A Dynamic Multi-path Routing For VANET

The number of vehicle electronic applications is increasing along with the significantlyrising of urban vehicles. This apps are mainly used in traffic accident alarm, road trafficinformation query, congestion warring, highway paid, video calls and other functions,passengers can also use VANET(Vehicular Ad-hoc Networks)to realize data sharing(e.g.,translating files, uploading video),game interconnection and Internet access services.VANET routing mechanism provides necessary support for the message transmissionamong vehicles in the above applications.However, finding a applicable protocol for routing during multi-hop forwarding inurban areas is still an not settled challenge, which is affected by three factors. Firstly, themajor hinder in VANET are non-uniform vehicles density, high speed mobility, and rapidchanges in network topology. Secondly, routing needs system adapt to large-scale networks.Wireless net is easily influenced by topographical features (i.e. buildings) and is limited incommunication range, which significantly hinders routing. Thirdly, VANET’s Emergencymessages require high packet delivery ratio and low network latency, the traditional routemodel can not meet this demand.Compared with traditional VANET(Vehicular Ad-Hoc Networks) routing techniques,geographic routing has been proven to be more fit for highly mobile scenes. Traditionalroutings use greedy modes or fixed forwarding paths to send packets. But, the dynamicfeatures of VANET such as fast changed topology, vehicles density and radio obstacles,could cause local maximum and sparse connectivity. Due to the characteristics of wirelesschannel, while there are too many packets transmit through a path, the delay and thenumber of packets loss will both increase clearly. We propose DMPR, a DynamicMulti-path Routing, combined with node location and digital map.DMPR change the general thinking of collection related information as weights tocalculate a transmission path. Every once in a period of time during the process oftransmission, DMPR chooses several paths from source to destination and monitors thedelays of every path, it dynamically allocates the amount of packets transmitted alongdifferent paths based on the transmission delays. DMPR suit for the scene in which sourcevehicle connects with destination vehicle for a long time, because a longer end-to-endconnection benefits dynamic optimization of packets transmission.This article uses the network simulation software NS2(Network Simulator version2)to verify DMPR. First, writing C++code to realize the logical mechanism of DMPR.Second, install the DMPR code to NS2and recompile. At last simulate the real city trafficinformation using MOVE and realize the experiment scene using OTCl based on thisinformation. To illustrate DMPR has a better transmission performance in urban environment, I compared DMPR with classical Ad-hoc routing protocols such as AODV,GPSR and GSR in the same scenario, the experiment show that DMPR perform better inthe respect of packet end to end delay and the packet delivery ratio.