Communication method and user device

Abstract

This communication method used in a mobile communication system comprises a step in which a first user device present in a first cell transmits, to a prescribed device, a request signal for requesting to provide broadcast control information for performing broadcasting to a second cell adjacent to the first cell. The prescribed device is a second user device existing in the second cell, a first base station for managing the first cell, or a second base station for managing the second cell.

Description

Communication method and user device

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

[0002] The 3rd Generation Partnership Project (3GPP) defines the technical specifications for NR (New Radio), a fifth-generation (5G) wireless access technology. Compared to LTE (Long Term Evolution), a fourth-generation (4G) wireless access technology, NR has features such as high speed, large capacity, high reliability, and low latency. 3GPP defines the technical specifications for 5G / NR multicast / broadcast services (MBS) (see, for example, Non-Patent Document 1).

[0003] 3GPP Technical Specification: TS 38.300 V17.1.0

[0004] A communication method according to a first aspect is a communication method used in a mobile communication system, comprising a step of transmitting a request signal from a first user device located in a first cell to a predetermined device, the request signal requesting provision of broadcast control information to be broadcast in a second cell adjacent to the first cell, wherein the predetermined device is a second user device located in the second cell, a first base station managing the first cell, or a second base station managing the second cell.

[0005] A user equipment according to a second aspect is a user equipment used in a mobile communication system, and includes a transmitter configured to transmit, when the user equipment is located in a first cell, a request signal to a predetermined device requesting provision of broadcast control information to be broadcast in a second cell adjacent to the first cell, wherein the predetermined device is another user equipment located in the second cell, a first base station managing the first cell, or a second base station managing the second cell.

[0006] 1 is a diagram illustrating a configuration of a mobile communication system according to an embodiment. FIG. 2 is a diagram illustrating a configuration of a UE (user equipment) according to an embodiment. FIG. 3 is a diagram illustrating a configuration of a gNB (base station) according to an embodiment. FIG. 4 is a diagram illustrating a protocol stack configuration of a radio interface of a user plane that handles data. FIG. 5 is a diagram illustrating a protocol stack configuration of a radio interface of a control plane that handles signaling (control signals). FIG. 6 is a diagram illustrating an example of operation of a mobile communication system regarding MBS broadcast reception according to an embodiment. FIG. 7 is a diagram illustrating an operation scenario of a mobile communication system according to an embodiment. FIG. 8 is a diagram illustrating a first operation pattern. FIG. 9 is a diagram illustrating an example of an operation flow in the first operation pattern. FIG. 10 is a diagram illustrating a second operation pattern. FIG. 11 is a diagram illustrating an example of an operation flow in the second operation pattern. FIG. 12 is a diagram illustrating a third operation pattern. FIG. 13 is a diagram illustrating an example of an operation flow in the third operation pattern. FIG. 14 is a diagram illustrating a fourth operation pattern. FIG. 15 is a diagram illustrating an example of an operation flow in the fourth operation pattern.

[0007] 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.

[0008] (1) Configuration of a Mobile Communication System FIG. 1 is a diagram showing the configuration of a mobile communication system according to an embodiment. The mobile communication system 1 conforms to the 3GPP standard 5th Generation System (5GS). While the following description uses 5GS as an example, the mobile communication system may also be at least partially based on an LTE (Long Term Evolution) system. The mobile communication system may also be at least partially based on a 6th Generation (6G) system.

[0009] The mobile communication system 1 includes a user equipment (UE) 100, a 5G radio access network (NG-RAN: Next Generation Radio Access Network) 10, and a 5G core network (5GC: 5G Core Network) 20. Hereinafter, the NG-RAN 10 may be simply referred to as the RAN 10 (or network 10). The 5GC 20 may be simply referred to as the core network (CN) 20.

[0010] The UE 100 is a mobile wireless communication device. The UE 100 may be any device that is used by a user. For example, the UE 100 may be a mobile phone terminal (including a smartphone) and / or a tablet terminal, a notebook PC, a communication module (including a communication card or a chipset), a sensor or a device provided in a sensor, a vehicle or a device provided in a vehicle (Vehicle UE), or an aircraft or a device provided in an aircraft (Aerial UE).

[0011] The NG-RAN 10 includes a base station (called a "gNB" in a 5G system) 200. The gNBs 200 are connected to each other via an Xn interface, which is an interface between base stations. The gNB 200 manages one or more cells. The gNB 200 performs wireless communication with a UE 100 that has established a connection with its own cell. The gNB 200 has a radio resource management (RRM) function, a routing function for user data (hereinafter simply referred to as "data"), a measurement control function for mobility control and scheduling, 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 wireless communication with the UE 100. One cell belongs to one carrier frequency (hereinafter simply referred to as "frequency").

[0012] 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.

[0013] The 5GC20 includes an AMF (Access and Mobility Management Function) and a UPF (User Plane Function) 300. The AMF performs various mobility controls for the UE 100. The AMF manages the mobility of the UE 100 by communicating with the UE 100 using NAS (Non-Access Stratum) signaling. The UPF controls data forwarding. The AMF and the UPF are connected to the gNB 200 via an NG interface, which is an interface between a base station and a core network.

[0014] 2 is a diagram showing the configuration of a UE 100 (user equipment) according to an embodiment. The UE 100 includes a receiving unit 110, a transmitting unit 120, and a control unit 130. The receiving unit 110 and the transmitting unit 120 constitute a wireless communication unit that performs wireless communication with the gNB 200.

[0015] The receiving unit 110 performs various reception operations 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.

[0016] The transmitting unit 120 performs various transmissions under the control of the control unit 130. The transmitting unit 120 includes an antenna and a transmitter. The transmitter converts a baseband signal (transmission signal) output by the control unit 130 into a radio signal and transmits it from the antenna.

[0017] The control unit 130 performs various controls and processes in the UE 100. Such processes include processes of each layer described below. 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 processes by the processor. The processor may include a baseband processor and a CPU (Central Processing Unit). The baseband processor performs modulation / demodulation and encoding / decoding of baseband signals. The CPU executes programs stored in the memory to perform various processes.

[0018] 3 is a diagram showing the configuration of a gNB 200 (base station) according to an embodiment. The gNB 200 includes a transmitter 210, a receiver 220, a controller 230, and a backhaul communication unit 240. The transmitter 210 and the receiver 220 constitute a wireless communication unit that performs wireless communication with the UE 100. The backhaul communication unit 240 constitutes a network communication unit that communicates with the CN 20.

[0019] The transmitting unit 210 performs various transmissions under the control of the control unit 230. The transmitting unit 210 includes an antenna and a transmitter. The transmitter converts a baseband signal (transmission signal) output by the control unit 230 into a radio signal and transmits it from the antenna.

[0020] The receiving unit 220 performs various types of reception under the control of the control unit 230. The receiving unit 220 includes an antenna and a receiver. The receiver converts a radio signal received by the antenna into a baseband signal (received signal) and outputs the baseband signal to the control unit 230.

[0021] The control unit 230 performs various controls and processes in the gNB 200. Such processes include processes for each layer, which will be described later. The control unit 230 includes at least one processor and at least one memory. The memory stores programs executed by the processor and information used in the processes by the processor. The processor may include a baseband processor and a CPU. The baseband processor performs modulation / demodulation and encoding / decoding of baseband signals. The CPU executes programs stored in the memory to perform various processes.

[0022] The backhaul communication unit 240 is connected to adjacent base stations via an Xn interface, which is an interface between base stations. The backhaul communication unit 240 is connected to the AMF / UPF 300 via an NG interface, which is an interface between a base station and a core network. Note that the gNB 200 is composed of a CU (Central Unit) and a DU (Distributed Unit) (i.e., functionally divided), and the two units may be connected by an F1 interface, which is a fronthaul interface.

[0023] FIG. 4 is a diagram showing the configuration of a protocol stack of a radio interface of a user plane that handles data.

[0024] 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.

[0025] The PHY layer performs encoding / decoding, modulation / demodulation, antenna mapping / demapping, and resource mapping / demapping. Data and control information are transmitted between the PHY layer of UE100 and the PHY layer of gNB200 via a physical channel. The PHY layer of UE100 receives downlink control information (DCI) transmitted from gNB200 on a physical downlink control channel (PDCCH). Specifically, UE100 performs blind decoding of the PDCCH using a radio network temporary identifier (RNTI) and acquires the successfully decoded DCI as DCI addressed to the UE. The DCI transmitted from gNB200 has a CRC parity bit scrambled by the RNTI added.

[0026] The MAC layer performs data priority control, retransmission processing using Hybrid Automatic Repeat reQuest (HARQ), random access procedures, etc. Data and control information are transmitted between the MAC layer of the UE 100 and the MAC layer of the gNB 200 via a transport channel. The MAC layer of the gNB 200 includes a scheduler. The scheduler determines the uplink and downlink transport format (transport block size, modulation and coding scheme (MCS)) and the resource blocks to be allocated to the UE 100.

[0027] The RLC layer transmits data to the receiving RLC layer using the functions of the MAC layer and PHY layer. Data and control information are transmitted between the RLC layer of the UE 100 and the RLC layer of the gNB 200 via a logical channel.

[0028] The PDCP layer performs header compression / decompression, encryption / decryption, and the like.

[0029] The SDAP layer maps IP flows, which are units for Quality of Service (QoS) control by the core network, to radio bearers, which are units for QoS control by the Access Stratum (AS). Note that if the RAN is connected to the EPC, SDAP may not be required.

[0030] 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).

[0031] The protocol stack of the radio interface of the control plane has an RRC (Radio Resource Control) layer and an NAS (Non-Access Stratum) layer instead of the SDAP layer shown in FIG.

[0032] RRC signaling for various settings is transmitted between the RRC layer of UE100 and the RRC layer of gNB200. The RRC layer controls logical channels, transport channels, and physical channels according to the establishment, re-establishment, and release of radio bearers. When there is a connection (RRC connection) between the RRC of UE100 and the RRC of gNB200, UE100 is in an RRC connected state. When there is no connection (RRC connection) between the RRC of UE100 and the RRC of gNB200, UE100 is in an RRC idle state. When the connection between the RRC of UE100 and the RRC of gNB200 is suspended, UE100 is in an RRC inactive state.

[0033] 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 300A. Note that the UE 100 has an application layer and the like in addition to the radio interface protocol. Also, a layer lower than the NAS layer is called an AS layer.

[0034] (2) Overview of MBS The mobile communication system 1 can perform resource-efficient distribution using multicast / broadcast services (MBS).

[0035] In the case of a broadcast communication service (also referred to as "MBS broadcast"), the same service and the same specific content data are simultaneously provided to all UEs 100 in a geographical area. That is, all UEs 100 within the broadcast service area are permitted to receive the data. The broadcast communication service is delivered to the UEs 100 using a broadcast session, which is a type of MBS session. The UEs 100 can receive the broadcast communication service in any of the RRC idle state, the RRC inactive state, and the RRC connected state. Such a delivery mode is sometimes referred to as Delivery Mode 2.

[0036] In the case of a multicast communication service (also referred to as "MBS multicast"), the same service and the same specific content data are simultaneously provided to a specific set of UEs. That is, not all UEs 100 within a multicast service area are permitted to receive the data. The multicast communication service is delivered to the UEs 100 using a multicast session, which is a type of MBS session. The UEs 100 can receive the multicast communication service in an RRC connected state using mechanisms such as Point-to-Point (PTP) and / or Point-to-Multipoint (PTM) delivery. The UEs 100 may also receive the multicast communication service in an RRC inactive (or RRC idle) state. Such a delivery mode is sometimes referred to as Delivery Mode 1.

[0037] The main logical channels used for MBS distribution are a Multicast Traffic Channel (MTCH), a Dedicated Traffic Channel (DTCH), and a Multicast Control Channel (MCCH). The MTCH is a PTM downlink channel for transmitting MBS data of either a multicast session or a broadcast session from the network 10 to the UE 100. The DTCH is a PTP channel for transmitting MBS data of a multicast session from the network 10 to the UE 100. The MCCH is a PTM downlink channel for transmitting MBS broadcast control information associated with one or more MTCHs from the network 10 to the UE 100. The Downlink Control Channel (DCCH) is also used in the configuration in distribution mode 1 (RRC Reconfiguration).

[0038] Regarding the configuration for MBS broadcast, the UE 100 in the RRC idle state, the RRC inactive state, or the RRC connected state receives the MBS configuration for the broadcast session (e.g., parameters required for MTCH reception) via the MCCH. The parameters required for MCCH reception (MCCH configuration) are provided via system information. Specifically, the system information block type 20 (SIB20) includes the MCCH configuration. Note that the system information block type 21 (SIB21) includes information on service continuity for MBS broadcast reception. The MCCH provides a list of all broadcast services, including ongoing sessions, transmitted on the MTCH. The broadcast session-related information includes the MBS session ID (e.g., TMGI (Temporary Mobile Group Identity)), associated G-RNTI scheduling information, and information on neighboring cells providing a specific service on the MTCH.

[0039] 6 is a diagram showing an example of the operation of the mobile communication system 1 regarding MBS broadcast reception according to the embodiment. The UE 100 is present in a cell of the gNB 200 and has selected the cell as a serving cell. Present in a cell means that the UE 100 has selected the cell as a serving cell, and the UE 100 may be in any RRC state (RRC idle state, RRC inactive state, or RRC connected state). "Present" is also referred to as "camping." In the following, a scenario in which the UE 100 is in the RRC idle state or the RRC inactive state will be mainly described.

[0040] In step S1, the UE 100 receives a system information block type 1 (SIB1) from the gNB 200. The system information (SI) consists of a master information block (MIB) and several system information blocks (SIBs), and is divided into minimum SI and other SI. The SI message is mapped to the broadcast control channel (BCCH) and dynamically carried on the downlink shared channel (DL-SCH). The scheduling of other SI is indicated by SIB1.

[0041] The minimum SI (Minimum SI) consists of basic information required for initial access and information for acquiring other SI. SIB1 is included in the minimum SI. SIB1 defines the scheduling of other system information blocks and includes information required for initial access. SIB1 is also referred to as RemainingMinimumSI (RMSI) and is periodically broadcast or transmitted to UE 100 in an RRC connected state in a dedicated manner.

[0042] Other SI includes all SIBs that are not broadcast in the minimum SI. These SIBs are broadcast periodically or broadcast on demand in response to a request from a UE 100 in an RRC idle state, an RRC inactive state, or an RRC connected state. Note that other SI can also be transmitted to a UE in an RRC connected state in a dedicated manner on the DL-SCH. SIB20 is included in other SI.

[0043] Scheduling information (SI Scheduling Info) in SIB1 indicates whether other SI is being broadcast. If SIB1 indicates that SIB20 is not being broadcast, UE100 that wants to acquire SIB20 transmits an On-demand SI Request requesting transmission of SIB20 to gNB200 (step S2).

[0044] Here, for a UE 100 in an RRC idle state and an RRC inactive state, a request for other SI (On-demand SI Request) triggers a random access procedure. In this case, MSG1 (i.e., a random access preamble) is used to indicate the requested other SI. When MSG1 is used, the minimum granularity of the request is one SI message (i.e., a set of SIBs), and multiple SI messages can be requested using one RACH preamble and / or PRACH resource.

[0045] In addition, if configured by the network, the UE 100 in the RRC connected state can send a request for other SI to the network in a dedicated manner (specifically, by dedicated signaling via the UL-DCCH). The gNB 200 responds with an RRC Reconfiguration message including the requested SIB. The network determines which requested SIB to deliver by dedicated or broadcast.

[0046] In step S3, UE100 receives SIB20 from gNB200 and obtains the MCCH configuration information contained in SIB20.

[0047] In step S4, UE100 receives MCCH from gNB200 based on SIB20 of step S3 and obtains MBS broadcast control information carried on the MCCH.

[0048] In step S5, UE100 receives MTCH from gNB200 based on the MCCH in step S4 and acquires MBS broad data carried on the MTCH.

[0049] (3) Operation of the mobile communication system Figure 7 is a diagram for explaining the operation scenario of the mobile communication system 1 according to the embodiment. In the example shown, cell a (first cell) is managed by gNB200a (first base station), and cell b (second cell) adjacent to cell a is managed by gNB200b (second base station). However, cell a and cell b may be managed by a single gNB200.

[0050] A UE 100 (first user equipment) present in cell a is receiving an MBS broadcast from cell a. The UE 100 is moving toward cell b and wants to continue receiving the MBS broadcast in cell b. In this case, when switching from cell a to cell b (cell reselection or handover), the UE 100 acquires SIB20 from cell b, and after receiving an MCCH from cell b based on the SIB20, it becomes possible to receive an MTCH. Therefore, there is a problem that the movement of the UE 100 causes an interruption in reception of the MBS service (service interruption).

[0051] Also, SIB20 may be included in other SI (Other SI), and cell b may not broadcast SIB20. If cell b does not broadcast SIB20, UE 100 needs to request SIB20 by On-demand SI Request (i.e., PRACH or dedicated signaling), which further extends the service interruption time.

[0052] In the embodiment, the UE 100 is enabled to acquire the SIB20 and / or MCCH (hereinafter also referred to as "SIB20 / MCCH") of the cell b at an earlier stage, thereby shortening the service interruption time.

[0053] Specifically, a UE 100a present in cell a transmits a request signal to a predetermined device requesting the provision of broadcast control information to be broadcast in a cell b adjacent to cell a. The predetermined device is another UE 100 (second user equipment) present in cell b, a gNB 200a managing cell a, or a gNB 200b managing cell b. This allows the UE 100a to obtain the broadcast control information directly or indirectly from the gNB 200b while present in cell a.

[0054] The broadcast control information includes on-demand system information (i.e., Other SI) broadcast in response to a request from the UE 100. In an embodiment, the broadcast control information includes a message (MBS broadcast control information) transmitted on the MCCH of the cell b, and / or a system information block (i.e., SIB20) indicating the configuration of the MCCH.

[0055] (3.1) First Operation Pattern The first operation pattern of the mobile communication system 1 according to the embodiment will be described below. Fig. 8 is a diagram for explaining the first operation pattern.

[0056] In the first operation pattern, the predetermined device is another UE 100b (second user device) located in cell b. The UE 100a (first user device) transmits a request signal to the UE 100b on a side link to request provision of broadcast control information to be broadcast in cell b. In the first operation pattern, the request signal is a transfer request message for requesting transfer of the broadcast control information.

[0057] The request signal (transfer request message) may include information indicating an MBS service in which the UE 100a is interested. The request signal (transfer request message) may include information identifying a cell in which the UE 100a is interested and / or information identifying broadcast information in which the UE 100a is interested. The request signal (transfer request message) may include information requesting the transfer of MCCH (MBS broadcast control information) without transferring SIB20 (MCCH configuration information).

[0058] The UE 100b that has received the request signal (transfer request message) may request the cell b to transmit the SIB 20. The UE 100b receives broadcast control information of the cell b. In response to receiving the request signal (transfer request message), the UE 100b transfers the broadcast control information to the UE 100a on the side link.

[0059] The UE 100a may send an inquiry to the UE 100b regarding the MBS service provided by the cell b.

[0060] The UE 100b may transmit, on the sidelink, a discovery message including at least one of information on a capability to transfer broadcast control information and information indicating an MBS service provided by the cell b. The UE 100a may receive the discovery message.

[0061] 9 is a diagram showing an example of an operation flow in the first operation pattern. UE 100a existing in cell a receives MBS broadcast data on the MTCH of cell a (step S101). UE 100a may be in an RRC idle state or an RRC inactive state in cell a.

[0062] In step S102, the UE 100b broadcasts a discovery message (specifically, a Model A discovery message) including the cell ID of cell b on the sidelink. The message may include information indicating that the UE 100b is capable of transmitting SIB20 / MCCH (that is, permits a transmission request) and / or information on the MBS service provided by cell b (such as TMGI). The message may further include a neighbor UE list. The neighbor UE list includes information indicating which UE 100 is located in which cell. The neighbor UE list is used by the UE 100a to identify which UE 100 to request transmission from when moving between cells.

[0063] In step S103, the UE 100a determines that it is located at the cell edge of the cell a (performs cell reselection), identifies the cell b, and recognizes that the SIB20 / MCCH of the cell b is necessary. Furthermore, the UE 100a recognizes that the UE 100b is present in the cell b based on the discovery message of step S102.

[0064] In step S104, the UE 100a transmits a transfer request of SIB20 / MCCH to the UE 100b. Here, if the UE 100a and the UE 100b are PC5-Connected (i.e., if there is a PC5 connection), the UE 100a may transmit the transfer request in a PC5-RRC message or a PC5-S message. On the other hand, if there is no PC5 connection between the UE 100a and the UE 100b, the UE 100a may transmit the transfer request in a Model A discovery message or a Model B discovery message.

[0065] The UE 100a may establish a PC5 connection with the UE 100b by recognizing that the UE 100b is present in cell b. For example, the UE 100a transmits a Direct Communication Request (PC5-S) or an RRC Reconfiguration Sidelink (PC5-RRC) as a connection request message to the UE 100b, and establishes a PC5 connection with the UE 100b. The connection request message may include, for example, information indicating that the connection request is for SIB20 / MCCH transfer only, as a Cause value. The UE 100b may use this information to determine whether to accept the connection request.

[0066] The transfer request message of step S104 may include at least one of the following information: - An inquiry about MBS service information (TMGI, etc.) provided by cell b; - MBS service information (TMGI, etc.) in which UE 100a is interested; - Cell ID in which UE 100a is interested (especially in the case where the cell ID was not broadcast by discovery in step S102); - Number of SIB in which UE 100a is interested (wants to be transferred) (especially SIB20, etc.); - Information indicating that UE 100a wants MCCH to be transferred (because MTCH can be received as long as MCCH information is available, and SIB20 does not necessarily have to be acquired).

[0067] The UE 100b receives the transfer request message from the UE 100a. If the UE 100b has already acquired the SIB20 / MCCH of the cell b, the UE 100b transfers the SIB20 / MCCH to the UE 100a via the side link (step S108).

[0068] On the other hand, if the UE 100b has not acquired the SIB20 / MCCH of the cell b, in step S105, the UE 100b transmits an on-demand SI request to the cell b. As a result, in steps S106 / S107, the UE 100b acquires the SIB20 / MCCH from the cell b. Here, if the UE 100b is in an RRC idle state or an RRC inactive state, the UE 100b transmits a PRACH-based on-demand SI request, and if the UE 100b is in an RRC connected state, the UE 100b transmits a dedicated signaling-based on-demand SI request.

[0069] In step S108, the UE 100b transfers the acquired SIB20 / MCCH to the UE 100a via the side link. For example, the UE 100b may encapsulate the acquired SIB20 / MCCH in any one of a Model A discovery message, a Model B discovery message (Response), or a PC5-RRC message and transmit the encapsulated message to the UE 100a.

[0070] In step S109, the UE 100a receives the MTCH (MBS broadcast data) of the cell b based on the SIB20 / MCCH transferred in step S108.

[0071] In response to the on-demand SI request in step S105, cell b starts broadcasting SIB 20. If UE 100a can directly receive SIB 20 from cell b, UE 100a may acquire SIB 20 directly from cell b. In this case, it is not necessary to transfer SIB 20 over the side link in step S108.

[0072] (3.2) Second Operation Pattern The second operation pattern of the mobile communication system 1 according to the embodiment will be described, focusing on differences from the first operation pattern described above. Fig. 10 is a diagram for explaining the second operation pattern.

[0073] In the second operation pattern, the specified device is gNB200b that manages cell b. UE100a located in cell a directly transmits a request signal to gNB200b requesting the provision of broadcast control information to be broadcast in cell b. Then, UE100a directly receives the broadcast control information broadcast in cell b.

[0074] In the second operation pattern, the gNB 200a may broadcast information in the cell a indicating whether or not to permit transmission of a request signal to the cell b. The UE 100a may transmit a request signal to the gNB 200b in response to the information indicating that transmission of a request signal to the cell b is permitted.

[0075] 11 is a diagram showing an example of an operation flow in the second operation pattern. The UE 100a existing in the cell a receives MBS broadcast data on the MTCH of the cell a (step S201).

[0076] In step S202, the gNB 200a (cell a) may broadcast information on whether the UE 100a may transmit an On-demand SI Request directly to the cell b. The information may include (a list of) cell IDs of neighboring cells that are permitted or prohibited from transmitting the On-demand SI Request.

[0077] In step S203, the UE 100a recognizes that it is located at the cell edge of the cell a (immediately before cell reselection) and recognizes that it must acquire the SIB20 / MCCH of the cell b. The UE 100a synchronizes with the cell b while being present in the cell a.

[0078] In step S204, the UE 100a acquires SIB1 from the cell b. When SIB20 is "notBroadcasted" in the SI Scheduling Info in the SIB1, the UE 100a determines to transmit an On-demand SI Request to the cell b. Note that the SIB1 may include information indicating whether or not the UE 100 residing in a cell other than the cell b is permitted to transmit an On-demand SI Request to the cell b.

[0079] The UE 100a acquires from cell b the system frame number (SFN) information of cell b and the PRACH resource information of cell b allocated to the On-demand SI Request. Specifically, the UE 100a acquires PRACH resource information for the On-demand SI Request from the SI-RequestConfig in the SI Scheduling Info. The RRC of the UE 100a notifies its MAC of the PRACH resource information and instructs its MAC to transmit a PRACH for the On-demand SI Request to cell b. Here, the RRC of the UE 100a may also notify its MAC that the PRACH resource configuration is temporary. The MAC of the UE 100a retains the current setting (the setting of cell a) and applies the temporary setting of cell b. Note that this information is applied only to the transmission of the On-demand SI Request. After the PRACH transmission for cell reselection (step S205), the MAC of the UE 100a may discard the PRACH resource information of cell b and reapply the retained setting of cell a.

[0080] In step S205, the UE 100a transmits an On-demand SI Request to the cell b.

[0081] In step S206, the UE 100a acquires the SIB 20 from the cell b.

[0082] In step S207, the UE 100a acquires the MCCH from the cell b.

[0083] In step S208, the UE 100a acquires the MTCH (MBS broadcast data) from the cell b.

[0084] (3.3) Third Operation Pattern The third operation pattern of the mobile communication system 1 according to the embodiment will be described, focusing on differences from the first and second operation patterns. Fig. 12 is a diagram for explaining the third operation pattern.

[0085] In the third operation pattern, the specified device is gNB200a. UE100a transmits a request signal to gNB200a (cell a) requesting the provision of broadcast control information to be broadcast in cell b. The request signal may be a signal requesting the start of broadcasting of the broadcast control information by cell b. Upon receiving the request signal, gNB200a requests gNB200b to start transmitting the broadcast control information. UE100a receives the broadcast control information from cell b.

[0086] 13 is a diagram showing an example of an operation flow in the third operation pattern. The UE 100a existing in the cell a receives MBS broadcast data on the MTCH of the cell a (step S301).

[0087] In step S302, the gNB200a (cell a) may broadcast information on whether or not to permit transmission of an On-demand SI Request for cell b. The gNB200a may broadcast the information in an SIB. The gNB200a may broadcast the information in an MCCH. Alternatively, the gNB200a (cell a) may broadcast information on whether or not cell b is broadcasting SIB20. The gNB200a (cell a) may broadcast the PRACH resources of cell a allocated to the On-demand SI Request for cell b. It is assumed that the PRACH resources are different from the PRACH resources allocated to the existing On-demand SI Request.

[0088] In step S303, the UE 100a recognizes that the UE 100a is located at the cell edge of the cell a (immediately before cell reselection).

[0089] In step S304, the UE 100a transmits an On-demand SI Request for the cell b to the cell a. The On-demand SI Request may be associated with at least one of the following information (for example, may include at least one of the following information): Information indicating whether the On-demand SI Request is a request for SIB20 broadcast in the cell a (similar to existing information) or a request for SIB20 broadcast in the cell b, A cell ID of the cell requesting the SIB20 broadcast (in the illustrated example, the cell ID of the cell b), Information indicating which SIB is required (SIB number).

[0090] These pieces of information may be notified from the UE 100a to the gNB 200a by dividing the PRACH resource and associating the information with each resource. Alternatively, in the case of a dedicated SI request, these pieces of information may be included as IEs.

[0091] In step S305, gNB200a requests gNB200b to start broadcasting SIB20 of cell b. The request may be sent in a message sent on the Xn interface (inter-base station interface). The request may be sent in a message sent on the NG interface (i.e., via AMF). The message of step S305 may include the information notified in the On-demand SI Request of step S304.

[0092] In step S306, in response to receiving the message in step S305, gNB200b starts broadcasting SIB20 in cell b. UE100a acquires the SIB20.

[0093] In step S307, the UE 100a acquires the MCCH from the cell b.

[0094] In step S308, the UE 100a acquires the MTCH (MBS broadcast data) from the cell b.

[0095] (3.4) Fourth Operation Pattern The fourth operation pattern of the mobile communication system 1 according to the embodiment will be described, focusing on the differences from the first to third operation patterns described above. The fourth operation pattern is a partial modification of the third operation pattern described above. Figure 14 is a diagram for explaining the fourth operation pattern.

[0096] In the fourth operation pattern, the UE 100a transmits a request signal to the gNB 200a (cell a) requesting that the broadcast control information be acquired from the gNB 200b (cell b) via the gNB 200a (cell a). Then, the UE 100a receives the broadcast control information from the gNB 200a.

[0097] 15 is a diagram showing an example of an operation flow in the fourth operation pattern. The operations in steps S401 to S404 are the same as those in the third operation pattern described above.

[0098] In step S405, gNB200a sends a message to gNB200b requesting that cell b's SIB20 / MCCH be acquired over the Xn interface.

[0099] In step S406, gNB200b transmits cell b's SIB20 / MCCH to gNB200a over the Xn interface.

[0100] In step S407, gNB200a transmits SIB20 / MCCH notified (shared) by gNB200b to UE100a by broadcast or dedicated signaling.

[0101] In step S408, the UE 100a acquires the MTCH (MBS broadcast data) from the cell b based on the SIB20 / MCCH.

[0102] (4) Other Embodiments In the above-described embodiment, an example has been described in which an MBS is assumed and the broadcast control information that a UE 100a residing in cell a acquires from cell b is SIB20 / MCCH. However, the embodiment is not limited to such broadcast control information related to MBS. For example, the UE 100a residing in cell a may acquire an SIB other than SIB20 from cell b. The following scenarios are possible as scenarios other than MBS.

[0103] A scenario in which reception resources are optimized in a side link by knowing resource pool information of another cell. In this scenario, the UE 100a residing in the cell a may acquire, from the cell b, an SIB related to the side link resource pool of the cell b.

[0104] In RAN slicing, a scenario in which it is desired to know the slices supported by other cells. In this scenario, the UE 100a existing in the cell a may acquire, from the cell b, an SIB related to the slices supported by the cell b.

[0105] In a non-public network (NPN), a scenario is desired in which it is desired to know whether another cell is NPN-compatible (whether it is public). In this scenario, the UE 100a residing in the cell a may acquire, from the cell b, an SIB regarding whether the cell b is NPN-compatible.

[0106] The above-described operational flows are not limited to being implemented independently, but can also be implemented by combining two or more operational flows. For example, some steps of one operational flow may be added to another operational flow, or some steps of one operational flow may be replaced with some steps of another operational flow. In each flow, it is not necessary to execute all steps, and only some steps may be executed.

[0107] In the above-described embodiments and examples, an example in which the base station is an NR base station (gNB) has been described, but the base station may be an LTE base station (eNB) or a 6G base station. The base station may also be a relay node such as an IAB (Integrated Access and Backhaul) node. The base station may also be a DU of the IAB node. The UE 100 may also be an MT (Mobile Termination) of the IAB node.

[0108] A program may be provided that causes a computer to execute each process performed by the UE 100 or the gNB 200. The program may be recorded on a computer-readable medium. Using a computer-readable medium, the program can be installed on a computer. Here, the computer-readable medium on which the program is recorded may be a non-transitory recording medium. The non-transitory recording medium is not particularly limited, and may be, for example, a recording medium such as a CD-ROM or a DVD-ROM. Furthermore, circuits that execute each process performed by the UE 100 or the gNB 200 may be integrated, and at least a portion of the UE 100 or the gNB 200 may be configured as a semiconductor integrated circuit (chip set, SoC: System on a chip).

[0109] As used in this disclosure, the terms "based on" and "depending on / in response to" do not mean "based only on" or "depending only on," unless expressly stated otherwise. The term "based on" means both "based only on" and "based at least in part on." Similarly, the term "depending on" means both "depending only on" and "depending at least in part on." The terms "include," "comprise," and variations thereof do not mean including only the listed items, but may mean including only the listed items or may include additional items in addition to the listed items. Additionally, the term "or," as used in this disclosure, is not intended to mean an exclusive or. Furthermore, any reference to elements using designations such as "first," "second," etc., as used in this disclosure does not generally limit the quantity or order of those elements. These designations may be used herein as a convenient method of distinguishing between two or more elements. Thus, a reference to a first and a second element does not imply that only two elements may be employed therein or that the first element must precede the second element in some way. In this disclosure, where articles are added by translation, such as a, an, and the in English, these articles shall include the plural unless the context clearly indicates otherwise.

[0110] The above describes the embodiments in detail with reference to the drawings, but the specific configuration is not limited to that described above, and various design changes can be made within the scope that does not deviate from the gist of the invention.

[0111] This application claims priority to U.S. Provisional Application No. 63 / 403,024 (filed September 1, 2022), the entire contents of which are incorporated herein by reference.

[0112] (5) Supplementary Notes The following are additional notes regarding the features of the above-described embodiment.

[0113] (Supplementary Note 1) A communication method used in a mobile communication system, comprising a step in which a first user device located in a first cell transmits a request signal to a predetermined device to request provision of broadcast control information to be broadcast in a second cell adjacent to the first cell, wherein the predetermined device is a second user device located in the second cell, a first base station that manages the first cell, or a second base station that manages the second cell.

[0114] (Supplementary Note 2) The communication method according to Supplementary Note 1, further comprising the step of the first user equipment acquiring the broadcast control information from the second base station while being located in the first cell.

[0115] (Supplementary Note 3) The communication method according to Supplementary Note 1 or 2, wherein the broadcast control information includes on-demand system information that is broadcast in response to a request from a user device.

[0116] (Supplementary Note 4) The communication method according to any one of Supplementary Notes 1 to 3, further comprising a step in which the first user equipment located in the first cell receives a multicast traffic channel (MTCH) of the first cell, and the broadcast control information includes a message transmitted on a multicast control channel (MCCH) of the second cell and / or a system information block indicating a configuration of the MCCH.

[0117] (Supplementary Note 5) The communication method according to any one of Supplementary Notes 1 to 4, wherein the predetermined device is the second user device, and the step of transmitting the request signal includes the step of transmitting the request signal to the second user device on a side link, and the request signal is a transfer request message for requesting transfer of the broadcast control information.

[0118] (Supplementary Note 6) The communication method according to Supplementary Note 5, further comprising: receiving, by the second user equipment, the broadcast control information of the second cell; and, in response to receiving the request signal, forwarding, by the second user equipment, the broadcast control information to the first user equipment on a sidelink.

[0119] (Supplementary Note 7) The communication method according to Supplementary Note 5 or 6, further comprising: the second user equipment transmitting, on a sidelink, a discovery message including at least one of information on a capability of forwarding the broadcast control information and information indicating an MBS service provided by the second cell; and the first user equipment receiving the discovery message.

[0120] (Supplementary Note 8) The communication method according to Supplementary Note 5 or 6, further comprising the step of the first user equipment transmitting, to the second user equipment, an inquiry regarding an MBS service provided by the second cell.

[0121] (Supplementary Note 9) The communication method according to any one of Supplementary Notes 5 to 8, wherein the forwarding request message includes information indicating an MBS service in which the first user device is interested.

[0122] (Supplementary Note 10) The communication method according to any one of Supplementary Notes 5 to 9, wherein the forwarding request message includes information identifying a cell in which the first user equipment is interested and / or information identifying broadcast information in which the first user equipment is interested.

[0123] (Supplementary Note 11) The communication method according to any one of Supplementary Notes 5 to 10, wherein the broadcast control information includes a message transmitted on a multicast control channel (MCCH) of the second cell and / or a system information block indicating a configuration of the MCCH, and the transfer request message includes information requesting that the message be transferred without transferring the system information block.

[0124] (Supplementary Note 12) The communication method according to any one of Supplementary Notes 5 to 11, wherein the broadcast control information includes a system information block indicating a configuration of a multicast control channel (MCCH) of the second cell, and the communication method further comprises a step in which the second user equipment, upon receiving the forwarding request message, requests the second cell to transmit the system information block.

[0125] (Supplementary Note 13) The communication method according to Supplementary Note 1, wherein the predetermined device is the second base station, and the step of transmitting the request signal includes the step of directly transmitting the request signal to the second base station.

[0126] (Supplementary Note 14) The communication method according to Supplementary Note 13, further comprising the step of the first base station broadcasting, in the first cell, information indicating whether or not transmission of the request signal to the second cell is permitted, wherein the step of transmitting the request signal includes the step of transmitting the request signal in response to the information indicating that transmission of the request signal to the second cell is permitted.

[0127] (Supplementary Note 15) The communication method according to Supplementary Note 13 or 14, further comprising the step of directly receiving, by the first user equipment located in the first cell, the broadcast control information broadcast in the second cell.

[0128] (Supplementary Note 16) The communication method according to Supplementary Note 1, wherein the predetermined device is the first base station, and wherein transmitting the request signal includes transmitting the request signal to the first base station.

[0129] (Supplementary Note 17) The communication method according to Supplementary Note 16, wherein the request signal is a signal requesting the second cell to start broadcasting the broadcast control information, and further comprising the step of the first user equipment receiving the broadcast control information from the second cell.

[0130] (Supplementary Note 18) The communication method according to Supplementary Note 16 or 17, further comprising the step of the first base station, upon receiving the request signal, requesting the second base station to start transmitting the broadcast control information.

[0131] (Supplementary Note 19) The communication method according to Supplementary Note 16, wherein the request signal is a signal requesting acquisition of the broadcast control information from the second base station via the first base station, and further comprising the step of the first user equipment receiving the broadcast control information from the first base station.

[0132] (Supplementary Note 20) A user equipment used in a mobile communication system, comprising: a transmitter that, when the user equipment is present in a first cell, transmits to a predetermined device a request signal requesting provision of broadcast control information to be broadcast in a second cell adjacent to the first cell, wherein the predetermined device is another user equipment present in the second cell, a first base station that manages the first cell, or a second base station that manages the second cell.

[0133] 1: Mobile communication system 10: RAN 20: CN 100: UE (user equipment) 110: Receiving unit 120: Transmitting unit 130: Control unit 200: gNB (base station) 210: Transmitting unit 220: Receiving unit 230: Control unit 240: Backhaul communication unit

Claims

1. A communication method for use in a mobile communication system, comprising: A first user device located in a first cell transmits a request signal to a predetermined device to request broadcast control information to be broadcast in a second cell adjacent to the first cell; The predetermined device is a second user device located in the second cell, a first network node that manages the first cell, or a second network node that manages the second cell. Communication methods.

2. The method further comprises: the first user equipment acquiring the broadcast control information from the second network node while the first user equipment is in the first cell. The communication method according to claim 1 .

3. The broadcast control information includes on-demand system information that is broadcast in response to a request from a user device. The communication method according to claim 1 .

4. The first user equipment located in the first cell further includes receiving a multicast traffic channel (MTCH) of the first cell; The broadcast control information includes a message transmitted on a multicast control channel (MCCH) of the second cell and / or a system information block indicating a configuration of the MCCH. A communication method according to any one of claims 1 to 3.

5. the predetermined device is the second user device, and transmitting the request signal includes transmitting the request signal to the second user equipment on a sidelink. The request signal is a transfer request message for requesting transfer of the broadcast control information. The communication method according to claim 1 .

6. The second user equipment receives the broadcast control information of the second cell; and and the second user equipment, in response to receiving the request signal, forwarding the broadcast control information to the first user equipment over a side link. The communication method according to claim 5.

7. The second user equipment transmits, on a side link, a discovery message including at least one of information regarding a capability of forwarding the broadcast control information and information indicating an MBS service provided by the second cell; and receiving the discovery message by the first user device. The communication method according to claim 5 or 6.

8. The method further includes the first user equipment sending an inquiry to the second user equipment regarding an MBS service provided by the second cell. The communication method according to claim 5 or 6.

9. The transfer request message includes information indicating an MBS service in which the first user device is interested. The communication method according to claim 5 or 6.

10. The transfer request message includes information identifying a cell of interest to the first user equipment and / or information identifying broadcast information of interest to the first user equipment. The communication method according to claim 5 or 6.

11. The broadcast control information includes a message transmitted on a multicast control channel (MCCH) of the second cell, and / or a system information block indicating a configuration of the MCCH; The transmission request message includes information requesting transmission of the message without transmitting the system information block. The communication method according to claim 5 or 6.

12. The broadcast control information includes a system information block indicating a configuration of a multicast control channel (MCCH) of the second cell; The second user equipment receiving the forwarding request message may further request the second cell to transmit the system information block. The communication method according to claim 5 or 6.

13. the predetermined device is the second network node, Transmitting the request signal includes transmitting the request signal directly to the second network node. The communication method according to claim 1 .

14. The method further comprises the first network node broadcasting, in the first cell, information indicating whether or not to permit transmission of the request signal to the second cell; Transmitting the request signal includes transmitting the request signal in response to the information indicating that transmission of the request signal to the second cell is permitted. The communication method according to claim 13.

15. The first user equipment located in the first cell further includes directly receiving the broadcast control information broadcast in the second cell. A communication method according to claim 13 or 14.

16. the predetermined device is the first network node, Transmitting the request signal includes transmitting the request signal to the first network node. The communication method according to claim 1 .

17. The request signal is a signal requesting the second cell to start broadcasting the broadcast control information, The method further comprises the first user equipment receiving the broadcast control information from the second cell.

17. The communication method according to claim 16.

18. The method further comprises the step of: the first network node receiving the request signal requests the second network node to start transmitting the broadcast control information.

18. A communication method according to claim 16 or 17.

19. the request signal is a signal requesting to obtain the broadcast control information from the second network node via the first network node; The method further comprises the first user equipment receiving the broadcast control information from the first network node.

17. The communication method according to claim 16.

20. A user device for use in a mobile communication system, comprising: A transmitter that transmits a request signal to a predetermined device to request broadcast control information to be broadcast in a second cell adjacent to the first cell when the user equipment is present in the first cell, The predetermined device is another user equipment located in the second cell, a first network node that manages the first cell, or a second network node that manages the second cell. User equipment.