Blind multiuser receiver for space-time coded CDMA signals in frequency-selective channels

Blind detection of a desired user´s signal in a direct sequence code division multiple access (DS-CDMA) system using multiple transmit and receive antennas and space-time (ST) block coding is considered. We consider Alamouti´s ST coding scheme for two transmit antennas designed for flat-fading channels, but allow the channel to be frequency-selective. Past work on blind detectors for ST-coded DS-CDMA systems is restricted to flat-fading channels. A (spreading) code-constrained inverse filter criterion (IFC)-based linear blind detector to detect a desired user´s signal for uncoded CDMA signals exploiting only a single transmit and single receive antenna was recently presented by Tugnait and Li. In ST-coded multi antenna CDMA systems, a user signal may be treated as the superposition of several virtual user signals derived from the same parent user. In this paper a novel approach combining the code-constrained IFC and a penalty function is developed to simultaneously extract all virtual users associated. with a given ST-coded user. Global minima of the proposed cost functions are analyzed.