Research On Reliable And Rapid Message Dissemination Protocol In VANETs

Vehicle Ad-hoc Networks(VANETs)is an organic combination of the Internet of Things(IoT)and Intelligent Transportation Systems(ITS),and is also an important application of IoT technology in dynamic scenarios.The main purpose of researching VANETs is to enhance transport safety and improve traffic efficiency.Among them,improving or designing an appropriate message dissemination algorithm to avoid potential traffic accidents has become one of the key research focus.Due to the rapid change of network topology and the unstable communication link,there are some problems such as high packet loss rate,high delay and network redundancy in the process of information transmission.Therefore,it is necessary to design a reasonable algorithm to improve link stability,reduce the channel competition and network overhead in the improvement and design of a algorithm.In view of the shortcoming of the existing information dissemination algorithms,such as large end-to-end delay and poor scalability,this paper studies the message dissemination technology under typical scenes of highways and urban streets.A reliable and rapid message dissemination algorithm and adaptive message dissemination algorithm are proposed.In view of the characteristics of fast moving speed,uneven distribution,frequent accessing and leaving the network under the highway scene,a reliable and rapid message dissemination(RRMD)algorithm is proposed.This algorithm employs a sender-oriented scheme that a source node dominates the selection of forwarders.We take account of the factors that may have an impact on the transmission of messages such as vehicle distribution characteristics,channel characteristics,link availability,signal collision probability,transmission delay and queuing delay.Then,The minimum end-to-end average delay model is designed to optimize the selection of relays.Thereby a reliable transmission path is established to ensure the reliability and timeliness of information dissemination.In the urban scene,compared with highways,the velocity and direction of vehicle are both changing,and the relatively complicated road environment and the presence of traffic lights make the vehicle density and the network topology change faster.Therefore,adaptive message dissemination(AMD)algorithm is proposed.The algorithm separately analyzes the status of communication links between vehicles on straight roads and intersections,study the influence of relative position between vehicles and direction of vehicle movement,the connectivity of the nearby network of the neighbor vehicles are also reasonably evaluated.Thereby a minimum delay model for relay selection is established,and the purpose of improving the reliability and timeliness of information transmission is achieved.In addition,according to the simulation analysis,the appropriate network density boundary value is obtained,which is used to evaluate the network density around the vehicle.In the segment with higher network density,a senderoriented scheme is employed.When partial vehicles are concentrated in a small range,and the time at which those vehicles choose to forward is in the same time slot,packet conflicts occur.This situation will be avoided by this scheme.When the network density is low,a hybrid scheme is adopted,which can ensure the vehicle with the highest priority can forward packets as quickly as possible,and the information transmission of each hop can be adapted to the change of network topology.Finally,we build a VANETs system level network simulation platform combined with OMNET and SUMO,and then verify the eectiveness of RRMD and AMD algorithm.In the highway scene,experiments were conducted on diverse source-to-destination distances and vehicle densities.The results show that the minimum end-to-end delay is achieved on the premise that the RRMD algorithm can guarantee a certain successful reception rate compared to other message dissemination algorithms.In the urban scene,the performance of the AMD algorithm is significantly improved compared to the Slotted 1-p algorithm and the TrAD algorithm in different network densities.