To maximize the long-term time-averaged secrecy rate of an energy harvesting wireless communication system, an online power control algorithm based on the Lyapunov optimization framework is proposed. The system is composed of a source node, a cooperative jamming node, and two destination nodes. The source node and the jamming node are powered by the energy harvesting device. Information sent to the two destination nodes is mutually confidential. Using the Lyapunov optimization framework, the original stochastic optimization problem is transformed into a per-time-slot optimization problem, and the power of the signal and that of the artificial noise are determined based on the current system state such as the power level of the batteries and channel coefficients. The fairness between the two destination nodes is considered too. Simulation results demonstrate that the proposed algorithm can effectively utilize the harvested energy and significantly improve the long-term averaged secrecy rate.
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