An online power-control algorithm for energy harvesting and secure transmission systems

Abstract

Here, we propose an online power-control strategy based on a Lyapunov optimization framework to optimize secrecy rate during the process of secure transmission in wireless communication systems with energy harvesting. We developed a system comprising one transmitter and two receivers that allow secure communication over a wireless fading channel. Additionally, this system includes an energy harvesting source node and two destination nodes that allow maintenance of information security between the two destination nodes. In each slot, the source node selects the destination node with the optimal channel state as the receiver of secret information, whereas the other destination node acts as an eavesdropper. Transmission power and the rate of information transfer are established according to current battery power and channel status, with constraints related to battery power converted into a virtual queue and the optimization target converted into a penalty. By optimizing the transmission power to minimize the instantaneous drift plus penalty function, the long-term average secrecy rate is maximized under the constraint condition. Furthermore, the transmission fairness of the two destination nodes is evaluated during the optimization process. Simulation results show that the proposed scheme effectively improved the long-term average secrecy rate of the system.