| Summary: | 碩士 === 國立臺灣大學 === 資訊工程學研究所 === 95 === With the development and popularity of wireless technologies, many challenges beyond the capability of wired networks have been emerging in recent years. Although wireless data networks extend the service of Internet, they still have many constraints. Specifically, at least one complete path between the source and the destination pair should be found before transferring data. But in many scenarios, this constraint is hard to conform. In opportunistic networks, nodes connect to each other intermittently and opportunistically. Neither scheduled routing nor predicted routing can be utilized in such networks. If we can deal with these problems, we can greatly extend the utility of wireless data networks.
In this thesis, we propose an efficient routing approach called H-EC. It is a hybrid forwarding scheme based on erasure coding and replication methods. H-EC improves the performance of previous works in small delay performance cases while still keep excellent results in worst delay performance cases. We also propose three message scheduling algorithms of H-EC and compare their different performances. From simulation results, we find that although transferring data in opportunistic networks is difficult, our proposed approaches make it practical. Being conscious that successful delivery is very hard, we further apply Layered Multiple Description Coding (LMDC) for transferring video file in opportunistic networks in order to let end users can read
incomplete video file. By LMDC based schemes, end users can
"preview" the video before completely receiving data. Moreover, LMDC based schemes decline the heavy variance in per frame quality.
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