On the Gaussian Z-interference channel

The optimality of the Han and Kobayashi achievable region (with Gaussian signaling) remains an open problem for Gaussian interference channels. In this paper we focus on the Gaussian Z-interference channel. We first show that using correlated (over time) Gaussian signals does not improve on the Han and Kobayashi achievable rate region. Secondly we compute the slope of the Han and Kobayashi achievable region with Gaussian signaling around the Sato's corner point.