Research On Vehicular Driving Model And Information Preferential Access

In the Vehicular Ad-Hoc Network(VANET),connectivity is a prerequisite for the existence of the network and the basis of network data transmission,which can guarantee the unicast and broadcast transmission of messages.The mobility of vehicles will directly affect the connectivity of the VANET and form different network topologies,then affecting the measurement and evaluation of network performance indicators such as transmission delay and packet loss rate.In addition,when the vehicles send messages simultaneously in high density situations,the shared channels are easily congested.Therefore,realizing the orderly transmission of messages and ensuring the priority channel access of safe messages is still an urgent problem to be solved.This paper conducts in-depth research on the related issues of vehicular mobility model,network connectivity and information preferential access in VANET.The major work and innovation are reflected in the following three aspects:(1)In order to study the influence degree of vehicle movement on network connectivity in the highway scene,the traffic flow in the highway is firstly modeled based on the theory of fluid mechanics.Secondly,a general formula is derived for the probability of full connectivity of vehicles on a certain section of highway.Thirdly,the changes of traffic flow in each section near the off-ramp and their influence on the probability of full connectivity of vehicles are analyzed.Finally,the minimum communication radiuses to achieve full connectivity of the VANET network under different arrival rates are given.The data analysis results show that the connectivity rate formula presented in this paper is consistent with the actual situation and can guide the actual deployment of VANET.(2)Aiming at the problem of how to reflect the real road traffic flow in the process of VANET simulation,a mobility model with active avoidance behavior is designed to simulate the actual road traffic flow.Firstly,the IDM＿LC model is determined as the basic model for subsequent research according to a basis for selecting the mobility model.Secondly,a mobility model with active avoidance behavior is designed in order to make up for the deficiencies of the IDM＿LC model,which enables ordinary vehicles to actively slow down or change lane in advance to avoid collision when encountering emergency vehicles,so as to ensure unimpeded traffic in front of the emergency vehicles.Finally,a simulation environment is built based on the network simulator NS-3 to verify the feasibility of the proposed model.The simulation results show that the model proposed in this paper is more consistent with the actual situation than the IDM＿LC model and can greatly shorten the travel time of emergency vehicles.(3)Aiming at the problem of how to realize the fast and orderly transmission of messages in VANET,a dynamic data priority assignment strategy is designed.The algorithm combines the dynamic factors,static factors and the size of the message to assign priority,and the priority can be continuously decreased with the passage of time and the expansion of transmission range,thereby limiting the spread of the message to the effective space-time range to reduce the waste of spectrum resources.The results of numerical analysis show that the priority assignment algorithm proposed in this paper can assign reasonable priority to messages according to their urgency and transmission requirements,and ensure the priority channel access for secure messages.