Network node and method therein facilitating management of multicast / broadcast service sessions

Abstract

The present disclosure provides a network node and methods therein that facilitate management of multicast / broadcast service sessions. The method (600) comprises receiving (610), from an access and mobility management function (AMF), an identifier (ID) of a next generation radio access network (NG-RAN) and an indication of a restart or failure of the NG-RAN.

Description

[0001] This application is a divisional application of the Chinese national phase application PCT / CN2022 / 142671 entitled “NETWORK NODES AND METHODS THEREINFOR FACILITATING MANAGEMENT OF MULTICAST / BROADCAST SERVICE SESSION” filed on December 28, 2022 (application number 202280086960.7). CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to PCT international application PCT / CN2021 / 143933, filed on December 31, 2021, entitled “NETWORK NODES AND METHODSTHEREIN FOR FACILITATING MANAGEMENT OF MULTICAST / BROADCAST SERVICE SESSION”, the entire contents of which are incorporated herein by reference. Technical Field

[0003] The present disclosure relates to communication technologies, and more particularly, to a network node and method therein for facilitating multicast / broadcast service (MBS) session management. Background Art

[0004] A broadcast MBS session refers to an MBS session for transmitting a broadcast communication service. A broadcast MBS session is characterized by content to be transmitted and a geographical area in which the broadcast MBS session is distributed.

[0005] The 3rd Generation Partnership Project (3GPP) Technical Specification (TS) 23.247, v17.0.0 (the entire contents of which are incorporated herein by reference) specifies architectural enhancements to fifth generation (5G) systems using New Radio (NR) to support multicast and broadcast communication services.

[0006] Overview of Multicast and Broadcast Communications

[0007] MBS is a point-to-multipoint service in which data is sent from a single source entity to multiple recipients, either to all users in a broadcast service area or to users in a multicast group. The corresponding types of MBS sessions are:

[0008] - Broadcasting sessions; and

[0009] -Multicast sessions.

[0010] The MBS architecture follows the 5G System (5GS) architecture principles and supports the distribution of MBS data from the 5GS portal to the Next Generation Radio Access Network (NG-RAN) nodes and then to the User Equipment (UE). The MBS architecture provides:

[0011] - Efficient utilization of RAN and Core Network (CN) resources, with a focus on radio interface efficiency;

[0012] -Efficient transmission of various multicast and broadcast services.

[0013] 5G MBS also provides functions such as local MBS service, authorization for multicast MBS, and Quality of Service (QoS) differentiation.

[0014] MBS services are delivered from a single data source (eg, an application service provider) to multiple UEs. Depending on many factors, there are several delivery methods that can be used to deliver MBS services in 5GS.

[0015] There are two possible delivery methods to send MBS data between the 5G Core (5GC) and NG-RAN:

[0016] -5GC separate MBS service delivery method: This method is only applicable to multicast MBS sessions. 5GC receives a single copy of the MBS data packet and delivers a separate copy of these MBS data packets to each UE via each UE protocol data unit (PDU) session, so for each such UE, a PDU session needs to be associated with the multicast session.

[0017] -5GC shared MBS service delivery method: This method is applicable to both broadcast MBS sessions and multicast MBS sessions. The 5GC receives a single copy of the MBS data packets and transmits a single copy of these MBS packets to the NG-RAN node, which then transmits these packets to one or more UEs.

[0018] All MBS deployments require a 5GC shared 5G MBS service delivery method. When there is an NG-RAN deployment with non-homogeneous support for 5G MBS, a 5GC separate MBS service delivery method is required to achieve mobility.

[0019] For a multicast session, a single copy of an MBS data packet received by the CN may be transmitted via a 5GC individual MBS service delivery method for certain UEs and via a 5GC shared MBS service delivery method for other UEs.

[0020] Between NG-RAN and UE, two delivery methods are available for MBS data packet transmission over the radio interface:

[0021] - Point-to-Point (PTP) delivery method: NG-RAN delivers a separate copy of the MBS data packet to each UE over the radio interface.

[0022] - Point-to-multipoint (PTM) delivery method: NG-RAN delivers a single copy of MBS data packets to multiple UEs over the radio interface.

[0023] NG-RAN may use a combination of PTP / PTM to deliver MBS data packets to the UE.

[0024] Figure 1 FIG. 2 shows a transmission method for MBS multicast / broadcast communication. Figure 1 As shown, the 5GC shared MBS service transmission method (using PTP or PTM transmission) and the 5GC independent MBS service transmission method can be used for multicast MBS sessions at the same time.

[0025] For MBS broadcast communications, only the 5GC shared MBS service transmission method using PTM transmission is applicable.

[0026] For MBS multicast communications, if the NG-RAN node supports 5G MBS, the network should use the 5GC shared MBS service delivery method for MBS data transmission.

[0027] For MBS multicast communication, switching between the 5GC shared MBS service delivery method and the 5GC independent MBS service delivery method is supported. UE mobility between RAN nodes that all support MBS and UE mobility between RAN nodes that support MBS and RAN nodes that do not support MBS are both supported.

[0028] For MBS multicast communication, switching between the PTP transmission method and the PTM transmission method for 5GC shared MBS service transmission should be supported. NG-RAN is the decision point for switching between the PTP transmission method and the PTM transmission method.

[0029] MBS system architecture

[0030] Figure 2 The 5G system architecture for MBS is shown. A service-based interface is used within the control plane. Figure 3 The 5G system architecture of MBS is shown in reference point notation. For details of functions and interfaces / reference points in the 5G system architecture, reference may be made to TS 23.247, v17.0.0, and a description thereof will be omitted here. Summary of the invention

[0031] An object of the present disclosure is to provide a network node and method therein for facilitating management of MBS sessions.

[0032] According to a first aspect of the present disclosure, a method in a multicast / broadcast session management function (MB-SMF) is provided. The method includes: receiving an ID of a NG-RAN and an indication of a restart or failure of the NG-RAN from an access and mobility management function (AMF).

[0033] In an embodiment, the ID of the multicast / broadcast service MBS session associated with the NG-RAN may be received together with the ID of the NG-RAN and an indication of a restart or failure of the NG-RAN.

[0034] In an embodiment, the ID of the NG-RAN, the indication of the restart or failure of the NG-RAN, and the ID of the MBS session may be included in the MBS Broadcast Context Status Notification Request.

[0035] In an embodiment, before the receiving operation, the method may further include: receiving a message including an ID of the NG-RAN from the AMF during a start-up or update procedure for the MBS session.

[0036] In an embodiment, the ID of the NG-RAN may be included in the N2 Session Management (SM) information container, or carried outside the N2 SM information container.

[0037] In an embodiment, the message may also include tunnel information of a DL tunnel for the MBS session. In an embodiment, the tunnel information may be included in an N2 SM information container. In an embodiment, the method may also include: maintaining a mapping between an ID of the NG-RAN and the tunnel information.

[0038] In an embodiment, the method may further include: in response to receiving the indication, sending a session modification request for releasing the DL tunnel corresponding to the NG-RAN to the MB-UPF. In an embodiment, the session modification request may include an ID of the MBS session and tunnel information.

[0039] In an embodiment, the method may further include: in response to receiving an indication of restart of the NG-RAN, sending a request to the AMF for resuming the MBS session towards the NG-RAN. In an embodiment, the request may include an ID of the NG-RAN and an ID of the MBS session.

[0040] In an embodiment, the request may be an MBS broadcast context update request or an MBS broadcast context create request.

[0041] In an embodiment, the request may also include an indication of MBS session resumption.

[0042] In an embodiment, the method may further include: receiving a response to a request for resuming an MBS session or an MBS broadcast context status notification request from the AMF. In an embodiment, the response or the MBS broadcast context status notification request may include an ID of the NG-RAN.

[0043] In an embodiment, the response or the MBS broadcast context status notification request may further include tunnel information of another DL tunnel for the MBS session. In an embodiment, the method may further include: maintaining a mapping between the ID of the NG-RAN and the tunnel information of the another DL tunnel.

[0044] According to a second aspect of the present disclosure, a method in an MB-SMF is provided. The method includes: receiving a report from a multicast / broadcast user plane function (MB-UPF), the report indicating: an error associated with tunnel information of a DL tunnel for a packet filtering control protocol (PFCP) session, or a failure or restart associated with an Internet Protocol (IP) address or a transport network IP address in the tunnel information. The method also includes: identifying the NG-RAN corresponding to the tunnel information, the IP address in the tunnel information, or the transport network IP address. The method includes: sending a request to the AMF for resuming an MBS session, the MBS session corresponding to the PFCP session, the IP address in the tunnel information, or the transport network IP address toward the NG-RAN. The request contains an ID of the NG-RAN and an ID of the MBS session.

[0045] In an embodiment, the report may be a PFCP session report or a node level report.

[0046] In an embodiment, before the receiving operation, the method may further include: receiving a message including an ID of the NG-RAN from the AMF during a start-up or update procedure for the MBS session.

[0047] In an embodiment, the ID of the NG-RAN may be included in the N2 SM information container, or carried outside the N2 SM information container.

[0048] In an embodiment, the message may also include tunnel information or a transport network IP address.

[0049] In an embodiment, the method may further include: maintaining a mapping between the ID of the NG-RAN and the tunnel information, the IP address in the tunnel information, or the transport network IP address.

[0050] In an embodiment, the method may further include: signaling the tunnel information or the transport network IP address to the MB-UPF.

[0051] In an embodiment, the method may further include: receiving, from the AMF, a response to the request for resuming the MBS session or an MBS broadcast context status notification request, the response or the MBS broadcast context status notification request including an ID of the NG-RAN.

[0052] In an embodiment, the response or the MBS broadcast context status notification request may also include tunnel information of another DL tunnel corresponding to the NG-RAN or another transport network IP address.

[0053] In an embodiment, the method may further include: maintaining a mapping between the ID of the NG-RAN and the tunnel information of the other DL tunnel, the IP address in the tunnel information of the other DL tunnel, or the IP address of the other transport network.

[0054] In an embodiment, the transport network IP address may be an IP address used for user plane path management.

[0055] In an embodiment, the request for resuming the MBS session may be an MBS broadcast context update request or an MBS broadcast context create request.

[0056] In an embodiment, the request for resuming the MBS session may further include an indication of MBS session resumption.

[0057] According to a third aspect of the present disclosure, a method in an AMF is provided. The method comprises: receiving a request from an MB-SMF for resuming an MBS session towards an NG-RAN. The request includes an ID of the NG-RAN.

[0058] In an embodiment, the request may also include an ID of the MBS session.

[0059] In an embodiment, before the receiving operation, the method may further include: sending another message including the ID of the NG-RAN to the MB-SMF during the start or update process for the MBS session. In an embodiment, the ID of the NG-RAN may be included in the N2 SM information container.

[0060] In an embodiment, the message may also include tunnel information of a DL tunnel corresponding to the NG-RAN. In an embodiment, the other message may also include tunnel information. In an embodiment, the tunnel information may be included in an N2 SM information container.

[0061] In an embodiment, before the receiving operation, the method may further include: sending a message including the ID of the NG-RAN to the MB-SMF during the start or update process for the MBS session. In an embodiment, the ID of the NG-RAN may be carried outside the N2 SM information container.

[0062] In an embodiment, the method may further include: receiving another message from the NG-RAN, the other message including tunnel information of a DL tunnel corresponding to the NG-RAN. In an embodiment, the message may further include tunnel information. In an embodiment, the tunnel information may be included in an N2 SM information container.

[0063] In an embodiment, after receiving the request for resuming the MBS session, the method may further include: sending a request to establish resources for the MBS session to the NG-RAN; receiving a response to the request to establish resources for the MBS session from the NG-RAN; and sending a response to the request for resuming the MBS session or an MBS broadcast context status notification request to the MB-SMF. In an embodiment, the response or the MBS broadcast context status notification request may include an ID of the NG-RAN.

[0064] In an embodiment, before receiving the request for resuming the MBS session, the method may further include: sending the ID of the NG-RAN, an indication of restarting the NG-RAN, and the ID of the MBS session to the MB-SMF.

[0065] In an embodiment, the ID of the NG-RAN, the indication of the restart of the NG-RAN, and the ID of the MBS session may be included in the MBS broadcast context status notification request.

[0066] In an embodiment, before sending an indication of restart of the NG-RAN, the method may further include: receiving an NG establishment request or an NG reset request from the NG-RAN, the NG reset request indicating the restart of the NG-RAN; and determining an ID of an MBS session associated with the NG-RAN.

[0067] In an embodiment, the message may also include tunnel information or a transport network IP address of a DL tunnel corresponding to the NG-RAN. In an embodiment, the other message may also include tunnel information or a transport network IP address. In an embodiment, the tunnel information or the transport network IP address may be included in an N2 SM information container.

[0068] In an embodiment, the method may further include: receiving another message from the NG-RAN, the other message including tunnel information or a transport network IP address of a DL tunnel corresponding to the NG-RAN. In an embodiment, the message may also include the tunnel information or the transport network IP address. In an embodiment, the tunnel information or the transport network IP address may be included in an N2 SM information container.

[0069] In an embodiment, after receiving the request for resuming the MBS session, the method may further include: sending a request to the NG-RAN to establish resources for the MBS session; receiving a response to the request to establish resources for the MBS session from the NG-RAN, the response including an ID of the NG-RAN and tunnel information of another DL tunnel corresponding to the NG-RAN or another transport network IP address; and sending a response to the request for resuming the MBS session or an MBS broadcast context status notification request to the MB-SMF, the response or the MBS broadcast context status notification request including an ID of the NG-RAN and tunnel information of the other DL tunnel corresponding to the NG-RAN or the other transport network IP address.

[0070] In an embodiment, the transport network IP address may be an IP address used for user plane path management.

[0071] In an embodiment, the request for resuming the MBS session may be an MBS broadcast context update request or an MBS broadcast context create request.

[0072] In an embodiment, the request for resuming the MBS session may further include an indication of MBS session resumption.

[0073] According to a fourth aspect of the present disclosure, a method in an AMF is provided, comprising: sending an ID of the NG-RAN and an indication of a failure of the NG-RAN to the MB-SMF.

[0074] In an embodiment, the ID of the multicast / broadcast service MBS session associated with the NG-RAN may be sent together with the ID of the NG-RAN and an indication of the failure of the NG-RAN.

[0075] In an embodiment, the ID of the NG-RAN, the indication of the failure of the NG-RAN, and the ID of the MBS session may be included in the MBS Broadcast Context Status Notification Request.

[0076] In an embodiment, before the sending operation, the method may further include: detecting a failure of the NG-RAN using a Stream Control Transmission Protocol (SCTP).

[0077] In an embodiment, before the sending operation, the method may further include: receiving a message including an ID of the NG-RAN from the NG-RAN during a start or update procedure for an MBS session; and sending another message including the ID of the NG-RAN to the MB-SMF. In an embodiment, the ID of the NG-RAN may be included in an N2 SM information container.

[0078] In an embodiment, the message may also include tunnel information of a DL tunnel corresponding to the NG-RAN. In an embodiment, the other message may also include tunnel information. In an embodiment, the tunnel information may be included in an N2 SM information container.

[0079] In an embodiment, before the sending operation, the method may further include: sending a message including the ID of the NG-RAN to the MB-SMF during the start or update process for the MBS session. In an embodiment, the ID of the NG-RAN may be carried outside the N2 SM information container.

[0080] In an embodiment, the method may further include: receiving another message from the NG-RAN, the other message including tunnel information of a DL tunnel corresponding to the NG-RAN. In an embodiment, the message may further include tunnel information. In an embodiment, the tunnel information may be included in an N2 SM information container.

[0081] According to a fifth aspect of the present disclosure, a method in an MB-UPF is provided. The method includes: receiving tunnel information or a transport network IP address of a DL tunnel associated with an MBS session from an MB-SMF. The method also includes: sending a report to the MB-SMF, the report indicating: an error associated with the tunnel information of a PFCP session corresponding to the MBS session, or a failure or restart associated with an IP address in the tunnel information or a transport network IP address.

[0082] In an embodiment, the report may be a PFCP session report or a node level report.

[0083] In an embodiment, before the sending operation, the method may further include: sending a packet to the NG-RAN based on the tunnel information; and receiving an indication indicating an error from the NG-RAN.

[0084] In an embodiment, the method may further include: receiving a session modification request for releasing a DL tunnel corresponding to the NG-RAN from the MB-SMF. In an embodiment, the session modification request may include an ID of the MBS session and tunnel information.

[0085] In an embodiment, after the receiving operation and before the sending operation, the method may also include: sending a request for user plane path management to the IP address in the tunnel information or the transport network IP address; and receiving a response from the IP address in the tunnel information or the transport network IP address, the response containing information from which a restart can be derived, or determining failure in response to not receiving a response to the request from the IP address in the tunnel information or the transport network IP address within a predetermined time period.

[0086] In an embodiment, the request for user plane path management may be a General Packet Radio Service (GPRS) Tunneling Protocol - User Plane (GTP-U) echo request. In an embodiment, the response may be a GTP-U echo response.

[0087] In an embodiment, the transport network IP address may be an IP address used for user plane path management.

[0088] According to a sixth aspect of the present disclosure, a method in NG-RAN is provided. The method includes: receiving a request to establish resources for an MBS session from an AMF. The method also includes: sending a response to the request to establish resources for an MBS session to the AMF. The response includes an ID of the NG-RAN and / or a transport network IP address corresponding to the NG-RAN.

[0089] In an embodiment, the ID of the NG-RAN and / or the transport network IP address is included in the N2 SM information container.

[0090] According to a seventh aspect of the present disclosure, a network node is provided. The network node includes a communication interface, a processor, and a memory. The memory includes instructions executable by the processor, whereby the network node can be operated to: perform the method according to the first aspect or the second aspect when implementing MB-SMF, or perform the method according to the third aspect or the fourth aspect when implementing AMF, or perform the method according to the fifth aspect when implementing MB-UPF, or perform the method according to the sixth aspect when implementing NG-RAN.

[0091] According to an eighth aspect of the present disclosure, a computer-readable storage medium is provided. The computer-readable storage medium has computer-readable instructions stored thereon. When the computer-readable instructions are executed by a processor of a network node, the network node is configured to: perform the method according to the first aspect or the second aspect when implementing MB-SMF, or perform the method according to the third aspect or the fourth aspect when implementing AMF, or perform the method according to the fifth aspect when implementing MB-UPF, or perform the method according to the sixth aspect when implementing NG-RAN.

[0092] Through the embodiments of the present disclosure, an MBS session lost due to a restart or failure of the NG-RAN may be recovered, so that one or more UEs within the coverage of the NG-RAN may receive the corresponding MBS service. BRIEF DESCRIPTION OF THE DRAWINGS

[0093] The above and other objects, features and advantages will become more apparent from the following description of the embodiments with reference to the accompanying drawings, in which:

[0094] Figure 1A transmission method for MBS multicast / broadcast communication is shown;

[0095] Figure 2 shows the 5G system architecture of MBS;

[0096] Figure 3 The 5G system architecture for MBS is shown in reference point notation;

[0097] Figure 4 schematically illustrates user plane data transmission;

[0098] Figure 5 is a sequence diagram illustrating an exemplary process of resuming a PDU session in a 5G system;

[0099] Figure 6 is a flowchart illustrating a method in an MB-SMF according to an embodiment of the present disclosure;

[0100] Figure 7 is a flowchart illustrating a method in an MB-SMF according to another embodiment of the present disclosure;

[0101] Figure 8 is a flowchart illustrating a method in an AMF according to an embodiment of the present disclosure;

[0102] Fig. 9 is a flowchart showing a method in an AMF according to another embodiment of the present disclosure;

[0103] Fig.10 is a flowchart illustrating a method in an MB-UPF according to an embodiment of the present disclosure;

[0104] Fig.11 is a flowchart illustrating a method in a NG-RAN according to an embodiment of the present disclosure;

[0105] Fig.12 is a sequence diagram illustrating an exemplary MBS session initiation procedure for broadcasting an MBS session according to an embodiment of the present disclosure;

[0106] Fig.13 is a sequence diagram illustrating an exemplary process of resuming an MBS session according to an embodiment of the present disclosure;

[0107] Fig.14 is a sequence diagram illustrating an exemplary process of handling NG-RAN failure according to another embodiment of the present disclosure;

[0108] Fig.15 is a sequence diagram illustrating an exemplary MBS session initiation procedure for broadcasting an MBS session according to another embodiment of the present disclosure;

[0109] Fig.16 is a sequence diagram illustrating an exemplary process of resuming an MBS session according to another embodiment of the present disclosure;

[0110] Fig.17 is a sequence diagram illustrating an exemplary process of resuming an MBS session according to another embodiment of the present disclosure;

[0111] Fig.18 is a block diagram of a network node according to an embodiment of the present disclosure;

[0112] Fig.19 is a block diagram of a network node according to another embodiment of the present disclosure;

[0113] Fig. 20 is a block diagram of a network node according to another embodiment of the present disclosure;

[0114] Fig.21 is a block diagram of a network node according to another embodiment of the present disclosure;

[0115] Fig. 22 is a block diagram of a network node according to another embodiment of the present disclosure;

[0116] Fig.23 is a block diagram of a network node according to another embodiment of the present disclosure; and

[0117] Fig.24 is a block diagram of a network node according to another embodiment of the present disclosure. DETAILED DESCRIPTION

[0118] As used herein, a network function may be implemented as a network element on dedicated hardware, or as a software instance running on dedicated hardware, or as a virtualized function instantiated on a suitable platform (eg, on a cloud infrastructure).

[0119] Hereinafter, references in this specification to "one embodiment," "an embodiment," "an example embodiment," etc. indicate that the described embodiment may include a particular feature, structure, or characteristic, but not necessarily every embodiment includes the particular feature, structure, or characteristic. Furthermore, these phrases do not necessarily refer to the same embodiment. Furthermore, when a particular feature, structure, or characteristic is described in conjunction with an embodiment, it should be considered that it is within the knowledge of those skilled in the art to implement such feature, structure, or characteristic in conjunction with other embodiments (whether explicitly described or not).

[0120] It should be understood that although the words "first" and "second" etc. can be used to describe various elements in this article, these elements should not be limited by these words. These terms are only used to distinguish elements from each other. For example, without departing from the scope of the exemplary embodiment, a first element can be referred to as a second element, and similarly, a second element can be referred to as a first element. As used herein, the word "and / or" includes any and all combinations of one or more of the related listed words.

[0121] The terms used herein are only for the purpose of describing specific embodiments and are not intended to limit the exemplary embodiments. As used herein, the singular forms "a", "an" and "the" are intended to also include the plural forms, unless the context clearly indicates otherwise. It will be further understood that when used herein, the words "comprise", "have", "include" indicate the presence of stated features, elements and / or components, etc., but do not exclude the presence or addition of one or more other features, elements, components and / or combinations thereof.

[0122] In the following description and claims, unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs.

[0123] Transmission between NG-RAN and MB-UPF via N3mb

[0124] According to TS 23.247, v17.0.0, unicast or multicast transmission via N3mb between NG-RAN and MB-UPF can be applied:

[0125] - If unicast transport over N3mb is applied, each NG-RAN allocates tunnel information (including IP address and Tunnel Endpoint Identifier (TEID)), which is provided to the MB-UPF (via Access and Mobility Management Function (AMF), Multicast / Broadcast Session Management Function (MB-SMF)) so that downlink (DL) MBS packets can be sent to this tunnel entity.

[0126] - If the application is delivered via N3mb's multicast, the NG-RAN does not provide tunnel information. Instead, the NG-RAN joins the multicast IP address provided by the MB-UPF.

[0127] Figure 4 The user plane data transmission is schematically shown. The MB-UPF acts as the MBS session anchor for the MBS session and, if the MBSTF participates in the MBS session, the MBSTF acts as the media anchor for the MBS service. The MB-UPF receives only one copy of the MBS data packet from the application function (AF) or the multicast / broadcast service transmission function (MBSTF).

[0128] The user plane between MBSTF and MB-UPF or between MB-UPF and AF can use multicast transmission or unicast tunnel for MBS session (depending on the capabilities of application and control interface). If the transport network does not support multicast transmission, the user plane uses unicast tunnel for MBS session. The user plane between MBSTF and AF can use unicast tunnel, multicast transmission or other means (for example, Hypertext Transfer Protocol (HTTP) download from external content delivery network (CDN)). If unicast is used for MBS session, after receiving the downlink MBS data, MB-UPF forwards the downlink MBS data without external IP header and tunnel header information.

[0129] The user plane from MB-UPF to NG-RAN (for shared transmission) and the user plane from MB-UPF to UPF (for separate transmission) can use multicast transmission via a common GTP-U tunnel for each MBS session, or use unicast transmission via a separate General Packet Radio Service (GPRS) Tunneling Protocol-User Plane (GTP-U) tunnel at NG-RAN or UPF for each MBS session. If the user plane uses unicast transmission, the transport layer destination is the IP address of the NG-RAN or UPF, each NG-RAN or UPF is allocated a tunnel separately, and the MBS session uses multiple GTP-U tunnels. If the user plane uses multicast transmission, both the RAN and UPF nodes use a common GTP-U tunnel. The GTP-U tunnel is identified as a transport layer destination by a common tunnel identifier (ID) and an IP multicast address, both of which are assigned by the 5GC.

[0130] The MB-SMF configures the MB-UPF to receive data packets related to the MBS session.

[0131] For shared transmission, if unicast transmission over N3mb is applicable, the MB-SMF configures the MB-UPF to replicate the received MBS data packets and forward them to multiple RAN nodes via separate GTP tunnels. For shared transmission, if multicast transmission over N3mb is applicable, the MB-SMF configures the MB-UPF to replicate the received MBS data and forward the data via a single GTP tunnel.

[0132] For standalone delivery, the MBS data received by the MB-UPF is copied to the UPF which performs the standalone delivery in the following manner:

[0133] -MB-SMF configures the MB-UPF to receive data packets related to the MBS session, replicate these data packets and forward them to multiple UPFs via multiple GTP tunnels (if the application is transmitted via unicast of N19mb), or forward them to multiple UPFs via a single GTP tunnel (if the application is transmitted via multicast of N19mb).

[0134] -SMF configures the UPF to: receive data packets related to the multicast session from MB-UPF through N19mb, copy these data packets, and forward them in multiple PDU sessions.

[0135] For SMF and UPF (for 5GC transmission only), the packet detection, replication and forwarding of the MBS session are implemented through the packet detection rule (PDR) and forwarding action rule (FAR) of the PDU session, in which the UE has joined the MBS session:

[0136] -SMF instructs UPF to associate the PFCP session of the PDU session with the MBS session.

[0137] - Use new PDR with source interface "core" to detect MBS data from N19mb.

[0138] NOTE: This PDR also contains the MBS Session ID to enable single detection of incoming MBS data for multiple PDU sessions at the UPF.

[0139] -For unicast transmission over N19mb, SMF requests UPF to allocate N19mb tunnel information (if not allocated).

[0140] -For multicast transmission over N19mb, the SMF includes the lower layer source specific multicast address information and C-TEID to the UPF.

[0141] - The action of FAR is set to "discard" if the SMF wants to maintain MBS data reception over N19mb but suspend data delivery of the PDU session to the UE (e.g. when the UE is switching from 5GC individual delivery to 5GC shared delivery due to the UE moving from NG-RAN without MBS support to NG-RAN with MBS support). Otherwise, the SMF shall remove the related PDR and FAR.

[0142] For details on user plane processing, see TS 29.244, V17.3.0, the entire contents of which are incorporated herein by reference.

[0143] For MB-SMF and MB-UPF, traffic duplication and forwarding of MBS sessions is achieved by using one PDR per MBS session, which detects incoming MBS data packets and points to one FAR that describes forwarding the data to multiple destinations (UPF or RAN nodes):

[0144] - A Packet Filtering Control Protocol (PFCP) session is created when an MBS session is started, regardless of whether the transmission over N3mb and N19mb is multicast or unicast.

[0145] -For multicast transmissions over N3mb and N19mb, the destination in the FAR contains the MB-UPF IP multicast distribution information.

[0146] - For unicast transmission over N3mb and N19mb, the FAR in the PFCP session can contain multiple destinations represented by the NG-RAN N3mb tunnel information and UPF N19mb tunnel information (if applicable).

[0147] Procedure for resuming PDU session in 5G system

[0148] 3GPP TS 23.527, v17.1.0 (the entire contents of which are incorporated herein by reference) specifies the recovery procedures in 5G systems. It covers two scenarios, namely NG-RAN failure and NG-RAN restart.

[0149] -When NG-RAN is restarted (or NG-RAN is restarted), NG-RAN will lose all session contexts and it will send a GTP-U error indication when receiving a DL packet from UPF towards an unknown GTP-U tunnel endpoint. UPF will then report the receipt of the GTP-U error indication to SMF so that SMF can decide whether to resume the MBS session in the restarted NG-RAN.

[0150] - In case of a (partial) failure of the NG-RAN without restart or when there is a user plane path between the NG-RAN and the UPF, the UP function can use the GTP-U echo request / response mechanism to detect such failure. That is, if the UPF does not receive the corresponding GTP-U echo response within the operator's configurable number of retries, the UPF will determine the failure of the GTP-U path and report the failure to the SMF.

[0151] TS 23.527, v17.1.0 also specifies the procedures supported in 5G systems for detecting and handling failures affecting user plane interfaces N3 and N9.

[0152] - Loss of GTP-U context

[0153] A GTP-U entity may lose its GTP-U context upon failure or restart. When a GTP-U node receives a G-PDU for which there is no corresponding GTP-U tunnel, the GTP-U node shall discard the G-PDU and return a GTP-U error indication to the sending node. Receipt of a GTP-U error indication is an indication to the sending GTP-U entity that the peer GTP-U entity can no longer receive user plane traffic on the corresponding GTP-U tunnel.

[0154] - User plane path failure

[0155] The GTP-U entity may detect user plane path failures by using the GTP-U Echo Request and Echo Response messages.

[0156] Figure 5 is a sequence diagram showing an exemplary process of resuming a PDU session in a 5G system. As shown in the figure, at 5.1, the user plane connection of the existing PDU session is activated. A downlink G-PDU will be sent to the NG-RAN. At 5.2, if the NG-RAN does not have a corresponding GTP-U context, the NG-RAN returns a GTP-U error indication. At 5.3, upon receiving the GTP-U error indication, the UPF shall identify the relevant PFCP session and send an error indication report to the SMF. At 5.4, for the GTP-U error indication received from the NG-RAN, the SMF shall modify the PFCP session to instruct the UPF to buffer downlink packets. At 5.5, if the user plane connection of the PDU session is deemed to be activated by the SMF, the SMF shall initiate a Namf_Communication_N1N2MessageTransfer service operation to request the NG-RAN to release the resources of the PDU session.

[0157] At 5.6, upon receiving a Namf_Communication_N1N2MessageTransfer request for transport of a PDU Session Resources Release command, the AMF shall:

[0158] - If the UE is in CM connected state for the access network type associated with the PDU Session, continue with the request;

[0159] - Otherwise, the request is rejected with an error indicating that the UE is in CM Idle state for the access network type associated with the PDU Session. At 5.7, if the AMF sends a PDU Session Resource Release Command to the NG-RAN, the resource release of the PDU Session is responded to by the SMF. At 5.8, the SMF initiates a Network Triggered Service Request procedure to reactivate the user plane connection for the PDU Session.

[0160] Some embodiments of the present disclosure provide solutions for recovering the MBS session in NG-RAN if the MBS session is lost due to NG-RAN failure or restart. These solutions may include one or more of the following features:

[0161] - As specified in sections 7.3.1 and 7.3.3 of TS 23.247, during MBS session start / update for broadcast, the AMF may provide the MB-SMF with the NG-RAN ID in addition to the N2 information received from the NG-RAN in the Namf_MBSBroadcast_ContextCreate response or Namf_MBSBroadcast_ContextNotify request (which is transparent to the AMF). Alternatively, the NG-RAN may include the NG-RAN ID in the N2 container, which is sent to the MB-SMF via the AMF. The MB-SMF may then maintain a mapping between the NG-RAN ID and the DL tunnel information (for unicast transmission over N3mb) for receiving MBS session data.

[0162] -NG-RAN failure / restart can be detected via the control plane (CP) or user plane (UP) as follows:

[0163] --CP solution - AMF detects NG-RAN failure / restart:

[0164] 1. When the AMF detects NG-RAN restart by receiving a NG SETUP REQUEST or NG RESET REQUEST from the NG-RAN, the AMF may inform the MB-SMF via Namf_MBSBroadcast_ContextStatusNotify of the NG-RAN ID (e.g., NG-RAN ID and an indication that the NG-RAN is restarted) and the affected MBS sessions.

[0165] 2. Upon receiving Namf_MBSBroadcast_ContextStatusNotify, MB-SMF may clear or release the user plane resources towards NG-RAN for the MBS session in MB-UPF by removing the DL tunnel information allocated by NG-RAN before the restart.

[0166] 3. The MB-SMF may resume the MBS session towards the AMF via triggering a Namf_MBSBroadcast_ContextUpdate including the NG-RAN ID and an optional “resume” indication.

[0167] 4. The AMF may establish MBS session resources towards the NG-RAN based on the NG-RAN ID received from the MB-SMF.

[0168] 5. For unicast transmission over N3mb, NG-RAN may return new DL tunnel information to AMF, which forwards the new DL tunnel information to MB-SMF. MB-SMF may then provide the new DL tunnel information to MB-UPF, requesting a copy of the MBS session data to be forwarded to the new DL tunnel endpoint.

[0169] (In the event of a NG-RAN failure or N2 path failure, the AMF may detect the NG-RAN failure or N2 path failure (e.g., in response to there being no more transport network layer (TNL) association in service), and inform the MB-SMF via Namf_MBSBroadcast_ContextStatusNotify of the NG-RAN ID (e.g., the NG-RAN ID and an indication of the failure of the NG-RAN or N2 path) and the affected MBS sessions. The MB-SMF may clear the user plane resources towards the NG-RAN for the MBS sessions in the MB-UPF by removing the DL tunnel information allocated by the NG-RAN before the failure.)

[0170] --UP solution - MB-UPF detects NG-RAN failure / restart:

[0171] 1a. For unicast transmission via N3mb:

[0172] 1a - Option 1: The MB-UPF may detect the loss of GTP-U context (due to NG-RAN failure / restart) in the NG-RAN via GTP-U Error Indication. The MB-UPF may accordingly inform the MB-SMF via PFCP Session Report.

[0173] 1a - Option 2: If an Echo Response is not received a configurable number of times after an Echo Request has been sent, the MB-UPF may detect a path failure towards the NG-RAN with the help of UP path management, and the MB-UPF may detect a NG-RAN restart via path management (e.g., the Echo Response contains a restart counter, and an incremented value of the restart counter indicates a restart). The MB-UPF may inform the MB-SMF accordingly via a node level report.

[0174] 1b. For multicast transmission via N3mb:

[0175] 1b-1: During MBS session start for broadcast as specified in section 7.3.1 of TS 23.247, when NG-RAN determines to use multicast transport over N3mb, NG-RAN provides MB-SMF with an additional transport network IP address of NG-RAN, and then provides MB-UPF with an additional transport network IP address of NG-RAN for UP path management. This transport network IP address may enable the peer GTP-U entity (i.e., MB-UPF) to send GTP-U echo requests and receive echo responses in order to detect potential failure / restart of NG-RAN.

[0176] 1b-2: When the MB-UPF detects a NG-RAN restart via UP path management (i.e., the GTP-U (e.g., Echo Response) contains a restart counter, and the incremented value of the restart counter indicates a restart), the MB-UPF may inform the MB-SMF accordingly via node level reporting.

[0177] 2. When the MB-UPF receives a GTP-U error indication or determines NG-RAN failure / restart through UP path management, the MB-UPF may inform the MB-SMF accordingly via PFCP session report or node report.

[0178] 3. The MB-SMF may then initiate resumption of the MBS session towards the NG-RAN in the same manner as steps 3 to 5 of the CP solution described above.

[0179] Figure 6 600 according to an embodiment of the present disclosure. The method may be performed by, for example, an MB-SMF (eg, Figure 2 or Figure 3 In an example, the method may be applied to the above CP solution, where the restart or failure of the NG-RAN is detected by the AMF.

[0180] At block 610, the MB-SMF receives from the AMF an ID of the NG-RAN and an indication of a restart or failure of the NG-RAN (NG-RAN failure or path failure). In an example, an ID of a multicast / broadcast service MBS session associated with the NG-RAN may be received together with the ID of the NG-RAN and the indication of a restart or failure of the NG-RAN. For example, the ID of the NG-RAN, the indication of a restart or failure of the NG-RAN, and the ID of the MBS session may be included in an MBS broadcast context status notification request (e.g., Namf_MBSBroadcast_ContextStatusNotify request). The ID of the NG-RAN may be included in the N2 SM information container (e.g., transparent to the AMF), or carried outside the N2 SM information container (e.g., added by the AMF).

[0181] In an example, prior to block 610, the MB-SMF may initiate a start-up or update procedure for an MBS session (eg, Fig.12 The MB-SMF receives a message (e.g., Namf_MBSBroadcast_ContextCreate response) containing the ID of the NG-RAN from the AMF in the MBS session start procedure shown in FIG. 1 . For example, for unicast transmission over N3mb, the message may also contain tunnel information of the DL tunnel for the MBS session, which may be contained in the N2 SM information container. Therefore, the MB-SMF may maintain a mapping between the ID of the NG-RAN and the tunnel information.

[0182] In an example, in response to receiving an indication of a restart or failure of the NG-RAN, the MB-SMF may send a session modification request (e.g., an N4mb session modification request) to the MB-UPF for releasing the DL tunnel corresponding to the NG-RAN. The session modification request may include the ID of the MBS session and the tunnel information.

[0183] In an example, in response to receiving an indication of restart of the NG-RAN in block 610, the MB-SMF may send a request (e.g., an MBSBroadcast_ContextUpdate request or an MBSBroadcast_ContextCreate request) to the AMF for resuming the MBS session toward the NG-RAN. The request may include an ID of the NG-RAN and an ID of the MBS session. The request may also include an indication of MBS session resumption.

[0184] In an example, after sending a request for resuming an MBS session, the MB-SMF may receive a response to the request for resuming the MBS session (e.g., a Namf_MBSBroadcast_ContextUpdate response) or an MBS broadcast context status notification request (e.g., a Namf_MBSBroadcast_ContextStatusNotify request) from the AMF. For example, the response or the MBS broadcast context status notification request may include the ID of the NG-RAN. For example, for unicast transmission over N3mb, the response or the MBS broadcast context status notification request may also include tunnel information of another DL tunnel for the MBS session. Therefore, the MB-SMF may maintain a mapping between the ID of the NG-RAN and the tunnel information of the other DL tunnel.

[0185] Figure 7 700 according to another embodiment of the present disclosure. The method may be performed by, for example, an MB-SMF (eg, Figure 2 or Figure 3 In an example, the method may be applied to the above-mentioned UP solution, wherein the restart or failure of the NG-RAN is detected by the MB-UPF.

[0186] At block 710, the MB-SMF receives a report from the MB-UPF indicating an error associated with tunnel information of a DL tunnel for a PFCP session (e.g., for unicast transmission over N3mb), or indicating a failure or restart associated with an IP address in the tunnel information (e.g., for unicast transmission over N3mb) or a transport network IP address (e.g., for multicast transmission over N3mb). Here, the transport network IP address may be an IP address for user plane path management. In an example, the report indicating the error may be a PFCP session report (e.g., an N4mb session report request), or the report indicating the failure or restart may be a node level report (e.g., an N4mb node report request).

[0187] At block 720, the MB-SMF identifies the NG-RAN corresponding to the tunnel information, the IP address in the tunnel information, or the transport network IP address.

[0188] At block 730, the MB-SMF sends a request to the AMF for resuming an MBS session corresponding to the PFCP session, the IP address in the tunnel information, or the transport network IP address towards the NG-RAN. For example, the request may include the ID of the NG-RAN and the ID of the MBS session. In an example, the request may also include an indication of MBS session resumption. In an embodiment, the request may be an MBSBroadcast_ContextUpdate request or an MBSBroadcast_ContextCreate request.

[0189] In an example, prior to block 710, the MB-SMF may initiate a start-up or update procedure for an MBS session (eg, Fig.15 In the MBS session start procedure shown in FIG. 1 , the MB-SMF receives a message (e.g., Namf_MBSBroadcast_ContextCreate response) from the AMF containing the ID of the NG-RAN. For example, the ID of the NG-RAN may be included in the N2 SM information container (e.g., transparent to the AMF), or carried outside the N2 SM information container (e.g., added by the AMF). In the example, the message may also contain tunnel information or a transport network IP address. Thus, the MB-SMF may maintain a mapping between the ID of the NG-RAN and the tunnel information, the IP address in the tunnel information, or the transport network IP address. The MB-SMF may signal the tunnel information or the transport network IP address to the MB-UPF (e.g., in an N4mb session update message).

[0190] In an example, for example, after block 730, the MB-SMF may receive a response to a request for resuming the MBS session (e.g., a Namf_MBSBroadcast_ContextUpdate response) or an MBS broadcast context status notification request (e.g., a Namf_MBSBroadcast_ContextStatusNotify request) from the AMF. For example, the response or the MBS broadcast context status notification request may include an ID of the NG-RAN. The response or the MBS broadcast context status notification request may also include tunnel information of another DL tunnel corresponding to the NG-RAN or another transport network IP address. Therefore, the MB-SMF may maintain a mapping between the ID of the NG-RAN and the tunnel information of the other DL tunnel, the IP address in the tunnel information of the other DL tunnel, or the other transport network IP address.

[0191] Figure 8 800 according to an embodiment of the present disclosure. The method may be performed by, for example, an AMF (e.g., Figure 2 or Figure 3In an embodiment, the method may be applied to the above-mentioned CP or UP solution.

[0192] At block 810, the AMF receives a request from the MB-SMF for resuming the MBS session towards the NG-RAN. For example, the request may include an ID of the NG-RAN. For example, the request may also include an ID of the MBS session. In an example, the request may also include an indication of MBS session resumption. In an example, the request may be an MBSBroadcast_ContextUpdate request or an MBSBroadcast_ContextCreate request.

[0193] In an example, prior to block 810, during a startup or update procedure for an MBS session (eg, Fig.12 or Fig.15 In the MBS session start procedure shown in FIG. 1 , the AMF may send another message (e.g., Namf_MBSBroadcast_ContextCreate response) containing the ID of the NG-RAN to the MB-SMF. For example, the ID of the NG-RAN may be included in the N2 SM information container. In the example, for example, for unicast transmission over N3mb, the message may also include tunnel information of the DL tunnel corresponding to the NG-RAN. In this case, the tunnel information may also be included in the other message. The tunnel information may be included in the N2SM information container (e.g., transparent to the AMF).

[0194] Alternatively, prior to block 810, in a startup or update procedure for an MBS session (eg, Fig.12 or Fig.15 In the MBS session start procedure shown in FIG. 1 , the AMF may send a message (e.g., Namf_MBSBroadcast_ContextCreate response) containing the ID of the NG-RAN to the MB-SMF. In an embodiment, the ID of the NG-RAN may be carried outside the N2 SM information container (e.g., added by the AMF).

[0195] In an example, for example, for unicast transmission over N3mb, before sending a message containing the ID of the NG-RAN, the AMF may receive another message (e.g., N2 message response) from the NG-RAN, the other message containing tunnel information of a DL tunnel corresponding to the NG-RAN. For example, the message may also contain the tunnel information. In an example, the tunnel information may be contained in an N2 SM information container.

[0196] In an example, after block 810, the AMF may send a request to the NG-RAN to establish resources for the MBS session (e.g., an MBS session resource establishment request). After sending the above request, the AMF may receive a response to the request to establish resources for the MBS session from the NG-RAN (e.g., an MBS session resource establishment response). The AMF may then send a response to the request to resume the MBS session (e.g., a Namf_MBSBroadcast_ContextUpdate response) or an MBS broadcast context status notification request (e.g., a Namf_MBSBroadcast_ContextStatusNotify request) to the MB-SMF. The response or the MBS broadcast context status notification request may include the ID of the NG-RAN.

[0197] In an example, for example, in the above CP solution, before block 810, the AMF may send the ID of the NG-RAN, the indication of the restart of the NG-RAN, and the ID of the MBS session to the MB-SMF. For example, the ID of the NG-RAN, the indication of the restart of the NG-RAN, and the ID of the MBS session may be included in an MBS broadcast context status notification request (e.g., Namf_MBSBroadcast_ContextStatusNotify request). Before sending the indication of the restart of the NG-RAN, the AMF may receive a NG establishment request or a NG reset request indicating the restart of the NG-RAN from the NG-RAN, and then determine the ID of the MBS session associated with the NG-RAN.

[0198] In an example, for example, in the above-mentioned UP solution, the message received from the NG-RAN may also include tunnel information or a transport network IP address of a DL tunnel corresponding to the NG-RAN. Here, the transport network IP address may be an IP address for user plane path management. In an embodiment, the other message sent to the MB-SMF may also include tunnel information or a transport network IP address. The tunnel information or the transport network IP address may be included in an N2 SM information container. Alternatively, the AMF may receive another message from the NG-RAN, which includes tunnel information or a transport network IP address of a DL tunnel corresponding to the NG-RAN. The message sent to the MB-SMF may also include tunnel information or a transport network IP address. The tunnel information or the transport network IP address may be included in an N2 SM information container.

[0199] In an embodiment, for example, in the above-mentioned UP solution, after block 810, the AMF may send a request for establishing MBS session resources (e.g., an MBS session resource establishment request) to the NG-RAN, and then receive a response to the request for establishing resources for the MBS session (e.g., an MBS session resource establishment response) from the NG-RAN. In an example, the response may include the ID of the NG-RAN and the tunnel information of another DL tunnel corresponding to the NG-RAN or another transport network IP address. The AMF may then send a response to the request for resuming the MBS session (e.g., a Namf_MBSBroadcast_ContextUpdate response) or an MBS broadcast context status notification request (e.g., a Namf_MBSBroadcast_ContextStatusNotify request) to the MB-SMF. In an example, the response or the MBS broadcast context status notification request may include the ID of the NG-RAN and the tunnel information of the other DL tunnel corresponding to the NG-RAN or the other transport network IP address.

[0200] Fig. 9 900 according to another embodiment of the present disclosure. The method may be performed by, for example, an AMF (e.g., Figure 2 or Figure 3 In an embodiment, the method can be applied to the above-mentioned CP or UP solution.

[0201] At step 910, the AMF sends the ID of the NG-RAN and an indication of the failure of the NG-RAN (NG-RAN failure or path failure) to the MB-SMF. In an example, the ID of the multicast / broadcast service MBS session associated with the NG-RAN may be sent together with the ID of the NG-RAN and the indication of the failure of the NG-RAN. For example, the ID of the NG-RAN, the indication of the failure of the NG-RAN, and the ID of the MBS session may be included in an MBS broadcast context status notification request (e.g., Namf_MBSBroadcast_ContextStatusNotify request).

[0202] In an example, prior to block 910, the AMF may use SCTP to detect failure of the NG-RAN.

[0203] In an example, prior to block 910, during a startup or update procedure for an MBS session (eg, Fig.12 or Fig.15In the MBS session start procedure shown in FIG. 1 ), the AMF may receive a message (e.g., N2 message response) containing the ID of the NG-RAN from the NG-RAN, and then send another message (e.g., Namf_MBSBroadcast_ContextCreate response) containing the ID of the NG-RAN to the MB-SMF. The ID of the NG-RAN may be included in the N2 SM information container (e.g., transparent to the AMF). In the example, for example, for unicast transmission over N3mb, the message may also include tunnel information of the DL tunnel corresponding to the NG-RAN, and the other message may also include the tunnel information. The tunnel information may be included in the N2 SM information container.

[0204] Alternatively, prior to block 910, in a startup or update procedure for an MBS session (eg, Fig.12 or Fig.15 In the MBS session start procedure shown in FIG. 1 ), the AMF may send a message (e.g., Namf_MBSBroadcast_ContextCreate response) containing the ID of the NG-RAN to the MB-SMF. For example, the ID of the NG-RAN may be carried outside the N2 SM information container (e.g., transparent to the AMF). In the example, for example, for unicast transmission over N3mb, before sending the message, the AMF may receive another message (e.g., N2 message response) from the NG-RAN, which contains tunnel information of the DL tunnel corresponding to the NG-RAN. Therefore, the message sent to the MB-SMF may also contain the tunnel information. The tunnel information may be contained in the N2 SM information container.

[0205] Fig.10 1 is a flow chart showing a method 1000 according to an embodiment of the present disclosure. The method may be implemented by, for example, an MB-UPF (e.g., Figure 2 or Figure 3 In an example, the method can be applied to the above UP solution.

[0206] At block 1010, for example, Fig.15 In the N4mb session update message in the MBS session start process shown, the MB-UPF receives tunnel information of the DL tunnel (e.g., for unicast transmission via N3mb) or the transport network IP address associated with the MBS session (e.g., for multicast transmission via N3mb) from the MB-SMF. Here, the transport network IP address can be an IP address for user plane path management.

[0207] At block 1020, the MB-UPF sends a report to the MB-SMF indicating an error associated with the tunnel information of the PFCP session corresponding to the MBS session (e.g., for unicast transmission over N3mb), or indicating a failure or restart associated with an IP address or a transport network IP address in the tunnel information (e.g., for multicast transmission over N3mb). In an example, the report indicating the error may be a PFCP session report (e.g., an N4mb session report request), or the report indicating the failure or restart may be a node level report (e.g., an N4mb node report request).

[0208] In an example, for example, for unicast transmission over N3mb, prior to block 1020, the MB-SMF may send packets to the NG-RAN based on the tunnel information (e.g., toward an IP address in the tunnel information), and then receive an indication from the NG-RAN indicating an error.

[0209] In an example, the MB-UPF may receive a session modification request (eg, N4mb session modification request) from the MB-SMF for releasing a DL tunnel corresponding to the NG-RAN. The session modification request may include an ID of the MBS session and tunnel information.

[0210] In an example, after block 1010 and before block 1020, the MB-UPF may send a request for user plane path management to an IP address in the tunnel information (e.g., for unicast transmission over N3mb) or a transport network IP address (e.g., for multicast transmission over N3mb). The MB-SMF may then receive a response from the IP address in the tunnel information or the transport network IP address containing information (restart counter) from which a restart may be derived, or determine failure in response to not receiving a response to the request from the IP address in the tunnel information or the transport network IP address within a predetermined time period. For example, the request for user plane path management may be a GTP-U echo request, and the response may be a GTP-U echo response.

[0211] Fig.11 1 is a flow chart showing a method 1100 according to an embodiment of the present disclosure. The method may be performed by, for example, an NG-RAN (or an NG-RAN node, which may be used interchangeably with NG-RAN in this document) (e.g., Figure 2 In an embodiment, the method may be applied to the above-mentioned CP or UP solution.

[0212] At block 1110, the NG-RAN receives a request from the AMF to establish resources for an MBS session (eg, an MBS session resource establishment request).

[0213] At block 1120, the NG-RAN sends a response to the request to establish resources for the MBS session (e.g., an MBS session resource establishment response) to the AMF. The response includes the ID of the NG-RAN and / or the transport network IP address corresponding to the NG-RAN. The ID of the NG-RAN and / or the transport network IP address are included in the N2 SM information container.

[0214] The following will refer to Figures 12 to 17 The above methods 600, 700, 800, 900, 1000 and 1100 are described in more detail.

[0215] Fig.12 is a sequence diagram showing an exemplary MBS session initiation procedure for broadcasting an MBS session according to an embodiment of the present disclosure. The procedure can be applied to the above-mentioned CP solution.

[0216] At 12.1, in order to establish a broadcast MBS session, the AF performs a temporary mobile group identity (TMGI) allocation and MBS session creation. The MBS service type indicates that it is a broadcast service. At 12.2, the MB-SMF may use the Network Repository Function (NRF) to discover the AMF based on the MBS service area and select an appropriate AMF. Then, if the service type is a broadcast service, the MB-SMF sends an MBS session resource establishment request (TMGI, lower layer multicast (LL MC) address and source host address, 5G QoS profile, MBS service area) message in parallel to the selected AMF. At 12.3, the AMF transmits a Namf_MBSBroadcast_ContextCreate request (TMGI, LL MC and source host address, N2 SM information (5G QoS profile)) message to all NG-RANs that support MBS in the MBS service area. The AMF may include the MBS service area.

[0217] At 12.4, the NG-RAN creates a broadcast MBS session context and stores the TMGI, QoS profile in the MBS session context. The LL MC address and source host address are optional parameters and are provided to the NG-RAN by the MB-SMF only when N3mb multicast transport is configured for use in the 5GC. If the NG-RAN prefers to use N3mb multicast transport (and if the LLMC address is available in the NG-RAN), the NG-RAN joins the multicast group (i.e., the LL MC address), or if the NG-RAN prefers to use N3mb point-to-point transport between the NG-RAN and the MB-UPF (or if the LL MC address is not available in the NG-RAN), the NG-RAN provides its N3mb DL tunnel information. At 12.5, the NG-RAN sends an International Group Management Protocol (IGMP) / Multicast Listener Discovery (MLD) join message to the AMF. At 12.6, the NG-RAN reports the successful establishment of the MBS session resources (which may include multiple MBS QoS flows) by sending an MBS Session Resources Setup Response (TMGI, N3mb DL Tunnel Information, NG-RAN ID) message to the AMF. The N3mb DL Tunnel Information is contained in the N2 SM Information container. The N3mb DL Tunnel Information is available only when point-to-point transport is applied between the MB-UPF and the NG-RAN. The NG-RAN ID may be contained in the N2 SM Information container. In this case, at step 12.7, the NG-RAN ID may be forwarded transparently. Alternatively, the NG-RAN ID may be carried outside the N2 SM Information container.

[0218] At 12.7, AMF transmits Namf_MBSBroadcast_ContextCreate response (TMGI, N3mbDL tunnel information, NG-RAN ID) to MB-SMF. When AMF receives the first successful response from NG-RAN, AMF shall respond with success. If all NG-RANs report failure, AMF shall respond with failure. MB-SMF stores the AMF that responded successfully as a downstream node in the MBS session context. At 12.8, if N3mb point-to-point transmission is to be used (i.e., N3mb DL tunnel information is present in the MBS session start response message from AMF), MB-SMF sends an N4mb session modification request to MB-UPF to allocate an N3mb point-to-point transmission tunnel for the duplicate MBS flow of the MBS session. Otherwise, step 12.8 can be skipped. At 12.9, NG-RAN advertises the TMGI representing the MBS service over the radio interface. Step 12.9 can be performed in parallel with step 12.6. At 12.10, the AF starts sending DL media streams to the MB-UPF using the N6mb tunnel, or optionally sends DL media streams to the MB-UPF in a non-tunneled manner, i.e., as IP multicast streams using the HL MC address. At 12.11, the MB-UPF sends the media streams to the NG-RAN via N3mb multicast transmission or point-to-point transmission. At 12.12, the NG-RAN sends the received DL media streams using DL point-to-multipoint (PTM) resources.

[0219] For further details of the MBS session initiation procedure, reference may be made to clause 7.3.1 of TS 23.247. Similarly, in the MBS session update procedure, the AMF may add the NG-RAN ID in the Namf_MBSBroadcast_ContextUpdate response towards the MB-SMF. For further details of the MBS session update procedure, reference may be made to clause 7.3.1 of TS 23.247.

[0220] Through the above process, for multicast transmission over N3mb, MB-SMF knows the NG-RAN ID of the NG-RAN that has joined the SSM (Source Specific Multicast Address) to receive the broadcast MBS session data, and for unicast transmission over N3mb, for each NG-RAN used for the MBS session, MB-SMF maintains the mapping between the NG-RAN DL tunnel information and the NG-RAN ID.

[0221] Fig.13 1 is a sequence diagram showing an exemplary process of recovering an MBS session according to an embodiment of the present disclosure. In this example, the MBS session is lost due to a restart of the NG-RAN. The process can be applied to the above-mentioned CP solution.

[0222] In this example, after the NG-RAN restarts, the NG-RAN sends an NG Establishment Request or an NG Reset Request to the AMF. The AMF then notifies the MB-SMF of the restart of the NG-RAN so that the MB-SMF can clear the related broadcast MBS session resources and resume the broadcast MBS session in the NG-RAN.

[0223] At 13.1, the NG-RAN sends an NG Setup Request or an NG Reset Request to the AMF, the NG Reset Request indicating the restart or reset of the NG-RAN. At 13.2, the AMF responds to the NG-RAN with an NG Setup Response or an NG Reset Response. At 13.3, the AMF checks the broadcast MBS sessions involving the NG-RAN. For each broadcast MBS session, the AMF sends a Namf_MBSBroadcast_ContextStatusNotify request to the relevant MB-SMF, which includes the ID of the MBS session (hereinafter referred to as the MBS session ID), the NG-RAN ID, and a parameter indicating the restart of the NG-RAN (hereinafter referred to as the NG-RAN restart). At 13.4, if the parameter indicates NG-RAN restart and the unicast transmission of N3mb is applicable to the restarted NG-RAN, the MB-SMF sends an N4mb session modification request including the MBS session ID and the NG-RAN DL tunnel ID (and optionally the NG-RAN ID) to the MB-UPF to release the N3mb DL tunnel. MB-UPF releases the N3mb DL tunnel and sends an N4mb session modification response to MB-SMF. For N3mb multicast transmission, step 13.4 may be optional, because MB-SMF can request MB-UPF to stop multicast transmission only when there is no other NG-RAN joining the MBS session.

[0224] At 13.5, the MB-SMF sends a Namf_MBSBroadcast_ContextStatusNotify response to the AMF. If the parameter indicates that a NG-RAN restart was received in step 13.3, the MB-SMF needs to resume the MBS session towards the restarted NG-RAN. Then, at 13.6, the MB-SMF sends a Namf_MBSBroadcast_ContextUpdate request to the AMF, which contains the MBS session ID, MBS QoS information, MBS tunnel information, MBS service area, an optional indication of MBS session resumption, and an optional NG-RAN ID. At 13.7, based on the indication of MBS session resumption and the NG-RAN ID, the AMF sends an MBS session resource establishment request / MBS session resource update request to the NG-RAN, which contains the MBS session ID, MBS tunnel information, MBS QoS information and MBS service area. If the NG-RAN ID is not provided, the AMF is also able to identify a restarted NG-RAN that is located in the MBS service area but has not yet established broadcast MBS session resources.

[0225] At 13.8, NG-RAN may join SSM based on the MBS tunnel information for multicast transmission of N3mb. At 13.9, NG-RAN allocates a new NG-RAN DL tunnel ID for unicast transmission of N3mb. NG-RAN sends an MBS session resource establishment response / MBS session resource update response containing the MBS session ID to AMF. If an NG-RAN DL tunnel ID is allocated, it needs to be included in the response. NG-RAN may also include the NG-RAN ID in the N2 SM information container to inform the MB-SMF of the NG-RAN ID. At 13.10, AMF sends a Namf_MBSBroadcast_ContextUpdate response to MB-SMF, which contains the MBS session ID, NG-RAN DL tunnel ID and N2 SM information container received in step 13.8. AMF may also include the NG-RAN ID outside the N2 SM information container. If the AMF sends a Namf_MBSBroadcast_ContextUpdate response, it may use the Namf_MBSBroadcast_ContextStatusNotify request / response to pass this information to the MB-SMF.

[0226] At 13.11, MB-SMF sends an N4mb session modification request containing the MBS session ID and the NG-RAN DL tunnel ID to the MB-UPF to establish the N3mb DL tunnel. The MB-UPF establishes the N3mb DL tunnel and sends an N4mb session modification response to the MB-SMF. For multicast transmission of N3mb, step 13.11 is also optional. If multicast transmission of N3mb has been established in the MB-UPF, the MB-SMF may not request multicast transmission from the MB-UPF again. At 13.12, if unicast over N3mb is applicable, the MB-UPF sends downlink data to the NG-RAN. If multicast over N3mb is applicable, the NG-RAN receives the downlink data after joining the SSM in step 13.8.

[0227] Fig.14 1 is a sequence diagram showing an exemplary process of handling NG-RAN failure according to an embodiment of the present disclosure. In this example, the MBS session is lost due to NG-RAN failure. The process can be applied to the above-mentioned CP solution.

[0228] In this example, the NG-RAN fails or the N2 path fails. The AMF detects the failure (e.g., in response to no transport network layer (TNL) association) and notifies the MB-SMF of the NG-RAN failure so that the MB-SMF can clear the related broadcast MBS session resources towards the NG-RAN.

[0229] At 14.1, upon NG-RAN failure or N2 path failure, the AMF detects the failure (e.g., in response to no transport network layer (TNL) association). The AMF checks the broadcast MBS sessions involving the NG-RAN. For each broadcast MBS session, the AMF sends a Namf_MBSBroadcast_ContextStatusNotify request to the relevant MB-SMF, which contains the MBS session ID, the NG-RAN ID, and a parameter indicating the failure of the NG-RAN (hereinafter referred to as NG-RAN failure). At 14.2, if the parameter indicates NG-RAN failure and unicast transmission of N3mb is applicable to the failed NG-RAN, the MB-SMF sends an N4mb session modification request containing the MBS session ID and the NG-RAN DL tunnel ID (and optionally the NG-RAN ID) to the MB-UPF to release the N3mb DL tunnel. The MB-UPF releases the N3mb DL tunnel and sends an N4mb session modification response to the MB-SMF. For N3mb multicast transmission, step 14.2 is optional, because MB-SMF can request MB-UPF to stop multicast transmission only when there is no other NG-RAN joining the MBS session. At 14.3, MB-SMF sends a Namf_MBSBroadcast_ContextStatusNotify response to AMF.

[0230] In the CP solution, for example, combined Fig.13 As described in or 14, AMF detects NG-RAN restart / failure or N2 path failure, and informs MB-SMF in a per-MBS session manner using ContextStatusNotify request. Then, MB-SMF correspondingly resumes the MBS session towards the restarted NG-RAN via AMF.

[0231] The CP solution covers both unicast and multicast transmissions over N3mb. When the NG-RAN ID is not included by the NG-RAN, the impact on the NG-RAN can be avoided. The CP solution is applicable to NG-RAN restart, NG-RAN failure, and path failure between AMF and NG-RAN.

[0232] On the other hand, in the UP solution:

[0233] -For unicast transmission via N3mb,

[0234] As already specified in clause 7.3.1 of TS 23.247, the NG-RAN provides the MB-UPF with the NG-RAN DL tunnel information so that the MB-UPF can send MBS data to the NG-RAN.

[0235] --If the GTP-U context is lost in NG-RAN (e.g. due to failure or restart), the MB-UPF will receive a GTP-U error indication when it sends MBS session data to NG-RAN based on the N3mb DL tunnel information. After receiving the GTP-U error indication, the MB-UPF will report the error indication to the MB-SMF. Fig.16 Describe further details.

[0236] --MB-UPF can perform path management by sending an echo request to NG-RAN. If MB-UPF detects a path failure towards NG-RAN or a restart of NG-RAN, MB-UPF reports the path failure or restart to MB-UPF. Fig.17 Describe further details.

[0237] - For multicast transmission via N3mb:

[0238] Currently, NG-RAN only joins SSM to receive downlink MBS data, so MB-UPF does not know whether NG-RAN can successfully receive MBS data.

[0239] --In order to implement path management over the N3mb user plane path, NG-RAN needs to provide the transport network IP address to allow MB-UPF to run a "GTP-U echo request" to detect a path failure towards NG-RAN or a restart of NG-RAN. When MB-UPF detects a user plane path failure towards NG-RAN or a restart of NG-RAN, MB-UPF will report the path failure or NG-RAN restart to MB-SMF. The following will refer to Fig.17 Describe further details.

[0240] Upon receiving a report indicating a path failure towards the NG-RAN, a restart of the NG-RAN, or a loss of the GTP-U context in the NG-RAN, the MB-SMF triggers MBS session resumption. Fig.16 and Fig.17 Describe further details.

[0241] Fig.15 is a sequence diagram showing an exemplary MBS session initiation process for broadcasting an MBS session according to another embodiment of the present disclosure. The process can be applied to the above-mentioned UP solution.

[0242] Fig.15 Steps 15.1 to 15.5 and steps 15.9 to 15.12 in Fig.12Steps 12.1 to 12.5 and steps 12.9 to 12.12 are the same as in the previous step, so their details will be omitted here.

[0243] At 15.6, in addition to the information described in conjunction with step 12.6, the N2 message response may also include the transport network IP address of the NG-RAN, for example in the N2 SM information container. This address is required for multicast transmission over N3mb for path management and is optional for unicast transmission of N3mb. After receiving the transport network IP address of the NG-RAN at step 15.6, the MB-SMF passes it to the MB-UPF at step 15.7, which may then perform path management (i.e., send a GTP-U echo request to the NG-RAN) to detect NG-RAN restart or failure of the path between the NG-RAN and the MB-UPF. After step 15.7, the MB-SMF maintains a mapping between the NG-RAN ID and the transport network IP address of the NG-RAN. Therefore, at 15.8, in addition to the information described in conjunction with step 12.8, the N4mb session update message may also include the received transport network IP address of the NG-RAN.

[0244] Fig.16 is a sequence diagram illustrating an exemplary process of recovering an MBS session according to an embodiment of the present disclosure. In this example, an MBS session with an activated user plane connection toward the MB-UPF is lost due to a restart or failure of the NG-RAN. The process can be applied to a UP solution where the MB-UPF detects a restart or failure of the NG-RAN. In this example, the restart or failure of the NG-RAN is indicated by a GTP-U error indication.

[0245] At 16.1, the MB-UPF sends a GTP-U packet to the NG-RAN. At 16.2, if the NG-RAN does not have a corresponding GTP-U context, the NG-RAN returns a GTP-U error indication. At 16.3, the MB-UPF identifies the relevant PFCP session and sends an error indication report to the MB-SMF. At 16.4, the MB-SMF modifies the PFCP session to release the downlink tunnel towards the NG-RAN. At 16.5, the MB-SMF initiates a Namf_MBSBroadcast_ContextUpdate request for the broadcast MBS session. In this request, the MB-SMF provides the AMF with the MBS session ID, MBS QoS information, multicast tunnel information and MBS service area, an optional indication for MBS session resumption, and an optional parameter NG-RAN ID. At 16.6, the AMF identifies the NG-RAN based on the indication of MBS session resumption and the NG-RAN ID. The AMF then sends an MBS session resource establishment request to the NG-RAN, which contains the MBS session ID, MBS QoS information, multicast tunnel information, and MBS service area. At 16.7, the NG-RAN can join the SSM based on the MBS tunnel information for multicast transmission of N3mb. The NG-RAN allocates NG-RAN DL tunnel information for unicast transmission over N3mb. The NG-RAN sends an MBS session resource establishment response containing the MBS session ID to the AMF. If the NG-RAN DL tunnel information is allocated, it needs to be included in the response. The NG-RAN can also include the NG-RAN ID in the N2SM information container to inform the MB-SMF of the NG-RAN ID. The NG-RAN can include the transport network IP address in the N2 SM information container, which is required for multicast transmission over N3mb and is optional for unicast transmission of N3mb. At 16.8, the AMF sends a Namf_MBSBroadcast_ContextUpdate response to the MB-SMF, which contains the MBS session ID, the N2 SM information container and / or the transport network IP address, and the N2 SM information container may include the NG-RAN ID. The AMF may also include the NG-RAN ID outside the N2 SM information container. If the AMF sends a Namf_MBSBroadcast_ContextUpdate response, it may use the Namf_MBSBroadcast_ContextStatusNotify request / response to pass this information to the MB-SMF.At 16.9, the MB-SMF sends an N4mb session modification request to the MB-UPF, which contains the MBS session ID and the NG-RAN DL tunnel ID and / or the transport network IP address. If new NG-RAN DL tunnel information is received, the MB-UPF establishes an N3mb DL tunnel for session data delivery. At 16.10, the MB-UPF sends downlink data to the NG-RAN via N3mb unicast transmission.

[0246] Fig.17 is a sequence diagram illustrating an exemplary process of recovering an MBS session according to another embodiment of the present disclosure. In this example, an MBS session with an activated user plane connection toward the MB-UPF is lost due to a restart or failure of the NG-RAN. The process can be applied to a UP solution where the MB-UPF detects a restart or failure of the NG-RAN. In this example, the restart or failure of the NG-RAN is indicated in a GTP-U echo response.

[0247] For NG-RAN restart, the following steps are performed. At 17.1, if the MB-UPF has received the transport network IP address for path management, the MB-UPF sends a GTP-U echo request to the NG-RAN. At 17.2, the NG-RAN sends a GTP-U echo response with an indication of the NG-RAN restart to the MB-UPF. At 17.3, the MB-UPF reports the NG-RAN restart to the MB-SMF using node level reporting along with the transport network IP of the NG-RAN. Then, for each affected broadcast MBS session, at 17.4 to 17.9, the MB-SMF triggers the MBS session recovery procedure, which are the same as steps 16.5 to 16.10, respectively, and their details will be omitted here.

[0248] For NG-RAN failure, the following steps are performed. At 17.1, the MB-UPF sends a GTP-U echo request to the NG-RAN. At 17.2, if a GTP-U echo response is not received from the NG-RAN one or more times, the MB-UPF may consider the NG-RAN to have failed or the user plane path towards the NG-RAN to have failed, and then report the NG-RAN failure (or N3mb path failure) at 17.3. Then, for each affected broadcast MBS session, at 17.4 to 17.9, the MB-SMF may trigger the MBS session recovery procedure, which are the same as steps 16.5 to 16.10, respectively, and their details will be omitted here.

[0249] The UP solution is applicable to NG-RAN restart, NG-RAN failure, and path failure between NG-RAN and MB-UPF. In the UP solution, NG-RAN needs to provide the transport network IP address for multicast transmission over N3mb.

[0250] Corresponding to the method 600 described above, a network node is provided. Fig.18 is a block diagram of a network node 1800 according to an embodiment of the present disclosure.

[0251] The network node 1800 may be, for example, Figure 2 or Figure 3 The MB-SMF shown above can be configured to perform Figure 6 The method 600 is described. Fig.18 As shown, the network node 1800 includes a receiving unit 1810, which is configured to receive an ID of the NG-RAN and an indication of restart or failure of the NG-RAN from the AMF.

[0252] In an embodiment, the ID of the multicast / broadcast service MBS session associated with the NG-RAN may be received together with the ID of the NG-RAN and an indication of a restart or failure of the NG-RAN.

[0253] In an embodiment, the ID of the NG-RAN, the indication of the restart or failure of the NG-RAN, and the ID of the MBS session may be included in the MBS Broadcast Context Status Notification Request.

[0254] In an embodiment, before the receiving operation, the receiving unit 1810 may also be configured to: receive a message including an ID of the NG-RAN from the AMF during the initiation or update process for the MBS session.

[0255] In an embodiment, the ID of the NG-RAN may be included in the N2 SM information container, or carried outside the N2 SM information container.

[0256] In an embodiment, the message may also include tunnel information of a DL tunnel for an MBS session. In an embodiment, the tunnel information may be included in an N2 SM information container. In an embodiment, the network node 1800 may also include a maintenance unit configured to maintain a mapping between an ID of the NG-RAN and the tunnel information.

[0257] In an embodiment, the network node 1800 may further include a sending unit configured to: in response to receiving the indication, send a session modification request for releasing the DL tunnel corresponding to the NG-RAN to the MB-UPF. In an embodiment, the session modification request may include an ID of the MBS session and tunnel information.

[0258] In an embodiment, the sending unit may be further configured to: in response to receiving an indication of restart of the NG-RAN, send a request to the AMF for resuming the MBS session towards the NG-RAN. In an embodiment, the request may include an ID of the NG-RAN and an ID of the MBS session.

[0259] In an embodiment, the request may be an MBS broadcast context update request or an MBS broadcast context create request.

[0260] In an embodiment, the request may also include an indication of MBS session resumption.

[0261] In an embodiment, the receiving unit 1810 may also be configured to: receive a response to a request for resuming an MBS session or an MBS broadcast context status notification request from the AMF. In an embodiment, the response or the MBS broadcast context status notification request may include an ID of the NG-RAN.

[0262] In an embodiment, the response or the MBS broadcast context status notification request may also include tunnel information of another DL tunnel for the MBS session. In an embodiment, the maintenance unit may also be configured to: maintain a mapping between the ID of the NG-RAN and the tunnel information of the another DL tunnel.

[0263] Unit 1810 is implemented as a pure hardware solution or as a combination of software and hardware, for example, it can be implemented by one or more of the following items: configured to perform the above description and for example in Figure 6 The actions shown are performed by a processor or microprocessor and appropriate software and a memory, a programmable logic device (PLD) or other electronic component or processing circuit for storing the software.

[0264] Corresponding to the method 700 described above, a network node is provided. Fig.19 is a block diagram of a network node 1900 according to another embodiment of the present disclosure.

[0265] The network node 1900 may be, for example, Figure 2 or Figure 3 The MB-SMF shown above can be configured to perform Figure 7 The method 700 is described. Fig.19As shown, the network node 1900 includes a receiving unit 1910, which is configured to receive a report from the MB-UPF, the report indicating: an error associated with the tunnel information of the DL tunnel for the PFCP session, or a failure or restart associated with the IP address in the tunnel information or the transport network IP address. The network node 1900 also includes an identification unit 1920, which is configured to: identify the NG-RAN corresponding to the tunnel information, the IP address in the tunnel information, or the transport network IP address. The network node 1900 also includes a sending unit 1930, which is configured to: send a request to the AMF for resuming the MBS session, the MBS session corresponding to the PFCP session, the IP address in the tunnel information, or the transport network IP address towards the NG-RAN. The request contains the ID of the NG-RAN and the ID of the MBS session.

[0266] In an embodiment, the report may be a PFCP session report or a node level report.

[0267] In an embodiment, before the receiving operation, the receiving unit 1910 may also be configured to: receive a message including an ID of the NG-RAN from the AMF during the initiation or update process for the MBS session.

[0268] In an embodiment, the ID of the NG-RAN may be included in the N2 SM information container, or carried outside the N2 SM information container.

[0269] In an embodiment, the message may also include tunnel information or a transport network IP address.

[0270] In an embodiment, the network node 1900 may further include a maintenance unit configured to maintain a mapping between the ID of the NG-RAN and the tunnel information, the IP address in the tunnel information, or the transport network IP address.

[0271] In an embodiment, the network node 1900 may further include a signaling unit configured to send a signal to the MB-UPF to notify the tunnel information or the transport network IP address.

[0272] In an embodiment, the receiving unit 1910 may also be configured to: receive a response to a request for resuming an MBS session or an MBS broadcast context status notification request from the AMF. In an embodiment, the response or the MBS broadcast context status notification request may include an ID of the NG-RAN.

[0273] In an embodiment, the response or the MBS broadcast context status notification request may also include tunnel information of another DL tunnel corresponding to the NG-RAN or another transport network IP address.

[0274] In an embodiment, the maintenance unit may further be configured to: maintain a mapping between the ID of the NG-RAN and the tunnel information of the other DL tunnel, the IP address in the tunnel information of the other DL tunnel, or the IP address of the other transport network.

[0275] In an embodiment, the transport network IP address may be an IP address used for user plane path management.

[0276] In an embodiment, the request for resuming the MBS session may be an MBS broadcast context update request or an MBS broadcast context create request.

[0277] In an embodiment, the request for resuming the MBS session may further include an indication of MBS session resumption.

[0278] Units 1910 to 1930 are implemented as a pure hardware solution or as a combination of software and hardware, for example, by one or more of the following: configured to perform the above description and, for example, in Figure 7 The actions shown are performed by a processor or microprocessor and appropriate software and a memory, a programmable logic device (PLD) or other electronic component or processing circuit for storing the software.

[0279] Corresponding to the method 800 described above, a network node is provided. Fig. 20 is a block diagram illustrating a network node 2000 according to another embodiment of the present disclosure.

[0280] The network node 2000 may be, for example, Figure 2 or Figure 3 The AMF shown above can be configured to perform Figure 8 The method 800 is described. Fig. 20 As shown, the network node 2000 includes a receiving unit 2010, which is configured to: receive a request for resuming an MBS session toward NG-RAN from the MB-SMF. The request includes an ID of the NG-RAN. The request may also include an ID of the MBS session.

[0281] In an embodiment, before the receiving operation, the receiving unit 2010 may also be configured to: send another message including the ID of the NG-RAN to the MB-SMF during the initiation or update process for the MBS session. In an embodiment, the ID of the NG-RAN may be included in the N2 SM information container.

[0282] In an embodiment, the message may also include tunnel information of a DL tunnel corresponding to the NG-RAN. In an embodiment, the other message may also include tunnel information. In an embodiment, the tunnel information may be included in an N2 SM information container.

[0283] In an embodiment, the network node 2000 may further include a sending unit configured to: send a message including an ID of the NG-RAN to the MB-SMF during the initiation or update process for the MBS session. In an embodiment, the ID of the NG-RAN may be carried outside the N2 SM information container.

[0284] In an embodiment, the receiving unit 2010 may be further configured to: receive another message from the NG-RAN, the other message including tunnel information of a DL tunnel corresponding to the NG-RAN. In an embodiment, the message may also include tunnel information. In an embodiment, the tunnel information may be included in an N2 SM information container.

[0285] In an embodiment, after receiving the request for resuming the MBS session, the sending unit may be further configured to: send a request to the NG-RAN to establish resources for the MBS session. In an embodiment, the receiving unit 2010 may be further configured to: receive a response to the request to establish resources for the MBS session from the NG-RAN. In an embodiment, the sending unit may be further configured to: send a response to the request for resuming the MBS session or a MBS broadcast context status notification request to the MB-SMF. In an embodiment, the response or the MBS broadcast context status notification request may include an ID of the NG-RAN.

[0286] In an embodiment, before receiving the request for resuming the MBS session, the sending unit may further be configured to: send the ID of the NG-RAN, an indication of restarting the NG-RAN, and the ID of the MBS session to the MB-SMF.

[0287] In an embodiment, the ID of the NG-RAN, the indication of the restart of the NG-RAN, and the ID of the MBS session may be included in the MBS broadcast context status notification request.

[0288] In an embodiment, before sending an indication of restart of NG-RAN, the receiving unit 2010 may also be configured to: send an NG establishment request or an NG reset request from NG-RAN, the NG reset request indicating restart of NG-RAN. In an embodiment, the network node 2000 may also include a determining unit configured to determine an ID of an MBS session associated with NG-RAN.

[0289] In an embodiment, the message may also include tunnel information or a transport network IP address of a DL tunnel corresponding to the NG-RAN. In an embodiment, the other message may also include the tunnel information or the transport network IP address. In an embodiment, the tunnel information or the transport network IP address may be included in an N2 SM information container.

[0290] In an embodiment, the receiving unit 2010 may be further configured to receive another message from the NG-RAN, the other message including tunnel information or a transport network IP address of a DL tunnel corresponding to the NG-RAN. In an embodiment, the message may also include the tunnel information or the transport network IP address. In an embodiment, the tunnel information or the transport network IP address may be included in an N2 SM information container.

[0291] In an embodiment, after receiving the request for resuming the MBS session, the sending unit may further be configured to: send a request to the NG-RAN to establish resources for the MBS session. In an embodiment, the receiving unit 2010 may further be configured to: receive a response to the request to establish resources for the MBS session from the NG-RAN. In an embodiment, the response may include an ID of the NG-RAN and tunnel information of another DL tunnel corresponding to the NG-RAN or another transport network IP address. In an embodiment, the sending unit may further be configured to: send a response to the request for resuming the MBS session or an MBS broadcast context status notification request to the MB-SMF. In an embodiment, the response or the MBS broadcast context status notification request may include an ID of the NG-RAN and tunnel information of another DL tunnel corresponding to the NG-RAN or another transport network IP address.

[0292] In an embodiment, the transport network IP address may be an IP address used for user plane path management.

[0293] In an embodiment, the request for resuming the MBS session may be an MBS broadcast context update request or an MBS broadcast context create request.

[0294] In an embodiment, the request for resuming the MBS session may further include an indication of MBS session resumption.

[0295] The unit 2010 is implemented as a pure hardware solution or as a combination of software and hardware, for example, it can be implemented by one or more of the following items: configured to perform the above description and for example in Figure 8 The actions shown are performed by a processor or microprocessor and appropriate software and a memory, a programmable logic device (PLD) or other electronic component or processing circuit for storing the software.

[0296] Corresponding to the method 900 described above, a network node is provided. Fig.21 is a block diagram illustrating a network node 2100 according to another embodiment of the present disclosure.

[0297] The network node 2100 may be, for example, Figure 2 or Figure 3 The AMF shown above can be configured to perform Fig. 9 The method 900 is described. Fig.21 As shown, the network node 2100 includes a sending unit 2110, which is configured to send an ID of the NG-RAN and an indication of a failure of the NG-RAN to the MB-SMF.

[0298] In an embodiment, the ID of the multicast / broadcast service MBS session associated with the NG-RAN may be sent together with the ID of the NG-RAN and an indication of the failure of the NG-RAN.

[0299] In an embodiment, the ID of the NG-RAN, the indication of the failure of the NG-RAN, and the ID of the MBS session may be included in the MBS Broadcast Context Status Notification Request.

[0300] In an embodiment, the network node 2100 may further include a detection unit, which is configured to: use SCTP to detect a failure of the NG-RAN before the sending operation.

[0301] In an embodiment, the network node 2100 may further include a sending unit configured to: receive a message including an ID of the NG-RAN from the NG-RAN during the initiation or update process for the MBS session. In an embodiment, the sending unit 2110 may further be configured to: send another message including the ID of the NG-RAN to the MB-SMF. In an embodiment, the ID of the NG-RAN may be included in the N2 SM information container.

[0302] In an embodiment, the message may also include tunnel information of a DL tunnel corresponding to the NG-RAN. In an embodiment, the other message may also include tunnel information. In an embodiment, the tunnel information may be included in an N2 SM information container.

[0303] In an embodiment, the sending unit 2110 may also be configured to: send a message including the ID of the NG-RAN to the MB-SMF during the start-up or update process for the MBS session. In an embodiment, the ID of the NG-RAN may be carried outside the N2 SM information container.

[0304] In an embodiment, the receiving unit may be further configured to: receive another message from the NG-RAN, the other message including tunnel information of a DL tunnel corresponding to the NG-RAN. In an embodiment, the message may also include tunnel information. In an embodiment, the tunnel information may be included in an N2 SM information container.

[0305] The unit 2110 is implemented as a pure hardware solution or as a combination of software and hardware, for example, it can be implemented by one or more of the following items: configured to perform the above description and for example in Fig. 9 The actions shown are performed by a processor or microprocessor and appropriate software and a memory, a programmable logic device (PLD) or other electronic component or processing circuit for storing the software.

[0306] Corresponding to the method 1000 described above, a network node is provided. Fig. 22 is a block diagram illustrating a network node 2200 according to another embodiment of the present disclosure.

[0307] The network node 2200 may be, for example, Figure 2 or Figure 3 The MB-UPF shown above can be configured to perform Fig.10 The method 1000 is described. Fig. 22 As shown, the network node 2200 includes a receiving unit 2210, which is configured to: receive tunnel information or a transport network IP address of a DL tunnel associated with an MBS session from the MB-SMF. The network node 2200 also includes a sending unit 2220, which is configured to send a report to the MB-SMF, the report indicating: an error associated with the tunnel information of the PFCP session corresponding to the MBS session, or a failure or restart associated with the IP address in the tunnel information or the transport network IP address.

[0308] In an embodiment, the report may be a PFCP session report or a node level report.

[0309] In an embodiment, before the sending operation, the sending unit 2220 may be further configured to: send a packet to the NG-RAN based on the tunnel information. In an embodiment, the receiving unit 2210 may be further configured to: receive an indication indicating an error from the NG-RAN.

[0310] In an embodiment, the receiving unit 2210 may be further configured to: receive a session modification request for releasing a DL tunnel corresponding to the NG-RAN from the MB-SMF. In an embodiment, the session modification request may include an ID of the MBS session and tunnel information.

[0311] In an embodiment, after the receiving operation and before the sending operation, the sending unit 2220 may also be configured to: send a request for user plane path management to the IP address in the tunnel information or the transport network IP address. In an embodiment, the receiving unit 2210 may also be configured to: receive a response containing information from which the restart can be derived from the IP address in the tunnel information or the transport network IP address. In an embodiment, the network node 2200 may also include a determining unit, which is configured to: determine failure in response to not receiving a response to the request from the IP address in the tunnel information or the transport network IP address within a predetermined time period.

[0312] In an embodiment, the request for user plane path management may be a GTP-U echo request.In an embodiment, the response may be a GTP-U echo response.

[0313] In an embodiment, the transport network IP address may be an IP address used for user plane path management.

[0314] Units 2210 to 2220 are implemented as a pure hardware solution or as a combination of software and hardware, for example, they may be implemented by one or more of the following items: configured to perform the above description and, for example, in Fig.10 The actions shown are performed by a processor or microprocessor and appropriate software and a memory, a programmable logic device (PLD) or other electronic component or processing circuit for storing the software.

[0315] Corresponding to the method 1100 described above, a network node is provided. Fig.23 is a block diagram illustrating a network node 2300 according to another embodiment of the present disclosure.

[0316] The network node 2300 may be, for example, Figure 2 or Figure 3 The NG-RAN (node) shown above can be configured to perform the above combined Fig.11 The method 1100 is described. Fig.23 As shown, the network node 2300 includes a receiving unit 2310, which is configured to: receive a request to establish resources for an MBS session from the AMF. The network node 2300 also includes a sending unit 2320, which is configured to: send a response to the request to establish resources for the MBS session to the AMF. The response includes an ID of the NG-RAN and / or a transport network IP address corresponding to the NG-RAN. In an embodiment, the ID of the NG-RAN and / or the transport network IP address are included in the N2SM information container.

[0317] Units 2310 to 2320 are implemented as a pure hardware solution or as a combination of software and hardware, for example, they may be implemented by one or more of the following: configured to perform the above description and, for example, in Fig.11 The actions shown are performed by a processor or microprocessor and appropriate software and a memory, a programmable logic device (PLD) or other electronic component or processing circuit for storing the software.

[0318] Fig.24 is a block diagram illustrating a network node 2400 according to another embodiment of the present disclosure.

[0319] The network node 2400 includes a communication interface 2410 , a processor 2420 , and a memory 2430 .

[0320] As an example, the network node 2400 may be Figure 2 or Figure 3 MB-SMF shown. The memory 2430 may contain instructions executable by the processor 2420, whereby the network node 2400 may be operable to: when implementing MB-SMF, perform, for example, the previously described Figure 6 Specifically, the memory 2430 may contain instructions executable by the processor 2420, whereby the network node 2400 may be operable to: when implementing MB-SMF, receive from the AMF an ID of the NG-RAN and an indication of a restart or failure of the NG-RAN.

[0321] In an embodiment, the ID of the multicast / broadcast service MBS session associated with the NG-RAN may be received together with the ID of the NG-RAN and an indication of a restart or failure of the NG-RAN.

[0322] In an embodiment, the ID of the NG-RAN, the indication of the restart or failure of the NG-RAN, and the ID of the MBS session may be included in the MBS Broadcast Context Status Notification Request.

[0323] In an example, the memory 2430 may also include instructions executable by the processor 2420, whereby the network node 2400 may be operable to: when implementing MB-SMF, prior to a receiving operation, receive a message including an ID of the NG-RAN from the AMF during a start-up or update process for an MBS session.

[0324] In an embodiment, the ID of the NG-RAN may be included in the N2 Session Management (SM) information container, or carried outside the N2 SM information container.

[0325] In an embodiment, the message may also include tunnel information for the DL tunnel of the MBS session. In an embodiment, the tunnel information may be included in an N2 SM information container. In an example, the memory 2430 may also include instructions executable by the processor 2420, whereby the network node 2400 may be operable to: maintain a mapping between the ID of the NG-RAN and the tunnel information when implementing the MB-SMF.

[0326] In an example, the memory 2430 may also include instructions executable by the processor 2420, whereby the network node 2400 may be operable to: when implementing the MB-SMF, in response to receiving the indication, send a session modification request to the MB-UPF for releasing the DL tunnel corresponding to the NG-RAN. In an embodiment, the session modification request may include an ID of the MBS session and tunnel information.

[0327] In an example, the memory 2430 may further include instructions executable by the processor 2420, whereby the network node 2400 may be operable to: when implementing the MB-SMF, in response to receiving an indication of a restart of the NG-RAN, send a request to the AMF for resuming the MBS session towards the NG-RAN. In an embodiment, the request may include an ID of the NG-RAN and an ID of the MBS session.

[0328] In an embodiment, the request may be an MBS broadcast context update request or an MBS broadcast context create request.

[0329] In an embodiment, the request may also include an indication of MBS session resumption.

[0330] In an example, the memory 2430 may also include instructions executable by the processor 2420, whereby the network node 2400 may be operable to: when implementing MB-SMF, receive from the AMF a response to a request for resuming an MBS session or an MBS broadcast context status notification request. In an embodiment, the response or the MBS broadcast context status notification request may include an ID of the NG-RAN.

[0331] In an embodiment, the response or the MBS broadcast context status notification request may also include tunnel information of another DL tunnel for the MBS session. In an example, the memory 2430 may also include instructions executable by the processor 2420, whereby the network node 2400 may be operated to: maintain a mapping between the ID of the NG-RAN and the tunnel information of the other DL tunnel when implementing the MB-SMF.

[0332] Alternatively, network node 2400 may be Figure 2 or Figure 3 MB-SMF shown. The memory 2430 may contain instructions executable by the processor 2420, whereby the network node 2400 may be operable to: when implementing MB-SMF, perform, for example, the previously described Figure 7The actions of the described process. Specifically, the memory 2430 may include instructions executable by the processor 2420, whereby the network node 2400 is operable to: when implementing MB-SMF, receive a report from the MB-UPF, the report indicating: an error associated with the tunnel information of the DL tunnel for the PFCP session, or a failure or restart associated with the IP address in the tunnel information or the transport network IP address. In an example, the memory 2430 also includes instructions executable by the processor 2420, whereby the network node 2400 is operable to: when implementing MB-SMF, identify the NG-RAN corresponding to the tunnel information, the IP address in the tunnel information, or the transport network IP address. In an example, the memory 2430 also includes instructions executable by the processor 2420, whereby the network node 2400 is operable to: when implementing MB-SMF, send a request to the AMF for resuming an MBS session, the MBS session corresponding to the PFCP session, the IP address in the tunnel information, or the transport network IP address towards the NG-RAN. The request includes the ID of the NG-RAN and the ID of the MBS session.

[0333] In an embodiment, the report may be a PFCP session report or a node level report.

[0334] In an example, the memory 2430 may also include instructions executable by the processor 2420, whereby the network node 2400 may be operable to: when implementing MB-SMF, prior to a receiving operation, receive a message including an ID of the NG-RAN from the AMF during a start-up or update process for an MBS session.

[0335] In an embodiment, the ID of the NG-RAN may be included in the N2 SM information container, or carried outside the N2 SM information container.

[0336] In an embodiment, the message may also include tunnel information or a transport network IP address.

[0337] In an example, the memory 2430 may also include instructions executable by the processor 2420, whereby the network node 2400 may be operable to: when implementing MB-SMF, maintain a mapping between the ID of the NG-RAN and the tunnel information, the IP address in the tunnel information, or the transport network IP address.

[0338] In an example, the memory 2430 may also contain instructions executable by the processor 2420, whereby the network node 2400 is operable to: signal the tunnel information or the transport network IP address to the MB-UPF when implementing the MB-SMF.

[0339] In an example, the memory 2430 may also include instructions executable by the processor 2420, whereby the network node 2400 may be operable to: when implementing MB-SMF, receive from the AMF a response to a request for resuming an MBS session or an MBS broadcast context status notification request, the response or the MBS broadcast context status notification request including an ID of the NG-RAN.

[0340] In an embodiment, the response or the MBS broadcast context status notification request may also include tunnel information of another DL tunnel corresponding to the NG-RAN or another transport network IP address.

[0341] In an example, the memory 2430 may also include instructions executable by the processor 2420, whereby the network node 2400 may be operable to: when implementing MB-SMF, maintain a mapping between the ID of the NG-RAN and the tunnel information of the other DL tunnel, the IP address in the tunnel information of the other DL tunnel, or the IP address of the other transport network.

[0342] In an embodiment, the transport network IP address may be an IP address used for user plane path management.

[0343] In an embodiment, the request for resuming the MBS session may be an MBS broadcast context update request or an MBS broadcast context create request.

[0344] In an embodiment, the request for resuming the MBS session may further include an indication of MBS session resumption.

[0345] Alternatively, network node 2400 may be Figure 2 or Figure 3 The memory 2430 may contain instructions executable by the processor 2420, whereby the network node 2400 may be operable to: when implementing the AMF, perform, for example, the previously combined Figure 8 The actions of the process described. Specifically, the memory 2430 may include instructions executable by the processor 2420, whereby the network node 2400 may be operated to: when implementing the AMF, receive a request from the MB-SMF for resuming the MBS session towards the NG-RAN. The request includes the ID of the NG-RAN. The request may also include the ID of the MBS session.

[0346] In an example, the memory 2430 further includes instructions executable by the processor 2420, whereby the network node 2400 is operable to: when implementing the AMF, before receiving the operation, in the process of initiating or updating the MBS session, send another message including the ID of the NG-RAN to the MB-SMF. In an embodiment, the ID of the NG-RAN may be included in the N2 SM information container.

[0347] In an embodiment, the message may also include tunnel information of a DL tunnel corresponding to the NG-RAN. In an embodiment, the other message may also include tunnel information. In an embodiment, the tunnel information may be included in an N2 SM information container.

[0348] In an example, the memory 2430 further includes instructions executable by the processor 2420, whereby the network node 2400 is operable to: when implementing the AMF, before receiving the operation, in the process of initiating or updating the MBS session, send a message including the ID of the NG-RAN to the MB-SMF. In an embodiment, the ID of the NG-RAN may be carried outside the N2 SM information container.

[0349] In an example, the memory 2430 further includes instructions executable by the processor 2420, whereby the network node 2400 is operable to: when implementing the AMF, receive another message from the NG-RAN, the other message including tunnel information of a DL tunnel corresponding to the NG-RAN. In an embodiment, the message may also include the tunnel information. In an embodiment, the tunnel information may be included in an N2 SM information container.

[0350] In an example, the memory 2430 further includes instructions executable by the processor 2420, whereby the network node 2400 is operable to: when implementing the AMF, after receiving the request for resuming the MBS session, send a request to the NG-RAN to establish resources for the MBS session. In an example, the memory 2430 further includes instructions executable by the processor 2420, whereby the network node 2400 is operable to: when implementing the AMF, receive a response to the request to establish resources for the MBS session from the NG-RAN. In an example, the memory 2430 further includes instructions executable by the processor 2420, whereby the network node 2400 is operable to: when implementing the AMF, send a response to the request for resuming the MBS session or a MBS broadcast context status notification request to the MB-SMF. In an embodiment, the response or the MBS broadcast context status notification request may include an ID of the NG-RAN.

[0351] In an example, the memory 2430 further includes instructions executable by the processor 2420, whereby the network node 2400 is operable to: when implementing the AMF, before receiving a request to resume the MBS session, send the ID of the NG-RAN, an indication of restart of the NG-RAN, and the ID of the MBS session to the MB-SMF.

[0352] In an embodiment, the ID of the NG-RAN, the indication of the restart of the NG-RAN, and the ID of the MBS session may be included in the MBS broadcast context status notification request.

[0353] In an example, the memory 2430 further includes instructions executable by the processor 2420, whereby the network node 2400 is operable to: when implementing the AMF, before sending an indication of the restart of the NG-RAN, receive a NG establishment request or a NG reset request from the NG-RAN, the NG reset request indicating the restart of the NG-RAN. In an example, the memory 2430 further includes instructions executable by the processor 2420, whereby the network node 2400 is operable to: when implementing the AMF, determine an ID of an MBS session associated with the NG-RAN.

[0354] In an embodiment, the message may also include tunnel information or a transport network IP address of a DL tunnel corresponding to the NG-RAN. In an embodiment, the other message may also include the tunnel information or the transport network IP address. In an embodiment, the tunnel information or the transport network IP address may be included in an N2 SM information container.

[0355] In an example, the memory 2430 further includes instructions executable by the processor 2420, whereby the network node 2400 is operable to: when implementing the AMF, receive another message from the NG-RAN, the other message including tunnel information or a transport network IP address of a DL tunnel corresponding to the NG-RAN. In an embodiment, the message may also include the tunnel information or the transport network IP address. In an embodiment, the tunnel information or the transport network IP address may be included in an N2 SM information container.

[0356] In an example, the memory 2430 further includes instructions executable by the processor 2420, whereby the network node 2400 is operable to: when implementing the AMF, after receiving the request for resuming the MBS session, send a request to the NG-RAN to establish resources for the MBS session. In an example, the memory 2430 further includes instructions executable by the processor 2420, whereby the network node 2400 is operable to: when implementing the AMF, receive from the NG-RAN a response to the request for establishing resources for the MBS session, the response including an ID of the NG-RAN and tunnel information of another DL tunnel corresponding to the NG-RAN or another transport network IP address. In an example, the memory 2430 further includes instructions executable by the processor 2420, whereby the network node 2400 is operable to: when implementing the AMF, send to the MB-SMF a response to the request for resuming the MBS session or an MBS broadcast context status notification request. In an example, the response or the MBS broadcast context status notification request may include the ID of the NG-RAN and the tunnel information of the other DL tunnel corresponding to the NG-RAN or the other transport network IP address.

[0357] In an embodiment, the transport network IP address may be an IP address used for user plane path management.

[0358] In an embodiment, the request for resuming the MBS session may be an MBS broadcast context update request or an MBS broadcast context create request.

[0359] In an embodiment, the request for resuming the MBS session may further include an indication of MBS session resumption.

[0360] Alternatively, network node 2400 may be Figure 2 or Figure 3 The memory 2430 may contain instructions executable by the processor 2420, whereby the network node 2400 may be operable to: when implementing the AMF, perform, for example, the previously combined Fig. 9 Specifically, the memory 2430 may contain instructions executable by the processor 2420, whereby the network node 2400 may be operable to: when implementing AMF, send an ID of the NG-RAN and an indication of the failure of the NG-RAN to the MB-SMF.

[0361] In an embodiment, the ID of the multicast / broadcast service MBS session associated with the NG-RAN may be sent together with the ID of the NG-RAN and an indication of the failure of the NG-RAN.

[0362] In an embodiment, the ID of the NG-RAN, the indication of the failure of the NG-RAN, and the ID of the MBS session may be included in the MBS Broadcast Context Status Notification Request.

[0363] In an example, the memory 2430 further includes instructions executable by the processor 2420, whereby the network node 2400 is operable to: when implementing the AMF, use SCTP to detect failure of the NG-RAN before sending an operation.

[0364] In an example, the memory 2430 further includes instructions executable by the processor 2420, whereby the network node 2400 is operable to: when implementing the AMF, before the sending operation, in a start or update process for an MBS session, receive a message from the NG-RAN containing an ID of the NG-RAN. In an example, the memory 2430 further includes instructions executable by the processor 2420, whereby the network node 2400 is operable to: when implementing the AMF, send another message containing an ID of the NG-RAN to the MB-SMF. In an embodiment, the ID of the NG-RAN may be included in the N2 SM information container.

[0365] In an embodiment, the message may also include tunnel information of a DL tunnel corresponding to the NG-RAN. In an embodiment, the other message may also include tunnel information. In an embodiment, the tunnel information may be included in an N2 SM information container.

[0366] In an example, the memory 2430 further includes instructions executable by the processor 2420, whereby the network node 2400 is operable to: when implementing the AMF, before the sending operation, in the process of starting or updating an MBS session, send a message including the ID of the NG-RAN to the MB-SMF. In an embodiment, the ID of the NG-RAN may be carried outside the N2 SM information container.

[0367] In an example, the memory 2430 further includes instructions executable by the processor 2420, whereby the network node 2400 is operable to: when implementing the AMF, receive another message from the NG-RAN, the other message including tunnel information of a DL tunnel corresponding to the NG-RAN. In an embodiment, the message may also include the tunnel information. In an embodiment, the tunnel information may be included in an N2 SM information container.

[0368] Alternatively, network node 2400 may be Figure 2 or Figure 3 The memory 2430 may contain instructions executable by the processor 2420, whereby the network node 2400 may be operable to: when implementing the MB-UPF, perform, for example, the previously described Fig.10 Actions of the described process. Specifically, the memory 2430 may include instructions executable by the processor 2420, whereby the network node 2400 is operable to: when implementing the MB-UPF, receive tunnel information or a transport network IP address of a DL tunnel associated with the MBS session from the MB-SMF. In the example, the memory 2430 also includes instructions executable by the processor 2420, whereby the network node 2400 is operable to: when implementing the MB-UPF, send a report to the MB-SMF, the report indicating: an error associated with the tunnel information of the PFCP session corresponding to the MBS session, or a failure or restart associated with the IP address in the tunnel information or the transport network IP address.

[0369] In an embodiment, the report may be a PFCP session report or a node level report.

[0370] In an example, the memory 2430 further includes instructions executable by the processor 2420, whereby the network node 2400 is operable to: when implementing the MB-UPF, before the sending operation, send a packet to the NG-RAN based on the tunnel information; and receive an indication indicating an error from the NG-RAN.

[0371] In an example, the memory 2430 further includes instructions executable by the processor 2420, whereby the network node 2400 is operable to: when implementing the MB-UPF, receive from the MB-SMF a session modification request for releasing a DL tunnel corresponding to the NG-RAN. In an embodiment, the session modification request may include an ID of the MBS session and tunnel information.

[0372] In an example, the memory 2430 further includes instructions executable by the processor 2420, whereby the network node 2400 is operable to: when implementing the MB-UPF, after the receiving operation and before the sending operation, send a request for user plane path management to the IP address in the tunnel information or the transport network IP address. In an example, the memory 2430 further includes instructions executable by the processor 2420, whereby the network node 2400 is operable to: when implementing the MB-UPF, receive a response from the IP address in the tunnel information or the transport network IP address, the response including information from which a restart can be derived, or determine a failure in response to not receiving a response to the request from the IP address in the tunnel information or the transport network IP address within a predetermined time period.

[0373] In an embodiment, the request for user plane path management may be a GTP-U echo request.In an embodiment, the response may be a GTP-U echo response.

[0374] In an embodiment, the transport network IP address may be an IP address used for user plane path management.

[0375] Alternatively, network node 2400 may be Figure 2 or Figure 3 The memory 2430 may contain instructions executable by the processor 2420, whereby the network node 2400 may be operable to: perform, for example, the previously described steps in conjunction with the implementation of the NG-RAN Fig.11 The actions of the process described. Specifically, the memory 2430 may include instructions executable by the processor 2420, whereby the network node 2400 is operable to: when implementing NG-RAN, receive a request from the AMF to establish resources for the MBS session; and send a response to the request to establish resources for the MBS session to the AMF. The response includes an ID of the NG-RAN and / or a transport network IP address corresponding to the NG-RAN. In an embodiment, the ID of the NG-RAN and / or the transport network IP address are included in the N2 SM information container.

[0376] The present disclosure also provides at least one computer program product in the form of a non-volatile or volatile memory, such as a non-transitory computer-readable storage medium, an electrically erasable programmable read-only memory (EEPROM), a flash memory, and a hard drive. The computer program product includes a computer program. The computer program includes: code / computer-readable instructions, which when executed by the processor 2420, causes the network node 2400 to: perform, for example, the previously described in conjunction with the MB-SMF implementation Figure 6 or Figure 7 The actions of the process described, or when implementing AMF, for example, the previously combined Figure 8 or Fig. 9 The actions of the process described above, or when implementing MB-UPF, for example, the previously combined Fig.10 The actions of the procedures described, or when implementing NG-RAN, are performed such as previously combined Fig.11 Describes the actions of a process.

[0377] The computer program product may be configured as a computer program code structured as computer program modules. The computer program modules may basically execute Figure 6 , Figure 7 , Figure 8 , Fig. 9 , Fig.10 or Fig.11 The actions of the process shown.

[0378] The processor may be a single CPU (central processing unit), but may also include two or more processing units. For example, the processor may include a general-purpose microprocessor; an instruction set processor and / or an associated chipset and / or a special-purpose microprocessor, such as an application-specific integrated circuit (ASIC). The processor may also include on-board memory for cache purposes. The computer program may be carried by a computer program product connected to the processor. The computer program product may include a non-transitory computer-readable storage medium storing the computer program. For example, the computer program product may be a flash memory, a random access memory (RAM), a read-only memory (ROM) or an EEPROM, and the above-mentioned computer program modules may be distributed on different computer program products in the form of memory in alternative embodiments.

[0379] The present disclosure has been described above with reference to its embodiments. It should be understood that various modifications, substitutions and additions may be made by those skilled in the art without departing from the spirit and scope of the present disclosure. Therefore, the scope of the present disclosure is not limited to the above specific embodiments, but is only limited by the appended claims.

[0380] The present disclosure also provides the following embodiments.

[0381] For 5GC, the network functions in the control plane are required to support NF (service) sets so that multiple NF service instances in the same NF (service) set share resources / session contexts for redundancy, thereby providing high reliability to 5G services. Therefore, there is no need to further specify the recovery process for NFs when the control plane fails.

[0382] UPF and MB-UPF do not introduce the concept of collection, and since UPF and MB-UPF are fully controlled by SMF and MB-SMF respectively, when there is a failure in UPF or MB-UPF, SMF or MB-SMF can always recover the session.

[0383] However, when there is a NG-RAN restart, there is a lack of mechanisms for resuming MBS sessions. For NG-RAN failures without restart, although the relevant resources in the core network can be released, the MBS sessions of the area served by the failed NG-RAN cannot be resumed, for example, the MB-UPF should not send a separate copy of the MBS session data to the NG-RAN that has failed.

[0384] Conclusion 1: Existing mechanisms in 5GC cannot recover MBS sessions when there is a failure / restart of a 5GC NF involved in the MBS session. 3GPP needs to specify a recovery procedure for recovering MBS sessions affected by NG-RAN restart.

[0385] Clauses 7.3.1 and 7.3.3 in 3GPP TS 23.247 specify how to start and update a broadcast MBS session. Since the MBS session update for broadcast can be used to update the broadcast area, for example, to add a new tracking area served by a new NG-RAN, this will be very similar to resuming an MBS session in a restarted NG-RAN, as if the restarted NG-RAN was a new NG-RAN serving a new tracking area.

[0386] Conclusion 2: The MB-SMF may use the procedure for broadcast MBS session update (as specified in clause 7.3.3 of 3GPP TS 23.247) to resume an MBS session in NG-RAN (from restart).

[0387] NG-RAN failure with and without restart

[0388] Detection of NG-RAN failures with and without restart

[0389] When the NG-RAN has been restarted, it is assumed that the NG-RAN will lose all its session contexts, including those for MBS sessions. No set concept is introduced for the RAN.

[0390] Detection via control plane path (AMF via N2):

[0391] After recovery from a restart or (partial) failure, the NG-RAN shall inform the AMF of the (partial) failure or restart using NG SETUP REQUEST or NG RESET as specified in 3GPP TS 38.413 as described below.

[0392] As specified in Section 8.2. RFC4960 for SCTP (which is the transport layer protocol for NGAP over the N2 interface), the AMF may also detect NG-RAN failures with restarts.

[0393] Conclusion 3: AMF can perform detection of NG-RAN failure with or without restart without any protocol impact on existing specifications. Such failure can be reported to MB-SMF via Namf_MBSBroadcast_ContextStatusNotify service operation.

[0394] Detection via user plane path (MB-UPF via N3mb):

[0395] The peer GTP-U entity (of the NG-RAN) MB-UPF may also detect NG-RAN failure with and without restart as follows:

[0396] When using unicast transmission over N3mb: (i.e., the NG-RAN has allocated a DLF-TEID to receive MBS session data)

[0397] The restarted NG-RAN will not recognize the DL F-TEID allocated by the NG-RAN before its restart, so the NG-RAN will send a GTP-U Error Indication. The GTP-U Error Indication will also be reported to the MB-SMF.

[0398] The MB-UPF will periodically send an Echo Request message to detect the activity of the GTP-U path identified by the IP address within the DL F-TEID. Thus, the MB-UPF will be able to detect a failure of the GTP-U path towards the NG-RAN and will also report to the MB-SMF if such a failure is detected.

[0399] Conclusion 4a: When using unicast transmission according to existing specifications, the MB-UPF shall be able to detect NG-RAN failures with and without restart. The MB-SMF shall obtain failure reports from the MB-UPF.

[0400] When using multicast transport over N3mb, the NG-RAN will join the multicast group, i.e. fetch the MBS session data from the lower layer source specific multicast address assigned by the MB-UPF. The MB-UPF will not be aware of any NG-RAN restart or failure.

[0401] Conclusion 4b: When multicast transport is used for N3mb interface, additional mechanisms need to be introduced, for example, even if NG-RAN decides to join the multicast group, NG-RAN needs to provide IP address to enable MB-UPF to send echo request to detect restart. Expected RAN3 impact.

[0402] Conclusion 4c: For the user plane solution, the MB-SMF needs to store the mapping information between the NG-RAN ID and the transport information provided by the NG-RAN (DL F-TEID (for unicast transmission) or separate IP address (for multicast transmission) for receiving MBS session data), so that upon receiving a failure report from the MB-UPF (which will only include the failed tunnel endpoint information (for GTP-U error indication report) or the remote GTP-U IP address (for GTP-U path failure)), the MB-SMF will be able to derive the NG-RAN ID in order to request the resumption of the MBS session via the restarted NG-RAN via the AMF.

[0403] In order to resume the broadcast MBS session, based on Conclusions 2, 3 and 4a to 4c, it is recommended that:

[0404] - The AMF shall detect NG-RAN failures with and without restart and report such failures to the MB-SMF for each MBS session via a Namf_MBSBroadcast_ContextNotify request with the NG-RAN ID and an indication of whether the NG-RAN was restarted or has failed without restarting;

[0405] - As specified in clause 7.3.3 of TS 23.247, the MB-SMF shall trigger an MBS session update for the broadcast session for each MBS session by sending a Namf_MBSBroadcast_ContextUpdate request message including the restarted NG-RANID.

[0406] - Upon receiving a GTP-U Error Indication Report or a GTP-U Path Failure Report (for unicast transmission), the MB-SMF may request the MB-UPF to modify the corresponding PFCP session (for MBS session) to remove the old DL F-TEID.

[0407] Note: When using multicast transport over N3mb, there are no additional user plane resources allocated for specific NG-RAN.

Claims

1. A method (600) in a multicast / broadcast session management function MB-SMF, include: An identifier ID of a Next Generation Radio Access Network NG-RAN and an indication of a restart or failure of the NG-RAN are received (610) from an Access and Mobility Management Function AMF.

2. The method (600) according to claim 1, in, An ID of a multicast / broadcast service MBS session associated with the NG-RAN is received together with the ID of the NG-RAN and an indication of a restart or failure of the NG-RAN.

3. The method (600) according to claim 2, in, The ID of the NG-RAN, the indication of the restart or failure of the NG-RAN, and the ID of the MBS session are included in the MBS Broadcast Context Status Notification Request.

4. The method (600) according to any one of claims 1 to 3, before the receiving (610), the method further comprises: include: receiving, from the AMF, a message including an ID of the NG-RAN during a start or update procedure for the MBS session; and / or The ID of the NG-RAN is contained in the N2 session management SM information container or carried outside the N2 SM information container.

5. The method (600) according to claim 4, further comprising: include: In response to receiving the indication, a session modification request for releasing the DL tunnel corresponding to the NG-RAN is sent to a multicast / broadcast user plane function MB-UPF, where the session modification request includes the ID of the MBS session and the tunnel information.

6. The method (600) according to any one of claims 1 to 5, further comprising: include: In response to receiving an indication of restart of the NG-RAN, sending a request to the AMF for resuming the MBS session towards the NG-RAN, the request including the ID of the NG-RAN and the ID of the MBS session.

7. The method (600) according to claim 6, in, The request is an MBS broadcast context update request or an MBS broadcast context create request; and / or The request also includes an indication of MBS session resumption.

8. A method (800) in an access and mobility management function AMF, include: A request for resuming a multicast / broadcast service MBS session towards a next generation radio access network NG-RAN is received (810) from a multicast / broadcast session management function MB-SMF, the request including an identifier ID of the NG-RAN.

9. The method according to claim 8, in, The request also includes the ID of the MBS session.

10. The method (800) of claim 9, before the receiving (810), the method further comprising: include: During the initiation or update process for the MBS session, sending another message including the ID of the NG-RAN to the MB-SMF, The NG-RAN ID is included in the N2 session management SM information container.

11. The method (800) of claim 8, before the receiving (810), the method further comprising: include: During the initiation or update process for the MBS session, sending a message including the ID of the NG-RAN to the MB-SMF, The NG-RAN ID is carried outside the N2 session management SM information container.

12. The method (800) according to any one of claims 8 to 11, after receiving (810) a request for resuming the MBS session, the method further include: sending a request to the NG-RAN to establish resources for the MBS session; receiving, from the NG-RAN, a response to the request to establish resources for the MBS session; as well as and sending a response to the request for resuming the MBS session or an MBS broadcast context status notification request to the MB-SMF, wherein the response or the MBS broadcast context status notification request includes the ID of the NG-RAN.

13. The method (800) according to any one of claims 8 to 12, before receiving (810) a request for resuming the MBS session, the method further comprising: include: sending the NG-RAN ID, the NG-RAN restart indication, and the MBS session ID to the MB-SMF; and / or The ID of the NG-RAN, the indication of restarting the NG-RAN, and the ID of the MBS session are included in the MBS broadcast context status notification request.

14. The method (800) according to claim 13, before sending the indication of restarting the NG-RAN, further comprising: include: receiving an NG setup request or an NG reset request from the NG-RAN, wherein the NG setup request or the NG reset request indicates a restart of the NG-RAN; as well as Determine an ID of an MBS session associated with the NG-RAN.

15. A network node (2400), comprising a communication interface (2410), a processor (2420) and a memory (2430), wherein the memory (2430) comprises instructions executable by the processor (2420), whereby the network node (2400) is operable to: perform a method according to any one of claims 1 to 7 when implementing a multicast / broadcast session management function MB-SMF, or perform a method according to any one of claims 8 to 14 when implementing an access and mobility management function AMF.

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