On achievable rate regions for the Gaussian interference channel

This paper analyzes achievable rate regions for the Gaussian IFC (interference channel). The achievable rate region is based on reducing one user´s transmit power to a point such that its message is decodeable to both receivers. The second receiver then does interference reduction. The main point of the paper is that the time-sharing of Sato´s region exceeds the convex closure of a sub-region of Han and Kobayashi for symmetric interference channel under moderate interference, and also the achievable rate region by TDM/ FDM. It follows that on degraded Gaussian IFC, the sum-capacity is achieved with the stronger user transmitting at its maximum rate (ignoring the interference), while the weaker user treats the stronger user as interference. For a one-sided Gaussian IFC with weak or moderate interference, the sum-capacity is achieved if the transmitter, which is not interfered sends its data at the maximal achievable rate of a single-user, and the second transmitter sends its data at the maximal possible rate where the interfering signal is treated as an additive Gaussian noise. We show that the sum-capacity of a one-sided Gaussian IFC implies the upper bound on the sum-capacity of a two-user Gaussian IFC.