The Estimate Feedback Equalizer: A Suboptimum Nonlinear Receiver

A recursive nonlinear equalizer has been developed. The Bayes estimation theory has been used to obtain an unrealizable nonlinear minimum mean-square error (MMSE) receiver for the reception of binary pulse-amplitude-modulation signals in the presence of intersymbol interference and noise. A realizable approximation to the Bayes structure has been derived as the combination of a matched filter and a nonlinear recursive equalizer structure. The equalizer has been made adaptive using a new algorithm that defines and maintains the time frame of reference and is constrained so that the equalizer's parameters always move toward their optimum values. Computer simulations have been used to demonstrate the properties of the estimate feedback equalizer (EFE) and to compare its performance to that of presently known equalizers.