Achievable sum-rate of simultaneous wireless information and power transfer in symmetric Gaussian interference channels

Abstract

Minimizing interference is the most desirable in conventional interference channels, but interfering signals can rather be exploited when information and power are transferred together. In simultaneous wireless information and power transfer (SWIPT) systems, transmission strategies should be devised by taking account for both information decoding and energy harvesting. Although the previous studies on SWIPT usually treat interference as noise (TIN), the efficiency of SWIPT can considerably be leveraged by interference decoding capability at receivers. To effectively exploit interference decoding capability, incorporating both rate splitting based on the Han-Kobayashi scheme and signal splitting based on a superposition of energy and information bearing signals, we propose a new transmission strategy for SWIPT in two-user symmetric Gaussian interference channel. We jointly optimize rate splitting ratio, signal splitting ratio, and power splitting ratio for each user to maximize the sum rate under energy harvesting constraints. In the strong interference condition, the solution to the formulated optimization problem is derived in closed form. We propose a simple algorithm to solve the problem in the weak interference condition. Interestingly, we reveal that the optimal splitting ratios are not always symmetric between users and present the corresponding sufficient conditions, while rate splitting ratio and transmit power symmetric between users are optimal in the conventional two-user symmetric interference channel without consideration of energy harvesting.