A method performed by a BS for cell selection or reselection is provided. The method includes transmitting, to a UE, allowed NPN information that is in a form of a CAG ID list or in a form of an SNPN ID list; and transmitting, to the UE, NPN information and area information associated with the NPN information via a SIB1, the NPN information including an NPN ID list. In a case that the allowed NPN information is in the form of the CAG ID list, the allowed NPN information enables the UE to perform a first procedure. In a case that the allowed NPN information is in the form of the SNPN ID list, the allowed NPN information enables the UE to perform a second procedure. ABS using the method is also provided.