以電腦搜尋之短非同調區塊碼; Short Noncoherent Block Codes Searched by Computers

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题名:	以電腦搜尋之短非同調區塊碼;Short Noncoherent Block Codes Searched by Computers
作者:	謝佩恩;Pei-en Hsieh
贡献者:	通訊工程研究所
关键词:	非同調區塊碼;noncoherent block codes
日期:	2011-07-11
上传时间:	2012-01-05 14:50:31 (UTC+8)
摘要:	幾種非同調區塊編碼架構，包括使用八點相位鍵移(8PSK)、八點扭轉振幅相位鍵移(8TAPSK)、十六點扭轉振幅相位鍵移(16TAPSK)及十六點的正交振幅調變(16QAM)非同調區塊編碼都已經被提出。但是這些區塊編碼架構在短的區塊無法得到令人滿意的錯誤效能，主要原因為這些有架構的碼在短的區塊所得到的最小非同調距離太小。本篇論文根據非同調距離去搜尋短的非同調區塊碼，由於短區塊碼的碼字個數不會太多，在非同調接收端可以將碼字一個一個測試，所以我們考慮沒有結構的碼，使用幾種演算法尋找一群碼字來組成碼，讓它具有大的最小非同調距離，並經由最佳的位元對應來得到較低的位元錯誤率，模擬結果亦顯示這種沒有架構的區塊碼有較好的錯誤效能。本篇論文藉由參考查表法相差編碼，我們使用另外一種建立相差編碼表的方式來解決多個點數不易建成群組數較少的相差編碼表的問題。本篇論文對於三十二點的正交振幅調變(32QAM)建立出16 個群組數的相差編碼表，它與相差編碼十六點的正交振幅調變(16QAM)的表具有相同群組數。藉由本研究提出的方法產生16 群組的三十二點的正交振幅調變(32QAM)相差編碼表，與相差編碼十六點的正交振幅調變(16QAM)比較，可得到較大的最小非同調距離及較好的錯誤效能。 Many noncoherent block coding schemes were proposed, such as using noncoherent block-coded 8PSK(NBC-8PSK), noncoherent block-coded Twisted amplitude and phase shift keying using eight signal point(NBC-8TAPSK), NBC-16TAPSK, and noncoherent block-coded quadrature amplitude modulation(16QAM). When the block length is very small, these schemes perform worse due to their small minimum noncoherent distance. In this thesis, we use computers to search short noncoherent block codes according to the noncoherent distance. Because the number of codeword is less, the noncoherent receiver can test the codeword one-by-one. The unstructured codes were composed from the codewords by several algorithms and their minimum noncoherent distance was longer. Additionally, we got the lower bit error rate by the optimum bit mapping. The results showed that the unstructured block code perform better. In this study, based on differential encoding by a look-up table, the varied differential encoding table was developed and solved that multiple points difficultly produce differential encoding table with less group. In this study, we constructed the differential encoding table for 32QAM and the table included sixteen groups. The number of groups is the same with the number of differential encoding table for 16QAM. The results showed that the differential encoder for 32QAM has larger minimum noncoherent distance and better error performance than the differential encoder for 16QAM.
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