Krylov algorithms for FEXT cancellation in upstream MIMO VDSL

Abstract

In this paper we show that Krylov subspace techniques are well suited for cancellation of Far End Crosstalk (FEXT) in MIMO Digital Subscriber Lines (DSL). These methods are computationally efficient for large dimensional DSL channel by exploiting special characteristics of the channel without the need of channel inversion. In particular we study the use of Generalized Minimum Residual (GMRES) Krylov iterative receiver, and exploits its ability to converge very rapidly close to the correct solution by initializing the iteration with the output of the Frequency Domain Equalizer (at each TP and tone). Analytical expressions for residuals are derived to demonstrate that the iterative receiver converges in just one iteration.