Please note that the content of this book primarily consists of articles available from Wikipedia or other free sources online. Orthogonal frequency-division multiplexing essentially identical to Coded OFDM and Discrete multi-tone modulation is a frequency-division multiplexing scheme utilized as a digital multi-carrier modulation method. A large number of closely-spaced orthogonal sub-carriers are used to carry data. The data is divided into several parallel data streams or channels, one for each sub-carrier. Each sub-carrier is modulated with a conventional modulation scheme at a low symbol rate, maintaining total data rates similar to conventional single-carrier modulation schemes in the same bandwidth.