Communication terminal apparatus, base station apparatus and communication method

A base station apparatus that transmits a radio signal to a communication terminal apparatus, said communication terminal apparatus receiving the radio signal, detecting a reception quality of the received signal, selecting a modulation method applicable to the radio signal from a plurality of modulation methods of varying transmission rates in accordance with the detected reception quality, and transmitting a command to request the selected modulation method to the base station apparatus, said base station apparatus comprising:

• a receiver that receives said command;
• a changer that changes the modulation method requested by the command with another modulation method;
• a modulator that modulates the radio signal by said another modulation method;
• a transmitter that transmits the modulated signal to the communication terminal apparatus;
• and
• a detector that detects a Doppler frequency from a received signal,
• wherein said changer changes the modulation method requested by the command with said another modulation method of a lower transmission rate in response to an increase in the detected Doppler frequency.