| Summary: | 碩士 === 國立高雄師範大學 === 光電與通訊工程學系 === 101 === Vehicle networks do not just provide traffic information but also improve vehicle safety when driving. Moreover, people develop them in order to increase convenience and efficiency too. However, due to the short transmission range of Wi-Fi and possible long distance between a vehicle to a destination, we need a better routing algorithm to use the shortest time to forward the packet with low message loss. Geographical Opportunistic Routing is a great routing algorithm to this problem. The simulation results show that it produces significantly higher delivery ratio and lower packet delay than other algorithms. However, after studying the processes, we found out some shortcomings, such as without considering whether the vehicles receive the packets was completed prior to the disconnection of the transmission range on the Wi-Fi and the ways to compare the METD values between two vehicles. Therefore, in addition to import the pre-detect mechanism; we also use the corrected RREQ and RREP packets to make the operation more flawless. Additionally, we use three strategies to study the value of METD, the first is time-based strategy, the second is distance-based strategy, and the third is hybrid strategy. We analyze and compare the strategies in different conditions under multiple simulations. The results show that distance-based strategy is better than time-based strategy in a small map; however, time-based strategy is better than length-based strategy in a large map. In conclusion, we are not only identifying possible causes but also offering a solution to improve time-based strategy.
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