Signal Processing 84 (2004) 1895–1908 Improved initialization for time domain equalization in ADSL Katleen Van Acker a , Geert Leus b,1 , Marc Moonen c,Ã , Thierry Pollet a a Alactel Bell, Access to Networks, Corporate Research Center, Francis Wellesplein 1, 2018 Antwerpen, Belgium b Faculty of Electrical Engineering, Mathematics, and Computer Science, Delft University of Technology, Mekelweg 4, 2628 CD Delft, The Netherlands c Department of Electrical Engineering (ESAT), Katholieke Universiteit Leuven, Kasteelpark Arenberg 10, 3001 Leuven, Belgium Received 11 March 2001; received in revised form 21 June 2004 Abstract An improved optimization algorithm for the time domain equalizer (TEQ) is developed for discrete multitone (DMT) based asymmetric digital subscriber line (ADSL). In contrast with existing algorithms, our algorithm explicitly disregards the unused tones in the cost function as well as in the non-triviality constraint. Simulation results are presented for the upstream channel. It is shown that the achievable bitrate is higher than for a popular existing algorithm. r 2004 Elsevier B.V. All rights reserved. Keywords: Discrete multitone; Equalization; ADSL 1. Introduction Equalization is required in a DMT-system to combat intercarrier and intersymbol interference [10]. Basically, the equalization relies on the insertion of a cyclic prefix and a 1-tap frequency domain equalizer. However, when the order of the channel impulse response is larger than the cyclic prefix length, interferences arise. Hence, additional equalization techniques are called for. Mostly time domain equalization to shorten the channel impulse response is then adopted [2–9,13–16]. Minimum mean-square error (MMSE) channel shortening is a well-known time domain equalizer design approach. The cost function is quadratic and has a unique minimum, which leads to low-complexity ARTICLE IN PRESS www.elsevier.com/locate/sigpro 0165-1684/$-see front matter r 2004 Elsevier B.V. All rights reserved. doi:10.1016/j.sigpro.2004.06.014 Ã Corresponding author. ESAT/SISTA, Katholieke Universiteit Leuven, Kasteelpark Arenberg 10, 3001 Heverlee, Belguim. Tel.: +32-1632-1927; fax: +32-1632-1970. E-mail addresses: katleen.van_acker@alcatel.be (K. Van Acker), leus@cas.et.tudelft.nl (G. Leus), marc.moonen@esat.kuleuven.ac.be (M. Moonen), thierry.pollet@alcatel.be (T. Pollet). 1 Also for correspondence.