A subspace-based iterative group blind multiuser detection and decoding for coded CDMA systems

A turbo multiuser receiver is proposed for the uplink of channel-coded code-division multiple-access (CDMA) systems with unknown interference. The proposed receiver consists of a first stage that performs soft interference cancellation and group blind linear minimum mean-square error (MMSE) filtering followed by a second stage of channel decoding. The proposed group blind filter satisfies the MMSE criterion to suppress the remained interference caused by known users based on the spreading sequences and the channel characteristics of these users and blindly suppress the remained interference caused other unknown users using a subspace-based method. The proposed receiver is suitable for suppressing high intercell interference. By exchanging soft information between the first and second stages, the receiver performance is improved through iteration. Simulation results show that the proposed group blind receiver significantly outperforms the conventional turbo multiuser detector in the presence of intercell interference.