On the Degrees of Freedom of the 3-user Gaussian interference channel: The symmetric case

Abstract

In this paper, the degrees of freedom (DOF) of the symmetric 3-user Gaussian interference channel is considered. It is shown that by using un-coded signaling, the achievable DOF is a discontinuous function of the channel parameter. More importantly, for the set of irrational channel gains, which has measure 1 in real numbers, it is proved that the total system's DOF, i.e., 3/2, is achievable. This result is obtained using Hurwitz's theorem in number theory.