Communication method, relay device, system, program, and chipset

Abstract

This communication method, which uses a relay device in a wireless communication system, comprises: a step in which a repeater included in the relay device relays a wireless signal transmitted between a base station and a user device; a step in which a control terminal included in the relay device performs wireless communication with the base station through a control link and controls the repeater; a step in which the control terminal detects that an obstacle occurs in the control link or the repeater; and a step in which the control terminal performs a prescribed control in response to the obstacle.

Description

Technical Field

[0001] The present disclosure relates to a communication method and a relay device 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 of the 5G system, enables broadband transmission in a high-frequency band compared to LTE (Long Term Evolution), which is a fourth-generation radio access technology.

[0003] Since radio signals (radio waves) in high-frequency bands such as the millimeter-wave band or the terahertz band have high directivity, reducing the coverage of base stations has become an issue. To solve such an issue, a type of repeater device that relays radio signals between a base station and a user device and can be controlled from a network has attracted attention (see, for example, Non-Patent Document 1). Such a repeater device can expand the coverage of a base station while suppressing the occurrence of interference, for example, by amplifying a radio signal received from the base station and transmitting it by directional transmission.

Prior Art Documents

Non-Patent Documents

[0004]

Non-Patent Document 1

Summary of the Invention

[0005] The communication method according to the first aspect is a communication method using a relay device in a mobile communication system, and includes steps of: a repeater included in the relay device relaying a radio signal transmitted between a base station and a user equipment; a control terminal included in the relay device performing wireless communication with the base station via a control link to control the repeater; the control terminal detecting that a failure has occurred in the control link or the repeater; and the control terminal performing predetermined control according to the failure.

[0006] The relay device according to the second aspect is a relay device used in a mobile communication system, and includes a repeater that relays a radio signal transmitted between a base station and a user equipment, and a control terminal that performs wireless communication with the base station via a control link to control the repeater. When the control terminal detects that a failure has occurred in the control link or the repeater, the control terminal performs predetermined control according to the failure.

Brief Description of Drawings

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Embodiments for Carrying Out the Invention

[0008] When controlling a relay device such as a repeater device from a network, the control technology for specifically how to control the relay device has not yet been established, and it is currently difficult to perform efficient coverage expansion using the relay device.

[0009] Therefore, an object of the present disclosure is to enable appropriate control of a relay device that performs relay transmission between a base station and a user device.

[0010] A mobile communication system according to an embodiment will be described with reference to the drawings. In the description of the drawings, the same or similar parts are denoted by the same or similar reference numerals.

[0011] (1) First Embodiment First, the first embodiment will be described. The relay device according to the first embodiment is a repeater device that can be controlled from a network.

[0012] (1.1) Overview of the Mobile Communication System FIG. 1 is a diagram showing the configuration of a mobile communication system according to the first embodiment. The mobile communication system 1 complies with the 5th Generation System (5GS) of the 3rd Generation Partnership Project (3GPP) (registered trademark; the same applies hereinafter). In the following, 5GS will be described as an example, but an LTE (Long Term Evolution) system may be at least partially applied to the mobile communication system. A 6th Generation (6G) system may be at least partially applied to the mobile communication system.

[0013] The mobile communication system 1 includes a User Equipment (UE) 100, a 5G Radio Access Network (NG-RAN) 10, and a 5G Core Network (5GC) 20. Hereinafter, NG-RAN 10 may be simply referred to as RAN 10. Also, 5GC 20 may be simply referred to as the Core Network (CN) 20.

[0014] UE 100 is a movable wireless communication device. UE 100 may be any device as long as it is a device used by a user. For example, UE 100 is a mobile phone terminal (including a smartphone) and / or a tablet terminal, a notebook PC, a communication module (including a communication card or a chipset), a sensor or a device provided in the sensor, a vehicle or a device provided in the vehicle (Vehicle UE), an aircraft or a device provided in the aircraft (Aerial UE).

[0015] NG-RAN 10 includes base stations (referred to as "gNB" in the 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 a term used to indicate the smallest unit of a wireless communication area. A "cell" is also used as a term to indicate a function or resource for performing wireless communication with the UE 100. One cell belongs to one carrier frequency (hereinafter simply referred to as "frequency").

[0016] The gNB 200 may be functionally split into a central unit (CU) and a distributed unit (DU). The CU controls the DU. The CU is a unit that includes upper layers included in the protocol stack described below, for example, the RRC layer, the SDAP layer, and the PDCP layer. The CU is connected to the core network via the NG interface, which is a backhaul interface. The CU is connected to an adjacent base station via the Xn interface, which is an interface between base stations. The DU forms a cell. The DU 202 is a unit that includes lower layers included in the protocol stack described below, for example, the RLC layer, the MAC layer, and the PHY layer. The DU is connected to the CU via the F1 interface, which is a fronthaul interface.

[0017] 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.

[0018] 5GC20 includes an AMF (Access and Mobility Management Function) and a UPF (User Plane Function) 300. The AMF performs various mobility controls and the like for the UE100. The AMF manages the mobility of the UE100 by communicating with the UE100 using NAS (Non-Access Stratum) signaling. The UPF performs data transfer control. The AMF and the UPF are connected to the gNB200 via the NG interface, which is an interface between the base station and the core network.

[0019] Figure 2 is a diagram showing the configuration of the protocol stack of the radio interface of the user plane that handles data.

[0020] 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.

[0021] The PHY layer performs encoding / decoding, modulation / demodulation, antenna mapping / demapping, and resource mapping / demapping. Between the PHY layer of the UE100 and the PHY layer of the gNB200, data and control information are transmitted via a physical channel. Note that the PHY layer of the UE100 receives downlink control information (DCI) transmitted on the physical downlink control channel (PDCCH) from the gNB200. Specifically, the UE100 performs blind decoding of the PDCCH using a radio network temporary identifier (RNTI) and acquires the DCI that has been successfully decoded as DCI addressed to itself. The DCI transmitted from the gNB200 has CRC parity bits scrambled by the RNTI added thereto.

[0022] In addition, gNB200 transmits a Synchronization Signal / PBCH block (SSB). For example, an SSB is composed of four consecutive OFDM (Orthogonal Frequency Division Multiplex) symbols, and a Primary Synchronization Signal (PSS), a Secondary Synchronization Signal (SSS), a Physical Broadcast Channel (PBCH) / Master Information Block (MIB), and a Demodulation Reference Signal (DMRS) of the PBCH are arranged. The bandwidth of the SSB is, for example, 240 consecutive subcarriers, that is, a bandwidth of 20 Resource Blocks (RBs).

[0023] The MAC layer performs priority control of data, retransmission processing by Hybrid Automatic Repeat reQuest (HARQ), and a random access procedure, etc. Between the MAC layer of UE100 and the MAC layer of gNB200, data and control information are transmitted via a transport channel. 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.

[0024] 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 a logical channel.

[0025] The PDCP layer performs header compression / expansion, encryption / decryption, etc.

[0026] The SDAP layer performs mapping between an IP flow, which is a unit for the core network to perform Quality of Service (QoS) control, and a radio bearer, which is a unit for the Access Stratum (AS) to perform QoS control. Note that when the RAN is connected to the EPC, the SDAP may not be necessary.

[0027] Figure 3 is a diagram showing the configuration of the protocol stack of the radio interface of the control plane that handles signaling (control signals).

[0028] 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 2.

[0029] Between the RRC layer of UE100 and the RRC layer of gNB200, RRC signaling for various settings is transmitted. The RRC layer controls the logical channel, transport channel, and physical channel 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.

[0030] 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 AMF300A. Note that UE100 has an application layer, etc. in addition to the protocol of the radio interface. Also, the layer below the NAS layer is called the AS layer.

[0031] (1.2) An example of the application scenario of the relay device Figures 4 and 5 are diagrams showing an example of the application scenario of the NCR device according to the first embodiment.

[0032] 5G / NR enables broadband transmission in high-frequency bands compared to 4G / LTE. Since wireless signals in high-frequency bands such as the millimeter-wave band or the terahertz band have high directivity, reducing the coverage of gNB200 becomes an issue. In Figure 4, UE100 may be located outside the coverage area of gNB200, for example, outside the area where it can directly receive wireless signals from gNB200. There may be an obstacle between gNB200 and UE100, and UE100 may not be able to communicate with gNB200 in line of sight.

[0033] As shown in Figure 4, a repeater device (500A), which is a type of relay device that relays wireless signals between gNB200 and UE100 and can be controlled from a network, is introduced into the mobile communication system 1. Hereinafter, such a repeater device is referred to as an NCR (Network-Controlled Repeater) device. Such a repeater device may also be referred to as a smart repeater device.

[0034] For example, the NCR device 500A amplifies and transmits the wireless signal (radio wave) received from gNB200 by directional transmission. Specifically, the NCR device 500A receives the wireless signal transmitted by gNB200 by beamforming. Then, the NCR device 500A amplifies the received wireless signal without demodulating and modulating it, and transmits the amplified wireless signal by directional transmission. Here, the NCR device 500A may transmit the wireless signal with a fixed directivity (beam). The NCR device 500A may also transmit the wireless signal with a variable (adaptive) directional beam. Thereby, the coverage of gNB200 can be efficiently extended. In the first embodiment, it is mainly assumed that the NCR device 500A is applied to the downlink communication from gNB200 to UE100, but the NCR device 500A can also be applied to the uplink communication from UE100 to gNB200.

[0035] Also, as shown in FIG. 5, a new UE (hereinafter referred to as "NCR-MT (Mobile termination)") 520A, which is a type of control terminal for controlling the NCR device 500A, is introduced. That is, the NCR device 500A is a type of repeater that relays radio signals transmitted between the gNB 200 and the UE 100. Specifically, it is an NCR-Fwd (Forward) 510A that changes the propagation state of the radio signal without demodulating and modulating the radio signal, and an NCR-MT 520A that performs wireless communication with the gNB 200 to control the NCR-Fwd 510A. In this way, the NCR-MT 520A controls the NCR device 500A in cooperation with the gNB 200 by establishing a wireless connection with the gNB 200 and performing wireless communication with the gNB 200. Thereby, efficient coverage expansion can be realized using the NCR device 500A. The NCR-MT 520A controls the NCR device 500A according to the control from the gNB 200.

[0036] The NCR-MT 520A may be configured separately from the NCR-Fwd 510A. For example, the NCR-MT 520A may be in the vicinity of the NCR-Fwd 510A and may be electrically connected to the NCR-Fwd 510A. The NCR-MT 520A may be connected to the NCR-Fwd 510A by wire or wirelessly. Alternatively, the NCR-MT 520A may be configured integrally with the NCR-Fwd 510A. The NCR-MT 520A and the NCR-Fwd 510A may be fixedly installed, for example, at the coverage edge (cell edge) of the gNB 200, or on the wall surface or window of some building. The NCR-MT 520A and the NCR-Fwd 510A may be installed on a vehicle or the like and may be movable. Also, one NCR-MT 520A may control a plurality of NCR-Fwd 510A.

[0037] In the example shown in FIG. 5, the NCR device 500A (NCR-Fwd510A) dynamically or quasi-statically changes the beam to be transmitted or received. For example, NCR-Fwd510A forms a beam toward each of the UEs 100a and 100b. Also, NCR-Fwd510A may form a beam toward the gNB 200. For example, NCR-Fwd510A transmits, by beamforming, a radio signal received from the gNB 200 toward the UE 100a in the communication resources between the gNB 200 and the UE 100a, and / or transmits, by beamforming, a radio signal received from the UE 100a toward the gNB 200. NCR-Fwd510A transmits, by beamforming, a radio signal received from the gNB 200 toward the UE 100b in the communication resources between the gNB 200 and the UE 100b, and / or transmits, by beamforming, a radio signal received from the UE 100b toward the gNB 200. Instead of or in addition to beam formation, NCR-Fwd510A may perform null formation (so-called null steering) toward a UE 100 (not shown) that is not a communication partner and / or an adjacent gNB 200 (not shown) for interference suppression.

[0038] FIG. 6 is a diagram showing an example of a control method of the NCR device 500A according to the first embodiment. As shown in FIG. 6, NCR-Fwd510A relays a radio signal (also referred to as a "UE signal") between the gNB 200 and the UE 100. The UE signal includes an uplink signal (also referred to as a "UE-UL signal") transmitted from the UE 100 to the gNB 200 and a downlink signal (also referred to as a "UE-DL signal") transmitted from the gNB 200 to the UE 100. NCR-Fwd510A relays the UE-UL signal from the UE 100 to the gNB 200 and relays the UE-DL signal from the gNB 200 to the UE 100. The radio link between NCR-Fwd510A and the UE 100 is also referred to as an "access link". The radio link between NCR-Fwd510A and the gNB 200 is also referred to as a "backhaul link".

[0039] The NCR-MT520A transmits and receives a wireless signal (hereinafter referred to as the "NCR-MT signal") to and from the gNB200. The NCR-MT signal includes an uplink signal (referred to as the "NCR-MT-UL signal") transmitted from the NCR-MT520A to the gNB200 and a downlink signal (referred to as the "NCR-MT-DL signal") transmitted from the gNB200 to the NCR-MT520A. The NCR-MT-UL signal includes signaling for controlling the NCR device 500A. The wireless link between the NCR-MT520A and the gNB200 is also referred to as the "control link".

[0040] Based on the NCR-MT-UL signal from the NCR-MT520A, the gNB200 directs a beam at the NCR-MT520A. Since the NCR device 500A is co-located with the NCR-MT520A, if the frequencies of the backhaul link and the control link are the same, when the gNB200 directs a beam at the NCR-MT520A, as a result, the beam will also be directed at the NCR-Fwd510A. The gNB200 uses the beam to transmit the NCR-MT-DL signal and the UE-DL signal. The NCR-MT520A receives the NCR-MT-DL signal. If the NCR-Fwd510A and the NCR-MT520A are at least partially integrated, in the NCR-Fwd510A and the NCR-MT520A, functions (such as antennas) for transmitting and receiving or relaying UE signals and / or NCR-MT signals may be integrated. Note that the beam includes a transmission beam and / or a reception beam. The beam is a general term for transmission and / or reception by control to maximize the power of the transmission wave and / or reception wave in a specific direction by adjusting / adapting antenna weights and the like.

[0041] FIG. 7 is a diagram showing a configuration example of a protocol stack in a mobile communication system 1 having an NCR device 500A according to the first embodiment. NCR-Fwd510A relays radio signals transmitted and received between gNB200 and UE100. NCR-Fwd510A has an RF (Radio Frequency) function of amplifying and relaying the received radio signals, and performs directional transmission by beamforming (for example, analog beamforming).

[0042] NCR-MT520A has at least one layer (entity) among PHY, MAC, RRC, and F1-AP (Application Protocol). F1-AP is a type of front-haul interface. NCR-MT520A exchanges downlink signaling and / or uplink signaling with gNB200 through at least one of PHY, MAC, RRC, and F1-AP. If NCR-MT520A is a type or part of a base station, NCR-MT520A may communicate with gNB200 through Xn-AP, which is an interface between base stations.

[0043] (1.3) Configuration Example of Relay Device FIG. 8 is a diagram showing a configuration example of an NCR device 500A, which is a relay device according to the first embodiment. The NCR device 500A includes an NCR-Fwd510A, an NCR-MT520A, and an interface 530.

[0044] The NCR-Fwd510A has a wireless unit 511A and an NCR control unit 512A. The wireless unit 511A has an antenna unit 511a including a plurality of antennas (a plurality of antenna elements), an RF circuit 511b including an amplifier, and a directivity control unit 511c for controlling the directivity of the antenna unit 511a. The RF circuit 511b amplifies and relays (transmits) the wireless signal transmitted and received by the antenna unit 511a. The RF circuit 511b may convert the wireless signal, which is an analog signal, into a digital signal, and then reconvert it into an analog signal after digital signal processing. The directivity control unit 511c may perform analog beamforming by analog signal processing. The directivity control unit 511c may perform digital beamforming by digital signal processing. The directivity control unit 511c may perform an analog and digital hybrid type of beamforming. The NCR control unit 512A controls the wireless unit 511A according to a control signal from the NCR-MT520A. The NCR control unit 512A may include at least one processor. The NCR control unit 512A may output information regarding the capabilities of the NCR device 500A to the NCR-MT520A.

[0045] The NCR-MT520A has a receiving unit 521, a transmitting unit 522, and a control unit 523. The receiving unit 521 performs various receptions under the control of the control unit 523. The receiving unit 521 includes an antenna and a receiver. The receiver converts a radio signal (radio signal) received by the antenna into a baseband signal (received signal) and outputs it to the control unit 523. The transmitting unit 522 performs various transmissions under the control of the control unit 523. The transmitting unit 522 includes an antenna and a transmitter. The transmitter converts a baseband signal (transmitted signal) output by the control unit 523 into a radio signal and transmits it from the antenna. The control unit 523 performs various controls in the NCR-MT520A. The control unit 523 includes at least one processor and at least one memory. The memory stores a program 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 a program stored in the memory to perform various processes. Also, the control unit 523 executes the functions of at least one layer of PHY, MAC, RRC, and F1-AP.

[0046] The interface 530 electrically connects the NCR-Fwd510A and the NCR-MT520A. The control unit 523 of the NCR-MT520A controls the NCR-Fwd510A via the interface 530.

[0047] In the first embodiment, the receiving unit 521 of the NCR-MT520A receives signaling (downlink signaling) used for the control of the NCR device 500A from the gNB200 by wireless communication. The control unit 523 of the NCR-MT520A controls the NCR device 500A based on the signaling. Thereby, the gNB200 can control the NCR-Fwd510A via the NCR-MT520A.

[0048] In the first embodiment, the control unit 523 of the NCR-MT520A may transmit NCR capability information indicating the capabilities of the NCR device 500A to the gNB200 via wireless communication. The NCR capability information is an example of uplink signaling from the NCR-MT520A to the gNB200. This enables the gNB200 to grasp the capabilities of the NCR device 500A.

[0049] (1.4) Configuration example of the base station FIG. 9 is a diagram showing a configuration example of the gNB200 according to the first embodiment. The gNB200 includes a transmission unit 210, a reception unit 220, a control unit 230, and a backhaul communication unit 240.

[0050] The transmission unit 210 performs various transmissions under the control of the control unit 230. The transmission unit 210 includes an antenna and a transmitter. The transmitter converts the baseband signal (transmission signal) output by the control unit 230 into a radio signal and transmits it from the antenna. The reception unit 220 performs various receptions under the control of the control unit 230. The reception unit 220 includes an antenna and a receiver. The receiver converts the radio signal received by the antenna into a baseband signal (reception signal) and outputs it to the control unit 230. The transmission unit 210 and the reception unit 220 may be capable of beamforming using a plurality of antennas.

[0051] The control unit 230 performs various controls in the gNB200. 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 processing by the processor. The processor may include a baseband processor and a CPU. The baseband processor performs modulation / demodulation and encoding / decoding of the baseband signal, etc. The CPU executes the programs stored in the memory to perform various processes.

[0052] 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.

[0053] In the first embodiment, the transmission unit 210 of the gNB 200 transmits, by wireless communication, signaling (downlink signaling) used for controlling the NCR-Fwd 510A to the NCR-MT 520A. As a result, the gNB 200 can control the NCR device 500A via the NCR-MT 520A. In the first embodiment, the reception unit 220 of the gNB 200 may receive, by wireless communication, NCR capability information indicating the capabilities of the NCR device 500A from the NCR-MT 520A.

[0054] (1.5) An example of downlink signaling FIG. 10 is a diagram showing an example of downlink signaling from the gNB 200 to the NCR-MT 520A according to the first embodiment.

[0055] gNB 200 (transmission unit 210) transmits downlink signaling to NCR-MT520A. The downlink signaling may be an RRC message which is signaling of the RRC layer (i.e., layer 3). The downlink signaling may be a MAC CE (Control Element) which is signaling of the MAC layer (i.e., layer 2). The downlink signaling may be downlink control information (DCI) which is signaling of the PHY layer (i.e., layer 1). The downlink signaling may be UE-specific signaling. The downlink signaling may be broadcast signaling. The downlink signaling may be a fronthaul message (e.g., an F1-AP message). If NCR-MT520A is a type or part of a base station, NCR-MT520A may communicate with gNB 200 via an Xn AP (Xn-AP) which is an interface between base stations.

[0056] For example, the gNB 200 (transmission unit 210) transmits, as downlink signaling, an NCR control signal that designates the operating state of the NCR device 500A to the NCR-MT520A that has established a radio connection with the gNB 200 (step S1A). The NCR control signal that designates the operating state of the NCR device 500A may be a MAC CE that is signaling at the MAC layer (layer 2) or DCI that is signaling at the PHY layer (layer 1). However, the NCR control signal may be included in an RRC Reconfiguration message, which is a type of UE-specific RRC message, and transmitted to the NCR-MT520A. The downlink signaling may be a message from a layer higher than the RRC layer (for example, the NCR application). The downlink signaling may encapsulate a message from a layer higher than the RRC layer and transmit it as a message from a layer below the RRC layer. Note that the NCR-MT520A (transmission unit 522) may transmit an uplink response message to the downlink signaling from the gNB 200. The response message may be transmitted in response to the NCR device 500A completing or receiving the settings specified by the downlink signaling. The NCR control signal may be referred to as Side Control Information.

[0057] The NCR control signal may include frequency control information that designates the center frequency of a radio signal (for example, a component carrier) to be relayed by the NCR-Fwd510A. When the NCR control signal received from the gNB 200 includes frequency control information, the NCR-MT520A (control unit 523) controls the NCR-Fwd510A to relay the radio signal at the center frequency indicated by the frequency control information (step S2A). The NCR control signal may include a plurality of frequency control information that designates different center frequencies. By including the frequency control information in the NCR control signal, the gNB 200 can specify, via the NCR-MT520A, the center frequency of the radio signal to be relayed by the NCR-Fwd510A.

[0058] The NCR control signal may include mode control information that specifies the operation mode of the NCR-Fwd510A. The mode control information may be associated with frequency control information (center frequency). The operation mode may be any one of a mode in which the NCR-Fwd510A performs omnidirectional transmission and / or reception, a mode in which the NCR-Fwd510A performs fixed-directional transmission and / or reception, a mode in which the NCR-Fwd510A performs transmission and / or reception using a variable-directional beam, and a mode in which the NCR-Fwd510A performs MIMO (Multiple Input Multiple Output) relay transmission. The operation mode may be any one of a beamforming mode (i.e., a mode that emphasizes desired wave improvement) and a null steering mode (i.e., a mode that emphasizes interference wave suppression). When the NCR control signal received from the gNB200 includes mode control information, the NCR-MT520A (control unit 523) controls the NCR-Fwd510A to operate in the operation mode indicated by the mode control information (step S2A). By including the mode control information in the NCR control signal, the gNB200 can specify the operation mode of the NCR-Fwd510A via the NCR-MT520A.

[0059] Here, the mode in which the NCR device 500A performs omnidirectional transmission and / or reception is a mode in which the NCR-Fwd510A performs relay in all directions, and may be referred to as an omnidirectional mode. The mode in which the NCR-Fwd510A performs transmission and / or reception with a fixed directivity may be a directive mode realized by one directive antenna. The mode may be a beamforming mode realized by applying fixed phase and amplitude control (antenna weight control) to a plurality of antennas. Any of these modes may be specified (set) by the gNB200 for the NCR-MT520A. The mode in which the NCR-Fwd510A performs transmission and / or reception with a variable directive beam may be a mode that performs analog beamforming. The mode may be a mode that performs digital beamforming. The mode may be a mode that performs hybrid beamforming. The mode may be a mode that forms an adaptive beam unique to the UE100. Any of these modes may be specified (set) by the gNB200 for the NCR-MT520A. Note that in the operation mode of performing beamforming, the beam control information described later may be provided from the gNB200 to the NCR-MT520A. The mode in which the NCR device 500A performs MIMO relay transmission may be a mode that performs SU (Single-User) spatial multiplexing. The mode may be a mode that performs MU (Multi-User) spatial multiplexing. The mode may be a mode that performs transmit diversity. Any of these modes may be specified (set) by the gNB200 for the NCR-MT520A using an NCR control signal. The operation mode may include a mode of turning on (activating) the relay transmission by the NCR-Fwd510A and a mode of turning off (deactivating) the relay transmission by the NCR-Fwd510A. Any of these modes may be specified (set) by the gNB200 for the NCR-MT520A using an NCR control signal.

[0060] The NCR control signal may include beam control information that specifies the transmission direction, transmission weight, or beam pattern when the NCR-Fwd510A performs directional transmission. The beam control information may be associated with frequency control information (center frequency). The beam control information may include a PMI (Precoding Matrix Indicator). The beam control information may include angle information for beamforming. When the NCR control signal received by the NCR-MT520A (control unit 523) from the gNB200 includes beam control information, the NCR-Fwd510A is controlled to form the transmission directivity (beam) indicated by the beam control information (step S2A). Since the NCR control signal includes beam control information, the gNB200 can control the transmission directivity of the NCR device 500A via the NCR-MT520A.

[0061] The NCR control signal may include output control information that specifies the degree of amplification (amplification gain) of the NCR-Fwd510A for amplifying a radio signal or the transmission power. The output control information may be information indicating the difference value (i.e., relative value) between the current amplification gain or transmission power and the target amplification gain or transmission power. When the NCR control signal received by the NCR-MT520A (control unit 523) from the gNB200 includes output control information, the NCR-Fwd510A is controlled to change to the amplification gain or transmission power indicated by the output control information (step S2A). The output control information may be associated with frequency control information (center frequency). The output control information may be information specifying any one of the amplifier gain, beamforming gain, and antenna gain of the NCR-Fwd510A. The output control information may be information specifying the transmission power of the NCR-Fwd510A.

[0062] When one NCR-MT520A controls a plurality of NCR-Fwd510A, the gNB200 (transmission unit 210) may transmit an NCR control signal to the NCR-MT520A for each NCR-Fwd510A. In this case, the NCR control signal may include an identifier of the corresponding NCR-Fwd510A (NCR identifier). The NCR-MT520A (control unit 523) that controls a plurality of NCR-Fwd510A determines the NCR-Fwd510A to which the NCR control signal is to be applied based on the NCR identifier included in the NCR control signal received from the gNB200. Note that even when the NCR-MT520A controls only one NCR-Fwd510A, the NCR identifier may be transmitted from the NCR-MT520A to the gNB200 together with the NCR control signal.

[0063] In this way, the NCR-MT520A (control unit 523) controls the NCR-Fwd510A based on the NCR control signal from the gNB200. Thereby, the gNB200 can control the NCR-Fwd510A via the NCR-MT520A.

[0064] (1.6) An example of uplink signaling FIG. 11 is a diagram showing an example of uplink signaling from the NCR-MT520A to the gNB200 according to the first embodiment.

[0065] The NCR-MT520A (transmission unit 210) transmits uplink signaling to the gNB 200. The uplink signaling may be an RRC message, which is signaling at the RRC layer. The uplink signaling may be a MAC CE, which is signaling at the MAC layer. The uplink signaling may be uplink control information (UCI), which is signaling at the PHY layer. The uplink signaling may be a fronthaul message (e.g., an F1-AP message). The uplink signaling may be an inter-base station message (e.g., an Xn-AP message). The uplink signaling may be a message from a layer higher than the RRC layer (e.g., an NCR application). The uplink signaling may encapsulate a message from a layer higher than the RRC layer and transmit it as a message from a layer below the RRC layer. That is, the uplink signaling stores a higher-layer message in a lower-layer container. Note that the gNB 200 (transmission unit 210) may transmit a response message to the uplink signaling from the NCR-MT520A on the downlink, and the NCR-MT520A (reception unit 521) may receive the response message.

[0066] For example, the NCR-MT520A (transmission unit 522) that has established a radio connection with the gNB 200 transmits NCR capability information indicating the capabilities of the NCR device 500A to the gNB 200 as uplink signaling (step S5A). The NCR-MT520A (transmission unit 522) may transmit the NCR capability information to the gNB 200 by including it in a UE Capability message or a UE Assistant Information message, which are types of RRC messages. The NCR-MT520A (transmission unit 522) may transmit the NCR capability information (NCR capability information and / or operating state information) to the gNB 200 in response to a request or inquiry from the gNB 200.

[0067] The NCR capability information may include corresponding frequency information indicating the frequencies supported by NCR-Fwd510A. The corresponding frequency information may be a numerical value or index indicating the center frequency of the frequencies supported by NCR-Fwd510A. The corresponding frequency information may also be a numerical value or index indicating the range of the frequencies supported by NCR-Fwd510A. When the NCR capability information received from NCR-MT520A by gNB200 (control unit 230) includes corresponding frequency information, gNB200 (control unit 230) can grasp the frequencies supported by NCR-Fwd510A based on the corresponding frequency information. Then, gNB200 (control unit 230) may set the center frequency of the radio signal targeted by NCR device 500A within the range of the frequencies supported by NCR-Fwd510A.

[0068] The NCR capability information may include mode capability information regarding the operation modes supported by the NCR-Fwd510A or the switching between operation modes. As described above, the operation modes may include at least one of the following modes: a mode in which the NCR-Fwd510A performs omnidirectional transmission and / or reception, a mode in which the NCR-Fwd510A performs fixed-directional transmission and / or reception, a mode in which the NCR-Fwd510A performs transmission and / or reception using a variable-directional beam, and a mode in which the NCR-Fwd510A performs MIMO (Multiple Input Multiple Output) relay transmission. The operation mode may be either a beamforming mode (i.e., a mode that emphasizes improving the desired wave) or a null steering mode (i.e., a mode that emphasizes suppressing interference waves). The mode capability information may indicate which of these operation modes the NCR-Fwd510A is capable of supporting. The mode capability information may also indicate which of these operation modes can be switched between. When the NCR capability information received from the NCR-MT520A includes mode capability information, the gNB200 (control unit 230) can determine the operation mode and mode switching supported by the NCR-Fwd510A based on the mode capability information. Then, the gNB200 (control unit 230) may set the operation mode of the NCR-Fwd510A within the determined operation mode and mode switching range.

[0069] The NCR capability information may include beam capability information indicating the beam variable range, beam variable resolution, or the number of variable patterns when the NCR-Fwd510A performs transmission and / or reception using a variable directional beam. The beam capability information may be, for example, information indicating the variable range of the beam angle (e.g., controllable within 30° to 90°) based on the horizontal direction or the vertical direction. The beam capability information may be information indicating the absolute angle. The beam capability information may be represented by the azimuth and / or elevation angle at which the beam is directed. The beam capability information may be information indicating the angle change for each variable step (e.g., 5° / step horizontally, 10° / step vertically). The beam capability information may be information indicating the number of variable steps (e.g., 10 steps horizontally, 20 steps vertically). The beam capability information may be information indicating the number of variable patterns of the beam in the NCR-Fwd510A (e.g., a total of 10 patterns from beam pattern 1 to 10). When the NCR capability information received from the NCR-MT520A by the gNB200 (control unit 230) includes the beam capability information, the gNB200 can grasp the beam angle change or beam pattern that the NCR-Fwd510A can support based on the beam capability information. Then, the gNB200 (control unit 230) may set the beam of the NCR-Fwd510A within the grasped range of the beam angle change or beam pattern. These beam capability information may be null capability information. In the case of null capability information, these beam capability information indicate the null control capability when null steering is performed.

[0070] The NCR capability information may include control delay information indicating the control delay time in the NCR device 500A. For example, the control delay information is the delay time (e.g., 1 ms, 10 ms, etc.) from the timing when the UE100 receives the NCR control signal or the timing when the completion of the setting for the NCR control signal is transmitted to the gNB200 until the control (change of the operation mode, and / or change of the beam) according to the NCR control signal is completed. When the NCR capability information received from the NCR-MT520A by the gNB200 (control unit 230) includes the control delay information, the gNB200 can grasp the control delay time in the NCR-Fwd510A based on the control delay information.

[0071] The NCR capability information may include amplification characteristic information regarding the amplification characteristics or output power characteristics of the radio signal in the NCR-Fwd510A. The amplification characteristic information may be information indicating the amplifier gain (dB), beamforming gain (dB), and antenna gain (dBi) of the NCR-Fwd510A. The amplification characteristic information may be information indicating the variable amplification range (e.g., 0 dB to 60 dB) in the NCR-Fwd510A. The amplification characteristic information may be information indicating the number of steps of the variable amplification degree (e.g., 10 steps) that the NCR-Fwd510A can change, or the amplification degree per variable step (e.g., 10 dB / step). The amplification characteristic information may be information indicating the variable range of the output power (e.g., 0 dBm to 30 dBm) of the NCR-Fwd510A. The amplification characteristic information may be information indicating the number of steps of the output power that the NCR-Fwd510A can change (e.g., 10 steps), or the output power per variable step (e.g., 10 dBm / step, or 10 dB / step).

[0072] The NCR capability information may include position information indicating the installation position of the NCR device 500A. The position information may include any one or more of latitude, longitude, and altitude. The position information may include information indicating the distance and / or installation angle of the NCR device 500A with respect to the gNB 200. The installation angle may be a relative angle with respect to the gNB 200, or may be a relative angle with respect to, for example, north, vertical, or horizontal. The installation position may be the position information of the location where the antenna unit 511a of the NCR-Fwd510A is installed.

[0073] The NCR capability information may include antenna information indicating the number of antennas of the NCR-Fwd510A. The antenna information may be information indicating the number of antenna ports of the NCR-Fwd510A. The antenna information may be information indicating the degree of freedom of directivity control (beam or null formation). The degree of freedom indicates how many beams can be formed (controlled), and is usually "(number of antennas)-1". For example, in the case of two antennas, the degree of freedom is 1. In the case of two antennas, a figure-eight beam pattern is formed, but since directivity control can be performed in only one direction, the degree of freedom is 1.

[0074] When the NCR-MT520A controls a plurality of NCR-Fwd510A, the NCR-MT520A (transmission unit 522) may transmit the NCR capability information to the gNB200 for each NCR-Fwd510A. In this case, the NCR capability information may include the number of NCR-Fwd510A and / or the identifier of the corresponding NCR-Fwd510A (NCR identifier). Also, when the NCR-MT520A controls a plurality of NCR-Fwd510A, the NCR-MT520A (transmission unit 522) may transmit information indicating at least one of the identifiers of the plurality of NCR-Fwd510A and the number of the plurality of NCR-Fwd510A. Note that the NCR identifier may be transmitted from the NCR-MT520A to the gNB200 together with the NCR capability information even when the NCR-MT520A controls only one NCR-Fwd510A.

[0075] (1.7) An example of the overall operation sequence FIG. 12 is a diagram showing an example of the overall operation sequence of the mobile communication system 1 according to the first embodiment. In the sequence diagrams referred to in the following embodiments, steps that are not essential are shown by broken lines. Although details will be described later, "NCR" in FIG. 12 may be read as "RIS".

[0076] In step S11, gNB 200 (transmission unit 210) broadcasts NCR support information indicating that gNB 200 supports NCR-MT520A. For example, gNB 200 (transmission unit 210) broadcasts a system information block (SIB) including the NCR support information. The NCR support information may be information indicating that NCR-MT520A is accessible. Alternatively, gNB 200 (transmission unit 210) may broadcast NCR non-support information indicating that gNB 200 does not support NCR-MT520A. The NCR non-support information may be information indicating that NCR-MT520A is inaccessible.

[0077] At this stage, NCR-MT520A may be in the RRC idle state or the RRC inactive state. NCR-MT520A (control unit 523) that has not established a radio connection with gNB 200 may determine that access to the gNB 200 is permitted in response to receiving the NCR support information from the gNB 200, and may perform an access operation to establish a radio connection with the gNB 200. NCR-MT520A (control unit 523) may perform cell reselection considering the gNB 200 (cell) that permits access as having the highest priority.

[0078] On the other hand, NCR-MT520A (control unit 523) that has not established a radio connection with gNB 200 may determine that access (connection establishment) to the gNB 200 is not possible when the gNB 200 is not broadcasting the NCR support information (or when broadcasting the NCR non-support information). Thereby, NCR-MT520A can establish a radio connection only with a gNB 200 that can handle NCR-MT520A.

[0079] In addition, when gNB200 is congested, gNB200 may broadcast access control information for restricting access from UE100. However, different from a normal UE100, NCR-MT520A can also be regarded as an entity on the network side. Therefore, NCR-MT520A may ignore the access control information from gNB200. For example, when NCR-MT520A (control unit 523) receives NCR support information from gNB200, even if the gNB200 is broadcasting access control information, it may perform operations for establishing a radio connection with the gNB200. For example, NCR-MT520A (control unit 523) may not execute (or may ignore) UAC (Unified Access Control). Alternatively, for either one or both of AC / AI (Access Category / Access Identity) used in UAC, special values indicating that it is an access of NCR-MT may be used.

[0080] In step S12, NCR-MT520A (control unit 523) starts a random access procedure for gNB200. In the random access procedure, NCR-MT520A (transmission unit 522) transmits a random access preamble (Msg1) and an RRC message (Msg3) to gNB200. Also, in the random access procedure, NCR-MT520A (reception unit 521) receives a random access response (Msg2) and an RRC message (Msg4) from gNB200.

[0081] In step S13, when establishing a radio connection with gNB200, NCR-MT520A (transmission unit 522) may send NCR-MT information indicating that the own UE is an NCR-MT to gNB200. For example, during the random access procedure with gNB200, NCR-MT520A (transmission unit 522) includes the NCR-MT information in a message for the random access procedure (e.g., Msg1, Msg3, Msg5) and sends it to gNB200. Based on the NCR-MT information received from NCR-MT520A, gNB200 (control unit 230) recognizes that the accessed UE100 is NCR-MT520A. gNB200 (control unit 230) can, for example, remove NCR-MT520A from the access restriction target (i.e., accept access). When the random access procedure is completed, NCR-MT520A transitions from the RRC idle state or the RRC inactive state to the RRC connected state.

[0082] In step S14, gNB200 (transmission unit 522) sends a capability inquiry message for inquiring about the capabilities of NCR-MT520A to NCR-MT520A. NCR-MT520A (reception unit 521) receives the capability inquiry message.

[0083] In step S15, NCR-MT520A (transmission unit 522) sends a capability information message including NCR capability information to gNB200. The capability information message may be an RRC message, for example, a UE Capability message. gNB200 (reception unit 220) receives the capability information message. Based on the received capability information message, gNB200 (control unit 230) grasps the capabilities of NCR device 500A.

[0084] In step S16, the gNB 200 (transmission unit 522) transmits a configuration message including various configurations related to the NCR device 500A to the NCR-MT 520A. The NCR-MT 520A (reception unit 521) receives the configuration message. The configuration message is a type of the above-described downlink signaling. The configuration message may be an RRC message, for example, an RRC Reconfiguration message.

[0085] In step S17, the gNB 200 (transmission unit 522) transmits a control instruction specifying the operating state of the NCR-Fwd 510A to the NCR-MT 520A. The control instruction may be the above-described NCR control signal (for example, L1 / L2 signaling). The NCR-MT 520A (reception unit 521) receives the control instruction. The NCR-MT 520A (control unit 523) controls the NCR-Fwd 510A according to the control instruction.

[0086] In step S18, the NCR-MT 520A controls the NCR device 500A according to the above configuration (and control instruction). Note that the NCR-MT 520A may control the NCR device 500A autonomously without depending on the control instruction from the gNB 200. For example, the NCR-MT 520A may control the NCR device 500A autonomously based on the position of the UE 100 and / or the information received by the NCR-MT 520A from the UE 100.

[0087] (1.8) Beam sweeping FIG. 13 is a diagram for explaining beam sweeping according to an embodiment.

[0088] gNB 200 performs beam sweeping in which it sequentially switches beams in different directions while transmitting. At this time, gNB 200 transmits different SSBs for each beam. The SSB is periodically transmitted from gNB 200 into the cell as an SSB burst composed of a plurality of SSBs. Each of the plurality of SSBs in one SSB burst is assigned an SSB index which is an identifier. The SSBs are transmitted with beamforming in different directions respectively. The NCR device 500A (NCR-MT520A) reports to gNB 200 during the random access channel (RACH) procedure which direction of the beam had good reception quality. Specifically, the NCR device 500A (NCR-MT520A) transmits a random access preamble to gNB 200 in a random access channel (RACH) occasion associated with the SSB index for which the reception quality of the beam was good. As a result, gNB 200 can grasp the optimal beam for the NCR device 500A (NCR-MT520A).

[0089] Note that such an SSB may be transmitted in the initial BWP (initial DL BWP). When the NCR device 500A (NCR-MT520A) is in the RRC connected state, a dedicated BWP may be set and activated for the NCR device 500A (NCR-MT520A). In the dedicated BWP, a channel state information reference signal (CSI-RS) may be used as a reference signal instead of the SSB. In the following, on the premise that there is a one-to-one relationship between the beam and the SSB (specifically, the SSB index), an example in which the beam information for identifying the beam is the SSB index will be mainly described. However, the beam may be associated with the CSI-RS. The beam information for identifying the beam may be the CSI-RS index.

[0090] (1.9) Carrier Aggregation and Dual Connectivity As will be described in the embodiments below, in the embodiments, the gNB 200 can set a plurality of serving cells for the NCR device 500A (NCR-MT520A) by means of carrier aggregation (CA) or dual connectivity (DC). Prior to the description of such operations, general CA and DC will be described.

[0091] FIG. 14 is a diagram for explaining CA. In CA, a plurality of component carriers (CCs) corresponding to a plurality of serving cells are aggregated, and the UE 100 can receive or transmit simultaneously on the plurality of CCs. The plurality of CCs may be continuous in the frequency direction. The plurality of CCs may be discontinuous.

[0092] When CA is set, there is only one RRC connection to the network (for example, the gNB 200) for the UE 100. In the establishment / re-establishment / handover of the RRC connection, one serving cell provides NAS mobility information, and in the re-establishment / handover of the RRC connection, one serving cell provides security input. The one serving cell is referred to as the primary cell (PCell). By setting a secondary cell (SCell) for the UE 100 together with the PCell, a set of serving cells can be formed. Therefore, the set of serving cells set for the UE 100 always consists of one PCell and one or more SCells. The reconfiguration, addition, and deletion of the SCell can be executed by RRC. Note that the primary cell is an MCG cell operating on the primary frequency where the UE 100 executes the initial connection establishment procedure or starts the connection re-establishment procedure. When the UE 100 receives an RRCSetup message from a cell in the initial connection establishment procedure, the UE 100 regards the cell as the primary cell.

[0093] FIG. 15 is a diagram for explaining DC. In DC, the UE 100 communicates with a master cell group (MCG) 201M managed by a master node (MN) 200M and a secondary cell group (SCG) 201S managed by a secondary node (SN) 200S. The MN 200M and the SN 200S are connected to each other via a network interface (specifically, an interface between base stations). The network interface may be an Xn interface or an X2 interface. Note that the MN 200M may be referred to as a master base station, and the SN 200S may be referred to as a secondary base station. In the following description of the embodiments, an example in which both the MN 200M and the SN 200S are gNBs 200 will be described, but at least one of the MN 200M and the SN 200S may be an LTE base station (eNB).

[0094] For example, DC is started when the MN 200M transmits a predetermined message (e.g., an SN Addition Request message) to the SN 200S and the MN 200M transmits an RRC reconfiguration (RRC Reconfiguration) message to the UE 100. In DC, the UE 100 in the RRC connected state has radio resources allocated from the schedulers of the MN 200M and the SN 200S respectively, and performs radio communication using the radio resources of the MN 200M and the radio resources of the SN 200S.

[0095] The MN200M may have a control plane connection with the core network. The MN200M provides the main radio resources of the UE100. The MN200M manages the MCG201M. The MCG201M is a group of serving cells associated with the MN200M. The MCG201M has a primary cell (PCell) and optionally one or more secondary cells (SCells). On the other hand, the SN200S may not have a control plane connection with the core network. The SN200S provides additional radio resources to the UE100. The SN200S manages the SCG201S. The SCG201S has a primary-secondary cell (PSCell) and optionally one or more SCells. Note that the PCell of the MCG201M and the PSCell of the SCG201S may be referred to as a special cell (SpCell).

[0096] (1.10) Operation of Relay Device Using Multiple Serving Cells The operation of a relay device (NCR device 500A) using multiple serving cells will be described. FIG. 16 is a diagram showing a configuration example when CA is set in the NCR device 500A (NCR-MT520A).

[0097] In the embodiment, the frequencies of the control link (i.e., the radio link between the NCR-MT520A and the gNB200) and the backhaul link (i.e., the radio link between the NCR-Fwd510A and the gNB200) are the same. This frequency is also referred to as the "predetermined frequency". Thereby, the channel states can be aligned in the control link and the backhaul link, and the simplification of the control of the NCR-Fwd510A can be realized. For example, based on the channel state information (CSI) feedback transmitted from the NCR-Fwd510A to the gNB200, the gNB200 can grasp the channel state of the backhaul link and perform appropriate beamforming and link adaptation (such as determination of MCS) for the backhaul link.

[0098] Therefore, when setting multiple serving cells in the NCR device 500A (NCR-MT520A), the gNB 200 sets the cell C2 corresponding to the frequency of the radio signal relayed by the NCR-Fwd510A (from another perspective, a component carrier) in the NCR device 500A (NCR-MT520A). This frequency is also referred to as the "operating frequency of the NCR-Fwd510A". The serving cell C2 is used for the control link and the backhaul link. The NCR-MT520A communicates with the gNB 200 via the control link in layer 1 and / or layer 2 (L1 / L2).

[0099] Here, the frequency of the serving cell C2 may be a frequency in the millimeter wave band (also referred to as "FR (Frequency Range) 2"). In such a high frequency band, it is difficult to achieve stable wireless communication. Therefore, in the embodiment, by setting a serving cell C1 with a different frequency from the serving cell C2 in the NCR device 500A (NCR-MT520A), it is possible to provide the RRC connection belonging to layer 3 (L3) at a different frequency. Thereby, the control link and the RRC connection can be separated. The serving cell C1 may be a frequency lower than the frequency of the serving cell C2, for example, a frequency in the Sub-6 band (also referred to as "FR1"). In the embodiment, the serving cell C1 is a primary cell, and the serving cell C2 is a secondary cell. Thereby, while stabilizing the RRC connection of the NCR-MT520A, simplification of the control of the NCR-Fwd510A can be realized.

[0100] FIG. 17 is a diagram showing a configuration example when DC is set in the NCR device 500A (NCR-MT520A).

[0101] In the case of DC, the serving cell C1 is provided in the MN (gNB) 200M, and the serving cell C2 is provided in the SN (gNB) 200S. For example, the serving cell C1 is a primary cell belonging to the MCG 201M of the MN 200M. The serving cell C2 is a secondary cell belonging to the SCG 201S of the SN 200S.

[0102] In this way, in the embodiment, NCR-Fwd510A relays a radio signal of a predetermined frequency transmitted between gNB200 and UE100. NCR-MT520A performs wireless communication with gNB200 to control NCR-Fwd510A. A plurality of serving cells including cell C1 corresponding to the predetermined frequency are set for NCR-MT520A by gNB200. Thereby, the channel states can be aligned on the control link and the backhaul link, and simplification of the control of NCR-Fwd510A can be realized. In the embodiment, cell C2 corresponding to the predetermined frequency is a secondary cell. Note that the secondary cell may be a primary / secondary cell (PSCell) in DC.

[0103] The secondary cell may be inactive (i.e., not used for communication) at the time of being set. NCR-MT520A having the secondary cell set may receive an activation instruction for activating the secondary cell from gNB200. In response to the reception of the activation instruction, NCR-MT520A may activate the operation of NCR-Fwd510A, that is, put it in a state where it can be used for relaying. Thereby, since the operation of NCR-Fwd510A can also be in an inactive state while the secondary cell is in an inactive state, power consumption by NCR-Fwd510A and the occurrence of unexpected interference can be suppressed.

[0104] NCR-MT520A may receive a deactivation instruction for deactivating the secondary cell from gNB200. In response to the reception of the activation instruction, NCR-MT520A may deactivate the operation of NCR-Fwd510A.

[0105] In the case of DC, MN200M may transmit information regarding NCR device 500A to SN200S on the network interface (interface between base stations). For example, MN200M may transmit information indicating that it is an SCG addition for NCR device 500A to SN200S at the time of SN Addition. MN200M may transmit the cell ID associated with NCR-Fwd510A (i.e., the cell identifier of cell C2) to SN200S. This facilitates the realization of the operation as shown in FIG. 17.

[0106] In the embodiment, a primary cell is used for the RRC connection between gNB200 and NCR-MT520A. A secondary cell is used for the control link between gNB200 and NCR-MT520A. This makes it possible to use different frequencies for the control link and the RRC connection (i.e., separate the control link and the RRC connection).

[0107] NCR-MT520A may receive an RRC message from gNB200 that includes configuration information for configuring a secondary cell. The configuration information may include information associating the secondary cell with NCR-Fwd510A. This makes it possible to explicitly specify the NCR-Fwd510A associated with the secondary cell even when, for example, NCR device 500A has a plurality of NCR-Fwd510A.

[0108] NCR-MT520A may receive from gNB200 a control signal (i.e., the above-described NCR control signal) for controlling NCR-Fwd510A via the control link. The NCR control signal may include identification information for identifying NCR-Fwd510A. This makes it possible to explicitly specify the NCR-Fwd510A to be controlled even when, for example, NCR device 500A has a plurality of NCR-Fwd510A.

[0109] (1.10.1) First operation example using a plurality of serving cells in a relay device FIG. 18 is a diagram showing a first operation example of using a plurality of serving cells by CA in the NCR device 500A.

[0110] In step S101, the NCR-MT520A establishes an RRC connection with the gNB200 and enters the RRC connected state. A primary cell (serving cell C1) of the gNB200 is assigned to the NCR-MT520A. Note that the NCR-MT520A may transmit the above-described NCR capability information to the gNB200. The NCR capability information may include information indicating support for control of the NCR-Fwd510A by a secondary cell.

[0111] In step S102, the gNB200 performs CA configuration for the NCR-MT520A. For example, the gNB200 transmits an RRC message (e.g., an RRC Reconfiguration message) including CA configuration information to the NCR-MT520A on the primary cell (serving cell C1). The NCR-MT520A receives the CA configuration information. The CA configuration information includes information associating the secondary cell (serving cell C2) to be configured in the NCR-MT520A with the NCR-Fwd510A. For example, the CA configuration information may include at least one list of a set of an identifier of the secondary cell (serving cell C2) and an identifier of the NCR-Fwd510A. The CA configuration information may include information indicating which secondary cell (serving cell C2) is to control the NCR-MT520A (i.e., establish a control link).

[0112] In step S103, the gNB200 transmits an activation instruction for the secondary cell to the NCR-MT520A. For example, the gNB200 transmits a MAC CE including the activation instruction to the NCR-MT520A on the primary cell (serving cell C1). The NCR-MT520A receives the activation instruction. The activation instruction may include an identifier of the secondary cell to be activated.

[0113] In step S104, in response to receiving the activation instruction, NCR-MT520A activates the secondary cell (serving cell C2) set in step S102. Further, NCR-MT520A may activate NCR-Fwd510A. When activating the secondary cell (serving cell C2), NCR-MT520A starts beam selection and CSI feedback in the secondary cell (serving cell C2). Note that the activation instruction for the secondary cell and the activation instruction for NCR-Fwd510A may be different signaling. In this case, NCR-MT520A may activate the secondary cell when receiving the activation instruction for the secondary cell, and may activate NCR-Fwd510A when receiving the activation instruction for NCR-Fwd510A.

[0114] In step S105, gNB200 transmits an NCR control signal (L1 / L2 signal) to NCR-MT520A on the control link in the secondary cell (serving cell C2). NCR-MT520A receives the NCR control signal (L1 / L2 signal). The NCR control signal may include an identifier of NCR-Fwd510A.

[0115] In step S106, NCR-MT520A controls NCR-Fwd510A according to the NCR control signal received in step S105.

[0116] Thereafter, in step S107, gNB200 transmits a deactivation instruction for the secondary cell to NCR-MT520A. For example, gNB200 transmits a MAC CE including the deactivation instruction to NCR-MT520A on the primary cell (serving cell C1) or the secondary cell (serving cell C2). NCR-MT520A receives the deactivation instruction. The deactivation instruction may include an identifier of the secondary cell to be deactivated.

[0117] In step S108, in response to receiving the deactivation instruction, NCR-MT520A deactivates the secondary cell (serving cell C2) activated in step S104. Also, NCR-MT520A may deactivate NCR-Fwd510A. When deactivating the secondary cell (serving cell C2), NCR-MT520A terminates beam selection and CSI feedback in the secondary cell (serving cell C2). Note that the deactivation instruction for the secondary cell and the deactivation instruction for NCR-Fwd510A may be different signaling. In this case, NCR-MT520A may deactivate the secondary cell when receiving the deactivation instruction for the secondary cell, and deactivate NCR-Fwd510A when receiving the deactivation instruction for NCR-Fwd510A.

[0118] FIG. 19 is a diagram showing a first operation example of using a plurality of serving cells by DC in the NCR device 500A. Duplicate descriptions for operations similar to those in the above-described CA case are omitted.

[0119] In step S201, NCR-MT520A establishes an RRC connection with MN200M (gNB200) and enters the RRC connected state. A primary cell (serving cell C1) of MN200M is allocated to NCR-MT520A. Note that NCR-MT520A may transmit the above-described NCR capability information to gNB200. The NCR capability information may include information indicating support for the control of NCR-Fwd510A by a secondary cell. Prior to step S202, an SN Addition Required message for requesting that SN addition is necessary may be transmitted from SN200S to MN200M. The message may include information indicating that NCR addition is requested. In response to receiving the message, MN200M may execute step S202.

[0120] In step S202, MN200M transmits an SN Addition Request message to SN200S on the inter-base station interface. SN200S receives the SN Addition Request message. The SN Addition Request message may include information indicating that it is for SCG addition for controlling the NCR device 500A. The SN Addition Request message may include information for associating NCR-Fwd510A with the secondary cell. For example, the SN Addition Request message may include a list containing at least one set of the identifier of NCR-Fwd510A, the identifier of the NCR device 500A, and / or the identifier of NCR-MT520A and the cell ID. The SN Addition Request message may include a list containing at least one set of the identifier of NCR-Fwd510A, the identifier of the NCR device 500A, and / or the identifier of NCR-MT520A and the frequency identifier.

[0121] In step S203, SN200S transmits an SN Addition Request Acknowledge message including an RRC Reconfiguration (RRC container) to be transmitted to NCR-MT520A to MN200M on the inter-base station interface. MN200M receives the SN Addition Request Acknowledge message. The RRC Reconfiguration (RRC container) includes DC setting information. The DC setting information includes information for associating the secondary cell (serving cell C2) to be set in NCR-MT520A with NCR-Fwd510A. For example, the DC setting information may include a list containing at least one set of the identifier of the secondary cell (serving cell C2) and the identifier of NCR-Fwd510A. The DC setting information may include information indicating which secondary cell (serving cell C2) is used to control NCR-MT520A (i.e., establish a control link). The DC setting information may include information indicating the operating frequency of NCR-Fwd510A.

[0122] In step S204, MN200M transmits the RRC Reconfiguration (DC configuration information) included in the SN Addition Request Acknowledge message received in step S203 to NCR-MT520A.

[0123] The operations in steps S205 to S210 are the same as the operations in steps S103 to S108 in FIG. 18. However, the activation instruction / deactivation instruction for the secondary cell may be transmitted from SN200S to NCR-MT520A. Note that prior to step S205 or S209, SN200S may transmit a message requesting activation or deactivation of NCR to MN200M. In response to receiving the message, MN200M may execute step S205 or S209. Also, SN200S may request MN200M to cancel (Remove) the NCR setting. In response to receiving the request, MN200M may transmit an SN Removal Request message to SN200S. The message may be a message for removing the setting of the NCR device 500A. For example, the message may be a message for removing the setting of NCR-Fwd510A.

[0124] (1.10.2) Second operation example using a plurality of serving cells in a relay device This operation example is an operation example related to a secondary cell deactivation timer (also referred to as "sCellDeactivationTimer"). sCellDeactivationTimer is a timer that gNB200 sets for UE100 in association with the secondary cell. sCellDeactivationTimer is a timer for deactivating the secondary cell in response to the fact that the time without data communication in the secondary cell continues for a predetermined time, and is used to measure the predetermined time. Thereby, it becomes possible to spontaneously deactivate an unused secondary cell.

[0125] FIG. 20 is a diagram for explaining the sCellDeactivationTimer. "A" to "C" in FIG. 20 show the content described in the 3GPP technical specification "TS38.321" (i.e., the MAC protocol specification), and "D" in FIG. 20 shows the content described in the 3GPP technical specification "TS38.331" (i.e., the RRC protocol specification).

[0126] As shown in "A" of FIG. 20, the UE 100 with the sCellDeactivationTimer set deactivates the secondary cell (SCell) associated with the sCellDeactivationTimer in response to the expiration of the sCellDeactivationTimer. Note that the sCellDeactivationTimer can be set individually for each secondary cell (SCell).

[0127] As shown in "B" of FIG. 20, the UE 100 with the sCellDeactivationTimer set starts or restarts the sCellDeactivationTimer in response to the activation of the secondary cell (SCell) associated with the sCellDeactivationTimer.

[0128] As shown in "C" of FIG. 20, the UE 100 with the sCellDeactivationTimer set restarts the sCellDeactivationTimer in response to receiving a DCI for resource allocation, specifically a DL assignment or UL grant, on the PDCCH of the secondary cell (SCell) associated with the sCellDeactivationTimer or the PDCCH of the serving cell that schedules the secondary cell (SCell). Also, the UE 100 restarts the sCellDeactivationTimer in response to receiving or transmitting data (MAC PDU) on the downlink or uplink resources pre-allocated by the configured grant.

[0129] As shown in "D" of FIG. 20, when the sCellDeactivationTimer is not set for the secondary cell, the UE 100 applies infinity as the timer value of the sCellDeactivationTimer for the secondary cell.

[0130] Assuming the operation of FIG. 20, when controlling the NCR-MT520A in the secondary cell (serving cell C2), that is, when providing a control link of the NCR-MT520A to the secondary cell (serving cell C2), there are the following problems. Specifically, if the sCellDeactivationTimer is set for the secondary cell (serving cell C2), there is a concern that the secondary cell (serving cell C2) may be deactivated due to the expiration of the sCellDeactivationTimer. For example, when the NCR control signal received on the control link is a MAC CE, or when the NCR control signal received on the control link is a non-scheduling DCI, it is considered that the NCR-MT520A does not restart the sCellDeactivationTimer in response to the reception of the NCR control signal. Therefore, a problem may occur in which the secondary cell (serving cell C2) is deactivated and the control of the NCR device 500A (NCR-MT520A) is interrupted.

[0131] Therefore, the gNB200 that sets the secondary cell (serving cell C2) associated with NCR-Fwd510A to NCR-MT520A does not set the sCellDeactivationTimer for the secondary cell. That is, the gNB200 avoids setting the SCell deactivation timer for the secondary cell that forms the control link of NCR-Fwd510A (setting the sCellDeactivationTimer for the secondary cell is prohibited). As a result, NCR-MT520A can prevent the secondary cell (serving cell C2) from being deactivated by the sCellDeactivationTimer because it applies an infinite value as the timer value of the sCellDeactivationTimer.

[0132] Alternatively, when the sCellDeactivationTimer is set for the secondary cell that forms the control link of NCR-Fwd510A, NCR-MT520A may ignore the timer value of the sCellDeactivationTimer (i.e., the set sCellDeactivationTimer) and apply an infinite value as the timer value of the sCellDeactivationTimer. Thereby, it is possible to prevent the secondary cell (serving cell C2) from being deactivated by the sCellDeactivationTimer.

[0133] (1.10.3) Third operation example using multiple serving cells in a relay device This operation example is a modified example of the above-described second operation example. In this operation example, NCR-MT520A restarts the sCellDeactivationTimer in response to receiving an NCR control signal for controlling NCR-Fwd510A from gNB200 via the control link of the secondary cell (serving cell C2). Thereby, it is possible to prevent the secondary cell (serving cell C2) from being deactivated by the sCellDeactivationTimer.

[0134] FIG. 21 is a diagram showing this operation example. Duplicate explanations for operations similar to the above-described first and second operation examples are omitted.

[0135] In step S301, NCR-MT520A establishes an RRC connection with gNB200 and enters the RRC connected state. A primary cell (serving cell C1) of MN200M is assigned to NCR-MT520A.

[0136] In step S302, gNB200 performs CA setting or DC setting for NCR-MT520A. Here, gNB200 sets a secondary cell (serving cell C2) that controls NCR-Fwd510A for NCR-MT520A. The setting includes the set timer value of sCellDeactivationTimer. The setting may include information specifying whether to restart sCellDeactivationTimer when receiving an NCR control signal (L1 / L2 signal), particularly DCI for NCR control. The information may include the cell ID of the secondary cell (serving cell C2) and / or the identifier of NCR-Fwd510A.

[0137] In step S303, gNB200 transmits an activation instruction for the secondary cell (serving cell C2) to NCR-MT520A.

[0138] In step S304, NCR-MT520A (or NCR device 500A) activates the secondary cell (serving cell C2) and NCR-Fwd510A in response to the reception of the activation instruction. Also, NCR-MT520A starts sCellDeactivationTimer set for the secondary cell (serving cell C2) in step S302.

[0139] In step S306, gNB200 transmits an NCR control signal (L1 / L2 signal) to NCR-MT520A on the control link in the secondary cell (serving cell C2).

[0140] In step S307, NCR-MT520A controls NCR-Fwd510A according to the NCR control signal. Also, NCR-MT520A restarts the sCellDeactivationTimer set for the secondary cell (serving cell C2) in step S302 in response to the reception of the NCR control signal (L1 / L2 signal).

[0141] Thereafter, when the sCellDeactivationTimer expires (step S308: YES), NCR-MT520A deactivates the secondary cell (serving cell C2). Also, NCR-MT520A (or NCR device 500A) may deactivate the corresponding NCR-Fwd510A.

[0142] (1.10.4) Fourth operation example using multiple serving cells in the relay device In this operation example, NCR-MT520A detects that a failure has occurred in the control link (i.e., the secondary cell). NCR-MT520A transmits information about the detected failure to gNB200 on the primary cell. Thereby, gNB200 can recognize that a failure has occurred in the control link.

[0143] FIG. 22 is a diagram showing this operation example. Duplicate descriptions of operations similar to the first to third operation examples described above are omitted.

[0144] In step S401, NCR-MT520A establishes an RRC connection with gNB200 and enters the RRC connected state. A primary cell (serving cell C1) of MN200M is assigned to NCR-MT520A.

[0145] In step S402, gNB200 performs CA configuration or DC configuration on NCR-MT520A. This configuration may include configurations related to monitoring of the control link (for example, the threshold of the quality of the control link). Here, gNB200 sets a secondary cell (serving cell C2) that controls NCR-Fwd510A for NCR-MT520A.

[0146] In step S403, gNB200 sends an activation instruction for the secondary cell (serving cell C2) to NCR-MT520A. In response to receiving the activation instruction, NCR-MT520A activates the secondary cell (serving cell C2) and NCR-Fwd510A.

[0147] In step S404, NCR-MT520A monitors the reception quality of the reference signals (SSB and / or CSI-RS) received on the control link. NCR-MT520A may perform this monitoring only when it is set by gNB200. The reception quality may be RSRP / RSRQ / SINR of the control link.

[0148] In step S405, NCR-MT520A determines whether a failure of the control link is detected. NCR-MT520A may determine whether a failure corresponding to a radio link failure (RLF) has occurred in the control link. NCR-MT520A may determine that a failure has occurred when the measured reception quality falls below a threshold. The threshold may be set by gNB200.

[0149] When it is determined that a failure of the control link has been detected (step S405: YES), in step S406, NCR-MT520A notifies gNB200 of the failure information of the control link on the primary cell. For example, NCR-MT520A transmits an RRC message such as an NCR Failure Information message to gNB200. gNB200 receives the message. The message may include an identifier of NCR-Fwd510A corresponding to the control link where the failure has occurred, an identifier of the secondary cell, and / or information on the frequency where the failure has occurred.

[0150] (1.11) Operations related to fault handling of the relay device The operation of the NCR device 500A according to the embodiment regarding fault handling will be described. In the following embodiments, a plurality of serving cells may not be set in the NCR device 500A. A plurality of serving cells may be set in the NCR device 500A.

[0151] As described above, NCR-Fwd510A relays the radio signal transmitted between gNB200 and UE100. NCR-MT520A performs radio communication with gNB200 via the control link to control NCR-Fwd510A. Here, in response to NCR-MT520A detecting that a failure has occurred in the control link or NCR-Fwd510A, predetermined control corresponding to the failure is performed. When a plurality of serving cells are set in the NCR device 500A as described above, NCR-MT520A may transmit the failure information of the control link or the failure information of NCR-Fwd510A to gNB200 on the primary cell.

[0152] (1.11.1) First operation example related to fault handling In this operation example, NCR-MT520A detects that a failure has occurred in the control link. In response to the occurrence of a failure in the control link, NCR-MT520A stops the operation of NCR-Fwd510A. If a failure occurs in the control link, problems such as the occurrence of interference may arise if NCR-Fwd510A operates in an uncontrolled state. Therefore, by stopping the operation of NCR-Fwd510A, the occurrence of such problems can be avoided. Note that NCR-MT520A may detect that the failure in the control link has been resolved. NCR-MT520A may also send a notification to gNB200 in response to the resolution of the failure.

[0153] FIG. 23 is a diagram showing this operation example. Duplicate explanations for operations similar to those in the above-described embodiments are omitted.

[0154] In step S501, NCR-MT520A establishes an RRC connection with gNB200 and enters the RRC connected state. gNB200 may send an NCR control signal (L1 / L2 signal) to NCR-MT520A on the control link. NCR-MT520A controls NCR-Fwd510A in response to the NCR control signal.

[0155] In step S502, NCR-MT520A may monitor the reception quality of the reference signals (SSB and / or CSI-RS) received on the control link. NCR-MT520A may perform such monitoring only when it is set by gNB200. The reception quality may be the RSRP / RSRQ / SINR of the control link.

[0156] In step S503, NCR-MT520A determines whether it has detected a failure in the control link. NCR-MT520A may determine whether a failure corresponding to a radio link failure (RLF) has occurred in the control link. NCR-MT520A may also determine that a failure has occurred when the measured reception quality falls below a threshold value. The threshold value may be set by gNB200.

[0157] For example, NCR-MT520A may determine that a control link failure has been detected when any of the following events occur: · A failure corresponding to RLF has occurred in the control link · RLF has occurred in the primary cell · RRC Reestablishment has been started · MCG Failure Information regarding an MCG failure has been sent to gNB200 · SCG Failure Information regarding an SCG failure has been sent to gNB200 · Transitioned to the RRC idle state or the RRC inactive state (for example, RRC Reestablishment has failed) · Connected to a cell different from the current serving cell

[0158] When it is determined that a control link failure has been detected (step S503: YES), in step S504, NCR-MT520A (or NCR device 500A) stops the operation of NCR-Fwd510A (that is, the relay operation of radio signals).

[0159] Thereafter, in step S505, NCR-MT520A may determine whether the control link failure has been resolved (returned to normal).

[0160] When it is determined that the control link failure has been resolved (step S505: YES), in step S506, NCR-MT520A may send a notification indicating that NCR-Fwd510A is in the stopped state to gNB200. In response to receiving the notification, gNB200 may perform setting / control on the NCR device 500A again. gNB200 may control the NCR device 500A to restore the previously performed setting / control state (that is, reactivate NCR-Fwd510A).

[0161] (1.11.2) Second operation example regarding failure handling In this operation example, gNB 200 sets the content of the customized control for NCR-Fwd 510A (i.e., control during a failure occurrence) in NCR-MT 520A. NCR-MT 520A detects that a failure has occurred in the control link. NCR-MT 520A performs the control of the content set by gNB 200 on NCR-Fwd 510A in response to the occurrence of the failure in the control link.

[0162] For example, when gNB 200 makes a setting to perform a predetermined operation on the NCR device 500A periodically, there may be a control method of continuing the operation of NCR-Fwd 510A even if a failure occurs in the control link. Therefore, gNB 200 may set in NCR-MT 520A whether to continue the operation of NCR-Fwd 510A when a failure occurs in the control link.

[0163] FIG. 24 is a diagram showing this operation example. Duplicate descriptions for operations similar to those in the above-described embodiments are omitted.

[0164] In step S601, NCR-MT 520A establishes an RRC connection with gNB 200 and enters the RRC connected state.

[0165] In step S602, gNB 200 transmits setting information indicating the control content of NCR-Fwd 510A at the time of a failure occurrence in the control link to NCR-MT 520A. gNB 200 may include the setting information in an RRC message (for example, an RRC Reconfiguration message) and transmit it to NCR-MT 520A. NCR-MT 520A receives the setting information. Also, gNB 200 may transmit an NCR control signal (L1 / L2 signal) to NCR-MT 520A on the control link. NCR-MT 520A controls NCR-Fwd 510A in response to the NCR control signal.

[0166] The setting information in step S602 may include information specifying any one of stopping the operation of NCR-Fwd510A, discarding the settings of NCR-Fwd510A, and continuing the operation of NCR-Fwd510A as the control content when a failure occurs in the control link. When continuing the operation of NCR-Fwd510A, the setting information may include an NCR control signal indicating a beamforming method or the like when a failure occurs in the control link.

[0167] In step S603, NCR-MT520A may monitor the reception quality of the reference signals (SSB and / or CSI-RS) received on the control link.

[0168] In step S604, NCR-MT520A determines whether a failure in the control link has been detected by the above method.

[0169] If it is determined that a failure in the control link has been detected (step S604: YES), in step S605, NCR-MT520A performs the control set in step S602 on NCR-Fwd510A. For example, NCR-MT520A (or NCR device 500A) may continue the operation of NCR-Fwd510A according to the content that has already been set and controlled. NCR-MT520A may continue the operation of NCR-Fwd510A according to the NCR control signal set in step S602.

[0170] The operations in steps S606 and S607 are the same as those in the above-described embodiment.

[0171] (1.11.3) Third operation example regarding failure handling In this operation example, NCR-MT520A detects that a failure has occurred in NCR-Fwd510A (for example, NCR-Fwd510A has malfunctioned). In response to the occurrence of the failure in NCR-Fwd510A, NCR-MT520A transmits the failure information of NCR-Fwd510A to gNB200.

[0172] FIG. 25 is a diagram showing this operation example. Duplicate explanations for operations similar to those in the above-described embodiments are omitted.

[0173] In step S701, NCR-MT520A establishes an RRC connection with gNB200 and enters the RRC connected state. gNB200 may perform settings regarding the monitoring of NCR-Fwd510A for NCR-MT520A. Also, gNB200 may transmit an NCR control signal (L1 / L2 signal) to NCR-MT520A on the control link. NCR-MT520A controls NCR-Fwd510A according to the NCR control signal.

[0174] In step S702, NCR-MT520A may monitor the operation of NCR-Fwd510A. For example, NCR-MT520A may monitor at least one of the load state, control delay time (control response time), and heat generation amount of NCR-Fwd510A.

[0175] In step S703, NCR-MT520A determines whether it has detected a failure of NCR-Fwd510A. For example, NCR-MT520A may determine that it has detected a control link failure when any of the following events occur: · A failure has occurred in NCR-Fwd510A · The processing of NCR-Fwd510A cannot keep up with the settings and controls from gNB200. For example, the control of NCR-Fwd510A cannot be performed for the NCR control signal from gNB200. · The load of NCR-Fwd510A (for example, the usage rate of hardware resources) has increased above a threshold value. Note that the threshold value may be set by gNB200. · A failure has occurred in the control link · An incorrect control value has been received in the NCR control signal (L1 / L2 signal) and / or RRC Reconfiguration message from gNB200. For example, it may be that a control value (such as a weight) not supported by NCR-Fwd510A has been received.

[0176] When it is determined that a failure of NCR-Fwd510A has been detected (step S703: YES), in step S704, NCR-MT520A transmits failure information regarding the detected failure to gNB200. gNB200 desires the failure information. For example, NCR-MT520A may transmit an RRC message including the failure information, such as a message like NCR Failure Information or a UE Assistance Information message, to gNB200.

[0177] The message may include at least one of the following information elements: · An information element indicating the occurrence of a failure of NCR-Fwd510A · An information element indicating a processing delay, increased load, or overheating of NCR-Fwd510A · An information element indicating the occurrence of a failure in the control link · Desired setting - control values of NCR-Fwd510A. For example, it may be a preference value for the upper limit of the number of antennas to be controlled and / or the upper limit of the frequency bandwidth. gNB200 may change the setting - control for NCR device 500A according to the desired setting - control value. · An identifier of NCR-Fwd510A in which the failure has occurred

[0178] gNB200 that has received the failure information in step S704 may transmit to NCR-MT520A information specifying any one of stopping the operation of NCR-Fwd510A, discarding the settings of NCR-Fwd510A, and continuing the operation of NCR-Fwd510A as the control content for dealing with the failure.

[0179] Thereafter, in step S7, NCR-MT520A may determine whether the failure of NCR-Fwd510A has been resolved (returned to normal).

[0180] When it is determined that the failure of NCR-Fwd510A has been resolved (step S705: YES), in step S706, NCR-MT520A may send a notification indicating that the failure of NCR-Fwd510A has been resolved to gNB200. The notification may include the identifier of NCR-Fwd510A for which the failure has been resolved.

[0181] (2) Second Embodiment Next, the second embodiment will be mainly described in terms of differences from the above-described first embodiment. The outline of the mobile communication system 1 and the configuration of gNB200 according to the second embodiment are the same as those of the first embodiment described above.

[0182] As shown in FIG. 26, the relay device according to the second embodiment is a RIS (Reconfigurable Intelligent Surface) device 500B that changes the propagation direction of incident radio waves (radio signals) by reflection or refraction. The "NCR" in the above-described first and second embodiments can be read as "RIS".

[0183] RIS is a type of repeater (hereinafter also referred to as "RIS-Fwd") that can perform beamforming (directivity control) in the same manner as NCR by changing the characteristics of the metamaterial. In the case of RIS, the range (distance) of the beam may also be changeable by controlling the reflection direction and / or refraction direction of each unit element. For example, a configuration may be adopted in which the reflection direction and / or refraction direction of each unit element is controlled, and the focus is directed at a nearby UE (the beam is directed) or at a distant UE (the beam is directed).

[0184] The RIS device 500B has a new UE (hereinafter referred to as "RIS-MT") 520B which is a control terminal for controlling the RIS-Fwd510B. The RIS-MT 520B controls the RIS-Fwd510B in cooperation with the gNB200 by establishing a wireless connection with the gNB200 and performing wireless communication with the gNB200. The RIS-Fwd510B may be a reflective RIS. Such a RIS-Fwd510B changes the propagation direction of the incident radio wave by reflecting the incident radio wave. Here, the reflection angle of the radio wave can be variably set. The RIS-Fwd510B reflects the radio wave incident from the gNB200 toward the UE100. The RIS-Fwd510B may be a transmissive RIS. Such a RIS-Fwd510B changes the propagation direction of the incident radio wave by refracting the incident radio wave. Here, the refraction angle of the radio wave can be variably set.

[0185] FIG. 27 is a diagram showing a configuration example of a RIS-Fwd (repeater) 510B and a RIS-MT (control terminal) 520B according to the second embodiment. The RIS-MT 520B includes a receiving unit 521, a transmitting unit 522, and a control unit 523. Such a configuration is the same as that of the first embodiment described above. The RIS-Fwd 510B includes a RIS 511B and a RIS control unit 512B. The RIS 511B is a metasurface configured using metamaterials. For example, the RIS 511B is configured by arranging very small structures in an array with respect to the wavelength of radio waves, and by making the structures have different shapes depending on the placement location, it is possible to arbitrarily design the direction of the reflected wave or / and the beam shape. The RIS 511B may be a transparent dynamic metasurface. The RIS 511B is configured by stacking a transparent glass substrate on a transparent metasurface substrate in which a large number of small structures are regularly arranged. By slightly moving the stacked glass substrate, it is possible to dynamically control three modes: a mode in which incident radio waves are transmitted, a mode in which part of the radio waves are transmitted and part are reflected, and a mode in which all radio waves are reflected. The RIS control unit 512B controls the RIS 511B in accordance with a RIS control signal from the control unit 523 of the RIS-MT 520B. The RIS control unit 512B may include at least one processor and at least one actuator. The processor decodes the RIS control signal from the control unit 523 of the RIS-MT 520B and drives the actuator according to the RIS control signal.

[0186] (3) Other Embodiments In the above-described embodiment, an example in which the gNB 200 controls the NCR device 500A has been described. However, the NCR device 500A (NCR-MT520A) may autonomously control the NCR-Fwd510A based on the settings from the gNB 200. FIG. 28 is a diagram showing an example of beam sweeping according to another embodiment. The gNB 200 transmits a plurality of beams (beams of SSB3 to SSB5 in the illustrated example) in the direction of the NCR device 500A with the same transmission weight for the backhaul link. The NCR device 500A (NCR-Fwd510A) autonomously transmits the plurality of beams (beams of SSB3 to SSB5) in different directions with different transmission weights for the access link. Under such a premise, the NCR device 500A (NCR-MT520A) may autonomously control the NCR-Fwd510A based on the settings from the gNB 200 when a failure occurs.

[0187] The above-described operation flows are not limited to being implemented separately and independently, and two or more operation flows can be combined and implemented. For example, some steps of one operation flow may be added to another operation flow, or some steps of one operation flow may be replaced with some steps of another operation flow. In each flow, it is not necessarily required to execute all steps, and only some steps may be executed.

[0188] In the above-described embodiment, an example in which the base station is an NR base station (gNB) has been described, but the base station may be an LTE base station (eNB). Further, 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.

[0189] A program may be provided that causes a computer to execute each process performed by the UE 100 (NCR-MT520A, RIS-MT520B) or the gNB 200. The program may be recorded on a computer-readable medium. By using the computer-readable medium, it is possible to install the program on the 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. Also, a circuit that executes each process performed by the UE 100 or the gNB 200 may be integrated, and at least a part of the UE 100 or the gNB 200 may be configured as a semiconductor integrated circuit (chipset, SoC: System on a chip).

[0190] As used in this disclosure, the terms "based on" and "depending on / in response to" do not mean "only based on" or "only in response to" unless otherwise specified. The term "based on" means both "only based on" and "at least partially based on". Similarly, the term "depending on" means both "only in response to" and "at least partially in response to". The terms "include", "comprise", and their variants do not mean including only the listed items, but may include only the listed items or may further include additional items in addition to the listed items. Also, the term "or" used in this disclosure is not intended to be an exclusive disjunction. Furthermore, any reference to elements using designations such as "first", "second", etc. used in this disclosure does not generally limit the quantity or order of those elements. These designations can be used in this specification as a convenient way to distinguish between two or more elements. Therefore, a reference to a first and a second element does not mean that only two elements can be employed there or that the first element must precede the second element in some form. In this disclosure, for example, when articles are added by translation, such as a, an, and the in English, these articles are assumed to include plural ones unless the context clearly indicates otherwise.

[0191] As described above in detail with reference to the drawings, the specific configuration is not limited to the above, and various design changes and the like can be made without departing from the gist.

[0192] This application claims the priority of Japanese Patent Application No. 2022-126137 (filed on August 8, 2022), and all of its content is incorporated into the specification of this application.

[0193] (4) Supplementary Note The features regarding the above-described embodiments are noted.

[0194] (Appendix 1) A communication method using a relay device in a mobile communication system, wherein a repeater included in the relay device relays a radio signal transmitted between a base station and a user device; a control terminal included in the relay device performs wireless communication with the base station via a control link to control the repeater; the control terminal detects that a failure has occurred in the control link or the repeater; and the control terminal performs predetermined control according to the failure. Communication method.

[0195] (Appendix 2) The detecting step includes a step of detecting that a failure has occurred in the control link, and the step of performing the predetermined control includes a step of stopping the operation of the repeater according to the occurrence of the failure in the control link. The communication method according to Appendix 1.

[0196] (Appendix 3) The base station further has a step of setting the content of the predetermined control for the repeater in the control terminal, the detecting step includes a step of detecting that a failure has occurred in the control link, and the step of performing the predetermined control includes a step of performing control of the content set by the base station on the repeater according to the occurrence of the failure in the control link. The communication method according to Appendix 1 or 2.

[0197] [[ID=#39]](Appendix 4) The step of setting the content of the predetermined control in the control terminal includes a step of setting whether to continue the operation of the repeater when a failure occurs in the control link. The communication method according to Appendix 3.

[0198] (Appendix 5) The step of detecting includes a step of detecting that a failure has occurred in the repeater. The step of performing the predetermined control includes a step of transmitting failure information of the repeater to the base station in response to the occurrence of a failure in the repeater. The communication method according to any one of Appendices 1 to 4.

[0199] (Appendix 6) A step of detecting that the failure has been resolved, and A step of transmitting a notification to the base station in response to the resolution of the failure. The communication method according to any one of Appendices 1 to 5.

[0200] (Appendix 7) A relay device used in a mobile communication system, A repeater that relays a radio signal transmitted between a base station and a user device, A control terminal that performs wireless communication with the base station via a control link and controls the repeater. When the control terminal detects that a failure has occurred in the control link or the repeater, the control terminal performs predetermined control according to the failure. Relay device.

Explanation of Signs

[0201] 1: Mobile communication system 100: UE 200: gNB 210: Transmission unit 220: Reception unit 230: Control unit 240: Backhaul communication unit 500A: NCR device 500B: RIS device 511A: Radio unit 511a: Antenna unit 511b: RF circuit 511c: Directivity control unit 512A: NCR control unit 512B: RIS control unit 521: Receiver unit 522: Transmitter unit 523: Control unit 530: Interface

Claims

1. A communication method using a relay device in a mobile communication system, comprising: a repeater included in the relay device relays a radio signal transmitted between a base station and a user equipment; a control terminal included in the relay device performs wireless communication with the base station via a control link to control the repeater; the control terminal transitions from an RRC connected state to an RRC inactive state; after the control terminal transitions to the RRC inactive state, the repeater continues to operate according to the set content received from the base station. A communication method.

2. The communication method according to claim 1, further comprising: the control terminal stops the operation of the repeater in response to a transition from the RRC connected state to the RRC idle state. The communication method according to claim 1.

3. The communication method according to claim 1, further comprising: the control terminal receives an RRC message indicating the set content from the base station in the RRC connected state. The communication method according to claim 1.

4. A relay device for performing wireless communication with a base station and a user equipment in a mobile communication system, comprising: a repeater that relays a radio signal transmitted between the base station and the user equipment; a control terminal that performs wireless communication with the base station via a control link to control the repeater, wherein the control terminal transitions from an RRC connected state to an RRC inactive state, and after the control terminal transitions to the RRC inactive state, the repeater continues to operate according to the set content received from the base station. A relay device.

5. A system including a relay device, a base station, and a user equipment in a mobile communication system, wherein the relay device includes a repeater that relays a radio signal transmitted between the base station and the user equipment; a control terminal that performs wireless communication with the base station via a control link to control the repeater, wherein the control terminal transitions from an RRC connected state to an RRC inactive state, and after the control terminal transitions to the RRC inactive state, the repeater continues to operate according to the set content received from the base station. A system.

6. A program for causing a relay device having a repeater and a control terminal to perform wireless communication with a base station and a user equipment in a mobile communication system, causing the relay device to execute a process of relaying a radio signal transmitted between the base station and the user equipment; causing the control terminal to execute a process of performing radio communication with the base station via a control link to control the relay device; causing the control terminal to execute a process of transitioning from an RRC connected state to an RRC inactive state; after the transition to the RRC inactive state, causing the relay device to execute a process of continuing to operate according to the set content received from the base station; Program.

7. A chipset for a relay device having a relay device and a control terminal that performs radio communication with a base station and a user equipment in a mobile communication system, causing the relay device to execute a process of relaying a radio signal transmitted between the base station and the user equipment; causing the control terminal to execute a process of performing radio communication with the base station via a control link to control the relay device; causing the control terminal to execute a process of transitioning from an RRC connected state to an RRC inactive state; after the transition to the RRC inactive state, causing the relay device to execute a process of continuing to operate according to the set content received from the base station; Chipset.

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