A new sum-rate outer bound for Gaussian Interference Channels with Generalized Feedback

Interference channels (IFC) with generalized feedback (GF) model wireless channels where every node overhears the transmission of other nodes and uses it to engage in cooperative communication strategies. The overheard signals, instead of being treated as interference, furnish the basis for cooperation among otherwise uncoordinated users. Although cooperative communications is not equivalent to virtual multi-input-multi-output (MIMO) communications, it has been shown to benefit the rate performance of all the involved source-destination pairs without increasing neither their transmit powers nor the channel bandwidth. This paper develops a new sum-rate outer bound for Gaussian IFC-GFs based on the idea of giving the receivers the least informative GF signal as side information. We compare our new outer bound with bounds available in the literature and numerically show for which network parameters our bound strictly improves on existing ones.