A novel reduced-complexity MAP equalizer using soft-statistics for decision-feedback ISI cancellation

A novel version of the reduced-state Bayesian maximum a posteriori probability/decision-feedback (MAP/DF) equalizer for ISI channels with long impulse responses is presented. The main feature of the proposed equalizer is that the soft-statistics generated by the MAP receiver are employed to recursively compute a suitable index of the actual reliability of the (soft) decisions feeding the DF filter. Therefore, in the presented equalizer the usual (over-optimistic) assumption of error-free decisions at the input of the feedback filter is relaxed and numerical results supporting the actual effectiveness of the proposed MAP/DF equalizer are provided for the so-called high-bit-rate digital subscriber line (HDSL) test-loop # 4.