Communication control method, network node, processor, program, and mobile communication system

Abstract

To provide a communication control method, user equipment, a network node, a processor, a program, and a system for providing a high-speed, high-capacity, high-reliability, and low-delay multicast and broadcast service (MBS).SOLUTION: A communication control method used in a mobile communication system includes: receiving, by user equipment (UE 100) in a radio resource control (RRC) connected state and from a base station (gNB 200), unicast signalling including an MBS configuration used for MBS reception; and performing, by the user equipment having transitioned from the RRC connected state to an RRC idle state or an RRC inactive state, the MBS reception by using the MBS configuration received in the RRC connected state.SELECTED DRAWING: Figure 8

Description

[Technical Field]

[0001] The present invention relates to a communication control method, a user device, and a processor used in a mobile communication system. [Background technology]

[0002] In recent years, the fifth generation (5G) mobile communication system has been attracting attention. NR (New Radio), the radio access technology (RAT) of the 5G system, has features such as high speed, large capacity, high reliability, and low latency compared to LTE (Long Term Evolution), the fourth generation radio access technology. [Prior art documents] [Non-patent literature]

[0003] [Non-Patent Document 1] 3GPP technical specification "3GPP TS 38.300 V16.3.0 (2020-09)" Summary of the Invention

[0004] The communication control method according to the first aspect is a communication control method used in a mobile communication system in which a base station provides a multicast broadcast service (MBS) to a user device, and includes the steps of: the user device in an RRC (Radio Resource Control) connected state receiving unicast signaling from the base station, the unicast signaling including an MBS setting required for MBS reception; and the user device that has transitioned from the RRC connected state to an RRC idle state or an RRC inactive state receiving the MBS using the MBS setting received in the RRC connected state.

[0005] A communication control method according to a second aspect is a communication control method used in a mobile communication system in which a base station provides a multicast broadcast service (MBS) to a user device, and includes the base station transmitting a broadcast message to the user device, the broadcast message including at least one of a first identifier indicating a first MBS session in which a first MBS setting required for MBS reception is provided by unicast signaling, and a second identifier indicating a second MBS session in which a second MBS setting required for MBS reception is provided by broadcast signaling.

[0006] A communication control method according to a third aspect is a communication control method used in a mobile communication system in which a base station provides a multicast broadcast service (MBS) to a user device, and includes the base station providing multiple MBS control channels in one cell transmitting a broadcast message to the user device for each of the multiple MBS control channels, the broadcast message including an RNTI (Radio Network Temporary Identifier) ​​used to receive the MBS control channel.

[0007] A communication control method according to a fourth aspect is a communication control method used in a mobile communication system that provides a multicast broadcast service (MBS) from a base station to a user device, and includes the steps of: the base station transmitting cell reselection control information including priority information indicating the priority of each cell or frequency in cell reselection and an MBS session identifier associated with the priority information; and the user device, which is in an RRC idle state or an RRC inactive state, performing the cell reselection using the priority information corresponding to the desired MBS session identifier based on the cell reselection control information from the base station.

[0008] A communication control method according to a fifth aspect is a communication control method used in a mobile communication system in which a base station provides a multicast broadcast service (MBS) to a user device, and includes the user device receiving an MBS session in an RRC connected state starting an RRC re-establishment process and performing cell selection in the RRC re-establishment process, wherein the cell selection includes preferentially selecting a cell that provides the MBS session.

[0009] A communication control method according to a sixth aspect is a communication control method used in a mobile communication system in which a base station provides a multicast broadcast service (MBS) to a user device, and includes the steps of: the user device receiving, from the base station, information indicating an initial BWP (Bandwidth part) used by the base station; the user device receiving, from the base station, an MBS setting required for MBS reception; and, if the MBS setting does not include a BWP setting, the user device receiving the MBS using the initial BWP. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a diagram illustrating a configuration of a mobile communication system according to an embodiment. [Figure 2] 1 is a diagram illustrating a configuration of a UE (user equipment) according to an embodiment. [Figure 3] A diagram showing the configuration of a gNB (base station) according to an embodiment. [Figure 4] FIG. 10 is a diagram showing the configuration of a protocol stack of a radio interface of a user plane that handles data. [Figure 5] FIG. 1 is a diagram showing the configuration of a protocol stack of a radio interface of a control plane that handles signaling (control signals). [Figure 6] FIG. 2 is a diagram illustrating a correspondence relationship between downlink logical channels and transport channels according to the embodiment. [Figure 7] FIG. 2 is a diagram showing a method for distributing MBS data according to an embodiment. [Figure 8] FIG. 4 is a diagram illustrating an example of operation according to the first embodiment. [Figure 9] FIG. 10 is a diagram showing a first modification of the first embodiment. [Figure 10] FIG. 10 is a diagram showing a second modification of the first embodiment. [Figure 11] FIG. 10 is a diagram showing a third modification of the first embodiment. [Figure 12] FIG. 10 is a diagram illustrating an example of operation according to the second embodiment. [Figure 13] FIG. 10 is a diagram illustrating an example of operation according to the third embodiment. [Figure 14] FIG. 10 is a diagram illustrating an example of operation according to the fourth embodiment. [Figure 15] FIG. 13 is a diagram illustrating an example of operation according to the fifth embodiment. [Figure 16] FIG. 13 is a diagram illustrating an example of operation according to the sixth embodiment. [Figure 17] FIG. 1 is a diagram illustrating two-stage configuration in LTE SC-PTM. [Figure 18] FIG. 1 illustrates a possible configuration diagram for NR MBS. DETAILED DESCRIPTION OF THE INVENTION

[0011] The introduction of multicast and broadcast services into the 5G system (NR) is being considered. The NR multicast and broadcast services are expected to provide improved services compared to the LTE multicast and broadcast services.

[0012] Therefore, an object of the present invention is to provide an improved multicast / broadcast service.

[0013] A mobile communication system according to an embodiment will be described with reference to the drawings. In the description of the drawings, the same or similar parts are denoted by the same or similar reference numerals.

[0014] (Configuration of a mobile communication system) First, the configuration of a mobile communication system according to an embodiment will be described. Fig. 1 is a diagram showing the configuration of a mobile communication system according to an embodiment. This mobile communication system complies with the 5th Generation System (5GS) of the 3GPP standard. In the following description, 5GS will be taken as an example, but the mobile communication system may be at least partially applied with an LTE (Long Term Evolution) system or at least partially applied with a sixth generation (6G) system.

[0015] As shown in FIG. 1, the mobile communication system includes a user equipment (UE) 100, a 5G radio access network (NG-RAN) 10, and a 5G core network (5GC) 20.

[0016] The UE 100 is a mobile wireless communication device. The UE 100 may be any device that is used by a user, and may be, for example, a mobile phone terminal (including a smartphone), a tablet terminal, a notebook PC, a communication module (including a communication card or a chipset), a sensor or a device provided in a sensor, a vehicle or a device provided in a vehicle (Vehicle UE), or an aircraft or a device provided in an aircraft (Aerial UE).

[0017] The NG-RAN 10 includes a base station (called a "gNB" in a 5G system) 200. The gNBs 200 are connected to each other via an Xn interface, which is an interface between base stations. The gNB 200 manages one or more cells. The gNB 200 performs wireless communication with a UE 100 that has established a connection with its own cell. The gNB 200 has a radio resource management (RRM) function, a routing function for user data (hereinafter simply referred to as "data"), a measurement control function for mobility control and scheduling, etc. The term "cell" is used to indicate the smallest unit of a wireless communication area. The term "cell" is also used to indicate a function or resource that performs wireless communication with a UE 100. One cell belongs to one carrier frequency.

[0018] In addition, gNBs can also connect to the Evolved Packet Core (EPC), which is the LTE core network. LTE base stations can also connect to 5GC. LTE base stations and gNBs can also be connected via a base station-to-base station interface.

[0019] The 5GC20 includes an Access and Mobility Management Function (AMF) and a User Plane Function (UPF) 300. The AMF performs various mobility controls for the UE 100. The AMF manages the mobility of the UE 100 by communicating with the UE 100 using NAS (Non-Access Stratum) signaling. The UPF controls data forwarding. The AMF and UPF are connected to the gNB 200 via an NG interface, which is an interface between a base station and a core network.

[0020] FIG. 2 is a diagram showing a configuration of the UE 100 (user equipment) according to the embodiment.

[0021] As shown in FIG. 2, the UE 100 includes a receiving unit 110, a transmitting unit 120, and a control unit .

[0022] The receiving unit 110 performs various types of reception under the control of the control unit 130. The receiving unit 110 includes an antenna and a receiver. The receiver converts a radio signal received by the antenna into a baseband signal (received signal) and outputs the baseband signal to the control unit 130.

[0023] The transmitting unit 120 performs various transmissions under the control of the control unit 130. The transmitting unit 120 includes an antenna and a transmitter. The transmitter converts a baseband signal (transmission signal) output by the control unit 130 into a radio signal and transmits it from the antenna.

[0024] The control unit 130 performs various controls in the UE 100. The control unit 130 includes at least one processor and at least one memory. The memory stores programs executed by the processor and information used in processing by the processor. The processor may include a baseband processor and a CPU (Central Processing Unit). The baseband processor performs modulation / demodulation and encoding / decoding of baseband signals. The CPU executes programs stored in the memory to perform various processes.

[0025] FIG. 3 is a diagram showing the configuration of a gNB200 (base station) according to the embodiment.

[0026] As shown in FIG. 3, the gNB 200 includes a transmitter 210, a receiver 220, a controller 230, and a backhaul communication unit 240.

[0027] The transmission unit 210 performs various transmissions under the control of the control unit 230. The transmission unit 210 includes an antenna and a transmitter. The transmitter converts a baseband signal (transmission signal) output by the control unit 230 into a radio signal and transmits it from the antenna.

[0028] The receiving unit 220 performs various types of reception under the control of the control unit 230. The receiving unit 220 includes an antenna and a receiver. The receiver converts a radio signal received by the antenna into a baseband signal (received signal) and outputs the baseband signal to the control unit 230.

[0029] The control unit 230 performs various controls in the gNB 200. The control unit 230 includes at least one processor and at least one memory. The memory stores programs executed by the processor and information used in processing by the processor. The processor may include a baseband processor and a CPU. The baseband processor performs modulation / demodulation and encoding / decoding of baseband signals. The CPU executes programs stored in the memory to perform various processes.

[0030] The backhaul communication unit 240 is connected to neighboring base stations via an inter-base station interface. The backhaul communication unit 240 is connected to the AMF / UPF 300 via a base station-core network interface. Note that the gNB is composed of a CU (Central Unit) and a DU (Distributed Unit) (i.e., functionally divided), and both units may be connected via an F1 interface.

[0031] FIG. 4 is a diagram showing the configuration of a protocol stack of a radio interface of a user plane that handles data.

[0032] As shown in Figure 4, the user plane radio interface protocol includes a physical (PHY) layer, a medium access control (MAC) layer, a radio link control (RLC) layer, a packet data convergence protocol (PDCP) layer, and a service data adaptation protocol (SDAP) layer.

[0033] The PHY layer performs encoding / decoding, modulation / demodulation, antenna mapping / demapping, and resource mapping / demapping. Data and control information are transmitted between the PHY layer of the UE 100 and the PHY layer of the gNB 200 via a physical channel.

[0034] The MAC layer performs data priority control, retransmission processing using Hybrid ARQ (HARQ), random access procedures, etc. Data and control information are transmitted between the MAC layer of UE 100 and the MAC layer of gNB 200 via a transport channel. The MAC layer of gNB 200 includes a scheduler. The scheduler determines the uplink and downlink transport format (transport block size, modulation and coding scheme (MCS)) and the resource blocks to be allocated to UE 100.

[0035] The RLC layer transmits data to the RLC layer on the receiving side using the functions of the MAC layer and PHY layer. Data and control information are transmitted between the RLC layer of the UE 100 and the RLC layer of the gNB 200 via logical channels.

[0036] The PDCP layer performs header compression / decompression and encryption / decryption.

[0037] The SDAP layer maps IP flows, which are the units for Quality of Service (QoS) control by the core network, to radio bearers, which are the units for QoS control by the Access Stratum (AS). Note that if the RAN is connected to the EPC, SDAP is not necessary.

[0038] FIG. 5 is a diagram showing the configuration of a protocol stack of a radio interface of a control plane that handles signaling (control signals).

[0039] As shown in FIG. 5, the protocol stack of the radio interface of the control plane has a Radio Resource Control (RRC) layer and a Non-Access Stratum (NAS) layer instead of the SDAP layer shown in FIG.

[0040] RRC signaling for various settings is transmitted between the RRC layer of UE100 and the RRC layer of gNB200. The RRC layer controls logical channels, transport channels, and physical channels according to the establishment, re-establishment, and release of radio bearers. When there is a connection (RRC connection) between the RRC of UE100 and the RRC of gNB200, UE100 is in an RRC connected state. When there is no connection (RRC connection) between the RRC of UE100 and the RRC of gNB200, UE100 is in an RRC idle state. When the connection between the RRC of UE100 and the RRC of gNB200 is suspended, UE100 is in an RRC inactive state.

[0041] The NAS layer located above the RRC layer performs session management, mobility management, etc. NAS signaling is transmitted between the NAS layer of the UE 100 and the NAS layer of the AMF 300B.

[0042] The UE 100 has an application layer and the like in addition to the radio interface protocol.

[0043] (MBS) Next, an MBS according to an embodiment will be described. The MBS is a service for transmitting data from the NG-RAN 10 to the UE 100 by broadcast or multicast, i.e., point-to-multipoint (PTM) data. The MBS may also be called an MBMS (Multimedia Broadcast and Multicast Service). Note that use cases (service types) of the MBS include public safety communications, mission-critical communications, V2X (Vehicle to Everything) communications, IPv4 or IPv6 multicast distribution, IPTV, group communications, and software distribution.

[0044] There are two types of MBS transmission methods in LTE: MBSFN (Multicast Broadcast Single Frequency Network) transmission and SC-PTM (Single Cell Point To Multipoint) transmission. Fig. 6 is a diagram showing the correspondence relationship between downlink logical channels and transport channels according to an embodiment.

[0045] As shown in Figure 6, the logical channels used for MBSFN transmission are the MTCH (Multicast Traffic Channel) and the MCCH (Multicast Control Channel), and the transport channel used for MBSFN transmission is the MCH (Multicast Channel). MBSFN transmission is designed primarily for multi-cell transmission, and in an MBSFN area consisting of multiple cells, each cell synchronously transmits the same signal (the same data) in the same MBSFN subframe.

[0046] The logical channels used for SC-PTM transmission are the Single Cell Multicast Traffic Channel (SC-MTCH) and the Single Cell Multicast Control Channel (SC-MCCH), and the transport channel used for SC-PTM transmission is the Downlink Shared Channel (DL-SCH). SC-PTM transmission is primarily designed for single-cell transmission, and transmits data by broadcast or multicast on a cell-by-cell basis. The physical channels used for SC-PTM transmission are the Physical Downlink Control Channel (PDCCH) and the Physical Downlink Shared Channel (PDSCH), which enable dynamic resource allocation.

[0047] In the following, an example in which an MBS is provided using the SC-PTM transmission method will be mainly described, but an MBS may also be provided using the MBSFN transmission method. Also, an example in which an MBS is provided by multicast will be mainly described. Therefore, MBS may be read as multicast. However, an MBS may also be provided by broadcast.

[0048] Furthermore, MBS data refers to data transmitted by MBS, the MBS control channel refers to MCCH or SC-MCCH, and the MBS traffic channel refers to MTCH or SC-MTCH. However, MBS data may also be transmitted by unicast. MBS data may also be called MBS packets or MBS traffic.

[0049] A network can provide different MBS services for each MBS session. An MBS session is identified by at least one of a Temporary Mobile Group Identity (TMGI) and a session identifier, and at least one of these identifiers is called an MBS session identifier. Such an MBS session identifier may also be called an MBS service identifier or a multicast group identifier.

[0050] FIG. 7 is a diagram showing a method for distributing MBS data according to an embodiment.

[0051] As shown in Fig. 7, MBS data (MBS Traffic) is distributed from a single data source (application service provider) to multiple UEs. A 5G CN (5GC) 20, which is a 5G core network, receives the MBS data from the application service provider, creates a copy of the MBS data (replication), and distributes the data.

[0052] From the 5GC20 point of view, two delivery methods are possible: Shared MBS Traffic delivery and Individual MBS Traffic delivery.

[0053] In shared MBS data delivery, a connection is established between NG-RAN 10, which is a 5G radio access network (5G RAN), and 5GC 20, and MBS data is delivered from 5GC 20 to NG-RAN 10. Hereinafter, such a connection (tunnel) will be referred to as an "MBS connection."

[0054] The MBS connection may be referred to as a Shared MBS Traffic delivery connection or shared transport. The MBS connection terminates in the NG-RAN 10 (i.e., the gNB 200). The MBS connection may have a one-to-one correspondence with an MBS session. The gNB 200 selects either PTP (Point-to-Point: unicast) or PTM (Point-to-Multipoint: multicast or broadcast) at its own discretion and transmits MBS data to the UE 100 using the selected method.

[0055] On the other hand, in individual MBS data delivery, a unicast session is established between the NG-RAN 10 and the UE 100, and the MBS data is delivered individually from the 5GC 20 to the UE 100. Such a unicast may be called a PDU session. The unicast (PDU session) terminates at the UE 100.

[0056] (First embodiment) Next, a first embodiment will be described.

[0057] In the first embodiment, it is mainly assumed that the MBS configuration required for receiving MBS data transmitted from the gNB 200 in PTM (hereinafter referred to as "PTM reception") is transmitted from the gNB 200 to the UE 100 by unicast signaling. Unicast signaling is sometimes called dedicated signaling. By using such unicast configuration, advanced MBS configuration such as bearer configuration can be performed individually for the UE 100.

[0058] However, such unicast configuration can be received by UE 100 in the RRC connected state, but cannot be received by UE 100 in the RRC idle state or the RRC inactive state. Therefore, assuming a case where only the unicast configuration is used, there is a concern that UE 100 in the RRC idle state or the RRC inactive state will not be able to receive the MBS.

[0059] The first embodiment is an embodiment that enables the UE 100 in the RRC idle state or the RRC inactive state to perform MBS reception even when only the unicast configuration is used.

[0060] In the first embodiment, the UE 100 in the RRC connected state receives unicast signaling including MBS configuration required for MBS reception from the gNB 200. Such MBS configuration includes at least one of configuration related to an MBS bearer and configuration related to an MBS traffic channel (e.g., scheduling information for the MBS traffic channel).

[0061] The unicast signaling used for the MBS configuration is, for example, an RRC Reconfiguration message. The unicast signaling used for the MBS configuration may also be an RRC Release message.

[0062] The UE 100 that has transitioned from the RRC connected state to the RRC idle state or the RRC inactive state performs MBS reception using the MBS configuration received in the RRC connected state.

[0063] Generally, a UE dedicated configuration set in the RRC connected state is discarded when the UE 100 leaves the RRC connected state (particularly when transitioning to the RRC idle state or the RRC inactive state). In contrast, in the first embodiment, the UE dedicated MBS configuration set in the RRC connected state is maintained rather than discarded, thereby enabling the UE 100 in the RRC idle state or the RRC inactive state to receive an MBS.

[0064] FIG. 8 is a diagram illustrating an example of operation according to the first embodiment.

[0065] As shown in Fig. 8, in step S101, UE 100 is in an RRC connected state in a cell of gNB 200. Here, UE 100 may notify gNB 200 that it will continue MBS reception in RRC idle state or RRC inactive state. Alternatively, UE 100 may notify gNB 200 that it does not wish to continue MBS reception in RRC idle state or RRC inactive state. These notifications may be notifications of UE 100's preferences. These notifications may be associated with an MBS session identifier (e.g., TMGI).

[0066] In step S102, the gNB 200 transmits an RRC Reconfiguration message including an MBS setting to the UE 100. The UE 100 receives the RRC Reconfiguration message.

[0067] The RRC Reconfiguration message may include usability information indicating whether the MBS configuration received in the RRC connected state is usable in the RRC idle state or the RRC inactive state (or whether MBS reception may be continued).

[0068] In step S103, the UE 100 stores and applies the MBS configuration included in the received RRC Reconfiguration message.

[0069] In step S104, UE100 receives MBS data (MBS traffic channel) from gNB200 using the MBS configuration applied in step S103.

[0070] Thereafter, in step S105, the gNB 200 transmits an RRC Release message to the UE 100 to transition the UE 100 to an RRC idle state or an RRC inactive state. The UE 100 receives the RRC Release message.

[0071] The RRC Release message may include the above-mentioned availability information. If the RRC Release message includes the availability information, the RRC Reconfiguration message does not need to include the availability information.

[0072] In step S106, the UE 100 transitions from the RRC connected state to the RRC idle state or the RRC inactive state.

[0073] In step S107, UE 100 maintains the MBS configuration stored and applied in step S103 without discarding it. If the RRC Reconfiguration message or the RRC Release message includes availability information and the availability information indicates "available", UE 100 may maintain the MBS configuration without discarding it. On the other hand, if the RRC Reconfiguration message or the RRC Release message includes availability information and the availability information indicates "unavailable", UE 100 may discard the MBS configuration.

[0074] In step S108, UE100 continues to receive MBS from gNB200.

[0075] (Modification 1 of the first embodiment) Next, a first modification of the first embodiment will be described.

[0076] In the first embodiment described above, since the UE 100 in the RRC idle state or the RRC inactive state cannot be controlled from the network (gNB 200), a problem arises as to how long the MBS setting once set is valid. If the UE 100 in the RRC idle state or the RRC inactive state can permanently use the MBS setting, the network side cannot change the MBS setting even if it wants to. This is because if the MBS setting is changed on the network side, the UE 100 will be unable to receive MBS. On the other hand, since the UE 100 cannot be aware of the change in MBS setting on the network side in advance, it will only become aware of the change in MBS setting when it is unable to receive MBS.

[0077] In a first modification of the first embodiment, the UE 100 in the RRC connected state receives information indicating the validity period of the MBS configuration from the time of receiving the MBS configuration or from the time of transition to the RRC idle state or the RRC inactive state, from the gNB 200. By defining such a validity period for the MBS configuration, the above-mentioned problem can be solved.

[0078] The UE 100 in the RRC connected state may receive information indicating the validity period of the MBS configuration and an MBS session identifier (for example, TMGI) associated with the information indicating the validity period. This makes it possible to determine the validity period of the MBS configuration for each MBS session (MBS service).

[0079] The UE 100 that transitions to the RRC idle state or the RRC inactive state to receive an MBS may transition to the RRC connected state and acquire a new MBS configuration in response to expiration of the validity period of the MBS configuration. This makes it possible to continue receiving the MBS even after the validity period of the MBS configuration has expired.

[0080] 9 is a diagram showing a first modification of the first embodiment. Here, differences from the first embodiment will be mainly described.

[0081] As shown in Figure 9, in step S201, UE100 is in an RRC connected state in the cell of gNB200.

[0082] In step S202, the gNB 200 transmits an RRC Reconfiguration message including an MBS setting to the UE 100. The UE 100 receives the RRC Reconfiguration message.

[0083] The RRC Reconfiguration message may include information (timer value) indicating the validity period of the MBS configuration. Here, the validity period of the MBS configuration may be the validity period from the time when the configuration is made in step S202. The validity period of the MBS configuration may be the validity period from the time when the UE 100 transitions to the RRC idle state or the RRC inactive state (step S206 described below). The validity period of the MBS configuration may be set according to, for example, a period during which the gNB 200 does not change the MBS configuration (modification period), or a period until the scheduled end of the MBS session. When the validity period of the MBS configuration is set to the validity period from the time when the configuration is made in step S202, the UE 100 starts a timer (validity period timer) in which the validity period of the MBS configuration is set when the configuration is made in step S202.

[0084] In step S203, the UE 100 stores and applies the MBS configuration included in the received RRC Reconfiguration message.

[0085] In step S204, UE100 receives MBS data (MBS traffic channel) from gNB200 using the MBS configuration applied in step S203.

[0086] Then, in step S205, the gNB 200 transmits an RRC Release message to the UE 100 to transition the UE 100 to an RRC idle state or an RRC inactive state. The UE 100 receives the RRC Release message.

[0087] The RRC Release message may include information (timer value) indicating the validity period of the MBS configuration. Here, the validity period of the MBS configuration may be the validity period from the time when the UE 100 transitions to the RRC idle state or the RRC inactive state (i.e., the time when the RRC Release message is received). The validity period of the MBS configuration may be set according to, for example, a period during which the gNB 200 does not change the MBS configuration or a period until the scheduled time when the MBS session ends. When the UE 100 receives the RRC Release message, it starts a timer (validity period timer) that sets the validity period of the MBS configuration.

[0088] In step S206, the UE 100 transitions from the RRC inactive state to the RRC idle state or the RRC inactive state.

[0089] In step S207, the UE 100 does not discard but maintains the MBS configuration stored and applied in step S203.

[0090] In step S208, UE100 continues receiving MBS from gNB200 until the validity period timer expires.

[0091] If the validity period timer has expired (step S209: YES), in step S210, the UE 100 performs an MBS reception cancellation process. The MBS reception cancellation process includes at least one of a process of stopping MBS reception, a process of canceling application of the MBS setting, and a process of discarding the MBS setting.

[0092] If the validity period timer expires and UE100 wishes to continue receiving MBS, in step S211, UE100 performs connection processing with gNB200.

[0093] For example, the UE 100 in the RRC idle state starts an RRC Setup procedure. In the RRC Setup procedure, the UE 100 may include information indicating that the purpose is to acquire the MBS reception setting as an information element (for example, Cause) in an RRC Setup Request message.

[0094] The UE 100 in the RRC inactive state starts an RRC Resume procedure. In the RRC Resume procedure, the UE 100 may include information indicating that the purpose is to acquire the MBS reception configuration as an information element (for example, Cause) in an RRC Resume Request message.

[0095] After UE100 transitions to the RRC connected state through connection processing with gNB200 (step S212), in step S213, UE100 receives an RRC Reconfiguration message including a new MBS setting from gNB200.

[0096] In this operation example, it is assumed that only unicast MBS setting is used, but it may also be assumed that broadcast MBS setting is also used. When the validity period timer expires (step S209: YES), the UE 100 performs MBS reception cancellation processing (step S210) and may also acquire the MBS setting from the MBS control channel broadcast from the gNB 200.

[0097] In this modification, the validity period of the MBS configuration may be different for each MBS session (TMGI) or may be common to all MBS sessions (only one). When the validity period of the MBS configuration is different for each MBS session, the UE 100 sets the validity period corresponding to the MBS session received by the UE 100 in a timer.

[0098] (Modification 2 of the first embodiment) Next, a second modification of the first embodiment will be described.

[0099] As described above, if the network (gNB200) changes the MBS settings (e.g., changes resources, etc.), a UE100 in an RRC idle state or an RRC inactive state may not be able to receive the desired MBS session.

[0100] In a second modification of the first embodiment, the UE 100, which transitions to an RRC idle state or an RRC inactive state and performs MBS reception, receives a notification indicating an update of the MBS configuration from the gNB 200. In response to receiving the notification, the UE 100 transitions to an RRC connected state and acquires a new MBS configuration. This allows the UE 100 to continue MBS reception using the new MBS configuration.

[0101] 10 is a diagram showing a second modification of the first embodiment. Here, differences from the first embodiment will be mainly described.

[0102] 10, steps S301 to S308 are the same as steps S101 to S108 in the first embodiment described above. However, in step S302, when configuring an MBS for the UE 100, the gNB 200 may notify the UE 100 of a configuration identifier (value tag value) associated with the MBS configuration.

[0103] In step S309, the gNB200 determines to change the MBS configuration. For example, the gNB200 determines at least one of changing the resources (time and frequency resources) for PTM transmission and stopping or starting PTM transmission.

[0104] In step S310, gNB200 notifies UE100 that is in RRC idle state or RRC inactive state.

[0105] The notification in step S310 may be system information (SIB: System Information Block) broadcast by the gNB 200. The notification may be a notification that the MBS configuration has changed and / or that the change is scheduled to occur within a certain period of time, or an instruction to perform connection processing (e.g., RRC Setup). The notification may include an identifier (e.g., TMGI) of the MBS session whose MBS configuration has changed.

[0106] The gNB200 may include the value tag value of the currently valid MBS setting in the SIB. Note that the gNB200 counts up (increments) the value tag value every time the MBS setting is changed. If the value tag value notified from the gNB200 in step S302 is the same as the value tag value included in the SIB received from the gNB200 in step S310, the UE100 determines that the current MBS setting is valid, and if the value tag values ​​are different, the UE100 determines that the current MBS setting is invalid.

[0107] The notification in step S310 may be a paging message including an identifier of an MBS session whose MBS configuration has been changed. For example, the gNB 200 includes an MBS session identifier whose configuration needs to be changed in a paging record included in the paging message. If the MBS session identifier desired by the UE 100 is included in the paging record, the UE 100 determines that it needs to reacquire the MBS configuration. Note that the UE 100 only needs to monitor normal paging occasions. The gNB 200 transmits a paging message including the MBS session identifier at all paging occasions of the UE 100 within a certain period of time.

[0108] In step S311, UE 100 that wishes to continue receiving MBS performs the above-mentioned MBS reception stop processing (step S311) in response to receiving the notification in step S310, and also performs the above-mentioned connection processing (step S312). Then, in step S313, UE 100 transitions to the RRC connected state, acquires new MBS reception settings, and continues MBS reception. This operation is the same as in Modification 1 of the first embodiment.

[0109] (Third Modification of the First Embodiment) Next, a third modification of the first embodiment will be described.

[0110] In this modification, it is assumed that the MBS configuration applied in the RRC connected state is different from the MBS configuration applied in the RRC idle state or the RRC inactive state.

[0111] In this modified example, the unicast signaling (RRC Reconfiguration message) sent from gNB200 to UE100 includes a first MBS setting required for MBS reception in the RRC connected state and a second MBS setting required for MBS reception in the RRC idle state or the RRC inactive state.

[0112] 11 is a diagram showing a third modification of the first embodiment. Here, differences from the first embodiment will be mainly described.

[0113] As shown in FIG. 11, in step S401, UE100 is in an RRC connected state in the cell of gNB200.

[0114] In step S402, the gNB 200 transmits an RRC Reconfiguration message including the first MBS configuration and the second MBS configuration to the UE 100. The UE 100 receives the RRC Reconfiguration message.

[0115] The first MBS configuration is an MBS reception configuration for the RRC connected state. The first MBS configuration includes MBS bearer configuration information. In the first MBS configuration, an MBS bearer may be associated with an MBS session identifier (e.g., G-RNTI). The first MBS configuration may include an identifier indicating that the configuration is for the RRC connected state, or an identifier indicating that the configuration should not be used in the RRC idle state or the RRC inactive state.

[0116] The first MBS configuration does not necessarily have to be exclusive to the RRC connected state, and may include an identifier indicating that the configuration may also be used in the RRC idle state or the RRC inactive state.

[0117] On the other hand, the second MBS configuration is an MBS reception configuration for the RRC idle state or the RRC inactive state. The second MBS configuration includes configuration information (e.g., scheduling information) related to the MBS traffic channel. The second MBS configuration may include an identifier indicating that the second MBS configuration is a reception configuration for the RRC idle state or the RRC inactive state, or may include an identifier indicating that the configuration should not be used in the RRC connected state. In the second MBS configuration, a configuration for the RRC idle state and a configuration for the RRC inactive state may be provided separately.

[0118] The second MBS configuration does not necessarily have to be dedicated to the RRC idle state or the RRC inactive state, and may include an identifier indicating that the second MBS configuration may also be used in the RRC connected state.

[0119] In step S403, the UE 100 stores and applies the first MBS configuration included in the received RRC Reconfiguration message, and stores the second MBS configuration.

[0120] In step S404, the UE 100 receives MBS data from the gNB 200 using the first MBS configuration applied in step S403. Here, the UE 100 may apply a second MBS configuration that is also valid in the RRC connected state. The UE 100 does not apply a second MBS configuration that is only valid in the RRC idle state or the RRC inactive state.

[0121] Thereafter, in step S405, the gNB 200 transmits an RRC Release message to the UE 100 to transition the UE 100 to an RRC idle state or an RRC inactive state. The UE 100 receives the RRC Release message.

[0122] In step S406, the UE 100 transitions from the RRC connected state to the RRC idle state or the RRC inactive state.

[0123] In step S407, UE 100 performs processing according to the identifier included in the first MBS configuration and the identifier included in the second MBS configuration. For example, UE 100 discards the first MBS configuration that is valid only in the RRC connected state. However, if UE 100 is in the RRC inactive state, UE 100 may retain the first MBS configuration. UE 100 either retains (does not discard) the second MBS configuration that is valid in the RRC idle state or the RRC inactive state, or continues to apply it (or applies it again).

[0124] In step S408, UE100 receives MBS data from gNB200 using the second MBS setting applied in step S407.

[0125] (Second embodiment) Next, the second embodiment will be described, focusing mainly on the differences from the first embodiment.

[0126] In the second embodiment, it is assumed that MBS configuration by unicast and MBS configuration by broadcast coexist. In the case where there are two such configuration methods, the UE 100 needs to appropriately determine which method to use to acquire the MBS configuration when receiving the MBS.

[0127] In the second embodiment, the gNB 200 transmits to the UE 100 a broadcast message including at least one of a first identifier (first MBS session identifier) ​​indicating a first MBS session in which a first MBS setting required for MBS reception is provided by unicast signaling, and a second identifier (second MBS session identifier) ​​indicating a second MBS session in which a second MBS setting required for MBS reception is provided by broadcast signaling. This broadcast message may be an SIB transmitted on a broadcast control channel, or may be MBS control information transmitted on an MBS control channel.

[0128] This allows the UE 100 to appropriately determine which method, unicast setting or broadcast setting, to use to acquire the MBS setting when receiving an MBS. The UE 100 receives either the first MBS setting (i.e., the MBS setting via unicast) or the second MBS setting (i.e., the MBS setting via broadcast) from the gNB 200 based on the broadcast message from the gNB 200 and the desired MBS session of the UE 100.

[0129] FIG. 12 is a diagram illustrating an example of operation according to the second embodiment.

[0130] 12, in step S501, the gNB 200 notifies the UE 100 (UE 100A, UE 100B) by SIB of a service (first MBS session identifier) ​​for which MBS configuration must be received by unicast signaling (e.g., an RRC Reconfiguration message) and / or a service (second MBS session identifier) ​​for which configuration can be received by broadcast signaling (e.g., an SC-MCCH). That is, the gNB 200 broadcasts a method for obtaining MBS configuration for each MBS session identifier by SIB (or SC-MCCH).

[0131] FIG. 12 shows an example in which the MBS session (first MBS session identifier) ​​to which the unicast setting is applied is MBS session #1, and the MBS session (second MBS session identifier) ​​to which the broadcast setting is applied is MBS session #2.

[0132] For example, an MBS session to which the unicast setting is applied is an MBS session that belongs to a multicast service (e.g., group communication), whereas an MBS session to which the broadcast setting is applied is an MBS session that belongs to a broadcast service (e.g., broadcasting, IPTV).

[0133] In step S502, UE 100A, which wishes to receive a multicast service, determines to receive MBS session #1 based on the SIB from gNB 200. On the other hand, in step S503, UE 100B, which wishes to receive a broadcast service, determines to receive MBS session #2 based on the SIB from gNB 200.

[0134] In step S504, when the UE 100A is in the RRC idle state or the RRC inactive state, the UE 100A performs a process of transitioning to the RRC connected state in order to receive the first MBS configuration (connection process).

[0135] In step S505, UE100A receives an RRC Reconfiguration message including the first MBS setting from gNB200.

[0136] In step S506, UE100A receives MBS data of MBS session #1 from gNB200 by applying the first MBS configuration received in step S505.

[0137] On the other hand, in step S507, UE 100B receives an MBS control channel including a second MBS configuration from gNB 200. For example, when UE 100B is in an RRC connected state, UE 100B attempts to receive an MBS control channel (e.g., SC-MCCH) without expecting to acquire an MBS configuration in an RRC Reconfiguration message from gNB 200. UE 100 in the RRC connected state may transmit RAI (Release Assistance Information) to gNB 200 to have the RRC connection released, and may transition to an RRC idle state or an RRC inactive state.

[0138] In step S508, UE100B receives MBS data of MBS session #2 from gNB200 by applying the second MBS setting received in step S507.

[0139] In this operation example, it can be considered that the gNB 200 broadcasts the MBS session identifiers that it can provide. If the UE 100 is interested in receiving an MBS session that the gNB 200 cannot provide, the UE 100 may receive the MBS data of the MBS session by establishing a unicast session with the 5GC 20.

[0140] In addition, in this operation example, gNB200 may send a broadcast message to UE100 that further includes a third identifier (third MBS session identifier) ​​indicating a third MBS session in which MBS configuration is provided by both unicast signaling and broadcast signaling.

[0141] (Third embodiment) Next, the third embodiment will be described, focusing mainly on the differences from the first and second embodiments.

[0142] In the third embodiment, it is assumed that multiple MBS control channels (for example, multiple SC-MCCHs) are configured in one cell of the gNB 200. This makes it possible to use different MBS control channels depending on the service requirements of the MBS session, for example.

[0143] When multiple MBS control channels are configured, it is conceivable that the RNTI of the PDCCH for transmitting each MBS control channel is different. Specifically, in the physical layer of the gNB 200, when transmitting a certain MBS control channel, a PDCCH to which the RNTI for the MBS control channel is applied is transmitted to the UE 100, thereby allocating resources of the PDSCH carrying the MBS configuration to the UE 100.

[0144] In this way, when the RNTI is different for each MBS control channel, it is necessary to specify which RNTI transmits which MBS control channel.

[0145] In the third embodiment, the gNB 200 that provides multiple MBS control channels in one cell transmits, for each of the multiple MBS control channels, a broadcast message including an RNTI used to receive the MBS control channel to the UE 100. This broadcast message may be an SIB transmitted on the broadcast control channel.

[0146] The RNTI used to receive the MBS control channel may be the RNTI applied to the MBS control channel (hereinafter referred to as "SC-RNTI"), or the RNTI applied to the change notification of the MBS control channel (hereinafter referred to as "SC-N-RNTI").

[0147] FIG. 13 is a diagram illustrating an example of operation according to the third embodiment.

[0148] 13, in step S601, the gNB 200 broadcasts an SIB including configuration information for each MBS control channel. This configuration information may include an SC-RNTI value for each MBS control channel, or may include an SC-RNTI value for each MBS session identifier. This configuration information may include an SC-N-RNTI value for each MBS control channel, or may include an SC-N-RNTI value for each MBS session identifier.

[0149] 13, the SIB includes a set of RNTI (SC-RNTI and / or SC-N-RNTI) #1 and MBS session identifier #1 for MBS control channel #1, and a set of RNTI (SC-RNTI and / or SC-N-RNTI) #2 and MBS session identifier #2 for MBS control channel #2.

[0150] In step S602, the UE 100A determines to receive the MBS session #1 based on the SIB from the gNB 200. Then, in step S603, the UE 100A attempts to receive the MBS control channel #1 by applying the RNTI #1 corresponding to the MBS session #1 based on the SIB from the gNB 200.

[0151] On the other hand, in step S604, the UE 100B decides to receive the MBS session #2 based on the SIB from the gNB 200. Then, in step S605, the UE 100B attempts to receive the MBS control channel #2 by applying the RNTI #2 corresponding to the MBS session #2 based on the SIB from the gNB 200.

[0152] In step S606, the UE 100A receives the MBS control channel #1 from the gNB 200. In step S607, the UE 100A receives the MBS data of the MBS session #1 from the gNB 200 using the MBS configuration included in the MBS control channel #1 received in step S606.

[0153] On the other hand, in step S608, the UE 100B receives the MBS control channel #2 from the gNB 200. In step S609, the UE 100B receives the MBS data of the MBS session #2 from the gNB 200 using the MBS configuration included in the MBS control channel #2 received in step S608.

[0154] (Fourth embodiment) Next, the fourth embodiment will be described, mainly focusing on differences from the first to third embodiments. The fourth embodiment is an embodiment related to cell reselection performed by the UE 100 in the RRC idle state or the RRC inactive state.

[0155] LTE introduces a mechanism for cell reselection that prioritizes a frequency that provides an MBMS session of interest or currently being received. However, this mechanism reselects a frequency (or a cell) depending on the UE 100, which is uncontrollable from the network perspective. Therefore, a method is desired that allows the UE 100 to receive a desired MBS session while still allowing network control.

[0156] In the fourth embodiment, the gNB 200 transmits cell reselection control information including priority information indicating the priority of each cell or frequency in cell reselection and an MBS session identifier associated with the priority information. The UE 100 in the RRC idle state or the RRC inactive state performs cell reselection using the priority information corresponding to the desired MBS session identifier of the UE 100, based on the cell reselection control information from the gNB 200. This enables network control while realizing cell reselection control that allows the UE 100 to receive the desired MBS session.

[0157] FIG. 14 is a diagram illustrating an example of operation according to the fourth embodiment.

[0158] As shown in FIG. 14, in step S701, the UE 100 may be in an RRC idle state or an RRC inactive state.

[0159] In step S702, the gNB 200 notifies the UE 100 of priority information (cell reselection priority) for each MBS session. For example, the gNB 200 broadcasts an SIB including priority information associated with the MBS session. Alternatively, the gNB 200 may transmit unicast signaling (e.g., an RRC Release message) including priority information associated with the MBS session to the UE 100. When transmitting an RRC Release message including priority information associated with the MBS session to the UE 100, the UE 100 transitions from the RRC connected state to the RRC idle state or the RRC inactive state in response to receiving this RRC Release message. An example using an SIB will be described below, but an RRC Release message may be used instead of the SIB.

[0160] The SIB includes multiple sets of MBS session identifiers and priority information for cells and / or frequencies. In the example shown in FIG. 14, priority information #1 is associated with MBS session identifier #1, and priority information #2 is associated with MBS session identifier #2. Priority information #1 is information such that frequency #1 is high priority, frequency #2 is medium priority, and frequency #3 is low priority. Priority information #2 is information such that frequency #1 is low priority, frequency #2 is medium priority, and frequency #3 is high priority. For example, prioritization is performed such that a high frequency is prioritized for an MBS session requiring high-speed communication, and a low frequency is prioritized for an MBS session requiring high reliability. Note that these priority information may be linked to a cell ID instead of a frequency.

[0161] In step S703, UE 100 controls cell reselection using priority information corresponding to its own desired MBS session, based on its own desired MBS session and the SIB from gNB 200. In this cell reselection control, UE 100 preferentially selects a frequency (or a cell) to which a higher priority is assigned in the priority information.

[0162] Here, in UE 100, a desired MBS session may be notified from an upper layer (NAS layer) to a lower layer (AS layer), and the AS layer may use this to perform cell reselection control. Also, when there are multiple desired MBS sessions, the upper layer (NAS layer) may notify the lower layer (AS layer) of the reception priority for each MBS session, and the lower layer (AS layer) may use priority information corresponding to the MBS session with the highest reception priority to perform cell reselection control.

[0163] In this operation example, the SIB may further include conventional priority information that is not associated with the MBS session identifier. Such conventional priority information is intended to be used by legacy UEs that do not support MBS or UEs 100 that are not interested in receiving MBS.

[0164] Incidentally, when an MBS session is associated with a network slice, gNB200 may broadcast frequency / cell priority information for each network slice. Information linking the MBS session identifier (e.g., TMGI) and the network slice identifier (e.g., S-NSSAI) may be notified to UE100 and / or gNB200 from the core network. UE100 performs cell (re)selection processing according to the frequency / cell priority information in the network slice associated with the MBS session it wishes to receive.

[0165] In such an example, the MBS session identifier in the above-described fourth embodiment may be read as a network slice identifier. Specifically, the gNB 200 transmits cell reselection control information including priority information indicating a priority for each cell or frequency in cell reselection and a network slice identifier associated with the priority information. The UE 100 in an RRC idle state or an RRC inactive state performs cell reselection using priority information corresponding to a desired network slice of the UE 100, based on the cell reselection control information from the gNB 200.

[0166] (Fifth embodiment) Next, the fifth embodiment will be described, mainly focusing on differences from the first to fourth embodiments. The fifth embodiment is an embodiment related to RRC reestablishment performed by the UE 100 in the RRC connected state.

[0167] When UE 100 in the RRC connected state detects a radio link failure (RLF) while receiving an MBS session and starts an RRC re-establishment process, if a cell that does not provide the MBS session is selected in cell selection during the RRC re-establishment process, there is a risk that MBS reception will be interrupted. In the fifth embodiment, the continuity of MBS reception is improved by preferentially selecting a cell that provides the MBS session in cell selection during the RRC re-establishment process.

[0168] In the fifth embodiment, when UE 100 receiving an MBS session in an RRC connected state starts an RRC re-establishment process, it performs cell selection in the RRC re-establishment process. In the cell selection, UE 100 preferentially selects a cell that provides the MBS session. This can improve the continuity of MBS reception.

[0169] FIG. 15 is a diagram illustrating an example of operation according to the fifth embodiment.

[0170] As shown in FIG. 15, in step S801, UE100 is in an RRC connected state in cell #1 of gNB200A.

[0171] In step S802, UE100 receives MBS data for the MBS session from gNB200A.

[0172] In step S803, UE100 may receive neighboring cell information from gNB200A, including an MBS session identifier of an MBS session provided by cell #2, which is a neighboring cell.

[0173] In step S804, UE100 detects RLF with gNB200A and starts the RRC re-establishment process.

[0174] In step S805, the UE 100 may receive MBS information broadcast by the gNB 200B (cell #2) during cell search. This MBS information may be an SIB including an MBS session identifier of an MBS session provided by the cell #2.

[0175] In step S806, UE100 identifies the MBS session provided by gNB200A (cell #2) based on the information received in step S803 or step S805.

[0176] In step S807, UE100 determines whether gNB200A (cell #2) provides the MBS session received in step S802.

[0177] If it is determined that the MBS session received in step S802 is provided by gNB200A (cell #2) (step S807: YES), in step S808, UE100 selects cell #2.

[0178] In step S809, the UE 100 accesses the selected cell #2 and performs RRC re-establishment, thereby continuing to receive the MBS session that is currently being received (that is of interest).

[0179] (Sixth embodiment) Next, the sixth embodiment will be described, focusing mainly on the differences from the first to fifth embodiments.

[0180] In NR, it is possible to limit the operating bandwidth of the UE 100 by configuring the UE 100 with a bandwidth part (BWP (Bandwidth part)) narrower than the frequency bandwidth of one cell, and such a BWP may be introduced for the MBS. When such a BWP for the MBS is introduced, it is considered that the BWP for the MBS is notified to the UE 100 in the MBS configuration. However, if information about the BWP for the MBS is not included in the MBS configuration, the UE 100 cannot identify the BWP for the MBS, and an unexpected error may occur.

[0181] In the sixth embodiment, the UE 100 receives, from the gNB 200, information indicating an initial BWP used by the gNB 200. The initial BWP is a BWP notified by an SIB and refers to a BWP used by the UE 100 for initial access to the gNB 200. The UE 100 uses the initial BWP until a BWP setting for the UE 100 is received from the gNB 200.

[0182] Furthermore, UE 100 receives an MBS setting required for MBS reception from gNB 200. Here, if the MBS setting does not include a BWP setting, UE 100 performs MBS reception using an initial BWP. In this way, by specifying the behavior of UE 100 when there is a defect in the MBS setting, it is possible to reduce the possibility of an unexpected error occurring.

[0183] FIG. 16 is a diagram illustrating an example of operation according to the sixth embodiment.

[0184] As shown in FIG. 16, in step S901, UE100 receives a SIB including initial BWP information from gNB200.

[0185] In step S902, UE100 receives MBS configuration from gNB200.

[0186] In step S903, UE100 determines whether the MBS configuration received from gNB200 includes a BWP configuration for MBS.

[0187] If the MBS configuration received from gNB200 includes the BWP configuration for MBS (step S903: YES), in step S904, UE100 applies the BWP configuration for MBS.

[0188] On the other hand, if the MBS configuration received from the gNB 200 does not include the configuration of the BWP for MBS (step S903: NO), in step S905, the UE 100 determines (assumes) that the MBS data of the PTM is transmitted in the initial BWP. A default value of the BWP for MBS may be set as the initial BWP.

[0189] In step S906, the UE 100 attempts to receive the MBS data in the set BWP.

[0190] (Other embodiments) The above-described embodiments and modifications are not limited to being implemented independently, but may be implemented by combining two or more examples.

[0191] In the above-described embodiment, an example in which the base station is an NR base station (gNB) has been described, but the base station may be an LTE base station (eNB). Also, the base station may be a relay node such as an IAB (Integrated Access and Backhaul) node. The base station may be a DU (Distributed Unit) of the IAB node.

[0192] A program may be provided that causes a computer to execute each process performed by the UE 100 or the gNB 200. The program may be recorded on a computer-readable medium. Using the computer-readable medium, the program can be installed on a computer. Here, the computer-readable medium on which the program is recorded may be a non-transitory recording medium. The non-transitory recording medium is not particularly limited, and may be, for example, a recording medium such as a CD-ROM or a DVD-ROM.

[0193] In addition, circuits that execute each process performed by UE100 or gNB200 may be integrated, and at least a part of UE100 or gNB200 may be configured as a semiconductor integrated circuit (chip set, SoC (System on a chip)).

[0194] The above describes the embodiments in detail with reference to the drawings, but the specific configuration is not limited to that described above, and various design changes can be made within the scope that does not deviate from the gist of the invention.

[0195] This application claims priority to U.S. Provisional Application No. 63 / 104044 (filed October 22, 2020), the entire contents of which are incorporated herein by reference.

[0196] (Addendum) ·introduction A revised work item on NR Multicast and Broadcast Services (MBS) was approved. The objectives of the work item are to:

[0197] -Specifies basic RAN functions for broadcast / multicast for UEs in RRC connected state. -Specifies a group scheduling mechanism that enables UEs to receive broadcast / multicast services. This objective includes specifying the extensions necessary to allow simultaneous operation with unicast reception. -Specifies support for dynamic change of broadcast / multicast service delivery between multicast (PTM) and unicast (PTP) with default UE service continuity. - Provide for support of basic mobility with service continuity. - Specify the necessary changes to the RAN architecture and interfaces, taking into account the consequences of SA2 SI in broadcast / multicast, assuming that the necessary coordination functions (such as those hosted by the MCE) are located in the gNB-CU. - Specifying changes required to improve the reliability of broadcast / multicast services, e.g., by UL feedback. The level of reliability should be based on the requirements of the application / service provided. - Study support for dynamic control of broadcast / multicast transmission areas within one gNB-DU and specify what, if anything, is needed to enable it.

[0198] -Specifies basic RAN functions for broadcast / multicast for UEs in RRC idle / RRC inactive state. -Specifies the changes necessary to enable reception of Point to Multipoint transmissions by UEs in the RRC Idle / RRC Inactive state, with the aim of maintaining maximum commonality between the RRC Connected state and the RRC Idle / RRC Inactive state for PTM reception configuration.

[0199] In RAN2#111-e, many companies proposed reusing the LTE SC-PTM mechanism for idle / inactive UEs, but as the chair summarized: many companies saw significant differences between the connected and idle / inactive solutions. - Chair: Many companies believe there is a big difference between idle and connected solutions, and further consideration is needed as to what that ultimately means. -Chair's view: There are many proposals to reuse (to a large extent or 100%) LTE SC-PTM for idle / inactive NR. Some companies are proposing to connect and control idle / inactive distributions as well.

[0200] This appendix discusses control plane considerations for NR MBS.

[0201] Discussion In LTE SC-PTM, configuration is provided by two messages: SIB20 and SC-MCCH. SIB20 provides SC-MCCH scheduling information, and SC-MCCH provides SC-MTCH scheduling information including G-RNTI and TMGI, and neighbor cell information.

[0202] The advantage of the two-stage configuration in LTE as shown in Figure 17 was that SC-MCCH scheduling was independent from SIB20 scheduling in terms of repetition period, duration, modification period, etc. The two-stage configuration facilitated frequent scheduling / updating of SC-MCCH, especially for delay-sensitive services and / or UEs that join the session late. According to WID, the same is true for NR MBS, as one of the applications is group communication, etc.

[0203] Observation 1: In LTE, the two-stage configuration using SIB20 and SC-MCCH lends itself to different scheduling of these control channels, which also lends itself to NR MBS.

[0204] Proposal 1: RAN2 should agree to use a two-stage configuration with different NR MBS messages, such as SIB20 and SC-MCCH in SC-PTM.

[0205] In addition to Proposal 1, NR MBS is envisioned to support the various types of use cases described in WID. It is noted that NR MBS should be appropriately designed for a variety of requirements, from latency-sensitive applications such as mission-critical and V2X to latency-tolerant applications such as IoT, in addition to other aspects of requirements ranging from lossless applications such as software distribution to UDP-type streaming such as IPTV.

[0206] Therefore, the design of the control channel should consider its flexibility and resource efficiency, otherwise, for example, when delay-tolerant and delay-sensitive services are configured together on one control channel, the control channel may need to be scheduled frequently to meet the delay requirements from the delay-sensitive service, which may result in more signaling overhead.

[0207] Objective A of SA2 SI is about enabling general MBS services over 5GS, and identified use cases that may benefit from this capability include (but are not limited to) public safety, mission-critical, V2X applications, transparent IPv4 / IPv6 multicast distribution, IPTV, over-the-air software distribution, group communications, and IoT applications.

[0208] Observation 2: The NR MBS control channel needs to be flexible and resource efficient for different types of use cases.

[0209] One possibility is to consider whether it is necessary to separate configuration channels for different use cases, as shown in Figure 18. For example, one control channel may frequently provide delay-sensitive services, while another control channel may sparsely provide delay-tolerant services. In LTE SC-PTM, a cell is limited to having only one SC-MCCH. However, considering that more use cases than LTE are expected, NR MBS should remove this restriction. If multiple SC-MCCHs are permitted in a cell, each SC-MCCH has different scheduling settings, such as a recurrence period, that can be optimized for a specific service. Further consideration is needed to determine how a UE identifies the SC-MCCH that provides the service of interest.

[0210] Proposal 2: RAN2 should discuss whether multiple control channels will be supported in a cell in NR MBS, similar to the multiple SC-MCCHs that were not available in LTE.

[0211] Furthermore, a new paradigm in NR is the support of on-demand SI transmission. This concept can be reused for the SC-MCCH of NR MBS, i.e., on-demand SC-MCCH. For example, the SC-MCCH for delay-tolerant services is provided on-demand, thereby optimizing signaling resource consumption. Of course, the network has other options to provide the SC-MCCH periodically, i.e., not on-demand, for delay-sensitive services, etc.

[0212] Proposal 3: RAN2 should discuss options for when control channels are provided on an on-demand basis, such as the on-demand SC-MCCH that was not available in LTE.

[0213] Another possibility that may be further considered is merging these messages, i.e., one-stage configuration, as shown in Figure 13. For example, the SIB provides SC-MTCH scheduling information directly, i.e., without the SC-MCCH. This would provide optimization for delay-tolerant services and / or power-sensitive UEs. For example, a UE may request the SIB (on-demand), and the gNB may start providing the SIB and corresponding services after requests from multiple UEs. These UEs do not need to monitor the repeatedly broadcasted SC-MCCH.

[0214] Proposal 4: RAN2 should discuss options such as SIB directly providing traffic channel configuration if multicast reception without SC-MCCH (i.e., one-stage configuration) is supported.

[0215] (dedicated signaling-based configuration) Some companies have proposed that MBS configuration be provided only through dedicated signaling. While dedicated signaling is simple for UEs in RRC Connected state for multicast services such as group communication, it means that UEs in idle / inactive states must always transition to RRC Connected state before receiving MBS services, even if they are only interested in broadcast services. This may result in unnecessary UE power consumption and may reduce future assurance, such as support for free-to-air services in future releases. Therefore, we believe that MBS configuration via broadcast signaling should become the baseline, as in Proposals 1 to 4, as in LTE SC-PTM.

[0216] However, it is believed that flexibility in network implementation and deployment policies is possible if the control channel can be provided via RRC reconfiguration, as shown in Figure 13. For example, the network may decide not to broadcast the MBS control channel and only provide configuration via dedicated signaling when necessary, such as for operators that do not offer broadcast services. As another example, it is beneficial for service continuity during handover if the target cell provides MBS configuration via a handover command.

[0217] Therefore, RAN2 needs to consider whether the RRC reconfiguration provides an MBS control channel.

[0218] Proposal 5: RAN2 needs to consider options for providing SC-MCCH when RRC reconfiguration is required, which was not available in LTE.

[0219] (Indication of Interest / Counting) LTE eMBMS specifies two methods for collecting UE's receiving / interested services, i.e., MBMS Interest Indication (MII) and MBMS Counting, to allow the network to make appropriate decisions on MBMS data delivery, including starting / stopping MBMS sessions. The MII triggered by the UE contains information related to the interested MBMS frequencies, interested MBMS services, MBMS priority, and MBMS ROM (Receive Only Mode). The Counting Response triggered by the network via a Counting Request for a specific MBMS service contains information related to the interested MBSFN area and MBMS service.

[0220] These methods were introduced for different purposes: MII is primarily used by the network to ensure that the UE can continue to receive the services it is interested in while in the connected state, while counting is used to allow the network to determine if a sufficient number of UEs are interested in receiving the service.

[0221] Observation 3: In LTE e MBMS, two kinds of UE assistance information are introduced for different purposes: MBMS Interest Indication is introduced for scheduling in the NB, and MBMS Counting is introduced for session control in the MCE.

[0222] For NR MBS, multicast services such as group communication use cases are expected, and the network has complete knowledge of the MBS services that UEs in the Connected state are receiving / interested in. Therefore, assistance information from the UE, such as the network's PTP / PTM distribution decisions, is not required. However, to our understanding, this does not apply to broadcast services or UEs in the Idle / Inactive state. Especially for broadcast services, the same problem solved by counting with MII in LTE eMBMS, i.e., Observation 3, still exists in NR MBS. Therefore, RAN2 needs to consider whether assistance information such as MII and counting can be useful for NR MBS.

[0223] Note that MBMS ROM information in MII and information about MBSFN area in Counting Response are not required in Rel-17, since ROM and SFN are not supported as described in WID.

[0224] Proposal 6: RAN2 needs to agree to introduce UE assistance information for NR MBS, e.g., MBMS interest indication and / or MBMS counting.

[0225] If you agree with Proposal 6, it is worth considering extensions to LTE eMBMS. In LTE eMBMS, even if the majority of UEs are in RRC idle state and receiving broadcast services, neither MII nor counting can collect information from idle UEs. In our understanding, this is one of the issues with LTE eMBMS from the perspective of session control and resource efficiency.

[0226] In NR MBS, the same problem can exist for idle / inactive UEs. For example, the network cannot know whether idle / inactive UEs are not receiving / interested in the broadcast service. Therefore, PTM transmissions may continue even if no UEs are receiving the service. If the gNB is aware of the interest of idle / inactive UEs, it can avoid such unnecessary PTMs. Conversely, if PTM is stopped while there are still idle / inactive UEs receiving the service, multiple UEs may request a connection simultaneously.

[0227] Therefore, it is worth considering whether to introduce a mechanism to collect UE assistance information, specifically for MBMS counting, from idle / inactive UEs. Obviously, it would be desirable for idle / inactive UEs to be able to report information without transitioning to RRC Connected. This could be achieved, for example, if PRACH resource partitioning associated with MBS services were introduced for such reporting.

[0228] Proposal 7: RAN2 should consider whether UE assistance information such as MBMS counting is also collected from UEs in idle / inactive state.

Claims

1. A communication control method used in a mobile communication system that provides a multicast broadcast service (MBS) from a network to a user device, comprising: The user equipment in an RRC (Radio Resource Control) connected state receives an RRC Release message from a radio access network node, the RRC Release message including multicast settings required for receiving a multicast service in the MBS; The user equipment that has transitioned from the RRC connected state to an RRC inactive state receives the multicast service using the multicast configuration received in the RRC connected state, The multicast configuration includes at least one of a configuration related to an MBS bearer and a configuration related to scheduling of an MBS traffic channel. Communication control method.

2. The method further includes the user equipment in the RRC connected state receiving, from the radio access network node, information indicating whether the multicast configuration received in the RRC connected state is to be usable in the RRC inactive state. The communication control method according to claim 1 .

3. The method further comprises the user equipment in the RRC connected state receiving, from the radio access network node, information indicating a validity period of the multicast configuration from a time point at which the multicast configuration was received or a time point at which the user equipment transitioned to the RRC inactive state. The communication control method according to claim 1 .

4. Receiving the information indicating the validity period includes receiving the information indicating the validity period and an MBS session identifier associated with the information indicating the validity period. The communication control method according to claim 3.

5. The method further includes the user equipment, which transitions to the RRC inactive state and receives the multicast service, transitioning to the RRC connected state and acquiring a new multicast configuration in response to expiration of the validity period. The communication control method according to claim 3.

6. the user equipment that has transitioned to the RRC inactive state and is receiving the multicast service receives a notification from the radio access network node indicating an update of the multicast configuration; The method further includes: the user equipment transitioning to the RRC connected state and acquiring a new multicast configuration in response to receiving the notification. The communication control method according to claim 1 .

7. A user equipment for use in a mobile communication system providing a multicast broadcast service (MBS), comprising: a communication unit configured to receive an RRC Release message from a radio access network node when the user equipment is in an RRC (Radio Resource Control) connected state, the RRC Release message including a multicast setting required for receiving a multicast service in the MBS; When the user equipment transitions from the RRC connected state to an RRC inactive state, the communication unit receives the multicast service using the multicast configuration received in the RRC connected state; The multicast configuration includes at least one of a configuration related to an MBS bearer and a configuration related to scheduling of an MBS traffic channel. User equipment.

8. A radio access network node for use in a mobile communication system providing a multicast broadcast service (MBS), comprising: a communication unit that transmits an RRC Release message to a user equipment in an RRC (Radio Resource Control) connected state, the RRC Release message including a multicast setting required for the user equipment to receive a multicast service in the MBS in an RRC inactive state; The multicast configuration includes at least one of a configuration related to an MBS bearer and a configuration related to scheduling of an MBS traffic channel. Radio access network node.

9. A device for use in a user device for carrying out the communication method according to claim 1. Processor.

10. The communication method according to claim 1 is executed by a user device. program.

11. A user equipment according to claim 7 and a radio access network node. Mobile communication system.

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