Adaptive off-diagonal MIMO canceller (ODMC) for VDSL upstream self FEXT mitigation

This contribution presents a linear off-diagonal MIMO canceller (ODMC) that aims at mitigating the upstream self far-end cross-talk (FEXT) that severely impacts the performance of very high speed digital subscriber line (VDSL) services at the central office (CO). The ODMC operates per frequency and is thus well suited for DMT-based VDSL systems. We introduce a low complexity and low latency adaptive algorithm that converges towards the optimum ODMC that simultaneously maximizes the distributed Shannon capacities of the upstream links, under mild assumptions for nominal VDSL systems. The adaptive algorithm does not require any matrix inversion and is designed to learn and engage the ODMC seamlessly while operating in data mode. Further, we prove that the optimum ODMC approximately achieves FEXT-free capacity. Simulations show that the FEXT-free capacity can be achieved in roughly 200 iterations.