高速移動環境下OFDM系統載波間干擾減抑技術之改善 ; Improvement of Inter-Carrier Interference Mitigation Technology for OFDM System in High-mobility Environment

NCUIR > College of Electrical Engineering & Computer Science > Graduate Institute of Communication Engineering > Electronic Thesis & Dissertation > Item 987654321/44488

Please use this identifier to cite or link to this item: http://ir.lib.ncu.edu.tw/handle/987654321/44488

Title:	高速移動環境下OFDM系統載波間干擾減抑技術之改善;Improvement of Inter-Carrier Interference Mitigation Technology for OFDM System in High-mobility Environment
Authors:	李怡樺;Yi-Hua Lee
Contributors:	通訊工程研究所
Keywords:	高速移動;載波間干擾;歐規數位電視地面廣播;High-mobility;ICI;DVB-T
Date:	2010-07-16
Issue Date:	2010-12-09 13:45:53 (UTC+8)
Publisher:	國立中央大學
Abstract:	DVB-T系統所採用的核心技術是正交分頻多工（OFDM）。此技術運用了多載波間正交特性以達到高頻譜效益。並藉由前置循環字首（Cyclic prefix）來抵抗多重路徑干擾以及多載波之特性以達到消除符碼間干擾（ISI, Inter-symbol Interference）；在高速移動環境下，DVB-T訊號經過時變的通道，接收到的訊號會產生都普勒擴展(Doppler Spread)的現象，破壞子載波間的正交性並進一步引起載波間干擾(ICI)；而載波間干擾會隨著移動速度上升而越加嚴重，導致系統性能下降。為了克服高速移動所引起的載波間干擾(Inter-carrier Interference，ICI)，本論文將前人方法加以改良，介紹了一套適合高速移動接收的通道估測和載波間干擾消除。本論文參考DVB-T系統，並且進一步的修改使其更合適於高速移動下的環境。針對所有受到ICI干擾的訊號，我們利用以下步驟：首先通道估測、其次.反覆式ICI消去方法，最後反覆使用最大近似（Maximum Likelihood，ML）偵測法推導出的向量投影方式搜索，抑制載波間干擾、降低其錯誤率，提昇系統速度。The core of DVB-T is OFDM system. By using multi-carriers and inserting cyclic prefix, this technology successfully eliminated the ISI effect and multi-path interference. In high-mobility environment, when DVB-T signals pass through the time-varying channel, the receive signals will have Doppler spread that can loss of sub-carrier orthogonality and cause the ICI. This ICI effect degrades the maximum allowed velocity of reception. To overcome the ICI which caused by the high-mobility, this thesis modifies other’s methods and introduces a method about the channel estimation and elimination of ICI which is suitable for high mobility reception. This thesis refers to the DVB-T standard, and further modifies it to suit in high-mobility environment. In high-mobility environment, the performance of wireless OFDM communication systems is degraded and limited by inter-carrier-interference (ICI) phenomenon. In this paper we proposed an algorithm based on maximum-likelihood criterion with improved performance in mitigation of ICI.
Appears in Collections:	[Graduate Institute of Communication Engineering] Electronic Thesis & Dissertation

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