Space-frequency modulation for MIMO coordinate copper units

The present paper provides Shannon performance bounds of MIMO cooperative copper units (CCU) in the presence of crosstalk originating in neighboring pairs. Limited here to just two pairs, MIMO CCU operates either in multiplexing or diversity modes transmitting independent or identical data streams. Contrary to the rank instability of frequency dispersive wireless channel, CCU always experience full rank MIMO channels. Nevertheless, the major gain inherent in CCU optimal joint processing does not stem from the channel full rank property but from the possibility to partially cancel the crosstalk. Capacity may indeed be largely increased if the crosstalk correlation experienced by the CCU paths of each impaired tone of the copper bandwidth is leveraged through maximum likelihood estimation. The paper gives the theoretical foundation of this result by deriving an original (according to our knowledge) form of the MIMO Shannon bound in terms of the Fisher information matrix. We finally address a space-frequency modulation (SFM) that combines the selection of the best precoder with the multicarrier modulation.