| Summary: | 碩士 === 國立中興大學 === 資訊科學與工程學系所 === 101 === In MANET, efficiency of routing protocols has been an important research topic. Ad-hoc On-demand Distance Vector (AODV) is one of the most popular routing protocol for MANET. AODV is also used in VANET. However, due to the different characteristics of the two networks, AODV protocol suffers poor performances when it is applied in VANET.
In this thesis, we propose a method called IAODV to improve AODV route discovery step when applied to VANET. Our method consists of two steps. The first step is AODV_RA. We use the position information from GPS to restrict the RREQ flooding area. Each node decides to rebroadcast RREQ messages based on the distance between itself and source or destination. If a node is not in this restricted area, it will not rebroadcast RREQ. On the other hand, in the first step, nodes only receive RREQ that are originated in this restricted area. In the second step, we use the velocity and direction information from GPS to calculate lifetime between itself and the previous node, and choose the appropriate node and then rebroadcast so as to minimize routing discovery frequency and control overhead. We use a network simulator – NS2 –as an experimental platform for verification. The simulation results show that our proposed IAODV effectively controls routing overhead. Overhead is reduced to approximately 50% of the original. It also successfully reduces route discovery frequency. The proposed method works extremely well for a large number of fast-moving vehicles. In this case, it can significantly reduce average delay and improve transmission success rate. Our method outperforms AODV particularly when VANET has fast-changing topology.
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