COMMUNICATION METHOD, REPEATER NODE, PROGRAM, CHIP SET, AND SYSTEM

Abstract

A communication method using a relay device including a repeater that performs a relay operation to relay wireless signals transmitted between a network and a user device, and a control terminal that receives a control signal used to control the repeater from the network comprises: a step in which the control terminal transitions to a radio resource control (RRC) idle state; and a step in which the relay device determines that there is no control from the network in response to the transition to the RRC idle state.

Description

Communication Method

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

[0002] In recent years, fifth-generation (5G) mobile communication systems have been attracting attention. NR (New Radio), a radio access technology of 5G systems, is capable of wideband transmission using higher frequency bands than LTE (Long Term Evolution), a fourth-generation radio access technology.

[0003] Radio signals (radio waves) in high-frequency bands such as millimeter waves or terahertz waves have a high degree of directionality, which poses a problem of reducing the coverage of base stations. To address this problem, repeater devices, which are a type of relay device that relays radio signals between a network and user devices and can be controlled from a network, have been attracting attention (see, for example, Non-Patent Document 1). Such repeater devices can, for example, amplify radio signals received from a base station and transmit them directionally, thereby expanding the coverage of the base station while suppressing interference. Such repeater devices are also referred to as NCRs (Network-Controlled Repeaters).

[0004] 3GPP contribution: RP-213700, “New SI: Study on NR Network-controlled Repeaters”

[0005] A communication method according to a first aspect is a communication method using a relay device having a relay that performs relaying operations to relay radio signals transmitted between a network and a user device, and a control terminal that receives a control signal from the network used to control the relay, and includes a step of the control terminal transitioning to a radio resource control (RRC) idle state, and a step of the relay device determining that there is no control from the network in response to the transition to the RRC idle state.

[0006] A communication method according to a second aspect is a communication method using a relay device having a relay that performs relaying operations to relay radio signals transmitted between a network and a user device, and a control terminal that receives a control signal from the network used to control the relay, and includes the steps of the control terminal receiving, in a Radio Resource Control (RRC) connected state, configuration information for configuring the relaying operation from the network, the control terminal transitioning to an RRC idle state or an RRC inactive state, and the relay device operating in accordance with the configuration information in the RRC idle state or the RRC inactive state for a period until a certain time has elapsed since the transition.

[0007] A communication method according to a third aspect is a communication method using a relay device having a relay that performs relaying operations to relay radio signals transmitted between a network and a user device, and a control terminal that receives a control signal from the network used to control the relay, and includes the steps of a network node included in the network transitioning the control terminal from a radio resource control (RRC) connected state to an RRC idle state, and the network node sending a paging request to a core network device included in the network, requesting paging from the core network device to the relay device.

[0008] 1 is a diagram illustrating a configuration of a mobile communication system according to an embodiment. FIG. 2 is a diagram illustrating a protocol stack configuration of a radio interface of a user plane that handles data. FIG. 3 is a diagram illustrating a protocol stack configuration of a radio interface of a control plane that handles signaling (control signals). FIG. 4 is a diagram illustrating an example of an application scenario of an NCR device (relay device) according to an embodiment. FIG. 5 is a diagram illustrating an example of an application scenario of an NCR device according to an embodiment. FIG. 6 is a diagram illustrating an example of a control method of an NCR device according to an embodiment. FIG. 7 is a diagram illustrating an example of a protocol stack configuration in a mobile communication system having an NCR device according to an embodiment. FIG. 8 is a diagram illustrating a specific configuration example of a mobile communication system 1 having an NCR device according to an embodiment. FIG. 9 is a diagram illustrating an example of a configuration of an NCR device according to an embodiment. FIG. 10 is a diagram illustrating a configuration example of a UE (user equipment) according to an embodiment. FIG. 11 is a diagram illustrating an example of a configuration of a gNB (base station) according to an embodiment. FIG. 12 is a diagram illustrating an operation according to a first embodiment. FIG. 13 is a diagram illustrating an operation example of an NCR device according to a modified example of the first embodiment. FIG. 14 is a diagram illustrating an operation example of an NCR device according to a second embodiment. FIG. 15 is a diagram illustrating an operation example of a mobile communication system according to a third embodiment. FIG. 16 is a diagram illustrating a relay device according to a fourth embodiment. FIG. 17 is a diagram illustrating a relay device according to a fourth embodiment.

[0009] 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.

[0010] (1) First Embodiment First, a description will be given of the first embodiment. A relay device according to the embodiment is a repeater device (that is, an NCR device) that can be controlled from a network.

[0011] (1.1) Overview of Mobile Communication System FIG. 1 is a diagram showing the configuration of a mobile communication system according to an embodiment.

[0012] The mobile communication system 1 conforms to the 5th Generation System (5GS) standard of the 3rd Generation Partnership Project (3GPP) (registered trademark; the same applies hereinafter). While the following description will be given using 5GS as an example, the mobile communication system may also be at least partially based on the Long Term Evolution (LTE) system. The mobile communication system may also be at least partially based on the 6th Generation (6G) system.

[0013] The mobile communication system 1 includes a user equipment (UE) 100, a 5G radio access network (NG-RAN: Next Generation Radio Access Network) 10, and a 5G core network (5GC: 5G Core Network) 20. Hereinafter, the NG-RAN 10 may be simply referred to as the RAN 10. Furthermore, the 5GC 20 may be simply referred to as the core network (CN) 20. The RAN 10 and the CN 20 constitute a network 5 of the mobile communication system 1.

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

[0015] The NG-RAN 10 includes a base station (referred to as "gNB" in the 5G system) 200. The gNBs 200 are connected to each other via an Xn interface, which is an interface between base stations. The gNB 200 manages one or more cells. The gNB 200 performs wireless communication with the UE 100 that has established a connection with its own cell. The gNB 200 has a radio resource management (RRM) function, a routing function for user data (hereinafter simply referred to as "data"), a measurement control function for mobility control and scheduling, etc. The term "cell" is used to indicate the smallest unit of a wireless communication area. The term "cell" is also used to indicate a function or resource for wireless communication with the UE 100. One cell belongs to one carrier frequency (hereinafter simply referred to as "frequency").

[0016] The gNB200 may be functionally divided into a central unit (CU) and a distributed unit (DU). The CU controls the DU. The CU is a unit including upper layers included in the protocol stack described below, such as an RRC layer, an SDAP layer, and a PDCP layer. The CU is connected to the core network via an NG interface, which is a backhaul interface. The CU is connected to neighboring base stations via an Xn interface, which is an interface between base stations. The DU forms a cell. The DU202 is a unit including lower layers included in the protocol stack described below, such as an RLC layer, a MAC layer, and a PHY layer. The DU is connected to the CU via an F1 interface, which is a fronthaul interface.

[0017] In addition, gNBs can also be connected to the Evolved Packet Core (EPC), which is the core network of LTE. LTE base stations can also be connected to 5GC. LTE base stations and gNBs can also be connected via an inter-base station interface.

[0018] The 5GC20 includes an AMF (Access and Mobility Management Function) and a UPF (User Plane Function) 300. The AMF performs various mobility controls for the UE 100. The AMF manages the mobility of the UE 100 by communicating with the UE 100 using NAS (Non-Access Stratum) signaling. The UPF controls data forwarding. The AMF and the UPF are connected to the gNB 200 via an NG interface, which is an interface between a base station and a core network.

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

[0020] The user plane radio interface protocol includes a physical (PHY) layer, a medium access control (MAC) layer, a radio link control (RLC) layer, a packet data convergence protocol (PDCP) layer, and a service data adaptation protocol (SDAP) layer.

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

[0022] In addition, the gNB 200 transmits a synchronization signal block (SSB: Synchronization Signal / PBCH block). For example, the SSB is composed of four consecutive OFDM (Orthogonal Frequency Division Multiplex) symbols, and includes a primary synchronization signal (PSS), a secondary synchronization signal (SSS), a physical broadcast channel (PBCH) / master information block (MIB), and a PBCH demodulation reference signal (DMRS). The bandwidth of the SSB is, for example, 240 consecutive subcarriers, that is, a bandwidth of 20 RBs.

[0023] The MAC layer performs data priority control, retransmission processing using Hybrid Automatic Repeat reQuest (HARQ), random access procedures, etc. Data and control information are transmitted between the MAC layer of the UE 100 and the MAC layer of the gNB 200 via a transport channel. The MAC layer of the gNB 200 includes a scheduler. The scheduler determines the uplink and downlink transport format (transport block size, modulation and coding scheme (MCS)) and the resource blocks to be allocated to the UE 100.

[0024] The RLC layer transmits data to the receiving RLC layer using the functions of the MAC layer and PHY layer. Data and control information are transmitted between the RLC layer of the UE 100 and the RLC layer of the gNB 200 via a logical channel.

[0025] The PDCP layer performs header compression / decompression, encryption / decryption, and the like.

[0026] The SDAP layer maps IP flows, which are units for Quality of Service (QoS) control by the core network, to radio bearers, which are units for QoS control by the Access Stratum (AS). Note that if the RAN is connected to the EPC, SDAP may not be required.

[0027] FIG. 3 is a diagram showing the configuration of a protocol stack of a radio interface of a 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 FIG.

[0029] RRC signaling for various settings is transmitted between the RRC layer of UE100 and the RRC layer of gNB200. The RRC layer controls logical channels, transport channels, and physical channels according to the establishment, re-establishment, and release of radio bearers. When there is a connection (RRC connection) between the RRC of UE100 and the RRC of gNB200, UE100 is in an RRC connected state. When there is no connection (RRC connection) between the RRC of UE100 and the RRC of gNB200, UE100 is in an RRC idle state. When the connection between the RRC of UE100 and the RRC of gNB200 is suspended, UE100 is in an RRC inactive state.

[0030] The NAS layer, which is located above the RRC layer, performs session management, mobility management, etc. NAS signaling is transmitted between the NAS layer of the UE 100 and the NAS layer of the AMF 300A. Note that the UE 100 has an application layer and the like in addition to the radio interface protocol. Also, a layer lower than the NAS layer is called an AS layer.

[0031] (1.2) Example of Application Scenario of Relay Device FIGS. 4 and 5 are diagrams showing an example of an application scenario of the NCR device according to the embodiment.

[0032] Compared to 4G / LTE, 5G / NR enables broadband transmission using higher frequency bands. Radio signals in high frequency bands, such as the millimeter wave band or terahertz wave band, have high line-of-sight properties, which poses a challenge in reducing the coverage of the gNB 200. In FIG. 4, the UE 100 may be located outside the coverage area of ​​the gNB 200, for example, outside an area where radio signals can be received directly from the gNB 200. A shield may exist between the gNB 200 and the UE 100, preventing the UE 100 from communicating with the gNB 200 within line-of-sight.

[0033] As shown in Figure 4, a repeater device (500A), which is a type of relay device that relays radio signals between the gNB 200 and the UE 100, and an NCR device 500A that can be controlled from the network is introduced into the mobile communication system 1. Such a repeater device may be referred to as a smart repeater device.

[0034] For example, the NCR device 500A amplifies a radio signal (radio wave) received from the gNB 200 and transmits it by directional transmission. Specifically, the NCR device 500A receives a radio signal transmitted by the gNB 200 by beamforming. The NCR device 500A then amplifies the received radio signal without demodulating or modulating it, and transmits the amplified radio signal by directional transmission. Here, the NCR device 500A may transmit a radio signal with a fixed directivity (beam). The NCR device 500A may also transmit a radio signal with a variable (adaptive) directional beam. This allows the coverage of the gNB 200 to be efficiently expanded.

[0035] Also, as shown in FIG. 5, a new UE (hereinafter referred to as "NCR-MT (Mobile termination)") 100B, which is a type of control terminal for controlling the NCR device 500A, is introduced. That is, the NCR device 500A relays radio signals transmitted between the gNB 200 and the UE 100, specifically, it has an NCR-Fwd (Forward) 510A, which is a type of repeater that changes the propagation state of the radio signal without demodulating or modulating the radio signal, and an NCR-MT 520A that controls the NCR-Fwd 510A by performing wireless communication with the gNB 200. 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. This makes it possible to achieve efficient coverage expansion using the NCR device 500A. The NCR-MT 520A controls the NCR device 500A under control from the gNB 200. The NCR-MT 520A also has functions similar to those of the UE 100.

[0036] The NCR-MT 520A may be configured separately from the NCR-Fwd 510A. For example, the NCR-MT 520A may be located near the NCR-Fwd 510A and 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 a wall or window of a building. The NCR-MT 520A and the NCR-Fwd 510A may be installed, for example, in a vehicle or the like and be mobile. Also, one NCR-MT 520A may control multiple NCR-Fwds 510A.

[0037] Note that the configuration is not limited to one in which the NCR-MT 520A directly controls one or more NCR-Fwds 510A, and may be one in which the NCR-MT 520A indirectly controls one or more NCR-Fwds 510A. For example, the NCR-MT 520A may control one or more NCR-Fwds 510A via a higher layer (for example, an application layer).

[0038] In the example shown in FIG. 5, the NCR device 500A (NCR-Fwd 510A) dynamically or quasi-statically changes the beam to be transmitted or received. For example, the NCR-Fwd 510A forms a beam toward each of the UE 100a and the UE 100b. The NCR-Fwd 510A may also form a beam toward the gNB 200. For example, in the communication resources between the gNB 200 and the UE 100a, the NCR-Fwd 510A transmits a radio signal received from the gNB 200 toward the UE 100a by beamforming, and / or transmits a radio signal received from the UE 100a toward the gNB 200 by beamforming. In the communication resources between the gNB 200 and the UE 100b, the NCR-Fwd 510A transmits a radio signal received from the gNB 200 toward the UE 100b by beamforming, and / or transmits a radio signal received from the UE 100b by beamforming toward the gNB 200. Instead of or in addition to beamforming, the NCR-Fwd 510A may form a null (so-called null steering) toward a UE 100 (not shown) and / or a neighboring gNB 200 (not shown) that is not a communication partner for interference suppression.

[0039] FIG. 6 is a diagram showing an example of a control method of the NCR device 500A according to the embodiment. As shown in FIG. 6, the NCR-Fwd 510A relays radio signals (also referred to as "UE signals") between the gNB 200 and the UE 100. The UE signals include uplink signals (also referred to as "UE-UL signals") transmitted from the UE 100 to the gNB 200 and downlink signals (also referred to as "UE-DL signals") transmitted from the gNB 200 to the UE 100. The NCR-Fwd 510A relays the UE-UL signals from the UE 100 to the gNB 200 and relays the UE-DL signals from the gNB 200 to the UE 100. The radio link between the NCR-Fwd 510A and the UE 100 is also referred to as an "access link." The wireless link between NCR-Fwd510A and gNB200 is also referred to as a "backhaul link."

[0040] The NCR-MT 520A transmits and receives radio signals (herein referred to as "NCR-MT signals") to and from the gNB 200. The NCR-MT signals include uplink signals (herein referred to as "NCR-MT-UL signals") transmitted from the NCR-MT 520A to the gNB 200, and downlink signals (herein referred to as "NCR-MT-DL signals") transmitted from the gNB 200 to the NCR-MT 520A. The NCR-MT-DL signals include signaling (e.g., NCR control signals) for controlling the NCR device 500A. The radio link between the NCR-MT 520A and the gNB 200 is also referred to as a "control link."

[0041] The gNB200 directs a beam to the NCR-MT520A based on the NCR-MT-UL signal from the NCR-MT520A. Because the NCR device 500A is co-located with the NCR-MT520A, if the backhaul link and the control link have the same frequency, when the gNB200 directs a beam to the NCR-MT520A, the beam will also be directed to the NCR-Fwd510A. The gNB200 uses this beam to transmit an NCR-MT-DL signal and a UE-DL signal. The NCR-MT520A receives the NCR-MT-DL signal. In addition, when the NCR-Fwd 510A and the NCR-MT 520A are at least partially integrated, the functions (e.g., antennas) for transmitting, receiving, or relaying UE signals and / or NCR-MT signals may be integrated in the NCR-Fwd 510A and the NCR-MT 520A. Note that the term "beam" includes a transmitting beam and / or a receiving beam. A beam is a general term for transmission and / or reception controlled to maximize the power of transmitted waves and / or received waves in a specific direction by adjusting / adapting antenna weights, etc.

[0042] 7 is a diagram showing an example of the configuration of a protocol stack in a mobile communication system 1 having an NCR device 500A according to an embodiment. The NCR-Fwd 510A relays radio signals transmitted and received between the gNB 200 and the UE 100. The NCR-Fwd 510A has an RF (Radio Frequency) function that amplifies and relays received radio signals, and performs directional transmission using beamforming (e.g., analog beamforming).

[0043] The NCR-MT 520A has at least one layer (entity) of PHY, MAC, RRC, and F1-AP (Application Protocol). The F1-AP is a type of fronthaul interface. The NCR-MT 520A exchanges signaling with the gNB 200 via at least one of PHY, MAC, RRC, and F1-AP. If the NCR-MT 520A is a type or part of a base station, the NCR-MT 520A may exchange signaling with the gNB 200 via an Xn AP (Xn-AP), which is an interface between base stations. The NCR-MT 520A may also have a NAS layer (entity). The NCR-MT 520A exchanges signaling with the AMF 300A via the NAS layer. The NAS layer may constitute the upper layer for the NCR-MT520A.

[0044] FIG. 8 is a diagram showing a specific example of the configuration of the mobile communication system 1 having the NCR device 500A according to the embodiment.

[0045] A backhaul link is established between the gNB200 and the NCR-Fwd510A. An access link is established between the UE100 and the NCR-Fwd510A. The NCR-Fwd510A relays radio signals transmitted between the gNB200 and the UE100 via the backhaul link and the access link. The NCR-Fwd510A changes the propagation state of the radio signal without demodulating or modulating the radio signal.

[0046] In addition, a control link is established between the gNB200 and Layer 1 and / or Layer 2 (L1 / L2) of the NCR-MT520A. The L1 / L2 of the NCR-MT520A transmits and receives L1 / L2 signaling with the gNB200 via the control link. An RRC connection is established between the gNB200 and the RRC of the NCR-MT520A. The RRC of the NCR-MT520A transmits and receives RRC messages with the gNB200 via the RRC connection. The NCR-MT520A receives downlink signaling (also referred to as an "NCR control signal" or simply "control signal") from the gNB200 via the RRC connection and / or the control link.

[0047] The gNB 200 (transmitter 210) transmits an NCR control signal to the NCR-MT 520A. The NCR control signal may be an RRC message, which is a control signal of the RRC layer (i.e., Layer 3). The NCR control signal may be a MAC Control Element (CE), which is a control signal of the MAC layer (i.e., Layer 2). The NCR control signal may be downlink control information (DCI), which is a control signal of the PHY layer (i.e., Layer 1). The NCR control signal may be UE-specific signaling. The NCR control signal may be broadcast signaling. The NCR control signal may be a fronthaul message (e.g., an F1-AP message). If the NCR-MT 520A is a type or part of a base station, the NCR-MT 520A may communicate with the gNB 200 via an Xn AP (Xn-AP), which is an inter-base station interface.

[0048] Hereinafter, an NCR control signal transmitted in an RRC message (and / or MAC CE) and used for static or semi-static control of the NCR-Fwd 510A will also be referred to as "NCR setting information" or simply "setting information." Here, the RRC message may be an RRC Reconfiguration message. The NCR setting information includes, for example, information for setting the NCR-Fwd 510A on / off. The NCR setting information may also include, for example, information for semi-static beam setting of the NCR-Fwd 510A.

[0049] On the other hand, the NCR control signal transmitted in the DCI (and / or MAC CE) and used for dynamic control of the NCR-Fwd 510A is also referred to as "NCR control information" or simply "control information." The NCR control information may also be referred to as side control information (SCI). The CRC bits of the PDCCH carrying the NCR control information are scrambled by a newly introduced dedicated RNTI. This dedicated RNTI is also referred to as "NCR-RNTI." The NCR control information may include, for example, information on dynamic beam control of the NCR-Fwd 510A. The NCR setting information may include information instructing dynamic on / off of the NCR-Fwd 510A.

[0050] For example, when the NCR-MT 520A is in the RRC connected state, the NCR device 500A can turn on or off the NCR-Fwd 510A according to the NCR control information (SCI) received from the gNB 200. On the other hand, after the NCR-MT 520A transitions to the RRC inactive state, the NCR device 500A can turn on or off the NCR-Fwd 510A according to the latest (last) setting information received from the gNB 200.

[0051] Also, if a radio link failure (RLF) with the gNB200 is detected by the NCR-MT520A, the NCR-MT520A performs cell selection and triggers RRC connection re-establishment (also referred to as "RRC re-establishment"). Here, if the NCR-MT520A enters an RRC idle state because a suitable cell cannot be found in the cell selection, the NCR device 500A turns off the NCR-Fwd510A. Note that the NCR-Fwd510A is off during the RRC re-establishment procedure.

[0052] The NCR control signal may include frequency control information that specifies the center frequency of the radio signal (e.g., component carrier) to be relayed by the NCR-Fwd 510A. When the NCR control signal received from the gNB 200 includes frequency control information, the NCR-MT 520A (control unit 523) controls the NCR-Fwd 510A to relay the radio signal having the center frequency indicated by the frequency control information (step S2A). The NCR control signal may include multiple pieces of frequency control information that specify different center frequencies. By including frequency control information in the NCR control signal, the gNB 200 can specify the center frequency of the radio signal to be relayed by the NCR-Fwd 510A via the NCR-MT 520A.

[0053] The NCR control signal may include mode control information that specifies the operation mode of the NCR-Fwd 510A. The mode control information may be associated with frequency control information (center frequency). The operation mode may be any of a mode in which the NCR-Fwd 510A performs omnidirectional transmission and / or reception, a mode in which the NCR-Fwd 510A performs fixed-directivity transmission and / or reception, a mode in which the NCR-Fwd 510A performs transmission and / or reception using a variable directional beam, and a mode in which the NCR-Fwd 510A performs MIMO (Multiple Input Multiple Output) relay transmission. The operation mode may be any of a beamforming mode (i.e., a mode that emphasizes improving the desired wave) and a null steering mode (i.e., a mode that emphasizes suppressing interference waves). When the NCR control signal received from the gNB 200 includes mode control information, the NCR-MT 520A (control unit 523) controls the NCR-Fwd 510A to operate in the operating mode indicated by the mode control information (step S2A). By including the mode control information in the NCR control signal, the gNB 200 can specify the operating mode of the NCR-Fwd 510A via the NCR-MT 520A.

[0054] Here, the mode in which the NCR device 500A performs omnidirectional transmission and / or reception is a mode in which the NCR-Fwd 510A performs omnidirectional relaying, and may be referred to as omni-mode. The mode in which the NCR-Fwd 510A performs fixed directional transmission and / or reception may be a directional mode realized by a single directional antenna. This mode may be a beamforming mode realized by applying fixed phase / amplitude control (antenna weight control) to multiple antennas. Any of these modes may be specified (set) by the gNB 200 to the NCR-MT 520A. The mode in which the NCR-Fwd 510A performs transmission and / or reception using a variable directional beam may be a mode in which analog beamforming is performed. This mode may be a mode in which digital beamforming is performed. This mode may be a mode in which hybrid beamforming is performed. This mode may be a mode in which an adaptive beam specific to the UE 100 is formed. Any of these modes may be specified (set) from the gNB 200 to the NCR-MT 520A. Note that in an operation mode in which beamforming is performed, beam control information, described below, may be provided from the gNB 200 to the NCR-MT 520A. The mode in which the NCR device 500A performs MIMO relay transmission may be a mode in which SU (Single-User) spatial multiplexing is performed. This mode may also be a mode in which MU (Multi-User) spatial multiplexing is performed. This mode may also be a mode in which transmit diversity is performed. Any of these modes may be specified (set) from the gNB 200 to the NCR-MT 520A. The operation modes may include a mode in which relay transmission by the NCR-Fwd 510A is turned on (activated) and a mode in which relay transmission by the NCR-Fwd 510A is turned off (deactivated). Any of these modes may be specified (set) by an NCR control signal from gNB200 to NCR-MT520A.

[0055] The NCR control signal may include beam control information that specifies the transmission direction, transmission weight, or beam pattern when the NCR-Fwd 510A 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 beam formation angle information. When the NCR control signal received from the gNB 200 includes beam control information, the NCR-MT 520A (control unit 523) controls the NCR-Fwd 510A to form the transmission directivity (beam) indicated by the beam control information. By including beam control information in the NCR control signal, the gNB 200 can control the transmission directivity of the NCR device 500A via the NCR-MT 520A.

[0056] The NCR control signal may include output control information that specifies the degree to which the NCR-Fwd 510A amplifies the radio signal (amplification gain) or transmission power. The output control information may be information indicating a difference value (i.e., a relative value) between the current amplification gain or transmission power and a target amplification gain or transmission power. When the NCR control signal received from the gNB 200 includes output control information, the NCR-MT 520A (control unit 523) controls the NCR-Fwd 510A to change the amplification gain or transmission power to the amplification gain or transmission power indicated by the output control information. The output control information may be associated with frequency control information (center frequency). The output control information may be information that specifies any one of the amplifier gain, beamforming gain, and antenna gain of the NCR-Fwd 510A. The output control information may be information that specifies the transmission power of the NCR-Fwd 510A.

[0057] When one NCR-MT 520A controls multiple NCR-Fwds 510A, the gNB 200 (transmitter 210) may transmit an NCR control signal to the NCR-MT 520A for each NCR-Fwd 510A. In this case, the NCR control signal may include an identifier (NCR identifier) ​​of the corresponding NCR-Fwd 510A. The NCR-MT 520A (controller 523) that controls multiple NCR-Fwds 510A determines the NCR-Fwd 510A to which the NCR control signal is applied based on the NCR identifier included in the NCR control signal received from the gNB 200. Note that the NCR identifier may be transmitted from the NCR-MT 520A to the gNB 200 together with the NCR control signal, even when the NCR-MT 520A controls only one NCR-Fwd 510A.

[0058] In this way, the NCR-MT 520A (control unit 523) controls the NCR-Fwd 510A based on the NCR control signal from the gNB 200. This enables the gNB 200 to control the NCR-Fwd 510A via the NCR-MT 520A.

[0059] (1.3) Configuration Example of Each Device A configuration example of each device in the mobile communication system 1 according to the embodiment will be described.

[0060] 9 is a diagram showing an example of the configuration of an NCR device 500A (relay device) according to an embodiment. The NCR device 500A includes an NCR-Fwd 510A, an NCR-MT 520A, and an interface 530.

[0061] The NCR-Fwd 510A includes a radio unit 511A and an NCR control unit 512A. The radio unit 511A includes an antenna unit 511a including multiple antennas (multiple antenna elements), an RF circuit 511b including an amplifier, and a directivity control unit 511c that controls the directivity of the antenna unit 511a. The RF circuit 511b amplifies and relays (transmits) radio signals transmitted and received by the antenna unit 511a. The RF circuit 511b may convert analog radio signals into digital signals and then reconvert them to analog signals after digital signal processing. The directivity control unit 511c may perform analog beamforming using analog signal processing. The directivity control unit 511c may perform digital beamforming using digital signal processing. The directivity control unit 511c may perform hybrid analog and digital beamforming. The NCR control unit 512A controls the radio unit 511A in response to control signals from the NCR-MT 520A. The NCR control unit 512A may include at least one processor.

[0062] The NCR-MT 520A 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 (wireless 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 on the NCR-MT 520A. The operations of the NCR-MT 520A (and the NCR device 500A) described above and below may be operations controlled by the control unit 523. The control unit 523 includes at least one processor and at least one memory. The memory stores programs executed by the processor and information used in processing by the processor. The processor may include a baseband processor and a CPU (Central Processing Unit). The baseband processor performs modulation / demodulation and encoding / decoding of baseband signals. The CPU executes programs stored in the memory to perform various processes. In addition, the control unit 523 executes the functions of at least one layer of PHY, MAC, RRC, and F1-AP.

[0063] The interface 530 electrically or logically connects the NCR-Fwd 510A and the NCR-MT 520A. The control unit 523 of the NCR-MT 520A controls the NCR-Fwd 510A via the interface 530. The interface 530 may be a logical entity of an upper layer (e.g., an application layer).

[0064] In the embodiment, the receiver 521 of the NCR-MT 520A receives signaling (NCR control signal) used to control the NCR device 500A from the gNB 200 via wireless communication. The controller 523 of the NCR-MT 520A controls the NCR device 500A based on the signaling. This enables the gNB 200 to control the NCR-Fwd 510A via the NCR-MT 520A.

[0065] (1.3.2) Example of configuration of user equipment Fig. 10 is a diagram showing the configuration of a UE 100 (user equipment) according to an embodiment. The UE 100 has a receiving unit 110, a transmitting unit 120, and a control unit 130. The receiving unit 110 and the transmitting unit 120 constitute a wireless communication unit that performs wireless communication with the gNB 200.

[0066] The receiving unit 110 performs various types of reception under the control of the control unit 130. The receiving unit 110 includes an antenna and a receiver. The receiver converts a radio signal received by the antenna into a baseband signal (received signal) and outputs the baseband signal to the control unit 130.

[0067] The transmitting unit 120 performs various transmissions under the control of the control unit 130. The transmitting unit 120 includes an antenna and a transmitter. The transmitter converts a baseband signal (transmission signal) output by the control unit 130 into a radio signal and transmits it from the antenna.

[0068] The control unit 130 performs various controls and processes in the UE 100. Such processes include processes of each layer described below. The operations of the UE 100 described above and below may be operations controlled by the control unit 130. The control unit 130 includes at least one processor and at least one memory. The memory stores programs executed by the processor and information used in the processing by the processor. The processor may include a baseband processor and a CPU. The baseband processor performs modulation / demodulation and encoding / decoding of baseband signals. The CPU executes programs stored in the memory to perform various processes.

[0069] (1.3.3) Configuration example of base station Fig. 11 is a diagram showing a configuration example of a gNB 200 (base station) according to an embodiment. The gNB 200 has a transmitter 210, a receiver 220, a controller 230, and a backhaul communication unit 240.

[0070] The transmitting unit 210 performs various transmissions under the control of the control unit 230. The transmitting unit 210 includes an antenna and a transmitter. The transmitter converts a baseband signal (transmission signal) output by the control unit 230 into a radio signal and transmits it from the antenna. The receiving unit 220 performs various receptions under the control of the control unit 230. The receiving unit 220 includes an antenna and a receiver. The receiver converts a radio signal received by the antenna into a baseband signal (reception signal) and outputs it to the control unit 230. The transmitting unit 210 and the receiving unit 220 may be capable of beamforming using multiple antennas.

[0071] The control unit 230 performs various controls in the gNB 200. The operations of the gNB 200 described above and below may be operations controlled by the control unit 230. The control unit 230 includes at least one processor and at least one memory. The memory stores programs executed by the processor and information used in processing by the processor. The processor may include a baseband processor and a CPU. The baseband processor performs modulation / demodulation and encoding / decoding of baseband signals. The CPU executes programs stored in the memory to perform various processes.

[0072] The backhaul communication unit 240 is connected to adjacent base stations via an inter-base station interface. The backhaul communication unit 240 is connected to the AMF / UPF 300 via a base station-core network interface. The gNB is composed of a CU (Central Unit) and a DU (Distributed Unit) (i.e., functionally divided), and the two units may be connected via an F1 interface.

[0073] In the embodiment, the transmitter 210 of the gNB 200 transmits signaling (NCR control signal) used to control the NCR-Fwd 510A to the NCR-MT 520A via wireless communication. This enables the gNB 200 to control the NCR device 500A via the NCR-MT 520A.

[0074] (1.4) Operation according to the first embodiment In the first embodiment, the case where gNB200 transitions NCR-MT520A to the RRC idle state (i.e., releases the RRC connection) is mainly assumed.

[0075] Here, it is possible to assume (Assumption 1) that the NCR-MT 520A is basically in the RRC connected state. Under this assumption, the NCR device 500A is always controllable by the network 5, so the gNB 200 does not release the RRC connection of the NCR-MT 520A. Therefore, the NCR-MT 520A can only enter the RRC idle state upon initial access (e.g., upon power-on) or RLF (more precisely, upon RRC re-establishment failure). The initial state of the NCR-Fwd 510A upon initial access is clear (i.e., off). The NCR-Fwd 510A is also off when transitioning to the RRC idle state due to RLF.

[0076] On the other hand, it is also possible to assume (Assumption 2) that the RRC connection of the NCR-MT 520A may be released by the gNB 200. This assumption allows the gNB 200 to release the RRC connection of the NCR-MT 520A for purposes such as power saving and / or reducing signaling overhead of the NCR device 500A. Therefore, the NCR-MT 520A may enter the RRC idle state due to all conventional conditions, such as initial access, RLF, and RRC release. After the NCR-MT 520A transitions to the RRC idle state, the NCR-Fwd 510A may be able to fall back to a conventional RF repeater.

[0077] The NCR device 500A is network-controlled by NCR control signals (e.g., side control information and RRC signaling). Assumption 1 is very simple, as there is no reason for the gNB200 to release the RRC connection of the NCR-MT520A in normal conditions. However, as in assumption 2, there may be cases where the gNB200 releases the RRC connection of the NCR-MT520A under specific conditions. Since it is necessary to allow for various gNB200 implementations, it is necessary to clarify the operation of the NCR device 500A in the RRC idle state due to RRC release.

[0078] Meanwhile, with regard to the operation of the NCR device 500A in the RRC inactive state, after the NCR-MT 520A transitions to the RRC inactive state, the NCR device 500A turns on or off the NCR-Fwd 510A according to the latest configuration information received from the gNB 200. Here, the NCR-MT 520A in the RRC inactive state can continue to be controlled by the gNB 200. In other words, the gNB 200 can always page the NCR-MT 520A by RAN paging (i.e., a call message sent at the discretion of the gNB 200).

[0079] In contrast, the NCR-MT 520A in the RRC idle state cannot be controlled by the gNB 200. This is because CN paging (i.e., a call message sent at the discretion of the AMF 300A) is required to establish an RRC connection for the NCR-MT 520A for transmitting side control information and configuration information. Therefore, it is desirable to consider the operation of the NCR device 500A in the RRC idle state separately from the operation in the RRC inactive state. The operation of the NCR-Fwd 510A in the RRC inactive state is consistent with the operation in the RRC connected state and is considered to be different from the operation of the NCR-Fwd 510A in the RRC idle state.

[0080] Furthermore, as described in Assumption 2 above, if the NCR device 500A is not controlled by the gNB 200, the NCR device 500A is considered to have the potential to fall back to a conventional RF repeater. On the other hand, in the RRC inactive state, the NCR device 500A turns on or off the NCR-Fwd 510A according to the latest setting received from the gNB 200, so the NCR device 500A in the RRC inactive state is considered unable to fall back to a conventional RF repeater. Therefore, the possibility of falling back to a conventional RF repeater may be available only when the NCR-MT 520A is in the RRC idle state.

[0081] A conventional RF repeater is an implementation technology from the perspective of network control. Therefore, when the NCR device 500A falls back to a conventional RF repeater, it is no longer a network-controlled repeater. In other words, when the NCR device 500A is no longer network-controlled (for example, when the NCR-MT 520A transitions to an RRC idle state), the operation of the NCR device 500A can be implementation-dependent. Thus, when the NCR device 500A is not controlled by the gNB 200 (for example, when the NCR-MT 520A transitions to an RRC idle state), the NCR device 500A may no longer be considered an NCR device 500A from the perspective of network control.

[0082] As described above, the operation of the NCR device 500A in the RRC idle state due to RRC release needs to be clear to allow for various gNB 200 implementations and should be different from the operation in the RRC inactive state. Furthermore, although the NCR-Fwd 510A is turned off when the NCR-MT 520A enters the RRC idle state due to a failure to find a suitable cell when an RLF occurs, there is no significant reason to distinguish between a transition to the RRC idle state due to an RRC release and a transition to the RRC idle state due to an RLF. Therefore, regardless of the cause of the transition to the RRC idle state, the NCR-Fwd 510A may need to be turned off when the NCR-MT 520A transitions to the RRC idle state. Furthermore, if the NCR device 500A is not considered a network-controlled repeater (e.g., when the NCR-MT 520A is in the RRC idle state), the NCR device 500A may be allowed to operate as a conventional RF repeater. Therefore, as in the case of RLF, it is also possible to turn off NCR-Fwd510A when NCR-MT520A is released to the RRC idle state by gNB200.

[0083] 12 is a diagram for explaining the operation according to the first embodiment. The NCR device 500A includes an NCR-Fwd 510A that performs a relay operation of relaying a wireless signal transmitted between the network 5 and the UE 100, and an NCR-MT 520A that receives a control signal (NCR control signal) used to control the NCR-Fwd 510A from the network 5.

[0084] In the first embodiment, the NCR-MT 520A determines that there is no control from the network 5 in response to transition from the RRC connected state to the RRC idle state. The NCR device 500A may perform a predetermined implementation-dependent operation in response to determining that there is no control from the network 5. The implementation-dependent operation may be a relay operation that does not depend on control from the network 5 (i.e., the operation of a conventional RF repeater). In this way, by autonomously operating as a conventional RF repeater, the operation of expanding the coverage of the gNB 200 can be continued. In this way, when the NCR device 500A according to the first embodiment transitions to the RRC idle state, it determines that there is no control from the network 5 and can operate as a conventional RF repeater.

[0085] FIG. 13 is a diagram showing an example of the operation of the NCR device 500A according to the first embodiment.

[0086] In step S101, NCR-MT 520A is in an RRC connected state in the cell of gNB 200. NCR-MT 520A in the RRC connected state receives an NCR control signal such as side control information from gNB 200 and controls NCR-Fwd 510A according to the NCR control signal.

[0087] In step S102, the NCR-MT 520A transitions to the RRC idle state. For example, the NCR-MT 520A transitions to the RRC idle state in response to receiving an RRC Release message from the gNB 200. Alternatively, the NCR-MT 520A may transition to the RRC idle state in response to detecting an RLF and failing to re-establish an RRC connection (i.e., not being able to find a suitable cell). Alternatively, the NCR-MT 520A may transition to the RRC idle state in response to initial access (power ON).

[0088] In step S103, the NCR-MT 520A determines (detects) that network control has been lost. The NCR-MT 520A may notify the upper layer that network control has been lost. As described in a modified example of the first embodiment, the NCR device 500A (NCR-MT 520A) may determine whether to behave as the NCR device 500A or perform implementation-dependent operations (e.g., conventional RF repeater operations). If the NCR device 500A (NCR-MT 520A) previously stores setting information for performing conventional RF repeater operations, it may read out the setting information.

[0089] In step S104, the NCR device 500A may begin implementation-dependent operation, for example, the NCR device 500A operates as a conventional RF repeater.

[0090] The operation of step S104 may be changed depending on the cause of transition to the RRC idle state. For example, the NCR device 500A may not operate as a conventional RF repeater or perform relaying (i.e., turn off the NCR-Fwd 510A) at the time of initial access.

[0091] Furthermore, the NCR device 500A may not perform relay operation when the NCR-MT 520A transitions to the RRC idle state due to an RLF. This is because relay operation would be wasted if the RLF were caused by poor reception levels (e.g., reference signal received power (RSRP)) from the cell. However, the NCR device 500A may perform relay operation (e.g., conventional RF repeater operation) when, for example, the reception level from the cell is higher than a threshold. The threshold may be set to the NCR-MT 520A by the gNB 200. For example, the gNB 200 sets the threshold using an NCR control signal. The threshold is not limited to the reception level (RSRP), and may be compared with other wireless quality indicators such as RSRQ and / or SINR. Note that the NCR device 500A may stop relay operation when the reception level from the cell (and / or other wireless quality indicators) is lower than a threshold. Here, the RLF may be considered as a type of threshold value.

[0092] Furthermore, when the NCR device 500A transitions to the RRC idle state in response to receiving an RRC Release message from the gNB 200, it may perform relay operation (e.g., conventional RF repeater operation). In this case, the NCR device 500A may perform relay operation by forming a beam under independent control, rather than a beam (i.e., antenna weight) specified by the network 5 (gNB 200). For example, the NCR device 500A calculates antenna weights using sensor-based position estimates of the UE 100 and gNB 200 and / or the direction of arrival of radio signals.

[0093] (1.5) Modification of the First Embodiment In the above-described first embodiment, an example was described in which the NCR device 500A performs a predetermined operation when the NCR-MT 520A transitions to the RRC idle state. In contrast, in this modification, the network 5 (gNB 200) can specify the operation of the NCR device 500A when the NCR-MT 520A transitions to the RRC idle state.

[0094] In this modified example, the NCR-MT 520A receives configuration information from the network 5 (gNB 200) indicating whether the NCR device 500A will perform relay operation (i.e., conventional RF repeater operation) independent of control from the network 5 after transitioning to the RRC idle state. The NCR device 500A performs operation based on the configuration information in response to determining that there is no control from the network 5. Thus, in this modified example, the gNB 200 configures the NCR-MT 520A as to whether the NCR device 500A may operate as a conventional RF repeater when the NCR-MT 520A transitions to the RRC idle state. This allows the gNB 200 to specify the operation of the NCR-MT 520A when the NCR-MT 520A transitions to the RRC idle state.

[0095] 14 is a diagram showing an example of the operation of an NCR device 500A according to a modification of the first embodiment. Here, differences from the operation in FIG. 13 will be mainly described, and overlapping descriptions will be omitted.

[0096] In step S131, NCR-MT520A is connected to gNB200, and NCR-Fwd510A is controlled using side control information, etc.

[0097] In step S132, the NCR-MT 520A receives configuration information from the gNB 200 that configures operation during transition to the RRC idle state. The configuration information indicates whether or not the gNB 200 is allowed to operate as a conventional RF repeater. For example, the gNB 200 transmits the configuration information to the NCR-MT 520A in an RRC Reconfiguration message. The gNB 200 may also transmit the configuration information to the NCR-MT 520A in an RRC Release message.

[0098] Here, gNB200 may associate information regarding the cause of RRC idle state transition and set it in NCR-MT520A. That is, gNB200 sets the operation at the time of RRC idle state transition in NCR-MT520A for each cause of RRC idle state transition. Here, the "cause" may be, for example, 1) at the time of RRC Release (i.e., when gNB200 intentionally transitions to RRC idle state), 2) when RLF occurs (specifically, when gNB200 unintentionally transitions to RRC idle state due to cell selection / RRC connection re-establishment failure, etc.), or 3) at the time of initial access. For example, when gNB200 transitions NCR-MT520A to RRC idle state in RRC Release, it may be permitted to operate as a conventional RF repeater. The gNB200 may be configured to turn off the NCR-Fwd510A (not permitting implementation-dependent relay operation) when the NCR-MT520A transitions to the RRC idle state due to an RLF.

[0099] The order of steps S131 and S132 may be reversed.

[0100] In step S133, NCR-MT 520A transitions to the RRC idle state.

[0101] In step S134, the NCR-MT 520A determines (detects) that network control has been lost.

[0102] In step S135, the NCR device 500A operates in accordance with the setting information in step S132, and controls the relay operation (NCR-Fwd 510A).

[0103] In this modified example, an example has been described in which the gNB 200 transmits configuration information for setting operation during RRC idle state transition to the NCR-MT 520A by dedicated signaling. However, the gNB 200 may transmit the configuration information by broadcast signaling (e.g., system information block (SIB)). For example, the gNB 200 broadcasts configuration information in the SIB indicating whether the NCR device 500A may operate as a conventional RF repeater. If operation as a conventional RF repeater is permitted, the NCR device 500A may behave as a conventional RF repeater. On the other hand, if not permitted, the NCR device 500A may behave as the NCR device 500A and operate in accordance with the technical specifications for the NCR device 500A (e.g., turning off the NCR-Fwd 510A in the RRC idle state).

[0104] (2) Second Embodiment The second embodiment will be described mainly focusing on the differences from the first embodiment. The second embodiment may be implemented in combination with the first embodiment.

[0105] As described above, after the NCR-MT 520A transitions to the RRC inactive state, the NCR device 500A can turn on or off the NCR-Fwd 510A according to the latest setting information received from the gNB 200. Similarly, even after the NCR-MT 520A transitions to the RRC inactive state, the NCR device 500A may turn on or off the NCR-Fwd 510A according to the latest setting information received from the gNB 200.

[0106] However, if it is assumed that the NCR-Fwd 510A permanently maintains the RRC idle state or the RRC inactive state after the NCR-MT 520A transitions to the RRC idle state or the RRC inactive state, there is a problem in that the NCR-Fwd 510A permanently continues to operate according to the current setting information (i.e., the latest setting information). For example, if the NCR device 500A in the RRC idle state or the RRC inactive state permanently turns on the NCR-MT 520A, unexpected interference or the like may occur in the network 5.

[0107] Therefore, in the second embodiment, the NCR device 500A controls the NCR-Fwd 510A with the current settings for a certain period after transitioning to the RRC idle state or the RRC inactive state. In other words, a time limit is set for the NCR device 500A in the RRC idle state or the RRC inactive state to continue operating in accordance with the current setting information (for example, turning the NCR-Fwd 510A on).

[0108] Specifically, in the second embodiment, first, the NCR-MT 520A receives setting information (NCR control signal) for setting relay operation from the gNB 200 in the RRC connected state. Second, the NCR-MT 520A transitions from the RRC connected state to the RRC idle state or the RRC inactive state. Third, the NCR device 500A retains the setting information (NCR control signal) for a period until a certain time has elapsed since the transition to the RRC idle state or the RRC inactive state, and performs operations in accordance with the setting information (NCR control signal).

[0109] The NCR device 500A may discard the setting information (NCR control signal) when a certain time has elapsed since transitioning to the RRC idle state or the RRC inactive state, thereby saving memory capacity of the NCR device 500A.

[0110] The NCR device 500A may initiate a procedure to transition to the RRC connected state when a certain time has elapsed since transitioning to the RRC idle state or the RRC inactive state. This procedure is an RRC connection establishment procedure when the NCR-MT 520A is in the RRC idle state, and an RRC connection restoration procedure when the NCR-MT 520A is in the RRC inactive state. By transitioning the NCR-MT 520A to the RRC connected state, the NCR-MT 520A can acquire a new NCR control signal (e.g., NCR setting information) from the gNB 200.

[0111] FIG. 15 is a diagram showing an example of the operation of the NCR device 500A according to the second embodiment.

[0112] In step S201, the NCR-MT 520A in the RRC connected state operates the NCR-Fwd 510A in accordance with the NCR control signal (NCR setting information and / or NCR control information) from the gNB 200. It is assumed that the NCR-MT 520A receives an NCR control signal from the gNB 200 to turn on the NCR-Fwd 510A.

[0113] In step S202, the NCR-MT 520A in the RRC connected state receives an RRC Release message including a timer setting from the gNB 200. The timer setting includes a timer value indicating a time to be set in a timer for measuring a certain period of time during which the NCR control signal continues to be applied. If the NCR device 500A includes multiple NCR-Fwds 510A, the timer value may be set for each NCR-Fwd 510A. For example, the timer value may be set in association with an NCR-Fwd ID (index).

[0114] In this operation example, gNB200 is assumed to transmit the timer setting to NCR-MT520A in an RRC Release message, but gNB200 may also transmit the timer setting to NCR-MT520A in an RRC Reconfiguration message.

[0115] In step S203, the NCR-MT 520A transitions to the RRC idle state or the RRC inactive state and starts a timer based on the timer setting. The NCR-MT 520A holds the current NCR control signal while the timer is running.

[0116] In step S204, the NCR-MT 520A controls the NCR-Fwd 510A based on the NCR control signal it holds while the timer is running. The NCR-MT 520A may notify the upper layer that the timer has started or is running, and the upper layer may control the NCR-Fwd 510A based on the notification.

[0117] In step S205, the NCR-MT 520A determines whether the timer has expired. If the timer has not expired (step S205: NO), in step S204, the NCR-MT 520A continues to control the NCR-Fwd 510A based on the NCR control signal it has stored.

[0118] On the other hand, if the timer has expired (step S205: YES), in step S206, the NCR-MT 520A turns off the NCR-Fwd 510A in response to the expiration of the timer. The NCR-MT 520A may notify the upper layer that the timer has expired, and the upper layer may control the NCR-Fwd 510A based on the notification.

[0119] In step S206, the NCR-MT 520A may discard the NCR control signal it is holding in response to the expiration of the timer.

[0120] In step S207, the NCR-MT 520A may initiate an RRC connection establishment procedure or an RRC connection recovery procedure in response to expiration of the timer, and transition to the RRC connected state. In this procedure, the NCR-MT 520A transmits an RRC Setup Request message or an RRC Resume Request message to the gNB 200 as Msg 3. The NCR-MT 520A may include information indicating that the connection request is for updating an NCR control signal (e.g., NCR setting information) in the Msg 3, for example, as a Cause IE. Alternatively, the NCR-MT 520A may notify the information in Msg 5. The NCR-MT 520A may be notified by PRACH (Physical Random Access Channel) partitioning of Msg 1. The NCR-MT 520A that has transitioned to the RRC connected state receives a new NCR control signal (for example, new NCR setting information) from the gNB 200.

[0121] Alternatively, in step S207, the NCR-MT 520A may start repeating operation as a conventional RF repeater without network control in response to expiration of the timer.

[0122] (3) Third Embodiment The third embodiment will be described mainly focusing on the differences from the first and second embodiments. The third embodiment may be implemented in combination with the first and / or second embodiments.

[0123] As described above, the gNB200 can call the NCR-MT520A in the RRC inactive state by gNB200-initiated paging (so-called RAN paging) and transition the NCR-MT520A to the RRC connected state. Therefore, it is easy for the gNB200 to control the NCR-MT520A (NCR device 500A).

[0124] On the other hand, gNB200 cannot call NCR-MT520A in the RRC idle state by RAN paging. Specifically, in order to call NCR-MT520A in the RRC idle state, it is necessary to use paging initiated by CN20 (specifically, AMF300A) (so-called CN paging). Therefore, it is difficult for gNB200 to control NCR-MT520A in the RRC idle state.

[0125] Therefore, in the third embodiment, the gNB 200 requests CN paging from the AMF 300A to call the NCR-MT 520A in the RRC idle state. This makes it possible to call the NCR-MT 520A in the RRC idle state and transition to the RRC connected state, making it easier for the gNB 200 to control the NCR-MT 520A (NCR device 500A).

[0126] Specifically, in the third embodiment, the gNB200 that transitions the NCR-MT520A from the RRC connected state to the RRC idle state sends a paging request to the AMF300A (core network device) requesting paging (i.e., CN paging) from the AMF300A to the NCR device 500A.

[0127] 16 is a diagram showing an example of operation of the mobile communication system 1 according to the third embodiment. It is assumed that communication between the gNB 200 and the AMF 300A is performed on the NG interface.

[0128] In step S301, the NCR device 500A (NCR-MT 520A) performs an initial connection procedure to the network 5. The initial connection procedure includes an RRC connection establishment procedure between the NCR-MT 520A and the gNB 200, and an authentication and registration procedure between the NCR-MT 520A and the AMF 300A.

[0129] In step S302, the AMF 300A may authenticate the NCR-MT 520A at the time of initial connection of the NCR-MT 520A. The AMF 300A may manage (retain) an identification ID associated with the UE ID of the NCR-MT 520A. Here, the UE ID may be an IMSI (International Mobile Subscriber Identity) or a 5G-S-TMSI (Temporary Mobile Subscriber Identity). The AMF 300A may notify the gNB 200 of the identification ID, for example, in a UE context setup message.

[0130] Alternatively, in step S302, the AMF 300A may manage (retain) the UE ID of the NCR-MT 520A as the UE ID of the NCR device 500A. The AMF 300A may manage (retain) the UE ID in association with the gNB 200 to which the NCR-MT 520A belongs (the gNB 200 communicating with the AMF 300A). The gNB 200 may notify the AMF 300A of the cell ID of the cell to which the NCR-MT 520A belongs, for example, in a UE context modification message. The AMF 300A may manage (retain) the UE ID in association with the cell ID.

[0131] In step S303, gNB200 may transmit an NCR control signal such as side control information to NCR-MT520A in the RRC connected state.

[0132] In step S304, NCR-MT520A may control NCR-Fwd510A in accordance with an NCR control signal received from gNB200.

[0133] In step S305, gNB200 transmits an RRC Release message to NCR-MT520A, causing NCR-MT520A to transition to an RRC idle state (step S307). Also, in step S306, gNB200 transmits a UE Context release message to AMF300A. gNB200 and AMF300A may retain the above-mentioned identification ID even after the UE context is deleted. AMF300A may retain the UE ID of NCR-MT520A even after the UE context is deleted. gNB200 and AMF300A may retain the above-mentioned cell ID even after the UE context is deleted.

[0134] In step S308, NCR-MT 520A may control NCR-Fwd 510A based on the NCR control signal last received from gNB 200. NCR-Fwd 510A may be on or off.

[0135] In step S309, the gNB200 determines to change the control (settings and operation) of the NCR device 500A in the RRC idle state. For example, the gNB200 determines to change the NCR setting information in order to change the scheduling of radio resources.

[0136] In step S310, gNB200 transmits a CN paging request to AMF300A. The CN paging request includes at least one of information indicating a request to call NCR device 500A, the above-mentioned identification ID, and the above-mentioned cell ID (specifically, the cell ID of the cell in which NCR device 500A in the RRC idle state is located, or the cell ID of the cell for which a setting change is required).

[0137] The AMF 300A that receives a CN paging request from the gNB 200 identifies which NCR device 500A to call based on the information included in the CN paging request. For example, when an identification ID is included in the CN paging request, the AMF 300A identifies the UE ID of the NCR device 500A associated with the identification ID. When a cell ID is included in the CN paging request, the AMF 300A identifies the UE ID of the NCR device 500A associated with the cell ID. Note that when a cell ID is not included in the CN paging request, the AMF 300A may call all NCR devices 500A associated with the gNB 200 that sent the request.

[0138] In step S311, AMF300A sends a paging message including the UE ID of the identified NCR device 500A to gNB200.

[0139] In step S312, gNB200 transmits a paging message from AMF300A on a paging control channel (PCCH). When NCR device 500A (NCR-MT520A) receives the paging message including its UE ID, it determines that it is being called.

[0140] In step S313, in response to receiving the paging message, NCR-MT520A performs an RRC connection establishment procedure with gNB200.

[0141] In step S314, NCR-MT 520A transitions from the RRC idle state to the RRC connected state.

[0142] (4) Fourth Embodiment Next, a fourth embodiment will be described, focusing on differences from the above-described embodiments. As shown in Fig. 17, the relay device according to the fourth embodiment is a Reconfigurable Intelligent Surface (RIS) device 500B that changes the propagation direction of an incident radio wave (wireless signal) by reflection or refraction. The term "NCR" in the above-described embodiments can be read as "RIS."

[0143] RIS is a type of repeater (hereinafter also referred to as "RIS-Fwd") that can perform beamforming (directivity control) similar to NCR by changing the properties of a metamaterial. In the case of RIS, the range (distance) of the beam may also be changed by controlling the reflection direction and / or refraction direction of each unit element. For example, the RIS may be configured to control the reflection direction and / or refraction direction of each unit element and to focus (direct the beam) on a nearby UE or a distant UE.

[0144] The RIS device 500B has a new UE (hereinafter referred to as "RIS-MT") 520B, which is a control terminal for controlling the RIS-Fwd 510B. The RIS-MT 520B establishes a wireless connection with the gNB 200 and performs wireless communication with the gNB 200, thereby controlling the RIS-Fwd 510B in cooperation with the gNB 200. The RIS-Fwd 510B may be a reflective RIS. Such a RIS-Fwd 510B changes the propagation direction of incident radio waves by reflecting the radio waves. Here, the reflection angle of the radio waves is variably settable. The RIS-Fwd 510B reflects radio waves incident from the gNB 200 toward the UE 100. The RIS-Fwd 510B may be a transparent RIS. Such a RIS-Fwd 510B changes the propagation direction of the radio waves by refracting the incident radio waves. Here, the refraction angle of the radio wave can be variably set.

[0145] FIG. 18 is a diagram showing an example configuration of a RIS-Fwd (repeater) 510B and a RIS-MT (control terminal) 520B according to an embodiment. The RIS-MT 520B includes a receiver 521, a transmitter 522, and a controller 523. This configuration is similar to that of the above-described embodiment. The RIS-Fwd 510B includes a RIS 511B and a RIS controller 512B. The RIS 511B is a metasurface configured using a metamaterial. For example, the RIS 511B is configured by arranging structures that are very small relative to the wavelength of radio waves in an array. By making the structures different shapes depending on the placement location, it is possible to arbitrarily design the direction and / or beam shape of the reflected waves. The RIS 511B may be a transparent dynamic metasurface. The RIS 511B may be configured by overlaying a transparent glass substrate on a transparent metasurface substrate on which a large number of small structures are regularly arranged, and by slightly moving the overlaid glass substrate, it may be possible to dynamically control three patterns: a mode that transmits incident radio waves, a mode that transmits some of the radio waves and reflects some of them, and a mode that reflects all of the radio waves. The RIS control unit 512B controls the RIS 511B in response to 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 in response to the RIS control signal.

[0146] (5) Other Embodiments In the above-described embodiment, an example has been described in which the relay device that performs relay transmission is the NCR device 500A or the RIS device 500B. However, the relay device that performs relay transmission is not limited to the NCR device 500A or the RIS device 500B, and may be an IAB (Integrated Access and Backhaul) node defined in the 3GPP technical specifications.

[0147] The above-described operational flows are not limited to being implemented independently, but can also be implemented by combining two or more operational flows. For example, some steps of one operational flow may be added to another operational flow, or some steps of one operational flow may be replaced with some steps of another operational flow. In each flow, it is not necessary to execute all steps, and only some steps may be executed.

[0148] In the above-described embodiments and examples, an example in which the base station is an NR base station (gNB) has been described, but the base station may be an LTE base station (eNB) or a 6G base station. The base station may also be a relay node such as an IAB (Integrated Access and Backhaul) node. The base station may also be a DU of the IAB node. The UE 100 may also be an MT (Mobile Termination) of the IAB node.

[0149] The term "network node" primarily refers to a base station, but may also refer to a core network device or a part of a base station (CU, DU, or RU). A network node may also be configured by a combination of at least a part of a core network device and at least a part of a base station.

[0150] In the above embodiment, an example in which the base station is an NR base station (gNB) has been described, but the base station may be an LTE base station (eNB). The base station may also be a relay node such as an IAB node. The base station may also be a DU (Distributed Unit) of the IAB node.

[0151] A program may be provided that causes a computer to execute each process performed by a communication device according to the above-described embodiment, for example, the UE 100 (NCR-MT520A, RIS-MT520B), the gNB 200, or the relay device. The program may be recorded on a computer-readable medium. Using a computer-readable medium, the program can be installed on a computer. Here, the computer-readable medium on which the program is recorded may be a non-transitory recording medium. The non-transitory recording medium is not particularly limited, and may be, for example, a recording medium such as a CD-ROM or a DVD-ROM. Furthermore, circuits that execute each process performed by the UE 100, the gNB 200, or the relay device may be integrated, and at least a portion of the UE 100, the gNB 200, or the relay device may be configured as a semiconductor integrated circuit (chipset, SoC: System on a chip).

[0152] The functions performed by the UE 100, the gNB 200 (network node), or the relay device may be implemented in circuitry or processing circuitry, including general-purpose processors, application-specific processors, integrated circuits, ASICs (Application Specific Integrated Circuits), a CPU (a Central Processing Unit), conventional circuits, and / or combinations thereof, programmed to perform the described functions. A processor includes transistors and other circuits and is considered to be circuitry or processing circuitry. A processor may also be a programmed processor that executes a program stored in memory. In this specification, circuitry, unit, or means refers to hardware that is programmed to perform the described functions or hardware that executes them. The hardware may be any hardware disclosed herein or any hardware known to be programmed or capable of performing the described functions. If the hardware is a processor, the circuitry, means, or unit is a combination of hardware and software used to configure the hardware and / or processor.

[0153] As used in this disclosure, the terms "based on" and "depending on / in response to" do not mean "based only on" or "depending only on," unless expressly stated otherwise. The term "based on" means both "based only on" and "based at least in part on." Similarly, the term "depending on" means both "depending only on" and "depending at least in part on." The terms "include," "comprise," and variations thereof do not mean including only the listed items, but may mean including only the listed items or may include additional items in addition to the listed items. Additionally, the term "or," as used in this disclosure, is not intended to mean an exclusive or. Furthermore, any reference to elements using designations such as "first," "second," etc., as used in this disclosure does not generally limit the quantity or order of those elements. These designations may be used herein as a convenient method of distinguishing between two or more elements. Thus, a reference to a first and a second element does not imply that only two elements may be employed therein or that the first element must precede the second element in some way. In this disclosure, where articles are added by translation, such as a, an, and the in English, these articles shall include the plural unless the context clearly indicates otherwise.

[0154] The above describes the embodiments in detail with reference to the drawings, but the specific configuration is not limited to that described above, and various design changes can be made within the scope that does not deviate from the gist of the invention.

[0155] This application claims priority from Japanese Patent Application No. 2023-014895 (filed February 2, 2023), the entire contents of which are incorporated herein by reference.

[0156] (6) Supplementary Notes The following are additional notes regarding the features of the above-described embodiment.

[0157] (Supplementary Note 1) A communication method using a relay device having a relay device that performs a relay operation to relay a radio signal transmitted between a network and a user device, and a control terminal that receives a control signal used to control the relay device from the network, the communication method comprising: a step of the control terminal transitioning to a radio resource control (RRC) idle state; and a step of the relay device determining that there is no control from the network in response to the transition to the RRC idle state.

[0158] (Supplementary Note 2) The communication method according to Supplementary Note 1, wherein the relay device performs a predetermined implementation-dependent operation in response to determining that the control from the network is not present.

[0159] (Supplementary Note 3) The communication method according to Supplementary Note 2, wherein the implementation-dependent operation is the relay operation that does not depend on the control from the network.

[0160] (Supplementary Note 4) The communication method according to any one of Supplementary Notes 1 to 3, comprising the steps of: the control terminal receiving, from the network, configuration information indicating whether the relay device will perform the relay operation independent of the control from the network after transitioning to the RRC idle state; and the relay device performing an operation based on the configuration information in response to determining that there is no control from the network.

[0161] (Supplementary Note 5) A communication method using a relay device having a relay device that performs a relay operation to relay radio signals transmitted between a network and a user device, and a control terminal that receives a control signal used to control the relay device from the network, the communication method comprising: a step in which the control terminal receives, from the network, configuration information for configuring the relay operation in a radio resource control (RRC) connected state; a step in which the control terminal transitions to an RRC idle state or an RRC inactive state; and a step in which the relay device operates in accordance with the configuration information in the RRC idle state or the RRC inactive state for only a period until a certain time has elapsed since the transition.

[0162] (Supplementary Note 6) The communication method according to Supplementary Note 5, further comprising the step of the relay device discarding the setting information when a certain time has elapsed since the transition.

[0163] (Supplementary Note 7) The communication method according to Supplementary Note 5 or 6, further comprising the step of initiating, by the relay device, a procedure for transitioning from the RRC idle state or the RRC inactive state to the RRC connected state when a certain time has elapsed since the transition.

[0164] (Supplementary Note 8) A communication method using a relay device having a relay that performs a relay operation to relay radio signals transmitted between a network and a user device, and a control terminal that receives a control signal from the network used to control the relay, the communication method comprising: a step in which a network node included in the network transitions the control terminal from a radio resource control (RRC) connected state to an RRC idle state; and a step in which the network node transmits a paging request to a core network device included in the network, requesting paging from the core network device to the relay device.

[0165] 1: Mobile communication system 100: UE 200: gNB 210: Transmitter 220: Receiver 230: Controller 240: Backhaul communication unit 500A: NCR device 510A: NCR-Fwd 520A: NCR-MT 500B: RIS device 511A: Wireless unit 511a: Antenna unit 511b: RF circuit 511c: Directivity control unit 512A: NCR control unit 512B: RIS control unit 521: Receiver 522: Transmitter 523: Controller 530: Interface

Claims

1. A communication method using a repeater node having a repeater function configured to perform a forwarding operation of a radio signal transmitted between a network and a user device, and a control terminal, comprising: The control terminal in a Radio Resource Control (RRC) Connected state receives, from the network, configuration information for configuring the forwarding operation; The control terminal transitions from the RRC connected state to an RRC inactive state; The repeater function continues the forwarding operation in accordance with the setting information in the RRC inactive state. Communication method.

2. The repeater node may further discard the configuration information when a predetermined time has elapsed since the transition. The communication method according to claim 1 .

3. The repeater node may further include initiating a procedure to transition from an RRC idle state or the RRC inactive state to the RRC connected state when a predetermined time has elapsed since the transition. The communication method according to claim 1 or 2.

4. A repeater node having a repeater function configured to perform a forwarding operation of a radio signal transmitted between a network and a user device, and a control terminal, the control terminal receives, in a radio resource control (RRC) connected state, configuration information for configuring the forwarding operation from the network; The control terminal transitions from the RRC connected state to an RRC inactive state, The repeater function continues the forwarding operation in accordance with the setting information in the RRC inactive state. Repeater node.

5. A repeater node having a repeater function configured to perform a forwarding operation of a radio signal transmitted between a network and a user device, and a control terminal, receiving, in a Radio Resource Control (RRC) Connected state, configuration information from the network for configuring the forwarding operation; A process of transitioning from the RRC connected state to an RRC inactive state; In the RRC inactive state, a process of continuing the forwarding operation in accordance with the setting information is executed. program.

6. A chipset for a repeater node having a repeater function configured to perform forwarding operations of radio signals transmitted between a network and a user device, and a control terminal, comprising: receiving, in a Radio Resource Control (RRC) Connected state, configuration information from the network for configuring the forwarding operation; A process of transitioning from the RRC connected state to an RRC inactive state; In the RRC inactive state, a process of continuing the forwarding operation in accordance with the setting information is executed. Chipset.

7. A system comprising a network, a user device, and a repeater node, The repeater node has a repeater function configured to perform a forwarding operation of radio signals transmitted between the network and the user equipment, and a control terminal; the control terminal receives, in a radio resource control (RRC) connected state, configuration information for configuring the forwarding operation from the network; The control terminal transitions from the RRC connected state to an RRC inactive state, The repeater function continues the forwarding operation in accordance with the setting information in the RRC inactive state. system.