Filtered multitone multicarrier modulation with partially overlapping sub-channels

Future wireless networks demand multicarrier modulation schemes with improved spectrum efficiency and superior spectrum containment. Orthogonal frequency division multiplexing (OFDM) has been the favorite technique in recent developments, but due to its limited spectrum containment, various alternative schemes are under consideration for future systems. Theoretically, it is not possible to reach maximum spectrum efficiency, high spectral containment, and orthogonality of subcarriers simultaneously, when using quadrature amplitude modulation (QAM) for subcarriers. This has motivated the study of non-orthogonal multicarrier modulation schemes. This paper focuses on the filtered multitone (FMT) scheme, one of the classical configurations of filter bank multicarrier (FBMC) modulation utilizing QAM subcarrier symbols. Our main aim is to improve the spectral efficiency of FMT by introducing controlled overlap of adjacent subchannels. An analytical model is developed for evaluating the tradeoffs between spectrum efficiency and intercarrier interference (ICI) introduced by the overlap. An efficient fast convolution waveform processing scheme is adopted for the generation of the proposed waveform. It allows effective adjustment of the roll-off and subcarrier spacing to facilitate waveform adaptation in real time. Analytical studies, confirmed by simulation results, indicate that the proposed FMT system can obtain significant spectral density improvement without requiring additional ICI cancellation techniques.