The Han-Kobayashi Region for a Class of Gaussian Interference Channels with Mixed Interference

A simple encoding scheme based on Sato's non-na\"ive frequency division is proposed for a class of Gaussian interference channels with mixed interference. The achievable region is shown to be equivalent to that of Costa's noiseberg region for the onesided Gaussian interference channel. This allows for an indirect proof that this simple achievable rate region is indeed equivalent to the Han-Kobayashi (HK) region with Gaussian input and with time sharing for this class of Gaussian interference channels with mixed interference.