To provide a method of reducing a signal to interference ratio of a mobile station suitable for an environment in which electric power control does not exist.

A base station apparatus to be used for a radio communication system includes a plurality of radio cells, while each of the radio cells includes a plurality of subcarrier block sets, and each of the subcarrier block sets includes a plurality of subcarrier blocks in which each of the subcarrier blocks includes a plurality of subcarriers. The base station apparatus has: a grouping means for extracting the plurality of subcarrier blocks, and for grouping the extracted subcarrier blocks to the subcarrier block sets; and an assigning means for assigning a transmission electric power level which is different from the other subcarrier block set to at least one subcarrier block set included in the radio cell of a cell cluster in the radio cell of the cell cluster by configuring the cell cluster by the radio cell and the other radio cell adjacent to the radio cell.