在向上鍵結正交分頻多重接取系統中，載波頻率偏移將會引進載波間干擾(ICI)和多重存取干擾(MAI)，將會降低系統效能。盲目載波估計演算法中以[1]所提出的多重信號特徵(MUSIC)受到相當關注，但這個演算法在硬體時作上有兩個高複雜度的運算須克服，分別是雜訊子空間的獲得及依解析度大量蒐尋估測參數，此外在無線傳輸單位是一個偵框，而通道和在波頻率偏移應該是隨著每一個符元變化，在每一個符元時間下做一次估計是沒有效率的，在此篇論文之中，我們引用了快速資料投影法(FDPM)來獲得雜訊子空間，並設計了一個迭代多重信號特徵演算法以快速完成一個偵框長度的載波頻率偏移的估測。

In OFDMA uplink systems, carrier frequency offset (CFO) would cause inter carrier interference (ICI) and multiple access interference (MAI), and would degrade the system performance. Blind CFO estimation algorithms have been proposed in lot of papers, and [1] proposed the MUSIC algorithm with excellent performance, but the MUSIC algorithm includes two operation that are hard for hardware to implement, to acquire the noise subspace and grid search procedure that depends on search resolution, besides, the wireless communication system transmission unit is frame, but the channel and CFO will change along the symbols, so if we estimate the CFO per symbol isn’t efficiency, so in this paper, we applied a fast data projection method (FDPM) to get the noise subspace and proposed a iterative MUSIC scheme to estimate the CFO over frame rapidly.

[1] M. O. Pun, M. Morelli, and C.-C. J. Kuo, “Maximum-likelihood synchronization and channel estimation for OFDMA uplink transmissions,” IEEE Trans. on Commun., vol. 54, issue 4, pp. 726-736, April 2006.
[2] Z. Wang and Q. Yin, “Multiuser Carrier Frequency Offsets Estimation for OFDMA Uplink with Generalized Carrier Assignment Scheme,” IEEE Trans. on Wireless Commun., vol. 8, issue 7, pp. 3347 – 3353, July 2009.
[3] M. Morelli, “Timing and frequency synchronization for the uplink of an OFDMA System,” IEEE Trans. Commun., vol. 52, no. 2, pp. 296-306, Feb. 2004
[4] J. Lee, S. Lee, K. J. Bang, S. Cha and D. Hong, “Carrier frequency offset estimation using ESPRIT for interleaved OFDMA uplink systems,” IEEE Trans. on Vehicular Technology, vol. 56 pp. 3227 -3231, Sep. 2007.
[5] Y. F. Wang and Y. F. Chen, “Iterative methods for blind carrier frequency offset estimation in OFDMA uplink,” in Proceedings of 4th IEEE International Conference on Circuits and Systems for Communications, 2008, pp.430-433.
[6] R Miao, J Xiong, L Gui, J Sun, “Iterative approach for multiuser carrier frequency offset estimation in interleaved OFDMA uplink,” IEEE Trans. Consumer Electronics., vol. 55, issue 3, pp. 1039-1044, Sep. 2009.
[7] Yang Lu and S. Attallah, “Adaptive noise subspace estimation algorithm suitable for VLSI implememtation,” IEEE Sig. Proc. Letter, vol. 16, issue 12, pp. 1075-1078, Sep. 2009.
[8] Z. Cao, U. Tureli and P. Liu, “Optimum subcarrier assignment for OFDMA uplink,” in Proc. Conference Record of the Thirty-Seventh Asilomar Conference on Signals, Systems and Computers, Nov. 2003, vol. 1, pp.708-712.
[9] Z. Cao, U. Tureli and Y. Yao, "Deterministic multiuser carrier- frequency offset estimation for interleaved OFDMA uplink," IEEE Trans. Commun., vol. 52, no. 9, pp. 1585-1594, Sep. 2004.
[10] B. Ramakrishnan, "Matched nonlinearities for frame synchronisation in presence of frequency offsets," IEE Electronics Letters, vol.45, issue 4, pp.236-237, Feb. 2009.
[11] N. L. Owsley, “Adaptive data orthogonalization,” in ICASSP’1978, 1978, pp. 109–112.
[12] G. Xu and T. Kailath, “Fast subspace decomposition,” IEEE Trans. on Signal Process., vol. 42, no. 3, pp. 539–551, Mar. 1994.
[13] F. Hansen and P. Y. Yalamov, “Computing symmetric rank-revealing decompositions via triangular factorization,” SIAM J. Matrix Analysis Appl., vol. 23, no. 2, pp. 443–458, 2001.
[14] J. F. Yang and M. Kaveh, “Adaptive eigensubspace algorithms for direction or frequency estimation and tracking,” IEEE Trans. Acoust.,Speech, Signal Process., vol. 36, pp. 241–251, Feb. 1988.
[15] I. Karasalo, “Estimating the covariance matrix by signal subspace averaging,” IEEE Trans. Acoust., Speech, Signal Process., vol. 34, pp.8–12, Feb. 1986.
[16] B. Yang, “Projection approximation subspace tracking,” IEEE Trans. on Signal Process., vol. 43, pp. 95–107, Jan. 1995.
[17] T. Chonavel, B. Champagne, and C. Riou, “Fast adaptive eigenvalue decomposition: A maximum likelihood approach,” Signal Process., vol. 83, pp. 307–324, 2003.
[18] X.G. Doukopoulos and G. V. Moustakides, “Fast and stable subspace tracking,” IEEE Trans. on Signal Proc. vol. 56, issue 4, pp. 1452 -1465 , Mar. 2008.
[19] X. G. Doukopoulos and G. V. Moustakides, “The fast data projection method for stable subspace tracking,” in Proc. EUSIPCO, Sep. 2005
[20] A. Barabell, “Improving the resolution performance of eigenstructure-based direction-finding algorithms”, in: Proceedings of the ICASSP’83, Boston, MA, USA, pp. 336–339, April 1983
[21] R. Roy, A. Paulraj and T. Kailath, “ESPRIT - a subspace rotation approach to estimation of parameters of cisoids in noise,” IEEE Trans. Acoust. Speech Signal Process. 34, pp. 1340–1342,Oct. 1986.
[22] R. Roy, T. Kailath, “ESPRIT: estimation of signal parameters via rotational invariance techniques,” IEEE Trans. Acoust. Speech Signal Process. 37, pp. 984–995, July 1989.
[23] M. Pesavento, A.B. Gershman, K.M. Wong, “Direction fnding using partly calibrated sensor arrays composed of multiple subarrays,” IEEE Trans. Signal Process. 50, pp. 2103–2115, Sep. 2002.
[24] F. Gao, A.B. Gershman, “A generalized ESPRIT approach to direction-of-arrival estimation,” IEEE Signal Process. Lett. 12, pp. 254–257, Mar. 2005.
[25] B. Friedlander, “The root-MUSIC algorithm for direction fnding with interpolated arrays,” Signal Processing 30, pp.15–25, 1993.
[26] F. Belloni, A. Richter, and V. Koivunen, “DOA estimation via manifold separation for arbitrary array structures,” IEEE Trans. Signal Process., vol. 55, no. 10, pp. 4800–4810, Oct. 2007.
[27] Z. Cao, U. Tureli, Yu-Dong Yao, and P. Honan, “Frequency synchronization for generalized OFDMA uplink,” in Proc. IEEE Global Telecomm. Conf., Nov. 2004, vol.2, pp. 1071-1075.
[28] M. R‥ ubsamen, A.B. Gershman, “Direction-of-arrival estimation fornon-uniform sensor arrays: from manifold separation to Fourier domain MUSIC methods,” IEEE Trans. Signal Process. 57, pp. 588-599, Feb. 2009.
[29] P. Stoica and A. Nehorai, “MUSIC, maximum likelihood,and Cramer-Rao bound,” IEEE Trans. on Acoustics, Speech and Signal Proc., vol. 37, no. 5, pp. 720-741, May 1989.
[30] WiMAX Forum® Mobile Release 1.0 Channel Model
[31] Y. R. Zheng and Cengshan Xiao, "Improved models for the generation of multiple uncorrelated Rayleigh fading waveforms," Communications Letters, IEEE , vol.6, no.6, pp. 256-258, June 2002.