Hybrid iterative multiuser receiver for a coded DS-CDMA system

The paper presents a suboptimum multiuser receiver for a multipath direct-sequence code division multiple access (DS-CDMA) system with forward error correction (FEC) coding. The complexity of the optimal joint receiver is well known to be exponential with the number of users and the memory of the FEC code. Therefore, we propose a hybrid structure which applies the turbo multiuser detection principle, not only to improve performance in the system, but also to reduce complexity in the receiver. This structure uses a moderate-complexity detector (MCD), based on a linear detection technique, on the first iteration of the receiver and then, for further iterations, a suboptimal radial basis function detector (SRBF) is applied. The aim of the MCD is solely to establish a level of confidence related to how likely the transmitted information can be correctly detected. Using this information, a preselection technique is applied to reduce the complexity of the optimal radial basis function detector which is used for subsequent iterations. These two modules together operate as the SRBF detector. Numerical results show that good performance is achieved by this hybrid receiver at a significantly reduced complexity.