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博碩士論文 etd-0215111-152835 詳細資訊
Title page for etd-0215111-152835
論文名稱
Title
窄頻無線感知網路系統之資料吞吐量分析
Analysis of Data Throughput in Narrow Band Cognitive Radio Networks
系所名稱
Department
畢業學年期
Year, semester
語文別
Language
學位類別
Degree
頁數
Number of pages
59
研究生
Author
指導教授
Advisor
召集委員
Convenor
口試委員
Advisory Committee
口試日期
Date of Exam
2010-07-08
繳交日期
Date of Submission
2011-02-15
關鍵字
Keywords
資料吞吐量、感知無線網路
throughput, cognitive radio
統計
Statistics
本論文已被瀏覽 5675 次,被下載 1360
The thesis/dissertation has been browsed 5675 times, has been downloaded 1360 times.
中文摘要
感知無線網路(Cognitive Radio network,CR network)是在探討沒有
執照(unlicensed)的使用者,如何當有執照(licensed)的使用者沒有在使
用頻段(frequency band)時,將頻段拿來利用,提昇頻段的使用率(frequency
reuse)。一般而言,我們稱沒有執照的使用者為次級使用者(Secondary User,
SU),有執照的使用者則稱之為優先使用者(Primary User,PU)。為了達到
頻段使用率的提昇,次級使用者必須持續的做頻譜偵測(spectrum sensing),
判斷目前頻段是否有優先使用者的存在,當判斷為優先使用者不存在頻段
時,則次級使用者則可以利用頻段傳輸資料;但是一旦偵測到優先使用者出
現在頻段的時候,必須空出頻段,將頻段的使用權歸還給優先使用者,盡可能的避免干擾(interference)到優先使用者。因此,頻譜偵測在感知無線網
路中扮演著非常重要的角色。在頻譜偵測技巧中,存在兩個重要機率值與之
息息相關,分別是正確偵測機率值(Probability of detection,Pd)和假警報
機率值(Probability of false alarm,Pf)。越高的正確偵測機率值,代表的是
優先使用者出現而且被次級使用者偵測出來的機率越高,優先使用者訊號被
保護的程度越好;在次級使用者的觀點而言,越低的假警報機率值,代表當
優先使用者沒出現時,次級使用者能夠更有機會使用頻段,因此在次級使用
者網路中能夠獲得較高的資料吞吐量(throughput)。
在本篇論文中,我們探討的問題是當優先使用者受到充分的保護下,
如何設計出一段偵測周期(sensing duration),使得次級使用者網路中的資料吞吐量達到最大值(maximize)。藉由數學上推導,用公式表示感知時間和
資料吞吐量的決策,並且利用能量偵測法(Energy Detection,ED)[4]的偵
測系統去證明我們所用公式表示出的問題,在次級使用者網路中,確實存在
一個最佳的(optimal)偵測時間,可以得到最高的次級使用者網路資料吞吐
量。在藉由合作式(cooperative)架構的概念,將次級使用者傳輸端數目增加為兩個,以此降低假警報機率值,提昇次級使用者網路的資料吞吐量。
Abstract
Cognitive radio network is discussing how to enhance frequency reuse by
allowing the unlicensed users to utilize the frequency bands of licensed users
when these bands are not currently being used. Generally speaking, we called
these unlicensed users as secondary users and these licensed users as primary
users. In order to enhance frequency reuse, the secondary users need to monitor
the spectrum continuously to avoid possible interference with the primary users,
and once the primary users are found to be active, the secondary users are
required to vacate the frequency bands. Therefore, spectrum sensing plays a
significant important role in cognitive radio network. There are two probability
values associated with spectrum sensing: probability of detection and probability
of false alarm. The higher the probability of detection means the better theprimary users are protected. However, from the secondary users’ perspective, the
lower the probability of false alarm, the more chances the frequency bands can
be reused when it is available, thus the higher the achievable throughput for the
secondary network.
In this thesis, we study the problem of designing the sensing duration to
maximize the achievable throughput for the secondary network under the
constraint that the primary user is sufficiently protected. We formulate the
sensing-throughput tradeoff problem mathematically, and use energy detection
(ED)[4] sensing scheme to prove that the formulated problem indeed has oneoptimal sensing time that yields the highest throughput for the secondary
network. We also discuss the case of two secondary users with the concept of
cooperative systems.
目次 Table of Contents
謝辭.........................................................................................................................III
摘要...................................................................................................................... IV
ABSTRACT......................................................................................................... VI
目錄.....................................................................................................................VII
圖索引.................................................................................................................. IX
表索引................................................................................................................... X
第一章簡介.......................................................................................................... 1
第二章窄頻感知無線網路.................................................................................. 4
2.1 窄頻感知無線網路系統架構................................................................ 4
2.2 窄頻感知無線網路訊號模型................................................................ 5
2.3 能量偵測法............................................................................................ 6
2.3.1 在能量偵測法下的正確偵測機率和假警報機率............................. 9
2.3.2 接收端的操作特性........................................................................... 11
2.4 感知時間和資料吞吐量的決策.......................................................... 14
2.4.1 在能量偵測法下的資料吞吐量....................................................... 17
第三章 合作式窄頻感知無線網路.................................................................... 20
3.1 合作式窄頻感知無線網路系統架構.................................................. 20
3.2 架構在融合決策的合作式頻譜感知.................................................. 21
3.3 偵測功率與資料吞吐量之探討.......................................................... 23
第四章模擬結果................................................................................................ 29
4.1 窄頻感知無線網路之模擬.................................................................. 29
4.1.1 能量偵測器的機率密度函數........................................................... 29
4.1.2 感知偵測時間................................................................................... 34
4.2 合作式窄頻感知無線網路之模擬...................................................... 36
4.2.1 感知偵測時間................................................................................... 38
第五章結論........................................................................................................ 43
附錄A 高斯分佈的期望值和變異數................................................................ 44
參考文獻.............................................................................................................. 47
參考文獻 References
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