A novel multiuser detection scheme combining adaptive MMSE receiver and parallel interference canceller for near-far resistance

Abstract

The adaptive minimum mean-squared error (MMSE) detector for direct-sequence code-division multiple access (DS-CDMA), is attractive because it has a simple structure. Also, the adaptive nature of the detector allows it to learn the required information and adjust it to the prevailing interference and noise environment. However, it shows performance degradation in a severe near-far environment. On the other hand, a parallel interference cancellation (PIC) detector has the potential to combat the near-far problem, since it is designed to subtract out interference. However, this performance depends on its data estimates. A novel multiuser detector is proposed to combat the near-far problem in DS-CDMA schemes. It utilizes the advantages of the two detectors by combining an adaptive MMSE multi-user detector and PIC detector. The focus of the paper is on the near-far resistance capability of the detector. Simulation studies shows that the proposed detector is immune to the near-far problem on top of its improved bit error rate.