Research On Dynamic Path Selection Based On VANET

The Vehicular Ad Hoc Networks VANET (Vehicular Ad Hoc Networks) as an emergingresearch topic is being more and more attention. Most of the existing traffic control systemsusing the traffic control center to deal with the traffic information, and the vehicle nodes as therecipient of information only. In this paper, in order to achieve dynamic path selection, andimprove the travel efficiency, using VANET to achieve Inter-Vehicle Communication, and thevehicle nodes dynamically adjusted the traveling route based on the real-time traffic information.On the basis of Dijkstra algorithm, this paper proposed the improved weight Dijkstraalgorithm, given different weights for the same section of the different travel direction, anddepicts the real condition of the road more reasonable. Then according to the relationshipbetween speed, traffic flow and vehicle density of the traffic flow theory, this article modified thecalculation method of the road weight, so that the road weight will be affect by distance, traveltime and vehicle speed at the same time. In order to make the calculation of the shortest pathmore reasonable and reliable, travel time is being as the main basis for path selection. Finally,using a sample road network as example, contrast the difference between Dijkstra algorithm andthe improved weight Dijkstra algorithm on the shortest path calculation.In this paper, broadcast is used to send traffic information, and dynamically set the timeinterval of the broadcast message based on the vehicle velocity. In order to capture the velocityinformation of the road, this paper defines the message frame, the acquisition mode and theprocess flow of the instantaneous velocity and the average velocity, and comparing the differencebetween the two velocity information. For instantaneous velocity, the speed update matrix in themessage frame is use to transfer speed information which collected in the past. For the averagevelocity, by collecting the speed information on the reverse road, when the vehicles are about toenter in the next road, plus and average the average velocity of the reverse road. When thevehicle into the next road, the calculation result will be spread to the other vehicle on the reverseroad, and help them to find out the traffic conditions ahead.When the traveling vehicle received the broadcast information, the first thing is to extractthe velocity information in the message frame and update the speed matrix and the weight matrix,and then re-calculate the weight of the road. Whenever the vehicles are about to enter the nextroad, they will use the improved weight Dijkstra algorithm to re-calculate the shortest path, andre-select the traveling route based on calculation, then achieve the dynamic path selection.Finally, this paper connects the traffic flow simulator SUMO and the network simulatorOMNET++to simulation, and using TraCI as middle-ware. Using broadcast as the way oftransmitting information, the article contrast the total traveling time when using the different path selection algorithm, and analyze the impact on the total driving time when the number ofvehicles involved in the experiment are changed, as well as the impact of road congestion on thepath selection algorithm. Simulation results show that:1. Using the improved weight Dijkstraalgorithm to calculate the shortest path, and to select path dynamically can effectively shortenthe traveling time of the vehicle.2. With the increase of the number of the vehicles whichachieve the dynamic path selection, the simulation vehicle’s total traveling time graduallyshortened.3. When the road congestion occurs, the improved weight Dijkstra algorithm willhave higher efficiency.