Belief-directed sequential probabilistic data association multiuser detector

We propose in this paper a novel soft-input-soft-output (SISO) multiuser detector for synchronous CDMA systems. The detector is called the belief-directed sequential probabilistic data association detector (BD-SPDAD). The BD-SPDAD is developed based on a general framework of the probabilistic data association detector (PDAD) proposed in (Y Huang et al, IEEE Int. Symp. on Inf. Theo., 2004). However, novel extensions to the general framework are proposed for the BD-SPDAD, which result in a low complexity sequential implementation. Specifically, the complexity of the BD-SPDAD is reduced from O(K³) of the original PDAD to O(K²), where K is the number of users in the system. Moreover, we show through simulation that the performance of the BD-SPDAD is comparable and even better than the original PDAD especially in high signal-to-noise regions.