Partial Crosstalk Cancellation for Upstream VDSL

Abstract

Crosstalk is a major problem in modern DSL systems such as VDSL. Many crosstalk cancellation techniques have been proposed to help mitigate crosstalk, but whilst they lead to impressive performance gains, their complexity grows with the square of the number of lines within a binder. In binder groups which can carry up to hundreds of lines, this complexity is outside the scope of current implementation. In this paper, we investigate partial crosstalk cancellation for upstream VDSL. The majority of the detrimental effects of crosstalk are typically limited to a small subset of lines and tones. Furthermore, significant crosstalk is often only seen from neighbouring pairs within the binder configuration. We present a number of algorithms which exploit these properties to reduce the complexity of crosstalk cancellation. These algorithms are shown to achieve the majority of the performance gains of full crosstalk cancellation with significantly reduced run-time complexity.