In adjusting transmission timings of frames sequentially transmitted from a radio network controller to a base transceiver station, the frame transmission schedule is changed in appropriate manner in response to a necessary Timing Adjustment control frame (TA). In a first period of time, which is a period of ignoring the received TA, the adjustment of the transmission timings of the frames is suspended. Also, out of the first period, the first period is varied in accordance with a variety of the delayed amount in transmission between the radio network controller and the base transceiver station. There is provided a period of ignoring a first control frame to be informed from the radio base transceiver station to the radio network controller. By setting the period to be a variable value, the synchronization control is accomplished with certainty.