Constant-gap results and cooperative strategies for a class of Interference Relay Channels

The capacity of a class of Interference Relay Channels (IRC) is investigated. We derive a novel outer and three inner bounds which are based on a careful use of all existing cooperative strategies together with the adequate interference decoding technique. Our main result is the necessity of three different cooperative strategies to achieve a constant gap to the capacity for each SNR regime of the Gaussian IRC. Surprisingly enough, this outcome appears to be in contrast with that of the standard Gaussian RC (Relay Channel) where several cooperative strategies yield constant-gap results in all regimes.