Communication control method

Abstract

A communication control method for use in a mobile communication system that provides a multicast broadcast service (MBS) from a base station to a user equipment is provided, wherein: the user equipment receives, from the base station, unicast signaling including MBS settings required for MBS reception while in an RRC connected state; and the user equipment performs MBS reception using the MBS settings received in the RRC connected state when having transitioned from the RRC connected state to an RRC idle state or an RRC inactive state.

Description

Technical Field

[0001] This invention relates to a communication control method used in a mobile communication system. Background Technology

[0002] In recent years, fifth-generation (5G) mobile communication systems have attracted much attention. Compared with Long Term Evolution (LTE), which is the fourth-generation radio access technology, New Radio (NR), the radio access technology (RAT) of 5G systems, has features such as high speed, large capacity, high reliability, and low latency.

[0003] List of cited references

[0004] Non-patent literature

[0005] Non-patent document 1: 3GPP technical specification "3GPP TS 38.300V16.3.0 (2020-09)" Summary of the Invention

[0006] In a first aspect, a communication control method is used in a mobile communication system providing multicast and broadcast services (MBS) from a base station to a user equipment, and includes: a user equipment in a radio resource control (RRC) connected state receiving from a base station unicast signaling including an MBS configuration for MBS reception; and a user equipment that has transitioned from an RRC connected state to an RRC idle state or an RRC inactive state performing MBS reception by using the MBS configuration received in the RRC connected state.

[0007] In a second aspect, a communication control method is used in a mobile communication system providing multicast and broadcast services (MBS) from a base station to a user equipment, and includes: sending a broadcast message from the base station to the user equipment, the broadcast message including at least one identifier selected from a group consisting of a first identifier and a second identifier, wherein the first identifier indicates a first MBS session in which a first MBS configuration for MBS reception is provided by using unicast signaling, and the second identifier indicates a second MBS session in which a second MBS configuration for MBS reception is provided by using broadcast signaling.

[0008] In a third aspect, a communication control method is used in a mobile communication system providing multicast and broadcast services (MBS) from a base station to a user equipment, and includes: a base station providing multiple MBS control channels in a cell sending a broadcast message to the user equipment, the broadcast message including a Radio Network Temporary Identifier (RNTI) for each of the multiple MBS control channels for receiving the MBS control channel among the multiple MBS control channels.

[0009] In a fourth aspect, a communication control method is used in a mobile communication system providing multicast and broadcast services (MBS) from a base station to a user equipment, and includes: a base station transmitting cell reselection control information, the cell reselection control information including priority information indicating the priority of each cell or the priority of each frequency during cell reselection, and an MBS session identifier associated with the priority information; and a user equipment in an RRC idle state or an RRC inactive state performing cell reselection based on the cell reselection control information from the base station, using the priority information corresponding to the desired MBS session identifier.

[0010] In a fifth aspect, a communication control method is used in a mobile communication system providing multicast and broadcast services (MBS) from a base station to a user equipment, and includes: initiating an RRC reconstruction process by a user equipment receiving an MBS session in an RRC connected state; and performing cell selection during the RRC reconstruction process. Performing the cell selection includes preferentially selecting a cell providing the MBS session.

[0011] In a sixth aspect, a communication control method is used in a mobile communication system providing multicast and broadcast services (MBS) from a base station to a user equipment, and includes: receiving from the base station by the user equipment information indicating an initial bandwidth portion (BWP) used by the base station; receiving from the base station by the user equipment an MBS configuration for MBS reception; and when the MBS configuration does not include a BWP configuration, performing MBS reception by the user equipment using the initial BWP. Attached Figure Description

[0012] Figure 1 This is a diagram illustrating the configuration of a mobile communication system according to an embodiment.

[0013] Figure 2 This is a diagram illustrating the configuration of a user equipment (UE) according to an embodiment.

[0014] Figure 3 This is a diagram illustrating the configuration of a base station (gNB) according to an embodiment.

[0015] Figure 4 This is a diagram illustrating the configuration of the protocol stack for the radio interface used for user plane data processing.

[0016] Figure 5 This is a diagram showing the configuration of the protocol stack of the radio interface that handles signaling (control signals) in the control plane.

[0017] Figure 6 This is a diagram illustrating the correspondence between downlink logical channels and downlink transport channels according to an embodiment.

[0018] Figure 7 This is a diagram illustrating a method for transmitting MBS data according to an embodiment.

[0019] Figure 8 This is a diagram illustrating an operational example according to the first embodiment.

[0020] Figure 9 The figure shows a variation 1 according to the first embodiment.

[0021] Figure 10 The figure shows a variation 2 according to the first embodiment.

[0022] Figure 11 The figure shows a variation 3 according to the first embodiment.

[0023] Figure 12 This is a diagram illustrating an operational example according to the second embodiment.

[0024] Figure 13 This is a diagram illustrating an operational example according to the third embodiment.

[0025] Figure 14 This is a diagram illustrating an operational example according to the fourth embodiment.

[0026] Figure 15 This is a diagram illustrating an operational example according to the fifth embodiment.

[0027] Figure 16 This is a diagram illustrating an operational example according to the sixth embodiment.

[0028] Figure 1 Figure 7 is a diagram illustrating a two-level configuration in LTE SC-PTM.

[0029] Figure 18 This is a diagram showing the configuration that enables NR MBS. Detailed Implementation

[0030] The introduction of multicast and broadcast services into 5G systems (NR) is under investigation. NR multicast and broadcast services need to provide enhanced services compared to LTE multicast and broadcast services.

[0031] In view of this, the present invention provides enhanced multicast and broadcast services.

[0032] A mobile communication system according to an embodiment will be described with reference to the accompanying drawings. In the description of the drawings, the same or similar reference numerals denote the same or similar parts.

[0033] Configuration of mobile communication system

[0034] First, the configuration of the mobile communication system according to an embodiment will be described. Figure 1 This diagram illustrates the configuration of a mobile communication system according to an embodiment. The mobile communication system conforms to the 3GPP 5th Generation System (5GS) standard. The following description uses 5GS as an example, but a Long Term Evolution (LTE) system or a 6th Generation (6G) system may be at least partially applicable to this mobile communication system.

[0035] like Figure 1 As shown, the mobile communication system includes a user equipment (UE) 100, a 5G radio access network (Next Generation Radio Access Network (NG-RAN)) 10, and a 5G core network (5GC) 20.

[0036] UE 100 is a mobile wireless communication device. UE 100 can be any device used by a user. Examples of UE 100 include mobile phone terminals (including smartphones), tablet terminals, laptop PCs, communication modules (including communication cards or chipsets), sensors or devices mounted on sensors, vehicles or devices mounted on vehicles (vehicle UE), or flying objects or devices mounted on flying objects (airborne UE).

[0037] NG-RAN 10 includes base stations (referred to as "gNBs" in 5G systems) 200. gNBs 200 are interconnected via the Xn interface, which serves as an inter-base station interface. Each gNB 200 manages one or more cells. gNBs 200 perform wireless communication with UEs 100 that have established connections to cells connected to them. gNBs 200 have Radio Resource Management (RRM) functions, functions for routing user data (hereinafter referred to as "data"), measurement and control functions for mobility control and scheduling, etc. "Cell" is used as a term to represent the smallest unit of a wireless communication area. "Cell" is also used as a term to represent the functions or resources used to perform wireless communication with UEs 100. A cell belongs to one carrier frequency.

[0038] Note that a gNB can connect to the Evolved Packet Core (EPC) corresponding to the LTE core network. LTE base stations can also connect to the 5GC. LTE base stations and gNBs can connect via an inter-base station interface.

[0039] The 5GC 20 includes Access and Mobility Management Functions (AMF) and User Plane Functions (UPF) 300. The AMF performs various types of mobility control for the UE 100. The AMF manages the mobility of the UE 100 by communicating with it using Non-Access Stratum (NAS) signaling. The UPF controls data transmission. The AMF and UPF are connected to the gNB 200 via the NG interface, which serves as the interface between the base station and the core network.

[0040] Figure 2 This is a diagram illustrating the configuration of UE 100 (User Equipment) according to an embodiment.

[0041] like Figure 2 As shown, UE 100 includes receiver 110, transmitter 120 and controller 130.

[0042] Receiver 110 performs various types of reception under the control of controller 130. Receiver 110 includes an antenna and receiving equipment. The receiving equipment converts the radio signals received through the antenna into baseband signals (received signals) and outputs the resulting signals to controller 130.

[0043] Transmitter 120 performs various types of transmissions under the control of controller 130. Transmitter 120 includes an antenna and a transmitting device. The transmitting device converts the baseband signal (transmit signal) output by controller 130 into a radio signal and transmits the obtained signal through the antenna.

[0044] Controller 130 performs various types of control within UE 100. Controller 130 includes at least one processor and at least one memory. The memory stores programs to be executed by the processor and information to be processed by the processor. The processor may include a baseband processor and a central processing unit (CPU). The baseband processor performs modulation and demodulation, encoding and decoding of baseband signals, etc. The CPU executes programs stored in the memory, thereby performing various types of processing.

[0045] Figure 3 This is a diagram illustrating the configuration of a gNB 200 (base station) according to an embodiment.

[0046] like Figure 3 As shown, the gNB 200 includes a transmitter 210, a receiver 220, a controller 230, and a backhaul communicator 240.

[0047] Transmitter 210 performs various types of transmissions under the control of controller 230. Transmitter 210 includes an antenna and a transmitting device. The transmitting device converts the baseband signal (transmit signal) output by controller 230 into a radio signal and transmits the obtained signal through the antenna.

[0048] Receiver 220 performs various types of reception under the control of controller 230. Receiver 220 includes an antenna and receiving equipment. The receiving equipment converts the radio signals received through the antenna into baseband signals (received signals) and outputs the resulting signals to controller 230.

[0049] The controller 230 performs various types of control over the gNB 200. The controller 230 includes at least one processor and at least one memory. The memory stores programs to be executed by the processor and information to be processed by the processor. The processor may include a baseband processor and a CPU. The baseband processor performs modulation and demodulation, encoding and decoding of baseband signals, etc. The CPU executes programs stored in the memory, thereby performing various types of processing.

[0050] The backhaul communicator 240 is connected to the adjacent base station via the inter-base station interface. The backhaul communicator 240 is also connected to the AMF / UPF 300 via the interface between the base station and the core network. Note that the gNB may include a central unit (CU) and a distributed unit (DU) (i.e., functions are divided), and these two units can be connected via the F1 interface.

[0051] Figure 4 This is a diagram illustrating the configuration of the protocol stack for the radio interface used for user plane data processing.

[0052] like Figure 4 As shown, the user plane radio interface protocol includes: Physical (PHY) layer, Media Access Control (MAC) layer, Radio Link Control (RLC) layer, Packet Data Convergence Protocol (PDCP) layer, and Service Data Adaptation Protocol (SDAP) layer.

[0053] The PHY layer performs encoding and decoding, modulation and demodulation, antenna mapping and demapping, and resource mapping and demapping. Data and control information are transmitted between the PHY layer of UE 100 and the PHY layer of gNB 200 via physical channels.

[0054] The MAC layer performs priority control of data, 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 the transport channel. The MAC layer of gNB 200 includes a scheduler. The scheduler determines the transmission format (transport block size, modulation and coding scheme (MCS)) in the uplink and downlink and the resource blocks to be allocated to UE 100.

[0055] The RLC layer transmits data to the receiving RLC layer using the functions of the MAC and PHY layers. Data and control information are transmitted between the RLC layer of UE 100 and the RLC layer of gNB 200 via a logical channel.

[0056] The PDCP layer performs header compression and decompression, as well as encryption and decryption.

[0057] The SDAP layer performs the mapping between IP flows (as a unit of QoS (Quality of Service) control performed by the core network) and radio bearers (as a unit of QoS control performed by the access layer (AS)). Note that SDAP may not be provided when the RAN is connected to the EPC.

[0058] Figure 5 This is a diagram showing the configuration of the protocol stack of the radio interface that handles signaling (control signals) in the control plane.

[0059] like Figure 5 As shown, the protocol stack of the control plane's radio interface includes a Radio Resource Control (RRC) layer and a Non-Access Stratum (NAS) layer, instead of... Figure 4 The SDAP layer is shown.

[0060] RRC signaling for various configurations is transmitted between the RRC layer of UE 100 and the RRC layer of gNB 200. The RRC layer controls logical channels, transport channels, and physical channels based on the establishment, reconstruction, and release of radio bearers. When a connection (RRC connection) exists between the RRC of UE 100 and the RRC of gNB 200, UE 100 is in the RRC connected state. When a connection (RRC connection) does not exist between the RRC of UE 100 and the RRC of gNB 200, UE 100 is in the RRC idle state. When the connection between the RRC of UE 100 and the RRC of gNB 200 is suspended, UE 100 is in the RRC inactive state.

[0061] The NAS layer, which is above the RRC layer, performs session management, mobility management, etc. NAS signaling is transmitted between the NAS layer of UE 100 and the NAS layer of AMF300B.

[0062] Note that UE 100 includes the application layer in addition to the radio interface protocol.

[0063] MBS

[0064] The MBS according to an embodiment will be described. MBS is a service in which NG-RAN 10 provides broadcast or multicast, i.e., point-to-multipoint (PTM) data transmission to UE 100. MBS may be referred to as Multimedia Broadcast and Multicast Service (MBMS). Note that use cases (service types) for MBS include public communications, mission-critical communications, V2X (vehicle-to-everything) communications, IPv4 or IPv6 multicast delivery, IPTV, group communications, and software delivery.

[0065] MBS transmission in LTE includes two schemes: Multicast-Broadcast Single Frequency Network (MBSFN) transmission and Single Cell Point-to-Multipoint (SC-PTM) transmission. Figure 6 This is a diagram illustrating the correspondence between downlink logical channels and downlink transport channels according to an embodiment.

[0066] like Figure 6 As shown, the logical channels used for MBSFN transmission are the Multicast Service Channel (MTCH) and the Multicast Control Channel (MCCH), while the transport channel used for MBSFN transmission is the Multicast Channel (MCH). MBSFN transmission is mainly designed for multi-cell transmission, and in an MBSFN area that includes multiple cells, each cell synchronously transmits the same signal (the same data) in the same MBSFN subframe.

[0067] The logical channels used for SC-PTM transmission are the Single Cell Multicast Service 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 corresponds to cell-by-cell broadcast or multicast data transmission. The physical channels used for SC-PTM transmission are the Physical Downlink Control Channel (PDCCH) and the Physical Downlink Shared Channel (PDSCH), and dynamic resource allocation is possible.

[0068] Although the following description will primarily focus on examples using the SC-PTM transport scheme to provide MBS, the MBSFN transport scheme can also be used. The description will primarily focus on examples using multicast to provide MBS. Accordingly, MBS can be interpreted as multicast. Note that MBS can also be provided using broadcast.

[0069] MBS data refers to data transmitted using MBS. The MBS control channel refers to MCCH or SC-MCCH, while the MBS traffic channel refers to MTCH or SC-MTCH. Note that MBS data can be transmitted using unicast. MBS data can also be referred to as MBS packets or MBS traffic.

[0070] The network can provide different MBS services for each MBS session. An MBS session is identified by at least one identifier selected from a group consisting of a Temporary Mobile Group Identifier (TMGI) and a session identifier, and at least one of these identifiers is called an MBS session identifier. This MBS session identifier can be referred to as an MBS service identifier or a multicast group identifier.

[0071] Figure 7 This is a diagram illustrating a method for transmitting MBS data according to an embodiment.

[0072] like Figure 7 As shown, MBS data (MBS service) is transmitted from a single data source (application service provider) to multiple UEs. The 5G CN (5GC) 20, which serves as the 5G core network, receives MBS data from the application service provider, creates a copy of the MBS data (performs replication), and transmits the MBS data.

[0073] From the perspective of 5GC 20, there are two possible transmission methods: shared MBS data transmission (shared MBS service transmission) and single MBS data transmission (single MBS service transmission).

[0074] In shared MBS data transmission, a connection is established between NG-RAN 10 and 5GC 20, which serve as the 5G radio access network (5G RAN), and MBS data is transmitted from 5GC 20 to NG-RAN 10. In the following description, this connection (tunnel) is referred to as an "MBS connection".

[0075] MBS connections can be referred to as shared MBS service delivery connections or shared transport. MBS connections terminate at NG-RAN 10 (i.e., gNB 200). An MBS connection can correspond to a one-to-one MBS session. gNB 200 decides for itself whether to use point-to-point (PTP: unicast) or point-to-multipoint (PTM: multicast or broadcast) methods to send MBS data to UE 100.

[0076] Conversely, in a single MBS data transmission, a unicast session is established between NG-RAN 10 and UE 100, and MBS data is transmitted separately from 5GC 20 to UE 100. This unicast can be referred to as a PDU session. The unicast (PDU session) terminates at UE 100.

[0077] First Embodiment

[0078] The first embodiment will be described.

[0079] The first embodiment primarily assumes the following scenario: unicast signaling is used to send the required MBS configuration from gNB 200 to UE 100 for receiving MBS data transmitted from gNB 200 using PTM (hereinafter referred to as "PTM reception"). This unicast signaling can be referred to as dedicated signaling. By using this unicast configuration, advanced MBS configuration (e.g., bearer configuration) can be performed separately for UE 100.

[0080] Note that UE 100 in RRC connected state can receive unicast configuration, while UE 100 in RRC idle state or RRC inactive state cannot receive unicast configuration. Therefore, assuming only unicast configuration is used, UE 100 in RRC idle state or RRC inactive state may not be able to perform MBS reception.

[0081] The first embodiment is an embodiment that enables UE 100 in an RRC idle state or an RRC inactive state to perform MBS reception even when using only unicast configuration.

[0082] In the first embodiment, UE 100 in RRC connected state receives unicast signaling from gNB 200 including MBS configuration required for MBS reception. This MBS configuration includes at least one configuration selected from the group consisting of configurations associated with MBS bearers and configurations associated with MBS service channels (e.g., scheduling information for MBS service channels).

[0083] Unicast signaling used for MBS configuration can be, for example, an RRC reconfiguration message. Unicast signaling used for MBS configuration can also be an RRC release message.

[0084] UE 100 that has transitioned from RRC connected state to RRC idle state or RRC inactive state uses the MBS configuration received in RRC connected state to perform MBS reception.

[0085] Typically, when UE 100 leaves the RRC connected state (especially when UE 100 transitions to the RRC idle or RRC inactive state), the UE-specific configuration (dedicated configuration) configured in the RRC connected state is discarded. Conversely, the first embodiment enables UE 100 in the RRC idle or RRC inactive state to perform MBS reception by maintaining, but not discarding, the UE-specific MBS configuration configured in the RRC connected state.

[0086] Figure 8 This is a diagram illustrating an operational example according to the first embodiment.

[0087] like Figure 8 As shown, in step S101, UE 100 is in RRC connected state within the cell of gNB 200. Here, UE 100 may notify gNB 200 that it will continue MBS reception in RRC idle or RRC inactive states. Alternatively, UE 100 may notify gNB 200 that it expects not to continue MBS reception in RRC idle or RRC inactive states. These notifications may be notifications regarding UE 100's expectations (preferences). These notifications may be associated with an MBS session identifier (e.g., TMGI).

[0088] In step S102, gNB 200 sends an RRC reconfiguration message including MBS configuration to UE 100. UE 100 receives the RRC reconfiguration message.

[0089] The RRC reconfiguration message may include availability information indicating whether the MBS configuration received in the RRC connected state is available in the RRC idle or RRC inactive state (or whether MBS reception can continue).

[0090] In step S103, UE 100 stores and applies the MBS configuration included in the received RRC reconfiguration message.

[0091] In step S104, UE 100 receives MBS data (MBS service channel) from gNB 200 using the MBS configuration applied in step S103.

[0092] Subsequently, in step S105, gNB 200 sends an RRC release message to UE 100 to enable UE 100 to transition to an RRC idle state or an RRC inactive state. UE 100 receives the RRC release message.

[0093] The RRC release message may include the aforementioned availability information. When the RRC release message includes the availability information, the RRC reconfiguration message does not need to include the availability information.

[0094] In step S106, UE 100 transitions from RRC connected state to RRC idle state or RRC inactive state.

[0095] In step S107, UE 100 maintains and does not discard the MBS configuration stored and applied in step S103. When the RRC reconfiguration message or RRC release message includes usage availability information and the usage availability information indicates "available," UE 100 may maintain and not discard the MBS configuration. Conversely, when the RRC reconfiguration message or RRC release message includes usage availability information and the usage availability information indicates "unavailable," UE 100 may discard the MBS configuration.

[0096] In step S108, UE 100 continues to receive MBS from gNB 200.

[0097] Variation 1 of the first embodiment

[0098] Variation 1 of the first embodiment will be described.

[0099] In the first embodiment described above, since the network (gNB 200) cannot control the UE 100 in the RRC idle or RRC inactive state, the validity period of the MBS configuration, once configured, may be indefinite. If the MBS configuration is permanently available to the UE 100 in the RRC idle or RRC inactive state, the network cannot change the MBS configuration even if it desires to. This is because a change in the MBS configuration in the network would prevent the UE 100 from performing MBS reception. On the other hand, since the UE 100 cannot know about the change in the MBS configuration in advance, it only becomes aware of the change when it becomes unable to perform MBS reception.

[0100] In a variant of the first embodiment, the UE 100 in the RRC connected state receives from the gNB 200 information indicating the validity period of the MBS configuration from the time the MBS configuration is received or from the time of transition to the RRC idle state or RRC inactive state. By defining such a validity period for the MBS configuration, the above-mentioned problem can be solved.

[0101] A UE 100 in RRC connected state can receive information indicating the validity period of the MBS configuration, as well as an MBS session identifier (e.g., TMGI) associated with the information indicating the validity period. Thus, the validity period of the MBS configuration can be defined for each MBS session (MBS service).

[0102] In response to the expiration of the MBS configuration validity period, UE 100, which performs MBS reception after transitioning to RRC idle state or RRC inactive state, can transition to RRC connected state and acquire a new MBS configuration. Therefore, MBS reception can continue even after the MBS configuration validity period has expired.

[0103] Figure 9 This diagram illustrates a variation 1 according to the first embodiment. Here, a description is given mainly regarding the differences from the first embodiment described above.

[0104] like Figure 9 As shown, in step S201, UE 100 is in RRC connected state in the cell of gNB 200.

[0105] In step S202, gNB 200 sends an RRC reconfiguration message including MBS configuration to UE 100. UE 100 receives the RRC reconfiguration message.

[0106] The RRC reconfiguration message may include information (timer value) indicating the validity period of the MBS configuration. Here, the validity period of the MBS configuration may be calculated from the time of configuration in step S202. The validity period of the MBS configuration may also be calculated from the time when UE 100 transitions to RRC idle or RRC inactive state (step S206 described later). The validity period of the MBS configuration can be configured based on, for example, a period during which gNB 200 does not change the MBS configuration (modification period) or a period until the end time of the scheduled MBS session. When the validity period of the MBS configuration is calculated from the time of configuration in step S202, UE 100 starts the timer (validity timer) that sets the validity period of the MBS configuration during configuration in step S202.

[0107] In step S203, UE 100 stores and applies the MBS configuration included in the received RRC reconfiguration message.

[0108] In step S204, UE 100 receives MBS data (MBS service channel) from gNB 200 using the MBS configuration applied in step S203.

[0109] Subsequently, in step S205, gNB 200 sends an RRC release message to UE 100 to enable UE 100 to transition to an RRC idle state or an RRC inactive state. UE 100 receives the RRC release message.

[0110] The RRC release message may include information (a timer value) indicating the validity period of the MBS configuration. Here, the validity period of the MBS configuration can be calculated from the time the UE 100 transitions to the RRC idle state or RRC inactive state (i.e., from the time the RRC release message is received). The validity period of the MBS configuration can be configured, for example, for a period during which the gNB 200 does not change the MBS configuration or for a period until the end time of the scheduled MBS session. When the RRC release message is received, the UE 100 starts the timer (validity timer) that sets the validity period of the MBS configuration.

[0111] In step S206, UE 100 transitions from RRC active state to RRC idle state or RRC inactive state.

[0112] In step S207, UE 100 maintains and does not discard the MBS configuration stored and applied in step S203.

[0113] In step S208, UE 100 continues to receive MBS from gNB 200 until the validity period timer expires.

[0114] When the validity period timer expires (step S209: Yes), in step S210, UE 100 performs MBS reception suspension processing. MBS reception suspension processing includes at least one selected from the group consisting of: processing to stop MBS reception, processing to cancel the application of MBS configuration, and processing to discard MBS configuration.

[0115] When the validity period timer expires and UE 100 still wants to continue receiving MBS, in step S211, UE 100 performs connection processing with gNB 200.

[0116] For example, UE 100, which is in RRC idle state, initiates an RRC establishment procedure. During the RRC establishment procedure, UE 100 may use information indicating that UE 100 intends to obtain MBS reception configuration as an information element (e.g., reason) in the RRC establishment request message.

[0117] UE 100, which is in an RRC inactive state, initiates an RRC recovery procedure. During the RRC recovery procedure, UE 100 may include information indicating that UE 100 intends to acquire MBS reception configuration as an information element (e.g., reason) in the RRC recovery request message.

[0118] After UE 100 transitions to RRC connected state through connection processing with gNB 200 (step S212), in step S213, UE 100 receives an RRC reconfiguration message from gNB 200 that includes the new MBS configuration.

[0119] This operational example assumes that only unicast MBS configuration is used, but it can also assume that broadcast MBS configuration is used. When the validity timer expires (step S209: Yes), UE 100 can perform MBS receive suspension processing (step S210) and also obtain MBS configuration from the MBS control channel sent from gNB 200 using broadcast.

[0120] In this variant, the validity period of the MBS configuration can be different for each MBS session (TMGI), or it can be common to all MBS sessions (only one). When the validity period of the MBS configuration is different for each MBS session, UE100 sets the validity period for the timer corresponding to the MBS session received by UE100.

[0121] Variation 2 of the first embodiment

[0122] Variation 2 of the first embodiment will be described.

[0123] As mentioned above, when the network (gNB 200) makes changes to the MBS configuration (e.g., changes to resources, etc.), the UE 100, which is in the RRC idle state or RRC inactive state, may not be able to receive the expected MBS session.

[0124] In a variant of the first embodiment, UE 100, after transitioning to an RRC idle state or an RRC inactive state, performs MBS reception and receives a notification from gNB 200 indicating an update to the MBS configuration. In response to receiving the notification, UE 100 transitions to an RRC connected state and acquires the new MBS configuration. Thus, UE 100 can continue MBS reception using the new MBS configuration.

[0125] Figure 10 This diagram illustrates a variation 2 according to the first embodiment. Here, a description is given mainly regarding the differences from the first embodiment described above.

[0126] like Figure 10 As shown, steps S301 to S308 are the same as and / or similar to steps S101 to S108 in the first embodiment described above. Note that in step S302, when performing MBS configuration for UE 100, gNB 200 may notify UE 100 of the configuration identifier (value tag value) associated with the MBS configuration.

[0127] In step S309, gNB 200 determines changes to the MBS configuration. For example, gNB 200 performs a determination regarding at least one selected from the group consisting of changes to resources (time and frequency resources) used for PTM transmission and the stopping or starting of PTM transmission.

[0128] In step S310, gNB 200 performs a notification to UE 100 which is in RRC idle state or RRC inactive state.

[0129] The notification in step S310 can be system information (System Information Block (SIB)) broadcast by the gNB 200. This notification can be an indication of changes to the MBS configuration and / or a notification that changes will occur within a certain time period, or it can be an indication for performing connection processing (e.g., RRC establishment). The notification may include an identifier (e.g., TMGI) of the MBS session whose MBS configuration will be changed.

[0130] The gNB 200 can include the value tag value of the currently valid MBS configuration in the SIB. Note that each time the gNB 200 changes the MBS configuration, the gNB 200 counts up the value tag value (increments the value tag value). When the value tag value notified from the gNB 200 in step S302 is the same as the value tag value included in the SIB received from the gNB 200 in step S310, the UE 100 determines that the current MBS configuration is valid; when these value tag values ​​are different from each other, the UE 100 determines that the current MBS configuration is invalid.

[0131] The notification in step S310 may be a paging message, which includes the identifier of the MBS session whose MBS configuration will be changed. For example, gNB 200 includes the MBS session identifier requesting the configuration change in the paging record included in the paging message. When the paging record contains the MBS session identifier expected by UE 100, UE 100 determines that it needs to obtain the MBS configuration again. Note that UE 100 may only monitor periodic paging opportunities. gNB 200 sends paging messages containing the MBS session identifier during all paging opportunities of UE 100 within a certain time period.

[0132] In step S311, in response to receiving the notification from step S310, the UE 100, which wishes to continue MBS reception, performs the MBS reception suspension process described above (step S311) and also performs the connection process described above (step S312). Then, in step S313, the UE 100 switches to RRC connected state and subsequently obtains a new MBS reception configuration to continue MBS reception. This operation is the same as and / or similar to the operation of variant 1 of the first embodiment.

[0133] Variation 3 of the first embodiment

[0134] Variation 3 of the first embodiment will be described.

[0135] This variant assumes that the MBS configuration applied in the RRC connected state is different from the MBS configuration applied in the RRC idle state or the RRC inactive state.

[0136] In this variant, the unicast signaling (RRC reconfiguration message) sent from gNB 200 to UE 100 includes a first MBS configuration required for MBS reception in RRC connected state and a second MBS configuration required for MBS reception in RRC idle state or RRC inactive state.

[0137] Figure 11 This diagram illustrates a variation 3 according to the first embodiment. Here, a description is given mainly regarding the differences from the first embodiment described above.

[0138] like Figure 11 As shown, in step S401, UE 100 is in RRC connected state in the cell of gNB 200.

[0139] In step S402, gNB 200 sends an RRC reconfiguration message to UE 100, including the first MBS configuration and the second MBS configuration. UE 100 receives the RRC reconfiguration message.

[0140] The first MBS configuration is the MBS receive configuration for the RRC connected state. The first MBS configuration includes MBS bearer configuration information. In the first MBS configuration, the MBS bearer and the MBS session identifier (e.g., G-RNTI) may be associated with each other. The first MBS configuration may include an identifier indicating that the configuration is for the RRC connected state, or it may include an identifier indicating that the configuration is not for the RRC idle state or the RRC inactive state.

[0141] The first MBS configuration is not necessarily exclusive to the RRC connected state. The first MBS configuration may include an identifier indicating that the configuration can also be used in the RRC idle state or the RRC inactive state.

[0142] Conversely, the second MBS configuration is an MBS receive configuration for the RRC idle state or the RRC inactive state. The second MBS configuration includes configuration information (e.g., scheduling information) related to the MBS traffic channel. The second MBS configuration may include an identifier indicating whether the configuration is for the RRC idle state or the RRC inactive state, or it may include an identifier indicating that the configuration is not for the RRC connected state. In the second MBS configuration, configurations for the RRC idle state and configurations for the RRC inactive state can be provided separately.

[0143] The second MBS configuration is not necessarily exclusive to the RRC idle or inactive state. The second MBS configuration may include an identifier indicating that the configuration can also be used in the RRC connected state.

[0144] In step S403, UE 100 stores and applies the first MBS configuration included in the received RRC reconfiguration message, and stores the second MBS configuration.

[0145] In step S404, UE 100 receives MBS data from gNB 200 using the first MBS configuration applied in step S403. Here, UE 100 may apply a second MBS configuration that is also valid for RRC connected state. UE 100 does not apply a second MBS configuration that is only valid for RRC idle state or RRC inactive state.

[0146] Subsequently, in step S405, gNB 200 sends an RRC release message to UE 100 to enable UE 100 to transition to an RRC idle state or an RRC inactive state. UE 100 receives the RRC release message.

[0147] In step S406, UE 100 transitions from RRC connected state to RRC idle state or RRC inactive state.

[0148] In step S407, UE 100 performs processing based on the identifier included in the first MBS configuration and the identifier included in the second MBS configuration. For example, UE 100 discards the first MBS configuration, which is only valid in the RRC connected state. Note that when UE 100 is in the RRC inactive state, UE 100 may retain the first MBS configuration. UE 100 retains (does not discard) the second MBS configuration, which is valid in the RRC idle state or the RRC inactive state, or continues to apply it (or applies it again).

[0149] In step S408, UE 100 receives MBS data from gNB 200 using the second MBS configuration applied in step S407.

[0150] Second Embodiment

[0151] The main focus will be on describing the differences between the second embodiment and the first embodiment.

[0152] The second embodiment assumes a situation where unicast MBS configuration and broadcast MBS configuration coexist. When both configuration methods exist, UE 100 needs to appropriately determine which method to use to obtain the MBS reception configuration.

[0153] In the second embodiment, gNB 200 sends a broadcast message to UE 100. The broadcast message includes at least one identifier selected from a group consisting of a first identifier (first MBS session identifier) ​​and a second identifier (second MBS session identifier). The first identifier indicates a first MBS session in which unicast signaling is used to provide the first MBS configuration required for MBS reception, while the second identifier indicates a second MBS session in which broadcast signaling is used to provide the second MBS configuration required for MBS reception. The broadcast message may be an SIB transmitted on a broadcast control channel, or it may be MBS control information transmitted on an MBS control channel.

[0154] Therefore, UE 100 can appropriately determine which method, unicast or broadcast, will be used to obtain the MBS configuration for MBS reception. Based on the broadcast message from gNB 200 and UE 100's desired MBS session, UE 100 receives one of the first MBS configuration (i.e., the MBS configuration using unicast) and the second MBS configuration (i.e., the MBS configuration using broadcast) from gNB 200.

[0155] Figure 12 This is a diagram illustrating an operational example according to the second embodiment.

[0156] like Figure 12 As shown, in step S501, gNB 200 uses SIB to notify UE 100 (UE 100A and UE 100B) that the service (first MBS session identifier) ​​for receiving MBS configuration needs to be received using unicast signaling (e.g., RRC reconfiguration message) and / or the service (second MBS session identifier) ​​for receiving said configuration can be received using broadcast signaling (e.g., SC-MCCH). In other words, gNB 200 uses SIB (or SC-MCCH) to broadcast a method for obtaining MBS configuration for each MBS session identifier.

[0157] Figure 12 An example is shown where the MBS session with unicast configuration applied (first MBS session identifier) ​​is MBS session #1, and the MBS session with broadcast configuration applied (second MBS session identifier) ​​is MBS session #2.

[0158] For example, an MBS session with a unicast configuration belongs to an MBS session for a multicast-based service (e.g., group communication). Conversely, an MBS session with a broadcast configuration belongs to an MBS session for a broadcast-based service (e.g., services related to broadcasting or IPTV).

[0159] In step S502, UE 100A, which expects to receive multicast-based services, determines to receive MBS session #1 based on the SIB from gNB 200. Conversely, in step S503, UE 100B, which expects to receive broadcast-based services, determines to receive MBS session #2 based on the SIB from gNB 200.

[0160] In step S504, when UE 100A is in RRC idle state or RRC inactive state, UE 100A performs a process to switch to RRC connected state (connection process) to allow UE 100A to receive the first MBS configuration.

[0161] In step S505, UE 100A receives an RRC reconfiguration message from gNB 200, which includes the first MBS configuration.

[0162] In step S506, UE 100A applies the first MBS configuration received in step S505, thereby receiving MBS data of MBS session #1 from gNB 200.

[0163] Conversely, in step S507, UE 100B receives an MBS control channel from gNB 200 that includes the second MBS configuration. For example, when UE 100B is in RRC connected state, UE 100B does not expect to obtain the MBS configuration from gNB 200 via an RRC reconfiguration message and attempts to receive an MBS control channel (e.g., SC-MCCH). UE 100 in RRC connected state can send a release assist information (RAI) to gNB 200 to release its RRC connection and transition to RRC idle or RRC inactive state.

[0164] In step S508, UE 100B applies the second MBS configuration received in step S507, thereby receiving MBS data for MBS session #2 from gNB 200.

[0165] Note that in this operational example, gNB 200 can be considered to be broadcasting an MBS session identifier that gNB 200 itself can provide. When UE 100 is interested in receiving an MBS session that gNB 200 cannot provide, UE 100 can establish a unicast session with 5GC 20 to receive the MBS data of that MBS session.

[0166] In this operational example, gNB 200 may send a broadcast message to UE 100, the broadcast message including a third identifier (third MBS session identifier) ​​indicating that a third MBS session is provided using both unicast signaling and broadcasting for MBS configuration.

[0167] Third Embodiment

[0168] The main focus will be on describing the differences between the third embodiment and the first and second embodiments.

[0169] The third embodiment assumes a scenario where multiple MBS control channels (e.g., multiple SC-MCCHs) are configured in a single cell of a gNB 200. Therefore, the MBS control channels can be appropriately used, for example, depending on the service requirements of the MBS session.

[0170] When configuring multiple MBS control channels, it is conceivable that the RNTIs used to transmit the PDCCHs for each MBS control channel are different. Specifically, when transmitting an MBS control channel in the physical layer of gNB 200, resources for carrying the MBS configuration PDSCH are allocated to UE 100 by sending a PDCCH with the RNTI applied to the MBS control channel.

[0171] In this way, when the RNTI is different for each MBS control channel, it is necessary to specify which RNTI is used to send to which MBS control channel.

[0172] In the third embodiment, a gNB 200 providing multiple MBS control channels in a cell sends a broadcast message to the UE 100. The broadcast message includes an RNTI for receiving the MBS control channel in each of the multiple MBS control channels. The broadcast message may be an SIB transmitted on a broadcast control channel.

[0173] The RNTI used to receive the MBS control channel can be an RNTI applied to the MBS control channel (hereinafter referred to as "SC-RNTI") or an RNTI applied to the change notification of the MBS control channel (hereinafter referred to as "SC-N-RNTI").

[0174] Figure 13 This is a diagram illustrating an operational example according to the third embodiment.

[0175] like Figure 13 As shown, in step S601, the gNB 200 broadcasts an SIB containing configuration information for each MBS control channel. The configuration information may include the SC-RNTI value for each MBS control channel, or it may include the SC-RNTI value for each MBS session identifier. Alternatively, the configuration information may include the SC-N-RNTI value for each MBS control channel, or it may include the SC-N-RNTI value for each MBS session identifier.

[0176] exist Figure 13 In the example shown, the SIB includes a set of RNTI (SC-RNTI and / or SC-N-RNTI)#1 and MBS session identifier #1 for MBS control channel #1. The SIB includes a set of RNTI (SC-RNTI and / or SC-N-RNTI)#2 and MBS session identifier #2 for MBS control channel #2.

[0177] In step S602, UE 100A determines MBS session #1 based on the SIB from gNB 200. Then, in step S603, UE 100A applies RNTI #1 corresponding to MBS session #1 based on the SIB from gNB 200 and attempts to receive MBS control channel #1.

[0178] Instead, in step S604, UE 100B determines to receive MBS session #2 based on the SIB from gNB 200. Then, in step S605, UE 100B applies RNTI #2 corresponding to MBS session #2 based on the SIB from gNB 200 and attempts to receive MBS control channel #2.

[0179] In step S606, UE 100A receives MBS control channel #1 from gNB 200. In step S607, UE 100A receives MBS data of MBS session #1 from gNB 200 using the MBS configuration included in MBS control channel #1 received in step S606.

[0180] Instead, in step S608, UE 100B receives MBS control channel #2 from gNB 200. In step S609, UE 100B receives MBS data of MBS session #2 from gNB 200 using the MBS configuration included in MBS control channel #2 received in step S608.

[0181] Fourth embodiment

[0182] The fourth embodiment will primarily describe the differences from the first through third embodiments. The fourth embodiment is an embodiment related to cell reselection performed by UE 100 in an RRC idle state or an RRC inactive state.

[0183] LTE introduces a mechanism for performing cell reselection, where frequencies used to provide or receive MBMS sessions of interest have the highest priority. However, in this mechanism, which frequency (or cell) is reselected depends on UE 100 and is uncontrollable from the network's perspective. Therefore, a scheme is desired that allows UE 100 to receive the desired MBMS sessions while also enabling network control.

[0184] In the fourth embodiment, gNB 200 sends cell reselection control information, which includes multiple priority information indicating the priority of each cell or frequency during cell reselection, and an MBS session identifier associated with the multiple priority information. Based on the cell reselection control information from gNB 200, UE 100, in RRC idle state or RRC inactive state, uses the priority information corresponding to UE 100's desired MBS session identifier to perform cell reselection. Thus, cell reselection control that allows UE 100 to receive the desired MBS session while simultaneously enabling network control can be achieved.

[0185] Figure 14 This is a diagram illustrating an operational example according to the fourth embodiment.

[0186] like Figure 14 As shown, in step S701, UE 100 can be in RRC idle state or RRC inactive state.

[0187] In step S702, gNB 200 notifies UE 100 of multiple priority information (cell reselection priority) for each MBS session. For example, gNB 200 broadcasts an SIB including multiple priority information associated with the MBS session. Alternatively, gNB 200 may send unicast signaling (e.g., an RRC release message) to UE 100 including multiple priority information associated with the MBS session. When an RRC release message including multiple priority information associated with the MBS session is sent to UE 100, UE 100 transitions from RRC connected state to RRC idle state or RRC inactive state in response to receiving the RRC release message. An example of using an SIB is described below; however, an RRC release message can be used instead of an SIB.

[0188] The SIB comprises multiple sets, each including an MBS session identifier and cell and / or frequency priority information. Figure 14 In the example shown, priority information #1 is associated with MBS session identifier #1, while priority information #2 is associated with MBS session identifier #2. Priority information #1 indicates that frequency #1 corresponds to high priority, frequency #2 to medium priority, and frequency #3 to low priority. Priority information #2 indicates that frequency #1 corresponds to low priority, frequency #2 to medium priority, and frequency #3 to high priority. For example, prioritization is: for MBS sessions requiring high-speed communication, higher frequencies are prioritized, while for MBS sessions requiring high reliability, lower frequencies are prioritized. Note that this priority information may not be associated with frequency but with cell ID.

[0189] In step S703, based on the desired MBS session of UE 100 and the SIB from gNB 200, UE 100 uses priority information corresponding to the desired MBS session of UE 100 to control cell reselection. In cell reselection control, UE 100 preferentially selects frequencies (or cells) with higher priority in the priority information.

[0190] Here, in UE 100, desired MBS sessions can be notified from the upper layer (NAS layer) to the lower layer (AS layer), and the AS layer can use the desired MBS sessions to perform cell reselection control. When multiple desired MBS sessions exist, the upper layer (NAS layer) notifies the lower layer (AS layer) of the reception priority of each MBS session, and the lower layer (AS layer) can perform cell reselection control by using the priority information corresponding to the MBS session with the highest reception priority.

[0191] Note that in this operational example, the SIB may also include known priority information that is not associated with the MBS session identifier. This known priority information is used by legacy UEs that do not support MBS and UE 100 that is not interested in MBS reception.

[0192] When an MBS session is associated with a network slice, gNB 200 can broadcast multiple priority information for the frequencies and / or cells of each network slice. Information regarding the association between the MBS session identifier (TMGI, etc.) and the network slice identifier (S-NSSAI, etc.) can be communicated from the core network to UE 100 and / or gNB 200. UE 100 performs cell (re)selection processing based on the priority information of the frequencies and / or cells in the network slice associated with the MBS session that UE 100 expects to receive.

[0193] In this example, the "MBS session identifier" in the fourth embodiment above can be replaced with a "network slice identifier". Specifically, the gNB 200 sends cell reselection control information, which includes multiple priority information indicating the priority of each cell or frequency during cell reselection, and a network slice identifier associated with the multiple priority information. Based on the cell reselection control information from the gNB 200, the UE 100, in RRC idle state or RRC inactive state, performs cell reselection using the priority information corresponding to the desired network slice of the UE 100.

[0194] Fifth embodiment

[0195] The main difference between the fifth embodiment and the first to fourth embodiments will be described. The fifth embodiment is an embodiment related to RRC reconstruction performed by UE 100 in RRC connected state.

[0196] When UE 100, in RRC connected state, detects a radio link failure (RLF) while receiving an MBS session, it initiates an RRC reconstruction process. During the RRC reconstruction process, it selects a cell that does not provide an MBS session during cell selection, which may interrupt MBS reception. In the fifth embodiment, during the RRC reconstruction process, a cell that provides an MBS session is preferentially selected during cell selection. Accordingly, the continuity of MBS reception is enhanced.

[0197] In the fifth embodiment, when UE 100, which is receiving an MBS session in RRC connected state, initiates RRC reconstruction processing, UE 100 performs cell selection during the RRC reconstruction process. In cell selection, UE 100 preferentially selects the cell providing the MBS session. This enhances the continuity of MBS reception.

[0198] Figure 15 This is a diagram illustrating an operational example according to the fifth embodiment.

[0199] like Figure 15 As shown, in step S801, UE 100 is in RRC connected state in cell #1 of gNB 200A.

[0200] In step S802, UE 100 receives MBS data of the MBS session from gNB 200A.

[0201] In step S803, UE 1 00 can receive neighboring cell information from gNB 200A, the neighboring cell information including the MBS session identifier provided by cell #2, which is a neighboring cell.

[0202] In step S804, UE 100 detects an RLF with gNB 200A and initiates RRC reconstruction processing.

[0203] In step S805, when performing a cell search, UE 100 may receive MBS information broadcast by gNB 200B (cell #2). The MBS information may be an SIB including the MBS session identifier of the MBS session provided by cell #2.

[0204] In step S806, UE 100 identifies the MBS session provided by gNB200A (cell #2) based on the information received in step S803 or step S805.

[0205] In step S807, UE 100 determines whether gNB 200A (cell #2) provides the MBS session that UE 100 has already received in step S802.

[0206] When UE 100 determines in step S808 that gNB 200A (cell #2) provides the MBS session that UE 100 has already received in step S802 (step S807: Yes), UE 100 selects cell #2.

[0207] In step S809, UE 100 accesses the selected cell #2 and performs RRC reconstruction, thereby continuing to receive the MBS sessions that UE 100 has already received (and is interested in).

[0208] Sixth Embodiment

[0209] The sixth embodiment will primarily describe the differences from the first to fifth embodiments.

[0210] In NR, the operating bandwidth of UE 100 can be limited by configuring a bandwidth portion (BWP) narrower than the frequency bandwidth of a cell for UE 100. This BWP can be introduced for MBS. When introducing such a BWP for MBS, it is conceivable to use the MBS configuration to inform UE 100 of the BWP for MBS. However, when the MBS configuration does not include information about the BWP for MBS, UE 100 cannot recognize the BWP for MBS, which may lead to unexpected errors.

[0211] In the sixth embodiment, UE 100 receives information from gNB 200 indicating the initial BWP to be used by gNB 200. The initial BWP refers to the BWP notified using SIB and is the BWP used by UE 100 to perform initial access to gNB 200. UE 100 uses the initial BWP before receiving BWP configuration for UE 100 from gNB 200.

[0212] UE 100 receives the MBS configuration required for MBS reception from gNB 200. Here, when the MBS configuration does not include BWP configuration, UE 100 uses the initial BWP to perform MBS reception. In this way, by defining the behavior of UE 100 in the event of a defective MBS configuration, unexpected errors are less likely to occur.

[0213] Figure 16 This is a diagram illustrating an operational example according to the sixth embodiment.

[0214] like Figure 16 As shown, in step S901, UE 100 receives SIB including initial BWP information from gNB 200.

[0215] In step S902, UE 100 receives MBS configuration from gNB 200.

[0216] In step S903, UE 100 determines whether the MBS configuration received from gNB 200 includes the configuration of BWP for MBS.

[0217] When the MBS configuration received from gNB 200 includes the configuration of BWP for MBS (step S903: Yes), in step S904, UE 100 applies the configuration of BWP for MBS.

[0218] Conversely, when the MBS configuration received from gNB 200 does not include the configuration of the BWP for MBS (step S903: No), in step S905, UE 100 determines (assuming) that the MBS data for PTM will be sent in the initial BWP. The default value of the BWP for MBS can be configured as the initial BWP.

[0219] In step S906, UE 100 attempts to receive MBS data in the configured BWP.

[0220] Other embodiments

[0221] The above embodiments and variations can be implemented not only individually and independently, but also in combination of two or more examples.

[0222] In the above embodiments, an example of an NR base station (gNB) was described; however, the base station could be an LTE base station (eNB). The base station could be a relay node, such as an Integrated Access and Backhaul (IAB) node. The base station could be a Distributed Unit (DU) of an IAB node.

[0223] A program may be provided that enables a computer to execute each procedure within the process performed by the UE 100 or gNB 200. The program may be recorded on a computer-readable medium. The computer-readable medium allows the program to 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 specifically limited and may, for example, be a recording medium such as a CD-ROM or DVD-ROM.

[0224] The circuitry used to perform the processing to be performed by UE 100 or gNB 200 can be integrated together, and at least a portion of UE 100 or gNB 200 can be configured as a semiconductor integrated circuit (chipset or system-on-chip (SoC)).

[0225] The embodiments have been described in detail above with reference to the accompanying drawings, but the specific configurations are not limited to those described above, and various design changes can be made without departing from the spirit of this disclosure.

[0226] This application claims priority to U.S. Provisional Application No. 63 / 104044 (filed October 22, 2020), the entire contents of which are incorporated herein by reference.

[0227] Additional notes

[0228] -introduction

[0229] The revision work project related to NR multicast and broadcast services (MBS) has been approved. The purpose of the work project is as follows.

[0230] - Define the basic broadcast / multicast RAN functions for UEs in RRC connected state.

[0231] - Define a group scheduling mechanism that allows UEs to receive broadcast / multicast services.

[0232] - The objectives include defining the extended functionality required to allow simultaneous operation with unicast reception.

[0233] - Defines support for dynamic changes in broadcast / multicast service delivery between multicast (PTM) and unicast (PTP) and predefined UE service continuity.

[0234] - Defines support for basic mobility and service continuity.

[0235] - Assuming the gNB-CU includes the required tuning functions (e.g., functions managed by the MCE), define the necessary changes to the RAN architecture and interfaces, taking into account the results of SA2 SI for broadcast / multicast.

[0236] - Define the changes needed to improve the reliability of broadcast / multicast services, for example, through UL feedback. The level of reliability should be based on the requirements of the application / service being provided.

[0237] - Investigate support for dynamic control of broadcast / multicast transmission zones in a gNB-DU, and define the conditions (if any) required to implement said support.

[0238] - Define the basic broadcast / multicast RAN functions for UEs in RRC idle / RRC inactive states.

[0239] - Define the changes required to enable a UE in RRC idle / RRC inactive state to receive point-to-multipoint transmission, in order to maximize the commonality of the configuration for PTM reception maintained between RRC connected state and RRC idle / RRC inactive state.

[0240] In RAN2#111-e, many companies proposed LTE SC-PTM reuse mechanisms for UEs in idle / inactive states; however, as the chair summarized below, many companies believe that there are significant differences between solutions for connected states and solutions for idle / inactive states.

[0241] -Chairman: Many companies believe there are significant differences between idle and connected state solutions. Further research is needed to determine what this ultimately means.

[0242] - The Chairman's observation: There are many proposals for reusing LTE SC-PTM (to a large extent or 100%) for idle / inactive NR. For example, some companies have also proposed connecting and controlling idle / inactive transmissions.

[0243] In this supplementary note, considerations regarding the control plane of NR MBS will be discussed.

[0244] -discuss

[0245] In LTE SC-PTM, configuration is provided through two messages (i.e., SIB 20 and SC-MCCH). SIB 20 provides SC-MCCH scheduling information, while SC-MCCH provides SC-MTCH scheduling information including G-RNTI and TMGI, as well as neighboring cell information.

[0246] like Figure 17 As shown, the advantage of the two-level LTE configuration is that SC-MCCH scheduling is independent of SIB 20 scheduling in terms of repetition period, duration, and change period. The two-level configuration facilitates frequent SC-MCCH scheduling / updates, especially for latency-sensitive services and / or UEs participating in sessions with latency. According to WID, one application is group communication, etc., therefore it is also applicable to NR MBS.

[0247] Observation 1: In LTE, the two-tier configuration using SIB 20 and SC-MCCH is useful for different scheduling operations of these control channels. This is also useful for NR MBS.

[0248] Proposal 1: RAN2 should agree to use a two-tier configuration for NR MBS that utilizes different messages (e.g., SIB 20 and SC-MCCH for SC-PTM).

[0249] In addition to Proposal 1, it is assumed that NR MBS supports the various types of use cases described in WID. It should be understood that, in addition to requirements ranging from lossless applications such as software forwarding to other aspects of UDP-type streaming such as IPTV, NR MBS should also be appropriately designed for a wide range of requirements, from latency-sensitive applications (e.g., mission-critical applications and V2X) to latency-tolerant applications (e.g., IoT).

[0250] Therefore, the design of control channels should consider both flexibility and resource efficiency. Otherwise, for example, when a control channel includes configurations for latency-tolerant services and latency-sensitive services, the control channel needs to be frequently scheduled to meet the latency requirements of the latency-sensitive services. This can lead to significant signaling overhead.

[0251] SA2 SI Object A relates to the implementation of general MBS services via 5GS. Specified use cases that may benefit from this functionality include (but are not limited to) public safety, mission-critical applications, V2X applications, transparent IPv4 / IPv6 multicast delivery, IPTV, wireless software delivery, group communications, and IoT applications.

[0252] Observation 2: The NR MBS control channel needs to be flexible in handling various types of use cases and have high resource efficiency.

[0253] As a possibility, such as Figure 18 As shown, the study investigated whether channel configurations need to be separated in different use cases. For example, one control channel provides latency-sensitive services frequently, while another control channel provides latency-tolerant services infrequently. A limitation of LTE SC-PTM is that a cell includes only one SC-MCCH. However, NR MBS can assume more use cases than LTE, and therefore should not have this limitation. When multiple SC-MCCHs are allowed within a cell, each SC-MCCH includes a scheduling configuration with different repetition periods that can be optimized for specific services. Further research is needed on how to identify the SC-MCCHs that provide the services of interest to the UE.

[0254] Proposal 2: RAN2 should discuss whether NR MBS cells support multiple control channels, specifically those with multiple SC-MCCHs (which are not supported in LTE).

[0255] A new paradigm for NR is supporting on-demand SI transmission. This concept can be reused in NR MBS for SC-MCCH, i.e., on-demand SC-MCCH. For example, SC-MCCH can be provided on demand for delay-tolerant services, thereby optimizing resource consumption for signaling. Of course, the network includes the option of periodically (i.e., not based on demand) providing SC-MCCH for delay-sensitive services.

[0256] Proposal 3: RAN2 should discuss the options provided when providing control channels on demand, which is the case with on-demand SC-MCCH (not included in LTE).

[0257] As another possibility, such as Figure 13 As shown, further research can be conducted on merging the aforementioned messages, i.e., first-level configuration. For example, the SIB directly provides SC-MTCH scheduling information, i.e., without SC-MCCH. This will provide optimization for latency-tolerant services and / or power-sensitive UEs. For example, a UE can request the SIB (on demand), and the gNB can begin providing the SIB and corresponding services after requests from multiple UEs. These UEs do not need to listen to repeatedly broadcast SC-MCCH.

[0258] Proposal 4: RAN2 should discuss options such as providing traffic channel configuration directly in the SIB when supporting multicast reception without using SC-MCCH (i.e., Level 1 configuration).

[0259] Configuration based on dedicated signaling

[0260] Some companies have proposed using only dedicated signaling to provide MBS configuration. This means that, in multicast services such as group communications, while dedicated signaling offers simplicity for UEs in RRC connected state, UEs in idle / inactive state, even if they are only interested in broadcast services, will always need to transition to RRC connected state to receive MBS services. This can lead to unnecessary power consumption in the UE and may reduce future guarantees, such as support for free broadcast services in future versions. Therefore, it is assumed that MBS configuration using broadcast signaling will be the baseline, as described in Proposals 1 through 4, in the same and / or similar manner to LTESC-PTM.

[0261] Note that, as Figure 13 As shown, assuming that RRC reconfiguration can be used to provide the control channel, this brings flexibility to network implementation and deployment strategies. For example, when commercial operators or others need to avoid broadcasting the MBS control channel and not provide broadcast services, the network can determine to provide configuration only using dedicated signaling. As another example, when the target cell uses a handover command to provide MBS configuration, this benefits service continuity during handover.

[0262] Therefore, in RAN2, it is necessary to investigate whether RRC reconfiguration provides the MBS control channel.

[0263] Proposal 5: In RAN2, it is necessary to study the option of RRC reconfiguration to provide SC-MCCH in cases where it is not present in LTE.

[0264] Interest indicators / counts

[0265] In LTE eMBMS, to enable the network to perform appropriate determinations regarding MBMS data transmission (including the start / stop of MBMS sessions), two types of methods are specified for collecting information on services received / of interest by the UE: MBMS Interest Indication (MII) and MBMS counting. The MII triggered by the UE includes information related to the MBMS frequency of interest, the MBMS service of interest, the MBMS priority, and the MBMS ROM (Receive Dedicated Mode). The counting response triggered by the network via a counting request for a specific MBMS service includes information related to the MBSFN area and the MBMS service of interest.

[0266] These methods have been introduced for various purposes. MII is primarily used by the network to ensure that UEs can continuously receive services of interest to them while in a connected state. Conversely, counting is used to enable the network to determine whether a sufficient number of UEs are interested in receiving services.

[0267] Observation 3: In LTE eMBMS, two types of UE assistance information are introduced for different purposes. In other words, MBMS interest indication is introduced for NB scheduling, and MBMS count is introduced for MCE session control.

[0268] In the case of NR MBS, multicast services for use cases such as group communication are desirable, and the network possesses complete knowledge of the MBS services that a connected UE is receiving / interested in. Therefore, auxiliary information from the UE, such as network determination of PTP / PTM transmissions, is not necessary. However, our understanding is that this does not apply to broadcast services and UEs in idle / inactive states. Specifically, in the case of broadcast services, NR MBS still suffers from the same problems addressed by counting in MII and LTE eMBMS (i.e., Observation 3). Therefore, in RAN2, it is necessary to investigate whether auxiliary information (e.g., MII, counting) is useful for NR MBS.

[0269] As stated in WID, since ROM and SFN are not supported in version 17, it should be noted that the MBMS ROM information of MII and the information related to the MBSFN area of ​​the count response are not required.

[0270] Proposal 6: In RAN2, for example, it is necessary to agree to introduce UE auxiliary information for NR MBS, such as MBMS interest indication and / or MBMS count.

[0271] If Proposal 6 can be agreed upon, it is worthwhile to study extended functions in addition to LTE eMBMS. In LTE eMBMS, even when most UEs are receiving broadcast services in RRC idle mode, it is impossible to collect MII and count information from UEs in idle mode. To our understanding, this is one of the problems with LTE eMBMS from the perspective of session control and resource efficiency.

[0272] In NR MBS, the same problem may exist with UEs in an idle / inactive state. For example, the network cannot know whether an idle / inactive UE is receiving or interested in broadcast services. Therefore, PTM transmissions may continue even if no UE is receiving services. This unnecessary PTM can be avoided if the gNB identifies the interest of idle / inactive UEs. Conversely, if PTM stops while there are idle / inactive UEs still receiving services, multiple UEs can request connections simultaneously.

[0273] Therefore, it is worthwhile to investigate whether to introduce a mechanism for collecting UE auxiliary information (specifically, MBMS counts) from UEs in an idle / inactive state. Needless to say, it is desirable for UEs in an idle / inactive state to be able to report information without switching to an RRC connection. For example, PRACH resource segmentation associated with MBS services could be implemented if such reporting were introduced.

[0274] Proposal 7: In RAN2, it is necessary to investigate whether UE auxiliary information such as MBMS counts should also be collected from UEs in an idle / inactive state.

Claims

1. A communication control method for use in a mobile communication system, the mobile communication system providing multicast and broadcast services (MBS) from a base station to a user equipment, the communication control method comprising: The user equipment receives information from the base station indicating the initial bandwidth portion (BWP) used by the base station; The user equipment receives the MBS configuration for MBS reception from the base station; When the MBS configuration does not include the BWP configuration, the user equipment uses the initial BWP to perform the MBS reception. as well as When the MBS configuration includes the BWP configuration, the user equipment uses the BWP configuration to perform the MBS reception.

2. A user equipment that provides multicast and broadcast services (MBS) from a base station to the user equipment, the user equipment comprising a controller, the controller: Receive information from the base station indicating the initial bandwidth portion (BWP) used by the base station; Receive MBS configuration for MBS reception from the base station; When the MBS configuration does not include the BWP configuration, the initial BWP is used to perform the MBS reception; as well as When the MBS configuration includes the BWP configuration, the MBS reception is performed using the BWP configuration.

3. A processor for controlling user equipment, providing multicast and broadcast services (MBS) from a base station to the user equipment, the processor performing the following processing: Receive information from the base station indicating the initial bandwidth portion (BWP) used by the base station; Receive MBS configuration for MBS reception from the base station; When the MBS configuration does not include the BWP configuration, the initial BWP is used to perform the MBS reception; as well as When the MBS configuration includes the BWP configuration, the MBS reception is performed using the BWP configuration.

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