The Strategy For UAV-enabled Secure Communication Systems Based On Trajectory Optimization And Resource Allocation

Unmanned Aerial Vehicle(UAV)has become a better solution in the field of wireless communication due to its features,such as flexible deployment,low cost and line-of-sight(LoS).At present,as a variety of substantial carriers,UAV has been applied in a variety of application scenarios in the field of wireless communication,such as UAV-enabled ubiquitous coverage,relay forwarding,mobile data collection and dissemination,mobile cloud computing and so on.However,the insecurity for wireless communication caused by the instability of wireless communication network and the broadcasting characteristics of media in wireless communication are also the key problems in UAV communication system.In fact,compared with the traditional static wireless communication system,UAV-enabled wireless communication system faces greater challenges,which is highlighted as:(1)the inherent openness of the wireless channel;(2)the dynamics of communication network for UAV.Based on the characteristics of wireless channel,it is the main direction in the future development of secure wireless communication to transform the disadvantages of wireless channel into the key factors to improve its security performance.Based on the tendency of future development and the above challenges,the physical layer security method which makes full use of the rich physical layer characteristics and resources of wireless channel to improve the security of wireless link has become one of the most promising methods in improving the security of UAV communication system.Based on the above background,this paper mainly considers two typical application scenarios for UAV communication systems,and studies different transmission strategies by optimizing the trajectory and resource allocation to improve the security of UAV communication in different communication scenarios by combining the technologies of physical layer security:cooperative jamming and artificial noise.The main research work as follows:(1)UAV-ground communication system assisted by extra friendly UAV jammer.This study proposes a scenario,in which an UAV is used as an extra friendly jamming node to transmit jamming signals and confuse the eavesdropping,helping the source UAV closer to the desired user on the ground.In this study,we jointly optimized the trajectory and transmission power of the source UAV and the jamming UAV to maximize the average secrecy rate achieved by the system.Because the objective optimization problem is non-convex,we solve the non-convex optimization problem to obtain its approximate convex problem,we proposed an iterative algorithm based on block coordinate descent.The numerical results show that the proposed algorithm can achieve a significant security gain compared with all benchmark schemes.(2)UAV-enabled data dissemination system via artificial noise.In this scenario,the secure data dissemination system with multiple ground users assisted by UAV is studied.The UAV in the system acts as a mobile base station to secretly communicate with multiple users located in ground.Artificial noise is introduced in order to reduce the energy consumption of the system and ensure the security between users,and assumed the UAV in the system to transmit useful information to the ground users while transmitting artificial noise.In addition,a mechanism of communication scheduling for ground users is introduced to adj ust the correspondence between UAV and ground users in real time.An optimization scheme by joint ground user scheduling,UAV trajectory and power splitting factor is proposed in each time slot to maximize the minimum average secrecy rate over a finite flight period.