Abstract: A method and apparatus for performing a L3handover between CNs in a packet-switched network are provided. When a UE moves from an old RAN to a new RAN, the UE sends a measurement report message including cell information to the old RAN. The old or new RAN determines whether to perform a L3 handover. If the L3 handover is required, a tunnel is established between the new RAN and a new CN. The UE performs a handover from the old RAN to the new RAN, without establishing a tunnel between the new RAN and an old CN. Upon detection of the movement of the UE, the new RAN sends a L2 handover complete message to the old RAN. After moving to the new RAN, the UE acquires a new IP address, performs the L3 handover, and communicates with the new CN through the new RAN.

Abstract: A method and apparatus is provided for communication between a first terminal capable of using both a Circuit Switched (CS) call and an Internet Protocol Multimedia Subsystem (IMS) session, and a second terminal capable of using the IMS session, in a communication system supporting a Combined CS call and IMS session (CSI service). If the second terminal sends a Session Initiation Protocol (SIP) request (INVITE) message to originate a voice service or a multimedia service including the voice service with the first terminal, a CSI Application Server (AS) of an IMS domain managing the first terminal separates a voice service-related component included in the request message from a multimedia service-related component, and generates and sends first and second request messages to the first terminal.

Abstract: A method and apparatus for performing an inter-RAN L2 handover and an inter-CN L3 handover in a packet-switched network are provided. When a UE connected to an old CN through the old RAN moves to a new RAN belonging to a new CN, an old RAN sends a handover required message to a new RAN. The new RAN acquires a new IP address for the UE from the new CN and sends a handover command message including the new IP address to the old RAN. The old RAN forwards the handover command message comprising an address of the new RAN to the UE. The UE performs an inter-RAN handover in response to the handover command message, to communicate with the old CN through the new RAN and performs an inter-CN handover based on the new IP address to communicate with the new CN through the new RAN.

Abstract: A method and apparatus performs handover from an OFDM-based E-UMTS system to a CDMA-based UMTS system. A UE in communication with a PDN via the E-UMTS system, measures signal strength of the UMTS system, and sends a measurement report message indicating the measured signal strength to the E-UMTS system. A radio access network (E-RAN) of the E-UMTS system, determines whether to perform handover from the E-UMTS system to the UMTS system based on the measured signal strength. If the handover is to be performed, a core network (E-CN) of the E-UMTS system generates a PDP context and an MM context for the UE in response to a handover request from the E-RAN. The E-CN sets up a data tunnel for the UE to a GGSN of the UMTS system using the PDP/MM context. After setting up the data tunnel, the E-CN sends to the UE a handover command message including information on a radio bearer (RB) to be used by the UE to access the UMTS system. The UE accesses the UMTS system using the RB information.

Abstract: A method for controlling a rate of a voice service in a mobile communication system supporting the voice service via a packet network. The method includes the steps of receiving a control message at a terminal from a radio network controller (RNC); if the control message indicates control of a downlink rate, determining a downlink rate according to the control message; setting a Change Mode Request (CMR) field of an uplink Voice over Internet Protocol (VoIP) packet according to the downlink rate, and transmitting the uplink VoIP packet from the terminal to the RNC; if the received control message indicates control of an uplink rate, determining an uplink rate according to the control message; and generating an uplink VoIP packet including uplink voice data generated according to the determined uplink rate and frame type (FT) information indicating the determined uplink rate, and transmitting the uplink VoIP packet from the terminal to the RNC.

Abstract: A system and method are provided for acquiring service information in an IP Multimedia Subsystem (IMS) network, which includes the steps of transferring, by a Mobile Station (MS), an IMS registration request message to the IMS network in order to use an IMS service, the MS supporting a CSI (Combinational CS (Circuit Switching) and IMS) service, and receiving a response message corresponding to the IMS registration request message from the IMS network and checking service information included in the response message.

Abstract: A method and apparatus for, upon generation of an event triggering a change in the state of a UE participating in a call, sending service information changed due to the state change to the other participating entity and notifying each user of the service information are provided. When a state change event occurs to a UE, the UE checks its available services and sends a message including service information indicating the available services to the other entity connected to the UE. Therefore, the other entity has knowledge of the actual available services of the UE in a changed environment.

Abstract: A method and apparatus for transmitting User Equipment (UE) capability information required for provisioning of a service to a network before a UE requests the service are provided. Before an outgoing or incoming call setup is requested for the UE, a signaling connection is established between the UE and a core network (CN) node to which the UE belongs. After the signaling connection is established, a message including UE capability information of the UE is received and stored for use when the call setup is requested.

Abstract: A seamless handoff system and method reduces delay and packet loss during handoff of user equipment (UE) from a Wireless Local Area Network (WLAN) network to a Universal Mobile Telecommunication System (UMTS) network. The handoff system and method performs pre-registration and pre-authentication processes before the occurrence of a handoff, buffers packets being delivered to a UE during a handoff period, and forwards the buffered packets to the UE after completion of the handoff, thereby reducing packet loss that can occur during handoff.

Abstract: A system and method for enabling fast authentication for a UE when a handoff occurs during a service in a UMTS-WLAN interworking network are provided. When the UE moves from the UMTS network to the WLAN or vice versa, it can advantageously reuse authentication information used in the old network for authentication and data encryption in the new network.

Abstract: A communication method and apparatus using the IP address of a gateway for an MN in a VPN are provided. When the MN is to access the VPN, the gateway acting an FA in the VPN performs a Mobile IP registration on behalf of the MN and is allocated a HoA for the MN from an HA. Therefore, the number of addresses required for the Mobile IP registration of the MN is reduced and overlap between an IP-in-IP tunnel for Mobile Internet and an IPsec tunnel for the VPN is avoided. As a result, packet transmission overhead is reduced.

Abstract: A method and system for providing information on mobile communication network-WLAN interworking are provided. In the mobile communication network-WLAN interworking system, interworking WLAN information is broadcast from a mobile communication network to a dual terminal, which has a mobile communication network interface and a WLAN interface. Upon receipt of a broadcasting message including information on an interworking WLAN, the dual terminal turns on its WLAN module and periodically scans for a nearby WLAN in a power save mode. Upon receipt of a broadcasting message including no interworking WLAN information, the dual terminal turns off the WLAN module.