State reduction in Viterbi detector using preliminary decisions

This paper presents a technique to reduce the number of states in the trell is of a conventional partial response Viterbi detector (PR-VD) using prelim inary decisions. The preliminary decisions are obtained from a lower order PR-VD which are used to shorten the tail of the higher order partial respon se. Since it does not use decision feedback to shorten the tail of the high er order PR, it does not suffer from error propagation. Theoretical analysi s is carried out to show the influence of error events in the preliminary a nd reduced state Viterbi detectors on the system performance, and to provid e possible ways to effectively implement the scheme. Simulation results are provided to bring out certain key features of the approach.