Low complexity decoders for channels with intersymbol-interference

This paper presents two decoders for reduced-state sequence estimation on channels with intersymbol interference (ISI). The decoding algorithms are based on a trellis description of the channel and the conventional Viterbi algorithm. The reduction of computational complexity is achieved by discarding all but a few most likely paths in the trellis. The decision to discard certain paths is based on the path metric and the minimum Euclidean distance in the trellis. An analysis of the error-event probability shows that the algorithms achieve the performance of the maximum likelihood sequence estimator at high signal-to-noise ratios. The computational complexity is derived and the two implementations are described in detail. Finally, simulation results for a severe ISI channel are provided