Research On Adaptive Congestion Control For CAMs Rate In Vehicular Ad Hoc Networks

The rise of the Internet era has accelerated the development of the Internet of Things.Under the development of the Internet of Things,in order to solve the current situation of daily traffic congestion,the vehicle-mounted self-organizing network technology(Vehicular Ad hoc network,VANET)has become the key technology of research.The vehicle-mounted selforganizing network technology is also called the Internet of Vehicles technology,which lays the foundation for the development of Intelligent Transportation System(ITS).At present,the Internet of Vehicles technology is the key technology of the current automotive industry research and the key technology of the intelligent transportation system.There are many systems in the Internet of Vehicles technology.Among them,the vehicle safety communication(Vehicular Safety Communication,VSC)that guarantees the transmission between vehicles is the most important system for the requirements of safety applications.The VSC communication system collects cooperative awareness messages(CAMs).Periodic transmission to other vehicles on a regular basis,this phenomenon causes the channel load to rise,causing congestion.Congestion issues will have a serious negative impact on safety applications,leading to problems such as traffic accidents,road congestion,and incorrect traffic decision information.How to solve these problems has become a hot spot in the study of VSC communication.This thesis introduces the development of VANET technology,analyzes the current deficiencies of congestion control in VANET,and designs a congestion control scheme for CAMs based on existing research.The main tasks of this thesis are as follows:(1)The main technologies of Telematics are described.The CAM document protocol and CAMs generation rules specified by the European Telecommunications Standards Institute(ETSI)are introduced.By connecting the micro road simulation platform SUOM(Simulation of Urban Mobility)with the network simulation platform OMNET++(Objective Modular Network Testbed in C++),a successful Telematics simulation platform has been set up to enable Telematics simulation in various scenarios.(2)The congestion control scheme of in-vehicle safety communication is studied,and it is found that the current congestion control of Telematics is mainly improved by limiting the transmission rate of CAMs or adjusting the competition window of the channel,etc.Limiting the transmission of CAMs messages will cause the basic safety information of Telematics communication to be transmitted not timely enough and the resource allocation of the communication network is not fair enough.In this thesis,we analyze and design the CAMs transmission rate combined with the channel competition window.On the one hand,considering the fairness of network resource allocation,we adopt the network utility maximization algorithm to iteratively calculate the CAMs rate so that the transmission rate of CAMs is optimal;on the other hand,we propose the adaptive channel congestion control by self-source detection and neighbor detection of CAMs messages,which can avoid the congestion This can avoid the hysteresis of congestion control.(3)Under the premise of considering the hidden station effect,single receiver and dual receiver are modeled separately,and the probability of receiving CAMs transmission is different for different receivers.In this thesis,we propose a new reception probability calculation model that combines single-receiver probability with dual-receiver probability,and the full consideration of CAMs reception probability under the proposed congestion control model is compared with other schemes.In order to assess the performance of the proposed scheme,through the Lanzhou city traffic scene experiment,verify that the construction of the practicability of the simulation platform,and the effectiveness of the CAMs oriented congestion control scheme,and with other congestion control schemes in cooperative consciousness message receiving probability,channel throughput,the average delay three schemes are compared.The experimental results show that the receiving probability of CAMs in this proposal is better than other control schemes,and the throughput is increased by about 10%.