Wavelet packet-based subband adaptive equalization

This paper proposes an adaptive algorithm for channel equalization in the Wavelet Packet Transform (WPT) domain. Adaptation to time-varying channels is achieved by the use of the orthogonal tree-structured time-varying filter bank associated to the WPT. The filter bank structure, that is, the type of decomposition, is obtained, for a fixed number of bands, as the one that leads to a quasi optimum convergence rate of the adaptive filters in the different subbands. A theorethical analysis is also provided: we show why a faster convergence is achieved; the Mean Squared Error (MSE) after the adaptive algorithm has converged is obtained and compared with that of the classical LMS alghorithm. Experimental results show the efficiency of the proposed scheme and illustrate the previously presented theoretical results.