A radio resource assignment method, wherein it is determined at a predetermined timing whether a cell is congested or not; the determination result is notified to adjacent base stations; results of determination of congestion or non-congestion received from adjacent base stations are stored; when it is determined that the base station is not congested, a check is made whether or not the adjacent base stations are congested; when the adjacent base stations are congested, the use of the resource blocks is restricted to decide an empty resource block; and information on the decided resource block is notified to the adjacent base stations. When it is determined that the base station is congested, the information on the empty resource blocks received from the adjacent base stations is checked, and the empty resource blocks are assigned to mobile terminal devices within the cell.