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

Technical Field

[0006] , , ,

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

Background Art

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

Prior Art Documents

Non-Patent Documents

[0003]

Non-Patent Document 1

Summary of the Invention

[0004] The communication control method according to the first aspect is a communication control method 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 regarding a mobile relay node.

[0005] The communication control method according to the second aspect is a communication control method used in a cellular communication system. The communication control method includes a step in which a mobile relay node transmits information regarding the mobile relay node.

[0006] The third aspect of the communication control method is a communication control method used in a cellular communication system. The communication control method includes the step of a source donor node sending a handover request message to a target donor node that includes information indicating that the mobile relay node is subject to handover. The communication control method also includes the step of the target donor node, upon receiving the handover request message, selecting a cell managed by the target donor node as the cell to which the mobile relay node will be handed over. [Brief explanation of the drawing]

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

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

[0009] [First Embodiment] (Configuration of a cellular communication system) An example configuration of a cellular communication system according to one embodiment will be described. The cellular communication system 1 according to one embodiment is a 3GPP 5G system. Specifically, the wireless access method in the cellular communication system 1 is NR (New Radio), which is a 5G wireless access method. However, LTE (Long Term Evolution) may be applied to the cellular communication system 1 at least partially. 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 a configuration example of a cellular communication system 1 according to an embodiment.

[0011] As shown in FIG. 1, the cellular communication system 1 includes a 5G core network (5GC) 10, user equipment (UE: User Equipment) 100, base station devices (hereinafter sometimes referred to as "base stations") 200-1, 200-2, and IAB nodes 300-1, 300-2. The base station 200 may be called a gNB.

[0012] Hereinafter, an example in which the base station 200 is an NR base station will be mainly described, but the base station 200 may be an LTE base station (i.e., eNB).

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

[0014] The 5GC 10 includes an AMF (Access and Mobility Management Function) 11 and a UPF (User Plane Function) 12. The AMF 11 is a device that performs various mobility controls for the UE 100. The AMF 11 manages information on the area where the UE 100 is located by communicating with the UE 100 using NAS (Non-Access Stratum) signaling. The UPF 12 is a device that performs transfer control of user data.

[0015] Each gNB 200 is a fixed radio communication node that manages one or more cells. A cell is a term used to indicate the smallest unit of a radio communication area. A cell may be used as a term to indicate a function or resource for performing radio communication with the UE 100. One cell belongs to one carrier frequency frequency. Hereinafter, the cell and the base station may sometimes be used without distinction.

[0016] Each gNB200 is interconnected with the 5GC10 via an interface called the NG interface. Figure 1 illustrates two gNB200-1 and gNB200-2 connected to the 5GC10.

[0017] Each gNB200 may be divided into a Central Unit (CU) and a Distributed Unit (DU). The CU and DU are interconnected via an interface called the F1 interface. The F1 protocol is a communication protocol between the CU and DU, and consists of the F1-C protocol, which is the control plane protocol, and the F1-U protocol, which is the user plane protocol.

[0018] Cellular communication system 1 supports IAB, which enables wireless relay of NR access using NR for backhaul. Donor gNB200-1 (or donor node; hereinafter sometimes referred to as "donor node") is the network-side NR backhaul termination node and is a donor base station with additional functions to support IAB. Backhaul can be multi-hop, via multiple hops (i.e., multiple IAB nodes 300).

[0019] Figure 1 shows an example where IAB node 300-1 is wirelessly connected to donor node 200-1, and IAB node 300-2 is wirelessly connected to IAB node 300-1, with the F1 protocol being transmitted over two backhaul hops.

[0020] The UE100 is a mobile wireless communication device that communicates wirelessly with a cell. The UE100 can be any device that communicates wirelessly with the gNB200 or IAB node 300. For example, the UE100 may be a mobile phone terminal and / or a tablet terminal, a notebook PC, a sensor or a device installed on a sensor, a vehicle or a device installed on a vehicle, an aircraft or a device installed on an aircraft. The UE100 connects wirelessly to the IAB node 300 or gNB200 via an access link. Figure 1 shows an example of the UE100 connecting wirelessly to IAB node 300-2. The UE100 communicates indirectly with donor node 200-1 via IAB node 300-2 and IAB node 300-1.

[0021] Figure 2 shows an example of the relationship between IAB node 300, parent nodes, and child nodes.

[0022] As shown in Figure 2, each IAB node 300 has an IAB-DU, which corresponds to the base station function unit, and an IAB-MT (Mobile Termination), which corresponds to the user equipment function unit.

[0023] On the IAB-MT's NR Uu radio interface, adjacent nodes (i.e., higher-level nodes) are called parent nodes. A parent node is the DU of the parent IAB node or donor node 200. The radio link between the IAB-MT and the parent node is called a backhaul link (BH link). Figure 2 shows an example where the parent nodes of IAB node 300 are IAB nodes 300-P1 and 300-P2. The direction toward the parent node is called upstream. From the perspective of UE100, the higher-level node of UE100 may be a parent node.

[0024] Adjacent nodes (i.e., lower-level nodes) on the NR access interface of an IAB-DU are called child nodes. The IAB-DU manages cells, similar to the gNB200. The IAB-DU terminates the NR Uu radio interface to the UE100 and lower-level IAB nodes. The IAB-DU supports the F1 protocol to the CU of donor node 200-1. Figure 2 shows an example where the child nodes of IAB node 300 are IAB nodes 300-C1 to 300-C3, but the child nodes of IAB node 300 may also include the UE100. The direction toward 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 Figure 2, adjacent nodes on the IAB-DU interface become child nodes, and adjacent nodes on the IAB-MT interface become parent nodes. The donor node 200 centrally manages, for example, the resources, topology, and route management of the IAB topology. The donor node 200 is a gNB that provides network access to the UE100 via the backhaul link and access link network.

[0026] (Base station configuration) Next, the configuration of the gNB200, which is a base station according to the embodiment, will be described. Figure 3 is a diagram showing an example of the configuration of the gNB200. As shown in Figure 3, the gNB200 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 with the IAB node 300. The wireless communication unit 210 includes a receiving unit 211 and a transmitting unit 212. The receiving unit 211 performs various types of reception under the control of the control unit 230. The receiving unit 211 includes an antenna and converts the wireless signal received by the antenna into a baseband signal (received signal) (downconvert) and outputs it to the control unit 230. The transmitting unit 212 performs various types of transmission under the control of the control unit 230. The transmitting unit 212 includes an antenna and converts the baseband signal (transmitted signal) output by the control unit 230 into a wireless signal (upconvert) and transmits it from the antenna.

[0028] The network communication unit 220 performs wired (or wireless) communication with 5GC10 and with other adjacent gNB200s. The network communication unit 220 has a receiving unit 221 and a transmitting unit 222. The receiving unit 221 performs various types of reception under the control of the control unit 230. The receiving unit 221 receives signals from the outside and outputs the received signals to the control unit 230. The transmitting unit 222 performs various types of transmission under the control of the control unit 230. The transmitting unit 222 transmits the transmission signals output by the control unit 230 to the outside.

[0029] The control unit 230 performs various controls in the gNB200. 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 for processing by the processor. The processor may include a baseband processor and a CPU. The baseband processor performs modulation, demodulation, encoding, decoding, etc., of the baseband signal. The CPU executes programs stored in the memory and performs various processing. The processor performs processing for each layer described later. In each of the embodiments shown below, the control unit 230 may perform each processing or operation in the gNB200.

[0030] (Configuration of relay nodes) Next, the configuration of the IAB node 300, which is a relay node (or relay node device; hereinafter sometimes referred to as "relay node") according to the embodiment, will be described. Figure 4 is a diagram showing an example of the configuration of the IAB node 300. As shown in Figure 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 with the gNB200 (BH link) and wireless communication with the UE100 (access link). 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 includes 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 the wireless signal received by the antenna into a baseband signal (received signal) (downconvert) and outputs it 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 the baseband signal (transmitted signal) output by the control unit 320 into a wireless signal (upconvert) and transmits it 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 for processing by the processor. The processor may include a baseband processor and a CPU. The baseband processor performs modulation, demodulation, encoding, and decoding of baseband signals. The CPU executes programs stored in the memory and performs various processes. The processor performs processing for each layer described later. In each of the embodiments shown below, the control unit 320 may perform each process or operation in the IAB node 300.

[0034] (User device configuration) Next, the configuration of the user device UE100 according to the embodiment will be described. Figure 5 is a diagram showing an example of the configuration of UE100. As shown in Figure 5, UE100 has a wireless communication unit 110 and a control unit 120.

[0035] The wireless communication unit 110 performs wireless communication on the access link, i.e., wireless communication with the gNB200 and wireless communication with the IAB node 300. The wireless communication unit 110 may also perform wireless communication on the side link, i.e., wireless communication with other UE100s. The wireless communication unit 110 has a receiving unit 111 and a transmitting unit 112. The receiving unit 111 performs various types of reception under the control of the control unit 120. The receiving unit 111 includes an antenna and converts the wireless signal received by the antenna into a baseband signal (received signal) (downconvert) and outputs it to the control unit 120. The transmitting unit 112 performs various types of transmission under the control of the control unit 120. The transmitting unit 112 includes an antenna and converts the baseband signal (transmitted signal) output by the control unit 120 into a wireless signal (upconvert) and transmits it 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 for processing by the processor. The processor may include a baseband processor and a CPU. The baseband processor performs modulation, demodulation, encoding, and decoding of baseband signals. The CPU executes programs stored in the memory and performs various processes. The processor performs processing for each layer described later. The control unit 120 may perform each process in the UE 100 in each of the embodiments shown below.

[0037] (Protocol stack configuration) Next, the configuration of the protocol stack according to the embodiment will be described. Figure 6 shows an example of a protocol stack for IAB-MT RRC connection and NAS connection.

[0038] As shown in Figure 6, the IAB-MT of IAB node 300-2 has a physical (PHY) layer, a MAC (Medium Access Control) layer, an RLC (Radio Link Control) layer, a PDCP (Packet Data Convergence Protocol) layer, an RRC (Radio Resource Control) layer, and a NAS (Non-Access Stratum) layer.

[0039] The PHY layer performs encoding and decoding, modulation and demodulation, antenna mapping and demapping, and resource mapping and demapping. Data and control information are transmitted between the PHY layer of IAB-MT at IAB node 300-2 and the PHY layer of IAB-DU at IAB node 300-1 via a physical channel.

[0040] The MAC layer performs data priority control, retransmission processing using Hybrid Automatic Repeat request (HARQ), and random access procedures. Data and control information are transmitted between the MAC layer of IAB-MT on IAB node 300-2 and the MAC layer of IAB-DU on IAB node 300-1 via a transport channel. The MAC layer of IAB-DU includes a scheduler. The scheduler determines the transport format (transport block size, modulation and coding scheme (MCS)) and allocated resource blocks for the up and down links.

[0041] The RLC layer uses the functions of the MAC layer and PHY layer to transmit data to the receiving RLC layer. Data and control information are transmitted between the RLC layer of IAB-MT on IAB node 300-2 and the RLC layer of IAB-DU on IAB node 300-1 via a logical channel.

[0042] The PDCP layer performs header compression / decompression, and encryption / decryption. Data and control information are transmitted between the PDCP layer of IAB-MT on IAB node 300-2 and the PDCP layer on donor node 200 via a wireless bearer.

[0043] The RRC layer controls the logical channel, transport channel, and physical channel in response to the establishment, re-establishment, and release of the radio bearer. RRC signaling for various settings is transmitted between the RRC layer of the IAB-MT on IAB node 300-2 and the RRC layer of donor node 200. If there is an RRC connection with donor node 200, the IAB-MT is in the RRC connected state. If there is no RRC connection with donor node 200, the IAB-MT is in the RRC idle state.

[0044] The NAS layer, located above the RRC layer, handles session management and mobility management, among other things. NAS signaling is transmitted between the NAS layer of IAB-MT on IAB node 300-2 and AMF11.

[0045] Figure 7 shows the protocol stack for the F1-U protocol. Figure 8 shows the protocol stack for the F1-C protocol. Here, an example is shown where donor node 200 is divided into CU and DU.

[0046] As shown in Figure 7, each of the IAB-MT on IAB node 300-2, the IAB-DU on IAB node 300-1, the IAB-MT on IAB node 300-1, and the DU on donor node 200 has a BAP (Backhaul Adaptation Protocol) layer as a layer above the RLC layer. The BAP layer is the layer that performs routing and bearer mapping / demapping. In backhaul, routing across multiple hops is possible because the IP layer is transmitted through the BAP layer.

[0047] In each backhaul link, the BAP layer's PDUs (Protocol Data Units) are transmitted via backhaul RLC channels (BH NR RLC channels). By configuring multiple backhaul RLC channels in each BH link, traffic prioritization and QoS (Quality of Service) control are possible. The mapping 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 Figure 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 Figure 7.

[0049] In the following, the processes or operations performed by the IAB-DU and IAB-MT of the IAB may be described simply as "IAB processes or operations." 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 IAB node 300-1 transmitting the message to IAB node 300-2. Similarly, the processes or operations of the DU or CU of donor node 200 may be described simply as "donor node processes or operations."

[0050] Furthermore, the upstream direction and the uplink (UL) direction may not be distinguished. Additionally, the downstream direction and the downlink (DL) direction may not be distinguished.

[0051] (Two scenarios) Currently, 3GPP is considering the introduction of mobile IAB nodes. A mobile IAB node is, for example, an IAB node that is in motion. A mobile IAB node may be a mobile IAB node, or an IAB node that has the capability to move, or an IAB node that is currently stationary but is certain to move in the future (or is expected to move in the future).

[0052] A mobile IAB node allows, for example, a UE100 under the mobile IAB node to move along with the mobile IAB node while receiving services from it. For example, a user (or UE100) riding in a vehicle can receive services via a mobile IAB node installed in the vehicle.

[0053] Furthermore, 3GPP is also discussing the possibility that mobile IAB nodes should provide services to UE100 without having any IAB nodes under their control.

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

[0055] Furthermore, 3GPP is considering the complexity of the following two scenarios regarding mobile IAB nodes.

[0056] (Scenario 1) The mobile IAB node connects only to the donor node. (Scenario 2) The mobile IAB node can also connect to the intermediate IAB node. Figure 9 is a diagram illustrating an example of a first scenario according to the first embodiment. In the example in Figure 9, a mobile IAB node 300M installed on a bus is shown moving while connecting to each DU (DU200-D1, etc.) of each donor node 200 (which may be referred to as "IAB-donor-DU"). 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] Figure 10 is a diagram illustrating an example of a second scenario according to the first embodiment. In the example in Figure 10, a mobile IAB node 300M installed on a bus is shown moving while connecting to each DU (such as DU200-D1A) of each donor node 200 (which may be referred to as "IAB-donor-DU"), as well as to an intermediate IAB node 300S (the IAB-DU included in the intermediate IAB node 300S). The second scenario is one in which the mobile IAB node 300M can connect to both the donor node 200 and the intermediate IAB node 300S.

[0058] Within 3GPP, some argue that Scenario 1 is less complex than Scenario 2, while others argue that Scenario 1 is more complex than Scenario 2.

[0059] In the first embodiment, a first scenario will be described. In the first scenario, for example, if the mobile IAB node 300M is unable to connect to the donor node 200, it is assumed that the mobile IAB node 300M will be disconnected from the network, and therefore will be unable to provide services to the subordinate UE 100. However, if the mobile IAB node 300M is able to connect to the donor node 200, it will be possible to provide services to the UE 100 appropriately.

[0060] Therefore, the objective of the first embodiment is to enable the mobile IAB node 300M to connect properly to the donor node 200.

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

[0062] (1.1) First example of operation: Donor node 200 broadcasts connection permission information to the mobile IAB node 300M.

[0063] (1.2) Second example of operation: Intermediate IAB node 300S notifies mobile IAB node 300M of connection denial information.

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

[0065] (1.4) Fourth example of operation: Mobile IAB node 300M is made cell selectable for cells included in the measurement configuration or conditional reconfiguration.

[0066] (1.5) Fifth example of operation: Donor node 200 notifies mobile IAB node 300M of the PRACH resources that it can use exclusively.

[0067] The first to fifth operation examples illustrate a scenario where 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 differs in each operation example. Specific examples of the information about the mobile relay node are explained in each operation example.

[0068] (1.1) First example of operation First, let's explain the first example of operation.

[0069] The first operational example is one in which donor node 200 broadcasts connection permission information to mobile IAB node 300M. Connection permission information is information that indicates permission to connect to, for example, a mobile relay node (for example, mobile IAB node 300M). In the first operational example, the information regarding the mobile relay node (for example, mobile IAB node 300M) is connection permission information. Then, in the first operational example, the donor node (for example, donor node 200) broadcasts the connection permission information.

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

[0071] Figure 11 is a diagram illustrating an example of the first operation.

[0072] As shown in Figure 11, in step S10, the donor node 200 transmits connection permission information. The donor node transmits connection permission information by broadcasting a System Information Block (SIB) containing the connection permission information. The mobile IAB node 300M receives the connection permission information.

[0073] The connection permission information may be information indicating that the mobile IAB node 300M is permitted to connect. Alternatively, the connection permission information may be information indicating that the node broadcasting the connection permission information is donor node 200 (or a cell of donor node 200). Alternatively, the connection permission information may be information indicating that it supports the mobile IAB node 300M. A cell broadcasting the connection permission information supports the mobile IAB node 300M and may be considered as a candidate cell for cell selection for the mobile IAB node 300M. This connection permission information is notified by an information element such as "Mobile-IAB-Supported". This connection permission information is a different information element from the existing information element "IAB-Supported". The mobile IAB node 300M may determine that it can access the cell if both "Mobile-IAB-Supported" and "IAB-Supported" are notified in the SIB. Alternatively, mobile IAB node 300M may determine that it can access the cell in question if "Mobile-IAB-Supported" is notified in the SIB (regardless of whether "IAB-Supported" is notified or not).

[0074] Furthermore, the CU (IAB-donor-CU) of donor node 200 may select the DU (IAB-donor-DU) of donor node 200 that will allow the mobile IAB node 300M to connect, and send an F1 message containing access connection permission information to the selected DU of donor node 200. In response to receiving the F1 message, the DU of donor node 200 may announce an SIB (e.g., SIB1) containing connection permission information. In this case, the CU of donor node 200 will not send an F1 message containing connection permission information to the DU of intermediate IAB node 300S that will not allow the mobile IAB node 300M to connect.

[0075] In step S11, the mobile IAB node 300M detects a Radio Link Failure (RLF). The mobile IAB node 300M may also detect an RLF if it detects the expiration of a timer related to a radio problem or measurement report. Alternatively, the mobile IAB node 300M may detect an RLF if 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 the RRC Reestablishment procedure. When the mobile IAB node 300M starts executing the RRC Reestablishment procedure, it first performs a cell selection procedure to select a suitable cell. At this time, the mobile IAB node 300M includes cells that have reported connection permission information (step S10) as candidates for selection in the cell selection procedure. Alternatively, the mobile IAB node 300M may prioritize the selection of cells that have reported connection permission information. Alternatively, the mobile IAB node 300M may exclude cells that have not reported connection permission 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 Reestablishment Request message to that cell and starts executing the RRC Reestablishment procedure.

[0077] Furthermore, the mobile IAB node 300M receives the cell ID of a cell managed by the donor node 200 from the donor node 200 when establishing synchronization with that cell, for example, before step S10. Therefore, the mobile IAB node 300M can identify the cell that has notified connection permission information based on that cell ID.

[0078] (1.2) Second example of operation Next, we will explain the second example of action. The second example of action will be explained focusing on the differences from the first example of action.

[0079] The second operational example shows an example where an intermediate IAB node 300S broadcasts connection denial information to a mobile IAB node 300M. Specifically, the information regarding the mobile relay node (e.g., mobile IAB node 300M) is connection denial information indicating that the mobile relay node's connection is not permitted. Then, the intermediate relay node (e.g., intermediate IAB node 300S) broadcasts the connection denial information.

[0080] This allows, for example, mobile IAB node 300M to identify cells that it does not allow to connect to. Therefore, mobile IAB node 300M can avoid connecting to cells managed by intermediate IAB node 300S. Thus, mobile IAB node 300M can properly connect to donor node 200.

[0081] Figure 12 is a diagram illustrating an example of the second example of operation.

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

[0083] Connection denial information may indicate that a connection to the mobile IAB node 300M is not permitted. Alternatively, connection denial information may indicate that the node broadcasting the connection denial information is an intermediate IAB node 300S (or a cell of an intermediate IAB node 300S). Alternatively, connection denial information may indicate that the mobile IAB node 300M is not supported. A cell broadcasting connection denial information may not support the mobile IAB node 300M and may not be considered as a candidate cell for mobile IAB node 300M cell selection. This 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 "Mobile-IAB-Not-Allowed" is notified, the mobile IAB node 300M will determine that access to that cell is prohibited (or that the cell does not support a connection to the mobile IAB node 300M).

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

[0085] In step S21, the mobile IAB node 300M detects the RLF, similar to the first operational example.

[0086] In step S22, the mobile IAB node 300M executes the RRC re-establishment procedure. Similar to the first example of operation, the mobile IAB node 300M first performs a cell selection procedure to select a suitable cell. At this time, the mobile IAB node 300M excludes cells that have reported connection denial information (step S20) from the list of candidates for cell selection in the cell selection procedure. The mobile IAB node 300M may also include cells that have not reported connection denial information as candidates for selection. The mobile IAB node 300M selects the cell with the best quality from among the candidates for selection. Then, the mobile IAB node 300M sends an RRC re-establishment request message to the selected cell and starts executing the RRC re-establishment procedure.

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

[0088] (Example of third action) Next, we will explain the third example of action. Again, we will focus on explaining the differences between this third example and the first example.

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

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

[0091] This allows, for example, mobile IAB node 300M to know which cells it can connect to. By designating cells managed by donor node 200 as connectable cells for mobile IAB node 300M, mobile IAB node 300M, upon receiving the connectable cell information, can appropriately connect to donor node 200.

[0092] Figure 13 is a diagram illustrating an example of operation related to the third operation example. Note that the mobile IAB node 300M may connect to a cell managed by the donor node 200 before starting the operation shown in Figure 13. Alternatively, the mobile IAB node 300M may connect to a cell managed by the intermediate IAB node 300S before starting the operation shown in Figure 13. The serving cell shown in Figure 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, if the mobile IAB node 300M connects to a cell managed by an intermediate IAB node, it can immediately hand over to a cell managed by donor node 200 by receiving an RRC Reconfiguration (HO Command) message from that cell.

[0094] As shown in Figure 13, in step S30, the serving cell sends connectable cell information to the mobile IAB node 300M, representing cells that the mobile IAB node 300M can connect to. The connectable cell information may be presented as a list of cell IDs of connectable cells (as an Allowed list). The serving cell may also send unconnectable cell information to the mobile IAB node 300M, representing cells that the mobile IAB node 300M cannot connect to (or are not connectable to). The unconnectable cell information may also be presented as a list of cell IDs of unconnectable cells (as a Block list). The serving cell may also send an RRCReconfiguration message to the mobile IAB node 300M containing the connectable cell information (or unconnectable cell information).

[0095] Furthermore, serving cells may update their connectable cell information (or unconnectable cell information) when various events occur.

[0096] For example, a serving cell may have updated connectable cell information set during a handover of the mobile IAB node 300M. The updated connectable cell information may be included in the RRC reconfiguration (HO command) message and sent.

[0097] Furthermore, for example, when Dual Connectivity is configured on 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 send an RRC reset message containing the updated connectable cell information to configure the updated connectable cell information.

[0098] In step S31, the mobile IAB node 300M detects the RLF, similar to the first operational example.

[0099] In step S32, the mobile IAB node 300M starts the RRC re-establishment procedure. The mobile IAB node 300M first executes the cell selection procedure. The mobile IAB node 300M considers the cells included in the connectable cell information as candidates for cell selection in the cell selection procedure. The mobile IAB node 300M may prioritize selecting cells included in the connectable cell information. On the other hand, the mobile IAB node 300M excludes cells represented by the unconnectable cell information from the candidates for cell selection in the cell selection procedure. The mobile IAB node 300M selects the cell with the best quality from the candidate cells. Then, the mobile IAB node 300M sends an RRC re-establishment request message to the selected cell.

[0100] (1.4) Fourth example of operation Next, we will explain the fourth example of action. The fourth example will also be explained focusing on the differences from the first example of action.

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

[0102] Specifically, the information regarding a mobile relay node (e.g., mobile IAB node 300M) is cell identification information (e.g., cell ID) included in either the measurement settings or conditional resets. Firstly, a donor node (e.g., donor node 200) transmits either the measurement settings or conditional resets to the mobile relay node. Secondly, the mobile relay node determines that a cell represented by the cell identification information included in either the measurement settings or conditional resets is a cell that the mobile relay node can connect to.

[0103] As a result, for example, if a cell ID included in either the measurement settings or conditional reset settings is a cell managed by the donor node 200, the mobile IAB node 300M can select the cell represented by that cell ID using a cell selection procedure. Therefore, the mobile IAB node 300M can properly connect to the donor node 200.

[0104] Furthermore, measurement settings and conditional resets are included in RRC messages, such as RRCReconfiguration messages, and sent to the mobile IAB node 300M. Therefore, the donor node 200 can use existing messages to notify the mobile IAB node 300M of the cells to which it can connect.

[0105] Measurement settings are one of the information elements (IEs) included in RRC messages, such as RRC reset messages. Measurement settings include configuration information for when the mobile IAB node 300M performs a measurement report. In particular, measurement settings include information about the cell that will be the measurement object. In the third example, the cell included in the measurement object is treated as a cell that can be connected to by the mobile IAB node 300M.

[0106] Furthermore, conditional reset is, for example, one of the information elements included in the RRC reset message. Conditional reset contains configuration information for when the mobile IAB node 300M performs a conditional handover (CHO). A conditional handover is a handover that is performed when one or more handover execution conditions are met. In particular, conditional reset includes information on candidate target cells (target SpCells). In the third operational example, the cell included in the conditional reset is treated as a cell that can be connected to by the mobile relay node.

[0107] Then, in the mobile IAB node 300M, the cell included in either the measurement settings or conditional resetting is designated as a candidate cell for selection in the cell selection procedure. By making the cell included in either the measurement settings or conditional resetting a cell managed by the donor node 200, the mobile IAB node 300M becomes able to connect to the donor node 200.

[0108] Figure 14 is a diagram illustrating an example of the fourth example of operation.

[0109] As shown in Figure 14, in step S40, the donor node 200 sets the measurement settings for the mobile IAB node 300M. Specifically, the donor node 200 sends an RRC message containing the measurement settings to the mobile IAB node 300M.

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

[0111] In step S41, the mobile IAB node 300M detects the RLF, similar to the first operational 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 selects the cells (or cell IDs) included in the measurement setting as candidate cells. The mobile IAB node 300M selects the cell with the best quality from the candidate cells and sends an RRC re-establishment request message to the selected cell.

[0113] Although the operation example shown in Figure 14 was explained using an example of measurement settings, the same procedure can be followed even in the case of conditional resetting. That is, the donor node 200 can set conditional resetting for conditional handover to the mobile IAB node 300M by sending an RRC resetting message including conditional resetting to the mobile IAB node 300M (step S40). Then, after the mobile IAB node 300M detects the RLF (step S41), it selects the cell represented by the cell ID included in the conditional resetting as a connectable cell and makes it a candidate for selection in the cell selection procedure (step S42).

[0114] (1.5) Example of the fifth operation Next, we will explain the fifth example of action. Again, we will focus on explaining the differences between this fifth example and the first example of action.

[0115] The fifth example of operation is one in which donor node 200 notifies mobile IAB node 300M of a PRACH resource that can be used exclusively by it.

[0116] Specifically, information regarding a mobile relay node (e.g., mobile IAB node 300M) is resource information concerning resources that the mobile relay node can use exclusively in random access procedures. The donor node (e.g., donor node 200) then broadcasts this resource information.

[0117] On the other hand, the mobile IAB node 300M can recognize a cell that has reported the resource information as a cell it can connect to. The mobile IAB node 300M can then select that cell as a candidate for selection in the cell selection procedure. The mobile IAB node 300M then uses the resource information to send a message (such as Msg1) to the cell selected from the candidates, thereby executing the random access procedure.

[0118] Thus, the mobile IAB node 300M recognizes the cell broadcasting the resource information as a cell it can connect to. Therefore, by making the cell broadcasting the resource information a cell managed by the donor node 200, the mobile IAB node 300M can connect to the donor node 200 appropriately. In addition, compared to the intermediate IAB node 300S, the mobile IAB node 300M is expected to experience more frequent changes in serving cells, such as handover or RRC re-establishment, due to its own movement. By providing the mobile IAB node 300M with different PRACH resources than the intermediate IAB node 300S, it becomes possible to prevent PRACH collisions or to effectively utilize wireless resources.

[0119] Figure 15 is a diagram illustrating an example of the fifth example of operation.

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

[0121] The CU of donor node 200 may select a DU (IAB-donor-DU) that will provide resources exclusively for mobile IAB node 300M and notify that DU that it has been selected as the DU that will provide resources exclusively for mobile IAB node 300M. The CU of donor node 200 may make this notification by sending an F1 message containing information indicating this selection to the DU of donor node 200. The DU of donor node 200 may, upon receiving this notification, report an SIB containing resource information. The CU of donor node 200 does not send this notification to the DU of intermediate IAB node 300S.

[0122] In step S51, the mobile IAB node 300M detects the RLF, similar to the first operational 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 reported resource information as candidates. and The mobile IAB node 300M may exclude cells that do not broadcast resource information from the selection candidates. The mobile IAB node 300M selects cells with good radio quality from the selection candidates. Then, the mobile IAB node 300M sends Msg1 to the selected cells using the resources represented by the resource information, and sends an RRC re-establishment request message (e.g., Msg3).

[0124] (Other examples of the first embodiment) The first example illustrates how connection permission information is used in the cell selection procedure within the RRC re-establishment procedure, but it is not limited to this. Connection permission information may also be used in general cell selection procedures other than the RRC re-establishment procedure. The connection permission information may also be used in the cell reselection procedure. That is, the IAB-MT of the mobile IAB node 300M may use cells for which connection permission information has been reported as candidates for selection in the cell selection procedure or within the cell selection procedure. Alternatively, the IAB-MT of the mobile IAB node 300M may prioritize the selection of cells for which connection permission information has been reported in the cell selection procedure or within the cell selection procedure.

[0125] Furthermore, the fifth example of operation may also be used in general cell selection procedures other than the RRC re-establishment procedure, or in the cell reselection procedure. That is, the IAB-MT of the mobile IAB node 300M may use cells for which resource information has been reported as candidates for cell selection in the cell selection procedure or cell reselection procedure. Alternatively, the IAB-MT of the mobile IAB node 300M may be configured to prioritize the selection of cells for which resource information has been reported in the cell selection procedure or cell selection procedure.

[0126] Furthermore, the second example of operation may also be used in general cell selection procedures other than the RRC re-establishment procedure, or in the cell reselection procedure. That is, the IAB-MT of the mobile IAB node 300M may exclude cells that have been reported as connection denied from the list of candidates for cell selection in the cell selection procedure or the cell reselection procedure.

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

[0128] The first scenario also applies to the second embodiment. In particular, initial access will be described in the second embodiment.

[0129] The first scenario is one in which the mobile IAB node 300M connects only to the donor node 200. For example, suppose the mobile IAB node 300M moves to a cell managed by the intermediate IAB node 300S. In such a case, if the mobile IAB node 300M attempts to connect to the cell managed by the intermediate IAB node 300S, considering the first scenario, it is possible that the connection itself will be rejected from the outset.

[0130] However, if we consider the mobile IAB node 300M as one of the network nodes, it may be preferable to allow the mobile IAB node 300M to connect to the intermediate IAB node 300S first, and then to connect to the donor node 200, rather than having the connection to the intermediate IAB node 300S refused from the outset.

[0131] Therefore, in the second embodiment, we will describe a case 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 in accordance with the first scenario. In such a case, the following processing is expected to take place.

[0132] • When mobile IAB node 300M is connected to intermediate IAB node 300S, it will perform a handover to donor node 200.

[0133] • A mobile IAB node 300M is restricted from functioning as a mobile IAB node 300M when connected to an intermediate IAB node 300S.

[0134] The second embodiment, including this process, will be described below.

[0135] In the second embodiment, the mobile IAB node 300M will ultimately be connected to the donor node 200. Therefore, the second embodiment, like the first embodiment, aims to ensure that the mobile IAB node 300M can be properly connected to the donor node 200.

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

[0137] (2.1) Sixth example of operation: Mobile IAB node 300M notifies that it is a mobile IAB node when connecting.

[0138] (2.2) Example 7 of operation: Donor node 200 imposes an F1 setup restriction on the mobile IAB node 300M.

[0139] (2.3) Example 8 of operation: Mobile IAB node 300M sends an F1 message to donor node 200 indicating whether or not it can operate as a mobile IAB node.

[0140] (2.4) Example 9 of operation: Mobile IAB node 300M sends an F1 message to donor node 200 with information to identify the RRC connection.

[0141] Examples 6 through 9 include cases where a mobile relay node (e.g., a mobile IAB node 300M) transmits information about the mobile relay node. The nature of this information will be explained within each example.

[0142] (2.1) Example of the 6th operation The sixth operational example is one in which mobile IAB node 300M notifies a cell that it is a mobile IAB node when connecting to it. Specifically, the information about a mobile relay node (for example, mobile IAB node 300M) is information indicating that it is a mobile relay node. The mobile relay node then sends information indicating that it is a mobile relay node to the cell to which it is connected.

[0143] Upon receiving information indicating that it is a mobile relay node, donor node 200 can recognize that mobile IAB node 300M has connected. Donor node 200 can then determine whether the cell receiving this information is managed by donor node 200 itself or by intermediate IAB node 300S, enabling it to appropriately process mobile IAB node 300M. For example, if mobile IAB node 300M connects to a cell managed by donor node 200's DU, the CU of donor node 200 can decide to accept the connection. Alternatively, if mobile IAB node 300M connects to a cell managed by intermediate IAB node 300S, the CU of donor node 200 can decide to hand over to a cell managed by donor node 200's DU. This allows mobile IAB node 300M to connect to donor node 200 appropriately.

[0144] Figure 16 is a diagram illustrating an example of the sixth example of operation.

[0145] As shown in Figure 16, in step S60, when the mobile IAB node 300M connects to the cell, it sends a message to the cell containing information indicating that it is a mobile IAB node. This message may be message 3 (Msg3) (RRCSetupRequest message) in the random access procedure. Alternatively, this message may be message 5 (Msg5) (RRCSetupComplete message). Alternatively, this message may be a UE Capability Information message. Including this information in the UE Capability Information message results in slower notification to the cell compared to including it in Msg3 or Msg5. Therefore, it is preferable to include it in Msg3 or Msg5.

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

[0147] In step S61, a cell that has received 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) sends, for example, an F1 message containing information indicating that it has received the information 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 containing information indicating that it is a mobile IAB node, it checks 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, thereby determining whether the mobile IAB node 300M has connected to a cell managed by the donor node 200.

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

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

[0151] On the other hand, in step S64, firstly, 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 sends an F1 message to the IAB-DU of the intermediate IAB node 300S containing information indicating the rejection of the connection of the mobile IAB node 300M. The IAB-DU of the intermediate IAB node 300S may then reject the connection by sending an RRCReject message or an RRCRelease message to the IAB-MT of the mobile IAB node 300M via message 4 (Msg4).

[0152] In step S64, secondly, 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 sends an F1 message containing an RRCReconfiguration (HO Command) message to the IAB-DU of the intermediate IAB node 300S. Then, the IAB-DU of the intermediate IAB node 300S may, upon receiving the F1 message, send an RRCReconfiguration (HO Command) message to the IAB-MT of the mobile IAB node 300M.

[0153] Furthermore, the sixth operational example is applicable not only to the first scenario. In other words, when the mobile IAB node 300M connects to a cell, it is sufficient for it to send information to that cell indicating that it is a mobile IAB node 300M, and it is also applicable to the second scenario (a scenario in which the mobile IAB node 300M can also connect to an intermediate IAB node).

[0154] (2.2) Example of the 7th operation Next, we will explain the seventh example of operation.

[0155] The seventh operational example describes an example in which donor node 200 restricts F1 setup for mobile IAB node 300M. Specifically, if a mobile relay node (e.g., mobile IAB node 300M) connects to a cell managed by a stationary intermediate relay node (e.g., intermediate IAB node 300S) that does not move, the donor node (e.g., donor node 200) sends F1 setup request transmission prohibition information to the mobile relay node, indicating that it is prohibited from sending an F1 setup request message.

[0156] As a result, for example, even if mobile IAB node 300M can connect to a cell managed by intermediate IAB node 300S, it cannot send an F1 setup request message, and therefore cannot establish an F1 connection, limiting its F1 connection with donor node 200. Consequently, mobile IAB node 300M cannot operate as a mobile IAB node (for example, by moving). In this case, donor node 200 can hand over mobile IAB node 300M to a cell managed by donor node 200, allowing mobile IAB node 300M to connect to that cell. Thus, mobile IAB node 300M can properly connect to donor node 200.

[0157] Thus, the seventh operational example is one in which the operation of the mobile IAB node is restricted by limiting F1 connectivity while still allowing the mobile IAB node 300M to connect to the intermediate IAB node 300S.

[0158] Figure 17 is a diagram illustrating an example of the seventh example of operation.

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

[0160] In step S71, the IAB-DU of the intermediate IAB node 300S sends an F1 message containing the RRC message to the CU of the donor node 200 upon receiving the RRC message. The IAB-DU of the intermediate IAB node 300S may also send an F1 message containing information indicating that the RRC message has been received to the CU of the donor node 200 upon receiving the RRC message.

[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 it is a connection to 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 has not connected to a cell managed by the donor node 200).

[0162] In step S73, the CU of the donor node 200 sends an F1 message to the IAB-DU of the intermediate IAB node 300S that contains F1 setup request transmission prohibition information indicating that the transmission of an F1 setup request is prohibited. This F1 setup request transmission prohibition information may be included in an RRC message, and the RRC message may be included in (or encapsulated in) the F1 message before transmission.

[0163] In step S74, the IAB-DU of the intermediate IAB node 300S sends an RRC message (for example, an RRCReconfiguration message) containing information to prohibit the transmission of an F1 setup request 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, the IAB-DU of mobile IAB node 300M, having received the F1 setup request transmission prohibition information, suspends the transmission of the F1 setup request message.

[0165] In step S76, the CU of the donor node 200 sends an F1 message to the IAB-DU of the intermediate IAB node 300S that contains F1 setup request transmission permission information indicating permission to send (or lift the prohibition on sending) F1 setup requests. For example, the CU of the donor node 200 generates an RRC message (e.g., an RRC reset message) that contains F1 setup request transmission permission information. Then, the CU of the donor node 200 sends an F1 message containing the RRC message to the IAB-DU of the intermediate IAB node 300S. Note that the RRC message may also be an HO command. In this case, the CU of the donor node 200 will cause 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, the IAB-DU of the intermediate IAB node 300S, upon receiving the F1 message, sends an RRC message (e.g., an RRC reset message) containing the permission information to send the F1 setup request to the IAB-MT of the mobile IAB node 300M. The IAB-MT of the mobile IAB node 300M receives the F1 setup request. request The transmission permission information is output to the upper layer (IAB-DU) of the mobile IAB node 300M.

[0167] Furthermore, information granting permission to send F1 setup requests may be implicitly communicated. For example, the CU of donor node 200 may generate an RRC message that does not include information prohibiting the sending of F1 setup requests. The mobile IAB node 300M may recognize that it is permitted to send F1 setup requests upon receiving such an RRC message that does not include the information prohibiting the sending of F1 setup requests.

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

[0169] In the seventh operational example, we described an example (step S75) in which the mobile IAB node 300M postpones sending an F1 setup request in response to receiving information prohibiting the transmission of an F1 setup request. For example, the information prohibiting the transmission of an F1 setup request may not be necessary. In this case, the IAB-DU of the mobile IAB node 300M will send an F1 setup request. request The transmission of the F1 setup request may be prohibited until the transmission permission information (step S77) is received. The IAB-DU of mobile IAB node 300M can transmit the F1 setup request once the F1 setup transmission permission information (step S77) is received. Therefore, at the time of RRC connection to intermediate IAB node 300S, mobile IAB node 300M can transmit the F1 setup request. requestIf transmission permission information is not received, the F1 setup request cannot be sent. In such cases, if mobile IAB node 300M connects to intermediate IAB node 300S, F1 connectivity to mobile IAB node 300M will be restricted.

[0170] (2.3) Example of operation #8 Next, we will explain the eighth example of operation.

[0171] Regarding the F1 settings for mobile IAB node 300M, new settings may be added in addition to the existing settings for IAB. For example, if mobile IAB node 300M can send information in the F1 message indicating whether or not it is capable of operating as a mobile IAB node, donor node 200 can appropriately configure the F1 settings for mobile IAB node 300M. For example, donor node 200 can appropriately configure the F1 settings for mobile IAB node 300M by imposing restrictions if it is capable of operating as a mobile IAB node, or by not imposing restrictions if it is not capable of operating as a mobile IAB node.

[0172] Therefore, the eighth example of operation describes an example in which the mobile IAB node 300M sends an F1 message to the donor node 200 indicating whether or not it is capable of operating as a mobile IAB node. In the following, 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 the operational capability information. The operational capability information may also be information indicating whether or not the mobile IAB node 300M will operate as a mobile IAB node.

[0173] Specifically, the information regarding a mobile relay node (e.g., mobile IAB node 300M) is operational status information indicating whether or not the mobile relay node is capable of operating as a mobile relay node. The mobile relay node transmits this operational status information to the donor node (e.g., donor node 200).

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

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

[0176] Firstly, instead of operational availability information, the mobile IAB node 300M may transmit information indicating that the mobile IAB node 300M is capable of being a mobile IAB node.

[0177] Secondly, instead of operational feasibility information, the mobile IAB node 300M may transmit information indicating that it prefers to operate as a mobile IAB node.

[0178] Thirdly, instead of operational capability information, the mobile IAB node 300M may transmit information indicating that its operation as a mobile IAB node is restricted. For example, this may occur if the mobile IAB node 300M is connected to an intermediate IAB node 300S, thereby restricting its operation as a mobile IAB node via an RRC message. In this case, the mobile IAB node 300M may connect to the intermediate IAB node 300S in a state similar to that of a stationary intermediate IAB node, without moving, because its operation as a mobile IAB node (e.g., movement) is restricted. When the mobile IAB node 300M transmits information indicating that its operation as a mobile IAB node is restricted, it may also transmit information indicating the cause. The cause information may be information indicating that it is connected to an intermediate IAB node 300S. The cause information may also be information indicating a wireless layer capability issue.

[0179] Fourth, the mobile IAB node 300M may transmit information indicating that its operation as a mobile IAB node is not restricted (or has been removed) instead of operational availability information. For example, the mobile IAB node 300M may transmit this information via an RRC message when the restriction has been removed (e.g., step S77 of the seventh operation example).

[0180] In step S81, the donor node 200 sets the appropriate F1 configuration for the mobile IAB node 300M based on the operational feasibility information.

[0181] (2.4) Example of Operation 9 Next, we will explain the ninth example of operation.

[0182] The ninth operational example shows that mobile IAB node 300M sends an F1 message to donor node 200 to identify the RRC connection.

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

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

[0185] Therefore, the ninth operational example describes an example in which a mobile relay node (for example, mobile IAB node 300M) sends an F1 message containing information for identifying the RRC connection (hereinafter sometimes referred to as "RRC connection identification information") to a donor node (for example, donor node 200). In the ninth operational example, the information about the mobile relay node is RRC connection identification information, which represents information for identifying the RRC connection of the mobile relay node to the donor node.

[0186] This allows, for example, the donor node 200 to use the RRC connection identification information received via the F1 connection to link the F1 connection information of the mobile IAB node 300M with the RRC connection information of the mobile IAB node 300M. Through this linking, the donor node 200 can then recognize that the mobile IAB node 300M has been connected on the F1 side, and can configure the appropriate F1 settings for the mobile IAB node 300M. The mobile IAB node 300M, having received the appropriate F1 settings from the donor node 200, can then connect to the donor node 200 properly.

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

[0188] Figure 19 is a diagram illustrating an example of the operation related to the ninth operation example.

[0189] As shown in Figure 19, in step S90, the IAB-MT of the mobile IAB node 300M executes the RRC connection establishment procedure to establish an RRC connection with the CU (RRC entity) of the donor node 200. The IAB-MT of the mobile IAB node 300M may output RRC connection identification 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 the F1 setup procedure to establish an F1 connection with the CU (F1 entity) of the donor node 200. When establishing the F1 connection, the IAB-DU of the mobile IAB node 300M sends an F1 message containing RRC connection identification information to the CU (F1 entity) of the donor node 200. This F1 message is, for example, an F1 setup request message. This F1 message includes, for example, an F1 context.

[0191] The RRC connection identification information may, firstly, be 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 UE100). The C-RNTI is issued by the donor node 200 and is used when establishing an RRC connection.

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

[0193] Secondly, RRC connection identification information may also be the RRC Transaction Identifier of the RRC message. The RRC Transaction Identifier is identification information used to identify each RRC procedure. The RRC Transaction Identifier is issued, for example, by donor node 200. The RRC Transaction Identifier is one of the information elements (IE) included in the RRC message.

[0194] In step S92, the CU of the donor node 200, upon receiving the F1 message, uses RRC connection identification information to link the F1 context with the RRC context. For example, the CU of the donor node 200 reads from memory an RRC context that has the same C-RNTI as the C-RNTI included in the F1 message and links it with the F1 context included in the F1 message. If the RRC context contains information indicating that the IAB node connected to the donor node 200 is the mobile IAB node 300M, then the donor node 200 can recognize, through this linking, that the mobile IAB node 300M has connected to the donor node 200 on the F1 side as well.

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

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

[0197] In the second embodiment, it was described that a mobile IAB node 300M is allowed to connect to an intermediate IAB node 300S, and even in such a case, a handover to a cell managed by the donor node 200 is performed. In the third embodiment, the handover of the mobile IAB node 300M is mainly described.

[0198] To hand over IAB node 300M to a cell managed by donor node 200, donor node 200 must select a target cell from among the cells it manages. If donor node 200 selects a cell managed by intermediate IAB node 300S as the target cell, the moving IAB node 300M will not be able to connect to donor node 200.

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

[0200] Thus, the handover destination for the migrated 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 is unable to accept the connection from the moving IAB node 300M, it will reject the handover request (HO REQUEST) from the source donor node 200S. In such cases, a handover delay (Too Late Handover) may occur while the source donor node 200S is processing another target donor node 200.

[0202] Therefore, the objective of the third embodiment is to enable the mobile IAB node 300M to properly hand over to the donor node 200. If the mobile IAB node 300M can properly hand over to the donor node 200, then, as in the first embodiment, the mobile IAB node 300M can properly connect to the donor node.

[0203] As mentioned above, in the following, the terms "migration" and "handover" of the 300M relocating IAB node may not be distinguished. For example, a handover request may be interpreted as a migration request.

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

[0205] (3.1) Tenth example of operation: Source donor node 200S sends information to target donor node 200T indicating that it is a handover of mobile IAB node 300M.

[0206] (3.2) Example 11 of operation: The first donor node 200-1 sends information to the adjacent donor node, the second donor node 200-2, indicating whether or not it can accept the handover of the mobile IAB node 300M.

[0207] (3.1) Example of Operation 10 For target donor node 200T, the selected target cell may change depending on whether the handover target is the moving IAB node 300M or not. As mentioned above, target donor node 200T must target a cell managed by target donor node 200T.

[0208] Therefore, in the 10th operational example, firstly, the source donor node (e.g., source donor node 200S) sends a handover request message to the target donor node (e.g., target donor node 200T) that includes information indicating that the mobile relay node (e.g., mobile IAB node 300M) is subject to handover. Secondly, in response to receiving the handover request message, the target donor node selects a cell under its management as the cell to which the mobile relay node will be handed over.

[0209] Thus, since the target cell is managed by the target donor node 200T, the handover destination for the mobile IAB node 300M will be the cell managed by the donor node 200. Therefore, the mobile IAB node 300M can be properly handed over to the donor node 200.

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

[0211] As shown in Figure 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 on the handover of the moving IAB node 300M.

[0213] In step S102, the source donor node 200S sends a HANDOVER REQUEST message to the target donor node 200T. The HANDOVER REQUEST message contains information indicating that the handover target is the moving 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 via 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 moving IAB node 300M. Conversely, the CU of the target donor node 200T does not select (or excludes) a cell managed by the DU of the subordinate intermediate IAB node 300S as the target cell, based on information indicating that the handover target is the moving IAB node 300M.

[0215] In step S104, the target donor node 200T sends a HANDOVER REQUEST ACKNOWLEDGE message to the source donor node 200S. The target donor node 200T generates an RRC Reconfiguration (HO Command) message containing configuration information for, for example, the mobile IAB node 300M to connect to the target cell, and sends a HANDOVER REQUEST ACKNOWLEDGE message containing this RRC Reconfiguration (HO Command) message to the source donor node 200S. The HANDOVER REQUEST ACKNOWLEDGE message is also one of the Xn messages. RRC Reconfiguration (HO Command) message This contains the cell ID of the target cell.

[0216] In step S105, the source donor node 200S, upon receiving the handover request acknowledgment message, sends the RRC reconfiguration (HO command) message to the moving 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) Example of Operation No. 11 Next, we will explain the 11th example of operation.

[0219] The 11th operational example describes an example in which the first donor node 200-1 sends information to its neighboring donor node, the second donor node 200-2, indicating whether or not it can accept the handover of the mobile IAB node 300M.

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

[0221] This allows, for example, the source donor node (second donor node 200-2) to determine whether the target donor node (first donor node 200-1) will accept the handover of mobile IAB node 300M based on the mobile relay node acceptance status information. Furthermore, the source donor node can limit the cells to be measured in the measurement configuration of mobile IAB node 300M to only those cells that mobile IAB node 300M can accept.

[0222] Then, the source donor node (second donor node 200-2), as a donor node capable of accepting the handover of the moving IAB node 300M, can send 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 the rejection of the handover request message after it has been sent. As a result, the mobile IAB node 300M can properly perform the handover and establish a connection to the target donor node (first donor node 200-1).

[0224] Figure 21 is a diagram illustrating an example of operation related to the 11th operation example. In Figure 21, the first donor node 200-1 and the second donor node 200-2 are, for example, neighboring donor nodes 200. The first donor node 200-1 may be the target donor node of the mobile IAB node 300M. The second donor node 200-2 may be the source donor node to which the mobile IAB node 300M is currently connected.

[0225] As shown in Figure 21, in step S110, the first donor node 200-1 sends an Xn message containing mobile relay node acceptance status information to the second donor node 200-2. The mobile relay node acceptance status information indicates either that the first donor node 200-1 can accept the mobile IAB node 300M, or that the first donor node 200-1 cannot accept the mobile IAB node 300M. The mobile relay node acceptance status information may include a list of cell IDs of acceptable cells. Alternatively, the mobile relay node acceptance status information may include a list of cell IDs of unacceptable cells. Whether a cell is acceptable or unacceptable is determined by whether or not it is a cell managed by the donor node 200 (first donor node 200-1). Alternatively, whether or not a cell is acceptable or unacceptable may be determined by whether or not it is a cell managed by the intermediate IAB node 300S. The second donor node 200-2 may, prior to step S110, request the first donor node 200-1 to provide information on whether it can accept a mobile relay node. The second donor node 200-2 may make this request by sending an Xn message containing this request to the first donor node 200-1.

[0226] In step S111, the second donor node 200-2 may configure the measurement configuration for the mobile IAB node 300M using information on whether it can accept mobile relay nodes. For example, the second donor node 200-2 may configure this by sending an RRC message to the mobile IAB node 300M that includes a measurement configuration that sets cells capable of accepting the mobile IAB node 300M as the measurement object.

[0227] In step S112, the second donor node 200-2 (source donor node) may decide on the handover of the mobile IAB node 300M and, based on the mobile relay node acceptance status information, determine which donor node 200 will receive the HANDOVER REQUEST message. That is, the second donor node 200-2 may use the mobile relay node acceptance status information to determine which donor node (or target donor node) manages a cell capable of accepting the mobile IAB node 300M.

[0228] [Other embodiments] A program may be provided that causes a computer to perform each of the processes performed by UE100, gNB200, or IAB node 300. The program may be recorded on a computer-readable medium. Using a computer-readable medium, it is possible to install the program on a computer. Here, the computer-readable medium on which the program is recorded may be a non-transient recording medium. The non-transient recording medium is not particularly limited, but may be a recording medium such as a CD-ROM or DVD-ROM.

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

[0230] The terms “based on” and “depending on” used in this disclosure do not mean “based solely on” or “depending solely on” unless otherwise specified. “Based on” means both “based solely on” and “at least partially on.” Similarly, “depending on” means both “at least partially on” and “at least partially on.” Furthermore, the terms “include,” “comprise,” and variations thereof do not mean that only the listed items are included; they may include only the listed items, or they may include additional items in addition to the listed items. Also, the term “or” used in this disclosure is not intended to mean exclusive OR. Moreover, any reference to elements using designations such as “first,” “second,” etc., used in this disclosure does not generally limit the quantity or order of those elements. These designations may be used herein as a convenient way to distinguish between two or more elements. Therefore, references to the first and second elements do not imply that only two elements may be adopted therein, or that the first element must precede the second element in any way. In this disclosure, where articles are added by translation, such as a, an, and the in English, these articles shall be plural unless it is clearly indicated by the context that they are not.

[0231] Although one embodiment has been described in detail above with reference to the drawings, the specific configuration is not limited to that described above, and various design changes can be made without departing from the gist of the invention. Furthermore, each embodiment, each operation example, or each process can be combined as appropriate, as long as they do not contradict each other.

[0232] This application claims priority to U.S. Provisional Application No. 63 / 395095 (filed August 4, 2022), the entirety of which is incorporated into the specification of this application.

[0233] (First Appendix)

[0234] (Note 1) A communication control method used in a cellular communication system, The step includes either a donor node or a stationary intermediate relay node that does not move, transmitting information about a mobile relay node. Communication control method.

[0235] (Note 2) The information relating to the mobile relay node is connection permission information indicating that connection to the mobile relay node is permitted, The transmission step includes the donor node broadcasting the connection permission information. The communication control method described in Appendix 1.

[0236] (Note 3) The mobile relay node further includes the step of designating the cell that has notified the connection permission information as a candidate for cell selection in the cell selection procedure. The communication control method described in Appendix 1 or Appendix 2.

[0237] (Note 4) The information relating to the mobile relay node is connection denial information indicating that connection to the mobile relay node is not permitted, The intermediate relay node further comprises the step of broadcasting the connection denial information. A communication control method as described in any of Appendix 1 to Appendix 3.

[0238] (Note 5) The mobile relay node further includes the step of excluding the cell that has reported the connection denial information from the list of candidates for cell selection in the cell selection procedure. A communication control method as described in any of Appendix 1 to Appendix 4.

[0239] (Note 6) The information relating to the mobile relay node is connectable cell information representing cells to which the mobile relay node can connect, The transmission step includes the step of either the donor node or the intermediate relay node transmitting the connectable cell information to the mobile relay node. A communication control method as described in any of Appendix 1 to Appendix 5.

[0240] (Note 7) The information relating to the mobile relay node is unconnectable cell information representing cells that cannot be connected to the mobile relay node, The transmission step includes the step of at least one of the donor node and the intermediate relay node transmitting the unconnectable cell information to the mobile relay node. A communication control method as described in any of Appendix 1 to Appendix 6.

[0241] (Note 8) The mobile relay node further includes the step of selecting cells represented by the connectable cell information as candidates for cell selection in the cell selection procedure, and excluding cells represented by the non-connectable cell information from the candidates for cell selection in the cell selection procedure. A communication control method as described in any of Appendix 1 to Appendix 7.

[0242] (Note 9) The information relating to the mobile relay node is cell identification information included in either the measurement settings or the conditional resetting, The transmission step includes the donor node transmitting either the measurement settings or the conditional reset settings to the mobile relay node. The mobile relay node further comprises the step of determining that a cell represented by the cell identification information included in either the measurement setting or the conditional reset is a cell that the mobile relay node can connect to. A communication control method as described in any of Appendix 1 to Appendix 8.

[0243] (Note 10) The information relating to the mobile relay node is resource information relating to resources that the mobile relay node can use exclusively in random access procedures, The transmission step includes the donor node notifying the resource information. A communication control method as described in any of Appendix 1 to Appendix 9.

[0244] (Note 11) The mobile relay node further includes the step of selecting the cell that has reported the resource information as a candidate cell in the cell selection procedure, and executing the random access procedure using the resource represented by the resource information for the cell selected from the candidate cell. A communication control method as described in any of Appendix 1 to Appendix 10.

[0245] (Note 12) A communication control method used in a cellular communication system, The mobile relay node transmits information about the mobile relay node. Communication control method.

[0246] (Note 13) The information relating to the mobile relay node is information indicating that the node itself is the mobile relay node, The aforementioned transmission step includes the step of the mobile relay node transmitting information indicating that it is the mobile relay node to the cell to which the mobile relay node is connected. The communication control method described in Appendix 12.

[0247] (Note 14) The donor node further includes the step of sending F1 setup request transmission prohibition information to the mobile relay node, indicating that the transmission of F1 setup requests is prohibited when the mobile relay node connects to a cell managed by a stationary intermediate relay node that has not moved. The communication control method described in Appendix 12 or Appendix 13.

[0248] (Note 15) The information relating to the mobile relay node is operational status information indicating whether or not the mobile relay node is capable of operating as the mobile relay node, The aforementioned transmission step includes the step of the mobile relay node transmitting the operational availability information to the donor node. A communication control method as described in any of Appendix 12 to Appendix 14.

[0249] (Note 16) The information relating to the mobile relay node is RRC connection identification information representing information for identifying the RRC connection of the mobile relay node to the donor node, The aforementioned transmission step includes the step of the mobile relay node transmitting an F1 message containing the RRC connection identification information to the donor node. A communication control method as described in any of Appendix 12 to Appendix 15.

[0250] (Note 17) A communication control method used in a cellular communication system, The source donor node sends a handover request message to the target donor node that includes information indicating that the mobile relay node is subject to handover. The step of the target donor node, upon receiving the handover request message, selecting a cell managed by the target donor node as the handover destination cell for the mobile relay node. Communication control method.

[0251] (Note 18) The method further includes the step of the target donor node transmitting mobile relay node acceptance information to the source donor node indicating whether or not it can accept the mobile relay node, The step of sending the handover request message includes the step of the source donor node sending the handover request message to the target donor node based on the mobile relay node acceptance information. The communication control method described in Supplementary Note 17.

[0252] (Supplementary Note 2) 1. Introduction In RAN#94e, a new work item related to mobile IAB was approved.

[0253] The detailed objectives of the WI are as follows. · Define migration / topology adaptation procedures to realize the mobility of IAB nodes, including the migration between donors of all mobile IAB nodes (complete migration). · Enhance the mobility of IAB nodes and their UEs, including aspects related to group mobility. Optimization for targeting surrounding UEs. · Note that in the solution, it should be avoided to touch on topics already discussed in Rel-17 or topics excluded from Rel-17, except for functional extensions specialized for IAB node mobility. · Mitigate interference due to IAB node mobility, including avoidance of potential conflicts between reference signals and control signals (such as PCI, RACH, etc.).

[0254] Note that at the beginning of the working period, RAN3 and RAN2 should discuss the potential complexity of the scenario where the mobile IAB node is connected to an intermediate IAB node compared to the scenario where the mobile IAB node is directly connected to an IAB donor.

[0255] [[ID=二十九]]In this supplementary note, from the perspective of RAN2, an analysis of the complexity in two topology scenarios is performed.

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

[0257] In Rel-18, mobile IAB node supports the following functions applicable to FR1 and FR2. • In-band and out-of-band backhaul. • Mobile IAB nodes do not have descendant IAB nodes and provide services only to UEs. The solution should support UE's HO and DC.

[0258] Furthermore, since mobile IAB nodes only provide services to UEs, it is made clear that mobile IAB nodes are always access IAB nodes.

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

[0260] WID explicitly states that intermediate IAB nodes should be static. On the other hand, the issue in RAN#96 is whether a mobile IAB node can connect only to an IAB donor, or also to an (intermediate) IAB node. Therefore, the two scenarios can be represented as shown in Figures 9 and 10, respectively.

[0261] Some companies believe that limiting mobile IAB nodes to only connect with IAB donors would reduce complexity, while others argue that such limitations would actually increase complexity. Therefore, the complexity of each scenario will be discussed in the following section.

[0262] Finding 1: A complexity analysis is needed regarding the scenario of whether mobile IAB nodes can connect only to IAB donors or also to intermediate IAB nodes.

[0263] 2.2 Complexity Analysis 2.2.1 Deployment and Coverage Generally, Rel-16 / 17IAB was introduced to support the efficient establishment of nationwide coverage, particularly to extend FR2 deployments. If a mobile IAB node can only connect to an IAB donor, the cells provided by the IAB node are unavailable to the mobile IAB node, resulting in many coverage holes from the mobile IAB node's perspective.

[0264] If a mobile IAB node is disconnected from the network, it is clear that service to the UE cannot be continued, and therefore, a large number of coverage holes will directly result in many service disruptions. Assuming that mobile IAB nodes are considered network nodes, similar to Rel-16 / 17 IAB nodes, such service disruptions are undesirable.

[0265] Mobile IAB in Scenario 1 node To achieve this, in addition to existing (or standard) deployment strategies, a special deployment strategy is needed to ensure coverage suitable for mobile IAB nodes. On the other hand, Scenario 2 allows for more flexible deployment. Therefore, the challenges in deployment may increase in Scenario 1 compared to Scenario 2.

[0266] Proposal 2: RAN2 should agree that if mobile IAB nodes only connect to IAB donors (Scenario 1), many coverage holes will occur, potentially compromising the service continuity of the mobile IAB nodes. This would increase deployment challenges.

[0267] 2.2.2 Network Interface Procedure (RAN3 Area) Regarding network interfaces such as F1AP and XnAP, some complexity is expected if the mobile IAB node can also connect to the intermediate IAB node (Scenario 2).

[0268] In the routing configuration (F1AP), when a mobile IAB node enters or exits the IAB topology, the IAB donor needs to update the configuration. In the case of Scenario 2, the IAB donor needs to update the routing configuration of each IAB node in the IAB topology, which makes the procedure complex and may cause an F1 reconfiguration waiting time.

[0269] Regarding the migration of mobile IAB nodes (XnAP), complete migration between donors of mobile IAB nodes and UE group mobility are planned to be considered in RAN3, but it is expected that there will be no 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 accept mobile IAB nodes, that is, the cells where the DU of the IAB donor provides services. Such information is used by the IAB donor for measurement configuration and handover decision-making.

[0270] Since RAN3 is leading in mobile IABWI, the complexity of the network interface has already been somewhat anticipated compared to other interfaces handled by the secondary working group (including RAN2). Whether the network interface can support Scenario 2 and whether to instruct other working groups to define the mechanism of Scenario 1 depends on RAN3.

[0271] Finding 2: When a mobile IAB node is only connected to an IAB donor (i.e., Scenario 1), the network interface procedure may become simpler. The details depend on RAN3.

[0272] 2.2.3 Uu Interface Procedure (RAN2 Area) Regarding the UAU interface, some complexities are expected when a mobile IAB node can only be connected to an intermediate IAB node (i.e., Scenario 1).

[0273] Regarding initial access, we should discuss whether a mobile IAB node can initiate the RRC connection establishment procedure to a cell provided by an intermediate IAB node. One option is to allow mobile IAB nodes to establish connections only to cells provided by an IAB donor DU, but in this case, it is questionable how the mobile IAB node would know whether a cell is provided by an IAB donor DU. On the other hand, if we consider the mobile IAB node as a network node, there is also the option that the mobile IAB node can establish connections to any cell. Therefore, a mobile IAB node can also connect to a cell provided by an intermediate IAB node, for example, for an OAM connection. However, in this case, since the mobile IAB node cannot connect to such a cell in Scenario 1, if a node connects to a cell provided by an intermediate IAB node, that node should not be operating 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 IAB donors (Scenario 1), considering that the mobile IAB node is a network node, RAN2 should discuss whether it is necessary to restrict connection attempts from the mobile IAB node to IAB donor DUs only.

[0275] Furthermore, regarding the initial access, we should discuss whether the mobile IAB node should notify the IAB-donor that it is an access from a mobile IAB node, similar to the existing IAB node indication in Msg5. While such indications may be necessary regardless of the scenario, in Scenario 1 in particular, the IAB donor needs to decide whether the IAB node can maintain its connection to the cell, depending on whether the cell is provided by the IAB donor DU or the intermediate IAB node's IAB-DU. In other words, such indications are more important in Scenario 1.

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

[0277] In Rel-16 / 17, only fixed IAB nodes were assumed, so the radio state of the backhaul link was considered stable. On the other hand, Rel-18 assumes mobile IAB nodes, so RLF and RRC re-establishment are no longer rare cases. 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 will fail, or at the very least, the mobile IAB node will 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 will 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: If a mobile IAB node only connects to an IAB donor (Scenario 1), RAN2 should discuss whether to optimize the RRC re-establishment procedure so that the mobile IAB node selects a mobile IAB-enabled cell.

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

[0280] Enhancements for use cases common to both scenarios are not excluded. The phrase "no special treatment" is intended to apply only as a comparison between scenarios.

[0281] Finding 3: When a mobile IAB node is also connected to an intermediate IAB node (Scenario 2), the mobile IAB node can connect to any cell (the cells provided by the IAB donor DU and the intermediate IAB node), so no special processing is required for accessing the mobile IAB node.

[0282] 2.3 Overview The summary of the above discussion is as follows:

[0283] [Table 1]

[0284] As shown in Table 1, each scenario has its advantages and disadvantages. Scenario 1 is superior in terms of F1 complexity, while Scenario 2 is superior in terms of deployment strategy and Uu complexity. From RAN2's perspective in particular, Scenario 2 is slightly more desirable. However, the final decision may be made by the main working group, namely RAN3.

[0285] Proposal 6: Adopting a scenario where the mobile IAB node also connects to the intermediate IAB node (i.e., Scenario 2) would have less impact on the specifications of RAN2, but the final decision should be left to RAN3.

Claims

1. A communication control method used in a cellular communication system, The source donor node sends a handover request message to the target donor node that includes information indicating that the mobile relay node is subject to handover, The target donor node, upon receiving the handover request message, selects a cell managed by the target donor node as the handover destination cell for the mobile relay node. Communication control method.

2. The target donor node further includes transmitting mobile relay node acceptance information to the source donor node indicating whether or not it can accept the mobile relay node, Sending the aforementioned handover request message includes the source donor node sending 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, A receiving unit that receives a handover request message from a source donor node containing information indicating that a mobile relay node is subject to handover, The system includes a control unit that, upon receiving the aforementioned handover request message, selects a cell managed by the target donor node as the handover destination cell for the mobile relay node. Target donor node.

4. A communication system comprising a source donor node, a target donor node, and a mobile relay node, The source donor node sends a handover request message to the target donor node that includes information indicating that the mobile relay node is subject to handover. Upon receiving the handover request message, the target donor node selects a cell under its management as the handover destination cell for the mobile relay node. Communication system.

5. A program for controlling a target donor node, The process involves receiving a handover request message from the source donor node that contains information indicating that the mobile relay node is subject to handover, Upon receiving the aforementioned handover request message, the target donor node is instructed to perform the following process: select the cell it manages as the handover destination cell for the mobile relay node. program.

6. A processor for controlling a target donor node, The process involves receiving a handover request message from the source donor node that contains information indicating that the mobile relay node is subject to handover, Upon receiving the aforementioned handover request message, the system performs the following steps: select the cell managed by the target donor node as the handover destination cell for the mobile relay node. Processor.

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