Generalized Degrees of Freedom of the Symmetric K-user Interference Channel with Feedback

The symmetric K user interference channel with fully connected topology is considered, in which (a) each receiver suffers interference from all other K - 1 transmitters, and (b) each transmitter has causal and noiseless feedback from its respective receiver. The number of generalized degrees of freedom (GDoF) is characterized in terms of alpha, where the interference-to-noise ratio (INR) is given by INR = SNR alpha. It is shown that the number of per-user GDoF of this network is the same as that of the 2-user interference channel with feedback, except for alpha - 1, for which existence of feedback does not help in terms of GDoF. The coding scheme proposed for this network, termed cooperative interference alignment, is based on two key ingredients, namely, interference alignment and interference decoding.