It is possible to provide a core network device, a radio communication base station device, and a radio communication method which can improve the radio resource use efficiency of the entire network without increasing UE battery consumption. According to the devices and the method, a user quantity counting unit (163) of UPE (160) counts the number of UE which have performed a position registration in each position registration area containing a plurality of cells. A user quantity comparing unit (164) selects MCT if the counted UE quantity is not smaller than a predetermined threshold value and SCT if the counted UE quantity is smaller than the predetermined threshold value, thereby appropriately performing switching between SCT and MCT in accordance with the UE quantity. Only when the SCT is selected by the UPE (160), eNB counts the number of users in the cell managed by the local device.