The Physical Layer Security Transmission Strategy Of Intelligent Reflecting Surface Assisted Cognitive Network

With the rapid growth of the number of mobile communication devices and the widespread application of wireless communications,next-generation wireless networks have put forward higher requirements for spectrum efficiency and large-scale links,which has also led to a gradual increase in the huge demand for radio spectrum resources.Cognitive radio technology is an effective solution to improve spectrum efficiency by allowing secondary users to share spectrum with primary users.However,the security problems caused by the highly dynamic and open nature of the cognitive network cannot be ignored.Aiming at the security problems of cognitive networks,recently,the intelligent reflecting surface can control the wireless propagation environment to enhance the security of the communication system has attracted widespread attention.Specifically,signals from different communication links can be coherently added to the required receivers to enhance the received signal energy,or destructive at unintended receivers to avoid information leakage.Therefore,this paper studies the physical layer security transmission strategy of the intelligent reflecting surface-assisted cognitive network.First,multiple eavesdropping scenarios are considered,and the use of intelligent reflecting surfaces and artificial noise to assist cognitive network security communication effectively improves the security rate of the secondary system.Secondly,it considers the cognitive network security communication scenario where the secondary user is untrusted.The secondary user may eavesdrop on the confidential information of the primary user,and uses the intelligent reflecting surface to assist communication to enhance the secrecy rate of the primary user.This article summarizes the main research content into the following two points:(1)The intelligent reflecting surface assists the secure communication of the cognitive network.In this scenario,the secondary user communicates with the base station legally and is limited by the interference temperature of the primary user in the presence of multiple eavesdroppers.In the research,we propose to jointly optimize the base station transmit beamforming and the intelligent reflecting surface's phase shift matrix to maximize the security rate of the secondary system.Since the target problem is a non-convex optimization problem,we propose continuous convex approximation and semi-definite relaxation techniques to deal with non-convex problems and obtain the optimal solution of the target problem through an alternating iterative algorithm.(2)Intelligent reflecting surface assists cognitive network security communication with untrusted secondary users.In this research,a new point of view is proposed,namely,the cognitive network security communication scenario where the secondary user is untrusted.In this cognitive network,both the primary user and the secondary user have specific signal transmitters and assist communication via intelligent reflecting surface.Among them,the secondary user is untrusted and may eavesdrop on the confidential information of the primary user.Our goal is to maximize the security rate of the primary user by jointly optimizing the beamforming of the primary user's transmitter and the secondary user's transmitter and the phase shift matrix of intelligent reflecting surface under the constraint of the minimum information rate of the secondary user.