What is OFDM?
OFDM is the multicarrier modulation technique at the heart of 4G LTE and 5G NR. It divides a wideband channel into hundreds or thousands of narrow, mutually orthogonal subcarriers transmitted simultaneously — each carrying an independently modulated data symbol. Orthogonality between subcarriers eliminates inter-carrier interference despite spectral overlap.
How Does OFDM Work?
Data bits are mapped to modulation symbols (QPSK, 16-QAM, 64-QAM, 256-QAM) and assigned to subcarriers. An Inverse FFT (IFFT) converts the frequency-domain symbols into a time-domain signal. A Cyclic Prefix is added to combat multipath interference. At the receiver, the CP is discarded, an FFT recovers all subcarriers simultaneously, and each is independently equalised and demodulated.
Use Cases
Downlink in all LTE and 5G NR deployments. Uplink in 5G NR (CP-OFDM) and Wi-Fi (802.11a/g/n/ac/ax). The flexible numerology of 5G NR (varying subcarrier spacing) is a key evolution over LTE’s fixed 15 kHz spacing.
3GPP / Standards Reference
3GPP TS 38.211 (Physical Channels and Modulation), IEEE 802.11 series
Related Terms
CP-OFDM | DFT-s-OFDM | QAM | PAPR | Numerology | ISI
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This glossary entry is part of the 5GWorldPro Complete 5G Glossary. To go deeper into 5G architecture and technology, explore our 5G Training courses.
