Decision feedback equalization of HDSL using a generalized adaptive IIR delay filter

Abstract

AbstractA decision feedback equalization scheme comprising of a generalized adaptive infinite impulse response delay filter in the feedback path is proposed and used for equalization of high‐rate digital subscriber loops including severe intersymbol interference and near‐end crosstalk colored noise. The feedback filter compensates the long postcursor intersymbol interference due to the high sampling rate and is composed of parallel sections having one, two or four coefficients and a delay element. The structures of the sections are determined adaptively and in a step‐by‐step procedure. Because of the parallel and, at most, two‐pole sections of the generalized adaptive infinite impulse response delay filter, the stability monitoring requires essentially no computations. To reduce the noise enhancement effect of the prefilter, an adaptive noise predictor is also used. Computer simulation results demonstrate the performance of the proposed structure compared to the conventional decision feedback equalizer with a finite impulse response feedback filter. The main advantage of the proposed system is the significant reduction in the number of coefficients and consequently the adaptation time.