Projection-based multiuser receiver over frequency selective channels

In multiuser communication, the receiver´s performance is degraded by multiuser interference (MUI) as well as multipath distortions. This paper aims at elimination of these side effects. By projecting the received data onto the orthogonal code space of interfering users, equivalent single user and MUI free data vectors are obtained. Since the projection matrix consists of orthonormal bases, the whiteness of original additive Gaussian noise is still preserved after projection operation. Therefore various detection techniques, e.g., constant modulus algorithm (CMA), subspace, 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 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 signal to noise ratios