都卜勒擴散環境中利用基於奇異值分解預編碼技術之正交分頻多工系統流通量最大化研究

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研究生：	陳忠琨 Chen, Chung-Kun
論文名稱：	都卜勒擴散環境中利用基於奇異值分解預編碼技術之正交分頻多工系統流通量最大化研究 SVD-Based Precoding for Throughput Maximization in OFDM Systems over Doppler Spread Environments
指導教授：	蔡育仁 Tsai, Yuh-Ren
口試委員:	黃政吉 Huang, Jeng-Ji 梁耀仁 Liang, Yao-Jen
學位類別：	碩士 Master
系所名稱：	電機資訊學院 - 通訊工程研究所 Communications Engineering
論文出版年：	2022
畢業學年度：	110
語文別：	英文
論文頁數：	88
中文關鍵詞：	正交分頻多工、都卜勒擴展、載波間際干擾
外文關鍵詞：	OFDM, Doppler Spread, ICI
相關次數：	點閱：3 下載：0
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最近幾年，正交分頻多工這項技術被廣泛地使用在很多通訊應用和標準。當基地台與使用者之間有相對運動，都卜勒效應就會產生、並且子載波之間會互相干擾。為了觀察都卜勒偏移所造成的影響，將反離散傅立葉轉換程序到離散傅立葉轉換程序之間的過程視為一個頻域通道，並以此頻域通道來觀察都卜勒效應的影響。在本文中，我們希望使用預編碼器與組合器來避免掉傳送訊號時遇到子載波間干擾的問題。將頻域通道進行奇異值分解，就可以得到一組最佳的預編碼器與組合器。從預編碼器到組合器的過程可以視為一個等效通道，此等效通道是由數個互相平行的子通道所構成。資料符號會被分配到這些子通道上而非子載波上。此外，在利用奇異值分解的正交分頻多工系統方法中，藉由利用注水填充演算法來分配傳送功率並接著執行位元數分配程序，此系統可以達到輸出位元最大化的目的。模擬結果顯示，不管是位元錯誤率還是位元傳輸速率，奇異值分解的正交分頻多工系統比起傳統的方法皆具有優勢，特別是在較大都卜勒效應的環境。此外，在通道估測結果不完美的情況，奇異值分解的正交分頻多工系統也能有較好的效能。

In recent years, orthogonal frequency-division multiplexing (OFDM) is adopted widely in many communication applications and standards. The relative motion between the base station and user will occur Doppler effect and cause inter-carrier interference. To observe the effect of the Doppler shift, the frequency-domain channel from IDFT to DFT will be considered. In our work, the precoder and combiner will be added to the OFDM system to avoid inter-carrier interference. Decomposing the frequency-domain channel by Singular Value Decomposition (SVD), the optimal precoder and combiner can be obtained. The process from precoder to combiner can be considered an equivalent channel which is comprised of parallel subchannels. Data symbols will be loaded on parallel subchannels rather than subcarriers. Moreover, the SVD OFDM system adopts the water-filling power allocation and bit-loading process to achieve the goal of throughput maximization. Simulation results show that the SVD OFDM system has the advantage of BER and throughput performance, especially in a large Doppler effect environment. In addition, it also has better performance when channel estimation is imperfect.

Abstract    I
中文摘要    II
致謝    III
Contents    IV
List of Figures    V
List of Tables    VII
Chapter 1    Introduction    1
1.1    General Background Information    1
1.2    Related Works    2
Chapter 2    System Model    4
2.1    OFDM System Model    4
2.2    Channel Model    6
Chapter 3    Conventional ICI Cancellation Methods    9
3.1    LS Conventional OFDM Method    9
3.2    MMSE Conventional OFDM Method    11
3.3    Parallel Interference Cancellation (PIC)    13
3.4    Serial Interference Cancellation (SIC)    16
Chapter 4    SVD-Based Precoding Method for OFDM Systems    19
4.1    Introduction of SVD-Based Precoding Method for OFDM Systems    19
4.2    Power Allocation and Bit Loading    23
4.2.1    Optimal Power Allocation for Throughput Maximization    26
4.3    Precoder and Combiner    30
4.4    The Comparison of PAPR    33
4.5    Power Gain Distribution    35
4.6    Computational Complexity    37
Chapter 5    Channel Estimation Error Model    39
5.1    First Type of Channel Error Model    39
5.2    Second Type of Channel Error Model    44
Chapter 6    Simulation Results    46
6.1    The Comparison of Channel Capacity    47
6.2    Performance Comparison in Perfect Channel Information Case    49
6.2.1    Different Maximum Doppler Shift Comparison of SVD System    49
6.2.2    The Comparison of SVD Systems and Conventional OFDM Methods    51
6.3    First Type Channel Estimation Error Model Performance    58
6.3.1    Different Error Cases Comparison of SVD OFDM System    58
6.3.2    The Comparison of SVD Systems and Conventional OFDM Methods    63
6.4    Second Type Channel Estimation Error Model Performance    74
6.4.1    Different Error Cases Comparison of SVD System    74
6.4.2    The Comparison of SVD Systems and Conventional OFDM Methods    76
Chapter 7    Conclusion    84
References    85

                                

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