Theoretical Research On The Physical Layer Security Of UAV Communication Systems

Unmanned aerial vehicles(UAV)communication systems can provide communication services on demand,which is especially suitable for the scenarios of rapid on-demand deployment or emergencies.Due to the broadcasting of the wireless channel and the mobility of the UAV,the security of the UAV communication system faces great challenges.Based on Shannon's information theory,the physical layer security(PLS)provides a good solution for the secrecy transmission of wireless communication and has become one of the cross-research hotspots in the fields of information secrecy and wireless communication.This thesis studies the secrecy performance of the UAV communication systems.The main research work of this thesis can be summarized as follows:1.Firstly,the secrecy performance of UAV internet of things(Io T)communication system is mathematically modeled to analyze the impact of system parameters on secrecy performance.The locations of the eavesdropping nodes around the source node are modeled by a homogeneous Poisson point process.Rician and Rayleigh model are used to describe the small-scale fading respectively when the ground-to-air link is in line-ofsight and non-line-of-sight propagation.The cumulative distribution function and probability density function of the signal-to-noise ratio(SNR)of the main link and the eavesdropping links are derived by using the random geometry theory and then derives the closed-form analytical expressions for the exact and asymptotic secrecy outage probability(SOP)and average secrecy rate(ASC).The results show that the secrecy diversity order(SDO)only depends on the path loss exponent of the ground link and the high SNR slope of the ASC is equal to 1.Moreover,the slope of SOP and ASC curves is independent of the altitude of the UAV and channel environment parameters.This thesis also analyzes the secrecy performance of the system when a friendly UAV is utilized to send artificial noise(AN)and derives the closed-form expressions of the SOP and ASC.The results show that the AN strategy can effectively improve the secrecy performance of the UAV Io T system.2.Based on non-orthogonal multiple access(NOMA)technology,the secrecy performance of the UAV NOMA system is studied.Considering the different quality of service requirements of users,a distance-based adaptive static power allocation strategy is adopted and the secrecy performance of the system when the UAV is in linear and circular trajectories is analyzed.The analytical expressions for the exact and asymptotic SOP of the UAV NOMA system are derived.The results show that the secrecy performance of the system can be effectively improved by adjusting the altitude,transmission power and environmental parameters of the UAV.