Optimum Decision Delay of the Finite-Length DFE

This work investigates the optimum decision delay and tap-length of the finite-length decision feedback equalizer. First we show that, if the feedback filter (FBF) length N/sub b/ is equal to or larger than the channel memory v and the decision delay /spl Delta/ is smaller than the feedforward filter (FFF) length N/sub f/, then only the first /spl Delta/+1 elements of the FFF can be nonzero. Based on this result we prove that the maximum effective FBF length is equal to the channel memory v, and if N/sub b//spl ges/v and N/sub f/ is long enough, the optimum decision delay that minimizes the MMSE is N/sub f/-1.