Research And Improvement Of GPSR Protocol In VANET Environment

Vehicle ad hoc network(VANET)is a multi hop distributed wireless self-organization network.It can improve the traffic safety by realizing the communication between vehicle and vehicle,vehicle and roadside unit.The highly open and dynamic nature of VANET will cause the nodes in the network to face all kinds of attacks and communication link disconnection problems,so it is very important to design a routing algorithm that can ensure the security and stability of the communication link.Therefore,based on the research and analysis of routing protocol,link expiration time prediction model and trust model in VANET,the GPSR protocol is improved considering communication stability and security.The main research contents are as follows:Aiming at the problem of communication link stability,GPSR protocol is improved based on link expiration time prediction model.Considering the limited direction of vehicle movement along the road,according to the information of road,vehicle position provided by GPS and the information of speed and direction provided by vehicle sensor,the relative motion state between nodes is judged,the link expiration time is calculated,and the routing decision considering link connectivity stability is made combining with the location of the destination node.Aiming at the problem of node communication security,a trust management model considering trust reliability is proposed in VANET environment,and GPSR protocol is improved based on the model.To solve the security problem caused by malicious nodes’ cooperative fraud,the model introduces the concept of trust reliability to distinguish trust and reliability.When the source of trust is unreliable,the trust reliability will decrease.At the same time,trust reliability can also be used to solve the dynamic problem of trust.In addition,the model also gives a reasonable trust initialization scheme for the newly added nodes,and the vehicle nodes can dynamically join and leave the network.To further optimize the routing performance,the GPSR protocol is improved by combining the link expiration time prediction model and the trust model considering the trust reliability.The protocol aggregates the above two decision-making indicators in the improved GPSR protocol in the routing decision algorithm,so as to achieve the purpose of improving communication stability and security.Based on NS2 network simulator and SUMO traffic flow simulation software,the simulation platform is built to evaluate the average end-to-end delay and packet delivery rate of GPSR and three improved GPSR protocols under different node density,node speed and malicious node ratio.The results show that under the same conditions,compared with GPSR protocol,GPSR protocol with link expiration time prediction model and trust management model has lower average end-to-end delay and higher packet delivery rate,which reflects good link stability and security.