In telecommunications , orthogonal frequency-division multiplexing ( OFDM ) is a type of digital transmission and a method of encoding digital data on multiple carrier frequencies. OFDM has developed into a popular scheme for wideband digital communication , used in applications such as digital television and audio broadcasting, DSL internet access , wireless networks, power line networks, and 4G/5G mobile communications [1] . OFDM is a frequency-division multiplexing (FDM) scheme used as a digital multi-carrier modulation method. It was introduced by Robert W. Chang of Bell Labs in 1966. [2][3][4] In OFDM, multiple closely spaced orthogonal subcarrier signals with overlapping spectra are transmitted to carry data in parallel. [5] Demodulation is based on Fast Fourier Transform algorithms. OFDM was improved by Weinstein and Ebert in 1971 with the introduction of a guard interval , providing better orthogonality in transmission channels affected by multipath propagation.[6] Each subcarrier (signal) is modulated with a conventional modulation scheme (such as quadrature amplitude modulation or phase shift keying ) at a low symbol rate . This maintains total data rates similar to conventional single-carrier modulation schemes in the same bandwidth.