WO2022229883A1

WO2022229883A1 - 5mbs amf involvement on signaling efficiency

Info

Publication number: WO2022229883A1
Application number: PCT/IB2022/053923
Authority: WO
Inventors: Jie LING; Juying GAN; Paul Schliwa-Bertling; Alexander Vesely; Shabnam Sultana
Original assignee: Telefonaktiebolaget Lm Ericsson (Publ)
Priority date: 2021-04-28
Filing date: 2022-04-27
Publication date: 2022-11-03

Abstract

A method performed by an Access and Mobility Management Function (AMF) for improving Fifth-Generation Multicast-Broadcast Services (5MBS) signaling in a Core Network (CN) is provided. The method includes receiving a multicast request from a network node in the CN and performing one or more actions in response to receiving the multicast request from the network node, independent of whether the AMF is aware that a User Equipment (UE) is joining the 5MBS. The method disclosed herein can improve signaling efficiency in multicast session activation and/or deactivation, independent of whether the AMF is aware of a UE's joining of the 5MBS.

Description

5MBS AMF INVOLVEMENT ON SIGNALING EFFICIENCY

Related Applications

[0001] This application claims the benefit of provisional patent application serial number 63/180,968, filed April 28, 2021, the disclosure of which is hereby incorporated herein by reference in its entirety.

Technical Field

[0002] The technology of the disclosure relates generally to improving signaling efficiency for Fifth Generation (5G) Multicast-Broadcast Services (5MBS).

Background

[0003] Third Generation Partnership Project (3GPP) previously developed the Multicast/Broadcast Multimedia Subsystem (MBMS) (e.g., in 3GPP TS 23.246 V16.1.0) for Third Generation (3G) networks for video multicast/broadcasting and streaming services and later introduced the evolved MBMS (eMBMS) for Evolved Packet System (EPS). In Rel-13 and Rel-14, the MBMS system has been updated to support new services such as Public Safety, Cellular Internet of Things (CIoT), and Vehicle to Everything (V2X).

[0004] The scope of a new Release-17 study in 3GPP System Aspects 2 (SA2) working group is to study both multicast requirements and use cases for CIoT, Public Safety, V2X etc., and dedicated broadcasting requirements and use cases. The study targets the 5G Release 17 and the New Radio (NR) radio access. The study results so far have been documented in the TR 23.757 VI.3.0 and the normative work has been documented in TS 23.247 VO.2.0.

[0005] In TS 23.247, the User Equipment (UE) join and multicast session establishment procedure is described in clause 7.2.1.3:

7.2.1.3 MBS join and Session establishment procedure

The following steps are executed before the UE requests to join the MBS session:

- The MBS Session has been configured.

- The UE registers in the Public Land Mobile Network (PLMN) and establishes a Protocol Data Unit (PDU) session. - The UE has known at least the MBS Session ID of a multicast group that the UE can join, e.g., via announcement.

[0006] Refer now to Figure 1:

1. To join the multicast group, the UE sends the PDU Session Modification Request (MBS Session ID). MBS Session ID indicates the multicast group that UE wants to join.

2. Per the received MBS Session ID, the Session Management Function (SMF) recognizes this is an MBS Session join request. The SMF authorizes the MBS Session join request, see clause 6.1.1.

3. If SMF has no information about the multicast context for the indicated MBS Session, SMF checks at the Network Function Repository Function (NRF) whether a multicast context for the indicated MBS Session exists in the system, by using Nnrf_NFDiscovery request (MBS Session ID). If a multicast context already exists in the NRF, the NRF responses with Nnrf_NFDiscovery response (MB-SMF ID).

4. By using Nsmf_MBSSession_Create request (MBS Session ID), SMF interacts with Multicast/Broadcast (MB) SMF to retrieve multicast Quality of Service (QoS) flow information of the indicated MBS session.

5. SMF responds to Access & Mobility Management Function (AMF) through Nsmf_PDUSession_UpdateSMContext response (N2 SM information (PDU Session ID, MBS Session ID, MB-SMF ID, multicast QoS flow information, updated PDU Session information, mapping between unicast QoS flow and multicast QoS flow information), N1 SM container (PDU Session Modification Command) to:

- create an MBS session context for the indicated MBS session in the Radio Access Network (RAN), if it does not exist already; and

- inform about the relation including the mapping information between the multicast context and the UE's PDU session to RAN.

Based on operator policy, the SMF may prepare for individual delivery fail-back. The SMF maps the received QoS information of the multicast QoS Flow into PDU Session's QoS Flow information, and includes the information of the QoS Flows and the mapping information about the QoS Flows in the SM information sent to RAN.

6. The N2 message, which includes the PDU session modification command information is sent to the NG-RAN.

If the MBS is not supported by NG-RAN, 5GC individual MBS traffic delivery may be used. Otherwise, 5GC shared MBS traffic delivery is adopted.

The NG-RAN uses the MBS Session ID to determine that the PDU Session Modification procedures corresponds to the indicated multicast session.

If the multicast QoS information is received, the associated unicast QoS flow information is not used to allocate the radio resource.

NOTE: It is NG-RAN that decides whether radio resource is allocated or not.

When the NG-RAN receives an MBS Session ID, but MBS Session context does not exist for that MBS Session ID, the NG-RAN uses the included MBS Session QoS information to allocate resources to serve this multicast session. Otherwise, the indicated MBS Session has been established

7. The RAN, AMF, SMF, and MB-SMF perform resources reservation for individual delivery and shared delivery. The SMF obtains the 5MBS capability of target NG- RAN via the accepted QoS Flow Id (QFI) information and determines the delivery mode between 5GC and RAN.

In TS 23.247, N2 based handover is described in clause 7.2.3.3:

7.2.3.3 N2 based hando ver

This clause describes the N2 based handover with the MBS Session established at the source 5G MBS-supporting NG-RAN.

[0007] Refer now to Figures 2A and 2B, the following additions apply compared to clause 4.9.1.3 of TS 23.502): 2. Source NG-RAN to S-AMF: Handover Required (RAN container (associated PDU session information)).

4. SMF to T-AMF: The T-AMF is provided with associated PDU Session information.

5. T-AMF to Target NG-RAN: The Target NG-RAN prepares the radio resource based on the received information.

- If the target NG-RAN does not support 5G MBS, the MBS Session information is not used. The target NG-RAN uses the associated mapping PDU Session information to allocate resource to deliver MBS data. The MBS data are transmitted as one of the QoS flows within the unicast PDU Session.

If the target NG-RAN supports 5G MBS, the target NG-RAN uses the MBS Session information to allocate resource to deliver the MBS data. If Target NG-RAN supports 5G MBS and the MBS delivery for the indicated MBS Session has not yet been established towards target NG-RAN, the target NG-RAN allocates the shared downlink tunnel information for receiving the MBS data from 5GC and steps 6 to 10 apply:

6. Target NG-RAN to T-AMF: Target NG-RAN node selects the AMF to reach MB- SMF and signals a multicast session distribution request towards AMF via the N2 Message (MBS Session ID). If the RAN node is configured to use a unicast transport for multicast distribution sessions, it allocates a downlink tunnel ID (an IP address and a GTP-U TEID) for the reception of the multicast distribution session and indicates the downlink tunnel information in the request.

7. T-AMF to MB-SMF: AMF invokes the Nmbsmf_MBSSession_Create Request (MBS session ID, [DL tunnel info]) Request towards the MB-SMF to establish the multicast distribution towards AMF.

8. MB-SMF to MB-UPF: MB-SMF invokes the N4 Session Modification procedure with MB-UPF. For unicast transport of the multicast distribution session, MB- SMF configures MB-UPF to transmit the multicast distribution session towards target NG-RAN node (using the received IP address and a GTP-U TEID). 9. MB-SMF to T-AMF: MB-SMF responds to AMF through the Nmbsmf_MBSSession_Create Response. For multicast transport of the multicast distribution, it indicates in the downlink tunnel information and the multicast address for the multicast session.

10. T-AMF to Target NG-RAN: AMF provides multicast session distribution response to Target NG-RAN node via the N2 Message.

11. Target NG-RAN to T-AMF: The target NG-RAN sends Flandover Request Ack to T-AMF.

12. The N2 SM message includes sufficient information to allow the SMF to know whether the target NG-RAN node supports 5G MBS and whether MBS Session Resources (in case the target NG-RAN node supports 5G MBS) have been established or PDU Session Resources to support 5GC individual MBS traffic delivery have been prepared in the target NG-RAN for the UE.

21. T-AMF to SMF: The AMF invokes Nsmf_PDUSession_UpdateSMContext request towards SMF, the message includes the received N2 SM message.

Based on the received N2 SM message, the SMF can differentiate two cases:

Case A) The Target NG-RAN supports 5G MBS. Step 22 applies and steps 23~29 are skipped.

22. SMF to UPF (PSA): The SMF invokes N4 Session Modification procedure with the UPF (PSA) only for unicast PDU Session. The SMF instructs the UPF to send the end marker packet towards the source NG-RAN and to send subsequent packets towards the target NG-RAN within the unicast PDU Session.

Case B) The target NG-RAN does not support 5G MBS. If the UPF (PSA) is not yet configured to forward multicast data via unicast, steps 23 to 29 apply.

23. SMF to UPF: The SMF may invokes N4 Session Modification procedure with UPF (PSA), the SMF instructs the UPF (PSA) to forward the multicast data received from the MB-UPF via the mapped unicast QoS Flow(s) of the PDU Session within the unicast PDU (i.e., 5GC Individual MBS traffic delivery method will be used). The SMF provides the mapping information between the multicast QFI and the corresponding mapped unicast QFI to the UPF (PSA), the UPF (PSA) forwards the multicast data via the PDU session based on the mapping information. If the delivery tunnel for the MBS session from MB-SMF to UPF is not established yet, the SMF instructs the UPF (PSA) to allocate a tunnel endpoint for the reception of multicast data from the MB-UPF.

If delivery of the multicast data from MB-UPF to UPF needs to be configured, steps 24 to 27 apply.

24. SMF to MB-SMF: The SMF invokes a Nmbsmf_MBSSession_Update (MBS session ID, SMF ID, DL tunnel info) request service operation to MB-SMF to establish the shared tunnel between the UPF(PSA) and MB-UPF.

25. MB-SMF to MB-UPF: The MB-SMF configures the MB-UPF with the received DL tunnel Info and instructs the MB-UPF to forward data of the MBS session to the UPF (PSA) via the tunnel. The MB-UPF starts to forward data of the MBS session to the UPF (PSA).

26. MB-SMF to SMF: The MB-SMF responds to SMF through Nmbsmf_MBSSession_Update response. If multicast data are transported via multicast, the MB-SMF provides endpoint information (e.g., the Common-TEID) including the transport multicast address.

27. SMF to UPF (PSA): The SMF invokes an N4 Session Modification procedure with the UPF (PSA). If multicast data are transported via multicast, the SMF provides endpoint information including the transport multicast address to the UPF (PSA) and the UPF (PSA) sends IGMP Join in order to receive data from the MB-UPF.

And for signaling efficiency, there are two pseudo Change Requests (pCRs) proposed: S2-2102941r02 and S2-2102942.

In S2-2102942, a solution to trigger MBS session activation in an efficient way is proposed. That is, the session activation request is handled in a per MBS session way, instead of per PDU session way.

7.2.1.X Multicast session activation [0008] Refer now to Figure 3:

1. The MB-SMF decides to activate the MBS session (or location dependent part of the multicast session), either based on a request from the NEF/MBSF and AF, or because the MB-UPF reports that it received data for the multicast session.

2. For each SMF the MB-SMF stored in the multicast context session (or location dependent part of the multicast session), it sends a multicast session activation request towards the SMF. The MB-SMF also provides the MBS session ID and for location dependent services area session ID.

3. The SMF determines the users in the multicast session (or location dependent part of the multicast session) it serves and for each user the AMF that handles the registration context of the user. It sends a multicast session activation request message to each such AMF and includes the multicast session ID and a list of the UEs with inactive PDU sessions that the AMF serves.

4. The AMF checks for each UE in the list whether it is IDLE and then determines the radio area of the UE. The AMF combines all radio areas determined in that manner and sends activation request indicating the MBS session ID to RAN nodes handling all those radio areas.

5. The RAN nodes pass the activation request to the UE.

Steps 6 to 8 apply separately for each IDLE UE in the multicast session.

6. UE reacts by sending a service request to the AMF.

7. The AMF requests the activation of the PDU session

8. The SMF activates the PDU session.

In S2-2102941r02, a solution to trigger MBS session deactivation in an efficient way is proposed. That is, the session deactivation request is handled in a per MBS session way, instead of per PDU session way.

7.2.1.X Multicast session deactivation

[0009] Refer now to Figure 4: 1. The MB-SMF decides to deactivate the MBS session (or location dependent part of the multicast session)., either based on a request from the NEF/MBSF and AF, or because the MB-UPF reports that it did not receive any data for the multicast session for a configured period.

2. For each AMF the MB-SMF stored in the multicast context session (or location dependent part of the multicast session), it sends a multicast session deactivation request towards the AMF. The MB-SMF includes the RAN node IDs of RAN nodes that previously registered via the AMF for shared delivery. The MB-SMF also provides the MBS session ID and for location dependent services area session ID.

3. For each RAN node indicated in message 2, the AMF sends a multicast session deactivation request. The AMF includes the MBS session ID and possible area session ID received in message 2. The RAN node handles the inactivation as defined in RAN specifications. UEs that have joined that multicast session can become IDLE. The N3 tunnel for 5GC Shared MBS delivery method shall not be released as long as the RAN node serves CM CONNECTED UEs within the multicast session

To enable the session deactivation can be handled in a per MBS session manner, S2- 2102941r02 further introduce a solution enable NG-RAN to register and de-register towards MB-SMF:

7.2.1.X Establishment of shared delivery toward RAN node [0010] Refer now to Figure 5:

1. A RAN node discovers that it needs to establish shared delivery for an MBS session because it serves at least one UE within the MBS session. This can occur after the UE joined the MBS session or as the result of handover of the UE. For location dependent services, the RAN node needs to establish shared delivery for the location dependent contents of an MBS session if it serves at least one UE assigned to an MBS session ID and area session ID. 2. The RAN node sends a multicast distribution request to the AMF and provides the TMGI as MBS session ID. If the RAN node is configured to use unicast transport for the shared delivery, it allocates a GTP tunnel endpoint and provides that endpoint. For location dependent services, the RAN node also provides the area session ID.

3. The AMF discovers the MB-SMF serving the multicast session using the NRF discovery service. It sends a Multicast distribution request to the MB-SMF, passing the parameters received in message 2. The AMF adds the ID of the RAN node.

4. If the MB-SMF received a GTP tunnel endpoint in message 3, it configures the MB-UPF to send multicast data for the multicast session (or location dependent content of the multicast session if an area session ID was received) towards that GTP tunnel endpoint via unicast transport.

5. The MB-SMF stores the AMF and RAN node ID in the context of the multicast session (or location dependent part of the multicast session if an area session ID was received) to enable subsequent signaling towards that RAN node.

6. The MB-SMF sends a multicast distribution response to the AMF. If it did not receive a GTP tunnel endpoint in message 3, it provides a GTP tunnel endpoint for multicast transport of the shared delivery.

7. The AMF forwards the multicast distribution response to the RAN node. If the RAN node received a GTP tunnel endpoint for multicast transport of the shared delivery, it uses that information to join the multicast transport.

7.2.1.X Release of shared delivery toward RAN node

[0011] Refer now to Figure 6:

1. A RAN node discovers that it needs to release shared delivery for an MBS session e.g., because it no longer serves at least one UE within the MBS session. This can occur after the UE left the MBS session or as the result of a handover of UEs. For location dependent services, the RAN node may release shared delivery for the location dependent contents of an MBS session if it no longer serves at least one UE assigned to an MBS session ID and area session ID.

2. The RAN node sends a multicast distribution release request to the AMF and provides the TMGI as MBS session ID. For location dependent services, the RAN node also provides the area session ID.

3. The AMF discovers the MB-SMF serving the multicast session using the NRF discovery service. It sends a Multicast distribution release request to the MB- SMF, passing the parameters received in message 2.

4. If unicast transport was used towards the RAN node, the MB-SMF configures the MB-UPF to terminate sending multicast data for the multicast session (or location dependent content of the multicast session if an area session ID was received) towards that RAN node.

5. The MB-SMF removes the RAN node ID from storage in the context of the multicast session (or location dependent part of the multicast session if an area session ID was received).

6. The MB-SMF sends a multicast distribution release response to the AMF.

7. The AMF forwards the multicast distribution release response to the RAN node. If the RAN node previously received a GTP tunnel endpoint for multicast transport of the shared delivery, it uses that information to leave the multicast transport. It releases local resources to receive the multicast data.

Summary

[0012] Embodiments disclosed herein include a method performed by an Access and Mobility Management Function (AMF) for improving Fifth-Generation Multicast-Broadcast Services (5MBS) signaling in a Core Network (CN). The method includes receiving a multicast request from a network node in the CN and performing one or more actions in response to receiving the multicast request from the network node, independent of whether the AMF is aware of a User Equipment (UE) joining the 5MBS. The method disclosed herein can improve signaling efficiency in multicast session activation and/or deactivation, independent of whether the AMF is aware of a UE's joining of the 5MBS. [0013] In one aspect, one method performed by an AMF for improving 5MBS signaling in a CN is provided. The method includes receiving a multicast request from a network node in the CN. The method also includes performing one or more actions in response to receiving the multicast request from the network node, independent of whether the AMF is aware of a UE is joining the 5MBS.

[0014] In another aspect, receiving the multicast request comprises receiving an indication that indicates the UE is joining the 5MBS.

[0015] In another aspect, receiving the multicast request comprises one of: receiving a multicast activation request from an MB-SMF and receiving a multicast deactivation request from the MB-SMF. Performing the one or more actions comprises in response to receiving the multicast activation request, sending the multicast activation request to an NG-RAN to perform one or more of following actions: activation of one or more UEs in CM-CONNECTED state and group notification to one or more UEs in CM-IDLE state. Performing the one or more actions also comprises in response to receiving the multicast deactivation request, determining an impacted NG-RAN based on information available at the AMF.

[0016] In another aspect, performing the one or more actions further comprises one of: registering the UE toward the SMF in response to receiving the multicast activation request and deregistering the UE toward the SMF in response to receiving the multicast deactivation request.

[0017] In another aspect, receiving the multicast request comprises one of receiving a multicast activation request from an SMF and receiving a multicast deactivation request from the SMF. Performing the one or more actions comprises in response to receiving the multicast activation request, sending the multicast activation request to an NG-RAN to perform one or more of the following actions: activation of one or more UEs in CM-CONNECTED state and group notification to one or more UEs in CM-IDLE state. Performing the one or more actions also comprises in response to receiving the multicast deactivation request, determining an impacted NG-RAN based on information available at the AMF.

[0018] In another aspect, receiving the multicast request comprises not receiving an indication that indicates the UE is joining the 5MBS.

[0019] In another aspect, receiving the multicast request comprises one of receiving a multicast activation request from an SMF and receiving a multicast deactivation request from the SMF. Performing the one or more actions comprises in response to receiving the multicast activation request, sending the multicast activation request to an NG-RAN to perform one or more of following actions: activation of one or more UEs in CM-CONNECTED state and group notification to one or more UEs in CM-IDLE state. Performing the one or more actions also comprises in response to receiving the multicast deactivation request, determining an impacted NG-RAN based on information available at the AMF. [0020] In one aspect, a network node is provided. The network node includes processing circuitry configured to cause the network node to receive a multicast request from a network node in the CN and perform one or more actions in response to receiving the multicast request from the network node, independent of whether the network node is aware of a UE is joining a 5MBS. [0021] In another aspect, the processing circuitry is further configured to cause the network node to perform any step performed by the AMF.

Brief Description of the Drawings

[0022] The accompanying drawing figures incorporated in and forming a part of this specification illustrate several aspects of the disclosure, and together with the description serve to explain the principles of the disclosure.

[0023] Figure 1 is a signal flow diagram illustrating Protocol Data Unit (PDU) session modification for multicast, as defined in Third Generation Partnership Project (3GPP) Technical Specification (TS) 23.247; [0024] Figures 2A and 2B are a signal flow diagram illustrating N2 based handover with Multicast-Broadcast Services (MBS) session, as defined in 3GPP TS 23.247;

[0025] Figure 3 is a signal flow diagram illustrating an MBS activation procedure initiated by a Multicast-Broadcast (MB) Session Management Function (SMF) (MB-SMF); [0026] Figure 4 is a signal flow diagram illustrating an MBS deactivation procedure initiated by an MB-SMF;

[0027] Figure 5 is a signal flow diagram illustrating a multicast distribution request procedure initiated by a Radio Access Network (RAN);

[0028] Figure 6 is a signal flow diagram illustrating a multicast distribution release procedure initiated by an RAN; [0029] Figure 7 illustrates one example of a cellular communications system in which embodiments of the present disclosure may be implemented; [0030] Figure 8 illustrates a wireless communication system represented as a 5G network architecture composed of core Network Functions (NFs), where interaction between any two NFs is represented by a point-to-point reference point/interface; [0031] Figure 9 illustrates a 5G network architecture using service-based interfaces between the NFs in the Control Plane (CP), instead of the point-to-point reference points/interfaces used in the 5G network architecture of Figure 8;

[0032] Figure 10 is a flowchart of an exemplary method performed by an Access and Mobility Management Function (AMF) according to an embodiment of the present disclosure for improving 5MBS signaling in a Core Network (CN); [0033] Figure 11 is a flowchart of an exemplary method performed by an AMF according to an embodiment of the present disclosure;

[0034] Figure 12 is a signal flow diagram illustrating multicast session establishment when an AMF is aware of a UE's joining of 5MBS;

[0035] Figures 13A and 13B are a signal flow diagram illustrating N2 based handover when the AMF is aware of the UE's joining of 5MBS;

[0036] Figure 14 is a signal flow diagram illustrating establishment of shared delivery toward Radio Access Network (RAN) node according to an embodiment of the present disclosure;

[0037] Figure 15 is a signal flow diagram illustrating release of shared delivery toward RAN according to an embodiment of the present disclosure;

[0038] Figure 16 is a signal flow diagram illustrating multicast deactivation according to an embodiment of the present disclosure;

[0039] Figure 17 is a signal flow diagram illustrating multicast activation according to an embodiment of the present disclosure; [0040] Figure 18 is a signal flow diagram illustrating establishment of shared delivery toward RAN node according to another embodiment of the present disclosure;

[0041] Figure 19 is a signal flow diagram illustrating release of shared delivery toward RAN according to another embodiment of the present disclosure;

[0042] Figure 20 is a signal flow diagram illustrating multicast deactivation according to another embodiment of the present disclosure;

[0043] Figure 21 is a signal flow diagram illustrating multicast activation according to another embodiment of the present disclosure; [0044] Figure 22 is a signal flow diagram illustrating establishment of shared delivery toward a RAN node according to another embodiment of the present disclosure;

[0045] Figure 23 is a signal flow diagram illustrating release of shared delivery toward a RAN node according to another embodiment of the present disclosure;

[0046] Figure 24 is a signal flow diagram illustrating multicast deactivation according to another embodiment of the present disclosure;

[0047] Figure 25 is a signal flow diagram illustrating multicast activation according to another embodiment of the present disclosure;

[0048] Figure 26 is a schematic block diagram of a network node according to some embodiments of the present disclosure;

[0049] Figure 27 is a schematic block diagram that illustrates a virtualized embodiment of the network node in Figure 26 according to some embodiments of the present disclosure; and

[0050] Figure 28 is a schematic block diagram of the network node in Figure 26 according to some other embodiments of the present disclosure.

Detailed Description

[0051] The embodiments set forth below represent information to enable those skilled in the art to practice the embodiments and illustrate the best mode of practicing the embodiments. Upon reading the following description in light of the accompanying drawing figures, those skilled in the art will understand the concepts of the disclosure and will recognize applications of these concepts not particularly addressed herein. It should be understood that these concepts and applications fall within the scope of the disclosure.

[0052] Radio Node: As used herein, a "radio node" is either a radio access node or a wireless communication device.

[0053] Radio Access Node: As used herein, a "radio access node" or "radio network node" or "radio access network node" is any node in a Radio Access Network (RAN) of a cellular communications network that operates to wirelessly transmit and/or receive signals. Some examples of a radio access node include, but are not limited to, a base station (e.g., a New Radio (NR) base station (gNB) in a Third Generation Partnership Project (3GPP) Fifth Generation (5G) NR network or an enhanced or evolved Node B (eNB) in a 3GPP Long Term Evolution (LTE) network), a high-power or macro base station, a low-power base station (e.g., a micro base station, a pico base station, a home eNB, or the like), a relay node, a network node that implements part of the functionality of a base station (e.g., a network node that implements a gNB Central Unit (gNB-CU) or a network node that implements a gNB Distributed Unit (gNB-DU)) or a network node that implements part of the functionality of some other type of radio access node.

[0054] Core Network Node: As used herein, a "core network node" is any type of node in a core network or any node that implements a core network function. Some examples of a core network node include, e.g., a Mobility Management Entity (MME), a Packet Data Network Gateway (P-GW), a Service Capability Exposure Function (SCEF), a Flome Subscriber Server (HSS), or the like. Some other examples of a core network node include a node implementing an Access and Mobility Management Function (AMF), a User Plane Function (UPF), a Session Management Function (SMF), an Authentication Server Function (AUSF), a Network Slice Selection Function (NSSF), a Network Exposure Function (NEF), a Network Function (NF) Repository Function (NRF), a Policy Control Function (PCF), a Unified Data Management (UDM), or the like.

[0055] Communication Device: As used herein, a "communication device" is any type of device that has access to an access network. Some examples of a communication device include, but are not limited to: mobile phone, smart phone, sensor device, meter, vehicle, household appliance, medical appliance, media player, camera, or any type of consumer electronic, for instance, but not limited to, a television, radio, lighting arrangement, tablet computer, laptop, or Personal Computer (PC). The communication device may be a portable, hand-held, computer-comprised, or vehicle- mounted mobile device, enabled to communicate voice and/or data via a wireless or wireline connection.

[0056] Wireless Communication Device: One type of communication device is a wireless communication device, which may be any type of wireless device that has access to (i.e., is served by) a wireless network (e.g., a cellular network). Some examples of a wireless communication device include, but are not limited to: a User Equipment device (UE) in a 3GPP network, a Machine Type Communication (MTC) device, and an Internet of Things (IoT) device. Such wireless communication devices may be, or may be integrated into, a mobile phone, smart phone, sensor device, meter, vehicle, household appliance, medical appliance, media player, camera, or any type of consumer electronic, for instance, but not limited to, a television, radio, lighting arrangement, tablet computer, laptop, or PC. The wireless communication device may be a portable, hand-held, computer-comprised, or vehicle-mounted mobile device, enabled to communicate voice and/or data via a wireless connection.

[0057] Network Node: As used herein, a "network node" is any node that is either part of the RAN or the core network of a cellular communications network/system. [0058] Transmission/Reception Point (TRP): In some embodiments, a TRP may be either a network node, a radio head, a spatial relation, or a Transmission Configuration Indicator (TCI) state. A TRP may be represented by a spatial relation or a TCI state in some embodiments. In some embodiments, a TRP may be using multiple TCI states. In some embodiments, a TRP may a part of the gNB transmitting and receiving radio signals to/from UE according to physical layer properties and parameters inherent to that element. In some embodiments, in Multiple TRP (multi-TRP) operation, a serving cell can schedule UE from two TRPs, providing better Physical Downlink Shared Channel (PDSCH) coverage, reliability and/or data rates. There are two different operation modes for multi-TRP: single Downlink Control Information (DCI) and multi- DCI. For both modes, control of uplink and downlink operation is done by both physical layer and Medium Access Control (MAC). In single-DCI mode, UE is scheduled by the same DCI for both TRPs and in multi-DCI mode, UE is scheduled by independent DCIs from each TRP.

[0059] In some embodiments, a set Transmission Points (TPs) is a set of geographically co-located transmit antennas (e.g., an antenna array (with one or more antenna elements)) for one cell, part of one cell or one Positioning Reference Signal (PRS) -only TP. TPs can include base station (eNB) antennas, Remote Radio Heads (RRHs), a remote antenna of a base station, an antenna of a PRS-only TP, etc. One cell can be formed by one or multiple TPs. For a homogeneous deployment, each TP may correspond to one cell.

[0060] In some embodiments, a set of TRPs is a set of geographically co-located antennas (e.g., an antenna array (with one or more antenna elements)) supporting TP and/or Reception Point (RP) functionality.

[0061] Note that the description given herein focuses on a 3GPP cellular communications system and, as such, 3GPP terminology or terminology similar to 3GPP terminology is oftentimes used. However, the concepts disclosed herein are not limited to a 3GPP system.

[0062] Note that, in the description herein, reference may be made to the term "cell"; however, particularly with respect to 5G NR concepts, beams may be used instead of cells and, as such, it is important to note that the concepts described herein are equally applicable to both cells and beams.

[0063] There currently exist certain challenge(s). Two proposed change requests (S2-2102941 r02 and S2-2102942) provided solutions to address the signaling efficiency issue. However, the proposed solutions excluded Access & Mobility Management Function (AMF) from the MBS session for shared delivery. As such, the following solutions are required:

- New Generation Radio Access Network (NG-RAN) register towards Multicast/Broadcast-Session Management Function (MB-SMF) (establishment shared delivery towards RAN node in S2-2102941r02).

- NG-RAN de-register towards MB-SMF (release shared delivery towards RAN node in S2-2102941r02)

- In Multicast Session Deactivation in S2-2102941r02, MB-SMF needs to pass RAN Node Ids towards AMF and let AMF duplicate the session deactivation requests towards the relevant NG-RAN nodes.

- In Multicast Session Activation in S2-2102942, Session Management Function (SMF) needs to pass UE Ids to AMF to enable AMF to send Multicast activation request to NG-RAN nodes for those CM-IDLE UEs.

[0064] There are several drawbacks in the solutions above:

- Inconsistent behavior between Multicast Activation Request (SMF involved) and Multicast Deactivation Request handling (SMF bypassed), which lead to a non coherent solution.

- If unicast transport applies over N3mb tunnel (i.e., unicast tunnel between MB- UPF and NG-RAN), NG-RAN needs to send DL Tunnel Endpoint towards MB-SMF for tunnel establishment. NG-RAN needs to release N3mb tunnel towards MB- SMF for tunnel release (e.g., when no UEs remain joined in the MBS session). However, if multicast transport applies over N3mb (i.e., multicast tunnel between MB-UPF and NG-RAN), NG-RAN can simply perform IGMP/MLD Join and Leave the IP Multicast Group/Source Address supported by the MB-UPF, instead of further communicating with MB-SMF. And thus, the registration and de- registration from NG-RAN to MB-SMF is not necessary. The solutions above mandate the registration and de-registration procedures.

- In Multicast Activation Request from SMF to AMF, included in the message are IDs of UEs that do not have user plane activated for the PDU Session, and UEs that have user plane activated for the PDU Session are not included. o Without including UEs with user plane activated in the SMF, it is assumed that whenever UE joins an MBS session, the NG-RAN will always establish N3mb tunnel (i.e., in the case of unicast transport over N3mb, NG-RAN establishes the N3mb tunnel with MB-UPF, and in the case of multicast transport over N3mb, NG-RAN perform IGMP/MLD join all the time). If state of UE changes between CM-IDLE and CM-CONNECTED for some other reasons which are not relevant with the MBS session, it is possible that NG-RAN establish and release N3mb tunnels frequently, o For UEs without user plane activated in the SMF but in CM-CONNECTED (e.g., due to other PDU Session activated), the AMF will not perform paging, as a result, such UEs (that previously joined the MBS Session) will not be added into the MBS Session in NG-RAN, and consequently such UEs will not be able to receive MBS data. o In Multicast Deactivation Request from MB-SMF to AMF, RAN Node Ids are included, while it is not a typical behavior for a session management function to be aware of RAN Node Ids.

[0065] Certain aspects of the present disclosure and their embodiments may provide solutions to the aforementioned or other challenges.

[0066] One aspect relates to an AMF getting the UE joining information from SMF when the UE joins (e.g., Figure 10, step 1000-1). In an N2 based handover, a target AMF can get the UE joining information from a source AMF directly. Specifically, options A and B can provide a coherent solution in Multicast Activation Request and Multicast Deactivation Request handling: Option A: SMF is not involved in activation and deactivation (e.g., Figure 10, steps

1000-2a.1000-2b.1002-la.1002-lb)

- AMF can register/de-register towards MB-SMF (e.g., Figure 10, steps 1000-2a, 1000- 2b), instead of NG-RAN.

- In a Multicast Deactivation Request sent from MB-SMF to AMF (e.g., Figure 10, step 1000-2 b), RAN Node Ids are not needed. AMF can determine the impacted NG-RANs based on its own information (e.g., Figure 10, step 1002-2a).

- Multicast Activation Request can be sent from MB-SMF to AMF directly as well (e.g., Figure 10, step 1000-1). Based on UE joining information and CM states, AMF can send multicast activation request to NG-RAN properly to activate CM-CONNECTED UEs and perform group notification for CM-IDLE UEs (e.g., Figure 10, 1002-la).

Option B: SMF is always involved in activation and deactivation fe.g.. Figure 10. steps

1000-3a. 1000-3b. 1002-3. 1002-4j

- AMF does not need to register/de-register towards MB-SMF.

- Multicast Deactivation Request sent from MB-SMF to SMF and from SMF to AMF (e.g., Figure 10, step 1000-3b). In the Multicast Deactivation Request, RAN Node Ids are not needed. AMF can determine the impacted NG-RANs based on its own information (e.g., Figure 10, step 1002-4).

- Multicast Activation Request can be sent from MB-SMF to SMF and from SMF to AMF as well (e.g., Figure 10, step 1000-3a). Based on UE joining information and CM states, AMF can send multicast activation request to NG-RAN properly to activate CM-CONNECTED UEs and perform group notification for CM-IDLE UEs (e.g., Figure 10, step 1002-3).

[0067] Another aspect relates to an AMF unaware of UE join information from SMF, as described in option C below (e.g., step 1000-4).

Qption-C: Follow what is currently included in the TS 23.247 vO.l.O and update S2-

2102941r02 and S2-2102942 to have a consistent distribution path: MB-SMF -> SMF ->

AMF -> NG-RAN:

NG-RAN & AMF does not need to register/de-register towards MB-SMF - Multicast Deactivation Request sent from MB-SMF to SMF and SMF to AMF (e.g., Figure 10, step 1000-5b). In order to send requests to proper NG-RANs, SMF provides all joined UE Ids to AMF (e.g., Figure 10, step 1002-6).

- Multicast Activation Request sent from MB-SMF to SMF and SMF to AMF (e.g., Figure 10, step 1000-5a). SMF provides all joined UE Ids to AMF. Based on UE CM states, AMF can send multicast activation request to NG-RAN properly to activate CM- CONNECTED UEs and perform group notification for CM-IDLE UEs (e.g., Figure 10, step 1002-5).

[0068] Embodiments disclosed herein involve at least the following key aspects:

AMF aware of UE join (e.g., Figure 10, step 1000-1)

[0069] AMF gather UE joining information and MBS session information in "UE join and multicast session establishment procedure" as well as in "N2 based handover procedure"

In case SMF is not involved in activation and deactivation, with the UE joining information and MBS session information:

- The AMF handles multicast session activation request from MB-SMF (e.g., Figure 10, steps 1000-2a, 1002-la), builds up radio area for CM-IDLE UEs, and sends multicast session activation request to NG-RANs for CM-IDLE and CM-CONNECTED UEs.

- The AMF handles multicast deactivation request from MB-SMF (e.g., Figure 10, steps 1000-2b, 1002-2a), and sends multicast session deactivation request to NG-RANs

- To enable above, the AMF needs to register towards MB-SMF when there are UEs joined, and de-register towards MB-SMF when there are no longer joined UEs.

In case SMF is always involved in activation and deactivation, with the UE joining information and MBS session information, AMF:

- Handles multicast session activation request from SMF (e.g., Figure 10, steps 1000- 3a, 1002-3), builds up radio area for all UEs in CM-IDLE (those UEs may be served by this particular SMF or by other SMFs), and sends multicast session activation request to NG-RANs to trigger group paging for CM-IDLE UEs and activate the MBS Session for CM-CONNECTED UEs). - Handles multicast deactivation request from SMF (e.g., Figure 10, steps 1002-3b, 1002-4) and sends multicast session deactivation request to NG-RANs for all joined UEs (those UEs may be served by this particular SMF or by other SMFs).

AMF not aware of UE join (e.g., step 1000-4)

In case AMF is unaware of UE join information from SMF, with the MBS session information and UE Ids provided by SMF:

- The AMF handles multicast session activation request from SMF (e.g., Figure 10, steps 1000-5a, 1002-5), builds up radio area for CM-IDLE UEs (served by this SMF), and sends multicast session activation request to NG-RANs to trigger group paging for CM-IDLE UEs and activate the MBS Session for CM-CONNECTED UEs), based on provided UE Ids.

- The AMF handles multicast deactivation request from SMF (e.g., Figure 10, steps 1000-5b, 1002-6) and sends multicast session deactivation request to NG-RANs based on provided UE Ids (served by this SMF).

- The AMF may be optimized to record the NG-RANs (and the radio areas) to which it has sent the multicast session activation/deactivation requests, to avoid duplicated requests.

[0070] There are, proposed herein, various embodiments which address one or more of the issues disclosed herein. In one aspect, a method performed by an AMF for improving 5MBS signaling in a CN is provided. The method includes receiving an 5MBS request from a network node in the CN. The method also includes performing one or more actions in response to receiving the 5MBS request from the network node.

[0071] Certain embodiments may provide one or more of the following technical advantage(s).

For option A and option B:

- AMF naturally has the UE CM states information and NG-RAN connectivity information. If AMF further evolves with the UE joining information (UE associated with the MBS session), a coherent solution can be achieved for signaling efficiency improvement for 5MBS multicast sessions. - With the UE joining information in the AMF, in session activation, the AMF can perform session activation towards NG-RAN nodes at one time for all the involved UEs.

Otherwise, if the NG-RAN does not receive information from the AMF, based on S2-2102941r02 and S2-2102942, it is possible the NG-RAN node may receive different activation requests for different UEs. For example, assume UE1 and UE2 are in CM-IDLE in the same NG-RAN, and SMF1 serves UE1 and SMF2 serves UE2. Regardless of whether those two UEs are served by the same AMF or not, when MBS session is activated, the NG-RAN receives an activation request via SMF1 and another activation request via SMF2. In case UE1 and UE2 are in different cells, the NG-RAN will also perform group notification separately.

The proposed solution is more efficient in multicast session activation in the following aspects:

- With the explicit multicast session activation request from AMF to NG-RAN, it is not necessary for NG-RAN to establish N3mb tunnel towards MB-UPF. So that, it avoids the issue that when the MBS session is inactive, the N3mb tunnel is frequently established and released due to UEs' CM state change.

- MB-SMF/MB-UPF are aware of NG-RAN N3mb DL Tunnel endpoint for unicast transport, without the necessity of being aware of NG-RAN Ids.

For option C:

- AMF's knowledge on UE CM states and NG-RAN connectivity information is not fully utilized.

- With the explicit multicast session activation request from AMF to NG-RAN, it is not necessary for NG-RAN to establish an N3mb tunnel towards MB-UPF. So that, it avoids the issue that when the MBS session is inactive, the N3mb tunnel is frequently established and released due to UEs' CM state change.

- MB-SMF/MB-UPF are aware of NG-RAN N3mb DL Tunnel endpoint for unicast transport, without the necessity of being aware of NG-RAN Ids. [0072] Figure 7 illustrates one example of a cellular communications system 700 in which embodiments of the present disclosure may be implemented. In the embodiments described herein, the cellular communications system 700 is a 5G system (5GS) including a Next Generation RAN (NG-RAN) and a 5G Core (5GC). In this example, the RAN includes base stations 702-1 and 702-2, which in the 5GS include NR base stations (gNBs) and optionally next generation eNBs (ng-eNBs) (e.g., LTE RAN nodes connected to the 5GC), controlling corresponding (macro) cells 704-1 and 704-2. The base stations 702-1 and 702-2 are generally referred to herein collectively as base stations 702 and individually as base station 702. Likewise, the (macro) cells 704-1 and 704-2 are generally referred to herein collectively as (macro) cells 704 and individually as (macro) cell 704. The RAN may also include a number of low power nodes 706-1 through 706-4 controlling corresponding small cells 708-1 through 708-4. The low power nodes 706-1 through 706-4 can be small base stations (such as pico or femto base stations) or RRHs, or the like. Notably, while not illustrated, one or more of the small cells 708-1 through 708-4 may alternatively be provided by the base stations 702. The low power nodes 706-1 through 706-4 are generally referred to herein collectively as low power nodes 706 and individually as low power node 706. Likewise, the small cells 708-1 through 708-4 are generally referred to herein collectively as small cells 708 and individually as small cell 708. The cellular communications system 700 also includes a core network 710, which in the 5G System (5GS) is referred to as the 5GC. The base stations 702 (and optionally the low power nodes 706) are connected to the core network 710.

[0073] The base stations 702 and the low power nodes 706 provide service to wireless communication devices 712-1 through 712-5 in the corresponding cells 704 and 708. The wireless communication devices 712-1 through 712-5 are generally referred to herein collectively as wireless communication devices 712 and individually as wireless communication device 712. In the following description, the wireless communication devices 712 are oftentimes UEs, but the present disclosure is not limited thereto.

[0074] Figure 8 illustrates a wireless communication system represented as a 5G network architecture composed of core Network Functions (NFs), where interaction between any two NFs is represented by a point-to-point reference point/interface.

Figure 8 can be viewed as one particular implementation of the system 700 of Figure 7. [0075] Seen from the access side the 5G network architecture shown in Figure 8 comprises a plurality of UEs 712 connected to either a RAN 702 or an Access Network (AN) as well as an AMF 800. Typically, the R(AN) 702 comprises base stations, e.g., such as eNBs or gNBs or similar. Seen from the core network side, the 5GC NFs shown in Figure 8 include a NSSF 802, an AUSF 804, a UDM 806, the AMF 800, a SMF 808, a PCF 810, and an Application Function (AF) 812.

[0076] Reference point representations of the 5G network architecture are used to develop detailed call flows in the normative standardization. The N1 reference point is defined to carry signaling between the UE 712 and AMF 800. The reference points for connecting between the AN 702 and AMF 800 and between the AN 702 and UPF 814 are defined as N2 and N3, respectively. There is a reference point, Nil, between the AMF 800 and SMF 808, which implies that the SMF 808 is at least partly controlled by the AMF 800. N4 is used by the SMF 808 and UPF 814 so that the UPF 814 can be set using the control signal generated by the SMF 808, and the UPF 814 can report its state to the SMF 808. N9 is the reference point for the connection between different UPFs 814, and N14 is the reference point connecting between different AMFs 800, respectively. N15 and N7 are defined since the PCF 810 applies policy to the AMF 800 and SMF 808, respectively. N12 is required for the AMF 800 to perform authentication of the UE 712. N8 and N10 are defined because the subscription data of the UE 712 is required for the AMF 800 and SMF 808.

[0077] The 5GC network aims at separating UP and CP. The UP carries user traffic while the CP carries signaling in the network. In Figure 8, the UPF 814 is in the UP and all other NFs, i.e., the AMF 800, SMF 808, PCF 810, AF 812, NSSF 802, AUSF 804, and UDM 806, are in the CP. Separating the UP and CP guarantees each plane resource to be scaled independently. It also allows UPFs to be deployed separately from CP functions in a distributed fashion. In this architecture, UPFs may be deployed very close to UEs to shorten the Round Trip Time (RTT) between UEs and data network for some applications requiring low latency.

[0078] The core 5G network architecture is composed of modularized functions. For example, the AMF 800 and SMF 808 are independent functions in the CP. Separated AMF 800 and SMF 808 allow independent evolution and scaling. Other CP functions like the PCF 810 and AUSF 804 can be separated as shown in Figure 8. Modularized function design enables the 5GC network to support various services flexibly. [0079] Each NF interacts with another NF directly. It is possible to use intermediate functions to route messages from one NF to another NF. In the CP, a set of interactions between two NFs is defined as service so that its reuse is possible. This service enables support for modularity. The UP supports interactions such as forwarding operations between different UPFs.

[0080] Figure 9 illustrates a 5G network architecture using service-based interfaces between the NFs in the CP, instead of the point-to-point reference points/interfaces used in the 5G network architecture of Figure 8. Flowever, the NFs described above with reference to Figure 8 correspond to the NFs shown in Figure 9. The service(s) etc. that a NF provides to other authorized NFs can be exposed to the authorized NFs through the service-based interface. In Figure 9 the service based interfaces are indicated by the letter "N" followed by the name of the NF, e.g., Namf for the service based interface of the AMF 800 and Nsmf for the service based interface of the SMF 808, etc. The NEF 900 and the NRF 902 in Figure 9 are not shown in Figure 8 discussed above. Flowever, it should be clarified that all NFs depicted in Figure 8 can interact with the NEF 900 and the NRF 902 of Figure 9 as necessary, though not explicitly indicated in Figure 8.

[0081] Some properties of the NFs shown in Figures 8 and 9 may be described in the following manner. The AMF 800 provides UE-based authentication, authorization, mobility management, etc. A UE 712 even using multiple access technologies is basically connected to a single AMF 800 because the AMF 800 is independent of the access technologies. The SMF 808 is responsible for session management and allocates Internet Protocol (IP) addresses to UEs. It also selects and controls the UPF 814 for data transfer. If a UE 712 has multiple sessions, different SMFs 808 may be allocated to each session to manage them individually and possibly provide different functionalities per session. The AF 812 provides information on the packet flow to the PCF 810 responsible for policy control in order to support QoS. Based on the information, the PCF 810 determines policies about mobility and session management to make the AMF 800 and SMF 808 operate properly. The AUSF 804 supports authentication function for UEs or similar and thus stores data for authentication of UEs or similar while the UDM 806 stores subscription data of the UE 712. The Data Network (DN), not part of the 5GC network, provides Internet access or operator services and similar. [0082] An NF may be implemented either as a network element on a dedicated hardware, as a software instance running on a dedicated hardware, or as a virtualized function instantiated on an appropriate platform, e.g., a cloud infrastructure.

[0083] Before discussing specific embodiments of the present disclosure, a method performed by an AMF for improving 5MBS signaling in a CN is first provided with reference to Figure 10. Figure 10 is a flowchart of an exemplary method performed by an AMF according to an embodiment of the present disclosure for improving 5MBS signaling in a CN.

[0084] The AMF is configured to receive a multicast request from a network node in the CN (step 1000). Accordingly, the AMF is configured to perform one or more actions in response to receiving the multicast request from the network node, independent of whether the AMF is aware of a UE is joining the 5MBS (step 1002).

[0085] The AMF may receive an indication that indicates the UE is joining the 5MBS (step 1000-1). In one embodiment, the AMF may receive a multicast activation request from an MB-SMF (step 1000-2a) or a multicast deactivation request from the MB-SMF (step 1000-2b). In response to receiving the multicast activation request, the AMF sends the multicast activation request to an NR-RAN to perform activation of one or more UEs in CM-CONNECTED state or group notification to one or more UEs in CM-IDLE state (step 1002-la). Accordingly, the AMF registers the UE toward the SMF (step 1002-lb). In response to receiving the multicast deactivation request, the AMF determines an impacted NG-RAN based on information available at the AMF (step 1002- 2a). Accordingly, the AMF deregisters the UE toward the SMF (step 1002-2b).

[0086] In another embodiment, the AMF may receive a multicast activation request from an SMF (step 1000-3a) or a multicast deactivation request from the SMF (step 1000-3b). In response to receiving the multicast activation request, the AMF sends the multicast activation request to an NG-RAN to perform activation of one or more UEs in CM-CONNECTED state or group notification to one or more UEs in CM-IDLE state (step 1002-3). In response to receiving the multicast deactivation request, the AMF determines an impacted NG-RAN based on information available at the AMF (step 1002- 4).

[0087] The AMF may not receive an indication that indicates the UE is joining the 5MBS (step 1000-4). In this regard, the AMF may receive a multicast activation request from an SMF (step 1000-5a) or receive a multicast deactivation request from the SMF (step 1000-5b). In response to receiving the multicast activation request, the AMF sends the multicast activation request to an NG-RAN to perform activation of one or more UEs in CM-CONNECTED state or group notification to one or more UEs in CM-IDLE state (step 1002-5). In response to receiving the multicast deactivation request, the AMF determines an impacted NG-RAN based on information available at the AMF (step 1002-6).

[0088] Figure 11 is a flowchart of an exemplary method performed by an AMF according to an embodiment of the present disclosure. The AMF may receive an indication that indicates a UE is joining the 5MBS (step 1100). The AMF is configured to receive a 5MBS request from a network node in the CN (step 1102). Accordingly, the AMF performs one or more actions in response to receiving the 5MBS request from the network node (step 1104).

[0089] In one embodiment, the AMF receives the indication that indicates the UE is joining the 5MBS (step 1100) and a multicast activation request from an MB-SMF (step 1102-1). Accordingly, the AMF sends the multicast activation request to an NG-RAN (step 1104-la) and registers the UE toward the MB-SMF (step 1104-lb).

[0090] In another embodiment, the AMF receives the indication that indicates the UE is joining the 5MBS (step 1100) and a multicast deactivation request from an MB-SMF (step 1102-2). Accordingly, the AMF sends the multicast deactivation request to an NG- RAN (step 1104-2a) and deregisters the UE toward the MB-SMF (step 1104-2b).

[0091] In another embodiment, the AMF receives the indication that indicates the UE is joining the 5MBS (step 1100) and a multicast activation request from an SMF (step 1102-3). Accordingly, the AMF sends the multicast activation request to an NG-RAN (step 1104-3).

[0092] In another embodiment, the AMF receives the indication that indicates the UE is joining the 5MBS (step 1100) and a multicast deactivation request from an SMF (step 1102-4). Accordingly, the AMF sends the multicast deactivation request to an NG-RAN (step 1104-4).

[0093] In another embodiment, the AMF does not receive the indication that indicates the UE is joining the 5MBS but receives a multicast activation request from an SMF (step 1102-5). Accordingly, the AMF sends the multicast activation request to an NG-RAN (step 1104-5). [0094] In another embodiment, the AMF does not receive the indication that indicates the UE is joining the 5MBS but receives a multicast deactivation request from an SMF (step 1102-6). Accordingly, the AMF sends the multicast deactivation request to an NG-RAN (step 1104-6).

[0095] Specific embodiments pertaining to the method described in Figure 10 are described below.

AMF aware of UE join

[0096] Refer now to Figure 12 for UE Join and Multicast session establishment (for both option A and B). The underlined texts below are new compared to "7.2.1.3 MBS join and Session establishment procedure" in chapter 2.1 of TS 23.247 vO.1.0.

In step 5. the SMF also pass the UE joining information and 5MBS session context information to the AMF in Nsmf PDUSession UpdateSMContext response. The AMF get the UE joining information and 5MBS session context, together with MB-SMF ID. The AMF store the 5MBS session context locally and associate with the Joined UEs. MB-SMF ID and multicast transport information fincludina multicast GTP tunnel endpointj of the shared delivery are stored as well.

Note: If UE join an inactive MBS session, in step 7 for resource reservation for shared delivery, the N3mb tunnel is not necessary to be established.

[0097] Refer now to Figures 13A and 13B for N2 based handover (for both option A and B). The underlined texts below are new compared to "7.2.3.3 N2 based handover" in chapter 2.1 of TS 23.247 vO.1.0.

In step 3, S-AMF include UE joining information to T-AMF in

Namf Communication CreateUEContext Request. In addition to UE joining information. S-AMF can pass the MB-SMF Id to T-AMF as well.

For the MBS session information, in step 4, if SMF has the MBS Session context, it can include it in Nsmf PDUSession UpdateSMContext response directly. Otherwise, the SMF may need to perform MB-SMF discovery as shown in step 3 and perform MBS QoS information query as shown in step 4 in "UE join and multicast session establishment" procedure. If S-AMF pass the MB-SMF Id in step 3. the SMF mav skip step 3 and perform step 4 only to get MBS QoS information from MB-SMF in "UE join and multicast session establishment" procedure. Besides the MBS QoS information, multicast transport information fincludina multicast GTP tunnel endoointj of the shared delivery is stored as well.

Note: If the UE target location information cannot be retrieved in step 3, step 6 to step

10 can be executed after step 20. In this case, T-AMF can get UE joining information in

Handover Notify in step 20. And AMF can get MBS QoS information, multicast transport information fincludina multicast GTP tunnelj of the shared delivery in

Nsmf PDUSession UpdateSMContext response as well.

[0098] Refer now to Figure 14 for establishment of shared delivery toward RAN node under Option A: SMF is not involved in activation and deactivation, with underlined texts indicating new additions and text in double brackets indicating deletions relative to original texts in TS 23.247 vO.1.0.

1. A RAN node discovers that it needs to establish shared delivery for an MBS session because it serves at least one UE within the MBS session. This can occur after the UE joined the MBS session or as the result of handover of the UE. For location dependent services, the RAN node needs to establish shared delivery for the location dependent contents of an MBS session if it serves at least one UE assigned to an MBS session ID and area session ID.

2. The RAN node sends a multicast distribution request to the AMF and provides the TMGI as MBS session ID. If the RAN node is configured to use unicast transport for the shared delivery, it allocates a GTP tunnel endpoint and provides that endpoint. For location dependent services, the RAN node also provides the area session ID. If the RAN node is configured to use multicast transport for the shared delivery, GTP Tunnel endpoint will not be included, and the RAN node can perform IGMP/MLD join directly.

3. Based on the MB-SMF ID associated with the MBS session stored locally in the

AMF, the AMF forwards the multicast distribution request to the MB-SMF. If GTP tunnel endpoint is provided bv RAN in step 2. [[the AMF discovers the MB- SMF serving the multicast session using the NRF discovery service.]] the AMF sends a Multicast distribution request to the MB-SMF, passing the parameters received in message 2. Only when it is the first time for the AMF to receive the multicast distribution request for the MBS session, the AMF adds the ID of the AMF [[RAN node]] to indicate the AMF register towards the MB-SMF.

If GTP tunnel endpoint is not provided bv RAN in step 2, which indicates NG-RAN will join multicast group directly. In this case, only when it is the first time for the AMF to receive the multicast distribution request for the MBS session, AMF sends Multicast Distribution Request with the AMF ID to indicate the AMF register towards the MB-SMF. Otherwise, step 3 to 6 can be skipped.

5. The MB-SMF stores the AMF [[and RAN node]] ID in the context of the multicast session (or location dependent part of the multicast session if an area session ID was received) to enable subsequent signalling towards that RAN node.

6. The MB-SMF sends a multicast distribution response to the AMF[[. If it did not receive a GTP tunnel endpoint in message 3, it provides a GTP tunnel endpoint for multicast transport of the shared delivery.]]

7. The AMF forwards the multicast distribution response to the RAN node. [[If the RAN node received a GTP tunnel endpoint for multicast transport of the shared delivery, it uses that information to join the multicast transport.]]

[0099] Refer now to Figure 15 for release of shared delivery toward RAN node under Option A: SMF is not involved in activation and deactivation, with underlined texts indicating new additions and text in double brackets indicating deletions relative to original texts in TS 23.247 vO.1.0. 1. A RAN node discovers that it needs to release shared delivery for an MBS session e.g., because it no longer serves at least one UE within the MBS session. This can occur after the UE left the MBS session or as the result of a handover of UEs. For location dependent services, the RAN node may release shared delivery for the location dependent contents of an MBS session if it no longer serves at least one UE assigned to an MBS session ID and area session ID.

2. The RAN node sends a multicast distribution release request to the AMF and provides the TMGI as MBS session ID. For location dependent services, the RAN node also provides the area session ID. If unicast transport applies. GTP Tunnel Endpoint for unicast transport is provided. For multicast transport, the RAN node performs IGMP/MLD leave directly, and sends the request without GTP Tunnel Endpoint.

3. The AMF discovers the MB-SMF serving the multicast session using the NRF discovery service. It The AMF sends a Multicast distribution release request to the MB-SMF, passing the parameters received in message 2 for unicast transport.

AMF will include its ID_r only when AMF detects it is the last NG-RAN serving the MBS session, to indicate it is going to de-reaister from the MB-SMF.

For multicast transport, the AMF will send the Multicast distribution release request to the MB-SMF with the AMF ID, only when there are no NG-RANs serving the MBS session. Otherwise, step 3 to step 6 can be skipped.

5. The MB-SMF removes the RAN node AMF ID from storage in the context of the multicast session (or location dependent part of the multicast session if an area session ID was received), when it receives the de-register AMF ID from the request.

6. The MB-SMF sends a multicast distribution release request to the AMF.

7. The AMF forwards the multicast distribution release response to the RAN node, if the RAN node previously received a GTP tunnel endpoint for multicast transport of the shared delivery, it uses that information to leave the multicast transport. It releases local resources to receive the multicast data. [0100] Refer now to Figure 16 for Multicast Deactivation under Option A: SMF is not involved in activation and deactivation, with underlined texts indicating new additions and text in double brackets indicating deletions relative to original texts in TS 23.247 vO.1.0.

3. The MB-SMF decides to deactivate the MBS session (or location dependent part of the multicast session)., either based on a request from the NEF/MBSF and AF, or because the MB-UPF reports that it did not receive any data for the multicast session for a configured period.

[[4.]] For each AMF the MB-SMF stored in the multicast context session (or location dependent part of the multicast session), it sends a multicast session deactivation request towards the AMF with the MBS Session ID. [[The MB-SMF includes the RAN node IDs of RAN nodes that previously registered via the AMF for shared delivery. The MB-SMF also provides the MBS session ID and for location dependent services area session ID.]]

3. [[For each RAN node indicated in message 2,]] Based on the involved NG-RAN information stored in the AMF, the AMF sends a multicast session deactivation request. The AMF includes the MBS session ID and possible area session ID received in message 2. The RAN node handles the inactivation as defined in RAN specifications. UEs that have joined that multicast session can become IDLE. The N3mb tunnel for 5GC Shared MBS delivery method shall not be released as long as the RAN node serves CM CONNECTED UEs within the multicast session

[0101] Refer now to Figure 17 for Multicast Activation under Option A: SMF is not involved in activation and deactivation, with underlined texts indicating new additions and text in double brackets indicating deletions relative to original texts in TS 23.247 vO.l.O.

2. For each AMF the MB-SMF stored in the multicast context session for location dependent part of the multicast session), it sends a multicast session activation request towards the AMF. The MB-SMF also provides the MBS session ID and for location dependent services area session ID.

4. The AMF checks for each UE associated with the MBS session. For each NG-RAN supporting 5MBS with the serving UEs. the AMF will determine the radio area of the CM-IDLE UEs. The AMF combines all radio areas determined in that manner and sends activation request indicating the MBS session ID to RAN nodes handling all those radio areas. If there are no CM-IDLE UEs but some CM- CONNECTED UEs in the NG-RAN, the AMF will also send activation request with the MBS session ID without the radio area.

5. The RAN nodes perform the MBS session activation to the CM-CONNECTED UEs_f if N3mb tunnel is not established, the NG-RAN established the N3mb tunnel fi.e., the NG-RAN performs "establishment of shared delivery towards RAN node"! If radio area is included, the NG-RAN performs group activation. Based on radio area.

Steps 6 to 8 apply separately for each CM-IDLE UE in the multicast session.

6. UE reacts by sending a service request to the AMF.

7. The AMF request the activation of the PDU session

8. The SMF activates the PDU session.

[0102] Refer now to Figure 18 for establishment of shared delivery toward RAN node under Option B: SMF is always involved in activation and deactivation, with underlined texts indicating new additions and text in double brackets indicating deletions relative to original texts in TS 23.247 vO.1.0.

1. A RAN node discovers that it needs to establish shared delivery for an MBS session because it serves at least one UE within the MBS session. This can occur after the UE joined the MBS session or as the result of handover of the UE. For location dependent services, the RAN node needs to establish shared delivery for the location dependent contents of an MBS session if it serves at least one UE assigned to an MBS session ID and area session ID. If the RAN node is configured to use multicast transport for the shared delivery, the RAN node can perform IGMP/MLD join directly, and step 2 to step 7 can be skipped.

2. The RAN node sends a multicast distribution request to the AMF and provides the TMGI as MBS session ID. If the RAN node is configured to use unicast transport for the shared delivery, it allocates a GTP tunnel endpoint and provides that endpoint. For location dependent services, the RAN node also provides the area session ID.

3. Based on the MB-SMF ID associated with the MBS session stored locally in the AMF. the AMF forwards the multicast distribution request to the MB-SMF.

5. [[The MB-SMF stores the AMF and RAN node ID in the context of the multicast session (or location dependent part of the multicast session if an area session ID was received) to enable subsequent signalling towards that RAN node.]]

6. The MB-SMF sends a multicast distribution request to the AMF. [[If it did not receive a GTP tunnel endpoint in message 3, it provides a GTP tunnel endpoint for multicast transport of the shared delivery.]]

[0103] Refer now to Figure 19 for release of shared delivery toward RAN node under Option B: SMF is always involved in activation and deactivation, with underlined texts indicating new additions and text in double brackets indicating deletions relative to original texts in TS 23.247 vO.1.0.

For multicast transport, the RAN node performs IGMP/MLD leave directly, and step 2 to step 7 can be skipped.

2. For unicast transport. The RAN node sends a multicast distribution release request to the AMF and provides the TMGI as MBS session ID. For location dependent services, the RAN node also provides the area session ID. The GTP Tunnel Endpoint for unicast transport is provided.

3. Based on the MB-SMF ID associated with the MBS session stored locally in the AMF, the AMF forwards the multicast distribution request to the MB-SMF. [[The AMF discovers the MB-SMF serving the multicast session using the NRF discovery service. It The AMF sends a Multicast distribution release request to the MB-SMF, passing the parameters received in message 2 for unicast transport.]]

5. [[The MB-SMF removes the RAN node AMF ID from storage in the context of the multicast session (or location dependent part of the multicast session if an area session ID was received), when it receives the de-register AMF ID from the request.]]

6. The MB-SMF sends a multicast distribution release request to the AMF.

7. The AMF forwards the multicast distribution release response to the RAN node. [[If the RAN node previously received a GTP tunnel endpoint for multicast transport of the shared delivery, it uses that information to leave the multicast transport. It releases local resources to receive the multicast data.]]

[0104] Refer now to Figure 20 for Multicast Deactivation under Option B: SMF is always involved in activation and deactivation, with underlined texts indicating new additions and text in double brackets indicating deletions relative to original texts in TS 23.247 vO.1.0. 1. The MB-SMF decides to deactivate the MBS session (or location dependent part of the multicast session)., either based on a request from the NEF/MBSF and AF, or because the MB-UPF reports that it did not receive any data for the multicast session for a configured period.

2. For each SMF the MB-SMF stored in the multicast context session for location dependent part of the multicast session), it sends a multicast session deactivation request towards the SMF. The MB-SMF also provides the MBS session ID and for location dependent services area session ID.

3. For each AMF with the serving UEs. the SMF sends a multicast session deactivation request towards the AMF with the MBS Session ID. Based on the involved NG-RAN information stored in the AMF, the AMF sends a multicast session deactivation request. The AMF includes the MBS session ID and possible area session ID received in message 2.

If the AMF receives multicast session deactivation request from the second SMF. the AMF can simply respond without taking further actions.

4. The RAN node handles the inactivation as defined in RAN specifications. UEs that have joined that multicast session can become IDLE. The N3mb tunnel for 5GC Shared MBS delivery method shall not be released as long as the RAN node serves CM CONNECTED UEs within the multicast session.

[0105] Refer now to Figure 21 for Multicast Activation under Option B: SMF is always involved in activation and deactivation, with underlined texts indicating new additions and text in double brackets indicating deletions relative to original texts in TS 23.247 vO.1.0.

2. For each SMF the MB-SMF stored in the multicast context session (or location dependent part of the multicast session), it sends a multicast session activation request towards the SMF. The MB-SMF also provides the MBS session ID and for location dependent services area session ID. 3. For each AMF with the serving UEs. the SMF sends a multicast session activation request towards the AMF with the MBS Session ID. The SMF also include area session ID for location dependent services.

4. The AMF checks for each NG-RAN service UEs associated with the MBS session.

For each NG-RAN supporting 5MBS with the serving UEs. the AMF will determine the radio area of the CM-IDLE UEs. The AMF combines all radio areas determined in that manner and sends activation request indicating the MBS session ID to RAN nodes handling all those radio areas. If there are no CM-IDLE UEs but some CM- CONNECTED UEs in the NG-RAN. the AMF will also send activation request with the MBS session ID without the radio area.

If the AMF receives multicast session activation request from the second SMF, the AMF can simply respond without taking further actions.

5. The RAN nodes perform the MBS session activation to the CM-CONNECTED UEs. if N3mb tunnel is not established_r the NG-RAN established the N3mb tunnel fi.e_r the NG-RAN performs "establishment of shared delivery towards RAN node"! If radio area is included, the NG-RAN performs group activation based on radio area.

Steps 6 to 8 apply separately for each CM-IDLE UE in the multicast session.

6. UE reacts by sending a service request to the AMF.

7. The AMF request the activation of the PDU session.

8. The SMF activates the PDU session.

AMF not aware of UE join

Option C: Follow what is currently included in the TS 23.247 vO.l.O and update S2- 2102941r02 and S2-2102942.

For option C, "UE join and multicast session establishment" and "N2 based handover" are not impacted.

[0106] Refer now to Figure 22 for establishment of shared delivery toward RAN node (same as Option B), with underlined texts indicating new additions and text in double brackets indicating deletions relative to original texts in TS 23.247 vO.l.O. 1. A RAN node discovers that it needs to establish shared delivery for an MBS session because it serves at least one UE within the MBS session. This can occur after the UE joined the MBS session or as the result of handover of the UE. For location dependent services, the RAN node needs to establish shared delivery for the location dependent contents of an MBS session if it serves at least one UE assigned to an MBS session ID and area session ID. If the RAN node is configured to use multicast transport for the shared delivery, the RAN node can perform IGMP/MLD join directly, and step 2 to step 7 can be skipped.

[0107] Refer now to Figure 23 for release of shared delivery toward RAN node (same as Option B), with underlined texts indicating new additions and text in double brackets indicating deletions relative to original texts in TS 23.247 vO.1.0. 1. A RAN node discovers that it needs to release shared delivery for an MBS session e.g., because it no longer serves at least one UE within the MBS session. This can occur after the UE left the MBS session or as the result of a handover of UEs. For location dependent services, the RAN node may release shared delivery for the location dependent contents of an MBS session if it no longer serves at least one UE assigned to an MBS session ID and area session ID.

3. Based on the MB-SMF ID associated with the MBS session stored locally in the

AMF. the AMF forwards the multicast distribution release request to the MB-SMF.

The AMF discovers the MB SMF serving the multicast session using the NRF discovery service. It The AMF sends a Multicast distribution release request to the

MB-SMF, passing the parameters received in message 2 for unicast transport.

5. The MB SMF removes the RAN node AMF ID from storage in the context of the multicast session (or location dependent part of the multicast session if an area session ID was received), when it receives the dc-rcgistcr AMF ID from the request.

6. The MB-SMF sends a multicast distribution release request to the AMF.

7. The AMF forwards the multicast distribution release response to the RAN node, if the RAN node previously received a GTP tunnel endpoint for multicast transport of the shared delivery, it uses that information to leave the multicast transport. It releases local resources to receive the multicast data. [0108] Refer now to Figure 24 for Multicast Deactivation, with underlined texts indicating new additions and text in double brackets indicating deletions relative to original texts in TS 23.247 vO.1.0.

Compared with option B, the difference is on step 3:

3. For each AMF with the serving UEs, the SMF sends a multicast session deactivation request towards the AMF with the MBS Session ID with the UE Ids who joined the MBS session. Based on UE Ids, the AMF filter the CM-CONNECTED UEs and determines the involved NG-RANs which serve those CM-CONNECTED UEs. The SMF also include area session ID for location dependent services.

If the AMF receives multicast session deactivation requests from the other SMFs, the AMF needs to handle them separately. The AMF mav be optimized to keep record of the NG-RANs which it has sent the multicast session deactivation requests, to avoid duplicated deactivation requests.

[0109] Refer now to Figure 25 for Multicast Activation, with underlined texts indicating new additions and text in double brackets indicating deletions relative to original texts in TS 23.247 vO.1.0.

Compared with option B, the difference is on step 3 and step 4:

3. For each AMF with the serving UEs. the SMF sends a multicast session activation request towards the AMF with the MBS Session ID with the UE Ids who joined the MBS session.

4. For each NG-RAN supporting 5MBS with the serving UEs, the AMF will determine the radio area of the CM-IDLE UEs. The AMF combines all radio areas determined in that manner and sends activation request indicating the MBS session ID to RAN nodes handling all those radio areas. If there are no CM-IDLE UEs but some CM- CONNECTED UEs in the NG-RAN. the AMF will also send activation request with the MBS session ID without the radio area. If the AMF receives multicast session activation requests from the other SMFs_r the AMF needs to handle them separately. The AMF may be optimized to keep record of the NG-RANs and the radio areas which it has sent the multicast session activation requests, to avoid duplicated activation requests.

[0110] Figure 26 is a schematic block diagram of a network node 2600 according to some embodiments of the present disclosure. The network node 2600 may be, for example, a core network node (e.g., SMF, MB-SMF, AMF). As illustrated, the network node 2600 includes one or more processors 2604 (e.g., Central Processing Units (CPUs), Application Specific Integrated Circuits (ASICs), Field Programmable Gate Arrays (FPGAs), and/or the like), memory 2606, and a network interface 2608. The one or more processors 2604 are also referred to herein as processing circuitry. The one or more processors 2604 operate to provide one or more functions of the network node 2600 as described herein (e.g., one or more functions of SMF, PCF, PGW-C, PCRF as described herein). In some embodiments, the function(s) are implemented in software that is stored, e.g., in the memory 2606 and executed by the one or more processors 2604.

[0111] Figure 27 is a schematic block diagram that illustrates a virtualized embodiment of the network node 2600 according to some embodiments of the present disclosure. Optional features are represented by dashed boxes. As used herein, a "virtualized" network node is an implementation of the network node 2600 in which at least a portion of the functionality of the network node 2600 is implemented as a virtual component(s) (e.g., via a virtual machine(s) executing on a physical processing node(s) in a networks)). As illustrated, in this example, the network node 2600 includes one or more processing nodes 2700 coupled to or included as part of a network(s) 2702. Each processing node 2700 includes one or more processors 2704 (e.g., CPUs, ASICs, FPGAs, and/or the like), memory 1006, and a network interface 2708. In this example, functions 2710 of the network node 2600 described herein (e.g., one or more functions of SMF, MB-SMF, AMF as described herein) are implemented at the one or more processing nodes 2700 or distributed across the two or more processing nodes 2700 in any desired manner. In some particular embodiments, some or all of the functions 2710 of the network node 2600 described herein are implemented as virtual components executed by one or more virtual machines implemented in a virtual environment(s) hosted by the processing node(s) 2700.

[0112] In some embodiments, a computer program including instructions which, when executed by at least one processor, causes the at least one processor to carry out the functionality of the network node 2600 or a node (e.g., a processing node 2700) implementing one or more of the functions 2710 of the network node 900 in a virtual environment according to any of the embodiments described herein is provided. In some embodiments, a carrier comprising the aforementioned computer program product is provided. The carrier is one of an electronic signal, an optical signal, a radio signal, or a computer readable storage medium (e.g., a non-transitory computer readable medium such as memory).

[0113] Figure 28 is a schematic block diagram of the network node 2600 according to some other embodiments of the present disclosure. The network node 2600 includes one or more modules 2800, each of which is implemented in software. The module(s) 2800 provide the functionality of the network node 2600 described herein. This discussion is equally applicable to the processing node 2700 of Figure 27 where the modules 2800 may be implemented at one of the processing nodes 2700 or distributed across multiple processing nodes 2700.

[0114] Any appropriate steps, methods, features, functions, or benefits disclosed herein may be performed through one or more functional units or modules of one or more virtual apparatuses. Each virtual apparatus may comprise a number of these functional units. These functional units may be implemented via processing circuitry, which may include one or more microprocessor or microcontrollers, as well as other digital hardware, which may include Digital Signal Processor (DSPs), special-purpose digital logic, and the like. The processing circuitry may be configured to execute program code stored in memory, which may include one or several types of memory such as Read Only Memory (ROM), Random Access Memory (RAM), cache memory, flash memory devices, optical storage devices, etc. Program code stored in memory includes program instructions for executing one or more telecommunications and/or data communications protocols as well as instructions for carrying out one or more of the techniques described herein. In some implementations, the processing circuitry may be used to cause the respective functional unit to perform corresponding functions according one or more embodiments of the present disclosure. [0115] While processes in the figures may show a particular order of operations performed by certain embodiments of the present disclosure, it should be understood that such order is exemplary (e.g., alternative embodiments may perform the operations in a different order, combine certain operations, overlap certain operations, etc.).

[0116] Some exemplary embodiments of the present disclosure are as follows. [0117] Embodiment 1: A method performed by an AMF for improving 5MBS signaling in a CN is provided. The method includes receiving (1102) a 5MBS request from a network node in the CN. The method also includes performing (1104) one or more actions in response to receiving the 5MBS request from the network node.

[0118] Embodiment 2: The method further comprising receiving (1100) an indication that indicates a UE is joining the 5MBS.

[0119] Embodiment 3: Receiving (1102) the 5MBS request comprises receiving (1102-1) a multicast activation request from a MB-SMF and performing (1104) the one or more actions comprises sending (1104-la) the multicast activation request to an NG- RAN (e.g., for activating CM-CONNECTED UEs or performing group notification to CM- IDLE UEs).

[0120] Embodiment 4: Performing (1104) the one or more actions further comprises registering (1104-lb) the UE toward the MB-SMF.

[0121] Embodiment 5: Receiving (1102) the 5MBS request comprises receiving (1102-2) a multicast deactivation request from an MB-SMF and performing (1104) the one or more actions comprises determining (1104-2a) an impacted NG-RAN based on information available at the AMF (e.g., without RAN Node Id).

[0122] Embodiment 6: Performing (1104) the one or more actions comprises deregistering (1104-2b) the UE toward the MB-SMF.

[0123] Embodiment 7: Receiving (1102) the 5MBS request comprises receiving (1102-3) a multicast activation request from an SMF and performing (1104) the one or more actions comprises sending (1104-3) the multicast activation request to an NG- RAN, (e.g., for activating CM-CONNECTED UEs or performing group notification to CM- IDLE UEs).

[0124] Embodiment 8: Receiving (1102) the 5MBS request comprises receiving (1102-4) a multicast deactivation request from an SMF and performing (1104) the one or more actions comprises determining (1104-4) an impacted NG-RAN based on information at the AMF (e.g., without RAN Node Id).

[0125] Embodiment 9: Receiving (1102) the 5MBS request comprises receiving (1102-5) a multicast activation request from an SMF and performing (1104) the one or more actions comprises sending (1104-5) the multicast activation request to an NG- RAN, (e.g., for activating CM-CONNECTED UEs or performing group notification to CM- IDLE UEs).

[0126] Embodiment 10: Receiving (1102) the 5MBS request comprises receiving (1102-6) a multicast deactivation request from an SMF and performing (1104) the one or more actions comprises determining (1104-6) an impacted NG-RAN based on information at the AMF (e.g., without RAN Node Id).

[0127] Embodiment 11: A communication system including a host computer comprising processing circuitry configured to provide user data and a communication interface configured to forward the user data to a cellular network for transmission to a UE. Wherein the cellular network comprises a base station having a radio interface and processing circuitry, the base station's processing circuitry configured to perform any of the steps of any of the previous embodiments.

[0128] Embodiment 12: The communication system further including the base station.

[0129] Embodiment 13: The communication system further including the UE, wherein the UE is configured to communicate with the base station.

[0130] Embodiment 14: The processing circuitry of the host computer is configured to execute a host application, thereby providing the user data and the UE comprises processing circuitry configured to execute a client application associated with the host application.

[0131] Embodiment 15: A method implemented in a communication system including a host computer, a base station, and a UE, the method comprising at the host computer, providing user data and at the host computer, initiating a transmission carrying the user data to the UE via a cellular network comprising the base station, wherein the base station performs any of the steps of any of the previous embodiments. [0132] Embodiment 16: The method further comprising, at the base station, transmitting the user data. [0133] Embodiment 17: The user data is provided at the host computer by executing a host application, the method further comprising, at the UE, executing a client application associated with the host application.

[0134] Embodiment 18: A UE configured to communicate with a base station, the UE comprising a radio interface and processing circuitry configured to perform the method of the previous 3 embodiments.

[0135] Embodiment 19: A communication system including a host computer comprising processing circuitry configured to provide user data and a communication interface configured to forward user data to a cellular network for transmission to a UE. The UE comprises a radio interface and processing circuitry, the UE's components configured to perform any of the steps of any of the previous embodiments.

[0136] Embodiment 20: The cellular network further includes a base station configured to communicate with the UE.

[0137] Embodiment 21: The processing circuitry of the host computer is configured to execute a host application, thereby providing the user data and the UE's processing circuitry is configured to execute a client application associated with the host application.

[0138] Embodiment 22: A method implemented in a communication system including a host computer, a base station, and a UE, the method comprising at the host computer, providing user data and at the host computer, initiating a transmission carrying the user data to the UE via a cellular network comprising the base station, wherein the UE performs any of the steps of any of the previous embodiments.

[0139] Embodiment 23: The method further comprising at the UE, receiving the user data from the base station.

[0140] Embodiment 24: A communication system including a host computer comprising communication interface configured to receive user data originating from a transmission from a UE to a base station. The UE comprises a radio interface and processing circuitry, the UE's processing circuitry configured to perform any of the steps of any of the previous embodiments.

[0141] Embodiment 25: The communication system further including the UE.

[0142] Embodiment 26: The communication system further including the base station, wherein the base station comprises a radio interface configured to communicate with the UE and a communication interface configured to forward to the host computer the user data carried by a transmission from the UE to the base station.

[0143] Embodiment 27: The processing circuitry of the host computer is configured to execute a host application and the UE's processing circuitry is configured to execute a client application associated with the host application, thereby providing the user data. [0144] Embodiment 28: The processing circuitry of the host computer is configured to execute a host application, thereby providing request data and the UE's processing circuitry is configured to execute a client application associated with the host application, thereby providing the user data in response to the request data.

[0145] Embodiment 29: A method implemented in a communication system including a host computer, a base station, and a UE, the method comprising at the host computer, receiving user data transmitted to the base station from the UE, wherein the UE performs any of the steps of any of the previous embodiments.

[0146] Embodiment 30: The method further comprising, at the UE, providing the user data to the base station.

[0147] Embodiment 31: The method further comprising at the UE, executing a client application, thereby providing the user data to be transmitted and at the host computer, executing a host application associated with the client application.

[0148] Embodiment 32: The method further comprising at the UE, executing a client application and at the UE, receiving input data to the client application, the input data being provided at the host computer by executing a host application associated with the client application. The user data to be transmitted is provided by the client application in response to the input data.

[0149] Embodiment 33: A communication system including a host computer comprising a communication interface configured to receive user data originating from a transmission from a UE to a base station, wherein the base station comprises a radio interface and processing circuitry, the base station's processing circuitry configured to perform any of the steps of any of the previous embodiments.

[0150] Embodiment 34: The communication system further including the base station.

[0151] Embodiment 35: The communication system further including the UE, wherein the UE is configured to communicate with the base station. [0152] Embodiment 36: The processing circuitry of the host computer is configured to execute a host application and the UE is configured to execute a client application associated with the host application, thereby providing the user data to be received by the host computer.

[0153] Embodiment 37: A method implemented in a communication system including a host computer, a base station, and a UE, the method comprising at the host computer, receiving, from the base station, user data originating from a transmission which the base station has received from the UE, wherein the UE performs any of the steps of any of the previous embodiments.

[0154] Embodiment 38: The method further comprising at the base station, receiving the user data from the UE.

[0155] Embodiment 39: The method further comprising at the base station, initiating a transmission of the received user data to the host computer.

[0156] At least some of the following abbreviations may be used in this disclosure. If there is an inconsistency between abbreviations, preference should be given to how it is used above. If listed multiple times below, the first listing should be preferred over any subsequent listing(s).

3GPP Third Generation Partnership Project

5G Fifth Generation

5GC Fifth Generation Core

5GS Fifth Generation System

5MBS Fifth-Generation Multicast-Broadcast Services

AF Application Function

AMF Access and Mobility Function

AN Access Network

AP Access Point

ASIC Application Specific Integrated Circuit

AUSF Authentication Server Function

CIoT Cellular Internet of Things

CN Core Network

CPU Central Processing Unit

DN Data Network

DSP Digital Signal Processor • eNB Enhanced or Evolved Node B

• EPS Evolved Packet System

• E-UTRA Evolved Universal Terrestrial Radio Access

• FPGA Field Programmable Gate Array

• gNB New Radio Base Station

• gNB-DU New Radio Base Station Distributed Unit

• HSS Home Subscriber Server

• IoT Internet of Things

• IP Internet Protocol

• LTE Long Term Evolution

• MBMS Multicast/Broadcast Multimedia Subsystem

• MME Mobility Management Entity

• MTC Machine Type Communication

• NEF Network Exposure Function

• NF Network Function

• NR New Radio

• NRF Network Function Repository Function

• NSSF Network Slice Selection Function

• OTT Over-the-Top

• PC Personal Computer

• PCF Policy Control Function

• PDU Protocol Data Unit

• P-GW Packet Data Network Gateway

• PLMN Public Land Mobile Network

• pCRs pseudo Change Requests

• QFI QoS Flow Id

• QoS Quality of Service

• RAM Random Access Memory

• RAN Radio Access Network

• ROM Read Only Memory

• RRH Remote Radio Head

• RTT Round Trip Time

• SCEF Service Capability Exposure Function • SMF Session Management Function

• SA2 System Aspects 2

• UDM Unified Data Management

• UE User Equipment

• UPF User Plane Function

• V2X Vehicle to Everything

[0157] Those skilled in the art will recognize improvements and modifications to the embodiments of the present disclosure. All such improvements and modifications are considered within the scope of the concepts disclosed herein.

Claims

1 . A method performed by an Access and Mobility Management Function, AMF, for improving Fifth-Generation Multicast-Broadcast Services, 5MBS, signaling in a Core Network, CN, the method comprising: receiving (1000) a multicast request from a network node in the CN; and performing (1002) one or more actions in response to receiving the multicast request from the network node, independent of whether the AMF is aware that a User Equipment, UE, is joining the 5MBS.

2. The method of claim 1, wherein receiving (1000) the multicast request comprises receiving (1000-1) an indication that indicates the UE is joining the 5MBS.

3. The method of claim 2, wherein: receiving (1000) the multicast request comprises one of: receiving (1000-2a) a multicast activation request from a Multicast- Broadcast Session Management Function, MB-SMF; and receiving (1002-2b) a multicast deactivation request from the MB-SMF; and performing (1002) the one or more actions comprises: in response to receiving (1000-2a) the multicast activation request, sending (1002-la) the multicast activation request to a New- Generation Radio Access Network, NG-RAN, to perform one or more of following actions: activation of one or more UEs in CM-CONNECTED state; and group notification to one or more UEs in CM-IDLE state; and in response to receiving (1000-2b) the multicast deactivation request, determining (1002-2a) an impacted NG-RAN based on information available at the AMF.

4. The method of claim 3, wherein performing (1002) the one or more actions further comprises one of: registering (1002-lb) the UE toward the SMF in response to receiving (1000-2a) the multicast activation request; and deregistering (1002-2b) the UE toward the SMF in response to receiving (1000- 2b) the multicast deactivation request.

5. The method of claim 2, wherein: receiving (1000) the multicast request comprises one of: receiving (1000-3a) a multicast activation request from a Session Management Function, SMF; and receiving (1000-3b) a multicast deactivation request from the SMF; and performing (1002) the one or more actions comprises: in response to receiving (1000-3a) the multicast activation request, sending (1002-3) the multicast activation request to a New- Generation Radio Access Network, NG-RAN, to perform one or more of following actions: activation of one or more UEs in CM-CONNECTED state; and group notification to one or more UEs in CM-IDLE state; and in response to receiving (1000-3b) the multicast deactivation request, determining (1002-4) an impacted NG-RAN based on information available at the AMF.

6. The method of claim 1, wherein receiving (1000) the multicast request comprises not receiving (1000-4) an indication that indicates the UE is joining the 5MBS.

7. The method of claim 6, wherein: receiving (1000) the multicast request comprises one of: receiving (1000-5a) a multicast activation request from a Session Management Function, SMF; and receiving (1000-5b) a multicast deactivation request from the SMF; and performing (1002) the one or more actions comprises: in response to receiving (1000-5a) the multicast activation request, sending (1002-5) the multicast activation request to a New- Generation Radio Access Network, NG-RAN, to perform one or more of following actions: activation of one or more UEs in CM-CONNECTED state; and group notification to one or more UEs in CM-IDLE state; and in response to receiving (1000-5b) the multicast deactivation request, determining (1002-6) an impacted NG-RAN based on information available at the AMF.

8. A network node (2600) comprising processing circuitry (2602) configured to cause the network node (2600) to: receive (1000) a multicast request from a network node in the CN; and perform (1002) one or more actions in response to receiving the multicast request from the network node, independent of whether the network node (2600) is aware that a User Equipment, UE, is joining a Fifth-Generation Multicast-Broadcast Services, 5MBS.

9. The network node (2600) of claim 8, wherein the processing circuitry (2602) is configured to cause the network node (2600) to perform any step in any of claims 2 to 7.