運用放大前送的無線網路編碼技術之研究

Wireless Network Coding by Amplify-and-Forward Method

謝學禮(Hsueh-Lee Hsieh)

指導教授 ： 王佳盈

中原大學/工學院/電機工程研究所/碩士(2007年)

https://doi.org/10.6840/cycu200700400

摘要

網路編碼應用於無線網路的傳輸上，可以提高其傳輸效率，並且增加傳輸的可靠度。在無線網路的傳輸中，可利用網路編碼的方法，在中間的節點將封包編碼組合，然後廣播給鄰近的節點。透由這樣的方式，訊息的交換會更有效率。
基本上將網路編碼應用於無線傳輸，可以區分成兩種不同的方式。第一種是解碼前送的方法 (Decode-and-Forward, DF)，即節點先將所有接收的訊息解出，然後再編碼廣播出去。第二種是放大前送的方法 (Amplify-and-Forward, AF)，是應用多路存取通道 (multiple access channel) 的特性，直接接收在通道上干擾相加的合成訊號，不透過解碼，直接將訊號放大轉送給鄰近的節點，由鄰近的節點自行解碼。在高訊雜比的情況下，這樣可以達到更高的傳送效率。
在本論文中，我們結合了放大前送和錯誤更正碼的技術，利用錯誤更正碼的特性，降低封包錯誤的機率，以減少重傳次數，從而達到更好的傳輸效率。我們也針對錯誤檢測及錯誤更正做進一步討論，並將兩者合併設計。透由理論和數值的分析，我們驗證了合併設計的好處。我們也比較和分析在不同的訊雜比情況下，各種系統的性能表現，由分析的結果可以得到，我們所提出的方法，在中間區段的訊雜比情況下，可以得到更好的傳輸效率。

關鍵字

放大前送 ； 網路編碼 ； 無線網路 ； 解碼前送 ； 錯誤更正碼

並列摘要

It is well known that network coding can be used in wireless transmission to increase the network throughput and robustness. The intermediate node receives messages from its neighbors and then encodes the messages before it broadcasts them to neighbors. By such a way, messages can be exchanged with more efficiency.
Basically, there are two kinds of methods to apply the network coding techniques. The first is called Decode-and-Forward (DF) method, in which the intermediate node decodes the received messages before its encoding process. The second is called Amplify-and-Forward (AF) method, in which the intermediate node doesn’t decode the received messages, in stead, it just amplifies and broadcasts the received summing wave signals. The neighbors should take the duty to decode the messages. In this case, the channel should be a multiple access channel.
In this thesis, we combine the AF method with error correction coding techniques. By using forward error correction code, the packet error rate is reduced, hence the average retransmission times per packet is also reduced and the whole system throughput is increased. We also discuss the issues of packet error detection. Then we propose a new method, which adopts the error correction code with detection and correction capabilities. Through the theoretical analysis and numerical results, it is seen that the proposed methods can further increase the network throughput. Compared with DF and AF methods, our proposed methods can get a higher network throughput at moderate signal-to-noise ratio (SNR).

並列關鍵字

amplify-and-forward ； decode-and-forward ； network coding ； wireless transmission ； error correction code

參考文獻

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