| In recent years,UAV have been widely used in the field of wireless communication due to their advantages of low deployment cost and flexibility.In disaster rescue,temporary battlefield environment and other scenarios,using UAV as air nodes can quickly establish a wireless communication system to provide information exchange services,but because the UAV will be limited by energy,and the channel between the UAV and the ground node will also be affected by the location,so how to improving the effectiveness and reliability of the UAV communication system under the resources of the UAV is a key problem that needs to be overcome in UAV communication.Based on this background,this thesis mainly studies a multiple UAV cooperative wireless relay system model,and studies the key technologies such as UAV position and power control,hoping to solve the problems such as UAV position and power control in multiple UAV relay system.Under the requirement of user communication quality to achieve the goal of improving the effectiveness of the communication system.This thesis’ s general innovations and work can be implied as follows:Firstly,a wireless relay communication model of multiple UAV cooperation under uplink communication link is proposed.Based on this model,a new optimization method based on UAV position and power control is proposed.This method takes the maximization of the system rate utility function as the optimization goal.Under the constraints of the given base station and user location,the optimal location of the UAV and the optimal transmission power of the user are obtained by jointly solving the methods of BCD,WMMSE and SCA.Simulation results show that compared with the benchmark scheme of position optimization alone,the proposed algorithm can effectively improve the user communication rate by about 14.4% when the UAV power is the same.Secondly,the wireless relay network model of uplink multiple UAV cooperation is extended to the two-way wireless relay model combined with uplink and downlink,and an algorithm is proposed to maximize the system rate utility function of user’s uplink and downlink through beamforming,UAV position and power control under the two-way link.The optimal position,precoding matrix and power forwarding factor of the UAV are obtained through the joint solution of BCD、 WMMSE and SCA.The simulation results show that compared with the position optimization alone,the proposed joint optimization algorithm can increase the communication rate by about 34.6% when the power of UAV is the same.The scheme proposed in this thesis can effectively improve the effectiveness of the wireless relay communication system for multiple UAV cooperation.The research content and results enrich the research connotation in the field of UAV communication.It is of great significance to promote the application of UAV relay communication system. |
