Title :
Adaptive bit rate maximizing time-domain equalizer design for DMT-based systems
Author :
Vanbleu, Koen ; Ysebaert, Geert ; Cuypers, Gert ; Moonen, Marc
Author_Institution :
DSL Bus. Unit, Broadcom Corp., Mechelen, Belgium
Abstract :
The classical discrete multitone receiver as used in, e.g., digital subscriber line (DSL) modems, combines a channel shortening time-domain equalizer (TEQ) with one-tap frequency-domain equalizers (FEQs). In a previous paper, the authors proposed a nonlinear bit rate maximizing (BM) TEQ design criterion and they have shown that the resulting BM-TEQ and the closely related BM per-group equalizers (PGEQs) approach the performance of the so-called per-tone equalizer (PTEQ). The PTEQ is an attractive alternative that provides a separate complex-valued equalizer for each active tone. In this paper, the authors show that the BM-TEQ and BM-PGEQ, despite their nonlinear cost criterion, can be designed adaptively, based on a recursive Levenberg-Marquardt algorithm. This adaptive BM-TEQ/BM-PGEQ makes use of the same second-order statistics as the earlier presented recursive least-squares (RLS)-based adaptive PTEQ. A complete range of adaptive BM equalizers then opens up: the RLS-based adaptive PTEQ design is computationally efficient but involves a large number of equalizer taps; the adaptive BM-TEQ has a minimal number of equalizer taps at the expense of a larger design complexity; the adaptive BM-PGEQ has a similar design complexity as the BM-TEQ and an intermediate number of equalizer taps between the BM-TEQ and the PTEQ. These adaptive equalizers allow us to track variations of transmission channel and noise, which are typical of a DSL environment.
Keywords :
adaptive signal processing; equalisers; higher order statistics; least squares approximations; modulation; recursive estimation; time-domain analysis; DMT-based systems; adaptive bit rate maximizing; discrete multitone receiver; frequency-domain equalizers; recursive Levenberg-Marquardt algorithm; recursive least squares method; second-order statistics; time-domain equalizer design; Algorithm design and analysis; Bit rate; Costs; DSL; Demodulation; Discrete Fourier transforms; Equalizers; Modems; OFDM modulation; Time domain analysis; Adaptive equalization; Levenberg–Marquardt; digital subscriber lines (DSLs); discrete multitone (DMT); iteratively reweighted separable nonlinear least-squares (IR-SNLLS) problems; time-domain equalization (TEQ);
Journal_Title :
Signal Processing, IEEE Transactions on
DOI :
10.1109/TSP.2005.861901