Distributed Crosstalk Management for Upstream VDSL Using Dynamic Power Control

Abstract

The severe interference from neighbor copper lines, commonly known as crosstalk, is a well-known limitation that can reduce the upstream rate of a victim user by 50% or more in dense VDSL (Very high bit-rate Digital Subscriber Lines) deployment. This problem has been partially addressed by the use of UPBO (Upstream Power BackOff). UPBO blindly controls transmit PSD (Power Spectral Densities) based on the pre-defined parameters and channel measurements without considering each user's target data rate. Although UPBO can provide fair protection against crosstalk, it still leaves room for practical improvement. This paper proposes a distributed algorithm that dynamically controls transmit power according to each line's need and capacity. The algorithm effectively improves data rates and line reaches in real VDSL deployment.