Semi-blind multiuser receiver for space-time coded CDMA systems

In [1], we introduced a linear blind multiuser receiver, referred to as the Capon receiver, for space-time (ST) coded COMA (code division multiple access) systems. The blind Capon receiver was shown to yield a similar performance to that of the optimum linear MMSE (minimum mean squared error) receiver which requires the CSI (channel state information). The proposed blind Capon receiver, however, needs to resolve a scalar ambiguity (with its blind channel estimate) that is inherent to all blind schemes. Furthermore, all blind receivers, including Capon, are relatively slow in convergence. To address these issues, we present herein a semi-blind Capon receiver by capitalizing on periodically inserted training symbols. We show via numerical examples that the semi-blind Capon receiver achieves a better performance than the training-assisted MMSE receiver in (slowly) time-varying channels, even though the latter incurs a much higher training overhead.