Network node and communication method

Abstract

This network node includes: a reception unit whereby a message including information about a first satellite for newly accommodating a terminal is received from a first network node; and a control unit that selects an operation related to a satellite change procedure on the basis of the information about the first satellite, information about a second satellite for accommodating another network-side terminal, and information indicating whether the network on which the network node is located is the originating network or the terminating network.

Description

Network node and communication method

[0001] This invention relates to network nodes and communication methods in a communication system.

[0002] 3GPP (registered trademark) (3rd Generation Partnership Project) standardizes technologies to achieve even greater system capacity, faster data transmission speeds, and lower latency in the wireless section. For example, the wireless communication method called NR (New Radio) or 5th Generation Mobile Communication System (5G) (hereinafter referred to as "NR" or "5G") specifies requirements to achieve a throughput of 10 Gbps or more while keeping the latency in the wireless section to 1 ms or less.

[0003] Furthermore, NR standardizes network architectures that include 5GC (5G Core Network) as an evolution of EPC (Evolved Packet Core), which is the core network in the LTE (Long Term Evolution) network architecture, and NG-RAN (Next Generation-RAN) as a successor to E-UTRAN (Evolved Universal Terrestrial Radio Access Network), which is the RAN (Radio Access Network) in the LTE network architecture (Non-Patent Documents 1 and 2, etc.).

[0004] As a standardized architecture framework for providing multimedia services (such as voice, video, text messages, etc.) on an IP (Internet Protocol) network, there is an IMS (IP Multimedia Subsystem) architecture. Also, as part of IMS, the specifications of an IMS data channel network, which is a new communication channel for supporting data transmission in a multimedia session, have also been standardized (see Non-Patent Document 3, etc.). In the IMS data channel network, data transmission and reception are efficiently performed on each of the transmitting side and the receiving side through a session management function or the like. As a result, in addition to media streams such as voice and video, auxiliary data such as text and files can also be exchanged simultaneously.

[0005] Also, in IMS voice communication's UE-satellite-UE communication, it is necessary to continue voice communication even when the satellite accommodating the terminal is changed. Currently, procedures for this are being studied. For example, (a) when different satellites connected using an Inter Satellite Link (ISL) accommodate different transmitting and receiving terminals, the optimal communication path between the satellites continues to be used even after the satellite accommodating one of the terminals has switched; (b) a ground fallback procedure of switching to a communication path via a ground device; (c) when the same satellite accommodates the transmitting and receiving terminals, after satellite switching, another same satellite will accommodate the transmitting and receiving terminals, and the optimal communication path via the satellite continues to be used; etc. are being studied (see Non-Patent Document 4). Note that the types of satellites handled are Geostationary Earth Orbit (GEO) satellites, Low Earth Orbit (LEO) satellites, and Medium Earth Orbit (MEO) satellites.

[0006] 3GPP TS 38.300 V18.3.0 (2024-09)3GPP TS 23.501 V19.1.0 (2024-09)3GPP TS 23.228 V19.0.0 (2024-09)3GPP TR 23.700-29 V19.0.0 (2024-06)3GPP TS 23.334 V18.1.0 (2024-06)3GPP TS 23.502 V19.1.0 (2024-09)

[0007] In discussions at 3GPP, the existing solution proposed was to introduce a new SDP (Session Description Protocol) attribute into SIP (Session Initiation Protocol) messages used for session establishment, modification, and termination. Furthermore, the existing solution involved using the SIP re-INVITE message twice, which is used when renegotiating an existing session.

[0008] However, as a result of discussions at 3GPP, it was decided that introducing a new SDP attribute should be avoided because it could cause malfunctions in each IMS AS (Application Server), not in terms of specifications but in implementation. Also, the procedure of using SIP re-INVITE messages twice was deemed cumbersome and lengthy. Furthermore, as a result of discussions at 3GPP, it was decided that processing should be performed in parallel as much as possible on both the sending and receiving sides to speed up the process, that connectivity with the new IMS AGW (Access Gateway) set up after a satellite change should be checked if possible, and that procedures should be addressed for when the connection between IMS AGWs is disconnected even though the satellite does not change.

[0009] Currently, no procedures or methods for resolving the above issues have been discussed. If the procedures for switching communication paths when satellites are changed are not properly implemented, the complexity of signaling processing and the resulting increase in processing delays may impair the continuity of IMS voice services.

[0010] This invention has been made in view of the above-mentioned problems, and aims to appropriately perform the procedure for switching communication paths when satellites are changed.

[0011] According to the disclosed technology, a network node is provided which includes a receiving unit that receives a message from a first network node containing information about a first satellite that will newly accommodate terminals, and a control unit that selects an operation related to a satellite change procedure based on the information about the first satellite, information about a second satellite that will accommodate terminals on the other network side, and information indicating whether the local network is sending or receiving data.

[0012] According to the disclosed technology, the procedure for switching communication paths when a satellite is changed can be properly implemented.

[0013] Figure 1 shows an example of the configuration of a communication system. Figure 2 shows an example of the configuration of a communication system in a roaming environment. Figure 3 shows an example of the configuration of an IMS data channel network. Figure 4 shows an example of a sequence showing the procedure for continuously using the optimal communication path between satellites in Example 1. Figure 5 shows an example of a sequence showing the ground fallback procedure in Example 2. Figure 6 shows an example of a sequence showing the procedure for continuously using the optimal communication path using one satellite in Example 3. Figure 7 shows an example of a sequence showing the ground fallback procedure when the inter-satellite link (ISL) connection between both networks is disconnected in Example 4. Figure 8 shows an example of the functional configuration of a base station and network node. Figure 9 shows an example of the functional configuration of a terminal. Figure 10 shows an example of the hardware configuration of a base station and terminal. Figure 11 shows an example of the configuration of a vehicle.

[0014] Embodiments of the present invention will be described below with reference to the drawings. The embodiments described below are merely examples, and the embodiments to which the present invention is applied are not limited to the embodiments described below.

[0015] In the following explanation, " / " means "and / or" unless otherwise specified, or unless the context makes it clear that it has a different meaning.

[0016] In the operation of the communication system of this embodiment, existing technologies will be used as appropriate. However, such existing technologies include, for example, existing LTE (Long Term Evolution), but are not limited to existing LTE. Furthermore, unless otherwise specified, the term "LTE" used in the following description has a broad meaning that includes LTE-Advanced and LTE-Advanced and later technologies (NR (New Radio), 5G, 5G-Advanced, 6G, etc.).

[0017] <System Configuration> (5G Core Architecture) Figure 1 shows an example of the configuration of a communication system.

[0018] The communication system in this embodiment includes a terminal 20, which is a UE20 (User Equipment), and multiple network nodes 30, including a core network 31. Hereinafter, one network node 30 will be assigned to each function, but one network node 30 may implement multiple functions, or multiple network nodes 30 may implement one function. Furthermore, the "connection" described below may be a logical connection or a physical connection.

[0019] In this embodiment, network node 30 may be referred to as a collective term for multiple network nodes, or as a single network node. In either case, when simply referred to as network node 30, it means one or more network nodes, not limited to a specific network node.

[0020] The core network 31 in Figure 1 is not limited to this configuration. For example, UPF30C (User Plane Function) may be included in the core network 31 as shown in Figure 1, or it may not be included in the core network 31, although this is not shown in Figure 1.

[0021] RAN30A (Radio Access Network) is a network node 30 having radio access functionality, and may include a base station 10. RAN30A is connected to UE20, AMF (Access and Mobility Management Function), and UPF30C (User Plane Function).

[0022] AMF30B is a network node 30 that has functions such as RAN interface termination, NAS (Non-Access Stratum) termination, registration management, connection management, reachability management, and terminal 20 mobility management.

[0023] UPF30C is a network node 30 that interconnects with the DN (Data Network) and has functions related to processing U-Plane data, such as a PDU (Protocol Data Unit) session point for external networks, packet routing and forwarding, and QoS (Quality of Service) handling for the user plane (U-Plane). UPF30C and DN constitute a network slice. In this embodiment, multiple network slices may be constructed in the communication network.

[0024] AMF30B is connected to UE20, RAN30A, SMF30E (Session Management Function), NSSF30F (Network Slice Selection Function), NEF30G (Network Exposure Function), NRF30H (Network Repository Function), UDM30I (Unified Data Management), AUSF30J (Authentication Server Function), PCF30K (Policy Control Function), and AF30L (Application Function). AMF30B, SMF30E, NSSF30F, NEF30G, NRF30H, UDM30I, AUSF30J, PCF30K, and AF30L are network nodes 30 that are interconnected via interfaces Namf, Nsmf, Nnssf, Nnef, Nnrf, Nudm, Nausf, Npcf, and Naf, respectively, based on their respective services.

[0025] SMF30E is a network node 30 that has functions such as session management, IP (Internet Protocol) address assignment and management for UE20, DHCP (Dynamic Host Configuration Protocol) functionality, RAP (Address Resolution Protocol) proxy, and roaming functionality.

[0026] NEF30G is a network node 30 that has the function of notifying other NFs (Network Functions) of their capabilities and events.

[0027] NSSF30F is a network node 30 that has functions such as selecting the network slice to which UE20 will connect, determining the allowed NSSAI (Network Slice Selection Assistance Information), determining the NSSAI to be set, and determining the AMF30B set to which UE20 will connect.

[0028] PCF30K is a network node 30 that has the function of controlling network policy. For example, in a satellite change procedure, PCF30K may send a message containing information related to the satellite change to other network nodes 30.

[0029] AF30L is a network node 30 that has the function of controlling the application server.

[0030] NRF30H is a network node 30 that has the ability to discover NF instances that provide services.

[0031] UDM30I is a network node 30 that manages subscriber data and authentication data. Although not shown in Figure 1, UDM30I is connected to the UDR (User Data Repository) which holds subscriber data and authentication data.

[0032] Figure 2 shows an example of the configuration of a communication system in a roaming environment.

[0033] The network in this embodiment consists of a terminal 20, which is a UE20, and multiple network nodes 30. Hereinafter, one network node 30 will be assigned to each function, but one network node 30 may implement multiple functions, or multiple network nodes 30 may implement one function. Furthermore, the "connection" described below may be a logical connection or a physical connection.

[0034] RAN30A is a network node 30 with wireless access capabilities and is connected to UE20, AMF30B, and UPF30C.

[0035] AMF30B is a network node 30 that has functions such as RAN interface termination, NAS (Non-Access Stratum) termination, registration management, connection management, reachability management, and terminal 20 mobility management.

[0036] UPF30C is a network node 30 that interconnects with DN and has functions related to processing U-Plane data, such as PDU session point to the outside, packet routing and forwarding, and U-Plane QoS handling. UPF30C and DN constitute a network slice. In this embodiment, multiple network slices may be constructed in the communication network.

[0037] AMF30B is connected to UE20, RAN30A, SMF30E, NSSF30F, NEF30G, NRF30H, UDM30I, AUSF30J, PCF30K, AF30L, and vSEPP30M (visited Security Edge Protection Proxy). AMF30B, SMF30E, NSSF30F, NEF30G, NRF30H, UDM30I, AUSF30J, PCF30K, and AF30L are network nodes 30 that are interconnected via interfaces Namf, Nsmf, Nnssf, Nnef, Nnrf, Nudm, Nausf, Npcf, and Naf, respectively, based on their respective services.

[0038] SMF30E is a network node 30 that has functions such as session management, IP address assignment and management for UE20, DHCP functionality, ARP proxy, and roaming functionality.

[0039] NEF30G is a network node 30 that has the function of notifying other NFs of its capabilities and events.

[0040] NSSF30F is a network node 30 that has functions such as selecting the network slice to which UE20 will connect, determining the allowed NSSAI, determining the NSSAI to be configured, and determining the AMF30B set to which UE20 will connect.

[0041] PCF30K is a network node 30 that has the function of controlling network policy. For example, in a satellite change procedure, PCF30K may send a message containing information related to the satellite change to other network nodes 30.

[0042] AF30L is a network node 30 having a function of controlling an application server.

[0043] NRF30H is a network node 30 having a function of discovering an NF instance that provides a service.

[0044] 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 operating in the visited network (VPLMN: Visited PLMN), and the hSEPP30N connected via the interface N32 is a SEPP operating in the home network (HPLMN: Home PLMN).

[0045] As shown in FIG. 2, the UE20 is in a roaming environment connected to the RAN30A and the AMF30B in the VPLMN. The VPLMN and the HPLMN are connected via the vSEPP30M and the hSEPP30N. The UE20 can communicate with the UDM30I of the HPLMN via, for example, the AMF30B of the VPLMN.

[0046] (IMS Architecture) FIG. 3 is a diagram showing an example of the configuration of an IMS data channel network.

[0047] The IMS data channel network in the present embodiment is composed of the UE20, which is a terminal 20, and a plurality of network nodes 30 in each of the originating network and the terminating network. Hereinafter, it is assumed that one network node 30 corresponds to each function, but a single network node 30 may implement a plurality of functions, or a plurality of network nodes 30 may implement a single function. Also, 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 3.

[0048] The terminating network may be called the terminal network.

[0049] IMS-AGW30O (Access Gateway) is a network node 30 that has gateway functions between the UE20 and the IMS network, as well as functions related to voice communication access processing.

[0050] P-CSCF (Proxy-Call Session Control Function) is a network node 30 that provides proxy functionality between the UE20b and the IMS network, as well as access control functionality for voice communications.

[0051] S-CSCF30Q (Serving-Call Session Control Function) is a network node 30 that has functions related to session control for UE20.

[0052] I-CSCF30R (Interrogate-Call Session Control Function) is a network node 30 that acts as the receiving connection point between networks (the originating network and the receiving network) in the IMS network. For example, it has the function of forwarding received SIP (Session Initiation Protocol) requests to the S-CSCF30Q on its own network side.

[0053] IMS-AS30S (IP Multimedia Subsystem Application Server) is a network node 30 in the IMS network that has functions such as communicating with DCSF30T for event notification, receiving data channel control instructions from DCSF30T and communicating with MF30U (Media Function). IMS-AS30S also receives a communication termination point registration request from DCSF30T (Data Channel Signaling Function), converts the received registration request into a SIP Register, and sends the SIP Register message to S-CSCF30Q. Furthermore, IMS-AS30S converts a data channel establishment request received from DCSF30T into a SIP INVITE and sends the SIP INVITE message to S-CSCF30Q.

[0054] DCSF30T (Data Channel Signaling Function) is a network node 30 that receives event reports from IMS-AS30S and has the function of deciding whether or not to allow the provision of data channel services based on those reports. DCSF30T also manages bootstrap data channels and application data channels via MF30U. Furthermore, DCSF30T has the function of retrieving verified data channel applications stored in DCAR (Data Channel Application Repository) and downloading them to UE20 via MF30U.

[0055] The MF30U (Media Function) is a network node 30 in the IMS network that has functions such as media resource management and data channel media traffic forwarding. The MF30U also processes media between the communication termination point, the DCAS30V1 (Data Channel Application Server), and the destination termination point based on configuration information received from the DCSF30T. The MF30U may also be called the DCMF (Data Channel Media Function) or the MRF (Multimedia Resource Function).

[0056] DCAS30V1 (Data Channel Application Server) is a network node 30 that provides data channel applications in the IMS network and functions as a communication termination point related to data channel services.

[0057] <Example> Below, we will describe the procedure for changing the satellite to which UE20 is connected, after applying the above communication system to NTN's satellite constellation communication.

[0058] In this embodiment, it is assumed that multiple low Earth orbit (LEO) satellites, each equipped with RAN30A and network nodes 30 handling the user plane of the core network 31 (specifically, ULCL, L-PSA, and IMS AGW), form a satellite constellation using interstellar links (ISL). Network nodes 30 handling the control plane of the core network 31 (specifically, AMF, SMF, PCF, P-CSCF, and IMS AS) are deployed on the ground. In addition, some of the network nodes 30 handling the user plane of the core network 31 are deployed on the ground (specifically, PSA; IMS AGW is deployed both on the low Earth orbit (LEO) satellites and on the ground).

[0059] In this embodiment, the impact of differences in subscriber information will not be considered.

[0060] In this embodiment, the terms "transmitting network" and "receiving network" are merely for convenience and do not necessarily have to be used to refer to the network in which the satellite change occurred. For example, the transmitting network may be the receiving network, or the receiving network may be the transmitting network. Alternatively, these networks may be distinguished by other names (e.g., the first network, the second network).

[0061] In this embodiment, the originating network may be called the originating side, originating network, etc. For example, a P-CSCF30P belonging to the originating network may be called an originating P-CSCF30P, etc. The receiving network may be called the receiving side, receiving network, etc. For example, a P-CSCF30P belonging to the receiving network may be called an incoming P-CSCF30P, etc. The originating P-CSCF30P and incoming P-CSCF30P together may be called originating and incoming P-CSCF30P, etc.

[0062] The details of the procedure in this embodiment will be explained below using sequence diagrams. Requests, responses, and notifications sent and received in the following procedure may be referred to as messages. For details of messages of existing specifications sent and received in the sequence diagrams, please refer to Non-Patent Documents 2 and 3.

[0063] In this embodiment, the sequence is executed on the premise that voice communication using a satellite constellation has been established between UE20a, which belongs to the transmitting network, and UE20b, which belongs to the receiving network.

[0064] In the description of the sequence in this embodiment, for the sake of notation, the spaces in IMS AS and IMS AGW may be replaced with hyphens.

[0065] This embodiment proposes procedures that do not use a new SDP attribute, procedures that use SIP re-INVITE only once, procedures that increase the scope of parallel processing on the sending and receiving sides, procedures for confirming connectivity with the new IMS-AGW30O, procedures for P-CSCF30P to determine whether the optimal communication path between satellites can be continued to be used, procedures that do not require P-CSCF30P to operate as a SIP B2B UA (Back-to-Back User Agent), and procedures for when the connection between IMS-AGW30Os is disconnected.

[0066] (Example 1) Procedures may be defined for continuously using the optimal communication path between satellites using an interstellar link (ISL).

[0067] Figure 4 shows an example sequence of steps for continuously using the optimal communication path between satellites in Example 1.

[0068] In this embodiment, when the satellite to which UE20a belonging to the transmitting network is connected is different from the satellite to which UE20b belonging to the receiving network is connected, the satellite to which UE20a belonging to the transmitting network is changed. The processing of each step is described below.

[0069] Step S101: 5GC31 sends an early notification message to P-CSCF30P1 regarding a change in the U-Plane. 5GC31 may refer to a specific network node, such as PCF30K or SMF30E. The message includes an identifier for the satellite that will newly accommodate the UL CL (Uplink Classifier) ​​and L-PSA (Local PDU (Protocol Data Unit) Session Anchor) handling the UE20a's voice media.

[0070] Step S102: P-CSCF30P1 determines that terminal-satellite-terminal communication can be continued by verifying the identifier of the satellite that will newly accommodate UE20a, which was received in step S101, the identifier of the satellite that will accommodate UE20b, which was acquired at the start of voice communication, and the information that associates the combination of satellite identifiers with the ISL status.

[0071] Step S103: Regarding the connection with UE20a, the IMS-AGW30O1 on the destination satellite is reserved and configured. Specifically, the IMS-AGW30O1 on the destination satellite reserves an IP address within its own device to receive IP packets from UE20a and notifies P-CSCF30P1. P-CSCF30P1 sets the IMS-AGW30O1 on the destination satellite with the IP address that UE20a has set within UE20a to receive IP packets, which was acquired at the start of voice communication. Note that the procedure for this step S103 has been specified in Non-Patent Document 5.

[0072] Step S104: Regarding the connection with IMS-AGW30O2, the reservation and configuration of IMS-AGW30O1 on the destination satellite are performed. Specifically, IMS-AGW30O1 on the destination satellite reserves an IP address within its own device to receive IP packets from IMS-AGW30O2 and notifies P-CSCF30P1. P-CSCF30P1 sets the IP address that IMS-AGW30O2 has set within IMS-AGW30O2 to receive IP packets, which was acquired at the start of voice communication, on IMS-AGW30O1 on the destination satellite. Note that the procedure for this step S104 has been specified in Non-Patent Document 5.

[0073] Step S104a: Connectivity checks may be performed between the destination satellite IMS-AGW30O1 and the remote satellite IMS-AGW30O2.

[0074] Step S105: Simultaneously modify the UL CL (Uplink Classifier), which is the function for distributing UE20a traffic, and the local U-Plane function (L-PSA: Local PDU (Protocol Data Unit) Session Anchor), and also update the UE20a's traffic filter. This ensures that traffic is distributed appropriately based on the new routing configuration and QoS flow. Note that the procedure for this step S105 has been specified in Non-Patent Document 6.

[0075] Step S106: 5GC31 sends a message (late notification) to P-CSCF30P1 regarding the change in the U-Plane. This message indicates that 5GC31 is ready to change its route to the destination satellite.

[0076] The following steps are performed so that UE20a and IMS-AGW30O2 send IP packets to IMS-AGW30O1 on the destination satellite.

[0077] Step S107: P-CSCF30P1 sends a SIP MESSAGE to IMS-AS30S1. The SIP MESSAGE includes information about the termination point for the incoming network within IMS-AGW30O1 of the originating network. The SIP MESSAGE includes information requesting the incoming network to send a SIP re-INVITE. The SIP MESSAGE also includes information requesting UE20a to send a SIP re-INVITE after receiving a response message to the SIP re-INVITE. The SIP MESSAGE sent by P-CSCF30P1 is transmitted to IMS AS30S1 via S-CSCF30Q1.

[0078] Step S108: IMS-AS30S1 sends a message (SIP re-INVITE) to P-CSCF30P2 on the receiving network requesting a change in voice call settings.

[0079] Step S109: IMS-AGW30O2 sets the IP address of IMS-AGW30O1 on the destination satellite in order to continue IP communication from UE20b to UE20a.

[0080] Step S110: P-CSCF30P2 sends a message (SIP re-INVITE) to UE20b regarding a request for a voice call configuration change.

[0081] Step S111: UE20b sends a message (SIP 200 OK) to P-CSCF30P2 indicating success in step S110.

[0082] Step S112: P-CSCF30P2 sends a message to IMS-AS30S1 indicating the success of step S108 (SIP 200 OK).

[0083] Step S113: IMS-AS30S1 sends a message (SIP re-INVITE) to P-CSCF30P1 regarding a request for a voice call configuration change.

[0084] Step S114: P-CSCF30P1 sends a message to UE20a requesting a voice call configuration change (SIP re-INVITE), which includes the message received in step S113. P-CSCF30P1 includes in the message information for the termination point for UE20a in IMS-AGW30O1 on the destination satellite.

[0085] Step S115: UE20a sends a message (SIP 200 OK) to P-CSCF30P1 indicating the success of step S114.

[0086] Step S116: P-CSCF30P1 sends (or forwards) the message from step S115 (SIP 200 OK) to IMS-AS30S1.

[0087] Step S117: 5GC31 releases the ULCL / L-PSA on the satellite (mobile source satellite) to which UE20a was previously connected. Note that the procedure for this step S117 has been specified in Non-Patent Document 6.

[0088] Step S118: P-CSCF30P1 releases IMS-AGW30O1 on the source satellite to which UE20a had been connected. Note that the procedure for this step S118 has been specified in Non-Patent Document 5.

[0089] Note that steps S108 to S112 and steps S113 to S116 operate independently and can be swapped.

[0090] According to the above embodiment, the network node 30 can appropriately perform the procedure for switching communication paths when the satellite changes.

[0091] (Example 2) A ground fallback procedure may be defined to switch from communication with the satellite to a communication path via ground equipment.

[0092] Figure 5 shows an example sequence illustrating the ground fallback procedure for switching to a communication path via ground equipment in Embodiment 2.

[0093] In this embodiment, we assume that during the satellite change procedure, communication is impossible between the satellite to which UE20a, belonging to the transmitting network, is connected and the satellite to which UE20b, belonging to the receiving network, is connected (i.e., the ISLs of both satellites are disconnected). The processing of each step is described below.

[0094] Step S201: 5GC31 sends an early notification message to P-CSCF30P1 regarding a change in the U-Plane. 5GC31 may refer to a specific network node, such as PCF30K or SMF30E. The message includes an identifier for the satellite that will newly accommodate the UL CL (Uplink Classifier) ​​and L-PSA (Local PDU (Protocol Data Unit) Session Anchor) handling the UE20a's voice media.

[0095] Step S202: P-CSCF30P1 determines that terminal-satellite-terminal communication is impossible to continue by verifying the identifier of the satellite that newly accommodates UE20a received in step S201, the identifier of the satellite that accommodates UE20b which was acquired at the start of voice communication, and the information that associates the combination of satellite identifiers with the ISL status.

[0096] Step S203: Regarding the connection with UE20a, the IMS-AGW30O1 on the ground is reserved and configured. Specifically, the IMS-AGW30O1 on the ground reserves an IP address within its own device to receive IP packets from UE20a and notifies P-CSCF30P1. P-CSCF30P1 then sets the IMS-AGW30O1 on the ground the IP address that UE20a has set within UE20a to receive IP packets, which was acquired at the start of voice communication. Note that the procedure for this step S203 has been specified in Non-Patent Document 5.

[0097] Step S204: Regarding the connection with IMS-AGW30O2, the IMS-AGW30O1 on the ground is reserved. Specifically, the IMS-AGW30O1 on the ground reserves an IP address within its own device to receive IP packets from IMS-AGW30O2 and notifies P-CSCF30P1. Note that the procedure for this step S204 has already been specified in Non-Patent Document 5.

[0098] Step S205: Update the traffic filter on the UE20a. This update is based on the settings in Step S203 and may, for example, provide high QoS for voice calls.

[0099] Furthermore, at the end of step S205, the IMS-AGW30O1 on the ground of the transmitting network will have completed the configuration of its IP address for UE20a. Therefore, at the end of step S205, if the IMS-AGW30O1 on the ground receives data such as voice media, it will be able to transmit that data to UE20a.

[0100] Step S206: P-CSCF30P1 sends a SIP MESSAGE to IMS-AS30S1. The SIP MESSAGE includes information about the termination point for the incoming network within IMS-AGW30O1 of the originating network. The SIP MESSAGE includes information requesting the incoming network to send a SIP re-INVITE. The SIP MESSAGE also includes information requesting UE20a to send a SIP re-INVITE after receiving a response message to the SIP re-INVITE. The SIP MESSAGE sent by P-CSCF30P1 is transmitted to IMS AS30S1 via S-CSCF30Q1.

[0101] Step S207: IMS-AS30S1 sends a message (SIP re-INVITE) to IMS-AS30S2 on the receiving network requesting a change in voice call settings.

[0102] Step S208: IMS-AS30S2 sends a message (SIP re-INVITE) to P-CSCF30P2 regarding a request for a voice call configuration change.

[0103] Step S209: Regarding the connection with UE20b, the IMS-AGW30O2 on the ground is reserved and configured. Specifically, the IMS-AGW30O2 on the ground reserves an IP address within its own device to receive IP packets from UE20b and notifies the P-CSCF30P2. The P-CSCF30P2 then sets the IMS-AGW30O2 on the ground the IP address that UE20b has set within UE20b to receive IP packets, which was acquired at the start of voice communication. Note that the procedure for this step S209 has been specified in Non-Patent Document 5.

[0104] Step S210: Regarding the connection with the ground IMS-AGW30O1 of the originating network, the ground IMS-AGW30O2 is reserved and configured. Specifically, the ground IMS-AGW30O2 reserves an IP address within its own device to receive IP packets from the ground IMS-AGW30O1 of the originating network and notifies P-CSCF30P2. P-CSCF30P2 sets the IP address that the ground IMS-AGW30O1 of the originating network has configured within its own device to receive IP packets, which was obtained in S208, on the ground IMS-AGW30O2. Note that the procedure for this step S210 has been specified in Non-Patent Document 5.

[0105] Step S211: Update the traffic filter on the UE20b. This update is based on the settings in step S209 and may, for example, provide high QoS for voice calls.

[0106] Step S212: P-CSCF30P2 sends a message (SIP re-INVITE) to UE20b requesting a change in voice call settings. In the message, P-CSCF30P2 includes information about the termination point for UE20b in the ground IMS-AGW30O2.

[0107] Step S213: UE20b sends a message to P-CSCF30P2 indicating a successful response in step S212 (SIP 200 OK).

[0108] Step S214: P-CSCF30P2 sends (or forwards) the message from step S213 (SIP 200 OK) to IMS-AS30S2.

[0109] Step S215: IMS-AS30S2 sends (or forwards) the message from step S214 (SIP 200 OK) to IMS-AS30S1.

[0110] Step S216: IMS-AS30S1 sends a message (SIP re-INVITE) to P-CSCF30P1 regarding a request for a voice call configuration change.

[0111] Step S217: The ground-based IMS-AGW30O1 configures the IP address of the ground-based IMS-AGW30O2 on the receiving network in order to continue IP communication from UE20a to UE20b.

[0112] Step S218: P-CSCF30P1 sends a message (SIP re-INVITE) to UE20a requesting a voice call configuration change, including the message received in step S216. P-CSCF30P1 includes information in the message regarding the termination point for UE20a in the ground IMS-AGW30O1.

[0113] Step S219: UE20a sends a message (SIP 200 OK) to P-CSCF30P1 indicating the success of step S218.

[0114] Step S220: P-CSCF30P1 sends (or forwards) the message from step S219 (SIP 200 OK) to IMS-AS30S1.

[0115] Step S221: 5GC31 releases the ULCL / L-PSA on the satellite to which UE20a was previously connected. Note that the procedure for this step S221 has been specified in Non-Patent Document 6.

[0116] Step S222: P-CSCF30P1 releases IMS-AGW30O1 on the satellite, which UE20a had previously connected to. Note that the procedure for this step S222 has been specified in Non-Patent Document 5.

[0117] According to the above embodiment, the network node 30 can appropriately switch from communication with the satellite to a communication path via ground equipment during the satellite change procedure.

[0118] (Example 3) Procedures may be defined for the continued use of the optimal communication path using one satellite. That is, when the same satellite accommodates the departure and arrival terminals, after a satellite switchover, a different identical satellite will accommodate the departure and arrival terminals, and procedures may be defined to ensure that the departure and arrival terminals continue to use the optimal communication path via satellite.

[0119] Figure 6 shows an example sequence of steps for continuously using the optimal communication path with one satellite in Example 3.

[0120] In this embodiment, when the satellite to which UE20a belonging to the sending network is connected and the satellite to which UE20b belonging to the receiving network is connected are the same, the satellite to which UE20a belonging to the sending network and UE20b belonging to the receiving network are changed. However, if the operation of Embodiment 1 is applied in the above case, the SIP re-INVITE message in step S108 of sequence diagram 4 of Embodiment 1 will be sent bidirectionally from both networks, causing a conflict, which may prevent both network nodes from properly performing subsequent processing.

[0121] The processing of each step is described below. The hyphen in the step code does not indicate the order of processing, but may indicate which network the processing is performed on. For example, if "-1" is appended to the step code, that step may mean that the processing is performed on the originating network. Also, if "-2" is appended to the step code, that step may mean that the processing is performed on the receiving network. In other words, if the codes of two steps are the same before the hyphen and only the hyphen differs, those two steps may be performed asynchronously. For example, "Step S301-1" and "Step S301-2" may be performed in either order or simultaneously.

[0122] Step S301-1: 5GC31a sends an early notification message to P-CSCF30P1 regarding a change in the U-Plane. 5GC31a may refer to a specific network node, such as PCF30K or SMF30E. The message includes an identifier for the satellite that will newly accommodate the UL CL (Uplink Classifier) ​​and L-PSA (Local PDU (Protocol Data Unit) Session Anchor) handling the UE20a's voice media.

[0123] Step S301-2: 5GC31b sends an early notification message to P-CSCF30P2 regarding a change in the U-Plane. 5GC31b may refer to a specific network node, such as PCF30K or SMF30E. The message includes an identifier for the satellite that will newly accommodate the UL CL (Uplink Classifier) ​​and L-PSA (Local PDU (Protocol Data Unit) Session Anchor) handling the UE20b's voice media.

[0124] Step S302-1: P-CSCF30P1 determines that "the same satellite is providing service to both the originating terminal (Mobile Originated UE) and the receiving terminal (Mobile Terminated UE). Terminal-satellite-terminal communication can continue."

[0125] Step S302-2: P-CSCF30P2 determines that "the same satellite is providing service to both the originating terminal (Mobile Originated UE) and the receiving terminal (Mobile Terminated UE). Terminal-satellite-terminal communication can continue."

[0126] Step S303-1: Regarding the connection with UE20a, reserve and configure IMS-AGW30O1 on the destination satellite. Specifically, IMS-AGW30O1 on the destination satellite reserves an IP address within its own device to receive IP packets from UE20a and notifies P-CSCF30P1. P-CSCF30P1 sets the IP address that UE20a has set within UE20a to receive IP packets, which was acquired at the start of voice communication, on IMS-AGW30O1 on the destination satellite. Note that the procedure for this step S303-1 has been specified in Non-Patent Document 5.

[0127] Step S303-2: Regarding the connection with UE20b, reserve and configure IMS-AGW30O2 on the destination satellite. Specifically, IMS-AGW30O2 on the destination satellite reserves an IP address within its own device to receive IP packets from UE20b and notifies P-CSCF30P2. P-CSCF30P2 sets the IP address that UE20b has set within UE20b to receive IP packets, which was acquired at the start of voice communication, on IMS-AGW30O2 on the destination satellite. Note that the procedure for this step S303-2 has been specified in Non-Patent Document 5.

[0128] Step S304-1: Regarding the connection with IMS-AGW30O2, reserve IMS-AGW30O1 on the destination satellite. Specifically, IMS-AGW30O1 on the destination satellite reserves an IP address within its own device to receive IP packets from IMS-AGW30O2 and notifies P-CSCF30P1. Note that the procedure for this step S304-1 has already been specified in Non-Patent Document 5.

[0129] Step S304-2: Regarding the connection with IMS-AGW30O1, reserve IMS-AGW30O2 on the destination satellite. Specifically, IMS-AGW30O2 on the destination satellite reserves an IP address within its own device to receive IP packets from IMS-AGW30O1 and notifies P-CSCF30P2. Note that the procedure for this step S304-2 has already been specified in Non-Patent Document 5.

[0130] Step S305-1: Simultaneously change the UL CL and L-PSA, which are functions for distributing traffic on the UE20a, and update the traffic filter on the UE20a. This will ensure that traffic is distributed appropriately based on the new routing configuration and QoS flow. Note that the procedure for this step S305-1 has been specified in Non-Patent Document 6.

[0131] Step S305-2: Simultaneously change the UL CL and L-PSA, which are functions for distributing traffic on the UE20b, and also update the traffic filter on the UE20b. This will ensure that traffic is distributed appropriately based on the new routing configuration and QoS flow. Note that the procedure for this step S305-2 has been specified in Non-Patent Document 6.

[0132] Step S306-1: 5GC31a sends a message (late notification) to P-CSCF30P1 regarding the change in the U-Plane. This message indicates that 5GC31a is ready to change its route to the destination satellite.

[0133] Step S306-2: 5GC31b sends a message (late notification) to P-CSCF30P2 regarding the change in the U-Plane. This message indicates that 5GC31b is ready to change its route to the destination satellite.

[0134] The subsequent steps may be ordered to avoid conflicts. For example, the network node 30 belonging to the originating network may lead the steps, or the network node 30 belonging to the receiving network may lead the steps. In the following, we will assume that the network node 30 belonging to the originating network leads the steps, and the network node 30 belonging to the receiving network leads the steps.

[0135] Step S307-1: P-CSCF30P1, belonging to the originating network, sends a SIP MESSAGE to IMS-AS30S1. The SIP MESSAGE includes information about the termination point for the receiving network within IMS-AGW30O1 of the originating network. The SIP MESSAGE includes information requesting the receiving network to send a SIP re-INVITE. The SIP MESSAGE also includes information requesting UE20a to send a SIP re-INVITE after receiving a response message to the SIP re-INVITE. The SIP MESSAGE sent by P-CSCF30P1 is transmitted to IMS AS30S1 via S-CSCF30Q1.

[0136] Step S307-2: The P-CSCF30P2 belonging to the incoming network waits for processing (interaction) from the outgoing network.

[0137] Step S308: IMS-AS30S1 sends a message (SIP re-INVITE) to IMS-AS30S2 on the receiving network requesting a change in voice call settings.

[0138] Step S309: IMS-AS30S2 sends a message (SIP re-INVITE) to P-CSCF30P2 regarding a request for a voice call configuration change.

[0139] Step S310: IMS-AGW30O2 on the destination satellite sets the IP address of IMS-AGW30O1 on the destination satellite in order to continue IP communication from UE20b to UE20a.

[0140] Step S311: P-CSCF30P2 sends a message (SIP re-INVITE) to UE20b requesting a change in voice call settings. P-CSCF30P2 includes in the message information for the termination point for UE20b in IMS-AGW30O2 on the destination satellite.

[0141] Step S312: UE20b sends a message to P-CSCF30P2 indicating a successful response to step S311 (SIP 200 OK).

[0142] Step S313: P-CSCF30P2 sends (or forwards) the message from step S312 (SIP 200 OK) to IMS-AS30S2.

[0143] Step S314: IMS-AS30S2 sends (or forwards) the message from step S313 (SIP 200 OK) to IMS-AS30S1.

[0144] Step S315: IMS-AS30S1 sends a message (SIP re-INVITE) to P-CSCF30P1 regarding a request for a voice call configuration change.

[0145] Step S316: IMS-AGW30O1 on the destination satellite sets the IP address of IMS-AGW30O2 on the destination satellite in the receiving network in order to continue IP communication from UE20a to UE20b.

[0146] Step S317: P-CSCF30P1 sends a message to UE20a requesting a voice call configuration change (SIP re-INVITE), which includes the message received in step S315. P-CSCF30P1 includes in the message information for the termination point for UE20a in IMS-AGW30O1 on the destination satellite.

[0147] Step S318: UE20a sends a message (SIP 200 OK) to P-CSCF30P1 indicating the success of step S317.

[0148] Step S319: P-CSCF30P1 sends (or forwards) the message from step S318 (SIP 200 OK) to IMS-AS30S1.

[0149] Step S320-1: 5GC31a releases the ULCL / L-PSA on the satellite (mobile source satellite) to which UE20a was previously connected. Note that the procedure for this step S320-1 has been specified in Non-Patent Document 6.

[0150] Step S320-2: 5GC31b releases the ULCL / L-PSA on the satellite (mobile source satellite) to which UE20b was previously connected. Note that the procedure for this step S320-2 has been specified in Non-Patent Document 6.

[0151] Steps S320-1 and S320-2 described above may be performed asynchronously.

[0152] Step S321-1: P-CSCF30P1 releases IMS-AGW30O1 on the mobile satellite to which UE20a had been connected. Note that the procedure for this step S321-1 has been specified in Non-Patent Document 5.

[0153] Step S321-2: P-CSCF30P2 releases IMS-AGW30O2 on the mobile satellite to which UE20b had been connected. Note that the procedure for this step S321-2 has been specified in Non-Patent Document 5.

[0154] Steps S321-1 and S321-2 described above may be performed asynchronously.

[0155] According to the above embodiment, when the same satellite accommodates UE20a in the transmitting network and UE20b in the receiving network, the network node 30 can appropriately perform the procedure for switching communication paths when the satellite changes.

[0156] (Example 4) A ground fallback procedure may be defined in the event that the intersatellite link (ISL) between the originating network and the receiving network is disconnected.

[0157] Figure 7 shows an example sequence illustrating the ground fallback procedure when the intersatellite link (ISL) connection between the two networks in Example 4 is disconnected.

[0158] In this embodiment, we assume a situation where, in a state where there is no change in satellites, communication is impossible between the satellite to which UE20a, which belongs to the transmitting network, and the satellite to which UE20b, which belongs to the receiving network, is connected (i.e., the ISLs of both satellites are disconnected).

[0159] The processing of each step is described below. The hyphen in the step code does not indicate the order of processing, but may indicate which network the processing is performed on. For example, if "-1" is appended to the step code, that step may mean that the processing is performed on the originating network. Also, if "-2" is appended to the step code, that step may mean that the processing is performed on the receiving network. In other words, if the codes of two steps are the same before the hyphen and only the hyphen differs, those two steps may be performed asynchronously. For example, "Step S401-1" and "Step S401-2" may be performed in either order or simultaneously.

[0160] Step S401-1: IMS-AGW30O1 on the satellite sends a message to P-CSCF30P1 indicating that the connection between IMS-AGW30O and P-CSCF30P1 has been lost (connectivity failure).

[0161] Step S401-2: IMS-AGW30O2 on the satellite sends a message to P-CSCF30P2 indicating that the connection between IMS-AGW30O and P-CSCF30P2 has been lost (connectivity failure).

[0162] Step S402-1: P-CSCF30P1 determines, based on the received message, that terminal-satellite-terminal communication cannot be continued.

[0163] Step S402-2: P-CSCF30P2 determines, based on the received message, that terminal-satellite-terminal communication cannot be continued.

[0164] Step S403-1: Regarding the connection with UE20a, the IMS-AGW30O1 on the ground is reserved and configured. Specifically, the IMS-AGW30O1 on the ground reserves an IP address within its own device to receive IP packets from UE20a and notifies P-CSCF30P1. P-CSCF30P1 then sets the IMS-AGW30O1 on the ground the IP address that UE20a has set within UE20a to receive IP packets, which was acquired at the start of voice communication. Note that the procedure for this step S403-1 has already been specified in Non-Patent Document 5.

[0165] Step S403-2: Regarding the connection with UE20b, the IMS-AGW30O2 on the ground is reserved and configured. Specifically, the IMS-AGW30O2 on the ground reserves an IP address within its own device to receive IP packets from UE20b and notifies the P-CSCF30P2. The P-CSCF30P2 then sets the IMS-AGW30O2 on the ground the IP address that UE20b has set within UE20b to receive IP packets, which was acquired at the start of voice communication. Note that the procedure for this step S403-2 has been specified in Non-Patent Document 5.

[0166] Step S404-1: Regarding the connection with IMS-AGW30O2, reserve the IMS-AGW30O1 on the ground. Specifically, the IMS-AGW30O1 on the ground reserves an IP address within its own device to receive IP packets from IMS-AGW30O2 and notifies P-CSCF30P1. Note that the procedure for this step S404-1 has already been specified in Non-Patent Document 5.

[0167] Step S404-2: Regarding the connection with IMS-AGW30O1, the IMS-AGW30O2 on the ground is reserved. Specifically, the IMS-AGW30O2 on the ground reserves an IP address within its own device to receive IP packets from IMS-AGW30O1 and notifies P-CSCF30P2. Note that the procedure for this step S404-2 has already been specified in Non-Patent Document 5.

[0168] Step S405-1: Update the traffic filter on the UE20a. This update is based on the settings in Step S403-1 and may, for example, provide high QoS for voice calls.

[0169] Step S405-2: Update the traffic filter on the UE20b. This update is based on the settings in Step S403-2 and may, for example, provide high QoS for voice calls.

[0170] The subsequent steps may be ordered to avoid conflicts. For example, the network node 30 belonging to the originating network may lead the steps, or the network node 30 belonging to the receiving network may lead the steps. In the following, we will assume that the network node 30 belonging to the originating network leads the steps, and the network node 30 belonging to the receiving network leads the steps.

[0171] Step S406-1: P-CSCF30P1, belonging to the originating network, sends a SIP MESSAGE to IMS-AS30S1. The SIP MESSAGE includes information about the termination point for the receiving network within IMS-AGW30O1 of the originating network. The SIP MESSAGE includes information requesting the receiving network to send a SIP re-INVITE. The SIP MESSAGE also includes information requesting UE20a to send a SIP re-INVITE after receiving a response message to the SIP re-INVITE. The SIP MESSAGE sent by P-CSCF30P1 is transmitted to IMS AS30S1 via S-CSCF30Q1.

[0172] Step S406-2: The P-CSCF30P2 belonging to the incoming network waits for processing (interaction) from the outgoing network.

[0173] Step S407: IMS-AS30S1 sends a message (SIP re-INVITE) to IMS-AS30S2 on the receiving network requesting a change in voice call settings.

[0174] Step S408: IMS-AS30S2 sends a message (SIP re-INVITE) to P-CSCF30P2 regarding a request for a voice call configuration change.

[0175] Step S409: The ground-based IMS-AGW30O2 sets itself to the IP address of the ground-based IMS-AGW30O1 in order to continue IP communication with the ground-based IMS-AGW30O1 on the originating network.

[0176] Step S410: P-CSCF30P2 sends a message (SIP re-INVITE) to UE20b requesting a change in voice call settings. P-CSCF30P2 includes information in the message about the termination point for UE20b in the ground IMS-AGW30O2.

[0177] Step S411: UE20b sends a message (SIP 200 OK) to P-CSCF30P2 indicating success in step S410.

[0178] Step S412: P-CSCF30P2 sends (or forwards) the message from step S411 (SIP 200 OK) to IMS-AS30S2.

[0179] Step S413: IMS-AS30S2 sends (or forwards) the message from step S412 (SIP 200 OK) to IMS-AS30S1.

[0180] Step S414: IMS-AS30S1 sends a message (SIP re-INVITE) to P-CSCF30P1 regarding a request for a voice call configuration change.

[0181] Step S415: The ground-based IMS-AGW30O1 configures the IP address of the ground-based IMS-AGW30O2 on the receiving network in order to continue IP communication from UE20a to UE20b.

[0182] Step S416: P-CSCF30P1 sends a message to UE20a requesting a voice call configuration change (SIP re-INVITE), which includes the message received in step S414. P-CSCF30P1 includes in the message information for the termination point for UE20a in the ground IMS-AGW30O1.

[0183] Step S417: UE20a sends a message (SIP 200 OK) to P-CSCF30P1 indicating the success of step S416.

[0184] Step S418: P-CSCF30P1 sends (or forwards) the message from step S417 (SIP 200 OK) to IMS-AS30S1.

[0185] Step S419-1: 5GC31a releases the ULCL / L-PSA on the satellite (mobile source satellite) to which UE20a was previously connected. Note that the procedure for this step S419-1 has been specified in Non-Patent Document 6.

[0186] Step S419-2: 5GC31b releases the ULCL / L-PSA on the satellite (mobile source satellite) to which UE20b was previously connected. Note that the procedure for this step S419-2 has been specified in Non-Patent Document 6.

[0187] Steps S419-1 and S419-2 described above may be performed asynchronously.

[0188] Step S420-1: P-CSCF30P1 releases IMS-AGW30O1 on the mobile satellite to which UE20a had been connected. Note that the procedure for this step S420-1 has been specified in Non-Patent Document 5.

[0189] Step S420-2: P-CSCF30P2 releases IMS-AGW30O2 on the mobile satellite to which UE20b had been connected. Note that the procedure for this step S420-2 has been specified in Non-Patent Document 5.

[0190] Steps S420-1 and S420-2 described above may be performed asynchronously.

[0191] According to the above embodiment, the network node 30 can appropriately switch to a communication path via ground equipment based on the status of inter-satellite communication, regardless of whether or not the satellite has been changed.

[0192] (Example 5) Network node 30 may switch between the above four embodiments with respect to the procedure for changing the satellite accommodating the user plane device (i.e., ULCL / L-PSA / IMS AGW) based on information about the satellite belonging to the opposing network (i.e., the receiving network if the device belongs to the transmitting network, or the transmitting network if the device belongs to the receiving network). Network node 30 may also switch between the above four embodiments after the procedure for changing the satellite to which the base station accommodating the terminal belongs.

[0193] The P-CSCF30P may select which of the four embodiments described above to use based on the information it has stored about the satellite accommodating the UE20 opposite to the network to which it belongs.

[0194] For example, P-CSCF30P may select Example 3 regarding the satellite change procedure. If P-CSCF30P selects Example 3, the decision may be made in a distributed manner based on information as to whether or not it is the one leading the sequence procedure in Figure 6. Alternatively, if P-CSCF30P selects Example 3, the decision may be made in a distributed manner using information as to whether P-CSCF30P itself is the originating or receiving side of the network.

[0195] For example, regarding the settings of the destination satellite IMS-AGW30O and the ground IMS-AGW30O, P-CSCF30P may use the stored termination point information of its own network UE20 and the opposing network IMS-AGW30O to perform the coordination procedure between P-CSCF30P and IMS-AGW30O in a different order than usual to perform the settings.

[0196] For example, P-CSCF30P may send a SIP MESSAGE containing the necessary information to IMS-AS30S, and IMS-AS30S may send a SIP re-INVITE.

[0197] For example, P-CSCF30P may select Example 4 with respect to the satellite change procedure. If P-CSCF30P selects Example 4, the decision may be made in a distributed manner based on information as to whether or not it is the one leading the sequence procedure in Figure 7. Alternatively, if P-CSCF30P selects Example 4, P-CSCF30P may make the decision in a distributed manner using information as to whether P-CSCF30P itself is the originating or receiving side of the network.

[0198] Information regarding whether the P-CSCF30P itself is the outgoing or incoming network device may be stored in the P-CSCF30P. For example, this information may be stored in the storage device 1002.

[0199] <Functional Configuration> An example of the functional configuration of the base station 10, terminal 20, and network node 30 that perform the processes and operations described above is described below. The base station 10, terminal 20, and network node 30 include the functions to implement the embodiments described above. However, the base station 10, terminal 20, and network node 30 may each have only some of the functions in the embodiments.

[0200] (Base Stations and Network Nodes) Figure 8 shows an example of the functional configuration of base stations and network nodes.

[0201] The base station 10 includes a transmitting unit 110, a receiving unit 120, a setting unit 130, and a control unit 140. The functional configuration shown in the figure is merely an example. The functional classifications and names of the functional units can be anything as long as they can perform the operations according to this embodiment. The network node 30 may have a functional configuration similar to that of 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.

[0202] The transmitting unit 110 includes the function of generating a signal to be transmitted to the terminal 20 and transmitting the signal wirelessly / wirelessly. The transmitting unit 110 also has the function of transmitting downlink (DL) / uplink (UL) control signals, etc., to the terminal 20.

[0203] The receiving unit 120 receives various signals transmitted from the terminal 20 and includes a function to obtain, for example, information from a higher layer from the received signals. The receiving unit 120 also receives inter-network node messages from other network nodes.

[0204] The setting unit 130 stores pre-configured setting information and various setting information to be transmitted to the terminal 20.

[0205] As described in the embodiment, the control unit 140 performs control related to settings, instructions, and notifications concerning the network node 30. The signal transmission function unit of the control unit 140 may be included in the transmission unit 110, and the signal reception function unit of the control unit 140 may be included in the reception unit 120. The control unit 140 may determine whether communication along the optimal path between satellites can be continuously established.

[0206] (Terminal) Figure 9 shows an example of the functional configuration of a terminal.

[0207] Terminal 20 includes a transmitting unit 210, a receiving unit 220, a setting unit 230, and a control unit 240. The functional configuration shown in Figure 9 is merely an example. The names of the functional categories and functional units can be anything as long as they can perform the operations according to this embodiment. The transmitting unit 210 and the receiving unit 220 may be collectively referred to as the communication unit.

[0208] The transmitting unit 210 creates a transmission signal from the transmission data and transmits the transmission signal wirelessly. The receiving unit 220 wirelessly receives various signals and obtains signals from higher layers from the received physical layer signals.

[0209] The receiving unit 220 has the function of receiving control signals or reference signals transmitted from the network node 30. A communication unit including a transmitting unit 210 and a receiving unit 220 may be configured.

[0210] The setting unit 230 stores various setting information received from the base station 10 by the receiving unit 220. The setting unit 230 also stores various setting information that has been set in advance.

[0211] The control unit 240 may include the signal transmission function in the control unit 240, which performs the processing described in the embodiment, in the transmission unit 210, and the signal reception function in the control unit 240, which is included in the reception unit 220.

[0212] <Hardware Configuration> The block diagrams (Figures 8 and 9) used in the description of the above embodiments show functional units. These functional blocks (components) are realized by any combination of at least one of hardware and software. Furthermore, the method of realizing each functional block is not particularly limited. That is, each functional block may be realized using one device that is physically or logically coupled, or it may be realized using two or more physically or logically separated devices that are directly or indirectly connected (for example, using wired or wireless connections). A functional block may be realized by combining the one device or the multiple devices with software.

[0213] Functions include, but are not limited to, judgment, decision, judgment, calculation, calculation, processing, derivation, investigation, exploration, confirmation, reception, transmission, output, access, resolution, selection, selection, establishment, comparison, assumption, expectation, assumption, broadcasting, notifying, communicating, forwarding, configuring, reconfiguring, allocating (mapping), and assigning. For example, a functional block (configuration part) that enables transmission is called a transmitting unit or transmitter. In all cases, as mentioned above, the method of implementation is not particularly limited.

[0214] Figure 10 shows an example of the hardware configuration of a base station and a terminal.

[0215] For example, the base station 10, terminal 20, etc. in this embodiment may function as a computer that processes the wireless communication method of this embodiment. The base station 10 and terminal 20 described above may be physically configured as a computer device including a processor 1001, storage device 1002, auxiliary storage device 1003, communication device 1004, input device 1005, output device 1006, bus 1007, etc.

[0216] In the following explanation, the term "device" can be read as "circuit," "device," "unit," etc. The hardware configuration of the base station 10 and terminal 20 may include one or more of the devices shown in the figure, or it may be configured to omit some of the devices.

[0217] Each function in the base station 10 and terminal 20 is realized by loading predetermined software (programs) onto hardware such as the processor 1001 and storage device 1002, which allows the processor 1001 to perform calculations, control communication by the communication device 1004, and control at least one of the reading and writing of data in the storage device 1002 and auxiliary storage device 1003.

[0218] The processor 1001 controls the entire computer, for example, by running an operating system (OS). The processor 1001 may consist of a central processing unit (CPU) that includes interfaces with peripheral devices, control devices, arithmetic units, registers, etc. For example, the control unit 140, control unit 240, etc., described above may be implemented by the processor 1001.

[0219] Furthermore, the processor 1001 reads programs (program code), software modules, or data from at least one of the auxiliary storage device 1003 and the communication device 1004 into the storage device 1002, and executes various processes accordingly. The program used is one that causes the computer to execute at least a part of the operations described in the above embodiment. For example, the control unit 140 of the base station 10 shown in Figure 8 may be implemented by a control program stored in the storage device 1002 and operated by the processor 1001. Also, for example, the control unit 240 of the terminal 20 shown in Figure 9 may be implemented by a control program stored in the storage device 1002 and operated by the processor 1001. Although the above-described processes have been explained as being executed by one processor 1001, they may be executed simultaneously or sequentially by two or more processors 1001. The processor 1001 may be implemented by one or more chips. The program may also be transmitted from the network via a telecommunications line.

[0220] The storage device 1002 is a computer-readable recording medium and may consist of at least one of the following: ROM (Read Only Memory), EPROM (Erasable Programmable ROM), EEPROM (Electrically Erasable Programmable ROM), RAM (Random Access Memory), etc. The storage device 1002 may also be called a register, cache, main memory, etc. The storage device 1002 can store executable programs (program code), software modules, etc., for implementing a communication method according to one embodiment of the present disclosure.

[0221] The auxiliary storage device 1003 is a computer-readable recording medium and may consist of at least one of the following: an optical disc 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 multipurpose disk, a Blu-ray® disk), a smart card, flash memory (e.g., a card, a stick, a key drive), a floppy® disk, a magnetic strip, etc. The above-mentioned storage medium may also be a database, server, or other suitable medium that includes at least one of the storage device 1002 and the auxiliary storage device 1003.

[0222] The communication device 1004 is hardware (transmitting / receiving device) for communicating between computers via at least one of a wired network and a wireless network, and is also referred to as a network device, network controller, network card, communication module, etc. The communication device 1004 may be configured to include, for example, a high-frequency switch, duplexer, filter, frequency synthesizer, etc., in order to implement at least one of FDD and TDD. For example, the transmitting / receiving antenna, amplifier section, transmitting / receiving section, transmission path interface, etc., may be implemented by the communication device 1004. The transmitting / receiving section may be implemented in a physically or logically separated manner, with a transmitting section and a receiving section.

[0223] The input device 1005 is an input device that accepts input from an external source (e.g., a keyboard, mouse, microphone, switch, button, sensor, etc.). The output device 1006 is an output device that outputs to an external source (e.g., a display, speaker, LED (Light-Emitting Diode) lamp, etc.). The input device 1005 and the output device 1006 may be configured as an integrated unit (e.g., a touch panel).

[0224] 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 different buses may be configured for each device.

[0225] Furthermore, the base station 10 and terminal 20 may be configured to include hardware such as a microprocessor, a digital signal processor (DSP), an ASIC (Application Specific Integrated Circuit), a PLD (Programmable Logic Device), and an FPGA (Field Programmable Gate Array), and some or all of each functional block may be realized by such hardware. For example, the processor 1001 may be implemented using at least one of these hardware components.

[0226] Figure 11 shows an example of a vehicle configuration.

[0227] 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 this disclosure may be applied to a communication device mounted on the vehicle 2001, for example, to the communication module 2013.

[0228] The drive unit 2002 consists of, for example, 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, which is operated by the user.

[0229] The electronic control unit 2010 consists of a microprocessor 2031, memory (ROM, RAM) 2032, and communication ports (I / O (Input / Output) ports) 2033. Signals from various sensors 2021 to 2029 installed in the vehicle 2001 are input to the electronic control unit 2010. The electronic control unit 2010 may also be called an ECU (Electronic Control Unit).

[0230] Signals from various sensors 2021 to 2029 include current signals from current sensor 2021 for sensing motor current, front or rear wheel rotation speed signals acquired by rotation speed sensor 2022, front or rear wheel air pressure signals acquired by air pressure sensor 2023, vehicle speed signals acquired by vehicle speed sensor 2024, acceleration signals acquired by acceleration sensor 2025, accelerator pedal depression signals acquired by accelerator pedal sensor 2029, brake pedal depression signals acquired by brake pedal sensor 2026, shift lever operation signals acquired by shift lever sensor 2027, and detection signals acquired by object detection sensor 2028 for detecting obstacles, vehicles, pedestrians, etc.

[0231] The Information Service Unit 2012 consists of various devices for providing (outputting) various types of information such as driving information, traffic information, and entertainment information, including a car navigation system, audio system, speakers, television, and radio, and one or more ECUs that control these devices. The Information Service Unit 2012 uses information acquired from external devices via a communication module 2013, etc., to provide various multimedia information and multimedia services to the occupants of the vehicle 2001. The Information Service Unit 2012 may include input devices that accept input from the outside (e.g., keyboard, mouse, microphone, switch, button, sensor, touch panel, etc.) and output devices that perform output to the outside (e.g., display, speaker, LED lamp, touch panel, etc.).

[0232] The driver assistance system unit 2030 consists of various devices that provide functions to prevent accidents or reduce the driver's workload, such as millimeter-wave radar, LiDAR (Light Detection and Ranging), cameras, positioning locators (e.g., GNSS (Global Navigation Satellite System)), map information (e.g., high-definition (HD) maps, autonomous vehicle (AV) maps), gyro systems (e.g., IMU (Inertial Measurement Unit), INS (Inertial Navigation System)), AI (Artificial Intelligence) chips, and AI processors, as well as one or more ECUs that control these devices. The driver assistance system unit 2030 also sends and receives various information via the communication module 2013 to realize driver assistance functions or autonomous driving functions.

[0233] The communication module 2013 can communicate with the microprocessor 2031 and components of the vehicle 2001 via its communication port. For example, the communication module 2013 sends and receives data via the communication port 2033 between the drive unit 2002, steering unit 2003, accelerator pedal 2004, brake pedal 2005, shift lever 2006, front wheels 2007, rear wheels 2008, axle 2009, the microprocessor 2031 and memory (ROM, RAM) 2032 in the electronic control unit 2010, and sensors 2021-29 provided in the vehicle 2001.

[0234] 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 external devices. For example, it can send and receive various types of information with external devices 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 or a mobile station.

[0235] The communication module 2013 may transmit at least one of the following to an external device via wireless communication: signals from the various sensors 2021-2028 input to the electronic control unit 2010, information obtained based on said signals, and information based on input from an external source (user) obtained via the information service unit 2012.

[0236] The electronic control unit 2010, various sensors 2021-2028, and information service unit 2012 may also be called input units that accept input. For example, the PUSCH transmitted by the communication module 2013 may include information based on the above input.

[0237] The communication module 2013 receives various information (traffic information, signal information, inter-vehicle information, etc.) transmitted from an external device and displays it on the information service unit 2012 provided in the vehicle 2001. The information service unit 2012 may also be called an output unit, which outputs information (for example, outputs information to devices such as displays and speakers 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 the external device 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 2021-2029, etc., provided in the vehicle 2001.

[0238] For example, embodiments of the present invention are as follows:

[0239] <1> A network node having a receiving unit that receives a message from a first network node containing information about a first satellite that will newly accommodate terminals, and a control unit that selects an operation related to the satellite change procedure based on the information about the first satellite, information about a second satellite that will accommodate terminals on the other network side, and information indicating whether the local network side is sending or receiving. <2> The network node according to <1>, wherein the information about the first satellite is information about a satellite that is scheduled to newly accommodate UL CL (Uplink Classifier) ​​and L-PSA (Local PDU (Protocol Data Unit) Session Anchor) that handle the voice media of the terminals, and the information about the second satellite is information about a satellite that will accommodate UL CL and L-PSA that handle the voice media of the terminals on the other network side. <3> A network node having a receiving unit that receives from a first network node information about a first satellite that will newly accommodate terminals on the other network side, and a message including a local network-bound termination point in a second network node on the other network side; and a control unit that selects an operation related to the satellite change procedure based on the information about the first satellite and the information about the second satellite that will accommodate terminals on the local network side. <4> The network node as described in <3>, wherein the information about the first satellite that will newly accommodate terminals on the other network side is information about a satellite that will newly accommodate a UL CL (Uplink Classifier) ​​and an L-PSA (Local PDU (Protocol Data Unit) Session Anchor) that handle the voice media of the terminals on the other network side, or information about a satellite in which a UL CL and an L-PSA that handle the voice media of the terminals on the other network side are not installed, and the information about the second satellite that will accommodate terminals on the local network side is information about a satellite that accommodates a UL CL and an L-PSA that handle the voice media of the terminals on the local network side. <5> A network node having a receiving unit that receives a message from a first network node notifying that the connection with the opposite network has been disconnected, and a control unit that selects an action related to the satellite change procedure based on information indicating whether the local network is sending or receiving.<6> A communication method performed by a network node, which includes the steps of: receiving a message from a first network node containing information about a first satellite that will newly accommodate terminals; and selecting an action related to a satellite change procedure based on the information about the first satellite, information about a second satellite that will accommodate terminals on the other network side, and information indicating whether the local network is sending or receiving data.

[0240] Any of the above configurations will allow for proper switching of communication paths when a satellite is changed.

[0241] <Supplement to Embodiments> Although these embodiments have been described above, the disclosed invention is not limited to these embodiments, and those skilled in the art will understand various modifications, alterations, alternatives, substitutions, etc. Specific numerical examples have been used to facilitate understanding of the invention, but unless otherwise specified, these numerical values ​​are merely examples, and any appropriate values ​​may be used.

[0242] In this embodiment, the duplexing scheme may be a time division duplex (TDD) scheme, a frequency division duplex (FDD) scheme, or any other scheme (such as flexible duplex).

[0243] In this embodiment, "configuring" wireless parameters means either pre-configuring predetermined values, or configuring wireless parameters notified by a base station or terminal.

[0244] In this embodiment, the core network 31 is referred to as a 5G core (5GC31), but this is for convenience of description and is not limited to 5G. For example, the 5G core (5GC31) may be a 6G core or an EPC (Evolved Packet Core).

[0245] The categorization of items in the above description is not essential to this embodiment, and matters described in two or more items may be used in combination as needed, and matters described in one item may be applied to matters described in another item (as long as they do not contradict each other).

[0246] The boundaries of functional units or processing units in a functional block diagram do not necessarily correspond to the boundaries of physical parts. Multiple functional units may operate within a single physical part, or one functional unit may operate within multiple physical parts.

[0247] The processing procedures described in the embodiments may be rearranged in order, as long as they do not contradict each other. For the convenience of explaining the processing, the base station 10 and terminal 20 have been described using functional block diagrams, but such devices may be implemented in hardware, software, or a combination thereof. The software operated by the processor of the base station 10 according to this embodiment and the software operated by the processor of the terminal 20 according to this embodiment may be stored in random access memory (RAM), flash memory, read-only memory (ROM), EPROM, EEPROM, registers, hard disk (HDD), removable disk, CD-ROM, database, server, or any other suitable storage medium.

[0248] The notification of information / messages is not limited to the embodiments described herein and may be carried out by other means. For example, the notification of information / messages may be carried out by physical layer signaling (e.g., DCI (Downlink Control Information), UCI (Uplink Control Information)), higher layer signaling (e.g., RRC (Radio Resource Control) signaling, MAC (Media Access Control) signaling), broadcast information (MIB (Master Information Block), SIB (System Information Block)), other signals, or combinations thereof. Information / messages notified by higher layer signaling may be called configuration information. Information / messages notified by physical layer signaling may be called control information. RRC signaling may also be called RRC messages, for example, RRC Connection Setup messages, RRC Connection Reconfiguration messages, etc.

[0249] Each aspect / embodiment described in this disclosure refers to LTE (Long Term Evolution), LTE-A (LTE-Advanced), SUPER 3G, IMT-Advanced, 4G (4th Generation mobile communication system), 5G (5th Generation mobile communication system), 5G-A (5G-Advanced), Beyond 5G, 6G (6th Generation mobile communication system), FRA (Future Radio Access), NR (New Radio), W-CDMA (Wideband-Code Division Multiple Access) (registered trademark), GSM (Global System for Mobile communications) (registered trademark), CDMA2000, UMB (Ultra Mobile Broadband), IEEE (Institute of Electrical and Electronics Engineers) 802.11 (Wi-Fi (registered trademark)), IEEE 802.16 (WiMAX (registered trademark)), IEEE 802.20, UWB (Ultra Wide It may be applied to at least one of the following: systems utilizing LTE-Band, Bluetooth®, or other appropriate systems, and next-generation systems extended based thereon. Alternatively, multiple systems may be applied in combination (for example, at least one of LTE and LTE-A combined with 5G).

[0250] The processing procedures, sequences, flowcharts, etc., of each aspect / embodiment described herein may be reordered, provided they are consistent with each other. For example, the methods described herein present various step elements in an exemplary order and are not limited to that specific order.

[0251] In this specification, specific operations performed by the base station 10 may, in some cases, be performed by its upper node. In a network consisting of one or more network nodes having a base station 10, it is clear that various operations performed for communication with the terminal 20 can be performed by the base station 10 and at least one of the other network nodes (for example, an MME (Mobility Management Entity) or an S-GW (Serving Gateway), etc., but not limited to these). Although the above example illustrates the case where there is one other network node besides the base station 10, the other network node may be a combination of multiple other network nodes (for example, an MME and an S-GW).

[0252] The information or signals described in this disclosure may be output from a higher layer (or lower layer) to a lower layer (or higher layer). They may also be input and output via multiple network nodes.

[0253] Input and output information may be stored in a specific location (e.g., memory) or managed using a management table. Input and output information may be overwritten, updated, or appended to. Output information may be deleted. Input information may be transmitted to other devices.

[0254] The determination in this disclosure may be made by a value represented by one bit (0 or 1), by a Boolean value (true or false), or by a numerical comparison (for example, a comparison with a predetermined value).

[0255] Software should be broadly interpreted to mean instructions, instruction sets, code, code segments, program code, programs, subprograms, software modules, applications, software applications, software packages, routines, subroutines, objects, executable files, execution threads, procedures, functions, and so on, whether they are called software, firmware, middleware, microcode, hardware description languages, or by any other name.

[0256] Furthermore, software, instructions, information, etc., may be transmitted and received via a transmission medium. For example, if software is transmitted from a website, server, or other remote source using at least one of wired technologies (such as coaxial cable, fiber optic cable, twisted pair, or digital subscriber line (DSL)) and wireless technologies (such as infrared or microwave), then at least one of these wired and wireless technologies is included in the definition of a transmission medium.

[0257] The information, signals, etc. described in this disclosure may be represented using any of the various different techniques. For example, the data, instructions, commands, information, signals, bits, symbols, chips, etc. that may be referred to throughout the above description may be represented by voltage, current, electromagnetic waves, magnetic fields or magnetic particles, optical fields or photons, or any combination thereof.

[0258] In addition, terms used 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 the channel and symbol may be a signal (signaling). Also, the signal may be a message. Furthermore, CC may be called carrier frequency, cell, frequency carrier, etc.

[0259] The terms “system” and “network” as used in this disclosure are interchangeable.

[0260] Furthermore, the information, parameters, etc., described in this disclosure may be expressed using absolute values, relative values ​​from a given value, or other corresponding information. For example, wireless resources may be indicated by an index.

[0261] The names used for the parameters described above are not restrictive in any way. Furthermore, the formulas and other expressions using these parameters may differ from those expressly disclosed in this disclosure. Various channels (e.g., PUCCH, PDCCH, etc.) and information elements can be identified by any suitable name, and therefore, the various names assigned to these various channels and information elements are not restrictive in any way.

[0262] In this disclosure, terms such as "Base Station (BS)", "wireless base station", "base station equipment", "fixed station", "NodeB", "eNodeB (eNB)", "gNodeB (gNB)", "access point", "transmission point", "reception point", "Transmission / Reception Point (TRP)", "cell", "sector", "cell group", "carrier", and "component carrier" may be used interchangeably. Base station 10 may also be referred to by terms such as macrocell, small cell, femtocell, and picocell.

[0263] Base station 10 can accommodate one or more (e.g., three) cells. If base station 10 accommodates multiple cells, the entire coverage area of ​​base station 10 can be divided into multiple smaller areas, each of which can also be provided with communication services by a base station subsystem (e.g., a Remote Radio Head (RRH)). The terms “cell” or “sector” refer to part or all of the coverage area of ​​at least one of the base station and / or base station subsystems that provide communication services in this coverage.

[0264] In this disclosure, the transmission of information by the base station 10 to the terminal 20 may be interpreted as the base station 10 instructing the terminal 20 to perform control or operation based on the information.

[0265] In this disclosure, terms such as "Mobile Station (MS)," "user terminal," "User Equipment (UE)," and "terminal" may be used interchangeably.

[0266] 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 appropriate term.

[0267] At least one of the base station 10 and the terminal 20 may be called a transmitting device, receiving device, communication device, control device, etc. At least one of the base station 10 and the terminal 20 may be a device mounted on a mobile body, the mobile body itself, etc. The mobile body refers to a movable object, and its speed of movement is arbitrary. This also includes the case when the mobile body is stationary. The mobile body includes, but is not limited to, vehicles, transport vehicles, automobiles, motorcycles, bicycles, connected cars, excavators, bulldozers, wheel loaders, dump trucks, forklifts, trains, buses, handcarts, rickshaws, ships and other watercraft, airplanes, rockets, satellites, drones (registered trademark), multicopters, quadcopters, balloons, and items mounted on them. The mobile body may also be a mobile body that moves autonomously based on operation commands. It may be a vehicle (e.g., a car, an airplane, etc.), an unmanned mobile body (e.g., a drone, an autonomous vehicle, etc.), or a robot (manned or unmanned). Furthermore, at least one of the base station and the mobile station may include devices that do not necessarily move during communication operations. For example, at least one of the base station 10 and the terminal 20 may be an IoT (Internet of Things) device such as a sensor.

[0268] Furthermore, the base station 10 in this disclosure may be read as a terminal 20. For example, the various aspects / embodiments of this disclosure may be applied to a configuration in which communication between the base station 10 and the terminal 20 is replaced with communication between multiple terminals 20 (which may be called, for example, D2D (Device-to-Device), V2X (Vehicle-to-Everything)). In such a case, the terminal 20 may have the functions that the base station 10 has as described above. Also, terms such as "uplink" and "downlink" may be read as terms corresponding to communication between terminals 20 (for example, "side"). For example, uplink channel, downlink channel, etc. may be read as side channel.

[0269] Similarly, the terminal 20 in this disclosure may be read as a base station 10. In this case, the base station 10 may be configured to have the functions that the terminal 20 has.

[0270] As used in this disclosure, the terms “determining” and “determining” may encompass a wide variety of actions. “Determining” may include, for example, judging, calculating, computing, processing, deriving, investigating, looking up, searching, or inquiring (e.g., searching in a table, database, or other data structure), or ascertaining. “Determining” may also include, for example, receiving (e.g., receiving information), transmitting (e.g., sending information), inputting, outputting, or accessing (e.g., accessing data in memory). Furthermore, "judgment" and "decision" can include considering something as having been "judged" or "decided" after resolving, selecting, choosing, establishing, comparing, etc. In other words, "judgment" and "decision" can include considering something as having been "judged" or "decided" after some action. Also, "judgment (decision)" can be reinterpreted as "assuming," "expecting," or "considering."

[0271] The terms “connected,” “coupled,” or any variation thereof, mean 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” with each other. The coupling or connection between elements may be physical, logical, or a combination thereof. For example, “connection” may be reinterpreted as “access.” As used in this disclosure, two elements may be considered to be “connected” or “coupled” with each other using at least one of one or more wires, cables, and printed electrical connections, and, in some non-limiting and non-exclusive examples, electromagnetic energy having wavelengths in the radio frequency domain, microwave domain, and optical (both visible and invisible) domain.

[0272] The reference signal can also be abbreviated as RS (Reference Signal), and may be called a pilot depending on the applicable standard.

[0273] In this disclosure, the phrase "based on" does not mean "based solely on" unless otherwise specified. In other words, the phrase "based on" means both "based solely on" and "based at least on."

[0274] Any reference to elements using designations such as “first,” “second,” etc., as used in this disclosure does not generally limit the quantity or order of those elements. These designations may be used in this disclosure as a convenient way to distinguish between two or more elements. Accordingly, references to first and second elements do not imply that only two elements may be employed, or that the first element must precede the second element in any way.

[0275] In the configuration of each of the above devices, "means" may be replaced with "part," "circuit," "device," etc.

[0276] Where the terms “include,” “including,” and their variations are used in this disclosure, these terms are intended to be inclusive, as is the term “comprising.” Furthermore, the term “or” as used in this disclosure is not intended to be exclusive OR.

[0277] A wireless frame may consist of one or more frames in the time domain. Each of these one or more frames in the time domain may be called a subframe. A subframe may further consist of one or more slots in the time domain. A subframe may have a fixed time length (e.g., 1 ms) that is independent of numerology.

[0278] Numerical logic may be communication parameters applied to at least one of the transmission and reception of a signal or channel. Numerical logic may include, for example, at least one of the following: subcarrier spacing (SCS), bandwidth, symbol length, cyclic prefix length, transmission time interval (TTI), number of symbols per TTI, radio frame configuration, specific filtering processes performed by the transceiver in the frequency domain, and specific windowing processes performed by the transceiver in the time domain.

[0279] A slot may consist of one or more symbols in the time domain (such as OFDM symbols or SC-FDMA (Single Carrier Frequency Division Multiple Access) symbols). A slot may also be a time unit based on neurology.

[0280] A slot may include multiple mini-slots. Each mini-slot may consist of one or more symbols in the time domain. Mini-slots may also be called sub-slots. Mini-slots may consist of fewer symbols than a slot. A PDSCH (or PUSCH) transmitted in a time unit larger than a mini-slot may be called a PDSCH (or PUSCH) mapping type A. A PDSCH (or PUSCH) transmitted using a mini-slot may be called a PDSCH (or PUSCH) mapping type B.

[0281] Wireless frames, subframes, slots, minislots, and symbols all represent units of time when transmitting a signal. Different names may be used for each of these terms.

[0282] For example, one subframe may be called a transmission time interval (TTI), multiple consecutive subframes may be called a TTI, or one slot or one minislot may be called a TTI. In other words, at least one of a subframe and a TTI may be a subframe in existing LTE (1 millisecond (ms)), a period shorter than 1 ms (e.g., 1-13 symbols), or a period longer than 1 ms. Note that the unit representing the TTI may be called a slot, minislot, etc., instead of a subframe.

[0283] Here, TTI refers to, for example, the smallest time unit for scheduling in wireless communication. For example, in an LTE system, the base station 10 schedules each terminal 20 to allocate wireless resources (such as the frequency bandwidth and transmission power available to each terminal 20) in TTI units. However, the definition of TTI is not limited to this.

[0284] TTI may be a transmission time unit for channel-encoded data packets (transport blocks), code blocks, code words, etc., or it may be a processing unit for scheduling, link adaptation, etc. When a TTI is given, the actual time interval (e.g., number of symbols) in which the transport block, code block, code word, etc. are mapped may be shorter than the TTI.

[0285] Furthermore, if one slot or one mini-slot is referred to as a TTI, then one or more TTIs (i.e., one or more slots or one or more mini-slots) may constitute the minimum time unit for scheduling. In addition, the number of slots (number of mini-slots) that make up the minimum time unit for scheduling may be controlled.

[0286] A TTI with a time length of 1 ms may also be called a normal TTI, long TTI, normal subframe, long subframe, slot, etc. A TTI shorter than a normal TTI may also be called a shortened TTI, short TTI, partial or fractional TTI, shortened subframe, short subframe, mini slot, sub slot, slot, etc.

[0287] Furthermore, long TTIs (e.g., normal TTIs, subframes, etc.) may be interpreted as TTIs with a time length exceeding 1 ms, and short TTIs (e.g., shortened TTIs, etc.) may be interpreted as TTIs with a TTI length less than that of a long TTI but 1 ms or more.

[0288] A resource block (RB) is a resource allocation unit in the time domain and frequency domain, and in the frequency domain, it may contain one or more consecutive subcarriers. The number of subcarriers in an RB may be the same regardless of the neurology, for example, 12. The number of subcarriers in an RB may be determined based on the neurology.

[0289] Furthermore, the time domain of the RB may contain one or more symbols and may be the length of one slot, one minislot, one subframe, or one TTI. One TTI, one subframe, etc., may each consist of one or more resource blocks.

[0290] One or more RBs may also be called a Physical RB (PRB), Subcarrier Group (SCG), Resource Element Group (REG), PRB pair, RB pair, etc.

[0291] Furthermore, a resource block may consist of one or more resource elements (REs). For example, one RE may be a radio resource area comprising one subcarrier and one symbol.

[0292] A Bandwidth Part (BWP), also known as a partial bandwidth, may represent a subset of consecutive common RBs (RBs) for a given neurology in a given carrier. Here, the common RBs may be identified by an index of RBs relative to a common reference point of the carrier. The PRBs may be defined and numbered within a given BWP.

[0293] A BWP may include a BWP for UL (UL BWP) and a BWP for DL ​​(DL BWP). One or more BWPs may be set within a single carrier for a UE.

[0294] At least one of the configured BWPs may be active, and the UE does not need to assume that it will transmit or receive a predetermined signal / channel outside of the active BWP. In this disclosure, terms such as "cell" and "carrier" may be read as "BWP".

[0295] The structures described above, such as wireless frames, subframes, slots, minislots, and symbols, are merely illustrative. For example, the number of subframes included in a wireless frame, the number of slots per subframe or wireless frame, the number of minislots included in a slot, the number of symbols and RBs included in a slot or minislot, the number of subcarriers included in an RB, and the number of symbols, symbol length, and cyclic prefix (CP) length within the TTI can be varied in various ways.

[0296] In this disclosure, if articles are added by translation, such as a, an, and the in English, this disclosure may include the fact that the noun following these articles is plural.

[0297] In this 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 "combine" may be interpreted similarly to "different."

[0298] Each aspect / embodiment described in this disclosure may be used individually, in combination, or switched between as needed during implementation. Furthermore, notification of specific information (e.g., notification that "X is") is not limited to explicit notification, but may also be implicit (e.g., by not providing such notification).

[0299] Although the present disclosure has been described in detail above, it will be 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 intent and scope of the present disclosure as defined by the claims. Accordingly, the descriptions in the present disclosure are illustrative and not intended to be restrictive in any way.

[0300] This patent application claims priority based on Japanese Patent Application No. 2024-194780, filed on November 6, 2024, and the entire contents of Japanese Patent Application No. 2024-194780 are incorporated herein by reference.

[0301] 10 Base station 20 Terminal, UE 30 (Multiple) network nodes 31 Core network 30O IMS-AGW 30P P-CSCF 30S IMS-AS 110 Transmitter 120 Receiver 130 Configuration unit 140 Control unit 210 Transmitter 220 Receiver 230 Configuration unit 240 Control unit

Claims

1. A network node having: a receiving unit that receives a message from a first network node containing information about a first satellite that will newly accommodate terminals; and a control unit that selects an operation related to the satellite change procedure based on the information about the first satellite, information about a second satellite that will accommodate terminals on the other network side, and information indicating whether the local network is sending or receiving data.

2. The network node according to claim 1, wherein the information of the first satellite is information of a satellite that is scheduled to newly accommodate a UL CL (Uplink Classifier) ​​and an L-PSA (Local PDU (Protocol Data Unit) Session Anchor) that handle the voice media of the terminal, and the information of the second satellite is information of a satellite that accommodates a UL CL and an L-PSA that handle the voice media of the other network terminal.

3. A network node having: a receiving unit that receives a message from a first network node containing information about a first satellite that will accommodate terminals on the other network side, and a message containing a local network-bound termination point in a second network node on the other network side; and a control unit that selects an operation related to the satellite change procedure based on the information about the first satellite and the information about the second satellite that will accommodate terminals on the local network side.

4. The network node according to claim 3, wherein the information of the first satellite that newly accommodates the other network terminal is information of the satellite that newly accommodates a UL CL (Uplink Classifier) ​​and L-PSA (Local PDU (Protocol Data Unit) Session Anchor) that handle the voice media of the other network terminal, or information of a satellite in which no UL CL and L-PSA that handle the voice media of the other network terminal are installed, and the information of the second satellite that accommodates the local network terminal is information of the satellite that accommodates a UL CL and L-PSA that handle the voice media of the local network terminal.

5. A network node having a receiving unit that receives a message from a first network node notifying that the connection with the peer network has been disconnected, and a control unit that selects an action related to the satellite change procedure based on information indicating whether the local network is sending or receiving a signal.

6. A communication method performed by a network node, comprising the steps of: receiving a message from a first network node containing information about a first satellite that will newly accommodate terminals; and selecting an action related to a satellite change procedure based on the information about the first satellite, information about a second satellite that will accommodate terminals on the other network side, and information indicating whether the local network is sending or receiving data.

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