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

Abstract

To provide a communication method, a repeater node, user equipment, a program, a chip set, and a system used in a mobile communication system.SOLUTION: In a communication method used in a relay device including a relay that performs a relay operation of relaying a radio signal transmitted between a network and a user equipment and a control terminal that receives a control signal used for control of the relay from the network in a mobile communication system, the method includes a step of causing the control terminal to transition to a radio resource control (RRC) connected state in a cell included in the network, a step of determining whether or not a condition that notification information indicating that the relay device is included in a message to be transmitted from the control terminal to the cell is satisfied, and a step of, in a case where it is determined that the condition is satisfied, and transmitting a message including the notification information from the control terminal to the cell.SELECTED DRAWING: Figure 13

Description

[Technical Field]

[0001] The present disclosure relates to a communication method, a repeater node, a user equipment, a program, a chipset, and a system 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 used in a relay device having a relay that performs relaying operations to relay radio signals transmitted between a network and a user device, and a control terminal that receives a control signal from the network used to control the relay, and includes the steps of: transitioning the control terminal to a radio resource control (RRC) connected state in a cell included in the network; determining whether a condition is met for including notification information indicating that the control terminal is the relay device in a message sent from the control terminal to the cell; and, in response to determining that the condition is met, transmitting the message including the notification information from the control terminal to the cell.

[0006] A communication method according to a second aspect is a communication method used in a relay device having a relay that performs relaying operations to relay radio signals transmitted between a network and a user device, and a control terminal that receives a control signal from the network used to control the relay, and includes the steps of: the control terminal, in a Radio Resource Control (RRC) connected state, initiating an RRC connection re-establishment procedure for a cell included in the network; including in an RRC re-establishment request message a Radio Network Temporary Identifier (RNTI) dedicated to the relay device that is assigned to the relay device or notification information indicating that the device itself is the relay device; and transmitting the RRC re-establishment request message including the RNTI dedicated to the relay device or the notification information from the control terminal to the cell. [Brief explanation of the drawings]

[0007] [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. 2 is a diagram illustrating an example of an application scenario of the NCR device (relay device) according to the first embodiment. [Figure 5] FIG. 2 is a diagram illustrating an example of an application scenario of the NCR device according to the first embodiment. [Figure 6] FIG. 3 is a diagram illustrating an example of a control method for the NCR device according to the first 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 a first embodiment. [Figure 8] 1 is a diagram illustrating a specific configuration example of a mobile communication system having an NCR device according to a first embodiment. [Figure 9] 1 is a diagram illustrating an example of the configuration of an NCR device according to a first 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. 4 is a diagram for explaining the operation according to the first embodiment. [Figure 13] FIG. 2 is a diagram illustrating an example of the operation of an NCR-MT (control terminal) according to the first embodiment. [Figure 14] FIG. 10 is a diagram illustrating an example of the operation of an NCR-MT according to a modification of the first embodiment. [Figure 15] FIG. 10 is a diagram for explaining RRC connection re-establishment by NCR-MT according to the second embodiment. [Figure 16] FIG. 1 is a diagram showing an RRC reestablishment request message defined in the 3GPP RRC technical specification (TS38.331). [Figure 17] FIG. 10 is a diagram illustrating an example of the operation of NCR-MT according to the second embodiment. [Figure 18] FIG. 10 is a diagram for explaining a RIS device (relay device) according to the third embodiment. [Figure 19] FIG. 10 is a diagram for explaining a RIS device (relay device) according to the third embodiment. [Figure 20]FIG. 1 illustrates a specific PRACH scenario (RO) for avoiding potential collisions. DETAILED DESCRIPTION OF THE INVENTION

[0008] 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.

[0009] (1) First embodiment A first embodiment will be described below. A relay device according to the embodiment is a repeater device (that is, an NCR device) that can be controlled from a network.

[0010] (1.1) Overview of mobile communication systems FIG. 1 is a diagram showing a configuration of a mobile communication system according to an embodiment.

[0011] 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.

[0012] 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.

[0013] The UE 100 is a mobile wireless communication device. The UE 100 may be any device that is used by a user. For example, the UE 100 may be a mobile phone terminal (including a smartphone), 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).

[0014] 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").

[0015] 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.

[0016] 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.

[0017] 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.

[0018] FIG. 2 is a diagram showing the configuration of a protocol stack of a radio interface of a user plane that handles data.

[0019] 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.

[0020] 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.

[0021] 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.

[0022] 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.

[0023] 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.

[0024] The PDCP layer performs header compression / decompression, encryption / decryption, etc.

[0025] 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.

[0026] 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).

[0027] 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.

[0028] 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.

[0029] 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.

[0030] (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.

[0031] 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.

[0032] 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.

[0033] 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.

[0034] 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.

[0035] 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 NCR-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.

[0036] 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).

[0037] 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.

[0038] 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."

[0039] 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."

[0040] 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.

[0041] 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).

[0042] 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.

[0043] 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.

[0044] 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.

[0045] 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.

[0046] 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.

[0047] 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.

[0048] On the other hand, an NCR control signal transmitted in L1 / L2 signaling, i.e., 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.

[0049] 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.

[0050] The NCR control signal (for example, 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.

[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 FIG. 12 is a diagram for explaining the operation according to the first embodiment.

[0075] First, the NCR-MT520A (NCR device 500A) in the RRC idle state in the cell of the gNB200, i.e., the NCR-MT520A camped on that cell, initiates an RRC connection establishment procedure. The RRC connection establishment procedure includes sending an RRC setup request message from the NCR-MT520A to the gNB200, sending an RRC setup message from the gNB200 to the NCR-MT520A, and sending an RRC setup complete message from the NCR-MT520A to the gNB200. The RRC setup complete message corresponds to message 5 (Msg5) of the random access procedure. The NCR-MT520A transitions to the RRC connected state through the RRC connection establishment procedure.

[0076] Second, the NCR-MT520A transmits to the gNB200 a message including notification information indicating that the NCR-MT520A is an NCR (also referred to as "NCR Node Indication" or "NCR Node Indication IE"). For example, the NCR-MT520A transmits to the gNB200 an RRC Setup Complete message (Msg5) including an NCR Node Indication, or a UE Capability Response message including an NCR Node Indication. In response to receiving a UE Capability Enquiry message from the gNB200, the NCR-MT520A transmits to the gNB200 a UE Capability Response message including information about the capabilities of the NCR-MT520A. The UE Capability Response message is also referred to as a UE Capability Information message. When gNB200 receives the NCR Node Indication, it can recognize that the device connected to its own cell is not UE100 but NCR-MT520A (NCR device 500A).

[0077] Third, the gNB 200 transmits an NCR control signal (particularly, NCR setting information) to the NCR-MT 520A. The NCR-MT 520A (NCR device 500A) controls the NCR-Fwd 510A in accordance with the received NCR control signal.

[0078] In this way, by transmitting NCR Node Indication from NCR-MT520A to gNB200, gNB200 can recognize that the device connected to its own cell is NCR-MT520A (NCR device 500A) and not UE 100. This allows gNB200 to transmit an NCR control signal (particularly, NCR setting information) to NCR-MT520A.

[0079] However, when a desired cell is specified as the connection destination of the NCR-MT520A, it is not desirable for the NCR-MT520A to receive an NCR control signal from an undesired cell that is not the desired cell (i.e., for the NCR-Fwd510A to be controlled by the undesired cell).

[0080] Specifically, the placement of conventional RF repeaters is determined by network planning and / or on-site RF measurements. Therefore, a desired cell is planned for each NCR device 500A. That is, the correspondence between the serving cell and the NCR device 500A can be determined by network planning. Such a desired cell can be configured in the NCR device 500A by, for example, a network operator entity (OAM: Operation, Administration, and Maintenance).

[0081] The NCR device 500A (NCR-MT520A) may be configured with a desired cell by, for example, OAM. Here, the desired cell may be a cell that the NCR-MT520A is planned to connect to. In this case, it is preferable that the NCR-MT520A avoids connecting to an undesired cell that is not the desired cell. Note that the desired cell may also be referred to as a planned cell. The undesired cell may also be referred to as a non-planned cell or an unplanned cell.

[0082] Here, the desired cell may be a cell that the NCR-MT520A is planned to camp on and / or connect to according to network planning. The frequency to which the desired cell belongs is also referred to as the "desired frequency." A cell that is not a desired cell is referred to as a "non-desired cell," and a frequency that is not a desired frequency is referred to as an "non-desired frequency." Information on a desired cell (e.g., the cell ID of a desired cell), information on a non-desired cell (e.g., the cell ID of a non-desired cell), information on a desired frequency (e.g., the frequency ID of a desired frequency), and / or information on a non-desired frequency (e.g., the frequency ID of a non-desired frequency) may be collectively referred to as "desired cell information." The desired cell information may include a list of cell IDs of each desired cell, a list of cell IDs of each non-desired cell, a list of frequency IDs of each desired frequency, and / or a list of frequency IDs of each non-desired frequency. The desired cell information may be preset in the NCR-MT520A by the OAM. The desired cell information may be preset in the memory of the NCR-MT520A at the time of shipping from the factory. The desired cell information may be preset in the NCR-MT520A from the gNB200 or AMF300A. The NCR-MT520A holds the preset desired cell information and uses the held desired cell information to determine whether to transmit an NCR Node Indication.

[0083] Alternatively, the desired cell may be the cell that last provided an NCR control signal to the NCR-MT520A, or a cell belonging to the frequency that last provided an NCR control signal to the NCR-MT520A. For example, when the NCR-MT520A is in the RRC connected state in a cell, it receives an NCR control signal from the cell and controls the NCR-Fwd510A according to the received NCR control signal. The cell or frequency that provides the NCR control signal to the NCR-MT520A can be considered to be the cell on which the NCR-MT520A is planned to camp and / or connect. Therefore, all cells (or all frequencies) that provided an NCR control signal to the NCR-MT520A may be considered to be desired cells (or desired frequencies). The NCR-MT520A retains and manages desired cell information related to the cells and / or frequencies that provided the NCR control signal, and uses the retained desired cell information to determine whether to transmit an NCR Node Indication.

[0084] Alternatively, the desired cell may be a cell belonging to the operating frequency of the NCR-Fwd510A. In other words, the desired cell may be a cell belonging to a frequency that the NCR-Fwd510A can relay. Such desired cell information may be preset in the NCR-MT520A from the OAM. Such desired cell information may be preset in the memory of the NCR-MT520A at the time of shipment from the factory. Such desired cell information may be preset in the NCR-MT520A from the gNB200 or the AMF300A.

[0085] The communication method according to the first embodiment is a method used in an NCR device 500A having an NCR-Fwd 510A that performs a relay operation of relaying radio signals transmitted between a network 5 and a UE 100, and an NCR-MT 520A that receives, from the network 5, an NCR control signal used to control the NCR-Fwd 510A. First, the NCR-MT 520A transitions to an RRC connected state in a cell included in the network 5. Second, the NCR-MT 520A determines whether a condition for including an NCR Node Indication in a message to be transmitted from the NCR-MT 520A to the cell (gNB 200) is satisfied. Third, in response to determining that the condition is satisfied, the NCR-MT 520A transmits a message including an NCR Node Indication from the NCR-MT 520A to the cell (gNB 200). As described above, the message may be an RRC setup complete message (Msg5) or a UE capability response message.

[0086] In the first embodiment, the NCR-MT520A determines whether the cell to which it is connected (also referred to as the "connected cell") is a desired cell. In response to determining that the connected cell is a desired cell, the NCR-MT520A transmits a message including an NCR Node Indication to the connected cell (gNB200). Note that the NCR-MT520A may also determine that the connected cell is a desired cell if the frequency of the cell to which it is connected is the desired frequency. In response to determining that the connected cell belongs to the desired frequency, the NCR-MT520A may also transmit a message including an NCR Node Indication to the connected cell (gNB200).

[0087] This allows the NCR-MT520A not to transmit an NCR Node Indication to the serving cell (gNB200) when it is determined that the serving cell is not a desired cell (i.e., the serving cell is an undesired cell). This makes it easier to avoid the NCR-MT520A receiving an NCR control signal from an undesired cell (i.e., the NCR-Fwd510A being controlled by an undesired cell).

[0088] In response to determining that the serving cell is not the desired cell, the NCR-MT520A may transmit information (also referred to as "release recommendation information") to the serving cell (gNB200) to prompt the network 5 to transition from the RRC connected state to another RRC state (e.g., RRC idle state). This allows the gNB200 to transition the NCR-MT520A to, for example, the RRC idle state based on the release recommendation information from the NCR-MT520A. As a result, the NCR-MT520A can easily reselect a desired cell through cell reselection. Note that, if handover or redirection of the NCR-MT520A is possible, the NCR-MT520A may transmit desired cell information to the serving cell (gNB200), and the gNB200 may cause the NCR-MT520A to perform handover or redirection to the desired cell.

[0089] FIG. 13 is a diagram showing an example of the operation of the NCR-MT520A according to the first embodiment.

[0090] In step S101, NCR-MT520A, which is in RRC idle state in a cell, initiates an RRC connection establishment procedure with the cell and establishes an RRC connection with the cell (gNB200).

[0091] In step S102, the NCR-MT 520A determines whether the connected cell is a desired cell.

[0092] If the serving cell is the desired cell (step S102: YES), in step S103, the NCR-MT 520A includes an NCR Node Indication in a message and transmits the message to the serving cell (gNB 200). As described above, the message may be Msg5. The message may be a response to the UE Capability Enquiry (UE Capability Response).

[0093] On the other hand, if the serving cell is not the desired cell (step S102: NO), in step S104, the NCR-MT 520A transmits the message not including the NCR Node Indication to the serving cell (gNB 200). For example, the NCR-MT 520A does not include the NCR Node Indication IE in the response message (UE Capability Response) to the UE Capability Enquiry.

[0094] In step S104, the NCR-MT 520A (NCR device 500A) may request the gNB 200 to release the RRC connection. For example, the NCR-MT 520A (NCR device 500A) may initiate a procedure for connection release in the NAS layer. In this procedure, the NAS layer of the NCR-MT 520A (NCR device 500A) may transmit to the AMF 300A a NAS message including information indicating connection release. Alternatively, the NCR-MT 520A may transmit to the gNB 200 a UE Assistance Information message including a ReleasePreference IE with "idle," "inactive," or "outOfConnected" set as the preferred RRC state (preferredRRC-State). In this procedure, the NCR-MT 520A may notify the gNB 200 of the reason for the RRC connection release. For example, the reason may be information for notifying that "connection to an undesired cell" and / or "reconnection to a desired cell" is required.

[0095] In the description of the operation according to the first embodiment, it is assumed that the NCR-MT520A transitions from the RRC idle state to the RRC connected state. However, it is also possible to assume that the NCR-MT520A transitions from the RRC inactive state to the RRC connected state. In that case, the above-mentioned RRC idle state should be read as the RRC inactive state, and the above-mentioned RRC connection establishment (RRC setup) should be read as the RRC connection recovery (RRC recovery). The same applies to the modified examples described below.

[0096] (1.5) Modifications of the Operation According to the First Embodiment The modified example of the first embodiment will be described mainly focusing on the differences from the first embodiment described above. This modified example may be implemented in combination with the first embodiment described above.

[0097] In the above-described first embodiment, the gNB200 transmits NCR setting information (NCR control signal) to the NCR-MT520A (NCR device 500A) based on the NCR Node Indication from the NCR-MT520A. That is, the gNB200 uses the NCR Node Indication to determine whether or not NCR setting is necessary. Therefore, if new NCR setting information is not necessary (for example, if the NCR device 500A already has valid NCR setting information), the NCR-MT520A may not need to transmit the NCR Node Indication to the gNB200. This can prevent unnecessary signaling from occurring.

[0098] In this modification, the NCR-MT520A determines whether or not it is necessary to acquire NCR setting information, which is setting information for the NCR device 500A, from the serving cell (gNB200). If it is determined that there is such a need, the NCR-MT520A transmits a message including an NCR Node Indication to the serving cell (gNB200).

[0099] For example, the NCR-MT 520A may determine whether the NCR device 500A has configuration information available in the serving cell. In response to determining that the NCR device 500A does not have configuration information available in the serving cell, the NCR-MT 520A may transmit a message including an NCR Node Indication to the serving cell (gNB 200).

[0100] The NCR-MT 520A may determine whether the NCR-Fwd 510A is on. In response to determining that the NCR-Fwd 510A is on, the NCR-MT 520A may transmit a message including an NCR Node Indication to the serving cell (gNB 200).

[0101] The NCR-MT520A may determine whether to perform relay operation dependent on an NCR control signal from the network 5. Here, the relay operation independent of an NCR control signal from the network 5 may be the same as that of a conventional RF repeater. In response to determining to perform relay operation dependent on an NCR control signal from the network 5, the NCR-MT520A may transmit a message including an NCR Node Indication to the serving cell (gNB200).

[0102] 14 is a diagram showing an example of operation of the NCR-MT520A according to a modification of the first embodiment. Prior to this operation, the NCR-MT520A may receive NCR setting information from the network 5. The NCR setting information may include information on an effective area in which the NCR setting information is valid. The effective area may be an area consisting of one or more cells, or may be an area consisting of one gNB200. After receiving the NCR setting information, the NCR-MT520A may move to another cell by cell reselection, for example, while retaining the NCR setting information in the RRC idle state or the RRC inactive state.

[0103] In step S111, NCR-MT520A, which is in RRC idle state in a cell, initiates an RRC connection establishment procedure with the cell and establishes an RRC connection with the cell (gNB200).

[0104] In step S112, the NCR-MT 520A determines whether or not NCR setting information is required. Specifically, the NCR-MT 520A determines whether or not it is necessary to acquire NCR setting information from the connected cell.

[0105] In step S112, the NCR-MT520A may make a determination based on whether or not there is a valid setting. If the NCR setting information that has already been received is valid (for example, if the connected cell is within the valid area), the NCR-MT520A determines that the NCR setting information is not necessary. On the other hand, if the NCR setting information that has already been received is invalid, the NCR-MT520A determines that the NCR setting information is necessary.

[0106] In step S112, the NCR-MT520A may make a determination based on the relay operation state. If the NCR-Fwd510A is off, the NCR-MT520A determines that NCR setting information is necessary. For example, if the NCR-MT520A is in the RRC idle state and the NCR-Fwd510A is set to be off when reselecting another cell, the NCR-Fwd510A may be off. On the other hand, if the NCR-Fwd510A is operating according to NCR setting information that has already been received, the NCR-MT520A determines that NCR setting information is not necessary. For example, if the NCR-MT520A is in the RRC inactive state, the NCR-Fwd510A may be operating according to NCR setting information that has already been received.

[0107] In step S112, the NCR-MT520A may make a determination based on the operating state of the device itself. If the NCR device 500A operates as a network-controlled repeater, the NCR-MT520A determines that the NCR setting information is necessary. On the other hand, if the NCR device 500A operates as a conventional RF repeater without network control, the NCR-MT520A determines that the NCR setting information is not necessary.

[0108] If it is determined that NCR setting information is necessary (step S112: YES), in step S113, the NCR-MT520A transmits a message including an NCR Node Indication to the serving cell (gNB200). When the serving cell (gNB200) receives the NCR Node Indication, it may transmit the NCR setting information to the NCR-MT520A.

[0109] On the other hand, if it is determined that NCR setting information is not necessary (step S112: NO), in step S114, the NCR-MT520A does not transmit NCR Node Indication to the serving cell (gNB200). The NCR-MT520A may transmit a message that does not include NCR Node Indication to the serving cell (gNB200). If the serving cell (gNB200) has not received NCR Node Indication, it does not need to transmit NCR setting information to the NCR-MT520A.

[0110] (2) Second embodiment The second embodiment will be described mainly focusing on the differences from the first embodiment described above. The second embodiment may be implemented in combination with the first embodiment.

[0111] The second embodiment relates to an RRC connection re-establishment performed by the NCR-MT 520A in the RRC connected state. Fig. 15 is a diagram for explaining the RRC connection re-establishment by the NCR-MT 520A.

[0112] The NCR-MT520A initiates an RRC connection re-establishment procedure in response to detecting (declaring) a radio link failure (RLF). In the illustrated example, the NCR-MT520A, which is in the RRC connected state in cell a of the gNB200a, detects (declares) an RLF in cell a. For example, the NCR-MT520A detects (declares) an RLF if the radio problem is not resolved by the time a first timer (e.g., timer T310) expires after detecting the RLF. Upon detecting an RLF, the NCR-MT520A 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.

[0113] Here, the NCR-MT 520A transmits an RRC re-establishment request message to cell b (gNB 200 b) selected in the cell selection after the RLF in order to attempt to re-establish the RRC connection. FIG. 16 is a diagram showing the RRC re-establishment request (RRCReestablishmentRequest) message specified in the 3GPP RRC technical specification (TS38.331). The RRC re-establishment request message includes "ReestabUE-Identity," which is the source identifier of the RRC re-establishment request message, so that the receiving gNB 200 can identify the UE context. In the current technical specification, "ReestabUE-Identity" includes the cell RNTI (C-RNTI) assigned to the source of the RRC re-establishment request message.

[0114] In the second embodiment, the NCR-MT 520A that transmits the RRC re-establishment request message includes, in place of this C-RNTI, the NCR-RNTI, which is an RNTI dedicated to the NCR device, in the RRC re-establishment request message. Alternatively, the NCR-MT 520A that transmits the RRC re-establishment request message may include the NCR-RNTI in addition to this C-RNTI in the RRC re-establishment request message. This allows the receiving gNB 200 (i.e., the gNB 200 that is the RRC connection re-establishment destination) to implicitly determine that the sender of the RRC re-establishment request message is the NCR-MT 520A, based on the NCR-RNTI. This enables the gNB 200 to perform operations such as, for example, prioritizing processing of the RRC connection re-establishment of the NCR-MT 520A.

[0115] Alternatively, the NCR-MT520A may include the above-mentioned NCR Node Indication in "ReestabUE-Identity." The NCR-MT520A may include the NCR Node Indication in an information element different from "ReestabUE-Identity," for example, in "ReestablishmentCause," which indicates the cause of re-establishment. In other words, the information to be included in the RRC re-establishment request message may be information that allows the receiving gNB200 (i.e., the gNB200 to which the RRC connection is re-established) to implicitly or explicitly recognize that the sender of the RRC re-establishment request message is the NCR-MT520A.

[0116] The communication method according to the second embodiment is a method used by an NCR device 500A having an NCR-Fwd 510A that performs a relay operation of relaying radio signals transmitted between a network 5 and a UE 100, and an NCR-MT 520A that receives an NCR control signal used to control the NCR-Fwd 510A from the network 5. First, the NCR-MT 520A in the RRC connected state initiates an RRC connection re-establishment procedure with a cell (also referred to as a "re-establishment cell") included in the network 5. Second, the NCR-MT 520A includes an NCR-RNTI assigned to its own device (NCR device) or an NCR Node Indication indicating that its own device is an NCR device in an RRC re-establishment request message. Third, the NCR-MT 520A transmits an RRC re-establishment request message including the NCR-RNTI or the NCR Node Indication to the re-establishment cell (gNB 200).

[0117] The NCR-MT 520A may handle multiple NCR-Fwds 510A, each assigned an NCR-RNTI. That is, the NCR-MT 520A may have multiple NCR-Fwds 510A, each assigned an NCR-RNTI. In this case, the NCR-MT 520A may include, in the RRC re-establishment request message, the NCR-RNTI of each of the multiple NCR-Fwds 510A (the NCR-RNTIs of all NCR-Fwds 510A) or the NCR-RNTI of a specific NCR-Fwd 510A among the multiple NCR-Fwds 510A.

[0118] FIG. 17 is a diagram showing an example of the operation of the NCR-MT520A according to the second embodiment.

[0119] In step S201, the NCR-MT 520A in the RRC connected state detects an RLF with a cell and initiates an RRC connection re-establishment procedure. The NCR-MT 520A selects a cell whose wireless quality satisfies a predetermined standard as a re-establishment cell through cell selection.

[0120] In step S202, the NCR-MT 520A includes (sets) the NCR-RNTI in the RRC re-establishment request message. The NCR-MT 520A may also include an NCR Node Indication in the RRC re-establishment request message. Here, the NCR-MT 520A may include the NCR-RNTI (or NCR Node Indication) in the RRC re-establishment request message only if the re-establishment cell is broadcasting an NCR-Supported IE (i.e., information indicating that the NCR device is supported) in SIB1.

[0121] Here, if the NCR-MT 520A handles only one NCR-Fwd 510A, the NCR-MT 520A includes the NCR-RNTI associated with that NCR-Fwd 510A (or NCR-MT 520A) in the RRC re-establishment request message.

[0122] On the other hand, if there are multiple NCR-Fwds 510A handled by the NCR-MT 520A, multiple NCR-RNTIs may be configured. In this case, the NCR-MT 520A may include all configured NCR-RNTIs in the RRC re-establishment request message. Alternatively, the NCR-MT 520A may include only one (or only some) of the multiple configured NCR-RNTIs in the RRC re-establishment request message. For example, when multiple NCR-RNTIs are configured, the NCR-MT 520A may include the NCR-RNTI of the first entry in the configuration list in the RRC re-establishment request message. In the case of carrier aggregation or dual connectivity, the NCR-MT 520A may include an NCR-RNTI associated with the NCR-Fwd 510A relaying the primary cell (PCell) or a cell in the master cell group (MCG) of the NCR-MT 520A in the RRC re-establishment request message. Alternatively, the NCR-RNTI to be included in the RRC re-establishment request message may be set in advance by the gNB200 to the NCR-MT520A.

[0123] In step S203, the NCR-MT520A transmits an RRC re-establishment request message including an NCR-RNTI (or NCR Node Indication) to the re-establishment cell (gNB200). Based on the NCR-RNTI (or NCR Node Indication), the re-establishment cell (gNB200) identifies that the message was sent from the NCR-MT520A. The re-establishment cell (gNB200) may perform processing such as preferentially accepting the RRC re-establishment request from the NCR-MT520A. Note that if the cell in which the RLF occurred and the re-establishment cell belong to different gNB200, the gNB200 managing the re-establishment cell may transmit a RETRIEVE UE CONTEXT REQUEST message over the Xn interface to the gNB200 managing the cell in which the RLF occurred, requesting transfer of the UE context of the NCR-MT520A (NCR device 500A). The gNB200 managing the re-established cell may include the NCR-RNTI received in the RRC re-establishment request message as the UE Context ID in the RETRIEVE UE CONTEXT REQUEST message. The gNB200 managing the cell where the RLF occurred may transmit the UE Context identified by the UE Context ID to the gNB200 managing the re-established cell. The UE Context may be an NCR-MT Context indicating the setting of NCR-MT and / or an NCR-Fwd Context indicating the setting (and / or control state) of NCR-Fwd.

[0124] (3) Third embodiment Next, a third embodiment will be described, focusing on differences from the above-described embodiments. As shown in Fig. 18, the relay device 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."

[0125] 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.

[0126] 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.

[0127] FIG. 19 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.

[0128] In the third embodiment, instead of the above-mentioned "NCR Node Indication", a "RIS Node Indication" indicating that the device itself is a RIS device may be used. The "RIS Node Indication" may be defined as information different from the "NCR Node Indication".

[0129] (4) Other embodiments In the above-described embodiment, an example has been described in which the relay device that performs relay transmission is the NCR device 500A or the RIS device 500B. However, the relay device that performs relay transmission is not limited to the NCR device 500A or the RIS device 500B, and may be an IAB (Integrated Access and Backhaul) node defined in the 3GPP technical specifications.

[0130] 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.

[0131] 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.

[0132] A program may be provided that causes a computer to execute each process performed by a communication device according to the above-described embodiment, for example, UE100 (NCR-MT520A, RIS-MT520B) or gNB200. The program may be recorded on a computer-readable medium. Using the computer-readable medium, the program can be installed on a computer. Here, the computer-readable medium on which the program is recorded may be a non-transitory recording medium. The non-transitory recording medium is not particularly limited, and may be, for example, a recording medium such as a CD-ROM or a DVD-ROM. Furthermore, circuits that execute each process performed by UE100 or gNB200 may be integrated, and at least a part of UE100 or gNB200 may be configured as a semiconductor integrated circuit (chip set, SoC: System on a chip).

[0133] 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.

[0134] A program may be provided that causes a computer to execute each process performed by the UE100, 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, the gNB200, or the relay device 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 (chip set, SoC: System on a chip).

[0135] 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.

[0136] 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.

[0137] 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.

[0138] This application claims priority to U.S. Provisional Application No. 63 / 445103 (filed February 13, 2023), the entire contents of which are incorporated herein by reference.

[0139] (5) Supplementary notes The following additional notes are about the features of the above-described embodiment.

[0140] (Appendix 1) A communication method for use in 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 method comprising: The control terminal transitions to a radio resource control (RRC) connected state in a cell included in the network; determining whether a condition for including notification information indicating that the control terminal is the relay terminal in a message transmitted from the control terminal to the cell is satisfied; transmitting the message including the notification information from the control terminal to the cell in response to determining that the condition is satisfied. Communication method.

[0141] (Appendix 2) The message is an RRC Setup Complete message or a UE Capability Response message. 1. A communication method as described in Appendix 1.

[0142] (Appendix 3) the determining step includes a step of determining whether the cell is a desired cell defined as a connection destination of the relay device; The transmitting step includes a step of transmitting the message including the notification information from the control terminal to the cell in response to the cell being determined to be the desired cell. 3. A communication method according to claim 1 or 2.

[0143] (Appendix 4) In response to the determination that the cell is not the desired cell, the control terminal further includes a step of transmitting information to the cell to prompt the network to transition from the RRC connected state to another RRC state. 3. A communication method as described in Appendix 3.

[0144] (Appendix 5) the determining step includes a step of determining whether or not it is necessary to acquire configuration information for the relay device from the cell; The step of transmitting includes a step of transmitting the message including the notification information from the control terminal to the cell in response to the determination that there is a need. 5. A communication method according to any one of claims 1 to 4.

[0145] (Appendix 6) the determining step includes a step of determining whether the relay device has the configuration information available in the cell; The transmitting step includes a step of transmitting the message including the notification information from the control terminal to the cell in response to a determination that the relay device does not have the configuration information available in the cell. 1. A communication method as described in Appendix 5.

[0146] (Appendix 7) the determining step includes determining whether the repeater is on; The transmitting step includes a step of transmitting the message including the notification information from the control terminal to the cell in response to the repeater being determined to be on. 7. A communication method according to claim 5 or 6.

[0147] (Appendix 8) the determining step includes a step of determining whether to perform the relay operation depending on the control signal from the network; The transmitting step includes a step of transmitting the message including the notification information from the control terminal to the cell in response to a determination that the relay operation depending on the control signal from the network is to be performed. 8. A communication method according to any one of appendices 5 to 7.

[0148] (Appendix 9) A communication method for use in 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 method comprising: The control terminal in a Radio Resource Control (RRC) Connected state initiates an RRC connection re-establishment procedure with a cell included in the network; a step of including, in an RRC re-establishment request message, a radio network temporary identifier (RNTI) dedicated to the relay device assigned to the relay device or notification information indicating that the relay device is the relay device; transmitting the RRC re-establishment request message including the relay device-specific RNTI or the notification information from the control terminal to the cell. Communication method.

[0149] (Appendix 10) The step of including includes, when the control terminal handles a plurality of relays each assigned with an RNTI dedicated to the relay device, a step of including, in the RRC re-establishment request message, an RNTI dedicated to the relay device of each of the plurality of relays or an RNTI dedicated to the relay device of a specific relay among the plurality of relays. 9. A communication method as set forth in Appendix 9.

[0150] (6) Supplementary notes 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.

[0151] This appendix discusses the remaining open / potential issues for RAN2 regarding NCR.

[0152] 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:

[0153] 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.

[0154] 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.

[0155] 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:

[0156] 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.

[0157] 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.

[0158] 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.

[0159] 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.

[0160] 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.

[0161] 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.

[0162] 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.

[0163] 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.

[0164] 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.

[0165] 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.

[0166] 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.

[0167] 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.

[0168] 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.

[0169] 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).

[0170] Proposal 1: RAN2 should agree to turn off NCR-Fwd when NCR-MT is released to idle state, as in the case of RLF.

[0171] 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.

[0172] 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.

[0173] 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.

[0174] 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 of reconfiguring the NCR can be avoided.

[0175] 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.

[0176] 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.

[0177] 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.

[0178] 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).

[0179] Proposal 3: RAN2 should discuss whether NCR-MT should discard the last configuration when RRC re-establishment to a different cell is initiated.

[0180] 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.

[0181] 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.

[0182] Observation 6: The NCR can configure the desired cell, for example, by OAM.

[0183] 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.

[0184] 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.

[0185] 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.

[0186] 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.

[0187] 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.

[0188] Observation 7: When NCR-Fwd is ON and NCR-MT is inactive, there is a possibility of reselecting a different cell.

[0189] 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).

[0190] 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.

[0191] 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.

[0192] In light of the above discussion, option 2 is preferable from the perspective of technical rationality.

[0193] Proposal 5: RAN2 should discuss whether to turn off NCR-Fwd when reselecting a cell with a different NCR-MT.

[0194] 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).

[0195] Proposal 6: RAN2 should discuss whether to enhance redirection to move NCR-MT from desired cell to desired cell (i.e., instead of handover).

[0196] 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.

[0197] 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.

[0198] 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).

[0199] In addition, RAN2 has already agreed to the following statement, which clearly suggests that NCR will be supported in NPN:

[0200] An NCR-MT capable of NPN should consider cellReservedForOtherUse to determine NPN-only cells.

[0201] 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.

[0202] Proposal 7: RAN2 should verify that NCR is supported in the NPN. Therefore, an NCR support indication is also added to each entry in the NPN Identity List in SIB1.

[0203] 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:

[0204] 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.

[0205] 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).

[0206] Proposal 8: RAN2 should discuss whether to define separate PRACH resources specific to NCR-MT. [Explanation of symbols]

[0207] 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 510B:RIS-Fwd 520B: RIS-MT 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. 1. A communication method using a repeater node having 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 method comprising: The control terminal in a Radio Resource Control (RRC) Connected state initiates an RRC connection re-establishment procedure with respect to a cell included in the network; and including in an RRC re-establishment request message a repeater node-specific Radio Network Temporary Identifier (RNTI) assigned to the repeater node. Communication method.

2. The RRC re-establishment request message includes an information element indicating the cause of the re-establishment. The communication method according to claim 1 .

3. 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 has a control unit that, in a radio resource control (RRC) connected state, initiates an RRC connection re-establishment procedure for a cell included in the network and includes a repeater node-dedicated radio network temporary identifier (RNTI) assigned to the repeater node in an RRC re-establishment request message. Repeater node.

4. 1. A user equipment for controlling a repeater equipment configured to perform forwarding operations of radio signals transmitted between a network and other user equipments, comprising: A control unit that, in a radio resource control (RRC) connected state, initiates an RRC connection re-establishment procedure for a cell included in the network and includes a user equipment-dedicated radio network temporary identifier (RNTI) assigned to the user equipment in an RRC re-establishment request message. User equipment.

5. 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; A process in which the control terminal in a radio resource control (RRC) connected state initiates an RRC connection re-establishment procedure with respect to a cell included in the network; and including a repeater node-specific Radio Network Temporary Identifier (RNTI) assigned to the repeater node in an RRC re-establishment request message. program.

6. 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, A process in which the control terminal in a radio resource control (RRC) connected state initiates an RRC connection re-establishment procedure with respect to a cell included in the network; and including a repeater node-specific Radio Network Temporary Identifier (RNTI) assigned to the repeater node in an RRC re-establishment request message. Chipset.

7. 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 has a control unit that, in a radio resource control (RRC) connected state, initiates an RRC connection re-establishment procedure for a cell included in the network and includes a repeater node-dedicated radio network temporary identifier (RNTI) assigned to the repeater node in an RRC re-establishment request message. system.

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