Communication control method

Abstract

A communication control method according to one aspect is used in a cellular communication system. The communication control method includes a step of a base station notifying a message including first information indicating a first frequency available in a mobile IAB cell managed by a mobile IAB node, and second information relating to access restriction of the mobile IAB cell. In addition, the communication control method includes a step of user equipment under the mobile IAB cell receiving the message.

Description

Communication Control Method

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

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

[0003] 3GPP TS 38.300 V17.5.0 (2023-06)

[0004] A communication control method according to a first aspect is a communication control method for use in a cellular communication system. The communication control method includes a step of broadcasting, by a base station, a message including first information indicating a first frequency available in a mobile IAB cell managed by a mobile IAB node and second information related to access restriction of the mobile IAB cell. The communication control method also includes a step of receiving, by a user equipment under the control of the mobile IAB cell, the message.

[0005] A communication control method according to a second aspect is a communication control method used in a cellular communication system. The communication control method includes a step in which a base station broadcasts a message including first information indicating a first frequency available in a mobile IAB cell managed by a mobile IAB node. The communication control method also includes a step in which a user equipment served by the mobile IAB cell receives the message. Here, the message includes a frequency list used in an inter-frequency cell reselection procedure. The first information is indicated by either an identifier indicated for each frequency entry in the frequency list and indicating whether the frequency is used in the mobile IAB cell, or a list of cell IDs of the mobile IAB cell indicated for each frequency entry in the frequency list.

[0006] A communication control method according to a third aspect is a communication control method used in a cellular communication system. The communication control method includes a step in which a base station broadcasts a message including second information related to access restriction of a mobile IAB cell. The communication control method also includes a step in which a user equipment (UE) under the control of the mobile IAB cell receives the message. Here, the second information includes either information indicating whether the mobile IAB cell is performing access restriction or identification information of a device permitted to access the mobile IAB cell. The identification information includes either a closed access group ID (CAG ID), a standalone non-public network ID (SNPN ID), or a tracking area code (TAC).

[0007] A communication control method according to a fourth aspect includes a user equipment receiving system information from a network, the system information including a frequency list used in an inter-frequency cell reselection procedure. The communication control method also includes the user equipment performing the inter-frequency cell reselection procedure based on the system information. At least one frequency entry in the frequency list includes a list of cell IDs of mobile IAB cells managed by a mobile IAB node. Performing the inter-frequency cell reselection procedure includes, when determining that the user equipment is located in a mobile vehicle, regarding a frequency to which the mobile IAB cell belongs, detected based on the list of cell IDs, as having the highest priority.

[0008] FIG. 1 is a diagram showing an example of the configuration of a cellular communication system according to the first embodiment. FIG. 2 is a diagram showing the relationship between an IAB node, parent nodes, and child nodes. FIG. 3 is a diagram showing an example of the configuration of a gNB (base station) according to the first embodiment. FIG. 4 is a diagram showing an example of the configuration of an IAB node (relay node) according to the second embodiment. FIG. 5 is a diagram showing an example of the configuration of a UE (user equipment) according to the first embodiment. FIG. 6 is a diagram showing an example of a protocol stack related to IAB-MT RRC connection and NAS connection. FIG. 7 is a diagram showing an example of a protocol stack related to the F1-U protocol. FIG. 8 is a diagram showing an example of a protocol stack related to the F1-C protocol. FIG. 9 is a diagram for explaining the problem according to the first embodiment. FIG. 10 is a diagram showing an example of the configuration of SIB4 according to the first embodiment. FIG. 11 is a diagram showing an example of the configuration of SIB1 according to the first embodiment. FIG. 12 is a diagram showing a first operation example according to the first embodiment. FIG. 13 is a diagram showing a second operation example according to the first embodiment. Fig. 14 is a diagram showing a third operation example according to the first embodiment. Fig. 15 is a diagram showing a third operation example according to the first embodiment. Fig. 16 is a diagram showing a UE's moving IAB cell reselection. Fig. 17 is a diagram showing an HSDN cell list for each entry in the inter-frequency carrier frequency list of SIB4. Fig. 18 is a diagram showing an NPN Identity Info List of SIB1. Fig. 19 is a diagram showing a UE's macro cell reselection.

[0009] A cellular communication system according to an embodiment will be described with reference to the drawings. In the description of the drawings, the same or similar parts are denoted by the same or similar reference numerals.

[0010] [First embodiment]

[0011] (Configuration of 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 radio access method in the cellular communication system 1 is NR (New Radio), which is a 5G radio access method. However, LTE (Long Term Evolution) may be applied at least in part to the cellular communication system 1. Furthermore, future cellular communication systems such as 6G may also be applied to the cellular communication system 1.

[0012] FIG. 1 is a diagram showing an example of the configuration of a cellular communication system 1 according to an embodiment.

[0013] 1, the cellular communication system 1 includes a 5G core network (5GC) 10, user equipment (UE) 100, base station devices (hereinafter sometimes referred to as "base stations") 200-1 and 200-2, and IAB nodes 300-1 and 300-2. The base station 200 may be referred to as a gNB.

[0014] In the following, we will mainly describe an example in which base station 200 is an NR base station, but base station 200 may also be an LTE base station (i.e., eNB).

[0015] In the following, base stations 200-1 and 200-2 may be referred to as gNB 200 (or base station 200), and IAB nodes 300-1 and 300-2 may be referred to as IAB node 300.

[0016] The 5GC 10 has an Access and Mobility Management Function (AMF) 11 and a User Plane Function (UPF) 12. The AMF 11 is a device that performs various mobility controls for the UE 100. The AMF 11 manages information about the area in which the UE 100 is located by communicating with the UE 100 using Non-Access Stratum (NAS) signaling. The UPF 12 is a device that performs transfer control of user data, etc.

[0017] Each gNB 200 is a fixed wireless communication node and manages one or more cells. A cell is used as a term indicating the smallest unit of a wireless communication area. A cell may also be used as a term indicating a function or resource for performing wireless communication with a UE 100. One cell belongs to one carrier frequency. Hereinafter, there may be cases where a cell and a base station are used interchangeably.

[0018] Each gNB 200 is interconnected with the 5GC 10 via an interface called an NG interface. In FIG. 1, two gNBs 200-1 and 200-2 connected to the 5GC 10 are illustrated.

[0019] Each gNB 200 may be divided into a central unit (CU) and a distributed unit (DU). The CU and DU are connected to each other via an interface called an F1 interface. The F1 protocol is a communication protocol between the CU and DU, and includes the F1-C protocol, which is a control plane protocol, and the F1-U protocol, which is a user plane protocol.

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

[0021] FIG. 1 shows an example in which IAB node 300-1 wirelessly connects with donor node 200-1, IAB node 300-2 wirelessly connects with IAB node 300-1, and the F1 protocol is transmitted over two backhaul hops.

[0022] The UE 100 is a mobile wireless communication device that performs wireless communication with a cell. The UE 100 may be any device that performs wireless communication with the gNB 200 or the IAB node 300. For example, the UE 100 is a mobile phone terminal and / or a tablet terminal, a laptop PC, a sensor or a device provided in a sensor, a vehicle or a device provided in a vehicle, or an aircraft or a device provided in an aircraft. The UE 100 wirelessly connects to the IAB node 300 or the gNB 200 via an access link. FIG. 1 shows an example in which the UE 100 is wirelessly connected to the IAB node 300-2. The UE 100 indirectly communicates with the donor node 200-1 via the IAB node 300-2 and the IAB node 300-1.

[0023] FIG. 2 is a diagram showing an example of the relationship between the IAB node 300, parent nodes, and child nodes.

[0024] 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.

[0025] An adjacent node (i.e., an upper node) on the NR Uu radio interface of the IAB-MT is called a parent node. The parent node is the parent IAB node or the DU of the donor node 200. The radio link between the IAB-MT and the parent node is called a backhaul link (BH link). FIG. 2 shows an example in which the parent nodes of the IAB node 300 are IAB nodes 300-P1 and 300-P2. The direction toward the parent node is called upstream. From the perspective of the UE 100, the upper node of the UE 100 may correspond to the parent node.

[0026] Adjacent nodes (i.e., lower nodes) on the NR access interface of the IAB-DU are called child nodes. The IAB-DU manages the cell, similar to the gNB 200. The IAB-DU terminates the NR Uu radio interface to the UE 100 and lower IAB nodes. The IAB-DU supports the F1 protocol to the CU of the donor node 200-1. In FIG. 2, an example is shown in which the child nodes of the IAB node 300 are IAB nodes 300-C1 to 300-C3, but the child nodes of the IAB node 300 may also include the UE 100. The direction toward the child nodes is called downstream.

[0027] Furthermore, all IAB nodes 300 connected to the donor node 200 via one or more hops form a directed acyclic graph (DAG) topology (hereinafter sometimes referred to as "topology") with the donor node 200 as the root. In this topology, as shown in FIG. 2, adjacent nodes on the IAB-DU interface are child nodes, and adjacent nodes on the IAB-MT interface are parent nodes. The donor node 200 centralizes, for example, resource, topology, and route management of the IAB topology. The donor node 200 is a gNB that provides network access to the UE 100 via a network of backhaul links and access links.

[0028] (Configuration of base station) Next, the configuration of the gNB 200, which is a base station according to the embodiment, will be described. Fig. 3 is a diagram showing an example configuration of the gNB 200. As shown in Fig. 3, the gNB 200 has a wireless communication unit 210, a network communication unit 220, and a control unit 230.

[0029] The wireless communication unit 210 performs wireless communication with the UE 100 and wireless communication with the IAB node 300. The wireless communication unit 210 has a receiving unit 211 and a transmitting unit 212. The receiving unit 211 performs various receptions under the control of the control unit 230. The receiving unit 211 includes an antenna, and converts (down-converts) a wireless signal received by the antenna into a baseband signal (received signal), and outputs the signal to the control unit 230. The transmitting unit 212 performs various transmissions under the control of the control unit 230. The transmitting unit 212 includes an antenna, and converts (up-converts) a baseband signal (transmitted signal) output by the control unit 230 into a wireless signal, and transmits the signal from the antenna.

[0030] The network communication unit 220 performs wired communication (or wireless communication) with the 5GC10 and wired communication (or wireless communication) with other adjacent gNBs 200. The network communication unit 220 has a receiving unit 221 and a transmitting unit 222. The receiving unit 221 performs various receptions under the control of the control unit 230. The receiving unit 221 receives a signal from the outside and outputs the received signal to the control unit 230. The transmitting unit 222 performs various transmissions under the control of the control unit 230. The transmitting unit 222 transmits the transmission signal output by the control unit 230 to the outside.

[0031] The control unit 230 performs various controls in the gNB 200. The control unit 230 includes at least one memory and at least one processor electrically connected to the memory. The memory stores programs executed by the processor and information used in processing by the processor. The processor may include a baseband processor and a CPU. The baseband processor performs modulation / demodulation, encoding / decoding, etc. of baseband signals. The CPU executes programs stored in the memory to perform various processes. The processor performs processing of each layer, which will be described later. Note that the control unit 230 may perform each process or operation in the gNB 200 in each of the embodiments shown below.

[0032] (Configuration of Relay Node) Next, a configuration of an IAB node 300, which is a relay node (or relay node device; hereinafter, may be referred to as a "relay node") according to an embodiment, will be described. FIG. 4 is a diagram showing an example configuration of the IAB node 300. As shown in FIG. 4, the IAB node 300 has a wireless communication unit 310 and a control unit 320. The IAB node 300 may have multiple wireless communication units 310.

[0033] The wireless communication unit 310 performs wireless communication (BH link) with the gNB 200 and wireless communication (access link) with the UE 100. The wireless communication unit 310 for BH link communication and the wireless communication unit 310 for access link communication may be provided separately.

[0034] The wireless communication unit 310 has a receiving unit 311 and a transmitting unit 312. The receiving unit 311 performs various types of reception under the control of the control unit 320. The receiving unit 311 includes an antenna, and converts (down-converts) a wireless signal received by the antenna into a baseband signal (received signal), and outputs the signal to the control unit 320. The transmitting unit 312 performs various types of transmission under the control of the control unit 320. The transmitting unit 312 includes an antenna, and converts (up-converts) a baseband signal (transmitted signal) output by the control unit 320 into a wireless signal, and transmits the signal from the antenna.

[0035] The control unit 320 performs various controls in the IAB node 300. The control unit 320 includes at least one memory and at least one processor electrically connected to the memory. The memory stores programs executed by the processor and information used in processing by the processor. The processor may include a baseband processor and a CPU. The baseband processor performs modulation / demodulation and encoding / decoding of baseband signals. The CPU executes programs stored in the memory to perform various processes. The processor performs processing of each layer, which will be described later. Note that the control unit 320 may perform each process or operation in the IAB node 300 in each of the embodiments described below.

[0036] (Configuration of User Device) Next, a configuration of the UE 100, which is a user device according to the embodiment, will be described. Fig. 5 is a diagram showing an example configuration of the UE 100. As shown in Fig. 5, the UE 100 includes a radio communication unit 110 and a control unit 120.

[0037] The wireless communication unit 110 performs wireless communication in an access link, i.e., wireless communication with the gNB 200 and wireless communication with the IAB node 300. The wireless communication unit 110 may also perform wireless communication in a side link, i.e., wireless communication with other UEs 100. The wireless communication unit 110 has a receiving unit 111 and a transmitting unit 112. The receiving unit 111 performs various receptions under the control of the control unit 120. The receiving unit 111 includes an antenna, and converts (down-converts) a wireless signal received by the antenna into a baseband signal (received signal), and outputs the signal to the control unit 120. The transmitting unit 112 performs various transmissions under the control of the control unit 120. The transmitting unit 112 includes an antenna, and converts (up-converts) a baseband signal (transmitted signal) output by the control unit 120 into a wireless signal, and transmits the signal from the antenna.

[0038] The control unit 120 performs various controls in the UE 100. The control unit 120 includes at least one memory and at least one processor electrically connected to the memory. The memory stores programs executed by the processor and information used in processing by the processor. The processor may include a baseband processor and a CPU. The baseband processor performs modulation / demodulation, encoding / decoding, etc. of baseband signals. The CPU executes programs stored in the memory to perform various processes. The processor performs processing of each layer, which will be described later. Note that the control unit 120 may be configured to perform each process in the UE 100 in each of the embodiments described below.

[0039] (Protocol Stack Configuration) Next, a description will be given of the configuration of a protocol stack according to the embodiment. Fig. 6 is a diagram showing an example of a protocol stack related to an IAB-MT RRC connection and a NAS connection.

[0040] As shown in FIG. 6, the IAB-MT of IAB node 300-2 has a physical (PHY) layer, a medium access control (MAC) layer, a radio link control (RLC) layer, a packet data convergence protocol (PDCP) layer, a radio resource control (RRC) layer, and a non-access stratum (NAS) layer.

[0041] The PHY layer performs encoding / decoding, modulation / demodulation, antenna mapping / demapping, and resource mapping / demapping. Data and control information are transmitted between the PHY layer of the IAB-MT of IAB node 300-2 and the PHY layer of the IAB-DU of IAB node 300-1 via a physical channel.

[0042] The MAC layer performs data priority control, retransmission processing using Hybrid Automatic Repeat reQuest (HARQ), random access procedures, etc. Data and control information are transmitted via transport channels between the MAC layer of the IAB-MT of IAB node 300-2 and the MAC layer of the IAB-DU of IAB node 300-1. The MAC layer of the IAB-DU includes a scheduler. The scheduler determines the uplink and downlink transport format (transport block size, modulation and coding scheme (MCS)) and the allocated resource blocks.

[0043] The RLC layer transmits data to the RLC layer on the receiving side using the functions of the MAC layer and PHY layer. Data and control information are transmitted between the RLC layer of the IAB-MT of IAB node 300-2 and the RLC layer of the IAB-DU of IAB node 300-1 via logical channels.

[0044] The PDCP layer performs header compression / decompression, and encryption / decryption. Data and control information are transmitted between the PDCP layer of the IAB-MT of the IAB node 300-2 and the PDCP layer of the donor node 200 via a radio bearer.

[0045] The RRC layer controls logical channels, transport channels, and physical channels in response to the establishment, re-establishment, and release of radio bearers. RRC signaling for various settings is transmitted between the RRC layer of the IAB-MT of the IAB node 300-2 and the RRC layer of the donor node 200. When there is an RRC connection with the donor node 200, the IAB-MT is in an RRC connected state. When there is no RRC connection with the donor node 200, the IAB-MT is in an RRC idle state.

[0046] The NAS layer, which is positioned above the RRC layer, performs session management, mobility management, etc. NAS signaling is transmitted between the NAS layer of the IAB-MT of the IAB node 300-2 and the AMF 11.

[0047] Figure 7 shows a protocol stack for the F1-U protocol. Figure 8 shows a protocol stack for the F1-C protocol. Here, an example is shown in which the donor node 200 is divided into a CU and a DU.

[0048] As shown in Figure 7, the IAB-MT of IAB node 300-2, the IAB-DU of IAB node 300-1, the IAB-MT of IAB node 300-1, and the DU of donor node 200 each have a BAP (Backhaul Adaptation Protocol) layer above the RLC layer. The BAP layer is a layer that performs routing processing and bearer mapping / demapping processing. In the backhaul, the IP layer is transmitted via the BAP layer, enabling routing over multiple hops.

[0049] In each backhaul link, PDUs (Protocol Data Units) of the BAP layer are transmitted by a backhaul RLC channel (BH NR RLC channel). By configuring multiple backhaul RLC channels in each BH link, traffic prioritization and QoS (Quality of Service) control are possible. The association between BAP PDUs and backhaul RLC channels is performed by the BAP layer of each IAB node 300 and the BAP layer of the donor node 200.

[0050] As shown in FIG. 8, the protocol stack of the F1-C protocol has an F1AP layer and an SCTP layer instead of the GTP-U layer and UDP layer shown in FIG.

[0051] In the following, the processing or operations performed by the IAB-DU and IAB-MT of the IAB may be simply described as the processing or operations of the "IAB." For example, the transmission of a BAP layer message from the IAB-DU of IAB node 300-1 to the IAB-MT of IAB node 300-2 will be described as the IAB node 300-1 sending the message to IAB node 300-2. In addition, the processing or operations of the DU or CU of the donor node 200 may also be simply described as the processing or operations of the "donor node."

[0052] Also, the upstream direction and the uplink (UL) direction may be used interchangeably, and the downstream direction and the downlink (DL) direction may be used interchangeably.

[0053] (Mobile IAB Node) Currently, 3GPP has begun discussions toward the introduction of mobile IAB nodes. A mobile IAB node is, for example, an IAB node that is moving. A mobile IAB node may be an IAB node that is capable of moving. Alternatively, a mobile IAB node may be an IAB node that is currently stationary but is certain to move in the future (or is expected to move in the future).

[0054] The mobile IAB node enables, for example, a UE 100 under the mobile IAB node to receive services from the mobile IAB node while moving in accordance with the movement of the mobile IAB node. For example, a case is envisioned in which a user (or UE 100) on a vehicle receives services via a mobile IAB node installed on the vehicle.

[0055] On the other hand, in contrast to mobile IAB nodes, there are also IAB nodes that do not move. Such IAB nodes are sometimes referred to as intermediate IAB nodes. An intermediate IAB node is, for example, an IAB node that does not move. Alternatively, the intermediate IAB node may be a stationary IAB node. Alternatively, the intermediate IAB node may be an IAB node that remains stationary (or does not move) and remains installed at its installation location. Alternatively, the intermediate IAB node may be a stationary IAB node that does not move. The intermediate IAB node may also be a fixed IAB node.

[0056] A mobile IAB node can also be connected to an intermediate IAB node. Also, a mobile IAB node can be connected to a donor node 200. A mobile IAB node can also change its connection destination due to movement (migration or handover). The connection source may be an intermediate IAB node. The connection source may be the donor node 200. Also, the connection destination may be an intermediate IAB node. The connection destination may be the donor node 200.

[0057] In the following, the terms "migration" of a mobile IAB node and "handover" of a mobile IAB node may be used interchangeably.

[0058] In the following description, a mobile IAB node may be referred to as a "mobile IAB node." The mobile IAB node may also be referred to as a "migrating IAB node." In either case, the mobile IAB node may also be referred to as a mobile IAB node. The mobile IAB node may also be a mobile relay node.

[0059] (Cell Reselection Procedure According to First Embodiment) Next, a cell reselection procedure according to the first embodiment will be described.

[0060] A UE 100 in an RRC idle state or an RRC inactive state performs a cell reselection procedure to transition from a current serving cell to a neighboring cell as it moves. Specifically, the UE 100 identifies a neighboring cell on which it should camp by the cell reselection procedure and reselects the identified neighboring cell. When the frequency (carrier frequency) of the current serving cell and the neighboring cell is the same, this is called intra-frequency, and when the frequency (carrier frequency) of the current serving cell and the neighboring cell is different, this is called inter-frequency. The current serving cell and the neighboring cell may be managed by the same gNB 200. The current serving cell and the neighboring cell may be managed by different gNBs 200.

[0061] Cell reselection procedures include intra-frequency cell reselection procedures and inter-frequency cell reselection procedures.

[0062] In the intra-frequency cell reselection procedure, cell reselection is performed based on the cell ranking. In the intra-frequency cell reselection procedure, for example, the following processing is performed.

[0063] First, the UE 100 performs a measurement process to measure radio quality for each of the serving cell and the neighboring cell. Specifically, the UE 100 measures RSRP and RSRQ of CD-SSB (Cell Defining-Synchronization Signal and PBCH block) for each of the serving cell and the neighboring cell.

[0064] Second, the UE 100 calculates a ranking criterion (Rs) for the serving cell and a ranking criterion (Rn) for the neighboring cell for all cells that satisfy the cell selection criterion S. The cell selection criterion S is a criterion for selecting a cell whose RSRP exceeds the RSRP minimum required level and whose RSRQ exceeds the RSRQ minimum required level.

[0065] The UE 100 basically reselects the cell with the highest rank from among the two ranking criteria Rs and Rn.

[0066] On the other hand, in the inter-frequency cell reselection procedure, cell reselection is performed based on absolute frequency priority. The frequency priority is provided from the gNB 200 to the UE 100 by broadcast signaling (e.g., a system information block) or dedicated signaling (e.g., an RRC Release message). In the inter-frequency cell reselection procedure, for example, the following processing is performed.

[0067] First, the UE 100 performs a measurement process (measurement) to measure the radio quality of each of the serving cell and the neighboring cell. Specifically, the UE 100 always measures the radio quality of a frequency having a higher priority than the priority of the frequency of the current serving cell. Furthermore, for a frequency having a priority equal to or lower than the priority of the frequency of the current serving cell, the UE 100 measures the radio quality of the frequency having the same priority or a lower priority when the radio quality of the current serving cell falls below a predetermined quality.

[0068] Second, the UE 100 performs a cell reselection process to reselect a cell on which the UE 100 camps based on the measurement result. Specifically, when the frequency priority of the neighboring cell is higher than the priority of the current serving cell and the neighboring cell satisfies a predetermined quality standard (i.e., a minimum required quality standard) for a predetermined period, the UE 100 may perform cell reselection to the neighboring cell. When the frequency priority of the neighboring cell is the same as the priority of the current serving cell, the UE 100 may rank the radio qualities of the neighboring cells and perform cell reselection to a neighboring cell having a higher rank than the rank of the current serving cell for a predetermined period. When the frequency priority of the neighboring cell is lower than the priority of the current serving cell, and when the radio quality of the current serving cell is lower than a radio quality threshold and the radio quality of the neighboring cell continues to be higher than another radio quality threshold for a predetermined period, the UE 100 may perform cell reselection to the neighboring cell.

[0069] Although the above example describes an example in which the UE 100 performs the cell reselection procedure, it is also possible for the IAB-MT of the IAB node 300 to perform the cell reselection procedure.

[0070] (Communication Control Method According to First Embodiment) Currently, the 3GPP is discussing the following issues regarding the cell reselection procedure of a mobile IAB node.

[0071] (Problem) In a situation where UE 100 is physically located in a moving vehicle but is not yet camped on a mobile IAB cell managed by a mobile IAB node (i.e., UE 100 is camped on a fixed cell that does not move), how can UE 100 identify neighboring mobile IAB cells, how can the priority of the mobile IAB cell (frequency and cell) be increased, and how can UE 100 be attracted to the mobile IAB cell? In particular, in a scenario of an inter-frequency cell reselection procedure, what should be done when the frequency priority of the mobile IAB cell is lower than others? Figure 9 is a diagram for explaining this problem according to the first embodiment.

[0072] As shown in Fig. 9, the UE 100 is located in a mobile vehicle. The vehicle is provided with a mobile IAB node 300M. The UE 100 is located in a cell managed by the mobile IAB node 300M. The cell managed by the mobile IAB node 300M may be referred to as a mobile IAB cell 300S. In the following, the mobile IAB node 300M and the mobile IAB cell 300S may be used interchangeably.

[0073] However, UE100 is camped on a cell (stationary cell or macro cell) managed by a fixed, non-moving gNB200. The gNB200 can be a serving cell for UE100. Hereinafter, the gNB200 may be referred to as a serving cell 200S. UE100 is camped on the serving cell 200S and is located in a vehicle, but has not yet camped on the mobile IAB cell 300S. However, the frequency used in the serving cell 200S and the frequency used in the mobile IAB cell 300S are different.

[0074] In such a situation, a problem has been pointed out as to how to camp the UE 100 on the moving IAB cell 300S when the UE 100 performs an inter-frequency cell reselection procedure.

[0075] To address the above problem, 3GPP has also discussed broadcasting the frequency used in the mobile IAB cell 300S by including it in assistance information in SIB4 (System Information Block type 4), and having the UE 100 identify the mobile IAB cell 300S using the assistance information in SIB4. That is, according to this discussion, by acquiring the frequency used in the mobile IAB cell 300S from SIB4, the UE 100 may be able to camp on the mobile IAB cell 300S by, for example, regarding the frequency as having the highest priority and performing an inter-frequency cell reselection procedure.

[0076] Meanwhile, 3GPP has also agreed to apply a Closed Access Group (CAG) to restrict access to the mobile IAB cell 300S. CAG is a technology that, for example, allows CAG subscribers to access the CAG cell and prevents non-CAG subscribers from accessing the CAG cell. The CAG is identified by a CAG ID, which indicates a unique identifier within a PLMN (Public Land Mobile Network). The CAG ID is used to control access of the UE 100 via the mobile IAB node 300M. The AMF 11 checks whether access of the UE 100 via the mobile IAB node 300M is permitted by the CAG ID.

[0077] The current 3GPP specifications for CAG are, for example, as follows: As shown in Figure 10, SIB4 includes an information element (IE) called the inter-frequency CAG cell list (interFreqCAG-CellList-r16). The inter-frequency CAG cell list includes a PLMN ID index (plmn-IdentityIndex-r16). The PLMN ID index (plmn-IdentityIndex-r16) indicates the entry numbers of both the PLMN ID information list (PLMN-IdentityInfoList) and the NPN ID information list (NPN-IdentityInfoList) included in SIB1. As shown in FIG. 11, each entry (NPNID information (NPN-IdentityInfo-r16)) of the NPNID information list (NPN-IdentityInfoList-r16) included in SIB1 includes a CAG ID (cag-Identity-r16). For example, if entry number #1 is included in the PLMNID index (plmn-IdentityIndex-r16) of SIB4, the first entry included in the NPNID information list (NPN-IdentityInfoList-r16) of SIB1 can be checked to confirm the CAG-ID (list) (e.g., CAG-ID #1) included in entry number #1.

[0078] However, even if the serving cell 200S broadcasts the frequency used by the mobile IAB cell 300S in the SIB4, if the serving cell 200S does not provide the CAG service, the serving cell 200S does not broadcast the CAG-ID. Therefore, the UE 100 cannot determine whether the mobile IAB cell 300S is an access-restricted cell. Even if the UE 100 acquires the frequency used by the mobile IAB cell 300S and performs the inter-frequency cell reselection procedure by regarding the frequency as the highest priority, if access to the mobile IAB cell 300S is restricted, the UE 100 may not be able to access the mobile IAB cell 300S. Therefore, the inter-frequency cell reselection procedure itself may be a useless operation in the UE 100.

[0079] Therefore, the first embodiment aims to suppress unnecessary operations in the cellular communication system 1.

[0080] Therefore, in the first embodiment, first, a base station (e.g., serving cell 200S) broadcasts a message including first information indicating a first frequency available in a mobile IAB cell (e.g., mobile IAB cell 300S) managed by a mobile IAB node (e.g., mobile IAB node 300M) and second information regarding access restriction in the mobile IAB cell. Second, a user equipment (e.g., UE 100) under the control of the mobile IAB cell receives the message.

[0081] As a result, for example, the UE 100 can determine whether or not access to the mobile IAB cell 300S is restricted based on the second information. Therefore, for example, when the UE 100 confirms that the mobile IAB cell 300S is not restricted based on the second information, the UE 100 can execute the inter-frequency cell reselection procedure using the first frequency available in the mobile IAB cell 300S. On the other hand, for example, when the UE 100 confirms that the mobile IAB cell 300S is restricted based on the second information, the UE 100 can also not execute the inter-frequency cell reselection procedure. Therefore, it is possible to suppress unnecessary operations in the UE 100, such as executing the inter-frequency cell reselection procedure even when access to the mobile IAB cell 300S is restricted.

[0082] In the following, the first information may be referred to as "basic information" and the second information may be referred to as "detailed information."

[0083] (1) First Operation Example According to First Embodiment Next, a first operation example according to the first embodiment will be described. The first operation example is based on the situation shown in Fig. 9. That is, the UE 100 is located in a mobile vehicle, but is camped on the macro cell 200S and is not camped on the mobile IAB cell 300S.

[0084] FIG. 12 is a diagram illustrating a first operation example according to the first embodiment.

[0085] As shown in FIG. 12, in step S10, the UE 100 is in an RRC idle state or an RRC inactive state.

[0086] In step S11, the serving cell 200S acquires detailed information. The serving cell 200S may receive detailed information from a network node. The network node may include a gNB 200 and a core network device. Specifically, the network node may be a donor node (IAB-donor). The network node may be a core network device (e.g., AMF 11). The core network device refers to a device included in the 5GC 10, such as the AMF 11 or the UPF 12. Hereinafter, the 5GC 10 and the core network device 10 may be used interchangeably. Note that the serving cell 200 may acquire detailed information from an OAM (Operations, Administration, and Maintenance) server. The operation of acquiring detailed information in the serving cell 200S will be described in a third operation example.

[0087] In step S12, the serving cell 200S broadcasts a message including basic information and detailed information.

[0088] First, the message may be SIB4. If the message is SIB4, the serving cell 200S may broadcast the basic information and detailed information by including them in SIB4 as assistance information of SIB4. Alternatively, the message may be a system information block other than SIB4. Alternatively, the message may be transmitted by dedicated signaling (e.g., an RRC message such as an RRCRelease message) rather than by broadcast signaling.

[0089] Second, the message includes basic information, such as information indicating frequencies available in the mobile IAB cell 300S.

[0090] The basic information may be an identifier (or flag information) indicated for each frequency entry in the frequency list, and may be indicated by the identifier (or flag information) indicating whether or not the frequency is used in the mobile IAB cell 300S. The frequency list is a list of frequencies used in an inter-frequency cell reselection procedure. For example, if the frequency list includes frequency f1 and frequency f2 as entries, the basic information may be indicated by "0" for frequency f1 (a frequency not used in the mobile IAB cell 300S) and "1" for frequency f2 (a frequency used in the mobile IAB cell 300S). The meanings of "0" and "1" may be reversed. This allows, for example, the UE 100 to easily determine, based on the identifier, whether or not the frequency is a frequency used in the mobile IAB cell 300S. Note that detailed information, described below, may be included for each frequency entry in the frequency list.

[0091] Alternatively, the basic information may be indicated by a list of cell IDs of the mobile IAB cells 300S indicated for each frequency entry in the frequency list. The frequency list is also a list of frequencies used in the inter-frequency cell reselection procedure. For example, if the frequency list includes frequency f1 and frequency f2 as entries, the basic information may be indicated by (a list of) cell IDs #1 of the mobile IAB cells for frequency f1 and (a list of) cell IDs #2 of the mobile IAB cells for frequency f2. This allows, for example, the UE 100 to grasp the cell IDs of the mobile IAB cells 300S for each frequency (e.g., cell ID #1 of the mobile IAB cell 300S for frequency f1, cell ID #2 of the mobile IAB cell 300S for frequency f2, etc.). In addition, for example, the UE 100 can also grasp the frequency used for each mobile IAB cell 300S (for example, the frequency f1 is used in the mobile IAB cell 300S of cell ID #1, and the frequency f2 is used in the mobile IAB cell 300S of cell ID #2). Note that detailed information, which will be described later, may be included for each frequency entry in the frequency list.

[0092] Alternatively, the basic information may be indicated by a list of frequencies available in the mobile IAB cell 300S. For example, the basic information may be indicated by a frequency list #1 available in the first mobile IAB cell 300S1, a frequency list #2 available in the second mobile IAB cell 300S2, or the like. This allows the UE 100 to easily confirm the frequencies used in the mobile IAB cell 300S by checking the frequency lists. Note that detailed information, which will be described later, may be included for each frequency entry in the list of frequencies available in the mobile IAB cell 300S.

[0093] Third, the message includes detailed information, such as information about access restrictions for the mobile IAB cell 300S.

[0094] The detailed information may include information indicating whether the mobile IAB cell 300S is performing access restriction. Alternatively, the detailed information may be information indicating a method of access restriction. The information indicating the method of access restriction may be, for example, information indicating that access is restricted by a CAG. The information may be information indicating that access is restricted by a forbidden TA. Note that the forbidden TA is a technology that prevents the UE 100 from making requests to the 5G system, except for emergency services, when the UE 100 is camped on a cell belonging to the forbidden TA, for example.

[0095] Alternatively, the detailed information may include a CAG ID that is permitted to access the mobile IAB cell 300S. For example, if the detailed information includes CAG ID #1, CAG ID #1 represents a CAG ID that is permitted to access the mobile IAB cell 300S. In this case, if CSG ID #1 is set for the UE 100, the UE 100 can access the mobile IAB cell 300S, and if CSG ID #1 is not set for the UE 100, the UE 100 cannot access the mobile IAB cell 300S. Instead of the CAG ID, a PNI-NPN ID (Public Network Integrated Non-Public Network) may be used. An NPN (Non-Public Network) is a network for non-public use and is sometimes referred to as a private network. A PNI-NPN is an NPN that receives support from a telecommunications carrier (PLMN), as opposed to an SNPN (Standalone Non-Public Network) that does not receive support for functions provided by the telecommunications carrier (PLMN). A PNI-NPN ID is identification information that distinguishes a PNI-NPN from other PNI-NPNs and is identified by a combination of a PLMN ID and a CAG ID (PLMN ID + CAG ID). Therefore, the detailed information may be represented by the PLMN ID + CAG ID instead of the CAG ID. For example, if the detailed information includes PNI-NPN ID #1, PNI-NPN ID #1 represents the PNI-NPN ID that is permitted to access the mobile IAB cell 300S.

[0096] Alternatively, the detailed information may include an SNPN ID that is permitted to access the mobile IAB cell 300S. The SNPN ID is identification information that distinguishes an SNPN from other SNPNs. The SNPN ID is represented by a combination of a PLMN ID and an NID (Network Identifier) ​​(PLMN ID+NID). The detailed information may be represented by the PLMN ID+NID instead of the SIPN ID. For example, if the detailed information includes SNPN ID#1, the SNPN ID#1 represents the SNPN ID that is permitted to access the mobile IAB cell 300S. In this case, if the UE 100 has SNPN ID#1 set thereto, the UE 100 can access the mobile IAB cell 300S, and if the UE 100 does not have SNPN ID#1 set thereto, the UE 100 cannot access the mobile IAB cell 300S.

[0097] Alternatively, the detailed information may include a Tracking Area Code (TAC) that is permitted to access the mobile IAB cell 300S. A TAC includes one or more cells and is a code assigned by a communication carrier (PLMN). For example, if the detailed information includes TAC#1, TAC#1 represents a TAC that is permitted to access the mobile IAB cell 300S. In this case, if TAC#1 is set for the UE 100, the UE 100 can access the mobile IAB cell 300S, and if TAC#1 is not set for the UE 100, the UE 100 cannot access the mobile IAB cell 300S.

[0098] As described above, the detailed information may include identification information that is permitted to be accessed in the mobile IAB cell 300S, and the identification information may include any of the CAG ID, the SNPN ID, and the TAC.

[0099] Whether or not the detailed information is referenced may be indicated by the presence or absence of an index (for example, a PLMNID index (plmn-IdentityIndex)). For example, if the message (SIB4) includes a PLMNID index, the reference destination of the lists (PLMNID information list and NPNID information list) included in SIB1 is referenced (and applied) by the PLMNID index, and if the message (SIB4) does not include a PLMNID index, the detailed information included in the message is referenced (and applied). Note that one SIB4 may include both the PLMNID index and the detailed information. In this case, UE100 references (and applies) the lists (PLMNID information list and NPNID information list) included in SIB1 according to the PLMNID index, and also references (and applies) the detailed information.

[0100] Note that the serving cell 200S does not need to broadcast detailed information if the mobile IAB cell 300S does not impose access restrictions, which makes it possible to eliminate unnecessary overhead.

[0101] Furthermore, the serving cell 200S may broadcast a message that includes basic information but does not include detailed information.The serving cell 200S may broadcast a message that includes detailed information but does not include basic information.

[0102] In step S13, the UE 100 receives a message broadcast from the serving cell 200S. The UE 100 executes an inter-frequency cell reselection procedure using detailed information included in the received message. The execution of this procedure will be described in the following operation example 2.

[0103] Note that the UE 100 may ignore (or not apply) the basic information and the detailed information if access to the moving IAB cell 300S is not set (or is not interested in) or is prohibited. This makes it possible to prevent unnecessary inter-frequency measurements (or unnecessary access restrictions) for the moving IAB cell 300S from occurring in a case where, for example, the UE 100 is not on a vehicle and would be better off camping on a stationary cell.

[0104] (2) Second Operation Example According to First Embodiment Next, a second operation example according to the first embodiment will be described. The second operation example represents an operation example in the UE 100 that has received the basic information and the detailed information. Specifically, when the UE 100 determines that the mobile IAB cell 300S is accessible based on the detailed information, the UE 100 considers a frequency (e.g., the first frequency) available in the mobile IAB cell 300S to be the highest priority, and executes an inter-frequency cell reselection procedure.

[0105] FIG. 13 is a diagram illustrating a second operation example according to the first embodiment.

[0106] As shown in FIG. 13, in step S200, UE 100 is in an RRC connected state.

[0107] In step S20, the NAS of the UE 100 may receive a NAS message including configuration information related to access control from the AMF 11, and may notify the AS of the UE 100 of the configuration information. The configuration information may include at least one of a CAG ID to which the UE 100 is permitted to access, an SNPN ID to which the UE 100 is permitted to access, and a TAC (Forbidden TA) to which the UE 100 is prohibited to access. Alternatively, the configuration information may include information indicating that the mobile IAB cell 300S is accessible (or that the UE 100 has access rights). The AS of the UE 100 sets the configuration information in the UE 100. Note that the configuration information may be pre-configured in the UE 100.

[0108] In step S21, the UE 100 transitions to an RRC idle state or an RRC inactive state.

[0109] In step S22, the UE 100 acquires the detailed information. The UE 100 acquires the detailed information by receiving the message of the first operation example (step S12).

[0110] In step S23, the UE 100 determines whether or not the UE 100 can access the moving IAB cell 300S based on the detailed information. Specifically, the UE 100 compares the setting information set for itself (step S21) with the detailed information (step S22) to determine whether or not the UE 100 can access the moving IAB cell 300S. For example, the UE 100 may determine that the UE 100 can access the moving IAB cell 300S in the following cases:

[0111] First, the UE 100 may determine that access to the mobile IAB cell 300S is possible when the mobile IAB cell 300S does not impose access restriction. For example, the UE 100 may determine that access to the mobile IAB cell 300S is possible when the detailed information includes information indicating that access restriction is not imposed or when the detailed information does not include identification information such as a CAG-ID that is permitted to access.

[0112] Secondly, when a CAG ID that is permitted to access is set for the UE 100, if the CAG ID is included in the detailed information, the UE 100 may determine that access to the moving IAB cell 300S is possible.

[0113] Thirdly, when an SNPN ID that is permitted to access is set for the UE 100, if the SNPN ID is included in the detailed information, the UE 100 may determine that access to the moving IAB cell 300S is possible.

[0114] Fourth, when a TAC to which access is prohibited is set for the UE 100, if a TAC other than the TAC is included in the detailed information, the UE 100 may determine that access to the mobile IAB cell 300S is possible.

[0115] Fifth, when the UE 100 does not receive detailed information including information on access restriction, the UE 100 may determine that access to the moving IAB cell 300S is possible.

[0116] In step S24, the UE 100 may further determine whether or not camping is necessary, which indicates whether or not to camp on the moving IAB cell 300S. Here, an example is shown in which the UE 100 determines whether or not camping is necessary, in addition to the access permission determination (step S23).

[0117] First, when the AS of the UE 100 detects that the UE 100 has boarded a mobile vehicle based on information received from a higher layer, the AS of the UE 100 may determine that the UE 100 should camp on the mobile IAB cell 300S. For example, when the AS of the UE 100 receives information indicating that the UE 100 has boarded a train equipped with the mobile IAB cell 300S via the NAS using a specific application service (e.g., Mobile Suica), the AS of the UE 100 may determine that the UE 100 should camp on the mobile IAB cell 300S.

[0118] Secondly, when the AS of the UE 100 detects that its own moving speed is equal to or greater than a predetermined speed, it may determine that it should camp on the moving IAB cell 300S. The AS of the UE 100 may acquire its own moving speed using a speed sensor or the like.

[0119] When the UE 100 determines that it should camp on the moving IAB cell 300S, the UE 100 may acquire detailed information (for example, receive a message (step S12 in FIG. 12 )). Alternatively, when the UE 100 determines that it should camp on the moving IAB cell 300S, the UE 100 may perform an access permission determination in step S23.

[0120] The UE 100 may simultaneously (or in parallel) execute the access permission determination in step S23 and the camping necessity determination in step S24. The UE 100 may perform the two determinations in any order.

[0121] In step S25, if the UE 100 determines that it is possible to access the mobile IAB cell 300S (and / or possible to camp on the mobile IAB cell 300S), it performs the inter-frequency cell reselection procedure, regarding the frequency available in the mobile IAB cell 300S as the highest priority. If the UE 100 determines that it is not possible to access the mobile IAB cell 300S, it may perform the inter-frequency cell reselection procedure, regarding the frequency available in the mobile IAB cell 300S as the lowest priority.

[0122] As described above, in the second operation example, when the UE 100 determines that it is not possible to access the moving IAB cell 300S, it is possible not to perform measurement processing (measurement) of the radio quality for the moving IAB cell 300S in the inter-frequency cell reselection procedure. Therefore, in the second embodiment, it is also possible to reduce the power consumption of the UE 100 compared to the case where the measurement processing is performed.

[0123] (3) Third Operation Example According to First Embodiment Next, a third operation example according to the first embodiment will be described. In the third operation example, a method for acquiring detailed information in the serving cell 200S will be described. Specifically, a mobile IAB node (e.g., mobile IAB node 300M) transmits detailed information (e.g., second information) to a network node. Then, a base station (e.g., serving cell 200S) receives the detailed information from a network node other than the base station. In the third operation example, an operation example in the case of a donor node 200 and an operation example in the case of a core network device 10 as the network node will be described.

[0124] (3.1) When the network is a donor node 200 Fig. 14 is a diagram illustrating a third operation example according to the first embodiment. Fig. 14 illustrates an operation example when the network node is a donor node 200, in which the serving cell 200S receives detailed information from the donor node 200 (network node).

[0125] 14, in step S30, detailed information is set for the mobile IAB node 300M. If the detailed information includes a CAG ID, the CAG ID is set for the mobile IAB node 300M. When the mobile IAB node 300M is permitted to operate as a (mobile) IAB node, the CAG ID may be set by an OAM server, or the CAG ID may be pre-configured. Similarly, when the detailed information includes other identification information, when the mobile IAB node 300M is permitted to operate as a (mobile) IAB node, the detailed information may be set by an OAM server, or the detailed information may be pre-configured.

[0126] In step S31, the mobile IAB node 300M transmits detailed information to the donor node 200.

[0127] First, the mobile IAB node 300M may transmit the detailed information to the donor node 200 when it makes an initial connection (initial access) to the donor node 200. Alternatively, the mobile IAB node 300M may transmit the detailed information to the donor node 200 when it connects by migration with the donor node 200 as the target donor node. Alternatively, the mobile IAB node 300M may transmit the detailed information to the donor node 200 when it establishes a new F1 connection with the donor node 200.

[0128] Second, the mobile IAB node 300M transmits the detailed information by sending an F1 message containing the detailed information to the donor node 200. The F1 message may be an F1 Setup Request message.

[0129] Third, the donor node 200 receives the detailed information. If the detailed information does not include identification information (or if the donor node 200 has not received the detailed information), the donor node 200 may determine that the mobile IAB node 300M that sent the detailed information does not perform access restriction.

[0130] The mobile IAB node 300M may transmit the detailed information to the core network device 10 (for example, the AMF 11) instead of the donor node 200. An example of operation in this case will be described in the next example of operation (3.2).

[0131] In step S32, the donor node 200 transmits the detailed information to the serving cell 200S. The donor node 200 may transmit the detailed information to other cells neighboring the serving cell 200S. Alternatively, the donor node 200 may transmit the detailed information to other gNBs neighboring the gNB accommodating the serving cell 200S. The serving cell 200S is the cell on which the UE 100 is camped in the situation shown in FIG. 9. The donor node 200 transmits the detailed information by transmitting an Xn message including the detailed information to the serving cell 200S. The Xn message may be an NG-RAN Node Configuration Update message. The serving cell 200S receives the detailed information.

[0132] In step S33, the serving cell 200S broadcasts a message including the detailed information. Step S33 corresponds to step S12 in FIG.

[0133] (3.2) When a network node receives from a core network device 10 Fig. 15 is a diagram illustrating a third operation example according to the first embodiment. Fig. 15 illustrates an operation example when the serving cell 200S receives detailed information from the core network device 10 (network node).

[0134] Step S40 is the same as step S30 in FIG.

[0135] In step S41, the mobile IAB node 300M transmits detailed information to the core network device 10.

[0136] First, the mobile IAB node 300M may transmit detailed information to the core network device 10 when it makes an initial connection (initial access) to a gNB under the core network device 10. Alternatively, the mobile IAB node 300M may transmit detailed information to the core network device 10 when it connects to a cell accommodated by a gNB under the core network device 10 through a cell reselection procedure.

[0137] Second, the mobile IAB node 300M may send the detailed information to the core network device 10 (e.g., AMF 11) by sending a NAS message including the detailed information to the core network device 10.

[0138] Third, the core network device 10 receives the detailed information. If the detailed information does not include identification information (or if the detailed information is not received), the core network device 10 may determine that the mobile IAB node 300M that sent the detailed information is not performing access restriction.

[0139] In step S42, the core network device 10 transmits the detailed information to the serving cell 200S. The core network device 10 may transmit the detailed information to other cells neighboring the serving cell 200S. Alternatively, the core network device 10 may transmit the detailed information to other gNBs neighboring the gNB accommodating the serving cell 200S. The serving cell 200S is the cell on which the UE 100 is camped in the situation shown in FIG. 9. The core network device 10 may transmit the detailed information to the serving cell 200S by transmitting an NG message including the detailed information to the serving cell 200S. The NG message may be an NG-RAN Node Configuration Update message. The serving cell 200S receives the detailed information.

[0140] In step S43, the serving cell 200S broadcasts a message including the detailed information. Step S43 corresponds to step S12 in FIG.

[0141] [Other Embodiments] The above-described operational flows are not limited to being implemented independently, but can be implemented by combining two or more operational flows. For example, some steps of one operational flow may be added to another operational flow, or some steps of one operational flow may be replaced with some steps of another operational flow. In each flow, it is not necessary to execute all steps, and only some steps may be executed.

[0142] In the above-described embodiments and examples, an example in which the base station is an NR base station (gNB) has been described, but the base station may be an LTE base station (eNB) or a 6G base station. The base station may also be a relay node such as an IAB (Integrated Access and Backhaul) node. The base station may also be a DU of the IAB node. The UE 100 may also be an MT (Mobile Termination) of the IAB node.

[0143] That is, the UE 100 may be a terminal function unit (a type of communication module) for a base station to control a repeater that relays signals. Such a terminal function unit is referred to as an MT. Examples of the MT include, in addition to the IAB-MT, an NCR (Network Controlled Repeater)-MT and a RIS (Reconfigurable Intelligent Surface)-MT.

[0144] The term "network node" primarily refers to a base station, but may also refer to a core network device or a part of a base station (CU, DU, or RU). A network node may also be configured by a combination of at least a part of a core network device and at least a part of a base station.

[0145] A program may be provided that causes a computer to execute each process performed by the UE 100, the gNB 200, or the mobile IAB node 300M. The program may be recorded on a computer-readable medium. Using a computer-readable medium, the program can be installed on a computer. Here, the computer-readable medium on which the program is recorded may be a non-transitory recording medium. The non-transitory recording medium is not particularly limited, and may be, for example, a recording medium such as a CD-ROM or a DVD-ROM. Furthermore, circuits that execute each process performed by the UE 100 or the gNB 200 may be integrated, and at least a portion of the UE 100, the gNB 200, or the mobile IAB node 300M may be configured as a semiconductor integrated circuit (chip set, SoC: System on a chip).

[0146] The functions performed by the UE 100 or the gNB 200 (network node) may be implemented in circuitry or processing circuitry, including general-purpose processors, application-specific processors, integrated circuits, ASICs (Application Specific Integrated Circuits), CPUs (Central Processing Units), conventional circuits, and / or combinations thereof, programmed to perform the described functions. A processor includes transistors and other circuits and is considered to be circuitry or processing circuitry. A processor may also be a programmed processor that executes a program stored in memory. In this specification, circuitry, unit, or means refers to hardware that is programmed to perform the described functions or hardware that executes them. The hardware may be any hardware disclosed herein or any hardware known to be programmed or capable of performing the described functions. If the hardware is a processor, the circuitry, means, or unit is a combination of hardware and software used to configure the hardware and / or processor.

[0147] As used in this disclosure, the terms "based on" and "depending on / in response to" do not mean "based only on" or "depending only on," unless expressly stated otherwise. The term "based on" means both "based only on" and "based at least in part on." Similarly, the term "depending on" means both "depending only on" and "depending at least in part on." The terms "include," "comprise," and variations thereof do not mean including only the listed items, but may mean including only the listed items or may include additional items in addition to the listed items. Additionally, the term "or," as used in this disclosure, is not intended to mean an exclusive or. Furthermore, any reference to elements using designations such as "first," "second," etc., as used in this disclosure does not generally limit the quantity or order of those elements. These designations may be used herein as a convenient method of distinguishing between two or more elements. Thus, a reference to a first and a second element does not imply that only two elements may be employed therein or that the first element must precede the second element in some way. In this disclosure, where articles are added by translation, such as a, an, and the in English, these articles shall include the plural unless the context clearly indicates otherwise.

[0148] Although one embodiment has been described in detail above with reference to the drawings, the specific configuration is not limited to the above, and various design changes can be made within the scope of the gist. Furthermore, the embodiments, operation examples, and processes can be appropriately combined within the scope of not being inconsistent.

[0149] This application claims priority to U.S. Provisional Application No. 63 / 531,085 (filed August 7, 2023), the entire contents of which are incorporated herein by reference.

[0150] (Appendix 1)

[0151] (Supplementary Note 1) A communication control method used in a cellular communication system, comprising: a step of a base station broadcasting a message including first information indicating a first frequency available in a mobile IAB cell managed by a mobile IAB node and second information related to access restriction of the mobile IAB cell; and a step of a user equipment under the control of the mobile IAB cell receiving the message.

[0152] (Supplementary Note 2) The communication control method according to Supplementary Note 1, wherein the message includes a frequency list used in an inter-frequency cell reselection procedure, and the first information is indicated by an identifier indicated for each frequency entry in the frequency list, the identifier indicating whether the frequency is used in the mobile IAB cell.

[0153] (Supplementary Note 3) The communication control method according to Supplementary Note 1 or Supplementary Note 2, wherein the message includes a frequency list used in an inter-frequency cell reselection procedure, and the first information is indicated by a list of cell IDs of the moving IAB cells indicated for each frequency entry in the frequency list.

[0154] (Supplementary Note 4) The communication control method according to any one of Supplementary Note 1 to Supplementary Note 3, wherein the first information is indicated by a list of the first frequencies.

[0155] (Supplementary Note 5) The communication control method according to any one of Supplementary Note 1 to Supplementary Note 4, wherein the second information includes information indicating whether the mobile IAB cell is performing access restriction.

[0156] (Supplementary Note 6) The communication control method according to any one of Supplementary Note 1 to Supplementary Note 5, wherein the second information includes identification information permitted to access in the mobile IAB cell, and the identification information includes any one of a CAG ID (Closed Access Group ID), an SNPN ID (Standalone Non-Public Network ID), and a TAC (Tracking Area Code).

[0157] (Supplementary Note 7) The communication control method according to any one of Supplementary Notes 1 to 6, wherein the message is an SIB4, and when a PLMNID index indicating a reference to a list included in SIB1 is included in the SIB4, the list included in the SIB1 is referenced, and when the PLMNID index is not included in the SIB4, the second information is referenced.

[0158] (Supplementary Note 8) The communication control method according to any one of Supplementary Notes 1 to 7, further comprising the step of, when the user equipment determines that the mobile IAB cell is accessible based on the second information, performing an inter-frequency cell reselection procedure by regarding the first frequency as the highest priority.

[0159] (Supplementary Note 9) The communication control method according to any one of Supplementary Notes 1 to 8, further comprising: receiving, by the base station, the second information from a network node other than the base station.

[0160] (Supplementary Note 10) The communication control method according to any one of Supplementary Notes 1 to 9, wherein the step of receiving the second information includes a step of the mobile IAB node transmitting the second information to the network node.

[0161] (Supplementary Note 11) The communication control method according to any one of Supplementary Notes 1 to 10, wherein the network node is a donor node or a core network device.

[0162] (Supplementary Note 12) A communication control method used in a cellular communication system, comprising: a step of a base station broadcasting a message including first information indicating a first frequency available in a mobile IAB cell managed by a mobile IAB node; and a step of a user equipment under the control of the mobile IAB cell receiving the message, wherein the message includes a frequency list used in an inter-frequency cell reselection procedure, and the first information is indicated by either an identifier indicated for each frequency entry in the frequency list and indicating whether the frequency is used in the mobile IAB cell, or a list of cell IDs of the mobile IAB cell indicated for each frequency entry in the frequency list.

[0163] (Supplementary Note 13) A communication control method used in a cellular communication system, comprising: a step of a base station broadcasting a message including second information related to access restriction of a mobile IAB cell managed by a mobile IAB node; and a step of a user equipment under the control of the mobile IAB cell receiving the message, wherein the second information includes either information indicating whether the mobile IAB cell is performing access restriction or not, or identification information of an access permitted in the mobile IAB cell, and the identification information includes either a CAG ID (Closed Access Group ID), an SNPN ID (Standalone Non-Public Network ID), or a TAC (Tracking Area Code).

[0164] (Second Appendix) Introduction WID for Mobile IAB aims to specify the procedures for UE mobility and IAB-MT mobility as follows:

[0165] The detailed objectives of WI are as follows: Define mobility / topology adaptation procedures to enable IAB node mobility, including inter-donor mobility (full mobility) of a mobile IAB node [RAN3, RAN2]. Mobile IAB nodes can be attached to fixed (intermediate) IAB nodes. Optimizations specific to scenarios where a mobile IAB node connects to a stationary (intermediate) IAB node or directly connects to an IAB donor DU are deprioritized. Mobility of dual-connected IAB nodes is deprioritized. Enhancements for IAB nodes to move with their UEs, including aspects related to group mobility. There are no optimizations for targeting surrounding UEs [RAN3, RAN2]. Note: Solutions should avoid touching on topics already discussed in Rel-17 or excluded from Rel-17, except for enhancements specific to IAB node mobility. Mitigation of interference due to IAB node movement, including avoidance of potential reference and control signal collisions (PCI, RACH, etc.) [RAN3, RAN2].

[0166] The following principles should be respected: - Mobile IAB nodes should be able to serve legacy UEs. - Solutions providing optimization for mobile IAB may involve enhancements to Rel-18 UEs.

[0167] This appendix discusses the details of the mobility enhancements for the mobile IAB.

[0168] Discussion Enhancement of UE cell reselection functionality Regarding the cell reselection functionality enhancement, RAN2#119bis-e agreed to the following confirmations, observations and assumptions: RAN2 confirms that mobile IAB needs to work with legacy UEs. RAN2 observes that if a UE camps on / attaches to a mobile IAB cell for an extended period of time, the UE may be considered to be onboarded on the mobile IAB cell (i.e., the UE needs to know that the mobile IAB cell is such a cell). The time period requires further study. Whether this is necessary requires further study.

[0169] RAN2 makes the following assumptions (which may be trivial) about UEs operating in mobile IAB cells: Assumption 1: From the viewpoint of the network of the mobile IAB cell, the configuration principles of legacy parameters (including cell (re)selection, cell reservation, and access restriction) are the same as for legacy IAB cells. Assumption 2: There is no impact on the operation of legacy UEs in terms of specifications. Assumption 3: The information of mobile IAB cells newly broadcast by R18 (if agreed) does not prohibit / control access for legacy UEs. Assumption 4: Non-enhancement capable UEs (including legacy UEs and non-enhancement capable R18 UEs) simply ignore the information of mobile IAB cells newly broadcast by R18 (if agreed).

[0170] RAN2 Assumptions: Mobile IAB Cell Broadcast Information: To support mobility in inactive / idle state for Rel-18 UEs, a 1-bit Mobile IAB Cell Type Indicator is introduced (further study is needed on whether this needs to be known to prove the UE is onboard). How this is used needs further study (may be implementation dependent).

[0171] RAN2 has not specified any modifications to prevent surrounding UEs from accessing mobile IAB nodes from the perspective of mobile IAB WI, but believes SA2 may be working on an applicable Rel-18 solution (wait for SA2).

[0172] RAN2#120 further agreed to the following assumptions: RAN2 assumes that the assumed mobile IAB cell type indication may be defined if the behavior of the associated UE is specified.

[0173] RAN2#121 further agreed on the following assumptions and considerations: Working Assumption: Cell reselection to mIAB cells supports UE prioritization, at least for inter-frequency cell reselection. Further consideration is needed for the case where a UE is unspecified in searching and measuring mIAB cells on different frequencies (autonomous search). Further consideration is needed for the case where such a search is possible without assistance frequency information.

[0174] RAN2#122 has agreed on these two issues and their solution directions as follows: RAN2 believes that if the UE is camped on an mIAB cell, the UE can prioritize (cell and / or frequency) using the mIAB cell indication, and if the UE is not yet camped on an mIAB cell, it can prioritize. If the detailed conditions for applying such prioritization can be specified (in either case), RAN2 will consider conditions based on the cell residence timer or mobility state.

[0175] R2 direction (a matter of agreement at a later stage; other directions are not considered): RAN2 recognizes that for idle / inactive UEs, the following two problems need to be addressed: - Problem 1: For a UE that is physically on a moving vehicle but not yet camped on a mobile IAB cell (i.e., the UE is camped on a stationary cell), how can such a UE identify nearby mobile IAB cells, prioritize the mobile IAB cell (frequency and cell), and be "pulled" to this mobile IAB cell (especially in inter-frequency scenarios where the mobile IAB cell has a low frequency priority)? - Problem 2: How can a UE physically on a moving vehicle avoid reselecting other non-IAB (stationary) cells after camping on a mobile IAB cell? - Such a UE can prioritize the highest ranked cell on frequency when broadcasting the mIAB cell type indicator in SIB1 for cell reselection. The UE can use the SIB4 assistance information, when broadcast, to identify the presence of such a mobile IAB cell. The SIB4 assistance information can include the frequency of the mIAB cell. Further discussion is needed to clarify the UEs for Problem 1 and Problem 2.

[0176] Solution to Problem 1 Regarding problem 1 of the RAN2#122 agreement, as shown in Figure 1, the UE is located in a moving vehicle but is camped on an outer stationary cell. According to this statement, it is assumed that the outer fixed cell is operating at F1 while the moving IAB cell is operating at F2. Since the vehicle is moving, the UE is assumed to be in a high-mobility state.

[0177] To solve this problem, RAN2 assumes that such a UE can prioritize the highest ranked cell on a frequency when broadcasting the mIAB cell type indicator in SIB1 for cell reselection, but the UE behavior is exactly the same as the existing HSDN mechanism.

[0178] When an HSDN-capable UE is in a high-mobility state, the UE always considers the HSDN cell as the highest priority (i.e., higher than any other network-configured priority). When an HSDN-capable UE is not in a high-mobility state, the UE always considers the HSDN cell as the lowest priority (i.e., lower than any other network-configured priority).

[0179] The HSDN mechanism specifies another behavior to deprioritize HSDN cells when the UE is in a low mobility state. If considered a potential problem, a mobile IAB cell can always remove the HSDN indication from its SIB when the mobile IAB (or train) is in a low mobility or stationary state.

[0180] Therefore, RAN2 should again discuss whether it can reuse the existing HSDN indication in SIB1 instead of introducing a new mobile IAB cell type indication.

[0181] Proposal 1: Regarding Problem 1, before deciding to introduce mobile IAB cell type indication in SIB1, RAN2 should discuss whether the existing HSDN indication in SIB1 can be reused for mobile IAB frequency / cell prioritization.

[0182] Another issue captured in the RAN2#122 agreement is how the UE identifies the frequency on which the mobile IAB cell operates. The solution is for the UE to use SIB4 assistance information, which lists the mobile IAB frequencies. As a starting point, in the HSDN mechanism, SIB4 provides an HSDN cell list for each entry in the inter-frequency carrier frequency list, as follows: With this information, the UE can know on which frequency the HSDN cell is operating without a blind / full search.

[0183] Meanwhile, SA2 decided to reuse CAGs to restrict access to mobile IAB cells, and RAN2 is currently discussing how to implement this in its specifications. SA2 also decided to reuse prohibited TAs for UEs that cannot use NPNs. This means that "premium" mobile IAB cells are accessible only to "premium" UEs, while "standard" mobile IAB cells are accessible to all UEs (e.g., special subscription fees for enterprise and residential customers for a premium vehicular 5G experience). In this sense, providing only frequency information in SIB4 is insufficient because "standard" UEs cannot access "premium" mobile IAB cells even if they prioritize mobile IAB frequencies / cells. As a result, these UEs not only waste battery power due to inter-frequency measurements, but also degrade the user experience. Therefore, it is worth considering whether SIB4 also provides CAG and TA information for each frequency.

[0184] Observation 1: Some UEs are not allowed to access some mobile IAB cells (i.e., due to CAG access restrictions), so these UEs do not need to prioritize mobile IAB frequencies / cells.

[0185] According to the current specification, the interFreqCAG-CellList is available in SIB4 for the Rel-16 NPN feature. This list provides the CAG and TA information for each frequency with an "index" of the PLMN ID (i.e., not "PLMN ID + CAG ID"). The index refers to the NPN Identity Info List in SIB1, as follows:

[0186] Therefore, if the serving cell (i.e., the external fixed cell) does not broadcast the PNI-NPN ID (i.e., "PLMN ID + CAG ID") of the mobile IAB cell on a different frequency, the current SIB4 may not function because the required PNI-NPN ID index is not present. Therefore, it is necessary to consider whether the serving cell must always broadcast the PNI-NPN ID of the mobile IAB cell, especially when the serving cell does not provide NPN service, and the limited number of PLMNs, PNI-NPNs, and SNPNs (maximum 12 in total). Therefore, it is necessary to discuss whether RAN2 can assume such network limitations. If not, a method can be considered to broadcast explicit CAG and TAC information of the mobile IAB cell in SIB4.

[0187] Proposal 2: Regarding problem 1, RAN2 should agree that the SIB4 assistance information includes CAG and TA information in addition to frequency information.

[0188] Proposal 3: If Proposal 2 is agreeable, RAN2 should further discuss whether the existing interFreqCAG-CellList in SIB4 really works in all deployment scenarios.

[0189] Solution to Problem 2 According to the RAN2#122 agreement, the UE is located in a moving vehicle and is camped on an external stationary cell as shown in Figure 2, but the UE should avoid reselecting the external stationary cell.

[0190] In this case, the solution to problem 1 above can be reused to prioritize operation of UEs with mobile IAB frequencies / cells, i.e., either the existing HSDN cell indication or the new mobile IAB cell type indication.

[0191] Proposal 4: For Problem 2, RAN2 should agree that the common solution to Problem 1 in Proposal 1 is applicable.

[0192] IAB-MT Access Restriction Enhancements Fixed IAB Node Access WID states that a mobile IAB node shall only serve UEs, which means that a mobile IAB node should not serve other IAB nodes as child nodes: - A mobile IAB node has no descendant IAB nodes and serves only UEs.

[0193] To ensure this requirement, RAN2#119e has agreed to the following: Not broadcasting the "iab-Support" indication is sufficient to prevent other IAB nodes from accessing the mobile IAB (with no further impact on the specification).

[0194] However, the agreement has not been fully discussed. In particular, the part "(without being affected by further specifications)" leaves open the question of whether it is truly sufficient to leave it up to the implementation. Since WID explicitly requires that mobile IAB nodes cannot access other mobile IAB nodes, it is considered necessary to clarify this assumption in the specification to avoid confusion in mobile IAB implementations. Therefore, it is desirable for the Stage 2 specification to incorporate the above agreement or clarify that "in this release, mobile IAB nodes cannot access other mobile IAB nodes."

[0195] Proposal 5: RAN2 should agree to include in the Stage 2 specification that if an IAB node acts as a mobile IAB node in this release, it will not set the IAB support IE in the SIB.

[0196] Mobile IAB Node Access In RAN2 #120, the following agreements have been reached for mobile IAB node access to parent nodes: Mobile IAB nodes can camp on and connect to legacy Rel-16 / Rel-17 IAB-capable cells. R2 assumes that a "supporting mobile-IAB" indication is provided by the Rel-18 mobile IAB-capable parent cell.

[0197] Based on the agreement, the correspondence between display availability and IAB node behavior is summarized in Table 1.

[0198] (Table 1) SIB indications and IAB node behavior

[0199] For Cases 1 and 4, the behavior of the mobile IAB node is clear, as shown in Table 1.

[0200] Proposal 6: RAN2 should agree to prohibit mobile IABs from accessing parent nodes that do not broadcast both the legacy IAB support IE and the new "supporting mobile-IAB" IE.

[0201] Proposal 7: RAN2 should agree that the mobile IAB evaluates parent nodes that broadcast both the legacy IAB-support IE and the new "supporting mobile-IAB" IE.

[0202] Regarding Case 2, it is unclear whether a mobile IAB node can access the parent node if the legacy IAB support IE is not present and a new indication is provided. Furthermore, it should be discussed whether it is valid for the parent node to broadcast only the new indication without the legacy IE. It is considered typical for a parent node to accept access from both legacy and mobile IAB nodes. However, it is also possible that the parent node is deployed solely to provide services to mobile IAB nodes. Therefore, maintaining configuration flexibility is a good idea.

[0203] Proposal 8: RAN2 should discuss whether it is a valid configuration for the new "supporting mobile IAB-node" IE to be broadcast while the legacy IAB-support IE is not provided (i.e., the case in Table 1).

[0204] In Case 3, i.e., when the legacy IAB-support IE is provided but the new indication is not, the mobile IAB node can access the parent node because, as cited above, RAN2 has agreed that "mobile IAB nodes can camp on and connect to legacy Rel-16 / Rel-17 IAB-capable cells." However, the expected behavior of the IAB node is the same as in Case 4. In Case 3, the mobile IAB node can access the parent node under certain conditions, while in Case 4, it can always access the parent node. For example, the mobile IAB node can access only if no cell broadcasting the new indication is found. As another example, the mobile IAB node may be configured, for example, by the AMF or OAM, in the authorization / validation process as to whether it is allowed to access a cell that does not broadcast the new indication. Therefore, RAN2 needs to clarify under what conditions a mobile IAB node can access a parent cell that does not broadcast the new indication.

[0205] Proposal 9: RAN2 needs to discuss under what conditions a mobile IAB node broadcasting the legacy IA supporting IE (case 3 in Table 1) but not providing the new "supporting mobile IAB-node" IE should be allowed to access the parent node (e.g., only if no cell broadcasting the new indication is found, access to the parent node should be allowed).

Claims

1. A communication control method comprising: a user equipment receiving system information from a network, the system information including a frequency list used in an inter-frequency cell reselection procedure; and the user equipment performing an inter-frequency cell reselection procedure based on the system information, wherein at least one frequency entry in the frequency list includes a list of cell IDs of mobile IAB cells managed by a mobile IAB node, and performing the inter-frequency cell reselection procedure includes: when it is determined that the user equipment is located inside a mobile vehicle, regarding a frequency to which the mobile IAB cell detected based on the list of cell IDs belongs as the highest priority.

2. The communication control method according to claim 1, further comprising the user equipment receiving from the network specific information relating to access restrictions for the mobile IAB cell, and performing the inter-frequency cell reselection procedure includes regarding a frequency to which the mobile IAB cell belongs as having the highest priority when it is determined based on the specific information that the mobile IAB cell is accessible.

3. The communication control method according to claim 1, wherein the predetermined information includes information indicating whether the mobile IAB cell is implementing access restriction.

4. The communication control method according to claim 1, wherein the specified information includes identification information permitted for access in the mobile IAB cell, and the identification information includes any one of a Closed Access Group ID (CAG ID), a Standalone Non-Public Network ID (SNPN ID), and a Tracking Area Code (TAC).

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