Research On Physical Layer Security Transmission Strategy Of Full-duplex Untrusted Relay System

Ensuring the confidentiality of communications is fundamental to securing any network.The broadcasting nature of wireless communication facilitates any eavesdropper to intercept the signal easily.Therefore,security is a topic that has been studied in wireless communication systems.The traditional approach is to employ cryptographic algorithms to ensure that only legitimate users can correctly interpret the messages,while all other entities fail to glean any useful information,thereby ensuring the security of the information.Due to its own channel characteristics,the wireless channel makes the user's channel unmeasurable and non-replicable to eavesdroppers,which reflects the inherent security properties of the wireless channel.The physical layer security technology cleverly uses this feature to plan the security mechanism from the signal level,providing new tools and means for solving the open problem of wireless communication.The core idea of physical layer security is not to rely on traditional encryption technology,by enhancing the legal channel(main channel)or reducing the communication performance of the eavesdropping channel,thereby creating the advantage of the main channel,preventing the eavesdropper from obtaining effective information to ensure information security transmission.The use of the spatial characteristics of the wireless channel by cooperative relay is an effective measure to increase the capacity of the main channel from the source node to the destination node.However,in many practical scenarios,cooperative relay may be untrusted.Research shows that based on untrusted relay It can also improve the physical layer security features.In addition,compared with half-duplex,full-duplex relay can better improve the security performance of the system and use spectrum efficiency more effectively,but full-duplex union introduces additional residual selfinterference,which interferes with the transmission of confidential information,resulting in the system decline in performance.Therefore,how to improve the security of the untrusted relay system in the presence of residual self-interference is the focus of this paper.(1)Full-duplex untrusted relay communication system based on orthogonal frequency division multiplexing(OFDM).In this paper,the full-duplex untrusted cooperative relay is extended to the OFDM system.In order to ensure the secure transmission of confidential information,a secure transmission strategy based on artificial noise interference sent by the source node is proposed.In the research,we proposed a joint optimization algorithm for the power allocation factor of the source node and the forwarding power of the relay node in each subcarrier to maximize the security rate of the system.But the optimization problem is a non-convex problem,this paper uses an iterative algorithm based on block coordinate descent and successive convex approximation to effectively solve the original non-convex problem.The simulation results show that,compared with the source power allocation and halfduplex benchmark scheme,the optimized scheme we propose has higher safety performance.(2)A full-duplex untrusted relay network model based on simultaneous wireless information and power transfer(SWIPT).Considering the problem of limited resources,in the full-duplex untrusted relay communication system,this paper proposes a physical layer security transmission scheme based on artificial noise interference and simultaneous wireless information and power transfer to address the information security and energy limitation problems.Among them,the untrusted relay with limited energy adopts power splitting or time switching strategy to realize SWIPT,and the source node sends confidential information and artificial noise.In order to maximize the security rate of the system,we established a joint optimization scheme of power allocation factor and power splitting factor/time switching factor,and analyzed the halfduplex power splitting/time switching scheme as the benchmark scheme.The simulation results show that compared with half-duplex relay,the proposed full-duplex scheme has better system security performance.At the same time,under high transmit signal-to-noise ratio,the power splitting full-duplex scheme has a higher security rate.