Outer bound and noisy-interference sum-rate capacity for symmetric Gaussian interference channels

A new outer bound on the capacity region of Gaussian interference channels is developed. The bound combines and improves existing genie-aided methods and is shown to give the sum-rate capacity for Gaussian interference channel with noisy interference as defined in this paper. Specifically, it is shown that if the channel coefficients and power constraints satisfy a simple condition then single-user detection at each receiver is sum-rate optimal, i.e., treating the interference as noise incurs no loss in performance. Finally, we generalize the noisy interference sum-rate capacity to m-user interference channels.