Research On Broadcast-based Messages Dissemination Algorithms In Vehicular Ad Hoc Networks

With the rapid growth of cars`and the development of the communication technology, thevehicle security applications have been paid more and more attention. Vehicular ad hoc Networks(VANET) is one of the most promising and important field in the intelligent transportation systemand the data dissemination-based security application in VANET need the help of broadcasting.Considered the characteristics of VANET, traditional broadcasting algorithms are not ideal. Thereare beacon information redundancy, big delay and unsteadiness of information transmission intraditional broadcasting algorithms. So new algorithms need to be designed. According to thecomplexity of the data dissemination, this thesis provides different algorithms for city scene androad scene to delivery data.Firstly, aim at the problems of large transmission delay and beacon information redundancyof emergency messages (EMs) in the scene, the emergency message broadcasting algorithm(EMBA) is researched in this thesis. This algorithm is the result of improving V-MCDS by addingvehicle coordinates, the direction, the speed and the timestamp information to the beacons. Theseinformation are used to estimate the location of vehicles in order to reduce times of beaconmessages exchange between vehicles. At the same time, the EMs`selection range of relayers isexpanded, so the store-and-forward mechanism is tried to be avoided and the transmission delayis shortened. At last, the road simulation scene is generated by VanetMobiSim and the EMBAalgorithm is simulated by NS2simulator. And the results,compared with V-MCDS, show thatEMBA algorithm has better performance in lower beacon redundancy and less transmission delay.Secondly, in the city scene, there is packet redundancy in the process of messagedissemination. To solve this problem, this paper proposes a traffic messages delivery algorithm(TMDA) based on node classification. The nodes involved in the messages transmission aredivided into three categories: portable nodes, semiportable nodes and static nodes. When amessage reaches a receiver, it will be processed by four sequences: redundancy check, positioncheck, distance check and delay assignment to control the forwarding of messages. At the sametime, the receiver broadcasting messages by utilizing pre-existing travel information forsemi-mobile vehicles. At last, the city simulation scene is generated by VanetMobiSim and theTMDA algorithm is simulated by NS2simulator. And the results, compared with flooding, showthat TMDA algorithm has better performance in end-to-end delay, the network reachability and the invoked broadcast.