| The integrated sensing and communications(ISAC)system can realize the joint sensing and communication function with the same spectrum,which not only saves spectrum resources,but also helps to realize the mutual promotion of sensing and communication functions.Similarly,the UAV system based on the integrated sensing and communication function(ISACUAV)can communicate with the ground user and detect the ground target at the same time,which has a wide range of application prospects.Although the good channel characteristics of UAVs are beneficial to the joint sensing and communication function,they are also vulnerable to eavesdroppers.In order to solve the problem of information security of ISAC-UAV system,this paper studies the security design problem of UAV as a tethered base station or a flying base station.Firstly,the research status of ISAC system and UAV system is introduced,and the current security problems of ISAC-UAV system are comprehensively analyzed.It also introduces the research status of physical layer security,and analyzes the technical methods that can solve the security problem of ISAC-UAV at present.Then,the basic principles of ISAC system and its physical layer security are introduced to pave the way for the subsequent security research of ISAC-UAV system.Then,the system security design problem when UAV is used as a static base station is studied,an algorithm to optimize the precoding matrix is proposed to maximize the secrecy rate,and the effects of transmit power,detection performance and energy constraints on the secrecy rate are analyzed by theory and simulation.In order to meet the basic performance and power requirements of the system,the algorithm proposes to achieve the maximum secrecy rate of the system by optimizing the precoding matrix under the constraints of total transmit power,detection performance and energy receiving threshold.In order to solve the constructed nonconvex problem,a BCD algorithm based on Taylor expansion and a BCD algorithm based on semidefinite relaxation are proposed respectively.The simulation results show that the BCD algorithm based on Taylor expansion has lower computational complexity and faster computation speed.The BCD algorithm based on semi-definite relaxation can compensate the performance loss of the BCD algorithm based on Taylor expansion and achieve higher secrecy rate performance.Finally,the system safety design problem when UAV is used as a flying base station is studied,and an algorithm to jointly optimize the flight trajectory and transmission power is proposed to ensure the system safety,and the influence of transmission power,flight time and detection performance on the security are analyzed through theory and simulation.In order to meet the practical application scenarios,the algorithm proposes to maximize the secrecy rate of the system by jointly optimizing the flight trajectory and the transmission power under the constraints of flight trajectory,transmit power and detection performance.To solve the constructed non-convex problem,an iterative optimization algorithm is proposed to optimize the transmit power and flight trajectory respectively.The simulation results show that there is a trade-off relationship between the security performance and detection performance of the system,and the secrecy rate can be enhanced by optimizing the flight trajectory and increasing the transmit power. |
