Orthogonal Frequency Division Multiplexing - parallel data transmission
Orthogonality: Subcarriers are spaced exactly 1/T Hz apart (where T is symbol duration). This ensures zero interference between carriers.
Parallel Transmission: Each subcarrier carries independent data. N subcarriers = N times the data rate!
FFT/IFFT: In practice, OFDM uses inverse FFT for modulation and FFT for demodulation - computationally efficient!
Cyclic Prefix: Guard interval prevents inter-symbol interference from multipath.
Applications: Wi-Fi (802.11a/g/n/ac/ax), LTE, 5G, DVB-T, DAB, xDSL.