Explain how OFDM works and its advantages in wireless systems.

OFDM (Orthogonal Frequency Division Multiplexing) divides a wideband channel into many narrowband orthogonal subcarriers. Each subcarrier carries a portion of data at a lower rate, making them resistant to frequency-selective fading. The orthogonality (subcarrier spacing = 1/symbol duration) allows overlapping spectra without interference. Implementation uses IFFT at transmitter and FFT at receiver. A cyclic prefix (guard interval) eliminates inter-symbol interference from multipath. Advantages: robust against multipath fading, high spectral efficiency, easy equalization (single-tap per subcarrier), and flexible resource allocation. Used in WiFi, LTE, 5G NR, and DVB.