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Title: | 頻譜共享中針對正交多頻分工主要使用者之智慧覆蓋式傳輸方法 Smart Overlay Transmission for Spectrum Sharing with OFDM-based Incumbents |
Authors: | Wei-Chen Wang 王瑋辰 |
Advisor: | 周俊廷(Chun-Ting Chou) |
Keyword: | 動態頻譜存取,覆蓋式傳輸,頻譜共享,共存,干擾管理, dynamic spectrum access (DSA),overlay transmission,spectrum sharing,coexistence,interference management, |
Publication Year : | 2015 |
Degree: | 碩士 |
Abstract: | 隨著無線裝置與應用的快速增長,無線頻譜資源日趨匱乏。為解決此問題,頻譜共享在過去十年被提出並研究。頻譜共享之概念為複數個使用者共同分享頻譜,且最近研究方向多針對於授權頻帶之頻譜共享。頻譜共享之傳輸方式通常被歸類為交織式、隱匿式與覆蓋式系統三者。
交織式為主流之傳輸方法,其使射頻裝置根據機率原則搜尋並使用空白之授權頻帶。然而於此方式下若主要使用者重新使用頻帶則此些射頻裝置必須立即停止傳輸,造成無法預期之服務中斷問題且伴隨之服務延遲可能極長且難以掌握。 在本論文中,我們提出了一個覆蓋式傳輸方法使主要與次級使用者可進行同步且零干擾之傳輸。我們的方法試用於正交多頻分工(OFDM)系統之主要使用者。藉由在正交多頻分工信號之循環前綴(CP)部分傳輸次級使用者之信號,可達到同步且零干擾之傳輸且前述無法預期之服務中斷問題可被解決。我們的方法已實作於軟體定義無線電USRP平台且應用於數位電視廣播系統(DVB-T)。實驗結果證實,即便數位電視接收器收到之次級使用者訊號強度大於數位電視訊號之1000倍,數位電視接收器亦不受到干擾。若將IEEE 802.11g之技術應用於本方法,使用電視頻帶之6 MHz頻寬則次級使用者將可達到970 kbps之媒介存取層吞吐率。 With the explosive growth of wireless devices and applications, wireless spectrum has become scarce. To solve this problem, spectrum sharing has been proposed in the past decade. Spectrum sharing is to share spectrum among multiple users and recent researches focus on sharing in licensed bands. The transmission schemes for spectrum sharing are commonly categorized into three paradigms including underlay, overlay and interweave. The mainstream scheme for spectrum sharing is interweave, where radio devices search for unused spectral bands and utilize these bands on an opportunistic basis. However, devices using interweave schemes must stop once primary users come back, which results in unpredictable service disruption. The corresponding service delay may be long and difficult to be estimated. In this thesis, we propose an overlay transmission scheme to enable simultaneous and interference-free transmission. Our solution works with OFDM-based primary users. By transmitting secondary data within the cyclic prefix (CP) of the OFDM symbols of primary users, simultaneous and interference-free transmission could be achieved and the service disruption caused by the unpredictable activities of the primary user could be alleviated. We have implemented our solution on the Universal Software Radio Peripherals (USRP) platform and applied to the Digital Video Broadcasting-Terrestrial (DVB-T) spectrum sharing networks. The experiment results show that the solution guarantees that even though the received secondary power strength is 30 dB higher than that of DVB-T transmitter, the DVB-T receivers would be still unaffected. When the IEEE 802.11g technologies is applied to our scheme in a 6 MHz TV band, secondary users could achieve a MAC-layer throughput of up to 970 kbps. |
URI: | http://tdr.lib.ntu.edu.tw/jspui/handle/123456789/19902 |
Fulltext Rights: | 未授權 |
Appears in Collections: | 電信工程學研究所 |
Files in This Item:
File | Size | Format | |
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ntu-104-1.pdf Restricted Access | 3.16 MB | Adobe PDF |
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