A radio resource control method in a mobile communication system for determining a transmission rate of user data transmitted by a mobile station via an uplink based on a maximum allowable transmission rate, include: notifying, at a radio network controller, an averaging period or a forgetting factor to a radio base station; calculating, at the radio base station, an averaging value of the maximum allowable transmission rates or an averaging value of parameters relating to the maximum allowable transmission rate, based on the averaging period or the forgetting factor; signaling, at the radio base station, the calculated averaging value to the radio network controller; and controlling, at the radio network controller, a radio resource in the radio base station, based on the signaled averaging value.