Research On Highly Energy-Efficient Robust Covert Transmission Technology For UAV Communication Systems

Unmanned aerial vehicle(UAV),as an air communication base station,can easily establish a line-of-sight(Lo S)channel with ground users due to its characteristics of strong mobility,flexible deployment,wide coverage,and low operating costs.It can effectively improve the communication capacity and coverage performance of the network and has been widely used in various fields.Owing to the broadcast characteristics of wireless communication channels,the secure transmission and privacy protection of link information has become a key problem in the research of UAV communication.In recent years,in order to deal with these security threats and challenges,different from traditional coding techniques and physical layer security methods from the perspective of information theory,covert communication focuses on hiding the existence of information to protect the transmitted signals from being detected by detector,which is an emerging secure communication.At the same time,due to the high energy consumption of the UAV itself and the limited battery power it carries,energy efficiency is an indispensable research point for UAV communication.In addition,the hidden detector exists passively in the communication environment,and its perfect location information is difficult to obtain,which greatly reduces the performance.Therefore,the impact of the detector’s position error on the energy efficiency performance of the system must also be considered.In this context,this paper designs different optimization schemes for energy-efficient robust covert transmission of UAV communication systems under two models respectively.The specific research contents are as follows:(1)For small fixed-wing UAVs with on-board limited energy,highly energy-efficient robust covert transmission for UAV communication systems is designed.Firstly,the UAV uplink data transmission link channel model and UAV propulsion power consumption model are constructed based on the discretization method,and the signal transmission between nodes and the covertness communication model based on the detection error probability are deduced.Secondly,under the consideration of detector’s location error,the optimization problem of UAV multi-user covert communication system is proposed with the energy efficiency of the system being the optimization index.Since the original problem is non-convex,it is decomposed into two sequential problems,and a joint iterative solution algorithm based on penalty function and successive convex approximation method(P-SCA)is proposed to obtain the global optimal solution of the original optimization problem.Finally,the simulation results verify the superiority of the proposed iterative algorithm and demonstrate the effective improvement of the system’s energy efficiency.(2)In order to further improve the covertness and the performance of energy efficiency,highly energy-efficient robust covert transmission for UAV communication systems based on auxiliary interference is designed,which other unscheduled ground users who are not currently communicating transmit artificial noise to interfere with both the UAV and detector at the same time.First,based on the discretization method,the UAV uplink data transmission link channel model,the signal model,the UAV propulsion power consumption model and the covertness communication model based on the detection error probability are constructed;secondly,the energy efficiency maximization problem of robust covert data collection in UAV multi-user communication system based on artificial noise is proposed,the original optimization problem is decomposed into two sub-problems of transmit power optimization and joint optimization of scheduling coefficient and UAV’s trajectory by using block coordinate descent(BCD)method.The Alternative Optimization(AO)iterative algorithm is proposed by introducing auxiliary variables and P-SCA method to obtain the global optimal solution.Finally,the superiority of the proposed alternative iterative algorithm is verified by simulation results,which shows that the energy efficiency performance of the system can still be effectively improved under artificial noise.