Communication control method, base station, mobile communication system, and program

Abstract

A communication control method for use in a mobile communication system. The communication control method comprises: a base station, shared by a plurality of core networks, receiving from each of the plurality of core networks an MBS service identifier indicating an MBS service provided by the core network; and the base station transmitting, to a plurality of items of user equipment belonging to a plurality of public land mobile networks (PLMN) corresponding to the plurality of core networks, MBS data belonging to the MBS service, by multicast or broadcast. The MBS service identifier is a unique identifier independent of the PLMNs.

Description

Technical Field

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

Background Art

[0002] In the 3GPP (3rd Generation Partnership Project) standard, the technical specifications of NR (New Radio), which is a 5th generation (5G) radio access technology, are defined. NR has characteristics such as high speed, large capacity, high reliability, and low latency compared to LTE (Long Term Evolution), which is a 4th generation (4G) radio access technology. Introducing a multicast / broadcast service (MBS) into such a 5G system has been considered.

[0003] One base station or one cell may be shared by a plurality of core networks belonging to different operators (Public Land Mobile Network: PLMN). In such a scenario, when the same MBS service is provided from each core network via the base station, a method has been proposed to reduce the usage amount of radio resources for MBS by the base station transmitting MBS data using radio resources common to a plurality of operators (see Non-Patent Document 1).

Prior Art Documents

Non-Patent Documents

[0004]

Non-Patent Document 1

Summary of the Invention

[0005] The communication control method according to the first aspect is a communication control method used in a mobile communication system. A base station shared by a plurality of core networks receives, from each of the plurality of core networks, an MBS service identifier indicating an MBS service provided by the core network. The base station transmits, to a plurality of user devices belonging to a plurality of PLMNs (Public Land Mobile Networks) corresponding to the plurality of core networks, MBS data belonging to the MBS service by multicast or broadcast. The MBS service identifier is a unique identifier independent of the PLMN.

[0006] The base station according to the second aspect is a base station shared by a plurality of core networks in a mobile communication system. The base station includes a network communication unit that receives, from each of the plurality of core networks, an MBS service identifier indicating an MBS service provided by the core network, and a radio communication unit that transmits, to a plurality of user devices belonging to a plurality of PLMNs corresponding to the plurality of core networks, MBS data belonging to the MBS service by multicast or broadcast. The MBS service identifier is a unique identifier independent of the PLMN.

[0007] The communication control method according to the third aspect is a communication control method used in a mobile communication system. A base station shared by a plurality of core networks transmits, to a plurality of user devices belonging to a plurality of PLMNs corresponding to the plurality of core networks, control information used for receiving an MBS traffic channel and / or receiving an MBS control channel. The base station transmits, using the MBS traffic channel, MBS data to the plurality of user devices by multicast or broadcast. The control information includes the PLMN identifier of each of the plurality of PLMNs.

[0008] The base station according to the fourth aspect is a base station shared by a plurality of core networks in a mobile communication system, and includes a wireless communication unit that transmits control information used for receiving an MBS traffic channel and / or receiving an MBS control channel to a plurality of user devices belonging to a plurality of PLMNs corresponding to the plurality of core networks. The wireless communication unit transmits MBS data to the plurality of user devices by multicast or broadcast using the MBS traffic channel. The control information includes the PLMN identifier of each of the plurality of PLMNs.

[0009] The user equipment according to the fifth aspect is a user equipment used in a mobile communication system, and includes a wireless communication unit that receives control information used for receiving an MBS traffic channel and / or receiving an MBS control channel from a base station shared by a plurality of core networks. The wireless communication unit receives MBS data transmitted by multicast or broadcast from the base station to a plurality of user devices belonging to a plurality of PLMNs corresponding to the plurality of core networks using the MBS traffic channel. The control information includes the PLMN identifier of each of the plurality of PLMNs.

Brief Description of Drawings

[0010]

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Embodiments for Carrying Out the Invention

[0011] In the current 3GPP technical specifications, a mechanism for facilitating the base station to transmit MBS data using wireless resources common to a plurality of core networks (a plurality of PLMNs) has not been introduced. Therefore, there is a problem that it is difficult to perform efficient MBS distribution.

[0012] Therefore, the present disclosure provides a communication control method, a base station, and a user device that enable efficient MBS distribution in a mobile communication system.

[0013] With reference to the drawings, a mobile communication system according to an embodiment will be described. In the description of the drawings, the same or similar parts are denoted by the same or similar reference numerals.

[0014] [First Embodiment] First, with reference to FIGS. 1 to 9, a mobile communication system according to the first embodiment will be described.

[0015] (Configuration of Mobile Communication System) FIG. 1 is a diagram showing the configuration of a mobile communication system according to the first embodiment. The mobile communication system 1 complies with the 5th Generation System (5GS) of the 3GPP standard. Hereinafter, the 5GS will be described as an example, but an LTE (Long Term Evolution) system may be at least partially applied to the mobile communication system. A 6th Generation (6G) system may be at least partially applied to the mobile communication system.

[0016] The mobile communication system 1 includes a user equipment (UE) 100, a 5G radio access network (NG-RAN) 10, and a 5G core network (5GC) 20. Hereinafter, the NG-RAN 10 may be simply referred to as the RAN 10. Also, the 5GC 20 may be simply referred to as the core network (CN) 20.

[0017] The UE 100 is a movable wireless communication device. The UE 100 may be any device as long as it is a device used by a user. For example, the UE 100 is a mobile phone terminal (including a smartphone) 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), an aircraft or a device provided in an aircraft (Aerial UE).

[0018] NG-RAN 10 includes base stations (referred to as "gNB" in the 5G system) 200. The gNBs 200 are interconnected via the Xn interface, which is an interface between base stations. The gNB 200 manages one or more cells. The gNB 200 performs wireless communication with the UE 100 that has established a connection with its own cell. The gNB 200 has functions such as a radio resource management (RRM) function, a routing function for user data (hereinafter simply referred to as "data"), and a measurement control function for mobility control and scheduling. A "cell" is used as a term indicating the smallest unit of a wireless communication area. A "cell" is also used as a term indicating a function or resource for performing wireless communication with the UE 100. One cell belongs to one carrier frequency.

[0019] Note that the gNB can also be connected to the EPC (Evolved Packet Core), which is the core network of LTE. The base station of LTE can also be connected to the 5GC. The base station of LTE and the gNB can also be connected via an interface between base stations.

[0020] The 5GC 20 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 performs transfer control of data. The AMF and the UPF are connected to the gNB 200 via the NG interface, which is an interface between the base station and the core network.

[0021] FIG. 2 is a diagram showing the configuration of the UE 100 (user equipment) according to the first 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.

[0022] The receiving unit 110 performs various receptions under the control of the control unit 130. The receiving unit 110 includes an antenna and a receiver. The receiver converts the radio signal received by the antenna into a baseband signal (received signal) and outputs it to the control unit 130.

[0023] 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 the baseband signal (transmission signal) output by the control unit 130 into a radio signal and transmits it from the antenna.

[0024] The control unit 130 performs various controls and processes in the UE 100. Such processes include the processes of each layer described later. The control unit 130 includes at least one processor and at least one memory. The memory stores programs executed by the processor and information used for the processing 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 the baseband signal, etc. The CPU executes the programs stored in the memory to perform various processes.

[0025] FIG. 3 is a diagram showing the configuration of the gNB 200 (base station) according to the first embodiment. The gNB 200 includes a transmitting unit 210, a receiving unit 220, a control unit 230, and a backhaul communication unit 240. The transmitting unit 210 and the receiving unit 220 constitute a wireless communication unit that performs wireless communication with the UE 100. The backhaul communication unit 240 constitutes a network communication unit that communicates with the CN 20.

[0026] 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 the baseband signal (transmission signal) output by the control unit 230 into a radio signal and transmits it from the antenna.

[0027] The receiving unit 220 performs various receptions under the control of the control unit 230. The receiving unit 220 includes an antenna and a receiver. The receiver converts the radio signal received by the antenna into a baseband signal (received signal) and outputs it to the control unit 230.

[0028] The control unit 230 performs various controls and processes in the gNB 200. Such processes include the processes of each layer described later. The control unit 230 includes at least one processor and at least one memory. The memory stores programs executed by the processor and information used for the processing by the processor. The processor may include a baseband processor and a CPU. The baseband processor performs modulation / demodulation and encoding / decoding of the baseband signal, etc. The CPU executes the programs stored in the memory to perform various processes.

[0029] The backhaul communication unit 240 is connected to an adjacent base station via a base station interface. The backhaul communication unit 240 is connected to the AMF / UPF 300 via a base station-core network interface. Note that the gNB is composed of a CU (Central Unit) and a DU (Distributed Unit) (i.e., functionally split), and the two units may be connected by an F1 interface.

[0030] FIG. 4 is a diagram showing the configuration of a protocol stack of a radio interface of a user plane that handles data.

[0031] The radio interface protocol of the user plane has a physical (PHY) layer, a MAC (Medium Access Control) layer, an RLC (Radio Link Control) layer, a PDCP (Packet Data Convergence Protocol) layer, and an SDAP (Service Data Adaptation Protocol) layer.

[0032] The PHY layer performs encoding / decoding, modulation / demodulation, antenna mapping / demapping, and resource mapping / demapping. Between the PHY layer of UE100 and the PHY layer of gNB200, data and control information are transmitted via physical channels.

[0033] The MAC layer performs priority control of data, retransmission processing by hybrid automatic repeat request (HARQ), and random access procedures, etc. Between the MAC layer of UE100 and the MAC layer of gNB200, data and control information are transmitted via transport channels. The MAC layer of gNB200 includes a scheduler. The scheduler determines the uplink and downlink transport formats (transport block size, modulation and coding scheme (MCS)) and the resource blocks allocated to UE100.

[0034] The RLC layer uses the functions of the MAC layer and the PHY layer to transmit data to the RLC layer on the receiving side. Between the RLC layer of UE100 and the RLC layer of gNB200, data and control information are transmitted via logical channels.

[0035] The PDCP layer performs header compression / decompression, encryption / decryption, etc.

[0036] The SDAP layer performs the mapping between the IP flow, which is the unit for the core network to perform QoS (Quality of Service) control, and the radio bearer, which is the unit for the access stratum (AS) to perform QoS control. Note that when the RAN is connected to the EPC, the SDAP may not be necessary.

[0037] Figure 5 is a diagram showing the configuration of the protocol stack of the radio interface of the control plane that handles signaling (control signals).

[0038] 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. 4.

[0039] Between the RRC layer of UE100 and the RRC layer of gNB200, RRC signaling for various settings is transmitted. The RRC layer controls the logical channel, transport channel, and physical channel in response to the establishment, re-establishment, and release of the radio bearer. When there is a connection (RRC connection) between the RRC of UE100 and the RRC of gNB200, UE100 is in the RRC connected state. When there is no connection (RRC connection) between the RRC of UE100 and the RRC of gNB200, UE100 is in the RRC idle state. When the connection between the RRC of UE100 and the RRC of gNB200 is suspended, UE100 is in the RRC inactive state.

[0040] The NAS layer located above the RRC layer performs session management, mobility management, etc. Between the NAS layer of UE100 and AMF30 0 of NAS signaling is transmitted between the NAS layer and the NAS layer.

[0041] Note that UE100 has an application layer etc. in addition to the protocol of the radio interface.

[0042] (Overview of MBS) The overview of the MBS according to the first embodiment will be described. MBS is a service that enables the transmission of data from the NG-RAN 10 to the UE 100 in a broadcast or multicast manner, that is, one-to-many (PTM: Point To Multipoint). As use cases (service types) of MBS, public security communication, mission-critical communication, V2X (Vehicle to Everything) communication, IPv4 or IPv6 multicast distribution, IPTV (Internet Protocol TeleVision), group communication, software distribution, etc. are assumed.

[0043] The broadcast service provides services to all UEs 100 within a specific service area for applications that do not require high-reliability QoS. The MBS session used for the broadcast service is called a broadcast session.

[0044] The multicast service provides services not to all UEs 100 but to a group of UEs 100 that participate in the multicast service. The MBS session used for the multicast service is called a multicast session. According to the multicast service, the same content can be provided to a group of UEs 100 in a more radio-efficient manner than the broadcast service.

[0045] FIG. 6 is a diagram showing an overview of MBS traffic distribution according to the first embodiment.

[0046] As shown in FIG. 6, MBS traffic (MBS data) is distributed from a single data source (application service provider) to multiple UEs. The 5G CN (5GC) 20, which is a 5G core network, receives MBS data from the application service provider, creates (Replication) copies of the MBS data, and distributes them.

[0047] From the perspective of 5GC20, there are two multicast delivery methods: 5GC Shared MBS Traffic delivery and 5GC Individual MBS Traffic delivery.

[0048] In the 5GC Individual MBS Traffic delivery method, 5GC20 receives a single copy of the MBS data packets and delivers individual copies of those MBS data packets to individual UEs 100 via a PDU session for each UE 100. Therefore, one PDU session per UE 100 needs to be associated with the multicast session.

[0049] In the 5GC Shared MBS Traffic delivery method, 5GC20 receives a single copy of the MBS data packets and delivers a single copy of those MBS packets to the RAN node (i.e., gNB200). The gNB200 receives the MBS data packets via the MBS tunnel connection and delivers them to one or more UEs 100.

[0050] From the perspective of the RAN (5G RAN) 10, for the wireless transmission of MBS data in the 5GC Shared MBS Traffic delivery method, there are two delivery methods: PTP (Point-to-Point) and PTM (Point-to-Multipoint). PTP means unicast, and PTM means multicast and broadcast.

[0051] In the PTP delivery method, the gNB200 wirelessly delivers individual copies of the MBS data packets to individual UEs 100. On the other hand, in the PTM delivery method, the gNB200 wirelessly delivers a single copy of the MBS data packets to a group of UEs 100. The gNB200 can dynamically determine whether to use PTM or PTP as the delivery method for MBS data to a single UE 100.

[0052] The PTP delivery method and the PTM delivery method mainly relate to the user plane. As control modes for MBS data delivery, there are two delivery modes: the first delivery mode and the second delivery mode. FIG. 7 is a diagram showing the delivery mode according to the first embodiment.

[0053] As shown in FIG. 7, the first delivery mode (Delivery mode 1) is a delivery mode available to the UE100 in the RRC connected state and is a delivery mode for high QoS requirements. The first delivery mode is used for the multicast session among the MBS sessions. However, the first delivery mode may also be used for the broadcast session. The first delivery mode may also be available to the UE100 in the RRC idle state or the RRC inactive state.

[0054] In the first embodiment, the setting of MBS reception in the first delivery mode is performed by UE-dedicated signaling. For example, the setting of MBS reception in the first delivery mode is performed by an RRC Reconfiguration message (or an RRC Release message), which is an RRC message transmitted unicast from the gNB200 to the UE100.

[0055] The setting of MBS reception includes MBS traffic channel setting information (hereinafter referred to as "MTCH setting information") regarding the setting of the MBS traffic channel that carries MBS data. The MTCH setting information includes MBS session information regarding the MBS session and scheduling information of the MBS traffic channel corresponding to this MBS session.

[0056] Note that the MBS traffic channel is a type of logical channel and may be called an MTCH (Multicast Traffic Channel). The MBS traffic channel is mapped to a DL-SCH (Downlink Shared Channel), which is a type of transport channel.

[0057] The second delivery mode (Delivery mode 2) is a delivery mode that can be used not only by the UE 100 in the RRC connected state but also by the UE 100 in the RRC idle state or the RRC inactive state, and is a delivery mode for low QoS requirements. The second delivery mode is used for the broadcast session among the MBS sessions. However, the second delivery mode may also be applicable to the multicast session.

[0058] The setting of MBS reception in the second delivery mode is performed by broadcast signaling. For example, the setting of MBS reception in the second delivery mode is performed by logical channels broadcast from the gNB 200 to the UE 100, such as the BCCH (Broadcast Control Channel) and / or the MCCH (Multicast Control Channel). Hereinafter, such a control channel may be referred to as an MBS control channel. The UE 100 can receive the BCCH and the MCCH using, for example, a dedicated RNTI predefined in the technical specifications.

[0059] Note that the network can provide different MBS services for each MBS session. The MBS session is identified by at least one of the TMGI (Temporary Mobile Group Identity), the session identifier, and the group RNTI (Radio Network Temporary Identifier). At least one of the TMGI and the session identifier is called an MBS session identifier (MBS session ID). The TMGI, the session identifier, and the group RNTI are collectively referred to as MBS session information.

[0060] (Operation of the mobile communication system) The operation of the mobile communication system 1 according to the first embodiment will be described. FIG. 8 is a diagram for explaining the operation according to the first embodiment.

[0061] Assume a scenario where one gNB200 (one cell) is shared by a plurality of CN20s belonging to different operators (PLMNs). In FIG. 8, an example is shown where one gNB200 (one cell) is shared by two CN20s, namely CN20A and CN20B, but one gNB200 (one cell) may also be shared by three or more CN20s. CN20A belongs to PLMN#1 and CN20B belongs to PLMN#2. Here, "#1" and "#2" mean the identifiers (PLMN IDs) of the PLMNs.

[0062] In the cell of gNB200, there are a plurality of UEs100 that are receiving or interested in receiving MBS services (MBS data) provided by multicast or broadcast. Here, UE100A1 to UE100A3 belong to PLMN#1, and UE100B1 to UE100B3 belong to PLMN#2. Hereinafter, when not distinguishing UE100A1 to UE100A3, they are simply called UE100A, and when not distinguishing UE100B1 to UE100B3, they are simply called UE100B. Note that an example is shown where the number of UEs100 belonging to each PLMN is three, but the number of UEs100 belonging to each PLMN may be one, two, or four or more.

[0063] In such a scenario, when providing the same MBS service from each CN20 via gNB200, gNB200 transmits MBS data using radio resources common to PLMN#1 and PLMN#2 (i.e., the same radio resources). Thereby, the amount of radio resources used for MBS distribution can be reduced compared to the case where gNB200 transmits MBS data using individual radio resources (i.e., different radio resources) for PLMN#1 and PLMN#2.

[0064] In the first embodiment, the gNB 200 shared by a plurality of CNs 20 (specifically, the gNB 200 that manages cells shared by a plurality of PLMNs) receives, from each of the plurality of CNs 20, an MBS service identifier (MBS service ID) indicating the MBS service provided by the CN 20. In the example of FIG. 8, the gNB 200 receives, from the CN 20A, the MBS service ID of the MBS service provided by the CN 20A, and receives, from the CN 20B, the MBS service ID of the MBS service provided by the CN 20B.

[0065] The MBS service ID is a unique identifier independent of the PLMN (i.e., a global identifier). The MBS service ID may be referred to as an MBS application ID. Based on the MBS service ID received from the CN 20, the gNB 200 can uniquely identify the MBS service provided by the CN 20. Therefore, the gNB 200 can determine whether the MBS services provided by the CN 20A and the CN 20B are the same based on the MBS service IDs received from the CN 20A and the CN 20B, respectively.

[0066] In response to receiving the same MBS service ID from the CN 20A and the CN 20B, the gNB 200 transmits MBS data belonging to the MBS service using radio resources common to the PLMN #1 and the PLMN #2. Therefore, when the MBS services provided by the CN 20A and the CN 20B are the same, the usage amount of radio resources for MBS distribution can be reduced.

[0067] Also, when the MBS services provided by the CN 20A and the CN 20B are the same, the gNB 200 may acquire MBS data from one of the CN 20A and the CN 20B. Therefore, since the gNB 200 does not have to acquire MBS data from the other CN 20, the usage amount of backhaul communication resources can also be reduced.

[0068] gNB200 may receive an MBS session start message including an MBS service ID from each of CN20A and CN20B. For example, when CN20A starts providing an MBS service, gNB200 receives an MBS session start message including the MBS service ID of the MBS service from CN20A. Similarly, when CN20B starts providing an MBS service, gNB200 receives an MBS session start message including the MBS service ID of the MBS service from CN20B. Thereby, gNB200 can efficiently grasp the MBS services provided by each of CN20A and CN20B. Note that the session start message may be an MBS session start scheduled message. gNB200 may broadcast the MBS session start scheduled message to UE100 in an SIB (such as MBS-SIB, etc.). UE100 may perform cell selection or cell reselection based on the SIB.

[0069] Based on the MBS service IDs received from each of CN20A and CN20B, gNB200 may send notification information indicating the necessity of providing the MBS service to any one of the CN20s. For example, in response to receiving the same MBS service identifier from CN20A and CN20B, gNB200 may send notification information indicating that it is not necessary to provide the MBS service to one of CN20A and CN20B. Thereby, the usage amount of backhaul communication resources for acquiring MBS data and the load on CN20 can be reduced.

[0070] gNB200 may receive information indicating whether to permit sharing radio resources and / or CN resources for transmitting MBS data with at least one of CN20A and CN20B with other CN20s. The information may be associated with the MBS service ID. The information may further include either the PLMN identifier for which resource sharing is permitted or information indicating the CN20 (or PLMN) that provides data (i.e., gNB200 acquires data) when resources are shared. If gNB200 receives the same MBS service identifier from CN20A and CN20B, and in response to CN20A and CN20B permitting sharing of radio resources and / or CN resources, gNB200 transmits MBS data belonging to the MBS service using radio resources common to PLMN#1 and PLMN#2 (i.e., the same radio resources). If at least one of CN20A and CN20B does not permit sharing radio resources and / or CN resources for transmitting MBS data with other CN20s, MBS distribution using radio resources common to PLMN#1 and PLMN#2 (i.e., the same radio resources) may be prohibited.

[0071] FIG. 9 is a diagram showing an example of operations according to the first embodiment. Note that not all steps in FIG. 9 necessarily need to be executed, and only some steps may be executed. Also, the order of steps in FIG. 9 may be changed.

[0072] In step S101, the AMF300A included in CN20A transmits an MBS session start message including an MBS session identifier (MBS session ID) corresponding to the MBS service and an MBS service ID that uniquely identifies the MBS service to gNB200 in order to start providing the MBS service in PLMN#1.

[0073] Here, the MBS session ID is an identifier unique to the PLMN. Therefore, even when CN20A and CN20B provide the same MBS service, the MBS session IDs of CN20A and CN20B can be different.

[0074] The MBS session start message is a message transmitted and received on the NG interface, for example, the NG-AP MBS Session Start (Activation) message. However, the MBS service ID may also be notified to gNB200 by a message other than the MBS session start message.

[0075] In step S102, gNB200 that has received the MBS session start message from AMF300A may send a response message to AMF300A. Here, since gNB200 has not detected that CN20A provides the MBS service that other CN20s also provide, it is assumed that gNB200 sends an affirmative response message to AMF300A. In response to receiving the affirmative response message from gNB200, CN20A may start providing the MBS service and start transmitting MBS data to gNB200.

[0076] In step S103, AMF300B included in CN20B sends a MBS session start message containing the MBS session ID corresponding to the MBS service and the MBS service ID that uniquely identifies the MBS service to gNB200 in order to start providing the MBS service in PLMN#2. Here, it is assumed that the MBS service provided by CN20B is the same as the MBS service provided by CN20A. Therefore, the MBS service ID sent by AMF300B in step S103 is the same as the MBS service ID sent by AMF300A in step S101.

[0077] Each of AMF300A and AMF300B may include information (permission information) indicating whether to permit sharing of radio resources (and backhaul CN resources) with other PLMNs in the MBS session start message and transmit it.

[0078] In addition, each of AMF300A and AMF300B (or CN20A and CN20B to which AMF300A and AMF300B belong, or other network functions (such as SMF) belonging to CN20A or CN20B) may obtain the MBS service ID from the MBS application server, for example, via an API (Application Programming Interface). Such an API may be provided by the NEF (Network Exposure Function).

[0079] Also, AMF300A and / or AMF300B may negotiate with the MBS application server about sharing of radio resources and / or CN resources. For example, AMF300A and / or AMF300B may notify the MBS application server that it is possible to share its CN resources with other CNs (other PLMNs), and one or more of the identifiers of other CNs (other PLMNs) that permit sharing. The MBS application server may transmit to AMF300A and / or AMF300B one or more of information specifying the AMF300 that provides MBS data (i.e., information specifying the master network side for the MBS service provision) and information about AMF300 that does not provide MBS data (i.e., information about the secondary network side for the MBS service provision: for example, PLMN identifier).

[0080] Since the gNB 200 that has received the MBS session start message from the AMF 300B finds that the MBS service ID received in step S103 is the same as the MBS service ID received in step S101, it detects that the MBS service that the CN 20B is about to start providing is being provided or is already provided by the CN 20A, and determines not to obtain the MBS data belonging to the said MBS service from the CN 20B.

[0081] In step S104, the gNB 200 sends a response message to the AMF 300B. Here, since the gNB 200 has detected that the CN 20A also provides the MBS service provided by the CN 20B, it sends a response message to the AMF 300B indicating that the provision of the said MBS service is unnecessary. The said response message may include at least one of the information indicating that the said MBS session is already being provided in another PLMN, the information indicating that the MBS tunnel connection of the said MBS session is unnecessary, and the information indicating that the MBS tunnel connection of the said MBS session is to be established but data transfer is unnecessary (stopped / suspended). In response to receiving the response message from the gNB 200, the CN 20B aborts the provision of the MBS service and does not send MBS data to the gNB 200.

[0082] The gNB 200 may send such a response message only when the CN 20A permits resource sharing. Alternatively, the gNB 200 may, at this stage, request permission for resource sharing from the AMF 300A and send the said response message only when the AMF 300 permits it.

[0083] In step S105, the CN 20A sends the MBS data belonging to the said MBS service to the gNB 200. The gNB 200 receives the MBS data.

[0084] In step S106, gNB200 transmits MBS data to UE100A and UE100B by multicast or broadcast using radio resources common to PLMN#1 and PLMN#2 (i.e., the same radio resources). Each of UE100A and UE100B receives the MBS data.

[0085] Note that in this operation sequence, it is assumed that CN20A (PLMN#1) permits resource sharing with other CNs (other PLMNs). However, it is also conceivable that CN20A (PLMN#1) does not permit resource sharing with other CNs (other PLMNs). In such a case, gNB200 may notify (request) AMF300A to stop (suspend) the data transfer of the MBS session, and may permit (request) AMF300B to start the data transfer of the MBS session. Prior to such an operation, gNB200 may inquire of AMF300B whether to permit resource sharing.

[0086] Thus, in the first embodiment, gNB200 shared by a plurality of CN20s (a plurality of PLMNs) receives an MBS service ID that uniquely identifies the MBS service from each of the plurality of CN20s, and determines whether the plurality of CN20s provide the same MBS service. Then, when gNB200 determines that the plurality of CN20s provide the same MBS service, gNB200 obtains MBS data belonging to the MBS service from only one CN20, and transmits the MBS data by multicast or broadcast using radio resources common to a plurality of PLMNs. Thereby, efficient MBS distribution can be performed in the mobile communication system 1.

[0087] [Second Embodiment] Next, with reference to FIGS. 10 to 13, differences between the second embodiment and the above-described first embodiment will be mainly described. In the second embodiment, the second delivery mode (Delivery mode 2) is mainly assumed. The configuration of the mobile communication system 1 is the same as that of the first embodiment described above.

[0088] The operation of the mobile communication system 1 according to the second embodiment will be described. The operation according to the second embodiment may be premised on the operation according to the above-described first embodiment. FIG. 10 is a diagram for explaining the operation according to the second embodiment.

[0089] As shown in FIG. 10, the gNB 200 broadcasts, on the MBS control channel (e.g., MCCH), to the UE 100 the MBS traffic channel setting information (MTCH setting information) used for receiving the MBS traffic channel (MTCH). The MTCH setting information includes an MBS session ID and MTCH scheduling information associated with the MBS session ID. The UE 100 acquires the MTCH scheduling information associated with the MBS session ID of the MBS service that the UE itself intends to receive, based on the MTCH setting information, and receives the MTCH. Note that the MTCH setting information may be referred to as PTM setting information.

[0090] However, as described above, the MBS session ID is a PLMN-specific identifier. Therefore, for example, when the UE 100B belonging to PLMN#2 receives the MBS service provided by the CN 20A belonging to PLMN#1, the UE 100B may not be able to correctly interpret the MBS session ID of PLMN#1. Thus, there is a concern that the UE 100B may not be able to receive the MTCH based on the MTCH setting information. Conversely, the same problem may occur when the UE 100A belonging to PLMN#1 receives the MBS service provided by the CN 20B belonging to PLMN#2.

[0091] In the second embodiment, the gNB 200 shared by a plurality of CN20s (CN20A and CN20B) transmits control information (MTCH setting information) used for receiving MTCH to a plurality of UEs 100 (UE100A and UE100B) belonging to a plurality of PLMNs (PLMN#1 and PLMN#2) corresponding to the plurality of CN20s. The MTCH setting information includes the PLMN identifiers of the respective PLMNs of the plurality of PLMNs. Specifically, the MTCH setting information includes a plurality of sets of an MBS session ID and a PLMN identifier (PLMN ID). That is, the MTCH setting information includes the MBS session ID for each PLMN. Thereby, the UE 100 can specify the MBS session ID of the PLMN to which it belongs in the MTCH setting information, and can correctly acquire the MTCH scheduling information.

[0092] FIG. 11 is a diagram showing an example of MTCH setting information according to the second embodiment. Here, it is assumed that the MTCH setting information is transmitted by the MCCH.

[0093] The MTCH setting information includes MTCH settings (MTCH-Info) for each PLMN. For example, the MTCH setting information includes an MTCH setting (MTCH-Info#1) for PLMN#1 and an MTCH setting (MTCH-Info#2) for PLMN#2. Here, it is assumed that the MTCH setting (MTCH-Info#1) for PLMN#1 and the MTCH setting (MTCH-Info#2) for PLMN#2 indicate the same MTCH (i.e., the same MBS service).

[0094] Each MTCH setting (MTCH-Info) includes a PLMN ID, an MBS session ID (TMGI), a G-RNTI, and MTCH scheduling information (Scheduling info). For example, the MTCH setting (MTCH-Info#1) for PLMN#1 includes the PLMN ID "#1" of PLMN#1, the MBS session ID "TMGI#A" of PLMN#1, a G-RNTI, and MTCH scheduling information (Scheduling info). The MTCH setting (MTCH-Info#2) for PLMN#2 includes the PLMN ID "#2" of PLMN#2, the MBS session ID "TMGI#B" of PLMN#2, a G-RNTI, and MTCH scheduling information (Scheduling info).

[0095] UE100A belonging to PLMN#1 receives the MTCH configuration information shown in FIG. 11. Assume that UE100A is interested in receiving the MBS session ID "TMGI#A" of PLMN#1. In this case, UE100A identifies the MTCH setting (MTCH-Info#1) that includes the PLMN ID "#1" of PLMN#1. Since the MBS session ID "TMGI#A" is included in the identified MTCH setting (MTCH-Info#1), UE100A recognizes that the MBS service of "TMGI#A" is provided, and attempts to receive MTCH based on the G-RNTI and MTCH scheduling information (Scheduling info) included in the identified MTCH setting (MTCH-Info#1). Specifically, UE100A is monitor the PDCCH at the timing indicated by the MTCH scheduling information (Scheduling info) and attempt to decode the PDCCH using the G-RNTI. And UE100A is receive MBS data in the radio resource (PDSCH) indicated by the PDCCH.

[0096] Similarly, UE100B belonging to PLMN#2 receives the MTCH configuration information shown in FIG. 11. Assume that UE100B is interested in receiving the MBS session ID "TMGI#B" of PLMN#2. In this case, UE100B identifies the MTCH configuration (MTCH-Info#2) that includes the PLMN ID "#2" of PLMN#2. Since the MBS session ID "TMGI#B" is included in the identified MTCH configuration (MTCH-Info#2), UE100B recognizes that the MBS service of "TMGI#B" is provided, and attempts to receive MTCH based on the G-RNTI and MTCH scheduling information (Scheduling info) included in the identified MTCH configuration (MTCH-Info#2). Specifically, UE100B is monitor the PDCCH at the timing indicated by the MTCH scheduling information (Scheduling info), and attempt to decode the PDCCH using the G-RNTI. Then, UE100B is receive MBS data in the radio resource (PDSCH) indicated by the PDCCH.

[0097] Here, when gNB200 transmits MBS data using radio resources common to PLMN#1 and PLMN#2, the G-RNTI and MTCH scheduling information (Scheduling info) included in the MTCH configuration (MTCH-Info#1) of PLMN#1 and the G-RNTI and MTCH scheduling information (Scheduling info) included in the MTCH configuration (MTCH-Info#2) of PLMN#2 are the same. Transmitting such identical information twice leads to a decrease in the utilization efficiency of radio resources.

[0098] Therefore, a configuration may be adopted in which the G-RNTI and MTCH scheduling information (Scheduling info) are unified in the MTCH configuration information. FIG. 12 is a diagram showing another example of the MTCH configuration information according to the second embodiment. Here, it is assumed that the MTCH configuration information is transmitted by the MCCH.

[0099] As shown in FIG. 12, the MTCH configuration information has MTCH-Cont as a common information element for both PLMN#1 and PLMN#2. In FIG. 12, an example is shown where the MTCH configuration information has three MTCH-Conts: MTCH-Cont#a, MTCH-Cont#b, and MTCH-Cont#c. Here, "#a", "#b", and "#c" are the indexes of the MTCH-Cont. The MTCH configuration (MTCH-Info#1) of PLMN#1 has the index "#a" of the MTCH-Cont instead of the G-RNTI and the MTCH scheduling information (Scheduling info). Similarly, the MTCH configuration (MTCH-Info#2) of PLMN#2 has the index "#a" of the MTCH-Cont instead of the G-RNTI and the MTCH scheduling information (Scheduling info).

[0100] UE100A belonging to PLMN#1 receives the MTCH configuration information shown in FIG. 12. Assume that UE100A is interested in receiving the MBS session ID "TMGI#A" of PLMN#1. In this case, UE100A identifies the MTCH configuration (MTCH-Info#1) including the PLMN ID "#1" of PLMN#1. Since the MBS session ID "TMGI#A" is included in the identified MTCH configuration (MTCH-Info#1), UE100A recognizes that the MBS service of "TMGI#A" is provided, and based on the index "#a" of the MTCH-Cont included in the identified MTCH configuration (MTCH-Info#1), UE100A obtains the G-RNTI and the MTCH scheduling information (Scheduling info) in MTCH-Cont#a and attempts to receive MTCH.

[0101] Similarly, UE100B belonging to PLMN#2 receives the MTCH configuration information shown in FIG. 12. Assume that UE100B is interested in receiving the MBS session ID "TMGI#B" of PLMN#2. In this case, UE100B identifies the MTCH configuration (MTCH-Info#2) including the PLMN ID "#2" of PLMN#2. Since the MBS session ID "TMGI#B" is included in the identified MTCH configuration (MTCH-Info#2), UE100B recognizes that the MBS service of "TMGI#B" is provided, and based on the index "#a" of MTCH-Cont included in the identified MTCH configuration (MTCH-Info#2), UE100B obtains the G-RNTI and MTCH scheduling information (Scheduling info) in MTCH-Cont#a and attempts to receive MTCH.

[0102] In the second embodiment, the MCCH (MTCH configuration information) may include adjacent cell information and / or adjacent frequency information for each PLMN. For example, MTCH-Info#1 may include information on adjacent cells and / or adjacent frequencies that provide the MBS service in PLMN#1. MTCH-Info#2 may include information on adjacent cells and / or adjacent frequencies that provide the MBS service in PLMN#2.

[0103] FIG. 13 is a diagram showing an example of the operation according to the second embodiment. Note that not all steps in FIG. 13 necessarily need to be executed, and only some steps may be executed.

[0104] gNB200 determines to transmit the MBS data of different PLMNs (different MBS sessions) in the same MBS service using the same radio resource (the same MTCH).

[0105] In step S201, gNB 200 transmits MTCH configuration information, for example, on the MCCH. As described above, the MTCH configuration information includes a plurality of MTCH configurations. Each MTCH configuration includes a PLMN ID and a TMGI (MBS session ID). Each MTCH configuration further includes a G-RNTI and scheduling information. Each of UE 100A and UE 100B receives the MTCH configuration information.

[0106] In step S202, gNB 200 transmits MBS data on the MTCH according to the scheduling indicated by the MTCH configuration information. UE 100A receives the MTCH of TMGI #A of PLMN #1 based on the MTCH configuration information received in step S201. UE 100B receives the MTCH of TMGI #B of PLMN #2 based on the MTCH configuration information received in step S201. Note that UE 100A and UE 100B actually receive the same MTCH.

[0107] Thus, in the second embodiment, gNB 200 shared by a plurality of CNs 20 (CN20A and CN20B) transmits MTCH configuration information used for receiving MTCH to a plurality of UEs 100 (UE100A and UE100B) belonging to a plurality of PLMNs (PLMN #1 and PLMN #2) corresponding to the plurality of CNs 20. The MTCH configuration information includes a plurality of sets of an MBS session ID and a PLMN ID. That is, the MTCH configuration information includes the MBS session ID for each PLMN. Thereby, UE 100 can identify the MBS session ID of the PLMN to which it belongs in the MTCH configuration information and can correctly receive the MTCH.

[0108] Note that the second embodiment is also applicable when the same MTCH is not used. That is, the second embodiment is applicable in a scenario where gNB 200 is shared by a plurality of CNs 20 (CN20A and CN20B).

[0109] [Modification Example of the Second Embodiment] Next, with reference to FIGS. 14 to 16, a modified example of the second embodiment will be mainly described focusing on the differences from the above-described second embodiment. In this modified example, it is assumed that a plurality of MCCHs are provided within one cell of the gNB 200. Also, it is assumed that the MCCH is provided for each PLMN. That is, the MCCH is specific to a PLMN.

[0110] FIG. 14 is a diagram showing an example of a plurality of MCCHs according to this modified example.

[0111] As shown in FIG. 14, the gNB 200 provides the UE 100 with MBS control channel configuration information, specifically, MCCH configuration information (scheduling information), by means of a system information block (SIB) transmitted by the BCCH. Hereinafter, such an SIB may be referred to as an MBS-SIB. The UE 100 receives the MCCH (i.e., MTCH configuration information) based on the MBS-SIB received from the gNB 200, and receives the MTCH (i.e., MBS data) based on the received MCCH. In this modified example, the gNB 200 configures a plurality of MCCHs (Multiple MCCHs) within one of its own cells. Each MCCH may have a different scheduling (e.g., transmission period) from one another.

[0112] FIG. 15 is a diagram showing an example of the MBS-SIB and MTCH configuration information according to this modified example.

[0113] As shown in FIG. 15, the MBS-SIB includes a plurality of sets of a PLMN ID and an MCCH ID (MBS control channel identifier). That is, the MBS-SIB includes an MCCH ID for each PLMN. The MCCH ID is an identifier that uniquely identifies the MCCH. The MBS-SIB may include MCCH configuration information (scheduling information) associated with the MCCH ID.

[0114] UE100A belonging to PLMN#1 receives the MBS-SIB shown in FIG. 15. UE100A identifies the MCCH ID "#1" associated with the PLMN ID "#1" of PLMN#1 based on the MBS-SIB, and receives the MCCH (MTCH configuration information) indicated by the MCCH ID "#1". The subsequent operations are the same as those in the second embodiment described above.

[0115] UE100B belonging to PLMN#2 receives the MBS-SIB shown in FIG. 15. UE100B identifies the MCCH ID "#2" associated with the PLMN ID "#2" of PLMN#2 based on the MBS-SIB, and receives the MCCH (MTCH configuration information) indicated by the MCCH ID "#2". The subsequent operations are the same as those in the second embodiment described above.

[0116] FIG. 16 is a diagram showing an example of the operation according to this modification example. Note that not all steps in FIG. 16 necessarily need to be executed, and only some steps may be executed.

[0117] gNB200 determines to transmit MBS data of different PLMNs (different MBS sessions) in the same MBS service using the same resource (the same MTCH).

[0118] In step S211, gNB200 transmits the MBS-SIB. As described above, the MBS-SIB includes information associating the PLMN ID and the MCCH ID. Each of UE100A and UE100B receives the MBS-SIB.

[0119] In step S212, gNB200 transmits a plurality of MCCHs. Each MCCH includes MTCH configuration information, that is, TMGI, G-RNTI, and MTCH scheduling information. Each MCCH also includes an MCCH ID. Each of UE100A and UE100B receives the MCCH corresponding to the PLMN to which it belongs based on the MBS-SIB received in step S211.

[0120] In step S213, gNB200 transmits MBS data on MTCH according to the scheduling indicated by the MTCH configuration information. UE100A receives the MTCH of TMGI#A of PLMN#1 based on the MCCH received in step S212. UE100B receives the MTCH of TMGI#B of PLMN#2 based on the MCCH received in step S212. UE100A and UE100B actually receive the same MTCH.

[0121] In this modification example, it is assumed that the MCCH is specific to a PLMN, but a MCCH independent of the PLMN may also be assumed. For example, when assuming FTA (Free-to-Air) or ROM (Receive Only Mode), etc., the MBS-SIB may not include the PLMN ID. Or, the MBS-SIB may include information indicating that the MCCH is independent of the PLMN (for example, ROM=true).

[0122] [Other Embodiments] In the above-described embodiment, the MBS data may be encrypted (for example, IPsec). It is also assumed that such encryption is performed using a PLMN-specific security key. When the MBS data provided by a PLMN is encrypted, there is a concern that a UE100 belonging to a PLMN different from the said PLMN may not be able to decrypt (decipher) the said MBS data even if it receives it. Therefore, the CN20 that transmits the encrypted MBS data to gNB200 may provide a security key to UE100 via gNB200. For example, CN20 notifies gNB200 of the security key in step S101 or S103 of FIG. 9, and gNB200 notifies UE100 of the security key by, for example, an RRC message. Alternatively, CN20 may notify UE100 of the security key by NAS signaling, or may notify UE100 of the security key from the application layer.

[0123] In the above embodiments, the PLMN may be an NPN (Non-Public Network). The PLMN ID may be read as an NPN ID. The PLMN and the NPN may share a RAN (Sharing).

[0124] Each of the above operation flows is not limited to being implemented separately and independently, and two or more operation flows can be combined and implemented. For example, some steps of one operation flow may be added to another operation flow. Also, some steps of one operation flow may be replaced with some steps of another operation flow.

[0125] In the above embodiments and examples, an example where 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. Also, the base station may be a relay node such as an IAB (Integrated Access and Backhaul) node. The base station may be a DU (Distributed Unit) of an IAB node. Also, the user equipment may be an MT (Mobile Termination) of an IAB node.

[0126] A program may be provided to cause a computer to execute each process performed by the UE100 or the gNB200. The program may be recorded on a computer-readable medium. Using the computer-readable medium, it is possible to install the program on a computer. Here, the computer-readable medium on which the program is recorded may be a non-transitory recording medium. The non-transitory recording medium is not particularly limited, but may be, for example, a recording medium such as a CD-ROM or a DVD-ROM. Also, a circuit that executes each process performed by the UE100 or the gNB200 may be integrated, and at least a part of the UE100 or the gNB200 may be configured as a semiconductor integrated circuit (chipset, SoC: System on a chip).

[0127] As used in this disclosure, the phrases "based on" and "depending on" do not mean "only based on" or "only depending on" unless otherwise specified. The phrase "based on" means both "only based on" and "at least partially based on". Similarly, the phrase "depending on" means both "only depending on" and "at least partially depending on". Also, "obtain / acquire" may mean obtaining information from stored information, obtaining information from information received from other nodes, or obtaining the information by generating the information. The terms "include", "comprise", and their variants do not mean including only the listed items, but may include only the listed items or may further include additional items in addition to the listed items. Also, the term "or" used in this disclosure is not intended to be an exclusive disjunction. Furthermore, any reference to an element using designations such as "first", "second", etc. used in this disclosure does not generally limit the quantity or order of those elements. These designations may be used in this specification as a convenient way to distinguish between two or more elements. Thus, a reference to a first and a second element does not mean that only two elements may be employed there or that the first element must precede the second element in any way. In this disclosure, for example, when articles are added by translation, such as a, an, and the in English, these articles are assumed to include plural ones unless the context clearly indicates otherwise.

[0128] As described above in detail with reference to the drawings, the specific configuration is not limited to the above, and various design changes and the like can be made without departing from the gist.

[0129] This application claims the priority of Japanese Patent Application No. 2021-118340 (filed on July 16, 2021), and all of its content is incorporated into the specification of this application.

Explanation of Reference Numerals

[0130] 1: Mobile communication system 10: RAN (NG-RAN / 5G RAN) 20: CN (5GC / 5G CN) 100: UE 110: Receiver 120: Transmitter 130: Control unit 200: gNB 210: Transmitter 220: Receiver 230: Control unit 240: Backhaul communication unit 300: AMF

Claims

1. A communication control method used in a mobile communication system, a base station shared by a plurality of core networks receives, from each of the plurality of core networks, an MBS service identifier indicating an MBS service provided by the core network; the base station transmits, to a plurality of user devices belonging to a plurality of PLMNs (Public Land Mobile Networks) corresponding to the plurality of core networks, MBS data belonging to the MBS service by multicast or broadcast; and the MBS service identifier is a unique identifier independent of the PLMN Communication control method.

2. The transmitting includes transmitting the MBS data using radio resources common to the plurality of PLMNs in response to the base station receiving the same MBS service identifier from the plurality of core networks. The communication control method according to claim 1.

3. The receiving includes receiving, from each of the plurality of core networks, an MBS session start message including the MBS service identifier. The communication control method according to claim 1 or 2.

4. The base station further receives, from each of the plurality of core networks, an MBS session identifier corresponding to an MBS service distributed by the core network, the MBS session identifier is a PLMN-specific identifier, and the MBS service identifier is an identifier different from the MBS session identifier. The communication control method according to claim 1 or 2.

5. The base station further includes transmitting, to any one of the plurality of core networks, notification information indicating whether or not to provide the MBS service based on the MBS service identifiers received from each of the plurality of core networks. The communication control method according to claim 1 or 2.

6. Transmitting the notification information includes, in response to the base station receiving the same MBS service identifier from the plurality of core networks, transmitting, to any one of the core networks, the notification information indicating that it is not necessary to provide the MBS service. The communication control method according to claim 5.

7. The base station further includes receiving information indicating whether to permit sharing of radio resources and / or core network resources for transmitting the MBS data with other core networks from any one of the plurality of core networks. The communication control method according to claim 1 or 2.

8. Transmitting the MBS data includes, in response to receiving the same MBS service identifier from the plurality of core networks and the plurality of core networks permitting sharing of the radio resources and / or the core network resources, transmitting the MBS data using radio resources common to the plurality of PLMNs. The communication control method according to claim 7.

9. A base station shared by a plurality of core networks in a mobile communication system, a network communication unit configured to receive, from each of the plurality of core networks, an MBS service identifier indicating an MBS service provided by the core network; and a wireless communication unit configured to multicast or broadcast MBS data belonging to the MBS service to a plurality of user devices belonging to a plurality of PLMNs corresponding to the plurality of core networks. The MBS service identifier is a unique identifier independent of the PLMN. Base station.

10. A mobile communication system having a base station shared by a plurality of core networks, The base station receives, from each of the plurality of core networks, an MBS service identifier indicating an MBS service provided by the core network, The base station multicasts or broadcasts MBS data belonging to the MBS service to a plurality of user devices belonging to a plurality of PLMNs corresponding to the plurality of core networks, The MBS service identifier is a unique identifier independent of the PLMN. Mobile communication system.

11. A program for controlling a base station shared by a plurality of core networks in a mobile communication system, A process of receiving, from each of the plurality of core networks, an MBS service identifier indicating an MBS service provided by the core network, A process of causing the base station to multicast or broadcast MBS data belonging to the MBS service to a plurality of user devices belonging to a plurality of PLMNs corresponding to the plurality of core networks, The MBS service identifier is a unique identifier independent of the PLMN. Program.

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