Optimal Precoding for Digital Subscriber Lines
Fernando Perez-Cruz, Massimiliano Rodrigues and S Verdu
In: International Conference on Communications (ICC), 19-23 May 2008, Beijing (China).
We determine the linear precoding policy that
maximizes the mutual information for general multiple-input
multiple-output (MIMO) Gaussian channels with arbitrary input
distributions, by capitalizing on the relationship between mutual
information and minimum mean squared error (MMSE). The
optimal linear precoder can be computed by means of a fixedpoint
equation as a function of the channel and the input
constellation.We show that diagonalizing the channel matrix does
not maximize the information transmission rate for nonGaussian
inputs. A full precoding matrix may significantly increase the
information transmission rate, even for parallel non-interacting
channels. We illustrate the application of our results to typical
Gigabit DSL systems.