Capon multiuser receiver for CDMA systems with space-time coding

We present in this paper a linear blind multiuser receiver, referred to as the Capon receiver, for code-division multiple-access (CDMA) systems utilizing multiple transmit antennas and space-time (ST) block coding. The Capon receiver is designed by exploiting signal structures imposed by both spreading and ST coding. We highlight the unique ST coding induced structure, which is shown to be critical in establishing several analytical results, including self-interference (i.e., spatially mixed signals of the same user) cancellation, receiver output signal-to-interference-and-noise ratio (SINR), and blind channel estimation of the Capon receiver. To resolve the scalar ambiguity intrinsic to all blind schemes, we propose a semi-blind implementation of the Capon receiver, which capitalizes on periodically inserted pilots and the interference suppression ability of the Capon filters, for (slowly) time-varying channels. Numerical examples are presented to compare the Capon receiver with several other training-assisted and (semi-)blind receivers and to illustrate the performance gain of ST-coded CDMA systems over those without ST coding.