A Decision Feedback Equalizer Incorporating Fixed Lag Smoothing

A new type of Decision Feedback Equalizer (DFE) incorporating xed lag smoothing is developed in this paper. The structure is motivated by the remark that, if one makes full use of the dependence of the observed data on a given transmitted symbol, delayed decisions may produce better estimates of the symbol. The resulting equalizer structure takes the form of a linear system followed by a special quantizer, hence is easily implemented. A full theoretical analysis of the initial version of the algorithm is not available, but a characterization of a simple version is provided. We demonstrate that compared to the DFE, the algorithm brings two kinds of improvements : (i) for a rst order channel, it is shown that the set of channels for which error recovery always occurs is larger than the corresponding region for the DFE ; (ii) the error probability is reduced by up to 50% for some channels in the case of high SNR. Simulations illustrate the average error recovery time of the smoother compared to the DFE. Considerable beneet is observed for many channels. Some other variants on the proposed structure are also presented.