METHOD AND APPARATUS FOR CONTROLLING MBS IN WIRELESS COMMUNICATION SYSTEM

The disclosure relates to a 5G or 6G communication system for supporting a higher data transmission rate. According to an embodiment of the disclosure, a method of controlling multicast and broadcast service (MBS) by a session management function (SMF) in a wireless communication system includes transmitting a first message including information about an MBS area and an MBS session identifier (ID) to an access and mobility management function (AMF), receiving a second message indicating that a user equipment receiving a service within the MBS area is located outside the MBS area from the AMF, determining that the UE is located outside the MBS area based on the second message, and processing a quality of service (QoS) flow applied to MBS traffic delivered by individual delivery.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit under 35 U.S.C. § 119(a) of a Korean patent application filed in the Korean Intellectual Property Office on Jun. 25, 2021, and assigned Serial No. 10-2021-0083366, the entire disclosure of which is incorporated herein by reference.

BACKGROUND

The disclosure relates to a method of providing multicast and broadcast service (MBS) to a user equipment (UE) in a wireless communication system, and more particularly, to a method of considering the mobility of a UE, when a 5thgeneration (5G) network provides MBS to the UE.

2. Description of Related Art

When multicast and broadcast service (MBS) is provided to a user equipment (UE) in a 5G network, a need for considering the mobility of the UE is emerging.

SUMMARY

To provide multicast and broadcast service (MBS), a 5G system (5GS) may receive MBS data from an application function (AF) or a content provider and transmit the received MBS data to a next generation radio access network (NG-RAN). The NR-RAN may transmit the MBS data, for example, to user equipments (UEs) subscribed to the MBS.

For a UE receiving the MBS from an NG-RAN within an MBS service area, when the NR-RAN does not have an MBS capability, the NR-RAN transmits MBS data to the UE in an individual delivery method. When the UE moves out of the MBS service area, there is a need for a method of discontinuing the MBS data delivery to the UE.

According to an embodiment of the disclosure, a method of controlling multicast and broadcast service (MBS) by a session management function (SMF) in a wireless communication system may include transmitting a first message including information about an MBS area and an MBS session identifier (ID) to an access and mobility management function (AMF), receiving a second message indicating that a user equipment receiving a service within the MBS area is located outside the MBS area from the AMF, determining that the UE is located outside the MBS area based on the second message, and processing a quality of service (QoS) flow applied to MBS traffic delivered by individual delivery.

According to an embodiment, processing the QoS flow applied to the MBS traffic may include deleting the QoS flow, or dropping data traffic applied to a packet detection rule for the QoS flow.

According to an embodiment, the method may further include receiving a third message including a session join request of the UE and the MBS session ID from the AMF, and the first message may be transmitted to the AMF in response to the third message.

According to an embodiment, the first message may be a subscribe message for receiving an event notification when the UE located within the MBS area moves out of the MBS area.

According to an embodiment, the method may further include storing mapping information between the MBS session ID and a notification correlation ID, and identifying that the second message is an event notification for the MBS session ID based on the mapping information.

According to an embodiment, the UE may move from within the MBS area to an outside of the MBS area through Xn handover or N2 handover.

According to an embodiment, when the UE is placed in an idle state after the transmission of the first message and transmits a service request later, the SMF may receive the second message from the AMF.

According to an embodiment of the disclosure, a method of controlling MBS by an AMF in a wireless communication system may include receiving a first message including information about an MBS area and an MBS session ID from an SMF, and transmitting a second message indicating that a user equipment receiving a service within the MBS area is located outside the MBS area to the SMF. A QoS flow applied to MBS traffic delivered by individual delivery may be processed based on the second message.

According to an embodiment, the method may further include transmitting a third message including a session join request of the UE and the MBS session ID to the SMF, and the first message may be received from the SMF in response to the third message.

According to an embodiment of the disclosure, an SMF device for controlling MBS in a wireless communication system may include a transceiver, and a controller configured to transmit a first message including information about an MBS area and an MBS session ID to an AMF, receive a second message indicating that a user equipment receiving a service within the MBS area is located outside the MBS area from the AMF, determine that the UE is located outside the MBS area based on the second message, and process a QoS flow applied to MBS traffic delivered by individual delivery.

According to an embodiment of the disclosure, an AMF device for controlling MBS in a wireless communication system may include a transceiver, and a controller configured to receive a first message including information about an MBS area and an MBS ID from an SMF, and transmit a second message indicating that a user equipment receiving a service within the MBS area is located outside the MBS area to the SMF. A QoS flow applied to MBS traffic delivered by individual delivery may be processed based on the second message.

According to the disclosure, when a UE using MBS in a 5thgeneration system (5GS) moves out of an MBS service area, the UE may be effectively restricted from using the MBS.

DETAILED DESCRIPTION

The operation principle of the disclosure will be described below in detail with reference to the accompanying drawings. A detailed description of a generally known function or structure of the disclosure will be avoided lest it should obscure the subject matter of the disclosure. Although the terms as described later are defined in consideration of functions in the disclosure, the terms may be changed according to the intention of a user or an operator, or customs. Therefore, the definitions should be made, not simply by the actual terms used but by the meanings of each term lying within.

In the following description, a term identifying an access node, terms indicating network entities, terms indicating messages, a term indicating an interface between network objects, terms indicating various types of identification information, and so on are provided by way of example, for convenience of description. Accordingly, the disclosure is not limited to the terms described below, and other terms indicating objects having equivalent technical meanings may be used.

For convenience of description below, terms and names defined in the standards for a 5thgeneration system (5GS) are used in the disclosure. However, the disclosure is not limited by the above terms and names, and may be equally applied to systems conforming to other standards.

There are two methods of delivering multicast and broadcast service (MBS) data to a next generation radio access network (NG-RAN) in a 5G core network: shared delivery and individual delivery. When the NG-RAN has an MBS capability, the MBS data may be transmitted from a multicast and broadcast user plane function (MB-UPF) device to the NG-RAN through a tunnel for shared delivery.

On the contrary, when the NG-RAN does not have the MBS capability, shared delivery is impossible. Therefore, MBS data received through the MB-UPF may be transmitted to a UE in an associated PDU session through a tunnel from a corresponding UPF to the NG-RAN by individual delivery.

Accordingly, for a UE receiving the MBS from an NG-RAN within an MBS service area, when the NG-RAN has no MBS capability, the NG-RAN transmits MBS data to the UE by individual delivery. When the UE moves out of the MBS service area, a method for discontinuing the MBS data delivery to the UE is required.

FIG.1illustrates a diagram of a situation in which MBS traffic control is required when a UE moves out of an MBS service area in a wireless communication system according to an embodiment of the disclosure.

When a UE which has received multicast traffic within a service area in the individual delivery method moves out of the service area, the UE may not receive the multicast traffic.

Referring toFIG.1, a wireless communication (or cellular) system may include a UE100, NG-RANs110and115as base stations (BSs), an access and mobility management function (AMF) device120, a protocol data unit (PDU) session management function (SMF) device130, a user plane function (UPF) device140of a PDU session, an multicast and broadcast-session management function (MB-SMF) device150, a multicast and broadcast-user plane function (MB-UPF) device160, a data network (DN)170, and an application function (AF)/application server (AS)180.

In describingFIG.1, each network function (NF) of a 5G system (5GS) will be described as a “network function device” or “network function”. However, those skilled in the art will understand that an NF and/or an NF device may be implemented in one or more specific servers, and that two or more NFs performing the same operation may be implemented in one server.

One NF or two or more NFs may be implemented in the form of one network slice in some cases. A network slice may be created based on a specific purpose. For example, a network slice may be configured to provide the same type of service to specific subscriber groups. For example, a network slice may be configured for a subscriber group to provide at least one of a maximum data rate, a data usage, or a guaranteed minimum data rate. In addition, a network slice may be implemented according to various purposes.

InFIG.1, an interface for a control message between nodes is marked with a thin dotted line, and a path through which data traffic is transmitted is marked with a thick line. For example, multicast data traffic may be delivered from the AF/AS180to the MB-UPF160. On the assumption that a serving NG-RAN (S-NG-RAN)110of the UE100does not have an MBS capability, the multicast data traffic may be transmitted to the S-NG-RAN110through the UPF140, and then to the UE100in the individual delivery method. General data traffic may be provided to the UE100through the DN170, the UPF140, and the S-NG-RAN110through an associated PDU session used for the individual delivery method. However, when the UE100moves out of an MBS service area (i.e., when the UE100is serviced by a target NG-RAN (T-NG-RAN)115outside the MBS service area), multicast data traffic should be controlled not to be transmitted to the T-NG-RAN115, although the general data traffic is still serviced to the UE100.

In general, to support the MBS in the 5GS, a cellular system for the MBS may be configured with the following NF devices and services.

The AF/AS180may be implemented, for example, as at least one of a vehicle to everything (V2X) application server, a consumer Internet of things (CIoT) application server, a mission critical push to talk (MCPTT) application, a content provider, a TV or audio service provider, or a streaming video service provider.

When requesting a multicast service from the MB-SMF150, the AF/AS180may request multicast service area (or MBS service area) information. The MB-SMF150may manage a multicast session, allocate a temporary mobile group identity (TMGI) to the multicast session, and control the MB-UPF160. The MB-UPF160may serve as a user plane function that receives data traffic for a multicast session and transmits the data traffic.

When the UE100wants to join the multicast session, the UE100may request to join the multicast session by a PDU session modification request message. Upon receipt of the multicast session join request, the SMF130may obtain context information about the multicast session from the MB-SMF150and manage mapping between the multicast session and a PDU session. The PDU session may be referred to as an associated PDU session.

The SMF130may store mapping information between a multicast session ID and a PDU session ID from a multicast session context, and mapping information between multicast quality of service (QoS) flow information in the case of the shared delivery method and unicast QoS flow information in the case of the individual delivery method, for delivery of multicast session traffic. The SMF130may apply QoS according to a used transmission method (the shared delivery method or the individual delivery method). A unicast QoS flow applied to the PDU session may be referred to as an associated QoS flow.

The SMF130may store a downlink (DL) packet detection rule (PDR) including a service data flow (SDF) template for mapping an SDF of a multicast session to an associated QoS flow. The SMF130may transmit the DL PDR to the UPF140, and when the individual delivery method is used, control to apply multicast service traffic through the associated QOS flow of the associated PDU session according to the associated QoS flow information, that is, a QoS profile.

In this specification, multicast session and MBS session are used interchangeably in the same meaning, and multicast session ID and MBS session ID are used interchangeably in the same meaning for specifying a multicast session. In addition, multicast service area and MBS service area are used interchangeably in the same meaning of an area allowing reception of a multicast service.

FIGS.2A and2Billustrate diagrams of a process of restricting MBS traffic transmission when a UE moves out of an MBS service area in a wireless communication system according to an embodiment of the disclosure.

According to an embodiment of the disclosure, when a network recognizes that a UE receiving multicast traffic (or MBS traffic) in the individual delivery method has moved out of a service area, the network may restrict the multicast traffic transmission.

Referring toFIGS.2A and2B, a multicast traffic control process may be performed through an associated PDU session used for the individual delivery method. According to an embodiment, when a UE200requests to join a multicast session, an SMF230may directly or indirectly perform event subscription in a PDU session modification procedure to request a notification from an AMF220and thus obtain location information about the UE200, when the UE200moves out of an MBS service area.

According to an embodiment, when the UE200requests to join the multicast session, the SMF230may recognize that the UE200is located outside the service area by an implicit subscription method, and delete an associated QoS flow (Alt 1).

According to another embodiment, the SMF230may recognize that the UE200is located outside the service area by an explicit subscription method, and delete the associated QoS flow (Alt 2).

Referring toFIG.2A, according to an embodiment, the AMF220may transmit an Nsmf_PDUSession_UpdateSMcontext request message (including a join request and an MBS session ID) to the SMF230in step1-1. Upon receipt of the join request, the SMF230may store (or generate), as an MBS session context for the MBS session ID, at least one of MBS service area information, mapping information between the MBS session ID and an associated PDU session ID, mapping information between multicast QoS flow information and associated QoS flow information, or updated QoS flow information for a PDU session, based on an MBS session context received from an MB-SMF. The MBS service area information may be a TAI list, a cell ID list, or an NG-RAN node ID list, the QoS flow information may include a QoS flow identifier (QFI) and a QoS profile, and the QoS profile may include information indicating a guaranteed bit rate (GBR) or a non-GBR, a 5G QoS Identifier (5QI), an allocation and retention priority (ARP), a guaranteed flow bit rate (GFBR), and a maximum flow bit rate (MFBR). The SMF230may store a DL PDR including an SDF template for mapping SDFs of the multicast session to the associated QoS flow.

An SDF template mapped to the associated QoS flow may include multicast IP address information and port information, or unicast IP address information and port information, or lower layer multicast address (LL MC address) information, for providing multicast data from an MB-UPF, which is a user plane anchor for the MBS session, to a UPF240. When individual delivery is applied, the SMF230may transmit, to a UE200, the MBS session ID, and the multicast IP address information and port information, the unicast IP address information and port information, or the LL MC address information, for the MBS session ID, which is information for receiving multicast traffic from the MB-UPF for the multicast session, along with the information about the SDF template mapped to the associated QoS flow in an N4 session establishment or N4 session modification process.

The UPF240may receive multicast traffic corresponding to the multicast session from the MB-UPF according to the information received from the SMF230, and deliver the multicast traffic to the UE200through the associated PDU session. The UPF240may receive one copy of the multicast traffic provided by the MB-UPF, for each MBS session, copy the multicast traffic to the associated PDU session of each UE joining the MBS session, and forward the copy, without the need for receiving the multicast traffic for each UE from the MB-UPF.

In step1-2, the SMF230may respond to the NG-RAN210with an Nsmf_PDUSession_UpdateSMcontext response message including at least one of the MBS service area information, the MBS session ID, or the mapping information between the MBS session ID and the PDU session ID to the AMF220. The SMF230may transmit the MBS service area information, the MBS session ID, the mapping information between the MBS session ID and the PDU session ID, the mapping information between the multicast QoS flow information and the associated QoS flow information, and the updated QoS flow information for the PDU session in an N2 SM container. Upon receipt of the Nsmf_PDUSession_UpdateSMcontext response message, the AMF220may notify the SMF230of the UE's movement out of the indicated MBS service area, when the UE200moves out of the MBS service area, as in step5-1.

According to another embodiment, in step2-1, the SMF230may directly transmit a Namf_EventExposure_subscribe message (including at least one of MBS service area information, the MBS session ID, or a notification correlation ID) to the AMF220to subscribe to event notification, so that when the UE200moves out of the MBS service area, a notification may be received. As in step2-2, the SMF230subscribed to the event notification may store mapping information between the MBS session ID and the notification correlation ID to determine an MBS session for which a notification is. When the UE200moves out of the MBS service area, the AMF220may notify the SMF230of the UE's movement as in step6-1.

When the UE200moves out of the MBS service area as in step3, the AMF220may recognize that the UE200has moved out of the MBS service area from information transmitted by the NG-RAN210in step4.

According to an embodiment, when a notification of a situation in which the UE200moves out of the MBS service area is requested indirectly as in steps1-1and1-2, the AMF220may notify the SMF230controlling the associated PDU session mapped to the MBS session that “the UE200has moved out of the MBS service area corresponding to the MBS session ID” by an Nsmf_PDUSession_UpdateSMcontext req message (indication=“UE out of service area”, [UE location] included).

The Nsmf_PDUSession_UpdateSMcontext req message may include an indication indicating that the UE200has moved out of the service area or location information about the UE200(e.g., a TAI, a cell ID, or an NG-RAN node ID of an NG-RAN to which the UE has moved), and may additionally include the MBS session ID.

Upon receipt of the Nsmf_PDUSession_UpdateSMcontext req message, the SMF230may recognize that the UE200has moved out of the service area of the multicast session as in step5-2. To control the UE200not to receive multicast service data through the associated PDU session mapped to the multicast session, the SMF230may delete the stored associated QoS flow of the associated PDU session mapped to the multicast QoS flow information of the multicast session, and the SDF template corresponding to the associated QoS flow in step5-2.

Even though the SMF230does not delete the associated QoS flow and the SDF template corresponding to the associated QoS flow, the UPF240which has received the multicast data traffic from the MB-UPF may control not to forward multicast data traffic corresponding to the DL PDR including the SDF template for the associated QoS flow of the associated PDU session of the UE200to the associated PDU session of the UE100or to drop the multicast data traffic. For example, the SMF230may transmit/receive an N4 Session Modification request/response to/from the UPF240so that an SDF corresponding to multicast data traffic from the multicast session may not be forwarded to the associated PDU session of the UE200or the multicast data traffic may be dropped, and thus the UE100may not receive any more multicast data, as in step5-3.

In step5-4, the SMF230may transmit updated QoS flow information in an N2 SM container of a Nsmf_PDUSession_UpdateSMcontext response message to the AMF220and the NG-RAN210. The SMF230may perform a PDU session modification procedure as in step7to synchronize the QoS flow information between the UE200and the network.

According to another embodiment, when the SMF230has directly requested an event notification for a situation in which the UE200moves out of the MBS service area from the AMF220as in steps2-1and2-2, the AMF220may indicate that the UE200has moved out of the MBS service area as in the requested event to the SMF230which has subscribed to the event notification by a Namf_EventExposure_Notify message (including at least one of the notification correlation ID, a UE location, or the MBS session ID) as in step6-1.

The Namf_EventExposure_Notify message may include event information indicating that the UE200has moved out of the service area, the notification correlation ID generated in step2-1during the subscription to the event notification, or location information about the UE200(e.g., a TAI, a cell ID or an NG-RAN node ID of an NG-RAN to which the UE has moved), may further include the MBS session ID, and may be delivered to the SMF230.

Upon receipt of the Namf_EventExposure_Notify message, the SMF230may recognize that the UE200has moved out of the service area of the multicast session, for the MBS session corresponding to the notification correlation ID as in step6-2. To control the UE200not to receive multicast service data through the associated PDU session mapped to the multicast session, the SMF230may delete the associated QoS flow of the associated PDU session mapped to the multicast QoS flow information of the multicast session, and the SDF template corresponding to the associated QoS flow, stored in the SMF230in step6-2.

Even though the SMF230does not delete the associated QoS flow and the SDF template corresponding to the associated QoS flow, the UPF240which has received the multicast data traffic from the MB-UPF may control not to forward multicast data traffic corresponding to the DL PDR including the SDF template for the associated QoS flow of the associated PDU session to the associated PDU session of the UE200or to drop the multicast traffic. For example, as in step6-3, the SMF230may transmit/receive an N4 Session Modification request/response to/from the UPF240so that an SDF corresponding to multicast data traffic from the multicast session may not be forwarded to the associated PDU session of the UE200or the multicast data traffic may be dropped, and thus the UE100may not receive any more multicast data.

As in step7, the SMF230may perform the PDU session modification procedure to synchronize the updated QoS flow information between the UE200and the network. The QoS flow information may be synchronized among the UE200, the NG-RAN210, and the core network in step7.

FIGS.3A and3Billustrate diagrams of a process of restricting MBS traffic transmission when a UE moves out of an MBS service area through handover according to an embodiment of the disclosure.

When a UE, which has received a multicast traffic service in the individual delivery method, moves out of a service area through Xn handover, a network may recognize the UE being out of the service area and restrict transmission of the multicast traffic to the UE.

Referring toFIG.3A, an SMF340may indirectly perform event subscription to an AMF330to request a notification in the case of a UE300out of an MBS service area in the process of processing a join request for a multicast session from the UE300to receive a multicast session service.

In step1-1, the UE300may request to join the multicast session by a PDU session modification request. When the AMF330transmits an Nsmf_PDUSession_UpdateSMcontext request message (including a join request and an MBS session ID) to the SMF340in step1-2, in the absence of an MBS session context for the multicast session ID for which the request is made, the SMF340may obtain multicast QoS flow information for the multicast session from an MB-SMF350in step1-3.

In step1-3, the SMF340may obtain mapping information between multicast QoS flow information for the multicast session and QoS flow information for an associated PDU session, or may request the QoS flow information for the associated PDU session corresponding received multicast QoS flow information from a PCF and receive the received QoS flow information for the associated PDU session. The SMF340may obtain the mapping information by autonomously generating the QoS flow information for the associated PDU session based on the received multicast QoS flow information.

In step1-4, the SMF340may store (or generate), as an MBS session context, at least one of MBS service area information for the MBS session ID, mapping information between the MBS session ID and an associated PDU session ID, mapping information between the multicast QoS flow information and the associated QoS flow information, or updated QoS flow information for a PDU session. The MBS service area information may be a TAI list, a cell ID list, or an NG-RAN node ID list, the QoS flow information may include a QFI and a QoS profile, and the QoS profile may include information indicating a GBR or a non-GBR, a 5QI, an ARP, a GFBR, and an MFBR.

The SMF340may store a DL PDR including an SDF template for mapping an SDF of the multicast session to an associated QoS flow. For example, the SDF template mapped to the associated QoS flow may include multicast IP address information and port information, or unicast IP address information and port information, or LL MC address information, for providing multicast data from an MB-UPF370, which is a user plane anchor for the MBS session, to a UPF360.

In step1-5, the SMF340may transmit an Nsmf_PDUSession_UpdateSMcontext response message including at least one of the MBS service area information, the MBS session ID, or the mapping information between the MBS session ID and the PDU session ID to the AMF330. The SMF340may respond to an NG-RAN with at least one of the MBS service area information, the MBS session ID, the mapping information between the MBS session ID and the PDU session ID, the mapping information between the multicast QoS flow information and the associated QoS flow information, or the updated QoS flow information for the PDU session in an N2 SM container. Upon receipt of the Nsmf_PDUSession_UpdateSMcontext response message, the AMF330may perform a multicast traffic transmission procedure with an NG-RAN node as in step1-6.

Subsequently, when the UE300receives a service from an S-NG-RAN310that does not support an MBS function, multicast data may be transmitted to the UE300through the associated PDU session in the individual delivery method as in step2. When the UE300performs Xn handover from the S-NG-RAN310to a T-NG-RAN320outside the multicast service area in steps3and4, the T-NG-RAN320may request data path switch by transmitting an N2 path switch request (including a UE location) to a core network as in step5. Upon receipt of the data path switch request, the AMF330may recognize that the UE200has moved out of the MBS service area as in step6.

In step7, the AMF330may transmit an Nsmf_PDUSession_UpdateSMcontext req message (indication=“UE out of service area”, [UE location] included) to the SMF340controlling the associated PDU session mapped to the MBS session. The Nsmf_PDUSession_UpdateSMcontext req message may include an indication indicating that the UE300has moved out of the service area or location information about the UE300(e.g., a TAI, a cell ID, or an NG-RAN node ID of an NG-RAN to which the UE has moved), and further include the MBS session ID.

Upon receipt of the Nsmf_PDUSession_UpdateSMcontext req message, the SMF340may recognize that the UE300has moved out of the service area of the multicast session as in step8. To control the UE300not to receive multicast service data through the associated PDU session mapped to the multicast session, the SMF340may delete the stored associated QoS flow of the associated PDU session mapped to the multicast QoS flow information for the multicast session, and the SDF template corresponding to the associated QoS flow.

Even though the SMF340does not delete the associated QoS flow and the SDF template corresponding to the associated QoS flow, the UPF360which has received the multicast data traffic from the MB-UPF may control not to forward multicast data traffic corresponding to the DL PDR including the SDF template for the associated QoS flow of the associated PDU session of the UE300to the associated PDU session to the UE100or to drop the multicast data traffic. For example, the SMF340may transmit/receive an N4 Session Modification request/response to/from the UPF360so that the SDF corresponding to multicast data traffic from the multicast session may not be forwarded to the associated PDU session of the UE300or the multicast data traffic may be dropped, and thus the UE300may not receive any more multicast data, as in step9.

In step10, the UPF360may transmit an N3 End marker message to the S-NG-RAN310, and the S-NG-RAN310may forward the message to the T-NG-RAN320.

As in steps11and12, the SMF340may transmit updated QoS flow information to the AMF330and the T-NG-RAN320in an N2 SM container of a Nsmf_PDUSession_UpdateSMcontext response message, so that the updated QoS flow information may be applied. Upon receipt of an N2 path switch request ACK in step12, the T-NG-RAN320may complete the handover by allowing the S-NG-RAN310to release resources in step13.

Since QoS flow information has been changed in the network, the SMF340may perform a PDU session modification procedure to synchronize the QoS flow information between the UE300and the network as in step14.

In step14-1, the SMF340may transmit and receive a Namf_Communication_N1M2Message Transfer message to and from the AMF330. In step14-2, the AMF330may transmit an N1 SM container including a PDU Session Modification Command to the T-NG-RAN320by a DL NAS message, and the T-NG-RAN320may transmit the DL NAS message to the UE300. In step14-3, the UE300may transmit an N1 SM container including a PDU Session Modification Command ack to the T-NG-RAN320by a UL NAS message, and the T-NG-RAN320may transmit a UL A NAS message to the AMF330.

In step14-4, the AMF330may transmit and receive an Nsmf_PDUSession_UpdateSMcontext request/response message to and from the SMF340, and in step14-5, the SMF340may transmit/receive an N4 Session Modification request/response message to and from the UPF360.

FIGS.4A and4Billustrate diagrams of a process of restricting MBS traffic transmission when a UE moves out of an MBS service area through handover according to another embodiment of the disclosure.

According to an embodiment of the disclosure, when a UE, which has received a multicast traffic service in the individual delivery method, moves out of a service area through Xn handover, a network may recognize the UE being out of the service area, and restrict transmission of multicast traffic to the UE.

Referring toFIG.4A, an SMF440may directly perform event subscription to an AMF430to request a notification in the case of a UE400out of an MBS service area.

As in step1, the UE400may request to join a multicast session by a PDU session modification request, to receive a multicast session service. When the AMF430transmits an Nsmf_PDUSession_UpdateSMcontext request message (including a join request and an MBS session ID) to the SMF440in the process of processing the join request for the multicast session, in the absence of an MBS session context for the multicast session ID for which the request is made, the SMF440receiving the join request may obtain multicast QoS flow information for the multicast session from an MB-SMF450.

The SMF440may obtain mapping information between the multicast QoS flow information for the multicast session and QoS flow information for an associated PDU session. The SMF440may request the QoS flow information for the associated PDU session corresponding the multicast QoS flow information from a PCF and receive the QoS flow information for the associated PDU session corresponding to the multicast QoS flow information. The SMF440may obtain the mapping information by autonomously generating the QoS flow information for the associated PDU session based on the multicast QoS flow information.

In step1-1, the SMF440may store (or generate), as an MBS session context for the MBS session ID, at least one of MBS service area information for the MBS session ID, mapping information between the MBS session ID and an associated PDU session ID, the mapping information between the multicast QoS flow information and the associated QoS flow information, or updated QoS flow information for a PDU session.

The MBS service area information may be a TAI list, a cell ID list, or an NG-RAN node ID list, the QoS flow information may include a QFI and a QoS profile, and the QoS profile may include information indicating a GBR or a non-GBR, a 5QI, an ARP, a GFBR, and an MFBR.

The SMF440may store a DL PDR including an SDF template for mapping an SDF of the multicast session to the associated QoS flow. For example, the SDF template mapped to the associated QoS flow may include at least one of multicast IP address information and port information, unicast IP address information and port information, or LL MC address information, for providing multicast data from an MB-UPF470, which is a user plane anchor for the MBS session, to a UPF460.

When the SMF440transmits a response to the AMF430by an Nsmf_PDUSession_UpdateSMcontext response message, the SMF440may transmit at least one of the MBS service area information, the MBS session ID, or the mapping information between the MBS session ID and the PDU session ID. The SMF440may respond to an NG-RAN with at least one of the MBS service area information, the MBS session ID, the mapping information between the MBS session ID and the PDU session ID, the mapping information between the multicast QoS flow information and the associated QoS flow information, or updated QoS flow information for the PDU session in an N2 SM container. Upon receipt of the Nsmf_PDUSession_UpdateSMcontext response message, the AMF430may perform a multicast traffic transmission procedure with an NG-RAN node.

When the UE400is located in a T-NG-RAN420that does not support an MBS function after joining, the SMF440transmits multicast data to the UE400in the individual delivery method. In step2, the SMF440may subscribe to event notification, requesting a notification in the case of the UE400being out of the MBS service area by directly transmitting a Namf_EventExposure_subscribe message (including at least one of the MBS service area information, the MBS session ID, or a notification correlation ID) to the AMF430.

As in step3, the SMF440which has subscribed to the event notification may store the mapping information between the MBS session ID and the notification correlation ID, to identify an MBS session for which a received notification is. When the UE400moves out of the MBS service area, the AMF430may notify the SMF440of the UE400being out of the MBS service area.

As in step4, when the UE400is located in the T-NG-RAN420that does not support the MBS function, multicast data may be transmitted to the UE400through the associated PDU session in the individual delivery method.

When the UE300performs Xn handover to the T-NG-RAN420outside the multicast service area in steps5and6, the T-NG-RAN420may request data path switch by transmitting an N2 path switch request (including a UE location) to a core network as in step7. Upon receipt of the data path switch request, the AMF430may recognize that the UE400has moved out of the MBS service area.

The AMF430may transmit a Nsmf_PDUSession_UpdateSMcontext req message to the SMF440controlling the associated PDU session in step8, and notify the UPF460of an associated change to modify a data path tunnel for the associated PDU session as in step9. In step10, the UPF460may transmit an N3 End marker message to an S-NG-RAN410, and the S-NG-RAN410may forward the message to the T-NG-RAN420.

As in steps11and12, the SMF440may transmit updated QoS flow information and tunnel endpoint information in an N2 SM container of a Nsmf_PDUSession_UpdateSMcontext response message to the AMF430and the T-NG-RAN420in a handover procedure. The T-NG-RAN420may receive an N2 path switch request ACK in step12and complete the handover by allowing the S-NG-RAN410to release resources in step13.

The AMF430, which has received the N2 path switch request message (including the UE location) from the T-NG-RAN420in step7according to the handover procedure may recognize that the UE400has moved out of the multicast service area as in step14. Because the SMF440has subscribed to the event notification for the case of the UE400being out of the multicast service area, the AMF430may transmit a Namf_EventExposure_Notify message (including the notification correlation ID, the UE location, and the MBS session ID) indicating “the UE out of the MBS service area” to the SMF440subscribed to the event notification.

The Namf_EventExposure_Notify message may include event information indicating the UE400being out of the service area, the notification correlation ID generated in step2during the subscription to the event notification, or location information about the UE400(e.g., a TAI, a cell ID, or an NG-RAN node ID of an NG-RAN to which the UE has moved), further include MBS session ID information, and be transmitted to the SMF440.

As in step16, upon receipt of the Namf_EventExposure_Notify message, the SMF440may recognize that the UE400has moved out of the service area of the multicast session, for the MBS session corresponding to the notification correlation ID, and control the UE400not to receive multicast service data through the associated PDU session mapped to the multicast session. The SMF440may delete the associated QoS flow of the associated PDU session mapped to the stored multicast QoS flow information for the multicast session, and the SDF template corresponding to the associated QoS flow.

Even though the SMF440does not delete the associated QoS flow and the SDF template corresponding to the associated QoS flow, the UPF460which has received the multicast data traffic from the MB-UPF470may control not to forward multicast data traffic corresponding to the DL PDR including the SDF template for the associated QoS flow of the associated PDU session of the UE400or to drop the multicast data traffic. For example, the SMF440may transmit/receive an N4 Session Modification request/response to/from the UPF460so that the SDF corresponding to multicast data traffic from the multicast session may not be forwarded to the associated PDU session of the UE400or the multicast data traffic may be dropped, and thus the UE300may not receive any more multicast data, as in step17.

As in step18, the SMF440may perform a PDU session modification procedure to synchronize updated QoS flow information between the UE400and the network (steps18-1to18-5), and the QoS flow information may be synchronized among the UE400, the NG-RAN420, and the core network.

According to an embodiment, steps14to17may be performed in parallel with or before the handover procedure, that is, steps8to13. Accordingly, when messages generated in the two procedures overlap, the messages may be integrated into one message and transmitted.

FIGS.5A and5Billustrate diagrams of a process of restricting MBS traffic transmission when a UE moves out of an MBS service area through handover according to another embodiment of the disclosure.

When a UE500, which has received a multicast traffic service in the individual delivery method, moves out of a service area through N2 handover, a network may recognize the UE being out of the service area, and restrict transmission of the multicast traffic to the UE500. An S-NG-RAN510that provides a service to the UE500may be switched to a T-NG-RAN520, and a serving AMF (S-AMF)530may be switched to a target AMF (T-AMF)580through the N2 handover.

Referring toFIG.5A, an SMF540may indirectly perform event subscription to the S-AMF530to request a notification in the case of the UE500out of an MBS service area in the process of processing a join request for a multicast session from the UE500to receive a multicast session service, as in step1-1. In step1-1, the UE500may request to join the multicast session by a PDU session modification request. When the S-AMF530transmits an Nsmf_PDUSession_UpdateSMcontext request message (including a join request and an MBS session ID) to the SMF540in step1-2, in the absence of an MBS session context for the multicast session ID for which the request is made, the SMF540receiving the join request may obtain multicast QoS flow information for the multicast session from an MB-SMF550in step1-3.

In step1-3, the SMF540may obtain mapping information between the multicast QoS flow information for the multicast session and QoS flow information for an associated PDU session. The SMF540may request the QoS flow information for the associated PDU session corresponding to the multicast QoS flow information from a PCF and receive the QoS flow information for the associated PDU session. The SMF540may obtain the mapping information by autonomously generating the QoS flow information for the associated PDU session based on the multicast QoS flow information.

The SMF540may store (or generate), as an MBS session context for the MBS session ID, at least one of MBS service area information for the MBS session ID, mapping information between the MBS session ID and an associated PDU session ID, mapping information between the multicast QoS flow information and the associated QoS flow information, or updated QoS flow information for the PDU session.

The MBS service area information may be a TAI list, a cell ID list, or an NG-RAN node ID list, the QoS flow information may include a QFI and a QoS profile, and the QoS profile may include information indicating a GBR or a non-GBR, a 5QI, an ARP, a GFBR, and an MFBR.

The SMF540may store a DL PDR including an SDF template for mapping an SDF of the multicast session to an associated QoS flow.

The SDF template mapped to the associated QoS flow may include multicast IP address information and port information, unicast IP address information and port information, or LL MC address information, for providing multicast data from an MB-UPF570, which is a user plane anchor for the MBS session, to a UPF560.

In step1-5, the SMF540may transmit an Nsmf_PDUSession_UpdateSMcontext response message including at least one of the MBS service area information, the MBS session ID, or the mapping information between the MBS session ID and the PDU session ID, as a response to the S-AMF530.

The SMF540may respond to an NG-RAN with at least one of the MBS service area information, the MBS session ID, the mapping information between the MBS session ID and the PDU session ID, the mapping information between the multicast QoS flow information and the associated QoS flow information, or updated QoS flow information for the PDU session in an N2 SM container.

Upon receipt of the Nsmf_PDUSession_UpdateSMcontext response message, the S-AMF530may perform a multicast traffic transmission procedure with an NG-RAN node as in step1-6.

When the UE500receives a service from the S-NG-RAN510that does not support an MBS function, multicast data may be transmitted to the UE500through the associated PDU session in the individual delivery method as in step2. When the UE500performs N2 handover to the T-NG-RAN520outside the multicast service area, the S-AMF530may transmit a handover command message to the UE500through the S-NG-RAN510as in step4in a handover preparation process in step3, and the UE500may transmit a handover confirm message to the T-NG-RAN520as in step5.

As in step6, the T-NG-RAN520may transmit a handover notify message to the T-AMF580. Upon receipt of the handover notify message, the T-AMF580may notify successful handover of the UE500to the T-NG-RAN520.

In step7, the T-AMF580may notify the S-AMF530of the successful handover to the T-NG-RAN520by a Namf_Communication_N2InfoNotify message, and the S-AMF530may delete a UE context existing in the S-NG-RAN510as in step14.

Upon receipt of the message in step6, the T-AMF580may recognize that the UE500has moved out of the multicast service area as in step8.

In step9, the T-AMF580may transmit an Nsmf_PDUSession_UpdateSMcontext req message (indication=“UE out of service area”, [UE location] included) to the SMF540controlling the associated PDU session mapped to the MBS session.

The Nsmf_PDUSession_UpdateSMcontext req message may include an indication indicating that the UE500has moved out of the service area or location information about the UE500(e.g., a TAI, a cell ID, or an NG-RAN node ID of an NG-RAN to which the UE has moved), further include the MBS session ID, and be transmitted to the SMF530.

Upon receipt of the Nsmf_PDUSession_UpdateSMcontext req message, the SMF530may recognize that the UE500has moved out of the service area of the multicast session and control the UE500not to receive multicast service data through the associated PDU session mapped to the multicast session as in step10. The SMF540may delete the associated QoS flow of the associated PDU session mapped to the stored multicast QoS flow information for the multicast session, and the SDF template corresponding to the associated QoS flow.

Even though the SMF530does not delete the associated QoS flow and the SDF template corresponding to the associated QoS flow, the UPF560which has received the multicast data traffic from the MB-UPF570may control not to forward multicast data traffic corresponding to the DL PDR including the SDF template for the associated QoS flow of the associated PDU session of the UE500to the associated PDU session to the UE100or drop the multicast data traffic. For example, the SMF540may transmit/receive an N4 Session Modification request/response to/from the UPF560so that the SDF corresponding to multicast data traffic from the multicast session may not be forwarded to the associated PDU session of the UE500or the multicast data traffic may be dropped, and thus the UE300may not receive any more multicast data, as in step11.

In step12, the SMF540may transmit a Nsmf_PDUSession_UpdateSMcontext response message (including the PDU session ID) to the T-AMF580, to notify that the handover is confirmed. When the UE500has moved to a new registration area, a registration procedure is performed as in step13.

Since the QoS flow information has been changed in the network, the SMF540may perform a PDU session modification procedure to synchronize the QoS flow information between the UE300and the network as in step15.

Steps15-1to15-4are performed in the same manner as descried before, and thus will not be described herein in detail.

According to an embodiment, step15may be performed after step12, or together with the registration procedure of step13without being performed separately. Accordingly, when messages generated in the two processes overlap, they may be integrated into one message and transmitted.

FIGS.6A and6Billustrate diagrams of a process of restricting MBS traffic transmission when a UE moves out of an MBS service area through handover according to another embodiment of the disclosure.

When a UE, which has received multicast traffic (or MBS traffic in the individual delivery method, moves out of a service area through N2 handover, a network may recognize the UE being out of the service area and restrict transmission of the multicast traffic to the UE.

Referring toFIGS.6A and6B, an SMF640may directly perform event subscription to an S-AMF630to request a notification in the case of a UE600out of an MBS service area.

As in step1, the UE600may request to join a multicast session by a PDU session modification request, to receive a multicast session service. The S-AMF630may transmit an Nsmf_PDUSession_UpdateSMcontext request message (including a join request and an MBS session ID) to the SMF640. In the absence of an MBS session context for the multicast session ID for which the request is made, the SMF640receiving the join request may obtain multicast QoS flow information for the multicast session from an MB-SMF650. Further, the SMF640may obtain mapping information between multicast QoS flow information for the multicast session and QoS flow information for an associated PDU session, or may request the QoS flow information for the associated PDU session corresponding the multicast QoS flow information from a PCF and receive the QoS flow information for the associated PDU session. The SMF640may obtain the mapping information by autonomously generate the QoS flow information for the associated PDU session based on the multicast QoS flow information.

As in step1-1, the SMF640may store (or generate), as an MBS session context for the MBS session ID, at least one of MBS service area information, the MBS session ID, mapping information between the MBS session ID and an associated PDU session ID, mapping information between the multicast QoS flow information and the associated QoS flow information, or updated QoS flow information for the PDU session.

The MBS service area information may be a TAI list, a cell ID list, or an NG-RAN node ID list, the QoS flow information may include a QFI and a QoS profile, and the QoS profile may include information indicating a GBR or a non-GBR, a 5QI, an ARP, a GFBR, and an MFBR

The SMF640may store a DL PDR including an SDF template for mapping an SDF of the multicast session to the associated QoS flow.

The SDF template mapped to the associated QoS flow may include multicast IP address information and port information, unicast IP address information and port information, or LL MC address information, for providing multicast data from an MB-UPF670, which is a user plane anchor for the MBS session, to a UPF660.

The SMF640may transmit an Nsmf_PDUSession_UpdateSMcontext response message including at least one of the MBS service area information, the MBS session ID, or the mapping information between the MBS session ID and the PDU session ID, as a response to the S-AMF630.

The SMF640may respond to an NG-RAN with at least one of the MBS service area information, the MBS session ID, the mapping information between the MBS session ID and the PDU session ID, the mapping information between the multicast QoS flow information and the associated QoS flow information, or updated QoS flow information for the PDU session in an N2 SM container. Upon receipt of the Nsmf_PDUSession_UpdateSMcontext response message, the S-AMF630may perform a multicast traffic transmission procedure with an NG-RAN node.

When the UE600is located in a T-NG-RAN620that does not support an MBS function after joining, the SMF640may transmit multicast data to the UE600through the associated PDU session in the individual delivery method.

In step2, the SMF640may subscribe to event notification, requesting a notification in the case of the UE600being out of the MBS service area by directly transmitting a Namf_EventExposure_subscribe message (including at least one of the MBS service area information, the MBS session ID, or a notification correlation ID) to the S-AMF630.

The subscribe message may include the MBS service area information, the MBS session ID, and the notification correlation ID. As in step3, the SMF640subscribed to the event notification may store mapping information between the MBS session ID and the notification correlation ID, to identify an MBS session for which a received notification is. When the UE600moves out of the MBS service area, the AMF430may notify the SMF640of the UE600being out of the MBS service area.

As in step4, when the UE600is located in an S-NG-RAN610that does not support the MBS function, multicast data may be transmitted to the UE600through the associated PDU session in the individual delivery method.

When the UE600performs N2 handover to the T-NG-RAN620outside the multicast service area, the S-AMF630may transmit a handover command message to the UE600through the S-NG-RAN610as in step6in a handover preparation process in step5, and the UE600may transmit a handover confirm message to the T-NG-RAN620in step7.

In step8, the T-NG-RAN620may transmit a handover notify message to the T-AMF680. Upon receipt of the handover notify message, the T-AMF680may notify successful handover of the UE600to the T-NG-RAN620.

In step9, the T-AMF680may notify the successful handover to the T-NG-RAN620to the S-AMF630by a Namf_Communication_N2InfoNotify message, and the S-AMF630may delete a UE context existing in the S-NG-RAN610as in step14.

Upon receipt of the message in step8, the T-AMF680may recognize that the UE600has moved out of the multicast service area as in step15. In step10, the T-AMF680may transmit an Nsmf_PDUSession_UpdateSMcontext req message to the SMF640and thus apply the message to the UPF660as in step11. The SMF640may notify the T-AMF680that the handover is confirmed by transmitting a Nsmf_PDUSession_UpdateSMcontext response message (including the PDU session ID) to the T-AMF680. When the UE600has moved to a new registration area, a registration procedure may be performed as in step13.

Upon receipt of the handover notify message from the T-NG-RAN620in step8according to the handover procedure, the T-AMF680may recognize that the UE600has moved out of the multicast service area as in step15. Because the SMF640has subscribed to the event notification for the case of the UE600being out of the multicast service area, the T-AMF680may transmit a Namf_EventExposure_Notify message (including the notification correlation ID, the UE location, and the MBS session ID) indicating “the UE out of the MBS service area” to the SMF640subscribed to the event notification.

The Namf_EventExposure_Notify message may include event information indicating the UE600being out of the service area, the notification correlation ID generated in step2during the subscription to the event notification, or location information about the UE600(e.g., a TAI, a cell ID, or an NG-RAN node ID of an NG-RAN to which the UE has moved), further include the MBS session ID, and be transmitted to the SMF640. Upon receipt of the Namf_EventExposure_Notify message, the SMF640may recognize that the UE600has moved out of the service area of the multicast session, for the MBS session corresponding to the notification correlation ID as in step17, and control the UE600not to receive multicast service data through the associated PDU session mapped to the multicast session.

The SMF640may delete the associated QoS flow of the associated PDU session mapped to the stored multicast QoS flow information for the multicast session, and the SDF template corresponding to the associated QoS flow.

Even though the SMF640does not delete the associated QoS flow and the SDF template corresponding to the associated QoS flow, the UPF660which has received the multicast data traffic from the MB-UPF may control not to forward multicast data traffic corresponding to the DL PDR including the SDF template for the associated QoS flow of the associated PDU session of the UE600to the associated PDU session to the UE400or to drop the multicast data traffic. For example, the SMF640may transmit/receive an N4 Session Modification request/response to/from the UPF660so that the SDF corresponding to multicast data traffic from the multicast session may not be forwarded to the associated PDU session of the UE600or the multicast data traffic may be dropped, and thus the UE600may not receive any more multicast data, as in step18.

As in step19, the SMF640may perform a PDU session modification procedure to synchronize updated QoS flow information between the UE and the network, and the QoS flow information may be synchronized among the UE600, the NG-RAN, and the core network.

According to an embodiment, steps15to19may be performed in parallel with or before the handover procedure, that is, steps9to14. Accordingly, when messages generated in the two procedures overlap, the messages may be integrated into one message and transmitted.

FIGS.7A and7Billustrate diagrams of a process of restricting MBS traffic transmission when a UE moves out of an MBS service area in an idle state according to an embodiment of the disclosure.

When the UE moves out of the MBS service area in the idle state and then wakes up, an MBS service may be restricted for the UE.

Referring toFIG.7A, an SMF730may indirectly perform event subscription to an AMF720to request a notification in the case of a UE700out of an MBS service area in the process of processing a join request for a multicast session from the UE700to receive a multicast session service.

In step1-1, the UE700may request to join the multicast session by a PDU session modification request. When the AMF720transmits an Nsmf_PDUSession_UpdateSMcontext request message (including a join request and an MBS session ID) to the SMF730in step1-2, in the absence of an MBS session context for the multicast session ID for which the request is made, the SMF730receiving the join request may obtain multicast QoS flow information for the multicast session from an MB-SMF740in step1-3.

In step1-3, the SMF730may obtain mapping information between multicast QoS flow information for the multicast session and QoS flow information for an associated PDU session, or may request the QoS flow information for the associated PDU session corresponding the multicast QoS flow information from a PCF and receive the QoS flow information for the associated PDU session.

The SMF730may obtain the mapping information by autonomously generating the QoS flow information for the associated PDU session based on the multicast QoS flow information.

The SMF730may store (or generate), as an MBS session context for the MBS session ID, at least one of MBS service area information, the MBS session ID, mapping information between the MBS session ID and an associated PDU session ID, mapping information between the multicast QoS flow information and the associated QoS flow information, or updated QoS flow information for the PDU session.

The MBS service area information may be a TAI list, a cell ID list, or an NG-RAN node ID list, the QoS flow information may include a QFI and a QoS profile, and the QoS profile may include information indicating a GBR or a non-GBR, a 5QI, an ARP, a GFBR, and an MFBR.

The SW′730may store a DL PDR including an SDF template for mapping an SDF of the multicast session to the associated QoS flow.

An SDF template mapped to the associated QoS flow may include multicast IP address information and port information, unicast IP address information and port information, or LL MC address information, for providing multicast data from an MB-UPF760, which is a user plane anchor for the MBS session, to a UPF750.

In step1-5, when the SMF730transmits an Nsmf_PDUSession_UpdateSMcontext response message to the AMF720, the SMF730may also transmit the MBS service area information, the MBS session ID, and mapping information between the MBS session ID and the PDU session ID. The SMF340may respond to an NG-RAN with the MBS service area information, the MBS session ID, the mapping information between the MBS session ID and the PDU session ID, the mapping information between the multicast QoS flow information and the associated QoS flow information, and the updated QoS flow information for the PDU session in an N2 SM container. Upon receipt of the Nsmf_PDUSession_UpdateSMcontext response message, the AMF720may perform a multicast traffic transmission procedure with an NG-RAN node as in step1-6.

A situation in which the UE700is later switched to the idle state as in step2is considered. When the UE700moves and is to be switched to a connected state, the UE700may transmit a service request message to the AMF720through an NG-RAN710as in steps3and4. The NG-RAN710may transmit location information about the UE700by an N2 message to the AMF720in step4, and the AMF720may recognize that the UE700has moved out of the service area as in step5.

In step6, the AMF720may transmit an Nsmf_PDUSession_UpdateSMcontext req message (indication=“UE out of service area”, [UE location] included) to the SMF730controlling the associated PDU session mapped to the MBS session.

The Nsmf_PDUSession_UpdateSMcontext req message may include an indication indicating that the UE700has moved out of the service area or location information about the UE700(e.g., a TAI, an ID, or an NG-RAN node ID of an NG-RAN to which the UE has moved), further include the MBS session ID, and be transmitted to the SMF730.

Upon receipt of the Nsmf_PDUSession_UpdateSMcontext req message, the SMF730may recognize that the UE700has moved out of the service area of the multicast session, and control the UE700not to receive multicast service data through the associated PDU session mapped to the multicast session as in step7.

The SMF730may delete the associated QoS flow of the associated PDU session mapped to the stored multicast QoS flow information for the multicast session, and the SDF template corresponding to the associated QoS flow.

Even though the SMF730does not delete the associated QoS flow and the SDF template corresponding to the associated QoS flow, the UPF750which has received multicast data traffic from the MB-UPF760may control not to forward multicast data traffic corresponding to the DL PDR including the SDF template for the associated QoS flow of the associated PDU session of the UE700to the associated PDU session to the UE700or to drop the multicast data traffic. For example, the SMF730may transmit/receive an N4 Session Modification request/response to/from the UPF750so that the SDF corresponding to multicast data traffic from the multicast session may not be forwarded to the associated PDU session of the UE700or the multicast data traffic may be dropped, and thus the UE700may not receive any more multicast data, as in step8.

The SMF730may transmit a Nsmf_PDUSession_UpdateSMcontext response message (including N2 SM info) to the AMF720in step9, the AMF720may transmit an N2 request to the NG-RAN710, and the NG-RAN710may perform a service request-based procedure with the UE700, such as allocation of resources by signaling.

Since QoS flow information has been changed in the network, the SMF730may perform a PDU session modification procedure to synchronize the QoS flow information between the UE700and the network as in step16.

According to an embodiment, step16may be performed after step8or in parallel with steps9to15. Accordingly, when messages generated in the two procedures overlap, the messages may be integrated into one message and transmitted.

FIGS.8A and8Billustrate diagrams of a process of restricting MBS traffic transmission when a UE moves out of an MBS service area in an idle state according to another embodiment of the disclosure.

According to an embodiment, when a UE800moves out of the MBS service area in the idle state and then wakes up, a process of restricting a multicast service may be required.

Referring toFIG.8A, the UE800may request to join a multicast session by a PDU session modification request, to receive a multicast session service. When an AMF820transmits an Nsmf_PDUSession_UpdateSMcontext request message (including a join request and an MBS session ID) to an SMF830, in the absence of an MBS session context for the multicast session ID for which the request is made, the SMF830receiving the join request may obtain multicast QoS flow information for the multicast session from an MB-SMF840.

The SMF830may obtain mapping information between the multicast QoS flow information for the multicast session and QoS flow information for an associated PDU session, or may request the QoS flow information for the associated PDU session corresponding the multicast QoS flow information from a PCF and receive the QoS flow information for the associated PDU session.

The SMF830may obtain the mapping information by autonomously generate the QoS flow information for the associated PDU session based on the multicast QoS flow information.

In step1-1, the SMF830may store (or generate), as an MBS session context for the MBS session ID, at least one of MBS service area information, the MBS session ID, mapping information between the MBS session ID and an associated PDU session ID, mapping information between the multicast QoS flow information and the associated QoS flow information, or updated QoS flow information for the PDU session.

The MBS service area information may be a TAI list, a cell ID list, or an NG-RAN node ID list, the QoS flow information may include a QFI and a QoS profile, and the QoS profile may include information indicating a GBR or a non-GBR, a 5QI, an ARP, a GFBR, and an MFBR.

The SMF830may store a DL PDR including an SDF template for mapping an SDF of the multicast session to the associated QoS flow.

The SDF template mapped to the associated QoS flow may include multicast IP address information and port information, unicast IP address information and port information, or LL MC address information, for providing multicast data from an MB-UPF860, which is a user plane anchor for the MBS session, to a UPF850.

When the SMF830transmits a response to the AMF820by an Nsmf_PDUSession_UpdateSMcontext response message, the SMF340may also transmit the MBS service area information, the MBS session ID, and the mapping information between the MBS session ID and the PDU session ID.

The SMF830may transmit the MBS service area information, the MBS session ID, the mapping information between the MBS session ID and the PDU session ID, the mapping information between the multicast QoS flow information and the associated QoS flow information, and the updated QoS flow information for the PDU session in an N2 SM container, as a response to an NG-RAN810.

Upon receipt of the Nsmf_PDUSession_UpdateSMcontext response message, the AMF820may perform a multicast traffic transmission procedure with an NG-RAN node.

When the UE800is located in the NG-RAN810that does not support an MBS function after joining, the SMF830may transmit multicast data to the UE800in the individual delivery method.

A situation in which the UE800is switched to the idle state as in step4is considered. When the UE800moves and is to be switched to the connected state, the UE800may transmit a service request message to the AMF820through the NG-RAN810as in steps5and6. The NG-RAN810may transmit location information about the UE800by an N2 message to the AMF820in step6, and the AMF820may recognize that the UE800has moved out of the service area as in step16.

As in step7, the AMF820may transmit an Nsmf_PDUSession_UpdateSMcontext req message to the SMF830. Upon receipt of the Nsmf_PDUSession_UpdateSMcontext req message, the SMF830may apply the contents of the message to the UPF850as in step8. The SMF830may transmit a Nsmf_PDUSession_UpdateSMcontext response message (including N2 SM info) to the AMF820in step9. The AMF820may transmit an N2 request message to the NG-RAN810in step10, and thus the NG-RAN810may perform a service request-based procedure with the UE800, such as allocation of resources by signaling as in step11.

Upon receipt of an N2 message from the NG-RAN810in step6, the AMF820may recognize that the UE800has moved out of the multicast service areas as in step16.

Because the SMF840has subscribed to the event notification for the case of the UE800being out of the multicast service area, the AMF820may transmit a Namf_EventExposure_Notify message (including the notification correlation ID, the UE location, and the MBS session ID) indicating “the UE out of the MBS service area” to the SMF830subscribed to the event notification.

The Namf_EventExposure_Notify message may include event information indicating the UE being out of the service area, the notification correlation ID generated in step2during the subscription to the event notification, or location information about the UE800(e.g., a TAI, a cell ID, or an NG-RAN node ID of an NG-RAN to which the UE has moved), further include the MBS session ID, and be transmitted to the SMF830.

As in step18, upon receipt of the Namf_EventExposure_Notify message, the SMF830may recognize that the UE800has moved out of the service area of the multicast session, for the MBS session corresponding to the notification correlation ID, and control the UE800not to receive multicast service data through the associated PDU session mapped to the multicast session.

The SMF830may delete the associated QoS flow of the associated PDU session mapped to the stored multicast QoS flow information for the multicast session, and the SDF template corresponding to the associated QoS flow.

Even though the SMF830does not delete the associated QoS flow and the SDF template corresponding to the associated QoS flow, the UPF850which has received multicast data traffic from the MB-UPF860may control not to forward multicast data traffic corresponding to the DL PDR including the SDF template for the associated QoS flow of the associated PDU session of the UE800to the associated PDU session to the UE800or to drop the multicast data traffic. For example, the SMF830may transmit/receive an N4 Session Modification request/response to/from the UPF850so that the SDF corresponding to multicast data traffic from the multicast session may not be forwarded to the associated PDU session of the UE800or may be dropped, and thus the UE800may not receive any more multicast data, as in step19.

As in step20, the SMF830may perform a PDU session modification procedure to synchronize the updated QoS flow information between the UE800and the network, and the QoS flow information may be synchronized among the UE800, the NG-RAN810, and the core network.

According to an embodiment, steps16to20may be performed in parallel with or before the handover procedure, that is, steps8to15. Accordingly, when messages generated in the two procedures overlap, the messages may be integrated into one message and transmitted.

FIG.9illustrates the structure of an SMF according to an embodiment of the disclosure.

An SMF described with reference toFIGS.1to8may correspond to the SMF ofFIG.9.

Referring toFIG.9, the SMF may include a transceiver910, a memory920, and a controller930. The SMF transceiver910, the controller930, and the memory920may operate according to the SMF communication methods described above. However, the components of the SMF are not limited to the above example. For example, the SMF may include more or fewer components than the above components. In addition, the transceiver910, the controller930, and the memory920may be implemented in the form of a single chip. Further, the controller930may include one or more processors.

The transceiver910collectively refers to a receiver of the SMF and a transmitter of the SMF, and may transmit and receive signals to and from other network entities. To this end, the transceiver910may include a radio frequency (RF) transmitter that up-converts the frequency of a transmitted signal and amplifies the up-converted signal, and an RF receiver that low-noise amplifies a received signal and down-converts the low-noise-amplified signal. However, this is only an embodiment of the transceiver910, and the components of the transceiver910are not limited to the RF transmitter and the RF receiver.

In addition, the transceiver910may receive a signal on a radio channel, output the received signal to the controller930, and transmit a signal received from the controller930on a radio channel.

The memory920may store a program and data required for the operations of the SMF. Further, the memory920may store control information or data included in a signal obtained at the SMF. The memory920may be configured as a storage medium such as read only memory (ROM), random access memory (RAM), a hard disk, a compact disk ROM (CD-ROM), a digital versatile disk (DVD), or a combination of these storage media. The memory920may be included in the processor930, not existing separately.

The controller930may control a series of processes so that the SMF operates according to the above-described embodiments of the disclosure. For example, the controller930may receive a control signal and a data signal through the transceiver910and process the received control signal and data signal. Further, the controller930may transmit a processed control signal and data signal through the transceiver910. There may be a plurality of controllers930, and the controller930may execute a program stored in the memory420to perform a control operation for the components of the SMF.

The controller930may control to transmit a first message including information about an MBS area and an MBS session ID to an AMF, control to receive a second message indicating that a UE receiving a service within the MBS area is located outside the MBS area from the AMF, determine that the UE is located outside the MBS area based on the second message, and process a QoS flow applied to MBS traffic delivered by individual delivery.

The controller930may delete the QoS flow or drop data traffic applied to a PDR (SDF template) for the QoS flow.

The controller930may control to receive a third message including a session join request of the UE and the MBS session ID from the AMF. The first message may be transmitted to the AMF in response to the third message.

According to an embodiment, the first message may be a subscribe message for receiving an event notification when the UE located in the MBS area moves out of the MBS area.

The controller930may store mapping information between the MBS session ID and a notification correlation ID, and identify that the second message is an event notification for the MBS session ID based on the mapping information.

FIG.10illustrates the structure of an AMF according to an embodiment of the disclosure.

The AMF described with reference toFIGS.1to8may correspond to the AMF ofFIG.10.

Referring toFIG.10, the SMF may include a transceiver1010, a memory1020, and a controller1030. The SMF transceiver1010, the controller1030, and the memory1020may operate according to the SMF communication method described above. However, the components of the SMF are not limited to the above-described example. For example, the SMF may include more or fewer components than the above components. In addition, the transceiver1010, the controller1030, and the memory1020may be implemented in the form of a single chip. Further, the controller1030may include one or more processors.

The transceiver1010collectively refers to a receiver of the SMF and a transmitter of the UE, and may transmit and receive signals to and from other network entities. To this end, the transceiver1010may include an RF transmitter that up-converts the frequency of a transmitted signal and amplifies the up-converted signal, and an RF receiver that low-noise amplifies a received signal and down-converts the low-noise-amplified signal. However, this is only an embodiment of the transceiver1010, and the components of the transceiver1010are not limited to the RF transmitter and the RF receiver.

In addition, the transceiver1010may receive a signal on a radio channel, output the received signal to the controller1030, and transmit a signal received from the controller1030on a radio channel.

The memory1020may store a program and data required for the operations of the SMF. Further, the memory1020may store control information or data included in a signal obtained at the AMF. The memory1020may be configured as a storage medium such as ROM, RAM, a hard disk, a CD-ROM, a DVD, or a combination of these storage media. The memory1020may be included in the controller1030, not existing separately.

The controller1030may control a series of processes so that the AMF operates according to the above-described embodiments of the disclosure. For example, the controller1030may receive a control signal and a data signal through the transceiver1030and process the received control signal and data signal. Further, the controller1030may transmit a processed control signal and data signal through the transceiver1010. There may be a plurality of controllers1030, and the controller1030may execute a program stored in the memory1020to perform a control operation for the components of the AMF.

The controller1030may control to receive a first message including information about an MBS area and an MBS session ID from an SMF, and control to transmit a second message indicating that a UE receiving a service within the MBS area is located outside the MBS area to the SMF. A QoS flow applied to MBS traffic delivered by individual delivery may be processed based on the second message.

Methods according to the embodiments described in the claims or specifications of the disclosure may be implemented in the form of hardware, software, or a combination of hardware and software.

When the methods are implemented in software, a computer-readable storage medium storing at least one program (software module) may be provided. The at least one program stored in the computer-readable storage medium are configured for execution by at least one processor in an electronic device. The at least one program includes instructions that cause the electronic device to execute the methods according to the embodiments described in the claims or specification of the disclosure.

The program (software module or software) may be stored in RAM, non-volatile memory including flash memory, ROM, electrically erasable programmable ROM (EEPROM), a magnetic disk storage device, a CD-ROM, a DVD, other types of optical storage devices, or a magnetic cassette. Alternatively, the program may be stored in a memory configured as a combination of some or all of them. In addition, a plurality of constituent memories may be included.

In addition, the program may be stored on an attachable storage device accessible through a communication network including a communication network such as the Internet, an intranet, a local area network (LAN), a wide area network (WAN), a storage area network (SAN), or a combination thereof. The storage device may be connected to a device implementing an embodiment of the disclosure through an external port. Additionally, a separate storage device on the communication network may be connected to the device implementing the embodiment of the disclosure.

In the specific embodiments of the disclosure described above, components included in the disclosure are expressed in a singular or plural form according to the specific embodiments. However, the singular or plural expression is appropriately selected for a presented context, for convenience of description, and the disclosure is not limited to a single component or a plurality of components. Even a component expressed as a plural form may be provided as a single one, or even a component expressed as a singular form may be provided in plurality. It should also be noted that functions recited in blocks may occur out of order in some alternative implementations. For example, two blocks shown as one after another may be executed substantially simultaneously or in a reverse order according to a corresponding function.