Investigating in OFDM Systems with SC Diversity Operating over Correlated-Weibull Frequency Selective Fading Channels
林聖傑、陳雍宗
E-mail: 9606962@mail.dyu.edu.tw
ABSTRACT
In this paper the system performance of OFDM (orthogonal frequency division multiplexing) with the cases of MRC (maximal ratio combining) and dual branch SC (selective combining) diversities over correlated-Gamma distributed and correlated-Weibull fading, respectively, are investigated. Since the reason of an alternative expression of the Q-function is adopted for deriving the results of average BER (bit-error rate) of the OFDM system, the obtained formulas are not only calculated much simpler but the conducting of numerical analysis is also arrived at easily and accurate. It is valuable to claim that the system performance of the OFDM system is definitely dominated by the propagation environments, which is decided by the fading parameters both of the Nakagami-m and Weibull distributed, of the transmission of the radio systems. Furthermore, both of the conditions of equal and unequal signal intensities at the output of SC diversities are adopted as the scenarios for the discussion of OFDM systems.
Keywords : OFDM signaling ; MRC ; SC ; Nakagami-m fading ; Weibull fading Table of Contents
封面內頁 簽名頁 博碩士論文暨電子檔案上網授權書... iii 中文摘要... iv 英文摘 要... v 誌謝... vi 目錄... vii 圖目
錄... x 第一章 緒論... 1 1.1 研究動機與目的... 1 1.2論文綱 要... 3 第二章 正交分頻多工系統... 4 2.1 OFDM基本原理... 4 2.2 OFDM 連續時間的模型... 8 2.3 OFDM系統離散時間模型... 10 2.4 OFDM系統之傅立葉轉
換... 10 2.5 OFDM系統與QAM調變結合之分析... 12 2.5.1 QAM-OFDM的工作原理... 16 第 三章 無線通訊衰落通道... 20 3.1無線通道信號衰落... 20 3.2衰落的形式分類... 22 3.2.1小尺度衰落... 22 3.2.1.1時間延遲擴散... 22 3.2.1.2時域上的變動性... 23 3.2.2大尺度衰落... 25 3.3衰落通道的數學模型... 25 3.4多重路徑及多重衰落...
26 3.5多重路徑衰落所造成的效應... 27 3.6通道統計分佈... 28 3.6.1 Normal (Gaussian) 衰落分 佈... 28 第四章 分集合成技術... 31 4.1分集合成技術... 31 4.1.1極化分
集... 32 4.1.2頻率分集... 33 4.1.2.1 選擇性合成... 34 4.1.2.2 最大比例合 成... 35 4.1.3空間分集... 37 4.1.4時間分集... 38 第五章 OFDM系統結合 最大比例合成和雙分支選擇性合成分集 於衰落環境中之效能分析... 40 5.1系統模型... 40 5.2衰落通道的PDF... 43 5.2.1加總之後的Nakagami-m統計分布... 43 5.3具相關性的瑋布分
佈... 44 5.4錯誤率效能分析... 48 5.4.1 OFDM系統結合雙分支SC合成之分析... 48 5.4.2 OFDM系統結合MRC合成之分析... 50 第六章 數值結果與討論... 52 第七章 結論...
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