Communication control method and mobile relay node.

Abstract

A communication control method according to an aspect of the present invention is used in a cellular communication system. The communication control method comprises a step for performing a predetermined process, when a mobile relay node connects to an intermediate relay node that remains stationary without moving. The predetermined process is either the mobile relay node stopping service to user equipment under the mobile relay node, or the mobile relay node operating as another intermediate relay node that remains stationary without moving.

Description

Technical Field

[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 the base station and the user equipment and perform relay 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 of performing a predetermined process when a mobile relay node connects to an intermediate relay node that is stationary without moving. The predetermined process is either that the mobile relay node stops providing services to user equipment under the mobile relay node or that the mobile relay node operates as another intermediate relay node that is stationary without moving.

[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 of connecting, as an intermediate relay node that is stationary without moving, to another intermediate relay node when a mobile relay node in the RRC idle state or the RRC inactive state receives an emergency call from a user equipment. [Brief explanation of the drawing]

[0006] [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. [Modes for carrying out the invention]

[0007] 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.

[0008] [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.

[0009] Figure 1 shows an example of the configuration of a cellular communication system 1 according to one embodiment.

[0010] As shown in Figure 1, the cellular communication system 1 includes a 5G core network (5GC) 10, user equipment (UE) 100, base station equipment (hereinafter sometimes referred to as "base stations") 200-1, 200-2, and IAB nodes 300-1, 300-2. Base station 200 may be called a gNB.

[0011] The following description will primarily focus on an example where base station 200 is an NR base station, but base station 200 may also be an LTE base station (i.e., an eNB).

[0012] In the following, base stations 200-1 and 200-2 may be referred to as gNB200 (or base station 200), and IAB nodes 300-1 and 300-2 may be referred to as IAB node 300.

[0013] 5GC 10 has an AMF (Access and Mobility Management Function) 11 and a UPF (User Plane Function) 12. The AMF 11 is a device that performs various mobility controls and the like 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 and the like.

[0014] 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 indicating a function or resource for performing radio communication with the UE 100. One cell belongs to one carrier frequency. Hereinafter, the cell and the base station may be used without distinction.

[0015] Each gNB 200 is interconnected with the 5GC 10 via an interface called the NG interface. In FIG. 1, two gNBs 200-1 and 200-2 connected to the 5GC 10 are illustrated.

[0016] Each gNB 200 may be divided into a Central Unit (CU) and a Distributed Unit (DU). The CU and the DU are interconnected via an interface called the F1 interface. The F1 protocol is a communication protocol between the CU and the DU, and includes an F1-C protocol which is a protocol for the control plane and an F1-U protocol which is a protocol for the user plane.

[0017] The cellular communication system 1 supports IAB that enables wireless relay of NR access by using NR for the backhaul. The donor gNB 200-1 (or donor node. Hereinafter, it may be referred to as "donor node") is the terminal node of the NR backhaul on the network side and is a donor base station equipped with additional functions to support IAB. The backhaul enables multi-hop via a plurality of hops (i.e., a plurality of IAB nodes 300).

[0018] In FIG. 1, an example is shown where the IAB node 300-1 is wirelessly connected to the donor node 200-1, the IAB node 300-2 is wirelessly connected to the IAB node 300-1, and the F1 protocol is transmitted through two backhaul hops.

[0019] The UE 100 is a mobile wireless communication device that performs wireless communication with a cell. The UE 100 may be any device as long as it can perform wireless communication with the gNB 200 or the IAB node 300. For example, the UE 100 is a mobile phone terminal and / or a tablet terminal, a notebook PC, a sensor or a device provided in a sensor, a vehicle or a device provided in a vehicle, an aircraft or a device provided in an aircraft. The UE 100 is wirelessly connected to the IAB node 300 or the gNB 200 via an access link. In FIG. 1, an example where the UE 100 is wirelessly connected to the IAB node 300-2 is shown. The UE 100 communicates indirectly with the donor node 200-1 via the IAB node 300-2 and the IAB node 300-1.

[0020] FIG. 2 is a diagram showing an example of the relationship between the IAB node 300, parent nodes, and child nodes.

[0021] As shown in FIG. 2, each IAB node 300 has an IAB-DU corresponding to a base station function unit and an IAB-MT (Mobile Termination) corresponding to a user equipment function unit.

[0022] 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.

[0023] 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.

[0024] 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.

[0025] (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.

[0026] 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.

[0027] 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.

[0028] 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.

[0029] (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.

[0030] 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.

[0031] 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.

[0032] 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.

[0033] (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.

[0034] 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.

[0035] 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 processing. The processor performs processing for each layer described later. The control unit 120 may perform each of the processing in the UE 100 in each of the embodiments shown below.

[0036] (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.

[0037] 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.

[0038] 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.

[0039] 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.

[0040] 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.

[0041] 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.

[0042] 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.

[0043] 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.

[0044] 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.

[0045] 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.

[0046] 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.

[0047] 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.

[0048] 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."

[0049] 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.

[0050] (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).

[0051] 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.

[0052] Furthermore, 3GPP is also discussing the possibility that mobile IAB nodes should provide services to UE100 without having any IAB nodes under their control.

[0053] On the other hand, in contrast to mobile IAB nodes, there are also IAB nodes that do not move. Such IAB nodes are sometimes 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.

[0054] Furthermore, 3GPP is considering the complexity of the following two scenarios regarding mobile IAB nodes.

[0055] (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.

[0056] 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. 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 connected to each DU (DU200-D1A, etc.) of each donor node 200, and is also connected to an intermediate IAB node 300S while moving. 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.

[0060] On the other hand, if mobile IAB node 300M is connected to intermediate IAB node 300S, and mobile IAB node 300M is allowed to operate as a mobile IAB node, similar to when it is connected to donor node 200, then the meaning of the first scenario becomes meaningless.

[0061] Therefore, when a mobile IAB node 300M is connected to an intermediate IAB node 300S, it may not be able to function as a mobile IAB node. In this case, the mobile IAB node 300M may function as an intermediate IAB node (i.e., a fixed IAB node) rather than a mobile IAB node. Alternatively, the mobile IAB node 300M may function as a UE100 for purposes such as OAM connectivity, and network connectivity may be permitted.

[0062] Thus, even in the first scenario, the mobile IAB node 300M may be allowed to connect to the intermediate IAB node 300S.

[0063] However, when mobile IAB node 300M connects to intermediate IAB node 300S, a problem arises as to what services can be provided to UE100 under mobile IAB node 300M. Providing the same services to UE100 as when mobile IAB node 300M is connected to donor node 200 would render the first scenario meaningless, as mentioned above.

[0064] Therefore, in the first embodiment, the objective is to appropriately restrict services to the UE100 under the mobile IAB node 300M when the mobile IAB node 300M is connected to the intermediate IAB node 300S.

[0065] In the first embodiment, the following three operational examples will be described in order.

[0066] (1.1) First example of operation: When mobile IAB node 300M connects to intermediate IAB node 300S, it stops providing services to UE100.

[0067] (1.2) Second example of operation: When mobile IAB node 300M is connected to intermediate IAB node 300S, it operates as an intermediate IAB node.

[0068] (1.3) Third example of operation: When a mobile IAB node 300M in an RRC idle or RRC inactive state receives an emergency call from UE100, it connects to intermediate IAB node 300S as an intermediate IAB node.

[0069] (1.1) First example of operation The first operational example shows how service to UE100 is stopped when a mobile IAB node 300M connects to an intermediate IAB node 300S. Specifically, when a mobile relay node (e.g., mobile IAB node 300M) connects to a stationary intermediate relay node (e.g., intermediate IAB node 300S) without moving, a predetermined process is performed. In the first operational example, the predetermined process is an example where the mobile relay node stops service to the user equipment (e.g., UE100) under its control.

[0070] Thus, for example, when a mobile IAB node 300M connects to an intermediate IAB node 300S, it is possible to stop services to the UE100 under the mobile IAB node 300M, thereby appropriately restricting services to that UE100.

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

[0072] As shown in Figure 11, in step S10, the mobile IAB node 300M connects to the intermediate IAB node 300S. Examples of cases in which the mobile IAB node 300M connects to the intermediate IAB node 300S include the following:

[0073] Firstly, the IAB-MT of the mobile IAB node 300M, which is in an RRC idle state, may connect to the intermediate IAB node 300S by sending an RRC Setup Request message to the IAB-DU of the intermediate IAB node 300S and executing the RRC connection establishment procedure.

[0074] Secondly, the IAB-MT of the mobile IAB node 300M, which is in an RRC inactive state, may connect to the intermediate IAB node 300S by sending an RRC ResumeRequest message to the IAB-DU of the intermediate IAB node 300S and executing the RRC connection resume procedure.

[0075] Thirdly, after the IAB-MT of the mobile IAB node 300M detects a Radio Link Failure (RLF), it requests RRC re-establishment (RRCRe est Alternatively, you can connect to the intermediate IAB node 300S by sending an `ablishmentRequest` message to the IAB-DU of the intermediate IAB node 300S and executing the RRC connection re-establishment procedure.

[0076] Fourth, the IAB-MT of the migrating IAB node 300M, which was connected to the donor node 200, may receive an RRC reconfiguration (HO command) message from the DU of the donor node 200 (source donor node), and then connect to the intermediate IAB node 300S via a handover (or migration).

[0077] Then, when the mobile IAB node 300M connects to the intermediate IAB node 300S, it recognizes that the connection destination is the intermediate IAB node 300S. For example, the mobile IAB node 300M may recognize that the connection destination is the intermediate IAB node 300S through the following process.

[0078] Firstly, the CU of the donor node 200 may send an F1 message to the IAB-DU of the mobile IAB node 300M that contains information indicating that the mobile IAB node 300M has connected to the intermediate IAB node 300S. Alternatively, the CU of the donor node 200 may send the F1 message to the IAB-DU of the intermediate IAB node 300S. Then, upon receiving the F1 message, the IAB-DU of the intermediate IAB node 300S may send an RRC message to the IAB-MT of the mobile IAB node 300M that contains information indicating that the mobile IAB node 300M has connected to the intermediate IAB node 300S. The IAB-MT of the mobile IAB node 300M may output this information to the higher-level node (IAB-DU). Thus, the mobile IAB node 300M may recognize that the destination is the intermediate IAB node 300S by receiving information from the donor node 200 indicating that the mobile IAB node 300M has connected to the intermediate IAB node 300S.

[0079] Secondly, the CU of the donor node 200 may send an F1 message to the IAB-DU of the mobile IAB node 300M that contains information indicating that it is prohibited from operating as a mobile IAB node. Alternatively, the CU of the donor node 200 may send the same F1 message to the IAB-DU of the intermediate IAB node 300S. Then, the IAB-DU of the intermediate IAB node 300S, upon receiving the F1 message, may send an RRC message to the IAB-MT of the mobile IAB node 300M that contains information indicating that it is prohibited from operating as a mobile IAB node. The IAB-MT of the mobile IAB node 300M may output this information to the higher-level node (IAB-DU). In this way, the mobile IAB node 300M may recognize that its destination is the intermediate IAB node 300S by receiving information from the donor node 200 indicating that it is prohibited from operating as a mobile IAB node.

[0080] Thirdly, when a mobile IAB node 300M connects to a cell that has not broadcast a mobile IAB node support notification (or has broadcast a mobile IAB node 300M non-support notification), it may recognize that the destination is an intermediate IAB node 300S. This notification may be included in the SIB broadcast.

[0081] In step S11, the mobile IAB node 300M stops providing services to the subordinate UE100. The IAB-DU of the mobile IAB node 300M may stop transmitting Synchronization Signal Blocks (SSBs), Master Information Blocks (MIBs), and / or System Information Blocks (SIBs). Alternatively, the mobile IAB node 300M may start broadcasting MIBs, including Cell Barred. Alternatively, the IAB-DU of the mobile IAB node 300M may send a message (e.g., an RRC message) to the UE100 instructing it to discard the MIBs and / or SIBs it has stored in memory. Alternatively, the UE100 may The If no SSB, MIB, and / or SIB are received from the intermediate IAB node 300S (for a certain period of time) without being based on a message, the MIB and / or SIB stored in memory may be discarded.

[0082] (1.2) Second example of operation Next, we will explain the second example of operation.

[0083] The second operational example shows how a mobile IAB node 300M can operate as an intermediate IAB node when connected to an intermediate IAB node 300S. Specifically, when a mobile relay node (e.g., mobile IAB node 300M) connects to a stationary intermediate relay node (e.g., intermediate IAB node 300S) without moving, a predetermined process is performed. In the second operational example, this predetermined process is the process by which the mobile relay node operates as another stationary intermediate relay node (e.g., an intermediate IAB node) without moving.

[0084] This means that, for example, the mobile IAB node 300M will be restricted from operating as a mobile IAB node (e.g., moving), but will be able to operate as an intermediate IAB node. Therefore, the mobile IAB node 300M can connect to the network as a normal IAB node and continue to provide services to the subordinate UE100. Consequently, the mobile IAB node 300M cannot provide services to the UE100 that are related to movement, but can provide services that are not related to movement. Thus, the mobile IAB node 300M can appropriately restrict the services provided to the UE100.

[0085] Figure 12 is a diagram illustrating an example of the second example of operation.

[0086] As shown in Figure 12, in step S20, the mobile IAB node 300M connects to the intermediate IAB node 300S. The example of the mobile IAB node 300M connecting to the intermediate IAB node 300S may be the same as in the first operation example. Recognizing that the mobile IAB node 300M has connected to the intermediate IAB node 300S may also be the same as in the first operation example.

[0087] In step S21, the mobile IAB node 300M stops operating as a mobile IAB node. That is, the mobile IAB node 300M switches to operating as an intermediate IAB node when it connects to the intermediate IAB node 300S. Alternatively, the mobile IAB node 300M may connect to the intermediate IAB node 300S and then switch to operating as an intermediate IAB node if at least one of the following conditions is met.

[0088] (Condition 1) The mobile IAB node 300M may switch to the operation of the intermediate IAB node 300S only if it determines that it is not in a moving state (or is stationary, or its speed is below a threshold). The mobile IAB node 300M may determine whether or not it is in a moving state by, for example, using a speed sensor. The mobile IAB node 300M may also determine whether or not it is in a moving state based on a GNSS (Global Navigation Satellite System) receiving signal by, for example, a GNSS (Global Navigation Satellite System) receiver.

[0089] (Condition 2) The mobile IAB node 300M may switch to the operation of the intermediate IAB node 300S only if there is a connection to a UE100 under it (e.g., an RRC connection). The mobile IAB node 300M does not need to switch to the operation of the intermediate IAB node 300S if there is no UE100 connected under it.

[0090] (Condition 3) The mobile IAB node 300M may switch to the intermediate IAB node 300S when it receives instructions from the donor node 200. For example, the mobile IAB node 300M may switch to the operation of the intermediate IAB node 300S in response to receiving a message containing information instructing it to switch to operation as an intermediate IAB node. This message may be sent as an F1 message from the CU of the donor node 200 to the IAB-DU of the mobile IAB node 300M.

[0091] The mobile IAB node 300M may operate as an intermediate relay node if it satisfies at least one of the predetermined conditions, with conditions 1 to 3 being predetermined conditions.

[0092] In step S22, the mobile IAB node 300M may continue providing service to the UE100. In this case, the mobile IAB node 300M may provide full service to the UE100. Since the mobile IAB node 300M is operating as an intermediate relay node, it may continue providing service to the UE100 in this way. Alternatively, the mobile IAB node 300M may transition to a limited service state and accept only emergency calls. In the limited service state, the mobile IAB node 300M can provide emergency service, the Earthquake and Tsunami Warning System (ETWS), and the Commercial Mobile Alert System (CMAS), while the provision of other services is restricted. In the second example, the mobile IAB node 300M will only provide emergency service to the UE100.

[0093] (Example of third action) Next, we will explain the third example of operation.

[0094] The third operational example is one in which a mobile IAB node 300M in an RRC idle or RRC inactive state receives an emergency call from UE100 and connects to intermediate IAB node 300S as an intermediate IAB node. Specifically, when a mobile relay node (e.g., mobile IAB node 300M) in an RRC idle or RRC inactive state receives an emergency call from a user device (e.g., UE100), it connects to another intermediate relay node (e.g., intermediate IAB node 300S) as a stationary intermediate relay node (e.g., intermediate IAB node) without moving.

[0095] This allows, for example, the mobile IAB node 300M to accept emergency calls from its subordinate UE100 even when the RRC is idle or inactive, and to provide emergency services to the subordinate UE100 by connecting to the network via the intermediate IAB node 300S. Therefore, the mobile IAB node 300M can appropriately restrict services to the UE100.

[0096] Figure 13 is a diagram illustrating an example of the third example of operation.

[0097] As shown in Figure 13, in step S30, the mobile IAB node 300M transitions from the RRC connected state to the RRC idle state or the RRC inactive state. For example, the mobile IAB node 300M was connected to the donor node 200, but because there was no traffic for a certain period of time, it receives an RRC release message (an RRC release message that does not include a suspendConfig, or an RRC release message that includes a suspendConfig), and transitions to the RRC idle state or the RRC inactive state.

[0098] In step S31, the mobile IAB node 300M transmits SSB, MIB, and SIB1 without a network connection. The operating state in which the mobile IAB node 300M transmits SSB, MIB, and SIB1 without a network connection is sometimes referred to as the initial operating mode. The mobile IAB node 300M is basically in a limited service state.

[0099] Firstly, the mobile IAB node 300M may transition to initial operating mode if configured by the donor node 200. For example, the IAB-DU of the mobile IAB node 300M may transition to initial operating mode when it receives an F1 message from the CU of the donor node 200 that contains information indicating that the mobile IAB node 300M will enter initial operating mode when it transitions to the RRC idle state or RRC inactive state.

[0100] Secondly, the mobile IAB node 300M may transition to the initial operating mode when it is stopped (or when its speed is below a threshold). For example, the mobile IAB node 300M may determine that it is stopped based on a speed sensor. For example, the mobile IAB node 300M may determine that it is stopped based on a GNSS received signal from the GNSS receiver.

[0101] In addition, during the initial operation mode, mobile IAB node 300M may transmit SIBs other than SIB1.

[0102] In step S32, UE100 makes an emergency call. UE100 makes this call, for example, by sending an RRC Setup Request message.

[0103] In step S33, upon receiving the call from the IAB-DU of the mobile IAB node 300M, which is in an RRC idle state, the IAB-MT of the mobile IAB node 300M sends an RRC setup request message to the IAB-DU of the intermediate IAB node 300S. The IAB-MT of the mobile IAB node 300M may also send the RRC setup request message with "emergency" as the EstablishmentCause. Subsequently, the IAB-MT of the mobile IAB node 300M executes the RRC connection establishment procedure with the IAB-DU of the intermediate IAB node 300S to establish an RRC connection and transition to the RRC connected state. Also, upon receiving the call from the IAB-DU of the mobile IAB node 300M, which is in an RRC inactive state, the IAB-MT of the mobile IAB node 300M sends an RRC recovery request message to the IAB-DU of the intermediate IAB node 300S. The IAB-MT of the mobile IAB node 300M may send the RRC recovery request message with "emergency" as the ResumeCause. Subsequently, the IAB-MT of the mobile IAB node 300M executes the RRC connection recovery procedure to the IAB-DU of the intermediate IAB node 300S to restore the RRC connection and transition to the RRC connected state.

[0104] Furthermore, the mobile IAB node 300M may be configured to send an RRC setup request message or an RRC recovery request message if it is stopped (or if its speed is below a threshold).

[0105] The mobile IAB node 300M, having transitioned to the RRC connected state, can connect to the network via the intermediate IAB node 300S and provide emergency services to the UE100.

[0106] [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.

[0107] 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).

[0108] 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.

[0109] 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.

[0110] This application claims priority to U.S. Provisional Application No. 63 / 395101 (filed August 4, 2022), the entirety of which is incorporated into the specification of this application.

[0111] (First Appendix) The features of the above-described embodiment are noted below.

[0112] (Note 1) A communication control method used in a cellular communication system, The system includes the function of performing a predetermined process when a mobile relay node connects to a stationary intermediate relay node without moving. The aforementioned predetermined process is, The mobile relay node suspends service to user devices under its control, and The mobile relay node either operates as another stationary intermediate relay node without moving. Communication control method.

[0113] (Note 2) Performing the predetermined processing includes the mobile relay node operating as the intermediate relay node if the predetermined conditions are met, The aforementioned predetermined conditions are: If the aforementioned mobile relay node is stationary, If the mobile relay node has a connection to the user device under its control, When the aforementioned mobile relay node receives instructions from the donor node, It is at least one of the following: The communication control method described in Appendix 1.

[0114] (Note 3) The mobile relay node, when operating as the intermediate relay node, further has the characteristic of accepting only emergency calls from the user device. The communication control method described in Appendix 1 or 2.

[0115] (Note 4) A communication control method used in a cellular communication system, When a mobile relay node in an RRC idle or RRC inactive state receives an emergency call from a user device, it will connect to another intermediate relay node as a stationary intermediate relay node without moving. Communication control method.

[0116] (Second Addendum) 1. Introduction RAN#94e approved a new work item related to mobile IAB.

[0117] The detailed objectives of WI are as follows: Define migration / topology adaptation procedures to achieve IAB node mobility, including donor-to-donor migration (complete migration) of the entire mobile IAB node. • Enhance the mobility of IAB nodes and their UEs, including aspects related to group mobility. Optimization for targeting surrounding UEs. • In the solution, we should avoid touching on topics already discussed in Rel-17 or topics excluded from Rel-17, with the exception of feature enhancements specifically for IAB node mobility. • Mitigation of interference through IAB node mobility, including avoidance of potential reference signal and control signal collisions (PCI, RACH, etc.).

[0118] Furthermore, at the beginning of the work period, RAN3 and RAN2 should discuss the potential complexity of the scenario in which a mobile IAB node connects to a static (intermediate) IAB node, compared to the scenario in which a mobile IAB node connects directly to an IAB donor.

[0119] This appendix analyzes the complexity in two topology scenarios from the perspective of RAN2.

[0120] 2. Discussion 2.1 Scenario In WID, it is explicitly assumed that a mobile IAB node does not have descendant IAB nodes, as follows:

[0121] In Rel-18, the mobile IAB supports the following features 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.

[0122] Furthermore, since mobile IAB nodes only provide services to UEs, it is made clear that mobile IAB nodes are always access IAB nodes.

[0123] Proposal 1: RAN2 should ensure that the mobile IAB node is always the access IAB node.

[0124] 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.

[0125] 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.

[0126] 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.

[0127] 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.

[0128] 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.

[0129] To implement mobile IAB in Scenario 1, a special deployment strategy is required to ensure coverage suitable for mobile IAB nodes, in addition to existing (or standard) deployment strategies. On the other hand, Scenario 2 allows for more flexible deployment. Therefore, the challenges in deployment may be greater in Scenario 1 than in Scenario 2.

[0130] 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.

[0131] 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).

[0132] In routing configuration (F1AP), the IAB donor needs to update its configuration when mobile IAB nodes enter or leave the IAB topology. In Scenario 2, the IAB donor needs to update the routing configuration for each IAB node in the IAB topology, which complicates the procedure and can result in F1 reconfiguration latency.

[0133] Regarding the migration of mobile IAB nodes (XnAP), RAN3 is expected to consider the complete migration of mobile IAB nodes between donors and the group mobility of UEs, but it is not expected that there will be a significant difference between Scenario 1 and Scenario 2. However, in Scenario 1, some information exchange is necessary between IAB donors to inform other donors of cells that can accept mobile IAB nodes, in other words, cells that an IAB donor's DU is servicing. This information will be used by IAB donors for measurement setup and handover decisions.

[0134] Since Mobile IABWI is led by RAN3, the complexity of the network interface is already somewhat expected compared to other interfaces handled by secondary working groups (including RAN2). Whether the network interface can support Scenario 2, and whether it directs other working groups to define the mechanism for Scenario 1, is ultimately up to RAN3.

[0135] Finding 2: If the mobile IAB node connects only to the IAB donor (i.e., Scenario 1), the network interface procedure may be simpler. Further details depend on RAN3.

[0136] 2.2.3 Uu Interface Procedure (RAN2 Area) Regarding the UAU interface, if a mobile IAB node can only connect to an intermediate IAB node (i.e., Scenario 1), some complications are expected.

[0137] Regarding initial access, we should discuss whether a mobile IAB node can initiate the RRC connection establishment procedure for cells provided by an intermediate IAB node. An 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 unclear how the mobile IAB node would know if a cell is provided by an IAB donor DU. Alternatively, if we consider the mobile IAB node as a network node, there is the option that it can establish connections to any cell. Therefore, a mobile IAB node could also connect to a cell provided by an intermediate IAB node, for example, for an OAM connection. However, in this case, since a 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.

[0138] 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.

[0139] 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.

[0140] 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.

[0141] 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.

[0142] 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.

[0143] On the other hand, if the mobile IAB node can also connect to an intermediate IAB node (Scenario 2), the mobile IAB node can connect to any cell, so no special processing is required.

[0144] 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.

[0145] 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.

[0146] 2.3 Overview The summary of the above discussion is as follows:

[0147] [Table 1]

[0148] 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.

[0149] 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 system includes the function of performing a predetermined process when a moving mobile relay node connects to a network that does not support the mobile relay node. The aforementioned predetermined process is, The mobile relay node includes operating as a fixed intermediate relay node. Communication control method.

2. Performing the predetermined processing includes the mobile relay node operating as the fixed intermediate relay node if the predetermined conditions are met, The aforementioned predetermined conditions are: If the aforementioned mobile relay node becomes stationary, If the mobile relay node has connections to user devices under its control, This is at least one of the following: the mobile relay node receives instructions from the donor node. The communication control method according to claim 1.

3. The mobile relay node, when operating as the fixed intermediate relay node, further has the characteristic of accepting only emergency calls from user equipment. The communication control method according to claim 1.

4. A mobile relay node that is in motion, When connected to a network that does not support the aforementioned mobile relay node, the control unit has a control unit that performs predetermined processing. The aforementioned predetermined process is, The mobile relay node includes operating as a fixed intermediate relay node. Mobile relay node.

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