ABSTRACT
Orthogonal frequency division multiplexing (OFDM) is recently becoming very popular, and has already been chosen as the transmission method for many wireless communications standards, such as the IEEE 802.11 wireless local area networks (WLAN) and IEEE 802.16 wireless metropolitan area networks (WMAN) also known as WiMAX. The basic principle of OFDM is to divide the available broadband wireless channel into a large number of narrowband orthogonal subcarriers. This enables OFDM systems to combat the effects of the channel frequency selectivity with low receiver complexity. Unfortunately, OFDM is very sensitive to time variations of the wireless channel. Channel time variations destroy the orthogonality of the OFDM subcarriers and cause energy to leak from one subcarrier to the adjacent subcarriers. The intercarrier interference (ICI) caused by this energy leakage severely degrades the performance of OFDM, and introduces an irreducible error floor.
