Communication methods, user devices, network nodes, programs, chipsets, and systems

Abstract

This invention provides communication methods, user equipment, network nodes, programs, chipsets, and systems for use in mobile communication systems that provide multicast / broadcast services (MBS). [Solution] The method comprises a network node (gNB) transmitting a first PTM (Point-to-Multipoint) configuration, including an MBS session identifier for a broadcast MBS session, on a first multicast control channel (MCCH) for broadcast communication services, and the network node transmitting a second PTM configuration, including an MBS session identifier for a multicast MBS session, on a second MCCH for multicast communication services, wherein one MBS session identifier identifies either one broadcast MBS session or one multicast MBS session.

Description

Technical Field

[0001] The present disclosure relates to a communication method used in a mobile communication system. Background Art

[0002] In 3GPP (3rd Generation Partnership Project), technical specifications for NR (New Radio), which is the fifth-generation (5G) radio access technology, have been stipulated. Compared with LTE (Long Term Evolution), which is the fourth-generation (4G) radio access technology, NR has characteristics such as high speed, large capacity, high reliability, and low latency. In 3GPP, technical specifications for 5G / NR multicast / broadcast service (MBS) have been stipulated.

[0003] In 3GPP Release 17, MBS multicast reception (that is, multicast reception) can only be performed by user equipment in a radio resource control (RRC) connected state (see, for example, Non-Patent Document 1). In contrast, in 3GPP Release 18, technical specifications are scheduled to be extended to enable user equipment in an RRC inactive state to perform multicast reception. Prior Art Documents Non-Patent Documents

[0004] Non-Patent Document 1 3GPP Technical Specification: TS 38.300 V17.3.0 Summary of Invention

[0005] The first aspect of the communication method is a method used in a mobile communication system that provides multicast / broadcast services (MBS). The communication method includes the steps of: a network node providing two types of MCCHs in its cell: a first multicast control channel (MCCH) for broadcast communication services and a second MCCH for multicast communication services; and the network node transmitting mapping information to a user device indicating the correspondence between an MBS session identifier of an MBS session and the type of MCCH that transmits the PTM (Point-to-Multipoint) settings corresponding to the MBS session.

[0006] The second aspect of the communication method is a method used in a mobile communication system that provides multicast / broadcast services (MBS). The communication method includes the steps of: a network node transmitting a first PTM (Point-to-Multipoint) setting, including the MBS session identifier of a broadcast MBS session, on a first multicast control channel (MCCH) for broadcast communication services; the network node transmitting a second PTM setting, including the MBS session identifier of a multicast MBS session, on a second MCCH for multicast communication services; and the network node controlling MCCH transmission so that it does not transmit PTM settings including the same MBS session identifier on the first MCCH and the second MCCH. [Brief explanation of the drawing]

[0007] [Figure 1] This is a diagram showing an example configuration of a mobile communication system according to the embodiment. [Figure 2] This figure shows an example configuration of a UE (User Equipment) according to the embodiment. [Figure 3] This figure shows an example configuration of a 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 is a diagram illustrating an example of system operation according to the embodiment. [Figure 7] This figure shows an example of a first operation pattern according to the embodiment. [Figure 8] This figure shows an example of gNB operation related to the second operation pattern. [Figure 9] This figure shows an example of UE operation related to the second operation pattern. [Modes for carrying out the invention]

[0008] A mobile communication system according to an embodiment will be described with reference to the drawings. In the drawings, identical or similar parts are denoted by the same or similar reference numerals.

[0009] (1) Example of system configuration Figure 1 shows an example configuration of a mobile communication system 1 according to an embodiment. The mobile communication system 1 conforms to the 5th Generation System (5GS) of the 3GPP standard. In the following explanation, 5GS will be used as an example, but the mobile communication system may also incorporate an LTE (Long Term Evolution) system at least partially. The mobile communication system may also incorporate a 6th Generation (6G) system at least partially.

[0010] The mobile communication system 1 comprises user equipment (UE) 100, a 5G radio access network (NG-RAN) 10, and a 5G core network (5GC) 20. Hereinafter, NG-RAN 10 may be simply referred to as RAN 10, and 5GC 20 may be simply referred to as the core network (CN) 20. RAN 10 and CN 20 constitute the network of the mobile communication system 1.

[0011] UE100 is a mobile wireless communication device. UE100 can be any device used by a user. For example, UE100 can be a mobile phone terminal (including smartphones) and / or a tablet terminal, a notebook PC, a communication module (including a communication card or chipset), a sensor or device attached to a sensor, a vehicle or device attached to a vehicle (Vehicle UE), or an aircraft or device attached to an aircraft (Aerial UE).

[0012] NG-RAN10 includes base stations (referred to as "gNBs" in 5G systems) 200. The gNBs 200 are interconnected via the Xn interface, which is an inter-base station interface. Each gNB 200 manages one or more cells. The gNB 200 performs wireless communication with UEs 100 that have established a connection with its own cell. The gNB 200 has radio resource management (RRM) functions, user data routing functions (hereinafter simply referred to as "data"), measurement and control functions for mobility control and scheduling, etc. "Cell" is used as a term to indicate the smallest unit of a wireless communication area. "Cell" is also used as a term to indicate a function or resource that performs wireless communication with the UE 100. One cell belongs to one carrier frequency (hereinafter simply referred to as "frequency").

[0013] Furthermore, gNBs can also connect to the EPC (Evolved Packet Core), which is the core network of LTE. LTE base stations can also connect to 5GCs. LTE base stations and gNBs can also be connected via an inter-base station interface.

[0014] 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.

[0015] Figure 2 shows an example configuration of UE100 (user device) according to an embodiment. UE100 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 gNB200.

[0016] 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.

[0017] 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.

[0018] The control unit 130 performs various types of control and processing in the UE 100. Such processing includes processing of each layer described later. The operations of the UE 100 described above and below may be operations controlled by the control unit 130. 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 / decoding, and the like on baseband signals. The CPU executes programs stored in the memory to perform various types of processing.

[0019] Figure 3 is a diagram showing a configuration example of a gNB 200 (base station) according to the embodiment. The gNB 200 includes a transmission unit 210, a reception unit 220, a control unit 230, and a backhaul communication unit 240. The transmission unit 210 and the reception unit 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.

[0020] The transmission unit 210 performs various types of transmission 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 from the control unit 230 into a wireless signal, and transmits the wireless signal from the antenna.

[0021] The reception unit 220 performs various types of reception under the control of the control unit 230. The reception unit 220 includes an antenna and a receiver. The receiver converts a wireless signal received by the antenna into a baseband signal (reception signal), and outputs the baseband signal to the control unit 230.

[0022] The control unit 230 performs various control and processing operations in the gNB200. Such processing includes processing in each layer described later. The operation of the gNB200 described above and below may also be controlled by the control unit 230. 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 operations.

[0023] 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.

[0024] Figure 4 shows the configuration of the protocol stack for the user plane's wireless interface that handles data.

[0025] 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.

[0026] 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.

[0027] 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.

[0028] 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.

[0029] The PDCP layer performs header compression / decompression, encryption / decryption, etc.

[0030] 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.

[0031] Figure 5 shows the configuration of the protocol stack of the wireless interface of the control plane that handles signaling (control signals).

[0032] 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.

[0033] 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.

[0034] The NAS layer (also simply referred to as "NAS"), 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, the layer below the NAS layer is called the AS layer (also simply referred to as "AS").

[0035] (2) Overview of MBS Mobile communication system 1 can perform resource-efficient distribution through multicast / broadcast services (MBS).

[0036] (2.1) MBS Broadcast In the case of broadcast communication services (also known as "MBS broadcast"), the same service and the same specific content data are provided simultaneously to all UE100s within a geographical area. That is, all UE100s within the broadcast service area are permitted to receive the data. Broadcast communication services are delivered to the UE100s using broadcast MBS sessions, which are a type of MBS session. UE100s can receive broadcast MBS sessions regardless of whether they are in the RRC idle, RRC inactive, or RRC connected state.

[0037] Broadcast communication services utilize Point-to-Multipoint (PTM) distribution. In PTM transmission, the gNB200 distributes a single copy of an MBS packet to a set (group) consisting of multiple UE100s. For example, the gNB200 schedules a group-common PDSCH, which has a Cyclic Redundancy Code (CRC) scrambled by a group-common RNTI (G-RNTI), using a group-common PDCCH.

[0038] For broadcast communication services, the UE100 receives a broadcast MBS session in the following steps: First, the UE100 receives a System Information Block Type 20 (SIB20) from the gNB200. The SIB20 contains the settings for a Multicast Control Channel (MCCH), which is a type of logical channel. Second, based on the SIB20, the UE100 receives the MCCH from the gNB200. The MCCH contains the PTM settings (PTM settings for broadcast). The PTM settings include the MBS session identifier (also called "TMGI (Temporary Mobile Group Identity)"), settings for a Multicast Traffic Channel (MTCH), which is a type of logical channel (MTCH settings), and settings for a Broadcast MRB, which is a Multicast Radio Bearer (MRB) for the broadcast MBS session. The information transmitted by the MCCH is sometimes called MBS broadcast control information. Third, based on the MCCH, the UE100 receives the MTCH. MTCH transmits broadcast MBS sessions (specifically, MBS data belonging to broadcast MBS sessions).

[0039] MCCH is a PTM downlink channel for transmitting MBS broadcast control information associated with one or more MTCHs from network 10 to UE100. MTCH is a PTM downlink channel for transmitting MBS data from either a multicast MBS session or a broadcast MBS session from network 10 to UE100.

[0040] Furthermore, the MTCH settings are associated with the MBS session identifier and are settings related to MTCH reception, and include at least one of the following, for example, group RNTI (G-RNTI), intermittent reception settings (DRX settings or scheduling information: MTCH transmission ON time, MTCH transmission period, reference time and time offset, HARQ retransmission settings), Layer 2 settings (PDCP settings, RLC settings), and physical channel settings (PDCCH settings, PDSCH settings, SSB mapping settings).

[0041] (2.2) MBS Multicast In the case of multicast communication services (also known as "MBS multicast"), the same service and the same specific content data are provided simultaneously to a specific set of UEs. That is, not all UE100s within a multicast service area are permitted to receive the data. Multicast communication services are delivered to UE100s using multicast MBS sessions, which are a type of MBS session.

[0042] UE100 can only receive multicast MBS sessions after joining the multicast MBS session. Joining a multicast MBS session may mean that UE100 is registered with network 5 (CN20) as a device capable of receiving the multicast MBS session.

[0043] For multicast communication services, 3GPP Release 17 allows only UE100s in an RRC-connected state to receive multicast MBS sessions. However, 3GPP Release 18 is planned to extend this so that UE100s in an RRC-inactive state can also receive multicast MBS sessions.

[0044] (2.2.1) Multicast reception in RRC connected state A UE100 in RRC connected state can receive multicast MBS sessions (specifically, MBS data belonging to a multicast MBS session) using mechanisms such as PTP (Point-to-Point) and / or PTM (Point-to-Multipoint) distribution.

[0045] In the case of multicast communication services, UE100 in the RRC connected state receives multicast MBS sessions in the following procedure. First, UE100 receives an RRC Reconfiguration message from gNB200. The RRC Reconfiguration message is transmitted on the Dedicated Control Channel (DCCH). The RRC Reconfiguration message transmits the settings for the MTCH for receiving multicast MBS sessions (MTCH settings) and the settings for the multicast MRB, which is the MRB for the multicast MBS session. Second, UE100 receives the MTCH based on the RRC Reconfiguration message. The MTCH transmits the multicast MBS session (specifically, the MBS data belonging to the multicast MBS session).

[0046] (2.2.2) Multicast reception in RRC inactive state A UE100 in an RRC inactive state can receive multicast MBS sessions (specifically, MBS data belonging to multicast MBS sessions) using the PTM distribution mechanism.

[0047] In the case of multicast communication services, a UE100 in an RRC inactive state can receive multicast MBS sessions in the following manner. First, the UE100 in an RRC inactive state receives a newly introduced system information block (also called the "new SIB") from the gNB200. The new SIB includes the configuration of a newly introduced MCCH (also called the "multicast MCCH"). Second, the UE100 in an RRC inactive state receives the multicast MCCH from the gNB200 based on the new SIB. The multicast MCCH includes the PTM configuration (multicast PTM configuration). The PTM configuration transmits the configuration for the MTCH for receiving multicast MBS sessions (MTCH configuration) and the configuration of the multicast MRB, which is the MRB for multicast MBS sessions. Third, the UE100 in an RRC inactive state receives the MTCH based on the multicast MCCH. The MTCH transmits the multicast MBS session (specifically, the MBS data belonging to the multicast MBS session).

[0048] If the gNB200 configures the UE100 to receive multicast in an RRC inactive state, it can send the PTM configuration to the UE100 using an RRC Release message that includes the suspend configuration. In this case, when the UE100 receives the RRC Release message containing the PTM configuration from the gNB200, it transitions to the RRC inactive state and receives multicast MBS sessions in the RRC inactive state.

[0049] In the following, to distinguish it from the newly introduced multicast MCCH, the conventional MCCH defined for MBS broadcasting will also be referred to as the "broadcast MCCH."

[0050] (2.2.3) Group Notifications If there is temporarily no data to send to UE100 in an active multicast MBS session, gNB200 may transition UE100 to the RRC inactive state. When the multicast MBS session is deactivated, gNB200 may transition UE100 to the RRC idle state or the RRC inactive state.

[0051] A gNB200 that supports MBS will use the group notification mechanism to notify UE100s that are in an RRC idle or RRC inactive state when a multicast MBS session is activated by CN20. For example, a gNB200 that supports MBS may use the group notification mechanism to notify UE100s that are in an RRC inactive state if a multicast MBS session is already activated and there is multicast MBS session data to be distributed on the gNB200.

[0052] Upon receiving a group notification, UE100 reconnects to network 5 or resumes the connection and transitions to the RRC connected state. The group notification is processed by the paging RNTI (P-RNTI) on the PDCCH, and the paging channel is monitored by UE100.

[0053] The group notification paging message includes an MBS session identifier used to page all UE100s in the RRC idle and RRC inactive states that are participating in the associated multicast MBS session. In other words, UE100s are not paged individually.

[0054] When UE100 transitions to the RRC Connected state, UE100 may stop monitoring group notifications associated with a particular multicast MBS session. In other words, UE100 stops checking for MBS session identifiers in paging messages. UE100 does not monitor group notifications if UE100 leaves this multicast MBS session, network 5 requests UE100 to leave, or network 5 releases the multicast MBS session.

[0055] Group notifications may be made via MCCH or via MCCH change notifications. When using MCCH, the determination may be made based on whether or not the MCCH setting for the MBS session of interest exists in the MCCH. When using MCCH change notifications, the group notification may be made in a predetermined bit of the DCI.

[0056] (3) System operation example The following describes an example of system operation according to the embodiment. Figure 6 is a diagram illustrating an example of system operation according to the embodiment.

[0057] The gNB200 provides two types of MCCHs within its cell: a first MCCH for broadcast communication services (also referred to as the "broadcast MCCH") and a second MCCH for multicast communication services (also referred to as the "multicast MCCH").

[0058] The gNB200 transmits the first PTM setting (also referred to as the "broadcast PTM setting"), which includes the MBS session identifier for the broadcast MBS session, via the broadcast MCCH. The gNB200 also transmits the second PTM setting (also referred to as the "multicast PTM setting"), which includes the MBS session identifier for the multicast MBS session, via the multicast MCCH.

[0059] Here, the quality of service (QoS) required for a multicast MBS session differs from that required for a broadcast MBS session. Therefore, by providing the multicast MCCH as a separate logical channel from the broadcast MCCH, it becomes easier to transmit PTM settings according to the required QoS. For example, the repetition period of the multicast MCCH may be set to be shorter than that of the broadcast MCCH. The modification period of the multicast MCCH may also be set to be shorter than that of the broadcast MCCH.

[0060] Thus, two types of MCCHs, broadcast MCCHs and multicast MCCHs, can coexist in a single cell. Therefore, UE100 (especially UE100 in an RRC inactive state) can receive broadcast MCCHs (broadcast PTM settings) and multicast MCCHs (multicast PTM settings). The following embodiment describes the operation of the mobile communication system 1 when the two types of MCCHs are coexisting.

[0061] (3.1) First operation pattern A first operation pattern according to the embodiment will be described.

[0062] Even in multicast MBS sessions, the required QoS requirements may not be very high. For example, subscription-based TV broadcasting services are a type of multicast communication service, but generally, the required QoS requirements are not very high. In such cases, even in multicast MBS sessions, it is more efficient to transmit PTM settings using the broadcast MCCH, and the method of transmitting multicast MBS session PTM settings using the broadcast MCCH can be adopted.

[0063] However, the UE100 can only determine which MBS session's PTM settings a given MCCH carries after it receives the MCCH and decodes the PTM settings. Assuming that the PTM settings for multicast MBS sessions can be transmitted via broadcast MCCHs, a UE100 receiving or interested in receiving multicast communication services would need to receive and decode both types of MCCHs, which increases the processing load and power consumption of the UE100.

[0064] Therefore, in the first operation pattern, the gNB200 sends mapping information (also referred to as "MCCH mapping information") to the UE100 that shows the correspondence between the MBS session identifier (TMGI) of the MBS session and the type of MCCH that transmits the PTM settings corresponding to the MBS session. For example, the gNB200 sends the MCCH mapping information in either an RRC Release message, a System Information Block (SIB), or a paging message (group notification).

[0065] The UE100 receives MCCH mapping information from the gNB200. Then, for example, in an RRC inactive state, the UE100 identifies the type of MCCH it should receive based on the MCCH mapping information. That is, the UE100 identifies, based on the MCCH mapping information, which type of MCCH transmits the PTM settings for the MBS session it is receiving or is interested in receiving, from among broadcast MCCHs and multicast MCCHs. As a result, the UE100 can receive and decode only the MCCHs that transmit the PTM settings for the MBS session it is receiving or is interested in receiving. Therefore, even when two types of MCCHs are mixed, the increase in the processing load and power consumption of the UE100 can be suppressed.

[0066] Figure 7 shows an example of the first operation pattern according to the embodiment.

[0067] In step S101, the gNB200 decides whether to transmit the PTM settings for a given MBS session via the broadcast MCCH or the multicast MCCH. Here, it is assumed that the MBS session identifier of the MBS session that the UE100 is receiving or interested in receiving is MBS session identifier #1. The gNB200 decides whether to notify the PTM settings for MBS session identifier #1 via the broadcast MCCH or the multicast MCCH. Furthermore, if the gNB200 provides multiple MBS sessions in its own cell, it may decide whether to transmit the PTM settings for each of those multiple MBS sessions (multiple MBS session identifiers) via the broadcast MCCH or the multicast MCCH.

[0068] In step S102, gNB200 sends MCCH mapping information to UE100 that shows the correspondence between the MBS session identifier (TMGI) of an MBS session and the type of MCCH that transmits the PTM settings corresponding to that MBS session. UE100 receives the MCCH mapping information. For example, the MCCH mapping information includes the MBS session identifier and the MCCH type information associated with that MBS session identifier. In the illustrated example, the MCCH mapping information is in list format and includes at least one set of MBS session identifiers and MCCH type information.

[0069] The MCCH type information may also indicate that the PTM settings for the corresponding MBS session are transmitted via the broadcast MCCH. For example, the MCCH type information may be set to 1 (true) only when the PTM settings for the corresponding MBS session are transmitted via the broadcast MCCH.

[0070] Alternatively, the MCCH type information may indicate that the PTM settings for the corresponding MBS session are transmitted via a multicast MCCH. For example, the MCCH type information may be set to 1 (true) only when the PTM settings for the corresponding MBS session are transmitted via a multicast MCCH.

[0071] Alternatively, the MCCH type information may indicate whether the PTM settings for the corresponding MBS session are transmitted using a broadcast MCCH or a multicast MCCH. For example, the MCCH type information may be set to one of two values: a first value indicating a broadcast MCCH and a second value indicating a broadcast MCCH.

[0072] Alternatively, the MCCH type information may be an identifier (LCID) of the logical channel that transmits the MCCH. The correspondence between the LCID and the MCCH type (broadcast MCCH, multicast MCCH) may be predetermined. That is, the correspondence may be fixed and hardcoded in the technical specification. Alternatively, the correspondence may be determined by the gNB200, and the setting value by the gNB200 may be broadcast as system information or similar.

[0073] Alternatively, the MCCH type information may be the intermittent reception (DRX) setting for transmitting the MCCH. If the DRX settings for the MCCH are listed and the MCCH and DRX setting are associated by specifying the index of the DRX setting list in each MCCH setting, the MCCH type information may be the index of that DRX setting.

[0074] Furthermore, under the premise that the MCCH settings for broadcast MCCHs are transmitted using SIB20 and the MCCH settings for multicast MCCHs are transmitted using the new SIB, the MCCH mapping information (MCCH type information) may be SIB mapping information (SIB type information).

[0075] The gNB200 may transmit MCCH mapping information to the RRC-connected UE100 via dedicated signaling. For example, if the UE100 is participating in a multicast MBS session, the gNB200 may transmit MCCH mapping information to the UE100 via dedicated signaling, showing the correspondence between the MBS session identifier of the multicast MBS session and the type of MCCH that transmits the PTM settings corresponding to the multicast MBS session.

[0076] The dedicated signaling may be an RRC Release message (specifically, an RRC Release message including a suspend setting) that transitions the UE100 from the RRC Connected state to the RRC Inactive state. The RRC Release message may also include the PTM settings for the multicast MBS session in which the UE100 is participating. If the gNB200 subsequently changes the PTM settings, the changed PTM settings may be transmitted via MCCH (broadcast MCCH or multicast MCCH).

[0077] Alternatively, gNB200 may transmit MCCH mapping information to UE100 via broadcast signaling. In this case, UE100 in all RRC states (RRC connected state, RRC inactive state, RRC idle state) may be able to receive the MCCH mapping information. For example, if gNB200 provides multiple MBS sessions in its cell, it may transmit MCCH mapping information to UE100 via broadcast signaling, associating each of the MBS session identifiers of those multiple MBS sessions with MCCH type information.

[0078] The broadcast signaling may be an SIB for MBS (e.g., SIB20 or New SIB). Alternatively, the broadcast signaling may be a System Information Block Type 1 (SIB1) that provides scheduling information for multiple SIBs, including an SIB for MBS. Alternatively, the broadcast signaling may be a paging message (group notification). The group notification includes an MBS session identifier for the activated multicast MBS session. When using group notifications, the MBS session identifier and MCCH type information may constitute MCCH mapping information.

[0079] In step S103, UE100 identifies the type of MCCH it should receive based on the MCCH mapping information from step S102. At this time, UE100 may be in an RRC inactive state. For example, if the MCCH mapping information includes the MBS session identifier #1 of an MBS session that UE100 is receiving or is interested in receiving, UE100 identifies either a broadcast MCCH or a multicast MCCH type based on the MCCH type information associated with the MBS session identifier #1 in the MCCH mapping information. Note that the MBS session that UE100 is interested in receiving may be a multicast MBS session in which UE100 is participating.

[0080] In step S104, UE100 may receive an SIB from gNB200 corresponding to the MCCH type identified in step S104. For example, if UE100 identifies a broadcast MCCH in step S104, it may receive SIB20 from gNB200 and obtain the broadcast MCCH setting. If UE100 identifies a multicast MCCH in step S104, it may receive a new SIB from gNB200 and obtain the multicast MCCH setting.

[0081] In step S105, UE100 receives the MCCH corresponding to the MCCH type identified in step S104 from gNB200 and obtains the PTM settings. For example, if UE100 identified a broadcast MCCH in step S104, it may receive the broadcast MCCH from gNB200 and obtain the broadcast PTM settings. If UE100 identified a multicast MCCH in step S104, it may receive the multicast MCCH from gNB200 and obtain the multicast PTM settings.

[0082] In step S106, UE100 receives the MBS session on the MTCH based on the PTM settings acquired in step S105.

[0083] In this example, it is assumed that there is one multicast MCCH in a single cell. However, multiple multicast MCCHs may be provided in a single cell. These multiple multicast MCCHs may be identifiable by identifiers (indexes). Under such assumptions, the MCCH type information in the MCCH mapping information may be the identifier (index) of one of the multiple multicast MCCHs, the logical channel identifier (LCID), and / or the corresponding DRX configuration index.

[0084] (3.2) Second operation pattern The second operation pattern according to the embodiment will be described primarily in terms of its differences from the first operation pattern described above. The second operation pattern may be implemented in combination with the first operation pattern described above.

[0085] As described above, when two types of MCCHs are mixed, if the gNB200 sends the PTM settings for a single MBS session using both the broadcast MCCH and the multicast MCCH, the UE100 is unsure which PTM settings to follow, which can lead to unexpected errors. In particular, if both the broadcast MCCH and the multicast MCCH contain different PTM settings for the same MBS session identifier, the UE100 is more likely to encounter errors.

[0086] In the second operating pattern, the gNB200 controls MCCH transmission to prevent the transmission of PTM settings containing the same MBS session identifier on both the broadcast MCCH and the multicast MCCH. That is, when the gNB200 provides both a broadcast MCCH and a multicast MCCH in its own cell, it controls the transmission of PTM settings for a single MBS session identifier on only one of the MCCHs (i.e., not on both MCCHs). This ensures that the broadcast PTM settings and multicast PTM settings do not contain PTM settings for the same MBS session, preventing unexpected errors.

[0087] UE100 performs MBS reception operations assuming that no PTM settings containing the same MBS session identifier are transmitted on the broadcast MCCH and multicast MCCH. If UE100 is not participating in a multicast MBS session, it may apply the broadcast PTM settings received on the broadcast MCCH. In other words, UE100 will not apply (ignore) the PTM settings provided on the multicast MCCH for that MBS session. On the other hand, if UE100 is participating in a multicast MBS session, it may apply the multicast PTM settings received on the multicast MCCH. In other words, UE100 will not apply (ignore) the PTM settings provided on the broadcast MCCH for that MBS session. This operation may be performed by UE100 in an RRC inactive state.

[0088] Figure 8 shows an example of the operation of the gNB200 related to the second operation pattern.

[0089] In step S201, the gNB200 determines the type of MCCH to be used for transmitting PTM settings for each MBS session provided by its cell.

[0090] In step S202, the gNB200 controls MCCH transmission so as not to send PTM settings containing the same MBS session identifier on the broadcast MCCH and the multicast MCCH.

[0091] Figure 9 shows an example of UE100 operation related to the second operation pattern.

[0092] In step S211, UE100 is receiving MBS or is interested in receiving MBS. UE100 may also be in an RRC inactive state.

[0093] If UE100 is participating in a multicast MBS session (step S212: YES), in step S213, UE100 receives a multicast MCCH from gNB200. In this case, UE100 receives the multicast MBS session on the MTCH based on the multicast PTM settings obtained on the multicast MCCH. In other words, UE100 prioritizes the PTM settings obtained on the multicast MCCH.

[0094] On the other hand, if UE100 is not participating in a multicast MBS session (step S212: NO), in step S214, UE100 receives a broadcast MCCH from gNB200. In this case, UE100 receives the broadcast MBS session on the MTCH based on the broadcast PTM settings obtained on the broadcast MCCH. In other words, UE100 prioritizes the PTM settings obtained on the broadcast MCCH.

[0095] (4) Other embodiments In the embodiments described above, multicast reception in the RRC inactive state was mainly explained, but the operation according to the embodiments described above may also be applied to multicast reception in the RRC idle state. In the case of the RRC idle state, the above-described RRC resume is read as RRC establishment.

[0096] 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. It is not necessary to execute all steps in each flow; only some steps may be executed.

[0097] 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.

[0098] In other words, UE100 may be a terminal function unit (a type of communication module) for a base station to control a repeater that performs signal relay. Such a terminal function unit is called an MT. Examples of MTs other than IAB-MT include NCR (Network Controlled Repeater)-MT and RIS (Reconfigurable Intelligent Surface)-MT.

[0099] Furthermore, the term "network node" primarily refers to a base station, but may also refer to a core network device or a part of a base station (CU, DU, or RU). Additionally, a network node may consist of a combination of at least a part of the core network device and at least a part of a base station.

[0100] 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).

[0101] The functions realized by UE100 or gNB200 (network node) may be implemented in circuitry or processing circuitry, including general-purpose processors, application-specific processors, integrated circuits, ASICs (Application Specific Integrated Circuits), CPUs (a Central Processing Unit), conventional circuits, and / or combinations thereof, programmed to realize the described functions. A processor, including transistors and other circuits, is considered circuitry or processing circuitry. A processor may be a programmed processor that executes a program stored in memory. In this specification, circuitry, unit, and means are hardware programmed to realize or perform the described functions. Such hardware may be any hardware disclosed herein, or any hardware known to be programmed to realize or perform the described functions. If such hardware is a processor that is considered to be a type of circuitry, then such circuitry, means, or unit is a combination of hardware and software used to constitute such hardware and / or processor.

[0102] The phrases “based on” and “depending on / in response to” 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.” The terms “include,” “comprise,” and variations thereof do not mean that only the listed items are included; they mean that only the listed items may be included, or that additional items may be included in addition to the listed items. Furthermore, the term “or” used in this disclosure is not intended to mean exclusive OR. Additionally, 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.

[0103] 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.

[0104] This application claims priority to U.S. Provisional Application No. 63 / 494322 (filed April 5, 2023), the entirety of which is incorporated into the specification of this application.

[0105] (5) Note The features of the above-described embodiment are noted below.

[0106] (Note 1) A communication method used in a mobile communication system that provides multicast / broadcast services (MBS), The network node provides two types of multicast control channels (MCCHs) in its cells: a first multicast control channel (MCCH) for broadcast communication services and a second MCCH for multicast communication services. The network node transmits mapping information to a user device indicating the correspondence between the MBS session identifier of an MBS session and the type of MCCH that transmits the PTM (Point-to-Multipoint) settings corresponding to the MBS session. Communication method.

[0107] (Note 2) The transmission step includes transmitting the mapping information in one of the following: an RRC release message, a system information block (SIB), or a paging message. The communication method described in Appendix 1.

[0108] (Note 3) The user device receives the mapping information, The user device further includes the step of identifying the type of MCCH that the user device should receive based on the mapping information. The communication method described in Appendix 1 or 2.

[0109] (Note 4) The user device further comprises the step of receiving the identified type of MCCH while the RRC is inactive. The communication method described in Appendix 3.

[0110] (Note 5) A communication method used in a mobile communication system that provides multicast / broadcast services (MBS), The network node transmits a first PTM (Point-to-Multipoint) configuration, including the MBS session identifier of the broadcast MBS session, on the first multicast control channel (MCCH) for the broadcast communication service. The network node transmits a second PTM configuration, including the MBS session identifier of the multicast MBS session, on a second MCCH for multicast communication services. The network node controls MCCH transmission so that it does not transmit PTM settings containing the same MBS session identifier on the first MCCH and the second MCCH. Communication method.

[0111] (Note 6) If the user device is not participating in the multicast MBS session, the first PTM settings received on the first MCCH are applied. If the user device is participating in the multicast MBS session, the step of applying the second PTM settings received on the second MCCH is also included. The communication method described in Appendix 5.

[0112] (Note 7) The step of applying the second PTM setting includes the step of the user device in an RRC inactive state applying the second PTM setting. The communication method described in Appendix 6. [Explanation of Symbols]

[0113] 1: Mobile communication systems 5: Network 10: RAN 20 :CN 100: UE (User Device) 110: Receiving unit 120: Transmitter 130: Control Unit 200:gNB (base station) 210: Transmitter 220: Receiving unit 230: Control Unit 240: Backhaul Communications Department

Claims

1. A communication method used in a mobile communication system that provides multicast / broadcast services (MBS), The network node transmits a first PTM (Point-to-Multipoint) configuration, including the MBS session identifier of the broadcast MBS session, on the first multicast control channel (MCCH) for the broadcast communication service, The network node transmits a second PTM setting, including the MBS session identifier of the multicast MBS session, on a second MCCH for multicast communication services. A single MBS session identifier identifies either a broadcast MBS session or a multicast MBS session. Communication method.

2. If the user device is not participating in the multicast MBS session, the first PTM setting received on the first MCCH shall be applied. If the user device is participating in the multicast MBS session, the second PTM setting received by the second MCCH is applied. The communication method according to claim 1.

3. A user device used in a mobile communication system that provides multicast / broadcast services (MBS), The receiving unit has a first PTM (Point-to-Multipoint) setting, which includes the MBS session identifier of a broadcast MBS session, received on a first multicast control channel (MCCH) for broadcast communication services, and a second PTM setting, which includes the MBS session identifier of a multicast MBS session, received on a second MCCH for multicast communication services. A single MBS session identifier identifies either a broadcast MBS session or a multicast MBS session. User device.

4. A network node used in a mobile communication system that provides multicast / broadcast services (MBS), The device has a transmitting unit that transmits a first PTM (Point-to-Multipoint) setting, including the MBS session identifier of a broadcast MBS session, on a first multicast control channel (MCCH) for broadcast communication services, and a second PTM setting, including the MBS session identifier of a multicast MBS session, on a second MCCH for multicast communication services. A single MBS session identifier identifies either a broadcast MBS session or a multicast MBS session. Network node.

5. A program for a user device used in a mobile communication system that provides multicast / broadcast services (MBS), wherein the user device has the following capabilities: The process involves receiving the first PTM (Point-to-Multipoint) setting, which includes the MBS session identifier of the broadcast MBS session, on the first multicast control channel (MCCH) for the broadcast communication service, The process involves receiving the second PTM settings, including the MBS session identifier of the multicast MBS session, on the second MCCH for multicast communication services, and then executing the following: A single MBS session identifier identifies either a broadcast MBS session or a multicast MBS session. program.

6. A chipset for user equipment used in a mobile communication system that provides multicast / broadcast services (MBS), The process involves receiving the first PTM (Point-to-Multipoint) setting, which includes the MBS session identifier of the broadcast MBS session, on the first multicast control channel (MCCH) for the broadcast communication service, The process of receiving the second PTM setting, including the MBS session identifier of the multicast MBS session, on the second MCCH for multicast communication services is performed. A single MBS session identifier identifies either a broadcast MBS session or a multicast MBS session. Chipset.

7. A system including user equipment and network nodes used in a mobile communication system that provides multicast / broadcast services (MBS), The user device has a receiving unit that receives a first PTM (Point-to-Multipoint) setting, including the MBS session identifier of a broadcast MBS session, from the network node on a first multicast control channel (MCCH) for broadcast communication services, and a second PTM setting, including the MBS session identifier of a multicast MBS session, from the network node on a second MCCH for multicast communication services. The network node has a transmission unit that transmits the first PTM setting to the user device via the first MCCH and the second PTM setting to the user device via the second MCCH. A single MBS session identifier identifies either a broadcast MBS session or a multicast MBS session. system.

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