Communication device, control method, and program

Abstract

A communication device according to one aspect of the present invention constitutes a backhaul network and comprises: a generation means for generating connection continuity information indicating an index of whether one or more upper-level connected Mobile BaseStation Relay (MBSR) connection links are stable; and a transmission means for transmitting the connection continuity information to another communication device.

Description

Communication device, control method, and program

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

[0002] The Third Generation Partnership Project (3GPP (registered trademark)) has formulated cellular communication standards. The 3GPP cellular communication standards (hereinafter referred to as "3GPP standards") are currently in the process of standardizing Integrated Access and Backhaul (IAB), which integrates access lines and backhaul lines.

[0003] In an IAB network, radio resources used for an access line between a base station (gNB) and user equipment (UE) are also used for a backhaul line. For example, in an IAB network, radio resources in a millimeter wave band such as the 28 GHz band are used (Patent Document 1).

[0004] IAB technology allows a relay device (IAB node) to relay communications between a base station device (IAB donor) and a terminal device via a wireless line, thereby enabling area coverage to be expanded more cheaply than when using a wired line such as optical fiber.

[0005] Typically, network topology formation in an IAB is achieved by an IAB node establishing a connection with an IAB donor or another IAB node that has the best received radio wave strength.

[0006] Currently, studies are being conducted to form a network topology suitable for use cases such as even lower latency, high-speed, and large-capacity communications, etc. For example, a technology has been proposed in which information regarding wireless link route settings is notified to lower-level IAB nodes based on wireless link measurement results in broadcast signals and downlink reference signals, thereby forming an appropriate communication link according to the usage situation (Patent Document 2).

[0007] 3GPP has been developing specifications for fixed base stations (IAB nodes that do not involve movement) up until Release 17, which is the standardization phase. Furthermore, Release 18 proposes a new use case, Vehicle Mounted Relay. Furthermore, architecture and protocol specifications for IAB nodes that involve movement, known as Mobile IAB or Mobile Base Station Relay (MBSR), are being developed.

[0008] JP2019-534625 Patent No. 7170727

[0009] If a UE or MBSR connects to another MBSR, and as a result the connection to the IAB donor has to go through multiple MBSRs, there is a high risk of the connection being lost because the MBSR involves movement.

[0010] The present invention has been made in consideration of at least one of the above-mentioned problems, and an object of one aspect of the present invention is to provide a mechanism that enables more stable communication in IAB.

[0011] A communication device according to one aspect of the present invention is a communication device that constitutes a backhaul network, and is characterized by having a generating means for generating connection continuity information that indicates whether the connection links of one or more MBSRs (Mobile Base Station Relays) connected to an upper level are stable, and a transmitting means for transmitting the connection continuity information to other communication devices.

[0012] According to the present invention, it is possible to provide a mechanism that enables more stable communication in the IAB.

[0013] 1 is a diagram illustrating an example of the configuration of an IAB network. 2 is a hardware functional block diagram of an MBSR. 3 is a software functional block diagram of an MBSR. 4 is a sequence diagram (embodiment 1) illustrating an example of connection processing in a UE and an MBSR. 5 is a flowchart illustrating an example of connection destination determination processing in a UE and an MBSR. 6 is a flowchart illustrating an example of MBSR hop count calculation and transmission processing in an MBSR. 7 is a sequence diagram (embodiment 2) illustrating an example of connection processing in a UE and an MBSR.

[0014] Each embodiment will be described in detail below with reference to the accompanying drawings.

[0015] [First Embodiment] FIG. 1 illustrates an example of the configuration of an IAB network according to an embodiment of the present disclosure.

[0016] 1, the following situation is assumed: In IAB network 100, there is a donor 101 that provides a connection to CN 130, and UE 110 or MBSR 107 is attempting to connect to IAB network 100. UE 110 or MBSR 107 wakes up from a sleep state to start a connection process with one of the IAB donors and nodes 101 to 106 that make up IAB network 100.

[0017] Here, CN stands for Core Network, and is responsible for various processes such as authentication of the terminal UE 110 and slice usage registration.

[0018] The UE 110 is a mobile terminal used by a bus passenger or a pedestrian. The MBSRs 104 to 107 are communication devices mounted on the bus and function as IAB nodes that move along with the movement of the bus.

[0019] In the IAB network 100, fixed IAB nodes 102 and 103, which do not involve mobility, are connected to an IAB donor 101, and mobile MBSRs 104-106 are connected below the IAB 102. Because an MBSR is a type of IAB node, for convenience of explanation, the MBSRs 104-106 are sometimes referred to as IAB nodes 104-106 or mIAB nodes 104-106. mIAB is an abbreviation for mobile IAB. Each IAB donor and IAB node 101-106, including the MBSR, periodically transmits a Master Information Block (MIB) and a System Information Block (SIB) as broadcast signals. UE 110 or MBSR 107 analyzes broadcast information from IAB nodes 101-106, including IAB donor 101 and MBSR, and determines that the received signal strength from MBSRs 104-106 is equal to or greater than a predetermined threshold, making them suitable candidates for connection. For example, assume that UE 110 or MBSR 107 determines as follows: That is, the received signal strength from MBSR 106 is the highest, followed by MBSR 105 and MBSR 104. Furthermore, MBSR 106 is three hops away from IAB node 102; similarly, MBSR 105 is two hops away, and MBSR 104 is one hop away. Here, the following terms are used to describe the number of hops: That is, the number of hops from the IAB donor 101 via IAB nodes including MBSR is simply called the number of hops, and the number of hops from the IAB donor 101 via only MBSR is called the MBSR hop count to distinguish it from the MBSR hop count.

[0020] Here, information indicating the stability of communication in the network (backhaul) between the MBSR and the IAB donor is referred to as connection continuity information. The connection continuity information may be, for example, the MBSR hop count. As described above, since the MBSR involves movement, the greater the MBSR hop count, the higher the possibility of communication interruption. Therefore, the MBSR hop count indicates the stability of communication. The MBSR hop count is broadcast as connection continuity information by being included in the broadcast information of the SIB transmitted by each MBSR 104-106. Here, the connection continuity information may be broadcast by the MIB or may be included in the SSB (Synchronization Signal Block). Furthermore, the hop count may be broadcast in addition to the MBSR hop count. Furthermore, the connection continuity information may be mobility information. The mobility information may include status information indicating whether the own station is moving or stationary, and location information indicating the moving speed and current location.

[0021] MBSR 106 has the largest number of MBSR hops, and therefore the risk of disconnection due to movement of its own station as well as movement of MBSRs 104 and 105 connected to it at higher levels is higher than that of the other MBSRs 104 and 105. MBSR 105 also has the second highest risk of disconnection, with an MBSR hop count of 2. Therefore, UE 110 or MBSR 107 determines MBSR 104, whose received radio wave strength is equal to or greater than a predetermined threshold and has the smallest number of MBSR hops, as the connection destination, and executes RRC (Radio Resource Control) connection processing.

[0022] In this way, by considering the number of MBSR hops in addition to the received radio wave strength as a condition for determining the connection destination, it is possible to select the MBSR 104 that has the lowest risk of connection interruption among the MBSRs 104 to 106 that involve movement as the connection destination.

[0023] In the above description, the conditions were explained in which the communication nodes with received radio wave strength above the threshold did not include the IAB nodes 102 and 103. However, if the IAB nodes 102 and 103 are stationary and include the IAB nodes 102 and 103, the IAB nodes 102 and 103 may be preferentially selected as connection destinations because they have a lower risk of disconnection than the MBSRs 104 to 106.

[0024] In this embodiment, it is assumed that the MBSRs 104 to 107 are mounted on buses, but they may also be IAB nodes mounted on other moving objects such as vehicles, aircraft, ships, or people.

[0025] FIG. 2 is a block diagram showing an example of the hardware configuration of the MBSRs 104 to 107 in this embodiment.

[0026] The MBSRs 104 to 107 are configured from the following hardware: a control unit 201 , a memory unit 202 , a wireless communication unit 203 , an antenna control unit 204 , an antenna 205 , a GPS communication unit 206 , a GPS antenna control unit 207 , a GPS antenna 208 , and an acceleration sensor 209 .

[0027] 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 also 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, for example, executing a control program stored in the storage unit 202.

[0028] The storage unit 202 includes one or more storage devices (memories), such as, for example, 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 (for example, control programs) executed by the control unit 201 and various information used in processing by the control unit 201. The various information may be, for example, connection continuity information such as the number of MBSR hops and mobility information in the MBSRs 104-106, and received radio wave intensity of other IAB donors and IAB nodes 101-106 including MBSRs.

[0029] The received radio wave strength may include, for example, a received signal strength indicator (RSSI) and a reference signal received quality (RSRQ). RSSI is an abbreviation for Received Signal Strength Indicator. RSRQ is an abbreviation for Reference Signal Received Quality. The received radio wave strength may also include reference signal received power (RSRP) and the like. In addition to the received radio wave strength, the various information may also include reception quality information, such as a modulation and coding scheme (MCS), a signal-to-noise ratio (SNR), a communication speed, and the like. MCS is an abbreviation for Modulation and Coding Scheme, and SNR is an abbreviation for Signal to Noise Ratio.

[0030] The wireless communication unit 203 performs processing related to wireless communication (cellular communication) that complies with 3GPP standards such as the LTE (Long Term Evolution) standard or the 5G (fifth generation) standard. However, the wireless communication unit 203 is also applicable to standards other than 5G (e.g., 5G Advanced, 6G, etc.). The wireless communication unit 203 includes circuits for communication processing, such as a baseband chip and an RF (radio frequency) chip.

[0031] The antenna control unit 204 controls the antenna 205 used for wireless communication performed by the wireless communication unit 203. The antenna control unit 204 is also capable of measuring the strength of the received radio wave based on the signal received by the antenna 205.

[0032] Measurement of received radio wave strength may be performed, for example, using SSBs periodically transmitted (broadcast) from the IAB donor and nodes 101 to 106 in the MBSR 107. The SSB is a synchronization signal / broadcast channel block (SS / PBCH block). The synchronization signal / broadcast channel block is 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 can detect the cell ID and reception timing when starting communication. In NR, the SSB is also used to measure the reception quality of each cell. The PBCH includes an MIB.

[0033] 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 is also capable of measuring communication quality information.

[0034] The GPS communication unit 206 receives signals from GPS (Global Positioning System) satellites to acquire current location information including location identification information such as longitude and latitude information used to generate mobility information, and current time information. Note that other satellite positioning systems of the GNSS (Global Navigation Satellite System) may be used instead of GPS.

[0035] The GPS antenna control unit 207 controls the GPS antenna 208 in the GPS communication unit 206 .

[0036] The acceleration sensor 209 measures the moving speed of the local station, which is used to generate mobility information. The moving speed measured by the acceleration sensor 209 is acquired by the control unit 201 and stored in the storage unit 202. Note that a speed sensor may be used instead of or in addition to the acceleration sensor 209. In this case, a speed sensor installed for another purpose (e.g., automatic brake control) in a vehicle such as a bus equipped with an MBSR may be used.

[0037] Here, the UE 110 may also be realized by a similar hardware configuration or a hardware configuration in which some functions are common.

[0038] FIG. 3 is a block diagram showing an example of the software functional configuration of the MBSRs 104 to 107.

[0039] The MBSRs 104 to 107 each include a signal transmitting unit 301, a signal receiving unit 302, a data storage unit 303, a connection control unit 304, a connection destination determining unit 305, a hop count calculation unit 306, a movement information generation unit 307, and a GPS control unit 308. 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.

[0040] The signal transmitting unit 301 and the signal receiving unit 302 control the wireless communication unit 203 to transmit and receive wireless signals between the IAB donor or other nodes (e.g., MBSRs 104 to 107) and the UE 110. The signal transmitting unit 301 and the signal receiving unit 302 transmit and receive wireless signals that comply with a 3GPP standard such as the LTE standard or the 5G standard.

[0041] The signal receiving unit 302 receives broadcast signals from the IAB donor or other nodes (e.g., the IAB donor 101, the IAB nodes 101 and 102, and the MBSRs 104 to 106). The signal receiving unit 302 also controls the antenna control unit 204 during wireless communication. The signal receiving unit 302 acquires received radio wave strength from the antenna control unit 204 and sends the acquired received radio wave strength to the data storage unit 303.

[0042] The data storage unit 303 stores various programs and various data (various information) in the storage unit 202 to hold them.

[0043] The connection control unit 304 performs processes related to the connection of the IAB network, such as transmitting and receiving Radio Resource Control (RRC) messages between the IAB donor or other nodes (e.g., MBSRs 104 and 107). RRC stands for Radio Resource Control. The connection control unit 304 also performs processes related to the connection with the UE 110 and the connection with the CN 130.

[0044] The connection destination determination unit 305 acquires the received radio wave strength of the IAB donor or other nodes (e.g., IAB donor 101, IAB nodes 101 and 102, MBSRs 104 to 106) stored in the data storage unit 303. The connection destination determination unit 305 also acquires connection continuity information from the broadcast information received by the signal receiving unit 302. Furthermore, the connection destination determination unit 305 determines the connection destination from the received radio wave strength and the connection continuity information. In this embodiment, the UE 110 or the MBSR 107 determines the MBSR 104 as the connection destination.

[0045] The hop number calculation unit 306 calculates the MBSR hop number in the own station from the broadcast information received by the signal receiving unit 302 , and includes the calculated number in a broadcast signal as connection continuity information, which is then transmitted from the signal transmitting unit 301 .

[0046] The movement information generation unit 307 acquires the movement speed measured by the acceleration sensor 209 from the data storage unit 303 and generates mobility information. The movement information generation unit 307 also generates mobility information from position information and time information from the GPS control unit. The movement information generation unit 307 includes the generated mobility information in a notification signal as connection continuity information and transmits the notification signal from the signal transmission unit 301.

[0047] The GPS control unit 308 performs communication in accordance with the GPS standard. The GPS control unit 308 also controls the antenna for GPS communication and calculates the current position and time from received GPS information. The GPS control unit 308 also outputs information in the NMEA (National Marine Electronics Association)-0183 format or the like, and stores the current position and time in the data storage unit 303 as necessary.

[0048] The MBSRs 104 to 107 determine whether they are located inside or outside the permitted area in which they can operate as an IAB node, based on the current location acquired by the GPS control unit 308 .

[0049] The UE 110 may also be realized by a software configuration similar to that of the MBSRs 104 to 107 or with some of the functional blocks in common.

[0050] 4 is a sequence diagram showing an example of connection between the UE 110 and the MBSR 107 according to this embodiment. In FIG. 4, it is assumed that the received radio wave intensity of the broadcast signals received by the UE 110 and the MBSR 107 from the IAB donor and the IAB nodes 101 to 103 is lower than a predetermined threshold.

[0051] In S400 to S402, the MBSRs 104 to 106 broadcast the MBSR hop counts included in SIB1. The MBSR hop counts included in SIB1 by the MBSRs 104 to 106 are 1 for MBSR 104, 2 for MBSR 105, and 3 for MBSR 106. The MBSR hop count for MBSR 104 is 1, and among the MBSRs 104 to 106, the risk of connection interruption is lowest.

[0052] In step S403, the UE 110 and the MBSR 107 receive the broadcast signals and measure the received radio wave intensity based on the broadcast signals from the MBSRs 104 to 106.

[0053] At S404, the UE 110 and the MBSR 107 wake up from a sleep state to connect to the mobile network.

[0054] In S405, the UE 110 and the MBSR 107 determine whether the received radio wave strength of the MBSRs 104 to 106 is equal to or greater than a threshold. The UE 110 and the MBSR 107 also determine which of the MBSRs 104 to 106 to connect to based on the number of MBSR hops from the MBSRs 104 to 106. The UE 110 and the MBSR 107 determine the MBSR 104 whose received radio wave strength is equal to or greater than the threshold and whose number of MBSR hops is the smallest as the connection destination.

[0055] In S406, the UE 110 and the MBSR 107 transmit a preamble, which is a randomly selected fixed pattern, to the MBSR 104 as a RACH (Random Access Channel) preamble message.

[0056] At S407, the MBSR 104 receives the RACH preamble message.

[0057] In S408, the MBSR 104 transmits to the UE 110 and the MBSR 107 a RACH response message indicating that the RACH preamble message has been received, and including transmission timing information and bandwidth allocation information.

[0058] In S409, the UE 110 and the MBSR 107 receive the RACH response message.

[0059] In S410, the UE 110 and the MBSR 107 transmit an RRC connection request to the MBSR 104 in accordance with the transmission timing and bandwidth allocation information of the RACH response message received in S409. The RRC connection request is an RRC connection request message.

[0060] At S411, the MBSR 104 receives an RRC connection request message.

[0061] In S412, the MBSR 104 responds to the RRC connection request by transmitting control information for RRC connection as an RRC connection setup message.

[0062] In S413, the UE 110 and the MBSR 107 receive an RRC connection setup message, thereby completing the RRC link connection.

[0063] In S414, the MBSR 107 transmits an RRC Setup Complete message including information that the MBSR itself is an MBSR, in order to indicate that a connection has been established as an IAB node.

[0064] In S415, the MBSR 104 receives the RRC Setup Complete message and identifies itself as the MBSR 107. In the case of the UE 110, the RRC Setup Complete messages of S414 and S415 are not transmitted or received.

[0065] In S416 and S417, an RRC link is established, and the UE 110 and the MBSR 107 start data communication with the CN 130 via the MBSR 104 and the IAB donor 101. The MBSR 107 also starts transmitting a broadcast signal including connection continuity information with the MBSR hop count set to 2.

[0066] FIG. 5 is a flowchart showing an example of a connection destination determination process in the UE 110 and the MBSR 107 according to this embodiment.

[0067] Here, a description will be given of a method for determining a connection destination in the UE 110 and the MBSR 107 at S405. The connection destination determination process is executed by the connection destination determination unit 305.

[0068] In S500, the UE 110 and the MBSR 107 receive the MBSR hop count as connection continuity information from the broadcast signals from the IAB donor and IAB nodes 101 to 106. In addition, the UE 110 and the MBSR 107 measure the received radio wave intensity from the broadcast signals from the IAB donor and IAB nodes 101 to 106.

[0069] In S501, the UE 110 and the MBSR 107 determine whether there are multiple IAB donors and nodes 101 to 106 whose received radio wave strength is equal to or greater than a predetermined threshold. If the result of the determination in S501 shows that multiple donors and nodes are not detected, the process proceeds to S502. If multiple donors and nodes are detected, the process proceeds to S503.

[0070] In S502, an attempt is made to connect to the IAB donor and nodes 101 to 106 with the best RSSI among the detected nodes.

[0071] In S503, it is determined whether or not there is an IAB donor 101 or fixed IAB nodes 102 and 103 among the IAB donors and nodes 101 to 106 whose received radio wave intensity is equal to or greater than a threshold. If the determination result in S503 indicates that the IAB donor 101 or fixed IAB nodes 102 and 103 is not detected, the determination in S505 is executed; if they are detected, the process in S504 is executed.

[0072] In S504, connection processing is performed with the IAB donor 101 and the fixed IAB nodes 102 and 103 with the best received radio wave strength.

[0073] In S505, it is determined whether there are multiple MBSRs 104 to 106 whose received radio wave strength is equal to or greater than the threshold and whose MBSR hop count is the minimum. If the determination in S505 shows that multiple MBSRs are not detected, the process in S506 is executed. If multiple MBSRs are detected, the process in S506 is executed.

[0074] In S506, connection processing is performed with an MBSR (for example, MBSR 104) that is a node whose received radio wave intensity is equal to or greater than a threshold and has the smallest number of MBSR hops.

[0075] In S507, connection processing is performed with the MBSRs 104 to 106 with the smallest number of MBSR hops and the highest received radio wave strength among the nodes with received radio wave strength equal to or greater than the threshold.

[0076] FIG. 6 is a flowchart showing an example of calculation of the MBSR hop count and transmission processing in the MBSR 107.

[0077] The process shown in FIG. 6 and described here is executed in the hop count calculation unit 306 after the MBSR 107 executes a connection process with the IAB donor and a node (e.g., the MBSR 104) and establishes an RRC link in S413.

[0078] At S600, an RRC connection is established in the MBSR 107.

[0079] In S601, it is determined whether the connection destination of the MBSR 107 is an MBSR (for example, MBSRs 104 to 106), and if it is an MBSR, the process of S603 is executed, and if not, the process of S602 is executed.

[0080] In S602, the MBSR 107 sets the MBSR hop count of its own station to one.

[0081] In S603, the MBSR 107 adds 1 to the MBSR hop count transmitted by an MBSR (e.g., MBSR 104) connected to its upper level. For example, when the MBSR 107 connects to the MBSR 104, the MBSR hop count of 1 reported by the MBSR 104 is added by 1, and the MBSR 107 sets the MBSR hop count to 2.

[0082] In S604, it is determined whether or not there are any IAB nodes 104-106 in the upper-connected MBSR that are currently stopped, and if there are, the process of S605 is executed. If there are no IAB nodes in the upper-connected MBSR, the process of S606 is executed. Here, the determination in S604 uses the mobility information included in the connection continuity information broadcast by the upper-connected MBSR 104. In other words, in this embodiment, the connection continuity information may include both the MBSR hop count and the mobility information.

[0083] In S605, the number of stopped MBSRs is subtracted from the MBSR hop count in the MBSR 107. For example, if the MBSR 104 is stopped, the MBSR 107 subtracts 1 from the MBSR hop count of 2 and reports 1 as the MBSR hop count as connection continuity information.

[0084] In S606, the MBSR 107 transmits the MBSR hop count as connection continuity information.

[0085] In the above example of the MBSR hop count calculation process, it is assumed that mobility information is included in the connection continuity information. However, this is not a limitation, and for example, mobility information may not be included in the connection continuity information. In this case, each MBSR 104-107 may determine whether or not its own station is stopped, and if it is stopped, it may subtract one from the MBSR hop count to be broadcast and include it in the broadcast signal and transmit it. Furthermore, if there is an IAB node 104-106 that updates its mobility information from stopped to moving, it may update the MBSR hop count in S605. Furthermore, if mobility information is not broadcast, the MBSR hop count to be broadcast by each MBSR 104-107 may be updated in response to the status update from stopped to moving.

[0086] In this embodiment, when only MBSRs 104 to 106 are detected as connection destination candidates with received radio wave strength equal to or greater than a threshold, UE 110 and MBSR 107 are able to connect to MBSR 104, which has a small MBSR hop count and a low risk of connection disconnection. Furthermore, MBSRs 104 to 107 calculate the MBSR hop count and transmit the calculated MBSR hop count in broadcast information as connection continuity information, thereby enabling MBSR 107 to determine MBSR 104 with a low risk of connection disconnection. Furthermore, by further including mobility information in the connection continuity information, it becomes possible to manage the MBSR hop count in accordance with the movement or stop state of MBSRs 104 to 106 connected to the upper layer.

[0087] The connection continuity information including the MBSR hop count and mobility information may be added to the mbsr-continuity-info field of the mbsr-Cellinfo of the SIB1 broadcast signal. Alternatively, the connection continuity information may be added to a reserved bit or field in another SSB or MIB.

[0088] As mentioned above, when MBSR implements a multi-hop connection, there is a high risk of disconnection for UEs and MBSRs that connect via multiple MBSRs as upper-level nodes. In Release 18, MBSR operation is limited to single-hop connections from IAB donors. However, support for multi-hop connections in MBSR is being discussed in Release 19, and future MBSRs may support this.

[0089] Furthermore, attempts to select a connection destination based on link quality, congestion, and number of hops at the upper connection node are known (Patent Document 2), but if MBSR is included in the connection destination candidates, it is necessary to take into account the connection continuity of the communication link.

[0090] In this regard, according to the present embodiment, as described above, connection continuity information including the MBSR hop count is generated and transmitted in the MBSRs 104 to 106, thereby realizing a connection that takes into consideration the connection continuity of the communication link between the UE 110 and the MBSR 107. This reduces the risk of connection interruption in the UE or MBSR that passes through the MBSR as a higher-level connecting node, even when the MBSR implements a multi-hop connection.

[0091] Furthermore, according to this embodiment, by generating and transmitting connection continuity information including mobility information in the MBSRs 104 to 106, the UE 110 and the MBSR 107 can utilize connection continuity that takes into account the mobility information of the MBSRs 104 to 106.

[0092] Second Embodiment In the first embodiment, an example has been described in which the UE 110 and the MBSR 107 connect to the MBSR 104 with a low risk of disconnection based on the MBSR hop count included in the broadcast signals from the IAB donor and the IAB nodes 101 to 106.

[0093] In the second embodiment, an example of a connection process will be described in which connection continuity information is included in a RACH response, which is a message when an RRC connection is established, instead of a broadcast signal. In the following, a description of parts common to the first embodiment will be omitted.

[0094] 7 is a sequence diagram showing an example of connection processing between the UE 110 and the MBSR 107 according to this embodiment. In FIG. 7, similar to FIG. 5 shown in the first embodiment, it is assumed that the received radio wave intensity of the broadcast signals from the IAB donor and the IAB nodes 101 to 103 is lower than a predetermined threshold.

[0095] In steps S700 to S702, the MBSRs 104 to 106 transmit SSB and SIB1 as broadcast signals.

[0096] In S703, the UE 110 and the MBSR 107 receive the broadcast signals from the MBSRs 104 to 106. The UE 110 and the MBSR 107 measure the received radio wave intensity based on the broadcast signals from the IAB donor and the MBSRs 104 to 106.

[0097] In step S704, the UE 110 and the MBSR 107 wake up from the sleep state to connect to the mobile network. The UE 110 and the MBSR 107 determine whether the received radio wave strength of the MBSRs 104 to 106 is equal to or greater than a threshold.

[0098] Here, the UE 110 and the MBSR 107 transmit the RACH preamble message from S705 onwards only to the MBSRs 104 to 106 whose received radio wave strength is equal to or greater than the threshold.

[0099] In S705, the UE 110 and the MBSR 107 transmit a preamble, which is a randomly selected fixed pattern, to the MBSR 106 as a RACH preamble message.

[0100] At S706, the MBSR 106 receives the RACH preamble message.

[0101] In S707, MBSR 106 transmits a RACH response message to UE 110 and MBSR 107, notifying that it has received the RACH preamble message and including transmission timing information and bandwidth allocation information. The MBSR hop count of 3 is also included in the RACH response message as connection continuity information, and the message is transmitted. Furthermore, mobility information may be included in the RACH response message as connection continuity information, and the message may be transmitted.

[0102] In steps S709 to S716, similar to steps S705 to S707, the UE 110 and MBSR 107 transmit RACH preamble messages to the MBSRs 104 and 105. The MBSRs 104 and 105 transmit RACH response messages to the UE 110 and MBSR 107, each including an MBSR hop count.

[0103] In S717, the UE 110 and the MBSR 107 determine which of the MBSRs 104 to 106 to connect to based on the number of MBSR hops from the MBSRs 104 to 106. The UE 110 and the MBSR 107 determine the MBSR 104 whose received radio wave strength is equal to or greater than a threshold and has the smallest number of MBSR hops as the connection destination.

[0104] The sequence of S718 to S725 for establishing an RRC connection and starting data communication is the same as that shown in FIG. 4 of the first embodiment, and therefore a description thereof will be omitted.

[0105] In this embodiment, the UE 110 and the MBSR 107 transmit a RACH preamble message only to connection destination candidates whose received radio wave strength is equal to or greater than a threshold, and determine the connection destination according to the MBSR hop count included in the RACH response message.

[0106] Here, connection continuity information including the MBSR hop count and mobility information may use a reserved bit in the RACH response message, or an mbsr-continuity-info field may be added to the UL grant field.

[0107] Other Embodiments In the first and second embodiments, the MBSRs 104 to 107 transmit the MBSR hop count as connection continuity information and the mobility information including the stopped or moving state information.

[0108] In addition to the above, the connection continuity information may be indication information at the level of single hop, multi-hop, or long hop according to the MBSR hop count. For example, the indication information may represent the MBSR hop count in three levels (stages): single hop when the MBSR hop count is 1, multi-hop when the MBSR hop count is 2 or 3, and long hop when the MBSR hop count is 4 or more. Furthermore, in addition to the MBSR hop count, the hop count may be added to the connection continuity information, or simply the hop count may be used. Furthermore, if multiple MBSRs with the smallest MBSR hop count are detected in S507, the MBSR with the smallest hop count may be selected instead of or in addition to the determination based on the received radio wave strength.

[0109] The mobility information may also include the moving speed measured by the acceleration sensor 209, and the connection continuity information may include indication information of the level and time at which the connection can be maintained based on the moving speed and location information detected by the GPS control unit 308. That is, the MBSR may indicate the length of time until the device moves out of a specific area where service provision is unavailable, based on the moving speed and location information. For example, the indication information may express the length of time until the device moves out of a specific area where service provision is unavailable, in multiple levels (stages). For example, level 1 may indicate the shortest time, and level 3 may indicate the longest time. Furthermore, the connection continuity information may include, as indication information, a level indicating a high risk of connection loss when the moving speed is fast and a low risk when the moving speed is slow.

[0110] Although each embodiment has been described in detail above, it is not limited to a specific embodiment, and various modifications and changes are possible within the scope of the claims. It is also possible to combine all or a plurality of components of the above-described embodiments.

[0111] The present invention is not limited to the above-described embodiments, and various modifications and variations can be made without departing from the spirit and scope of the present invention. Therefore, the following claims are appended to apprise the public of the scope of the present invention.

[0112] This application claims priority based on Japanese Patent Application No. 2024-066208, filed April 16, 2024, the entire contents of which are incorporated herein by reference.

Claims

1. A communications device that constitutes a backhaul network, characterized by having: a generating means for generating connection continuity information that indicates whether the connection links of one or more upper-level connected MBSRs (Mobile Base Station Relays) are stable; and a transmitting means for transmitting the connection continuity information to other communications devices.

2. The communication device according to claim 1, wherein said transmission means transmits said connection continuity information by including it in an mbsr-Cellinfo field of an SIB (System Information Block) 1 or a RACH (Random Access Channel) response.

3. The communication device according to claim 1 or 2, wherein the connection continuity information indicates a first hop count, which is the number of hops counted for only communication devices whose type is MBSR.

4. A communication device according to claim 3, which operates as an MBSR, characterized in that the generation means sets the first hop count represented by the connection continuity information to 1 when the communication device connected to the upper level is a base station or a fixed IAB (Integrated Access and Backhaul) node.

5. A communication device as described in claim 3 or 4, further comprising a receiving means for receiving the connection continuity information generated by another communication device that is a higher-level connection destination, wherein when the higher-level connection destination is an MBSR, the generating means sets the first hop count represented by the connection continuity information generated to a value that is one greater than the first hop count represented by the connection continuity information received from the MBSR of the connection destination.

6. The communication device according to any one of claims 3 to 5, wherein said transmission means further transmits mobility information of the MBSR of said connection destination in addition to said connection continuity information.

7. The communication device according to claim 6, wherein the mobility information is information relating to the movement state of the MBSR, including at least one of information indicating whether or not the device is moving, information indicating whether or not the device is stopped, information indicating the speed of movement, and location information.

8. The communication device described in claim 6 or 7, characterized in that the receiving means further receives the mobility information from the other communication device, and the generating means changes the connection continuity information in accordance with the mobility information received from the other communication device.

9. A communication device as described in any one of claims 3 to 8, characterized in that the generation means sets the first hop count represented by the connection continuity information to a value obtained by subtracting the number of MBSRs for which the mobility information is stopped in one or more MBSRs connected to an upper level.

10. A communication device as described in any one of claims 3 to 9, characterized in that when the mobility information in one or more MBSRs connected to an upper level is updated from a first state indicating stopped to a second state indicating moving, the generation means sets the first hop count represented by the connection continuity information generated to a value obtained by adding the number of MBSRs whose mobility information has been updated to the second state.

11. A communication device described in any one of claims 1 to 10, characterized in that the connection continuity information indicates, in addition to or instead of the first hop count, a second hop count, which is the number of hops from an upper-connected base station to the own station.

12. A communication device as described in any one of claims 1 to 11, characterized in that the connection continuity information includes level information indicating the level or time of connection continuity related to the connection link, and the generation means generates the level information according to the first hop count or the level information according to the mobility information.

13. A communication device characterized by having: a receiving means for receiving connection continuity information indicating whether the connection link of one or more MBSRs (Mobile Base Station Relays) is stable from another communication device connected to said one or more MBSRs; and a selecting means for selecting a new upper communication device to connect to based on said connection continuity information.

14. The communication device described in claim 13, characterized in that the receiving means receives the connection continuity information from each of the multiple other communication devices as connection destination candidates, and when the multiple other communication devices are multiple MBSRs, the selecting means selects the MBSR with the highest connection continuity represented by the connection continuity information.

15. The communication device described in claim 13 or 14, characterized in that the connection continuity information represents a first hop count, which is the number of hops counted only for communication devices whose type is MBSR, and when multiple other communication devices are multiple MBSRs, the selection means selects an MBSR whose received radio wave strength is above a threshold and whose first hop count is the smallest.

16. A control method for controlling communications of communication devices that constitute a backhaul network, comprising: a step of generating connection continuity information that indicates whether the connection links of one or more upper-level connected MBSRs (Mobile Base Station Relays) are stable; and a transmission step of transmitting the connection continuity information.

17. A program for causing a computer of a communication device that constitutes a backhaul network to execute the steps of: generating connection continuity information that indicates whether the connection links of one or more upstream connected MBSRs (Mobile Base Station Relays) are stable; and transmitting the connection continuity information.

18. A method for controlling a communication device, comprising: a receiving step of receiving connection continuity information indicating whether the connection links of one or more MBSRs (Mobile Base Station Relays) are stable from another communication device that is connected to the one or more MBSRs; and a selecting step of selecting a new upper communication device to connect to based on the connection continuity information.

19. A program for causing a computer of a communication device to execute the following steps: a receiving step of receiving connection continuity information indicating whether the connection link of one or more MBSRs (Mobile Base Station Relays) is stable from another communication device connected to said one or more MBSRs; and a selection step of selecting a new upper communication device to connect to based on the connection continuity information.

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