Research On Optimal Transmission Strategy Of Full-duplex Two-way UAV Relay

Unmanned Aerial Vehicle(UAV)technology is developing rapidly,and its application cost is also decreasing.In the field of wireless communication,UAV can be equipped with a variety of communication equipment such as small base stations,sensors,receivers,etc.to form UAV communication,is an important part of the new generation of air-space-ground integrated communication.UAV communication has the advantages of flexible deployment in the air,3D mobility,high enough flight height and higher probability Line of Sight(Lo S)link with ground nodes,Therefore,UAV communication has become a current research hotspot,and it is also one of the important directions for the development of 6G communication.When the UAV acts as an air relay,it can cooperate in ultra-long-distance communication,and can also help restore communication transmission between users with communication impairments.However,the UAV-assisted relay communication system still faces many challenges,such as the capacity of the UAV-assisted relay communication,the total energy consumption and mission completion time of the UAV.This thesis studies the UAV as a full-duplex two-way relay(FD-TWR)in the air to further improve the relay communication capacity.At present,the research on UAV relay mainly focuses on the trajectory or resources.In terms of scheduling,consider the simpler half-duplex mode.Half-duplex is more convenient for system implementation,but there is still room for optimization in the utilization of time slot resources and frequency resources.In FD-TWR mode,users can simultaneously transmit signals in both directions,which greatly improves the utilization of timefrequency resources and increases communication capacity.In addition,this thesis also studies the UAV FD-TWR service scenario,in the case of a certain amount of tasks,by optimizing its trajectory and ground resource scheduling,to solve the problem of minimum task energy consumption and minimum task time.The main innovations and work of this thesis are as follows:This thesis firstly studies the performance-optimized transmission strategy of the multi-pair user UAV FD-TWR system.The FD-TWR network utilizes the same timefrequency resources through full-duplex relay nodes to simultaneously complete an efficient two-way data transmission mode between two full-duplex user nodes.Taking advantage of the on-demand and flexible deployment of UAVs,the UAV-based FDTWR network can further enhance the coverage of collaborative communication.To this end,the research uses UAVs to assist multiple pairs of ground users to carry out two-way relay communication.By jointly optimizing multiple variables such as UAV flight trajectory,time scheduling of ground users,and user transmit power allocation,the average minimum achievable rate of transmission between pairs of users is maximized.In the process of communication service,the UAV adopts the Physical Layer Network Coding(PNC)relay transmission protocol,and uses the Time Discretization(TD)method to discretize the continuous variables of the original problem.Due to the non-convexity of the research problem,a variety of convex optimization methods are used,such as Successive Convex Approximation(SCA)processing,Block Coordinate Descent(BCD)and other methods.The solution is solved and optimized in an alternate iterative manner,which realizes the rapid solution of the problem.The simulation results show that this method can improve the overall communication reachable rate of the system compared with the benchmark scheme.This thesis further studies the optimization strategy of flight energy consumption and completion time of UAV FD-TWR network.And under the conditions of different relay communication throughput requirements,the problems of minimizing the total energy consumption and mission completion time of the system are solved.Among them,UAV FD-TWR uses Time Division Multiple Access(TDMA)technology to provide communication relay services for multiple pairs of users on the ground,and use the Path Discretization(PD)method to discretize multiple continuous variables in the problem.Then,using methods such as SCA and BCD,it is divided into multiple sub-problems related to user task scheduling,launch power and the trajectory of the UAV,and use the UAV trajectory initialization method based on the Travelling Salesman Problem(TSP).Iterate through multiple steps until the optimization converges.The simulation results show that the optimized resources are reasonably scheduled,and the optimized UAV trajectory can also improve the overall communication quality,minimize the mission total energy consumption and completion time.And further analyze the trade-off between task energy consumption and time under different goals.