An anchor radio base station 310A comprises: a control unit 316A that decodes an uplink signal before decoding received from UE 10, without receiving an uplink signal before decoding from a non-anchor radio base station 310B through a backhaul network; and an interface 315A that notifies the non-anchor radio base station of necessity to transmit the uplink signal before decoding through the backhaul network in case of failure in decoding the uplink signal before decoding received from the radio terminal. A non-anchor radio base station 310B comprises: an interface 315B that transmits the uplink signal before decoding to the anchor radio base station when the non-anchor radio base station is notified of the necessity to transmit the uplink signal before decoding, by the anchor radio base station.