成功大學博碩士論文系統

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研究生：	葉明宸 Yeh, Ming-chen
論文名稱：	使用循環穩態偵測無線通道之正交分頻多工信號 Detection of OFDM Signals in Wireless Channels Using Cyclostationarity
指導教授：	賴癸江 Lai, Kuei-Chiang
學位類別：	碩士 Master
系所名稱：	電機資訊學院 - 電腦與通信工程研究所 Institute of Computer & Communication Engineering
論文出版年：	2009
畢業學年度：	97
語文別：	中文
論文頁數：	45
中文關鍵詞：	循環穩態、特徵曲線、偵測理論、正交分頻多工調變(OFDM)
外文關鍵詞：	OFDM, cyclostationarity, detection theory
相關次數：	點閱：94 下載：2
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一般而言，調變信號其自相關函數在時間軸上為週期函數，我們則稱之具有循環穩態性(cyclostationarity)。而不同調變方式的信號會有不同的循環穩態性，故可由接收到信號的循環穩態性來判斷某特定調變信號是否存在。
當OFDM信號在無線通道傳輸時，會受到雜訊的干擾，或是因遮避(Shadowing)效應造成振幅、相位的失真，頻率偏差(Frequency Offset)，多路徑(Multi-path)干擾等問題。本論文推導與分析OFDM信號在上述各種模型假設下的循環穩態性。並與理想狀況下的特徵曲線做比較，提出一類似功率偵測器(Energy-like Detector)的偵測方式，可適用在上述的模型假設下。並模擬驗證相較於功率偵測器，較不受白雜訊的功率大小影響，故具有不亞於功率偵測器的偵測效能。

The autocorrelation function of modulated signals is periodic in time, and thus exhibits the so-called cyclostationarity. In general, different modulated signals have distinct cyclostationary features. Therefore, we can determine if a modulated signal is present or not by examining the cyclostationarity feature of the received signal.
When transmitted over wireless channels, the OFDM signal is subject to noise corruption, phase and amplitude distortions, frequency offset, the Doppler spread, and multi-path interference. In this thesis, we derive and analyze the cyclostationarity feature of the OFDM signal based on the models mentioned above, and compare with that based on the ideal model (i.e., without any noise and distortions). As a result, we propose the energy-like detector (ELD) for the detection of the OFDM signal. Simulation results demonstrate that the ELD performs slightly better than the conventional energy detector (ED) in many signals and channel conditions because it is less prone to the corruption of the white noise.

目錄

中文摘要…………………………………………………………………I
英文摘要……………………………………………………………II
誌謝………………………………………………………………III
目錄……………………………………………………………………IV
表目錄……………………………………………………………VI
圖目錄…………………………………………………………VII


第一章 導論……………………………………1
	1.1 前言……………………………………………………………1
	1.2 動機…………………………………………………………2

第二章 文獻介紹…………………………………………3
	2.1 循環穩態(Cyclostationarity) 的定義…………………………………………3
	2.2 推導正交分頻多工調變(OFDM) 信號的循環穩態…………………………4
	2.3循環穩態特徵曲線圖(Cyclostationary Characteristics) ………………………7
	2.4 偵測理論--Neyman-Pearson Theorem (NP法則) ……………………………8

第三章 個人研究部分—無線傳輸通道上可能面臨的問題………………10
	3.1可加性白色高斯雜訊(AWGN) 對OFDM 信號之CAF所產生的影響……11
3.1.1.a  理論上白雜訊的循環穩態性………………………………………11
		3.1.1.b  估測白雜訊的循環穩態性…………………………………………11
3.1.2.a  OFDM信號在白雜訊干擾下的循環穩態性………………………14
3.1.2.b 估測OFDM 信號在白雜訊干擾下的循環穩態性…………………15
3.1.3 根據NP法則畫ROC討論偵測效能…………………………………21
3.2 OFDM 在雷利衰減通道下的循環穩態性……………………………………22
		3.2.1.a  無都普勒效應情況下的推論( )………………………………22
	3.2.1.b  模擬估測……………………………………………………………24
		3.2.2  都普勒效應(Doppler Effect)的影響…………………………………26
	3.3 頻率偏差(Frequency Offset) 對OFDM 信號之CAF  所產生的影響……32
	3.4 多重路徑(Multi-path) 對OFDM 信號之CAF 所產生的影響……………34
	3.5 由分析特徵曲線後所提之偵測方式…………………………………………36
		3.5.1 比較各種傳輸通道模型下OFDM 信號的CAF ……………………36
		3.5.2 類-功率偵測(Energy-Like Detection, ELD) 理論……………………36
		3.5.3  ELD與功率偵測器(Energy Detector, ED) 的比較…………………37
3.5.3.a 在單一路徑與功率偵測器效能的比較 ……………………………38
3.5.3.b 在多路徑與功率偵測器效能的比較 ………………………………40

第四章 結論 ………………………………………………………………43
	4.1  結論 …………………………………………………………………………43
	4.2  未來展望 ……………………………………………………………………43

參考文獻 ……………………………………………………………………………44
                                    

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校內：2011-07-24公開
校外：2011-07-24公開

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