On Gaussian Interference Channels with Constellation-Based Transmitters

In this letter, we study a two-user Gaussian Interference Channel (GIC) with constellation-based transmitters where both transmitters utilize PSK signaling and both receivers treat interference as noise. It is verified that if one user rotates its constellation appropriately compared to the constellation of the other user, the achievable sum-rate in the network considerably increases. Due to the fact that the noise plus interference at each receiver is mixed-Gaussian, there is no closed formula for the sum-rate. Using Fano's inequality, a lower bound is developed on the sum-rate in the network. The lower bound is tight in the sense that it identifies the optimal value for the angle of rotation. Moreover, it is demonstrated that the proposed lower bound can be larger than the exact value of sum-rate achieved by random Gaussian codes or Time-Division-Multiplexing (TDM).