Each of a plurality of first radio units are installed in a plurality of first cells making up a first area, each of a plurality of second radio units are installed in a plurality of second cells making up a second area being separated from the first area, a first radio control unit is constantly connected to a plurality of the first radio units that serve about half of traffic peak in the first area and constantly connected to a plurality of the second radio units that serve about half of traffic peak in the second area, a second radio control unit is constantly connected to the remaining plurality of the first radio units and constantly connected to the remaining plurality of the second radio units, and an upper controller is connected to the first radio control unit and the second radio control unit.