Blind turbo multiuser detector with unknown intercell interferences

Abstract

We consider the problem of iterative blind multiuser detection for multi-input-multi-output (MIMO) systems, which consist of K uplink asynchronous DS-CDMA users and n/sub R/ receive antennae, in presence of both intra- and intercell interference. The proposed receiver typically has only the knowledge of the first spreading codes of K/sub in/ /spl les/ K users inside the cell and ignore unknown interference of K - K/sub in/ users outside the cell. The proposed schemes in this paper present two types of iterative blind receivers motivated from the concept of generalized sidelobe canceller (GSC) to separate the problem into two components one in constrained subspace (inner cell space : H/sub in/) and one orthogonal to it (unknown interference plus noise space). The knowledge of intracell channel matrix H/sub in/ is required for our algorithms. So, two types of blind channel estimation both subspace and POR (power of R) methods are used for comparative performances as channel estimation and bit error rate (BER) of iterative receiver. The proposed detectors utilize the computation of log likelihood ratios (LLRs) fed from their turbo decoders at previous iteration to blindly suppress intracell interferences and residuals interferences left by iterative process. The computations of LLRs from iterative blind multiuser detector are refined to their turbo decoders by iterative fashions.