ABSTRACT
Orthogonal frequency-division multiplexing (OFDM) is an effective modulation scheme to combat ISI in a high-rate environment. By using parallel orthogonal subcarriers along with cyclicprefix, ISI can be removed completely as long as the cyclic-prefix is larger than the maximum delay spread of the channel [4]. OFDM can also be used as an effective multiple access scheme [4,5]. In particular, orthogonal frequency-division multiple-access (OFDMA) has been widely considered as one of the most promising multiple access schemes for the next-generation systems [4,5]. OFDMA has been adopted in the 3GPP-LTE (long-term evolution) [6] and IEEE 802.16e [7] specifications.
