Asymptotically optimal CDMA receiver: perfect MAI cancellation

Multiple access interference (MAI) as well as multipath distortions are two major obstacles in multiuser communication. The MAI in the received data vectors can be eliminated by projecting the received data onto the subspace orthogonal to the code space of interfering users. After this operation, an equivalent single user model with AWGN is obtained. Therefore various detection techniques, e.g., maximum SNR, subspace, constrained optimization, iterative least squares with projection (ILSP), etc. can be successfully applied to estimate transmitted symbols and the multipath channel of the desired user, but with reduced complexity and asymptotically optimal performance. The proposed receiver is simulated by ILSP and constrained optimization method and its performance compared with the RAKE receiver and the decorrelating receiver. Much lower bit error probability is achieved for a wide range of SNRs.