Caching And Trajectory Design Of UAV Communication Networks

In the future,the explosive growth of data transmission in mobile networks and the shortage of ground communication resources will cause bottlenecks in communication performance.It is urgent to expand new communication dimensions into space.To solve this problem,unmanned aerial vehicle(UAV)with high mobility and line-of-sight transmission can be used to expand network coverage and improve communication throughput.However,there are still some problems in UAV-assisted wireless networks.Firstly,since the wireless backhaul connecting the UAV and the core network is limited,network congestion is prone to occur during the peak-traffic time,which will degrade the user experience.Secondly,due to the broadcast characteristic of wireless channels,there is serious interference problem in UAV-assisted networks.Besides,UAV transmission is easy to be eavesdropped due to the open physical channels and line-of-sight channels.Therefore,in this paper,UAV-assisted wireless network is studied.Caching is used to reduce the pressure of the backhaul.Interference alignment is utilized to cancel the interference perfectly.Jamming signal is designed to destroy eavesdropping.Furthermore,UAV trajectory and the user scheduling can be optimized to improve the sum rate of UAV served edge users and the security of the UAV-relaying-assisted network.Specifically speaking,the work includes:(1)As for UAV-aided dense small-cell networks:Firstly,caching is used to relieve the pressure of the wireless backhaul at peak-traffic time.Next,the precoding matrices of small-cell base stations are designed to align the interference to the direction of the UAV interference.Decoding matrices are designed to cancel interference.Then,jamming signal is designed to only disrupt eavesdropping without affecting the legitimate transmission.(2)As for UAV-aided offloading at the edges of multiple cells:Firstly,a system model of UAV-assisted edge network transmission is constructed.Next,the UAV trajectory and time scheduling are optimized to maximize the sum rate of UAV served edge users based on the rate requirements for the users served by small-cell base station.Besides,a low-complexity iterative algorithm based on continuous convex optimization is used to solve the optimization problem.(3)As for UAV-relaying-assisted secure transmission:Firstly,caching is used to ensure the secure transmission for cache-enabled users.Then,the UAV trajectory and time scheduling are optimized to maximize the minimum average secrecy rate of uncached users.Besides,an iterative algorithm based on continuous convex optimization is used to solve the optimization problem.(4)As for UAV-aided emergency communication network:Firstly,dual UAVs and device-to-device(D2D)transmission are used in disaster areas to achieve rapid communication recovery.Then,user association is optimized to maximize the weighted sum rate of UAV-served users and the total number of users served via D2D connections.Besides,the learning-based clustering algorithm and relaxed algorithm are proposed to solve the optimization problem.