Joint Signaling Strategies for Approaching the Capacity of Twisted Pair Channels

A technique is presented for jointly optimizing the signaling in the two directions of transmission on a twisted pair communications channel. It is then applied to twisted pair channel models with monotonic channel response and crosstalk transfer functions. While the signaling strategy presented in this paper can achieve only a lower bound on the true channel capacity, it is a significant improvement over existing signaling schemes. In particular, in contrast with existing schemes, the maximum information rate for the joint signaling strategy increases without bound as the SNR approaches infinity. It is also shown through numerical results that the proposed signaling strategy generalizes naturally to more practical non-monotonic twisted pair channel models incorporating bridge taps and other non-idealities. Finally, the form of the optimal signaling strategy suggests a relatively straightforward implementation using multicarrier modulation