Communication method, user device, and base station

Abstract

A communication method executed by a user device in a mobile communication system that provides a multicast / broadcast service (MBS) comprises: a step for receiving, from a first public land mobile network (PLMN), configuration information for configuring wireless environment measurement for broadcast reception from a second PLMN different from the first PLMN; a step for carrying out wireless environment measurement for the broadcast reception from the second PLMN, on the basis of the configuration information, when performing the broadcast reception; and a step for transmitting measurement information, including a measurement result of the wireless environment measurement, to the first PLMN.

Description

Communication method, user equipment, and base station

[0001] The present disclosure relates to a communication method, a user equipment, and a base station for use in a mobile communication system.

[0002] The 3rd Generation Partnership Project (3GPP) (registered trademark; the same applies hereinafter) 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 also defines the technical specifications for 5G / NR multicast / broadcast services (MBS).

[0003] 3GPP Technical Specification: TS 38.300 V17.4.0

[0004] A communication method according to a first aspect is a communication method executed by a user device in a mobile communication system that provides a multicast / broadcast service (MBS), and includes the steps of: receiving, from a first PLMN (Public Land Mobile Network), configuration information for configuring radio environment measurement in response to broadcast reception from a second PLMN different from the first PLMN; when receiving a broadcast from the second PLMN, performing radio environment measurement in response to the broadcast reception based on the configuration information; and transmitting measurement information including measurement results of the radio environment measurement to the first PLMN.

[0005] A user device according to a second aspect is a user device used in a mobile communication system that provides a multicast / broadcast service (MBS), and includes: a receiving unit that receives, from a first PLMN (Public Land Mobile Network), configuration information for configuring radio environment measurement in response to broadcast reception from a second PLMN different from the first PLMN; a control unit that, when receiving a broadcast from the second PLMN, performs radio environment measurement in response to the broadcast reception based on the configuration information; and a transmitting unit that transmits measurement information including measurement results of the radio environment measurement to the first PLMN.

[0006] A base station according to a third aspect is a base station belonging to a first PLMN (Public Land Mobile Network) in a mobile communication system that provides a multicast / broadcast service (MBS), and includes: a step of transmitting, to a user device, configuration information for configuring radio environment measurement in response to broadcast reception from a second PLMN different from the first PLMN; and a receiving unit that receives, from the user device, measurement information including measurement results of the radio environment measurement in response to the broadcast reception from the second PLMN.

[0007] 1 is a diagram showing an example of the configuration of a mobile communication system according to an embodiment. FIG. 2 is a diagram showing an example of the configuration of a UE (user equipment) according to an embodiment. FIG. 3 is a diagram showing an example of the configuration of a gNB (base station) according to an embodiment. FIG. 4 is a diagram showing the configuration of a protocol stack of a radio interface of a user plane that handles data. FIG. 5 is a diagram showing the configuration of a protocol stack of a radio interface of a control plane that handles signaling (control signals). FIG. 6 is a diagram for explaining an operation scenario of a mobile communication system according to an embodiment. FIG. 7 is a diagram showing an example of the operation of a UE according to an embodiment. FIG. 8 is a diagram showing an example of the operation of Immediate MDT in a mobile communication system according to an embodiment. FIG. 9 is a diagram showing an example of the operation of Logged MDT in a mobile communication system according to an embodiment. FIG. 10 is a diagram showing an example of the operation of a mobile communication system according to a modified example.

[0008] A user device may receive an MBS broadcast from a public land mobile network (PLMN) while being located in another PLMN. Such an MBS broadcast may be a broadcast-only service such as a general television broadcast or radio broadcast.

[0009] It is believed that by having the other PLMN understand the radio environment when a user device receives a broadcast from the other PLMN, the other PLMN can easily perform network optimization related to MBS.

[0010] However, the user equipment may not be able to perform uplink transmission to the other PLMN, which may cause the other PLMN to be unable to understand the radio environment and thus make it difficult to perform network optimization.

[0011] Therefore, an object of the present disclosure is to facilitate network optimization related to MBS.

[0012] 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.

[0013] (1) System Configuration Example Fig. 1 is a diagram showing a configuration example of a mobile communication system 1 according to an embodiment. The mobile communication system 1 conforms to the 3GPP standard 5th Generation System (5GS). Although 5GS will be described below as an example, the mobile communication system may be at least partially based on an LTE (Long Term Evolution) system. The mobile communication system may be at least partially based on a 6th Generation (6G) system.

[0014] 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. The RAN 10 and the CN 20 constitute the network of the mobile communication system 1.

[0015] 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).

[0016] The NG-RAN 10 includes a base station (referred to as "gNB" in the 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 the 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, etc. 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").

[0017] 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.

[0018] 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.

[0019] 2 is a diagram illustrating an example 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 configure a wireless communication unit that performs wireless communication with the gNB 200.

[0020] 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.

[0021] 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.

[0022] The control unit 130 performs various controls and processes in the UE 100. Such processes include processes of each layer described below. The operations of the UE 100 described above and below may be operations under the control of the control unit 230. 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 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 baseband signals. The CPU executes programs stored in the memory to perform various processes.

[0023] The UE 100 may include a positioning unit for acquiring location information indicating the geographical position (latitude, longitude, altitude) of the UE 100, for example, a GNSS (Global Navigation Satellite System) receiver.

[0024] 3 is a diagram showing an example of the configuration of a gNB 200 (base station) according to an embodiment. The gNB 200 has 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.

[0025] 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.

[0026] 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.

[0027] The control unit 230 performs various controls and processes in the gNB 200. Such processes include processes for each layer described below. The operations of the gNB 200 described above and below may be operations under the control of the control unit 230. The control unit 230 includes at least one processor and at least one memory. The memory stores programs executed by the processor and information used in 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 baseband signals. The CPU executes programs stored in the memory to perform various processes.

[0028] 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.

[0029] FIG. 4 is a diagram showing the configuration of a protocol stack of a radio interface of a user plane that handles data.

[0030] 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.

[0031] 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 successfully decoded DCI as DCI addressed to the UE. The DCI transmitted from gNB200 has a CRC (Cyclic Redundancy Code) parity bit scrambled by the RNTI added.

[0032] 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.

[0033] 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.

[0034] The PDCP layer performs header compression / decompression, encryption / decryption, and the like.

[0035] 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.

[0036] 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).

[0037] 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.

[0038] 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.

[0039] The NAS layer (also simply referred to as "NAS") 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 referred to as the AS layer (also simply referred to as "AS").

[0040] (2) Overview of MBS The mobile communication system 1 can perform resource-efficient distribution using multicast / broadcast services (MBS).

[0041] (2.1) MBS Broadcast 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 session in any of the RRC idle state, RRC inactive state, and RRC connected state. Note that the MBS session can be identified by an MBS session ID (e.g., TMGI (Temporary Mobile Group Identity)).

[0042] Point-to-Multipoint (PTM) delivery is applied to broadcast communication services. In the case of PTM transmission, the gNB 200 delivers a single copy of an MBS packet to a set (group) of multiple UEs 100. For example, the gNB 200 schedules a group-common PDSCH scrambled by a G-RNTI (Group RNTI), which is a group-common RNTI, using a group-common PDCCH having a CRC scrambled by the G-RNTI.

[0043] In the case of a broadcast communication service, the UE 100 receives a broadcast session in the following procedure. First, the UE 100 receives a system information block type 20 (SIB20) from the gNB 200. The SIB20 includes a configuration of a multicast control channel (MCCH), which is a type of logical channel. Second, the UE 100 receives the MCCH from the gNB 200 based on the SIB20. The MCCH includes a PTM configuration. The PTM configuration transmits a configuration for a multicast traffic channel (MTCH), which is a type of logical channel, and a configuration of a broadcast MRB, which is a multicast radio bearer (MRB) for the broadcast session. The information transmitted by the MCCH is sometimes referred to as MBS broadcast control information. Third, the UE 100 receives the MTCH based on the MCCH. The MTCH transmits the broadcast session (specifically, MBS data belonging to the broadcast session).

[0044] The MCCH is a PTM downlink channel for transmitting MBS broadcast control information associated with one or more MTCHs from the network 10 to the UE 100. The MTCH is a PTM downlink channel for transmitting MBS data of either a multicast session or a broadcast session from the network 10 to the UE 100.

[0045] (2.2) MBS Multicast 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.

[0046] The UE 100 can receive the multicast session only after joining the multicast session (session join). Joining the multicast session may mean being registered in the network 5 (CN 20) as the UE 100 that can receive the multicast session.

[0047] In the case of a multicast communication service, only UEs 100 in an RRC connected state can receive a multicast session in 3GPP Release 17. On the other hand, in 3GPP Release 18, this will be extended so that UEs 100 in an RRC inactive state can also receive a multicast session.

[0048] (3) Operation of the Mobile Communication System The operation of the mobile communication system 1 according to the embodiment will be described with reference to FIGS.

[0049] (3.1) Operation Scenario FIG. 6 is a diagram for explaining an operation scenario of the mobile communication system 1 according to the embodiment.

[0050] A UE 100 existing in an overlapping area of ​​cell a and cell b communicates with cell a. That is, cell a is the serving cell of UE 100, and cell b 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 a. Cell a may operate at a frequency (carrier frequency) a, and cell b may operate at a frequency (carrier frequency) b. Such a frequency relationship is also referred to as inter-frequency.

[0051] Cell a is managed by gNB200a. Cell b is managed by gNB200b. Cell a (gNB200a) belongs to a first network, a public land mobile network (PLMN) 5a. Cell b (gNB200b) belongs to a second network, PLMN 5b, which is different from the first network. Such a PLMN relationship is also referred to as inter-PLMN.

[0052] The gNB 200a and the CN 20a are included in the PLMN 5a. The gNB 200b and the CN 20b are included in the PLMN 5b. Generally, one operator is assigned one PLMN identifier. Each cell broadcasts the identifier of the PLMN to which it belongs.

[0053] When UE100 is in an RRC connected state in cell a, UE100 performs data communication with cell a (gNB200a). Specifically, UE100 is assigned a C-RNTI from gNB200a as an RRC connection identifier. gNB200a assigns radio resources to UE100 by scheduling for UE100. On the other hand, when UE100 is in an RRC idle state or an RRC inactive state in cell a, UE100 monitors paging from cell a (gNB200a). Specifically, UE100 monitors paging transmitted from cell a (gNB200a) at paging reception timing (paging opportunity) determined according to parameters such as its own UE identifier.

[0054] In an embodiment, cell b (gNB200b) transmits MBS data belonging to a broadcast session in PTM (i.e., broadcasts by MBS broadcast).

[0055] The UE 100 may have a SIM (Subscriber Identity Module) corresponding to the PLMN 5a, but may not have a SIM corresponding to the PLMN 5b. For example, cell b (gNB 200b) may provide a broadcast session in ROM (Receive-Only Mode) and / or FTA (Free-To-Air). ROM is a mode in which MBS reception is possible even for a UE 100 that does not have a SIM (Subscriber Identity Module) and / or does not have a service contract with an operator (PLMN). FTA is an application (service) that enables free broadcast content broadcast. FTA may be one aspect of ROM. The MBS broadcast provided in FTA may be provided so that it can be used by all users who are not mobile subscribers. In such a case, the UE 100 may be able to receive an MBS broadcast from the PLMN 5b (also referred to as "broadcast reception"), but may not be able to perform unicast communication (e.g., uplink transmission) with the PLMN 5b.

[0056] Alternatively, UE 100 may have both a SIM corresponding to PLMN 5a and a SIM corresponding to PLMN 5b. Such UE 100 is also referred to as a Multi-SIM UE or a Multi-USIM (Universal Subscriber Identity Module) UE. In such a case, UE 100 is capable of receiving broadcasts from PLMN 5b and is also capable of unicast communication (e.g., uplink transmission) with PLMN 5b.

[0057] In the following embodiment, a scenario is mainly assumed in which the UE 100 has a SIM corresponding to the PLMN 5a but does not have a SIM corresponding to the PLMN 5b, and uplink transmission to the PLMN 5b is not possible. The UE 100 receives an MBS broadcast provided by the PLMN 5b in a ROM or FTA. Such an MBS broadcast may be a broadcast-only service such as a general television broadcast or radio broadcast.

[0058] Here, if the PLMN 5b is aware of the radio environment when the UE 100 receives broadcasts from the PLMN 5b, it is considered that the PLMN 5b can easily perform network optimization related to the MBS. However, there are cases where the UE 100 is unable to perform uplink transmission to the PLMN 5b. Therefore, the PLMN 5b cannot understand the radio environment, making it difficult for the PLMN 5b to perform network optimization related to the MBS.

[0059] In the embodiment, the PLMN 5a configures the UE 100 to perform radio environment measurement for the PLMN 5b, for example, based on a prior contract with the PLMN 5b, and collects measurement results of the radio environment measurement from the UE 100. That is, the gNB 200a of the PLMN 5a configures the UE 100 to collect and report area quality information of the PLMN 5b. Then, the PLMN 5a provides the collected measurement information to the PLMN 5b. This makes it easy for the PLMN 5b to perform network optimization related to the MBS.

[0060] In the embodiment, a server 400 may be provided that temporarily stores the measurement information when the measurement information is provided from the PLMN 5a to the PLMN 5b. Alternatively, the measurement information may be provided directly from the PLMN 5a to the PLMN 5b without going through the server 400.

[0061] (3.2) Example of UE Operation FIG. 7 is a diagram showing an example of the operation of the UE 100 according to the embodiment.

[0062] In step S1, the UE 100 receives, from the PLMN 5a (first PLMN), setting information for setting radio environment measurement for broadcast reception from a PLMN 5b (second PLMN) different from the PLMN 5a.

[0063] Prior to step S1, the UE 100 may transmit interest information indicating an interest in receiving broadcasts from the PLMN 5b to the gNB 200a belonging to the PLMN 5a. The gNB 200a belonging to the PLMN 5a may transmit the setting information to the UE 100 based on the interest information.

[0064] The setting information in step S1 may include at least one of session information (session identifier) ​​indicating a broadcast session provided by the PLMN 5b and PLMN information (PLMN identifier) ​​indicating the PLMN 5b. The setting information in step S1 may include a TMGI combining the PLMN identifier and the session identifier.

[0065] In step S2, when UE 100 existing in PLMN 5a receives a broadcast from PLMN 5b, UE 100 performs radio environment measurement for the broadcast reception based on the setting information in step S1.

[0066] The radio environment measurement in step S2 may be performed by the UE 100 in an RRC idle state or an RRC inactive state in the PLMN 5a. In this case, the UE 100 in the RRC idle state or the RRC inactive state may store measurement information obtained by performing the radio environment measurement as a measurement log, and may transmit the measurement log to the PLMN 5a later when connected to the PLMN 5a. Such a measurement and reporting method is also called logged MDT (Minimization of Drive Test).

[0067] Alternatively, the radio environment measurement in step S2 may be performed by the UE 100 in an RRC connected state in the PLMN 5a. In this case, the UE 100 in the RRC connected state may immediately transmit measurement information obtained by performing the radio environment measurement to the PLMN 5a (gNB 200a). Such a measurement and reporting method is also referred to as Immediate MDT.

[0068] In step S3, the UE 100 in the RRC connected state in the PLMN 5a transmits measurement information (which may be a measurement log) including the measurement results of the radio environment measurement in step S2 to the PLMN 5a.

[0069] In step S2, the UE 100, which is present in the PLMN 5a and receives a broadcast from the PLMN 5b, may measure at least one of communication status information indicating a communication load and / or a communication capacity with the PLMN 5a and communication status information indicating a communication load and / or a communication capacity with the PLMN 5b. In step S3, the UE 100 may transmit measurement information further including the communication status information to the PLMN 5a.

[0070] The measurement information of step S3 may further include at least one of location information indicating the geographical position of UE 100 when the radio environment measurement of step S2 was performed, and time information indicating the timing when the radio environment measurement of step S2 was performed.

[0071] (3.3) Example of Operation of Immediate MDT FIG. 8 is a diagram showing an example of operation of immediate MDT in the mobile communication system 1 according to the embodiment.

[0072] In step S100, the UE 100 is in an RRC connected state in the PLMN 5a. Specifically, the UE 100 is in a state in which an RRC connection with the gNB 200a in the PLMN 5a is established.

[0073] In step S101, the UE 100 may transmit an MBS Interest Indication message including information indicating an interest in receiving an MBS broadcast from the PLMN 5b to the gNB 200a in the PLMN 5a. The information may include at least one of session information (session identifier) ​​indicating the broadcast session that the UE 100 is interested in receiving and PLMN information (PLMN identifier) ​​indicating the PLMN 5b that provides the broadcast session that the UE 100 is interested in receiving. The information may be a TMGI that combines the PLMN identifier and the session identifier. The information may include information indicating a frequency (MBS frequency) that provides the broadcast session that the UE 100 is interested in receiving. The gNB 200a may recognize that the UE 100 is interested in receiving the broadcast based on the MBS Interest Indication message from the UE 100.

[0074] In step S102, the gNB 200a in the PLMN 5a performs configuration related to measurement and reporting related to broadcast reception of the PLMN 5b by transmitting configuration information to the UE 100. The UE 100 receives the configuration information from the gNB 200a in the PLMN 5a. The configuration information includes at least one piece of information (configuration parameters) selected from the following 1) to 5).

[0075] 1) Setting of measurement object: The measurement object may be at least one of a session identifier, a PLMN identifier, and a TMGI. The measurement object may be an indicator indicating that measurement and reporting of another PLMN is to be performed. The UE 100 may perform measurement only when broadcast reception is being performed for the PLMN and / or broadcast session specified by the measurement object.

[0076] 2) Setting of Measurement Content: The measurement content may be at least one of RSRP (Reference Signals Received Power), RSRQ (Reference Signal Received Quality), and SINR (Signal-to-Interference-plus-noise ratio) of PLMN 5b. The measurement content may be at least one of BER (Bit Error Rate), BLER (Block Error Rate), and PER (Packet Error Rate) of MBS data received by UE 100 from PLMN 5b.

[0077] 3) Setting of communication state information to be measured: The communication state information is information regarding the state of simultaneous communication (shared processing) with two PLMNs 5 in the UE 100. The communication state information makes it easy to identify the cause of degradation of the MBS reception quality in the UE 100.

[0078] The communication state information measured by the UE 100 may be a communication load and / or a processing load with the PLMN 5a. The communication state information measured by the UE 100 may be a communication capacity and / or a processing capability remaining for receiving an MBS broadcast in the PLMN 5b.

[0079] Here, the communication status information may be the time width and / or period of a time-division gap period, i.e., a period during which communication with PLMN 5a is interrupted, when such a gap period is provided for MBS broadcast reception from PLMN 5b. The communication status information may also be the time width and / or frequency during which unicast scheduling from PLMN 5a is performed. The communication status information may also be the time width and / or frequency during which scheduling is free (unassigned) for reception from PLMN 5b. The communication status information may also be whether or not unicast scheduling from PLMN 5a has collided with the MBS broadcast reception timing from PLMN 5b, or the frequency of such collision. The communication status information may also be the processing load and / or capacity (processor load, memory load, etc.) used in unicast communication from PLMN 5a while receiving the MBS broadcast from PLMN 5b. The communication status information may also be the processing load and / or capacity used for MBS broadcast reception from PLMN 5b. The communication status information may be the total processing load used for both unicast communication in PLMN 5a and MBS broadcast reception in PLMN 5b.

[0080] 4) Setting of measurement events: The measurement event may be an event triggered by a single measurement, or an event triggered by an event to start periodic measurements. These events may be an event that the reception quality (RSRP and / or BER) deteriorates below a threshold, and the setting may include the threshold. These events may be an event that the reception processing load (CPU load, etc.) deteriorates below a threshold, and the setting may include the threshold.

[0081] The measurement event may be a measurement period when periodic measurements are performed.

[0082] 5) Setting of Reporting Conditions: The reporting conditions may be conditions for reporting immediately (at any time) after measurement. When the UE 100 includes the measurement information in a Measurement Report message and transmits the measurement information to the PLMN 5a, the reporting conditions may be information for setting a transmission condition of the Measurement Report message.

[0083] In step S103, the UE 100 in the RRC connected state in the PLMN 5a starts receiving an MBS broadcast session of the PLMN 5b.

[0084] In step S104, the UE 100 in the RRC connected state in the PLMN 5a performs radio environment measurement related to broadcast reception from the PLMN 5b in accordance with the configuration information in step S102. For example, the UE 100 performs measurement of the configured measurement content for the configured measurement target at the configured measurement event. The UE 100 may measure the configured communication state information. The UE 100 may also acquire location information indicating the geographical location of the UE 100 at the time of measurement.

[0085] In step S105, the UE 100 transmits measurement information including the measurement result of step S104 to the gNB 200a of the PLMN 5a. The UE 100 may transmit the measurement information by including it in a Measurement Report message, which is one of the RRC messages. The measurement information may include location information indicating the geographical location of the UE 100 at the time of measurement. The measurement information may include an ID (login ID or user ID) assigned to the UE 100 by the PLMN 5b and / or the IMSI (International Mobile Subscription Identity) of the UE 100. The measurement information may include cause information of the deterioration of each measurement content (e.g., BLER). The cause information may be the communication status information or may be information indicating a simplified cause classification. The cause classification may be one of the following: deterioration of wireless reception quality (e.g., deterioration of BLER), configuration malfunction (e.g., mismatch between gap setting and MBS reception opportunity), or deterioration of processing load on UE100 (e.g., increase in processing load related to unicast communication and / or decrease in processing capacity related to MBS reception).

[0086] The PLMN 5a may provide the measurement information received from the UE 100 in step S105 to the PLMN 5b, for example, via a server. The PLMN 5b may use the measurement information to perform network optimization in the PLMN 5b, for example, to change various setting parameters in the PLMN 5b. Note that the PLMN 5a may use at least a part of the measurement information to perform network optimization in the PLMN 5a, for example, to change various setting parameters in the PLMN 5a.

[0087] (3.4) Example of Logged MDT Operation FIG. 9 is a diagram showing an example of logged MDT operation in the mobile communication system 1 according to the embodiment.

[0088] In step S130, the UE 100 is in an RRC connected state in the PLMN 5a. Specifically, the UE 100 is in a state in which an RRC connection with the gNB 200a in the PLMN 5a is established.

[0089] In step S131, the UE 100 may send an MBS Interest Indication message including information indicating an interest in receiving the MBS broadcast of the PLMN 5b to the gNB 200a of the PLMN 5a. Details of the MBS Interest Indication are similar to the operation of the Immediate MDT described above. The gNB 200a may recognize that the UE 100 is interested in receiving the broadcast based on the MBS Interest Indication message from the UE 100.

[0090] In step S132, the gNB 200a in PLMN 5a performs configuration related to measurement and reporting related to broadcast reception in PLMN 5b by transmitting configuration information to the UE 100. The UE 100 receives the configuration information from the gNB 200a in PLMN 5a. The configuration information includes at least one piece of information (configuration parameters) from 1) to 5) above. However, in the case of logged MDT, the information (configuration parameters) in 4) and 5) above may have the following content.

[0091] 4) Setting logging events: Logging refers to storing measurement information as a measurement log. A logging event may be an event triggered by a single logging operation, or an event triggered by an event that starts periodic logging. These events may be events indicating that the reception quality (RSRP and / or BER) has deteriorated below a threshold, and the setting may include the threshold. These events may be events indicating that the reception processing load (e.g., CPU load) has deteriorated below a threshold, and the setting may include the threshold.

[0092] The logging event may be a logging period when periodic logging is performed.

[0093] 5) Setting of Reporting Conditions: The setting of reporting conditions includes information for setting conditions for transmitting a measurement log. The conditions may include at least one of the following a) to c).

[0094] a) Time: For example, a condition is set that the measurement log being held is to be reported at a certain time (for example, midnight) every day.

[0095] b) Period: For example, a condition is set that the measurement log being held is reported every predetermined time (for example, one hour). Alternatively, a condition may be set that the measurement log being held is reported every time the state of receiving the MBS broadcast from PLMN 5b reaches a predetermined time (for example, one hour).

[0096] c) Log Data Size: For example, a condition is set such that the held log is reported every time the total data size of the held measurement log exceeds a predetermined size (for example, 1 MB).

[0097] The reporting condition may be a condition for transmitting a log retention indication indicating that a measurement log is retained.

[0098] In step S133, the UE 100 transitions from the RRC connected state to the RRC idle state or the RRC inactive state in the PLMN 5a. Note that the configuration information in step S132 may be held in the UE 100 until the UE 100 transitions to the RRC idle state or the RRC inactive state, and may be applied when the UE 100 transitions to the RRC idle state or the RRC inactive state.

[0099] In step S134, the UE 100 in the RRC idle state or the RRC inactive state in the PLMN 5a starts receiving the MBS broadcast session of the PLMN 5b.

[0100] In step S135, the UE 100 in the RRC idle state or the RRC inactive state in the PLMN 5a performs radio environment measurement related to broadcast reception from the PLMN 5b in accordance with the configuration information in step S132. For example, the UE 100 performs measurement and logging of the configured measurement content for the configured measurement target in the configured logging event. The UE 100 may measure the configured communication state information. The UE 100 may acquire location information indicating the geographical location of the UE 100 at the time of measurement and time information indicating the measurement timing.

[0101] In step S136, the UE 100 in the RRC idle state or the RRC inactive state in the PLMN 5a holds the measurement information including the measurement result of step S135 as a measurement log.

[0102] In addition, the UE 100 may repeatedly perform the operations of steps S134 to S136 while in the RRC idle state or the RRC inactive state.

[0103] In step S137, the UE 100 transitions from the RRC idle state or the RRC inactive state to the RRC connected state in the PLMN 5a.

[0104] In step S138, the UE 100 in the RRC connected state in the PLMN 5a transmits a log retention indication (Availability Indication) indicating that the measurement log is retained to the gNB 200a in the PLMN 5a. The log retention indication may be an information element different from the log retention indication indicating that the measurement log is retained in a general logged MDT.

[0105] In step S139, the gNB200a of the PLMN5a transmits a log transmission request (UE Information Request) to the UE100 requesting the transmission of a measurement log.

[0106] In step S140, in response to receiving the log transmission request, the UE 100 in the RRC connected state in the PLMN 5a transmits a message (UE Information Response message) including the measurement log it holds to the gNB 200a in the PLMN 5a. The message may include the same content as the Measurement Report message in step S105.

[0107] The PLMN 5a may provide the measurement information (measurement log) received from the UE 100 in step S140 to the PLMN 5b, for example, via a server. The PLMN 5b may use the measurement information to perform network optimization in the PLMN 5b, for example, to change various setting parameters in the PLMN 5b. Note that the PLMN 5a may use at least a part of the measurement information to perform network optimization in the PLMN 5a, for example, to change various setting parameters in the PLMN 5a.

[0108] (4) Modified Example of Operation of Mobile Communication System A modified example of operation of the above-described mobile communication system 1 will be described. In the above-described embodiment, the PLMN 5a receives measurement information of the PLMN 5b by the UE 100 from the UE 100 and can decipher the received measurement information. However, from the perspective of the PLMN 5b, there may be a security problem if the PLMN 5a can decipher the measurement information of the PLMN 5b.

[0109] In this modification, the UE 100 encrypts the measurement information (measurement log) in a manner that allows it to be decrypted in the PLMN 5b but not in the PLMN 5a. The UE 100 then transmits the encrypted measurement information to the PLMN 5a. Here, the UE 100 may transmit to the PLMN 5a a message (Measurement Report message or UE Information Response message) that includes the encrypted measurement information in a container addressed to the PLMN 5b. The container forms part of the message and stores the measurement information addressed to the PLMN 5b.

[0110] This modification is applicable to both the Immediate MDT and the Logged MDT described above. The following describes the operation of the mobile communication system 1 according to this modification, focusing on differences from the above embodiment.

[0111] FIG. 10 is a diagram showing an example of the operation of the mobile communication system 1 according to this modification.

[0112] In step S200, an upper layer (e.g., an application layer or a NAS) of the UE 100 holds encryption information used for encryption. The encryption information includes information on an encryption method and an encryption key. The encryption information is information that is unknown to the PLMN 5b but known to the PLMN 5a.

[0113] Here, as a method for the UE 100 to hold the encrypted information, there are the following methods 1 to 3.

[0114] Method 1: When the user subscribes to the PLMN 5b, an encryption method and an encryption key are assigned, and the UE 100 stores them.

[0115] Method 2: The encryption method and encryption key are written in advance in the USIM (or ROM) of the UE 100 at the time of shipping from the factory and / or at the time of signing the contract.

[0116] Method 3: An encryption method and an encryption key are provided by a viewing application (for example, a TV viewing application) installed on the UE 100.

[0117] The operations from step S201 to step S207 are the same as those in the above-described embodiment.

[0118] In step S208, the UE 100 encrypts the measurement information (measurement log) by using the encryption information held in step S200. In the UE 100, the encryption information may be provided from an upper layer to a lower layer (a layer that performs encryption).

[0119] In step S209, UE100 stores the measurement information (measurement log) encrypted in step S208 in a container in the Measurement Report message or a container in the UE Information Response message, and transmits the message to gNB200a in PLMN5a.

[0120] In step S210, the gNB 200a in PLMN 5a may extract the encrypted data from the container in the message of step S209 and send the extracted encrypted data to the CN 20a in PLMN 5a or the server 400. The gNB 200a in PLMN 5a may also send the data to the gNB 200a or the CN 20b in PLMN 5b if there is a direct interface with PLMN 5b.

[0121] In step S211, the CN 20a or the server 400 of the PLMN 5a transmits the encrypted data to the PLMN 5b.

[0122] In step S212, the PLMN 5b decrypts (decrypts) the encrypted data using encryption information shared with the UE 100, and acquires measurement information (measurement log).

[0123] In step S213, the PLMN 5b performs network optimization such as area optimization of the PLMN 5b using the information acquired in step S212.

[0124] (5) Other Embodiments In the above-described embodiment, a scenario was assumed in which UE 100 residing in PLMN 5a receives an MBS broadcast from PLMN 5b. However, a scenario in which UE 100 residing in PLMN 5a receives an MBS multicast from PLMN 5b may also be assumed. Therefore, broadcast reception in the operation according to the above-described embodiment may be read as multicast reception.

[0125] 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.

[0126] 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.

[0127] That is, the UE 100 may be a terminal function unit (a type of communication module) for a base station to control a repeater that relays signals. Such a terminal function unit is referred to as an MT. Examples of the MT include, in addition to the IAB-MT, an NCR (Network Controlled Repeater)-MT and a RIS (Reconfigurable Intelligent Surface)-MT.

[0128] The term "network node" primarily refers to a base station, but may also refer to a core network device or a part of a base station (CU, DU, or RU). A network node may also be configured by a combination of at least a part of a core network device and at least a part of a base station.

[0129] 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).

[0130] The functions performed by the UE 100 or the gNB 200 (network node) may be implemented in circuitry or processing circuitry, including general-purpose processors, application-specific processors, integrated circuits, ASICs (Application Specific Integrated Circuits), CPUs (Central Processing Units), conventional circuits, and / or combinations thereof, programmed to perform the described functions. A processor includes transistors and other circuits and is considered to be circuitry or processing circuitry. A processor may also be a programmed processor that executes a program stored in memory. In this specification, circuitry, unit, or means refers to hardware that is programmed to perform the described functions or hardware that executes them. The hardware may be any hardware disclosed herein or any hardware known to be programmed or capable of performing the described functions. If the hardware is a processor, the circuitry, means, or unit is a combination of hardware and software used to configure the hardware and / or processor.

[0131] 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.

[0132] 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.

[0133] This application claims priority from Japanese Patent Application No. 2023-101316 (filed June 21, 2023), the entire contents of which are incorporated herein by reference.

[0134] (6) Supplementary Notes The following are additional notes regarding the features of the above-described embodiment.

[0135] (Supplementary Note 1) A communication method executed by a user device in a mobile communication system that provides a multicast / broadcast service (MBS), comprising: a step of receiving, from a first PLMN (Public Land Mobile Network), configuration information for configuring radio environment measurement for broadcast reception from a second PLMN different from the first PLMN; a step of performing radio environment measurement for broadcast reception from the second PLMN based on the configuration information when receiving the broadcast from the second PLMN; and a step of transmitting measurement information including measurement results of the radio environment measurement to the first PLMN.

[0136] (Supplementary Note 2) The communication method according to Supplementary Note 1, further comprising the steps of: transmitting interest information indicating an interest in receiving broadcasts from the second PLMN to a network node belonging to the first PLMN; and transmitting the configuration information to the user device based on the interest information by the network node.

[0137] (Supplementary Note 3) The communication method according to Supplementary Note 1 or 2, wherein the configuration information includes at least one of session information indicating a broadcast session provided by the second PLMN and PLMN information indicating the second PLMN.

[0138] (Supplementary Note 4) The communication method according to any one of Supplementary Notes 1 to 3, further comprising a step in which the user equipment in a radio resource control (RRC) idle state or an RRC inactive state stores the measurement information obtained by performing the radio environment measurement as a measurement log, and the setting information includes information for setting a trigger condition for transmitting the measurement log or a notification indicating that the measurement log is stored to the second PLMN.

[0139] (Supplementary Note 5) The communication method according to any one of Supplementary Notes 1 to 4, wherein the step of measuring the radio environment includes a step in which the user equipment, which receives broadcasts from the second PLMN while being present in the first PLMN, measures at least one of communication status information indicating a communication load and / or a communication capacity with the first PLMN and communication status information indicating a communication load and / or a communication capacity with the second PLMN, and the step of transmitting the measurement information includes a step of transmitting the measurement information, which further includes the communication status information, to the first PLMN.

[0140] (Supplementary Note 6) The communication method according to Supplementary Note 5, wherein the setting information includes information for setting measurement of the communication state information.

[0141] (Supplementary Note 7) The communication method according to any one of Supplementary Notes 1 to 6, wherein the measurement information further includes at least one of location information indicating a geographical location of the user device when the radio environment measurement was performed and time information indicating a timing when the radio environment measurement was performed.

[0142] (Supplementary Note 8) The communication method according to any one of Supplementary Notes 1 to 7, further comprising the step of encrypting the measurement information in a manner that can be decrypted in the second PLMN but cannot be decrypted in the first PLMN, wherein the step of transmitting the measurement information includes the step of transmitting the encrypted measurement information to the first PLMN.

[0143] (Supplementary Note 9) The communication method according to Supplementary Note 8, wherein the step of transmitting the measurement information includes a step of transmitting, to the first PLMN, a message including the encrypted measurement information in a container addressed to the second PLMN.

[0144] (Supplementary Note 10) A user equipment used in a mobile communication system that provides a multicast / broadcast service (MBS), comprising: a receiving unit that receives, from a first PLMN (Public Land Mobile Network), setting information for setting radio environment measurement for broadcast reception from a second PLMN different from the first PLMN; a control unit that, when receiving a broadcast from the second PLMN, performs radio environment measurement for the broadcast reception based on the setting information; and a transmitting unit that transmits measurement information including measurement results of the radio environment measurement to the first PLMN.

[0145] (Supplementary Note 11) A network node belonging to a first PLMN (Public Land Mobile Network) in a mobile communication system providing a multicast / broadcast service (MBS), the network node comprising: a step of transmitting, to a user equipment, configuration information for configuring radio environment measurement in response to broadcast reception from a second PLMN different from the first PLMN; and a receiving unit that receives, from the user equipment, measurement information including a measurement result of the radio environment measurement in response to the broadcast reception from the second PLMN.

[0146] 1: Mobile communication system 5: Network 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 executed by a user device in a mobile communication system providing a multicast / broadcast service (MBS), comprising: receiving configuration information from a first PLMN (Public Land Mobile Network) for setting radio environment measurement for broadcast reception from a second PLMN different from the first PLMN; when receiving a broadcast from the second PLMN, performing radio environment measurement for the broadcast reception based on the configuration information; and transmitting measurement information including the measurement results of the radio environment measurement to the first PLMN.

2. The communication method according to claim 1, further comprising: transmitting interest information indicating an interest in receiving broadcasts from the second PLMN to a network node belonging to the first PLMN; and the network node transmitting the setting information to the user device based on the interest information.

3. The communication method according to claim 1, wherein the setting information includes at least one of session information indicating a broadcast session provided by the second PLMN and PLMN information indicating the second PLMN.

4. The communication method of claim 1, further comprising the user equipment in a radio resource control (RRC) idle state or an RRC inactive state retaining the measurement information obtained by performing the radio environment measurement as a measurement log, and the setting information includes information for setting a trigger condition for transmitting the measurement log or a notification indicating the retention of the measurement log to the second PLMN.

5. The communication method according to claim 1, wherein the performing of the radio environment measurement includes the user equipment receiving a broadcast from the second PLMN while present in the first PLMN measuring at least one of communication status information indicating a communication load and / or a communication capacity with the first PLMN and communication status information indicating a communication load and / or a communication capacity with the second PLMN, and the transmitting of the measurement information includes transmitting the measurement information further including the communication status information to the first PLMN.

6. The communication method according to claim 5, wherein the setting information includes information for setting the measurement of the communication state information.

7. The communication method according to claim 1, wherein the measurement information further includes at least one of location information indicating the geographical location of the user device when the radio environment measurement was performed, and time information indicating the timing when the radio environment measurement was performed.

8. A communication method according to any one of claims 1 to 7, further comprising encrypting the measurement information in a manner that can be decrypted in the second PLMN but cannot be decrypted in the first PLMN, and transmitting the measurement information includes transmitting the encrypted measurement information to the first PLMN.

9. The method of claim 8, wherein transmitting the measurement information includes transmitting a message to the first PLMN including the encrypted measurement information in a container addressed to the second PLMN.

10. A user equipment used in a mobile communication system providing a multicast / broadcast service (MBS), comprising: a receiving unit that receives setting information from a first PLMN (Public Land Mobile Network) for setting radio environment measurement for broadcast reception from a second PLMN different from the first PLMN; a control unit that, when receiving a broadcast from the second PLMN, performs radio environment measurement for the broadcast reception based on the setting information; and a transmitting unit that transmits measurement information including measurement results of the radio environment measurement to the first PLMN.

11. A network node belonging to a first PLMN (Public Land Mobile Network) in a mobile communication system providing a multicast / broadcast service (MBS), comprising: a network node that transmits, to a user device, configuration information for configuring radio environment measurement for broadcast reception from a second PLMN different from the first PLMN; and a receiving unit that receives, from the user device, measurement information including measurement results of the radio environment measurement for the broadcast reception from the second PLMN.

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