Performance of reduced-complexity decoding algorithms for turbo TCM signals in Rayleigh fading channels

Turbo trellis-coded modulation (TTCM) is a promising bandwidth-efficient transmission scheme, particularly suited for applications in wireless communication systems. Turbo TCM results from the combination of Ungerboeck´s TCM technique with the idea of turbo coding. In this paper, turbo TCM transmission with reduced-complexity decoding algorithms in Rayleigh fading channels is studied. In particular, we examine performance of two recently proposed modifications of the Log-MAP algorithm, that is, Log-MAP-n and Log-MAP delta algorithms which offer substantial decoding effort savings with respect to conventional Log-MAP. Simulated performance of simplified algorithms are compared to those of optimal Log-MAP and low-complexity Max-Log-MAP.