On Symmetry Properties of Intrinsic Interference in FBMC-OQAM Systems

Filter bank multicarrier with offset quadrature amplitude modulation (FBMC-OQAM) is a modulation technique which is widely considered as a strong contender to replace cyclic prefixed orthogonal frequency division multiplexing (CP-OFDM), for the future 5th generation (5G) of mobile wireless communication networks. FBMC-OQAM exhibits good spectral confinement properties, high spectral efficiency and immunity to synchronization errors, mainly due to its prototype filter's localization properties. But these desirable traits come with the loss of orthogonality, rendering it only orthogonal for real symbols with imaginary interference appearing in both the frequency and time domains. In this work, we prove a set of symmetry properties of this interference for a general class of FMBC-OQAM systems, and use these relationships to derive autocorrelation matrices for interference from neighboring symbols and also for noise contributions. These matrices find application in receiver design and also in channel estimation. The derived symmetry properties are also demonstrated through numerical examples for various standard prototype filter designs.