盲蔽式載波頻率偏移估測法於正交分頻多重存取系統效能分析

Performance Analysis of Blind Carrier Frequency Offset Estimator in OFDMA Systems

王思尹(Szu-Yin Wang)

指導教授 ： 呂振森

國立臺北科技大學/電資學院/電機工程系研究所/碩士(2013年)

https://doi.org/10.6841/NTUT.2013.00440

摘要

正交分頻多重存取(OFDMA)技術提供良好的頻譜效益與可靠的多重存取，以避免多路徑傳輸的影響。載波頻率偏移（CFO）對於OFDMA系統影響很大，會因為不同使用者載波頻率偏移而產生載波間干擾（ICI）與多用戶存取干擾（MAI），使系統效能大幅降低。本論文針對接收端本地震盪器為非理想狀態所造成的頻率偏移進行研究，使用盲蔽式最小重建錯誤估測法(MRE)，探討載波頻率偏移在正交分頻多重存取系統的影響。為避免MAI干擾，選用區塊(Block)載波配置法，使用MRE載波頻率偏移估測法結合MAI干擾消除法來改善系統效能。由電腦模擬分析，此估測法能準確的估測出載波頻率偏移，以提升系統效能。

關鍵字

正交分頻多重存取 ； 載波頻率偏移 ； 最小重建錯誤估測法 ； 多用戶存取干擾

並列摘要

The technique of orthogonal frequency division multiple access (OFDMA) has the excellent bandwidth efficiency and good resistance to multi-path effects while providing reliable multiple access capability. However, the performance of the OFDMA system is extremely influenced by carrier frequency offsets (CFO). The carrier frequency offset of each user will result in both inter-carrier interference (ICI) and multiple access interference (MAI) which causes severe degradation on the system performances. In this thesis, we focus on the carrier frequency offsets induced by the imperfection of local oscillator’s frequency at receiver in OFDMA systems. We investigate the effects of carrier frequency offsets in the OFDMA system by using the blind minimum reconstruction error (MRE) estimation. To avoid the effect of multiple access interference, we choose the block carrier assignment scheme and use the MRE carrier frequency offset estimation method integrating with MAI cancelling methods to improve the system performance. According to the computer simulations, this method gives good estimation of CFOs and therefore increases the system’s performance.

並列關鍵字

OFDMA ； carrier frequency offset ； minimum reconstruction error estimation ； multiple access interference

參考文獻

[1] R. W. Chang, “Synthesis of band-limited orthogonal signals for multichannel data transmission,” Bell systems Technical Journal, vol. 46, pp. 1775-1796, December 1966.

[4] Li. Ye(EDT) Stuber Gordon, Orthogonal Frequency Division Multiplexing for Wireless Communications., Atlanta :Baker & Tayl, pp. 113-139, 2006.

[5] M. Morelli , C.-C. J. Kuo and M.-O. Pun “Synchronization techniques for orthogonal frequency division multiple access (OFDMA): A tutorial review”, Proc. IEEE, vol. 95, no. 7, pp.1394 -1427 2007.

[6] W. Zhang , X.-G. Xia and P. C. Ching "Clustered pilot tones for carrier frequency offset estimation in OFDM systems", IEEE Trans. Wireless Commun., vol. 6, no. 1, pp.101 -109 2007.

[7] Yuping Zhao and Sven-Gustav Häggman, “Intercarrier Interference Self-Cancellation Scheme for OFDM Mobil Communication Systems,” IEEE Transaction on Communications, vol. 49, no.7, pp. 1185-1191, July 2001.