臺灣博碩士論文加值系統

本論文針對正交分頻多工(Orthogonal Frequency Division Multiplexing, OFDM)的技術，在數位影音廣播(Digital Video Broadcast, DVB)行動通訊系統的架構中，探討在多路徑延遲(Multi-Path Delay Spread)環境中之效能，並進而提出路徑延遲之估計方法。本文提出之估計方法應用在數位影音廣播行動通訊系統中的正交分頻多工次載波(Sub-Carrier)之載波串列的循環字首(Cyclic Prefix)長度之調整，可以改善多重路徑延遲的符際干擾(Inter Symbol Interference, ISI)問題。

In this thesis, we investigate the effect of multi-path wireless channels for the Orthogonal Frequency Division Multiplexing (OFDM) communication systems. In the European specification standard, the different modes by the number of sub-carriers, for example, 2K, 4K and 8K, etc., are used to combat the multi-path delay spread due the different transmission channels. We propose an estimation scheme to accurately estimate the multi-path delay spread and then the proper cyclic prefix can be added to reduce the inter-symbol interference (ISI).

摘要..................................................................................................... I
Abstract............................................................................................... II
誌謝...................................................................................................III
目錄...................................................................................................IV
圖目錄............................................................................................. VII
表目錄................................................................................................X
第一章 緒論........................................................................................1
1.1 研究背景.................................................................................1
1.2 研究動機及目的......................................................................3
1.3 論文架構.................................................................................4
第二章 歐規數位影音廣播系統簡介...................................................5
2.1 歐規數位影音廣播之地面式系統規格....................................5
2.1.1 DVB-T 系統規格簡介....................................................5
2.1.2 DVB-T 及DVB-H 系統參數..........................................7
2.2 正交分頻多工系統簡介及架構...............................................9
2.2.1 OFDM 簡介....................................................................9
2.2.2 OFDM 基本概念...........................................................10
2.2.3 OFDM 之正交性...........................................................13
2.3 無線通訊之多路徑延遲現象.................................................14
2.3.1 衰減的模型..................................................................15
2.3.2 時間延遲擴散..............................................................16
2.4 保護區間...............................................................................18
2.4.1 循環字首的放置..........................................................19
2.5 雷利(Rayleigth)衰減分佈......................................................21
第三章 正交分頻多工之路徑延遲效應.............................................23
3.1 系統架構模型的建立............................................................23
3.1.1 主要路徑及次要路徑傳輸模式.....................................26
3.1.2 系統模擬參數..............................................................27
3.2 基於OFDM 次載波模式分配之效能....................................28
3.2.1 路徑訊號強度...............................................................28
3.2.2 次載波模式...................................................................34
3.3 基於OFDM 護衛區間分配之效能........................................38
第四章 估計OFDM 無線通訊系統路徑延遲....................................43
4.1 系統架構模型及參數設定....................................................43
4.2 提出多路徑延遲時間演算公式.............................................46
4.3 估計多路徑延遲之效能........................................................47
4.3.1 設定訊號雜訊比單位量...............................................48
4.3.2 延遲效應基準參數值...................................................50
第五章 結論與未來研究方向.........................................................61
參考文獻...........................................................................................62

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