Alien crosstalk cancellation for multipair digital subscriber line systems

Abstract

An overview of alien crosstalk cancellation for DSL systems withmultiple pairs is here presented. It is shown that when a commoncrosstalk source affects the receivers of multiple pairs, thenoise exhibits a certain correlation among the pairs. Ina DMT system, the frequency-domain noise samples are most stronglycorrelated between pairs when they correspond to the same tone.Thus, noise decorrelationalgorithms applied independently for each tone can providesignificant performance enhancements. Three possible methods aredescribed for noise decorrelation, one is suitablefor two-sided coordination and two are suited for receivercoordination among the pairs. It is theoretically proven that thedata-rate performance of these three methods is identical from theperspective of the sum rate over all pairs. Simulation resultscorresponding to an ADSL2+ two-pair system with a T1 disturber arepresented to illustrate the noise correlation property and toindicate the potential performance benefits.