Signal Processing Computationally efficient joint partial crosstalk cancellation and multi-user power control algorithm in xDSL networks

Far-end crosstalk (FEXT) is the major limitation to achieve high data rates in very high bit rate digital subscriber line (VDSL) systems. Full crosstalk cancellation (FCC) techniques have been proposed to mitigate the effect of crosstalk. However, these are too complex for application in typical VDSL binders. Considering the fact that there are only a few strongest cross-talkers that contribute to main part of crosstalk, the crosstalk cancellation can be simplified to line selection (LS), tone selection (TS) and joint line-tone selection (JLTS) partial crosstalk cancellation (PCC). These all result in much less online complexity. In this paper, first, we propose a new modified JLTS algorithm with significantly lower initialisation complexity than the optimal JLTS (OJLTS) algorithm and approximately with similar performance. Then a novel joint algorithm is presented that combines the multi-user power control technique with the PCC scheme to achieve near the capacity rates. We also consider dynamic online complexity constraint for each user. This joint algorithm leads to a much larger online complexity reduction (around 60% for long lines) and higher data rates at the expense of slightly higher initialisation complexity. The performance of the proposed algorithm is verified by some simulation results and compared with current algorithms that use flat power spectral densities (PSDs) and other existing joint algorithms. Copyright © 2009 John Wiley & Sons, Ltd.