Communication device, control method, and program

Abstract

To provide a mechanism for realizing a DC connection in a manner that makes it easy to maintain a stable connection.SOLUTION: A communication device capable of operating as an IAB (Integrated Access and Backhaul) donor includes: evaluation means for evaluating the possibility of disconnection regarding a second communication device in a first situation in which there is the second communication device connected to the device itself via a first communication device, or in a second situation in which there is the second communication device directly connected to the device itself; 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 an SN from among the one or more base stations on the basis of the evaluation result by the evaluation means and the base station types of the one or more base stations.SELECTED DRAWING: Figure 2

Description

[Technical Field]

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

[0002] 3GPP (3rd Generation Partnership Project) is currently working on standardizing IAB (Integrated Access and Backhaul) as a communication technology for backhaul.

[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 compared to conventional wired communications such as optical fiber.

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

[0007] Currently, 3GPP is actively discussing vehicle-mounted relay, a use case in the upcoming Rel-18, and MBSR as a specification to realize this use case. MBSR stands for Mobile Base Station Relay. For example, the discussion item "Mobile Base Station Relay Authorization and Configuration" envisions the following: In urban environments or during large-scale events in designated areas, MBSRs temporarily mounted on vehicles will 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 pose 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 speeds and increased connection redundancy. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] Special Publication No. 2019-534625 Summary of the Invention [Problem to be solved by the invention]

[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. The UE will connect 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 will connect to the MBSR. However, unlike conventional fixed base stations, MBSRs are mobile, so the connection to an MBSR is more likely to be disconnected than to a fixed base station. One way to increase 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, so connection redundancy does not improve significantly. The MN is responsible for selecting the SN, and the base station with the best signal quality with the UE is generally assigned. The UE reports the signal quality with the UE via a Measurement Report. Therefore, if an MBSR is nearby, the MBSR with the best 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 for realizing a DC connection in a manner that makes it easier to maintain a stable connection. [Means for solving the problem]

[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, an evaluation means for evaluating a possibility of disconnection of 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 a base station type 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; The present invention is characterized in that it has 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 type of the one or more base stations. [Effects of the Invention]

[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. [Brief explanation of the drawings]

[0014] [Figure 1] FIG. 2 is a hardware block diagram of an IAB node. [Figure 2] FIG. 1 is a software functional block diagram of an IAB node. [Figure 3] 1 is a configuration example of a communication system according to a first embodiment. [Figure 4] 2 shows a data format according to the first embodiment. [Figure 5] FIG. 10 is a sequence diagram of an SN addition process according to the first embodiment. [Figure 6] FIG. 1 is a flow chart of the SN addition process for an IAB donor in the first embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0015] Each embodiment will be described in detail below 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] The communication device according to the present 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 that conforms 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 or 6G).

[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 functional 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 performs cellular network communication such as LTE or 5G compliant with the 3GPP standard with a terminal device.

[0026] 204 is a data storage unit that stores the software itself, IAB routing information, information about 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 the 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 neighboring 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] FIG. 3 shows an example of the configuration of a communication system according to this embodiment.

[0034] Figure 3(a) shows an example of a UE with low connection strength. 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] Using FIG. 3(a), the general flow of how IAB donor 1 (301) assigns an SN to a UE (303) will be explained.

[0036] First, 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, MBSR1 (302).

[0037] Mobility information is information about the movement of communication devices, such as location information, movement speed, movement direction, status (stopped, moving), stop time, and expected stop time. The IAB donor 1 (301) calculates the relative position change of the UE (303) and MBSR1 (302) from the mobility information of the two devices and evaluates the connection strength based on the expected change in radio wave quality. The mobility information is notified to the IAB donor from the UE (303) and MBSR1 (302). This notification is made using RRC (Radio Resource Control) messages. RRC messages are a Layer 3 protocol of the Control Plane (CP) for controlling wireless communication between base stations and communication devices. Mobility information can be notified by defining a new RRC message, or it can be notified by including it in an existing RRC message. For example, it can be notified by including it in a Measurement Report. The Measurement Report is a list summarizing the radio wave quality 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. 3(a), since MBSR1 (302) is moving, the connection strength of UE (303) is evaluated as low.

[0039] Next, the IAB donor 1 (301) determines how to select the SN to assign to the UE (303). The SN selection method is determined based on 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 the 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 the 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. 3(a), 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 base station type 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 it receives directly. However, due to obstructions or relative positions, the base stations from which the UE (303) and IAB donor 1 (301) can receive SIB1 may differ. Therefore, the UE (303) notifies the IAB node 1 (301) of type information, which summarizes the types of surrounding base stations received. An RRC message is used for this notification. A new RRC message can be defined for notification, or it can be included in an existing RRC message. For example, it can be included in a Measurement Report. Since the Measurement Report summarizes radio wave quality information for each base station, type information is added to it. An example data format for a Measurement Report including type information is shown in Figure 4. Details will be described later.

[0042] In the case of Figure 3(a), IAB Donor 2 (304) and MBSR2 (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 MBSR2 (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 one 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. 3(a), IAB donor 2 (304), which is of the type "IAB donor" that is less likely to cleave, is selected as the SN.

[0045] 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).

[0046] Figure 3(b) shows an example where the UE connection strength is high. The only difference from Figure 3(a) is that the UE (303) is directly connected to IAB Donor 1 (301); 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. 3(b), IAB donor 1 (301) does not move, so the connection strength with the UE is evaluated as high.

[0049] Next, the IAB Donor 1 (301) determines how to select the SN to be assigned to the UE (303).

[0050] In the case of Figure 3(b), the connection strength of the UE (303) is evaluated as high, so the SN is selected based on the radio wave quality of the base station. The radio wave quality is notified by 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. 3(b), MBSR2 (305) close to the UE (303) has good radio wave quality and is selected as the SN.

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

[0056] In addition to the conventional information about the radio wave quality of surrounding base stations, the Measurement Report (401) includes MobilityInfo (409), which is mobility information. 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 described with reference to the sequence diagram of FIG.

[0059] Figure 5 shows the sequence of the SN addition process in this embodiment, based on the general SN addition process sequence in the 3GPP standard. It shows the sequence in the communication system of Figure 3(a). Note that this embodiment mainly relates to SN addition during DC connection, but can also be applied when changing the SN added during DC connection afterwards.

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

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

[0062] 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.

[0063] Upon receiving the Measurement Report, IAB Donor 1 (301) evaluates the connection strength of the UE, determines the SN selection method, and selects an SN. In the case of Figure 3(a), IAB Donor 2 (304) is selected as the SN.

[0064] The subsequent steps are in accordance with the general SN addition processing sequence in the 3GPP standard.

[0065] IAB Donor 1 (301) sends an SgNB Addition Request (S505) to IAB Donor 2 (304).

[0066] Upon receiving the SgNB Addition Request (S505), IAB Donor 2 (304) sends an SgNB Addition Request Acknowledge (S506) to IAB Donor 1 (301).

[0067] The IAB donor 1 (301) transmits an RRC Connection Reconfiguration (S507) to the UE (303).

[0068] The UE (303) transmits an RRC Connection Reconfiguration Complete (S508) to the IAB donor 1 (301).

[0069] IAB Donor 1 (301) sends SgNB Reconfiguration Complete (S509) to IAB Donor 2 (304).

[0070] Finally, a Random Access procedure (S510) is performed between the UE (303) and the IAB donor 2 (304) to establish a connection.

[0071] Next, the process performed by the IAB donor 1 (301) when determining a method for selecting an SN to be assigned to the UE (303) will be described with reference to the flow chart of FIG.

[0072] FIG. 6 shows the flow of the SN addition process for an IAB donor in this embodiment.

[0073] In S601, the IAB donor 1 (301) receives a measurement report from the MBSR1 (302) and the UE (303).

[0074] In S602, the IAB Donor 1 (301) analyzes the received Measurement Report and obtains mobility information of the MBSR1 (302) and the UE (303).

[0075] 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 above-mentioned 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).

[0076] The evaluation method is arbitrary, but is as described above under the circumstances described in FIG. 3(a). More specifically, the evaluation may be performed as follows based on the mobility information of the MBSR1 (302). 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 situation of radio wave obstructions, such as buildings, between the MBSR1 302 and the UE 303 may be evaluated based on the direction of movement. This is because, for example, when millimeter waves are used, the influence of obstructions such as buildings is significant due to their highly rectilinear propagation characteristics.

[0077] On the other hand, when the state of the MBSR1 (302) is stopped, the possibility of disconnection of the UE (303) connection 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 the MBSR1 (302) is stopped and the planned stop time is longer than a threshold, the possibility of disconnection of the UE (303) connection 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 the MBSR1 (302) is moving but the moving speed is lower than a threshold, the possibility of disconnection of the UE (303) connection may be evaluated as being lower than a predetermined standard, and the connection strength may be determined to be high.

[0078] 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 above in FIG. 3(a), the following may be performed. 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 to be 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 to be lower than a predetermined standard, and the connection strength is determined to be high.

[0079] 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 signal strength), the number of hops, etc. may also be evaluated. For example, under the circumstances described above in FIG. 3(a), 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 as being higher than a predetermined standard, and the connection strength may be determined to be weak.

[0080] In a situation different from that described in FIG. 3(a) above, when the UE 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 UE (303) connection may be evaluated as being lower than a predetermined standard, and the connection strength may be determined to be high.

[0081] 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.

[0082] In S605, 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 their types.

[0083] In S606, the IAB donor 1 (301) checks whether the base station type included in the Measurement Report received from the UE (303) is a fixed base station (gNB, IAB donor, IAB node) and whether the UE (303) can connect to it. If connection is possible, proceed to S607.

[0084] In S607, the 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 process.

[0085] In S606, if the UE (303) cannot connect to the fixed base station, the process proceeds to S608.

[0086] 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).

[0087] 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.

[0088] In S610, IAB Donor 1 (301) selects the inactive MBSR as the SN, sends an SN addition request, and ends the process.

[0089] 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.

[0090] In S612, the 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.

[0091] 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, the IAB donor 1 (301) obtains status information of base stations to which the UE (303) can connect from 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 a Measurement Report, and notify the IAB donor 1 (301). In this case, the status information may be added to the MeasResultNR (404).

[0092] [Other embodiments] In the first embodiment, when the UE (303) cannot connect to a fixed base station or a stopped MBSR, the SN is set to a base station with good radio wave quality. However, in this case, the UE (303) connects to two base stations, not including a fixed base station, via DC. If the locations of the two base stations change, the connection strength is expected to weaken. Therefore, when the UE (303) cannot connect to a fixed base station or a stopped MBSR, the UE (303) changes its parent node to an IAB node or a fixed base station under an IAB node. The change of the UE (303)'s connection destination (parent node) 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, it is possible to establish a DC including a fixed base station with high connection strength, even if the UE (303) cannot connect to a fixed base station or a stopped MBSR.

[0093] In addition, in this embodiment, a recording medium storing software program code for implementing the above-described functions may be provided to a system or device. Then, a computer (CPU, MPU) of the system or device may read and execute the program code stored on the recording medium. In this case, the program code itself read from the storage medium implements the functions of the above-described embodiment, and the storage medium storing the program code constitutes this embodiment. The functions can also be implemented by a circuit (e.g., an ASIC or FPGA) that implements one or more functions. ASIC stands for Application Specific Integrated Circuit. FPGA stands for Field Programmable Gate Array. Furthermore, some or all of the various processes described in the above flowcharts can be implemented by having a hardware circuit cooperate with a processor such as a CPU or MPU.

[0094] 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.

[0095] In addition, 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. OS is an abbreviation for Operating System.

[0096] Furthermore, the program code read from the storage medium is written to a memory provided on a function expansion board inserted into the computer or a function expansion unit connected to the computer. Then, based on the instructions of the program code, a CPU provided on 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 IAB donor function described above can also be provided by cooperative operation of separate RUs, DUs, and CUs (Radio Units, Distributed Units, and Central Units). In this case, the RUs control the antenna and radio waves, the DUs perform modulation / demodulation and media access control (MAC), and the CUs control the RUs and DUs under their control and act as a bridge to the core network. In this case, the control shown in Figure 6 is primarily performed by the IAB CU constituting the IAB donor. In this case, the IAB CUs can achieve cooperative operation by exchanging control signals with DUs connected to a network such as a fiber network and RUs connected to the DUs.

[0097] In addition, the following supplementary notes are disclosed regarding the above-described embodiment.

[0098] [Appendix 1] A communication device capable of operating as an IAB (Integrated Access and Backhaul) donor, an evaluation means for evaluating a possibility of disconnection of 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 a base station type 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; A communication device characterized by having 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 type of the one or more base stations.

[0099] [Appendix 2] The communication device described in Appendix 1, characterized in that the selection means selects the one base station from 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.

[0100] [Appendix 3] 3. The communication device according to claim 1, wherein the base station type includes type information that can identify a fixed base station.

[0101] [Appendix 4] 4. The communication device according to claim 1, wherein, when the first communication device is a fixed base station in the first situation, the evaluation means evaluates that the possibility of disconnection is higher than the predetermined standard.

[0102] [Appendix 5] a second acquiring means for acquiring mobility information of the first communication device; the mobility information includes at least one of location information, a moving speed, a moving direction, a stopped or moving state, a stopped time, and a scheduled stopped time; The communication device according to any one of Supplementary Notes 1 to 4, characterized in that the evaluation means evaluates the possibility of disconnection based on the mobility information of the first communication device when the first communication device is not a fixed base station in the first situation.

[0103] [Appendix 6] The mobile station further includes a third acquiring means for acquiring mobility information from a Mobile Base Station Relay (MBSR); The mobility information includes a stationary or moving state; The base station type includes type information that can identify a fixed base station and type information that can identify an MBSR, The communication device according to any one of Supplementary Notes 1 to 5, wherein, 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, the selection means selects a stopped MBSR from among the one or more base stations as the one base station based on the base station type and the mobility information.

[0104] [Appendix 7] a means for changing the connection destination of the second communication device; 7. The communication device according to claim 1, 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 communication device changes the connection destination of the second communication device to another fixed base station different from the own device.

[0105] [Appendix 8] The communication device according to any one of Supplementary Notes 1 to 7, characterized in that the fixed base station represented by the base station type includes a gNB (next generation Node B), an IAB node, or an IAB donor.

[0106] [Appendix 9] 9. The communication device according to claim 1, wherein in the second situation, the evaluation means evaluates that the possibility of disconnection is lower than a predetermined standard.

[0107] [Appendix 10] Further, a fourth acquisition means for acquiring radio wave quality of the one or more base stations is provided, The communication device according to any one of appendices 1 to 9, wherein the selection means selects the base station from among the one or more base stations based on radio wave quality when the evaluation means evaluates that the possibility of disconnection is lower than a predetermined standard.

[0108] [Appendix 11] 11. The communication device according to claim 10, wherein the selection means selects a base station having the highest radio wave quality as the one base station from among the one or more base stations.

[0109] [Appendix 12] 12. The communication device according to claim 1, wherein the first acquisition means acquires the base station type using an SIB1 or an RRC message.

[0110] [Appendix 13] The communication device according to claim 12, wherein the base station type is included in a Measurement Report.

[0111] [Appendix 14] The communication device according to claim 10, wherein the fourth acquiring means acquires the radio wave quality using a Measurement Report.

[0112] [Appendix 15] The communication device according to any one of Supplementary Notes 1 to 14, wherein the mobility information is obtained by an RRC message.

[0113] [Appendix 16] The communication device described in Supplementary Note 15, characterized in that the mobility information is included in a Measurement Report. [Explanation of symbols]

[0114] 101 Hardware Configuration 102 Control section 103 Storage section 104 Wireless Communication Department 105 Communication antenna control unit 201 Software Features 202 signal transmitting unit (transmitting means) 203 signal receiving unit (first to fourth acquisition means) 204 Data storage unit 205 Connection control section 206 Connection strength evaluation unit (evaluation means) 207 SN selection method determination unit (determination means) 208 SN selection unit (selection means) 209 Message detection unit 210 Message Generation Unit 301 IAB donors 302 MBSR 303 UE 304 IAB donors 305 MBSR

Claims

1. A communication device capable of operating as an IAB (Integrated Access and Backhaul) donor, comprising: an evaluation means for evaluating a possibility of disconnection of a second communication device in a first situation where a second communication device is connected to the own device via a first communication device, or in a second situation where a second communication device is connected directly to the own device; a first acquisition means for acquiring a base station type of one or more base stations to which the second communication device can connect; means for assigning a SN (Secondary Node) to the second communication device; A communication device characterized by having 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 type of the one or more base stations.

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

4. 4. The communication device according to claim 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 second acquiring means for acquiring mobility information of the first communication device; the mobility information includes at least one of location information, a moving speed, a moving direction, a stopped or moving state, a stopped time, and a scheduled stopped time; 5. The communication device according to claim 4, wherein the evaluation means evaluates the possibility of disconnection based on the mobility information of the first communication device when the first communication device is not a fixed base station in the first situation.

6. a third acquiring means for acquiring mobility information from a Mobile Base Station Relay (MBSR); The mobility information includes a stationary or moving state; the base station type includes type information capable of identifying a fixed base station and type information capable of identifying an MBSR; 2. The communication device according to claim 1, wherein, 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, the selection means selects a stopped MBSR 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 means for changing the connection destination of the second communication device; 2. The communication device according to claim 1, characterized in that, 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 own device.

8. The communication device according to claim 3 , wherein the fixed base station comprises a next generation node B (gNB), an IAB node, or an IAB donor.

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

10. a fourth acquisition means for acquiring radio wave quality of the one or more base stations; 2. The communication device according to claim 1, wherein the selection means selects the one base station from the one or more base stations based on radio wave quality when the evaluation means evaluates that the possibility of disconnection is lower than a predetermined standard.

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

12. The communication device according to claim 1 , wherein the first acquisition means acquires the base station type from an 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. 11. 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 communication of a communication device capable of operating as an IAB (Integrated Access and Backhaul) donor, comprising: an evaluation step of evaluating a possibility of disconnection of 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 step of acquiring base station types of one or more base stations to which the second communication device can connect; assigning a secondary node (SN) to the second communication device; A control method comprising a selection step of 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 type of the one or more base stations.

18. A computer of a communication device capable of operating as an IAB (Integrated Access and Backhaul) donor, an evaluation step of evaluating a possibility of disconnection of 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 step of acquiring base station types of one or more base stations to which the second communication device can connect; assigning a secondary node (SN) to the second communication device; A program for executing a selection process of selecting one base station as the SN from among the one or more base stations based on the evaluation result from the evaluation process and the base station type of the one or more base stations.

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