PURPOSE: To reduce the hardware and to improve the reliability by using the hardware of a supervisory channel for an idle channel when a control channel in a controller of a radio base station is at fault to allow the software to make the control channel duplicate.

CONSTITUTION: When an incoming control channel PCH and an outgoing control channel ACH of a subscriber of a travelling object are faulty due to a hardware fault caused by an equipment fault or a propagation path fault caused by fading in a radio area, idle channels S1-S3 not in use for communication are searched. Then the content of frame constitution of supervisory channels SC1-SC3 of the channels S1, S2, S3 is replaced into the content of the control channels PCH, ACH of the same constitution to cause the similar operation to the control channels duplicate effectively. Thus, the control channels are made in duplicate without increasing the hardware of the controller of a radio base station to process the control channels to improve the reliability of the system.