A new receiver structure is proposed €or trellis- coded modulation on multipath fading intersymbol interference (ISI) channels that permits the use of large-state trellis codes. The receiver uses a sequential sequence estimator With the Fano algorithm, and a channel estimator consisting of a fast nom- cursive start-up algorithm for training and the LMS algorith for tracking. During the tracking mode, the channel estimates are updated dynamically by using recent tentative decisions produced by the sequential sequence estimator. This approach results in good tracking even on rapidly varying channels, and reduces the degradation in performance of the sequential sequence estimator due to channel estimation error. The effect of fading is mitigated using both implicit time diversity in the form of interleaved trellis-coded modulation and explicit antenna diversity.

Systematic trellis-coded modulation (STCM) is a novel approach to coded modulation, which enables symbol-by-symbol detection of trellis-coded data. A set of design rules, which guarantees nonzero coding gain, and codes with asymptotic coding gains of 3.0-5.4 dB are presented. STCM is well suited for operation in a dual-mode receiver. During normal operation the receiver uses a sequence estimation algorithm such as MLSE or SSE. When the channel introduces severe distortion, as is the case during a deep fade, the decoder switches to a systematic decoding algorithm, which is simple to implement, and guarantees BER performance that is better than uncoded modulation. The authors demonstrate the performance of various STCM codes with a dual-mode receiver on multipath fading channels.>