Adaptive Maximum-Likelihood Receiver for Carrier-Modulated Data-Transmission Systems

TLDR

Maximum‑likelihood sequence estimation is revisited for intersymbol‑interference channels. The paper derives a uniform receiver structure for linear carrier‑modulated data‑transmission systems that uses a modified Viterbi algorithm for decision making. The receiver processes the matched‑filter output directly, avoiding squaring operations by using only multiplications with discrete pulse amplitudes, incorporates redundant‑coding decoding, and jointly approximates the matched filter with a transversal filter while estimating ISI and controlling carrier phase and timing. The receiver achieves superior error performance compared to a zero‑forcing equalizer with symbol‑by‑symbol decisions, and the paper explains the underlying reasons and limits.

Abstract

A new look is taken at maximum-likelihood sequence estimation in the presence of intersymbol interference. A uniform receiver structure for linear carrier-modulated data-transmission systems is derived which for decision making uses a modified version of the Viterbi algorithm. The algorithm operates directly on the output signal of a complex matched filter and, in contrast to the original algorithm, requires no squaring operations; only multiplications by discrete pulse-amplitude values are needed. Decoding of redundantly coded sequences is included in the consideration. The reason and limits for the superior error performance of the receiver over a conventional receiver employing zero-forcing equalization and symbol-by-symbol decision making are explained. An adjustment algorithm for jointly approximating the matched filter by a transversal filter, estimating intersymbol interference present at the transversal filter output, and controlling the demodulating carrier phase and the sample timing, is presented.