COMMUNICATION METHOD, AGGREGATION UNIT, DISTRIBUTION UNIT, MOBILE COMMUNICATION SYSTEM, CHIP SET, AND PROGRAM

Abstract

This communication method, which is used in a communication system for providing a multicast / broadcast service (MBS), includes a step in which an aggregation unit included in a base station transmits MBS-related information to a distribution unit included in the base station on a network interface between the aggregation unit and the distribution unit. The MBS-related information relates to a user device receiving or interested in receiving an MBS service provided by a secondary cell under the distribution unit.

Description

Communication method, aggregation unit, and distribution unit

[0001] The present disclosure relates to a communication method, an aggregation unit, and a distribution unit for use in a mobile communication system.

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

[0003] 3GPP Technical Specification: TS 38.300 V17.1.0

[0004] A communication method according to a first aspect is a communication method for use in a mobile communication system providing a multicast / broadcast service (MBS), comprising a step of an aggregation unit included in a base station transmitting MBS-related information to a distributed unit included in the base station over a network interface between the aggregation unit and the distributed unit, the MBS-related information being information about user equipment receiving or interested in receiving an MBS service provided in a secondary cell under the control of the distributed unit.

[0005] According to a second aspect, an aggregation unit is included in a base station in a mobile communication system providing a multicast / broadcast service (MBS), and includes a transmitter configured to transmit MBS-related information to a distributed unit included in the base station over a network interface between the aggregation unit and the distributed unit, the MBS-related information being information about user equipment receiving or interested in receiving an MBS service provided in a secondary cell under the control of the distributed unit.

[0006] A distributed unit according to a third aspect is a distributed unit included in a base station in a mobile communication system providing a multicast / broadcast service (MBS), and includes a receiving unit configured to receive MBS-related information from an aggregation unit included in the base station over a network interface between the aggregation unit and the distributed unit, the MBS-related information being information about user equipment receiving or interested in receiving an MBS service provided in a secondary cell under the control of the distributed unit.

[0007] 1 is a diagram showing the configuration of a mobile communication system according to an embodiment. FIG. 2 is a diagram showing the configuration of a UE (user equipment) according to an embodiment. FIG. 3 is a diagram showing the configuration of a gNB (base station) according to an embodiment. FIG. 4 is a diagram showing the configuration of a protocol stack of a radio interface of a user plane that handles data. FIG. 5 is a diagram showing the configuration of a protocol stack of a radio interface of a control plane that handles signaling (control signals). FIG. 6 is a diagram for explaining an overview of the operation of a mobile communication system according to an embodiment. FIG. 7 is a diagram showing a first operation example of the mobile communication system according to an embodiment. FIG. 8 is a diagram showing a second operation example of the mobile communication system according to an embodiment.

[0008] 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.

[0009] (1) Configuration of a Mobile Communication System FIG. 1 is a diagram showing the configuration of a mobile communication system according to an embodiment. The mobile communication system 1 conforms to the 3GPP standard 5th Generation System (5GS). While the following description uses 5GS as an example, the mobile communication system may also be at least partially based on an LTE (Long Term Evolution) system. The mobile communication system may also be at least partially based on a 6th Generation (6G) system.

[0010] The mobile communication system 1 includes a user equipment (UE) 100, a 5G radio access network (NG-RAN: Next Generation Radio Access Network) 10, and a 5G core network (5GC: 5G Core Network) 20. Hereinafter, the NG-RAN 10 may be simply referred to as the RAN 10. Furthermore, the 5GC 20 may be simply referred to as the core network (CN) 20.

[0011] The UE 100 is a mobile wireless communication device. The UE 100 may be any device that is used by a user. For example, the UE 100 may be a mobile phone terminal (including a smartphone) and / or a tablet terminal, a notebook PC, a communication module (including a communication card or a chipset), a sensor or a device provided in a sensor, a vehicle or a device provided in a vehicle (Vehicle UE), or an aircraft or a device provided in an aircraft (Aerial UE).

[0012] The NG-RAN 10 includes a base station (called a "gNB" in a 5G system) 200. The gNBs 200 are connected to each other via an Xn interface, which is an interface between base stations. The gNB 200 manages one or more cells. The gNB 200 performs wireless communication with a UE 100 that has established a connection with its own cell. The gNB 200 has a radio resource management (RRM) function, a routing function for user data (hereinafter simply referred to as "data"), a measurement control function for mobility control and scheduling, and the like. The term "cell" is used to indicate the smallest unit of a wireless communication area. The term "cell" is also used to indicate a function or resource for wireless communication with the UE 100. One cell belongs to one carrier frequency (hereinafter simply referred to as "frequency").

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

[0014] The 5GC20 includes an AMF (Access and Mobility Management Function) and a UPF (User Plane Function) 300. The AMF performs various mobility controls for the UE 100. The AMF manages the mobility of the UE 100 by communicating with the UE 100 using NAS (Non-Access Stratum) signaling. The UPF controls data forwarding. The AMF and the UPF are connected to the gNB 200 via an NG interface, which is an interface between a base station and a core network.

[0015] 2 is a diagram showing the configuration of a UE 100 (user equipment) according to an embodiment. The UE 100 includes a receiving unit 110, a transmitting unit 120, and a control unit 130. The receiving unit 110 and the transmitting unit 120 constitute a wireless communication unit that performs wireless communication with the gNB 200.

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

[0017] The transmitting unit 120 performs various transmissions under the control of the control unit 130. The transmitting unit 120 includes an antenna and a transmitter. The transmitter converts a baseband signal (transmission signal) output by the control unit 130 into a radio signal and transmits it from the antenna.

[0018] The control unit 130 performs various controls and processes in the UE 100. Such processes include processes of each layer described below. The control unit 130 includes at least one processor and at least one memory. The memory stores programs executed by the processor and information used in the processes by the processor. The processor may include a baseband processor and a CPU (Central Processing Unit). The baseband processor performs modulation / demodulation and encoding / decoding of baseband signals. The CPU executes programs stored in the memory to perform various processes.

[0019] 3 is a diagram showing the configuration of a gNB 200 (base station) according to an embodiment. The gNB 200 includes a transmitter 210, a receiver 220, a controller 230, and a backhaul communication unit 240. The transmitter 210 and the receiver 220 constitute a wireless communication unit that performs wireless communication with the UE 100. The backhaul communication unit 240 constitutes a network communication unit that communicates with the CN 20.

[0020] The transmitting unit 210 performs various transmissions under the control of the control unit 230. The transmitting unit 210 includes an antenna and a transmitter. The transmitter converts a baseband signal (transmission signal) output by the control unit 230 into a radio signal and transmits it from the antenna.

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

[0022] The control unit 230 performs various controls and processes in the gNB 200. Such processes include processes for each layer, which will be described later. The control unit 230 includes at least one processor and at least one memory. The memory stores programs executed by the processor and information used in the processes by the processor. The processor may include a baseband processor and a CPU. The baseband processor performs modulation / demodulation and encoding / decoding of baseband signals. The CPU executes programs stored in the memory to perform various processes.

[0023] The backhaul communication unit 240 is connected to adjacent base stations via an Xn interface, which is an interface between base stations. The backhaul communication unit 240 is connected to the AMF / UPF 300 via an NG interface, which is an interface between a base station and a core network. Note that the gNB 200 is composed of a CU (Central Unit) and a DU (Distributed Unit) (i.e., functionally divided), and the two units may be connected by an F1 interface, which is a fronthaul interface.

[0024] FIG. 4 is a diagram showing the configuration of a protocol stack of a radio interface of a user plane that handles data.

[0025] The user plane radio interface protocol includes a physical (PHY) layer, a medium access control (MAC) layer, a radio link control (RLC) layer, a packet data convergence protocol (PDCP) layer, and a service data adaptation protocol (SDAP) layer.

[0026] The PHY layer performs encoding / decoding, modulation / demodulation, antenna mapping / demapping, and resource mapping / demapping. Data and control information are transmitted between the PHY layer of UE100 and the PHY layer of gNB200 via a physical channel. The PHY layer of UE100 receives downlink control information (DCI) transmitted from gNB200 on a physical downlink control channel (PDCCH). Specifically, UE100 performs blind decoding of the PDCCH using a radio network temporary identifier (RNTI) and acquires the successfully decoded DCI as DCI addressed to the UE. The DCI transmitted from gNB200 has a CRC parity bit scrambled by the RNTI added.

[0027] The MAC layer performs data priority control, retransmission processing using Hybrid Automatic Repeat reQuest (HARQ), random access procedures, etc. Data and control information are transmitted between the MAC layer of the UE 100 and the MAC layer of the gNB 200 via a transport channel. The MAC layer of the gNB 200 includes a scheduler. The scheduler determines the uplink and downlink transport format (transport block size, modulation and coding scheme (MCS)) and the resource blocks to be allocated to the UE 100.

[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 RLC layer of the UE 100 and the RLC layer of the gNB 200 via a logical channel.

[0029] The PDCP layer performs header compression / decompression, encryption / decryption, and the like.

[0030] The SDAP layer maps IP flows, which are units for Quality of Service (QoS) control by the core network, to radio bearers, which are units for QoS control by the Access Stratum (AS). Note that if the RAN is connected to the EPC, SDAP may not be required.

[0031] FIG. 5 is a diagram showing the configuration of a protocol stack of a radio interface of a control plane that handles signaling (control signals).

[0032] The protocol stack of the radio interface of the control plane has an RRC (Radio Resource Control) layer and an NAS (Non-Access Stratum) layer instead of the SDAP layer shown in FIG.

[0033] RRC signaling for various settings is transmitted between the RRC layer of UE100 and the RRC layer of gNB200. The RRC layer controls logical channels, transport channels, and physical channels according to the establishment, re-establishment, and release of radio bearers. When there is a connection (RRC connection) between the RRC of UE100 and the RRC of gNB200, UE100 is in an RRC connected state. When there is no connection (RRC connection) between the RRC of UE100 and the RRC of gNB200, UE100 is in an RRC idle state. When the connection between the RRC of UE100 and the RRC of gNB200 is suspended, UE100 is in an RRC inactive state.

[0034] The NAS layer, which is located above the RRC layer, performs session management, mobility management, etc. NAS signaling is transmitted between the NAS layer of the UE 100 and the NAS layer of the AMF 300A. Note that the UE 100 has an application layer and the like in addition to the radio interface protocol. Also, a layer lower than the NAS layer is called an AS layer.

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

[0036] In the case of a broadcast communication service (also referred to as "MBS broadcast"), the same service and the same specific content data are simultaneously provided to all UEs 100 in a geographical area. That is, all UEs 100 within the broadcast service area are permitted to receive the data. The broadcast communication service is delivered to the UEs 100 using a broadcast session, which is a type of MBS session. The UEs 100 can receive the broadcast communication service in any of the following states: RRC idle state, RRC inactive state, and RRC connected state.

[0037] In the case of a multicast communication service (also referred to as "MBS multicast"), the same service and the same specific content data are simultaneously provided to a specific set of UEs. That is, not all UEs 100 within a multicast service area are permitted to receive the data. The multicast communication service is delivered to the UEs 100 using a multicast session, which is a type of MBS session. The UEs 100 can receive the multicast communication service in an RRC connected state using mechanisms such as PTP (Point-to-Point) and / or PTM (Point-to-Multipoint) delivery. The UEs 100 may receive the multicast communication service in an RRC inactive (or RRC idle) state.

[0038] In the following, MBS broadcast will be mainly described, however, the embodiment is not limited to MBS broadcast and can be applied to MBS multicast.

[0039] A UE 100 in an RRC idle state, an RRC inactive state, or an RRC connected state receives MBS configuration for a broadcast session (e.g., parameters required for MTCH reception) via the MCCH. The parameters required for MCCH reception (MCCH configuration) are provided via system information. Specifically, system information block type 20 (SIB20) includes the MCCH configuration. Note that SIB type 21 includes information on service continuity for MBS broadcast reception. The MCCH provides a list of all broadcast services, including ongoing sessions, transmitted on the MTCH, and the related information for the broadcast session includes the MBS session ID, associated G-RNTI scheduling information, and information on neighboring cells providing a specific service on the MTCH.

[0040] To ensure service continuity for MBS broadcast, UE100 in the RRC connected state can send an MBS Interest Indication (MII) message, which is an RRC message, to gNB200 providing SIB21, containing the following information: - A list of MBS frequencies that the UE is interested in receiving - A priority between receiving all listed MBS frequencies and receiving unicast bearers - A list of MBS broadcast services (service IDs) that UE100 is interested in receiving (if SIB20 is scheduled on the PCell of UE100).

[0041] Note that the transmission of the MBS Interest Indication message can be implicitly enabled / disabled by the presence of SIB21.

[0042] When gNB200 provides RRC configuration and / or downlink allocation to UE100, it enables UE100 to receive MBS services in which UE100 is interested based on the MBS Interest Indication message.

[0043] (3) Overview of Carrier Aggregation In the embodiment, the UE 100 is configured with carrier aggregation (CA) by the gNB 200. In CA, multiple component carriers (CCs) corresponding to multiple serving cells are aggregated, and the UE 100 can simultaneously receive or transmit on multiple CCs. The multiple CCs may be contiguous in the frequency direction. The multiple CCs may be discontinuous.

[0044] When CA is configured, the UE 100 has only one RRC connection with the network (e.g., gNB 200). In RRC connection establishment / re-establishment / handover, one serving cell provides NAS mobility information, and in RRC connection re-establishment / handover, one serving cell provides security input. This one serving cell is called a primary cell (PCell). The primary cell is an MCG cell operating on a primary frequency on which the UE 100 performs an initial connection establishment procedure or starts a connection re-establishment procedure. If the UE 100 receives an RRCSetup message from a cell during the initial connection establishment procedure, the UE 100 considers the cell to be the primary cell. A set of serving cells can be formed by configuring a secondary cell (SCell) together with the PCell in the UE 100. Therefore, the set of serving cells configured for the UE 100 is composed of one PCell and one or more SCells. Reconfiguration, addition, and deletion of SCells can be performed by RRC.

[0045] To enable the UE 100 to reduce its power consumption when CA is configured, a cell activation / deactivation mechanism is supported. When an SCell is deactivated, the UE 100 does not need to receive the corresponding PDCCH or PDSCH, and does not need to perform corresponding uplink and / or CQI measurements. On the other hand, when an SCell is active, the UE 100 can receive the PDSCH and PDCCH and perform CQI measurements.

[0046] If one or more SCells are configured in UE100, gNB200 can activate and deactivate the configured SCells. When an SCell is configured, it is deactivated unless the RRC parameter "sCellState" is set to active for the SCell. A configured SCell is activated and deactivated in the following manner: UE100 receives an SCell Activation / Deactivation MAC CE from gNB200. gNB200 configures an RRC parameter "sCellDeactivationTimer" timer for each configured SCell. UE100 deactivates the corresponding SCell when the timer expires. gNB200 configures the RRC parameter "sCellState" for each configured SCell. If the parameter is set, UE 100 activates the corresponding SCell at the time of SCell configuration.

[0047] The UE 100 can receive MBS broadcast data and MCCH from the PCell or one SCell at a certain timing. Note that UE dedicated RRC signaling may be used to provide SIB20 of the SCell.

[0048] (4) Operation of the Mobile Communication System FIG. 6 is a diagram for explaining an outline of the operation of the mobile communication system 1 according to the embodiment.

[0049] In the embodiment, the gNB 200 is functionally divided into a central unit (CU) 250 and a distributed unit (DU) 260. While FIG. 6 shows an example in which there is one DU 260, the number of DUs 260 may be two or more. Each of the CU 250 and the DU 260 may have a hardware configuration as shown in FIG. 3.

[0050] The CU 250 is a logical node including the RRC, SDAP, and PDCP layers (protocols) of the gNB 200. The CU 250 controls the operation of the DU. The CU 250 is connected to the DU 260 via an F1 interface, which is a fronthaul interface. The CU is connected to a neighboring base station via an Xn interface, which is an inter-base station interface.

[0051] DU260 is a logical node including the RLC, MAC, and PHY layers (protocols) of gNB200. DU260 forms one or more cells. In FIG. 6, an example is shown in which DU260 forms two cells (cell C1, cell C2) under the control of DU260, but there may be two or more cells under the control of DU260.

[0052] In such an operating scenario, assume that UE 100, for which carrier aggregation is configured by gNB 200, is receiving or is interested in receiving an MBS service (e.g., an MBS broadcast) provided in cell C2, where cell C1 is the PCell of UE 100 and cell C2 is the SCell of UE 100.

[0053] As described above, the gNB 200 can activate / deactivate the SCell by transmitting an SCell Activation / Deactivation MAC CE to the UE 100. Since the MAC layer is included in the DU 260, the DU 260 transmits the SCell Activation / Deactivation MAC CE to the UE 100.

[0054] However, since the MII message is an RRC message and is transmitted from the UE 100 to the CU 250 on the RRC layer, the DU 260 cannot grasp the contents of the MII message. Therefore, the DU 260 cannot grasp that the UE 100 is receiving or is interested in receiving the MBS broadcast provided by the cell C2. Therefore, the DU 260 may deactivate the SCell by transmitting an SCell Deactivation MAC CE to the UE 100. When the SCell is deactivated, the UE 100 may be unable to receive the MBS broadcast provided by the cell C2. This problem may occur not only in the case of MBS broadcast but also in the case of MBS multicast.

[0055] Therefore, in the embodiment, the CU 250 transmits MBS-related information to the DU 260 over the F1 interface between the CU 250 and the DU 260. The MBS-related information is information about the UE 100 that is receiving or has an interest in receiving an MBS service (e.g., MBS broadcast) provided in the SCell (cell C2) under the control of the DU 260. This enables the DU 260 to activate / deactivate the SCell taking into account the MBS interest of the UE 100, thereby improving service continuity in the UE 100. Note that in the embodiment, the term "MBS service" mainly refers to MBS broadcast, but may also refer to MBS multicast.

[0056] The CU 250 may send a UE Context Setup Request message including the MBS-related information or a UE Context Modification Request message including the MBS-related information to the DU 260. These messages are F1 messages associated with the UE 100 and are suitable for transmitting MBS-related information.

[0057] The CU 250 receives an MBS interest notification (MII), which is an RRC message, from the UE 100. The CU 250 transmits MBS-related information to the DU 260 based on the MBS interest notification (MII).

[0058] The DU 260 determines activation and deactivation of the SCell for the UE 100 based on the MBS-related information received from the CU 250. Depending on the result of the determination, the DU 260 may transmit to the UE 100 an SCell Activation / Deactivation MAC CE, which is a medium access control element (MAC CE) indicating an activation instruction or a deactivation instruction of the SCell.

[0059] In an embodiment, the MBS-related information transmitted from the CU 250 to the DU 260 may be information indicating whether activation of the SCell is requested. The MBS-related information may include information indicating the reason for the request.

[0060] The MBS-related information transmitted from CU250 to DU260 may include at least one of the following: information indicating the MBS service that UE100 is receiving or is interested in receiving (e.g., a service ID such as TMGI); information indicating the MBS frequency that UE100 is receiving or is interested in receiving; and information regarding the cell that is providing the MBS service or MBS frequency (e.g., a cell ID).

[0061] 7 is a diagram showing a first operation example of the mobile communication system 1 according to the embodiment. In this operation example, the CU 250 transmits at least a part of the MII received from the UE 100 to the DU 260 as MBS-related information.

[0062] In step S101, the UE 100 is receiving or is interested in receiving an MBS service (eg, an MBS broadcast) provided in cell C2 (SCell).

[0063] In step S102, UE 100 transmits MII to CU 250. As described above, MII includes information on MBS services of interest (TMGI), information on MBS frequencies of interest, and information on unicast and MBS reception priority. CU 250 receives MII. In the case of MBS multicast, CU 250 may receive information included in MII from the core network instead of receiving MII from UE 100.

[0064] In step S103, the CU 250 transmits a UE Context Setup Request message or a UE Context Modification Request message including MBS-related information to the DU 260 over the F1 interface. The MBS-related information includes information on MBS services of interest to the UE 100 (TMGI) and / or information on MBS frequencies of interest to the UE 100. The MBS-related information may include a cell ID and / or a frequency identifier of a cell (cell C2) that provides an MBS service of interest to the UE 100. Alternatively, the MBS-related information may include a cell ID and / or a frequency identifier of a cell that should not be deactivated (i.e., should remain active) because the UE 100 is interested in receiving MBS.

[0065] In step S104, the DU 260 identifies a cell C2 (SCell) that provides an MBS service of interest to the UE 100 based on the MBS-related information from the CU 250. The DU 260 may identify a cell (SCell) that does not provide an MBS service of interest to the UE 100. The DU 260 may identify a cell (SCell) that provides an MBS service that the UE 100 is no longer interested in. The DU 260 determines activation / deactivation of the SCell.

[0066] In step S105, the DU 260 transmits an SCell Activation / Deactivation MAC CE to the UE 100 as necessary. Here, the DU 260 activates the cell C2 (SCell) that provides the MBS service of interest to the UE 100. The DU 260 may activate / deactivate the SCell that does not provide the MBS service of interest to the UE 100 according to the traffic situation of unicast transmission. Here, the description will be given assuming that the DU 260 instructs the UE 100 to activate the cell C2 (SCell).

[0067] In step S106, UE100 activates cell C2 (SCell) in response to the instruction of DU260 in step S105.

[0068] Thereafter, in step S107, it is assumed that the UE 100 is no longer interested in the MBS service (for example, MBS broadcast).

[0069] In step S108, the UE 100 notifies the CU 250 by the MII that the UE 100 is no longer interested in the MBS service. In the case of MBS multicast, the CU 250 may receive information indicating that the UE 100 is no longer interested in the MBS service from the core network.

[0070] In step S109, the CU 250 sends a UE Context Setup Request message or a UE Context Modification Request message including MBS-related information reflecting the MII of step S108 to the DU 260. The message may include information on cells that can be deactivated (are allowed).

[0071] In step S110, the DU 260 determines whether to deactivate the cell C2 (SCell) based on the MBS-related information from the CU 250. Here, the description will proceed assuming that it has been determined that the cell C2 (SCell) is to be deactivated.

[0072] In step S111, the DU 260 transmits an SCell Deactivation MAC CE to the UE 100.

[0073] In step S112, the UE 100 deactivates the SCell in response to the reception of the SCell Deactivation MAC CE in step S111.

[0074] 8 is a diagram showing a second operation example of the mobile communication system 1 according to the embodiment. In this operation example, the CU 250 transmits a request based on the MII received from the UE 100 to the DU 260. Operations that overlap with those in the first operation example described above will not be described again.

[0075] In step S201, the UE 100 is receiving or is interested in receiving an MBS service (e.g., an MBS broadcast) provided in cell C2 (SCell).

[0076] In step S202, the UE 100 transmits the MII to the CU 250. In the case of MBS multicast, the CU 250 may receive information such as that included in the MII from the core network, instead of receiving the MII from the UE 100.

[0077] In step S203, the CU 250 identifies an SCell providing the MBS service based on the MII (or information received from the core network). Here, it is assumed that the CU 250 identifies that the identified SCell is in an inactive state.

[0078] In step S204, the CU 250 transmits a UE Context Setup Request message or a UE Context Modification Request message to the DU 260, which includes MBS-related information indicating a request for SCell activation to the DU 260. The message includes at least one of the following: a cell ID of the cell to be activated; a Cause: information indicating that the UE 100 is interested in receiving an MBS service (e.g., MBS broadcast); a TMGI: an identifier indicating the MBS service to which the SCell activation applies; and an MBS frequency: an identifier indicating the frequency on which the UE 100 is interested in receiving an MBS service (e.g., MBS broadcast).

[0079] In step S205, the DU 260 activates (or maintains the activation of) the SCell whose activation is requested by the CU 250 in step S204. The DU 260 may activate the SCell by transmitting an SCell Activation MAC CE to the UE 100 as necessary. The UE 100 activates the SCell (step S206). Note that after the SCell is activated, the DU 260 may return a response to the CU 250 over the F1 interface. In this state, the DU 260 may be prohibited from deactivating the SCell.

[0080] Thereafter, in step S207, it is assumed that the UE 100 is no longer interested in the above MBS service (for example, MBS broadcast).

[0081] In step S208, the UE 100 transmits an MII indicating that the UE 100 is no longer interested in the MBS service to the CU 250. In the case of MBS multicast, the CU 250 may receive information indicating that the UE 100 is no longer interested in the MBS service from the core network.

[0082] In step S209, the CU 250 transmits an F1 message including MBS-related information indicating the release of the SCell's active state (i.e., deactivation permission) based on the MII in step S208 (or information received from the core network). The contents (items) of the information are the same as those in step S204. The DU 260 deactivates the SCell for which the restriction has been released, as necessary (steps S210 and S211).

[0083] (5) Other Embodiments The above-described operational flows are not limited to being implemented independently, but can be implemented by combining two or more operational flows. For example, some steps of one operational flow may be added to another operational flow, or some steps of one operational flow may be replaced with some steps of another operational flow. In each flow, it is not necessary to execute all steps, and only some steps may be executed.

[0084] In the above-described embodiments and examples, an example in which the base station is an NR base station (gNB) has been described, but the base station may be an LTE base station (eNB) or a 6G base station. The base station may also be a relay node such as an IAB (Integrated Access and Backhaul) node. The base station may also be a DU of the IAB node. The UE 100 may also be an MT (Mobile Termination) of the IAB node.

[0085] A program may be provided that causes a computer to execute each process performed by UE100 or gNB200 (CU250, DU260). The program may be recorded on a computer-readable medium. Using a computer-readable medium, the program can be installed on a computer. Here, the computer-readable medium on which the program is recorded may be a non-transitory recording medium. The non-transitory recording medium is not particularly limited, and may be, for example, a recording medium such as a CD-ROM or DVD-ROM. Furthermore, circuits that execute each process performed by UE100 or gNB200 may be integrated, and at least a portion of UE100 or gNB200 (CU250, DU260) may be configured as a semiconductor integrated circuit (chipset, SoC: System on a chip).

[0086] As used in this disclosure, the terms "based on" and "depending on / in response to" do not mean "based only on" or "depending only on," unless expressly stated otherwise. The term "based on" means both "based only on" and "based at least in part on." Similarly, the term "depending on" means both "depending only on" and "depending at least in part on." The terms "include," "comprise," and variations thereof do not mean including only the listed items, but may mean including only the listed items or may include additional items in addition to the listed items. Additionally, the term "or," as used in this disclosure, is not intended to mean an exclusive or. Furthermore, any reference to elements using designations such as "first," "second," etc., as used in this disclosure does not generally limit the quantity or order of those elements. These designations may be used herein as a convenient method of distinguishing between two or more elements. Thus, a reference to a first and a second element does not imply that only two elements may be employed therein or that the first element must precede the second element in some way. In this disclosure, where articles are added by translation, such as a, an, and the in English, these articles shall include the plural unless the context clearly indicates otherwise.

[0087] The above describes the embodiments in detail with reference to the drawings, but the specific configuration is not limited to that described above, and various design changes can be made within the scope that does not deviate from the gist of the invention.

[0088] This application claims priority to U.S. Provisional Application No. 63 / 395,933 (filed August 8, 2022), the entire contents of which are incorporated herein by reference.

[0089] (6) Supplementary Notes The following are additional notes regarding the features of the above-described embodiment.

[0090] (Supplementary Note 1) A communication method used in a mobile communication system that provides a multicast / broadcast service (MBS), comprising a step in which an aggregation unit included in a base station transmits MBS-related information to a distributed unit included in the base station over a network interface between the aggregation unit and the distributed unit, the MBS-related information being information about user equipment that is receiving or has an interest in receiving an MBS service provided in a secondary cell under the control of the distributed unit.

[0091] (Supplementary Note 2) The communication method according to Supplementary Note 1, wherein the network interface is an F1 interface, and the step of transmitting the MBS-related information includes the step of transmitting a UE Context Setup Request message including the MBS-related information or a UE Context Modification Request message including the MBS-related information to the distributed unit.

[0092] (Supplementary Note 3) The communication method according to Supplementary Note 1 or 2, further comprising the step of the aggregation unit receiving an MBS interest notification, which is a Radio Resource Control (RRC) message, from the user equipment, and wherein the step of transmitting the MBS-related information includes the step of transmitting the MBS-related information to the distributed units based on the MBS interest notification.

[0093] (Supplementary Note 4) The communication method according to any one of Supplementary Notes 1 to 3, further comprising the step of the distributed unit determining activation and deactivation of the secondary cell for the user equipment based on the MBS-related information received from the aggregation unit.

[0094] (Supplementary Note 5) The communication method according to Supplementary Note 4, further comprising the step of the distributed unit sending, to the user equipment, a Medium Access Control and Control Element (MAC CE) indicating an activation instruction or a deactivation instruction of the secondary cell according to a result of the determination.

[0095] (Supplementary Note 6) The communication method according to any one of Supplementary Notes 1 to 5, wherein the MBS-related information is information indicating whether activation of the secondary cell is requested.

[0096] (Supplementary Note 7) The communication method according to Supplementary Note 6, wherein the MBS-related information includes information indicating a reason for the request.

[0097] (Supplementary Note 8) The communication method according to any one of Supplementary Notes 1 to 7, wherein the MBS-related information includes at least one of information indicating an MBS service that the user device is receiving or is interested in receiving, information indicating an MBS frequency that the user device is receiving or is interested in receiving, and information regarding a cell that provides the MBS service or the MBS frequency.

[0098] (Supplementary Note 9) An aggregation unit included in a base station in a mobile communication system that provides a multicast / broadcast service (MBS), comprising: a transmitter that transmits MBS-related information to a distributed unit included in the base station over a network interface between the aggregation unit and the distributed unit, the MBS-related information being information about user equipment that is receiving or has an interest in receiving an MBS service provided in a secondary cell under the control of the distributed unit.

[0099] (Supplementary Note 10) A distributed unit included in a base station in a mobile communication system that provides a multicast / broadcast service (MBS), the distributed unit comprising: a receiving unit that receives MBS-related information from an aggregation unit included in the base station on a network interface between the aggregation unit and the distributed unit, the MBS-related information being information about user equipment that is receiving or has an interest in receiving an MBS service provided in a secondary cell under the control of the distributed unit.

[0100] 1: Mobile communication system 10: RAN 20: CN 100: UE (user equipment) 110: Receiving unit 120: Transmitting unit 130: Control unit 200: gNB (base station) 210: Transmitting unit 220: Receiving unit 230: Control unit 240: Backhaul communication unit 250: CU (aggregation unit) 260: DU (distributed unit)

Claims

1. A communication method for use in a mobile communication system providing a multicast / broadcast service (MBS), comprising: a step of an aggregation unit included in a network node transmitting MBS related information to a distribution unit included in said network node on a network interface between said aggregation unit and said distribution unit; The MBS-related information is information about MBS services that user equipment in a cell under the distributed unit is receiving or is interested in receiving. Communication methods.

2. The network interface is an F1 interface, The step of transmitting the MBS-related information includes the step of transmitting a UE Context Setup Request message including the MBS-related information or a UE Context Modification Request message including the MBS-related information to the distributed unit. The communication method according to claim 1 .

3. The method further comprises receiving, by the aggregation unit, an MBS interest indication from the user equipment, the MBS interest indication being a Radio Resource Control (RRC) message; The step of transmitting the MBS-related information includes the step of transmitting the MBS-related information to the distributed unit based on the MBS interest notification. The communication method according to claim 1 .

4. The MBS-related information includes at least one of information indicating an MBS service that the user equipment is receiving or is interested in receiving, information indicating an MBS frequency that the user equipment is receiving or is interested in receiving, and information regarding a cell that provides the MBS service or the MBS frequency. The communication method according to claim 1 .

5. An aggregation unit included in a network node in a mobile communication system providing a Multicast / Broadcast Service (MBS), comprising: a transmitting unit for transmitting MBS-related information to a distributed unit included in the network node through a network interface between the aggregation unit and the distributed unit; The MBS-related information is information about MBS services that user equipment in a cell under the distributed unit is receiving or is interested in receiving. Aggregation unit.

6. A distributed unit included in a network node in a mobile communication system providing a multicast / broadcast service (MBS), comprising: a receiving unit for receiving MBS-related information from an aggregation unit included in the network node on a network interface between the aggregation unit and the distribution unit; The MBS-related information is information about MBS services that user equipment in a cell under the distributed unit is receiving or is interested in receiving. Distributed units.

7. A mobile communication system providing a multicast / broadcast service (MBS), comprising: A network node including an aggregation unit and a distribution unit, The aggregation unit transmits MBS-related information to the distribution unit over a network interface between the aggregation unit and the distribution unit; The MBS-related information is information about MBS services that user equipment in a cell under the distributed unit is receiving or is interested in receiving. Mobile communication system.

8. A chipset for controlling an aggregation unit included in a network node in a mobile communication system providing a multicast / broadcast service (MBS), comprising: Execute a process of transmitting MBS-related information to a distributed unit included in the network node on a network interface between the aggregation unit and the distributed unit; The MBS-related information is information about MBS services that user equipment in a cell under the distributed unit is receiving or is interested in receiving. Chipset.

9. A program for controlling an aggregation unit included in a network node in a mobile communication system providing a multicast / broadcast service (MBS), comprising: causing the aggregation unit to execute a process of transmitting MBS-related information to a distribution unit included in the network node on a network interface between the aggregation unit and the distribution unit; The MBS-related information is information about MBS services that user equipment in a cell under the distributed unit is receiving or is interested in receiving. program.

10. A chipset for controlling a distributed unit included in a network node in a mobile communication system providing a multicast / broadcast service (MBS), comprising: receiving MBS-related information from an aggregation unit included in the network node on a network interface between the aggregation unit and the distribution unit; The MBS-related information is information about MBS services that user equipment in a cell under the distributed unit is receiving or is interested in receiving. Chipset.

11. A program for controlling a distributed unit included in a network node in a mobile communication system providing a multicast / broadcast service (MBS), comprising: causing the distributed unit to perform a process of receiving MBS-related information from an aggregation unit included in the network node on a network interface between the aggregation unit and the distributed unit; The MBS-related information is information about MBS services that user equipment in a cell under the distributed unit is receiving or is interested in receiving. program.