在合作式通訊系統中, 為達到如多重輸入多重輸出(MIMO) 相同效果的空間多樣性增益(spatialdiversity gains) , 不同的使用者會彼此幫助傳輸, 使信號經中繼點(Relay) 的轉傳到達目的端。本論文主要探討放大後傳輸(Amplify-and-Forward) 合作式通訊系統中的盲式通道估測。在過往的研究下, 多是中繼點在合作的情況下進行傳送, 因此目的端可以完整地接收到經由中繼點傳送的資訊, 假設完成通道估測。然而, 在實際情況下, 中繼點的合作與否並非可信賴的, 因此當中繼點發生異常行為時, 將使通道估測效能有所影響。本論文在合作式通訊系統有直接傳輸路徑(With Direct Path)
模型的情況下, 提出一個檢測機制以解決此一問題。目的端將用直接傳輸路徑的資訊, 輔助經中繼點傳輸的資訊, 利用其各自的機率密度函數結合成一個概似比(Likelihood Ratio) 。利用此檢測機制在接收端做檢測, 可彌補因中繼點發生異常, 造成接收端通道資訊不足的情形, 讓通道估測更加精準。本論文使用均方差(Mean Square Error) 來判定通道估測效能, 並經由數學推導及電腦模擬, 驗證我們提出的檢測方法確實能夠達到強健通道估測的效果。

In order to achieve the same performance of spatial diversity in MIMO, cooperative communicationsis employed to transmit signals via relays to destinations. In most existing studies,all relays were assumed cooperative and they can relay the signals transmitted from source tothe destination. However, in actual application, some relays may be selfish and don’t transmit signals to destinations. This thesis proposes a method combining relay and direct transmission to improve the channel estimation when the relay is selfish. The cooperative mechanism used in this work contains a direct and a relay transmission. The proposed method first will detect the relay is selfish or not with likelihood ratio. After detecting, the destination utilizes the direct transmission to help estimate the channel in relay transmission with least square estimation.
In simulation result, this thesis uses mean square error to evaluate the performance of the proposed method. It shows that the proposed method can decrease means square error of channel estimation.

摘要 i
Abstract ii
目錄 iii
圖目錄 iv
表目錄 v
1 序論 1
2 系統模型 5
2.1 放大後傳輸合作式通訊系統模型 5
2.2 中繼點之異常行為 8
3 合作式通訊中繼點發生異常之穩健通道估測 9
3.1 中繼點隨機發生異常之檢測 9
3.2 中繼點隨機發生異常之最小平方估測法 13
4 數值模擬結果和分析 15
5 結論 23

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