臺灣博碩士論文加值系統

多輸入多輸出系統是利用傳送端與接收端使用多根天線來改善系統效能，不僅可以對抗衰落之影響也可以提升傳輸率，而正交分頻多工將訊號切割成數個子載波來傳送資料，使得頻率選擇性衰落通道可簡化成平坦衰落通道，智慧型天線早期是應用在軍事科技上，將它運用在商業通訊系統中，不僅可以增加系統容量，也能消除同調頻率干擾，由於這三種技術擁有許多不同的優點，因此結合三種技術為主要架構將會成為未來無線通訊系統趨勢。
本論文提出高速移動下應用波束合成機制之多輸入多輸出正交分頻多工系統，是將智慧型天線群組架設在高鐵或火車上，並且利用車速來切換估測訊號到達演算法，當車速低時，都卜勒對智慧型天線影響較小，選擇複雜度較低的快速傅立葉估測演算法，反之，則事先儲存的不同車速下所有角度之都卜勒偏移量，透過車速從記憶體中選擇當時車速的所有角度之都卜勒偏移量，利用對應的方式估測出訊號到達方向與都卜勒偏移量，並給予補償，而其主要架構是基站與智慧型天線群組進行垂直分層時空碼正交分頻多工技術，並且利用每車廂內的無線分享器與使用者溝通增加傳輸速率。本論文所提出機制，經由模擬可得知，若車速為30km/h時，與傳統垂直分層時空碼正交分頻多工系統相比，可以改善約5dB系統效能，若車速增加為60km/h時，仍然可以改善其系統效能，而隨著車速增加到300km/h時，不僅解決了因高速移動下波束合成偏移問題，同時也降低都卜勒造成載波之間干擾，改善系統效能越明顯，這對於現今無線通訊技術是非常有益的。

The Multiple Input Multiple Output (MIMO) System improves its performance with the multiple antennas at the transmitter and receiver. It not only combats the impact of fading, but also enhances the data transmission rate. Orthogonal Frequency Division Multiplexing (OFDM) divides signals into multiple sub-carriers to transmit the data. The selective frequency fading channel will as a result be transformed into the simpler flat fading channel. Smart antenna had been previously used by the military. Now, with its application in commercial communication systems, it will increase the system capacity as well as eliminate the co-channel interference. Consider the three systems have their distinctive advantages, integrating them will become the trend and the common practice in future wireless communication systems.
This thesis proposes the applying of beamforming scheme for MIMO-OFDM systems in high speed mobility by setting smart antenna sets on high-speed railway or railway carriages. The Direction of Arrival Algorithms are switched according to the speeds. When the train travels at low speed, the Doppler exerts less influence to smart antennas, making it possible to switch to the Fast Fourier Transform Algorithm. If, however, the train moves at high speed, the different angles of Doppler shifts occurring at different speeds will then be measured and saved. Afterwards, the data of Doppler shift in all angles at the then-moving speed will be extracted and thus, through mapping, the direction of arrival and Doppler shift can be retrieved, which will then be compensated. The scheme proposed here facilitates the communication between the base station and the smart antenna set with VBLAST-OFDM and therefore enhances the data rate. A wireless access point is set in each carriage so that users can access the communication network more efficiently. It has been found through simulation that, compared with the conventional VBLAST-OFDM, the scheme proposed here can improve the performance by approximately 5dB at the speed of 30 km/hr and still works appropriately when the carriage speeds up to 60 km/hr. When accelerated to 300km/hr, it can further eliminate the beam-forming shift caused by high-speed mobility and moderate the inter-subcarrier interference brought about by the Doppler. Such scheme will be beneficial to modern wireless communication technology.

中文摘要 i
英文摘要 ii
誌謝 iv
目錄 v
表目錄 vi
圖目錄 vii
第一章 緒論 1
1.1 前言 1
1.2 多輸入多輸出正交分頻多工系統 1
1.3 智慧型天線結合多輸入多輸出正交分頻多工系統 2
1.4 動機與目的 2
1.5 論文概述 3
第二章 多輸入多輸出正交分頻多工系統 4
2.1 正交分頻多工系統 4
2.1.1 簡介 4
2.1.2 基本原理 4
2.1.3 系統架構 5
2.1.4 特性與優點 7
2.2 多輸入多輸出系統 8
2.2.1 簡介 8
2.2.2 分集増益架構 9
2.2.2.1 時空塊狀碼2x1 9
2.2.2.2 時空塊狀碼2x2 11
2.2.3 垂直分層時空碼架構 13
2.2.4 等化器方法 15
2.2.4.1 強迫為零估測法 15
2.2.4.2 最小均方誤差估測法 16
2.2.5 干擾消除方式 17
2.2.5.1 線性偵測法 17
2.2.5.2 依序式干擾消除法 17
2.2.5.3 階層式依序干擾消除法 18
2.2.6 模擬結果 19
第三章 智慧型天線結合多輸入多輸出正交分頻多工系統 25
3.1 智慧型天線 25
3.1.1 智慧型天線簡介與基本概念 25
3.1.2 智慧型天線優點 25
3.1.3 智慧型天線架構 27
3.1.4 空間特徵 29
3.1.5 估測訊號到達演算法 30
3.1.5.1 多重訊號分類演算法 31
3.1.5.2 訊號旋轉變異數參數估測 33
3.1.5.3 快速傅立業估測訊號到達演算法 34
3.1.5.4 空間平滑技術 36
3.2 波束合成演算法 38
3.2.1 主要方向到達法 38
3.3 波束合成結合垂直分層時空碼之架構 39
3.3.1波束合成結合垂直分層時空碼之架構模擬與分析 42
3.4 波束合成之多輸入多輸出正交分頻多工應用SUI通道模型模擬與分析 43
3.4.1 SUI通道模型簡介 43
3.4.2 路徑損耗 43
3.4.3 多重路徑延遲輪廓 46
3.4.4 均方根延遲擴展 47
3.4.5 角度擴展 48
3.4.6 都卜勒偏移 48
3.4.7 波束合成之垂直分層時空碼正交分頻多工應用於SUI通道模型模擬與分析 51
第四章 高速移動下應用波束合成機制之多輸入多輸出正交分頻多工系統 57
4.1 簡介 57
4.2 高速移動下應用波束合成機制之多輸入多輸出正交分頻多工系統 58
4.3 模擬與結果 61
第五章 結論 70
參考文獻 72

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