Rate Splitting is Approximately Optimal for Fading Gaussian Interference Channels

In this paper, we study the 2-user Gaussian interference-channel with feedback and fading links. We show that for a class of fading models, when no channel state information at transmitter (CSIT) is available, the rate-splitting schemes for static interference channel, when extended to the fading case, yield an approximate capacity region characterized to within a constant gap. We also show a constant-gap capacity result for the case without feedback. Our scheme uses rate-splitting based on average interference-to-noise ratio (inr). This scheme is shown to be optimal to within a constant gap if the fading distributions have the quantity log (E[inr]) - E [log(inr)] uniformly bounded over the entire operating regime. We show that this condition holds in particular for Rayleigh fading and Nakagami fading models. The capacity region for the Rayleigh fading case is obtained within a gap of 2.83 bits for the feedback case, and within 1.83 bits for the non-feedback case.