A base transceiver station includes a baseband signal processor outputting a frequency notification signal indicating a carrier frequency for modulating a baseband signal, in combination with a baseband signal and a radio transmitter and receiver modulating the baseband signal from the baseband signal processor with the carrier frequency designated by the frequency notification signal so as to produce a radio transmission signal. By allowing the baseband signal processor to output the baseband signal and the frequency notification signal to the radio transmitter and receiver, the radio transmitter and receiver is immediately informed of the carrier frequency for modulation of the arriving baseband signal so that the radio transmitter and receiver is capable of generating a radio transmission signal efficiently and properly.