Generalized degrees of freedom of the symmetric gaussian interference channel with partial unidirectional transmitter cooperation

Abstract

We consider a two-user symmetric Gaussian Interference Channel (IC), in which one encoder is connected to the other by a unidirectional orthogonal cooperative link with specific capacity. In this setup, we employ a simplified Han-Kobayashi scheme used in [1], along with cooperative communication. We characterize the generalized degrees of freedom [1] of the channel for interference-limited regimes by comparing the achievable sum-rate with some existing upper bounds and also with a new upper bound, introduced in this paper. In particular, we express the number of degrees of freedom available for communication as a function of the interference-to-noise ratio and the multiplexing gain of the cooperative link. In addition, we give the sum-capacity of the channel for the strong interference regime when the capacity of the cooperative link is large enough in terms of the channel parameters. Finally, we show that for noise-limited regimes, treating interference as noise and not using the cooperative link, offer a sum-rate that is at most one bit less than the sum-capacity of the channel.