Radio communication base station apparatus and radio communication method used for multi-carrier communication

A base station apparatus comprising:

• an allocator configured to perform a first allocation, in which a resource block included in at least two of groups that are inconsecutive in a frequency domain among a plurality of groups is allocated to a mobile station apparatus, or a second allocation, in which consecutive resource blocks included in one of the plurality of groups are allocated to a mobile station apparatus, wherein the resource blocks, each of which is comprised of a plurality of subcarriers that are consecutive in the frequency domain, are divided into the plurality of groups, each of which is comprised of a predetermined number of the resource blocks that are consecutive in the frequency domain;
• and
• a transmitter configured to transmit, to the mobile station apparatus, control information including both information distinguishing between the first allocation and the second allocation and information indicating the resource block allocated to the mobile station apparatus.