Layered space-time multiuser detection over wireless uplink systems

In this paper, we investigate the use of layered space-time, also known as Vertical-Bell Laboratories Layered Space-Time (V-BLAST) scheme, for multiuser detection in fading channels. The multiple transmit antennas in V-BLAST are treated as individual mobile station transmitters, while the base station consists of multiple receive antennas. In the proposed system, users are organized in groups and allocated a unique spreading code within the same group. Using these codes, we are able to separate the different groups, and layered space-time algorithm is then invoked to further remove the remaining interference between users. A decorrelator-type receiver based layered space-time detection is proposed for both complex and real constellations. For the latter case, we derive our receiver after evaluating and comparing the performance of two decorrelators based on the V-BLAST scheme. It is demonstrated that a significant performance improvement and increase in system capacity is obtained with very low spreading factors. Further results are also introduced by considering reduced complexity receivers based on Serial Layered Space-time Group Multiuser detection, and Parallel Layered Space-time Group Multiuser detection.