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研究生:吳金寶
研究生(外文):Chen-pao Wu
論文名稱:無線區域網路時序頻率同步之研究及硬體實現
論文名稱(外文):Research and Implementation on Timing and Frequency Synchronization for Wireless LANs
指導教授:黃穎聰黃穎聰引用關係
指導教授(外文):Yin-Tsung Hwang
學位類別:碩士
校院名稱:國立雲林科技大學
系所名稱:電子與資訊工程研究所
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:106
中文關鍵詞:相位追蹤取樣時脈偏差估測通道估測時序與頻率同步正交分頻多工802.11a快速傅利葉轉換
外文關鍵詞:Timing and Frequency synchronizationOFDM802.11aFFTChannel estimationPhase trackingSampling clock offset estimation
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  • 被引用被引用:1
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OFDM技術由於其頻寬效率及對抗頻率選擇性衰減上有很好的效能,近年來已被廣泛的應用在各種無線傳輸技術上,如無線區域網路WLAN中的IEEE 802.11a/g。然而OFDM對頻率偏移效應相當敏感,這是由於接收端與發射端間頻率誤差的結果;它會引起內部載波干擾,且會破壞OFDM信號組的正交性。其他如時序同步、取樣頻率偏移以及多重路徑通道效應,同樣會造成系統效能的下降。因此,在接收端需要有一個良好的時序頻率同步系統來還原信號。在本篇論文中,我們基於IEEE 802.11a無線區域網路的架構上,探討有關時序頻率同步、通道估測及相位追踪等演算法的研究,並提出了一個新式時序頻率同步演算法。這個演算法包括時域上的訊框起始點偵測,訊框的時序估測與頻率偏移估測及補償。為了配合實際環境的需要與實驗的真實性,我們加入白色高斯雜訊以及多重路徑衰變通道下並在電腦作軟硬體的模擬。根據模擬結果,我們所提出的架構可以獲得良好的同步效果。在硬體實現方面,我們也提出降低運算複雜度的架構並驗證之。
Due its performance edges in channel bandwidth efficiency and in combating frequency selective fading, OFDM based wireless transmission techniques have become increasingly popular these days. The OFDM technique has been adopted in various applications such as wireless LAN. In this thesis, our focus will be on the synchronization problem. First of all, the performance of an OFDM system is very sensitive to the carrier frequency offset. This will destroy the orthogonality among sub-carriers and lead to inter-carrier interference (ICI). Secondly, frame detection error and sampling timing error also have crucial impact on the system performance. These problems are further complicated by the effect of multi-path fading. Therefore, a robust synchronization block capable of tackling these problems must be employed at the receiver side. In this thesis, based on the system requirement of the IEEE 802.11a standard, we investigate timing and frequency synchronization, channel estimation, phase tracking algorithms and propose a novel timing and frequency synchronization algorithm. The algorithm consists of different processing blocks for frame detection, fine time synchronization, frequency offset estimation in time domain. To make the simulation as close to the real system as possible, the channel model adopted is the combination of an IEEE compliant multipath fading channel and AWGN channel. Simulation results indicate the proposed scheme can achieve satisfactory synchronization. In implementation, we propose reducing the structure of computing complexity and improve it.
中文摘要 -------------------------------------------------------------------------- i
英文摘要 -------------------------------------------------------------------------- ii
誌謝 -------------------------------------------------------------------------- iii
目錄 -------------------------------------------------------------------------- iv
表目錄 -------------------------------------------------------------------------- vi
圖目錄 -------------------------------------------------------------------------- vii
一、 緒論-------------------------------------------------------------------- 1
1.1 前言-------------------------------------------------------------------- 1
1.2 研究動機-------------------------------------------------------------- 2
1.3 論文架構-------------------------------------------------------------- 3
二、 無線通訊系統標準及同步問題----------------------------------- 4
2.1 正交分頻多工系統-------------------------------------------------- 4
2.1.1 正交分頻多工調變原理-------------------------------------------- 5
2.1.2 保護區間及循環字首----------------------------------------------- 8
2.2 IEEE 802.11實體層規範------------------------------------------- 10
2.2.1 IEEE 802.11a 實體層架構概述----------------------------------- 10
2.2.2 前序區塊-------------------------------------------------------------- 13
2.2.3 信號區塊-------------------------------------------------------------- 15
2.2.4 資料區塊-------------------------------------------------------------- 16
2.2.5 視窗化----------------------------------------------------------------- 21
2.3 正交分頻多工的同步問題----------------------------------------- 23
2.3.1 通道效應-------------------------------------------------------------- 23
2.3.2 訊符時序同步誤差的影響----------------------------------------- 25
2.3.3 載波頻率偏移-------------------------------------------------------- 27
三、 時序與頻率的同步-------------------------------------------------- 31
3.1 訊框偵測及頻率同步----------------------------------------------- 31
3.1.1 延遲和關聯的演算法[3] ------------------------------------------- 32
3.1.2 低複雜度訊框同步[4] ---------------------------------------------- 34
3.2 細微時序同步-------------------------------------------------------- 35
3.2.1 匹配濾波器----------------------------------------------------------- 35
3.2.2 高訊號能量系數選擇匹配濾波器--------------------------------- 37
3.3 相位旋轉誤差-------------------------------------------------------- 40
3.3.1 通道估測-------------------------------------------------------------- 42
3.3.2 相位誤差追踪-------------------------------------------------------- 45
3.4 新式時序及頻率同步演算法-------------------------------------- 47
3.4.1 新式訊框偵測及頻率同步----------------------------------------- 48
3.4.2 新式細微時序同步-------------------------------------------------- 50
3.5 訊框偵測的錯誤率比較-------------------------------------------- 54
3.5.1 訊框偵測錯誤率、平均值及變異值比較----------------------- 55
3.5.2 位元錯誤率及封包錯誤率比較----------------------------------- 58
四、 硬體實現-------------------------------------------------------------- 61
4.1 硬體架構-------------------------------------------------------------- 61
4.1.1 訊框偵測架構之選定----------------------------------------------- 62
4.1.2 訊框偵測及頻率同步----------------------------------------------- 62
4.1.3 新式細微時序同步-------------------------------------------------- 72
4.1.4 快速傅利葉轉換[8] ------------------------------------------------- 73
4.1.5 通道估測、通道效應修正、相位誤差追踪及取樣時脈偏差估測-------------------------------------------------------------------- 81
4.2 所需硬體分析-------------------------------------------------------- 86
4.3 電路模擬結果-------------------------------------------------------- 87
4.3.1 訊框偵測模擬-------------------------------------------------------- 87
4.3.2 頻率估測模擬-------------------------------------------------------- 88
4.3.3 細微時序同步模擬-------------------------------------------------- 89
4.3.4 快速傅利葉轉換摸擬------------------------------------------------ 89
五、 結論與未來研究方向----------------------------------------------- 91
5.1 結論-------------------------------------------------------------------- 91
5.2 未來研究方向-------------------------------------------------------- 91
參考文獻 -------------------------------------------------------------------------- 93
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