多點訊息交換的無線網路編碼之研究

Study on Multi-node Information Exchange with Wireless Network Coding

鄭力銘(Li-Ming Zheng)

指導教授 ： 王佳盈

中原大學/工學院/電機工程研究所/碩士(2009年)

https://doi.org/10.6840/cycu200901119

摘要

最近幾年網路編碼被廣泛的研究。在無線網路的傳輸上，利用網路編碼的技術可以提高其傳輸效率及可靠度。舉例而言，如果兩個節點必須透過中間節點來交換資訊，使用傳統的方法，我們須要四次才能完成，而使用網路編碼，則只須要三次甚至兩次便可以完成。
基本上，這裡有兩種常見的傳輸模式。一種稱之為解碼前送(Decode-and-Forward, DF) ，就是先讓中間節點將個別收到的訊息先解碼，然後利用XOR的運算方式將收到的訊息編碼，然後再廣播給鄰近的節點。另一種稱為放大前送(Amplify-and-Forward, AF)，它是利用多路存取通道(multiple access channel)的特性，由中間節點直接同時接收兩端傳送過來的類比訊號，不需透過解碼，直接將訊號放大後轉送給鄰近的節點，由鄰近的節點自行解碼。
在本論文中，我們在上述問題延伸，假設有三個節點，想透過中間節點的幫助互相交換訊息，我們想知道可以傳送多快，以及應該如何傳送。我們針對解碼前送、放大前送，以及不同的調變狀況，提出幾個基本的傳送方法，並且做了相關的模擬結果。我們從中可以看到，與傳統的傳輸方式相比，網路編碼確實可以大幅提升傳輸的效能。

關鍵字

放大前送 ； 解碼前送 ； 無線網路 ； 網路編碼

並列摘要

Network coding has been researched massively in recent years. It can be used in wireless network to improve the transmission throughput and reliability. For example, if two nodes want to exchange information with the help of an intermediate node, we need four time slots with traditional method, yet we only need three or even two time slots with network coding.
Basically, there are two ways to apply the techniques of network coding to this case of wireless transmissions. The first method is called Decode-and-Forward (DF) method, in which the intermediate node decodes the received messages first, then encodes again and broadcasts them to its neighbors. The second method is called Amplify-and-Forward (AF) method, in which the intermediate node receives the transmitted signals simultaneously through the multiple access channels; it then just amplifies the received signal and broadcast them to its neighbors.
In this thesis, we extend the problem to three nodes case, that is, if three nodes want to exchange information with each other with the help of an intermediate node, how fast can it achieve and how can we achieve that? We focus on the throughput of the transmission by using DF and AF methods. We propose some basic protocols and also give the simulation results. It is seen that by using network coding, the performance is much improved when compared to the traditional method.

並列關鍵字

amplify-and-forward ； decode-and-forward ； network coding ； wireless transmission

參考文獻

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[7] P.Larsson, N.Johansson, “Interference cancellation in wireless relaying networks,” May 2003 patent WO 2004/102981.