The maximum Han-Kobayashi sum-rate for Gaussian interference channels

The best known achievable rate region for the two-user Gaussian interference channel is due to the Han-Kobayashi (HK) scheme. The HK achievable region includes the regions achieved by all other known schemes. However, mathematical expressions that characterize the HK region are complicated and involve a time sharing variable and two arbitrary power splitting variables. Accordingly, the boundary points of the HK region, and in particular the maximum HK sum-rate, are not known in general. This paper studies the sum-rate of the HK scheme with Gaussian inputs. For the weak interference class, this study fully characterizes the maximum achievable sum-rate and shows that the weak interference class is partitioned into five regions. For each region, the optimal power splitting and the corresponding maximum achievable sum-rate are expressed in closed forms. Moreover, we show that the same approach can be adopted to characterize all boundary points.