Modeling And Analysis Of Network Connectivity And Roadside Unit Deployment For Vehicular Adhoc Networks

Vehicular Ad Hoc Networks(VANETs)are currently receiving more and more attention from both industry and academia.As part of an Intelligent Transportation System(ITS),a VANET originates from traditional Mobile Ad Hoc Networks(MANETs)and is a special type of MANET designed particularly for communication between vehicles.A VANET has a highly dynamic characteristic,which limits the timeliness and efficiency of data dissemination.Network connectivity is an important metric for measuring the highly dynamic characteristic of a VANET.This dissertation studies the network connectivity problem in VANETs and focuses on the modeling and analysis of network connectivity in different highway road scenarios.The main work and contributions of this dissertation including the following four aspects:Firstly,the information delivery delay in a highway road scenario with roadside units(RSUs)is studied and a theoretical analysis model is established for analyzing and calculating the incident information delivery delay.In establishing the model,it is assumed that the neighboring RSUs are disconnected and an incident randomly occurs between two neighboring RSUs.The incident information is collected by passing vehicles.The model takes into account the vehicle driving speed,the vehilce density on the road,the probability that an incident occurs and the distance between two neighboring RSUs.The accuracy and effectiveness of the theoretical analysis model are verified through simulation results.The derived theoretical analysis model can be used to estimate the maximum deployment distance allowed between two neighbor RSUs under a given delay constraint for time-critical applications,which can provide a reference for the RSU deployment in such scenarios.Secondly,the network connectivity in a highway road scenario with one entry/exit is studied and a theoretical analysis model is established for analyzing and calculating the network connectivity probability.In establishing the model,the network connectivity probability is analyzed according to the distribution of the entry/exit location on the highway road,and a closed loop formula of the network connectivity probability in each case is derived,taking into account the vehicle arrival rate,the vehicle moving speed,the vehicle communication radius and the probability that a vehicle drives through the entry/exit.The accuracy and effectiveness of the theoretical analysis model are verified through simulation results.The derived theoretical analysis model can be used to analyze the impacts of major parameters on the network connectivity in such scenarios,and provide a reference for analyzing other network performance in highway scenarios with entries/exits.Then,the network connectivity in a highway road scenario with one entry/exit and one RSU deployed at the entry/exit is studied and a theoretical analysis model is established for analyzing and calculating the network connectivity probability.In establishing the model,the network connectivity probability is analyzed according to the distribution of the entry/exit location on the highway road,and a closed loop formula of the network probability in each case is derived,taking into account the vehicle arrival rate,the vehicle moving speed,the vehicle communication radius and the probability that a vehicle drives through the entry/exit.The accuracy and the effectiveness of the theoretical analysis model are verified through simulation results.Based on the derived theoretical analysis model,a comparison between the scenario with one RSU deployed at the entry/exit and that with no RSU deployed at the entry/exit is presented in terms of the network connectivity probability.It is demonstrated that the deployment of an RSU at the entry/exit can improve the network connectivity.The derived theoretical analysis model can be used to analyze the impacts of major parameters on the network connectivity in such scenarios,and provide a reference for determining the deployment positions of RSUs in different highway scenarios.Finally,the network connectivity in a highway road scenario with one entry/exit and multiple RSUs deployed on the highway road is studied,and a theoretical analysis model is established for analyzing and calculating the network connectivity probability.In establishing the model,the highway road is divided into several sub-segments,each with two RSUs deployed at both ends,respectively.The network connectivity of each sub-segment is analyzed and a formula of the connectivity probability on each sub-segment is derived.The network connectivity probability on the overall highway road is then derived based on the connectivity probability on each sub-segment.The accuracy and effectiveness of the theoretical analysis model are verified through simulation results.Based on the derived theoretical analysis model,a comparison between the scenario with no RSU deployed and that with multiple RSUs deployed on the highway road is presented.It is demonstrated that the deploying multiple RSUs on the highway road can improve the network connectivity.The derived theoretical analysis model can be used to analyze the impacts of major parameters on the network connectivity in such scenarios,and provide a reference for determining the number of RSUs to be deployed in different highway scenarios.