Optimal rate splitting in the two-user symmetric Gaussian interference channel

This paper studies rate splitting for the Han-Kobayashi (HK) transmission scheme in the two-user symmetric Gaussian interference channel. We derive the optimal rate split between common and private messages for maximizing the achievable sum rate, and present a closed-form expression of the corresponding power split. It was reported in literature that an asymmetric rate split between two users can maximize the sum rate in the two-user symmetric Gaussian interference channel when the HK scheme without time sharing is employed. However, we proved that the result in literature is incorrect and showed that the symmetric power split always attains the maximum sum rate. We also derived the optimal symmetric rate split for the simplified HK scheme.