Distributed units, central units, and methods therefor

Abstract

The present invention relates to a method and apparatus for providing Multicast and Broadcast Services (MBS), the method being performed by a base station comprising: sending a message to a network node including first information identifying a tunnel associated with an MBS session, where the message indicates that the tunnel is a shared tunnel, and upon sending the message, receiving, via the shared tunnel, a user plane protocol data unit for the MBS session for transmission to a UE.

Description

[Technical Field]

[0001] The present disclosure relates to wireless communication systems and devices therein that operate in accordance with Third Generation Partnership Project (3GPP) standards or equivalents or derivatives thereof. The present disclosure has particular, but not exclusive, relevance to improvements relating to multimedia broadcast session management in so-called "5G" (or "next generation") systems. [Background technology]

[0002] The latest evolution of the 3GPP standards is referred to as "5G" or "New Radio" (NR). These terms refer to evolving communications technologies that support a variety of applications and services. Various details of 5G networks are described, for example, in the "NGMN 5G White Paper" V1.0 by the Next Generation Mobile Networks (NGMN) Alliance, available at https: / / www.ngmn.org / 5g-white-paper.html. 3GPP intends to support 5G through the so-called 3GPP NextGen (NextGen) Radio Access Network (RAN) and 3GPP NextGen Core (NGC) network.

[0003] Under 3GPP standards, a base station (e.g., an "eNB" in 4G or a "gNB" in 5G) is a node through which communication devices (user equipment or "UE") connect to a core network and communicate with other communication devices or remote servers. For simplicity, this application uses the term base station to refer to any such base station.

[0004] In the 5G architecture, the gNB internal structure may be split into two parts known as the Central Unit (CU) and the Distributed Unit (DU), connected by an F1 interface. In this "split" architecture, the generally "upper" CU layer (e.g., but not necessarily or exclusively, PDCP) and the generally "lower" DU layer (e.g., but not necessarily or exclusively, RLC / MAC / PHY) may be implemented separately. Thus, for example, in each gNB, some gNB upper layer CU functions may be implemented centrally (e.g., by a single processing unit or in a cloud-based or virtualized system), while lower layer DU functions may be kept local.

[0005] For simplicity, this application uses the terms mobile device, user device, or UE to refer to any communication device that can connect to a core network via one or more base stations.

[0006] The communication devices may be mobile communication devices, such as, for example, mobile phones, smartphones, user equipment, personal digital assistants, laptop / tablet computers, web browsers, e-book readers, and / or the like. Such mobile (or generally fixed) devices are typically operated by a user. However, 3GPP standards also enable so-called “Internet of Things” (IoT) devices (e.g., narrowband IoT (NB-IoT) devices) to be connected to the network, which typically include various metering instruments, telemetry instruments, monitoring systems, tracking and detection equipment, in-vehicle safety systems, vehicle maintenance systems, road sensors, digital billboards, point-of-sale (POS), remote control systems, and the like. In effect, the Internet of Things is a network of devices (or “things”) equipped with appropriate electronics, software, sensors, network connections, and / or the like, enabling these devices to collect and exchange data with each other and with other communication devices. It will be understood that IoT devices are sometimes referred to as machine-type communication (MTC) communication devices or machine-to-machine (M2M) communication devices.

[0007] For simplicity, the present application will often refer to mobile devices in the specification, however, it will be understood that the described techniques can be implemented on any communication device (mobile and / or generally fixed) that can connect to a communication network to transmit / receive data, regardless of whether such communication device is controlled by human input or software instructions stored in memory.

[0008] One of the recent features being developed on the existing 5G framework is called Multicast and Broadcast Services (MBS). This feature aims to enhance the capabilities of 5G New Radio and 5G Core networks for the large-scale deployment of reliable, low-latency, resource-efficient, and wide-area multicast and broadcast services. 3GPP is currently specifying the details of MBS for media distribution over mobile broadband networks. MBS (or "NR MBS" for 5G) aims to reuse cellular infrastructure, such as so-called Low Power Low Tower (LPLT) infrastructure. One of the main use cases is the distribution of linear / live media content to smartphones, tablets, vehicles, and other mobile (or fixed) devices. MBS is designed to use existing (or already specified) 3GPP infrastructure, but can provide more efficient delivery of multicast / broadcast traffic than unicast communications using the same infrastructure. Details of the architectural enhancements for MBS are described in 3GPP Technical Specification (TS) 23.247 V 17.0.0, the contents of which are incorporated herein by reference.

[0009] In establishing a legacy user plane tunnel, the tunnel may be created for the UE by sending UE context setup request / response messages between tunnel endpoints (e.g., between a distributed unit and a corresponding central unit in the case of an F1 user plane, or between a base station and a corresponding user plane function). These messages contain UE-specific information (e.g., UE F1AP ID / NGAP ID) that uniquely associates the tunnel with a particular UE.

[0010] On the other hand, MBS uses a shared tunnel to deliver user plane data (e.g., F1 / NG user plane) to multiple UEs subscribed to a particular service to benefit from more efficient delivery of multicast / broadcast traffic. Thus, during session activation for an MBS, a shared tunnel is established, or if there is already a shared tunnel established for a given MBS, the tunnel is shared for the MBS session. When a UE joins an MBS service, an MBS session is established for that service on the user plane, which is transmitted (using multicast) through the appropriate shared tunnel. More specifically, traffic for an MBS service is transmitted using multicast via the serving base station or its distributed unit through the shared user plane tunnel for that MBS service. Note that this is quite different from unicast, which uses a dedicated user plane tunnel for each UE. Summary of the Invention [Problem to be solved by the invention]

[0011] The inventors have recognized that existing tunnel establishment procedures require UE-specific information that is incompatible with the multicast transmission used by MBS. Therefore, it is necessary to either introduce a common tunnel establishment procedure for unicast and multicast use, or modify the legacy UE context setup procedure to support the setup of a shared user plane tunnel between the respective endpoints.

[0012] The inventors have also recognized that a similar problem may arise during handover of a UE receiving MBS traffic, which may require a session modification (e.g., over the N4 interface) for a shared user plane tunnel. For example, it may be necessary to add / modify a shared user plane tunnel in a new cell when the UE is being handed over to that cell. Similarly, if a shared user plane tunnel is not used by any UEs due to handover (or all UEs have left the corresponding MBS session), it may be advantageous to delete the MBS session associated with that tunnel in the serving user plane function (UPF). However, current session / tunnel management procedures are not suitable for such MBS-related procedures. [Means for solving the problem]

[0013] Accordingly, the present invention seeks to provide a method, and associated apparatus, that addresses or at least alleviates (at least some of) the above-mentioned problems.

[0014] In one aspect, the present invention provides a method performed by a base station for providing multicast and broadcast services (MBS), the method comprising: sending a message to a network node including first information identifying a tunnel associated with an MBS session, wherein the message indicates that the tunnel is a shared tunnel; and upon sending the message, receiving, via the shared tunnel, a user plane protocol data unit for the MBS session for transmission to a UE.

[0015] In one aspect, the present invention provides a method performed by a base station for providing multicast and broadcast services (MBS), the method comprising: receiving a request from a network node to set up a tunnel associated with an MBS session as a shared tunnel, wherein the request includes second information of the MBS session and first information identifying the tunnel; and upon receiving the message, receiving a user plane protocol data unit for the MBS session via the shared tunnel for transmission to a UE.

[0016] In one aspect, the present invention provides a method performed by a network node for providing multicast and broadcast services (MBS), the method comprising: receiving a message from a base station including first information identifying a tunnel associated with an MBS session, wherein the message indicates that the tunnel is a shared tunnel; and, upon receiving the message, transmitting a user plane protocol data unit for the MBS session to a user equipment (UE) via the shared tunnel.

[0017] In one aspect, the present invention provides a method performed by a network node, the method comprising: sending a request to a base station to set up a tunnel associated with a multicast and broadcast service (MBS) session as a shared tunnel for providing MBS, the request comprising second information of the MBS session and first information identifying the tunnel, the shared tunnel adapted to be used by the base station to transmit user plane protocol data units for the MBS session.

[0018] In one aspect, the present invention provides a method performed by a first core network node for managing at least one Multicast and Broadcast Service (MBS) session provided using a shared tunnel, the method comprising: sending a session management message to a second core network node for managing a user plane associated with the at least one MBS session, wherein the message comprises at least one of information identifying one or more MBS sessions to be added at the second core network node, information identifying one or more MBS sessions to be modified at the second core network node, and information identifying one or more MBS sessions to be deleted at the second core network node.

[0019] In one aspect, the present invention provides a method performed by a second core network node for managing a user plane associated with at least one Multicast and Broadcast Service (MBS) session provided using a shared tunnel, the method comprising receiving from a first core network node a session management message including at least one of information identifying one or more MBS sessions to be added at the second core network node, information identifying one or more MBS sessions to be modified at the second core network node, and information identifying one or more MBS sessions to be removed at the second core network node.

[0020] In one aspect, the present invention provides a base station for providing multicast and broadcast services (MBS), the base station comprising: means for transmitting to a network node a message including first information identifying a tunnel associated with an MBS session, the message indicating that the tunnel is a shared tunnel; and means for receiving, upon transmitting the message, a user plane protocol data unit for the MBS session via the shared tunnel for transmission to a UE.

[0021] In one aspect, the present invention provides a base station for providing multicast and broadcast services (MBS), the base station apparatus comprising: means for receiving a request from a network node to set up a tunnel associated with an MBS session as a shared tunnel, the request including second information of the MBS session and first information identifying the tunnel; and means for receiving, upon receiving the message, a user plane protocol data unit for the MBS session via the shared tunnel for transmission to a UE.

[0022] In one aspect, the present invention provides a network node for providing a multicast and broadcast service (MBS), the network node comprising: means for receiving from a base station a message including first information identifying a tunnel associated with an MBS session, the message indicating that the tunnel is a shared tunnel; and means for, upon receiving the message, transmitting a user plane protocol data unit for the MBS session to a user equipment (UE) via the shared tunnel.

[0023] In one aspect, the present invention provides a network node, the network node comprising: means for transmitting to a base station a request to set up a tunnel associated with a multicast and broadcast service (MBS) session as a shared tunnel for providing MBS, the request including second information of the MBS session and first information identifying the tunnel, the shared tunnel being adapted to be used by the base station for transmitting user plane protocol data units for the MBS session.

[0024] In one aspect, the present invention provides a first core network node for managing at least one Multicast and Broadcast Service (MBS) session provided by using a shared tunnel, the first core network node comprising: means for sending a session management message to a second core network node for managing a user plane associated with the at least one MBS session, the message including at least one of information identifying one or more MBS sessions to be added at the second core network node, information identifying one or more MBS sessions to be modified at the second core network node, and information identifying one or more MBS sessions to be removed at the second core network node.

[0025] In one aspect, the present invention provides a second core network node for managing a user plane associated with at least one Multicast and Broadcast Service (MBS) session provided by using a shared tunnel, the second core network node comprising means for receiving from a first core network node a session management message including at least one of information identifying one or more MBS sessions to be added at the second core network node, information identifying one or more MBS sessions to be modified at the second core network node, and information identifying one or more MBS sessions to be removed at the second core network node. [Effects of the Invention]

[0026] Aspects of the present invention extend to corresponding systems, apparatus, and computer program products, such as computer-readable storage media having stored thereon instructions operable to program a programmable processor to perform the methods described above or recited in the aspects and possibilities set forth in the claims, and / or to program a computer suitably adapted to provide an apparatus recited in any of the claims.

[0027] Each feature disclosed in this specification (including the term claims) and / or shown in the drawings may be incorporated into the present invention independently (or in combination) with any other disclosed and / or shown feature. In particular, but not limited to, any feature of a claim depending from a particular independent claim may be introduced into that independent claim in any combination or individually.

[0028] Embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings, in which: [Brief explanation of the drawings]

[0029] [Figure 1] 1 is a schematic diagram of a mobile (cellular or wireless) telecommunications system in which embodiments of the present invention may be applied; [Figure 2] 1 is a schematic diagram of a mobile (cellular or wireless) telecommunications system in which embodiments of the present invention may be applied; [Figure 3] 2 is a schematic block diagram of a mobile device forming part of the system shown in FIG. 1; [Figure 4] 2 is a schematic block diagram of an access network node (eg, a base station) forming part of the system shown in FIG. 1; [Figure 5] 2 is a schematic block diagram of an access network node (eg, a base station) forming part of the system shown in FIG. 1; [Figure 6] FIG. 2 is a schematic block diagram of a core network node forming part of the system shown in FIG. 1; [Figure 7] FIG. 1 is a schematic signaling (timing) diagram illustrating some embodiments of the present invention. [Figure 8] FIG. 1 is a schematic signaling (timing) diagram illustrating some embodiments of the present invention. [Figure 9] FIG. 1 is a schematic signaling (timing) diagram illustrating some embodiments of the present invention. [Figure 10] FIG. 1 is a schematic signaling (timing) diagram illustrating some embodiments of the present invention. [Figure 11] FIG. 1 is a schematic signaling (timing) diagram illustrating some embodiments of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0030] <Summary>

[0031] 1 and 2 are schematic diagrams of a mobile (cellular or wireless) telecommunications system 1 in which embodiments of the present disclosure may be applied.

[0032] In this system 1, users of mobile devices 3 (UE) may communicate with each other and other users via base stations 5 (and other access network nodes) and a core network 7 using an appropriate 3GPP Radio Access Technology (RAT), e.g., Evolved Universal Terrestrial Radio Access (E-UTRA) and / or 5G RAT. It will be appreciated that many base stations 5 form a (Radio) Access Network or (R)AN. As will be appreciated by those skilled in the art, for purposes of illustration, one mobile device 3 and three base stations 5 are shown. -1 ~5 -3 is shown in FIG. 1, but when implemented the system will typically include other base stations / (R)AN nodes and mobile devices (UEs).

[0033] Each base station 5 controls (directly or via other nodes such as home base stations, relays, remote radio heads, distributed units, and / or the like) one or more associated cells. Base stations 5 that support next generation / 5G protocols may be referred to as "gNBs." It will be appreciated that some base stations 5 may be configured to support both 4G and 5G protocols, and / or any other 3GPP or non-3GPP communication protocol.

[0034] It will be appreciated that the functionality of the gNB5 (referred to herein as a "distributed" gNB) may be divided between one or more distributed units (DUs) and a central unit (CU), where the CU typically performs higher level functions and communication with the next-generation core, and the DU performs lower level functions and communication over the air interface with neighboring UEs (i.e., in cells operated by the gNBs). The distributed gNB includes the following functional units:

[0035] gNB Central Unit (gNB-CU): A logical node that hosts the Radio Resource Control (RRC), Service Data Adaptation Protocol (SDAP) and Packet Data Convergence Protocol (PDCP) layers of a gNB (or the RRC and PDCP layers of an en-gNB) that controls the operation of one or more gNB-DUs. The gNB-CU terminates the F1 interface connected to the gNB-DU.

[0036] gNB Distributed Unit (gNB-DU) 5D: A logical node that hosts the Radio Link Control (RLC), Media Access Control (MAC), and Physical (PHY) layers of a gNB or en-gNB, and its operation is partly controlled by the gNB-CU. One gNB-DU supports one or multiple cells. One cell is supported by only one gNB-DU. The gNB-DU terminates the F1 interface connected to the gNB-CU.

[0037] gNB-CU-Control Plane (gNB-CU-CP) 5C: A logical node that hosts the control plane part of the RRC and PDCP protocols of the gNB-CU for the en-gNB or gNB. The gNB-CU-CP terminates the E1 interface connected to the gNB-CU-UP and the F1-C interface connected to the gNB-DU.

[0038] gNB-CU-User Plane (gNB-CU-UP) 5U: A logical node that hosts the user plane part of the PDCP protocol of the gNB-CU for the en-gNB and the user plane parts of the PDCP and SDAP protocols of the gNB-CU for the gNB. The gNB-CU-UP terminates the E1 interface connected to the gNB-CU-CP and the F1-U interface connected to the gNB-DU.

[0039] A mobile device 3 and its serving base station 5 are connected via an appropriate air interface (e.g., the so-called "NR" air interface, the "Uu" interface, and / or the like). Neighboring base stations 5 are connected to each other via appropriate inter-base station interfaces (e.g., the so-called "Xn" interface, the "X2" interface, and / or the like). The base stations 5 are also connected to core network nodes via appropriate interfaces (e.g., the so-called "NG-U" interface (for the user plane), the so-called "NG-C" interface (for the control plane), and / or the like).

[0040] The core network 7 (e.g., EPC in the case of LTE, NGC in the case of NR / 5G) typically includes logical nodes (or "functions") for supporting communications in the telecommunications system 1 and for (among other things) subscriber management, mobility management, charging, security, and call / session management. For example, the core network 7 in a "next generation" / 5G system includes user plane and control plane entities, such as one or more Control Plane Functions (CPFs) and one or more User Plane Functions (UPFs). The so-called Access and Mobility Management Function (AMF) in 5G, or Mobility Management Entity (MME) in 4G, is responsible for handling connectivity and mobility management tasks for mobile devices 3. The so-called Session Management Function (SMF) is responsible for handling communication sessions for mobile devices 3, such as session establishment, modification, and release. 1, the core network 7 includes one or more AMFs 9, one or more UPFs 10, and one or more SMFs 11. It will be appreciated that nodes or functions may have different names in different systems.

[0041] Further details of the core network 7 are shown in Figure 2, which also shows the interfaces between each network node. As can be seen, the core network 7 may typically include, among other things, an Authentication Server Function (AUSF), a Unified Data Management (UDM) entity, a Policy Control Function (PCF), and an Application Function (AF). The core network 7 is connected (via the UPF 10) to a Data Network (DN), such as the Internet or a similar Internet Protocol (IP)-based network. The core network 7 may also be connected to an Operations and Management (OAM) function (not shown).

[0042] In this system 1, multicast and broadcast service (MBS) functionality is provided to the UE 3 via the UE's serving base station 5 and associated core network nodes such as a UPF 10 and an SMF 11. The UPF 10 may be an MBS-specific UPF, in which case it may be referred to as an MB-UPF 10M (e.g., dedicated to providing MBS functionality). Similarly, the SMF 11 may be an MBS-specific SMF, in which case it may be referred to as an MB-SMF 11M. However, it will be appreciated that any suitable UPF 10 / SMF 11 may be used for MBS.

[0043] MBS traffic is distributed over shared user plane tunnels as needed. Specifically, MBS user plane data for a given service (e.g., F1-U / NG-U data) is delivered to UEs that have subscribed to that particular service over the associated shared tunnel using multicast transmission.

[0044] When a first UE joins an MBS service, an MBS session is established for that service on the user plane between the core network 7 and the UE's serving base station 5 (and, if applicable, between units of a distributed gNB that handle the user plane). For any UE (at least one UE) interested in that MBS service, a shared user plane tunnel can be used to transmit MBS traffic via multicast through a given serving base station or its distributed units.

[0045] To realize the sharing of user plane tunnels between UEs 3, nodes of this network (e.g., base stations 5 and AMF 9) are configured to indicate when a tunnel is a shared tunnel using an appropriate indicator. For example, this indicator may be used when the tunnel is associated with a UE 3 (e.g., the tunnel is set up or modified for an MBS that the UE 3 has joined). The Transport Network Layer (TNL) address of the shared tunnel is used as transport layer information in F1-U / NG-U session management signaling when the UE 3 joins the MBS service.

[0046] Specifically, when an MBS session is requested for a UE 3, the base station 5 used as the endpoint of the NG-U transport bearer for that MBS session (and / or the gNB-DU endpoint of the F1 transport bearer) is used as the user plane TNL address of the UE 3 for delivery of MBS traffic (downlink protocol data units). Signaling messages exchanged between the tunnel endpoints include an indicator (field or flag) that the tunnel is a shared tunnel (as opposed to a tunnel used by only a single UE). Effectively, this option reuses the existing (legacy) UE Context Setup (Modify) Request and Response messages to set up a shared F1-U / NG-U tunnel by including an appropriate shared tunnel indicator in the response (when configuring the TNL address for the session).

[0047] Upon receiving a request from the first UE 3 interested in the MBS session, the AMF 9 requests the (central unit of) the base station 5 to set up (or modify) the UE context so that the associated F1-U / NG-U tunnel is configured as a shared tunnel. If the shared tunnel indicator is present, the base station 5 (DU) knows that the tunnel is a shared tunnel that can be shared by subsequent UEs, and the base station 5 (or DU) also indicates that the shared tunnel is to be used in its response to the AMF 9 (or CU).

[0048] Alternatively, instead of or in addition to an explicit indicator, an appropriate (non-UE-related) F1AP / NGAP message may be used to set up a shared tunnel for the MBS. For example, the central unit of the base station 5 may be configured to send an appropriate F1AP signaling message (e.g., a "Shared F1-U GTP Tunnel Setup Request" message and / or the like) to the distributed unit to set up a shared tunnel for the UE 3. Similarly, the AMF 9 may be configured to send an appropriate NGAP signaling message (e.g., a "Shared NG-U GTP Tunnel Setup Request" message and / or the like) to the serving base station 5 to set up a shared tunnel for the UE 3. In this case, the message itself serves as the shared tunnel indicator (although an explicit indicator / flag may be included in the message if necessary).

[0049] In either case, it will be appreciated that the messages used to configure the MBS session do not include UE-specific information (e.g., UE F1AP ID / NGAP ID) that uniquely associates the tunnel with a particular UE 3 (although such UE-specific information, e.g., UE ID, may be included for other purposes). Even if such information is included, the shared tunnel indicator notifies the base station 5 that the tunnel can be shared between UEs 3.

[0050] To support handover of UE 3 receiving MBS via the shared tunnel, the session management messages exchanged between SMF 11 and UPF 10 (over the N4 interface) are adapted to include relevant MBS session parameters. For example, when performing handover-related signaling for UE 3, SMF 11 may provide one or more of the following parameters (along with the relevant N4 session ID) to UPF 10:

[0051] MBS session to add / modify list (if there is no ongoing MBS session in the target base station, SMF11 includes any newly added MBS session), which may include one or more (per MBS session) of the following: MBS context, Quality of Service (QoS) flows, MBS session ID, Temporary Mobile Group Identity (TMGI), UE Identifier (UE ID), UL NG-U UP TNL information, DL QoS flows per TNL information; and MBS sessions to delete list (not limited to UE mobility scenarios, deletes a particular MBS session when the last UE3 leaves that MBS session), including the MBS session ID for each MBS session to be deleted.

[0052] Advantageously, using at least some of the above parameters, the UPF 10 can track which UE 3 uses which MBS session using the correct shared tunnel even after handover, and maintain the MBS session of the UE 3. This approach may be particularly useful in the case of an Xn-based handover from an MBS supporting NG-RAN node (base station 5) to another NG-RAN node (currently specified in clause 7.2.3.2 of 3GPP TS 23.247).

[0053] <User Equipment (UE)> FIG. 3 is a block diagram illustrating the main components of the mobile device (UE) 3 shown in FIG. 1. As shown, the UE 3 includes transceiver circuitry 31 operable to transmit signals to and receive signals from connected nodes via one or more antennas 33. While not necessarily shown in FIG. 3, the UE 3 naturally has all the usual functionality of a conventional mobile device (e.g., a user interface 35), which may be provided by any one or any combination of hardware, software, and firmware, as appropriate. A controller 37 controls the operation of the UE 3 in accordance with software stored in memory 39. The software may be pre-installed in memory 39 and / or downloaded, for example, via the telecommunications network 1 or from a removable data storage device (RMD). The software includes, among other things, an operating system 41, a communications control module 43, and an MBS module 45.

[0054] The communication control module 43 is responsible for processing (generating / sending / receiving) signaling messages and uplink / downlink data packets between the UE 3 and other nodes, including the (R)AN node 5 and core network nodes. The signaling may include RRC signaling (to and from the (R)AN node 5) and / or NG-C / NG-U signaling (to and from the core network 7).

[0055] The MBS module 45 is responsible for handling signaling related to multimedia broadcast services.

[0056] <Access network node (base station)> FIG. 4 is a block diagram illustrating the main components of the base station 5 (or a similar access network node) shown in FIG. 1. As shown, the base station 5 includes a transceiver circuit 51 for transmitting signals to and receiving signals from user equipment (e.g., mobile device 3) via one or more antennas 53, and a network interface 55 for transmitting signals to and receiving signals from the core network 7 and neighboring base stations. The base station 5 includes a controller 57 that controls the operation of the base station 5 in accordance with software stored in memory 59. The software may be pre-installed in the memory 59 and / or downloaded, for example, via the telecommunications network 1 or from a removable data storage device (RMD). The software includes, among other things, an operating system 61 and at least a communication control module 63. Although not shown in FIG. 4, the network interface 55 also typically includes a base station-to-base station interface portion (e.g., Xn and / or the like) and a core network interface portion (e.g., NG-C / NG-U / N2 / N3).

[0057] The communications control module 63 is responsible for processing (generating / sending / receiving) signaling between the base station 5 and other nodes, such as the UE 3 and core network nodes. Such signaling may include, for example, control data for managing the operation of the mobile device 3 (e.g., non-access stratum, radio resource control, system information, paging, and / or the like). It will be understood that the communications control module 63 may include several sub-modules (or “layers”) for supporting specific functions. For example, the communications control module 63 may include a PHY sub-module, a MAC sub-module, an RLC sub-module, a PDCP sub-module, an SDAP sub-module, an IP sub-module, an RRC sub-module, etc.

[0058] As shown in FIG. 5, if the base station 5 comprises a distributed gNB or en-gNB, the network interface 55 also comprises an E1 interface and an F1 interface (F1-C for the control plane and F1-U for the user plane) for communicating signals between the respective functions of the distributed gNB or en-gNB. In this case, the software also includes at least one of a gNB-CU-CP module 5C, a gNB-CU-UP module 5U, and a gNB-DU module 5D. If present, the gNB-CU-CP module 5C hosts the control plane portions of the RRC layer and PDCP layer of the distributed gNB or en-gNB. If present, the gNB-CU-UP module 5U hosts the user plane portions of the PDCP and SDAP layer of the distributed gNB or the user plane portion of the PDCP layer of the distributed en-gNB. If present, the gNB-DU module 5D hosts the RLC, MAC, and PHY layers of the distributed gNB or en-gNB.

[0059] Those skilled in the art will appreciate that the central units (e.g., 5C and / or 5U) may be implemented and physically located with the base stations, or may be implemented remotely as a single physical entity or as a cloud-based or virtualized system. It will also be appreciated that a single central unit may serve multiple base stations 5.

[0060] <Core network node> FIG. 6 is a block diagram illustrating the main components of the core network node (e.g., AMF 9, UPF 10, or SMF 11) shown in FIG. 1 . As shown, the core network node includes transceiver circuitry 71 operable to transmit signals to and receive signals from connected UEs 3 via one or more antennas 73, and to transmit signals to and receive signals from other network nodes (directly or indirectly) via a network interface 75. Signals may be transmitted to and received from UEs 3 directly and / or via base stations 5 or other (R)AN nodes, as appropriate. The network interface 75 typically includes an appropriate base station interface (e.g., S1 / NG-C / NG-U). A controller 77 controls the operation of the core network node in accordance with software stored in memory 79. The software may be pre-installed in memory 79 and / or downloaded, for example, via the telecommunications network 1 or from a removable data storage device (RMD). The software includes, among other things, an operating system 81, a communication control module 83, and an MBS module 85 (optional).

[0061] The communication control module 83 is responsible for handling (generating / sending / receiving) signaling between the core network nodes and other nodes such as UE3, (R)AN nodes and other core network nodes.

[0062] When present in, for example, the MB-SMF or MB-UPF, the MBS module 85 is responsible for processing signaling (control signaling and / or MBS traffic) related to multimedia broadcast services, which may include signaling related to MBS session and shared tunnel management and related parameters.

[0063] <Detailed explanation> The following is a description of some exemplary procedures performed by nodes of the system shown in FIG. 1 to support MBS sessions over shared tunnels.

[0064] <Option 1 - F1-U / NG-U Session Management> As can be seen from Figures 1 and 2, the NG-U (NG User Plane) protocol is used between the UE 3 and the core network (UPF 10) and is carried over the N3 interface between the base station 5 and the core network 7. When a distributed base station 5 is involved, the F1-U (F1 User Plane) protocol is carried over the central unit 5 of the distributed base station 5. U and the distributed unit 5D in charge of the MBS user plane.

[0065] The F1 Application Protocol (F1AP) is specified in 3GPP TS 38.473 V16.7.0, and the NG Application Protocol (NGAP) is specified in 3GPP TS 38.413 V16.7.0. In this example, the UE context setup procedure is adapted to associate a shared user plane tunnel (F1-U shared tunnel and / or NG-U shared tunnel) with a specific MBS session (and any UEs for which the corresponding MBS traffic is intended). In particular, one or more of the following F1AP / NGAP messages may be used for this purpose: UE Context Setup Request, UE Context Setup Response, UE Context Modification Request, and UE Context Modification Response (see Figures 9 and 10).

[0066] For an NG-U shared tunnel, the NG-RAN node 5 (e.g., base station / gNB) and the UPF 11 are the tunnel endpoints. In this case, when the shared tunnel is being set up for an MBS session, an appropriate NGAP message (e.g., UE Context Change Response) may be sent by the base station 5 to the AMF 9 to confirm the change of the UE context for the MBS (when the UE 3 joins the MBS).

[0067] In the case of an F1-U shared tunnel (or the F1 portion of an NG-U shared tunnel), the gNB-DU 5D and the gNB-CU 5U are the tunnel endpoints. An F1-U shared tunnel may be associated with a particular UE 3 by modifying the associated UE context to receive MBS traffic using multicast. For example, when such a shared tunnel is set up for an MBS session (when the UE 3 joins the MBS), an appropriate F1AP message (e.g., a UE context setup response) may be sent by the gNB-DU 5D to the gNB-CU 5U to confirm the UE context change.

[0068] The TNL address of the shared tunnel is used as transport layer information (Tunnel Endpoint Identifier or "TEID") in the associated F1-U / NG-U session management signaling for UEs 3 joining (or leaving) an MBS session. The TNL address of the session is configured in the shared tunnel indicator. The TEID associated with the base station 5 used as the endpoint of the NG-U transport bearer (and / or the gNB-DU endpoint of the F1 transport bearer) may be used as transport layer information for any UEs 3 joining the same MBS session. Thus, downlink Protocol Data Units (PDUs) belonging to the corresponding MBS traffic are delivered to the correct user plane TNL address (for transmission to the UEs 3) using multicast.

[0069] For any other UEs 3 that join the same MBS session after the first UE 3 establishes the shared F1-U / NG-U tunnel, the UE context setup (or modification) request need only reference the previously established F1-U / NG-U tunnel for the given MBS traffic (e.g., by indicating the user plane TNL address of the tunnel endpoint and / or any other suitable information associated with the tunnel endpoint).

[0070] The TEID of the shared tunnel is included in the context setup (modification) request signaling for other UEs 3 participating in the same MBS session. Upon receiving a tunnel TEID that is already used for a shared tunnel, the base station 5 (distributed unit) knows that this is a shared NG-U (F1-U) tunnel.

[0071] <Option 2 - Non-UE related F1AP / NGAP messages> In this example, non-UE-related F1AP / NGAP messages are used to set up a shared F1-U / NG-U tunnel for the MBS session. Such non-UE-related messages may be used instead of or in addition to explicit indicators (as in option 1).

[0072] For example, a "shared tunnel setup request" F1AP message (or a "shared F1-U GTP tunnel setup request" message and / or the like) may be used by the central unit of the base station 5 to request the distributed unit to set up a shared F1 user plane tunnel for the UE 3 (for a particular MBS session). Similarly, a "shared tunnel setup request" NGAP message (or a "shared NG-U GTP tunnel setup request" message and / or the like) may be used by the AMF 9 to request the serving base station 5 to set up a shared NG-U tunnel for the UE 3. It will be appreciated that when one of these messages is used, there is no need to include an explicit shared tunnel indicator information element or flag, as the message itself serves as the shared tunnel indicator.

[0073] <Message and Information Elements> Further details of the F1AP / NGAP messages and some example information elements (for both options 1 and 2) are provided below. It will be appreciated that other suitable messages and information elements may be used to convey information indicating (or identifying) the shared tunnels assigned to one or more MBS sessions, as desired.

[0074] F1AP Context Setup Request / UE Context Modification Response (based on 3GPP TS 38.473) This message is used to confirm the success of the UE context setup / modification (when the UE 3 joins an MBS session).

[0075] Direction: gNB-DU5D to gNB-CU5U [Table 1]

[0076] As shown in the last line above, the "DL UP TNL Info" information element contains the user plane (UP) transport layer information (TNL address) appropriate for a given MBS session. Effectively, this information identifies the gNB-DU endpoint of the F1 transport bearer used for delivery of MBS traffic over the shared user plane tunnel. Initial Context Setup Response (based on 3GPP TS 38.413) This message is sent by the NG-RAN node (base station 5) to the AMF 9 to confirm the setup of the UE context for the MBS session.

[0077] Direction: NG-RAN node 5 to AMF9 [Table 2]

[0078] In this case, if a shared tunnel is being set up, the "PDU Session Resource Setup Response Forwarded" information element contains the appropriate user plane (UP) transport layer information (TNL Address) for the given MBS session at the base station 5. Effectively, this information element identifies the endpoints of the NG-U transport bearers (at the base station 5) used for delivering MBS traffic over the shared user plane tunnel and includes an indicator that this is a shared tunnel (see details below). It will be appreciated that when a "shared tunnel" is set up for a first UE, it is effectively a UE-specific tunnel (until the tunnel is associated with other UEs in a subsequent initial context setup procedure).

[0079] UP Transport Layer Information (based on 3GPP TS 38.473, section 9.3.2.1) This information element identifies the F1 transport bearer associated with the Data Radio Bearer (DRB). It contains a transport layer address and a tunnel endpoint identifier. The transport layer address is the IP address used for F1 user plane transport. The tunnel endpoint identifier is the gNB-CU5 U It is used for user plane transport between the gNB-DU5D and the gNB-DU5D. [Table 3]

[0080] In this example, the "UP Transport Layer Information" information element includes an appropriate indication ("Shared Tunnel Indicator" field) that the corresponding tunnel is a shared tunnel. It will be appreciated that any other appropriate indication or information element or field may be used, for example, "MBS Tunnel", "Multicast Tunnel", "Tunnel Type: MBS", "Tunnel Type: Shared", "Tunnel Type: Multicast", and / or the like.

[0081] (Based on 3GPP TS 38.413, section 9.3.2.2) U Transport Layer Information This information element is used to provide NG User Plane (NG-U) transport layer information associated with a PDU session (in this case an MBS session) for an NG-RAN node and UPF pair, which corresponds to an IP address and a tunnel endpoint identifier. [Table 4]

[0082] In this example, the "UP Transport Layer Information" information element includes an appropriate indication ("Shared Tunnel Indicator" field) that the corresponding tunnel is a shared tunnel. It will be appreciated that any other appropriate indication or information element or field may be used, for example, "MBS Tunnel", "Multicast Tunnel", "Tunnel Type: MBS", "Tunnel Type: Shared", "Tunnel Type: Multicast", and / or the like.

[0083] Shared Tunnel Setup Request (F1AP) This message is sent by the central unit of the NG-RAN node (base station 5) to the distributed units to request a shared tunnel for the MBS session that UE 3 is joining. The message, which may be referred to as a "Shared F1-U GTP Tunnel Setup Request," includes the following information: an identifier of the central unit (e.g., "gNB-CU Shared F1AP ID"), an identifier of the distributed unit (e.g., "gNB-DU Shared F1AP ID"), a multicast radio bearer identifier ("MRB ID"), and an MBS session ID (e.g., TMGI). It will be appreciated that the message may also include a shared tunnel indicator (e.g., in an "UP Transport Layer Information" information element or similar), although such an indication may be redundant since the distributed unit and central unit identifiers already indicate that this particular tunnel is not a UE-specific tunnel.

[0084] Direction: gNB-CU5C to gNB-DU5D [Table 5]

[0085] In this example, the shared tunnel setup request message uses identifiers of the distributed unit and the central unit (e.g., "gNB-CU shared F1AP ID" and "gNB-DU shared F1AP ID") instead of UE-specific identifiers as in the case of UE-specific tunnels (e.g., "gNB-CU UE F1AP ID" and "gNB-DU UE F1AP ID", respectively), which allows other UEs to reuse the same tunnel for delivering MBS traffic via multicast.

[0086] Shared Tunnel Setup Request (NGAP) This message is sent by the AMF 9 to the serving base station 5 to request a shared tunnel for the MBS session that the UE 3 is joining. The message, which may be referred to as a "Shared NG-U GTP Tunnel Setup Request," includes the following information: an identifier of the AMF 9 (e.g., "AMF Shared NGAP ID"), an identifier of the base station 5 (e.g., "RAN Shared NGAP ID"), and an MBS session ID (e.g., TMGI). It will be appreciated that the message may also include a shared tunnel indicator (e.g., in an "UP Transport Layer Information" information element or similar), although such an indication may be redundant since the distributed unit and central unit identifiers already indicate that this particular tunnel is not a UE-specific tunnel.

[0087] Direction: AMF9 to gNB5 [Table 6]

[0088] After the shared F1-U / NG-U tunnel is established for the first UE 3, any other UEs 3 participating in the same MBS session can be configured to use the pre-established shared tunnel. This may be achieved by including a shared tunnel identifier (TEID) in the MRB configuration portion of the UE Context Setup / Modify message or the Initial UE Context Setup / Modify message. Upon receiving the shared tunnel TEID, the distributed unit / base station knows that the MBS session is provided over the shared F1-U / NG-U tunnel.

[0089] <Timing diagram> Below is a description of the relevant steps of a procedure for establishing a shared tunnel for UE 3 to receive MBS traffic (FIG. 7) and a procedure for deactivating the shared tunnel (FIG. 8) using the signaling messages and information elements described above. It will be appreciated that the procedure shown in FIG. 7 (or a similar procedure) may also be used to associate an already established shared tunnel with UE 3 and / or any further UEs 3, if desired.

[0090] The current procedures for MBS session activation and MBS session deactivation are shown in Figures 7.2.5.2-1 and 7.2.5.3-1 of 3GPP TS 23.247, respectively. Figure 7 is based on Figure 7.2.5.2-1 (MBS session activation procedure), but the messages have been adapted to support shared tunnels. Note that in this procedure, steps 2 to 10 and steps 11 to 14 can be performed in parallel.

[0091] As shown in step 1, session activation is triggered by an MBS-specific SMF (denoted as "MB-SMF11M"). For example, session activation may be triggered by an Application Function (AF) requesting MB-SMF11M to activate an MBS session for UE3, or by a User Plane Function (UPF) receiving multicast data for UE3 and notifying MB-SMF11M.

[0092] The SMF 11 determines which connection modes of UEs 3 have joined the MBS session and contacts the AMFs 9 of these UEs 3 (see step 8).

[0093] If a shared tunnel does not exist for a given MBS session via the base station 5 serving the UE 3, a new shared tunnel for the MBS session is set up in step 10a. Effectively, step 10a is a procedure for the establishment of a shared distribution to an NG-RAN node. This procedure is based on clause 7.2.1.4 of 3GPP TS 23.247, but the messages are adapted to use shared tunnel endpoints as described above with reference to option 1 or option 2.

[0094] If a shared tunnel exists for the MBS session but UE 3 does not use this tunnel, a PDU session modification procedure is performed in step 10b for UE 3 to join the multicast session via the shared tunnel. This procedure is based on steps 9 to 12 of clause 7.2.1.3 of 3GPP TS 23.247, but the steps are adapted to use a shared tunnel endpoint as described above with reference to option 1 or option 2.

[0095] When a new shared tunnel is established for UE 3 or UE 3 is configured to join an existing shared tunnel, steps 11 to 15 are performed.

[0096] Figure 8 is based on Figure 7.2.5.3-1 of 3GPP TS 23.247 (MBS Session Deactivation Procedure), but in this case the messages are adapted to use the shared tunnel endpoints described above with reference to option 1 or option 2.

[0097] Advantageously, using these procedures, the nodes involved in the user plane (i.e., UE, base station 5 (CU / DU), and UPF 10) can use appropriate shared tunnels for multicast delivery of MBS traffic and delete any shared tunnels that are no longer required.

[0098] N4 session management (e.g. handover / UE mobility) Clause 5.8.2.11 of 3GPP TS 23.501 describes parameters used for N4 session management. Below is a description of some MBS session parameters that may be used in N4 session management to support the provision of MBS over a shared tunnel.

[0099] Session management messages are exchanged between the SMF 11 and the UPF 10 via the N4 interface. In this system, the N4 interface messages are adapted to also include relevant MBS session parameters. For example, when performing handover-related signaling for the UE 3, the SMF 11 may provide one or more of the following parameters (along with the relevant N4 session ID) to the UPF 10: MBS session to add / modify list (if there is no ongoing MBS session in the target base station, SMF11 includes any newly added MBS session), which may include one or more (per MBS session) of the following: MBS context, Quality of Service (QoS) flows, MBS session ID, Temporary Mobile Group Identity (TMGI), UE Identifier (UE ID), UL NG-U UP TNL information, DL QoS flows per TNL information; and MBS sessions to delete list (delete a particular MBS session when the last UE3 leaves that MBS session), containing the MBS session ID for each MBS session to be deleted.

[0100] In effect, the MBS session for adding / modifying list information element includes information identifying any MBS sessions to be added or modified in the UPF 10, and the MBS session for deleting list information element includes information identifying any MBS sessions to be deleted in the UPF 10. It will be appreciated that providing information identifying one or more MBS sessions to be deleted is not limited to UE mobility, and this information may also be provided to the UPF 10 whenever there is an MBS shared tunnel that is no longer used by any UE (e.g., when all UEs have left the corresponding MBS session).

[0101] Advantageously, using at least some of the above parameters, the UPF 10 can track which UE 3 uses which MBS session using the correct shared tunnel even after handover, and maintain the MBS session of the UE 3. This approach may be particularly useful in the case of an Xn-based handover from an MBS supporting NG-RAN node (base station 5) to another NG-RAN node.

[0102] FIG. 9 illustrates schematically a (F1AP) UE context setup procedure, including a “UE context setup request” and a “UE context setup response” message, which may be adapted to include information identifying a shared tunnel and / or a shared tunnel indicator.

[0103] FIG. 10 illustrates schematically a (NGAP) UE context modification procedure, including a “UE context modification request” and a “UE context modification response” message, which may be adapted to include information identifying a shared tunnel and / or a shared tunnel indicator.

[0104] Figure 11 shows in schematic form the details of an exemplary Xn-based handover procedure. Figure 11 is a signaling (timing) diagram based on Figure 7.2.3.2-1 of 3GPP TS 23.247. However, in this case, the "N4 Session Modification" message (e.g., in step 3, 4, 6 or 8) is adapted to include information identifying any MBS sessions to be added, modified or deleted by the UPF 10 (e.g., MBS sessions for adding / modifying lists and / or MBS sessions for deleting the above-mentioned list information elements).

[0105] For the sake of completeness, it will be appreciated that the SMF 11 may also provide one or more of the following parameters to the UPF 10: -Packet Detection Rules (PDR) containing information for classifying traffic (Protocol Data Unit: PDU) arriving at the UPF 10 Forwarding Action Rules (FAR) containing information on whether forwarding, blocking, or buffering should be applied to the traffic identified by the PDR. Multi-Access Rules (MAR) containing information on how to handle traffic steering, switching, and splitting for MA PDU sessions Usage Reporting Rules (URR) containing information defining how traffic identified by the PDR should be considered, as well as how specific measurements should be reported -QoS Enforcement Rules (QER) containing information related to QoS enforcement of traffic identified by the PDR Session Reporting Rules (SRR) containing information for requesting the UP function to detect and report events of a PDU session that are not related to a specific PDR of the PDU session or that are not related to traffic usage measurements -Detection requirements -Port management information container in 5GS, and -Bridge information

[0106] <Modifications and Alternatives> Detailed embodiments have been described above. Those skilled in the art will appreciate that numerous variations and alternatives can be made to the above embodiments while still benefiting from the invention embodied therein. By way of example, only some of these alternatives and variations are described herein.

[0107] It will be appreciated that the above-mentioned shared tunnel may be provided using the GPRS Tunneling Protocol (GTP). Accordingly, the tunnel may also be referred to as a (shared) GTP tunnel or a GTP user plane (GTP-U) tunnel. While the term "shared tunnel" is used in this description to illustrate the inventive concept, it will be appreciated that the tunnel may be used by only a single UE and, in that case, is not shared (e.g., initially) by other UEs. However, regardless of the number of UEs using the tunnel, it is possible to adapt the user plane tunnel for sharing among multiple UEs by using an appropriate shared tunnel indicator, MBS tunnel indicator, and / or the like.

[0108] In the above description, the F1AP interface and associated messages are used as an example to explain the operation of the present invention between units of a distributed base station device. However, it will be understood that any other suitable interface or message may be used. Similarly, the NGAP interface and associated messages are used as an example to explain the operation of the present invention between a node of an access network (or RAN) (e.g., a base station device) and a node of a core network. However, it will be understood that any other access network-to-core network interface or access network-to-core network message may be used. It will be understood that in other publications, the same interface and / or message may have a different name than that described in the above example.

[0109] Base stations in a 5G / NR communication system are commonly referred to as New Radio Base Stations ("NR-BSs"), or "gNBs," although it will be understood that they may also be referred to using the term "eNB" (or 5G / NR eNB), which is commonly associated with Long Term Evolution (LTE) base stations (also commonly referred to as "4G" base stations). 3GPP TS 38.300 V 16.7.0 and 3GPP TS 37.340 V 16.7.0 define, among other things, the following nodes:

[0110] gNB: A node that provides NR user plane and control plane protocol termination towards the UE and is connected to the 5G core network (5GC) via the NG interface.

[0111] ng-eNB: A node that provides E-UTRA user plane and control plane protocol termination towards the UE and is connected to the 5GC via the NG interface.

[0112] En-gNB: A node that provides NR user plane and control plane protocol termination towards the UE and acts as a secondary node in E-UTRA-NR dual connectivity (EN-DC).

[0113] NG-RAN node: Either a gNB or a ng-eNB.

[0114] It will be understood that the above embodiments may be applied to 5G New Radio System and LTE System (E-UTRAN), and any future generation system. A base station supporting E-UTRA / 4G protocols may be referred to as an "eNB," and a base station supporting Next Generation / 5G protocols may be referred to as a "gNB." It will be understood that some base stations may be configured to support both 4G and 5G protocols, and / or any other 3GPP or non-3GPP communication protocol.

[0115] In the above description, for ease of understanding, the UE, access network node, and data network node (base station) are described as having several separate modules (such as a communications control module). These modules may be provided in this manner for specific applications, such as when an existing system is modified to implement the present invention; however, in other applications, such as systems designed from the beginning with the features of the present invention in mind, these modules may not be identifiable as separate entities, as these modules may be incorporated into an overall operating system or code. These modules may be implemented in software, hardware, firmware, or a combination thereof.

[0116] Each control unit may comprise any suitable form of processing circuitry including, for example (but not limited to), one or more hardware-implemented computer processors, microprocessors, central processing units (CPUs), arithmetic logic units (ALUs), input / output (IO) circuitry, internal memory / cache (program and / or data), processing registers, communication buses (e.g., control buses, data buses and / or address buses), direct memory access (DMA) facilities, hardware or software-implemented counters, pointers and / or timers, and / or the like.

[0117] In the above embodiments, a number of software modules have been described. Those skilled in the art will understand that the software modules may be provided in compiled or uncompiled form and may be supplied to the UE, access network node, and data network node as signals, via a computer network, on a recording medium, or the like. Furthermore, the functionality performed by some or all of this software may be implemented using one or more dedicated hardware circuits. However, the use of software modules is preferred because it facilitates updating the UE, access network node, and data network node to update their functionality.

[0118] The above embodiments are also applicable to "non-mobile" or generally fixed user equipment.

[0119] The message may include a base station to core network protocol message or a base station distributed unit to central unit protocol message.

[0120] The message may include a response to a message requesting the setup of an associated UE context for the UE (e.g., a UE context setup response or a shared F1-U GTP tunnel setup response), or a response to a message requesting a UE context modification (e.g., a UE context modification response or a shared F1-U GTP tunnel modification response).

[0121] The method performed by the base station device may further include receiving a request from the network node including the information (e.g., a UE context setup request or a UE context modification request).

[0122] The request may include at least one of a "shared tunnel setup request," a "shared GTP tunnel setup request," a "shared NG-U GTP tunnel setup request," and a "shared F1-U GTP tunnel setup request."

[0123] The network node may include at least one of a central unit of a base station device (e.g., a gNB-CU) and a core network node for mobility management (e.g., an access and mobility management function).

[0124] The information identifying the tunnel may include transport layer information including a Transport Network Layer (TNL) address of the base station device or a distributed unit of the base station device and a GPRS tunnel endpoint identifier.

[0125] At least one of information identifying a tunnel associated with an MBS session and information indicating that the tunnel is a shared tunnel may be included in a "UP transport layer information" information element.

[0126] The shared tunnel may comprise at least one of a user plane tunnel between a central unit and a distributed unit of a base station device (e.g., an F1-U tunnel), and a user plane tunnel between a core network node and a base station (e.g., an NG-U tunnel).

[0127] The information identifying one or more MBS sessions to be added and / or the information identifying one or more MBS sessions to be modified may include, for each MBS session to be added / modified, at least one of an MBS context, information identifying associated Quality of Service (QoS) flows, an MBS session identifier, a Temporary Mobile Group Identity (TMGI), a UE Identifier (UE ID), Transport Network Layer (TNL) information for the uplink (UL) NG-U user plane, and a Downlink (DL) QoS flow for each TNL information.

[0128] Various other modifications will be apparent to those skilled in the art and will not be described in further detail here.

[0129] [References] [1] 3GPP Technical Specification (TS) 23.247 V 17.0.0 [2] 3GPP TS 23.501 [3] 3GPP TS 37.340 V16.7.0 [4] 3GPP TS 38.300 V16.7.0 [5] 3GPP TS 38.413 V16.7.0 [6] 3GPP TS 38.473 V16.7.0

[0130] Although the present invention has been described above with reference to the embodiments, the present invention is not limited to the above. Various modifications that can be understood by those skilled in the art can be made to the configuration and details of the present invention within the scope of the present invention.

[0131] The program can be stored and provided to a computer device using any type of non-transitory computer-readable medium. Non-transitory computer-readable media include any type of tangible storage medium. Examples of non-transitory computer-readable media include magnetic storage media (e.g., floppy disks, magnetic tapes, hard disk drives, etc.), magneto-optical storage media (e.g., magneto-optical disks), CD-ROMs (read-only memories), CD-Rs, CD-R / Ws, and semiconductor memories (e.g., mask ROMs, PROMs (programmable ROMs), EPROMs (erasable PROMs), flash ROMs, RAMs (random access memories), etc.). The program may be provided to a computer device using any type of temporary computer-readable medium. Examples of temporary computer-readable media include electrical signals, optical signals, and electromagnetic waves. The temporary computer-readable medium can provide the program to a computer device via wired communication lines such as electric wires and optical fibers, or wireless communication lines.

[0132] For example, some or all of the embodiments disclosed above can be described as follows, but are not limited to the following: (Appendix 1) 1. A method performed by a base station for providing Multicast and Broadcast Services (MBS), the method comprising: sending a message to a network node including first information identifying a tunnel associated with an MBS session, wherein the message indicates that the tunnel is a shared tunnel; upon sending the message, receiving, via the shared tunnel, a user plane protocol data unit for the MBS session for transmission to a UE. A method comprising: (Appendix 2) 2. The method of claim 1, wherein the message includes second information of the MBS session. (Appendix 3) 3. The method of claim 1 or 2, wherein the message comprises a base station to core network protocol message or a base station distributed unit to central unit protocol message. (Appendix 4) 4. The method of any one of Supplementary Notes 1 to 3, wherein the message comprises a response to a message requesting setup of an associated UE context for the UE, or a response to a message requesting UE context modification. (Appendix 5) 5. The method of any one of Supplementary Notes 1 to 4, further comprising receiving a request from the network node including the first information. (Appendix 6) 1. A method performed by a base station for providing Multicast and Broadcast Services (MBS), the method comprising: receiving a request from a network node to set up a tunnel associated with an MBS session as a shared tunnel, wherein the request includes second information of the MBS session and first information identifying the tunnel; upon receiving the message, receiving a user plane protocol data unit for the MBS session via the shared tunnel for transmission to a UE; A method comprising: (Appendix 7) 7. The method of claim 6, wherein the request is non-UE-related signaling. (Appendix 8) 1. A method performed by a network node for providing Multicast and Broadcast Services (MBS), said method comprising: receiving a message from a base station including first information identifying a tunnel associated with an MBS session, wherein the message indicates that the tunnel is a shared tunnel; Upon receiving the message, sending a user plane protocol data unit for the MBS session to a user equipment (UE) via the shared tunnel. A method comprising: (Appendix 9) 9. The method of claim 8, wherein the network node comprises at least one of a central unit of the base station and a core network node for mobility management. (Appendix 10) 1. A method performed by a network node, the method comprising: transmitting a request to a base station to set up a tunnel associated with a Multicast and Broadcast Services (MBS) session as a shared tunnel to provide MBS services, the request including second information of the MBS session and first information identifying the tunnel; wherein the shared tunnel is adapted to be used by the base station to transmit user plane protocol data units for the MBS session. method. (Appendix 11) 11. The method of any one of Supplementary Notes 1 to 10, wherein the first information includes transport layer information and a Transport Network Layer (TNL) address of the base station or a distributed unit of the base station. (Appendix 12) 12. The method of claim 11, wherein the first information is included in a "UP Transport Layer Information" information element. (Appendix 13) the shared tunnel: a user plane tunnel between a central unit and a distributed unit of the base station; and User plane tunnel between a core network node and the base station 13. The method of any one of claims 1 to 12, comprising at least one of: (Appendix 14) 1. A method performed by a first core network node for managing at least one Multicast and Broadcast Services (MBS) session provided using a shared tunnel, the method comprising: sending a session management message to a second core network node to manage a user plane associated with the at least one MBS session, the message comprising: information identifying one or more MBS sessions to be added at the second core network node; information identifying one or more MBS sessions to be modified at the second core network node; and information identifying one or more MBS sessions to be deleted at the second core network node; Contains at least one of method. (Appendix 15) 1. A method performed by a second core network node for managing a user plane associated with at least one Multicast and Broadcast Services (MBS) session provided using a shared tunnel, the method comprising: information identifying one or more MBS sessions to be added at the second core network node; information identifying one or more MBS sessions to be modified at the second core network node; and information identifying one or more MBS sessions to be deleted at the second core network node; receiving a session management message from a first core network node, the session management message including at least one of: (Appendix 16) Information identifying one or more MBS sessions to be added and / or information identifying one or more MBS sessions to be changed is, for each MBS session to be added / changed, MBS Context, Information identifying the associated Quality of Service (QoS) flow; MBS session identifier, Temporary Mobile Group Identity (TMGI), UE Identifier (UE ID), Uplink (UL) NG-U user plane Transport Network Layer (TNL) information, and Downlink (DL) QoS flow per TNL information 16. The method of claim 14 or 15, comprising at least one of: (Appendix 17) A base station for providing multicast and broadcast services (MBS), means for transmitting a message to a network node including first information identifying a tunnel associated with an MBS session, the message indicating that the tunnel is a shared tunnel; means for receiving, upon sending the message, a user plane protocol data unit for the MBS session via the shared tunnel for transmission to a UE; A base station comprising: (Appendix 18) A base station for providing Multicast and Broadcast Services (MBS), comprising: means for receiving a request from a network node to set up a tunnel associated with an MBS session as a shared tunnel, the request including second information of the MBS session and first information identifying the tunnel; means for receiving, upon receiving a message, a user plane protocol data unit for the MBS session via the shared tunnel for transmission to a UE; A base station comprising: (Appendix 19) A network node for providing Multicast and Broadcast Services (MBS), comprising: means for receiving, from a base station, a message including first information identifying a tunnel associated with an MBS session, the message indicating that the tunnel is a shared tunnel; means for transmitting, upon receiving the message, a user plane protocol data unit for the MBS session to a user equipment (UE) via the shared tunnel; A network node comprising: (Appendix 20) a network node, means for transmitting to a base station a request to set up a tunnel associated with a Multicast and Broadcast Services (MBS) session as a shared tunnel to provide MBS services, the request including second information of the MBS session and first information identifying the tunnel; the shared tunnel is adapted to be used by the base station to transmit user plane protocol data units for the MBS session. Network node. (Appendix 21) A first core network node for managing at least one Multicast and Broadcast Services (MBS) session provided using a shared tunnel, the first core network node comprising: means for transmitting a session management message to a second core network node for managing a user plane associated with the at least one MBS session, the message comprising: information identifying one or more MBS sessions to be added at the second core network node; information identifying one or more MBS sessions to be modified at the second core network node; and information identifying one or more MBS sessions to be deleted at the second core network node; means including at least one of a first core network node comprising: (Appendix 22) A second core network node for managing a user plane associated with at least one Multicast and Broadcast Services (MBS) session provided by using a shared tunnel, the second core network node comprising: information identifying one or more MBS sessions to be added at the second core network node; information identifying one or more MBS sessions to be modified at the second core network node; and information identifying one or more MBS sessions to be deleted at the second core network node; means for receiving from the first core network node a session management message including at least one of: a second core network node comprising:

[0133] This application claims the benefit of priority to UK Patent Application No. 2118978.2 filed on December 23, 2021, the disclosure of which is incorporated herein by reference in its entirety. [Explanation of symbols]

[0134] 1. Telecommunications Systems 3. Mobile Devices 5 base station 7 Core Network 9 AMF 10 UPF 11 SMF

Claims

1. A distributed unit of a base station providing Multicast and Broadcast Services (MBS), comprising: means for transmitting, to a central unit of the base station, a message including a set of first information indicating a user plane tunnel between the central unit and the distributed unit associated with an MBS session, a radio bearer identifier of a radio bearer for the MBS corresponding to the user plane tunnel, an F1 application protocol identifier (F1AP ID) associated with the central unit, and an F1AP ID associated with the distributed unit; wherein the message indicates that the user plane tunnel is a shared tunnel; means for receiving, in response to sending the message, a user plane protocol data unit for the MBS session via the shared tunnel for transmission to a user equipment (UE); A distributed unit comprising:

2. The distributed unit described in claim 1, wherein the first information includes a transport layer address and a General Packet Radio Service (GPRS) Tunneling Protocol (GTP) Tunnel Endpoint Identifier (GTP-TEID).

3. A distributed unit of a base station providing Multicast and Broadcast Services (MBS), comprising: means for receiving, from a central unit of the base station, a request to set up a user plane tunnel between the central unit and the distributed units associated with an MBS session as a shared tunnel, wherein the request includes second information of the MBS session and first information identifying the user plane tunnel; means for receiving, in response to receiving the request, a user plane protocol data unit for the MBS session via the shared tunnel for transmission to a user equipment (UE); A distributed unit comprising:

4. A central unit of a base station providing Multicast and Broadcast Services (MBS), comprising: means for receiving, from a distributed unit of the base station, a message including a set of first information indicating a user plane tunnel between the central unit and the distributed unit associated with an MBS session, a radio bearer identifier of a radio bearer for the MBS corresponding to the user plane tunnel, an F1 application protocol identifier (F1AP ID) associated with the central unit, and an F1AP ID associated with the distributed unit; wherein the message indicates that the user plane tunnel is a shared tunnel; means for transmitting a user plane protocol data unit for the MBS session via the shared tunnel for transmission to a user equipment (UE) in response to receiving the message; A central unit comprising:

5. A central unit of a base station providing Multicast and Broadcast Services (MBS), comprising: means for sending to a distributed unit of the base station a request to set up a user plane tunnel between the central unit and the distributed unit associated with an MBS session as a shared tunnel, wherein the request includes second information of the MBS session and first information identifying the user plane tunnel; a central unit, the shared tunnel configured to be used by the distributed units to transmit user plane protocol data units for the MBS session;

6. 1. A method in a distributed unit of a base station providing Multicast and Broadcast Services (MBS), comprising: sending a message to a central unit of the base station, the message including a set of first information indicating a user plane tunnel between the central unit and the distributed unit associated with an MBS session, a radio bearer identifier of a radio bearer for the MBS corresponding to the user plane tunnel, an F1 application protocol identifier (F1AP ID) associated with the central unit, and an F1AP ID associated with a distributed unit, wherein the message indicates that the user plane tunnel is a shared tunnel; receiving, in response to sending the message, a user plane protocol data unit for the MBS session for transmission to a user equipment (UE) via the shared tunnel; A method comprising:

7. 1. A method in a distributed unit of a base station providing Multicast and Broadcast Services (MBS), comprising: receiving a request from a central unit of the base station to set up a user plane tunnel between the central unit and the distributed units associated with an MBS session as a shared tunnel, wherein the request includes second information of the MBS session and first information identifying the user plane tunnel; In response to receiving the request, receiving a user plane protocol data unit for the MBS session for transmission to a user equipment (UE) via the shared tunnel; and A method comprising:

8. 1. A method in a central unit of a base station providing Multicast and Broadcast Services (MBS), comprising: receiving a message from a distributed unit of the base station, the message including a set of first information indicating a user plane tunnel between the central unit and the distributed unit associated with an MBS session, a radio bearer identifier of a radio bearer for the MBS corresponding to the user plane tunnel, an F1 application protocol identifier (F1AP ID) associated with the central unit, and an F1AP ID associated with the distributed unit, wherein the message indicates that the user plane tunnel is a shared tunnel; In response to receiving the message, transmitting a user plane protocol data unit for the MBS session via the shared tunnel for transmission to a user equipment (UE); A method comprising:

9. 1. A method in a central unit of a base station providing Multicast and Broadcast Services (MBS), comprising: sending a request to a distributed unit of the base station to set up a user plane tunnel between the central unit and the distributed unit associated with an MBS session as a shared tunnel, wherein the request includes second information of the MBS session and first information identifying the user plane tunnel; The method, wherein the shared tunnel is configured to be used by the distributed unit to transmit user plane protocol data units for the MBS session.

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