The Approximate Capacity Region of the Phase-Fading, Very Strong, K-User Gaussian Interference Channel

Consider the K-user Gaussian interference channel with static channel coefficients. Recent efforts have characterized the capacity region to within a constant gap for several important special cases, including two-user, very weak, many-to-one, and one-to-many interference channels. The general case remains open, primarily due to the challenge of characterizing the achievable rate for interference alignment strategies outside of the very high signal-to-noise ratio (SNR) limit. This paper argues that some of these difficulties can be overcome if the phases of the channel coefficients are time-varying. The main result is a constant-gap approximation of the capacity region of phase-fading, Gaussian K-user interference channels where all receivers are in the very strong interference regime.