臺灣大學: 電信工程學研究所廖婉君葉書豪Yeh, Shu-HaoShu-HaoYeh2013-03-272018-07-052013-03-272018-07-052012http://ntur.lib.ntu.edu.tw//handle/246246/252618隨機路由和內部流通網路編碼都是利用無線網路中廣播的特性來有效增加網路吞吐量的方法。但是它們兩個適用在不同的場合。隨機路由在通道環境不好的情況下其吞吐量是可以有效率可以改善的，主要是因為它有很多傳送者的選擇可以將封包送達目的地。相反的，內部流通網路編碼在環境品質不好的情況下會喪失很多編碼的機會。另外，內部流通網路編碼在多條流量交會於一個節點的時候，會有更多的編碼機會，但是這個情況在現今主流的外部流通編碼下的隨機路由協定，MORE，其吞吐量的改善會隨著流量的增加而減少。 在本篇論文中，我們提出了一個有效率的隨機路由網路編碼資訊的協定，階層式網路編碼，同時善用了隨機路由中外部流通網路編碼和內部流通網路編碼的優點。在通道環境不好的情況下，每位傳送者所收到線性組合過的編碼封包都不盡相同。在這篇論文最大的挑戰就是每位傳送者根據他收到的所有封包的組合中，決定一個適當的封包集合來使用內部網路流通編碼。為了解決這個問題，我們提出了兩個低複雜度的演算法。透過模擬顯示出我們所提出的階層式網路編碼協定在多流量的環境下，吞吐量是優於MORE，並且也說明了我們所提出的演算法是可以有效結合內部流通網路編碼和外部流通網路編碼的優秀方法。Opportunistic routing (OR) and inter-flow network coding are two promising techniques to improve the system throughput by exploiting the broadcast nature of wireless medium. However, they are suitable in different scenarios. Opportunistic routing is expected to be more effective in highly lossy network, because it has more chances for a packet to make progress toward the destination. In contrast, inter-flow network coding degrades coding opportunities under poor channel quality. On the other hand, inter-flow network coding is expected to have more coding opportunities when multiple flows cross at a node, while the throughput gains of MORE, the state-of-the-art intra-flow network coding based opportunistic routing protocol, decreases with an increased number of flows. In this work, we propose a new efficient network coding-based opportunistic routing protocol called Hierarchical Network Coding (HNC), which takes advantage of both intra-flow network coding based opportunistic routing and inter-flow network coding for lossy wireless networks. In a lossy environment, each linear combination of packets (i.e., coded packet) may not be able to arrive at each forwarder intact. The challenge of this work is to determine which packets to be XORed for transmission at each forwarder based on the partially received packets within all combinations. To tackle the problem, we propose two heuristic packet selection algorithms. We compare the performance via simulations, which show that the proposed HNC outperforms MORE in multiple-flow scenario, demonstrating that our proposed heuristic algorithms are indeed excellent solutions to combine the inter-flow network coding and intra-flow network coding.1319935 bytesapplication/pdfen-US隨機路由內部流通網路編碼外部流通網路編碼無線網路opportunistic routinginter-flow network codingintra-flow network codingwireless networkthesishttp://ntur.lib.ntu.edu.tw/bitstream/246246/252618/1/ntu-101-R99942061-1.pdf