Advanced Low-Complexity Multicarrier Schemes Using Fast-Convolution Processing and Circular Convolution Decomposition

Filter-bank-based waveform processing has been suggested as an alternative for the plain cyclic-prefix (CP) orthogonal frequency-division multiplexing (OFDM) based schemes in fifth-generation and future wireless communication systems. This is because of the new requirements, such as asynchronous and mixed numerology scenarios supporting multi-service operation in a common framework, including enhanced mobile broadband, low-latency high-reliability communications, and low-rate machine-type communications (MTC). Nevertheless, advanced multicarrier waveforms impose significantly increased computational complexity compared to the CP-OFDM scheme. Multirate fast-convolution (FC) processing has recently been proposed as an effective implementation for advanced waveforms, such as filtered OFDM (F-OFDM) and filter-bank multicarrier (FBMC) schemes, providing extreme flexibility in the subband spectral control. In this paper, we investigate the computational complexity of FC-based waveform processing and propose two computationally efficient schemes using the idea of circular convolution decomposition. The first scheme targets at narrow bandwidth scenarios, such as MTC. The second scheme considers dense spectral use of non-overlapping subbands. Both schemes achieve significant reduction in the computational complexity compared to direct FC and polyphase filter-bank-based implementations. This reduction in the complexity is achieved without performance loss with respect to direct FC processing. Mathematical analyses are provided for both schemes, along with evaluation and comparison of the computational complexities considering F-OFDM and FBMC waveforms in long-term-evolution-like scenarios.