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Please use this identifier to cite or link to this item: http://ntour.ntou.edu.tw:8080/ir/handle/987654321/35715

Title: 感知無線電系統利用能量分布最大可能性之頻譜感測技術
Energy-based Maximum Likelihood Spectrum Sensing Methods for Cognitive Radio
Authors: Szu-Hsien Lu
呂思賢
Contributors: NTOU:Department of Communications Navigation and Control Engineering
國立臺灣海洋大學:通訊與導航工程學系
Keywords: 感知無線電;頻譜空隙;能量檢測;門檻值;能量最大可能性檢測
Cognitive Radio;Spectrum Hole;Energy Detection;Threshold;Energy-based Maximum Likelihood Detection
Date: 2013
Issue Date: 2013-10-07T02:58:11Z
Abstract: 隨著無線通訊逐年發展、對頻譜資源需求的日益增加,突顯出無線頻譜嚴重缺少且不敷使用之情況。根據美國聯邦通訊委員會(Federal Communications Commission in the United States, FCC)所提出的研究報告顯示,問題出在大部分的頻帶於特定時間內並無充分使用,為提高頻譜的利用率,感知無線電(Cognitive Radio, CR)系統因此被提出。 如何準確及快速偵測到主要用戶(Primary User, PU)是否存在,並尋找頻譜空隙提供次級用戶(Secondary User, SU)使用,成為實現感知無線電的重要關鍵。本論文將採用不須預先瞭解接收訊號額外資訊的能量檢測(Energy Detection, ED)進行分析研究。首先利用能量最大可能性(Energy-based Maximum Likelihood)演算法,在不用直接計算出門檻值(Threshold, TH)的情況下,間接取得與最佳門檻值(Optimal Threshold)相同的系統效能。其次提出一個雙門檻值(Double Threshold, DT)方法,在犧牲些許偵測效能的情況下,減少偵測時間的方法。最後提出結合滯後門檻值(Hysteresis Threshold, HT)並進行修正的想法,在低訊雜比(Signal to Noise Ratio, SNR)的環境下,能達到相較於滯後門檻值HT更佳的偵測錯誤率(Probability of Error, Pe)。
As the fast development of modern wireless communication, the demand of larger spectrum allocation shows the serious shortage problem of the radio spectrum. According to the research of Federal Communications Commission in the United States (FCC), the problem lies in insufficient usage of the frequency band during allocation. To improve the utilization of wireless spectrum, the Cognitive Radio (CR) had been proposed currently. The key issue of applying the Cognitive Radio successfully is how to sense exactly and quickly whether or not the Primary User (PU) exists, and looking for the spectrum holes to provide to the Secondary User (SU). In this thesis, the Energy based Detection (ED) CR is analyzed due to its simple advantage at the detection. First of all, instead of knowing the Threshold (TH) exactly, an Energy-based Maximum Likelihood Detection (EMLD) is proposed to have the same performance as the optimal threshold. Second, a Double Threshold (DT) method is promoted at the price of reducing some performance to reduce the sensing time. Final, combining the Hysteresis Threshold (HT) concept, a HT method is also proposed in this thesis. It has the lower probability of error (Pe) than the conventional Hysteresis Threshold especially under the low SNR scenarios.
URI: http://ethesys.lib.ntou.edu.tw/cdrfb3/record/#G0010067001
http://ntour.ntou.edu.tw/handle/987654321/35715
Appears in Collections:[通訊與導航工程學系] 博碩士論文

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