标题: | 无线网路编码与压缩 Network coding and compression in wireless networks |
作者: | 石维伦 Shi, Wei-Lun 陈志成 Chen, Jyh-Cheng 资讯科学与工程研究所 |
关键字: | 无线区域网路;网路编码;监听;霍夫曼树;霍夫曼编码;Wireless LANs;Network Coding;overhearing;Huffman tree;Huffman code |
公开日期: | 2012 |
摘要: | 由于通讯技术在这近20年来突飞猛进,无线区域网路(Wireless LANs)的分布密度越来越高,在餐厅、车站或图书馆等公共场合都可以侦测到Wi-Fi的讯号,尤其在人口密集的场所,甚至可以同时侦测到数个无线基地台所发出的讯号。伴随着无线区域网路以及行动装置(例如智慧型手机或平板电脑)的高度普及,透过无线区域网路传递的资料量越来越多,在这个情况下有效的网路编码(Network Coding)可以减少传输的资料量,促进无线频宽的利用率。 许多系统利用广播的特性来提升无线网路的容量及效能,传统的方法专注于偷听(overhearing)整个封包,但近年来多数设计者认为偷听封包的内容会更有效率。针对此方法,我们利用封包内容重复出现的机率,将接收的封包内容建成一棵霍夫曼树(Huffman tree),并利用霍夫曼编码(Huffman code)来编码封包内容。为了证明我们提出方法的实际性及可行性,我们到许多不同的公共场所搜集实际的封包资料进行分析,并且将霍夫曼编码的演算法实作在Linux核心上,利用Linux系统架设的无线路由器来编码传递封包。最后我们根据实做的结果来验证霍夫曼编码的可行性,并利用分析资料的结果来验证实作的正确性。 In the past two decades, communications technologies have been improved. The densiry of wireless Local Area Networks (LANs) becomes higher and higher. Now we can detect Wi-Fi signals in many places, including restaurants, train stations, libraries, especially in densely populated areas. We can even detect several signals from different wireless base stations in the same space. As wireless LANs and mobile devices become much popular, more and more data are transferred through wireless LANs. In many cases, network coding can reduce the amount of data transmitted, and improve channel utilization. Many wireless systems have leveraged the nature of broadcast to improve wireless capacity and performance. While conventional approaches have focused on overhearing entire packets, recent designs have argued that focusing on overheard content may be more effective. For this reason, we utilize the probability of packet repeats to build a Huffman tree. We then use Huffman codes to encode packets. In order to demonstrate the feasibility and practicality of the proposed method, we analyze actual packets collected from different public areas. We also implement the Huffman coding algorithm in Linux kernel and setup a wireless router to encode transmitted packets in Linux system. Finally, we prove the practicality of Huffman encoding by Linux implementation. |
URI: | http://140.113.39.130/cdrfb3/record/nctu/#GT070056100 http://hdl.handle.net/11536/72999 |
显示于类别: | Thesis |