FBMC-OQAM for 6G-narrow band communications: advanced receivers with short prototype filter

Abstract This study investigates the coexistence of NarrowBand Internet of Things (NB-IoT) systems utilizing Filter Bank Multi-Carrier with Offset Quadrature Amplitude Modulation (FBMC-OQAM). We analyze the fundamental trade-off between prototype filter length, end-to-end latency, and spectral efficiency, demonstrating that a shorter filter reduces latency by 50% at the cost of a 12.9% spectral efficiency penalty due to increased Inter-Carrier Interference (ICI). To mitigate this interference, we introduce a computationally efficient FREquency SHift (FRESH) equalizer that exploits signal cyclostationarity. We evaluate the ability of three equalizers–linear, widely linear (WL), and the proposed FRESH—to suppress ICI under different signal conditions. Our results show that the FRESH equalizer outperforms both conventional approaches, especially for non-second-order circular (NSOC) and cyclostationary signals, while maintaining a favorable complexity-performance balance. This work highlights the potential of FRESH equalization as an effective solution for latency-critical NB-IoT systems in beyond 5G networks.