Iterative multiuser detection for convolutionally coded asynchronous DS-CDMA

A soft-input, soft-output multiuser detection algorithm based on the log-MAP algorithm is presented for asynchronous multiple access networks. The algorithm is applied to a convolutionally coded direct sequence code division multiple access (DS-CDMA) system. The proposed receiver architecture consists of a log-MAP multiuser detector followed by a log-MAP channel decoder. Information is fed back from the channel decoder to the multiuser detector, and processing proceeds in an iterative fashion analogous to the decoding of turbo codes. Simulation results show that the performance of a heavily loaded power controlled DS-CDMA system approaches the single-user bound for both additive white Gaussian noise (AWGN) and fully-interleaved Rayleigh flat-fading channels.