Blind low rate multiuser detection for multirate multicarrier CDMA systems using antenna array

A space-time low rate blind multiuser detector for synchronous uplink multirate multicarrier CDMA systems with antenna arrays at the base station is proposed to mitigate multiple access interference and introduce spatial diversity. After high rate physical users are modelled as several corresponding low rate virtual users, the space-time signature vectors of the low rate virtual users are derived. Then, these space-time signature vectors are estimated blindly based on a subspace projection algorithm to realize multirate multiuser detection without computing the ambiguous complex factor between the true and the estimated signature vectors. The proposed scheme can increase system performance and capacity by introducing spatial domain processing. Simulation results demonstrate that the performance of the proposed scheme is close to that of a minimum mean-square error multiuser detector with perfect channel information and that it can increase the system capacity about two times to employ a two-element antenna array.