Communication method, user device, mobile communication system, program, and chipset

Abstract

Provided is a communication method for use in a mobile communication system that provides a multicast / broadcast service (MBS), the method comprising: a step in which a user equipment in which a plurality of serving cells are configured uses the plurality of serving cells to communicate with a network; and a step in which the user equipment, in order to perform MBS reception in a separate cell different from the plurality of serving cells, transmits request information requesting releasing or deactivation of any of the plurality of serving cells, from the user equipment to the network.

Description

Communication Method

[0001] The present disclosure relates to a communication method 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 used in a mobile communication system that provides multicast / broadcast services (MBS), and includes the steps of: a user equipment configured with multiple serving cells communicating with a network using the multiple serving cells; and a step of the user equipment transmitting request information to the network requesting the release or deactivation of one of the multiple serving cells in order to receive MBS from another cell different from the multiple serving cells.

[0005] A communication method according to a second aspect is a communication method used in a mobile communication system providing a multicast / broadcast service (MBS), the method comprising the steps of: a user equipment (UE) having one or more serving cells configured communicating with a network using the one or more serving cells; the user equipment showing an interest in receiving MBS in another cell different from the one or more serving cells; and the user equipment determining whether a transmission condition for transmitting request information to the network for receiving MBS in the other cell is satisfied. The request information is information requesting setting an MBS gap or information requesting release or deactivation of a serving cell. The determining step includes determining whether a condition is satisfied that the network does not provide a system information block including information on a frequency to be used for receiving MBS.

[0006] 1 is a diagram illustrating a configuration of a mobile communication system according to an embodiment. FIG. 2 is a diagram illustrating a configuration of a UE (user equipment) according to an embodiment. FIG. 3 is a diagram illustrating a configuration of a gNB (base station) according to an embodiment. FIG. 4 is a diagram illustrating a protocol stack configuration of a radio interface of a user plane that handles data. FIG. 5 is a diagram illustrating a protocol stack configuration of a radio interface of a control plane that handles signaling (control signals). FIG. 6 is a diagram illustrating an MBS Interest Indication message. FIG. 7 is a diagram illustrating a start process of an MBS Interest Indication procedure. FIG. 8 is a diagram illustrating carrier aggregation (CA). FIG. 9 is a diagram illustrating dual connectivity (DC). FIG. 10 is a diagram illustrating an example of operation of a mobile communication system according to an embodiment. FIG. 11 is a diagram illustrating another example of operation of a mobile communication system according to an embodiment. FIG. 12 is a diagram illustrating an example of operation of a UE according to an embodiment. FIG. 13 is a diagram illustrating an example of operation of a mobile communication system according to a modified example.

[0007] 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.

[0008] (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.

[0009] 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.

[0010] 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).

[0011] 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").

[0012] 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.

[0013] 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.

[0014] 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.

[0015] 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.

[0016] 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.

[0017] 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.

[0018] 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.

[0019] 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.

[0020] 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.

[0021] 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.

[0022] 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.

[0023] FIG. 4 is a diagram showing the configuration of a protocol stack of a radio interface of a user plane that handles data.

[0024] 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.

[0025] 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.

[0026] 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.

[0027] 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.

[0028] The PDCP layer performs header compression / decompression, encryption / decryption, and the like.

[0029] 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.

[0030] 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).

[0031] 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.

[0032] 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.

[0033] 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.

[0034] (2) Overview of MBS The mobile communication system 1 can perform resource-efficient distribution using multicast / broadcast services (MBS).

[0035] 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.

[0036] 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.

[0037] 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.

[0038] 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 a multicast control channel (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 (SIB21) includes information on service continuity for MBS broadcast reception. The MCCH provides a list of all broadcast services, including ongoing sessions, transmitted on the multicast traffic channel (MTCH). The broadcast session-related information includes an MBS session identifier (e.g., TMGI (Temporary Mobile Group Identity)), associated G-RNTI scheduling information, and information on neighboring cells providing a specific service on the MTCH.

[0039] 6 is a diagram showing an MBS Interest Indication message defined in the 3GPP technical specification for RRC: TS38.331. The MBS Interest Indication message (hereinafter also simply referred to as "MBS Interest Indication") is an RRC message transmitted from the UE 100 to the network (gNB 200).

[0040] The MBS Interest Indication message (hereinafter also referred to simply as "MBS Interest Indication (MII)") is used to notify the network that the UE 100 is receiving or is interested in receiving, or is no longer receiving or is not interested in receiving, an MBS broadcast service via a broadcast MRB.

[0041] To ensure service continuity of MBS broadcast, the UE 100 in the RRC connected state can send an MBS interest notification message, which is an RRC message including the following information, to the gNB 200 that provides the SIB 21: mbs-FreqList (MBS frequency list) A list of MBS frequencies that the UE is interested in receiving mbs-Priority (MBS priority) Priority between receiving all listed MBS frequencies and receiving unicast bearers mbs-ServiceList (MBS service list)

[0042] A list of MBS broadcast services (service IDs) that the UE 100 is interested in receiving (if SIB20 is scheduled on the PCell of the UE 100).

[0043] Note that the transmission of the MBS Interest Indication message can be implicitly enabled / disabled by the presence of SIB21.

[0044] 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.

[0045] FIG. 7 is a diagram showing the initiation process of the MBS interest notification procedure defined in the 3GPP technical specification for RRC: TS38.331.

[0046] An MBS-capable UE 100 in the RRC Connected state can initiate this procedure in several cases, such as upon successful establishment / resumption of a connection, upon entering or leaving a broadcast service area, upon starting or stopping an MBS broadcast session, upon change of interest, upon change of priority between MBS broadcast and unicast / multicast reception, upon change to the PCell which broadcasts SIB21, upon reception of SIB20 in the SCell via dedicated signaling, and upon handover.

[0047] (3) Overview of Carrier Aggregation FIG. 8 is a diagram for explaining carrier aggregation (CA). In an embodiment, carrier aggregation (CA) is configured in the UE 100 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 also be discontinuous.

[0048] 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 initiates a connection re-establishment procedure. If the UE 100 receives an RRC Setup 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.

[0049] 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.

[0050] 9 is a diagram for explaining dual connectivity (DC). In DC, the UE 100 communicates with a master cell group (MCG) 201M managed by a master node (MN) 200M and a secondary cell group (SCG) 201S managed by a secondary node (SN) 200S. The MN 200M and the SN 200S are connected to each other via a network interface (specifically, an inter-base station interface). The network interface may be an Xn interface or an X2 interface. The MN 200M may be referred to as a master base station, and the SN 200S may be referred to as a secondary base station. Both the MN 200M and the SN 200S may be gNBs 200.

[0051] For example, DC is started when MN200M sends a predetermined message (for example, an SN Addition Request message) to SN200S, and MN200M sends an RRC reconfiguration message to UE100. In DC, UE100 in the RRC connected state is assigned radio resources from the respective schedulers of MN200M and SN200S, and performs radio communication using the radio resources of MN200M and the radio resources of SN200S.

[0052] The MN 200M may have a control plane connection with the core network. The MN 200M provides the primary radio resources for the UE 100. The MN 200M manages the MCG 201M. The MCG 201M is a group of serving cells associated with the MN 200M. The MCG 201M has a primary cell (PCell) and optionally has one or more secondary cells (SCells). On the other hand, the SN 200S may not have a control plane connection with the core network. The SN 200S provides additional radio resources to the UE 100. The SN 200S manages the SCG 201S. The SCG 201S has a primary / secondary cell (PSCell) and optionally has one or more SCells. The PCell of the MCG 201M and the PSCell of the SCG 201S are sometimes referred to as special cells (SpCells).

[0053] In an embodiment, the UE 100 may receive MBS broadcast data and MCCH from the PCell or one SCell at a time, and UE dedicated RRC signaling may be used to provide SIB20 for the SCell.

[0054] (4) Operation of the Mobile Communication System Fig. 10 is a diagram for explaining an example of the operation of the mobile communication system 1 according to the embodiment. Note that the numbers indicated by "#" in Fig. 10 may represent identifiers or indexes.

[0055] UE 100, which exists in an overlapping area of ​​cell #1 and cell #2, communicates with cell #1. That is, cell #1 is the serving cell of UE 100, and cell #2 is a neighboring cell of the serving cell. UE 100 is in an RRC connected state, an RRC idle state, or an RRC inactive state in cell #1.

[0056] Cell #1 operates on frequency (carrier frequency) #1, and cell #2 operates on frequency (carrier frequency) #2. This frequency relationship is called inter-frequency. Cell #1 is managed by gNB200#1, and cell #2 is managed by gNB200#2. Cell #1 (gNB200#1) and cell #2 (gNB200#2) belong to different operators. Specifically, cell #1 (gNB200#1) belongs to public land mobile network (PLMN) #1, and cell #2 (gNB200#2) belongs to PLMN #2. This type of PLMN relationship is called inter-PLMN.

[0057] gNB200#1 and CN20#1 are included in network 50#1 of PLMN#1 (first PLMN). gNB200#2 and CN20#2 are included in network 50#2 of PLMN#2 (second PLMN). Generally, one operator is assigned one PLMN identifier. Each cell broadcasts the identifier of the PLMN to which it belongs.

[0058] UE100 in an RRC connected state in cell #1 performs data communication with cell #1 (gNB200#1). Specifically, UE100 is assigned a C-RNTI from gNB200#1 as an RRC connection identifier. gNB200#1 assigns radio resources to UE100 by scheduling for UE100.

[0059] UE100 in RRC idle state or RRC inactive state in cell #1 monitors paging from cell #1 (gNB200#1). Specifically, UE100 monitors paging transmitted from cell #1 (gNB200#1) at paging reception timing (paging opportunity) determined according to parameters such as its own UE identifier.

[0060] In an embodiment, cell #2 (gNB200#2) transmits MBS data belonging to an MBS session (e.g., a broadcast session) in PTM. Specifically, cell #2 (gNB200#2) transmits MBS by MBS broadcast. Cell #2 (gNB200#2) may provide an MBS session in ROM (Receive-Only Mode) and / or FTA (Free-To-Air). ROM is a mode in which MBS reception is possible even for UE100 that does not have a SIM (Subscriber Identity Module) and / or does not have a service contract with an operator (PLMN). For example, UE100 may be a device (e.g., a television receiver) that does not have uplink transmission capability but has downlink reception capability. FTA is an application (service) that enables free broadcast content broadcasting. The FTA may be one aspect of the ROM. The MBS session provided by the FTA may be made available to all users who are not mobile subscribers. Hereinafter, when there is no particular distinction between the ROM and the FTA, they will be referred to as ROM / FTA.

[0061] For example, UE 100 belongs to PLMN #1. UE 100 may have a SIM of PLMN #1 and / or a service contract with PLMN #1. In the description of the embodiment, it is assumed that UE 100 is interested in receiving an MBS session provided by PLMN #2, i.e., cell #2 (gNB200 #2). It is assumed that the MBS session provided by cell #2 (gNB200 #2) via ROM / FTA can be received by UE 100 belonging to PLMN #1. However, it may be assumed that the MBS session provided by cell #2 (gNB200 #2) via broadcast / PTM can be received by UE 100 belonging to PLMN #1, regardless of whether it is via ROM / FTA or not.

[0062] Here, since UE100 has a limited number of its own receivers, it is difficult for it to receive MBS from cell #2 (gNB200#2) while maintaining communication with cell #1 (gNB200#1). Specifically, it is difficult for UE100 to receive MBS from cell #2 (frequency #2), which is an inter-frequency, while maintaining cell #1 (frequency #1) as its own serving cell (serving frequency). For example, UE100 having only one receiver cannot receive MBS from cell #2 (frequency #2) while receiving from cell #1 (frequency #1). Even if UE100 has multiple receivers, in a scenario where all of the multiple receivers are being used in communication with network 50#1 (for example, carrier aggregation), UE100 cannot receive MBS from cell #2 (frequency #2).

[0063] Here, if gNB200#1 (network 50#1) is aware of UE100's MBS interest and gNB200#2's MBS transmission setting (particularly, MBS timing), it can communicate with UE100, for example, perform data communication or paging transmission, to avoid that timing. This allows UE100 to receive MBS from cell #2 (gNB200#2) at that timing. However, in an inter-PLMN scenario, gNB200#1 and gNB200#2 belong to different PLMNs, so it is difficult to share MBS transmission settings through network cooperation.

[0064] Therefore, the UE 100 according to the embodiment transmits an MBS gap request to cell #1 (gNB 200 #1) including information on the MBS gap that the UE 100 requests to be set (i.e., information on the MBS reception timing at which the UE 100 receives MBS from cell #2). The MBS gap is a period during which the UE 100 suspends communication between the UE 100 and cell #1 in order to receive MBS from cell #2. The MBS gap request may be auxiliary information for cell #1 (gNB 200 #1) to set an MBS gap in the UE 100.

[0065] The MBS gap request may be included in an RRC message transmitted from UE 100 to cell #1 (gNB 200 #1). The RRC message may be a UE Assistance Information message. The RRC message may be an MBS Interest Indication message. Alternatively, the MBS gap request may be included in a NAS message transmitted from UE 100 to CN 20 #1 (AMF 300A) via cell #1 (gNB 200 #1). The NAS message may be a CONFIGURATING UPDATE COMPLETE message, a REGISTRATING REQUEST message, or a SERVICE REQUEST message.

[0066] A network device included in network 50#1, for example, gNB200#1 or CN20#1 (AMF300A), receives the message from UE100 via cell #1. This enables the network device to communicate with UE100, for example, perform data communication or paging transmission, so as to avoid the MBS reception timing when UE100 receives MBS from cell #2.

[0067] (4.1) Basic Operational Example Regarding Gap Request In this operational example, gNB200#1 receives an MBS gap request from UE100 and transmits an MBS gap setting indicating the setting of the MBS gap to UE100 via cell #1. UE100 receives the MBS gap setting from cell #1. Based on the MBS gap setting from gNB200#1, UE100 suspends data communication with cell #1 during the MBS gap and receives MBS from cell #2. This enables UE100 to receive MBS from cell #2 while maintaining an RRC connected state with cell #1 (gNB200#1).

[0068] In this operation example, UE100 generates requested gap information indicating the MBS gap setting requested by UE100 based on the MCCH setting of cell #2 and / or the MTCH setting of cell #2. UE100 transmits a message including the requested gap information to cell #1 (gNB200#1). Cell #1 (gNB200#1) receives the message including the requested gap information and transmits an MBS gap setting based on the requested gap information to UE100. This allows the MBS gap to be appropriately set in UE100.

[0069] 11 is a diagram showing this operation example. In the following description of the embodiment, cell #1 (gNB200#1) may be read as network 50#1 (PLMN#1), and cell #2 (gNB200#2) may be read as network 50#2 (PLMN#2).

[0070] In step S100, UE100 is in an RRC connected state in cell #1.

[0071] In step S101, the UE 100 is receiving an MBS or is interested in receiving an MBS. For example, the UE 100 is receiving or is interested in receiving an MBS session (e.g., a broadcast session) provided by the ROM / FTA. The UE 100 may have previously acquired higher layer information indicating a correspondence between an MBS session (MBS session identifier) ​​and a frequency (frequency identifier). The higher layer information may further include information indicating a start time of the MBS session and / or information indicating an MBS service area in which the MBS session is provided. The UE 100 may determine a desired MBS frequency that provides the MBS session (desired MBS session) based on the higher layer information. Such higher layer information may be provided as a User Service Description (USD) or may be provided by a NAS message (e.g., a RESITRATION ACCEPT message, a CONFIGURATION UPDATE COMMAND message, or a PDU SESSION ESTABLISHMENT ACCEPT message).

[0072] In step S102, UE 100 may receive MBS information from cell #1 (gNB 200 #1) indicating the correspondence between MBS sessions and frequencies provided by network 50 #1 and / or the MBS sessions provided by cell #1 in ROM / FTA. Such MBS information may be information broadcast in the SIB or MCCH of cell #1. For example, MBS information indicating the correspondence between MBS sessions and frequencies provided by network 50 #1 may include multiple sets of MBS session identifiers and frequency identifiers. UE 100 can determine which MBS sessions are provided at which frequencies based on such MBS information. Note that the MBS information indicating the MBS sessions provided by cell #1 in ROM / FTA may include an MBS session identifier list of MBS sessions provided by cell #1 in ROM / FTA. UE 100 can determine which MBS sessions cell #1 provides in ROM / FTA based on such MBS information.

[0073] In step S103, UE 100 recognizes that the desired MBS session is not provided by network 50#1 based on the MBS information received in step S102. For example, UE 100 may recognize that the desired MBS session is not provided by network 50#1 based on MBS information indicating the correspondence between MBS sessions and frequencies provided by network 50#1 if the desired MBS session and / or the desired MBS frequency is not indicated in the MBS information. UE 100 may recognize that the desired MBS session and / or the desired MBS frequency can be provided by another network, i.e., network 50#2, if the desired MBS frequency providing the desired MBS session to which ROM / FTA is applied is not indicated in the MBS information.

[0074] In step S104, the UE 100 may receive MBS information from the cell #2 (gNB 200 #2) indicating the correspondence between the MBS session and the frequency provided by the network 50 #2 and / or the MBS session provided by the cell #2 in ROM / FTA. Such MBS information may be information broadcast in the SIB or MCCH of the cell #2. Based on the MBS information, the UE 100 may confirm that the desired MBS session and / or the desired MBS frequency is provided from the cell #2.

[0075] Also, in step S104, UE 100 receives MBS reception configuration in cell #2 from cell #2. Such MBS reception configuration includes MCCH configuration information broadcast in the SIB (SIB20) of cell #2 and / or MTCH configuration information broadcast in the MCCH of cell #2. For example, UE 100 receives MCCH configuration information via SIB20 transmitted on the BCCH from cell #2, and then receives MTCH configuration information by receiving the MCCH from gNB 200 based on the MCCH configuration information. The MCCH configuration information includes scheduling information of the MCCH, i.e., information indicating the MCCH reception timing (MCCH reception opportunity). The MTCH configuration information includes scheduling information of the MTCH, i.e., information indicating the MTCH reception timing (MTCH reception opportunity). Such MCCH reception timing (MCCH reception opportunity) and / or MTCH reception timing (MTCH reception opportunity) corresponds to the MBS reception timing at which UE 100 receives MBS from cell #2. Specifically, the MTCH reception timing constituting the MBS reception timing may be the MTCH reception timing associated with the desired MBS session among the MTCH reception timings indicated for each MBS session by the MCCH.

[0076] In step S105, the UE 100 determines a gap pattern setting for an MBS gap for interrupting data communication with cell #1 based on the MBS reception timing determined in step S104, and generates requested gap information indicating the determined gap pattern setting. A gap pattern refers to a periodically repeated MBS gap pattern. The requested gap information includes information indicating the start timing of the gap pattern (such as a system frame number and / or a subframe number) and information indicating the gap pattern, such as a bitmap for each subframe or a period (cycle length) of the MBS gap. The requested gap information may also include information indicating the duration of each MBS gap. The UE 100 determines the requested gap pattern in accordance with the timing of cell #1 (such as a system frame number). When determining the requested gap pattern, the UE 100 may add to the requested gap pattern a time (margin) required for a frequency change of the receiver of the UE 100 and / or a measurement time for establishing synchronization with cell #2.

[0077] In step S106, UE 100 transmits an RRC message including the request gap information generated in step S105 to cell #1 (gNB 200 #1). UE 100 may further include a desired MBS session identifier (e.g., TMGI) and / or a desired MBS frequency identifier associated with the request gap information in the RRC message.

[0078] In step S107, cell #1 (gNB200#1) generates an MBS gap setting indicating an MBS gap setting (gap pattern) based on the requested gap information in the RRC message received from UE100 in step S106, and transmits the MBS gap setting to UE100. For example, cell #1 (gNB200#1) transmits an RRC reconfiguration message including the MBS gap setting to UE100. The type of information included in the MBS gap setting may be the same as the type of information included in the requested gap information. Cell #1 (gNB200#1) may further include a cell identifier and / or a cell group identifier associated with the MBS gap setting in the RRC reconfiguration message. Cell #1 (gNB200#1) may include multiple sets of MBS gap settings and cell identifiers and / or cell group identifiers in the RRC reconfiguration message.

[0079] In step S108, UE100 suspends data communication with cell #1 (gNB200#1) during the MBS gap indicated by the MBS gap setting received from cell #1 (gNB200#1) in step S107, and receives MBS for the desired MBS session from cell #2 (gNB200#2). Specifically, UE100 changes (tunes) the receiver's reception frequency from frequency #1 to frequency #2, and then receives MBS from cell #2 (gNB200#2), i.e., receives MTCH (and MCCH). Cell #1 (gNB200#1) does not allocate radio resources to the UE100 during the set MBS reception gap.

[0080] Here, when the UE 100 uses multiple serving cells (or multiple cell groups) for communication with the network 50 # 1 (i.e., in the case of carrier aggregation or dual connectivity), the UE 100 identifies the serving cell (and / or cell group) to which the MBS gap setting is applied based on the cell identifier and / or cell group identifier in the RRC reconfiguration message, and uses the receiver assigned to the identified serving cell (and / or cell group) to receive MBS from cell # 2 (gNB 200 # 2). Note that receivers assigned to serving cells (and / or cell groups) other than the identified serving cell (and / or cell group) may remain in the same frequency / serving cell and continue receiving from the serving cell.

[0081] When UE100 is no longer interested in receiving MBS from cell #2 (gNB200#2) (step S109), UE100 may notify cell #1 (gNB200#1) (step S110). UE100 may send the notification in an RRC message, for example, a UE Assistance Information message or an MBS Interest Indication message. The notification may be a gap release request. The notification may be an MBS reception gap request that does not include a requested gap pattern. Cell #1 (gNB200#1) may remove (release) the MBS reception gap setting from UE100 based on the notification (step S111).

[0082] By such operation, UE100 can receive MBS broadcasts from cell #2 (gNB200#2) using an MBS gap while continuing unicast communication with cell #1 (gNB200#1), even if the number of its own receivers is limited.

[0083] (4.2) Gap Request During CA / DC FIG. 12 is a diagram for explaining another example of the operation of the mobile communication system 1 according to the embodiment.

[0084] In this operation example, it is assumed that a plurality of serving cells (in the illustrated example, serving cell #1a and serving cell #1b) are set by CA or DC in network 50 #1 for UE 100. In the illustrated example, serving cell #1a and serving cell #1b have different frequencies (carrier frequencies), with serving cell #1a operating at frequency #1 and serving cell #1b operating at frequency #2.

[0085] UE 100 communicates with network 50#1 using the multiple serving cells. For example, UE 100 has two receivers 111 and 112. Receivers 111 and 112 may support different frequencies. For example, UE 100 uses receiver 111 for unicast reception from serving cell #1a and receiver 112 for unicast reception from serving cell #1b. Note that one receiver may correspond to one radio (RF chain).

[0086] Thus, when UE100 uses different receivers during CA or DC, there is a problem that network 50#1 (gNB200#1) does not know which receiver to apply the MBS gap to. Here, not all receivers of UE100 support all frequencies, and it is necessary to use a receiver that supports MBS frequencies for MBS reception. However, network 50#1 (gNB200#1) may not know such information.

[0087] In this operation example, the UE 100 transmits an MBS gap request to the network 50#1, the MBS gap request including information on the MBS gap that the UE 100 requests to be set in order to receive MBS from another cell #2 different from the plurality of serving cells #1a and #1b. Here, the MBS gap request further includes identification information regarding a target serving cell among the plurality of serving cells for which the MBS gap is to be set. This allows the network 50#1 (e.g., gNB 200#1) to appropriately determine which serving cell should have an MBS gap set based on the identification information.

[0088] The other cell #2 belongs to another network 50#2 operated by a different operator (PLMN #2) than the operator (PLMN #1) of the network 50#1. That is, this operation example mainly assumes an inter-PLMN scenario. However, this operation example is not limited to the inter-PLMN scenario and can also be applied to an intra-PLMN scenario.

[0089] The identification information included in the MBS gap request includes at least one of an identifier of the target serving cell, an identifier of the cell group to which the target serving cell belongs, and an identifier of the frequency of the target serving cell.

[0090] 13 is a diagram showing an example of the operation of UE 100. In the illustrated example, in the serving PLMN (network 50#1) of UE 100, UE 100 uses RF chain #1 for communication with PCell and RF chain #2 for communication with SCell. For example, UE 100 uses RF chain #1 (receiver #1) for unicast reception from PCell and RF chain #2 (receiver #2) for unicast reception from SCell.

[0091] Periodic MBS gaps are set in the PCell. During the MBS gaps, the UE 100 suspends unicast reception from the PCell of the serving PLMN (network 50#1) and receives MBS data transmitted via an MTCH of another PLMN (network 50#2) via RF chain #1 (receiver #1). Hereinafter, an example will be described in which the MTCH transmission in the other PLMN (network 50#2) is an MBS broadcast, but this is not limited to MBS broadcast and may be MBS multicast. Note that, in each MBS gap, a tuning period for tuning the RF chain #1 (receiver #1) is provided before and after each MTCH period.

[0092] 14 is a diagram showing this operation example. Here, a description of operations that overlap with the above-described operation example will be omitted.

[0093] Steps S200 to S204 are the same as those in the above-described operation example, except that in this operation example, the UE 100 is interested in receiving an MBS broadcast provided by another PLMN (PLMN #2) (step S201).

[0094] In step S205, the UE 100 determines a target serving cell for the MBS gap. For example, the UE 100 identifies an RF chain / receiver that supports the frequency of the MBS broadcast of which the UE 100 is interested, and identifies a serving cell with which the RF chain / receiver is communicating as a target serving cell.

[0095] In steps S206 and S207, the UE 100 generates and transmits an RRC message including an MBS gap request. The gNB 200 #1 receives the RRC message. As described above, the RRC message may be an MBS Interest Indication message. The RRC message may be a UE Assistance Information message. The UE Assistance Information message is an example of an RRC message that the UE 100 can transmit autonomously.

[0096] The RRC message (MBS gap request) includes identification information indicating the serving cell to which the request should be applied. The RRC message (MBS gap request) may include gap information such as the above-mentioned information, such as the start timing, period, pattern (bitmap), and MBS gap length of the MBS gap. The identification information also includes at least one of an identifier of the target serving cell (physical cell ID or cell index), an identifier of a cell group to which the target serving cell belongs (e.g., an MCG / SCG identifier or a DRX group identifier), and an identifier of the frequency of the target serving cell (e.g., an ARFCN (Absolute Radio-Frequency Channel Number) or band combination). The RRC message (MBS gap request) may also include an MBS session identifier (such as TMGI) to which the request should be applied.

[0097] In step S208, gNB200 considers the MBS gap request of step S207 and performs MBS gap setting on UE100. Here, gNB200#1 performs MBS gap setting by specifying a cell ID, etc. gNB200#1 may also perform MBS gap setting by specifying the receiver of UE100. Steps S209 to S212 are the same as the above-described operation example.

[0098] (4.3) Gap Request Transmission Conditions As described above, the MBS gap request includes information on the MBS gap requested (desired) by the UE 100, such as information on the start timing, period, pattern (bitmap), MBS gap length, etc. Such an MBS gap is determined based on the MTCH configuration (i.e., MTCH scheduling information) of the MBS service (e.g., MBS broadcast) in which the UE 100 is interested.

[0099] In the above-described operation example, if gNB200#1 and gNB200#2 belong to the same PLMN, i.e., in an intra-PLMN scenario, gNB200#1 may be aware of the MTCH scheduling information of gNB200#2. Under such an assumption, gNB200#1 can identify the TMGI and / or frequency of the MBS service in which UE100 is interested and understand the MTCH scheduling based on an MBS Interest Indication message from UE100.

[0100] Therefore, even if there is no MBS gap request from UE100, gNB200#1 may set an MBS gap to UE100 based on the MBS interest notification message, so that the transmission of an MBS gap request by UE100 may be a wasteful process. In the following explanation of the operation example, the conditions (trigger conditions) under which UE100 transmits an MBS gap request will be explained. The following operation example may be implemented in combination with the above-mentioned operation example.

[0101] 15 is a diagram showing an example of the operation of the UE 100. In this example of the operation, it is mainly assumed that the MBS gap request is transmitted in a message different from the MBS Interest Indication message.

[0102] In step S301, the UE 100 in an RRC connected state in which one or more serving cells are set communicates with the network 50#1 using the one or more serving cells.

[0103] In step S302, the UE 100 is interested in receiving an MBS in another cell (which may be a different frequency) different from the one or more serving cells. That is, the UE 100 determines that it desires to receive an MBS in the other cell.

[0104] In step S303, the UE 100 determines whether the transmission condition (trigger condition) of the MBS gap request is satisfied. The condition includes at least one of the following: a first condition indicating that the serving cell and the other cell belong to different operators (different PLMNs #1); a second condition indicating that an MBS interest notification message cannot be transmitted to the serving cell; a third condition indicating that the serving cell requests or allows transmission of an MBS gap request; and a fourth condition that the gNB 200 #1 (network 50 #1) does not provide an SIB containing information on the frequency targeted for MBS reception (i.e., the frequency providing the MBS session / MBS service that the UE 100 is interested in receiving).

[0105] Of the first to fourth conditions, the first condition may be a required condition, and the second to fourth conditions may be optional conditions. However, even in an intra-PLMN scenario, it is possible that a gNB does not know the MTCH scheduling of other gNBs. Therefore, the first condition may not be a required condition.

[0106] When the first condition is used, the UE 100 may determine to generate and transmit an MBS gap request in response to determining that an MBS session (e.g., a broadcast session) that the UE 100 is interested in receiving is provided by a PLMN other than the current serving PLMN. Here, the UE 100 identifies an MBS service ID, specifically, a TMGI, that the UE 100 is interested in receiving. The TMGI includes a PLMN identifier (plmn-Id) and a service identifier (serviceId) and is used to identify the MBS session. The service identifier uniquely identifies an MBS service (or, from another perspective, an MBS session) within the PLMN. Therefore, the UE 100 can identify the PLMN that provides the MBS session that the UE 100 is interested in receiving, using the PLMN identifier (plmn-Id) included in the TMGI. The UE 100 determines whether the identified PLMN is provided by the PLMN to which the UE 100 is currently connected (selected PLMN).

[0107] When the second condition is used, the UE 100 may determine to generate and transmit an MBS gap request in response to determining that transmission of the MBS interest notification message is not permitted by SIB21. For example, the UE 100 may determine whether the serving cell is actually broadcasting SIB21. Alternatively, the UE 100 may determine whether SIB type 1 (SIB1) indicates that broadcasting of SIB21 is scheduled.

[0108] When the third condition is used, the UE 100 may determine the generation and transmission of an MBS gap request in response to determining that the serving cell (gNB200#1) requests or permits the transmission of a gap request rather than an MBS interest notification message. For example, the UE 100 may determine whether or not the gNB 200#1 indicates by SIB that it requests (or permits) the transmission of an MBS gap request. Alternatively, the UE 100 may determine whether or not it has received a UE-specific configuration (e.g., an RRC Reconfiguration message) from the gNB 200#1 that requests (or permits) the transmission of an MBS gap request.

[0109] When the fourth condition is used, UE100 acquires an SIB from gNB200#1 and checks whether information on the frequency (i.e., the frequency of interest) that provides the MBS session (MBS service) that UE100 is interested in receiving is included in the SIB. If gNB200#1 does not provide information on the frequency of interest in the SIB, it can be assumed that the MBS session that UE100 is interested in receiving is provided by a PLMN different from the serving PLMN to which gNB200#1 belongs. Or, even if the MBS session is provided by the same PLMN, it can be assumed that gNB200#1 does not have configuration information (such as the transmission period of MCCH and / or MTCH) on the frequency that provides the MBS session that UE100 is interested in receiving. Therefore, UE100 transmits an MBS gap request to gNB200#1 based on the fact that gNB200#1 does not provide information on the frequency of interest in the SIB (step S304). Here, the SIB used to determine the fourth condition is at least one of: SIB4: SIB for NR inter-frequency cell reselection SIB5: SIB for Inter-RAT (LTE) cell reselection SIB21: SIB for MBS service continuity If SIB1 indicates that these SIBs are not broadcast, the UE 100 requests gNB 200 #1 to transmit the SIB and then acquires the SIB. Note that the fourth condition can also be considered a specific example (subordinate concept) of the first condition.

[0110] If it is determined that the transmission condition (trigger condition) of the MBS gap request is satisfied (step S303: YES), in step S304, the UE 100 generates an MBS gap request and transmits the MBS gap request to the serving cell (gNB 200 #1). The UE 100 may transmit a UE assistance information message including the MBS gap request to the serving cell (gNB 200 #1). Note that the UE 100 may determine that the transmission condition (trigger condition) of the MBS gap request is satisfied in response to one of the first to fourth conditions being satisfied. Alternatively, the UE 100 may determine that the transmission condition (trigger condition) of the MBS gap request is satisfied in response to two or three of the first to fourth conditions being satisfied.

[0111] On the other hand, if it is determined that the transmission condition (trigger condition) of the MBS gap request is not satisfied (step S303: NO), the UE 100 does not transmit the MBS gap request. The UE 100 may transmit an MBS interest notification message to the serving cell (gNB200#1) without transmitting the MBS gap request (step S305). In that case, the UE 100 may include a 1-bit flag (gap request flag) requesting the setting of an MBS gap in the MBS interest notification message. The UE 100 may include a gap request flag associated with an entry in the mbs-FreqList (MBS frequency list) or an entry in the mbs-ServiceList (MBS service list) in the MBS interest notification message.

[0112] In this operation example, it is assumed that the MBS gap request is transmitted in a message different from the MBS interest notification message, for example, in a UE assistance information message. However, the MBS gap request may be transmitted as an information element (IE) of the MBS interest notification message. In this case, the determination of the second condition may be unnecessary. Alternatively, even if SIB21 is not broadcast, the UE 100 may be permitted to transmit the MBS interest notification message only when the gap request IE is included.

[0113] In addition, in this operation example, the transmission conditions for the MBS gap request have been described, but this operation example may also be applied to the transmission of an SCell release request (or an SCell deactivation request) described later. That is, the MBS gap request in this operation example may be read as an SCell release request (or an SCell deactivation request).

[0114] (4.4) Example of modification of operation of mobile communication system In the above-described embodiment, UE100 sends a message including requested gap information (MBS gap request) to gNB200#1, and then gNB200#1 sets an MBS gap in UE100 by sending an MBS gap setting based on the requested gap information to UE100.

[0115] In contrast, in this modification, instead of setting such an MBS gap, gNB200#1 releases one of the multiple serving cells of UE100 (e.g., serving cells #1a and #1b). The released serving cell is at least one secondary cell (SCell). By performing such cell release, one of the multiple receivers of UE100 (e.g., receivers 111 and 112) becomes available for MBS reception (particularly broadcast reception) in neighboring cell #2 (frequency #2).

[0116] The release of the SCell may be the release of the SCell configuration, i.e., de-configuration. Instead of the release of the SCell, the deactivation of the SCell may be used. The deactivation is the stopping of use of the SCell, without releasing the SCell configuration. In the following, the release of the SCell will be mainly described, but this may also be interpreted as the deactivation of the SCell. Furthermore, the "MBS gap" according to the above-described embodiment and its modified examples may also be interpreted as the "SCell release (or SCell deactivation)."

[0117] In this embodiment, UE100, which communicates with network 50#1 (gNB200#1) using multiple serving cells, transmits request information to network 50#1 (gNB200#1) requesting the release or deactivation of one of the serving cells in order to receive MBS from another cell different from the multiple serving cells. Specifically, the request information is information requesting the release or deactivation of an SCell among the multiple serving cells. The request information may include an identifier of the serving cell to be released or deactivated. The request information may include an identifier of the frequency to be released or deactivated.

[0118] This allows the network 50 #1 (gNB200 #1) to appropriately release or deactivate the SCell of the UE 100. As a result, the UE 100 can use the receiver that was used for communication with the SCell to receive MBS in the neighboring cell #2 (frequency #2). Here, since the primary cell (PCell) is maintained without being released, the UE 100 can maintain the RRC connected state with the network 50 #1 (gNB200 #1). Therefore, the UE 100 can receive MBS (e.g., broadcast reception) from the neighboring cell #2 (frequency #2) belonging to another PLMN while maintaining the RRC connected state with the network 50 #1 (gNB200 #1).

[0119] Thereafter, when UE100 terminates MBS reception of neighboring cell #2 (frequency #2), it may transmit notification information regarding the termination to network 50 #1 (gNB200 #1). This enables network 50 #1 (gNB200 #1) to set a new SCell for UE100 or activate a set SCell.

[0120] 16 is a diagram showing this operation example. Here, a duplicated description of operations that overlap with the above-described operation example will be omitted.

[0121] Steps S400 to S404 are the same as those in the above-described operation example. However, in this operation example, it is assumed that CA or DC is configured in UE100, and multiple serving cells are configured in UE100. It is also assumed that all of the receivers (e.g., receivers 111 and 112) possessed by UE100 are used for communication with the multiple serving cells. Under this assumption, UE100 is interested in receiving an MBS session (MBS service) provided by cell #2 (gNB200#2) belonging to another PLMN (PLMN#2) (step S401). The MBS session may be a broadcast session. UE100 may identify the MBS session and frequency (interested frequency) of its interest using USD (User Service Description) information provided by a higher layer.

[0122] In step S405, the UE 100 identifies a receiver among its multiple receivers that desires to release the corresponding serving cell. For example, the UE 100 may compare the supported frequency for each receiver with a frequency (interested frequency) that provides an MBS session (MBS service) that the UE 100 is interested in receiving, and identify the receiver that supports the interested frequency. Furthermore, the UE 100 may identify a cell ID of a serving cell (PCell / SCell (including PSCell)) that the receiver is using for communication. The UE 100 may identify a band combination supported by the receiver.

[0123] In step S406, the UE 100 generates an SCell release request message based on the determination result of step S405. The message may be an RRC message, such as a UE assistance information (UAI) message, an MBS interest notification (MII) message, or a newly defined RRC message.

[0124] The message may include information about the receiver identified in step S405 (for example, the cell ID). The message may include an identifier of an interest frequency (and / or a band number to which the interest frequency belongs). The message may include a combination of frequency bands that the UE 100 wishes to release.

[0125] The message may include information indicating a request for MBS reception. The information may be a message name or an IE name of the message (e.g., "MBS SCell release request"). The information may be information set in a Cause field of the message. The message may include, as associated information, a TMGI indicating an MBS session that the UE 100 is interested in receiving.

[0126] In step S407, the UE 100 transmits the RRC message of the SCell release request generated in step S406 to the gNB 200 #1. The gNB 200 #1 receives the message.

[0127] In step S408, gNB200#1 decides to release the SCell based on the message received from UE100 in step S407, and transmits an RRC Reconfiguration message including information to release the SCell to UE100. For example, gNB200#1 decides to release the SCell indicated by the cell ID in the message, or the SCell belonging to the frequency identifier or band number in the message. UE100 releases the specified SCell in response to receiving the RRC Reconfiguration message.

[0128] In addition, when deactivating the SCell instead of releasing the SCell, the gNB 200 #1 transmits an SCell deactivation MAC CE instead of an RRC Reconfiguration message to the UE 100. In response to receiving the MAC CE, the UE 100 deactivates the specified SCell.

[0129] In step S409, UE100 receives MBS for the desired MBS session from cell #2 (gNB200#2) using the receiver used for communication with the SCell released (or deactivated) in step S408. For example, UE100 changes (tunes) the receiving frequency of the receiver from frequency #1 to frequency #2, and then receives MBS from cell #2 (gNB200#2), i.e., receives MTCH (and MCCH).

[0130] When UE100 is no longer interested in receiving MBS from cell #2 (gNB200#2) (step S410), in step S411, UE100 may notify cell #1 (gNB200#1). UE100 may transmit the notification in an RRC message, for example, a UE Assistance Information message or an MBS Interest Indication message. The notification may be a notification indicating that the receiver used for MBS reception is available for use. The notification may request SCell configuration or SCell activation. In step S412, cell #1 (gNB200#1) may configure SCell or activate SCell for UE100.

[0131] By the operation of this modified example, UE100 can, for example, continue unicast communication with cell #1 (gNB200#1) even if the number of its own receivers is limited, while receiving MBS from cell #2 (gNB200#2) using a receiver whose corresponding secondary cell has been released.

[0132] (5) Other Embodiments The above-described embodiments have been described primarily in terms of inter-PLMN scenarios. However, the embodiments are also applicable to intra-PLMN scenarios. Furthermore, the above-described embodiments have illustrated an example of requesting and configuring a static MBS gap using an RRC message, but this is not limiting. The UE 100 may dynamically request an MBS gap using Layer 1 or Layer 2 (L1 / L2) signaling, and the gNB 200 may similarly dynamically configure the MBS gap. For example, the UE 100 may notify the gNB 200 that an MBS gap is required in a time slot after the current time slot. The notification includes information indicating the time slot in which the gap is required (e.g., the number of slots after which the gap is required). Upon receiving the request, the gNB 200 may recognize that a gap will be applied in the time slot (the UE 100 does not perform reception processing), or the gNB 200 may explicitly configure the UE 100 to apply an MBS gap in the time slot. The L1 / L2 signaling is DCI and / or MAC CE. The L1 / L2 signaling may include at least a portion of the information elements included in the RRC message. The L1 / L2 signaling may be transmitted from the UE 100 when the UE 100 is permitted to transmit from the gNB 200 (for example, when configured in RRC Reconfiguration).

[0133] Similarly, UE100 may dynamically request SCell release (or SCell deactivation) using Layer 1 or Layer 2 (L1 / L2) signaling, and gNB200 may similarly dynamically configure SCell release (or SCell deactivation).

[0134] The above-described operational flows are not limited to being implemented independently, but can also be implemented by combining two or more operational flows. For example, some steps of one operational flow may be added to another operational flow, or some steps of one operational flow may be replaced with some steps of another operational flow. In each flow, it is not necessary to execute all steps, and only some steps may be executed.

[0135] 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.

[0136] Also, the term "network node" primarily refers to a base station, but may also refer to a device in the core network or part of a base station (CU, DU, or RU).

[0137] A program may be provided that causes a computer to execute each process performed by the UE 100 or the gNB 200. 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 a DVD-ROM. Furthermore, circuits that execute each process performed by the UE 100 or the gNB 200 may be integrated, and at least a portion of the UE 100 or the gNB 200 may be configured as a semiconductor integrated circuit (chip set, SoC: System on a chip).

[0138] 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.

[0139] 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.

[0140] This application claims priority to U.S. Provisional Application No. 63 / 411,243 (filed September 29, 2022), the entire contents of which are incorporated herein by reference.

[0141] (6) Supplementary Notes The following are additional notes regarding the features of the above-described embodiment.

[0142] (Supplementary Note 1) A communication method used in a mobile communication system that provides a multicast / broadcast service (MBS), comprising: a step of a user equipment configured with multiple serving cells communicating with a network using the multiple serving cells; and a step of the user equipment transmitting request information to the network, the request information requesting the release or deactivation of any one of the multiple serving cells, in order to receive MBS from another cell different from the multiple serving cells.

[0143] (Supplementary Note 2) The communication method according to Supplementary Note 1, wherein the request information is information requesting release or deactivation of a secondary cell among the plurality of serving cells.

[0144] (Supplementary Note 3) The communication method according to Supplementary Note 1 or 2, wherein the request information includes at least one of an identifier of a serving cell to be released or deactivated and an identifier of a frequency to be released or deactivated.

[0145] (Supplementary Note 4) The communication method according to any one of Supplementary Notes 1 to 3, further comprising the step of, when the user equipment terminates reception of the MBS of the other cell, transmitting notification information regarding the termination to the network.

[0146] (Supplementary Note 5) A communication method used in a mobile communication system that provides a multicast / broadcast service (MBS), comprising: a step of a user equipment, configured with one or more serving cells, communicating with a network using the one or more serving cells; a step of the user equipment becoming interested in receiving MBS in another cell different from the one or more serving cells; and a step of the user equipment determining whether a transmission condition for transmitting request information to the network for receiving MBS in the other cell is satisfied, wherein the request information is information requesting setting an MBS gap or information requesting release or deactivation of a serving cell, and the determining step includes a step of determining whether a condition is satisfied that the network does not provide a system information block including information on frequencies to be used for receiving MBS is satisfied.

[0147] (Supplementary Note 6) The communication method according to any one of Supplementary Notes 1 to 5, wherein the other cell is a cell belonging to another network of an operator different from an operator of the network.

[0148] (7) Supplementary Notes Supplementary notes on the above embodiments are provided below. Introduction The work item on enhanced MBS (eMBS) includes the objective of supporting UE shared processing for MBS broadcast and unicast as follows: - Specify an extension to Uu signaling to enable UE to use shared processing for MBS broadcast and unicast reception, including reporting of UE capabilities and related assistance information for simultaneous reception of unicast reception in RRC Connected and MBS broadcast reception from the same or different operators.

[0149] In RAN2#119e, the following was agreed upon: - RAN2 will focus on solutions targeting multi-RxUEs (i.e., no special enhancements for 1RxUEs).

[0150] Discussion Gap Configuration The justification for WID specifies that the UE receives an interesting MBS service from another operator, i.e., inter-PLMN MBS reception.

[0151] The Rel-17 NRMBS broadcast solution allows UEs to receive broadcast services only in the downlink. However, in typical broadcast use cases, UEs may need to simultaneously receive broadcast services and unicast services from the same or a different operator's network. Some UEs may share hardware resources between broadcast and unicast services. Therefore, for such UEs, unicast connectivity may be affected by broadcast reception. This paper focuses on the cases of unicast reception in RRC Connected and broadcast reception (including emergency and public safety broadcasts) from the same or a different operator.

[0152] In the case of shared operation, the UE can use the same receiver for MBS broadcast and unicast. As mentioned above, MBS services may be provided by different operators and therefore on different frequencies. If one receiver is used for different frequencies, the UE must tune its RF chain to these frequencies in a TDD manner. Therefore, for shared operation, an additional gap is required for MBS broadcast reception. During this gap, the gNB avoids scheduling DL transmissions for unicast, so the UE can receive the desired MBS broadcast on another frequency / operator. This is similar to the measurement gap in inter-frequency measurements or the MUSIM gap in inter-PLMN operation.

[0153] Observation 1: The UE can tune its RF chain to a frequency different from the MBS frequency during gaps when the gNB does not schedule unicast transmission or reception.

[0154] Regarding gaps, the question is whether existing MUSIM gaps can be reused for MBS reception. Technically, MUSIM gaps could be extended for MBS reception, for example by adding periodicity or length. However, in the current specification, MUSIM gaps are limited to MUSIM purposes as follows: It is clear that the current MUSIM gaps are not intended to be used for MBS reception.

[0155] If the UE requires a gap pattern for MUSIM purposes such as cell identification and measurement, paging monitoring, SIB acquisition, and / or on-demand SI request for a target cell of the target network, the network may provide one or more per-UE MUSIM gap patterns for simultaneous monitoring of all frequency layers for MUSIM via MUSIM-GapConfig.

[0156] Furthermore, using the same gap for different purposes is expected to introduce unnecessary complexity. Indeed, the MUSIM gap was introduced in Rel-17 separately from the existing measurement gaps, which is simpler from both the network and UE perspectives, as well as from the specification and implementation perspective. Therefore, it would be desirable to introduce an additional gap specific to inter-frequency / inter-PLMN MBS reception, distinct from the MUSIM gap.

[0157] Proposal 1: RAN2 should agree to introduce an additional gap for inter-frequency (and inter-PLMN) reception of MBS broadcasts in RRC Connected, i.e., an "MBS gap".

[0158] Gap Assistance Information If Proposal 1 is acceptable, the gNB needs to configure MBS gaps for the UE, but the gNB does not know what gap pattern the UE requires. Therefore, the UE needs to send assistance information to inform the gNB of the details of the required gaps. This is because the current network (i.e., the selected PLMN) does not know the details of MBS broadcast configurations of different operators, such as MTCH scheduling information. This is similar to the MUSIM assistance introduced in UAI.

[0159] Proposal 2: RAN2 should agree to introduce additional assistance information from the UE into the MBS gap configuration, especially when the interesting MBS broadcast is provided by another PLMN.

[0160] If Proposal 2 is acceptable, it is worth considering what kind of assistance information will be required. Currently, a UE can notify a gNB of an MBS Interest Indication (MII). The MII includes the TMGI, frequency, and priority of MBS broadcast and unicast. If the same operator provides the MBS broadcast of interest, the gNB may know the MTCH scheduling information for a specific TMGI provided on a different frequency, so the current MII will be sufficient.

[0161] Note that regardless of whether the gNB provides MBS services, the gNB must provide SIB21 to enable the UE to transmit the MII.

[0162] Proposal 3: In the case of an intra-PLMN, RAN2 should agree to use the existing MBS interest notification as the assistance information for the MBS gap.

[0163] Since the gNB of the selected network does not know the MBS broadcast settings of different networks, if a different operator provides the desired MBS broadcast, the UE needs to provide the gNB with a gap pattern. The gap pattern needs to be based on the MTCH scheduling information of the different operator, but the reference needs to be based on the selected network. Furthermore, the RF tuning time can also be included, and how to set the gap pattern is left to the UE implementation.

[0164] Proposal 4: In the inter-PLMN case, RAN2 should agree that the UE requests a gap pattern from the gNB, and the gap pattern can cover the RF tuning time and MTCH scheduling period of different PLMNs.

[0165] RAN2 #119e proposed additional information for the MII similar to the ROM of LTEe MBMS, such as ROM frequency, ROM subcarrier spacing, and bandwidth. However, since the subcarrier spacing and bandwidth of different operators' MBS transmissions do not convey time-domain information such as MTCH occasion, it is unclear how these can support NR gNBs. Also, in NRMBS, the frequency of the MII can be determined based on the USD even if such a frequency is not listed in SIB21. Therefore, the existing frequency information of the MII can be used in the same way as the ROM frequency of LTEe MBMS.

[0166] Observation 2: The extension of MBS interest notification for ROM support in LTE eMBMS is not directly applicable to the shared processing of NRMBS.

[0167] Other Considerations Some companies have commented that in RAN2#119e the gap mechanism is complex from a network perspective. In this case, it is up to the network implementation to allow MBS gaps and the corresponding assistance information. However, the fundamental question remains whether the UE can receive MBS services from another network if all of its receivers are used for unicast transmissions in the serving network (e.g., if the UE is unable to receive the desired MBS service due to carrier aggregation configuration).

[0168] Although it would no longer be a "shared process," one simple way to enable a UE to use one of its receivers for MBS reception would be for the gNB to deconfigure or deactivate one of the UE's currently active SCells. However, since the gNB may not know if / when the UE prefers SCell deconfiguration / deactivation, it is worth discussing whether additional assistance information, such as SCell deconfiguration / deactivation for MBS reception, in addition to the MBS gap described above, would be useful. If it is recognized as useful, it should be discussed whether the current MII contents, i.e., frequency and priority, work for this purpose.

[0169] Proposal 5: RAN2 should further discuss whether the UE is allowed to notify the gNB of the priority regarding the reconfiguration or deactivation of the SCell for MBS reception from different PLMNs.

[0170] 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

Claims

1. A communication method used in a mobile communication system that provides a multicast / broadcast service (MBS), comprising: A user device with a plurality of serving cells configured to communicate with a network using the plurality of serving cells; The user device receiving information regarding the MBS frequency in a non-serving cell, which is a cell different from the plurality of serving cells and is a non-serving cell of the user device; The user device transmitting a first MBS Interest Indication (MII) including information regarding the MBS frequency in the non-serving cell to the network in order to perform MBS reception from the non-serving cell; The user device transmitting a second MII to the network when ending the MBS reception in the non-serving cell. A communication method.

2. A user device used in a mobile communication system that provides a multicast / broadcast service (MBS), comprising: A wireless communication unit with a plurality of serving cells configured to communicate with a network using the plurality of serving cells; The wireless communication unit includes: A receiving unit that receives information regarding the MBS frequency in a non-serving cell, which is a cell different from the plurality of serving cells and is a non-serving cell of the user device; A transmitting unit that transmits a first MBS Interest Indication (MII) including information regarding the MBS frequency in the non-serving cell to the network in order to perform MBS reception from the non-serving cell, and transmits a second MII to the network when ending the MBS reception in the non-serving cell. A user device.

3. A mobile communication system that provides a multicast / broadcast service (MBS), comprising: A user device with a plurality of serving cells configured to communicate with a network using the plurality of serving cells; The user device receiving information regarding the MBS frequency in a non-serving cell, which is a cell different from the plurality of serving cells and is a non-serving cell of the user device; In order for the user equipment to receive MBS from the non-serving cell, the user equipment transmits a first MBS Interest Indication (MII) including information on the MBS frequency in the non-serving cell to the network. When the user equipment finishes receiving MBS from the non-serving cell, the user equipment transmits a second MII to the network. Mobile communication system.

4. A user equipment used in a mobile communication system that provides a multicast / broadcast service (MBS), a plurality of serving cells are set, and a process of communicating with a network using the plurality of serving cells; a process of receiving information on the MBS frequency in the non-serving cell from a non-serving cell different from the plurality of serving cells; In order to receive MBS from the non-serving cell, a first MBS Interest Indication (MII) including information on the MBS frequency in the non-serving cell is transmitted to the network, and when the MBS reception from the non-serving cell is terminated, a second MII is transmitted to the network. A process of executing Program.

5. A chipset of a user equipment used in a mobile communication system that provides a multicast / broadcast service (MBS), a plurality of serving cells are set, and communication with a network is performed using the plurality of serving cells; receiving information on the MBS frequency in the non-serving cell from a non-serving cell different from the plurality of serving cells; In order to receive MBS from the non-serving cell, a first MBS Interest Indication (MII) including information on the MBS frequency in the non-serving cell is transmitted to the network, and when the MBS reception from the non-serving cell is terminated, a second MII is transmitted to the network. A process of executing Chipset.