Research On Key Techniques Of Connectivity In Vehicular Ad Hoc Networks

With the acceleration of industrialization process in China and the improvement of national living standard,car travel has become a common way of travel,however,the problems followed by such as road congestion,traffic safety,environmental pollution have become increasingly serious,which have been the researching focus in the field of moderm transportation.In order to alleviate the problem of urban road congestion,improve the efficiency of travel and resource utilization,China began the research about Intelligent Traffic System(ITS).Vehicle Ad Hoc Network(VANET)is an indispensable part of intelligent transportation,the transmission of various information in ITS can be carried out through the VANET,so it is necessary to study the VANET.Connectivity is commonly used to describe the quality of communication in the Internet of Vehicles,but the establishment of the communication link between network nodes is not able to reach 100%in the actual communication scenario.Based on the study of vehicle to vehicle communication and vehicle to infrastructure communication research status and relevant literature,this paper researches on the connectivity of VANET from several aspects,the main research contents and innovation points are as follows:First,in this paper,modeling analysis of multi-hop inter-vehicle communication based on spatial dependency in the highway scenario is studied,analysis results provide an effective way for the design and performance evaluation of the vehicle to vehicle communication system in the VANET.The multi-hop connectivity probability is studied under the single-lane and two-lane highway models.Considering the vehicle density,vehicle distribution,the minimum safety distance of the vehicle and the single-hop communication radius,the multi-hop connectivity probability is analyzed under the Unit-disk model and the log-normal shadow fading model in single-lane model.Under the two-lane model,the spatial dependence problem of vehicle is analyzed and a multi-hop communication model based on the intersection area is proposed.Simulation results show that the proposed model is more consistent with the actual vehicle communication scenario,the communication probability relate to the channel environment,vehicle distance,vehicle density and other factors.Second,vehicle to infrastructure communication is an important way of communication in vehicle communication system.The communication performance is poor when the distance between base stations is far,so that a vehicle to infrastructure communication model based on inter-vehicle communication is proposed in this paper.First of all,different types of vehicles on the highway is considered,the one hop communication radii of these vehicles are different.Then,according to the distance between the base stations,the general theoretical expressions of the connection probabilities of proposed model are deduced in five situations.Finally,detailed simulation results are compared.Third,in vehicle communication scenario,vehicle clustering is an aggregation way.This paper studies the connectivity of inter-vehicle communication from two aspects:forwarding process and catch-up process.Multi-hop communication of intra-clustering vehicles is researched in forwarding process,and the catch-up process mainly analyzes the communication between clusters.Simulation results show that the cluster size has a great influence on the communication probability of inter-vehicle communication in forwarding process,and the research of the catch-up process shows that the initial distance between vehicles has a certain relationship with the probability of overtaking success.The research of vehicle connectivity probability provides a theoretical basis for evaluating the movement behavior of vehicles.