Patent ID: 7839841

Claim:
A mobile station configured to receive a Voice over Internet Protocol (VoIP) service based on an IP Multimedia Subsystem (IMS) by interfacing with a VoIP gateway when the mobile station is located indoors and by interfacing with a broadband wireless access system when the mobile station is located outdoors, the mobile station comprising: a cordless phone signal processor for exchanging a cordless phone signal with the VoIP gateway when the mobile station is located indoors; a Session Initiation Protocol (SIP) message processor for processing an SIP message exchanged with the IMS through the broadband wireless communication system; and a broadband wireless access system processor for communicating with the broadband wireless access system when the mobile station is located outdoors; wherein the SIP message processor and the broadband wireless access system processor are not driven when the cordless phone signal processor receives the cordless phone signal from the VoIP gateway, and the SIP message processor and the broadband wireless access system processor are driven when the cordless phone signal processor does not receive the cordless phone signal from the VoIP gateway.