Research On Secrecy Energy Efficiency Of UAV-ground Communication System For Physical Layer Security

Low-latitude unmanned aerial vehicle(UAV)is considered to be a promising technology in assisting ground wireless communication(improve channel capacity,provide seamless access service,enhance wireless coverage,etc.)due to its inherent characteristics such as controllable movement,rapid deployment,and high probability line-of-sight(Lo S)link.At present,as airborne communication platforms(mobile base stations,mobile relays),UAVs are widely used in communication scenarios such as relay forwarding,seamless coverage,data distribution,edge caching,and mobile computing.However,there are many problems when UAVs are used for wireless communication.For example,although Lo S link can enhance the capacity of wireless channel and greatly improve the performance of wireless communication system,such Lo S link is also more prone to being intercepted by terrestrial eavesdroppers,thus leading to a new security threat.In order to achieve secure communication,PLS technology has become an effective approach to enable secure wireless communication,where the rich physical layer features and resources of the wireless channel can be effectively exploited to enhance the security of the wireless link and achieve secure transmission.Secondly,UAV’s on-board energy is another major problem due to the size and weight limitations of UAV,which limits the sustainability and performance of UAV communication systems.The energy consumption of UAV in auxiliary communication mainly depends on its own battery,and the energy consumption is directly related to the secure communication throughput that can be achieved before the UAV is recalled and recharged.Therefore,improving the energy efficiency of UAV can not only increase the communication system throughput but also extend the life cycle of the communication system.The above challenges need to be addressed when UAVs are used in practical communication scenarios.Focusing on the above problems,this paper comprehensively weighs the relationship between the communication throughput and energy consumption of UAV,takes the secrecy energy efficiency of the communication system as the evaluation index,combines PLS technology and UAV communication technology to maximize the secrecy energy efficiency of UAV-ground communication system.The main research work is as follows:(1)For the scenario of multiple eavesdropping nodes,the joint trajectory design and resource optimization to maximize the secrecy energy efficiency for UAV-ground communication system.In the UAV-ground communication scenario,where a fixedwing UAV act as an airborne mobile base station tries to transmit confidential information to a terrestrial legitimate destination in the present of multiple terrestrial eavesdroppers.In particular,our goal is to establish an optimization model aiming at maximizing the worst-case secrecy energy efficiency of UAV communication system.However,the formulated problem is challenging to solve because of its large-scale nonconvexity.In order to solve the problem effectively,we first decouple the above optimization problem into two subproblems of UAV transmit power control and flight trajectory design,and then propose an efficient iterative algorithm by adopting block coordinate descent method and Dinkelbach’s algorithm as well as successive convex approximation techniques to seek a suboptimal solution.The simulation results verify the effectiveness and reliability of the proposed algorithm.Finally,simulation results are provided to validate that our proposed secrecy energy efficiency maximization algorithm is superior to two benchmark schemes of secure rate maximization and constrained energy minimization for the UAV-ground communication system.(2)UAV-assisted multi-user data secure distribution method under secrecy energy efficiency criteria.In the system,a fixed-wing UAV serves as a mobile base station to distribute data to multiple untrusted users on the ground.In this scenario,we introduce artificial noise technology to further enhance secure communication,and maximize the minimum secrecy energy efficiency of the system by jointly optimizing ground multiuser scheduling,artificial noise distribution coefficient and UAV flight trajectory.The formulated problem is challenging to solve because of its large-scale non-convexity.To solve the problem effectively,we first decouple the above optimization problem into three subproblems: user scheduling,noise allocation,and trajectory design.Then,a minimum system secrecy energy efficiency maximize algorithm is proposed by adopting block coordinate descent method and Dinkelbach’s algorithm as well as successive convex approximation techniques to seek a high-quality suboptimal solution.The simulation results verify the feasibility and robustness of the proposed algorithm,and show that the algorithm can effectively improve the secrecy energy efficiency of the system.