Efficient multiuser detectors for intersymbol interference channels

A general framework is developed for addressing problems of multiuser detection in wireless communication systems operating in the presence of time- and/or frequency-selective fading due to multipath propagation. In particular, a state-space description of the canonical multiple-access system as a multiple-input multiple-output linear system is used to obtain minimum mean-square error multiuser equalizers having efficient recursive implementations in the form of Kalman filters. These algorithms effectively suppress both intersymbol and interuser (multiple-access) interference, yielding near-far resistant receivers that can reduce power control requirements. More generally, the equalizers make efficient use of all available temporal, spectral, and spatial diversity in the system, and can be used in conjunction with both conventional CDMA and more recently proposed spread-signature CDMA systems. Decision-feedback implementations of the equalizers are also described.