An outer bound for the Gaussian interference channel with a relay

A novel sum-rate outer bound for the Gaussian interference channel with a relay is presented. The outer bound is obtained by adapting the genie-aided approach developed for interference channels in [1]. The cut-set bound for this channel is also derived and is shown to be much looser than the new bound. The new bound is also compared to an achievable rate region we introduced in previous work. We show that the inner and outer bounds are close in the regime of strong interference where receivers can decode both messages. The capacity region in strong interference for the discrete memoryless degraded channel is also presented.