Rate-reach performance improvements in ADSL interference environment using adaptive wavelet threshold

Adaptive filtering has been shown to mitigate the effect of near end crosstalk (NEXT) in an ADSL receiver. This paper discusses the cancellation of NEXT and far end crosstalk (FEXT) using a non-parametric wavelet denoising technique. Crosstalk noise is estimated using heuristic Steinpsilas unbiased risk estimate (SURE) and Bayesian risk minimization shrinkage function. The noise level estimated by a shrinkage function is used by thresholding rules to mitigate the effect of noise in the signal. A comparison of rates achieved using these shrinkage functions with three thresholding techniques viz; soft thresholds, hard thresholds and a garrote threshold have been presented. Results obtained with AWGN, 24 ADSL NEXT and 24 ADSL FEXT disturbers show a significant improvement in Rate reach performance upwards of 4 Mbps. The computational complexity in the wavelet denoising technique is independent of the number of crosstalk sources and hence can be suitable candidate for a practical deployment of mitigation of cross talk.