BASE STATION, NETWORK NODE, FIRST CORE NETWORK NODE, SECOND CORE NETWORK NODE, AND A METHOD PERFORMED BY THEM

The present invention relates to a wireless communication system and devices thereof operating according to the 3rd Generation Partnership Project (3GPP) standards or equivalents or derivatives thereof. A method performed by a base station (5) for providing Multicast and Broadcast Services (MBS) is disclosed. The method comprises transmit, to a network node, a message including first information identifying a tunnel associated with an MBS session, wherein the message indicates that the tunnel is a shared tunnel; and receive, via the shared tunnel, user plane protocol data unit for the MBS session for transmitting to the UE (3), upon transmitting the message.

TECHNICAL FIELD

The present invention relates to a wireless communication system and devices thereof operating according to the 3rd Generation Partnership Project (3GPP) standards or equivalents or derivatives thereof. The disclosure has particular but not exclusive relevance to improvements relating to multimedia broadcast session management in the so-called ‘5G’ (or ‘Next Generation’) systems.

BACKGROUND ART

The latest developments of the 3GPP standards are referred to as ‘5G’ or ‘New Radio’ (NR). These terms refer to an evolving communication technology that supports a variety of applications and services. Various details of 5G networks are described in, for example, the ‘NGMN 5G White Paper’ V1.0 by the Next Generation Mobile Networks (NGMN) Alliance, which document is available from https://www.ngmn.org/5g-white-paper.html. 3GPP intends to support 5G by way of the so-called 3GPP Next Generation (NextGen) radio access network (RAN) and the 3GPP NextGen core network (NGC).

Under the 3GPP standards, the base station (e.g. an ‘eNB’ in 4G or a ‘gNB’ in 5G) is a node via which communication devices (user equipment or ‘UE’) connect to a core network and communicate to other communication devices or remote servers. For simplicity, the present application will use the term base station to refer to any such base stations.

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, typically ‘higher’, CU layers (for example, but not necessarily or exclusively), PDCP) and the typically ‘lower’, DU layers (for example, but not necessarily or exclusively, RLC/MAC/PHY) may be implemented separately. Thus, for example, the higher layer CU functionality for a number of gNBs may be implemented centrally (for example, by a single processing unit, or in a cloud-based or virtualised system), whilst retaining the lower layer DU functionality locally, in each of the gNB.

For simplicity, the present application will use the term mobile device, user device, or UE to refer to any communication device that is able to connect to the core network via one or more base stations.

Communication devices might be, for example, mobile communication devices such as mobile telephones, smartphones, user equipment, personal digital assistants, laptop/tablet computers, web browsers, e-book readers and/or the like. Such mobile (or even generally stationary) devices are typically operated by a user. However, 3GPP standards also make it possible to connect so-called ‘Internet of Things’ (IoT) devices (e.g. Narrow-Band IoT (NB-IoT) devices) to the network, which typically comprise automated equipment, such as various measuring equipment, telemetry equipment, monitoring systems, tracking and tracing devices, in-vehicle safety systems, vehicle maintenance systems, road sensors, digital billboards, point of sale (POS) terminals, remote control systems, and the like. Effectively, the Internet of Things is a network of devices (or “things”) equipped with appropriate electronics, software, sensors, network connectivity, and/or the like, which enables these devices to collect and exchange data with each other and with other communication devices. It will be appreciated that IoT devices are sometimes also referred to as Machine-Type Communication (MTC) communication devices or Machine-to-Machine (M2M) communication devices.

For simplicity, the present application often refers to mobile devices in the description but it will be appreciated that the technology described can be implemented on any communication devices (mobile and/or generally stationary) that can connect to a communications network for sending/receiving data, regardless of whether such communication devices are controlled by human input or software instructions stored in memory.

One of the recent features being developed over the existing 5G framework is referred to as Multicast and Broadcast Services (MBS). This functionality aims to enhance 5G New Radio and 5G Core Network capabilities for a reliable, low latency, resource efficient, and massive deployment of a wide array of multicast and broadcast services. 3GPP is currently specifying the details of MBS for media distribution over mobile broadband networks. MBS (or ‘NR MBS’ in 5G) aims to reuse cellular infrastructure such as the so-called Low Power Low Tower (LPLT) infrastructure. One of the main use cases is the delivery of linear/live media content to smartphones, tablets, vehicles, and other mobile (or stationary) devices. Although MBS is designed to use existing (or already specified) 3GPP infrastructure, it can provide a more efficient delivery of multicast/broadcast traffic than unicast communication using the same infrastructure. Details of architectural enhancements for MBS may be found in the in 3GPP Technical Specification (TS) 23.247 V17.0.0, the contents of which are incorporated herein by reference.

In legacy user plane tunnel establishment, a tunnel may be created for a UE by transmitting UE context setup request/response messages between the tunnel endpoints (e.g. between a Distributed Unit and a corresponding Central Unit in case of F1 user plane or between the base station and a corresponding user plane function). These messages include UE specific information (e.g., UE FIAP ID/NGAP ID) which in turn uniquely associates the tunnel to a particular UE.

On the other hand, MBS employs shared tunnels for delivering user plane data (e.g. F1/NG user plane) to multiple UEs that have joined a particular service in order to benefit from a more efficient delivery of multicast/broadcast traffic. Thus, during session activation for MBS, a shared tunnel is established or if there is an already established shared tunnel for the 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 via the appropriate shared tunnel (using multicast). More specifically, traffic for the MBS service is transmitted using multicast, via the serving base station or a distributed unit thereof, over the shared user plane tunnel of that MBS service. Note that it is quite different to unicast which uses a dedicated user plane tunnel per UE.

The inventors have realised that the existing tunnel establishment procedures require UE specific information which are not compatible with the multicast transmission employed by MBS. Thus, it would be necessary to introduce a common tunnel establishment procedure for unicast and multicast use or to modify the legacy UE context setup procedure to support setting up of shared user plane tunnels between the respective endpoints.

The inventors have also realised that similar issues may arise during handover of UEs receiving MBS traffic which may require session modification (e.g. over the N4 interface) with respect to a shared user plane tunnel. For example, it may be necessary to add/modify a shared user plane tunnel in a new cell when a UE is being handed over to that cell. Similarly, when a shared user plane tunnel is not used by any UE due to handover (or when all UEs have left the corresponding MBS session), it may be beneficial to remove the MBS session relating to that tunnel at the serving user plane function (UPF). However, current session/tunnel management procedures are not suitable for such MBS related procedures.

SUMMARY OF INVENTION

Solution to Problem

Accordingly, the present invention seeks to provide methods and associated apparatus that address or at least alleviate (at least some of) the above-described issues.

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

In one aspect, the invention provides a method performed by a base station for providing Multicast and Broadcast Services (MBS), the method comprising: receiving, from a network node, a request for setting up for 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 receiving, via the shared tunnel, user plane protocol data unit for the MBS session for transmitting to the UE, upon receiving the message.

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

In one aspect, the invention provides a method performed by a network node the method comprising: transmitting, to a base station for providing Multicast and Broadcast Services (MBS), a request for setting 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: wherein the shared tunnel is adapted to be used, by the base station, for transmitting user plane protocol data unit for the MBS session.

In one aspect, the invention provides 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: 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 including at least one of: information identifying one or more MBS session to be added at the second core network node: information identifying one or more MBS session to be modified at the second core network node; and information identifying one or more MBS session to be removed at the second core network node.

In one aspect, the invention provides 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: receiving, from a first core network node, a session management message including at least one of: information identifying one or more MBS session to be added at the second core network node: information identifying one or more MBS session to be modified at the second core network node; and information identifying one or more MBS session to be removed at the second core network node.

In one aspect, the invention provides a base station for providing Multicast and Broadcast Services (MBS), comprising: means for transmitting, to a network node, a message including first information identifying a tunnel associated with an MBS session, wherein the message indicates that the tunnel is a shared tunnel; and means for receiving, via the shared tunnel, user plane protocol data unit for the MBS session for transmitting to the UE, upon transmitting the message.

In one aspect, the invention provides a base station for providing Multicast and Broadcast Services (MBS), the base station apparatus comprising: means for receiving, from a network node, a request for setting 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, via the shared tunnel, user plane protocol data unit for the MBS session for transmitting to the UE, upon receiving the message.

In one aspect, the invention provides 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, wherein the message indicates that the tunnel is a shared tunnel; and means for transmitting, via the shared tunnel, user plane protocol data unit for the MBS session to a user equipment (UE), upon receiving the message.

In one aspect, the invention provides a network node comprising: means for transmitting, to a base station for providing Multicast and Broadcast Services (MBS), a request for setting 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: wherein the shared tunnel is adapted to be used, by the base station, for transmitting user plane protocol data unit for the MBS session.

In one aspect, the invention provides 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 including at least one of: information identifying one or more MBS session to be added at the second core network node: information identifying one or more MBS session to be modified at the second core network node; and information identifying one or more MBS session to be removed at the second core network node.

In one aspect, the invention provides 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 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 session to be added at the second core network node: information identifying one or more MBS session to be modified at the second core network node; and information identifying one or more MBS session to be removed at the second core network node.

Advantageous Effects of Invention

Aspects of the invention extend to corresponding systems, apparatus, and computer program products such as computer readable storage media having instructions stored thereon which are operable to program a programmable processor to carry out a method as described in the aspects and possibilities set out above or recited in the claims and/or to program a suitably adapted computer to provide the apparatus recited in any of the claims.

Each feature disclosed in this specification (which term includes the claims) and/or shown in the drawings may be incorporated in the invention independently of (or in combination with) any other disclosed and/or illustrated features. In particular but without limitation the features of any of the claims dependent from a particular independent claim may be introduced into that independent claim in any combination or individually.

DESCRIPTION OF EMBODIMENTS

FIG.1andFIG.2illustrate schematically a mobile (cellular or wireless) telecommunication system1to which embodiments of the invention may be applied.

In this system1, users of mobile devices3(UEs) can communicate with each other and other users via base stations5(and other access network nodes) and a core network7using an appropriate 3GPP radio access technology (RAT), for example, an Evolved Universal Terrestrial Radio Access (E-UTRA) and/or 5G RAT. It will be appreciated that a number of base stations5form a (radio) access network or (R)AN. As those skilled in the art will appreciate, whilst one mobile device3and three base stations5A-5C are shown inFIG.1for illustration purposes, the system, when implemented, will typically include other base stations/(R) AN nodes and mobile devices (UEs).

Each base station5controls one or more associated cells (either directly or via other nodes such as home base stations, relays, remote radio heads, distributed units, and/or the like). A base station5that supports Next Generation/5G protocols may be referred to as a ‘gNBs’. It will be appreciated that some base stations5may be configured to support both 4G and 5G, and/or any other 3GPP or non-3GPP communication protocols.

It will be appreciated that the functionality of a gNB5(referred to herein as a ‘distributed’ gNB) may be split between one or more distributed units (DUs) and a central unit (CU) with a CU typically performing higher level functions and communication with the next generation core and with the DU performing lower level functions and communication over an air interface with UEs in the vicinity (i.e. in a cell operated by the gNB). A distributed gNB includes the following functional units;

gNB Central Unit (gNB-CU): a logical node hosting Radio Resource Control (RRC), Service Data Adaptation Protocol (SDAP) and Packet Data Convergence Protocol (PDCP) layers of the gNB (or 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 with the gNB-DU.

gNB Distributed Unit (gNB-DU)5D: a logical node hosting Radio Link Control (RLC), Medium Access Control (MAC) and Physical (PHY) layers of the gNB or en-gNB, and its operation is partly controlled by 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 with the gNB-CU.

gNB-CU-Control Plane (gNB-CU-CP)5C: a logical node hosting the RRC and the control plane part of the PDCP protocol of the gNB-CU for an en-gNB or a gNB. The gNB-CU-CP terminates the E1 interface connected with the gNB-CU-UP and the F1-C interface connected with the gNB-DU.

gNB-CU-User Plane (gNB-CU-UP)5U: a logical node hosting the user plane part of the PDCP protocol of the gNB-CU for an en-gNB, and the user plane part of the PDCP protocol and the SDAP protocol of the gNB-CU for a gNB. The gNB-CU-UP terminates the E1 interface connected with the gNB-CU-CP and the F1-U interface connected with the gNB-DU.

The mobile device3and its serving base station5are connected via an appropriate air interface (for example the so-called ‘NR’ air interface, the ‘Uu’ interface, and/or the like). Neighbouring base stations5are connected to each other via an appropriate base station to base station interface (such as the so-called ‘Xn’ interface, the ‘X2’ interface, and/or the like). The base stations5are also connected to the core network nodes via an appropriate interface (such as the so-called ‘NG-U’ interface (for user-plane), the so-called ‘NG-C’ interface (for control-plane), and/or the like).

The core network7(e.g. the EPC in case of LTE or the NGC in case of NR/5G) typically includes logical nodes (or ‘functions’) for supporting communication in the telecommunication system1, and for subscriber management, mobility management, charging, security, call/session management (amongst others). For example, the core network7of a ‘Next Generation’/5G system will include user plane entities 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 the Mobility Management Entity (MME) in 4G, is responsible for handling connection and mobility management tasks for the mobile devices3. The so-called Session Management Function (SMF) is responsible for handling communication sessions for the mobile devices3such as session establishment, modification and release. In the example shown inFIG.1, the core network7includes one or more AMF(s)9, one or more UPF(s)10, and one or more SMF(s)11. It will be appreciated that the nodes or functions may have different names in different systems.

Further details of the core network7are shown inFIG.2which also shows the interfaces between respective network nodes. As can be seen, the core network7may typically include an Authentication Server Function (AUSF), a Unified Data Management (UDM) entity, a Policy Control Function (PCF), an Application Function (AF), amongst others. The core network7is coupled (via the UPF10) to a Data Network (DN), such as the Internet or a similar Internet Protocol (IP) based network. The core network7may also be coupled to an Operations and Maintenance (OAM) function (not shown).

In this system1, Multicast and Broadcast Services (MBS) functionality is provided to UEs3via their serving base station5and associated core network nodes such as the UPF10and the SMF11. The UPF10may be an MBS specific UPF in which case it may be referred to as the MB-UPF10M (e.g. dedicated to the provision of MBS functionality). Similarly, the SMF11may be an MBS specific SMF in which case it may be referred to as the MB-SMF11M. However, it will be appreciated that any suitable UPF10/SMF11may be used for MBS.

MBS traffic is distributed over shared user plane tunnels, when appropriate. Specifically, MBS user plane data (e.g. F1-U/NG-U data) for a given service is delivered over an associated shared tunnel, using multicast transmission, to those UEs that have joined that particular service.

When the first UE joins an MBS service, an MBS session is established for that service on the user plane between the core network7and the UE's serving base station5(and between units of a distributed gNB handling the user plane, if applicable). For any UE (at least one UE) interested in that MBS service, the MBS traffic can be transmitted via multicast, via a given serving base station or a distributed unit thereof, using the shared user plane tunnel.

In order to realise sharing of the user plane tunnel(s) among UEs3, the nodes of this network (e.g. the base station5and the AMF9) are configured to use an appropriate indicator to indicate when a tunnel is a shared tunnel. For example, this indicator may be used when the tunnel is associated with the UE3(e.g. the tunnel being set up or modified for an MBS that the UE3has joined). The Transport Network Layer (TNL) address of the shared tunnel is used as the Transport Layer Information in F1-U/NG-U session management signalling when the UE3joins the MBS service.

Specifically, when an MBS session is requested for a UE3, the base station5that is used as the endpoint of the NG-U transport bearer of that MBS session (and/or the gNB-DU endpoint of the F1 transport bearer) is used as the user plane TNL address for the UE3for the delivery of MBS traffic (downlink Protocol Data Units). The signalling messages exchanged with the tunnel endpoints include the indicator (a field or a flag) that the tunnel is a shared tunnel (as opposed to a tunnel that is to be used by a single UE only). Effectively, this option re-uses existing (legacy) UE context setup (modification) request and response messages to setup 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).

Upon receiving a request from the first UE3that is interested in the MBS session, the AMF9requests (the Central Unit of) the base station5to set up (or modify) the UE context so that the associated F1-U/NG-U tunnel is configured as a shared tunnel. When the shared tunnel indicator is present, the base station5(DU) is aware that the tunnel is a shared tunnel which can be shared by subsequent UEs, and the base station5(or DU) also indicates that a shared tunnel is used in its response to the AMF9(or the CU).

Alternatively, instead of an explicit indicator, or in addition to it, an appropriate (non-UE associated) FIAP/NGAP message may be used to setup a shared tunnel for the MBS. For example, the central unit of the base station5may be configured to send an appropriate FIAP signalling message (e.g. a ‘Shared F1-U GTP tunnel setup request’ message and/or the like) to the distributed unit for setting up a shared tunnel for a UE3. Similarly, the AMF9may be configured to send an appropriate NGAP signalling message (e.g. a ‘Shared NG-U GTP tunnel setup request’ message and/or the like) to the serving base station5for setting up a shared tunnel for the UE3. In this case, the message itself acts as the shared tunnel indicator (although an explicit indicator/flag may be included in the message if appropriate).

In any case, it will be appreciated that the messages used for configuring the MBS session do not include UE specific information (e.g., UE F1AP ID/NGAP ID) which uniquely associates the tunnel to a particular UE3(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 informs the base station that the tunnel can be shared among UEs3.

To support handover of UEs3receiving MBS over shared tunnels, session management messages exchanged (over the N4 interface) between the SMF11and the UPF10are adapted to include the relevant MBS session parameters. For example, when performing handover related signalling for a UE3, the SMF11may provide one or more of the following parameters to the UPF10(together with an associated N4 Session ID):MBS session to add/modify list (the SMF11includes any newly added MBS session in case there is no ongoing MBS session in the target base station) which may include one or more of the following (per MBS session): 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; and DL QoS Flow per TNL Information; andMBS session to remove list (to remove a particular MBS session in case the last UE3has left that MBS session, not limited to UE mobility scenario): MBS session ID(s) for each MBS session to be removed.

Beneficially, using at least some of the above parameters the UPF10is able to keep track of which UE3uses which MBS session(s) and maintain the MBS session(s) for the UE3even after handover, using the correct shared tunnel(s). This approach may be particularly useful in case of Xn based handover from an MBS supporting NG-RAN node (base station5) to another NG-RAN node (currently specified in clause 7.2.3.2 of 3GPP TS 23.247).

FIG.3is a block diagram illustrating the main components of the mobile device (UE)3shown inFIG.1. As shown, the UE3includes a transceiver circuit31which is operable to transmit signals to and to receive signals from the connected node(s) via one or more antenna33. Although not necessarily shown inFIG.3, the UE3will of course have all the usual functionality of a conventional mobile device (such as a user interface35) and this may be provided by any one or any combination of hardware, software and firmware, as appropriate. A controller37controls the operation of the UE3in accordance with software stored in a memory39. The software may be pre-installed in the memory39and/or may be downloaded via the telecommunication network1or from a removable data storage device (RMD), for example. The software includes, among other things, an operating system41, a communications control module43and an MBS module45.

The communications control module43is responsible for handling (generating/sending/receiving) signalling messages and uplink/downlink data packets between the UE3and other nodes, including (R) AN nodes5and core network nodes. The signalling may comprise RRC signalling (to/from the (R) AN nodes5) and/or NG-C/NG-U signalling (to/from the core network7).

The MBS module45is responsible for handling signalling relating to multimedia broadcast services.

FIG.4is a block diagram illustrating the main components of a base station5(or a similar access network node) shown inFIG.1. As shown, the base station5has a transceiver circuit51for transmitting signals to and for receiving signals from user equipment (such as the mobile device3) via one or more antenna53, a network interface55for transmitting signals to and for receiving signals from the core network7and neighbouring base stations. The base station5has a controller57to control the operation of the base station5in accordance with software stored in a memory59. The software may be pre-installed in the memory59and/or may be downloaded via the telecommunication network1or from a removable data storage device (RMD), for example. The software includes, among other things, an operating system61, and at least a communications control module63. Although not shown inFIG.4, the network interface55will also typically include 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).

The communications control module63is responsible for handling (generating/sending/receiving) signalling between the base station5and other nodes, such as the UE3and the core network nodes. Such signalling may include, for example, control data for managing operation of the mobile device3(e.g. Non-Access Stratum, Radio Resource Control, system information, paging, and/or the like). It will be appreciated that the communications control module63may include a number of sub-modules (or ‘layers’) to support specific functionalities. For example, the communications control module63may 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.

As shown inFIG.5, when the base station5comprises a distributed gNB or en-gNB, the network interface55also includes an E1 interface and an F1 interface (F1-C for control plane and F1-U for user plane) to communicate signals between respective functions of the distributed gNB or en-gNB. In this case, the software also includes at least one of: a gNB-CU-CP module5C, a gNB-CU-UP module5U, and a gNB-DU module5D. If present, the gNB-CU-CP module5C hosts the RRC layer and the control plane part of the PDCP layer of the distributed gNB or en-gNB. If present, the gNB-CU-UP module5U hosts the user plane part of the PDCP and the SDAP layers of the distributed gNB or the user plane part of the PDCP layer of the distributed en-gNB. If present, the gNB-DU module5D hosts the RLC, MAC, and PHY layers of the distributed gNB or en-gNB.

It will be understood by a person skilled in the art that the central unit (e.g.5C and/or5U) may be implemented and physically located with the base station or may be implemented at a remote location, as a single physical element or as a cloud-based or virtualised system. It will also be understood that a single central unit may serve multiple base stations5.

FIG.6is a block diagram illustrating the main components of a core network node shown inFIG.1(e.g. the AMF9, the UPF10, or the SMF11). As shown, the core network node includes a transceiver circuit71which is operable to transmit signals to and to receive signals from connected UE(s)3via one or more antenna73and to transmit signals to and to receive signals from other network nodes (either directly or indirectly) via a network interface75. Signals may be transmitted to and received from the UE(s)3either directly and/or via the base station5or other (R) AN nodes, as appropriate. The network interface75typically includes an appropriate base station interface (such as S1/NG-C/NG-U). A controller77controls the operation of the core network node in accordance with software stored in a memory79. The software may be pre-installed in the memory79and/or may be downloaded via the telecommunication network1or from a removable data storage device (RMD), for example. The software includes, among other things, an operating system81, a communications control module83, and an MBS module85(optional).

The communications control module83is responsible for handling (generating/sending/receiving) signalling between the core network node and other nodes, such as the UE3, (R) AN nodes, and other core network nodes.

If present, e.g. in an MB-SMF or MB-UPF, the MBS module85is responsible for handling signalling relating to multimedia broadcast services (control signalling and/or MBS traffic). The signalling may comprise signalling relating to MBS sessions and shared tunnel management and associated parameters.

DETAILED DESCRIPTION

The following is a description of some exemplary procedures performed by the nodes of the system shown inFIG.1to support MBS sessions over shared tunnels.

As can be seen inFIG.1andFIG.2, the NG-U (NG user plane) protocol is used between the UE3and the core network (UPF10), carried over the N3 interface between the base station5and the core network7. When a distributed base station5is involved, the F1-U (F1 user plane) protocol is used between the central unit5C of the distributed base station5and the distributed unit5D responsible for the MBS user plane.

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 the present 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) to a particular MBS session (and any UE for which the corresponding MBS traffic is intended). In particular, one or more of the following FIAP/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 (seeFIG.9andFIG.10).

In case of an NG-U shared tunnel, the NG-RAN node5(e.g. base station/gNB) and the UPF11are the tunnel endpoints. In this case, when a shared tunnel has been set up for an MBS session, an appropriate NGAP message (e.g. UE Context Modification Response) may be sent by the base station5to the AMF9to confirm the modification of a UE context for MBS (upon the UE3joining the MBS).

In case of an F1-U shared tunnel (or the F1 portion of an NG-U shared tunnel), the gNB-DU5D and the gNB-CU5U are the tunnel endpoints. The F1-U shared tunnel may be associated with a particular UE3by modifying the associated UE context for receiving MBS traffic using multicast. For example, when such a shared tunnel has been set up for an MBS session (upon the UE3joining the MBS), an appropriate FIAP message (e.g. UE Context Setup Response) may be sent by the gNB-DU5D to the gNB-CU5U to confirm the modification of a UE context.

The TNL address of the shared tunnel is used as the Transport Layer Information (Tunnel Endpoint Identifier or ‘TEID’) in associated F1-U/NG-U session management signalling for UEs3joining (or leaving) the MBS session. The TNL address for the session is configured with a shared tunnel indicator. The TEID associated with the base station5that is 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 the Transport Layer Information for any UE3joining the same MBS session. Thus, downlink protocol data units (PDUs) that belong to the corresponding MBS traffic are delivered to the correct user plane TNL address (for transmission to the UE(s)3) using multicast.

For any other UE3joining the same MBS session after the first UE3has established a shared F1-U/NG-U tunnel, the UE context setup (or modification) requests only need to reference the previously established F1-U/NG-U tunnel for the given MBS traffic (e.g. by indicating the user plane TNL address for the tunnel endpoint and/or any other suitable information associated with the tunnel endpoint).

The TEID of the shared tunnel is included in context setup (modification) request signalling for other UEs3joining the same MBS session. Upon reception of the tunnel TEID already used for a shared tunnel, the base station5(distributed unit) knows that this is a shared NG-U (F1-U) tunnel.

In this example, non-UE associated F1AP/NGAP messages are used to setup a shared F1-U/NG-U tunnel for an MBS session. Such non-UE associated messages may be used instead of an explicit indicator (as in option 1), or in addition to it.

For example, a ‘Shared tunnel setup request’ FIAP message (alternatively, a ‘Shared F1-U GTP tunnel setup request’ message and/or the like) may be used by the central unit of the base station5to request the distributed unit to set up a shared F1 user plane tunnel for a UE3(for a particular MBS session). Similarly, a ‘Shared tunnel setup request’ NGAP message (alternatively, a ‘Shared NG-U GTP tunnel setup request’ message and/or the like) may be used by the AMF9to request the serving base station5to set up a shared NG-U tunnel for the UE3. It will be appreciated when one of these messages is used it is not necessary to include an explicit shared tunnel indicator information element or flag since the message itself acts as the shared tunnel indicator.

<Messages and Information Elements>

Further details of the FIAP/NGAP messages and some exemplary information elements are shown below (for both options 1 and 2). It will be appreciated that other suitable messages and information elements may be used, if appropriate, to convey information indicating (or identifying) a shared tunnel allocated to one or more MBS session.

This message is used to confirm successful setup/modification of a UE context (upon a UE3joining an MBS session).

As shown in the last row above, the ‘DL UP TNL Information’ information element includes appropriate user plane (UP) Transport Layer Information (TNL address) for a given MBS session. Effectively, this information identifies the gNB-DU endpoint of the F1 transport bearer to be used for delivery of MBS traffic over a shared user plane tunnel.

Initial Context Setup Response (based on 3GPP TS 38.413) This message is sent by the NG-RAN node (base station5) to the AMF9to confirm the setup of a UE context for an MBS session.

In this case, when a shared tunnel is set up, the ‘PDU Session Resource Setup Response Transfer’ information element includes appropriate user plane (UP) Transport Layer Information (TNL address) for the given MBS session at the base station5. Effectively, this information element identifies the endpoint of the NG-U transport bearer (at the base station5) to be used for delivery of MBS traffic over a shared user plane tunnel and includes an indicator that this is a shared tunnel (see details below). It will be appreciated that when the ‘shared tunnel’ is set up for the first UE, it is effectively a UE specific tunnel (until the tunnel is associated with other UEs, in subsequent Initial Context Setup procedures).

UP Transport Layer Information (based on 3GPP TS 38.473, clause 9.3.2.1) This information element identifies an F1 transport bearer associated to a Data Radio Bearer (DRB). It contains a Transport Layer Address and a Tunnel Endpoint Identifier. The Transport Layer Address is an IP address to be used for the F1 user plane transport. The Tunnel Endpoint Identifier is to be used for the user plane transport between the gNB-CU5C and the gNB-DU5D.

In this example, the ‘UP Transport Layer Information’ information element includes an appropriate indication (‘Shared tunnel indicator’ field) to indicate that the corresponding tunnel is a shared tunnel. It will be appreciated that any other suitable indication or information element or field may be used, e.g. ‘MBS tunnel’, ‘multicast tunnel’, ‘tunnel type: MBS’, ‘tunnel type: shared’, ‘tunnel type: multicast’, and/or the like.

P Transport Layer Information (based on 3GPP TS 38.413, clause 9.3.2.2) This information element is used to provide the NG user plane (NG-U) transport layer information associated with a PDU session (in this case an MBS session) for an NG-RAN node-UPF pair. It corresponds to an IP address and a Tunnel Endpoint Identifier.

In this example, the ‘UP Transport Layer Information’ information element includes an appropriate indication (‘Shared tunnel indicator’ field) to indicate that the corresponding tunnel is a shared tunnel. It will be appreciated that any other suitable indication or information element or field may be used, e.g. ‘MBS tunnel’, ‘multicast tunnel’, ‘tunnel type: MBS’, ‘tunnel type: shared’, ‘tunnel type: multicast’, and/or the like.

Shared Tunnel Setup Request (F1AP)

This message is sent by the central unit of the NG-RAN node (base station5) to the distributed unit to request a shared tunnel for an MBS session that the UE3intends to join. 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. a ‘gNB-CU shared F1AP ID’); an identifier of the distributed unit (e.g. a ‘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 indication may be redundant since the identifiers of the distributed unit and the central unit already indicate that this particular tunnel is not a UE specific tunnel.

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 case of a UE specific tunnel (e.g. ‘gNB-CU UE F1AP ID’ and ‘gNB-DU UE F1AP ID’, respectively). This allows reusing the same tunnel for other UEs to deliver MBS traffic via multicast.

Shared tunnel setup request (NGAP)

This message is sent by the AMF9to the serving base station5to request a shared tunnel for an MBS session that the UE3intends to join. The message, which may be referred to as a ‘Shared NG-U GTP tunnel setup request’ includes the following information: an identifier of the AMF9(e.g. a ‘AMF Shared NGAP ID’); an identifier of the base station5(e.g. a ‘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 indication may be redundant since the identifiers of the distributed unit and the central unit already indicate that this particular tunnel is not a UE specific tunnel.

After the shared F1-U/NG-U tunnel has been established for the first UE3, any other UE3joining the same MBS session can be configured to use the pre-established shared tunnel. This may be achieved by including the identifier of the shared tunnel (TEID) in the MRB configuration part of the UE context setup/modification message or the Initial UE context setup/modification message. Upon reception of the TEID of the shared tunnel, the distributed unit/base station knows that the MBS session will be provided via a shared F1-U/NG-U tunnel.

The following is a description of the relevant steps of a procedure for establishing a shared tunnel for a UE3for receiving MBS traffic (FIG.7) and a procedure for deactivating a shared tunnel (FIG.8), using the signalling messages and information elements described above. It will be appreciated that the procedure illustrated inFIG.7(or a similar procedure) may also be used for associating an already established shared tunnel to the UE3and/or to any further UEs3, if appropriate.

The current procedures for MBS session activation and MBS session deactivation are illustrated in FIGS. 7.2.5.2-1 and 7.2.5.3-1 of 3GPP TS 23.247, respectively.FIG.7is based on FIG. 7.2.5.2-1 (MBS session activation procedure) but the messages have been adapted to support shared tunnels. Note: In this procedure, steps 2 to 10 and steps 11 to 14 can be executed in parallel.

As shown in step 1, session activation is triggered by an MBS specific SMF (denoted ‘MB-SMF11M’). For example, session activation may be triggered upon an application function (AF) requesting the MB-SMF11M to activate an MBS session for a UE3or a user plane function (UPF) receiving multicast data for the UE3and notifying the MB-SMF11M.

The SMF11determines which connected mode UEs3have joined the MBS session and contacts the AMF9of these UEs3(see step8).

If there is no shared tunnel for the given MBS session via the base station5serving a UE3, then a new shared tunnel is set up for the MBS session in steps 10a. Effectively, step10ais a procedure for establishment of shared delivery toward the NG-RAN node. This procedure is based on clause 7.2.1.4 of 3GPP TS23.247 but the messages have been adapted to use the shared tunnel endpoints as described above with reference to option 1 or option 2.

If there is a shared tunnel for the MBS session but the UE3does not use this tunnel, then, in step10b, a PDU Session modification procedure is performed for the UE3to 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 TS23.247. However, the steps have been adapted to use the shared tunnel endpoints as described above with reference to option 1 or option 2.

Once a new shared tunnel has been established for the UE3or the UE3has been configured to join an existing shared tunnel, then the steps 11 to 15 are performed.

FIG.8is based on FIG. 7.2.5.3-1 of 3GPP TS 23.247 (MBS session deactivation procedure). In this case, however, the messages have been adapted to use the shared tunnel endpoints described above with reference to option 1 or option 2.

Beneficially, using these procedures, the nodes involved with the user plane (i.e. the UE, the base station5(CU/DU), and the UPF10) can use an appropriate shared tunnel for multicast delivery of MBS traffic and remove any shared tunnel that is no longer required.

Clause 5.8.2.11 of 3GPP TS 23.501 describes the parameters used for N4 session management. The following is a description of some MBS session parameters that may be used in N4 session management to support the provision of MBS over shared tunnels.

Session management messages are exchanged between the SMF11and the UPF10over the N4 interface. In this system, the N4 interface messages are adapted to include the relevant MBS session parameters as well. For example, when performing handover related signalling for a UE3, the SMF11may provide one or more of the following parameters to the UPF10(together with an associated N4 Session ID):MBS session to add/modify list (the SMF11includes any newly added MBS session in case there is no ongoing MBS session in the target base station) which may include one or more of the following (per MBS session): 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; and DL QoS Flow per TNL Information; andMBS session to remove list (to remove a particular MBS session in case the last UE3has left that MBS session): MBS session ID(s) for each MBS session to be removed.

Effectively, the MBS session to add/modify list information element includes information identifying any MBS session to be added or modified at the UPF10, and the MBS session to remove list information element includes information identifying any MBS session to be removed at the UPF10. It will be appreciated that the provision of information identifying one or more MBS session to be removed is not limited to UE mobility and this information may be provided to the UPF10whenever 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).

Beneficially, using at least some of the above parameters the UPF10is able to keep track of which UE3uses which MBS session(s) and maintain the MBS session(s) for the UE3even after handover, using the correct shared tunnel(s). This approach may be particularly useful in case of Xn based handover from an MBS supporting NG-RAN node (base station5) to another NG-RAN node.

FIG.9illustrates schematically the (F1AP) UE context setup procedure, including the ‘UE Context Setup Request’ and ‘UE Context Setup Response’ messages which may be adapted to include information identifying the shared tunnel and/or a shared tunnel indicator.

FIG.10illustrates schematically the (NGAP) UE context modification procedure, including the ‘UE Context Modification Request’ and ‘UE Context Modification Response’ messages which may be adapted to include information identifying the shared tunnel and/or a shared tunnel indicator.

FIG.11illustrates schematically the details of an exemplary Xn based handover procedure.FIG.11is signalling (timing) diagram based on FIG. 7.2.3.2-1 of 3GPP TS 23.247. However, in this case, the ‘N4 Session Modification’ messages (e.g. in steps 3, 4, 6, or 8) are adapted to include information identifying any MBS session to be added, modified, or removed by the UPF10(e.g. the MBS session to add/modify list and/or MBS session to remove list information elements described above).

For sake of completeness, it will be appreciated that the SMF11may also provide one or more of the following parameters to the UPF10:Packet Detection Rules (PDR) that contain information to classify traffic (PDU(s)) arriving at the UPF10;Forwarding Action Rules (FAR) that contain information on whether forwarding, dropping or buffering is to be applied to a traffic identified by PDR(s);Multi-Access Rules (MAR) that contain information on how to handle traffic steering, switching and splitting for a MA PDU Session;Usage Reporting Rules (URR) contains information that defines how traffic identified by PDR(s) shall be accounted as well as how a certain measurement shall be reported;QoS Enforcement Rules (QER), that contain information related to QoS enforcement of traffic identified by PDR(s);Session Reporting Rules (SRR) that contain information to request the UP function to detect and report events for a PDU session that are not related to specific PDRs of the PDU session or that are not related to traffic usage measurement.Trace Requirements;Port Management Information Container in 5GS; andBridge Information.

Detailed embodiments have been described above. As those skilled in the art will appreciate, a number of modifications and alternatives can be made to the above embodiments whilst still benefiting from the inventions embodied therein. By way of illustration only a number of these alternatives and modifications will now be described.

It will be appreciated that the above described shared tunnel may be provided using the GPRS Tunnelling Protocol (GTP). Thus, the tunnel may also be referred to as a (shared) GTP tunnel or a GTP user plane (GTP-U) tunnel. Although the term ‘shared tunnel’ is used in this description for sake of illustrating the inventive concept, it will be appreciated that a tunnel may be used by a single UE only, in which case it is not shared by other UE (e.g. initially). However, regardless of the number of UEs using a tunnel, by using an appropriate shared tunnel indicator, an MBS tunnel indicator, and/or the like, it is possible to adapt a user plane tunnel for sharing among a plurality of UEs.

In the above description, the FIAP interface and associated messages were used as examples to illustrate the operation of the invention between units of a distributed base station apparatus. However, it will be appreciated that any other suitable interface or messages may be used. Similarly, the NGAP interface and associated messages were used as examples to illustrate the operation of the invention between a node (e.g. a base station apparatus) of an access network (or RAN) and a node of a core network. However, it will be appreciated that any other access network to core network interface or access network to core network messages may be used. It will be appreciated that in other releases the same interfaces and/or messages may have different names than the ones described in the above example.

Whilst a base station of a 5G/NR communication system is commonly referred to as a New Radio Base Station (‘NR-BS’) or as a ‘gNB’ it will be appreciated that they may be referred to using the term ‘eNB’ (or 5G/NR eNB) which is more typically associated with Long Term Evolution (LTE) base stations (also commonly referred to as ‘4G’ base stations). 3GPP TS 38.300 V16.7.0 and 3GPP TS 37.340 V16.7.0 define the following nodes, amongst others:

gNB: node providing NR user plane and control plane protocol terminations towards the UE, and connected via the NG interface to the 5G core network (5GC).

ng-eNB: node providing E-UTRA user plane and control plane protocol terminations towards the UE, and connected via the NG interface to the 5GC.

En-gNB: node providing NR user plane and control plane protocol terminations towards the UE, and acting as Secondary Node in E-UTRA-NR Dual Connectivity (EN-DC).

NG-RAN node: either a gNB or an ng-eNB.

It will be appreciated that the above embodiments may be applied to 5G New Radio and LTE systems (E-UTRAN), and any future generation systems. A base station that supports E-UTRA/4G protocols may be referred to as an ‘eNB’ and a base station that supports NextGeneration/5G protocols may be referred to as a ‘gNBs’. It will be appreciated that some base stations may be configured to support both 4G and 5G protocols, and/or any other 3GPP or non-3GPP communication protocols.

In the above description, the UE, the access network node, and the data network node are described for ease of understanding as having a number of discrete modules (such as the communication control modules). Whilst these modules may be provided in this way for certain applications, for example where an existing system has been modified to implement the invention, in other applications, for example in systems designed with the inventive features in mind from the outset, these modules may be built into the overall operating system or code and so these modules may not be discernible as discrete entities. These modules may also be implemented in software, hardware, firmware, or a mix of these.

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

In the above embodiments, a number of software modules were described. As those skilled in the art will appreciate, the software modules may be provided in compiled or un-compiled form and may be supplied to the UE, the access network node, and the data network node as a signal over a computer network, or on a recording medium. Further, the functionality performed by part or all of this software may be performed using one or more dedicated hardware circuits. However, the use of software modules is preferred as it facilitates the updating of the UE, the access network node, and the data network node in order to update their functionalities.

The above embodiments are also applicable to ‘non-mobile’ or generally stationary user equipment.

The message may comprise a base station to core network protocol message or a base station distributed unit to central unit protocol message.

The message may include a response to a message requesting setting up of the 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 UE context modification (e.g. a UE Context Modification Response or a Shared F1-U GTP Tunnel Modification Response).

The method performed by the base station apparatus may further comprise receiving, from the network node, a request including the information (e.g. a UE Context Setup Request or a UE Context Modification Request).

The request may comprise 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’.

The network node may include at least one of a central unit of the base station apparatus (e.g. gNB-CU) and a core network node for mobility management (e.g. an Access and Mobility Management Function).

The information identifying the tunnel may comprise a Transport Layer Information, which includes a Transport Network Layer (TNL) address and a GPRS Tunnel Endpoint Identifier of the base station apparatus or a distributed unit of the base station apparatus.

At least one of the information identifying the tunnel associated with an MBS session and the information indicating that the tunnel is a shared tunnel may be included in an ‘UP Transport Layer Information’ information element.

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

The information identifying one or more MBS session to be added and/or the information identifying one or more MBS session to be modified may include at least one of the following, for each MBS session to be added/modified: 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): uplink (UL) NG-U user plane Transport Network Layer (TNL) Information; and downlink (DL) QoS Flow per TNL Information.

LIST OF REFERENCES

Although the present invention has been described with reference to the exemplary embodiments, the present invention is not limited to the above. Various changes 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 invention.

A method performed by a base station for providing Multicast and Broadcast Services (MBS), the method comprising:transmitting, to a network node, a message including first information identifying a tunnel associated with an MBS session, wherein the message indicates that the tunnel is a shared tunnel; andreceiving, via the shared tunnel, user plane protocol data unit for the MBS session for transmitting to the UE, upon transmitting the message.

The method according to supplementary note 1, wherein the message includes second information of the MBS session.

The method according to supplementary note 1 or 2, wherein the message includes a base station to core network protocol message or a base station distributed unit to central unit protocol message.

The method according to any one of supplementary notes 1 to 3, wherein the message includes a response to a message requesting setting up of an associated UE context for the UE or a response to a message requesting UE context modification.

The method according to any one of supplementary notes 1 to 4, further comprising receiving, from the network node, a request including the first information.

A method performed by a base station for providing Multicast and Broadcast Services (MBS), the method comprising:receiving, from a network node, a request for setting up for 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; andreceiving, via the shared tunnel, user plane protocol data unit for the MBS session for transmitting to the UE, upon receiving the message.

The method according to supplementary note 6, wherein the request is non-UE-associated signalling.

A method performed by a network node for providing Multicast and Broadcast Services (MBS), the method comprising:receiving, from a base station, a message including first information identifying a tunnel associated with an MBS session, wherein the message indicates that the tunnel is a shared tunnel; andtransmitting, via the shared tunnel, user plane protocol data unit for the MBS session to a user equipment (UE), upon receiving the message.

The method according to supplementary note 8, wherein the network node includes at least one of a central unit of the base station and a core network node for mobility management.

A method performed by a network node the method comprising:transmitting, to a base station for providing Multicast and Broadcast Services (MBS), a request for setting 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;wherein the shared tunnel is adapted to be used, by the base station, for transmitting user plane protocol data unit for the MBS session.

The method according to any one of supplementary notes 1 to 10, wherein the first information includes a Transport Layer Information and a Transport Network Layer (TNL) address of the base station or a distributed unit of the base station.

The method according to supplementary note 11, wherein the first information is included in an ‘UP Transport Layer Information’ information element.

The method according to any one of supplementary notes 1 to 12, wherein the shared tunnel includes at least one of:a user plane tunnel between a central unit and a distributed unit of the base station, anda user plane tunnel between a core network node and the base station.

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: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 including at least one of:information identifying one or more MBS session to be added at the second core network node;information identifying one or more MBS session to be modified at the second core network node; andinformation identifying one or more MBS session to be removed at the second core network node.

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:receiving, from a first core network node, a session management message including at least one of:information identifying one or more MBS session to be added at the second core network node;information identifying one or more MBS session to be modified at the second core network node; andinformation identifying one or more MBS session to be removed at the second core network node.

The method according to supplementary note 14 or 15, wherein the information identifying one or more MBS session to be added and/or the information identifying one or more MBS session to be modified includes at least one of the following, for each MBS session to be added/modified: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);uplink (UL) NG-U user plane Transport Network Layer (TNL) Information; anddownlink (DL) QoS Flow per TNL Information.

A base station for providing Multicast and Broadcast Services (MBS), comprising:means for transmitting, to a network node, a message including first information identifying a tunnel associated with an MBS session, wherein the message indicates that the tunnel is a shared tunnel; andmeans for receiving, via the shared tunnel, user plane protocol data unit for the MBS session for transmitting to the UE, upon transmitting the message.

A base station for providing Multicast and Broadcast Services (MBS), the base station apparatus comprising:means for receiving, from a network node, a request for setting 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; andmeans for receiving, via the shared tunnel, user plane protocol data unit for the MBS session for transmitting to the UE, upon receiving the message.

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, wherein the message indicates that the tunnel is a shared tunnel; andmeans for transmitting, via the shared tunnel, user plane protocol data unit for the MBS session to a user equipment (UE), upon receiving the message.

A network node comprising:means for transmitting, to a base station for providing Multicast and Broadcast Services (MBS), a request for setting 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;wherein the shared tunnel is adapted to be used, by the base station, for transmitting user plane protocol data unit for the MBS session.

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 including at least one of:information identifying one or more MBS session to be added at the second core network node;information identifying one or more MBS session to be modified at the second core network node; andinformation identifying one or more MBS session to be removed at the second core network node.

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 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 session to be added at the second core network node;information identifying one or more MBS session to be modified at the second core network node; andinformation identifying one or more MBS session to be removed at the second core network node.

This application is based upon and claims the benefit of priority from United Kingdom patent application No. 2118978.2, filed on Dec. 23, 2021, the disclosure of which is incorporated herein in its entirety by reference.

REFERENCE SIGNS LIST