DMT Time Domain Equalization Based on ARMA Models

This paper describes a novel approach for the design of a time domain equalizer for a discrete multi tone (DMT) digital subscriber loop (DSL) modem. The key role of the equalizer is to act upon the equivalent digital channel impulse response at the receiving end to yield a combined impulse response with a linear phase characteristic. Using two-port channel models from the ANSI VDSL standard it is shown how group delay characteristics of typical channels can be modeled by small order polynomials that fall into one of the following categories; all-zero mixed phase, all-pole mixed phase, ARMA minimum phase, and finally ARMA maximum phase systems. A discussion follows to suggest a suitable algorithm based on Prony´s method for finding appropriate minimum phase channel models which can be inverted to give equalizer blocks