Communication method, repeater node, program, chipset, system, and user device

Abstract

To provide a communication method using a repeater device which can be controlled from a network.SOLUTION: The communication method uses a repeater node having a repeater device configured to perform a forwarding operation of a radio signal transmitted between a network and a user equipment, and a control terminal supporting a function of the user equipment. The communication method includes receiving, by a control terminal in a radio resource control (RRC) connected state in a first cell, control configuration information used for controlling a repeater apparatus from a network, transferring, by the repeater apparatus, a radio signal based on last control configuration information received from the network when the control terminal transitions from the RRC connected state to an RRC inactive state in the first cell, and stopping, by the repeater apparatus, transfer of the radio signal when the control terminal selects a second cell different from the first cell in the RRC inactive state.SELECTED DRAWING: Figure 8

Description

[Technical Field]

[0001] The present disclosure relates to a communication method, a repeater node, a program, a chipset, a system, and a user equipment for use in a mobile communication system. [Background technology]

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

[0003] Radio signals (radio waves) in high frequency bands such as millimeter waves or terahertz waves have a tendency to propagate in a highly directional manner, which poses a problem of reducing the coverage of base stations. To solve 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 expand the coverage of base stations while suppressing interference, for example, by amplifying radio signals received from base stations and transmitting them directionally. Such repeater devices are also called NCRs (Network-Controlled Repeaters). [Prior art documents] [Non-patent literature]

[0004] [Non-Patent Document 1] 3GPP contribution: RP-213700, “New SI: Study on NR Network-controlled Repeaters” Summary of the Invention

[0005] A communication method according to a first aspect is a communication method using a relay device having a relay device 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 device, the method comprising: the control terminal receiving, from the network, a control setting used to control the relay device; the control terminal initiating an RRC connection re-establishment procedure based on the detection of a radio link failure (RLF); and the control terminal releasing the control setting in response to the initiation of the RRC connection re-establishment procedure.

[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 equipment, 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, which is in a radio resource control (RRC) connected state in a first cell, initiating an RRC connection re-establishment procedure with a second cell based on detection of a radio link failure (RLF) in the first cell; and, if the RRC connection re-establishment with the second cell is successful, the relay device controlling the relaying operation based on whether the second cell is the same cell as the first cell.

[0007] A relay device according to a third aspect comprises a relay that performs a relaying 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, wherein the control terminal initiates an RRC connection re-establishment procedure with a second cell when a radio link failure (RLF) is detected in a first cell while in a radio resource control (RRC) connected state in the first cell, and when the RRC connection re-establishment with the second cell is successful, controls the relaying operation based on whether the second cell is the same cell as the first cell. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a diagram illustrating a configuration of a mobile communication system according to an embodiment. [Figure 2] FIG. 10 is a diagram showing the configuration of a protocol stack of a radio interface of a user plane that handles data. [Figure 3] FIG. 1 is a diagram showing the configuration of a protocol stack of a radio interface of a control plane that handles signaling (control signals). [Figure 4] FIG. 1 is a diagram illustrating an example of an application scenario of an NCR device (relay device) according to an embodiment. [Figure 5] FIG. 1 is a diagram illustrating an example of an application scenario of an NCR device according to an embodiment. [Figure 6] FIG. 10 is a diagram illustrating an example of a control method for an NCR device according to an embodiment. [Figure 7] 1 is a diagram illustrating an example of the configuration of a protocol stack in a mobile communication system having an NCR device according to an embodiment. [Figure 8] 1 is a diagram showing a specific example of the configuration of a mobile communication system 1 having an NCR device according to an embodiment. [Figure 9] FIG. 1 is a diagram illustrating an example of the configuration of an NCR device according to an embodiment. [Figure 10] 1 is a diagram illustrating a configuration of a UE (user equipment) according to an embodiment. [Figure 11] A diagram showing an example configuration of a gNB (base station) according to an embodiment. [Figure 12] FIG. 10 is a diagram showing a first scenario according to the first embodiment. [Figure 13] FIG. 10 is a diagram showing a second scenario according to the first embodiment. [Figure 14] FIG. 2 is a diagram illustrating an example of the operation of the NCR device (NCR-MT) according to the first embodiment. [Figure 15] FIG. 2 is a diagram illustrating a first operation example of the NCR device (NCR-MT) according to the first embodiment. [Figure 16] FIG. 10 is a diagram illustrating a second operation example of the NCR device (NCR-MT) according to the first embodiment. [Figure 17]FIG. 10 is a diagram illustrating a third operation example of the NCR device (NCR-MT) according to the first embodiment. [Figure 18] FIG. 10 is a diagram for explaining a scenario according to the second embodiment. [Figure 19] FIG. 10 is a diagram illustrating an example of operation of the mobile communication system according to the second embodiment. [Figure 20] FIG. 10 is a diagram illustrating an example of the operation of a mobile communication system according to a modification of the second embodiment. [Figure 21] FIG. 10 is a diagram for explaining a RIS device (relay device) according to the third embodiment. [Figure 22] FIG. 10 is a diagram for explaining a RIS device according to a third embodiment. [Figure 23] FIG. 1 illustrates a specific PRACH scenario (RO) for avoiding potential collisions. DETAILED DESCRIPTION OF THE INVENTION

[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 a 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 systems FIG. 1 is a diagram showing a 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 LTE (Long Term Evolution) 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. 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 used by a user. For example, the UE 100 may be a mobile phone terminal (including a smartphone) and / or a tablet terminal, a laptop 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 a UE 100 that has established a connection with its own cell. The gNB 200 has a radio resource management (RRM) function, a routing function for user data (hereinafter simply referred to as "data"), a measurement control function for mobility control and scheduling, 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 that performs wireless communication with a UE 100. One cell belongs to one carrier frequency (hereinafter simply referred to as "frequency").

[0016] The gNB 200 may be functionally divided into a central unit (CU) and distributed units (DUs). The CU controls the DUs. 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 DUs form cells. The DU 202 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 connect to the Evolved Packet Core (EPC), which is the LTE core network. LTE base stations can also connect to 5GC. LTE base stations and gNBs can also be connected via a base station-to-base station interface.

[0018] The 5GC20 includes an Access and Mobility Management Function (AMF) and a User Plane Function (UPF) 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 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] The gNB 200 also transmits a synchronization signal block (SSB: Synchronization Signal / PBCH block). For example, the SSB is composed of four consecutive Orthogonal Frequency Division Multiplex (OFDM) symbols, and includes 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) for the PBCH. The bandwidth of the SSB is, for example, 240 consecutive subcarriers, i.e., 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 UE100 and the MAC layer of gNB200 via transport channels. The MAC layer of gNB200 includes a scheduler, which determines the uplink and downlink transport format (transport block size, modulation and coding scheme (MCS)) and the resource blocks to be allocated to UE100.

[0024] The RLC layer transmits data to the RLC layer on the receiving side 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 logical channels.

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

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

[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 a Radio Resource Control (RRC) layer and a Non-Access Stratum (NAS) 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 referred to as an AS layer.

[0031] (1.2) Example of application scenario for relay devices 4 and 5 are diagrams illustrating an example of an application scenario of the NCR device according to the embodiment.

[0032] 5G / NR enables broadband transmission using higher frequency bands than 4G / LTE. 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 a radio signal can be received directly from the gNB 200. There may be an obstruction between the gNB 200 and the UE 100, preventing the UE 100 from communicating with the gNB 200 within line-of-sight.

[0033] 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 a 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 the radio signal with a fixed directivity (beam). The NCR device 500A may also transmit the 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 includes an NCR-Fwd (Forward) 510A, which is a type of repeater that relays radio signals transmitted between the gNB 200 and the UE 100, specifically, that changes the propagation state of the radio signals without demodulating or modulating the radio signals, and an NCR-MT 520A that controls the NCR-Fwd 510A by wirelessly communicating with the gNB 200. In this way, the NCR-MT 520A establishes a wireless connection with the gNB 200 and communicates wirelessly with the gNB 200, thereby controlling the NCR device 500A in cooperation with the gNB 200. This enables 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-MT520A also has the same functions as the UE100.

[0036] The NCR-MT520A may be configured separately from the NCR-Fwd510A. For example, the NCR-MT520A may be located near the NCR-Fwd510A and electrically connected to the NCR-Fwd510A. The NCR-MT520A may be connected to the NCR-Fwd510A via a wired or wireless connection. Alternatively, the NCR-MT520A may be configured integrally with the NCR-Fwd510A. The NCRs-MT520A and the NCR-Fwd510A may be fixedly installed, for example, at the coverage edge (cell edge) of the gNB200 or on a wall or window of a building. The NCR-MT520A and the NCR-Fwd510A may be mobile, installed in a vehicle, for example. Furthermore, one NCR-MT520A may control multiple NCR-Fwd510A.

[0037] The NCR-MT520A is not limited to a configuration in which it directly controls one or more NCR-Fwd510A, but may also be a configuration in which it indirectly controls one or more NCR-Fwd510A. For example, the NCR-MT520A may control one or more NCR-Fwd510A via a higher layer (e.g., an application layer).

[0038] 5, the NCR device 500A (NCR-Fwd 510A) dynamically or quasi-statically changes a 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 resource 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, in order to suppress interference.

[0039] FIG. 6 is a diagram illustrating an example of a control method of the NCR device 500A according to the embodiment. As illustrated 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 UE-UL signals from the UE 100 to the gNB 200 and 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 radio link between the NCR-Fwd 510A and the gNB 200 is also referred to as a "backhaul link."

[0040] The NCR-MT520A transmits and receives wireless signals (herein referred to as "NCR-MT signals") to and from the gNB200. The NCR-MT signals include uplink signals (herein referred to as "NCR-MT-UL signals") transmitted from the NCR-MT520A to the gNB200 and downlink signals (herein referred to as "NCR-MT-DL signals") transmitted from the gNB200 to the NCR-MT520A. The NCR-MT-DL signals include signaling (e.g., NCR control signals) for controlling the NCR device 500A. The wireless link between the NCR-MT520A and the gNB200 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 is also directed to the NCR-Fwd510A. The gNB200 uses the beam to transmit an NCR-MT-DL signal and a UE-DL signal. The NCR-MT520A receives the NCR-MT-DL signal. Note that when the NCR-Fwd510A and the NCR-MT520A are at least partially integrated, the NCR-Fwd510A and the NCR-MT520A may be integrated with functions (e.g., antennas) for transmitting, receiving, or relaying UE signals and / or NCR-MT signals. 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 the transmitting wave and / or receiving wave in a specific direction by adjusting / adapting the antenna weight, 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 wireless signals transmitted and received between the gNB 200 and the UE 100. The NCR-Fwd 510A has an RF (Radio Frequency) function for amplifying and relaying received wireless signals, and performs directional transmission using beamforming (e.g., analog beamforming).

[0043] The NCR-MT520A 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-MT520A exchanges signaling with the gNB200 via at least one of PHY, MAC, RRC, and F1-AP. If the NCR-MT520A is a type or part of a base station, the NCR-MT520A may exchange signaling with the gNB200 via an Xn AP (Xn-AP), which is an interface between base stations. The NCR-MT520A may also have an NAS layer (entity). The NCR-MT520A exchanges signaling with the AMF300A via the NAS layer. The NAS layer may constitute an upper layer for the NCR-MT520A.

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

[0045] A backhaul link is established between the gNB 200 and the NCR-Fwd 510A. An access link is established between the UE 100 and the NCR-Fwd 510A. The NCR-Fwd 510A relays wireless signals transmitted between the gNB 200 and the UE 100 via the backhaul link and the access link. The NCR-Fwd 510A changes the propagation state of the wireless signals without demodulating or modulating the wireless signals.

[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 gNB200 (transmitter 210) transmits an NCR control signal to the NCR-MT520A. 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 CE (Control Element), 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-dedicated 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-MT520A is a type or part of a base station, the NCR-MT520A may communicate with the gNB200 via an Xn AP (Xn-AP), which is an inter-base station interface.

[0048] Hereinafter, the NCR control signal transmitted in the 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 to on / off. The NCR setting information may also include, for example, information on 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 for 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 in accordance with 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 in accordance with the latest (last) setting information received from the gNB 200.

[0051] Furthermore, if the NCR-MT520A detects a radio link failure (RLF) with the gNB200, 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 the 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 connection re-establishment procedure.

[0052] The NCR control signal may include frequency control information that specifies the center frequency of a radio signal (e.g., a component carrier) to be relayed by the NCR-Fwd510A. When the NCR control signal received from the gNB200 includes frequency control information, the NCR-MT520A (control unit 523) controls the NCR-Fwd510A to relay a radio signal having a 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 gNB200 can specify, via the NCR-MT520A, the center frequency of a radio signal to be relayed by the NCR-Fwd510A.

[0053] The NCR control signal may include mode control information that specifies an 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 one 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 one of a beamforming mode (i.e., a mode that prioritizes improving a desired wave) and a null steering mode (i.e., a mode that prioritizes 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 operation mode indicated by the mode control information (step S2A). When the NCR control signal includes mode control information, the gNB 200 can specify the operation mode of the NCR-Fwd 510A via the NCR-MT 520A.

[0054] Here, the mode in which the NCR device 500A performs non-directional transmission and / or reception is a mode in which the NCR-Fwd510A performs omnidirectional relaying, and may be referred to as omni-mode. The mode in which the NCR-Fwd510A performs fixed-directivity transmission and / or reception may be a directional mode achieved by a single directional antenna. This mode may be a beamforming mode achieved by applying fixed phase and amplitude control (antenna weight control) to multiple antennas. Any of these modes may be specified (set) by the gNB200 to the NCR-MT520A. The mode in which the NCR-Fwd510A 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 UE100 is formed. Any of these modes may be specified (set) by the gNB200 to the NCR-MT520A. In addition, in the operation mode in which beamforming is performed, beam control information, which will be 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 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) by the gNB200 to the NCR-MT520A. The operation modes may include a mode in which relay transmission by the NCR-Fwd510A is turned on (activated) and a mode in which relay transmission by the NCR-Fwd510A is turned off (deactivated). Any of these modes may be specified (set) by the gNB200 to the NCR-MT520A by an NCR control signal.

[0055] 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 beam formation angle information. When the NCR control signal received from the gNB200 includes beam control information, the NCR-MT520A (control unit 523) controls the NCR-Fwd510A to form the transmission directivity (beam) indicated by the beam control information. When the NCR control signal includes beam control information, the gNB200 can control the transmission directivity of the NCR device 500A via the NCR-MT520A.

[0056] The NCR control signal may include output control information that specifies the degree to which the NCR-Fwd510A amplifies the radio signal (amplification gain) or transmission power. The output control information may be information indicating a difference (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 gNB200 includes output control information, the NCR-MT520A (control unit 523) controls the NCR-Fwd510A 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-Fwd510A. The output control information may be information that specifies the transmission power of the NCR-Fwd510A.

[0057] When one NCR-MT 520A controls multiple NCR-Fwd 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-Fwd 510A determines the NCR-Fwd 510A to which the NCR control signal should be 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 along with the NCR control signal, even when the NCR-MT 520A controls only one NCR-Fwd 510A.

[0058] In this way, the NCR-MT520A (control unit 523) controls the NCR-Fwd510A based on the NCR control signal from the gNB 200. This enables the gNB 200 to control the NCR-Fwd510A via the NCR-MT520A.

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

[0060] (1.3.1) Example of relay device configuration 9 is a diagram showing an example of the configuration of an NCR device 500A (relay device) according to the 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 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 a control signal from the NCR-MT 520A. The NCR control unit 512A may include at least one processor.

[0062] 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 (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-MT520A. The operations of the NCR-MT520A (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 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 baseband signals. The CPU executes programs stored in the memory to perform various processes. The control unit 523 also performs the functions of at least one of the PHY, MAC, RRC, and F1-AP layers.

[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 a higher 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 user device configuration 10 is a diagram showing the configuration of a UE 100 (user equipment) according to the 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 under the control of 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, etc. The CPU executes programs stored in the memory to perform various processes.

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

[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 under the control of 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 neighboring 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. Note that the gNB is composed of a CU (Central Unit) and a DU (Distributed Unit) (i.e., functionally divided), and both 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 by wireless communication, thereby enabling the gNB 200 to control the NCR device 500A via the NCR-MT 520A.

[0074] (1.4) Operation according to the first embodiment As described above, when the NCR-MT520A detects a radio link failure (RLF) with the gNB200, the NCR-MT520A performs cell selection and triggers RRC connection re-establishment (also referred to as "RRC re-establishment"). Here, if the NCR-MT520A transitions to the 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 turned off during the RRC connection re-establishment procedure.

[0075] However, the NCR-MT520A may change its serving cell (also called the "camp cell") due to radio conditions, such as interference with Frequency Range (FR) 2. Therefore, it is worth considering what happens if the NCR-MT520A selects a different cell.

[0076] 12 is a diagram showing a first scenario according to the first embodiment. In the following first and second scenarios, the NCR device 500A (NCR-MT520A) is in an RRC connected state in cell a managed by gNB200a. Cell b adjacent to cell a is managed by gNB200b, which is different from gNB200a. However, cells a and b may be managed by the same gNB200. The NCR device 500A (NCR-MT520A) is assumed to be performing relay operation in accordance with an NCR control signal received from cell a (gNB200a) (i.e., NCR-Fwd510A is on).

[0077] In the first scenario, first, the NCR-MT 520A in the RRC connected state detects (declares) an RLF for cell a and initiates cell selection and RRC connection re-establishment. During these procedures, the NCR-Fwd 510A is turned off.

[0078] Second, the NCR-MT520A selects the same cell a by cell selection and starts an RRC connection re-establishment procedure with cell a. If the RRC connection re-establishment procedure with cell a is completed successfully (i.e., the RRC connection re-establishment is successful), the NCR-MT520A maintains the RRC connected state in cell a.

[0079] In the first scenario, it is considered efficient for the NCR-Fwd 510A to autonomously resume relay operation according to the NCR control signal (also referred to as the "latest NCR control signal") last received from cell a before detecting RLF, i.e., to turn on the NCR-Fwd 510A. Since the NCR device 500A has the latest NCR control signal (NCR setting information) provided by the same cell a, it can resume operation with the latest NCR control signal (NCR setting information). This avoids signaling and delays for reconfiguring the NCR device 500A.

[0080] Thus, in the first scenario of the first embodiment, when the NCR device 500A (NCR-MT520A) successfully re-establishes an RRC connection to the same cell, it performs recovery processing to apply the latest NCR control signal (NCR setting information) to the relay operation.

[0081] On the other hand, the gNB 200 may not want to automatically resume operation of the NCR-Fwd 510A because an RLF has occurred in the NCR-MT 520A. Therefore, the gNB 200 may have an option to explicitly indicate whether to allow the NCR-Fwd 510A to perform a recovery process, i.e., whether to resume operation according to the latest NCR control signal or to keep the NCR-Fwd 510A off.

[0082] FIG. 13 is a diagram showing a second scenario according to the first embodiment.

[0083] In the second scenario, first, the NCR-MT 520A in the RRC connected state detects (declares) an RLF for cell a and initiates cell selection and RRC connection re-establishment. During these procedures, the NCR-Fwd 510A is turned off.

[0084] Second, the NCR-MT 520A selects cell b through cell selection and performs an RRC connection re-establishment procedure with cell b. If the RRC connection re-establishment procedure with cell b is completed successfully (i.e., successful), the NCR-MT 520A maintains the RRC connected state in cell b.

[0085] In the second scenario, the latest NCR control signal (NCR setting information) held by the NCR-MT 520A is provided by the last serving cell a, not by the new cell b. Therefore, the NCR device 500A considers that a new NCR control signal (NCR setting information) will be provided from the new cell b. In this case, it is preferable that the NCR-MT 520A discards the latest NCR control signal (e.g., the latest instruction by the NCR setting information (RRC setting) and / or side control information) when selecting another cell b (or when transmitting an RRC re-establishment request message to another cell b).

[0086] Thus, in the second scenario of the first embodiment, when the NCR device 500A (NCR-MT 520A) successfully re-establishes an RRC connection to another cell b, it keeps the NCR-Fwd 510A off and discards the latest NCR control signal.

[0087] 14 is a diagram showing an example of operation of the NCR device 500A (NCR-MT520A) according to the first embodiment. This operation is performed by the NCR device 500A, which includes an NCR-Fwd 510A that performs a relay operation of relaying a radio 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.

[0088] In the first embodiment, the NCR-MT 520A in the RRC connected state in the first cell initiates an RRC connection re-establishment procedure with the second cell based on the detection of RLF in the first cell. If the RRC connection re-establishment with the second cell is successful, the NCR device 500A controls the relay operation based on whether the second cell is the same cell as the first cell.

[0089] Here, the first cell may be any one of the cell that configured and controlled the NCR device 500A (the cell provided the last configuration), the latest serving cell of the NCR device 500A (the last serving cell), and the cell where the RLF occurred (the cell caused the RLF). Alternatively, the first cell may be a cell (desired cell or planned cell) that has been predetermined in station placement design or the like as a cell to which the NCR device 500A should connect. Meanwhile, the second cell may be any one of a cell whose radio quality satisfies a cell selection criterion, a cell discovered by cell selection, and a target cell for RRC connection re-establishment.

[0090] As shown in FIG. 14, in step S11, the NCR-MT 520A in the RRC connected state in the first cell receives an NCR control signal from the first cell. The NCR control signal includes information indicating whether to turn on or off the NCR-Fwd 510A. Here, it is assumed that the NCR control signal includes information indicating to turn on the NCR-Fwd 510A (i.e., to perform relay operation). The NCR device 500A performs relay operation in accordance with the NCR control signal. The NCR control signal may also include setting information indicating whether to permit recovery processing. Note that if the NCR device 500A has multiple NCR-Fwds 510A, the NCR control signal may also include setting information indicating whether to permit recovery processing for each of the multiple NCR-Fwds 510A. The NCR control signal (NCR setting information by RRC and / or NCR control information by L1 / L2 signaling) held by the NCR device 500A (NCR-MT 520A) may be referred to as an NCR-Fwd context.

[0091] In step S12, the NCR-MT520A, which is in the RRC connected state in the first cell, detects (declares) RLF in the first cell. For example, the NCR-MT520A detects (declares) RLF if the wireless problem is not resolved by the time a first timer (e.g., timer T310) expires after detecting it. When the NCR-MT520A detects RLF, it starts a second timer (e.g., timer T311) and attempts cell selection and RRC connection re-establishment while the second timer is running. Note that if the RRC connection re-establishment is not successful by the time the second timer expires, the NCR-MT520A transitions to the RRC idle state.

[0092] The NCR-MT520A turns off the NCR-Fwd510A in response to RLF detection, and also retains the latest NCR control signal.

[0093] In step S13, when the NCR-MT 520A finds a suitable second cell through cell selection, it initiates an RRC connection re-establishment procedure for the second cell. The RRC connection re-establishment procedure includes transmitting an RRC re-establishment request message from the NCR-MT 520A to the second cell and transmitting an RRC re-establishment message from the second cell to the NCR-MT 520A.

[0094] In step S14, the NCR-MT520A determines whether the RRC connection re-establishment was successful. For example, if the RRC connection re-establishment is not successful before the second timer expires, the NCR-MT520A determines that the RRC connection re-establishment has failed (step S14: NO). If it determines that the RRC connection re-establishment has failed (step S14: NO), the NCR-MT520A transitions from the RRC connected state to the RRC idle state in step S15. In this case, the NCR-MT520A keeps the NCR-Fwd510A off. The NCR-MT520A may also discard the most recent NCR control signal.

[0095] On the other hand, if it is determined that the RRC connection re-establishment was successful (step S14: YES), then in step S16, the NCR-MT 520A determines whether the second cell with which the RRC connection was re-established is the same cell as the first cell. If the second cell is a cell different from the first cell (step S16: NO), then in step S17, the NCR-MT 520A keeps the NCR-Fwd 510A off and discards the latest NCR control signal it has stored.

[0096] If the second cell is the same cell as the first cell (step S16: YES), in step S18, the NCR-MT520A may determine whether recovery processing is permitted based on the configuration information received from the first cell. If recovery processing is not permitted (step S18: NO), in step S17, the NCR-MT520A keeps the NCR-Fwd510A off and discards the latest NCR control signal it has stored. If recovery processing is permitted (step S18: YES), the process proceeds to step S19.

[0097] In step S19, the NCR-MT 520A performs a restoration process in which the latest NCR control signal is applied to the relay operation in the second cell based on the fact that the second cell is the same cell as the first cell. In this operation example, the latest NCR control signal includes information indicating that the NCR-Fwd 510A should be turned on (i.e., the relay operation should be performed). Therefore, the NCR device 500A turns on the NCR-Fwd 510A and resumes the relay operation.

[0098] (1.4.1) First Operation Example of the First Embodiment 15 is a diagram showing a first operation example of the NCR device 500A (NCR-MT520A) according to the first embodiment. In this operation example, the first cell and the second cell are the same cell (cell a). Here, differences from the above operation example will be mainly described.

[0099] In this operation example, if the NCR-MT 520A is successful in re-establishing an RRC connection with the same cell, the NCR-MT 520A restores the operation of the NCR-Fwd 510A in accordance with the latest NCR control signal.

[0100] In step S101, the NCR-MT 520A is in an RRC connected state with the cell a, and receives an NCR control signal (setting and control information related to the NCR device 500A) from the cell a.

[0101] In step S102, the NCR-MT 520A detects the RLF for the cell a and starts the RRC connection re-establishment procedure. Here, the NCR device 500A stops (turns off) the operation of the NCR-Fwd 510A. The NCR device 500A also holds the latest NCR control signal.

[0102] In step S103, the NCR-MT 520A selects cell a and initiates the RRC connection re-establishment procedure.

[0103] In step S104, the NCR-MT520A successfully re-establishes a connection with cell a. The NCR-MT520A may notify the upper layer of the re-establishment of a connection with the same cell.

[0104] In step S105, the NCR-MT 520A restores the latest setting (control) information upon reestablishing connection with the same cell, and applies the latest setting (control) information to the relay operation (NCR-Fwd 510A). The NCR-Fwd 510A is turned on or off according to the setting (control).

[0105] (1.4.2) Second Operation Example of First Embodiment 16 is a diagram showing a second operation example of the NCR device 500A (NCR-MT520A) according to the first embodiment. In this operation example, the first cell and the second cell are the same cell (cell a). Here, differences from the above operation example will be mainly described.

[0106] In this operation example, the gNB200 configures the NCR-MT520A with a setting as to whether or not to permit recovery processing that applies the latest settings (control) to the operation of the NCR-Fwd510A when the RRC connection with the same cell is successfully re-established. If the NCR-MT520A does not perform recovery processing when the RRC connection with the same cell is successfully re-established based on this setting, the NCR-MT520A discards the latest settings (control). Note that if the NCR-MT520A handles multiple NCR-Fwd510As, the gNB200 may configure the NCR-MT520A with information regarding which NCR-Fwd510As to perform recovery processing (or not to perform recovery).

[0107] In step S111, the NCR-MT 520A is in an RRC connected state with cell a and receives an NCR control signal (setting and control information related to the NCR device 500A) from cell a. The setting includes setting information indicating whether or not to perform recovery processing when re-establishing an RRC connection to the same cell.

[0108] When the NCR-MT520A handles multiple NCR-Fwd510A, the setting information may be applied to all of the multiple NCR-Fwd510A. Alternatively, the setting information may be associated with each individual NCR-Fwd510A. For example, the management ID of the NCR-Fwd510A and the setting information may be set as a set (list). Alternatively, the operating frequency (and / or relay cell ID) and the setting information may be set as a set by implicitly identifying the NCR-Fwd510A by the operating frequency of the NCR-Fwd510A and / or the cell ID (relay cell ID) of the relaying cell.

[0109] In step S112, NCR-MT520A detects RLF for cell a.

[0110] In step S113, NCR-MT 520A selects cell a and initiates the RRC connection re-establishment procedure.

[0111] In step S114, the NCR-MT520A successfully re-establishes an RRC connection with cell a. The NCR-MT520A may notify higher layers that the RRC connection with the same cell has been successfully re-established. In addition, the NCR-MT520A may notify higher layers of whether or not the NCR-Fwd510A needs to restore its operation.

[0112] If the restoration process is permitted (step S115: YES), in step S116, the NCR-Fwd 510A restores the latest settings (control) upon re-establishment of the RRC connection with cell a, and applies the latest settings (control) to the relay operation (NCR-Fwd 510A). The NCR-Fwd 510A is turned on or off according to the settings (control).

[0113] On the other hand, if the recovery process is not permitted (step S115: NO), in step S117, the NCR-MT 520A discards the latest settings (control) without recovering the operation of the NCR-Fwd 510A. Note that this discarding operation may be performed when an RLF is detected (step S112) or when re-establishment of the RRC connection starts (step S113) if the recovery setting does not recover the operation of the NCR-Fwd 510A.

[0114] Furthermore, when the NCR-MT 520A handles a plurality of NCR-Fwd 510A, the NCR-MT 520A may perform the determination in step S115 for each of the plurality of NCR-Fwd 510A.

[0115] In this operation example, in the RRC connection establishment procedure (step S113), cell a (gNB 200) may transmit an RRC re-establishment message including information on whether or not to restore the operation of NCR-Fwd 510A to NCR-MT 520A. NCR-MT 520A may make the determination of step S115 based on the information in the RRC re-establishment message. Such an operation is also applicable to the above-mentioned first operation example.

[0116] (1.4.3) Third Operation Example of the First Embodiment 17 is a diagram showing a third operation example of the NCR device 500A (NCR-MT520A) according to the first embodiment. In this operation example, the first cell and the second cell are different cells (cell a and cell b). Here, differences from the above operation examples will be mainly described.

[0117] In this operation example, if the NCR-MT520A successfully re-establishes an RRC connection to a different cell, it does not restore NCR-Fwd510A operation (it remains off). Furthermore, if the NCR-MT520A successfully re-establishes an RRC connection to a different cell, it discards the most recent NCR control signal (setting and control information). If the RRC connection to a different cell is successfully re-established, it is assumed that a new NCR control signal will be provided from the new cell. Operating the new cell using the settings and control of the original cell may result in malfunction, so the settings and control of the original cell are discarded.

[0118] In step S121, the NCR-MT 520A is in an RRC connected state with the cell a, and receives an NCR control signal (setting and control information related to the NCR device 500A) from the cell a.

[0119] In step S122, the NCR-MT 520A detects the RLF for the cell a and starts the RRC connection re-establishment procedure, where the NCR device 500A stops (turns off) the operation of the NCR-Fwd 510A.

[0120] In step S123, NCR-MT 520A selects cell b and initiates the RRC connection re-establishment procedure.

[0121] In step S124, the NCR-MT 520A successfully re-establishes the RRC connection with cell b. The NCR-MT 520A may notify the upper layer of the re-establishment of the RRC connection with a different cell.

[0122] In step S125, the NCR-MT520A keeps the NCR-Fwd510A off, and discards the latest NCR control signal (settings and control).

[0123] (1.5) Modification of the First Embodiment In the above-described first embodiment, an example has been described in which the NCR device 500A controls the relay operation based on whether the second cell is the same cell as the first cell.

[0124] However, an effective area in which the same NCR control signal can be used in other cells may be set to the NCR-MT 520A by the network 5 (gNB 200). The effective area is an area consisting of one or more cells. For example, the gNB 200 transmits an NCR control signal including configuration information and / or control information related to relay operation and area information indicating the effective area of ​​the configuration information and / or control information to the NCR-MT 520A. The area information may be a list of cell IDs or (a list of) frequency IDs. The area information may be information for identifying the gNB 200, such as a gNB ID or any ID for identifying the gNB (for example, a part of the gNB ID may be used (shortened), or a number form different from the gNB ID may be used). The information may be broadcast by the gNB 200 via an SIB, and the UE 100 may use the broadcast information to determine whether the cell where RRC has been re-established belongs to the effective area. When the NCR-MT520A detects RLF for the first cell and successfully re-establishes an RRC connection with the second cell, it determines whether the second cell belongs to the coverage area. If the NCR-MT520A determines that the second cell belongs to the coverage area, it performs a recovery process to apply the configuration information and / or control information received from the first cell to relay operation. On the other hand, if the NCR-MT520A determines that the second cell does not belong to the coverage area, it discards the configuration information and / or control information received from the first cell and keeps the NCR-Fwd510A off.

[0125] Such an effective area may be determined by negotiation between gNBs 200. For example, the gNB 200 transmits an NCR control signal (NCR setting information) to be set in the NCR device 500A of its own cell to a neighboring gNB. If the neighboring gNB determines that the NCR control signal is applicable to its own cell, it may permit its own cell as an effective area for the NCR control signal.

[0126] (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.

[0127] 18 is a diagram for explaining a scenario according to the second embodiment. The second embodiment focuses on the UE 100 that performs wireless communication with the gNB 200 via the NCR device 500A.

[0128] As described above, when the NCR-MT 520A detects RLF in cell a and re-establishes an RRC connection to another cell b, the NCR device 500A (NCR-Fwd 510A) no longer relays the cell a. Specifically, the NCR-Fwd 510A is turned off, and then the NCR-Fwd 510A relays the other cell b.

[0129] Here, it is assumed that the UE 100, which performs wireless communication with the gNB 200 via the NCR device 500A, is located in the extended coverage (also referred to as "relay coverage" or "indirect coverage") of the cell a formed by the NCR device 500A. When the NCR-MT 520A detects RLF in the cell a and re-establishes an RRC connection to another cell b, an RLF also occurs in the wireless communication between the cell a and the UE 100. In this case, it is considered better for the UE 100 to quickly select, for example, the cell b to which the NCR device 500A is currently connected and re-establish the RRC connection. However, there is a problem in that the UE 100 does not know to which cell the NCR device 500A has re-established the RRC connection.

[0130] Therefore, in the second embodiment, information on a target cell (candidate cell) for RRC connection re-establishment when RLF is detected is provided from the gNB 200a to the UE 100, thereby facilitating the RRC connection re-establishment of the UE 100. Specifically, the second embodiment relates to an operation in a mobile communication system 1 in which an NCR device 500A that performs wireless communication with the gNB 200a performs a relay operation to relay wireless communication between the UE 100 and the gNB 200a. The UE 100 receives, from the gNB 200a via the NCR device 500A, recommendation information (also referred to as "reference information") indicating a cell and / or frequency that is recommended to be selected when RLF occurs in wireless communication with the gNB 200. Then, when RLF is detected, the UE 100 performs cell selection to select a target cell for RRC connection re-establishment based on the recommendation information. This can facilitate the RRC connection re-establishment of the UE 100.

[0131] The UE 100 may receive broadcast signaling (e.g., a system information block (SIB)) including the recommended information from the gNB 200a. The SIB is transmitted using an MCS that has higher error resilience than dedicated signaling, so that even the UE 100 located in the extended coverage of the cell a can easily receive the recommended information.

[0132] The UE 100 may generate log information regarding the RRC connection re-establishment using the recommended information. Then, the UE 100 may transmit the log information to the network 5. This allows the network 5 to understand the usage status of the recommended information and use it for, for example, network optimization.

[0133] Fig. 19 is a diagram showing an example of the operation of the mobile communication system 1 according to the second embodiment. In Fig. 19, cell a and cell b may be managed by the same gNB 200 (i.e., Intra-gNB). Cell a and cell b may be managed by different gNBs 200 (i.e., Inter-gNB).

[0134] In step S201, the UE 100 is in an RRC connected state with the cell a via the NCR device 500 A. That is, the UE 100 is located in the extended coverage provided by the NCR device 500 A. The UE 100 performs radio communication with the cell a (gNB 200) via the NCR device 500 A (step S202).

[0135] In step S203, the NCR device 500A detects RLF for the cell a and starts the RRC connection re-establishment procedure. At this time, the NCR-Fwd 510A is turned off. Therefore, the relay of the link between the cell a and the UE 100 is interrupted, and the UE 100 also detects a radio problem.

[0136] In step S204, it is assumed that the NCR device 500A has successfully re-established an RRC connection to another cell b using a different frequency, for example. The gNB 200 managing cell a recognizes that the NCR device 500A has re-established an RRC connection to cell b. For example, in the case of an intra-gNB, since it is the same gNB, it can recognize that the NCR device 500A has re-established an RRC connection to cell b. In the case of an inter-gNB, the gNB 200a managing cell a can recognize that the NCR device 500A has re-established an RRC connection to cell b by receiving a Context Fetch (Context Retrieval) message requesting context information of the NCR device 500A from the gNB 200b managing cell b.

[0137] In step S205, cell a (gNB200) transmits recommended information to UE100 for use in cell selection. UE100 receives the recommended information. For example, the recommended information includes information for identifying cell b as a target cell to be selected by UE100 in cell selection. The recommended information may include a cell ID of cell b and / or an ID of a frequency to which cell b belongs. The recommended information may include timestamp information (time information) for reference in log information, which will be described later. Cell a (gNB200) may broadcast the recommended information in an SIB. Alternatively, cell a (gNB200) may transmit the recommended information to UE100 by dedicated signaling.

[0138] When the recommended information is transmitted by the SIB, the UE 100 that is not in the extended coverage of the NCR device 500A (i.e., the UE 100 that is in the direct coverage of cell a) may also receive the recommended information. However, since such a UE 100 has a good radio condition and does not perform RRC connection re-establishment or cell selection, it is considered that there is no significant impact.

[0139] Note that instead of transmitting information about cell b with which the NCR device 500A has actually re-established an RRC connection as the recommended information, the cell a (gNB200) may transmit information about one or more candidate neighbor cells as the recommended information. In this case, the recommended information may include a cell ID list and / or a frequency ID list. Furthermore, in this case, the cell a (gNB200) may transmit the recommended information to the UE 100 by dedicated signaling before the NCR device 500A detects an RLF. The dedicated signaling may be transmitted from the cell a (gNB200) to the UE 100 via the NCR device 500A (NCR-Fwd510A).

[0140] In step S206, the UE 100 detects the RLF and selects a target cell for RRC connection re-establishment. Here, it is assumed that the UE 100 selects the cell b based on the recommended information.

[0141] The UE 100 may generate log information related to the recommended information. The log information includes at least one of information indicating whether the recommended information was provided, information indicating whether the recommended information was used, and content of the recommended information. The log information may include at least one of information on the SSB in which the RLF occurred and information on the SSB selected in cell selection. The SSB information can be used by the network 5 to determine whether the UE 100 is in the extended coverage of the NCR device 500A. The log information may include at least one of information on the cell (cell a) in which the RLF occurred and information on the cell (b) selected in cell selection. The log information may include at least one of information on the frequency in which the RLF occurred and information on the frequency selected in cell selection. The log information may include information on the elapsed time since the start of T311. This allows the network 5 to determine how quickly a cell was selected.

[0142] In step S207, UE100 initiates an RRC connection re-establishment procedure for cell b selected in step S206. If the RRC connection re-establishment is successful, UE100 may transmit log information to cell b (gNB200) and resume data communication. On the other hand, if the RRC connection re-establishment fails, UE100 may store the log information and transmit the log information to gNB200 later when connected to network 5.

[0143] (2.1) Modification of the Second Embodiment The modified example of the second embodiment will be described, focusing mainly on the differences from the second embodiment.

[0144] In the second embodiment described above, when the recommended information is transmitted by the SIB, the UE 100 that is not in the extended coverage of the NCR device 500A (i.e., the UE 100 that is in the direct coverage of cell a) may also receive the recommended information. Here, from the viewpoint of the UE 100, the presence of the NCR device 500A is not recognized, and therefore the UE 100 side cannot determine whether the NCR device 500A is present. Therefore, it is difficult for the UE 100 that receives the SIB including the recommended information to determine whether or not to use the recommended information.

[0145] In this modification, the UE 100 receives, from the gNB 200, notification information indicating whether or not the NCR device 500A is intervening in the wireless communication between the UE 100 and the gNB 200 (i.e., whether the UE 100 is in the direct coverage or in the extended coverage). The UE 100 determines, based on the notification information, whether or not the NCR device 500A is intervening in the wireless communication between the UE 100 and the gNB 200. This makes it easier for the UE 100, which has received an SIB including recommended information, to determine whether or not to use the recommended information. For example, when the UE 100 determines that the NCR device 500A is intervening in the wireless communication between the UE 100 and the gNB 200 and detects the occurrence of an RLF, the UE 100 may perform cell selection based on the recommended information.

[0146] Fig. 20 is a diagram showing an example of operation of the mobile communication system 1 according to this modification. In Fig. 20, the cells a and b may be managed by the same gNB 200 (Intra-gNB). The cells a and b may be managed by different gNBs 200 (Inter-gNB).

[0147] In step S211, the NCR device 500A performs a random access procedure to connect to cell a (gNB 200). Specifically, the NCR-MT 520A of the NCR device 500A selects an SSB and transmits a random access preamble associated with the selected SSB to the gNB 200 on a physical random access channel (PRACH). The random access procedure adjusts the timing advance. The timing advance is a parameter for adjusting the transmission timing of the NCR device 500A to compensate for propagation delay.

[0148] In step S212, the gNB 200 identifies an SSB to be relayed by the NCR device 500A. The gNB 200 may transmit the SSB (step S213), and the NCR device 500A (NCR-Fwd 510A) may relay the SSB to the UEFI (step S214). The UE 100 may receive the relayed SSB.

[0149] In step S215, UE 100 performs a random access procedure to connect to cell a (gNB 200). Specifically, UE 100 selects an SSB and transmits a random access preamble associated with the selected SSB to gNB 200 on the PRACH. The timing advance is adjusted by the random access procedure.

[0150] In step S216, gNB200 identifies the SSB to which UE100 belongs and the timing advance of UE100.

[0151] In step S217, gNB200 estimates whether UE100 is in the direct coverage or extended coverage of cell a based on the SSB and / or timing advance identified in step S216.

[0152] In the method of estimation using SSB, if the SSB of the NCR device 500A matches the SSB of the UE 100, the gNB 200 can estimate that the UE 100 is in the extended coverage. On the other hand, if the SSB of the NCR device 500A does not match the SSB of the UE 100, the gNB 200 can estimate that the UE 100 is in the direct coverage. However, this method is based on the premise that the UE 100 in the direct coverage does not receive the SSB relayed by the NCR device 500A.

[0153] In the estimation method using timing advance, the gNB 200 can estimate that the UE 100 is in the extended coverage area if the timing advance of the UE 100 is equal to or greater than a threshold. On the other hand, the gNB 200 can estimate that the UE 100 is in the direct coverage area if the timing advance of the UE 100 is less than a threshold. Here, the threshold can be the value of the timing advance of the NCR device 500A.

[0154] The gNB200 may improve the accuracy of the estimation by combining the method of estimating using SSB and the method of estimating using timing advance.

[0155] In step S218, the gNB 200 transmits a coverage notification indicating whether the UE 100 is in direct coverage or extended coverage. The coverage notification can be transmitted to the UE 100 by dedicated signaling, for example, in an RRC Reconfiguration message. The coverage notification may also be transmitted in an SIB. The UE 100 receives the coverage notification. Note that step S218 may be performed simultaneously with step S205 in FIG. 19.

[0156] The coverage notification may include information indicating whether the UE 100 is in direct coverage or extended coverage. In the case of an SIB (e.g., SIB1), the coverage notification may include information indicating whether the SSB corresponding to the SIB is in direct coverage or extended coverage. The coverage notification may include information indicating which SSB the recommendation information should be applied to when selected. The coverage notification may include a timing advance threshold (e.g., the timing advance value of the NCR device 500A for each SSB). In this case, the UE 100 determines that it is in direct coverage if the timing advance value it manages is less than the threshold, and determines that it is in extended coverage if the timing advance value it manages is equal to or greater than the threshold. The coverage notification may include information linking which SSBs are in direct coverage and which SSBs are in extended coverage. The coverage notification may include information indicating whether or not the above-mentioned recommended information should be used during RLF (when re-establishing an RRC connection).

[0157] The UE 100 may transition to an RRC idle state or an RRC inactive state based on the coverage notification, or may remain in an RRC connected state.

[0158] The UE 100 may determine whether to apply or ignore the recommendation information provided in the SIB based on the coverage notification. For example, if the UE 100 determines that it is in extended coverage, it takes the recommendation information received in the SIB into account in cell selection for the RRC connection re-establishment procedure after detecting RLF. On the other hand, if the UE 100 determines that it is in direct coverage, it ignores the recommendation information received in the SIB after detecting RLF.

[0159] Note that the operation of this modified example does not necessarily have to be an operation premised on the above-described second embodiment. The operation of this modified example may also be useful in other scenarios in which it is desired to know whether the UE 100 is located in the direct coverage or the extended coverage.

[0160] (3) Third embodiment Next, a third embodiment will be described, focusing on differences from the above-described embodiments. As shown in Fig. 21, the repeater according to the third 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. "NCR" in the above-described embodiments can be read as "RIS."

[0161] 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 metamaterials. 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, the RIS may be configured to be able 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.

[0162] 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 waves is variably settable.

[0163] FIG. 22 is a diagram showing an example configuration of a RIS-Fwd (repeater) 510B and a RIS-MT (control terminal) 520B according to the third 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 made of metamaterial. For example, the RIS 511B is configured by arranging structures that are very small compared to the wavelength of radio waves in an array. By making the structures different shapes depending on their placement, 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 RIS511B 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. 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 RIS511B in response to a RIS control signal from the control unit 523 of the RIS-MT520B. 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-MT520B and drives the actuator in response to the RIS control signal.

[0164] (4) Other embodiments In the above-described second embodiment, an issue that occurs when the NCR device 500A (NCR-MT520A) detects RLF has been described as an example. However, a similar issue may occur when handover of the NCR device 500A (NCR-MT520A) from cell a to cell b fails. Therefore, the operation according to the second embodiment may be applied to a scenario in which handover of the NCR device 500A (NCR-MT520A) is performed from cell a to cell b.

[0165] 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.

[0166] 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.

[0167] 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). Also, the base station may be a relay node such as an IAB node. Also, the base station may be a DU (Distributed Unit) of the IAB node. Also, the UE 100 may be an MT (Mobile Termination) of the IAB node.

[0168] Furthermore, the term "network node" primarily refers to a base station, but may also refer to a core network device or part of a base station (CU, DU, or RU). A network node may also be configured by a combination of at least part of a core network device and at least part of a base station.

[0169] A program may be provided that causes a computer to execute each process performed by a communication device according to the above-described embodiments, for example, the UE100 (NCR-MT520A, RIS-MT520B), the gNB200, or the relay device. The program may be recorded on a computer-readable medium. The computer-readable medium can be used to install the program on a computer. Here, the computer-readable medium on which the program is recorded may be a non-transitory recording medium. The non-transitory recording medium is not particularly limited, 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 UE100 or the gNB200 may be integrated, and at least a part of the UE100, the gNB200, or the relay device may be configured as a semiconductor integrated circuit (chipset, SoC: System on a chip).

[0170] The functions performed by the UE 100, gNB 200 (network node), or 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 (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 a memory. In this specification, a circuit, unit, or means is hardware that is programmed to perform or executes the described functions. The hardware may be any hardware disclosed in this specification or any hardware known to be programmed to perform or execute the described functions. When the hardware is a processor, which is considered to be a type of circuitry, the circuit, means, or unit is a combination of hardware and software used to configure the hardware and / or processor.

[0171] 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.

[0172] 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.

[0173] This application claims priority to U.S. Provisional Application No. 63 / 445,077 (filed February 13, 2023), the entire contents of which are incorporated herein by reference.

[0174] (5) Supplementary Notes The following additional notes are about the features of the above-described embodiment.

[0175] (Appendix 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 control terminal in a radio resource control (RRC) connected state in a first cell initiating an RRC connection re-establishment procedure with a second cell based on detection of a radio link failure (RLF) in the first cell; and if the RRC connection re-establishment with the second cell is successful, the relay device controls the relay operation based on whether the second cell is the same cell as the first cell. Communication method.

[0176] (Appendix 2) The control terminal further comprises receiving the control signal from the first cell before detecting the RLF; The step of controlling includes a step of performing a recovery process in the second cell to apply the control signal to the relay operation when the second cell is the same cell as the first cell. 1. A communication method as described in Appendix 1.

[0177] (Appendix 3) the relay device further comprising turning off the relay during the RRC connection re-establishment procedure; the control signal includes information indicating whether to turn the repeater on or off; The applying step includes turning on the repeater in response to the success of the RRC connection re-establishment if the information indicates turning on the repeater. 2. A communication method as described in Appendix 2.

[0178] (Appendix 4) the control signal includes setting information indicating whether or not the recovery process is permitted; The step of controlling includes a step of performing the recovery process in the second cell when the second cell is the same cell as the first cell and the setting information indicates permission for the recovery process. 4. A communication method according to claim 2 or 3.

[0179] (Appendix 5) The controlling step includes a step of discarding the control signal when the second cell is the same cell as the first cell and the configuration information does not indicate permission for the recovery process. 4. A communication method as described in Appendix 4.

[0180] (Appendix 6) When the relay device has a plurality of relays, the control signal includes setting information indicating whether or not the restoration process is permitted for each of the plurality of relays. 6. A communication method according to claim 4 or 5.

[0181] (Appendix 7) the relay device further comprising turning off the relay during the RRC connection re-establishment procedure; The controlling step includes keeping the repeater off if the second cell is a different cell than the first cell. 7. A communication method according to any one of appendices 1 to 6.

[0182] (Appendix 8) The step of controlling includes a step of discarding the control signal received from the first cell when the second cell is a cell different from the first cell. 8. A communication method according to any one of claims 1 to 7.

[0183] (Appendix 9) the control signal includes setting information and / or control information related to the relay operation, and area information indicating an effective area of ​​the setting information and / or the control information, The step of controlling includes a step of performing, in the second cell, a recovery process of applying the configuration information and / or the control information received from the first cell to the relay operation, when the second cell belongs to the effective area. 9. A communication method according to any one of appendices 1 to 8.

[0184] (Appendix 10) a repeater that performs a relay operation of relaying a wireless signal transmitted between a network and a user device; a control terminal that receives a control signal used to control the repeater from the network; The control terminal Initiating an RRC connection re-establishment procedure with a second cell when in a radio resource control (RRC) connected state in a first cell based on a radio link failure (RLF) being detected in the first cell; If the RRC connection with the second cell is successfully re-established, the relay operation is controlled based on whether the second cell is the same cell as the first cell. Relay device.

[0185] (Addendum) 1. Introduction In RAN#97e, the Network Controlled Repeater (NCR) work item was approved. RAN2#119bis-e and RAN2#120 achieved significant progress with many agreements.

[0186] This appendix discusses the remaining open / potential issues for RAN2 regarding NCR.

[0187] 2. Discussion 2.1.NCR-Fwd ON / OFF related matters 2.1.1. Open Issues Regarding RRC Releases At RAN2#120, the following agreement was reached:

[0188] NCR-Fwd ON / OFF: When NCR-MT is in RRC connected mode, NCR-Fwd can be turned ON or OFF according to the side control information received from the gNB. After NCR-MT enters RRC inactive mode, NCR-Fwd can be turned ON or OFF according to the last configuration received from the gNB. Further consideration is needed regarding release to RRC idle state.

[0189] NCR-MT RLF: After NCR-MT declares RLF, NCR-MT performs cell selection and triggers RRC re-establishment; If no suitable cell is found and NCR-MT enters RRC idle state, NCR-Fwd is OFF; During the RRC re-establishment procedure, NCR-Fwd is OFF.

[0190] One of the open questions is whether it is a valid case for the gNB to release the NCR-MT to the idle state. According to the discussion in RAN2#120, there are two camps regarding the RRC state of the NCR-MT:

[0191] Assumption 1: NCR-MT is fundamentally connected: Under this assumption, the gNB never releases the NCR-MT, since NCR must always be controllable by the network. Therefore, the NCR-MT can only be in the idle state upon initial access (power-on) or RLF (more precisely, upon RRC re-establishment failure). Since the state of NCR-Fwd upon initial access is clear (i.e., it should be OFF) and the state upon RLF is already agreed upon (i.e., it should also be OFF), there is no need to specify any additional NCR behavior when the gNB releases the NCR-MT to the idle state.

[0192] Assumption 2: gNB can release NCR-MT: In this assumption, the RRC idle state has already been agreed upon by RAN2, allowing the gNB to release the NCR-MT for NCR power savings, signaling overhead reduction, etc. Therefore, the NCR-MT may be put into idle state by all legacy conditions, such as initial access, RLF, RRC release, etc. Some companies have stated that after transitioning to idle state, the NCR-Fwd may fall back to the legacy RF repeater.

[0193] Observation 1: Regarding whether gNB should return NCR-MT to idle state, there were two arguments related to whether it is necessary to specify the ON / OFF behavior of NCR-Fwd.

[0194] Assumption 1 is very simple, as NCR is always network-controlled by side control information and RRC signaling, and there is no reason for a gNB to release the NCR-MT under normal conditions. However, as with assumption 2, smart gNB implementations may release the NCR-MT under certain conditions, such as to save power or reduce signaling overhead. In this sense, the specification should be tolerant of various gNB implementations, and the behavior of NCR during idle state due to RRC release should be generally clarified.

[0195] Observation 2: In normal operation, there is no reason for a gNB to put the NCR-MT in idle state, but under certain conditions, the gNB implementation may allow RRC release.

[0196] On the other hand, regarding the NCR behavior during inactivity, RAN2 states that after the WA:NCR-MT enters RRC inactive mode, the NCR-Fwd can be turned ON or OFF according to the last configuration received from the gNB. In other words, since the gNB can always page the NCR-MT via RAN paging, it is reasonable to align the NCR behavior with that of the connected mode, as agreed upon by RAN2 (i.e., "no specific enhancements"). Needless to say, the NCR-MT in idle mode cannot be controlled by the gNB, since CN paging is required to establish an RRC connection for transmitting side control information and configuration. Therefore, the NCR behavior during idle mode must be considered separately from that during inactivity mode.

[0197] Observation 3: The behavior of NCR-Fwd in the inactive state should be consistent with that in the connected state and different from that in the idle state.

[0198] In addition, as stated in Assumption 2 above, if the NCR is not controlled by the gNB, it is considered that the NCR may fall back to a legacy RF repeater. Since RAN2 agrees that "NCR-Fwd can be turned ON or OFF according to the last configuration received from the gNB," it is clear that an inactive NCR cannot fall back to a legacy RF repeater. In other words, the possibility of fallback to a legacy RF repeater is only available when the NCR-MT is idle.

[0199] The legacy RF repeater is an implementation technology from the perspective of network control. Therefore, when the NCR falls back to the legacy RF repeater, it is no longer a network-controlled repeater. In other words, when a node is no longer an NCR (for example, when the NCR-MT transitions to the idle state), the behavior of the NCR can be anything depending on the implementation.

[0200] Observation 4: According to the current agreement, an inactive NCR cannot fall back to a legacy RF repeater, i.e. it must follow the last configuration received from the gNB as agreed upon by RAN2.

[0201] Observation 5: If an NCR is not controlled by the gNB (e.g., if the NCR-MT transitions to an idle state), the node may no longer be considered an NCR from the network control perspective.

[0202] As discussed in Remarks 2 and 3, the behavior of NCR in idle state with RRC release should be clarified to allow for various gNB implementations and should be different from inactive state.

[0203] As mentioned above, RAN2 has already agreed on the NCR behavior due to RLF: "When a suitable cell cannot be found and NCR-MT enters RRC idle state, NCR-Fwd is turned OFF." Based on this agreement, there is no meaningful reason to distinguish between transition to idle state due to RRC release and RLF. Therefore, when NCR-MT transitions to idle state, NCR-Fwd should be turned OFF regardless of the cause of the state transition.

[0204] This behavior does not prevent implementation-specific behavior, so even if the node is not considered an NCR (e.g., when the NCR-MT is idle), the node can still operate as a legacy RF repeater (i.e., "fallback" behavior).

[0205] Proposal 1: RAN2 should agree to turn off NCR-Fwd when NCR-MT is released to idle state, as in the case of RLF.

[0206] 2.1.2 Potential Issues with RRC Re-establishment Currently, the RAN2 agreement seems to only assume that the NCR-MT always resides in the same cell. However, the NCR-MT may change its serving / camping cell due to radio conditions such as FR2 outages, even though NCR mobility is not supported. Therefore, it is worth discussing what happens if the NCR-MT (re)selects a different cell.

[0207] RAN2#120 agreed to the following statement: About NCR-MT RLF: After NCR-MT declares RLF, NCR-MT performs cell selection and triggers RRC re-establishment; If no suitable cell is found and NCR-MT enters RRC idle state, NCR-Fwd is OFF; During the RRC re-establishment procedure, NCR-Fwd is OFF.

[0208] Regarding RRC re-establishment, the following steps and potential issues will be identified as agreed: Step 1: NCR-MT declares RLF and initiates cell selection and RRC re-establishment. During these procedures, NCR-Fwd is OFF as previously agreed. Step 2a: If NCR-MT selects the same cell and RRC re-establishment is completed successfully, NCR-Fwd returns to ON according to the last configuration. Step 2b: If the NCR-MT selects a different cell and the RRC re-establishment is completed successfully, determine whether NCR-Fwd should be turned OFF.

[0209] Regarding the potential problem of step 2a, since the NCR is configured from the same cell, NCR-Fwd can generally be expected to resume operation with the last configuration it was in. In this case, the signaling overhead for reconfiguring the NCR can be avoided.

[0210] On the other hand, since the RLF occurred in the NCR-MT, the gNB may not prioritize such automatic resumption of NCR-Fwd operation, e.g., in such a case the gNB may change the NCR configuration. Therefore, it is an option for the gNB to explicitly indicate whether the NCR-Fwd operation should be resumed with the last configuration or turned off, e.g., by performing an RRC reconfiguration in advance or by performing an RRC reestablishment in time.

[0211] Alternatively, NCR-Fwd should be OFF even after successful RRC re-establishment to the same cell. This can be either a hard-coded rule or a gNB indication as described above. In this case, when NCR-MT declares RLF (or starts the RRC re-establishment procedure), the last RRC configuration (and the last indication by side control information) should be discarded.

[0212] Proposal 2: RAN2 should discuss whether NCR-Fwd should resume operation with the last configuration if RRC re-establishment to the same cell is successful.

[0213] Regarding the potential problem of step 2b, the last configuration that the NCR-MT has is the one provided by the last serving cell, not the one provided by the new cell. Therefore, it is easy for the NCR to receive a new configuration from the new cell. In this case, the NCR-MT needs to discard the last RRC configuration (and the last indication from the side control information) when selecting a different cell (or sending an RRC re-establishment request towards a different cell).

[0214] Proposal 3: RAN2 should discuss whether NCR-MT should discard the last configuration when RRC re-establishment to a different cell is initiated.

[0215] 2.1.3 Potential issues with cell reselection At RAN2#120, the following statement was agreed upon: NCR-MT mandatorily supports cell reselection and RRM measurements in RRC idle and RRC inactive states. In Rel-18, NCR-MT does not support handover and RRM measurements in the RRC Connected state.

[0216] One potential problem with cell reselection is the preferential treatment of a particular cell. In the case of legacy RF repeaters, their deployment is determined by network planning and / or field RF measurements. Therefore, it is assumed that desired cell(s) are planned for each NCR, i.e., network planning determines the relationship between the serving cell and the NCR. Such desired cells may be configured into NCRs by OAM.

[0217] Observation 6: The NCR can configure the desired cell, for example, by OAM.

[0218] In this case, the NCR-MT should avoid camping (or connecting) on ​​undesirable cells. Therefore, the NCR-MT should prefer desirable cells over undesirable cells. While cell selection allows for implementation-specific behavior (i.e., the IAB-MT selects any suitable cell), cell reselection consists of a set of deterministic behaviors according to the specification (inter-frequency cell reselection criteria, ranking, etc.). Therefore, standard support is required to ensure NCR network planning.

[0219] The simplest approach is to enhance the prioritization of cell reselection. Similar to MBS and sidelink frequencies (which are prioritized based on UE preferences), the NCR-MT can prioritize the desired cell. This enhancement allows the NCR-MT to constantly perform measurements and attempt to reselect to the desired cell, minimizing the chance of camping on / connecting to an undesired cell.

[0220] Another aspect is to define an NCR-specific offset for intra-frequency cell reselection (i.e., within the R criteria), since considering that NCRs may be deployed at the cell edge (i.e., extending the coverage of a macro cell), the ranking may cause the NCR-MT to reselect an undesirable cell on the same frequency.

[0221] Proposal 4: RAN2 should discuss whether NCR-MT is allowed to prioritize the desired cell (i.e., the cell of interest) in the cell reselection procedure.

[0222] Another potential issue concerns mobility in inactive mode. RAN2 agreed that after the NCR-MT transitions to RRC inactive mode, the NCR-Fwd can be turned on or off according to the last setting received from the gNB. Based on this agreement, after the NCR-MT becomes inactive, the NCR-MT may reselect a different cell due to, for example, blocking FR2. There is no problem if the NCR-Fwd is off, but if the NCR-Fwd is on, the same issue as in Section 2.1.2 may occur.

[0223] Observation 7: When NCR-Fwd is ON and NCR-MT is inactive, there is a possibility of reselecting a different cell.

[0224] In this scenario, we need to clarify how the NCR should behave. Possible options are: Option 1: NCR-Fwd will remain ON at the last setting based on the current agreement. Option 2: Similar to suggestion 3 above, turn NCR-Fwd OFF (or allow NCR-MT to discard the last setting).

[0225] Option 1 is the same as the agreement that "after NCR-MT enters inactive mode, NCR-Fwd can be ON or OFF according to the last configuration received from the gNB" and "WA:RRC inactive is supported optionally without specific functional extensions", so it can be said that Option 1 is efficient in terms of minimizing standardization efforts.

[0226] Option 2 seems reasonable from a technical point of view, because the configuration is provided by another cell (i.e., the last serving cell), and it is somewhat unnatural for NCR-Fwd to operate on configuration that the current cell does not know. This is because the reselected cell may have different resources available for NCR. Therefore, since RAN2 also agrees that cell reselection is mandatory support, option 2 is a fail-safe mechanism.

[0227] In light of the above discussion, option 2 is preferable from the perspective of technical rationality.

[0228] Proposal 5: RAN2 should discuss whether to turn off NCR-Fwd when reselecting a cell with a different NCR-MT.

[0229] Another potential problem occurs when the NCR-MT connects to an undesired cell after cell reselection or RRC reestablishment. From the NCR's perspective, it needs to reconnect to the desired cell. From the gNB's perspective, the RRC connection with this NCR-MT ultimately makes no sense. RAN2 has already agreed that the NCR-MT does not support handovers. Therefore, the only option the gNB can take is to release the NCR-MT. However, since the NCR-MT transitions to the idle state and follows the cell reselection procedure, there is no guarantee that the NCR-MT will camp on / reconnect to the desired cell. In this case, redirection could be enhanced to camp the NCR-MT on the desired cell. However, the question remains as to whether the gNB can acquire the NCR's desired cell (e.g., the cell configured by OAM).

[0230] Proposal 6: RAN2 should discuss whether to enhance redirection to move NCR-MT from desired cell to desired cell (i.e., instead of handover).

[0231] 2.2. Access Control Issues 2.2.1. Open Issues Regarding NPN Support At RAN2#120, the following agreement was reached on matters requiring further consideration: Introduce NCR support indication per PLMN in SIB1.

[0232] Deploying NCR in NPNs is also beneficial and there is potential market demand. For example, NPN frequencies are planned in the high bands of FR1 (4.9 GHz) and FR2 (28 GHz) in Japan. In these frequencies, extending coverage with NCR is often important. Another example is that NPNs, due to their local / closed area nature, may offer better performance in URLLC use cases such as smart factories. In such cases, low-latency repeaters are more suitable than high-latency relays.

[0233] From a specification perspective, the NCR support indication is assumed to be a one-bit indication added to each entry of the PLMN Identity Info List in SIB1, similar to the IAB support indication. To support NCR in an NPN, all that is required is to add the same indication to each entry of the NPN Identity Info List, similar to IAB. Therefore, the standardization effort is expected to be minimal (almost zero). Furthermore, in PLMN networks, no signaling overhead is incurred (i.e., the NPN Identity Info List is an optional IE and therefore does not exist in such networks).

[0234] In addition, RAN2 has already agreed to the following statement, which clearly suggests that NCR will be supported in NPN:

[0235] An NCR-MT capable of NPN should consider cellReservedForOtherUse to determine NPN-only cells.

[0236] Considering the above, we believe that there is no need for "artificial" restrictions on the introduction of NCR in NPNs. Therefore, RAN2 should confirm that NCR is supported in NPNs, which will resolve the previous considerations.

[0237] Proposal 7: RAN2 should verify that NCR is supported in the NPN. Therefore, an NCR support indication will be added to each entry in the NPN Identity List in SIB1.

[0238] 2.2.2 Potential Issues with PRACH Resources In IAB, specific PRACH occasions (ROs) can be provided to avoid potential collisions. These occasions are defined in the following IEs to extend the common configuration of the UE:

[0239] Since NCR is considered a network node as well as an IAB node, PRACH collisions with UEs should also be avoided. For UEs within the extended coverage provided by NCR, the preamble transmitted by the UE is forwarded to the gNB by NCR, whereas in the case of IAB, the preamble transmitted by the UE is terminated by the IAB node. Therefore, it is considered to be a more serious problem for NCR. Therefore, it is considered to be a more serious problem for NCR in terms of PRACH collisions at the gNB receiving side.

[0240] In this sense, it is worth considering whether PRACH resources separated from the UE should be provided to the NCR-MT. If so, further consideration is needed as to whether the separated PRACH resources are defined by a separate RO (as in Rel-16 IAB) or by PRACH partitioning (i.e., as part of Rel-17 RedCap, SDT, slicing, and Feature Combination Preambles specified for coverage extension).

[0241] Proposal 8: RAN2 should discuss whether to define separate PRACH resources specific to NCR-MT. [Explanation of symbols]

[0242] 1: Mobile communication system 100:UE 200 :gNB 210: Transmission unit 220: Receiving unit 230: Control unit 240: Backhaul communication unit 500A:NCR device 510A: NCR-Fwd 520A: NCR-MT 500B :RIS device 511A: Wireless unit 511a: Antenna part 511b :RF circuit 511c: Directivity control unit 512A: NCR control section 512B: RIS control unit 521: Receiving unit 522: Transmission unit 523: Control unit 530: Interface

Claims

1. A communication method using a repeater node, the repeater node comprising: a repeater device configured to perform a forwarding operation of radio signals transmitted between a network and a user equipment; and a control terminal supporting the functions of the user equipment, The control terminal in a radio resource control (RRC) connected state in a first cell receives control configuration information used to control the repeater device from the network; When the control terminal transitions from the RRC connected state to an RRC inactive state in the first cell, the repeater device forwards the radio signal based on last control setting information received from the network; When the control terminal selects a second cell different from the first cell when the control terminal is in the RRC inactive state, the repeater device stops forwarding the radio signal. Communication method.

2. A repeater node comprising: a repeater device configured to perform a forwarding operation of radio signals transmitted between a network and a user equipment; and a control terminal supporting the functions of the user equipment, The control terminal a receiving unit that receives control setting information used to control the repeater device from the network when the control terminal is in a radio resource control (RRC) connected state in a first cell; a control unit that, when the control terminal transitions from the RRC connected state to an RRC inactive state in the first cell, causes the repeater device to forward the radio signal based on last control setting information received from the network; The control unit causes the repeater device to stop forwarding the radio signal when the control terminal selects a second cell different from the first cell while the control terminal is in the RRC inactive state. Repeater node.

3. a repeater node including a repeater device configured to perform a forwarding operation of a radio signal transmitted between a network and a user device, and a control terminal supporting the functions of the user device; receiving control configuration information used to control the repeater device from the network when the control terminal is in a radio resource control (RRC) connected state in a first cell; When the control terminal transitions from the RRC connected state to an RRC inactive state in the first cell, a process of causing the repeater device to forward the radio signal based on last control setting information received from the network; When the control terminal is in the RRC inactive state and selects a second cell different from the first cell, the control terminal causes the repeater device to stop forwarding the radio signal. program.

4. A chipset for a repeater node, comprising: a repeater device configured to perform forwarding operations of radio signals transmitted between a network and a user equipment; and a control terminal supporting the functions of said user equipment, receiving control configuration information used to control the repeater device from the network when the control terminal is in a radio resource control (RRC) connected state in a first cell; When the control terminal transitions from the RRC connected state to an RRC inactive state in the first cell, a process of causing the repeater device to forward the radio signal based on last control setting information received from the network; When the control terminal is in the RRC inactive state and selects a second cell different from the first cell, the control terminal causes the repeater device to stop forwarding the radio signal. Chipset.

5. A system including a network, a user equipment, and a repeater node, The repeater node comprises a repeater device configured to perform a forwarding operation of radio signals transmitted between the network and the user equipment, and a control terminal supporting the functions of the user equipment; The control terminal a receiving unit that receives control setting information used to control the repeater device from the network when the control terminal is in a radio resource control (RRC) connected state in a first cell; a control unit that, when the control terminal transitions from the RRC connected state to an RRC inactive state in the first cell, causes the repeater device to forward the radio signal based on last control setting information received from the network; The control unit causes the repeater device to stop forwarding the radio signal when the control terminal selects a second cell different from the first cell while the control terminal is in the RRC inactive state. system.

6. A user equipment for controlling a repeater equipment configured to perform a forwarding operation of a radio signal transmitted between a network and another user equipment, a receiving unit that receives control configuration information used to control the repeater device from the network when the user equipment is in a radio resource control (RRC) connected state in a first cell; a control unit that, when the user equipment transitions from the RRC connected state to an RRC inactive state in the first cell, causes the repeater device to forward the radio signal based on last control setting information received from the network; The control unit causes the repeater device to stop forwarding the radio signal when the user equipment selects a second cell different from the first cell when the user equipment is in the RRC inactive state. User equipment.

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