What is FBMC?
FBMC (Filter Bank Multicarrier) is an advanced multicarrier modulation technique that was considered as an alternative to CP-OFDM for 5G NR. Unlike conventional OFDM, FBMC applies per-subcarrier filtering using a bank of prototype filters, which significantly reduces out-of-band emissions and eliminates the need for a cyclic prefix — improving spectral efficiency. While 3GPP ultimately selected CP-OFDM and DFT-s-OFDM for 5G NR, FBMC remains relevant for future wireless systems and dynamic spectrum access scenarios.
How Does FBMC Work?
In FBMC, each subcarrier is individually filtered using a well-localised prototype filter (typically an IOTA or PHYDYAS filter) combined with OQAM (Offset QAM) modulation. The filter bank ensures that each subcarrier has very low sidelobes, providing excellent frequency localisation. This means FBMC signals have minimal out-of-band leakage, enabling operation in fragmented or shared spectrum without guard bands. The trade-off is increased implementation complexity (longer filter impulse response), higher latency (due to filter ramp-up/down), and challenges with MIMO integration compared to CP-OFDM.
Use Cases
Dynamic spectrum access and cognitive radio, fragmented spectrum aggregation without guard bands, coexistence between different radio access technologies, future 6G waveform candidates, and unlicensed spectrum operation.
3GPP / Standards Reference
3GPP TR 38.802 (Study on NR access technology), 5G PPP METIS-II project (waveform evaluation), IEEE literature on filter bank multicarrier techniques
Related Terms
OFDM | CP-OFDM | DFT-s-OFDM | OQAM | UF-OFDM
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