Joint partial crosstalk cancellation and modified iterative water-filling algorithm for upstream VDSL systems

Abstract

Full crosstalk cancellation (FCC) techniques have been proposed to mitigate the effect of crosstalk in upstream xDSL systems. However, these are too complex for application in typical VDSL binders. Partial crosstalk cancellation (PCC) technique limits the cancellation to cross-talkers that cause severe interference to the other lines. It can be simplified to line selection, tone selection and joint line-tone selection (JLTS) techniques. In addition, much more online complexity reduction can be obtained by joint using multi-user power control and PCC algorithms. However, the joint solution suffers from very high start-up complexity that makes it impractical. In this paper first, we propose a new modified JLTS algorithm with significantly lower start-up complexity than the optimal JLTS algorithm and approximately with similar performance. Secondly, we use modified iterative water-filling (IWF) algorithm as a multi-user power control technique joined with one of existing PCC schemes while considering dynamic online complexity constraint for each user. This leads to an efficient very low start-up and online complexity joint algorithm that can achieve near the capacity rates. The bit-rate increase of the proposed joint algorithm is demonstrated by some simulation results and compared with the current proposed joint algorithms and independent solution that use flat PSDs.