Physical Layer Security Transmission In UAV Communication

UAV technology first appeared in the 1930 s.It was first used as an drone for military training.During the two world wars,it gradually developed and applied in military reconnaissance,intelligence collection and communication,and then it was widely used in military strike and military monitoring to reduce crew damage.With the reduction of UAV cost and volume,civil UAV is developing rapidly.Nowadays,UAV has been gradually used in urban management,agriculture,geology,meteorology,power,emergency rescue and disaster relief,video shooting and other industries.At the same time,it has also been widely concerned and studied by academia and industry.UAV is also developed in combination with mobile communication technology.In the sudden geological and natural disasters,UAV can quickly restore communication.In the area where the communication infrastructure is not perfect or there are too many end users(such as the stadium hosting the event),even though the current communication base station can meet the existing communication needs of users,it is difficult to meet the needs of future communication with large capacity,high speed,low delay and high reliability,and the combination of UAV and wireless communication can provide a solution to this problem.UAV can be used as an air assisted mobile relay.It can connect the signal source and the receiver by establishing a line of sight communication link.The communication performance of the signal source and the receiver can be significantly improved and improved by relaying and forwarding.In addition,due to the dynamic deployment of UAV,it can adjust the flight state in real time according to the actual communication scene and physical environment,and has certain adaptability to complex environment,so as to improve the adaptability and anti-interference ability of the system.With the development of the fifth generation mobile communication network(5g),the future mobile wireless communication is facing great challenges due to the high broadband,low delay communication scenarios,and the service requirements of flexible mobile deployment anytime,anywhere.Because of its unique functions and characteristics,UAV can act as a flexible communication support device in the air and play an important role in 5g network,which is helpful to further improve the network capacity and communication rate of 5g communication network,and also to further expand the coverage area of the network,which makes the wireless communication system based on UAV become a very competitive wireless communication system in the future Competitive reference scheme.It is worth noting that the wireless channel has the broadcast characteristic,which makes the nodes in the communication range can receive the signal sent by the signal source,which makes the wireless communication completely exposed to the eavesdropper and the attacker,and it is easy to be attacked by them.In addition,the Airto-Ground link when the UAV communicates with the ground is mainly based on the link,which aggravates this kind of security risk.It can be seen that security is a crucial issue to build and maintain the current and wireless communication network and operation.Before that,encryption based on cryptography is the main method of traditional research on wireless communication security,and the premise of this encryption method is that the key is not stolen by the eavesdropper,or the eavesdropper can not break the key within a certain period of time.However,the computing performance of the computer is gradually improving,and this premise is gradually eliminated and broken,which makes the traditional secure communication mode based on cryptography threatened.In this context,researchers began to study the physical layer security in wireless communication.Physical layer security technology is a good supplementary security technology of upper layer security technology,which makes full use of the characteristics of physical layer(such as the uniqueness and reciprocity of physical channel information)to realize the encryption of information,so that the legitimate receiver and the eavesdropper can be distinguished,so as to improve the security performance of communication system.The traditional security strategy based on cryptography is mainly realized by encryption technology,while physical layer security technology does not need the design and distribution of key,and also avoids complex algorithm,but it can still effectively provide security for wireless communication,which makes physical layer security technology more suitable for future large-scale,distributed wireless communication network than traditional security technology.Based on the above,the goal of this paper is to use the physical layer security related technology in the UAV Communication System against the eavesdropping of malicious eavesdroppers to improve the security performance of the system.This paper mainly studies two problems: one is the physical layer security problem of UAV assisted mobile relay wireless communication system.The scheme of joint optimization of UAV flight path and transmission power is adopted to maximize the security capacity of UAV Communication System and improve the security performance of the system.The other is to use another UAV as a friendly jammer to send artificial interference noise.The other is to use one UAV to send data signal and interference noise at the same time to interfere with the eavesdropper's eavesdropping,so as to improve the security performance of the system.In the process of optimization,the non-convex problem is transformed into the approximate suboptimal convex problem by using the sequence convex programming method,and then the convex optimization method is used to solve it.In order to solve the two coupling problems of trajectory optimization and power distribution,this paper divides them into two sub-problems,and proposes a fixed alternative iterative optimization algorithm to solve the other step-by-step optimization.