Research On VANET Routing Protocol In Urban Traffic Scene

Vehicular ad hoc network provides a new way to solve the problem of traffic congestion,improve the safety of vehicle driving and establish security early warning mechanism,etc.VANET routing protocol is the core technology in the vehicle network.Compared with the traditional ad hoc network,it has many unique features.This is result that the research of VANET routing protocol has certain difficulties.Among them,the complex scene of VANET is a problem that needs to be resolved.In this dissertation,the VANET routing protocol and scenario model based on the urban environment is studied,and three points of the research is completed:1.The traditional random waypoint model is simple and easy to use,but it can not reflect the real traffic scene.Therefore,the scene model is proposed in this dissertation based on the IDM_IM model,which is included in the traffic flow software Vanet Mobisim.Through the simulation,the reliability of the model is analyzed,which provides the network carrier for the performance evaluation of the routing protocol.2.Aiming at the defects of the GPSR protocol using greedy algorithm to select routing forwarding path in the urban scene,a improved GPSR protocol is proposed in this dissertatiom.When it selects the candidate neighbor set,it takes a combination of the density of traffic flow in the sections where the neighbor node are located,the moving direction of each neighbor node,real time distance between neighbor nodes and destination nodes.According to the position of the forwarding node,it can be divided into the intersection mode and the section mode,which makes the node that is close to the destination node and satisfies the requirement of link quality priority forwarding packets.The simulation results show that the proposed protocol does better than GPSR and GPCR in routing overhead,routing delay and delivery success rate.3.Aiming at the problem that the link quality is unstable in the urban scene,and the route forwarding is easy to be influenced by the density of the traffic flow,a vector-angle-cluster and bridge nodes-based routing protocol is proposed in this dissertation.In VAC-BNR protocol,the urban road is divided into intersection area and inter-intersection direct road segment.In intersection area,the appropriate vehicles are selected to be bridge nodes,and they fill the connectivity gap between disconnected links.Then in inter-intersection direct road segment,VAC-BNR protocol uses vector angle to identify whether the vehicles belong to cluster.The utility of each node in cluster is computed,and the node with highest utility is considered to transmit data.Compared with other similar protocols,the packet forwarding rate in the low traffic density is improved obviously,and the routing overhead is also well controlled.