Research On Probability Routing Algorithm And Cache Management Strategy In Vehicular Ad Hoc Network

In recent years,with the development of ITS(Intelligent Traffic System)related technologies,Vehicular Ad Hoc Network(VANET)has become a hot spot in its research.Vehicular Ad Hoc Network has a very significant application in traffic condition early warning,auxiliary driving and online information exchange,which not only improves traffic efficiency,but also meets people’s travel needs.In VANET,due to the rapid movement of vehicle nodes and uneven distribution density,the network topology formed by vehicle nodes is disconnected from time to time,which makes the successful transmission of messages extremely challenging.In order to solve the problems faced by VANET,combining with the characteristics of message transmission mechanism-"carry-store-forward" and intermittent connection between nodes to transmit messages of Delay Tolerant Network(DTN),studying and designing a routing algorithm which can also improve the successful delivery rate of messages and reduce the network load in VANET environment has become a very meaningful work.In view of the poor performance of existing routing algorithms in VANET environment,this thesis carries out the following research and improvement.(1)Under the background of limited storage capacity of new energy electric vehicles,aiming at the problems that the Prophet algorithm still has certain limitations in the process of selecting the next hop node,an improved probabilistic routing algorithm based on continuous encounter time and node energy(CTAE-Prophet)is proposed.In this algorithm,when selecting a relay node,the vehicle node carrying the message will comprehensively consider the probability of successfully transmitting the message between the nodes,the continuous connection time between the nodes and the remaining energy of the node,and give priority to the message to the arrival high-quality nodes with high probability of destination node,long time of continuous encounter and more remaining energy.CTAE-Prophet algorithm not only overcomes the instability of the link caused by the short connection time between the vehicle nodes,but also avoids the problem that the message cannot be successfully transmitted due to the energy shortage of the nodes.(2)In order to solve the problems of network congestion due to the limited cache space of nodes in network,this paper comprehensively considers the existence time of messages,the number of nodes that have transmitted messages and the size of message packets to calculate the message efficiency value,a buffer management strategy based on message efficiency(MEBM)is proposed.The specific design of the MEBM is as follows:when the node needs to receive new packets,but the network is congested due to insufficient remaining buffer,the node will compare the message efficiency value in the cache,and priority will be given to delete the message with low efficiency value to release the cache to alleviate congestion.(3)Using the DTN simulation software ONE platform for simulation experiments,the rationality of the CTAE-Prophet algorithm and the MEBM algorithm was tested.In the process of experiment,the results of other algorithms are compared with those of the algorithms designed in this thesis,and finally the advantages of the CTAE-Prophet algorithm and the MEBM algorithm in improving message delivery success rate and reducing network load rate is proved.