Adaptive MMSE detection for asynchronous dual-rate CDMA systems: time-varying versus time-invariant receivers

We deal with the problem of blind adaptive MMSE interference suppression in asynchronous dual-rate CDMA networks. Since MMSE detection of the high-rate users requires periodically time-varying processing, the conventional recursive-least-squares (RLS) algorithm does not converge to the true optimum solution. As a consequence, a modified blind "cyclic" RLS algorithm is derived, suited for decoding the high-rate users, which typically requires periodically time-varying processing. Furthermore, simulation results are also presented, showing that the modified RLS algorithm outperforms the conventional RLS in most cases of practical importance.