Radio network controller and mobile communication control method

In a mobile communication system, same downlink signals can be transmitted to a mobile station via a plurality of base stations. A radio network controller (100) in the mobile station includes an acquirer (100a) configured to acquire a reception quality of the downlink signal in the mobile station; a determiner (100b) configured to determine, based on an acquired reception quality, whether or not to transmit the same downlink signals to the mobile station via a first base station managing a first cell in which the mobile station is located and a second base station managing a second cell adjacent to the first cell; and an instructor (100d) configured to instruct the second base station to transmit the downlink signal to the mobile station.