Research On The Routing Protocol Based On Location Information In VANETs

Vehicular ad hoc networks is a special kind of mobile ad hoc networks,which have their own special characteristics: the speed of vehicles changes rapidly,network topology changes rapidly and vehicles are required to follow the road layout and so on.Based on the characteristics of wireless devices,communication modes are divided into two types: vehicle-to-vehicle and vehicle-to-roadside.As a critical part of Intelligent Transportation System,vehicular ad hoc networks provide a large number of application,which can be classified into comport application and safe application.Routing in this network has been researched widely,but many challenges in location information routing protocol are still require to be addressed.This paper makes a detailed research on the routing protocol based on location information.Firstly,in order to solve the problem of unstable connectivity and high bit error rate,which are caused by rapid changes in the density of vehicles on the road,while the transmission radius remained unchanged,a variable transmission range routing protocols based on vehicle density is proposed.According to different vehicle density,node can adjust the farthest transmission distance and reduce the transmission latency of the message,which can ensure high connection probability of the network.It is analyzed by homogeneous Poisson point process model,and based on this,the change conditions of transmission range with different vehicle density is deduced.Furthermore,mathematical calculate formula of average latency is obtained according to the theoretical analysis.At last,variable transmission range routing protocol based on vehicle density and fixed transmission range routing protocol are compared by simulation.The simulated results show that the proposed protocol can be applied in actual environments,and the message can be transmitted fast from source node to destination node under the condition of high connection probability.Secondly,the relay node needs to be found in the range of forwarding when packets data is forwarded.In order to reduce the complexity of searching relay nodes,which can reduce the average number of hops from source node to destination node in the process of forwarding,an adaptive routing protocol based on directional transmission is proposed.Forwarding angle and the average distance of one-hop progress are the two key parameters of the routing protocol.Firstly,in order to reduce the forwarding range,a forwarding angle always award to the destination node is designed,which can reduce the number of nodes in the forwarding range and simplify the calculation of searching relay nodes.And then,in order to reduce the average number of hops,optimal or sub-optimal neighbor nodes are chosen adaptively as relay node based on the distance of progress in the forwarding range.Simulation results show that the proposed routing protocol is superior in terms of both the average number of hops and the average distance of one-hop progress,with which the data packets can be transmitted to the destination node.Finally,a reliability routing protocol based on vehicle density is proposed,which can reduce the complexity of the forwarding node finding an optimal or sub-optimal node in forwarding range,reduce the average number of hops and enhance the reliability of the link.Firstly,the unite block is set by the forwarding node according to the vehicle density in the road.And the forwarding range is cut into several equal blocks.Then the farthest block away from the forwarding node is selected.In the selected block,the neighbor node which has the longest link time is chosen as a relay node to forward according to the principle of reliability finally.Compared with EG-RAODV,the simulated results of the proposed routing protocol show less average number of hops and larger average distance of one-hop progress,which means it can transmit the data packet to destination node more quickly.