Research On Opportunistic Routing For Vehicular Ad-Hoc Network Based On Geographical Position

The fast moving of vehicle nodes makes routing technology become one of the greatest challenges of the Vehicular Ad-hoc Network(VANET).The proposal of opportunistic routing has provided an effective method to solve above problem.Different from traditional routing,opportunistic routing can take advantage of the chances of encounter which brought by mobile vehicle nodes for effective communication,which can be a good deal with the problems such as unstable link and frequent changes of network topology in VANET with fast nodes.Aiming at the above problems in the research of VANET routing protocols and on the premise of science research related research status,this paper has carried out the following work mainly:(1)In view of the different communication opportunities brought about by the city road traffic density changes,this paper proposes a Geographic and Density-based Opportunistic Routing(GDOR).GDOR chooses one-to-one transmission or two distributed transmission adaptively based on the local traffic density.In the low density area,GDOR improves delivery performance by two distributed transmission to diffuse duplicates because it generally has a low network load.In the high density area,it ensures the continuity of transmission so that GDOR chooses one-to-one transmission to reduce the network load.All of the above transmission would calculate the node forwarding priorities through effective weight calculation formula to ensure its reliability and robustness.(2)In view of the node congestion problem in the opportunistic network,this paper proposes a cache management strategy of message retreat.The strategy makes full use of the collaboration between the nodes to transfer the messages with low store value to the surrounding neighbors when the local node suffers node congestion.This strategy would try to reduce the packet loss compared to other congestion strategy and ensure the packet delivery ratio partly.(3)Using VanetMobiSim and NS3 build network simulation platform and realizing the bundle protocol in opportunistic routing,this paper simulates real urban road environment to experiment and verify the routing and retreat algorithm proposed in this paper.The results show that GDOR behaves better in packet delivery ratio,end-to-end delay and routing overhead compared other two protocols and the strategy of message retreat can make its work to ensure the packet delivery ratio.