Communication method, user equipment, chip set, program, and mobile communication system

Abstract

To provide a communication method and user equipment for enhancing a multicast broadcast service (MBS).SOLUTION: A method includes: user equipment receiving a predetermined system information block (SIB) that includes information indicating a correspondence relationship between an MBS area identifier and a frequency from a serving cell; generating an MBS interest indication (MII) including a list indicating a frequency of interest being an MBS frequency that UE is receiving or is interested in receiving; and transmitting the MII to the serving cell, where the generating comprises making the list include the frequency of interest when the frequency of interest is indicated in USD(User Service Description) even when the predetermined SIB does not comprise the frequency of interest, in the case of receiving the predetermined SIB.SELECTED DRAWING: Figure 10

Description

[Technical Field]

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

[0002] The 3GPP (3rd Generation Partnership Project) (registered trademark; the same applies hereinafter) standard defines the technical specifications for NR (New Radio), a fifth-generation (5G) radio access technology. Compared to LTE (Long Term Evolution), a fourth-generation (4G) radio access technology, NR features high speed, large capacity, high reliability, and low latency. Discussions are underway within 3GPP to formulate technical specifications for 5G / NR multicast broadcast services (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 compared to 4G / LTE multicast broadcast services.

[0005] Therefore, an object of the present disclosure is to provide a communication method and a user device that enable 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 equipment in a mobile communication system that provides a multicast broadcast service (MBS), and includes the steps of receiving from a serving cell a predetermined system information block (SIB) including frequency information indicating a correspondence relationship between an identifier of an MBS service and a frequency that provides the MBS service, generating an MBS interest notification including a list of interest frequencies that are MBS frequencies that the user equipment is receiving or is interested in receiving, and transmitting the MBS interest notification to the serving cell. Even if the interest frequency is not included in the predetermined SIB, the user equipment includes the interest frequency in the list if it is indicated by higher layer information.

[0007] A user device according to a second aspect is a user device used in a mobile communication system that provides a multicast broadcast service (MBS), and includes: a receiver that receives from a serving cell a predetermined system information block (SIB) including frequency information indicating a correspondence between an identifier of an MBS service and a frequency that provides the MBS service; a controller that generates an MBS interest notification including a list of interest frequencies that are MBS frequencies that the user device is receiving or is interested in receiving; and a transmitter that transmits the MBS interest notification to the serving cell. Even if the interest frequency is not included in the predetermined SIB, the controller includes the interest frequency in the list if it is indicated by higher layer information. [Brief explanation of the drawings]

[0008] [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. 1 is a diagram illustrating an overview of MBS traffic distribution according to an embodiment. [Figure 7] FIG. 10 is a diagram illustrating a distribution mode according to the embodiment. [Figure 8] FIG. 10 is a diagram illustrating an example of internal processing related to MBS reception in a UE according to an embodiment. [Figure 9] FIG. 10 is a diagram illustrating another example of internal processing related to MBS reception in the UE according to the embodiment. [Figure 10] FIG. 2 is a diagram for explaining an overview of an MII according to an embodiment. [Figure 11] FIG. 2 is a diagram illustrating an example of the configuration of an SIBx1 according to an embodiment. [Figure 12] 10 is a diagram illustrating the operation of option 1 according to the embodiment, specifically, an example of specification changes in 3GPP technical specification TS38.331. [Figure 13] FIG. 10 is a diagram illustrating the operation of option 2 according to the embodiment, specifically, an example of specification changes in 3GPP technical specification TS38.331. [Figure 14] FIG. 10 is a diagram illustrating the operation of option 3 according to the embodiment, specifically, an example of specification changes in 3GPP technical specification TS38.331. [Figure 15] FIG. 10 is a diagram illustrating the operation of option A according to the embodiment, specifically, an example of specification changes in 3GPP technical specification TS38.331. [Figure 16] FIG. 10 is a diagram illustrating an operation example 1 of option B according to the embodiment, specifically, a specification change example in 3GPP technical specification TS38.331. [Figure 17] FIG. 10 is a diagram illustrating an operation example 2 of option B according to the embodiment, specifically, a specification change example in 3GPP technical specification TS38.331. [Figure 18] FIG. 10 is a diagram illustrating an operation example 1 of option C according to the embodiment, specifically, a specification change example in 3GPP technical specification TS38.331. [Figure 19]FIG. 10 is a diagram illustrating an operation example 2 of option C according to the embodiment, specifically, a specification change example in 3GPP technical specification TS38.331. [Figure 20] FIG. 1 is a diagram illustrating a first configuration example of an MII according to an embodiment, specifically, a specification modification example in 3GPP technical specification TS38.331. [Figure 21] FIG. 10 is a diagram illustrating a modification of the first configuration example of the MII according to the embodiment, specifically, a modification of the specifications in the 3GPP technical specification TS38.331. DETAILED DESCRIPTION OF THE INVENTION

[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] (1) Configuration of mobile communication system FIG. 1 is a diagram showing the configuration of a mobile communication system according to an embodiment. The mobile communication system 1 conforms to the 3GPP standard 5th Generation System (5GS). In the following description, 5GS is used as an example, but the mobile communication system may also be at least partially applied to an LTE (Long Term Evolution) system. Furthermore, the mobile communication system may also 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 may be a mobile phone terminal (including a smartphone), a tablet terminal, a laptop 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 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 (hereinafter simply referred to as "frequency").

[0014] 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.

[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 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.

[0016] 2 is a diagram showing the configuration of a UE 100 (user equipment) according to the 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 constitute a wireless communication unit that performs wireless communication with the gNB 200.

[0017] 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.

[0018] 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.

[0019] The control unit 130 performs various controls and processes in the UE 100. Such processes include processes of each layer, which will be described later. 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 the 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 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.

[0023] The control unit 230 performs various controls and processes in the gNB 200. Such processes include processes for each layer, which will be described later. 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 neighboring 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 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 encoding / decoding, modulation / demodulation, antenna mapping / demapping, and resource mapping / demapping. Data and control information are transmitted between the PHY layer of UE100 and the PHY layer of gNB200 via a physical channel. The PHY layer of UE100 receives downlink control information (DCI) transmitted from gNB200 on a physical downlink control channel (PDCCH). Specifically, UE100 performs blind decoding of the PDCCH using a radio network temporary identifier (RNTI) and acquires successfully decoded DCI as DCI addressed to the UE. The DCI transmitted from gNB200 has CRC parity bits scrambled by the RNTI added.

[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 transport channels. The MAC layer of gNB200 includes a scheduler, which determines the uplink and downlink transport format (transport block size, modulation and coding scheme (MCS)) and the resource blocks to be allocated to UE100.

[0029] 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.

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

[0031] 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.

[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] 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.

[0035] The NAS layer, which is 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 300A. Note that the UE 100 has an application layer and the like in addition to the radio interface protocol. Also, a layer lower than the NAS layer is referred to as an AS layer.

[0036] (2) Overview of MBS Next, 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 communications, mission-critical communications, V2X (Vehicle to Everything) communications, IPv4 or IPv6 multicast distribution, IPTV (Internet protocol television), group communications, and software distribution.

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

[0038] A multicast service provides services not to all UEs 100 but to a group of UEs 100 participating in the multicast service (multicast session). An MBS session used for a multicast service is called a multicast session. A multicast service can provide the same content to a group of UEs 100 in a more wirelessly efficient manner than a broadcast service.

[0039] FIG. 6 is a diagram illustrating an overview of MBS traffic distribution 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 (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 packet 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 for 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 distribution modes 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 related to an MBS session (including an MBS session identifier, described below) and scheduling information for the MBS traffic channel corresponding to this MBS session. The scheduling information for the MBS traffic channel may include a discontinuous reception (DRX) configuration for the MBS traffic channel. The discontinuous reception setting may include one or more parameters of a timer value (On Duration Timer) that defines the 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 that defines the maximum time until retransmission (retransmission timer), and a timer value that defines the minimum interval until DL allocation of HARQ retransmission (HARQ RTT timer).

[0051] The MBS traffic channel is a type of logical channel and is sometimes 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 not only by the UE 100 in the RRC connected state but also by the UE 100 in the RRC idle state or the 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 the MCCH using, for example, a dedicated RNTI predefined in a technical specification. 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, UE100 may receive MBS data in the following three procedures. First, UE100 receives MCCH configuration information from gNB200 via an SIB (MBS SIB) transmitted on the BCCH. Second, UE100 receives MCCH from gNB200 based on the MCCH configuration information. The MCCH transmits MTCH configuration information. Third, UE100 receives MTCH (MBS data) based on the MTCH configuration information. Hereinafter, MTCH configuration information and / or MCCH configuration information may be referred to as MBS reception configuration.

[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 configuration (MTCH configuration 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, application server, etc., and an IP multicast address indicating the 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 internal processing related to MBS reception of the UE 100 according to the embodiment. Fig. 9 is a diagram showing another example of internal processing related to MBS reception of the UE 100 according to the embodiment.

[0058] An MBS Radio Bearer (MRB) is a radio bearer that carries a multicast session or a broadcast session. That is, an MRB may be associated with a multicast session or a broadcast session.

[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 RRC signaling, one MRB can be configured as "PTM only," "PTP only," or "both PTM and PTP." The type of such an MRB can be changed by RRC signaling.

[0060] 8 shows an example 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 a PTP-only MRB, MRB#2 is a PTM-only MRB, and MRB#3 is a PTM-only MRB. 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 the 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] 9 shows an example 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 associated with a DTCH and the other leg 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] (3) Overview of MBS Interest Notification Next, an outline of an MBS Interest Indication (MII) according to an embodiment will be described. Fig. 10 is a diagram for explaining an outline of an MII according to an embodiment.

[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] In step S3, UE100 receives an SIB for MBS service continuity (hereinafter referred to as "SIBx1") from gNB200 (serving cell). SIBx1 is an SIB indicating a correspondence (mapping) between MBS services and frequencies. An example configuration of SIBx1 will be described later. Note that SIBx1 is a SIB different from the above-mentioned MBS SIB. UE100 may receive SIBx1 from gNB200 before step S1 or before step S2.

[0066] The UE 100 is capable of transmitting an MBS Interest Indication (MII) to a serving cell that provides SIBx1, i.e., a serving cell that has a function for MBS service continuity. That is, the UE 100 transmits an MII to a serving cell only if the serving cell provides SIBx1. The MII is a type of RRC message and is used to notify the network that the UE 100 is receiving or is interested in receiving an MBS broadcast service via a broadcast MRB. The network (gNB 200) can control MBS service delivery or handover the UE 100 to an appropriate cell based on the MII.

[0067] In step S4, an MII transmission trigger (trigger event) occurs in the UE 100. Types of MII transmission triggers (trigger events) include, for example, when connection establishment is successful, when entering or leaving a broadcast service area, when an MBS broadcast session starts or stops, when an MBS interest changes, when a priority between MBS broadcast reception and unicast reception changes, when a cell (primary cell) that broadcasts an SIB for MBS service continuity is changed, and the like.

[0068] In step S5, the UE 100 generates an MII. The MII includes at least one of a frequency list (MBS frequency list) that is a list of MBS frequencies that the UE 100 is receiving or is interested in receiving, priority information that indicates the priority of whether to prioritize receiving all the listed MBS frequencies or receiving a unicast bearer, and a TMGI list that is a list of MBS sessions that the UE 100 is receiving or is interested in receiving. The following description will mainly focus on the frequency list in the MII.

[0069] Step S5 includes step S51 of identifying an MBS frequency that the UE 100 is receiving or is interested in receiving (hereinafter referred to as an "interesting frequency"), and step S52 of setting the identified interesting frequency in a frequency list. Steps S51 and S52 will be described in detail later.

[0070] In step S6, UE100 transmits the MII to gNB200 (serving cell).

[0071] 11 is a diagram illustrating a configuration example of an SIBx1 according to the embodiment. The SIBx1 is used by the UE 100 to derive a frequency (MBS frequencies of interest) that provides a desired MBS service (desired MBS session) that the UE 100 is receiving or is interested in receiving.

[0072] Hereinafter, the term "MBS service" is used as a term that encompasses the concept of "MBS session." An identifier of an MBS service is referred to as an "MBS service identifier." The MBS service identifier may be the above-mentioned MBS session identifier (e.g., TMGI). The MBS service identifier may be an MBS service area identifier (MBS SAI). The MBS service identifier may be referred to as an MBS SAI.

[0073] As shown in FIG. 11 , SIBx1 may include at least one of mbs-SAI-IntraFreq-r17 and mbs-SAI-InterFreqList-r17. The mbs-SAI-IntraFreq-r17 includes MBS-SAI-List-r17, which is a list of MBS service identifiers for MBS services provided in intra-frequencies (i.e., the same frequency as the serving cell). The mbs-SAI-InterFreqList-r17 includes MBS-SAI-InterFreq-r17, which indicates, for each inter-frequencies (i.e., a frequency different from that of the serving cell), a correspondence relationship (mapping) between the frequency and the MBS service provided in the frequency. The MBS-SAI-InterFreq-r17 includes a frequency identifier (ARFCN-ValueNR) indicating a downlink carrier frequency (dl-CarrierFreq-r17) and a list of MBS service identifiers (mbs-SAI-List-r17).

[0074] (4) Operation according to the embodiment Next, the operation according to the embodiment will be described.

[0075] In frequency prioritization during cell reselection, UE 100 in the RRC idle state or the RRC inactive state identifies a frequency that provides a desired MBS service based on SIBx1 and assigns the highest priority to the identified frequency. However, if frequency information (mbs-SAI-IntraFreq-r17, mbs-SAI-InterFreqList-r17) is not provided in SIBx1, UE 100 is assumed to identify a frequency of interest that provides a desired MBS service based on higher layer information, User Service Description (USD), and assign the highest priority to the identified frequency of interest.

[0076] Here, the USD is provided to the UE 100, for example, from an Application Function (AF) / Multicast Broadcast Service Function (MBSF) in the network. Such a USD is an example of higher layer information provided from the network in a layer higher than the RRC layer (specifically, the application layer). The USD may be referred to as service announcement information. The USD includes information indicating the correspondence between an MBS service and a frequency. The USD may include at least one set of an MBS service identifier and frequency information. For example, the USD may include at least one of an MBS session identifier that identifies an MBS session, information on the start and end times of the MBS session, an SAI that indicates an MBS service area in which the MBS session is provided, and information on the frequency in which the MBS session is provided.

[0077] The above-described cell reselection control based on USD assumes the following scenario. Specifically, even if the gNB 200 provides SIBx1, there are cases where the gNB 200 does not provide neighboring frequency information (mbs-SAI-InterFreqList-r17) in SIBx1. For example, when the MBS service is provided uniformly in a certain frequency / area, the UE 100 can derive an appropriate frequency of interest from the frequency information provided in the USD even if all cells in the area do not broadcast neighboring frequency information. Therefore, by controlling cell reselection with the frequency of interest as the highest priority, service continuity of the broadcast service can be ensured.

[0078] On the other hand, for UE 100 in the RRC connected state, frequencies of interest are identified based on SIBx1 to generate a frequency list in the MII. However, if neighboring frequency information is not provided in SIBx1, UE 100 cannot properly identify frequencies of interest. While it is assumed that frequencies of interest are identified based on USD for UE 100 in the RRC idle state or RRC inactive state, there is a problem in that such an operation is not assumed for UE 100 in the RRC connected state. In the following embodiments, a method and operation for solving such a problem will be described.

[0079] As described above, the UE 100 receives from the serving cell a predetermined SIB (SIBx1) that may include frequency information indicating a correspondence between an identifier of an MBS service (MBS service identifier) ​​and a frequency that provides the MBS service (step S3 in FIG. 10). The UE 100 generates an MII that includes a frequency list indicating frequencies of interest, which are MBS frequencies that the UE 100 is receiving or is interested in receiving (step S5 in FIG. 10), and transmits the MII to the serving cell (step S6 in FIG. 10).

[0080] In the embodiment, when generating the MII, the UE 100 includes its own frequency of interest in the frequency list even if the frequency of interest is not indicated in a predetermined SIB (SIBx1). This allows the network to know the frequency of interest of the UE 100 based on the frequency list in the MII even if frequency information (especially, mbs-SAI-InterFreqList-r17) is not provided in the SIBx1.

[0081] For example, even if the frequency of interest is not indicated in a predetermined SIB, the UE 100 includes the frequency of interest in the frequency list based on higher layer information (USD) that is information indicating a correspondence relationship between an identifier of an MBS service (MBS service identifier) ​​and a frequency that provides the MBS service and that is held by the UE 100. That is, the UE 100 includes the frequency of interest in the frequency list based on USD instead of SIBx1.

[0082] The UE 100 may include the frequency of interest in the frequency list based on a SIB for cell reselection received from a serving cell instead of the SIBx1. The SIB for cell reselection is an SIB provided by the serving cell and indicates an inter-frequency different from the frequency of the serving cell. The SIB for cell reselection may be SIB type 4 (SIB4) and / or SIB type 5 (SIB5) specified in the 3GPP technical specifications.

[0083] Such a cell reselection SIB includes one or more sets of inter-frequency identifiers and cell reselection parameters (e.g., frequency priorities). The inter-frequency indicated in the cell reselection SIB corresponds to the frequency of a neighboring cell, and is therefore considered to be a frequency available to the UE 100. The UE 100 includes such available frequencies as frequencies of interest in its frequency list. However, since the desired MBS service is not necessarily provided on the inter-frequency indicated in the cell reselection SIB, the UE 100 includes the frequencies of interest in its frequency list using the cell reselection SIB in combination with USD.

[0084] (4.1) Identifying the frequency of interest Options 1 to 3 of the operation of specifying the frequency of interest according to the embodiment will be described below. The UE 100 specifies the frequency of interest according to any of the following options 1 to 3.

[0085] (4.1.1) Option 1 In option 1, when generating an MII, the UE 100 identifies a frequency of interest based on higher layer information (USD) regardless of frequency information in a predetermined SIB (SIBx1). That is, the UE 100 identifies a frequency of interest based on USD information without checking the frequency information provided in the SIBx1.

[0086] FIG. 12 is a diagram showing the operation of option 1 according to the embodiment, specifically, an example of specification changes in 3GPP technical specification TS38.331.

[0087] The UE 100 regards frequencies for which the conditions of steps S102 to S104 are satisfied as MBS frequencies of interest (step S101).

[0088] Step S102 is a determination of the condition that at least one MBS session (desired MBS service) that the UE 100 is receiving or interested in receiving via the broadcast MRB is in progress or is about to be started.

[0089] Step S103a is a determination of the condition that, for a certain frequency, a service identifier indicated in a USD for a desired MBS service is included in SIBx1 acquired from a PCell (serving cell). In option 1, this condition determination is omitted. That is, the UE 100 identifies an interesting frequency based on the USD, regardless of frequency information included in the SIBx1.

[0090] Step S104 is a determination of the condition that the supportedBandCombination of UE100 included in the UE-NR-Capability includes at least one frequency band combination including a set of frequencies of interest (MBS frequencies of interest) (i.e., UE100 can simultaneously receive broadcast MRBs on the set of frequencies of interest).

[0091] In this way, by omitting (disabling) the condition determination in step S103a, even if the SIBx1 does not include adjacent frequency information (and an MBS service identifier in the adjacent frequency), the UE 100 can identify an interesting frequency (MBS frequencies of interest) based on the USD. For example, the UE 100 reads a service identifier and information on a frequency that provides the service from the USD, and identifies a frequency that provides a service of interest (desired MBS service) as an interesting frequency.

[0092] In addition, UE 100 may determine whether to omit (disable) the condition determination in step S103a based on an instruction (or permission) from gNB 200. For example, gNB 200 may notify UE 100, via SIBx1, of information permitting or instructing omission of the condition determination in step S103a (or identification of an interesting frequency based on USD information).

[0093] (4.1.2) Option 2 In option 2, when generating an MII, the UE 100 identifies a frequency of interest based on higher layer information (USD) in response to the UE 100 recognizing that a predetermined SIB (SIBx1) does not include frequency information. That is, the UE 100 identifies a frequency of interest based on frequency information provided in USD only when frequency information is not provided in SIBx1.

[0094] FIG. 13 is a diagram showing the operation of option 2 according to the embodiment, specifically, an example of specification changes in 3GPP technical specification TS38.331.

[0095] The operations other than step S103b are the same as those of Option 1 described above.

[0096] In step S103b, UE 100 first determines a condition that, for a certain frequency, a service identifier indicated for a desired MBS service in USD is included in SIBx1 acquired from the PCell (serving cell). Second, if frequency information for the MBS service (MBS session) is unavailable in SIBx1, UE 100 determines a frequency for the desired MBS service using USD. Specifically, if UE 100 recognizes that adjacent frequency information (and / or an MBS service identifier in an adjacent frequency) is not provided, UE 100 reads a service identifier (such as SAI) and frequency information providing the service from USD, and identifies a frequency providing the service of interest as a frequency of interest.

[0097] In this way, by adding a judgment based on USD to the condition judgment of step S103b, UE100 can identify frequencies of interest (MBS frequencies of interest) based on USD even if SIBx1 does not include adjacent frequency information (and MBS service identifiers in adjacent frequencies).

[0098] (4.1.3) Option 3 In option 3, when generating an MII, the UE 100 identifies an interesting frequency based on the SIB for cell reselection and higher layer information in response to the UE 100 recognizing that a predetermined SIB (SIBx1) does not include frequency information. For example, when frequency information is not provided in SIBx1, the UE 100 identifies, as an interesting frequency, a frequency that matches a frequency associated with a desired MBS service in USD from among the frequencies provided in SIB4 and / or SIB5.

[0099] FIG. 14 is a diagram showing the operation of Option 3 according to the embodiment, specifically, an example of specification changes in 3GPP technical specification TS38.331.

[0100] The operations other than step S103c are the same as those of Option 1 described above.

[0101] In step S103c, UE 100 first determines whether a service identifier indicated for a desired MBS service in USD for a certain frequency is included in SIBx1 acquired from the PCell (serving cell). Second, if frequency information for the MBS service (MBS session) is unavailable in SIBx1, UE 100 makes a determination based on SIB4 and / or SIB5. Specifically, if UE 100 recognizes that neighboring frequency information (and / or an MBS service identifier in the neighboring frequency) is not provided in SIBx1, UE 100 reads a service identifier (such as SAI) and frequency information providing the service from USD. Then, if a frequency providing a service of interest is included in SIB4 (and / or SIB5), UE 100 identifies the frequency as an interesting frequency.

[0102] In this way, by adding a judgment based on USD and SIB4 and / or SIB5 to the condition judgment of step S103c, UE100 can identify the frequency of interest (MBS frequencies of interest) based on USD and SIB4 and / or SIB5 even if SIBx1 does not include adjacent frequency information (and MBS service identifier in the adjacent frequency).

[0103] In addition, UE 100 may determine whether to make a determination based on SIB4 and / or SIB5 in step S103c based on an instruction (or permission) from gNB 200. For example, gNB 200 may notify UE 100 of information permitting or instructing a determination based on SIB4 and / or SIB5 in step S103c in SIBx1. Under such a premise, in step S103c, in response to an instruction to use SIB4 and / or SIB5 in SIBx1 instead of frequency information being unavailable in SIBx1, UE 100 may read a service identifier (SAI, etc.) and frequency information providing the service from USD, and if a frequency providing the service of interest is included in SIB4 (and / or SIB5), UE 100 may identify the frequency as a frequency of interest.

[0104] (4.2) Setting the frequency of interest to the frequency list Options A to C of the operation of setting the frequency of interest in the frequency list according to the embodiment will be described below. The UE 100 sets the frequency of interest in the frequency list according to any of the following options A to C.

[0105] The operation of identifying a frequency of interest in (4.1) above makes it possible to identify a frequency of interest even if neighboring frequency information is not provided in the SIBx1. However, it is assumed that the frequency identifier (ARFCN: Absolute radio-frequency channel number) provided in the SIBx1 is set in the frequency list in the MII. Therefore, even if a frequency of interest is identified, the frequency of interest cannot be included in the MII. Options A to C can solve this problem.

[0106] (4.2.1) Option A In Option A, when generating the MII, the UE 100 sets all MBS interest frequencies identified based on the higher layer information (USD) in the frequency list, regardless of the frequency information in the predetermined SIB (SIBx1). That is, the UE 100 sets all interest frequencies identified by the operation of identifying interest frequencies in (4.1) above in the MII.

[0107] FIG. 15 is a diagram showing the operation of option A according to the embodiment, specifically, an example of specification changes in the 3GPP technical specification TS38.331.

[0108] If there are any frequencies of interest (MBS frequencies of interest) identified by the operation of identifying frequencies of interest in (4.1) above (step S201), UE 100 sets the frequencies of interest in a frequency list (mbs-FreqList) in step S202a. Specifically, UE 100 includes all frequencies of interest in the frequency list regardless of the frequency information in SIBx1. UE 100 may convert the frequency information in USD into an ARFCN value before including it in the MBS frequency list.

[0109] When the UE 100 identifies frequencies of interest without using frequency information in the SIBx1 in the operation of identifying frequencies of interest in the above-described (4.1), the UE 100 may perform an operation of including all frequencies of interest in the frequency list regardless of the frequency information in the SIBx1. In other words, when the UE 100 identifies frequencies of interest using frequency information in the SIBx1, the UE 100 may perform an operation of including frequencies of interest in the frequency list using the frequency information in the SIBx1.

[0110] Note that the UE 100 may determine whether to include all frequencies of interest in the frequency list regardless of the frequency information in the SIBx1 based on an instruction (or permission) from the gNB 200. For example, the gNB 200 notifies the UE 100 in the SIBx1 of information that permits or instructs the inclusion of all frequencies of interest in the frequency list regardless of the frequency information in the SIBx1.

[0111] (4.2.2) Option B In Option B, when generating the MII, the UE 100 sets all MBS interest frequencies identified based on the higher layer information (USD) in the frequency list in response to the UE 100 recognizing that the predetermined SIB (SIBx1) does not include frequency information. That is, the UE 100 sets all interest frequencies in the MII only if frequency information is not provided in the SIBx1.

[0112] FIG. 16 is a diagram showing an operation example 1 of option B according to the embodiment, specifically, a specification change example in 3GPP technical specification TS38.331.

[0113] If there are any frequencies of interest (MBS frequencies of interest) identified by the operation of identifying frequencies of interest in (4.1) above (step S201), UE 100 sets the frequencies of interest in a frequency list (mbs-FreqList) in step S202b. Here, UE 100 includes the frequencies of interest in the frequency list (mbs-FreqList) in descending order of interest. As identifiers of frequencies of interest to be set in the frequency list (mbs-FreqList), absoluteFrequencySSB is used for serving frequencies, and ARFCN-ValueNR included in SIBx1 is used for neighboring frequencies. However, if there is no frequency identifier (ARFCN-ValueNR) for the desired MBS service in SIBx1, UE 100 includes all frequencies of interest in the frequency list.

[0114] FIG. 17 is a diagram showing an operation example 2 of option B according to the embodiment, specifically, a specification change example in 3GPP technical specification TS38.331.

[0115] When there are frequencies of interest (MBS frequencies of interest) identified by the operation of identifying frequencies of interest in (4.1) above (step S201), and frequency information (mbs-SAI-InterFreqList) exists in the SIBx1, the UE 100 sets the frequencies of interest in the frequency list (mbs-FreqList) in the MII in step S202c. Here, the UE 100 includes the frequencies of interest in the frequency list (mbs-FreqList) in order of decreasing interest. As identifiers of the frequencies of interest to be set in the frequency list (mbs-FreqList), absoluteFrequencySSB is used for the serving frequency, and ARFCN-ValueNR included in the SIBx1 is used for the adjacent frequency.

[0116] On the other hand, if there is no frequency information (mbs-SAI-InterFreqList) in the SIBx1, the UE 100 sets the frequencies of interest to the frequency list (mbs-FreqList) in the MII in step S203. Here, the UE 100 sets all MBS frequencies of interest identified based on the higher layer information (USD) to the frequency list.

[0117] In option B, the UE 100 may convert the frequency information of the USD into an ARFCN value and include it in the MBS frequency list.

[0118] (4.2.3) Option C In option C, when generating the MII, the UE 100 sets all MBS interest frequencies identified based on the SIB for cell reselection and the higher layer information (USD) in the frequency list in response to the UE 100 recognizing that the predetermined SIB (SIBx1) does not include frequency information. That is, when frequency information is not provided in SIBx1, the UE 100 sets the ARFCN included in SIB4 (and / or SIB5) in the MII.

[0119] FIG. 18 is a diagram showing an operation example 1 of option C according to the embodiment, specifically, a specification change example in the 3GPP technical specification TS38.331.

[0120] If there are any MBS frequencies of interest identified by the operation of identifying frequencies of interest in (4.1) above (step S201), UE 100 sets the frequencies of interest in a frequency list (mbs-FreqList) in step S202d. Here, UE 100 includes the frequencies of interest in the frequency list (mbs-FreqList) in descending order of interest. As identifiers of frequencies of interest to be set in the frequency list (mbs-FreqList), absoluteFrequencySSB is used for the serving frequency, and ARFCN-ValueNR included in SIBx1 is used for the adjacent frequencies. However, if there is no frequency identifier (ARFCN-ValueNR) for the desired MBS service in SIBx1, UE 100 includes the frequency identifier (ARFCN-ValueNR) included in SIB4 (and / or SIB5) for the adjacent frequencies in the frequency list. That is, if UE100 recognizes that adjacent frequency information (and / or MBS service identifier in adjacent frequency) is not provided in SIBx1, it sets the frequency (ARFCN value) broadcast in SIB4 (and / or SIB5) from among the frequencies of interest in the frequency list.

[0121] FIG. 19 is a diagram showing an operation example 2 of option C according to the embodiment, specifically, a specification change example in 3GPP technical specification TS38.331.

[0122] When there are frequencies of interest (MBS frequencies of interest) identified by the operation of identifying frequencies of interest in (4.1) above (step S201), and frequency information (mbs-SAI-InterFreqList) exists in the SIBx1, the UE 100 sets the frequencies of interest in the frequency list (mbs-FreqList) in the MII in step S202e. Here, the UE 100 includes the frequencies of interest in the frequency list (mbs-FreqList) in order of decreasing interest. As identifiers of the frequencies of interest to be set in the frequency list (mbs-FreqList), absoluteFrequencySSB is used for the serving frequency, and ARFCN-ValueNR included in the SIBx1 is used for the adjacent frequency.

[0123] On the other hand, when frequency information (mbs-SAI-InterFreqList) does not exist in SIBx1, UE100 sets the frequency of interest to the frequency list (mbs-FreqList) in MII in step S204. Here, UE100 includes the frequency identifier (ARFCN-ValueNR) included in SIB4 (and / or SIB5) for the adjacent frequency in the frequency list. In other words, when UE100 recognizes that adjacent frequency information (and / or MBS service identifier in the adjacent frequency) is not provided in SIBx1, UE100 sets the frequency (ARFCN value) broadcast in SIB4 (and / or SIB5) from among the frequencies of interest in the frequency list.

[0124] Note that UE 100 may determine whether to perform an operation of setting the ARFCN value included in SIB4 and / or SIB5 in the frequency list based on an instruction (or permission) from gNB 200. For example, gNB 200 may notify UE 100 in SIBx1 of information permitting or instructing the operation of setting the ARFCN value included in SIB4 and / or SIB5 in the frequency list. Under such a premise, UE 100 may set the frequency (ARFCN value) broadcast in SIB4 (and / or SIB5) from among the frequencies of interest in the frequency list in response to an instruction (or permission) to use SIB4 and / or SIB5 in SIBx1 instead of frequency information not being provided in SIBx1.

[0125] Instead of frequency information being not provided in SIBx1, UE100 may set the frequency (ARFCN value) from among the frequencies of interest that is broadcast in SIB4 (and / or SIB5) in the frequency list in response to identifying the frequencies of interest using SIB4 and / or SIB5 in the operation of identifying the frequencies of interest described above in (4.1).

[0126] (4.3) MII configuration example Configuration examples 1 and 2 of the MII according to the embodiment will be described. The UE 100 may transmit an MII having the characteristics of the following configuration example 1 or 2 to the serving cell (gNB 200).

[0127] (4.3.1) MII configuration example 1 In the first configuration example of the MII, the UE 100 assigns an information source identifier to the frequency list (mbs-FreqList) indicating on what information the frequencies of interest were identified and / or set. That is, when the UE 100 reports the frequencies of interest without using SIBx1, the UE 100 notifies the gNB 200 that the frequencies of interest are based on USD (or SIB4 and / or SIB5).

[0128] As described above, if the frequency list is not specified or set based on SIBx1, it may be preferable to notify the information source to the gNB 200. For example, the gNB 200 may perform different operations depending on the information source when processing the frequency list notified by the UE 100.

[0129] FIG. 20 is a diagram showing a first configuration example of the MII according to the embodiment, specifically, a specification modification example in the 3GPP technical specification TS38.331.

[0130] The MII includes MBSInterestIndication-r17-IEs. The MBSInterestIndication-r17-IEs includes at least one of a frequency list (mbs-FreqList-r17) that is a list of MBS frequencies that the UE 100 is receiving or is interested in receiving, priority information (mbs-Priority-r17) that indicates the priority of whether to prioritize reception of all listed MBS frequencies or reception of a unicast bearer, and a TMGI list (mbs-ServiceList-r17) that is a list of MBS sessions that the UE 100 is receiving or is interested in receiving.

[0131] In this configuration example 1, each entry (CarrierFreqMBS-r17) of the frequency list (mbs-FreqList-r17) includes an MBS-frequency and Source-info. The MBS-frequency is a frequency identifier (ARFCN-ValueNR) of the frequency of interest. The Source-info is an information source identifier that indicates the information source referenced when identifying or setting the frequency of interest. The Source-info indicates at least one of SIBx1, SIB4, SIB5, and USD as the information source. Note that if Source-info is not present in the MII, it may implicitly indicate that SIBx1 is the information source, or that SIB4 and / or SIB5 are the information source, or that USD is the information source.

[0132] FIG. 21 is a diagram showing a modification of the first configuration example of the MII according to the embodiment, specifically, a modification of the specifications in the 3GPP technical specification TS38.331.

[0133] In this modified example, the MBSInterestIndication-r17-IEs in the MII is configured to be able to include, instead of mbs-FreqList-SIBx1-r17, which corresponds to the existing frequency list, any of mbs-FreqList-SIB4-r17, which is a frequency list of interesting frequencies whose information source is SIB4, mbs-FreqList-SIB5-r17, which is a frequency list of interesting frequencies whose information source is SIB5, and mbs-FreqList-USD-r17, which is a frequency list of interesting frequencies whose information source is USD.

[0134] If the information source is SIB4, UE100 sets the frequency of interest to mbs-FreqList-SIB4-r17, if the information source is SIB5, UE100 sets the frequency of interest to mbs-FreqList-SIB5-r17, and if the information source is USD, UE100 sets the frequency of interest to mbs-FreqList-USD-r17.

[0135] However, the SIB4 and SIB5 lists may be combined into one list, for example, mbs-RfeqList-SIB4-SIB5-r17.

[0136] (4.3.2) MII configuration example 2 In the second example of the MII configuration, the UE 100 classifies each of the frequencies of interest according to the information source on which the frequencies are identified. Then, the UE 100 sets each of the frequencies of interest in a corresponding list from among the lists for each information source. That is, the UE 100 classifies the frequencies of interest according to the information source, includes them in the corresponding list, and reports them via the MII.

[0137] In this way, the UE 100 classifies the information sources for all frequencies of interest and then reports them to the network (gNB 200) by MII. By providing all frequencies of interest to the network, it is possible to encourage the gNB 200 to make more advanced decisions and contribute to information collection on the network side.

[0138] In MII configuration example 2, the same MII configuration as in Fig. 21 can be adopted. UE 100 performs the following processes for the identified frequency of interest. First, UE 100 includes a frequency that matches a neighboring frequency (ARFCN) provided in SIBx1 in a frequency list for which SIBx1 is the information source. Second, UE 100 includes a frequency that matches a neighboring frequency (ARFCN) provided in SIB4 and / or SIB5 in a frequency list for which SIB4 and / or SIB5 is the information source. Third, UE 100 includes a frequency that matches a frequency provided in USD in a frequency list for which USD is the information source.

[0139] (Other embodiments) The above-mentioned operational flows are not limited to being implemented independently, but can also 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.

[0140] In the above-described 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 also be a relay node such as an IAB (Integrated Access and Backhaul) node. The base station may also be a DU of the IAB node. The UE 100 may also be an MT (Mobile Termination) of the IAB node.

[0141] A program may be provided that causes a computer to execute each process performed by UE100 or gNB200. The program may be recorded on a computer-readable medium. The computer-readable medium can be used to install the program 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. Furthermore, 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).

[0142] As used in this disclosure, the terms "based on" and "depending on" do not mean "based only on" or "depending only on," unless expressly stated otherwise. The term "based on" means both "based only on" and "based at least in part on." Similarly, the term "depending on" means both "depending only on" and "depending at least in part on." Furthermore, the terms "include," "comprise," and variations thereof do not mean including only the listed items, but may mean including only the listed items or may include additional items in addition to the listed items. Furthermore, the term "or," as used in this disclosure, is not intended to mean an exclusive or. Furthermore, any reference to elements using designations such as "first," "second," etc., as used in this disclosure does not 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, a 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 way. In this disclosure, where articles are added by translation, such as a, an, and the in English, these articles shall include the plural unless the context clearly indicates otherwise.

[0143] 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.

[0144] This application claims priority to U.S. Provisional Application No. 63 / 308,561 (filed February 10, 2022), the entire contents of which are incorporated herein by reference.

[0145] (Addendum) introduction In RAN2#116bis-e, MBS, idle / inactive mode procedures, and CR during RRC were mentioned as work item completion topics for further discussion. The open issue list covers a wide range of important issues that are likely to be discussed via email. However, issues arising from the interest frequency of MBS interest notifications are not included in the list, which may adversely affect the continuity of broadcast services in some deployments.

[0146] This appendix discusses potential issues regarding the frequency of interest reported in MBS interest notices.

[0147] Discussion Deployment Scenarios in TS38.304 In RAN2#116bis-e, it was agreed that it is up to the UE implementation whether to use SIBy or USD frequency information for frequency prioritization in the cell reselection procedure.

[0148] If SIBy is provided in a cell but frequency mapping for the service is not provided, the UE can preferentially use the frequency indicated in USD.

[0149] It is up to the UE implementation how it uses the information in the USD (e.g., along with other explicit knowledge) to determine whether (or how) to prioritize frequencies for specific frequencies / frequencies within the USD.

[0150] Observation 1: It is up to the UE implementation whether to use SIBy or USD frequency information for frequency prioritization during cell reselection.

[0151] Therefore, the CR in TS38.304 captures the conditions for a UE to prioritize frequencies, i.e., 2) below. In particular, the last condition of 2), i.e., "SIBy is provided in the serving cell but does not provide frequency mapping for the service, and the frequency is included in the USD of the service," is different from LTE eMBMS.

[0152] If an MBS broadcast capable UE is receiving or interested in receiving an MBS broadcast service and can only receive it by camping on a frequency on which this MBS broadcast service is offered, the UE may consider that frequency as its highest priority during the MBS broadcast session if the following two conditions are met, as specified in TS38.300:

[0153] 1) The cell reselected by the UE based on the frequency priority of the MBS provides SIBx.

[0154] SIBx is the MBS SIB that carries the MCCH configuration. The SIBx name will be updated later to align with other RAN2 specifications.

[0155] 2) One of the following: The SIBy of the serving cell indicates one or more identities (e.g., SAIs) of the frequency, and the same identities (e.g., SAIs) are / are indicated for this MBS broadcast service in the MBS User Service Description (USD) specified in TS 26.346, or SIBy is not offered in the serving cell and the frequency is included in the USD of the service, or SIBy is provided in the serving cell, but the frequency mapping of the service is not provided and the frequency is included in the USD of the service.

[0156] Note: It is up to the UE implementation how to use the information in the USD to decide whether or not to prioritize frequencies for specific / any frequencies included in the USD.

[0157] According to the last condition (i.e., "SIB is provided in the serving cell but does not provide frequency mapping for the service, and the frequency is included in the USD for the service"), deployments are also envisaged in which the gNB does not provide frequency information in SIBy (or SIBx1 in CR during RRC), even if SIBy itself is broadcast.

[0158] Observation 2: Even if SIBy is broadcast, the gNB may not provide frequency information in SIBy.

[0159] Potential service continuity issues with RRC Connected For connected UEs, the gNB ensures the continuity of broadcast services by considering the MBS interest notification sent by the UE. The MBS interest notification may optionally contain three pieces of information: the frequency of interest, the service of interest, and the priority between unicast and broadcast.

[0160] The currently running CR captures how the UE determines the frequencies of interest contained in the MBS interest notification as follows (this is almost the same as that for LTE eMBMS):

[0161] 5.x.4.3 Determining MBS Frequencies of Interest The UE shall:

[0162] 1> A frequency is considered to be part of the MBS's interesting frequencies if it meets the following conditions:

[0163] 2> At least one MBS session that the UE is receiving or is interested in receiving via broadcast MRB is in progress or is about to be started, and NOTE 1: The UE can determine whether a session is in progress from the start and stop times indicated in the User Service Description (USD) by referring to TS38.300 or TS23.247.

[0164] 2> For at least one SIBx1 of these MBS sessions obtained from the PCell, it contains one or more MBS SAIs indicated in the USD of that session for that frequency; and NOTE 2: Even if the NG-RAN does not (temporarily) use the broadcast MRB for the session, the UE still considers the frequency as part of the MBS target frequency (i.e., the UE does not check whether the session is indicated on the MCCH).

[0165] 2> The UE's supportedBandCombination included in UE-NR-Capability includes at least one band combination that includes a set of MBS frequencies of interest (i.e., the UE is capable of receiving broadcast MRBs simultaneously on the set of MBS frequencies of interest).

[0166] NOTE 3: When evaluating whether a UE can simultaneously receive broadcast MRBs on a set of MBS frequencies of interest, the UE does not consider the currently configured serving frequencies. That is, the UE only considers the MBS frequencies of interest for reception, regardless of whether they can be received together with the current serving cell.

[0167] Note: USD / SAI terminology will be updated to match the SA2 specification.

[0168] The UE can determine the frequency of interest only if all conditions (i.e., the three "2>" parts above) are met. In particular, for the second condition (i.e., "for at least one of these MBS sessions, SIBx1 obtained from the PCell includes one or more MBS SAIs indicated in the USD of this session for that frequency"), SIBx1 (or SIBy) must provide an MBS SAI for that frequency.

[0169] Observation 3: The UE is allowed to determine the frequency of interest reported in the MBS Interest Notification if the SAI for this frequency is provided in SIBx1.

[0170] The details of the SAI for NR MBS have not yet been determined, but it is expected to be similar to SIB15 for LTE eMBMS, and has already been captured in a running CR as shown in Figure 11.

[0171] As with LTE eMBMS, SAI lists are provided for intra-frequency and inter-frequency use. For inter-frequency use ("mbs-SAI-InterFreqList-r17", which includes "dl-CarrierFreq-r17" and "mbs-SAI-List-r17"), the SAI list is obviously associated with the DL carrier frequency (the so-called "frequency information").

[0172] Considering observation 2 above, it may be acceptable in some deployments for the gNB not to provide frequency information, which means that the gNB does not provide an SAI list for that frequency.

[0173] Observation 4: If the gNB does not provide frequency information, similar to Observation 2, the gNB does not provide a SAI list for different frequencies.

[0174] In this case, the UE cannot consider this frequency as an interesting frequency and therefore cannot report it in the MBS interest notification as in Observation 3 above, which means that the gNB does not consider the continuation of broadcast services on that frequency.

[0175] Observation 5: If the UE does not provide an SAI list in SIBx1 as in Observation 4, it cannot determine the interest frequency of the MBS interest notification as in Observation 3.

[0176] It is a bit strange that if SIBx1 (or SIBy) does not provide an SAI list (or does not provide frequency information), connected UEs cannot use the frequency information of USD for MBS interest notification, as in Finding 5, while idle / inactive UEs can use frequencies in USD for cell reselection even if SIBy (or SIBx1) does not provide frequency information (or has no SAI list), as in Finding 1. In other words, in this deployment scenario, continuity of broadcast services is ensured for idle / inactive UEs, but not for connected UEs.

[0177] Observation 6: In some deployments, broadcast service continuity is not ensured for connected UEs based on Observation 5, while continuity is ensured for idle / inactive UEs based on Observation 1.

[0178] Based on the above findings, RAN2 should discuss whether it is necessary to align the handling of frequency information in USD between cell reselection and MBS interest notification. If so, several solutions can be considered, as follows:

[0179] Option 1: Delete the condition "For at least one of these MBS sessions, the SIBx1 obtained from the PCell contains one or more MBS SAIs for the frequency, as indicated in the USD for this session."

[0180] Option 2: After the condition "or if no such frequency for an MBS session is available in SIBx1, the frequency may be determined by the USD", there is an additional condition "The SIBx1 obtained from the PCell for at least one of these MBS sessions contains one or more MBS SAIs for the frequency as indicated in the USD for that session".

[0181] Both options allow the UE to determine the frequencies of interest (if reported by the MBS Interest Notification), ensuring continuity of broadcast services in all deployment scenarios.

[0182] Proposal 1: RAN2 should discuss whether UEs can include USD frequencies in their MBS interest notifications even if the frequencies are not available in SIBx1, similar to the prioritization of frequencies in cell reselection.

[0183] Proposal 2: If Proposal 1 is accepted, RAN2 will further discuss whether to adopt Option 1 and delete the sentence "2> For at least one of these MBS sessions, the SIBx1 obtained from the PCell contains one or more MBS SAIs for the frequency indicated by the USD for this session," or adopt Option 2 and add the following condition to Clause 5.x.4.3 of the TS 38.331 Implementation CR: "Or if no frequency for the MBS session is available in the SIBx1, the frequency may be determined by the USD."

[0184] Another related issue is in the currently implemented CR, section 5.x.4.5 "Configuring the content of the MBS interest notification", the procedure of which is very similar to that of LTE eMBMS.

[0185] 5.x.4.5 Setting the content of MBS interest notifications The UE shall configure the content of the MBS interest notification as follows:

[0186] 1>If the set of MBS frequencies of interest determined according to 5.x.4.3 is not empty.

[0187] 2> Include mbs-FreqList and, if applicable, set it to include the MBS frequencies of interest sorted in ascending order using the absoluteFrequencySSB of the serving frequency and the ARFCN-ValueNR (for neighboring frequencies) included in SIBx1.

[0188] As stated in "ARFCN-ValueNR (for adjacent frequencies) included in SIBx1," if the gNB does not provide frequency information in SIBx1, the UE cannot include the frequencies it is interested in in the MBS interest notification, even if it has determined the frequencies (for example, through Proposal 2 above).

[0189] Observation 7: If the gNB does not provide frequency information in SIBx1, the UE will not include the frequencies it is interested in, even if it has determined them.

[0190] If Proposal 1 above is agreed to, the following three options will be considered to resolve the issue:

[0191] Option A: Delete the statement "ARFCN-ValueNR (for adjacent frequencies) included in SIBx1."

[0192] Option B: Change the alternative condition "Include mbs-FreqList of MBS sessions of interest from USD" to "ARFCN-ValueNR (for adjacent frequencies) included in SIBx1."

[0193] Option C: An alternative condition is to include the ARFCN in SIB4 (NR inter-frequency) and / or SIB5 (Inter-RAT inter-frequency) instead of SIBx1.

[0194] In all options, the UE can report the frequency of interest regardless of whether the gNB provides frequency information in SIBx1, thus ensuring broadcast service continuity in all deployment scenarios.

[0195] Proposal 3: If Proposal 1 is agreed, RAN2 will further discuss whether to adopt Option A and delete the statement "ARFCN-ValueNR (for adjacent frequencies) included in SIBx1," adopt Option B and add an alternative condition "includes mbs-FreqList of MBS sessions of interest from USD," or adopt Option C and add an alternative condition referring to ARFCN in SIB4 and SIB5 to 5.x.4.3 of the TS 38.331 running CR.

[0196] (Appendix 2) The following additional notes are about the features of the above-described embodiment.

[0197] (1) A communication method performed by a user device in a mobile communication system that provides a multicast broadcast service (MBS), comprising: receiving a predetermined system information block (SIB) from a serving cell, the SIB including frequency information indicating a correspondence between an identifier of an MBS service and a frequency that provides the MBS service; generating an MBS interest notification that includes a list of interest frequencies, which are MBS frequencies that the user device is receiving or is interested in receiving; transmitting the MBS interest notification to the serving cell; The user device includes the frequency of interest in the list even if the frequency of interest is not indicated in the predetermined SIB. Communication method.

[0198] (2) The user device includes the frequency of interest in the list based on higher layer information that the user device has, which is information indicating a correspondence relationship between an identifier of an MBS service and a frequency that provides the MBS service, even if the frequency of interest is not indicated in the predetermined SIB. The communication method described in (1) above.

[0199] (3) The frequency information indicates a correspondence relationship between an identifier of an MBS service and an inter-frequency that provides the MBS service and is different from the frequency of the serving cell. The communication method according to (1) or (2) above.

[0200] (4) The generating step includes a step of identifying the frequency of interest based on the higher layer information, regardless of the frequency information in the predetermined SIB. A communication method according to any one of (1) to (3) above.

[0201] (5) The generating step includes a step of identifying the frequency of interest based on the higher layer information in response to the user device recognizing that the predetermined SIB does not include the frequency information. A communication method according to any one of (1) to (4) above.

[0202] (6) receiving a cell reselection SIB from the serving cell, the SIB indicating an inter-frequency different from a frequency of the serving cell; The generating step includes a step of identifying the frequency of interest based on the SIB for cell reselection and the higher layer information in response to the user equipment recognizing that the predetermined SIB does not include the frequency information. A communication method according to any one of (1) to (5) above.

[0203] (7) The generating step includes a step of setting all MBS interest frequencies identified based on the higher layer information in the list, regardless of the frequency information in the predetermined SIB. A communication method according to any one of (1) to (6) above.

[0204] (8) The generating step includes a step of setting all MBS interest frequencies identified based on the higher layer information in the list in response to the user equipment recognizing that the predetermined SIB does not include the frequency information. A communication method according to any one of (1) to (7) above.

[0205] (9) The generating step includes a step of setting all MBS interest frequencies identified based on the SIB for cell reselection and the higher layer information in the list in response to the user equipment recognizing that the predetermined SIB does not include the frequency information. A communication method according to any one of (1) to (8) above.

[0206] (10) The generating step includes the step of providing the list with a source identifier indicating on what basis the frequencies of interest represented in the list were identified and / or set. A communication method according to any one of (1) to (9) above.

[0207] (11) The generating step includes: classifying each of the frequencies of interest by the information source on which the frequencies of interest were identified; and placing each of the frequencies of interest in a corresponding one of the source-specific lists. A communication method according to any one of (1) to (10) above.

[0208] (12) A user device for use in a mobile communication system that provides a multicast broadcast service (MBS), comprising: A receiver that receives a predetermined system information block (SIB) from a serving cell, the SIB including frequency information indicating a correspondence relationship between an identifier of an MBS service and a frequency that provides the MBS service; a control unit that generates an MBS interest notification including a list of interest frequencies that are MBS frequencies that the user device is receiving or is interested in receiving; a transmitter that transmits the MBS interest notification to the serving cell, The control unit includes the frequency of interest in the list even if the frequency of interest is not indicated in the predetermined SIB. User equipment. [Explanation of symbols]

[0209] 1: Mobile communication system 10:RAN 20 :CN 100:UE 110: Receiving unit 120: Transmitter 130: Control unit 200 :gNB 210: Transmission unit 220: Receiving unit 230: Control unit 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 predetermined system information block (SIB) from a serving cell, the SIB including information indicating a correspondence relationship between an MBS area identifier and a frequency; generating an MBS interest notification that includes a list of interest frequencies that are MBS frequencies that the user device is receiving or is interested in receiving; transmitting the MBS interest notification to the serving cell; The generating includes, when the predetermined SIB is received, including the frequency of interest in the list even if the frequency of interest is not included in the predetermined SIB, if the frequency of interest is indicated in a USD (User Service Description). Communication method.

2. The USD includes an identifier of an MBS service, information indicating a service area in which the MBS service is provided, and a frequency in which the MBS service is provided. The communication method according to claim 1 .

3. The predetermined SIB includes information indicating a correspondence relationship between an identifier of an MBS service and an inter-frequency that provides the MBS service and is different from the frequency of the serving cell. The communication method according to claim 1 .

4. The generating step includes populating the list with all MBS interest frequencies identified based on the USD. The communication method according to claim 1 .

5. The generating step includes identifying the frequency of interest based on the USD in response to the user device recognizing that the predetermined SIB does not include the information. The communication method according to claim 1 .

6. receiving a cell reselection SIB from the serving cell, the SIB indicating an inter-frequency different from a frequency of the serving cell; The generating step includes identifying the frequency of interest based on the cell reselection SIB and the USD information in response to the user equipment recognizing that the predetermined SIB does not include the information. The communication method according to claim 5.

7. The generating includes, in response to the user equipment recognizing that the predetermined SIB does not include the information, populating the list with all MBS interest frequencies identified based on the USD. The communication method according to claim 4.

8. The generating step includes, in response to the user equipment recognizing that the predetermined SIB does not include the information, setting all MBS interest frequencies identified based on the cell reselection SIB and the USD to the list. The communication method according to claim 7.

9. The generating step includes providing the list with a source identifier indicating on what basis the frequencies of interest represented in the list were identified and / or set. A communication method according to any one of claims 1 to 8.

10. The generating step comprises: classifying each of the frequencies of interest by the information source on which the frequencies of interest were identified; and placing each of the frequencies of interest in a corresponding one of the source-specific lists. A communication method according to any one of claims 1 to 8.

11. The generating step includes generating priority information indicating a priority between reception of the MBS frequency and reception of a unicast signal. The communication method according to claim 1 .

12. A user equipment for use in a mobile communication system providing a multicast broadcast service (MBS), comprising: a receiving unit that receives a predetermined system information block (SIB) including information indicating a correspondence relationship between an MBS area identifier and a frequency from a serving cell; a control unit for generating an MBS interest notification including a list of interest frequencies, which are MBS frequencies that the user device is receiving or is interested in receiving; a transmitter that transmits the MBS interest notification to the serving cell; When the control unit receives the predetermined SIB, even if the frequency of interest is not included in the predetermined SIB, if the frequency of interest is indicated by a USD (User Service Description), the control unit includes the frequency of interest in the list. User equipment.

13. 1. A chipset for a user equipment for use in a mobile communication system providing a multicast broadcast service (MBS), comprising: receiving a predetermined system information block (SIB) from a serving cell, the SIB including information indicating a correspondence relationship between an MBS area identifier and a frequency; an interest frequency, which is an MBS frequency that the user device is receiving or is interested in receiving; generating an MBS Notice of Interest that includes a list of transmitting the MBS Interest Notification to the serving cell; The generating process includes, when the predetermined SIB is received, even if the frequency of interest is not included in the predetermined SIB, if the frequency of interest is indicated by a USD (User Service Description), including the frequency of interest in the list. Chipset.

14. A user device for use in a mobile communication system providing a multicast broadcast service (MBS), receiving a predetermined system information block (SIB) from a serving cell, the SIB including information indicating a correspondence relationship between an MBS area identifier and a frequency; an interest frequency, which is an MBS frequency that the user device is receiving or is interested in receiving; generating an MBS Notice of Interest that includes a list of transmitting the MBS interest notification to the serving cell; The generating process includes, when the predetermined SIB is received, even if the frequency of interest is not included in the predetermined SIB, if the frequency of interest is indicated by a USD (User Service Description), including the frequency of interest in the list. program.

15. A mobile communication system including a user device and providing a multicast broadcast service (MBS), The user device Receive a predetermined system information block (SIB) from a serving cell, the SIB including information indicating a correspondence relationship between an MBS area identifier and a frequency; generating an MBS interest notification including a list of interest frequencies that are MBS frequencies that the user device is receiving or is interested in receiving; sending the MBS Interest Notification to the serving cell; When the predetermined SIB is received, even if the frequency of interest is not included in the predetermined SIB, if the frequency of interest is indicated by a USD (User Service Description), the frequency of interest is included in the list. Mobile communication system.

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