本論文提出一種Cost-based CLEAN 演算法，能在室內超寬頻系統中，精準地偵測密集性多重路徑，以提昇選擇性耙式接收機的效能。耙式接收機利用多重路徑的參數資訊以解決密集性多重路徑干擾的問題，但由於增益係數小的路徑，對於系統效能的助益不大，所以選擇性耙式接收機只利用最強的幾個路徑，以減少耙式接收機之耙指(Finger) 的個數，降低系統複雜度。選擇性耙式接收機需要精準的通道多重路徑偵測，以訂立適當的耙式接收機之耙指個數及參數，因此探討如何運用CLEAN 演算法偵測最佳路徑組合，以提升選擇性耙式接收機的效能，是本篇論文主要探討之議題。CLEAN 演算法利用獲取訊號的最大相關性為搜尋路徑的依據，以迭代的方式偵測路徑，若有相近的路徑或某路徑的訊號特別強，容易發生路徑的錯誤偵測，進而影響接收機的效能；而在以代價函數為基礎的CLEAN 演算法中，利用演化式規畫(Evolutionary Programming ，或縮寫EP) 的EP-based CLEAN 演算法方式，在任意空間中搜尋可使代價函數最小化的多重路徑時間和大小，以獲得精確的路徑偵測且提昇相鄰路徑的解析度，然而由於盲目地搜尋，使得EP-based CLEAN 演算法，需要較長的運算時間；因此本論文結合代價函數和CLEAN 演算法的迭代方法，提出另一種Cost-based CLEAN 演算法，從交互相關性的峰值附近，搜尋能使區域代價函數最小化的位置，再運用CLEAN 演算法，以迭代的方式移除傳送訊號的自相關成分，並記錄路徑的延遲時間和增益係數的大小，以達到代價函數的最小化，較快獲得準確的路徑偵測。經由IEEE802.15.3a 的超寬頻通道驗證，相較於CLEAN 演算法，本論文所提出的Cost-based CLEAN 演算法可較準確偵測多重路徑，且有效提升選擇性耙式接收機的效能。

In this thesis, we propose a cost-based CLEAN algorithm to accurately find dense multi-path parameters and improve the performance of selective RAKE receiver in indoor UWB systems. RAKE receiver can resolve the dense multi-path interference problems with the multi-path parameters. Because the weak paths are of lower valuable for system performance improvement, selective RAKE receiver combines only the strongest multi-path components and reduce the number of fingers to lower the complexity of RAKE receiver. However, selective RAKE receiver needs accurate multi-path detection to decide the suitable number and parameters of fingers. In order to improve the performance of selective RAKE receiver, the main issue in this thesis is to detect the best paths of channel with the CLEAN algorithm. CLEAN algorithm uses the correlation of the received signal and the template signal as the basis for searching paths. If there are closely adjacent paths, or if one of signal paths is relatively stronger, the detection error of paths may occur and thus affects the performance of the receiver. EP-based CLEAN algorithm uses the cost function and the evolutionary programming (EP) to search the multi-path delay times and gain coefficients for minimizing the cost function. Accurate multi-path detection and high resolution of adjacent paths can be obtained. However, EP-based CLEAN algorithm makes a time-consuming blind search. In the thesis, a CLEAN algorithm based on the cost function is proposed. The proposed cost-based CLEAN algorithm searches the delay times near the peaks of the cross-correlation for local minimum of the cost function, and then uses CLEAN algorithm to extract autocorrelation components and obtain the accurate multi-path detection. By testing the IEEE802.15.3a UWB channel models, and comparing with CLEAN algorithm, the cost-based CLEAN algorithm in the thesis can achieve better detection accuracy in multi-path searching, and improve the performance of selective RAKE receiver.

誌謝. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . i
中文摘要. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ii
英文摘要. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . iii
目錄. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . iv
圖目錄. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . vi
表目錄. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . viii
1 緒論. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
1.1 研究背景. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
1.2 研究目的. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
1.3 論文結構. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
2 文獻回顧. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
2.1 超寬頻系統. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
2.1.1 超寬頻脈波訊號. . . . . . . . . . . . . . . . . . . . . . . . . 4
2.1.2 IEEE802.15.3a 通道模型. . . . . . . . . . . . . . . . . . . . 5
2.1.3 選擇性耙式接收機. . . . . . . . . . . . . . . . . . . . . . . . 9
2.2 訊號模型(Signal Model) . . . . . . . . . . . . . . . . . . . . ..10
2.2.1 傳送訊號. . . . . . . . . . . . . . . . . . . . . . . . . . . . .10
2.2.2 通道脈衝響應. . . . . . . . . . . . . . . . . . . . . . . . . . 11
2.2.3 接收訊號. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
2.3 CLEAN 演算法用於多重路徑偵測. . . . . . . . . . . . . 12
2.3.1 交互相關性(Cross-correlation) . . . . . . . . . .. . . 12
2.3.2 CLEAN 演算法用於多重路徑偵測. . . . . . . . . . . 14
2.3.3 CLEAN 演算法的問題. . . . . . . . . . . . . . .. . . . . . 15
3 Cost-based CLEAN 演算法. . . . . . . . . . . . . . . . . . 18
3.1 代價函數(Cost Function) . . . . . . . . . . . . . . . . . 18
3.2 Cost-based CLEAN 演算法用於多重路徑偵測. . . 19
3.3 不同CLEAN 演算法之差異點探討. . . . . . . . . . . . . . .21
4 電腦模擬及結果探討. . . . . . . . . . . . . . . . . . . . . . . . . . . 24
4.1 選擇式耙式接收機的效能分析. . . . . . . . . . . . . . . . . 24
4.2 系統參數設定與模擬. . . . . . . . . . . . . . . . . . . . . . . .. . 26
4.2.1 模擬結果探討. . . . . . . . . . . . . . . . . . . . . . . . . . 27
4.2.2 CLEAN 演算法的問題改善. . . . . . . . . . . . . . .. . . . 30
4.3 系統參數影響與分析. . . . . . . . . . . . . . . . . . . . . . . . . 31
4.3.1 選擇性耙式接收機耙指數目影響. . . . . . . . . . . . . .31
4.3.2 CLEAN 演算法的臨界值影響. . . . . . . . . . . . . . . . 34
4.3.3 超寬頻脈波波形(Template) 影響. . . . . . . . . . . . . 37
4.3.4 最低代價搜索對通道環境影響. . . . . . . . . . . . . . . 40
5 結論與建議. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44
5.1 結論. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44
5.2 未來工作建議及探討. . . . . . . . . . . . . . . . . . . . . . . . . 45
參考文獻. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46

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