Research On Power Control Strategy To Optimize Energy Efficiency In Wireless Secure Communication Systems With Energy Harvesting

The broadcasting characteristics of wireless channels make the signals transmitted in wireless communication system easy to be wiretapped by unexpected receivers.This thesis studies the transmission power control algorithm for the maximization of the energy use efficiency in security communication systems with energy harvesting.Based on the current channel state and battery state information,the Lyapunov optimization framework is applied to transform and solve the optimization problem while maximizing the long-term average secrecy rate of the system under the harvested energy constraint.The main contents are as follows:The problem of transmission power control of a security communication system is studied,which is composed of one source and two receivers.The information sent to one receiver needs to be kept secret from the other.In each time slot,the source node selects a receiver as the destination to receive the confidential information according to the channel states.The optimization problem of the transmission power for the maximization of the long-term average secrecy rate under the constraint of harvested energy is constructed.The constraints of the battery operation and energy consumption are transformed into a virtual queue stability problem by using the Lyapunov optimization framework.The optimization object is used as a penalty term to formulate a drift-plus-penalty function and the original long-term average optimization problem is converted into a drift-plus-penalty minimization problem per time slot and solved.The performance of the algorithm is verified by simulation.The results show that the proposed algorithm can achieve a higher average secrecy rate than the comparison algorithms.The joint power control problem in a system consisting of a source node,a cooperative jamming node,and two receivers is studied,where the source node and the jamming node are powered by harvested energy.The cooperative jamming node sends artificial noise while the source node is transmitting information to improve the security performance of the system.The Lyapunov optimization framework is used to transform the joint control problem of the signal power and the artificial noise power under the constraints of energy into an instantaneous drift-plus-penalty minimization problem.The optimization problem is solved by using the KKT condition.The performance of the algorithm is verified by simulation.The simulation results show that the cooperative jamming can effectively promote the secrecy rate and significantly improve the system's security performance.