An efficient multistage MMSE multiuser receiver for asynchronous CDMA systems with space-time coding

An adaptive MMSE detection scheme equipped with multiple transmitter and receiver antennas for asynchronous space-time block coded (STBC) CDMA systems is presented. A computationally efficient version of this MMSE detection scheme is developed for implementation in real-time systems; it utilizes a correlation-subtraction architecture based on the reduced-dimension multistage matrix Wiener filter (MMWF) introduced by P. Thanyasrisung et al. (see IEEE Milcom, p.569-73, 2000). With this multistage structure of the MMSE receiver, the tasks of an explicit estimation of the covariance matrix and its inversion are released. In simulations it is shown that the full-rank steady-state performance is achieved at a significantly lower rank and a much smaller number of observed data samples. Moreover, the performance advantage of ST-coded CDMA systems is evaluated as well.