| The UAV network is an indispensable part of the space-ground integrated network.It utilizes the advantages of rapid maneuvering and flexible deployment of UAVs and plays an important role in emergency communication,data collection and other industries.However,compared with traditional ground links,the Lo S air-to-ground links of UAV networks cover a wider range,are more likely to be eavesdropped or interfered by illegal users,and face more severe security challenges.Traditional encryption technology and physical layer security technology are designed to ensure the security of information content and cannot protect the information transmission process.Covert communication technology is a safe transmission technology to protect the information transmission process.It ”hides” information in environmental noise,making illegal users cannot detect the transmission of information,providing a strong security guarantee for the UAV network.Covert communication performance analysis is an important part of covert communication research.By optimizing and analyzing various performance indicators of covert communication systems,it provides theoretical support for the design of covert transmission systems.How to optimize and analyze the covert communication performance of the UAV network is the main research problem of this paper.At present,some researchers have studied the covert communication performance of UAV networks.However,the existing research work still has the following limitations:(1)The existing researches mainly use environmental noise or artificial noise sent by independent interfering nodes to realize the covert communication of the UAV network.It is impossible to control the noise power in the environment flexibly to improve the covert communication performance of the UAV network,which is difficult to meet the higher UAV network concealment requirements.(2)The existing covert communication jamming methods cannot effectively interfere with the monitoring nodes when the jamming nodes are far away from the monitoring nodes,which leads to the easy detection of the legitimate node information transmission process.It is urgent to design a reasonable external jamming node-assisted UAV network covert transmission mechanism,to ensure the safe transmission of information in the UAV network.In view of the above problems,this thesis systematically studies the covert communication mechanism of UAV networks in cooperative jamming scenarios,and proposes the corresponding performance analysis method.By using the uncertainty of cooperative interference noise,covert transmission methods of UAV networks are designed,which not only ensure covertness but also maximize the covert transmission rate.The main work and contributions of this thesis are as follows:(1)Performance analysis of UAV network covert communication in the scenario of cooperative interference of destination nodesThis thesis introduces the destination nodes cooperative jamming technology,establishes a UAV network covert communication model in the destination node cooperative jamming scenario.Under the assumption that the UAV is flying at a fixed altitude,calculates the mathematical expression of the system covert outage probability,transmission outage probability,maximum covert transmission rate,covert energy efficiency and other indicators.Taking the flight position of the UAV node,the transmission power of the source node,and the average interference power of the destination node as the variables,and the covert outage probability and the transmission outage probability as the constraints,an optimization problem with the goal of maximizing the covert transmission rate is constructed.By using traditional probability theory,asymptotic analysis and extreme point analysis,the analytical solution to the problem of maximizing the covert transmission rate is obtained? On this basis,the covert performance,transmission performance and covert energy efficiency of the system are analyzed? The simulation results show that the cooperative interference of destination nodes can effectively improve the covert performance of the system? The distance between the eavesdroppers node and the destination node has a great influence on the maximum covert transmission rate of the system.(2)The UAV node-assisted UAV network covert communication model and its performance analysisIn this thesis,external UAV jamming nodes are used to interfere with monitoring nodes,and a UAV network covert communication model assisted by UAV jamming nodes is established,and the optimal detection threshold and minimum detection error probability of monitoring nodes in the model are deduced.Mathematical expressions of system transmission interruption probability and maximum concealment transmission rate,and analysis of system covert performance and transmission performance? By using extreme analysis methods,the analytical solutions and closed-form solutions of the optimal flight positions of the UAV source node and the UAV interference node are solved respectively,and the maximum covert transmission rate of the system is obtained? The simulation results show that the UAV network assisted by the UAV jamming node has better covert communication performance than the traditional UAV network when the monitoring node is far away from the source node.The UAV network covert communication model and performance analysis method proposed in this thesis ensure the safe transmission of information in the UAV network,taking into account the covert performance and transmission performance of the system.It has certain theoretical and practical significance for promoting the research and application of UAV network covert communication. |
