A Family of MMSE-Based Decision Feedback Equalizers and Their Properties for FBMC/OQAM Systems

Filter bank multi-carrier based on offset quadrature amplitude modulation (FBMC/OQAM) suffers from inter-symbol interference and inter-subchannel interference in multi-path fading channels. By exploiting the special structures of the FBMC/OQAM signal and the resulting correlation matrix and assuming perfect estimation of channel and noise power, we study the properties of the decision feedback equalizer (DFE) designed by the minimum mean square error criterion. The study leads to efficient and mathematically equivalent computation of DFE coefficients. Consequently, the DFE requires a smaller complexity in computing the equalizer coefficients than the linear equalizer, while achieving a significant performance gain in highly frequency-selective channels. Building upon the proposed efficient computation of DFE, we develop DFE-based detectors-namely, two-stage DFE and multi-band DFE-so that a better detection performance can be obtained more efficiently. Complexity analysis and simulation results demonstrate the efficacy of the proposed computation method and the DFE-based detectors.