Communication device, control method, and program

Abstract

Disclosed is a communication device operable as an Integrated Access and Backhaul (IAB) donor and characterized by having: an evaluation means for evaluating possibility of disconnection related to a second communication device in a first situation where a second communication device connected to the own device via a first communication device exists or in a second situation where a second communication device directly connected to the own device exists; a first acquisition means for acquiring the base station type of one or more base stations to which the second communication device can be connected; a means for allocating an secondary node (SN) to the second communication device; and a selection means for selecting one base station as SN from among the one or more base stations on the basis of the evaluation result by the evaluation means and the base station type of the one or more base stations.

Description

Communication device, control method, and program

[0001] The present disclosure relates to a communication device, a control method, and a program.

[0002] In the 3GPP (3rd Generation Partnership Project), standardization of IAB (Integrated Access and Backhaul) as a communication technology for backhaul is progressing.

[0003] The IAB technology is a technology that simultaneously uses millimeter-wave wireless communication in the 28 GHz band or the like, which is used for access communication between a base station and user equipment (UE), as backhaul communication (Patent Document 1).

[0004] In backhaul communications using IAB technology, relay devices called IAB nodes relay communications from IAB donors, which are base stations, via millimeter wave communications.

[0005] By using IAB technology, it is possible to expand area coverage at a lower cost than conventional wired communications using optical fiber, etc.

[0006] Up until now, 3GPP (registered trademark) has been formulating specifications for fixed base stations (IAB nodes that do not move) up to Rel-17.

[0007] Currently, 3GPP is planning to actively discuss Vehicle Mounted Relay, a use case in the next Rel-18, and MBSR, a specification to realize this use case. MBSR is an abbreviation for Mobile Base Station Relay. For example, the discussion item "Mobile Base Station Relay Authorization and Configuration" assumes the following: In urban environments or during large-scale events in designated areas, MBSRs temporarily installed in vehicles are expected to function as relays and provide services to UEs to achieve special coverage and connectivity. Vehicle-mounted MBSRs can provide services while moving, which is likely to create various requirements that cannot be met by specifications based on fixed base stations that have been discussed so far.

[0008] 3GPP has also standardized a technology called Dual Connectivity (DC). In DC, a UE simultaneously connects to two base stations called a Master Node (MN) and a Secondary Node (SN). The UE then communicates using component carriers supported by the two base stations. This enables faster communication and increased connection redundancy.

[0009] Special Publication No. 2019-534625

[0010] As MBSR becomes more widespread and widely used, it is expected that UEs will increasingly connect to MBSRs rather than fixed base stations, especially outdoors in urban areas. A UE connects to the nearby base station with the best signal quality. A nearby MBSR has better signal quality than a distant fixed base station, so the UE connects to the MBSR. However, unlike conventional fixed base stations, MBSRs are mobile, so the connection to the MBSR is more likely to be disconnected than to a fixed base station. One method for improving connection redundancy is to assign an SN to the UE and establish a connection via DC. However, if the assigned SN is an MBSR, the connection to the SN is also more likely to be disconnected, and connection redundancy does not improve significantly. The MN is responsible for selecting the SN, and a base station with good signal quality with the UE is generally assigned. The signal quality with the UE is notified by the UE via a Measurement Report. Therefore, if an MBSR is present in the vicinity of the UE, the MBSR with good signal quality will be selected as the SN.

[0011] The present invention has been made in consideration of at least one of the above-described problems, and an object of one aspect of the present invention is to provide a mechanism that can realize a DC connection in a manner that makes it easier to maintain a stable connection.

[0012] A communication device according to one aspect of the present invention is a communication device operable as an IAB (Integrated Access and Backhaul) donor, and is characterized by having: evaluation means for evaluating the possibility of disconnection of a second communication device in a first situation in which a second communication device exists that connects to the communication device via a first communication device; first acquisition means for acquiring base station types of one or more base stations to which the second communication device can connect; means for assigning an SN (Secondary Node) to the second communication device; and selection means for selecting one base station as the SN from among the one or more base stations based on the evaluation result by the evaluation means and the base station types of the one or more base stations.

[0013] According to one aspect of the present invention, it is possible to provide a mechanism that can realize a DC connection in a manner that makes it easier to maintain a stable connection.

[0014] FIG. 1 is a hardware block diagram constituting an IAB node; FIG. 2 is a software function block diagram of an IAB node; FIG. 3 is a configuration example of a communication system in the first embodiment; FIG. 4 is a configuration example of a communication system in the first embodiment; FIG. 5 is a data format in the first embodiment; FIG. 6 is a sequence diagram of an SN addition process in the first embodiment; and FIG. 7 is a flow diagram of an SN addition process of an IAB donor in the first embodiment.

[0015] Hereinafter, each embodiment will be described in detail with reference to the accompanying drawings. In the following description, the "number ***" in TS*** represents the number of the technical specification in the 3GPP standard.

[0016] [First Embodiment] A communication device according to this embodiment will be described in detail below with reference to the drawings. Note that the technical scope of the present invention is determined by the claims and is not limited to the individual embodiments described below.

[0017] FIG. 1 is a block diagram showing an example of the hardware configuration of an IAB donor according to this embodiment.

[0018] The entire device is designated by 101. A control unit 102 controls the entire device by executing a control program stored in a storage unit 103.

[0019] Reference numeral 103 denotes a storage unit that stores a control program executed by the control unit 102 and various information such as cell information, connected terminal information, IAB routing information, and location information.

[0020] The various operations described below are performed by the control unit 102 executing a control program stored in the storage unit 103.

[0021] Reference numeral 104 denotes a wireless communication unit for performing cellular network communication such as LTE or 5G conforming to the 3GPP standard. Note that, although the cellular network communication performed by the wireless communication unit is described here as being 5G, it is also applicable to cellular network communication other than 5G (for example, 5G Advanced, 6G, etc.).

[0022] Reference numeral 105 denotes a communication antenna control unit that controls an antenna for wireless communication performed by the wireless communication unit 104 .

[0023] FIG. 2 is a block diagram showing an example of the configuration of software function blocks of an IAB donor that executes communication control functions.

[0024] 201 indicates the entire software function block.

[0025] Reference numeral 202 denotes a signal transmitting unit, and 203 denotes a signal receiving unit, which perform cellular network communication such as LTE or 5G compliant with the 3GPP standard with a terminal device.

[0026] Reference numeral 204 denotes a data storage unit that stores and holds the software itself, IAB routing information, information on connected terminals, location information, movement route information, and the like.

[0027] Reference numeral 205 denotes a connection control unit that controls an antenna for wireless communication performed by the wireless communication unit 104 .

[0028] Reference numeral 206 denotes a connection strength evaluation unit that evaluates the connection strength of subordinate communication devices.

[0029] 207 is an SN selection method determination unit that determines a method for selecting an SN to be assigned to a subordinate communication device.

[0030] 208 is an SN selection unit that selects an SN to be assigned to a subordinate communication device.

[0031] 209 is a message detection unit that detects messages such as RRC messages and broadcast information from surrounding IAB nodes, UEs, and IAB donors.

[0032] 210 is a message generation unit that generates messages such as RRC messages and broadcast information to be transmitted to neighboring IAB nodes, UEs, and IAB donors.

[0033] 3A and 3B show an example of the configuration of a communication system according to this embodiment.

[0034] Figure 3A shows an example in which the UE's connection strength is low. MBSR1 (302) is connected to IAB donor 1 (301), and UE (302) is connected to MBSR1 (302). IAB donor 2 (304) and MBSR2 (305) are located around UE (303), and the UE (303) can detect radio waves from each of them. MBSR1 (302) is moving. Note that MBSRs are sometimes called mobile IAB nodes.

[0035] The general flow of how IAB Donor 1 (301) allocates an SN to a UE (303) will be explained using FIG. 3A.

[0036] First, the IAB Donor 1 (301) evaluates the connection strength of the UE (303) based on the mobility information of the UE (303) and its parent node, the MBSR1 (302).

[0037] Mobility information is information about the movement of a communication device, such as location information, movement speed, movement direction, status (stopped, moving), stop time, and scheduled stop time. The IAB donor 1 (301) calculates the relative position change between the UE (303) and the MBSR1 (302) from the mobility information of the two devices and evaluates the connection strength from the expected change in radio wave quality. The mobility information is notified to the IAB donor from the UE (303) and the MBSR1 (302). RRC (Radio Resource Control) messages are used for notification. The RRC message is a Layer 3 protocol of the CP (Control Plane) for controlling wireless communication between a base station and a communication device. The mobility information can be notified by defining a new RRC message, or it can be notified by being included in an existing RRC message. For example, it can be notified by being included in a Measurement Report. The Measurement Report is a list summarizing the radio wave qualities of surrounding base stations (neighboring cells) detected by the UE (303) and MBSR1 (302), and is notified to the IAB donor periodically or when a specific condition is triggered. An example of the data format of the Measurement Report (401) including mobility information is shown in Figure 4. Details will be described later.

[0038] In the case of FIG. 3A, the MBSR1 (302) is moving, so the connection strength of the UE (303) is evaluated as low.

[0039] Next, the IAB donor 1 (301) determines a method for selecting an SN to be assigned to the UE (303). The method for selecting an SN is determined according to the connection strength of the UE (303). When the connection strength is high, the possibility of disconnection from the parent node (MBSR1 (302)) is low, so the criterion for selecting an SN is radio wave quality as before. When the connection strength is low, the possibility of disconnection from the parent node (MBSR1 (302)) is high, so the criterion for selecting an SN is the type of base station, not radio wave strength. Examples of types include gNB, IAB donor, IAB node, and MBSR. By selecting a base station whose type is a fixed base station (gNB, IAB donor, IAB node) as the SN, it is possible to select an SN that is less likely to be disconnected. gNB stands for next generation NodeB. MBSR is also called mIAB node (mobile IAB node).

[0040] In the case of FIG. 3A, the connection strength of the UE (303) is evaluated as low, so the SN is selected based on the type of base station.

[0041] Each base station broadcasts the type of base station by including it in a broadcast signal. A possible broadcast signal to be used is SIB1 (System Information Block type 1). The IAB donor 1 (301) may manage the types of surrounding base stations from the SIB1 received directly. However, it is possible that the base stations from which the UE (303) and the IAB donor 1 (301) can receive SIB1 may differ due to obstructions, positional relationships, etc. Therefore, the UE (303) notifies the IAB node 1 (301) of type information summarizing the types of surrounding base stations received. An RRC message is used for the notification. A new RRC message can be defined for notification, or the information may be included in an existing RRC message for notification. For example, the information may be included in a Measurement Report for notification. Since the Measurement Report summarizes information on radio wave quality for each base station, type information is added to it. An example of the data format of the Measurement Report including type information is shown in Fig. 4. Details will be described later.

[0042] In the case of Figure 3A, IAB Donor 2 (304) and MBSR 2 (305) exist around UE (303). The UE includes type information received from each base station in a Measurement Report and notifies IAB Donor 1 (301). The type of IAB Donor 2 is "IAB Donor" and the type of MBSR 2 (305) is "MBSR".

[0043] Finally, the IAB donor 1 (301) checks the type information received from the UE (303) and selects an SN according to the type. The type of base station selected as the SN is a type that is unlikely to disconnect from the UE. Specifically, it is selected from "gNB", "IAB donor", and "IAB node". Even if the type is "MBSR", the IAB donor 1 (301) may determine that there is a low possibility of disconnection if it determines that there is a low possibility of movement based on the mobility information.

[0044] In the case of FIG. 3A, IAB donor 2 (304), which is of the type "IAB donor" that is less likely to cleave, is selected as the SN.

[0045] After the SN is selected, the SN is added according to the SN addition sequence standardized by 3GPP, and the UE connects to the SN. The SN addition sequence is standardized in TS37.340 (10.2).

[0046] Figure 3B shows an example where the UE has a high connection strength. The only difference from Figure 3A is that the UE (303) is directly connected to IAB Donor 1 (301), and the rest is the same.

[0047] First, the IAB donor 1 (301) evaluates the connection strength of the UE (303) based on the mobility information of the UE (303) and the IAB donor 1 (301) which is the parent node.

[0048] In the case of FIG. 3B, IAB Donor 1 (301) is not mobile, and therefore the strength of the connection with the UE is evaluated as high.

[0049] Next, the IAB Donor 1 (301) decides how to select the SN to assign to the UE (303).

[0050] In the case of Fig. 3B, since the connection strength of the UE (303) is evaluated as high, the SN is selected based on the radio wave quality of the base station, which is notified from the UE (303) in a Measurement Report.

[0051] Finally, the IAB donor 1 (301) checks the radio wave quality received from the UE (303) and selects an SN according to the radio wave quality. The selected SN is a base station with good radio wave quality.

[0052] In the case of FIG. 3B, MBSR2 (305) close to UE (303) has good radio wave quality and is selected as SN.

[0053] In this way, in this embodiment, when the UE is connected to a base station that is likely to be disconnected, the fixed base station is preferentially selected as the SN over the MBSR. Conversely, when the UE is connected to a base station that is unlikely to be disconnected, the MBSR with good communication quality is preferentially selected as the SN.

[0054] After selecting the SN, the SN is added according to the SN addition sequence standardized by 3GPP, and the UE connects to the SN. The SN addition sequence is standardized in TS37.340 (10.2).

[0055] FIG. 4 shows an example of the data format of a Measurement Report in this embodiment.

[0056] In addition to the conventional information about the radio wave quality of surrounding base stations, MeasResults 402, the Measurement Report 401 also includes mobility information MobilityInfo 409. MobilityInfo 409 includes information about the movement of the communication device itself, such as location information, movement speed, movement direction, status (status indicating whether the device is stopped or moving), stop time, and planned stop time.

[0057] MeasResults (402) includes MeasResultListNR (403), which is a list of information about the radio wave quality of neighboring cells. MeasResultListNR (403) includes information about the radio wave quality of neighboring cells, MeasResultNR (404) and (408). These are prepared for each base station detected by the communication device. MeasResultNR (404) includes an ID PhysCellID (405) that identifies the base station (cell), type information (406) added in this embodiment, and measResults (407), which is information about radio wave quality. The type information is set to any one of "gNB", "IAB donor", "IAB node", and "MBSR".

[0058] Next, the process up to the connection between the UE (303) and the SN will be explained using the sequence diagram of FIG.

[0059] 5 shows a sequence of an SN addition process in this embodiment based on a general SN addition process sequence in the 3GPP standard. It shows a sequence in the communication system of FIG. 3A. This embodiment mainly relates to SN addition during DC connection, but can also be applied to subsequent changes to an SN added during DC connection.

[0060] First, the IAB donor 2 (304) broadcasts SIB1 (S501). SIB1 includes type-related information. SIB1 is received by the UE (303) and the MBSR1 (302). The "type-related information" included in SIB1 is the same as the type information described in FIG. 4.

[0061] The MBSR2 (305) also broadcasts SIB1 (S502). SIB1 includes information about the type. SIB1 is received by the UE (303) and MBSR1 (302).

[0062] Next, the UE (303) transmits a Measurement Report (S503) to the IAB Donor 1 (301). The Measurement Report includes its own mobility information and the radio wave quality and type of surrounding base stations.

[0063] Similarly, MBSR1 (302) transmits a Measurement Report (S504) to IAB Donor1 (301). The Measurement Report includes its own mobility information and the radio wave quality and type of surrounding base stations.

[0064] Upon receiving the Measurement Report, the IAB Donor 1 (301) evaluates the connection strength of the UE, determines the SN selection method, and selects the SN. In the case of Figure 3A, the IAB Donor 2 (304) is selected as the SN.

[0065] The subsequent steps are the same as the general SN addition processing sequence in the 3GPP standard.

[0066] IAB Donor 1 (301) sends an SgNB Addition Request (S505) to IAB Donor 2 (304).

[0067] Upon receiving the SgNB Addition Request (S505), IAB Donor 2 (304) sends an SgNB Addition Request Acknowledge (S506) to IAB Donor 1 (301).

[0068] The IAB Donor 1 (301) sends an RRC ConnectionReconfiguration (S507) to the UE (303).

[0069] The UE (303) sends an RRC ConnectionReconfigurationComplete (S508) to the IAB Donor 1 (301).

[0070] IAB Donor 1 (301) sends SgNB Reconfiguration Complete (S509) to IAB Donor 2 (304).

[0071] Finally, a Random Access procedure (S510) is performed between the UE (303) and the IAB donor 2 (304) to establish a connection.

[0072] Next, the process when the IAB donor 1 (301) determines the method for selecting the SN to be assigned to the UE (303) will be described with reference to the flow chart of FIG.

[0073] FIG. 6 shows the flow of the process of adding an IAB donor's SN in this embodiment.

[0074] At S601, the IAB Donor 1 (301) receives a Measurement Report from the MBSR1 (302) and the UE (303).

[0075] At S602, the IAB Donor 1 (301) analyzes the received Measurement Report and obtains the mobility information of the MBSR1 (302) and the UE (303).

[0076] In S603, the IAB donor 1 (301) evaluates the connection strength of the UE (303) based on the acquired mobility information. In this embodiment, the connection strength evaluation unit 206 evaluates the connection strength based on the mobility information (information related to the movement of the communication device itself, such as location information, movement speed, movement direction, status (status indicating whether stopped or moving), stop time, and scheduled stop time).

[0077] The evaluation method is arbitrary, but is as described above under the circumstances described in FIG. 3A above. More specifically, the evaluation may be performed based on the mobility information of the MBSR1 (302) as follows: That is, when the state of the MBSR1 (302) is moving, the possibility of disconnection of the UE (303)'s connection may be evaluated to be higher than a predetermined standard, and the connection strength may be determined to be weak. Alternatively, when the state of the MBSR1 (302) is moving and the moving speed is higher than a threshold, the possibility of disconnection of the UE (303)'s connection may be evaluated to be higher than a predetermined standard, and the connection strength may be determined to be weak. Alternatively, when the state of the MBSR1 (302) is moving and the moving direction is away from the UE (303), the possibility of disconnection of the UE (303)'s connection may be evaluated to be higher than a predetermined standard, and the connection strength may be determined to be weak. In this case, the radio wave shielding situation, such as buildings, between the MBSR1 (302) and the UE (303) may be evaluated based on the moving direction. This is because, for example, when millimeter waves are used, the influence of shielding such as buildings is significant due to the highly rectilinear propagation characteristics.

[0078] On the other hand, when the state of MBSR1 (302) is stopped, the possibility of disconnection of the connection of the UE (303) may be evaluated as being lower than a predetermined standard, and the connection strength may be determined to be high. Alternatively, when the state of MBSR1 (302) is stopped and the planned stop time is longer than a threshold, the possibility of disconnection of the connection of the UE (303) may be evaluated as being lower than a predetermined standard, and the connection strength may be determined to be high. Alternatively, when the state of MBSR1 (302) is moving but the moving speed is lower than a threshold, the possibility of disconnection of the connection of the UE (303) may be evaluated as being lower than a predetermined standard, and the connection strength may be determined to be high.

[0079] Furthermore, when evaluating the connection strength of the UE (303), the mobility information of the UE (303) may also be evaluated. For example, under the circumstances described in FIG. 3A above, the following may be true. That is, when the MBSR1 (302) is moving and the moving speed of the MBSR1 (302) relative to the UE (303) is higher than a threshold, the possibility of disconnection may be evaluated as being higher than a predetermined standard, and the connection strength may be determined to be weak. Furthermore, when it is determined whether the UE (302) is moving together with the MBSR based on a comparison of the moving speed and moving direction of the MBSR1 (302) with the moving speed and moving direction of the UE (303), the connection strength may be determined to be high. This means that in cases where it is considered that a user carrying a UE is riding in the MBSR, the possibility of disconnection is evaluated as being lower than a predetermined standard, and the connection strength is determined to be high.

[0080] Furthermore, when evaluating the connection strength of the UE (303), the positional relationship between the opposing communication device and the UE (303), the communication strength (radio wave strength), the number of hops, etc. may also be evaluated. For example, under the circumstances described in the above-mentioned FIG. 3A, the following may be true. That is, if the state of the MBSR1 (302) is moving and the distance between the UE (303) and the MBSR1 (302) is longer than a threshold, the possibility of disconnection may be evaluated to be higher than a predetermined standard, and the connection strength may be determined to be weak.

[0081] In addition, as a situation different from the situation described in Fig. 3A above, when the UE (303) is connected to a fixed base station such as an IAB node instead of the MBSR1 (302), the following may be true: the possibility of disconnection of the connection of the UE (303) may be evaluated as being lower than a predetermined standard, and the connection strength may be determined to be high.

[0082] In S604, the method for selecting an SN is determined based on the evaluation result of the connection strength of the UE (303). If the connection strength is evaluated as weak, the process proceeds to S605, where an SN is selected based on the type of base station. If the connection strength is not evaluated as weak, the process proceeds to S611, where an SN is selected based on the radio wave quality of the base station.

[0083] In S605, the IAB donor 1 (301) analyzes the Measurement Report received from the UE (303) and confirms the base stations to which the UE (303) can connect and their types.

[0084] In S606, the IAB donor 1 (301) confirms whether the base station of the type included in the Measurement Report received from the UE (303) is a fixed base station (gNB, IAB donor, IAB node) can be connected to the UE (303). If connection is possible, proceed to S607.

[0085] In S607, IAB Donor 1 (301) selects a connectable fixed base station as the SN, sends an SN addition request (SGNB Addition Request) to the fixed base station, and completes the processing.

[0086] In S606, if the UE (303) cannot connect to the fixed base station, the process proceeds to S608.

[0087] In S608, the IAB donor 1 (301) checks the status (status indicating whether the UE (303) is stationary or moving) of the base station to which the UE (303) can connect. The status is obtained from the mobility information included in the Measurement Report received by the IAB donor 1 (301) from the MBSR1 (302).

[0088] In S609, the IAB donor 1 (301) checks whether the UE (303) can connect to a base station whose status is "stopped" and whose type is "MBSR". If the connection is possible, proceed to S610. If the connection is not possible, proceed to S612.

[0089] In S610, IAB Donor 1 (301) selects the suspended MBSR as the SN, sends an SN addition request, and ends the process.

[0090] In S611, the IAB donor 1 (301) analyzes the Measurement Report received from the UE (303) and checks the base stations to which the UE (303) can connect and the radio wave quality thereof.

[0091] In S612, IAB donor 1 (301) selects a base station with good radio wave quality as the SN, transmits an SN addition request, and ends the process.

[0092] Incidentally, the following has been described as a method by which the IAB donor 1 (301) obtains status information of base stations to which the UE (303) can connect. That is, in S608, it has been described that the IAB donor 1 (301) obtains status information of base stations to which the UE (303) can connect from the mobility information included in the Measurement Report received from each base station. However, the UE (303) may obtain status information from each base station, include it in the Measurement Report, and notify the IAB donor 1 (301). In this case, the status information may be added to the MeasResultNR (404).

[0093] [Other Embodiments] In the first embodiment, when the UE (303) cannot connect to a fixed base station or a stopped MBSR, the base station with the best radio wave quality is set as the SN. However, in this case, the UE (303) connects to two base stations, not including a fixed base station, via DC, and it is expected that the connection strength will weaken if the locations of the two base stations change. Therefore, when the UE (303) cannot connect to a fixed base station or a stopped MBSR, the parent node of the UE (303) is changed to an IAB node or a fixed base station under an IAB node. The change of the connection destination (parent node) of the UE (303) is realized by the IAB donor transmitting RRC Reconfiguration to the UE via the previous IAB node. RRC Reconfiguration is specified in TS 38.331 (5.3.5). After the UE's connection destination is changed, by assigning an SN to the UE according to the first embodiment, even if the UE (303) cannot connect to a fixed base station or a stopped MBSR, it is possible to construct a DC including a fixed base station with high connection strength.

[0094] In addition, in this embodiment, a recording medium on which software program code that realizes the above-described functions is recorded may be supplied to a system or device. The computer (CPU, MPU) of the system or device may then read and execute the program code stored on the recording medium. In this case, the program code itself read from the recording medium realizes the functions of the above-described embodiment, and the recording medium on which the program code is stored constitutes this embodiment. The functions may also be realized by a circuit (e.g., an ASIC or FPGA) that realizes one or more functions. ASIC is an abbreviation for Application Specific Integrated Circuit.

[0095] FPGA is an abbreviation for Field Programmable Gate Array. In addition, by having a hardware circuit cooperate with a processor such as a CPU or an MPU, it is possible to realize some or all of the various processes described in the above flowcharts.

[0096] Examples of storage media that can be used to supply the program code include flexible disks, hard disks, optical disks, magneto-optical disks, CD-ROMs, CD-Rs, magnetic tapes, non-volatile memory cards, ROMs, and DVDs.

[0097] Furthermore, the above-mentioned functions may be realized not only by the computer executing the read program code, but also by the operating system (OS) running on the computer performing some or all of the actual processing based on the instructions of the program code.

[0098] Furthermore, the program code read from the storage medium is written into a memory provided on a function expansion board inserted into the computer or a function expansion unit connected to the computer.

[0099] Based on the instructions of the program code, a CPU provided in the function expansion board or function expansion unit may perform some or all of the actual processing to realize the above-mentioned functions. Note that the separate RU / DU / CU (Radio Unit / Distributed Unit / Central Unit) may cooperate to provide the IAB donor function of the above-mentioned embodiment. In this case, the RU controls the antenna and radio waves, the DU performs modulation / demodulation and MAC (Media Access Control), and the CU controls the RUs / DUs under its control and acts as a bridge to the core network. In this case, the control shown in FIG. 6 is mainly performed by the IAB CU constituting the IAB donor.

[0100] In this case, the IAB CU may achieve cooperative operation by exchanging control signals with the DU connected to a network such as a fiber network and the RU connected to the DU.

[0101] The present invention is not limited to the above-described embodiments, and various modifications and variations can be made without departing from the spirit and scope of the present invention. Therefore, the following claims are appended to apprise the public of the scope of the present invention.

[0102] This application claims priority based on Japanese Patent Application No. 2024-059332, filed April 2, 2024, the entire contents of which are incorporated herein by reference.

Claims

1. A communications device capable of operating as an IAB (Integrated Access and Backhaul) donor, comprising: an evaluation means for evaluating the possibility of disconnection of a second communications device in a first situation where a second communications device is connected to the communications device via a first communications device, or in a second situation where a second communications device is connected directly to the communications device; a first acquisition means for acquiring the base station types of one or more base stations to which the second communications device can connect; a means for assigning an SN (Secondary Node) to the second communications device; and a selection means for selecting one base station as the SN from among the one or more base stations based on the evaluation result by the evaluation means and the base station types of the one or more base stations.

2. The communication device according to claim 1, characterized in that the selection means selects the one base station from among the one or more base stations based on the base station type when the evaluation means evaluates that the possibility of disconnection is higher than a predetermined standard in the first situation.

3. The communication device according to claim 1 or 2, characterized in that the base station type includes type information that can identify a fixed base station.

4. A communication device according to any one of claims 1 to 3, wherein the evaluation means evaluates that the possibility of disconnection is higher than the predetermined standard when the first communication device is a fixed base station in the first situation.

5. A communication device as described in any one of claims 1 to 4, further comprising a second acquisition means for acquiring mobility information of the first communication device, the mobility information including at least one of location information, movement speed, movement direction, stopped or moving state, stopped time, and planned stop time, and the evaluation means, when the first communication device is not a fixed base station in the first situation, evaluates the possibility of disconnection based on the mobility information of the first communication device.

6. A communication device according to any one of claims 1 to 5, further comprising a third acquisition means for acquiring mobility information from an MBSR (Mobile Base Station Relay), wherein the mobility information includes a state of being stopped or moving, and the base station type includes type information capable of identifying a fixed base station and type information capable of identifying an MBSR, and wherein the selection means, in the first situation, if the evaluation means evaluates that the possibility of disconnection is higher than a predetermined standard and if the one or more base stations do not include a fixed base station based on the base station type, selects an MBSR that is stopped from among the one or more base stations as the one base station based on the base station type and the mobility information.

7. A communication device according to any one of claims 1 to 6, further comprising a means for changing the connection destination of the second communication device, wherein when the evaluation means evaluates that the possibility of disconnection is higher than a predetermined standard and when the selection means selects MBSR as the one base station, the connection destination of the second communication device is changed to another fixed base station different from the device itself.

8. The communication device according to any one of claims 1 to 7, wherein the fixed base station includes a next generation node B (gNB), an IAB node, or an IAB donor.

9. The communication device according to any one of claims 1 to 8, wherein in the second situation, the evaluation means evaluates that the possibility of disconnection is lower than a predetermined standard.

10. A communication device as claimed in any one of claims 1 to 9, further comprising a fourth acquisition means for acquiring the radio wave quality of said one or more base stations, wherein said selection means selects said one base station from said one or more base stations based on the radio wave quality when said evaluation means evaluates that the possibility of disconnection is lower than a predetermined standard.

11. The communication device according to claim 10, wherein said selection means selects the base station with the highest radio wave quality as said one base station from among said one or more base stations.

12. The communication device according to any one of claims 1 to 10, wherein the first acquisition means acquires the base station type from SIB1 or an RRC message.

13. The communication device according to claim 12, wherein the base station type is included in a measurement report.

14. The communication device according to claim 10, wherein the fourth acquisition means acquires the radio wave quality in the form of a Measurement Report.

15. The communication device according to claim 5 or 6, wherein the mobility information is acquired by an RRC message.

16. The communication device according to claim 5 or 6, wherein the mobility information is included in a Measurement Report.

17. A control method for controlling communications of a communication device capable of operating as an IAB (Integrated Access and Backhaul) donor, comprising: an evaluation step for evaluating the possibility of disconnection for a second communication device in a first situation in which a second communication device connects to the device via a first communication device, or in a second situation in which a second communication device connects directly to the device; a first acquisition step for acquiring base station types of one or more base stations to which the second communication device can connect; a step for assigning an SN (Secondary Node) to the second communication device; and a selection step for selecting one base station as the SN from among the one or more base stations based on the evaluation result of the evaluation step and the base station types of the one or more base stations.

18. A program for causing a computer of a communication device capable of operating as an IAB (Integrated Access and Backhaul) donor to execute the following steps: an evaluation step for evaluating the possibility of disconnection for a second communication device in a first situation in which a second communication device connects to the device via a first communication device, or in a second situation in which a second communication device connects directly to the device; a first acquisition step for acquiring the base station types of one or more base stations to which the second communication device can connect; a step for assigning an SN (Secondary Node) to the second communication device; and a selection step for selecting one base station as the SN from among the one or more base stations based on the evaluation result from the evaluation step and the base station types of the one or more base stations.

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