Independent component analysis for phase and residual frequency offset compensation in oqam multicarrier systems

Phase noise in the offset quadrature amplitude modulation (OQAM) multicarrier system results in not only constellation rotation but also crosstalk from the unique intrinsic imaginary interference (IMI). Therefore, the method for phase and residual frequency offset (RFO) compensation should be designed specifically to address this. In this article, we exploit the statistical difference of the OQAM signal and the IMI, and propose a novel independent component analysis (ICA) based method for phase and RFO compensation. It is proved that the signal exhibits the minimal entropy with the probability distribution deviating from the Gaussian one the most when the phase is correctly compensated. Several metrics and a recursive algorithm are proposed to separate the signal and the IMI. Simulations and experiments are performed to verify the proposed theory and to compare the ICA method with modified blind phase search (M-BPS), constellation classification (CC), and Kalman filtering (KL). It is shown that the ICA method exhibits significantly better tolerance to the laser linewidth and RFO than CC and KL, and greatly reduces the complexity compared to M-BPS. Therefore, the proposed ICA method can be the most promising solution for phase and RFO compensation in OQAM multicarrier systems.