Research On Routing Protocol Based On Path Constraint For VANET

As an important application in the field of intelligent transportation,VANET can achieve the communication between terminal and terminal in the intelligent traffic environment and the function of information sharing,which makes our daily trip scene more intelligent and convenient.In the process of VANET communication,the routing protocol is important and it will affect the efficiency of the entire VANET network.In the traditional mobile ad hoc network,the design of routing protocols is based on the topology and location information of the network,which is determined by the characteristics of itself,such as the frequently changing topology.VANET has more other features than mobile ad hoc networks: 1)fast moving nodes;2)node movement is constrained by traffic road shape.These characteristics have great influence on routing selection.First of all,the rapid mobility of nodes will cause the wireless links between vehicles to be easily interrupted.Secondly,the change of the node’s moving direction makes the selection of the optimal intermediate nodes more difficult,and the road shape is an important factor affecting the direction of the node’s movement.At present,most of the geographical location based routing protocols only take into account the movement speed of the nodes,and rarely take into account the change of vehicle routing path caused by different road shapes(such as direct road,turning intersection)in the actual traffic environment.Based on the VANET characteristics discussed above,a routing scheme based on path constraints is proposed.In view of the nodes on the direct path,the scheme calculates the timely location of the neighbor nodes and predicts the microscopic motion trajectories of the nodes according to the periodic broadcast time interval,in order to carry out the accurate data packet forwarding and effectively solve the problem.The problem of frequent interruption of wireless links caused by the rapid movement of nodes is solved.Secondly,for nodes at the turning intersection,by judging the consistency between the microscopic motion direction of the neighbor nodes and the location of the target nodes,the nodes which are selected by the greedy forwarding algorithm are closer to the target nodes,but because of the micro distance,the nodes are more close to the target nodes.The distance between the node and the node is more and more distant from the point of view of the moving direction.The choice of the better intermediate forwarding node can effectively solve the problem of the difficulty in selecting the middle node at the turning intersection.The scheme changes the selection strategy of the greedy forwarding algorithm,and by judging the analysis of the road situation and the microscopic movement of the nodes.Instead of selecting nodes closer to the target node,we choose a more reliable intermediate node conservatively,so as to improve the overall efficiency,We name it CPCR scheme.To sum up,CPCR scheme is more suitable for practical traffic and road environment than GPSR protocol,and it improves the performance of routing.In this paper,we use the network simulation tool NS-2 to establish the communication environment of VANET network,and use the traffic simulation tool SUMO to establish the mobile model environment of vehicle nodes.Experiments are carried out in different number of nodes to achieve the purpose of having more intermediate selection nodes,and compare with the GPSR routing protocol,in order to study the actual performance of the CPCR routing scheme.Experimental results show that in the actual traffic enviroment the CPCR routing scheme has improved in three aspects: packet delivery rate,network delay and data throughput.