Comparison between two methods for delayed decision feedback sequence estimation

The paper deals with the design of suboptimal receivers for data transmission over frequency selective channels. The complexity of maximum likelihood sequence estimation (MLSE) turns out be exponential in the channel memory. Hence, when dealing with channels with long memory, suboptimal reception must be considered. Among the suboptimal methods, the delayed decision feedback sequence estimation (DDFSE) plays an important role. This receiver is based on a Viterbi processor where the channel memory is truncated. The memory truncation is compensated by a per-survivor decision feedback equalizer. The DDFSE was originally proposed by Duel-Hallen and Heegard (1989), where the whitened matched filter was considered as a front-end. Our contribution is to extend the principles of MLSE and DDFSE to the case where the mean-square whitened matched filter is adopted as a front-end. Simulation results show that our proposed design of the DDFSE gives substantial benefits when a severe frequency selective channel is considered.