Method for access network node, method for core network node, method for user equipment, access network node, core network node and user equipment

Abstract

A method for an access network node is provided. The method comprises: transmitting a first message to a user equipment (UE), where the UE is in an RRCINACTIVE state, the first message comprising a query of a capability of the UE to receive a multicast / broadcast service (MBS), the RRC being radio resource control; and receiving a second message from the UE if the UE has information identifying at least one MBS that the UE is available, the second message including a list of one or more MBS sessions that the UE may support if the UE is in the RRCINACTIVE state.

Description

Technical Field

[0001] The present disclosure relates to wireless communication systems and apparatus thereof operating in accordance with the Third Generation Partnership Project (3GPP) standards or their equivalents or derivatives. The present disclosure relates in particular, but not exclusively, to improvements relating to session management of multimedia broadcast sessions operating in accordance with so-called "5G" (or "next generation") systems or similar systems. Background Art

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

[0003] Under the 3GPP standards, a base station (e.g., "eNB" in 4G or "gNB" in 5G) is a node via which a communication device (user equipment or "UE") connects to the core network and communicates with other communication devices or remote servers. For simplicity, this application will use the term base station or access network node to refer to any such base station. For simplicity, this application will use the term 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, a smart phone, a user device, a personal digital assistant, a laptop / tablet computer, a web browser, an e-book reader and / or the like. Such a mobile (or even generally stationary) device is usually operated by a user. However, the 3GPP standard also makes it possible to connect so-called "Internet of Things" (IoT) devices (e.g., narrowband IoT (NB-IoT) devices) to a network, which typically include automated equipment such as various measuring devices, telemetry equipment, monitoring systems, tracking and tracing devices, vehicle interior safety systems, vehicle maintenance systems, road sensors, digital billboards, point of sale (POS) terminals, remote control systems and the like. In fact, 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 makes it possible for 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 it will be understood that the described techniques can be implemented on any communication device (mobile and / or generally stationary) that can connect to a communication network for sending / receiving data, regardless of whether such communication device is controlled by human input or by software instructions stored in memory.

[0006] One of the recent features being developed on the existing 5G framework is called Multicast and Broadcast Service (MBS). This functionality is intended to enhance the 5G new air interface and 5G core network capabilities for reliable, low latency, resource-efficient and large-scale deployment of a large number of multicast and broadcast services. 3GPP is currently specifying the details of MBS for media distribution on mobile broadband networks. Some of the identified use cases that can benefit from MBS include public safety and mission-critical services, vehicle-to-everything (V2X) applications, IPTV, live video, software delivery, and IoT applications to various smart phones, tablets, vehicles and other mobile (or stationary) devices. Although MBS is designed to use existing (or already specified) 3GPP infrastructure, MBS can provide more efficient delivery of multicast / broadcast traffic compared to unicast communications using the same infrastructure. Details of the architectural enhancements for MBS can be found in 3GPP Technical Specification (TS) 23.247V17.2.0.

[0007] To facilitate resource-efficient delivery of multicast / broadcast services, 3GPP has developed NR broadcast / multicast as part of Release 17 (Rel-17) of the NR standard, with the goal of enabling general MBS services over 5G telecommunication networks. In more detail, for Rel-17 MBS, two delivery modes for MBS were agreed upon:

[0008] Delivery Mode 1 (multicast only), which can handle higher QoS services; and

[0009] Delivery Mode 2 (broadcast only), which focuses on lower QoS services.

[0010] Rel-17 MBS provides basic functionality to support MBS services, but it has been recognized that resource efficiency and capacity need to be improved and other issues need to be addressed to meet the stringent use cases proposed for MBS.

[0011] For example, according to Rel-17, the radio access network (RAN) specifies multicast transmissions only for UEs in an RRC connected state (sometimes referred to as RRC_CONNECTED mode), and thus UEs in other RRC connected states, i.e., in an RRC inactive state and in an RRC idle state (sometimes referred to as RRC_INACTIVE mode and RRC_IDLE mode, respectively), do not receive such transmissions (this situation may not fully meet the requirements of, e.g., mission-critical services, especially in the case where a cell serves many UEs (e.g., according to TR 23.774)). In addition, always keeping the UE in an RRC connected state is not efficient from the perspective of the base station as well as from the perspective of the UE (e.g., in terms of resource usage, power, etc.).

[0012] The discloser has recognised that there are a number of problems with current approaches to providing MBS functionality, particularly in the context of UE RRC connection state transitions and UE mobility. Accordingly, the present disclosure seeks to provide methods and associated apparatus for solving or at least alleviating at least some of the above problems.

[0013] Citation List

[0014] Patent Literature

[0015] Patent document 1: WO2022 / 086121A1

[0016] Patent document 2: WO2022 / 239690A1

[0017] Non-patent literature

[0018] Non-patent document 1: 3GPP TS23.247

[0019] Non-patent document 2: 3GPP TS23.003

[0020] Non-patent document 3: 3GPP TS23.003

[0021] Non-patent document 4: 3GPP TS24.116

[0022] Non-patent document 5: 3GPP TR 23.774

[0023] Non-patent document 6: 3GPP TS 38.413

[0024] Non-patent document 7: 3GPP TS 38.473

[0025] Non-patent document 8: 3GPP TS 38.401

[0026] Non-patent document 9: 3GPP TS 38.300

[0027] Non-patent document 10: 3GPP TS 37.340 Summary of the invention

[0028] Problem that the invention aims to solve

[0029] The present disclosure is directed to providing apparatus and related methods that are intended to at least partially help satisfy one or more of the above-mentioned needs.

[0030] Solutions for solving problems

[0031] According to one aspect, a method for an access network node is provided, the method comprising:

[0032] Transmitting a first message to a user equipment (UE) in an RRC_INACTIVE state, wherein the first message is used to indicate a capability of the UE to receive a multicast / broadcast service (MBS), where RRC is radio resource control;

[0033] In a case where the UE has information for identifying at least one MBS available to the UE, a second message is received from the UE, the second message being used to indicate one or more MBS sessions that the UE in the RRC_INACTIVE state can support, wherein:

[0034] 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.

[0035] According to another aspect, there is provided a method for an access network node having a central unit and a distributed unit, the method comprising:

[0036] Receiving, by means of the central unit, an indication of at least one multicast / broadcast service session, i.e. at least one MBS session accessible to a user equipment, i.e. UE, in an RRC_INACTIVE state from a core network node, RRC being Radio Resource Control;

[0037] transmitting, by the central unit, the indication to the distributed unit;

[0038] receiving, with the central unit, a response from the distributed unit; and

[0039] The indication is transmitted to the UE using the distributed unit.

[0040] According to another aspect, there is provided a method for a first access network node, the method comprising:

[0041] Information is transmitted to a user equipment, i.e., UE, being served by the first access network node, wherein the information includes a list of ongoing multicast / broadcast service sessions, i.e., an MBS session list, of a second access network node adjacent to the first access network node, or a neighbor cell / frequency list of at least one adjacent access network node having at least one ongoing MBS session.

[0042] According to another aspect, a method performed by a source access network node is provided for handing over a user equipment (UE) to a target access network node, the method comprising:

[0043] A conditional handover request message is transmitted to the target access network node, where the conditional handover request message includes multicast / broadcast service configuration information (MBS configuration information) for the UE.

[0044] According to another aspect, a method performed by a target access network node is provided for handover of a user equipment (UE) from a source access network node, the method comprising:

[0045] receiving a conditional handover request message from the source access network node, wherein the conditional handover request message includes multicast / broadcast service configuration information (MBS configuration information) for the UE;

[0046] In the case that there is no ongoing MBS session in the target access network node, an MBS session is established with the core network.

[0047] According to another aspect, a method for a core network node is provided, the method comprising:

[0048] A message is transmitted to another core network node, the message including an indication of one or more multicast / broadcast service sessions, ie, one or more MBS sessions, accessible to a user equipment, ie, UE, in RRC_INACTIVE state, RRC being Radio Resource Control.

[0049] According to another aspect, a method for a core network node is provided, the method comprising:

[0050] A message is transmitted to an access network node, the message including an indication of one or more multicast / broadcast service sessions, ie, one or more MBS sessions, that a user equipment, ie, UE, in RRC_INACTIVE state can access, RRC being Radio Resource Control.

[0051] According to another aspect, a method for a user equipment (UE) is provided, the method comprising:

[0052] receiving a first message from an access network node, the first message being used to indicate a capability of a UE in an RRC_INACTIVE state to receive a multicast / broadcast service, i.e., an MBS, where RRC is radio resource control;

[0053] transmitting, based on the information identifying at least one MBS available to the UE, a second message to the access network node, the second message being used to indicate one or more MBS sessions that the UE in the RRC_INACTIVE state can support; and

[0054] While the UE is in the RRC_INACTIVE state, at least one MBS corresponding to the one or more MBS sessions is received.

[0055] According to another aspect, a method for a user equipment (UE) is provided, the method comprising:

[0056] An indication of one or more multicast / broadcast service sessions, ie one or more MBS sessions, accessible to a UE in RRC_INACTIVE state is received from a distributed unit of an access network node, RRC being Radio Resource Control.

[0057] According to another aspect, a method for a user equipment (UE) is provided, the method comprising:

[0058] Information is received from a first access network node, the information comprising a list of ongoing multicast / broadcast service sessions, i.e., an MBS session list, of a second access network node adjacent to the first access network node, or a neighbor cell / frequency list of at least one adjacent access network node having at least one ongoing MBS session.

[0059] According to another aspect, there is provided an access network node, comprising:

[0060] means for transmitting a first message to a user equipment (UE) in RRC_INACTIVE state, the first message being used to indicate the capability of the UE to receive a multicast / broadcast service (MBS), RRC being Radio Resource Control; and

[0061] means for receiving, if the UE has information identifying at least one MBS available to the UE, a second message from the UE indicating one or more MBS sessions that the UE in the RRC_INACTIVE state can support, wherein

[0062] 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.

[0063] According to another aspect, an access network node is provided, comprising a central unit and a distributed unit, wherein:

[0064] The central unit comprises:

[0065] means for receiving from a core network node an indication of at least one multicast / broadcast service session, i.e. at least one MBS session, accessible to a user equipment, i.e. UE, in RRC_INACTIVE state, RRC being Radio Resource Control;

[0066] means for transmitting said indication to said distributed unit; and

[0067] means for receiving a response from said distributed unit; and

[0068] The distributed unit comprises:

[0069] means for transmitting the indication to the UE.

[0070] According to another aspect, there is provided a first access network node, comprising:

[0071] A component for transmitting information to a user equipment, i.e., UE, being served by the first access network node, the information comprising a list of ongoing multicast / broadcast service sessions, i.e., an MBS session list, of a second access network node adjacent to the first access network node, or a neighbor cell / frequency list of at least one adjacent access network node having at least one ongoing MBS session.

[0072] According to another aspect, a source access network node is provided for handing over a user equipment (UE) to a target access network node, the source access network node comprising:

[0073] A component is used to transmit a conditional handover request message to the target access network node, wherein the conditional handover request message includes multicast / broadcast service configuration information (MBS configuration information) for the UE.

[0074] According to another aspect, a target access network node is provided for handover of a user equipment (UE) from a source access network node, the target access network node comprising:

[0075] A component configured to receive a conditional handover request message from the source access network node, wherein the conditional handover request message includes multicast / broadcast service configuration information (MBS configuration information) for the UE;

[0076] A component for establishing an MBS session with a core network when no ongoing MBS session exists in the target access network node.

[0077] According to another aspect, a core network node is provided, comprising:

[0078] Means for transmitting a message to another core network node, the message comprising an indication of one or more multicast / broadcast service sessions, ie one or more MBS sessions, to which a user equipment, ie UE, in RRC_INACTIVE state can access, RRC being Radio Resource Control.

[0079] According to another aspect, a core network node is provided, comprising:

[0080] Means for transmitting a message to an access network node, the message comprising an indication of one or more multicast / broadcast service sessions, ie one or more MBS sessions, to which a user equipment, ie UE, in RRC_INACTIVE state can access, RRC being Radio Resource Control.

[0081] According to another aspect, a user equipment (UE) is provided, comprising:

[0082] A means for receiving a first message from an access network node, the first message being used to indicate a capability of a UE in an RRC_INACTIVE state to receive a multicast / broadcast service, i.e., MBS, RRC being Radio Resource Control;

[0083] means for transmitting, to the access network node, a second message based on the information identifying at least one MBS available to the UE, the second message indicating one or more MBS sessions that the UE in the RRC_INACTIVE state can support; and

[0084] While the UE is in the RRC_INACTIVE state, at least one MBS corresponding to the one or more MBS sessions is received.

[0085] According to another aspect, a user equipment (UE) is provided, comprising:

[0086] Means for receiving, from a distributed unit of an access network node, an indication of one or more multicast / broadcast service sessions, ie one or more MBS sessions, accessible to a UE in RRC_INACTIVE state, RRC being Radio Resource Control.

[0087] According to another aspect, a user equipment (UE) is provided, comprising:

[0088] A component for receiving information from a first access network node, wherein the information includes a list of ongoing multicast / broadcast service sessions, i.e., an MBS session list, of a second access network node adjacent to the first access network node, or a neighbor cell / frequency list of at least one adjacent access network node having at least one ongoing MBS session.

[0089] Each feature disclosed in this specification (which term includes the claims) and / or shown in the drawings may be incorporated into the present disclosure independently of (or in combination with) any other disclosed and / or exemplified feature. In particular, but not limitingly, features of any claim in a claim dependent upon a particular independent claim may be introduced into that independent claim in any combination or alone.

[0090] Effects of the Invention

[0091] According to the present disclosure, a method for a user equipment, a method for an access network node, a user equipment, and an access network node may be provided. BRIEF DESCRIPTION OF THE DRAWINGS

[0092] Example embodiments of the present disclosure will now be described by way of example with reference to the accompanying drawings, in which:

[0093] Figure 1 Schematically illustrating a mobile (cellular or wireless) telecommunication system to which example embodiments of the present disclosure may be applied;

[0094] Figure 2 Schematically illustrating a mobile (cellular or wireless) telecommunication system to which example embodiments of the present disclosure may be applied;

[0095] Figure 3 is formed Figure 1 and Figure 2 A schematic block diagram of a mobile device that is part of the system shown;

[0096] Figure 4 is formed Figure 1 and Figure 2 A schematic block diagram of an access network node (e.g., a base station) that is part of the system shown;

[0097] Figure 5 is formed Figure 1 and Figure 2 A schematic block diagram of an access network node (e.g., a base station) that is part of the system shown;

[0098] Figure 6 is formed Figure 1 and Figure 2 A schematic block diagram of a core network node that is part of the system shown;

[0099] Figure 7 Schematically illustrated in Figure 1 and Figure 2 Some exemplary ways in which the present disclosure may be implemented in the system shown;

[0100] Figure 8 Schematically illustrated in Figure 1 and Figure 2 Some exemplary ways in which the present disclosure may be implemented in the system shown;

[0101] Fig. 9 Schematically illustrated in Figure 1 and Figure 2 Some exemplary ways in which the present disclosure may be implemented in the system shown; and

[0102] Fig.10 Schematically illustrated in Figure 1 and Figure 2 Some exemplary ways in which the present disclosure may be implemented in the system shown. DETAILED DESCRIPTION

[0103] <Overview>

[0104] Figure 1 A mobile (cellular or wireless) telecommunication system 1 is schematically illustrated to which example embodiments of the present disclosure may be applied.

[0105] In the system 1, users of mobile devices 3 (UE) can communicate with each other and other users via base stations 5 and other access network nodes forming a radio access network (RAN), via which the UE communicates with an associated core network 7 using an appropriate 3GPP radio access technology (RAT) (e.g., Evolved Universal Terrestrial Radio Access (E-UTRA) and / or 5G RAT). It will be appreciated that a plurality of base stations 5 form a (radio) access network or (R)AN. As will be appreciated by those skilled in the art, although for purposes of illustration only, the base stations 5 are described in detail below. Figure 1Four mobile devices 3 and a base station (in Figure 1 5), but the system when implemented will typically include other base stations / (R)AN nodes and / or mobile devices (UEs).

[0106] Each base station 5 controls one or more associated cells (either directly or via other nodes such as home base stations, repeaters, remote radio heads, distributed units, and / or the like). Base stations 5 that support next generation / 5G protocols may be referred to as "gNBs" and 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 protocols.

[0107] The mobile device 3 and its serving base station 5 are connected via a suitable air interface (e.g., a so-called "NR" air interface, a "Uu" interface, and / or the like). The neighboring base stations 5 are connected via a suitable base station-to-base station interface (such as a so-called "Xn" interface, an "X2" interface, and / or the like, Figure 1 The base stations 5 are also connected to the core network nodes via appropriate interfaces, such as the so-called "NG-U" interface (for the user plane), the so-called "NG-C" interface (for the control plane), and / or the like.

[0108] 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 telecommunications system 1 and for subscriber management, mobility management, billing, security, call / session management (among others). For example, the core network 7 of a "next generation" / 5G system will include user plane entities and control plane entities, such as one or more control plane functions (CPFs) and one or more user plane functions (UPFs) 8-3. Examples of CPFs are the so-called Access and Mobility Management Function (AMF) 8-1 in 5G or the Mobility Management Entity (MME) in 4G, which is responsible for handling connection and mobility management tasks for mobile devices 3. Another example of a CPF is the so-called Session Management Function (SMF) 8-2, which is responsible for handling communication sessions for mobile devices 3, such as session establishment, modification and release.

[0109] In addition to other nodes / functions not described here, the core network 7 may also 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. Figure 1 Several service-based interfaces are illustrated in , namely:

[0110] Nmbsmf: The service-based interface exposed by MB-SMF.

[0111] Npcf: Service-based interface exposed by PCF.

[0112] Namf: A service-based interface exposed by AMF.

[0113] Nnef: Service-based interface exposed by NEF.

[0114] Nnrf: A service-based interface exposed by NRF.

[0115] Nudm: Service-based interface exposed by UDM.

[0116] In addition, Figure 1 Several reference points are illustrated in , namely:

[0117] N2: Reference point between NG-RAN and AMF.

[0118] N3: Reference point between NG-RAN and UPF.

[0119] N3mb: Reference point between RAN and MB-UPF.

[0120] N4mb: Reference point between MB-SMF and MB-UPF.

[0121] N6mb: Reference point between MB-UPF and AF / AS.

[0122] N19mb: Reference point between UPF and MB-UPF.

[0123] Nmb1: Reference point between MB-SMF and MBSF.

[0124] Nmb2: Reference point between MBSF and MBSTF.

[0125] Nmb9: Reference point between MB-UPF and MBSTF.

[0126] Nmb10: Reference point between MBSF and AF.

[0127] The core network 7 (via UPF 8-3) is coupled to a data network (not shown), such as the Internet or a similar Internet Protocol (IP)-based network, etc.

[0128] Various network operators deploy their base stations 5 and associated core networks 7 to provide services in a given area (e.g., a country). Each network can also be referred to as a Public Land Mobile Network (PLMN), and each network is uniquely identified by its PLMN identifier (PLMNID). 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).

[0129] Multicast and Broadcast Service (MBS) functionality (which, for example, provides resource-efficient transmission to multiple end users who need to receive the same service) can be provided to UE 3 via the serving base station 5 of UE 3 and associated core network nodes (such as UPF 8-3 and SMF 8-2, etc.). UPF 8-3 can be an MBS-specific UPF, in which case UPF 8-3 can be referred to as MB-UPF 8-5 (e.g., dedicated to the provision of MBS functionality). Similarly, SMF 8-2 can be an MBS-specific SMF, in which case SMF 8-2 can be referred to as MB-SMF 8-4. However, it will be understood that any suitable UPF / SMF can be used for MBS.

[0130] Each UE 3 interested in MBS monitors the system information broadcast by the base station 5 and determines the resources for the relevant control channel and data channel (MCCH and MTCH, respectively). The base station 5 also broadcasts a corresponding identifier (MBS session ID or Temporary Mobile Group Identity (TMGI)) for each MBS session provided in its cell. If UE 3 finds its own PLMN ID in the system information for a given cell, UE 3 is allowed to access that cell.

[0131] TMGI is an MBS session identifier that uniquely identifies a specific MBS service. TMGI has three parts: an MBMS service ID part; a Mobile Country Code (MCC) part; and a Mobile Network Code (MNC) part. 3GPP TS 38.413, clause 9.3.1 defines the three parts of TMGI as follows:

[0132] 1) MBMS Service ID consisting of three octets. The MBMS Service ID consists of a 6-bit fixed-length hexadecimal number between 000000 and FFFFFF. The MBMS Service ID uniquely identifies the MBMS bearer service within the PLMN. The structure of the MBMS Service ID for receive-only mode services is defined in 3GPP TS 24.116;

[0133] 2) A three-digit Mobile Country Code (MCC). With the exception of MCC value 901, which does not identify any country and is globally assigned by the International Telecommunication Union (ITU), the MCC uniquely identifies the country of residence of the Broadcast-Multicast Service Center (BM-SC); and

[0134] 3) A Mobile Network Code (MNC) consisting of two or three digits (depending on the assignment to the PLMN by the National Numbering Plan Administrator of the PLMN). The MNC identifies the PLMN to which the BM-SC belongs, except for the MNC value 56 when the MCC value is 901 (which does not identify any PLMN). For more information on the use of TMGI, see 3GPP TS 23.246.

[0135] 3GPP TS23.003 defines the part of PLMN ID as follows:

[0136] 1) The three-digit Mobile Country Code (MCC). The MCC uniquely identifies the country of residence for the mobile subscription; and

[0137] 2) Mobile Network Code (MNC), which (depending on the assignment to the PLMN by the National Numbering Plan Administrator of the PLMN) consists of two or three digits for 3GPP network applications. The MNC identifies the home PLMN of the mobile subscription in its country of residence, or the MNC together with the MCC and the Network Identifier (NID) identifies the Standalone Non-Public Network (SNPN) of the mobile subscription. The length of the MNC (two or three digits) depends on the value of the MCC.

[0138] The list of PLMNs supported in a cell is indicated in the relevant system information. Specifically, System Information Block Type 1 (SIB1) includes the list of supported PLMNs in the plmn-IdentityInfoList information element (which is included in the so-called CellAccessRelatedInfo information element of SIB1).

[0139] The MBS session establishment procedure has been standardized by 3GPP in TS23.247. Specifically, clause 7.2.1.3 defines the current procedure and associated session establishment procedure for joining a multicast session. In addition, the multicast session management procedure is defined in 3GPP TS 38.413 (per clause 8.18). The contents of these documents are incorporated herein by reference.

[0140] like Figure 1 As shown, there is a single UE 3-1 having a connection with the NG-RAN 5, and a group of three UEs also having corresponding connections with the NG-RAN 5. The UE 3-1 receives data for its MBS session in a point-to-point (PTP) manner, while the UE group 3-2 receives data for its MBS session in a point-to-multipoint (PTM) manner.

[0141] However, and as mentioned above, there are several issues with the current MBS session management procedures that need to be addressed, particularly as the procedures described above currently only apply to UEs in an RRC connected state.

[0142] Figure 2 1 illustrates more details of the core network 7, which also shows the interfaces between the various network nodes. As can be seen, the core network 7 may generally include an authentication server function (AUSF), a unified data management (UDM) entity, a policy control function (PCF), an application function (AF), and others (e.g., as described above for Figure 1 The core network 7 is coupled (via the UPF) to a data network (DN) 8-14, such as the Internet or a similar Internet Protocol (IP) based network. The core network 7 may also be coupled to an operation and maintenance (OAM) function (not shown).

[0143] In the following, solutions to the problems of current MBS session provisioning and management will be outlined.First, however, a discussion of several nodes forming part of the system 1 will be explained.

[0144] <User Equipment (UE)>

[0145] Figure 3 is an example Figure 1 and Figure 2 3 is a block diagram of the main components of a mobile device (UE) 3. As shown, the UE 3 includes a transceiver circuit 31 that is operable to transmit signals to one or more connected nodes and receive signals from one or more connected nodes via one or more antennas 33. Although not necessarily Figure 33, but of course the UE 3 will have all the usual functionality of a conventional mobile device (such as a user interface 35 etc.), and this may be provided by any one or any combination of hardware, software and firmware as appropriate. The controller 37 controls the operation of the UE 3 according to the software stored in the memory 39. For example, the software may be pre-installed in the memory 39 and / or may be downloaded via the telecommunications network 1 or from a removable data storage device (RMD). The software includes an operating system 41, a communication control module 43 and an MBS module 45, among others.

[0146] The communication control module 43 is responsible for handling (generating / sending / receiving) signaling messages and uplink / downlink data packets between the UE 3 and other nodes (including the (R)AN node 5 and the core network node). The signaling may include RRC signaling (to / from the (R)AN node 5) and / or NG-C / NG-U signaling (to / from the core network 7 (via the RAN)).

[0147] The MBS module 45 is responsible for handling signaling related to the multimedia broadcast service.

[0148] <Access Network Node (Base Station)>

[0149] Figure 4 is an example Figure 1 Block diagram of the main components of the base station 5 (or similar access network node) shown. As shown, the base station 5 has: a transceiver circuit 51 for transmitting signals to and receiving signals from user equipment (such as a mobile device 3, etc.) via one or more antennas 53; a network interface 55 for transmitting signals to and receiving signals from the core network 7 and adjacent base stations. The base station 5 has a controller 57 to control the operation of the base station 5 according to software stored in the memory 59. For example, the software may be pre-installed in the memory 59 and / or may be downloaded via the telecommunications network 1 or from a removable data storage device (RMD). The software includes an operating system 61 and at least a communication control module 63, as well as other. Although in Figure 4 Not shown, the network interface 55 will typically also include a base station to base station interface portion (e.g., Xn and / or the like) and a core network interface portion (e.g., NG-C / NG-U / N2 / N3).

[0150] The communication control module 63 is responsible for handling (generating / sending / receiving) signaling between the base station 5 and other nodes (such as UE 3 and core network nodes, etc.). Such signaling may include, for example, control data for managing the operation of the mobile device 3 (e.g., non-access stratum (NAS), radio resource control (RRC), system information, paging and / or the like). The signaling may include signaling for configuring the UE 3 for receiving MBS sessions and signaling for configuring other nodes to provide MBS sessions. It will be understood that the communication control module 63 may include multiple sub-modules (or "layers") to support specific functionality. 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, etc.

[0151] In the 5G architecture, the internal structure of the base station (gNB or en-gNB) can be split into two parts called the Central Unit (CU) and the Distributed Unit (DU) connected by the F1 interface. In this "split" architecture, the usually "higher" CU layers (e.g., but not necessarily or exclusively), PDCP and the usually "lower" DU layers (e.g., but not necessarily or exclusively, RLC / MAC / PHY) can be implemented separately. Thus, for example, the higher layer CU functionality for multiple gNBs can be implemented centrally (e.g., by a single processing unit or in a cloud-based or virtualized system) while keeping the lower layer DU functionality locally in each gNB.

[0152] like Figure 5 As shown, 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) to communicate signals between the various functions of the distributed base station. In this case, the software stored in the base station 5 also includes at least one of the following items: a gNB-CU-CP module 5C, a gNB-CU-UP module 5U, and a gNB-DU module 5D. If present, the gNB-CU-CP module 5C hosts the control plane 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 SDAP layer and the PDCP 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 layer, MAC layer, and PHY layer of the distributed base station (gNB or en-gNB).

[0153] Those skilled in the art will appreciate that the central unit (e.g., 5C and / or 5U) may be implemented and physically located with a base station, or may be implemented as a single physical element or as a cloud-based or virtualized system at a remote location. It will also be appreciated that a single central unit may serve multiple base stations 5.

[0154] <Core Network Node>

[0155] Figure 6 is an example Figure 1 and Figure 2 8-1, SMF 8-2, UPF 8-3, etc. As shown, the core network node includes a transceiver circuit 71, which is operable to transmit signals to other network nodes and receive signals from these other network nodes via a network interface 75 (directly or indirectly). Depending on the circumstances, signals can be sent to one or more UEs 3 and received from one or more UEs 3 via a base station 5 or other (R)AN node. 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 the software stored in the memory 79. For example, the software can be pre-installed in the memory 79 and / or can be downloaded via the telecommunications network 1 or from a removable data storage device (RMD). The software includes an operating system 81, a communication control module 83 and an optional MBS module 85, as well as others.

[0156] The communication control module 83 is responsible for handling (generating / sending / receiving) signaling between the core network node and other nodes (such as UE 3, (R)AN node and other core network nodes, etc.).

[0157] If present (e.g., in MB-SMF 8-4 or MB-UPF 8-5), the MBS module 85 is responsible for handling signaling (control signaling and / or MBS traffic) related to the multimedia broadcast service. The signaling may include signaling related to the provision of MBS sessions via the RAN / base station, and signaling for configuring other nodes to provide MBS sessions via the RAN / base station.

[0158] <Detailed description>

[0159] As mentioned above, there are several problems with MBS session management. The following detailed description sets out several solutions to these problems.

[0160] 1.RRC_INACTIVE mode configuration

[0161] According to Rel-17 MBS, when an MBS session is activated, the RAN node 5 sends a paging message including a list of TMGIs identifying the different MBS sessions available via the RAN node 5. If the UE 3 is interested in an MBS session with a TMGI on the list, current standards specify that the UE 3 should transition to RRC_CONNECTED mode to be able to receive MBS transmissions. However, a UE operating according to the latest version of the 3GPP NR standard (Release 18) can be in one of three potential RRC modes (connected states) with its serving base station:

[0162] 1)RRC_CONNECTED;

[0163] 2)RRC_INACTIVE; or

[0164] 3)RRC_IDLE.

[0165] The state RRC_INACTIVE is a state that enables the UE to quickly recover to the RRC_CONNECTED state, and it is proposed that the UE should be able to receive MBS transmissions even in the RRC_INACTIVE state (although without the usual high reliability of the service guaranteed by being in the RRC_CONNECTED state and as long as the MBS service allows). Therefore, as long as the UE 3 can transition to RRC_INACTIVE mode, the UE does not need to transition to RRC_CONNECTED mode if the MBS service allows the UE to access the MBS service when in RRC_INACTIVE mode. If it can be avoided, it is mutually beneficial for the network and for the UE that the UE does not transition to / remain in the RRC_CONNECTED mode, because resources can be saved on both the network and UE sides.

[0166] in this regard, Figure 7 A procedure between a UE 3 and a RAN node 5 (such as a gNB or the like) of a telecommunications system 1 is illustrated by which the network determines the capability of the UE 3 to support an RRC_INACTIVE mode configuration in the context of an MBS session. In step 1, the RAN node 5 sends a query to determine the capability of the UE to receive MBS in RRC_INACTIVE mode. The query (which may be referred to as a UE RRC_INACTIVE support query) may be sent in a dedicated RRC message (e.g., UEcapablityenquiry, RRCSetupComplete, or another appropriate message), in a paging message, in a system information block (SIB), or in signaling over a multicast control channel (such as an MBMS control channel (MCCH), an MBS control channel (MCCH), or the like).

[0167] In step 2, the UE 3 reports whether it can support the RRC_INACTIVE state. The response may be referred to as a 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 may advantageously configure RRC_INACTIVE mode support for the UE and manage the relevant MBS sessions for the UE taking into account the received report.

[0168] When UE 3 does not need to transition to the RRC_CONNECTED state to receive MBS transmission, changes to the current procedure are needed to inform UE 3.

[0169] The first option associates each TMGI in the TMGI list broadcasted by the RAN node 5 with an indication. If the indication is set to, for example, "yes", then if a UE operating according to the latest version of the standard (i.e., a Release 18 (Rel-18) UE) wishes to receive the MBS transmission, the UE transitions to RRC_CONNECTED mode, whereas if the indication is set to, for example, "no", then if the UE wishes to receive the MBS transmission, the UE will not transition to RRC_CONNECTED mode. The structure of the modified paging message may be in the following format:

[0170]

[0171] Thus, in this case, the indication indicates whether the corresponding MBS service allows the UE to receive the MBS service in the RRC_INACTIVE state, and thus UEs capable of operating in the RRC_INACTIVE state can decide whether they need to transition to the RRC_CONNECTED state based on one or more indications for one or more MBS services they wish to receive.

[0172] According to an alternative option, the UE may instead be configured to not transition to RRC_CONNECTED mode even if the paging message includes a TMGI in which the UE is interested.

[0173] 2.RRC state transition

[0174] An MBS-capable UE may transition from the RRC_CONNECTED state to the RRC_INACTIVE state to, for example, save power and enhance the capacity of the serving cell (by minimizing the signaling overhead associated with keeping the UE in the RRC_CONNECTED state).

[0175] Similarly, an MBS-capable UE may transition from the RRC_INACTIVE state to the RRC_CONNECTED state in the case where the UE moves to the edge of the serving cell and the network establishes another point-to-point (PTP) connection leg (leg) of an MBS radio bearer (MRB) to enhance the reliability of the MBS service received by the UE. In addition, in the case where the UE is ready for cell reselection to a neighbor cell, but the neighbor cell operates according to an earlier version of the standard and therefore does not support receiving MBS services in the RRC_INACTIVE state (e.g., the neighboring RAN node operates according to Release 17), when the UE selects a neighbor cell, the UE will need to transition to the RRC_CONNECTED state to maintain the MBS service.

[0176] One way to control these problems is for the RAN node 5 to configure the UE in the RRC_INACTIVE state with a StateTransitConfig parameter, which defines the RRC state transition thresholds for controlling transitions between the RRC_INACTIVE state and the RRC_CONNECTED state (and is described in detail below). The StateTransitConfig parameter may be provided to the UE in the SIB, over a multicast control channel (e.g., MCCH), or via a paging message.

[0177] Accordingly, if the UE is in RRC_CONNECTED state instead, the StateTransitConfig parameter may be configured by the RAN node 5 and provided to the UE via dedicated RRC signaling. In the event that the UE has received the StateTransitConfig parameter in the SIB, over the MCCH or via a paging message (i.e. the UE received the parameter while it was in RRC_INACTIVE state), then the StateTransitConfig parameter provided by the dedicated RRC signaling takes precedence and overrides the StateTransitConfig parameter received while the UE was in RRC_INACTIVE state.

[0178] The thresholds included in the StateTransitConfig parameter can include the following conditions:

[0179] RRC_CONNECTED to RRC_INACTIVE conditions

[0180] RSRP>RSRPConnectedtoInactivethres

[0181] RSRQ>RSRQConnectedtoInactivethres

[0182] RRC_INACTIVE to RRC_CONNECTED conditions

[0183] RSRP <RSRPInactivetoConnectedthres

[0184] RQ <RSRQInactivetoConnectedthres

[0185] Where: RSRP is the reference signal received power and RSRQ is the reference signal received quality. These are the measurement results of the received signal measured by the UE and will be well known to those of ordinary skill in the art.

[0186] The StateTransitConfig parameter may be associated with each TMGI so that the requirements for transitioning between RRC states may differ depending on the MBS service received by the UE. The StateTransitConfig parameter may be communicated to the UE, for example, in a message carrying a configuration such as RRC_INACTIVE-SUPPORTIVE-configuration. The structure of such a message may be in the following format:

[0187]

[0188] Reference will now be made to yet another example embodiment for controlling RRC state transitions in the context of split MRBs (MBS radio bearers). In this regard, it may be beneficial for the UE to transition from the RRC_INACTIVE state to the RRC_CONNECTED state to ensure the reliability of the desired MBS service in the event that the reference signal received power (RSRP) / reference signal received quality (RSRQ) of a point-to-multipoint (PTM) connection segment does not meet a configured threshold. To facilitate this state transition, the UE may establish an RRC connection to the network and utilize a modified RRCSetupComplete message to inform the network which one or more MBS services require reliability enhancement, for example, by the network configuring an additional PTP connection segment in the MRB. The structure of the modified RRCSetupComplete may take the following format:

[0189]

[0190] 3. MBS session establishment

[0191] The management procedures for MBS session establishment and association are specified in 3GPP TS 23.247. One such procedure specified in clause 7.2.1.4 of the standard concerns "Establishment of shared delivery towards RAN nodes" (shared delivery means delivery of MBS services to UEs via multicast transmission). However, the current procedures do not inform the gNB-CU and one or more gNB-DUs whether the UE 3 is allowed to operate in the RRC_INACTIVE state for this particular MBS session. Therefore, in Figure 8 A modified “Setup of shared delivery towards RAN nodes” signalling diagram that addresses the above issues is presented in and will be discussed below.

[0192] In step 1, when the NG-RAN node 5 serves at least one UE 3 within a multicast MBS session, the NG-RAN node 5 decides to establish shared delivery for the multicast MBS session. For location-dependent services, if the NG-RAN node 5 serves at least one UE assigned to an MBS session ID and an area session ID, the NG-RAN node 5 needs to establish shared delivery for the location-dependent content of the multicast MBS session.

[0193] Then, in step 2, the NG-RAN sends an N2MBS Session Request message (including one or more of MBS Session ID, [Regional Session ID], N2SM information ([Unicast DL Tunnel Info])) towards the AMF 8-1. If the NG-RAN node 5 is configured to use unicast transmission for shared delivery, the NG-RAN node 5 allocates a GTP tunnel endpoint and provides the unicast DL tunnel information in the request, which includes the GTP tunnel endpoint and the NG-RAN node 5 address. For location-dependent MBS services, the NG-RAN node 5 also provides the regional session ID.

[0194] In step 3, AMF 8-1 selects the MB-SMF 8-4 that serves the multicast MBS session, for example, using the NRF discovery service or locally stored information. AMF 8-1 invokes the Nmbsmf_MBSSession_ContextUpdate request (including one or more of the MBS session ID, [regional session ID], N2SM information) to the MB-SMF 8-4. 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.

[0195] Step 4 is indicated by a dotted line and is conditional on the MB-SMF 8-4 receiving the unicast DL tunnel information in step 3. If so, the MB-SMF 8-4 configures the MB-UPF 8-5 to send the multicast data for the multicast MBS session (or the location-dependent content of the multicast MBS session if a regional session ID is received) towards the GTP tunnel endpoint via unicast transmission.

[0196] Continuing now with reference to step 5, the MB-SMF 8-4 stores the information of the AMF 8-1 (e.g. the AMF ID) in the MBS multicast MBS session context (or the location-dependent part of the multicast MBS session context in the case where a regional session ID is received) to enable subsequent signaling towards that AMF 8-1.

[0197] The above steps are unchanged relative to the current process outlined in TS23.247. The following steps 6 to 8 represent modifications and additions to the corresponding steps currently outlined in TS23.247 to address the above issues. Going to step 6, MBS-SMF 8-4 sends a message (which may be referred to as an Nmbsmf_MBSSession_ContextUpdate response message) to AMF 8-1, which includes, in addition to any other appropriate parameters, an MBS session RRC_INACTIVE allow indicator and a TMGI. The MBS session RRC_INACTIVE allow indicator indicates whether the TMGI allows the UE to receive the corresponding MBS service in the RRC_INACTIVE state. In addition, if MB-SMF 8-4 does not receive unicast DL tunnel information in step 3, MB-SMF 8-4 provides multicast DL tunnel information, which includes a transport multicast address (e.g., a lower layer source specific IP multicast address (LL SSM)) and a GTP tunnel endpoint for a shared delivered multicast transmission.

[0198] Then, in step 7, the AMF 8-1 sends an N2MBS message to the NG-RAN node 5, which includes the MBS session RRC_INACTIVE allowed indicator and the TMGI, together with any additional related parameters. Finally, in step 8, the NG-RANgNB provides the MBS session RRC_INACTIVE allowed indicator and the TMGI to the UE 3 via, for example, the system information block (SIB) (or alternatively through the multicast control channel (MCCH), in a paging message, or in an RRC Release (RRC Release) message). As a result of the UE 3 receiving the MBS session RRC_INACTIVE allowed indicator and the associated TMGI, the UE 3 will be able to use the MBS service corresponding to the TMGI in the RRC_INACTIVE state, thereby beneficially eliminating the need for the UE 3 to transition to the RRC_CONNECTED state.

[0199] To ensure that the multicast context is set up correctly, such as Fig. 9 As shown, the current multicast context setting (defined in TS 38.473 at clause 8.14.6) is modified to include the MBS session RRC_INACTIVE allow indicator. Fig. 9 As illustrated in step 1 of the embodiment, the gNB-CU 5A sends a message (sometimes referred to as MULTICAST CONTEXT SETUP REQUEST) to the gNB-DU 5B, which includes Figure 8 The MBS session RRC_INACTIVE permission indicator and the associated TMGI received in step 7 of the . In step 2, the gNB-DU 5B acknowledges receipt of the message sent by the gNB-CU 5A by sending a message (sometimes referred to as a MULTICAST CONTEXT SETUP RESPONSE message) to the gNB-CU 5A. Therefore, after the above process, both the gNB-CU 5A and one or more gNB-DUs 5B know whether the UE is allowed to operate in RRC_INACTIVE mode for the MBS session, and thus the gNB-CU can configure appropriate MRBs for the UE 3 and the RLC entities in the gNB-DU.

[0200] 4.RRC_INACTIVE mode mobility

[0201] As discussed above in accordance with Release 17 of the MBS standard, the UE should transition to the RRC_CONNECTED state to register for MBS services with the core network. However, in accordance with the more recent Release 18, after the registration process, the UE may freely transition to the RRC_INACTIVE state (according to the conditions described above in the example embodiment entitled "RRC State Transition"). It should be understood that when a UE operating in the RRC_INACTIVE state is in mobility and undergoes cell reselection, the UE does not need to transition to RRC_CONNECTED mode to achieve cell reselection. However, if a neighbor cell (to which the UE wishes to reselect (and therefore camp on)) does not have an ongoing PTM MBS session for the UE to receive in the camping cell, the UE will transition to the RRC_CONNECTED state.

[0202] According to Release 17, since only UEs in RRC_CONNECTED state are supported for multicast, multicast configuration is not scheduled in MCCH, but instead is scheduled in the RRCReconfiguration message, which is only available when the UE is in RRC_CONNECTED state (RRCReconfiguration message is used for handover and provides all neighbor cell information). Therefore, the following provides a solution that facilitates providing multicast configuration for UEs operating in RRC_INACTIVE mode without the need for RRC state transition.

[0203] According to this example embodiment, a new channel (multicast channel, MCCH) is provided for UEs operating in the RRC_INACTIVE state, whereby the channel can provide a multicast configuration for RRC_INACTIVE UEs. It will be understood that the new MCCH is scheduled in a system information block (SIB), because RRC_INACTIVE UEs can still receive SIBs, and therefore in the following discussion, references to SIB-MCCH refer to the UE reading the SIB to obtain the scheduling of the MCCH.

[0204] Regarding the handling of mobility of UEs in RRC_INACTIVE state, in a first example, the serving cell provides a list of ongoing MBS sessions of neighbor cells in SIB-MCCH (or SIB itself). This allows RRC_INACTIVE UEs to find out which neighbor 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 of the neighbor cell, then:

[0205] RRC_INACTIVE The UE may transition to the RRC_CONNECTED state. Then, after handover to the target cell, the UE triggers the MBS Join procedure as set forth in the MBS Join procedure of clause 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 Join procedure as set forth in the MBS Join procedure of clause 7.2.1.3 of 3GPP TS 23.247; or alternatively

[0206] A UE operating in the RRC_INACTIVE state may give priority to other neighbor cells that support the desired MBS session. If there are no other cells that support the MBS session, the UE will perform regular cell reselection to a cell that does not support the MBS session, and then transition to the RRC_CONNECTED state to trigger the MBS Join procedure set forth in the MBS Join procedure of clause 7.2.1.3 of 3GPP TS23.247. The serving cell may send a list of supported cells / supported frequencies for the desired MBS session to the UE in one of the following messages: paging message, RRC Release message, RRC dedicated message, SIB message, and message through MCCH.

[0207] The base station may use the following RRC_INACTIVE-SUPPORTIVE-indication message to inform the UE which MBS service can be received when the UE is in the RRC_INACTIVE state:

[0208]

[0209] In the second example, the serving cell only broadcasts (in its SIB-MCCH) a list of neighbor cells / frequencies with ongoing MBS services. If the UE is planning to reselect a neighbor cell, the UE can check whether the neighbor cell has ongoing MBS services based on the information broadcast by its current serving cell, and if the neighbor cell has ongoing MBS services, the UE reads the neighbor cell's MCCH to obtain a list of MBS sessions supported by the neighbor cell. In this way, the UE can check whether the desired MBS session is ongoing in the neighbor cell before deciding to reselect to the neighbor cell.

[0210] If the UE reselects a cell that does not have any ongoing MBS session, the UE shall transition to RRC_CONNECTED to trigger the MBS join procedure described in clause 7.2.1.3 of TS 23.247.

[0211] 5. Handover Optimization

[0212] As specified in the current standard (3GPP TS 38.401, at clause 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 session for the UE to hand over to the target cell. Currently, if there is no ongoing MBS session in the target gNB, the target gNB shall start the MBS session establishment procedure in the target cell as per clause 7.2.1.3 of 3GPP TS23.247; however, if there is no ongoing MBS session for the UE undergoing the handover procedure, it will take a long time to establish the MBS session in the target gNB during the handover. In the following references Fig.10 A solution to this problem is proposed in the description of Fig.10 Represents an abridged and modified version of the “Inter-gNB Handover involving gNB-CU-UP change” signalling diagram of clause 8.9.4 of TS 38.401).

[0213] First, refer to Fig.10 In step 1, 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 the MBS configuration for the UE that may be the subject of the handover to the target as part of the RRC configuration. Conditional handover is a pre-handover before the handover conditions are met.

[0214] In step 2, in case no MBS session exists in the target gNB, the target gNB-CU-CP 5-4 (e.g., as per clause 7.2.1.3 of TS 23.247) establishes an MBS session with the core network (typically with the MB-SMF).

[0215] In this way, if an MBS session is not already established before the actual handover of the UE, the target gNB beneficially "pre-establishes" the MBS session. This process is much faster than using a normal handover process where the UE would first have to handover to the target base station before subsequently requesting MBS services from the target base station, which would then attempt to establish MBS services with the core network if no MBS services already exist.

[0216] Then, in step 3, the gNB-CU-CP 5-4 sends a BEARER CONTEXT SETUP REQUEST message to set up the bearer context in the gNB-CU-UP 5-3, which contains the UL TNL address information for S1-U or NG-U, and (if necessary) the DL TNL address information for X2-U. For NG-RAN, the gNB-CU-CP 5-4 decides the mapping of flows to DRBs and sends the generated SDAP and PDCP configurations to the gNB-CU-UP 5-3. Since the handover is conditional, the BEARER CONTEXT SETUP REQUEST message indicates that the included security context will be ignored and no downlink packets will be initiated until the UE successfully accesses the target.

[0217] In step 3a, the gNB-CU-UP 5-3 responds with a BEARER CONTEXT SETUP RESPONSE message, which contains UL TNL address information for F1-U and DL TNL address information for S1-U or NG-U, and (if necessary) UL TNL address information for X2-U or Xn-U.

[0218] Then, in step 4, the F1UE context setup procedure is performed to establish one or more bearers in the gNB-DU 5-2.

[0219] Finally, the target gNB-CU-CP 5-4 responds with a HANDOVER REQUEST ACKNOWLEDGE message to the source gNB-CU-CP 5-1 in step 5. Since the handover process is conditional, the target gNB-CU-CP 5-4 ensures that the EARLY STATUS TRANSFER information is forwarded to the correct gNB-CU-UP 5-3 (e.g., a separate UE-associated signaling connection over the Xn interface for each gNB-CU-UP).

[0220] <Modification and Replacement>

[0221] Detailed example embodiments are described above. As will be appreciated by those skilled in the art, many modifications and substitutions may be made to the above example embodiments while still benefiting from the disclosures embodied in these embodiments. Many of these substitutions and modifications will now be described only by way of example.

[0222] For simplicity, the above description refers to MBS. However, MBS functionality may also be referred to as Multimedia Broadcast / Multicast Service (MBMS) functionality or similar.

[0223] Although base stations of 5G / NR communication systems are often referred to as new radio base stations ("NR-BS") or as "gNBs", it will be understood that they may be referred to using the term "eNB" (or 5G / NR eNB) which is more typically associated with long term evolution (LTE) base stations (also often referred to as "4G" base stations). 3GPP TS 38.300 V16.7.0 and 3GPP TS 37.340 V16.7.0 define the following nodes, among others:

[0224] gNB: A node that provides NR user plane and control plane protocol termination towards the UE and is connected to the 5G Core Network (5GC) via the NG interface.

[0225] ng-eNB: A node that provides E-UTRA user plane and control plane protocol termination towards the UE and is connected to the 5GC via the NG interface.

[0226] En-gNB: A node that provides NR user plane and control plane protocol termination towards the UE and acts as a secondary node in E-UTRA-NR Dual Connectivity (EN-DC).

[0227] NG-RAN node: gNB or ng-eNB.

[0228] It will be appreciated that the above example embodiments may be applied to 5G new air interface and LTE systems (E-UTRAN) as well as any future generation systems. Base stations supporting E-UTRA / 4G protocols may be referred to as "eNBs", and base stations supporting next generation / 5G protocols may be referred to as "gNBs". It will be appreciated that some base stations may be configured to support both 4G and 5G protocols, and / or any other 3GPP or non-3GPP communication protocols.

[0229] In the above description, for ease of understanding, the UE, access network node, and data network node are described as having multiple discrete modules (such as communication control modules, etc.). Although these modules may be provided in this way for certain applications, for example, in the case where an existing system has been modified to implement the present disclosure, in other applications, such as in a system designed from the outset to take advantage of the present inventive features, these modules may be built into the entire operating system or code, and therefore these modules may not be discernible as discrete entities. These modules may also be implemented in software, hardware, firmware, or a mixture of these.

[0230] Each controller may include any suitable form of processing circuitry, including (but not limited to) for example: one or more hardware-implemented computer processors; microprocessors; central processing units (CPUs); arithmetic logic units (ALUs); input / output (IO) circuits; internal memory / cache (program and / or data); processing registers; communications buses (e.g., control, data and / or address buses); direct memory access (DMA) functionality; hardware or software-implemented counters, pointers and / or timers; and / or the like.

[0231] In the above example embodiments, a plurality of software modules are described. As will be appreciated by those skilled in the art, the software modules may be provided in compiled or uncompiled form and may be supplied to the UE, access network node, and data network node as a signal via a computer network or on a recording medium. In addition, one or more dedicated hardware circuits may be used to perform the functionality performed by part or all of the software. However, the use of software modules is preferred because the use facilitates updating the UE, access network node, and data network node to update their functionality.

[0232] The above example embodiments are also applicable to "non-mobile" or generally stationary user equipment.

[0233] Reception of the information may be via the MBS Control Channel (MCCH) or via application layer procedures.

[0234] The core network functions may include at least one of a function for access and mobility management and a function for session management.

[0235] Various other modifications will be apparent to those skilled in the art and will not be described in further detail here.

[0236] Although the present disclosure has been described with reference to exemplary embodiments, the present disclosure is not limited to the above. Various changes that can be understood by those skilled in the art can be made to the structure and details of the present disclosure within the scope of the present disclosure.

[0237] This application is based upon and claims the benefit of priority from UK patent application 2211642.0 filed on August 9, 2022, the disclosure of which is incorporated herein in its entirety by reference.

[0238] Any type of non-transitory computer-readable medium may be used to store and provide the program to a computer device. Non-transitory computer-readable media include any type of tangible storage media. Examples of non-transitory computer-readable media include magnetic storage media (such as floppy disks, magnetic tapes, hard disk drives, etc.), optical magnetic storage media (such as magneto-optical disks), CD-ROMs (read-only memories), CD-Rs, CD-R / Ws, and semiconductor memories (such as mask ROMs, PROMs (programmable ROMs), EPROMs (erasable PROMs), flash ROMs, RAMs (random access memories), etc.). Any type of transient computer-readable medium may be used to provide the program to a computer device. Examples of transient computer-readable media include electrical signals, optical signals, and electromagnetic waves. Transient computer-readable media may provide the program to a computer device via a wired communication line (such as electrical wires and optical fibers, etc.) or a wireless communication line.

[0239] For example, all or part of the exemplary exemplary embodiments disclosed above may be described as, but not limited to, the following supplementary notes.

[0240] (Supplementary Note 1)

[0241] A method for accessing a network node, the method comprising:

[0242] In case that a user equipment (UE) is in an RRC_INACTIVE state, transmitting a first message to the UE, the first message including a query on the UE's ability to receive a multicast / broadcast service (MBS), RRC being radio resource control; and

[0243] In a case where the UE has information identifying at least one MBS available to the UE, a second message is received from the UE, the 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.

[0244] (Supplementary Note 2)

[0245] The method according to Supplementary Note 1, wherein the first message is transmitted in a dedicated RRC message, in a paging message, in a system information block (SIB), or through a multicast control channel.

[0246] (Supplementary Note 3)

[0247] The method according to Supplementary Note 1 or 2, wherein the first message is a UE RRC_INACTIVE support query message.

[0248] (Supplementary Note 4)

[0249] The method according to Supplementary Note 3, wherein the second message is a UE RRC_INACTIVE support report message.

[0250] (Supplementary Note 5)

[0251] A method for accessing a network node, the method comprising:

[0252] A paging message is transmitted to a user equipment (UE) in RRC_INACTIVE state, the paging message comprising a list of at least one temporary mobile group identity (TMGI) associated with available corresponding multicast / broadcast service sessions (MBS sessions), RRC being Radio Resource Control, wherein:

[0253] The paging message includes:

[0254] a corresponding indication associated with each TMGI in the list, the corresponding indication being used to indicate:

[0255] Whether the UE needs to transition to the RRC_CONNECTED state to receive the corresponding MBS session associated with each TMGI, or

[0256] whether the UE is able to remain in the RRC_INACTIVE state to receive the corresponding MBS sessions associated with each TMGI; or

[0257] An indication for configuring the UE to not transition to the RRC_CONNECTED state in response to receiving the paging message if the UE is a Release 18 or higher UE.

[0258] (Supplementary Note 6)

[0259] The method according to Supplementary Note 5, wherein the indication is an RRC-CONNECTEDINDICATION-R18 indication.

[0260] (Supplementary Note 7)

[0261] A method for accessing a network node, the method comprising:

[0262] A multicast / broadcast service (MBS) with a temporary mobile group identity (TMGI) is used to transmit parameters associated with the TMGI to a user equipment (UE), wherein the parameters indicate the following conditions, which, when met, cause the UE to transition from an RRC_CONNECTED state to an RRC_INACTIVE state or from the RRC_INACTIVE state to the RRC_CONNECTED state, where RRC is radio resource control.

[0263] (Supplementary Note 8)

[0264] According to the method described in Supplementary Note 7, wherein the parameter is transmitted in a system information block, i.e., SIB, via a multicast channel, in a paging message, or in dedicated RRC signaling.

[0265] (Supplementary Note 9)

[0266] According to the method described in Supplementary Note 7 or 8, wherein the condition includes whether one or more received signal metrics are greater than or less than a threshold level.

[0267] (Supplementary Note 10)

[0268] According to the method described in Supplementary Note 9, wherein

[0269] The conditions for transitioning the UE from the RRC_CONNECTED state to the RRC_INACTIVE state include whether the reference signal received power, i.e., RSRP, measured by the UE is greater than a first threshold, and / or whether the reference signal received quality, i.e., RSRQ, measured by the UE is greater than a second threshold; or

[0270] The conditions for transitioning the UE from the RRC_CONNECTED state to the RRC_INACTIVE state include whether the reference signal received power, i.e., RSRP, measured by the UE is less than a third threshold, and / or whether the reference signal received quality, i.e., RSRQ, measured by the UE is less than a fourth threshold.

[0271] (Supplementary Note 11)

[0272] According to the method described in any one of Supplementary Notes 7 to 10, wherein the parameter is the StateTransitConfig parameter.

[0273] (Supplementary Note 12)

[0274] According to the method described in any one of Supplementary Notes 7 to 11, wherein the indication is transmitted as part of RRC_INACTIVE - SUPPORTIVE - configuration.

[0275] (Supplementary Note 13)

[0276] A method for an access network node, the method comprising:

[0277] Providing a multicast / broadcast service, i.e., MBS, to a user equipment, i.e., UE, via an MBS radio bearer, i.e., MRB;

[0278] Receiving from the UE for the MBS Serve Notification of request for reliability enhancement; and

[0279] The reliability enhancement is provided.

[0280] (Supplementary Note 14)

[0281] The method according to Supplementary Note 13, wherein the notification is received in an RRCSetupComplete message.

[0282] (Supplementary Note 15)

[0283] A method according to Supplementary Note 13 or 14, wherein the notification includes a list of at least one TMGI, for which reliability enhancement is requested for an MBS service associated with at least one TMGI in the list, or wherein the notification includes a list of at least one MBS radio bearer, i.e., at least one MRB, associated with the MBS service requiring reliability enhancement.

[0284] (Supplementary Note 16)

[0285] According to the method described in any one of Supplementary Notes 13 to 15, the reliability enhancement includes the access network node providing an additional point-to-point connection segment, namely, a PTP connection segment, in the MRB.

[0286] (Supplementary Note 17)

[0287] A method for an access network node, the access network node having a central unit and a distributed unit, the method comprising:

[0288] Receiving, by the central unit, from a core network node, an indication of at least one multicast / broadcast service session, i.e. at least one MBS session, to which a user equipment, i.e. UE, can access if the UE is in an RRC_INACTIVE state, RRC being Radio Resource Control;

[0289] transmitting, by the central unit, the indication to the distributed unit;

[0290] receiving, with the central unit, a response from the distributed unit; and

[0291] The indication is transmitted to the UE using the distributed unit.

[0292] (Supplementary Note 18)

[0293] The method according to Supplementary Note 17, wherein the indication comprises, for each MBS session in the at least one MBS session, an RRC_INACTIVE permission indicator and a temporary mobile group identity (TMGI).

[0294] (Supplementary Note 19)

[0295] A method for a core network node, the method comprising:

[0296] A message is transmitted to the second core network node, the message comprising an indication of one or more multicast / broadcast service sessions, ie, one or more MBS sessions, to which the user equipment, ie, the UE, can access when the UE is in the RRC_INACTIVE state.

[0297] (Supplementary Note 20)

[0298] According to the method described in Supplementary Note 19, the core network node is a multicast / broadcast session management function, namely MB-SMF, and the second core network node is an access management function, namely AMF.

[0299] (Supplementary Note 21)

[0300] The method according to Supplementary Note 19 or 20, wherein the message is a Nmbsmf_MBSSession_ContextUpdate response message.

[0301] (Supplementary Note 22)

[0302] A method for a core network node, the method comprising:

[0303] A message is transmitted to an access network node, the message comprising an indication of one or more multicast / broadcast service sessions, ie one or more MBS sessions, that the user equipment, ie UE, can access if the UE is in RRC_INACTIVE state, RRC being Radio Resource Control.

[0304] (Supplementary Note 23)

[0305] According to the method described in Supplementary Note 22, the core network node is an access management function, namely AMF.

[0306] (Supplementary Note 24)

[0307] The method according to Supplementary Note 22 or 23, wherein the message is an N2MBS message.

[0308] (Supplementary Note 25)

[0309] A method for a first access network node, the method comprising:

[0310] Information is transmitted to a user equipment, i.e., UE, being served by the first access network node, wherein the information includes a list of ongoing multicast / broadcast service sessions, i.e., an MBS session list, of a second access network node adjacent to the first access network node, or a neighbor cell / frequency list of at least one adjacent access network node having at least one ongoing MBS session.

[0311] (Supplementary Note 26)

[0312] The method according to Supplementary Note 25, wherein the transmitting transmits the information via a system information block or a multicast control channel.

[0313] (Supplementary Note 27)

[0314] The method according to Supplementary Note 25 or 26, wherein the serving cell sends the supported cell / supported frequency list for the MBS session list to the UE in one of the following messages: a paging message, an RRC Release message, an RRC dedicated message, a SIB message, and a message via the MCCH.

[0315] (Supplementary Note 28)

[0316] A method performed by a source access network node for handing over a user equipment (UE) to a target access network node, the method comprising:

[0317] A conditional handover request message is transmitted to the target access network node, where the conditional handover request message includes MBS configuration information for the UE.

[0318] (Supplementary Note 29)

[0319] A method performed by a target access network node for handing over a user equipment (UE) from a source access network node, the method comprising:

[0320] receiving a conditional handover request message from the source access network node, where the conditional handover request message includes MBS configuration information for the UE;

[0321] In the case that there is no ongoing MBS session in the target access network node, an MBS session is established with the core network.

[0322] (Supplementary Note 30)

[0323] The method according to Supplementary Note 29, wherein the establishing is performed before the UE is handed over to the target access network node.

[0324] (Supplementary Note 31)

[0325] The method according to Supplementary Note 29 or 30, wherein the establishment is performed in response to receiving the conditional handover request.

[0326] (Supplementary Note 32)

[0327] A method for a user equipment, i.e., UE, the method comprising:

[0328] When the UE is in the RRC_INACTIVE state, receiving a first message from an access network node, the first message including a query about the UE's ability to receive multicast / broadcast services, i.e., MBS, where RRC is Radio Resource Control; and

[0329] Based on information for identifying at least one MBS available to the UE, transmitting a second message to the access network node, the 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.

[0330] (Supplementary Note 33)

[0331] A method for a user equipment, i.e., UE, where the UE is in the RRC_INACTIVE state, and RRC is Radio Resource Control, the method comprising:

[0332] Receiving a paging message from an access network node, the paging message including a list of at least one temporary mobile group identifier, i.e., at least one TMGI, associated with a corresponding available multicast / broadcast service session, i.e., MBS session, wherein:

[0333] The paging message includes:

[0334] A corresponding indication associated with each TMGI in the list, the corresponding indication being used to indicate:

[0335] Whether the UE needs to transition to the RRC_CONNECTED state to receive the relevant MBS session, or

[0336] Whether the UE can remain in the RRC_INACTIVE state to receive the relevant MBS session; or

[0337] An indication for configuring the UE not to transition to the RRC_CONNECTED state in response to receiving the paging message when the UE is a UE of version 18 or higher.

[0338] (Supplementary Note 34)

[0339] A method used by a user equipment, i.e., UE, the method comprising:

[0340] Receiving a multicast / broadcast service (MBS) with a temporary mobile group identity (TMGI);

[0341] receiving a parameter associated with the TMGI from an access network node, wherein the parameter indicates a condition that, when satisfied, causes the UE to transition from an RRC_CONNECTED state to an RRC_INACTIVE state or from the RRC_INACTIVE state to the RRC_CONNECTED state, RRC being Radio Resource Control; and

[0342] transitioning between the RRC_CONNECTED state and the RRC_INACTIVE state based on the parameter.

[0343] (Supplementary Note 35)

[0344] A method used by a user equipment (UE), the method comprising:

[0345] When the UE is in the RRC_INACTIVE state, receiving an MBS from an access network node via an MBS radio bearer, i.e., an MRB, where the MBS is a multicast / broadcast service;

[0346] When the signal strength of the MRB is lower than a threshold, transition to the RRC_CONNECTED state; and

[0347] A notification for requesting reliability enhancement for the MBS service is transmitted to the access network node.

[0348] (Supplementary Note 36)

[0349] A method for a user equipment (UE), the method comprising:

[0350] An indication of one or more multicast / broadcast service sessions, ie, one or more MBS sessions, that a user equipment, ie, UE, can access if the UE is in an RRC_INACTIVE state is received from a distributed unit of an access network node.

[0351] (Supplementary Note 37)

[0352] A method for a user equipment (UE), the method comprising:

[0353] Information is received from a first access network node, the information comprising a list of ongoing multicast / broadcast service sessions, i.e., an MBS session list, of a second access network node adjacent to the first access network node, or a neighbor cell / frequency list of at least one adjacent access network node having at least one ongoing MBS session.

[0354] (Supplementary Note 38)

[0355] An access network node, comprising:

[0356] means for transmitting a first message to a user equipment (UE) if the UE is in RRC_INACTIVE state, the first message comprising a query on the capability of the UE to receive a multicast / broadcast service (MBS), RRC being Radio Resource Control; and

[0357] Means for receiving, if the UE has information identifying at least one MBS available to the UE, a second message from the UE, the second message comprising a list of one or more MBS sessions that the UE can support if the UE is in the RRC_INACTIVE state.

[0358] (Supplementary Note 39)

[0359] An access network node, comprising:

[0360] Means for transmitting a paging message to a user equipment (UE) in RRC_INACTIVE state, the paging message comprising a list of at least one temporary mobile group identity (TMGI) associated with available corresponding multicast / broadcast service sessions (MBS sessions), RRC being Radio Resource Control, wherein:

[0361] The paging message includes:

[0362] a corresponding indication associated with each TMGI in the list, the corresponding indication being used to indicate:

[0363] Whether the UE needs to transition to the RRC_CONNECTED state to receive the corresponding MBS session associated with each TMGI, or

[0364] whether the UE is able to remain in the RRC_INACTIVE state to receive the corresponding MBS sessions associated with each TMGI; or

[0365] An indication for configuring the UE to not transition to the RRC_CONNECTED state in response to receiving the paging message if the UE is a Release 18 or higher UE.

[0366] (Supplementary Note 40)

[0367] An access network node, comprising:

[0368] A component for transmitting parameters associated with a Temporary Mobile Group Identity (TMGI) to a User Equipment (UE) using a Multicast / Broadcast Service (MBS), wherein the parameters indicate conditions which, when satisfied, cause 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, where RRC is Radio Resource Control.

[0369] (Supplementary Note 41)

[0370] An access network node, comprising:

[0371] A component for providing a Multicast / Broadcast Service (MBS) to a User Equipment (UE) via an MBS Radio Bearer (MRB);

[0372] A component for receiving from the UE a notification for requesting reliability enhancement for the MBS service; and

[0373] A component for providing the reliability enhancement.

[0374] (Supplementary Note 42)

[0375] An access network node having a central unit and a distributed unit, wherein,

[0376] The central unit includes:

[0377] A component for receiving from a core network node an indication of at least one Multicast / Broadcast Service session (at least one MBS session) to which the UE can access when the UE is in the RRC_INACTIVE state, where RRC is Radio Resource Control;

[0378] A component for transmitting the indication to the distributed unit; and

[0379] A component for receiving a response from the distributed unit; and

[0380] The distributed unit includes;

[0381] A component for transmitting the indication to the UE.

[0382] (Supplementary Note 43)

[0383] A core network node, comprising:

[0384] Means for transmitting a message to an access network node, the message comprising an indication of one or more multicast / broadcast service sessions, ie one or more MBS sessions, to which a user equipment, ie UE, can access if the UE is in RRC_INACTIVE state, RRC being Radio Resource Control.

[0385] (Supplementary Note 44)

[0386] A first access network node, comprising:

[0387] A component for transmitting information to a user equipment, i.e., UE, being served by the first access network node, the information comprising a list of ongoing multicast / broadcast service sessions, i.e., an MBS session list, of a second access network node adjacent to the first access network node, or a list of neighbor cells / frequencies of at least one adjacent access network node having at least one ongoing MBS session.

[0388] (Supplementary Note 45)

[0389] A source access network node is used for handing over a user equipment (UE) to a target access network node, the source access network node comprising:

[0390] A component is used to transmit a conditional handover request message to the target access network node, wherein the conditional handover request message includes MBS configuration information for the UE.

[0391] (Supplementary Note 46)

[0392] A target access network node, used for handover of a user equipment (UE) from a source access network node, the target access network node comprising:

[0393] A component for receiving a conditional handover request message from the source access network node, wherein the conditional handover request message includes MBS configuration information for the UE;

[0394] In the case that there is no ongoing MBS session in the target access network node, an MBS session is established with the core network.

[0395] (Supplementary Note 47)

[0396] A user equipment, namely, UE, includes:

[0397] means for receiving a first message from an access network node if the UE is in RRC_INACTIVE state, the first message comprising a query on the capability of the UE to receive a multicast / broadcast service, i.e., MBS, RRC being Radio Resource Control; and

[0398] means for transmitting, to the access network node, a second message based on the information identifying at least one MBS available to the UE, the second message comprising a list of one or more MBS sessions that the UE can support when the UE is in the RRC_INACTIVE state.

[0399] (Supplementary Note 48)

[0400] A user equipment, namely, UE, includes:

[0401] means for receiving a paging message from an access network node and if the UE is in RRC_INACTIVE state, the paging message comprising a list of at least one temporary mobile group identity, i.e. at least one TMGI, associated with available respective multicast / broadcast service sessions, i.e. respective MBS sessions, RRC being Radio Resource Control, wherein:

[0402] The paging message includes:

[0403] a corresponding indication associated with each TMGI in the list, the corresponding indication being used to indicate:

[0404] Whether the UE needs to transition to the RRC_CONNECTED state to receive the associated MBS session, or

[0405] whether the UE is able to remain in the RRC_INACTIVE state to receive the related MBS session; or

[0406] An indication for configuring the UE to not transition to the RRC_CONNECTED state in response to receiving the paging message if the UE is a Release 18 or higher UE.

[0407] (Supplementary Note 49)

[0408] A user equipment, namely, UE, includes:

[0409] Component for receiving a multicast / broadcast service, MBS, with a temporary mobile group identity, TMGI;

[0410] means for receiving a parameter associated with the TMGI from an access network node, wherein the parameter indicates a condition which, if satisfied, causes the UE to transition from an RRC_CONNECTED state to an RRC_INACTIVE state or vice versa, RRC being Radio Resource Control; and

[0411] Means for transitioning between the RRC_CONNECTED state and the RRC_INACTIVE state based on the parameter.

[0412] (Supplementary Note 50)

[0413] A user equipment, namely, UE, includes:

[0414] means for receiving MBS from an access network node via an MBS radio bearer, i.e., an MRB, if the UE is in RRC_INACTIVE state, the MBS being a multicast / broadcast service;

[0415] means for transitioning to an RRC_CONNECTED state if the signal strength of the MRB is below a threshold; and

[0416] Means for transmitting to the access network node a notification requesting reliability enhancement for the MBS service.

[0417] (Supplementary Note 51)

[0418] A user equipment, namely, UE, includes:

[0419] Means for receiving, from a distributed unit of an access network node, an indication of one or more multicast / broadcast service sessions, ie, one or more MBS sessions, to which a user equipment, ie, UE, can access when the UE is in RRC_INACTIVE state.

[0420] (Supplementary Note 52)

[0421] A user equipment, namely, UE, includes:

[0422] A component for receiving information from a first access network node, wherein the information includes a list of ongoing multicast / broadcast service sessions, i.e., an MBS session list, of a second access network node adjacent to the first access network node, or a list of neighbor cells / frequencies of at least one adjacent access network node having at least one ongoing MBS session.

[0423] Reference numerals list

[0424] 1 Telecommunications networks and systems

[0425] 3 UE

[0426] 5 NG-RAN, Base Stations

[0427] 7 Core Network

[0428] 8-1 AMF

[0429] 8-2 SMF

[0430] 8-3 UPF

[0431] 8-4 MB-SMF

[0432] 8-5 MB-UPF

[0433] 8-6 MBSF

[0434] 8-7 MBSTF

[0435] 8-8 NEF

[0436] 8-9 AF

[0437] 8-10 PCF

[0438] 8-11 NRF

[0439] 8-12 UDM

[0440] 8-13 AUSF

[0441] 8-14 DN

Claims

1. A method for accessing a network node, the method include: Transmitting a first message to a user equipment (UE) in an RRC_INACTIVE state, wherein the first message is used to indicate a capability of the UE to receive a multicast / broadcast service (MBS), where RRC is radio resource control; In a case where the UE has information for identifying at least one MBS available to the UE, receiving a second message from the UE, the second message being used to indicate one or more MBS sessions that the UE in the RRC_INACTIVE state can support, wherein: 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.

2. The method according to claim 1, further comprising: include: Transmitting a temporary mobile group identity (TMGI) associated with one or more available MBS sessions and an indication corresponding to the TMGI to the UE in the RRC_INACTIVE state, wherein: The indication indicates whether the UE should remain in the RRC_INACTIVE state if the UE receives at least one MBS corresponding to one or more MBS sessions associated with the TMGI.

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

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

5. The method according to any one of claims 1 to 4, further comprising: include: Transmitting a temporary mobile group identity (TMGI) associated with one or more available MBS sessions and parameters corresponding to the TMGI to the UE in the RRC_INACTIVE state, wherein: The parameter indicates a condition for causing the UE to move from the RRC_CONNECTED state to the RRC_INACTIVE state or from the RRC_INACTIVE state to the RRC_CONNECTED state.

6. The method according to claim 5, in, The conditions include whether one or more received signal metrics are greater than or less than a threshold level.

7. The method according to claim 5 or 6, in, The condition for causing the UE to move from the RRC_CONNECTED state to the RRC_INACTIVE state includes whether a reference signal received power (RSRP) measured by the UE is greater than a first threshold, and / or whether a reference signal received quality (RSRQ) measured by the UE is greater than a second threshold; or The conditions for causing the UE to move from the RRC_CONNECTED state to the RRC_INACTIVE state include whether the reference signal received power, i.e., RSRP, measured by the UE is less than a third threshold, and / or whether the reference signal received quality, i.e., RSRQ, measured by the UE is less than a fourth threshold.

8. The method according to any one of claims 1 to 7, further comprising: include: receiving, from the UE, a notification for requesting reliability enhancement for the at least one MBS; as well as The reliability enhancement is provided.

9. The method according to claim 8, in, The notification includes: at least one TMGI, wherein for the at least one TMGI, reliability enhancement is requested for an MBS associated with the at least one TMGI, or At least one MBS radio bearer, ie, MRB, corresponds to an MBS requiring reliability enhancement.

10. The method according to claim 9, in, The reliability enhancement includes the access network node providing an additional point-to-point connection segment, namely, a PTP connection segment, in the MRB.

11. A method for an access network node, the access network node having a central unit and a distributed unit, the method include: Receiving, by means of the central unit, an indication of at least one multicast / broadcast service session, i.e. at least one MBS session accessible to a user equipment, i.e. UE, in an RRC_INACTIVE state from a core network node, RRC being Radio Resource Control; transmitting, by the central unit, the indication to the distributed unit; receiving, by the central unit, a response from the distributed unit; as well as The indication is transmitted to the UE using the distributed unit.

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

13. A method for a first access network node, the method include: Information is transmitted to a user equipment, i.e., UE, being served by the first access network node, wherein the information includes a list of ongoing multicast / broadcast service sessions, i.e., an MBS session list, of a second access network node adjacent to the first access network node, or a neighbor cell / frequency list of at least one adjacent access network node having at least one ongoing MBS session.

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

15. The method according to claim 13 or 14, further comprising: include: A supported cell / supported frequency list for the MBS session list is transmitted to the UE.

16. A method performed by a source access network node for handing over a user equipment (UE) to a target access network node, the method include: A conditional handover request message is transmitted to the target access network node, where the conditional handover request message includes multicast / broadcast service configuration information (MBS configuration information) for the UE.

17. A method performed by a target access network node for handing over a user equipment (UE) from a source access network node, the method include: receiving a conditional handover request message from the source access network node, wherein the conditional handover request message includes multicast / broadcast service configuration information (MBS configuration information) for the UE; In the case that there is no ongoing MBS session in the target access network node, an MBS session is established with the core network.

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

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

20. A method for a core network node, the method include: A message is transmitted to another core network node, the message including an indication of one or more multicast / broadcast service sessions, ie, one or more MBS sessions, accessible to a user equipment, ie, UE, in RRC_INACTIVE state, RRC being Radio Resource Control.

21. A method for a core network node, the method include: A message is transmitted to an access network node, the message including an indication of one or more multicast / broadcast service sessions, ie, one or more MBS sessions, that a user equipment, ie, UE, in RRC_INACTIVE state can access, RRC being Radio Resource Control.

22. A method for a user equipment (UE), the method include: receiving a first message from an access network node, the first message being used to indicate a capability of a UE in an RRC_INACTIVE state to receive a multicast / broadcast service, i.e., an MBS, where RRC is radio resource control; transmitting, based on the information identifying at least one MBS available to the UE, a second message to the access network node, the second message being used to indicate one or more MBS sessions that the UE in the RRC_INACTIVE state can support; as well as While the UE is in the RRC_INACTIVE state, at least one MBS corresponding to the one or more MBS sessions is received.

23. The method according to claim 22, further comprising: include: 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, wherein: The indication indicates whether the UE should remain in the RRC_INACTIVE state if the UE receives at least one MBS corresponding to one or more MBS sessions associated with the TMGI.

24. The method according to claim 23, in, The indication indicates that the UE should remain in the RRC_INACTIVE state if the UE receives at least one MBS corresponding to one or more MBS sessions associated with the TMGI.

25. The method according to claim 23, in, The indication indicates that the UE should move to the RRC_CONNECTED state if the UE receives at least one MBS corresponding to one or more MBS sessions associated with the TMGI.

26. The method according to any one of claims 22 to 25, further comprising: include: receiving a temporary mobile group identity (TMGI) associated with one or more available MBS sessions and parameters corresponding to the TMGI from the access network node, wherein: The parameter indicates a condition for causing the UE to move from the RRC_CONNECTED state to the RRC_INACTIVE state or from the RRC_INACTIVE state to the RRC_CONNECTED state.

27. The method according to claim 26, in, The conditions include whether one or more received signal metrics are greater than or less than a threshold level.

28. The method according to claim 26 or 27, in, The condition for causing the UE to move from the RRC_CONNECTED state to the RRC_INACTIVE state includes whether a reference signal received power (RSRP) measured by the UE is greater than a first threshold, and / or whether a reference signal received quality (RSRQ) measured by the UE is greater than a second threshold; or The conditions for causing the UE to move from the RRC_CONNECTED state to the RRC_INACTIVE state include whether the reference signal received power, i.e., RSRP, measured by the UE is less than a third threshold, and / or whether the reference signal received quality, i.e., RSRQ, measured by the UE is less than a fourth threshold.

29. The method according to any one of claims 22 to 28, further comprising: include: transmitting, to the access network node, a notification for requesting reliability enhancement for the at least one MBS; as well as The reliability enhancement is provided.

30. The method according to claim 29, in, The notification includes: at least one TMGI, wherein for the at least one TMGI, reliability enhancement is requested for an MBS associated with the at least one TMGI, or At least one MBS radio bearer, ie, MRB, corresponds to an MBS requiring reliability enhancement.

31. The method according to claim 30, in, The reliability enhancement includes the access network node providing an additional point-to-point connection segment, namely, a PTP connection segment, in the MRB.

32. A method for a user equipment (UE), the method include: An indication of one or more multicast / broadcast service sessions, ie one or more MBS sessions, accessible to a UE in RRC_INACTIVE state is received from a distributed unit of an access network node, RRC being Radio Resource Control.

33. A method for a user equipment (UE), the method include: Information is received from a first access network node, the information comprising a list of ongoing multicast / broadcast service sessions, i.e., an MBS session list, of a second access network node adjacent to the first access network node, or a neighbor cell / frequency list of at least one adjacent access network node having at least one ongoing MBS session.

34. An access network node, include: A means for transmitting a first message to a user equipment (UE) in RRC_INACTIVE state, the first message being used to indicate the capability of the UE to receive a multicast / broadcast service (MBS), RRC being Radio Resource Control; as well as means for receiving, if the UE has information identifying at least one MBS available to the UE, a second message from the UE indicating one or more MBS sessions that the UE in the RRC_INACTIVE state can support, wherein 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.

35. An access network node having a central unit and a distributed unit, in, The central unit comprises: means for receiving from a core network node an indication of at least one multicast / broadcast service session, i.e. at least one MBS session, accessible to a user equipment, i.e. UE, in RRC_INACTIVE state, RRC being Radio Resource Control; means for transmitting said indication to said distributed unit; and means for receiving a response from said distributed unit; and The distributed unit comprises: means for transmitting the indication to the UE.

36. A first access network node, include: A component for transmitting information to a user equipment, i.e., UE, being served by the first access network node, the information comprising a list of ongoing multicast / broadcast service sessions, i.e., an MBS session list, of a second access network node adjacent to the first access network node, or a neighbor cell / frequency list of at least one adjacent access network node having at least one ongoing MBS session.

37. A source access network node, used for handing over a user equipment (UE) to a target access network node, wherein the source access network node include: A component is used to transmit a conditional handover request message to the target access network node, wherein the conditional handover request message includes multicast / broadcast service configuration information (MBS configuration information) for the UE.

38. A target access network node, for handing over a user equipment (UE) from a source access network node, wherein the target access network node include: A component configured to receive a conditional handover request message from the source access network node, wherein the conditional handover request message includes multicast / broadcast service configuration information (MBS configuration information) for the UE; A component for establishing an MBS session with a core network when no ongoing MBS session exists in the target access network node.

39. A core network node, include: Means for transmitting a message to another core network node, the message comprising an indication of one or more multicast / broadcast service sessions, ie one or more MBS sessions, to which a user equipment, ie UE, in RRC_INACTIVE state can access, RRC being Radio Resource Control.

40. A core network node, include: Means for transmitting a message to an access network node, the message comprising an indication of one or more multicast / broadcast service sessions, ie one or more MBS sessions, to which a user equipment, ie UE, in RRC_INACTIVE state can access, RRC being Radio Resource Control.

41. A user equipment, namely, UE, include: A means for receiving a first message from an access network node, the first message being used to indicate a capability of a UE in an RRC_INACTIVE state to receive a multicast / broadcast service, i.e., MBS, RRC being Radio Resource Control; means for transmitting, to the access network node, a second message based on the information identifying at least one MBS available to the UE, the second message being used to indicate one or more MBS sessions that the UE in the RRC_INACTIVE state can support; as well as While the UE is in the RRC_INACTIVE state, at least one MBS corresponding to the one or more MBS sessions is received.

42. A user equipment, namely, UE, include: Means for receiving, from a distributed unit of an access network node, an indication of one or more multicast / broadcast service sessions, ie one or more MBS sessions, accessible to a UE in RRC_INACTIVE state, RRC being Radio Resource Control.

43. A user equipment, namely, UE, include: A component for receiving information from a first access network node, wherein the information includes a list of ongoing multicast / broadcast service sessions of a second access network node adjacent to the first access network node, i.e., an MBS session list, or a neighbor cell / frequency list of at least one adjacent access network node having at least one ongoing MBS session.

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