在本論文中，我們提出一個改良式的卡爾曼估測器，用來估測正交分頻多工系統中時變性的通道增益，此估測器主要是利用預先編碼的技術，並結合了最小均方誤差等化器來提高通道估測的準確性。使用預先編碼主要是為了使資料具備多樣性，進一步達到資料保護的效果，以避免卡爾曼濾波器因為疊帶數值不正確而造成發散。在本論文中，我們除了闡述系統架構和原理之外，並以電腦模擬分析誤碼率(Bit Error Rate，BER)，電腦模擬結果證明了不論通道是否隨著時間而變化，使用改良式的卡爾曼估測器，確實能提升系統的整體效能。

In this thesis, a modified Kalman filter is proposed for time varying channel estimation in orthogonal frequency division multiplexing (OFDM). The proposed scheme adopts pre-coding scheme and minimum mean squared error (MMSE) equalizer to improve system performance. By using pre-coding schemes, information can be protected by signal diversities, which prevent Kalman filter to disperse due to erroneous data signals. In this investigation, the proposed system architecture is verified by using simulation experiments. Simulation results demonstrate that the proposed schemes substantially improve system performances under verious channel conditions.

中文摘要......................................................................................................................Ⅰ
Abstract........................................................................................................................Ⅱ
圖目錄..........................................................................................................................Ⅴ
第一章　導論................................................................................................................1
1.1研究動機..........................................................................................................1
1.2論文架構..........................................................................................................2
第二章、正交分頻多工簡介........................................................................................3
2.1OFDM之系統架構與特性...............................................................................3
2.1.1簡介傳統分頻多工調變技術...............................................................4
2.1.2簡介正交分頻多工調變技術...............................................................6
2.1.2.1頻寬使用效率............................................................................8
2.1.2.2正交性........................................................................................9
2.1.2.3循環字首..................................................................................10
2.2 簡介OFDM 系統的優缺點.........................................................................12
第三章 OFDM通道估測技術介紹............................................................................14
3.1介紹利用指標示通道估測法去做通道估測................................................15
3.1.1領航訊號的編排規則.........................................................................15
3.2介紹利用盲蔽式通道估測法去做通道估測........................................16
第四章 卡爾曼估測器之介紹....................................................................................19
4.1簡介卡爾曼濾波器........................................................................................19
4.1.1簡介基本型卡爾曼濾器.....................................................................19
4.2介紹利用卡爾曼濾波器去估側通道..................................................23 4.3 介紹修正型卡爾曼濾波器去估側通道.......................................................26
第五章 模擬................................................................................................................30
第六章 結論和外來展望............................................................................................36
參考文獻......................................................................................................................37

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