ABSTRACT
This chapter is an introduction to multiuser detection for code division multiple-access systems operating over fading channels. It mainly focuses on the relevant case of slow frequency-selective fading channels, which are frequently encountered in multiuser high-data-rate communications over wireless links. First, the problem of multiuser detection with known channel state information is considered, i.e., assuming knowledge of the channel impulse response, either for all active users or for the user of interest only. In particular, the optimum multiuser detector, the linear multiuser detectors, and interference cancellation receivers are reviewed and compared. Then, the focus of the chapter is shifted toward the problem of adaptive and blind multiuser detection with no channel state information. First, multiuser channel estimation techniques based on the least squares criterion are reviewed and then several linear detectors, requiring knowledge of the spreading code of the user of interest only, are illustrated and compared. In particular, the chapter emphasis is on recursive least squares (RLS) trained adaptive multiuser detection and on the exposition of blind techniques for joint suppression of multiuser interference and intersymbol interference.
