JP4654834B2 - Mobile communication system, switching center server, mobile terminal apparatus, and handover method used therefor - Google Patents

Description

  The present invention relates to a mobile communication system, an exchange server, a mobile terminal apparatus, and a handover method used therefor, and more particularly, to a communication method for moving a wireless communication network of a different communication system by installing a plurality of wireless functions in a terminal.

  Conventionally, in this type of communication method, a plurality of wireless functions are installed in a terminal, so that it is possible to move to each other corresponding to a plurality of different communication methods. In this case, when the terminal moves between different wireless communication networks and across different signal systems, the call is temporarily disconnected and accompanied by reconnection, so the terminal needs to be aware of disconnection / reconnection. It is.

  As techniques similar to the above, there are techniques for simultaneously sending data to different types of wireless systems (for example, see Patent Document 1), techniques for taking over a session for IP (Internet Protocol) communication (for example, see Patent Document 2), and the like. is there.

JP-A-2005-027119 Japanese Patent Publication No. 2004-527928

  However, with the conventional communication method described above, it is impossible to move while continuing the voice call due to the difference between the call methods. For example, CS (Circuit Switched) call processing between W-LAN (Wireless-Local Area Network) and W-CDMA (Wideband-Code Division Multiple Access) is performed by a call processing node on the W-LAN side using CSCF. (Call Session Control Function), which is different from MSC (Mobile Switching Center) which is a call processing node on the W-CDMA side.

  In addition, since the signal handled by the terminal is based on SIP (Session Initiated Protocol) on the W-LAN side and different from the CC (Call Control) basis on the W-CDMA side, a call session between the W-LAN and W-CDMA can be performed. A maintained handover cannot be realized. In addition, since said patent document 1, 2 is not the technique regarding the handover which maintained the telephone call session, said problem cannot be solved.

  Accordingly, an object of the present invention is to provide a mobile communication system, an exchange server, a mobile terminal apparatus, and a handover method used for them that can solve the above-described problems and realize a handover that maintains a call session. .

A mobile communication system according to the present invention includes a call processing node that performs call processing in a first communication area in which a communication area of a mobile terminal device is limited, and a communication area of the mobile terminal device that is wider than the first communication area. A mobile communication system including an exchange server that performs an exchange process in two communication areas,
When the mobile terminal device determines whether or not to switch to the second communication area when the quality of the first communication area deteriorates, and performs switching to the second communication area. Means for performing movement notification processing to notify the call processing node of suspension of call processing on the first communication area side and movement of the own terminal to the second communication area when judged. ,
The mobile terminal device registers from the second communication area side to the call processing node via the switching center server, and reappears from the call processing node to the mobile terminal device via the switching center server. I'm calling.

The exchange server according to the present invention constitutes a mobile communication system together with a call processing node that performs call processing in a first communication area where a call area of the mobile terminal device is limited, and the call area of the mobile terminal device is the first communication area. An exchange server that performs exchange processing in a second communication area that is wider than the communication area of
When the mobile terminal device moves to the second communication area triggered by a deterioration in quality of the first communication area, the mobile terminal device relays a registration for the call processing node from the mobile terminal device, and A re-call from the processing node to the mobile terminal device is relayed.

A mobile terminal apparatus according to the present invention performs a call processing node that performs call processing in a first communication area in which a call area is limited, and an exchange process in a second communication area in which the call area is wider than the first communication area. A mobile terminal device constituting a mobile communication system together with an exchange server,
Means for determining whether or not to switch to the second communication area when the quality of the first communication area deteriorates, and the call processing when determining to switch to the second communication area Means for performing a movement notification process for informing the node of the suspension of the call process on the first communication area side and the movement of the terminal to the second communication area;
By re-registering the call processing node from the second communication area side via the switching center server, the call processing node re-calls the call processing node via the switching center server .

The handover method according to the present invention includes a call processing node that performs call processing in a first communication area in which a call area of a mobile terminal device is limited, and a second call area that is wider than the first communication area of the mobile terminal device. A handover method used in a mobile communication system including an exchange server that performs an exchange process in a communication area of
Call processing on the first communication area side with respect to the call processing node when the mobile terminal apparatus determines to switch to the second communication area when the quality of the first communication area deteriorates A movement notification process for communicating the suspension of the terminal and the movement of the terminal to the second communication area,
The mobile terminal device performs registration for the call processing node from the second communication area side via the exchange server,
The call processing node re-calls the mobile terminal device via the switching center server .

  That is, the mobile communication system of the present invention provides a method that enables a handover from a W-LAN (Wireless-Local Area Network) area to a W-CDMA (Wideband-Code Division Multiple Access) area while maintaining a call. Is.

  More specifically, in the mobile communication system of the present invention, W-CDMA / CS (Circuit Switched: circuit switching) [3GPP (3rd Generation Partnership Project) CS] triggered by deterioration of W-LAN quality as a trigger. Is determined to switch to the S-CSCF (Serving-Call Session Control Function), and a suspension notification process is performed to notify the suspension on the W-LAN side and the transition to the W-CDMA / CS to the S-CSCF (Serving-Call Session Control Function). .

  In the mobile communication system of the present invention, the mobile terminal device performs registration (registration) from the W-CDMA / CS side, and re-calls from the S-CSCF to the mobile terminal device, so that W-LAN and W-CDMA / Handover with CS is realized.

  In the mobile communication system of the present invention, as described above, the difference between the different call systems is absorbed, and the control apparatus of the sub system with respect to the call control apparatus of the main system acts as a terminal. Realization of call control by a call control device of a system and implementation of handover between different systems are attempted.

  In the mobile communication system according to the present invention, the mobile terminal device notifies the S-CSCF of the movement (Suspend + Call Forwarding request), thereby enabling the S-CSCF to notify the movement to the W-CDMA / CS and the CS side. Thus, registration to the same S-CSCF is performed via MSC-IWF (Mobile Switching Center-Inter Working Function), and a call session can be maintained by re-calling from the S-CSCF.

  Conventionally, in movement across different radio systems between different radios, the call is once disconnected and accompanied by reconnection, so that it is necessary to make the opposite terminal aware of disconnection / reconnection. On the other hand, in the mobile communication system of the present invention, the MSC-IWF converts the W-CDMA / CS signal procedure into a SIP (Session Initiated Protocol) signal, and cooperates with the S-CSCF to recognize the opposite terminal. Therefore, it is possible to move between different radios and across different signal systems while maintaining a call.

  Accordingly, in the mobile communication system of the present invention, it is possible to move between a W-LAN environment where the call area is limited and a W-CDMA / CS area where the call area is wide, and the W-LAN and W-CDMA / CS. Can be achieved. That is, in the mobile communication system of the present invention, it is possible to realize a handover that maintains a call session.

  In the mobile communication system of the present invention, the MSC-IWF absorbs the difference between the W-CDMA / CS scheme and the IP packet-based SIP scheme, so that the wireless efficiency is good for the W-CDMA / CS area. It is possible to use SIP-based service equipment while continuing to provide services using the W-CDMA / CS scheme.

  According to the present invention, the configuration and operation as described below can provide an effect that a handover maintaining a call session can be realized.

  Next, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing the configuration of a mobile communication system according to an embodiment of the present invention. In FIG. 1, a mobile communication system according to an embodiment of the present invention includes a mobile terminal device 1, an MSC-IWF (Mobile Switching Center-Inter Working Function) 2, an S-CSCF (Serving-Call Session Control Function) 3, Fixed terminal apparatus 4, W-CDMA / CS (Wideband-Code Division Multiple Access / Circuit Switched) [3GPP (3rd Generation Partnership Project) CS] 100, and W-LAN (WirelessWK) IP (Internet Protocol) Multime And ia Subsystem) 300, and a PSTN (Public Switched Telephone Network) network 400..

  MSC-IWF2 supports Core Network Protocol Iu interface as an MSC server for the W-CDMA / CS100 side when the mobile terminal device 1 is in W-CDMA / CS100, and supports 3GPP standard MM (Mobility Management) for providing a mobility function is supported.

  Further, the MSC-IWF 2 operates as a pseudo SIP (Session Initiated Protocol) terminal for the IMS 300 side. In this case, the MSC-IWF 2 performs signal interworking between Iu and SIP, and the call processing of the mobile terminal device 1 is performed by the S-CSCF 3 on the IMS 300 side.

  When the mobile terminal device 1 is in the W-LAN 200, the S-CSCF 3 directly performs SIP call processing [registration (registration) processing, SIP Invite processing from the mobile terminal device 1] as a normal IMS node. Further, when the mobile terminal apparatus 1 is in the W-CDMA / CS 100, the S-CSCF 3 regards the MSC-IWF 2 as a SIP terminal and performs the above SIP call processing.

  When the mobile terminal apparatus 1 determines switching to the W-CDMA / CS 100 triggered by the deterioration of the quality of the W-LAN 200, the mobile terminal apparatus 1 temporarily stops the S-CSCF 3 on the W-LAN 200 side and moves to the W-CDMA / CS 100. A movement notification (Suspend) process for transmission is performed.

  The mobile terminal device 1 performs registration from the W-CDMA / CS 100 side and realizes a handover between the W-LAN 200 and the W-CDMA / CS 100 by re-calling from the S-CSCF 3 to the mobile terminal device 1. Yes.

  In the present embodiment, the difference between different call modes is absorbed, and the call control device of the main mode is controlled by the control device of the secondary mode acting as a terminal with respect to the call control device of the main mode. And realization of handover between different systems.

  The mobile terminal device 1 makes a notification of movement to the S-CSCF 3 (signal a1 Suspend + Call Forwarding request in FIG. 3), thereby enabling the S-CSCF 3 to be notified of movement to the W-CDMA / CS 100, and for W-CDMA / CS / Registration (signals a3, a4, a5 in FIG. 3) to the same S-CSCF3 via the MSC-IWF2 on the CS 100 side, and a re-call (signals a8, a9 in FIG. 3) from the S-CSCF3 This makes it possible to maintain a call session.

  Conventionally, in movement across different radio systems between different radios, the call is once disconnected and accompanied by reconnection, so that it is necessary to make the opposite terminal aware of disconnection / reconnection. In contrast, in this embodiment, the MSC-IWF2 converts the W-CDMA / CS signal procedure as a SIP signal and cooperates with the S-CSCF3 to maintain the call without making the other terminal aware of it. It is possible to move between different radios and across different signal systems. As a result, the mobile terminal can be moved between the W-LAN environment where the call area is limited and the W-CDMA / CS area where the call area is wide, and the W-LAN and W-CDMA / CS are integrated. It becomes possible.

  In addition, MSC-IWF2 continues to provide services using the wirelessly efficient CS method for W-CDMA / CS areas by absorbing the difference between the W-CDMA / CS method and the IP packet-based SIP method. Thus, it becomes possible to use the SIP-based service facility.

  FIG. 2 is a block diagram showing a detailed configuration of a mobile communication system according to an embodiment of the present invention. In FIG. 2, the mobile terminal apparatus 1 of FIG. 1 is connected to the W-LAN wireless terminal device 6 over the air and holds a voice session by SIP / RTP (Real Time Protocol). 5 shows a configuration in which the connection is continuously switched without making the opposite terminal aware of the call while maintaining the call.

  That is, the mobile communication system according to an embodiment of the present invention includes a mobile terminal device 1, an MSC-IWF2, an S-CSCF3, a 3GPP wireless terminal device 5, a W-LAN wireless terminal device 6, an HSS / HLR ( It consists of a Home Subscriber Server / Home Location Register (MG) 7 and an MGCF / MGW (Media Gateway Control Function / Media Gateway) 8.

  FIG. 3 is a sequence chart showing the operation of the mobile communication system according to an embodiment of the present invention, FIG. 4 is a diagram showing a call control signal protocol stack when the W-LAN is in the area, and FIG. 5 is the 3GPP CS area. It is a figure which shows the call control signal protocol stack at the time. As shown in FIG. 5, since the MSC-IWF2 converts the S-CSCF3 into the same protocol stack as that of the SIP terminal, the S-CSCF3 also receives a call control signal from the W-CDMA / CS located terminal. It can be handled in the same way as a SIP message from a terminal in the area.

  The call control method when the W-CDMA / CS is located is in accordance with the 3GPP standard [3GPP TS 23.018 (2004-09) “Basic call handling; Technica realization” (hereinafter referred to as non-patent document 1)]. The call control method at the time of serving and the call control method from the MSC-IWF2 to the S-CSCF3 are described in 3GPP standard [3GPP TS23.228 (2005-06) “IP Multimedia Subsystem (IMS); Stage2” (hereinafter, Non-Patent Document 2). ))].

  The mobile terminal device 1 is a multi-mode terminal of the W-LAN 200 and the W-CDMA / CS 100, and the connection from the W-LAN wireless terminal device 6 to the 3GPP wireless terminal device 5 is triggered by the deterioration of the radio wave state of the W-LAN 200. Has the ability to switch.

  The W-LAN wireless termination device 6 terminates the W-LAN wireless physical layer and only converts the physical layer to Ether (registered trademark) or the like, and is not involved in call control. The S-CSCF 3 provides SIP-based call control to the mobile terminal device 1 in accordance with the 3GPP standard (Non-patent Document 2). As a function of the S-CSCF 3 for call control, a location registration function, outgoing / incoming control, and a call transfer function to a service providing node are provided.

  Location registration can be performed according to the 3GPP standard (FIG. 5.1 of Non-Patent Document 2), the mobile terminal device 1 transmits a SIP Register message to the S-CSCF 3, and the S-CSCF 3 receives the IP (Internet Protocol) address of the mobile terminal device 1. This is realized by registering to HSS / HLR7 at the same time.

  In accordance with the 3GPP standard (Figure 5.12 of Non-Patent Document 2), the S-CSCF 3 that receives the Invite message performs call control, and then performs call control to the service providing node and the called call control node according to the retained policy. Invite message is transferred.

  Further, as shown in FIG. 3, when the S-CSCF 3 receives the “Suspend + Call Forwarding request” from the mobile terminal device 1, the S-CSCF 3 stops signal transmission to the mobile terminal device 1 via the W-LAN 200, and the SIP- from the MSC-IWF2. By performing call transfer in response to the registration, a handover function from the W-LAN 200 to the W-CDMA / CS 100 is provided.

  Since the MGCF / MGW8 is connected to the 3GPP IMS network 300 and the PSTN network 400, the physical layer conversion, the SIP message received from the S-CSCF 3, and the ISUP (ISDN (Integrated Services Digital Network) User Part) on the PSTN network 400 side are provided. Conversion of a call control signal such as a signal (FIG. 5.16 of Non-Patent Document 2) is performed.

  The 3GPP wireless termination device 5 represents a node group that performs 3GPP wireless termination and control, and performs control of the BTS 31 and transfer of call control signals from the mobile terminal device 1 to the BTS (Base Transceiver Station) 31 that terminates the 3GPP radio. RNC (Radio Network Controller) 32. In accordance with the 3GPP standard (Non-Patent Document 1), a 3GPP wireless termination / control and a path replacement function accompanying movement are provided.

  MSC-IWF2 is the Core GP of 3GPP standard [3GPP TS 24.008 (2005-01) “Mobile radio interface Layer 3 specification; Core network protocols; Stage 3”] (hereinafter referred to as Non-Patent Document 3). 3GPP standard (Non-patent Document 3) MM in order to support 3GPP standard mobility functions. Moreover, in order to behave as a SIP terminal with respect to the S-CSCF 3, it has an inter-conversion function between Call Control (CC) Protocol and SIP.

  As for location registration, when “Waiting for Call Forwarding” is set in the SIP Registration response returned by the S-CSCF 3 in order to realize handover between the W-LAN 200 and the W-CDMA / CS 100, the mobile terminal apparatus 1 In the Registration Accept notification, “Follow On” is set, and the mobile terminal device 1 is instructed to maintain the location registration radio resource and to be able to continue the transmission of SETUP.

  The operation of the mobile communication system according to the embodiment of the present invention will be described with reference to FIGS.

  First, the mobile terminal device 1 communicates directly with the S-CSCF 3 via the SIP via the W-LAN wireless terminal device 6 using the SIP message, and registers the location using the IP address assigned to the mobile terminal device 1. When the mobile terminal device 1 starts voice communication, the mobile terminal device 1 makes a voice call with the fixed terminal device 4 via the MGCF / MGW 8 and the PSTN network 400.

  After the mobile terminal apparatus 1 determines the switching to W-CDMA / CS 100 triggered by the deterioration of the quality of the W-LAN 200, the W-LAN 200 side temporarily changes to the S-CSCF 3 used in the SIP call session. Suspend processing for transmitting the suspension and movement to the W-CDMA / CS 100 is performed, and a “Suspend + Call Forwarding request” is transmitted (see a1 in FIG. 3).

  When the S-CSCF 3 receives the “Suspend + Call Forwarding request”, the S-CSCF 3 returns a “Suspend + Call Forwarding response” to the request (see a2 in FIG. 3), and the corresponding mobile terminal device 1 tries to move from the W-LAN 200 to the W-CDMA / CS 100. And the downstream packet is stopped.

  The mobile terminal apparatus 1 performs CS location registration in the MSC-IWF 2 via the W-CDMA / CS 100 (see a3 in FIG. 3). The MSC-IWF 2 performs location registration with the HSS / HLR 7 as a W-CDMA / CS terminal process triggered by 3GPP location registration from the mobile terminal device 1 (see a4 in FIG. 3).

  The MSC-IWF 2 transmits a SIP Register message to the S-CSCF 3 as a SIP terminal simulation (see a 5 in FIG. 3), and performs a registration process.

  The S-CSCF 3 that has received the SIP Register message recognizes that the corresponding mobile terminal device 1 has moved from the W-LAN 200 to the W-CDMA / CS 100 and transfers the connected call to the mobile terminal device 1. To start incoming call processing. At this time, since the MSC-IWF2 is shown as a terminal to the S-CSCF3, the S-CSCF3 notifies the SIP Register response (see a6 in FIG. 3) that the incoming call processing is started.

  When receiving the SIP Register response, the MSC-IWF 2 notifies the mobile terminal device 1 of the completion of location registration of the W-CDMA / CS 100 (see a7 in FIG. 3). At that time, since the incoming call processing is continuously activated, the MSC-IWF 2 sets Follow ON and informs the mobile terminal device 1 to hold the radio link.

  When the S-CSCF 3 transmits a SIP Register response, the S-CSCF 3 transmits an Invite message to the MSC-IWF 2 as an incoming call process to the mobile terminal device 1 for transferring the connected call (see a8 in FIG. 3). When receiving the Invite message, the MSC-IWF 2 transmits a SETUP to the mobile terminal device 1 as an incoming call request (see a9 in FIG. 3).

  When the incoming call processing via the MSC-IWF 2 is completed between the mobile terminal device 1 and the S-CSCF 3, a call using the W-CDMA / CS 100 becomes possible, and the W-LAN 200 to the W-CDMA / CS 100 becomes available. The handover process is completed.

  Conventionally, in a movement between different radios and across different signal systems, a call is temporarily disconnected and accompanied by reconnection. Therefore, it is necessary to make the opposite terminal aware of disconnection / reconnection. On the other hand, in the present embodiment, the MSC-IWF2 converts the 3GPP CS signal procedure into a SIP signal and cooperates with the S-CSCF3 to maintain the call without making the opposite terminal aware of it. It is possible to move across different signal systems between different radios. As a result, in this embodiment, it is possible to move between a W-LAN environment where the call area is limited and a 3GPP area where the call area is wide, and it is possible to combine W-LAN and 3GPP.

  In this embodiment, MSC-IWF2 continued to provide services using the radio efficient CS scheme for 3GPP areas by absorbing the difference between the 3GPP CS scheme and the IP packet-based SIP scheme. The SIP-based service facility can be used as it is.

  In the present invention, the destination environment of the mobile terminal device 1 is set to W-CDMA / CS100 (3GPP CS) in the above embodiment, but the destination radio environment and communication method are GSM (Global System Mobile). communication) and other communication methods.

  In the present invention, in the above embodiment, the wireless environment of the movement source is W-LAN. However, as long as IP communication is possible, connection by Bluetooth (registered trademark) or other connection methods may be used. .

It is a block diagram which shows the structure of the mobile communication system by one Example of this invention. It is a block diagram which shows the detailed structure of the mobile communication system by one Example of this invention. 6 is a sequence chart showing an operation of the mobile communication system according to the embodiment of the present invention. It is a figure which shows the call control signal protocol stack at the time of W-LAN presence. It is a figure which shows the call control signal protocol stack at the time of 3GPP CS service area.

Explanation of symbols

1 Mobile terminal 2 MSC-IWF
3 S-CSCF
4 Fixed terminal device 5 3GPP wireless terminal device 6 W-LAN wireless terminal device 7 HSS / HLR
8 MGCF / MGW
100 W-CDMA / CS
200 W-LAN
300 IMS
400 PSTN network

Claims (28)

A call processing node that performs call processing in a first communication area in which a call area of the mobile terminal device is limited, and exchange processing in a second communication area in which the call area of the mobile terminal device is wider than the first communication area. A mobile communication system including a switching center server to perform,
When the mobile terminal device determines whether or not to switch to the second communication area when the quality of the first communication area deteriorates, and performs switching to the second communication area Means for performing a movement notification process for notifying the call processing node of the suspension of the call process on the first communication area side and the movement of the terminal to the second communication area when judged. And
The mobile terminal device registers from the second communication area side to the call processing node via the switching center server, and reappears from the call processing node to the mobile terminal device via the switching center server. A mobile communication system characterized by calling.   2. The mobile communication system according to claim 1, wherein the first communication area is a communication area of an IP (Internet Protocol) communication system, and the second communication area is a communication area of a mobile communication system.   The first communication area is a W-LAN (Wireless-Local Area Network) area, and the second communication area is a W-CDMA / CS (Wideband-Code Division Multiple Access / Circuit Switched) area. The mobile communication system according to claim 2.   4. The mobile communication according to claim 3, wherein the call processing node is an S-CSCF (Serving-Call Session Control Function), and the exchange server is an MSC-IWF (Mobile Switching Center-Inter Working Function). system.   5. The mobile communication system according to claim 4, wherein the MSC-IWF includes means for converting a call processing scheme signal procedure in the W-CDMA / CS area into a SIP (Session Initiated Protocol) signal.   The mobile communication system according to claim 5, wherein the MSC-IWF operates as a SIP terminal for the S-CSCF.   The MSC-IWF performs the registration on the same S-CSCF when the registration is performed on the S-CSCF by the mobile terminal device. The mobile communication system described.   The mobile communication system according to any one of claims 5 to 7, wherein the MSC-IWF absorbs a difference between a W-CDMA / CS scheme and an IP (Internet Protocol) packet-based SIP scheme. A mobile communication system is configured together with a call processing node that performs call processing in a first communication area in which a communication area of the mobile terminal device is limited, and a second communication area of the mobile terminal device is wider than the first communication area. An exchange server that performs exchange processing in a communication area,
When the mobile terminal device moves to the second communication area triggered by a deterioration in quality of the first communication area, the mobile terminal device relays a registration for the call processing node from the mobile terminal device, and A switching center server that relays a re-call from the processing node to the mobile terminal device.   The exchange server according to claim 9, wherein the first communication area is a communication area of an IP (Internet Protocol) communication method, and the second communication area is a communication area of a mobile communication method.   The first communication area is a W-LAN (Wireless-Local Area Network) area, and the second communication area is a W-CDMA / CS (Wideband-Code Division Multiple Access / Circuit Switched) area. The exchange server according to claim 10.   12. The exchange server according to claim 11, wherein the call processing node is an S-CSCF (Serving-Call Session Control Function), and its own apparatus is an MSC-IWF (Mobile Switching Center-Inter Working Function).   13. The exchange server according to claim 12, further comprising means for converting a signal procedure of a call processing method in the W-CDMA / CS area into a SIP (Session Initiated Protocol) signal.   The exchange server according to claim 13, wherein the exchange server operates as a SIP terminal for the S-CSCF.   The exchange server according to any one of claims 12 to 14, wherein the registration is performed on the same S-CSCF when the registration to the S-CSCF is performed by the mobile terminal device. .   The exchange server according to any one of claims 13 to 15, which absorbs a difference between a W-CDMA / CS system and an IP (Internet Protocol) packet-based SIP system. A mobile communication system together with a call processing node that performs call processing in a first communication area where the call area is limited, and an exchange server that performs switching processing in a second communication area where the call area is wider than the first communication area A mobile terminal device comprising:
Means for determining whether or not to switch to the second communication area when the quality of the first communication area deteriorates, and the call processing when determining to switch to the second communication area Means for performing a movement notification process for informing the node of the suspension of the call process on the first communication area side and the movement of the terminal to the second communication area;
By performing the registration to the call processing node via the switching center server from said second communication area side, characterized in that it is recalling through the switching center server from the call processing node Mobile terminal device.   18. The mobile terminal apparatus according to claim 17, wherein the first communication area is a communication area of an IP (Internet Protocol) communication method, and the second communication area is a communication area of a mobile communication method.   The first communication area is a W-LAN (Wireless-Local Area Network) area, and the second communication area is a W-CDMA / CS (Wideband-Code Division Multiple Access / Circuit Switched) area. The mobile terminal apparatus according to claim 18.   The mobile terminal according to claim 18, wherein the call processing node is an S-CSCF (Serving-Call Session Control Function), and the switching center server is an MSC-IWF (Mobile Switching Center-Inter Working Function). apparatus. A call processing node that performs call processing in a first communication area in which a call area of the mobile terminal device is limited, and exchange processing in a second communication area in which the call area of the mobile terminal device is wider than the first communication area. A handover method used in a mobile communication system including a switching center server to perform,
Call processing on the first communication area side with respect to the call processing node when the mobile terminal apparatus determines to switch to the second communication area when the quality of the first communication area deteriorates A movement notification process for communicating the suspension of the terminal and the movement of the terminal to the second communication area,
The mobile terminal device performs registration for the call processing node from the second communication area side via the exchange server,
A handover method characterized by re-calling the mobile terminal device from the call processing node via the exchange server .   The handover method according to claim 21, wherein the first communication area is a communication area of an IP (Internet Protocol) communication method, and the second communication area is a communication area of a mobile communication method.   The first communication area is a W-LAN (Wireless-Local Area Network) area, and the second communication area is a W-CDMA / CS (Wideband-Code Division Multiple Access / Circuit Switched) area. The handover method according to claim 22.   The handover method according to claim 23, wherein the call processing node is an S-CSCF (Serving-Call Session Control Function), and the exchange server is an MSC-IWF (Mobile Switching Center-Inter Working Function). .   The handover method according to claim 24, wherein the MSC-IWF converts a signal procedure of a call processing method in the W-CDMA / CS area into a SIP (Session Initiated Protocol) signal.   The handover method according to claim 25, wherein the MSC-IWF operates as a SIP terminal for the S-CSCF.   The MSC-IWF performs the registration to the same S-CSCF when the registration is performed on the S-CSCF by the mobile terminal device. The described handover method.   The handover method according to any one of claims 25 to 27, wherein the MSC-IWF absorbs a difference between a W-CDMA / CS scheme and an IP (Internet Protocol) packet-based SIP scheme.

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