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.