Performance Analysis And Optimization Of Wireless Powered Relaying Systems Based On Physical Layer Security

Due to the broadcast nature of the radio frequency signal transmitting in free space,wireless communications inevitably suffer from the threat of illegal eavesdropping.Traditionally,information security is generally guaranteed through high-layer encryption mechanisms.In recent years,the physical layer security,as a promising information security technology,has been receiving the widespread attention in academy and industry.To ensure the security of information transmission,the physical layer security technology takes advantage of the random characteristics of the wireless channel,such as fading,noise and interference,to prevent the eavesdropping node from decoding the intercepted signal correctly.The paper considers a massive multiple-input multiple-output(M-MIMO)wireless powered relaying system,where a source node transmits the confidential information to the destination node with the assistance of a reliable relay node,while an illegal eavesdropper node attempts to intercept the information from the relay node.With limited energy supply,the source node transmits information and energy to the relay node simultaneously,and the relay node forwards the information with the harvested energy.First,under the condition that the relay can obtain imperfect channel state information(CSI)of the legitimate channel and no CSI of the wiretap channel,the secrecy outage capacity is deduced and analyzed respectively when the relay adopts amplify-and-forward(AF)and decode-and-forward(DF)protocol.Additionally,the paper makes asymptotic analysis on the secrecy performance of the proposed system,and the ultimate performance is obtained.Further,to improve the security performance of the system,we propose the capacity maximization power allocation scheme and the relay forwarding protocol switch scheme.Then,In order to investigate the performance of the system from the aspects of both security and energy utility,the total power consumption model of the AF relaying system is established,and then the paper gives the expression of the secrecy energy efficiency of the system.Next,the transmit power of the source node is optimized and we propose the energy-efficient power allocation scheme to maximize the secrecy energy efficiency of the system.Finally,taking into account the requirements of green communication,the paper introduces the path loss of the free space model,and obtains the explicit expression of secrecy energy efficiency of DF wireless powered relaying system.Then,by designing the power transmission scheme of the source node,the goal of maximizing the secrecy energy efficiency of the system is realized.At last,the numerical simulation validates the effectiveness of the optimization algorithm,and the performance of the system is compared under different parameters.