Trellis-based multiuser receivers for asynchronous trellis coded DS-CDMA systems

We propose a new reduced-complexity multiuser receiver for asynchronous trellis-coded CDMA systems in AWGN channels. Based on the coding information of a subset of users and the set partitioning principles inherent in TCM, reduced-state trellises are constructed. The Viterbi algorithm is thus used to jointly decode the trellis codes of this subset of users and equalize the multiuser interference of the channel. As a special case of the proposed receiver, we study a structure that decodes only one user and equalizes the multiuser interference. Simulation results show that the performance of the new reduced complexity receiver approaches the trellis-coded single-user bound for both low and high-interference channels. Moreover, we compare the performance of the proposed receiver with that of previously proposed suboptimal structures. Our scheme is found to significantly outperform previously known suboptimal structures