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研究生:李昆霖
研究生(外文):Kun-Lin Lee
論文名稱:結合滑動視窗與尋峰演算法以改善正交分頻多工系統之訊框同步效能
論文名稱(外文):Improvement of Frame Synchronization in OFDM Systems by Using the Combination of Sliding Window and Peak Search Algorithms
指導教授:曾德樟
口試委員:陸清達譚旦旭曾德樟
學位類別:碩士
校院名稱:國立臺北科技大學
系所名稱:電子工程系研究所
學門:工程學門
學類:電資工程學類
論文種類:學術論文
畢業學年度:104
中文關鍵詞:訊框同步、正交分頻多工系統、時間延遲
外文關鍵詞:rame synchronizationOFDMtiming delay
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在無線通訊系統中,正交分頻多工(Orthogonal Frequency Division Multiplexing, OFDM)系統利用相互正交的子載波來傳送資料,因而具有高頻譜使用效率之優點,但此系統之缺點為接收端對於訊框訊號和頻率的同步較為敏感;因此,在多路徑傳輸過程中所產生的時間延遲,在接收端可能造成接收訊號起始點之誤判,進而影響訊框同步(frame synchronization)之準確性,使得訊號解調時的錯誤率增加,故本文針對接收端訊框不同步的狀況進行討論並且提出改善方法。
在有限的頻寬下,為對抗多路徑傳輸所造成之時間延遲,本論文提出利用單一前導訊號(preamble signal)來做訊框同步估測,並結合滑動視窗(sliding window)演算法和尋峰(peak search)演算法做訊框同步之估測與校正,並以訊框同步之成功機率和時間偏移平均值及同步時之時間均方誤差來評估訊框同步之估測效能。由電腦模擬結果顯示,本論文所提方法確實能有效提升訊框同步的估測效能。
In wireless communication systems, orthogonal frequency division multiplexing (OFDM) system utilizes mutually orthogonal subcarriers with various frequencies to transmit data. It has the advantage of high spectral efficiency. Nevertheless, the disadvantage of this system is that its receiver is sensitive to frame and frequency synchronization signals. Furthermore, the time delay generated from multipath transmission might lead to the misjudgment of the starting point of frame signals , which could affect the accuracy of frame synchronization and increase the error rate of demodulation signal. As a result, this thesis focuses on frame non-synchronization and makes proposals for improvement.
In order to solve the problem of time delay generated from multipath transmission, this thesis presents a unitary preamble signal to do synchronous estimation. In addition, it is combined with sliding window and peak search algorithms to do frame estimation and correction so as to improve the success rate of frame synchronization, mean of timing offset and reduce mean square error. Simulation results indicate that the proposed method can actually enhance the estimation performance of frame synchronization.
摘 要 i
ABSTRACT ii
誌 謝 iii
目錄 iv
表目錄 vi
圖目錄 vii
第一章 緒論 1
1.1 前言 1
1.2 研究背景與動機 1
1.3 研究方法 3
1.4 各章內容 3
第二章 正交分頻多工系統 4
2.1 正交分頻多工技術簡介 4
2.1.1 單載波與多載波調變 4
2.1.2 分頻多工與正交分頻多工 5
2.1.3 正交分頻多工系統之正交特性 6
2.2 正交分頻多工系統架構 7
2.2.1 傅立葉轉換與反傅立葉轉換 8
2.2.2 保護區間及循環字首 8
2.3 訊框同步錯誤的影響 13
2.3.1 訊框時間偏移 13
2.4 正交分頻多工的優點與缺點 14
2.5 訊框同步估測環境介紹 15
2.6 訊框同步之評估方式 16
2.6.1 訊框同步成功機率之估算 16
2.6.2 訊框同步之時間均方誤差 17
2.6.3 訊框同步之時間偏移平均值 17
第三章 訊框同步演算法 18
3.1 傳統演算法介紹 18
3.1.1 SC演算法 18
3.1.2 MZB滑動視窗演算法(MZB1) 21
3.1.3 MZB尋峰演算法(MZB2) 24
3.2 結合滑動視窗演算法與尋峰演算法 26
3.2.1 前導訊號之測試實驗 26
3.2.2 本文所提方法 30
第四章 實驗結果與討論 33
4.1 訊框同步之系統模擬參數設定 33
4.2 訊框同步成功機率之模擬實驗 34
4.3 訊框同步時間均方誤差之模擬實驗 37
4.4 訊框同步時間偏移平均值模擬實驗 40
第五章 結論與未來展望 43
參考文獻 44
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