Network node and communication method

Abstract

This network node comprises: a reception unit that receives, from a first network node, a first message for requesting path switching associated with a base station change, the first message including a satellite identifier; a control unit that recognizes that a satellite in which a source base station is located and a satellite in which a destination base station is located are different; and a transmission unit that transmits, to a second network node, a second message for inquiring whether to switch between an uplink classifier (ULCL) and a local user plane function, the second message including a destination satellite identifier. The reception unit receives a third message for rejecting switching between the ULCL and the local user plane function, said message being transmitted from the second network node. The transmission unit transmits, to a base station, a fourth message for requesting confirmation of a cell identifier by a terminal.

Description

Network node and communication method

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

[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 38.331 V18.0.0 (2023-12) 3GPP TS 38.413 V18.0.0 (2023-12)

[0007] In satellite constellation communications, voice media is routed over the satellite constellation whenever possible, but if routing over the satellite constellation is not possible, it is routed via the ground. This routing is called ground fallback because it falls back to the terrestrial network.

[0008] However, no method for performing Ground Fallback is specified, and in particular, Ground Fallback cannot be performed without packet loss.

[0009] The present invention has been made in view of the above points, and has as its object to perform ground fallback without packet loss in a wireless communication system using a satellite.

[0010] According to the disclosed technology, there is provided a network node having: a receiver that receives from a first network node a first message, including a satellite identifier, requesting route switching accompanying a base station change; a controller that recognizes that the satellite on which a source base station is located is different from the satellite on which a destination base station is located; and a transmitter that transmits to a second network node a second message, including a destination satellite identifier, inquiring whether or not to switch an Uplink Classifier (ULCL) and a local user plane function, wherein the receiver receives a third message transmitted from the second network node that rejects the switching of the ULCL and the local user plane function, and the transmitter transmits to the base station a fourth message requesting confirmation of a cell identifier by a terminal.

[0011] According to the disclosed technology, ground fallback can be performed without packet loss in a wireless communication system using a satellite.

[0012] FIG. 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 a ninth sequence diagram in an embodiment of the present invention. FIG. 10 is a diagram showing an example of a tenth sequence diagram in an embodiment of the present invention. FIG. 11 is a diagram showing an example of the functional configuration of a base station 10 and a network node 30 in an embodiment of the present invention. FIG. 12 is a diagram showing an example of the functional configuration of a terminal 20 in an embodiment of the present invention. FIG. 13 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. 14 is a diagram showing an example of the 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) In 3GPP, in satellite constellation communications, the P-CSCF determines whether to route voice media over the satellite constellation or via terrestrial routing.

[0035] In satellite constellation communications, voice media is routed over the satellite constellation whenever possible, but if routing over the satellite constellation is not possible, it is routed via terrestrial networks. This routing is called ground fallback because it falls back to the terrestrial network. However, there is no standard for how to perform ground fallback, and in particular, it is not possible to perform ground fallback without packet loss.

[0036] In this embodiment, a procedure for performing ground fallback without packet loss in a wireless communication system using a satellite will be described.

[0037] In this embodiment, it is assumed that a base station, an uplink classifier (ULCL), and multiple low-earth orbit satellites (LEOs) equipped with UPFs form a satellite constellation using an inter-satellite link (ISL). The ULCL has the function of selectively allocating uplink traffic between N9 interfaces.

[0038] Satellite communications operators prepare dedicated equipment for satellite constellation communications, primarily base stations, ULCLs, and UPFs deployed in LEO, and intermediate devices deployed on the ground that communicate with satellite-based devices, while mobile communications operators prepare network nodes, such as AMFs and SMFs, deployed on the ground, as satellite constellation utilization equipment.

[0039] In addition, this embodiment assumes a scenario in which the source satellite and the opposing satellite are in the same orbit (on the same satellite constellation), and the source satellite and the destination satellite are in different orbits (on different satellite constellations), and the source satellite and the destination satellite are close to each other at the time of switching.

[0040] In this scenario, the P-CSCF of the network where the handover occurred decides to execute Ground Fallback. The SMF that receives the notification from the P-CSCF does not configure the destination ULCL or L-UPF. Furthermore, it is assumed that the terminal sends a SIP re-INVITE. After that, the P-CSCF and the P-CSCF of the opposite network configure the terrestrial IMS AGW before notifying the terminal, notify the terminal of the termination point of the terrestrial IMS AGW, and release the satellite ULCL / L-UPF / IMS AGW. By switching the user plane route according to this procedure, Ground Fallback can be performed without packet loss.

[0041] 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 4-5, etc.

[0042] 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.

[0043] 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.

[0044] In this sequence, after satellite-based voice communication is established between terminal 20A, which is the calling terminal, and terminal 20B, which is the called terminal, handover is performed by switching the satellite connected to terminal 20A. Here, the destination satellite is equipped with base station 10C, ULCL 30E3, local IMS AGWFL 3, and local UPF (L-PSA5) 30D5L3, which is the fifth termination point (PSA5) of the PDU session. Also, UPF may be expressed as a termination point of a PDU session; for example, UPF (R-PSA1) 30D1R may be expressed as UPF 30D1R or PSA1.

[0045] (Satellite Transfer (Xn Handover)) The following describes a procedure for satellite transfer in which the satellite accommodating the calling terminal 20A is 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. The processing of each step will be described below.

[0046] S501: The base station 10A transmits a handover request to the base station 10C.

[0047] S502: The base station 10C transmits a handover request acknowledgement including a handover command to the base station 10A as a response to the handover request received in S501.

[0048] S503: 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.

[0049] S504: The base station 10A sends an SN status transfer to the base station 10C.

[0050] S505: 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.

[0051] S506: The base station 10C transmits to the AMF 30A a request message (Path Switch request) requesting a path change accompanying a change of base station.

[0052] S507: 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 S506.

[0053] S508: 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 and a satellite ID, and is expressed as, for example, Nsmf_PDUSession_UpdateSMContext request (SmContextUpdateData (satellite constellation id, satellite id)).

[0054] S509: Based on the fact that the satellite ID stored for terminal 20A is different from the satellite ID received in S508, SMF 30B recognizes that the satellite on which base station 10A of the source station is located is different from the satellite on which base station 10C of the destination station is located.

[0055] S510: SMF 30B sends a request message (PFCP Session Modification request) for updating the user data transfer path to ULCL 30E.

[0056] S511: ULCL 30E transmits to SMF 30B a response message (PFCP Session Modification response) to the request message received in S510.

[0057] S512: SMF 30B sends a response message (Nsmf_PDUSession_UpdateSMContext response) to AMF 30A in response to the request message received in S508.

[0058] S513: The AMF 30A transmits to the base station 10C a response message (Path Switch request response) in response to the request message received in S506.

[0059] S514: The base station 10C transmits a message (UE Context Release) requesting the release of the terminal context to the base station 10A.

[0060] 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.

[0061] S521: SMF 30B recognizes that the satellite where the source base station is located is different from the satellite where the destination base station is located, recognizes that base station switching and satellite ID switching are necessary, and sets a policy to execute switching for the ULCL and local UPF (L-UPF) deployed on the satellite. Here, L-UPF may also be expressed as PDU session termination point (L-PSA).

[0062] S522: 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).

[0063] S523: SMF 30B transmits to PCF 30C a message (Nsmf_EventExposure_Notify request) that includes a satellite ID, inquires about whether to switch between the ULCL and L-UPF, and notifies the PCF 30C of an event that includes an indication (EARLY) that indicates that the ULCL and L-UPF (L-PSA) have not yet been moved. For example, this message is expressed as Nsmf_EventExposure_Notify request (NsmfEventExposureNotification (eventNotifs (event=SAT_UP_PATH_CH, dnaiChgType=EARLY, satellite type, satellite constellation id, satellite id= a target satellite id, OnSatteliteLpsaUlcl=true, OnSatteliteMediaRoutingToTatgetNetwork=false))).

[0064] S524: The PCF 30C sends a response message (Nsmf_EventExposure_Notify response) to the message received in S523 to the SMF 30B.

[0065] S525: PCF 30C transmits to P-CSCF 30G a message (Npcf_PolicyAuthorization_Notify request) that includes a satellite ID, inquires about whether to switch the ULCL and L-UPF, and notifies P-CSCF 30G of an event that includes an indication (EARLY) that indicates that the ULCL and L-PSA have not yet been moved. For example, this message is expressed as Npcf_PolicyAuthorization_Notify request (EventsNotification (evNotifs (event=SAT_UP_PATH_CH), dnaiChgType=EARLY, satellite type, satellite constellation id, satellite id= a target satellite id, OnSatteliteLpsaUlcl=true, OnSatteliteMediaRoutingToTatgetNetwork=false)).

[0066] S526: The P-CSCF 30G transmits to the PCF 30C a response message (Npcf_PolicyAuthorization_Notify response) in response to the message received in S525.

[0067] S527: If the satellite constellation IDs of the originating and destination terminals remain the same even after switching between the ULCL and L-UPF, the P-CSCF30G determines that satellite media routing is possible. Here, it is assumed that the satellite constellation IDs are different. That is, since the source satellite ID and the destination satellite ID are not included in the same satellite constellation ID, it recognizes that the destination satellite ID and the opposite satellite ID are not included in the same satellite constellation ID, and determines that voice media cannot be routed on the satellite constellation. That is, since switching between the destination ULCL and the destination L-UPF makes satellite media routing impossible, the P-CSCF30G determines to perform Ground Fallback.

[0068] S528: P-CSCF 30G transmits to PCF 30G a message (Npcf_EventExposure_AppRelocationInfo request) indicating that switching between ULCL and L-UPF is rejected. For example, this message is expressed as Npcf_EventExposure_AppRelocationInfo request (AckOfNotify (ackResult (afStatus=RELOC_NO_ALLOWED))).

[0069] S529: The PCF 30G transmits to the P-CSCF 30G a response message (Npcf_EventExposure_AppRelocationInfo response) in response to the message received in S528.

[0070] S530: PCF 30G sends a message (Nsmf_EventExposure_AppRelocationInfo request) indicating that switching between ULCL and L-UPF is rejected to SMF 30B. For example, this message is expressed as Nsmf_EventExposure_AppRelocationInfo request (AckOfNotify (ackResult (afStatus=RELOC_NO_ALLOWED))).

[0071] S531: The SMF 30B sends a response message (Nsmf_EventExposure_AppRelocationInfo response) to the message received in S530 to the PCF 30C.

[0072] S532: The SMF 30B determines to execute Ground Fallback based on the instruction received in S530 indicating that relocation is not possible.

[0073] S533: The SMF 30B decides not to execute the setting of the destination ULCL (ULCL 30E) and the destination L-UPF (UPF 30D5L3).

[0074] S534: SMF30B decides to send an instruction to enable the terminal 20A to recognize the NR cell ID after movement so that the terminal 20A can send a SIP re-INVITE in subsequent processing and can recognize the change in PANI as a trigger for this.

[0075] The process following S534 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.

[0076] S541: SMF 30B transmits a request message (Namf_Communication_N1N2MessageTransfer request) to AMF 30A, requesting confirmation of the NR cell ID from terminal 20A. 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))))))).

[0077] S542: AMF 30A sends a response message (Namf_Communication_N1N2MessageTransfer response) to SMF 30B in response to the request message received in S541.

[0078] S543: 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)).

[0079] S544: The base station 10C transmits to the AMF 30A a response message (Location Report) in response to the request message received in S543.

[0080] S545: 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.

[0081] S546: The terminal 20A transmits to the base station 10C a response message (RRCReconfigurationComplete) in response to the message received in S545.

[0082] S547: 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.

[0083] S548: 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.

[0084] S549: The P-CSCF 30G maintains the setting of the IMS AGW 30FL on the source satellite without changing it, and executes the setting of the IMS AGW 30FR on the ground.

[0085] S550: The P-CSCF 30G transmits to the IMS AGW 30FR a request message (H.248 ADD request) requesting settings related to the addition of voice communication control.

[0086] S551: The IMS AGW 30FR acquires and sets resources of the termination point on its own device side related to data transmission with the destination side.

[0087] S552: The IMS AGW 30FR transmits to the P-CSCF 30G a response message (H.248 ADD response) in response to the request message received in S550.

[0088] S553: ​​P-CSCF30G determines not to transmit satellite-related information to the destination network because it is to execute Ground Fallback.

[0089] S554: The P-CSCF30G recognizes that the source network terrestrial IMS AGW30FR is in the process of being configured and cannot process voice media even if it receives it from the destination network. However, the P-CSCF30G2 of the opposite destination network also recognizes that it has started Ground Fallback and is executing the configuration of the terrestrial IMS AGW30FR2, and decides to transmit the IP address of the termination point of the source network terrestrial IMS AGW30FR2.

[0090] The process following S554 will be described. Fig. 7 is a diagram showing an example of a fourth sequence diagram according to an embodiment of the present invention. The process of each step will be described below.

[0091] S561: The P-CSCF 30G sends a message (SIP re-INVITE) to the S-CSCF 30H requesting an update of the voice communication status, including the termination point on the originating ground IMS AGW 30FR2 side. For example, the message is expressed as SIP re-INVITE (PANI(access-type=3GPP-NR-SAT, utran-cell-id-3gpp=MCC+MNC+TAC+NR cell ID), SDP offer (c= the originating ground IMS AGW IP address)).

[0092] S562: The S-CSCF 30H transmits the message (SIP re-INVITE) received in S561 to the I-CSCF 30I.

[0093] S563: The I-CSCF 30I transmits the message (SIP re-INVITE) received in S562 to the S-CSCF 30H2.

[0094] S564: The S-CSCF 30H2 transmits the message (SIP re-INVITE) received in S563 to the P-CSCF 30G2.

[0095] S565: P-CSCF30G2 determines that the message (SIP re-INVITE) received in S564 does not contain satellite-related information, and therefore determines that it is not possible to route voice media over the satellite constellation, and decides to perform Ground Fallback.

[0096] S566: The P-CSCF30G2 maintains the settings of the IMS AGW 30FL2 on the satellite without changing them, and executes the settings of the IMS AGW 30FR2 on the ground.

[0097] S567: The P-CSCF 30G2 transmits to the IMS AGW 30FR2 a request message (H.248 ADD request) requesting additional settings for voice communication control.

[0098] S568: The IMS AGW 30FR2 acquires and sets resources of its own termination point related to data transmission with the destination side.

[0099] S569: The IMS AGW 30FR2 transmits to the P-CSCF 30G2 a response message (H.248 ADD response) to the request message received in S567.

[0100] S570: P-CSCF30G2 normally sets the IP address of the termination point in IMS AGW30FR2 on the ground of the destination network in the c= line in the SDP of the SIP message, but taking into account that IMS AGW30FR2 is in the process of being configured and is in voice communication, it sets a value related to IMS AGW30FL2 on the satellite.

[0101] S571: The P-CSCF 30G2 sends, to the terminal 20B, a message (SIP re-INVITE) requesting an update of the state of voice communication, including the termination point on the IMS AGW 30FL2 side on the satellite of its own network, regarding data transmission with the terminal 20B. For example, this message is expressed as SIP re-INVITE (SDP offer (c= the terminating satellite IMS AGW IP address)).

[0102] S572: The terminal 20B sends to the P-CSCF 30G2 a success response (SIP 200 OK) to the message received in S571. 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)).

[0103] S573: The P-CSCF 30G2 transmits to the IMS AGW 30FR2 a request message (H.248 MOD request) requesting settings related to modification of voice communication control.

[0104] S574: The IMS AGW 30FR2 sets a termination point on the destination side for data transmission with the destination side.

[0105] S575: The IMS AGW 30FR2 transmits to the P-CSCF 30G2 a response message (H.248 MOD response) in response to the request message received in S573.

[0106] S576: The P-CSCF 30G2 transmits to the IMS AGW 30FR2 a request message (H.248 ADD request) requesting additional settings for voice communication control.

[0107] S577: The IMS AGW 30FR2 sets an originating termination point for data destined for the originating network, and requests acquisition of resources for the termination point on the IMS AGW 30FR2 side.

[0108] S578: The IMS AGW 30FR2 transmits to the P-CSCF 30G2 a response message (H.248 ADD response) in response to the request message received in S576.

[0109] S579: The P-CSCF30G2 determines not to transmit the satellite-related information to the source network side.

[0110] S580: The P-CSCF 30G2 sends to the S-CSCF 30H2 a successful response (SIP 200 OK) to the message received in S564, including a termination point in the ground IMS AGW 30FR2 for data transmission with the calling party. For example, the successful response 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 ground IMS AGW IP address)).

[0111] S581: The S-CSCF 30H2 transmits the success response (SIP 200 OK) received in S580 to the I-CSCF 30I.

[0112] S582: The I-CSCF 30I transmits the success response (SIP 200 OK) received in S581 to the S-CSCF 30H.

[0113] S583: The S-CSCF 30H transmits the success response (SIP 200 OK) received in S582 to the P-CSCF 30G.

[0114] S584: The P-CSCF 30G transmits to the IMS AGW 30FR a request message (H.248 MOD request) requesting settings related to modification of voice communication control.

[0115] S585: The IMS AGW 30FR sets a termination point on the destination side for data transmission with the destination side.

[0116] S586: The IMS AGW 30FR transmits to the P-CSCF 30G a response message (H.248 MOD response) in response to the request message received in S584.

[0117] S587: The P-CSCF 30G transmits to the IMS AGW 30FR a request message (H.248 ADD request) requesting settings related to the addition of voice communication control.

[0118] S588: The IMS AGW 30FR sets an originating termination point for data destined for the originating network, and requests acquisition of resources for the termination point on the IMS AGW 30FR's side.

[0119] S589: The IMS AGW 30FR sends a response message (H.248 ADD response) to the request message received in S587 to the P-CSCF 30G. At this point, the configuration of the terrestrial IMS AGW 30FR is completed. At this point, the voice media route remains unchanged. However, if the source terminal 20A sends voice media to the source network terrestrial IMS AGW 30FR, it will be transmitted to the destination terminal 20B via the destination network terrestrial IMS AGW 30FR2. The same applies to the direction from the destination network to the source network.

[0120] The current data flow of uplink (UL) media (voice signals) and downlink (DL) media (voice signals) will be described. Figure 8 shows an example of a fifth sequence diagram according to an embodiment of the present invention. The processing of each step will be described below.

[0121] As shown in S601, DL media is received via the IMS AGW 30FL of the source satellite. That is, the DL media is received from the terminating terminal 20B via the base station 10B, ULCL 30E2, UPF 30D4L, IMS AGW 30FL2, IMS AGW 30FL, UPF 30D2L, ULCL 30E, and base station 10C, and then by the terminal 20A.

[0122] As shown in S602, the UL media is transmitted via the terrestrial IMS AGW 30FR. That is, the UL media is transmitted from the originating terminal 20A to the terminal 20B via the base station 10C, ULCL 30E, UPF 30D1R, IMS AGW 30FR, IMS AGW 30FR2, UPF 30D3R, ULCL 30E2, and base station 10B.

[0123] The process following S590 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.

[0124] S611: Since the setting of the terrestrial IMS AGW 30FR has been completed, the P-CSCF 30G determines to transmit a notification (SIP UPDATE) to the destination network side in order to notify the terminal 20B.

[0125] S612: The P-CSCF 30G sends to the S-CSCF 30H a message (UPDATE) requesting an update of the voice communication status, including the termination point on the terrestrial IMS AGW 30FR side related to data transmission with the destination network. For example, this message is expressed as UPDATE (SDP offer (c= the originating ground IMS AGW IP address)).

[0126] S613: The S-CSCF 30H transmits the message (UPDATE) received in S612 to the I-CSCF 30I.

[0127] S614: The I-CSCF 30I transmits the message (UPDATE) received in S613 to the S-CSCF 30H2.

[0128] S615: The S-CSCF 30H2 transmits the message (UPDATE) received in S614 to the P-CSCF 30G2.

[0129] S616: In response to the message (UPDATE) received in S615, the P-CSCF30G2 generates a message (UPDATE) in which the original value (the IP address of the termination point in the destination network terrestrial IMS AGW30FR2) is set in the c= line in the SDP of the SIP message.

[0130] S617: The P-CSCF 30G2 transmits the message (UPDATE) generated in S616 to the terminal 20B. For example, this message is expressed as UPDATE (SDP offer (c=the terminating ground IMS AGW IP address)).

[0131] S618: The terminal 20B transmits to the P-CSCF 30G2 a response message (200 OK(UPDATE)) in response to the message (UPDATE) received in S617. For example, the response message is expressed as 200 OK(UPDATE) (PANI(access-type=3GPP-NR-SAT, utran-cell-id-3gpp=MCC+MNC+TAC+NR cell ID), SDP answer (c= the terminating UE IP address)).

[0132] S619: P-CSCF30G2 transmits to S-CSCF30H2 a response message (200 OK (UPDATE)) in response to the message (UPDATE) received in S615. For example, the response message is expressed as 200 OK (UPDATE) (PANI (access-type=3GPP-NR-SAT, utran-cell-id-3gpp=MCC+MNC+TAC+NR cell ID), SDP answer (c= the terminating ground IMS AGW IP address)).

[0133] S620: The S-CSCF 30H2 transmits the message (200 OK (UPDATE)) received in S619 to the I-CSCF 30I.

[0134] S621: The I-CSCF 30I transmits the message (200 OK (UPDATE)) received in S620 to the S-CSCF 30H.

[0135] S622: The S-CSCF 30H transmits the message (200 OK (UPDATE)) received in S621 to the P-CSCF 30G.

[0136] The current data flow of uplink (UL) media (voice signals) and downlink (DL) media (voice signals) will be described. Figure 10 shows an example of a seventh sequence diagram according to an embodiment of the present invention. The processing of each step will be described below.

[0137] As shown in S631, the UL media is transmitted via the terrestrial IMS AGW 30FR. That is, the UL media is transmitted from the originating terminal 20A to the terminal 20B via the base station 10C, ULCL 30E, UPF 30D1R, IMS AGW 30FR, IMS AGW 30FR2, UPF 30D3R, ULCL 30E2, and base station 10B.

[0138] As shown in S632, the DL media is received via the terrestrial IMS AGW 30FR. That is, the DL media is received from the terminal 20B on the receiving side via the base station 10B, ULCL 30E2, UPF 30D3R, IMS AGW 30FR2, IMS AGW 30FR, UPF 30D1R, ULCL 30E, and base station 10C, and then by the terminal 20A.

[0139] The process following S622 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.

[0140] S641: The P-CSCF 30G transmits to the PCF 30C a request message (Npcf_PolicyAuthorization_Create request) requesting the SMF 30B to release the source ULCL 30E and the source UPF 30D2L.

[0141] S642: The PCF 30C transmits to the P-CSCF 30G a response message (Npcf_PolicyAuthorization_Create response) in response to the request message received in S641.

[0142] S643: The PCF 30C sends a request message (Npcf_SMPolicyControl_UpdateNotify request) to the SMF 30B requesting that the source ULCL 30E and the source UPF 30D2L be released.

[0143] S644: The SMF 30B sends to the PCF 30C a response message (Npcf_SMPolicyControl_UpdateNotify response) in response to the request message received in S643.

[0144] S645: SMF 30B sends a request message (Namf_Communication_N1N2MessageTransfer request) for updating the setting of the PDU session resource to AMF 30A. For example, this message is expressed as Namf_Communication_N1N2MessageTransfer request (N1N2MessageTransferReqData(n2InfoContainer(smInfo(n2InfoContent(PDU Session Resource Modify Request Transfer))))).

[0145] S646: AMF 30A sends a response message (Namf_Communication_N1N2MessageTransfer response) to SMF 30B in response to the request message received in S645.

[0146] S647: The AMF 30A transmits a request message (PDU Session Resource Modify Request) for updating the PDU session resource settings to the base station 10C. For example, the message is expressed as PDU Session Resource Modify Request (PDU Session Resource Modify Request Transfer).

[0147] S648: The base station 10C sends a response message (PDU Session Resource Modify response) to the request message received in S647 to the AMF 30A.

[0148] S649: AMF 30A sends a request message (Nsmf_PDUSession_UpdateSMContext request) requesting a context update of the PDU session to SMF 30B. For example, the request message is expressed as Nsmf_PDUSession_UpdateSMContext request (SmContextUpdateData(n2SmInfo(PDU Session Resource Modify Response Transfer))).

[0149] S650: SMF 30B sends a response message (Nsmf_PDUSession_UpdateSMContext response) to AMF 30A in response to the request message received in S649.

[0150] S651: SMF 30B sends a request message (PFCP Session Modification request) to UPF 30D1R to update the user data transfer path.

[0151] S652: UPF 30D1R sends a response message (PFCP Session Modification response) to the request message received in S651 to SMF 30B.

[0152] S653: SMF 30B sends a request message (PFCP Session Deletion request) to UPF 30D2L to release the user data transfer path.

[0153] S654: UPF 30D2L sends a response message (PFCP Session Deletion response) to the request message received in S653 to SMF 30B.

[0154] S655: SMF 30B sends a request message (PFCP Session Deletion request) to ULCL 30E to release the user data transfer path.

[0155] S656: ULCL 30E transmits to SMF 30B a response message (PFCP Session Deletion response) to the request message received in S655.

[0156] S657: The P-CSCF 30G transmits to the IMS AGW 30FL a request message (H.248 SUBTRACT request) requesting settings related to the deletion of control of voice communication (i.e., release of the IMS AGW 30FL).

[0157] S658: The IMS AGW 30FL deletes the setting.

[0158] S659: The IMS AGW 30FL transmits to the P-CSCF 30G a response message (H.248 SUBTRACT response) in response to the request message received in S657.

[0159] The process following S659 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.

[0160] S661: P-CSCF30G2 sends a request message (Npcf_PolicyAuthorization_Create request) to PCF30C2 requesting SMF30B2 to release ULCL30E2 on the satellite and UPF30D4L on the satellite.

[0161] S662: The PCF 30C2 transmits to the P-CSCF 30G2 a response message (Npcf_PolicyAuthorization_Create response) in response to the request message received in S661.

[0162] S663: PCF 30C2 sends a request message (Npcf_SMPolicyControl_UpdateNotify request) to SMF 30B2 requesting that ULCL 30E2 on the satellite and UPF 30D4L on the satellite be released.

[0163] S664: The SMF 30B2 sends to the PCF 30C2 a response message (Npcf_SMPolicyControl_UpdateNotify response) in response to the request message received in S663.

[0164] S665: SMF 30B2 sends a request message (Namf_Communication_N1N2MessageTransfer request) to AMF 30A2 for updating the PDU session resource settings. For example, this message is expressed as Namf_Communication_N1N2MessageTransfer request (N1N2MessageTransferReqData(n2InfoContainer(smInfo(n2InfoContent(PDU Session Resource Modify Request Transfer))))).

[0165] S666: AMF 30A2 sends a response message (Namf_Communication_N1N2MessageTransfer response) to SMF 30B2 in response to the request message received in S665.

[0166] S667: The AMF 30A2 transmits a request message (PDU Session Resource Modify Request) for updating the PDU session resource settings to the base station 10B. For example, the message is expressed as PDU Session Resource Modify Request (PDU Session Resource Modify Request Transfer).

[0167] S668: The base station 10B transmits to the AMF 30A2 a response message (PDU Session Resource Modify response) to the request message received in S667.

[0168] S669: 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))).

[0169] S670: SMF30B2 sends a response message (Nsmf_PDUSession_UpdateSMContext response) to AMF30A2 in response to the request message received in S669.

[0170] S671: SMF30B2 sends a request message (PFCP Session Modification request) to UPF30D3R to update the user data transfer path.

[0171] S672: UPF 30D3R sends a response message (PFCP Session Modification response) to the request message received in S671 to SMF 30B2.

[0172] S673: SMF30B2 sends a request message (PFCP Session Deletion request) to UPF30D4L to release the user data transfer path.

[0173] S674: UPF 30D4L sends a response message (PFCP Session Deletion response) to the request message received in S673 to SMF 30B2.

[0174] S675: SMF30B2 sends a request message (PFCP Session Deletion request) to ULCL30E2 to release the user data transfer path.

[0175] S676: ULCL 30E2 transmits to SMF 30B2 a response message (PFCP Session Deletion response) to the request message received in S675.

[0176] S677: The P-CSCF 30G2 transmits to the IMS AGW 30FL2 a request message (H.248 SUBTRACT request) requesting settings related to the deletion of control of voice communication (i.e., release of the IMS AGW 30FL2).

[0177] S678: The IMS AGW 30FL2 deletes the setting.

[0178] S679: The IMS AGW 30FL2 transmits to the P-CSCF 30G2 a response message (H.248 SUBTRACT response) in response to the request message received in S677.

[0179] The current data flow of uplink (UL) media (voice signals) and downlink (DL) media (voice signals) will be described. Figure 13 shows an example of a tenth sequence diagram according to an embodiment of the present invention. The processing of each step will be described below.

[0180] As shown in S681, the UL media is transmitted via the terrestrial IMS AGW 30FR. That is, the UL media is transmitted from the originating terminal 20A to the terminal 20B via the base station 10C, UPF 30D1R, IMS AGW 30FR, IMS AGW 30FR2, UPF 30D3R, and base station 10B.

[0181] As shown in S682, the DL media is received via the terrestrial IMS AGW 30FR. That is, the DL media is received from the terminal 20B on the receiving side via the base station 10B, the UPF 30D3R, the IMS AGW 30FR2, the IMS AGW 30FR, the UPF 30D1R, and the base station 10C, and then by the terminal 20A.

[0182] According to the above-described embodiment, ground fallback can be performed without packet loss in a wireless communication system using a satellite.

[0183] (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.

[0184] <Base Station 10 and Network Node 30> Fig. 14 is a diagram showing an example of the functional configuration of the base station 10 and the network node 30. As shown in Fig. 14, 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. 14 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.

[0185] 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.

[0186] 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.

[0187] 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.

[0188] <Terminal 20> Fig. 15 is a diagram showing an example of the functional configuration of the terminal 20. As shown in Fig. 15, 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. 15 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.

[0189] 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.

[0190] The setting unit 230 stores various setting information received from the network node 30 by the receiving unit 220 in a storage device, and reads it out from the storage device as needed. The setting unit 230 also stores setting information that is set in advance.

[0191] 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.

[0192] (Hardware Configuration) The block diagrams (FIGS. 14 and 15) 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 connected directly or indirectly (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.

[0193] 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.

[0194] 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. 16 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.

[0195] 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.

[0196] 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.

[0197] 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.

[0198] 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. 14 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. 15 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.

[0199] 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.

[0200] 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.

[0201] 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.

[0202] The input device 1005 is an input device (e.g., a keyboard, a mouse, a microphone, a switch, a button, a sensor, etc.) that accepts 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).

[0203] 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.

[0204] 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.

[0205] Fig. 17 shows an example configuration of a vehicle 2001. As shown in Fig. 17, 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.

[0206] 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.

[0207] 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).

[0208] 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.

[0209] 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.

[0210] 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.

[0211] 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.

[0212] 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.

[0213] 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.

[0214] 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.

[0215] <Additional Notes> (Additional Note 1) A network node comprising: a receiver that receives from a first network node a first message, including a satellite identifier, requesting route switching accompanying a base station change; a controller that recognizes that the satellite on which a source base station is located is different from the satellite on which a destination base station is located; and a transmitter that transmits, to a second network node, a second message, including a destination satellite identifier, inquiring whether or not to switch an ULCL (Uplink Classifier) ​​and a local user plane function, wherein the receiver receives a third message transmitted from the second network node that rejects the switching of the ULCL and the local user plane function, and the transmitter transmits, to the base station, a fourth message requesting confirmation of a cell identifier by a terminal. (Supplementary Item 2) A network node having: a receiving unit that receives a first message from a first network node, including a destination satellite identifier, inquiring whether or not to switch between an ULCL (Uplink Classifier) ​​and a local user plane function; a control unit that recognizes that the destination satellite identifier and the opposing satellite identifier are not included in the same satellite constellation identifier because the source satellite identifier and the destination satellite identifier are not included in the same satellite constellation identifier, and determines that voice media cannot be routed on the satellite constellation; and a transmitting unit that transmits a second message to the first network node, refusing to switch between the ULCL (Uplink Classifier) ​​and a local user plane function.(Supplementary Item 3) The network node according to Supplementary Item 2, wherein the receiving unit receives a first message from a terminal requesting an update of a voice communication state, and after completing configuration of a terrestrial IMS AGW (IP Multimedia Subsystem Access Gateway), the transmitting unit transmits to the terminal, as a response to the first message, a second message responding to the request for update of the voice communication state, including a termination point on the terrestrial IMS AGW side for data transmission with the terminal, the transmitting unit transmits to a second network node a third message requesting an update of the voice communication state, including a termination point on the terrestrial IMS AGW side for data transmission with a terminating side, the transmitting unit transmits to the first network node a fourth message requesting release of a source ULCL (Uplink Classifier) ​​and a source local user plane function, and the transmitting unit transmits to the source IMS AGW a fifth message requesting release of the source IMS AGW.(Supplementary Item 4) A system comprising: a receiving unit that receives a first message requesting an update of a voice communication state from a first network node; a control unit that recognizes that the first message does not include satellite-related information and therefore it is impossible to route voice media on a satellite constellation; and a transmitting unit that transmits a second message requesting an update of the voice communication state, including an IMS AGW (IP Multimedia Subsystem Access Gateway) side termination point on its own network satellite for data transmission with the terminal, to a terminal, wherein after completing configuration of a terrestrial IMS AGW, the transmitting unit transmits to the first network node, as a response to the first message, a third message responding to the request for update of the voice communication state, including an IMS AGW side termination point on the terrestrial IMS AGW side for data transmission with a calling side; the receiving unit receives from the first network node a fourth message requesting an update of the voice communication state; the transmitting unit transmits to the terminal a fifth message requesting an update of the voice communication state, including an IMS AGW side termination point on the terrestrial IMS AGW side for data transmission with the terminal; and the transmitting unit transmits a fifth message requesting an update of the voice communication state, including an IMS AGW side termination point on the satellite Uplink Layer CL (ULCL) a sixth message requesting release of an Uplink Classifier (ULCL) and local user plane functions on the satellite, and the transmitter transmits a seventh message to the on-satellite IMS AGW, requesting release of the on-satellite IMS AGW. (Supplementary Item 5) A communication method executed by a network node, comprising: the steps of: receiving, from a first network node, a first message requesting route switching accompanying a base station change, the message including a satellite identifier; recognizing that the satellite on which a source base station is located is different from the satellite on which a destination base station is located; transmitting, to a second network node, a second message inquiring whether to switch the Uplink Classifier (ULCL) and local user plane functions, the second message including the destination satellite identifier; receiving, from the second network node, a third message rejecting the switch of the ULCL and local user plane functions; and transmitting, to a base station, a fourth message requesting confirmation of a cell identifier by a terminal.

[0216] Any of Supplementary Items 1 to 5 enables ground fallback to be performed without packet loss in a wireless communication system using a satellite.

[0217] (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.

[0218] 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.

[0219] 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).

[0220] 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.

[0221] 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).

[0222] 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.

[0223] 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.

[0224] In the present disclosure, the determination may be made by a value represented by one bit (0 or 1), by a Boolean value (true or false), or by a comparison of numerical values ​​(e.g., comparison with a predetermined value).

[0225] 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.

[0226] 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.

[0227] 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.

[0228] 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.

[0229] As used in this disclosure, the terms "system" and "network" are used interchangeably.

[0230] Furthermore, the information, parameters, etc. described in the present disclosure may be expressed using absolute values, relative values ​​from a predetermined value, or other corresponding information. For example, a radio resource may be indicated by an index.

[0231] 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.

[0232] 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.

[0233] 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.

[0234] 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.

[0235] In this disclosure, the terms "Mobile Station (MS)," "user terminal," "User Equipment (UE)," "terminal," and the like may be used interchangeably.

[0236] 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.

[0237] 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.

[0238] 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.

[0239] 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.

[0240] 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.

[0241] 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.

[0242] The reference signal may be abbreviated as RS (Reference Signal) or may be called a pilot depending on the applicable standard.

[0243] 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."

[0244] 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.

[0245] The "means" in the configuration of each of the above devices may be replaced with "part," "circuit," "device," etc.

[0246] 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.

[0247] 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.

[0248] 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."

[0249] 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).

[0250] 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.

[0251] 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 comprising: a receiver that receives from a first network node a first message, including a satellite identifier, requesting route switching due to a change in base station; a controller that recognizes that the satellite on which the source base station is located is different from the satellite on which the destination base station is located; and a transmitter that transmits to a second network node a second message, including a destination satellite identifier, inquiring whether or not to switch between an Uplink Classifier (ULCL) and a local user plane function, wherein the receiver receives a third message transmitted from the second network node rejecting the switching of the ULCL and the local user plane function; and the transmitter transmits to the base station a fourth message requesting confirmation of a cell identifier by the terminal.

2. A network node having: a receiving unit that receives a first message from a first network node, including a destination satellite identifier, inquiring whether or not to switch between an ULCL (Uplink Classifier) ​​and a local user plane function; a control unit that recognizes that the destination satellite identifier and the opposing satellite identifier are not included in the same satellite constellation identifier because the source satellite identifier and the destination satellite identifier are not included in the same satellite constellation identifier, and determines that voice media cannot be routed on the satellite constellation; and a transmitting unit that transmits a second message to the first network node, refusing to switch between the ULCL (Uplink Classifier) ​​and a local user plane function.

3. The network node according to claim 2, wherein the receiving unit receives a first message from a terminal requesting an update of a voice communication state, and after completing configuration of a terrestrial IMS AGW (IP Multimedia Subsystem Access Gateway), the transmitting unit transmits to the terminal, as a response to the first message, a second message responding to the request for updating the voice communication state, including a termination point on the terrestrial IMS AGW side for data transmission with the terminal, the transmitting unit transmits to a second network node a third message requesting an update of the voice communication state, including a termination point on the terrestrial IMS AGW side for data transmission with a terminating side, the transmitting unit transmits to the first network node a fourth message requesting release of a source ULCL (Uplink Classifier) ​​and a source local user plane function, and the transmitting unit transmits to the source IMS AGW a fifth message requesting release of the source IMS AGW.

4. A system comprising: a receiving unit that receives a first message requesting an update of a voice communication state from a first network node; a control unit that recognizes that the first message does not include satellite-related information and therefore it is impossible to route voice media on a satellite constellation; and a transmitting unit that transmits a second message requesting an update of the voice communication state, including an IMS AGW (IP Multimedia Subsystem Access Gateway) termination point on its own network satellite for data transmission with the terminal, to the terminal; wherein after completing configuration of a terrestrial IMS AGW, the transmitting unit transmits to the first network node, as a response to the first message, a third message responding to the request for an update of the voice communication state, including an IMS AGW termination point on the terrestrial IMS AGW for data transmission with a calling side; the receiving unit receives from the first network node a fourth message requesting an update of the voice communication state; the transmitting unit transmits to the terminal a fifth message requesting an update of the voice communication state, including an IMS AGW termination point on the terrestrial IMS AGW for data transmission with the terminal; and the transmitting unit transmits a fifth message requesting an update of the voice communication state, including an IMS AGW termination point on the satellite Uplink Layer CL (ULCL) a sixth message requesting the release of an on-satellite local user plane function to the on-satellite IMS AGW, and the transmitter transmits a seventh message requesting the release of the on-satellite IMS AGW, to the on-satellite IMS AGW.

5. A communication method executed by a network node, comprising the steps of: receiving from a first network node a first message requesting route switching accompanying a base station change, the message including a satellite identifier; recognizing that the satellite on which the source base station is located is different from the satellite on which the destination base station is located; sending to a second network node a second message including the destination satellite identifier, inquiring whether or not to switch the ULCL (Uplink Classifier) ​​and local user plane function; receiving from the second network node a third message rejecting the switch of the ULCL and local user plane function; and sending to a base station a fourth message requesting confirmation of the cell identifier by the terminal.

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