Two-stage receivers for DS/CDMA systems

In this paper, a two-stage decoding scheme is proposed for direct-sequence code-division multiple access (DS/CDMA) systems. Specifically, to ease the complexity, the virtual subcodes are first synthesized from the real transmitting (spreading) code. The optimum combining weight vector for each sub-code is then constructed in accordance with the linearly constrained minimum variance (LCMV) criterion. Finally, the subcode weights are converted back into a full-dimension weight vector acting on the original code via a dimension recovery transformation and post-combining. Numerical results demonstrate that the proposed two-stage receiver can approach the same performance of the MMSE receiver with lower computation complexity required.