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論文名稱 Title |
在無循環字首的正交分頻多工系統中使用疊加序列技術之通道估測研究 Channel Estimation for the Superimposed Training Scheme in OFDM Systems without Cyclic Prefix |
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系所名稱 Department |
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畢業學年期 Year, semester |
語文別 Language |
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學位類別 Degree |
頁數 Number of pages |
47 |
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研究生 Author |
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指導教授 Advisor |
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召集委員 Convenor |
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口試委員 Advisory Committee |
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口試日期 Date of Exam |
2008-07-26 |
繳交日期 Date of Submission |
2008-08-11 |
關鍵字 Keywords |
資料估測最大似然法、通道估測、正交載波分頻多工、干擾消除、疊加序列 channel estimation, superimposed training, OFDM, ML data detection, interference cancellation |
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統計 Statistics |
本論文已被瀏覽 5738 次,被下載 4 次 The thesis/dissertation has been browsed 5738 times, has been downloaded 4 times. |
中文摘要 |
在無線通訊中,頻寬使用效率一直是非常重要的議題,為了能將頻寬使用效率發揮到極致,這裡採用無循環字首之疊加序列正交載波分頻多工系統(Orthogonal Frequency Division Multiplexing-Superimposed Training, OFDM-ST),我們亦證明了其與有加循環字首之疊加序列正交載波分頻多工系統(Cyclic-Prefix Orthogonal Frequency Division Multiplexing-Superimposed Training, CP-OFDM-ST)擁有相同效能的通道估測結果。 然而節省掉循環字首所造成的載波間干擾(Inter-Carrier Interference, ICI)與符元間干擾(Inter-Symbol Interference, ISI),將會大幅影響整個系統的效能,為了提升整個系統的表現,因此我們提出了一個疊代的最大似然演算法,結合干擾消除、通道估測與資料估測。最後由模擬結果也可以發現,我們所提出的架構有效增進系統效能的表現,且完全沒有多餘的訊號(Redundancy),其有效傳輸速率遠大於傳統有加循環字首之疊加序列正交載波分頻多工系統。 |
Abstract |
Bandwidth efficiency is a critical concern in wireless communications. To fully utilize the available bandwidth, the superimposed training (ST) scheme is adopted in this thesis for orthogonal frequency division multiplexing (OFDM) systems without using the cyclic prefix (CP) and the guard interval (GI). It is shown that the performance of the channel estimation using the ST scheme is the same for both the proposed architecture, denoted as OFDM-ST, and the conventional OFDM system with CP, denoted as CP-OFDM-ST. In addition, since the CP is not added in the proposed system, leading to substantial increase in both the inter-symbol interference (ISI) and the inter-carrier interference (ICI), an interference cancellation scheme is derived. To further improve the performance of channel estimation using ST scheme, the joint ML data detection and channel estimation method is investigated. The simulation results illustrate that the proposed algorithm enhances the systems performance significantly. Finally, it is demonstrated that the proposed structure has a much better effective data rate than the CP-OFDM-ST system. |
目次 Table of Contents |
Chapter 1 Introduction........................................................1 Chapter 2 System Model....................................................4 2.1 OFDM System Model....................................................4 2.2 Proposed OFDM-ST System Model...........................8 Chapter 3 Channel Estimation.......................................13 3.1 Analysis of Interference.............................................13 3.2 Mean Square Error of Channel Estimation............15 Chapter 4 Iterative Maximum Likelihood Data Detection and Channel Estimation................................16 4.1 Previous Scheme Combine Interference Cancellation.......................................................................16 4.2 Proposed Iterative Maximum Likelihood Data Detection and Channel Estimation Combine Interference Cancellation.................................................18 Chapter 5 Simulation Results........................................23 Chapter 6 Conclusions and Future Works...................32 6.1 Conclusions................................................................32 6.2 Future Works...............................................................33 Abbreviation........................................................................34 Reference...........................................................................36 |
參考文獻 References |
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