A signaling processing method for allocating a UATI (Unicast Access Terminal Identifier) to a given AT (Access Terminal) in a mobile communication system including ANs (Access Networks) each having an BS (Access Network Controller), for communicating by radio with ATs, and at least one DLR (Data Location Register) connected to BSs, for storing a plurality of UATIs, which can be allocated to the ATs, and managing the remaining UATIs that are not allocated. Upon receipt of a UATI Request message from the AT, the BS transmits a UATI Allocate Request message to the DLR. Upon receipt of the UATI Allocate Request message, the DLR allocates one of the remaining UATIs to the AT and transmits a UATI Allocate Response message including the allocated UATI to the BS. Upon receipt of the UATI Allocate Response message, the BS transmits a UATI Allocate message including the allocated UATI to the AT.