Application of shaping to discrete multitone modulation

The application of shaping to discrete multitone (DMT) modulation is investigated as a means for obtaining additional gain in applications requiring high-performance transceivers. DMT modulation differs from single-carrier modulation in that a number of parallel tones are used for transmission and the constellation sizes and transmit power vary across these tones. Shaping gains ranging from 0.5-1.0 dB are derived through simple extensions of existing single-carrier shaping techniques. Examples for the asymmetric digital subscriber line service illustrate the gains achieved by the DMT shaping techniques.