Communication Control Method

Abstract

To provide a communication control method, user equipment, a network node, and a mobile communication system that achieve an improved multicast broadcast service (MBS).SOLUTION: A communication control method used in a mobile communication system providing a MBS includes: a base station 200 setting, to user equipment 100, an MBS bearer split into a point-to-point (PTP) communication path and a point-to-multipoint (PTM) communication path; and the base station transmitting, to the user equipment, an instruction to individually activate or deactivate the PTP communication path and the PTM communication path.SELECTED DRAWING: Figure 8

Description

[Technical Field]

[0001] The present invention relates to a communication control method used in a mobile communication system. [Background technology]

[0002] In recent years, the fifth generation (5G) mobile communication system has been attracting attention. NR (New Radio), the radio access technology (RAT) of the 5G system, has features such as high speed, large capacity, high reliability, and low latency compared to LTE (Long Term Evolution), the fourth generation radio access technology. [Prior art documents] [Non-patent literature]

[0003] [Non-Patent Document 1] 3GPP technical specification "3GPP TS 38.300 V16.3.0 (2020-09)" Summary of the Invention

[0004] A communication control method according to a first aspect is a communication control method used in a mobile communication system that provides a multicast broadcast service (MBS) from a base station to a user device, and includes the steps of the base station setting an MBS bearer separated into a PTP (Point-to-Point) communication path and a PTM (Point To Multipoint) communication path in the user device, and the base station sending instructions to the user device to individually activate or deactivate the PTP communication path and the PTM communication path.

[0005] A communication control method according to a second aspect is a communication control method used in a mobile communication system that provides a multicast broadcast service (MBS), and includes the steps of: the base station setting an MBS bearer separated into a PTP (Point-to-Point) communication path and a PTM (Point To Multipoint) communication path in the user device; the user device determining whether a predetermined condition is met after at least one of the PTP communication path and the PTM communication path is activated; and, if the predetermined condition is determined to be met, the user device deactivating the activated communication path without receiving an instruction to deactivate the activated communication path from the base station.

[0006] A communication control method according to a third aspect is a communication control method used in a mobile communication system that provides a multicast broadcast service (MBS), and includes the steps of: the base station setting an MBS bearer separated into a PTP (Point-to-Point) communication path and a PTM (Point To Multipoint) communication path in the user device; the user device determining whether or not a predetermined condition is satisfied; and, if the user device determines that the predetermined condition is satisfied, canceling the MBS bearer without receiving an instruction to cancel the MBS bearer from the base station.

[0007] A communication control method according to a fourth aspect is a communication control method used in a mobile communication system that provides a multicast broadcast service (MBS), and includes the steps of the base station setting up an MBS bearer for a plurality of user devices, and the base station multicasting an instruction to de-setup the MBS bearer to the plurality of user devices. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a diagram illustrating a configuration of a mobile communication system according to an embodiment. [Figure 2]FIG. 1 is a diagram illustrating a configuration of a UE (user equipment) according to an embodiment. [Figure 3] A diagram showing the configuration of a gNB (base station) according to one embodiment. [Figure 4] FIG. 10 is a diagram showing the configuration of a protocol stack of a radio interface of a user plane that handles data. [Figure 5] FIG. 1 is a diagram showing the configuration of a protocol stack of a radio interface of a control plane that handles signaling (control signals). [Figure 6] FIG. 2 is a diagram illustrating a correspondence relationship between downlink logical channels and transport channels according to an embodiment. [Figure 7] FIG. 1 is a diagram illustrating a method for distributing MBS data according to an embodiment. [Figure 8] FIG. 1 illustrates a split MBS bearer according to one embodiment. [Figure 9] FIG. 10 is a diagram illustrating an example 1 of operations related to activation and deactivation of legs according to an embodiment. [Figure 10] FIG. 10 is a diagram illustrating an example 2 of operations related to activation and deactivation of legs according to an embodiment. [Figure 11] FIG. 10 is a diagram illustrating an example of a MAC CE that stores an indication value for each bearer identifier (or logical channel identifier) ​​according to an embodiment. [Figure 12] FIG. 10 illustrates automatic deactivation of a leg according to one embodiment. [Figure 13] FIG. 10 illustrates automatic de-establishment of an MBS bearer according to one embodiment. [Figure 14] FIG. 10 illustrates a multicast deconfiguration according to one embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0009] The introduction of multicast and broadcast services into the 5G system (NR) is being considered. The NR multicast and broadcast services are expected to provide improved services compared to the LTE multicast and broadcast services.

[0010] Therefore, an object of the present invention is to provide an improved multicast / broadcast service.

[0011] 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.

[0012] (Configuration of a mobile communication system) First, the configuration of a mobile communication system according to an embodiment will be described. Fig. 1 is a diagram showing the configuration of a mobile communication system according to an embodiment. This mobile communication system conforms to the 5th Generation System (5GS) of the 3GPP standard. In the following description, 5GS will be taken as an example, but the mobile communication system may be at least partially applied with an LTE (Long Term Evolution) system or at least partially applied with a 6th Generation (6G) system.

[0013] As shown in FIG. 1, the mobile communication system includes a user equipment (UE) 100, a 5G radio access network (NG-RAN) 10, and a 5G core network (5GC) 20.

[0014] The UE 100 is a mobile wireless communication device. The UE 100 may be any device that is used by a user, and may be, for example, a mobile phone terminal (including a smartphone), 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).

[0015] The NG-RAN 10 includes a base station (called a "gNB" in a 5G system) 200. The gNBs 200 are connected to each other via an Xn interface, which is an interface between base stations. The gNB 200 manages one or more cells. The gNB 200 performs wireless communication with a UE 100 that has established a connection with its own cell. The gNB 200 has a radio resource management (RRM) function, a routing function for user data (hereinafter simply referred to as "data"), a measurement control function for mobility control and scheduling, 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 that performs wireless communication with a UE 100. One cell belongs to one carrier frequency.

[0016] In addition, gNBs can also connect to the Evolved Packet Core (EPC), which is the LTE core network. LTE base stations can also connect to 5GC. LTE base stations and gNBs can also be connected via a base station-to-base station interface.

[0017] The 5GC20 includes an Access and Mobility Management Function (AMF) and a User Plane Function (UPF) 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 UPF are connected to the gNB 200 via an NG interface, which is an interface between a base station and a core network.

[0018] FIG. 2 is a diagram showing a configuration of a UE 100 (user equipment) according to an embodiment.

[0019] As shown in FIG. 2, the UE 100 includes a receiving unit 110, a transmitting unit 120, and a control unit .

[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 in the UE 100. 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 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] FIG. 3 is a diagram showing the configuration of a gNB200 (base station) according to one embodiment.

[0024] As shown in FIG. 3, the gNB 200 includes a transmitter 210, a receiver 220, a controller 230, and a backhaul communication unit 240.

[0025] The transmission unit 210 performs various transmissions under the control of the control unit 230. The transmission unit 210 includes an antenna and a transmitter. The transmitter converts a baseband signal (transmission signal) output 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 in the gNB 200. 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 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 neighboring base stations via an inter-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 divided), and both units may be connected via an F1 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] As shown in Figure 4, 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 the UE 100 and the PHY layer of the gNB 200 via a physical channel.

[0032] The MAC layer performs data priority control, retransmission processing using Hybrid ARQ (HARQ), random access procedures, etc. Data and control information are transmitted between the MAC layer of UE 100 and the MAC layer of gNB 200 via a transport channel. The MAC layer of 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 UE 100.

[0033] The RLC layer transmits data to the RLC layer on the receiving side 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 logical channels.

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

[0035] The SDAP layer maps IP flows, which are the units for QoS control by the core network, to radio bearers, which are the units for QoS control by the AS (Access Stratum). Note that if the RAN is connected to the EPC, SDAP is not necessary.

[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] As shown in FIG. 5, the protocol stack of the radio interface of the control plane has a Radio Resource Control (RRC) layer and a Non-Access Stratum (NAS) 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 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 300B.

[0040] The UE 100 has an application layer and the like in addition to the radio interface protocol.

[0041] (MBS) Next, an MBS according to one embodiment will be described. The MBS is a service for transmitting data from the NG-RAN 10 to the UE 100 by broadcast or multicast, i.e., point-to-multipoint (PTM) data. The MBS may also be called an MBMS (Multimedia Broadcast and Multicast Service). Note that use cases (service types) of the MBS include public safety communications, mission-critical communications, V2X (Vehicle to Everything) communications, IPv4 or IPv6 multicast distribution, IPTV, group communications, and software distribution.

[0042] There are two types of MBS transmission methods in LTE: MBSFN (Multicast Broadcast Single Frequency Network) transmission and SC-PTM (Single Cell Point To Multipoint) transmission. Fig. 6 is a diagram showing the correspondence relationship between downlink logical channels and transport channels according to one embodiment.

[0043] As shown in Figure 6, the logical channels used for MBSFN transmission are the MTCH (Multicast Traffic Channel) and the MCCH (Multicast Control Channel), and the transport channel used for MBSFN transmission is the MCH (Multicast Control Channel). MBSFN transmission is designed primarily for multi-cell transmission, and in an MBSFN area consisting of multiple cells, each cell synchronously transmits the same signal (the same data) in the same MBSFN subframe.

[0044] The logical channels used for SC-PTM transmission are the Single Cell Multicast Traffic Channel (SC-MTCH) and the Single Cell Multicast Control Channel (SC-MCCH), and the transport channel used for SC-PTM transmission is the Downlink Shared Channel (DL-SCH). SC-PTM transmission is primarily designed for single-cell transmission, and transmits data by broadcast or multicast on a cell-by-cell basis. The physical channels used for SC-PTM transmission are the Physical Downlink Control Channel (PDCCH) and the Physical Downlink Shared Channel (PDSCH), which enable dynamic resource allocation.

[0045] In the following, an example in which an MBS is provided using the SC-PTM transmission method will be mainly described, but an MBS may also be provided using the MBSFN transmission method. Also, an example in which an MBS is provided by multicast will be mainly described. Therefore, MBS may be read as multicast. However, an MBS may also be provided by broadcast.

[0046] Furthermore, MBS data refers to data transmitted by MBS, the MBS control channel refers to MCCH or SC-MCCH, and the MBS traffic channel refers to MTCH or SC-MTCH. However, MBS data may also be transmitted by unicast. MBS data may also be called MBS packets or MBS traffic.

[0047] A network can provide different MBS services for each MBS session. An MBS session is identified by at least one of a Temporary Mobile Group Identity (TMGI) and a session identifier, and at least one of these identifiers is called an MBS session identifier. Such an MBS session identifier may also be called an MBS service identifier or a multicast group identifier.

[0048] FIG. 7 is a diagram showing a method for distributing MBS data according to an embodiment.

[0049] As shown in Fig. 7, MBS data (MBS Traffic) is distributed from a single data source (application service provider) to multiple UEs. A 5G CN (5GC) 20, which is a 5G core network, receives the MBS data from the application service provider, creates a copy of the MBS data (replication), and distributes the data.

[0050] From the 5GC20 point of view, two delivery methods are possible: Shared MBS Traffic delivery and Individual MBS Traffic delivery.

[0051] In shared MBS data delivery, a connection is established between NG-RAN 10, which is a 5G radio access network (5G RAN), and 5GC 20, and MBS data is delivered from 5GC 20 to NG-RAN 10. Hereinafter, such a connection (tunnel) will be referred to as an "MBS connection."

[0052] The MBS connection may be referred to as a Shared MBS Traffic delivery connection or shared transport. The MBS connection terminates in the NG-RAN 10 (i.e., the gNB 200). The MBS connection may have a one-to-one correspondence with an MBS session. The gNB 200 selects either PTP (Point-to-Point: unicast) or PTM (Point-to-Multipoint: multicast or broadcast) at its own discretion and transmits MBS data to the UE 100 using the selected method.

[0053] On the other hand, in individual MBS data delivery, a unicast session is established between the NG-RAN 10 and the UE 100, and the MBS data is delivered individually from the 5GC 20 to the UE 100. Such a unicast may be called a PDU session. The unicast (PDU session) terminates at the UE 100.

[0054] (Split MBS bearer) Next, a split MBS bearer according to one embodiment will be described.

[0055] The gNB200 can set an MBS bearer separated into a PTP communication path and a PTM communication path (hereinafter referred to as a "split MBS bearer" as appropriate) to the UE100. This allows the gNB200 to dynamically switch the transmission of MBS data to the UE100 between PTP (PTP communication path) and PTM (PTM communication path). Alternatively, the gNB200 can improve reliability by dual-transmitting the same MBS data using both PTP (PTP communication path) and PTM (PTM communication path).

[0056] The predetermined layer that terminates splitting is the MAC layer (HARQ), the RLC layer, the PDCP layer, or the SDAP layer. In the following, an example in which the predetermined layer that terminates splitting is the PDCP layer will be mainly described, but the predetermined layer may be the MAC layer (HARQ), the RLC layer, or the SDAP layer.

[0057] 8 is a diagram showing a split MBS bearer according to one embodiment. Hereinafter, a PTP communication path is referred to as a PTP leg, and a PTM communication path is referred to as a PTM leg. Furthermore, a functional unit corresponding to each layer is referred to as an entity.

[0058] 8, each of the PDCP entity of the gNB 200 and the PDCP entity of the UE 100 separates an MBS bearer, which is a bearer (data radio bearer) used for MBS, into a PTP leg and a PTM leg. Note that a PDCP entity is provided for each bearer.

[0059] Each of the gNB 200 and the UE 100 has two RLC entities, one MAC entity, and one PHY entity, each of which is provided for each leg. A PHY entity may be provided for each leg. In the case of dual connectivity in which the UE 100 communicates with two gNBs 200, the UE 100 may have two MAC entities.

[0060] The PHY entity transmits and receives data of the PTP leg using a Cell Radio Network Temporary Identifier (C-RNTI) that is assigned one-to-one to the UE 100. The PHY entity transmits and receives data of the PTM leg using a Group Radio Network Temporary Identifier (G-RNTI) that is assigned one-to-one to the MBS session. The C-RNTI is different for each UE 100, but the G-RNTI is a common RNTI for multiple UEs 100 receiving one MBS session.

[0061] In order to perform PTM transmission (multicast or broadcast) of MBS data from gNB200 to UE100 using a PTM leg, a split MBS bearer must be set from gNB200 to UE100 and the PTM leg must be activated. In other words, even if a split MBS bearer is set to UE100, gNB200 cannot perform PTM transmission of MBS data using this PTM leg if the PTM leg is in a deactivation state.

[0062] Furthermore, in order for the gNB200 and the UE100 to perform PTP transmission (unicast) of MBS data using a PTP leg, a split MBS bearer must be set from the gNB200 to the UE100, and the PTP leg must be activated. In other words, even if a split MBS bearer is set to the UE100, the gNB200 cannot perform PTP transmission of MBS data using this PTP leg if the PTP leg is in an inactive state.

[0063] In a state in which the PTM leg is activated, the UE 100 monitors a PDCCH (Physical Downlink Control Channel) to which a G-RNTI associated with the MBS session is applied (i.e., the UE 100 performs blind decoding of the PDCCH using the G-RNTI). The UE 100 may monitor the PDCCH only at a scheduling opportunity for the MBS session.

[0064] When the PTM leg is deactivated, UE 100 does not monitor the PDCCH to which the G-RNTI associated with the MBS session is applied (i.e., does not perform blind decoding of the PDCCH using the G-RNTI).

[0065] UE 100 monitors a PDCCH to which a C-RNTI is applied when a PTP leg is activated. When discontinuous reception (DRX) is configured in a PTP leg, UE 100 monitors the PDCCH in a configured on duration (OnDuration). When a cell (frequency) associated with an MBS session is designated, UE 100 may monitor the PDCCH of the cell even if the cell is deactivated.

[0066] In a state in which the PTP leg is deactivated, the UE 100 may monitor a PDCCH to which a C-RNTI is applied in preparation for normal unicast downlink transmission other than MBS data. However, when a cell (frequency) associated with an MBS session is specified, the UE 100 may not monitor the PDCCH for the MBS session.

[0067] It is assumed that the split MBS bearer as described above is set up by an RRC message transmitted from the RRC entity of the gNB 200 to the RRC entity of the UE 100. In the following, under the assumption that bearer splitting is performed, the operation of efficiently controlling bearer splitting will be mainly described.

[0068] (Activating and Deactivating Legs) The activation and deactivation of legs according to one embodiment will now be described.

[0069] FIG. 9 is a diagram illustrating a first example of operations related to activation and deactivation of legs according to an embodiment.

[0070] As shown in Fig. 9, in step S101, the RRC entity of the gNB 200 transmits an RRC message including the configuration of the split MBS bearer (split bearer) shown in Fig. 8 to the UE 100. The RRC message is, for example, an RRC Reconfiguration message. The RRC entity of the UE 100 establishes the split MBS bearer based on the configuration included in the RRC message received from the gNB 200. The following mainly describes an example in which the UE 100 establishes one split MBS bearer, but the UE 100 may establish multiple split MBS bearers according to the configuration from the gNB 200.

[0071] When performing bearer setup using an RRC message (RRC Reconfiguration message), gNB200 may use the same message to instruct UE100 on the initial state of each leg (i.e., activation or deactivation of each leg). When transmitting an RRC message including bearer setup for a split MBS bearer to UE100, the RRC entity of gNB200 includes an instruction to activate or deactivate each leg in the RRC message along with the bearer setup.

[0072] Such an RRC message may include at least one of an identifier of the leg (PTP leg, PTM leg) that is the target of the instruction and an identifier indicating either activation or deactivation. The RRC message may also include an identifier (e.g., TMGI, G-RNTI, session identifier, QoS flow identifier, bearer identifier) ​​associated with the MBS session (split MBS bearer) that is the target of the instruction.

[0073] In step S102, gNB200 sends instructions to UE100 to activate or deactivate the PTP leg and PTM leg individually.

[0074] Here, the MAC entity of the gNB200 may transmit a MAC control element (MAC CE) including the instruction to the UE100. The MAC entity of the UE100 receives the MAC CE from the gNB200. Alternatively, the PHY entity of the gNB200 may transmit downlink control information (DCI) including the instruction to the UE100. The PHY entity of the UE100 receives the DCI from the gNB200.

[0075] Such a MAC CE or DCI may include at least one of an identifier of the leg (PTP leg, PTM leg) that is the target of the instruction and an identifier indicating either activation or deactivation. The MAC CE or DCI may also include an identifier (e.g., TMGI, G-RNTI, session identifier, QoS flow identifier, bearer identifier) ​​associated with the MBS session (split MBS bearer) that is the target of the instruction.

[0076] By using MAC CE or DCI to indicate activation and deactivation of each leg, more dynamic control is possible than when using RRC messages.

[0077] UE100 starts the process of receiving data using the C-RNTI in response to receiving an instruction to activate the PTP leg. UE100 starts the process of receiving MBS data using the G-RNTI in response to receiving an instruction to activate the PTM leg. On the other hand, UE100 ends the process of receiving data using the C-RNTI in response to receiving an instruction to deactivate the PTP leg. UE100 ends the process of receiving MBS data using the G-RNTI in response to receiving an instruction to deactivate the PTM leg.

[0078] In step S102, the gNB 200 may transmit (PTM transmission) an instruction to activate or deactivate a PTP leg to the UE 100 via the PTM leg in the activated state. This allows the PTP legs of multiple UEs 100 to be activated or deactivated collectively by PTM.

[0079] The gNB 200 may transmit (PTM transmission) an instruction to deactivate the PTM leg to the UE 100 via the activated PTM leg. This allows the PTM legs of multiple UEs 100 to be deactivated collectively by PTM.

[0080] In step S102, the gNB 200 may transmit (PTP transmission) an instruction to activate or deactivate the PTM leg to the UE 100 via the PTP leg in the activated state. This allows the PTM leg to be individually activated or deactivated for each UE 100.

[0081] The gNB 200 may transmit (PTP transmission) an instruction to deactivate the PTP leg to the UE 100 via the PTP leg in the activated state. This allows the PTP leg to be deactivated individually for each UE 100.

[0082] In step S103, in response to receiving the instruction to activate at least one of the PTP leg and the PTM leg from the gNB 200 in step S102, the UE 100 may transmit a response to the received instruction to the gNB 200. This response may be transmitted, for example, from the MAC entity of the UE 100 to the gNB 200 via the PTP leg. After transmitting the response, the UE 100 may start a data reception operation on the activated leg.

[0083] The gNB 200 transmits data through the activated leg in response to receiving the response from the UE 100. That is, after receiving the response, the gNB 200 starts a data transmission operation on the leg.

[0084] In addition, in response to receiving an instruction to deactivate at least one of the PTP leg and the PTM leg from gNB200 in step S102, UE100 may send a response to the received instruction to gNB200.

[0085] 10 is a diagram showing an operation example 2 relating to activation and deactivation of legs according to one embodiment. The basic operation of operation example 2 is similar to operation example 1, so differences from operation example 1 will be mainly described here. Note that operation example 2 can be used in combination with operation example 1.

[0086] In operation example 2, gNB200 transmits an instruction to activate or deactivate both the PTP leg and the PTM leg to UE100. For example, the MAC entity of gNB200 includes both a control instruction for the PTP leg and a control instruction for the PTM leg in a MAC CE that instructs activation or deactivation of the legs.

[0087] As shown in Fig. 10, in step S201, the RRC entity of the gNB 200 transmits an RRC message including the configuration of the split MBS bearer (split bearer) shown in Fig. 8 to the UE 100. As described above, the RRC message may include information for configuring the initial state of each leg. The information for configuring the initial state of each leg may be information similar to an instruction included in a MAC CE or DCI, which will be described later.

[0088] In step S202, the gNB 200 transmits an instruction to activate or deactivate both the PTP leg and the PTM leg to the UE 100. As described above, the instruction is included in the MAC CE or DCI.

[0089] Here, the MAC CE or DCI includes an indication of activation of both the PTP leg and the PTM leg (e.g., "1"), or deactivation of both the PTP leg and the PTM leg (e.g., "0"). Activation of both the PTP leg and the PTM leg may be activation of a split MBS bearer and / or activation of duplication using two legs. Also, deactivation of both the PTP leg and the PTM leg may be deactivation of a split MBS bearer and / or deactivation of duplication using two legs.

[0090] The MAC CE or DCI may include identifiers (e.g., TMGI, G-RNTI, session identifier, QoS flow identifier, bearer identifier) ​​associated with the MBS session (split MBS bearer) that is the subject of the instruction. The MAC CE or DCI may include an activation or deactivation instruction for each such identifier.

[0091] FIG. 11 is a diagram illustrating an example of a MAC CE (1 octet) that stores an indication value for each bearer identifier (or logical channel identifier) ​​according to an embodiment. As shown in FIG. 11, in the MAC CE, M1 to M8 correspond to bearers #1 to #8 (or logical channels #1 to #8). Each field of M1 to M8 is 1 bit, and an indication value of activation (e.g., "1") or deactivation (e.g., "0") is stored in each field.

[0092] Step S203 is the same as in operation example 1. The UE 100 may transmit a response to the gNB 200.

[0093] In operation example 2, the PDCP entity of UE 100 may perform a process of discarding duplicate packets of two identical MBS packets transmitted by duplication when both the PTP leg and the PTM leg are activated.

[0094] When the PTP leg is deactivated, the RRC entity of the UE 100 may transmit a message (RAI: Release Assistance Information / preference) to the gNB 200 to prompt the gNB 200 to release the RRC connection. Alternatively, the UE 100 may be permitted to transmit the RAI even when dynamic switching between the PTP leg and the PTM leg is being configured.

[0095] (Automatic leg deactivation) Automatic deactivation of legs according to one embodiment will now be described: Figure 12 is a diagram illustrating automatic deactivation of legs according to one embodiment.

[0096] 12, in step S301, the gNB 200 and the UE 100 establish a split MBS bearer divided into a PTP leg and a PTM leg. The gNB 200 activates at least one of the PTP leg and the PTM leg.

[0097] In step S302, the UE 100 determines whether a predetermined condition is satisfied after at least one of the PTP leg and the PTM leg is activated. The predetermined condition may be a condition in which data is not received from the gNB 200 for a predetermined time in the activated leg.

[0098] If it is determined that the predetermined condition is met (step S302: YES), in step S303, UE100 deactivates the activated leg even if it does not receive an instruction to deactivate the activated leg from gNB200.

[0099] This allows UE100 to voluntarily deactivate activated legs that are not receiving data from gNB200, eliminating the need to perform reception processing (monitoring) for those legs and reducing the power consumption of UE100.

[0100] The above-mentioned predetermined time (timer value) may be set by the gNB 200 to the UE 100, for example, by an RRC message. Different timer values ​​may be set for the PTM leg and the PTP leg. The UE 100 may consider that the gNB 200 has authorized the UE 100 to perform automatic deactivation when the timer value is set. The UE 100 resets the timer every time it receives data on an activated leg, and deactivates the leg when the timer expires.

[0101] Such automatic deactivation of legs may be applicable only to PTM legs or only to PTP legs, or the legs to which automatic deactivation is to be applied may be configured (specified) by the gNB 200 to the UE 100, for example, by an RRC message.

[0102] As the above-mentioned predetermined conditions, conditions similar to conditions 1 to 3 described below may be used.

[0103] (MBS bearer automatic de-configuration) Next, automatic deconfiguration of an MBS bearer according to an embodiment will be described. Here, an example of automatically deconfiguring a split MBS bearer will be described, but an MBS bearer that is not split may also be automatically deconfigured.

[0104] FIG. 13 is a diagram illustrating automatic de-establishment of an MBS bearer according to one embodiment.

[0105] 13, in step S401, the gNB 200 and the UE 100 establish a split MBS bearer divided into a PTP leg and a PTM leg. The gNB 200 may activate at least one of the PTP leg and the PTM leg.

[0106] In step S302, the UE 100 determines whether a predetermined condition is satisfied. The predetermined condition is any one of the following conditions 1 to 3, or a combination of two or more of the following conditions 1 to 3.

[0107] Condition 1: Both the PTP leg and the PTM leg are deactivated. For example, when both legs of one split MBS bearer are deactivated, the UE 100 determines that the bearer has been released from the setup, and discards the setup (step S403).

[0108] The UE 100 may wait for a certain period of time to elapse after both legs are deactivated, and may deactivate the MBS bearer if neither leg is activated before the certain period of time has elapsed. The certain period of time may be configured in the UE 100 by the gNB 200, for example, via an RRC message. For example, the UE 100 starts a timer when both legs are deactivated, stops the timer when either leg is activated, and deactivates the MBS bearer when the timer expires.

[0109] Alternatively, condition 1 may be a condition in which no data is received from gNB200 for a predetermined period of time on both the PTP leg and the PTM leg, similar to the automatic deactivation of the legs described above.

[0110] Condition 2: A condition in which the UE 100 transmits a notification to the gNB 200 indicating that it is no longer interested in receiving MBS. For example, when the UE 100 loses interest in receiving the MBS, the UE 100 stops receiving the MBS and notifies the gNB 200 that the UE 100 is no longer interested in receiving the MBS. In this case, the UE 100 considers that the MBS bearer setup has been released, and discards the setup of the bearer (step S403).

[0111] The notification sent by the UE 100 may include an identifier for the MBS session for which the UE 100 is no longer interested in receiving the MBS. The notification may be sent from the UE 100 to the gNB 200 via a PTP leg.

[0112] This notification may be an RRC message sent to gNB200 or may be NAS signaling sent to the core network (e.g., AMF).

[0113] In the case of NAS signaling, the core network (e.g., AMF) may notify the gNB 200 of the release of the bearer for the UE 100, or may exclude the UE 100 from the destination of the MBS connection (shared traffic). Also, within the UE 100, the NAS layer may notify the AS layer of the release of the split MBS bearer.

[0114] In addition, if UE100 confirms that gNB200 has received the notification through a lower layer ACK or the like, or if it receives a notification via NAS signaling, it may consider that the split MBS bearer setting has been released and discard the setting of the bearer.

[0115] Condition 3: The UE 100 determines that the MBS transmission from the gNB 200 has ended. For example, when ending MBS transmission, gNB200 transmits a notification (end marker) indicating the end of MBS transmission to UE100. Alternatively, UE100 determines the end of MBS transmission based on the session end time included in pre-stored MBS session delivery schedule information (USD: User Service Description). When UE100 determines that MBS transmission has ended, it considers that the MBS bearer setup has been released and discards the setup of the bearer (step S403).

[0116] If it is determined that the above-described predetermined conditions are satisfied (step S402: YES), in step S403, the UE 100 cancels the split MBS bearer configuration (i.e., discards the configuration related to the split MBS bearer) even if it does not receive an instruction to cancel the configuration of the split MBS bearer from the gNB 200. The UE 100 may cancel all MBS-related configurations (dedicated configurations). The UE 100 may notify the upper layer (NAS) that the split MBS bearer configuration has been canceled. This notification may include information (Cause) indicating the content of the condition satisfied in step S402.

[0117] In this way, by automatically canceling the setup of unnecessary MBS bearers, it is possible to reduce the processing load and power consumption of the UE 100 while eliminating the need for the gNB 200 to instruct each UE 100 to cancel the setup.

[0118] (Cancel multicast settings) Next, a description will be given of a cancellation of configuration according to one embodiment. In the above-described automatic cancellation of configuration, efficiency is improved by the UE 100 voluntarily canceling the configuration of the MBS bearer. In contrast, in this embodiment, an instruction to cancel the configuration of the MBS bearer is transmitted from the gNB 200 to a plurality of UEs 100 by multicast, thereby performing efficient cancellation of configuration. The MBS bearer that is cancelled by multicast may be a split MBS bearer or may be an unsplit MBS bearer.

[0119] 14 is a diagram illustrating multicast configuration cancellation according to an embodiment. In FIG. 14, it is assumed that each of a plurality of UEs 100 (UEs 100A to 100C) establishes an MBS bearer with the gNB 200 and receives MBS data belonging to the same MBS session from the gNB 200.

[0120] When the gNB 200 determines to release the MBS bearers for the multiple UEs 100, the gNB 200 transmits an instruction to release the MBS bearer setup using multicast (G-RNTI). The gNB 200 may transmit the instruction to release the MBS bearer setup via a PTM leg.

[0121] Such an MBS bearer release instruction is a MAC CE, an RRC message, an RLC Control PDU, a PDCP Control PDU, or an SDAP Control PDU. The gNB 200 may explicitly indicate to the UE 100 which MBS bearer is to be released by including an identifier (e.g., a G-RNTI, a TMGI, a session identifier, or a QoS flow identifier) ​​related to the MBS session for which the MBS bearer is to be released in the MBS bearer release instruction. Alternatively, when there is a one-to-one correspondence between an MBS session and a G-RNTI, the gNB 200 may implicitly indicate which MBS bearer is to be released by using the G-RNTI used to transmit the MBS bearer release instruction.

[0122] UE 100 releases (discards) the target bearer setup when it receives an MBS bearer release instruction from gNB 200. UE 100 may release (discard) the setup immediately upon receiving the MBS bearer release instruction, or, if UE 100 is performing an MBS reception operation, may release (discard) the setup upon completion of the reception operation.

[0123] (Other embodiments) The above-mentioned 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.

[0124] In the above embodiment, an example in which the base station is an NR base station (gNB) has been described, but the base station may also be an LTE base station (eNB). 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 (Distributed Unit) of the IAB node.

[0125] 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 the 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.

[0126] In addition, circuits that execute each process performed by UE100 or gNB200 may be integrated, and at least a part of UE100 or gNB200 may be configured as a semiconductor integrated circuit (chipset, SoC).

[0127] 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.

[0128] This application claims priority from Japanese Patent Application No. 2020-176328 (filed October 20, 2020), the entire contents of which are incorporated herein by reference. [Explanation of symbols]

[0129] 10:NG-RAN (5G RAN) 20:5GC(5G CN) 100:UE 110: Receiving unit 120: Transmitter 130: Control unit 200 :gNB 210: Transmission unit 220: Receiving unit 230: Control unit 240: Backhaul communication unit

Claims

1. A communication control method used in a mobile communication system that provides a multicast broadcast service (MBS) from a network node to a user device, comprising: said user equipment receiving information relating to a multicast session from said network node; and if the user equipment receives the information from the network node without receiving data for the multicast session for a predetermined period of time, stopping monitoring using a Group Radio Network Temporary Identifier (G-RNTI) for the multicast session. Communication control method.

2. A user equipment provided with a multicast and broadcast service (MBS) from a network node, comprising: a receiving unit for receiving information about a multicast session from the network node; a control unit that stops monitoring using a G-RNTI (Group Radio Network Temporary Identifier) ​​for the multicast session when there is no data for the multicast session for a predetermined period and the information is received from the network node. User equipment.

3. 1. A chipset for a user equipment to be provided with a multicast broadcast service (MBS) from a network node, comprising: receiving information about a multicast session from the network node; If the user equipment receives the information from the network node without receiving data for the multicast session for a predetermined period of time, the user equipment stops monitoring using a Group Radio Network Temporary Identifier (G-RNTI) for the multicast session. Chipset.

4. A user equipment that receives a multicast and broadcast service (MBS) from a network node, receiving information about a multicast session from the network node; and if the user equipment receives the information from the network node without receiving data for the multicast session for a predetermined period of time, the user equipment stops monitoring using a Group Radio Network Temporary Identifier (G-RNTI) for the multicast session. program.

5. 1. A mobile communication system for providing a multicast and broadcast service (MBS) from a network node to user equipment, comprising: the network node transmitting information regarding a multicast session to the user equipment; If the user equipment receives the information from the network node without receiving data for the multicast session for a predetermined period of time, the user equipment stops monitoring using a Group Radio Network Temporary Identifier (G-RNTI) for the multicast session. Mobile communication system.

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