Interference channels with source cooperation in the strong cooperation regime: Symmetric capacity to within 2 bits/s/Hz with Dirty Paper Coding

The capacity region of the Gaussian interference channel with two source-destination pairs where the sources can cooperate is not known. Prabhakaran and Viswanath showed that the sum-rate capacity can be achieved to within 19 bits/s/Hz by using a combination of superposition coding and zero-forcing. This paper only focuses on the symmetric capacity, i.e., the maximum equal rate point that the two sources can simultaneously achieve in a Gaussian interference channel with symmetric channel gains, in the strong cooperation regime, i.e., when the cooperation link is stronger than either the direct link or the interference link. In this setting, it is showed that the “binning+superposition” achievable scheme of Yang and Tuninetti, implemented with Gaussian codebooks and Dirty Paper Coding, achieves the symmetric capacity to within 2 bits/s/Hz-thereby considerably reducing the previously known gap. The extension of this gap-result to other regimes is also discussed.