COMMUNICATION CONTROL METHOD, USER EQUIPMENT, AND PROCESSOR

Abstract

A first embodiment relates to a communication control method implemented by a user equipment in a mobile communication system that provides a multicast / broadcast service (MBS). The communication control method comprises: in a Radio Resource Control (RRC) connected state, receiving MBS data from a base station; managing a timer for counting the time in which transmission and reception of data and signaling with the base station is not performed; and, in response to the expiry of the timer, transitioning from the RRC connected state to an RRC idle state. The managing of the timer includes, when receiving the MBS data transmitted by multicast or broadcast, controlling not to start the timer even if the MBS data is received.

Description

[Technical field]

[0001] The present disclosure relates to a communication control method and a user device for use 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 executed by a user device in a mobile communication system that provides a multicast / broadcast service (MBS). The communication control method includes receiving MBS data from a base station in an RRC connected state, managing a timer that measures a time during which data and signaling are not transmitted or received from the base station, and transitioning from the RRC connected state to an RRC idle state in response to expiration of the timer. Managing the timer includes controlling the timer so as not to start the timer even when the MBS data transmitted by multicast or broadcast is received.

[0005] A communication control method according to a second aspect is a communication control method executed by a user device in a mobile communication system that provides a multicast / broadcast service (MBS). The communication control method includes managing a timer that measures a time during which no data is transmitted or received from the base station, and transitioning from an RRC connected state to an RRC idle state in response to expiration of the timer. Managing the timer includes In When receiving MBS data to be transmitted from the base station, restarting the timer by sending or receiving restart information before the timer expires.

[0006] A user device according to a third aspect includes a processor that executes the communication control method according to the first or second aspect. [Brief description of the drawings]

[0007] [Figure 1] 1 is a diagram showing a configuration of a mobile communication system according to an embodiment; [Diagram 2] FIG. 1 is a diagram illustrating a configuration of a UE (user equipment) according to an embodiment. [Diagram 3] A diagram showing the configuration of a gNB (base station) according to one embodiment. [Figure 4] A diagram showing the configuration of a protocol stack of a wireless interface of a user plane that handles data. [Diagram 5] FIG. 2 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 showing a correspondence relationship between downlink logical channels and transport channels according to an embodiment. [Figure 7] FIG. 2 is a diagram illustrating a method for distributing MBS data according to an embodiment. [Figure 8] A diagram showing a split MBS bearer according to one embodiment. [Figure 9]FIG. 4 is a diagram illustrating an example of an operation of a first operation pattern according to an embodiment. [Figure 10] FIG. 11 is a diagram illustrating an example of an operation of a second operation pattern according to an embodiment. [Figure 11] FIG. 11 is a diagram illustrating an example of an operation of a third operation pattern according to an embodiment. [Figure 12] FIG. 13 is a diagram illustrating an example of an operation of a fourth operation pattern according to an embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] The introduction of multicast and broadcast services to the 5G system (NR) is being considered. It is hoped that the NR multicast and broadcast services will provide improved services compared to the LTE multicast and broadcast services.

[0009] Therefore, an object of the present disclosure is to provide a communication control method and a user device that realize an improved multicast / broadcast service.

[0010] 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.

[0011] (Configuration of a mobile communication system) First, a configuration of a mobile communication system according to an embodiment will be described. FIG. 1 is a diagram showing a configuration of a mobile communication system according to an embodiment. This mobile communication system complies with the 3GPP standard 5th Generation System (5GS). In the following description, 5GS will be taken as an example, but the mobile communication system may be at least partially applied to an LTE (Long Term Evolution) system. Also, the mobile communication system may be at least partially applied to a 6th Generation (6G) system.

[0012] 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.

[0013] 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 is 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).

[0014] The NG-RAN 10 includes a base station (called "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, and the like. The term "cell" is used to indicate the smallest unit of a wireless communication area. The term "cell" is also used to indicate a function or resource for performing wireless communication with the UE 100. One cell belongs to one carrier frequency.

[0015] 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.

[0016] 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 Non-Access Stratum (NAS) 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.

[0017] FIG. 2 is a diagram showing a configuration of a UE 100 (user equipment) according to an embodiment.

[0018] As shown in FIG. 2, the UE 100 includes a receiving unit 110, a transmitting unit 120, and a control unit .

[0019] The receiving unit 110 performs various receptions under the control of the control unit 130. The receiving unit 110 includes an antenna and a receiver. The receiver converts a radio signal received by the antenna into a baseband signal (received signal) and outputs the baseband signal to the control unit 130.

[0020] The transmission unit 120 performs various transmissions under the control of the control unit 130. The transmission 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.

[0021] 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 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 processing.

[0022] FIG. 3 is a diagram showing the configuration of a gNB 200 (base station) according to one embodiment.

[0023] As shown in FIG. 3, the gNB 200 includes a transmitter 210, a receiver 220, a control unit 230, and a backhaul communication unit 240.

[0024] 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.

[0025] The receiving unit 220 performs various receptions under the control of the control unit 230. The receiving unit 220 includes an antenna and a receiver. The receiver converts a radio signal received by the antenna into a baseband signal (received signal) and outputs the baseband signal to the control unit 230.

[0026] 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 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 processing.

[0027] The backhaul communication unit 240 is connected to adjacent 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., the functions are divided), and both units may be connected to each other via an F1 interface.

[0028] FIG. 4 is a diagram showing the configuration of a protocol stack of a radio interface of a user plane that handles data.

[0029] As shown in FIG. 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.

[0030] 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.

[0031] 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 UE100 and the MAC layer of gNB200 via a transport channel. The MAC layer of gNB200 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 assigned to UE100.

[0032] The RLC layer transmits data to the RLC layer on the receiving side by using the functions of the MAC layer and the 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.

[0033] The PDCP layer performs header compression / decompression and encryption / decryption.

[0034] The SDAP layer maps IP flows, which are units for QoS (Quality of Service) control by the core network, to radio bearers, which are units for QoS control by the AS (Access Stratum). Note that if the RAN is connected to the EPC, the SDAP is not necessary.

[0035] 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).

[0036] 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.

[0037] Between the RRC layer of the UE 100 and the RRC layer of the gNB 200, RRC signaling for various settings is transmitted. 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 the UE 100 and the RRC of the gNB 200, the UE 100 is in an RRC connected state. When there is no connection (RRC connection) between the RRC of the UE 100 and the RRC of the gNB 200, the UE 100 is in an RRC idle state. When the connection between the RRC of the UE 100 and the RRC of the gNB 200 is suspended, the UE 100 is in an RRC inactive state.

[0038] The NAS layer, which is located above the RRC layer, performs session management, mobility management, etc. NAS signaling is transmitted between the NAS layer of the UE 100 and the NAS layer of the AMF 300B.

[0039] In addition, the UE 100 has an application layer and the like in addition to the protocol of the radio interface.

[0040] (MBS) Next, an MBS according to an embodiment will be described. The MBS is a service that enables broadcast or multicast, that is, point-to-multipoint (PTM) data transmission from the NG-RAN 10 to the UE 100. The MBS may be called a Multimedia Broadcast and Multicast Service (MBMS). Note that use cases (service types) of the MBS include public safety communication, mission critical communication, V2X (Vehicle to Everything) communication, IPv4 or IPv6 multicast distribution, IPTV (Internet Protocol TeleVision), group communication, and software distribution.

[0041] 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 a correspondence relationship between downlink logical channels and transport channels according to one embodiment.

[0042] As shown in FIG. 6, the logical channels used for MBSFN transmission are MTCH (Multicast Traffic Channel) and MCCH (Multicast Control Channel), and the transport channel used for MBSFN transmission is MCH (Multicast Traffic Channel). t MBSFN transmission is primarily designed for multi-cell transmission, where each cell in an MBSFN area transmits the same signal (the same data) synchronously in the same MBSFN subframe.

[0043] The logical channels used for SC-PTM transmission are the SC-MTCH (Single Cell Multicast Traffic Channel) and the SC-MCCH (Single Cell Multicast Control Channel), and the transport channel used for SC-PTM transmission is the DL-SCH (Downlink Shared Channel). SC-PTM transmission is designed primarily 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 PDCCH (Physical Downlink Control Channel) and the PDSCH (Physical Downlink Shared It is a QoS Channel, which allows dynamic resource allocation.

[0044] In the following, an example in which an MBS is provided using a method similar to 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.

[0045] Moreover, MBS data refers to data provided by the MBS. The MBS control channel refers to the MCCH or SC-MCCH. The MBS traffic channel refers to the MTCH or SC-MTCH. However, the MBS data may be transmitted by unicast. The MBS data may be called an MBS packet or MBS traffic.

[0046] 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 be called an MBS service identifier or a multicast group identifier.

[0047] The MBS sessions include multicast sessions and broadcast sessions.

[0048] A multicast session is a session for delivering a multicast service. The multicast service provides services to a group of UEs 100 participating in the multicast session for applications that require reliable QoS. The multicast session is available to UEs 100 in the RRC connected state. In the multicast session, MBS data is transmitted by multicast. The UE 100 needs to be in the RRC connected state to receive the multicast session.

[0049] A broadcast session is a session for delivering a broadcast service. The broadcast service provides a service to all UEs 100 within a specific service area. The broadcast session is available to UEs 100 in all RRC states (RRC idle state, RRC inactive state, and RRC connected state).

[0050] FIG. 7 is a diagram showing a method for delivering MBS data according to an embodiment.

[0051] 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 (replication) of the MBS data, and distributes it.

[0052] From the 5GC20 point of view, two delivery methods are possible: Shared MBS Traffic delivery and Individual MBS Traffic delivery.

[0053] In the 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) is referred to as an "MBS connection."

[0054] The MBS connection may be referred to as a Shared MBS Traffic delivery connection or a 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 the MBS session.

[0055] gNB200 selects either PTP (Point-to-Point: unicast) or PTM (Point-to-Multipoint: multicast or broadcast) transmission method at its own discretion, and transmits MBS data to UE100 using the selected transmission method.

[0056] On the other hand, in the 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) is terminated at the UE 100.

[0057] (Split MBS Bearer) Next, a split MBS bearer according to one embodiment will be described.

[0058] The gNB200 can set an MBS bearer separated into a PTP communication path and a PTM communication path (hereinafter, appropriately referred to as a "split MBS bearer") 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 enhance reliability by dually transmitting the same MBS data using both PTP (PTP communication path) and PTM (PTM communication path).

[0059] The predetermined layer that terminates the split 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 the split 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.

[0060] 8 is a diagram showing a split MBS bearer according to an embodiment. In the following, a PTP communication path is called a PTP leg, and a PTM communication path is called a PTM leg. Also, a functional unit corresponding to each layer is called an entity. Also, in the PTM leg, MBS data is transmitted by multicast.

[0061] As shown in Fig. 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.

[0062] Each of the gNB 200 and the UE 100 has two RLC entities provided for each leg, one MAC entity, and one PHY entity. The 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.

[0063] 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.

[0064] In order to perform PTM transmission (multicast or broadcast) of MBS data from the gNB 200 to the UE 100 using a PTM leg, a split MBS bearer needs to be set from the gNB 200 to the UE 100, and the PTM leg needs to be activated. In other words, even if a split MBS bearer is set to the UE 100, the gNB 200 cannot perform PTM transmission of MBS data using this PTM leg if the PTM leg is in a deactivation state.

[0065] Also, 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.

[0066] 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., blind decoding of the PDCCH is performed using the G-RNTI). The UE 100 may monitor the PDCCH only at a scheduling opportunity for the MBS session.

[0067] In a state in which the PTM leg is deactivated, the UE 100 does not monitor the PDCCH to which the G-RNTI associated with the MBS session is applied (that is, does not perform blind decoding of the PDCCH using the G-RNTI).

[0068] UE 100 monitors the PDCCH to which the C-RNTI is applied when the PTP leg is activated. When discontinuous reception (DRX) is set in the PTP leg, UE 100 monitors the PDCCH in the set on duration (OnDuration). When a cell (frequency) associated with an MBS session is specified, UE 100 may monitor the PDCCH of the cell even if the cell is deactivated.

[0069] 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.

[0070] It is assumed that the split MBS bearer described above is configured by an RRC message (e.g., an RRC Reconfiguration message) sent by the RRC entity of gNB200 to the RRC entity of UE100.

[0071] (RRC State Transition due to Data Inactivity Timer) Next, an RRC state transition due to a data inactivity timer according to one embodiment will be described.

[0072] In the current specifications of 5G / NR, a data inactivity timer is defined. The data inactivity timer is a timer that measures a time during which data and signaling between the UE 100 and the gNB 200 are not transmitted or received.

[0073] The UE 100 in the RRC connected state may have a data inactivity timer set by the gNB 200. The UE 100 transitions from the RRC connected state to the RRC idle state in response to expiration of the data inactivity timer.

[0074] When the data inactivity timer is set, the UE 100 starts the data inactivity timer in response to transmission or reception of data or signaling. The UE 100 restarts the data inactivity timer in response to transmission or reception of data or signaling before the data inactivity timer expires. Note that "restarting the data inactivity timer" means resetting and restarting the data inactivity timer.

[0075] An example of transmitting or receiving data is when the MAC entity of the UE 100 transmits or receives a MAC SDU over a Dedicated Traffic Channel (DTCH) logical channel, which is a dedicated logical channel for data transmission.

[0076] An example of transmitting or receiving signaling is when the MAC entity of the UE 100 transmits or receives a MAC SDU via a Dedicated Control Channel (DCCH) logical channel. The DCCH logical channel is a dedicated logical channel for transmitting signaling. For details of the data inactivity timer, see, for example, "5.19 Data inactivity monitoring" of 3GPP TS 38.321 V16.3.0 and "5.3.8.5 UE actions upon the expiry of DataInactivityTimer" of 3GPP TS 38.331 V16.3.0.

[0077] (First operation pattern) Next, a first operation pattern according to one embodiment will be described.

[0078] If the above-described data inactivity timer is applied when the UE 100 receives MBS data transmitted by multicast, the following problem occurs.

[0079] The gNB 200 sets up an MBS bearer for the UE 100 in the RRC connected state, and starts transmitting MBS data by multicast. At this point, the gNB 200 recognizes that the UE 100 is in the RRC connected state. When the UE 100 receives the MBS data transmitted by multicast, the UE 100 starts a data inactivity timer. Then, when the data inactivity timer is running, if the radio condition at the UE 100 deteriorates, the UE 100 cannot successfully receive the MBS data and does not restart the data inactivity timer. After that, the UE 100 transitions to an RRC idle state in response to the expiration of the data inactivity timer. This causes a problem of RRC state mismatch between the gNB 200 and the UE 100. As described above, the MBS data may be provided not only by multicast but also by broadcast.

[0080] On the other hand, when receiving data transmitted by normal unicast, the UE 100 generally transmits feedback information (e.g., delivery confirmation information (ACK / NACK)) regarding the reception of the data to the gNB 200. Therefore, even if the UE 100 transitions to the RRC idle state due to deterioration of the radio condition as described above, the gNB 200 can infer that the UE 100 has transitioned to the RRC idle state in response to not receiving feedback information from the UE 100. Therefore, the problem of the mismatch of the RRC states is not significant.

[0081] However, there are cases where the UE 100 is not configured to transmit feedback information when receiving MBS data transmitted by multicast, in which case the problem of RRC state mismatch becomes prominent.

[0082] Note that UE 100 receiving MBS data transmitted by multicast refers to any of the following: 1) UE 100 has an MBS bearer set with only a PTM leg and receives MBS data via the MBS bearer, 2) UE 100 has a split MBS bearer set with a PTM leg and a PTP leg and receives MBS data via the PTM leg, or 3) UE 100 receives MBS data using the G-RNTI.

[0083] In a first operation pattern according to an embodiment, the UE 100 manages a data inactivity timer. In the management of the data inactivity timer, when the UE 100 receives MBS data transmitted by multicast, the UE 100 controls not to start the data inactivity timer even if the UE 100 receives the MBS data. As a result, the UE 100 does not start the data inactivity timer, so there is no transition to the RRC idle state in response to the expiration of the data inactivity timer, and the above-mentioned problem of inconsistency of the RRC states is resolved.

[0084] In the first operation pattern, when the UE 100 receives MBS data transmitted by unicast, the UE 100 starts or restarts the data inactivity timer in response to the reception of the MBS data. As described above, in the case of unicast, the transmission of feedback information is set, so the problem of RRC state mismatch is not significant.

[0085] Note that UE 100 receiving MBS data transmitted by unicast refers to any of the following: 1) UE 100 has an MBS bearer set with only a PTP leg and receives MBS data via the MBS bearer, 2) UE 100 has a split MBS bearer set with a PTM leg and a PTP leg and receives MBS data via the PTP leg, or 3) UE 100 receives MBS data using the C-RNTI.

[0086] 9 is a diagram illustrating an example of an operation of a first operation pattern according to an embodiment. In an initial state of FIG. 9, the UE 100 is in an RRC connected state, and a data inactivity timer is set in the UE 100 by the gNB 200.

[0087] 9, in step S101, the gNB 200 transmits MBS data by multicast. The UE 100 receives the MBS data transmitted by multicast.

[0088] In step S102, UE 100 receives MBS data transmitted by multicast, but controls not to start the data inactivity timer. Note that even if the data inactivity timer has already been started at this point, UE 100 controls not to restart the data inactivity timer. For example, before step S102, UE 100 starts the data inactivity timer in response to transmission and reception of data (data other than MBS data) by normal unicast, and in step S102, UE 100 controls not to restart the data inactivity timer.

[0089] In step S103, the gNB 200 instructs the UE 100 to receive the MBS data by unicast. The UE 100 receives this instruction from the gNB 200. Here, this instruction may be an RRC Reconfiguration message for setting up an MBS bearer having only a PTP leg, or may be an instruction for activating a PTP leg of a split MBS bearer already set up in the UE 100 (e.g., a MAC CE (Control Element) or DCI (Donwlink Control Information)).

[0090] In step S104, the gNB 200 transmits the MBS data by unicast to the UE 100. The UE 100 receives the MBS data transmitted by unicast.

[0091] In step S105, the UE 100 starts a data inactivity timer in response to receiving the MBS data transmitted by unicast.

[0092] In steps S106 to S107, the UE 100 restarts the data inactivity timer in response to receiving the MBS data transmitted by unicast.

[0093] (Second movement pattern) Next, a second operation pattern according to one embodiment will be described, focusing mainly on the differences from the above-mentioned operation patterns.

[0094] In the second operation pattern, even when the UE 100 receives MBS data transmitted by unicast, the UE 100 controls not to start the data inactivity timer even when the UE 100 receives the MBS data. This simplifies the process of determining whether or not to start the data inactivity timer in the UE 100.

[0095] 10 is a diagram illustrating an example of an operation of a second operation pattern according to an embodiment. In this example of operation, it is assumed that the UE 100 is in an RRC connected state and a data inactivity timer is set in the UE 100 by the gNB 200.

[0096] 10, in step S201, the gNB 200 transmits MBS data by unicast or multicast. The UE 100 receives the MBS data.

[0097] In step S202, UE 100 receives MBS data, but controls not to start the data inactivity timer. Note that even if the data inactivity timer has already started at this point, UE 100 controls not to restart the data inactivity timer. For example, before step S202, UE 100 starts the data inactivity timer in response to transmission and reception of data (data other than MBS data) in normal unicast, and in step S202, UE 100 controls not to restart the data inactivity timer.

[0098] (Third movement pattern) Next, a third operation pattern according to one embodiment will be described, focusing mainly on the differences from the above-mentioned operation patterns.

[0099] In the third operation pattern, UE100 controls the data inactivity timer to start / not start when receiving MBS data in accordance with the configuration information from gNB200.

[0100] 11 is a diagram illustrating an example of an operation of a third operation pattern according to an embodiment. In this example of operation, it is assumed that the UE 100 is in an RRC connected state and a data inactivity timer is set in the UE 100 by the gNB 200.

[0101] 11, in step S301, the gNB 200 transmits configuration information for setting whether or not to start a data inactivity timer upon reception of MBS data to the UE 100. The UE 100 receives the configuration information from the gNB 200.

[0102] The configuration information is transmitted to the UE 100 by, for example, an RRC Reconfiguration message. The configuration information may further include an identifier (such as TMGI) of an MBS session corresponding to the MBS data. For example, the configuration information includes, for each of a plurality of MBS sessions in which the gNB 200 is stopped, a set of an identifier (such as TMGI) of the MBS session and information for setting whether or not to start a data inactivity timer upon reception of MBS data belonging to the MBS session.

[0103] In step S302, the gNB 200 transmits the MBS data. The UE 100 receives the MBS data.

[0104] In step S303, when the UE 100 receives the MBS data, the UE 100 controls to start / not start the data inactivity timer in accordance with the setting information received in step S301.

[0105] In the third operation pattern, the setting information may be information for setting whether to transmit feedback information (e.g., delivery confirmation information (ACK / NACK)) for the MBS data. In this case, the UE 100 starts the data inactivity timer when receiving the MBS data for which the transmission of the feedback information is set, and controls not to start the data inactivity timer when receiving the MBS data for which the transmission of the feedback information is not set.

[0106] (4th movement pattern) Next, a fourth movement pattern according to one embodiment will be described, focusing mainly on the differences from the above-mentioned movement patterns.

[0107] As described above, in the current 5G / NR specifications, the data inactivity timer is intended for data and signaling transmitted and received by unicast. When the UE 100 receives MBS data transmitted by multicast, the UE 100 starts the data inactivity timer when transmitting and receiving data by normal unicast. When the data inactivity timer is operating and data is not transmitted and received by normal unicast, the UE 100 transitions to the RRC idle state upon expiration of the data inactivity timer. Since the UE 100 needs to be in the RRC connected state in order to receive MBS data transmitted by multicast, the UE 100 that transitions to the RRC idle state cannot receive MBS data transmitted by multicast.

[0108] In the fourth operation pattern, when the UE 100 receives MBS data transmitted by multicast, the UE 100 resumes the data inactivity timer by transmitting resumption information to the gNB 200 before the data inactivity timer expires. In the current specification, it is specified that the UE 100 resumes the data inactivity timer when it transmits signaling. Therefore, in response to the transmission of the resumption information, the UE 100 resumes the data inactivity timer. Therefore, the UE 100 does not transition to the RRC idle state in response to the expiration of the data inactivity timer, and can continuously receive the MBS data transmitted by multicast.

[0109] 12 is a diagram illustrating an example of an operation of a fourth operation pattern according to an embodiment. In this example of operation, it is assumed that the UE 100 is in an RRC connected state and a data inactivity timer is set in the UE 100 by the gNB 200.

[0110] 12, in step S401, the UE 100 starts a data inactivity timer. Here, for example, the UE 100 starts the data inactivity timer in response to transmission and reception of unicast data (data other than MBS data). The UE 100 may start the data inactivity timer in response to transmission and reception of signaling.

[0111] In step S402, the gNB 200 transmits the MBS data by multicast. The UE 100 receives the MBS data transmitted by multicast.

[0112] In step S403, the UE 100 determines whether the remaining time before the data inactivity timer expires is equal to or less than a threshold. The threshold may be a value set by the UE 100 itself. Alternatively, the threshold may be a value set by the gNB 200 to the UE 100.

[0113] If the remaining time is less than the threshold (step S 403 : YES), in step S404, UE100 transmits resumption information to gNB200. UE100 may transmit the resumption information by an RRC message. Also, UE100 may transmit the resumption information by a MAC CE. The resumption information may be information for notifying gNB200 that a data inactivity timer is reset and resumed. The resumption information may be a 1-bit flag indicating that UE100 continuously receives MBS data. In addition, in response to receiving the resumption information, gNB200 may transmit a response to the resumption information to UE100.

[0114] In step S405, in response to the transmission of the resumption information, the UE 100 resets and resumes the data inactivity timer.

[0115] In the fourth operation pattern, the UE 100 may periodically transmit the resumption information before the data inactivity timer expires.

[0116] In the above description, in S403, the remaining time before the data inactivity timer expires is compared with the threshold value, but this is not limited to the above. UE 100 may have a separate timer for transmitting resumption information. UE 100 starts and restarts the timer when transmitting the resumption information, and transmits the resumption information again when the timer expires. UE 100 stops (or discards) the timer when it no longer receives MBS data (when it is no longer interested in receiving, or when MBS data transmission or MBS session ends). The value of the timer may be set by gNB 200.

[0117] In the fourth operation pattern, the resumption information may be transmitted from the gNB200. Specifically, the gNB200 manages a data inactivity timer in the same manner as the UE100, and the gNB200 starts / resumes the data inactivity timer in response to transmission and reception of data by unicast with the UE100. In this case, if the gNB200 is transmitting MBS data, and the remaining time of the data inactivity timer managed by the gNB200 is equal to or less than a threshold, the gNB200 transmits the resumption information to the UE100 by unicast. In response to receiving the resumption information, the UE100 resumes the data inactivity timer managed by the UE100. In addition, the gNB200 may reset and resume the data inactivity timer managed by the gNB200 in response to receiving the resumption information from the UE100.

[0118] (Other embodiments) In each of the above operation patterns, the handling of the timer associated with MBS data reception has been described under the assumption that the data inactivity timer is set in the UE 100. However, when the gNB 200 transmits MBS data by multicast (PTM), the operation of not setting the data inactivity timer in the UE 100 is considered. In this case, in the RRC Reconfiguration message, the MBS setting (or PTM setting) and the data inactivity timer setting can be set exclusively. Alternatively, when the MBS setting (or PTM setting) is performed, the UE 100 may ignore the data inactivity timer even if it is set. In other words, the data inactivity timer may be considered not to be set.

[0119] The above-mentioned motion patterns are not limited to being performed independently, but can be performed by combining two or more motion patterns. For example, some steps of one motion pattern may be added to another motion pattern. Also, some steps of one motion pattern may be replaced with some steps of another motion pattern.

[0120] 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 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.

[0121] 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 in a computer-readable medium. Using the computer-readable medium, it is possible to install the program in the computer. Here, the computer-readable medium on which the program is recorded may be a non-transient recording medium. The non-transient recording medium is not particularly limited, and may be, for example, a recording medium such as a CD-ROM or a DVD-ROM.

[0122] In addition, circuits that execute each process performed by UE100 or gNB200 may be integrated, and at least a portion of UE100 or gNB200 may be configured as a semiconductor integrated circuit (chip set, SoC: System on a chip).

[0123] As used in this disclosure, the terms "based on" and "depending on" do not mean "based only on" or "depending only on," unless otherwise specified. The term "based on" means both "based only on" and "based at least in part on." Similarly, the term "depending on" means both "based only on" and "based at least in part on." Additionally, "obtain / acquire" may mean obtaining information from stored information, from information received from other nodes, or by generating information. The terms "include," "comprise," and variations thereof do not mean including only the items listed, but may include only the items listed, or may include additional items in addition to the items listed. Additionally, the term "or" as used in this disclosure is not intended to be an exclusive or. Additionally, any reference to elements using designations such as "first," "second," etc., as used in this disclosure is not intended to 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, 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 manner. In this disclosure, where articles are added by translation, such as a, an, and the in English, these articles are intended to include the plural unless the context clearly indicates otherwise.

[0124] 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, etc. are possible without departing from the spirit of the invention.

[0125] This application claims priority to Japanese Patent Application No. 2021-079265 (filed May 7, 2021), the entire contents of which are incorporated herein by reference. [Explanation of symbols]

[0126] 10: NG-RAN (5G RAN) 20: 5GC (5G CN) 100:UE 110: Receiving unit 120: Transmitter 130: Control section 200: gNB 210: Transmission unit 220: Receiving unit 230: Control section 240: Backhaul communication unit

Claims

1. A communication control method executed by a user device in a mobile communication system providing a multicast and broadcast service (MBS), comprising: receiving MBS data from a network in a Radio Resource Control (RRC) connected state; Managing a data inactivity timer used to monitor data inactivity; transitioning from the RRC connected state to an RRC idle state in response to expiration of the data inactivity timer; Managing the data inactivity timer includes, when receiving the MBS data transmitted by broadcast, controlling so as not to start the data inactivity timer even if the MBS data is received. Communications control method.

2. Managing the data inactivity timer further includes, when receiving the MBS data transmitted by unicast, starting or restarting the data inactivity timer in response to receiving the MBS data. The communication control method according to claim 1 .

3. A user equipment in a mobile communication system providing a multicast and broadcast service (MBS), A receiving unit that receives MBS data from a network in an RRC (Radio Resource Control) connected state; A control unit that manages a data inactivity timer used for monitoring data inactivity, The control unit is transitioning from the RRC connected state to an RRC idle state in response to expiration of the data inactivity timer; When the MBS data transmitted by broadcast is received, the data inactivity timer is not started even if the MBS data is received. User equipment.

4. A processor for controlling a user device in a mobile communication system providing a multicast and broadcast service (MBS), comprising: A process of receiving MBS data from a network in an RRC (Radio Resource Control) connected state; managing a data inactivity timer used to monitor data inactivity; transitioning from the RRC connected state to an RRC idle state in response to expiration of the data inactivity timer; When receiving the MBS data transmitted by broadcast, a process of controlling not to start the data inactivity timer even if the MBS data is received is executed. Processor.

Images