在偏移正交振幅調變濾波器組多載波系統中，多重路徑通道所造成的符元間干擾與子通道間干擾對整體系統之效能通常有很大的影響。為了處理此問題，文獻中有一階段的等化方式如最小均方誤差線性等化與決策回授等化來降低上述干擾所造成的影響。另外，文獻中亦有兩階段最小均方誤差線性等化器的等化方式，其運作方式為第一階段為利用最小均方誤差線性等化器產生相鄰子通道的決策訊號來做子通道間干擾消除的處理，並不處理符元間干擾的問題；第二階段為使用最小均方誤差線性等化器來處理符元間干擾。本論文以兩階段架構為基礎，使用不同之等化方式，並與一階段架構來進行效能和複雜度之比較。本論文亦透過數學推導證明：在兩階段等化方面，第二階段的等化器係數會和文獻中一階段等化器係數具有相同的對稱性質，可同以降低計算等化器係數的複雜度。

Filter bank multicarrier (FBMC) systems based on offset quadrature amplitude modulation (OQAM) suffer from inter-symbol interference (ISI) and inter-subchannel interference (ICI) in multipath fading channels. To deal with these problems, one-stage detectors, such as linear equalization (LE) and decision feedback equalization (DFE) designed based on the minimum mean square error (MMSE) criterion, were proposed to jointly reduce the effects of ISI and ICI . Alternatively, the two-stage detector separately deals with the ICI and ISI in the first and second stage, respectively. Specifically, the first stage uses the LE to generate tentative symbol decisions on adjacent subchannels; these tentative decisions are then used to regenerate and cancel the ICI. The resulting signal is considered to be corrupted by the ISI only, which is suppressed in the second stage by the LE. In the thesis, we study the performance and complexity of the two-stage architecture by using different combinations of sub-detectors in each stage, and make comparisons with the one-stage architecture. In addition, we show that, with the MMSE criterion, the equalizer coefficients of the LE and DFE in the second stage of the two-stage structure possesses certain symmetric properties that can be exploited to cut in half the complexity of calculating the equalizer coefficients.

[1] B.R. Saltzberg,“Performance of an Efficient Parallel Data Transmission System,” IEEE Trans. Commum. Tech., vol. 15, no.6, PP. 805-811, Dec. 1967.
[2] P. Siohan, C. Siclet, and N. Lacaille, “Analysis and design of OFDM/OQAM systems based on filterbank theory,” IEEE Trans. Signal Processing, vol. 50, no. 5, pp. 1170–1183, May 2002.
[3] D.S. Walhauser, L.G. Baltar and J.A. Nossek,“MMSE subcarrier equalization for filter bank based multicarrier systems,” IEEE SPAWC 2008, pp. 525-529, Recife, 6-9 July 2008.
[4] D.S. Walhauser, L.G. Baltar and J.A. Nossek,“Adaptive equalization for filter bank based multicarrier systems,” IEEE ISCAS 2008, pp. 3098-3101, Seattle WA, 18-21 May 2008.
[5] L.G. Baltar, D.S. Waldhauser and J.A. Nossek,“MMSE subchannel decision feedback equalization for filter bank based multicarrier systems,” IEEE ISCAS 2009, pp. 2802-2805, Taipei, 24-27 May 2009.
[6] D.S. Walhauser, L.G. Baltar and J.A. Nossek,“Adaptive decision feedback equalization for filter bank based multicarrier systems,” IEEE ISCAS 2009, pp. 2794-2797 Taipei, 24-27 May 2009.
[7] A. Ikhlef and J. Louveaux,“An enhanced MMSE per subchannel equalizer for highly frequency selective channels for FBMC/OQAM systems,” IEEE SPAWC 2009, pp. 186-190, Perugia, 21-24 June 2009.
[8] M.G. Bellanger,“Specification and design of a prototype filter for filter bank based multicarrier transmission,” IEEE Int. Conf. Acoustics, Speech, and Signal Processing, vol.4, pp. 2417-2420, Salt Lake City, 07-11 May 2001.
[9] A. Viholainen, T. Ihalainen, T.H. Stitz, M. Renfors and B.G.Bellanger,“Prototype filter design for filter bank based multicarrier transmission,” IEEE, Signal Processing Conference, pp. 1359-1363, Glasgow, 24-28 Aug. 2009.
[10] C. Lele, P. Siohan, R. Legouable and J.-P. Javaudin,“Preamble-based channel estimation techniques for OFDM/OQAM over the powerline,” ISPLC 2007, pp. 59-64, Pisa, 26-28 March 2007.
[11] T. Karp and N. J. Fliege, “Computationally efficient realization of MDFT filter banks,” Proc. EUSIPCO ’96, vol. 2, pp. 1183–1186, September 1996.
[12] J. G. Andrews, S. Buzzi, Wan Choi, S. V. Hanly, A. Lozano, A. C. K. Soong, J. C. Zhang, "What Will 5G Be?" IEEE Journal on Selected Areas in Communications, vol.32, no.6, pp.1065--1082, June 2014.
[13] B. Farhang-Boroujeny, "OFDM versus filter bank multicarrier," IEEE Signal Processing Magazine, April 2011, pp. 92-112.
[14] P. Banelli, S. Buzzi, G. Colavolpe, A. Modenini, F. Rusek, A. Ugolini, "Modulation Formats and Waveforms for 5G Networks: Who Will Be the Heir of OFDM?: An overview of alternative modulation schemes for improved spectral efficiency," IEEE Signal Processing Magazine, vol.31, no.6, pp.80-93, Nov. 2014.
[15] B. Farhang-Boroujeny and R. Kempter, “Multicarrier communication techniques for spectrum sensing and communication in cognitive radios,” IEEE Commun. Mag. (Special Issue on Cognitive Radios for Dynamic Spectrum Access), vol. 46, no 4, pp. 80–85, Apr. 2008.
[16] J.Smee and Norman C. Beaulieu, “On the Equivalence of the Simultaneous and Separate MMSE Optimizations of a DFE FFF and FBF, ” IEEE Trans. Commum. Tech., vol. 45, no.2, Feb. 1997.
[17] Chun-Ting Chen, “Linear and non-linear equalization for FBMC/OQAM systems based on the criterion of minimum mean square error, ”Institute of Computer and Communication Engineering National Cheng Kung University Thesis for Master of Science, July 2016.