Iterative equalization/decoding of TCM for frequency-selective fading channels

The severity of frequency-selective fading channels necessitates the combining of multiple diversity sources to achieve acceptable performance. Traditional techniques often perform the combining of different sources of diversity separately which may result in a significant performance degradation (uncoded systems, for example, outperform TCM codes when used in an interleaved frequency-selective fading channel with separate decoding and equalization). Recently, it was demonstrated that soft decision equalization techniques are necessary and sufficient for the application of TCM techniques over such channels. This enabling feature was obtained with relatively simple, low-latency non-iterative algorithms. In this paper we investigate the applicability of more complex iterative equalization/decoding algorithms. Several configurations are examined using simulation and further improvements are demonstrated.