Communication methods, relay devices, mobile communication systems, programs, and chipsets

Abstract

This invention provides an efficient relay device that automatically resumes relay operation if another cell is selected during relay operation and then returned to the original cell. [Solution] In a mobile communication system, the communication method performed by the relay device (NCR device) 500A includes the steps of: receiving setting information related to relay operation from the first cell a; performing the relay operation using the setting information when the control terminal is in a radio resource control (RRC) inactive state in the first cell; stopping the relay operation when cell reselection is performed from the first cell to the second cell b; and resuming the relay operation using the setting information when cell reselection is performed to the first cell within a predetermined time after cell reselection to the second cell.

Description

Technical Field

[0001] The present disclosure relates to a communication method, a relay device, a mobile communication system, a program, and a chipset.

Background Art

[0002] In recent years, the fifth-generation (5G) mobile communication system has attracted attention. NR (New Radio), which is a radio access technology of the 5G system, enables broadband transmission in a high-frequency band compared to LTE (Long Term Evolution), which is a fourth-generation radio access technology.

[0003] Since a radio signal (radio wave) in a high-frequency band such as a millimeter-wave band or a terahertz-wave band has high directivity, reducing the coverage of a base station becomes an issue. In order to solve such an issue, a repeater device that relays a radio signal between a network and a user device, which is a type of repeater device that can be controlled from the network, has attracted attention (for example, see Non-Patent Document 1).

[0004] Such a repeater device can expand the coverage of a base station while suppressing the occurrence of interference by, for example, amplifying a radio signal received from a base station and transmitting it by directional transmission. Such a repeater device is also referred to as an NCR (Network-controlled Repeater).

Prior Art Documents

Non-Patent Documents

[0005]

Non-Patent Document 1

Summary of the Invention

[0006] A communication method according to the first embodiment is a communication method executed by a relay device having a relay device that performs a relay operation to relay radio signals transmitted between a base station and a user device, and a control terminal that receives control signals used to control the relay device from the base station, comprising the steps of: receiving setting information relating to the relay operation from a first cell; performing the relay operation using the setting information when the control terminal is in a radio resource control (RRC) inactive state in the first cell; stopping the relay operation when cell reselection from the first cell to a second cell is performed; and resuming the relay operation using the setting information when cell reselection to the first cell is performed within a predetermined time after cell reselection to the second cell.

[0007] The relay device according to the second embodiment includes a relay unit that performs a relay operation to relay radio signals transmitted between a base station and a user device, and a control terminal that receives control signals used to control the relay unit from the base station, wherein the control terminal includes a receiving unit that receives setting information relating to the relay operation from a first cell, and a control unit that controls the relay unit to perform the relay operation using the setting information when the control terminal is in a radio resource control (RRC) inactive state in the first cell, wherein the control unit stops the relay operation when a cell is reselected from the first cell to a second cell, and resumes the relay operation using the setting information when a cell is reselected to the first cell within a predetermined time after the cell is reselected to the second cell.

[0008] A third communication method is a communication method executed by a relay device having a relay unit that performs a relay operation to relay radio signals transmitted between a base station and a user device, and a control terminal that receives control signals from the base station for use in controlling the relay unit, the method comprising: receiving first setting information relating to the relay operation from the base station; receiving second setting information from the base station regarding whether or not the control terminal performs beam interference detection processing with the base station in a radio resource control (RRC) inactive state; and, when the control terminal is in the RRC inactive state, controlling the relay operation based on the first setting information and controlling the detection processing based on the second setting information.

[0009] A relay device according to a fourth embodiment includes a relay unit that performs a relay operation to relay radio signals transmitted between a base station and a user device, and a control terminal that receives control signals used to control the relay unit from the base station, wherein the control terminal includes a receiving unit that receives first setting information relating to the relay operation from the base station and second setting information from the base station regarding whether or not the control terminal performs beam interference detection processing with the base station in a radio resource control (RRC) inactive state, and a control unit that controls the relay operation based on the first setting information and controls the detection processing based on the second setting information when the control terminal is in the RRC inactive state. [Brief explanation of the drawing]

[0010] [Figure 1] This diagram shows the configuration of a mobile communication system according to an embodiment. [Figure 2] This diagram shows the protocol stack configuration of the user plane wireless interface that handles data. [Figure 3] This diagram shows the protocol stack configuration of the wireless interface of the control plane that handles signaling (control signals). [Figure 4] This figure shows an example of an application scenario for the NCR device (relay device) according to the embodiment. [Figure 5] This figure shows an example of an application scenario for the NCR device according to the embodiment. [Figure 6] This figure shows an example of a control method for an NCR device according to an embodiment. [Figure 7] This diagram illustrates an example of the protocol stack configuration in an NCR device according to an embodiment. [Figure 8] This figure shows an example configuration of an NCR device according to the embodiment. [Figure 9] This diagram shows the configuration of the UE (User Equipment) according to the embodiment. [Figure 10] This figure shows an example configuration of a gNB (base station) according to the embodiment. [Figure 11] This is a diagram illustrating the operation of the mobile communication system according to the first embodiment. [Figure 12] This is a diagram illustrating the operation of the mobile communication system according to the first embodiment. [Figure 13] This is a flowchart showing an example of the operation of the NCR device according to the first embodiment. [Figure 14] This is a diagram illustrating the operation of the mobile communication system according to the second embodiment. [Figure 15] This is a flowchart showing an example of the operation of the NCR device according to the second embodiment. [Figure 16] This is a diagram illustrating the RIS device (relay device) according to the third embodiment. [Figure 17] This is a diagram illustrating the RIS device (relay device) according to the third embodiment. [Modes for carrying out the invention]

[0011] A mobile communication system according to an embodiment will be described with reference to the drawings. In the drawings, identical or similar parts are denoted by the same or similar reference numerals.

[0012] (1) First Embodiment First, the first embodiment will be described. The relay device according to the embodiment is a repeater device (i.e., NCR device) that can be controlled from a network.

[0013] (1.1) Overview of the mobile communication system FIG. 1 is a diagram showing the configuration of a mobile communication system according to the embodiment.

[0014] The mobile communication system 1 complies with the 5th generation system (5GS: 5th Generation System) of the 3rd Generation Partnership Project (3GPP) (registered trademark; the same applies hereinafter). Hereinafter, 5GS will be described as an example, but the LTE (Long Term Evolution) system may be at least partially applied to the mobile communication system. The 6th generation (6G) system may be at least partially applied to the mobile communication system.

[0015] The mobile communication system 1 includes a user equipment (UE: User Equipment) 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, NG-RAN 10 may be simply referred to as RAN 10. Also, 5GC 20 may be simply referred to as the core network (CN) 20. RAN 10 and CN 20 constitute the network 5 of the mobile communication system 1.

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

[0017] NG-RAN10 includes base stations (referred to as "gNBs" in 5G systems) 200. The gNBs 200 are interconnected via the Xn interface, which is an inter-base station interface. Each gNB 200 manages one or more cells. The gNB 200 performs wireless communication with UEs 100 that have established a connection with its own cell. The gNB 200 has radio resource management (RRM) functions, user data routing functions (hereinafter simply referred to as "data"), measurement and control functions for mobility control and scheduling, etc. "Cell" is used as a term to indicate the smallest unit of a wireless communication area. "Cell" is also used as a term to indicate a function or resource that performs wireless communication with the UE 100. One cell belongs to one carrier frequency (hereinafter simply referred to as "frequency").

[0018] The gNB200 may be functionally divided into a Central Unit (CU) and a Distributed Unit (DU). The CU controls the DU. The CU is a unit that includes the upper layers of the protocol stack described later, such as the RRC layer, SDAP layer, and PDCP layer. The CU is connected to the core network via the NG interface, which is the backhaul interface. The CU is connected to neighboring base stations via the Xn interface, which is the inter-base station interface. The DU forms a cell. The DU202 is a unit that includes the lower layers of the protocol stack described later, such as the RLC layer, MAC layer, and PHY layer. The DU is connected to the CU via the F1 interface, which is the fronthaul interface.

[0019] Furthermore, gNBs can also connect to the EPC (Evolved Packet Core), which is the core network of LTE. LTE base stations can also connect to 5GCs. LTE base stations and gNBs can also be connected via an inter-base station interface.

[0020] The 5GC20 includes the AMF (Access and Mobility Management Function) and the UPF (User Plane Function) 300. The AMF performs various mobility controls for the UE100. The AMF manages the mobility of the UE100 by communicating with it using NAS (Non-Access Stratum) signaling. The UPF controls data transfer. The AMF and UPF are connected to the gNB200 via the NG interface, which is the base station-core network interface.

[0021] Figure 2 shows the configuration of the protocol stack for the user plane's wireless interface that handles data.

[0022] The user plane radio interface protocol consists of a physical (PHY) layer, a MAC (Medium Access Control) layer, an RLC (Radio Link Control) layer, a PDCP (Packet Data Convergence Protocol) layer, and an SDAP (Service Data Adaptation Protocol) layer.

[0023] The PHY layer performs encoding / decoding, modulation / demodulation, antenna mapping / demapping, and resource mapping / demapping. Data and control information are transmitted between the UE100's PHY layer and the gNB200's PHY layer via a physical channel. The UE100's PHY layer receives downlink control information (DCI) transmitted from the gNB200 over the physical downlink control channel (PDCCH). Specifically, the UE100 performs blind decoding of the PDCCH using a Radio Network Temporary Identifier (RNTI) and acquires the successfully decoded DCI as the DCI addressed to its own UE. The DCI transmitted from the gNB200 has Cyclic Redundancy Code (CRC) bits, which are scrambled by the RNTI, added to it.

[0024] The gNB200 also transmits Synchronization Signal (SSB) blocks (PBCH blocks). For example, an SSB consists of four consecutive OFDM (Orthogonal Frequency Division Multiplex) symbols, containing 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 an SSB is, for example, 240 consecutive subcarriers, i.e., a bandwidth of 20 RB.

[0025] The MAC layer performs data priority control, retransmission processing using Hybrid Automatic Repeat request (HARQ), and random access procedures. Data and control information are transmitted between the MAC layer of the UE100 and the MAC layer of the gNB200 via the transport channel. The MAC layer of the gNB200 includes a scheduler. The scheduler determines the transport format for the up and down links (transport block size, modulation and coding scheme (MCS)) and the resource blocks to be allocated to the UE100.

[0026] The RLC layer transmits data to the receiving RLC layer using the functions of the MAC layer and PHY layer. Data and control information are transmitted between the UE100's RLC layer and the gNB200's RLC layer via a logical channel.

[0027] The PDCP layer performs header compression / decompression, encryption / decryption, etc.

[0028] The SDAP layer maps IP flows, which are the units under which the core network performs QoS (Quality of Service) control, to wireless bearers, which are the units under which the AS (Access Stratum) performs QoS control. Note that if the RAN is connected to the EPC, SDAP is not required.

[0029] Figure 3 shows the configuration of the protocol stack of the wireless interface of the control plane that handles signaling (control signals).

[0030] The control plane's wireless interface protocol stack includes an RRC (Radio Resource Control) layer and a NAS (Non-Access Stratum) layer, instead of the SDAP layer shown in Figure 2.

[0031] RRC signaling for various settings is transmitted between the RRC layer of the UE100 and the RRC layer of the gNB200. The RRC layer controls the logical channel, transport channel, and physical channel in response to the establishment, re-establishment, and release of the radio bearer. If there is a connection (RRC connection) between the RRC of the UE100 and the RRC of the gNB200, the UE100 is in the RRC connected state. If there is no connection (RRC connection) between the RRC of the UE100 and the RRC of the gNB200, the UE100 is in the RRC idle state. If the connection between the RRC of the UE100 and the RRC of the gNB200 is suspended, the UE100 is in the RRC inactive state.

[0032] The NAS layer, located above the RRC layer, handles session management and mobility management, among other things. NAS signaling is transmitted between the UE100's NAS layer and the AMF300A's NAS layer. The UE100 also has application layers and other components in addition to its wireless interface protocol. Furthermore, layers below the NAS layer are referred to as AS (Access Stratum).

[0033] (1.2) Examples of application scenarios for relay devices Figures 4 and 5 show an example of an application scenario for the NCR device according to the embodiment.

[0034] 5G / NR enables broadband transmission using high frequency bands compared to 4G / LTE. However, since radio signals in high frequency bands such as millimeter waves or terahertz waves have high directivity, reducing the coverage of gNB200 becomes a challenge. In Figure 4, UE100 may be located outside the coverage area of ​​gNB200, for example, outside the area where radio signals can be received directly from gNB200. There may also be obstacles between gNB200 and UE100, preventing UE100 from communicating with gNB200 within line of sight.

[0035] As shown in Figure 4, a repeater device (500A), which is a type of relay device that relays wireless signals between gNB200 and UE100, is introduced into the mobile communication system 1 as an NCR device 500A that can be controlled from network 5. Such a repeater device may also be called a smart repeater device.

[0036] For example, the NCR device 500A amplifies the radio signal (radio wave) received from the gNB200 and transmits it via directional transmission. Specifically, the NCR device 500A receives the radio signal transmitted by the gNB200 via beamforming. The NCR device 500A then amplifies the received radio signal without demodulation or modulation, and transmits the amplified radio signal via directional transmission. Here, the NCR device 500A may transmit the radio signal with a fixed directionality (beam). The NCR device 500A may transmit the radio signal with a variable (adaptive) directional beam. This allows for efficient expansion of the gNB200's coverage.

[0037] Furthermore, as shown in Figure 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, will be introduced. Specifically, the NCR device 500A includes an NCR-Fwd (Forward) 510A, which is a type of repeater that relays the radio signal transmitted between the gNB 200 and the UE 100, and changes the propagation state of the radio signal without demodulating or modulating the radio signal, and an NCR-MT 520A, which controls the NCR-Fwd 510A by performing wireless communication with the gNB 200.

[0038] In this way, the NCR-MT520A establishes a wireless connection with the gNB200 and communicates wirelessly with it, thereby controlling the NCR device 500A in cooperation with the gNB200. This enables efficient coverage expansion using the NCR device 500A. The NCR-MT520A controls the NCR device 500A according to the control from the gNB200. The NCR-MT520A also has functions similar to the UE100.

[0039] 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 it. The NCR-MT520A may be connected to the NCR-Fwd510A by wire or wireless connection. Alternatively, the NCR-MT520A may be configured integrally with the NCR-Fwd510A. The NCR-MT520A and NCR-Fwd510A may be fixedly installed, for example, on the coverage edge (cell edge) of the gNB200, or on the wall or window of some building. The NCR-MT520A and NCR-Fwd510A may be installed, for example, on a vehicle and be movable. Furthermore, one NCR-MT520A may control multiple NCR-Fwd510A units.

[0040] Furthermore, the configuration is not limited to one or more NCR-MT520A directly controlling one or more NCR-Fwd510A units; it may also be a configuration in which one or more NCR-MT520A indirectly controls one or more NCR-Fwd510A units. For example, one or more NCR-MT520A units may be controlled via a higher layer (e.g., an application layer).

[0041] In the example shown in Figure 5, the NCR device 500A (NCR-Fwd510A) dynamically or quasi-statically changes the beam being transmitted or received. For example, NCR-Fwd510A forms beams toward UE100a and UE100b, respectively. NCR-Fwd510A may also form a beam toward gNB200. For example, in a communication resource between gNB200 and UE100a, NCR-Fwd510A transmits a radio signal received from gNB200 toward UE100a by beamforming, and / or transmits a radio signal received from UE100a toward gNB200 by beamforming. The NCR-Fwd510A transmits radio signals received from gNB200 toward UE100b by beamforming, and / or transmits radio signals received from UE100b toward gNB200, in the communication resources between gNB200 and UE100b. In lieu of or in addition to beamforming, the NCR-Fwd510A may also perform null formation (so-called null steering) toward UE100 (not shown) and / or adjacent gNB200 (not shown) that are not communication partners, for interference suppression.

[0042] Figure 6 shows an example of a control method for the NCR device 500A according to the embodiment.

[0043] The NCR-Fwd510A relays radio signals (also referred to as "UE signals") between the gNB200 and the UE100. The UE signals include an uplink signal (also referred to as the "UE-UL signal") transmitted from the UE100 to the gNB200 and a downlink signal (also referred to as the "UE-DL signal") transmitted from the gNB200 to the UE100. The NCR-Fwd510A relays the UE-UL signal from the UE100 to the gNB200 and also relays the UE-DL signal from the gNB200 to the UE100. The radio link between the NCR-Fwd510A and the UE100 is also referred to as the "access link." The radio link between the NCR-Fwd510A and the gNB200 is also referred to as the "backhaul link."

[0044] The NCR-MT520A transmits and receives radio signals (referred to here as "NCR-MT signals") with the gNB200. The NCR-MT signals include an uplink signal (referred to as "NCR-MT-UL signals") transmitted from the NCR-MT520A to the gNB200 and a downlink signal (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 radio link between the NCR-MT520A and the gNB200 is also referred to as the "control link".

[0045] Based on the NCR-MT-UL signal from NCR-MT520A, gNB200 directs its beam toward NCR-MT520A. Since NCR equipment 500A is co-located with NCR-MT520A, if the backhaul link and control link have the same frequency, when gNB200 directs its beam toward NCR-MT520A, the beam will also be directed toward NCR-Fwd510A. gNB200 uses this beam to transmit the NCR-MT-DL signal and the UE-DL signal. NCR-MT520A receives the NCR-MT-DL signal. If NCR-Fwd510A and NCR-MT520A are at least partially integrated, the functions for transmitting, receiving, or relaying the UE signal and / or NCR-MT signal (e.g., an antenna) may be integrated in both NCR-Fwd510A and NCR-MT520A. The term "beam" includes both the transmitting beam and / or the receiving beam. A beam is a general term for controlled transmission and / or reception aimed at maximizing the power of the transmitted and / or received waves in a specific direction by adjusting / adapting antenna weights, etc.

[0046] Figure 7 is a diagram illustrating an example of the protocol stack configuration in the NCR device 500A according to this embodiment.

[0047] The NCR-Fwd510A relays the radio signals transmitted and received between the gNB200 and the UE100. The NCR-Fwd510A has an RF (Radio Frequency) function that amplifies and relays the received radio signals and performs directional transmission using beamforming (e.g., analog beamforming).

[0048] The NCR-MT520A has entities at each of the following layers: Layer 1 and / or Layer 2 (L1 / L2), RRC, and NAS. The L1 / L2 (especially PHY, MAC) and RRC of the NCR-MT520A are also referred to as the "AS of the NCR-MT520A".

[0049] The NCR-MT520A may have at least one of the following: an OAM (Operation, Administration, Maintenance) client that communicates with the OAM server 400, a NAS layer that communicates with the AMF300A, and an F1-AP (Application Protocol) layer. The OAM client, NAS layer, and F1-AP layer of the NCR-MT520A are also referred to as the "upper layers of the NCR-MT520A" with respect to the AS of the NCR-MT520A.

[0050] A backhaul link is established between the gNB200 and the NCR-Fwd510A. An access link is established between the UE100 and the NCR-Fwd510A. The NCR-Fwd510A relays the radio signals transmitted between the gNB200 and the UE100 via the backhaul link and the access link. The NCR-Fwd510A changes the propagation state of the radio signals without demodulating or modulating them.

[0051] Furthermore, a control link is established between the gNB200 and the L1 / L2 of the NCR-MT520A. The L1 / L2 of the NCR-MT520A transmits and receives L1 / L2 signaling to and from 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 to and from the gNB200 via the RRC connection. The NCR-MT520A receives downlink signaling (also referred to as "NCR control signals" or simply "control signals") from the gNB200 via the RRC connection and / or the control link.

[0052] 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 at the RRC layer (i.e., Layer 3). The NCR control signal may be a MAC CE (Control Element), which is a control signal at the MAC layer (i.e., Layer 2). The NCR control signal may be downlink control information (DCI), which is a control signal at the PHY layer (i.e., Layer 1). The NCR control signal may be UE individual 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 AP (Xn-AP) of the inter-base station interface Xn.

[0053] In the following, NCR control signals transmitted in RRC messages (and / or MAC CEs) and used for static or quasi-static control of the NCR-Fwd510A will also be referred to as "NCR configuration information (NCR settings)" or simply "configuration information." Such configuration information may also be referred to as "Side Control Configuration." Here, the RRC message may be an RRC Reconfiguration message. NCR configuration information may include, for example, information for setting the on / off state of the NCR-Fwd510A. NCR configuration information may also include, for example, information for quasi-static beam settings of the NCR-Fwd510A.

[0054] On the other hand, the NCR control signals transmitted in L1 / L2 signaling, i.e., DCI (and / or MAC CE), and used for the dynamic control of the NCR-Fwd510A are also referred to as "NCR control information" or simply "control information." NCR control information may also be referred to as "Side Control Information." 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." NCR control information may include, for example, information for the dynamic beam control of the NCR-Fwd510A. NCR setting information may include information instructing the dynamic on / off of the NCR-Fwd510A.

[0055] For example, when NCR-MT520A is in the RRC connected state, NCR device 500A can turn NCR-Fwd510A on or off according to the NCR control information received from gNB200. On the other hand, after NCR-MT520A transitions to the RRC inactive state, NCR device 500A can turn NCR-Fwd510A on or off according to the latest (last) setting information received from gNB200.

[0056] The NCR control signals held by the NCR device 500A (NCR-MT520A) (for example, NCR setting information by RRC and / or NCR control information by L1 / L2 signaling) may also be referred to as the NCR-Fwd context.

[0057] Furthermore, if a wireless link failure (RLF) with the gNB200 is detected by the NCR-MT520A, the NCR-MT520A performs cell selection and triggers RRC connection re-establishment (also referred to as "RRC re-establishment"). If the NCR-MT520A enters an RRC idle state because a suitable cell cannot be found during cell selection, the NCR device 500A turns off the NCR-Fwd510A. The NCR-Fwd510A remains off during the RRC connection re-establishment procedure.

[0058] The NCR control signal may include frequency control information that specifies the center frequency of the radio signal (e.g., component carrier) that the NCR-Fwd510A is to relay. If the NCR control signal received from the gNB200 includes frequency control information, the NCR-MT520A (control unit 523) controls the NCR-Fwd510A to relay the radio signal with the center frequency indicated by the frequency control information (step S2A). The NCR control signal may include multiple frequency control information that specify different center frequencies. By including frequency control information in the NCR control signal, the gNB200 can specify the center frequency of the radio signal that the NCR-Fwd510A should relay via the NCR-MT520A.

[0059] The NCR control signal may include mode control information that specifies the operating mode of the NCR-Fwd510A. The mode control information may be associated with frequency control information (center frequency). The operating mode may be any of the following modes: a mode in which the NCR-Fwd510A performs omnidirectional transmission and / or reception; a mode in which the NCR-Fwd510A performs fixed directional transmission and / or reception; a mode in which the NCR-Fwd510A performs transmission and / or reception with a variable directional beam; or a mode in which the NCR-Fwd510A performs MIMO (Multiple Input Multiple Output) relay transmission. The operating mode may be either a beamforming mode (i.e., a mode that prioritizes desired wave improvement) or a null steering mode (i.e., a mode that prioritizes interference wave suppression). The NCR-MT520A (control unit 523) controls the NCR-Fwd510A to operate in the operating mode indicated by the mode control information if the NCR control signal received from the gNB200 includes mode control information (step S2A). By including mode control information in the NCR control signal, the gNB200 can specify the operating mode of the NCR-Fwd510A via the NCR-MT520A.

[0060] Here, the mode in which the NCR device 500A performs omnidirectional transmission and / or reception is the mode in which the NCR-Fwd510A performs omnidirectional relay, and may be called omnimode. The mode in which the NCR-Fwd510A performs fixed directional transmission and / or reception may be a directional mode realized by a single directional antenna. This mode may also be a beamforming mode realized by applying fixed phase and amplitude control (antenna weight control) to multiple antennas. Any of these modes may be specified (set) from the gNB200 to the NCR-MT520A. The mode in which the NCR-Fwd510A performs transmission and / or reception with a variable directional beam may be an analog beamforming mode. This mode may also be a digital beamforming mode. This mode may also be a hybrid beamforming mode. This mode may also be a mode that forms an adaptive beam specific to the UE100. Any of these modes may be specified (set) from the gNB200 to the NCR-MT520A. In addition, in the beamforming operation mode, beam control information described later may be provided from gNB200 to NCR-MT520A. The mode in which the NCR device 500A performs MIMO relay transmission may be a SU (Single-User) spatial multiplexing mode. This mode may also be a MU (Multi-User) spatial multiplexing mode. This mode may also be a transmit diversity mode. Any of these modes may be specified (set) from gNB200 to NCR-MT520A. The operation mode may include a mode that turns on (activates) relay transmission by NCR-Fwd510A and a mode that turns off (deactivates) relay transmission by NCR-Fwd510A. Any of these modes may be specified (set) from gNB200 to NCR-MT520A by NCR control signals.

[0061] 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 PMI (Precoding Matrix Indicator). The beam control information may also 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. By including beam control information in the NCR control signal, the gNB200 can control the transmission directivity of the NCR device 500A via the NCR-MT520A.

[0062] 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 the transmit power. The output control information may also be information that indicates the difference (i.e., relative value) between the current amplification gain or transmit power and the target amplification gain or transmit power. If the NCR control signal received from the gNB200 includes output control information, the NCR-MT520A (control unit 523) controls the NCR-Fwd510A to change to the amplification gain or transmit 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 also be information that specifies one of the amplifier gain, beamforming gain, or antenna gain of the NCR-Fwd510A. The output control information may also be information that specifies the transmit power of the NCR-Fwd510A.

[0063] When one NCR-MT520A controls multiple NCR-Fwd510A units, the gNB200 (transmitter 210) may transmit an NCR control signal to the NCR-MT520A for each NCR-Fwd510A unit. In this case, the NCR control signal may include the identifier of the corresponding NCR-Fwd510A unit (NCR identifier). The NCR-MT520A (control unit 523) controlling multiple NCR-Fwd510A units determines which NCR-Fwd510A unit to which the NCR control signal is applied based on the NCR identifier included in the NCR control signal received from the gNB200. Note that even when the NCR-MT520A controls only one NCR-Fwd510A unit, the NCR identifier may be transmitted from the NCR-MT520A to the gNB200 unit along with the NCR control signal.

[0064] In this way, the NCR-MT520A (control unit 523) controls the NCR-Fwd510A based on the NCR control signal from the gNB200. This allows the gNB200 to control the NCR-Fwd510A via the NCR-MT520A.

[0065] (1.3) Examples of configurations for each device An example of the configuration of each device in the mobile communication system 1 according to this embodiment will be described.

[0066] (1.3.1) Example of relay device configuration Figure 8 shows an example configuration of the NCR device 500A (relay device) according to the embodiment. The NCR device 500A includes an NCR-Fwd510A, an NCR-MT520A, and an interface 530.

[0067] The NCR-Fwd510A comprises a wireless unit 511A and an NCR control unit 512A. The wireless unit 511A includes an antenna section 511a containing multiple antennas (multiple antenna elements), an RF circuit 511b including an amplifier, and a directional control unit 511c that controls the directivity of the antenna section 511a. The RF circuit 511b amplifies and relays (transmits) the wireless signals transmitted and received by the antenna section 511a. The RF circuit 511b may convert the analog wireless signals into digital signals and then convert them back to analog signals after digital signal processing. The directional control unit 511c may perform analog beamforming by analog signal processing. The directional control unit 511c may perform digital beamforming by digital signal processing. The directional control unit 511c may perform hybrid analog and digital beamforming. The NCR control unit 512A controls the wireless unit 511A according to control signals from the NCR-MT520A. The NCR control unit 512A may include at least one processor.

[0068] The NCR-MT520A comprises a receiving unit 521, a transmitting unit 522, and a control unit 523. The receiving unit 521 performs various types of reception under the control of the control unit 523. The receiving unit 521 includes an antenna and a receiver. The receiver converts the radio signal (radio signal) received by the antenna into a baseband signal (received signal) and outputs it to the control unit 523. The transmitting unit 522 performs various types of transmission under the control of the control unit 523. The transmitting unit 522 includes an antenna and a transmitter. The transmitter converts the baseband signal (transmitted signal) output by the control unit 523 into a radio signal and transmits it from the antenna. The control unit 523 performs various controls in the NCR-MT520A. The operation of the NCR-MT520A (and NCR device 500A) described above and below may be controlled by the control unit 523. The control unit 523 includes at least one processor and at least one memory. The memory stores programs executed by the processor and information used in processing by the processor. The processor may include a baseband processor and a CPU (Central Processing Unit). The baseband processor performs modulation, demodulation, encoding, and decoding of baseband signals. The CPU executes programs stored in memory and performs various processes. The control unit 523 also performs the functions of at least one layer of the PHY, MAC, RRC, and F1-AP.

[0069] Interface 530 electrically or logically connects the NCR-Fwd510A and the NCR-MT520A. The control unit 523 of the NCR-MT520A controls the NCR-Fwd510A via interface 530. Interface 530 may also be a logical entity at a higher layer (e.g., the application layer).

[0070] In this embodiment, the receiver 521 of the NCR-MT520A receives signaling (NCR control signal) used to control the NCR device 500A wirelessly from the gNB200. The control unit 523 of the NCR-MT520A controls the NCR device 500A based on this signaling. This enables the gNB200 to control the NCR-Fwd510A via the NCR-MT520A.

[0071] (1.3.2) Example of user device configuration Figure 9 shows the configuration of UE100 (user device) according to an embodiment. UE100 includes 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 gNB200.

[0072] 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 the radio signal received by the antenna into a baseband signal (received signal) and outputs it to the control unit 130.

[0073] The transmitting unit 120 performs various types of transmissions under the control of the control unit 130. The transmitting unit 120 includes an antenna and a transmitter. The transmitter converts the baseband signal (transmission signal) output by the control unit 130 into a wireless signal and transmits it from the antenna.

[0074] The control unit 130 performs various control and processing operations in the UE 100. Such processing includes processing in each layer described later. The operation of the UE 100 described above and later may also be controlled by the control unit 130. The control unit 130 includes at least one processor and at least one memory. The memory stores programs executed by the processor and information used for processing by the processor. The processor may include a baseband processor and a CPU. The baseband processor performs modulation, demodulation, encoding, and decoding of baseband signals. The CPU executes programs stored in memory and performs various processing operations.

[0075] (1.3.3) Example of base station configuration Figure 10 shows an example configuration of a gNB200 (base station) according to an embodiment. The gNB200 includes a transmitting unit 210, a receiving unit 220, a control unit 230, and a backhaul communication unit 240.

[0076] The transmitting unit 210 performs various types of transmissions under the control of the control unit 230. The transmitting unit 210 includes an antenna and a transmitter. The transmitter converts the baseband signal (transmission signal) output by the control unit 230 into a radio signal and transmits it from the antenna. The receiving unit 220 performs various types of receptions under the control of the control unit 230. The receiving unit 220 includes an antenna and a receiver. The receiver converts the radio signal received by the antenna into a baseband signal (received signal) and outputs it to the control unit 230. The transmitting unit 210 and the receiving unit 220 may be capable of beamforming using multiple antennas.

[0077] The control unit 230 performs various controls on the gNB200. The operation of the gNB200 described above and below may also be controlled by the control unit 230. The control unit 230 includes at least one processor and at least one memory. The memory stores programs executed by the processor and information used for processing by the processor. The processor may include a baseband processor and a CPU. The baseband processor performs modulation, demodulation, encoding, and decoding of baseband signals. The CPU executes programs stored in memory and performs various processing.

[0078] The backhaul communication unit 240 is connected to an adjacent base station via an inter-base station interface. The backhaul communication unit 240 is connected to the AMF / UPF300 via a base station-core network interface. The gNB may consist of a CU (Central Unit) and a DU (Distributed Unit) (i.e., functionally separated), and the two units may be connected via an F1 interface.

[0079] In this embodiment, the gNB200's transmitter 210 transmits signaling (NCR control signals) used to control the NCR-MT520A to the NCR-MT520A via wireless communication. This enables the gNB200 to control the NCR device 500A via the NCR-MT520A.

[0080] (1.4) Operation according to the first embodiment Figures 11 and 12 are diagrams illustrating the operation of the mobile communication system 1 according to the first embodiment.

[0081] As shown in STEP 1 of Figure 11, the NCR device 500A is in an RRC connected state in cell a (first cell) of gNB200a. gNB200a sends an RRC Reconfiguration message containing the NCR settings to the NCR device 500A. The NCR device 500A receives the RRC Reconfiguration message containing the NCR settings from gNB200a (cell a) and performs relay operations using the NCR settings.

[0082] In this embodiment, the NCR setting includes a periodic beam indication. With the periodic beam indication, the period and beam setting are performed by the RRC. The NCR device 500A performs periodic beamforming based on the periodic beam indication.

[0083] As shown in STEP 2 of Figure 11, gNB200a sends an RRC Release message, including the suspend setting, to NCR device 500A. NCR device 500A receives the RRC Release message from gNB200a (cell a) and transitions to the RRC inactive state.

[0084] In this embodiment, the RRC Release message for transitioning the NCR-MT520A from the RRC connected state to the RRC inactive state includes a timer value.

[0085] After the NCR-MT520A transitions to the RRC inactive state, the NCR-MT520A controls the NCR-Fwd510A according to the latest (last) NCR settings. In this embodiment, the NCR-MT520A controls the NCR-Fwd510A to continue periodic beamforming operation according to the NCR settings (latest settings) received in STEP 1.

[0086] As shown in STEP 3 of Figure 12, the NCR-MT520A, in an RRC inactive state, performs cell reselection from cell a (first cell) to cell b (second cell). In response to the cell reselection to cell b (second cell), the NCR-MT520A turns off the NCR-Fwd510A (i.e., stops relay operation).

[0087] In this embodiment, the NCR-MT520A starts a timer with the timer value set as described above in response to a cell reselection from cell a to cell b. At least while the timer is running, the NCR-MT520A retains the NCR settings (latest settings) without discarding them, even if the NCR-Fwd510A is off.

[0088] In the illustrated example, cell b is managed by gNB200b, which is different from gNB200a, which manages cell a. However, cells a and b may be managed by the same gNB200.

[0089] As shown in STEP 4 of Figure 12, if the NCR-MT520A re-selects cell a within a predetermined time after re-selecting cell b, it resumes relay operation using the NCR settings (latest settings). Specifically, if the NCR-MT520A re-selects cell a before the timer expires, it resumes periodic beamforming using the NCR settings (latest settings).

[0090] Thus, if the NCR-MT520A is in an RRC inactive state, and the original cell is re-selected within a predetermined period after re-selecting a different cell, the NCR-Fwd510A will be restored to its latest settings (turned on). On the other hand, if the NCR-MT520A is in an RRC inactive state, and the original cell is re-selected after a predetermined period has elapsed after re-selecting a different cell, the NCR-Fwd510A will remain off.

[0091] This allows the NCR-MT520A to spontaneously resume relay operations after temporarily camping in another cell and then returning to its original cell, thus enabling efficient control of relay operations.

[0092] Figure 13 is a flowchart showing an example of the operation of the NCR device 500A according to the first embodiment.

[0093] In step S11, the NCR-MT520A in RRC connected state receives the NCR setting from the gNB200. The NCR setting includes a periodic beam indication. The NCR-MT520A may store the cell ID of the serving cell (cell a) at the time the NCR setting was made.

[0094] In step S12, the NCR-MT520A in RRC connected state performs relay operation with periodic beamforming using the NCR settings received in step S11.

[0095] In step S13, the NCR-MT520A, in the RRC connected state, receives an RRC Release message from the gNB200 that includes a timer value. This RRC Release message includes a suspend setting, and the NCR-MT520A transitions to the RRC inactive state according to this suspend setting.

[0096] In step S14, the NCR-MT520A, which is in an RRC inactive state, continues relay operation with periodic beamforming using the NCR settings received in step S11.

[0097] In step S15, the NCR-MT520A, which is in an RRC inactive state, performs cell reselection to another cell (cell b). In response to the cell reselection to another cell (cell b), the NCR-MT520A, which is in an RRC inactive state, turns off the NCR-Fwd510A and starts the timer set with the timer value received in step S13.

[0098] In step S16, the NCR-MT520A determines whether or not to re-select the original cell (cell a), which is the cell on which the NCR settings were applied. The NCR-MT520A may also identify the original cell by comparing the stored cell ID with the cell ID of the re-selected cell.

[0099] If the original cell (cell a) is re-selected (step S16: YES), in step S17, the NCR-MT520A determines whether the timer started in step S15 is still running (not yet expired). If it is determined that the timer has expired (step S17: NO), the NCR-MT520A keeps the NCR-Fwd510A off. The NCR-MT520A may discard the NCR settings (latest settings) it holds when the timer expires.

[0100] On the other hand, if it is determined that the timer is operating (step S17: YES), in step S18, the NCR-MT520A turns on the NCR-Fwd510A and restarts the relay operation with periodic beamforming using the NCR settings (latest settings).

[0101] (2) Second Embodiment The second embodiment will be described primarily in terms of its differences from the first embodiment. The second embodiment is an embodiment relating to beam fault detection and recovery performed by the NCR-MT520A. The second embodiment may be implemented separately and independently from the first embodiment. The second embodiment may also be implemented in combination with the first embodiment.

[0102] (2.1) Overview of beam fault detection and recovery This section provides an overview of general beam fault detection and recovery. General beam fault detection (also known as "BFD") and beam fault recovery (also known as "BFR") are performed by the UE100 in the RRC connected state. For beam fault detection, the gNB200 sets the UE100 to either SSB or CSI (Channel State Information)-RS as the reference signal (RS) for BFD. The MAC entity of the RRC connected UE100 declares (detects) a beam fault when the number of beam fault instance indicators from the physical layer reaches a threshold (maximum count value) set by the gNB200, before the timer set by the gNB200 expires.

[0103] After a beam fault is detected in the primary cell (PCell), the MAC entity of UE100 performs the following actions: - Trigger BFR by initiating a random access procedure with PCell; - Select the appropriate beam for BFR (if gNB200 provides dedicated random access resources to a particular beam, that will be prioritized by UE100); - If the random access procedure includes race-based random access, include a beam failure indicator in the PCell in the BFR (Beam Failure Recovery) MAC CE (Control Element).

[0104] Once the random access procedure is complete, UE100 considers the PCell's BFR to be complete.

[0105] On the other hand, as described above, the NCR device 500A can continue relay operation according to the latest NCR settings even if the NCR-MT520A transitions from the RRC connected state to the RRC inactive state. Therefore, it is desirable that the NCR-MT520A can perform BFD and BFR even in the RRC inactive state. For example, if the NCR device 500A is in the RRC inactive state and the NCR-Fwd510A is on, it is possible to turn off the NCR-Fwd510A in response to detecting a beam interference with the gNB200.

[0106] In the following second embodiment, we will describe the operation that enables appropriate control of BFD and BFR performed by the NCR-MT520A in an RRC inactive state.

[0107] (2.2) Operation according to the second embodiment Figure 14 is a diagram illustrating the operation of the mobile communication system 1 according to the second embodiment.

[0108] As shown in STEP 1 of Figure 14, the NCR device 500A is in the RRC connected state in the gNB200 cell. The gNB200 sends an RRC Reconfiguration message containing the NCR settings to the NCR device 500A. The NCR device 500A receives the RRC Reconfiguration message containing the NCR settings from the gNB200 and performs relay operation using the NCR settings. The NCR settings may include a periodic beam indication. That is, the NCR settings include information to configure relay operation with periodic beamforming, and the NCR-Fwd510A is set to ON. Such configuration information is an example of first configuration information related to relay operation. The NCR-MT520A receives first configuration information related to relay operation from the gNB200.

[0109] As shown in STEP 2 of Figure 14, the gNB200 sends an RRC Release message, including the suspend setting, to the NCR device 500A. The NCR device 500A receives the RRC Release message from the gNB200 and transitions to the RRC inactive state.

[0110] In this embodiment, the RRC Reconfiguration message sent from gNB200 to NCR-MT520A in STEP1, or the RRC Release message sent from gNB200 to NCR-MT520A in STEP2, includes second configuration information regarding whether or not NCR-MT520A performs beam fault detection (BFD) with gNB200 while RRC is inactive. That is, NCR-MT520A receives second configuration information from gNB200 regarding whether or not NCR-MT520A performs beam fault detection with gNB200 while RRC is inactive.

[0111] However, instead of providing the second configuration information to the NCR-MT520A via dedicated signaling, the gNB200 may provide the second configuration information to the NCR-MT520A via broadcast signaling. For example, the gNB200 may send a System Information Block (SIB) containing the second configuration information to the UE100.

[0112] As shown in STEP 3 of Figure 14, after the NCR-MT520A transitions to the RRC inactive state, the NCR-MT520A controls the NCR-Fwd510A according to the latest NCR settings. In this embodiment, the NCR-MT520A in the RRC inactive state controls the relay operation (NCR-Fwd510A) based on the first setting information and controls the BFD (and BFR) based on the second setting information.

[0113] In this embodiment, the NCR-MT520A receives second setting information from the gNB200 regarding whether or not to perform beam fault detection processing with the gNB200 when the RRC is inactive. When the NCR-MT520A is in the RRC inactive state, it controls the BFD (and BFR) based on the second setting information. This makes it possible to appropriately control the BFD (and BFR) performed by the NCR-MT520A when the RRC is inactive.

[0114] Furthermore, the basic operation of BFD performed by the NCR-MT520A in the RRC inactive state may be an application of a general BFD operation. The MAC entity of the NCR-MT520A may perform BFD in the RRC inactive state by continuously using the BFD reference signal (RS), timer value, and maximum count value set by the gNB200 when the RRC is connected. Specifically, the MAC entity of the NCR-MT520A in the RRC inactive state will declare (detect) a beam fault if the number of beam fault instance indicators from the physical layer reaches the threshold (maximum count value) set by the gNB200 before the timer set by the gNB200 expires.

[0115] Alternatively, at least one of the reference signal (RS), timer value, and maximum count value for the RRC inactive state may be a parameter independent of the reference signal (RS), timer value, and maximum count value for the RRC connected state. The second configuration information may include information for setting at least one of the reference signal (RS), timer value, and maximum count value for the RRC inactive state. If the second configuration information includes such information, the NCR-MT520A may be considered specified (configured) to perform BFD in the RRC inactive state.

[0116] In this embodiment, the second setting information may include information specifying whether or not the NCR-MT520A performs detection processing (BFD) in the RRC inactive state. That is, the gNB200 may set whether or not to perform BFD in the RRC inactive state in the NCR-MT520A.

[0117] In this embodiment, when the NCR-MT520A is in the RRC inactive state, it may initiate an RRC connection resume to transition to the RRC connected state in response to a beam fault detected by the detection process (BFD). That is, if the NCR-MT520A detects a beam fault while in the RRC inactive state, it may perform an RRC connection resume and transition to the RRC connected state. For example, when the NCR-MT520A initiates an RRC connection resume, it selects an available beam before transmitting a random access preamble (Msg1) on the physical random access channel (PRACH), and transmits Msg1 using the PRACH resource associated with that beam (SSB index). The gNB200, from the resource that received Msg1, identifies the beam (SSB index) selected by the NCR-MT520A and transmits a random access response (Msg2) using the antenna weight corresponding to that beam. Msg2 includes UL grant, and NCR-MT520A sends an RRC Resume Request message (Msg3) to gNB200. Then, NCR-MT520A receives an RRC Resume message (Msg4) from gNB200 and transitions to the RRC Connected state.

[0118] In this embodiment, the second setting information may include information specifying whether or not to continue relay operation when NCR-MT520A detects a beam fault while RRC is inactive. For example, gNB200 may set NCR-MT520A whether to turn off NCR-Fwd510A or keep it on when it detects a beam fault while RRC is inactive.

[0119] In this embodiment, when the RRC is inactive, the NCR-MT520A may stop relay operation if a beam fault is detected by the detection process (BFD) and it fails to identify a candidate beam that meets predetermined quality criteria. For example, if the NCR-MT520A detects a beam fault while in the RRC inactive state and fails to acquire a new beam that meets the quality criteria (within a certain time and within a certain number of recovery attempts), it may turn off the NCR-Fwd510A.

[0120] Figure 15 is a flowchart showing an example of the operation of the NCR device 500A according to the second embodiment.

[0121] In step S21, the NCR-MT520A receives an RRC Reconfiguration message from the gNB200, which includes the NCR settings. The NCR settings include first configuration information relating to relay operation. The first configuration information includes configuration information indicating that the NCR-Fwd510A is turned on. The first configuration information may also include a periodic beam indication. The NCR settings may further include second configuration information relating to whether the NCR-MT520A performs beam fault detection (BFD) with the gNB200 in the RRC inactive state. Hereafter, this second configuration information will also be referred to as the "BFD / BFR setting for the RRC inactive state".

[0122] In step S22, the NCR-MT520A in the RRC connected state may perform relay operation using the ON-state NCR-Fwd510A based on the first configuration information included in the NCR settings received in step S11.

[0123] In step S23, the NCR-MT520A, in the RRC connected state, receives an RRC Release message from the gNB200 that includes a suspend setting. The NCR-MT520A transitions to the RRC inactive state according to the suspend setting. The RRC Release message may also include BFD / BFR settings (second configuration information) for the RRC inactive state.

[0124] The BFD / BFR setting for the RRC inactive state includes at least one of the following setting information: a) to c).

[0125] a) Setting to determine whether or not to perform BFD when RRC is inactive.

[0126] b) Settings for handling when a beam fault is detected while the RRC is inactive: For example, the setting may include information specifying whether or not to resume the RRC connection if a beam fault is detected while the RRC is inactive.

[0127] b1) If RRC connection resume is not performed, the setting may include information specifying whether to turn off the NCR-Fwd510A while maintaining the RRC inactive state, or to keep the NCR-Fwd510A on according to the latest setting.

[0128] b2) If RRC connection resume is not performed, the setting may include information specifying whether or not BFR is performed.

[0129] b3) When performing BFR, the setting may include a parameter that specifies the conditions for determining BFR failure. This parameter may include a timer value for the determination and / or an upper limit on the number of attempts for the determination. In this case, the NCR-MT520A in RRC inactive state may determine that BFR has failed if it fails to find (capture) a candidate beam that meets the predetermined quality criteria within the time of the timer value, or if the random access procedure to a candidate beam that meets the predetermined quality criteria is unsuccessful. The NCR-MT520A in RRC inactive state may also determine that BFR has failed if the number of times a candidate beam that does not meet the predetermined quality criteria has been found has reached the upper limit, or if the number of times the random access procedure to a candidate beam that meets the predetermined quality criteria has failed has reached the upper limit.

[0130] b4) When performing BFR, the setting may include information specifying how to handle BFR failure. For example, this information may include information specifying whether or not NCR-MT520A will perform RRC connection resume. If RRC resume is not performed (i.e., the RRC inactive state continues), this information may include information specifying whether or not NCR-Fwd510A will be turned off or kept on.

[0131] In step S24, the NCR-MT520A that has transitioned to the RRC inactive state, and the NCR-MT520A that is in the RRC connected state, will perform relay operation using the ON NCR-Fwd510A based on the first setting information included in the NCR settings (latest settings). Also, the NCR-MT520A in the RRC inactive state will perform BFD based on the BFD / BFR settings (second setting information) for the RRC inactive state.

[0132] In step S25, the NCR-MT520A, which is in an RRC inactive state, checks whether a beam fault has been detected by BFD. If no beam fault has been detected, the process returns to step S24.

[0133] If a beam fault is detected (step S25: YES), in step S26, the NCR-MT520A in the RRC inactive state performs the operation specified in the BFD / BFR setting (second setting information) for the RRC inactive state (e.g., BFR and / or RRC connection resume).

[0134] (2.1) Example of modification of the second embodiment In the second embodiment, an example was described in which the gNB200 explicitly sets whether or not beam fault detection (BFD) and / or beam fault recovery (BFR) should be performed to the NCR-MT520A, but the embodiment is not limited to this. The NCR-MT520A can determine whether or not beam fault detection and / or beam fault recovery processing should be performed in the RRC inactive state based on the operating state of the NCR-Fwd510A.

[0135] In other words, when NCR-MT520A transitions to the RRC inactive state, if NCR-Fwd510A is in the ON state (for example, performing periodic beamforming operations), NCR-MT520A performs beam fault detection and / or beam fault recovery processing in the RRC inactive state. However, if NCR-Fwd510A is in OFF control (not performing relay operations), it does not perform beam fault detection and / or beam fault recovery processing in the RRC inactive state. This allows NCR-MT520A to determine whether or not beam fault detection and / or beam fault recovery processing in the RRC inactive state is necessary without explicit settings from gNB200.

[0136] (3) Third Embodiment Next, the differences between the third embodiment and the embodiments described above will be explained. As shown in Figure 16, the relay device according to the third embodiment is a RIS (Reconfigurable Intelligent Surface) device 500B that changes the propagation direction of incident radio waves (wireless signals) by reflection or refraction. "NCR" in the embodiments described above can be read as "RIS".

[0137] 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 the metamaterial. In the case of RIS, the beam range (distance) may also be changed by controlling the reflection direction and / or refraction direction of each unit element. For example, in addition to controlling the reflection direction and / or refraction direction of each unit element, it may be possible to configure it to focus on (direct the beam towards) a nearby UE or to focus on (direct the beam towards) a distant UE.

[0138] The RIS device 500B has a new UE (hereinafter referred to as "RIS-MT") 520B, which is a control terminal for controlling the RIS-Fwd510B. The RIS-MT 520B controls the RIS-Fwd510B in cooperation with the gNB200 by establishing a wireless connection with the gNB200 and performing wireless communication with the gNB200. The RIS-Fwd510B may be a reflective type RIS. Such a RIS-Fwd510B changes the propagation direction of radio waves by reflecting the incident radio waves. Here, the reflection angle of the radio waves is variable. The RIS-Fwd510B reflects the radio waves incident from the gNB200 toward the UE 100. The RIS-Fwd510B may also be a transmissive type RIS. Such a RIS-Fwd510B changes the propagation direction of radio waves by refracting the incident radio waves. Here, the refraction angle of the radio waves is variable.

[0139] Figure 17 shows an example configuration of the RIS-Fwd (repeater) 510B and RIS-MT (control terminal) 520B according to the second embodiment. The RIS-MT 520B has a receiving unit 521, a transmitting unit 522, and a control unit 523. This configuration is the same as that of the embodiment described above. The RIS-Fwd 510B has a RIS 511B and a RIS control unit 512B. The RIS 511B is a metasurface constructed using metamaterials. For example, the RIS 511B is constructed by arranging very small structures in an array relative to the wavelength of radio waves, and by making the shape of the structures different depending on the arrangement location, it is possible to arbitrarily design the direction of the reflected wave and / or the beam shape. The RIS 511B may also be a transparent dynamic metasurface. RIS511B is constructed by layering a transparent glass substrate on top of a metasurface substrate, which has a large number of small structures arranged regularly. By moving the layered glass substrate slightly, it may be possible to dynamically control three patterns: a mode in which incident radio waves are transmitted, a mode in which some radio waves are transmitted and some are reflected, and a mode in which all radio waves are reflected. The RIS control unit 512B controls RIS511B in accordance with the RIS control signal from the control unit 523 of 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 RIS-MT520B and drives the actuator in accordance with the RIS control signal.

[0140] (4) Other embodiments In the above-described embodiment, an example was given in which the relay device performing relay transmission is an NCR device 500A or a RIS device 500B. However, the relay device performing relay transmission is not limited to an NCR device 500A or a RIS device 500B, but may also be an IAB (Integrated Access and Backhaul) node as defined in the 3GPP technical specifications.

[0141] Each of the above-described operation flows can be performed not only independently, but also in combination of two or more operation flows. For example, some steps of one operation flow may be added to another operation flow, or some steps of one operation flow may be replaced with some steps of another operation flow. It is not necessary to execute all steps in each flow; only some steps may be executed.

[0142] In the above embodiment, an example was described in which the base station is an NR base station (gNB), but the base station may also be an LTE base station (eNB). Furthermore, the base station may be a relay node such as an IAB node. The base station may also be a DU (Distributed Unit) of an IAB node.

[0143] In the embodiments and examples described above, an example in which the base station is an NR base station (gNB) was described, but the base station may also be an LTE base station (eNB) or a 6G base station. Furthermore, the base station may also be a relay node such as an IAB (Integrated Access and Backhaul) node. The base station may also be a DU of an IAB node. Furthermore, UE100 may be an MT (Mobile Termination) of an IAB node.

[0144] In other words, UE100 may be a terminal function unit (a type of communication module) for a base station to control a repeater that performs signal relay. Such a terminal function unit is called an MT. Examples of MTs other than IAB-MT include NCR (Network Controlled Repeater)-MT and RIS (Reconfigurable Intelligent Surface)-MT.

[0145] Furthermore, the term "network node" primarily refers to a base station, but may also refer to a core network device or a part of a base station (CU, DU, or RU). Additionally, a network node may consist of a combination of at least a part of the core network device and at least a part of a base station.

[0146] A program may be provided that causes a computer to execute each of the processes performed by the communication device according to the above embodiment, for example, UE100 (NCR-MT520A, RIS-MT520B) or gNB200. The program may be recorded on a computer-readable medium. Using a computer-readable medium, it is possible to install the program on a computer. Here, the computer-readable medium on which the program is recorded may be a non-transient recording medium. The non-transient recording medium is not particularly limited, but may be a recording medium such as a CD-ROM or DVD-ROM. Furthermore, the circuits that execute each of the processes performed by UE100 or gNB200 may be integrated, and at least a part of UE100 or gNB200 may be configured as a semiconductor integrated circuit (chipset, SoC: System on a chip).

[0147] A program may be provided that causes a computer to execute each process performed by the UE100, gNB200, or relay device. The program may be recorded on a computer-readable medium. Using a computer-readable medium, it is possible to install the program on a computer. Here, the computer-readable medium on which the program is recorded may be a non-transient recording medium. The non-transient recording medium is not particularly limited, but may be a recording medium such as a CD-ROM or DVD-ROM. In addition, the circuits that execute each process performed by the UE100, gNB200, or relay device may be integrated, and at least a part of the UE100, gNB200, or relay device may be configured as a semiconductor integrated circuit (chipset, SoC: System on a chip).

[0148] The functions realized by UE100, gNB200 (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), CPUs (a Central Processing Unit), conventional circuits, and / or combinations thereof, programmed to realize the described functions. A processor, including transistors and other circuits, is considered circuitry or processing circuitry. A processor may be a programmed processor that executes a program stored in memory. In this specification, circuitry, unit, and means are hardware programmed to realize or perform the described functions. Such hardware may be any hardware disclosed herein, or any hardware known to be programmed to realize or perform the described functions. If such hardware is a processor that is considered to be a type of circuitry, then such circuitry, means, or unit is a combination of hardware and software used to constitute such hardware and / or processor.

[0149] The phrases “based on” and “depending on / in response to” used in this disclosure do not mean “based solely on” or “depending solely on” unless otherwise specified. “Based on” means both “based solely on” and “at least partially on.” Similarly, “depending on” means both “at least partially on” and “at least partially on.” The terms “include,” “comprise,” and variations thereof do not mean that only the listed items are included; they mean that only the listed items may be included, or that additional items may be included in addition to the listed items. Furthermore, the term “or” used in this disclosure is not intended to mean exclusive OR. Additionally, any reference to elements using designations such as “first,” “second,” etc., used in this disclosure does not generally limit the quantity or order of those elements. These designations may be used herein as a convenient way to distinguish between two or more elements. Therefore, references to the first and second elements do not imply that only two elements may be adopted therein, or that the first element must precede the second element in any way. In this disclosure, where articles are added by translation, such as a, an, and the in English, these articles shall be plural unless it is clearly indicated by the context that they are not.

[0150] Although the embodiments have been described in detail above with reference to the drawings, the specific configuration is not limited to those described above, and various design changes can be made without departing from the gist of the invention.

[0151] This application claims priority to U.S. Provisional Application No. 63 / 501479 (filed May 11, 2023), the entirety of which is incorporated into the specification of this application.

[0152] (5) Appendix A The features of the above-described embodiment are noted below.

[0153] (Note 1) A communication method performed by a relay device having a relay device that performs relay operations to relay wireless signals transmitted between a network node and a user device, and a control terminal that receives control signals used to control the relay device from the network node, The steps include receiving setting information related to the relay operation from the first cell, When the control terminal is in an inactive state for wireless resource control (RRC) in the first cell, the relay operation is performed using the setting information. If cell reselection from the first cell to the second cell is performed, the relay operation is stopped. The process includes the step of restarting the relay operation using the setting information if the cell selection to the second cell is performed and then the cell selection to the first cell is performed within a predetermined time. Communication method.

[0154] (Note 2) The steps include receiving a timer value that determines the predetermined time from the first cell, The method further includes the step of starting a timer with a set timer value in response to the re-selection of the cell from the first cell to the second cell. The communication method described in Appendix 1.

[0155] (Note 3) The process further includes receiving an RRC release message from the first cell to transition the control terminal from the RRC connected state to the RRC inactive state. The RRC release message includes the timer value. The communication method described in Appendix 2.

[0156] (Note 4) The step of resuming the relay operation includes, if the cell selection to the first cell is performed before the timer expires, the step of resuming the relay operation using the setting information. The communication method described in Appendix 2 or 3.

[0157] (Note 5) The aforementioned configuration information includes the settings for periodic beamforming in the relay operation. The step of resuming the relay operation includes the step of resuming the periodic beamforming using the setting information. The communication method described in any of the appendices 1 to 4.

[0158] (Note 6) A relay device that performs relaying operations to relay wireless signals transmitted between a network node and a user device, The system includes a control terminal that receives control signals used for controlling the relay from the network node, The aforementioned control terminal is A receiving unit that receives setting information related to the relay operation from the first cell, The control unit includes, when the control terminal is in a wireless resource control (RRC) inactive state in the first cell, a control unit that controls the repeater to perform the relay operation using the setting information, The control unit, If cell reselection is performed from the first cell to the second cell, the relay operation is stopped. If the cell selection to the first cell is performed within a predetermined time after the cell selection to the second cell, the relay operation using the setting information is resumed. Relay device.

[0159] (Note 7) A communication method performed by a relay device having a relay device that performs relay operations to relay wireless signals transmitted between a network node and a user device, and a control terminal that receives control signals used to control the relay device from the network node, The steps include receiving first configuration information relating to the relay operation from the network node, The steps include: receiving second configuration information from the network node regarding whether the control terminal performs beam fault detection processing with the network node while the radio resource control (RRC) is inactive; The control terminal has a step of controlling the relay operation based on the first setting information and controlling the detection process based on the second setting information when the RRC is inactive. Communication method.

[0160] (Note 8) The second setting information includes information specifying whether the control terminal performs the detection process while the RRC is inactive. The communication method described in Appendix 7.

[0161] (Note 9) When the control terminal is in the RRC inactive state, the detection process detects the beam fault and further includes the step of initiating an RRC connection resume to transition the control terminal to the RRC connected state. The communication method described in Appendix 7 or 8.

[0162] (Note 10) The second setting information includes information specifying whether or not to continue the relay operation when the control terminal detects the beam fault while the RRC is inactive. The communication method described in any of the appendices 7 to 9.

[0163] (Note 11) When the control terminal is in the RRC inactive state, the relay operation is further stopped in response to the detection process detecting the beam fault and failing to identify a candidate beam that meets predetermined quality criteria. The communication method described in any of the appendices 7 to 10.

[0164] (Note 12) A relay device that performs relaying operations to relay wireless signals transmitted between a network node and a user device, The system includes a control terminal that receives control signals used for controlling the relay from the network node, The aforementioned control terminal is A receiving unit that receives first setting information relating to the relay operation from the network node and second setting information relating to whether or not the control terminal performs beam fault detection processing with the network node while the radio resource control (RRC) is inactive, The control unit includes, when the control terminal is in the RRC inactive state, a control unit that controls the relay operation based on the first setting information and controls the detection process based on the second setting information. Relay device.

[0165] (6) Appendix B 1. Introduction RAN#99 approved a three-month extension for the work item concerning network control repeaters (NCRs) to resolve the remaining issues in RAN2#119bis-e, RAN2#120, and RAN2#121.

[0166] This addendum discusses the unresolved / potential (open / potential) issues of RAN2 remaining in NCR.

[0167] 2. Discussion 2.1. Wake-up Timer As agreed in RAN2, "the network should be able to send NCR-MTs to RRC idle," so gNBs can intentionally put NCR-MTs into idle state through policies such as NCR power saving or network congestion. However, since RAN paging cannot be used on idle NCR-MTs, gNBs have no way to transition NCR-MTs to connected, i.e., unreachable state. Therefore, once an NCR is released into idle state, it is clear that it is no longer a network control repeater and is treated similarly to, for example, a legacy RF repeater.

[0168] Finding 1: Even if gNB intentionally puts NCR-MT into an idle state due to policies such as NCR power saving or network congestion, gNB cannot page NCR-MT.

[0169] To address this issue, RAN2#121bis-e discussed whether to rely on the OAM implementation or introduce a wake-up timer, but the conclusion was postponed as follows.

[0170] Proposal 1: In Rel-18, do not define a "Wake-up Timer" IE in the RRC Release message.

[0171] "We want to ensure network control in a simple way. The NAS can trigger service requests and registration requests." "Since NCR-WRD is off when RRC is idle, its original intent is no longer valid, and the sole purpose is to return to RRC connected. We believe there are several implementation-specific ways to achieve this. There is no time to send LS to CT1." "The main motivation for opposing the timer is its impact on the NAS, but that impact seems minor. If the impact on the NAS is significant, we will agree to the OAM solution," is another perspective. Some argue that "the biggest challenge isn't the impact of NAS, but rather the motivation for having such timers." Another approach is to handle the timer at the AS (Automated System) and notify the NAS (Network Attached System) when the timer expires. Since OAM (Operational Ambulance) is static and cannot be used in this case, gNB (Gross Neural Network) control is preferable. There's also the idea that "in the same case, it might be handled by OAM. RAN3 agrees that OAM will be supported." There is also the view that "it is necessary to consider whether interoperability is a key issue within the scope of NCR." Some believe that "both solutions will work." Further consideration is needed regarding the above.

[0172] Therefore, this issue should be discussed thoroughly, a conclusion should be reached, and the Rel-17 NCR WI should be completed.

[0173] 2.1.1. OAM-based solutions In other words, the OAM server generates DL OAM traffic (U-plane data) which triggers the AMF to start CN paging to the NCR-MT. However, it is assumed that there is no way for the OAM server to know that the NCR-MT is idle, since there is no way for the gNB to send UL OAM traffic (U-plane data, for example, indicating that it has been released to IDLE) when the NCR-MT is released, i.e., when the NCR-MT receives an RRC release.

[0174] Finding 2: Since NCR-MT has no way to send UL OAM traffic after being released by gNB, OAM does not know whether NCR-MT is idle or not.

[0175] Furthermore, it is somewhat unnatural for the gNB to intentionally release the NCR-MT for some purpose while the OAM server is forced to reconnect the NCR-MT. To resolve these issues, some kind of coordination between the gNB-OAM and NCR-OAM would need to be considered. However, this would either increase the operator workload or eliminate multi-vendor interoperability.

[0176] Finding 3: DL OAM traffic could be an option to trigger AMF to page idle NCR-MTs, but this would require coordination between gNB-OAM and NCR-OAM, leading to decreased network operational efficiency and reduced interoperability.

[0177] Another implementation option is to use an OAM client on the NCR-MT. The OAM client can use not only the NCR-MT's release state but also fault states (RLF, RRC restart failure, etc.) and initial access states (power on, etc.) to determine the NCR-MT's transition to an idle state. In the case of faults and initial access, the OAM client may generate UL OAM traffic (i.e., U-plane data) for purposes such as establishing a connection with the OAM server. The UL packets trigger the RRC connection establishment procedure, as is currently the case. In other words, in the case of an idle NCR-MT, RRC connection establishment is an automatic process, so the NCR-MT will start establishing an RRC connection immediately after being released from the gNB.

[0178] Finding 4: The use of UL OAM traffic is another possible trigger for the NCR-MT to initiate RRC connection establishment, but this may occur immediately after the gNB releases the NCR-MT into an idle state.

[0179] Based on the above observations, these implementations do not function correctly on their own, as OAM-based solutions may cause other problems.

[0180] On the other hand, the advantage of OAM-based solutions is that they do not affect the specifications.

[0181] Observation 5: The advantage of OAM-based solutions is that they do not affect specifications.

[0182] 2.1.2. Timer-based solutions A wake-up timer was proposed as a trigger for the NCR-MT to return to RRC connectivity, and this was discussed in RAN2#121 offline, online, and RAN2#121bis-e offline, online. The idea is that the NCR-MT starts a timer (if configured for RRC release), and when the timer expires, the NCR-MT initiates the RRC connectivity establishment procedure. This simple solution solves the problem mentioned in Finding 3 (especially if the OAM server does not implement automatic generation of DL traffic such as keep-alive messages), and allows the gNB to control idle NCR-MTs.

[0183] Regarding keep-alive messages as an OAM-based solution, a great many unnecessary messages are required, especially if the gNB rarely idles the NCR-MT, but this depends on the gNB implementation.

[0184] Finding 6: The wake-up timer can solve the issues identified in Finding 3, especially when the OAM server does not implement so-called keep-alive messages and RRC connection control is entirely under the control of the gNB.

[0185] Some companies were concerned about the extent to which RAN2#121bis-e would affect NAS specifications. Generally, the following two approaches are possible.

[0186] AS-based approach When the wake-up timer expires, the AS can behave as if it had received a paging message, i.e., the AS can show the NAS the UE-ID (i.e., UE-Identity). The NAS can also behave as if the access attempt is an MT access (i.e., Access Identity 0 and Access Category 0 for "MT_acc"), so the AS can set the cause of establishment with the MT access according to the NAS access attempt. Since the expiration of the wake-up timer means that the network (i.e., gNB) calls back the NCR-MT to Connected, this cause of establishment (i.e., MT access) is considered to be in line with the current definition. This solution has no (or little) impact on the NAS specification, but the AS specification needs to be slightly modified for the behavior when the timer expires.

[0187] • NAS-based approach • When the wake-up timer expires, the AS notifies the NAS, and the NAS requests the establishment of a signaling connection. This is considered a new definition of an access attempt, and in addition to the slight impact on the AS specification due to the new behavior upon timer expiration, it may be necessary to add procedural descriptions (or annotations) to the NAS specification, for example.

[0188] Another option is for the AS to transfer the wake-up timer value when RRC release is enabled. The NAS would then process the timer and request the establishment of a signaling connection upon timer expiration. This solution would require the timer processing to be defined in the NAS specification, in addition to the new definition of access attempts described above. Therefore, this option, along with the new behavior in the AS specification, would have the greatest impact on the NAS specification.

[0189] Based on the above analysis, it can be concluded that the timer should be handled by the AS to minimize the potential impact on the NAS. Furthermore, an AS-based approach is preferable because it minimizes (or avoids) the impact on other WGs. In this sense, it can be said that there are no longer any major concerns regarding the impact on the NAS specifications.

[0190] Finding 7: The wake-up timer does not affect (or has very little effect on) the operation of the NAS, as long as the timer is handled by the AS.

[0191] If the OAM-based solution discussed in the previous section is preferred, it should be noted that gNB always chooses not to set the timer on RRC release. In other words, this choice is not harmful and ensures efficient network operation and interoperability.

[0192] Proposal 1: RAN2 should agree to introduce a wake-up timer so that the gNB can control the idle NCR-MT and establish an RRC connection.

[0193] Proposal 2: RAN2 should discuss whether the AS behaves as if it has received a paging message, i.e., whether the AS displays its UE-ID to the NAS when the wake-up timer expires.

[0194] If we can agree to Proposal 1, we need to discuss the timer value. According to existing mechanisms related to access restriction / prohibition during idle periods, 300 seconds (or 5 minutes) is a common period for the UE to exclude a prohibited cell from being candidates for cell reselection, and this could be the minimum value for this timer. According to the discussion in RAN2#121bis-e, there is an example where gNBs do not use NCRs during periods of low traffic (e.g., at night) and may leave the NCRs idle. Therefore, an upper limit of 12 hours for the timer value seems reasonable. If the timer value is 8 bits, the mapping would be, for example, "300 seconds (5 minutes), 10 minutes, 30 minutes, 60 minutes (1 hour), 3 hours, 12 hours".

[0195] Proposal 3: RAN2 should discuss the value range for the wake-up timer (e.g., from 300 seconds to 12 hours).

[0196] Proposal 4: RAN2 should discuss how many bits the wake-up timer setting is (e.g., the baseline is 8 bits).

[0197] Another possibility is a prohibition timer, which causes the NCR-MT to start a timer (if configured with RRC release), and while the timer is running, the NCR-MT is prohibited from initiating the RRC connection establishment procedure. This solution resolves the issues in Finding 3 (especially if the OAM server implements frequent automatic generation of DL traffic such as keep-alive messages) and the challenges in Finding 4, and the gNB can also control idle NCR-MTs.

[0198] Finding 8: The prohibition timer, like Finding 4, can resolve the issues identified in Finding 3 (especially when keep-alive messages occur frequently), and the RRC connection control of the NCR-MT is entirely under the control of the gNB.

[0199] In other words, the NCR-MT in an idle state can also be network-controlled. This is considered more efficient because it does not require two separate timers for the wake-up timer and the disable timer.

[0200] Finding 9: Integrating the wake-up timer and the disable timer into a single timer is efficient and feasible.

[0201] Proposal 5: If Proposal 1 is agreed upon, RAN2 should further discuss whether to prohibit the NCR-MT from initiating the establishment of an RRC connection while the wake-up timer is running, i.e., whether the wake-up timer also functions as a prohibit timer (there is only one timer).

[0202] If Proposal 5 is accepted, it is clear that RRC connection establishment via UL traffic (e.g., UL OAM client packets) will be prohibited, but it is worth considering whether the same is truly true for DL ​​traffic (e.g., DL OAM server packets). If RRC connection establishment via DL traffic is prohibited, the NCR will be unreachable from the network / OAM client while the timer is running. Therefore, the prohibit timer should only apply to RRC connection establishment via UL traffic. For example, if the gNB wants to prevent the NCR-MT from returning to connected via DL traffic (e.g., via an OAM server keep-alive message). Therefore, whether this restriction should be configurable by the gNB is another issue.

[0203] Proposal 6: If Proposal 5 can be agreed upon, RAN2 should further discuss whether the prohibition timer can be applied only to UL traffic (such as OAM clients), i.e., whether RRC connection establishment is permitted for DL ​​traffic (such as OAM servers and paging inbounds) when the timer is running.

[0204] Proposal 7: If Proposal 6 can be agreed upon, RAN2 should further discuss whether the restrictions can be set by gNB, i.e., whether the ban timer applies only to UL traffic, or to both DL traffic and UL traffic.

[0205] 2.2. Beam monitoring inactive in RRC One of the reasons for this is that RAN2#120 agreed on the on / off operation of NCR-Fwd in connected and inactive states for NCR-MT.

[0206] NCR-FW 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 gNB. After the NCR-MT enters RRC inactive mode, the NCR-Fwd can be turned on or off according to the last settings received from the gNB. Further consideration is needed regarding the release to RRC idols.

[0207] And finally, RAN2#121bis-e agreed to use the idle NCR-MT.

[0208] When NCR-MT is in the RRC idle state, NCR-Fwd is off.

[0209] Based on the above agreement, the basic principles of NCR are considered to be as follows: • When NCR-MT is connected or inactive, NCR-Fwd is under the control of gNB. • NCR-Fwd is considered out of control by gNB when NCR-MT is idle.

[0210] Finding 10: When NCR-MT is inactive, NCR-Fwd is under the control of gNB.

[0211] Another factor is that RAN2#121 agreed that NCR-MT would resume RRC connectivity immediately after cell re-selection to a different cell and provide new side control settings.

[0212] If an NCR-MT in an RRC inactive state re-selects a different cell from the last serving cell that received the side control settings, the NCR-FWD will be turned off. After cell re-selection, the NCR-MT will resume receiving side control settings from the new gNB (possible through network configuration using existing specifications). Further consideration is needed for cases where the NCR-MT moves to an acceptable cell and returns, and when no cell is found.

[0213] Finding 11: If NCR-MT re-selects a different cell, NCR-Fwd is already off, and NCR-MT must re-establish the RRC connection to the new cell to provide side control settings.

[0214] In addition to these, RAN2#121bis-e discusses whether beam monitoring of the backhaul link is necessary when the NCR-MT is inactive.

[0215] Proposal 4: If necessary, beam monitoring of the backhaul link when the NCR-MT is in an RRC inactive state can be implemented.

[0216] Some people say, "I'm not against it, but I have doubts about what 'implementation' actually means." Some have raised the question, "What happens if NCR-FWD selects a new beam while RRC is inactive?" Another perspective is that "whether or not to send the UE to RRC inactive depends on the network, and the network needs to be aware of that situation (for example, whether the beam can be changed), in which case it can keep the UE connected to the RRC." Some argue, "In this case, can we agree that NCR-FWD should be turned off?" Some argue that "in an inactive state, we want to prevent the beam from being altered without the network noticing." The above points may be discussed further.

[0217] A key point in the above discussion was what happens when a beam failure is detected by an inactive NCR-MT. According to the previous discussion, the possible actions are as follows:

[0218] • Alt.1: If a beam fault is detected, or if beam fault recovery fails, turn off NCR-Fwd. • Alt.2: If a beam fault is detected, the NCR-MT will reactivate the RRC connection.

[0219] Considering the principle of Finding 10, Alt.1 is unacceptable because it would mean that NCR-Fwd can be automatically turned off even if NCR-MT is still camping in the cell where the last side control setting was provided. Alternatively, Alt.1 could mean that NCR can control whether NCR-Fwd is on or off even if NCR-MT is connected, which is not only inappropriate but also violates the agreements of RAN2 above.

[0220] On the other hand, Alt.2 can be considered a type of NCR operation during cell reselection as described in Finding 11. That is, in Alt.2, the NCR-MT needs to acquire a new side control setting when a beam fault occurs. Therefore, Alt.2 is considered a viable solution, but there may be cases where the NCR-Fwd needs to be turned off when a beam fault is detected, as in Alt.1. Meanwhile, in offline discussions, it has been pointed out that the gNB monitors the end-to-end radio link with the UE, and therefore such faults can be detected by the implementation. This is rather consistent with the principle identified in Finding 10, namely that when the NCR-MT is inactive, the NCR is under the control of the gNB.

[0221] In summary, Alt.2 is a visible solution, but at the same time, it is not essential. Considering the time remaining to address other essential issues, beam monitoring in an inactive state does not need to be supported, at least for Rel-18.

[0222] Proposal 8: RAN2 should agree that beam monitoring in inactive mode will not be supported in this release.

[0223] 2.3. Frequency Prioritization in Cell Reselection As background, RAN2#120 agreed to the following statement. NCR-MT supports cell reselection and RRM measurement in RRC idle and RRC inactive states.

[0224] In Rel-18, NCR-MT does not support handover or RRM measurement with RRC Connected.

[0225] The problem in cell reselection lies in prioritizing specific cells. For legacy RF repeaters, placement is determined by network planning and / or field RF measurements. Therefore, it is assumed that the desired cell(s) are planned for each NCR. That is, the network planning determines the relationship between serving cells and NCRs. Such desired cells may be assigned to NCRs by the OAM (Operational Amplifier).

[0226] Finding 12: The NCR can configure a desired cell, for example, by OAM, where the desired cell refers to the cell to which the NCR-MT is to camp on and / or connect.

[0227] In fact, RAN3 supports Stage-2 specification BL CR, and allows the OAM server to configure the NCR (i.e., the OAM client) for permitted and prohibited cell lists.

[0228] XY OAM side view The transport connection between the NCR node and its OAM is provided by the NCR-MT's PDU session. The NCR may configure a list of gNB cells on which the NCR-MT is allowed to connect, and / or a list of gNB cells on which the NCR-MT is prohibited from connecting.

[0229] Since NCR-MT is a type of UE, it is self-evident that NCR-MT must adhere to the idle / inactive mode operation specified in TS38.304. In the RAN2#121bis-e email discussion, some companies believed that the Stage-2 specification described above could be overridden by NCR implementations to override the TS38.304-specific operation. However, this is inconsistent with the common sense of the 3GPP specification suite and its implementation. Therefore, standard support is needed to ensure NCR network planning is reliable.

[0230] Furthermore, RAN3 allows NCRs to connect to permitted cells, meaning it makes no guarantees about camping on permitted cells. Similarly, the Stage-2 specification states that NCRs are not allowed to connect to prohibited cells, meaning it makes no assumptions to avoid camping on prohibited cells. In such cases, we need to consider what happens if the UE cannot camp on a permitted cell (due to frequency priority and / or radio conditions), even if the permitted cell meets the S criteria, and what happens if the UE does camp on a prohibited cell (since the RAN3 specification does not mention camping on, but simply states not to connect to a cell).

[0231] Finding 13: The specifications for the permitted and prohibited cell lists in Stage-2 of RAN3 do not mean that the NCR-MT implementation is permitted to override the cell reselection procedure strictly defined in TS38.304.

[0232] The simplest approach is to enhance the priority processing for cell reselection. Similar to MBS frequencies and sidelink frequencies (which are prioritized according to the UE's preference), exceptions to NCR-MT's priority processing can be defined, allowing permitted cells to be given the highest priority and prohibited cells the lowest. This enhancement would allow NCR-MT to always measure and attempt to reselect permitted cells, and attempt not to reselect prohibited cells. Therefore, these exceptions should be defined at least per frequency level whenever NCR-MT requires such prioritization, i.e., when the cell list is set by the OAM.

[0233] The simplest approach is to enhance the priority processing for cell reselection. Similar to MBS frequencies and sidelink frequencies (which are prioritized according to the UE's preference), exceptions to NCR-MT's priority processing can be defined, allowing permitted cells to be given the highest priority and prohibited cells the lowest. This enhancement would allow NCR-MT to always measure and attempt to reselect permitted cells, and attempt not to reselect prohibited cells. Therefore, these exceptions should be defined at least per frequency level whenever NCR-MT requires such prioritization, i.e., when the cell list is set by the OAM.

[0234] Proposal 9: RAN2 should agree that NCR-MT should consider certain frequencies as having the highest or lowest priority based on the expected functions of NCR-MT (e.g., if the permitted cell list and / or prohibited cell list are set by OAM).

[0235] Considering that NCR-MTs are positioned at the cell edges (i.e., extending macrocell coverage), ranking could cause NCR-MTs to re-select undesirable cells at the same frequency.

[0236] Proposal 10: RAN2 should discuss whether the NCR-MT is permitted to prioritize a specific cell (a cell of interest) in the in-frequency cell reselection procedure.

[0237] 2.4 RRC release with redirection RAN2#121bis-e has agreed to continue supporting redirection for UEs as before. RAN2 verifies that RRC release with redirection is applicable to NCR-MT, and that NCR-Fwd is off when NCR-MT selects a new cell due to redirection (this does not affect the specifications).

[0238] As defined by RAN3, NCR is configured with an allowed cell list and / or a prohibited cell list, so NCR-MT can identify the frequencies of allowed / prohibited cells using inter-frequency cell reselection information provided, for example, by SIB4. Since cell selection is performed when redirection is configured, it is up to the NCR-MT implementation which cells at the identified frequencies it selects.

[0239] On the other hand, since gNB may not be aware of the frequencies of interest to NCR-MT or the allowed / denied cell lists set on NCR by NCR's OAM, the challenge remains of how gNB can identify specific frequencies for redirection, i.e., how to configure redirectedCarrierInfo IE.

[0240] Finding 14: It is unclear how gNB sets redirectedCarrierInfo on RRC release, as it may not know the allowed / denied cell list set in the NCR by OAM and the corresponding frequencies on which these cells operate.

[0241] That is, the operator inputs all the allow / deny lists set by the NCR's OAM into each NCR within the coverage of the gNB. This solution does not affect the specifications, but it imposes an excessive load on the operator every time an NCR is deployed in the network.

[0242] Another solution is to enable the NCR-MT to notify the gNB of the allow / deny cell list through UE Assistance Information, UE Capability, etc. This automatic configuration reduces the operator's workload regarding this configuration, but it is approved by the RAN pre-requisite.

[0243] Therefore, RAN2 should discuss how to address this issue, at least in Rel-18 NCR.

[0244] Proposal 11: RAN2 should discuss whether the gNB can identify specific frequencies set in the redirectedCarrierInfo IE within RRC release based on OAM implementation or new UE reports.

Explanation of Signs

[0245] 1: Mobile communication system 100: UE 200: gNB 210: Transmission unit 220: Reception unit 230: Control unit 240: Backhaul communication unit 300A: AMF 400: OAM server 500A: NCR device 510A: NCR-Fwd 520A: NCR-MT 500B: RIS device 510B: RIS-Fwd 520B: RIS-MT 511A: Radio unit 511a: Antenna unit 511b: RF circuit 511c: Directivity control unit 512A: NCR control unit 512B: RIS control unit 521: Receiver 522: Transmitter 523: Control unit 530: Interface

Claims

1. A communication method performed by a relay device having a relay device that performs relay operations to relay wireless signals transmitted between a network node and a user device, and a control terminal that receives control information used to control the relay device from the network node, When the control terminal is in a wireless resource control (RRC) connected state in the first cell managed by the network node, it receives the control information from the first cell. The control terminal, after transitioning from the RRC connected state to the RRC inactive state, controls the relay operation by the relay device based on the control information last received from the first cell. The control terminal has the following characteristics: If it re-selects a cell different from the first cell, it stops the relay operation. Communication method.

2. A relay device that performs relaying operations to relay wireless signals transmitted between a network node and a user device, The system includes a control terminal that receives control information used for controlling the relay from the network node, The aforementioned control terminal is When the first cell managed by the network node is in a wireless resource control (RRC) connected state, a receiving unit receives the control information from the first cell, The control unit includes, after transitioning from the RRC connected state to the RRC inactive state, controlling the relay operation by the repeater based on the control information last received from the first cell, and stopping the relay operation if a cell different from the first cell is selected again. Relay device.

3. A mobile communication system comprising a network node, user equipment, and relay equipment, The relay device is, A relay device that performs relay operations to relay wireless signals transmitted between the network node and the user device, The system includes a control terminal that receives control information used for controlling the relay from the network node, The aforementioned control terminal is When the first cell managed by the network node is in a wireless resource control (RRC) connected state, a receiving unit receives the control information from the first cell, The control unit includes, after transitioning from the RRC connected state to the RRC inactive state, controlling the relay operation by the repeater based on the control information last received from the first cell, and stopping the relay operation if a cell different from the first cell is selected again. Mobile communication system.

4. A relay device having a relay unit that performs relay operations to relay wireless signals transmitted between a network node and a user device, and a control terminal that receives control information used to control the relay unit from the network node, When the first cell managed by the network node is in a Wireless Resource Control (RRC) connected state, the process of receiving the control information from the first cell is performed. After transitioning from the RRC connected state to the RRC inactive state, the process controls the relay operation by the relay device based on the control information last received from the first cell. If a cell different from the first cell is selected again, the process of stopping the relay operation is executed. program.

5. A relay device chipset comprising a relay unit that performs relay operations to relay wireless signals transmitted between a network node and a user device, and a control terminal that receives control information used to control the relay unit from the network node, When the first cell managed by the network node is in a Wireless Resource Control (RRC) connected state, the control information is received from the first cell, After transitioning from the RRC connected state to the RRC inactive state, the relay operation by the repeater is controlled based on the control information last received from the first cell. If the control terminal re-selects a cell different from the first cell, the relay operation is stopped and the following is performed. Chipset.

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