Communication control method, user equipment, processor, network device, mobile communication system, and program

Abstract

To provide a communication control method and a base station for achieving an improved multicast broadcast service (MBS).SOLUTION: A communication control method is used in a mobile communication system for providing an MBS from a base station gNB to user equipment UE. The communication control method includes: broadcasting, by the base station, an MBS system information block; and transmitting, by the base station, scheduling information of an MBS traffic channel on an MBS control channel, wherein the MBS system information block includes a search space identifier for the user equipment to receive the MBS control channel, and the search space identifier indicates a search space that is a resource range to be decoded by the user equipment in a physical downlink control channel associated with the MBS control channel.SELECTED DRAWING: Figure 10

Description

Technical Field

[0001] The present disclosure relates to a communication control method and a base station used in a mobile communication system.

Background Art

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

Prior Art Documents

Non-Patent Documents

[0003]

Non-Patent Document 1

Summary of the Invention

[0004] A communication control method according to a first aspect is a communication control method used in a mobile communication system that provides a multicast / broadcast service (MBS) from a base station to a user equipment. The base station broadcasts an MBS system information block, and the base station transmits scheduling information of an MBS traffic channel on an MBS control channel. The MBS system information block includes a search space identifier for the user equipment to receive the MBS control channel, and the search space identifier indicates a search space that is a resource range to be decoded by the user equipment in a physical downlink control channel associated with the MBS control channel.

[0005] The communication control method according to the second aspect is a communication control method used in a mobile communication system that provides a multicast / broadcast service (MBS) from a base station to a user equipment, the base station broadcasting a predetermined system information block used for scheduling of an MBS system information block, the base station broadcasting the MBS system information block, and the base station transmitting scheduling information of an MBS traffic channel on an MBS control channel, the predetermined system information block including a search space identifier for the user equipment to receive the MBS control channel, the search space identifier indicating a search space that is a resource range to be decoded by the user equipment in a physical downlink control channel associated with the MBS control channel.

[0006] The communication control method according to the third aspect is a communication control method used in a mobile communication system that provides a multicast / broadcast service (MBS) from a base station to a user equipment, the base station broadcasting the MBS system information block, and the base station transmitting, on an MBS control channel, scheduling information of an MBS traffic channel and a search space identifier for the user equipment to receive the MBS traffic channel, the search space identifier indicating a search space that is a resource range to be decoded by the user equipment in a physical downlink control channel associated with the MBS traffic channel.

[0007] The communication control method according to the fourth aspect is a communication control method used in a mobile communication system that provides a multicast / broadcast service (MBS) from a base station to a user equipment, wherein the base station that manages a cell transmits a notification message regarding MBS transmission in an adjacent cell different from the cell to the user equipment in the first cell, the notification message includes a search space identifier for the user equipment to receive a predetermined channel provided in the adjacent cell different from the cell, the search space identifier includes a search space identifier indicating a search space that is a resource range to be decoded by the user equipment in a physical downlink control channel associated with the predetermined channel provided in the adjacent cell, and the predetermined channel is an MBS control channel or an MBS traffic channel provided in the adjacent cell.

[0008] The communication control method according to the fifth aspect is a communication control method used in a mobile communication system that provides a multicast / broadcast service (MBS) from a base station to a user equipment, wherein the base station that manages a cell broadcasts an MBS system information block for the MBS, and the base station transmits a plurality of MBS control channels in the cell, the MBS system information block includes a radio network temporary identifier (RNTI) for notifying a change in each of the plurality of MBS control channels, and the change notification RNTI is an RNTI used for the user equipment to receive a change notification indicating that the content of the corresponding MBS control channel has changed.

[0009] The base station according to the sixth aspect includes a processor that executes the communication control method according to any one of the first to fifth aspects.

Brief Description of the Drawings

[0010]

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Mode for Carrying Out the Invention

[0011] It has been considered to introduce multicast and broadcast services into the 5G system (NR). It is desired that the multicast and broadcast services of NR provide services improved over those of the multicast and broadcast services of LTE.

[0012] Therefore, an object of the present disclosure is to provide a communication control method for realizing an improved multicast / broadcast service.

[0013] 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.

[0014] (Configuration of Mobile Communication System) First, the configuration of the mobile communication system according to the embodiment will be described. FIG. 1 is a diagram showing the configuration of the mobile communication system according to the embodiment. This mobile communication system complies with the 5th Generation System (5GS) of the 3GPP standard. In the following, 5GS will be taken as an example for description, but an LTE (Long Term Evolution) system may be at least partially applied to the mobile communication system.

[0015] As shown in FIG. 1, the mobile communication system includes a User Equipment (UE) 100, a 5G Radio Access Network (NG-RAN) 10, and a 5G Core Network (5GC) 20.

[0016] The UE 100 is a movable wireless communication device. The UE 100 may be any device as long as it is a device used by a user. For example, the UE 100 may be a mobile phone terminal (including a smartphone), a tablet terminal, a notebook PC, a communication module (including a communication card or a chipset), a sensor or a device provided on the sensor, a vehicle or a device provided on the vehicle (Vehicle UE), and / or an aircraft or a device provided on the aircraft (Aerial UE).

[0017] NG-RAN 10 includes base stations (referred to as "gNB" in a 5G system) 200. The gNBs 200 are interconnected via the Xn interface, which is an interface between base stations. The gNB 200 manages one or more cells. The gNB 200 performs wireless communication with the UE 100 that has established a connection with its cell. The gNB 200 has functions such as a radio resource management (RRM) function, a routing function for user data (hereinafter simply referred to as "data"), and a measurement control function for mobility control and scheduling. A "cell" is used as a term indicating the smallest unit of a wireless communication area. A "cell" is also used as a term indicating a function or resource for performing wireless communication with the UE 100. One cell belongs to one carrier frequency.

[0018] Note that the gNB can also be connected to the EPC (Evolved Packet Core), which is the core network of LTE. The base station of LTE can also be connected to the 5GC. The base station of LTE and the gNB can also be connected via an interface between base stations.

[0019] The 5GC 20 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 performs transfer control of data. The AMF and the UPF are connected to the gNB 200 via the NG interface, which is an interface between the base station and the core network.

[0020] Figure 2 is a diagram showing the configuration of the UE 100 (user equipment) according to the embodiment.

[0021] As shown in Figure 2, the UE 100 includes a receiving unit 110, a transmitting unit 120, and a control unit 130.

[0022] The receiving unit 110 performs various receptions under the control of the control unit 130. The receiving unit 110 includes an antenna and a receiver. The receiver converts the radio signal received by the antenna into a baseband signal (received signal) and outputs it to the control unit 130.

[0023] 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 the baseband signal (transmission signal) output by the control unit 130 into a radio signal and transmits it from the antenna.

[0024] The control unit 130 performs various controls in the UE 100. The control unit 130 includes at least one processor and at least one memory. The memory stores programs executed by the processor and information used for the processing by the processor. The processor may include a baseband processor and a CPU (Central Processing Unit). The baseband processor performs modulation / demodulation and encoding / decoding of the baseband signal, etc. The CPU executes the programs stored in the memory and performs various processes.

[0025] FIG. 3 is a diagram showing the configuration of the gNB 200 (base station) according to the embodiment.

[0026] As shown in FIG. 3, the gNB 200 includes a transmitting unit 210, a receiving unit 220, a control unit 230, and a backhaul communication unit 240.

[0027] 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 the baseband signal (transmission signal) output by the control unit 230 into a radio signal and transmits it from the antenna.

[0028] The receiving unit 220 performs various receptions under the control of the control unit 230. The receiving unit 220 includes an antenna and a receiver. The receiver converts the radio signal received by the antenna into a baseband signal (received signal) and outputs it to the control unit 230.

[0029] The control unit 230 performs various controls in the gNB 200. The control unit 230 includes at least one processor and at least one memory. The memory stores programs executed by the processor and information used for the processor's processing. The processor may include a baseband processor and a CPU. The baseband processor performs modulation / demodulation and encoding / decoding of baseband signals, etc. The CPU executes programs stored in the memory to perform various processes.

[0030] The backhaul communication unit 240 is connected to an adjacent base station via a base station interface. The backhaul communication unit 240 is connected to the AMF / UPF 300 via a base station-core network interface. Note that the gNB is composed of a CU (Central Unit) and a DU (Distributed Unit) (i.e., functionally split), and the two units may be connected by an F1 interface.

[0031] Figure 4 is a diagram showing the configuration of a protocol stack of a radio interface of a user plane that handles data.

[0032] As shown in Figure 4, the radio interface protocol of the user plane has a physical (PHY) layer, a MAC (Medium Access Control) layer, an RLC (Radio Link Control) layer, a PDCP (Packet Data Convergence Protocol) layer, and an SDAP (Service Data Adaptation Protocol) layer.

[0033] The PHY layer performs encoding / decoding, modulation / demodulation, antenna mapping / demapping, and resource mapping / demapping. Data and control information are transmitted between the PHY layer of the UE 100 and the PHY layer of the gNB 200 via a physical channel.

[0034] The MAC layer performs functions such as priority control of data, retransmission processing by Hybrid ARQ (HARQ), and random access procedures. Between the MAC layer of UE100 and the MAC layer of gNB200, data and control information are transmitted via transport channels. The MAC layer of gNB200 includes a scheduler. The scheduler determines the uplink and downlink transport formats (transport block size, modulation and coding scheme (MCS)) and the resource blocks allocated to UE100.

[0035] The RLC layer uses the functions of the MAC layer and the PHY layer to transmit data to the RLC layer on the receiving side. Between the RLC layer of UE100 and the RLC layer of gNB200, data and control information are transmitted via logical channels.

[0036] The PDCP layer performs header compression / expansion and encryption / decryption.

[0037] The SDAP layer performs the mapping between the IP flow, which is the unit for the core network to perform QoS (Quality of Service) control, and the radio bearer, which is the unit for the AS (Access Stratum) to perform QoS control. Note that when the RAN is connected to the EPC, the SDAP may not be necessary.

[0038] Figure 5 is a diagram showing the configuration of the protocol stack of the radio interface of the control plane that handles signaling (control signals).

[0039] As shown in Figure 5, 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 Figure 4.

[0040] Between the RRC layer of UE100 and the RRC layer of gNB200, RRC signaling for various settings is transmitted. The RRC layer controls logical channels, transport channels, and physical channels in response 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 the RRC connected state. When there is no connection (RRC connection) between the RRC of UE100 and the RRC of gNB200, UE100 is in the RRC idle state. When the connection between the RRC of UE100 and the RRC of gNB200 is suspended, UE100 is in the RRC inactive state.

[0041] The NAS layer located above the RRC layer performs session management, mobility management, etc. NAS signaling is transmitted between the NAS layer of UE100 and the NAS layer of AMF300.

[0042] In addition, UE100 has an application layer, etc., in addition to the radio interface protocol.

[0043] (MBS) Next, MBS according to an embodiment will be described. MBS is a service that enables the transmission of data from NG-RAN10 to UE100 in a broadcast or multicast manner, that is, one-to-many (PTM: Point To Multipoint). MBS may be called MBMS (Multimedia Broadcast and Multicast Service). The use cases (service types) of MBS include public security communication, mission-critical communication, V2X (Vehicle to Everything) communication, IPv4 or IPv6 multicast distribution, IPTV (Internet protocol television), group communication, and software distribution, etc.

[0044] In LTE, there are two types of MBS transmission methods, namely MBSFN (Multicast Broadcast Single Frequency Network) transmission and SC-PTM (Single Cell Point To Multipoint) transmission. FIG. 6 is a diagram showing the correspondence between the downlink logical channel and transport channel according to an embodiment.

[0045] As shown in FIG. 6, the logical channels used for MBSFN transmission are MTCH (Multicast Traffic Channel) and MCCH (Multicast Control Channel), and the transport channel used for MBSFN transmission is MCH (Multicast Channel). MBSFN transmission is mainly designed for multi-cell transmission. In an MBSFN area composed of multiple cells, each cell synchronously transmits the same signal (same data) in the same MBSFN subframe.

[0046] The logical channels used for SC-PTM transmission are SC-MTCH (Single Cell Multicast Traffic Channel) and SC-MCCH (Single Cell Multicast Control Channel), and the transport channel used for SC-PTM transmission is DL-SCH (Downlink Shared Channel). SC-PTM transmission is mainly designed for single-cell transmission, and data is transmitted in a broadcast or multicast manner on a cell-by-cell basis. The physical channels used for SC-PTM transmission are PDCCH (Physical Downlink Control Channel) and PDSCH (Physical Downlink Shared Channel), and dynamic resource allocation is possible.

[0047] In what follows, an example in which MBS is provided using a method similar to the SC-PTM transmission method will be mainly described, but MBS may be provided using the MBSFN transmission method. Also, an example in which MBS is provided by multicast will be mainly described. For this reason, MBS may be read as multicast. However, MBS may be provided by broadcast.

[0048] Also, MBS data refers to the data provided by MBS, the MBS control channel refers to MCCH or SC-MCCH, and the MBS traffic channel refers to MTCH or SC-MTCH. However, MBS data may be transmitted by unicast. MBS data may also be called MBS packets or MBS traffic.

[0049] The MBS control channel is a one-to-many (PTM) downlink channel used to transmit MBS control information from gNB200 to UE100. The MBS control channel is mapped to a type of transport channel, DL-SCH (Downlink Shared Channel).

[0050] The MBS traffic channel is a one-to-many (PTM) downlink channel used to transmit MBS data from gNB200 to UE100. The MBS traffic channel is a type of logical channel and is mapped to DL-SCH. The MBS traffic channel and the MBS session are associated one-to-one.

[0051] DL-SCH is mapped to a type of physical channel, PDSCH (Physical Downlink Shared Channel). PDSCH is scheduled by DCI (Downlink Control Information) carried on a type of physical channel, PDCCH (Physical Downlink Control Channel).

[0052] The network can provide different MBS services for each MBS session. An MBS session is identified by at least one of a TMGI (Temporary Mobile Group Identity) and a session identifier, and at least one of these identifiers is called an MBS session identifier. Such an MBS session identifier may also be referred to as an MBS service identifier or a multicast group identifier.

[0053] FIG. 7 is a diagram showing a method for delivering MBS data according to an embodiment.

[0054] As shown in FIG. 7, MBS data (MBS Traffic) is delivered from a single data source (application service provider) to a plurality of UEs. The 5G core network 5G CN (5GC) 20 receives MBS data from the application service provider, creates (Replication) copies of the MBS data, and distributes them.

[0055] From the perspective of the 5GC 20, two delivery methods are possible: shared MBS data delivery and individual MBS data delivery.

[0056] In shared MBS data delivery, a connection is established between the NG-RAN 10, which is a 5G radio access network (5G RAN), and the 5GC 20, and the 5GC 20 distributes MBS data to the NG-RAN 10. Hereinafter, such a connection (tunnel) is called an "MBS connection".

[0057] The MBS connection may also be referred to as a Shared MBS Traffic delivery connection or a shared transport. The MBS connection terminates at the NG-RAN 10 (i.e., gNB 200). The MBS connection may correspond one-to-one with an MBS session.

[0058] gNB 200 selects either a PTP (Point-to-Point: unicast) or PTM (Point-to-Multipoint: multicast or broadcast) transmission method based on its own judgment, and transmits MBS data to UE 100 using the selected transmission method.

[0059] On the other hand, in individual MBS data distribution, a unicast session is established between NG-RAN 10 and UE 100, and MBS data is individually distributed from 5GC 20 to UE 100. Such unicast may also be referred to as a PDU session. The unicast (PDU session) terminates at UE 100.

[0060] (Channel correspondence) Next, the channel correspondence according to an embodiment will be described.

[0061] FIG. 8 is a diagram showing the channel correspondence according to an embodiment. Each channel shown in FIG. 8 is provided in one cell. In FIG. 8, an example is illustrated in which a plurality of MBS control channels are provided in one cell, but only one MBS control channel may be provided in one cell.

[0062] Also, although each block shown in FIG. 8 represents one channel, the description of "PDCCH" in each block means that the radio resource (PDSCH) of the channel is allocated by the PDCCH at the physical layer. That is, it is assumed that the broadcast control channel, the MBS control channel, and the MBS traffic channel are all mapped to the DL-SCH.

[0063] First, the gNB 200 broadcasts SIB type 1 on the broadcast control channel. SIB type 1 includes scheduling information of the MBS system information block (MBS SIB) (hereinafter referred to as "MBS SIB scheduling information"). The MBS SIB scheduling information is information for scheduling a message (SI message described later) that carries the MBS SIB. The MBS SIB is a system information block for MBS and is a type of OSI (Other System Information) described later.

[0064] Second, the gNB 200 broadcasts the MBS SIB on the broadcast control channel according to the scheduling by SIB type 1. The MBS SIB includes information indicating the scheduling of the MBS control channel (hereinafter referred to as "MBS control channel scheduling information"). Note that the MBS SIB is transmitted at a period scheduled by a predetermined SIB (for example, SIB type 1). The MBS control channel scheduling information is information for specifying candidate time positions at which the MBS control channel can be transmitted. Such candidate time positions may be referred to as an MBS control channel transmission window. Such candidate time positions may be composed of a predetermined number of time units arranged periodically. The time unit may be a slot. Also, the time unit may be a subframe. The MBS control channel scheduling information includes a Repetition period (retransmission period), an Offset (offset value of the SFN for scheduling), a Start point (scheduling start subframe / slot), a Duration (scheduling period from the Start point), and / or a Modification period (modification period), etc.

[0065] Note that the gNB 200 may provide a plurality of MBS control channels in the cells it manages. For example, each MBS control channel is associated with a different service quality requirement (or service category). This enables the configuration of an MBS control channel optimized according to the service quality requirement. In this case, the MBS SIB may schedule each of the plurality of MBS control channels (MCCH#1 and MCCH#2). Different scheduling can be applied to each MBS control channel. Note that the MBS control channel is transmitted at the period indicated by the MBS SIB.

[0066] Thirdly, the gNB 200 broadcasts MBS traffic channel scheduling information on the MBS control channel according to the MBS control channel scheduling information. The MBS traffic channel scheduling information is information for specifying candidate time positions at which the MBS traffic channel can be transmitted. Such candidate time positions may be composed of a predetermined number of time units arranged periodically. The time unit may be a slot. Also, the time unit may be a subframe. The MBS traffic channel scheduling information includes an On duration timer, a DRX inactivity timer, a Scheduling period (transmission period), and / or a Start offset (transmission SFN offset value), etc.

[0067] In FIG. 8, an example is shown in which MCCH#1 indicates one MBS traffic channel (MTCH#1) and MCCH#2 indicates two MBS traffic channels (MTCH#2 and MTCH#3). MTCH#1 is an MBS traffic channel that transmits MBS data (Data for delay sensitive service) of a delay-sensitive type of MBS service. MTCH#2 and MTCH#3 are MBS traffic channels that transmit MBS data (Data for typical service) of a general MBS service.

[0068] Fourth, the gNB 200 transmits MBS data (e.g., PTM transmission) on the MBS traffic channel according to the MBS traffic channel scheduling information.

[0069] (Search Space) Next, the search space according to an embodiment will be described.

[0070] In the 5G / NR specification, for the purpose of reducing the number of blind decoding times in the UE 100, the resource range to be blindly decoded by the UE 100 in the PDCCH is limited. Such a resource range is a time-frequency resource range, which is composed of a plurality of resource blocks in the frequency direction and a plurality of symbols in the time direction. Such a resource range is called a search space. In one embodiment, the gNB 200 provides a plurality of search spaces in its own cell. The gNB 200 provides search space setting information for setting a plurality of search spaces in its own cell by using the SIB type 1 or RRC Reconfiguration message. Thereby, the setting of each search space can be dynamically changed, and resource optimization is possible.

[0071] The search space configuration information includes, for each of a plurality of search spaces, a set of a search space identifier that identifies the search space and a search space parameter that configures the search space. The search space parameter specifies a plurality of resource blocks and a plurality of symbols that constitute the search space. The search space parameter includes, for example, ControlResourceSetID, monitoringSlotPeriodicityAndOffset, and / or monitoringSymbolsWithinSlot, etc. ControlResourceSetID is a parameter used to specify resource blocks, and monitoringSlotPeriodicityAndOffset and monitoringSymbolsWithinSlot are parameters used to specify symbols.

[0072] In one embodiment, gNB200 configures, in its own cell, one special search space (hereinafter referred to as the "specific search space") that is different from the above-mentioned plurality of search spaces. The specific search space is a search space in which UE100 can identify a plurality of resource blocks and a plurality of symbols that constitute the specific search space, that is, a scheduling and resource range, according to a preset rule. UE100 can identify the scheduling and resource range of the specific search space even without search space configuration information from gNB200 for the specific search space.

[0073] gNB200 assigns a search space identifier "0" to the specific search space. The specific search space may be called search space zero. gNB200 does not assign the search space identifier "0" to the above-mentioned plurality of search spaces for the purpose of distinguishing the specific search space from the above-mentioned plurality of search spaces. For example, the search spaces include the search space "0" which is the specific search space and the search spaces "1" to "4" which are other search spaces.

[0074] In one embodiment, the gNB 200 associates a different search space with each type of downlink message transmitted in the cell of the gNB 200. The types of downlink messages are, for example, system information messages (SI messages), paging messages, and the like. The SI message is a message used to carry system information blocks other than SIB type 1. System information blocks other than SIB type 1 are referred to as OSI (Other System Information). For example, the gNB 200 associates the SI message with a search space (search space #1) identified by the search space identifier "1" in the search space configuration information, and associates the paging message with a search space (search space #2) identified by the search space identifier "2" in the search space configuration information, and transmits information indicating this association in SIB type 1. Hereinafter, the search space associated with the SI message carrying OSI is referred to as the "search space for OSI".

[0075] (First operation example of a mobile communication system) Next, a first operation example of the mobile communication system 1 according to one embodiment will be described.

[0076] In this first operation example, it is assumed that a search space is allocated to the MBS control channel. In this case, it is considered that either a specific search space (for example, search space "0") or another search space (for example, search spaces "1" to "4") is allocated to the MBS control channel. Here, the scheduling of the MBS control channel is different when the search space "0" is used and when it is otherwise (search spaces "1", etc.). Note that a search space different from the search space for OSI may be allocated to the MBS control channel. In this case, even if the UE 100 knows the search space for OSI, it cannot receive the MBS control channel.

[0077] Under such a premise, in order for the UE100 to receive the MBS control channel, it is necessary to identify a search space associated with the MBS control channel. However, the UE100 cannot determine which search space it should perform blind decoding on to receive the MBS control channel.

[0078] In the first operation example, the gNB200 broadcasts the MBS SIB and transmits the scheduling information of the MBS traffic channel on the MBS control channel. The MBS SIB includes a search space identifier for the UE100 to receive the MBS control channel. The search space identifier indicates a search space, which is the resource range to be decoded by the UE100 in the physical downlink control channel associated with the MBS control channel. Thereby, the UE100 can determine which search space it should perform blind decoding on to receive the MBS control channel.

[0079] In the first operation example, when multiple MBS control channels are provided within one cell of the gNB200, the MBS SIB may include a search space identifier for each of the multiple MBS control channels. Thereby, even when multiple MBS control channels are provided within one cell of the gNB200, the UE100 can determine which search space it should perform blind decoding on to receive each MBS control channel.

[0080] In this first operation example, when the MBS control channel is not associated with a specific search space, the gNB 200 may broadcast an MBS SIB that further includes MBS control channel scheduling information indicating the scheduling of the MBS control channel. As described above, the specific search space is a search space in which the UE 100 can identify the scheduling and resource range of the MBS control channel according to a preset rule. Thereby, even when the MBS control channel is not associated with a specific search space, the UE 100 can grasp the scheduling of the MBS control channel.

[0081] FIG. 9 is a diagram showing a first operation example of the mobile communication system 1.

[0082] As shown in FIG. 9, in step S101, the gNB 200 broadcasts SIB type 1. SIB type 1 includes search space setting information and MBS SIB scheduling information. The UE 100 receives SIB type 1 from the gNB 200.

[0083] In step S102, the gNB 200 broadcasts the MBS SIB based on the scheduling indicated by the MBS SIB scheduling information included in SIB type 1. The UE 100 receives the MBS SIB based on the scheduling indicated by the MBS SIB scheduling information included in SIB type 1. The MBS SIB includes MBS control channel scheduling information.

[0084] In the first operation example, the MBS SIB further includes a search space identifier (hereinafter referred to as the "MBS control channel search space identifier") for the UE 100 to receive the MBS control channel. The MBS control channel search space identifier is one of the search space identifiers included in the search space setting information in SIB type 1. Here, the gNB 200 associates one of a plurality of search spaces (for example, search spaces "1" to "4") set by the search space setting information in SIB type 1 with the MBS control channel. The gNB 200 includes the search space identifier of the search space associated with the MBS control channel in the MBS SIB.

[0085] If a plurality of MBS control channels are provided in the cell managed by the gNB 200, the gNB 200 may associate different search spaces with each MBS control channel. In this case, in step S102, the gNB 200 broadcasts an MBS SIB including the MBS control channel search space identifier corresponding to each of the plurality of MBS control channels. The MBS SIB in this case includes, for example, for each of the plurality of MBS control channels, a set of the identifier of the MBS control channel and the MBS control channel search space identifier corresponding to the MBS control channel. The identifier of the MBS control channel may be the above-described MBS session identifier. The identifier of the MBS control channel may be a channel identifier assigned to the MBS control channel. The identifier of the MBS control channel may be an RNTI (Radio Network Temporary Identifier) assigned to the MBS control channel.

[0086] In the first operation example, gNB200 may include MBS control channel scheduling information in the MBS SIB only when the specific search space is not associated with the MBS control channel. Here, when the MBS control channel is associated with a specific search space, UE100 can identify the resource range based on a preset rule without relying on the MBS control channel scheduling information. Therefore, in this case, the MBS control channel scheduling information is unnecessary. For this reason, gNB200 includes the MBS control channel scheduling information in the MBS SIB when the MBS control channel is not associated with a specific search space.

[0087] In step S103, UE100 identifies the resource range of the PDCCH to be decoded for receiving the MBS control channel based on the MBS control channel scheduling information and the MBS control channel search space identifier included in the MBS SIB received in step S102. Specifically, first, UE100 determines the range of the reception timing of the MBS control channel from the MBS control channel scheduling information included in the MBS SIB received in step S102. Second, UE100 obtains the search space parameters corresponding to the MBS control channel search space identifier included in the MBS SIB received in step S102 from the SIB type 1 received in step S101, and identifies the resource range of the PDCCH from the obtained search space parameters.

[0088] When UE100 receives an MBS SIB including the MBS control channel search space identifier corresponding to each of the plurality of MBS control channels, based on such an MBS SIB, UE100 identifies the resource range to be decoded for receiving the MBS control channel of its interest. Specifically, UE100 obtains the MBS control channel search space identifier associated with the MBS control channel of its interest, and identifies the resource range of the PDCCH to be decoded according to the obtained MBS control channel search space identifier.

[0089] In step S104, gNB200 transmits MBS traffic channel scheduling information on the MBS control channel. UE100 receives the MBS control channel. Here, first, UE100 performs decoding (blind decoding) on the resource range specified in step S103 to obtain DCI carried on the PDCCH. Second, UE100 receives the PDSCH scheduled by the DCI and receives the MBS control channel (MBS traffic channel scheduling information) mapped to the PDSCH.

[0090] In step S105, gNB200 transmits MBS data on the MBS traffic channel. UE100 receives the MBS traffic channel (MBS data) based on the MBS traffic channel scheduling information received in step S104.

[0091] (Second operation example of the mobile communication system) Next, a second operation example of the mobile communication system 1 according to an embodiment will be mainly described in terms of differences from the above-described first operation example.

[0092] In the above-described first operation example, it was mainly assumed that a dedicated search space is allocated for the MBS control channel. In contrast, in the second operation example, an example of sharing the search space of the MBS control channel and the search space of the OSI will be described. Thereby, it is not necessary to broadcast the information of the search space of the MBS control channel in the MBS SIB, and an efficient operation can be realized.

[0093] In this second operation example, gNB 200 broadcasts SIB type 1 used for scheduling of MBS SIB, broadcasts MBS SIB, and transmits scheduling information of the MBS traffic channel on the MBS control channel. Here, SIB type 1 includes a search space identifier for the UE 100 to receive the MBS control channel. Specifically, the search space identifier is commonly applied to the MBS SIB, system information blocks other than SIB type 1, and the MBS control channel.

[0094] FIG. 10 is a diagram showing a second operation example of the mobile communication system 1. Here, descriptions overlapping with those of the above-described first operation example are omitted.

[0095] As shown in FIG. 10, in step S201, gNB 200 broadcasts SIB type 1. SIB type 1 includes search space setting information and MBS SIB scheduling information. In the second operation example, SIB type 1 further includes an MBS control channel search space identifier. UE 100 receives SIB type 1 from gNB 200.

[0096] In step S202, UE 100 receives MBS SIB based on SIB type 1. MBS SIB includes MBS control channel scheduling information.

[0097] In the second operation example, MBS SIB does not include an MBS control channel search space identifier.

[0098] In step S203, UE 100 specifies a resource range to be decoded for receiving the MBS control channel based on the MBS control channel scheduling information received in step S202 and the MBS control channel search space identifier received in step S201.

[0099] The operations in steps S204 to S205 are the same as the operations in steps S104 to S105.

[0100] In the second operation example, the MBS control channel search space identifier may be information that is commonly applied to both the MBS SIB and the OSI. That is, the search space associated with the SI message that carries the OSI may be the same as the search space associated with the MBS control channel. In this case, in step S201, SIB type 1 may include information indicating that the search space associated with the SI message is the same as the search space associated with the MBS control channel. Such information may be notified from the gNB 200 to the UE 100 by other means.

[0101] In the second operation example, when the search space associated with the SI message that carries the OSI is the same as the search space associated with the MBS control channel and the search space associated with the SI message that carries the OSI is a specific search space, the UE 100 may skip receiving the MBS SIB (the operation in step S202). In such a case, the UE 100 can identify the resource range based on a preset rule without depending on the MBS control channel scheduling information. Therefore, in this case, the MBS control channel scheduling information is unnecessary, and the UE 100 skips receiving the MBS SIB including the MBS control channel scheduling information.

[0102] (Third operation example of the mobile communication system) Next, the third operation example of the mobile communication system 1 according to one embodiment will be mainly described with differences from the above-described first and second operation examples.

[0103] In the above-described first and second operation examples, the search space of the MBS control channel was mainly described. However, it is also assumed that a search space is allocated to the MBS traffic channel. In this third operation example, the search space of the MBS traffic channel will be described.

[0104] In this third operation example, the gNB 200 transmits, on the MBS control channel, the scheduling information of the MBS traffic channel and the search space identifier for the UE 100 to receive the MBS traffic channel. The search space identifier indicates a search space that is a resource range to be decoded by the UE 100 in a physical downlink control channel associated with the MBS traffic channel. Thereby, even when a search space is allocated to the MBS traffic channel, the UE 100 can identify the search space allocated to the MBS traffic channel.

[0105] In this operation example 3, the gNB 200 may transmit a search space identifier for each of a plurality of MBS traffic channels. That is, the gNB 200 may specify a search space for each MBS traffic channel. Thereby, since different search spaces can be allocated for each MBS traffic channel, it becomes easier to alleviate congestion in the search space.

[0106] In this operation example 3, when the MBS traffic channel is not associated with a specific search space (for example, search space "0"), the gNB 200 transmits, on the MBS control channel, the scheduling information of the MBS traffic channel and the search space identifier. When the MBS traffic channel is associated with a specific search space, the gNB 200 transmits the search space identifier without transmitting the scheduling information of the MBS traffic channel. For a specific search space, since the UE 100 can derive its scheduling and resource range by itself, the transmission of the scheduling information of the MBS traffic channel can be made unnecessary.

[0107] FIG. 11 is a diagram showing a third operation example of the mobile communication system 1. Here, descriptions overlapping with the above-described first and second operation examples are omitted.

[0108] As shown in FIG. 11, in step S301, UE 100 receives the MBS control channel. The MBS control channel carries MBS traffic channel scheduling information.

[0109] In the third operation example, the MBS control channel further carries a search space identifier (hereinafter referred to as the "MBS traffic channel search space identifier") for UE 100 to receive the MBS traffic channel. The MBS traffic channel search space identifier includes one of the search space identifiers included in the search space setting information in SIB type 1. Here, gNB 200 associates one of the plurality of search spaces set by the search space setting information in SIB type 1 with the MBS traffic channel. gNB 200 includes the search space identifier of the search space associated with the MBS traffic channel in the MBS traffic channel search space identifier.

[0110] In step S302, UE 100 specifies a resource range to be decoded in order to receive the MBS traffic channel based on the MBS traffic channel scheduling information and the MBS traffic channel search space identifier received in step S301.

[0111] In step S303, UE 100 receives the MBS traffic channel. Here, first, UE 100 performs decoding (blind decoding) on the resource range specified in step S302 to obtain the DCI carried on the PDCCH. Second, UE 100 receives the PDSCH scheduled by the DCI and receives the MBS traffic channel mapped to the PDSCH. UE 100 receives the MBS data carried by the MBS traffic channel.

[0112] In the third operation example, the MBS control channel carries MBS traffic channel scheduling information corresponding to each of a plurality of MBS traffic channels. gNB 200 may associate a different search space with each MBS traffic channel. In this case, in step S301, the MBS control channel includes, for each of the plurality of MBS traffic channels, a set of an identifier of the MBS traffic channel and an MBS traffic channel search space identifier corresponding to the MBS traffic channel. The identifier of the MBS traffic channel is a TMGI, a session identifier, or an MBS service identifier. In step S305, UE 100 identifies a resource range to be decoded in order to receive an MBS traffic channel (MBS session) of its own interest.

[0113] In the third operation example, when gNB 200 associates a specific search space with an MBS traffic channel, the MBS control channel may not transmit the MBS traffic channel scheduling information corresponding to the MBS traffic channel. Here, when the MBS traffic channel is associated with a specific search space, UE 100 can identify the resource range based on a preset rule without depending on the MBS traffic channel scheduling information. Therefore, gNB 200 does not transmit such MBS traffic channel scheduling information. In the third operation example, an example in which the MBS control channel notifies the MBS traffic channel search space identifier has been shown, but the MBS traffic channel search space identifier may be notified by SIB type 1 or an MBS SIB. In this case, it is not necessary for the MBS control channel to notify the MBS traffic channel search space identifier.

[0114] (Fourth Operation Example of Mobile Communication System) Next, the differences between the fourth operation example of the mobile communication system 1 according to an embodiment and the first to third operation examples described above will be mainly described.

[0115] In the above first to third operation examples, the operations of the gNB200 within its own cell have been mainly described. In this fourth operation example, the gNB200 also notifies the UE100 in its own cell of information regarding adjacent cells. FIG. 12 is a diagram showing an example of the operating environment in this fourth operation example. As shown in FIG. 12, gNB200A manages cell C1, gNB200B manages cell C2, and the UE100 is located in the overlapping area of cells C1 and C2. However, one gNB200 may manage cells C1 and C2.

[0116] In this fourth operation example, the gNB200 (gNB200A) that manages cell C1 transmits a notification message regarding MBS transmission in an adjacent cell C2 different from cell C1 to the UE100 in cell C1. The notification message includes a search space identifier for the UE100 to receive a predetermined channel provided in the adjacent cell C2. The predetermined channel is an MBS control channel or an MBS traffic channel provided in the adjacent cell C2. The search space identifier indicates a search space that is a resource range to be decoded by the UE100 in a physical downlink control channel associated with the predetermined channel provided in the adjacent cell C2. Thereby, the UE100 that receives the notification message from cell C1 can identify the search space of the MBS control channel or the MBS traffic channel provided in the adjacent cell C2 based on the notification message.

[0117] In this fourth operation example, when the UE100 determines, based on the search space identifier included in the notification message from cell C1, that the search space of the predetermined channel provided in the adjacent cell C2 is a specific search space (for example, search space "0"), the UE100 may omit receiving the scheduling information of the predetermined channel transmitted from the adjacent cell C2 and may also receive the predetermined channel provided in the adjacent cell C2. Thereby, the reception of the MBS control channel or the MBS traffic channel of the adjacent cell C2 can be efficiently performed.

[0118] FIG. 13 is a diagram showing a fourth operation example of the mobile communication system 1. Here, descriptions overlapping with the above-described first to third operation examples are omitted. Here, it is assumed that gNB 200A manages cell C1 and gNB 200B manages cell C2, but one gNB 200 may manage cells C1 and C2. UE 100 may be in the RRC idle state or the RRC inactive state.

[0119] As shown in FIG. 13, in step S401, gNB 200A transmits a notification message regarding MBS transmission in cell C2 in cell C1. UE 100 receives the notification message in cell C1. The notification message may be an MBS SIB. Also, the notification message may be a message transmitted on an MBS control channel.

[0120] The notification message includes a search space identifier for UE 100 to receive a predetermined channel (MBS control channel or MBS traffic channel) provided in cell C2. Such a search space identifier includes one of the search space identifiers included in the search space setting information in SIB type 1 broadcast in cell C2. Thereby, when UE 100 camping on cell C1 changes its serving cell from cell C1 to cell C2, if UE 100 only acquires SIB type 1 of cell C2, it can grasp the search space associated with the predetermined channel (MBS control channel or MBS traffic channel) of cell C2.

[0121] In step S401, gNB200A may notify the search space identifier of cell C2 in step S401 only when a specific search space (search space "0") is allocated to a predetermined channel in adjacent cell C2. Regarding the specific search space, since UE100 can derive the scheduling and resource range by itself, if it is known that it is search space "0", the reception of SIB type 1 of adjacent cell C2 can be omitted. When search space "1" is allocated to a predetermined channel in adjacent cell C2, gNB200A may not notify the search space identifier of cell C2 in step S401, but implicitly indicate that it is not search space "0".

[0122] Alternatively, in step S401, gNB200A may notify the search space identifier of cell C2 in step S401 only when a specific search space (search space "0") is not allocated to a predetermined channel in adjacent cell C2.

[0123] In step S402, UE100 determines to perform MBS reception from cell C2. For example, when UE100 reaches the cell edge of cell C1 (reception cell change at the same frequency) or when the MBS service in the current cell C1 stops due to a network setting change (reception cell change at a different frequency), UE100 may determine to perform MBS reception from cell C2.

[0124] In step S403, UE100 may receive SIB type 1 from cell C2.

[0125] In step S404, the UE 100 identifies the scheduling and resource range to be decoded for receiving a predetermined channel of the adjacent cell C2 based on the search space identifier of the adjacent cell C2 included in the notification message received in step S401. Here, if the UE 100 receives the SIB type 1 of the adjacent cell C2 in step S403, it may further identify the scheduling and resource range to be decoded for receiving a predetermined channel of the adjacent cell C2 based on the search space parameters included in the SIB type 1.

[0126] In step S405, the UE 100 receives a predetermined channel of the cell C2. Here, if the search space identifier notified in step S401 is the search space "0", the UE 100 skips receiving the MBS SIB of the adjacent cell C2 and receives the MBS control channel. Further, if possible, the UE 100 may skip receiving the MBS control channel and directly receive the MBS traffic channel. On the other hand, if the search space identifier notified in step S401 is not the search space "0", the UE 100 receives the MBS SIB of the adjacent cell C2.

[0127] In the above-described fourth operation example, it was assumed that there is one predetermined channel in the adjacent cell C2, but a plurality of predetermined channels may be provided in the adjacent cell C2. When a plurality of predetermined channels are provided in the adjacent cell C2, the notification message transmitted in step S401 may include a search space identifier for each of the plurality of predetermined channels. Thereby, even when a plurality of predetermined channels are provided in the adjacent cell C2, the UE 100 can identify the search space for receiving a desired predetermined channel.

[0128] Also, in the above-described fourth operation example, the notification message may include bandwidth part information indicating the bandwidth part in which the predetermined channel is transmitted for each of a plurality of predetermined channels in the adjacent cell C2. The bandwidth part is a part of the entire bandwidth of the adjacent cell C2. The bandwidth part may be a BWP defined in the 5G / NR specification. Also, the bandwidth part may be a CFR (Common Frequency Resource). Thereby, even when the predetermined channel is transmitted in a limited bandwidth part, the UE 100 can appropriately receive the predetermined channel. Hereinafter, an example in which the bandwidth part is a BWP (BandWidth Part) will be described.

[0129] For example, the gNB 200A includes, in the notification message (MBS SIB and / or MBS control channel) transmitted in step S401, the transmission BWP information and / or search space identifier for each MBS control channel of the adjacent cell C2. In this case, the notification message includes, for each of the plurality of MBS control channels, a set of the identifier of the MBS control channel and the search space identifier corresponding to the MBS control channel. The identifier of the MBS control channel is, for example, an MBS control channel identifier, a channel identifier assigned to the MBS control channel, or an RNTI assigned to the MBS control channel.

[0130] The gNB 200A may also include, in the notification message transmitted in step S401, the transmission BWP information and / or search space identifier for each MBS traffic channel of the adjacent cell C2. In this case, the notification message includes, for each of the plurality of MBS traffic channels, a set of the identifier of the MBS traffic channel and the search space identifier corresponding to the MBS traffic channel. The identifier of the MBS traffic channel is, for example, an MBS traffic channel identifier, a channel identifier assigned to the MBS traffic channel, or an RNTI assigned to the MBS traffic channel.

[0131] UE100 receives a notification message from gNB200A, obtains from the notification message the transmission BWP information and / or search space identifier of the MBS control channel and MBS traffic channel corresponding to the MBS service of interest in the neighboring cell C2, and identifies the transmission resources in the frequency direction and / or transmission opportunities in the time direction for which reception is to be attempted. Then, UE100 receives the MBS control channel and / or MBS traffic channel of interest on the identified resources / opportunities.

[0132] (Fifth operation example of the mobile communication system) Next, the fifth operation example of the mobile communication system 1 according to an embodiment will be mainly described with differences from the above-described first to fourth operation examples.

[0133] In the above-described first to fourth operation examples, the operations related to the identification of the search space were mainly described. In this fifth operation example, the operations related to the change notification of the MBS control channel (hereinafter referred to as "MBS control channel change notification") will be described. The MBS control channel change notification is a notification indicating that the content of the MBS control channel, that is, the scheduling information of the MBS traffic channel, has been changed.

[0134] A radio network temporary identifier (RNTI) for change notification is applied to the MBS control channel change notification. The RNTI for change notification is an RNTI used for UE100 to receive an MBS control channel change notification indicating that the content of the corresponding MBS control channel has been changed. Note that the MBS control channel change notification is assumed to be used at the start of the MBS session. In this case, the MBS control channel change notification notifies UE100 of the start of the MBS session. However, the MBS control channel change notification may also be used during the session.

[0135] When multiple MBS control channels are provided in one cell, multiple MBS control channel change notifications are also provided. However, the UE 100 cannot grasp which MBS control channel change notification corresponds to which MBS control channel, and there is a risk of receiving unnecessary MBS control channel change notifications.

[0136] In this fifth operation example, the gNB 200 that manages the cell broadcasts the MBS SIB. The gNB 200 transmits multiple MBS control channels in the cell. The MBS SIB includes a change notification RNTI for each of the multiple MBS control channels. Thereby, even when multiple MBS control channels are transmitted in the cell, the UE 100 can grasp the change notification RNTI corresponding to each of the multiple MBS control channels.

[0137] In this fifth operation example, the UE 100 selects one change notification RNTI from among the multiple change notification RNTIs included in the MBS SIB based on the MBS service received by the UE 100 among the multiple MBS control channels. Thereby, even when multiple MBS control channels are transmitted in the cell, the UE 100 can specify the change notification RNTI corresponding to the MBS control channel corresponding to the MBS service received by the UE 100.

[0138] FIG. 14 is a diagram showing a fifth operation example of the mobile communication system 1. Here, descriptions overlapping with the above-described first to fourth operation examples are omitted.

[0139] As shown in FIG. 14, in step S501, the gNB 200 broadcasts SIB type 1. The SIB type 1 includes search space setting information and MBS SIB scheduling information. The UE 100 receives the SIB type 1 from the gNB 200.

[0140] In step S502, gNB 200 broadcasts the MBS SIB based on the scheduling indicated by the MBS SIB scheduling information included in SIB type 1. UE 100 receives the MBS SIB based on the scheduling indicated by the MBS SIB scheduling information included in SIB type 1. The MBS SIB includes MBS control channel scheduling information. In this operation example 5, gNB 200 broadcasts the correspondence information between the MBS control channel and the change notification RNTI in the MBS SIB. For example, gNB 200 broadcasts a set of the change notification RNTI and the MBS session identifier (TMGI, session ID, or the RNTI of the MBS control channel) in the MBS SIB. When an ID is assigned to the MBS control channel, gNB 200 may broadcast a set of the change notification RNTI and the MBS control channel ID in the MBS SIB. UE 100 receives the MBS SIB and identifies the change notification RNTI corresponding to the MBS control channel (MBS service). Note that the MBS session may not have been started at this point.

[0141] In step S503, UE 100 performs monitoring (PDCCH monitoring) using the change notification RNTI. Here, UE 100 may monitor only the change notification RNTI associated with the MBS service of interest. Note that at this point, monitoring (PDCCH monitoring) using the MBS control channel RNTI may not be performed.

[0142] When UE 100 receives the change notification RNTI from gNB 200 (step S504), in step S505, UE 100 starts receiving the MBS control channel (monitoring the MBS control channel RNTI).

[0143] In step S506, UE 100 receives the MBS control channel from gNB 200.

[0144] In step S507, UE100 receives an MBS traffic channel from gNB200 based on the received MBS control channel.

[0145] (Other embodiments) Each of the above operation flows (each operation example) is not limited to being implemented separately and independently, and two or more operation flows (operation examples) can be combined and implemented. For example, some steps of one operation flow may be added to another operation flow. Also, some steps of one operation flow may be replaced with some steps of another operation flow.

[0146] In the above embodiment, an example where the base station is an NR base station (gNB) has been described, but the base station may be an LTE base station (eNB). Also, the base station may be a relay node such as an IAB (Integrated Access and Backhaul) node. The base station may be the DU (Distributed Unit) of the IAB node.

[0147] A program for causing a computer to execute each process performed by UE100 or gNB200 may be provided. The program may be recorded on a computer-readable medium. Using a computer-readable medium, it is possible to install the program 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, but may be, for example, a recording medium such as a CD-ROM or a DVD-ROM.

[0148] Also, a circuit for executing each process performed by UE100 or gNB200 may be integrated, and at least a part of UE100 or gNB200 may be configured as a semiconductor integrated circuit (chipset, SoC (System on a chip)).

[0149] Although the embodiments have been described in detail with reference to the drawings above, the specific configuration is not limited to the above, and various design changes and the like can be made without departing from the gist.

[0150] This application claims the priority of U.S. Provisional Application No. 63 / 169,334 (filed on April 1, 2021), and all of its contents are incorporated herein by reference.

Claims

1. A communication control method used in a mobile communication system that provides a multicast broadcast service (MBS) from a network device to a user device, comprising: the network device broadcasting an MBS system information block; the network device transmitting scheduling information of an MBS traffic channel on an MBS control channel, wherein the MBS system information block includes information regarding a search space for the user device to receive the MBS control channel, and the information regarding the search space includes information specifying a ControlResourceSetID Communication control method.

2. A user device that communicates with a network device that provides a multicast broadcast service (MBS), comprising: a receiving unit that receives an MBS system information block from the network device, wherein the receiving unit receives scheduling information of an MBS traffic channel on an MBS control channel, the MBS system information block includes information regarding a search space for the user device to receive the MBS control channel, and the information regarding the search space includes information specifying a ControlResourceSetID User device.

3. A processor that controls a user device that communicates with a network device that provides a multicast broadcast service (MBS), comprising: a process of receiving an MBS system information block from the network device; a process of receiving scheduling information of an MBS traffic channel on an MBS control channel, wherein the MBS system information block includes information regarding a search space for the user device to receive the MBS control channel, and the information regarding the search space includes information specifying a ControlResourceSetID Processor.

4. A network device that provides a multicast broadcast service (MBS) to a user device, comprising: a transmitting unit that broadcasts an MBS system information block, wherein the transmitting unit transmits scheduling information of an MBS traffic channel on an MBS control channel, The MBS system information block includes information regarding a search space for the user equipment to receive the MBS control channel. The information regarding the search space includes information specifying a Control Resource Set ID. Network device. **Claim 5** A mobile communication system for providing a multicast broadcast service (MBS) from a network device to a user equipment, wherein the network device broadcasts an MBS system information block, wherein the network device transmits scheduling information of an MBS traffic channel on an MBS control channel, wherein the MBS system information block includes information regarding a search space for the user equipment to receive the MBS control channel, wherein the information regarding the search space includes information specifying a Control Resource Set ID. Mobile communication system. **Claim 6** A program for controlling a user equipment communicating with a network device providing a multicast broadcast service (MBS), the program causing the user equipment to execute a process of receiving an MBS system information block from the network device and a process of receiving scheduling information of an MBS traffic channel on an MBS control channel, wherein the MBS information block includes information regarding a search space for the user equipment to receive the MBS control channel, wherein the information regarding the search space includes information specifying a Control Resource Set ID. Program. ​

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