Communications apparatus and communications system using multicarrier transmission mode

A base station accommodated in a communications system for exchange of information with a mobile station by a multicarrier transmission mode, the base station comprising:

• a transmission data generator configured to generate frequency band information indicating which frequency band is to be used for transmission of data information with a mobile station;
• and
• a transmitter configured to transmit the frequency band information by using a specific frequency band which is set from among a plurality of frequency band assigned to the communications system, and to transmit data information by using at least one frequency band set from among said plurality of frequency bands;
• wherein
• the frequency band set as said at least one frequency band set from among said plurality of frequency bands, other than the specific frequency band, is made variable, wherein at the time of establishing the wireless channel, the frequency band usable by the mobile station is restricted, and said at least one frequency band, other than the specific frequency band, are dynamically assigned within that restricted frequency band.