Reliable And Ordered Group Message Publication And Subscription In Vehicular Networks

Vehicular ad hoc networks is the core content of intelligent transportation. The group messages in vehicular ad hoc networks is a new research direction. In vehicular ad hoc networks, communication group must guarantee the credibility and order of the messages. To realize reliable and ordered group messages publication and subscription in vehicular ad hoc networks, we mainly study the problem of group messages in vehicular ad hoc networks.The routing protocol in vehicular ad hoc networks is the basis for the realization of the group messages in the vehicular ad hoc networks. I study the routing protocols in vehicular ad hoc networks, such as AODV protocol, GPSR protocol, CPCR protocol, GPSRJ+ protocol. This paper analyzed the advantages and disadvantages of each kind of protocol and the environment for application.I use laptop computers to simulate the cars in vehicular ad hoc networks and use the desktops to simulate the RSUs in vehicular ad hoc networks. I also use a server to simulate intermediate system of publish and subscribe model in vehicular ad hoc networks.Group messages in vehicular ad hoc networks must guarantee the order of messages. The ordering of messages is the causal ordering of the messages. If there is a causal relationship between the two messages in logic, it is necessary to ensure that all group members receive the messages in causal ordering. Otherwise it will cause group members confused and have some negative effects. I have studied message tree algorithm, Lamport Logical Clock algorithm, Vector Clock algorithm, and so on. In order to guarantee the causal ordering of messages, the algorithm generates a large amount of redundant information. Vector Clock algorithm can be improved in some aspects to reduce the redundant information, so it can reduce the occupancy of network bandwidth and improve network transmission efficiency.Group messages in vehicular ad hoc networks must ensure the reliability of the message. Reliability is the atomic nature of the message in the group messages. The atomic requirement for each group of information must be received by all members or not received by all group members. The 2Pc protocol can guarantee the atomic nature of group messages. Through the experimental, it is proved that the 2Pc protocol can guarantee that the group messages in vehicular ad hoc networks has the atomic property.