Communication methods, user devices, chipsets, programs, and mobile communication systems

Abstract

Provided is a communication method executed by user equipment in a mobile communication system that provides multicast-broadcast services (MBS), the communication method comprising receiving from a serving cell a predetermined system information block (SIB) that may contain frequency information indicating correspondences between identifiers of MBS services and the frequencies on which the MBS services are provided; generating an MBS interest notification that includes a list indicating frequencies of interest, which are MBS frequencies that the user equipment is receiving or interested in receiving; and transmitting the MBS interest notification to the serving cell, wherein the user equipment includes the frequencies of interest in the list if the frequencies of interest are indicated by higher-layer information, even in the case where the frequencies of interest are not included in the predetermined SIB.

Description

Technical Field

[0001] The present disclosure relates to a communication method and a user device used in a mobile communication system.

Background Art

[0002] In the 3GPP (3rd Generation Partnership Project) standard, the technical specifications of NR (New Radio), which is the 5th generation (5G) radio access technology, are defined. NR has characteristics such as high speed, large capacity, high reliability, and low latency compared to LTE (Long Term Evolution), which is the 4th generation (4G) radio access technology. In 3GPP, discussions are being held to formulate the technical specifications of 5G / NR's multicast broadcast service (MBS) (see, for example, Non-Patent Document 1).

Prior Art Documents

Non-Patent Documents

[0003]

Non-Patent Document 1

Summary of the Invention

[0004] It is desired that the 5G / NR multicast broadcast service provides a service improved from the 4G / LTE multicast broadcast service.

[0005] Therefore, an object of the present disclosure is to provide a communication method and a user device that can realize an improved multicast broadcast service.

[0006] A communication method according to the first embodiment is a communication method performed by a user device in a mobile communication system that provides a multicast broadcast service (MBS), comprising the steps of: receiving a predetermined system information block (SIB) from a serving cell, which includes frequency information indicating a correspondence between an identifier for an MBS service and the frequency on which the MBS service is provided; generating an MBS interest notification which includes a list of interest frequencies that the user device is receiving or is interested in receiving; and transmitting the MBS interest notification to the serving cell. The user device includes the interest frequency in the list even if the interest frequency is not included in the predetermined SIB, if it is indicated in higher-layer information.

[0007] The user device according to the second embodiment is a user device used in a mobile communication system that provides a multicast broadcast service (MBS), and comprises: a receiving unit that receives a predetermined system information block (SIB) from a serving cell, which includes frequency information indicating the correspondence between an identifier for an MBS service and the frequency on which the MBS service is provided; a control unit that generates an MBS interest notification which includes a list of interest frequencies that the user device is receiving or is interested in receiving; and a transmitting unit that transmits the MBS interest notification to the serving cell. The control unit includes the interest frequency in the list even if the interest frequency is not included in the predetermined SIB, if it is indicated in higher-layer information. [Brief explanation of the drawing]

[0008] [Figure 1] This diagram shows the configuration of a mobile communication system according to an embodiment. [Figure 2] This diagram shows the configuration of the UE (User Equipment) according to the embodiment. [Figure 3] This diagram shows the configuration of the gNB (base station) according to the embodiment. [Figure 4] This diagram shows the protocol stack configuration of the user plane wireless interface that handles data. [Figure 5] This diagram shows the protocol stack configuration of the wireless interface of the control plane that handles signaling (control signals). [Figure 6] This diagram shows an overview of MBS traffic distribution according to the embodiment. [Figure 7] This figure shows the distribution mode according to the embodiment. [Figure 8] This figure shows an example of internal processing related to MBS reception in a UE according to the embodiment. [Figure 9] This figure shows another example of the internal processing related to MBS reception in the UE according to the embodiment. [Figure 10] This is a diagram illustrating the overview of the MII according to the embodiment. [Figure 11] This figure shows an example configuration of SIBx1 according to the embodiment. [Figure 12] This figure shows the operation of Option 1 according to the embodiment, specifically, an example of a specification change in the 3GPP technical specification TS38.331. [Figure 13] This figure shows the operation of Option 2 according to the embodiment, specifically, an example of a specification change in the 3GPP technical specification TS38.331. [Figure 14] This figure shows the operation of option 3 according to the embodiment, specifically, an example of a specification change in the 3GPP technical specification TS38.331. [Figure 15] This figure shows the operation of option A according to the embodiment, specifically, an example of a specification change in the 3GPP technical specification TS38.331. [Figure 16] This figure shows an example of operation of option B according to the embodiment, specifically, an example of a specification change in the 3GPP technical specification TS38.331. [Figure 17] This figure shows an example of operation of option B according to the embodiment, specifically, an example of a specification change in the 3GPP technical specification TS38.331. [Figure 18] This figure shows an example of operation of option C according to the embodiment, specifically, an example of a specification change in the 3GPP technical specification TS38.331. [Figure 19]FIG. 2 shows an operation example 2 of Option C according to an embodiment, specifically, an example of a specification change in 3GPP technical specification TS38.331. [Figure 20] FIG. 3 shows a configuration example 1 of MII according to an embodiment, specifically, an example of a specification change in 3GPP technical specification TS38.331. [Figure 21] FIG. 4 shows a modified example of the configuration example 1 of MII according to an embodiment, specifically, an example of a specification change in 3GPP technical specification TS38.331.

MODE FOR CARRYING OUT 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 complies with the 5th generation system (5GS) of the 3GPP standard. Hereinafter, the 5GS will be described as an example, but the LTE (Long Term Evolution) system may be at least partially applied to the mobile communication system. Also, the 6th generation (6G) system may be at least partially applied to the mobile communication 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 RAN 10. Also, the 5GC 20 may be simply referred to as the core network (CN) 20.

[0012] UE100 is a mobile wireless communication device. UE100 can be any device as long as it is used by a user. For example, UE100 can be a mobile phone terminal (including smartphones), a tablet terminal, a notebook PC, a communication module (including a communication card or a chipset), a sensor or a device provided for a sensor, a vehicle or a device provided for a vehicle (Vehicle UE), an aircraft or a device provided for an aircraft (Aerial UE).

[0013] NG-RAN10 includes base stations (referred to as "gNB" in the 5G system) 200. The gNBs 200 are interconnected via the 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 UE100 that has established a connection with its cell. The gNB 200 has functions such as a radio resource management (RRM) function, a routing function for user data (hereinafter simply referred to as "data"), and a measurement control function for mobility control and scheduling. "Cell" is used as a term indicating the smallest unit of a wireless communication area. "Cell" is also used as a term indicating a function or resource for performing wireless communication with the UE100. One cell belongs to one carrier frequency (hereinafter simply referred to as "frequency").

[0014] Note that the gNB can also be connected to the EPC (Evolved Packet Core) which is the core network of LTE. The base stations of LTE can also be connected to 5GC. The base stations of LTE and the gNB can also be connected via an interface between base stations.

[0015] The 5GC20 includes the AMF (Access and Mobility Management Function) and the UPF (User Plane Function) 300. The AMF performs various mobility controls for the UE100. The AMF manages the mobility of the UE100 by communicating with it using NAS (Non-Access Stratum) signaling. The UPF controls data transfer. The AMF and UPF are connected to the gNB200 via the NG interface, which is the base station-core network interface.

[0016] Figure 2 shows the configuration of UE100 (user device) according to an embodiment. UE100 comprises 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 gNB200.

[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 the radio signal received by the antenna into a baseband signal (received signal) and outputs it to the control unit 130.

[0018] The transmitting unit 120 performs various types of transmissions under the control of the control unit 130. The transmitting unit 120 includes an antenna and a transmitter. The transmitter converts the baseband signal (transmission signal) output by the control unit 130 into a wireless signal and transmits it from the antenna.

[0019] The control unit 130 performs various control and processing operations in the UE 100. Such processing includes processing in each layer 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 for processing by the processor. The processor may include a baseband processor and a CPU (Central Processing Unit). The baseband processor performs modulation, demodulation, encoding, and decoding of baseband signals. The CPU executes programs stored in memory and performs various processing operations.

[0020] Figure 3 shows the configuration of the gNB200 (base station) according to the embodiment. The gNB200 comprises a transmitter 210, a receiver 220, a control unit 230, and a backhaul communication unit 240. The transmitter 210 and receiver 220 constitute a wireless communication unit that performs wireless communication with the UE100. The backhaul communication unit 240 constitutes a network communication unit that communicates with the CN20.

[0021] The transmitting unit 210 performs various types of transmissions under the control of the control unit 230. The transmitting unit 210 includes an antenna and a transmitter. The transmitter converts the 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 the radio signal received by the antenna into a baseband signal (received signal) and outputs it to the control unit 230.

[0023] The control unit 230 performs various control and processing in the gNB200. Such processing includes processing in each layer 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 for processing by the processor. The processor may include a baseband processor and a CPU. The baseband processor performs modulation, demodulation, encoding, and decoding of baseband signals. The CPU executes programs stored in memory and performs various processing.

[0024] The backhaul communication unit 240 is connected to an adjacent base station via the Xn interface, which is an inter-base station interface. The backhaul communication unit 240 is connected to the AMF / UPF300 via the NG interface, which is an inter-base station-core network interface. The gNB200 may consist of a CU (Central Unit) and a DU (Distributed Unit) (i.e., functionally separated), and the two units may be connected by the F1 interface, which is a fronthaul interface.

[0025] Figure 4 shows the configuration of the protocol stack for the user plane's wireless interface that handles data.

[0026] The user plane radio interface protocol consists of a physical (PHY) layer, a MAC (Medium Access Control) layer, an RLC (Radio Link Control) layer, a PDCP (Packet Data Convergence Protocol) layer, and an SDAP (Service Data Adaptation Protocol) 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 UE100's PHY layer and the gNB200's PHY layer via a physical channel. The UE100's PHY layer receives downlink control information (DCI) transmitted from the gNB200 over the physical downlink control channel (PDCCH). Specifically, the UE100 performs blind decoding of the PDCCH using a Radio Network Temporary Identifier (RNTI) and acquires the successfully decoded DCI as the DCI addressed to its own UE. The DCI transmitted from the gNB200 has a CRC parity bit added, which is scrambled by the RNTI.

[0028] The MAC layer performs data priority control, retransmission processing using Hybrid Automatic Repeat request (HARQ), and random access procedures. Data and control information are transmitted between the MAC layer of the UE100 and the MAC layer of the gNB200 via the transport channel. The MAC layer of the gNB200 includes a scheduler. The scheduler determines the transport format for the up and down links (transport block size, modulation and coding scheme (MCS)) and the resource blocks to be allocated to the UE100.

[0029] The RLC layer transmits data to the receiving RLC layer using the functions of the MAC layer and PHY layer. Data and control information are transmitted between the UE100's RLC layer and the gNB200's RLC layer via a logical channel.

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

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

[0032] Figure 5 shows the configuration of the protocol stack of the wireless interface of the control plane that handles signaling (control signals).

[0033] The control plane's wireless interface protocol stack includes an RRC (Radio Resource Control) layer and a NAS (Non-Access Stratum) layer, instead of the SDAP layer shown in Figure 4.

[0034] RRC signaling for various settings is transmitted between the RRC layer of the UE100 and the RRC layer of the gNB200. The RRC layer controls the logical channel, transport channel, and physical channel in response to the establishment, re-establishment, and release of the radio bearer. If there is a connection (RRC connection) between the RRC of the UE100 and the RRC of the gNB200, the UE100 is in the RRC connected state. If there is no connection (RRC connection) between the RRC of the UE100 and the RRC of the gNB200, the UE100 is in the RRC idle state. If the connection between the RRC of the UE100 and the RRC of the gNB200 is suspended, the UE100 is in the RRC inactive state.

[0035] The NAS layer, located above the RRC layer, handles session management and mobility management, among other things. NAS signaling is transmitted between the UE100's NAS layer and the AMF300A's NAS layer. The UE100 also has application layers and other components in addition to its wireless interface protocol. Furthermore, layers below the NAS layer are referred to as the AS layer.

[0036] (2) Overview of MBS Next, an overview of the MBS according to the embodiment will be described. MBS is a service that enables broadcast or multicast, i.e., point-to-multipoint (PTM) data transmission from NG-RAN10 to UE100. Use cases (service types) of MBS are envisioned to include public security 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 provides service to all UE100s within a specific service area for applications that do not require high reliability QoS. The MBS session used for the broadcast service is referred to as a broadcast session.

[0038] Multicast services provide services not to all UE100s, but to groups of UE100s participating in a multicast service (multicast session). The MBS session used for multicast services is called a multicast session. Multicast services allow the same content to be delivered to a group of UE100s in a more wirelessly efficient manner compared to broadcast services.

[0039] Figure 6 shows an overview of MBS traffic distribution according to the embodiment.

[0040] MBS traffic (MBS data) is delivered from a single data source (application service provider) to multiple UEs. The 5G core network, 5G CN (5GC)20, receives MBS data from application service providers, creates copies of the MBS data (replication), and delivers them.

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

[0042] In the 5GC individual MBS traffic distribution method, the 5GC20 receives a single copy of MBS data packets and distributes individual copies of those MBS data packets to individual UE100s via a PDU session for each UE100. Therefore, one PDU session per UE100 needs to be associated with the multicast session.

[0043] In the 5GC shared MBS traffic distribution method, the 5GC20 receives a single copy of MBS data packets and distributes that single copy of MBS packets to the RAN nodes (i.e., gNB200). The gNB200 receives the MBS data packets via the MBS tunnel connection and distributes them to one or more UE100s.

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

[0045] In the PTP distribution method, the gNB200 wirelessly distributes individual copies of MBS data packets to each UE100. On the other hand, in the PTM distribution method, the gNB200 wirelessly distributes a single copy of MBS data packets to a group of UE100s. The gNB200 can dynamically decide whether to use PTM or PTP as the method for distributing MBS data to a single UE100.

[0046] The PTP and PTM distribution methods primarily concern the user plane. There are two control modes for MBS data distribution: the first distribution mode and the second distribution mode.

[0047] Figure 7 shows a distribution mode according to an embodiment.

[0048] Delivery mode 1 (DM1) is a delivery mode available to UE100 in an RRC connected state and is a delivery mode for high QoS requirements. Delivery mode 1 is used for multicast sessions within MBS sessions. However, delivery mode 1 may also be used for broadcast sessions. Delivery mode 1 may also be available to UE100 in an RRC idle or RRC inactive state.

[0049] In the first distribution mode, MBS reception is configured via UE-dedicated signaling. For example, in the first distribution mode, MBS reception is configured via an RRC message (or RRC Release message), which is a unicast RRC message sent from gNB200 to UE100.

[0050] The MBS reception settings include MBS traffic channel configuration information (hereinafter referred to as "MTCH configuration information") relating to the settings of the MBS traffic channel that transmits MBS data. The MTCH configuration information includes MBS session information relating to the MBS session (including the MBS session identifier described later) and scheduling information for the MBS traffic channel corresponding to this MBS session. The scheduling information for the MBS traffic channel may also include intermittent reception (DRX) settings for the MBS traffic channel. The intermittent receive setting may include one or more of the following parameters: an On Duration Timer that defines the On Duration (reception period), an Inactivity Timer that extends the On Duration, a Scheduling Period or DRX Cycle, a Start Offset or DRX Cycle Offset for the start subframe of the Scheduling Period or DRX Cycle, a Slot Offset for the start of the On Duration Timer, a Retransmission Timer that defines the maximum time until retransmission, and a HARQ RTT Timer that defines the minimum interval until DL assignment for HARQ retransmission.

[0051] The MBS traffic channel is a type of logical channel and is sometimes called an MTCH. The MBS traffic channel is mapped to the Down Link-Shared Channel (DL-SCH), which is a type of transport channel.

[0052] Delivery mode 2 (DM2) is a delivery mode that can be used not only by UE100s in the RRC connected state, but also by UE100s in the RRC idle or RRC inactive state, and is a delivery mode for low QoS requirements. Delivery mode 2 is used for broadcast sessions within MBS sessions. However, delivery mode 2 may also be applicable to multicast sessions.

[0053] In the second distribution mode, MBS reception is configured via broadcast signaling. For example, in the second distribution mode, MBS reception is configured via a logical channel broadcast from the gNB200 to the UE100, such as a broadcast control channel (BCCH) and / or multicast control channel (MCCH). The UE100 can receive the BCCH and MCCH using a dedicated RNTI predefined in the technical specifications, for example. The RNTI for BCCH reception may be an SI-RNTI, and the RNTI for MCCH reception may be an MCCH-RNTI.

[0054] In the second distribution mode, UE100 may receive MBS data in the following three steps: First, UE100 receives MCCH configuration information via SIB (MBS SIB) transmitted over BCCH from gNB200. Second, UE100 receives MCCH from gNB200 based on the MCCH configuration information. MCCH transmits MTCH configuration information. Third, UE100 receives MTCH (MBS data) based on the MTCH configuration information. Hereafter, MTCH configuration information and / or MCCH configuration information may be referred to as MBS reception settings.

[0055] In the first and second distribution modes, the UE100 may receive the MTCH using the group RNTI (G-RNTI) assigned by the gNB200. G-RNTI corresponds to the RNTI for MTCH reception. G-RNTI may be included in the MBS reception settings (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 the following: TMGI (Temporary Mobile Group Identity), source-specific IP multicast address (consisting of a source unicast IP address such as an application function or application server, and an IP multicast address indicating the destination address), session identifier, and G-RNTI. At least one of the TMGI, source-specific IP multicast address, and session identifier is referred to as the MBS session identifier. The TMGI, source-specific IP multicast address, session identifier, and G-RNTI are collectively referred to as MBS session information.

[0057] Figure 8 shows an example of the internal processing related to MBS reception in the UE100 according to the embodiment. Figure 9 shows another example of the internal processing related to MBS reception in the UE100 according to the embodiment.

[0058] A single MBS radio bearer (MRB) is a single radio bearer that transmits either a multicast session or a broadcast session. That is, an MRB may be associated with a multicast session, or it may be associated with a broadcast session.

[0059] The MRB and its corresponding logical channel (e.g., MTCH) are configured from gNB200 to UE100 via RRC signaling. The MRB configuration procedure may be separate from the data radio bearer (DRB) configuration procedure. RRC signaling allows a single MRB to be configured as "PTM only," "PTP only," or "both PTM and PTP." The type of MRB can be changed via RRC signaling.

[0060] Figure 8 shows an example where MRB#1 is associated with a multicast session and a dedicated traffic channel (DTCH), MRB#2 is associated with a multicast session and MTCH#1, and MRB#3 is associated with a broadcast session and MTCH#2. In other words, 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 cell RNTI (C-RNTI), and MTCH is scheduled using G-RNTI.

[0061] The UE100's PHY layer processes user data (received data) received on the PDSCH, one of the physical channels, and sends it to the Downlink Shared Channel (DL-SCH), one of the transport channels. The UE100's MAC layer (MAC entity) processes data received on the DL-SCH and sends the received data to the corresponding logical channel (corresponding RLC entity) based on the logical channel identifier (LCID) contained in the header (MAC header) of the received data.

[0062] Figure 9 shows an example where DTCH and MTCH are associated with an MRB that is associated with a multicast session. Specifically, one MRB is split into two legs, one leg is associated with DTCH and the other leg is associated with MTCH. These two legs are joined at the PDCP layer (PDCP entity). In other words, this MRB is both a PTM and a PTP MRB. Such an MRB is sometimes called a split MRB.

[0063] (3) Overview of MBS Interest Notification Next, an overview of the MBS Interest Indication (MII) according to the embodiment will be described. Figure 10 is a diagram illustrating the overview of the MII according to the embodiment.

[0064] UE100 is in the RRC connected state (step S1) and is receiving or interested in receiving an MBS session (step S2).

[0065] In step S3, UE100 receives an SIB (hereinafter referred to as "SIBx1") for MBS service continuity from gNB200 (serving cell). SIBx1 is an SIB that shows the correspondence (mapping) between MBS services and frequencies. An example configuration of SIBx1 will be described later. Note that SIBx1 is a different SIB from the MBS SIB mentioned above. UE100 may also receive SIBx1 from gNB200 before step S1 or before step S2.

[0066] UE100 is capable of sending MBS Interest Indications (MIIs) to serving cells that provide SIBx1, i.e., serving cells that have the functionality for MBS service continuity. In other words, UE100 sends an MII to a serving cell only if that serving cell provides SIBx1. An MII is a type of RRC message used to notify the network that UE100 is receiving or interested in receiving MBS broadcast services via the broadcast MRB. Based on the MII, the network (gNB200) can control the distribution of MBS services or hand over UE100 to the appropriate cell.

[0067] In step S4, UE100 experiences an MII transmission trigger (trigger event). Examples of MII transmission triggers (trigger events) include successful connection establishment, entering or leaving a broadcast service area, starting or stopping an MBS broadcast session, a change in MBS interest, a change in priority between MBS broadcast reception and unicast reception, and a change to a cell that broadcasts an SIB for MBS service continuity (primary cell).

[0068] In step S5, UE100 generates an MII. The MII includes at least one of the following: a frequency list (MBS frequency list), which is a list of MBS frequencies that UE100 is receiving or interested in receiving; priority information, which indicates the priority between receiving all the listed MBS frequencies and receiving unicast bearers; and a TMGI list, which is a list of MBS sessions that UE100 is receiving or interested in receiving. The frequency list in the MII will be described primarily below.

[0069] Step S5 includes step S51, which identifies an MBS frequency that UE100 is receiving or is interested in receiving (hereinafter referred to as the "interest frequency"), and step S52, which sets the identified interest frequency in the frequency list. Details of steps S51 and S52 will be described later.

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

[0071] Figure 11 shows an example configuration of SIBx1 according to the embodiment. SIBx1 is used by UE100 to derive the MBS frequencies of interest that provide the desired MBS service (desired MBS session) that UE100 is receiving or is interested in receiving.

[0072] In the following, the term "MBS service" will be used to refer to a concept that includes "MBS session." The identifier for an MBS service will be referred to as the "MBS service identifier." The MBS service identifier may also be the MBS session identifier (e.g., TMGI) mentioned above. The MBS service identifier may also be the MBS service area identifier (MBS SAI). The MBS service identifier may sometimes be written as MBS SAI.

[0073] As shown in Figure 11, SIBx1 may include at least one of mbs-SAI-IntraFreq-r17 and mbs-SAI-InterFreqList-r17. mbs-SAI-IntraFreq-r17 includes MBS-SAI-List-r17, which is a list of MBS service identifiers for MBS services provided at intra frequencies (i.e., the same frequencies as the serving cell). mbs-SAI-InterFreqList-r17 includes, for each inter-frequency (i.e., a frequency different from the serving cell), MBS-SAI-InterFreq-r17 indicating the correspondence (mapping) between that frequency and the MBS services provided at that frequency. MBS-SAI-InterFreq-r17 includes a frequency identifier (ARFCN-ValueNR) indicating the 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] When UE100 is in an RRC idle or RRC inactive state, it identifies the frequency providing the desired MBS service based on SIBx1 during frequency prioritization in cell reselection, and sets the identified frequency as the highest priority. However, if frequency information (mbs-SAI-IntraFreq-r17, mbs-SAI-InterFreqList-r17) is not provided in SIBx1, it is assumed that the frequency of interest providing the desired MBS service will be identified based on the higher-layer information USD (User Service Description), and the identified frequency of interest will be set as the highest priority.

[0076] Here, USD is provided to UE100 from, for example, the AF (Application Function) / MBSF (Multicast Broadcast Service Function) in the network. Such USD is an example of higher-layer information provided from the network at a layer higher than the RRC layer (specifically, the application layer). USD may also be called service announcement information. USD includes information indicating the correspondence between MBS services and frequencies. USD may include at least one set of MBS service identifier and frequency information. For example, USD may include at least one of the following: an MBS session identifier that identifies an MBS session, information on the start and end times of the MBS session, a SAI indicating the MBS service area where the MBS session is provided, and information on the frequency on which the MBS session is provided.

[0077] The USD-based cell reselection control described above assumes the following scenario: Specifically, even if gNB200 provides SIBx1, it may not provide adjacent frequency information (mbs-SAI-InterFreqList-r17) in SIBx1. For example, if MBS service is provided uniformly across a certain frequency / area, even if not all cells in that area broadcast adjacent frequency information, UE100 can derive the appropriate frequency of interest from the frequency information provided in USD. Therefore, by controlling cell reselection with that frequency of interest as the highest priority, the continuity of broadcast service can be ensured.

[0078] On the other hand, for UE100 in the RRC connected state, the frequency of interest is identified based on SIBx1 in order to generate the frequency list in MII. However, if adjacent frequency information is not provided in SIBx1, UE100 cannot properly identify the frequency of interest. While it is assumed that UE100 in the RRC idle or RRC inactive state will identify the frequency of interest based on USD, there is a problem in that such operation is not assumed for UE100 in the RRC connected state. The following embodiments will describe methods and operations to solve this problem.

[0079] As described above, UE100 receives a predetermined SIB (SIBx1) from the serving cell which may include frequency information indicating the correspondence between an MBS service identifier (MBS service identifier) ​​and the frequency on which the MBS service is provided (step S3 in Figure 10). UE100 generates an MII which includes a frequency list indicating frequencies of interest, which are MBS frequencies that it is receiving or is interested in receiving (step S5 in Figure 10), and transmits the MII to the serving cell (step S6 in Figure 10).

[0080] In this embodiment, when generating the MII, the UE100 includes its frequency of interest in the frequency list even if its frequency of interest is not indicated in a predetermined SIB (SIBx1). This allows the network to determine the UE100's frequency of interest based on the frequency list in the MII, even if frequency information (especially mbs-SAI-InterFreqList-r17) is not provided in SIBx1.

[0081] For example, even if the frequency of interest is not indicated in a predetermined SIB, UE100 includes the frequency of interest in its frequency list based on higher-layer information (USD) held by UE100, which indicates the correspondence between the identifier of the MBS service (MBS service identifier) ​​and the frequency that provides the MBS service. In other words, UE100 includes the frequency of interest in its frequency list based on USD instead of SIBx1.

[0082] UE100 may include frequencies of interest in its frequency list based on a cell reselection SIB received from a serving cell, instead of SIBx1. The cell reselection SIB is an SIB provided by a serving cell that indicates an inter-frequency different from the frequency of that serving cell. The cell reselection SIB may be an SIB type 4 (SIB4) and / or an SIB type 5 (SIB5) as defined in the 3GPP technical specifications.

[0083] Such a cell reselection SIB contains one or more sets of inter-frequency identifiers and cell reselection parameters (e.g., frequency priority). The inter-frequency indicated in the cell reselection SIB corresponds to the frequency of the adjacent cell and is therefore considered an available frequency for UE100. UE100 includes frequencies of interest in its frequency list, limited to such available frequencies. However, since the desired MBS service may not be available at the inter-frequency indicated in the cell reselection SIB, UE100 includes frequencies of interest in its frequency list in conjunction with the cell reselection SIB and USD.

[0084] (4.1) Operation to identify the frequency of interest Options 1 to 3 for identifying the frequency of interest according to the embodiment will be described below. The UE100 identifies the frequency of interest by any of the following options 1 to 3.

[0085] (4.1.1) Option 1 In Option 1, when generating the MII, the UE100 identifies frequencies of interest based on higher layer information (USD), regardless of the frequency information in the predetermined SIB (SIBx1). In other words, the UE100 identifies frequencies of interest based on USD information without checking the frequency information provided in SIBx1.

[0086] Figure 12 shows the operation of Option 1 according to the embodiment, specifically, an example of a specification change in the 3GPP Technical Specification TS38.331.

[0087] UE100 considers the frequencies that satisfy the conditions of steps S102 to S104 as the frequencies of interest (MBS frequencies) (step S101).

[0088] Step S102 is to determine whether at least one MBS session (desired MBS service) is in progress or about to be started, which UE100 is receiving or interested in receiving via the broadcast MRB.

[0089] Step S103a is to determine whether, for a given frequency, the service identifier indicated in USD for the desired MBS service is included in the SIBx1 obtained from the PCell (serving cell). In Option 1, this condition check is omitted. That is, UE100 identifies the frequency of interest based on USD, regardless of the frequency information included in the SIBx1.

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

[0091] Thus, by omitting (disabling) the conditional check in step S103a, UE100 can identify MBS frequencies of interest based on USD even if SIBx1 does not contain adjacent frequency information (and MBS service identifiers in adjacent frequencies). For example, UE100 reads the service identifier and information about the frequency that provides the service from USD and identifies the frequency providing the service of interest (desired MBS service) as the frequency of interest.

[0092] Furthermore, UE100 may decide whether or not to omit (disable) the condition check in step S103a based on instructions (or permission) from gNB200. For example, gNB200 may notify UE100 via SIBx1 of information permitting or instructing the omission of the condition check in step S103a (or the identification of interest frequencies based on USD information).

[0093] (4.1.2) Option 2 In Option 2, when generating the MII, UE100 identifies frequencies of interest based on higher-layer information (USD) if it recognizes that a predetermined SIB (SIBx1) does not contain frequency information. In other words, UE100 identifies frequencies of interest based on the frequency information provided in USD only if frequency information is not provided in SIBx1.

[0094] Figure 13 shows the operation of Option 2 according to the embodiment, specifically, an example of a specification change in the 3GPP technical specification TS38.331.

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

[0096] In step S103b, UE100 first determines whether the service identifier for the desired MBS service in USD is included in the SIBx1 obtained from the PCell (serving cell) for a given frequency. Second, if frequency information for the MBS service (MBS session) is unavailable in SIBx1, UE100 determines the frequency for the desired MBS service using USD. Specifically, if UE100 recognizes that adjacent frequency information (and / or MBS service identifiers in adjacent frequencies) is not provided, it reads the service identifier (SAI, etc.) and frequency information for the service in question from USD and identifies the frequency providing the service of interest as the frequency of interest.

[0097] Thus, by adding a USD-based determination as a conditional determination in step S103b, UE100 can identify MBS frequencies of interest based on USD even if SIBx1 does not contain adjacent frequency information (and MBS service identifiers in adjacent frequencies).

[0098] (4.1.3) Option 3 In Option 3, when generating the MII, UE100 identifies frequencies of interest based on the cell reselection SIB and higher-layer information, depending on whether UE100 recognizes that a predetermined SIB (SIBx1) does not contain frequency information. For example, if frequency information is not provided in SIBx1, UE100 identifies frequencies of interest from among the frequencies provided in SIB4 and / or SIB5 that match the frequencies associated with the desired MBS service in USD.

[0099] Figure 14 shows the operation of option 3 according to the embodiment, specifically, an example of a specification change in the 3GPP technical specification TS38.331.

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

[0101] In step S103c, UE100 first determines whether the service identifier for a desired MBS service in USD is included in SIBx1 obtained from the PCell (serving cell) for a given frequency. Second, if frequency information for the MBS service (MBS session) is unavailable in SIBx1, UE100 makes a determination based on SIB4 and / or SIB5. Specifically, if UE100 recognizes that adjacent frequency information (and / or MBS service identifiers in adjacent frequencies) is not provided in SIBx1, it reads the service identifier (SAI, etc.) and the frequency information for the service in question from USD. Then, if the frequency providing the service of interest is included in SIB4 (and / or SIB5), UE100 identifies that frequency as the frequency of interest.

[0102] Thus, by adding a determination based on USD and SIB4 and / or SIB5 as a conditional determination in step S103c, UE100 can identify MBS frequencies of interest based on USD and SIB4 and / or SIB5 even if SIBx1 does not contain adjacent frequency information (and MBS service identifiers in adjacent frequencies).

[0103] Furthermore, UE100 may decide whether or not to perform a determination based on SIB4 and / or SIB5 in step S103c based on instructions (or permission) from gNB200. For example, gNB200 may notify UE100 in SIBx1 of information permitting or instructing a determination based on SIB4 and / or SIB5 in step S103c. Under such conditions, in step S103c, UE100 may read a service identifier (such as SAI) and frequency information providing the service from USD in response to an instruction in SIBx1 to use SIB4 and / or SIB5 instead of the frequency information being unavailable in SIBx1, and if the frequency providing the service of interest is included in SIB4 (and / or SIB5), then identify that frequency as the frequency of interest.

[0104] (4.2) Setting the frequency of interest to the frequency list Options A to C for setting the frequency of interest to the frequency list according to the embodiment will be described below. The UE100 sets the frequency of interest to the frequency list using one of the following options A to C.

[0105] The above-mentioned (4.1) procedure for identifying frequencies of interest makes it possible to identify frequencies of interest even when adjacent frequency information is not provided in SIBx1. However, the frequency list in the MII is expected to be set with the frequency identifier (ARFCN: Absolute radio-frequency channel number) provided in SIBx1. Therefore, even if a frequency of interest is identified, it cannot be included in the MII. Options A through C solve this problem.

[0106] (4.2.1) Option A In Option A, when generating the MII, the UE100 sets all MBS interest frequencies identified based on the upper layer information (USD) into the frequency list, regardless of the frequency information in the predetermined SIB (SIBx1). In other words, the UE100 sets all interest frequencies identified by the interest frequency identification operation described in (4.1) above into the MII.

[0107] Figure 15 shows the operation of option A according to the embodiment, specifically, an example of a specification change in the 3GPP technical specification TS38.331.

[0108] If there are any MBS frequencies of interest identified by the frequency identification operation described in (4.1) above (step S201), UE100 sets the frequencies of interest in the frequency list (mbs-FreqList) in step S202a. Specifically, UE100 includes all frequencies of interest in the frequency list regardless of the frequency information in SIBx1. UE100 may also include the USD frequency information in the MBS frequency list after converting it to an ARFCN value.

[0109] If the UE100 performs the identification of frequencies of interest in the above-mentioned (4.1) without using the frequency information in SIBx1, it may perform the operation of including all frequencies of interest in the frequency list regardless of the frequency information in SIBx1. In other words, if the UE100 performs the identification of frequencies of interest using the frequency information in SIBx1, it may perform the operation of including the frequencies of interest in the frequency list using the frequency information in SIBx1.

[0110] Furthermore, UE100 may decide whether or not to include all frequencies of interest in the frequency list, regardless of the frequency information in SIBx1, based on instructions (or permission) from gNB200. For example, gNB200 may notify UE100 in SIBx1 of permission or instructions to include all frequencies of interest in the frequency list, regardless of the frequency information in SIBx1. (4.2.2) Option B In Option B, when generating the MII, UE100 sets all MBS interest frequencies identified based on the higher-layer information (USD) into the frequency list if UE100 recognizes that a predetermined SIB (SIBx1) does not contain frequency information. In other words, UE100 sets all interest frequencies into the MII only if frequency information is not provided in SIBx1.

[0111] Figure 16 shows an example of operation of option B according to the embodiment, specifically an example of a specification change in the 3GPP technical specification TS38.331.

[0112] If UE100 has identified MBS frequencies of interest through the frequency identification operation described in (4.1) above (step S201), it sets the frequencies of interest in the frequency list (mbs-FreqList) in step S202b. Here, UE100 includes the frequencies of interest in the frequency list (mbs-FreqList) in order of decreasing interest. For serving frequencies, absoluteFrequencySSB is used as the identifier for the frequencies of interest to be set in the frequency list (mbs-FreqList), and for adjacent frequencies, ARFCN-ValueNR included in SIBx1 is used. However, if there is no frequency identifier (ARFCN-ValueNR) for the desired MBS service in SIBx1, UE100 includes all frequencies of interest in the frequency list.

[0113] Figure 17 shows an example of operation of option B according to the embodiment, specifically an example of a specification change in the 3GPP technical specification TS38.331.

[0114] If UE100 has identified interest frequencies (MBS frequencies of interest) through the interest frequency identification operation described in (4.1) above (step S201), and if frequency information (mbs-SAI-InterFreqList) exists in SIBx1, then in step S202c, UE100 sets the interest frequencies in the frequency list (mbs-FreqList) in MII. Here, UE100 includes the interest frequencies in the frequency list (mbs-FreqList) in order of decreasing interest. For serving frequencies, absoluteFrequencySSB is used as the identifier for the interest frequencies to be set in the frequency list (mbs-FreqList), and for adjacent frequencies, ARFCN-ValueNR included in SIBx1 is used.

[0115] On the other hand, if frequency information (mbs-SAI-InterFreqList) does not exist in SIBx1, step S203 sets the frequencies of interest in the frequency list (mbs-FreqList) in MII. Here, UE100 sets all MBS frequencies of interest identified based on the upper layer information (USD) into the frequency list.

[0116] In Option B, UE100 may include the MBS frequency list after converting the USD frequency information to an ARFCN value.

[0117] (4.2.3) Option C In Option C, when generating the MII, UE100 sets all MBS interest frequencies identified based on the cell reselection SIB and upper layer information (USD) into the frequency list, depending on whether UE100 recognizes that a predetermined SIB (SIBx1) does not contain frequency information. That is, if frequency information is not provided in SIBx1, UE100 sets the ARFCNs included in SIB4 (and / or SIB5) into the MII.

[0118] Figure 18 shows an example of operation of option C according to the embodiment, specifically an example of a specification change in the 3GPP technical specification TS38.331.

[0119] If UE100 has identified MBS frequencies of interest through the frequency identification operation described in (4.1) above (step S201), it sets the frequencies of interest in the frequency list (mbs-FreqList) in step S202d. Here, UE100 includes the frequencies of interest in the frequency list (mbs-FreqList) in order of decreasing interest. For serving frequencies, absoluteFrequencySSB is used as the identifier for the frequencies of interest to be set in the frequency list (mbs-FreqList), and for adjacent frequencies, ARFCN-ValueNR included in SIBx1 is used. However, if there is no frequency identifier (ARFCN-ValueNR) for the desired MBS service in SIBx1, UE100 includes the frequency identifier (ARFCN-ValueNR) included in SIB4 (and / or SIB5) in the frequency list for adjacent frequencies. In other words, if UE100 recognizes that adjacent frequency information (and / or MBS service identifiers in adjacent frequencies) is not provided in SIBx1, it sets the frequencies (ARFCN values) from among the frequencies of interest that are broadcast in SIB4 (and / or SIB5) into the frequency list.

[0120] Figure 19 shows an example of operation of option C according to the embodiment, specifically an example of a specification change in the 3GPP technical specification TS38.331.

[0121] If UE100 has identified interest frequencies (MBS frequencies of interest) through the interest frequency identification operation described in (4.1) above (step S201), and if frequency information (mbs-SAI-InterFreqList) exists in SIBx1, then in step S202e, UE100 sets the interest frequencies in the frequency list (mbs-FreqList) in MII. Here, UE100 includes the interest frequencies in the frequency list (mbs-FreqList) in order of decreasing interest. For serving frequencies, absoluteFrequencySSB is used as the identifier for the interest frequencies to be set in the frequency list (mbs-FreqList), and for adjacent frequencies, ARFCN-ValueNR included in SIBx1 is used.

[0122] On the other hand, if frequency information (mbs-SAI-InterFreqList) does not exist in SIBx1, step S204 sets the frequency of interest in the frequency list (mbs-FreqList) in MII. Here, UE100 includes the frequency identifier (ARFCN-ValueNR) contained in SIB4 (and / or SIB5) for adjacent frequencies in the frequency list. That is, if UE100 recognizes that adjacent frequency information (and / or MBS service identifiers for adjacent frequencies) is not provided in SIBx1, it sets the frequency (ARFCN value) announced in SIB4 (and / or SIB5) from among the frequencies of interest in the frequency list.

[0123] Furthermore, UE100 may decide whether or not to set the ARFCN values ​​included in SIB4 and / or SIB5 into the frequency list based on instructions (or permission) from gNB200. For example, gNB200 may notify UE100 in SIBx1 of information permitting or instructing the operation to set the ARFCN values ​​included in SIB4 and / or SIB5 into the frequency list. Under such conditions, UE100 may, in lieu of providing frequency information in SIBx1, set the frequencies (ARFCN values) announced in SIB4 (and / or SIB5) from among the frequencies of interest into the frequency list, in response to instructions (or permission) in SIBx1 to use SIB4 and / or SIB5.

[0124] In lieu of the fact that frequency information is not provided in SIBx1, UE100 may set the frequencies (ARFCN values) announced in SIB4 (and / or SIB5) from among the frequencies of interest in the frequency list, depending on the fact that the frequencies of interest have been identified using SIB4 and / or SIB5 in the frequency identification operation of the frequencies of interest described in (4.1) above.

[0125] (4.3) Example of MII configuration Configuration examples 1 and 2 of the MII according to the embodiment will be described below. The UE100 may transmit an MII having the characteristics of the following configuration example 1 or 2 to the serving cell (gNB200).

[0126] (4.3.1) Example of MII configuration 1 In MII Configuration Example 1, UE100 assigns a source identifier to the frequency list (mbs-FreqList) indicating the information on which the frequencies of interest were identified and / or set. That is, if UE100 reports frequencies of interest without using SIBx1, it notifies gNB200 that it is based on USD (or on SIB4 and / or SIB5).

[0127] As described above, if the frequency list is not identified or set based on SIBx1, it is preferable to notify the gNB200 of the information source. For example, when the gNB200 processes the frequency list notified by the UE100, it can perform different processing depending on the information source.

[0128] Figure 20 shows an example configuration of MII according to the embodiment, specifically an example of specification changes in the 3GPP technical specification TS38.331.

[0129] MII includes MBSInterestIndication-r17-IEs. MBSInterestIndication-r17-IEs is 、U It includes at least one of the following: a frequency list (mbs-FreqList-r17), which is a list of MBS frequencies that the E100 is receiving or is interested in receiving; priority information (mbs-Priority-r17), which indicates the priority between receiving all listed MBS frequencies and receiving unicast bearers; and a TMGI list (mbs-ServiceList-r17), which is a list of MBS sessions that the UE100 is receiving or is interested in receiving.

[0130] In this configuration example 1, each entry (CarrierFreqMBS-r17) in the frequency list (mbs-FreqList-r17) includes MBS-frequency and Source-info. MBS-frequency is the frequency identifier (ARFCN-ValueNR) of the frequency of interest. Source-info is a source identifier indicating the source referenced when identifying or setting the frequency of interest. Source-info indicates at least one of SIBx1, SIB4, SIB5, or USD as the source. If Source-info is not present in the MII, it may implicitly indicate that SIBx1 is the source, or that SIB4 and / or SIB5 is the source, or that USD is the source.

[0131] Figure 21 shows an example of a modification to the configuration example 1 of the MII according to the embodiment, specifically an example of a specification change in the 3GPP technical specification TS38.331.

[0132] In this example of modification, the MBSInterestIndication-r17-IEs in the MII is configured to include one of the following: mbs-FreqList-SIB4-r17, which is a frequency list of interest frequencies whose source is SIB4; mbs-FreqList-SIB5-r17, which is a frequency list of interest frequencies whose source is SIB5; or mbs-FreqList-USD-r17, which is a frequency list of interest frequencies whose source is USD, instead of mbs-FreqList-SIBx1-r17, which corresponds to the existing frequency list.

[0133] UE100 sets the frequency of interest to mbs-FreqList-SIB4-r17 if the information source is SIB4, to mbs-FreqList-SIB5-r17 if the information source is SIB5, and to mbs-FreqList-USD-r17 if the information source is USD.

[0134] However, the lists for SIB4 and SIB5 may be combined into a single file, for example, mbs-RfeqList-SIB4-SIB5-r17.

[0135] (4.3.2) Example of MII configuration 2 In MII Configuration Example 2, UE100 classifies each frequency of interest according to the information source on which it was identified. Then, UE100 sets each frequency of interest into the corresponding list within the list of information sources. In other words, UE100 classifies the frequencies of interest by information source and reports them in MII, including them in the corresponding list.

[0136] In this way, the UE100 classifies the information source for all frequencies of interest and reports it to the network (gNB200) via MII. By providing all frequencies of interest to the network, it is possible to facilitate more sophisticated decision-making by the gNB200 and contribute to information gathering on the network side.

[0137] In MII Configuration Example 2, a configuration similar to that in Figure 21 can be adopted. UE100 then processes the identified frequency of interest as follows: of The following processing steps are performed: First, UE100 includes frequencies that match adjacent frequencies (ARFCNs) provided in SIBx1 in the frequency list for which SIBx1 is the source. Second, UE100 includes frequencies that match adjacent frequencies (ARFCNs) provided in SIB4 and / or SIB5 in the frequency list for which SIB4 and / or SIB5 is the source. Third, UE100 includes frequencies that match frequencies provided in USD in the frequency list for which USD is the source.

[0138] (Other embodiments) Each of the above-described operation flows can be performed not only independently, but also in combination of two or more operation flows. For example, some steps of one operation flow may be added to another operation flow, or some steps of one operation flow may be replaced with some steps of another operation flow.

[0139] In the embodiments and examples described above, an example in which the base station is an NR base station (gNB) was described, but the base station may also be an LTE base station (eNB) or a 6G base station. Furthermore, 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 an IAB node. Furthermore, UE100 may be an MT (Mobile Termination) of an IAB node.

[0140] A program may be provided that causes a computer to execute each process performed by the UE100 or gNB200. The program may be recorded on a computer-readable medium. Using a computer-readable medium, it is possible to install the program on 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, but may be a recording medium such as a CD-ROM or DVD-ROM. Alternatively, the circuits that execute each process performed by the UE100 or gNB200 may be integrated, and at least a part of the UE100 or gNB200 may be configured as a semiconductor integrated circuit (chipset, SoC: System on a chip).

[0141] The terms “based on” and “depending on” used in this disclosure do not mean “based solely on” or “depending solely on” unless otherwise specified. “Based on” means both “based solely on” and “at least partially on.” Similarly, “depending on” means both “at least partially on” and “at least partially on.” Furthermore, the terms “include,” “comprise,” and variations thereof do not mean that only the listed items are included; they may include only the listed items, or they may include additional items in addition to the listed items. Also, the term “or” used in this disclosure is not intended to mean exclusive OR. Moreover, any reference to elements using designations such as “first,” “second,” etc., used in this disclosure does not generally limit the quantity or order of those elements. These designations may be used herein as a convenient way to distinguish between two or more elements. Therefore, references to the first and second elements do not imply that only two elements may be adopted therein, or that the first element must precede the second element in any way. In this disclosure, where articles are added by translation, such as a, an, and the in English, these articles shall be plural unless it is clearly indicated by the context that they are not.

[0142] Although the embodiments have been described in detail above with reference to the drawings, the specific configuration is not limited to those described above, and various design changes can be made without departing from the gist of the invention.

[0143] This application claims priority to U.S. Provisional Application No. 63 / 308561 (filed February 10, 2022), the entirety of which is incorporated into the specification of this application.

[0144] (Note) introduction RAN2#116bis-e mentions MBS, idle / inactive mode procedures, and CRs during RRC execution as prerequisites for further discussion toward work item completion. The open issue list covers a wide range of important issues that are likely to be discussed via email. However, issues stemming from the frequency of interest in MBS interest notifications are not included in the list, which could negatively impact the continuity of broadcast services in some deployments.

[0145] This addendum discusses potential issues regarding the frequency of interests reported in MBS interest notifications.

[0146] Discussion Deployment scenarios in TS38.304 In RAN2#116bis-e, it was agreed that whether to use SIBy or USD frequency information for frequency prioritization in the cell reselection procedure is up to the UE implementation.

[0147] If SIBy is provided within a cell but frequency mapping for that service is not provided, the UE can preferentially use the frequencies indicated in USD.

[0148] How the UE implementation uses information within USD to determine whether (or how) to prioritize frequencies for specific frequencies / frequency ranges within USD is up to them (e.g., along with other explicit knowledge).

[0149] Observation 1: Whether to use SIBy or USD frequency information for frequency prioritization during cell re-selection depends on the UE implementation.

[0150] Therefore, the CR running TS38.304 captures the conditions for prioritizing the frequencies of interest to the UE, namely, conditions 2) and below. In particular, the last condition of 2), namely "SIBy is provided by the serving cell but does not provide frequency mapping for the service, and the frequency is included in the USD for the service," is different from LTE eMBMS.

[0151] If a UE capable of MBS broadcasting is receiving or interested in receiving the MBS broadcast service and can only receive it by camping on the frequency on which the MBS broadcast service is provided, the UE may consider that frequency to be of priority during the MBS broadcast session, provided that the following two conditions are met, as specified in TS38.300:

[0152] 1) The cells re-selected by the UE based on MBS frequency priority are providing SIBx.

[0153] SIBx is an MBS SIB that carries the MCCH configuration. The name SIBx is scheduled to be updated later to align with other RAN2 specifications.

[0154] 2) Any of the following The SIBy of a serving cell indicates one or more IDs (e.g., SAI) for that frequency, and the MBS user service description (USD) specified in TS26.346 indicates / indicates the same ID (e.g., SAI) for this MBS broadcast service, or, SIBy is not provided in the serving cell, and its frequency is included in the USD of this service, or SIBy is provided in the serving cell, but frequency mapping for the service is not provided, and the frequency is included in the USD for that service.

[0155] Note: Certain frequencies included in USD / ZhouHow USD information is used to decide whether or not to prioritize frequencies based on wavenumber is up to the UE implementation.

[0156] According to the last condition (i.e., "SIB is provided in the serving cell but does not provide frequency mapping for the service, and its frequency is included in the USD for the service"), even if SIBy itself is broadcast, a scenario is anticipated where gNB does not provide frequency information in SIBy (or SIBx1 in CR during RRC execution).

[0157] Finding 2: Even if SIBy is broadcast, gNB may not provide frequency information via SIBy.

[0158] Potential service continuity issues in RRC Connected

[0159] For connected UEs, the gNB ensures broadcast service continuity by considering MBS interest notices sent from the UE. These MBS interest notices may include three pieces of information: the frequency of interest, the service of interest, and the priority between unicast and broadcast.

[0160] In the currently running CR, we have captured the following regarding how the UE determines the frequencies of interest to be included in the MBS interest notification (this is almost identical to that of LTE eMBMS):

[0161] 5.x.4.3 Determining the MBS frequency of interest The UE shall perform the following: 1> A frequency is considered to be part of MBS's range of frequencies of interest if it meets the following conditions: 2> At least one MBS session is in progress or about to be started that the UE is receiving or interested in receiving via broadcast MRB, and Note 1: The UE can refer to TS38.300 or TS23.247 and determine whether a session is in progress based on the start and end times shown in the User Service Description (USD).

[0162] 2>For at least one SIBx1 of these MBS sessions obtained from PCell, include one or more MBS SAIs indicated in the USD of that session for that frequency. and

[0163] Note 2: Even if NG-RAN does not (temporarily) use the broadcast MRB for the session, the UE will still consider the frequency to be part of the MBS target frequency (i.e., the UE will not check whether the session is directed on the MCCH).

[0164] 2> The UE supportedBandCombination included in UE-NR-Capability must include a combination of at least one band that contains the 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).

[0165] Note 3: When the UE evaluates whether it can simultaneously receive broadcast MRBs on a set of MBS frequencies of interest, the UE does not consider the currently configured serving frequencies. In other words, the UE considers only the MBS frequencies of interest for reception, regardless of whether they can be received together with the current serving cell.

[0166] Note: USD / SAI terminology will be updated to match the SA2 specification.

[0167] The UE can only determine the frequencies of interest 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, the SIBx1 obtained from PCell includes one or more MBS SAIs for that frequency as indicated in the USD for this session"), the SIBx1 (or SIBy) must provide an MBS SAI for that frequency.

[0168] Finding 3: If SAI is provided for this frequency in SIBx1, the UE is permitted to determine the frequency of interest reported in the MBS interest notice.

[0169] While the details of NR MBS's SAI are yet to be determined, it is expected to be similar to LTE eMBMS's SIB15, and is already being captured in CR as shown in Figure 11.

[0170] Similar to LTE eMBMS, SAI lists are provided separately for intra-frequency and inter-frequency use. For inter-frequency use (including "mbs-SAI-InterFreqList-r17" which contains "dl-CarrierFreq-r17" and "mbs-SAI-List-r17"), the SAI list is, of course, associated with the DL carrier frequency (the so-called "frequency information").

[0171] Considering Finding 2 above, it is acceptable in some deployments for the gNB not to provide frequency information, which means that the gNB does not provide a SAI list for that frequency.

[0172] Finding 4: If the gNB does not provide frequency information, similar to Finding 2, the gNB will not provide a list of SAIs for different frequencies.

[0173] In this case, the UE cannot consider this frequency as a frequency of interest, and therefore cannot report it in the MBS interest notice as described in Finding 3 above. This means that the continuation of broadcast service on that frequency is not being considered by the gNB.

[0174] Finding 5: If UE does not provide an SAI list in SIBx1 as in Finding 4, it is not possible to determine the interest frequency of MBS interest notifications as in Finding 3.

[0175] As in Finding 5, if SIBx1 (or SIBy) does not provide a SAI list (or frequency information), connected UEs cannot use USD frequency information for MBS interest notifications. On the other hand, as in Finding 1, if SIBy (or SIBx1) does not provide frequency information (or there is no SAI list), idle / inactive UEs can use frequencies within USD for cell reselection, which is somewhat odd. In other words, in this deployment scenario, broadcast service continuity is ensured for idle / inactive UEs, but not for connected UEs.

[0176] Finding 6: In some deployments, the continuity of broadcast services is not ensured for UEs that are connected based on Finding 5, while continuity is ensured for UEs that are idle / inactive based on Finding 1.

[0177] 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 notifications. If alignment is necessary, several solutions can be considered, as follows:

[0178] Option 1: Remove the condition "For at least one of these MBS sessions, the SIBx1 obtained from PCell includes one or more MBS SAIs for that frequency, as indicated in the USD for this session."

[0179] Option 2: The condition "or if there is no such frequency available for an MBS session in SIBx1, the frequency may be determined by USD" is followed by the additional condition "for at least one of these MBS sessions, the SIBx1 obtained from PCell includes one or more MBS SAIs for that frequency, as indicated by the USD for that session."

[0180] In either option, the UE can determine the frequencies of interest, ensuring continuity of broadcast services in all deployment scenarios (if reported by MBS interest notifications).

[0181] Proposal 1: RAN2 should discuss whether UEs can include USD frequencies in MBS interest notices even if frequencies are not provided in SIBx1, similar to frequency prioritization in cell reselection.

[0182] Proposal 2: If Proposal 1 is agreed upon, RAN2 will further discuss whether to adopt option 1 and remove the sentence “2>For at least one of these MBS sessions, the SIBx1 obtained from PCell contains one or more MBS SAIs for the relevant frequency indicated by USD for this session,” or to adopt option 2 and add the condition to section 5.x.4.3 of the TS 38.331 execution CR “or if there is no relevant frequency for an MBS session available in the SIBx1, the frequency may be determined by USD.”

[0183] Another related issue lies in section 5.x.4.5 of the currently running CR, "Configuring the Content of MBS Interest Notifications," whose procedure is very similar to that of LTE eMBMS.

[0184] 5.x.4.5MBS Interest Notification Content Settings The UE shall configure the content of the MBS interest notification as follows: If the set of MBS frequencies of interest determined according to 1>5.x.4.3 is not empty. 2>Include mbs-FreqList and, if applicable, configure 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.

[0185] As indicated by "ARFCN-ValueNR (for adjacent frequencies) included in SIBx1," if the gNB does not provide frequency information in SIBx1, the UE cannot include the frequencies of interest in the MBS interest notification, even if it has determined the frequencies of interest (as per proposal 2 above, for example).

[0186] Finding 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.

[0187] If Proposal 1 above is agreed upon, the following three options will be considered to resolve the problem.

[0188] Option A: Remove the description "ARFCN-ValueNR (for adjacent frequencies) included in SIBx1".

[0189] Option B: Change the alternative condition "Includes mbs-FreqList of MBS sessions of interest from USD" to "ARFCN-ValueNR (for adjacent frequencies) included in SIBx1".

[0190] Option C: The alternative condition is to list the ARFCN in SIB4 (NR inter-frequency) and / or SIB5 (Inter-RAT inter-frequency) instead of SIBx1.

[0191] Regardless of the option chosen, the UE can report the target frequency regardless of whether the gNB provides frequency information via SIBx1. Therefore, continuity of broadcast services is guaranteed in all deployment scenarios.

[0192] Proposal 3: If Proposal 1 is agreed upon, RAN2 will further discuss whether to adopt option A and remove the description "ARFCN-ValueNR (for adjacent frequencies) included in SIBx1", adopt option B and add the alternative condition "includes mbs-FreqList of MBS sessions of interest from USD", or adopt option C and add the alternative condition to CR 5.x.4.3 running TS 38.331 that references ARFCN in SIB4 and SIB5.

[0193] (Note 2) The features of the above-described embodiment are noted below.

[0194] (1) A communication method performed by user equipment in a mobile communication system that provides multicast broadcast services (MBS), The steps include receiving a predetermined system information block (SIB) from a serving cell, which may include frequency information indicating the correspondence between an identifier for an MBS service and the frequency on which the MBS service is provided, The steps include generating an MBS interest notification which includes a list of interest frequencies that the user device is receiving or is interested in receiving, The step of sending 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.

[0195] (2) Even if the interest frequency is not indicated in the predetermined SIB, the user device includes the interest frequency in the list based on higher-layer information held by the user device, which indicates the correspondence between the identifier of the MBS service and the frequency that provides the MBS service. The communication method described in (1) above.

[0196] (3) The frequency information indicates the correspondence between an identifier for the MBS service and an inter-frequency that provides the MBS service and is different from the frequency of the serving cell. The communication method described in (1) or (2) above.

[0197] (4) The generation step includes identifying the frequency of interest based on the upper layer information, regardless of the frequency information in the predetermined SIB. The communication method described in any of (1) through (3) above.

[0198] (5) The generation step includes identifying the frequency of interest based on the higher-layer information, depending on whether the user device recognizes that the predetermined SIB does not contain the frequency information. The communication method described in any of (1) through (4) above.

[0199] (6) The method further includes the step of receiving a cell reselection SIB from the serving cell that exhibits an inter frequency different from the frequency of the serving cell, The generation step includes identifying the frequency of interest based on the cell reselection SIB and the higher layer information, in response to the user device recognizing that the predetermined SIB does not contain the frequency information. The communication method described in any of (1) through (5) above.

[0200] (7) The generation step includes setting all MBS interest frequencies identified based on the upper layer information, regardless of the frequency information in the predetermined SIB, into the list. The communication method described in any of (1) through (6) above.

[0201] (8) The generation step includes setting all MBS interest frequencies identified based on the higher layer information into the list, in response to the user device recognizing that the predetermined SIB does not contain the frequency information. The communication method described in any of (1) through (7) above.

[0202] (9) The generation step includes, in response to the user device recognizing that the predetermined SIB does not contain the frequency information, setting all MBS interest frequencies identified based on the cell reselection SIB and the higher layer information into the list. The communication method described in any of (1) through (8) above.

[0203] (10) The generating step includes assigning to the list a source identifier that indicates on what information the interest frequencies shown in the list were identified and / or set. The communication method described in any of (1) through (9) above.

[0204] (11) The above generation step is, The steps include classifying each of the aforementioned interest frequencies according to the information source on which they were identified, The step includes setting each of the aforementioned interest frequencies to the corresponding list among the lists of information sources. The communication method described in any of (1) through (10) above.

[0205] (12) A user device used in a mobile communication system that provides multicast broadcast services (MBS), A receiving unit that receives a predetermined system information block (SIB) from a serving cell, which may include frequency information indicating the correspondence between an identifier for an MBS service and the frequency on which the MBS service is provided. A control unit that generates an MBS interest notification, which includes a list of interest frequencies that the user device is receiving or is interested in receiving, The system includes a transmission unit 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 shown in the predetermined SIB. User device. [Explanation of symbols]

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

Claims

1. A communication method performed by user equipment in a mobile communication system that provides multicast broadcast services (MBS), Receiving a predetermined system information block (SIB) from a serving cell, which includes information indicating the correspondence between MBS area identifiers and frequencies, To generate 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; The MBS interest notification is transmitted to the serving cell. The above generation includes, when receiving the predetermined SIB, including the interest frequency in the list even if the interest frequency is not included in the predetermined SIB, if the interest frequency is indicated in the USD (User Service Description). Communication method.

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

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

4. The above generation includes setting all MBS interest frequencies identified based on the USD into the list. The communication method according to claim 1.

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

6. The system further includes receiving a cell reselection SIB from the serving cell that exhibits an inter frequency different from the frequency of the serving cell. The generation described above includes identifying the frequency of interest based on the cell reselection SIB and the USD information, in response to the user device recognizing that the predetermined SIB does not contain the information. The communication method according to claim 5.

7. The generation described above includes setting all MBS interest frequencies identified based on the USD into the list, in response to the user device recognizing that the predetermined SIB does not contain the information described above. The communication method according to claim 4.

8. The generation described above includes setting all MBS interest frequencies identified based on the cell reselection SIB and the USD into the list, in response to the user device recognizing that the predetermined SIB does not contain the information described above. The communication method according to claim 7.

9. The above generation includes assigning to the list a source identifier that indicates on what information the interest frequencies shown in the list were identified and / or set. The communication method according to any one of claims 1 to 8.

10. The above generation is, Each of the aforementioned frequencies of interest is classified according to the information source on which it was identified, This includes setting each of the aforementioned interest frequencies to the corresponding list among the lists of information sources. The communication method according to any one of claims 1 to 8.

11. The above generation includes generating priority information indicating the priority of whether to prioritize receiving the MBS frequency or receiving the unicast, The communication method according to claim 1.

12. A user device used in a mobile communication system that provides multicast broadcast services (MBS), A receiving unit that receives a predetermined system information block (SIB) from a serving cell, which includes information indicating the correspondence between MBS area identifiers and frequencies, A control unit that generates an MBS interest notification, which includes a list of interest frequencies that the user device is receiving or is interested in receiving, The system includes a transmission unit that transmits the aforementioned MBS interest notification to the serving cell, When the control unit is receiving 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), it will include the frequency of interest in the list. User device.

13. A chipset for user equipment used in a mobile communication system that provides multicast broadcast services (MBS), A process of receiving a predetermined system information block (SIB) from a serving cell, which includes information indicating the correspondence between MBS area identifiers and frequencies, The interest frequency is an MBS frequency that the user device is receiving or is interested in receiving. The process of generating an MBS interest notification that includes the list shown, The process of sending the aforementioned MBS interest notification to the serving cell is performed, The generation process includes, when the predetermined SIB is received, the process of including the interest frequency in the list even if the interest frequency is not included in the predetermined SIB, if the interest frequency is indicated by USD (User Service Description). Chipset.

14. In a user device used in a mobile communication system that provides multicast broadcast services (MBS), A process of receiving a predetermined system information block (SIB) from a serving cell, which includes information indicating the correspondence between MBS area identifiers and frequencies, The interest frequency is an MBS frequency that the user device is receiving or is interested in receiving. The process of generating an MBS interest notification that includes the list shown, The process of sending the aforementioned MBS interest notification to the serving cell is performed, The generation process includes, when the predetermined SIB is received, the process of including the interest frequency in the list even if the interest frequency is not included in the predetermined SIB, if the interest frequency is indicated by USD (User Service Description). program.

15. In a mobile communication system equipped with user devices and providing multicast broadcast services (MBS), The User device is A predetermined system information block (SIB) containing information indicating the correspondence between MBS area identifiers and frequencies is received from the serving cell. The system generates 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. The aforementioned MBS interest notification is sent to the serving cell. When receiving the predetermined SIB, even if the frequency of interest is not included in the predetermined SIB, if the frequency of interest is indicated in the USD (User Service Description), the frequency of interest is included in the list. Mobile communication system.

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