Relay Management And Power Control In UAV Assisted Internet Of Vehicles

5G technology has further improved the capacity of the Internet of Vehicles,users put forward higher requirements for communication quality,and mobile relay technology has been further developed to meet the indicators of low latency,high speed and high reliability.Due to the characteristics of high mobility,convenient deployment and low energy consumption,drones are often introduced as mobile relays in the Internet of Vehicles.With the increasing number of connected cars,the wireless resources of the Internet of Vehicles are facing important challenges,and reasonable power control is very necessary while ensuring communication quality.In order to further improve the performance of the Internet of Vehicles,mobile Unmanned Aerial Vehicle(UAV)relays no longer meet the fixed trajectory and random walk models,and their trajectory can be optimized,and their flexible mobility can be used to actively build favorable channel conditions and forward information at appropriate locations.In the multi-relay vehicle networking,the choice of relay will also affect the communication quality,and reasonable relay selection can be made according to relevant parameter indicators,signal-to-noise ratio,optimization goals,clustering technology,etc.Therefore,reasonable relay management and design of joint optimization schemes are the keys to improving the performance of the Internet of Vehicles in an all-round way.This thesis studies the joint optimization scheme of mobile UAV relay assisted Internet of Vehicles in different scenarios and working modes.Firstly,aiming at the poor communication speed of non-dense vehicle networks,a scheme of jointly optimizing the UAV trajectory and channel power allocation to maximize throughput is proposed.Link splitting is carried out by summation transformation and other mathematical means,and the power allocation of parallel subchannels is carried out by water injection algorithm.An iterative algorithm based on time slots is proposed to continuously update the source vehicle position and UAV position of adjacent time slots.A joint optimization algorithm based on time slot allocation is designed.The simulation results show that the scheme can significantly improve the throughput of the system.Secondly,aiming at the poor communication reliability of dense vehicle networks,a scheme of joint relay selection,UAV trajectory optimization and node power allocation is proposed to minimize the outage probability.Dynamic clustering and relay selection of vehicles are carried out by the improved K-means clustering algorithm.The trajectory optimization and power allocation were converted into third-and fourth-degree equation problems by the Lagrange method,respectively,and the gradient ascent method was used to solve them alternately iteratively.The simulation results show that the scheme not only achieves a lower communication outage probability,but also accelerates the system convergence speed and improves the system stability.Finally,for duplex communication and Internet of Vehicles,a scheme for jointly optimizing UAV trajectory and bidirectional power allocation to take into account reliability and speed is proposed.The information causal constraints caused by incomplete self-interference elimination and UAV processing delay are fully considered.Through relaxation technology and extreme value method to solve the bidirectional power allocation of UAV,and continuous convex optimization technology to solve the UAV position,an joint optimization algorithm based on continuous approximation is designed.The simulation results show that the scheme can significantly reduce the communication outage probability while ensuring the information transmission rate.