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Convergence and Steady-State Behavior of a Hybrid Decision Feedback Equalizer
Kyu-Min KANG Gi-Hong IM
IEICE TRANSACTIONS on Communications
Publication Date: 2002/12/01
Print ISSN: 0916-8516
Type of Manuscript: PAPER
Category: Fundamental Theories
hybrid-type decision feedback equalizer, phase-splitting equalizer, LMS algorithm, excess mean-square error (MSE), xDSL environment,
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In this paper, we analyze the convergence and steady-state behavior of the least mean-square (LMS) adaptive filtering algorithm for a finite-length phase-splitting hybrid-type decision feedback equalizer (H-DFE). With some approximations, we derive an iterative expression for the excess mean-square error (MSE) of the H-DFE, which is composed of three statistically dependent excess MSEs; that is, the excess MSEs of the feedforward filter (FFF), intersymbol interference predictive feedback filter (ISI-FBF), and noise predictive feedback filter (NP-FBF) taps. Computer simulation and analytical results show that the average eigenvalue of the input signal for the NP-FBF taps of the H-DFE is time-varying, whereas those for the FFF and ISI-FBF taps are fixed. Nevertheless, the H-DFE can be implemented with fixed step sizes that ensure the convergence of the LMS algorithm without performance degradation from the standpoint of convergence speed, as well as steady-state performance for digital subscriber line (xDSL) applications.