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研究生:吳濟廷
研究生(外文):Chi-Ting Wu
論文名稱:以一階頻域LMS等化器係數為通道資訊於OFDM系統解碼器
論文名稱(外文):Using the Weighting Value of One-Tap Frequency Domain LMS Equalizer as Channel State Information for Viterbi Decoder of OFDM systems
指導教授:高永安高永安引用關係
指導教授(外文):Yung-An Kao
學位類別:碩士
校院名稱:長庚大學
系所名稱:電機工程研究所
學門:工程學門
學類:電資工程學類
論文種類:學術論文
論文出版年:2005
畢業學年度:93
語文別:中文
論文頁數:68
中文關鍵詞:通道資訊正交分頻多工系統維特比解碼器時間平均法
外文關鍵詞:channel state informationOFDMViterbi decodertime-average method
相關次數:
  • 被引用被引用:2
  • 點閱點閱:173
  • 評分評分:
  • 下載下載:0
  • 收藏至我的研究室書目清單書目收藏:0
在本論文中,我們探討了在正交分頻多工系統中,加入通道資訊輔助Viterbi解碼器之效能分析,同時由於通道效應以及雜訊的影響,等化過後的訊號會有大小以及相角上的衰減,因此我們也提出了一個嶄新的觀念,即在Viterbi演算法中加入了等化後訊號大小以及相角衰減之考量機制。通道資訊則來自於不同子載波上之一階頻域LMS等化器係數,相較於一般的OFDM接收端架構,由於加入了對於每個子載波間不同的信賴程度以及等化後訊號的大小及相角考量機制,可以看出此一方法有較佳之效能。
在本論文的模擬中,亦比較不同通道資訊取得的情形,包括利用規格中的已知訊號以及LMS錯誤訊號,經由模擬結果可看出,本論文所提出的方法與其他兩種方法之間所造成之效能差異,並且,可以發現由於在不斷更新係數的情形下,相較於其他方法更能忠實地反應出通道效應,進而輔助Viterbi解碼。此外,我們在更新係數時亦利用時間平均法,使得估測更為準確。
In the thesis, the Viterbi decoder with aided channel state information (CSI) for OFDM based system is investigated. At the same time, due to the channel and noise effect, equalized signal suffers the magnitude and phase degradation. Therefore, we propose a novel concept which is to consider the magnitude and phase degradation of equalized signal in Viterbi algorithm. The CSI is obtained from the weighting values of one-tap frequency domain LMS equalizers on different subcarriers. Comparing to conventional OFDM receiver structure, because we use the different reliable degrees of each subcarrier and take into account of magnitude and phase degradation of equalized signals, we could see the better performance is obtained.
In the following, the simulations from different CSI, like long training symbols and LMS error signal, are also included. From the simulation results, we could see the different performances between the proposed method and other two manners. Simultaneously, we could observe clearly that through the updating coefficients, the proposed method could reflect the channel state more precisely. Moreover, the time-average methods are also applied when updating coefficients, which make estimation more accurately.
指導教授推薦書 i
口試委員會審定書 ii
論文著作授權書 iii
誌謝 iv
中文摘要 v
Abstract vi
目錄 vii
圖表目錄 ix
第一章 序論 1
1.1 引言 1
1.2 研究動機與目的 2
1.3 本篇論文架構 4
第二章 OFDM技術簡介 5
2.1 OFDM發展過程 5
2.1.1 傳統OFDM架構 7
2.1.2 基於DFT之OFDM架構 9
2.2 OFDM的特性 10
2.2.1 OFDM正交性 10
2.2.2 OFDM保護區間 12
2.3 OFDM接收端的問題 13
2.4 OFDM外部接收端 15
2.4.1 BPSK、QPSK之soft decision方法 16
2.4.2 16QAM、64QAM之soft decision方法 17
2.5 OFDM系統方塊圖及訊號的數學模型 20
2.6 等化 22
2.7 總結 23
第三章 一階頻域LMS等化器係數應用於OFDM解碼器之效能分析 25
3.1 一般通道資訊輔助Viterbi解碼之方式 25
3.1.1 利用long training signal反應通道狀況 26
3.1.2 利用LMS錯誤訊號反應通道狀況 27
3.2 一階頻域LMS等化器 28
3.2.1 正規化LMS頻域等化器 30
3.2.2 LMS頻域等化器係數的平均行為 31
3.3 等化後之訊號 34
3.3.1 平均值偏移行為 34
3.3.2 時間平均法 36
3.4 利用LMS係數輔助Viterbi解碼器之理論與方法 38
3.4.1 BPSK、QPSK調變下之數值平均值變動量考量方法 41
3.4.2 16QAM、64QAM調變下之數值平均值變動量考量方法 45
第四章 一階LMS頻域等化器係數應用於OFDM系統中之模擬分析 46
4.1 IEEE 802.11a系統規格簡介 46
4.2 模擬環境以及參數設定 49
4.3 加入通道資訊輔助Viterbi解碼之模擬分析 50
4.4 考量平均值偏移量之模擬分析 57
第五章 結論與未來展望 65
Reference 66
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