A Coded and Shaped Discrete Multitone System

Abstract

In this paper, we show how coding and constellation shaping may provide significant gains to a discrete multi-tone (DMT) system transmitting over spectrally-shaped channels. First, we present and analyze a concatenated coding scheme consisting of an inner trellis code and outer block code when applied to DMT modulation, and we address some of the implementation issues associated with this scheme. Some laboratory test results for a DMT prototype employing the coding scheme are presented. Next, we propose a method for applying Forney's trellis shaper across the tones in a DMT system to realize significant shaping gain. To illustrate the coding and shaping gains achieved, we use scenarios indicative of the newly introduced asymmetric digital subscriber line service. By combining a powerful coding scheme, shaping, and DMT modulation, we arrive at an implementable transceiver that can provide very high data rates over spectrally-shaped channels. © 1995 IEEE