error (MMSE) based receiver is proposed and analyzed. Via the simple assumption of a probability distribution for the delay estimation errors, the proposed receiver can achieve performance superior to that of the conventional MMSE receiver. The performances of this improved receiver and the conventional MMSE receiver are compared in terms of mean squared error, probability of error, and asymptotic multiuser eeciency (AME). As the original deenition of AME does not consider mismatched channels, the behavior of three single-user receivers bearing imperfect delay estimation is also investigated. These single user receivers are employed to deene a more appropriate AME. Finally, an eecient update mechanism to accommodate dynamic channel statistics, and thus practical implementation, is proposed.