Combined equalization for dmt-based modem receiver

Abstract

A DMT modem () is disclosed, in which a combined time domain equalizer and per-tone equalizer is applied to a received DMT signal. The combined equalizer includes a first FFT function () that is applied to a set of samples in a time-domain signal after the application of a time domain equalizer (). The first FFT function () produces an initial FFT result, that is accumulated with a sliding FFT () performed upon difference values in the time domain samples. The sliding FFT results are applied to a per-ton equalizer () which applies a set of complex coefficients determined in training of the modem. A simple 1-tap FEQ () then can recover the signal. The combined equalizer enables per-tone equalization, in a manner that is compatible with conventional DSL training standards. According to a second embodiment, the per-tone equalization is performed only on selected tones of the multitone signal.