Research On VANET Connectivity Based On Temporal Network Under Fading Channel

As one of the most promising research fields of intelligent transportation system(ITS),VANET is a special mobile self-organizing.And the connectivity is one of the main performance parameters in network performance evaluation.The high-speed movement between vehicles and the transmission of signals between vehicles have an important impact on network connectivity,and the study of VANET channel fading characteristics is an important prerequisite for studying VANET connectivity.In this paper,because of the dynamic characteristics of VANET,the temporal reachability network model based storage-and-forward mechanism was built.The obstacle-based channel model for VANET was built,and which vehicles and buildings are the main obstacles that obstruct the communication between vehicles.The main work is summarized as the following two aspects:(1)The temporal model of VANET as(τ,δ)reachability graph model is built based on the dynamic characteristics of VANET.This model not only describes the information transmission time,but also can capture the store-and-forward mechanism in VANET.The characteristics of temporal topology of VANET are studied by simulation experiment.The relations of the information transmission time τ and the maximum tolerated delay time δ to the out-degrees,asymmetry and reachability ratio of packets are analyzed.The results show that compared to the instantaneous and the static network model,the temporal network model can capture the information transmission process in VANET better,and the decrease of transmission time τ or the increase of maximum tolerated delay time δ contributes to the improvement of temporal connectivity in VANET,thus raising the transmission efficiency of VANET topology control and protocol development with new guidance.(2)The obstacle-based channel model for VANET was built based on urban scene,and study the connectivity characteristics of VANET when is as a static network and a dynamic network respectively.Taking network density,global network efficiency,link duration and other parameters as quantitative indicators to evaluate connectivity,study the evolution of VANET connectivity with time under the three kinds of channel model(unit disk model,lognormal shadowing and obstacle-based channel model)using for simulation experiment.The results show that the unit disk model overestimates the connectivity of VANET,and obstacle-based channel model can describe the fading characteristics of the channel in urban scenario more accurately.The results also show that the store-and-forward mechanism can improve the temporal connectivity and stability of the network,this is helpful to improve the efficiency of packet transmission.