Research On The Mobility Models And Routing Algorithm Of City VANETs

The vehicular ad hoc networks(VANETs),as a part of intelligent transportation system,are fundamentally different from traditional wireless ad hoc networks due to some parameters,such as high node mobility,uneven distribution and frequent topology changes etc.These characteristics will make the data communication more unstable and the routing link more fragile.In city VANETs,four important issues not only can strongly affect the performance of routing protocols,but also prompt us to redesign more suitable routing protocols.Those issues are intermittent connectivity,traffic light at intersections,three-dimensional and traffic accident city scenarios.Therefore,we study and design the vehicular mobility model based on real city map,we also construct different routing algorithm in different scenarios.The major works are outlined as follows,(1)Firstly,we proposed a city vehicular mobility model by SUMO and city map.Then,the proposed mobility model is used to verify the performance of FLOODING,AODV,DSDV,DSR in city VANETs.(2)After a traffic accident,vehicles should broadcast emergency data as quickly as possible to avoid multiple collisions.Flooding protocol is a simple and efficiently broadcast algorithm in above situation.But delay time and delivery ratio performances are unreliable in high vehicle density and sending rate.Meanwhile,broadcast storm becomes a usual problem.Then,we proposed a cluster-based recursive broadcast(CRB)algorithm for propagating emergency messages in VANETs.The simulation results show that the proposed algorithm not only avoids broadcast storm problem,but also outperforms the flooding one even in high vehicle density and message send rate.(3)Many sources in VANETs will have different information to send,and then they may select the same relay simultaneously,this scenario can be called relay collision.In order to solve above relay collision problem in VANETs,we propose a cluster-based relay selection algorithm.The simulation results show that the cluster-based relay selection algorithm not only avoids relay collision,but also outperforms the random relay selection one even in high-speed scenario.