Communication method, user equipment, and network node

Abstract

A communication method according to a first aspect of the present disclosure is executed by a relay node in a cellular communication system, and comprises: a step for transmitting, to a donor node, a message including information for determining one of a mobile relay node configuration and a stationary relay node configuration as the configuration of the relay node; and a step for receiving, from the donor node, configuration information indicating the details of the configuration of the relay node.

Description

COMMUNICATION METHOD, USER EQUIPMENT, AND NETWORK NODE

[0001] The present disclosure relates to a communication method, a user equipment, and a network node for use in a cellular communication system.

[0002] In the 3GPP (Third Generation Partnership Project) (registered trademark, the same applies hereinafter), a standardization project for cellular communication systems, a relay node called an IAB (Integrated Access and Backhaul) node has been introduced (see, for example, Non-Patent Document 1). Specifically, one or more relay nodes intervene in communication between a base station and a user device and perform relay operations for this communication.

[0003] 3GPP TS 38.300 V17.6.0 (2023-09)

[0004] The present disclosure relates to a technique for enabling a relay node to operate according to an appropriate setting, either a mobile relay node setting or a stationary relay node setting, in a cellular communication system incorporating mobile relay node functionality.

[0005] A communication method according to a first aspect of the present disclosure is a communication method performed by a relay node in a cellular communication system, comprising the step of transmitting an RRC Setup Complete message to the donor node, the RRC Setup Complete message including either a first indicator indicating that the relay node is to connect as a mobile relay node or a second indicator indicating that the relay node is to connect as a stationary relay node.

[0006] A communication method according to a second aspect of the present disclosure is a communication method executed by a network node in a cellular communication system, comprising: receiving an RRC Setup Complete message from the relay node, the RRC Setup Complete message including either a first indicator indicating that the relay node is to connect as a mobile relay node or a second indicator indicating that the relay node is to connect as a stationary relay node; and establishing a connection with the relay node based on either the first indicator or the second indicator.

[0007] A relay node according to a third aspect of the present disclosure is a relay node used in a cellular communication system, and includes a transmitter that transmits an RRC Setup Complete message to the donor node, the RRC Setup Complete message including either a first indicator indicating that the relay node is to connect as a mobile relay node or a second indicator indicating that the relay node is to connect as a stationary relay node.

[0008] A network node according to a fourth aspect of the present disclosure is a network node used as a donor node in a cellular communication system, and includes: a receiving unit that receives an RRC Setup Complete message from the relay node, the RRC Setup Complete message including either a first indicator indicating that the relay node is to connect as a mobile relay node or a second indicator indicating that the relay node is to connect as a stationary relay node; and a control unit that establishes a connection with the relay node based on either the first indicator or the second indicator.

[0009] A communication method according to a fifth aspect of the present disclosure is a communication method executed by a relay node in a cellular communication system, comprising the steps of: determining whether the relay node is configured as a mobile relay node by a network; and controlling the operation of the relay node based on whether the relay node is configured as a mobile relay node and the mobility state of the relay node.

[0010] A relay node according to a sixth aspect of the present disclosure is a relay node used in a cellular communication system, and includes a control unit that determines whether the relay node is configured as a mobile relay node by a network, and controls operation of the relay node based on whether the relay node is configured as a mobile relay node and the mobility state of the relay node.

[0011] A network node according to a seventh aspect of the present disclosure is a network node for use as a donor node in a cellular communication system, and comprises a transmitter configured to transmit a radio resource control (RRC) message to the relay node, the radio resource control message including information for identifying whether the relay node is to be configured as a mobile relay node.

[0012] 1 is a diagram illustrating an example of the configuration of a cellular communication system according to an embodiment. A diagram illustrating an example of the relationship between an IAB node, a parent node, and a child node. A diagram illustrating an example of the configuration of a gNB, which is a network node according to an embodiment. A diagram illustrating an example of the configuration of an IAB node, which is a relay node according to an embodiment. A diagram illustrating an example of the configuration of a UE, which is a user equipment according to an embodiment. A diagram illustrating an example of a protocol stack related to IAB-MT RRC connection and NAS connection. A diagram illustrating a protocol stack related to the F1-U protocol. A diagram illustrating a protocol stack related to the F1-C protocol. A diagram illustrating an example of an application scenario of a mobile IAB node according to an embodiment. A diagram illustrating an overview of the operation of a cellular communication system according to a first embodiment. A diagram illustrating an example of the operation of an IAB node in a first operation pattern according to an embodiment. A diagram illustrating an example of the operation of an IAB node in a second operation pattern according to an embodiment. A diagram for explaining Msg5 (RRC Setup Complete message) in the second operation pattern according to an embodiment. A diagram illustrating an example of the operation of an IAB node in a third operation pattern according to an embodiment. A diagram illustrating an example of the operation of an IAB node in a fourth operation pattern according to an embodiment. A diagram illustrating an overview of the operation of an IAB node according to a second embodiment. 10A and 10B are diagrams illustrating an example of an operation of an IAB node in a first operation pattern according to a second embodiment.

[0013] A cellular communication system according to an embodiment will be described with reference to the drawings.

[0014] (1) First Embodiment A first embodiment will be described. In the drawings, the same or similar parts are denoted by the same or similar reference numerals.

[0015] (1.1) System Configuration An example configuration of a cellular communication system according to an embodiment will be described. The cellular communication system 1 according to an embodiment is a 3GPP 5G system. Specifically, the radio access method in the cellular communication system 1 is NR (New Radio), which is a 5G radio access method. However, LTE (Long Term Evolution) may be applied at least partially to the cellular communication system 1. Furthermore, future cellular communication systems such as 6G may also be applied to the cellular communication system 1.

[0016] 1 is a diagram showing an example of the configuration of a cellular communication system 1 according to an embodiment. The cellular communication system 1 includes a 5G core network (5GC) 10, user equipment (UE) 100, base station devices (hereinafter sometimes referred to as "base stations") 200-1 and 200-2, and IAB nodes 300-1 and 300-2. The base station 200 may be referred to as a gNB.

[0017] In the following, an example in which the base station 200 is an NR base station will be mainly described, but the base station 200 may also be an LTE base station (i.e., an eNB). Note that, in the following, the base stations 200-1 and 200-2 may be referred to as gNB 200 (or base station 200), and the IAB nodes 300-1 and 300-2 may be referred to as IAB nodes 300.

[0018] The 5GC 10 has an AMF (Access and Mobility Management Function) 11 and a UPF (User Plane Function) 12. The AMF 11 is a device that performs various mobility controls for the UE 100. The AMF 11 manages information about the area in which the UE 100 is located by communicating with the UE 100 using NAS (Non-Access Stratum) signaling. The UPF 12 is a device that performs user data transfer control, etc.

[0019] Each gNB200 is a fixed wireless communication node and manages one or more cells. Cell is used as a term indicating the smallest unit of a wireless communication area. Cell is sometimes used as a term indicating a function or resource for wireless communication with UE100. One cell belongs to one carrier frequency. Hereinafter, cells and base stations may be used interchangeably. Each gNB200 is interconnected with 5GC10 via an interface called an NG interface. Figure 1 illustrates two gNBs, 200-1 and 200-2, connected to 5GC10. Each gNB200 may be divided into a central unit (CU) and a distributed unit (DU). The CU and DU are interconnected via an interface called an F1 interface. The F1 protocol is a communication protocol between the CU and DU, and includes the F1-C protocol, which is a control plane protocol, and the F1-U protocol, which is a user plane protocol.

[0020] The cellular communication system 1 supports IAB, which enables wireless relay of NR access using NR for backhaul. The donor gNB 200-1 (or donor node, hereinafter sometimes referred to as the "donor node") is the terminal node of the NR backhaul on the network side and is a donor base station with additional functions that support IAB. The backhaul can be multi-hopped via multiple hops (i.e., multiple IAB nodes 300). Figure 1 shows an example in which the IAB node 300-1 is wirelessly connected to the donor node 200-1, the IAB node 300-2 is wirelessly connected to the IAB node 300-1, and the F1 protocol is transmitted over two backhaul hops.

[0021] The UE 100 is a mobile wireless communication device that performs wireless communication with a cell. The UE 100 may be any device that performs wireless communication with the gNB 200 or the IAB node 300. For example, the UE 100 is a mobile phone terminal and / or a tablet terminal, a laptop PC, a sensor or a device provided in a sensor, a vehicle or a device provided in a vehicle, or an aircraft or a device provided in an aircraft. The UE 100 wirelessly connects to the IAB node 300 or the gNB 200 via an access link. FIG. 1 shows an example in which the UE 100 is wirelessly connected to the IAB node 300-2. The UE 100 indirectly communicates with the donor node 200-1 via the IAB node 300-2 and the IAB node 300-1.

[0022] FIG. 2 is a diagram showing an example of the relationship between the IAB node 300, parent nodes, and child nodes.

[0023] Each IAB node 300 has an IAB-DU corresponding to a base station function unit and an IAB-MT (Mobile Termination) corresponding to a user equipment function unit.

[0024] An adjacent node (i.e., an upper node) on the NR Uu radio interface of the IAB-MT is called a parent node. The parent node is the parent IAB node or the DU of the donor node 200. The radio link between the IAB-MT and the parent node is called a backhaul link (BH link). FIG. 2 shows an example in which the parent nodes of the IAB node 300 are IAB nodes 300-P1 and 300-P2. The direction toward the parent node is called upstream. From the perspective of the UE 100, the upper node of the UE 100 may correspond to the parent node.

[0025] Adjacent nodes (i.e., lower nodes) on the NR access interface of the IAB-DU are called child nodes. The IAB-DU manages the cell, similar to the gNB 200. The IAB-DU terminates the NR Uu radio interface to the UE 100 and lower IAB nodes. The IAB-DU supports the F1 protocol to the CU of the donor node 200-1. In FIG. 2, an example is shown in which the child nodes of the IAB node 300 are IAB nodes 300-C1 to 300-C3, but the child nodes of the IAB node 300 may also include the UE 100. The direction toward the child nodes is called downstream.

[0026] In addition, all IAB nodes 300 connected to the donor node 200 via one or more hops form a directed acyclic graph (DAG) topology (hereinafter sometimes referred to as "topology") with the donor node 200 as the root. In this topology, as shown in FIG. 2, adjacent nodes on the IAB-DU interface are child nodes, and adjacent nodes on the IAB-MT interface are parent nodes. The donor node 200 centralizes, for example, resource, topology, route management, etc. of the IAB topology. The donor node 200 is a gNB that provides network access to the UE 100 via a network of backhaul links and access links.

[0027] (1.2) Network Node Configuration Next, the configuration of the gNB 200, which is a network node according to the embodiment, will be described. Fig. 3 is a diagram showing an example configuration of the gNB 200. The gNB 200 has a wireless communication unit 210, a network communication unit 220, and a control unit 230.

[0028] The wireless communication unit 210 performs wireless communication with the UE 100 and wireless communication with the IAB node 300. The wireless communication unit 210 has a receiving unit 211 and a transmitting unit 212. The receiving unit 211 performs various receptions under the control of the control unit 230. The receiving unit 211 includes an antenna, and converts (down-converts) a wireless signal received by the antenna into a baseband signal (received signal), and outputs the signal to the control unit 230. The transmitting unit 212 performs various transmissions under the control of the control unit 230. The transmitting unit 212 includes an antenna, and converts (up-converts) a baseband signal (transmitted signal) output by the control unit 230 into a wireless signal, and transmits the signal from the antenna.

[0029] The network communication unit 220 performs wired communication (or wireless communication) with the 5GC10 and wired communication (or wireless communication) with other adjacent gNBs 200. The network communication unit 220 has a receiving unit 221 and a transmitting unit 222. The receiving unit 221 performs various receptions under the control of the control unit 230. The receiving unit 221 receives a signal from the outside and outputs the received signal to the control unit 230. The transmitting unit 222 performs various transmissions under the control of the control unit 230. The transmitting unit 222 transmits the transmission signal output by the control unit 230 to the outside.

[0030] The control unit 230 performs various controls in the gNB 200. The control unit 230 includes at least one memory and at least one processor electrically connected to the memory. The memory stores programs executed by the processor and information used in processing by the processor. The processor may include a baseband processor and a CPU. The baseband processor performs modulation / demodulation, encoding / decoding, etc. of baseband signals. The CPU executes programs stored in the memory to perform various processes. The processor performs processing of each layer, which will be described later. Note that the control unit 230 may perform each process or operation in the gNB 200 in each of the embodiments shown below.

[0031] (1.3) Configuration of Relay Node Next, the configuration of the IAB node 300, which is a relay node according to the embodiment, will be described. Fig. 4 is a diagram showing an example configuration of the IAB node 300. The IAB node 300 has a wireless communication unit 310 and a control unit 320. The IAB node 300 may have multiple wireless communication units 310.

[0032] The wireless communication unit 310 performs wireless communication (BH link) with the gNB 200 and wireless communication (access link) with the UE 100. The wireless communication unit 310 for BH link communication and the wireless communication unit 310 for access link communication may be provided separately.

[0033] The wireless communication unit 310 has a receiving unit 311 and a transmitting unit 312. The receiving unit 311 performs various types of reception under the control of the control unit 320. The receiving unit 311 includes an antenna, and converts (down-converts) a wireless signal received by the antenna into a baseband signal (received signal), and outputs the signal to the control unit 320. The transmitting unit 312 performs various types of transmission under the control of the control unit 320. The transmitting unit 312 includes an antenna, and converts (up-converts) a baseband signal (transmitted signal) output by the control unit 320 into a wireless signal, and transmits the signal from the antenna.

[0034] The control unit 320 performs various controls in the IAB node 300. The control unit 320 includes at least one memory and at least one processor electrically connected to the memory. The memory stores programs executed by the processor and information used in processing by the processor. The processor may include a baseband processor and a CPU. The baseband processor performs modulation / demodulation and encoding / decoding of baseband signals. The CPU executes programs stored in the memory to perform various processes. The processor performs processing of each layer, which will be described later. Note that the control unit 320 may perform each process or operation in the IAB node 300 in each of the embodiments described below.

[0035] (1.4) Configuration of User Equipment Next, a configuration of the UE 100, which is a user equipment according to the embodiment, will be described. Fig. 5 is a diagram showing an example configuration of the UE 100. The UE 100 includes a radio communication unit 110 and a control unit 120.

[0036] The wireless communication unit 110 performs wireless communication in an access link, i.e., wireless communication with the gNB 200 and wireless communication with the IAB node 300. The wireless communication unit 110 may also perform wireless communication in a side link, i.e., wireless communication with other UEs 100. The wireless communication unit 110 has a receiving unit 111 and a transmitting unit 112. The receiving unit 111 performs various receptions under the control of the control unit 120. The receiving unit 111 includes an antenna, and converts (down-converts) a wireless signal received by the antenna into a baseband signal (received signal), and outputs the signal to the control unit 120. The transmitting unit 112 performs various transmissions under the control of the control unit 120. The transmitting unit 112 includes an antenna, and converts (up-converts) a baseband signal (transmitted signal) output by the control unit 120 into a wireless signal, and transmits the signal from the antenna.

[0037] The control unit 120 performs various controls in the UE 100. The control unit 120 includes at least one memory and at least one processor electrically connected to the memory. The memory stores programs executed by the processor and information used in processing by the processor. The processor may include a baseband processor and a CPU. The baseband processor performs modulation / demodulation, encoding / decoding, etc. of baseband signals. The CPU executes programs stored in the memory to perform various processes. The processor performs processing of each layer, which will be described later. Note that the control unit 120 may be configured to perform each process in the UE 100 in each of the embodiments described below.

[0038] (1.5) Protocol Stack Configuration Next, a description will be given of the configuration of a protocol stack according to the embodiment. Fig. 6 is a diagram showing an example of a protocol stack related to an IAB-MT RRC connection and a NAS connection.

[0039] The IAB-MT of IAB node 300-2 has a physical (PHY) layer, a medium access control (MAC) layer, a radio link control (RLC) layer, a packet data convergence protocol (PDCP) layer, a radio resource control (RRC) layer, and a non-access stratum (NAS) layer.

[0040] 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 IAB-MT of IAB node 300-2 and the PHY layer of the IAB-DU of IAB node 300-1 via a physical channel.

[0041] The MAC layer performs data priority control, retransmission processing using Hybrid Automatic Repeat reQuest (HARQ), random access procedures, etc. Data and control information are transmitted via transport channels between the MAC layer of the IAB-MT of IAB node 300-2 and the MAC layer of the IAB-DU of IAB node 300-1. The MAC layer of the IAB-DU includes a scheduler. The scheduler determines the uplink and downlink transport format (transport block size, modulation and coding scheme (MCS)) and the allocated resource blocks.

[0042] The RLC layer transmits data to the RLC layer on the receiving side using the functions of the MAC layer and PHY layer. Data and control information are transmitted between the RLC layer of the IAB-MT of IAB node 300-2 and the RLC layer of the IAB-DU of IAB node 300-1 via logical channels.

[0043] The PDCP layer performs header compression / decompression, and encryption / decryption. Data and control information are transmitted between the PDCP layer of the IAB-MT of the IAB node 300-2 and the PDCP layer of the donor node 200 via a radio bearer.

[0044] The RRC layer controls logical channels, transport channels, and physical channels in response to the establishment, re-establishment, and release of radio bearers. RRC signaling for various settings is transmitted between the RRC layer of the IAB-MT of the IAB node 300-2 and the RRC layer of the donor node 200. When there is an RRC connection with the donor node 200, the IAB-MT is in an RRC connected state. When there is no RRC connection with the donor node 200, the IAB-MT is in an RRC idle state.

[0045] The NAS layer, which is positioned above the RRC layer, performs session management, mobility management, etc. NAS signaling is transmitted between the NAS layer of the IAB-MT of the IAB node 300-2 and the AMF 11.

[0046] Figure 7 shows a protocol stack for the F1-U protocol. Figure 8 shows a protocol stack for the F1-C protocol. Here, an example is shown in which the donor node 200 is divided into a CU and a DU.

[0047] As shown in Figure 7, the IAB-MT of IAB node 300-2, the IAB-DU of IAB node 300-1, the IAB-MT of IAB node 300-1, and the DU of donor node 200 each have a BAP (Backhaul Adaptation Protocol) layer as a layer above the RLC layer. The BAP layer is a layer that performs routing processing and bearer mapping / demapping processing. In the backhaul, the IP layer is transmitted via the BAP layer, enabling routing over multiple hops.

[0048] In each backhaul link, PDUs (Protocol Data Units) of the BAP layer are transmitted by a backhaul RLC channel (BH NR RLC channel). By configuring multiple backhaul RLC channels in each BH link, traffic prioritization and QoS (Quality of Service) control are possible. The association between BAP PDUs and backhaul RLC channels is performed by the BAP layer of each IAB node 300 and the BAP layer of the donor node 200.

[0049] As shown in FIG. 8, the protocol stack of the F1-C protocol has an F1AP layer and an SCTP layer instead of the GTP-U layer and UDP layer shown in FIG.

[0050] In the following, the processing or operations performed by the IAB-DU and IAB-MT of the IAB may be simply described as the processing or operations of the "IAB." For example, the transmission of a BAP layer message from the IAB-DU of IAB node 300-1 to the IAB-MT of IAB node 300-2 will be described as the IAB node 300-1 transmitting the message to the IAB node 300-2. In addition, the processing or operations of the DU or CU of the donor node 200 may also be simply described as the processing or operations of the "donor node." In addition, the upstream direction and the uplink (UL) direction may be used without distinction. In addition, the downstream direction and the downlink (DL) direction may be used without distinction.

[0051] (1.6) Mobile IAB Node Currently, 3GPP has begun discussions toward the introduction of mobile IAB nodes. A mobile IAB node is, for example, an IAB node that is moving. A mobile IAB node may be an IAB node that is capable of moving. Alternatively, a mobile IAB node may be an IAB node that is currently stationary but is certain to move in the future (or is expected to move in the future).

[0052] The mobile IAB node enables, for example, a UE 100 under the mobile IAB node to receive services from the mobile IAB node while moving in accordance with the movement of the mobile IAB node. For example, a case is envisioned in which a user (or UE 100) on a vehicle receives services via a mobile IAB node installed on the vehicle.

[0053] On the other hand, in contrast to mobile IAB nodes, there are also IAB nodes that do not move. Such IAB nodes are sometimes referred to as intermediate IAB nodes. An intermediate IAB node is, for example, an IAB node that does not move. Alternatively, the intermediate IAB node may be a stationary IAB node. Alternatively, the intermediate IAB node may be an IAB node that remains stationary (or does not move) and remains installed at its installation location. Alternatively, the intermediate IAB node may be a stationary IAB node that does not move. The intermediate IAB node may also be a fixed IAB node.

[0054] A mobile IAB node can also be connected to an intermediate IAB node. Also, a mobile IAB node can be connected to a donor node 200. A mobile IAB node can also change its connection destination due to movement (migration or handover). The connection source may be an intermediate IAB node. The connection source may be the donor node 200. Also, the connection destination may be an intermediate IAB node. The connection destination may be the donor node 200.

[0055] In the following, there may be no distinction between the movement of a mobile IAB node (migration) and the handover of a mobile IAB node (handover). In the following, a mobile IAB node may be referred to as a "mobile IAB node" or a "migrating IAB node." In either case, the mobile IAB node may be referred to as a mobile IAB node. The mobile IAB node may also be a mobile relay node.

[0056] FIG. 9 is a diagram illustrating an example of an application scenario of a mobile IAB node according to an embodiment.

[0057] In the illustrated example, a mobile IAB node (mIAB node) 300M is provided in a mobile vehicle (e.g., a vehicle such as a train or a bus). The UE 100 is located in the mobile vehicle and is in an RRC connected state connected to the cell of the mobile IAB node 300M. A cell managed by the mobile IAB node 300M may be referred to as a mobile IAB cell (mIAB cell). The IAB-MT of the mobile IAB node 300M is in an RRC connected state connected to the cell (stationary cell or macro cell) of the gNB 200. In the illustrated example, the gNB 200 is a donor node of the mobile IAB node 300M. The donor node is the gNB 200 (or parent IAB node) to which the IAB node 300 is connected. The mobile IAB node 300M performs relay operations to relay communications between the gNB200 (donor node) and the UE100.

[0058] In an embodiment, the mobile IAB node 300M may be an IAB node 300 configured as a mobile IAB node by a network (e.g., a donor node). When configured as a mobile IAB node by the network, the IAB node 300 functions (operates) as a mobile IAB node 300M. The mobile IAB node 300M may be an IAB node 300 that does not support child nodes. The mobile IAB node 300M may be an IAB node 300 that is newly introduced in Release 18 of the 3GPP standard. The state in which the IAB node 300 is configured as a mobile IAB node may be referred to as a mobile IAB state (mobile IAB mode).

[0059] On the other hand, when the IAB node 300 is configured as a stationary IAB node by the network, it functions (operates) as a stationary IAB node. A stationary IAB node may be a conventional IAB node 300, i.e., an IAB node 300 prior to Release 17 (Release 16 or 17) of the 3GPP standard. A stationary IAB node may also be an IAB node 300 that supports child nodes. The state in which the IAB node 300 is configured as a stationary IAB node may be referred to as a stationary IAB state (stationary IAB mode).

[0060] In the embodiment, the donor node (gNB200) may broadcast both the conventional "IAB Support IE" and the Release 18 "mobile IAB Support IE" in the system information block type 1 (SIB1). In other words, the donor node (gNB200) may support both the conventional IAB node (stationary IAB node) and the mobile IAB node introduced in Release 18.

[0061] (1.7) System Operation According to First Embodiment Next, the operation of the cellular communication system 1 according to the first embodiment will be described.

[0062] (1.7.1) Operation Overview The IAB node 300 cannot operate in both stationary and mobile IAB node modes at the same time. Therefore, the donor node configures the IAB node 300 as either a stationary IAB node or a mobile IAB node. That is, the donor node can configure one IAB node 300 as either a stationary IAB node or a mobile IAB node. However, it is difficult for the donor node to grasp the status of whether the IAB node 300 is installed in a vehicle and whether the vehicle is moving. Therefore, there is a problem in that it is difficult for the donor node to appropriately determine whether to configure the IAB node 300 as a stationary IAB node or a mobile IAB node.

[0063] FIG. 10 is a diagram showing an outline of the operation of the cellular communication system 1 according to the first embodiment.

[0064] In step S11, the IAB node 300 transmits to the donor node (gNB 200) a message including information for determining whether the IAB node 300 is set to a mobile IAB node or a stationary IAB node. The donor node (gNB 200) receives the message from the IAB node 300.

[0065] In step S12, the donor node (gNB200), specifically the CU of the donor node (gNB200), determines either a mobile IAB node setting or a stationary IAB node setting as the setting for the IAB node 300 based on the information contained in the message of step S11.

[0066] In step S13, the donor node (gNB 200) transmits a message (for example, an RRC Reconfiguration message) including configuration information indicating the configuration content (IAB node configuration) determined in step S12 to the IAB node 300. The IAB node 300 receives the message from the donor node (gNB 200). The IAB node 300 functions (operates) as a mobile IAB node or a stationary IAB node based on the configuration information included in the message of step S12.

[0067] As described above, in the first embodiment, the IAB node 300 transmits to the donor node (gNB 200) a message including information for determining whether the IAB node 300 should be set as a mobile IAB node or a stationary IAB node. This allows the donor node (gNB 200) to appropriately determine whether the IAB node 300 should be set as a stationary IAB node or a mobile IAB node.

[0068] For example, in step S11, the IAB node 300 may, in response to desiring or requesting stationary IAB node configuration, transmit a message including a first indicator (also referred to as a "stationary IAB node indicator") indicating that stationary IAB node configuration is desired or requested to the donor node (gNB 200). The first indicator may be preference information (notification of desire) indicating that the IAB node 300 desires stationary IAB node configuration. The first indicator may be request information (notification of necessity) indicating that the IAB node 300 requires stationary IAB node configuration. In this way, the donor node (gNB 200) can understand that the IAB node 300 desires or requests stationary IAB node configuration in response to receiving the first indicator.

[0069] Alternatively, in step S11, the IAB node 300 may, in response to desiring or requesting mobile IAB node configuration, transmit to the donor node (gNB 200) a message including a second indicator (also referred to as a "mobile IAB node indicator") indicating that the IAB node 300 desires or requests mobile IAB node configuration. The second indicator may be preference information (notification of desire) indicating that the IAB node 300 desires mobile IAB node configuration. The second indicator may be request information (notification of necessity) indicating that the IAB node 300 requires mobile IAB node configuration. In this way, the donor node (gNB 200) can understand that the IAB node 300 desires or requests mobile IAB node configuration in response to receiving the second indicator.

[0070] Alternatively, in step S11, the IAB node 300 may transmit to the donor node (gNB 200) a message including a first indicator indicating that stationary IAB node configuration is desired or requested and a second indicator indicating that mobile IAB node configuration is desired or requested, in response to the fact that there is no desired or requested configuration for the IAB node 300 (i.e., either mobile IAB node configuration or stationary IAB node configuration is acceptable). In this way, the donor node (gNB 200) can understand, in response to receiving both the first indicator and the second indicator, that there is no desired or requested configuration for the IAB node 300. In addition, if the IAB node 300 does not have a desired or required setting for its own IAB node 300 (i.e., either a mobile IAB node setting or a stationary IAB node setting is acceptable), the IAB node 300 may send a message to the donor node (gNB200) including a third indicator indicating that either a mobile IAB node setting or a stationary IAB node setting is acceptable.

[0071] In step S11, the IAB node 300 may transmit a message including mobility information indicating the mobility state of the IAB node 300 to the donor node (gNB 200). This allows the donor node (gNB 200) to determine whether to set the IAB node 300 as a stationary IAB node or a mobile IAB node, taking into account the mobility state of the IAB node 300 based on the mobility information. Here, the mobility information may be information indicating the mobility speed of the IAB node 300. The mobility information may also be information indicating the possibility of the IAB node 300 moving (e.g., the ability of the IAB node 300 to move).

[0072] In step S11, the IAB-MT of the IAB node 300 may send a message to the CU of the donor node (gNB200) containing information for determining whether the IAB node 300 is set to a mobile IAB node or a stationary IAB node.

[0073] The message may be an RRC message, which is a message of the RRC layer. For example, the message may be Msg 5 used in a random access procedure. Msg 5 may be an RRC Setup Complete message used to confirm that the establishment of an RRC connection has been successfully completed. Msg 5 may be an RRC Resume Complete message used to confirm that the resumption of an RRC connection has been successfully completed.

[0074] Alternatively, the message may be a message different from Msg5. The message different from Msg5 may be, for example, a UE Assistance Information message. The UE Assistance Information message is an RRC message used to notify the network of UE assistance information. In this case, the IAB node 300 may start a timer upon transmission of the message (UE Assistance Information message), and may control not to transmit the next message (specifically, a UE Assistance Information message including information for determining either mobile IAB node configuration or stationary IAB node configuration) while the timer is running. This makes it possible to prevent UE Assistance Information messages including information for determining either mobile IAB node configuration or stationary IAB node configuration from being transmitted frequently.

[0075] Alternatively, in step S11, the IAB-DU of the IAB node 300 may transmit to the CU of the donor node (gNB 200) a message including information for determining either a mobile IAB node setting or a stationary IAB node setting as the setting of the IAB node 300. The message may be an F1 message, which is a message of the F1 layer (F1-C protocol).

[0076] In step S13, the CU of the donor node (gNB 200) may transmit an RRC message including information for specifying whether to set the IAB node 300 as a mobile IAB node to the IAB-MT of the IAB node 300. In response to receiving the RRC message, the IAB-MT of the IAB node 300 can determine whether the IAB node 300 has been set as a mobile IAB node or a stationary IAB node.

[0077] (1.7.2) Specific Operation Examples First to fourth operation patterns will be described as specific operation examples of the cellular communication system 1 according to the first embodiment. The first to fourth operation patterns may be implemented independently, or two or more operation patterns may be implemented in combination.

[0078] (1.7.2.1) First Operation Pattern The donor node (gNB200) decides whether to configure the IAB node 300 as a mobile IAB node. Here, when the IAB node 300 performs initial access (i.e., random access procedure), the IAB-MT of the IAB node 300 is in the RRC idle state. Therefore, the donor node (gNB200) does not know information such as whether the accessing IAB node 300 is installed on a vehicle (train, etc.), whether it is moving (whether there is a possibility of moving), etc. In the first operation pattern, the preference or request for whether to be configured as a mobile IAB node is expressed by two indicators of Msg5, namely, the first indicator and the second indicator.

[0079] In the first operation pattern according to the first embodiment, if the IAB-MT of IAB node 300 desires to be configured as a mobile IAB node, it transmits a second indicator (mobile IAB node indicator) in Msg 5. If the IAB-MT of IAB node 300 does not care whether it is configured as a stationary IAB node or a mobile IAB node (i.e., no preference), it transmits both the first indicator (stationary IAB node indicator) and the second indicator (mobile IAB node indicator) in Msg 5.

[0080] 11 is a diagram showing an example of the operation of the IAB node 300 in the first operation pattern according to the first embodiment. Here, it is assumed that the IAB-MT of the IAB node 300 is in the RRC idle state at the start of the operation.

[0081] In step S101, the IAB node 300 determines its IAB node configuration desire (request) based on whether the IAB node 300 is operating a mobile IAB node function and / or whether the IAB node 300 is installed in an environment where it should operate as a mobile IAB node (e.g., installed on a train). Such information may be written to the memory of the IAB node 300, for example, when the IAB node 300 is shipped from the factory and / or when it is installed. Such information may be notified to the AS (the IAB-MT of the IAB node 300) from an upper layer (the NAS or an application). Step S101 may be performed after step S102.

[0082] In step S102, the IAB-MT of the IAB node 300 initiates an RRC connection setup procedure (ie, a random access procedure for initial access).

[0083] Here, the random access procedure includes transmitting a random access preamble (Msg1) from the IAB-MT of the IAB node 300 to the donor node (gNB200), transmitting a random access response (Msg2) from the donor node (gNB200) to the IAB-MT of the IAB node 300, transmitting an RRC Setup Request message (Msg3) from the IAB-MT of the IAB node 300 to the donor node (gNB200), transmitting an RRC Setup message (Msg4) from the donor node (gNB200) to the IAB-MT of the IAB node 300, and transmitting an RRC Setup Complete message (Msg5) from the IAB-MT of the IAB node 300 to the donor node (gNB200). In addition, the IAB-MT of the IAB node 300 transitions from the RRC idle state to the RRC connected state in response to receiving the RRC Setup message (Msg4).

[0084] In step S103, the IAB-MT of IAB node 300 determines whether or not it desires (requests) mobile IAB node setup. If it desires (requests) mobile IAB node setup (step S103: YES), in step S104, the IAB-MT of IAB node 300 includes a second indicator (mobile IAB node indicator) in Msg 5 (RRC Setup Complete message).

[0085] On the other hand, if a stationary IAB node setting is desired (requested) (step S103: NO, step S105: YES), in step S106, the IAB-MT of the IAB node 300 includes a first indicator (stationary IAB node indicator) in Msg5 (RRC Setup Complete message).

[0086] If either the mobile IAB node setting or the stationary IAB node setting is acceptable (step S105: NO), in step S107, the IAB-MT of IAB node 300 includes both the first indicator (stationary IAB node indicator) and the second indicator (mobile IAB node indicator) in Msg 5 (RRC Setup Complete message).

[0087] Then, in step S108, the IAB-MT of the IAB node 300 transmits Msg5 (RRC Setup Complete message) including an indicator to the donor node (gNB 200). As a result, the donor node (gNB 200) can understand, from the indicator included in Msg5, whether or not the IAB node 300 desires (requests) to be configured as a mobile IAB. The donor node (gNB 200) can then appropriately configure the IAB node 300 (for example, RRC configuration, F1 configuration, etc.) taking into account such desires (requests).

[0088] (1.7.2.2) Second Operation Pattern In the second operation pattern according to the first embodiment, the IAB-MT of the IAB node 300 transmits Msg5 including mobility information indicating its own mobility status to the donor node (gNB 200). The mobility information may not only notify the current mobility status of the IAB node 300 but also the possibility (capability) of future mobility.

[0089] 12 is a diagram illustrating an example of the operation of the IAB node 300 in the second operation pattern according to the first embodiment. Here, it is assumed that the IAB-MT of the IAB node 300 is in the RRC idle state at the start of the operation. FIG. 13 is a diagram illustrating Msg 5 (RRC Setup Complete message) in the second operation pattern according to the first embodiment.

[0090] 12 , in step S201, the IAB node 300 determines that it is operating a mobile IAB node function and / or that it is installed in an environment where it should operate as a mobile IAB node (for example, that it is installed in a vehicle such as a train), and determines its movement state, such as its current movement speed and / or future movement possibility (movement capability). Step S201 may be performed after step S202.

[0091] The IAB node 300 may detect its state of being installed in a vehicle using, for example, at least one of its own moving speed and changes in the propagation environment. The moving speed can be determined by positioning performed periodically by the IAB node 300, for example, by positioning using a Global Navigation Satellite System (GNSS) receiver. The IAB node 300 may recognize that it is installed in a vehicle based on its own moving speed being high (e.g., the moving speed exceeding a threshold). The IAB node 300 may estimate its moving speed from Doppler measurements.

[0092] In step S202, the IAB-MT of the IAB node 300 initiates an RRC connection setup procedure (ie, a random access procedure for initial access).

[0093] In step S203, the IAB-MT of the IAB node 300 includes the mobility information indicating the mobility state identified in step S201 in Msg5 (RRC Setup Complete message).

[0094] For example, if the IAB node 300 is currently moving, the IAB-MT of the IAB node 300 may include information indicating the moving speed in Msg 5 (RRC Setup Complete message), as shown in (a) of Figure 13. In the illustrated example, the IAB-MT of the IAB node 300 includes "mobilityState," an information element indicating the level of its own moving speed (normal, medium, high), in Msg 5 (RRC Setup Complete message).

[0095] If the IAB node 300 is currently moving, the IAB-MT of the IAB node 300 may include information indicating that it is moving in Msg 5 (RRC Setup Complete message), as shown in (b) of Figure 13. In the illustrated example, the IAB-MT of the IAB node 300 includes "iab-MovingIndication," an information element indicating that it is moving, in Msg 5 (RRC Setup Complete message).

[0096] If the IAB node 300 (is not currently moving but has the potential (capability) to move in the future), the IAB-MT of the IAB node 300 may include information indicating the potential (capability) to move in the future in Msg 5 (RRC Setup Complete message), as shown in (c) or (d) of Figure 13. In the example of (c) of Figure 13, the IAB-MT of the IAB node 300 sets "mobility-in-future," an information element indicating the potential (capability) to move in the future, to "mobilityState" in Msg 5 (RRC Setup Complete message). In the example of (d) of FIG. 13, the IAB-MT of IAB node 300 includes "iab-FutureMovingIndication," an information element indicating the possibility (capability) of moving in the future, in Msg 5 (RRC Setup Complete message) as an information element separate from "mobility-in-future."

[0097] If the IAB node 300 does not move (does not have mobility capability), the IAB-MT of the IAB node 300 may include information indicating that the IAB node 300 does not move (does not have mobility capability) in Msg 5 (RRC Setup Complete message), as shown in (e) of Figure 13. In the illustrated example, the IAB-MT of the IAB node 300 includes "iab-stationaryIndication," an information element indicating that the IAB node 300 does not move (does not have mobility capability), as an information element separate from "mobility-in-future," in Msg 5 (RRC Setup Complete message).

[0098] Then, in step S204, the IAB-MT of the IAB node 300 transmits Msg5 (RRC Setup Complete message) including the mobility information to the donor node (gNB 200). As a result, the donor node (gNB 200) can grasp the mobility status of the IAB node 300 from the mobility information included in Msg5. Then, the donor node (gNB 200) can appropriately configure the IAB node 300 (for example, RRC configuration, F1 configuration, etc.) to determine whether or not to set it as a mobile IAB, taking into account such mobility status.

[0099] (1.7.2.3) Third Operation Pattern In the third operation pattern according to the first embodiment, the IAB-MT of the IAB node 300 transmits an indicator (first indicator and / or second indicator) related to the first operation pattern described above to the donor node (gNB 200) in a UE Assistance Information message, which is a message different from Msg 5. The IAB-MT of the IAB node 300 may transmit mobility information related to the second operation pattern described above to the donor node (gNB 200) in a UE Assistance Information message. The UE Assistance Information message including the indicator and / or mobility information may be transmitted with limited frequency by a timer.

[0100] 14 is a diagram showing an example of the operation of the IAB node 300 in the third operation pattern according to the first embodiment. Here, it is assumed that the IAB-MT of the IAB node 300 is in the RRC connected state at the start of the operation.

[0101] In step S301, the IAB-MT of the IAB node 300 determines information (indicator and / or movement information) for determining whether the setting of the IAB node 300 is a mobile IAB node setting or a stationary IAB node setting, in the same manner as in the first and second operation patterns described above.

[0102] In step S302, the IAB-MT of the IAB node 300 transmits a message (here, a UE Assistance Information message) including an indicator and / or mobility information to the donor node (gNB 200). Based on the indicator and / or mobility information included in Msg5, the donor node (gNB 200) determines settings (e.g., RRC settings, F1 settings, etc.) such as whether or not to configure the IAB node 300 as a mobile IAB, and transmits an RRC Reconfiguration message including information indicating the settings to the IAB-MT of the IAB node 300. The IAB-MT of the IAB node 300 receives the RRC Reconfiguration message. Note that the settings may or may not match the notification content of step S301. For example, the IAB node 300 may desire a mobile IAB setup, but the donor node (gNB 200) may perform a stationary IAB node setup.

[0103] In step S303, the IAB-MT of the IAB node 300 starts a timer when transmitting the UE Assistance Information message in step S302 or when receiving the RRC Reconfiguration message. The RRC Reconfiguration message may include a setting value (timer value) that determines the time length of the timer. In this case, the IAB-MT of the IAB node 300 may start the timer to which the timer value is set when receiving the RRC Reconfiguration message.

[0104] In step S304, the IAB-MT of the IAB node 300 determines whether it has detected a predetermined event that triggers the transmission of a UE Assistance Information message including an indicator and / or mobility information. Here, the predetermined event may be any of the following: a change in the IAB node configuration preference (request), a change in mobility state, a difference between the IAB node configuration by the RRC Reconfiguration message and its preference (request), or a periodic trigger (periodic transmission).

[0105] If a predetermined event is detected, in step S305, the IAB-MT of the IAB node 300 determines whether the timer started in step S303 has expired. If the timer is running (step S305: NO), the IAB-MT of the IAB node 300 suspends (does not transmit) the transmission of a UE Assistance Information message including an indicator and / or mobility information.

[0106] On the other hand, if the timer has expired (step S305: YES), in step S306, the IAB-MT of the IAB node 300 transmits a UE Assistance Information message including an indicator and / or mobility information to the donor node (gNB 200). Then, the process returns to step S302.

[0107] (1.7.2.4) Fourth Operation Pattern In the fourth operation pattern according to the first embodiment, the IAB-DU of the IAB node 300, rather than the IAB-MT of the IAB node 300, transmits a message including an indicator (first indicator and / or second indicator) related to the first operation pattern to the donor node (gNB 200). This message may be, for example, an F1 Setup Request message. The IAB-DU of the IAB node 300 may transmit a message (F1 Setup Request message) including mobility information related to the second operation pattern to the donor node (gNB 200).

[0108] 15 is a diagram illustrating an example of the operation of the IAB node 300 in the fourth operation pattern according to the first embodiment. Here, an example in which the indicator is included in the F1 Setup Request message will be described, but movement information may also be included in the F1 Setup Request message.

[0109] In step S401, IAB node 300 determines its IAB node configuration desires (requirements) based on whether it is operating a mobile IAB node function and / or whether it is installed in an environment where it should operate as a mobile IAB node (e.g., installed on a train). Such information may be written to the memory of IAB node 300, for example, when IAB node 300 is shipped from the factory and / or when it is installed. Step S401 may be performed after step S402.

[0110] In step S402, the IAB-DU of the IAB node 300 initiates an F1 setup procedure to set up an F1 interface with the donor node (gNB 200).

[0111] In step S403, the IAB-DU of IAB node 300 determines whether or not it desires (requests) mobile IAB node setup. If it desires (requests) mobile IAB node setup (step S403: YES), in step S404, the IAB-DU of IAB node 300 includes a second indicator (mobile IAB node indicator) in the F1 Setup Request message.

[0112] On the other hand, if a stationary IAB node setup is desired (requested) (step S403: NO, step S405: YES), in step S406, the IAB-DU of the IAB node 300 includes a first indicator (stationary IAB node indicator) in the F1 Setup Request message.

[0113] If either the mobile IAB node configuration or the stationary IAB node configuration is acceptable (step S405: NO), in step S407, the IAB-DU of the IAB node 300 includes both the first indicator (stationary IAB node indicator) and the second indicator (mobile IAB node indicator) in the F1 Setup Request message. Alternatively, the IAB-DU of the IAB node 300 may include a third indicator, indicating that either the mobile IAB node configuration or the stationary IAB node configuration is acceptable, in the F1 Setup Request message.

[0114] Then, in step S408, the IAB-DU of the IAB node 300 transmits an F1 Setup Request message including an indicator to the CU of the donor node (gNB 200). As a result, the donor node (gNB 200) can understand, based on the indicator included in the F1 Setup Request message, whether the IAB node 300 desires (requests) to be configured as a mobile IAB. The donor node (gNB 200) can then appropriately configure the IAB node 300 (e.g., RRC configuration, F1 configuration, etc.) taking into account such desires (requests).

[0115] (1.8) Modification of the First Embodiment In the first embodiment described above, the IAB node 300 can recognize that it has been configured as a mobile IAB node in accordance with the inclusion of IAB configuration information (information elements) for Release 18 as the RRC configuration and F1 configuration for the IAB node 300. However, imposing a restriction that Release 18 functions cannot be applied to stationary IAB nodes may reduce the flexibility of deployment. It is also possible to apply only Release 16 or 17 functions to the IAB node 300 and operate it as a mobile IAB node. Therefore, in this modification, the donor node (gNB 200) explicitly notifies the IAB node 300 of an information element (also referred to as "specific information") for specifying whether to configure the IAB node 300 as a mobile IAB node by including it in the RRC Reconfiguration. The IAB-MT of the IAB node 300 can determine whether or not movement is permitted based on such RRC settings (specific information).

[0116] In this modified example, the donor node (gNB200) may broadcast both the conventional "IAB Support IE" and the Release 18 "mobile IAB Support IE" in SIB1. In other words, the donor node (gNB200) may support both the conventional IAB node (stationary IAB node) and the mobile IAB node introduced in Release 18. The IAB-MT of the IAB node 300 may send both the first indicator and the second indicator to the donor node (gNB200) in Msg5 during the connection process (random access procedure). The donor node (gNB 200) decides whether to operate (configure) the IAB node 300 as a stationary IAB node or as a mobile IAB node, and transmits an RRC Reconfiguration message to the IAB-MT of the IAB node 300 according to the decision. Here, the RRC Reconfiguration message includes an information element indicating that the IAB node 300 is permitted to move or an information element indicating that the IAB node 300 is to be operated as a mobile IAB node. The IAB-MT of the IAB node 300 determines whether it has been configured (authorized, operated) as a stationary IAB node or configured (authorized, operated) as a mobile IAB node based on the information element (or the presence or absence of the information element).

[0117] (2) Second Embodiment The system operation according to the second embodiment will be described, focusing on the differences from the first embodiment. The system operation according to the second embodiment may be implemented in combination with the system operation according to the first embodiment.

[0118] (2.1) Overview of Operation Fig. 16 is a diagram showing an overview of the operation of the IAB node 300 according to the second embodiment. In the second embodiment, it is assumed that the IAB-MT of the IAB node 300 is in an RRC connected state.

[0119] In step S21, the IAB node 300 determines whether the IAB node 300 has been set as a mobile IAB node by the network (donor node).

[0120] In step S22, the IAB node 300 controls the operation of its own IAB node 300 based on whether or not the own IAB node 300 is set as a mobile IAB node and the movement state of the own IAB node 300.

[0121] As described in the modification of the first embodiment above, the IAB node 300 may receive, from the donor node (gNB 200), an RRC message (RRC Reconfiguration message) including information for determining whether or not to configure the IAB node 300 as a mobile IAB node prior to step S21. In step S21, the IAB node 300 may determine whether or not the IAB node 300 is configured as a mobile IAB node based on the information included in the RRC message (RRC Reconfiguration message). Alternatively, in step S21, the IAB node 300 may determine whether or not the IAB node 300 is configured as a mobile IAB node based on whether or not IAB configuration information (information elements) for Release 18 is included in the RRC message (RRC Reconfiguration message).

[0122] In step S22, if the IAB node 300 is set as a stationary IAB node and movement of the IAB node 300 is detected, the IAB node 300 may perform predetermined processing including at least one of sending a message to the donor node (gNB 200) and stopping relay operation. This makes it possible to prevent the IAB node 300 from operating as a stationary IAB node in a situation where it becomes inappropriate for the IAB node 300 to operate as a stationary IAB node.

[0123] Here, the predetermined processing may include, for example, transmitting to the donor node (gNB200) a message requesting release of the RRC connection between the donor node (gNB200) and the IAB node 300, cancellation of the RRC configuration, or reconfiguration of the RRC configuration. The predetermined processing may include transmitting to the donor node (gNB200) a message for notifying the movement. The predetermined processing may include stopping at least one of signal transmission to the donor node (gNB200) and signal transmission to the UE100. The predetermined processing may include broadcasting information for restricting access of the UE100 to the IAB node 300.

[0124] On the other hand, if the IAB node 300 is set as a mobile IAB node and the stationary (stopped) state of the IAB node 300 is detected, in step S22, the IAB node 300 may transmit a message to the donor node (gNB 200). This makes it possible to prevent the IAB node 300 from operating as a mobile IAB node in a situation where it becomes inappropriate for the IAB node 300 to operate as a mobile IAB node.

[0125] Here, the IAB node 300 may send a message to the donor node (gNB200) requesting a change to the settings of a stationary IAB node different from the mobile IAB node as a message transmission to the donor node (gNB200). The IAB node 300 may send a message to the donor node (gNB200) to notify the donor node (gNB200) of stationary status as a message transmission to the donor node (gNB200). Also, here, the IAB node 300 may resume signal transmission that was stopped in response to the above-mentioned movement detection. Also, the IAB node 300 may cancel the access restriction that was implemented in response to the above-mentioned movement detection.

[0126] (2.2) Specific Operation Examples As specific operation examples of the cellular communication system 1 according to the second embodiment, a first operation pattern and a second operation pattern will be described.

[0127] (2.2.1) First Operation Pattern In the first operation pattern according to the second embodiment, the IAB node 300 configured as a stationary IAB node performs a predetermined process in response to detection of its own movement (for example, movement of a vehicle on which the IAB node 300 is installed). The predetermined process includes at least one of sending a message to the donor node (gNB 200) requesting connection release or configuration cancellation, sending a message to the donor node (gNB 200) notifying the detection of movement, and the IAB node 300 stopping its own transmission (transmitter). Note that the IAB node 300 configured as a stationary IAB node may also perform a predetermined process in response to its own continued movement for a predetermined period of time.

[0128] FIG. 17 is a diagram illustrating an example of the operation of the IAB node 300 in the first operation pattern according to the second embodiment.

[0129] In step S501, the IAB node 300 is configured as a stationary IAB node.

[0130] In step S502, the IAB node 300 detects that it is moving (has started moving). For example, the IAB node 300 may detect the movement using its GNSS receiver. The IAB node 300 may also detect the movement by receiving speed information from a vehicle.

[0131] In step S503, the IAB node 300 performs at least one of the following operations 1) to 3): 1) The IAB-MT of the IAB node 300 transmits a message to the CU of the donor node (gNB 200) requesting RRC connection release, RRC deconfiguration, or RRC reconfiguration. The message may be an RRC message, for example, a UE Assistance Information message.

[0132] 2) The IAB-DU of the IAB node 300 sends a message to the CU of the donor node (gNB 200) requesting F1 connection release, F1 setting cancellation, or F1 setting change. The message may be an F1 message (F1-C message).

[0133] 3) The IAB-MT or IAB-DU of the IAB node 300 sends a message to the CU of the donor node (gNB 200) notifying it that it has detected its movement. The message may be an RRC message or an F1 message (F1-C message).

[0134] When the CU of the donor node (gNB200) receives the message of step S503, it may transmit a message (e.g., an RRC Reconfiguration message) to the IAB node 300 to perform appropriate processing, such as canceling the IAB setting or changing to a mobile IAB setting. The IAB node 300 may receive the message (step S504). The CU of the donor node (gNB200) may perform handover of the UE 100 connected to the IAB node 300 to a neighboring cell (e.g., a macrocell).

[0135] In step S505, the IAB-MT and / or IAB-DU of the IAB node 300 stops its transmission (backhaul link transmission and / or access link transmission). In this case, in step S503, the IAB node 300 may notify the CU of the donor node (gNB 200) of the transmission stop.

[0136] In step S505, the IAB-DU of the IAB node 300 may broadcast information for access restriction in the information element "cellBarred" in the master information block (MIB) and / or the information element "cellReservedForOtherUse" or "cellReservedForFutureUse" in SIB1. This can restrict the UE 100 in the RRC idle state or the RRC inactive state from newly reselecting the cell of the IAB node 300 (mIAB cell).

[0137] (2.2.2) Second Operation Pattern In the second operation pattern according to the second embodiment, the IAB node 300 configured as a mobile IAB node performs a predetermined process when it detects its own stationary state (for example, when the vehicle on which the IAB node 300 is installed is stationary). The predetermined process may include transmitting a message to the donor node (gNB 200) requesting or requesting a change to the stationary IAB configuration. The predetermined process may include transmitting a message to the donor node (gNB 200) notifying that it has detected stationary state. Note that the IAB node 300 configured as a mobile IAB node may perform a predetermined process when its stationary state continues for a predetermined period of time.

[0138] FIG. 18 is a diagram illustrating an example of the operation of the IAB node 300 in the first operation pattern according to the second embodiment.

[0139] In step S601, the IAB node 300 is configured as a mobile IAB node.

[0140] In step S602, the IAB node 300 detects that it is stationary. For example, the IAB node 300 may detect that it is stationary using its GNSS receiver. The IAB node 300 may also detect that it is stationary by receiving speed information from a vehicle.

[0141] In step S603, the IAB node 300 performs at least one of the following operations 1) and 2).

[0142] 1) The IAB-MT or IAB-DU of the IAB node 300 sends a message to the CU of the donor node (gNB 200) requesting or requesting a change to the static IAB setting. The message may be an RRC message, for example, a UE Assistance Information message.

[0143] 2) The IAB-MT or IAB-DU of the IAB node 300 sends a message to the CU of the donor node (gNB 200) notifying it that it has detected its stationary status. The message may be an RRC message or an F1 message (F1-C message).

[0144] When the CU of the donor node (gNB200) receives the message of step S603, it may transmit a message (e.g., an RRC Reconfiguration message) to the IAB node 300 to perform appropriate processing, such as canceling the mobile IAB setting or changing to a static IAB setting. The IAB node 300 may receive the message (step S604). Here, the IAB node 300 may resume signal transmission that was stopped in response to the above-mentioned movement detection. The IAB node 300 may also cancel the access restriction that was implemented in response to the above-mentioned movement detection.

[0145] (3) Other Embodiments In the above embodiment, an example in which the relay node is an IAB node has been described, but the relay node may be a network-controlled repeater device. Such a repeater device is also called an NCR (Network Controlled Repeater) node. The NCR device that is a relay node has an NCR-MT and an NCR-Fwd (Forwarding). The IAB-MT in the above embodiment may be an NCR-MT.

[0146] The above-described operational flows are not limited to being implemented independently, but can also be implemented by combining two or more operational flows. For example, some steps of one operational flow may be added to another operational flow, or some steps of one operational flow may be replaced with some steps of another operational flow. In each flow, it is not necessary to execute all steps, and only some steps may be executed.

[0147] In the above-described embodiments and examples, an example in which the base station is an NR base station (gNB) has been described, but the base station may be an LTE base station (eNB) or a 6G base station. The base station may also be a relay node such as an IAB (Integrated Access and Backhaul) node. The base station may also be a DU of the IAB node. The UE 100 may also be an MT (Mobile Termination) of the IAB node.

[0148] That is, the UE 100 may be a terminal function unit (a type of communication module) for a base station to control a repeater that relays signals. Such a terminal function unit is referred to as an MT. Examples of the MT include, in addition to the IAB-MT, an NCR (Network Controlled Repeater)-MT and a RIS (Reconfigurable Intelligent Surface)-MT.

[0149] The term "network node" primarily refers to a base station, but may also refer to a core network device or a part of a base station (CU, DU, or RU). A network node may also be configured by a combination of at least a part of a core network device and at least a part of a base station.

[0150] A program may be provided that causes a computer to execute each process performed by the UE 100, the gNB 200, or the IAB node. The program may be recorded on a computer-readable medium. Using a computer-readable medium, the program can be installed on a computer. Here, the computer-readable medium on which the program is recorded may be a non-transitory recording medium. The non-transitory recording medium is not particularly limited, and may be, for example, a recording medium such as a CD-ROM and / or a DVD-ROM. Furthermore, circuits that execute each process performed by the UE 100 or the gNB 200 may be integrated, and at least a portion of the UE 100, the gNB 200, or the IAB node may be configured as a semiconductor integrated circuit (chip set, SoC: System on a chip).

[0151] The functions performed by the UE 100, the gNB 200, or the IAB node may be implemented in circuitry or processing circuitry, including general-purpose processors, application-specific processors, integrated circuits, ASICs (Application Specific Integrated Circuits), a CPU (a Central Processing Unit), conventional circuits, and / or combinations thereof, programmed to perform the described functions. A processor includes transistors and other circuits and is considered to be circuitry or processing circuitry. A processor may also be a programmed processor that executes a program stored in memory. In this specification, circuitry, unit, or means refers to hardware that is programmed to perform the described functions or hardware that executes them. The hardware may be any hardware disclosed herein or any hardware known to be programmed or capable of performing the described functions. If the hardware is a processor, the circuitry, means, or unit is a combination of hardware and software used to configure the hardware and / or processor.

[0152] As used in this disclosure, the terms "based on" and "depending on / in response to" do not mean "based only on" or "depending only on," unless expressly stated otherwise. The term "based on" means both "based only on" and "based at least in part on." Similarly, the term "depending on" means both "depending only on" and "depending at least in part on." The terms "include," "comprise," and variations thereof do not mean including only the listed items, but may mean including only the listed items or may include additional items in addition to the listed items. Additionally, the term "or," as used in this disclosure, is not intended to mean an exclusive or. Furthermore, any reference to elements using designations such as "first," "second," etc., as used in this disclosure does not generally limit the quantity or order of those elements. These designations may be used herein as a convenient method of distinguishing between two or more elements. Thus, a reference to a first and a second element does not imply that only two elements may be employed therein or that the first element must precede the second element in some way. In this disclosure, where articles are added by translation, such as a, an, and the in English, these articles shall include the plural unless the context clearly indicates otherwise.

[0153] Although one embodiment has been described in detail above with reference to the drawings, the specific configuration is not limited to the above, and various design changes can be made within the scope of the gist. Furthermore, the embodiments, operation examples, and processes can be appropriately combined within the scope of not being inconsistent.

[0154] This application claims priority to U.S. Provisional Application No. 63 / 594,302 (filed October 30, 2023), the entire contents of which are incorporated herein by reference.

[0155] (4) First Supplementary Note The following is a supplementary note regarding the features of the above-described embodiment.

[0156] (Supplementary Note 1) A communication method executed by a relay node in a cellular communication system, comprising: a step of transmitting a message to the donor node including information for determining whether the relay node is configured as a mobile relay node or a stationary relay node; and a step of receiving configuration information indicating the configuration content of the relay node from the donor node.

[0157] (Supplementary Note 2) The communication method according to Supplementary Note 1, wherein the relay node transmits the message to the donor node, the message including a first indicator indicating that the stationary relay node configuration is desired or requested, in response to the desire or request for the stationary relay node configuration.

[0158] (Supplementary Note 3) The communication method according to Supplementary Note 1 or 2, wherein the relay node transmits the message to the donor node, the message including a second indicator indicating that the mobile relay node configuration is desired or requested, in response to the desire or request for the mobile relay node configuration.

[0159] (Supplementary Note 4) The communication method according to any one of Supplementary Notes 1 to 3, wherein the relay node transmits the message to the donor node, the message including a first indicator indicating that the stationary relay node configuration is desired or requested, and a second indicator indicating that the mobile relay node configuration is desired or requested, in response to there being no desired or requested configuration for the relay node.

[0160] (Supplementary Note 5) The communication method according to any one of Supplementary Notes 1 to 4, wherein the relay node transmits the message to the donor node, the message including movement information indicating a movement state of the relay node.

[0161] (Supplementary Note 6) The communication method according to Supplementary Note 5, wherein the movement information is information indicating a movement speed of the relay node.

[0162] (Supplementary Note 7) The communication method according to Supplementary Note 5, wherein the movement information is information indicating a possibility that the relay node will move.

[0163] (Supplementary Note 8) The communication method according to any one of Supplementary Notes 1 to 7, wherein the relay node includes a mobile termination (MT), and the MT transmits the message including the information to the donor node.

[0164] (Supplementary Note 9) The communication method according to Supplementary Note 8, wherein the message is Msg5 used in a random access procedure.

[0165] (Supplementary Note 10) The communication method according to Supplementary Note 8, wherein the message is a message different from Msg5 used in a random access procedure.

[0166] (Supplementary Note 11) The communication method according to Supplementary Note 10, wherein the relay node starts a timer when transmitting the message, and controls so as not to transmit the next message while the timer is running.

[0167] (Supplementary Note 12) The communication method according to any one of Supplementary Notes 1 to 7, wherein the relay node includes a Distributed Unit (DU), and the DU transmits the message including the information to the donor node.

[0168] (Supplementary Note 13) The communication method according to any one of Supplementary Notes 1 to 12, wherein the relay node includes an MT (Mobile Termination), the configuration information includes information for specifying whether or not to configure the relay node as the mobile relay node, and the MT receives an RRC message including the configuration information from the donor node.

[0169] (Supplementary Note 14) A relay node used in a cellular communication system, comprising: a transmitter that transmits a message to the donor node, the message including information for determining whether the relay node is configured as a mobile relay node or a stationary relay node; and a receiver that receives, from the donor node, configuration information indicating the configuration content of the relay node.

[0170] (Supplementary Note 15) A network node used as a donor node in a cellular communication system, comprising: a receiver that receives from the relay node a message including information for determining either a mobile relay node setting or a stationary relay node setting as a setting of the relay node; and a transmitter that transmits to the relay node setting information indicating the setting content of the relay node.

[0171] (Supplementary Note 16) A communication method executed by a relay node in a cellular communication system, comprising: a step of identifying whether or not the relay node is set as a mobile relay node by a network; and a step of controlling an operation of the relay node based on whether or not the relay node is set as a mobile relay node and a mobility state of the relay node.

[0172] (Supplementary Note 17) The communication method according to Supplementary Note 16, further comprising the step of receiving a Radio Resource Control (RRC) message from a donor node included in the network, wherein the RRC message includes information for determining whether or not the relay node is configured as the mobile relay node, and the relay node determines whether or not the relay node is configured as the mobile relay node based on the information included in the RRC message.

[0173] (Supplementary Note 18) The communication method according to Supplementary Note 16 or 17, wherein the step of controlling the operation includes a step of performing predetermined processing including at least one of sending a message to a donor node and stopping relay operation when the relay node is set as a stationary relay node different from the mobile relay node and movement of the relay node is detected.

[0174] (Supplementary Note 19) The communication method according to Supplementary Note 18, wherein the step of performing the predetermined processing includes the step of transmitting a message to the donor node requesting release of a Radio Resource Control (RRC) connection between the donor node and the relay node, cancellation of an RRC configuration, or reconfiguration of an RRC configuration.

[0175] (Supplementary Note 20) The communication method according to Supplementary Note 18 or 19, wherein the step of performing the predetermined process includes a step of transmitting a message to the donor node to notify the donor node of the movement.

[0176] (Supplementary Note 21) The communication method according to any one of Supplementary Notes 18 to 20, wherein the step of performing the predetermined process includes a step of stopping at least one of signal transmission to the donor node and signal transmission to the user device.

[0177] (Supplementary Note 22) The communication method according to any one of Supplementary Notes 18 to 20, wherein the step of performing the predetermined process includes a step of broadcasting information for restricting access of user devices to the relay node.

[0178] (Supplementary Note 23) The communication method according to any one of Supplementary Notes 16 to 22, wherein the relay node transmits a message to the donor node when the relay node is configured as the mobile relay node and when the relay node is detected to be stationary.

[0179] (Supplementary Note 24) The communication method according to Supplementary Note 23, wherein the relay node transmits the message to the donor node to request a change to a configuration of a stationary relay node different from the mobile relay node.

[0180] (Supplementary Note 25) The communication method according to Supplementary Note 23 or 24, wherein the relay node transmits the message for notifying the quiescing to the donor node.

[0181] (Supplementary Note 26) A relay node used in a cellular communication system, comprising: a control unit that determines whether or not the relay node is set as a mobile relay node by a network; and the control unit controls operation of the relay node based on whether or not the relay node is set as a mobile relay node and a mobility state of the relay node.

[0182] (Supplementary Note 27) A network node for use as a donor node in a cellular communication system, comprising: a transmitter configured to transmit a Radio Resource Control (RRC) message to a relay node, the RRC message including information for identifying whether the relay node is to be configured as a mobile relay node.

[0183] (5) Appendix 2 1. Introduction The Rel-18 Work Item (WI) on Mobile IAB aims to support mobility of IAB nodes, whereas in Rel-16 / 17, IAB nodes were assumed to be stationary. In RAN2#123-bis, the following open issues were identified:

[0184] From the R2 perspective, a Rel-18 mobile IAB node is not supported to operate simultaneously as a Rel-16 / 17 IAB node, for example, since it does not support child IAB nodes. This means that there are restrictions on the network when configuring simultaneous use of R-18 mIAB functionality and Rel-16 / 17 IAB functionality (details require further study). Whether an IAB node can send both MSG5 indications to the network, and whether the network must decide or the IAB node must decide, requires further study.

[0185] This appendix discusses the remaining issues of the IAB-MT access procedure.

[0186] 2. Discussion 2.1 Open Issues Regarding IAB-MT Configuration 2.1.1 Decision on Mobile or Stationary IAB-MT Configuration The above agreement requires further consideration as to whether the network or the IAB node decides to configure the IAB-MT in a mobile IAB-MT configuration. The general assumption is that it is up to the network to decide how to configure the IAB-MT. That is, if the IAB node is stationary, the network configures the node with a Rel-16 / 17 stationary IAB; otherwise, the network configures the node with a Rel-18 mobile IAB. It is clear to apply the same principle to this issue.

[0187] Proposal 1: RAN2 should agree that the IAB donor decides whether the accessing IAB-MT is to be configured as a mobile IAB-MT or a stationary IAB-MT.

[0188] On the other hand, considering that the accessing IAB-MT is still in idle mode, only the IAB-MT can know whether it is installed in a vehicle or whether it is currently / potentially moving, i.e., whether it needs to be configured as a mobile IAB-MT. Therefore, the IAB-MT needs to inform the network of its preference as to whether it wants to be configured as a stationary IAB node or a mobile IAB node, or whether it doesn't matter in some cases. The indication in Msg5 can be used to notify this preference.

[0189] It should be noted that this indication may mean more than a "preference." For example, it may be a "request," especially if the IAB-MT is mobile, because the IAB node should be configured with a mobile IAB, not a stationary IAB.

[0190] Proposal 2: RAN2 should agree that if an IAB node wishes to be configured with a mobile IAB-MT, the IAB-MT will only send a Rel-18 mobile IAB node indication in Msg5.

[0191] Proposal 3: RAN2 needs to discuss whether the IAB-MT can send both Rel-18 mobile IAB node indication and conventional IAB node indication in Msg5 if the IAB node does not have preference.

[0192] After the IAB donor decides to allow the accessing IAB-MT to operate as a mobile IAB-MT, the IAB-MT is configured through dedicated signaling, i.e., RRC reconfiguration. Normally, it is assumed that the IAB-MT can identify whether it is configured as a mobile IAB-MT by checking for mobile IAB-specific configuration. However, the dedicated signaling IEs are exactly the same between Rel-17 (stationary IAB) and Rel-18 (mobile IAB). That is, since there are no new Rel-18 IEs in RRC reconfiguration, like in TS38.331's ongoing CR, the IAB-MT cannot know whether it is configured as a mobile IAB. Therefore, a one-bit flag needs to be introduced in RRC reconfiguration to explicitly allow the IAB-MT to operate as a mobile IAB. For example, a stationary IAB node, on the other hand, needs to operate as described in Proposal 5 below.

[0193] Proposal 4: RAN2 should agree to introduce a one-bit indication in the RRC reconfiguration to inform the IAB-MT whether it is authorized to operate as a mobile IAB node.

[0194] If an IAB donor decides to configure an accessing IAB-MT as a stationary IAB node, the IAB-MT must not move. However, a train on which an IAB node configured as a stationary IAB node is installed may start moving. Since a stationary IAB node obviously cannot stop a train, it is desirable for the IAB node to, for example, stop DL transmission, report a change in preference / state to the donor (e.g., via UAI), be deconfigured from the stationary IAB node configuration, and reconfigure with a mobile IAB node configuration. RAN2 needs to discuss what to do when it detects that a stationary IAB-MT has started moving.

[0195] Proposal 5: RAN2 should discuss what to do if a stationary IAB-MT detects movement (e.g., stop transmitting, indicate movement to IAB donor, etc.).

[0196] Note: Alternatively, the mechanisms of Proposal 2 through Proposal 5 could be implemented by IAB-DU via F1-AP rather than IAB-MT via RRC. However, given that the issue was identified in RAN2 and this is the last meeting before Rel-18 Stage 3 is finalized, it is preferable to specify this in RAN2.

[0197] 2.2 Other Issues Regarding IAB-MT Access Restrictions 2.2.1 Access of Stationary IAB Nodes WID states that a mobile IAB node serves only UEs. This means that a mobile IAB node must not serve other IAB nodes as child nodes. A mobile IAB node must not have any subordinate IAB nodes. That is, it must only serve UEs.

[0198] To ensure this requirement, RAN2#119e has agreed to the following: Not broadcasting the "iab-Support" indication is sufficient to prevent other IAB nodes from accessing the mobile IAB (no impact on the specification).

[0199] However, this agreement was reached without sufficient discussion. Regarding the "(no impact on the specification)" part in particular, it is questionable whether it is really sufficient to leave it to the implementation. Since WID clearly requires that mobile IAB nodes are not permitted to access other mobile IAB nodes, the specification needs to clarify this assumption to avoid confusion in mobile IAB implementations. Therefore, it is desirable for the Stage 2 specification to reflect the above agreement or clarify that "in this release, mobile IAB nodes cannot access other mobile IAB nodes."

[0200] Proposal 6: RAN2 should agree to reflect in this release in the Stage 2 specification that an IAB node shall not set the IAB Support IE in the SIB when acting as a mobile IAB node.

[0201] 2.2.2 Mobile IAB Node Access In RAN2#120, the following agreements have been reached for mobile IAB nodes to access parent nodes: Mobile IAB nodes can camp on and connect to legacy Rel-16 / Rel-17 IAB capable cells. R2 assumes that a "supporting mobile-IAB" indication is provided by a Rel-18 mobile IAB capable parent cell.

[0202] Based on these agreements, the mapping between indication availability and IAB node behavior can be summarized in Table 1 (Indications in SIB and IAB node behavior).

[0203] 2.2 Other Issues Related to IAB-MT Access Restrictions 2.2.2 Mobile IAB Node Access For cases 1 and 4, both IEs are either unavailable or available, so the behavior of the mobile IAB node is as shown in Table 1.

[0204] Proposal 7: RAN2 should agree to prohibit mobile IAB access to parent nodes that do not broadcast both the legacy IAB support IE and the new "Mobile IAB Support" IE.

[0205] Proposal 8: RAN2 should agree to allow mobile IAB access to parent nodes that broadcast both the legacy IAB support IE and the new "Mobile IAB Support" IE.

[0206] Regarding Case 2, it is unclear whether a mobile IAB node can access the parent node if the new indication is provided but the legacy IAB support IE is absent. Furthermore, it is necessary to discuss whether it is a valid case for the parent node to broadcast only the new indication without the legacy IE. While it is possible that a parent node may be deployed to serve only mobile IAB nodes, it is a common case for a parent node to accept access from both legacy and mobile IAB nodes. Given these possibilities, it may be beneficial to allow some flexibility in various configurations.

[0207] Proposal 9: RAN2 should discuss whether it is a valid configuration for the conventional IAB support IE not to be provided and the new "Mobile IAB Node Support" IE to be broadcast (i.e., Case 2 in Table 1).

[0208] For Case 3, i.e., when the legacy IAB support IE is provided but the new indication is not present, the mobile IAB node can access the parent node because RAN2 has agreed as described above that "a mobile IAB node can camp on and connect to a legacy Rel-16 / Rel-17 IAB-capable cell." However, the expected behavior of the IAB node is the same as in Case 4. In Case 3, the mobile IAB node can access the parent node under certain conditions, whereas in Case 4, the mobile IAB node can always access the parent node. For example, the mobile IAB node can access the parent node only if it cannot find any cells broadcasting the new indication. As another example, whether the mobile IAB node is allowed to access cells that do not broadcast the new indication can be configured. For example, this can be configured by the AMF or OAM during the authorization / validation process. Therefore, RAN2 needs to clarify the conditions under which the mobile IAB node can access a parent node that does not broadcast the new indication.

[0209] Proposal 10: RAN2 needs to discuss the conditions under which a mobile IAB node is allowed to access a parent node that broadcasts the legacy IAB support IE but does not provide the new "Mobile IAB Node Support" IE (i.e., Case 3 in Table 1). For example, only if no cell broadcasting the new indication can be found, is the parent node allowed to be accessed.

Claims

1. A communication method performed by a relay node in a cellular communication system, comprising: transmitting an RRC Setup Complete message to the donor node, the RRC Setup Complete message including either a first indicator indicating that the relay node connects as a mobile relay node or a second indicator indicating that the relay node connects as a stationary relay node.

2. The communication method according to claim 1, wherein the RRC Setup Complete message is Msg5 used in a random access procedure.

3. The communication method according to claim 1, wherein when the first indicator is included in the RRC Setup Complete message, the second indicator is not included in the RRC Setup Complete message, and when the second indicator is included in the RRC Setup Complete message, the first indicator is not included in the RRC Setup Complete message.

4. A communication method executed by a network node in a cellular communication system, comprising: receiving an RRC Setup Complete message from the relay node, the RRC Setup Complete message including either a first indicator indicating that the relay node is to connect as a mobile relay node or a second indicator indicating that the relay node is to connect as a stationary relay node; and establishing a connection with the relay node based on either the first indicator or the second indicator.

5. The communication method according to claim 4, wherein the RRC Setup Complete message is Msg5 used in a random access procedure.

6. The communication method according to claim 4, wherein if the first indicator is included in the RRC Setup Complete message, the second indicator is not included in the RRC Setup Complete message, and if the second indicator is included in the RRC Setup Complete message, the first indicator is not included in the RRC Setup Complete message.

7. A relay node in a cellular communication system, comprising: a transmitter configured to transmit an RRC Setup Complete message to the donor node, the RRC Setup Complete message including either a first indicator indicating that the relay node connects as a mobile relay node or a second indicator indicating that the relay node connects as a stationary relay node.

8. The relay node according to claim 7, wherein the RRC Setup Complete message is Msg5 used in a random access procedure.

9. The relay node according to claim 7, wherein if the first indicator is included in the RRC Setup Complete message, the second indicator is not included in the RRC Setup Complete message, and if the second indicator is included in the RRC Setup Complete message, the first indicator is not included in the RRC Setup Complete message.

10. A network node in a cellular communication system, comprising: a receiving unit that receives an RRC Setup Complete message from the relay node, the RRC Setup Complete message including either a first indicator indicating that the relay node is to connect as a mobile relay node or a second indicator indicating that the relay node is to connect as a stationary relay node; and a control unit that establishes a connection with the relay node based on either the first indicator or the second indicator.

11. The network node according to claim 10, wherein the RRC Setup Complete message is Msg5 used in a random access procedure.

12. The network node of claim 10, wherein if the first indicator is included in the RRC Setup Complete message, the second indicator is not included in the RRC Setup Complete message, and if the second indicator is included in the RRC Setup Complete message, the first indicator is not included in the RRC Setup Complete message.

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