| Summary: | 碩士 === 國立虎尾科技大學 === 光電與材料科技研究所 === 101 === The quickly development of wireless communication technology makes the vehicular ad-hoc networks (VANETs) popularly been discussed in the recent year. In the inter-vehicle communication, the vehicles share the real-time traffic information for drivers to avoid road congestions and accidents to increase the safety effectively. For the passengers, VANETs can provide Internet services, real-time information and live-chat. These benefits let passengers feel more convenient in the journey. These services need a stable wireless network communication connection to ensure the success of data delivery. In VANETs, the high-speed mobile environment may cause communication connection becoming unstable. Many technologies used in ad-hoc network are unsuitable for VANETs. How to keep a stable communication connection on the high mobile environment has become an important topic. Current, most of the research focuses on extending the lifetime of path and finding the shortest path. However, in the high mobile environment, considering only the lifetime of path but ignoring the number of nearby vehicles of a node will make connection failed more frequently. The payment introduces greater cost on communication. Therefore, this paper focuses on designing the methods to retain the communication path in the high mobility communication environment. Firstly, we build the shortest path that has a long lifetime. Next, the remaining connection time will be estimated and trigger the local route repair procedure before the communication connection between inter-vehicle fails. The sender and the receiver will not feel the disconnection, and the route can be repaired seamlessly. The bidirectional local route repair is used to reduce the route reconnection time of the unidirectional route rebuilding procedure used in AODV. At the same time, the number of communication packets is also decreased. A method referring to the density of the nearby vehicles for choosing proper nodes to rebuild the route is proposed. The number of times to rebuild the route from source to destination that causes by lacking nodes while performing the route rebuilding can be reduced.
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