Metho and apparatus for acquiring cell identifier in radio communication system

Provided is a method for acquiring a cell identifier by a source cell in a radio communication system. The method comprises the following steps: receiving information about a new cell from user equipment (UE) in the source cell; acquiring an evolved universal terrestrial radio access (ETURA) cell global identifier (ECGI) of the new cell from the UE if it is determined, based on the information about the new cell, that there is no neighbor relationship with the new cell; determining whether a public land mobile network identifier (PLMN ID) in the ECGI is included in a mapping table between a primary PLMN and a shared PLMN; and acquiring an X2 internet protocol (IP) address of the new cell from an evolved packet core (EPC) according to a result of the determination.