Differential and coherent decorrelating multiuser receivers for space-time coded CDMA systems

We consider the problem of multiuser receiver design for code-division multiple-access (CDMA) systems that utilize (differential) space-time block coding for transmission. In particular, we propose two differential and one coherent receivers for such systems. The differential receivers do not require the channel state information (CSI) for detection and, even so, are resistant to multiuser interference (MUI) and time-varying channel fading. The coherent receiver requires only the CSI of the desired user for detection. It yields improved performance over the differential receivers when reliable channel estimates are available (e.g., in slowly fading channels). The proposed differential/coherent receivers are decorrelative schemes that decouple the detection of different users. Both long and short spreading codes can be employed in these schemes. Numerical examples are presented to demonstrate the effectiveness of the proposed receivers.