臺灣博碩士論文加值系統

無線感測網路系統為近年來十分熱門的無線通訊技術，該系統是由偵測對象、感測器裝置以及處理中心三部分所組成。本篇論文中，實際考慮受雜訊干擾之目標信號偵測，而為了節省傳輸頻寬及減少訊息傳輸時之能量消耗，每個感測器將其觀測資料量化為單一位元後，再傳送至處理中心。在過去相關文獻中，其假定的局部感測環境為各個區域的感測器所受到環境雜訊干擾之功率皆相同，但實際情況中，即便各個感測節點分佈的位置再接近，環境的雜訊功率仍然有所差異，因此，我們針對此點，進一步地考慮各個感測器所接收之環境雜訊功率皆相異。本篇論文中，感測器與處理中心間之傳輸通道為非理想通道，由於無線通訊的特性，更明確地設定通道為瑞利衰落通道。處理中心彙整感測器所傳送之觀測資料後，根據這些資訊，採用分散式最大似然估計法作為處理訊號之準則，判斷感測器所偵測之目標信號為何。而為了能使估計結果更加精準，我們藉由設計量化閾值來嘗試最小化估計誤差。在本篇論文中，模擬結果證實此組量化閾值確實使估計結果更為準確。

In this thesis, we study the problem of distributed estimation of an unknown deterministic parameter via wireless sensor networks (WSNs) in a noisy environment. While most recent works focused on a homogeneous sensing field, we consider the general inhomogeneous case. To conserve the bandwidth resource, each sensor observation is quantized into a one-bit message, which is then transmitted to the fusion center (FC). In our study, the communication links between sensors and the FC are imperfect and modeled as i.i.d. Rayleigh fading channels. Based on one-bit quantized observations transmitted from local sensors, the maximum-likelihood (ML) fusion rule is adopted at the FC for parameter estimation. The Cramér–Rao Lower Bound (CRLB) is derived in a closed-form. We then study the optimal local quantization threshold design via CRLB minimization. Computer simulations are used to illustrate the performance of the proposed scheme.

摘要 i
Abstract ii
誌謝 iii
目錄 iv
表目錄 v
圖目錄 vii
中英對照表　 viii
第一章 緒論 1
1.1 研究背景 ............................................... 1
1.2 相關文獻探討 ..................................…… 1
1.3 論文架構 ............................................... 2
第二章 無線感測網路之系統模型 ………. 3
2.1 系統簡介 ................................................ 3
2.2 系統模型 ................................................ 3
2.2.1 觀測資料之量化與傳輸 ........................ 3
2.2.2 解碼錯誤率 ............................................ 4
第三章 未知參數之估計法則 6
3.1 分散式最大似然估計法 ........................ 6
3.1.1 牛頓法分析 .................................. 6
3.2 Cramér–Rao Lower Bound (CRLB) ........... 7
3.3 同質感測環境下之估計分析 ................ 8
3.3.1 環境設定.............................. 8
3.3.2 估計法比較 ............................ 9
3.4 BPSK 調變訊號之估計分析 ........ 9
3.4.1 系統模型設定 ..................... 9
3.5 模擬結果 ......................................... 11
第四章 感測器之量化閾值設計 18
4.1 設計準則 ................................................ 18
4.2 最佳化模型 ............................................ 18
4.3 模擬結果 ................................................ 19
第五章 結論 27
參考文獻 28
附錄ㄧ (2.5)式證明 ................................... 30
附錄二 (3.19)式證明 ................................. 32
附錄三 定理3.2證明 ................................ 34
附錄四 推論3.3證明 ................................ 37
附錄五 定理3.4證明 ................................ 38


Mandrain Abstract i
English Abstract ii
Acknowledgement iii
Contents iv
List of Figures v
1 Introduction 1
1.1 Overview………………………………………………………………………………...1
1.2 Contribution……………………………………………………………………………...2
1.3 Organization……………………………………………………………………………..3
2 System Model and Overview of Previous Work 5
3 Beamforming Design in the Presence of Imperfect Quantized S-R Link SNR 9
3.1 Conditional Average SNR……………………………………………………………….9
3.2 Closed-Form Suboptimal Solution……………………………………………………..12
3.3 Simulation Results ………………………………………………………………….13
4 Beamforming Design Under Imperfect Quantized S-R Link SNR and R-D Link Channel
Estimation Errors 17
4.1 Exact Formula for the Conditional Average SNR……………………………………...18
4.2 Approximation for the Conditional Average SNR……………………………………..21
4.3 Design of Beamforming Weights………………………………………………………23
4.4 Simulation Results……………………………………………………………………...24
Conclusion 30
Appendix 31
References 51
Publication List 54

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