Communication device, control method, and program

Abstract

To provide a mechanism allowing a MBSR to continuously receive stable services, where the MBSR moves to or exists in an area that is so difficult for radio waves to reach that may disconnect a wireless link between a parent node and the MBSR.SOLUTION: A communication device having an operation function of a Mobile Base Station Relay (MBSR) has relay request transmitting means for transmitting a relay request to another communication device having the operation function of the MBSR so that communication is performed between the own node and a master node via other communication device when a wireless link between the own node and the master node is disconnected.SELECTED DRAWING: Figure 1

Description

Technical Field

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

Background Art

[0002] Cellular communication standards are being established in the 3rd Generation Partnership Project (3GPP (registered trademark)). In the cellular communication standards in 3GPP (hereinafter referred to as "3GPP standards"), the standardization of Integrated Access and Backhaul (IAB) that integrates an access line and a backhaul line is in progress (see Patent Document 1).

[0003] In IAB, the radio resources used for the access line between a base station (gNB) and a user terminal (UE, User Equipment) are also used in the backhaul line. For example, in IAB, radio resources in the millimeter wave band such as the 28 GHz band can be used. By using IAB, a relay device (IAB node) can relay communication between a base station device (IAB donor) and a terminal device by a wireless line, and the area coverage can be expanded at a lower cost compared with the case of using a wired line such as an optical fiber.

[0004] So far, specifications have been established for fixed base stations (IAB nodes without mobility) up to Release 17, which is the standardization phase of 3GPP.

[0005] The current 3GPP is moving forward to the Release 18 phase. In this phase, discussions on use cases such as Vehicle Mounted Relay are actively underway. In addition, discussions on mobile IAB or Mobile BaseStation Relay (MBSR) are actively carried out for formulating architectures and protocol specifications to realize such use cases. In IAB using millimeter waves, in locations where radio waves from IAB nodes are difficult to reach due to the influence of obstacles such as in urban areas with buildings, it has been difficult for MBSR to continue the connection to the IAB donor and IAB nodes (coverage of communication services).

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0007] In 3GPP Release 18, in order to simply add MBSR to the IAB topology, standardization is progressing in the direction of restricting further connection of IAB nodes under MBSR. That is, MBSR only supports single-hop. On the other hand, if a multi-hop configuration in which another MBSR is further connected under MBSR can be constructed, the flexibility of the path can be enhanced. In this case, it is assumed that the cell coverage area can be flexibly expanded.

[0008] One aspect of the present invention aims to provide a mechanism that enables an MBSR moving to or existing in an area where radio waves are difficult to reach and the wireless link with the parent node is disconnected to continuously receive stable communication services.

Means for Solving the Problems

[0009] A communication device as one aspect of the present invention is a communication device having the operating function of MBSR (Mobile Base Station Relay), and when a radio link between its own node and the parent node is disconnected, it has relay request means for transmitting a relay request to another communication device having the operating function of MBSR so that communication is performed between its own node and the parent node via the other communication device.

Advantages of the Invention

[0010] According to one aspect of the present invention, it is possible to provide a mechanism that enables an MBSR that moves to or exists in an area where radio waves are difficult to reach and where the radio link with the parent node is disconnected to continuously receive a stable communication service.

Brief Description of the Drawings

[0011]

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Embodiments for Carrying Out the Invention

[0012] Hereinafter, each embodiment will be described in detail with reference to the accompanying drawings. In the following description, "number ***" in TS*** represents the number of the technical specification (Technical Specification) in the 3GPP standard.

[0013] By the way, in Release 18 of 3GPP, in order to simply add MBSR to the IAB topology, standardization is progressing in the direction of restricting further connection of IAB nodes under MBSR. That is, MBSR only supports single-hop. On the other hand, if a multi-hop configuration in which another MBSR is further connected under MBSR can be constructed, it is assumed that the flexibility of the path can be increased and the cell coverage area can be flexibly expanded. Therefore, the following embodiments aim to provide a specific mechanism for realizing the IAB topology in the multi-hop configuration.

[0014] Also, assuming a specific use case, in a situation where MBSR loses connection with the IAB donor and no other connectable nodes can be detected, even if there is another MBSR nearby, it cannot be connected. For this reason, until MBSR finds a parent node, there is a problem that data communication cannot be performed (service interruption state) in the UEs under the MBSR. However, the MBSR specification that only supports single-hop does not have a means (trigger) to request relay to another MBSR. Therefore, one of the purposes of the following embodiments is to further provide a mechanism of an operation that serves as a trigger for another MBSR to start operating as a relay node for an MBSR in a state where there is no connectable parent node. Also, one of the purposes of the following embodiments is, as another aspect, to improve the convenience of cellular communication.

[0015] First, FIG. 1 shows a mobile wireless communication system such as a 5G system including a radio integrated access and backhaul network that supports MBSR of a communication system 100. Here, mainly, 5G will be described, but it is also applicable to beyond 5G (for example, 5G Advanced, 6G, etc.).

[0016] The communication system 100 is composed of a plurality of UEs 120 to 123, a core network 150, a main base station 110, and MBSRs 101 to 102 mounted on vehicles 111 to 112. The vehicles 111 to 112 may be in any form such as a bus, a train, a taxi, a car, etc. Vehicles 113, MBSR 103, and remote UE 123 respectively represent the states after vehicles 112, MBSR 102, and remote UE 122 have moved. That is, vehicles 113, MBSR 103, and remote UE 123 are respectively the same as vehicles 112, MBSR 102, and remote UE 122. However, these distinctions are for convenience of explanation and may not necessarily coincide with the timing of connection interruption described later. The main base station 110, also called the IAB donor 110, is connected to the core network 150 via a wired link 140 (preferably an optical fiber or other wired means). In each of the embodiments described below, the IAB donor 110 is a 5G base station (gNB) equipped with additional functions for supporting the IAB function as defined in the 3GPP TS 38.300 v 17.2.0 specification.

[0017] MBSRs 101 and 102, also called mobile IAB nodes, are mounted on vehicles 111 and 112 and provide network coverage and capacity expansion. The IAB donor 110 can communicate not only with UEs inside the vehicle such as remote UEs 121 and 122 (123) but also with UEs outside the vehicle such as UE 120. Therefore, the IAB donor 110 and MBSRs 101, 102 form a backhaul network or an IAB network, or an IAB topology that accommodates UEs 121 to 122. The terms IAB network and IAB topology are used interchangeably hereinafter. The specifications of IAB are defined in several 3GPP standard documents as follows. -TS 38.300 RAN Architecture (V 17.2.0) -TS 38.321 MAC Protocol (V 17.2.0) -TS 38.331 Radio Resource Control (RRC) Protocol (V 17.2.0) -TS 38.340 Backhaul Adaptation Protocol Layer (V 17.2.0) -TS 38.401 RAN Architecture (V 17.2.0) -TS 38.423 Xn Application Protocol (V 17.2.0) -TS 38.473 F1 Application Protocol (V 17.2.0) Here, referring to FIG. 1, an overview until the problem of single-hop of MBSR occurs will be described.

[0018] The IAB donor 110 is wirelessly connected to the subordinate MBSR 101 via the wireless backhaul link 141, and similarly is wirelessly connected to the MBSR 102 via the wireless backhaul link 142. Data communication with the UE 121 in the vehicle 111 where the MBSR 101 is installed is possible, and data communication with the UE 122 in the vehicle 112 where the MBSR 102 is installed is possible.

[0019] However, when the vehicle 112 moves in the direction of the arrow 160 and moves to the position of the vehicle 113, the MBSR 102 mounted on the vehicle moves to the MBSR 103, and the UE 122 in the vehicle moves to the UE 123. In that case, the MBSR 103 may be hidden in the shadow of a shield 130 such as a building. In this case, the radio wave intensity of the wireless backhaul link 142 with the IAB donor 110 gradually attenuates, and finally the wireless link is disconnected and a radio link failure (RLF) occurs.

[0020] After RLF, MBSR103 tries to search for and connect to IAB donor 110 which was connected as the parent node before. However, due to obstacles 130 and 131, the connection cannot be established. As a result, MBSR103 is in a state where the subordinate UE123 cannot perform data communication (service interruption state). By searching for a base station (including IAB donors and IAB nodes) that can be connected as the parent node, MBSR103 can detect MBSR101 with high received power as the parent node. Also in this case, if MBSR101 only supports single-hop, MBSR101 will reject the connection request from MBSR103. As a result, the service interruption state in MBSR103 will continue.

[0021] Next, a mechanism that can at least partially solve such problems will be described in detail through each embodiment.

[0022] Figure 2A is a hardware functional block diagram of MBSR102 in each embodiment described below. Here, the configuration of MBSR102 will be described, but the same may apply to MBSR101.

[0023] MBSR102 is composed of hardware including a control unit 201, a memory unit 202, a wireless communication unit 203, and a communication antenna control unit 204.

[0024] The control unit 201 controls the entire device by executing a control program stored in the storage unit 202. The control unit 201 is composed of one or more processors such as a CPU or an MPU, for example, and controls the entire communication device by executing the control program read into the RAM which is the storage unit 202. Each process performed by the control unit 201 described in the flowchart to be described later can also be realized using a hardware circuit such as an ASIC or an FPGA. Note that ASIC is an abbreviation for Application Specific Integrated Circuit. FPGA is an abbreviation for Field Programmable Gate Array. Also, by the cooperation of the hardware circuit and a processor such as a CPU or an MPU, the processes described in the flowchart to be described later can be realized.

[0025] The storage unit 202 stores the control program executed by the control unit 201 and various information such as the connected UE information and the connection strength with the base station or the IAB donor 110. The storage unit 202 may include a main storage unit and an auxiliary storage unit. The main storage unit is, for example, a ROM (Read Only Memory) or a RAM (Random Access Memory). The main storage unit may store or temporarily store programs and data such as an OS (Operating System) which is basic software executed by the control unit 201 and application software. The auxiliary storage unit is, for example, an HDD (Hard Disk Drive) or an SSD (Solid State Drive), and may store data related to application software. For example, a control program stored in a non-volatile storage area is expanded into a RAM (Random Access Memory) and executed by a processor constituting the control unit 201. In this way, the control unit 201 and the storage unit 202 may function as a so-called computer.

[0026] The wireless communication unit 203 performs cellular network communication such as 5G compliant with the 3GPP standard. Specifically, it performs communication control of RAN (Radio Access Network) such as 5G NR (New Radio), and communication control of upper layers to perform cellular network communication. Although 5G is exemplified as an example of cellular network communication, it is not limited thereto, and the control of this embodiment can also be realized based on cellular network communication such as 5G Advanced / 6G. In this case, the wireless communication unit 203 shall perform cellular network communication such as 5G Advanced or 6G compliant with the 3GPP standard.

[0027] The communication antenna control unit 204 controls the antenna used for the wireless communication executed in the wireless communication unit 203.

[0028] The GPS communication unit 205 receives satellite signals from GPS (Global Positioning System) satellites and acquires position information of the current position including position identification information such as longitude and latitude information, and current time information. Note that the GPS communication unit 205 may have a function of measuring (positioning) the current position based on satellite signals. Note that, instead of or in addition to GPS, other GNSS (Global Navigation Satellite System) may be used.

[0029] The GPS antenna control unit 206 controls the antenna (not shown) for GPS communication performed by the GPS communication unit 205.

[0030] Figure 2B is a software functional block diagram of MBSR in each embodiment described below. Here, the configuration of MBSR102(103) will be described, but the same may apply to MBSR101.

[0031] The software function block 301 is stored in the storage unit 202 and executed by the control unit 201. The software function block 301 includes a signal transmission unit 302, a signal reception unit 303, a data storage unit 304, a connection control unit 305, a network configuration information management unit 306, a relay request processing unit 307, and a signal generation unit 308. Further, the software function block 301 includes a GPS signal processing unit 309 and a mode switching unit 310.

[0032] The signal transmission unit 302 and the signal reception unit 303 control the wireless communication unit 203 via the control unit 201 and perform cellular network communication such as LTE and 5G compliant with the 3GPP standard between the IAB donor 110 and other MBSRs and UEs 122.

[0033] The data storage unit 304 controls and manages the physical storage unit 202 and stores and holds the software itself, connection information with the IAB donor 110, information about the UE 122, etc. Information between nodes can be collected by communication packets (hereinafter referred to as BAP control packets) associated with notification signals and various control PDUs of the BAP. Information from the UE can be collected, for example, in the RRC status.

[0034] The connection control unit 305 controls the communication antenna control unit 204 via the control unit 201 during wireless communication. The connection control unit 305 generates a connection control signal based on information (described below) generated by the network configuration information management unit 306. Also, in the MBSR 102(103), when the connection control unit 305 receives a relay - dedicated connection (connection in the relay mode) response from another communication device (in this embodiment, the MBSR 101 described later), it determines the connection to the other communication device.

[0035] The network configuration information management unit 306 manages the configuration information of the IAB network including the local station. The network configuration information management unit 306 also manages the type information of the UE, IAB node, and MBSR that make connection requests to the local station.

[0036] The relay request processing unit 307 functions in the MBSR 102(103) (the second, fourth, and sixth embodiments described later). When the radio link with the parent node is disconnected, the relay request processing unit 307 performs various processes for a relay request to another MBSR (in this embodiment, the MBSR 101 described later). For example, the relay request processing unit 307 generates a relay request triggered by the disconnection of the radio link with the parent node. At this time, the relay request processing unit 307 may determine another MBSR (in this embodiment, the MBSR 101 described later) that is the destination of the relay request. When receiving notification signals from a plurality of other MBSRs before and after the disconnection of the radio link, the relay request processing unit 307 may determine one of the plurality of other MBSRs as the other MBSR that is the destination of the relay request. In this case, for example, one MBSR with the highest communication quality may be determined as the other MBSR that is the destination of the relay request.

[0037] The signal generation unit 308 manages and transmits various signals generated by the connection control unit 305. Also, in the MBSR 102(103), the signal generation unit 308 cooperates with the relay request processing unit 307 to generate a signal related to a relay request (described later). The relay request may be generated, for example, by adding a parameter "relay request" to the reserved area of the RRC SetUp Request message. It may also be generated by adding information indicating a relay request to the notification information (SS / PBCH Block). This will be described later with reference to FIGS. 10A and 10B.

[0038] The GPS signal processing unit 309 performs communication compliant with the GPS standard. The GPS signal processing unit 309 controls the antenna for GPS communication performed by the GPS communication unit 205 and calculates the current position and time from the received GPS information. Then, the GPS signal processing unit 309 outputs information in the NMEA (National Marine Electronics Association)-0183 format or the like, and performs a storage process of the current position and time to the data storage unit 304 as necessary.

[0039] The mode switching unit 310 functions in the MBSR 101. The mode switching unit 310 switches the operating mode between the normal mode and the relay mode. In the present embodiment, the mode switching unit 310 switches from the normal mode to the relay mode in response to a request from the IAB donor 110 (request to transition to the relay mode) described later. Alternatively, in addition to or instead of this, the mode switching unit 310 switches from the normal mode to the relay mode in response to a request from the MBSR when the radio link with the IAB donor 110 is disconnected.

[0040] In the normal mode, the DU (Distributed Unit) that serves as the radio function unit of the MBSR 101 can be connected only to the UE, and other IAB nodes (including the MBSR) cannot be connected. That is, the normal mode corresponds to a single-hop mode in which the UE can be connected but the subordinate child nodes cannot be connected.

[0041] The relay mode means a mode in which the MBSR is not connected to the UE and only relays other MBSRs as child nodes. The relay mode can support multi-hop, and corresponds to a mode in which only the MBSR can be connected to the DU of the radio function unit.

[0042] Note that the normal mode may be a mode that allows connection of normal IAB nodes and UEs other than the MBSR, although connection of the MBSR below is not allowed. Also, the relay mode may be a mode that allows connection of other IAB nodes including the MBSR. Also, the relay mode may be a mode that allows connection of other IAB nodes including the MBSR and the UE.

[0043] Regarding the activation of the new DU of MBSR101 (hereinafter also referred to as "new DU") described below, first, it is necessary to confirm that it is in a situation where it can be allocated bandwidth. Then, after such confirmation, a functional unit equivalent to the software function block 301 will be created. At this time, a new cell with a frequency different from that of the cell formed by the original DU will be formed. At this time, MBSR101 will activate two DUs in a dual-boot manner, and various methods can be adopted for this. An antenna and a hardware mechanism for the second DU can be prepared separately, and the processor of MBSR101 can control the antenna and the hardware mechanism to activate a new DU. Also, the antenna and the hardware mechanism can be shared, and multiple DUs can be activated software-wise. In this case, MBSR101 activates multiple tasks corresponding to the software function block 301 that performs control to realize the function as a DU. The tasks activated in accordance with the MBSR101 clause access the antenna and the hardware mechanism using time-division technology or the like, and the functions equivalent to the existing DU and the functions equivalent to the new DU can be substantially realized simultaneously.

[0044] FIG. 2C is a block diagram showing an example of the hardware configuration 401 of the IAB donor 110 according to the present embodiment.

[0045] The hardware configuration 401 includes a control unit 402, a storage unit 403, a wireless communication unit 404, and a communication antenna control unit 405.

[0046] The control unit 402 controls the entire device by executing a control program stored in the storage unit 403. The control unit 402 is constituted by, for example, one or more processors such as a CPU or an MPU, and controls the entire communication device by executing the control program read into the RAM which is the storage unit 403. Each process performed by the control unit 402 described in the flowchart to be described later can also be realized using a hardware circuit such as an ASIC or an FPGA. Also, by the cooperation of the hardware circuit and a processor such as a CPU or an MPU, the processes described in the flowchart to be described later can be realized.

[0047] The storage unit 403 stores the control program executed by the control unit 402 and various types of information such as cell information, connection terminal information, IAB routing information, and location information. The storage unit 403 may include a main storage unit and an auxiliary storage unit. The control unit 402 and the storage unit 403 may function as a so-called computer.

[0048] The wireless communication unit 404 performs cellular network communication such as LTE and 5G compliant with the 3GPP (registered trademark) standard.

[0049] The communication antenna control unit 405 controls an antenna (not shown) for wireless communication performed by the wireless communication unit 404.

[0050] FIG. 2D is a block diagram showing an example of the hardware configuration of the IAB donor 110 according to the present embodiment.

[0051] The software function 501 includes a signal transmission unit 502, a signal reception unit 503, a data storage unit 504, a connection control unit 505, an information detection unit 506, a peripheral node determination unit 507, and a mode change instruction generation unit 508.

[0052] The signal transmission unit 502 and the signal reception unit 503 perform cellular network communication such as LTE and 5G compliant with the 3GPP standard with the terminal device. Note that the control plane signal is received by the signal reception unit 503.

[0053] In the present embodiment, the signal transmission unit 502 transmits a transition instruction generated by the mode change instruction generation unit 508 (described later) to an MBSR that becomes a relay candidate (described later).

[0054] Also, in the present embodiment, the signal reception unit 503 acquires information that can determine whether the opposing communication device is an MBSR (i.e., an IAB node of a type involving movement). Such information is optional and may be, for example, information that explicitly or implicitly indicates that it is an MBSR, or information that explicitly or implicitly indicates that it is not an MBSR. In the present embodiment, such information is IAB node type information, the details of which will be described later.

[0055] The data storage unit 504 stores and holds software itself, IAB routing information, information regarding connected terminals, current time information, location information, movement route information, and the like.

[0056] The connection control unit 505 controls the antennas for wireless communication performed by the wireless communication unit 104.

[0057] The notification information detection unit 506 detects notification information of surrounding base stations and MBSRs.

[0058] When the wireless link with one MBSR is disconnected, the surrounding node determination unit 507 determines whether there are other nodes connectable to the one MBSR in the vicinity of the one MBSR. An example of the determination method will be described later in relation to S302 in FIG. 3 below.

[0059] The mode change instruction generation unit 508 generates a transition request to the relay mode (a change instruction to the relay mode). The transition request to the relay mode is transmitted to an MBSR that will be a relay candidate (described later). The generation conditions and the like of the transition request to the relay mode will be described later.

[0060] <First Embodiment: Relay Request from IAB Donor to MBSR (Without UE)> FIG. 3 shows the processing flow of generating a mode change instruction to the relay mode of the IAB donor 110 in the present embodiment (the same applies to the third and fifth embodiments described later).

[0061] The IAB donor 110 determines whether the connection with the subordinate MBSR has been disconnected (S300). In this example, it is assumed that the connection with the MBSR 103 has been disconnected as described above. In this case, the IAB donor 110 acquires the location information of each subordinate node (for example, an IAB node or an MBSR) (S301). Note that the IAB donor 110 may directly acquire the location information of each subordinate node from each node using an RRC message. The location information may be included in a Measurement Report. Also, the IAB donor 110 may acquire the location information of each node from the core network 150. Then, based on the location information, the IAB donor 110 determines whether there are other nodes (here, IAB nodes) or other IAB donors to which the MBSR 103 can be connected in the vicinity of the MBSR 103 (S302). The vicinity of the MBSR 103 may be defined in advance as an area within a predetermined distance centered on the location of the MBSR 103.

[0062] If there are other nodes to which MBSR103 can be connected, connect MBSR103 via the other nodes (S304). On the other hand, if there are no other nodes to which MBSR103 can be connected, the IAB donor 110 determines whether there is one or more other MBSRs to which MBSR103 can be connected (S303). If there is only one other MBSR to which MBSR103 can be connected, the process ends. On the other hand, if there is only one other MBSR to which MBSR103 can be connected, a transition request (change instruction to the relay mode) to the relay mode is sent to the other MBSR (S307). When there are a plurality of other MBSRs to which MBSR103 can be connected (S305), it may be as follows, for example. That is, based on the Measurement Report previously obtained from each other MBSR, the other MBSR with the highest communication quality with MBSR103 is determined as the relay candidate (S306). Note that the communication quality between MBSR103 and each other MBSR may be notified from each other MBSR to the IAB donor 110 using the spare area "nonCriticalExtension". This spare area is defined by the Measurement Report message format defined in Section 6.2.2 of TS38.331. For example, a field "communication information of MBSR" indicating the communication quality may be added to the spare area. In this case, the field of the communication information of MBSR may include communication status information (delay time, etc.).

[0063] In this case, the IAB donor 110 sends a transition request (change instruction to the relay mode) to the other MBSR with the highest communication quality (S307).

[0064] Note that in FIG. 3, step S306 may be omitted. In this case, the other MBSR closest to the position of MBSR103 where the disconnection is detected may be determined as the relay candidate, or the other MBSR may be determined as the relay candidate based on other criteria.

[0065] FIG. 4 shows the processing flow of mode determination of MBSR in this embodiment (the same applies to the second to fourth embodiments described later).

[0066] MBSR is connected to the network as normal-mode MBSR (S401). When there is a mode change instruction from the IAB donor 110 (S402), it checks for the presence of UEs connected to itself (S403). If there are connected UEs, it starts up a new DU in relay mode (S406). If there are no connected UEs, it operates itself in relay mode (S405). If it does not receive a change instruction in S402, it continues to operate in normal mode (S404). At this time, as a method of newly starting up the relay mode, multiple DUs may be started up using virtualization technology. Also, depending on the communication performance of its own station, it may be possible to provide services by splitting functions.

[0067] Figure 5 is a sequence diagram showing the flow from when the IAB donor 110 detects the disconnection from the MBSR 103 until the MBSR 103 is connected to the MBSR 101 operating as a relay node.

[0068] The MBSR 101 notifies that it is capable of operating as a relay node (S501). An SSB (Synchronization Signal Block) message is used for this notification. However, as the information notified in S501, it is also possible to newly define rsinfo in the nonCriticalExtension defined in SIB1 (or another SIB other than SIB1) and notify information indicating that it is capable of operating in relay mode. Alternatively, the MBSR 101 may notify that it is capable of operating as a relay node via an F1 message or an RRC message.

[0069] MBSR103 receives the notification signal from MBSR101, but does not respond at this stage because it is connected to the parent node (IAB donor 110). Subsequently, when MBSR103 moves and is hidden in the shadow of an obstacle, the wireless connection with the IAB donor 110 of the parent node is disconnected. When the IAB donor 110 detects that the connection with the subordinate MBSR103 has been disconnected (S502), it sends a connection request in relay mode to MBSR101, which is another child node in the connection (S503). At this time, the connection request may be sent on the condition that it can be confirmed from the location information, etc. that MBSR103 is in a connectable state.

[0070] Here, for the transmission signal from the IAB donor 110 to MBSR101, a parameter of "connection request to MBSR during disconnection" is added to the reserved area of the RRC Reconfiguration message, which is the RRC protocol in FIG. 6. Alternatively, a parameter of "connection request to MBSR during disconnection" may be added to the reserved area of the PDUType of S901 in the BAP message in FIG. 7 to send the connection request. BAP is an abbreviation for Backhaul Adaptation Protocol.

[0071] In this embodiment, it is assumed that MBSR101 is not connected to the UE and is operating in relay mode in response to the response from IAB donor 110 (see S405 in FIG. 4). Specifically, MBSR101 that has received a request from IAB donor 110 switches from the normal mode that supports only single-hop to the relay mode (S504). That is, MBSR101 responds to IAB donor 110 that it can be connected in relay mode (S504), and switches from the normal mode to the relay mode (S505). Then, MBSR101 transmits, by means of a notification signal, that it is operating in relay mode (S505A). Further, as a means for notifying that it is operating in relay mode, instead of notification, it may be unicast to MBSR103 using the RRC Reconfiguration message of the RRC protocol. At this time, the message format for notifying the relay request may be included in the RRC Reconfiguration message of the RRC protocol shown in FIG. 11 to be described later.

[0072] Since MBSR103 recognizes MBSR101 that can be connected as a parent node, it decides to connect MBSR101 as a parent node (S506). Then, MBSR103 executes a random access procedure for connecting to MBSR101 (S507), requests a connection via an RRC SetUp Request message or the like, and completes the connection (S508). IAB donor 110 performs backhaul (BH) path setting with MBSR103 via MBSR101, and establishes a BH RLC channel for data communication (S509). BH RLC is an abbreviation for Backhaul Radio Link Control. Through this series of sequences, UE123 connected to MBSR103 can perform data communication.

[0073] <Second Embodiment: Relay Request from MBSR with Connection Interruption to Another MBSR (Without UE)> FIG. 8 shows a flowchart of MBSR103 that has been disconnected from the parent node. After detecting the disconnection from the parent node at S801, MBSR103 notifies other MBSRs of the relay request (S802). When a response or notification is received from relay-capable MBSR101 (S803), MBSR103 attempts to connect to relay-capable MBSR101 (S804). If no other connectable MBSR is found at S803, other relay-capable MBSRs are searched for.

[0074] Note that in FIG. 8, it is assumed that there is one relay-capable MBSR (MBSR101). However, as shown in FIG. 8A, there may also be a case where responses or notifications are received from multiple MBSRs (YES in S803A). In this case, for example, based on the responses or notifications from each MBSR, the MBSR with the highest communication quality may be determined as the relay candidate (S803B). For example, the MBSR with the highest received signal strength related to the responses or notifications from each MBSR may be determined as the relay candidate (S803B).

[0075] FIG. 9 is a sequence diagram showing the flow until connection is established by MBSR103 that has been disconnected requesting relay to other MBSR101.

[0076] Also in this embodiment, similar to the above-described first embodiment, it is assumed that MBSR101 is not connected to the UE and is operable in relay mode in response to a response from IAB donor 110 (see S405 in FIG. 4).

[0077] MBSR101 notifies that it is capable of operating as a relay node (S901). MBSR103 receives the notification signal from MBSR101, but does not respond at this stage because it is still connected to the parent node. Thereafter, when MBSR103 moves and is hidden in the shadow of an obstacle, the wireless connection with IAB donor 110 of the parent node is disconnected, and it is detected that the connection to the parent node has been lost (S902).

[0078] Since MBSR103 recognizes that it can relay the notification signal from MBSR101, it is transmitted by adding the parameter "relay request" to the reserved area of the RRC SetUp Request message for MBSR101 (S903).

[0079] Alternatively, when MBSR103 has not received the notification from MBSR101 in S901, it may add information indicating a relay request to the notification information (SS / PBCH Block) and transmit it. At this time, the message format for notifying the relay request may be included in the SIB1 message shown in Fig. 10A. The SIB1 message has parameters such as SIB1-v1700-IEs, and the parameter "relay request" is added to the "Reason of NonAccess" which is the reserved area. Also, the message format for transmitting the relay request may be such that the parameter "relay request" is added to the "parameter for notifying that it is an IAB node" shown in Fig. 10B.

[0080] MBSR101 that has received the relay request of MBSR103 checks (requests) whether it can operate as a relay node for the parent node's IAB donor 110 (S904). The IAB donor 110 responds that MBSR101 can operate in the relay mode (S905). MBSR101 that has received the response from the IAB donor 110 switches from the normal mode that supports only single-hop to the relay mode (S906). MBSR101 transmits a notification signal indicating that it is operating in the relay mode (S907). Also, as a means for notifying the operation as the relay mode, instead of notification, it may be unicast to MBSR103 using the RRC Reconfigration message of the RRC protocol. At this time, the message format for notifying the relay request may be included in the RRC Reconfigration message of the RRC protocol shown in Fig. 11.

[0081] Since MBSR103 recognized MBSR101 that can be connected as a parent node, it decided to connect to MBSR101 as a parent node and executed a random access procedure (S908). MBSR103 requested a connection via an RRC SetUp Request message or the like and completed the connection (S909). The IAB donor 110 set up a backhaul path to MBSR103 via MBSR101 and established a BH RLC channel for data communication (S910). Through this series of sequences, UE123 connected to MBSR103 becomes capable of data communication.

[0082] In addition, in FIG. 9, MBSR101 operates in relay mode in response to a request from the IAB donor 110 (S904, S905). However, in a modification, MBSR101 may operate in relay mode in response to a relay request from MBSR103 (S903).

[0083] <Third Embodiment: Relay Request from IAB Donor to MBSR (with UE)> FIG. 12 is a sequence diagram showing that the IAB donor 110 that detected the disconnected MBSR103 requests relay to another MBSR101.

[0084] This embodiment assumes that the MBSR101 having a relay function is connected to the UE121 below (S1201). That is, in this embodiment, unlike the above-described first and second embodiments, the case where MBSR101 is connected to UE121 is assumed. In this case, MBSR101 can operate in relay mode while starting a new DU in response to a response from the IAB donor 110 (see S406 in FIG. 4). Note that, unlike this assumption, when MBSR101 is not connected to UE121, it may be the same as in the above-described first and second embodiments.

[0085] MBSR101 notifies that it can operate as a relay node (S1202). MBSR103 receives the notification signal from MBSR101, but does not respond at this stage because it is connected to the parent node. Subsequently, when MBSR103 moves and hides in the shadow of an obstacle, the wireless connection with the IAB donor 110 of the parent node is disconnected. The IAB donor 110 detects that the connection with the subordinate MBSR103 has been disconnected (S1203). Then, if the IAB donor 110 can confirm that it is in a connectable state based on the location information of MBSR103 and the like for another connected child node MBSR101, it sends a connection request in relay mode (S1204). Here, for the transmission signal from the IAB donor 110 to MBSR101, a parameter of "connection request to the disconnecting MBSR" is added to the reserved area of the RRC Reconfiguration message, which is the RRC protocol in FIG. 6. Alternatively, a parameter of "connection request to the disconnecting MBSR" may be added to the reserved area of the PDUType of S901 of the BAP message in FIG. 7 to send a connection request.

[0086] The IAB donor 110 responds to MBSR101 that it may operate in relay mode (S1205). At this time, MBSR101 is connected to the UE, and simultaneously implementing relay connections with other nodes in the same DU may increase complexity. Therefore, MBSR101 newly activates a different DU2 (192) from the DU1 (191) connected to the UE121 and uses it for relay with MBSR103 (S1206). MBSR101 sends a notification signal indicating that it is operating in relay mode (S1207).

[0087] Since MBSR103 recognized MBSR101 that can be connected as a parent node upon receiving the above notification signal, it decides to connect to MBSR101 as a parent node and executes a random access procedure to MBSR101 (S1208). Then, it requests a connection via an RRC SetUp Request message or the like and completes the connection (S1209). IAB donor 110 performs backhaul path setting with MBSR103 via DU2 (192) of MBSR101 and establishes a BH RLC channel for data communication (S1210).

[0088] Through this series of sequences, UE123 connected to MBSR103 becomes capable of data communication.

[0089] <Fourth Embodiment: Relay Request to Another MBSR (with UE) by Disconnected MBSR> FIG. 13 is a sequence diagram showing the flow until connection is established by requesting relay to another MBSR101 by MBSR103 that has been disconnected. However, this embodiment assumes that MBSR101 connected to UE121 and is operating in a relay mode while starting a new DU in response to a response from IAB donor 110 (see S406 in FIG. 4). Note that, different from this assumption, when MBSR101 is not connected to UE121, it may be the same as in the above-described first and second embodiments.

[0090] MBSR101 notifies that it can operate as a relay node (S1302). MBSR103 receives the notification signal from MBSR101, but does not respond at this stage because it is connected to the parent node. Then, when MBSR103 moves and is hidden in the shadow of an obstacle, the radio connection with IAB donor 110 of the parent node is disconnected, and it detects that the connection to the parent node has been lost (S1303).

[0091] MBSR103 recognizes that it can relay the notification signal from MBSR101. Therefore, MBSR103 transmits to MBSR101 by adding the parameter "relay request" to the reserved area of the RRC SetUp Request message (S1304). Alternatively, similar to the third embodiment, when MBSR103 has not received the notification in S1302, it may add information indicating the relay request to the relay-capable notification information (SS / PBCH Block) and transmit it.

[0092] MBSR101 that has received the relay request of MBSR103 checks whether it can operate as a relay node for the parent node IAB donor 110 (S1305). The IAB donor 110 responds that MBSR101 can operate in the relay mode (S1306).

[0093] Here, when MBSR101 operates as the "relay mode", the complexity increases when establishing a connection with other nodes via DU1 (191) that is connected to UE121. Therefore, a new DU2 (192) different from DU1 (191) that is connected to UE121 is newly activated and used for relaying with MBSR103 (S1307).

[0094] MBSR101 transmits, by a notification signal, that it is operating in the relay mode (S1308). Also, as a means for notifying the operation as the relay mode, instead of notification, it may be transmitted to MBSR103 using the RRC Reconfigration message.

[0095] Since MBSR103 recognized MBSR101 that can be connected as a parent node, it decided to connect to MBSR101 as a parent node and executed a random access procedure to MBSR101 (S1309). Then, it requested a connection via an RRC SetUp Request message or the like and completed the connection (S1310). The IAB donor 110 performs backhaul path setting with MBSR103 via the DU2 (192) of MBSR101 and establishes a BH RLC channel for data communication (S1311). Through this series of sequences, the UE123 connected to MBSR103 becomes capable of data communication.

[0096] <Fifth Embodiment: Relay Request from IAB Donor to Another MBSR (with UE)> FIG. 14 shows the processing flow of mode determination of MBSR in this embodiment (the same applies to the sixth embodiment described later). The MBSR is connected to the network as a normal-mode MBSR (S1401). When there is a mode change instruction from the IAB donor (S1402), it checks whether there is a UE connected to itself (S1403). If there is a connected UE, after releasing the connection with the connected UE, it operates in the relay mode (S1406). If there is no connected UE, it operates itself in the relay mode (S1405). If it does not receive a change instruction in S1402, it continues to operate in the normal mode (S1404).

[0097] FIG. 15 is a sequence diagram showing the flow from when the IAB donor detects the disconnection from MBSR103 until it is connected by requesting relay to another MBSR101.

[0098] In this embodiment, different from the above-described first embodiment and second embodiment, it is assumed that MBSR101 is connected to UE121. In this case, MBSR101 can operate in the relay mode after releasing the connection with the connected UE in response to the response from the IAB donor 110 (see S1406 in FIG. 14). Note that, different from this assumption, when MBSR101 is not connected to UE121, it may be the same as in the above-described first embodiment and second embodiment.

[0099] Specifically, referring to FIG. 15, in this embodiment, another MBSR has UE121 under its jurisdiction and is connected to MBSR101 to continue data communication (S1501).

[0100] MBSR101 notifies that it can operate as a relay node (S1502). MBSR103 receives the notification signal from MBSR101, but does not respond at this stage because it is connected to the parent node. Subsequently, when MBSR103 moves and is hidden in the shadow of an obstacle, the wireless connection with the IAB donor 110 of the parent node is disconnected. When the IAB donor 110 detects that the connection with the subordinate MBSR103 has been disconnected (S1503), it sends a connection request in relay mode to another connected child node MBSR101 (S1504). At this time, the connection request may be sent on the condition that it can be confirmed from the position information of MBSR103, etc. that it is in a connectable state. Here, the transmission signal from the IAB donor 110 to MBSR101 adds a parameter of "connection request to the MBSR being disconnected" to the reserved area of the RRC Reconfiguration message, which is the RRC protocol in FIG. 6. Or, a parameter of "connection request to the MBSR being disconnected" may be added to the reserved area of the PDUType of S901 of the BAP message in FIG. 7 to send a connection request.

[0101] The IAB donor 110 responds that MBSR101 may operate in relay mode (S1505). Here, when MBSR101 switches from the normal mode to the relay mode, the complexity increases when maintaining the connection with the UE while making connections with other nodes. Therefore, MBSR101 releases the connection with UE121 using the RRC Release message (or notifies other connectable IAB nodes) and operates dedicatedly for relaying with MBSR103 (S1506, S1507).

[0102] MBSR101 transmits a notification signal indicating that it operates in the relay mode (S1508). Since MBSR103 recognizes MBSR101 that can be connected as a parent node, it decides to connect to MBSR101 as a parent node. Then, it executes a random access procedure for connecting to MBSR101 (S1509), requests a connection via an RRC SetUp Request message or the like, and completes the connection (S1510). IAB donor 110 performs backhaul path setting with MBSR103 via MBSR101 and establishes a BH RLC channel for data communication (S1511). Through this series of sequences, UE123 connected to MBSR103 becomes capable of data communication.

[0103] <Sixth Embodiment: Relay Request to Another MBSR (with UE) by Disconnected MBSR> FIG. 16 is a sequence diagram showing the flow until connection is established by requesting relay to another MBSR101 by MBSR103 that has been disconnected.

[0104] In this embodiment, different from the above-described first and second embodiments, it is assumed that MBSR101 is connected to UE121. In this case, MBSR101, in response to the response from IAB donor 110, disconnects the connection with the connected UE and then can operate in the relay mode (see S1406 in FIG. 14). Note that, different from this assumption, when MBSR101 is not connected to UE121, it may be the same as in the above-described first and second embodiments.

[0105] Specifically, referring to FIG. 16, in this embodiment, another MBSR has UE121 under its control and is connected to MBSR101 to continue data communication (S1601).

[0106] MBSR101 notifies that it can operate as a relay node (S1602). MBSR103 receives the notification signal from MBSR101 but does not respond at this stage because it is connected to the parent node. Subsequently, when MBSR103 moves and hides in the shadow of an obstacle, the wireless connection with the IAB donor 110 of the parent node is disconnected, and it detects that the connection to the parent node has been lost (S1603).

[0107] Since MBSR103 recognizes that it can relay using the notification signal from MBSR101, it sends a message to MBSR101 by adding the parameter "relay request" to the reserved area of the RRC SetUp Request message (S1604). Alternatively, similar to the third embodiment, if it has not received S1602 (MBSR101 can operate as a relay node), it may add information indicating the relay request to the relay-capable notification information (SS / PBCH Block) and send it.

[0108] MBSR101, which has received the relay request from MBSR103, checks whether it can operate as a relay node for the IAB donor 110 (S1605). The IAB donor 110 responds that MBSR101 can operate in the relay mode (S1606). Here, when MBSR101 operates in the "relay mode", the complexity increases when maintaining the connection with the UE while establishing connections with other nodes. Therefore, MBSR101 disconnects the connection with UE121 and uses it for relaying with MBSR103 (S1607, S1608).

[0109] MBSR101 transmits a notification signal indicating that it is operating in the relay mode (S1609). Also, instead of notification, an RRC Reconfigration message may be used to send it to MBSR103 as a means of notifying the operation in the relay mode. Since MBSR103 recognizes MBSR101 that can be connected as a parent node, it decides to connect to MBSR101 as a parent node and executes a random access procedure for connecting to MBSR101 (S1610). Then, it requests a connection via an RRC SetUp Request message or the like and completes the connection (S1611). The IAB donor 110 performs backhaul (BH) path setting with MBSR103 via the DU2 (192) of MBSR101 and establishes a BH RLC channel for data communication (S1612).

[0110] Through this series of sequences, UE123 connected to MBSR103 becomes capable of data communication.

[0111] <Other Embodiments> In the above-described embodiment, the case where the MBSR that has received a relay request starts operating in the relay mode is exemplified. However, it can also be configured to be able to reject the relay request as necessary. The MBSR that has received a relay request can determine to reject the relay request according to its own resource shortage situation or the like. When it determines to reject the relay request, it notifies the device that is the source of the relay request of a message indicating that the relay request is rejected. In this case, the device that is the source of the request and has received the message indicating rejection may send the relay request to other candidate devices. For example, when the frequency resources available to itself are already in shortage in existing communications or when the number of UEs already connected to the MBSR is more than a predetermined number, etc., the MBSR that has received the relay request may reject the relay request. By this process, it is possible to prevent adverse effects on existing communications.

[0112] This embodiment can also be implemented by supplying a program that realizes one or more functions of the above-described embodiments to a system or apparatus via a network or a storage medium, and causing one or more processors in a computer of the system or apparatus to read and execute the program. It can also be implemented by a circuit (for example, ASIC or FPGA) that realizes one or more functions.

[0113] As described above in detail for each embodiment, the present invention is not limited to a specific embodiment, and various modifications and changes are possible within the scope described in the claims. It is also possible to combine all or a plurality of the constituent elements of the above-described embodiments.

[0114] In addition, the following supplementary notes are disclosed regarding the above embodiments.

[0115] [Supplementary Note 1] A communication device having an operating function of MBSR (Mobile BaseStation Relay), characterized by having relay request means for transmitting a relay request so that communication is performed between a self-node and a parent node via another communication device having an operating function of MBSR when a wireless link between the self-node and the parent node is disconnected.

[0116] [Supplementary Note 2] The communication device according to Supplementary Note 1, wherein the relay request means transmits the relay request triggered by a detection event for detecting a disconnection of a wireless link between the self-node and the parent node.

[0117] [Supplementary Note 3] The communication device according to Supplementary Note 1 or 2, further comprising destination determination means for determining the other communication device as the transmission destination of the relay request based on a notification signal received before or after a wireless link between the self-node and the parent node is disconnected.

[0118] [Supplementary Note 4] The transmission destination determination means determines, when there are a plurality of transmission sources of the notification signal, the transmission source with the highest communication quality among the plurality of transmission sources as the other communication device that is the transmission destination of the relay request, for the communication device according to Supplementary Note 3.

[0119] [Supplementary Note 5] The relay request means transmits the relay request by using an SSB (Synchronization Signal Block) message or an RRC (Radio Resource Control) message, for the communication device according to any one of Supplementary Notes 1 to 4.

[0120] [Supplementary Note 6] The communication device according to any one of Supplementary Notes 1 to 5, further comprising connection determination means for determining a connection to the other communication device when there is a connection response dedicated for relaying from the other communication device.

[0121] [Supplementary Note 7] A communication device that functions as an IAB (Integrated Access and Backhaul) donor, having transmission means for transmitting a relay request to a second MBSR under its control to perform relay of the disconnected first MBSR when the radio link with the first MBSR being connected as a child node is disconnected, for the communication device.

[0122] [Supplementary Note 8] further having determination means for determining whether or not a target node that can be connected in the vicinity of the first MBSR and functions as an IAB donor or an IAB node exists under its control, The transmission means transmits the relay request to the second MBSR when the determination means determines that the target node does not exist, for the communication device according to Supplementary Note 7.

[0123] [Supplementary Note 9] The determination means determines the presence or absence of the target node among the one or more nodes based on the position information of one or more subordinate nodes, and the communication device according to appended claim 8.

[0124] [Appended claim 10] The transmission means transmits the relay request to the second MBSR triggered by a detection event for detecting disconnection of the radio link with the first MBSR, and the communication device according to any one of appended claims 7 to 9.

[0125] [Appended claim 11] The transmission means transmits the relay request to the second MBSR when receiving a notification that the second MBSR is capable of relaying, and the communication device according to any one of appended claims 7 to 10.

[0126] [Appended claim 12] The transmission means uses a BAP (Backhaul Adaptation Protocol) message or an RRC (Radio Resource Control) message, and the communication device according to any one of appended claims 7 to 11.

Explanation of reference signs

[0127] 100 Communication system 101 MBSR 102 MBSR 103 MBSR 110 IAB donor (master base station) 111 Vehicle 112 Vehicle 113 Vehicle 130 Shelter 131 Shelter 140 Wired link 141 Wireless backhaul link 142 Wireless backhaul link 150 Core network 201 Control unit 202 Storage unit 203 Wireless Communication Unit 204 Communication Antenna Control Unit 205 GPS Communication Unit 206 GPS Antenna Control Unit 302 Signal Transmission Unit (An example of relay request means) 303 Signal Reception Unit 304 Data Storage Unit 305 Connection Control Unit (An example of connection determination means) 306 Network Configuration Information Management Unit 307 Relay Request Processing Unit (An example of destination determination means) 308 Signal Generation Unit 309 GPS Signal Processing Unit 310 Mode Switching Unit 402 Control Unit 403 Storage Unit 404 Wireless Communication Unit 405 Communication Antenna Control Unit 502 Signal Transmission Unit (An example of transmission means) 503 Signal Reception Unit 504 Data Storage Unit 505 Connection Control Unit 506 Notification Information Detection Unit 507 Peripheral Node Judgment Unit (An example of judgment means) 508 Mode Change Instruction Generation Unit

Claims

1. A communication device having an operating function of MBSR (Mobile Base Station Relay), wherein when a wireless link between its own node and a parent node is disconnected, a relay request means is provided for transmitting a relay request to another communication device having an operating function of MBSR so that communication is performed between its own node and the parent node via the other communication device, characterized in that the communication device has the relay request means.

2. The communication device according to claim 1, wherein the relay request means transmits the relay request triggered by a detection event for detecting a disconnection of a wireless link between its own node and a parent node.

3. The communication device according to claim 1, further comprising a transmission destination determination means for determining the other communication device as the transmission destination of the relay request based on a notification signal received before or after a wireless link between its own node and a parent node is disconnected.

4. The communication device according to claim 3, wherein when there are a plurality of transmission sources of the notification signal, the transmission destination determination means determines, as the other communication device as the transmission destination of the relay request, a transmission source having the highest communication quality among the plurality of transmission sources.

5. The communication device according to claim 1, wherein the relay request means transmits the relay request using an SSB (Synchronization Signal Block) message or an RRC (Radio Resource Control) message.

6. The communication device according to any one of claims 1 to 5, further comprising a connection determination means for determining a connection to the other communication device when there is a relay-exclusive connection response from the other communication device.

7. A communication device functioning as an IAB (Integrated Access and Backhaul) donor, wherein when a wireless link with a first MBSR being connected as a child node is disconnected, a transmission means is provided for transmitting a relay request to a second MBSR under its control so that the first MBSR with the disconnected link is relayed, characterized in that the communication device has the transmission means.

8. The communication device further comprises a determination means for determining whether a target node that can be connected to the first MBSR and functions as an IAB donor or an IAB node exists under its control. The communication device according to claim 7, wherein the transmitting means transmits the relay request to the second MBSR when the determination means determines that the target node does not exist.

9. The communication device according to claim 8, wherein the determination means determines the presence or absence of the target node among the one or more nodes based on the location information of the one or more subordinate nodes.

10. The communication device according to claim 7, wherein the transmitting means transmits the relay request to the second MBSR triggered by a detection event that detects a disconnection of the wireless link with the first MBSR.

11. The communication device according to claim 7, wherein the transmitting means transmits the relay request to the second MBSR when receiving a notification that relay is possible from the second MBSR.

12. The communication device according to any one of claims 7 to 11, wherein the transmitting means uses a BAP (Backhaul Adaptation Protocol) message or an RRC (Radio Resource Control) message.

13. A control method for controlling communication of a communication device having an operating function of an MBSR (Mobile BaseStation Relay), The control method includes a step of transmitting a relay request to another communication device having an operating function of an MBSR so that communication is performed between the own node and the parent node via the other communication device when the wireless link between the own node and the parent node is disconnected.

14. A program for causing a computer of a communication device having an operating function of an MBSR (Mobile BaseStation Relay) to execute a step of transmitting a relay request to another communication device having an operating function of an MBSR so that communication is performed between the own node and the parent node via the other communication device when the wireless link between the own node and the parent node is disconnected.

15. A control method for controlling communication of a communication device functioning as an IAB (Integrated Access and Backhaul) donor, A control method characterized by having a transmission step of transmitting a relay request to a subordinate second MBSR to relay the disconnected first MBSR when the wireless link with the first MBSR being connected as a sub-node is disconnected.

16. In a computer of a communication device functioning as an IAB (Integrated Access and Backhaul) donor, A program for causing the computer to execute a transmission step of transmitting a relay request to a subordinate second MBSR to relay the disconnected first MBSR when the wireless link with the first MBSR being connected as a sub-node is disconnected.

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