A radio access bearer in a mobile communication system is controlled by disposing a radio resource control layer having radio access bearers in a user side, disposing a radio link control layer, a media access control layer, and a physical layer in the user side beneath the radio resource control layer in succession, measuring a traffic volume of the media access control layer and radio link control layer in the user side by using the media access control layer in the user side to produce traffic volume measurements, comparing the traffic volume measurements to at least one of an upper critical value and a lower critical value provided to the media access control layer in the user side from a radio resource control layer in a network side of the communication system through the radio resource control layer in the user side of the system, and forwarding a comparison result and the traffic volume measurements to the radio resource control layer in the network side through the radio resource control layer in the user side, and controlling the radio access bearer in the user side through the radio resource control layer in the network side according to a result of the comparison.