Achieving high capacities in CDMA systems using multiuser detection based on BLAST

In this paper, we investigate the use of layered spacetime scheme, known as V-BLAST, for multiuser detection over the uplink of a DS/CDMA communication system. The multiple transmit antennas in V-BLAST are treated as individual mobile station transmitters, while the base station consists of multiple receive antennas. The layered space-time algorithm is then invoked to detect the signals from all users. In addition, CDMA is also applied. Groups of users are arranged and allocated the same signature sequence or spreading code. The groups of users are first separated using the group spreading codes, and the layered space-time detection algorithm is then invoked to further remove the remaining interference. It is demonstrated that a significant performance improvement and increase in system capacity are obtained with very low spreading factors.