Research On Geographic Routing Protocol For City Environment In VANET

Vehicular Ad-hoc Networks(VANET) is an important part of the future intelligent transportation systems.It provides a good platform for communication between different vehicles.It not only improve traffic safety, but also meet the comfort needs of the user ,such as communications and entertainment.In the city VANET, nodes move fast, network topology changes frequently, the mobile node's path topology is constrainted by roads,there are a lot of buildings and other features. a lot of routing protocols in this environment,communication performance will be greatly decreased.Therefore, the routing protocol design of urban environments has become a major challenge in Vehicular Ad-hoc Networks research.Firstly,the main structures, characteristics and major challenges of VANET in urban environment are introduced in this paper.Then this paper summarizes sevaral typical routing protocols in VANET including routing protocols based on topology, geographic routing protocols and cross-layer routing protocols.Then,there are some typical vehicular mobile models are introduced.according to the characteristics of the city environment and vehicle movement,and based on the analysis of relevant existing routing protocols,we propose a novel cross-layer geographic routing protocol,CCMGR. CCMGR routing protocol use the vehicle movement information, the local road information, cross-layer information of wireless links,through Between Intersections Node Selection Algorithm(BINSA) and In Intersections Selection Algorithm(AINSA) to ensure the efficiency and reliability of communication.Protocol features are as follows:(1)At the intersection, according to the vehicle position and direction, local road density, cross-layer wireless link SNIR , AINSA calculates the weight values of every neighbor node by Weigh Decision Method then selects the node which weight value of node is smaller as the next hop node.(2) between the intersections, BINS A use node forwards probability method to select the next node based on the position and direction of the vehicle, in order to select the best forwarding node in the transmission path,the use of prediction mechanism predicts the movement position of the vehicle to improve the accuracy of the selected node,reduce transmission delay.(3) The fast-moving vehicle, resulting in network connecttion break up ,so CCMGR also introduces store and forward mechanism to ensure reliable information transmission. In addition, the use of dynamic "HELLO" broadcast mechanism to reduce the impact of beacon transmission interval.Finally the article uses network simulator NS3 with realistic vehicular movement trace file generated by node model simulation generator Bonnmotion tool to simulates proposed routing protocol CCMGR and other classic routing protocols.Simulation results show that the proposed routing protocol CCMGR has a higher packet delivery ratio and lower average end to end delay for VANET communications under urban environment.