Communication method and relay device

Abstract

A communication method using a relay device, the relay device comprising: a relay apparatus configured to perform a relay operation for relaying a radio signal transmitted between a network and a user equipment; and a control terminal configured to receive a control signal for controlling the relay device from a network, the communication method comprising the steps of: when the control terminal is in a radio resource control (RRC) idle state or an RRC inactive state in a first cell and the relay device is turned on, transmitting the control signal to the control terminal; performing, by the control terminal, a cell reselection to a second cell different from the first cell; and turning off, by the relay device, the relay device on the basis of the cell reselection.

Description

Technical Field

[0001] The present disclosure relates to a communication method and a relay device for a mobile communication system. Background Art

[0002] In recent years, fifth-generation (5G) mobile communication systems have attracted considerable attention. Compared to Long Term Evolution (LTE), the fourth-generation radio access technology, New Radio (NR), the radio access technology for 5G systems, enables broadband transmission via high-frequency bands.

[0003] Because radio signals (radio waves) in high-frequency bands such as the millimeter wave band and the terahertz band are highly linear, a reduction in base station coverage is a problem. To address this issue, attention has been focused on repeater devices, which are network-controlled relays that relay radio signals between the network and user equipment (see, for example, Non-Patent Document 1). These repeater devices, for example, amplify radio signals received from a base station and transmit them in a directional manner, extending the base station's coverage while suppressing interference. These repeater devices are called network-controlled repeaters (NCRs).

[0004] Reference List

[0005] Non-patent literature

[0006] Non-Patent Document 1: 3GPP Contribution: RP-213700, "New SI: Study on NR Network-controlled Repeaters" Summary of the Invention

[0007] A communication method according to a first aspect is a communication method using a relay device, the relay device including: a relay device configured to perform a relay operation for relaying a radio signal sent between a network and a user equipment; and a control terminal configured to receive a control signal for controlling the relay device from the network, the communication method including: when the control terminal transitions from a radio resource control (RRC) connected state to an RRC idle state or an RRC inactive state in a first cell, causing the relay device to continue the relay operation; when the control terminal is in the RRC idle state or the RRC inactive state in the first cell, performing, by the control terminal, cell reselection to a second cell different from the first cell; and based on the cell reselection, causing the relay device to stop the relay operation.

[0008] The relay device according to the second aspect includes: a relay device, configured to perform a relay operation for relaying a radio signal sent between a network and a user equipment; and a control terminal, configured to receive a control signal for controlling the relay device from the network, wherein the control terminal: causes the relay device to continue the relay operation when the control terminal transitions from a radio resource control (RRC) connected state to an RRC idle state or an RRC inactive state in a first cell; performs cell reselection to a second cell different from the first cell when the control terminal is in the RRC idle state or the RRC inactive state in the first cell; and causes the relay device to stop the relay operation based on the cell reselection. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1 is a diagram showing a configuration of a mobile communication system according to an embodiment.

[0010] Figure 2 is a diagram showing a configuration of a protocol stack of a radio interface of a user plane processing data.

[0011] Figure 3 1 is a diagram showing a configuration of a protocol stack of a radio interface of a control plane that processes signaling (control signals).

[0012] Figure 4 is a diagram showing an example of an application scenario of an NCR device (relay device) according to an embodiment.

[0013] Figure 5 is a diagram showing an example of an application scenario of an NCR apparatus according to an embodiment.

[0014] Figure 6 is a diagram illustrating an example of a control method for an NCR device according to an embodiment.

[0015] Figure 7 is a diagram showing an example of a configuration of a protocol stack in a mobile communication system including an NCR device according to an embodiment.

[0016] Figure 8 is a diagram showing a specific example of the configuration of a mobile communication system 1 having an NCR device according to the embodiment.

[0017] Figure 9 is a diagram showing an example of a configuration of an NCR apparatus according to an embodiment.

[0018] Figure 10 is a diagram showing a configuration of a user equipment (UE) according to an embodiment.

[0019] Figure 11 is a diagram showing an example of a configuration of a gNB (base station) according to an embodiment.

[0020] Figure 12 is a diagram showing a general cell reselection process.

[0021] Figure 13 is a diagram illustrating the operation according to the first embodiment.

[0022] Figure 14 is a diagram showing an example of the operation of the NCR apparatus according to the first embodiment.

[0023] Figure 15 is a diagram showing an example of the operation of the NCR apparatus according to the first variation of the first embodiment.

[0024] Figure 16 is a diagram showing an example of the operation of the NCR apparatus according to the second variation of the first embodiment.

[0025] Figure 17 is a diagram showing an example of the operation of the mobile communication system according to the third variation of the first embodiment.

[0026] Figure 18 is a diagram illustrating an example of the operation according to the second embodiment.

[0027] Figure 19 is a diagram showing an example of another operation according to the second embodiment.

[0028] Figure 20 is a diagram showing an example of the operation of the NCR apparatus according to the second embodiment.

[0029] Figure 21 is a diagram showing an example of the operation of the NCR apparatus according to the second embodiment.

[0030] Figure 22 is a diagram showing a RIS device (relay device) according to a third embodiment.

[0031] Figure 23 is a diagram showing a RIS apparatus according to a third embodiment.

[0032] Figure 24 is a diagram illustrating a specific PRACH scenario (RO) for avoiding the possibility of collision. DETAILED DESCRIPTION

[0033] The mobile communication system according to the embodiment will be described with reference to the accompanying drawings. In the description of the drawings, the same or similar parts are denoted by the same or similar reference numerals.

[0034] (1) First embodiment

[0035] First, a first embodiment will be described. A relay device according to the embodiment is a repeater device (ie, an NCR device) that can be controlled from a network.

[0036] (1.1) Overview of mobile communication systems

[0037] Figure 1 is a diagram showing a configuration of a mobile communication system according to an embodiment.

[0038] The mobile communication system 1 is a fifth-generation system (5GS) compliant with the 3rd Generation Partnership Project (3GPP (registered trademark) standard. Hereinafter, the 5GS will be described by way of example, but the Long Term Evolution (LTE) system may be at least partially applied to this mobile communication system. Alternatively, the sixth-generation (6G) system may be at least partially applied to this mobile communication system.

[0039] Mobile communication system 1 includes 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, NG-RAN 10 may be simply referred to as RAN 10. 5GC 20 may be simply referred to as core network (CN) 20. RAN 10 and CN 20 constitute network 5 of mobile communication system 1.

[0040] UE 100 is a mobile wireless communication device. As long as UE 100 is used by a user, UE 100 may be any device. Examples of UE 100 include mobile phones (including smartphones), tablets, notebook computers, communication modules (including communication cards or chipsets), sensors or devices installed on sensors, vehicles or devices installed on vehicles (vehicle UEs), and aircraft and devices installed on aircraft (aircraft UEs).

[0041] The NG-RAN 10 includes base stations (referred to as "gNBs" in 5G systems) 200. The gNBs 200 are interconnected via an Xn interface, which serves as an inter-base station interface. Each gNB 200 manages one or more cells. A gNB 200 performs wireless communications with a UE 100 that has established a connection to a cell of a gNB 200. The gNB 200 performs functions such as radio resource management (RRM), routing user data (hereinafter referred to as "data"), and measurement control for mobility control and scheduling. "Cell" is a term used to denote the smallest unit of a wireless communication area. It is also used to denote functions or resources used to perform wireless communications with a UE 100. One cell belongs to one carrier frequency (hereinafter referred to as "frequency").

[0042] The gNB 200 can be functionally divided into a central unit (CU) and a distributed unit (DU). The CU controls the DU. The CU, for example, includes upper layers included in the protocol stack described below, such as the RRC layer, SDAP layer, and PDCP layer. The CU is connected to the core network via the NG interface (a backhaul interface). The CU is connected to neighboring base stations via the Xn interface (an inter-base station interface). The DU forms a cell. The DU 202, for example, includes lower layers included in the protocol stack described below, such as the RLC layer, MAC layer, and PHY layer. The DU is connected to the CU via the F1 interface (a fronthaul interface).

[0043] The gNB can be connected to the Evolved Packet Core (EPC), which corresponds to the LTE core network. LTE base stations can also be connected to the 5GC. LTE base stations and gNBs can be connected via an inter-base station interface.

[0044] The 5GC 20 includes an access and mobility management function (AMF) and a user plane function (UPF) 300. The AMF performs various types of mobility control for the UE 100, among other functions. The AMF manages the mobility of the UE 100 by communicating with the UE 100 using non-access stratum (NAS) signaling. The UPF controls data transmission. The AMF and UPF are connected to the gNB 200 via the NG interface, which is the interface between the base station and the core network.

[0045] Figure 2 is a diagram showing a configuration of a protocol stack of a radio interface of a user plane processing data.

[0046] The user plane radio interface protocol includes the physical layer (PHY), the medium access control layer (MAC), the radio link control layer (RLC), the packet data convergence protocol (PDCP) layer, and the service data adaptation protocol layer (SDAP).

[0047] 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 the UE 100 and the PHY layer of the gNB 200 via physical channels. The PHY layer of the UE 100 receives downlink control information (DCI) transmitted from the gNB 200 via the Physical Downlink Control Channel (PDCCH). Specifically, the UE 100 performs blind decoding on the PDCCH using the Radio Network Temporary Identifier (RNTI) and retrieves the successfully decoded DCI as DCI addressed to the UE. CRC bits scrambled by the RNTI are added to the DCI transmitted from the gNB 200.

[0048] gNB 200 transmits a synchronization signal block (SSB: synchronization signal / PBCH block). For example, an SSB consists of four consecutive orthogonal frequency division multiplexing (OFDM) symbols and includes a primary synchronization signal (PSS), a secondary synchronization signal (SSS), a physical broadcast channel (PBCH) / master information block (MIB), and a demodulation reference signal (DMRS) for the PBCH. The SSB bandwidth is, for example, 240 consecutive subcarriers, or 20 RBs.

[0049] The MAC layer performs data priority control, retransmission processing using hybrid automatic repeat request (HARQ), random access procedures, and other tasks. Data and control information are transmitted between the MAC layer of the UE 100 and the MAC layer of the gNB 200 via transport channels. The MAC layer of the gNB 200 includes a scheduler. The scheduler determines the transport format (transport block size, modulation and coding scheme (MCS)) in the uplink and downlink, as well as the resource blocks to be allocated to the UE 100.

[0050] The RLC layer transmits data to the receiving RLC layer using the functions of the MAC layer and the PHY layer. Data and control information are transmitted between the RLC layer of the UE 100 and the RLC layer of the gNB 200 via logical channels.

[0051] The PDCP layer performs header compression / decompression, encryption / decryption, etc.

[0052] The SDAP layer performs mapping between IP flows (which are the unit for Quality of Service (QoS) control in the core network) and radio bearers (which are the unit for QoS control in the access stratum (AS)). Note that when the RAN is connected to the EPC, SDAP does not need to be provided.

[0053] Figure 3 1 is a diagram showing a configuration of a protocol stack of a radio interface of a control plane that processes signaling (control signals).

[0054] The protocol stack of the radio interface of the control plane includes the Radio Resource Control (RRC) layer and the Non-Access Stratum (NAS) layer, instead of Figure 2 The SDAP layer is shown.

[0055] RRC signaling for various configurations is transmitted between the RRC layer of the UE 100 and the RRC layer of the gNB 200. The RRC layer controls logical channels, transport channels, and physical channels according to the establishment, re-establishment, and release of radio bearers. When a connection (RRC connection) exists between the RRC layer of the UE 100 and the RRC layer of the gNB 200, the UE 100 is in the RRC connected state. When no connection (RRC connection) exists between the RRC layer of the UE 100 and the RRC layer of the gNB 200, the UE 100 is in the RRC idle state. When the connection between the RRC layer of the UE 100 and the RRC layer of the gNB 200 is suspended, the UE 100 is in the RRC inactive state.

[0056] The NAS layer located above the RRC layer performs session management, mobility management, etc. NAS signaling is sent between the NAS layer of the UE 100 and the NAS layer of the AMF 300A. The UE 100 includes an application layer in addition to the protocol of the radio interface. The layer lower than the NAS layer is called the AS layer.

[0057] (1.2) Examples of relay device application scenarios

[0058] Figure 4 and Figure 5 An example of an application scenario of the NCR device according to the embodiment is shown.

[0059] Compared to 4G / LTE, 5G / NR is capable of broadband transmission via high-frequency bands. Since radio signals in high-frequency bands such as the millimeter wave band and the terahertz band have high linearity, the reduction in the coverage range of the gNB 200 is a problem. Figure 4 In the present embodiment, UE 100 may be located outside the coverage of gNB 200, for example, outside the area where UE 100 can directly receive radio signals from gNB 200. UE 100 may not be able to communicate with gNB 200 within line of sight due to obstacles between gNB 200 and UE 100.

[0060] like Figure 4 As shown, a repeater device (500A) is introduced into the mobile communication system 1. This repeater device (500A) is a relay device that relays radio signals between the gNB 200 and the UE 100. This repeater device (500A) is an NCR device 500A that can be controlled from the network. This type of repeater device can be called a smart repeater device.

[0061] For example, the NCR device 500A amplifies the radio signal (radio waves) received from the gNB 200 and transmits it using directional transmission. Specifically, the NCR device 500A receives the radio signal transmitted by the gNB 200 using beamforming. The NCR device 500A amplifies the received radio signal without demodulating or modulating it, and transmits the amplified radio signal using directional transmission. Here, the NCR device 500A can transmit the radio signal with fixed directivity (beam). Alternatively, the NCR device 500A can transmit the radio signal using a variable (adaptive) directional beam. This effectively expands the coverage of the gNB 200.

[0062] In addition, if Figure 5 As shown, a new UE (hereinafter referred to as an "NCR-MT (Mobile Terminal)") 100B is introduced. This new UE 100B is a control terminal for controlling an NCR device 500A. Specifically, the NCR device 500A includes an NCR-Fwd (Forward) 510A, a type of relay device that relays radio signals transmitted between the gNB 200 and the UE 100. Specifically, it changes the propagation state of the radio signals without demodulating or modulating the radio signals; and an NCR-MT 520A, which performs wireless communication with the gNB 200 to control the NCR-Fwd 510A. Thus, the NCR-MT 520A cooperates with the gNB 200 to control the NCR device 500A by establishing a wireless connection and performing wireless communication with the gNB 200. Consequently, the NCR device 500A can achieve efficient coverage expansion. The NCR-MT 520A controls the NCR device 500A according to the control from the gNB 200. The NCR-MT 520A also has the same functions as those of the UE 100.

[0063] The NCR-MT 520A can be configured separately from the NCR-Fwd 510A. For example, the NCR-MT 520A can be located near the NCR-Fwd 510A and electrically connected to it. The NCR-MT 520A can be connected to the NCR-Fwd 510A via a wired or wireless connection. Alternatively, the NCR-MT 520A can be configured integrally with the NCR-Fwd 510A. The NCR-MT 520A and NCR-Fwd 510A can be fixedly installed at the coverage edge (cell edge) of the gNB 200, or, for example, mounted on a wall or window of any building. The NCR-MT 520A and NCR-Fwd 510A can be installed in a vehicle or other device and can be mobile. One NCR-MT 520A can control multiple NCR-Fwds 510As.

[0064] The configuration is not limited to the configuration in which the NCR-MT 520A directly controls one or more NCR-Fwds 510A, and may be a configuration in which the NCR-MT 520A indirectly controls one or more NCR-Fwds 510A. For example, the NCR-MT 520A may control one or more NCR-Fwds 510A via an upper layer (eg, application layer).

[0065] exist Figure 5 In the illustrated example, NCR device 500A (NCR-Fwd 510A) dynamically or quasi-statically changes the beam to be transmitted or received. For example, NCR-Fwd 510A forms a beam toward each of UE 100a and UE 100b. NCR-Fwd 510A can also form a beam toward gNB 200. For example, in the communication resources between gNB 200 and UE 100a, NCR-Fwd 510A transmits radio signals received from gNB 200 to UE 100a using beamforming and / or transmits radio signals received from UE 100a to gNB 200 using beamforming. In communication resources between the gNB 200 and the UE 100b, the NCR-Fwd 510A transmits radio signals received from the gNB 200 to the UE 100b using beamforming and / or transmits radio signals received from the UE 100b to the gNB 200 using beamforming. As an alternative to or in addition to beamforming, the NCR-Fwd 510A may also perform null forming (so-called null steering) with respect to a UE 100 (not shown) that is not a communication partner and / or a neighboring gNB 200 (not shown) to suppress interference.

[0066] Figure 6 1 is a diagram showing an example of a control method for the NCR device 500A according to an embodiment. Figure 6 As shown, NCR-Fwd 510A relays radio signals (also referred to as "UE signals") between gNB 200 and UE 100. UE signals include uplink signals (referred to as "UE-UL signals") transmitted from UE 100 to gNB 200 and downlink signals (referred to as "UE-DL signals") transmitted from gNB 200 to UE 100. NCR-Fwd 510A relays UE-UL signals from UE 100 to gNB 200 and relays UE-DL signals from gNB 200 to UE 100. The radio link between NCR-Fwd 510A and UE 100 is also referred to as an "access link." The radio link between NCR-Fwd 510A and gNB 200 is also referred to as a "backhaul link."

[0067] NCR-MT 520A transmits and receives radio signals (referred to herein as "NCR-MT signals") to and from gNB 200. NCR-MT signals include uplink signals (referred to herein as "NCR-MT-UL signals") transmitted from NCR-MT 520A to gNB 200 and downlink signals (referred to herein as "NCR-MT-DL signals") transmitted from gNB 200 to NCR-MT 520A. NCR-MT-DL signals include signaling for controlling NCR device 500A (e.g., NCR control signals). The radio link between NCR-MT 520A and gNB 200 is also referred to as a "control link."

[0068] The gNB 200 steers a beam toward the NCR-MT 520A based on the NCR-MT-UL signal from the NCR-MT 520A. Because the NCR device 500A and the NCR-MT 520A are co-located, when the backhaul link and the control link have the same frequency and the gNB 200 steers a beam toward the NCR-MT 520A, the beam is ultimately steered toward the NCR-Fwd 510A. The gNB 200 uses this beam to transmit the NCR-MT-DL signal and the UE-DL signal. The NCR-MT 520A receives the NCR-MT-DL signal. When the NCR-Fwd 510A and the NCR-MT 520A are at least partially integrated, the functionality (e.g., antenna) for transmitting, receiving, or relaying UE and / or NCR-MT signals can be integrated into the NCR-Fwd 510A and the NCR-MT 520A. A beam includes a transmission beam and / or a reception beam. A beam is a general term for transmission and / or reception controlled by adjusting / adapting antenna weights, etc., to maximize the power of transmission and / or reception waves in a specific direction.

[0069] Figure 7 This figure shows an example of a protocol stack configuration in a mobile communication system 1 including an NCR device 500A according to an embodiment. The NCR-Fwd 510A relays radio signals transmitted and received between the gNB 200 and the UE 100. The NCR-Fwd 510A has a radio frequency (RF) function that amplifies and relays received radio signals, and performs directional transmission using beamforming (e.g., analog beamforming).

[0070] The NCR-MT 520A includes at least one layer (entity) selected from the group consisting of PHY, MAC, RRC, and application protocol (F1-AP). F1-AP is a type of fronthaul interface. The NCR-MT 520A exchanges signaling with the gNB 200 using at least one of PHY, MAC, RRC, and F1-AP. When the NCR-MT 520A is a base station or part of a base station, the NCR-MT 520A can exchange signaling with the gNB 200 using an Xn AP (Xn-AP), which is an interface between base stations. The NCR-MT 520A may also include a NAS layer (entity). The NAS layer allows the NCR-MT 520A to exchange signaling with the AMF 300A. The NAS layer may constitute an upper layer of the NCR-MT 520A.

[0071] Figure 8 is a diagram showing a specific example of the configuration of the mobile communication system 1 including the NCR device 500A according to the embodiment.

[0072] A backhaul link is established between the gNB 200 and the NCR-Fwd 510A. An access link is established between the UE 100 and the NCR-Fwd 510A. The NCR-Fwd 510A relays radio signals transmitted between the gNB 200 and the UE 100 via the backhaul link and the access link. The NCR-Fwd 510A modifies the propagation state of the radio signals without demodulating or modulating the radio signals.

[0073] In addition, a control link is established between gNB 200 and Layer 1 (L1) and / or Layer 2 (L2) of NCR-MT 520A. The L1 / L2 of NCR-MT 520A sends and receives L1 / L2 signaling to and from gNB 200 via the control link. An RRC connection is established between gNB 200 and the RRC of NCR-MT 520A. The RRC of NCR-MT 520A sends and receives RRC messages to and from gNB 200 via the RRC connection. NCR-MT 520A receives downlink signaling (also referred to as "NCR control signals" or simply "control signals") from gNB 200 via the RRC connection and / or the control link.

[0074] The gNB 200 (transmitter 210) transmits an NCR control signal to the NCR-MT 520A. The NCR control signal can be an RRC message, which is a control signal at the RRC layer (i.e., Layer 3). It can be a MAC control element (CE), which is a control signal at the MAC layer (i.e., Layer 2). It can be downlink control information (DCI), which is a control signal at the PHY layer (i.e., Layer 1). It can be UE-specific signaling, broadcast signaling, or a fronthaul message (e.g., an F1-AP message). When the NCR-MT 520A is a base station of a certain type or part of a base station, the NCR-MT 520A can communicate with the gNB 200 via an Xn AP (Xn-AP), where Xn is an inter-base station interface.

[0075] Hereinafter, an NCR control signal transmitted in an RRC message (and / or MAC CE) and used to statically or semi-statically control the NCR-Fwd 510A is also referred to as "NCR configuration information" or simply "configuration information." Here, the RRC message may be an RRC reconfiguration message. The NCR configuration information includes, for example, information for configuring the NCR-Fwd 510A to be turned on or off. The NCR configuration information may also include, for example, information for semi-static beam configuration of the NCR-Fwd 510A.

[0076] Meanwhile, the NCR control signal transmitted in L1 / L2 signaling (i.e., DCI (and / or MAC CE)) and used to dynamically control the NCR-Fwd 510A is also referred to as "NCR control information" or simply "control information." The NCR control information may also be referred to as secondary control information (SCI). The cyclic redundancy code (CRC) bits of the PDCCH carrying the NCR control information are scrambled by a newly introduced dedicated RNTI. The dedicated RNTI is also referred to as the "NCR-RNTI." The NCR control information may include, for example, information for dynamically beam-steering the NCR-Fwd 510A. The NCR configuration information may include information for instructing the dynamic on / off switching of the NCR-Fwd 510A.

[0077] For example, when the NCR-MT 520A is in the RRC connected state, the NCR device 500A can turn on or off the NCR-Fwd 510A according to the NCR control information (SCI) received from the gNB 200. On the other hand, after the NCR-MT 520A transitions to the RRC inactive state, the NCR device 500A can turn on or off the NCR-Fwd 510A according to the latest configuration information received from the gNB 200.

[0078] Furthermore, an NCR control signal (eg, NCR configuration information through RRC and / or NCR control information through L1 / L2 signaling) held by the NCR device 500A (NCR-MT 520A) may be referred to as an NCR-Fwd context.

[0079] Additionally, when NCR-MT 520A detects a radio link failure (RLF) with gNB 200, it performs cell selection and triggers RRC connection reestablishment (also referred to as "RRC reestablishment"). When NCR-MT 520A enters the RRC idle state due to failure to find a suitable cell during cell selection, NCR device 500A deactivates NCR-Fwd 510A. During the RRC connection reestablishment process, NCR-Fwd 510A remains deactivated.

[0080] The NCR control signal may include frequency control information specifying the center frequency of the radio signal (e.g., component carrier) to be relayed by NCR-Fwd 510A. When the NCR control signal received from gNB 200 includes frequency control information, NCR-MT 520A (controller 523) controls NCR-Fwd 510A to relay the target radio signal whose center frequency is indicated by the frequency control information (step S2A). The NCR control signal may include multiple pieces of frequency control information specifying different center frequencies. Since the NCR control signal includes frequency control information, gNB 200 can specify the center frequency of the radio signal to be relayed by NCR-Fwd 510A via NCR-MT 520A.

[0081] The NCR control signal may include mode control information for specifying the operating mode of the NCR-Fwd 510A. The mode control information may be associated with frequency control information (center frequency). The operating mode may be any of the following: a mode in which the NCR-Fwd 510A performs non-directional transmission and / or reception, a mode in which the NCR-Fwd 510A performs fixed directional 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 multiple-input multiple-output (MIMO) relay transmission. The operating mode may be any of a beamforming mode (i.e., a mode that emphasizes improving desired waves) and a null generation mode (i.e., a mode that emphasizes suppressing interference waves). When the NCR control signal received from gNB 200 includes the mode control information, NCR-MT 520A (controller 523) controls NCR-Fwd 510A so that NCR-Fwd 510A operates in the operating mode indicated by the mode control information (step S2A). Because the NCR control signal includes the mode control information, gNB 200 can specify the operating mode of NCR-Fwd 510A via NCR-MT 520A.

[0082] 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 relaying in all directions and can be referred to as the omnidirectional mode. The mode in which the NCR-Fwd 510A performs fixed directional transmission and / or reception can be a directional mode implemented using a single directional antenna. This mode can be a beamforming mode implemented by applying fixed phase and amplitude control (antenna weight control) to multiple antennas. Any of these modes can be specified (set) from 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 can be a mode for performing analog beamforming, a mode for performing digital beamforming, a mode for performing hybrid beamforming, or a mode for forming an adaptive beam specific to the UE 100. Any of these modes can be specified (set) from the gNB 200 to the NCR-MT 520A. In the beamforming operation mode, the gNB 200 can provide the NCR-MT 520A with beam control information (described below). The MIMO relay transmission mode of the NCR device 500A can be a mode for single-user (SU) spatial multiplexing, a mode for multi-user (MU) spatial multiplexing, or a mode for transmit diversity. The gNB 200 can specify (set) any of these modes to the NCR-MT 520A. The operation modes can include a mode for turning on (activating) relay transmission by the NCR-Fwd 510A and a mode for turning off (deactivating) relay transmission by the NCR-Fwd 510A. The gNB 200 can specify (set) any of these modes to the NCR-MT 520A.

[0083] The NCR control signal may include beam steering information, which specifies the transmission direction, transmission weight, or beam pattern when the NCR-Fwd 510A performs directional transmission. The beam steering information may be associated with frequency control information (center frequency). The beam steering information may include a precoding matrix indicator (PMI). The beam steering information may include beamforming angle information. When the NCR control signal received from the gNB 200 includes the beam steering information, the NCR-MT 520A (controller 523) controls the NCR-Fwd 510A to form the transmission directionality (beam) indicated by the beam steering information. When the NCR control signal includes the beam steering information, the gNB 200 may control the transmission directionality of the NCR device 500A via the NCR-MT 520A.

[0084] The NCR control signal may include output control information for specifying the degree to which the NCR-Fwd 510A amplifies radio signals (amplification gain) or the transmission power. The output control information may indicate the difference (i.e., 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 the output control information, the NCR-MT 520A (controller 523) controls the NCR-Fwd 510A to change the amplification gain or transmission power indicated by the output control information. The output control information may be associated with frequency control information (center frequency). The output control information may specify any of the amplification gain, beamforming gain, and antenna gain of the NCR-Fwd 510A. The output control information may also specify the transmission power of the NCR-Fwd 510A.

[0085] 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) controlling multiple NCR-Fwds 510A determines the NCR-Fwd 510A to which the NCR control signal is to be applied based on the NCR identifier included in the NCR control signal received from the gNB 200. Even if the NCR-MT 520A controls only one NCR-Fwd 510A, the NCR identifier may be transmitted from the NCR-MT 520A to the gNB 200 along with the NCR control signal.

[0086] Therefore, the NCR-MT 520A (controller 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.

[0087] (1.3) Example of configuration of each device

[0088] An example of the configuration of each device in the mobile communication system 1 according to the embodiment will be described.

[0089] (1.3.1) Example of relay device configuration

[0090] Figure 91 shows an example of a configuration of an NCR device 500A (relay device) according to the embodiment. The NCR device 500A includes an NCR-Fwd 510A, an NCR-MT 520A, and an interface 530 .

[0091] NCR-Fwd 510A includes a wireless unit 511A and an NCR controller 512A. Wireless unit 511A includes an antenna 511a, which includes multiple antennas (multiple antenna elements); an RF circuit 511b, which includes an amplifier; and a directivity controller 511c, which controls the directivity of antenna 511a. RF circuit 511b amplifies and relays (transmits) radio signals transmitted and received by antenna 511a. RF circuit 511b can convert analog radio signals into digital signals and, after digital signal processing, convert the digital signals back into analog signals. Directivity controller 511c can perform analog beamforming through analog signal processing. Directivity controller 511c can also perform digital beamforming through digital signal processing. Directivity controller 511c can also perform hybrid analog and digital beamforming. NCR controller 512A controls wireless unit 511A in response to control signals from NCR-MT 520A. NCR controller 512A may include at least one processor.

[0092] NCR-MT 520A includes a receiver 521, a transmitter 522, and a controller 523. Receiver 521 performs various types of reception under the control of controller 523. Receiver 521 includes an antenna and a receiving device. The receiving device converts radio waves (radio signals) received by the antenna into baseband signals (received signals) and outputs the received signals to controller 523. Transmitter 522 performs various types of transmission under the control of controller 523. Transmitter 522 includes an antenna and a transmitting device. The transmitting device converts baseband signals (transmitted signals) output by controller 523 into radio signals and transmits the radio signals from the antenna. Controller 523 performs various types of control within NCR-MT 520A. The operations of NCR-MT 520A (and NCR device 500A) described above and below may be controlled by controller 523. Controller 523 includes at least one processor and at least one memory. The memory stores programs to be executed by the processor and information to be used by the processor for processing. The processor may include a baseband processor and a central processing unit (CPU). The baseband processor performs modulation and demodulation, encoding and decoding of baseband signals. The CPU executes programs stored in the memory to perform various types of processing. The controller 523 performs the functions of at least one layer selected from the group consisting of PHY, MAC, RRC, and F1-AP.

[0093] The interface 530 electrically or logically connects the NCR-Fwd 510A and the NCR-MT 520A. The controller 523 of the NCR-MT 520A controls the NCR-Fwd 510A via the interface 530. The interface 530 may be a logical entity of an upper layer (eg, an application layer).

[0094] In this embodiment, receiver 521 of NCR-MT 520A receives signaling (NCR control signal) for controlling NCR device 500A from gNB 200 via wireless communication. Controller 523 of NCR-MT 520A controls NCR device 500A based on this signaling. This enables gNB 200 to control NCR-Fwd 510A via NCR-MT 520A.

[0095] (1.3.2) User Equipment Configuration Example

[0096] Figure 10 FIG1 is a diagram showing the configuration of UE 100 (User Equipment) according to an embodiment. UE 100 includes a receiver 110, a transmitter 120, and a controller 130. Receiver 110 and transmitter 120 constitute a wireless communicator that performs wireless communication with gNB 200.

[0097] The receiver 110 performs various reception operations under the control of the controller 130 . The receiver 110 includes an antenna and a receiving device. The receiving device converts a radio signal received by the antenna into a baseband signal (received signal) and outputs the resulting signal to the controller 130 .

[0098] The transmitter 120 performs various transmissions under the control of the controller 130. The transmitter 120 includes an antenna and a transmitting device. The transmitting device converts a baseband signal (transmission signal) output by the controller 130 into a radio signal and transmits the resulting signal through the antenna.

[0099] Controller 130 performs various control and processing within UE 100. This processing includes processing at various layers, which will be described later. The operations of UE 100 described above and below may also be performed under the control of controller 130. Controller 130 includes at least one processor and at least one memory. The memory stores programs to be executed by the processor and information to be used by the processor for processing. The processor may include a baseband processor and a CPU. The baseband processor performs modulation and demodulation, encoding and decoding of baseband signals, and the like. The CPU executes programs stored in the memory, thereby performing various types of processing.

[0100] (1.3.3) Base station configuration example

[0101] Figure 11A diagram illustrating an example configuration of a gNB 200 (base station) according to an embodiment. The gNB 200 includes a transmitter 210, a receiver 220, a controller 230, and a backhaul communicator 240.

[0102] Transmitter 210 performs various transmissions under the control of controller 230. Transmitter 210 includes an antenna and a transmitting device. The transmitting device converts the baseband signal (transmitted signal) output by controller 230 into a radio signal and transmits the resulting signal via the antenna. Receiver 220 performs various types of reception under the control of controller 230. Receiver 220 includes an antenna and a receiving device. The receiving device converts the radio signal received by the antenna into a baseband signal (received signal) and outputs the resulting signal to controller 230. Transmitter 210 and receiver 220 may be capable of using multiple antennas for beamforming.

[0103] Controller 230 performs various types of control for gNB 200. The operations of gNB 200 described above and below may be performed under the control of controller 230. Controller 230 includes at least one processor and at least one memory. The memory stores programs to be executed by the processor and information to be used for processing in the processor. The processor may include a baseband processor and a CPU. The baseband processor performs modulation and demodulation, encoding and decoding of baseband signals, and the like. The CPU executes the programs stored in the memory to perform various types of processing.

[0104] Backhaul communicator 240 is connected to neighboring base stations via an inter-base station interface. Backhaul communicator 240 is connected to AMF / UPF 300 via an interface between the base station and the core network. The gNB may include a central unit (CU) and a distributed unit (DU) (i.e., the functions are divided), and these two units may be connected via the F1 interface.

[0105] In an embodiment, the transmitter 210 of the gNB 200 transmits signaling (NCR control signal) for controlling 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.

[0106] (1.4) Overview of Cell Reselection

[0107] NCR-MT 520A supports cell reselection in RRC idle state or RRC inactive state.

[0108] Figure 12This figure illustrates a general cell reselection process. An NCR-MT 520A in the RRC Idle or RRC Inactive state performs a cell reselection procedure to switch from the current serving cell to a neighboring cell. Specifically, the NCR-MT 520A uses the cell reselection procedure to identify the neighboring cell on which the NCR-MT 520A should camp and reselects the identified neighboring cell. When the current serving cell and the neighboring cell have the same frequency (carrier frequency), this is called intra-frequency. When the current serving cell and the neighboring cell have different frequencies (carrier frequencies), this is called inter-frequency. The current serving cell and the neighboring cell can be managed by the same gNB 200 or by different gNBs 200.

[0109] In step S11, the NCR-MT 520A performs frequency prioritization based on the priority (also known as "absolute priority," "cell reselection priority," or "dedicated priority") of each frequency specified from the gNB 200 (e.g., via a system information block (SIB) or an RRC release message). Specifically, the NCR-MT 520A manages the frequency priority of each frequency specified from the gNB 200.

[0110] In step S12, the NCR-MT 520A performs a measurement process to measure the radio quality of each serving cell and neighboring cells. The NCR-MT 520A measures the received power and quality of reference signals transmitted by the serving cell and neighboring cells (specifically, the cell-defined synchronization signal and the PBCH block (CD-SSB)). For example, the NCR-MT 520A always measures the radio quality of frequencies with a higher priority than the current serving cell. Furthermore, if the radio quality of the current serving cell falls below a predetermined quality, the NCR-MT 520A measures the radio quality of frequencies with a lower priority than the current serving cell.

[0111] In step S13, NCR-MT 520A performs a cell reselection process to reselect the cell on which NCR-MT 520A will camp based on the measurement results in step S12. For example, when the frequency priority of a neighboring cell is higher than that of the current serving cell and the neighboring cell meets a predetermined quality standard (i.e., a minimum required quality standard) within a predetermined time period, NCR-MT 520A may perform cell reselection to the neighboring cell. When the frequency priority of the neighboring cell is the same as that of the current serving cell, NCR-MT 520A may rank the radio quality of the neighboring cells and perform cell reselection to the neighboring cell that ranked higher than the current serving cell within the predetermined time period. When the frequency priority of the neighboring cell is lower than that of the current serving cell and the radio quality of the current serving cell remains below a certain threshold while the radio quality of the neighboring cell remains above another threshold for a predetermined time period, NCR-MT 520A may perform cell reselection to the neighboring cell.

[0112] (1.5) Operation according to the first embodiment

[0113] The first embodiment is an embodiment related to cell reselection of the NCR device 500A (NCR-MT 520A) in the RRC inactive state or the RRC idle state.

[0114] Figure 13 This figure illustrates the operation according to the first embodiment. In the illustrated example, NCR device 500A (NCR-MT 520A) is initially in the RRC connected state in cell a, which is managed by gNB 200a. Cell b, adjacent to cell a, is managed by gNB 200b, which is different from gNB 200a. However, cells a and b may be managed by the same gNB 200. It is assumed that NCR device 500A (NCR-MT 520A) performs relay operations based on NCR control signals received from cell a (gNB 200a) (i.e., NCR-Fwd 510A is in the open state).

[0115] Next, NCR-MT 520A receives an RRC release message including the suspended configuration from cell a (gNB 200) and transitions to the RRC Inactive state. NCR-MT 520A, in the RRC Inactive state, maintains NCR-Fwd 510A in the open state based on the latest NCR control signal (specifically, NCR configuration information) received from gNB 200. This operation is applicable not only in the RRC Inactive state but also in the RRC Idle state.

[0116] Third, after the NCR-MT 520A transitions to the RRC inactive state (or RRC idle state) in cell a, the NCR-MT 520A may reselect another cell b, for example, due to congestion in frequency range (FR) 2. In this case, when the NCR-Fwd 510A is in the off state, there is no problem, but when the NCR-Fwd 510A is in the on state, the latest NCR configuration information held by the NCR device 500A may be provided by cell a and may not be suitable for cell b.

[0117] It is necessary to clarify how the NCR device 500A operates in this scenario. There are two possible options:

[0118] Option 1: The NCR-Fwd 510A remains open and holds the latest NCR configuration information.

[0119] Option 2: Turn off NCR-Fwd 510A. The NCR device 500A may discard the latest NCR configuration information.

[0120] From the perspective of simplifying the operation of NCR-MT 520A, Option 1 is preferable. However, NCR-Fwd 510A operating in another cell, B, based on the latest NCR configuration information provided by cell A (i.e., the previous serving cell), may be problematic. For example, the reselected cell B may have a different set of resources available to NCR device 500A. Therefore, from a technical feasibility perspective, Option 2 is more preferable.

[0121] In the first embodiment, when NCR-MT 520A is in the RRC idle state or RRC inactive state in a first cell (e.g., cell a) and NCR-Fwd 510A is in the on state, NCR-MT 520A performs cell reselection to a second cell (e.g., cell b) that is different from the first cell. Based on the cell reselection from the first cell to the second cell, NCR device 500A (NCR-MT 520A) turns off NCR-Fwd 510A. That is, when NCR-MT 520A reselects to a different cell, NCR device 500A controls NCR-Fwd 510A to turn it off.

[0122] When the NCR-MT 520A is in the RRC idle state or the RRC inactive state in the first cell, the NCR device 500A (NCR-MT 520A) may retain the NCR control signal received from the first cell (the latest NCR control signal). In response to cell reselection from the first cell to the second cell, the NCR-MT 520A may discard the latest NCR control signal (also referred to as "NCR-Fwd context") retained by the NCR-MT 520A.

[0123] After cell reselection from the first cell to the second cell, the NCR-MT 520A can be converted to the RRC connection state in the second cell to obtain the NCR control signal from the second cell. For example, the NCR-MT 520A in the RRC idle state in the second cell is converted to the RRC connection state through the RRC connection establishment process. The NCR-MT 520A in the RRC inactive state in the second cell is converted to the RRC connection state through the RRC connection recovery process. The NCR-MT 520A converted to the RRC connection state in the second cell receives a new NCR control signal related to the relay operation from the second cell. The NCR device 500A controls the relay operation based on the NCR control signal received from the second cell. Hereinafter, the RRC connection establishment process and the RRC connection recovery process may be collectively referred to as the "RRC connection process".

[0124] Figure 14 is a diagram showing an example of the operation of the NCR apparatus 500A according to the first embodiment.

[0125] In step S101, the NCR-MT 520A in the RRC connected state in the cell a receives an NCR control signal including information (NCR configuration information or NCR control information) indicating that the NCR-MT 520A is in the open state from the cell a (gNB 200), and controls the NCR-Fwd 510A so that the NCR-Fwd 510A is opened.

[0126] In step S102, NCR-MT 520A transitions to the RRC idle state or the RRC inactive state. NCR-MT 520A transitions to the RRC idle state or the RRC inactive state by receiving an RRC release message from cell a (gNB 200). NCR-MT 520A holds the latest NCR control signal. For example, NCR-MT 520A holds information indicating that NCR-MT 520A is in the open state (NCR configuration information or NCR control information). Based on the latest NCR control signal, NCR device 500A maintains NCR-Fwd 510A in the open state.

[0127] In step S103, NCR-MT 520A, which is in the RRC idle state or the RRC inactive state in cell a, reselects cell b according to cell reselection. Cell b is a cell different from the current cell a and a cell different from the most recently configured (and controlled) cell a. Cell b may be a cell different from the desired cell to which NCR device 500A is to connect according to the site installation design (communication service area design).

[0128] In step S104, the NCR-MT 520A controls the NCR-Fwd 510A so that the NCR-Fwd 510A is turned off in response to the reselection of the cell b. The NCR-MT 520A may discard the latest NCR control signal held by the NCR-MT 520A.

[0129] In step S105, NCR-MT 520A may initiate an RRC connection procedure (RRC connection establishment procedure or RRC connection recovery procedure) for cell b to transition to the RRC connected state in response to the reselection of cell b. The RRC connection establishment procedure includes sending an RRC setup request message from NCR-MT 520A to cell b and then sending an RRC setup message from cell b to NCR-MT 520A. The RRC connection recovery procedure includes sending an RRC recovery request message from NCR-MT 520A to cell b and then sending an RRC recovery message from cell b to NCR-MT 520A. Upon completion of the RRC connection procedure, NCR-MT 520A transitions to the RRC connected state.

[0130] The NCR-MT 520A may initiate the RRC connection procedure for the cell b only when at least one of the following first and second conditions is satisfied.

[0131] The first condition is that cell b is a desired cell. In other words, the condition is that, assuming that one or more cells to which the NCR-MT 520A is to connect are determined in the site installation design, cell b corresponds to the predetermined cell.

[0132] Second condition: cell b transmits SIB1 including information indicating support for NCR devices (NCR Support IE).

[0133] The NCR-MT 520A, which has transitioned to the RRC connected state in the cell b, receives a new NCR control signal from the cell b and controls (eg, turns on) the NCR-Fwd 510A according to the received NCR control signal.

[0134] (1.6) First Variation of the First Embodiment

[0135] The first variation of the first embodiment will be described focusing mainly on differences from the first embodiment.

[0136] For example, if the geographic location of NCR device 500A does not change even when NCR-MT 520A performs cell reselection, it is assumed that there is no problem even if NCR-Fwd 510A continues to operate in its original configuration. Therefore, gNB 200 may be able to configure whether to disable NCR-Fwd 510A when NCR device 500A reselects cell b. In this variant, gNB 200 managing cell a configures NCR-MT 520A whether to disable NCR-Fwd 510A during cell reselection.

[0137] NCR-MT 520A receives configuration information (also referred to as "on / off configuration information") from cell a (gNB 200) specifying whether to disable NCR-Fwd 510A during cell reselection. If the on / off configuration information indicates that NCR-Fwd 510A should be disabled during cell reselection, NCR device 500A disables NCR-Fwd 510A in response to cell reselection to cell b.

[0138] Figure 15 1 is a diagram showing an example of the operation of the NCR apparatus 500A according to the first variation of the first embodiment. Here, differences from the above-described first embodiment will be described, and duplicate descriptions will be omitted.

[0139] In step S131, NCR-MT 520A, in the RRC connected state in cell a, receives an NCR control signal from cell a (gNB 200) and controls NCR-Fwd 510A based on the NCR control signal to turn on NCR-Fwd 510A. The NCR control signal may include on / off configuration information. Alternatively, the on / off configuration information may be broadcast in the SIB in cell a. NCR-MT 520A receives the on / off configuration information. The on / off configuration information may include a configuration regarding whether NCR-Fwd 510A can operate as a conventional RF repeater (i.e., an RF repeater that does not rely on network control) while the NCR-Fwd 510A remains in the on state. Furthermore, when the NCR device 500A has multiple NCR-Fwds 510A (ie, the NCR-MT 520A handles multiple NCR-Fwds 510A), the on / off configuration information may include information for configuring on / off of each of the multiple NCR-Fwds 510A during cell reselection.

[0140] In step S132, the NCR-MT 520A transitions to the RRC idle state or the RRC inactive state. It is assumed that the NCR-Fwd 510A is controlled to be turned on according to the latest NCR control signal. The NCR-MT 520A holds the latest NCR control signal.

[0141] In step S133 , the NCR-MT 520A, which has transitioned to the RRC idle state or the RRC inactive state in the cell a, reselects the cell b through cell reselection.

[0142] In step S134, the NCR-MT 520A determines whether the on / off configuration information configured by cell a (gNB 200) indicates that the NCR-Fwd 510A is in the off state. If the NCR device 500A has multiple NCR-Fwds 510A, the NCR-Fwd 510A may perform the determination of step S134 for each of the multiple NCR-Fwds 510A.

[0143] If the on / off configuration information indicates that NCR-Fwd 510A is in the off state (step S134: Yes), in step S135, NCR-MT 520A controls NCR-Fwd 510A to turn off NCR-Fwd 510A in response to reselecting cell b. NCR-MT 520A may discard the most recent NCR control signal held by NCR-MT 520A. The operation in step S136 is the same as that in the first embodiment described above.

[0144] When the on / off configuration information indicates that the NCR-Fwd 510A is on (step S134: No), in step S137, the NCR-MT 520A keeps the NCR-Fwd 510A on even if the cell b is reselected. The NCR device 500A can operate the NCR-Fwd 510A as a conventional RF repeater.

[0145] (1.7) Second variation of the first embodiment

[0146] The second variation of the first embodiment will be described focusing mainly on the differences from the first embodiment. This variation can be implemented in combination with the first variation described above.

[0147] The network 5 (gNB 200) can configure the NCR-MT 520A with a valid area for use in other cells using the same NCR control signal. A valid area consists of one or more cells. For example, the gNB 200 transmits an NCR control signal to the NCR-MT 520A. The NCR control signal includes NCR configuration information and / or NCR control information related to relay operations, as well as area information indicating the valid area for the NCR configuration information and / or NCR control information. The area information can be a list of cell IDs or a list of frequency IDs.

[0148] The area information may be information for identifying the gNB 200, such as the gNB ID or a freely selected ID for identifying the gNB (for example, a portion of the gNB ID may be used (shortened), or the ID may be in a numbering format different from the gNB ID). This identification information may be broadcast in an SIB from the gNB 200, and the UE 100 may use this broadcast information to determine whether the cell in which the RRC has been reestablished belongs to the valid area.

[0149] In this variant, NCR-MT 520A receives an NCR control signal from cell a (gNB 200). This NCR control signal includes information indicating that NCR-Fwd 510A should be enabled, as well as area information indicating the valid area for this information. If cell b is not within the valid area, NCR device 500A disables NCR-Fwd 510A in response to cell reselection to cell b. On the other hand, if cell b is within the valid area, NCR device 500A maintains NCR-Fwd 510A enabled even after cell reselection to cell b.

[0150] Figure 16 1 is a diagram showing an example of the operation of the NCR apparatus 500A according to the second variation of the first embodiment. Here, differences from the above-described first embodiment will be described, and duplicate descriptions will be omitted.

[0151] In step S151, NCR-MT 520A, which is in the RRC connected state in cell a, receives an NCR control signal from cell a (gNB 200) and controls NCR-Fwd 510A to turn on NCR-Fwd 510A based on the NCR control signal. The NCR control signal includes area information indicating a valid area. The valid area can be configured jointly for both NCR configuration information and NCR control information. The valid area can also be configured separately for each of the NCR configuration information and NCR control information.

[0152] In step S152, the NCR-MT 520A transitions to the RRC idle state or the RRC inactive state. It is assumed that the NCR-Fwd 510A is controlled to be turned on according to the latest NCR control signal. The NCR-MT 520A holds the latest NCR control signal.

[0153] In step S153, the NCR-MT 520A, which has transitioned to the RRC idle state or the RRC inactive state in cell a, reselects cell b through cell reselection. The NCR-MT 520A may notify an upper layer that cell b has been reselected.

[0154] In step S154, the NCR-MT 520A determines whether the cell b belongs to the valid area based on the area information configured by the cell a (gNB 200).

[0155] When it is determined that the cell b belongs to the valid area (step S154 : Yes), in step S155 , the NCR device 500A (NCR-MT 520A) controls the NCR-Fwd 510A according to the latest NCR control signal so as to turn on the NCR-Fwd 510A.

[0156] On the other hand, if it is determined that cell b does not belong to the valid area (step S154: No), in step S156, the NCR device 500A (NCR-MT 520A) turns off NCR-Fwd 510A. NCR-MT 520A may discard the NCR control signal held by NCR-MT 520A. NCR-MT 520A may notify the upper layer that cell b does not belong to the valid area (cell b, which does not belong to the valid area, has been reselected). The operation of step S157 is the same as that of the first embodiment described above.

[0157] (1.8) Third variation of the first embodiment

[0158] The third variation of the first embodiment will be described focusing mainly on the differences from the first embodiment. The third variation can be implemented in combination with the above variations.

[0159] The validity area can be determined through negotiation between gNBs 200. For example, a gNB 200 transmits an NCR control signal (NCR configuration information) to a neighboring gNB, indicating that the NCR device 500A is to be configured in its own cell. If the neighboring gNB determines that the NCR control signal is applicable to its own cell, the neighboring gNB may allow its own cell to be the validity area of ​​the NCR control signal.

[0160] For example, gNB 200b, which manages cell b, obtains NCR configuration information configured by gNB 200a in NCR device 500A from gNB 200a, which manages cell a. gNB 200b may send a notification to gNB 200a indicating the result of determining whether the NCR configuration information is valid in cell b based on the obtained NCR configuration information. If the NCR configuration information obtained from gNB 200a is also valid in cell b, gNB 200b may omit the configuration of NCR configuration information for NCR-MT 520A from gNB 200b.

[0161] For example, when cell b relays the same resources as cell a, or when the NCR device 500A in cell b relays the radio signal of cell a, it can be determined that the NCR configuration information obtained from gNB 200a is valid in cell b.

[0162] Figure 17 This figure illustrates an example of the operation of mobile communication system 1 according to the third variant of the first embodiment. Differences from the first embodiment described above will be described here, and repeated descriptions will be omitted. It is assumed that communication between gNB 200a and gNB 200b is performed over the Xn interface, for example. It is assumed that NCR-MT 520A is connected to cell a and controls NCR-Fwd 510A based on NCR control signals from cell a.

[0163] In step S171, gNB 200b may query gNB 200a for the NCR configuration information of NCR device 500A in cell a. At this time, NCR device 500A may not have moved to cell b.

[0164] In step S172, gNB 200a transmits an Xn message (e.g., a gNB Configuration Update message) including NCR configuration information to gNB 200b. The NCR configuration information may be notified as a combination of the identifier of the NCR device 500A and the NCR configuration information (e.g., in a list format).

[0165] In step S173, gNB 200b may determine whether the NCR configuration information can be used in its own cell (cell b) based on the NCR configuration information from gNB 200a, and notify gNB 200a of the determination result. Here, it is assumed that the NCR configuration information can be used in cell b.

[0166] gNB 200a can configure the area in which the current NCR configuration information continues to apply to NCR-MT 520A (see the second variant). Based on this configuration, even after reselecting cell b, NCR device 500A controls NCR-Fwd 510A according to the current NCR configuration information.

[0167] Alternatively, a scenario in which NCR device 500A is handed over from cell a to cell b can be assumed. When gNB 200a determines the handover, if the NCR configuration information has already been notified to gNB 200b, or if it is confirmed that the NCR configuration information can be used, gNB 200a may not include the NCR configuration information in the handover request message sent to gNB 200b. Furthermore, when gNB 200a determines the target cell for the handover, gNB 200a may preferably select another cell that can use the NCR configuration information as the target cell.

[0168] (2) Second embodiment

[0169] Next, the second embodiment will be described mainly focusing on the differences from the first embodiment. The first embodiment and its variations can be implemented in combination with the second embodiment.

[0170] The basic scenario assumed in the second embodiment is the same as that in the first embodiment. However, in the second embodiment, the NCR-Fwd 510A is closed upon initiation of the RRC connection procedure, rather than upon cell reselection as in the first embodiment.

[0171] Specifically, in the second embodiment, when NCR-MT 520A is in the RRC Idle state or the RRC Inactive state in a first cell and NCR-Fwd 510A is in the Open state, NCR-MT 520A initiates an RRC Connection procedure (RRC Connection Establishment or RRC Connection Recovery) for a second cell to transition to the RRC Connected state. Upon initiation of the RRC Connection procedure, NCR device 500A deactivates NCR-Fwd 510A. In the second embodiment, the second cell is the target cell for the RRC Connection Establishment or RRC Connection Recovery.

[0172] However, in the second embodiment, when the second cell is the same cell as the first cell, the NCR device 500A may initiate the RRC connection procedure or keep the NCR-Fwd 510A in an open state.

[0173] Figure 18 is a diagram illustrating an example of operation according to the second embodiment. Hereinafter, the operation when the NCR-MT 520A is in the RRC inactive state rather than the RRC idle state will be mainly described. However, in the following description, the RRC inactive state may be understood as the RRC idle state, and the RRC connection recovery may be understood as the RRC connection establishment.

[0174] First, NCR device 500A (NCR-MT 520A) is in the RRC connected state in cell a, which is managed by gNB 200a. Cell b, which is adjacent to cell a, is managed by gNB 200b, which is different from gNB 200a. However, cells a and b may be managed by the same gNB 200. It is assumed that NCR device 500A (NCR-MT 520A) is performing relay operations based on NCR control signals received from cell a (gNB 200a) (i.e., NCR-Fwd 510A is in the on state).

[0175] Next, NCR-MT 520A receives an RRC release message including the suspended configuration from cell a (gNB 200) and transitions to the RRC Inactive state. NCR-MT 520A, in the RRC Inactive state, maintains NCR-Fwd 510A in the open state based on the latest NCR control signal (specifically, NCR configuration information) received from gNB 200.

[0176] Third, after NCR-MT 520A transitions to the RRC inactive state in cell a, NCR-MT 520A reselects another cell b, for example, due to congestion in FR2. In the second embodiment, NCR device 500A does not turn off NCR-Fwd 510A during cell reselection, but instead keeps NCR-Fwd 510A turned on. However, NCR device 500A can operate NCR-Fwd 510A as a conventional RF repeater.

[0177] Fourth, NCR-MT 520A, having reselected cell b in the RRC Inactive state, initiates an RRC connection recovery procedure with cell b. Based on the initiation of the RRC connection recovery procedure, NCR device 500A disables NCR-Fwd 510A. Having transitioned to the RRC Connected state in cell b, NCR-MT 520A receives a new NCR control signal from cell b and controls (e.g., enables) NCR-Fwd 510A based on the received new NCR control signal.

[0178] Figure 19 is a diagram showing an example of another operation according to the second embodiment. In the shown example, it is assumed that the NCR-MT 520A performs RRC connection recovery with the original cell a without performing cell reselection.

[0179] First, NCR device 500A (NCR-MT 520A) is in the RRC connected state in cell a managed by gNB 200a. It is assumed that NCR device 500A (NCR-MT 520A) performs relay operations based on NCR control signals received from cell a (gNB 200a) (i.e., NCR-Fwd 510A is in the on state).

[0180] Next, NCR-MT 520A receives an RRC release message including the suspended configuration from cell a (gNB 200) and transitions to the RRC inactive state. While NCR-MT 520A is in the RRC inactive state, NCR device 500A maintains NCR-Fwd 510A in the open state based on the latest NCR control signal (specifically, NCR configuration information) received from gNB 200.

[0181] Third, the NCR-MT 520A in the RRC inactive state initiates the RRC connection recovery procedure with the cell a. In this case, the NCR device 500A keeps the NCR-Fwd 510A in the open state even if the RRC connection recovery procedure is initiated.

[0182] Figure 20 1 is a diagram showing an example of the operation of the NCR apparatus 500A according to the second embodiment. Here, differences from the above-described first embodiment will be described, and duplicate descriptions will be omitted.

[0183] In step S201, the NCR-MT 520A in the RRC connected state in the first cell receives an NCR control signal including information (NCR configuration information or NCR control information) indicating that the NCR-MT 520A is in the open state from the first cell (gNB200), and controls the NCR-Fwd 510A so that the NCR-Fwd 510A is opened.

[0184] In step S202, NCR-MT 520A transitions to the RRC inactive state. NCR-MT 520A holds the latest NCR control signal. For example, NCR-MT 520A holds information indicating that NCR-MT 520A is in the open state (NCR configuration information or NCR control information). Based on the latest NCR control signal, NCR device 500A maintains NCR-Fwd 510A in the open state.

[0185] The NCR-MT 520A in the RRC idle state or RRC inactive state in the first cell may reselect a cell different from the first cell as the second cell. Alternatively, the NCR-MT 520A may maintain the same cell as the first cell as the second cell without performing cell reselection.

[0186] In step S203, the NCR-MT 520A initiates an RRC connection recovery process for the second cell. For example, the NCR-MT 520A sends an RRC recovery request process to the second cell.

[0187] The NCR-MT 520A may initiate the RRC connection procedure of the second cell only when at least one of the following first and second conditions is satisfied.

[0188] First condition: the second cell is a desired cell. In other words, the condition is that, assuming that one or more cells to which the NCR-MT 520A is to connect are determined in the site installation design, the second cell corresponds to the predetermined cell.

[0189] Second condition: the second cell sends SIB1 including information indicating support for NCR devices (NCR Support IE).

[0190] In step S204, the NCR-MT 520A determines whether the second cell is the same cell as the first cell. The case where the second cell is a cell different from the first cell corresponds to Figure 19 On the other hand, the case where the second cell is the same cell as the first cell corresponds to Figure 20 The situation in .

[0191] If it is determined that the second cell is a different cell from the first cell (step S204: No), in step S205, the NCR device 500A (NCR-MT 520A) controls the NCR-Fwd 510A to turn off the NCR-Fwd 510A in response to the initiation of the RRC connection recovery procedure. The NCR-MT 520A may discard the most recent NCR control signal held by the NCR-MT 520A. In this case, after the NCR-MT 520A transitions to the RRC connected state of the second cell, the NCR-MT 520A may receive a new NCR control signal from the second cell and control (e.g., turn on) the NCR-Fwd 510A based on the received NCR control signal.

[0192] On the other hand, when it is determined that the second cell is the same cell as the first cell (step S204: Yes), in step S206, even if the RRC connection recovery procedure is started, the NCR device 500A (NCR-MT 520A) keeps the NCR-Fwd 510A in the on state according to the latest NCR control signal held by the NCR device 500A.

[0193] In this operation example, the operation when the NCR-MT 520A transitions from the RRC inactive state to the RRC connected state has been described, but the operation when the NCR-MT 520A transitions from the RRC idle state to the RRC connected state can be the same as that when the NCR-MT 520A transitions from the RRC idle state to the RRC connected state. Figure 20 Alternatively, the operations when the NCR-MT 520A transitions from the RRC idle state to the RRC connected state may be partially the same as those in Figure 20 When the NCR-MT 520A is in the RRC idle state, the gNB 200 may not have the context of the NCR device 500A, so it may be undesirable to continue to open the control. Figure 21 As shown, when the NCR-MT 520A transitions from the RRC idle state to the RRC connected state, regardless of whether the cell is the same, the NCR device 500A can uniformly close the NCR-Fwd 510A when the RRC connection establishment process is started.

[0194] Furthermore, in the second embodiment, each variation of the above-described first embodiment can be applied.

[0195] For example, the NCR control signal may include on / off configuration information indicating whether to shut down the NCR-Fwd 510A during RRC connection recovery, similar to the first variant of the first embodiment. Alternatively, the on / off configuration information may be broadcast in the SIB in cell a. The NCR-MT 520A receives the on / off configuration information. The on / off configuration information may include configuration regarding whether the NCR-Fwd 510A can operate as a conventional RF repeater (i.e., an RF repeater that does not rely on network control) while the NCR-Fwd 510A remains on. If the NCR device 500A includes multiple NCR-Fwds 510A (i.e., the NCR-MT 520A handles multiple NCR-Fwds 510A), the on / off configuration information may include information for configuring whether each of the multiple NCR-Fwds 510A should be turned on or off during RRC connection recovery. For example, NCR-MT 520A may receive on / off configuration information from cell a specifying whether to disable NCR-Fwd 510A during RRC connection recovery. If the on / off configuration information indicates that NCR-Fwd 510A should be disabled during RRC connection recovery, NCR device 500A may disable NCR-Fwd 510A in response to initiating the RRC connection recovery procedure. The on / off configuration information may be broadcast via an SIB from cell b (gNB 200b).

[0196] The NCR control signal may include configuration information indicating the activation of NCR-Fwd 510A and area information indicating the valid area of ​​the configuration information, similar to the second variation of the first embodiment. When cell b is not within the valid area, NCR device 500A may deactivate NCR-Fwd 510A in response to the initiation of the RRC connection recovery procedure. When cell b is within the valid area, NCR device 500A may maintain NCR-Fwd 510A in the activated state even if the RRC connection recovery procedure is initiated.

[0197] The gNB 200b managing cell b can obtain the configuration information configured by gNB 200a in the NCR device 500A from the gNB 200a managing cell a, similar to the third variant of the first embodiment.

[0198] (3) Third embodiment

[0199] Next, the differences between the third embodiment and the above-mentioned embodiments will be mainly described. Figure 22As shown, the relay device according to the third embodiment is a reconfigurable smart surface (RIS) device 500B, which changes the direction of propagation of incident radio waves (radio signals) by reflection or refraction. The "NCR" in the above embodiments can be understood as "RIS".

[0200] The RIS is a type of relay device (hereinafter referred to as "RIS-Fwd") that can perform beamforming (directivity control) similar to NCR by changing the properties of metamaterials. The RIS can change the range (distance) of a beam by controlling the reflection and / or refraction direction of each unit element. For example, the RIS can be configured to control the reflection and / or refraction direction of each unit element and focus (steer) the beam on nearby UEs or distant UEs.

[0201] The RIS device 500B includes a new UE (hereinafter referred to as "RIS-MT") 520B, which serves as a control terminal for controlling the RIS-Fwd 510B. The RIS-MT 520B controls the RIS-Fwd 510B in cooperation with the gNB 200 by establishing a wireless connection and performing wireless communications with the gNB 200. The RIS-Fwd 510B may be a reflective RIS. This type of RIS-Fwd 510B reflects incident radio waves to change their propagation direction. The reflection angle of the radio signal can be variably set. The RIS-Fwd 510B reflects radio waves incident from the gNB 200 toward the UE 100. The RIS-Fwd 510B may be a transmissive RIS. This type of RIS-Fwd 510B refracts incident radio waves to change their propagation direction. The reflection angle of the radio signal can be variably set.

[0202] Figure 23An example configuration of a RIS-Fwd (relay device) 510B and a RIS-MT (control terminal) 520B according to the third embodiment is shown. RIS-MT 520B includes a receiver 521, a transmitter 522, and a controller 523. This configuration is similar to that of the previous embodiment. RIS-Fwd 510B includes a RIS 511B and a RIS controller 512B. RIS 511B is a metasurface configured using metamaterials. For example, RIS 511B is constructed by arranging extremely small structures corresponding to the wavelength of a radio wave in an array. By varying the shapes of the structures depending on their placement, the direction and / or beam shape of the reflected wave can be arbitrarily designed. RIS 511B can be a transparent dynamic metasurface. RIS 511B can be configured by stacking a transparent glass substrate on a transparent version of a metasurface substrate regularly provided with a large number of microstructures. By subtly moving the stacked glass substrates, it can dynamically control three modes: a mode that transmits an incident radio signal, a mode that transmits a portion of the radio signal and reflects a portion thereof, and a mode that reflects all of the radio signal. RIS controller 512B controls RIS 511B in response to RIS control signals from controller 523 in RIS-MT 520B. RIS controller 512B may include at least one processor and at least one actuator. The processor interprets the RIS control signals from controller 523 in RIS-MT 520B to drive the actuators in response to the RIS control signals.

[0203] (4) Other embodiments

[0204] In the first embodiment described above, an example has been described in which an NCR-MT 520A in an RRC inactive state or an RRC idle state performs cell reselection. In the second embodiment described above, an example has been described in which an NCR-MT 520A in an RRC inactive state or an RRC idle state performs an RRC connection procedure (RRC connection recovery procedure or RRC connection establishment procedure). However, the operations according to the above embodiments and their variations can be applied to handovers performed by an NCR-MT 520A in an RRC connected state. For example, the cell reselection in the first embodiment described above can be understood as a handover. The RRC connection procedure (RRC connection recovery procedure or RRC connection establishment procedure) in the second embodiment described above can also be understood as a handover.

[0205] In the above embodiment, an example has been described in which the relay device performing relay transmission is the NCR device 500A or the RIS device 500B. However, the relay device performing relay transmission is not limited to the NCR device 500A or the RIS device 500B and may be an integrated access and backhaul (IAB) node defined in the technical specifications of 3GPP.

[0206] Each of the above-described operational flows is not limited to being executed individually and independently, but can be executed by combining two or more operational flows. For example, some steps in one operational flow can be added to another operational flow, or some steps in one operational flow can be replaced with some steps in another operational flow. In each flow, not all steps need to be executed, and only some steps can be executed.

[0207] In the above embodiments, an example has been described in which the base station is an NR base station (gNB), but the base station may be an LTE base station (eNB). The base station may be a relay node such as an IAB node. The base station may be a distributed unit (DU) of an IAB node. Furthermore, the UE 100 may be a mobile terminal (MT) of an IAB node.

[0208] The term "network node" primarily refers to a base station, but may also refer to a core network device or a portion of a base station (CU, DU, or RU). A network node may be configured by combining at least a portion of a core network device and at least a portion of a base station.

[0209] A program may be provided for causing a computer to execute each process performed by a communication device according to the above-described embodiments (e.g., UE 100 (NCR-MT 520A and RIS-MT 520B), gNB 200, or relay device). This program may be recorded on a computer-readable medium. The computer-readable medium enables the program to be installed on a computer. The computer-readable medium on which the program is recorded may be a non-transitory recording medium. The non-transitory recording medium is not specifically limited and may be, for example, a recording medium such as a CD-ROM or DVD-ROM. Furthermore, the circuitry for executing each process performed by user equipment 100, base station 200, or relay device may be integrated, and at least some of user equipment 100, base station 200, and relay device may be configured as a semiconductor integrated circuit (chipset or system-on-chip (SoC)).

[0210] The functions implemented by the user equipment 100, gNB 200 (network node), or relay device may be implemented in circuitry or processing circuitry, including a general-purpose processor, a dedicated processor, an integrated circuit, an application-specific integrated circuit (ASIC), a central processing unit (CPU), conventional circuitry, and / or combinations thereof, programmed to implement the described functions. A processor may include transistors and other circuitry and may be considered a circuit or processing circuit. A processor may be a programmed processor that executes a program stored in memory. The circuits, units, and devices herein are hardware programmed to implement the described functions, or hardware that performs the described functions. The hardware may be any hardware disclosed herein, or any hardware programmed to implement the described functions or known to perform the described functions. When the hardware is a processor that is considered to be some type of circuit, the circuit, device, or unit is a combination of the hardware and software used to configure the hardware and / or processor.

[0211] Unless otherwise expressly stated, the phrases "based on" and "depending on / in response to" used in this disclosure do not mean "only based on" and "only depending on / in response to". The phrase "based on" means both "only based on" and "at least partially based on". The phrase "depending on" means both "only depending on" and "at least partially depending on". The terms "include", "comprising" and their variations do not mean "only including the items described", but rather mean "may only include the items described" or "may include not only the items described but also other items". The term "or" used in this disclosure is not intended to be an "exclusive or". In addition, any reference to elements using names such as "first" and "second" in this disclosure does not generally limit the number or order of these elements. These names can be used herein as a convenient method to distinguish between two or more elements. Therefore, a reference to a first element and a second element does not mean that only two elements can be used there or that the first element needs to be in some way before the second element. For example, when English articles such as "a" and "the" are added in this disclosure by translation, these articles include the plural unless the context clearly indicates otherwise.

[0212] The embodiment has been described in detail above with reference to the accompanying drawings, but the specific configuration is not limited to the above configuration, and various design changes can be made without departing from the gist of the present disclosure.

[0213] This application claims priority to U.S. Provisional Patent Application No. 63 / 445,096 (filed on February 13, 2023), the entire contents of which are incorporated herein by reference.

[0214] (5) Supplement

[0215] Features related to the above-described embodiment are described below as a supplement.

[0216] (Supplement 1)

[0217] A communication method using a relay apparatus, the relay apparatus comprising: a relay device configured to perform a relay operation for relaying a radio signal transmitted between a network and a user equipment; and a control terminal configured to receive a control signal for controlling the relay device from the network, the communication method comprising the following steps:

[0218] When the control terminal is in a radio resource control (RRC) idle state or an RRC inactive state in the first cell and the relay device is in an on state, performing cell reselection to a second cell different from the first cell by the control terminal; and

[0219] Based on cell reselection, the relay device is shut down by the relay apparatus.

[0220] (Supplement 2)

[0221] The communication method according to Supplement 1 further includes the following steps:

[0222] When the control terminal is in the RRC idle state or the RRC inactive state in the first cell, retaining, by the relay device, a control signal received from the first cell; and

[0223] In response to the cell reselection, the control signal retained by the control terminal is discarded by the control terminal.

[0224] (Supplement 3)

[0225] The communication method according to Supplement 1 or 2 further includes the following steps:

[0226] After the cell reselection, the control terminal switches to the RRC connected state in the second cell; and

[0227] A new control signal related to the relay operation is received from the second cell by the control terminal that has transitioned to the RRC connected state in the second cell.

[0228] (Supplement 4)

[0229] The communication method according to Supplement 3 further includes the following steps:

[0230] The relay operation is controlled by the relay device based on a control signal received from the second cell.

[0231] (Supplement 5)

[0232] The communication method according to any one of Supplements 1 to 4, further comprising the following steps:

[0233] receiving, by the control terminal, configuration information from the first cell, the configuration information specifying whether to shut down the relay device during cell reselection,

[0234] The shutting down includes: shutting down the relay device in response to cell reselection when the configuration information indicates shutting down the relay device during cell reselection.

[0235] (Supplement 6)

[0236] The communication method according to any one of Supplements 1 to 5, wherein:

[0237] The control signal includes information indicating that the relay device is turned off and area information indicating an effective area of ​​the information, and

[0238] The shutting down includes shutting down the relay device in response to the cell reselection when the second cell does not belong to the valid area.

[0239] (Supplement 7)

[0240] The communication method according to any one of Supplements 1 to 6, further comprising:

[0241] The second network node managing the second cell obtains configuration information from the first network node managing the first cell, where the configuration information is configured for the relay device by the first network node.

[0242] (Supplement 8)

[0243] The communication method according to Supplement 7 further comprising:

[0244] The second network node sends a notification to the first network node, where the notification indicates a result of determining, based on the acquired configuration information, whether the configuration information is valid in the second cell.

[0245] (Supplement 9)

[0246] A relay device, comprising:

[0247] a relay device configured to perform a relay operation for relaying a radio signal transmitted between the network and the user equipment; and

[0248] A control terminal is configured to receive a control signal for controlling the relay device from the network, wherein:

[0249] The control terminal:

[0250] When the control terminal is in a radio resource control (RRC) idle state or an RRC inactive state in the first cell and the relay device is in an on state, performing cell reselection to a second cell different from the first cell; and

[0251] Based on cell reselection, the relay device is turned off.

[0252] (6) Supplement

[0253] 1. Introduction

[0254] In RAN #97e, work items on the Network Control Forwarder (NCR) have been agreed upon, and significant progress has been made on many protocols in RAN2 #119bis-e and RAN2 #120.

[0255] In this supplement, unresolved / potential issues regarding NCR for RAN2 are discussed.

[0256] 2. Discussion

[0257] 2.1. NCR-Fwd Open / Close Related Matters

[0258] 2.1.1. Unresolved issues related to RRC release

[0259] In RAN2 #120, the following agreement was reached.

[0260] For NCR-Fwd on / off:

[0261] When the NCR-MT is in RRC connected mode, NCR-Fwd can be turned on or off according to the auxiliary control information received from the gNB.

[0262] When the NCR-MT enters RRC inactive mode, it can turn NCR-Fwd on or off according to the last configuration received from the gNB.

[0263] Further study is needed for release to RRC idle state.

[0264] RLF of NCR-MT:

[0265] After the NCR-MT declares RLF, the NCR-MT performs cell selection and triggers RRC re-establishment;

[0266] When no suitable cell is found and the NCR-MT is in the RRC idle state, the NCR-Fwd is in the closed state;

[0267] During the RRC re-establishment process, NCR-Fwd is in the disabled state.

[0268] An unresolved issue is whether it is reasonable for the gNB to release the NCR-MT to the idle state. According to the discussion in RAN2 #120, there are two views on the RRC state of the NCR-MT:

[0269] Assumption 1: NCR-MT is basically connected:

[0270] Under this assumption, the gNB will not release the NCR-MT, as the NCR must always be controllable by the network. Therefore, the NCR-MT may only be in the Idle state during initial access (power on) or RLF (specifically, during RRC reestablishment failure). Because the NCR-Fwd state resulting from initial access is well-defined (i.e., NCR-Fwd will be in the Off state) and the state resulting from RLF is already agreed upon (i.e., NCR-Fwd will also be in the Off state), no additional NCR operations need to be defined when the gNB releases the NCR-MT to the Idle state.

[0271] Assumption 2: gNB can release NCR-MT:

[0272] In this scenario, since RAN2 has already agreed to the RRC Idle state, the gNB can release the NCR-MT for NCR power savings, signaling overhead reduction, etc. Therefore, the NCR-MT may transition to the Idle state for all traditional conditions such as initial access, RLF, and RRC release. Some companies have stated that after transitioning to the Idle state, the NCR-Fwd may fall back to a traditional RF forwarder.

[0273] Observation 1: There are two debates on whether the on / off operation of NCR-Fwd needs to be defined and whether the gNB should return the NCR-MT to the idle state.

[0274] Assumption 1 is straightforward because the NCR is always network-controlled via auxiliary control information and RRC signaling, so the gNB does not need to release the NCR-MT in normal state. However, in smart gNB implementations, the NCR-MT can be released under specific conditions, such as for power conservation and signaling overhead reduction, similar to Assumption 2. Therefore, the specification should allow for various gNB implementations and should generally clarify the operation of NCR during idle state based on RRC release.

[0275] Observation 2: In normal operation, the gNB is not required to put the NCR-MT into the idle state, but under certain conditions, depending on the gNB implementation, RRC release may be allowed.

[0276] On the other hand, regarding NCR operation in the inactive state, after RAN2 transitions the WA:NCR-MT to RRC inactive mode, NCR-Fwd can be enabled or disabled based on the last configuration received from the gNB. Specifically, since the gNB can always page the NCR-MT via RAN paging, it is reasonable to align NCR operation with connected state operation (i.e., "without specific functional enhancements"), as agreed upon by RAN2. It will be understood that, since CN paging is required to establish the RRC connection for transmitting auxiliary control information and this configuration, an NCR-MT in the idle state cannot be controlled by the gNB. Therefore, NCR operation in the idle state needs to be considered separately from NCR operation in the inactive state.

[0277] Observation 3: The operation of NCR-Fwd in the inactive state is consistent with that in the connected state and should be different from that in the idle state.

[0278] Furthermore, as described in Assumption 2 above, the inventors believe that when the NCR is not controlled by the gNB, the NCR may fall back to a traditional RF forwarder. Since RAN2 agrees that "NCR-Fwd can be turned on or off based on the last configuration received from the gNB," it is clear that an inactive NCR cannot fall back to a traditional RF forwarder. In other words, fallback to a traditional RF forwarder is only possible when the NCR-MT is in an idle state.

[0279] Traditional RF repeaters are an implementation technology for network control. Therefore, when an NCR falls back to a traditional RF repeater, it is no longer a network control repeater. In other words, when a node is no longer an NCR (for example, when an NCR-MT transitions to an idle state), the NCR's operation can be whatever is implemented.

[0280] Observation 4: According to the current protocol, an inactive NCR cannot fall back to a legacy RF repeater. That is, it must follow the last configuration received from the gNB, as agreed upon by RAN2.

[0281] Observation 5: When an NCR is not controlled by the gNB (e.g., when an NCR-MT transitions to the idle state), the node may not be considered an NCR from the network control perspective.

[0282] As discussed in Observations 2 and 3, the operation of the NCR in the idle state following RRC release should be clarified and distinguished from the operation in the inactive state in order to support various gNB implementations.

[0283] As mentioned above, RAN2 has agreed that "when no suitable cell is found and the NCR-MT is in the RRC Idle state, the NCR-Fwd state will be turned off" for NCR operation due to RLF. Based on this agreement, there is no clear reason to distinguish transitions to the Idle state due to RRC release from transitions to the Idle state due to RLF. Therefore, when the NCR-MT transitions to the Idle state, the NCR-Fwd state will be turned off, regardless of the reason for the state transition.

[0284] Since this operation does not preclude implementation-specific operation, a node may operate as a conventional RF repeater (ie, “fallback” operation) even if it is not considered an NCR (eg, when the NCR-MT is in the idle state).

[0285] Recommendation 1: RAN2 should agree to turn off NCR-Fwd when NCR-MT is released to idle state (e.g. in case of RLF).

[0286] 2.1.2. Potential Issues with RRC Reestablishment

[0287] Currently, the RAN2 protocol simply assumes that an NCR-MT always resides in the same cell. However, even if NCR mobility is not supported, an NCR-MT may change its serving / camped cell due to radio conditions such as FR2 congestion. Therefore, it is worth discussing what happens when a cell with a different NCR-MT is (re)selected.

[0288] RAN2 #120 agrees with the following description.

[0289] For NCR-MT RLF:

[0290] After the NCR-MT declares RLF, the NCR-MT performs cell selection and triggers RRC re-establishment;

[0291] When no suitable cell is found and the NCR-MT is in the RRC idle state, the NCR-Fwd is in the closed state;

[0292] During the RRC re-establishment process, NCR-Fwd is in the disabled state.

[0293] For RRC re-establishment, the following steps and potential issues are identified according to the protocol:

[0294] Step 1: NCR-MT declares RLF and starts cell selection and RRC re-establishment. During these procedures, NCR-Fwd is in the closed state, as agreed.

[0295] Step 2a: When NCR-MT selects the same cell and successfully completes RRC re-establishment, NCR-Fwd returns to the open state according to the previous configuration.

[0296] Step 2b: When the NCR-MT selects a different cell and successfully completes the RRC re-establishment, it determines whether to close the NCR-Fwd.

[0297] Regarding the potential problem of step 2a, since the NCR has the configuration provided by the same cell, it is usually assumed that the NCR-Fwd can resume operation with the previous configuration. In this case, the signaling overhead for reconfiguring the NCR can be avoided.

[0298] On the other hand, since RLF has occurred in the NCR-MT, the gNB may not prioritize automatically resuming NCR-Fwd operation, and in this case, for example, the gNB may change the NCR configuration. Therefore, explicitly instructing the gNB whether to resume NCR-Fwd operation using the last configuration or to disable NCR-Fwd is an option for performing RRC reconfiguration in advance or performing RRC reestablishment within a certain timeframe.

[0299] As another option, NCR-Fwd can be left in the OFF state even after a successful RRC re-establishment with the same cell. This can be a hard-coded definition or an indication from the gNB as described above. In this case, when the NCR-MT declares RLF (or initiates the RRC re-establishment procedure), the last RRC configuration (and the last indication of using secondary control information) will be discarded.

[0300] Recommendation 2: RAN2 should discuss whether NCR-Fwd should resume operation with the previous configuration when RRC re-establishment to the same cell is successful.

[0301] Regarding the potential issue in step 2b, the NCR-MT's last configuration was provided by the previous serving cell, not the new cell. Therefore, it's easy to provide the NCR with a new configuration from the new cell. In this case, the NCR-MT needs to discard the last RRC configuration (and the last indication of using auxiliary control information) when selecting a different cell (or when sending an RRC re-establishment request to a different cell).

[0302] Recommendation 3: RAN2 should discuss whether NCR-MT will discard the previous configuration when initiating RRC re-establishment to a different cell.

[0303] 2.1.3. Potential Problems with Cell Reselection

[0304] In RAN2 #120, the following agreement was reached.

[0305] NCR-MT basically supports cell reselection and RRM measurement in RRC idle state and RRC inactive state.

[0306] In Release 18, NCR-MT does not support handover and RRM measurements in the RRC connected state.

[0307] One potential issue with cell reselection is prioritizing specific cells. For traditional RF repeaters, deployment is determined by network planning and / or on-site RF measurements. Therefore, it is assumed that desired cells are planned for each NCR. In other words, network planning determines the relationship between serving cells and NCRs. These desired cells may be assigned to NCRs by OAM.

[0308] Observation 6: The NCR can configure the desired cell, for example, through OAM.

[0309] In this scenario, NCR-MTs should avoid camping on undesired cells. Therefore, NCR-MTs should prioritize desired cells over undesired cells. While cell selection broadly allows for specific implementations (i.e., IAB-MTs select any suitable cell as long as it is suitable), cell reselection consists of a set of deterministic operations based on specifications (inter-frequency cell reselection criteria, ranking, etc.). Therefore, standard support is required to ensure NCR network planning.

[0310] The simplest approach is to enhance the priority handling of cell reselection. NCR-MT can prioritize the desired cell, similar to the MBS frequency or sidelink frequency (the priority can vary depending on the UE's preference). This enhancement allows the NCR-MT to continuously perform measurements in an attempt to reselect the desired cell and minimizes the possibility of camping on / connecting to an undesired cell.

[0311] Another aspect is to define an NCR-specific offset for intra-frequency cell reselection (i.e., within the R criterion). This is because when the inventors consider that NCRs may be deployed at the cell edge (i.e., the coverage of the macro cell may be extended), the ranking may cause the NCR-MT to reselect an undesired cell on the same frequency.

[0312] Recommendation 4: RAN2 should discuss whether to allow NCR-MT to prioritize desired cells (i.e., cells of interest) during cell reselection.

[0313] Another potential issue is mobility in inactive mode. RAN2 agreed that "after an NCR-MT transitions to RRC inactive mode, NCR-Fwd may be turned on or off based on the last configuration received from the gNB." Based on this agreement, after an NCR-MT transitions to inactive mode, it may reselect to a different cell due to, for example, an interruption in FR2. This presents no issues when NCR-Fwd is turned off, but the same issues described in Section 2.1.2 may arise when NCR-Fwd is turned on.

[0314] Observation 7: When NCR-MT is inactive with NCR-Fwd turned on, it may reselect to a different cell.

[0315] In this scenario, it is necessary to clarify how NCR will operate. Possible options are as follows:

[0316] Option 1: Based on the current protocol, NCR-Fwd remains enabled in the previous configuration.

[0317] Option 2: Disable NCR-Fwd (or discard the previous configuration in NCR-MT), similar to suggestion 3 above.

[0318] Since Option 1 has the same protocol matters as “NCR-Fwd can be turned on or off according to the last configuration received from the gNB after the NCR-MT has entered the inactive mode” and “WA:RRC inactive mode is freely supported without specific functional enhancements”, Option 1 may be effective because the standardization effort is minimized.

[0319] From a technical perspective, Option 2 is considered a reasonable approach. This is because the configuration is already provided by another cell (i.e., the previous serving cell), and NCR-Fwd operates somewhat unnaturally when it cannot identify the current cell's configuration. This is because the reselected cell may have different resources available for NCR. Therefore, since RAN2 has also agreed that cell reselection is mandatory, Option 2 can be considered a fail-safe mechanism.

[0320] Based on the above discussion, option 2 is more desirable from a technical rationality perspective.

[0321] Recommendation 5: RAN2 should discuss whether NCR-Fwd should be disabled when NCR-MT reselects to a different cell.

[0322] Another potential issue arises when an NCR-MT connects to an undesired cell after cell reselection or RRC reestablishment. For the NCR, it's necessary to reconnect to the desired cell. From the gNB's perspective, the RRC connection with the NCR-MT is ultimately meaningless. RAN2 has agreed that "NCR-MTs do not support handovers." Therefore, the only approach the gNB can take is to release the NCR-MT. However, since the NCR-MT will follow the cell reselection process after transitioning to the idle state, there's no guarantee that the NCR-MT will camp on or reconnect to the desired cell. In this case, redirection could be enhanced to ensure that the NCR-MT camps on the desired cell. However, whether the gNB can acquire the NCR's desired cell (e.g., the cell set by OAM) remains an issue.

[0323] Recommendation 6: RAN2 should discuss whether to enhance redirection to move NCR-MT from desired cell to desired cell (instead of handover).

[0324] 2.2. Access Control Issues

[0325] 2.2.1. Unresolved issues regarding NPN support

[0326] In RAN2 #120, the following was agreed upon as matters to be considered:

[0327] Introduce NCR support indication to each PLMN in SIB1.

[0328] The inventors believe that deploying NCRs within NPNs is also beneficial and has potential market demand. For example, in Japan, NPN frequencies are planned within the high-frequency bands of FR1 (4.9 GHz) and FR2 (28 GHz). At these frequencies, NCR coverage extension is often crucial. As another example, due to the local / closed-area nature of NPNs, NPNs may demonstrate higher performance in URLLC use cases such as smart factories. In such cases, low-latency repeaters are more suitable than high-latency repeaters.

[0329] From a specification perspective, the NCR support indication is assumed to be a 1-bit indication added to each entry of the PLMN Identity Information List in SIB1, similar to the IAB support indication. To support NCR in an NPN, it is only necessary to add the same indication to each entry of the NPN Identity Information List, similar to the IAB. Therefore, the standardization effort is expected to be minimal (close to zero). Furthermore, in PLMN networks, no signaling overhead is incurred (i.e., since the NPN Identity Information List is an arbitrary IE, it does not exist in such networks).

[0330] In addition, RAN2 has agreed to the following statement, which clearly instructs NPN to support NCR.

[0331] NCR-MTs that support NPN should consider using cellReservedForOtherUse for NPN-only cell determination.

[0332] In view of the above, the inventors believe that there is no need to impose "artificial" restrictions on the introduction of NCR by NPN. Therefore, RAN2 should confirm that NPN supports NCR, which will resolve the previous considerations.

[0333] Recommendation 7: RAN2 should confirm that the NPN supports NCR. Therefore, an NCR support indication should also be added to each entry of the NPN identity list in SIB1.

[0334] 2.2.2. Potential Issues with PRACH Resources

[0335] In IAB, specific PRACH scenarios (RO) can be provided to avoid possible conflicts. Such opportunities are defined in the following IE to extend the general configuration of UE.

[0336] Because the NCR is considered a network node, such as an IAB node, PRACH collisions with UEs should also be avoided. For UEs within the extended coverage provided by the NCR, the preamble transmitted by the UE is forwarded by the NCR to the gNB, whereas in the case of IAB, the preamble transmitted by the UE is terminated by the IAB node. Therefore, the present inventors believe that this is a more serious issue for the NCR. Therefore, the present inventors believe that PRACH collisions on the gNB receive side are a more serious issue for the NCR.

[0337] Therefore, it is worth considering whether NCR-MTs should be provided with PRACH resources separate from the UE. When this is required, further consideration needs to be given to whether the separate PRACH resources should be defined by separate ROs (as described in Release 16 IAB) or by PRACH segmentation (i.e., as part of the feature combination preamble defined in Release 17 RedCap, SDT, slicing, and for coverage extension).

[0338] Recommendation 8: RAN2 should discuss whether to define separate PRACH resources specific to NCR-MT.

[0339] Reference numerals

[0340] 1: Mobile communication system

[0341] 100:UE

[0342] 200: gNB

[0343] 210: Transmitter

[0344] 220: Receiver

[0345] 230: Controller

[0346] 240: Backhaul Communicator

[0347] 500A: NCR device

[0348] 510A:NCR-Fwd

[0349] 520A:NCR-MT

[0350] 500B: RIS device

[0351] 510B:RIS-Fwd

[0352] 520B:RIS-MT

[0353] 511A: Wireless unit

[0354] 511a: Antenna

[0355] 511b: RF circuit

[0356] 511c: Directional Controller

[0357] 512A: NCR controller

[0358] 512B:RIS controller

[0359] 521: Receiver

[0360] 522: Transmitter

[0361] 523: Controller

[0362] 530: Interface.

Claims

1. A communication method using a relay device, the relay device comprising: a relay device configured to perform a relay operation for relaying a radio signal transmitted between the network and the user equipment; and a control terminal configured to receive a control signal for controlling the relay device from the network, the communication method comprising the following steps: When the control terminal transitions from a radio resource control (RRC) connected state to an RRC idle state or an RRC inactive state in the first cell, causing the relay device to continue the relay operation; When the control terminal is in the RRC idle state or the RRC inactive state in the first cell, the control terminal performs cell reselection to a second cell different from the first cell; as well as Based on the cell reselection, the relay apparatus causes the relay device to stop the relay operation.

2. The communication method according to claim 1, further comprising the steps of: When the control terminal is in the RRC idle state or the RRC inactive state in the first cell, retaining, by the relay device, a control signal received from the first cell; as well as In response to the cell reselection, the control signal retained by the control terminal is discarded by the control terminal.

3. The communication method according to claim 1 or 2, further comprising the following steps: After the cell reselection, the control terminal switches to the RRC connected state in the second cell; as well as A new control signal related to the relay operation is received from the second cell by the control terminal that has transitioned to the RRC connected state in the second cell.

4. The communication method according to claim 3, further comprising: The relay operation is controlled by the relay device based on a control signal received from the second cell.

5. The communication method according to claim 1 or 2, further comprising: receiving, by the control terminal, configuration information from the first cell, the configuration information specifying whether to cause the relay device to stop the relay operation during cell reselection, The causing the relay device to stop the relay operation includes: when the configuration information instructs the relay device to stop the relay operation during the cell reselection, causing the relay device to stop the relay operation in response to the cell reselection. The communication method according to claim 1 , wherein: The control signal includes information instructing the relay device to continue the relay operation and area information indicating a valid area of ​​the information, and The shutting down includes: when the second cell does not belong to the valid area, in response to the cell reselection, causing the relay device to stop the relay operation.

7. The communication method according to claim 1, further comprising: The second network node managing the second cell obtains configuration information from the first network node managing the first cell, where the configuration information is configured for the relay device by the first network node.

8. The communication method according to claim 7, further comprising: The second network node sends a notification to the first network node, where the notification indicates a result of determining, based on the acquired configuration information, whether the configuration information is valid in the second cell.

9. A relay device, comprising: a relay device configured to perform a relay operation for relaying a radio signal transmitted between the network and the user equipment; as well as A control terminal is configured to receive a control signal for controlling the relay device from the network, wherein: The control terminal: When the control terminal transitions from a radio resource control (RRC) connected state to an RRC idle state or an RRC inactive state in the first cell, causing the relay device to continue the relay operation; When the control terminal is in the RRC idle state or the RRC inactive state in the first cell, performing cell reselection to a second cell different from the first cell; as well as Based on the cell reselection, the relay device is caused to stop the relay operation.

Images