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研究生:陳玉蓁
研究生(外文):Yu-Zhen Chen
論文名稱:通用於IEEE 802.11n與IEEE 802.11a/g之訊符時間同步演算法
論文名稱(外文):Interoperable Symbol Timing Synchronization Algorithm between IEEE 802.11n and IEEE 802.11a/g
指導教授:林信標林信標引用關係
口試委員:張文鐘李志鵬尤信程林丁丙
口試日期:2012-06-29
學位類別:碩士
校院名稱:國立臺北科技大學
系所名稱:電腦與通訊研究所
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:2012
畢業學年度:100
語文別:中文
論文頁數:82
中文關鍵詞:IEEE 802.11n時間同步技術循環位移分集(CSD)技術
外文關鍵詞:IEEE 802.11nsymbol timing synchronization algorithmcyclic shift diversity(CSD)
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  • 被引用被引用:1
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目前市面上較廣為被使用的規格為IEEE 802.11a/b/g/n,其中,802.11n為Wi-Fi聯盟中最新的標準。802.11n為了向下相容802.11a/g,在規格中新增了循環位移分集(Cyclic Shift Diversity, CSD )技術,用以增加空間分集(Spatial Diversity)和避免產生非預期結果的波束成型(Beamforming)技術。
802.11a/g所使用的傳統同步方法,皆假設訊符時間同步起始於preamble的起始位置,但802.11a/g訊符時間同步所使用的preamble實際上是會受到自動增益控制完成時間的影響;除此此外,在802.11n標準加入CSD技術後,更多了偽多重路徑的問題,導致使用交相關運算會產生多時間結果。為了解決這些問題,本論文提出一個新的同步方法。首先,運用兩種皆基於最大正規化相關(MNC)的演算法其之間的特性,偵測出L-LTF之GI起始位置做為粗略的時間同步;當在訊號雜訊比低於15dB時運用跳格交相關做為精確的時間同步。
本論文所提出之粗略的時間同步演算法,模擬於TGn B與TGn D的通道模型下,當SNR在15dB到30B之間,其均方根誤差(MSE)的平均分別為0.93和6.3,低於同樣考慮到實際情況與CSD影響之參考文獻同步方法。但由於在SNR低於15dB時,粗略的時間同步準確度明顯的下降,故本論文參考相關文獻,在訊雜比低於15dB時加入精確時間同步,其準確度會有明顯的改善。其最終0dB到30dB之間整體均方根誤差的平均分別為5.92和12.6,故證明了本論文所提出之訊符時間同步方法不僅解決了傳統同步方法之問題其準確度亦優於參考獻。


The IEEE 802.11a/b/g/n standards are widely used on current market, among all of the above standards, the 802.11n is the latest standard in Wi-Fi Alliance. For the interoperability between 802.11n and 802.11a/g devices, the cyclic shift diversity (CSD) technique is adopted for achieving spatial diversity and for avoiding undesired beamforming result in 802.11n standard.
The conventional synchronization methods used in 802.11a/g assumed that symbol timing synchronization starts at the beginning of preamble, but preamble is affected by the processing time of the automatic gain control (AGC). Moreover, when the CSD scheme is adopted in 802.11n standard, it induces a pseudo multipath problem which generates multiple possible timing results in cross-correlation calculation. In order to solve these problems, a novel symbol timing synchronization method is devised in the thesis. The proposed method estimates a coarse time-offset of GI start point of L-LTF using the correlation between two kinds of maximum normalized correlation (MNC) - based algorithm firstly, and predicts the fine timing offset of short training symbols (STSs) start point using jumping cross-correlation when the signal noise rate (SNR) less than 15dB.
Without fine timing synchronization, the simulation results show that the mean square error (MSE) of estimation under the TGn B and TGn D channel at SNR equal to 15dB and 30dB are 0.93 and 6.3 respectively. Compared to the reference synchronization methods, our proposed method shows better promised results. Thought synchronization accuracy has salient decreasing while the SNR is less than 15dB, the estimation accuracy can be significantly improved by applying jumping cross-correlation method to find the timing offset from related references at low SNR case. As shown in the simulation results, the proposed timing synchronization method not only solve the conventional synchronization issues but also have better accuracy of synchronization than references methods.


摘 要 i
ABSTRACT iii
誌 謝 v
目 錄 vii
表目錄 ix
圖目錄 x
第一章 緒論 1
1.1 前言 1
1.2 研究動機與目的 1
1.3 論文架構 2
第二章 無線區域網路通用標準IEEE 802.11整體架構與技術介紹 4
2.1 無線區域網路系統之技術發展 4
2.1.1 正交分頻多工技術(OFDM) 5
2.1.2多重輸入多重輸出-正交分頻多工技術(MIMO-OFDM) 8
2.1.3 循環位移分集技術( Cyclic Shift Diversity ,CSD ) 10
2.2簡介IEEE 802.11a系統架構 13
2.2.1 IEEE 802.11a之系統規格簡介 13
2.2.2 IEEE 802.11a之傳送訊框格式 17
2.2.3 IEEE 802.11a之同步訊號欄位 19
2.3簡介IEEE 802.11n系統架構 21
2.3.1 IEEE 802.11n之系統規格簡介 21
2.3.2 IEEE 802.11n之傳送訊框格式 26
2.3.3 IEEE 802.11n之同步訊號欄位 29
第三章 無線區域網路系統之訊符時間同步 32
3.1 傳統的訊符時間同步演算法 32
3.2 訊框加入CSD技術對訊符時間同步之影響 39
3.3 通用的訊符時間同步演算法 43
3.3.1 通用之粗略的時間同步 43
3.3.2 通用之精確的時間同步 53
第四章 模擬結果與分析 59
4.1 模擬環境 59
4.1.1 模擬情境 59
4.1.2 模擬通道 60
4.2 模擬結果 64
4.2.1 模擬的訊符時間同步演算法架構 64
4.2.2 模擬結果的分析 68
第五章 結論 79
參考文獻 80


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