Group Metric Decoding for Synchronous Frequency-Selective Rayleigh Fading Multiple-Access Channels

|We propose the new Group Metric (GM) decoder for convolutionally coded synchronous multiple-access channels. The GM decoder makes decoding decisions for one user, but incorporates multiuser information in its metrics. This decoder will have a reduced complexity which is exponential in the sum of encoder memory and the number of users. The soft-decision maximum-likelihood (ML) joint decoder can be readily described as in [1]. This optimal decoder su ers from a high complexity requirement which is exponential in the product of encoder memory and the number of users. Numerical results show that the performance gap between the GM and ML decoders can be small.