Abstract: An apparatus and a method for supporting a communication network in a portable terminal are provided. The method includes receiving a registration confirmation message from a first base station, determining whether the first base station satisfies a switching condition to a packet switching mode, switching a mode of the portable terminal from a circuit switching mode to the packet switching mode when the first base station satisfies the switching, and registering the portable terminal in a first communication network through the first base station in the packet switching mode.

Abstract: A method and an apparatus for performing a Radio Access Technology (RAT) search for an emergency call in a terminal supported by a plurality of communication networks are provided. The method includes identifying at least one communication network which supports a voice telecommunication among the plurality of communication networks providing support in a communication-limited state in which the communication function of the terminal is limited, and performing the RAT search for the identified at least one communication network.