Improved rates and coding for the MIMO two-way relay channel

The Gaussian multiple-input multiple-output two-way relay channel is considered. By applying linear pre- and post-processing, the channel matrices are transformed into triangular form having equal diagonals. Over the obtained triangular channels, dirty-paper coding is applied, yielding parallel symmetric scalar two-way relay channels; thus, reducing the coding task to that of coding over the scalar symmetric two-way relay channel. Any existing coding technique can then be readily applied over these resulting channels. This technique allows to obtain new achievable rates in the symmetric case.