Method and apparatus for setting up call in mobile communication system

摘要

The time required to set up a voice call in an exemplary embodiment, in which Circuit Switched Fallback (CSFB) is used, is reduced to provide a voice call service to a User Equipment (UE) in a Long Term Evolution (LTE) system. If a voice call occurs in a UE while the UE accesses the LTE system, the UE using CSFB switches to a 2G/3G legacy system, recycles system information for a 2G/3G cell that the UE has accessed before, and immediately proceeds with voice call setup without receiving system information unnecessary for a CSFB process.

主权项

1. A method for performing a circuit switched fallback (CSFB) procedure by a terminal in a mobile communication system, the method comprising:
receiving a first control message including switching information from a first communication system based on a packet switched service to a second communication system based on a circuit switched service, from a base station; switching a serving cell from a first cell of the first communication system to a second cell of the second communication system based on the switching information; receiving first information from the second cell; determining whether second information of the second cell is stored; determining whether the second information has been changed based on a value tag included in the first information if the second information is stored; and transmitting a second control message without reception of the second information to the second cell if the value tag indicates that the second information has not been changed, wherein the second information is previously acquired in the second communication system.