Research On Theory And Method Of Wireless Transmission In Caching UAV Assisted Communication

Due to its strong mobility,low cost,and ease of deployment,Unmanned Aerial Vehicle(UAV)-assisted wireless communication technology is considered to be one of the key technologies with great application prospects in the forthcoming the 5th Generation Mobile Communication System(5G)and the Beyond 5G(B5G).However,UAVs can only provide users with data transmission services through the wireless backhaul links established with ground base stations,the capacity-limited wireless backhaul links will degrade UAV transmission rates.UAV-assisted communication based on edge caching can effectively reduce the load of wireless backhaul links,improve the performance of UAV-assisted communication networks,and provide users with better service quality.However,the current research on cache-enabled UAV-assisted wireless communication has not considered the improvement of the performance of UAV-assisted relay communication systems by caching and the impacts of cache capacity on the location of UAV relays.For the above problems,the following research work has been done in this paper.Firstly,we study the key technologies in cache-based UAV-assisted wireless communication,explaining the edge caching technology and relay technology in detail respectively.In addition,the differences between the air-to-ground channel model and the traditional ground transmission model are also introduced,as well as three commonly used air-to-ground channel models in researches.Secondly,for a caching UAV relay system in downlink single-user communication scenario,the design method of UAV horizontal position and the effects of edge caching technology on UAV relay communication system performance and UAV horizontal position are studied.Based on the ‘system average achievable rate maximization' principle,a UAV horizontal position design method is proposed,and we obtain a semi-closed expression for the optimal UAV position.Simulation results verify the correctness of the proposed location design,and reveal the impacts of the cache capacity on the UAV location and the average achievable rate of the system,showing that the cache technology can help improve the transmission performance of the UAV relay system.Finally,for a caching UAV relay system in downlink multi-user communication scenario,we study the problem of UAV Three-Dimensional(3D)location deployment.Based on the principle of ‘system average achievable sum rate maximization',we propose an optimal UAV 3D(UAV horizontal position and vertical position)design method by using iterative algorithm.Simulation results demonstrate that the proposed method can effectively improve the system average achievable sum rate compared with the traditional method that UAV located in the user-centered,and show that the proposed method can adjust the position of the UAV in time according to the change of the user's position,thereby providing users with more high quality communication services.