Isotropic filter design for MIMO filter bank multicarrier communications

Although orthogonal frequency division multiplexing (OFDM) has been the dominant technology for broadband communications in the past, a number of researchers have noted the shortcomings of OFDM in frequency-selective fast-fading channels, e.g., underwater acoustic channels. Hence, alternative systems that use filter banks for multicarrier (FBMC) modulation have been proposed. The widely studied FBMC systems use offset quadrature amplitude modulation (OQAM) or cosine modulated filter bank (CMFB) to maximize the transmission efficiency. However, unfortunately, such systems are not extendable to transmission over multiple-input multiple-output (MIMO) channels. The emphasis of this paper is on a class of FBMC systems in which data symbols are conventional QAM and, thus, support MIMO channels. Unlike OQAM/CMFB-based systems, the FBMC systems considered in this paper suffer some bandwidth loss. We develop a novel filter design that minimizes this bandwidth loss.