Communication control method, user device, network node, and mobile relay node

Abstract

A communication control method according to one aspect is used in a cellular communication system. The communication control method comprises a step of a user equipment transmitting a first connection request notification, indicating a request to connect to a mobile integrated access and backhaul (IAB) cell, to a base station. The communication control method also comprises a step of the base station, in response to receiving the first connection request notification, transmitting to the user device a first message including a first measurement configuration which allows the user equipment to designate the mobile IAB cell as a measurement target.

Description

Communication Control Method

[0001] The present disclosure relates to a communication control method for use 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 V17.5.0 (2023-06)

[0004] A communication control method according to a first aspect is a communication control method used in a cellular communication system, the communication control method including a step of transmitting, from a user equipment (UE) to a base station, a first connection desire notification indicating a desire to connect to a mobile IAB cell, and a step of transmitting, in response to receiving the first connection desire notification, a first message to the user equipment (UE) including a measurement configuration that enables the user equipment to measure the mobile IAB cell.

[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 including a step of transmitting, from a user equipment (UE) device to a mobile IAB cell, a second connection desire notification indicating a desire to connect to a base station, and a step of transmitting, from the mobile IAB cell to the user equipment, a third message including a measurement configuration that enables the user equipment to target the base station for measurement in response to receiving the second connection desire notification.

[0006] 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 a use case according to the first embodiment. FIG. 10 is a diagram showing an example of an operation according to the first embodiment. FIG. 11 is a diagram showing an example of an operation according to the second embodiment.

[0007] The present disclosure aims to enable a cell to transmit measurement configurations to a user equipment at an appropriate time.

[0008] 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.

[0009] [First embodiment] (Configuration of cellular communication system) An example configuration of a cellular communication system according to one embodiment will be described. A 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 partially to the cellular communication system 1. Furthermore, future cellular communication systems such as 6G may also be applied to the cellular communication system 1.

[0010] FIG. 1 is a diagram showing an example of the configuration of a cellular communication system 1 according to an embodiment.

[0011] 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.

[0012] 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).

[0013] 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.

[0014] 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.

[0015] 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.

[0016] 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.

[0017] 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.

[0018] 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).

[0019] 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.

[0020] 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 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.

[0021] FIG. 2 is a diagram showing an example of the relationship between the IAB node 300, parent nodes, and child nodes.

[0022] 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.

[0023] 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.

[0024] 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.

[0025] Furthermore, all IAB nodes 300 connected to the donor node 200 via one or more hops form a directed acyclic graph (DAG) topology (hereinafter sometimes referred to as "topology") with the donor node 200 as the root. In this topology, as shown in 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.

[0026] (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.

[0027] 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.

[0028] 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.

[0029] 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.

[0030] (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.

[0031] 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.

[0032] 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.

[0033] The control unit 320 performs various controls in the IAB node 300. The control unit 320 includes at least one memory and at least one processor electrically connected to the memory. The memory stores programs executed by the processor and information used 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.

[0034] (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.

[0035] 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.

[0036] The control unit 120 performs various controls in the UE 100. The control unit 120 includes at least one memory and at least one processor electrically connected to the memory. The memory stores programs executed by the processor and information used 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.

[0037] (Protocol Stack Configuration) Next, a description will be given of the configuration of a protocol stack according to the embodiment. Fig. 6 is a diagram showing an example of a protocol stack related to an IAB-MT RRC connection and a NAS connection.

[0038] 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.

[0039] 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.

[0040] 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.

[0041] 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.

[0042] 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.

[0043] 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.

[0044] 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.

[0045] 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.

[0046] 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.

[0047] 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.

[0048] 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.

[0049] 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."

[0050] 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.

[0051] (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).

[0052] 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.

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

[0054] 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.

[0055] In the following, the terms "migration" of a mobile IAB node and "handover" of a mobile IAB node may be used interchangeably.

[0056] In the following description, a mobile IAB node may be referred to as a "mobile IAB node." The mobile IAB node may also be referred to as a "migrating IAB node." In either case, the mobile IAB node may also be referred to as a mobile IAB node. The mobile IAB node may also be a mobile relay node.

[0057] (Handover According to First Embodiment) One of the mobility controls of the UE 100 in the RRC connected state is handover. The handover is, for example, a technique in which the UE 100 switches the cell to which it is connected. By the handover, for example, the UE 100 can connect to a cell with good wireless quality and receive the provision of a service.

[0058] The UE 100 measures the radio quality between the cell in accordance with the measurement configuration (MeasConfig) received from the gNB 200. The measurement configuration includes configuration information for the UE 100 to perform measurement processing and transmit a measurement report (MeasurementReport) to the gNB 200. The measurement configuration is transmitted from the gNB 200 to the UE 100 using dedicated signaling (an RRC message such as an RRCReconfiguration message or an RRCResume message).

[0059] The measurement configuration includes a measurement object (MeasObject), a report configuration (ReportConfig), a measurement ID (MeasID), and a measurement gap (MeasGap).

[0060] The measurement object may include information for identifying the measurement object. Specifically, the measurement object may include information indicating whether the measurement object is a synchronization signal block (SSB), a channel state information reference signal (CSI-RS), or both a synchronization signal block and a channel state information reference signal. Alternatively, the measurement object may include the frequency of the synchronization signal block (SSB) to be measured, or the frequency of the channel state information reference signal to be measured. Alternatively, the measurement object may include information indicating the frequency and time position of the measurement object. Alternatively, the measurement object may include a list of cells to be measured (whitelist) and / or a list of cells not to be measured (blacklist).

[0061] The reporting configuration includes information for specifying criteria for triggering a measurement report. Specifically, the reporting configuration may include information such as a reporting interval when the measurement report is performed periodically. Alternatively, the reporting configuration may include information regarding each event when the measurement report is performed based on an event trigger (e.g., each event, and a threshold, offset value, and / or hysteresis value used for each event). Examples of events include a serving cell becoming better than a threshold (event A1), a serving cell becoming worse than a threshold (event A2), a neighboring cell becoming better than the serving cell by an offset (event A3), a neighboring cell becoming better than a threshold (event A4), and a serving cell becoming worse than a first threshold and a neighboring cell becoming better than a second threshold (event A5). Alternatively, the reporting configuration may include information indicating whether the measurement quality (reception quality) is to be measured using Reference Signal Received Power (RSRP), Reference Signal Received Quality (RSRQ), or Signal to Interference plus Noise Ratio (SINR).

[0062] The measurement ID is used to identify the configuration information (MeasurementConfig) and links the measurement target with the measurement report.

[0063] The measurement gap includes information for setting a period (measurement gap) during which measurement is performed in the UE 100.

[0064] The UE 100 that has received the measurement configuration measures the reception quality of the cell according to the measurement configuration. The UE 100 may measure at least one beam of the cell and average the measurement results to measure the reception quality. The UE 100 transmits a measurement report including the reception quality as a measurement result (MeasResults) to the gNB 200 according to the measurement configuration.

[0065] Based on the reception quality, gNB200 decides to perform handover (Handover Decision). When gNB200 decides to perform handover, it transmits to UE100 an RRC message (e.g., an RRC reconfiguration message) (or a handover command) including information necessary for accessing the target cell. By receiving the RRC message, UE100 understands that handover is possible, and can start connection to the target cell using the information included in the RRC message.

[0066] (Communication Control Method According to First Embodiment) FIG. 9 is a diagram illustrating an example of a use case according to the first embodiment.

[0067] As shown in Figure 9, gNB200 is a fixed base station that does not move. gNB200 manages (or accommodates) macrocell 200S. Hereinafter, gNB200 and macrocell 200S may be used interchangeably. UE100 is in an RRC connected state with macrocell 200S.

[0068] For example, assume the following situation: UE 100 is on a moving vehicle such as a train or a bus. The moving vehicle is provided with a mobile IAB node 300M. The mobile IAB node 300M has a cell that it manages (or accommodates). This cell may be referred to as a mobile IAB cell (or mobile IAB cell 300S). Meanwhile, the macrocell 200S transmits a measurement configuration (MeasConfig) to the UE 100. The measurement configuration includes information about the mobile IAB cell 300S, such as the cell ID of the mobile IAB cell 300S and the frequency used by the mobile IAB cell 300S.

[0069] Under the above assumption, for example, the UE 100 can transmit a measurement report (Measurement Report) that targets the mobile IAB cell 300S by using information about the mobile IAB cell 300S included in the measurement configuration. This enables the UE 100 to perform handover to the mobile IAB cell 300S.

[0070] However, the mobile IAB cell 300S (and the mobile IAB node 300M) moves. The macrocell 200S does not know when the mobile IAB cell 300S will enter or leave the cell. Therefore, the mobile IAB cell 300S is not necessarily located in an area close to the macrocell 200S as shown in FIG. 9 . Even if the macrocell 200S transmits a measurement configuration (MeasConfig) including information about the mobile IAB cell 300S to the UE 100 even though the mobile IAB cell 300S is not located in an area close to the macrocell 200S, the measurement process for the mobile IAB cell 300S may be wasted in the UE 100, resulting in unnecessary power consumption. Furthermore, the resources used to transmit the measurement configuration (MeasConfig) may also be wasted.

[0071] On the other hand, even if the mobile IAB cell 300S is located in an area close to the macrocell 200S, for example, the UE 100 may be located at the side of a road or a railroad rather than being in a moving vehicle. In such a case, it may be considered that the UE 100 does not need to transmit a measurement report for the mobile IAB cell 300S.

[0072] Therefore, the first embodiment aims to enable the cell to transmit the measurement configuration to the UE 100 at an appropriate timing.

[0073] Therefore, in the first embodiment, first, the user equipment (e.g., UE 100) transmits a first connection desire notification indicating a desire to connect to the mobile IAB cell (e.g., mobile IAB cell 300S) to the base station (e.g., macro cell 200S). Second, in response to receiving the first connection desire notification, the base station transmits to the user equipment a first message including a measurement configuration (e.g., measurement configuration (MeasConfig)) that enables the user equipment to measure the mobile IAB cell.

[0074] In this way, by receiving the notification of desire to connect to the mobile IAB cell 300S, the macrocell 200S can confirm that the UE 100 desires to connect to the mobile IAB cell 300S. Therefore, for example, by transmitting the measurement configuration (MeasConfig) at the timing when the macrocell 200S confirms that the UE 100 desires to connect to the mobile IAB cell 300S, the measurement configuration is not transmitted to the UE 100 that does not desire to connect to the mobile IAB cell 300S, and the measurement configuration can be transmitted at an appropriate timing. Furthermore, the UE 100 can transmit a measurement report that targets the mobile IAB cell 300S as a measurement target in accordance with the measurement configuration (MeasConfig), and therefore handover to the mobile IAB cell 300S is also possible.

[0075] In addition, in the current 3GPP specifications, there is a technology called "proximity indication" (for example, 3GPP TS36.300 V17.5.0 and 3GPP TS36.331 V17.5.0). The proximity indication is a technology in which, when UE 100 in an RRC connected state detects proximity to a CSG member cell (including a HeNB (Home evolved Node B)) using an autonomous search procedure, it transmits a proximity indication to the serving cell, thereby receiving a measurement configuration (Measurement Config) from the serving cell. With this measurement configuration, UE 100 can transmit a measurement report targeting the CSG member cell, and handover to the CSG member cell becomes possible.

[0076] However, the CSG member cell is assumed to be a fixed cell, and is not intended for the mobile IAB cell 300S. Therefore, if a proximity instruction is used when the distance to the mobile IAB cell 300S is the same between a UE 100 on a moving vehicle and a UE 100 beside a railroad track, the UE 100 beside a railroad track will also transmit a measurement report for the mobile IAB cell 300S based on the measurement setting received from the macro cell 200S. Therefore, the measurement process for the mobile IAB cell 300S in the UE 100 may be wasted.

[0077] In this way, in the proximity instruction, even UE 100 that does not need to report a measurement report to the moving IAB cell 300S may receive measurement settings from the macrocell 200S, so it may not be said that the measurement settings are received from the macrocell 200S at the appropriate time.

[0078] (Example of Operation According to First Embodiment) Next, an example of operation according to the first embodiment will be described.

[0079] Fig. 10 is a diagram illustrating an example of operation according to the first embodiment. Before the example of operation illustrated in Fig. 10 is started, for example, the situation is assumed to be as illustrated in Fig. 9. That is, it is assumed that the UE 100 is connected to the macrocell 200S as a serving cell.

[0080] As shown in FIG. 10, in step S10, the UE 100 is in an RRC connected state with the macro cell 200S.

[0081] In step S11, the macrocell 200S may perform a transmission setting of a connection desire notification (e.g., a first connection desire notification) for the UE 100. Specifically, the macrocell 200S may transmit, to the UE 100, an RRC message (e.g., a second message) including information including a transmission setting of the connection desire notification (in the first embodiment, this may be referred to as “connection desire notification setting information” or first connection desire notification setting information).

[0082] First, the macrocell 200S may perform the setting for transmitting a connection request notification in response to the inflow of the mobile IAB cell 300S into its area. The macrocell 200S may perform the setting in response to receiving a message (e.g., an Xn message) including information indicating that the mobile IAB cell 300S has entered its own cell from a neighboring gNB (which may be, for example, a donor node (IAB-donor) of the mobile IAB node 300M). Alternatively, the macrocell 200S may perform the setting in response to receiving a message (e.g., an NG message) including information indicating that the mobile IAB cell 300S has entered its own cell from a core network device (e.g., the AMF 11).

[0083] Second, the connection desire notification setting information may include information about the mobile IAB cell 300S. The information about the mobile IAB cell 300S may be a cell ID of the mobile IAB cell 300S. Alternatively, the information about the mobile IAB cell 300S may be identification information used for access restriction in the mobile IAB cell 300S. The identification information may be any of a Closed Access Group ID (CAG ID), a Public Land Mobile Network ID (PLMN ID), a Public Network Integrated Non-Public Network (PNI-NPN ID), a Standalone Non-Public Network ID (SNPN ID), a Network Identifier (NID), and a Tracking Area Code (TAC). Note that, in subsequent step S13, the UE 100 may transmit a connection desire notification when it desires connection to the mobile IAB cell 300S that matches the information about the mobile IAB cell 300S.

[0084] The RRC message used in step S11 may be an RRC reconfiguration message.

[0085] In step S12, the UE 100 determines that it is possible to connect to the moving IAB cell 300S.

[0086] First, whether or not the UE 100 is connectable may be determined based on whether or not the UE 100 should camp on the mobile IAB cell 300S. When the AS of the UE 100 detects that the UE 100 has boarded a mobile vehicle based on information received from a higher layer, the AS of the UE 100 may determine that the UE 100 should camp on the mobile IAB cell 300S (i.e., determine that the UE 100 is connectable). Specifically, when the AS of the UE 100 receives information indicating that the UE 100 has boarded a train equipped with the mobile IAB cell 300S via the NAS by a specific application service (e.g., a fare payment system or application using NFC (Near Field Communication)), the AS may determine that the UE 100 should camp on the mobile IAB cell 300S (i.e., determine that the UE 100 is connectable). Alternatively, the AS of the UE 100 may determine that the UE 100 should camp on the mobile IAB cell 300S (i.e., determine that the UE 100 is connectable) when it detects that its own moving speed is equal to or greater than a predetermined speed. The AS of the UE 100 may acquire its own moving speed by using a speed sensor, etc. The predetermined speed may be set by an RRC message, etc. from the macrocell 200S.

[0087] Secondly, whether or not connection is possible may be determined based on whether or not the UE 100 detects a mobile IAB cell type indication (mIAB cell type indication or mIAB-cell indication). The mobile IAB cell type indication is, for example, an indication indicating that the UE itself is the mobile IAB cell 300S. The mobile IAB cell type indication is, for example, included in system information (for example, SIB1) broadcast from the mobile IAB cell 300S. The UE 100 may determine that connection to the mobile IAB cell 300S is possible by continuing to detect the mobile IAB cell type indication for a certain period of time or more. The UE 100 may set the certain period of time by receiving an RRC message (for example, an RRC reconfiguration message) including the certain period of time from the macro cell 200S.

[0088] Whether or not connection is possible may be determined depending on the implementation of UE 100.

[0089] In step S13, when the UE 100 determines that connection to the moving IAB cell 300S is possible, the UE 100 transmits a connection desire notification (for example, a first connection desire notification) to the macro cell 200S.

[0090] First, the determination that the connection is possible may be that the connection is possible in the determination of step S12. Alternatively, the determination that the connection is possible may be that the UE 100 is determined to be connected to the moving IAB cell 300S. The AS of the UE 100 may determine that the connection should be made by receiving a notification from a higher layer that the UE 100 should be connected to the moving IAB cell 300S.

[0091] Second, the connection desire notification may be a notification that the UE 100 desires a measurement configuration including the frequency used by the mobile IAB cell 300S and / or the cell ID of the mobile IAB cell 300S. Alternatively, the connection desire notification may be a notification that the UE 100 desires a handover to the frequency used by the mobile IAB cell 300S and / or a notification that the UE 100 desires a handover to the mobile IAB cell 300S. Alternatively, the connection desire notification may be a notification that the UE 100 is located near the mobile IAB cell 300S. Alternatively, the connection desire notification may be a notification that the UE 100 is on-boarding a moving vehicle. Alternatively, the connection desire notification may be a notification that the UE 100 desires a measurement configuration that enables the UE 100 to measure the mobile IAB cell 300S (or the frequency used by the mobile IAB cell 300S).

[0092] Third, the connection desire notification may include at least one of the frequency used by the mobile IAB cell 300S, the cell ID of the mobile IAB cell 300S, and identification information used for access restriction in the mobile IAB cell 300S. The UE 100 may transmit a connection desire notification including at least one of the frequency, the cell ID, and the identification information by using at least one of the frequency, the cell ID, and the identification information included in the connection desire notification setting information received in step S11. Alternatively, the connection desire notification may include location information of the UE 100. If the macrocell 200S knows the location of the mobile IAB cell 300S, it may select an appropriate mobile IAB cell 300S based on the location information acquired from the UE 100 and transmit to the UE 100 a measurement configuration that enables the mobile IAB cell 300S to be the measurement target. The UE 100 may acquire location information using a GNSS receiver. The UE 100 may acquire location information based on a PRS (Positioning Reference Signal) received from the macrocell 200S.

[0093] The UE 100 may transmit an RRC message including a connection desire notification. The UE 100 may transmit a MAC control element (MAC CE) including the connection desire notification. The UE 100 may transmit a downlink control signal (DCI) including the connection desire notification. The UE 100 may also receive connection desire notification setting information (step S11) and transmit a connection desire notification according to the setting information.

[0094] In step S14, in response to receiving the connection desire notification, the macrocell 200S transmits an RRC message (e.g., a first message) including a measurement configuration (MeasConfig) to the UE 100. The measurement configuration includes, for example, the frequency of the moving IAB cell 300S and / or the cell ID of the moving IAB cell 300S. The measurement configuration can be, for example, a measurement configuration that allows the UE 100 to measure the moving IAB cell 300S. Instead of transmitting an RRC message including the measurement configuration, the macrocell 200S may transmit an RRC message (e.g., an RRC reconfiguration message) indicating a handover command to the UE 100. The RRC message includes information necessary for the UE 100 to access the moving IAB cell 300S, and the UE 100 can hand over (or connect) to the moving IAB cell 300S based on the information.

[0095] After receiving the measurement configuration, the UE 100 performs measurement processing on the moving IAB cell 300S in accordance with the measurement configuration and transmits the measurement result as a measurement report to the macro cell 200S. Upon receiving the measurement report, the macro cell 200S decides to perform handover and transmits an RRC reconfiguration message (or handover command) to the UE 100. The UE 100 starts a connection to the moving IAB cell 300S by using information included in the RRC reconfiguration message.

[0096] Second Embodiment Next, a second embodiment will be described, focusing on the differences from the first embodiment.

[0097] In the first embodiment, an example has been described in which the UE 100 transmits a connection desire notification to the macro cell 200S, the macro cell 200S transmits a message including measurement configuration to the UE 100, and the UE 100 performs handover from the macro cell 200S to the mobile IAB cell 300S. In the second embodiment, an example will be described in which the UE 100 transmits a connection desire notification to the mobile IAB cell 300S, the mobile IAB cell 300S transmits a message including measurement configuration, and the UE 100 performs handover from the mobile IAB cell 300S to the macro cell 200S.

[0098] Specifically, first, the user equipment (e.g., UE 100) transmits a second connection desire notification indicating a desire to connect to a base station (e.g., macro cell 200S) to the mobile IAB cell (e.g., mobile IAB cell 300S). Second, in response to receiving the second connection desire notification, the mobile IAB cell transmits to the user equipment a third message (e.g., RRC message) including a measurement configuration (e.g., measurement configuration (MeasConfig)) that allows the user equipment to measure the base station.

[0099] As a result, for example, the mobile IAB cell 300S can transmit the measurement configuration to the UE 100 in response to receiving a connection desire notification from the UE 100, and therefore can transmit the measurement configuration to the UE 100 at the timing when it is confirmed that the UE 100 desires to connect to the macro cell 200S. Therefore, the mobile IAB cell 300S can transmit the measurement configuration to the UE 100 at an appropriate timing.

[0100] (Operation example according to the second embodiment) Fig. 11 is a diagram showing an operation example shown in the first embodiment. The operation example shown in Fig. 11 may be performed after the operation example (first embodiment) shown in Fig. 10 is performed.

[0101] As shown in FIG. 11, in step S20, UE 100 is in an RRC connected state with respect to moving IAB cell 300S.

[0102] In step S21, the mobile IAB cell 300S may perform transmission setting of a connection desire notification (e.g., a second connection desire notification) to the UE 100. Specifically, the mobile IAB cell 300S may transmit an RRC message (e.g., a fourth message) including information including transmission setting of the connection desire notification (in the second embodiment, this may be referred to as "connection desire notification setting information" or second connection desire notification setting information) to the UE 100. The connection desire notification setting information may include the cell ID of the macro cell 200S, or may include identification information (such as a CAG ID) used for access restriction in the macro cell 200S.

[0103] In step S22, the UE 100 determines that it can connect to the macrocell 200S. For example, the AS of the UE 100 may determine that it can connect to the macrocell 200S when it detects that the UE 100 has dismounted from a mobile vehicle based on information received from a higher layer. Specifically, the AS of the UE 100 may determine that it can connect to the macrocell 200S when it receives information indicating that the UE 100 has dismounted from a train equipped with the mobile IAB cell 300S via the NAS using a specific application service (e.g., a fare payment system or application using NFC). Alternatively, the AS of the UE 100 may determine that it can connect to the macrocell 200S when it detects that its own moving speed is less than a predetermined speed. The predetermined speed may be set by an RRC message or the like from the mobile IAB cell 300S. Note that whether or not it can connect may be determined depending on the implementation of the UE 100, as in the first embodiment.

[0104] In step S23, when the UE 100 determines that connection to the macro cell 200S is possible, the UE 100 transmits a connection desire notification (for example, a second connection desire notification) to the moving IAB cell 300S.

[0105] First, the determination that the connection is possible may be that the connection is possible in the determination of step S22. Alternatively, the determination that the connection is possible may be that the UE 100 is determined to be connected to the macrocell 200S. The AS of the UE 100 may determine that the UE 100 should be connected to the macrocell 200S by receiving a notification from a higher layer that the UE 100 should be connected to the macrocell 200S.

[0106] Second, the connection desire notification may be a notification that the UE 100 desires a measurement configuration including a frequency used in the macrocell 200S and / or a cell ID of the macrocell 200S. Alternatively, the connection desire notification may be a notification that the UE 100 desires a handover to a frequency used in the macrocell 200S and / or a notification that the UE 100 desires a handover to the macrocell 200S. Alternatively, the connection desire notification may be a notification that the UE 100 is located near the moving IAB cell 300S. Alternatively, the connection desire notification may be a notification that the UE 100 has gotten off-boarding from a moving vehicle. Alternatively, the connection desire notification may be a notification that the UE 100 desires a measurement configuration that enables the UE 100 to measure the macrocell 200S (or a frequency used in the macrocell 200S).

[0107] Third, the connection desire notification may include at least one of a frequency used in the macrocell 200S, a cell ID of the macrocell 200S, and identification information used for access restriction in the macrocell 200S. The UE 100 may transmit a connection desire notification including at least one of the frequency, the cell ID, and the identification information by using at least one of the frequency, the cell ID, and the identification information included in the connection desire notification setting information received in step S21. Alternatively, the connection desire notification may include location information of the UE 100.

[0108] The UE 100 may transmit an RRC message including a connection desire notification. The UE 100 may transmit a MAC control element (MAC CE) including the connection desire notification. The UE 100 may transmit a downlink control signal (DCI) including the connection desire notification. The UE 100 may also receive connection desire notification setting information (step S21) and transmit a connection desire notification according to the setting information.

[0109] In step S24, in response to receiving the connection desire notification, the moving IAB cell 300S transmits an RRC message (e.g., a third message) including a measurement configuration (MeasConfig) to the UE 100. The measurement configuration may be, for example, a measurement configuration that allows the UE 100 to measure the macro cell 200S. Instead of transmitting the RRC message including the measurement configuration, the moving IAB cell 300S may transmit an RRC message (e.g., an RRC reconfiguration message) indicating a handover command to the UE 100. The RRC message includes information necessary for the UE 100 to access the macro cell 200S, and the UE 100 can perform handover (or connection) to the macro cell 200S based on the information.

[0110] After receiving the measurement configuration, the UE 100 performs measurement processing for the macro cell 200S in accordance with the measurement configuration and transmits the measurement result as a measurement report to the moving IAB cell 300S. The moving IAB cell 300S determines to perform handover based on the measurement report and transmits an RRC reconfiguration message (or handover command) to the UE 100. The UE 100 starts a connection to the macro cell 200S by using information included in the RRC reconfiguration message.

[0111] [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.

[0112] 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.

[0113] 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.

[0114] A program may be provided that causes a computer to execute each process performed by the UE 100, the gNB 200, or the mobile IAB node 300M. The program may be recorded on a computer-readable medium. Using a computer-readable medium, the program can be installed on a computer. Here, the computer-readable medium on which the program is recorded may be a non-transitory recording medium. The non-transitory recording medium is not particularly limited, and may be, for example, a recording medium such as a CD-ROM or a DVD-ROM. Furthermore, circuits that execute each process performed by the UE 100 or the gNB 200 may be integrated, and at least a portion of the UE 100, the gNB 200, or the mobile IAB node 300M may be configured as a semiconductor integrated circuit (chip set, SoC: System on a chip).

[0115] The functions performed by the UE 100, the gNB 200, or the mobile IAB node 300M 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.

[0116] 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.

[0117] 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.

[0118] This application claims priority from Japanese Patent Application No. 2023-130079 (filed August 9, 2023), the entire contents of which are incorporated herein by reference.

[0119] (Supplementary Note) (Supplementary Note 1) A communication control method used in a cellular communication system, comprising: a step in which a user equipment transmits to a base station a first connection desire notification indicating a desire to connect to a mobile IAB cell; and a step in which the base station, in response to receiving the first connection desire notification, transmits to the user equipment a first message including a measurement configuration that enables the user equipment to measure the mobile IAB cell.

[0120] (Supplementary Note 2) The communication control method according to Supplementary Note 1, further comprising the steps of: the base station transmitting to the user equipment a second message including first connection desire notification setting information indicating setting information for transmitting the first connection desire notification; and the user equipment receiving the second message, wherein the step of transmitting the first connection desire notification includes the user equipment transmitting the first connection desire notification in accordance with the first connection desire notification setting information.

[0121] (Supplementary Note 3) The communication control method according to Supplementary Note 1 or Supplementary Note 2, wherein the step of transmitting the first connection desire notification includes a step of transmitting the first connection desire notification when the user equipment determines that connection to the mobile IAB cell is possible.

[0122] (Supplementary Note 4) The communication control method according to any one of Supplementary Note 1 to Supplementary Note 3, wherein the first connection request notification includes at least one of a frequency used in the mobile IAB cell, a cell ID of the mobile IAB cell, and identification information used for access restriction in the mobile IAB cell.

[0123] (Supplementary Note 5) A communication control method used in a cellular communication system, comprising: a step in which a user equipment transmits a second connection desire notification to a mobile IAB cell, the second connection desire notification indicating a desire to connect to a base station; and a step in which the mobile IAB cell, in response to receiving the second connection desire notification, transmits a third message to the user equipment, the third message including a measurement configuration that enables the user equipment to target the base station for measurement.

[0124] (Supplementary Note 6) The communication control method according to any one of Supplementary Notes 1 to 5, further comprising: a step in which the mobile IAB cell transmits to the user equipment a fourth message including second connection desire notification setting information indicating setting information for transmitting the second connection desire notification; and a step in which the user equipment receives the fourth message, wherein the step of transmitting the second connection desire notification includes a step in which the user equipment transmits the second connection desire notification in accordance with the second connection desire notification setting information.

[0125] (Supplementary Note 7) The communication control method according to any one of Supplementary Notes 1 to 6, wherein the step of transmitting the second connection desire notification includes a step of transmitting the second connection desire notification when the user equipment determines that connection to the base station is possible.

[0126] (Supplementary Note 8) The communication control method according to any one of Supplementary Note 1 to Supplementary Note 5, wherein the second connection request notification includes at least one of a frequency used by the base station, a cell ID of the base station, and identification information used for access restriction in the base station.

[0127] 1: Mobile communication system 10: 5GC (CN) 100: UE 110: Wireless communication unit 111: Receiving unit 112: Transmitting unit 120: Control unit 200: gNB, donor node, base station 210: Wireless communication unit 211: Receiving unit 212: Transmitting unit 220: Network communication unit 230: Control unit 200S: Macro cell 300: IAB node (relay node) 310: Wireless communication unit 311: Receiving unit 312: Transmitting unit 320: Control unit 300M: Mobile IAB node (mobile relay node) 300S: Mobile IAB cell

Claims

1. A communication control method used in a cellular communication system, The user device sends a first connection request notification to the network node indicating a desire to connect to a cell of the mobile relay node, The network node, upon receiving the first connection request notification, transmits a first message to the user device, which includes measurement settings that enable the user device to measure the cell. Communication control method.

2. The network node sends a second message to the user device, which includes first connection request notification setting information indicating setting information for sending the first connection request notification. The user device further includes receiving the second message, Sending the first connection request notification includes the user device sending the first connection request notification in accordance with the first connection request notification setting information. The communication control method according to claim 1.

3. Sending the first connection request notification includes sending the first connection request notification when the user device determines that it is possible to connect to the cell. The communication control method according to claim 1.

4. The first connection request notification includes at least one of the frequency used in the cell, the cell ID of the cell, and identification information used for access control in the cell. The communication control method according to claim 1.

5. A communication control method used in a cellular communication system, The user device sends a second connection request notification to the mobile relay node cell indicating a desire to connect to a network node, The cell, upon receiving the second connection request notification, sends a third message to the user device, which includes measurement settings that enable the user device to measure the network node. Communication control method.

6. The cell sends a fourth message to the user device, which includes second connection request notification setting information indicating setting information for sending the second connection request notification. The user device further includes receiving the fourth message, Sending the second connection request notification includes the user device sending the second connection request notification in accordance with the second connection request notification setting information. The communication control method according to claim 5.

7. Sending the second connection request notification includes sending the second connection request notification when the user device determines that it is possible to connect to the network node. The communication control method according to claim 5.

8. The second connection request notification includes at least one of the frequency used by the network node, the cell ID of the network node, and identification information used for access control at the network node. The communication control method according to claim 5.

9. A user device, A transmitting unit that sends a first connection request notification to a network node indicating a desire to connect to a cell of a mobile relay node, The user device includes a receiving unit that receives a first message from the network node, which includes a measurement setting that allows the cell to be the target of measurement. User device.

10. A network node, A receiving unit that receives a first connection request notification from the user device indicating a desire to connect to a cell of a mobile relay node, The system includes a transmitting unit that, upon receiving the first connection request notification, transmits a first message to the user device, which includes measurement settings that enable the user device to measure the cell. Network node.

11. A user device, A transmission unit that sends a second connection request notification indicating a desire to connect to a network node to the cell of a mobile relay node, The system includes a receiving unit that receives a third message from the cell of the mobile relay node, which includes a measurement setting that allows the network node to be the measurement target. User device.

12. A mobile relay node, A receiving unit that receives a second connection request notification from the user device indicating a desire to connect to a network node, The system includes a transmitting unit that, upon receiving the second connection request notification, transmits a third message to the user device, which includes measurement settings that enable the user device to target the network node for measurement. Mobile relay node.