Publish/Subscribe Based Data Distribution For Vehicular Ad Hoc Networks

Vehicular ad hoc network facilitates the application of wireless mobile ad hoc networking technology in road traffic,with the aim of exchanging and sharing information between vehicles.Compared to traditional mobile ad hoc networks,vehicular ad hoc network has the features of high-speed mobility,sufficient energy,advanced auxiliary equipment,predictable node location,frequent varying network topology,unreliable wireless channel and unstable link among vehicles.Traditional data dissemination protocols of the Internet and mobile ad hoc networks are hard to be used in fast-moving vehicular network,so it is of great significance to design a good data distribution algorithm for this special kind of mobile network.In vehicular ad hoc networks,vehicles are influenced by roads,traffic rules,human factors and many other factors,and have unique characteristics of spatial distribution and network topology.These features of vehicular ad hoc network are the design basis of data dissemination protocol.In road traffic environment,a driver may want to get some information about the environment around him,or he may want to post some live information to other vehicles without knowing who owns or needs the information.To this end,the publish/subscribe model can be used to achieve the independence between information suppliers and consumers in time and space.Every user can submit a subscription request or publish an event at any time and any place.Hence,the publishers and subscribers do not need to know each other.Therefore,this thesis adopts the publish/subscribe communication model to realize the data distribution in vehicular ad hoc networks,focusing on the matching problem between subscriptions and events,as well as the data distribution scheme in road traffic.The matching algorithm and routing mechanism take essential role in publish/subscribe systems,where matching algorithm realizes the matching between published events and subscription requests,while routing mechanism is responsible for transmitting messages from the source node to the destination node.This thesis firstly studies the background and development of vehicular ad hoc network and publish/subscribe systems,and then focuses on current event matching algorithms in content-based publish/subscribe systems and existing routing strategy in vehicular ad hoc networks.The main work of this thesis includes the following two aspects:(1)Matching algorithm based on compound logic in publish/subscribe systems.In order to improve the expression capability of publish/subscribe systems,and enable users to propose more precise subscription requests efficiently,this thesis focuses on matching algorithms which support compound predicates for content-based publish/subscribe systems.By using index structures and transforming the complex expressions,the proposed algorithm can not only find proper recipients for emerging events,but also identify matched events for new subscription requests accurately.Theoretical analysis and experimental results show that the proposed algorithm has good matching efficiency.(2)Data distribution scheme in vehicular ad hoc networks based on the publish/subscribe paradigm.Through clustering vehicles nodes,we select a cluster head in certain geographical area,which is responsible for the management of member nodes' published events and subscription requests.The cluster head executes the matching algorithm within the cluster and communicate with other clusters,so as to determine the source and destination nodes of the event message and then conduct the data transmission.The corresponding data maintenance and distribution scheme for the highway and urban road scenes are developed respectively.The simulation results show that the cluster selection and maintenance scheme has high stability and reduces the cost of data maintenance,while the data distribution scheme can effectively reduce the network load while ensuring high event receiving rate.