WO2023008468A1 - Device, base station, and communication method - Google Patents

Abstract

This device comprises: a reception unit that receives information pertaining to a multicast broadcast service (MBS) session; a control unit that identifies, on the basis of the information pertaining to the MBS session, a plurality of terminals associated with the MBS session; and a transmission unit that transmits a message including a plurality of items of notification information pertaining to a change in each of a plurality of PDU sessions used in the transmission of MBS data to the plurality of terminals.

Description

Apparatus, base station and communication method Cross-reference to related applications

This application is based on Japanese Patent Application No. 2021-124662 filed on July 29, 2021, and claims the benefit of its priority. incorporated herein by reference.

The present disclosure relates to devices, base stations and communication methods.

In the Third Generation Partnership Project (3GPP), an international standardization organization, Long Term Evolution (LTE), which is the 3.9th generation Radio Access Technology (RAT), and LTE-Advanced, which is the 4th generation RAT As a successor, Release 15 of New Radio (NR), which is a fifth generation (5G) RAT, has been specified (for example, Non-Patent Document 1).

In addition, Release 15 of 5G Core Network (5GC), which is the 5th generation CN, has been specified as a successor to Evolved Packet Core (EPC), which is the 4th generation Core Network (CN) (for example, , Non-Patent Document 2).

　Currently, 3GPP is considering supporting the Multicast Broadcast Service (MBS), which is a transmission service for multicast data and/or broadcast data. MBS in 5GC is also called 5MBS and the like. MBS supports an individual mode that transmits multicast data and/or broadcast data (hereinafter referred to as "MBS data") via protocol data unit (PDU) sessions set for each terminal. is being considered.

However, for example, when each PDU session used for transmitting MBS data to each terminal is changed due to various factors such as update of QoS of session for MBS (hereinafter referred to as "MBS session"), As a result of the procedure for modification of each PDU session being performed for each terminal, resource consumption on the network side (hereinafter referred to as "network resources") may increase.
One object of the present disclosure is to provide an apparatus, a base station, and a communication method capable of appropriately controlling changes in PDU sessions used for transmission of MBS data.

A device according to an aspect of the present disclosure includes a receiver that receives information about a multicast broadcast service (MBS) session, and a controller that identifies a plurality of terminals associated with the MBS session based on the information about the MBS session. and a transmission unit configured to transmit a message including one or more pieces of notification information regarding changes in each of the plurality of PDU sessions used for transmission of MBS data to the plurality of terminals. .

According to one aspect of the present disclosure, it is possible to appropriately control changes in PDU sessions used for transmission of MBS data.

FIG. 1 is a diagram showing an example of an outline of a communication system according to this embodiment. FIG. 2 is a diagram showing an example of a transmission mode of MBS data according to this embodiment. FIG. 3 is a diagram illustrating an example of a procedure for notifying a change of a PDU session related to MBS. FIG. 4 is a diagram illustrating an example of an MBS-related PDU session change response procedure. FIG. 5 is a diagram illustrating an example of a first notification integration procedure according to this embodiment. FIG. 6A is a diagram showing an example of a UE list according to this embodiment. FIGS. 6B to 6D are diagrams showing an example of a message including a PDU session change command according to this embodiment. FIG. 7 is a diagram illustrating an example of a second notification integration procedure according to this embodiment. FIG. 8 is a diagram illustrating an example of a third notification integration procedure according to this embodiment. FIG. 9 is a diagram showing an example of the first response integration procedure according to this embodiment. FIGS. 10A and 10B are diagrams showing an example of a message including a PDU session change command ACK according to this embodiment. FIG. 11 is a diagram showing an example of the second response integration procedure according to this embodiment. FIG. 12 is a diagram showing an example of the hardware configuration of each device in the communication system according to this embodiment. FIG. 13 is a diagram showing an example of a functional block configuration of a terminal according to this embodiment. FIG. 14 is a diagram showing an example of the functional block configuration of the base station according to this embodiment. FIG. 15 is a diagram showing an example of the functional block configuration of the CN device according to this embodiment.

An embodiment of the present disclosure will be described with reference to the accompanying drawings. In addition, in each figure, the thing which attached|subjected the same code|symbol may have the same or the same structure.

FIG. 1 is a diagram showing an example of an outline of a communication system according to this embodiment. As shown in FIG. 1, a communication system 1 includes a terminal 10, a base station 20, a core network (CN) 30, and provides MBS.

The terminal 10 is, for example, a predetermined terminal or device such as a smartphone, a personal computer, an in-vehicle terminal, an in-vehicle device, a stationary device, a telematics control unit (TCU), or the like. Terminal 10 may also be called a User Equipment (UE), a Mobile Station (MS), a User Terminal, a Radio apparatus, a subscriber terminal, an access terminal, and so on. The terminal 10 may be mobile or stationary.

The terminal 10 is configured to be able to communicate using at least one of LTE, LTE-Advanced, NR, etc. as a radio access technology (Radio Access Technology: RAT) for the base station 20, but not limited to this, It may be configured to be communicable using RAT of the sixth generation or later. In addition, the terminal 10 is not limited to the access network defined by 3GPP as described above (3GPP access network). may access.

The base station 20 forms one or more cells and communicates with the terminal 10 using the cell. Base station 20 includes gNodeB (gNB), en-gNB, radio access network (RAN), access network (AN), next generation radio access network (Next Generation-Radio Access Network: NG-RAN ) node, low-power node, Central Unit (CU), Distributed Unit (DU), gNB-DU, Remote Radio Head (RRH), integrated access and back It may also be called a hall (Integrated Access and Backhaul/Backhauling: IAB) node, device, or the like. The base station 20 is not limited to one node, and may be composed of a plurality of nodes (for example, a combination of a lower node such as DU and an upper node such as CU).

The CN 30 is, for example, 5GC, but is not limited to this, and may be an EPC or a 6th generation or later core network. CN 30, for example, Access and Mobility Management Function (AMF) 31, Session Management Function (SMF) 32, User Plane Function (UPF) 33, Multicast Broadcast (MB)-SMF 34, Multicast Broadcast (MB)-UPF 35, Multicast Broadcast Service Function (MBSF) 36, Network Exposure Function (NEF) 37, Application Function (AF) and/or Application Server (AS) (hereinafter referred to as "AF/AS") 38, Policy and Charging Control Function (PCF) 39, etc. Including function.

Note that the functions included in the CN 30 (hereinafter also referred to as "CN functions") are not limited to those shown in FIG. Also, the names of the functions and interfaces shown in FIG. 1 are merely examples, and other names may be used as long as they have equivalent or similar functions. Moreover, a plurality of CN functions shown in FIG. 1 may be provided in a single device, or one CN function shown in FIG. 1 may be configured by a plurality of devices. A device that constitutes part or all of each function of the core network 30 is called a “CN device”. An interface may also be referred to as a reference point.

Also, the number of terminals 10, base stations 20, and CN devices shown in FIG. 1 may be one or more. It goes without saying that one or more terminals 10 may be connected to one base station 20 . Also, multiple base stations 20 may be connected via an Xn interface. Also, each of the plurality of base stations 20 may be connected to the AMF 31 via the N2 interface. Also, a plurality of AMFs 31 may be connected to the SMF 32 via the N11 interface and to the MB-SMF 34 via the N11mb interface.

The AMF 31 is a CN device that manages access and/or mobility of the terminal 10. The AMF 31 is connected to the base station 20 via the N2 interface and to the terminal 10 via the N1 interface. The AMF 31 performs non-access stratum (NAS)-related C-plane processing (for example, registration management, connection management, mobility management), etc., and transmits and/or receives NAS messages to and from the terminal 10 .

The SMF 32 is a CN device that manages sessions, and controls, for example, session establishment, update and release. The SMF 32 is connected to the AMF 31 via the N11 interface and to the UPF 33 via the N4 interface.

The UPF 33 is a CN device that serves as a connection point to a data network (DN) (not shown), and performs, for example, routing and transfer of packets. The UPF 33 is connected to the SMF 32 via the N4 interface and to the base station 20 via the N3 interface. The UPF 33 is the first user plane device that performs processing related to the U plane. A logical connection relationship between the terminal 10 and the DN via the UPF 33 may be called a PDU session. Information about each PDU session is stored within a given context (eg, "SM context" and/or "N4 session context"). SM context may be maintained in SMF32 and AMF31. The N4 session context may be maintained in SMF32 and UPF33.

Downlink data from the DN is transmitted from the UPF 33 to the base station 20 via the N3 tunnel, and transmitted from the base station 20 to the terminal 10 via the radio bearer. On the other hand, uplink data from the terminal 10 is transmitted from the terminal 10 to the base station 20 via the radio bearer, transmitted from the base station 20 to the UPF 33 via the N3 tunnel, and transmitted from the UPF 33 to the DN. Note that the N3 tunnel is a tunnel for transmitting encapsulated IP (Encapsulated Internet Protocol) packets, and may be called a U-plane tunnel or the like. The PDU session may be configured by connecting the radio bearer between the terminal 10 and the base station 20 and the N3 tunnel between the base station 20 and the UPF 33 .

The MB-SMF 34 is a CN device that manages MBS sessions, and controls, for example, establishment, update and release of MBS sessions. MB-SMF 34 is connected to AMF 31 via the N11mb interface and to MB-UPF 35 via the N4mb interface. The MB-SMF 34 is also connected to the SMF 32 via the N16mb interface, to the MBSF 36 via the Nmb1 interface, to the NEF 37 via the N29mb interface, and to the AF/AS 38 via the Nmb13 interface. An MBS session is also called a multicast broadcast (MB) session or the like.

Note that joining (joining) to an MBS session includes a NAS message from the terminal 10 to the AMF 31 (for example, "UL NAS MB Session Join Request"), a request message from the AMF 31 to the MB-SMF 34 (for example, "MB Session Request" ), a response message from MB-SMF 34 to AMF 31 in response to the request message (eg, “MB Session Response”), a NAS message from AMF 31 to terminal 10 in response to the response message (eg, “DL NAS MB Session Join Accept ”) may be accepted.

The MB-UPF 35 is a CN device that controls transmission of MBS data from a DN (not shown). Downlink MBS data from a DN (not shown) is transmitted from MB-UPF 35 to base station 20 or UPF 33 . The MB-UPF 35 is connected to the base station 20 via the N3mb interface and to the AF/AS 38 via the N6mb interface. Also, the MB-UPF 35 is connected to the UPF 33 via the N19mb interface, and is connected to the UPF 33 via the N9 interface. MB-UPF 35 is a second user plane device that performs processing related to the U plane.

The NEF 37 provides an interface to the AF/AS 38 for MBS procedures including MBS session and QoS management. The NEF 37 is connected to the MB-SMF 34 via the N29mb interface and to the AF/AS 38 via the N33 interface. Also, the NEF 37 is connected to the PCF 39 via the N30 interface. MBSF 36 provides service-level functions for supporting MBS, such as selection of MB-SMF for MBS sessions. MBSF 36 is connected to NEF 37 via Nmb5 interface and to PCF 39 via Nmb12 interface.

The AF/AS 38 is a CN device used for at least one of MBS session configuration, distribution of information on service reception, session establishment, session release, and data transfer. Information about service reception may be, for example, an IP multicast address, parameters about the service (eg, service start time), and the like. AF/AS 38 is connected to NEF 37 via N33 interface and to MB-UPF 35 via N6mb interface. AF/AS 38 is also connected to MBSF 36 via at least one of the Nmb10 interface, the xMB-C interface and the MB2-C interface.

The PCF 39 is a CN device that controls policy and/or charging. A policy is information about priorities for Quality of Service (QoS). When updating the QoS of the MBS session, the PCF 39 may notify the SMF 32 and/or the MB-SMF 34 of the policy indicating the updated priority. The PCF 39 is also connected to the SMF 32 via the N7 interface and to the MB-SMF 34 via the N7mb interface.

In the communication system 1 as described above, MBS data is registered by a message (e.g., join or leave message) of a multicast distribution control protocol (e.g., Internet Group Management Protocol (IGMP) or Multicast Listener Discovery (MLD)). It is distributed to each terminal 10 that has been (registered). Supporting an individual mode and a shared mode as MBS data delivery modes for each terminal 10 is under consideration.

In individual mode, MBS data (a single copy of MBS data) received by CN 30 is sent to each terminal 10 via a PDU session for each terminal 10 (for example, a single unicast PDU session with each terminal 10). is transmitted to The individual mode is also called the first transmission mode, Individual MBS Traffic delivery, Ind-mode, and so on. A terminal 10 in dedicated mode can receive MBS data regardless of whether the base station 20 forming the serving cell supports MBS.

In shared mode, MBS data (a single copy of MBS data) received by CN 30 is transmitted to base station 20 via a shared transport (Shared Transport) with base station 20, and a terminal under the control of base station 20 10 is transmitted by Point To Point (PTP) or Point To Multi-point (PTM). The shared mode is also called a second transmission mode, Shared MBS Traffic delivery, Shared-mode, and so on. A terminal 10 in shared mode can receive MBS data when a base station 20 forming a serving cell supports MBS.

FIG. 2 is a diagram showing an example of the MBS data transmission mode according to this embodiment. As shown in FIG. 2, MBS data from a DN (not shown) is received by MB-UPF 35 within CN 30 .

In shared mode, the MB-UPF 35 transmits received MBS data to the base station 20 via shared transport. A shared transport is a shared tunnel within the CN 30, also called a shared downlink CN tunnel (Shred downlink CN Tunnel), N3 tunnel, and so on. The base station 20 transmits the MBS data received from the MB-UPF 35 via the shared transport to the terminal 10 under its control by PTM or PTP. In shared mode, MBS data for a large number of terminals 10 are bundled into one stream, so U-plane overhead in CN 30 can be reduced compared to dedicated mode.

In individual mode, MB-UPF 35 transfers the received MBS data to UPF 33 via the N9 tunnel. Note that the N9 tunnel is the tunnel of the N9 interface. The UPF 33 replicates the MBS data received from the MB-UPF 35 and transmits the replicated MBS data to each terminal 10 through a PDU session individually established with each terminal 10 . In the individual mode, even if the terminal 10 is handed over to the base station 20 that does not support MBS, the terminal 10 can continue to receive MBS data.

In the individual mode, MBS data is transmitted using a PDU session set for each terminal 10 . Therefore, for example, when the PDU session for each terminal 10 is changed due to various factors such as changing the QoS of the MBS session, the change procedure for each PDU session is performed for each terminal 10, resulting in consumption of network resources. may increase. Here, changing each PDU session means changing at least one of policy, priority and QoS rule of each PDU session, for example.

An example of a change procedure for each PDU session when updating the QoS of the MBS session will be described with reference to FIGS. In the following, alphabetical letters (a, b, c...) after step Sxxx (x is an arbitrary number) indicate one or more steps included in step Sxxx, and the one or more steps are collectively referred to as step Sxxx. may be

FIG. 3 shows an example of a notification procedure for changing PDU sessions related to MBS. FIG. 4 shows an example of a PDU session change response procedure for MBS. In FIGS. 3 and 4, as an example, it is assumed that terminals 10A to 10C participate in the same MBS session, but the number of terminals 10 is not limited to this, and may be one or more. Also, in FIG. 3, it is assumed that the terminals 10A to 10C are connected to the same base station 20 and AMF 31, but the present invention is not limited to this. Multiple terminals 10 may participate in the MBS session via the same and/or different base stations 20 and the same and/or different SMFs 32 .

As shown in FIG. 3, in step S100, a procedure for updating the AF session with required QoS (AF session with required QoS update procedure) is performed.

In step S100a, the AF 38 transmits to the NEF 37 a message (for example, "Nnef_AFsessionWithQoSUpdate request") requesting MBS session prioritization according to the requested QoS. The message may include, for example, information about the MBS session (hereinafter referred to as "MBS session information"). The MBS session information includes at least one of, for example, an MBS session identifier (hereinafter referred to as "MBS session ID"), an MBS session priority (hereinafter referred to as "MBS session priority"), and QoS rules. It's okay.

In step S100b, the NEF 37 authenticates the MBS session priority request from the AF 38 and applies a policy to control QoS for the authenticated AF.

In step S100c, the NEF 37 implements a policy update procedure with the PCF 39. Specifically, the NEF 37 transmits to the PCF 39 a message requesting policy update (for example, “Npcf_PolicyAuthorization Update request”). When approving the request from NEF 37, PCF 39 derives the parameters for the requested QoS, determines whether the QoS is allowed, and sends a response message indicating the decision result (for example, "Npcf_PolictAuthorization Update response" ) to NEF37

In step S100d, the NEF 37 sends a response message (for example, "Nnef_AFsessionWithQoSUpdateresponse") to the priority request in step S100a to the AF38.

In step S100e, when the PCF 39 succeeds or fails to change the resource corresponding to the QoS update, it sends a notification message (for example, "Npcf_PolicyAuthorization Notify") to the NEF 37 to notify the success or failure of the change.

In step S100f, the NEF 37 transmits a notification message (for example, "Nnef_AFsessionWithQoS Notify") to the AF 38 in response to the notification message from the PCF 39 to notify the success or failure of the QoS update of the AF session. When the AF session update procedure in step S100 is completed as described above, the policy update by the PCF 39 triggers the PDU session change procedure.

In step S101, the PCF 39-led policy modification procedure (hereinafter referred to as "PCF initiated Service Management (SM) policy association modification procedure") is implemented. The PCF 39 may generate a policy for the MBS session and notify the SMF 32 of the generated policy. The policy may include, for example, MBS session priority and/or MBS session ID.

In step S102, a procedure is performed to transfer the N1 message to the terminal 10 and/or the N2 message to the base station 20 via the AMF31. Specifically, in step S102a, the SMF 32 transmits to the AMF 31 a message for transferring the N1 message and/or the N2 message (for example, "Namf_Communication_N1N2MessageTransfer"). The transfer message includes, for example, the MBS session priority for which QoS is updated, the MBS session ID, and the notification information regarding the modification of the PDU session (hereinafter referred to as "PDU Session Modification Command"). At least one may be included. In step S102b, the AMF 31 may transmit to the SMF 32 a response message (for example, "Namf_Communication_N1N2MessageTransferResponse") to the transfer message.

Here, the PDU session change command includes, for example, a PDU session identifier (hereinafter referred to as “PDU session ID”), priority (hereinafter referred to as “PDU session priority”), and information on QoS (eg, QoS rule etc.).

In step S103, the SMF 32 generates RAN parameters related to the change of the PDU session, and transmits a message notifying the generated parameters (for example, "Nsmf_PDU_Session_SMContextStatusNotify") to the AMF 31.

In step S104, the AMF 31 transmits a message (hereinafter referred to as "N2 message") via the N2 interface to the base station 20. The N2 message may include a PDU session change command. The N2 message may also be called "N2 PDU Session Request".

In step S105, the base station 20 and the terminal 10 carry out a procedure for modifying Access Network (AN)-specific resources (hereinafter referred to as "AN-specific resource modification of transport"). For example, the base station 20 may implement RRC Connection Reconfiguration, which changes necessary RAN resources related to PDU sessions with the UE. Specifically, the base station 20 transmits to the terminal 10 an RRC message including a PDU session change command (for example, a message used for reconfiguring an RRC connection, which is referred to as an “RRC Reconfiguration message”). good too.

In step S106 of FIG. 4, the terminal 10 transmits an RRC message. The RRC message from the terminal 10 may include response information regarding the modification of the PDU session (hereinafter referred to as "PDU Session Modification Command ACK"). An RRC message including a command ACK (for example, a message used for notifying the completion of RRC connection reconfiguration, which is referred to as an “RRC reconfiguration complete (RRCReconfigurationComplete) message”) may be transmitted to the terminal 10 .

In step S107, the base station 20 transmits to the AMF 31 an N2 message (for example, "N2 NAS uplink transfer" or "N2 PDU Session Ack") including the PDU session change command ACK received in step S106.

In step S108, update the association between AMF 31 and SMF 32 to support the PDU session and/or provide SMF 32 with information (eg, N1/N2 SM information) received from terminal 10 or base station 20 A procedure (hereafter, "Nsmf_PDUSession_UpdateSMContext service operation") is performed. Specifically, in step S108a, the AMF 31 transmits to the SMF 32 a message (eg, “Nsmf_PDUSession_UpdateSMContextRequest”) including the information received from the base station 20 (eg, PDU session change command ACK). In step S108b, the AMF 31 receives from the SMF 32 a response message (for example, "Nsmf_PDUSession_UpdateSMContextResponse") to the message. The SM context may be updated in AMF 31 and/or SMF 32 in step S108.

In step S109, an N4 Session Modification procedure is implemented. When the SMF 32 receives a trigger to update the existing PDU session (for example, receives "Nsmf_PDUSession_UpdateSMContext Request" in step S108a), in step S109a, the SMF 32 sends a request message (for example, "N4 session Modification Request"). UPF 33 updates the parameters of the N4 session context in response to the request message. The parameters may include QoS-related rules (eg, QoS Enforcement Rule (QER)) and the like. In step S109b, the SMF 32 receives from the UPF 33 a response message (for example, "N4 session Modification Response") to the request message. The N4 session context may be updated in SMF 32 and/or UPF 33 in step S109.

In step S110, the SMF 32 notifies the PCF 39 of whether or not the policy has been changed in accordance with step S101.

As described above, in the PDU session change notification procedure shown in FIG. 3, steps S101 to S105 may be repeated for each of the terminals 10A to 10C. Similarly, in the PDU session change response procedure shown in FIG. 4, steps S106-S110 may be repeated for each of the terminals 10A-10C. This may result in increased consumption of network resources.

Therefore, in the present embodiment, a plurality of terminals 10 associated with an MBS session are specified, and a plurality of PDU session change commands for each of the plurality of terminals 10 are collectively transmitted instead of individually transmitted (hereinafter, " "Notification Consolidation") to prevent increased consumption of network resources. In addition, in the present embodiment, by collectively transmitting the PDU session change command ACK from at least one of the plurality of terminals 10 instead of transmitting them individually (hereinafter referred to as "response integration"), network resources are consumed. Prevent growth.

(notification integration)
In notification integration, a CN device (eg, SMF 32 or AMF 31) receives MBS session information and identifies multiple terminals 10 associated with the MBS session indicated by the MBS session information. The CN device also sends a message containing multiple PDU session change commands for multiple terminals 10 respectively. Thus, in notification aggregation, a message containing multiple PDU session change commands is transmitted.

Although the MBS session ID will be described below as an example of the MBS session information, it is not limited to this. As noted above, the MBS session information may include any information regarding the MBS session, such as, for example, MBS session ID and/or MBS session priority. Also, the MBS session ID hereinafter can be rephrased as MBS session information.

<First notification integration procedure>
In the first notification integration procedure, the SMF 32 receives the MBS session ID and identifies each terminal 10 associated with the MBS session indicated by the MBS session ID. The CN device also sends a message containing each PDU session change command for each identified terminal 10 .

Also, the SMF 32 transmits to the AMF 31 a message containing information about each identified terminal 10 and each PDU session change command for each identified terminal 10 . Also, SMF 32 may receive the MBS session ID from PCF 39 via MB-SMF 34 .

FIG. 5 is a diagram showing an example of the first notification integration procedure according to this embodiment. FIG. 5 will be described with a focus on differences from FIG. Step S200 in FIG. 5 is the same as step S100 in FIG.

Step S201 in FIG. 5 differs from step S101 in FIG. 3 in that the "PCF initiated SM policy association modification procedure" is performed between the PCF 39 and MB-SMF 34. In step S201a, the PCF 39 sends a message containing the MBS session ID to the MB-SMF 34. The message may be a message for notification of policy update for the MBS session (eg, "Npcf_SMPolicyControl_UpdateNotify request"). In step S201b, MB-SMF 34 sends to PCF 39 a response message (for example, "Npcf_SMPolicyControl_UpdateNotifyresponse") to the message received in step S201a.

In step S202, MB-SMF 34 transmits a message including the MBS session ID to SMF 32 in response to the message received from PCF 39 in step S201a. The message may be a message for notifying the SMF 32 of policy update.

At step 203, based on the MBS session ID notified from MB-SMF 34, SMF 32 identifies terminals 10A to 10C associated with the MBS session indicated by the MBS session ID. The SMF 32 generates a list (hereinafter referred to as "UE list") including information on the identified terminals 10A-10C. The information about each terminal 10 may include, for example, at least one of an identifier of each terminal 10 (hereinafter referred to as "terminal ID") and an identifier of a PDU session of each terminal 10 (hereinafter referred to as "PDU session ID"). . The terminal ID may be, for example, at least one of a Global Unique Temporary Identifier (GUTI), a Permanent Equipment Identifier (PEI), a Subscription Concealed Identifier (SUCI), and the IP address of the terminal 10. The UE list may be generated for each AMF 31 that has terminals 10 participating in the MBS session under its control.

FIG. 6(A) is a diagram showing an example of a UE list according to this embodiment. For example, as shown in FIG. 6A, in step S203 of FIG. 5, the SMF 32 determines the terminal IDs of the terminals 10A to 10C participating in the MBS session and the PDU session IDs of the PDU sessions set in the terminals 10A to 10C. may generate a UE list containing

In step S204, the SMF 32 transmits to the AMF 31 a message (for example, "Nsmf_PDUSession_UpdateSMContextResponse") including the UE list generated in step S203.

In step S205a, the SMF 32 sends to the AMF 31 a message (for example, "Namf_Communication_N1N2MessageTransfer") containing a single PDU session change command corresponding to the MBS session of the MBS session ID received in step S202. FIG. 6B is a diagram showing an example of a message including multiple PDU session change commands according to this embodiment. As shown in FIG. 6B, the message from SMF 32 to AMF 31 may contain a single PDU session change command corresponding to a single MBS session. Steps S205b and S206 in FIG. 5 are the same as steps S102b and S103 in FIG. The PDU session change command may include information about QoS corresponding to the MBS session.

In step S207, the AMF 31 duplicates (copies) the PDU session change command received in step S205a based on the UE list received in step S204, and generates PDU session change commands #1 to #3. For example, the AMF 31 may include terminal 10-specific PDU session information (eg, PDU session ID, etc.) in the PDU session change commands #1 to #3 based on the UE list.

FIG. 6(C) is a diagram showing another example of a message including multiple PDU session change commands according to this embodiment. As shown in FIG. 6C, the message (for example, "Namf_Communication_N1N2MessageTransfer") may include PDU session change commands #1 to #3 for the PDU sessions of the terminals 10A to 10C, respectively. PDU session change commands #1-#3 may be included within the S1 SM container within the message. Thus, in step S207 of FIG. 5, a single PDU session change command contained in "Namf_Communication_N1N2MessageTransfer" is duplicated into multiple PDU session change commands for each of multiple terminals 10 identified in the UE list. AMF 31 sends to base station 20 a message (eg, “N2 message”) containing each PDU session change command for each terminal 10 identified in the UE list. As shown in FIG. 6(C), the N2 message in step S207 may include PDU session change commands #1 to #3 for the PDU sessions of the terminals 10A to 10C, respectively.

In steps S208a to S208c, based on the N2 message from the AMF 31, the base station 20 sends PDU session change commands #1 to #3 including PDU session change commands #1 to #3 to the terminals 10A to 10C, respectively. (eg, three RRC reconfiguration messages shown in FIG. 6(C)) are transmitted.

As described above, in FIG. 5, the PDU session change commands #1 to #3 are included in separate messages in the RAN between the base station 20 and the terminals 10A to 10C. On the other hand, on the network side, the PDU session change command corresponding to the MBS session is duplicated in PDU session change commands #1 to #3 for the terminals 10A to 10C, and the duplicated PDU session change commands #1 to #3 are combined into a single It is included in a message and transmitted from SMF 32 to AMF 31 and from AMF 31 to base station 20 .

Note that the message from SMF 32 to AMF 31 in step S205a of FIG. Although it is assumed that the PDU session change commands #1 to #3 of 10A to 10C are duplicated, the present invention is not limited to this. PDU session change commands #1 to #3 may be included in the message (for example, Namf_Communication_N1N2MessageTransfer) from SMF 32 to AMF 31 in step S205a. In this case, the notification of the UE list in step S204 may be omitted.

According to the first change integration procedure, since the UE list is generated by the SMF 32, the PDU session change notification procedure is repeated for each terminal 10 corresponding to the same MBS session (for example, the terminals 10A to 10C in FIG. 3). Steps S101 to S105 are repeated for each) can be prevented. Therefore, consumption of network resources can be reduced.

<Second notification integration procedure>
The second notification integration procedure differs from the first notification integration procedure in that SMF 32 receives the MBS session ID from PCF 39 without going through MB-SMF 34 . Differences from the first notification integration procedure will be mainly described below.

FIG. 7 is a diagram showing an example of the second notification integration procedure according to this embodiment. FIG. 7 will be described with a focus on differences from FIG. Steps S300 and S302-S307 of FIG. 7 are the same as steps S200 and S203-S208 of FIG.

Step S301 in FIG. 7 differs from step S201 in FIG. 5 in that the "PCF initiated SM policy association modification procedure" is performed between the PCF 39 and SMF 32. In step S301a, the PCF 39 sends a message containing the MBS session ID to the SMF 32. The message may be a message for notification of policy update for the MBS session (eg, "Npcf_SMPolicyControl_UpdateNotify request"). In step S301b, the SMF 32 sends to the PCF 39 a response message (for example, "Npcf_SMPolicyControl_UpdateNotifyresponse") to the message received in step S301a.

According to the second change integration procedure, the message including the MBS session ID is transmitted from the PCF 39 to the SMF 32 without going through the MB-SMF 34. Therefore, for example, as shown in FIG. The consumption of network resources can be reduced compared to transmitting the MBS session ID to the SMF 32 via the SMF 32 .

<Third notification integration procedure>
The third notification integration procedure differs from the first and second modification integration procedures in that the AMF 31 instead of the SMF 32 identifies each terminal 10 associated with the MBS session indicated by the MBS session ID. The third notification integration procedure can be combined with the first or second change integration procedure. Differences from the first and second change integration procedures will be mainly described below.

Specifically, in the third notification integration procedure, the AMF 31 receives the MBS session ID from the SMF 32 and identifies each terminal 10 associated with the MBS session indicated by the MBS session ID. Also, the AMF 31 transmits to the base station 20 a message containing each PDU session change command used for transmission of MBS data for each identified terminal 10 .

The SMF 32 may receive the MBS session ID from the PCF 39 via the MB-SMF 34. Alternatively, SMF 32 may receive the MBS session ID from PCF 39 without going through MB-SMF 34 .

FIG. 8 is a diagram showing an example of a third notification integration procedure according to this embodiment. In FIG. 8, the description will focus on differences from FIG. 5 or FIG. 8, steps S200 to S202 in FIG. 5 or steps S300 to S301 in FIG. 7 are performed before step S400.

　In step S400 of FIG. 8, the SMF 32 transmits a message containing the MBS session ID (for example, "Nsmf_PDUSession_UpdateSMContextResponse"), which is different from step S204 or S303 of FIG. 5 for transmitting the message containing the UE list.

In step S401a, the SMF 32 transfers the PDU session change commands #1 to #3 of the terminals 10A to 10C identified based on the MBS session ID to separate messages (eg, "Namf_Communication_N1N2MessageTransfer" of the terminals 10A to 10C). may be sent including That is, steps S401a-S402 may be performed by terminals 10A-10C, respectively.

In step S403, based on the MBS session ID notified from SMF 32, AMF 31 identifies terminals 10A to 10C associated with the MBS session indicated by the MBS session ID. AMF 31 generates the UE list. A UE list may be generated for each base station 20 that has a terminal 10 participating in the MBS session under its control.

In step S404, the AMF 31 transmits to the base station 20 a message (eg, "N2 message") including PDU session change commands #1-#3 for the terminals 10A-10C identified in the UE list. Steps S405a-405c are similar to steps 208a-208c of FIG. 5 or steps S307a-S307c of FIG.

According to the third change integration procedure, the UE list is generated by the AMF 31, and the PDU session change command for each terminal 10 in the UE list is included in a single message and transmitted to the base station 20. Therefore, for example, as shown in FIG. 3, the consumption of network resources can be reduced compared to the case where the PDU session change command for each terminal 10 is transmitted from the AMF 31 to the base station 20 in separate messages.

(response integration)
In response aggregation, a specific device (eg, AMF 31 or base station 20) receives at least one of multiple PDU session change command ACKs (response information) of multiple terminals 10 identified based on MBS session information. do. A particular device uses a timer to control transmission of a message including at least one of the plurality of PDU session change command ACK. Thus, in response aggregation, multiple PDU session change command ACKs are combined and transmitted in one message instead of being transmitted in separate messages. Therefore, consumption of network resources can be reduced compared to the case where a plurality of messages are transmitted.

<First response integration procedure>
In a first response aggregation procedure, the base station 20 receives from the AMF 31 a message containing multiple PDU session change commands for each of multiple terminals 10 identified based on the MBS session ID. The base station 20 receives at least one of a plurality of PDU session change command ACKs corresponding to each of the plurality of PDU session change commands. The base station 20 uses a timer to control the transmission of messages containing at least one of a plurality of PDU session change command ACK. The first response integration procedure can be combined with at least one of the first through third change integration procedures.

FIG. 9 is a diagram showing an example of the first response integration procedure according to this embodiment. In FIG. 9, the description will focus on the differences from FIGS. 9, steps S200 to S206 in FIG. 5, steps S300 to S305 in FIG. 7, or steps S400 to S403 in FIG. 8 are performed before step S500. Steps S500 and S501 of FIG. 9 are similar to steps S207 and S208 of FIG. 5, steps S306 and S307 of FIG. 7, and steps S404 and S405 of FIG.

At step S502 in FIG. 9, the base station 20 starts a timer. For example, the base station 20 may start a timer upon receiving an N2 message containing PDU session change commands #1-#3 in step S500. The set value of the timer may be determined in advance by specifications, or may be notified from another device (for example, AMF 31).

In steps S503a to S503c, the base station 20 transmits a plurality of RRC messages (for example, three RRC reconfiguration complete messages shown in FIG. 10A) including PDU session change commands ACK#1 to #3, respectively, to the terminals 10A to 503c. Receive from 10C.

At step S504, the base station 20 determines whether the timer started at step S502 expires. Also, the base station 20 determines whether PDU session change commands ACK#1 to #3 have been received from the terminals 10A to 10C before the timer expires. If the timer has not expired and the PDU session change commands ACK#1 to #3 have not been received, the base station 20 repeats step S504. On the other hand, when the timer expires or receives the PDU session change commands ACK#1 to #3 before the timer expires, the base station 20 proceeds to step S505.

When the timer expires, the base station 20 identifies UEs from messages (for example, N2 messages) containing one or more PDU session change command ACKs received before the timer expires, and checks them against the UE list. Base station 20 sends a response message containing the UE list to AMF 31 . On the other hand, if all of the PDU session change commands ACK#1 to #3 are received before the timer expires, the base station 20 identifies the PDU session change commands ACK#1 to #3 and compares them with the UE list. do. Send a message to the AMF 31 containing the UE list. In FIG. 9, PDU session change commands ACK#1 to #3 are received before the timer expires, so in step S505, the base station 20 receives the PDU session change commands as shown in FIG. 10B. ACKs from #1 to #3 are identified and checked against the UE list. Send the N2 message containing the UE list to the AMF31.

In step S506a, the AMF 31 identifies UEs from one or more PDU session change command ACKs (here, PDU session change command ACKs #1 to #3) received from the base station 20, and checks them against the UE list. Send a message containing the UE list (eg, “Nsmf_PDUSession_UpdateSMContextRequest”) to SMF32. In step S506b, the SMF 32 sends a response message (for example, "Nsmf_PDUSession_UpdateSMContextResponse") to the message to the AMF 31.

As described above, in FIG. 9, the PDU session change commands ACK#1 to #3 are included in separate messages in the RAN between the base station 20 and the terminals 10A to 10C. On the other hand, on the network side, the PDU session change commands ACK#1-#3 for the terminals 10A-10C are included in a single message and transmitted from the base station 20 to the AMF31 and from the AMF31 to the SMF32.

According to the first response integration procedure, UEs are identified from the PDU session change command ACKs received from multiple terminals 10 in the UE list and compared with the UE list, which are received before the timer expires. The list of UEs is contained in a single message and transmitted on the network side (eg from base station 20 to AMF 31, from AMF 31 to SMF 32). Therefore, for example, as shown in FIG. 5, consumption of network resources can be reduced compared to the case where the PDU session change command ACK of a plurality of terminals 10 is transmitted in separate messages on the network side.

<Second response integration procedure>
In the second response aggregation procedure, the AMF 31 on behalf of the base station 20 includes in a single message at least one PDU session change command ACK of the terminals 10 identified in the UE list. Different from the integration procedure. The second response integration procedure can be combined with at least one of the first through third change integration procedures. Differences from the first response integration procedure will be mainly described below.

Specifically, in the second response integration procedure, the AMF 31 transmits to the base station 20 a message containing multiple PDU session change commands for each of the multiple terminals 10 identified based on the MBS session IDs. The base station 20 receives at least one of a plurality of PDU session change command ACKs corresponding to each of the plurality of PDU session change commands. AMF 31 uses a timer to control the transmission of a message containing at least one of a plurality of PDU session change command ACK.

FIG. 11 is a diagram showing an example of the second response integration procedure according to this embodiment. In FIG. 11, the description will focus on the differences from FIGS. 11, steps S200 to S206 in FIG. 5, steps S300 to S305 in FIG. 7, or steps S400 to S403 in FIG. 8 are performed before step S600. Steps S600 and S601 of FIG. 11 are the same as steps S207 and S208 of FIG. 5, steps S306 and S307 of FIG. 7, and steps S404 and S405 of FIG.

At step S602 in FIG. 11, the AMF 31 starts a timer. For example, AMF 31 may start a timer in response to sending a message (eg, N2 message) including PDU session change commands #1-#3 in step S600. Alternatively, AMF 31 may start a timer in response to receiving a message (not shown) containing PDU session change commands #1-#3 from SMF 32 . The set value of the timer may be determined in advance by specifications, or may be notified from another device (for example, AMF 31).

Steps S603a-603c are the same as steps S503a-503c in FIG. In steps S604a-604c, the base station 20 sends the PDU session change commands ACK#1-#3 received from the terminals 10A-10C, respectively, to the AMF 31 in separate N2 messages.

At step S605, the AMF 31 determines whether the timer started at step S602 expires. Also, the AMF 31 determines whether PDU session change commands ACK#1 to #3 have been received from the terminals 10A to 10C before the timer expires. If the timer has not expired and the PDU session change commands ACK#1 to #3 have not been received, the AMF 31 repeats step S605. On the other hand, when the timer expires or receives the PDU session change commands ACK#1 to #3 before the timer expires, the AMF 31 proceeds to step S606a.

When the timer expires, the AMF 31 identifies the UE from one or more PDU session change command ACKs received until the timer expires, and checks it against the UE list. AMF 31 sends a message (eg, “Nsmf_PDUSession_UpdateSMContextRequest”) containing the UE list to SMF 32 . On the other hand, if the PDU session change command ACK#1-#3 is received before the timer expires, the AMF 31 identifies the UE from the PDU session change command ACK#1-#3 and checks it against the UE list. Send a message to SMF 32 containing the UE list. In FIG. 11, PDU session change commands ACK#1 to #3 are received before the timer expires. Identify UEs from 1 to #3 and check against the UE list. Send a message to SMF 32 containing the UE list. In step S606b, the SMF 32 sends a response message (for example, "Nsmf_PDUSession_UpdateSMContextResponse") to the message to the AMF 31.

As described above, in FIG. 11, the PDU session change commands ACK#1 to #3 are included in separate messages in the RAN between the base station 20 and the terminals 10A to 10C. On the other hand, on the network side, the PDU session change commands ACK#1-#3 for the terminals 10A-10C are included in a single message and transmitted from the AMF 31 to the SMF 32. FIG.

According to the second response integration procedure, UEs are identified from the PDU session change command ACKs received from multiple terminals 10 in the UE list and compared with the UE list, which are received before the timer expires. The UE list is included in a single message and transmitted on the network side (eg from AMF 31 to SMF 32). Therefore, for example, as shown in FIG. 5, consumption of network resources can be reduced compared to the case where the PDU session change command ACK of a plurality of terminals 10 is transmitted in separate messages on the network side.

(Configuration of communication system)
Next, the configuration of each device of the communication system 1 as described above will be described. Note that the following configuration is for showing the configuration required in the description of the present embodiment, and does not exclude that each device has functional blocks other than those illustrated.

<Hardware configuration>
FIG. 12 is a diagram showing an example of the hardware configuration of each device in the communication system according to this embodiment. Each device within the communication system 1 can be any device shown in FIG. Reference numeral “30” in FIG. 12 denotes a CN device in CN 30, and generically refers to AMF 31, SMF 32, UPF 33, MB-SMF 34, MB-UPF 35, MBSF 36, NEF 37, AF/AS 38, and PCF 39.

Each device in the communication system 1 includes a processor 11, a storage device 12, a communication device 13 for wired or wireless communication, an input device for receiving various input operations, and an input/output device 14 for outputting various information.

The processor 11 is, for example, a CPU (Central Processing Unit) and controls each device within the communication system 1 . The processor 11 may read and execute the program from the storage device 12 to execute various processes described in this embodiment. Each device within the communication system 1 may be configured with one or more processors 11 . Each device may also be called a computer.

The storage device 12 is composed of storage such as memory, HDD (Hard Disk Drive) and/or SSD (Solid State Drive). The storage device 12 may store various types of information necessary for execution of processing by the processor 11 (for example, programs executed by the processor 11, etc.).

The communication device 13 is a device that communicates via a wired and/or wireless network, and may include, for example, network cards, communication modules, chips, antennas, and the like. Further, the communication device 13 may include an amplifier, an RF (Radio Frequency) device that performs processing related to radio signals, and a BB (BaseBand) device that performs baseband signal processing.

For example, the RF device generates a radio signal to be transmitted from the antenna A by performing D/A conversion, modulation, frequency conversion, power amplification, etc. on the digital baseband signal received from the BB device. Further, the RF device generates a digital baseband signal by performing frequency conversion, demodulation, A/D conversion, etc. on the radio signal received from the antenna, and transmits the digital baseband signal to the BB device. The BB device performs a process of converting a digital baseband signal into a packet and a process of converting the packet into a digital baseband signal.

The input/output device 14 includes input devices such as keyboards, touch panels, mice and/or microphones, and output devices such as displays and/or speakers.

The hardware configuration described above is just an example. Each device in the communication system 1 may omit part of the hardware shown in FIG. 11, or may include hardware not shown in FIG. Also, the hardware shown in FIG. 12 may be configured by one or a plurality of chips.

<Functional block configuration>
≪Device≫
FIG. 13 is a diagram showing an example of a functional block configuration of a terminal according to this embodiment. As shown in FIG. 13 , terminal 10 includes receiver 101 , transmitter 102 , and controller 103 . Note that the receiving unit 101 and the transmitting unit 102 may be collectively referred to as a "communication unit".

All or part of the functions realized by the receiving unit 101 and the transmitting unit 102 can be realized using the communication device 13. All or part of the functions realized by the receiving unit 101 and the transmitting unit 102 and the control unit 103 can be realized by the processor 11 executing a program stored in the storage device 12 . Also, the program can be stored in a storage medium. The storage medium storing the program may be a non-transitory computer readable medium. The non-temporary storage medium is not particularly limited, but may be a storage medium such as a USB memory or CD-ROM, for example.

The receiving unit 101 receives MBS data. Specifically, the receiving unit 101 receives MBS data via a PDU session for each terminal 10 in the individual mode. On the other hand, in the shared mode, receiving section 101 receives MBS data transmitted from MB-UPF 35 to base station 20 via the shared tunnel from base station 20 .

The receiving section 101 receives various messages from the base station 20 or the CN device. For example, the receiver 101 may receive PDU session change commands, N1 messages, NAS messages and RRC messages. Also, the receiving unit 101 may receive an RRC reconfiguration message including a PDU session change command.

Note that "receiving" may include, for example, performing processing related to reception, such as at least one of signal reception, demapping, demodulation, decoding, and measurement. For example, receiving section 101 may measure a downlink signal and generate the terminal state information based on the result of the measurement.

The transmission unit 102 transmits various messages to the base station 20 or CN device. The transmitter 102 may transmit PDU session change command ACK, N1 message, NAS message and RRC message. Also, the transmitting unit 102 may transmit an RRC reconfiguration complete message including the PDU session change command ACK. Note that "transmitting" may include performing processing related to transmission, such as at least one of encoding, modulation, mapping, and signal transmission.

The control unit 103 performs various controls in the terminal 10. Specifically, the control unit 103 may control reception of MBS data using a PDU session for each terminal 10 . Also, the control unit 103 may control the change of the PDU session for each terminal 10 according to the PDU session change command for each terminal 10 .

≪Base station≫
FIG. 14 is a diagram showing an example of the functional block configuration of the base station according to this embodiment. As shown in FIG. 14, the base station 20 includes a receiver 201, a transmitter 202, and a controller 203. FIG. Note that the receiving unit 201 and the transmitting unit 202 may be collectively referred to as a "communication unit".

All or part of the functions realized by the receiving unit 201 and the transmitting unit 202 can be realized using the communication device 13. All or part of the functions realized by the receiving unit 201 and the transmitting unit 202 and the control unit 203 can be realized by the processor 11 executing a program stored in the storage device 12 . Also, the program can be stored in a storage medium. The storage medium storing the program may be a computer-readable non-temporary storage medium. The non-temporary storage medium is not particularly limited, but may be a storage medium such as a USB memory or CD-ROM, for example.

The receiving unit 201 receives various messages from the terminal 10, another base station 20, or the CN device. Specifically, the receiving unit 201 receives a message (eg, N2 message) including a plurality of PDU session change commands (notification information) from the CN device (eg, AMF 31). Each PDU session change command is notification information regarding the change of each PDU session for transmission of MBS data for each terminal 10 identified based on the MBS session information.

Also, the receiving unit 201 receives a message (eg, RRC reconfiguration complete message) including the PDU session change command ACK (response information) from each terminal 10 specified based on the MBS session information. Each PDU session command ACK is response information about changing each PDU session for transmission of MBS data for each terminal 10 identified based on the MBS session information.

The transmission unit 202 transmits various messages from the terminal 10, other base stations 20, or CN devices. Specifically, the transmitting unit 202 transmits a message (eg, N2 message) including at least one of a plurality of PDU session change command ACKs to the CN device (eg, AMF 31).

For example, when the timer expires, the transmitting unit 202 may transmit a message including one or more PDU session command ACKs received by the receiving unit 201 before the timer expires (eg, FIG. 9). Further, when the receiving unit 201 receives the plurality of PDU session change command ACKs before the timer expires, the transmitting unit 202 may transmit a message including the plurality of PDU session change command ACKs ( For example, FIG. 9).

Also, the transmitting unit 202 transmits a message (eg, RRC reconfiguration message) including a PDU session change command to each terminal 10 identified based on the MBS session information.

The control unit 203 performs various controls in the base station 20. Specifically, the control unit 203 may use a timer to control transmission of a message including at least one of the plurality of PDU session change commands ACK (eg, FIG. 9). Also, the control unit 203 may start the timer in response to receiving a message including multiple PDU session change commands.

<<CN device>>
FIG. 15 is a diagram showing an example of the functional block configuration of the CN device according to this embodiment. The CN device in FIG. 15 is, for example, SMF32 or AMF31, but other CN devices may have similar functional block configurations. The CN device comprises a receiver 301 , a transmitter 302 and a controller 303 . Note that the receiving unit 301 and the transmitting unit 302 may be collectively referred to as a "communication unit".

All or part of the functions realized by the receiving unit 301 and the transmitting unit 302 can be realized using the communication device 13. All or part of the functions realized by the receiving unit 301 and the transmitting unit 302 and the control unit 303 can be realized by the processor 11 executing a program stored in the storage device 12 . Also, the program can be stored in a storage medium. The storage medium storing the program may be a computer-readable non-temporary storage medium. The non-temporary storage medium is not particularly limited, but may be a storage medium such as a USB memory or CD-ROM, for example.

The receiving unit 301 receives various messages from the terminal 10, the base station 20, or other CN devices. Specifically, receiving section 301 receives MBS session information from other CN devices. For example, the receiver 301 of the SMF 32 may receive MBS session information from the PCF 39 via the MB-SMF 34 (eg, FIG. 5). Alternatively, the receiver 301 of the SMF 32 may receive MBS session information from the PCF 39 without going through the MB-SMF 34 (eg, FIG. 7). Also, the receiving unit 301 of the AMF 31 may receive MBS session information from the SMF 32 (eg, FIG. 8).

The receiving unit 301 receives at least one of a plurality of PDU session commands ACK. The multiple PDU session command ACKs may correspond to multiple PDU sessions used for transmission of MBS data for multiple terminals 10 identified based on the MBS session information. For example, the receiver 301 of the AMF 31 may receive a message (eg, "N2 message") including at least one of the plurality of PDU session command ACKs from the base station 20 (eg, FIG. 9). Also, the receiving unit 301 of the SMF 32 may receive a message (for example, “Nsmf_PDUSession_UpdateSMContextRequest”) including at least one of the plurality of PDU session command ACKs from the AMF 31 (for example, FIG. 9 or 11).

The transmission unit 302 transmits various messages to the terminal 10, the base station 20, or other CN devices. Specifically, the transmitter 302 transmits a message including multiple PDU session change commands. For example, the transmitting unit 302 of the SMF 32 transmits a message (eg, "Nsmf_PDUSession_UpdateSMContext Response") including the UE list (information on multiple terminals 10) identified based on the MBS session information to the AMF 31 (eg, FIG. 5 or 7).

In addition, the transmission unit 302 of the SMF 32 transmits a message (eg, "Namf_Communication_N1N2MessageTransfer") including multiple PDU session change commands to the AMF 31 (eg, FIGS. 5, 7, or 8). The sending unit 302 of the AMF 31 sends a message (eg, “N2 message”) containing multiple PDU session change commands to the AMF 31 (eg, FIG. 5 or 7).

Also, the transmitting unit 302 of the AMF 31 may transmit a message (eg, "Nsmf_PDUSession_UpdateSMContextRequest") including at least one of the plurality of PDU session command ACKs to the SMF 32 (eg, FIG. 9 or 11).

The control unit 303 performs various controls in the CN device. Specifically, the control unit 303 identifies one or more terminals 10 associated with the MBS session based on the MBS session information. For example, the control unit 303 of the SMF 32 may identify the terminal 10 based on MBS session information (eg, FIG. 5 or 7). Alternatively, the control unit 303 of the AMF 31 may identify the terminal 10 based on MBS session information (eg, FIG. 8).

As described above, according to the communication system 1 according to the present embodiment, a plurality of pieces of information (for example, a plurality of PDU session change commands or Multiple PDUs Session Change Command ACK) are transmitted in a single message on the network side. Therefore, it is possible to improve the utilization efficiency of resources on the network side.

(Modification)
In the above embodiments, multiple pieces of information (for example, multiple PDU session change commands or multiple PDU session change command ACKs) are included in a single message on the network side, but the present invention is not limited to this. For example, a single PDU session change command from SMF 32 may be replicated into multiple PDU session change commands at base station 20 . Alternatively, multiple PDU session change command ACKs from each of multiple terminals 10 may be integrated into a single PDU session change command ACK at the base station 20 or AMF 31 .

(supplement)
Various signals, information and parameters in the above embodiments may be signaled in any layer. That is, the above-mentioned various signals, information, parameters are higher layers (eg, Non Access Stratum (NAS) layer, RRC layer, MAC layer, etc.), lower layers (eg, physical layer), etc. Signals, information, may be replaced by parameters. Further, the notification of the predetermined information is not limited to being performed explicitly, but may be performed implicitly (for example, by not notifying the information or using other information).

Also, the names of various signals, information, parameters, IEs, channels, time units, and frequency units in the above embodiments are merely examples, and may be replaced with other names. For example, a slot may be named any unit of time having a predetermined number of symbols. Also, RB may be any name as long as it is a frequency unit having a predetermined number of subcarriers.

In addition, the use of the terminal 10 in the above embodiment (for example, for RedCap, IoT, etc.) is not limited to those illustrated, as long as it has similar functions, any use (for example, eMBB, URLLC, Device-to- Device (D2D), Vehicle-to-Everything (V2X), etc.). Also, the format of various information is not limited to the above embodiment, and may be appropriately changed to bit representation (0 or 1), true/false value (Boolean: true or false), integer value, character, or the like. Also, singularity and plurality in the above embodiments may be interchanged.

The embodiments described above are for facilitating understanding of the present disclosure, and are not for limiting interpretation of the present disclosure. Flowcharts, sequences, elements included in the embodiments, their arrangement, indexes, conditions, and the like described in the embodiments are not limited to those illustrated and can be changed as appropriate. Moreover, it is possible to partially replace or combine at least part of the configurations described in the above embodiments.

Claims (7)

1. a receiver for receiving information about a Multicast Broadcast Service (MBS) session;
   a control unit that identifies a plurality of terminals associated with the MBS session based on information about the MBS session;
   a transmission unit for transmitting a message including one or more notification information regarding changes in each of a plurality of PDU sessions used for transmission of MBS data to the plurality of terminals;
   A device comprising
2. the device is a Session Management Function (SMF);
   The transmitting unit transmits information about the plurality of terminals and the message including the one or more notification information to an Access and Mobility Management Function (AMF).
   A device according to claim 1 .
3. The receiving unit receives information about the MBS session from Policy and Charging Control Function (PCF) via Multicast Broadcast (MB)-SMF;
   3. Apparatus according to claim 2.
4. The receiving unit receives information about the MBS session from Policy and Charging Control Function (PCF) without going through Multicast Broadcast (MB)-SMF;
   3. Apparatus according to claim 2.
5. the device is an Access and Mobility Management Function (AMF);
   wherein the transmission unit transmits the message including the plurality of notification information to a base station;
   A device according to claim 1 .
6. A message of multiple PDU sessions used for transmission of MBS data to multiple terminals identified based on information about a Multicast Broadcast Service (MBS) session, the message including multiple notification information about changes in each of the multiple PDU sessions. a receiver for receiving
   a transmission unit that transmits a plurality of messages each including the plurality of notification information to the plurality of terminals;
   base station.
7. receiving information about a Multicast Broadcast Service (MBS) session;
   identifying a plurality of terminals associated with the MBS session based on information about the MBS session;
   transmitting a message containing one or more notification information regarding changes in each of a plurality of PDU sessions used for transmission of MBS data to the plurality of terminals;
   A communication method in a device having

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