4 - Multiuser detection techniques for multiple-access coherent antipodal chaos-shift-keying systems

Abstract

This chapter discusses the use of linear and nonlinear multiuser detectors in a multiple-access antipodal chaos-shift-keying (CSK) system (MA- antipodal chaos shift keying (ACSK)). It reviews the development of some analytical techniques for evaluation of the bit error rates (BERs) of the system. The multiuser detection is effective to combat the multiple-access interference (MAI) in conventional direct-sequence code-division-multiple-access (DS-CDMA) systems. Based on the available spreading codes, the operating principle of a multiuser detector is to cancel the interference between the users, and to jointly decode the transmitted symbols. The suboptimum multiuser detectors are broadly classified into: the linear detectors and the subtractive interference cancellation detectors. For the linear detectors, a linear transformation is performed at the receiver to mitigate the MAI. For the decorrelating detector, the interference can be completely eliminated. The parallel interference cancellation (PIC) detector is a nonlinear multiuser detector that cancels the total interference for all the users simultaneously. The detector requires accurate knowledge of the spreading sequences of all the users as well as an estimation of the transmitted symbols.