於無線通訊系統中，由於通道所造成之衰減會導致訊號失真，因此處理通道之效應已廣泛的被討論。本篇論文以常數模演算法為基礎之空時區塊編碼(Space-Time Block Code)多輸入多輸出(Multiple-Input Multiple-Output, MIMO)單載波頻率等化系統(Single-Carrier Frequency-Domain Equalization, SC-FDE)進行通道估測，於接收端使用一切換準則，此切換準則會根據目前通道特性於盲目(Blind)通道估測法與決策迴授(Decision Feedback)估測法之間作切換進行通道估測，進而增加系統效能。根據模擬結果顯示，在空時區區塊編碼多輸入多輸出單載波頻率等化系統下使用盲目通道估測法與決策迴授法之間作自動切換的方式會得到較僅使用盲目通道估測法或決策迴授法更佳的性能。

The time-varying channel environment can lead to signal distortion in a wireless system, therefore, how to deal with the effects of a mobile channel has been widely studied. This thesis studies a multiple-input multiple-output (MIMO) constant modulus algorithm based semi-blind single-carrier frequency-domain equalizer (SC-FDE) system which adopts space-time block code (STBC) for MIMO channel equalization. At the receiver, an automatic switching scheme is applied based on the present channel status to switch the channel tracking algorithm between blind channel estimation and decision feedback estimation method in order to improve the system performance. From simulation results, we show that the switching method for channel estimation in the MIMO STBC SC-FDE system can gain better performance than that using only blind channel estimation method or decision feedback method.

[1] J. Coon, J. Siew, M. Beach, A. Nix, S. Armour, and J. McGeehan,“A comparison of MIMO-OFDM and MIMO-SCFDE in WLAN
environments,”in Proc. GLOBECOM 2003, vol. 6, Dec. 2003, pp.3296–3301.
[2] D. Falconer, S. Ariyavisitakul, A. Benyamin-Seeyar, and B. Eidson,“Frequency domain equalization for single-carrier broadband wireless systems,”IEEE Commun. Mag., vol. 40, no. 4, pp. 58–66, Apr. 2002.
[3] H. Sari, G. Karam, and I. Jeanclaude, “Transmission techniques for digital terrestrial TV broadcasting,”IEEE Commun. Mag., vol. 33, no. 2, pp. 100–109, Feb. 1995.
[4] 3rd Generation Partnership Project (3GPP); Technical Specification Group Radio Access Network; Physical Layer Aspects for Evolved TRA,http://www.3gpp.org/ftp/Specs/html-info/25814.htm.
[5] F. Pancaldi, G. Vitetta, R. Kalbasi, N. Al-Dhahir, M. Uysal, and H. Mheidat, “Single-carrier frequency domain equalization,”IEEE Signal Process. Mag., vol. 25, no. 5, pp. 37–56, Sep. 2008.
[6] R. Murch and K. Letaief, “Antenna systems for broadband wireless access,”IEEE Commun. Mag., vol. 40, no. 4, pp. 76–83, Apr. 2002.
[7] S. Alamouti, “A simple transmit diversity technique for wireless communications,”IEEE J. Select. Areas Commun., vol. 16, no. 8, pp. 1451–1458, Oct. 1998.
[8] V. Tarokh, A. Naguib, N. Seshadri, and A. Calderbank, “Space-time codes for high data rate wireless communication: performance criteria in the presence of channel estimation errors, mobility, and multiple
paths,”IEEE Trans. Commun., vol. 47, no. 2, pp. 199–207, Feb. 1999.
[9] N. Al-Dhahir, “Single-carrier frequency-domain equalization for space-time block-coded transmissions over frequency-selective fading channels,”IEEE Commun. Lett., vol. 5, no. 7, pp. 304–306, July 2001.
[10] J.-s. Baek and J. soo Seo, “Efficient design of block adaptive equalization and diversity combining for space-time block-coded singlecarrier systems,”IEEE Trans. Wireless Commun., vol. 7, no. 7, pp.2603–2611, July 2008.
[11] S. Zhou and G. Giannakis, “Single-carrier space-time block-coded transmissions over frequency-selective fading channels,”IEEE Trans. Inform. Theory, vol. 49, no. 1, pp. 164–179, Jan. 2003.
[12] D. Kim, U.-K. Kwon, and G.-H. Im, “Pilot position selection and detection for channel estimation of SC-FDE,”IEEE Commun. Lett., vol. 12, no. 5, pp. 350–352, May 2008.
[13] J. Li and Y. Du, “Channel estimation schemes for sc-fde/fs system,”in IEEE Symposium on Computers and Communications, June 2006, pp. 155–160.
[14] S. Werner, M. Enescu, and V. Koivunen, “Low-complexity timedomain channel estimators for mobile wireless ofdm systems,”in IEEE Workshop on Signal Processing Systems Design and Implementation,
June 2005, pp. 245–250.
[15] M. Chiani, “Introducing erasures in decision-feedback equalization to reduce error propagation,”IEEE Trans. Commun., vol. 45, no. 7, pp. 757–760, July 1997.
[16] D. Godard, “Self-recovering equalization and carrier tracking in two-dimensional data communication systems,”IEEE Trans. Commun., vol. 28, no. 11, pp. 1867–1875, Nov. 1980.
[17] Y. Sato, “A method of self-recovering equalization for multilevel amplitude-modulation systems,”IEEE Trans. Commun., vol. 23, no. 6, pp. 679–682, June 1975.
[18] K. N. Oh and Y. O. Chin, “Modified constant modulus algorithm:blind equalization and carrier phase recovery algorithm,”in Proc. 1995 IEEE Int. Conf. Commun., vol. 1, June 1995, pp. 498–502.
[19] R. K. Martin, “Fast-converging blind adaptive channel-shortening and frequency-domain equalization,”IEEE Trans. Signal Processing, vol. 55, no. 1, pp. 102–110, Jan. 2007.
[20] S.Haykin, Communication Systems. 4thed.New York:John Wiley, Sons,Inc., 2001. [21] G. Picchi and G. Prati, “Blind equalization and carrier recovery using a "Stop-and-Go" decision-directed algorithm,”IEEE Trans. Commun., vol. 35, no. 9, pp. 877–887, Sep. 1987.
[22] A. Benveniste and M. Goursat, “Blind equalizers,”IEEE Trans. Commun., vol. 32, no. 8, pp. 871–883, Aug. 1984.
[23] C.-M. Wu, The OFDM System with a Semi -Blind Channel Tracking Algorithm. Master Thesis, Department of Communication Engineering, National Central University, Taoyuang, Taiwan, July, 2008.
[24] M. Failli, “Digital land mobile radio communications COST 207,”European Commission, Tech. Rep., 1989.
[25] Y. Li and X. Huang, “The simulation of independent rayleigh faders,”IEEE Trans. Commun., vol. 50, no. 9, pp. 1503–1514, Sep. 2002.