Abstract: Provided is a handover method, in which a call manager of a network having a Circuit Switching (CS) network, a Long Term Evolution (LTE) network, and an Internet Protocol Multimedia Subsystem (IMS) network, provides handover, from the LTE network to the CS network, to a terminal that uses one radio channel. The handover method includes upon receiving a request for handover from the terminal via a node of the LTE network, establishing a line to a Mobile Switching Center (MSC) of the CS network; sending, to the call manager, a request for a change in a session to another party's terminal in communication with the terminal, to establish an Internet Protocol (IP) bearer between the call manager and the other party's terminal; and sending a handover command to the terminal during the establishment of an IP bearer, to establish a radio channel to the base station of the CS network.

Abstract: A method and system for processing a call change request in an IMS are provided, in which a network entity receives a call request message requesting a first call from a calling UE, stores call information and caller information of the call request message, forwards the call request message to a called UE, acquires, upon receipt of a call change request message requesting change of the first call to a second call from the called UE during the first call, the caller information of the calling UE using an old call information included in the call change request message and the stored call information, inserts the caller information in receiver information of the call change request message, delivers the call change request message to the calling UE, and establishes the second call between the calling UE and the called UE by replacing the first call with the second call.

Abstract: A method and system in which upon occurrence of a P-CSCF failure, a network sends an IMS reregistration request message to a UE. An S-CSCF or an AS monitors a P-CSCF to detect occurrence of a failure in the P-CSCF. Upon detecting the occurrence of a P-CSCF failure, the S-CSCF or the AS sends a request message for IMS reregistration to the UEs being served by the failed P-CSCF. In this manner, the UE can continuously receive the service even though a failure occurs in the P-CSCF.

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 method for supporting a communication service of an idle mode terminal located in a common routing area in a mobile communication system that includes a Node B, an Access Gateway (AGW), and a Home Subscriber Server (HSS), and has a Long Term Evolution (LTE) network and a 3rd Generation (3G) network connected to each other to perform transmission/reception. The AGW receives tracking area information of the LTE network, including routing area information of the 3G network, from the idle mode terminal via the Node B. The AGW sends common routing area indication information and identification information of the terminal to the HSS if the routing area information is coincident with the tracking area information. The HSS stores the common routing area indication information and the identification information of the terminal, and sends a response message according to the indication information.

Abstract: Disclosed is a method and system for mutually exchanging capability information of UEs for communication between a Circuit-Switched (CS) and IMS services (CSI) UE, which can use a CS call for voice communication while using an IMS session for PS service, and an IMS UE which uses an IMS session for both voice communication and PS service. A MGCF performs interworking of capability information between a CS message and an IMS message so that the IMS UE can process UE capability information through an IMS session request/response. When a call request message containing no capability information is created from a UE not supporting capability exchange, a CSI AS transfers the call request message to a peer UE after inserting estimable capability information of the UE into the call request message, and stores capability information of the counterpart UE for the UE.

Abstract: A method and apparatus is provided for reducing a signaling overhead in routing area update performed by a mobile station in a mobile communication system. The method includes grouping cells of the mobile communication system into predetermined cell groups by the network entity, wherein each of the predetermined cell groups is a minimum unit for routing area update; determining cell group identifiers of the cell groups by the network entity; and determining metric information for determining a shape of the routing area by the network entity.

Abstract: A method and apparatus for communications of a UE using an IP address in a mobile communication system are provided. When the UE moves from an old subnet managed by an old gateway to a new subnet managed by a new gateway, the UE determines whether there are allocated radio resources. In the absence of the allocated radio resources, the UE determines whether an IP-based application service is in progress. If the IP-based application service is in progress, the UE determines to reuse an old IP address in the new subnet. If the IP-based application service is not in progress, the UE determines to use a new IP address in the new subnet. Then the UE sends to the new gateway an RAU request message including an indication indicating whether the old IP address or the new IP address will be used in the new subnet.

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: Provided is a method for optimizing a current tunnel authentication for a 3G-WLAN interworking system that includes a UE, WLAN, PDG and AAA Server, wherein the UE has been previously authenticated by the AAA Server. The method includes intimating the AAA Server to derive a TSK for a current tunnel establishment request.

Abstract: Method and system for facilitating tunnel management in the 3G-WLAN interworking systems providing dynamic configuration of maximum number of IP Security Protocol (IPsec) tunnels allowed per Internet Key Exchange (IKE) Security Association (SA) at the Packet Data Gateway (PDG) during the initial tunnel establishment procedure. Authentication Authorization and Accounting (AAA) server is notified of the new IPsec tunnel established between the user equipment (UE) and the PDG.

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.