Communication control method, user equipment, cellular communication system, program, and chip set

Abstract

A communication control method according to one aspect is used in a cellular communication system. The communication control method comprises a step for receiving, from a mobile IAB cell by user equipment, mobile IAB cell type information indicating the fact of being a mobile IAB cell. Further, the communication control method comprises a step for performing, by the user equipment, either: an inter-frequency cell reselection procedure in which the frequency priority of a frequency used by the mobile IAB cell is considered the highest priority; or an inter-frequency cell reselection procedure in which the frequency priority of a frequency used in the mobile IAB cell is considered the lowest priority.

Description

Communication control method, user device, cellular communication system, program, and chipset

[0001] The present disclosure relates to a communication control method, a user device, a cellular communication system, a program, and a chipset used in a cellular communication system.

[0002] In the Third Generation Partnership Project (3GPP) (registered trademark, the same applies hereinafter), a standardization project for cellular communication systems, the introduction of a new relay node called an Integrated Access and Backhaul (IAB) node is being considered (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 V17.3.0 (2022-12)

[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 including a step of receiving, by a user equipment, mobile IAB cell type information from the mobile IAB cell, the mobile IAB cell indicating that the mobile IAB cell is a mobile IAB cell, and a step of performing, by the user equipment, an inter-frequency cell reselection procedure by regarding a frequency priority of a frequency used in the mobile IAB cell as the highest priority.

[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 user equipment (UE) receives, from a network, connection authorization information indicating whether or not connection to a mobile IAB cell is authorized. The communication control method also includes a step in which the user equipment receives, from the mobile IAB cell, mobile IAB cell type information indicating that the mobile IAB cell is a mobile IAB cell. The communication control method further includes a step in which the user equipment performs a predetermined process on the mobile IAB cell based on the connection authorization information, or does not perform a predetermined process on the mobile IAB cell. The predetermined process is at least one of regarding the mobile IAB cell as unrestricted, camping on the mobile IAB cell, and performing an RRC connection to the mobile IAB cell.

[0006] A user equipment according to a third aspect is a user equipment in a cellular communication system, the user equipment including: a receiving unit that receives, from a mobile IAB (Integrated Access and Backhaul) cell, mobile IAB cell type information indicating that the mobile IAB cell is a mobile IAB cell; and a control unit that performs an inter-frequency cell reselection procedure by regarding a frequency priority of a frequency used in the mobile IAB cell as the highest priority.

[0007] A cellular communication system according to a fourth aspect is a cellular communication system having a mobile Integrated Access and Backhaul (IAB) cell and a user equipment, wherein the user equipment receives, from the mobile IAB cell, mobile IAB cell type information indicating that the mobile IAB cell is a mobile IAB cell, and the user equipment performs an inter-frequency cell reselection procedure by regarding a frequency priority of a frequency used by the mobile IAB cell as the highest priority.

[0008] A program according to a fifth aspect causes a computer of a user equipment in a cellular communication system to perform the following processes: receiving, from a mobile IAB (Integrated Access and Backhaul) cell, mobile IAB cell type information indicating that the mobile IAB cell is a mobile IAB cell; and performing an inter-frequency cell reselection procedure by regarding a frequency priority of a frequency used in the mobile IAB cell as the highest priority.

[0009] A chipset according to a sixth aspect is a chipset for a user equipment in a cellular communication system, the chipset performing a process of receiving, from a mobile Integrated Access and Backhaul (IAB) cell, mobile IAB cell type information indicating that the mobile IAB cell is a mobile IAB cell, and a process of performing an inter-frequency cell reselection procedure by regarding a frequency priority of a frequency used by the mobile IAB cell as the highest priority.

[0010] FIG. 1 is a diagram showing an example of the configuration of a cellular communication system according to one embodiment. FIG. 2 is a diagram showing the relationship between an IAB node, parent nodes, and child nodes. FIG. 3 is a diagram showing an example of the configuration of a gNB (base station) according to one embodiment. FIG. 4 is a diagram showing an example of the configuration of an IAB node (relay node) according to one embodiment. FIG. 5 is a diagram showing an example of the configuration of a UE (user equipment) according to one embodiment. FIG. 6 is a diagram showing an example of a protocol stack related to an IAB-MT RRC connection and a NAS connection. FIG. 7 is a diagram showing an example of a protocol stack related to the F1-U protocol. FIG. 8 is a diagram showing an example of a protocol stack related to the F1-C protocol. FIG. 9 is a diagram showing an example of an operation according to the first embodiment. FIG. 10 is a diagram showing an example of an operation according to the second embodiment.

[0011] An object of the present disclosure is to provide a communication control method that enables a user equipment that receives mobile IAB cell type information to perform appropriate processing.

[0012] 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.

[0013] [First embodiment]

[0014] (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.

[0015] FIG. 1 is a diagram showing an example of the configuration of a cellular communication system 1 according to an embodiment.

[0016] 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.

[0017] 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).

[0018] 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.

[0019] 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.

[0020] 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.

[0021] 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.

[0022] 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.

[0023] 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).

[0024] 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.

[0025] 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.

[0026] FIG. 2 is a diagram showing an example of the relationship between the IAB node 300, parent nodes, and child nodes.

[0027] 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.

[0028] 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.

[0029] 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.

[0030] 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.

[0031] (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.

[0032] 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.

[0033] 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.

[0034] 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.

[0035] (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.

[0036] 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.

[0037] 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.

[0038] 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.

[0039] (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.

[0040] 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.

[0041] 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.

[0042] (Protocol Stack Configuration) Next, a protocol stack configuration according to the embodiment will be described. Fig. 6 is a diagram showing an example of a protocol stack related to an IAB-MT RRC connection and a NAS connection.

[0043] 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.

[0044] 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.

[0045] 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.

[0046] 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.

[0047] 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.

[0048] 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.

[0049] 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.

[0050] 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.

[0051] 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.

[0052] 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.

[0053] 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.

[0054] 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."

[0055] 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.

[0056] (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).

[0057] 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.

[0058] 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.

[0059] 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.

[0060] In the following, the terms "migration" of a mobile IAB node and "handover" of a mobile IAB node may be used interchangeably.

[0061] In the following description, the 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 be referred to as a mobile IAB node.

[0062] (Cell Reselection Procedure According to First Embodiment) Next, a cell reselection procedure according to the first embodiment will be described.

[0063] 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 an intra-frequency, and when the frequency (carrier frequency) of the current serving cell and the neighboring cell is different, this is called an inter-frequency. The current serving cell and the neighboring cell may be managed by the same gNB 200 or may be managed by different gNBs 200.

[0064] Cell reselection procedures include intra-frequency cell reselection procedures and inter-frequency cell reselection procedures.

[0065] 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.

[0066] 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.

[0067] 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. Rs and Rn are calculated using the following formulas, respectively.

[0068] Rs = Q ｍｅａｓ，ｓ +Q ｈｙｓｔ -Qoffset ｔｅｍｐ...(1) Rn=Q ｍｅａｓ，ｎ -Qoffset-Qoffset ｔｅｍｐ ...(2) In formula (1), Q ｍｅａｓ，ｓ represents the reference signal received power (RSRP) (measurement value) for the serving cell. ｍｅａｓ，ｎ represents the RSRP (measurement) for the neighboring cell. ｔｅｍｐ Qoffset is an offset value for adjusting (RSRP) used in the ranking criteria (Rn) for neighboring cells.

[0069] The UE 100 basically reselects the cell with the highest rank from among the two ranking criteria Rs and Rn.

[0070] The cell selection criterion S is a criterion for selecting a cell whose RSRP exceeds the minimum required RSRP level and whose RSRQ exceeds the minimum required RSRQ level.

[0071] 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.

[0072] 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.

[0073] 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.

[0074] 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.

[0075] (Communication Control Method According to First Embodiment) Next, a communication control method according to the first embodiment will be described.

[0076] A mobile IAB node can broadcast mobile IAB cell type information (mobile-IAB cell type indication) (or mobile relay node cell type information) indicating that the node itself is a mobile IAB node. The mobile IAB cell type information is, for example, 1-bit information. The UE 100 that receives the mobile IAB cell type information can determine that the cell that transmitted the information is a cell of a mobile IAB node. After determining that the cell is a mobile IAB cell, the UE 100 can perform appropriate processing, such as executing a cell (re)selection procedure for the cell.

[0077] Therefore, the first embodiment aims to enable the UE 100 that has received the mobile IAB cell type information to perform appropriate processing.

[0078] Therefore, in the first embodiment, an example will be described in which the UE 100 performs a predetermined operation in the inter-frequency cell reselection procedure when receiving the mobile IAB cell type information from the cell.

[0079] Specifically, first, the user equipment (e.g., UE 100) receives mobile IAB cell type information from the mobile IAB cell indicating that the mobile IAB cell is a mobile IAB cell. Second, the user equipment performs either an inter-frequency cell reselection procedure by regarding the frequency priority of the frequency used in the mobile IAB cell as the highest priority, or an inter-frequency cell reselection procedure by regarding the frequency priority of the frequency used in the mobile IAB cell as the lowest priority.

[0080] In this way, when the UE 100 receives the mobile IAB cell type information, the UE 100 performs the inter-frequency cell reselection procedure by setting the frequency priority of the frequency used in the cell that broadcasted the mobile IAB cell type information to the highest priority, or by setting the frequency priority to the lowest priority. This allows the UE 100 to reselect the mobile IAB cell or not reselect the mobile IAB cell, and enables the UE 100 to appropriately perform processing (in the first embodiment, the inter-frequency cell reselection procedure) when the mobile IAB cell type information is received.

[0081] (Example of Operation According to First Embodiment) Next, an example of operation according to the first embodiment will be described.

[0082] 9 is a diagram illustrating an example of operation according to the first embodiment. Note that, hereinafter, the cell of the mobile IAB node 300-M may be referred to as a "mobile IAB cell."

[0083] As shown in FIG. 9, in step S10, the UE 100 transitions to an RRC idle state or an RRC inactive state.

[0084] In step S11, the mobile IAB cell 300-M broadcasts mobile IAB cell type information indicating that the mobile IAB cell is a mobile IAB cell. The mobile IAB cell 300-M may broadcast the mobile IAB cell type information using an SIB.

[0085] The order of steps S10 and S11 may be reversed.

[0086] In step S12, the UE 100 receives the mobile IAB cell type information, and then performs either an inter-frequency cell reselection procedure by regarding the frequency priority of the frequency used in the mobile IAB cell as the highest priority, or an inter-frequency cell reselection procedure by regarding the frequency priority of the frequency used in the mobile IAB cell as the lowest priority.

[0087] First, the operation of the UE 100 regarding the frequency as the highest frequency priority may be applied when the UE 100 is moving at high speed. For example, the UE 100 acquires its own moving speed from speed information or location information (the location information may be, for example, measurement information by a GPS or an acceleration sensor. The location information may be information calculated from the number of cells passed through in a certain period), compares the speed with a speed threshold, and if its moving speed is faster than the speed threshold (i.e., in the case of high-speed movement), performs an operation of regarding the frequency priority of the frequency used in the moving IAB cell as the highest frequency priority. The speed threshold may be set (or broadcast) in advance by the gNB 200. Alternatively, instead of regarding the frequency as the highest frequency priority, the UE 100 may apply a special frequency priority to the frequency and perform an inter-frequency cell reselection procedure. The special frequency priority may be broadcast from the gNB 200 and received by the UE 100 in advance. The special frequency priority is a frequency priority used in the inter-frequency cell reselection procedure, and may be broadcast from the gNB 200 using an information element (IE) different from the frequency priority included in SIB4 (hereinafter, sometimes referred to as "normal frequency priority"). The special frequency priority may be broadcast using an SIB (e.g., SIB4, etc.). Furthermore, the operation of the UE 100 regarding the frequency as the highest priority may be performed when permitted by the network. The permission may be notified in advance to the UE 100 from the network by connection permission information. Details of the connection permission information will be described in the second embodiment. In the UE 100, by regarding the frequency as the highest frequency priority, it is possible to make it easier to reselect the moving IAB cell 300-M in the inter-frequency cell reselection procedure.

[0088] Second, the operation of the UE 100 regarding the frequency as the lowest priority may be applied when the UE 100 is moving at a low speed (or is stationary). For example, the UE 100 may acquire its own moving speed from speed information or location information, compare it with a speed threshold, and perform the operation of regarding the frequency as the lowest priority when its moving speed is equal to or less than the speed threshold (i.e., when the UE 100 is moving at a low speed or is stationary). Alternatively, instead of regarding the frequency as the lowest frequency priority, the UE 100 may perform an inter-frequency cell reselection procedure for the frequency using normal frequency priority. Furthermore, the operation of the UE 100 regarding the frequency used in the mobile IAB cell 300-M as the lowest frequency priority may be performed when the UE 100 is not permitted by the network. This non-permission may be notified to the UE 100 in advance by the network using connection permission information. By regarding the frequency as the lowest frequency priority, the UE 100 is more likely to reselect a cell other than the mobile IAB cell. Furthermore, by setting the frequency to normal frequency priority, the UE 100 can treat the moving IAB cell in the same way as other cells and execute the inter-frequency cell reselection procedure.

[0089] (Another Example According to First Embodiment) In the first embodiment, the UE 100 performs the inter-frequency cell reselection procedure by regarding the frequency used in the mobile IAB cell as the highest priority, or performs the inter-frequency cell reselection procedure by regarding the frequency as the lowest priority. However, this is not limited to this. For example, the UE 100 may perform the inter-frequency cell reselection procedure by regarding the mobile IAB cell itself as the highest priority, or by regarding the mobile IAB cell itself as the lowest priority. That is, the UE 100 may perform the inter-frequency cell reselection procedure by regarding the mobile IAB cell itself as the highest priority, or by performing the inter-frequency cell reselection procedure by regarding the mobile IAB cell itself as the lowest priority.

[0090] Second Embodiment Next, a second embodiment will be described, focusing on the differences from the first embodiment.

[0091] In the second embodiment, an example will be described in which, when permitted by the network, the UE 100 camps on the moving IAB cell 300-M or makes an RRC connection to the moving IAB cell 300-M.

[0092] Specifically, first, the user equipment (e.g., UE 100) receives connection authorization information from the network indicating whether or not connection to the mobile IAB cell is authorized. Second, the user equipment receives mobile IAB cell type information from the mobile IAB cell indicating that the cell is a mobile IAB cell. Third, the user equipment performs a predetermined process on the mobile IAB cell based on the connection authorization information, or does not perform a predetermined process on the mobile IAB cell. Here, the predetermined process is at least one of regarding the mobile IAB cell as unrestricted, camping on the mobile IAB cell, and performing an RRC connection to the mobile IAB cell.

[0093] In this way, when UE 100 receives the mobile IAB cell type information and is permitted to connect to the mobile IAB cell, UE 100 can regard the mobile IAB cell as not barred (Not barred), camp on the mobile IAB cell, and perform RRC connection. On the other hand, even when UE 100 receives the mobile IAB cell type information, if UE 100 is not permitted to connect to the mobile IAB cell, UE 100 can regard the mobile IAB cell as barred (Barred), cannot camp on the mobile IAB cell, and cannot perform RRC connection.

[0094] Therefore, for example, it is possible to permit a specific user who has made a contract to connect to the mobile IAB cell 300-M, and not permit other users to connect to the mobile IAB cell 300-M, and such control can be performed on the network side. As a result, for example, the UE 100 that has received the mobile IAB cell type information can perform appropriate processing.

[0095] (Example of Operation According to Second Embodiment) Next, an example of operation according to the second embodiment will be described.

[0096] FIG. 10 is a diagram illustrating an example of operation according to the second embodiment.

[0097] As shown in FIG. 10 , the UE 100 may execute a registration procedure with the network and perform initial registration with the network (e.g., AMF 11). The network may include connection authorization information in authentication information or configuration information used in the registration procedure and transmit the information to the UE 100. The connection authorization information is, for example, information indicating whether or not connection to the mobile IAB cell 300-M is permitted. The UE 100 may also transmit a connection authorization request to the network. The network may determine whether or not the UE 100 is permitted to connect to the mobile IAB cell 300-M based on subscriber information (e.g., service contract information). The network may transmit connection authorization information to the UE 100 according to the determination of whether or not connection is permitted. The UE 100 that has received the connection authorization information can determine whether or not connection to the mobile IAB cell 300-M is permitted. For example, the AMF 11 may transmit the connection permission information to the UE 100 by using a NAS message such as a Security Mode Command message or a Registration Accept message. Alternatively, the connection permission information may be written in advance in a storage medium such as a SIM (Subscriber Identity Module) in the UE 100. In either case, whether the connection permission information is received from the AMF 11 or written in advance in the UE 100, an upper layer (for example, a NAS layer) of the UE 100 may manage the connection permission information. In this case, the upper layer may output the connection permission information to the AS layer.

[0098] In step S22, the mobile IAB cell 300-M broadcasts the mobile IAB cell type information. The mobile IAB cell 300-M may broadcast the mobile IAB cell type information using the SIB. Note that a normal cell that is not the mobile IAB cell 300-M does not broadcast the mobile IAB cell type information. The normal cell may be a non-moving cell such as the gNB 200, a cell of a fixed IAB node that does not move, a macro cell, a large cell, a small cell, or an indoor cell.

[0099] In step S23, the mobile IAB cell 300-M performs either a predetermined process on the mobile IAB cell 300-M or does not perform a predetermined process on the mobile IAB cell 300-M based on the connection permission information. Here, the predetermined process is, for example, at least one of considering the mobile IAB cell as not barred, camping on the mobile IAB cell 300-M, and performing an RRC connection to the mobile IAB cell 300-M. Specifically, the process is as follows.

[0100] First, if the connection authorization information indicates that connection to the mobile IAB cell is permitted, the UE 100 determines that camping and / or RRC connection to the mobile IAB cell 300-M is possible. That is, the UE 100 may regard the mobile IAB cell 300-M as a not-barred cell. Alternatively, the UE 100 may perform a cell reselection procedure with the mobile IAB cell 300-M as a candidate for cell reselection. Specifically, as described in the first embodiment, the UE 100 may perform an inter-frequency cell reselection procedure by regarding the frequency priority of the frequency used in the mobile IAB cell 300-M as the highest frequency priority. Alternatively, the UE 100 may apply special frequency priority to the frequency used in the mobile IAB cell 300-M as described in the first embodiment. Furthermore, the UE 100 may perform an intra-frequency cell reselection procedure with the ranking criterion (Rn or Rs) of the moving IAB cell 300-M set to the highest rank. Alternatively, the UE 100 may perform an RRC connection to the moving IAB cell 300-M. Specifically, the UE 100 may perform the RRC connection by transmitting an RRC message such as an RRC connection establishment request (RRCSetupRequest) message or an RRC recovery request (RRCResumeRequest) message to the moving IAB cell 300-M.

[0101] Second, if the connection authorization information does not permit connection to the mobile IAB cell, the UE 100 determines that camping on the mobile IAB cell 300-M and / or RRC connection to the mobile IAB cell 300-M is not possible. That is, the UE 100 may regard the mobile IAB cell 300-M as a barred cell. Alternatively, the UE 100 may perform a cell reselection procedure without considering the mobile IAB cell 300-M as a candidate for cell reselection. That is, the UE 100 does not perform cell reselection to the mobile IAB cell 300-M. Alternatively, as described in the first embodiment, the frequency of the mobile IAB cell 300-M may be regarded as the lowest priority, or normal frequency priority may be applied to the frequency of the mobile IAB cell 300-M. Furthermore, the UE 100 may perform an intra-frequency cell reselection procedure with the ranking criterion (Rn or Rs) of the mobile cell 300-M set to the lowest rank. Alternatively, the UE 100 does not establish an RRC connection to the moving IAB cell 300-M. Specifically, the UE 100 may not transmit an RRC message related to RRC connection establishment, such as an RRC connection establishment request message and an RRC recovery request message, to the moving IAB cell 300-M.

[0102] [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.

[0103] 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.

[0104] 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.

[0105] A program may be provided that causes a computer to execute each process performed by the UE 100, the gNB 200, or the IAB node 300. The program may be recorded on a computer-readable medium. Using the computer-readable medium, it is possible to install the program on a computer. Here, the computer-readable medium on which the program is recorded may be a non-transitory recording medium. The non-transitory recording medium is not particularly limited, and may be, for example, a recording medium such as a CD-ROM or a DVD-ROM.

[0106] In addition, circuits that perform each process performed by UE100, gNB200, or IAB node 300 may be integrated, and at least a portion of UE100 or gNB200 may be configured as a semiconductor integrated circuit (chipset, SoC: System on a chip).

[0107] The functions performed by the UE 100, the gNB 200 (network node), or the IAB node 300 may be implemented in circuitry or processing circuitry, including general-purpose processors, application-specific processors, integrated circuits, ASICs (Application Specific Integrated Circuits), a CPU (a Central Processing Unit), conventional circuits, and / or combinations thereof, programmed to perform the described functions. A processor includes transistors and other circuits and is considered to be circuitry or processing circuitry. A processor may also be a programmed processor that executes a program stored in memory. In this specification, circuitry, unit, or means refers to hardware that is programmed to perform the described functions or that executes the described functions. 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.

[0108] 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.

[0109] 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.

[0110] This application claims priority from Japanese Patent Application No. 2023-019955 (filed February 13, 2023), the entire contents of which are incorporated herein by reference.

[0111] (Supplementary Note) (Supplementary Note 1) A communication control method used in a cellular communication system, comprising: a step in which a user equipment receives, from a mobile IAB cell, mobile IAB cell type information indicating that the cell is a mobile IAB cell; and a step in which the user equipment performs one of the following: performing an inter-frequency cell reselection procedure by regarding the frequency priority of a frequency used in the mobile IAB cell as the highest priority; and performing the inter-frequency cell reselection procedure by regarding the frequency priority of the frequency used in the mobile IAB cell as the lowest priority.

[0112] (Supplementary Note 2) The communication control method according to Supplementary Note 1, wherein the step of performing any one of the steps includes a step of, when the user equipment is moving at a speed faster than a speed threshold, performing the inter-frequency cell reselection procedure by regarding the frequency priority as the highest priority.

[0113] (Supplementary Note 3) The communication control method according to Supplementary Note 1 or Supplementary Note 2, wherein the step of performing any one of the steps includes a step of, when the user equipment is moving at a speed faster than a speed threshold, applying a special frequency priority to the frequency priority and performing the inter-frequency cell reselection procedure.

[0114] (Supplementary Note 4) The communication control method according to any one of Supplementary Notes 1 to 3, wherein the step of performing any one of the steps includes a step of, when the user equipment is moving at a speed equal to or less than a speed threshold, performing the inter-frequency cell reselection procedure while regarding the frequency priority as the lowest priority.

[0115] (Supplementary Note 5) The communication control method according to any one of Supplementary Notes 1 to 4, wherein the step of performing any one of the steps includes a step of, when the user equipment is moving at a speed equal to or less than a speed threshold, performing the inter-frequency cell reselection procedure using frequency priority broadcast in SIB4.

[0116] (Supplementary Note 6) A communication control method used in a cellular communication system, comprising: a step in which a user equipment receives connection permission information from a network, the connection permission information indicating whether or not connection to a mobile IAB cell is permitted; a step in which the user equipment receives mobile IAB cell type information from the mobile IAB cell, the mobile IAB cell indicating that the cell is the mobile IAB cell; and a step in which the user equipment performs a predetermined process on the mobile IAB cell based on the connection permission information, or does not perform the predetermined process on the mobile IAB cell, wherein the predetermined process is at least one of regarding the mobile IAB cell as unrestricted, camping on the mobile IAB cell, and performing an RRC connection to the mobile IAB cell.

[0117] (Supplementary Note 7) The communication control method according to any one of Supplementary Notes 1 to 6, wherein the step of performing the predetermined processing includes a step in which the user equipment performs the predetermined processing if the connection permission information indicates that connection to the mobile IAB cell is permitted, and does not perform the predetermined processing if the connection permission information indicates that connection to the mobile IAB cell is not permitted.

[0118] 1: Mobile communication system 10: 5GC 11: AMF 100: UE 110: Wireless communication unit 120: Control unit 200: Donor node (gNB) 210: Wireless communication unit 230: Control unit 300: IAB node 300-M: Mobile IAB node (mobile IAB cell) 310: Wireless communication unit 320: Control unit

Claims

1. A communication control method for use in a cellular communication system, comprising: receiving, by the user equipment, mobile Integrated Access and Backhaul (IAB) cell type information from the mobile IAB cell, the mobile IAB cell indicating that the mobile IAB cell is a mobile IAB cell; the user equipment performing an inter-frequency cell reselection procedure by considering a frequency priority of a frequency used in the mobile IAB cell as the highest priority; The mobile IAB cell is a cell that restricts connections to other IAB nodes using connection permission information that indicates that connection to the mobile IAB cell is permitted. Communication control method.

2. A user equipment in a cellular communication system, comprising: a receiving unit that receives, from a mobile IAB cell, mobile IAB cell type information indicating that the mobile IAB cell is a mobile IAB cell; a control unit that performs an inter-frequency cell reselection procedure by regarding a frequency priority of a frequency used in the mobile IAB cell as the highest priority; The mobile IAB cell is a cell that restricts connections to other IAB nodes using connection permission information that indicates that connection to the mobile IAB cell is permitted. User equipment.

3. a mobile IAB (Integrated Access and Backhaul) cell; a user equipment; and a cellular communication system comprising: The user equipment receives, from the mobile IAB cell, mobile IAB cell type information indicating that the mobile IAB cell is a mobile IAB cell; the user equipment performs an inter-frequency cell reselection procedure by considering the frequency priority of the frequency used in the mobile IAB cell as the highest priority; The mobile IAB cell is a cell that restricts connections to other IAB nodes using connection permission information that indicates that connection to the mobile IAB cell is permitted. Cellular communication systems.

4. A computer of a user device in a cellular communication system, receiving, from the mobile IAB cell, mobile IAB cell type information indicating that the mobile IAB cell is a mobile IAB cell; and performing an inter-frequency cell reselection procedure by regarding the frequency priority of the frequency used in the mobile IAB cell as the highest priority; The mobile IAB cell is a cell that restricts connections to other IAB nodes using connection permission information that indicates that connection to the mobile IAB cell is permitted. program.

5. A chipset for a user equipment in a cellular communication system, comprising: receiving, from the mobile IAB cell, mobile IAB cell type information indicating that the mobile IAB cell is a mobile IAB cell; performing an inter-frequency cell reselection procedure by regarding the frequency priority of the frequency used by the mobile IAB cell as the highest priority; The mobile IAB cell is a cell that restricts connections to other IAB nodes using connection permission information that indicates that connection to the mobile IAB cell is permitted. Chipset.