Noncoherent multiuser detection of DS-CDMA over multipath fading channels

The problem of joint channel estimation and multiple access interference suppression for an asynchronous code-division multiple-access system is studied. A low-complexity sliding-window scheme is proposed for channel tracking based on the expectation maximization (EM) algorithm and a noncoherent maximum a posteriori probability (MAP) multiuser detector. By exploiting the features of the discrete random phase ambiguities of channel estimates using the EM algorithm, the proposed scheme can track channel phase even if the channel is in a deep fade. In conjunction with iterative soft interference cancellation, the proposed detector can achieve a near single user system performance with polynomial complexity in the number of users.