| With the development of urban transport,road congestion is getting worse and worse.In order to solve the urban traffic congestion resulting from the unbalanced use of roads,this paper presents a vehicle dynamic navigation algorithm DNV based on real-time traffic information in VANET(Vehicular Ad hoc Network).Firstly,this paper studies the infrastructure section of CVIS.Then the process and simulation results of DNV algorithms is given.The infrastructure section of CVIS includes roadside node deployment and the communication mechanism study of CVIS.Roadside node deployment is critical for road traffic information collection,it will directly affect the dynamic navigation algorithm.In order to meet the communication coverage at maximum deployment cost savings,this paper is minimum node deployment with full connectivity coverage.Firstly,the architecture model of road-side node deployment is given,and then on this basis for bilateral and unilateral deployment of ordinary roads,the formula of Minimum number of nodes required to achieve full coverage connectivity are obtained,and the specific deployment scheme is given.Finally,the deployment scenarios of different scenes,such as the ordinary roads,tunnels,ramp,main roads,crossroads,and viaducts are analyzed in detail.Simulation experiments about several schemes of ordinary roads node deployment show that the widening of the road,the advantages of bilateral deployment is even more obvious.When the width is 30m,the node spacing of bilateral deployment is 25.6%higher than that of unilateral,and the number of nodes required is reduced by about 20%.Then,on the basis of full coverage of the deployment,the communication mechanism of CVIS is put forward.This system is the solution of CVIS jointly constructed by the 3G Internet and wireless sensor based on ZigBee protocol.The network is divided into vehicles,roadside ordinary nodes,the cluster node,server four levels.Using the Internet to complete long-distance communications of vehicle-to-server,roadside cluster-to-server,make up the wireless sensor network zigbee protocol limitations on transmission distance.Roadside-node-to-vehicle,vehicle-to-vehicle communication is through the WSN zigbee protocol,which makes full use of the advantages of WSN in the close range transmission.The paper has researched each level network communication protocol and function implementation of information collection system in detail,including vehicle-to-roadside,vehicle-to-vehicle,vehicle-to-servers,roadside cluster-node-to-server,roadside cluster-node-to-ordinary-node.The algorithm DNV preferentially employs vehicle-to-vehicle(v2v)communication to transmit request packet(RQP),response packet(RSP),collect the real-time traffic information in VANET,and calculate the expected travel time,get the optimal path.For regular low-traffic roads v2v communication is not effective,so roadside unit is equipped for these roads and vehicle-to-roadside(v2r)communication is employed.Then a path with the less travel time than the static shortest path road is given by the algorithm.Compared to the traditional static optimal path algorithm,DNV can dynamically update the route,bypass the congested road without public invest of large number of roadside units.Simulation results show that,compared to the traditional Dijkstra algorithm,the proposed algorithm has shorter path travel time.The travel time of the 1st 2nd and 4th simulation results is 17%,7%and 10%less than that of Dijkstra algorithm.The 3rd and 5th DNV simulation gives the same path as Dijkstra algorithm. |
