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

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

Technical Field

[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.

Background Art

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

Prior Art Documents

Non-Patent Documents

[0003]

Non-Patent Document 1

Summary of the Invention

[0004] The communication control method according to the first aspect is a communication control method used in a cellular communication system. The communication control method includes a step in which a user device receives mobile IAB cell type information indicating that the user device is a mobile IAB cell from the mobile IAB cell. Further, the communication control method includes a step in which the user device executes an inter-frequency cell reselection procedure by regarding the frequency priority of the frequency used in the mobile IAB cell as the highest priority.

[0005] The second aspect of the communication control method is a communication control method used in a cellular communication system. The communication control method includes the step of a user device receiving connection permission information from a network indicating whether or not connection to a mobile IAB cell is permitted. The communication control method also includes the step of the user device receiving mobile IAB cell type information from the mobile IAB cell indicating that it is a mobile IAB cell. Furthermore, the communication control method includes the step of the user device either performing a predetermined process on the mobile IAB cell based on the connection permission information, or not performing a predetermined process on the mobile IAB cell. The predetermined process is at least one of the following: considering the mobile IAB cell to be unrestricted, camping the mobile IAB cell, and making an RRC connection to the mobile IAB cell.

[0006] The user device according to the third embodiment is a user device in a cellular communication system. The user device includes a receiving unit that receives mobile IAB (Integrated Access and Backhaul) cell type information from a mobile IAB cell indicating that it is a mobile IAB cell, and a control unit that considers the frequency priority of the frequencies used by the mobile IAB cell as the highest priority and executes an inter-frequency cell reselection procedure.

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

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

[0009] The chipset according to the sixth embodiment is a chipset for a user device in a cellular communication system. The chipset performs the following processes: receiving mobile IAB cell type information from a mobile IAB (Integrated Access and Backhaul) cell indicating that it is a mobile IAB cell; and executing an inter-frequency cell reselection procedure, considering the frequency priority of the frequency used by the mobile IAB cell as the highest priority. [Brief explanation of the drawing]

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

Embodiment for Implementing the Invention

[0011] The present disclosure aims to provide a communication control method that enables a user device that has received mobile IAB cell type information to perform appropriate processing.

[0012] A cellular communication system according to an embodiment will be described while referring 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) A configuration example of a cellular communication system according to an embodiment will be described. The cellular communication system 1 according to an 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 at least partially applied to the cellular communication system 1. Also, future cellular communication systems such as 6G may be applied to the cellular communication system 1.

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

[0016] As shown in FIG. 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, an example where the base station 200 is an NR base station will be mainly described, but the base station 200 may be an LTE base station (i.e., eNB).

[0018] Note that in the following, the base stations 200-1 and 200-2 may be respectively referred to as gNB 200 (or base station 200), and the IAB nodes 300-1 and 300-2 may be referred to as IAB node 300.

[0019] The 5GC 10 includes an AMF (Access and Mobility Management Function) 11 and a UPF (User Plane Function) 12. The AMF 11 is a device that performs various mobility controls for the UE 100. The AMF 11 manages information on the area where the UE 100 is located by communicating with the UE 100 using NAS (Non-Access Stratum) signaling. The UPF 12 is a device that performs transfer control of user data and the like.

[0020] Each gNB 200 is a fixed wireless communication node that manages one or more cells. A cell is a term indicating the smallest unit of a wireless communication area. A cell may be used as a term indicating a function or resource for performing wireless communication with the UE 100. One cell belongs to one carrier frequency. In the following, the cell and the base station may sometimes be used without distinction.

[0021] Each gNB 200 is interconnected with the 5GC 10 via an interface called the NG interface. In FIG. 1, two gNBs 200-1 and 200-2 connected to the 5GC 10 are illustrated.

[0022] Each gNB200 may be divided into a Central Unit (CU) and a Distributed Unit (DU). The CU and DU are interconnected via an interface called the F1 interface. The F1 protocol is a communication protocol between the CU and DU, and consists of the F1-C protocol, which is the control plane protocol, and the F1-U protocol, which is the user plane protocol.

[0023] Cellular communication system 1 supports IAB, which enables wireless relay of NR access using NR for backhaul. Donor gNB200-1 (or donor node; hereinafter sometimes referred to as "donor node") is the network-side NR backhaul termination node and is a donor base station with additional functions to support IAB. Backhaul can be multi-hop, via multiple hops (i.e., multiple IAB nodes 300).

[0024] Figure 1 shows an example where IAB node 300-1 is wirelessly connected to donor node 200-1, and IAB node 300-2 is wirelessly connected to IAB node 300-1, with the F1 protocol being transmitted over two backhaul hops.

[0025] The UE100 is a mobile wireless communication device that communicates wirelessly with a cell. The UE100 can be any device that communicates wirelessly with the gNB200 or IAB node 300. For example, the UE100 may be a mobile phone terminal and / or a tablet terminal, a notebook PC, a sensor or a device installed on a sensor, a vehicle or a device installed on a vehicle, an aircraft or a device installed on an aircraft. The UE100 connects wirelessly to the IAB node 300 or gNB200 via an access link. Figure 1 shows an example of the UE100 connecting wirelessly to IAB node 300-2. The UE100 communicates indirectly with donor node 200-1 via IAB node 300-2 and IAB node 300-1.

[0026] Figure 2 shows an example of the relationship between IAB node 300, parent nodes, and child nodes.

[0027] As shown in Figure 2, each IAB node 300 has an IAB-DU, which corresponds to the base station function unit, and an IAB-MT (Mobile Termination), which corresponds to the user equipment function unit.

[0028] On the IAB-MT's NR Uu radio interface, adjacent nodes (i.e., higher-level nodes) are called parent nodes. A parent node is the DU of the parent IAB node or donor node 200. The radio link between the IAB-MT and the parent node is called a backhaul link (BH link). Figure 2 shows an example where the parent nodes of IAB node 300 are IAB nodes 300-P1 and 300-P2. The direction toward the parent node is called upstream. From the perspective of UE100, the higher-level node of UE100 may be a parent node.

[0029] Adjacent nodes (i.e., lower-level nodes) on the NR access interface of an IAB-DU are called child nodes. The IAB-DU manages cells, similar to the gNB200. The IAB-DU terminates the NR Uu radio interface to the UE100 and lower-level IAB nodes. The IAB-DU supports the F1 protocol to the CU of donor node 200-1. Figure 2 shows an example where the child nodes of IAB node 300 are IAB nodes 300-C1 to 300-C3, but the child nodes of IAB node 300 may also include the UE100. The direction toward child nodes is called downstream.

[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 Figure 2, adjacent nodes on the IAB-DU interface become child nodes, and adjacent nodes on the IAB-MT interface become parent nodes. The donor node 200 centrally manages, for example, the resources, topology, and route management of the IAB topology. The donor node 200 is a gNB that provides network access to the UE100 via the backhaul link and access link network.

[0031] (Base station configuration) Next, the configuration of the gNB200, which is a base station according to the embodiment, will be described. Figure 3 is a diagram showing an example of the configuration of the gNB200. As shown in Figure 3, the gNB200 has a wireless communication unit 210, a network communication unit 220, and a control unit 230.

[0032] The wireless communication unit 210 performs wireless communication with the UE 100 and with the IAB node 300. The wireless communication unit 210 includes a receiving unit 211 and a transmitting unit 212. The receiving unit 211 performs various types of reception under the control of the control unit 230. The receiving unit 211 includes an antenna and converts the wireless signal received by the antenna into a baseband signal (received signal) (downconvert) and outputs it to the control unit 230. The transmitting unit 212 performs various types of transmission under the control of the control unit 230. The transmitting unit 212 includes an antenna and converts the baseband signal (transmitted signal) output by the control unit 230 into a wireless signal (upconvert) and transmits it from the antenna.

[0033] The network communication unit 220 performs wired (or wireless) communication with 5GC10 and with other adjacent gNB200s. The network communication unit 220 has a receiving unit 221 and a transmitting unit 222. The receiving unit 221 performs various types of reception under the control of the control unit 230. The receiving unit 221 receives signals from the outside and outputs the received signals to the control unit 230. The transmitting unit 222 performs various types of transmission under the control of the control unit 230. The transmitting unit 222 transmits the transmission signals output by the control unit 230 to the outside.

[0034] The control unit 230 performs various controls in the gNB200. The control unit 230 includes at least one memory and at least one processor electrically connected to the memory. The memory stores programs executed by the processor and information used for processing by the processor. The processor may include a baseband processor and a CPU. The baseband processor performs modulation, demodulation, encoding, decoding, etc., of the baseband signal. The CPU executes programs stored in the memory and performs various processing. The processor performs processing for each layer described later. In each of the embodiments shown below, the control unit 230 may perform each processing or operation in the gNB200.

[0035] (Configuration of relay nodes) Next, the configuration of the IAB node 300, which is a relay node (or relay node device; hereinafter sometimes referred to as "relay node") according to the embodiment, will be described. Figure 4 is a diagram showing an example of the configuration of the IAB node 300. As shown in Figure 4, the IAB node 300 has a wireless communication unit 310 and a control unit 320. The IAB node 300 may have multiple wireless communication units 310.

[0036] The wireless communication unit 310 performs wireless communication with the gNB200 (BH link) and wireless communication with the UE100 (access link). The wireless communication unit 310 for BH link communication and the wireless communication unit 310 for access link communication may be provided separately.

[0037] The wireless communication unit 310 includes a receiving unit 311 and a transmitting unit 312. The receiving unit 311 performs various types of reception under the control of the control unit 320. The receiving unit 311 includes an antenna and converts the wireless signal received by the antenna into a baseband signal (received signal) (downconvert) and outputs it to the control unit 320. The transmitting unit 312 performs various types of transmission under the control of the control unit 320. The transmitting unit 312 includes an antenna and converts the baseband signal (transmitted signal) output by the control unit 320 into a wireless signal (upconvert) and transmits it from the antenna.

[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 for processing by the processor. The processor may include a baseband processor and a CPU. The baseband processor performs modulation, demodulation, encoding, and decoding of baseband signals. The CPU executes programs stored in the memory and performs various processes. The processor performs processing for each layer described later. In each of the embodiments shown below, the control unit 320 may perform each process or operation in the IAB node 300.

[0039] (User device configuration) Next, the configuration of the user device UE100 according to the embodiment will be described. Figure 5 is a diagram showing an example of the configuration of UE100. As shown in Figure 5, UE100 has a wireless communication unit 110 and a control unit 120.

[0040] The wireless communication unit 110 performs wireless communication on the access link, i.e., wireless communication with the gNB200 and wireless communication with the IAB node 300. The wireless communication unit 110 may also perform wireless communication on the side link, i.e., wireless communication with other UE100s. The wireless communication unit 110 has a receiving unit 111 and a transmitting unit 112. The receiving unit 111 performs various types of reception under the control of the control unit 120. The receiving unit 111 includes an antenna and converts the wireless signal received by the antenna into a baseband signal (received signal) (downconvert) and outputs it to the control unit 120. The transmitting unit 112 performs various types of transmission under the control of the control unit 120. The transmitting unit 112 includes an antenna and converts the baseband signal (transmitted signal) output by the control unit 120 into a wireless signal (upconvert) and transmits it from the antenna.

[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 for processing by the processor. The processor may include a baseband processor and a CPU. The baseband processor performs modulation, demodulation, encoding, and decoding of baseband signals. The CPU executes programs stored in the memory and performs various processes. The processor performs processing for each layer described later. The control unit 120 may perform each process in the UE 100 in each of the embodiments shown below.

[0042] (Protocol stack configuration) Next, the configuration of the protocol stack according to the embodiment will be described. Figure 6 shows an example of a protocol stack for IAB-MT RRC connection and NAS connection.

[0043] As shown in Figure 6, the IAB-MT of IAB node 300-2 has a physical (PHY) layer, a MAC (Medium Access Control) layer, an RLC (Radio Link Control) layer, a PDCP (Packet Data Convergence Protocol) layer, an RRC (Radio Resource Control) layer, and a NAS (Non-Access Stratum) layer.

[0044] The PHY layer performs encoding and decoding, modulation and demodulation, antenna mapping and demapping, and resource mapping and demapping. Data and control information are transmitted between the PHY layer of IAB-MT at IAB node 300-2 and the PHY layer of IAB-DU at IAB node 300-1 via a physical channel.

[0045] The MAC layer performs data priority control, retransmission processing using Hybrid Automatic Repeat request (HARQ), and random access procedures. Data and control information are transmitted between the MAC layer of IAB-MT on IAB node 300-2 and the MAC layer of IAB-DU on IAB node 300-1 via a transport channel. The MAC layer of IAB-DU includes a scheduler. The scheduler determines the transport format (transport block size, modulation and coding scheme (MCS)) and allocated resource blocks for the up and down links.

[0046] The RLC layer uses the functions of the MAC layer and PHY layer to transmit data to the receiving RLC layer. Data and control information are transmitted between the RLC layer of IAB-MT on IAB node 300-2 and the RLC layer of IAB-DU on IAB node 300-1 via a logical channel.

[0047] The PDCP layer performs header compression / decompression, and encryption / decryption. Data and control information are transmitted between the PDCP layer of IAB-MT on IAB node 300-2 and the PDCP layer on donor node 200 via a wireless bearer.

[0048] The RRC layer controls the logical channel, transport channel, and physical channel in response to the establishment, re-establishment, and release of the radio bearer. RRC signaling for various settings is transmitted between the RRC layer of the IAB-MT on IAB node 300-2 and the RRC layer of donor node 200. If there is an RRC connection with donor node 200, the IAB-MT is in the RRC connected state. If there is no RRC connection with donor node 200, the IAB-MT is in the RRC idle state.

[0049] The NAS layer, located above the RRC layer, handles session management and mobility management, among other things. NAS signaling is transmitted between the NAS layer of IAB-MT on IAB node 300-2 and AMF11.

[0050] Figure 7 shows the protocol stack for the F1-U protocol. Figure 8 shows the protocol stack for the F1-C protocol. Here, an example is shown where donor node 200 is divided into CU and DU.

[0051] As shown in Figure 7, each of the IAB-MT on IAB node 300-2, the IAB-DU on IAB node 300-1, the IAB-MT on IAB node 300-1, and the DU on donor node 200 has a BAP (Backhaul Adaptation Protocol) layer as a layer above the RLC layer. The BAP layer is the layer that performs routing and bearer mapping / demapping. In backhaul, routing across multiple hops is possible because the IP layer is transmitted through the BAP layer.

[0052] In each backhaul link, the BAP layer's PDUs (Protocol Data Units) are transmitted via backhaul RLC channels (BH NR RLC channels). By configuring multiple backhaul RLC channels in each BH link, traffic prioritization and QoS (Quality of Service) control are possible. The mapping between BAP PDUs and backhaul RLC channels is performed by the BAP layer of each IAB node 300 and the BAP layer of the donor node 200.

[0053] As shown in Figure 8, the protocol stack of the F1-C protocol has an F1AP layer and an SCTP layer instead of the GTP-U layer and UDP layer shown in Figure 7.

[0054] In the following, the processes or operations performed by the IAB-DU and IAB-MT of the IAB may be described simply as "IAB processes or operations." For example, the transmission of a BAP layer message from the IAB-DU of IAB node 300-1 to the IAB-MT of IAB node 300-2 will be described as IAB node 300-1 transmitting the message to IAB node 300-2. Similarly, the processes or operations of the DU or CU of donor node 200 may be described simply as "donor node processes or operations."

[0055] Furthermore, the upstream direction and the uplink (UL) direction may not be distinguished. Additionally, the downstream direction and the downlink (DL) direction may not be distinguished.

[0056] (Mobile IAB node) Currently, 3GPP is considering the introduction of mobile IAB nodes. A mobile IAB node is, for example, an IAB node that is in motion. A mobile IAB node may be a mobile IAB node, or an IAB node that has the capability to move, or an IAB node that is currently stationary but is certain to move in the future (or is expected to move in the future).

[0057] A mobile IAB node allows, for example, a UE100 under the mobile IAB node to move along with the mobile IAB node while receiving services from it. For example, a user (or UE100) riding in a vehicle could receive services via a mobile IAB node installed in 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 called intermediate IAB nodes. An intermediate IAB node is, for example, an IAB node that does not move. Alternatively, an intermediate IAB node may be a stationary IAB node. Alternatively, an intermediate IAB node may be an IAB node that remains stationary (or does not move) in its installation location. Alternatively, an intermediate IAB node may be an IAB node that remains stationary without moving. An intermediate IAB node may be a fixed IAB node.

[0059] A mobile IAB node can also connect to an intermediate IAB node. Furthermore, a mobile IAB node can connect to donor node 200. A mobile IAB node can also change its connection destination through migration or handover. The source of the connection may be an intermediate IAB node. The source of the connection may also be donor node 200. Furthermore, the destination may be an intermediate IAB node. The destination of the connection may also be donor node 200.

[0060] In the following, the terms "migration" and "handover" of a moving IAB node may not be used interchangeably.

[0061] Furthermore, in the following, a moving IAB node may also be referred to as a "mobile IAB node." The same moving IAB node may also be referred to as a "migrating IAB node." In either case, it may be written as a moving IAB node.

[0062] (Cell reselection procedure according to the first embodiment) Next, the cell reselection procedure according to the first embodiment will be described.

[0063] A UE100 in an RRC idle or RRC inactive state performs a cell reselection procedure as it moves from its current serving cell to an adjacent cell. Specifically, the UE100 identifies the adjacent cell to which it should camp on using the cell reselection procedure and reselects the identified adjacent cell. When the current serving cell and the adjacent cell have the same frequency (carrier frequency), it is called an intra-frequency, and when the current serving cell and the adjacent cell have different frequencies (carrier frequencies), it is called an inter-frequency. The current serving cell and the adjacent cell may be managed by the same gNB200, or they may be managed by different gNB200s.

[0064] There are two types of cell reselection procedures: intra-frequency cell reselection and inter-frequency cell reselection.

[0065] The intra-frequency cell reselection procedure reselects cells based on their ranking. For example, the intra-frequency cell reselection procedure performs the following processes:

[0066] Firstly, the UE100 performs a measurement process to measure the wireless quality for both the serving cell and the adjacent cells. Specifically, the UE100 measures the RSRP and RSRQ of the CD-SSB (Cell Defining-Synchronization Signal and PBCH block) for both the serving cell and the adjacent cells.

[0067] Secondly, UE100 calculates the ranking criterion for the serving cell (Rs) and the ranking criterion for adjacent cells (Rn) 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 equation (1), Q meas,s This represents the Reference Signal Received Power (RSRP) (measured value) for the serving cell. Also, in equation (2), Q meas,n This represents the RSRP (measured value) relative to adjacent cells. Qoffset tempQoffset is a temporary offset value. Qoffset is an adjustment offset value (of RSRP) used in the ranking criterion (Rn) for adjacent cells.

[0069] In UE100, the highest-ranked cell is basically re-selected from the two ranking criteria, Rs and Rn.

[0070] The cell selection criterion S is the criterion for selecting cells where the RSRP exceeds the minimum RSRP requirement level and the RSRQ exceeds the minimum RSRQ requirement level.

[0071] On the other hand, the inter-frequency cell reselection procedure performs cell reselection based on absolute frequency priority. Frequency priority is provided from gNB200 to UE100 via broadcast signaling (e.g., system information block) or dedicated signaling (e.g., RRC release (RRCRelease) message). The inter-frequency cell reselection procedure performs the following processes, for example:

[0072] Firstly, the UE100 performs a measurement process to measure the radio quality of both the serving cell and adjacent cells. Specifically, the UE100 always measures the radio quality of frequencies with a higher priority than the current serving cell's frequency priority. Furthermore, for frequencies with the same or lower priority as the current serving cell's frequency priority, the UE100 measures the radio quality of frequencies with the same or lower priority if the current serving cell's radio quality falls below a predetermined quality.

[0073] Secondly, UE100 performs a cell reselection process to re-select the cell to which it will camp on, based on the measurement results. Specifically, UE100 may reselect a cell to an adjacent cell if the frequency priority of the adjacent cell is higher than the priority of the current serving cell, and the adjacent cell meets a predetermined quality standard (i.e., the minimum required quality standard) for a predetermined period. If the frequency priority of the adjacent cell is the same as the priority of the current serving cell, UE100 may rank the wireless quality of the adjacent cell and reselect a cell to an adjacent cell that has a higher rank than the current serving cell for a predetermined period. If the frequency priority of the adjacent cell is lower than the priority of the current serving cell, and the wireless quality of the current serving cell is lower than a wireless quality threshold, and the wireless quality of the adjacent cell remains higher than another wireless quality threshold for a predetermined period, UE100 may reselect a cell to that adjacent cell.

[0074] The example described above illustrates how UE100 performs the cell reselection procedure, but it is also possible for IAB-MT on IAB node 300 to perform the cell reselection procedure.

[0075] (Communication control method according to the 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 (or mobile relay node cell type information) indicating that it is a mobile IAB node. Mobile IAB cell type information is, for example, 1 bit of information. Upon receiving mobile IAB cell type information, UE100 can determine that the cell that transmitted the information is a mobile IAB node cell. After determining that the cell is a mobile IAB cell, UE100 can perform appropriate processing on the cell, such as executing a cell (re)selection procedure.

[0077] Therefore, the objective of the first embodiment is to enable the UE100, which receives the mobile IAB cell type information, to process it appropriately.

[0078] Therefore, in the first embodiment, an example is described in which UE100 performs a predetermined operation in the inter-frequency cell reselection procedure when it receives moving IAB cell type information from a cell.

[0079] Specifically, firstly, the user device (e.g., UE100) receives mobile IAB cell type information from the mobile IAB cell indicating that it is a mobile IAB cell. Secondly, the user device either performs an inter-frequency cell reselection procedure considering the frequency priority of the frequencies used by the mobile IAB cell as the highest priority, or performs an inter-frequency cell reselection procedure considering the frequency priority of the frequencies used by the mobile IAB cell as the lowest priority.

[0080] Thus, when UE100 receives mobile IAB cell type information, it performs an inter-frequency cell reselection procedure with the frequency priority of the frequency used by the cell that broadcast the mobile IAB cell type information set as the highest priority, or performs an inter-frequency cell reselection procedure with the frequency priority set as the lowest priority. This allows UE100 to reselect a mobile IAB cell or not to reselect a mobile IAB cell, enabling it to perform appropriate processing (inter-frequency cell reselection procedure in the first embodiment) when it receives mobile IAB cell type information.

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

[0082] Figure 9 is a diagram illustrating an example of operation according to the first embodiment. In the following, the cells of the mobile IAB node 300-M may be referred to as "mobile IAB cells".

[0083] As shown in Figure 9, in step S10, UE100 transitions to either the RRC idle state or the RRC inactive state.

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

[0085] Note that the order of steps S10 and S11 can be reversed.

[0086] In step S12, UE100 receives the mobile IAB cell type information. Then, UE100 either performs the inter-frequency cell reselection procedure assuming the frequency priority of the frequencies used in the mobile IAB cell is the highest priority, or performs the inter-frequency cell reselection procedure assuming the frequency priority of the frequencies used in the mobile IAB cell is the lowest priority.

[0087] Firstly, the operation of UE100 to consider the frequency in question as the highest frequency priority may be applied when UE100 is moving at high speed. For example, UE100 may obtain its own moving speed from speed information or position information (such as measurement information from GPS or an accelerometer; such position information may be calculated from the number of cells passed over a certain period of time), compare it with a speed threshold, and if its moving speed is faster than the speed threshold (i.e., in the case of high-speed movement), it may perform the operation of considering 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 gNB200. Alternatively, instead of considering the frequency in question as the highest frequency priority, UE100 may apply a special frequency priority to the frequency in question and execute the inter-frequency cell reselection procedure. The special frequency priority may be broadcast by gNB200 and received in advance by UE100. Special frequency priorities are frequency priorities used in the inter-frequency cell reselection procedure and may be announced by gNB200 using information elements (IE) different from the frequency priorities included in SIB4 (hereinafter sometimes referred to as "normal frequency priorities"). Special frequency priorities may be announced using an SIB (e.g., SIB4). Furthermore, the UE100 may only consider the frequency in question as having the highest priority if permitted by the network. Such permission may be notified to the UE100 in advance from the network through connection permission information. Details of the connection permission information will be described in the second embodiment. By considering the frequency in question as having the highest frequency priority, the UE100 can make it easier to reselect the moving IAB cell 300-M in the inter-frequency cell reselection procedure.

[0088] Secondly, the operation of UE100 to consider the frequency in question as the lowest priority may be applied when UE100 is moving at a low speed (or stationary). For example, UE100 may obtain its own moving speed from speed information or position information, compare it with a speed threshold, and if its moving speed is less than or equal to the speed threshold (i.e., moving at a low speed or stationary), it may perform the operation to consider the frequency in question as the lowest priority. Alternatively, instead of considering the frequency in question as the lowest frequency priority, UE100 may execute the inter-frequency cell reselection procedure using the normal frequency priority for that frequency. Furthermore, the operation of UE100 to consider the frequency used by the moving IAB cell 300-M as the lowest frequency priority may be performed only when it is not permitted by the network. This lack of permission may be notified to UE100 in advance from the network through connection permission information. By considering the frequency in question as the lowest frequency priority, UE100 can more easily reselect cells other than the moving IAB cell. Furthermore, by setting the frequency in question as the normal frequency priority, the UE100 can treat the moving IAB cell the same as other cells and execute the inter-frequency cell reselection procedure.

[0089] (Other examples according to the first embodiment) In the first embodiment, the UE100 was described as executing an inter-frequency cell reselection procedure with the frequency used in the mobile IAB cell as the highest priority, or with the frequency used as the lowest priority, but is not limited to this. B-C Considering the letter as having the highest priority, or the mobile IA B-C The moving IAB cell may be considered to have the lowest priority. In other words, UE100 may execute the inter-frequency cell reselection procedure by considering the moving IAB cell itself as having the highest priority, or by considering the moving IAB cell itself as having the lowest priority and executing the inter-frequency cell reselection procedure.

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

[0091] In the second embodiment, an example is described in which UE100 camps at mobile IAB cell 300-M or establishes an RRC connection to mobile IAB cell 300-M when permitted by the network.

[0092] Specifically, firstly, the user device (e.g., UE100) receives connection permission information from the network indicating whether or not it is permitted to connect to the mobile IAB cell. Secondly, the user device receives mobile IAB cell type information from the mobile IAB cell indicating that it is a mobile IAB cell. Thirdly, based on the connection permission information, the user device either performs a predetermined process on the mobile IAB cell or refrains from performing a predetermined process on the mobile IAB cell. Here, the predetermined process is at least one of the following: considering the mobile IAB cell to be unrestricted, camping the mobile IAB cell, and making an RRC connection to the mobile IAB cell.

[0093] Thus, when UE100 receives mobile IAB cell type information, if connection to the mobile IAB cell is permitted, it can consider the mobile IAB cell as not barred, camp it, or establish an RRC connection. On the other hand, even if UE100 receives mobile IAB cell type information, if connection to the mobile IAB cell is not permitted, it cannot consider the mobile IAB cell as barred, camp it, or establish an RRC connection.

[0094] Therefore, for example, it becomes possible to allow specific users who have a contract to connect to mobile IAB cell 300-M, while denying other users access to mobile IAB cell 300-M. This kind of control can be performed on the network side. As a result, for example, UE100, upon receiving mobile IAB cell type information, can process it appropriately.

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

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

[0097] As shown in Figure 10, UE100 may perform a registration procedure with the network and perform initial registration with the network (e.g., AMF11). The network may send connection permission information to UE100, including authentication information or configuration information used in the registration procedure. Connection permission information is, for example, information indicating whether or not connection to the mobile IAB cell 300-M is permitted. UE100 may also send a request for connection permission to the mobile IAB cell 300-M to the network. The network may determine whether or not UE100 can connect to the mobile IAB cell 300-M based on subscriber information (e.g., service contract information). The network may send connection permission information to UE100 according to its determination of whether or not connection is permitted. Upon receiving the connection permission information, UE100 can determine whether or not connection to the mobile IAB cell 300-M is permitted. For example, AMF11 may send connection permission information to UE100 using NAS messages such as a Security Mode Command message or a Registration Accept message. Alternatively, connection permission information may be pre-written in a storage medium such as a SIM (Subscriber Identity Module) in the UE100. Whether the connection permission information is received from the AMF11 or pre-written in the UE100, in either case, the upper layer of the UE100 (e.g., the NAS layer) 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 mobile IAB cell type information. The mobile IAB cell 300-M may also broadcast mobile IAB cell type information using SIB. Note that regular cells that are not mobile IAB cell 300-M do not broadcast mobile IAB cell type information. Regular cells may include gNB200, cells of fixed IAB nodes that do not move, macrocells, large cells, small cells, indoor cells, etc.

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

[0100] Firstly, if the connection permission information permits connection to the mobile IAB cell, UE100 determines that mobile IAB cell 300-M is campable and / or RRC connectable. That is, UE100 may consider mobile IAB cell 300-M as a not-barred cell. Alternatively, UE100 may execute the cell reselection procedure with mobile IAB cell 300-M as a candidate for cell reselection. Specifically, UE100 may execute the inter-frequency cell reselection procedure by considering the frequency priority of the frequencies used by mobile IAB cell 300-M as the highest frequency priority, as described in the first embodiment. Alternatively, UE100 may apply a special frequency priority to the frequencies used by mobile IAB cell 300-M, as described in the first embodiment. Furthermore, UE100 may execute the intra-frequency cell reselection procedure with the ranking criterion (Rn or Rs) of mobile IAB cell 300-M set to the highest rank. Alternatively, UE100 may establish an RRC connection to mobile IAB cell 300-M. Specifically, UE100 may establish an RRC connection by sending an RRC message, such as an RRCSetupRequest message or an RRCResumeRequest message, to mobile IAB cell 300-M.

[0101] Secondly, if the connection permission information does not permit connection to the mobile IAB cell, UE100 determines that mobile IAB cell 300-M is not campable and / or RRC connectable. That is, UE100 may consider mobile IAB cell 300-M to be a barred cell. Alternatively, UE100 may execute the cell reselection procedure without considering mobile IAB cell 300-M as a candidate for cell reselection. That is, UE100 does not reselect mobile IAB cell 300-M. Alternatively, as described in the first embodiment, the frequency of mobile IAB cell 300-M may be considered the lowest priority, or the normal frequency priority may be applied to the frequency of mobile IAB cell 300-M. Also, UE100 may consider mobile IAB The intra-frequency cell reselection procedure may be executed with the ranking criterion (Rn or Rs) of cell 300-M set to the lowest rank. Alternatively, UE100 may not establish an RRC connection to mobile IAB cell 300-M. Specifically, UE100 may not send RRC messages related to RRC connection establishment, such as RRC connection establishment request messages and RRC recovery request messages, to mobile IAB cell 300-M.

[0102] [Other embodiments] Each of the above-described operation flows can be performed not only independently, but also in combination of two or more operation flows. For example, some steps of one operation flow may be added to another operation flow, or some steps of one operation flow may be replaced with some steps of another operation flow. It is not necessary to execute all steps in each flow; only some steps may be executed.

[0103] In the embodiments and examples described above, an example in which the base station is an NR base station (gNB) was described, but the base station may also be an LTE base station (eNB) or a 6G base station. Furthermore, 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 an IAB node. Furthermore, UE100 may be an MT (Mobile Termination) of an IAB node.

[0104] Furthermore, 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). Additionally, a network node may consist of a combination of at least a part of the core network device and at least a part of a base station.

[0105] A program may be provided that causes a computer to perform each of the processes performed by UE100, gNB200, or IAB node 300. The program may be recorded on a computer-readable medium. Using a computer-readable medium, it is possible to install the program on a computer. Here, the computer-readable medium on which the program is recorded may be a non-transient recording medium. The non-transient recording medium is not particularly limited, but may be a recording medium such as a CD-ROM or DVD-ROM.

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

[0107] The functions realized by UE100, gNB200 (network node), or 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), CPUs (a Central Processing Unit), conventional circuits, and / or combinations thereof, programmed to realize the described functions. A processor, including transistors and other circuits, is considered circuitry or processing circuitry. A processor may be a programmed processor that executes a program stored in memory. In this specification, circuitry, unit, and means are hardware programmed to realize or perform the described functions. Such hardware may be any hardware disclosed herein, or any hardware known to be programmed to realize or perform the described functions. If such hardware is a processor that is considered to be a type of circuitry, then such circuitry, means, or unit is a combination of hardware and software used to constitute such hardware and / or processor.

[0108] The phrases “based on” and “depending on / in response to” used in this disclosure do not mean “based solely on” or “depending solely on” unless otherwise specified. “Based on” means both “based solely on” and “at least partially on.” Similarly, “depending on” means both “at least partially on” and “at least partially on.” The terms “include,” “comprise,” and variations thereof do not mean that only the listed items are included; they mean that only the listed items may be included, or that additional items may be included in addition to the listed items. Furthermore, the term “or” used in this disclosure is not intended to mean exclusive OR. Additionally, any reference to elements using designations such as “first,” “second,” etc., used in this disclosure does not generally limit the quantity or order of those elements. These designations may be used herein as a convenient way to distinguish between two or more elements. Therefore, references to the first and second elements do not imply that only two elements may be adopted therein, or that the first element must precede the second element in any way. In this disclosure, where articles are added by translation, such as a, an, and the in English, these articles shall be plural unless it is clearly indicated by the context that they are not.

[0109] Although one embodiment has been described in detail above with reference to the drawings, the specific configuration is not limited to that described above, and various design changes can be made without departing from the gist of the invention. Furthermore, each embodiment, each operation example, or each process can be combined as appropriate, within the bounds of consistency.

[0110] This application claims priority to Japanese Patent Application No. 2023-019955 (filed February 13, 2023), and all of its contents are incorporated into the specification of this application.

[0111] (Note) (Note 1) A communication control method used in a cellular communication system, The user device receives mobile IAB cell type information from the mobile IAB cell indicating that it is a mobile IAB cell, The user device has the step of either performing an inter-frequency cell reselection procedure with the frequency priority of the frequency used in the mobile IAB cell considered to be the highest priority, or performing the inter-frequency cell reselection procedure with the frequency priority of the frequency used in the mobile IAB cell considered to be the lowest priority. Communication control method.

[0112] (Note 2) The step of performing any of the above includes the step of executing the inter-frequency cell reselection procedure, with the frequency priority being the highest priority, if the user device is moving at a speed faster than the speed threshold. The communication control method described in Appendix 1.

[0113] (Note 3) The step of performing any of the above includes, if the user device is moving at a speed faster than a speed threshold, the step of applying a special frequency priority to the frequency priority and performing the inter-frequency cell reselection procedure. The communication control method described in Appendix 1 or Appendix 2.

[0114] (Note 4) The step of performing any of the above includes the step of executing the inter-frequency cell reselection procedure, with the frequency priority being considered the lowest priority, if the user device is moving at a speed below the speed threshold. A communication control method as described in any of Appendix 1 to Appendix 3.

[0115] (Note 5) The step of performing any of the above includes, if the user device is moving at a speed below the speed threshold, the step of executing the inter-frequency cell reselection procedure using the frequency priority announced in SIB4. A communication control method as described in any of Appendix 1 to Appendix 4.

[0116] (Note 6) A communication control method used in a cellular communication system, The user device receives connection permission information from the network indicating whether or not it is permitted to connect to the mobile IAB cell, The user device receives mobile IAB cell type information from the mobile IAB cell indicating that it is the mobile IAB cell, The user device has the step of either performing a predetermined process on the mobile IAB cell based on the connection permission information, or not performing the predetermined process on the mobile IAB cell, The predetermined processing is at least one of the following: considering the mobile IAB cell to be unrestricted, camping the mobile IAB cell, and establishing an RRC connection to the mobile IAB cell. Communication control method.

[0117] (Note 7) The step of performing the predetermined processing includes the step of performing the predetermined processing if the user device indicates that the connection permission information permits connection to the mobile IAB cell, and not performing the predetermined processing if the connection permission information indicates that connection to the mobile IAB cell does not permit. A communication control method as described in any of Appendix 1 to Appendix 6. [Explanation of Symbols]

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

Claims

1. A communication control method used in a cellular communication system, The user device receives mobile IAB (Integrated Access and Backhaul) cell type information from the mobile IAB cell, indicating that the mobile IAB is a mobile IAB (Integrated Access and Backhaul) cell. The user device executes an inter-frequency cell reselection procedure, considering the frequency priority of the frequencies 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 permission to connect to the mobile IAB cell. Communication control method.

2. A user device in a cellular communication system, A receiving unit that receives mobile IAB (Integrated Access and Backhaul) cell type information from the mobile IAB cell, indicating that it is a mobile IAB (Integrated Access and Backhaul) cell, The system includes a control unit that executes an inter-frequency cell reselection procedure, considering the frequency priority of the frequencies used in the moving 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 permission to connect to the mobile IAB cell. User device.

3. Moving IAB (Integrated Access and Backhaul) cells, A cellular communication system having a user device, The user device receives mobile IAB (Integrated Access and Backhaul) cell type information from the mobile IAB cell, indicating that it is a mobile IAB (Integrated Access and Backhaul) cell. The user device executes the inter-frequency cell reselection procedure, considering the frequency priority of the frequencies 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 permission to connect to the mobile IAB cell. Cellular communication system.

4. In the computer of the user device in the cellular communication system, A process to receive mobile IAB (Integrated Access and Backhaul) cell type information from the mobile IAB cell, indicating that it is a mobile IAB (Integrated Access and Backhaul) cell, The process of executing the inter-frequency cell reselection procedure, with the frequency priority of the frequency used in the aforementioned moving IAB cell being considered as the highest priority, is performed. The mobile IAB cell is a cell that restricts connections to other IAB nodes using connection permission information that indicates permission to connect to the mobile IAB cell. program.

5. A chipset for a user device in a cellular communication system, A process to receive mobile IAB (Integrated Access and Backhaul) cell type information from the mobile IAB cell, indicating that it is a mobile IAB (Integrated Access and Backhaul) cell, The process of executing the inter-frequency cell reselection procedure, with the frequency priority of the frequency used in the aforementioned moving IAB cell being considered as the highest priority, is executed. The mobile IAB cell is a cell that restricts connections to other IAB nodes using connection permission information that indicates permission to connect to the mobile IAB cell. Chipset.

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