Iterative semi-blind space-time multiuser detection for MC-CDMA uplink system

Abstract

Iterative multiuser detection and space-time coding are two promising techniques to increase the capacity and performance of coded multiuser systems in wireless channels. We present iterative multiuser detection schemes for space-time block coded multicarrier CDMA system with multiple transmit and receive antennas. We consider a more general case of an uplink system in the presence of both intracell and intercell interferences. We propose two types of iterative semi-blind space-time receivers for such an uplink environment. The first is based on the minimum mean square error criterion and the second is a hybrid scheme, based on a combination of parallel interference cancellation and linear multiuser detection. These iterative receivers are derived using a subspace approach, utilizing known users' information for the computation of log-likelihood ratios (LLRs), while blindly suppressing the unknown interference. The LLRs are refined successively during the iterative process by using the extrinsic information available through decoding of all known users. Turbo code is used for channel coding. Simulation results in a frequency-selective Rayleigh fading environment are presented to verify the performance of the proposed schemes.