臺灣博碩士論文加值系統

在合作式頻譜感知認知無線電網路中，應用合作式通訊系統的架構可以產生空間分集(Spatial diversity)的增益特性，其特性改善系統在衰減通道中傳送之錯誤率效能，然而為了達到此架構較好的系統效能，傳統合作式頻譜感知架構通常會使用全部的認知無線電(Cognitive Radio)幫忙感知(Sensing)，但是這樣傳統傳輸架構會增加計算複雜度及在同一個觀測時間間隔(Observation Interval)可能會導致控制信道的開銷增加。於是在本研究中我們提出一種新的檢測方式在合作頻譜感知認知無線電網路上，以此來減少認知無線電使用次數和增加檢測的準確度，其方式是在認知無線電將本地檢測(Local Decision)結果傳送至融合中心(Fusion Center)前多乘上一個權重(Weight)，及在融合中心設置一組失誤機率(Miss Probability)的門檻值(Threshold)檢測認知無線電的失誤機率判斷是否需要加入其他的認知無線電幫忙感知訊號。最後，我們將採用模擬，來驗證我們所提出的方法較傳統方法節省認知無線電的個數。

In cognitive radio with cooperative spectrum sensing, the application of cooperation can bring spatial diversity gain, which can improve the detection error – rate performance in fading channel environments. In this aspect, conventional cooperative spectrum sensing usually employs all cognitive radio (CR) elements to help sensing the environment. However, this comes with high computational complexity and large processing delay. In this research, we propose a new detection way based on the cooperative spectrum sensing. Specifically, our method can reduce the number of CR processing while achieving a certain error – rate performance. In addition, the local decision results will multiply weighting factors before they are sent to the fusion center. In the fusion center, a threshold is set based on the miss probability to help to determine whether more CR elements are needed for farther enhancing the final decision. Finally, we will employ simulations will with various setting to verify our proposed method for the saving in CR forwarding.

目錄
誌謝 I
中文摘要 II
ABSTRACT III
第一章 緒論 1
第二章 頻譜感知技術 3
2.1頻譜感測介紹 3
2.2 本地頻譜感知技術(LOCAL SENSING TECHNIQUES) 5
2.2.1 匹配濾波器(Matched Filter) 5
2.2.2 循環檢測(Cyclostationary Detection) 6
2.2.3 能量檢測(Energy Detector) 7
2.3 合作式頻譜感知 15
2.3.1組合規則(Combining Rule) 17
第三章 基於權重法排序瞬時訊雜比介紹 22
3.1系統模型 22
3.2排序瞬時的訊雜比方法 23
3.3權重式合作式頻譜感知WCSS(A WEIGHTED COOPERATIVE SPECTRUM SENSING) 29
3.4結合排序瞬時訊雜比方法和權重方法 34
第四章 結論與未來方向 41
參考文獻 42

圖目錄
圖1.1 認知無線電對頻譜的使用示意圖 1
圖2.1 檢測機率示意圖 4
圖2.2 循環檢測示意圖 6
圖2.3 能量檢測示意圖 8
圖2.4 單門檻值示意圖 10
圖2.5 在AWGN通道下，模擬結果跟理論值的曲線圖 12
圖2.6 在RAYLEIGH FADING通道下，模擬結果跟理論值的曲線圖 14
圖2.7 不同通道下，理論值的曲線圖 15
圖2.8 合作式頻譜感知有遮蔽效應的示意圖 16
圖2.9 或規則、和規則、多數決投票規則在瑞利通道下的效能比較 19
圖2.10 或規則、和規則、多數決投票規則在瑞利通道下的效能比較 19
圖2.11 或規則、和規則、多數決投票規則在瑞利通道下的效能比較 20
圖3.1 合作式頻譜感知示意圖 22
圖3.2 排序瞬時的訊雜比方法流程圖 27
圖3.3 傳統合作式頻譜感知系統使用多數決的方法，有排序跟無排序平均用的次級用戶個數比較 28
圖3.4 合作式頻譜感知增加權重示意圖 29
圖3.5權重式合作式頻譜感知(WCSS)流程圖 32
圖3.6 增加權重跟多數決投票規則在瑞利通道下的效能比較 33
圖3.7 合作式頻譜感測增加權重示意圖 34
圖3.8 優先使用通道瞬時訊雜比較好的次級用戶示意圖 35
圖3.9 優先使用通道瞬時訊雜比較好及次好的次級用戶示意圖 35
圖3.10 使用次級用戶到達到我們預設的偵測機率或全部次級用戶都使用示意圖 36
圖3.11結合排序瞬時訊雜比方法和權重方法流程圖 36
圖3.12 在使用增加權重的方法下有排序跟無排序平均用的次級用戶個數比較 37
圖3.13 在使用增加權重的方法下有排序跟無排序平均用的次級用戶個數比較 38
圖3.14 增加權重跟多數決投票規則在瑞利通道下的效能比較 39
圖3.15 不同平均訊雜比時，權重法有排序跟無排序平均用的次級用戶個數比較 40

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