Joint Prototype Filter and Symbol Distribution Optimization for Sidelobe Suppression of FBMC-OQAM Signals

A new sidelobe suppression method is proposed for filter bank multi-carrier systems using offset quadrature amplitude modulation (FBMC-OQAM), where we jointly optimize the prototype filter and the symbol distribution to minimize the normalized stopband energy of FBMC-OQAM signals. Firstly, we investigate the relationship between both the signal sidelobe and the prototype filter as well as the symbol distribution by deriving the general power spectral density (PSD) expression of the FBMC-OQAM signals of each subcarrier. Then, we investigate the impact of the prototype filter and the symbol distribution on the symbol reconstruction by deriving the inter-symbol interference (ISI) and inter-carrier interference (ICI) expressions of FBMC-OQAM systems. Based on the PSD and ISI/ICI expressions derived, we formulate and solve the joint prototype filter and symbol distribution optimization problem. Our simulations demonstrated that the proposed joint prototype filter and symbol distribution optimization method achieves lower normalized stopband energy and better sidelobe suppression of the first sidelobe than the single-parameter based prototype filter optimization methods.