Research And Implementation Of Transmission Optimization Algorithm For Different Applications In Vanet

As an important part of the Intelligent Transport System(ITS),vehicular ad hoc networks(VANETs)should have the ability to guarantee the quality of service(QoS)of all kinds of applications in it.However,vehicular network is different from the general mobile ad hoc networks(MAVENTs).The high-speed movement of vehicle nodes leads to frequent changes of vehicular network topology,unstable links between vehicles,and high dynamic changes of channel quality.These characteristics make it a challenge to guarantee the QoS of various vehicular applications.The business in the Internet of vehicles is mainly divided into two categories:one is the security business,whose purpose is to improve traffic safety and protect the life and property safety of drivers and passengers;the other is the non security business(also known as entertainment business),whose purpose is to improve the travel comfort of drivers or passengers.The QoS requirements of these services are often different.For example,security services have strict requirements on delay and reliability,while non security services have strict requirements on packet delivery ratio.To guarantee the QoS of these services,its essence is to guarantee their transmission performance.Therefore,this thesis aims to explore the QoS guarantee technology,and designs the corresponding resource allocation and routing protocol mechanism for multi hop unicast entertainment service and basic security message broadcasting service which is the representatives of security services in vehicular network.For the broadcasting service of the basic safety message in the VANETs,the resource allocation mechanism based on self-learning window value is studied to provide service differentiation for different priority messages.Firstly,the broadcasting priority of basic safety message is calculated according to the driving state of the vehicle,which is the content of basic safety message.Then,the priority of basic safety message is redivided according to the environment of the vehicle.Then,based on the enhanced distributed channel access(EDCA)mechanism of IEEE 802.11p,a resource allocation mechanism based on self-learning window value is proposed.The mechanism adjusts the window value of each queue with different priority by considering the latest network state and packet transmission results,so as to achieve service differentiation and improve fairness.Finally,the effectiveness of the proposed mechanism is verified on NS3 simulation platform.The experimental results show that the proposed mechanism improves the network performance and transmission reliability.For the entertainment message based on multi hop unicast transmission,the routing mechanism based on communication quality and multi hop evaluation is studied.Considering the high dynamic of the vehicular network,we adopt the routing mechanism based on intersection.Firstly,in order to evaluate the communication quality of the road,the model of road connectivity probability and delay is established,and the optimal next intersection is selected by combining the local and global road connectivity probability,delay and distance to the destination node.Then,based on reinforcement learning,a multi hop evaluation mechanism is proposed to evaluate the long-term return of the next hop decision in the selected path,and the optimal next hop is selected to improve the reliability of transmission.Finally,the proposed mechanism is verified on NS3 simulation platform,and the simulation results show that the proposed algorithm reduces the delay and improves the throughput.In order to verify the algorithm proposed in this paper,we design and implement a differentiated service and routing verification system.The system is a front-end and back-end separation system.The front-end uses native HTML/CSS/JavaScript,and the back-end is based on SpringBoot framework.The system mainly includes two modules:DiffServ module and routing module.In each module,users can set simulation parameters and one click simulation,and the system will display the simulation results under the setting scenario,including delay and throughput.Finally,we test the system and verify the feasibility and effectiveness of the system.