Semi-blind space-time receiver for multiuser detection of DS/CDMA signals in multipath channels

We consider the design of a new space-time receiver that is useful in heavily loaded DS/CDMA systems when only small data records are used in detection. This property is desirable for detection of users of high mobility in crowded systems. The receiver is based on the integration of ESPRIT-based space-time beamforming with multiuser detection based on the constant modulus (CM) property. The beamformer exploits the shift invariance property of the space-time data matrices across the antenna array, and extracts the desired signal along with a small amount of interference. The subsequent multiuser detection stage, which uses the analytical constant modulus algorithm (ACMA), then easily detects the desired signal. In order to avoid association and convergence problems, a small number of zero (off) symbols are added in each block (hence the term semi-blind) so that the ACMA yields a unique solution in a one-shot procedure. Computer simulation results demonstrate that the proposed receiver has a significant performance advantage compared to several other receivers, in the above difficult scenario. Thus the receiver may be a useful candidate for detection in dynamic and crowded systems.