Communication apparatus, base station, and codec mode switching method

A base station, for use in a communication system including a user equipment, a first set of user equipments including the user equipments which support a codec mode request message, and a second set of user equipments which do not support the codec mode request message, the base station comprising:

• a receiver, which, in operation, receives a notification from the user equipment of capability information indicating that the user equipment supports the codec mode request message;
• and
• a transmitter, which, in operation, transmits, to the user equipment, in response to the capability information, the codec mode request message including a codec mode, wherein the base station sends the codec mode request message only to the first set of user equipments in response to the capability information received therefrom, and does not send the codec mode request message to the second set of user equipments.