此論文探討多種應用於適應性陣列波束構成和分碼多重接取多使用者偵測之技術。近年來，利用特徵空間技術來處理陣列訊號的相關問題變得非常重要，因為它不僅能提供較好的解析能力，使陣列能保護所欲訊號和可對數個相近的干擾源作抑制，也為陣列提供較快的收斂速度。首先，本論文的目的主要是對於適應性陣列波束構成器在不完美和實際操作環境下提出具有強健性且有效的處理方式以增加廣義式基於特徵空間技術的性能。另外，在建構擁有快速收斂能力的基於特徵空間的干擾消除器時，必須先估計干擾訊號所形成的干擾子空間，並令權重向量垂直於此空間。然而，基於特徵空間的干擾消除器有一個極嚴重的缺點，就是在干擾源數目過度估測的情形下，對於導引角度誤差極為敏感；為了解決這個問題，我們亦提出一校正導引角度的方法，來降低此種干擾消除器只要一點點導引角度誤差，所欲接收訊號就會被視為干擾而完全消去，不論其輸入訊號雜訊比的高低。
對於同步分碼多重接取系統，我們分析直接型式和廣義式旁波消除器架構的基於特徵空間多使用者偵測器在所欲使用者展頻碼吻合和不吻合時的性能；其中，廣義式旁波消除器的架構可處理當所欲使用者的訊號功率低於雜訊功率的情況。另外，在盲目多使用者偵測限制條件下，提出一基於子空間的技巧以解決展頻碼不吻合造成廣義式旁波消除器性能衰竭的缺點。
適應性H∞濾波演算法已經被證實較遞迴最小平方演算法對於模態誤差和任意雜訊環境具有較不敏感的優點。無論如何， 演算法的缺點是有非常大的計算量，我們利用子權重切割技巧所形成的基於 演算法確實可降低傳統適應性 演算法的計算複雜度，且幾乎可維持系統原來的性能；最後並將此基於 演算法應用至陣列波束構成器和盲目多使用者偵測器上。
論文的最後，在非同步分碼多重接取系統我們提出新的分集技術以對抗多重路徑衰減效應。此技術係在多重限制最小變異演算法架構下配合適當的限制矩陣和響應向量之選取，可以達成增加分集能力和抑制多重接取干擾。另外，基於降低由多重限制最小變異演算法則所產生雜訊放大問題，我們亦建議結合訊號子空間來映射多重限制最小變異偵測器的權重之處理方式，達成降低多重限制最小變異偵測器權重的雜訊放大問題。

Several issues on the problems of the adaptive array beamforming and code-division multiple access (CDMA) multiuser detection are investigated in this dissertation. Recently, based on the decomposition of observation vector space into two orthogonal eigenspace, the eigenspace-based (ESB) and the generalized eigenspace-based (GEIB) array signal processing techniques have been widely discussed due to their superior performance over conventional techniques. At first, the purpose of this dissertation is mainly to present robust and efficient algorithms for further enhancing the performance of ESB and GEIB techniques under imperfect and practical operation environments. We also propose a method of corrected steering angles to combat the supersensitivity of eigenanalysis interference canceler (EIC) to source number overestimation and steering angle errors.
We analyze the performance of several ESB multiuser detectors, including conventional direct-form detector and generalized sidelobe canceler (GSC) for synchronous CDMA system with and without desired user code mismatch. We also present a way of resolving spreading code mismatch in blind multiuser detection with subspace-based technique. Furthermore, the structure of GSC can be utilized to deal with the case of the desired user's SNR < 0 dB.
Next, algorithm for adaptive H∞ filter has demonstrated the advantage of reduction of sensitivity to modeling error (due to finite tap number) and suitability for arbitrary ambient noise over recursive least squares (RLS) algorithm. However, the computational burden of the H∞ algorithm is enormous. In order to reduce the computational complexity, subweight partition scheme is employed to an H∞-based algorithm. The computation burden of the conventional adaptive H∞ algorithm can be mitigated with slight performance degradation. The H∞-based algorithm is then further extended to the adaptive beamformer and blind multiuser detector.
Finally, we present new diversity techniques for multiuser detection under multipath fading channels in asynchronous CDMA systems. The enhanced capacity of diversity for multipath channels can be achieved by appropriately utilizing the constraint matrix and the response vector in multiple constraint minimum variance (MCMV) algorithm. Moreover, the proposed techniques offer gratifying multiple access interference (MAI) suppression. We also incorporate the signal subspace-based projection into MCMV detector, so that the noise enhancement in the MCMV criterion can be reduced.

Contents
Acknowledgments d
中文摘要 i
Abstract iii
Contents I
List of Tables IV
List of Figures V
Chapter 1. Introduction 1
1.1 Motivation and Historical Perspective 1
1.2 Organization of this Dissertation 6
Chapter 2. A Robust Generalized Eigenspace-Based Beamformer 9
2.1 Introduction 9
2.2 GEIB Algorithm and Problem Description 10
2.2.1 Array data model 10
2.2.2 The generalized eigenspace-based beamformer 11
2.2.3 Problem description 12
2.3 The Proposed Robust Technique 13
2.4 Computer Simulation 16
2.5 Conclusion 19
Chapter 3. An Eigenanalysis Interference Canceler with Robust Capabilities 26
3.1 Introduction 26
3.2 Array Data Model and the Eigenanalysis Interference Canceler 27
3.2.1 Array data model 27
3.2.2 The eigenanalysis interference canceler 28
3.3 The Proposed Robust Technique 29
3.4 Simulation Results 31
3.5 Conclusion 32
Chapter 4. Eigenspace-Based Multiuser Detection
for Synchronous CDMA Systems 40
4.1 Introduction 40
4.2 Signal Model 42
4.3 The Eigenspace-Based Multiuser Detector 43
4.3.1 The eigenspace-based multiuser detector 43
4.3.2 Comparsion with the decorrelating detector 45
4.3.3 Performance analysis 46
4.3.4 Simulation results 47
4.4 The Eigenspace-Based Approach for the Blind Multiuser Detection 49
4.4.1 The multiuser detector based on the GSC structure 49
4.4.2 The eigenspace-based estimated scheme 50
4.4.3 Performance analysis 51
4.4.4 Simulation results 52
4.5 Conclusion 53
Chapter 5. Low Computational Complexity H∞ Filtering Algorithms 66
5.1 Introduction 66
5.2 GSC-Based Subweight Partition 68
5.2.1 The structure of generalized sidelobe canceler 68
5.2.2 Subweight partition scheme 69
5.3 Adaptive H∞ Algorithms 70
5.3.1 The conventional adaptive algorithm 72
5.3.2 The adaptive H∞-based algorithm 72
5.3.3 Computational complexity analysis 73
5.4 Applications 74
5.4.1 Adaptive H∞ array beamforming 74
5.4.2 Blind adaptive H∞ multiuser detection 76
Chapter 6. Blind Adaptive Multiuser Detection for Asynchronous CDMA System
in the Presence of Multipath Fading 89
6.1 Introduction 89
6.2 Signal Model 91
6.3 The Proposed Techniques 93
6.3.1 The multiple constrained minimum variance detector 93
6.3.2 The generalized eigenspace-based detector 94
6.4 Performance Analysis 96
6.4.1 Multiple-access interference suppressing analysis 96
6.4.2 Computational complexity analysis 97
6.5 Simulation Results 98
6.6 Conclusion 100
Chapter 7. Conclusions 108
Bibliography 110
Abbreviations 116

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