MMSE-based partial crosstalk cancellation for upstream VDSL

Abstract

In current DSL systems, crosstalk is a major source of performance degradation. For upstream VDSL scenarios with in-domain crosstalk and AWGN, it has been shown that the crosstalk can be effectively mitigated using a linear zero-forcing canceler. Furthermore, the complexity can be reduced by only canceling the crosstalk from major crosstalkers, which is referred to as partial crosstalk cancellation. However, such approach does not work well in scenarios that also have out-of-domain (alien) crosstalk. As alien crosstalk is spatially correlated, the zero-forcing canceler performs very poorly, hence alternative structures for the canceler have to be examined. In this paper, we first demonstrate that an MMSE-based linear and nonlinear crosstalk canceler provides improved performance compared to the zero-forcing canceler in this scenario and then present efficient algorithms to perform partial crosstalk cancellation with these MMSE-based cancelers.