Performance of linear crosstalk cancelation in fourth generation wired broadband access networks

The International Telecommunication Union (ITU) is currently working on a standard for the next digital subscriber line (DSL) generation, called G.fast. It uses frequencies up to 200MHz and targets bit-rates of up to 1 Gbps over a single twisted-pair line. Crosstalk coupling represents a major limitation on such high frequencies. Hence, in this work we compare the performance of two prominent linear crosstalk cancellation schemes depending on transmission directions, zero-forcing linear equalization (ZFE) for upstream and diagonalizing precoding (DP) for downstream, when applied in a G.fast context. Both schemes require accurate channel state information. Simulation results reveal that even small estimation errors can severely limit the bit-rates achievable by ZFE and DP in some particular scenarios.