Gaussian Fading Interference Channels: Power Control

In this paper we consider power allocation policies for 2-user Gaussian interference channels (IFC) with ergodic fading, perfectly known at all terminals. Based on recently found outer bounds on the capacity region of unfaded IFCs, we determine the power allocation that maximizes a sum-rate outer bound. With this power allocation both users are simultaneously active when the power of the interfering signals is small relative to the power of the intended signals. Otherwise, only the user with the largest fading gain is active, similar to multi-access and broadcast channels. By considering a simplified version of the Han-Kobayashi region, we derive the power allocation that maximizes a sum-rate inner bound. Numerical results for iid Rayleigh fading show that the inner and our bounds are very close to one another. The structure of the determined power allocation policies suggests that practical power allocations can be designed based on only a bit of channel state information.