COMMUNICATION METHOD, USER EQUIPMENT, CHIPSET, PROGRAM, AND MOBILE COMMUNICATION SYSTEM

Abstract

Provided is a communication method for execution by a user device in a mobile communication system that provides multicast broadcast service (MBS), the communication method comprising: a step for receiving, from a base station, setting information setting conditions for permitting transmission of an MBS notification of interest to the base station, regarding an MBS session that the user device is receiving or is interested in receiving; and a step for transmitting the MBS notification of interest in response to the conditions set by the setting information being fulfilled.

Description

[Technical field]

[0001] The present disclosure relates to a communication method for use in a mobile communication system. [Background technology]

[0002] The 3GPP (3rd Generation Partnership Project) standard defines technical specifications for NR (New Radio), a fifth-generation (5G) wireless access technology. Compared with LTE (Long Term Evolution), a fourth-generation (4G) wireless access technology, NR has features such as high speed, large capacity, high reliability, and low latency. Discussions are underway in 3GPP to formulate technical specifications for 5G / NR multicast broadcast service (MBS) (see, for example, Non-Patent Document 1). [Prior art documents] [Non-patent literature]

[0003] [Non-Patent Document 1] 3GPP contribution: RP-201038, “WID revision: NR Multicast and Broadcast Services” Summary of the Invention

[0004] It is expected that 5G / NR multicast broadcast services will provide improved services over 4G / LTE multicast broadcast services.

[0005] Therefore, an object of the present disclosure is to provide a communication method that enables an improved multicast broadcast service to be realized.

[0006] A communication method according to a first aspect is a communication method executed by a user device in a mobile communication system that provides a multicast broadcast service (MBS), and includes the steps of receiving configuration information from the base station that sets conditions under which the user device is permitted to transmit to a base station an MBS interest notification regarding an MBS session that the user device is receiving or is interested in receiving, and performing a transmission process of the MBS interest notification in response to the condition set by the configuration information being satisfied.

[0007] A communication method according to a second aspect is a communication method executed by a user device in a mobile communication system that provides a multicast broadcast service (MBS), and includes the steps of: transmitting a first MBS interest notification to a base station, the first MBS interest notification including information indicating one or more MBS frequencies that the user device is receiving or is interested in receiving from a combination of multiple frequencies that the user device can receive simultaneously; receiving carrier aggregation (CA) setting information from the base station; and, when the combination is changed according to the CA setting information and the MBS frequency that the user device is receiving or is interested in receiving is changed, transmitting a second MBS interest notification to the base station, the second MBS interest notification including information indicating the changed MBS frequency. [Brief description of the drawings]

[0008] [Figure 1] 1 is a diagram showing a configuration of a mobile communication system according to an embodiment. [Diagram 2] FIG. 2 is a diagram illustrating a configuration of a UE (user equipment) according to an embodiment. [Diagram 3] A diagram showing the configuration of a gNB (base station) according to an embodiment. [Figure 4] A diagram showing the configuration of a protocol stack of a wireless interface of a user plane that handles data. [Diagram 5] FIG. 2 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 showing an overview of MBS traffic distribution according to an embodiment. [Figure 7] FIG. 13 is a diagram illustrating a distribution mode according to the embodiment. [Figure 8] FIG. 2 is a diagram showing an example of internal processing related to MBS reception in a UE according to an embodiment. [Figure 9] FIG. 11 is a diagram showing another example of internal processing related to MBS reception of the UE according to the embodiment. [Figure 10] FIG. 1 is a diagram for explaining an overview of an MII. [Figure 11] FIG. 2 is a diagram showing a first operation example of the mobile communication system according to the embodiment. [Figure 12] FIG. 11 is a diagram for explaining trigger setting information in a first operation example of the mobile communication system according to the embodiment. [Figure 13] FIG. 11 is a diagram for explaining trigger type information (trigger type ID) and prohibition time setting information (prohibition timer value) in a second operation example of the mobile communication system according to the embodiment. [Figure 14] FIG. 11 is a diagram showing a second operation example of the mobile communication system according to the embodiment. [Figure 15] FIG. 11 is a diagram for explaining trigger type information (trigger type ID) and prohibition time setting information (prohibition timer value) in a second operation example of the mobile communication system according to the embodiment. [Figure 16] FIG. 11 is a diagram for explaining trigger type information (trigger type ID) and prohibition time setting information (prohibition timer value) in a second operation example of the mobile communication system according to the embodiment. [Figure 17] FIG. 11 is a diagram for explaining trigger type information (trigger type ID) and decentralization information in a third operation example of the mobile communication system according to the embodiment. [Figure 18] FIG. 11 is a diagram for explaining trigger type information (trigger type ID) and decentralization information in a third operation example of the mobile communication system according to the embodiment. [Figure 19] FIG. 11 is a diagram showing a third operation example of the mobile communication system according to the embodiment. [Figure 20]FIG. 11 is a diagram showing an operation of a UE according to a modified example of the operation of the mobile communication system according to the embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] 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.

[0010] (Configuration of a mobile communication system) FIG. 1 is a diagram showing a configuration of a mobile communication system according to an embodiment. The mobile communication system 1 complies with the 3GPP standard 5th Generation System (5GS). In the following description, 5GS is taken as an example, but the mobile communication system may be at least partially applied to an LTE (Long Term Evolution) system. Also, the mobile communication system may be at least partially applied to a 6th Generation (6G) system.

[0011] The mobile communication system 1 includes a user equipment (UE) 100, a 5G radio access network (NG-RAN) 10, and a 5G core network (5GC) 20. Hereinafter, the NG-RAN 10 may be simply referred to as the RAN 10. The 5GC 20 may be simply referred to as the core network (CN) 20.

[0012] The UE 100 is a mobile wireless communication device. The UE 100 may be any device that is used by a user. For example, the UE 100 is 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).

[0013] The NG-RAN 10 includes a base station (called "gNB" in the 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 the 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, and the like. 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 for performing wireless communication with the UE 100. One cell belongs to one carrier frequency (hereinafter simply referred to as "frequency").

[0014] In addition, gNBs can also be connected to the Evolved Packet Core (EPC), which is the core network of LTE. LTE base stations can also be connected to 5GC. LTE base stations and gNBs can also be connected via an inter-base station interface.

[0015] 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 Non-Access Stratum (NAS) signaling. The UPF controls data forwarding. The AMF and the UPF are connected to the gNB 200 via an NG interface, which is an interface between a base station and a core network.

[0016] 2 is a diagram showing a configuration of a UE 100 (user equipment) according to an embodiment. The UE 100 includes a receiving unit 110, a transmitting unit 120, and a control unit 130. The receiving unit 110 and the transmitting unit 120 configure a wireless communication unit that performs wireless communication with the gNB 200.

[0017] The receiving unit 110 performs various receptions 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.

[0018] The transmission unit 120 performs various transmissions under the control of the control unit 130. The transmission 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.

[0019] The control unit 130 performs various controls and processes in the UE 100. Such processes include processes of each layer described below. 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 the processes 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.

[0020] 3 is a diagram showing a configuration of a gNB 200 (base station) according to an embodiment. The gNB 200 includes a transmitter 210, a receiver 220, a controller 230, and a backhaul communication unit 240. The transmitter 210 and the receiver 220 constitute a wireless communication unit that performs wireless communication with the UE 100. The backhaul communication unit 240 constitutes a network communication unit that performs communication with the CN 20.

[0021] 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.

[0022] The receiving unit 220 performs various receptions 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.

[0023] The control unit 230 performs various controls and processes in the gNB 200. Such processes include processes of each layer described below. 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 the processes 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.

[0024] The backhaul communication unit 240 is connected to adjacent base stations via an Xn interface, which is an interface between base stations. The backhaul communication unit 240 is connected to the AMF / UPF 300 via an NG interface, which is an interface between a base station and a core network. Note that the gNB 200 may be configured (i.e., functionally divided) with a CU (Central Unit) and a DU (Distributed Unit), and both units may be connected to each other via an F1 interface, which is a fronthaul interface.

[0025] FIG. 4 is a diagram showing the configuration of a protocol stack of a radio interface of a user plane that handles data.

[0026] 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.

[0027] The PHY layer performs coding / 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. The PHY layer of the UE 100 receives downlink control information (DCI) transmitted from the gNB 200 on a physical downlink control channel (PDCCH). Specifically, the UE 100 performs blind decoding of the PDCCH using a radio network temporary identifier (RNTI) and acquires the successfully decoded DCI as DCI addressed to the UE. The DCI transmitted from the gNB 200 has CRC parity bits scrambled by the RNTI added thereto.

[0028] The MAC layer performs data priority control, retransmission processing using Hybrid Automatic Repeat reQuest (HARQ), random access procedures, etc. Data and control information are transmitted between the MAC layer of UE100 and the MAC layer of gNB200 via a transport channel. The MAC layer of gNB200 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 assigned to UE100.

[0029] The RLC layer transmits data to the RLC layer on the receiving side by using the functions of the MAC layer and the 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 a logical channel.

[0030] The PDCP layer performs header compression / decompression, encryption / decryption, etc.

[0031] The SDAP layer maps IP flows, which are units for QoS (Quality of Service) control by the core network, to radio bearers, which are units for QoS control by the AS (Access Stratum). Note that if the RAN is connected to the EPC, the SDAP is not necessary.

[0032] 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).

[0033] 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.

[0034] Between the RRC layer of the UE 100 and the RRC layer of the gNB 200, RRC signaling for various settings is transmitted. The RRC layer controls logical channels, transport channels, and physical channels in response to establishment, re-establishment, and release of radio bearers. When there is a connection (RRC connection) between the RRC of the UE 100 and the RRC of the gNB 200, the UE 100 is in an RRC connected state. When there is no connection (RRC connection) between the RRC of the UE 100 and the RRC of the gNB 200, the UE 100 is in an RRC idle state. When the connection between the RRC of the UE 100 and the RRC of the gNB 200 is suspended, the UE 100 is in an RRC inactive state.

[0035] The NAS layer, which is located above the RRC layer, performs session management, mobility management, and the like. NAS signaling is transmitted between the NAS layer of the UE 100 and the NAS layer of the AMF 300A. The UE 100 has an application layer and the like in addition to the radio interface protocol. The layer below the NAS layer is called the AS layer.

[0036] (Overview of MBS) An overview of the MBS according to the embodiment will be described. The MBS is a service that enables broadcast or multicast, i.e., point-to-multipoint (PTM) data transmission from the NG-RAN 10 to the UE 100. Possible use cases (service types) of the MBS include public safety communication, mission-critical communication, V2X (Vehicle to Everything) communication, IPv4 or IPv6 multicast distribution, IPTV (Internet protocol television), group communication, and software distribution.

[0037] The broadcast service provides a service to all UEs 100 within a specific service area for applications that do not require highly reliable QoS. An MBS session used for the broadcast service is called a broadcast session.

[0038] The multicast service provides services not to all UEs 100 but to a group of UEs 100 participating in the multicast service (multicast session). The MBS session used in the multicast service is called a multicast session. The multicast service allows the same content to be provided to a group of UEs 100 in a more wirelessly efficient manner than the broadcast service.

[0039] FIG. 6 is a diagram showing an overview of MBS traffic delivery according to the embodiment.

[0040] MBS traffic (MBS data) is distributed from a single data source (application service provider) to multiple UEs. A 5G core network, 5G CN (5GC) 20, receives the MBS data from the application service provider, creates a copy of the MBS data (replication), and distributes it.

[0041] From the 5GC20 perspective, two multicast delivery methods are possible: 5GC Shared MBS Traffic delivery and 5GC Individual MBS Traffic delivery.

[0042] In the 5GC individual MBS traffic delivery method, the 5GC 20 receives a single copy of MBS data packets and delivers individual copies of those MBS data packets to individual UEs 100 via a PDU session for each UE 100. Therefore, one PDU session for each UE 100 needs to be associated with the multicast session.

[0043] In the 5GC shared MBS traffic delivery method, the 5GC 20 receives a single copy of MBS data packets and delivers the single copy of those MBS packets to a RAN node (i.e., the gNB 200). The gNB 200 receives the MBS data packets via an MBS tunnel connection and delivers them to one or more UEs 100.

[0044] From the perspective of the RAN (5G RAN) 10, there are two possible delivery methods for transmitting MBS data over the air in the 5GC shared MBS traffic delivery method: PTP (Point-to-Point) and PTM (Point-to-Multipoint). PTP stands for unicast, and PTM stands for multicast and broadcast.

[0045] In the PTP distribution method, the gNB 200 distributes individual copies of the MBS data packets wirelessly to each UE 100. On the other hand, in the PTM distribution method, the gNB 200 distributes a single copy of the MBS data packet wirelessly to a group of UEs 100. The gNB 200 can dynamically determine whether to use PTM or PTP as the distribution method for MBS data to one UE 100.

[0046] The PTP distribution method and the PTM distribution method are mainly related to the user plane. There are two control modes for MBS data distribution: a first distribution mode and a second distribution mode.

[0047] FIG. 7 is a diagram showing a distribution mode according to the embodiment.

[0048] The first delivery mode (Delivery mode 1: DM1) is a delivery mode that can be used by the UE 100 in the RRC connected state, and is a delivery mode for high QoS requirements. The first delivery mode is used for a multicast session among MBS sessions. However, the first delivery mode may also be used for a broadcast session. The first delivery mode may also be available to the UE 100 in the RRC idle state or the RRC inactive state.

[0049] The setting of MBS reception in the first distribution mode is performed by UE-dedicated signaling. For example, the setting of MBS reception in the first distribution mode is performed by an RRC Reconfiguration message (or an RRC Release message), which is an RRC message transmitted by unicast from the gNB 200 to the UE 100.

[0050] The MBS reception configuration includes MBS traffic channel configuration information (hereinafter referred to as "MTCH configuration information") related to the configuration of an MBS traffic channel that transmits MBS data. The MTCH configuration information includes MBS session information (including an MBS session identifier described later) related to an MBS session, and scheduling information of the MBS traffic channel corresponding to this MBS session. The scheduling information of the MBS traffic channel may include a discontinuous reception (DRX) configuration of the MBS traffic channel. The discontinuous reception configuration may include one or more parameters of a timer value (On Duration Timer) that defines an on-duration (On Duration: reception period), a timer value (Inactivity Timer) that extends the on-duration, a scheduling interval or DRX cycle (Scheduling Period, DRX Cycle), an offset value of the start subframe of the scheduling or DRX cycle (Start Offset, DRX Cycle Offset), a start delay slot value of the on-duration timer (Slot Offset), a timer value (Retransmission Timer) that defines the maximum time until retransmission, and a timer value (HARQ RTT Timer) that defines the minimum interval until DL allocation of HARQ retransmission.

[0051] The MBS traffic channel is a type of logical channel and may be referred to as an MTCH. The MBS traffic channel is mapped to a Down Link-Shared CHannel (DL-SCH), which is a type of transport channel.

[0052] The second delivery mode (Delivery mode 2: DM2) is a delivery mode that can be used by UE 100 in the RRC connected state as well as UE 100 in the RRC idle state or RRC inactive state, and is a delivery mode for low QoS requirements. The second delivery mode is used for a broadcast session among MBS sessions. However, the second delivery mode may also be applicable to a multicast session.

[0053] The setting of MBS reception in the second distribution mode is performed by broadcast signaling. For example, the setting of MBS reception in the second distribution mode is performed by a logical channel broadcast from the gNB 200 to the UE 100, such as a broadcast control channel (BCCH) and / or a multicast control channel (MCCH). The UE 100 can receive the BCCH and MCCH using a dedicated RNTI predefined in the technical specifications, for example. The RNTI for BCCH reception may be SI-RNTI, and the RNTI for MCCH reception may be MCCH-RNTI.

[0054] In the second distribution mode, UE 100 may receive MBS data in the following three procedures. First, UE 100 receives MCCH setting information by a SIB (MBS SIB) transmitted on a BCCH from gNB 200. Second, UE 100 receives an MCCH from gNB 200 based on the MCCH setting information. The MCCH transmits MTCH setting information. Third, UE 100 receives an MTCH (MBS data) based on the MTCH setting information. Hereinafter, MTCH setting information and / or MCCH setting information may be referred to as MBS reception setting.

[0055] In the first distribution mode and the second distribution mode, the UE 100 may receive the MTCH using a group RNTI (G-RNTI) assigned by the gNB 200. The G-RNTI corresponds to an RNTI for MTCH reception. The G-RNTI may be included in the MBS reception setting (MTCH setting information).

[0056] The 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), a source-specific IP multicast address (consisting of a source unicast IP address of an application function or application server, etc., and an IP multicast address indicating a destination address), a session identifier, and a G-RNTI. At least one of the TMGI, the source-specific IP multicast address, and the session identifier is called an MBS session identifier. The TMGI, the source-specific IP multicast address, the session identifier, and the G-RNTI are collectively called MBS session information.

[0057] Fig. 8 is a diagram showing an example of an internal process related to MBS reception of the UE 100 according to the embodiment. Fig. 9 is a diagram showing another example of an internal process related to MBS reception of the UE 100 according to the embodiment.

[0058] One MBS Radio Bearer (MRB) is one radio bearer that transmits a multicast session or a broadcast session. That is, there are cases where a multicast session is associated with an MRB and cases where a broadcast session is associated with an MRB.

[0059] The MRB and corresponding logical channels (e.g., MTCH) are configured in the UE 100 from the gNB 200 by RRC signaling. The MRB configuration procedure may be separated from the data radio bearer (DRB) configuration procedure. In the RRC signaling, one MRB can be configured with "PTM only", "PTP only", or "both PTM and PTP". The type of such an MRB can be changed by RRC signaling.

[0060] In FIG. 8, an example is shown in which a multicast session and a dedicated traffic channel (DTCH) are associated with MRB#1, a multicast session and MTCH#1 are associated with MRB#2, and a broadcast session and MTCH#2 are associated with MRB#3. That is, MRB#1 is an MRB with PTP only, MRB#2 is an MRB with PTM only, and MRB#3 is an MRB with PTM only. Note that DTCH is scheduled using the cell RNTI (C-RNTI). MTCH is scheduled using the G-RNTI.

[0061] The PHY layer of the UE 100 processes user data (received data) received on a PDSCH, which is one of the physical channels, and transmits the data to a downlink shared channel (DL-SCH), which is one of the transport channels. The MAC layer (MAC entity) of the UE 100 processes data received on the DL-SCH, and transmits the received data to a corresponding logical channel (corresponding RLC entity) based on a logical channel identifier (LCID) included in a header (MAC header) included in the received data.

[0062] In FIG. 9, an example is shown in which a DTCH and an MTCH are associated with an MRB associated with a multicast session. Specifically, one MRB is split into two legs, one leg is associated with a DTCH, and the other leg is associated with an MTCH. The two legs are combined in the PDCP layer (PDCP entity). That is, the MRB is an MRB for both PTM and PTP. Such an MRB is sometimes called a split MRB.

[0063] (Summary of MBS Notice of Interest) An overview of an MBS Interest Indication (MII) according to an embodiment will be described below. Fig. 10 is a diagram for explaining the overview of the MII.

[0064] The UE 100 is in an RRC connected state (step S1) and is receiving or is interested in receiving an MBS session (step S2).

[0065] The UE 100 performs a transmission process of the MII (i.e., an MII procedure) in response to the occurrence of an MII transmission trigger (trigger event) (step S3). Specifically, the UE 100 generates an MII (step S4) and transmits the MII to the serving cell (gNB 200) (step S5). The MII may be transmitted by a UE Assistance Information message, which is a type of RRC message. The MII may also be transmitted by a newly defined message (MII message).

[0066] For example, types of MII transmission triggers (trigger events) include when a connection is successfully established, when entering or leaving a broadcast service area, when an MBS broadcast session is started or stopped, when MBS interest changes, when the priority between MBS broadcast reception and unicast reception changes, when there is a change to the cell (primary cell) that broadcasts SIBs for MBS service continuity, etc.

[0067] The MII may include at least one of an MBS frequency list, which is a list of MBS frequencies that UE100 is receiving or is interested in receiving, priority information indicating whether to prioritize receiving all listed MBS frequencies or receiving a unicast bearer, and a TMGI list, which is a list of MBS sessions that UE100 is receiving or is interested in receiving.

[0068] In addition, the transmission of the MII may be limited to only a serving cell that broadcasts an SIB for service continuity of the MBS (hereinafter, referred to as "SIBx1"), that is, a serving cell having a function for service continuity of the MBS. The UE 100 may transmit the MII to the serving cell only when the serving cell transmits the SIBx1.

[0069] (Mobile communication system operation) The operation of the mobile communication system 1 according to the embodiment will be described.

[0070] There is a concern that network congestion may occur when a large number of MIIs are transmitted from the UE 100. For example, when many UEs 100 transmit MIIs at the same time or when each UE 100 transmits MIIs frequently, network congestion may occur.

[0071] As a scenario in which many UEs 100 transmit MII at the same time, a scenario in which many UEs 100 transmit MII at the same time with "start or stop of MBS broadcast session" as a trigger condition (trigger event) is assumed. This is because it is an event common to all UEs 100 that are interested in the MBS broadcast session. Considering such a scenario, for example, when the type of trigger condition is "session start", it is possible to distribute MII transmission in the time direction and / or frequency direction. Also, for example, when the type of trigger condition is "session stop", it is possible to turn off MII transmission.

[0072] A scenario in which each UE 100 frequently transmits MII is assumed to be, for example, a scenario in which the UE 100 frequently changes its interest according to user preferences. Trigger conditions that may cause this problem may be "change of interest" and "change of priority between MBS broadcast reception and unicast reception". Considering such a scenario, it may be considered to set a prohibition timer in the UE 100 to prohibit frequent MII transmission.

[0073] In the mobile communication system 1 according to the embodiment, the gNB 200 transmits to the UE 100 configuration information that sets a condition under which the UE 100 is permitted to transmit to the gNB 200 an MII related to an MBS session that the UE 100 is receiving or is interested in receiving. The UE 100 receives the configuration information from the gNB 200 (serving cell). The UE 100 performs a transmission process of the MII in response to the condition set by the configuration information being satisfied.

[0074] According to such an operation, the gNB 200 can finely control the transmission of the MII by the configuration information. Therefore, it is possible to prevent many UEs 100 from transmitting MII at the same time, or prevent each UE 100 from frequently transmitting MII. As a result, it is possible to avoid network congestion caused by the MII. Note that the transmission process of the MII may include the transmission of a scheduling request (SR) for the MII transmission and / or the transmission of a buffer status report (BSR).

[0075] In addition, the gNB 200 may transmit the configuration information to the UE 100 by an SIB (for example, SIBx1) which is a broadcast message, or an RRC Reconfiguration which is a UE dedicated message. The gNB 200 may transmit the configuration information to the UE 100 by an RRC Release which is a UE dedicated message that transitions the UE 100 to an RRC idle state or an RRC inactive state. The UE 100 receives a message including the configuration information from the gNB 200, and stores the received configuration information.

[0076] In the following, a first operation example to a third operation example of the mobile communication system 1 according to the embodiment will be described. The first operation example to the third operation example may be implemented separately and independently. In addition, the first operation example to the third operation example may be implemented by combining two or more operation examples.

[0077] (1) First operation example In this operation example, the setting information transmitted from the gNB 200 to the UE 100 includes trigger setting information for setting a type of trigger condition to be applied in the UE 100 among multiple types of trigger conditions defined as trigger conditions for triggering transmission of the MII. The UE 100 triggers the transmission process of the MII in response to the fact that a trigger condition of a type set by the trigger setting information among the multiple types of trigger conditions is satisfied. In this manner, the gNB 200 performs on (enable) / off (disable) control for each trigger condition. For example, in a situation where the load on the gNB 200 is high, network congestion can be reduced by turning off MII transmission for a specific trigger condition type.

[0078] Fig. 11 is a diagram showing a first operation example of the mobile communication system 1 according to the embodiment. Here, differences from the operation in Fig. 10 will be mainly described.

[0079] 11, in step S11, the gNB 200 transmits, to the UE 100, configuration information including trigger configuration information for setting a type of a trigger condition to be applied in the UE 100. The UE 100 receives the configuration information including the trigger configuration information, and stores the received configuration information.

[0080] In step S12, the UE 100 determines whether or not the trigger condition of the type set in step S11 is satisfied.

[0081] If it is determined that the trigger condition of the type set in step S11 is satisfied (step S12: YES), in step S4, the UE 100 generates an MII. Then, in step S5, the UE 100 transmits the MII to the gNB 200. The gNB 200 receives the MII.

[0082] On the other hand, if it is determined that the trigger condition of the type set in step S11 is not satisfied (step S12: NO), the MII transmission process (steps S4 and S5) is not performed. Note that if the result in step S12 is "NO", the process may return to step S12 again.

[0083] FIG. 12 is a diagram for explaining the trigger setting information in this operation example.

[0084] As shown in FIG. 12, an identifier is assigned to each trigger condition type. In FIG. 12, an example is shown in which a trigger type ID "1" indicates "success in establishing a connection", a trigger type ID "2" indicates "entering or leaving a broadcast service area", a trigger type ID "3" indicates "starting or stopping an MBS broadcast session", a trigger type ID "4" indicates "changing an interest in an MBS", a trigger type ID "5" indicates "changing the priority between MBS broadcast reception and unicast reception", and a trigger type ID "6" indicates "changing to a primary cell that broadcasts SIBx1". Note that the correspondence between the trigger type ID and the contents of the trigger type is not limited to the example shown in FIG. 12, and the contents of the trigger type are also not limited to the example shown in FIG. 12. For example, different IDs may be assigned to "starting an MBS broadcast session" and "stopping an MBS broadcast session".

[0085] The trigger setting information may be a list of trigger type IDs indicating types of trigger conditions to be applied in the UE 100. Alternatively, the trigger setting information may be a list of trigger type IDs indicating types of trigger conditions not to be applied in the UE 100.

[0086] The trigger setting information may be a bit string indicating, by bit position, the type of trigger condition to be applied or not applied in the UE 100. For example, a 6-bit bit string associated with the trigger type IDs "1" to "6" is specified, and the type of trigger condition to be applied in the UE 100 is represented by True (1), and the type of trigger condition not to be applied in the UE 100 is represented by False (0).

[0087] As a specific example, when only the trigger type IDs "1", "3", and "5" are applied, the bit string is "101010". In this case, the UE 100 performs the MII transmission process only when the trigger conditions of the types indicated by the trigger type IDs "1", "3", and "5" are satisfied. That is, the UE 100 does not perform the MII transmission process even if the trigger conditions of the types indicated by the trigger type IDs "2", "4", and "6" are satisfied. Note that, although an example in which the trigger type IDs are numbered from "1" has been shown, they may be numbered from "0". Also, in the example of the bit string "101010", an example in which the Most Significant Bit (MSB) corresponds to the trigger type ID "1" and the Least Significant Bit (LSB) corresponds to the trigger type ID "6" has been shown, but the correspondence may be reversed. That is, the bit string is "010101", the LSB corresponds to the trigger type ID "1", and the MSB corresponds to the trigger type ID "6".

[0088] The trigger configuration information may be configured by a combination ID indicating a combination of trigger condition types to be applied or not applied in the UE 100. For example, a table that specifies an ID for each possible combination of trigger condition types to be applied or not applied in the UE 100 may be shared between the UE 100 and the gNB 200, and the type of trigger condition to be applied or not applied in the UE 100 may be specified by such a combination ID.

[0089] (2) Second operation example In this operation example, the setting information transmitted from the gNB 200 to the UE 100 includes prohibition time setting information (so-called prohibition timer value) that sets the prohibition time from transmitting the nth (n≧1) MII until the transmission of the n+1th MII is enabled. The UE 100 transmits the current MII in response to the prohibition time set by the prohibition time setting information having elapsed since the previous MII transmission (i.e., the prohibition timer has expired). This makes it possible to suppress frequent MII transmission by the UE 100. Specifically, since the transmission of the MII is prohibited during the prohibition time (i.e., while the prohibition timer is operating), it is possible to control the UE 100 so that it does not transmit the MII frequently, for example, even if the UE 100 frequently changes its MBS interest.

[0090] The prohibition timer may be associated with only a specific trigger condition. That is, the UE 100 may manage the prohibition timer for each trigger condition. In this case, the setting information transmitted from the gNB 200 to the UE 100 may further include trigger type information associated with the prohibition time setting information. The trigger type information is information indicating a type of trigger condition to which the prohibition time is applied among multiple types of trigger conditions defined as trigger conditions for triggering the transmission of the MII.

[0091] For example, as shown in Fig. 13, the setting information transmitted from the gNB 200 to the UE 100 includes a plurality of sets of trigger type information (trigger type ID) and prohibition time setting information (prohibition timer value). Fig. 13 shows an example in which a prohibition timer value "A" is set for a trigger type ID "1", a prohibition timer value "B" is set for a trigger type ID "2", and a prohibition timer value "C" is set for a trigger type ID "3". However, prohibition timer values ​​may not be set for all trigger types, and prohibition timer values ​​may be set only for some trigger types. Also, a common prohibition timer value may be set for a plurality of trigger type IDs, and a prohibition timer value may not be set independently (individually) for each trigger type ID.

[0092] When the trigger condition and the prohibition timer value are associated with each other, the UE 100 manages the prohibition timer for each trigger condition. For example, the UE 100 transmits the previous MII in response to the trigger condition of a type indicated by the trigger type information (hereinafter, referred to as a "specific trigger condition") being satisfied, and then transmits the current MII in response to the elapse of the prohibition time associated with the specific trigger condition (i.e., the prohibition timer expires) and the specific trigger condition being satisfied.

[0093] However, the UE 100 may manage a common prohibition timer for all trigger types without associating a trigger condition with a prohibition timer value. In this case, the UE 100 transmits the current MII when the prohibition time set by the prohibition time setting information has elapsed since the previous MII was transmitted (i.e., the prohibition timer has expired), regardless of the trigger condition.

[0094] Fig. 14 is a diagram showing a second operation example of the mobile communication system 1 according to the embodiment. Here, differences from the operation in Fig. 10 will be mainly described. Also, the description will be given taking as an example a case in which a trigger condition is associated with a timer value.

[0095] In step S21, the gNB 200 transmits configuration information including prohibition time setting information (prohibition timer value) and trigger type information to the UE 100. The UE 100 receives the configuration information including the prohibition time setting information and the trigger type information, and stores the received configuration information.

[0096] Here, multiple or a single prohibition timer value may be set for multiple trigger conditions. For example, when a common prohibition timer is used, an identifier indicating whether or not a timer is applied may be associated with each trigger condition, and a single prohibition timer value may be set, as shown in Fig. 15. Alternatively, an identifier (prohibition timer ID) indicating which prohibition timer value is assigned may be associated with each trigger condition, and each of the multiple prohibition timer values ​​may be associated with a prohibition timer ID, as shown in Fig. 16.

[0097] In step S3, an MII transmission trigger event occurs in the UE 100. The type of the trigger that occurs here is hereinafter referred to as a "specific trigger condition." The specific trigger condition may be, for example, "MBS interest has changed."

[0098] In step S4, the UE 100 generates an MII.

[0099] In step S5, the UE 100 transmits the MII to the serving cell (gNB 200). The gNB 200 receives the MII from the UE 100.

[0100] In step S22, when a prohibition timer value is associated with the specific trigger condition, the UE 100 starts (starts) a prohibition timer to which the prohibition timer value associated with the specific trigger condition is set.

[0101] In step S23, an MII transmission trigger event occurs in the UE 100.

[0102] In step S24, the UE 100 determines whether the transmission trigger event occurring in step S23 corresponds to a specific trigger condition (for example, "MBS interest has changed"). If the transmission trigger event occurring in step S23 does not correspond to the specific trigger condition (step S24: NO), for example, "start of a broadcast session", the UE 100 performs MII transmission processing (steps S27 and S28).

[0103] On the other hand, if the transmission trigger event that has occurred in step S23 corresponds to the specific trigger condition (step S24: YES), in step S25, the UE 100 determines whether or not a prohibition timer associated with the specific trigger condition has expired.

[0104] If the prohibition timer has not expired, that is, if the prohibition timer is running (step S25: NO), in step S26, UE 100 ignores the transmission trigger event that occurred in step S23 and does not perform MII transmission processing. Alternatively, in step S26, UE 100 suspends MII transmission in response to the transmission trigger event that occurred in step S23 until the prohibition timer expires.

[0105] On the other hand, if the prohibition timer has expired (step S25: YES), in steps S27 and S28, UE 100 performs MII transmission processing in response to the transmission trigger event that occurred in step S23. Note that, when the timer expires, if a reserved trigger condition exists, UE 100 may transmit an MII according to the trigger condition.

[0106] In this operation example, when the UE 100 transitions to the RRC idle state or the RRC inactive state, the UE 100 may stop the prohibition timer. Whether to stop the prohibition timer or to continue the timer operation may be set in the UE 100 by the gNB 200 (for each trigger condition).

[0107] (3) Third operation example In this operation example, the configuration information includes distribution information for distributing the transmission of multiple MIIs by multiple UEs 100 in the time direction and / or frequency direction. The UE 100 transmits the MII at a timing and / or frequency determined based on the distribution information. By distributing the transmission of multiple MIIs by multiple UEs 100 in the time direction and / or frequency direction, it is possible to suppress the occurrence of network congestion caused by the MIIs.

[0108] The distributed information may be associated with only a specific trigger condition. That is, the UE 100 may manage MII transmission control according to the distributed information for each trigger condition. In this case, the configuration information transmitted from the gNB 200 to the UE 100 may further include trigger type information associated with the distributed information. The UE 100 may transmit the MII at a timing and / or frequency determined based on the distributed information in response to the trigger condition of the type indicated by the trigger type information being satisfied.

[0109] The method of associating the trigger condition with the decentralized information may be the same as that of the second operation example described above. For example, when common decentralized information is used, an identifier indicating whether or not the decentralized information is applied may be associated with each trigger condition, and a single value may be set for the decentralized information, as shown in Fig. 17. Alternatively, an identifier (decentralized information ID) indicating which decentralized information is assigned may be associated with each trigger condition, and each of the multiple decentralized information may be associated with a decentralized information ID, as shown in Fig. 18.

[0110] However, the UE 100 may apply common distribution information to all trigger types without associating the trigger condition with the distribution information. In this case, the UE 100 determines the timing and / or frequency of transmitting the MII based on the distribution information for each MII transmission, regardless of the trigger condition.

[0111] Fig. 19 is a diagram showing a third operation example of the mobile communication system 1 according to the embodiment. Here, differences from the operation in Fig. 10 will be mainly described. Also, the description will be given taking as an example a case in which a trigger condition is associated with decentralization information.

[0112] In step S31, the gNB 200 transmits configuration information including the decentralization information and the trigger type information to the UE 100. The UE 100 receives the configuration information including the decentralization information and the trigger type information, and stores the received configuration information.

[0113] In step S3, an MII transmission trigger event occurs in the UE 100. The type of the trigger that occurs here is hereinafter referred to as a "specific trigger condition."

[0114] In step S32, when the distribution information is associated with the specific trigger condition, the UE 100 determines the timing and / or frequency at which to transmit the MII, based on the distribution information associated with the specific trigger condition.

[0115] In step S4, the UE 100 generates an MII. Note that step S4 may be performed before step S32.

[0116] In step S5, the UE 100 transmits the MII to the serving cell (gNB 200) at the timing and / or frequency determined in step S32. The gNB 200 receives the MII from the UE 100.

[0117] (3.1) Example of frequency-direction dispersion The distributed information may include cell information for setting a cell from which UE 100 transmits MII. This makes it possible to distribute the transmission of MII in the frequency direction. For example, gNB 200 instructs UE 100 in which carrier aggregation (CA) is set to transmit MII in a primary cell (PCell) or a secondary cell (SCell) by distributed information (cell information). UE 100 transmits MII to the set cell.

[0118] The cell information may be a cell ID indicating a cell from which UE 100 transmits MII. When consecutive numbers (order of configuration) are assigned to SCells, the cell information may be an SCell number indicating an SCell from which UE 100 transmits MII. The cell information may not specify a specific cell, but may simply indicate that any SCell is acceptable. When there is no such instruction, UE 100 may determine to transmit MII on a PCell. Note that the cell information may be frequency information (e.g., ARFCN) instead of a cell ID, or may be a combination of a cell ID and frequency information.

[0119] In addition, a rule may be specified that if CA is configured, MII transmission is always permitted only on the SCell. In that case, the UE 100 configured with CA transmits the MII on the SCell, not on the PCell. Under the assumption that such a rule exists, the CA configuration information by which the gNB 200 configures the CA in the UE 100 can be regarded as a kind of distributed information.

[0120] (3.2) Example of time-domain decentralization The distribution information may include timing control information for controlling the timing at which the UE 100 transmits the MII. This makes it possible to distribute the transmission of the MII in the time direction. The timing control information may be information for setting the on (enable) / off (disable) of a process for distributing the MII transmission timing between the UEs in the time direction, and may include a parameter (e.g., a threshold value, etc.) used in the process.

[0121] (3.2.1) First pattern of time-direction decentralization The UE 100 may determine the timing of transmitting the MII based on the timing control information and an identifier (hereinafter, referred to as "UE-ID") unique to the UE 100. Alternatively, the UE 100 may determine the timing of transmitting the MII based on the timing control information and a random number generated by the UE 100. This makes it possible to more reliably distribute the timings at which the multiple UEs 100 transmit multiple MIIs in the time direction.

[0122] For example, the UE 100 [UE-ID] mod [frame number]=0 It is permitted to transmit MII in frames that satisfy

[0123] [UE-ID]=[5G-S-TMSI] mod [frame limit] Also, the upper frame limit may be set to 10 (for subframes) or 1024 (for radio frames).

[0124] Alternatively, UE 100 sets a threshold (0 to 1), generates a random number, and is permitted to transmit if this random number is equal to or greater than (or less than) the threshold. However, the population of UEs 100 transmitting MII decreases with each attempt. If the probability that MII can be transmitted is constant, the number of UEs 100 transmitting MII with each attempt also decreases, and the delay in transmitting MII may become larger than necessary. Therefore, control may be performed so that the probability that MII can be transmitted increases as the number of attempts increases. Specifically, scaling based on a threshold may be performed so as to keep the number of UEs 100 transmitting MII with each attempt constant. Specifically,

[0125] [Applied threshold] = [Initial threshold] + [Scaling value] × ([Number of trials] - 1) For example, in the case of [initial threshold] = 0.5, [scaling value] = 0.1, and the third trial, the [threshold to be applied] is 0.5 + 0.1 × (3-1) = 0.7. Here, [initial threshold] means the threshold set by the gNB200.

[0126] Or, [Applied threshold] = [Previously applied threshold] + [Scaling value] It is also possible to use the following.

[0127] First attempt only, [Last applied threshold] = [Initial threshold] - [Scaling value] It is also possible to use the following.

[0128] (3.2.2) The second pattern of time-dependent decentralization The UE 100 may determine the timing of transmitting the MII based on the timing control information and the MBS session start timing recognized by the UE 100. The UE 100 can recognize the MBS session start timing, for example, from USD (User Service Description), which is higher layer information. Specifically, it is assumed that the USD includes information on the session start timing (such as time).

[0129] First, the UE 100 reads the TMGI of interest and the session start timing of the TMGI from the USD.

[0130] Secondly, the UE 100 transmits the MII at an appropriate timing before the session start timing.

[0131] Alternatively, the gNB 200 may transmit timing control information to the UE 100 instructing how long before the session start timing the transmission of the MII is to be started. Such timing control information is information indicating how long before the transmission of the MII is to be started, and may be expressed by, for example, a Radio frame, a Subframe, or a Hyper frame. In addition, such timing control information may be expressed by time information (seconds, minutes, hours, etc.).

[0132] The UE 100 may determine whether to transmit the MII in the following manner in accordance with the instruction. For example, the UE 100 may

[0133] [UE-ID] mod [elapsed time] = 0 The transmission of MII is permitted when the elapsed time satisfies the above. Here, the elapsed time may be, for example, seconds, minutes, or radio frames.

[0134] [UE-ID]=[5G-S-TMSI] mod [information about how long ago] It is also possible to use the following.

[0135] Instead of such a method using UE-ID, the above-mentioned method of distributing in the time direction may be used. In this case, the method of distributing in the time direction is applied from the point in time [how long ago]. Also, the gNB 200 may notify the UE 100 of timing information indicating the timing at which MII transmission is permitted. The timing information may be a pattern of radio frames or subframes and / or a reference point (e.g., a start radio frame). The timing information may be associated with the trigger type.

[0136] (Example of modification of operation of mobile communication system) A modification of the operation of the mobile communication system according to the embodiment will be described.

[0137] When carrier aggregation (CA) is configured in the UE 100, the MBS frequency that the UE 100 is receiving, is interested in receiving, or can receive may be changed according to the CA status. In this case, if a change occurs from the MBS frequency list notified to the gNB 200 in the previous MII, it is possible to notify the gNB 200 of the latest MBS frequency of interest.

[0138] FIG. 20 is a diagram showing the operation of UE 100 according to this modification.

[0139] In step S41, the UE 100 transmits a first MII including information indicating one or more MBS frequencies that the UE 100 is receiving or is interested in receiving among a combination of multiple frequencies that the UE 100 can simultaneously receive, to the gNB 200. Specifically, the UE 100 transmits the first MII including an MBS frequency list consisting of MBS frequencies of interest that can be simultaneously received.

[0140] In step S42, the UE 100 receives CA setting information related to the setting of carrier aggregation (CA) from the gNB 200. The CA setting information is transmitted from the gNB 200 to the UE 100 by, for example, RRC Reconfiguration. The CA setting information is information on setting, changing, or canceling CA.

[0141] When the combination is changed according to the CA setting information and the MBS frequency that UE 100 is receiving or is interested in receiving is changed (step S43: YES), UE 100 transmits a second MII including information indicating the changed MBS frequency to gNB 200 in step S44. Specifically, UE 100 reevaluates the frequencies of interest and checks whether there is a change in the frequencies that can be simultaneously received due to the current CA setting. If there is a change, UE 100 identifies the frequencies of interest that can be simultaneously received, sets the identified frequencies to the frequency information of the MII, and transmits the MII.

[0142] In this way, when CA is set (changed), UE 100 transmits an MII if there is a change in the information of the simultaneously receivable frequencies of interest reported in the previous MII. Here, a specific example will be described. First, it is assumed that UE 100 has notified gNB 200 that an MBS of interest is provided in frequency F4 and frequency F5, and that UE 100 is interested in F5 in the MII. Here, it is assumed that UE 100 supports the following two combinations (Band combinations) as combinations of simultaneously receivable frequencies.

[0143] ·Band combination#1:F1, F2, F3, F4 ·Band combination#2:F1, F2, F4, F5

[0144] It is also assumed that CA of F1 and F2 is set in the UE 100. In this case, both Band combination #1 and Band combination #2 can be used.

[0145] Third, an SCell of F3 is added to UE 100 by CA configuration. As a result, UE 100 can only use Band combination #1. Fourth, the frequency of interest of UE 100 changes from F5 to F4. Fifth, UE 100 determines that F4 should be notified by MII, and notifies gNB 200 of F4 by MII.

[0146] (Other embodiments) The above-mentioned operational flows are not limited to being implemented separately and independently, but can be implemented by combining two or more operational flows. For example, some steps of one operational flow may be added to another operational flow, or some steps of one operational flow may be replaced with some steps of another operational flow.

[0147] In the above-mentioned embodiment and example, 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) or a 6G base station. The base station may be a relay node such as an IAB (Integrated Access and Backhaul) node. The base station may be a DU of the IAB node. The UE 100 may be an MT (Mobile Termination) of the IAB node.

[0148] A program may be provided that causes a computer to execute each process performed by UE100 or gNB200. The program may be recorded in a computer-readable medium. Using the computer-readable medium, it is possible to install the program in a computer. Here, the computer-readable medium on which the program is recorded may be a non-transient recording medium. The non-transient recording medium is not particularly limited, and may be, for example, a recording medium such as a CD-ROM or a DVD-ROM. In addition, a circuit that executes 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).

[0149] As used in this disclosure, the terms "based on" and "depending on" do not mean "based only on" or "depending only on," unless otherwise specified. The term "based on" means both "based only on" and "based at least in part on." Similarly, the term "depending on" means both "based only on" and "based at least in part on." Additionally, "obtain / acquire" may mean obtaining information from stored information, from information received from other nodes, or by generating information. The terms "include," "comprise," and variations thereof do not mean including only the items listed, but may include only the items listed, or may include additional items in addition to the items listed. Additionally, the term "or" as used in this disclosure is not intended to be an exclusive or. Additionally, any reference to elements using designations such as "first," "second," etc., as used in this disclosure is not intended to generally limit the quantity or order of those elements. These designations may be used herein as a convenient method of distinguishing between two or more elements. Thus, reference to a first and a second element does not imply that only two elements may be employed therein or that the first element must precede the second element in some manner. In this disclosure, where articles are added by translation, such as a, an, and the in English, these articles are intended to include the plural unless the context clearly indicates otherwise.

[0150] 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, etc. are possible without departing from the spirit of the invention.

[0151] This application claims priority to U.S. Provisional Application No. 63 / 296,238 (filed January 4, 2022), the entire contents of which are incorporated herein by reference.

[0152] (Appendix 1) 1. Introduction A revised work item for NR Multicast and Broadcast Services (MBS) was approved in RAN2#88. Significant progress was made in RAN2#116e on the details of the MBS Notice of Interest (MII).

[0153] This appendix considers the remaining issues regarding MBS notices of interest.

[0154] 2. Discussion 2.1. Message Definition The currently ongoing CR of TS38.331 includes the following items requiring further consideration:

[0155] Further study is required as to whether MII (MBMS Interest Indication) will be reported in UE Assistance Information or in a new RRC message, and whether the MII information will use a separate IE or be directly included in the RRC message structure.

[0156] In LTE, the MBMS Interest Indication (MII) is separated from the UAI (UE Assistance Information). This is because the preconditions are different: the acquisition of SIB15 for the MII and RRC Connection Reconfiguration for the UAI. On the other hand, the In-device Coexistence Indication (IDC), which was a separate message in LTE, is integrated into the UAI in NR. This is considered feasible because the preconditions for IDC and UAI are the same in LTE (and NR), namely RRC Connection Reconfiguration.

[0157] Observation 1: Whether MBS Interest Notification can be integrated with UE Assistance Information depends on whether the preconditions are consistent between the two messages.

[0158] In NR MBS, neighboring frequency information in the SIB is required to generate an MBS interest notification message including the above IE. In addition, if the UE can obtain the SIB from the serving cell, the transmission of the MBS interest notification is permitted, but this is already known in the approved CR under the condition "if SIBx1 is broadcast from the PCell", as in LTE eMBMS. Therefore, it does not match the RRC Reconfiguration, which is a precondition of the UAI. Therefore, the MBS interest notification should be a separate message from the UAI, as in LTE eMBMS.

[0159] Proposal 1: RAN2 should agree to define the MBS Interest Notification as a new message, i.e., separate from the UAI.

[0160] Proposal 2: RAN2 should agree to allow the UE to send an MBS interest notification if it can obtain an MBS-specific SIB (i.e., SIBx1) from the serving cell (i.e., as a pre-condition).

[0161] 2.2. Other triggers and network controls The following issues requiring further consideration have been incorporated into the current implementation CR:

[0162] Other triggers and network controls require further consideration.

[0163] In RAN2#116e, various triggers for MBS interest notifications have been agreed upon. The UE confirms that it can initiate MII procedures upon successful connection establishment, upon entering or leaving a broadcast service area, upon starting or stopping an MBS broadcast session, upon change of interest, upon change of priority between MBS broadcast reception and unicast reception, and upon change to PCell broadcast SIBx1. Other triggers and network controls require further study.

[0164] Regarding additional triggers, it is considered necessary to send an MBS interest notification when the frequency list is changed. In RAN2#116e, the following was agreed upon regarding the detailed operation of the method for setting the frequency of interest.

[0165] During the MII, the UE is required to report only the set of MBS frequencies that the UE is capable of receiving simultaneously, i.e., the UE supports at least one band combination and is capable of receiving the indicated set of frequencies.

[0166] The UE shall not consider the currently configured serving frequency when evaluating the simultaneously receivable frequencies for reporting in the MII, i.e., it shall only consider the MBS frequencies it is interested in receiving, regardless of whether they can be received together with the current serving cell.

[0167] According to the above agreement, when the carrier aggregation configuration is updated (e.g., adding or removing an SCell), the frequency list may be changed since it may affect the combination of bandwidths that the UE can currently operate on. In this case, it may be necessary to report the latest interest frequency to the serving cell if it is different from the frequency list reported in the previous MBS interest notification. Therefore, the RAN2 needs to consider whether to send an MBS interest notification when the frequencies of the serving cell and non-serving cells are changed due to a change in the configuration of the serving cell.

[0168] Proposal 3: RAN2 should consider whether to send an MBS interest notification when the UE's interested frequency changes due to a serving cell configuration change.

[0169] For network control, it would certainly be useful to manage the transmission of MBS interest notifications from a large number of UEs to avoid network congestion. Issues that cause resource overload include "spikes" of MBS interest notifications and "frequent" MBS interest notifications.

[0170] Observation 2: If many UEs send MBS interest notifications suddenly, or if a UE sends MBS interest notifications too frequently, network congestion may occur.

[0171] The transmission surge occurs when a huge number of UEs transmit MBS interest notifications at the same time. Since this is a common event for all UEs interested in the MBS broadcast session, a possible trigger for this issue could be "MBS broadcast session start or stop". In particular, if the session stops, the gNB already knows that the MBS broadcast session was stopped by the CN, so it can determine that the UE is no longer interested in this TMGI even without the MBS interest notification. Considering these scenarios, network control could be to spread the MBS interest notification in the time and / or frequency domain (e.g., session start) or to turn on / off the MBS interest notification at this event (e.g., session stop).

[0172] Frequent transmission occurs when the UE frequently changes its interests due to user preferences, etc. Possible triggers for this problem include "changes in interests" and "changes in priority between MBS broadcast reception and unicast reception." A possible network control is to set a prohibition timer in the UE.

[0173] As for the other triggers, i.e. "successful connection establishment", "entering or leaving the broadcast service area", "changing to the PCell broadcasting SIBx1", it can be assumed that they are sufficiently randomized (in time) or already controlled by the network, so they do not pose any major issues.

[0174] Given the above discussion, it has been confirmed that different triggers may require different control methods, i.e., spreading, on / off, inhibit timers, and furthermore, other triggers may not require any enforcement. Therefore, RAN2 needs to discuss whether network control should be considered and, if so, which triggers require what kind of network control.

[0175] Proposal 4: RAN2 should discuss network control to prevent UE from making sudden and frequent transmissions due to MBS interest notification.

[0176] Proposal 5: RAN2 should discuss whether to apply different network control methods to different triggers of MBS interest notification.

[0177] 2.3.Early notification to improve BWP switching behavior This consideration has been incorporated in the current running CR based on the RAN2 agreement that "MBS interest notifications are sent after security activation (it can still be discussed whether additional optimizations are needed for better BWP switching behavior)." Further investigation is required to determine whether additional optimizations are necessary to improve the switching behavior of the BWP.

[0178] Further investigation is required as to whether further optimization is required for better BWP switching behavior.

[0179] The service continuity problem occurs when the UE transitions to the connected state. Specifically, if the serving cell configures the UE with a dedicated BWP that is not aligned with the CFR, the UE cannot continue to receive the broadcast session. Although such a configuration can be avoided after the MBS interest notification, the problem occurs due to the configuration made before the MBS interest notification, i.e. before the activation of AS security.

[0180] It has been noted that an inactive UE can set up a dedicated BWP in Msg4 (RRC Resume), and it has been proposed to provide a one-bit indication in Msg3 to inform the serving cell that the UE is receiving the MBS broadcast session. The serving cell has the UE context for the inactive UE, which includes the previously reported MBS interest indication. Although this interest information is not up-to-date, the serving cell is expected to predict whether a UE moving from inactive to connected is receiving the broadcast session. Therefore, it is not important to extend Msg3, given that the message size is limited.

[0181] It is proposed to introduce an early "broadcast reception" indication in Msg5, which is information for the serving cell to set up a dedicated BWP at the next RRC Reconfiguration. This solution is a simple extension, but it is useful.

[0182] According to the LS from SA3, they are only concerned about reporting the TMGI list before AS security activation. Moreover, it explicitly states that other information (frequency list and priority information) can be reported before AS security activation. Therefore, it is considered that the UE can send an early MBS interest notification, which is sent with Msg5 and contains full content other than the TMGI list, i.e., frequency list and priority information instead of the 1-bit indication above. When the gNB receives the early MBS interest notification in Msg5, it can determine whether this UE is receiving a broadcast session because the MBS interest notification is for the second delivery mode. Also, the full content may be useful for the gNB to determine the appropriate configuration for different frequencies (e.g., SCell configuration) even if the TMGI that the UE is interested in is not yet known. Since these contents are finally reported after AS security activation, there is no signaling overhead if they are reported in the early MBS interest notification.

[0183] Furthermore, it is worth considering whether additional information is required in the early MBS interest notification. For example, the UE reports the CFRs on which it is receiving the MBS broadcast session of interest in the early MBS interest notification. The CFR information may be used by the gNB to determine the appropriate dedicated BWP, for example, such that such CFRs are part of the dedicated BWP. As another example, the UE reports the Cell ID on which the MBS broadcast session of interest is provided in the early MBS interest notification.

[0184] Proposal 6: RAN2 should consider whether to send an early MBS interest notification with Msg5 containing full content other than the TMGI list, i.e., frequency list and priority information.

[0185] Proposal 7: RAN2 should further discuss whether it would be useful for additional information to be reported in the Early MBS Interest Notification, e.g., CFR or Cell ID of interest.

[0186] 2.4. MBS Interest Notification for Multicast Sessions RAN2 currently assumes that MBS Interest Notification is supported for broadcast sessions and not for multicast sessions. RAN2#115e agreed on the basic contents of MBS Interest Notification, i.e. MBS frequency list, priority, and TMGI list.

[0187] For multicast sessions, it is considered common understanding that the core network informs the gNB of the UE's interest because there is a session join procedure at the higher layers. The UE's interest is considered to apply to MBS services. Also, the gNB may know the frequency of the MBS of the UE's interest and the cell providing the MBS service. However, the priority between MBS reception and unicast may not be provided by the core network because it is purely AS-related information. In other words, it is strange for the UE to convey priority information to the core network in the session join procedure.

[0188] Observation 3: In a multicast session, the core network provides the MBS service of interest to the UE to the gNB, and the gNB may know the MBS frequency / cell, but the core network and the gNB may not know the UE’s AS priority between the MBS and unicast.

[0189] The priority information is also useful for the gNB for scheduling and handover decisions, as well as for LTE eMBMS, and is considered relevant for service continuity. Therefore, the UE needs to notify the gNB of its priority information also for multicast sessions. In this sense, RAN2 should agree that MBS interest notification should be supported also for multicast services / first delivery mode.

[0190] Proposal 8: RAN2 should agree that MBS interest notification is also supported in multicast sessions / first delivery mode, at least for the UE to inform the gNB of the priority between MBS reception and unicast reception.

[0191] (Appendix 2) Features relating to the above-described embodiment will now be described.

[0192] (1) A communication method performed by a user device in a mobile communication system providing a multicast broadcast service (MBS), comprising: receiving, from the base station, configuration information that configures conditions under which the user equipment is permitted to transmit to the base station an MBS interest notification regarding an MBS session that the user equipment is receiving or is interested in receiving; and performing a process of transmitting the MBS interest notification in response to the condition set by the setting information being satisfied. Communication methods.

[0193] (2) The performing of the transmission process includes not performing the transmission process when the condition set by the setting information is not satisfied, and performing the transmission process in response to the condition set by the setting information being satisfied. The communication method described in (1) above.

[0194] (3) the setting information includes trigger setting information for setting a type of the trigger condition to be applied in the user device among a plurality of types of trigger conditions defined as trigger conditions for triggering the transmission of the MBS interest notification; The performing of the transmission process includes triggering the transmission process in response to a trigger condition of the type set by the trigger setting information among the multiple types of trigger conditions being satisfied. The communication method according to (1) or (2) above.

[0195] (4) the setting information includes prohibition time setting information for setting a prohibition time from transmission of an n-th (n≧1) MBS interest notification until transmission of the (n+1)th MBS interest notification is enabled, The transmission process includes transmitting the current MBS interest notification in response to the elapse of the prohibition time set by the prohibition time setting information since the previous MBS interest notification was transmitted. A communication method according to any one of (1) to (3) above.

[0196] (5) The setting information further includes trigger type information associated with the prohibition time setting information, The trigger type information is information indicating a type of trigger condition to which the prohibition time is applied, among a plurality of types of trigger conditions defined as trigger conditions for triggering transmission of the MBS interest notification. The communication method according to (4) above.

[0197] (6) The transmission process includes transmitting the previous MBS interest notification in response to the trigger condition of the type indicated by the trigger type information being satisfied, and then transmitting the current MBS interest notification in response to the prohibition time set by the prohibition time setting information elapsed and the trigger condition of the type indicated by the trigger type information being satisfied. The communication method according to (5) above.

[0198] (7) The setting information includes distribution information for distributing transmissions of a plurality of MBS interest notifications by a plurality of user devices including the user device in a time direction and / or a frequency direction, The performing of the transmission process includes transmitting the MBS interest notification at a timing and / or a frequency determined based on the distribution information. A communication method according to any one of (1) to (6) above.

[0199] (8) The setting information further includes trigger type information associated with the decentralization information, The performing of the transmission process includes transmitting the MBS interest notification at the timing and / or the frequency determined based on the distribution information in response to a trigger condition of the type indicated by the trigger type information being satisfied. The communication method according to (7) above.

[0200] (9) The decentralization information includes cell information for setting a cell from which the user equipment transmits the MBS interest notification. The communication method according to (7) or (8) above.

[0201] (10) The decentralization information includes timing control information for controlling a timing at which the user device transmits the MBS interest notification. The communication method according to (7) or (8) above.

[0202] (11) The performing of the transmission process includes determining the timing for transmitting the MBS interest notification based on the timing control information and an identifier unique to the user device. The communication method according to (10) above.

[0203] (12) The performing of the transmission process includes determining the timing to transmit the MBS interest notification based on the timing control information and a random number generated by the user device. The communication method according to (10) above.

[0204] (13) The performing of the transmission process includes determining the timing to transmit the MBS interest notification based on the timing control information and an MBS session start timing recognized by the user device. The communication method according to (10) above.

[0205] (14) A communication method performed by a user device in a mobile communication system providing a multicast broadcast service (MBS), comprising: Transmitting a first MBS interest notification to a base station, the first MBS interest notification including information indicating one or more MBS frequencies that the user device is receiving or is interested in receiving from a combination of multiple frequencies that the user device can simultaneously receive; Receiving carrier aggregation (CA) setting information from the base station regarding a configuration of CA; When the combination is changed according to the CA setting information and an MBS frequency that the user device is receiving or is interested in receiving is changed, a second MBS interest notification including information indicating the changed MBS frequency is transmitted to the base station. Communication methods. [Explanation of symbols]

[0206] 1: Mobile communication systems 10:RAN 20 :CN 100:UE 110: Receiving unit 120: Transmitter 130: Control section 200: gNB 210: Transmission unit 220: Receiving unit 230: Control section 240: Backhaul communication unit

Claims

1. A communication method performed by a user equipment in a mobile communication system providing a multicast broadcast service (MBS), comprising: receiving a broadcast message from a network node, the broadcast message including information regarding conditions for determining whether it is permitted to send an MBS interest notification to the network node for an MBS session; and determining whether or not to perform a process for transmitting the MBS interest notification based on the information. Communication methods.

2. The information is configuration information that sets a condition under which the MBS interest notification is permitted to be transmitted to the network node. The communication method according to claim 1 .

3. The method further includes not performing the transmission process when the condition set by the setting information is not satisfied, and performing the transmission process in response to the condition set by the setting information being satisfied. The communication method according to claim 2 .

4. The setting information includes trigger setting information for setting a type of the trigger condition to be applied in the user device among a plurality of types of trigger conditions defined as trigger conditions for triggering the transmission of the MBS interest notification, The performing of the transmission process includes triggering the transmission process in response to a trigger condition of the type set by the trigger setting information among the multiple types of trigger conditions being satisfied. The communication method according to claim 3.

5. The setting information includes prohibition time setting information for setting a prohibition time from the transmission of an n-th (n≧1) MBS interest notification until the transmission of an n+1-th MBS interest notification is enabled, The transmission process includes transmitting the current MBS interest notification in response to the elapse of the prohibition time set by the prohibition time setting information since the previous MBS interest notification was transmitted. The communication method according to claim 3.

6. The setting information further includes trigger type information associated with the prohibition time setting information, The trigger type information is information indicating a type of trigger condition to which the prohibition time is applied among a plurality of types of trigger conditions defined as trigger conditions for triggering transmission of the MBS interest notification. The communication method according to claim 5.

7. The transmission process includes transmitting the previous MBS interest notification in response to the trigger condition of the type indicated by the trigger type information being satisfied, and then transmitting the current MBS interest notification in response to the prohibition time set by the prohibition time setting information elapsed and the trigger condition of the type indicated by the trigger type information being satisfied. The communication method according to claim 6.

8. The setting information includes distribution information for distributing transmissions of a plurality of MBS interest notifications by a plurality of user devices including the user device in a time direction and / or a frequency direction, The performing of the transmission process includes transmitting the MBS interest notification at a timing and / or a frequency determined based on the decentralization information. The communication method according to claim 3.

9. The setting information further includes trigger type information associated with the decentralization information, The performing of the transmission process includes transmitting the MBS interest notification at the timing and / or the frequency determined based on the decentralization information in response to a trigger condition of the type indicated by the trigger type information being satisfied. The communication method according to claim 8.

10. The distributed information includes cell information for setting a cell from which the user equipment transmits the MBS interest notification.

10. The communication method according to claim 8 or 9.

11. The decentralization information includes timing control information for controlling a timing at which the user device transmits the MBS interest notification.

10. The communication method according to claim 8 or 9.

12. The performing of the transmission process includes determining the timing for transmitting the MBS interest notification based on the timing control information and an identifier unique to the user equipment. The communication method according to claim 11.

13. The performing of the transmission process includes determining the timing to transmit the MBS interest notification based on the timing control information and a random number generated by the user device. The communication method according to claim 11.

14. The performing of the transmission process includes determining the timing to transmit the MBS interest notification based on the timing control information and an MBS session start timing recognized by the user equipment. The communication method according to claim 11.

15. A user device, a receiver for receiving from a network node a broadcast message including information regarding conditions for determining whether a network node is permitted to transmit an MBS interest notification for a Multicast Broadcast Service (MBS) session; a control unit that determines whether or not to perform a process of transmitting the MBS interest notification based on the information. User equipment.

16. A chipset for a user equipment, comprising: receiving a broadcast message from a network node, the broadcast message including information regarding conditions for determining whether a network node is permitted to transmit an MBS interest notification for a Multicast Broadcast Service (MBS) session; and determining whether or not to perform a process of transmitting the MBS interest notification based on the information. Chipset.

17. A user device includes: receiving a broadcast message from a network node, the broadcast message including information regarding conditions for determining whether a network node is permitted to transmit an MBS interest notification for a Multicast Broadcast Service (MBS) session; and determining whether or not to perform a process of transmitting the MBS interest notification based on the information. program.

18. A mobile communication system providing a multicast broadcast service (MBS), comprising: receiving a broadcast message from a network node, the broadcast message including information regarding conditions for determining whether an MBS interest notification for an MBS session is permitted to be sent to the network node; A user device that determines whether or not to perform a process of transmitting the MBS interest notification based on the information. Mobile communication system.

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