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  • 學位論文

載波頻率偏移估測法於正交分頻多工系統之效能改進

Performance Improvement of Carrier Frequency Offset Estimation Methods in OFDM System

指導教授 : 呂振森
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摘要


隨著使用者需求日益漸增,對頻寬的要求越來越重要,OFDM是一種具有高頻譜效率的調變技術,可以在有限頻寬下進行高資料量傳送。然而OFDM對頻率同步之錯誤非常敏感,只要有些許載波頻率偏差,就會造成載波間干擾,使系統效能大幅降低。故本論文針對接收端本地振盪器非理想狀況所造成的頻率偏移進行研究,以載波頻率偏移估測演算法為研究基礎進行改良,提出結合偏移量補償法的載波頻率偏移估測新方法。此一方法主要是套用在近年來提出的使用領導符碼搭配MLE結合ICI自我消除演算法上,可在相同頻寬效益及不增加過多計算複雜度的情況下來改善系統效能。經由電腦模擬證明,此一方法不僅能增加獲取載波頻率偏移量的範圍,亦對系統效能有明顯的改善。

並列摘要


With increasing demands from users, the issue of bandwidth efficiency becomes more and more important. The OFDM is a modulated technology with high bandwidth efficiency. It can provide high data rates with limited bandwidth. However, one of the drawbacks is their extreme sensitivity to frequency synchronization errors. With slight carrier frequency offset (CFO), it will result in the inter-carrier interference (ICI) which causes severe degradation on the system performances. Therefore, this thesis is mainly to research into the carrier frequency offset estimation methods for the CFO induced by imperfections of local oscillator’s frequency at receiver. A new carrier frequency offset estimation method combined with offset compensation was proposed. This method is based on the recent pilot-based carrier frequency offset estimation method which integrates with maximum likelihood estimation and ICI Self-cancellation algorithm. The proposed method can improve the system’s performance without increasing a lot of complexity under the same bandwidth efficiency. According to the computer simulation, our results show that it can not only extend the estimation rage of carrier frequency offset, but also increase the system performance.

參考文獻


[1]R. W. Chang, “Synthesis of band-limited orthogonal signals for multichannel data transmission,”Bell Systems Technical Journal, vol. 46, December 1966, pp. 1775-1796.
[4]Yuping Zhao and Sven-Gustav Häggman, “Intercarrier Interference Self-Cancellation Scheme for OFDM Mobile Communication Systems” IEEE Transation on Communications, vol. 49, no. 7, July 2001, pp. 1185-1191.
[5]Wei Zhang, Xiang-Gen Xia and Ching, P.C, "Clustered pilot tones for carrier frequency offset estimation in OFDM systems," IEEE Transctions on Wiress Communications, no. 1, January 2007, pp. 101-109.
[6]Li. Ye(EDT) Stuber Gordon, Orthogonal Frequency Division Multiplexing for Wireless Communications, Atlanta :Baker & Tayl, 2006, pp. 113-139.
[7]Morelli, M., Kuo, C.-C.J. and Pun, M.-O., “Synchronization Techniques for Orthogonal Frequency Division Multiple Access (OFDMA): A Tutorial Review,” Proceedings of the IEEE, vol. 95, no. 7, July 2007, pp. 1394-1427.

被引用紀錄


葉育辰(2011)。廣義傅利葉演算技術應用於正交分頻多工系統之效能改進〔碩士論文,國立臺北科技大學〕。華藝線上圖書館。https://doi.org/10.6841/NTUT.2011.00352
佘家瑋(2012)。載波干涉-正交分頻多工系統之效能改進〔碩士論文,國立臺北科技大學〕。華藝線上圖書館。https://www.airitilibrary.com/Article/Detail?DocID=U0006-2008201217484600
黃信嘉(2012)。結合時域和頻域載波頻率估測法以改善正交分頻多工系統之載波間干擾〔碩士論文,國立臺北科技大學〕。華藝線上圖書館。https://www.airitilibrary.com/Article/Detail?DocID=U0006-0308201212165000

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