Mobile communication system, relay device, and network device

Abstract

This mobile communication system comprises a network and a relay device that performs relay transmission for relaying a wireless signal transmitted between the network and a user device. The relay device connects to a cell selected by cell selection or cell reselection, to perform the relay transmission. Cell information identifying a desired cell that is determined as a connection destination of the relay device is communicated between the network and the relay device, or between entities in the network.

Description

Mobile communication system, relay device, and network device

[0001] The present disclosure relates to a mobile communication system, a relay device, and a network device used in the mobile communication system.

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

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

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

[0005] A mobile communication system according to a first aspect includes a network and a relay device that relays radio signals transmitted between the network and a user device. The relay device connects to a cell selected by cell selection or cell reselection and performs the relay transmission. A network device that operates the network sets, to the relay device, cell information regarding a connected cell to which the relay device can connect.

[0006] A relay device according to a second aspect is a relay device used in a mobile communication system, and includes a relay unit that relays radio signals transmitted between a network and a user device, and a control terminal that connects to a cell selected by cell selection or cell reselection and controls the relay transmission. The control terminal receives cell information about a connecting cell to which the relay device can connect from a network device that operates the network.

[0007] A network device according to a third aspect is a network device that operates a mobile communication system and includes a communication unit that communicates with a relay device or another network device. The relay device is a device that relays radio signals transmitted between the network and a user device. The communication unit sets cell information regarding a connected cell to which the relay device can connect to the relay device.

[0008] 1 is a diagram illustrating a configuration of a mobile communication system according to an embodiment. FIG. 1 is a diagram illustrating a protocol stack configuration of a radio interface of a user plane that handles data. FIG. 2 is a diagram illustrating a protocol stack configuration of a radio interface of a control plane that handles signaling (control signals). FIG. 2 is a diagram illustrating an example of an application scenario of a relay device (NCR device) according to the first embodiment. FIG. 3 is a diagram illustrating an example of an application scenario of a relay device (NCR device) according to the first embodiment. FIG. 4 is a diagram illustrating an example of a control method of a relay device (NCR device) according to the first embodiment. FIG. 4 is a diagram illustrating an example of a protocol stack configuration in a mobile communication system having a relay device (NCR device) according to the first embodiment. FIG. 5 is a diagram illustrating an example of a configuration of a relay device (NCR device) according to the first embodiment. FIG. 6 is a diagram illustrating an example of a configuration of a base station (gNB) according to an embodiment. FIG. 7 is a diagram illustrating an example of downlink signaling from a base station (gNB) to a control terminal (NCR-MT) according to the first embodiment. FIG. 8 is a diagram illustrating an example of uplink signaling from a control terminal (NCR-MT) to a base station (gNB) according to the first embodiment. FIG. 9 is a diagram illustrating an example of an overall operation sequence of a mobile communication system according to the first embodiment. FIG. 10 is a diagram illustrating beam sweeping according to the first embodiment. FIG. 11 is a diagram illustrating an operation related to load balancing according to the first embodiment. 1 is a diagram for explaining a link (connection) between an NCR device and a gNB according to the first embodiment. FIG. 2 is a diagram for explaining an operation example of a mobile communication system according to a first operation pattern of load balancing according to the first embodiment. FIG. 3 is a diagram for explaining connection control of a relay device (NCR device) to a desired cell according to the first embodiment. FIG. 4 is a diagram for explaining an operation example of a mobile communication system according to a first operation pattern of connection control according to the first embodiment. FIG. 5 is a diagram for explaining an operation example of a mobile communication system according to a second operation pattern of connection control according to the first embodiment. FIG. 6 is a diagram for explaining an operation example of a mobile communication system according to a third operation pattern of connection control according to the first embodiment. FIG. 7 is a diagram for explaining an operation example of a mobile communication system according to a fourth operation pattern of connection control according to the first embodiment. FIG. 8 is a diagram for explaining another operation example of a mobile communication system according to the fourth operation pattern of connection control according to the first embodiment.FIG. 10 is a diagram showing an example of operation of a mobile communication system relating to a fifth operation pattern of connection control according to the first embodiment. FIG. 11 is a diagram showing an example of operation of a mobile communication system relating to a sixth operation pattern of connection control according to the first embodiment. FIG. 12 is a diagram for explaining a relay device (RIS device) according to the second embodiment. FIG. 13 is a diagram for explaining a relay device (RIS device) according to the second embodiment. FIG. 14 is a diagram showing a multi-beam NCR. FIG. 15 is a diagram showing options for a management model of a multi-beam repeater. FIG. 16 is a diagram showing CA / DC settings for NCR-MT.

[0009] A mobile communication system according to an embodiment will be described with reference to the drawings. In the description of the drawings, the same or similar parts are denoted by the same or similar reference numerals.

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

[0011] (1.1) Overview of the Mobile Communication System FIG. 1 is a diagram showing the configuration of a mobile communication system according to this embodiment. The mobile communication system 1 conforms to the 5th Generation System (5GS) of the 3rd Generation Partnership Project (3GPP) (registered trademark; the same applies hereinafter) standard. While the following description will be given using 5GS as an example, the mobile communication system may also be at least partially based on the Long Term Evolution (LTE) system. The mobile communication system may also be at least partially based on the 6th Generation (6G) system.

[0012] The mobile communication system 1 includes a user equipment (UE) 100, a 5G radio access network (NG-RAN: Next Generation Radio Access Network) 10, and a 5G core network (5GC: 5G Core Network) 20. Hereinafter, the NG-RAN 10 may be simply referred to as the RAN 10. Furthermore, the 5GC 20 may be simply referred to as the core network (CN) 20. The RAN 10 and the CN 20 constitute a network 5 of the mobile communication system 1.

[0013] The UE 100 is a mobile wireless communication device. The UE 100 may be any device that is used by a user. For example, the UE 100 may be a mobile phone terminal (including a smartphone) and / or a tablet terminal, a notebook PC, a communication module (including a communication card or a chipset), a sensor or a device provided in a sensor, a vehicle or a device provided in a vehicle (Vehicle UE), or an aircraft or a device provided in an aircraft (Aerial UE).

[0014] The NG-RAN 10 includes a base station (referred to as "gNB" in the 5G system) 200. The gNBs 200 are connected to each other via an Xn interface, which is an interface between base stations. The gNB 200 manages one or more cells. The gNB 200 performs wireless communication with the UE 100 that has established a connection with its own cell. The gNB 200 has a radio resource management (RRM) function, a routing function for user data (hereinafter simply referred to as "data"), a measurement control function for mobility control and scheduling, etc. The term "cell" is used to indicate the smallest unit of a wireless communication area. The term "cell" is also used to indicate a function or resource for wireless communication with the UE 100. One cell belongs to one carrier frequency (hereinafter simply referred to as "frequency").

[0015] The gNB200 may be functionally divided into a central unit (CU) and a distributed unit (DU). The CU controls the DU. The CU is a unit including upper layers included in the protocol stack described below, such as an RRC layer, an SDAP layer, and a PDCP layer. The CU is connected to the core network via an NG interface, which is a backhaul interface. The CU is connected to neighboring base stations via an Xn interface, which is an interface between base stations. The DU forms a cell. The DU202 is a unit including lower layers included in the protocol stack described below, such as an RLC layer, a MAC layer, and a PHY layer. The DU is connected to the CU via an F1 interface, which is a fronthaul interface.

[0016] In addition, gNBs can also be connected to the Evolved Packet Core (EPC), which is the core network of LTE. LTE base stations can also be connected to 5GC. LTE base stations and gNBs can also be connected via an inter-base station interface.

[0017] The 5GC20 includes an AMF (Access and Mobility Management Function) and a UPF (User Plane Function) 300. The AMF performs various mobility controls for the UE 100. The AMF manages the mobility of the UE 100 by communicating with the UE 100 using NAS (Non-Access Stratum) signaling. The UPF controls data forwarding. The AMF and the UPF are connected to the gNB 200 via an NG interface, which is an interface between a base station and a core network.

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

[0019] The user plane radio interface protocol includes a physical (PHY) layer, a medium access control (MAC) layer, a radio link control (RLC) layer, a packet data convergence protocol (PDCP) layer, and a service data adaptation protocol (SDAP) layer.

[0020] The PHY layer performs encoding / decoding, modulation / demodulation, antenna mapping / demapping, and resource mapping / demapping. Data and control information are transmitted between the PHY layer of UE100 and the PHY layer of gNB200 via a physical channel. The PHY layer of UE100 receives downlink control information (DCI) transmitted from gNB200 on a physical downlink control channel (PDCCH). Specifically, UE100 performs blind decoding of the PDCCH using a radio network temporary identifier (RNTI) and acquires successfully decoded DCI as DCI addressed to the UE. The DCI transmitted from gNB200 has a CRC (Cyclic Redundancy Code) parity bit scrambled by the RNTI added.

[0021] In addition, the gNB 200 transmits a synchronization signal block (SSB: Synchronization Signal / PBCH block). For example, the SSB is composed of four consecutive OFDM (Orthogonal Frequency Division Multiplex) symbols, and includes a primary synchronization signal (PSS), a secondary synchronization signal (SSS), a physical broadcast channel (PBCH) / master information block (MIB), and a PBCH demodulation reference signal (DMRS). The bandwidth of the SSB is, for example, 240 consecutive subcarriers, that is, a bandwidth of 20 RBs.

[0022] The MAC layer performs data priority control, retransmission processing using Hybrid Automatic Repeat reQuest (HARQ), random access procedures, etc. Data and control information are transmitted between the MAC layer of the UE 100 and the MAC layer of the gNB 200 via a transport channel. The MAC layer of the gNB 200 includes a scheduler. The scheduler determines the uplink and downlink transport format (transport block size, modulation and coding scheme (MCS)) and the resource blocks to be allocated to the UE 100.

[0023] The RLC layer transmits data to the receiving RLC layer using the functions of the MAC layer and PHY layer. Data and control information are transmitted between the RLC layer of the UE 100 and the RLC layer of the gNB 200 via a logical channel.

[0024] The PDCP layer performs header compression / decompression, encryption / decryption, and the like.

[0025] The SDAP layer maps IP flows, which are units for Quality of Service (QoS) control by the core network, to radio bearers, which are units for QoS control by the Access Stratum (AS). Note that if the RAN is connected to the EPC, SDAP may not be required.

[0026] FIG. 3 is a diagram showing the configuration of a protocol stack of a radio interface of a control plane that handles signaling (control signals).

[0027] The protocol stack of the radio interface of the control plane has an RRC (Radio Resource Control) layer and an NAS (Non-Access Stratum) layer instead of the SDAP layer shown in FIG.

[0028] RRC signaling for various settings is transmitted between the RRC layer of UE100 and the RRC layer of gNB200. The RRC layer controls logical channels, transport channels, and physical channels according to the establishment, re-establishment, and release of radio bearers. When there is a connection (RRC connection) between the RRC of UE100 and the RRC of gNB200, UE100 is in an RRC connected state. When there is no connection (RRC connection) between the RRC of UE100 and the RRC of gNB200, UE100 is in an RRC idle state. When the connection between the RRC of UE100 and the RRC of gNB200 is suspended, UE100 is in an RRC inactive state.

[0029] The NAS layer, which is located above the RRC layer, performs session management, mobility management, etc. NAS signaling is transmitted between the NAS layer of the UE 100 and the NAS layer of the AMF 300A. Note that the UE 100 has an application layer and the like in addition to the radio interface protocol. Also, a layer lower than the NAS layer is called an AS layer.

[0030] (1.2) Example of Application Scenario of Relay Device FIGS. 4 and 5 are diagrams showing an example of application scenario of the NCR device according to this embodiment.

[0031] Compared to 4G / LTE, 5G / NR enables broadband transmission using higher frequency bands. Radio signals in high frequency bands, such as the millimeter wave band or terahertz wave band, have high line-of-sight properties, which poses a challenge in reducing the coverage of the gNB 200. In FIG. 4, the UE 100 may be located outside the coverage area of ​​the gNB 200, for example, outside an area where radio signals can be received directly from the gNB 200. A shield may exist between the gNB 200 and the UE 100, preventing the UE 100 from communicating with the gNB 200 within line-of-sight.

[0032] As shown in Figure 4, a repeater device (500A), which is a type of relay device that relays radio signals between the gNB 200 and the UE 100 and can be controlled from a network, is introduced into the mobile communication system 1. Hereinafter, such a repeater device will be referred to as an NCR (Network-Controlled Repeater) device. Such a repeater device may also be referred to as a smart repeater device.

[0033] For example, the NCR device 500A amplifies a radio signal (radio wave) received from the gNB 200 and transmits it by directional transmission. Specifically, the NCR device 500A receives a radio signal transmitted by the gNB 200 by beamforming. The NCR device 500A then amplifies the received radio signal without demodulating or modulating it, and transmits the amplified radio signal by directional transmission. Here, the NCR device 500A may transmit a radio signal with a fixed directivity (beam). The NCR device 500A may transmit a radio signal with a variable (adaptive) directional beam. This allows the coverage of the gNB 200 to be efficiently expanded. In this embodiment, it is mainly assumed that the NCR device 500A is applied to downlink communication from the gNB 200 to the UE 100, but the NCR device 500A can also be applied to uplink communication from the UE 100 to the gNB 200.

[0034] Also, as shown in FIG. 5, a new UE (hereinafter referred to as "NCR-MT (Mobile termination)") 100B, which is a type of control terminal for controlling the NCR device 500A, is introduced. That is, the NCR device 500A relays radio signals transmitted between the gNB 200 and the UE 100, specifically, it has an NCR-Fwd (Forward) 510A, which is a type of repeater that changes the propagation state of the radio signal without demodulating or modulating the radio signal, and an NCR-MT 520A that controls the NCR-Fwd 510A by performing wireless communication with the gNB 200. In this way, the NCR-MT 520A controls the NCR device 500A in cooperation with the gNB 200 by establishing a wireless connection with the gNB 200 and performing wireless communication with the gNB 200. This makes it possible to achieve efficient coverage expansion using the NCR device 500A. NCR-MT520A controls NCR device 500A in accordance with control from gNB200.

[0035] The NCR-MT 520A may be configured separately from the NCR-Fwd 510A. For example, the NCR-MT 520A may be located near the NCR-Fwd 510A and electrically connected to the NCR-Fwd 510A. The NCR-MT 520A may be connected to the NCR-Fwd 510A by wire or wirelessly. Alternatively, the NCR-MT 520A may be configured integrally with the NCR-Fwd 510A. The NCR-MT 520A and the NCR-Fwd 510A may be fixedly installed, for example, at the coverage edge (cell edge) of the gNB 200 or on a wall or window of a building. The NCR-MT 520A and the NCR-Fwd 510A may be installed, for example, in a vehicle or the like and be mobile. Also, one NCR-MT 520A may control multiple NCR-Fwds 510A.

[0036] In the example shown in FIG. 5, the NCR device 500A (NCR-Fwd 510A) dynamically or quasi-statically changes the beam to be transmitted or received. For example, the NCR-Fwd 510A forms a beam toward each of the UE 100a and the UE 100b. The NCR-Fwd 510A may also form a beam toward the gNB 200. For example, in the communication resources between the gNB 200 and the UE 100a, the NCR-Fwd 510A transmits a radio signal received from the gNB 200 toward the UE 100a by beamforming, and / or transmits a radio signal received from the UE 100a toward the gNB 200 by beamforming. In the communication resources between the gNB 200 and the UE 100b, the NCR-Fwd 510A transmits a radio signal received from the gNB 200 toward the UE 100b by beamforming, and / or transmits a radio signal received from the UE 100b by beamforming toward the gNB 200. Instead of or in addition to beamforming, the NCR-Fwd 510A may form a null (so-called null steering) toward a UE 100 (not shown) and / or a neighboring gNB 200 (not shown) that is not a communication partner for interference suppression.

[0037] FIG. 6 is a diagram showing an example of a control method of the NCR device 500A according to this embodiment. As shown in FIG. 6, the NCR-Fwd 510A relays radio signals (also referred to as "UE signals") between the gNB 200 and the UE 100. The UE signals include uplink signals (also referred to as "UE-UL signals") transmitted from the UE 100 to the gNB 200 and downlink signals (also referred to as "UE-DL signals") transmitted from the gNB 200 to the UE 100. The NCR-Fwd 510A relays the UE-UL signals from the UE 100 to the gNB 200 and relays the UE-DL signals from the gNB 200 to the UE 100. The radio link between the NCR-Fwd 510A and the UE 100 is also referred to as an "access link." The wireless link between NCR-Fwd510A and gNB200 is also referred to as a "backhaul link."

[0038] The NCR-MT 520A transmits and receives radio signals (herein referred to as "NCR-MT signals") to and from the gNB 200. The NCR-MT signals include uplink signals (herein referred to as "NCR-MT-UL signals") transmitted from the NCR-MT 520A to the gNB 200, and downlink signals (herein referred to as "NCR-MT-DL signals") transmitted from the gNB 200 to the NCR-MT 520A. The NCR-MT-UL signals include signaling for controlling the NCR device 500A. The radio link between the NCR-MT 520A and the gNB 200 is also referred to as a "control link."

[0039] The gNB200 directs a beam to the NCR-MT520A based on the NCR-MT-UL signal from the NCR-MT520A. Because the NCR device 500A is co-located with the NCR-MT520A, if the backhaul link and the control link have the same frequency, when the gNB200 directs a beam to the NCR-MT520A, the beam will also be directed to the NCR-Fwd510A. The gNB200 uses this beam to transmit an NCR-MT-DL signal and a UE-DL signal. The NCR-MT520A receives the NCR-MT-DL signal. In addition, when the NCR-Fwd 510A and the NCR-MT 520A are at least partially integrated, the functions (e.g., antennas) for transmitting, receiving, or relaying UE signals and / or NCR-MT signals may be integrated in the NCR-Fwd 510A and the NCR-MT 520A. Note that the term "beam" includes a transmitting beam and / or a receiving beam. A beam is a general term for transmission and / or reception controlled to maximize the power of transmitted waves and / or received waves in a specific direction by adjusting / adapting antenna weights, etc.

[0040] 7 is a diagram showing an example of the configuration of a protocol stack in a mobile communication system 1 having an NCR device 500A according to this embodiment. The NCR-Fwd 510A relays radio signals transmitted and received between the gNB 200 and the UE 100. The NCR-Fwd 510A has an RF (Radio Frequency) function that amplifies and relays received radio signals, and performs directional transmission using beamforming (e.g., analog beamforming).

[0041] The NCR-MT 520A has at least one layer (entity) of PHY, MAC, RRC, and F1-AP (Application Protocol). The F1-AP is a type of fronthaul interface. The NCR-MT 520A exchanges downlink signaling and / or uplink signaling (described below) with the gNB 200 via at least one of PHY, MAC, RRC, and F1-AP. If the NCR-MT 520A is a type or part of a base station, the NCR-MT 520A may exchange with the gNB 200 via an Xn AP (Xn-AP), which is an inter-base station interface.

[0042] 8 is a diagram showing an example of the configuration of an NCR device 500A, which is a relay device according to this embodiment. The NCR device 500A includes an NCR-Fwd 510A, an NCR-MT 520A, and an interface 530.

[0043] The NCR-Fwd 510A includes a radio unit 511A and an NCR control unit 512A. The radio unit 511A includes an antenna unit 511a including multiple antennas (multiple antenna elements), an RF circuit 511b including an amplifier, and a directivity control unit 511c that controls the directivity of the antenna unit 511a. The RF circuit 511b amplifies and relays (transmits) radio signals transmitted and received by the antenna unit 511a. The RF circuit 511b may convert analog radio signals into digital signals and then reconvert them to analog signals after digital signal processing. The directivity control unit 511c may perform analog beamforming using analog signal processing. The directivity control unit 511c may perform digital beamforming using digital signal processing. The directivity control unit 511c may perform hybrid analog and digital beamforming. The NCR control unit 512A controls the radio unit 511A in response to control signals from the NCR-MT 520A. The NCR control unit 512A may include at least one processor. The NCR control unit 512A may output information regarding the capabilities of the NCR device 500A to the NCR-MT 520A.

[0044] The NCR-MT 520A has a receiving unit 521, a transmitting unit 522, and a control unit 523. The receiving unit 521 performs various receptions under the control of the control unit 523. The receiving unit 521 includes an antenna and a receiver. The receiver converts a radio signal (wireless signal) received by the antenna into a baseband signal (received signal) and outputs it to the control unit 523. The transmitting unit 522 performs various transmissions under the control of the control unit 523. The transmitting unit 522 includes an antenna and a transmitter. The transmitter converts a baseband signal (transmitted signal) output by the control unit 523 into a radio signal and transmits it from the antenna. The control unit 523 performs various controls in the NCR-MT 520A. 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 / decoding, etc. of baseband signals. The CPU executes programs stored in memory to perform various processes. The control unit 523 also executes the functions of at least one of the PHY, MAC, RRC, and F1-AP layers.

[0045] The interface 530 electrically connects the NCR-Fwd 510A and the NCR-MT 520A. The control unit 523 of the NCR-MT 520A controls the NCR-Fwd 510A via the interface 530.

[0046] In this embodiment, the receiver 521 of the NCR-MT 520A receives signaling (downlink signaling) used to control the NCR device 500A from the gNB 200 via wireless communication. The controller 523 of the NCR-MT 520A controls the NCR device 500A based on the signaling. This enables the gNB 200 to control the NCR-Fwd 510A via the NCR-MT 520A.

[0047] In this embodiment, the control unit 523 of the NCR-MT 520A may transmit NCR capability information indicating the capabilities of the NCR device 500A to the gNB 200 via wireless communication. The NCR capability information is an example of uplink signaling from the NCR-MT 520A to the gNB 200. This enables the gNB 200 to grasp the capabilities of the NCR device 500A.

[0048] (1.4) Configuration example of base station Figure 9 is a diagram showing a configuration example of the gNB 200 according to this embodiment. The gNB 200 has a transmitter 210, a receiver 220, a controller 230, and a backhaul communication unit 240.

[0049] The transmitting unit 210 performs various transmissions under the control of the control unit 230. The transmitting unit 210 includes an antenna and a transmitter. The transmitter converts a baseband signal (transmission signal) output by the control unit 230 into a radio signal and transmits it from the antenna. The receiving unit 220 performs various receptions under the control of the control unit 230. The receiving unit 220 includes an antenna and a receiver. The receiver converts a radio signal received by the antenna into a baseband signal (reception signal) and outputs it to the control unit 230. The transmitting unit 210 and the receiving unit 220 may be capable of beamforming using multiple antennas.

[0050] The control unit 230 performs various controls in the gNB 200. The control unit 230 includes at least one processor and at least one memory. The memory stores programs executed by the processor and information used in processing by the processor. The processor may include a baseband processor and a CPU. The baseband processor performs modulation / demodulation and encoding / decoding of baseband signals. The CPU executes programs stored in the memory to perform various processes.

[0051] The backhaul communication unit 240 is connected to adjacent base stations via an inter-base station interface. The backhaul communication unit 240 is connected to the AMF / UPF 300 via a base station-core network interface. The gNB is composed of a CU (Central Unit) and a DU (Distributed Unit) (i.e., functionally divided), and the two units may be connected via an F1 interface.

[0052] In this embodiment, the transmitter 210 of the gNB 200 transmits signaling (downlink signaling) used to control the NCR-Fwd 510A to the NCR-MT 520A via wireless communication. This enables the gNB 200 to control the NCR device 500A via the NCR-MT 520A. In this embodiment, the receiver 220 of the gNB 200 may receive NCR capability information indicating the capabilities of the NCR device 500A from the NCR-MT 520A via wireless communication.

[0053] (1.5) Example of downlink signaling Figure 10 is a diagram showing an example of downlink signaling from gNB200 to NCR-MT520A in this embodiment.

[0054] The gNB 200 (transmitter 210) transmits downlink signaling to the NCR-MT 520A. The downlink signaling may be an RRC message, which is signaling of the RRC layer (i.e., Layer 3). The downlink signaling may be a MAC CE (Control Element), which is signaling of the MAC layer (i.e., Layer 2). The downlink signaling may be downlink control information (DCI), which is signaling of the PHY layer (i.e., Layer 1). The downlink signaling may be UE-specific signaling. The downlink signaling may be broadcast signaling. The downlink signaling may be a fronthaul message (e.g., an F1-AP message). If NCR-MT520A is a type or part of a base station, NCR-MT520A may interact with gNB200 via Xn's AP (Xn-AP), which is an inter-base station interface.

[0055] For example, the gNB200 (transmitter 210) transmits an NCR control signal specifying the operating state of the NCR device 500A as downlink signaling to the NCR-MT 520A that has established a wireless connection with the gNB200 (step S1A). The NCR control signal specifying the operating state of the NCR device 500A may be a MAC CE, which is signaling of the MAC layer (layer 2), or a DCI, which is signaling of the PHY layer (layer 1). However, the NCR control signal may be included in an RRC Reconfiguration message, which is a type of UE-specific RRC message, and transmitted to the NCR-MT 520A. The downlink signaling may be a message of a layer higher than the RRC layer (for example, an NCR application). The downlink signaling may be a message of a layer higher than the RRC layer encapsulated in a message of a layer below the RRC layer and transmitted. In addition, the NCR-MT 520A (transmitter 522) may transmit a response message in response to the downlink signaling from the gNB 200 via the uplink. The response message may be transmitted in response to the NCR device 500A completing the setting specified in the downlink signaling or receiving the setting. The NCR control signal may be referred to as Side Control Information.

[0056] The NCR control signal may include frequency control information that specifies the center frequency of the radio signal (e.g., component carrier) to be relayed by the NCR-Fwd 510A. When the NCR control signal received from the gNB 200 includes frequency control information, the NCR-MT 520A (control unit 523) controls the NCR-Fwd 510A to relay the radio signal having the center frequency indicated by the frequency control information (step S2A). The NCR control signal may include multiple pieces of frequency control information that specify different center frequencies. By including frequency control information in the NCR control signal, the gNB 200 can specify the center frequency of the radio signal to be relayed by the NCR-Fwd 510A via the NCR-MT 520A.

[0057] The NCR control signal may include mode control information that specifies the operation mode of the NCR-Fwd 510A. The mode control information may be associated with frequency control information (center frequency). The operation mode may be any of a mode in which the NCR-Fwd 510A performs omnidirectional transmission and / or reception, a mode in which the NCR-Fwd 510A performs fixed-directivity transmission and / or reception, a mode in which the NCR-Fwd 510A performs transmission and / or reception using a variable directional beam, and a mode in which the NCR-Fwd 510A performs MIMO (Multiple Input Multiple Output) relay transmission. The operation mode may be any of a beamforming mode (i.e., a mode that emphasizes improving the desired wave) and a null steering mode (i.e., a mode that emphasizes suppressing interference waves). When the NCR control signal received from the gNB 200 includes mode control information, the NCR-MT 520A (control unit 523) controls the NCR-Fwd 510A to operate in the operating mode indicated by the mode control information (step S2A). By including the mode control information in the NCR control signal, the gNB 200 can specify the operating mode of the NCR-Fwd 510A via the NCR-MT 520A.

[0058] Here, the mode in which the NCR device 500A performs omnidirectional transmission and / or reception is a mode in which the NCR-Fwd 510A performs omnidirectional relaying, and may be referred to as omni-mode. The mode in which the NCR-Fwd 510A performs fixed directional transmission and / or reception may be a directional mode realized by a single directional antenna. This mode may be a beamforming mode realized by applying fixed phase / amplitude control (antenna weight control) to multiple antennas. Any of these modes may be specified (set) by the gNB 200 to the NCR-MT 520A. The mode in which the NCR-Fwd 510A performs transmission and / or reception using a variable directional beam may be a mode in which analog beamforming is performed. This mode may be a mode in which digital beamforming is performed. This mode may be a mode in which hybrid beamforming is performed. This mode may be a mode in which an adaptive beam specific to the UE 100 is formed. Any of these modes may be specified (set) from the gNB 200 to the NCR-MT 520A. Note that in an operation mode in which beamforming is performed, beam control information, described below, may be provided from the gNB 200 to the NCR-MT 520A. The mode in which the NCR device 500A performs MIMO relay transmission may be a mode in which SU (Single-User) spatial multiplexing is performed. It may also be a mode in which MU (Multi-User) spatial multiplexing is performed. This mode may also be a mode in which transmit diversity is performed. Any of these modes may be specified (set) from the gNB 200 to the NCR-MT 520A. The operation modes may include a mode in which relay transmission by the NCR-Fwd 510A is turned on (activated) and a mode in which relay transmission by the NCR-Fwd 510A is turned off (deactivated). Any of these modes may be specified (set) by an NCR control signal from gNB200 to NCR-MT520A.

[0059] The NCR control signal may include beam control information that specifies the transmission direction, transmission weight, or beam pattern when the NCR-Fwd 510A performs directional transmission. The beam control information may be associated with frequency control information (center frequency). The beam control information may include a PMI (Precoding Matrix Indicator). The beam control information may include beam formation angle information. When the NCR control signal received from the gNB 200 includes beam control information, the NCR-MT 520A (control unit 523) controls the NCR-Fwd 510A to form the transmission directivity (beam) indicated by the beam control information (step S2A). By including beam control information in the NCR control signal, the gNB 200 can control the transmission directivity of the NCR device 500A via the NCR-MT 520A.

[0060] The NCR control signal may include output control information that specifies the degree to which the NCR-Fwd 510A amplifies the radio signal (amplification gain) or transmission power. The output control information may be information indicating a difference value (i.e., a relative value) between the current amplification gain or transmission power and the target amplification gain or transmission power. When the NCR control signal received from the gNB 200 includes output control information, the NCR-MT 520A (control unit 523) controls the NCR-Fwd 510A to change the amplification gain or transmission power to the amplification gain or transmission power indicated by the output control information (step S2A). The output control information may be associated with frequency control information (center frequency). The output control information may be information that specifies any one of the amplifier gain, beamforming gain, and antenna gain of the NCR-Fwd 510A. The output control information may be information that specifies the transmission power of the NCR-Fwd 510A.

[0061] When one NCR-MT 520A controls multiple NCR-Fwds 510A, the gNB 200 (transmitter 210) may transmit an NCR control signal to the NCR-MT 520A for each NCR-Fwd 510A. In this case, the NCR control signal may include an identifier (NCR identifier) ​​of the corresponding NCR-Fwd 510A. The NCR-MT 520A (controller 523) that controls multiple NCR-Fwds 510A determines the NCR-Fwd 510A to which the NCR control signal is applied based on the NCR identifier included in the NCR control signal received from the gNB 200. Note that the NCR identifier may be transmitted from the NCR-MT 520A to the gNB 200 together with the NCR control signal, even when the NCR-MT 520A controls only one NCR-Fwd 510A.

[0062] In this way, the NCR-MT 520A (control unit 523) controls the NCR-Fwd 510A based on the NCR control signal from the gNB 200. This enables the gNB 200 to control the NCR-Fwd 510A via the NCR-MT 520A.

[0063] (1.6) Example of uplink signaling Figure 11 is a diagram showing an example of uplink signaling from NCR-MT520A to gNB200 in this embodiment.

[0064] The NCR-MT 520A (transmitter 210) transmits uplink signaling to the gNB 200. The uplink signaling may be an RRC message, which is signaling of the RRC layer. The uplink signaling may be a MAC CE, which is signaling of the MAC layer. The uplink signaling may be uplink control information (UCI), which is signaling of the PHY layer. The uplink signaling may be a fronthaul message (e.g., an F1-AP message). The uplink signaling may be an inter-base station message (e.g., an Xn-AP message). The uplink signaling may be a message of a layer higher than the RRC layer (e.g., an NCR application). The uplink signaling may be a message of a layer higher than the RRC layer encapsulated in a message of a layer lower than the RRC layer and transmitted. That is, the uplink signaling stores an upper layer message in a lower layer container. Note that the gNB 200 (transmitter 210) transmits a response message to the uplink signaling from the NCR-MT 520A on the downlink, and the NCR-MT 520A (receiver 521) may receive the response message.

[0065] For example, the NCR-MT 520A (transmitter 522) that has established a wireless connection with the gNB 200 transmits NCR capability information indicating the capabilities of the NCR device 500A to the gNB 200 as uplink signaling (step S5A). The NCR-MT 520A (transmitter 522) may include the NCR capability information in a UE Capability message or a UE Assistant Information message, which are types of RRC messages, and transmit the message to the gNB 200. The NCR-MT 520A (transmitter 522) may transmit the NCR capability information (NCR capability information and / or operation status information) to the gNB 200 in response to a request or inquiry from the gNB 200.

[0066] The NCR capability information may include supported frequency information indicating frequencies supported by the NCR-Fwd 510A. The NCR capability information may include mode capability information regarding operation modes supported by the NCR-Fwd 510A or switching between operation modes. The NCR capability information may include beam capability information indicating the beam variable range, beam variable resolution, or number of variable patterns when the NCR-Fwd 510A transmits and / or receives using a variable directional beam. The NCR capability information may include control delay information indicating the control delay time in the NCR device 500A. The NCR capability information may include amplification characteristic information regarding the amplification characteristics or output power characteristics of the radio signal in the NCR-Fwd 510A. The NCR capability information may include location information indicating the installation location of the NCR device 500A. The NCR capability information may include antenna information indicating the number of antennas the NCR-Fwd 510A has. When NCR-MT 520A controls multiple NCR-Fwd 510A, NCR-MT 520A (transmitter 522) may transmit NCR capability information to gNB 200 for each NCR-Fwd 510A.

[0067] (1.7) Example of Overall Operation Sequence Fig. 12 is a diagram showing an example of the overall operation sequence of the mobile communication system 1 according to this embodiment. In the sequence diagrams referred to in the following embodiments, non-essential steps are indicated by dashed lines. Note that, as will be described in detail later, "NCR" in Fig. 12 may be read as "RIS".

[0068] In step S11, gNB200 (transmitter 210) broadcasts NCR support information indicating that gNB200 supports NCR-MT520A. For example, gNB200 (transmitter 210) broadcasts a system information block (SIB) including NCR support information. The NCR support information may be information indicating that NCR-MT520A is accessible. Alternatively, gNB200 (transmitter 210) may broadcast NCR non-support information indicating that gNB200 does not support NCR-MT520A. The NCR non-support information may be information indicating that NCR-MT520A is inaccessible.

[0069] At this stage, the NCR-MT 520A may be in an RRC idle state or an RRC inactive state. The NCR-MT 520A (control unit 523), which has not established a wireless connection with the gNB 200, may determine that access to the gNB 200 is permitted in response to receiving NCR support information from the gNB 200, and may perform an access operation to establish a wireless connection with the gNB 200. The NCR-MT 520A (control unit 523) may perform cell reselection by regarding the gNB 200 (cell) to which access is permitted as having the highest priority.

[0070] On the other hand, if the NCR-MT520A (control unit 523) that has not established a wireless connection with the gNB200 does not broadcast NCR support information (or broadcasts NCR non-support information), it may determine that it is unable to access (establish a connection with) the gNB200. This allows the NCR-MT520A to establish a wireless connection only with gNB200 that can handle the NCR-MT520A.

[0071] In addition, when the gNB200 is congested, the gNB200 may broadcast access restriction information that restricts access from the UE100. However, unlike a normal UE100, the NCR-MT520A can also be considered a network-side entity. Therefore, the NCR-MT520A may ignore the access restriction information from the gNB200. For example, when the NCR-MT520A (control unit 523) receives NCR support information from the gNB200, it may perform an operation to establish a wireless connection with the gNB200 even if the gNB200 is broadcasting access restriction information. For example, the NCR-MT520A (control unit 523) may not execute (or may ignore) UAC (Unified Access Control). Alternatively, a special value indicating that the access is an NCR-MT access may be used for either or both of the AC / AI (Access Category / Access Identity) used in the UAC.

[0072] In step S12, the NCR-MT 520A (control unit 523) initiates a random access procedure for the gNB 200. In the random access procedure, the NCR-MT 520A (transmitting unit 522) transmits a random access preamble (Msg1) and an RRC message (Msg3) to the gNB 200. Also, in the random access procedure, the NCR-MT 520A (receiving unit 521) receives a random access response (Msg2) and an RRC message (Msg4) from the gNB 200.

[0073] In step S13, when establishing a wireless connection with the gNB 200, the NCR-MT 520A (transmitter 522) may transmit NCR-MT information indicating that its own UE is an NCR-MT to the gNB 200. For example, during a random access procedure with the gNB 200, the NCR-MT 520A (transmitter 522) includes the NCR-MT information in a random access procedure message (e.g., Msg1, Msg3, Msg5) and transmits it to the gNB 200. Based on the NCR-MT information received from the NCR-MT 520A, the gNB 200 (controller 230) recognizes that the accessed UE 100 is the NCR-MT 520A, and can, for example, exclude the NCR-MT 520A from the access restriction target (i.e., accept access). Once the random access procedure is completed, the NCR-MT 520A transitions from the RRC idle state or the RRC inactive state to the RRC connected state.

[0074] In step S14, gNB200 (transmitter 522) transmits a capability inquiry message to NCR-MT520A to inquire about the capabilities of NCR-MT520A. NCR-MT520A (receiver 521) receives the capability inquiry message.

[0075] In step S15, the NCR-MT 520A (transmitter 522) transmits a capability information message including NCR capability information to the gNB 200. The capability information message may be an RRC message, for example, a UE Capability message. The gNB 200 (receiver 220) receives the capability information message. The gNB 200 (controller 230) determines the capabilities of the NCR device 500A based on the received capability information message.

[0076] In step S16, the gNB200 (transmitter 522) transmits a configuration message including various settings related to the NCR device 500A to the NCR-MT 520A. The NCR-MT 520A (receiver 521) receives the configuration message. The configuration message is a type of the downlink signaling described above. The configuration message may be an RRC message, for example, an RRC Reconfiguration message.

[0077] In step S17, the gNB 200 (transmitter 522) transmits a control instruction specifying the operating state of the NCR-Fwd 510A to the NCR-MT 520A. The control instruction may be the above-mentioned NCR control signal (e.g., L1 / L2 signaling). The NCR-MT 520A (receiver 521) receives the control instruction. The NCR-MT 520A (controller 523) controls the NCR-Fwd 510A in accordance with the control instruction.

[0078] In step S18, the NCR-MT 520A controls the NCR device 500A according to the above settings (and control instructions). Note that the NCR-MT 520A may autonomously control the NCR device 500A without relying on control instructions from the gNB 200. For example, the NCR-MT 520A may autonomously control the NCR device 500A based on the location of the UE 100 and / or information received by the NCR-MT 520A from the UE 100.

[0079] (1.8) Beam Sweeping FIG. 13 is a diagram for explaining beam sweeping according to the embodiment.

[0080] The gNB200 performs beam sweeping, which sequentially switches beams in different directions while transmitting. At this time, the gNB200 transmits a different SSB for each beam. The SSBs are periodically transmitted from the gNB200 to the cell as SSB bursts consisting of multiple SSBs. Each of the multiple SSBs in an SSB burst is assigned an SSB index, which is an identifier. The SSBs are beamformed and transmitted in different directions. The NCR device 500A (NCR-MT520A) reports to the gNB200 during the random access channel (RACH) procedure which direction the beam had good reception quality. Specifically, the NCR device 500A (NCR-MT520A) transmits a random access preamble to the gNB200 in a random access channel (RACH) occasion associated with the SSB index for which the beam had good reception quality. As a result, gNB200 can determine the optimal beam for NCR device 500A (NCR-MT520A).

[0081] Note that such an SSB may be transmitted in an initial BWP (initial DL BWP). When the NCR device 500A (NCR-MT 520A) is in an RRC connected state, a dedicated BWP may be configured and activated in the NCR device 500A (NCR-MT 520A). In the dedicated BWP, a channel state information reference signal (CSI-RS) may be used as a reference signal instead of an SSB. Hereinafter, an example in which beam information identifying a beam is an SSB index will be mainly described, assuming that there is a one-to-one relationship between a beam and an SSB (specifically, an SSB index). However, a beam may be associated with a CSI-RS. The beam information identifying a beam may be a CSI-RS index.

[0082] (1.9) Operation Related to Load Balancing FIG. 14 is a diagram for explaining the operation related to load balancing according to this embodiment.

[0083] The NCR device 500A extends the coverage of the cell of the gNB 200S by relaying radio signals between the gNB 200S and the UE 100. In the illustrated example, there is one UE 100 connected to the gNB 200S via the NCR device 500A, but there may be multiple UEs 100.

[0084] As the coverage is expanded by the NCR device 500A, the cell of the gNB200S must accommodate more UEs. As a result, the load on the cell of the gNB200S increases, and the possibility of overload increases.

[0085] Here, by handing over the NCR device 500A from the cell (source cell) of the gNB200S to the cell (target cell) of the adjacent base station gNB200T, the load of the cell of the gNB200S can be distributed to the cell of the gNB200T. In the following, a scenario in which the NCR device 500A is handed over for the purpose of load distribution is mainly assumed. However, this is not limited to handing over the NCR device 500A for the purpose of load distribution, and may also be handover for the purpose of improving the radio conditions of the NCR device 500A. In addition, in the following, the gNB200S is also referred to as the source gNB (source base station) 200S, and the gNB200T is also referred to as the target gNB (target base station) 200S.

[0086] In this embodiment, the gNB200S corresponding to the source cell (first cell) transmits a message to connect the NCR device 500A to the target cell (second cell) to the gNB200T corresponding to the target cell over the Xn interface (inter-base station interface). The message includes information about the NCR device 500A. This allows the NCR device 500A to be handed over appropriately. Here, the gNB200S is an example of a first network node, and the gNB200T is an example of a second network node. The Xn interface is also an example of a network interface.

[0087] In the following description of this embodiment, an example of an inter-base station handover of the NCR device 500A, specifically, an inter-CU handover, will be mainly described. However, this embodiment is not limited to an inter-base station handover, and may also be an intra-base station handover (intra-CU handover). In the case of an intra-base station handover, the first network node may be a CU or a source DU, the second network node may be a target DU, and the network interface may be an F1 interface.

[0088] Although this embodiment mainly describes handover operations, it may also be applied to dual connectivity (DC) operations in which the NCR device 500A simultaneously communicates with the gNB200S and the gNB200T. In this case, the first network node may be the gNB200S (master node), the second network node may be the gNB200T (secondary node), the network interface may be an F1 interface, and the message may be a secondary node addition request message.

[0089] Figure 15 is a diagram for explaining the link (connection) between the NCR device 500A and the gNB200S in this embodiment.

[0090] A backhaul link is established between the gNB200S and the NCR-Fwd510A of the NCR device 500A. An access link is established between the UE100 and the NCR-Fwd510A of the NCR device 500A. The NCR device 500A (NCR-Fwd510A), which relays radio signals transmitted between the gNB200S and the UE100, changes the propagation state of the radio signals without demodulating or modulating the radio signals.

[0091] In addition, a control link is established between the gNB200S and Layer 1 and / or Layer 2 (L1 / L2) of the NCR device 500A (NCR-MT520A). An RRC connection is established between the gNB200S and the RRC of the NCR device 500A (NCR-MT520A). The RRC of the NCR device 500A (NCR-MT520A) transmits and receives RRC messages related to handover with the gNB200S via the RRC connection. The NCR device 500A (NCR-MT520A) switches the RRC connection from the source gNB200S to the target gNB200T through handover.

[0092] (1.9.1) First operation pattern for load balancing In this operation pattern, the source gNB200S notifies the target gNB200T that it is a handover request from the NCR device 500A. The source gNB200S may also notify the target gNB200T that it is a load balancing handover. Furthermore, the source gNB200S may notify the target gNB200T of the number of UEs 100 to be subsequently handed over to the NCR device 500A. Such notification allows the target gNB200T to appropriately determine whether to accept the handover request from the source gNB200S.

[0093] FIG. 16 is a diagram showing an example of the operation of the mobile communication system 1 according to this operation pattern.

[0094] In step S101, the source gNB 200S decides to hand over the NCR device 500A. The source gNB 200S may decide to hand over the NCR device 500A in response to the discovery of a cell with better wireless quality based on a measurement report message from the NCR device 500A (NCR-MT 520A). The source gNB 200S may decide to hand over the NCR device 500A in response to the increase in its own load and the need for load balancing.

[0095] In step S102, the source gNB200S transmits a handover request message to the target gNB200T over the Xn interface, requesting handover of the NCR device 500A from the source cell of the source gNB200S to the target cell of the target gNB200T. The target gNB200T receives the handover request message. The handover request message includes at least one of the following information (a1) to (c1):

[0096] (a1) Information indicating a handover of the NCR device 500A (i.e., NCR indication): This is flag information indicating that the target of the handover is the NCR device 500A. This allows the target gNB 200T to perform control such as preferentially accepting the handover of the NCR device 500A over the handover of the UE 100. This flag information is defined separately from information indicating that the target of the handover is an IAB (Integrated Access and Backhaul) node. As described below, when the relay device is a RIS device, the flag information may be information indicating that the target of the handover is a RIS device. Note that the flag information may be information indicating that the target NCR device or RIS device has been authenticated.

[0097] (b1) Information indicating that the NCR device 500A is to be handed over to distribute the load of the source gNB200S (source cell) to the target gNB200T (target cell): If the purpose of the handover is load distribution, the source gNB200S includes information indicating that the load distribution is related to the NCR device 500A in the handover request. This allows the target gNB200T to make a decision to accept the handover taking into account the purpose of the handover. If the purpose of the handover is to involve the movement of an NCR device or a RIS device, the information in (b1) may be information indicating that the device is moving, or information indicating that the device has mobility (is mobile).

[0098] (c1) Information indicating the number of UEs 100 to be handed over in connection with the handover of the NCR device 500A: This information indicates, for example, the number of UEs 100 connected to the source gNB 200S via the NCR device 500A. The source gNB 200S may identify the number of UEs 100 communicating using the same SSB as the NCR device 500A as the number of UEs 100 to be handed over in connection with the handover of the NCR device 500A. This information may also be information on the throughput (and / or amount of radio resources) required to accommodate the UEs 100.

[0099] In step S103, the target gNB200T determines whether to accept the handover request of step S102. That is, the target gNB200T that has received the handover request message determines whether to permit the handover of the NCR device 500A based on the information contained in the handover request message. The target gNB200T may determine to accept the handover request if it has the ability to control the NCR device 500A and / or if it can maintain its own load below a certain level even if the NCR device 500A and UE100 are handed over to it. Here, the explanation will proceed assuming that the target gNB200T has determined to accept (permit) the handover request.

[0100] In step S104, the target gNB200T transmits a Handover Request Acknowledge message, which is a response message indicating that the handover is permitted, to the source gNB200S over the Xn interface. The source gNB200S receives the Handover Request Acknowledge message. The target gNB200T may include in the Handover Request Acknowledge message an instruction as to whether the NCR device 500A (NCR-MT520A) continues to operate according to the control of the source gNB200S during the handover. The instruction may be an instruction as to whether to continue to operate according to the current control after the handover.

[0101] In step S105, the source gNB200S transmits an RRC Reconfiguration message including information in the Handover Request Acknowledge message, i.e., a handover command (Handover Command) instructing a handover to the target gNB200T (target cell) to the NCR device 500A (NCR-MT 520A). The NCR device 500A (NCR-MT 520A) receives the handover command. The handover command may include the instruction included in the Handover Request Acknowledge message in step S104.

[0102] In step S106, in response to receiving the handover command in step S105, the NCR device 500A (NCR-MT 520A) starts accessing the target gNB 200T (target cell) specified in the handover command. The NCR device 500A (NCR-MT 520A) may transmit an RRC Reconfiguration Complete message to the target gNB 200T (target cell) during this access. The NCR device 500A (NCR-MT 520A) may continue to control the NCR device 500A (NCR-Fwd 510A) during handover in accordance with the instructions included in the handover command.

[0103] (1.9.2) Second Operation Pattern of Load Balancing As described above, when control of the NCR device 500A is transferred to another cell (target cell) due to handover, it is desirable that the other cell be able to control the NCR device 500A more quickly and accurately after the handover. In this operation pattern, the source gNB 200S notifies the target gNB 200T of control information and / or context information of the NCR device 500A. That is, in the second operation pattern, the handover request message includes at least one of control information used to control the NCR device 500A and context information of the NCR device 500A. This allows the target gNB 200T to control the NCR device 500A more quickly and accurately after the handover. Note that this operation pattern may be implemented in combination with the first operation pattern described above.

[0104] 17 is a diagram showing an example of operation of the mobile communication system 1 according to this operation pattern. Description of operations that overlap with the operations of the first operation pattern described above will be omitted.

[0105] In step S201, the source gNB200S decides to handover the NCR device 500A.

[0106] In step S202, the source gNB200S transmits a handover request message to the target gNB200T over the Xn interface, requesting handover of the NCR device 500A from the source cell of the source gNB200S to the target cell of the target gNB200T. The target gNB200T receives the handover request message. The handover request message includes at least one of the following information (a2) to (c2):

[0107] (a2) Control information (beam information) indicating the beam to be applied to the NCR device 500A: The control information may include the SSB index that the target gNB 200T applies to the NCR device 500A. In this case, the target gNB 200T may infer the optimal beam to be applied to the NCR device 500A, for example, from the SSB index and a measurement report message of the UE 100 currently located within the target gNB 200T. The control information may include the SSB index to be applied by the target cell. The source gNB 200S may identify the SSB index, for example, from a measurement report message of the NCR device 500A (NCR-MT 520A).

[0108] (b2) Control information for controlling the operation of the NCR device 500A: This control information includes NCR control information corresponding to the above-mentioned NCR control signal, for example, at least one of the weight, (output) beam angle, and transmission output (gain) applied by the source gNB 200S to the NCR device 500A. The control information may also include control time information indicating the time (timing) at which this NCR control information is applied. For example, the target gNB 200T may estimate that many UEs 100 are present in the direction of the most frequently used beam control setting, and use this as a reference when controlling the NCR device 500A.

[0109] (c2) Context information of the NCR device 500A: The context information includes, for example, information indicating that the operation of the NCR device 500A has been authorized by the network (core network, radio access network, and / or network monitoring device).

[0110] In step S203, the target gNB200T determines whether to accept the handover request of step S102. Here, the description will proceed assuming that the target gNB200T has determined to accept (permit) the handover request.

[0111] The operations from step S204 to step S206 are the same as those in the first operation pattern described above.

[0112] In step S207, after the NCR device 500A connects to the target gNB200T's cell (target cell), the target gNB200T performs communication control for the NCR device 500A based on the information contained in the handover request message of step S202.

[0113] (1.10) Connection Control of Relay Device to Desired Cell FIG. 18 is a diagram for explaining connection control of the NCR device 500A to the desired cell.

[0114] The NCR device 500A is assumed to be installed to expand the coverage area of ​​the base station device 200, and it is assumed that the NCR device 500A is installed based on a station placement design. In this case, the cell to which the NCR device 500A is connected is predetermined. Hereinafter, this cell is also referred to as a "desired cell." That is, which cell the NCR device 500A (specifically, the NCR-MT 520A) connects to and is controlled is determined based on the station placement design. In the illustrated example, cell a of the gNB 200a is the desired cell, and neighboring cell b of this cell is a cell that is not a desired cell (also referred to as a "non-desired cell"). Note that, although an example is shown in which cell b is the cell of the gNB 200b, cell b may also be the cell of the gNB 200a.

[0115] Which cell is set as the desired cell depends on the policy of the network operator. For example, a cell that satisfies at least one of the following conditions may be set as the desired cell: A cell that supports the NCR device 500A, A cell that has a coverage hole (dead zone) or is adjacent to a coverage hole, A cell that can accommodate a small number of UEs during normal operation.

[0116] Furthermore, it is assumed that the NCR device 500A is installed in a location where the wireless environment is poor (or complex), such as a cell edge, for the purpose of coverage extension. In the illustrated example, the NCR device 500A is installed to perform coverage extension to a target area outside of cells a and b. Specifically, the NCR device 500A is installed in an area where cells a and b overlap, i.e., in the cell edge areas of cells a and b. In this example, since cell a is the desired cell, it is assumed that the NCR device 500A connects to cell a to extend the coverage of cell a.

[0117] Here, when the NCR-MT 520A of the NCR device 500A is in an RRC idle state (or an RRC inactive state), the NCR-MT 520A may perform cell selection or cell reselection. In cell selection, the NCR-MT 520A selects a cell (also referred to as a "suitable cell") that meets a predetermined quality standard as a serving cell, for example, when powered on. In cell reselection, the NCR-MT 520A selects, for example, a cell with the best wireless quality (also referred to as a "best cell") as a new serving cell.

[0118] In such cell selection or cell reselection, the NCR-MT 520A does not determine whether the candidate cell is a desired cell, so the NCR-MT 520A may select (or reselect; the same applies below) an undesired cell. For example, the NCR-MT 520A may select a cell other than the desired cell by cell selection upon initial connection (e.g., when powered on), upon RRC re-establishment, or upon redirection. Furthermore, when a radio link failure (RLF) or an RRC release occurs after cell selection, the NCR-MT 520A may select an undesired cell that is the best cell by cell reselection. For example, if the radio quality (e.g., RSRP) of the desired cell is poor, such an undesired cell is more likely to be selected.

[0119] When the NCR-MT 520A selects an undesired cell and connects to the undesired cell, the undesired cell is expected to move the NCR-MT 520A (NCR device 500A) to the desired cell. For example, the undesired cell may transmit a redirection instruction to the NCR-MT 520A, causing the NCR-MT 520A to transition to an RRC idle state, select (camp) a desired cell, and connect the NCR-MT 520A to the desired cell. Alternatively, the undesired cell may transmit a handover instruction to the NCR-MT 520A, causing the NCR-MT 520A to hand over to the desired cell while remaining in an RRC connected state. The handover operation is the same as that described above. However, if the purpose of the handover is to move the NCR device 500A to a desired cell, the source gNB may include information indicating that the move is the purpose in the handover request. The target gNB may accept the handover request based on the information.

[0120] However, there is a risk that the non-desired cell may not know the desired cell of the NCR device 500A (NCR-MT 520A). The network operator, specifically, the OAM (Operation Administration and Maintenance) can configure all gNBs 200, but as the number of NCR devices 500A increases, such work becomes difficult. Therefore, in the following embodiment, a connection control mechanism that automatically (or effortlessly) enables the NCR device 500A to be connected to the desired cell will be described.

[0121] Specifically, the NCR device 500A, which performs relay transmission to relay radio signals transmitted between the network 5 and the UE 100, connects to a cell selected by cell selection or cell reselection and performs relay transmission. In the connection control according to this embodiment, cell information (also referred to as "desired cell information") specifying a desired cell determined as a connection destination of the NCR device 500A is communicated between the network 5 and the NCR device 500A or between entities within the network 5. This allows an appropriate device / entity in the mobile communication system 1 to acquire information about the desired cell, making it easy to connect the NCR device 500A to the desired cell.

[0122] For example, the NCR device 500A includes an NCR-Fwd 510A (repeater) that performs relay transmission to relay radio signals transmitted between the network 5 and the UE 100, and an NCR-MT 520A (control terminal) that connects to a cell selected by cell selection or cell reselection and controls relay transmission. The NCR-MT 520A communicates with the network 5 cell information that identifies a desired cell that is determined as a connection destination for the device itself.

[0123] A network device (e.g., gNB200 or AMF300A) provided in the network 5 has a communication unit (e.g., backhaul communication unit 240) that communicates with the NCR device 500A or another network device (e.g., gNB200 or AMF300A). The communication unit communicates cell information that identifies a desired cell defined as a connection destination of the NCR device 500A with the NCR device 500A or another network device.

[0124] (1.10.1) First operation pattern of connection control In this operation pattern, the NCR device 500A (NCR-MT 520A) transmits cell information to the cell to which the NCR device 500A is connected. This allows the gNB 200 managing the cell to identify the desired cell of the NCR device 500A and facilitates moving (and connecting) the NCR device 500A to the desired cell. For example, when the NCR device 500A connects to an undesired cell, it notifies the gNB 200 managing the undesired cell of the cell ID of the desired cell.

[0125] FIG. 19 is a diagram showing an example of operation of the mobile communication system 1 according to this operation pattern.

[0126] In step S301, the NCR-MT 520A holds desired cell information in advance. The desired cell information may be set in the NCR-MT 520A in advance by OAM. The desired cell information may be set in advance in the USIM (Universal Subscriber Identity Module Card) of the NCR-MT 520A. The NCR-MT 520A may automatically recognize the desired cell and hold the desired cell information, as in the second operation pattern described below.

[0127] The desired cell information includes at least one of a cell ID (desired cell ID), a gNB ID, and a frequency identifier (ARFCN: Absolute Radio-Frequency Channel Number) for the desired cell. The cell ID may be an NCGI (NR Cell Global Identifier) ​​and / or a PCI (Physical Cell Identifier) ​​(hereinafter the same).

[0128] In step S302, the NCR-MT 520A connects to the current serving cell. The NCR-MT 520A may establish a connection from an RRC idle state (or an RRC inactive state). The NCR-MT 520A may access and connect via handover. Here, the NCR-MT 520A may check the cell ID of the cell.

[0129] In step S303, the NCR-MT 520A may determine whether the current serving cell is a desired cell based on the desired cell information it holds. The process of step S304, which will be described later, may be executed if the determination result of step S303 is YES.

[0130] In step S304, the NCR-MT 520A transmits a message including information about the desired cell to the current serving cell. The message may be an existing RRC message such as a UE Assistance Information message, or a newly defined message (e.g., an NCR-MT Information message).

[0131] In step S305, gNB200 may determine whether its own cell (NCR-MT520A's serving cell) is a desired cell based on desired cell information from NCR-MT520A.

[0132] If the own cell (NCR-MT 520A's serving cell) is not the desired cell (step S305: NO), in step S306, the gNB 200 performs handover or redirection processing to move the NCR device 500A to the desired cell based on the desired cell information from the NCR-MT 520A. Specific examples of redirection will be described later. The NCR-MT 520A connects to the desired cell by handover or redirection to the desired cell.

[0133] (1.10.2) Second Operation Pattern of Connection Control This operation pattern is an operation pattern in which the NCR-MT 520A autonomously recognizes a desired cell. Specifically, when the NCR-MT 520A (NCR device 500A) receives setting information related to relay transmission (also referred to as "NCR setting") from any cell in the network 5, it regards the cell that transmitted the setting information as the desired cell. In other words, the NCR-MT 520A regards the cell that last performed NCR setting for itself as the desired cell. Thus, according to this operation pattern, the NCR-MT 520A can autonomously recognize a desired cell, under the assumption that non-desired cells do not perform NCR setting for the NCR-MT 520A.

[0134] 20 is a diagram showing an example of operation of the mobile communication system 1 according to this operation pattern. Description of operations that overlap with the above-described operation patterns will be omitted.

[0135] In step S401, the gNB200 maintains a desired cell list indicating the desired cell information of each NCR device 500A (NCR-MT520A). The desired cell list may be a list consisting of the IDs of each NCR device 500A (NCR-MT520A) whose own cell is the desired cell. The ID of the NCR device 500A (NCR-MT520A) may be the existing NG-5G-S-TMSI (Temporary Mobile Subscriber Identity) or IMSI (International Mobile Subscriber Identity). The ID may be a newly defined ID dedicated to the NCR device. The desired cell list may be set in the gNB200 by OAM. Alternatively, the desired cell list may be notified to gNB200 by AMF300A and set, as in the third operation pattern described below.

[0136] In step S402, the NCR-MT 520A connects to the current serving cell.

[0137] In step S403, gNB200 may determine whether its own cell (the serving cell of NCR-MT520A) is a desired cell based on the desired cell list it holds.

[0138] If the own cell (the serving cell of the NCR-MT 520A) is the desired cell (step S403: YES), in step S404, the gNB 200 performs NCR configuration on the NCR-MT 520A. The gNB 200 may also control the NCR device 500A using the above-mentioned Side Control Information.

[0139] In step S405, the NCR-MT 520A regards the current serving cell as a desired cell and stores the desired cell information. After that, if the NCR-MT 520A connects to a non-desired cell due to a deterioration in wireless conditions or the like, it notifies the non-desired cell of the desired cell information (see the first operation pattern described above).

[0140] In this operation example, it can be considered that the gNB200 implicitly notifies the NCR-MT520A that its own cell is a desired cell by the NCR setting information. However, the gNB200 may explicitly notify the NCR-MT520A that its own cell is a desired cell. For example, the gNB200 may transmit a desired cell notification to the NCR-MT520A indicating that its own cell is a desired cell.

[0141] Also, if step S403 is NO, gNB200 may notify NCR-MT520A that its own cell is not a desired cell. For example, gNB200 may send an undesired cell notification to NCR-MT520A indicating that its own cell is not a desired cell. In this case, NCR-MT520A does not perform the processing of step S405.

[0142] (1.10.3) Third Operation Pattern of Connection Control In this operation pattern, it is assumed that the AMF300A, which is a mobility management device, holds and manages the correspondence between the NCR device 500A and the desired cell (i.e., a desired cell list). The correspondence may be set by the OAM, or the correspondence information may be provided to the AMF300A from another CN function (NF: Network Function). Under this premise, the AMF300A transmits desired cell information to the gNB200. That is, each gNB200 under the AMF300A is notified of the desired cell information from the AMF300A. This eliminates the need to manually set the desired cell information in the NCR device 500A and / or each gNB200.

[0143] 21 is a diagram showing an example of operation of the mobile communication system 1 according to this operation pattern. Description of operations that overlap with the above-described operation patterns will be omitted.

[0144] In step S501, NCR-MT520A connects to the cell of gNB200 and establishes an RRC connection.

[0145] In step S502, the NCR-MT 520A transmits a NAS message for a registration request to the AMF 300A. The NAS message may include the ID of the NCR device 500A (NCR-MT 520A).

[0146] In step S503, the AMF 300A performs authentication processing of the NCR-MT 520A (NCR device 500A) based on the registration request. If authentication of the NCR-MT 520A is successful, the AMF 300A derives the desired cell of the NCR-MT 520A based on the desired cell list held therein.

[0147] In step S504, AMF300A transmits a UE Context Setup message (or a UE Context Modification message), which is an NG-AP (Application Protocol) message, to gNB200. The message includes desired cell information in the UE Context of NCR-MT520A. gNB200 checks the desired cell information of the UE Context.

[0148] In step S505, gNB200 determines whether its own cell (the serving cell of NCR-MT520A) is a desired cell based on the desired cell information. If its own cell is a desired cell (step S505: YES), in step S507, gNB200 performs NCR setting on NCR-MT520A (see the second operation pattern described above).

[0149] On the other hand, if the own cell is not the desired cell (step S505: NO), in step S506, the gNB200 moves and connects the NCR-MT520A (NCR device 500A) to the desired cell by handover or redirection. Alternatively, the gNB200 may release the RRC connection of the NCR-MT520A.

[0150] (1.10.4) Fourth Operation Pattern of Connection Control In this operation pattern, as in the second and third operation patterns described above, it is assumed that the gNB 200 knows the desired cell of the NCR device 500A. Under this assumption, desired cell information is exchanged in advance between the gNBs 200. For example, the gNB 200 transmits to an adjacent gNB association information that associates the ID of the NCR device 500A it manages with the desired cell ID. Note that, assuming that the NCR-MT 520A (NCR device 500A) does not move, information about the NCR device 500A only needs to be exchanged between adjacent gNBs, and information exchange may be performed via the Xn interface, which is an interface between base stations.

[0151] 22 is a diagram showing an example of operation of the mobile communication system 1 according to this operation pattern. Description of operations that overlap with the above-described operation patterns will be omitted.

[0152] In step S601, gNB200a transmits an Xn message to adjacent gNB200b, which includes correspondence information between the ID of the NCR device 500A managed by itself and the desired cell information of the NCR device 500A.

[0153] In step S602, the gNB 200b that has received the association information stores the association information. When the NCR device 500A accesses the gNB 200b, the gNB 200b may refer to the association information and move and connect the NCR device 500A to a desired cell.

[0154] This operation example is an example of information exchange between adjacent gNB200. However, as in the third operation pattern described above, if AMF300A knows the desired cell of NCR device 500A, desired cell information may be notified in advance to gNB200 in the area managed by AMF300A. That is, AMF300A notifies each gNB200 in the area managed by AMF300A of association information between the desired cell and NCR device 500A. Figure 23 is a diagram showing another operation example of the mobile communication system 1 according to this operation pattern.

[0155] In steps S631 and S632, AMF300A transmits an NG message including association information that associates the NCR device 500A it manages with information about the desired cell of the NCR device 500A to each gNB200 it manages (connects to).

[0156] Each gNB 200 that receives the association information stores the association information. When the NCR device 500A accesses itself, each gNB 200 may refer to the association information and move and connect the NCR device 500A to a desired cell.

[0157] (1.10.5) Fifth Operation Pattern of Connection Control In each of the above operation patterns, an example has been described in which the gNB200 issues a redirection instruction to the NCR-MT520A. By the gNB200 sending an RRC Release message containing redirection information to the NCR-MT520A as a redirection instruction, the NCR-MT520A transitions to the RRC idle state, camps on another cell, and connects to that other cell. However, with the current redirection specification, the redirection destination can only be specified on a frequency basis, and the redirection destination cannot be specified on a cell-by-cell basis. In this operation pattern, the redirection destination can be specified on a cell-by-cell basis, allowing the NCR-MT520A to move and connect to the desired cell. That is, in this operation pattern, NCR-MT520A (NCR device 500A) receives a redirection instruction including a desired cell ID from one of the cells in network 5, and upon receiving the redirection instruction, transitions to an RRC idle state and selects the desired cell indicated by the desired cell ID.

[0158] 24 is a diagram showing an example of operation of the mobile communication system 1 according to this operation pattern. Description of operations that overlap with the above-described operation patterns will be omitted.

[0159] In step S701, NCR-MT520A connects to an undesired cell, which is the cell of gNB200b.

[0160] In step S702, gNB200b determines whether its own cell (the serving cell of NCR-MT520A) is a desired cell, in the same manner as the first and third operation patterns described above, and if its own cell is not the desired cell, derives and identifies the desired cell.

[0161] In step S703, gNB200b transmits a redirection instruction to NCR-MT520A. The redirection instruction may be an RRC Release message including redirectedCarrierInfo, an existing information element indicating the redirection destination frequency, or a new information element for redirection of NCR device 500A. In this operation pattern, gNB200b includes the cell ID of the desired cell (desired cell ID) in the RRC Release message.

[0162] In step S704, in response to receiving the redirection instruction, NCR-MT 520A transitions to an RRC idle state.

[0163] In step S705, the NCR-MT 520A selects a cell (desired cell) with the cell ID specified in the redirection instruction and camps on that cell. Here, the NCR-MT 520A may select that cell if it satisfies a predetermined quality criterion (i.e., a suitable cell). The predetermined quality criterion may be a quality criterion (S-criterion) specified exclusively for the NCR-MT 520A. The quality criterion may be a criterion that is more relaxed than a normal quality criterion, and a parameter (e.g., a wireless quality threshold) may be set in the SIB or the like.

[0164] In step S706, the NCR-MT 520A connects to the desired cell, which is the redirection destination cell, and establishes an RRC connection.

[0165] If the NCR-MT 520A is unable to select a desired cell, i.e., if the cell (desired cell) with the cell ID specified in the redirection instruction is not a suitable cell, it may select an appropriate suitable cell (non-desired cell) and camp on it. In this case, the NCR-MT 520A may store the fact that it was unable to select a desired cell as log information. The log information includes the cell ID of the desired cell. When the NCR-MT 520A connects to a certain cell, it may transmit a report including the log information to the cell. Such log information may be used for optimization of network operation.

[0166] (1.10.6) Sixth Operation Pattern of Connection Control In this operation pattern, the NCR-MT 520A receives from the network 5 a list of cells that are permitted as connection destinations or camping destinations for the NCR device 500A (also referred to as an "Allowed cell list") and / or a list of cells that are prohibited as connection destinations or camping destinations for the NCR device 500A (also referred to as a "Block cell list"). This list is an example of cell information for identifying a desired cell. The NCR-MT 520A can connect to the desired cell based on this list.

[0167] 25 is a diagram showing an example of operation of the mobile communication system 1 according to this operation pattern. Description of operations that overlap with the above-described operation patterns will be omitted.

[0168] In step S801, the NCR-MT 520A connects to a cell of the gNB 200b. The cell may be a non-desired cell. The NCR-MT 520A may not recognize the desired cell.

[0169] In step S802, gNB200b acquires desired cell information. For example, gNB200b may acquire information on the desired cell (or cells) of NCR-MT520A from AMF300A in the same manner as in the third operation pattern described above. Alternatively, gNB200b may have the information set by OAM.

[0170] In step S803, the NCR-MT 520A (NCR device 500A) may transmit capability information of its own NCR-Fwd 510A to the gNB 200. The capability information may include information on the frequencies supported by the NCR-Fwd 510A. The gNB 200b may generate (a list of) cell IDs to which the NCR-MT 520A should camp / connect (or can camp / connect) from the capability information.

[0171] In step S804, the gNB 200b transmits the Allowed cell list and / or the Block cell list to the NCR-MT 520A. The NCR-MT 520A stores the received list.

[0172] In step S805, gNB200b transitions NCR-MT520A to an RRC idle state (or an RRC inactive state). NCR-MT520A retains the list even after transitioning to the RRC idle state (or an RRC inactive state).

[0173] In step S806, the NCR-MT 520A may perform cell reselection by regarding the cell (frequency) included in the allowed cell list as the highest priority. The NCR-MT 520A may perform cell reselection by regarding the cell (frequency) included in the blocked cell list as the lowest priority. As a result, the NCR-MT 520A (re)selects a desired cell according to the list.

[0174] In step S807, NCR-MT 520A connects to the desired cell and establishes an RRC connection.

[0175] (2) Second Embodiment Next, a second embodiment will be described, focusing on differences from the above-described embodiments. As shown in Fig. 26, the relay device according to the second embodiment is a Reconfigurable Intelligent Surface (RIS) device 500B that changes the propagation direction of an incident radio wave (wireless signal) by reflection or refraction. The term "NCR" in the above-described embodiment can be read as "RIS."

[0176] RIS is a type of repeater (hereinafter also referred to as "RIS-Fwd") that can perform beamforming (directivity control) similar to NCR by changing the properties of a metamaterial. In the case of RIS, the range (distance) of the beam may also be changed by controlling the reflection direction and / or refraction direction of each unit element. For example, the RIS may be configured to control the reflection direction and / or refraction direction of each unit element and to focus (direct the beam) on a nearby UE or a distant UE.

[0177] The RIS device 500B has a new UE (hereinafter referred to as "RIS-MT") 520B, which is a control terminal for controlling the RIS-Fwd 510B. The RIS-MT 520B establishes a wireless connection with the gNB 200 and performs wireless communication with the gNB 200, thereby controlling the RIS-Fwd 510B in cooperation with the gNB 200. The RIS-Fwd 510B may be a reflective RIS. Such a RIS-Fwd 510B changes the propagation direction of incident radio waves by reflecting the radio waves. Here, the reflection angle of the radio waves is variably settable. The RIS-Fwd 510B reflects radio waves incident from the gNB 200 toward the UE 100. The RIS-Fwd 510B may be a transparent RIS. Such a RIS-Fwd 510B changes the propagation direction of the radio waves by refracting the incident radio waves. Here, the refraction angle of the radio wave can be variably set.

[0178] FIG. 27 is a diagram showing an example configuration of a RIS-Fwd (repeater) 510B and a RIS-MT (control terminal) 520B according to this embodiment. The RIS-MT 520B has a receiver 521, a transmitter 522, and a controller 523. This configuration is similar to that of the above-described embodiment. The RIS-Fwd 510B has a RIS 511B and a RIS controller 512B. The RIS 511B is a metasurface constructed using a metamaterial. For example, the RIS 511B is constructed by arranging structures that are very small relative to the wavelength of radio waves in an array. By making the structures different shapes depending on the placement location, it is possible to arbitrarily design the direction and / or beam shape of the reflected waves. The RIS 511B may be a transparent dynamic metasurface. The RIS 511B may be configured by overlaying a transparent glass substrate on a transparent metasurface substrate on which a large number of small structures are regularly arranged, and by slightly moving the overlaid glass substrate, it may be possible to dynamically control three patterns: a mode that transmits incident radio waves, a mode that transmits some of the radio waves and reflects some of them, and a mode that reflects all of the radio waves. The RIS control unit 512B controls the RIS 511B in response to a RIS control signal from the control unit 523 of the RIS-MT 520B. The RIS control unit 512B may include at least one processor and at least one actuator. The processor decodes the RIS control signal from the control unit 523 of the RIS-MT 520B and drives the actuator in response to the RIS control signal.

[0179] (3) Other Embodiments In the above-described connection control to the desired cell, the NCR-MT 520A may control the selection (or reselection) of the desired cell in the cell selection or cell reselection process. For example, the NCR-MT 520A that holds desired cell information may perform cell selection or cell reselection only for the desired cell based on the desired cell information. In the cell selection or cell reselection process, the NCR-MT 520A may control the selection of the desired cell by, for example, applying an infinite offset to the measurement result of the radio quality measured for the desired cell.

[0180] In the above embodiment, an example has been described in which the relay device that performs relay transmission is the NCR device 500A or the RIS device 500B. However, the relay device that performs relay transmission is not limited to the NCR device 500A or the RIS device 500B, and may be an IAB (Integrated Access and Backhaul) node defined in the 3GPP technical specifications.

[0181] The above-described operational flows are not limited to being implemented independently, but can also be implemented by combining two or more operational flows. For example, some steps of one operational flow may be added to another operational flow, or some steps of one operational flow may be replaced with some steps of another operational flow. In each flow, it is not necessary to execute all steps, and only some steps may be executed.

[0182] Also, the term "network node" primarily refers to a base station, but may also refer to a device in the core network or part of a base station (CU, DU, or RU).

[0183] In the above embodiment, an example in which the base station is an NR base station (gNB) has been described, but the base station may be an LTE base station (eNB). The base station may also be a relay node such as an IAB node. The base station may also be a Distributed Unit (DU) of the IAB node. The UE 100 may also be a Mobile Termination (MT) of the IAB node.

[0184] A program may be provided that causes a computer to execute each process performed by the communication device according to the above-described embodiment, for example, the UE100 (NCR-MT520A, RIS-MT520B) or the gNB200. The program may be recorded on a computer-readable medium. Using a computer-readable medium, the program can be installed on a computer. Here, the computer-readable medium on which the program is recorded may be a non-transitory recording medium. The non-transitory recording medium is not particularly limited, and may be, for example, a recording medium such as a CD-ROM or a DVD-ROM. Furthermore, circuits that execute each process performed by the UE100 or the gNB200 may be integrated, and at least a portion of the UE100 or the gNB200 may be configured as a semiconductor integrated circuit (chip set, SoC: System on a chip).

[0185] As used in this disclosure, the terms "based on" and "depending on / in response to" do not mean "based only on" or "depending only on," unless expressly stated otherwise. The term "based on" means both "based only on" and "based at least in part on." Similarly, the term "depending on" means both "depending only on" and "depending at least in part on." The terms "include," "comprise," and variations thereof do not mean including only the listed items, but may mean including only the listed items or may include additional items in addition to the listed items. Additionally, the term "or," as used in this disclosure, is not intended to mean an exclusive or. Furthermore, any reference to elements using designations such as "first," "second," etc., as used in this disclosure does not generally limit the quantity or order of those elements. These designations may be used herein as a convenient method of distinguishing between two or more elements. Thus, a reference to a first and a second element does not imply that only two elements may be employed therein or that the first element must precede the second element in some way. In this disclosure, where articles are added by translation, such as a, an, and the in English, these articles shall include the plural unless the context clearly indicates otherwise.

[0186] The above describes the embodiments in detail with reference to the drawings, but the specific configuration is not limited to that described above, and various design changes can be made within the scope that does not deviate from the gist of the invention.

[0187] This application claims priority to U.S. Provisional Application No. 63 / 421,779 (filed November 2, 2022), the entire contents of which are incorporated herein by reference.

[0188] (4) Supplementary Note 1 The following is a supplementary note regarding the features of the above-described embodiment.

[0189] (Supplementary Note 1) A mobile communication system comprising: a network; and a relay device that performs relay transmission to relay radio signals transmitted between the network and a user device, wherein the relay device connects to a cell selected by cell selection or cell reselection to perform the relay transmission; and between the network and the relay device, or between entities within the network, cell information that identifies a desired cell that is determined as a connection destination of the relay device is communicated.

[0190] (Supplementary Note 2) The mobile communication system according to Supplementary Note 1, wherein the relay device transmits the cell information to a cell to which the relay device is connected.

[0191] (Supplementary Note 3) The mobile communication system according to Supplementary Note 1 or 2, wherein the relay device receives setting information related to the relay transmission from any one of cells in the network, and regards the cell that has transmitted the setting information as the desired cell.

[0192] (Supplementary Note 4) The mobile communication system according to any one of Supplementary Notes 1 to 3, wherein the network includes a mobility management device and a network node, and the mobility management device transmits the cell information to the network node.

[0193] (Supplementary Note 5) The mobile communication system according to any one of Supplementary Notes 1 to 4, wherein the network includes a first network node and a second network node, and the first network node transmits the cell information to the second network node.

[0194] (Supplementary Note 6) The mobile communication system according to Supplementary Note 4, wherein the mobility management device transmits, to the network node, association information that associates identification information indicating the relay device with the cell information.

[0195] (Supplementary Note 7) The mobile communication system according to any one of Supplementary Notes 1 to 6, wherein the relay device receives a redirection instruction including the cell information from any one of the cells of the network, and transitions to a radio resource control (RRC) idle state in response to receiving the redirection instruction, and selects the desired cell indicated by the cell information.

[0196] (Supplementary Note 8) The mobile communication system according to any one of Supplementary Notes 1 to 7, wherein the cell information includes a list of cells that are permitted as a connection destination or camping destination for the relay device and / or a list of cells that are prohibited as a connection destination or camping destination for the relay device, and the relay device receives the list from any cell of the network.

[0197] (Supplementary Note 9) The mobile communication system according to any one of Supplementary Notes 1 to 8, wherein the relay device is a device that changes a propagation state of a radio signal transmitted between the network and the user device without demodulating or modulating the radio signal.

[0198] (Supplementary Note 10) A relay device used in a mobile communication system, comprising: a repeater that performs relay transmission to relay a radio signal transmitted between a network and a user device; and a control terminal that connects to a cell selected by cell selection or cell reselection and controls the relay transmission, wherein the control terminal communicates cell information that identifies a desired cell determined as a connection destination of the relay device with the network.

[0199] (Supplementary Note 11) A network device provided in a network of a mobile communication system, comprising: a communication unit that communicates with a relay device or another network device, wherein the relay device is a device that performs relay transmission to relay a radio signal transmitted between the network and a user device, and the communication unit communicates cell information that identifies a desired cell that is determined as a connection destination of the relay device with the relay device or the other network device.

[0200] (5) Supplementary Note 2 Introduction In RAN#97e, a new work item on Network Controlled Repeaters (NCRs) was approved. In RAN2#119bis-e, the first discussion on NCRs took place, and the following agreement was reached:

[0201] Agreements RAN2 confirms that NCR-MT will use RRC signaling to receive side control information. How the side control information itself is transmitted (via RRC, DCI, or MAC CE) is left to RAN1 (RAN2 can discuss RAN1's ​​initial decision and reconsider if necessary). NCR-MT will support RRC Connected and RRC Idle states, and support for RRC Inactive state is something that requires further study (e.g., whether to support it as an option or not). NCR-MT will support SRB0 / 1 / 2, and DRB is optional. The maximum number of DRBs requires further study. NCR-MT shall ignore cellBarred, cellReservedForOperatorUse, cellReservedForFutureUse, cellReservedForOtherUse, intraFreqReselection indication and UAC configuration when broadcasted in the system information. - RRM functions supported by NCR-MR: - Cell selection is mandatory - Cell reselection, RLM, BFD, BFR require further study.

[0202] In this appendix, further consideration of the RAN2 issue for NCR is discussed.

[0203] Discussion Support for RRC Inactive RAN2 has postponed the decision on whether to support the RRC Inactive state of NCR as an option. NCR-MT supports RRC Connected and RRC Idle states, and the RRC Inactive state is something that needs further study (whether to support it as an option or not).

[0204] Considering that the NCR is a network node and generally has no interest in its power supply, RRC inactivity is not very useful because it was introduced primarily to save UE power. Regarding IAB-MT, RRC inactivity was also confirmed to be unhelpful, but it was supported without optimization. This was primarily intended to minimize standardization efforts. Compared to IAB, NCR is expected to be simpler and less complex. Therefore, supporting unnecessary features, even if optional, should be avoided as much as possible.

[0205] For UE, RRC inactivity is mandatory to be supported by capability signaling, i.e., NCR-MT does not send the corresponding capability bit, therefore, NCR should not support RRC inactivity.

[0206] Proposal 1: RAN2 should agree that NCR-MT does not support the RRC inactive state.

[0207] Number of supported DRBs RAN2 has agreed that NCR will support DRBs as an option, but it has not yet decided how many DRBs it can support. NCR-MT supports SRB0 / 1 / 2, and DRBs are optional. The maximum number of DRBs needs further consideration.

[0208] Referring to the capabilities of RedCap UE, the maximum number of supported DRBs is 8, which is one possibility. On the other hand, since DRBs are mainly intended for transporting OAM traffic, one or two DRBs can meet the minimum requirements.

[0209] Proposal 2: RAN2 should assume that the maximum number of DRBs for NCR-MT is 2-8.

[0210] Support for cell reselection, RLM, BFD, BFR RAN2 agreed that NCR will support cell reselection, but cell reselection, RLM, BFD, BFR require further study. RRM functions supported by NCR-MR: Cell selection is mandatory. Cell reselection, RLM, BFD, BFR require further study.

[0211] NCR aims to extend the coverage of FR2, so control links, backhaul links, and access links may be operated in FR2. In FR2, the radio wave conditions change significantly, making signals susceptible to interference such as time-dependent interference.

[0212] Regarding RLM, if the control link is poor, the gNB cannot control the NCR, so the NCR-MT needs to periodically monitor the quality of the control link. Furthermore, if the backhaul link and the access link are on the same channel, it is equally important to monitor the quality of these links.

[0213] For BFD and BFR, it is considered effective for the NCR-MT to recover the beam because there is a possibility of beam dropout during FR2 operation. Also, for backhaul link beamforming, the gNB needs to know the appropriate beam of the NCR-MT.

[0214] In addition, RAN1 agreed to support adaptive beams for control and backhaul links in the detailed considerations. Therefore, BFD and BFR are especially required for adaptive beams.

[0215] Agreed The following points should be capabilities of NCR: ・ UL simultaneous transmission on C-link and backhaul links ・ Adaptive beam for C-link / backhaul links ・ Note 1: Fixed beam for C-link / backhaul links is the default function. ・ Note 2: TDM UL transmission for C-link and backhaul links is the default function. ・ Consideration: How to define adaptive beam function for C-link / backhaul links.

[0216] From the above, RLM, BFD, and BFR are considered essential, especially for FR2 deployment. These functions may not be necessary for a specific NCR implementation, such as supporting only FR1 with fixed beams, or for a specific deployment policy, such as placing NCRs only in line-of-sight locations. However, they function to recover from error cases and abnormal conditions. Therefore, RLM, BFD, and BFR can be supported.

[0217] Proposal 3: RAN2 should agree that NCR-MT supports RLM, BFD, and BFR.

[0218] Cell reselection may not be required frequently under normal conditions, but it may be required when a failure occurs. Also, cell reselection is necessary when the signal is blocked in FR2. On the other hand, some companies may not need this function. Therefore, optional support for cell reselection is considered to satisfy various requirements and enable several implementation options.

[0219] Proposal 4: RAN2 should agree that NCR-MT optionally supports cell reselection.

[0220] The current agreement supports only cell selection as a mobility function. Cell selection is largely implementation-dependent, allowing the NCR-MT to select any suitable cell. The OAM can configure the NCR-MT to select a desired cell to which it should connect. However, in some cases, for example, due to signal quality, the NCR-MT may camp on / connect to an undesired cell instead of the desired cell. This erroneous state can occur regardless of whether cell reselection and / or handover are supported. In this case, consideration should be given to how the undesired cell can cause the NCR-MT to camp on / return to the desired cell. Currently, redirection and handover are considered as possible solutions. However, it is unclear how the undesired cell can identify the desired cell to which the NCR-MT should connect.

[0221] Proposal 5: RAN2 should discuss how the NCR-MT moves to the desired cell to which it should connect, and how the desired cell is identified by the undesired cell to which the NCR-MT mistakenly connects.

[0222] NCR Capability Signal Another issue is how the gNB knows the capabilities of the NCR-Fwd (operating frequency, number and resolution of beamforming, output power and dynamic range, etc.), since the NCR-Fwd is an RF repeater and does not support any protocol. It is very easy to assume that the NCR-MT will inform the gNB of the capabilities of the connected NCR-Fwd in addition to its own (i.e., NCR-MT) capabilities.

[0223] For this purpose, it is an option to define a new Capability message, i.e., NCR-FwdCapability message, or to define a new IE in the existing Capability signaling. Further consideration is required as to what NCR-Fwd capabilities need to be reported to the gNB.

[0224] Proposal 6: RAN2 should agree that the NCR-MT notifies the gNB of the NCR-Fwd capabilities, for example, in a new NCR-Fwd Capability message. Further consideration is needed as to what capabilities need to be reported.

[0225] Multi-Beam NCR It is also worth discussing whether NCR can handle multiple beams, as shown in Figure 1. This could potentially improve spectral efficiency, coverage, and scheduling flexibility for multiple UEs.

[0226] A simple RF repeater does not have resource block selectivity, i.e. it simply amplifies and forwards all signals within the system bandwidth with a single weight (beamforming vector), whereas an advanced RF repeater can manage multiple beams for multiple UEs.

[0227] For such advanced RF repeaters, sub-band operation was proposed in RAN1. As indicated in the previous RAN1#110bis-e meeting, there is significant support for frequency-selective sub-band operation. RAN1 postponed discussion of SCI enhancements for sub-band operation until RAN4 submitted its conclusions on FR2 to RAN1. If RAN4 concludes that doing so is beneficial, this feature should be supported. In that case, RAN2 must provide the signaling and configuration to support sub-band operation.

[0228] Therefore, from a RAN2 perspective, it is important that the Rel-18 NCR supports the implementation of such advanced RF repeaters.

[0229] Proposal 7: RAN2 should agree on signaling and configuration to support NCR that can simultaneously process multiple beams for different UEs.

[0230] If multi-beam NCR is supported, from the perspective of RAN2, this leads to the discussion of whether one NCR node (or one NCR-MT) can support multiple NCR-Fwds. Similarly, it is also possible to consider whether one NCR-Fwd can support the control of multiple "antenna array subgroups." If there are multiple NCR-Fwds, the NCR needs to simultaneously handle different beamforming vectors for each NCR-Fwd instructed by the gNB.

[0231] For example, when the NCR is located at the cell edge, multiple NCR-Fwds are required to handle different beams for different access links belonging to different gNBs.

[0232] These cases affect not only the NCR configuration but also the design of side control information. Therefore, RAN2 should discuss configuration models to enable various implementations of multi-beam NCR.

[0233] Proposal 8: For example, whether one NCR-MT controls multiple NCR-Fwds and / or whether one NCR-Fwd supports multiple antenna array subgroups.

[0234] Deployment Options TR38.867 incorporates assumptions about the operating frequencies of the NCR-MT and NCR-Fwd. Furthermore, at least one of the NCR-MT's carriers must operate in the frequency band transferred from the NCR-Fwd. NCR-MT and NCR-Fwd operating in the same frequency band are prioritized for investigation. As a baseline, the C-link and backhaul link (at least when the NCR-MT and NCR-Fwd are operating in the same frequency band) are expected to experience the same large-scale channel characteristics, i.e., Type-A and Type-D channel characteristics (if applicable).

[0235] The intention is to simplify the procedures for the control link by utilizing the same channel conditions as the backhaul link.

[0236] Observation 1: The control link and backhaul link operating at the same frequency have the same radio channel conditions.

[0237] On the other hand, it is also worth considering whether the NCR-MT can support carrier aggregation (CA) or dual connectivity (DC) to achieve robust control plane connectivity. For example, as shown in Figure 30, the NCR-MT can be configured with a PCell in FR1 (for RC connection) and an SCell in FR2 (for Side Control information, on the same frequency as the NCR-Fwd).

[0238] As long as the SCell for the control link operates on the same frequency as the NCR-Fwd for the backhaul link, we believe that the CA / DC configuration for the NCR-MT does not violate the RAN plenary decision and TR restrictions. Furthermore, the robust RRC connection of the FR1 / PCell provides various advantages, considering that the NCR is a network node. This is very similar to the CP / UP split configuration specified by the IAB.

[0239] Proposal 9: For more robust C-plane connectivity, RAN2 should discuss whether to configure NCR-MT with carrier aggregation or dual connectivity. Another scenario is improving the user plane using CA / DC. The gNB configures the UE with CA or DC to achieve high bandwidth and high data rates. In this case, the NCR-Fwd needs to transmit multiple carriers. If these carriers are intraband, only one control link may work to some extent to control the NCR of these carriers. However, if these carriers are interband, there is no correlation between the control link and the backhaul link, that is, they operate on different frequencies, so it is questionable whether only one control link will work. Therefore, RAN2 needs to discuss whether / how NCR will work for multiple carriers when the UE is configured with CA or DC.

[0240] Proposal 10: To support high bandwidth in the U-plane, RAN2 should discuss whether and how the NCR should transmit multiple carriers on the backhaul link and access link when the UE is configured with carrier aggregation or dual connectivity.

[0241] 1: Mobile communication system 100: UE 200: gNB 210: Transmitter 220: Receiver 230: Controller 240: Backhaul communication unit 500A: NCR device 510A: NCR-Fwd 520A: NCR-MT 500B: RIS device 511A: Wireless unit 511a: Antenna unit 511b: RF circuit 511c: Directivity control unit 512A: NCR control unit 512B: RIS control unit 521: Receiver 522: Transmitter 523: Controller 530: Interface

Claims

1. A network, and a relay device that performs relay transmission for relaying a radio signal transmitted between the network and a user device, wherein the relay device connects to a cell selected by cell selection or cell reselection and performs the relay transmission, and a network device that operates the network sets cell information regarding a prohibited cell in which connection of the relay device is prohibited in the relay device A mobile communication system.

2. The relay device specifies a cell that becomes a candidate for cell reselection of the relay device based on the cell information The mobile communication system according to Claim 1.

3. The cell information includes a list of cells prohibited as a connection destination of the relay device, The mobile communication system according to Claim 1.

4. A relay device used in a mobile communication system, a repeater that performs relay transmission for relaying a radio signal transmitted between a network and a user device, and a control terminal that controls the relay transmission by connecting to a cell selected by cell selection or cell reselection, wherein the control terminal is set with cell information regarding a prohibited cell in which connection of the relay device is prohibited from a network device that operates the network A relay device.

5. A network device that operates a mobile communication system, comprising a communication unit that communicates with a relay device, wherein the relay device is a device that performs relay transmission for relaying a radio signal transmitted between the network and a user device, and the communication unit sets cell information regarding a prohibited cell in which connection of the relay device is prohibited in the relay device A network device.

6. A communication method executed by a relay device used in a mobile communication system, comprising the steps of: setting, in the relay device, cell information regarding a prohibited cell in which connection of the relay device is prohibited from a network device that operates the network; connecting to a cell selected by cell selection or cell reselection; controlling relay transmission for relaying a radio signal transmitted between the network and a user device; and performing the relay transmission A communication method.

7. A program to be executed by a relay device used in a mobile communication system, comprising a process of setting, in the relay device, cell information regarding a prohibited cell in which connection of the relay device is prohibited from a network device that operates the network A process of connecting to a cell selected by cell selection or cell reselection, a process of controlling relay transmission for relaying a radio signal transmitted between the network and the user equipment, and a process of performing the relay transmission, and causing the program to execute. **Claim 8**: A chipset for a relay device used in a mobile communication system, a process of setting, by a network device that operates a network, cell information regarding a prohibited cell in which connection of the relay device is prohibited, in the relay device, a process of connecting to a cell selected by cell selection or cell reselection, a process of controlling relay transmission for relaying a radio signal transmitted between the network and the user equipment, and a process of performing the relay transmission, and causing the chipset to execute.