Adaptive DSL Crosstalk Precancellation Design Using Low-Rate Feedback From End Users

The performance of extensions of digital subscriber line to higher data rates (VDSL) is limited by the effects of crosstalk among the wires in a bundle. For the downstream, a precoder can compensate for this. Without knowledge of the crosstalk channel matrix, the problem is to compute a suitable precoder based on limited feedback from the receivers. In this letter, an adaptive precoder design algorithm is derived. The algorithm works on a per-tone basis and assumes that each receiver sends back the sign of the symbol error to the transmitter. The algorithm computes the precoder iteratively using this information, without the need to estimate the crosstalk channel as an intermediate step. The asymptotic and acquisition performance is verified by simulations