Network node, base station, and communication method

Abstract

This network node comprises: a control unit that recognizes that the same satellite accommodates both a transmitting terminal and a receiving terminal, and recognizes that switching of an Internet protocol multimedia subsystem (IMS) access gateway (AGW) on the satellite occurs simultaneously in a transmission network and a reception network; and a transmission unit that transmits, to a first network node, a first message including termination point information of the IMS AGW on a destination satellite and requesting an update of a state of voice communication.

Description

Network node, base station, and communication method

[0001] The present invention relates to a network node, a base station, and a communication method in a communication system.

[0002] 3GPP (registered trademark) (3rd Generation Partnership Project) is currently studying a wireless communication system called 5G or NR (New Radio) (hereinafter, the wireless communication system will be referred to as "5G" or "NR") in order to achieve a larger system capacity, a higher data transmission speed, and a lower latency in wireless sections. Various wireless technologies are being studied for 5G to meet the requirements of achieving a throughput of 10 Gbps or more while keeping latency in wireless sections to 1 ms or less.

[0003] In NR, a network architecture including 5GC (5G Core Network) corresponding to EPC (Evolved Packet Core), which is the core network in the network architecture of LTE (Long Term Evolution), and NG-RAN (Next Generation - Radio Access Network) corresponding to E-UTRAN (Evolved Universal Terrestrial Radio Access Network), which is the RAN (Radio Access Network) in the network architecture of LTE, is being considered (for example, Non-Patent Document 1).

[0004] Furthermore, as an IMS (IP Multimedia Subsystem) architecture that supports the data channel capabilities of terminals, specifications for an IMS data channel network are being studied (see, for example, Non-Patent Document 2). In the IMS data channel network, a Data Channel Signalling Function (DCSF) having a signaling function, a Media Function (MF) having a media-related function, and a Data Channel Application Server (DCAS) that is an application server are arranged on both the calling and called sides.

[0005] Furthermore, in 3GPP Rel-19, in order to realize IMS voice terminal-satellite-terminal communication (UE-satellite-UE communication), reducing the impact on existing specifications when deploying 5GC network functions and IMS components on satellites is an issue (see, for example, Non-Patent Document 3). Here, terminal-satellite-terminal communication refers to terminal-to-terminal communication under routing that keeps user plane traffic within the satellite. The types of satellites handled include geostationary satellites (GEO), low Earth orbit satellites (LEO), and medium Earth orbit satellites (MEO). Furthermore, for low Earth orbit satellites and medium Earth orbit satellites, satellite constellations can be formed without using inter-satellite links (ISLs) or using inter-satellite links.

[0006] 3GPP TS 23.501 V18.5.0 (2024-06) 3GPP TS 23.228 V18.6.0 (2024-06) 3GPP TR23.700-29 V19.0.0 (2024-06) 3GPP TS 38.300 V18.2.0 (2024-06) IETF RFC5407 (2008-12) IETF RFC3261 (2002-06) 3GPP TS 38.331 V18.0.0 (2023-12) 3GPP TS 38.413 V18.0.0 (2023-12) 3GPP TS 23.502 V18.7.0 (2024-06)

[0007] In 3GPP, in satellite constellation communications using a satellite IMS access gateway (IMS AGW), switching of the satellite IMS AGW due to satellite movement is being considered, and a scenario in which the satellite accommodating one of two terminals in communication is switched is being considered.

[0008] However, no consideration has been given to the procedure for switching between satellites simultaneously accommodating two terminals in communication using a quasi-earth-fixed (see Non-Patent Document 4) service link.

[0009] The present invention has been made in view of the above-mentioned points, and an object of the present invention is to switch between satellites that simultaneously accommodate two terminals in communication using a quasi-terrestrial fixed service link in a wireless communication system using a satellite.

[0010] According to the disclosed technology, there is provided a network node having: a control unit that recognizes that the same satellite accommodates both a calling terminal and a called terminal, and that switching of an Internet Protocol Multimedia Subsystem (IMS) Access Gateway (AGW) on the satellite will occur simultaneously in the calling network and the called network; and a transmission unit that transmits to a first network node a first message requesting an update of the voice communication status, including termination point information of the IMS AGW on the destination satellite.

[0011] According to the disclosed technique, in a wireless communication system using a satellite, it is possible to switch between satellites that simultaneously accommodate two terminals that are communicating using a quasi-terrestrial fixed service link.

[0012] 1 is a diagram for explaining an example of a communication system. FIG. 1 is a diagram for explaining an example of a communication system in a roaming environment. FIG. 2 is a diagram for explaining an example of an IMS data channel network. FIG. 2 is a diagram showing an example of a first sequence diagram in an embodiment of the present invention. FIG. 3 is a diagram showing an example of a second sequence diagram in an embodiment of the present invention. FIG. 4 is a diagram showing an example of a third sequence diagram in an embodiment of the present invention. FIG. 5 is a diagram showing an example of a fourth sequence diagram in an embodiment of the present invention. FIG. 6 is a diagram showing an example of a fifth sequence diagram in an embodiment of the present invention. FIG. 7 is a diagram showing an example of a sixth sequence diagram in an embodiment of the present invention. FIG. 8 is a diagram showing an example of a seventh sequence diagram in an embodiment of the present invention. FIG. 9 is a diagram showing an example of an eighth sequence diagram in an embodiment of the present invention. FIG. 10 is a diagram showing an example of a ninth sequence diagram in an embodiment of the present invention. FIG. 11 is a diagram showing an example of an eleventh sequence diagram in an embodiment of the present invention. FIG. 12 is a diagram showing an example of a twelfth sequence diagram in an embodiment of the present invention. FIG. 13 is a diagram showing an example of a functional configuration of a base station 10 and a network node 30 in an embodiment of the present invention. FIG. 14 is a diagram showing an example of a functional configuration of a terminal 20 in an embodiment of the present invention. FIG. 15 is a diagram showing an example of the hardware configuration of a base station 10, a terminal 20, and a network node 30 in an embodiment of the present invention. FIG. 16 is a diagram showing an example of a configuration of a vehicle 2001 in an embodiment of the present invention.

[0013] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. Note that the embodiment described below is an example, and the embodiment to which the present invention is applied is not limited to the following embodiment.

[0014] In the operation of the wireless communication system according to the embodiment of the present invention, existing technology is used as appropriate. However, the existing technology is, for example, the existing LTE, but is not limited to the existing LTE. Furthermore, the term "LTE" used in this specification has a broad meaning including LTE-Advanced, and systems subsequent to LTE-Advanced (e.g., NR), or wireless LAN (Local Area Network), unless otherwise specified.

[0015] Furthermore, in the embodiments of the present invention, "configuring" radio parameters and the like may mean that predetermined values ​​are pre-configured, or that radio parameters notified from the network node 30 or the terminal 20 are set.

[0016] Fig. 1 is a diagram illustrating an example of a communication system. As shown in Fig. 1, the communication system is composed of a UE, which is a terminal 20, and multiple network nodes 30. Hereinafter, it is assumed that one network node 30 corresponds to each function, but multiple functions may be realized by one network node 30, or multiple network nodes 30 may realize one function. Furthermore, the "connection" described below may be a logical connection or a physical connection.

[0017] The RAN (Radio Access Network) is a network node 30 having a radio access function, which may include a base station 10, and is connected to a UE, an AMF (Access and Mobility Management Function), and a UPF (User Plane Function). The AMF is a network node 30 having functions such as terminating the RAN interface, terminating the NAS (Non-Access Stratum), registering management, connecting management, reachability management, and terminal mobility management. The UPF is a network node 30 having functions related to processing user plane data, such as a PDU (Protocol Data Unit) session point to the outside that interconnects with the DN (Data Network), packet routing and forwarding, and user plane Quality of Service (QoS) handling. The UPF and the DN constitute a network slice. In the wireless communication network according to the embodiment of the present invention, multiple network slices are constructed.

[0018] The AMF is connected to the UE, RAN, SMF (Session Management function), NSSF (Network Slice Selection Function), NEF (Network Exposure Function), NRF (Network Repository Function), UDM (Unified Data Management), AUSF (Authentication Server Function), PCF (Policy Control Function), and AF (Application Function). The AMF, SMF, NSSF, NEF, NRF, UDM, AUSF, PCF, and AF are network nodes 30 that are mutually connected via interfaces based on their respective services, Namf, Nsmf, Nnssf, Nnef, Nnrf, Nudm, Nausf, Npcf, and Naf.

[0019] The SMF is a network node 30 having functions such as session management, UE IP (Internet Protocol) address allocation and management, DHCP (Dynamic Host Configuration Protocol) function, ARP (Address Resolution Protocol) proxy, and roaming function. The NEF is a network node 30 having a function of notifying other NFs (Network Functions) of capabilities and events. The NSSF is a network node 30 having functions such as selecting a network slice to which a UE connects, determining an allowed NSSAI (Network Slice Selection Assistance Information), determining an NSSAI to be set, and determining an AMF set to which a UE connects. The PCF is a network node 30 having a function of controlling network policies. The AF is a network node 30 having a function of controlling application servers. The NRF is a network node 30 having a function of discovering NF instances that provide services. The UDM is a network node 30 that manages subscriber data and authentication data. The UDM is connected to a UDR (User Data Repository) that stores the data.

[0020] Fig. 2 is a diagram illustrating an example of a communication system in a roaming environment. As shown in Fig. 2, the network is composed of a UE, which is a terminal 20, and multiple network nodes 30. Hereinafter, it is assumed that one network node 30 corresponds to each function, but multiple functions may be realized by one network node 30, or multiple network nodes 30 may realize one function. Furthermore, the "connection" described below may be a logical connection or a physical connection.

[0021] The RAN is a network node 30 having a radio access function, and is connected to the UE, the AMF, and the UPF. The AMF is a network node 30 having functions such as RAN interface termination, NAS termination, registration management, connection management, reachability management, and mobility management. The UPF is a network node 30 having functions such as a PDU session point to the outside that interconnects with the DN, packet routing and forwarding, and user plane QoS handling. The UPF and the DN constitute a network slice. In the wireless communication network according to the embodiment of the present invention, multiple network slices are constructed.

[0022] The AMF is connected to the UE, RAN, SMF, NSSF, NEF, NRF, UDM, AUSF, PCF, AF, and SEPP (Security Edge Protection Proxy). The AMF, SMF, NSSF, NEF, NRF, UDM, AUSF, PCF, and AF are network nodes 30 that are interconnected via respective service-based interfaces, Namf, Nsmf, Nnssf, Nnef, Nnrf, Nudm, Nausf, Npcf, and Naf.

[0023] The SMF is a network node 30 having functions such as session management, UE IP address allocation and management, DHCP function, ARP proxy, and roaming function. The NEF is a network node 30 having a function of notifying other NFs of capabilities and events. The NSSF is a network node 30 having functions such as selecting a network slice to which a UE connects, determining an allowed NSSAI, determining a configured NSSAI, and determining an AMF set to which a UE connects. The PCF is a network node 30 having a function of controlling network policies. The AF is a network node 30 having a function of controlling application servers. The NRF is a network node 30 having a function of discovering NF instances that provide services. The SEPP is a non-transparent proxy that filters control plane messages between PLMNs (Public Land Mobile Networks). The vSEPP shown in FIG. 2 is a SEPP in the visited network, and the hSEPP is a SEPP in the home network.

[0024] As shown in Figure 2, a UE is in a roaming environment connected to a RAN and an AMF in a Visited PLMN (VPLMN). The VPLMN and a Home PLMN (HPLMN) are connected via a vSEPP and an hSEPP. The UE can communicate with a UDM in the HPLMN via the AMF in the VPLMN, for example.

[0025] Fig. 3 is a diagram illustrating an example of an IMS data channel network. As shown in Fig. 3, the IMS data channel network is configured with a terminal 20 (UE) and multiple network nodes 30 in each of an originating network and a terminating network. Hereinafter, it is assumed that one network node 30 corresponds to each function, but multiple functions may be realized by one network node 30, or multiple network nodes 30 may realize one function. Furthermore, the "connection" described below may be a logical connection or a physical connection. The network node 30 has, for example, the following functions described in Non-Patent Document 2:

[0026] The IMS-AGW (Access Gateway) is a network node 30 having a gateway function between the UE and the IMS network, a function related to access processing for voice communication, and the like.

[0027] A P-CSCF (Proxy-Call Session Control Function) is a network node 30 that has a proxy function between the UE and the IMS network, an access control function for voice communication, and the like.

[0028] The S-CSCF (Serving-Call Session Control Function) is a network node 30 having functions related to session control for the UE.

[0029] The I-CSCF (Interrogate-Call Session Control Function) is a connection point on the destination network side between networks (e.g., between the source network side and the destination network side) in the IMS network, and is a network node 30 that has, for example, the function of forwarding a received SIP request to the S-CSCF of its own network.

[0030] An IMS AS (IP Multimedia Subsystem Application Server) is a network node 30 in an IMS network that has functions such as communicating with a DCSF for event notification and receiving data channel control instructions from the DCSF to communicate with an MF. The IMS AS also receives a communication termination point registration request from a DCSF (Data Channel Signalling Function), converts the received registration request into a SIP Register, and sends it to a Serving-Call Session Control Function (S-CSCF). The IMS AS also converts a data channel establishment request received from the DCSF into a SIP INVITE and sends it to the S-CSCF.

[0031] The DCSF (Data Channel Signaling Function) is a network node 30 that has functions such as receiving an event report from the IMS-AS and determining whether to allow the provision of a data channel service, managing the bootstrap data channel, and performing HTTP web server functions.

[0032] An MF (Media Function) is a network node 30 in an IMS network that has functions such as media resource management and forwarding of data channel media traffic. The MF processes media between a DCAS (Data Channel Application Server), which is a communication termination point, and a destination termination point based on configuration information received from a DCSF. The MF may also be called a DCMF (Data Channel Media Function). The MF may also be called an MRF (Multimedia Resource Function).

[0033] A DCAS (Data Channel Application Server) is a network node 30 having functions such as a communication termination point for media and signaling in the IMS network.

[0034] (Example) This example describes a procedure for switching between satellites that simultaneously accommodate two terminals communicating using a quasi-terrestrial fixed service link in a satellite-based wireless communication system. In this procedure, it is necessary to consider the occurrence of SIP re-INVITE crossings. Regarding the occurrence of such crossings, see Section 3.3.1 of Non-Patent Document 5. In a situation where such crossings occur, both terminals reject each other with an error code (491). Therefore, Section 14.1 of Non-Patent Document 6 describes a procedure in which the terminal that sent the SIP INVITE retransmits the SIP re-INVITE after a time period between 2.1 and 4 seconds has elapsed, and the opposite terminal retransmits the SIP re-INVITE between 0 and 2 seconds. However, due to the large signal delays in satellite constellation communications, simply delaying the time period described above may result in repeated crossings, potentially causing satellite switching failure.

[0035] In this embodiment, if the P-CSCF on the terminating side (the P-CSCF on the side receiving the SIP INVITE) recognizes that one satellite using a quasi-terrestrial fixed service link accommodates both the calling terminal and the called terminal, and if it determines that a terminal handover has occurred due to switching of the quasi-terrestrial fixed service link, it does not perform an operation to make the called terminal send a SIP re-INVITE. As a result, only the calling terminal sends a SIP re-INVITE, making it possible to prevent crossover of SIP re-INVITEs. Note that in the above-described operation, the operations on the calling and called sides may be reversed so that the calling terminal does not send a SIP re-INVITE and the called terminal sends a SIP re-INVITE.

[0036] In this embodiment, it is assumed that a plurality of low-earth-orbit satellites (LEOs) equipped with base stations, ULCLs (Uplink Classifiers), UPFs, and IMS AGWs form a satellite constellation using inter-satellite links (ISLs). The ULCLs have a function to selectively distribute uplink traffic between N9 interfaces.

[0037] A base station deployed on a satellite constellation performs quasi-terrestrial fixed beam switching, and when initiating a handover associated with the quasi-terrestrial fixed beam switching, the base station transmits a message requesting a handover, including a reason for the handover, to another base station.

[0038] Satellite communications operators prepare dedicated equipment for satellite constellation communications, primarily base stations, ULCLs, UPFs, and IMS AGWs deployed in LEOs, as well as intermediate devices deployed on the ground that communicate with satellite-based devices. On the other hand, mobile communications operators prepare network nodes, primarily AMFs, SMFs, and P-CSCFs, deployed on the ground, as satellite constellation utilization equipment.

[0039] The details of the processing in this embodiment will be explained below using sequence diagrams. Requests, responses, notifications, etc. sent and received in the procedures shown below may be called messages (e.g., request messages). For details of existing specifications related to messages sent and received in this sequence diagram, see Non-Patent Documents 7-9, etc.

[0040] On the originating side, AMF 30A, SMF 30B, PCF 30C, P-CSCF 30G, S-CSCF 30H, HSS 30J, remote IMS AGW 30FR, and remote UPF (R-PSA1) 30D1R, which is the first termination point of the PDU session (PDU Session Anchor 1, PSA1), are deployed on the ground. Meanwhile, base station 10A, ULCL 30E, local IMS AGW 30FL, and local UPF (L-PSA2) 30D2L, which is the second termination point (PSA2) of the PDU session, are deployed on the satellite to which terminal 20A connects.

[0041] Similarly, on the terminating side, AMF 30A2, SMF 30B2, PCF 30C2, P-CSCF 30G2, S-CSCF 30H2, HSS 30J2, remote IMS AGW 30FR2, and remote UPF (R-PSA3) 30D3R, which is the third termination point (PSA3) of the PDU session, are deployed on the ground. Meanwhile, base station 10B, ULCL 30E2, local IMS AGW 30FL2, and local UPF (L-PSA4) 30D4L, which is the fourth termination point (PSA4) of the PDU session, are deployed on the satellite to which terminal 20B connects.

[0042] This sequence shows a handover procedure that occurs when a voice communication using the same satellite is established between terminal 20A, which is a calling terminal, and terminal 20B, which is a called terminal, and then the satellite is switched. Here, the calling terminal's destination includes base station 10C, ULCL 30E3, local IMS AGW 30FL3, and local UPF (L-PSA5) 30D5L3, which is the fifth termination point (PSA5) of the PDU session. The called terminal's destination includes base station 10D, ULCL 30E4, local IMS AGW 30FL4, and local UPF (L-PSA6) 30D6L3, which is the sixth termination point (PSA6) of the PDU session. The UPF may also be referred to as a termination point of a PDU session; for example, UPF (R-PSA1) 30D1R may be referred to as UPF 30D1R or PSA1.

[0043] (Handover Procedure in Satellite Switching) This section describes a satellite transfer procedure in which a satellite accommodating both the originating terminal 20A and the terminal 20B is simultaneously switched to another satellite after an IMS voice call (start of voice communication) is completed. FIG. 4 is a diagram showing an example of a first sequence diagram in an embodiment of the present invention. The sequence diagram in FIG. 4 shows an Xn handover procedure. Here, it is assumed that the network nodes (e.g., P-CSCF, etc.) on the originating and terminating sides recognize that the originating terminal 20A and the terminal 20B are accommodated by the same satellite. The processing of each step will be described below.

[0044] S501: The base station 10B transmits a request message (Handover Request) requesting a handover to the base station 10D. The request message includes information indicating that the cause of the handover is a quasi-earth-fixed beam switch (Cause=quasi-earth-fixed beam switch).

[0045] S502: The base station 10D transmits a handover request acknowledgement including a handover command to the base station 10B as a response to the request message received in S501.

[0046] S503: The base station 10B transmits a message (RRCReconfiguration) requesting execution of settings related to radio resource control (RRC) to the terminal 20B. The message includes a handover command.

[0047] S504: The base station 10B sends an SN status transfer to the base station 10D.

[0048] S505: The terminal 20B transmits a message to the base station 10D notifying that the RRC-related settings have been completed. The message includes a handover confirmation.

[0049] S506: The base station 10D transmits a request message (Path Switch request) to the AMF 30A2 to request a path change associated with a base station change. The request message includes information indicating that the cause of the handover is quasi-earth-fixed beam switch (Cause=quasi-earth-fixed beam switch).

[0050] S507: AMF30A2 recognizes the satellite constellation ID and satellite ID currently accommodating terminal 20A based on the correspondence between the transport layer settings and the identifier of the source base station that it recognized in advance, and the transport layer settings of the request message received in S506.

[0051] S508: AMF 30A2 transmits a request message (Nsmf_PDUSession_UpdateSMContext request) to SMF 30B2 requesting path switching accompanying a change in base station. The request message includes a satellite constellation ID, a satellite ID, and information indicating that the cause of the handover is quasi-earth-fixed beam switch (Cause=quasi-earth-fixed beam switch), and is expressed as, for example, Nsmf_PDUSession_UpdateSMContext request (SmContextUpdateData(satellite constellation id, satellite id, Handover cause=quasi-earth-fixed beam switch)).

[0052] S509: SMF30B2 sends a request message (PFCP Session Modification request) to ULCL30E2 to update the user data transfer path.

[0053] S510: ULCL 30E2 transmits to SMF 30B2 a response message (PFCP Session Modification response) to the request message received in S509.

[0054] S511: SMF30B2 sends a response message (Nsmf_PDUSession_UpdateSMContext response) to AMF30A2 in response to the request message received in S508.

[0055] S512: The AMF 30A2 transmits to the base station 10D a response message (Path Switch request response) in response to the request message received in S506.

[0056] S513: The base station 10D transmits a message (UE Context Release) requesting the release of the terminal context to the base station 10B.

[0057] Next, we will explain the procedures related to changing the ULCL and the termination point (PSA) in the PDU session when switching satellites. Figure 5 is a diagram showing an example of a second sequence diagram in an embodiment of the present invention. Below, we will explain the processing of each step.

[0058] S521: SMF30B2 recognizes the base station switch and satellite ID switch, and decides to execute the switch for the ULCL and local UPF (L-UPF) deployed on the satellite. Here, the L-UPF may be expressed as a PDU session termination point (L-PSA).

[0059] S522: Using the event subscription set when the voice call was made, SMF30B2 decides to inquire of the P-CSCF via the PCF whether to allow switching from the pre-movement ULCL and pre-movement L-UPF to the destination ULCL and destination L-UPF (L-PSA).

[0060] S523: SMF 30B2 transmits to PCF 30C2 a message (Nsmf_EventExposure_Notify request) inquiring about whether to switch between the ULCL and L-UPF and notifying the event including an indication (EARLY) indicating that the ULCL and L-UPF (L-PSA) have not yet been moved. The message includes information indicating that the cause of the handover is quasi-earth-fixed beam switching (Cause=quasi-earth-fixed beam switch) and information indicating that the satellite beam type is quasi-earth-fixed (satellite beam type=quasi-earth-fixed). Also, for example, the message is expressed as Nsmf_EventExposure_Notify request (NsmfEventExposureNotification (eventNotifs(event=SAT_UP_PATH_CH, dnaiChgType=EARLY, Handover cause=quasi-earth-fixed beam switch, satellite type, satellite beam type=quasi-earth-fixed, satellite constellation id, satellite id= a target satellite id, OnSatteliteLpsaUlcl=true, OnSatteliteMediaRoutingToTatgetNetwork=false))).

[0061] S524: The PCF 30C2 sends a response message (Nsmf_EventExposure_Notify response) to the message received in S523 to the SMF 30B2.

[0062] S525: PCF30C2 transmits to P-CSCF30G2 a message (Npcf_PolicyAuthorization_Notify request) inquiring about whether to switch the ULCL and L-UPF and notifying the event including an indication (EARLY) indicating that the ULCL and L-PSA have not yet been moved. The message includes information indicating that the cause of the handover is quasi-earth-fixed beam switching (Cause=quasi-earth-fixed beam switch) and information indicating that the satellite beam type is quasi-earth-fixed (satellite beam type=quasi-earth-fixed). Also, for example, the message is expressed as Npcf_PolicyAuthorization_Notify request (EventsNotification (evNotifs(event=SAT_UP_PATH_CH), dnaiChgType=EARLY, Handover cause=quasi-earth-fixed beam switch, satellite type, satellite beam type=quasi-earth-fixed, satellite constellation id, satellite id= a target satellite id, OnSatteliteLpsaUlcl=true, OnSatteliteMediaRoutingToTatgetNetwork=false)).

[0063] S526: The P-CSCF 30G2 transmits to the PCF 30C2 a response message (Npcf_PolicyAuthorization_Notify response) in response to the message received in S525.

[0064] S527: The P-CSCF30G2 determines that the satellite constellation IDs of the originating and terminating terminals are the same even after switching between the ULCL and L-UPF, and that media routing on the satellite is possible. The P-CSCF30G2 also recognizes that it is necessary to start setting up the destination IMS AGW30FL4.

[0065] S528: The P-CSCF30G2 recognizes that the originating terminal 20A and the terminating terminal 20B are deployed on the same satellite and that this satellite is the source satellite for the handover. The P-CSCF30G2 also recognizes that the source satellite uses a quasi-earth-fixed beam and that other satellites in the same satellite constellation also use quasi-earth-fixed beams. The P-CSCF30G2 also recognizes information indicating that the cause of the handover is a quasi-earth-fixed beam switch (Cause = quasi-earth-fixed beam switch) contained in the message received in S525. Based on this information, the P-CSCF30G2 also recognizes that ULCL and L-PSA (UPF) switching will occur simultaneously in the originating network and terminating network. The P-CSCF30G2 also recognizes that its own device belongs to the terminating network. Based on the above recognition, the P-CSCF30G2 also determines not to execute the procedure for changing satellites and instead decides to follow the procedure of the originating network. In this embodiment, it is assumed that the calling side initiates the switching.

[0066] That is, when it is assumed that the switching will occur simultaneously in the originating network and the terminating network, the P-CSCF30G2 recognizes the rules regarding which of the originating network or the terminating network will temporarily suspend processing, and if the network to which the P-CSCF30G2 belongs is a network that complies with the rules, it decides to initiate the switching, and if the network to which the P-CSCF30G2 belongs is not a network that complies with the rules, it decides to follow the procedure of the other network.

[0067] S529: P-CSCF30G2 sends to PCF30C2 a message (Npcf_EventExposure_AppRelocationInfo request) instructing that the switching between ULCL and L-UPF be temporarily put on hold. This message includes information instructing that the switching between ULCL and L-PSA be temporarily put on hold (RELOC_ON_HOLD). For example, this message is expressed as Npcf_EventExposure_AppRelocationInfo request(AckOfNotify(ackResult(afStatus=RELOC_ON_HOLD))).

[0068] S530: The PCF 30C2 transmits to the P-CSCF 30G2 a response message (Npcf_EventExposure_AppRelocationInfo response) in response to the message received in S529.

[0069] S531: PCF 30C2 sends to SMF 30B2 a message (Nsmf_EventExposure_AppRelocationInfo request) instructing that the switching between ULCL and L-UPF be temporarily put on hold. This message includes information instructing that the switching between ULCL and L-PSA be temporarily put on hold (RELOC_ON_HOLD). For example, this message is expressed as Nsmf_EventExposure_AppRelocationInfo request (AckOfNotify (ackResult(afStatus=RELOC_ON_HOLD))).

[0070] S532: The SMF 30B2 sends a response message (Nsmf_EventExposure_AppRelocationInfo response) to the message received in S531 to the PCF 30C2.

[0071] S533: The SMF30B2 temporarily suspends and does not execute the process related to switching between the ULCL and L-PSA (setting of the ULCL and L-PSA at the destination).

[0072] The process following S533 will be described below. Fig. 6 is a diagram showing an example of a third sequence diagram according to an embodiment of the present invention. The process of each step will be described below.

[0073] S541: The base station 10A transmits a request message (Handover Request) requesting a handover to the base station 10C. The request message includes information indicating that the cause of the handover is quasi-earth-fixed beam switch (Cause=quasi-earth-fixed beam switch).

[0074] S542: The base station 10C transmits a handover request acknowledgement including a handover command to the base station 10A as a response to the request message received in S541.

[0075] S543: The base station 10A transmits a message (RRCReconfiguration) requesting execution of settings related to radio resource control (RRC) to the terminal 20A. The message includes a handover command.

[0076] S544: The base station 10A sends an SN status transfer to the base station 10C.

[0077] S545: The terminal 20A transmits a message to the base station 10C notifying that the RRC-related settings have been completed. The message includes a handover confirmation.

[0078] S546: The base station 10C transmits a request message (Path Switch request) to the AMF 30A to request a path change associated with a base station change. The request message includes information indicating that the cause of the handover is quasi-earth-fixed beam switch (Cause=quasi-earth-fixed beam switch).

[0079] S547: AMF 30A recognizes the satellite constellation ID and satellite ID currently accommodating terminal 20A based on the correspondence between the transport layer settings and the identifier of the source base station that it recognized in advance, and the transport layer settings of the request message received in S546.

[0080] S548: AMF 30A sends a request message (Nsmf_PDUSession_UpdateSMContext request) requesting path switching accompanying a change in base station to SMF 30B. The request message includes a satellite constellation ID, a satellite ID, and information indicating that the cause of the handover is quasi-earth-fixed beam switch (Cause=quasi-earth-fixed beam switch), and is expressed as, for example, Nsmf_PDUSession_UpdateSMContext request (SmContextUpdateData(satellite constellation id, satellite id, Handover cause=quasi-earth-fixed beam switch)).

[0081] S549: SMF 30B sends a request message (PFCP Session Modification request) to ULCL 30E to update the user data transfer path.

[0082] S550: ULCL 30E sends a response message (PFCP Session Modification response) to the request message received in S549 to SMF 30B.

[0083] S551: SMF 30B sends a response message (Nsmf_PDUSession_UpdateSMContext response) to AMF 30A in response to the request message received in S548.

[0084] S552: The AMF 30A transmits to the base station 10C a response message (Path Switch request response) in response to the request message received in S556.

[0085] S553: ​​The base station 10C transmits a message (UE Context Release) requesting the release of the terminal context to the base station 10A.

[0086] Next, we will explain the procedures related to changing the ULCL and the termination point (PSA) in the PDU session when switching satellites. Figure 7 is a diagram showing an example of a fourth sequence diagram in an embodiment of the present invention. Below, we will explain the processing of each step.

[0087] S561: SMF 30B recognizes the base station switch and the satellite ID switch, and decides to execute the switch for the ULCL and the local UPF (L-UPF) deployed on the satellite. Here, the L-UPF may be expressed as the PDU session termination point (L-PSA).

[0088] S562: Using the event subscription set when the voice call was made, SMF30B decides to inquire of the P-CSCF via the PCF whether to allow switching from the pre-movement ULCL and pre-movement L-UPF to the destination ULCL and destination L-UPF (L-PSA).

[0089] S563: SMF 30B transmits to PCF 30C a message (Nsmf_EventExposure_Notify request) inquiring about whether to switch between the ULCL and L-UPF and notifying the event including an indication (EARLY) indicating that the ULCL and L-UPF (L-PSA) have not yet been moved. The message includes information indicating that the cause of the handover is quasi-earth-fixed beam switching (Cause=quasi-earth-fixed beam switch) and information indicating that the satellite beam type is quasi-earth-fixed (satellite beam type=quasi-earth-fixed). Also, for example, the message is expressed as Nsmf_EventExposure_Notify request (NsmfEventExposureNotification (eventNotifs(event=SAT_UP_PATH_CH, dnaiChgType=EARLY, Handover cause=quasi-earth-fixed beam switch, satellite type, satellite beam type=quasi-earth-fixed, satellite constellation id, satellite id= a target satellite id, OnSatteliteLpsaUlcl=true, OnSatteliteMediaRoutingToTatgetNetwork=false))).

[0090] S564: The PCF 30C sends a response message (Nsmf_EventExposure_Notify response) to the message received in S563 to the SMF 30B.

[0091] S565: PCF 30C transmits to P-CSCF 30G a message (Npcf_PolicyAuthorization_Notify request) inquiring about whether to switch between the ULCL and L-UPF and notifying an event including an indication (EARLY) indicating that the ULCL and L-PSA have not yet been moved. The message includes information indicating that the cause of the handover is quasi-earth-fixed beam switch (Cause=quasi-earth-fixed beam switch) and information indicating that the satellite beam type is quasi-earth-fixed (satellite beam type=quasi-earth-fixed). Also, for example, the message is expressed as Npcf_PolicyAuthorization_Notify request (EventsNotification (evNotifs(event=SAT_UP_PATH_CH), dnaiChgType=EARLY, Handover cause=quasi-earth-fixed beam switch, satellite type, satellite beam type=quasi-earth-fixed, satellite constellation id, satellite id= a target satellite id, OnSatteliteLpsaUlcl=true, OnSatteliteMediaRoutingToTatgetNetwork=false)).

[0092] S566: The P-CSCF 30G transmits to the PCF 30C a response message (Npcf_PolicyAuthorization_Notify response) in response to the message received in S565.

[0093] S567: The P-CSCF30G determines that the satellite constellation IDs of the originating and terminating terminals are the same even after switching between the ULCL and L-UPF, and that media routing on the satellite is possible. The P-CSCF30G also recognizes that it is necessary to start setting up the destination IMS AGW30FL3.

[0094] S568: The P-CSCF 30G recognizes that the originating terminal 20A and the terminating terminal 20B are deployed on the same satellite and that this satellite is the source satellite of the handover. The P-CSCF 30G also recognizes that the source satellite uses a quasi-earth-fixed beam and that other satellites in the same satellite constellation also use quasi-earth-fixed beams. The P-CSCF 30G also recognizes that the cause of the handover is a quasi-earth-fixed beam switch (Cause=quasi-earth-fixed beam switch) contained in the message received in S565. The P-CSCF 30G also recognizes that its own device belongs to the originating network. Based on this recognition, the P-CSCF 30G also determines to execute a procedure for changing satellites.

[0095] S569: P-CSCF 30G transmits a message (Npcf_EventExposure_AppRelocationInfo request) indicating approval of the switching between ULCL and L-UPF to PCF 30C. For example, this message is expressed as Npcf_EventExposure_AppRelocationInfo request (AckOfNotify (ackResult (afStatus=SUCCESS))).

[0096] S570: The PCF 30C transmits to the P-CSCF 30G a response message (Npcf_EventExposure_AppRelocationInfo response) in response to the message received in S569.

[0097] S571: PCF 30C sends a message (Nsmf_EventExposure_AppRelocationInfo request) to SMF 30B indicating approval of the switching between ULCL and L-UPF.

[0098] S572: The SMF 30B sends a response message (Nsmf_EventExposure_AppRelocationInfo response) to the message received in S571 to the PCF 30C.

[0099] S573: The SMF 30B determines to execute the setting of the destination ULCL (ULCL 30E) and the destination L-UPF (UPF 30D5L3).

[0100] S574: The SMF 30B selects the destination ULCL (ULCL 30E) and the destination L-UPF (UPF 30D5L3) based on the satellite ID to which the destination base station 10C belongs.

[0101] The process following S574 will be described. Fig. 8 is a diagram showing an example of a fifth sequence diagram according to an embodiment of the present invention. The process of each step will be described below.

[0102] S581: SMF30B sends a request message (PFCP Session Establishment request) to UPF30D5L3 requesting the establishment of a path for transferring user data for uplink (UL).

[0103] S582: UPF 30D5L3 sends a response message (PFCP Session Establishment response) to the request message received in S581 to SMF 30B. The response message includes a packet detection rule (PDR) in which information indicating the UL data termination point (TEID for UL in PSA5) is set. For example, the response message is expressed as PFCP Session Establishment response (PDR = TEID (Tunnel Endpoint IDentifier) ​​for UL in PSA5).

[0104] S583: The SMF 30B transmits a request message (PFCP Session Establishment request) to the ULCL 30E3 requesting establishment of a path for transferring user data. The request message includes information for setting a dummy value as a UL traffic filter for the destination L-UPF (UPF 30D5L3) and information for setting the termination point of the source IMS AGW (IMS AGW 30FL) as a UL traffic filter for the source ULCL (ULCL 30E). For example, the request message includes a first request message for UL for PSA5, a second request message for UL for PSA1, a third request message for UL originating from the base station 10B, a fourth request message for DL, a fifth request message for tunnel UL, and a sixth request message for tunnel DL. Furthermore, the first request message is expressed as a PFCP Session Establishment request (Traffic filter for UL to PSA5=dummy value, FAR=PSA5 UL TEID), the second request message is expressed as a PFCP Session Establishment request (Traffic filter for UL to PSA1=default, FAR=PSA1 UL TEID), the fourth request message is expressed as a PFCP Session Establishment request (FAR=target gNB DL TEID), the fifth request message is expressed as a PFCP Session Establishment request (Traffic filter for UL to source ULCL=source satellite IMS AGW IP address, FAR=source ULCL UL TEID), and the sixth request message is expressed as a PFCP Session Establishment request (PDR request), where FAR indicates a Forwarding Action Rule.

[0105] S584: ULCL 30E3 transmits a response message (PFCP Session Establishment response) to the request message received in S583 to SMF 30B. Note that the response message to the third request message is expressed as PFCP Session Establishment response (PDR=target ULCL UL TEID), the response message to the fourth request message is expressed as PFCP Session Establishment response (PDR=target ULCL DL TEID), and the response message to the sixth request message is expressed as PFCP Session Establishment response (PDR=target ULCL DL forwarding TEID).

[0106] S585: SMF 30B sends a request message (PFCP Session Modification request) for updating the user data forwarding path for the tunnel DL to ULCL 30E. For example, this request message is expressed as PFCP Session Modification request (FAR = target ULCL DL forwarding TEID).

[0107] S586: ULCL 30E transmits to SMF 30B a response message (PFCP Session Modification response) to the request message received in S585.

[0108] S587: The SMF 30B sends a request message (PFCP Session Modification request) for updating the DL user data transfer path to the UPF 30D1R. For example, the request message is expressed as a PFCP Session Modification request (FAR=target ULCL DL TEID).

[0109] S588: UPF30D1R sends a response message (PFCP Session Modification response) to the request message received in S587 to SMF30B.

[0110] S589: The SMF 30B sends a request message (PFCP Session Modification request) for updating the DL user data transfer path to the UPF 30D 5L3. For example, the request message is expressed as PFCP Session Modification request (FAR = target ULCL DL TEID).

[0111] S590: UPF30D5L3 sends a response message (PFCP Session Modification response) to the request message received in S589 to SMF30B.

[0112] S591: SMF 30B sends a request message (Namf_Communication_N1N2MessageTransfer request) for updating the setting of PDU session resources to AMF 30A. For example, the request message is expressed as Namf_Communication_N1N2MessageTransfer request (N1N2MessageTransferReqData(n2InfoContainer(smInfo(n2InfoContent(PDU Session Resource Modify Request Transfer(UL NG-U UP TNL Information=target ULCL UL TEID)))))).

[0113] S592: AMF 30A sends a response message (Namf_Communication_N1N2MessageTransfer response) to SMF 30B in response to the request message received in S591.

[0114] S593: The AMF 30A transmits a request message (PDU Session Resource Modify Request) for updating the setting of the PDU session resource to the base station 10C. For example, the message is expressed as PDU Session Resource Modify Request (PDU Session Resource Modify Request Transfer (UL NG-U UP TNL Information = target ULCL UL TEID)).

[0115] S594: The base station 10C sends a response message (PDU Session Resource Modify response) to the request message received in S593 to the AMF 30A.

[0116] S595: AMF 30A sends a request message (Nsmf_PDUSession_UpdateSMContext request) requesting a PDU session context update to SMF 30B. For example, the request message is expressed as Nsmf_PDUSession_UpdateSMContext request (SmContextUpdateData(n2SmInfo(PDU Session Resource Modify Response Transfer))).

[0117] S596: SMF 30B sends a response message (Nsmf_PDUSession_UpdateSMContext response) to AMF 30A in response to the request message received in S595.

[0118] The process following S596 will be described. Fig. 9 is a diagram showing an example of a sixth sequence diagram according to an embodiment of the present invention. The process of each step will be described below.

[0119] S601: SMF30B uses the event subscription set when the voice call is made to determine to notify the P-CSCF via the PCF that the destination ULCL and destination L-UPF have been set.

[0120] S602: SMF 30B sends a message (Nsmf_EventExposure_Notify) to PCF 30C notifying the completion of switching between the ULCL and L-UPF, and notifying the event including an indication (LATE) indicating that the transition to the ULCL and L-UPF of the satellite after the transition has occurred. The message includes information indicating that the cause of the handover is quasi-earth-fixed beam switching (Cause=quasi-earth-fixed beam switch) and information indicating that the satellite beam type is quasi-earth-fixed (satellite beam type=quasi-earth-fixed). Also, for example, the request message is expressed as Nsmf_EventExposure_Notify request (NsmfEventExposureNotification(eventNotifs(event=SAT_UP_PATH_CH, dnaiChgType=LATE, Handover cause=quasi-earth-fixed beam switch, satellite type, satellite beam type=quasi-earth-fixed, satellite constellation id, satellite id= a target satellite id, OnSatteliteLpsaUlcl=true, OnSatteliteMediaRoutingToTatgetNetwork=false))).

[0121] S603: The PCF 30C sends a response message (Nsmf_EventExposure_Notify response) to the message received in S602 to the SMF 30B.

[0122] S604: The PCF 30C transmits to the P-CSCF 30G a message (Npcf_PolicyAuthorization_Notify request) notifying the completion of switching between the ULCL and the L-UPF, and notifying the P-CSCF 30G of an event including an indication (LATE) indicating that the transition to the ULCL and the L-UPF of the satellite after the transition has been completed. The message includes information indicating that the cause of the handover is quasi-earth-fixed beam switching (Cause=quasi-earth-fixed beam switch) and information indicating that the satellite beam type is quasi-earth-fixed (satellite beam type=quasi-earth-fixed). Also, for example, the request message is expressed as Npcf_PolicyAuthorization_Notify request(EventsNotification(evNotifs(event=SAT_UP_PATH_CH), dnaiChgType=LATE, Handover cause=quasi-earth-fixed beam switch, satellite type, satellite beam type=quasi-earth-fixed, satellite constellation id, satellite id= a target satellite id, OnSatteliteLpsaUlcl=true, OnSatteliteMediaRoutingToTatgetNetwork=false)).

[0123] S605: The P-CSCF 30G transmits to the PCF 30C a response message (Npcf_PolicyAuthorization_Notify response) in response to the message received in S604.

[0124] S606: The P-CSCF 30G recognizes that the destination IMS AGW 30FL3 needs to be configured.

[0125] S607: The P-CSCF 30G transmits to the PCF 30C a message (Npcf_EventExposure_AppRelocationInfo request) indicating that the switching between the ULCL and the L-UPF is approved.

[0126] S608: The PCF 30C transmits to the P-CSCF 30G a response message (Npcf_EventExposure_AppRelocationInfo response) in response to the message received in S607.

[0127] S609: PCF 30C sends a message (Nsmf_EventExposure_AppRelocationInfo request) to SMF 30B indicating approval of the switching between ULCL and L-UPF.

[0128] S610: The SMF 30B sends a response message (Nsmf_EventExposure_AppRelocationInfo response) to the message received in S609 to the PCF 30C.

[0129] S611: SMF30B determines to enable the terminal 20A to recognize the change in PANI (P-Access-Network-Info) in the SIP header, i.e., to send an instruction to have the terminal 20A confirm the NR cell ID after movement.

[0130] S612: SMF 30B sends a request message (Namf_Communication_N1N2MessageTransfer request) related to the PANI change in terminal 20A to AMF 30A. For example, the request message is expressed as Namf_Communication_N1N2MessageTransfer request (N1N2MessageTransferReqData (n2InfoContainer (smInfo (n2InfoContent (Location Reporting Control (Location Reporting Request Type (Event Type = one time change of IMS PANI in UE))))))).

[0131] S613: AMF 30A sends a response message (Namf_Communication_N1N2MessageTransfer response) to SMF 30B in response to the request message received in S612.

[0132] S614: The AMF 30A transmits a message (Location Reporting Control) to the base station 10C requesting the terminal 20A to confirm the NR cell ID. For example, the message is expressed as Location Reporting Control (Location Reporting Request Type (Event Type = one time change of IMS PANI in UE)).

[0133] S615: The base station 10C transmits to the AMF 30A a response message (Location Report) in response to the request message received in S614.

[0134] S616: AMF 30A sends a request message (Nsmf_PDUSession_UpdateSMContext request) requesting a PDU session context update to SMF 30B. For example, the request message is expressed as Nsmf_PDUSession_UpdateSMContext request (SmContextUpdateData (n2SmInfo (Location Report))).

[0135] S617: SMF 30B sends a response message (Nsmf_PDUSession_UpdateSMContext response) to AMF 30A in response to the request message received in S616.

[0136] S618: The base station 10C transmits to the terminal 20A a message (RRCReconfiguration) related to RRC configuration, which includes information requesting the terminal 20A to acquire system information (SIB) of the serving cell and transmit a measurement report.

[0137] S619: The terminal 20A transmits to the base station 10C a response message (RRCReconfigurationComplete) in response to the message received in S618.

[0138] S620: Terminal 20A recognizes that the NR cell ID of the current accommodating cell is different from the NR cell ID set in the message requesting the start of voice communication, recognizes that the contents of PANI will change, and therefore recognizes that a re-INVITE needs to be sent.

[0139] S621: The terminal 20A sends a message (SIP re-INVITE) to the P-CSCF 30G requesting an update of the voice communication status, including the NR cell ID of the current accommodating cell.

[0140] S622: The P-CSCF 30G determines to set up the IMS AGW 30FL3 on the destination satellite while maintaining the setting of the IMS AGW 30FL on the source satellite.

[0141] S623: The P-CSCF 30G transmits to the IMS AGW 30FL3 a request message (H.248 ADD request) requesting settings related to (addition of) voice communication control.

[0142] S624: The IMS AGW 30FL3 acquires and sets resources of its own termination point related to data transmission with the destination side.

[0143] S625: The IMS AGW 30FL3 transmits to the P-CSCF 30G a response message (H.248 ADD response) in response to the request message received in S623.

[0144] The process following S625 will be described. Fig. 10 is a diagram showing an example of a seventh sequence diagram according to an embodiment of the present invention. The process of each step will be described below.

[0145] S631: The P-CSCF30G recognizes that switching between ULCL and L-PSA will occur simultaneously in the originating network and the terminating network. The P-CSCF30G also recognizes that the P-CSCF30G2 on the terminating network side will configure the IMS AGW30FL4 on the destination satellite, and determines to configure the IMS AGW30FL3 on the destination satellite on the originating network side in the c= line in the SDP of the SIP message.

[0146] S632: The P-CSCF 30G sends to the S-CSCF 30H a message (SIP re-INVITE) requesting an update of the voice communication status, including the termination point on the destination IMS AGW 30FL3 side. For example, this message is expressed as SIP re-INVITE (PANI (access-type=3GPP-NR-SAT, utran-cell-id-3gpp=MCC+MNC+TAC+NR cell ID), PSI (satellite-type=LEO CONSTELLATION, satellite constellation id, satellite-id), SDP offer (c= the originating target satellite IMS AGW IP address, a=satellite-optimal-routing-capable)). Here, because PANI cannot be transmitted to other networks, a new private header field (P-Satellite-Info (PSI) Header Field) is used.

[0147] S633: The S-CSCF 30H transmits the message (SIP re-INVITE) received in S632 to the I-CSCF 30I.

[0148] S634: The I-CSCF 30I transmits the message (SIP re-INVITE) received in S633 to the S-CSCF 30H2.

[0149] S635: The S-CSCF 30H2 transmits the message (SIP re-INVITE) received in S634 to the P-CSCF 30G2.

[0150] S636: The P-CSCF 30G2 determines to set up an IMS AGW 30FL4 on the destination satellite at the current time.

[0151] S637: The P-CSCF 30G2 transmits to the IMS AGW 30FL4 a request message (H.248 ADD request) requesting settings related to (addition of) voice communication control.

[0152] S638: The IMS AGW 30FL4 acquires and sets resources of its own termination point related to data transmission with the destination side.

[0153] S639: The IMS AGW 30FL4 transmits to the P-CSCF 30G2 a response message (H.248 ADD response) in response to the request message received in S637.

[0154] S640: The P-CSCF 30G2 determines to set the IMS AGW 30FL4 on the source satellite on the destination network side in the c= line in the SDP of the SIP message.

[0155] S641: The P-CSCF 30G2 sends a message (SIP re-INVITE) requesting an update of the voice communication state, including the termination point on the source IMS AGW 30FL side, to the terminal 20B. For example, this message is expressed as SIP re-INVITE (SDP offer (c= the terminating source satellite IMS AGW IP address)).

[0156] S642: The terminal 20B sends a success response (SIP 200 OK) to the P-CSCF 30G2. For example, this message is expressed as SIP 200 OK (PANI(access-type=3GPP-NR-SAT, utran-cell-id-3gpp=MCC+MNC+TAC+NR cell ID), SDP answer (c= the terminating UE IP address)).

[0157] The process following S642 will be described. Fig. 11 is a diagram showing an example of an eighth sequence diagram according to an embodiment of the present invention. The process of each step will be described below.

[0158] S651: The P-CSCF 30G2 determines that the satellite constellation IDs of the originating and terminating terminals are the same even after switching between the LCL and L-UPF, and that media routing on the satellite is possible. The P-CSCF 30G2 also recognizes that it is necessary to start setting up the destination IMS AGW 30FL4.

[0159] S652: The P-CSCF 30G2 determines to cause the SMF 30B2 to start setting the destination IMS AGW 30FL4.

[0160] S653: P-CSCF30G2 transmits to PCF30C2 a message (Npcf_EventExposure_AppRelocationInfo request) indicating approval of the switching between ULCL and L-UPF. For example, this message is expressed as Npcf_EventExposure_AppRelocationInfo request (AckOfNotify (ackResult (afStatus=SUCCESS))).

[0161] S654: The PCF 30C2 transmits to the P-CSCF 30G2 a response message (Npcf_EventExposure_AppRelocationInfo response) in response to the message received in S653.

[0162] S655: PCF 30C2 sends a message (Nsmf_EventExposure_AppRelocationInfo request) to SMF 30B2 indicating approval of the switching between ULCL and L-UPF.

[0163] S656: The SMF 30B2 sends a response message (Nsmf_EventExposure_AppRelocationInfo response) to the message received in S655 to the PCF 30C2.

[0164] S657: The SMF 30B2 determines to execute the setting of the destination ULCL (ULCL 30E) and the destination L-UPF (UPF 30D5L3).

[0165] S658: The SMF 30B2 selects the destination ULCL (ULCL 30E) and the destination L-UPF (UPF 30D5L3) based on the satellite ID to which the destination base station 10C belongs.

[0166] The process following S658 will be described. Fig. 12 is a diagram showing an example of a ninth sequence diagram according to an embodiment of the present invention. The process of each step will be described below.

[0167] S661: SMF302B sends a request message (PFCP Session Establishment request) to UPF30D6L3 requesting the establishment of a path for transferring user data for the uplink (UL).

[0168] S662: UPF 30D6L3 sends a response message (PFCP Session Establishment response) to the request message received in S661 to SMF 30B2. The response message includes a packet detection rule (PDR) in which information indicating the UL data termination point (TEID for UL in PSA6) is set. For example, the response message is expressed as PFCP Session Establishment response (PDR = TEID (Tunnel Endpoint IDentifier) ​​for UL in PSA6).

[0169] S663: The SMF 30B2 transmits a request message (PFCP Session Establishment request) to the ULCL 30E4, requesting the establishment of a path for transferring user data. The request message includes information for setting a dummy value as the UL traffic filter for the destination L-UPF (UPF 30D6L3) and information for setting the termination point of the source IMS AGW (IMS AGW 30FL2) as the UL traffic filter for the source ULCL (ULCL 30E2). For example, the request message includes a first request message for UL for PSA6, a second request message for UL for PSA3, a third request message for UL originating from the base station 10D, a fourth request message for DL, a fifth request message for tunnel UL, and a sixth request message for tunnel DL. Furthermore, the first request message is expressed as a PFCP Session Establishment request (Traffic filter for UL to PSA6=dummy value, FAR=PSA6 UL TEID), the second request message is expressed as a PFCP Session Establishment request (Traffic filter for UL to PSA3=default, FAR=PSA3 UL TEID), the fourth request message is expressed as a PFCP Session Establishment request (FAR=target gNB DL TEID), the fifth request message is expressed as a PFCP Session Establishment request (Traffic filter for UL to source ULCL=source satellite IMS AGW IP address, FAR=source ULCL UL TEID), and the sixth request message is expressed as a PFCP Session Establishment request (PDR request), where FAR indicates a Forwarding Action Rule.

[0170] S664: ULCL 30E4 transmits to SMF 30B2 a response message (PFCP Session Establishment response) to the request message received in S663. Note that the response message to the third request message is expressed as PFCP Session Establishment response (PDR = target ULCL UL TEID), the response message to the fourth request message is expressed as PFCP Session Establishment response (PDR = target ULCL DL TEID), and the response message to the sixth request message is expressed as PFCP Session Establishment response (PDR = target ULCL DL forwarding TEID).

[0171] S665: The SMF 30B2 transmits a request message (PFCP Session Modification request) for updating the user data forwarding path for the tunnel DL to the ULCL 30E2. For example, the request message is expressed as a PFCP Session Modification request (FAR = target ULCL DL forwarding TEID).

[0172] S666: ULCL 30E2 transmits to SMF 30B2 a response message (PFCP Session Modification response) to the request message received in S665.

[0173] S667: The SMF 30B2 sends a request message (PFCP Session Modification request) for updating the DL user data transfer path to the UPF 30D3R. For example, the request message is expressed as PFCP Session Modification request (FAR=target ULCL DL TEID).

[0174] S668: UPF 30D3R sends a response message (PFCP Session Modification response) to the request message received in S667 to SMF 30B2.

[0175] S669: The SMF 30B2 sends a request message (PFCP Session Modification request) to the UPF 30D6L3 to update the DL user data transfer path. For example, the request message is expressed as PFCP Session Modification request (FAR = target ULCL DL TEID).

[0176] S670: UPF 30D6L3 sends a response message (PFCP Session Modification response) to the request message received in S669 to SMF 30B2.

[0177] S671: SMF 30B2 sends a request message (Namf_Communication_N1N2MessageTransfer request) for updating the setting of PDU session resources to AMF 30A2. For example, the request message is expressed as Namf_Communication_N1N2MessageTransfer request (N1N2MessageTransferReqData(n2InfoContainer(smInfo(n2InfoContent(PDU Session Resource Modify Request Transfer(UL NG-U UP TNL Information=target ULCL UL TEID)))))).

[0178] S672: AMF 30A2 sends a response message (Namf_Communication_N1N2MessageTransfer response) to SMF 30B2 in response to the request message received in S671.

[0179] S673: The AMF 30A2 transmits a request message (PDU Session Resource Modify Request) for updating the PDU session resource settings to the base station 10D. For example, the message is expressed as PDU Session Resource Modify Request (PDU Session Resource Modify Request Transfer (UL NG-U UP TNL Information = target ULCL UL TEID)).

[0180] S674: The base station 10D transmits to the AMF 30A2 a response message (PDU Session Resource Modify response) to the request message received in S673.

[0181] S675: AMF 30A2 sends a request message (Nsmf_PDUSession_UpdateSMContext request) to SMF 30B2 requesting a PDU session context update. For example, the request message is expressed as Nsmf_PDUSession_UpdateSMContext request (SmContextUpdateData (n2SmInfo(PDU Session Resource Modify Response Transfer))).

[0182] S676: SMF30B2 sends a response message (Nsmf_PDUSession_UpdateSMContext response) to AMF30A2 in response to the request message received in S675.

[0183] The process following S676 will be described below. Fig. 13 is a diagram showing an example of a tenth sequence diagram according to an embodiment of the present invention. The process of each step will be described below.

[0184] S681: SMF30B2 uses the event subscription set when the voice call was made to decide to notify the P-CSCF via the PCF that the destination ULCL and destination L-UPF have been set.

[0185] S682: SMF 30B2 sends a message (Nsmf_EventExposure_Notify) to PCF 30C2 notifying the completion of switching between the ULCL and L-UPF, and notifying the event including an indication (LATE) indicating that the transition to the ULCL and L-UPF of the satellite after the transition has occurred. The message includes information indicating that the cause of the handover is quasi-earth-fixed beam switching (Cause=quasi-earth-fixed beam switch) and information indicating that the satellite beam type is quasi-earth-fixed (satellite beam type=quasi-earth-fixed). Also, for example, the request message is expressed as Nsmf_EventExposure_Notify request (NsmfEventExposureNotification(eventNotifs(event=SAT_UP_PATH_CH, dnaiChgType=LATE, Handover cause=quasi-earth-fixed beam switch, satellite type, satellite beam type=quasi-earth-fixed, satellite constellation id, satellite id= a target satellite id, OnSatteliteLpsaUlcl=true, OnSatteliteMediaRoutingToTatgetNetwork=false))).

[0186] S683: The PCF 30C2 sends a response message (Nsmf_EventExposure_Notify response) to the message received in S682 to the SMF 30B2.

[0187] S684: PCF30C2 sends to P-CSCF30G2 a message (Npcf_PolicyAuthorization_Notify request) notifying the completion of switching between the ULCL and L-UPF, and notifying the event including an indication (LATE) indicating that the transition to the ULCL and L-UPF of the satellite after the transition has occurred. The message includes information indicating that the cause of the handover is quasi-earth-fixed beam switching (Cause=quasi-earth-fixed beam switch) and information indicating that the satellite beam type is quasi-earth-fixed (satellite beam type=quasi-earth-fixed). Also, for example, the request message is expressed as Npcf_PolicyAuthorization_Notify request(EventsNotification(evNotifs(event=SAT_UP_PATH_CH), dnaiChgType=LATE, Handover cause=quasi-earth-fixed beam switch, satellite type, satellite beam type=quasi-earth-fixed, satellite constellation id, satellite id= a target satellite id, OnSatteliteLpsaUlcl=true, OnSatteliteMediaRoutingToTatgetNetwork =false)).

[0188] S685: The P-CSCF 30G2 transmits to the PCF 30C2 a response message (Npcf_PolicyAuthorization_Notify response) in response to the message received in S684.

[0189] S686: The P-CSCF 30G2 transmits to the IMS AGW 30FL4 a request message (H.248 MOD request) requesting settings related to (modification of) control of voice communication.

[0190] S687: The IMS AGW 30FL4 sets a termination point on the destination side for data transmission with the destination side.

[0191] S688: The IMS AGW 30FL4 transmits to the P-CSCF 30G2 a response message (H.248 MOD response) in response to the request message received in S686.

[0192] S689: The P-CSCF 30G2 transmits to the IMS AGW 30FL4 a request message (H.248 ADD request) requesting settings related to (addition of) voice communication control.

[0193] S690: The IMS AGW 30FL4 acquires and sets resources of its own termination point related to data transmission with the calling side.

[0194] S691: The IMS AGW 30FL4 transmits to the P-CSCF 30G2 a response message (H.248 ADD response) in response to the request message received in S689.

[0195] S692: The P-CSCF 30G2 determines to set the termination point of the IMS AGW 30FL4 of the destination satellite in the traffic filter of ULCLE4.

[0196] S693: The P-CSCF 30G2 sends to the PCF 30C2 a request message (Npcf_PolicyAuthorization_Create request) requesting the SMF 30B2 to set the termination point of the destination IMS AGW 30FL4 in the UL traffic filter for the destination L-UPF (UPF 30D6L3). For example, this message is expressed as Npcf_PolicyAuthorization_Create request (the target satellite IMS AGW IP address).

[0197] S694: The PCF 30C2 transmits to the P-CSCF 30G2 a response message (Npcf_PolicyAuthorization_Create response) in response to the request message received in S693.

[0198] S695: The PCF 30C2 sends to the SMF 30B2 a request message (Npcf_SMPolicyControl_UpdateNotify request) requesting that the termination point of the destination IMS AGW 30FL4 be set in the UL traffic filter for the destination L-UPF (UPF 30D6L3). For example, this message is expressed as Npcf_SMPolicyControl_UpdateNotify request (the target satellite IMS AGW IP address).

[0199] S696: The SMF 30B2 sends to the PCF 30C2 a response message (Npcf_SMPolicyControl_UpdateNotify response) in response to the request message received in S695.

[0200] S697: The SMF 30B2 sends, to the ULCL 30E4, a request message (PFCP Session Modification request) requesting a packet forwarding setting update, including information for setting the termination point of the destination IMS AGW 30FL4 as the UL traffic filter for the destination L-UPF (UPF 30D6L3). For example, the request message is expressed as PFCP Session Modification request (Traffic filter for UL to PSA6= the target satellite IMS AGW IP address, FAR=PSA6 UL TEID).

[0201] S698: ULCL 30E4 sends a response message (PFCP Session Modification response) to the request message received in S697 to SMF 30B2.

[0202] The process following S698 will be described. Fig. 14 is a diagram showing an example of an eleventh sequence diagram according to an embodiment of the present invention. The process of each step will be described below.

[0203] S701: The P-CSCF 30G2 determines to set the IMS AGW 30FL4 on the destination satellite on the destination network side in the c= line in the SDP of the SIP message (SIP 200 OK) received in S642.

[0204] S702: The P-CSCF 30G2 sends a success response (SIP 200 OK) to the S-CSCF 30H2. The message includes information about the IMS AGW 30FL4 on the satellite after switching on the destination network side. For example, the message is expressed as SIP 200 OK (PANI (access-type=3GPP-NR-SAT, utran-cell-id-3gpp=MCC+MNC+TAC+NR cell ID), PSI (satellite-type=LEO CONSTELLATION, satellite constellation id, satellite-id), SDP answer (c= the terminating target satellite IMS AGW IP address, a=satellite-optimal-routing-capable)).

[0205] S703: The S-CSCF 30H2 transmits the success response (SIP 200 OK) received in S702 to the I-CSCF 30I.

[0206] S704: The I-CSCF 30I transmits the success response (SIP 200 OK) received in S703 to the S-CSCF 30H.

[0207] S705: The S-CSCF 30H transmits the success response (SIP 200 OK) received in S704 to the P-CSCF 30G.

[0208] S706: The P-CSCF 30G transmits to the IMS AGW 30FL3 a request message (H.248 MOD request) requesting settings related to (modification of) control of voice communication.

[0209] S707: The IMS AGW 30FL3 sets a termination point on the destination side for data transmission with the destination side.

[0210] S708: The IMS AGW 30FL3 transmits to the P-CSCF 30G a response message (H.248 MOD response) in response to the request message received in S706.

[0211] S709: The P-CSCF 30G transmits to the IMS AGW 30FL3 a request message (H.248 ADD request) requesting settings related to (addition of) voice communication control.

[0212] S710: The IMS AGW 30FL3 acquires and sets resources of its own termination point related to data transmission with the calling side.

[0213] S711: The IMS AGW 30FL3 transmits to the P-CSCF 30G a response message (H.248 ADD response) in response to the request message received in S709.

[0214] S712: Before indicating the termination point of the IMS AGW 30FL3 on the destination satellite to the terminal 20A, the P-CSCF 30G determines to set the termination point in the traffic filter of the ULCL 30E3.

[0215] S713: The P-CSCF 30G sends a request message (Npcf_PolicyAuthorization_Create request) to the PCF 30C, requesting the SMF 30B to set the termination point of the destination IMS AGW 30FL3 in the UL traffic filter for the destination L-UPF (UPF 30D5L3). For example, this message is expressed as Npcf_PolicyAuthorization_Create request (the target satellite IMS AGW IP address).

[0216] S714: The PCF 30C transmits to the P-CSCF 30G a response message (Npcf_PolicyAuthorization_Create response) in response to the request message received in S713.

[0217] S715: The PCF 30C sends to the SMF 30B a request message (Npcf_SMPolicyControl_UpdateNotify request) requesting that the termination point of the destination IMS AGW 30FL3 be set in the UL traffic filter for the destination L-UPF (UPF 30D5L3). For example, this message is expressed as Npcf_SMPolicyControl_UpdateNotify request (the target satellite IMS AGW IP address).

[0218] S716: The SMF 30B sends to the PCF 30C a response message (Npcf_SMPolicyControl_UpdateNotify response) in response to the request message received in S715.

[0219] S717: The SMF 30B sends to the ULCL 30E3 a request message (PFCP Session Modification request) requesting a packet forwarding setting update, which includes information for setting the termination point of the destination IMS AGW 30FL3 as a UL traffic filter for the destination L-UPF (UPF30D5L3). For example, the request message is expressed as PFCP Session Modification request (Traffic filter for UL to PSA3= the target satellite IMS AGW IP address, FAR=PSA5 UL TEID).

[0220] S718: ULCL 30E3 sends a response message (PFCP Session Modification response) to the request message received in S717 to SMF 30B.

[0221] S719: The P-CSCF 30G sends a success response (SIP 200 OK) to the terminal 20A. For example, the message is expressed as SIP 200 OK (SDP answer (c=the target satellite IMS AGW IP address)).

[0222] The process following S719 will be described. Fig. 15 is a diagram showing an example of a twelfth sequence diagram according to an embodiment of the present invention. The process of each step will be described below.

[0223] S721: The P-CSCF 30G determines to transmit a notification (UPDATE) to the destination network side because the setting in the destination IMS AGW 30FL3 on the satellite has been completed.

[0224] S722: The P-CSCF 30G sends to the S-CSCF 30H a message (UPDATE) requesting an update of the voice communication status, including information about the termination point on the destination IMS AGW 30FL3 side. For example, the message is expressed as UPDATE (PANI (access-type=3GPP-NR-SAT, utran-cell-id-3gpp=MCC+MNC+TAC+NR cell ID), PSI (satellite-type=LEO CONSTELLATION, satellite constellation id, satellite-id), SDP offer (c= the originating target satellite IMS AGW IP address, a=satellite-optimal-routing-capable)).

[0225] S723: The S-CSCF 30H transmits the message (UPDATE) received in S722 to the I-CSCF 30I.

[0226] S724: I-CSCF 30I transmits the message (UPDATE) received in S723 to S-CSCF 30H2.

[0227] S725: The S-CSCF 30H2 transmits the message (UPDATE) received in S724 to the P-CSCF 30G2.

[0228] S726: P-CSCF30G2 deletes PANI and PSI from the message (UPDATE) received in S725, and generates a message in which the attribute (a=satellite-optimal-routing-capable) indicating that the SDP offer has media routing capability over the satellite is deleted from the SDP offer.

[0229] S727: The P-CSCF 30G2 transmits the message (UPDATE) generated in S726 to the terminal 20B.

[0230] S728: The terminal 20B transmits to the P-CSCF 30G2 a response message (200 OK (UPDATE)) in response to the message received in S727.

[0231] S729: P-CSCF 30G2 transmits the message (200 OK (UPDATE)) received in S728 to S-CSCF 30H2.

[0232] S730: The S-CSCF 30H2 transmits the message (200 OK (UPDATE)) received in S729 to the I-CSCF 30I.

[0233] S731: The I-CSCF 30I transmits the message (200 OK (UPDATE)) received in S730 to the S-CSCF 30H.

[0234] S732: The S-CSCF 30H transmits the message (200 OK (UPDATE)) received in S731 to the P-CSCF 30G.

[0235] According to the above-described embodiment, in a satellite-based wireless communication system, it is possible to switch between satellites that simultaneously accommodate two terminals communicating using a quasi-terrestrial fixed service link, and also to seamlessly continue voice communication between the terminals before and after the switch.

[0236] (Device Configuration) Next, a description will be given of an example of the functional configuration of the base station 10, network node 30, and terminal 20 that perform the processes and operations described above. The base station 10, network node 30, and terminal 20 include functions for performing the above-described embodiments. However, the base station 10, network node 30, and terminal 20 may each include only a part of the functions of the embodiments.

[0237] <Base Station 10 and Network Node 30> Fig. 16 is a diagram showing an example of the functional configuration of the base station 10 and the network node 30. As shown in Fig. 16, the base station 10 has a transmitting unit 110, a receiving unit 120, a setting unit 130, and a control unit 140. The functional configuration shown in Fig. 16 is merely an example. As long as the operations according to the embodiment of the present invention can be performed, the names of the functional divisions and functional units may be any. Note that the network node 30 may have the same functional configuration as the base station 10. Furthermore, a network node 30 having multiple different functions in the system architecture may be composed of multiple network nodes 30 separated by function.

[0238] The transmitter 110 includes a function of generating a signal to be transmitted to the terminal 20 or another network node 30 and transmitting the signal by wire or wirelessly. The receiver 120 includes a function of receiving various signals transmitted from the terminal 20 or another network node 30 and acquiring, for example, information of a higher layer from the received signal. A communication unit including the transmitter 110 and the receiver 120 may be configured.

[0239] The setting unit 130 stores preset setting information and various setting information to be transmitted to the terminal 20 in a storage device, and reads out the information from the storage device as needed.

[0240] The control unit 140 performs the processes described in the embodiments, etc. The control unit 140 also performs processes related to communication with the terminal 20. The function unit related to signal transmission in the control unit 140 may be included in the transmitting unit 110, and the function unit related to signal reception in the control unit 140 may be included in the receiving unit 120.

[0241] <Terminal 20> Fig. 17 is a diagram showing an example of the functional configuration of the terminal 20. As shown in Fig. 17, the terminal 20 has a transmitting unit 210, a receiving unit 220, a setting unit 230, and a control unit 240. The functional configuration shown in Fig. 17 is merely an example. As long as the operations related to the embodiment of the present invention can be performed, the names of the functional divisions and functional units may be any. In addition, a communication device that becomes a resource holder 20 may have the same functional configuration as the terminal 20.

[0242] The transmitter 210 creates a transmission signal from transmission data and transmits the transmission signal wirelessly. The receiver 220 receives various signals wirelessly and acquires higher layer signals from the received physical layer signals. The receiver 220 also has a function of receiving control signals, reference signals, etc. transmitted from the network node 30. A communication unit including the transmitter 210 and the receiver 220 may be configured.

[0243] The setting unit 230 stores various pieces of setting information received from the network node 30 by the receiving unit 220 in a storage device, and reads them out from the storage device as needed. The setting unit 230 also stores setting information that is set in advance.

[0244] The control unit 240 performs the processes described in the embodiments. The function unit related to signal transmission in the control unit 240 may be included in the transmitting unit 210, and the function unit related to signal reception in the control unit 240 may be included in the receiving unit 220.

[0245] (Hardware Configuration) The block diagrams (FIGS. 16 and 17) used to explain the above embodiments show functional blocks. These functional blocks (components) are realized by any combination of at least one of hardware and software. Furthermore, the method for realizing each functional block is not particularly limited. That is, each functional block may be realized using a single device that is physically or logically coupled, or may be realized using two or more physically or logically separated devices that are directly or indirectly connected (for example, using wires, wirelessly, etc.) and these multiple devices. The functional block may be realized by combining software with the single device or the multiple devices.

[0246] Functions include, but are not limited to, judgment, determination, assessment, calculation, computation, processing, derivation, investigation, search, confirmation, reception, transmission, output, access, resolution, selection, selection, establishment, comparison, assumption, expectation, consideration, broadcasting, notifying, communicating, forwarding, configuring, reconfiguring, allocating, mapping, and assignment. For example, a functional block (component) that performs transmission is called a transmitting unit or transmitter. As mentioned above, there are no particular limitations on how these functions are implemented.

[0247] For example, the base station 10, the network node 30, the terminal 20, etc. according to an embodiment of the present disclosure may function as a computer that performs processing of the wireless communication method of the present disclosure. Fig. 18 is a diagram illustrating an example of the hardware configuration of the base station 10 and the terminal 20 according to an embodiment of the present disclosure. The network node 30 may have the same hardware configuration as the base station 10. The above-described base station 10 and the terminal 20 may be physically configured as a computer device including a processor 1001, a storage device 1002, an auxiliary storage device 1003, a communication device 1004, an input device 1005, an output device 1006, a bus 1007, etc.

[0248] In the following description, the term "apparatus" can be interpreted as a circuit, a device, a unit, etc. The hardware configuration of the base station 10 and the terminal 20 may be configured to include one or more of the apparatuses shown in the drawings, or may be configured to exclude some of the apparatuses.

[0249] Each function in the base station 10 and the terminal 20 is realized by loading specified software (programs) onto hardware such as the processor 1001, the memory device 1002, etc., so that the processor 1001 performs calculations, controls communication by the communication device 1004, and controls at least one of reading and writing data in the memory device 1002 and the auxiliary memory device 1003.

[0250] The processor 1001 controls the entire computer by running, for example, an operating system. The processor 1001 may be configured as a central processing unit (CPU) including an interface with peripheral devices, a control device, an arithmetic unit, a register, etc. For example, the above-mentioned control unit 140, control unit 240, etc. may be realized by the processor 1001.

[0251] Furthermore, the processor 1001 reads programs (program codes), software modules, data, etc. from at least one of the auxiliary storage device 1003 and the communication device 1004 into the storage device 1002 and executes various processes in accordance with the programs. The programs used are those that cause a computer to execute at least some of the operations described in the above-described embodiments. For example, the control unit 140 of the base station 10 shown in FIG. 16 may be implemented by a control program stored in the storage device 1002 and running on the processor 1001. Furthermore, for example, the control unit 240 of the terminal 20 shown in FIG. 17 may be implemented by a control program stored in the storage device 1002 and running on the processor 1001. While the above-described various processes have been described as being executed by one processor 1001, they may also be executed simultaneously or sequentially by two or more processors 1001. The processor 1001 may be implemented by one or more chips. The programs may also be transmitted from a network via a telecommunications line.

[0252] The storage device 1002 is a computer-readable recording medium and may be configured, for example, by at least one of a read-only memory (ROM), an erasable programmable read-only memory (EPROM), an electrically erasable programmable read-only memory (EEPROM), a random access memory (RAM), etc. The storage device 1002 may also be called a register, a cache, a main memory, etc. The storage device 1002 can store executable programs (program codes), software modules, etc. for implementing a communication method according to an embodiment of the present disclosure.

[0253] The secondary storage device 1003 is a computer-readable recording medium, and may be, for example, at least one of an optical disk such as a CD-ROM (Compact Disc ROM), a hard disk drive, a flexible disk, a magneto-optical disk (e.g., a compact disk, a digital versatile disk, a Blu-ray (registered trademark) disk), a smart card, a flash memory (e.g., a card, a stick, a key drive), a floppy (registered trademark) disk, a magnetic strip, etc. The above-mentioned storage medium may be, for example, a database, a server, or other appropriate medium including at least one of the storage device 1002 and the secondary storage device 1003.

[0254] The communication device 1004 is hardware (transmission / reception device) for communicating between computers via at least one of a wired network and a wireless network, and is also referred to as, for example, a network device, a network controller, a network card, a communication module, etc. The communication device 1004 may be configured to include a high-frequency switch, a duplexer, a filter, a frequency synthesizer, etc. to realize at least one of frequency division duplex (FDD) and time division duplex (TDD). For example, a transmission / reception antenna, an amplifier unit, a transmission / reception unit, a transmission path interface, etc. may be realized by the communication device 1004. The transmission / reception unit may be implemented as a transmission unit and a reception unit that are physically or logically separated.

[0255] The input device 1005 is an input device (e.g., a keyboard, a mouse, a microphone, a switch, a button, a sensor, etc.) that receives input from the outside. The output device 1006 is an output device (e.g., a display, a speaker, an LED lamp, etc.) that outputs to the outside. Note that the input device 1005 and the output device 1006 may be integrated into one device (e.g., a touch panel).

[0256] Furthermore, each device such as the processor 1001 and the storage device 1002 is connected by a bus 1007 for communicating information. The bus 1007 may be configured using a single bus, or may be configured using different buses between each device.

[0257] Furthermore, the base station 10 and the terminal 20 may be configured to include hardware such as a microprocessor, a digital signal processor (DSP), an application specific integrated circuit (ASIC), a programmable logic device (PLD), or a field programmable gate array (FPGA), and some or all of the functional blocks may be realized by the hardware. For example, the processor 1001 may be implemented using at least one of these pieces of hardware.

[0258] Fig. 19 shows an example configuration of a vehicle 2001. As shown in Fig. 19, the vehicle 2001 includes a drive unit 2002, a steering unit 2003, an accelerator pedal 2004, a brake pedal 2005, a shift lever 2006, front wheels 2007, rear wheels 2008, an axle 2009, an electronic control unit 2010, various sensors 2021 to 2029, an information service unit 2012, and a communication module 2013. Each aspect / embodiment described in the present disclosure may be applied to a communication device mounted on the vehicle 2001, and may be applied to the communication module 2013, for example.

[0259] The drive unit 2002 is configured, for example, by an engine, a motor, or a hybrid of an engine and a motor. The steering unit 2003 includes at least a steering wheel (also called a handle) and is configured to steer at least one of the front wheels and the rear wheels based on the operation of the steering wheel operated by the user.

[0260] The electronic control unit 2010 is composed of a microprocessor 2031, a memory (ROM, RAM) 2032, and a communication port (IO port) 2033. Signals are input to the electronic control unit 2010 from various sensors 2021 to 2029 provided in the vehicle 2001. The electronic control unit 2010 may also be called an ECU (Electronic Control Unit).

[0261] The signals from the various sensors 2021 to 2029 include a current signal from a current sensor 2021 that senses the current of the motor, a rotation speed signal of the front and rear wheels obtained by a rotation speed sensor 2022, an air pressure signal of the front and rear wheels obtained by an air pressure sensor 2023, a vehicle speed signal obtained by a vehicle speed sensor 2024, an acceleration signal obtained by an acceleration sensor 2025, an accelerator pedal depression amount signal obtained by an accelerator pedal sensor 2029, a brake pedal depression amount signal obtained by a brake pedal sensor 2026, a shift lever operation signal obtained by a shift lever sensor 2027, and a detection signal for detecting obstacles, vehicles, pedestrians, etc. obtained by an object detection sensor 2028.

[0262] The information service unit 2012 is composed of various devices, such as a car navigation system, an audio system, speakers, a television, and a radio, for providing (outputting) various types of information, such as driving information, traffic information, and entertainment information, and one or more ECUs for controlling these devices. The information service unit 2012 uses information acquired from external devices via the communication module 2013 or the like to provide various types of multimedia information and multimedia services to the occupants of the vehicle 2001. The information service unit 2012 may include input devices (e.g., a keyboard, a mouse, a microphone, a switch, a button, a sensor, a touch panel, etc.) that accept input from the outside, and may also include output devices (e.g., a display, a speaker, an LED lamp, a touch panel, etc.) that output information to the outside.

[0263] The driving assistance system unit 2030 is composed of various devices that provide functions for preventing accidents and reducing the driving burden on the driver, such as millimeter-wave radar, LiDAR (Light Detection and Ranging), cameras, positioning locators (e.g., GNSS, etc.), map information (e.g., high-definition (HD) maps, autonomous vehicle (AV) maps, etc.), gyro systems (e.g., IMU (Inertial Measurement Unit), INS (Inertial Navigation System), etc.), AI (Artificial Intelligence) chips, and AI processors, as well as one or more ECUs that control these devices. In addition, the driving assistance system unit 2030 transmits and receives various information via the communication module 2013 to realize the driving assistance function or the autonomous driving function.

[0264] The communication module 2013 can communicate with the microprocessor 2031 and components of the vehicle 2001 via the communication port. For example, the communication module 2013 transmits and receives data via the communication port 2033 to and from the drive unit 2002, steering unit 2003, accelerator pedal 2004, brake pedal 2005, shift lever 2006, front wheels 2007, rear wheels 2008, axle 2009, microprocessor 2031 and memory (ROM, RAM) 2032 in the electronic control unit 2010, and sensors 2021 to 29, which are provided in the vehicle 2001.

[0265] The communication module 2013 is a communication device that can be controlled by the microprocessor 2031 of the electronic control unit 2010 and can communicate with an external device. For example, it transmits and receives various information to and from the external device via wireless communication. The communication module 2013 may be located either inside or outside the electronic control unit 2010. The external device may be, for example, a base station, a mobile station, or the like.

[0266] The communication module 2013 may transmit at least one of signals from the above-mentioned various sensors 2021-2028 input to the electronic control unit 2010, information obtained based on the signals, and information based on input from the outside (user) obtained via the information service unit 2012 to an external device via wireless communication. The electronic control unit 2010, the various sensors 2021-2028, the information service unit 2012, etc. may be referred to as input units that accept input. For example, the PUSCH transmitted by the communication module 2013 may include information based on the above-mentioned input.

[0267] The communication module 2013 receives various information (traffic information, traffic signal information, vehicle-to-vehicle information, etc.) transmitted from external devices and displays it on an information service unit 2012 provided in the vehicle 2001. The information service unit 2012 may be called an output unit that outputs information (for example, outputs information to a device such as a display or speaker based on the PDSCH (or data / information decoded from the PDSCH) received by the communication module 2013). The communication module 2013 also stores the various information received from external devices in a memory 2032 that can be used by the microprocessor 2031. Based on the information stored in the memory 2032, the microprocessor 2031 may control the drive unit 2002, steering unit 2003, accelerator pedal 2004, brake pedal 2005, shift lever 2006, front wheels 2007, rear wheels 2008, axles 2009, sensors 2021 to 2029, etc. provided in the vehicle 2001.

[0268] <Additional Notes> (Additional Item 1) A network node comprising: a control unit that recognizes that the same satellite accommodates both a calling terminal and a called terminal, and that switching of an Internet Protocol Multimedia Subsystem (IMS) Access Gateway (AGW) on the satellite will occur simultaneously in the calling network and the called network, and a transmission unit that transmits to a first network node a first message requesting an update of the voice communication status, including termination point information of the IMS AGW on the destination satellite. (Additional Item 2) A base station deployed on a satellite constellation, comprising: a control unit that performs quasi-terrestrial fixed beam switching, and a transmission unit that, when initiating a handover associated with quasi-terrestrial fixed beam switching, transmits to another base station a message requesting handover, including information indicating that the cause of the handover is quasi-terrestrial fixed beam switching. (Additional Item 3) A network node comprising: a receiving unit that receives, from a base station, a first message requesting path switching, including information indicating that the cause of the handover is quasi-terrestrial fixed beam switching, and a transmission unit that transmits to the first network node a second message requesting path switching associated with a change of base station, including the information. (Supplementary Item 4) A network node comprising: a transmitter that transmits a first message to a first network node inquiring whether or not to switch an ULCL (Uplink Classifier) ​​and PDU (Protocol Data Unit) session termination point; a receiver that receives a second message from the first network node instructing that the switch be temporarily suspended; and a controller that suspends execution of configuration of a destination ULCL and PDU session termination point, wherein the receiver receives a third message from the first network node approving the switch, and the controller executes the configuration.(Supplementary Item 5) A communication method executed by a network node, comprising: a step of recognizing that the same satellite accommodates both a calling terminal and a called terminal; a step of recognizing that switching of an IMS (Internet Protocol Multimedia Subsystem) AGW (Access Gateway) on the satellite will occur simultaneously in the calling network and the called network; and a step of sending a first message to a first network node requesting an update of the voice communication status, including termination point information of the IMS AGW on the destination satellite.

[0269] Any of the above items 1 to 5 makes it possible to switch between satellites that simultaneously accommodate two terminals in communication using a quasi-terrestrial fixed service link in a wireless communication system using a satellite.

[0270] (Supplementary Notes on the Embodiments) Although the embodiments of the present invention have been described above, the disclosed invention is not limited to such embodiments, and those skilled in the art will understand various modifications, alterations, alternatives, and substitutions. While specific numerical examples have been used to facilitate understanding of the invention, unless otherwise specified, these numerical values ​​are merely examples, and any appropriate values ​​may be used. The division of items in the above description is not essential to the present invention; matters described in two or more items may be used in combination as needed, and matters described in one item may apply to matters described in another item (as long as there is no contradiction). Boundaries between functional units or processing units in functional block diagrams do not necessarily correspond to boundaries between physical components. The operations of multiple functional units may be performed by a single physical component, or the operations of a single functional unit may be performed by multiple physical components. The order of processing steps described in the embodiments may be reversed as long as there is no contradiction. For convenience of processing description, the base station 10 and terminal 20 have been described using functional block diagrams, but such devices may be realized by hardware, software, or a combination thereof. The software operated by the processor of the base station 10 in accordance with an embodiment of the present invention and the software operated by the processor of the terminal 20 in accordance with an embodiment of the present invention may each be stored in random access memory (RAM), flash memory, read-only memory (ROM), EPROM, EEPROM, register, hard disk (HDD), removable disk, CD-ROM, database, server, or any other suitable storage medium.

[0271] Furthermore, the notification of information is not limited to the aspects / embodiments described in the present disclosure, and may be performed using other methods. For example, the notification of information may be performed by physical layer signaling (e.g., Downlink Control Information (DCI), Uplink Control Information (UCI)), higher layer signaling (e.g., Radio Resource Control (RRC) signaling, Medium Access Control (MAC) signaling), broadcast information (Master Information Block (MIB), System Information Block (SIB)), other signals, or a combination thereof. Furthermore, the RRC signaling may be referred to as an RRC message, and may be, for example, an RRC Connection Setup message, an RRC Connection Reconfiguration message, or the like.

[0272] Each aspect / embodiment described in the present disclosure may be implemented using any of the following standards: LTE (Long Term Evolution), LTE-Advanced (LTE-A), SUPER 3G, IMT-Advanced, 4G (4th generation mobile communication system), 5G (5th generation mobile communication system), 6th generation mobile communication system (6G), xth generation mobile communication system (xG) (xG (x is, for example, an integer or a decimal number)), FRA (Future Radio Access), NR (new Radio), New radio access (NX), Future generation radio access (FX), W-CDMA (registered trademark), GSM (registered trademark), CDMA2000, UMB (Ultra Mobile Broadband), IEEE 802.11 (Wi-Fi (registered trademark)), IEEE 802.16 (WiMAX (registered trademark)), IEEE 802.17 (WiMAX (registered trademark)), IEEE 802.19 (WiMAX (registered trademark)), IEEE 802.20 (WiMAX (registered trademark)), IEEE 802.21 (Wi-Fi (registered trademark)), IEEE 802.22 (WiMAX (registered trademark)), IEEE 802.23 (WiMAX (registered trademark)), IEEE 802.24 (WiMAX (registered trademark)), IEEE 802.25 (WiMAX (registered trademark)), IEEE 802.26 (WiMAX (registered trademark)), IEEE 802.27 (WiMAX (registered trademark)), IEEE 802.28 (WiMAX (registered trademark)), IEEE 802.29 (WiMAX (registered trademark)), IEEE 802.30 (WiMAX (registered trademark)), IEEE 802.31 (Wi-Fi (registered trademark)), IEEE 802.32 (WiMAX (registered trademark)), IEEE 802.33 (WiMAX (registered trademark)), IEEE 802.34 ( The present invention may be applied to at least one of systems using 802.20, UWB (Ultra-Wide Band), Bluetooth (registered trademark), or other suitable systems, and next-generation systems that are extended, modified, created, or defined based on these systems. The present invention may also be applied to a combination of multiple systems (e.g., a combination of LTE and / or LTE-A with 5G).

[0273] The order of the procedures, sequences, flowcharts, etc. of each aspect / embodiment described herein may be rearranged unless it is consistent. For example, the methods described in this disclosure present elements of various steps using an example order and are not limited to the particular order presented.

[0274] In this specification, a specific operation described as being performed by the base station 10 may be performed by its upper node in some cases. In a network consisting of one or more network nodes having the base station 10, it is clear that various operations performed for communication with the terminal 20 may be performed by at least one of the base station 10 and another network node other than the base station 10 (such as, but not limited to, an MME or an S-GW). Although the above example illustrates a case where there is one other network node other than the base station 10, the other network node may be a combination of multiple other network nodes (such as an MME and an S-GW).

[0275] The information, signals, etc. described in the present disclosure may be output from a higher layer (or a lower layer) to a lower layer (or a higher layer), or may be input / output via multiple network nodes.

[0276] Input and output information may be stored in a specific location (for example, memory) or may be managed using a management table. Input and output information may be overwritten, updated, or added to. Output information may be deleted. Input information may be sent to another device.

[0277] In the present disclosure, the determination may be made based on a value represented by one bit (0 or 1), a Boolean value (true or false), or a numerical comparison (e.g., comparison with a predetermined value).

[0278] Software shall be construed broadly to mean instructions, instruction sets, code, code segments, program code, programs, subprograms, software modules, applications, software applications, software packages, routines, subroutines, objects, executable files, threads of execution, procedures, functions, etc., whether referred to as software, firmware, middleware, microcode, hardware description language, or otherwise.

[0279] Software, instructions, information, etc. may also be transmitted or received over a transmission medium. For example, if software is transmitted from a website, server, or other remote source using wired technologies (such as coaxial cable, fiber optic cable, twisted pair, Digital Subscriber Line (DSL)), and / or wireless technologies (such as infrared, microwave), then these wired and / or wireless technologies are included within the definition of transmission media.

[0280] The information, signals, etc. described in this disclosure may be represented using any of a variety of different technologies. For example, data, instructions, commands, information, signals, bits, symbols, chips, etc. that may be referred to throughout the above description may be represented by voltages, currents, electromagnetic waves, magnetic fields or magnetic particles, optical fields or photons, or any combination thereof.

[0281] Note that terms described in this disclosure and terms necessary for understanding this disclosure may be replaced with terms having the same or similar meanings. For example, at least one of a channel and a symbol may be a signal (signaling). Furthermore, a signal may be a message. Furthermore, a component carrier (CC) may be called a carrier frequency, a cell, a frequency carrier, etc.

[0282] As used in this disclosure, the terms "system" and "network" are used interchangeably.

[0283] Furthermore, the information, parameters, etc. described in the present disclosure may be expressed using absolute values, may be expressed using relative values ​​from a predetermined value, or may be expressed using other corresponding information. For example, a radio resource may be indicated by an index.

[0284] The names used for the above-described parameters are not intended to be limiting in any way. Furthermore, the mathematical expressions using these parameters may differ from those explicitly disclosed in this disclosure. The various channels (e.g., PUCCH, PDCCH, etc.) and information elements may be identified by any suitable names, and therefore the various names assigned to these various channels and information elements are not intended to be limiting in any way.

[0285] In the present disclosure, terms such as "base station (BS)," "radio base station," "base station device," "fixed station," "NodeB," "eNodeB (eNB)," "gNodeB (gNB)," "access point," "transmission point," "reception point," "transmission / reception point," "cell," "sector," "cell group," "carrier," and "component carrier" may be used interchangeably. A base station may also be referred to by terms such as a macrocell, a small cell, a femtocell, and a picocell.

[0286] A base station can accommodate one or more (e.g., three) cells. When a base station accommodates multiple cells, the overall coverage area of ​​the base station can be partitioned into multiple smaller areas, and each smaller area can also be provided with communication services by a base station subsystem (e.g., a small indoor base station (RRH: Remote Radio Head)). The terms "cell" or "sector" refer to part or all of the coverage area of ​​a base station and / or base station subsystem that provides communication services within that coverage.

[0287] In the present disclosure, the base station transmitting information to a terminal may be interpreted as the base station instructing the terminal to control or operate based on the information.

[0288] In this disclosure, the terms "Mobile Station (MS)," "user terminal," "User Equipment (UE)," "terminal," and the like may be used interchangeably.

[0289] A mobile station may also be referred to by those skilled in the art as a subscriber station, mobile unit, subscriber unit, wireless unit, remote unit, mobile device, wireless device, wireless communication device, remote device, mobile subscriber station, access terminal, mobile terminal, wireless terminal, remote terminal, handset, user agent, mobile client, client, or some other suitable terminology.

[0290] At least one of the base station and the mobile station may be referred to as a transmitting device, a receiving device, a communication device, etc. At least one of the base station and the mobile station may be a device mounted on a mobile object, the mobile object itself, etc. The mobile object refers to a movable object, and may move at any speed. Naturally, this also includes cases where the mobile object is stationary. Examples of the mobile object include, but are not limited to, vehicles, transport vehicles, automobiles, motorcycles, bicycles, connected cars, excavators, bulldozers, wheel loaders, dump trucks, forklifts, trains, buses, handcars, rickshaws, ships and other watercraft, airplanes, rockets, satellites, drones (registered trademark), multicopters, quadcopters, balloons, and objects mounted thereon. The mobile object may also be a mobile object that moves autonomously based on an operational command. It may be a vehicle (e.g., a car, an airplane, etc.), an unmanned mobile object (e.g., a drone, an autonomous vehicle, etc.), or a robot (manned or unmanned). At least one of the base station and the mobile station may be a device that does not necessarily move during communication operations. For example, at least one of the base station and the mobile station may be an IoT (Internet of Things) device such as a sensor.

[0291] Furthermore, a base station in the present disclosure may be read as a user terminal. For example, the aspects / embodiments of the present disclosure may be applied to a configuration in which communication between a base station and a user terminal is replaced with communication between multiple terminals 20 (which may be called, for example, Device-to-Device (D2D) or Vehicle-to-Everything (V2X)). In this case, the terminal 20 may be configured to have the functions of the base station 10 described above. Furthermore, terms such as "uplink" and "downlink" may be read as terms corresponding to terminal-to-terminal communication (for example, "side"). For example, terms such as an uplink channel and a downlink channel may be read as a side channel.

[0292] Similarly, the user terminal in the present disclosure may be read as a base station, in which case the base station may be configured to have the functions of the user terminal described above.

[0293] As used in this disclosure, the terms "determining" and "determining" may encompass a wide variety of actions. "Determining" and "determining" may include, for example, judging, calculating, computing, processing, deriving, investigating, looking up, searching, inquiring (e.g., searching in a table, database, or other data structure), ascertaining, and the like. "Determining" and "determining" may also include receiving (e.g., receiving information), transmitting (e.g., sending information), input, output, accessing (e.g., accessing data in memory), and the like. Furthermore, "judgment" and "decision" can include regarding resolving, selecting, choosing, establishing, comparing, etc. as having been "judged" or "decided." In other words, "judgment" and "decision" can include regarding some action as having been "judged" or "decided." Furthermore, "judgment (decision)" can be interpreted as "assuming," "expecting," "considering," etc.

[0294] The terms "connected," "coupled," or any variation thereof, refer to any direct or indirect connection or coupling between two or more elements, and may include the presence of one or more intermediate elements between two elements that are "connected" or "coupled" to each other. The coupling or connection between elements may be physical, logical, or a combination thereof. For example, "connected" may be read as "access." As used in this disclosure, two elements may be considered to be "connected" or "coupled" to each other using one or more wires, cables, and / or printed electrical connections, as well as electromagnetic energy having wavelengths in the radio frequency range, microwave range, and optical (both visible and invisible) range, as some non-limiting and non-exhaustive examples.

[0295] The reference signal may be abbreviated as RS (Reference Signal) or may be called a pilot depending on the applicable standard.

[0296] As used in this disclosure, the phrase "based on" does not mean "based only on," unless expressly stated otherwise. In other words, the phrase "based on" means both "based only on" and "based at least on."

[0297] As used in this disclosure, any reference to an element using a designation such as "first," "second," etc. does not generally limit the quantity or order of those elements. These designations may be used in this disclosure as a convenient method of distinguishing between two or more elements. Thus, a reference to a first and a second element does not imply that only two elements may be employed or that the first element must in some way precede the second element.

[0298] The "means" in the configuration of each of the above devices may be replaced with "part," "circuit," "device," etc.

[0299] When the terms "include," "including," and variations thereof are used in this disclosure, these terms are intended to be inclusive, similar to the term "comprising." Furthermore, when the term "or" is used in this disclosure, it is not intended to be an exclusive or.

[0300] In this disclosure, where articles are added by translation, such as a, an, and the in English, the disclosure may include that the nouns following these articles are in the plural form.

[0301] In the present disclosure, the term "A and B are different" may mean "A and B are different from each other." The term may also mean "A and B are each different from C." Terms such as "separate" and "coupled" may also be interpreted in the same way as "different."

[0302] The aspects / embodiments described in this disclosure may be used alone, in combination, or switched depending on the implementation. Notification of predetermined information (e.g., notification that "X is true") is not limited to explicit notification, but may be implicit (e.g., not notifying the predetermined information).

[0303] Although the present disclosure has been described in detail above, it is clear to those skilled in the art that the present disclosure is not limited to the embodiments described herein. The present disclosure can be implemented in modified and altered forms without departing from the spirit and scope of the present disclosure as defined by the claims. Therefore, the description of the present disclosure is intended to be illustrative and does not have any limiting meaning on the present disclosure.

[0304] 10 Base station 110 Transmitter 120 Receiver 130 Setting unit 140 Control unit 20 Terminal 210 Transmitter 220 Receiver 230 Setting unit 240 Control unit 30 Network node 1001 Processor 1002 Storage device 1003 Auxiliary storage device 1004 Communication device 1005 Input device 1006 Output device 2001 Vehicle 2002 Drive unit 2003 Steering unit 2004 Accelerator pedal 2005 Brake pedal 2006 Shift lever 2007 Front wheels 2008 Rear wheels 2009 Axle 2010 Electronic control unit 2012 Information service unit 2013 Communication module 2021 Current sensor 2022 RPM sensor 2023 Tire pressure sensor 2024 Vehicle speed sensor 2025 Acceleration sensor 2026 Brake pedal sensor 2027 Shift lever sensor 2028 Object detection sensor 2029 Accelerator pedal sensor 2030 Driving assistance system unit 2031 Microprocessor 2032 Memory (ROM, RAM) 2033 Communication port (IO port)

Claims

1. A network node having: a control unit that recognizes that the same satellite accommodates both a calling terminal and a called terminal, and that switching of an IMS (Internet Protocol Multimedia Subsystem) AGW (Access Gateway) on the satellite will occur simultaneously in the calling network and the called network; and a transmission unit that transmits a first message to a first network node requesting an update of the voice communication status, including termination point information of the IMS AGW on the destination satellite.

2. A base station deployed on a satellite constellation, comprising: a control unit that performs quasi-terrestrial fixed beam switching; and a transmission unit that, when initiating a handover associated with quasi-terrestrial fixed beam switching, transmits a message requesting a handover to another base station, the message including information indicating that the cause of the handover is quasi-terrestrial fixed beam switching.

3. A network node having: a receiving unit that receives, from a base station, a first message requesting a path change, the first message including information indicating that the cause of the handover is a quasi-terrestrial fixed beam change; and a transmitting unit that transmits, to a first network node, a second message including the information, the second message requesting a path change due to a change in base station.

4. A network node comprising: a transmitter that transmits a first message to a first network node inquiring whether or not to switch an ULCL (Uplink Classifier) ​​and PDU (Protocol Data Unit) session termination point; a receiver that receives a second message from the first network node instructing that the switch be temporarily suspended; and a controller that suspends execution of configuration of a destination ULCL and PDU session termination point, wherein the receiver receives a third message from the first network node approving the switch, and the controller executes the configuration.

5. A communication method executed by a network node, comprising: a step of recognizing that the same satellite accommodates both a calling terminal and a called terminal; a step of recognizing that switching of an IMS (Internet Protocol Multimedia Subsystem) AGW (Access Gateway) on the satellite will occur simultaneously in the calling network and the called network; and a step of sending a first message to a first network node requesting an update of the voice communication status, including termination point information of the IMS AGW on the destination satellite.

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