Crosstalk identification in xDSL systems

摘要

Crosstalk among telephone lines in the same or neighboring bundlesnis a major impairment in current xDSL systems. This paper proposes annovel idea of an impartial third party that identifies the crosstalkncoupling functions among the twisted pairs in these xDSL systems. Thencrosstalk identification technique includes the following four majornprocedures: (1) the transmitted and received signals from each DSL modemnfor a predefined time period are collected and sent to the third party;n(2) the signals are resampled according to the clock rate of thenreceiver of interest; (3) the signals' timing differences are estimatednby cross correlation; and (4) the crosstalk coupling functions arenestimated using the least-squares method. The performance of the crossncorrelation and least-squares methods is analyzed to determine thenamount of data needed for identification. Simulation results show thatnthe proposed methods can identify the crosstalk functions accurately andnare consistent with theoretical analysis. These identified crosstalknfunctions can be used to significantly improve the data rate (e.g.,nmultiuser detection) and to facilitate provisioning, maintenance, andndiagnosis of the xDSL systems