Self-updating algorithm for crosstalk cancellation as old users offline

Crosstalk is a major factor in inducing performance degradation of the next generation very-high bit-rate digital subscriber line (VDSL) system. Many crosstalk cancellation methods such as Zero-forcing (ZF) algorithm, First-Order (FO) algorithm, iterative crosstalk cancellation algorithm etc. have been proposed. These methods are based on the assumption that the number of users and the crosstalk environment remains unchanged. In actual access environment, the old users are often offline or the new users are on-line, causing the crosstalk environment changed. Therefore, self-updating crosstalk cancellers are often needed. In this paper, we propose a fast algorithm for updating the ZF crosstalk cancellers when the old users are offline. Simulation results based on measured data demonstrate that the proposed self-updating ZF algorithm maintains the same performance as the original ZF algorithm and dramatically reducing the computational complexity.