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研究生:吳柏賢
研究生(外文):Po-Hsien Wu
論文名稱:在正交頻分多工系統中頻域分數間距等化器的效能分析
論文名稱(外文):Performance Analysis on Frequency Domain Fractionally Spaced Equalizer in OFDM systems
指導教授:許大山
指導教授(外文):Da-Shan Shiu
學位類別:碩士
校院名稱:國立臺灣大學
系所名稱:電信工程學研究所
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:2008
畢業學年度:97
語文別:英文
論文頁數:37
中文關鍵詞:正交頻分多工都卜勒等化器多倍取樣分數間距
外文關鍵詞:OFDMdopplerequalizeroversamplefractionally spaced
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在正交頻分多工系統(OFDM)中,系統的效能對於都卜勒效應或傳送端和接收端的頻率不同所造成的頻率誤差非常敏感。
在此篇論文中,我們提出了一個新的壓抑載波間干擾的技術,為Q-tap的分數間距最小平均平方誤差等化器(Q-tap FSMMSE Equalizer)。在跟傳統的最小平均平方誤差等化器(MMSE Equalizer)的比較下,我們提出方法之計算的複雜度可大幅度的降低而不會犠牲太多的效能。”分數間距”指的是等化器tap之間距為子載波間距的分數倍。此方法之效能對於傳送端與接收端之間中心頻率不同步不敏感。模擬也展示出,在陸地數位電視廣播(DVB-T)的接收端擁有高移動速度的情境下,對相同的Q之下,Q-tap二分之一倍的分數間距最小平均平方誤差等化器比Q-tap最小平均平方誤差等化器有更好的效能。
Orthogonal frequency division multiplexing (OFDM) digital communication system is very sensitive to frequency errors caused by doppler effect or frequency differences between transmitter and receiver local oscillators.
In this thesis, we propose a new intercarrier interference (ICI) suppression scheme, Q-tap fractionally spaced MMSE (FSMMSE) equalizer. "Fractionally spaced" means the spacing of equalizer tap is a fraction of subcarrier spacing. The performance of this method is not sensitive to the unsynchronized center frequency. Simulation also show that Q-tap "1/2" FSMMSE equalizer has better performance than Q-taps MMSE equalizer with the same Q under the scenario of DVB-T receiver with very high mobile speed.
Contents 1
List of Figures 3
1 Introduction 1
1.1 Motivation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
1.2 Contribution and Organization . . . . . . . . . . . . . . . . . 2
2 Background 4
2.1 Equalizer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
2.1.1 Fractionally Spaced Equalizer . . . . . . . . . . . . . . 4
2.2 Channel Model . . . . . . . . . . . . . . . . . . . . . . . . . . 8
2.2.1 The Channel Model as A Linear Time-Varying System 8
2.2.2 Channel Autocorrelation Function and Power Spectra . 9
2.2.3 Statistical Channel Models . . . . . . . . . . . . . . . . 12
2.2.4 Propagation Scenario in This Thesis . . . . . . . . . . 13
3 The Performance Analysis on Fractionally spaced Equalizer
over time variant channel in OFDM Systems 16
3.1 OFDM Signal Model . . . . . . . . . . . . . . . . . . . . . . . 17
3.1.1 Frequency Domain Representation of The OFDM Signal 20
3.2 Low Complexity ICI Cancelation . . . . . . . . . . . . . . . . 24
3.2.1 Q-tap Equalizer . . . . . . . . . . . . . . . . . . . . . . 24
3.2.2 OFDM Fractionally Spaced Q-tap Equalizer . . . . . . 26
3.2.3 The Performance Analysis under Same Equalizer Com-
plexity . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
4 Simulation 31
4.1 An Example Study for DVB-T Receiver . . . . . . . . . . . . 31
5 Conclusions 34
Bibliography 35
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[16] Hsiao-Chun Wu, "Analysis and characterization of intercarrier and interblock interferences for wireless mobile OFDM systems," IEEE Trans. Broadcasting, vol. 52, Issue 2, June 2006, pp. 203-210.
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