Performance and complexity trade off in CDMA multiuser communications

In this paper, we describe a new tree-based CDMA receiver that can optimally trade complexity for detection performance. It yields the detector with the best detection performance for a given desired complexity level. Alternatively, it yields the lowest complexity receiver for any given desired detection performance. We describe a technique for designing receivers with linear complexity (including the optimal linear detector and decorrelator). We then explain how we can increase performance at the expense of a minimal increase in complexity. We show that as complexity increases to the level of that of the optimal receiver, our design approach automatically produces the optimal receiver. We also explain how our approach can be used with a minimum-mean-square-error design criterion and coded CDMA transmission. Finally, we illustrate with several examples the superiority of the receivers designed with our approach and discuss their advantages.