Rapid Transmission Mechanism Design Of Real-Time Traffic Information Based On VANETs

Though cars bring convenient commuting,they cause a lot of traffic problems.Not only traffic accidents,vehicle breakdown,road damage,and other temporary conditions can lead to a sharp decline in road capacity.Therefore,how to comprehensively use the new technology of sensors,communications,and the Internet to improve traffic efficiency is an important issue.To solve this problem,the vehicular ad-hoc networks(VANETs)came into being.In VANETs,vehicles as mobile nodes can use the sensors equipped on them to sense and process real-time traffic information such as traffic accidents and road congestion.If this kind of information can be transmitted to vehicles in need or uploaded to the traffic information center to assist in monitoring,controlling and dispatching traffic flow,that will effectively avoid traffic accidents,alleviate traffic congestion and improve travel efficiency.Thus,how to design an effective information transmission mechanism to ensure the less transmission delay has become a hotspot and a difficulty point in VANETs.Considering the problem of rapid information transmission,this paper focuses on the network layer and the transport layer.Based on the in-depth research of the relevant transmission methods in VANETs,this paper designs rapid information transmission mechanisms in the decentralized and centralized vehicular networks respectively.The main content in this paper are summar as follows:Firstly,for the environment unsupported by communication infrastructure(RSU)in VANETs,this paper proposes a rapid information transmission mechanism in decentralized vehicular networks by integrating IP network architecture and information-centric network architecture(ICN).The difficulty of this problem is that the traffic conditions are complex,such as the uneven density of vehicles and the diverse range of vehicle speed,which leads to many factors affecting transmission performance,thus it is hard to modeling mathematically.To solve this problem,this paper takes the lead in simulating the effects of vehicle density,content size and vehicle mobility on the performance of IP-based VANET and ICN-based VANET.Next,the relationship between these factors and the delay of the two transmission methods is quantitatively described by mathematical models.Then,a utility function is developed to measure the switching benefits and costs.Based on the above analysis,an adaptive transmission methods switching algorithm is designed,which can guarantee the timely information dissemination adaptively according to the traffic conditions.This algorithm can effectively switch to a better transmission mwthods.Thus,it can greatly reduce the average transmission delay.Secondly,for the environment supported by communication infrastructure(RSU)in VANETs,this paper proposes a rapid information transmission mechanism in centralized vehicular networks through the cooperation of V2 V and V2 I.It can flexibly select the appropriate uploading method under different roadside unit(RSU)layout.Based on this,the vehicles can upload the complete information to the RSU as soon as possible.The related works have strong assumptions in the delay analysis of V2 V and V2 I,which cannot adapt to the characteristics of large channel quality fluctuations in VANETs.And they ignore the influence of data volume on the transmission mechanism.To solve this problem,the communication process of V2 V and V2 I is analyzed first.The performance of V2 V is mainly affected by the distance between vehicles,so the connectivity of the vehicle needs to be considered in the transmission process.The performance of V2 I is not only affected by the distance between the vehicle and the RSU,but also by vehicle speed,the channel bandwidth,and the condition of channel utilization.Then,based on the above analysis,an adaptive cooperative rapid information uploading algorithm is proposed combined with real-time traffic conditions.The algorithm is divided into two steps.The first step is to select the best relay node,and the second step is to decide the best transmission method,which greatly shortens the delay of vehicles uploading information to the RSU and ensures the integrity of the information uploading at the same time.Finally,the real traffic simulation scenario in Shanghai was generated by using SUMO,and the adaptive transmission system platform was designed based on ndnSIM.The simulation is carried out on this platform.Extensive simulation results demonstrate the effectiveness of the proposed algorithms.To be specific,the transmission delay of the transmission method switching algorithm can be decreased by 88.2% over the transmission method based on IP architecture and 37.6% over the transmission method based on ICN architecture.Meanwhile,the adaptive cooperative rapid information uploading algorithm can reduce the transmission delay by about 50% compared to the one-hop transmission alone and 10% to 30% compared to two-hop transmission alone.