A radio base station includes a step-A where a second radio access network device inside a second radio access network notifies a first radio access network device inside a first radio access network of access information comprising at least one of either load information or barring information. Step-B includes a mobile station on standby in a cell under the first radio access network device, upon moving to an area in which the cell under the first radio access network device and the cell under the second radio access network device overlap, transmits a communication initiation request signal to the first radio access network device. Step-C includes the first radio access network device decides regarding in which of the cell under the first radio access network device or the cell under the second radio access network device. The communication of the mobile station should be initiated based on the access information.