Effective Relaying in Two-user Interference Channel with Different Models of Channel Output Feedback

In this paper, we study the impact of channel output feedback architectures on the capacity of two-user interference channel. For a two-user interference channel, a feedback link can exist between receivers and transmitters in 9 canonical architectures, ranging from only one feedback link to four-feedback links. We derive exact capacity region for the deterministic interference channel and constant-gap capacity region for the Gaussian interference channel for all but two of the 9 architectures (or models). We find that the sum-capacity in deterministic interference channel with only one feedback link, from any one receiver to its own transmitter, is identical to the interference channel with four feedback links; for the Gaussian model, the gap is bounded for all channel gains. However, one feedback link is not sufficient to achieve the whole capacity region of four feedback links. To achieve the full capacity region requires at least two feedback links. To prove the results, we derive several new outer bounds, and give a new three-layer coding achievability scheme, which splits every message into a private, common and relaying message layers.