Radio base station apparatus, mobile terminal apparatus and radio communication method

A radio communication method for a mobile communication system that performs radio communications by using a plurality of component carriers that is a system band of the LTE system, the radio communication method comprising:

• in a radio base station apparatus, coding control signals of transport blocks corresponding to a plurality of component carriers jointly;
• assigning a coded control signal to one or plural component carriers and transmitting the coded control signal;
• in a mobile terminal apparatus, separating the coded control signal from reception data received from the radio base station apparatus;
• and
• decoding the coded control signal to obtain control information of the transport blocks corresponding to the component carriers,
• wherein the coding step includes the coded control signal coded by the coding section is a variable-size signal by joint coding in accordance with a number of transport blocks assigned to a mobile terminal apparatus as a communication target and the coding section codes the control signals including information for specifying a size of the variable-size signal for two-step coding.