Alien crosstalk elimination in digital subscriber line systems

Elimination of alien crosstalk in coordinated digital subscriber line systems is investigated in this study. In the upstream, the process of crosstalk elimination may take advantage of available coordination at the receiver side. As the signal received at the coordinated terminals can be corrupted by alien crosstalk, the reception process involves passing the signals received at the coordinated terminals through a spatial whitening operation. As part of the contribution in this study, a method is proposed to obtain the spatial whitening filter coefficients. These coefficients are estimated from the cyclic spectrum of alien crosstalk received at the coordinated system terminals, where transmission at the coordinated system is controlled to allow separating the cyclic spectra of both coordinated system and alien crosstalk signals. This study includes evaluation of the whitening receiver performance taking into account the effects of estimation errors. Theoretical derivations are illustrated by numerical results obtained for VDSL2 application.