Decision-feedback equalization with fixed-lag smoothing in nonlinear channels

Significant error rates are common in nonlinear communication and digital storage channels, due to nonlinear intersymbol interference (ISI). The decision-feedback equalizer (DFE) is often used to combat ISI, by providing nonlinear feedforward and feedback filters to compensate the nonlinear distortion. This paper presents recent work on a DFE that incorporates fixed-lag smoothing, termed the FLS DFE. We derive the FLSDFE estimator for the case of binary-phase-shift keying inputs to a digital communication channel described by a truncated Volterra series. Simulation results are presented, showing the existence of ‘resonance’ phenomena within a state-space model of filtering-error propagation. The FLSDFE is shown to experience equalization performance that is strongly channel-dependent, highlighting a potential problem with robustness.