Research On Emergency Message Transmission Mechanism In Vehicular Ad Hoc Network

Vehicular Ad-hoc Network(VANET)uses wireless communication network technology to build an efficient intelligent transportation system,which can improve the safety and efficiency of road traffic.The security application provided by VANET is used to ensure the fast and reliable transmission of security messages,especially emergency messages caused by traffic accidents such as traffic accidents and road collapses.Due to the limited transmission range of a single vehicle,relay nodes are required to forward emergency messages.Therefore,multi-hop broadcast technology is used.This thesis studies the selection of relay nodes in multi-hop broadcast technology,aiming at improving the reliability and efficiency of emergency message transmission.Due to the high-speed mobility of the vehicle,the vehicle’s message to the neighboring vehicle nodes has hysteresis,which makes it difficult to accurately determine the situation of surrounding vehicles.This thesis combines the advantages of fuzzy logic in dealing with inaccurate messages,and proposes a fuzzy logic-based relay node selection mechanism.The mechanism comprehensively considers the coverage of the vehicle,the channel busy ratio and the moving factors.By establishing appropriate fuzzy inference rules to achieve the forwarding priority of the vehicle as the relay node,the vehicle will forward the neighboring vehicle nodes with the highest priority as the next.Effectively reduce the number of relay nodes.The simulation results show that compared with the existing broadcasting scheme,the proposed scheme has better performance in terms of packet delivery rate,average one-hop delay and proportion of relay nodes.In the traffic congestion section where the vehicle is in a dense area,the fuzzy logicbased relay node selection mechanism is accordingly optimized to maintain good performance under traffic congestion.In order to make the emergency message transmission fast and reliable in both traffic flow and congested road sections,a relay node selection mechanism based on vehicle density is proposed to ensure the reliability and timeliness of emergency message transmission under different vehicle densities.The simulation results show that compared with the existing broadcasting scheme,the proposed scheme can adapt to the environment under different vehicle densities,and has better performance in packet delivery rate,average one-hop delay,relay node ratio and broadcast redundancy.