近年來, 空時區塊編碼(Space-Time Block Coding, STBC) 已被證實在無線傳輸系統中可達到傳輸分集性(Transmit diversity) 的效果。目前相關的研究大多假設中繼端(Relay node) 是完美同步。因此, 從中繼端傳送到目的端(Destination node) 的傳送訊號皆是同時間傳送與接收。然而, 在實際的系統, 由於中繼端發射訊號的時間皆不同,導致接收訊號彼此間具有時間延遲, 若缺乏完美同步時, 將產生符際干擾(Inter SymbolInterference, ISI) 。此時, 時間延遲將損害空時編碼的正交特性, 導致效能嚴重下降。本論文提出一個利用富立業轉換(Fourier Transform) 進行通道與時間延遲估測法, 藉由富立業轉換與最小平方(Least Square, LS) 估測法估測時間延遲與通道資訊並加以補償, 使得空時區塊編碼能夠在接收端維持正交性。在本論文的模擬結果中, 本論文所提出之方法確實能有效改善時間延遲對於合作式網路的效能影響, 並且較其他方法具有較佳之效能。

In recent years, relay communication has been proved to achieve the transmis-sion diversity order with space-time block coding (STBC). Most research assumedthat the relay nodes are in perfect synchronization. However, in actual, becausethe transmitting time at each relay is different, the signals from different relays received at destination will interfere with each other. Inter-symbol interference (ISI) iscaused. Besides, the time synchronization error will reduce orthogonality of space-time block coding and result in serious performance degrade. This thesis proposes a time delay compensation method by using Fourier transform and Least Square(LS)estimation method. The destination node can utilize the estimated time delay tosynchronize the received signal. Then, the space-time coding will maintain orthogonality at the receiver. Simulation results show that the proposed method caneffectively improve the performance of cooperative networks when imperfect timesynchronization exists.

論文審定書. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . i
中文摘要. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ii
英文摘要. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . iii
第一章序論. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
第二章系統理論基礎. . . . . . . . . . . . . . . . . . . . . . . . . . . 2
2.1 合作式通訊網路. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
2.2 空時編碼. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
2.3 寬頻通訊系統. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
第三章時間延遲處理 6
3.1 系統架構. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
3.2 一般ISI 消除方法. . . . . . . . . . . . . . . . . . . . . . . . . . .... 8
3.3 時間偏移與通道估測法的設計. . . . . . . . . . . . . . . . . . 10
3.3.1 均方誤差. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13
第四章模擬結果 . . . . .. . .. . . . . .. . .. . . . . .. . .. . . 14
4.1 模擬參數設定. . . . . . . . . . . . . . . . . . . . . . . . . .. . .. 14
4.2 模擬圖. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
第五章結論. . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . 21
參考文獻. . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . .22

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