basic concept of OFDM is quite simple [4]–[7]. Data is transmitted in parallel on a number of different frequencies, and

as a result the symbol period is much longer than for a serial

system with the same total data rate. Because the symbol period

is longer, ISI affects at most one symbol, and equalization is

simplified. In most OFDM implementations any residual ISI is

removed by using a form of guard interval called a cyclic prefix.

When frequency division multiplexing (FDM) is used in conventional wireless systems, or wavelength division multiplexing

(WDM) is used in optical systems, information is also transmitted on a number of different frequencies simultaneously.