This paper proposes a semi-blind algorithm for frequency-domain (post-FFT) soft-decision concurrent equalization in OFDM systems. The objective is to improve system performance by increasing data throughput or decreasing power requirements, when compared with pilot based conventional channel estimation techniques. The Constant Modulus Algorithm and the Soft Decision-Directed technique were concurrently employed to adjust the coefficients of a post-FFT equalizer bank. The algorithm works in a semi-blind mode because it uses channel information, obtained from pilot subcarriers, to initialize and to supervise the equalizer bank when pilots are present, otherwise remaining blind in the equalization process. To support such a concurrent equalization, the system should provide pilot subcarriers only in the first symbol of each OFDM super-frame, allowing algorithm initialization when the receiver is turned on. In the remaining super-frame symbols, pilot subcarriers can be suppressed to increase the overall system throughput. © 2009 IEEE. 211216IARIAColieri, S., Ergen, M., Puri, A., Bahai, A., A study of channel estimation in OFDM systems (2002) Proc. of the IEEE 56th Vehicular Technology Conf, 2, pp. 894-898. , FallHeath, R., Giannakis, G., Exploiting Input Cyclostationarity for Blind Channel Identification in OFDM Systems (1999) IEEE Trans. on Sig. Processing, 47 (3). , MarchChen, S., Chng, E., Concurrent Constant Modulus Algorithm and Soft Decision Directed Scheme for Fractionally-Spaced Blind Equalization (2004) 2004 IEEE Int. Conf. on Communications, , Paris, Francede Castro, F., de Castro, M., Arantes, D., Concurrent Blind Deconvolution for Channel Equalization (2001) IEEE Int. Conf. on Comm, ICC2001, pp. 366-371. , Helsinki, Finland, JuneD' Agostini, F., Carboni, S., de Castro, M., de Castro, F., Von Trindade, D., Adaptive Concurrent Equalization Applied to Multicarrier OFDM Systems (2008) IEEE Trans. on Broadcasting, 54 (3). , SeptemberJohnson, C.R., Schniter, P., Endres, T.J., Behm, J.D., Brown, D.R., Casas, R.A., Blind Equalization Using Constant Modulus Criterion: A review (1998) Proc. of the IEEE, 86 (10). , OctoberShun-lan, L., Ming-zeng, D., A New Blind Equalization Scheme for QAM Systems Based on Fractionally-Spaced Equalizer (2007) IEEE Int. Conf. on Comm., Circuits and Systems, Kokura, , Japan, JulyRao, W., Han, Y., Guo, Y., A New Family of Combination Blind Equalization with a New Constant Modulus Algorithm Based on Variable Slope Error Function (2006) The 8th Int. Conf. on Signal Processing, ICSP2006 Proceedings, , BeijingHadef, M., Weiss, S., A Fast Converging Concurrent Affine Projection Algorithm for Blind Multiuser Equalisation (2005) The 2nd IEE/EURASIP Conf. on DSPenabledRadio, , University of Southampton, SeptS. Chen, S. McLaughlin, P.M. Grant and B. Mulgrew, MultiStage Blind Clustering Equaliser, IEEE Trans. on Comm., 43, No. 2/3/4, February/March/Abril/ 1995Haykin, S., (1996) Adaptive Filter Theory, , 3rd ed, Prentice Hall, Upper Saddle River, New JerseyITU Radiocommunication Study Groups: Document 6E/TEMP/131-E, Guidelines and Techniques for the Evaluation of DTTB Systems, March 19, 2003