A Low Complexity Linear Precoding Technique for Next Generation VDSL Downstream Transmission Over Copper

In this paper, we study a simplified linear precoding scheme for far-end crosstalk (FEXT) cancellation in very high bit-rate digital subscriber line (VDSL) downstream transmission. We compare the proposed method to zero-forcing (ZF) FEXT cancellation and show that for multipair VDSL systems the method achieves rates that are close to the ZF precoding method. We also derive simple lower bounds on the performance that allows us to predict the performance of the proposed algorithm on each tone. We end up with testing the proposed method on theoretical and empirical channels. This is the first extensive study of VDSL precoding on measured channel data. The proposed method is less complex than ZF precoding and, therefore, alleviates the computational load at the initialization and tracking of precoded VDSL or VDSL2 systems. Finally, we discuss implementation complexity in terms of total Silicon area and show that the method has favorable implementation complexity, since only channel coefficients need to be stored during steady-state transmission.