OFDM: Orthogonal Frequency Division Multiplexing
OFDM is like having thousands of tiny radio stations broadcasting in parallel, each carrying a small piece of your data. It's how WiFi, 4G, and 5G achieve blazing speeds.
Toggle to see how all subcarriers add together into the transmitted waveform.
| Standard | Channel BW | Subcarrier Spacing | FFT Size | CP Duration |
|---|---|---|---|---|
| 802.11a/g | 20 MHz | 312.5 kHz | 64-pt | 800 ns |
| 802.11n/ac | 20–160 MHz | 312.5 kHz | 64–512-pt | 800 ns |
| 802.11ax (WiFi 6) | 20–160 MHz | 78.125 kHz | 256–2048-pt | 800–3200 ns |
| LTE (4G) | 1.4–20 MHz | 15 kHz | 128–2048-pt | 4.7 μs |
| 5G NR (FR1) | 5–100 MHz | 15–60 kHz | 256–4096-pt | 0.59–4.7 μs |
| DVB-T2 | 6–8 MHz | 2.7–111 kHz | 1K–32K-pt | 28–532 μs |
First WiFi to use OFDMA, assigning subsets of subcarriers to different users for dense deployments.
Downlink OFDMA with 15 kHz subcarrier spacing. 1,200 data subcarriers in 20 MHz. SC-FDMA uplink reduces handset PA demands.
Scalable numerology from 15 kHz to 240 kHz subcarrier spacing. Supports beamforming on thousands of antennas per base station.
Digital terrestrial broadcast uses up to 32,768 subcarriers for maximum frequency diversity in single-frequency networks (SFN).
Discrete Multi-Tone (DMT) — OFDM on copper telephone pairs. VDSL2 uses 4,096 subcarriers at 4.3125 kHz spacing for gigabit DSL.
Coded OFDM broadcast. Uses 1,536 subcarriers in 1.5 MHz bandwidth. The CP handles the long multipath of urban terrain.