6.1 What You Will Learn
Multicarrier modulation schemes have been adopted in several recent communication standards. The basic concept of a multicarrier system is to split the bistream into “sub-bitstreams” and transmit them in parallel over a given channel . A distinct carrier frequency, called subcarrier or tone in this context, is associated to each sub-bitstream. This scheme is similar to frequency division multiplexing (FDM), but in multicarrier all sub-bitstreams are derived from a unique bitstream instead of being independent signal sources as typically found in FDM. In the multicarrier literature, the frequency bandwidth used by each substream is called subchannel. Each subchannel uses a bandwidth for its respective individual substream, which is smaller than the total bandwidth BW of used to transmit all substreams. This has an impact on the ISI that the channel imposes to each substream and simplifies the equalization process at the receiver.