COMMUNICATION CONTROL METHOD, TARGET DONOR NODE, COMMUNICATION SYSTEM, PROGRAM, AND PROCESSOR

Abstract

A communication control method according to an aspect of the present invention is used in a cellular communication system. The communication control method includes a step in which either a donor node or a stationary intermediate relay node that does not move transmits information pertaining to a mobile relay node.

Description

Communication Control Method

[0001] The present disclosure relates to a communication control method for use in a cellular communication system.

[0002] The Third Generation Partnership Project (3GPP), a standardization project for cellular communication systems, is considering the introduction of a new relay node called an Integrated Access and Backhaul (IAB) node (see, for example, Non-Patent Document 1). One or more relay nodes intervene in communication between a base station and a user device and relay this communication.

[0003] 3GPP TS 38.300 V17.1.0 (2022-06)

[0004] A communication control method according to a first aspect is a communication control method for use in a cellular communication system, comprising a step of transmitting information about a mobile relay node from either a donor node or a stationary intermediate relay node.

[0005] A communication control method according to a second aspect is a communication control method for use in a cellular communication system, the communication control method comprising the step of transmitting, by a mobile relay node, information relating to the mobile relay node.

[0006] A communication control method according to a third aspect is a communication control method for use in a cellular communication system, the communication control method comprising the steps of: a source donor node transmitting a handover request message to a target donor node, the handover request message including information indicating that a mobile relay node is a handover target; and a target donor node selecting, in response to receiving the handover request message, a cell managed by the target donor node as a handover destination cell for the mobile relay node.

[0007] FIG. 1 is a diagram showing an example of the configuration of a cellular communication system according to one embodiment. FIG. 2 is a diagram showing the relationship between an IAB node, parent nodes, and child nodes. FIG. 3 is a diagram showing an example of the configuration of a gNB (base station) according to one embodiment. FIG. 4 is a diagram showing an example of the configuration of an IAB node (relay node) according to one embodiment. FIG. 5 is a diagram showing an example of the configuration of a UE (user equipment) according to one embodiment. FIG. 6 is a diagram showing an example of a protocol stack related to an IAB-MT RRC connection and a NAS connection. FIG. 7 is a diagram showing an example of a protocol stack related to the F1-U protocol. FIG. 8 is a diagram showing an example of a protocol stack related to the F1-C protocol. FIG. 9 is a diagram showing an example of a first scenario according to the first embodiment. FIG. 10 is a diagram showing an example of a second scenario according to the first embodiment. FIG. 11 is a diagram showing an example of an operation related to a first operation example. FIG. 12 is a diagram showing an example of an operation related to a second operation example. FIG. 13 is a diagram showing an example of an operation related to a third operation example. Fig. 14 is a diagram showing an operation example according to the fourth operation example. Fig. 15 is a diagram showing an operation example according to the fifth operation example. Fig. 16 is a diagram showing an operation example according to the sixth operation example. Fig. 17 is a diagram showing an operation example according to the seventh operation example. Fig. 18 is a diagram showing an operation example according to the eighth operation example. Fig. 19 is a diagram showing an operation example according to the ninth operation example. Fig. 20 is a diagram showing an operation example according to the tenth operation example. Fig. 21 is a diagram showing an operation example according to the eleventh operation example.

[0008] A cellular communication system according to an embodiment will be described with reference to the drawings. In the description of the drawings, the same or similar parts are denoted by the same or similar reference numerals.

[0009] [First embodiment] (Configuration of cellular communication system) An example configuration of a cellular communication system according to one embodiment will be described. A cellular communication system 1 according to one 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.

[0010] FIG. 1 is a diagram showing an example of the configuration of a cellular communication system 1 according to an embodiment.

[0011] 1, 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.

[0012] In the following, we will mainly describe an example in which base station 200 is an NR base station, but base station 200 may also be an LTE base station (i.e., eNB).

[0013] In the following, base stations 200-1 and 200-2 may be referred to as gNB 200 (or base station 200), and IAB nodes 300-1 and 300-2 may be referred to as IAB node 300.

[0014] The 5GC 10 has an Access and Mobility Management Function (AMF) 11 and a User Plane Function (UPF) 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 Non-Access Stratum (NAS) signaling. The UPF 12 is a device that performs transfer control of user data, etc.

[0015] Each gNB 200 is a fixed wireless communication node and manages one or more cells. A cell is used as a term indicating the smallest unit of a wireless communication area. A cell may also be used as a term indicating a function or resource for performing wireless communication with a UE 100. One cell belongs to one carrier frequency. Hereinafter, there may be cases where a cell and a base station are used interchangeably.

[0016] Each gNB 200 is interconnected with the 5GC 10 via an interface called an NG interface. In FIG. 1, two gNBs 200-1 and 200-2 connected to the 5GC 10 are illustrated.

[0017] Each gNB 200 may be divided into a central unit (CU) and a distributed unit (DU). The CU and DU are connected to each other 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.

[0018] 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).

[0019] FIG. 1 shows an example in which IAB node 300-1 wirelessly connects with donor node 200-1, IAB node 300-2 wirelessly connects with IAB node 300-1, and the F1 protocol is transmitted over two backhaul hops.

[0020] 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.

[0021] FIG. 2 is a diagram showing an example of the relationship between the IAB node 300, parent nodes, and child nodes.

[0022] As shown in FIG. 2, 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.

[0023] 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.

[0024] 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.

[0025] Furthermore, 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, and route management 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.

[0026] (Configuration of base station) Next, the configuration of the gNB 200, which is a base station according to the embodiment, will be described. Fig. 3 is a diagram showing an example configuration of the gNB 200. As shown in Fig. 3, the gNB 200 has a wireless communication unit 210, a network communication unit 220, and a control unit 230.

[0027] 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.

[0028] 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.

[0029] 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.

[0030] (Configuration of Relay Node) Next, a configuration of an IAB node 300, which is a relay node (or relay node device; hereinafter, may be referred to as a "relay node") according to an embodiment, will be described. FIG. 4 is a diagram showing an example configuration of the IAB node 300. As shown in FIG. 4, 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.

[0031] 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.

[0032] 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.

[0033] 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.

[0034] (Configuration of User Device) Next, a configuration of the UE 100, which is a user device according to the embodiment, will be described. Fig. 5 is a diagram showing an example configuration of the UE 100. As shown in Fig. 5, the UE 100 includes a radio communication unit 110 and a control unit 120.

[0035] 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.

[0036] 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.

[0037] (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.

[0038] As shown in FIG. 6, 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.

[0039] 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.

[0040] 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.

[0041] 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.

[0042] 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.

[0043] 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.

[0044] 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.

[0045] 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.

[0046] 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 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.

[0047] 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.

[0048] 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.

[0049] 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 sending the message to 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."

[0050] Also, the upstream direction and the uplink (UL) direction may be used interchangeably, and the downstream direction and the downlink (DL) direction may be used interchangeably.

[0051] (Two Scenarios) 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 allows, 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 user (or UE 100) on a vehicle can receive services via a mobile IAB node installed on the vehicle.

[0053] In 3GPP, it is also being discussed that a mobile IAB node should provide services to UE 100 without having an IAB node under its control.

[0054] On the other hand, in contrast to mobile IAB nodes, there are also IAB nodes that do not move. Such IAB nodes may be 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 is installed at an installation location and is stationary (or does not move). Alternatively, the intermediate IAB node may be a stationary IAB node that does not move. Alternatively, the intermediate IAB node may be a fixed IAB node.

[0055] 3GPP is considering the following two scenarios regarding mobile IAB nodes, and how complex each scenario is.

[0056] (First Scenario) The Mobile IAB Node Connects Only to the Donor Node (Second Scenario) The Mobile IAB Node Can Also Connect to Intermediate IAB Nodes FIG. 9 is a diagram illustrating an example of the first scenario according to the first embodiment. The example of FIG. 9 illustrates an example in which a mobile IAB node 300M installed on a bus moves while connected to each DU (such as DU 200-D1) (which may also be referred to as an "IAB-donor-DU") of each donor node 200. The first scenario is a scenario in which the mobile IAB node 300M connects to the donor node 200 without connecting to an intermediate IAB node. "Connecting only to the donor node" means connecting to the donor node 200 without connecting to an intermediate IAB node.

[0057] 10 is a diagram illustrating an example of a second scenario according to the first embodiment. The example of FIG. 10 illustrates an example in which a mobile IAB node 300M installed on a bus is moving while connecting to each DU (such as DU 200-D1A) (which may also be referred to as an "IAB-donor-DU") of each donor node 200 and also connecting to an intermediate IAB node 300S (an IAB-DU included in the intermediate IAB node 300S). In this way, the second scenario is a scenario in which the mobile IAB node 300M can connect to both the donor node 200 and the intermediate IAB node 300S.

[0058] In 3GPP, some say that the first scenario is less complex than the second scenario, while others say that the first scenario is more complex than the second scenario.

[0059] In the first embodiment, a first scenario will be described. In the first scenario, for example, if the mobile IAB node 300M cannot connect to the donor node 200, the mobile IAB node 300M is considered to be disconnected from the network, and it is assumed that the mobile IAB node 300M cannot provide services to the subordinate UE 100. However, if the mobile IAB node 300M can connect to the donor node 200, it will be possible to appropriately provide services to the UE 100.

[0060] Therefore, the first embodiment aims to enable the mobile IAB node 300M to connect to the donor node 200 appropriately.

[0061] In the first embodiment, the following five operation examples will be described in order.

[0062] (1.1) First operation example: The donor node 200 broadcasts connection permission information for the mobile IAB node 300M.

[0063] (1.2) Second operation example: The intermediate IAB node 300S broadcasts connection denial information of the mobile IAB node 300M.

[0064] (1.3) Third operation example: The serving cell sets a list of selectable cells for the mobile IAB node 300M.

[0065] (1.4) Fourth Operation Example: The mobile IAB node 300M is capable of cell selection from cells included in the measurement configuration or conditional reconfiguration.

[0066] (1.5) Fifth operation example: The donor node 200 broadcasts the PRACH resources that can be exclusively used by the mobile IAB node 300M.

[0067] Note that the first to fifth operation examples are examples in which either a donor node (e.g., donor node 200) or a stationary intermediate relay node (e.g., intermediate IAB node 300S) transmits information about a mobile relay node (e.g., mobile IAB node 300M). The information about the mobile relay node is different in each operation example. Specific examples of the information about the mobile relay node will be described in each operation example.

[0068] (1.1) First Operation Example First, the first operation example will be described.

[0069] The first operation example is an example in which the donor node 200 broadcasts connection permission information for the mobile IAB node 300M. The connection permission information is, for example, information indicating that connection of a mobile relay node (e.g., the mobile IAB node 300M) is permitted. In the first operation example, information related to the mobile relay node (e.g., the mobile IAB node 300M) is connection permission information. In the first operation example, the donor node (e.g., the donor node 200) broadcasts the connection permission information.

[0070] As a result, for example, the mobile IAB node 300M that has received the connection permission information can recognize that the cell of the donor node 200 that broadcast the connection permission information is a connectable cell. Then, by connecting to that cell, the mobile IAB node 300M can connect to the donor node 200. Therefore, the mobile IAB node 300M can connect to the donor node 200 appropriately.

[0071] FIG. 11 is a diagram illustrating an example of operation according to the first example of operation.

[0072] 11 , in step S10, the donor node 200 transmits connection permission information. The donor node transmits the connection permission information by broadcasting a system information block (SIB) including the connection permission information. The mobile IAB node 300M receives the connection permission information.

[0073] The connection permission information may be information indicating that connection of the mobile IAB node 300M is permitted. Alternatively, the connection permission information may be information indicating that the node broadcasting the connection permission information is the donor node 200 (or the cell of the donor node 200). Alternatively, the connection permission information may be information indicating that the mobile IAB node 300M is supported. The cell broadcasting the connection permission information supports the mobile IAB node 300M, and may be considered as a candidate cell for cell selection by the mobile IAB node 300M. Note that the connection permission information is notified, for example, by an information element called "Mobile-IAB-Supported." The connection permission information is an information element different from the existing information element "IAB-Supported." The mobile IAB node 300M may determine that the cell is accessible when both "Mobile-IAB-Supported" and "IAB-Supported" are notified in the SIB. Alternatively, the mobile IAB node 300M may determine that the cell is accessible when "Mobile-IAB-Supported" is notified in the SIB (regardless of whether "IAB-Supported" is notified).

[0074] The CU (IAB-donor-CU) of the donor node 200 may select a DU (IAB-donor-DU) of the donor node 200 that authorizes the connection of the mobile IAB node 300M, and may transmit an F1 message including access connection authorization information to the selected DU of the donor node 200. In response to receiving the F1 message, the DU of the donor node 200 may broadcast an SIB (e.g., SIB1) including the connection authorization information. In this case, the CU of the donor node 200 does not transmit an F1 message including connection authorization information to the DU of the intermediate IAB node 300S that does not authorize the connection of the mobile IAB node 300M.

[0075] In step S11, the mobile IAB node 300M detects a Radio Link Failure (RLF). The mobile IAB node 300M may detect an RLF when it detects the expiration of a timer related to a radio problem or a measurement report. Alternatively, the mobile IAB node 300M may detect an RLF when its IAB-MT receives a backhaul radio link failure indication (BH RLF Indication) from the donor node 200.

[0076] In step S12, the mobile IAB node 300M executes an RRC reestablishment procedure. When the mobile IAB node 300M starts executing the RRC reestablishment procedure, it first executes a cell selection procedure to select a suitable cell. At this time, the mobile IAB node 300M sets cells that have broadcast connection authorization information (step S10) as candidate cells for cell selection in the cell selection procedure. Alternatively, the mobile IAB node 300M may preferentially select cells that have broadcast connection authorization information. Alternatively, the mobile IAB node 300M may exclude cells that have not broadcast connection authorization information from the selection candidates. Then, the mobile IAB node 300M selects the cell with the best quality from the selection candidates. The mobile IAB node 300M sends an RRC re-establishment request (RRCReestablishmentRequest) message to the cell to initiate the execution of the RRC re-establishment procedure.

[0077] Note that, for example, prior to step S10, when establishing synchronization with a cell managed by the donor node 200, the mobile IAB node 300M receives the cell ID of the cell from the donor node 200. Therefore, the mobile IAB node 300M can determine the cell that broadcast the connection permission information based on the cell ID.

[0078] (1.2) Second Operation Example Next, the second operation example will be described, focusing on the differences from the first operation example.

[0079] The second operation example is an example in which the intermediate IAB node 300S broadcasts connection denial information for the mobile IAB node 300M. Specifically, the information about the mobile relay node (e.g., the mobile IAB node 300M) is connection denial information indicating that connection of the mobile relay node is not permitted. Then, the intermediate relay node (e.g., the intermediate IAB node 300S) broadcasts the connection denial information.

[0080] This allows the mobile IAB node 300M to know, for example, the cells that do not permit the mobile IAB node 300M to connect to. This allows the mobile IAB node 300M to avoid connecting to a cell managed by the intermediate IAB node 300S. This allows the mobile IAB node 300M to properly connect to the donor node 200.

[0081] FIG. 12 is a diagram illustrating an example of operation according to the second example of operation.

[0082] 12, in step S20, the intermediate IAB node 300S broadcasts connection denial information. The intermediate IAB node 300S broadcasts an SIB (e.g., SIB1) including the connection denial information. The mobile IAB node 300M receives the connection denial information.

[0083] The connection denial information may be information indicating that connection of the mobile IAB node 300M is not permitted. Alternatively, the connection denial information may be information indicating that the node broadcasting the connection denial information is the intermediate IAB node 300S (or the cell of the intermediate IAB node 300S). Alternatively, the connection denial information may be information indicating that the mobile IAB node 300M is not supported. The cell broadcasting the connection denial information may be a cell that does not support the mobile IAB node 300M and is not considered as a candidate cell for cell selection by the mobile IAB node 300M. Note that the connection denial information is notified, for example, by an information element called "Mobile-IAB-Not-Allowed." Even if the existing information element "IAB-Supported" is notified, if the "Mobile-IAB-Not-Allowed" is notified, the mobile IAB node 300M determines that access to the cell is prohibited (or that the cell does not support the connection of the mobile IAB node 300M).

[0084] The CU of the donor node 200 may select a DU (intermediate IAB-DU) of the intermediate IAB node 300S that does not permit connection of the mobile IAB node 300M, and transmit an F1 message including connection denial information to the selected DU. In response to receiving the F1 message, the DU of the intermediate IAB node 300S may broadcast an SIB including the connection denial information. In this case, the CU of the donor node 200 does not transmit an F1 message including connection denial information to the DU of the donor node 200 that permits connection of the mobile IAB node 300M.

[0085] In step S21, the mobile IAB node 300M detects an RLF, similarly to the first operation example.

[0086] In step S22, the mobile IAB node 300M executes the RRC re-establishment procedure. As in the first operation example, the mobile IAB node 300M first executes a cell selection procedure to select a suitable cell. At this time, the mobile IAB node 300M excludes cells that have broadcast connection denial information (step S20) from the cell selection candidate sets in the cell selection procedure. The mobile IAB node 300M may also set cells that do not broadcast connection denial information as selection candidate sets. The mobile IAB node 300M selects the cell with the best quality from the selection candidate sets. Then, the mobile IAB node 300M transmits an RRC re-establishment request message to the selected cell and starts execution of the RRC re-establishment procedure.

[0087] Note that the mobile IAB node 300M can connect to, for example, the cell of the intermediate IAB node 300S. When the mobile IAB node 300M establishes synchronization with a cell managed by the intermediate IAB node 300S, the mobile IAB node 300M receives the cell ID of the cell from the cell. Therefore, the mobile IAB node 300M can identify the cell that broadcast the connection denial information by linking the cell ID with the connection denial information (step S20) included in the SIB.

[0088] (Third Operation Example) Next, a third operation example will be described. The third operation example will also be described, focusing on the differences from the first operation example.

[0089] The third operation example is an example in which, when a mobile IAB node 300M connects to either a cell managed by the donor node 200 or a cell managed by an intermediate IAB node, that cell (i.e., the serving cell) sets a list of cells from which the mobile IAB node 300M can select a cell.

[0090] Specifically, the information about the mobile relay node (e.g., the mobile IAB node 300M) is connectable cell information that indicates cells to which the mobile relay node can be connected. Then, either the donor node (e.g., the donor node 200) or the intermediate relay node (e.g., the intermediate IAB node 300S) transmits the connectable cell information to the mobile relay node.

[0091] This allows, for example, the mobile IAB node 300M to know the cells to which the mobile IAB node 300M can connect. By setting the cells managed by the donor node 200 as the cells to which the mobile IAB node 300M can connect, the mobile IAB node 300M that has received the connectable cell information can appropriately connect to the donor node 200.

[0092] Fig. 13 is a diagram illustrating an example of operation according to the third operation example. Note that the mobile IAB node 300M may be connected to a cell managed by the donor node 200 before starting the operation shown in Fig. 13. Alternatively, the mobile IAB node 300M may be connected to a cell managed by the intermediate IAB node 300S before starting the operation shown in Fig. 13. The serving cell illustrated in Fig. 13 may be a cell managed by the donor node 200. The serving cell may also be a cell managed by the intermediate IAB node 300S.

[0093] However, when the mobile IAB node 300M connects to a cell managed by an intermediate IAB node, it can immediately perform a handover to a cell managed by the donor node 200 by receiving an RRC Reconfiguration (HO Command) message from the cell.

[0094] As shown in FIG. 13 , in step S30, the serving cell transmits, to the mobile IAB node 300M, connectable cell information indicating cells to which the mobile IAB node 300M can connect. The connectable cell information may be expressed in the form of a list of cell IDs of connectable cells (as an Allowed list). The serving cell may transmit, to the mobile IAB node 300M, non-connectable cell information indicating cells to which the mobile IAB node 300M cannot connect (or cells that are not connectable). The non-connectable cell information may also be expressed in the form of a list of cell IDs of non-connectable cells (as a Block list). The serving cell may transmit, to the mobile IAB node 300M, an RRC Reconfiguration message including the connectable cell information (or non-connectable cell information).

[0095] The serving cell may update the connectable cell information (or connectable cell information) when various events occur.

[0096] For example, the serving cell may be set to updated connectable cell information at the time of handover of the mobile IAB node 300M. The updated connectable cell information may be transmitted in an RRC reconfiguration (HO command) message.

[0097] Furthermore, for example, when dual connectivity is set in the mobile IAB node 300M and the secondary cell group (SCG) is changed, the connectable cell information may be updated. The master node (serving cell) may transmit an RRC reconfiguration message including the updated connectable cell information, thereby setting the updated connectable cell information.

[0098] In step S31, the mobile IAB node 300M detects an RLF, similarly to the first operation example.

[0099] In step S32, the mobile IAB node 300M initiates the RRC re-establishment procedure. The mobile IAB node 300M first executes the cell selection procedure. The mobile IAB node 300M sets cells included in the connectable cell information as candidate cells for cell selection in the cell selection procedure. The mobile IAB node 300M may preferentially select cells included in the connectable cell information. On the other hand, the mobile IAB node 300M excludes cells indicated by the inaccessible cell information from the candidate cells for cell selection in the cell selection procedure. The mobile IAB node 300M selects the cell with the best quality from the candidate cells for selection. Then, the mobile IAB node 300M transmits an RRC re-establishment request message to the selected cell.

[0100] (1.4) Fourth Operation Example Next, a fourth operation example will be described. The fourth operation example will also be described, focusing on the differences from the first operation example.

[0101] The fourth operation example is an example in which a cell included in the measurement configuration or the conditional reconfiguration is determined to be a cell to which the mobile IAB node 300M can connect.

[0102] Specifically, the information about the mobile relay node (e.g., mobile IAB node 300M) is cell identification information (e.g., cell ID) included in either the measurement configuration or the conditional reconfiguration. First, a donor node (e.g., donor node 200) transmits either the measurement configuration or the conditional reconfiguration to the mobile relay node. Second, the mobile relay node determines that a cell represented by the cell identification information included in either the measurement configuration or the conditional reconfiguration is a cell to which the mobile relay node can connect.

[0103] This allows the mobile IAB node 300M to select, by a cell selection procedure, a cell represented by a cell ID included in either the measurement configuration or the conditional reconfiguration, assuming that the cell ID is a cell managed by the donor node 200. Thus, the mobile IAB node 300M can be properly connected to the donor node 200.

[0104] Furthermore, the measurement configuration and the conditional reconfiguration are included in an RRC message such as an RRC Reconfiguration message and transmitted to the mobile IAB node 300M. Therefore, the donor node 200 can use existing messages to notify the mobile IAB node 300M of cells to which the mobile IAB node 300M can connect.

[0105] The measurement configuration is one of the information elements (IEs) included in an RRC message such as an RRC reconfiguration message. The measurement configuration includes configuration information for when the mobile IAB node 300M performs a measurement report. In particular, the measurement configuration includes information on a cell that is a measurement object. In the third operation example, the cell included in the measurement object is treated as a connectable cell for the mobile IAB node 300M.

[0106] Furthermore, the conditional reconfiguration is, for example, one of the information elements included in the RRC reconfiguration message. The conditional reconfiguration includes configuration information when the mobile IAB node 300M performs a conditional handover (CHO). The conditional handover is executed when one or more handover execution conditions are satisfied. In particular, the conditional reconfiguration includes information on a candidate target cell (target SpCell). In the third operation example, the cell included in the conditional reconfiguration is treated as a connectable cell for the mobile relay node.

[0107] Then, the mobile IAB node 300M sets the cell included in either the measurement configuration or the conditional reconfiguration as a candidate cell for cell selection in the cell selection procedure. By setting the cell included in either the measurement configuration or the conditional reconfiguration as a cell managed by the donor node 200, the mobile IAB node 300M can connect to the donor node 200.

[0108] FIG. 14 is a diagram illustrating an example of operation according to the fourth example of operation.

[0109] 14, in step S40, the donor node 200 configures the measurement configuration for the mobile IAB node 300M. Specifically, the donor node 200 transmits an RRC message including the measurement configuration to the mobile IAB node 300M.

[0110] The measurement configuration includes one or more cell IDs. The measurement configuration may include information associated with the cell IDs and indicating that the mobile IAB node 300M can connect to the cell. The mobile IAB node 300M recognizes the cell represented by the cell ID included in the measurement configuration as a cell to which the mobile IAB node 300M can connect.

[0111] In step S41, the mobile IAB node 300M detects an RLF, similarly to the first operation example.

[0112] In step S42, the mobile IAB node 300M starts executing the RRC re-establishment procedure. The mobile IAB node 300M first executes the cell selection procedure. At this time, the mobile IAB node 300M sets the cell (or cell ID) included in the measurement configuration as a selection candidate cell. The mobile IAB node 300M selects the cell with the best quality from the selection candidates and transmits an RRC re-establishment request message to the selected cell.

[0113] 14 has been described using an example of measurement configuration, but the operation can be similarly performed in the case of conditional reconfiguration. That is, the donor node 200 can configure the conditional reconfiguration of conditional handover for the mobile IAB node 300M by transmitting an RRC reconfiguration message including the conditional reconfiguration to the mobile IAB node 300M (step S40). Then, after detecting an RLF (step S41), the mobile IAB node 300M sets the cell indicated by the cell ID included in the conditional reconfiguration as a connectable cell and as a selection candidate in the cell selection procedure (step S42).

[0114] (1.5) Fifth Operation Example Next, a fifth operation example will be described. The fifth operation example will also be described, focusing on the differences from the first operation example.

[0115] The fifth operation example is an example in which the donor node 200 broadcasts PRACH resources that can be exclusively used by the mobile IAB node 300M.

[0116] Specifically, the information about the mobile relay node (e.g., mobile IAB node 300M) is resource information about resources that the mobile relay node can use exclusively in the random access procedure, and the donor node (e.g., donor node 200) broadcasts the resource information.

[0117] Meanwhile, the mobile IAB node 300M can recognize the cell that broadcasted the resource information as a cell to which it can connect. The mobile IAB node 300M can set the cell as a candidate cell for selection in the cell selection procedure. The mobile IAB node 300M then executes the random access procedure by transmitting a message (such as Msg1) to a cell selected from the candidate cells using the resource information.

[0118] In this way, the mobile IAB node 300M recognizes the cell that broadcasts the resource information as a cell to which the mobile IAB node 300M can connect. Therefore, by setting the cell that broadcasts the resource information as a cell managed by the donor node 200, the mobile IAB node 300M can appropriately connect to the donor node 200. Furthermore, compared to the intermediate IAB node 300S, it is expected that the mobile IAB node 300M will undergo serving cell change processes, such as handover or RRC re-establishment, more frequently due to its own movement. By providing the mobile IAB node 300M with PRACH resources that are different from those of the intermediate IAB node 300S, it is possible to prevent PRACH collisions or make effective use of radio resources.

[0119] FIG. 15 is a diagram illustrating an example of operation according to the fifth example of operation.

[0120] As shown in Fig. 15, in step S50, the donor node 200 broadcasts resource information. The resource information is, for example, information regarding resources that the mobile IAB node 300M can use exclusively in the random access procedure. The resource information is used, for example, in the IAB-MT of the mobile IAB node 300M when executing the random access procedure. The DU of the donor node 200 may broadcast an SIB (for example, SIB1) including the resource information. The mobile IAB node 300M receives the broadcast resource information.

[0121] The CU of the donor node 200 may select a DU (IAB-donor-DU) that provides resources dedicated to the mobile IAB node 300M, and notify the DU that it has been selected as the DU that provides resources dedicated to the mobile IAB node 300M. The CU of the donor node 200 may perform this notification by sending an F1 message including information representing the selection to the DU of the donor node 200. The DU of the donor node 200 may receive this notification and broadcast an SIB including resource information. The CU of the donor node 200 does not perform this notification to the DU of the intermediate IAB node 300S.

[0122] In step S51, the mobile IAB node 300M detects an RLF, similarly to the first operation example.

[0123] In step S52, the mobile IAB node 300M starts executing the RRC re-establishment procedure. The mobile IAB node 300M first starts the cell selection procedure and selects cells that have broadcast resource information as selection candidates. The mobile IAB node 300M may exclude cells that do not broadcast resource information from the selection candidates. The mobile IAB node 300M selects a cell with good wireless quality from the selection candidates. The mobile IAB node 300M then transmits Msg1 to the selected cell using the resources indicated in the resource information, and transmits an RRC re-establishment request message (e.g., Msg3).

[0124] (Another Example of the First Embodiment) In the first operation example, the connection authorization information is described as being used in the cell selection procedure in the RRC re-establishment procedure, but the present invention is not limited to this. The connection authorization information may also be used in a general cell selection procedure other than the RRC re-establishment procedure. The connection authorization information may also be used in a cell reselection procedure. That is, the IAB-MT of the mobile IAB node 300M may set the cell for which the connection authorization information has been broadcast as a candidate cell for selection in the cell selection procedure or the cell selection procedure. Alternatively, the IAB-MT of the mobile IAB node 300M may preferentially select the cell for which the connection authorization information has been broadcast in the cell selection procedure or the cell selection procedure.

[0125] Furthermore, the fifth operation example may also be used in a general cell selection procedure other than the RRC re-establishment procedure, or in a cell reselection procedure. That is, the IAB-MT of the mobile IAB node 300M may set the cell for which resource information has been broadcast as a candidate cell for cell selection in the cell selection procedure or cell reselection procedure. Alternatively, the IAB-MT of the mobile IAB node 300M may preferentially select the cell for which resource information has been broadcast in the cell selection procedure or cell selection procedure.

[0126] Furthermore, the second operation example may also be used in a general cell selection procedure other than the RRC re-establishment procedure, or in a cell reselection procedure. That is, the IAB-MT of the mobile IAB node 300M may exclude the cell for which the connection denial information has been broadcast from cell selection candidates in the cell selection procedure or the cell reselection procedure.

[0127] Second Embodiment Next, a second embodiment will be described.

[0128] The second embodiment is also an example in which the first scenario is applied. In particular, the second embodiment will explain initial access.

[0129] The first scenario is a scenario in which the mobile IAB node 300M connects only to the donor node 200. For example, assume that the mobile IAB node 300M moves to a cell managed by the intermediate IAB node 300S. In such a case, when the mobile IAB node 300M attempts to connect to the cell managed by the intermediate IAB node 300S, taking the first scenario into consideration, it is conceivable that the connection itself may be rejected from the start.

[0130] However, considering that the mobile IAB node 300M is a network node, it may be preferable to allow the mobile IAB node 300M to connect to the intermediate IAB node 300S and then to the donor node 200, rather than having the connection to the intermediate IAB node 300S rejected from the start.

[0131] Therefore, in the second embodiment, a case will be described in which the mobile IAB node 300M is allowed to connect to the intermediate IAB node 300S, and then connects to the donor node 200 according to the first scenario. In such a case, the following processing is assumed to be performed.

[0132] When the mobile IAB node 300M connects to the intermediate IAB node 300S, it performs a handover to the donor node 200.

[0133] When the mobile IAB node 300M is connected to an intermediate IAB node 300S, the mobile IAB node 300M is restricted from operating as a mobile IAB node 300M.

[0134] The second embodiment will be described below, including such processing.

[0135] In the second embodiment, the mobile IAB node 300M will ultimately connect to the donor node 200. Therefore, similar to the first embodiment, the second embodiment also aims to enable the mobile IAB node 300M to be appropriately connected to the donor node 200.

[0136] The second embodiment will be described in the following order.

[0137] (2.1) Sixth Operation Example: When connecting, the mobile IAB node 300M notifies that it is a mobile IAB node.

[0138] (2.2) Seventh operation example: The donor node 200 restricts the F1 setup for the mobile IAB node 300M.

[0139] (2.3) Eighth Operation Example: The mobile IAB node 300M transmits an F1 message to the donor node 200 indicating whether or not it can operate as a mobile IAB node.

[0140] (2.4) Ninth operation example: The mobile IAB node 300M transmits information for identifying the RRC connection to the donor node 200 in an F1 message.

[0141] Note that the sixth to ninth operation examples include examples in which a mobile relay node (e.g., mobile IAB node 300M) transmits information related to the mobile relay node. The type of information related to the mobile relay node will be explained in each operation example.

[0142] (2.1) Sixth Operation Example In the sixth operation example, the mobile IAB node 300M notifies the cell that it is a mobile IAB node when connecting to the cell. Specifically, the information about the mobile relay node (e.g., the mobile IAB node 300M) is information indicating that the node itself is a mobile relay node. Then, the mobile relay node transmits information indicating that the node itself is a mobile relay node to the cell to which the mobile relay node is connected.

[0143] The donor node 200, which has received information indicating that it is a mobile relay node, can determine that the mobile IAB node 300M has connected. The donor node 200 can then determine whether the cell from which the information was received is a cell managed by the donor node 200 itself or a cell managed by the intermediate IAB node 300S, thereby enabling it to appropriately execute processing for the mobile IAB node 300M. For example, if the mobile IAB node 300M connects to a cell managed by the DU of the donor node 200, the CU of the donor node 200 can decide to accept the connection. Furthermore, for example, if the mobile IAB node 300M connects to a cell managed by the intermediate IAB node 300S, the CU of the donor node 200 can decide to perform a handover to a cell managed by the DU of the donor node 200. This allows the mobile IAB node 300M to appropriately connect to the donor node 200.

[0144] FIG. 16 is a diagram illustrating an example of operation according to the sixth example of operation.

[0145] As shown in FIG. 16 , in step S60, when the mobile IAB node 300M connects to a cell, it transmits a message to the cell including information indicating that it is a mobile IAB node. This message may be message 3 (Msg 3) (RRC Setup Request message) in the random access procedure. Alternatively, this message may be message 5 (Msg 5) (RRC Setup Complete message). Alternatively, this message may be a UE Capability Information (UECapability Information) message. Including this information in the UE Capability Information message slows down notification to the cell compared to including it in Msg 3 or Msg 5. Therefore, it is preferable to include this information in Msg 3 or Msg 5.

[0146] The cell to which the mobile IAB node 300M is connected may be a cell managed by the donor node 200. The cell may also be a cell managed by the intermediate IAB node 300S.

[0147] In step S61, a cell that receives information indicating that it is a mobile IAB node (a cell managed by the DU of the donor node 200 or a cell managed by the IAB-DU of the intermediate IAB node 300S) transmits, for example, an F1 message including information indicating that the information has been received to the CU of the donor node 200.

[0148] In step S62, the CU of the donor node 200 determines whether the mobile IAB node 300M has connected to a cell managed by the donor node 200. When the CU of the donor node 200 receives an F1 message including information indicating that the node is a mobile IAB node, the CU determines whether the mobile IAB node 300M has connected to a cell managed by the donor node 200 by checking whether the F1 connection in the F1 message is the DU of the donor node 200 or the IAB-DU of the intermediate IAB node 300S.

[0149] If the CU of the donor node 200 determines that the mobile IAB node 300M is connected to a cell managed by the donor node 200 (i.e., the F1 connection is the DU of the donor node 200) (YES in step S62), the process proceeds to step S63. On the other hand, if the CU of the donor node 200 determines that the mobile IAB node 300M is not connected to a cell managed by the donor node 200 (i.e., the F1 connection is the IAB-DU of the intermediate IAB node 300S) (NO in step S62), the process proceeds to step S64.

[0150] In step S63, the CU of the donor node 200 may accept the connection of the mobile IAB node 300M.

[0151] On the other hand, in step S64, first, the CU of the donor node 200 may reject the connection of the mobile IAB node 300M. In this case, the CU of the donor node 200 transmits an F1 message including information indicating the rejection of the connection of the mobile IAB node 300M to the IAB-DU of the intermediate IAB node 300S. Then, the IAB-DU of the intermediate IAB node 300S may reject the connection by transmitting an RRC Reject message or an RRC Release message to the IAB-MT of the mobile IAB node 300M using message 4 (Msg4).

[0152] Secondly, in step S64, the CU of the donor node 200 may hand over the mobile IAB node 300M to a cell managed by the donor node 200. In this case, the CU of the donor node 200 transmits an F1 message including an RRC Reconfiguration (HO Command) message to the IAB-DU of the intermediate IAB node 300S. Then, in response to receiving the F1 message, the IAB-DU of the intermediate IAB node 300S may transmit an RRC Reconfiguration (HO Command) message to the IAB-MT of the mobile IAB node 300M.

[0153] The sixth operation example is applicable not only to the first scenario, but also to the second scenario (a scenario in which the mobile IAB node 300M can connect to an intermediate IAB node) as long as the mobile IAB node 300M can transmit information indicating that the mobile IAB node 300M is the mobile IAB node 300M when connecting to the cell.

[0154] (2.2) Seventh Operation Example Next, a seventh operation example will be described.

[0155] In the seventh operation example, an example will be described in which the donor node 200 restricts the F1 setup for the mobile IAB node 300M. Specifically, when a mobile relay node (e.g., the donor node 200) connects to a cell managed by a stationary intermediate relay node (e.g., the intermediate IAB node 300S), the donor node (e.g., the donor node 200) transmits F1 setup request transmission prohibition information indicating that transmission of an F1 setup request message is prohibited to the mobile relay node.

[0156] As a result, for example, even if the mobile IAB node 300M can connect to a cell managed by the intermediate IAB node 300S, it cannot transmit an F1 setup request (F1 SETUP REQUEST) message, and therefore the F1 connection cannot be established, and the F1 connection with the donor node 200 is restricted. As a result, the mobile IAB node 300M cannot operate as a mobile IAB node (for example, move). In this case, the donor node 200 can hand over the mobile IAB node 300M to a cell managed by the donor node 200, allowing the mobile IAB node 300M to connect to that cell. Therefore, the mobile IAB node 300M can be properly connected to the donor node 200.

[0157] In this way, the seventh operation example is an example in which the mobile IAB node 300M is permitted to connect to the intermediate IAB node 300S, but its operation as a mobile IAB node is restricted by restricting the F1 connection.

[0158] FIG. 17 is a diagram illustrating an example of operation according to the seventh example of operation.

[0159] As shown in FIG. 17 , in step S70, the IAB-MT of the mobile IAB node 300M initiates connection to a cell managed by the intermediate IAB node 300S and transmits an RRC message (e.g., Msg3 (RRCSetupRequest message)) to the cell. As in the sixth operation example, the RRC message may include information indicating that the node itself is a mobile IAB node. In this case, also in the seventh operation example, the information related to the mobile relay node (e.g., the mobile IAB node 300M) is information indicating that the node itself is a mobile relay node.

[0160] In step S71, in response to receiving the RRC message, the IAB-DU of the intermediate IAB node 300S transmits an F1 message including the RRC message to the CU of the donor node 200. In response to receiving the RRC message, the IAB-DU of the intermediate IAB node 300S may transmit an F1 message including information indicating that the RRC message has been received to the CU of the donor node 200.

[0161] In step S72, the CU of the donor node 200 confirms that the F1 connection that received the F1 message is the IAB-DU of the intermediate IAB node 300S. For example, when the CU of the donor node 200 receives the F1 message, it confirms that the connection is with the IAB-DU of the intermediate IAB node 300S by checking the F1 connection of the F1 message. This allows the CU of the donor node 200 to confirm that the mobile IAB node 300M has connected to a cell managed by the intermediate IAB node 300S (or that the mobile IAB node 300M is not connected to a cell managed by the donor node 200).

[0162] In step S73, the CU of the donor node 200 transmits an F1 message including F1 setup request transmission prohibition information indicating that transmission of an F1 setup request is prohibited to the IAB-DU of the intermediate IAB node 300S. The F1 setup request transmission prohibition information is included in an RRC message, and the RRC message may be transmitted by being included in (or encapsulated into) the F1 message.

[0163] In step S74, the IAB-DU of the intermediate IAB node 300S transmits an RRC message (e.g., an RRCReconfiguration message) including F1 setup request transmission prohibition information to the IAB-MT of the mobile IAB node 300M. The IAB-MT of the mobile IAB node 300M outputs the F1 setup request transmission prohibition information to the upper layer (IAB-DU) of the mobile IAB node 300M.

[0164] In step S75, in response to receiving the F1 setup request transmission prohibition information, the IAB-DU of the mobile IAB node 300M suspends transmission of the F1 setup request (F1 SETUP REQUEST) message.

[0165] In step S76, the CU of the donor node 200 transmits an F1 message including F1 setup request transmission permission information indicating permission (or lifting of prohibition) to transmit an F1 setup request to the IAB-DU of the intermediate IAB node 300S. For example, the CU of the donor node 200 generates an RRC message (e.g., an RRC reconfiguration message) including the F1 setup request transmission permission information. Then, the CU of the donor node 200 transmits an F1 message including the RRC message to the IAB-DU of the intermediate IAB node 300S. Note that the RRC message may be an HO command. In this case, the CU of the donor node 200 causes the mobile IAB node 300M connected to the cell managed by the IAB-DU of the intermediate IAB node 300S to perform a handover.

[0166] In step S77, in response to receiving the F1 message, the IAB-DU of the intermediate IAB node 300S transmits an RRC message (e.g., an RRC reconfiguration message) including the F1 setup request transmission authorization information to the IAB-MT of the mobile IAB node 300M. The IAB-MT of the mobile IAB node 300M outputs the received F1 setup transmission authorization information to the upper layer (IAB-DU) of the mobile IAB node 300M.

[0167] The F1 setup request transmission permission information may be implicitly notified. For example, the CU of the donor node 200 may generate an RRC message that does not include the F1 setup request transmission prohibition information. The mobile IAB node 300M may recognize that transmission of the F1 setup request is permitted in response to receiving the RRC message that does not include the F1 setup request transmission prohibition information.

[0168] In step S78, the IAB-DU of the mobile IAB node 300M transmits an F1 setup request to the CU of the donor node 200 in response to receiving the F1 setup request transmission permission information.

[0169] In the seventh operation example, an example was described in which the mobile IAB node 300M suspends transmission of an F1 setup request in response to receiving F1 setup request transmission prohibition information (step S75). For example, the F1 setup request transmission prohibition information may not be necessary. In this case, the IAB-DU of the mobile IAB node 300M may prohibit transmission of an F1 setup request until it receives F1 setup transmission permission information (step S77). The IAB-DU of the mobile IAB node 300M is enabled to transmit an F1 setup request when it receives F1 setup transmission permission information (step S77). Therefore, when the mobile IAB node 300M establishes an RRC connection with the intermediate IAB node 300S, it cannot transmit an F1 setup request unless it receives F1 setup transmission permission information. Even in such a case, when the mobile IAB node 300M connects to the intermediate IAB node 300S, the F1 connection to the mobile IAB node 300M is restricted.

[0170] (2.3) Eighth Operation Example Next, an eighth operation example will be described.

[0171] Regarding the F1 setting for the mobile IAB node 300M, in addition to the existing IAB setting, there is a possibility that a new setting will be added. For example, if the mobile IAB node 300M can transmit information indicating whether it can operate as a mobile IAB node in an F1 message, the donor node 200 can appropriately perform the F1 setting for the mobile IAB node 300M. For example, the donor node 200 can impose a restriction if the mobile IAB node 300M can operate as a mobile IAB node, or not impose a restriction if the mobile IAB node 300M cannot operate as a mobile IAB node, thereby making it possible to appropriately perform the F1 setting for the mobile IAB node 300M.

[0172] Therefore, in the eighth operation example, an example will be described in which the mobile IAB node 300M transmits information indicating whether or not it is capable of operating as a mobile IAB node to the donor node 200 in an F1 message. Hereinafter, the information indicating whether or not the mobile IAB node 300M is capable of operating as a mobile IAB node may be referred to as operation capability information. The operation capability information may be information indicating whether or not the mobile IAB node 300M operates as a mobile IAB node.

[0173] Specifically, the information about the mobile relay node (e.g., mobile IAB node 300M) is operable / unavailable information indicating whether the mobile relay node is operable as a mobile relay node. The mobile relay node transmits the operable / unavailable information to the donor node (e.g., donor node 200).

[0174] Fig. 18 is a diagram illustrating an example of operation according to the eighth operation example. Note that before the operation illustrated in Fig. 18 is started, the mobile IAB node 300M may be directly connected to the donor node 200. The mobile IAB node 300M may be connected to the donor node 200 via an intermediate IAB node 300S.

[0175] In step S80, the IAB-DU of the mobile IAB node 300M sends an F1 message including operational availability information to the CU of the donor node 200. The F1 message may be an F1 setup request message or a gNB-DU configuration update message.

[0176] First, the mobile IAB node 300M may transmit information indicating that the mobile IAB node 300M has the capabilities of a mobile IAB node, instead of the operational availability information.

[0177] Second, the mobile IAB node 300M may transmit information indicating that the mobile IAB node 300M prefers to operate as a mobile IAB node, instead of the operable / unavailable information.

[0178] Third, instead of the operation capability information, the mobile IAB node 300M may transmit information indicating that the operation of the mobile IAB node 300M as a mobile IAB node is restricted. For example, this may be the case when the mobile IAB node 300M connects to the intermediate IAB node 300S and its operation as a mobile IAB node 300M is restricted via an RRC message. In this case, the operation (e.g., movement) of the mobile IAB node 300M as a mobile IAB node is restricted, and the mobile IAB node 300M may connect to the intermediate IAB node 300S in the same state as a stationary intermediate IAB node without moving. When transmitting information indicating that its operation as a mobile IAB node is restricted, the mobile IAB node 300M may transmit the information together with cause information. The cause information may be information indicating that the mobile IAB node 300M is connected to the intermediate IAB node 300S. The cause information may be information indicating a problem with wireless layer capability.

[0179] Fourth, instead of the operation capability information, the mobile IAB node 300M may transmit information indicating that operation as a mobile IAB node is not restricted (or the restriction has been lifted). For example, the mobile IAB node 300M may transmit information indicating that the restriction has been lifted through an RRC message (e.g., step S77 in the seventh operation example).

[0180] In step S81, the donor node 200 performs appropriate F1 setting for the mobile IAB node 300M based on the operation capability information.

[0181] (2.4) Ninth Operation Example Next, a ninth operation example will be described.

[0182] The ninth operation example is an example in which the mobile IAB node 300M transmits information for identifying the RRC connection to the donor node 200 using an F1 message.

[0183] For example, it is assumed that the mobile IAB node 300M executes an RRC connection establishment procedure with the donor node 200 to establish an RRC connection with the donor node 200. Also, it is assumed that the mobile IAB node 300M executes an F1 setup procedure with the donor node 200 to establish an F1 connection with the donor node 200. In this case, the CU of the donor node 200 will have two entities: an RRC connection and an F1 connection.

[0184] In such a case, even if the donor node 200 can recognize the RRC connection as the mobile IAB node 300M on the RRC side (i.e., the CU of the donor node 200), the F1 connection may not be recognized as the mobile IAB node 300M on the F1 side (i.e., the CU of the donor node 200).

[0185] Therefore, in the ninth operation example, an example will be described in which a mobile relay node (e.g., mobile IAB node 300M) transmits an F1 message including information for identifying an RRC connection (hereinafter, may be referred to as "RRC connection identification information") to a donor node (e.g., donor node 200). In the ninth operation example, the information related to the mobile relay node is RRC connection identification information representing information for identifying the RRC connection of the mobile relay node with the donor node.

[0186] As a result, for example, the donor node 200 can use the RRC connection identification information received via the F1 connection to link information about the F1 connection of the mobile IAB node 300M with information about the RRC connection of the mobile IAB node 300M. This linking allows the donor node 200 to recognize that the mobile IAB node 300M is connected, even on the F1 side, and enables the donor node 200 to set an appropriate F1 setting for the mobile IAB node 300M. By receiving the appropriate F1 setting from the donor node 200, the mobile IAB node 300M can be properly connected to the donor node 200.

[0187] In the following, information related to the F1 connection of the mobile IAB node 300M may be referred to as the "F1 context." Also, information related to the RRC connection of the mobile IAB node 300M may be referred to as the "RRC context."

[0188] FIG. 19 is a diagram illustrating an operation example according to the ninth operation example.

[0189] 19, in step S90, the IAB-MT of the mobile IAB node 300M executes an RRC connection establishment procedure to establish an RRC connection with (the RRC entity of) the CU of the donor node 200. The IAB-MT of the mobile IAB node 300M may output RRC connection-specific information to the upper layer (IAB-DU) of the mobile IAB node 300M.

[0190] In step S91, the IAB-DU of the mobile IAB node 300M executes an F1 setup procedure to establish an F1 connection with (the F1 entity of) the CU of the donor node 200. When establishing the F1 connection, the IAB-DU of the mobile IAB node 300M transmits an F1 message including RRC connection-specific information to (the F1 entity of) the CU of the donor node 200. The F1 message is, for example, an F1 setup request message. The F1 message includes, for example, an F1 context.

[0191] The RRC connection specific information may be, first, a Cell-Radio Network Temporary Identifier (C-RNTI). The C-RNTI is identification information used to distinguish the mobile IAB node 300M from other IAB nodes (or the UE 100). The C-RNTI is issued by the donor node 200 and is used during RRC connection.

[0192] The RRC connection specific information may further include the cell ID of the cell to which the mobile IAB node 300M is connected.

[0193] Secondly, the RRC connection specific information may be an RRC transaction ID (RRC-TransactionIdentifier) ​​of the RRC message. The RRC transaction ID is identification information used to identify each RRC procedure. The RRC transaction ID is issued by, for example, the donor node 200. The RRC transaction ID is one of the information elements (IEs) included in the RRC message.

[0194] In step S92, in response to receiving the F1 message, the CU of the donor node 200 associates the F1 context with the RRC context using the RRC connection identification information. For example, the CU of the donor node 200 reads from memory an RRC context having the same C-RNTI as the C-RNTI included in the F1 message, and associates the RRC context with the F1 context included in the F1 message. If the RRC context includes information indicating that the IAB node connected to the donor node 200 is the mobile IAB node 300M, the donor node 200 can recognize from the F1 side that the mobile IAB node 300M has connected to the donor node 200 through this association.

[0195] In step S93, the CU of the donor node 200 performs appropriate F1 configuration for the IAB-DU of the mobile IAB node 300M, taking into account the RRC state of the mobile IAB node 300M.

[0196] Third Embodiment Next, a third embodiment will be described.

[0197] In the second embodiment, a description has been given of allowing the mobile IAB node 300M to connect to the intermediate IAB node 300S, and even in such a case, causing handover to the cell managed by the donor node 200. In the third embodiment, a description will be given mainly of handover of the mobile IAB node 300M.

[0198] In order to hand over the mobile IAB node 300M to a cell managed by the donor node 200, the donor node 200 needs to select a target cell from among the cells managed by the donor node 200. This is because if the donor node 200 selects a cell managed by the intermediate IAB node 300S as the target cell, the mobile IAB node 300M will not be able to connect to the donor node 200.

[0199] Furthermore, even if the cell to which the mobile IAB node 300M is currently connected is a cell managed by the donor node 200 (source donor node), when the mobile IAB node 300M performs a handover, the cell managed by the donor node 200 (target donor node) must be the target cell.

[0200] In this way, the handover destination of the mobile IAB node 300M also needs to be a cell managed by the donor node 200.

[0201] On the other hand, if the target donor node 200T cannot accept the connection of the mobile IAB node 300M, it will reject the handover request (HO REQUEST) from the source donor node 200S. In such a case, a handover delay (Too Late Handover) may occur while the source donor node 200S is performing processing for another target donor node 200.

[0202] Therefore, the third embodiment aims to enable the mobile IAB node 300M to be properly handed over to the donor node 200. If the mobile IAB node 300M can be properly handed over to the donor node 200, the mobile IAB node 300M can be properly connected to the donor node, as in the first embodiment.

[0203] As described above, hereinafter, the terms "migration" of the mobile IAB node 300M and "handover" of the mobile IAB node 300M may be used interchangeably. For example, a "handover request" may be read as a "movement request."

[0204] In the third embodiment, an example of operation will be described in the following order.

[0205] (3.1) Tenth operation example: The source donor node 200S transmits information indicating a handover of the mobile IAB node 300M to the target donor node 200T.

[0206] (3.2) Eleventh Operation Example: The first donor node 200-1 transmits information indicating whether or not the first donor node 200-1 can accept the handover of the mobile IAB node 300M to the second donor node 200-2, which is an adjacent donor node.

[0207] (3.1) Tenth Operation Example In the target donor node 200T, the target cell to be selected may change depending on whether the handover target is the mobile IAB node 300M or not. As described above, the target donor node 200T needs to select a cell managed by the target donor node 200T as the target cell.

[0208] Therefore, in the tenth operation example, first, a source donor node (e.g., source donor node 200S) transmits a handover request message including information indicating that a mobile relay node (e.g., mobile IAB node 300M) is a handover target to a target donor node (e.g., target donor node 200T). Second, in response to receiving the handover request message, the target donor node selects a cell managed by the target donor node as a handover destination cell for the mobile relay node.

[0209] In this way, since the cell managed by the target donor node 200T becomes the target cell, the handover destination of the mobile IAB node 300M becomes the cell managed by the donor node 200. Therefore, the mobile IAB node 300M can be handed over to the donor node 200 appropriately.

[0210] Fig. 20 is a diagram illustrating an operation example according to Operation Example 10. In Fig. 20, it is assumed that the mobile IAB node 300M is connected to a donor node (source donor node 200S).

[0211] As shown in FIG. 20, in step S100, the mobile IAB node 300M may send a measurement report to the source donor node 200S.

[0212] In step S101, the source donor node 200S decides to handover the mobile IAB node 300M.

[0213] In step S102, the source donor node 200S transmits a handover request (HANDOVER REQUEST) message to the target donor node 200T. The handover request message includes information indicating that the handover target is the mobile IAB node 300M. The handover request message is one of the Xn messages.

[0214] In step S103, the target donor node 200T decides to accept the handover request by the handover request message. At this time, the CU of the target donor node 200T selects a cell managed by the DU of the target donor node 200T as the target cell based on information indicating that the handover target is the mobile IAB node 300M. Conversely, the CU of the target donor node 200T does not select (or excludes) as the target cell a cell managed by the DU of the subordinate intermediate IAB node 300S based on information indicating that the handover target is the mobile IAB node 300M.

[0215] In step S104, the target donor node 200T transmits a handover request acknowledgement message to the source donor node 200S. The target donor node 200T generates, for example, an RRC Reconfiguration (HO Command) message including configuration information for the mobile IAB node 300M to connect to the target cell, and transmits a handover request acknowledgement message including the RRC Reconfiguration (HO Command) message to the source donor node 200S. The handover request acknowledgement message is also one of the Xn messages. The RRC Reconfiguration (HO Command) includes the cell ID of the target cell.

[0216] In step S105, in response to receiving the handover request acknowledgement message, the source donor node 200S transmits the RRC reconfiguration (HO command) message to the mobile IAB node 300M.

[0217] In step S106, the mobile IAB node 300M initiates a connection to the target cell in response to receiving the RRC reconfiguration (HO command) message.

[0218] (3.2) Eleventh Operation Example Next, an eleventh operation example will be described.

[0219] The eleventh operation example will be described as an example in which the first donor node 200-1 transmits information indicating whether or not the first donor node 200-1 can accept the handover of the mobile IAB node 300M to the second donor node 200-2, which is an adjacent donor node.

[0220] Specifically, first, the target donor node (e.g., first donor node 200-1) transmits mobile relay node acceptance information indicating whether or not it is possible to accept a mobile relay node (e.g., mobile IAB node 300M) to the source donor node (e.g., second donor node 200-2). Second, the source donor node transmits a handover request message to the target donor node based on the mobile relay node acceptance information.

[0221] As a result, for example, the source donor node (second donor node 200-2) can determine whether or not the target donor node (first donor node 200-1) will accept handover of the mobile IAB node 300M based on the mobile relay node acceptance / non-acceptance information. Also, the source donor node can limit cells to be measured to cells that can be accepted by the mobile IAB node 300M in the measurement configuration of the mobile IAB node 300M.

[0222] Then, the source donor node (second donor node 200-2), as a donor node capable of accepting the handover of the mobile IAB node 300M, can transmit a handover request message to the first donor node 200-1.

[0223] Therefore, the source donor node (second donor node 200-2) can avoid a handover delay (too late handover) caused by rejecting the handover request after transmitting the handover request message. Therefore, the mobile IAB node 300M can properly perform handover and can also properly connect to the target donor node (first donor node 200-1).

[0224] 21 is a diagram illustrating an example of operation according to the eleventh example of operation. In FIG. 21, the first donor node 200-1 and the second donor node 200-2 are, for example, donor nodes 200 adjacent to each other. The first donor node 200-1 may be a target donor node of the mobile IAB node 300M. Furthermore, the second donor node 200-2 may be a source donor node to which the mobile IAB node 300M is currently connected.

[0225] As shown in FIG. 21 , in step S110, the first donor node 200-1 transmits an Xn message including mobile relay node acceptance information to the second donor node 200-2. The mobile relay node acceptance information is information indicating whether the first donor node 200-1 is capable of accepting the mobile IAB node 300M or whether the first donor node 200-1 is unable to accept the mobile IAB node 300M. The mobile relay node acceptance information may include a list of cell IDs of acceptable cells. Alternatively, the mobile relay node acceptance information may include a list of cell IDs of unacceptable cells. Whether a cell is acceptable or unacceptable is determined based on whether the cell is managed by the donor node 200 (first donor node 200-1). Alternatively, whether a cell is acceptable or unacceptable may be determined based on whether the cell is managed by the intermediate IAB node 300S. Prior to step S110, the second donor node 200-2 may request the first donor node 200-1 to provide the mobile relay node acceptance / non-acceptance information. The second donor node 200-2 may make the request by transmitting an Xn message including the request to the first donor node 200-1.

[0226] In step S111, the second donor node 200-2 may configure a measurement configuration for the mobile IAB node 300M using the mobile relay node acceptance information. For example, the second donor node 200-2 configures the measurement configuration by transmitting, to the mobile IAB node 300M, an RRC message including a measurement configuration that sets a cell that can accept the mobile IAB node 300M as a measurement object.

[0227] In step S112, the second donor node 200-2 (source donor node) may determine a handover of the mobile IAB node 300M and may determine a donor node 200 to which a handover request (HANDOVER REQUEST) message is to be sent based on the mobile relay node acceptance information. That is, the second donor node 200-2 may use the mobile relay node acceptance information to determine a donor node (or a target donor node) that manages a cell that can accept the mobile IAB node 300M.

[0228] [Other embodiments] 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 300. The program may be recorded on a computer-readable medium. Using the computer-readable medium, it is possible to install the program on a computer. Here, the computer-readable medium on which the program is recorded may be a non-transitory recording medium. The non-transitory recording medium is not particularly limited, and may be, for example, a recording medium such as a CD-ROM or a DVD-ROM.

[0229] In addition, circuits that perform each process performed by UE100, gNB200, or IAB node 300 may be integrated, and at least a portion of UE100 or gNB200 may be configured as a semiconductor integrated circuit (chipset, SoC: System on a chip).

[0230] As used in this disclosure, the terms "based on" and "depending on" 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." Furthermore, 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. Furthermore, as used in this disclosure, the term "or" 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.

[0231] 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 without departing from the spirit of the invention. Furthermore, the embodiments, operation examples, or processes can be combined as appropriate within a consistent range.

[0232] This application claims priority to U.S. Provisional Application No. 63 / 395,095 (filed August 4, 2022), the entire contents of which are incorporated herein by reference.

[0233] (Appendix 1)

[0234] (Supplementary Note 1) A communication control method for use in a cellular communication system, comprising the step of transmitting information about a mobile relay node from either a donor node or a stationary intermediate relay node that does not move.

[0235] (Supplementary Note 2) The communication control method according to Supplementary Note 1, wherein the information regarding the mobile relay node is connection permission information indicating that connection of the mobile relay node is permitted, and the transmitting step includes a step in which the donor node notifies the connection permission information.

[0236] (Supplementary Note 3) The communication control method according to Supplementary Note 1 or Supplementary Note 2, further comprising the step of the mobile relay node designating the cell to which the connection permission information has been broadcast as a candidate cell for selection in a cell selection procedure.

[0237] (Supplementary Note 4) The communication control method according to any one of Supplementary Notes 1 to 3, wherein the information regarding the mobile relay node is connection denial information indicating that connection of the mobile relay node is not permitted, and further comprising a step in which the intermediate relay node notifies the connection denial information.

[0238] (Supplementary Note 5) The communication control method according to any one of Supplementary Note 1 to Supplementary Note 4, further comprising the step of: the mobile relay node excluding the cell to which the connection denial information has been broadcast from candidates for cell selection in a cell selection procedure.

[0239] (Supplementary Note 6) The communication control method described in any one of Supplementary Notes 1 to 5, wherein the information about the mobile relay node is connectable cell information indicating a cell to which the mobile relay node can be connected, and the transmitting step includes a step in which either the donor node or the intermediate relay node transmits the connectable cell information to the mobile relay node.

[0240] (Supplementary Note 7) The communication control method according to any one of Supplementary Notes 1 to 6, wherein the information about the mobile relay node is non-connectable cell information indicating a cell to which the mobile relay node cannot connect, and wherein the transmitting step includes a step in which at least one of the donor node and the intermediate relay node transmits the non-connectable cell information to the mobile relay node.

[0241] (Supplementary Note 8) The communication control method according to any one of Supplementary Notes 1 to 7, further comprising a step in which the mobile relay node sets a cell represented by the connectable cell information as a candidate cell for selection in a cell selection procedure, and excludes a cell represented by the inconnectable cell information from the candidate cell for selection in the cell selection procedure.

[0242] (Supplementary Note 9) The communication control method according to any one of Supplementary Notes 1 to 8, wherein the information about the mobile relay node is cell identification information included in either a measurement configuration or a conditional reconfiguration, and the transmitting step includes a step in which the donor node transmits either the measurement configuration or the conditional reconfiguration to the mobile relay node, and further includes a step in which the mobile relay node determines that a cell represented by the cell identification information included in either the measurement configuration or the conditional reconfiguration is a cell to which the mobile relay node can connect.

[0243] (Supplementary Note 10) The communication control method according to any one of Supplementary Notes 1 to 9, wherein the information about the mobile relay node is resource information about resources that can be exclusively used by the mobile relay node in a random access procedure, and the transmitting step includes a step in which the donor node broadcasts the resource information.

[0244] (Supplementary Note 11) The communication control method according to any one of Supplementary Notes 1 to 10, further comprising the step of: the mobile relay node designating the cell to which the resource information has been broadcast as a candidate cell for selection in a cell selection procedure; and executing the random access procedure for a cell selected from the candidate cells by utilizing the resources indicated by the resource information.

[0245] (Supplementary Note 12) A communication control method for use in a cellular communication system, comprising: a step in which a mobile relay node transmits information relating to said mobile relay node.

[0246] (Supplementary Note 13) The communication control method according to Supplementary Note 12, wherein the information relating to the mobile relay node is information indicating that the node itself is the mobile relay node, and the transmitting step includes a step in which the mobile relay node transmits information indicating that the node itself is the mobile relay node to a cell to which the mobile relay node is connected.

[0247] (Supplementary Note 14) The communication control method according to Supplementary Note 12 or Supplementary Note 13, further comprising a step of: a donor node transmitting F1 setup request transmission prohibition information to the mobile relay node, indicating that transmission of an F1 setup request is prohibited when the mobile relay node connects to a cell managed by an intermediate relay node that is stationary without moving.

[0248] (Supplementary Note 15) The communication control method according to any one of Supplementary Notes 12 to 14, wherein the information about the mobile relay node is operable / unoperable information indicating whether the mobile relay node is operable as the mobile relay node, and the transmitting step includes a step in which the mobile relay node transmits the operable / unoperable information to a donor node.

[0249] (Supplementary Note 16) The communication control method according to any one of Supplementary Notes 12 to 15, wherein the information about the mobile relay node is RRC connection identification information representing information for identifying an RRC connection of the mobile relay node to a donor node, and wherein the transmitting step includes a step of the mobile relay node transmitting an F1 message including the RRC connection identification information to the donor node.

[0250] (Supplementary Note 17) A communication control method for use in a cellular communication system, comprising: a step of a source donor node transmitting a handover request message to a target donor node, the handover request message including information indicating that a mobile relay node is a target for handover; and a step of the target donor node selecting, in response to receiving the handover request message, a cell managed by the target donor node as a cell to which the mobile relay node is to be handed over.

[0251] (Supplementary Note 18) The communication control method according to Supplementary Note 17, further comprising a step in which the target donor node transmits mobile relay node acceptance / non-acceptance information indicating whether the mobile relay node can be accepted to the source donor node, and the step of transmitting the handover request message comprises a step in which the source donor node transmits the handover request message to the target donor node based on the mobile relay node acceptance / non-acceptance information.

[0252] (Second Addendum) 1. Introduction A new work item on mobile IAB was approved in RAN#94e.

[0253] The detailed objectives of WI are as follows: - Define migration / topology adaptation procedures to enable IAB node mobility, including inter-donor migration (full migration) of entire mobile IAB nodes. - Enhance mobility of IAB nodes and their UEs, including aspects related to group mobility. Optimizations for targeting surrounding UEs. - Note that solutions should avoid touching on topics already discussed in Rel-17 or topics excluded from Rel-17, with the exception of enhancements specific to IAB node mobility. - Mitigation of interference due to IAB node mobility, including avoidance of potential reference and control signal collisions (PCI, RACH, etc.).

[0254] It should be noted that at the beginning of the work period, RAN3 and RAN2 should discuss the potential complications of a scenario in which a mobile IAB node connects to a stationary (intermediate) IAB node versus a scenario in which a mobile IAB node connects directly to an IAB donor.

[0255] In this appendix, we perform a complexity analysis in two topology scenarios from the perspective of RAN2.

[0256] 2. Discussion 2.1 Scenario In WID, it is explicitly assumed that a mobile IAB node does not have any descendant IAB nodes, as follows:

[0257] In Rel-18, the mobile IAB supports the following features that apply to FR1 and FR2: In-band and out-of-band backhaul. A mobile IAB node has no descendant IAB nodes and serves only UEs. The solution should support HO and DC for UEs.

[0258] It also clarifies that a mobile IAB node is always an access IAB node because it serves only UEs.

[0259] Proposal 1: RAN2 should ensure that a mobile IAB node is always an access IAB node.

[0260] While WID explicitly states that intermediate IAB nodes should be stationary, the issue in RAN#96 is whether a mobile IAB node can connect only with the IAB donor or also with (intermediate) IAB nodes. Therefore, the two scenarios can be depicted in Figures 9 and 10, respectively.

[0261] Some companies believe that complexity would be reduced if mobile IAB nodes only connected with IAB donors, while others argue that such a restriction would actually increase complexity. Therefore, the complexity of each scenario is discussed in the next section.

[0262] Observation 1: A complexity analysis is needed for the scenario where a mobile IAB node can only connect with the IAB donor or can also connect with intermediate IAB nodes.

[0263] 2.2 Complexity Analysis 2.2.1 Deployment and Coverage In general, Rel-16 / 17 IAB was introduced to support the efficient establishment of nationwide coverage, especially for extending FR2 deployments. If a mobile IAB node can only connect with an IAB donor, there will be many coverage holes from the perspective of the mobile IAB node, since the cells provided by the IAB node are unavailable to the mobile IAB node.

[0264] If a mobile IAB node is disconnected from the network, it is obvious that it cannot continue to provide service to the UE, and therefore, many coverage holes will directly result in many service interruptions. Assuming that a mobile IAB node is considered a network node in the same way as an IAB node in Rel-16 / 17, such service interruptions are undesirable.

[0265] To implement mobile IAB in Scenario 1, special deployment strategies are required to ensure adequate coverage for mobile IAB nodes in addition to existing (or normal) deployment strategies. On the other hand, Scenario 2 allows for more flexible deployment. Therefore, Scenario 1 may present more deployment challenges than Scenario 2.

[0266] Proposal 2: RAN2 should agree that if a mobile IAB node only connects with the IAB donor (Scenario 1), service continuity for the mobile IAB node may not be ensured due to the large number of coverage holes, which increases deployment challenges.

[0267] 2.2.2 Network Interface Procedures (RAN3 Domain) For network interfaces such as F1AP and XnAP, some complications are expected if the mobile IAB node can also connect to intermediate IAB nodes (Scenario 2).

[0268] In routing configuration (F1AP), the IAB donor needs to update the configuration when a mobile IAB node enters or leaves the IAB topology. In scenario 2, the IAB donor needs to update the routing configuration for each IAB node in the IAB topology, which can complicate the procedure and introduce latency for F1 reconfiguration.

[0269] Regarding mobile IAB node migration (XnAP), RAN3 will consider full migration of mobile IAB nodes between donors and group mobility of UEs, but it is not expected that there will be any significant difference between Scenario 1 and Scenario 2. However, in Scenario 1, some information exchange is required between IAB donors to inform other donors of the cells that can accommodate mobile IAB nodes, in other words, the cells in which the IAB donor's DUs are serving. Such information is used by the IAB donors for measurement configuration and handover decisions.

[0270] Because the Mobile IABWI is led by RAN3, the complexity of the network interface is already somewhat intended compared to other interfaces addressed in secondary working groups (including RAN2). It is up to RAN3 to decide whether the network interface can support Scenario 2 and whether to direct other working groups to specify mechanisms for Scenario 1.

[0271] Observation 2: If the mobile IAB node only connects with the IAB donor (i.e., scenario 1), the network interface procedure may be simpler. The details are up to RAN3.

[0272] 2.2.3 Uu Interface Procedures (RAN2 Domain) With regard to the Uu interface, some complications are expected if the mobile IAB node can only connect with intermediate IAB nodes (i.e., scenario 1).

[0273] Regarding initial access, it should be discussed whether a mobile IAB node can initiate an RRC connection establishment procedure to a cell served by an intermediate IAB node. One option is to allow a mobile IAB node to establish a connection only to a cell served by an IAB donor DU. However, in this case, the question remains as to how the mobile IAB node knows whether the cell is served by an IAB donor DU or not. On the other hand, if the mobile IAB node is considered a network node, the option is also available for the mobile IAB node to establish a connection to any cell. Therefore, the mobile IAB node can also connect to a cell served by an intermediate IAB node, for example, for OAM connections. However, in this case, since the mobile IAB node cannot connect to such a cell in Scenario 1, if the node connects to a cell served by an intermediate IAB node, the node should not operate as a mobile IAB node and may be controlled (i.e., restricted) in some way by the network.

[0274] Proposal 3: If a mobile IAB node is only allowed to connect with the IAB donor (Scenario 1), RAN2 should consider whether the mobile IAB node is a network node and should limit its connection attempts to only the IAB donor DU.

[0275] Furthermore, it should be discussed whether, for the initial access, the mobile IAB node should notify the IAB-donor that it is the mobile IAB node's access, as in the existing IAB node indication in Msg 5. While such indication may be necessary regardless of the scenario, especially in Scenario 1, the IAB donor must decide whether the IAB node can continue to connect to the cell depending on whether the cell is provided by the IAB-donor DU or the IAB-DU of an intermediate IAB node. In other words, such indication is more important in Scenario 1.

[0276] Proposal 4: In particular, when a mobile IAB node only connects with an IAB donor (scenario 1), RAN2 should discuss whether the mobile IAB node needs to send a new indication (e.g., mobile IAB node indication) in the RRC connection establishment procedure.

[0277] In Rel-16 / 17, only fixed IAB nodes were assumed, so the radio conditions of the backhaul link were considered stable. On the other hand, in Rel-18, mobile IAB nodes are assumed, so RLF and RRC re-establishment are no longer rare. When a mobile IAB node initiates RRC re-establishment, the IAB-MT first performs cell selection. In Scenario 1, if the mobile IAB node selects a cell provided by an intermediate IAB node, the next RRC re-establishment may fail, or at least the mobile IAB node may not be able to connect to the cell provided by the intermediate IAB node and may not function as a mobile IAB node after RRC re-establishment. This may cause a service interruption for the UE. Therefore, in Scenario 1, the mobile IAB node is optimized to preferentially select a cell provided by the IAB donor UE.

[0278] Proposal 5: When a mobile IAB node only connects with an IAB donor (scenario 1), RAN2 should discuss whether to optimize the mobile IAB node to select a mobile IAB-capable cell in the RRC re-establishment procedure.

[0279] On the other hand, if the mobile IAB node can also connect to intermediate IAB nodes (scenario 2), the mobile IAB node can connect to any cell, so no special processing is required.

[0280] Note that enhancements for use cases common to both scenarios are not excluded. "No special treatment" is intended to apply only as a comparison between scenarios.

[0281] Observation 3: When a mobile IAB node also connects to an intermediate IAB node (scenario 2), no special processing is required for the mobile IAB node's access because the mobile IAB node can connect to any cell (the cell served by the IAB donor DU and the intermediate IAB node).

[0282] 2.3 Summary The summary of the above discussion is as follows.

[0283]

[0284] As shown in Table 1, there are advantages and disadvantages between the scenarios. Scenario 1 is superior in terms of F1 complexity, while scenario 2 is superior in terms of deployment policy and Uu complexity. Scenario 2 is slightly more preferable, especially from the perspective of RAN2. However, the final decision is likely to be made by the main working group, i.e., RAN3.

[0285] Proposal 6: By adopting scenario 2, in which the mobile IAB node also connects to intermediate IAB nodes, the impact on RAN2 in terms of specifications will be reduced, but the final decision should be left to RAN3.

Claims

1. A communication control method for use in a cellular communication system, comprising: sending a handover request message to a target donor node, the handover request message including information indicating that the mobile relay node is a handover target; and in response to receiving the handover request message, the target donor node selects a cell managed by the target donor node as a handover destination cell for the mobile relay node. Communications control method.

2. The target donor node further includes transmitting mobile relay node acceptance information indicating whether the target donor node is capable of accepting the mobile relay node to the source donor node; and transmitting the handover request message includes the source donor node transmitting the handover request message to the target donor node based on the mobile relay node acceptance information. The communication control method according to claim 1.

3. A target donor node, comprising: a receiving unit for receiving a handover request message from a source donor node, the handover request message including information indicating that the mobile relay node is a handover target; and a control unit that selects a cell managed by the target donor node as a handover destination cell of the mobile relay node in response to receiving the handover request message. Target donor node.

4. A communication system comprising a source donor node, a target donor node and a mobile relay node, comprising: The source donor node sends a handover request message to the target donor node, the handover request message including information indicating that the mobile relay node is a handover target; In response to receiving the handover request message, the target donor node selects a cell managed by the target donor node as a handover destination cell for the mobile relay node. Communication systems.

5. A program for controlling a target donor node, comprising: receiving a handover request message from a source donor node, the handover request message including information indicating that the mobile relay node is a handover target; In response to receiving the handover request message, the target donor node selects a cell managed by the target donor node as a handover destination cell for the mobile relay node. program.

6. A processor for controlling a target donor node, comprising: receiving a handover request message from a source donor node, the handover request message including information indicating that the mobile relay node is a handover target; In response to receiving the handover request message, a process of selecting a cell managed by the target donor node as a handover destination cell for the mobile relay node is executed. Processor.