Mobile communication device and control method thereof, and program
Patent Information
- Application Number
- JP2022124992
- Authority / Receiving Office
- JP · JP
- Patent Type
- Applications
- Current Assignee / Owner
- Filing Date
- 2022-08-04
- Publication Date
- 2025-07-22
AI Technical Summary
Existing mobile IAB nodes lack a mechanism to distinguish between group handovers for UEs under their control, leading to inadequate communication control during handover processes.
A mobile communication device with a relay function that determines whether to perform group handover for each UE by evaluating predetermined conditions, such as communication quality, enabling individual communication control for UEs inside and outside the vehicle.
Enables appropriate communication control for each UE, ensuring seamless communication continuity during handovers by distinguishing between group and individual handover scenarios.
Smart Images
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Abstract
Description
[Technical field]
[0001] The present invention relates to a mobile communication device, a control method thereof, and a program. [Background technology]
[0002] In the 3rd Generation Partnership Project (3GPP (registered trademark)), standardization of IAB (Integrated Access and Backhaul) as a communication technology for backhaul is progressing. In IAB, radio resources used for an access line between a base station and a user terminal (UE: User Equipment) are also used for a backhaul line. For example, in IAB, millimeter wave band radio resources such as 28 GHz band are used (Patent Document 1). By using IAB for a backhaul line, a relay device (IAB node) can relay communication between a base station device (IAB donor) and UE by a radio line, thereby improving the connectivity of a radio access network.
[0003] To further improve the connectivity of radio access networks, mobile IAB nodes mounted on vehicles such as buses, taxis, and trains are being considered. The use of mobile IAB nodes is expected to provide good communication services in vehicles, as well as improve communication quality in areas with locally poor radio wave conditions or congested areas. As the mobile IAB node moves, it performs handover to switch the connection destination to another IAB donor or IAB node. When a relay node that relays communication between a mobile station (wireless terminal) and a base station, such as a mobile IAB node, performs handover, a technology has been proposed that determines and assists the handover of a mobile station under the relay node (Patent Document 2). [Prior art documents] [Patent documents]
[0004] [Patent Document 1] Special Publication No. 2019-534625 [Patent Document 2] Patent No. 5800024 Summary of the Invention [Problem to be solved by the invention]
[0005] When a mobile IAB node performs a handover, there has been no mechanism provided to distinguish whether or not a group handover that switches the connection destination together with the node should be performed for each UE under the node. For this reason, it is not possible to realize appropriate communication control (handover processing) individually for UEs located inside and outside a vehicle equipped with a mobile IAB node, for example.
[0006] The present invention provides a technique for performing appropriate communication control individually for each wireless terminal (UE) under its control when a mobile communication device having a relay function (mobile IAB node) performs handover. [Means for solving the problem]
[0007] A mobile communications device according to one embodiment of the present invention is a mobile communications device having a relay function for relaying communications between a radio base station and a radio terminal, and is characterized in that it is equipped with a decision means for performing a decision process for deciding, before performing a handover to switch a connection destination for communications with a core network to another radio base station or another communications device having the relay function, whether or not to switch the connection destination together with the mobile communications device, for each radio terminal connected to the mobile communications device, based on whether or not a predetermined condition is satisfied, and a control means for performing communication control for a handover to switch the connection destination from the mobile communications device to another radio base station, for a radio terminal that has been determined by the decision process not to be a target for switching the connection destination together with the mobile communications device. Effect of the Invention
[0008] According to the present invention, when a mobile communication device having a relay function (mobile IAB node) performs handover, it becomes possible to perform appropriate communication control individually for each wireless terminal (UE) under its control. [Brief description of the drawings]
[0009] [Figure 1] FIG. 1 illustrates an example of the configuration of a wireless communication system. [Diagram 2] Block diagram showing an example of the hardware configuration of an IAB node [Diagram 3] Block diagram showing an example of the functional configuration of an IAB node [Figure 4] A flowchart showing an example of a handover process procedure in an IAB node. [Diagram 5] 1 is a flowchart showing an example of a procedure for determining a UE to be a group handover target (S401). [Figure 6] A sequence diagram showing an example of a handover process for a UE that is not a target of group handover. [Figure 7] A sequence diagram showing an example of a group handover process for a UE that is a target of the group handover. [Figure 8] FIG. 11 is a sequence diagram showing an example of a group handover process for a UE that is a target of group handover (second embodiment); DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0010] Hereinafter, the embodiments will be described in detail with reference to the attached drawings. Note that the following embodiments do not limit the invention according to the claims. Although the embodiments describe a number of features, not all of these features are essential to the invention, and the features may be combined in any manner. Furthermore, in the attached drawings, the same reference numbers are used for the same or similar configurations, and duplicated descriptions are omitted.
[0011] [Embodiment 1] 1 illustrates a configuration example of a wireless communication system according to an embodiment of the present disclosure. The wireless communication system 100 is configured as a relay communication system using IAB (Integrated Access and Backhaul) defined in the 3GPP cellular communication standard. The wireless communication system 100 includes IAB donors 101 and 102 connected to a core network (CN) 130, and an IAB node 103. The CN 130 includes one or more network nodes (control nodes) that perform various processes such as authentication of a user equipment (UE) and registration of use of a network slice.
[0012] The IAB donors 101 and 102 are radio base stations of a radio access network connected to the CN 130, and can provide communication services to UEs located within their respective coverage areas (cells). The IAB donors 101 and 102 establish radio connections with terminal functions (Mobile Terminations) of IAB nodes (e.g., IAB node 103) located within their respective coverage areas. The IAB donors 101 and 102 perform settings using BAP (Backhaul Adaptation Protocol) to enable the wirelessly connected IAB nodes to function as relay devices (communication devices with relay functions).
[0013] The IAB node 103 is an example of a mobile communication device (mobile communication node) having a relay function for relaying communication between an IAB donor, which is a radio base station, and a UE, which is a radio terminal. The relay function is relaying by IAB in 3GPP. The IAB node 103 can also connect to another IAB node that is directly or indirectly connected to the IAB donor 101. In this case, the IAB node 103 establishes a connection with the IAB donor 101 through the relay of the other IAB node, and sets a communication path. The communication between the IAB node 103 and the IAB donor 101 is performed via the other IAB node.
[0014] In the example of FIG. 1, the IAB donor 101 is connected to the IAB node 103, and a communication path is set through the IAB donor 101 and the IAB node 103. The IAB node 103 is configured as a mobile IAB node mounted on the bus 140. The IAB node 103 can move within the coverage area of another IAB donor (wireless base station) or IAB node (relay device) as the bus 140 moves. The IAB node 103 forms a coverage area (cell) that can provide communication services to UEs located inside and outside the bus 140. In this embodiment, an example is used in which the IAB node 103 is mounted on the bus 140, but the IAB node 103 may be an IAB node mounted on a moving object or person, such as a vehicle other than a bus, an aircraft, or a ship.
[0015] UEs 110 and 111 are mobile terminals used by passengers of bus 140. UE 112 is, for example, a mobile terminal used by a pedestrian located outside bus 140, or a mobile terminal used by a user in a vehicle located outside bus 140 or a mobile terminal mounted on the vehicle. UEs 110 to 112 are located within the coverage area of IAB node 103. In the example of FIG. 1, all of UEs 110 to 112 are also located within the coverage area of IAB donor 101, but are connected to IAB node 103, which has better communication quality (radio signal strength) of wireless communication.
[0016] It is assumed that the UEs 110 to 112 are continuing communication for executing applications such as a call, a video conference, or an online game with the CN 130 via the IAB node 103 and the IAB donor 101. These applications are examples of applications for using services that do not permit disconnection of a communication connection. In this case, the IAB donor 101 and the IAB node 103 hold session information for continuing communication between each UE and the CN 130.
[0017] The IAB node 103 mounted on the bus 140 establishes a wireless connection with the IAB donor 101 within the coverage area of the IAB donor 101. When the radio wave strength (received signal strength) of the communication path 120 between the IAB donor 101 and the IAB node 103 decreases as the bus 140 moves in the traveling direction 141, the IAB node 103 switches (hands over) the connection destination from the IAB donor 101 to another IAB donor or node.
[0018] In the example of Fig. 1, the IAB donor 102 forms a coverage area ahead in the traveling direction 141 of the bus 140. For example, when the radio wave strength (received signal strength) of the broadcast signal received from the IAB donor 102 becomes good (for example, becomes a predetermined level or higher), the IAB node 103 performs a handover from the IAB donor 101 to the IAB donor 102. As a result, the IAB node 103 switches the connection destination for communication with the CN 130 from the IAB donor 101 to the IAB donor 102. That is, the IAB node 103 switches the communication path for communication with the CN 130 from the communication path 120 via the IAB donor 101 to the communication path 122 via the IAB donor 102.
[0019] When the IAB node 103 performs handover as described above, for example, a group handover may be performed collectively for all UEs (under the IAB node 103) connected to the IAB node 103, in which the connection destination is switched to the IAB donor 102. However, a situation may be assumed in which it is desirable to perform different communication control (handover processing) for each UE under the IAB node 103 according to its communication situation. For example, in the example of FIG. 1, it may be desirable to perform appropriate communication control individually for the UEs 110 and 111 located within the bus 140 and the UE 112 located outside the bus 140. Specifically, it is expected that the communication quality of the UEs 110 and 111 within the bus 140 is maintained even after the handover by performing a group handover together with the IAB node 103. On the other hand, the communication quality of the UE 112 outside the bus 140 may be maintained by performing a handover to another radio base station rather than performing a group handover together with the IAB node 103.
[0020] Therefore, the IAB node 103 of this embodiment is configured to be able to distinguish whether or not to perform group handover (group HO) for each subordinate UE when performing handover to another IAB donor or node. This makes it possible to realize appropriate communication control (handover processing) for each UE located inside and outside the bus 140 on which the IAB node 103 is mounted, for example.
[0021] Specifically, before performing handover to another IAB donor or node, the IAB node 103 performs a decision process for determining whether or not each UE currently connected to the IAB node 103 is a target of group HO that switches the connection destination together with the IAB node 103. In the decision process, the IAB node 103 decides whether or not each UE currently connected to the IAB node 103 is a target of group HO based on whether or not a predetermined condition (group HO condition) described later is satisfied. The IAB node 103 further performs communication control for handover to switch the connection destination from the IAB node 103 to another radio base station for UEs determined not to be targets of group HO by the decision process. In addition, the IAB node 103 performs group HO with the IAB donor 102 as the handover destination for UEs determined to be targets of group HO by the decision process. In this way, for example, even if each UE currently connected to the IAB node 103 is executing an application that does not allow disconnection of the communication connection, communication control can be performed so that the application can be executed seamlessly after the handover of the IAB node 103.
[0022] In the following, it is assumed that, through the above-mentioned determination process, UEs (UEs 110 and 111) located inside bus 140 are determined as UEs subject to group HO, and UEs (UE 112) located outside bus 140 are determined as UEs not subject to group HO.
[0023] In the example of Fig. 1, the IAB node 103 performs the following communication control for each UE connected to the IAB node 103 according to the result of the above-mentioned determination process. The IAB node 103 executes group HO for UEs (UEs 110 and 111) located within the bus 140 that have been determined as UEs subject to group HO, in order to switch the connection destination to the IAB donor 102 together with the IAB node 103.
[0024] On the other hand, for a UE (UE 112) located outside the bus 140 that has been determined as a UE not subject to group HO, the IAB node 103 performs communication control to perform handover to the IAB donor 101 when a deterioration in communication quality is predicted. As a result, the communication path for communication between the UE 112 and the CN 130 is switched from the communication path 121 via the IAB node 103 to the communication path 123 via the IAB donor 101.
[0025] <Device configuration> Fig. 2(A) is a block diagram showing an example of a hardware configuration of the IAB node 103. The IAB node 103 includes a control unit 201, a storage unit 202, a wireless communication unit 203, an antenna control unit 204, and an antenna 205. Note that the IAB node 103 may further include other hardware components, or may not include some of the components shown in Fig. 2(A).
[0026] The control unit 201 includes one or more processors such as a CPU (Central Processing Unit) or an MPU (Micro Processing Unit). The control unit 201 may include an FPGA (Field Programmable Gate Array), a DSP (Digital Signal Processor), an ASIC (Application Specific Integrated Circuit), or the like. The control unit 201 controls the entire device by executing a control program stored in the storage unit 202, for example.
[0027] The storage unit 202 includes one or more storage devices (memories), such as a RAM (random access memory), a ROM (read only memory), a HDD (hard disk drive), and an SSD (solid state drive). The storage unit 202 is configured to store various programs (e.g., control programs) executed by the control unit 201, and various information (e.g., session information and communication quality information related to UE, and communication quality information related to IAB donors 101 and 102) used in processing by the control unit 201.
[0028] The session information includes information such as an identifier (ID) indicating a virtual communication path for data communication executed by an application. The session information may include the temporarily buffered data itself. The communication quality information includes information related to communication quality such as a received signal strength indicator (RSSI), a modulation and coding scheme (MCS), a signal to noise ratio (SNR), and a communication speed.
[0029] The wireless communication unit 203 performs processing related to wireless communication (cellular communication) conforming to 3GPP standards such as the LTE (Long Term Evolution) standard or the 5G (5th generation) standard. The wireless communication unit 203 includes circuits for communication processing, such as a baseband chip and an RF (radio frequency) chip. The antenna control unit 204 controls an antenna 205 used for wireless communication performed by the wireless communication unit 203. The antenna control unit 204 can also measure communication quality based on a signal received by the antenna 205. The antenna control unit 204 may generate, for example, an RSSI indicating received signal strength or an SNR as communication quality information indicating the measurement result.
[0030] 3 is a block diagram showing an example of a functional configuration of IAB node 103. IAB node 103 includes a signal transmitting unit 301, a signal receiving unit 302, a data storage unit 303, a connection control unit 304, a UE management unit 305, and a session management unit 306. The functions of each block shown in FIG. 3 can be realized by the control unit 201 executing a control program stored in the storage unit 202.
[0031] The signal transmission unit 301 and the signal reception unit 302 control the wireless communication unit 203 to transmit and receive wireless signals with other IAB donors or nodes (e.g., IAB donors 101, 102) and UEs (e.g., UEs 110 to 112). The signal transmission unit 301 and the signal reception unit 302 transmit and receive wireless signals compliant with 3GPP standards such as the LTE standard or 5G standard. The data storage unit 303 stores various programs and various data (various information) in the storage unit 202 for retention.
[0032] The connection control unit 304 performs processes related to the connection and disconnection of the UE, such as the transmission and reception of radio resource control (RRC) messages, which are carried out between the UE and the CN 130. The connection control unit 304 further performs processes related to the connection with other IAB donors or nodes and the connection with the CN 130. The connection control unit 304 performs the handover process of the IAB node 103 itself and the handover process of the UE (under the IAB node 103) connected to the IAB node 103. Also, the connection control unit 304 controls the antenna control unit 204 during wireless communication. The connection control unit 304 acquires communication quality information from the antenna control unit 204 and sends the acquired communication quality information to the data storage unit 303 or the UE management unit 305.
[0033] The UE management unit 305 determines and manages the UEs to be the target of group HO and the UEs not to be the target of group HO (excluded from the target) during the handover of the IAB node 103. The session management unit 306 manages the session information of the applications being executed by the UEs connected to the IAB node 103. When a UE connected to the IAB node 103 is handed over, the session management unit 306 transfers the session information of the UE to the handover destination via the signal transmission unit 301.
[0034] <Handover Process of IAB Node> 4 is a flowchart showing an example of a procedure of handover processing (HO processing) in the IAB node 103 according to this embodiment. Here, an example will be described in which the IAB node 103 is connected to the IAB donor 101 and performs HO processing to switch the connection destination from the IAB donor 101 to the IAB donor 102.
[0035] First, in S400, the IAB node 103 judges whether or not it is necessary to switch (handover) the connection destination (IAB donor or node). That is, the IAB node 103 judges whether or not it is necessary to switch the connection destination from the currently connected IAB node 103 to another IAB donor or node. For example, when the IAB node 103 detects that the RSSI in the communication with the IAB donor 101 has dropped below a predetermined threshold, it judges that it is necessary to switch the connection destination. This judgment is not limited to the RSSI, and may be made using other parameter values (e.g., SNR) indicating the communication quality in the communication with the currently connected IAB donor or node. In addition, when the IAB node 103 is a bus or the like, the planned route may be determined. In this way, when the planned route is determined, in addition to the communication quality, candidate information of the connection destination and location information of the connection destination are stored in the IAB node 103 as a pre-processing. Then, in addition to the communication quality, the IAB node 103 may be configured to determine whether or not it is necessary to switch, taking into consideration the stored information and the location information of the moving IAB node 103 as auxiliary information.
[0036] In S400, if the IAB node 103 determines that switching of the connection destination is not necessary, the determination in S400 is repeated, for example, at a predetermined time interval or according to a condition associated with movement. Here, the condition associated with movement may be, for example, the departure, stop, or change in the traveling direction of the bus 140, or a condition based on position information or the like (for example, the bus 140 has moved a predetermined distance). On the other hand, if the IAB node 103 determines that switching of the connection destination is necessary, the process proceeds to S401.
[0037] In S401, the IAB node 103 performs a process of determining whether or not each UE connected to the IAB node 103 is a target for group HO (a process of determining UEs that are a target of group HO) according to the procedure in FIG. 5 described later. In this manner, when it is determined that handover of the IAB node 103 is necessary (when execution of handover is predicted), the IAB node 103 performs a process of determining UEs that are a target of group HO. In this process, the IAB node 103 distinguishes between UEs that are a target of group HO and UEs that are not a target of group HO for each UE (UEs 110 to 112 in this example) that are connected to the IAB node 103. When the process of S401 is completed, the IAB node 103 proceeds to S402. In the following, a case in which UEs 110 and 111 are determined as UEs that are a target of group HO and UE 112 is determined as UEs that are not a target of group HO by the process of S401 is used as an example.
[0038] In S402, the IAB node 103 determines whether or not there is a UE that is not a group HO target among the UEs connected to the IAB node 103 as a result of the determination process in S401. If there is a UE that is not a group HO target, the IAB node 103 proceeds to the process in S403, and if there is no UE that is not a group HO target, the IAB node 103 proceeds to the process in S404. In S403, the IAB node 103 executes the HO process from the IAB node 103 to another IAB donor or node for each UE that is not a group HO target (UE 112 in this example). An example of the HO process for each UE that is not a group HO target will be described later with reference to FIG. 6. When the IAB node 103 completes the HO process for all UEs that are not a group HO target, the IAB node 103 proceeds to the process in S404.
[0039] In S404, the IAB node 103 determines whether or not there is a UE that is a target of the group HO as a result of the determination process in S401. If there is a UE that is a target of the group HO, the IAB node 103 proceeds to S405, and if there is no UE, the IAB node 103 proceeds to S406.
[0040] In S405, the IAB node 103 decides to execute a group HO process to perform handover together with the UEs (UEs 110 and 111 in this example) that are the targets of group HO to another IAB donor or node (IAB donor 102 in this example). Through the group HO process, the UEs that are the targets of group HO are also handed over to the handover destination of the IAB node 103 (IAB donor 102 in this example) that was determined as the IAB node 103 moved. When performing handover to the handover destination determined as the IAB node 103 moved, the IAB node 103 performs group HO by performing handover to the handover destination together with the UEs that were determined to be targets of group HO. An example of this group HO process will be described later with reference to FIG. 7.
[0041] On the other hand, in S406, since there is no UE that is a target of group HO, the IAB node 103 decides to execute HO processing for only the local station to the handover destination (in this example, the IAB donor 102) determined in conjunction with the movement of the IAB node 103.
[0042] When the process of S405 or S406 is completed, the IAB node 103 ends the process according to the procedure of FIG.
[0043] <Processing for Determining UEs Subject to Group HO (S401)> 5 is a flowchart showing an example of a procedure of a decision process (group HO target UE decision process) executed in the above-mentioned S401 according to this embodiment to decide whether or not to make each UE connected to the IAB node 103 a target of group HO. This decision process is executed by the UE management unit 305 in the IAB node 103.
[0044] In addition to being executed in S401, the determination process according to the procedure in Fig. 5 may be executed at a different timing. For example, when the IAB node 103 (UE management unit 305) receives a connection request from a new UE, the determination process according to the procedure in Fig. 5 may be executed at the timing of permitting the connection. Also, the IAB node 103 (UE management unit 305) may execute the determination process according to the procedure in Fig. 5 at regular timing, or at timing based on the departure, stop, change in direction of the bus 140, location information, etc. The UE management unit 305 manages information indicating the execution result of the determination process as management information, and updates the management information every time the determination process is executed.
[0045] In this determination process, the IAB node 103 determines whether or not each UE connected to the IAB node 103 is a target for group HO based on whether or not the UE satisfies a predetermined group HO condition. The IAB node 103 determines UEs that satisfy the group HO condition as UEs that are a target for group HO. On the other hand, the IAB node 103 determines UEs that do not satisfy the group HO condition as UEs that are not a target for group HO (UEs that are not a target for group HO).
[0046] First, in S500, the IAB node 103 selects, as a UE to be processed, one of the UEs connected to the IAB node 103 for which the decision as to whether or not to make the UE a target of group HO has not been completed, and proceeds to S501.
[0047] In S501, the IAB node 103 judges whether the UE to be processed satisfies a predetermined group HO condition. In this embodiment, the group HO condition is that the communication quality between the IAB node 103 and the UE to be processed is good. More specifically, the communication quality (parameter value indicating the communication quality) is set to be equal to or higher than a predetermined threshold as the group HO condition. For a UE with good communication quality with the IAB node 103, there is a high possibility that the communication quality can be maintained by performing group HO at the time of handover of the IAB node 103 and continuing the communication with the IAB node 103. For this reason, the IAB node 103 of this embodiment judges that the group HO condition is satisfied when the communication quality with the UE to be processed is equal to or higher than a predetermined threshold, and judges that the group HO condition is not satisfied when the communication quality is not equal to or higher than the predetermined threshold. The predetermined threshold may be a threshold larger than a second predetermined threshold used for judging whether to simply handover a UE with deteriorated communication quality to another base station when the IAB node 103 has not judged to switch its connection destination. For example, even if a UE has normal or slightly poor communication quality with node 103 and is determined not to require handover when the second predetermined threshold is used as the judgment criterion, the UE can be configured to be determined not to satisfy the group HO condition in S501.
[0048] The parameter value indicating the communication quality may be, for example, a value of RSSI, SNR, MCS, communication speed, or signal-to-interference-and-noise ratio (SINR), or may be a value based on a combination of one or more of them. Here, an example in which RSSI is used as the parameter value indicating the communication quality will be described. When RSSI is used as the parameter value indicating the communication quality, the RSSI may be acquired in the IAB node 103 by measurement based on a received signal from the UE to be processed. Alternatively, the IAB node 103 may receive the RSSI acquired by measurement performed in the UE as a measurement report from the UE.
[0049] Here, the measurement of communication quality in the UE may be performed, for example, using an SSB periodically transmitted (broadcast) from the IAB node 103. The SSB is a synchronization signal / broadcast channel block (SS / PBCH Block) composed of a synchronization signal (SS) and a physical broadcast channel (PHCH). The SSB is periodically transmitted from the base station mainly so that the UE detects a cell ID and a reception timing at the start of communication. In NR, the SSB is also used to measure the reception quality of each cell. In this embodiment, the IAB donors 101, 102 and the IAB node 103 periodically transmit the SSB. The UEs 110 to 112 can measure communication quality (reception quality) using the SSB received from the IAB donors 101, 102 and the IAB node 103.
[0050] If the UE to be processed satisfies the group HO condition (for example, if the RSSI is equal to or greater than the threshold), the IAB node 103 advances the process from S501 to S502. In S502, the IAB node 103 determines that the UE to be processed is a UE to be subject to group HO, and advances the process to S504. On the other hand, if the UE to be processed does not satisfy the group HO condition (for example, if the RSSI is not equal to or greater than the threshold), the IAB node 103 advances the process from S501 to S503. In S503, the IAB node 103 determines that the UE to be processed is a UE that is not subject to group HO (a UE not subject to group HO), and advances the process to S504.
[0051] In S504, the IAB node 103 determines whether or not the process has been completed for all UEs connected to the IAB node 103. If the process has been completed for all UEs, the IAB node 103 ends the determination process according to the procedure in Fig. 5, and if the process has not been completed for all UEs, the process returns to S500, selects the next UE to be processed, and executes the process of S501 again.
[0052] Note that a condition other than the above-mentioned condition (communication quality (a parameter value indicating communication quality) being equal to or greater than a predetermined threshold) may be set as the group HO condition. For example, the above-mentioned group HO condition may be set as follows: the parameter value indicating communication quality is equal to or greater than a threshold for a predetermined period of time and is within a predetermined range.
[0053] <HO process for UE not covered by group HO> 6 is a sequence diagram showing an example of an HO process for a UE (UE 112) that is not a target of group HO according to the present embodiment. As in the above example, it is assumed that UE 112 is determined as a UE that is not a target of group HO by the process of determining UEs that are target of group HO (S401).
[0054] In S600, the UE 112 is performing data communication for executing an application via the CN 130. Data related to the application is relayed between the UE 112 and the CN 130 by the IAB donor 101 and the IAB node 103. In S403 of FIG. 4, the IAB node 103 executes the process according to this sequence for each UE that is not a target of HO.
[0055] In S602, the IAB node 103 causes the UE 112 to measure communication quality based on a received signal from each IAB donor or node (in this example, the IAB donors 101 and 102) around the UE 112. The UE 112 measures the reception quality of the SSB transmitted from each IAB donor or node around the UE 112 according to an instruction from the IAB node 103. Then, in S603, the UE 112 transmits the measurement result in S602 (in this example, the measurement result of the reception quality corresponding to each of the IAB donors 101 and 102) to the IAB node 103.
[0056] In S604, the IAB node 103 determines a handover destination of the UE 112 based on the measurement result received from the UE 112. In this example, the IAB donor 101 is determined as the handover destination of the UE 112. In S605, the IAB node 103 requests the IAB donor 101 determined as the handover destination of the UE 112 to accept the handover of the UE 112. In this example, the IAB donor 101 permits the handover of the UE 112 to the IAB donor 101 in response to the request from the IAB node 103.
[0057] The IAB node 103 performs handover processing of the UE 112 to the IAB donor 101 in response to permission from the IAB donor 101. Specifically, in S606, the IAB node 103 instructs the UE 112 to handover to the IAB donor 101. Furthermore, in S607, the IAB node 103 transfers session information of the UE 112 to the IAB donor 101.
[0058] In S608, the UE 112 that has received the handover instruction from the IAB node 103 performs a synchronization process with the IAB donor 101 for handover from the IAB node 103 to the IAB donor 101. Specifically, the UE 112 receives an SSB broadcast from the IAB donor 101, and establishes a connection with the IAB donor 101 by performing a synchronization process with the IAB donor 101 using the received SSB. Note that the UE 112 may maintain the connection with the IAB node 103 at this stage without disconnecting it.
[0059] Furthermore, the IAB donor 101, which has received the session information of the UE 112 transferred from the IAB node 103, transmits a path switching request for the communication path for communication with the UE 112 to the CN 130 (a network node in the CN 130) in S609. When the CN 130 permits path switching based on the received request, it switches the communication path for communication with the UE 112 from the communication path via the IAB node 103 to the communication path via the IAB donor 101 in S610 and S611. At that time, the use of the session information of the UE 112 that has been transferred from the IAB node 103 to the IAB donor 101 is started. Furthermore, the UE 112 disconnects the connection with the IAB node 103.
[0060] After the switching of the communication path is completed, in S612, the UE 112 seamlessly continues the communication for the running application between the UE 112 and the CN 130 via the IAB donor 101. Through the above sequence, the handover process for the UE 112 that is not a target of the group HO at the time of the handover of the IAB node 103 is performed.
[0061] <HO process for UEs subject to group HO> 7 is a sequence diagram showing an example of HO processing (group HO processing) for group HO target UEs (UEs 110 and 111) according to the present embodiment. As in the above example, it is assumed that UEs 110 and 111 are determined as group HO target UEs by the group HO target UE determination processing (S401).
[0062] The IAB node 103 determines (S405) to execute group HO processing for UEs that are group HO targets, in response to detection (S400) of a drop in RSSI in communication with the connected IAB donor 101. However, in this example, a case will be described in which the HO processing of the IAB node 103 and the group HO processing of UEs that are group HO targets are executed under the control of the IAB donor 101.
[0063] In S700, the UEs 110 and 111 are performing data communication for executing an application via the CN 130. Relay of data related to the application between the UEs 110 and 111 and the CN 130 is performed by the IAB donor 101 and the IAB node 103.
[0064] In S701, the IAB donor 101 detects a decrease in RSSI (RSSI based on a received signal from the IAB node 103) in communication with the IAB node 103. For example, the IAB donor 101 determines that the RSSI has decreased when the RSSI in communication with the IAB node 103 falls below a predetermined threshold. In response to the detection of the decrease in RSSI in communication with the IAB node 103, the IAB donor 101 causes the IAB node 103 to measure communication quality to determine a handover destination from the IAB donor 101.
[0065] Specifically, in S702, the IAB donor 101 causes the IAB node 103 to measure communication quality based on a received signal from each IAB donor or node (in this example, the IAB donor 102) around the IAB node 103. The IAB node 103 measures the reception quality of the SSB transmitted from each IAB donor or node around the IAB node 103 according to an instruction from the IAB donor 101. Thereafter, in S703, the IAB node 103 transmits the measurement result in S702 (in this example, the measurement result of the reception quality corresponding to the IAB donor 102) to the IAB donor 101.
[0066] In S704, the IAB donor 101 determines a handover destination of the IAB node 103 based on the measurement result received from the IAB node 103. In this example, the IAB donor 102 is determined as the handover destination of the IAB node 103. In S705, the IAB donor 101 requests the IAB donor 102 determined as the handover destination of the IAB node 103 to accept the handover of the IAB node 103. In this example, the IAB donor 102 allows the handover of the IAB node 103 to the IAB donor 102 in response to the request from the IAB donor 101.
[0067] The IAB donor 101 performs handover processing of the IAB node 103 to the IAB donor 102 in response to permission from the IAB donor 102. Specifically, in S706, the IAB donor 101 instructs the IAB node 103 to perform handover to the IAB donor 102. In S707, the IAB node 103 that has received the handover instruction from the IAB donor 101 transfers session information of UEs (in this example, UEs 110 and 111) that are targets of group HO among UEs currently connected to the IAB node 103 to the IAB donor 101. In S708, the IAB donor 101 transfers the session information of the IAB node 103 and the session information of UEs 110 and 111 that are targets of group HO transferred from the IAB node 103 to the IAB donor 102.
[0068] The IAB node 103 which has received the handover instruction from the IAB donor 101 further performs a synchronization process with the IAB donor 102 in S709 for a handover (group HO) from the IAB donor 101 to the IAB donor 102. Specifically, the IAB node 103 receives an SSB broadcast from the IAB donor 102, and establishes a connection with the IAB donor 102 by performing a synchronization process with the IAB donor 102 using the received SSB. Note that the IAB node 103 may maintain the connection with the IAB donor 101 at this stage without disconnecting it.
[0069] Also, in S710, the IAB donor 101 transmits a path switching request for the communication path for communication with the IAB node 103 to the CN 130 (a network node in the CN 130). When the CN 130 permits the path switching based on the received request, in S711 and S712, the CN 130 switches the communication path for communication with the IAB node 103 from the communication path via the IAB donor 101 to the communication path via the IAB donor 102. At this time, the use of the session information of the IAB node 103 and the session information of the UEs 110 and 111 that have been transferred to the IAB donor 102 is started. Also, the IAB node 103 disconnects the connection with the IAB donor 101.
[0070] After the switching of the communication path is completed, in S713, the UEs 110 and 111 seamlessly continue the communication for the running application between the UEs 110 and 111 and the CN 130 via the IAB node 103 and the IAB donor 102. Through the above sequence, handover processing (group HO processing) is performed between the IAB node 103 and the UEs 110 and 111 that are subject to group HO among the UEs connected to the IAB node 103.
[0071] Finally, the handover process of the UE when the IAB node 103 (not shown) has not determined to switch its own connection destination will be described. When it has not determined to switch its own connection destination, the IAB node 103 determines whether to perform handover process based on the above-mentioned second predetermined threshold and the measurement result of the reception quality of the radio waves of the surrounding IAB nodes received from each UE. For example, for a UE whose communication quality between the UE and the IAB node has deteriorated to such an extent that it is desirable to perform a handover immediately, control is performed to handover to another base station. The mechanism for handing over to another base station is the same as the process shown in FIG. 6, so the description is omitted. The difference from the process when it has been determined to switch its own connection destination described above is that the second predetermined threshold, which is smaller than the above-mentioned predetermined threshold, is used to determine whether to perform handover. In the handover process using this second predetermined threshold, a UE whose communication quality with the node 103 is normal or slightly poor is not determined to require handover. On the other hand, for UEs whose communication quality is worse than normal or slightly poor, it is determined that handover is necessary, and handover processing is executed.
[0072] As described above, before performing handover of a connection destination for communication with the CN 130 to another IAB donor or node (for example, when execution of handover is predicted), the IAB node 103 of the present embodiment performs a decision process for deciding whether or not to switch the connection destination together with the IAB node 103, based on whether or not a predetermined condition is satisfied for each UE currently connected to the IAB node 103. The IAB node 103 further performs communication control for handover to switch the connection destination from the IAB node 103 to another radio base station for UEs determined not to be targets for switching the connection destination together with the IAB node 103 by the decision process. In addition, the IAB node 103 performs group HO with the IAB donor 102 as the handover destination for UEs determined to be targets for switching the connection destination together with the IAB node 103 by the decision process.
[0073] In this way, the IAB node 103 is configured to be able to distinguish whether or not group HO should be performed for each subordinate UE when performing handover to another IAB donor or node. Therefore, for example, appropriate communication control (handover processing) can be realized individually for UEs located inside and outside the bus 140 on which the IAB node 103 is mounted. Therefore, according to this embodiment, when the IAB node 103 performs handover, it becomes possible to perform appropriate communication control individually for the subordinate UEs.
[0074] [Embodiment 2] In the first embodiment, an example has been described in which the HO process of the IAB node 103 and the group HO process of the group HO target UE are executed under the control of the IAB donor 101. In the second embodiment, an example will be described in which the HO process of the IAB node 103 and the group HO process of the group HO target UE are actively executed by the IAB node 103. In the following, a description of parts common to the first embodiment will be omitted.
[0075] 8 is a sequence diagram showing an example of HO processing (group HO processing) for group HO target UEs (UEs 110 and 111) according to this embodiment. As in the above example, it is assumed that UEs 110 and 111 are determined as group HO target UEs by the group HO target UE determination processing (S401).
[0076] Upon detecting a drop in RSSI in communication with the connected IAB donor 101 (S400), the IAB node 103 determines to execute group HO processing for the UEs that are targets of group HO (S405).
[0077] In S800, the UEs 110 and 111 are performing data communication for executing an application via the CN 130. Relay of data related to the application between the UEs 110 and 111 and the CN 130 is performed by the IAB donor 101 and the IAB node 103.
[0078] In S801, the IAB node 103 detects a decrease in RSSI (RSSI based on a received signal from the IAB donor 101) in communication with the IAB donor 101. For example, the IAB node 103 determines that the RSSI has decreased when the RSSI in communication with the IAB donor 101 falls below a predetermined threshold. In response to the detection of the decrease in RSSI in communication with the IAB donor 101, the IAB node 103 performs measurement of communication quality to determine a handover destination from the IAB donor 101.
[0079] Specifically, in S802, the IAB node 103 performs communication quality measurement based on received signals from each IAB donor or node around the IAB node 103 (measurement of reception quality of SSB transmitted from each IAB donor or node). In S803, the IAB node 103 determines the handover destination of the IAB node 103 based on the measurement result in S802. In this example, the IAB node 103 detects that the reception quality (RSSI) of the SSB received from the IAB donor 102 is good (e.g., is equal to or higher than a predetermined threshold), and determines the IAB donor 102 as the handover destination from the IAB donor 101.
[0080] In S804, the IAB node 103 requests the IAB donor 102 determined as the handover destination to perform a group HO together with the UEs (UEs 110 and 111 in this example) that are the targets of the group HO. In this example, the IAB donor 102 permits the group HO to the IAB donor 102 in response to the request from the IAB node 103. In S805, the IAB donor 102 transmits an authorization response indicating that the group HO to the IAB donor 102 is permitted to the IAB node 103. In response to the authorization from the IAB donor 102, the IAB node 103 performs the group HO process to the IAB donor 102 by the following process.
[0081] In S806, the IAB donor 102 requests the IAB donor 101, which is the handover source of the IAB node 103, to transfer session information for group HO to the IAB donor 102 by the IAB node 103. Upon receiving the request from the IAB donor 102, in S807, the IAB donor 101 requests the IAB node 103 to transfer session information of the UEs (UEs 110 and 111 in this example) that are targets of the group HO. In response to the request from the IAB donor 101, in S808, the IAB node 103 transfers the session information of the UEs 110 and 111 that are targets of the group HO to the IAB donor 101. In S809, the IAB donor 101 transfers the session information of the IAB node 103 and the session information of the UEs 110 and 111 that are targets of the group HO that was transferred from the IAB node 103 to the IAB donor 102.
[0082] Thereafter, in S810, the IAB node 103 performs synchronization processing with the IAB donor 102 for handover (group HO) from the IAB donor 101 to the IAB donor 102. Specifically, the IAB node 103 receives an SSB broadcast from the IAB donor 102, and performs synchronization processing with the IAB donor 102 using the received SSB, thereby establishing a connection with the IAB donor 102. After establishing a connection with the IAB donor 102, the IAB node 103 transmits a disconnection request to the IAB donor 101 in S811.
[0083] The IAB donor 101, which has received the disconnection request from the IAB node 103, transmits a path switching request for the communication path for communication with the IAB node 103 to the CN 130 (a network node in the CN 130) in S813. When the CN 130 permits path switching based on the received request, in S813 and S814, the communication path for communication with the IAB node 103 is switched from the communication path via the IAB donor 101 to the communication path via the IAB donor 102. At this time, the use of the session information of the IAB node 103 and the session information of the UEs 110 and 111 that have been transferred to the IAB donor 102 is started. After that, in S815, the IAB donor 101 disconnects the connection (communication path) between the IAB donor 101 and the IAB node 103.
[0084] After the switching of the communication path is completed, in S816, the UEs 110 and 111 seamlessly continue the communication for the running application between the UEs 110 and 111 and the CN 130 via the IAB node 103 and the IAB donor 102. Through the above sequence, handover processing (group HO processing) is performed between the IAB node 103 and the UEs 110 and 111 that are subject to group HO among the UEs connected to the IAB node 103.
[0085] As described above, in this embodiment, even if the IAB node 103 actively executes its own HO process and group HO process for group HO target UEs, it is possible to obtain the same effects as those of the first embodiment. That is, when the IAB node 103 performs handover, it becomes possible to perform appropriate communication control for each UE under its control.
[0086] [Other embodiments] In the above embodiment, the condition (group HO condition) for determining that a UE connected to the IAB node 103 is a target for group HO is that the communication quality (e.g., RSSI) between the UE and the IAB node 103 is equal to or higher than a predetermined threshold. The group HO condition may be set to a different condition.
[0087] For example, the group HO condition may be that the UE is connected to the IAB node 103 and is in a communication state in which communication is being performed (e.g., a state in which communication is being performed for executing an application). The communication state in which the UE is in communication may include, for example, an RRC INACTIVE state and an RRC CONNECTED state among the RRC states. Alternatively, the group HO condition may be that the UE continues such a communication state for a predetermined time.
[0088] In addition, other group HO conditions may be defined using movement information or location information of the IAB node 103. For example, such a condition may be defined as a UE moving in the same movement direction as the IAB node 103 for a predetermined time. In this case, as shown in Fig. 2(B), the IAB node 103 may further include an IMU (Inertial Measurement Unit) 211, a GPS (Global Positioning System) control unit 212, and a GPS antenna 213. This allows the IAB node 103 to obtain information indicating the moving direction and position of the own station. The IAB node 103 may also obtain information indicating the moving direction and position from each connected UE.
[0089] Also, the IAB node 103 may transmit two types of broadcast signals (e.g., SSB) with different signal levels (radio signal strength), and determine whether or not to subject a UE to group HO based on whether or not the UE can receive such a broadcast signal. In this case, the group HO condition may be set as a UE that can receive at least the broadcast signal with the lower signal level of the two types of broadcast signals with different signal levels (radio signal strength) transmitted from the IAB node 103.
[0090] Even when such various group HO conditions are used, it is possible to obtain the same effects as those in the first and second embodiments. That is, when the IAB node 103 performs handover, it becomes possible to perform appropriate communication control individually for the subordinate UEs.
[0091] The present invention can also be realized by a process in which a program for implementing one or more of the functions of the above-described embodiments is supplied to a system or device via a network or a storage medium, and one or more processors in a computer of the system or device read and execute the program. The present invention can also be realized by a circuit (e.g., ASIC) that implements one or more of the functions.
[0092] The disclosure of this specification includes the following mobile communication device, control method thereof, and program. (Item 1) A mobile communication device having a relay function for relaying communication between a wireless base station and a wireless terminal, a determination means for performing a determination process for determining, before a handover is performed to switch a connection destination for communication with a core network to another radio base station or another communication device having the relay function, whether or not a wireless terminal connected to the mobile communication device is to be a target for switching a connection destination together with the mobile communication device, based on whether or not a predetermined condition is satisfied; a control means for performing communication control for handover to switch a connection destination from the mobile communication device to another radio base station for a radio terminal determined not to be a target for switching a connection destination together with the mobile communication device by the determination process; A mobile communication device comprising: (Item 2) The control means executes the group handover for the wireless terminal determined by the determination process to be a target for switching the connection destination together with the mobile communication device. 2. The mobile communication device according to item 1, (Item 3) When performing a handover to a handover destination determined in association with the movement of the mobile communication device, the control means performs a handover to the handover destination together with a wireless terminal determined to be a target for switching a connection destination together with the mobile communication device, thereby executing a group handover. 3. The mobile communication device according to item 2, (Item 4) a determination unit that determines whether or not handover of the mobile communication device to another radio base station or another communication device is required based on a communication quality between the mobile communication device and the radio base station to which the mobile communication device is connected or the communication device having a relay function; The decision means performs the decision process when it is determined that a handover of the mobile communication device is necessary. 4. The mobile communication device according to claim 1, wherein the first and second inputs are connected to the first and second inputs. (Item 5) The predetermined condition is that a parameter value indicating communication quality between the mobile communication device and a wireless terminal currently connected to the mobile communication device is equal to or greater than a predetermined threshold value. 5. A mobile communication device according to any one of items 1 to 4. (Item 6) The parameter value indicating the communication quality is a received signal strength indicator (RSSI) obtained by a measurement based on a received signal from a wireless terminal connected to the mobile communication device. 6. The mobile communication device according to item 5, (Item 7) The parameter value indicating the communication quality is an RSSI obtained by a wireless terminal connected to the mobile communication device through measurement based on a report signal transmitted from the mobile communication device, and is the RSSI received as a measurement report from the wireless terminal. 6. The mobile communication device according to item 5, (Item 8) The broadcast signal is an SSB (synchronization signal / broadcast channel block). 8. The mobile communication device according to item 7, characterized in that (Item 9) The predetermined condition is that a parameter value indicating communication quality between the mobile communication device and a wireless terminal connected to the mobile communication device is equal to or greater than a threshold value for a predetermined period of time and is within a predetermined range. 5. A mobile communication device according to any one of items 1 to 4. (Item 10) The predetermined condition is that a wireless terminal connected to the mobile communication device is in a communication state in which the wireless terminal is communicating with the core network. 5. A mobile communication device according to any one of items 1 to 4. (Item 11) The predetermined condition is that a wireless terminal connected to the mobile communication device continues to communicate with the core network for a predetermined period of time. 5. A mobile communication device according to any one of items 1 to 4. (Item 12) The communication state includes an RRC INACTIVE state and an RRC CONNECTED state among RRC (Radio Resource Control) states. 12. A mobile communication device according to item 10 or 11, characterized in that (Item 13) The predetermined condition is that a wireless terminal connected to the mobile communication device is moving in the same direction as the mobile communication device for a predetermined period of time. 5. A mobile communication device according to any one of items 1 to 4. (Item 14) The predetermined condition is that a wireless terminal connected to the mobile communication device is able to receive at least a first broadcast signal and a second broadcast signal having a lower signal level than the first broadcast signal, both of which are transmitted from the mobile communication device. 5. A mobile communication device according to any one of items 1 to 4. (Item 15) The relay function is a relay function using IAB (Integrated Access and Backhaul) in 3GPP (3rd Generation Partnership Project), the wireless base station is an IAB donor; The mobile communication device is a mobile IAB node. 15. A mobile communication device according to any one of claims 1 to 14. (Item 16) A method for controlling a mobile communication device having a relay function for relaying communication between a wireless base station and a wireless terminal, comprising the steps of: a step of performing a decision process for deciding whether or not to switch a connection destination for communication with a core network to another radio base station or another communication device having the relay function, for each radio terminal connected to the mobile communication device, based on whether or not a predetermined condition is satisfied, and whether or not to switch the connection destination together with the mobile communication device, before performing a handover to switch the connection destination for communication with a core network to another radio base station or another communication device having the relay function; performing communication control for handover for switching a connection destination from the mobile communication device to another wireless base station for a wireless terminal determined not to be a target for switching a connection destination together with the mobile communication device by the determination process; A control method comprising: (Item 17) Item 17. A program for causing a computer to execute each step of the control method according to item 16.
[0093] The invention is not limited to the above-described embodiments, and various modifications and variations are possible without departing from the spirit and scope of the invention. Accordingly, the following claims are appended to apprise the public of the scope of the invention. [Explanation of symbols]
[0094] 100: wireless communication system, 101, 102: IAB donor, 103: IAB node, 110 to 112: UE, 130: CN
Claims
1. A mobile communication device having a relay function for relaying communication between a wireless base station and a wireless terminal, before performing a handover that switches a connection destination for communication with a core network to another wireless base station or another communication device having the relay function, for each wireless terminal connected to the mobile communication device, based on whether a predetermined condition is satisfied, determining means for performing a determination process of determining whether to be a target for switching the connection destination together with the mobile communication device; control means for performing communication control for handover for switching the connection destination from the mobile communication device to another wireless base station for a wireless terminal determined not to be a target for switching the connection destination together with the mobile communication device by the determination process; A mobile communication device comprising the above.
2. The control means executes a group handover for a wireless terminal determined to be a target for switching the connection destination together with the mobile communication device by the determination process. The mobile communication device according to claim 1, characterized in that.
3. When performing a handover to a handover destination determined as the mobile communication device moves, the control means executes a group handover by performing the handover to the handover destination together with a wireless terminal determined to be a target for switching the connection destination together with the mobile communication device. The mobile communication device according to claim 2, characterized in that.
4. The mobile communication device further comprises determination means for determining whether a handover of the mobile communication device to another wireless base station or another communication device is necessary based on the communication quality between the wireless base station to which the mobile communication device is connected or a communication device having the relay function, When it is determined that a handover of the mobile communication device is necessary, the determination means performs the determination process. The mobile communication device according to claim 1, characterized in that.
5. The predetermined condition is that a parameter value indicating the communication quality between the wireless terminal connected to the mobile communication device and the mobile communication device is equal to or greater than a predetermined threshold value. The mobile communication device according to any one of claims 1 to 4, characterized in that.
6. The parameter value indicating the communication quality is an RSSI (Received Signal Strength Indicator) obtained by measurement based on a received signal from a wireless terminal connected to the mobile communication device. The mobile communication device according to claim 5, characterized in that.
7. The parameter value indicating the communication quality is the RSSI obtained by measurement based on a notification signal transmitted from the mobile communication device by a wireless terminal connected to the mobile communication device, and is the RSSI received as a measurement report from the wireless terminal. The mobile communication device according to claim 5, characterized in that.
8. The notification signal is an SSB (Synchronization Signal / Notification Channel Block). The mobile communication device according to claim 7, characterized in that.
9. The predetermined condition is that a parameter value indicating the communication quality between the wireless terminal connected to the mobile communication device and the mobile communication device is equal to or greater than a threshold value over a predetermined time and within a predetermined range. The mobile communication device according to any one of claims 1 to 4, characterized in that.
10. The predetermined condition is that the wireless terminal connected to the mobile communication device is in a communication state of communicating with the core network. The mobile communication device according to any one of claims 1 to 4, characterized in that.
11. The predetermined condition is that the wireless terminal connected to the mobile communication device continues a communication state of communicating with the core network for a predetermined time. The mobile communication device according to any one of claims 1 to 4, characterized in that.
12. The communication state includes an RRC (Resource Control) INACTIVE state and an RRC CONNECTED state among RRC (Resource Control) states. The mobile communication device according to claim 10, characterized in that.
13. The predetermined condition is that the wireless terminal connected to the mobile communication device moves in the same moving direction as the mobile communication device over a predetermined time. The mobile communication device according to any one of claims 1 to 4, characterized in that.
14. The predetermined condition is that the wireless terminal connected to the mobile communication device can receive at least the second notification signal among a first notification signal transmitted from the mobile communication device and a second notification signal having a lower signal level than the first notification signal. The mobile communication device according to any one of claims 1 to 4, characterized in that.
15. The relay function performs relay by IAB (Integrated Access and Backhaul) in 3GPP (3rd Generation Partnership Project), The radio base station is an IAB donor, The mobile communication device is a mobile IAB node. The mobile communication device according to any one of claims 1 to 4, characterized in that...
16. A control method for a mobile communication device having a relay function for relaying communication between a radio base station and a radio terminal, comprising: Before performing a handover to switch a connection destination for communication with a core network to another radio base station or another communication device having the relay function, for each radio terminal connected to the mobile communication device, based on whether a predetermined condition is satisfied, performing a determination process of determining whether to be a target to switch the connection destination together with the mobile communication device; For a radio terminal determined not to be a target to switch the connection destination together with the mobile communication device by the determination process, performing communication control for a handover to switch the connection destination from the mobile communication device to another radio base station; A control method characterized by including the above.
17. A program for causing a computer to execute each step of the control method according to claim 16.
18. Before performing a handover to switch a connection destination of a mobile communication device having a relay function to another radio base station or another communication device having the relay function for communication with a core network, for each radio terminal connected to the mobile communication device, based on whether a predetermined condition is satisfied, performing a determination process of determining whether to be a target to switch the connection destination together with the mobile communication device; For a radio terminal determined not to be a target to switch the connection destination together with the mobile communication device by the determination process, performing a control process of performing communication control for a handover to switch the connection destination from the mobile communication device to another radio base station; A control method characterized by including the above.