Patent ID: 8045985

Claim:
A method for providing a voice service without discontinuance in a mobile communication system, comprising: receiving a system information block from a first network system and checking whether the voice service is available in the first network system; if the voice service is not available in the first network system, receiving a selection from a user for whether to use the voice service through a second network system or use a packet service through the first network system; when the user selects to use the voice service through the second network system, driving a timer, changing a network system mode to the second network system, and executing a location area update; after the location area update, providing the voice service through the second network system; checking whether the timer has expired while the voice service is provided through the second network system; when the timer has expired and the user is in the middle of communication, driving the timer again and providing the voice service through the second network system; and when the timer has expired and the user is not in the middle of communication, changing the network system mode to the first network system, receiving a system information block from the first network system, and checking whether the voice service is available.