A communication control method for a base station apparatus and a mobile terminal apparatus performing transmission and reception in a plurality of component carriers, comprising the steps of: in the base station apparatus: performing channel coding of information bits; performing a rate matching process of the coded bits after the channel coding; and transmitting transmission data to match a coded bit length after rate matching, to a mobile terminal apparatus; and in the mobile terminal apparatus: receiving the transmission data; performing channel decoding of the received data; and when an error is found with the received data, storing part of the received data in a soft buffer memory of the mobile terminal apparatus in accordance with the size of the soft buffer memory of the mobile terminal apparatus, wherein in the base station apparatus the rate matching process is performed after a certain amount of the coded bits after the channel coding are discarded, wherein the discarding process is performed in accordance with the size of the soft buffer memory corresponding to performing transmission using a single component carrier, regardless of the number of component carriers being actually used in the mobile terminal apparatus. in the base station apparatus: performing channel coding of information bits; performing a rate matching process of the coded bits after the channel coding; and transmitting transmission data to match a coded bit length after rate matching, to a mobile terminal apparatus; performing channel coding of information bits; performing a rate matching process of the coded bits after the channel coding; and transmitting transmission data to match a coded bit length after rate matching, to a mobile terminal apparatus; and in the mobile terminal apparatus: receiving the transmission data; performing channel decoding of the received data; and when an error is found with the received data, storing part of the received data in a soft buffer memory of the mobile terminal apparatus in accordance with the size of the soft buffer memory of the mobile terminal apparatus, wherein in the base station apparatus the rate matching process is performed after a certain amount of the coded bits after the channel coding are discarded, wherein the discarding process is performed in accordance with the size of the soft buffer memory corresponding to performing transmission using a single component carrier, regardless of the number of component carriers being actually used in the mobile terminal apparatus. receiving the transmission data; performing channel decoding of the received data; and when an error is found with the received data, storing part of the received data in a soft buffer memory of the mobile terminal apparatus in accordance with the size of the soft buffer memory of the mobile terminal apparatus, wherein in the base station apparatus the rate matching process is performed after a certain amount of the coded bits after the channel coding are discarded, wherein the discarding process is performed in accordance with the size of the soft buffer memory corresponding to performing transmission using a single component carrier, regardless of the number of component carriers being actually used in the mobile terminal apparatus.