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研究生:羅勳章
研究生(外文):Shun-Chang Lo
論文名稱:室內環境下極化分集多輸入多輸出系統之通道模型與量測分析
論文名稱(外文):Polarization Diversity MIMO Channel Modeling and Measurements Analysis for Indoor Environments
指導教授:李學智李學智引用關係
指導教授(外文):Hsueh-Jyh Li
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:2007
畢業學年度:95
語文別:英文
論文頁數:83
中文關鍵詞:多輸入多輸出正交分頻多工通道量測相關函數多輸入多輸出通道容量
外文關鍵詞:Multiple-Input Multiple-Output (MIMO)Orthogonal Frequency Division Multiplexing (OFDM)channel measurementcorrelation functionMIMO capacity
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在本論文中,我們使用四種極化分集技術並探討在多輸入多輸出系統之通道特性和傳輸效能。目前一般多輸入多輸出系統的天線設置方法,是在傳送與接收兩端皆採用垂直極化。然而,正交極化具有好的隔離效果,在室內的環境下,傳送與接收兩端天線都採用對稱的正交極化方式,通道容量會比傳統上的極化方式來得高。
依據量測的資料,我們分析與討論影響通道容量的參數,包括特徵值與相關係數等,另外還提出一種新的方法來分析通道容量,此法針對不同的極化型態並考慮天線的接收功率和極化的影響。數值分析結果證明,這個通道容量分析方法會非常貼近實際室內環境的通道容量。
在無線通訊系統中,結合正交分頻多工與多輸入多輸出的系統在頻率選擇衰落(frequency-selective fading)通道的環境下能提升資料傳輸速率。VBLAST是一種藉由使用多根天線傳送來得到高速傳輸速率的空間多工架構。我們使用下一世代無線網路的規格(IEEE 802.11n)的通道模型作為模擬的通道。當傳輸天線的數量增加,不同天線間互相干擾的情況會變嚴重;此外,在相關性通道內,干擾消除的動作沒辦法表現良好。因此,增加天線數量可以提升系統效能,但在相關性通道下卻不盡然。
In this thesis we have discussed four polarization diversity antenna configurations of MIMO schemes in their channel characteristics or transmission performance. For a general MIMO system, we usually use vertically co-polarized antenna arrays at both transmitter and receive ends. However, we know that using cross-polarized antenna scheme symmetrically in both ends; the capacity is higher than conventional antenna polarization scheme under the indoor environment due to the high isolation between orthogonal polarizations.
According to measurement data, we analyze and discuss some factors that can affect the channel capacity, like eigenvalues and correlation coefficients etc. Besides, we also propose a novel analysis method of channel capacity including the normalization received power and polarization effect for different polarization schemes. Simulation results show that our proposed analysis method is close to the realistic measurement of the indoor environment.
The combination of MIMO signal processing with OFDM is regarded as a promising solution for enhancing the data rates of wireless communication systems operating in frequency-selective fading environments. VBLAST is a spatial multiplexing scheme and can provide huge data rate by using multiple antennas. Channel model adopted by next-generation WLAN standard (IEEE 802.11n) is used in our simulation. In the correlated channel, the interference cancellation cannot work well when more antennas are used. Consequently, using more antennas cannot guarantee the higher performance in the correlated channel.
Contents

Abstract I
Contents III
List of Figures VII
List of Tables XI

Chapter1 Introduction 1
1.1 Motivation 1
1.2 Organization of the Thesis 3

Chapter2 Indoor Channel Properties and Channel Modeling 5
2.1 Introduction 5
2.2 Doppler Effect for Indoor Channel Model 7
2.3 Parameters of Multipath Channels 9
2.3.1 Coherent Bandwidth and Coherent Time 10
2.4 Diversity Techniques 12
2.4.1 Space Diversity 13
2.4.2 Polarization Diversity 15

Chapter3 Correlation Properties and Capacity for MIMO Radio Channel 17
3.1 Introduction 17
3.2 Spatial Correlation Property of MIMO system 18
3.3 Effect of Different Polarization Combinations on MIMO system 20
3.4 Basic Concept of MIMO System 22
3.4.1 Channel Model 22
3.4.2 Subchannel Correlations 23
3.4.3 Channel Capacity 25
3.4.3.1 SISO System Capacity 25
3.4.3.2 SIMO and MISO System Capacity 25
3.4.3.3 MIMO System Capacity with Equal Power 27
3.5 Experiment Description 28
3.5.1 Measurement Setup 29
3.5.2 Measurement Environment 30
3.5.3 Antenna Configuration 32
3.6 Measured Data Analysis and Results 33
3.6.1 Experiment for Different Polarization 33
3.6.2 Eigenvalue, Subchannel Correlation and Capacity Analysis 34
3.6.3 Proposed Channel Capacity Analysis 40

Chapter4 Comparison of Polarization Diversity MIMO Schemes under OFDM Modulation 47
4.1 Introduction 47
4.2 MIMO-OFDM 48
4.2.1 Introduction 48
4.2.2 Concept and Technique of OFDM 49
4.2.3 Concept and Technique of MIMO 52
4.2.4 MIMO-OFDM System Description and Signal Model 54
4.3 V-BLAST system 59
4.3.1 Introduction 59
4.3.2 System Model 60
4.3.3 ZF-VBLAST Detection Algorithm 61
4.3.4 MMSE-VBLAST Detection Algorithm 63
4.4 Simulator of Narrowband and Wideband Fading Channel 64
4.5 Simulation Results and Analysis 66
4.5.1 Simulation Setup 67
4.5.2 Simulation with Model A 69
4.5.3 Simulation with Model B 70

Chapter 5 Conclusion 75

Reference 79

Publication of the author 85
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