Abstract
We characterize theÌý symmetric Ìý capacity Ìýof the two-userÌý Gaussian Ìý interference Ìý channel Ìýwith feedback Ìý to Ìý within Ìý1Ìý bit /s/Hz. The result makes use of a deterministic modelÌý to Ìýprovide insights into theÌý Gaussian Ìý channel . We derive a new outer boundÌý to Ìýshow that a proposed scheme can achieve theÌý symmetric Ìý capacity Ìý to Ìý within Ìý one Ìý bit Ìýfor allÌý channel Ìýparameters.Ìý One Ìýconsequence of the result is thatÌý feedback ÌýprovidesÌý unbounded Ìýgain, i.e., the gain becomes arbitrarily large for certainÌý channel parameters. It is a surprising result becauseÌý feedback Ìýhas been so far knownÌý to Ìýprovide no gain in memoryless point- to -pointÌý channels Ìýand only power gain ( bounded Ìýgain) in the multiple access channels . The gain comes from usingÌý feedback Ìý to Ìýfully exploit the side information provided by the broadcast nature of the wireless medium.