Access network node, user equipment, method of access network node, and method of user equipment

Abstract

A method for an access network node is provided. The method includes transmitting, to a User Equipment (UE), a first message that includes an inquiry about the UE's ability to receive Multicast / Broadcast Service (MBS) when the UE is in a Radio Resource Control (RRC)_INACTIVE state, and receiving, from the UE, a second message that includes a list of one or more MBS sessions that the UE can support when the UE is in the RRC_INACTIVE state if the UE has information identifying at least one MBS available to the UE.

Description

Technical Field

[0001] The present disclosure relates to a wireless communication system and a device thereof that operate according to the specifications of the 3rd Generation Partnership Project (3GPP (registered trademark)), specifications equivalent thereto, or derivative specifications thereof. The present disclosure has a non-specific and non-exclusive relevance to improvements in session management of multimedia broadcast sessions that operate according to so-called "5G" (or "next generation") systems and the like.

Background Art

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

[0003] Under the 3GPP specifications, a base station (e.g., a 4G "eNB" or a 5G "gNB") is a node for a communication device (User Equipment, i.e., "UE") to connect to the core network and communicate with other communication devices or remote servers. For simplicity, this application uses the terms base station or access network node to refer to any such base station. For simplicity, this application uses the terms mobile device, user device, or UE to refer to any communication device that can connect to the core network via one or more base stations.

[0004] The communication device may be, for example, a mobile communication device such as a mobile phone, smartphone, user equipment, personal digital assistant, laptop / tablet computer, web browser, e-book reader, and / or the like. Such mobile (or generally fixed) devices are typically operated by a user. However, the 3GPP specifications also enable connecting so-called "Internet of Things" (IoT) devices (e.g., Narrow-Band IoT (NB-IoT) devices) to the network, which typically include various measurement devices, telemetry devices, monitoring systems, tracking and tracing devices, in-vehicle safety systems, vehicle maintenance systems, road sensors, digital billboards, point-of-sale (POS) terminals, and remote control systems and other automated devices. Effectively, the Internet of Things is a network of devices (or "things") equipped with appropriate electronic devices, software, sensors, network connectivity, and / or the like, which enables these devices to collect data and exchange data with each other and with other communication devices. It will be understood that IoT devices are sometimes also referred to as Machine-Type Communication (MTC) communication devices or Machine-to-Machine (M2M) communication devices.

[0005] For simplicity, this application often refers to mobile devices in the description, but the technology described can be implemented on any communication device (mobile and / or generally fixed) that can connect to a communication network to send / receive data, whether the communication device is controlled by human input or by software instructions stored in memory.

[0006] One of the recent features developed for the existing 5G framework is called Multicast and Broadcast Services (MBS). This feature aims to enhance the performance of 5G New Radio and 5G Core Networks to deploy various multicast and broadcast services in a reliable, low-latency, resource-efficient, and large-scale manner. 3GPP is currently specifying the details of MBS for media delivery via mobile broadband networks. Some of the use cases identified as benefiting from MBS include public safety and mission-critical services, Vehicle to Everything (V2X) applications, IPTV, live video, software delivery, and IoT applications to various smartphones, tablets, vehicles, and other mobile (or fixed) devices. MBS is designed to use the existing (or already specified) 3GPP infrastructure, but can provide more efficient delivery of multicast / broadcast traffic than unicast communication using the same infrastructure. Details of the architectural enhancements for MBS can be found in 3GPP Technical Specification (TS) 23.247 V17.2.0.

[0007] To facilitate resource-efficient multicast / broadcast service delivery, 3GPP developed NR broadcast / multicast as part of Release 17 (Rel-17) of the NR standard with the aim of enabling common MBS services over 5G telecommunications networks. More specifically, the following two delivery modes for MBS were agreed upon for Rel-17 MBS.

[0008] Delivery mode 1 (multicast only) that can handle higher QoS services, and Delivery mode 2 (broadcast only) focused on lower QoS services.

[0009] Rel-17 MBS provides the basic functions to support MBS services, but it is recognized that it is necessary to improve resource efficiency and capacity and address other issues to meet the stringent use cases proposed for MBS.

[0010] For example, according to Rel-17, the Radio Access Network (RAN) specifies only multicast transmission for UEs in the RRC connected state (sometimes called the RRC_CONNECTED mode). Therefore, UEs in other RRC connection states, namely the RRC inactive state and the RRC idle state (sometimes called the RRC_INACTIVE mode and the RRC_IDLE mode respectively), do not receive such transmissions. This situation may not fully meet the requirements of, for example, mission critical services, especially in an environment where a cell serves many UEs (e.g., according to TR 23.774). Furthermore, keeping the UE always in the RRC connected state is not efficient from the perspective of the base station as well as from the perspective of the UE (e.g., regarding resource usage, power, etc.).

[0011] The presenters recognize that there are several problems with the current approach for providing the MBS function, particularly from the perspective of UE RRC connection state transition and UE mobility. Therefore, the present disclosure aims to provide a method and related apparatus for addressing (at least in part) or at least mitigating the above problems.

Prior Art Documents

Patent Documents

[0012]

Patent Document 1

Patent Document 2

Non-Patent Documents

[0013]

Non-Patent Document 1

Non-Patent Document 2

Non-Patent Document 3

Non-Patent Document 4

Non-Patent Document 5

Non-Patent Document 6

Non-Patent Document 7

Non-Patent Document 8

Non-Patent Document 9

Non-Patent Document 10

Summary of the Invention

Problems to be Solved by the Invention

[0014] The present disclosure aims to provide an apparatus and a related method that at least partially contribute to meeting one or more of the above-mentioned needs.

Means for Solving the Problem

[0015] According to one aspect, a method for an access network node is provided, the method comprising: transmitting a first message indicating the capabilities of user equipment (UE) that receives a multicast / broadcast service (MBS) to UEs in the radio resource control (RRC)_INACTIVE state; receiving, from a UE in the RRC_INACTIVE state, a second message indicating one or more MBS sessions that the UE in the RRC_INACTIVE state can support, if the UE has information identifying at least one MBS available to the UE; while the UE is in the RRC_INACTIVE state, providing at least one MBS corresponding to one or more MBS sessions to the UE.

[0016] According to another aspect, a method for an access network node having a central unit and a distributed unit is provided, the method comprising: receiving, by the central unit, an indication of at least one multicast / broadcast service (MBS) session accessible by a user equipment (UE) in the radio resource control (RRC)_INACTIVE state from a core network node; transmitting, by the central unit, an indication to the distributed unit; receiving, by the central unit, a response from the distributed unit; transmitting, by the distributed unit, an indication to the UE and including.

[0017] According to another aspect, a method for a first access network node is provided, the method comprising: transmitting information including an ongoing Multicast / Broadcast Service (MBS) session list of a second access network node adjacent to the first access network node, or an adjacent cell / frequency list of at least one adjacent access network node having at least one ongoing MBS session, to a User Equipment (UE) served by the first access network node comprising.

[0018] According to another aspect, a method performed by a source access network node for handover of a User Equipment (UE) to a target access network node is provided, the method comprising: transmitting a conditional handover request message including Multicast / Broadcast Service (MBS) configuration information for the UE to the target access network node comprising.

[0019] According to another aspect, a method performed by a target access network node for handover of a User Equipment (UE) from a source access network node is provided, the method comprising: receiving a conditional handover request message including Multicast / Broadcast Service (MBS) configuration information for the UE from the source access network node; and establishing an MBS session with the core network when there is no ongoing MBS session in the target access network node comprising.

[0020] According to another aspect, a method for a core network node is provided, the method comprising: sending, to a further core network node, a message comprising an indication of one or more multicast / broadcast service (MBS) sessions accessible to a user equipment (UE) in a radio resource control (RRC)_INACTIVE state comprising.

[0021] According to another aspect, a method for a core network node is provided, the method comprising: sending, to an access network node, a message comprising an indication of one or more multicast / broadcast service (MBS) sessions accessible to a user equipment (UE) in a radio resource control (RRC)_INACTIVE state comprising.

[0022] According to another aspect, a method for a user equipment (UE) is provided, the method comprising: receiving, from an access network node, a first message indicating the capabilities of the UE in a radio resource control (RRC)_INACTIVE state to receive a multicast / broadcast service (MBS); and sending, to the access network node, a second message indicating one or more MBS sessions that the UE in the RRC_INACTIVE state can support, based on information identifying at least one MBS available to the UE Receiving, while the UE is in the RRC_INACTIVE state, at least one MBS corresponding to one or more MBS sessions including.

[0023] According to another aspect, a method for a User Equipment (UE) is provided, the method comprising Receiving, from a distributed unit of an access network node, an indication of one or more Multicast / Broadcast Service (MBS) sessions accessible to a Radio Resource Control (RRC)_INACTIVE state UE including.

[0024] According to another aspect, a method for a User Equipment (UE) is provided, the method comprising Receiving, from a first access network node, information including an ongoing Multicast / Broadcast Service (MBS) session list of a second access network node adjacent to the first access network node, or an adjacent cell / frequency list of at least one adjacent access network node having at least one ongoing MBS session including.

[0025] According to another aspect, an access network node is provided, the access network node comprising means for transmitting, to a Radio Resource Control (RRC)_INACTIVE state UE, a first message indicating the capabilities of a User Equipment (UE) that receives Multicast / Broadcast Service (MBS) means for receiving, from a UE, a second message indicating one or more MBS sessions that the UE in the RRC_INACTIVE state can support when the UE has information identifying at least one MBS available to the UE, While the UE is in the RRC_INACTIVE state, at least one MBS corresponding to one or more MBS sessions is provided to the UE.

[0026] According to another aspect, an access network node having a central unit and a distributed unit is provided, The central unit is means for receiving, from a core network node, an indication of at least one multicast / broadcast service (MBS) session accessible to a user equipment (UE) in a radio resource control (RRC)_INACTIVE state, means for sending an indication to the distributed unit, means for receiving a response from the distributed unit and comprising The distributed unit is means for sending an indication to the UE and comprising

[0027] According to another aspect, a first access network node is provided, and the access network node is means for sending, to a user equipment (UE) served by the first access network node, information including a list of ongoing multicast / broadcast service (MBS) sessions of a second access network node adjacent to the first access network node, or a list of adjacent cells / frequencies of at least one adjacent access network node having at least one ongoing MBS session and comprising

[0028] According to another aspect, a source access network node is provided for handover of a user equipment (UE) to a target access network node, and the source access network node means for transmitting a conditional handover request message including multicast / broadcast service (MBS) configuration information for the UE to the target access network node is provided with.

[0029] According to another aspect, a target access network node is provided for handover of a user equipment (UE) from a source access network node, and the target access network node means for receiving a conditional handover request message including multicast / broadcast service (MBS) configuration information for the UE from the source access network node, and means for establishing an MBS session with the core network when there is no ongoing MBS session in the target access network node is provided with.

[0030] According to another aspect, a core network node is provided, and the core network node means for transmitting a message including an indication of one or more multicast / broadcast service (MBS) sessions accessible by a user equipment (UE) in the radio resource control (RRC)_INACTIVE state to a further core network node is provided with.

[0031] According to another aspect, a core network node is provided, and the core network node Means for transmitting a message including an indication of one or more multicast / broadcast service (MBS) sessions accessible to a user equipment (UE) in a Radio Resource Control (RRC)_INACTIVE state to an access network node comprises.

[0032] According to another aspect, a user equipment (UE) is provided, and the UE means for receiving, from an access network node, a first message indicating the capabilities of a UE in a Radio Resource Control (RRC)_INACTIVE state for receiving a multicast / broadcast service (MBS); and means for transmitting, to the access network node, a second message indicating one or more MBS sessions that the UE in the RRC_INACTIVE state can support, based on information identifying at least one MBS available to the UE; and receiving at least one MBS corresponding to one or more MBS sessions while the UE is in the RRC_INACTIVE state includes.

[0033] According to another aspect, a user equipment (UE) is provided, and the UE means for receiving, from a distributed unit of an access network node, an indication of one or more multicast / broadcast service (MBS) sessions accessible to a UE in a Radio Resource Control (RRC)_INACTIVE state comprises.

[0034] According to another aspect, a User Equipment (UE) is provided, and the UE means for receiving, from a first access network node, information including a list of ongoing Multicast / Broadcast Service (MBS) sessions of a second access network node adjacent to the first access network node, or a list of adjacent cells / frequencies of at least one adjacent access network node having at least one ongoing MBS session is provided.

[0035] Each feature disclosed and / or illustrated in this specification (where the term includes the claims) may be incorporated into the present disclosure independently of (or in combination with) any other disclosed and / or illustrated feature. Without limitation, in particular, any feature of any claim dependent on a particular independent claim may be introduced into that independent claim in any combination or individually.

Advantages of the Invention

[0036] According to the present disclosure, it is possible to provide a method for a user equipment, a method for an access network node, a user equipment, and an access network node.

[0037] Hereinafter, embodiments of the present disclosure will be described by way of example with reference to the accompanying drawings.

Brief Description of the Drawings

[0038]

Figure 1

Figure 2

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DETAILED DESCRIPTION OF THE INVENTION

[0039] <SUMMARY> FIG. 1 schematically illustrates a mobile (cellular or wireless) telecommunications system 1 to which embodiments of the present disclosure may be applied.

[0040] In System 1, users of mobile devices 3 (UEs) can communicate with each other and with other users via a base station 5 and other access network nodes that form a radio access network (RAN). Through these access network nodes, the UEs communicate with the associated core network 7 using an appropriate 3GPP radio access technology (RAT), e.g., using Evolved Universal Terrestrial Radio Access (E-UTRA) and / or 5G RAT. It will be understood that several base stations 5 form an (radio) access network, i.e., a (R)AN. As will be understood by those skilled in the art, FIG. 1 shows, for illustrative purposes, four mobile devices 3 and one base station (included in NG-RAN 5 in FIG. 1), but the system will typically include other base stations / (R)AN nodes and / or mobile devices (UEs) when implemented.

[0041] Each base station 5 controls 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 station 5 that supports the next-generation / 5G protocol may be referred to as a "gNB" and may form part of the NG-RAN. It will be understood that some base stations 5 may be configured to support both 4G and 5G, and / or any other 3GPP or non-3GPP communication protocol.

[0042] The mobile device 3 and its serving base station 5 are connected via a suitable air interface (e.g., the so-called "NR" air interface, "Uu" interface, and / or the like). Adjacent base stations 5 are connected to each other via a suitable inter-base station interface (such as the so-called "Xn" interface, "X2" interface, and / or the like, not shown in FIG. 1). The base station 5 is also connected to the core network node via a suitable interface (such as the so-called "NG-U" interface (in the case of the user plane), the so-called "NG-C" interface (in the case of the control plane), and / or the like).

[0043] The core network 7 (e.g., EPC in the case of LTE or NGC in the case of NR / 5G) typically includes logical nodes (or "functions") for supporting communications in the telecommunication system 1, especially for subscriber management, mobility management, billing, security, and call / session management. For example, the core network 7 of a "next-generation" / 5G system includes user plane entities and control plane entities such as one or more Control Plane Functions (CPF) and one or more User Plane Functions (UPF) 8-3. Examples of CPF include the so-called Access and Mobility Management Function (AMF) 8-1 in 5G, or the Mobility Management Entity (MME) in 4G that is responsible for handling connection and mobility management tasks of the mobile device 3. Another exemplary CPF is the so-called Session Management Function (SMF) 8-2 that is responsible for handling communication sessions of the mobile device 3, such as session establishment, modification, and release.

[0044] In addition to other nodes / functions not described in this book, the core network 7 may further include a Multicast / Broadcast Session Management Function (MB-SMF) 8-4, a Multicast / Broadcast User Plane Function (MB-UPF) 8-5, a Multicast / Broadcast Service Function (MBSF) 8-6, a Multicast / Broadcast Service Transport Function (MBSTF) 8-7, a Network Exposure Function (NEF) 8-8, an Application Function (AF) 8-9, a Policy Control Function (PCF) 8-10, a Network Repository Function (NRF) 8-11, and a Unified Data Management (UDM) entity 8-12. Some service-based interfaces are illustrated in Figure 1 and are specifically as follows.

[0045] Nmbsmf: Service-based interface presented by MB-SMF. Npcf: Service-based interface presented by PCF. Namf: Service-based interface presented by AMF. Nnef: Service-based interface presented by NEF. Nnrf: Service-based interface presented by NRF. Nudm: Service-based interface presented by UDM.

[0046] Furthermore, several reference points are illustrated in FIG. 1, specifically as follows.

[0047] N2: The reference point between the NG-RAN and the AMF. N3: The reference point between the NG-RAN and the UPF. N3mb: The reference point between the RAN and the MB-UPF. N4mb: The reference point between the MB-SMF and the MB-UPF. N6mb: The reference point between the MB-UPF and the AF / AS. N19mb: The reference point between the UPF and the MB-UPF. Nmb1: The reference point between the MB-SMF and the MBSF. Nmb2: The reference point between the MBSF and the MBSTF. Nmb9: The reference point between the MB-UPF and the MBSTF. Nmb10: The reference point between the MBSF and the AF.

[0048] The core network 7 is connected to a data network (not shown) such as the Internet or a similar network based on the Internet Protocol (IP) (via the UPF 8-3).

[0049] Various network operators deploy their own base stations 5 and associated core networks 7 to provide services in a given area (e.g., a country). Each network may be referred to as a Public Land Mobile Network (PLMN) and is uniquely identified by its PLMN identifier (PLMN ID). The PLMN ID consists of a Mobile Country Code (MCC) and a Mobile Network Code (MNC). Each subscriber (i.e., UE 3) belongs to a PLMN and uses the services of the associated core network 7 and access network (i.e., base station 5).

[0050] For example, a Multicast and Broadcast Services (MBS) function that provides resource - efficient transmission to multiple end - users that require reception of the same service can be provided to the UE 3 via the serving base station 5 and associated core network nodes such as the UPF 8 - 3 and the SMF 8 - 2. The UPF 8 - 3 may be a UPF specific to MBS, in which case it may be referred to as the MB - UPF 8 - 5 (e.g., specialized for the provision of the MBS function). Similarly, the SMF 8 - 2 may be an SMF specific to MBS, in which case it may be referred to as the MB - SMF 8 - 4. However, it will be understood that any suitable UPF / SMF may be used for MBS.

[0051] Each UE 3 interested in MBS monitors the system information broadcast by the base station 5 and determines the resources used for the associated control channel and data channel (MCCH and MTCH respectively). The base station 5 also broadcasts a respective identifier (MBS session ID or Temporary Mobile Group Identity, TMGI) for each MBS session provided in its cell. When the UE 3 finds its PLMN ID in the system information of a given cell, access to that cell is permitted.

[0052] The TMGI is an MBS session identifier that uniquely identifies a specific MBS service. The TMGI has three parts, namely, the MBMS service ID part, the Mobile Country Code (MCC) part, and the Mobile Network Code (MNC) part. 3GPP TS 38.413, Section 9.3.1 defines the three parts of the TMGI as follows. 1) The MBMS service ID consists of 3 octets. The MBMS service ID is composed of 6-digit fixed-length hexadecimal numbers from 000000 to FFFFFF. The MBMS service ID uniquely identifies the MBMS bearer service within the PLMN. The structure of the MBMS service ID for services in the reception-only mode is defined in 3GPP TS 24.116. 2) The Mobile Country Code (MCC) consisting of 3 digits. The MCC uniquely identifies the country where the Broadcast-Multicast Service Centre (BM-SC) is located. However, the MCC value 901 does not identify any country and is globally allocated by the International Telecommunication Union (ITU). 3) The Mobile Network Code (MNC) consisting of 2 or 3 digits (depending on the allocation to the PLMN by the national numbering plan administrator). The MNC identifies the PLMN to which the BM-SC belongs. However, the MNC value 56 when the MCC value is 901 does not identify any PLMN. For details on the operation of the TMGI, refer to 3GPP TS 23.246.

[0053] 3GPP TS 23.003 defines each part of the PLMN ID as follows. 1) The Mobile Country Code (MCC) consisting of 3 digits. The MCC uniquely identifies the country where the mobile subscription is located. 2) A two- or three-digit Mobile Network Code (MNC) (depending on the allocation to a PLMN by the national numbering plan administrator) for use in 3GPP networks. The MNC identifies the home PLMN of a mobile subscription within a country or, together with the MCC and the Network Identifier (NID), identifies a Stand-alone Non-Public Network (SNPN) of a mobile subscription. The length of the MNC (two or three digits) depends on the value of the MCC.

[0054] The list of PLMNs supported in a cell is indicated in the relevant system information. Specifically, the System Information Block type 1 (SIB1) includes the list of supported PLMNs within the plmn-IdentityInfoList information element (which is included in the so-called CellAccessRelatedInfo information element of SIB1).

[0055] The MBS session establishment procedure is standardized by 3GPP in TS 23.247. Specifically, section 7.2.1.3 defines the current procedure for participating in a multicast session and the related session establishment procedure. In addition, the multicast session management procedure is defined in 3GPP TS 38.413 (by section 8.18). The content of these documents is incorporated herein by reference.

[0056] As shown in Figure 1, there is one UE 3-1 connected to the NG-RAN 5, and a group of three UEs are also each connected to the NG-RAN 5. UE 3-1 receives the data of its MBS session in a Point-To-Point (PTP) manner, and the group of UEs 3-2 receives the data of its MBS session in a Point-To-Multipoint (PTM) manner.

[0057] However, as described above, it is necessary to address some issues regarding the current MBS session management procedure. In particular, the above procedure is currently only applicable to UEs in the RRC connected state.

[0058] Figure 2 illustrates further details of the core network 7 and also shows the interfaces between the respective network nodes. As can be seen from the figure, the core network 7 typically includes, among other things (as described above with respect to FIG. 1), 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 coupled to data networks (DNs) 8-14 such as the Internet or a similar network based on the Internet Protocol (IP) (via the UPF). The core network 7 may also be connected to an Operations and Maintenance (OAM) function (not shown).

[0059] The following outlines solutions to the problems of current MBS session provision and management. However, first, the considerations of some of the nodes forming part of System 1 will be described.

[0060] <User Equipment (UE)> Figure 3 is a block diagram illustrating the main components of the mobile device (UE) 3 shown in FIGS. 1 and 2. As shown, UE 3 includes a transceiver circuit 31 that operates to transmit signals to and receive signals from one or more connected nodes via one or more antennas 33. Although not necessarily shown in FIG. 3, UE 3 of course has all the normal functions of a conventional mobile device (such as user interface 35), which may be provided by any one or any combination of hardware, software, and firmware as required. The controller 37 controls the operation of UE 3 according to software stored in the memory 39. The software may be pre-installed in the memory 39 and / or may be 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 communication control module 43, and an MBS module 45.

[0061] The communication control module 43 is responsible for processing (generating / transmitting / receiving) signaling messages and uplink / downlink data packets between UE 3 and other nodes including (R)AN node 5 and core network nodes. The signaling may include RRC signaling to / from (R)AN node 5 and / or NG-C / NG-U signaling to / from core network 7 (via RAN).

[0062] The MBS module 45 is responsible for processing signaling related to multimedia broadcast services.

[0063] <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 (such as mobile device 3) via one or more antennas 53, and a network interface 55 for transmitting signals to the core network 7 and neighboring base stations and receiving signals from the core network 7 and neighboring base stations. The base station 5 includes a controller 57 for controlling the operation of the base station 5 according to software stored in the memory 59. The software may be pre-installed in the memory 59 and / or may be downloaded, for example, via the telecommunication 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 typically also includes a base station-base station interface section (such as Xn and / or the like) and a core network interface section (such as NG-C / NG-U / N2 / N3).

[0064] The communication control module 63 is responsible for processing (generating / transmitting / 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 (such as non-access stratum, radio resource control, system information, paging, and / or the like) for managing the operation of the mobile device 3. The signaling may include signaling for configuring the UE 3 to receive an MBS session and signaling for configuring other nodes to provide an MBS session. It will be understood that the communication control module 63 may include a plurality of sub-modules (or "layers") to support specific functions. For example, the communication 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, and the like.

[0065] In the 5G architecture, the internal structure of a base station (gNB or en-gNB) can be divided into two parts known as the Central Unit (CU) and the Distributed Unit (DU), which are connected by the F1 interface. In this "split" architecture, typically the "upper" CU layer (not necessarily or exclusively, for example), PDCP, and typically the "lower" DU layer (not necessarily or exclusively, for example, RLC / MAC / PHY) can be implemented separately. Thus, for example, in each of the gNBs, while the lower layer DU functions are held locally, the upper layer CU functions of several gNBs can be implemented centrally (e.g., by a single processing unit, or in a cloud-based or virtualized system).

[0066] As shown in FIG. 5, when the base station 5 includes a distributed base station (gNB or en-gNB), the network interface 55 also includes an E1 interface and an F1 interface (F1-C for the control plane and F1-U for the user plane) for transmitting signals between the respective functions of the distributed base station. In this case, the software stored in the base station 5 also includes at least one of the gNB-CU-CP module 5C, the gNB-CU-UP module 5U, and the gNB-DU module 5D. If present, the gNB-CU-CP module 5C hosts the control plane portion of the RRC layer and the PDCP layer of the distributed base station (gNB or en-gNB). If present, the gNB-CU-UP module 5U hosts the user plane portion of the PDCP layer and the 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 base station (gNB or en-gNB).

[0067] The central unit (e.g., 5C and / or 5U) may be implemented and physically located together with the base station, or may be implemented remotely as a single physical element, or as a cloud-based system or a virtualized system, which would be understood by those skilled in the art. It will also be understood that a single central unit may serve multiple base stations 5.

[0068] <Core network node> Figure 6 is a block diagram illustrating the main components of the core network node (e.g., AMF 8-1, SMF 8-2, UPF 8-3, etc.) shown in FIGS. 1 and 2. As shown, the core network node includes a transceiver circuit 71 that operates to transmit and receive signals (directly or indirectly) to and from other network nodes via a network interface 75. The signals may be transmitted to and received from one or more UEs 3 via the base station 5 or other (R)AN nodes as required. The network interface 75 typically includes an appropriate base station interface (such as S1 / NG-C / NG-U, etc.). The controller 77 controls the operation of the core network node according to software stored in the memory 79. The software may be pre-installed in the memory 79 and / or downloaded, for example, via the telecommunication 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 any MBS module 85.

[0069] The communication control module 83 is responsible for handling (generating / transmitting / receiving) signaling between the core network node and other nodes such as the UE 3, (R)AN nodes, and other core network nodes.

[0070] When present, for example, within the MB-SMF 8-4 or the MB-UPF 8-6, the MBS module 85 is responsible for processing signaling related to multimedia broadcast services (control signaling and / or MBS traffic). The signaling may include signaling related to the provision of MBS sessions via the RAN / base station, and signaling for configuring other nodes for providing MBS sessions via the RAN / base station.

[0071] <Detailed Description> As described above, there are several issues in MBS session management. The following detailed description shows some solutions to these issues.

[0072] 1. RRC_INACTIVE Mode Configuration According to Rel-17 MBS, when an MBS session is activated, the RAN node 5 sends a paging message containing a list of TMGIs that identify each available MBS session via the RAN node 5. If the UE 3 is interested in an MBS session with a TMGI on the list, the current standard specifies that the UE 3 must transition to the RRC_CONNECTED mode in order to receive MBS transmissions. However, a UE operating according to the latest version (Release 18) of the 3GPP NR standard can be in any one of three possible RRC modes (connected state) with its serving base station:

[0073] 1) RRC_CONNECTED, 2) RRC_INACTIVE, or 3) RRC_IDLE.

[0074] The RRC_INACTIVE state is a state in which the UE can quickly return to the RRC_CONNECTED state, and it is proposed that the UE should be able to receive MBS transmissions while in the RRC_INACTIVE state (however, there is no normal high service reliability guaranteed when in the RRC_CONNECTED state and MBS services are permitted). Therefore, if UE 3 can transition to the RRC_INACTIVE mode, if the MBS service permits the UE to access the MBS service while in the RRC_INACTIVE mode, the UE does not need to transition to the RRC_CONNECTED mode. Since resources can be saved on both the network side and the UE side, the fact that the UE does not transition to / continue in the RRC_CONNECTED mode is mutually beneficial for the network and the UE.

[0075] In this regard, FIG. 7 illustrates the procedure between UE 3 of the telecommunication system 1 and a RAN node 5 (such as a gNB), by which the network determines the ability of UE 3 that supports the RRC_INACTIVE mode configuration in the context of the MBS session. In step 1, the RAN node 5 sends an inquiry to determine the ability of the UE to receive MBS in the RRC_INACTIVE mode. (Sometimes called a UE RRC_INACTIVE support inquiry) This inquiry can be sent in a dedicated RRC message (e.g., UEcapablityenquiry, RRCSetupComplete, or another suitable message), in a paging message, in a System Information Block (SIB), or in signaling on a multicast control channel (e.g., MBMS Control Channel (MCCH), MBS Control Channel (MCCH), etc.).

[0076] In step 2, UE 3 reports whether it can support the RRC_INACTIVE state. This response may be referred to as the UE RRC_INACTIVE support report and may also include a list of MBS sessions that the UE is interested in receiving. Upon receiving this information, the network can beneficially configure RRC_INACTIVE mode support for the UE and manage the relevant MBS sessions for the UE considering the received report.

[0077] If UE 3 does not need to transition to the RRC_CONNECTED state to receive MBS transmissions, changes to the current procedure are required to notify UE 3.

[0078] The first option is to associate an indication with each TMGI in the TMGI list broadcast by RAN node 5. If this indication is set to, for example, "yes", then when the UE desires to receive its MBS transmission, a UE operating according to the latest version of the standard (i.e., a Release 18 (Rel-18) UE) will transition to the RRC_CONNECTED mode, while if this indication is set to, for example, "no", the UE will not transition to the RRC_CONNECTED mode when it desires to receive its MBS transmission. The structure of the modified paging message can take the following form.

[0079] Paging::=SEQUENCE { Paging-v1700-IEs::=SEQUENCE { pagingRecordList-v1700 PagingRecordList-v1700 OPTIONAL,--Need N pagingGroupList-r17 PagingGroupList-r17 OPTIONAL, } PagingGroupList-r18::=SEQUENCE(SIZE(1..maxNrofPageGroup-r18))OF MBSService MBSService ::= SEQUENCE { TMGI RRCCONNECTEDINDICATION - R18 }

[0080] Therefore, in this case, this indication instructs whether to permit the UE to receive the corresponding MBS service in the RRC_INACTIVE state, so the UE operating in the RRC_INACTIVE state can determine whether it needs to transition to the RRC_CONNECTED state based on one or more indications of one or more MBS services it wants to receive.

[0081] According to an alternative option, the UE may instead be configured not to transition to the RRC_CONNECTED mode even when the paging message contains the TMGI that the UE is interested in.

[0082] 2. RRC State Transition The MBS - capable UE can transition from the RRC_CONNECTED state to the RRC_INACTIVE state, for example, to save power (by minimizing the signaling overhead involved in keeping the UE in the RRC_CONNECTED state) and increase the capacity of the serving cell.

[0083] Similarly, an MBS-capable UE can transition from the RRC_INACTIVE state to the RRC_CONNECTED state when the UE moves to the edge of the serving cell and the network establishes another point-to-point (PTP) segment of the MBS Radio Bearer (MRB) to enhance the reliability of the MBS service received by the UE. Further, if the UE is ready to reselect an adjacent cell but the adjacent cell operates according to an older release standard and thus does not support the MBS service in the RRC_INACTIVE state (e.g., when the adjacent RAN node operates according to Release 17), the UE needs to transition to the RRC_CONNECTED state to maintain the MBS service when selecting the adjacent cell.

[0084] One way to control these issues is for the RAN node 5 to configure the RRC_INACTIVE state UE with the StateTransitConfig parameter, which sets the RRC state transition thresholds used to control the transition between the RRC_INACTIVE state and the RRC_CONNECTED state (detailed below). The StateTransitConfig parameter can be indicated to the UE in the SIB, on the multicast control channel (e.g., MCCH), or by the paging message.

[0085] Correspondingly, when the UE is instead in the RRC_CONNECTED state, the StateTransitConfig parameter may be configured by the RAN node 5 and provided to the UE by dedicated RRC signaling. If the UE has already received the StateTransitConfig parameter in the SIB, on the MCCH, or by the paging message (i.e., if the UE received this parameter when it was in the RRC_INACTIVE state), the StateTransitConfig parameter provided by the dedicated RRC signaling takes precedence, thereby overwriting the StateTransitConfig parameter received when the UE was in the RRC_INACTIVE state.

[0086] The thresholds included in the StateTransitConfig parameter may include the following conditions. Conditions for RRC_CONNECTED to RRC_INACTIVE RSRP>RSRPConnectedtoInactivethres RSRQ>RSRQConnectedtoInactivethres Conditions for RRC_INACTIVE to RRC_CONNECTED RSRP<RSRPInactivetoConnectedthres RSRQ<RSRQInactivetoConnectedthres Here, RSRP is the reference signal received power, and RSRQ is the reference signal received quality. These are the measured values of the received signals measured by the UE and are well-known to those skilled in the art.

[0087] Since the StateTransitConfig parameters can be associated with each TMGI, the requirements for transitioning between RRC states can vary depending on the MBS services received by the UE. The StateTransitConfig parameters can be communicated to the UE in a message that carries a configuration (such as RRC_INACTIVE-SUPPORTIVE-configuration). The structure of such a message can take the following form.

[0088] RRC_INACTIVE-SUPPORTIVE-configuration::=SEQUENCE { MBSservice TMGI StateTransitConfig }

[0089] Next, refer to further embodiments for controlling RRC state transitions in the context of split MRBs (MBS Radio Bearers). In this regard, when the reference signal received power (RSRP) / reference signal received quality (RSRQ) in a point-to-multipoint (PTM) segment does not meet the configured threshold, it may be beneficial for the UE to transition from the RRC_INACTIVE state to the RRC_CONNECTED state in order to ensure the reliability of the desired MBS services. To facilitate this state transition, the UE establishes an RRC connection to the network and can notify the network in a modified RRCSetupComplete message which one or more MBS services, for example those that require an improved reliability achieved by the network configuring additional PTP segments with MRBs, are involved. The structure of the modified RRCSetupComplete can take the following form.

[0090] RRCSetupComplete::=SEQUENCE { rrc-transition Identifier RRC-transition Identifier, criticalExtensions CHOICE { rrcSetupComplete RRCSetupComplete-IEs, criticalExtensionsFuture SEQUENCE {} } } o RRCSetupComplete-IEs::=SEQUENCE { selectedPLMN-Identity INTEGER(1..maxPLMN), registeredAMF RegisteredAMF OPTIONAL, guami-Type ENUMERATED {native,mapped} OPTIONAL, ………………. } OPTIONAL, } o RRCSetupComplete-v1810-IEs::=SEQUENCE { MBS-reliability-r18 TMGI-list OPTIONAL,or MBS-reliability-r18 MRB-id-list OPTIONAL, } o}

[0091] 3. MBS Session Establishment The MBS session establishment procedure and related management procedures are specified in 3GPP TS 23.247. One such procedure specified in section 7.2.1.4 of this standard is related to "establishment of joint delivery to RAN nodes" (joint delivery means the delivery of MBS services to UEs by multicast transmission). However, the current procedure does not notify the gNB-CU and one or more gNB-DUs whether UE 3 is permitted to operate in the RRC_INACTIVE state for this specific MBS session. Therefore, a modified signaling diagram for "establishment of joint delivery to RAN nodes" to address the above-mentioned problem is presented in Figure 8 and will be described below.

[0092] In step 1, when the NG-RAN node 5 serves at least one UE 3 in the multicast MBS session, it decides to establish joint delivery for the multicast MBS session. In the case of location-dependent services, the NG-RAN node 5 needs to establish joint delivery for the location-dependent content of the multicast MBS session when serving at least one UE assigned the MBS session ID and area session ID.

[0093] Then, in step 2, the NG-RAN sends an N2 MBS session request message towards the AMF 8-1 (including one or more of the MBS session ID, [area session ID], N2 SM information ([unicast DL tunnel information])). If the NG-RAN node 5 is configured to use unicast transport for joint delivery, the NG-RAN node 5 allocates a GTP tunnel endpoint and provides the unicast DL tunnel information including the GTP tunnel endpoint and the NG-RAN node 5 address in its request. In the case of location-dependent MBS services, the NG-RAN node 5 also provides the area session ID.

[0094] In step 3, the AMF 8-1 selects, for example, using the NRF discovery service or information stored locally, the MB-SMF 8-4 that serves the multicast MBS session. The AMF 8-1 invokes an Nmbsmf_MBSSession_ContextUpdate request to the MB-SMF 8-4, including one or more of (MBS session ID, [area session ID], N2 SM information). The AMF 8-1 stores information of one or more NG-RAN nodes (e.g., NG-RAN node ID) for subsequent signaling related to the multicast MBS session.

[0095] Step 4 is indicated by a dotted line and is conditional on the MB-SMF 8-4 receiving unicast DL tunnel information in step 3. If so, the MB-SMF 8-4 configures the MB-UPF 8-5 to send multicast data (or location-dependent content of the multicast MBS session if an area session ID is received) for the multicast MBS session towards its GTP tunnel endpoint by unicast transport.

[0096] Continuing to refer to step 5, the MB-SMF 8-4 stores the information of the AMF 8-1 (e.g., AMF ID) in the MBS multicast MBS session context (or the location-dependent part of the multicast MBS session context if an area session ID is received) to enable subsequent signaling towards its AMF 8-1.

[0097] As outlined in TS 23.247, the above steps have not been changed in relation to the current procedure. The following steps 6 to 8 represent amendments and additions to the corresponding steps currently outlined in TS 23.247 to address the issues identified above. Turning to step 6, the MBS-SMF 8-4 sends a message (sometimes referred to as the Nmbsmf_MBSSession_ContextUpdate response message) to the AMF 8-1 that includes, among other any other appropriate parameters, the MBS session RRC_INACTIVE permission indicator and the TMGI. The MBS session RRC_INACTIVE permission indicator indicates whether the TMGI permits the UE to receive the corresponding MBS service in the RRC_INACTIVE state. Further, if the MB-SMF 8-4 did not receive the unicast DL tunnel information in step 3, the MB-SMF 8-4 provides multicast DL tunnel information that includes a transport multicast address (e.g., Lower Layer Source Specific IP Multicast: LL SSM) and a GTP tunnel endpoint for co-delivery multicast transport.

[0098] Next, in step 7, the AMF 8-1 sends an N2 MBS message including the MBS session RRC_INACTIVE permission indicator and the TMGI to the NG-RAN node 5, together with any additional relevant parameters. Finally, in step 8, the NG-RAN gNB provides the UE 3 with the MBS session RRC_INACTIVE permission indicator and the TMGI, for example, by (or instead of) a System Information Block (SIB), on a Multicast Control Channel (MCCH), in a paging message, or in an RRCRelease message. As a result of the UE 3 receiving the MBS session RRC_INACTIVE permission indicator and the associated TMGI, the UE 3 can utilize the MBS service corresponding to this TMGI in the RRC_INACTIVE state, thereby beneficially avoiding the need for the UE 3 to transition to the RRC_CONNECTED state.

[0099] To ensure that the multicast context is correctly set up, the setup of the current multicast context (as defined in Section 8.14.6 of TS 38.473) is modified to include the MBS session RRC_INACTIVE permission indicator, as shown in Figure 9. As illustrated in step 1 of Figure 9, the gNB-CU 5A sends a message (which may be called MULTICAST CONTEXT SETUP REQUEST) containing the MBS session RRC_INACTIVE permission indicator received in step 7 of Figure 8 and the associated TMGI to the gNB-DU 5B. The gNB-DU 5B confirms the reception of the message sent by the gNB-CU 5A by sending a message (which may be called MULTICAST CONTEXT SETUP RESPONSE message) to the gNB-CU 5A in step 2. Thus, according to the above procedure, both the gNB-CU 5A and one or more gNB-DUs 5B know whether the UE is permitted to operate in the RRC_INACTIVE mode for the MBS session. Therefore, the gNB-CU can configure appropriate MRBs for the UE 3 and the RLC entities in the gNB-DU.

[0100] 4. RRC_INACTIVE Mode Mobility As described above according to Release 17 of the MBS standard, the UE must transition to the RRC_CONNECTED state to register for MBS services in the core network. However, according to the more recent Release 18, after the registration procedure, the UE can freely transition to the RRC_INACTIVE state (according to the conditions described above in the embodiment entitled "RRC State Transition"). It should be understood that when a UE operating in the RRC_INACTIVE state is moving and performing cell reselection, the UE does not need to transition to the RRC_CONNECTED mode to achieve cell reselection. However, if the neighboring cell that the UE wants to reselect (and thus camp on) does not have an ongoing PTM MBS session for reception by the UE in the camping cell, the UE transitions to the RRC_CONNECTED state.

[0101] According to Release 17, since multicast is only supported for UEs in the RRC_CONNECTED state, the multicast configuration is not scheduled on the MCCH. Instead, it is scheduled in the RRCReconfiguration message, which is only available when the UE is in the RRC_CONNECTED state (the RRCReconfiguration message is used for handover and provides all neighboring cell information). Therefore, a solution is provided below to facilitate the provision of a multicast configuration for UEs operating in the RRC_INACTIVE mode without requiring an RRC state transition.

[0102] According to this embodiment, a new channel (multicast channel, MCCH) is provided for UEs operating in the RRC_INACTIVE state. Therefore, this channel can provide a multicast configuration for RRC_INACTIVE UEs. RRC_INACTIVE UEs can receive the System Information Block (SIB) as before. Therefore, the new MCCH is scheduled in the SIB. Thus, in the following description, it will be understood that references to SIB-MCCH refer to UEs that read the SIB to obtain the scheduling of the MCCH.

[0103] Regarding handling the mobility of UEs in the RRC_INACTIVE state, in the first example, the serving cell provides a list of ongoing MBS sessions in neighboring cells in the SIB-MCCH (or the SIB itself). This enables the RRC_INACTIVE UE to know which neighboring cells have MBS sessions that the UE is interested in. However, if the UE is interested in an MBS session that is not ongoing in the list of supported MBS sessions in the neighboring cells, An RRC_INACTIVE UE can transition to the RRC_CONNECTED state. And after handover to the target cell, the UE triggers the MBS participation procedure described in Section 7.2.1.3 of 3GPP TS 23.247. However, if there is no ongoing MBS session in the target cell, the network establishes the MBS participation procedure described in Section 7.2.1.3 of 3GPP TS 23.247, or A UE operating in the RRC_INACTIVE state can prioritize other adjacent cells that support the desired MBS session. If there are no other cells that support the MBS session, the UE performs normal cell reselection for cells that do not support the MBS session, and then transitions to the RRC_CONNECTED state and triggers the MBS participation procedure described in Section 7.2.1.3 of 3GPP TS 23.247. The serving cell can send the UE a list of cells / frequencies that support the desired MBS session in one of the paging message, RRCRelease message, RRC dedicated message, SIB message, or a message on the MCCH.

[0104] The base station can notify the UE of which MBS services can be received when the UE is in the RRC_INACTIVE state using the following RRC_INACTIVE - SUPPORTIVE - indication message. RRC_INACTIVE - SUPPORTIVE - indication::=SEQUENCE { MBSservice TMGI RRCINACTIVESUPPORTIVE RRCINACTIVESUPPORTIVE(true,false) }

[0105] In the second example, the serving cell broadcasts (in its SIB-MCCH) only a list of adjacent cells / frequencies having ongoing MBS services. When the UE attempts to reselect an adjacent cell, the UE can check from the information broadcast by its currently serving cell whether the adjacent cell has an ongoing MBS service. If so, the UE reads the MCCH of the adjacent cell to obtain the list of MBS sessions supported by the adjacent cell. In this way, the UE can check whether a desired MBS session is ongoing in the adjacent cell before deciding to reselect the adjacent cell.

[0106] If the UE reselects a cell without an ongoing MBS session, the UE transitions to RRC_CONNECTED and triggers the MBS participation procedure described in section 7.2.1.3 of TS 23.247.

[0107] 5. Optimization of Handover As specified in the current standard (3GPP TS 38.401, section 8.9.4), as part of the handover procedure, the source gNB sends a handover request message to the target gNB. The handover request message has the MBS configuration as part of its RRC context information, i.e., the handover request message includes details of the MBS sessions for the UE to be handed over to the target cell. Currently, if there is no ongoing MBS session in the target gNB, the target gNB has to start the MBS session establishment procedure in the target cell according to section 7.2.1.3 of 3GPP TS 23.247. However, if there is no ongoing MBS session for the UE performing the handover procedure, it takes a long time to establish an MBS session in the target gNB during handover. In the following description with reference to Figure 10, a solution to this problem is proposed (Figure 10 corresponds to a simplified and modified version of the signaling diagram of "Inter-gNB handover with gNB-CU-UP change" in section 8.9.4 of TS 38.401).

[0108] First, referring to step 1 in FIG. 10, the source gNB-CU-CP 5-1 sends a conditional handover request message to the target gNB-CU-CP 5-4. The handover request message includes, as part of the RRC configuration, the MBS configuration for the UEs that may be the target of the handover to the target. The conditional handover is a kind of pre-handover before the handover condition is satisfied.

[0109] In step 2, if there is no MBS session at the target gNB, the target gNB-CU-CP 5-4 establishes an MBS session establishment with the core network, usually with the MB-SMF (for example, in accordance with section 7.2.1.3 of TS 23.247).

[0110] In this way, the target gNB beneficially "pre-establishes" the MBS session if the MBS session has not been established yet before the UE's handover is actually executed. This procedure is much faster than using the normal handover procedure, where the UE has to first hand over to the target base station, then request the MBS service from the target base station, and then the target base station tries to establish an MBS session with the core network if the MBS session does not exist yet.

[0111] Then, in step 3, gNB-CU-CP 5-4 sends a BEARER CONTEXT SETUP REQUEST message that includes UL TNL address information for S1-U or NG-U and, if necessary, DL TNL address information for X2-U to set up a bearer context at gNB-CU-UP 5-3. In the case of NG-RAN, gNB-CU-CP 5-4 determines the mapping of flows to DRBs and sends the generated SDAP and PDCP configurations to gNB-CU-UP 5-3. Since this handover is conditional, the BEARER CONTEXT SETUP REQUEST message instructs that the included security context should be ignored and that the transmission of downlink packets should not be started until the UE has successfully accessed the target.

[0112] In step 3a, gNB-CU-UP 5-3 responds with a BEARER CONTEXT SETUP RESPONSE message that includes UL TNL address information for F1-U, DL TNL address information for S1-U or NG-U, and, if necessary, UL TNL address information for X2-U or Xn-U.

[0113] Then, in step 4, an F1 UE context setup procedure is executed at gNB-DU 5-2 to set up one or more bearers.

[0114] Finally, in step 5, the target gNB-CU-CP 5-4 responds to the source gNB-CU-CP 5-1 with a HANDOVER REQUEST ACKNOWLEDGE message. Since this handover procedure is conditional, the target gNB-CU-CP 5-4 ensures that the EARLY STATUS TRANSFER information is transferred to the appropriate gNB-CU-UP 5-3 (e.g., via a separate UE-related signaling connection on the Xn interface of each gNB-CU-UP).

[0115] <Amendments and Alternatives> Detailed embodiments have been described above. As those skilled in the art will understand, several amendments and alternatives can be made to those embodiments while further benefiting from the disclosure embodied in the above embodiments. By way of example only, some of these alternatives and amendments will be described here.

[0116] The above description refers to MBS for simplicity. However, the MBS function may also be referred to as, for example, the Multimedia Broadcast / Multicast Services (MBMS) function. Base stations in a 5G / NR communication system are generally referred to as New Radio Base Stations (“NR-BS”) or “gNBs”, but it will be understood that they may more typically be referred to using the term “eNB” (or 5G / NR eNB), which is associated with Long Term Evolution (LTE) base stations (commonly also referred to as “4G” base stations). 3GPP TS 38.300 V16.7.0 and 3GPP TS 37.340 V16.7.0 define, inter alia, the following nodes.

[0117] gNB: A node that provides protocol termination for the NR user plane and control plane towards the UE and is connected to the 5G Core Network (5GC) via the NG interface. ng-eNB: A node that provides protocol termination for the E-UTRA user plane and control plane towards the UE and is connected to the 5GC via the NG interface. En-gNB: A node that provides protocol termination for the NR user plane and control plane towards the UE and functions as a secondary node in E-UTRA-NR Dual Connectivity (EN-DC). NG-RAN node: either gNB or ng-eNB.

[0118] It will be understood that the above embodiments may be applicable to 5G New Radio and LTE systems (E-UTRAN), as well as any future generation systems. Base stations that support the E-UTRA / 4G protocol may be referred to as "eNBs", and base stations that support the NextGeneration / 5G protocol may be referred to as "gNBs". It will be understood that some base stations may be configured to support both the 4G protocol and the 5G protocol, and / or any other 3GPP or non-3GPP communication protocol.

[0119] In the above description, for ease of understanding, the UE, access network node, and data network node are described as having several individual modules (such as a communication control module). These modules may be provided in this way in certain applications, for example, where an existing system has been modified to implement the present disclosure, but in other applications, such as a system designed from the beginning with the features of the present invention in mind, these modules may be incorporated into the overall operating system or code, and thus these modules may not be distinguishable as individual entities. These modules may be implemented in software, hardware, firmware, or a combination thereof.

[0120] Each controller may include, for example (but not limited to), one or more hardware-implemented computer processors, microprocessors, central processing units (CPUs), arithmetic logic units (ALUs), input / output (I / O) circuits, internal memory / cache (program and / or data), processing registers, communication buses (e.g., control bus, data bus, and / or address bus), direct memory access (DMA) functions, hardware or software-implemented counters, pointers, and / or timers, and / or any other suitable form of processing circuitry including the like.

[0121] In the above embodiments, some software modules have been described. As will be understood by those skilled in the art, software modules may be provided in compiled form or in non-compiled form, and may be supplied to the UE, access network nodes, and data network nodes via a computer network, or on a recording medium, as a signal. Further, the functions executed by some or all of this software may be executed using one or more dedicated hardware circuits. However, the use of software modules is preferred as it facilitates the updating of the UE, access network nodes, and data network nodes to update their functions.

[0122] The above embodiments are also applicable to "non-mobile" or generally stationary user equipment.

[0123] Receiving of information may be performed by an MBS control channel (MCCH) or by application layer procedures.

[0124] The core network functions may include at least one of functions for access and mobility management and functions for session management.

[0125] Various other modifications will be apparent to those skilled in the art and are not described in further detail herein.

[0126] Although the present disclosure has been described with reference to exemplary embodiments, the present disclosure is not limited thereto. Various changes that can be understood by those skilled in the art can be made to the configuration and details of the present disclosure within the scope of the present disclosure.

[0127] This application is based on UK Patent Application No. 2211642.0 filed on August 9, 2022, and claims the benefit of its priority, and the disclosure of the UK Patent Application is incorporated herein by reference in its entirety.

[0128] The program can be stored using any type of non-transitory computer-readable medium and provided to a computer device. Non-transitory computer-readable media include any type of tangible storage medium. Examples of non-transitory computer-readable media include magnetic storage media (such as floppy disks, magnetic tapes, hard disk drives, etc.), magneto-optical storage media (such as magneto-optical disks), CD-ROM (Compact Disc Read-Only Memory), CD-R, CD-R / W, and semiconductor memories (such as mask ROM, PROM (Programmable ROM), EPROM (Erasable PROM), flash ROM, RAM (Random Access Memory), etc.). The program may be provided to a computer device using any type of transitory computer-readable medium. Examples of transitory computer-readable media include electrical signals, optical signals, and electromagnetic waves. The transitory computer-readable medium can provide the program to the computer device via wired communication lines such as wires and optical fibers, or wireless communication lines.

[0129] For example, all or part of the exemplary embodiments disclosed above can be described as follows, but are not limited thereto. (Appendix 1) A method for an access network node, transmitting a first message to a User Equipment (UE) including an inquiry about the UE's ability to receive Multicast / Broadcast Service (MBS) when the UE is in the Radio Resource Control (RRC)_INACTIVE state, receiving, from the UE, a second message including a list of one or more MBS sessions that the UE can support when the UE is in the RRC_INACTIVE state if the UE has information identifying at least one MBS available to the UE, including the method. (Appendix 2) The method according to Appendix 1, wherein the first message is transmitted on a dedicated RRC message, a paging message, a System Information Block (SIB), or a multicast control channel. (Appendix 3) The method according to Appendix 1 or Appendix 2, wherein the first message is a UE RRC_INACTIVE support inquiry message. (Appendix 4) The method according to Appendix 3, wherein the second message is a UE RRC_INACTIVE support report message. (Appendix 5) A method for an access network node, transmitting a paging message including a list of at least one Temporary Mobile Group Identity (TMGI) associated with each available Multicast / Broadcast Service (MBS) session to a User Equipment (UE) in the Radio Resource Control (RRC)_INACTIVE state, including a paging message being each instruction associated with each TMGI in a list, each instruction being whether the UE needs to transition to the RRC_CONNECTED state to receive each MBS session associated with each TMGI, or whether the UE can continue to be in the RRC_INACTIVE state to receive each MBS session associated with each TMGI each instruction indicating when the UE is a UE after Release 18, an instruction to configure the UE not to transition to the RRC_CONNECTED state in response to receiving a paging message A method including. (Appendix 6) The method according to Appendix 5, wherein the instruction is an RRCCONNECTEDINDICATION-R18 instruction. (Appendix 7) A method for an access network node, including transmitting parameters associated with a Temporary Mobile Group Identity (TMGI) to a User Equipment (UE) using a Multicast / Broadcast Service (MBS) having the TMGI, the parameters indicating conditions that, when satisfied, cause the UE to transition from the Radio Resource Control (RRC)_CONNECTED state to the RRC_INACTIVE state or from the RRC_INACTIVE state to the RRC_CONNECTED state A method. (Appendix 8) The method according to Appendix 7, wherein the parameters are transmitted to the UE in a System Information Block (SIB), on a multicast channel, in a paging message, or by dedicated RRC signaling. (Appendix 9) The condition is the method according to Appendix 7 or 8, including whether one or more received signal measurement values are greater than or less than a threshold level. (Appendix 10) The condition for transitioning the UE from the RRC_CONNECTED state to RRC_INACTIVE includes whether the Reference Signal Received Power (RSRP) measured by the UE is greater than a first threshold and / or whether the Reference Signal Received Quality (RSRQ) measured by the UE is greater than a second threshold, or The condition for transitioning the UE from the RRC_CONNECTED state to RRC_INACTIVE includes whether the Reference Signal Received Power (RSRP) measured by the UE is less than a third threshold and / or whether the Reference Signal Received Quality (RSRQ) measured by the UE is less than a fourth threshold. The method according to Appendix 9. (Appendix 11) The condition is the method according to any one of Appendices 7 to 10, where the parameter is the StateTransitConfig parameter. (Appendix 12) The indication is transmitted as part of the RRC_INACTIVE - SUPPORTIVE - configuration, and the method is according to any one of Appendices 7 to 11. (Appendix 13) A method for an access network node, comprising: Providing a Multicast / Broadcast Service (MBS) to a User Equipment (UE) by means of a Multicast / Broadcast Service Radio Bearer (MRB); Receiving, from the UE, a notification requesting improvement in the reliability of the MBS service; Provisioning improvement in reliability. A method including (Appendix 14) The method according to Appendix 13, wherein the notification is received in an RRCSetupComplete message. (Appendix 15) The method according to Appendix 13 or 14, wherein the notification includes a list of at least one TMGI for which reliability improvement is required for an MBS service associated with at least one TMGI in the list, or the notification includes a list of at least one MBS Radio Bearer (MRB) associated with an MBS service that requires reliability improvement. (Appendix 16) The method according to any one of Appendices 13 to 15, wherein the reliability improvement includes the access network node provisioning an additional point-to-point (PTP) section with the MRB. (Appendix 17) A method for an access network node having a central unit and a distributed unit, receiving, by the central unit, an indication of at least one multicast / broadcast service (MBS) session accessible to a user equipment (UE) when the UE is in a radio resource control (RRC)_INACTIVE state from a core network node; sending, by the central unit, an indication to the distributed unit; receiving, by the central unit, a response from the distributed unit; sending, by the distributed unit, an indication to the UE; A method including (Appendix 18) The method according to Appendix 17, wherein the indication includes an RRC_INACTIVE permission indicator and a Temporary Mobile Group Identity (TMGI) for each of the at least one MBS session. (Appendix 19) A method for a core network node, When a user equipment (UE) is in the RRC_INACTIVE state, sending a message including an indication of one or more multicast / broadcast service (MBS) sessions accessible to the UE to a second core network node, A method comprising the above. (Appendix 20) The method according to Appendix 19, wherein the core network node is a multicast / broadcast session management function MB-SMF, and the second core network node is an access management function AMF. (Appendix 21) The method according to Appendix 19 or 20, wherein the message is an Nmbsmf_MBSSession_ContextUpdate response message. (Appendix 22) A method for a core network node, When a user equipment (UE) is in the radio resource control (RRC)_INACTIVE state, sending a message including an indication of one or more multicast / broadcast service (MBS) sessions accessible to the UE to an access network node, A method comprising the above. (Appendix 23) The method according to Appendix 22, wherein the core network node is an access management function AMF. (Appendix 24) The method according to Appendix 22 or 23, wherein the message is an N2 MBS message. (Appendix 25) A method for a first access network node, Transmitting information including a list of ongoing Multicast / Broadcast Service (MBS) sessions of a second access network node adjacent to a first access network node, or a list of adjacent cells / frequencies of at least one adjacent access network node having at least one ongoing MBS session, to a User Equipment (UE) served by the first access network node, A method comprising: (Appendix 26) The transmitting is the method according to Appendix 25, wherein the information is transmitted by a system information block or a multicast control channel. (Appendix 27) The serving cell transmits a supported cell / list of supported frequencies of the MBS session list to the UE by one of a paging message, an RRCRelease message, an RRC dedicated message, an SIB message, or a message on the MCCH, according to the method described in Appendix 25 or 26. (Appendix 28) A method performed by a source access network node for handover of a User Equipment (UE) to a target access network node, Transmitting a conditional handover request message including MBS configuration information for the UE to the target access network node, A method comprising: (Appendix 29) A method performed by a target access network node for handover of a User Equipment (UE) from a source access network node, Receiving, from the source access network node, a conditional handover request message including MBS configuration information for the UE, Establishing an MBS session with the core network when there is no ongoing MBS session in the target access network node, A method including (Appendix 30) Establishing, which is the method described in Appendix 29 and is executed before the UE is handed over to the target access network node. (Appendix 31) Establishing, which is the method described in Appendix 29 or 30 and is executed in response to receiving a conditional handover request. (Appendix 32) A method for a User Equipment (UE), Receiving, from an access network node, a first message including an inquiry about the UE's ability to receive Multicast / Broadcast Service (MBS) when the UE is in the Radio Resource Control (RRC)_INACTIVE state; Based on information identifying at least one MBS available to the UE, sending, to the access network node, a second message including a list of one or more MBS sessions that the UE can support when the UE is in the RRC_INACTIVE state; A method including. (Appendix 33) A method for a User Equipment (UE) in the Radio Resource Control (RRC)_INACTIVE state, Receiving, from an access network node, a paging message including a list of at least one Temporary Mobile Group Identity (TMGI) associated with each available Multicast / Broadcast Service (MBS) session, Including, The paging message being Each indication associated with each TMGI in the list, and each indication being Whether the UE needs to transition to the RRC_CONNECTED state to receive the related MBS session, or Whether the UE can continue to be in the RRC_INACTIVE state to receive the related MBS session Each indication showing this, or When the UE is a UE after Release 18, an indication to configure the UE not to transition to the RRC_CONNECTED state in response to receiving a paging message Including Method. (Appendix 34) A method for a User Equipment (UE), Receiving a Multicast / Broadcast Service (MBS) having a Temporary Mobile Group Identity (TMGI), Receiving parameters associated with the TMGI from an access network node, the parameters indicating conditions that, when satisfied, cause the UE to transition from the Radio Resource Control (RRC)_CONNECTED state to the RRC_INACTIVE state or from the RRC_INACTIVE state to the RRC_CONNECTED state, Transitioning between the RRC_CONNECTED state and the RRC_INACTIVE state based on the parameters, Including (Appendix 35) A method for a User Equipment (UE), When the UE is in the RRC_INACTIVE state, receiving a Multicast / Broadcast Service (MBS) from an access network node via an MBS Radio Bearer (MRB), When the signal strength of the MRB falls below a threshold value, transitioning to the RRC_CONNECTED state, and sending a notification requesting an improvement in the reliability of the MBS service to an access network node, and A method comprising the above. (Appendix 36) A method for a User Equipment (UE), when the UE is in the RRC_INACTIVE state, receiving an indication of one or more Multicast / Broadcast Service (MBS) sessions accessible to the UE from a distributed unit of an access network node, A method comprising the above. (Appendix 37) A method for a User Equipment (UE), receiving from a first access network node information including an ongoing Multicast / Broadcast Service (MBS) session list of a second access network node adjacent to the first access network node, or an adjacent cell / frequency list of at least one adjacent access network node having at least one ongoing MBS session, A method comprising the above. (Appendix 38) An access network node, means for sending a first message to the UE including an inquiry about the UE's ability to receive a Multicast / Broadcast Service (MBS) when the UE is in the Radio Resource Control (RRC)_INACTIVE state, means for receiving, from a UE, a second message including a list of one or more MBS sessions that the UE can support when the UE is in the RRC_INACTIVE state, if the UE has information identifying at least one MBS available to the UE; An access network node comprising (Appendix 39) An access network node, means for transmitting a paging message including a list of at least one Temporary Mobile Group Identity (TMGI) associated with each available Multicast / Broadcast Service (MBS) session to a User Equipment (UE) in the Radio Resource Control (RRC)_INACTIVE state comprising wherein the paging message includes respective indications associated with each TMGI in the list, each indication indicating whether the UE needs to transition to the RRC_CONNECTED state to receive each MBS session associated with each TMGI, or whether the UE can continue to be in the RRC_INACTIVE state to receive each MBS session associated with each TMGI respective indications, or if the UE is a UE after Release 18, an indication for configuring the UE not to transition to the RRC_CONNECTED state in response to receiving the paging message including An access network node. (Appendix 40) An access network node, Means for transmitting parameters associated with a Temporary Mobile Group Identity (TMGI) to a User Equipment (UE) using a Multicast / Broadcast Service (MBS) having the TMGI, where the parameters indicate conditions that, when satisfied, cause the UE to transition from a Radio Resource Control (RRC)_CONNECTED state to an RRC_INACTIVE state, or from an RRC_INACTIVE state to an RRC_CONNECTED state. An access network node. (Appendix 41) An access network node, Means for providing a Multicast / Broadcast Service (MBS) to a User Equipment (UE) by means of an MBS Radio Bearer (MRB), Means for receiving a notification from the UE requesting an improvement in the reliability of the MBS service, Means for provisioning an improvement in reliability An access network node comprising. (Appendix 42) An access network node having a central unit and a distributed unit, where the central unit Means for receiving, from a core network node, an indication of at least one Multicast / Broadcast Service (MBS) session accessible by the UE when the UE is in a Radio Resource Control (RRC)_INACTIVE state, Means for transmitting an indication to the distributed unit, Means for receiving a response from the distributed unit and comprising, The distribution unit means for sending an instruction to the UE comprises an access network node. (Appendix 43) A core network node, means for sending a message including an instruction of one or more multicast / broadcast service (MBS) sessions accessible to the user equipment (UE) when the UE is in the radio resource control (RRC)_INACTIVE state to the access network node comprises a core network node. (Appendix 44) A first access network node, means for sending information including a list of ongoing multicast / broadcast service (MBS) sessions of a second access network node adjacent to the first access network node or a list of adjacent cells / frequencies of at least one adjacent access network node having at least one ongoing MBS session to a user equipment (UE) served by the first access network node comprises a first access network node. (Appendix 45) A source access network node for handover of a user equipment (UE) to a target access network node, wherein the source access network node means for sending a conditional handover request message including MBS configuration information for the UE to the target access network node comprises a source access network node. (Appendix 46) A target access network node for handover of a user equipment (UE) from a source access network node, the target access network node comprising: means for receiving, from the source access network node, a conditional handover request message including MBS configuration information for the UE; establishing an MBS session with the core network when there is no ongoing MBS session in the target access network node; A target access network node comprising the above. (Appendix 47) A user equipment (UE) comprising: means for receiving, from an access network node, a first message including an inquiry about the UE's ability to receive a multicast / broadcast service (MBS) when the UE is in a radio resource control (RRC)_INACTIVE state; means for transmitting, to the access network node, a second message including a list of one or more MBS sessions that the UE can support when the UE is in the RRC_INACTIVE state, based on information identifying at least one MBS available to the UE; A user equipment comprising the above. (Appendix 48) A user equipment (UE), wherein the UE: means for receiving, from an access network node, a paging message including a list of at least one temporary mobile group identity (TMGI) associated with each available multicast / broadcast service (MBS) session when the UE is in a radio resource control (RRC) INACTIVE state; A user equipment comprising the above. The paging message is each instruction associated with each TMGI in the list, and each instruction is whether the UE needs to transition to the RRC_CONNECTED state to receive the associated MBS session, or whether the UE can continue to be in the RRC_INACTIVE state to receive the associated MBS session each instruction indicating, or when the UE is a UE after Release 18, an instruction to configure the UE not to transition to the RRC_CONNECTED state in response to receiving the paging message including a user equipment. (Appendix 49) a user equipment (User Equipment: UE), means for receiving a multicast / broadcast service (MBS) having a temporary mobile group identity (TMGI), means for receiving parameters associated with the TMGI from an access network node, the parameters indicating conditions for transitioning the UE from the radio resource control (RRC)_CONNECTED state to the RRC_INACTIVE state or from the RRC_INACTIVE state to the RRC_CONNECTED state when satisfied, means for transitioning between the RRC_CONNECTED state and the RRC_INACTIVE state based on the parameters a user equipment comprising. (Appendix 50) a user equipment (User Equipment: UE), When the UE is in the RRC_INACTIVE state, means for receiving a multicast / broadcast service (MBS) from an access network node via a multicast / broadcast service radio bearer (MRB); means for transitioning to the RRC_CONNECTED state when the signal strength of the MRB falls below a threshold; means for transmitting a notification requesting an improvement in the reliability of the MBS service to the access network node A user equipment comprising the above. (Appendix 51) A user equipment (UE), means for receiving, from a distributed unit of an access network node, an indication of one or more multicast / broadcast service (MBS) sessions accessible by the UE when the UE is in the RRC_INACTIVE state A user equipment comprising the above. (Appendix 52) A user equipment (UE), means for receiving, from a first access network node, information including a list of ongoing multicast / broadcast service (MBS) sessions of a second access network node adjacent to the first access network node, or a list of adjacent cells / frequencies of at least one adjacent access network node having at least one ongoing MBS session A user equipment comprising the above.

Explanation of Signs

[0130] 1 Telecommunication network, telecommunication system 3 UE 5 NG-RAN, base station 7 Core network 8-1 AMF 8-2 SMF 8-3 UPF 8-4 MB-SMF 8-5 MB-UPF 8-6 MBSF 8-7 MBSTF 8-8 NEF 8-9 AF 8-10 PCF 8-11 NRF 8-12 UDM 8-13 AUSF 8-14 DN

Claims

1. transmitting a first message indicating the capabilities of a user equipment (UE) that receives a multicast / broadcast service (Multicast / Broadcast Service: MBS) to the UE in the radio resource control (Radio Resource Control: RRC)_INACTIVE state; when the UE has information identifying at least one MBS available to the UE, receiving, from the UE, a second message indicating one or more MBS sessions that the UE in the RRC_INACTIVE state can support; comprising; while the UE is in the RRC_INACTIVE state, at least one MBS corresponding to the one or more MBS sessions is provided to the UE; A method for an access network node.

2. further comprising transmitting to the UE in the RRC_INACTIVE state a temporary mobile group identity (Temporary Mobile Group Identity: TMGI) associated with one or more available MBS sessions and an indication corresponding to the TMGI; the indication indicates whether the UE should remain in the RRC_INACTIVE state when the UE receives at least one MBS corresponding to the one or more MBS sessions associated with the TMGI; The method according to claim 1.

3. the indication indicates that the UE should remain in the RRC_INACTIVE state when the UE receives at least one MBS corresponding to the one or more MBS sessions associated with the TMGI; The method according to claim 2.

4. the indication indicates that the UE should transition to the RRC_CONNECTED state when the UE receives at least one MBS corresponding to the one or more MBS sessions associated with the TMGI; The method according to claim 2.

5. further comprising transmitting, to the UE in the RRC_INACTIVE state, a Temporary Mobile Group Identity (TMGI) associated with one or more available MBS sessions and parameters corresponding to the TMGI, wherein the parameters indicate conditions for transitioning the UE from the RRC_CONNECTED state to the RRC_INACTIVE state or from the RRC_INACTIVE state to the RRC_CONNECTED state, The method according to any one of claims 1 to 4.

6. wherein the conditions include whether one or more received signal measurement values are greater than, less than, or equal to a threshold level, The method according to claim 5.

7. wherein the conditions for transitioning the UE from the RRC_CONNECTED state to the RRC_INACTIVE state include whether the Reference Signal Received Power (RSRP) measured by the UE is greater than a first threshold and / or whether the Reference Signal Received Quality (RSRQ) measured by the UE is greater than a second threshold, or wherein the conditions for transitioning the UE from the RRC_CONNECTED state to the RRC_INACTIVE state include whether the Reference Signal Received Power (RSRP) measured by the UE is less than a third threshold and / or whether the Reference Signal Received Quality (RSRQ) measured by the UE is less than a fourth threshold, The method according to claim 5 or 6.

8. receiving, from the UE, a notification requesting improvement in reliability of the at least one MBS, provisioning the improvement in reliability, further comprising The method according to any one of claims 1 to 7.

9. wherein the notification is the at least one TMGI associated with at least one MBS for which improvement in reliability is requested, or At least one MBS Radio Bearer (MRB) corresponding to an MBS that requires reliability improvement comprising The method according to claim 8

10. The reliability improvement includes the access network node provisioning an additional point-to-point (PTP) segment on the MRB The method according to claim 9

11. A method for an access network node having a central unit and a distributed unit, comprising receiving, by the central unit, an indication of at least one multicast / broadcast service (MBS) session accessible by a user equipment (UE) in the radio resource control (RRC)_INACTIVE state from a core network node transmitting, by the central unit, the indication to the distributed unit receiving, by the central unit, a response from the distributed unit transmitting, by the distributed unit, the indication to the UE A method comprising

12. The indication includes, for each of the at least one MBS session, an RRC_INACTIVE permission indicator and a temporary mobile group identity (TMGI) The method according to claim 11

13. Transmitting, by the first access network node, information including an ongoing multicast / broadcast service (MBS) session list of a second access network node adjacent to the first access network node, or an adjacent cell / frequency list of at least one adjacent access network node having at least one ongoing MBS session, to a user equipment (UE) served by the first access network node A method of a first access network node comprising

14. The transmitting is performed by transmitting the information via a system information block or a multicast control channel The method according to claim 13

15. Transmitting to the UE a list of supported cells / frequencies of the list of the MBS sessions further comprising the method according to claim 13 or 14

16. A method performed by a source access network node for handover of a user equipment (UE) to a target access network node, comprising transmitting to the target access network node a conditional handover request message including multicast / broadcast service (MBS) configuration information for the UE a method comprising

17. A method performed by a target access network node for handover of a user equipment (UE) from a source access network node, comprising receiving from the source access network node a conditional handover request message including multicast / broadcast service (MBS) configuration information for the UE establishing an MBS session with a core network when there is no ongoing MBS session in the target access network node a method comprising

18. wherein the establishing is performed before the UE is handed over to the target access network node, the method according to claim 17

19. wherein the establishing is performed in response to receiving the conditional handover request, the method according to claim 17 or 18

20. Transmitting to a further core network node a message including an indication of one or more multicast / broadcast service (MBS) sessions accessible to a user equipment (UE) in a radio resource control (RRC)_INACTIVE state a method of a core network node comprising

21. Transmitting, to an access network node, a message including an indication of one or more multicast / broadcast service (MBS) sessions accessible to a user equipment (UE) in a Radio Resource Control (RRC)_INACTIVE state. A method for a core network node, including the above. Claim 22 Receiving, from an access network node, a first message indicating the ability of a user equipment (UE) in a Radio Resource Control (RRC)_INACTIVE state to receive a multicast / broadcast service (MBS). Based on information identifying at least one MBS available to the UE, transmitting, to the access network node, a second message indicating one or more MBS sessions that the UE in the RRC_INACTIVE state can support. Receiving at least one MBS corresponding to the one or more MBS sessions while the UE is in the RRC_INACTIVE state. A method for a UE, including the above. Claim 23 Further including receiving, from the access network node, a temporary mobile group identity (TMGI) associated with one or more available MBS sessions and an indication corresponding to the TMGI. The indication indicates whether the UE should remain in the RRC_INACTIVE state when the UE receives at least one MBS corresponding to the one or more MBS sessions associated with the TMGI. The method according to claim 22. Claim 24 The indication indicates that the UE should remain in the RRC_INACTIVE state when the UE receives at least one MBS corresponding to the one or more MBS sessions associated with the TMGI. The method according to claim 23. Claim 25 The indication is that when the UE receives at least one MBS corresponding to the one or more MBS sessions related to the TMGI, the UE should transition to the RRC_CONNECTED state. The method according to claim 23. **Claim 26** Further comprising receiving from the access network node a Temporary Mobile Group Identity (TMGI) related to one or more available MBS sessions and a parameter corresponding to the TMGI, wherein the parameter indicates a condition for causing the UE to transition from the RRC_CONNECTED state to the RRC_INACTIVE state or from the RRC_INACTIVE state to the RRC_CONNECTED state. The method according to any one of claims 22 to 25. **Claim 27** The condition includes whether one or more received signal measurement values are greater than or less than a threshold level. The method according to claim 26. **Claim 28** The condition for causing the UE to transition from the RRC_CONNECTED state to the RRC_INACTIVE state includes whether the Reference Signal Received Power (RSRP) measured by the UE is greater than a first threshold and / or whether the Reference Signal Received Quality (RSRQ) measured by the UE is greater than a second threshold, or The condition for causing the UE to transition from the RRC_CONNECTED state to the RRC_INACTIVE state includes whether the Reference Signal Received Power (RSRP) measured by the UE is less than a third threshold and / or whether the Reference Signal Received Quality (RSRQ) measured by the UE is less than a fourth threshold. The method according to claim 26 or 27. **Claim 29** Sending a notification to the access network node requesting improvement in the reliability of the at least one MBS, Provisioning the improvement in reliability. The method according to any one of claims 22 to 28, further comprising

30. The notification is the at least one TMGI associated with at least one MBS for which reliability improvement is required, or at least one MBS Radio Bearer (MRB) corresponding to an MBS that requires reliability improvement comprising the method according to claim 29.

31. The reliability improvement includes the access network node provisioning an additional point-to-point (PTP) section on the MRB, the method according to claim 30.

32. Receiving, from a distributed unit of an access network node, an indication of one or more multicast / broadcast service (MBS) sessions accessible by a radio resource control (RRC)_INACTIVE state user equipment (UE) A method for a UE comprising

33. Receiving, from the first access network node, information including an ongoing multicast / broadcast service (MBS) session list of a second access network node adjacent to the first access network node, or an adjacent cell / frequency list of at least one adjacent access network node having at least one ongoing MBS session A method for a user equipment (UE) comprising

34. Means for transmitting, to the UE in radio resource control (RRC)_INACTIVE state, a first message indicating the ability of a user equipment (UE) to receive a multicast / broadcast service (MBS); Means for receiving, from the UE, a second message indicating one or more MBS sessions that the UE in RRC_INACTIVE state can support, if the UE has information identifying at least one MBS available to the UE; comprising While the UE is in the RRC_INACTIVE state, at least one MBS corresponding to the one or more MBS sessions is provided to the UE, access network node.

35. An access network node having a central unit and a distributed unit, wherein the central unit, means for receiving from a core network node an indication of at least one multicast / broadcast service (MBS) session to which a user equipment (UE) in a Radio Resource Control (RRC)_INACTIVE state can access; means for transmitting the indication to the distributed unit; means for receiving a response from the distributed unit and comprising, wherein the distributed unit, means for transmitting the indication to the UE and comprising, access network node.

36. Means for transmitting to a user equipment (UE) served by the first access network node information including an ongoing multicast / broadcast service (MBS) session list of a second access network node adjacent to the first access network node, or an adjacent cell / frequency list of at least one adjacent access network node having at least one ongoing MBS session and comprising, the first access network node.

37. A source access network node for handover of a user equipment (UE) to a target access network node, wherein the source access network node, means for transmitting to the target access network node a conditional handover request message including multicast / broadcast service (MBS) configuration information for the UE and comprising, source access network node.

38. A target access network node for handover of a user equipment (UE) from a source access network node, wherein the target access network node means for receiving, from the source access network node, a conditional handover request message including multicast / broadcast service (MBS) configuration information for the UE; means for establishing an MBS session with a core network when there is no ongoing MBS session in the target access network node; A target access network node comprising the above.

39. means for transmitting, to a further core network node, a message including an indication of one or more multicast / broadcast service (MBS) sessions accessible by a user equipment (UE) in a radio resource control (RRC)_INACTIVE state A core network node comprising the above.

40. means for transmitting, to an access network node, a message including an indication of one or more multicast / broadcast service (MBS) sessions accessible by a user equipment (UE) in a radio resource control (RRC)_INACTIVE state A core network node comprising the above.

41. means for receiving, from an access network node, a first message indicating the capability of a user equipment (UE) in a radio resource control (RRC)_INACTIVE state that receives a multicast / broadcast service (MBS); means for transmitting, to the access network node, a second message indicating one or more MBS sessions supportable by the UE in the RRC_INACTIVE state, based on information identifying at least one MBS available to the UE; receiving, while the UE is in the RRC_INACTIVE state, at least one MBS corresponding to the one or more MBS sessions; A UE comprising the above.

42. means for receiving, from a distributed unit of an access network node, an indication of one or more Multicast / Broadcast Service (MBS) sessions accessible by the UE in the Radio Resource Control (RRC)_INACTIVE state; A user equipment (UE) comprising the above.

43. means for receiving, from the first access network node, information including a list of ongoing Multicast / Broadcast Service (MBS) sessions of a second access network node adjacent to the first access network node, or a list of adjacent cells / frequencies of at least one adjacent access network node having at least one ongoing MBS session; A user equipment (UE) comprising the above.

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