Optimal user ordering and time labeling for decision feedback detection in asynchronous CDMA

A strategy for user ordering and time labeling for a decision feedback (DF) detector in asynchronous Code-Division Multiple Access (CDMA) communications is discussed. Ordering and labeling would at first appear to be of a complexity exponential in K, the number of users. Surprisingly, optimal sequencing requires only O(K⁴) operations, and is needed only once per packet: it is thus a cheap way to obtain an often marked improvement in performance, compared to power-ordering and chronological labeling.