Mobile communication method and radio base station

A radio base station that functions as a second radio base station in a mobile communication system in which a first radio base station and the second radio base station are mixed, comprising:

• a scheduling information reception unit configured to receive scheduling information including information specifying a radio resource from the first radio base station, when the first radio base station assigns a radio resource for a control channel through which the first mobile station that is in communication in a first cell under the control of the first radio base station transmits downlink control information or uplink control information;
• and
• a radio resource assignment unit configured to assign a radio resource for a control channel through which the second mobile station that is in communication in a second cell under the control of the second radio base station transmits downlink control information or uplink control information, based on the scheduling information,
• wherein the radio resource assignment unit is configured to assign the radio resource so that a region in which the first mobile station searches for receiving the downlink control information and a region in which the second mobile station searches for receiving the downlink control information do not overlap.