Base station and network node

Abstract

A base station according to the present invention comprises: a control unit that makes a determination to move a terminal carrying out voice communication by using a first network system from the first network system to a second network system; and a transmission unit that transmits, to a network node that manages movement of the terminal and on the basis of the determination, a terminal context release request message that includes first information requesting continuity of the voice communication.

Description

Base Station and Network Node

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

[0002] 3GPP (Registered Trademark) (3rd Generation Partnership Project)'s 5GS (5G System) and 6GS (6G System) each have independent network functions (NFs: Network Functions), and a method for continuing voice communication between these different systems is being studied.

[0003] 3GPP TS 23.502 V19.2.0(2025-01)3GPP TS 23.228 V19.1.0(2024-12)3GPP TS 23.334 V18.1.0(2024-06)

[0004] For example, if the UPF (User Plane Function) is not used as a combo node, a change in the IP address may occur, making it difficult to continue the session of IMS voice communication. Thus, in the conventional specification, there is a possibility that voice communication may be interrupted during network migration.

[0005] The base station in this embodiment includes a control unit that determines to move a terminal performing voice communication using a first network system from the first network system to a second network system, and a transmission unit that transmits a terminal context release request message including first information requesting continuity of voice communication to a network node that performs mobility management of the terminal based on the determination.

[0006] According to this embodiment, even when a movement occurs between 5GS and 6GS, IMS voice communication can be continued without interruption.

[0007] This is a diagram illustrating an example of a communication system. This is a diagram illustrating an example of a communication system in a roaming environment. This is a diagram illustrating an example of an IMS data channel network. This is a sequence diagram showing an example of the operation procedure of the communication system in Embodiment 1. This is a sequence diagram showing an example of the operation procedure of the communication system in Embodiment 1. This is a sequence diagram showing an example of the operation procedure of the communication system in Embodiment 1. This is a sequence diagram showing an example of the operation procedure of the communication system in Embodiment 1. This is a sequence diagram showing an example of the operation procedure of the communication system in Embodiment 2. This is a sequence diagram showing an example of the operation procedure of the communication system in Embodiment 2. This is a sequence diagram showing an example of the operation procedure of the communication system in Embodiment 2. This is a diagram showing an example of the functional configuration of a base station and network node in this embodiment. This is a diagram showing an example of the functional configuration of a terminal in this embodiment. This is a diagram showing an example of the hardware configuration of a base station, terminal and network node in this embodiment. This is a diagram showing an example of the configuration of a vehicle in this embodiment.

[0008] This embodiment will be described below with reference to the drawings. Note that the embodiments described below are examples, and the embodiments to which the present invention applies are not limited to those described below.

[0009] In the operation of the wireless communication system of this embodiment, existing technologies will be used as appropriate. Existing technologies include, for example, existing communication methods based on 3GPP standards such as NR (New Radio) (5G) / 5GC (5G Core network). However, existing technologies are not limited to NR / 5GC, but also include LTE, LTE-Advanced and NR (5G) and later methods, or wireless LAN (Local Area Network).

[0010] In this embodiment, "configuring" wireless parameters means that predetermined values ​​are pre-configured, or that wireless parameters notified by the network node or terminal 20 are configured.

[0011] Figure 1 is a diagram illustrating an example of a communication system. As shown in Figure 1, the communication system consists of a UE (User Interface) as a terminal and multiple network nodes. Hereafter, one network node will be assumed to correspond to each function, however, one network node may implement multiple functions, or multiple network nodes may implement one function. Furthermore, the "connection" described below may be a logical connection or a physical connection.

[0012] The RAN (Radio Access Network) is a network node having wireless access functionality, which may include a base station 10, and is connected to the UE, AMF (Access and Mobility Management Function), and UPF (User plane function). The AMF is a network node having functions such as terminating the RAN interface, terminating the NAS (Non-Access Stratum), registration management, connection management, reachability management, and terminal mobility management. The UPF is a network node interconnected with the DN (Data Network) and having functions related to user plane data processing, such as PDU (Protocol Data Unit) session point to the outside, packet routing and forwarding, and user plane QoS (Quality of Service) handling. The UPF and DN constitute a network slice. In the wireless communication network of this embodiment, multiple network slices are constructed.

[0013] AMF is connected to UE, RAN, SMF (Session Management function), NSSF (Network Slice Selection Function), NEF (Network Exposure Function), NRF (Network Repository Function), UDM (Unified Data Management), AUSF (Authentication Server Function), PCF (Policy Control Function), and AF (Application Function). AMF, SMF, NSSF, NEF, NRF, UDM, AUSF, PCF, and AF are network nodes that are interconnected via interfaces based on their respective services: Namf, Nsmf, Nnssf, Nnef, Nnrf, Nudm, Nausf, Npcf, and Naf.

[0014] SMF is a network node with functions such as session management, IP (Internet Protocol) address allocation and management for UEs, DHCP (Dynamic Host Configuration Protocol) functionality, ARP (Address Resolution Protocol) proxy, and roaming functionality. NEF is a network node with the function of notifying other NFs (Network Functions) of capabilities and events. NSSF is a network node with functions such as selecting the network slice to which the UE connects, determining the allowed NSSAI (Network Slice Selection Assistance Information), determining the NSSAI to be set, and determining the AMF set to which the UE connects. PCF is a network node with the function of controlling network policies. AF is a network node with the function of controlling application servers. NRF is a network node with the function of discovering NF instances that provide services. UDM is a network node that manages subscriber data and authentication data. UDM is connected to UDR (User Data Repository) which holds this data.

[0015] Figure 2 is a diagram illustrating an example of a communication system in a roaming environment. As shown in Figure 2, the network consists of a terminal 20 (UE) and multiple network nodes. Hereafter, one network node will be assigned to each function, however, one network node may implement multiple functions, or multiple network nodes may implement one function. Furthermore, the "connection" described below may be a logical connection or a physical connection.

[0016] The RAN is a network node with wireless access capabilities and is connected to the UE, AMF, and UPF. The AMF is a network node with functions such as RAN interface termination, NAS termination, registration management, connection management, reachability management, and mobility management. The UPF is a network node interconnected with the DN, acting as a PDU session point to the outside world, routing and forwarding packets, and handling QoS for the user plane. The UPF and DN constitute a network slice. In the wireless communication network of this embodiment, multiple network slices are constructed.

[0017] AMF is connected to UE, RAN, SMF, NSSF, NEF, NRF, UDM, AUSF, PCF, AF, and SEPP (Security Edge Protection Proxy). AMF, SMF, NSSF, NEF, NRF, UDM, AUSF, PCF, and AF are network nodes that are interconnected via interfaces based on their respective services: Namf, Nsmf, Nnssf, Nnef, Nnrf, Nudm, Nausf, Npcf, and Naf.

[0018] SMF is a network node with functions such as session management, IP address allocation and management for UEs, DHCP functionality, ARP proxy, and roaming functionality. NEF is a network node with the function of notifying other NFs of capabilities and events. NSSF is a network node with functions such as selecting the network slice to which a UE connects, determining which NSSAIs are allowed, determining which NSSAIs are configured, and determining which AMF set a UE connects to. PCF is a network node with the function of controlling network policies. AF is a network node with the function of controlling application servers. NRF is a network node with the function of discovering NF instances that provide services. SEPP is an opaque proxy that filters control plane messages between PLMNs (Public Land Mobile Networks). vSEPP shown in Figure 2 is SEPP in the visited network, and hSEPP is SEPP in the home network.

[0019] As shown in Figure 2, the UE is in a roaming environment connected to the RAN and AMF in the Visited PLMN. The Visited PLMN and Home PLMN are connected via vSEPP and hSEPP. The UE can communicate with the UDM of the Home PLMN, for example, via the AMF of the Visited PLMN.

[0020] Figure 3 is a diagram illustrating an example of an IMS data channel network. As shown in Figure 3, the IMS data channel network consists of a terminal 20 (UE) and multiple network nodes in both the originating network and the terminating network. Hereafter, one network node will be assigned to each function, however, one network node may implement multiple functions, or multiple network nodes may implement one function. Also, the "connection" described below may be a logical connection or a physical connection. A network node may have the following functions, for example.

[0021] IMS-AGW (Access Gateway) is a network node that functions as a gateway between the UE and the IMS network, and also has functions related to voice communication access processing.

[0022] P-CSCF (Proxy-Call Session Control Function) is a network node that provides proxy functionality between the UE and IMS network, as well as access control functions for voice communications.

[0023] S-CSCF (Serving-Call Session Control Function) is a network node that has functions related to session control for the User Agent (UE).

[0024] An I-CSCF (Interrogate-Call Session Control Function) is a network node in an IMS network that serves as a connection point between networks (e.g., a caller and a caller) and has functions such as forwarding received SIP requests to its own network's S-CSCF.

[0025] The IMS AS (IP Multimedia Subsystem Application Server) is a network node in the IMS network that has functions such as communicating with the DCSF (Data Channel Signalling Function) for event notification, and receiving data channel control instructions from the DCSF and communicating with the MF (Movement Function). The IMS AS also receives registration requests for communication termination points from the DCSF, converts the received registration requests into SIP Registers, and sends them to the S-CSCF (Serving-Call Session Control Function). Furthermore, the IMS AS converts data channel establishment requests received from the DCSF into SIP INVITEs and sends them to the S-CSCF.

[0026] DCSF (Data Channel Signaling Function) is a network node that receives event reports from IMS-AS and has functions such as deciding whether or not to allow the provision of data channel services, managing bootstrap data channels, and HTTP web server functionality.

[0027] A Media Function (MF) in an IMS network is a network node that performs functions such as media resource management and data channel media traffic forwarding. The MF processes media between the Data Channel Application Server (DCAS), which is the communication termination point, and the destination termination point, based on configuration information received from the Data Channel Application Server (DCSF). The MF may also be called a Data Channel Media Function (DCMF). Furthermore, the MF may also be called a Multimedia Resource Function (MRF).

[0028] DCAS (Data Channel Application Server) is a network node that has functions such as being a communication termination point for media and signaling in the IMS network.

[0029] 3GPP's 5GS and 6GS each have independent network functions, but methods for maintaining voice communication between these different systems are being considered. For example, if a UPF (User Plane Function) is not used as a combo node, a change in IP address may occur, potentially making it difficult to continue IMS voice communication sessions. Thus, under the current specifications, voice communication may be interrupted during network migrations.

[0030] According to this embodiment, even if movement occurs between 5GS and 6GS, IMS voice communication can be continued without interruption. The following describes each embodiment of this design.

[0031] In this embodiment, 5GS is an example of the first system, and 6GS is an example of the second system. However, the first system and the second system may be any different system. For example, the first system may be 6GS, and the second system may be a successor to 6GS.

[0032] (Example 1) Example 1 shows a method for continuing IMS voice communication when migrating from 5GS to 6GS.

[0033] An example of the operation of the communication system of Embodiment 1 will be explained using Figures 4A-4E. Figure 4A-4E shows a series of operations, but this embodiment may be applied to some of the steps in the figure or to any combination of multiple steps.

[0034] In the example in Figure 4, an IMS voice call is in progress, and the 5GS (5G System) is providing service to UE 20. UE 20 has a PDU session held within 6GS, and the PCF stores the IP address for that PDU session.

[0035] In step S101 of Figure 4A, the RAN (gNB 10) decides to move UE 20, which is communicating using 5GS, to 6GS. For example, gNB 10 evaluates the connectivity status and network conditions of UE 20 and selects the optimal target network (6GS).

[0036] In step S102, gNB 10 sends a UE Context Release request (voiceContinuityRequestIndication) to AMF 30A. A UE Context Release Request (Terminal Context Release Request Message) is a message for releasing the UE context. The voiceContinuityRequestIndication included in the UE Context Release Request is an example of information requesting the continuity of voice communication.

[0037] In step S103, based on the instructions, AMF 30A decides to notify IMS via SMF 30B before sending the UE Context Release Command to gNB 10. AMF 30A works with SMF 30B to notify the IMS network and support the maintenance of IMS sessions during the migration.

[0038] In step S104, AMF 30A sends an Nsmf_PDUSession_UpdateSMContext request (voiceContinuityRequestIndication) to SMF 30B. The Nsmf_PDUSession_UpdateSMContext request is a request message to update the session context. The voiceContinuityRequestIndication included in the Nsmf_PDUSession_UpdateSMContext request indicates a request to guarantee the continuity of IMS voice communication.

[0039] In step S105, SMF 30B sends an Nsmf_PDUSession_UpdateSMContext response to AMF 30A. The Nsmf_PDUSession_UpdateSMContext response is a response message that notifies AMF 30A that SMF 30B has completed the session context update process.

[0040] In step S106, SMF 30B sends an Npcf_SMPolicyControl_Update request (voiceContinuityRequestIndication) to 5G 6G PCF 30H. The Npcf_SMPolicyControl_Update request is a request message to send policy control information to the PCF. 5G 6G PCF 30H is an example of a network node that performs policy control.

[0041] In step S107, the 5G 6G PCF 30H sends the Npcf_SMPolicyControl_Update response to the SMF 30B. The PCF notifies the SMF that it has accepted the policy update and completed the process.

[0042] In step S108, the 5G 6G PCF 30H sends the Npcf_PolicyAuthorization_Notify request (voiceContinuityRequestIndication, UE IP address of 6GS PDU session) to the P-CSCF 30I. The Npcf_PolicyAuthorization_Notify request is a message for notifying policy information to the IMS network (P-CSCF). The Npcf_PolicyAuthorization_Notify request includes information requesting the continuity of voice communication and the UE IP address of the 6GS PDU session.

[0043] In step S109, if there is a DL SIP message, the P-CSCF 30I buffers the DL SIP message. In this step, the P-CSCF 30F temporarily performs a buffering process to prevent the loss of downlink SIP messages due to the change of the IP-CAN. This makes it possible to avoid session interruption. The DL SIP message is an example of a message related to voice communication for the terminal.

[0044] In step S110, the P-CSCF 30I sends the Npcf_PolicyAuthorization_Notify response to the 5G 6G PCF 30H.

[0045] In step S111 of Figure 4B, P-CSCF 30I sends Configure AGW Connection Point (towards UE) (Remote Connection Address = UE IP address of 6GS PDU session) to IMS AGW 30J. Configure AGW Connection Point (a message requesting connection point configuration) is used to configure IMS AGW 30G to recognize the new connection destination (e.g., the UE's IP address in 6GS) and correctly transfer data when migrating from 5GS to 6GS. Configure AGW Connection Point includes a Remote Connection Address indicating the new IP address of the UE (the address of the PDU session). In this step, the Remote Connection Address indicates the UE IP address of the 6GS PDU session. Configure AGW Connection Point may also include Port Information indicating the port number used for transferring the media stream.

[0046] The IMS AGW 30G configures media routing using the specified IP address and port based on the Configure AGW Connection Point received from the P-CSCF 30I.

[0047] In step S112, the IMS AGW 30J sends a Configure AGW Connection Point Ack to the P-CSCF 30I. The Configure AGW Connection Point Ack contains information indicating that the configuration based on the received Configure AGW Connection Point is complete.

[0048] In step S113, the P-CSCF 30I sends an Npcf_PolicyAuthorization_Update request (voiceContinuityPrepared) to the 5G 6G PCF 30H. The Npcf_PolicyAuthorization_Update request may include session information and policy information. The session information is information related to the IMS session. The policy information includes information related to the QoS of the service, resource requirements, and continuity of voice communication. In step S113, voiceContinuityPrepared is set in the policy information. voiceContinuityPrepared indicates that the necessary preparations for maintaining IMS voice communication have been completed.

[0049] In step S114, the 5G 6G PCF 30H sends an Npcf_PolicyAuthorization_Update response to the P-CSCF 30I.

[0050] In step S115, the 5G 6G PCF 30H sends an Npcf_SMPolicyControl_UpdateNotify request (voiceContinuityPrepared) to the SMF 30B.

[0051] In step S116, the SMF 30B sends an Npcf_SMPolicyControl_UpdateNotify response to the 5G 6G PCF 30H.

[0052] In step S117, the SMF 30B sends an Nsmf_PDUSession_SMContextStatusNotify request (voiceContinuityPrepared) to the AMF 30A.

[0053] In step S118, the AMF 30A sends an Nsmf_PDUSession_SMContextStatusNotify response to the SMF 30B.

[0054] In step S119, the AMF 30A decides to send a UE Context Release Command based on the instructions. The UE Context Release Command (terminal context release instruction message) is a message used to release resources that were being used on the original network when the UE 20 migrates to a different network, such as from 5GS to 6GS.

[0055] In step S120, the AMF 30A sends a UE Context Release Command (voiceContinuityPrepared) to the gNB 10. The UE Context Release Command may include a UE identifier, a Cause (cause code), and additional information. The UE identifier is identification information to identify the UE to be released (e.g., AMF UE NGAP ID). The Cause (cause code) indicates the reason for context release (e.g., normal release or abnormal release). Normal release is set when the UE transitions normally. Abnormal release is set when the session terminates abnormally or a network error occurs. Additional information is additional information depending on the specific use, for example, voiceContinuityPrepared and QoS-related information. voiceContinuityPrepared is an example of information to ensure the continuity of voice communication or information indicating that preparations to ensure the continuity of voice communication have been made (or completed).

[0056] In step S121, the gNB 10 sends RRCRelease (redirection, voiceContinuityPrepared) to the UE 20. RRCRelease is an example of a message requesting the release of the radio (RRC) connection. RRCRelease includes voiceContinuityPrepared and redirection. The redirection included in RRCRelease is an example of information requesting redirection (reconnection) to the destination network system (e.g., 6GS).

[0057] In step S122, gNB 10 sends UE Context Release Complete to AMF 30A. UE Context Release Complete is a message indicating that the release process for resources associated with the UE has been completed.

[0058] In step S123, AMF 30A sends an Nsmf_PDUSession_UpdateSMContext request to SMF 30B.

[0059] In step S124, SMF 30B sends a PFCP Session Modification request to UPF 30C.

[0060] In step S125, UPF 30C sends a PFCP Session Modification response to SMF 30B.

[0061] In step S126, SMF 30B sends the Nsmf_PDUSession_UpdateSMContext response to AMF 30A.

[0062] In step S127 of Figure 4C, the IMS AGW 30J transmits DL voice media to the 6G UPF 30G.

[0063] In step S128, the 6G UPF 30G sends a PFCP Session Report request (Downlink Data Report) to the 6G SMF 30F.

[0064] In step S129, the 6G SMF 30F sends a Namf_Communication_N1N2MessageTransfer request to the 6G AMF 30E.

[0065] In step S130, the 6G AMF 30E sends the Namf_Communication_N1N2MessageTransfer response to the 6G SMF 30F.

[0066] In steps S128-S130, the presence of downlink data is notified from the 6G SMF 30D to the 6G AMF 30C using the PFCP protocol and SBI interface within the 6GS core network, and appropriate communication processing is performed.

[0067] In step S131, the 6G AMF 30E may suppress paging using other IPR mechanisms.

[0068] In step S132 of Figure 4D, UE 20 moves to 6GS.

[0069] In step S133, UE 20 sends an RRCSetupRequest to 6G NB 30D.

[0070] In step S134, the 6G NB 30D sends RRCSetup to the UE 20.

[0071] In step S135, UE 20 sends RRCSetupComplete (dedicatedNAS-Message (Registration request)) to 6G NB 30D. If the UE is dual-registered, a Service request may be used instead of a Registration request.

[0072] In step S136, the 6G NB 30D sends an Initial UE message (NAS-PDU (Registration request)) to the 6G AMF 30E. This message contains a Registration Request based on the NAS protocol, indicating that UE 20 requests registration on the 6G system. This procedure is the initial action to establish the UE's connection to 6GS.

[0073] In step S137, the 6G AMF 30E sends an Nsmf_PDUSession_UpdateSMContext request to the 6G SMF 30F. The Nsmf_PDUSession_UpdateSMContext request is a request message to the 6G SMF 30F to update the PDU session context and adapt it to the new network environment.

[0074] In step S138, the 6G SMF 30F sends a PFCP Session Modification request to the 6G UPF 30G. The PFCP Session Modification request is a message used to update the user plane (UP) resources of a PDU session and configure them to support the new 6GS environment.

[0075] In step S139, the 6G UPF 30G sends a PFCP Session Modification response to the 6G SMF 30F. The PFCP Session Modification response is a message that notifies the 6G SMF 30F that the session update process in the 6G UPF 30G has been successfully completed.

[0076] In step S140, the 6G SMF 30F sends an Nsmf_PDUSession_UpdateSMContext response to the 6G AMF 30E. This response is a message to notify the 6G AMF 30E that the session context update is complete.

[0077] In step S141, the 6G AMF 30E sends a PDU Session Resource Setup request to the 6G NB 30D. This message contains instructions for configuring the network resources necessary to provide the PDU session resource to the UE 20.

[0078] In step S142, the 6G NB 30D sends an RRCReconfiguration to the UE 20. This procedure sends the configuration information necessary for the RRC connection to the UE 20 and reserves the resources.

[0079] In step S143 of Figure 4E, UE 20 sends RRCReconfigurationComplete to 6G NB 30D. RRCReconfigurationComplete indicates the completion of resource configuration.

[0080] In step S144, the 6G NB 30D sends a PDU Session Resource Setup response to the 6G AMF 30E. The PDU Session Resource Setup response indicates that the PDU session resource setup for the UE is complete.

[0081] In step S145, the 6G AMF 30E sends an Nsmf_PDUSession_UpdateSMContext request to the 6G SMF 30F. This message is a request for an additional session update.

[0082] In step S146, the 6G SMF 30F sends a PFCP Session Modification request to the 6G UPF 30G. This message is used to update the session information within the UPF.

[0083] In step S147, the 6G UPF 30G sends a PFCP Session Modification response to the 6G SMF 30F. This message is a response indicating that the session update has been successfully completed.

[0084] In step S148, the 6G SMF 30F sends an Nsmf_PDUSession_UpdateSMContext response to the 6G AMF 30E.

[0085] In step S149, the 6G AMF 30E sends a Downlink NAS Transport (NAS-PDU (Registration accept)) to the 6G NB 30D. This message is a NAS message indicating that the UE's registration has been approved.

[0086] In step S150, the 6G NB 30D sends DLInformationTransfer (dedicatedNAS-Message(Registration accept))) to the UE 20. This message is a dedicated NAS message that includes Registration Accept.

[0087] In step S151, the 6G UPF 30G transmits DL voice media to the UE 20. DL voice media is the downlink data of the IMS voice media.

[0088] In step S152, UE 20 sends a SIP Register to P-CSCF 30I. UE 20 re-registers with the IMS network to ensure the continuity of voice communication. A SIP Register (registration request message) is a message used by a terminal (UE 20) to register its location with a SIP network (e.g., the IMS network). The SIP Register includes the IP address of UE 20. The IP address of UE 20 is included, for example, in the Contact header of the SIP Register. The Contact header specifies destination information that the IMS network uses to send subsequent SIP messages.

[0089] In step S153, P-CSCF 30I sends SIP 200 OK to UE 20.

[0090] In step S154, if buffered DL SIP messages exist (in step S109), P-CSCF 30I sets the destination IP address of the DL SIP message to the target IP address (the IP address of UE 20 included in the SIP register) and sends the DL SIP message to UE 20. This ensures that buffered SIP messages are sent to UE 20 during network migration.

[0091] According to Embodiment 1, it is possible to prevent interruptions in IMS voice communication during movement between 5GS and 6GS. Furthermore, by ensuring the independence of 5GS and 6GS, the complexity of the system can be reduced and the efficiency of the network can be improved.

[0092] (Example 2) Example 2 shows a method for continuing IMS voice communication when UE 20 does not have a PDU session in 6GS.

[0093] An example of the operation of the communication system of Embodiment 2 will be explained using Figures 5A-5C. Figures 5A-5C are diagrams showing a series of operations, and this embodiment may be applied to some of the steps shown in the figure or to any combination of some of the steps.

[0094] In the example shown in Figure 5A-5C, an IMS voice call is in progress, and 5GS is providing service to UE 20. Embodiment 2 assumes that UE 20 does not maintain a PDU session within 6GS.

[0095] In step S201 of Figure 5A, the RAN (gNB 10) decides to move UE 20, which is communicating using 5GS, to 6GS. For example, gNB 10 evaluates the connectivity status and network conditions of UE 20 and selects the optimal target network (6GS).

[0096] In step S202, gNB 10 sends a UE Context Release request (voiceContinuityRequestIndication) to AMF 30A. This message includes a request to release the UE context and instructions to ensure the continuity of IMS voice communication.

[0097] In step S203, AMF 30A decides, based on the instructions, to notify IMS via SMF 30B before sending the UE Context Release Command to gNB 10.

[0098] In step S204, AMF 30A sends an Nsmf_PDUSession_UpdateSMContext request (voiceContinuityRequestIndication) to SMF 30B. This request contains information to ensure the continuity of IMS voice communication.

[0099] In step S205, SMF 30B sends the Nsmf_PDUSession_UpdateSMContext response to AMF 30A.

[0100] In step S206, SMF 30B sends an Npcf_SMPolicyControl_Update request (voiceContinuityRequestIndication) to 5G 6G PCF 30H.

[0101] In step S207, the 5G 6G PCF 30H sends an Npcf_SMPolicyControl_Update response to the SMF 30B.

[0102] In step S208, the 5G / 6G PCF 30H sends an Npcf_PolicyAuthorization_Notify request (voiceContinuityRequestIndication) to the P-CSCF 30I. This request includes a policy notification for the IMS network and contains the information necessary to ensure the continuity of voice communication.

[0103] In step S209, if a DL SIP message exists, P-CSCF 30I temporarily buffers it.

[0104] In step S210, P-CSCF 30I sends an Npcf_PolicyAuthorization_Notify response to 5G 6G PCF 30H.

[0105] In step S211, P-CSCF 30I sends Configure AGW Connection Point (towards UE) to IMS AGW 30J. This message includes a Remote Connection Address with a dummy value. The dummy value is a temporary value before the actual IP address is set.

[0106] In step S212 of Figure 5B, the IMS AGW 30J sends a Configure AGW Connection Point Ack to the P-CSCF 30I.

[0107] In step S213, P-CSCF 30I sends an Npcf_PolicyAuthorization_Update request (voiceContinuityPreparedAtIms) to 5G 6G PCF 30H.

[0108] In step S214, the 5G 6G PCF 30H sends the Npcf_PolicyAuthorization_Update response to the P-CSCF 30I.

[0109] In step S215, the 5G 6G PCF 30H sends an Npcf_SMPolicyControl_UpdateNotify request (voiceContinuityPreparedAtIms) to the SMF 30B.

[0110] In step S216, SMF 30B sends an Npcf_SMPolicyControl_UpdateNotify response to 5G 6G PCF 30H.

[0111] In step S217, SMF 30B sends an Nsmf_PDUSession_SMContextStatusNotify request (voiceContinuityPreparedAtIms) to AMF 30A.

[0112] In step S218, AMF 30A sends an Nsmf_PDUSession_SMContextStatusNotify response to SMF 30B.

[0113] In step S219, the AMF 30A decides to send a UE Context Release Command based on the instructions. This message instructs the UE to release its RRC resources and includes information to ensure the continuity of IMS voice communication.

[0114] In step S220, the AMF 30A sends a UE Context Release Command (voiceContinuityPreparedAtIms) to the gNB 10. This message includes a flag indicating that IMS voice communication is ready.

[0115] In step S221, gNB 10 sends RRCRelease (redirection, voiceDLBufferedAtIms) to UE 20. It releases the RRC resource and notifies the UE of the network destination. This message also includes information indicating the presence of buffered voice communication data.

[0116] In step S222, gNB 10 sends UE Context Release Complete to AMF 30A. This message indicates that the UE context release process has been successfully completed.

[0117] In step S223, AMF 30A sends an Nsmf_PDUSession_UpdateSMContext request to SMF 30B. This request initiates preparations to deactivate the session.

[0118] In step S224, SMF 30B sends a PFCP Session Modification request to UPF 30C. This message instructs UPF to update the session to deactivate it.

[0119] In step S225, UPF 30C sends a PFCP Session Modification response to SMF 30B. This response notifies UPF that the session modification has been successfully completed.

[0120] In step S226, SMF 30B sends an Nsmf_PDUSession_UpdateSMContext response to AMF 30A, notifying AMF that the session update process is complete.

[0121] In step S227 of Figure 5C, UE 20 moves to 6GS. UE 20 is redirected to the specified target network and initiates a new network connection.

[0122] In step S228, the registration procedure for 6GS is performed. In this procedure, the UE is registered with 6GS via the NAS protocol.

[0123] In step S229, the PDU session establishment procedure in 6GS is performed. UE 20 establishes a new PDU session to enable data communication within 6GS.

[0124] In step S230, UE 20 sends the SIP Register to P-CSCF 30I. UE 20 re-registers with the IMS network to ensure voice communication in the new network environment.

[0125] In step S231, P-CSCF 30I sends SIP 200 OK to UE 20. The IMS network accepts the registration and notifies the UE of the result.

[0126] In step S232, if buffered DL SIP messages exist, P-CSCF 30I sends DL SIP messages to UE 20 with the destination IP address set to the target IP address. This message forwarding provides the UE with SIP data that was temporarily held during the network migration.

[0127] In step S233, UE 20 sends a SIP re-INVITE (SDP offer (c= UE IP address of 6GS PDU session)) to P-CSCF 30I. The SIP re-INVITE (voice call configuration change request message) includes an SDP offer. The SDP offer includes, for example, session information, network information, media attributes, and information indicating the transmission and reception direction of the session. Session information includes a session identifier (e.g., session ID). Network information includes the IP address, network port number, and media attributes used for transmitting and receiving media streams. Media information includes requests for available media types (e.g., voice, video), available codecs (e.g., AMR, EVS), and bandwidth.

[0128] In step S233, the "c" (the IP address to which the media is connected) of the SDP offer is set to the IP address of the UE of the PDU session of the destination (changed) network system (6GS). In other words, the SIP re-INVITE SDP offer includes information indicating that the network system accommodating the voice communication is changing.

[0129] In step S234, P-CSCF 30I sends the message Configure AGW Connection Point (towards UE) (Remote Connection Address=UE IP address of 6GS PDU session) to IMS AGW 30J. This message configures a connection point for transferring voice media to the UE within 6GS.

[0130] In step S235, the IMS AGW 30J sends a Configure AGW Connection Point Ack to the P-CSCF 30I. This response indicates that the connection point configuration has been successfully completed.

[0131] In step S236, P-CSCF 30I sends a SIP re-INVITE to IMS AS 30K.

[0132] In step S237, IMS AS 30K sends SIP 200 OK to P-CSCF 30I.

[0133] In step S238, P-CSCF 30I sends SIP 200 OK to UE 20.

[0134] In step S239, the IMS AGW 30J sends the DL voice media to the UE 20. The buffered voice media is provided to the UE by the IMS AGW, and the voice communication continues.

[0135] According to Embodiment 2, even in the case of IMS voice communication where there is no PDU session held within 6GS, interruption of IMS voice communication during movement between 5GS and 6GS can be prevented. Furthermore, by ensuring the independence of 5GS and 6GS, the complexity of the system can be reduced and the efficiency of the network can be improved.

[0136] As described above, this embodiment, including embodiments 1 and 2, prevents SIP session interruptions and loss of voice communication during network migration by performing temporary buffering of SIP messages using P-CSCF and temporary buffering of voice media using UPF or IMS AGW.

[0137] Furthermore, according to this embodiment, IMS voice communication can be continued even when 5GS and 6GS each have independent network functions. The communication method based on this embodiment can minimize interference between each network system and reduce system complexity.

[0138] Furthermore, according to this embodiment, by using temporary connection information (dummy value) in the IMS AGW, the communication procedure when establishing a new PDU session within 6GS is simplified. The communication method based on this embodiment reduces the processing load during network migration and enables efficient system operation.

[0139] Furthermore, the communication method based on this embodiment is not limited to 5GS and 6GS, but can also be applied to transitions between different systems (for example, between 6GS and its successor systems). Therefore, it has the flexibility to be applicable even in next-generation network environments.

[0140] Furthermore, according to this embodiment, after network migration, the UE can quickly re-register and establish a PDU session within 6GS, minimizing migration time while ensuring the continuity of IMS voice communication.

[0141] (Device Configuration) Next, an example of the functional configuration of the base station 10, network node 30, and terminal 20 that perform the processing and operations described above will be explained. The base station 10, network node, and terminal 20 include the functions to perform the embodiments described above. However, the base station 10, network node, and terminal 20 may each have only some of the functions in the embodiments.

[0142] <Base Station and Network Nodes> Figure 6 shows an example of the functional configuration of a base station 10 and a network node. As shown in Figure 6, the base station 10 has a transmitting unit 110, a receiving unit 120, a setting unit 130, and a control unit 140. The functional configuration shown in Figure 6 is merely an example. The functional classifications and names of the functional units can be anything as long as they can perform the operation according to this embodiment. Note that the network node may have the same functional configuration as the base station 10. Furthermore, a network node having multiple different functions in the system architecture may be composed of multiple network nodes separated by function.

[0143] The transmitting unit 110 includes the function of generating a signal to be transmitted to the terminal 20 or other network node and transmitting the signal by wire or wireless. The receiving unit 120 includes the function of receiving various signals transmitted from the terminal 20 or other network node and obtaining information from the received signal, for example, information of a higher layer. A communication unit including the transmitting unit 110 and the receiving unit 120 may be configured.

[0144] The setting unit 130 stores pre-configured setting information and various setting information to be transmitted to the terminal 20 in a storage device, and reads them from the storage device as needed.

[0145] The control unit 140 performs the processes described in the embodiment. The control unit 140 also performs processing related to communication with the terminal 20. The signal transmission function in the control unit 140 may be included in the transmission unit 110, and the signal reception function in the control unit 140 may be included in the reception unit 120.

[0146] <Terminal> Figure 7 is a diagram showing an example of the functional configuration of terminal 20. As shown in Figure 7, terminal 20 has a transmitting unit 210, a receiving unit 220, a setting unit 230, and a control unit 240. The functional configuration shown in Figure 7 is merely an example. Any functional classification and name of functional unit is acceptable as long as it can perform the operation according to this embodiment. In addition, the communication device that becomes the resource holder 20 may have a functional configuration similar to that of terminal 20.

[0147] 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. The receiving unit 220 also has the function of receiving control signals or reference signals transmitted from network nodes. A communication unit including the transmitting unit 210 and the receiving unit 220 may be configured.

[0148] The setting unit 230 stores various setting information received from network nodes by the receiving unit 220 in a storage device and reads it from the storage device as needed. The setting unit 230 also stores pre-configured setting information.

[0149] The control unit 240 performs the processing described in the embodiment. The signal transmission function in the control unit 240 may be included in the transmission unit 210, and the signal reception function in the control unit 240 may be included in the reception unit 220.

[0150] (Hardware Configuration) The block diagrams (Figures 6 and 7) 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.

[0151] Functions include, but are not limited to, judgment, decision, determination, 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.

[0152] For example, the base station 10, network node, terminal 20, etc. in one embodiment of the present disclosure may function as a computer that processes the wireless communication method of the present disclosure. Figure 8 is a diagram showing an example of the hardware configuration of the base station 10 and terminal 20 according to one embodiment of the present disclosure. The network node may have a hardware configuration similar to that of the base station 10. The base station 10 and terminal 20 described above may be physically configured as a computer device including a processor 1001, a storage device 1002, an auxiliary storage device 1003, a communication device 1004, an input device 1005, an output device 1006, a bus 1007, etc.

[0153] 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 without some of the devices.

[0154] 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.

[0155] The processor 1001 controls the entire computer, for example, by running an operating system. 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.

[0156] 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 6 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 7 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.

[0157] 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.

[0158] 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.

[0159] 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 frequency division duplex (FDD) and time division duplex (TDD). For example, the transmitting and receiving antenna, amplifier section, transmitting and receiving section, transmission path interface, etc., may be implemented by the communication device 1004. The transmitting and receiving section may be implemented in a physically or logically separated manner, with a transmitting section and a receiving section.

[0160] 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 lamp, etc.). The input device 1005 and the output device 1006 may be configured as an integrated unit (e.g., a touch panel).

[0161] 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.

[0162] 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.

[0163] Figure 9 shows an example of the configuration of vehicle 2001. As shown in Figure 9, 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 vehicle 2001, for example, to the communication module 2013.

[0164] 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.

[0165] The electronic control unit 2010 consists of a microprocessor 2031, memory (ROM, RAM) 2032, and communication ports (IO 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).

[0166] Signals from various sensors 2021 to 2029 include current signals from current sensor 2021 for sensing motor current, front and rear wheel rotation speed signals acquired by rotation speed sensor 2022, front and 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.

[0167] 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.).

[0168] 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), 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 transmits and receives various information via the communication module 2013 to realize driver assistance functions or autonomous driving functions.

[0169] 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.

[0170] 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.

[0171] 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. The electronic control unit 2010, the various sensors 2021-2028, the information service unit 2012, etc., may also be called input units that accept input. For example, the PUSCH transmitted by the communication module 2013 may include the information based on the above input.

[0172] 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.

[0173] <Note> (Note 1) A base station comprising: a control unit that decides to move a terminal performing voice communication using a first network system (e.g., 5GS) from the first network system to a second network system (e.g., 6GS); and a transmission unit that, based on the decision, transmits a terminal context release request message containing first information requesting the continuity of voice communication to a network node (e.g., AMF) that manages the movement of the terminal.

[0174] (Appendix 2) The base station according to Appendix 1, comprising a receiving unit that receives a terminal context release instruction message from the network node, which includes information indicating that preparations have been made to ensure the continuity of voice communication, and the transmitting unit that transmits to the terminal a message requesting the release of the wireless connection, which includes the first information and second information requesting redirection to the second network system.

[0175] (Note 3) A network node (e.g., P-CSCF) comprising: a control unit that buffers messages related to voice communication to a terminal; a receiving unit that receives a registration request message including the IP address of the terminal from the terminal; and a transmitting unit that sends the buffered message, with the IP address of the terminal set as the destination IP address, to the terminal.

[0176] (Note 4) The receiving unit receives a message from a network node that performs policy control (e.g., PCF) that includes information requesting the continuity of voice communication, and after receiving the message, the control unit buffers a message relating to voice communication for the terminal, as described in Note 3.

[0177] (Note 5) A network node comprising: a receiving unit that receives a message containing information requesting the continuity of voice communication from a network node that performs policy control; and a transmitting unit that sends a message to an IMS access gateway requesting it to buffer voice media or to configure a connection point indicating the destination of the voice media.

[0178] Any of the provisions in Appendix 1-5 can prevent interruptions to IMS voice communication during travel between 5GS and 6GS. Furthermore, ensuring the independence of 5GS and 6GS reduces system complexity and improves network efficiency.

[0179] (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. The division of items in the above description is not essential to the present invention, and matters described in two or more items may be combined 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). The boundaries of functional units or processing units in the functional block diagram do not necessarily correspond to the boundaries of physical parts. The operation of multiple functional units may be physically performed by one part, or the operation of one functional unit may be physically performed by multiple parts. The processing procedures described in the embodiments may be rearranged 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 realized 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 any suitable storage medium such as random access memory (RAM), flash memory, read-only memory (ROM), EPROM, EEPROM, register, hard disk (HDD), removable disk, CD-ROM, database, server, or other appropriate storage medium.

[0180] Furthermore, notification of information is not limited to the embodiments described herein and may be carried out by other means. For example, notification of information may be carried out by physical layer signaling (e.g., DCI (Downlink Control Information), UCI (Uplink Control Information)), upper layer signaling (e.g., RRC (Radio Resource Control) signaling, MAC (Medium Access Control) signaling), broadcast information (MIB (Master Information Block), SIB (System Information Block)), other signals, or combinations thereof. Also, RRC signaling may be called RRC messages, and may be, for example, RRC Connection Setup messages, RRC Connection Reconfiguration messages, etc.

[0181] 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), 6th generation mobile communication system (6G), xth generation mobile communication system (xG) (xG (where x is, for example, an integer or decimal)), FRA (Future Radio Access), NR (new Radio), New radio access (NX), Future generation radio access (FX), W-CDMA (registered trademark), GSM (registered trademark), CDMA2000, UMB (Ultra Mobile Broadband), IEEE 802.11 (Wi-Fi (registered trademark)), IEEE 802.16 (WiMAX (registered trademark)), IEEE 802.20 may apply to at least one system utilizing UWB (Ultra-WideBand), Bluetooth®, or other appropriate systems, and to next-generation systems extended, modified, created, or defined based thereon. Alternatively, multiple systems may be applied in combination (e.g., a combination of at least one of LTE and LTE-A with 5G).

[0182] 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.

[0183] 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 or S-GW, 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).

[0184] 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.

[0185] 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.

[0186] 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).

[0187] 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.

[0188] 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 technology (such as coaxial cable, fiber optic cable, twisted pair, or digital subscriber line (DSL)) and wireless technology (such as infrared or microwave), then at least one of these wired and wireless technologies is included in the definition of a transmission medium.

[0189] 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.

[0190] 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, a signal may be a message. Furthermore, a component carrier (CC) may be called a carrier frequency, cell, frequency carrier, etc.

[0191] The terms “system” and “network” as used in this disclosure are interchangeable.

[0192] 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.

[0193] 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.

[0194] 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", "cell", "sector", "cell group", "carrier", and "component carrier" may be used interchangeably. Base stations may also be referred to by terms such as macrocell, small cell, femtocell, and picocell.

[0195] A base station can accommodate one or more (e.g., three) cells. If a base station accommodates multiple cells, the entire coverage area of ​​the base station can be divided into multiple smaller areas, each of which may 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 that coverage.

[0196] In this disclosure, the transmission of information by a base station to a terminal may be interpreted as the base station instructing the terminal to perform control or operation based on the information.

[0197] In this disclosure, terms such as "Mobile Station (MS)," "user terminal," "User Equipment (UE)," and "terminal" may be used interchangeably.

[0198] 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 several other appropriate terms.

[0199] At least one of the base station and the mobile station may be called a transmitting device, a receiving device, a communication device, etc. At least one of the base station and the mobile station may also 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 and the mobile station may be an IoT (Internet of Things) device such as a sensor.

[0200] Furthermore, the term "base station" in this disclosure may be interpreted as "user terminal." For example, the various aspects / embodiments of this disclosure may be applied to a configuration in which communication between a base station and a user terminal is replaced with communication between multiple terminals 20 (which may be called, for example, D2D (Device-to-Device), V2X (Vehicle-to-Everything)). In this case, the terminals 20 may have the functions that the base station 10 has. Also, terms such as "uplink" and "downlink" may be interpreted as terms corresponding to terminal-to-terminal communication (for example, "side"). For example, uplink channel, downlink channel, etc., may be interpreted as side channel.

[0201] Similarly, the term "user terminal" in this disclosure may be replaced with "base station." In this case, the base station may be configured to have the same functions as the user terminal described above.

[0202] 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 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."

[0203] 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.

[0204] The reference signal can also be abbreviated as RS (Reference Signal), and may be called a pilot depending on the applicable standard.

[0205] 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."

[0206] Any reference to elements using the designations “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 the 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.

[0207] In the configuration of each of the above devices, "means" may be replaced with "part," "circuit," "device," etc.

[0208] Where the terms “include,” “including,” and variations thereof 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 mean exclusive OR.

[0209] In this disclosure, if articles are added through translation, such as a, an, and the in English, this disclosure may include the fact that the noun following these articles is plural.

[0210] 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."

[0211] 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).

[0212] 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. Therefore, the descriptions in the present disclosure are illustrative and not intended to be restrictive in any way.

[0213] 10 Base station 110 Transmitting unit 120 Receiving unit 130 Setting unit 140 Control unit 20 Terminal 210 Transmitting unit 220 Receiving unit 230 Setting unit 240 Control unit 30 Network node 1001 Processor 1002 Storage device 1003 Auxiliary storage device 1004 Communication device 1005 Input device 1006 Output device 2001 Vehicle 2002 Drive unit 2003 Steering unit 2004 Accelerator pedal 2005 Brake pedal 2006 Shift lever 2007 Front wheel 2008 Rear wheel 2009 Axle 2010 Electronic control unit 2012 Information service unit 2013 Communication module 2021 Current sensor 2022 Rotation speed sensor 2023 Air pressure sensor 2024 Vehicle speed sensor 2025 Acceleration sensor 2026 Brake pedal sensor 2027 Shift lever sensor 2028 Object detection sensor 2029 Accelerator pedal sensor 2030 Driver assistance system unit 2031 Microprocessor 2032 Memory (ROM, RAM) 2033 Communication port (I / O port)

Claims

1. A base station comprising: a control unit that decides to move a terminal performing voice communication using a first network system from the first network system to a second network system; and a transmission unit that, based on the decision, transmits a terminal context release request message containing first information requesting the continuity of voice communication to a network node that manages the movement of the terminal.

2. The base station according to claim 1, comprising a receiving unit that receives a terminal context release instruction message from the network node, which includes information indicating that preparations have been made to ensure the continuity of voice communication, and the transmitting unit that transmits to the terminal a message requesting the release of the wireless connection, which includes the first information and second information requesting redirection to the second network system.

3. A network node comprising: a control unit that buffers messages related to voice communication to a terminal; a receiving unit that receives a registration request message from the terminal that includes the terminal's IP address; and a transmitting unit that sends the buffered message, with the terminal's IP address set as the destination IP address, to the terminal.

4. The network node according to claim 3, wherein the receiving unit receives a message from a network node that performs policy control, which includes information requesting the continuity of voice communication, and after receiving the message, the control unit buffers a message relating to voice communication for the terminal.

5. A network node comprising: a receiving unit that receives a message containing information requesting the continuity of voice communication from a network node that performs policy control; and a transmitting unit that sends a message to an IMS (IP Multimedia Subsystem) access gateway requesting it to buffer voice media or to configure a connection point indicating the destination of the voice media.

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