Low-Complexity Symbol Reconstruction Based on Direct Symbol Decision for FBMC-OQAM Systems

In this paper, we propose a series of low-complexity symbol reconstruction methods for filter-bank multicarrier with offset quadrature amplitude modulation (FBMC-OQAM) systems, where the key is direct symbol decision. Specifically, by analyzing the distribution characteristics of the demodulated OQAM symbols at the receiver, we firstly propose an interference avoidance based direct symbol decision (IAD) method that employs dual pilot symbols, avoiding the interference term and eliminating the need for guard symbols. Then, we observe that the decision coefficients on each subcarrier can be obtained from a straight line, which is determined by the demodulated OQAM symbols of multiple identical pilot symbols. Based on this, we propose a line fitting based IAD (LF-IAD) method that improves the symbol reconstruction performance by utilizing multiple identical pilot symbols. To minimize the symbol distortion, we further propose a minimum symbol distortion based IAD (MIAD) method and a line fitting based MIAD (LF-MIAD) method. Through complexity analysis, we show that all proposed methods have lower complexities than the traditional interference approximation method (IAM). Simulation results also demonstrate that both the proposed LF-IAD and LF-MIAD methods achieve significant bit error ratio (BER) perfor-mance improvement.