臺灣博碩士論文加值系統

在本論文中提出一個可以用來提高數位電視廣播(DVB-T)的通道估測效能的方法。數位電視廣播(DVB-T)通道的估測主要分成二個步驟，領航信號(Pilot signal)的估測及通道係數(Channel coefficient)的內插(interpolation)，內插的準確性對通道估測的效能影響很大，同時和訊雜比(Signal-to-Noise Ratio)相關，我們使用OFDM符元(Symbols)通道係數結合的方法，複製估測的通道係數到一個OFDM符元相同子載波上，和兩次一維內插相比，我們提出的方法沒有延遲OFDM符碼時間同時節省六個OFDM符碼記憶空間及一次內插。和頻域線性內插相比，電腦的模擬證明，我們所提出的方法可以有效的提高估測效能。

This thesis proposes a method to improve the channel-estimation performance in Digital Video Broadcasting-Terrestrial (DVB-T) Systems. In DVB-T, the channel estimation is carried out through two processes of pilot signal estimation and channel coefficient interpolation, and thus the performance of the channel estimation is seriously affected by the accuracy of the interpolation. Since the accuracy of the interpolation depends on signal-to-noise ratio, we use symbols channel coefficients combining method. The method is to copy the estimated channel coefficients corresponding to the same subcarriers in other OFDM symbols. This method has the advantages of no OFDM symbol time delay and save six OFDM symbol memory and one interpolation when it is compared with two one-dimension interpolation schemes. The computer simulation results show that the proposed method improves the estimation performance when it is compared with the frequency-domain linear interpolation.

中文摘要 ...................................................................................................... i
英文摘要 ..................................................................................................... ii
誌謝 ............................................................................................................ iii
目錄 ............................................................................................................ iv
圖目錄 ........................................................................................................ vi
表目錄 ........................................................................................................ viii
第一章 正交分頻多工系統之簡介 ................................................................... 1
1-1 系統簡介 ........................................................................................................ 1
1-2 基於快速傅立葉轉換之正交分頻多工系統 ................................................ 4
1-3 護衛間隔的放置 ............................................................................................ 5
1-4 正交分頻多工系統之優缺點 ........................................................................ 7
第二章 正交分頻多工之應用－數位影像廣播之地面廣播(DVB-T) .................................................................................................... 9
2-1 系統簡介 ........................................................................................................ 9
2-2 傳輸訊號及碼框結構 .................................................................................. 13
2-3 參考訊號 ...................................................................................................... 15
2-3-1 連續領航訊號(Continual Pilots) ........................................................ 16
2-3-2 傳輸參數訊號(Transmission Parameter Signaling, TPS) .................. 17
2-3-3 散射領航訊號(Scattered Pilots) ......................................................... 19
第三章 通道模型與通道估測 .......................................................................... 20
3-1 通道模型-非時變通道(Time-invariant channel) ......................................... 20
3-2 通道模型-時變通道(Time-variant channel) ................................................ 24
3-3 通道估測 ...................................................................................................... 26
3-3-1 最小平方誤差法 (Least Square estimation ) ..................................... 27
3-3-2 線性內插(Linear Interpolation) .......................................................... 29
3-3-3 兩次一維內插(Two one-Dimension Interpolation) ............................ 30
3-3-3-1 時間域內插(Time-domain Interpolation) ................................ 31
3-3-3-2 頻率域線性內插(Frequency-domain Linear Interpolation) ... 32
3-3-4 符元通道係數結合(Symbols Channel Coefficients Combine) ....... 33
3-3-5 轉換域處理(Transform-domain processing)通道估測法 .................. 36
第四章 電腦模擬與結果分析 .......................................................................... 41
4-1 模擬系統模型 .............................................................................................. 42
4-2 非時變通道之位元錯誤率模擬與分析 ...................................................... 43
4-3 時變通道之錯誤率模擬與分析 .................................................................. 46
第五章 結論與未來研究方向 ............................................................................ 50
參考文獻 ................................................................................................................... 52

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