The Investigation Of Secure Transmission In Cooperative Cognitive Radio Networks

As a cooperative-based technology,cooperative cognitive radio technology not only solves the problem of spectrum resource shortage for secondary users,but also improves the transmission performance of primary users with the assistance of secondary users.However,with the rapid development of wireless communication,the security problem of cooperative cognitive radio network caused by the broadcast characteristics of wireless channels and the unauthorized characteristics of secondary users has become more and more serious.Considering that the traditional encryption algorithm and the high complexity of key distribution management are not applicable to cooperative cognitive radio networks,this thesis employs physical layer security technology based on the characteristics of wireless channels to ensure secure transmission of users.The advancement of 5G and IoT technology has led to a sharp increase in the number of network nodes.It has become another difficult problem to achieve continuous energy supply for all nodes.Therefore,this thesis fiurther considers that secondary users in cooperative cognitive radio networks are energy-constrained devices.The use of energy harvesting technology to achieve self-energy supply for secondary users is proposed.In view of the above description,this thesis studies the problem of secure and reliable transmission of primary users without direct link in cooperative cognitive radio networks based on energy harvesting technology.The main research contents are as follows:(1)Firstly,the problem of secure transmission of cooperative cognitive radio networks based on harvest-use mode energy harvesting technology is studied.Aiming at the risk of eavesdropping,a two-phase cooperative jamming strategy is proposed to ensure secure transmission of the primary user.Secondary users acting as helpers use RF energy harvesting technology to harvest energy during the first phase of communication,and use the energy for signal forwarding and interference transmission in the second phase.According to communication process,the optimization equation is established to maximize the secrecy rate of the primary user.For the non-convex optimization problem,an alternative optimization algorithm is proposed to obta:in a feasible optimal solution.The simulation results further prove the effectiveness of the proposed strategy and the convergence of algorithms.(2)Secondly,the relay selection problem of cooperative cognitive radio networks based on harvest-store-use mode energy harvesting technology is studied.Here,considering the non-authorization of secondary users,two cases of trusted and untrusted secondary users are analyzed separately.For the case of multiple secondary users with energy harvesting function as alternative relays,a relay selection strategy based on both channel state information and battery state information is proposed.According to the characteristics of the charge and discharge behavior of secondary users'batteries,the energy of secondary users',batteries is modeled as a finite-state Markov chain,and its steady-state distrnbution is obtained through analysis.Furthermore,the transmission outage performance of the primary user is analyzed in two cases.The influence of different parameters on outage performance is further studied through simulation(3)Finally,considering the user's personal rationality,the relay selection strategy mentioned above is no longer applicable to energy-constrained secondary systems Therefore,a relay selection strategy for secondary systems based on Vickrey auction is proposed.Through reasonable deduction and analysis,the honesty and personal rationality of both bidders are verified,and the complete relay selection process is givenThis thesis consists of 5 chapters,including 24 figures,3 tables and 82 references.