Research On Routing Algorithms For VANET Based On Geographic Information

As the transportation industry is booming,improving the efficiency of road traffic is getting more and more attention,and VANET has become an important part of intelligent transportation system.Routing algorithm is a key link in VANET,which directly affects the communication performance of the network.The vehicle movement nodes in VANET tend to have large speed,which leads to rapid changes in network topology and unstable communication links,etc.Therefore,it is very important to design a reliable routing algorithm applicable to VANET,which is important for data transmission in VANET.In this thesis,the classical GPSR routing algorithm is studied and analyzed.Two forwarding modes of GPSR are mainly studied,and some shortcomings of its application in VANET are analyzed.An improved GPSR-SN algorithm is proposed to solve the problems that the communication link is not stable enough when greedy forwarding and the path redundancy is easily caused when perimeter forwarding.GPSR-SN algorithm determines the optimal communication area by calculating the maximum communication radius in greedy forwarding,and further selects the node with the largest cumulative communication time as the next hop to ensure the stability of the communication link;During perimeter forwarding,by calculating the angle of the connection between the neighbor node and the source-destination node,the neighbor node closest to the destination node is selected as the next hop,and a reasonable communication path is established to reduce the path redundancy in the perimeter forwarding process.Under the joint simulation platform of SUMO and NS-3,the simulation experiments of GPSR and GPSR-SN algorithm in different scenarios are carried out.The experimental results show that compared with GPSR algorithm,GPSRSN algorithm has improved performance,reduced packet loss rate,shortened average end-to-end delay,improved average throughput and reduced average hop counts,and is more suitable for application in VANET.This thesis also proposes an improved GPSR-ET algorithm based on extended table and two-hand rule.The algorithm extends the neighbor table,and introduces the reject table and the latest send table,so as to reduce the probability of path cycle and select the best path.At the same time,the right-hand rule applied in perimeter forwarding is improved to two-hand rule,which reduces the number of routing hops and network overhead.The proposed GPSR-ET algorithm and the traditional GPSR algorithm are simulated,and their performance indexes in different simulation scenarios are compared.The results show that compared with GPSR algorithm,GPSR-ET algorithm has improved performance in packet loss rate,average end-to-end delay,average throughput and average hop counts.The effectiveness of the proposed algorithm is verified by experiments.