OFDM (Orthogonal Frequency-Division Multiplexing) is a digital modulation scheme that transmits data in parallel over many closely spaced, mutually orthogonal subcarriers. Splitting a high-rate stream into many low-rate subcarriers makes the signal robust to multipath fading and allows simple frequency-domain equalisation. It is the physical-layer foundation of Wi-Fi, LTE, 5G, DVB, and many other modern broadband systems.
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- The orthogonality of subcarriers, implemented efficiently with the FFT, lets them overlap in frequency without interference, maximising spectral efficiency. A cyclic prefix absorbs multipath delay spread to prevent inter-symbol interference, while the main drawbacks are sensitivity to frequency offset and a high peak-to-average power ratio that stresses transmitters.