Iterative multi-user detection of trellis code multiple access using a posteriori probabilities

Iterative detectors for trellis code multiple access (TCMA) are suggested as an alternative to the joint maximum likelihood sequence detector (MLSD). Interleavers are introduced in the TCMA system as a new feature to separate the users. This implies that MLSD is now too complex to implement. The conventional interference cancellation (IC) detector has lower complexity, but its performance is shown to be far from acceptable. Another iterative detector having close to single user performance is therefore suggested. Instead of using IC, this detector updates the branch metric for every iteration and avoids the standard Gaussian approximation. It is also shown that the users can be detected when the interleaver is the only user specific feature in the TCMA system.