EURASIP Journal on Applied Signal Processing 
Volume 2006 (2006), Article ID 70387, 9 pages
doi:10.1155/ASP/2006/70387

Intra-Symbol Windowing for Egress Reduction in DMT Transmitters

Gert Cuypers,1 Koen Vanbleu,2 Geert Ysebaert,3 and Marc Moonen1

 1ESAT/SCD-SISTA, Katholieke Universiteit Leuven, Heverlee 3001, Belgium
2Broadcom Corporation, Mechelen 2800, Belgium
3Alcatel Bell, Antwerp 2018, Belgium
Received 28 December 2004; Revised 20 July 2005; Accepted 22 July 2005

Abstract

Discrete multitone (DMT) uses an inverse discrete Fourier transform (IDFT) to modulate data on the carriers. The high sidelobes of the IDFT filter bank used can lead to spurious emissions (egress) in unauthorized frequency bands. Applying a window function within the DMT symbol can alleviate this. However, window functions either require additional redundancy or will introduce distortions that are generally not easy to compensate for. In this paper, a special class of window functions is constructed that corresponds to a precoding at the transmitter. These do not require any additional redundancy and need only a modest amount of additional processing at the receiver. The results can be used to increase the spectral containment of DMT-based wired communications such as ADSL and VDSL (i.e., asymmetric, resp., very-high-bitrate digital subscriber loop).