正交分頻多工技術以良好的頻譜效益且具有抵抗多路徑衰減通道效應能力，成為現今高速無線傳輸技術主流。正交分頻多工系統中，當多路徑衰落通道延遲擴散超出保護區間時，則造成相鄰區塊干擾(Inter-Block Interference，IBI)效應。因此正交分頻多工系統若欲於通道延遲擴散較大的環境運作，則須使用區塊干擾消除方法以避免嚴重性能衰減。本論文主要探討OFDM系統之區塊干擾消除議題，除了探討時域循環性旋積信號還原及頻域等化器區塊干擾消除方法之性能外，本論文亦提出頻域適應性通道預測法，此方法可用於重建多路徑衰落通道響應，且具有適用於不同延遲擴散通道環境之彈性，毋須事先猜測通道環境特性。經由電腦模擬結果顯示，此方法所重建之通道響應具有較小之歸一化均方差(NMSE)，在循環性旋積信號還原區塊干擾消除方法應用上亦有較佳之封包錯誤率(PER)。

Orthogonal Frequency Division Multiplexing (OFDM) is a promising technique for high data rate transmission. It has higher bandwidth efficiency and is more immune to the effect of multipath dispersion, as compared to the single carrier technique. However, as multipath dispersion exceeding the guard interval used in the system for multipath protection, inter-block interference (IBI) occurs and that results in significant degradation on system performance. In this thesis, the issue of IBI cancellation is investigated. Both time- and frequency-domain cancellation methods are studied and compared. A new frequency-domain channel prediction based on recursive least square (RLS) algorithm is proposed to accurately reconstruct the channel impulse response. Accurate channel reconstruction is a necessity for time-domain IBI cancellation to work properly. Computer simulations show that our new method of channel reconstruction can improve the cancellation performance very significantly.

目錄
頁次
中文摘要………………………………………………………………………... i
英文摘要………………………………………………………………………... ii
誌謝……………………………………………………………………………... iii
目錄....................................................................................................................... iv
圖目錄................................................................................................................... vi
表目錄................................................................................................................... viii
第一章 簡介....................................................................................................... 1
第二章 OFDM傳輸技術基本原理................................................................... 3
2.1 多載波調變原理......................................................................... 3
2.2 IFFT/FFT實現............................................................................ 8
2.3 循環前置碼................................................................................. 9
2.4 視窗法與接收端等化器............................................................. 12
第三章 IEEE 802.11a無線區域網路標準介紹................................................ 15
3.1 實體層碼框架構......................................................................... 15
3.2 PLCP前序信號........................................................................... 18
3.3 Signal Field................................................................................. 19
3.4 Data Field.................................................................................... 20
3.4.1 Service Field, Tail and Pad bits....................................... 20
3.4.2 攪亂器和迴旋編碼器..................................................... 21
3.4.3 資料位元交錯與子載波調變映射................................. 23
3.4.4 領航子載波與視窗法..................................................... 25
3.5 PMD規範.................................................................................... 26
第四章 通道模型與數位濾波器設計............................................................... 29
4.1 多路徑衰落通道模型. ............................................................... 29
4.2 數位濾波器設計......................................................................... 32
4.3 前置失真..................................................................................... 36
第五章 OFDM系統區塊干擾消除................................................................... 43
5.1 區塊干擾效應表述..................................................................... 43
5.2 區塊干擾消除方法..................................................................... 47
5.2.1 循環性旋積信號還原區塊干擾消除法......................... 47
5.2.2 頻域等化器..................................................................... 49
5.3 通道脈衝響應重建..................................................................... 49
5.3.1 通道內插法與最小平方法............................................. 51
5.3.2 頻域適應性通道預測法................................................. 53
5.4 模擬結果與分析......................................................................... 59
5.4.1 歸一化均方差................................................................. 59
5.4.2 封包錯誤率..................................................................... 66
第六章 結論與未來展望................................................................................... 76
參考文獻............................................................................................................... 77
個人簡歷………………………………………………………………………... 80

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