Control device and IAB node, and control method and program thereof

Abstract

To provide a technique to appropriately execute flow control processing in an IAB network.SOLUTION: A control unit of an integrated access and backhaul (IAB) network determines a condition for an IAB node relaying the connection between an IAB donor and a user device via a backhaul link to trigger execution of flow control processing for a downlink traffic in a route including the IAB node, the condition for the amount of data buffered in a downlink buffer of the IAB node, for each one or more IAB nodes in the IAB network based on the network configuration of the IAB network, and notifies the determined conditions to the one or more IAB nodes.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present invention relates to a control device and an IAB node, as well as a control method and program therefor. [Background technology]

[0002] The 3GPP (3rd Generation Partnership Project) is currently standardizing IAB (Integrated Access and Backhaul) as a communication technology for backhaul. The IAB technology utilizes millimeter-wave wireless communication, such as the 28 GHz band, which is used for access communication between a base station and user equipment (UE), as backhaul communication (Patent Document 1).

[0003] In a backhaul communication network using IAB technology (hereinafter referred to as an IAB network), relay devices called IAB nodes relay communications from IAB donors, which correspond to conventional base stations, to the destination UE. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Special Publication No. 2019-534625 Summary of the Invention [Problem to be solved by the invention]

[0005] When an IAB network is composed of multiple IAB nodes, congestion between an IAB donor and a higher-level IAB node affects communication throughout the entire IAB network. Therefore, flow control processing is performed between the IAB nodes and the IAB donor as a congestion countermeasure.

[0006] The present invention has been made in view of the above-mentioned problems, and has an object to provide a technique for appropriately executing flow control processing in an IAB network. [Means for solving the problem]

[0007] In order to solve the above problem, the control device according to the present invention comprises: A control device for an IAB (Integrated Access and Backhaul) network, a determining means for determining, for each one or more IAB nodes of the IAB network based on a network configuration of the IAB network, a condition of the amount of data buffered in a downlink buffer of the IAB node, which is used to trigger the execution of a flow control process for downlink traffic in a path including the IAB node, the IAB node relaying a connection between an IAB donor and a user device via a backhaul link; a notification means for notifying each of the one or more IAB nodes of the condition determined by the determination means; The present invention is characterized by comprising: [Effects of the Invention]

[0008] The present invention can provide a technique for appropriately performing flow control processing in an IAB network. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a diagram illustrating an example of an IAB network according to an embodiment of the present invention. [Figure 2] Hardware functional block diagram of the IAB donor 101 and IAB nodes 102 to 105 according to this embodiment. [Figure 3] Software functional block diagram of the IAB donor 101 and IAB nodes 102 to 105 in the present invention. [Figure 4] 1 is an explanatory diagram of an IAB network configuration and buffer load according to a first embodiment; [Figure 5]1 is a flowchart illustrating an example of a threshold value determination process according to the first embodiment; [Figure 6] FIG. 1 is a sequence diagram showing a threshold determination process and a process when a threshold is exceeded according to the first embodiment; [Figure 7] An explanatory diagram of an IAB network configuration and buffer load according to a second embodiment. [Figure 8] 10 is a flowchart illustrating an example of a threshold value determination process according to the second embodiment. [Figure 9] FIG. 10 is a sequence diagram showing a threshold value determination process and a process when the threshold value is exceeded according to the second embodiment; [Figure 10] FIG. 1 is a diagram showing an example of an IAB network according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. Note that the following embodiments do not limit the scope of the present invention, and not all of the combinations of features described in the embodiments are necessarily essential to the solution of the present invention.

[0011] In the IAB (Integrated Access and Backhaul) network according to this embodiment, control is performed between an IAB donor and an IAB node, and between a higher-level IAB node and a lower-level IAB node, via a BAP (Backhaul Adaptation Protocol).

[0012] The control device also notifies each IAB node of conditions regarding the amount of data buffered in the IAB node's buffer. When the amount of data buffered in the buffer satisfies the condition, each IAB node sends a notification to the control device, thereby performing flow control processing in the IAB network. In this embodiment, the control device is described as a CU (Central Unit) of the IAB donor, but the control device may be provided in a network node other than the IAB donor.

[0013] Flow control instructions are also supported at the BAP layer, allowing an IAB node to send feedback information about available buffer size for incoming BH RLC (Backhaul Radio Link Control) channels or BAP sublayer destinations to its parent node. The parent node can then forward the feedback information about available buffer size to the IAB donor. Feedback can be sent proactively when buffer load exceeds a certain threshold, or based on polling by the parent node, and flow control operations can be triggered based on this buffer threshold.

[0014] In this embodiment, an example will be described in which a threshold is dynamically set to notify an IAB donor that the amount of data buffered in the buffer of an IAB node (buffer data amount) has exceeded a threshold (buffer threshold).

[0015] First Embodiment 1 is a diagram showing an example of an IAB network according to this embodiment. In the IAB network 100, there is an IAB donor 101 that provides a connection to a CN (core network) 130, and the IAB donor 101 forms an IAB network including IAB nodes 102 to 105. Here, the CN is responsible for various processes such as authentication of UEs (user equipment) 110 to 119, which are terminals.

[0016] The IAB donor 101 controls the IAB nodes 102 to 105 in an integrated manner, forms an area covered by the IAB donor 101, and provides network access to the UEs 110 to 119 connected to the IAB donor 101 via access links.

[0017] In the IAB network 100, communication packets (hereinafter referred to as BAP data packets) conforming to the format of a BAP (Backhaul Adaptation Protocol) data PDU (Protocol Data Unit) are used as communication packets. For example, an IP (Internet Protocol) packet addressed to the UE 118 from the CN 130 is converted into a BAP data packet in the IAB donor 101 and transferred into the IAB network 100. The transferred BAP data packet passes through each of the IAB nodes 102 to 105, is converted back into an IP packet in the IAB node 105, and is delivered to the destination UE 118. Similarly, an IP packet from the UE 118 is converted into a BAP data packet in the IAB 105, is converted back into an IP packet in the IAB donor 101 via the IAB network 100, and is transferred to the CN 130.

[0018] The IAB nodes 102-105 each have a buffer and use the buffer to store BAP data packets. In one example, the IAB nodes 102-105 each have an uplink buffer for storing BAP data packets of uplink traffic and a downlink buffer for storing BAP data packets of downlink traffic. Furthermore, in the IAB network 100, the IAB donor 101 sets a condition regarding the amount of data buffered in the buffer using BAP data packets for the subordinate IAB nodes 102-105. In the following example, a threshold is set as the condition regarding the amount of data, and when the amount of data buffered in the buffer of any of the IAB nodes 102-105 meets the condition, the IAB donor 101 is notified. Based on the notification, the IAB donor 101 performs flow control for traffic passing through the IAB node that sent the notification.

[0019] The following describes a method for setting a buffer threshold for each IAB node in a network including IAB nodes 102 to 105, such as IAB network 100 shown in FIG. 1, in order to efficiently carry out communication throughout the IAB network.

[0020] In this embodiment, downlink communication in which a communication packet from the CN 130 is transferred to the UEs 102 to 105 via the IAB donor 101 will be described.

[0021] FIG. 2 is a hardware functional block diagram of the IAB donor 101 and the IAB nodes 102 to 105 in the present invention.

[0022] IAB donor 101 and IAB nodes 102 to 105 each include a control unit 202, a storage unit 203, a wireless communication unit 204, and an antenna control unit 205. Control unit 202 executes a control program stored in storage unit 203 to control the entire device.

[0023] The control program executed by the control unit 202 stores various information such as information on UEs connected to the device and buffer usage status in the storage unit 203. The IAB donor 101 also stores network configuration information of the IAB nodes 102 to 105 in the storage unit 203. In the case of a tree topology, the network configuration information includes identifiers of parent and child nodes, identifiers of IAB nodes that make up a path, and information on user devices connected to the IAB nodes 102 to 105.

[0024] The wireless communication unit 204 is a wireless communication unit for performing cellular network communication such as LTE or 5G that conforms to the 3GPP standard. The wireless communication unit 204 also has a buffer (a backhaul link buffer for connection between nodes) for use in backhaul communication. The IAB donor 101 may also be additionally provided with a communication unit for connection with a core network. The antenna control unit 205 controls the antenna used for wireless communication performed by the wireless communication unit 204.

[0025] Fig. 3 is a software functional block diagram of the IAB donor 101 and IAB nodes 102 to 105 according to this embodiment. The software functional blocks shown in Fig. 3 include a signal transmitting / receiving unit 301, a data storage unit 302, a connection control unit 303, a buffer threshold management unit 304, a session management unit 305, and a buffer status management unit 306. These software functional blocks are realized by the control unit 201 of the IAB donor 101 and the IAB nodes 102 to 105 executing a program stored in the storage unit 202 and controlling the entire device.

[0026] Note that some software function blocks may be omitted depending on the device. For example, the IAB donor 101 may have all of the software function blocks, while the IAB nodes 102 to 105 may not have the buffer threshold manager 304, the session manager 305, and the buffer status manager 306.

[0027] The signal transmitting / receiving unit 301 controls the wireless communication unit 203 via the control unit 201, and performs cellular network communication such as LTE or 5G conforming to the 3GPP standard between the IAB nodes 102 to 105 and the UEs 110 to 119. The data storage unit 302 controls and manages the storage unit 203, which is the entity, and stores and holds the software itself, routing information of the IAB nodes 102 to 105, information on the UEs 110 to 118, and the like.

[0028] The connection control unit 303 controls the antenna control unit 205 via the control unit 202 during wireless communication. The buffer threshold management unit 304 determines the buffer threshold to be set in each IAB node from information collected by the IAB donor 101 from the session management unit 305 and the buffer status management unit 306, and notifies each IAB node of the threshold. The session management unit 305 stores and manages information (number, number of node stages, number of backhaul links) of the IAB nodes and UEs connected to the IAB donor 101 and IAB nodes 102 to 105.

[0029] The buffer status management unit 306 stores and manages the buffer size available at each IAB node collected from each IAB node 102 to 105. Note that the buffer status information is collected, for example, by a BAP data packet or a communication packet conforming to various BAP control PDUs (hereinafter referred to as a BAP control packet).

[0030] The buffer threshold management unit 304, session management unit 305, and buffer status management unit 306 hold the latest information for each IAB node, and past information is stored in the data storage unit 302. A detailed method for determining the buffer threshold will be described later.

[0031] 4 is a diagram showing a network configuration of the IAB network 100 according to the first embodiment and an example of setting buffer thresholds to be set in the IAB nodes 102 to 105. In the IAB network 100, buffers (backhaul link buffers) secured in inter-node links from the IAB donor 101 to each of the IAB nodes 102 to 105 are denoted as L1 to L4. Note that the backhaul link buffers shown in FIG. 4 will be described as downlink buffers used for downlink communication from the IAB donor 101 to the UEs 110 to 118.

[0032] In the first embodiment, the IAB donor 101 determines the buffer threshold (B) of each IAB node according to the number (N) of IAB nodes connected on the communication path of the IAB network 100, and uses the buffers equally among the connected IAB nodes.

[0033] In the example of Figure 4, there are four IAB nodes 102 to 105 connected to the IAB donor 101 via the downlink buffer L1, which is the connection between the IAB donor 101 and the IAB node 102, so N is used equally as N=4. For example, if the upper limit of the available bandwidth of the downlink buffer L1 is set to B1, which is the buffer size that allows 80% of the bandwidth to be available within the IAB network 100, the link buffer B1 of the IAB node 102 directly connected to L1 can be determined according to the following formula 1.

[0034] B1=4 / 5×L1 (1) Furthermore, the upper limit Bn (n=1 to 4) of the buffer size that each IAB node can use in Ln (n=1 to 4) can be determined according to the following formula (2).

[0035] Bn=B1×1 / N (2) If the usable buffer size differs for each IAB node due to the hardware and software specifications, the upper limit is set to 80% of the buffer size of each node, and the smaller of Bn and 80% of the buffer size of each node is set as the upper limit of the buffer size.

[0036] Fig. 5 is a flowchart showing a method for determining a threshold value at an IAB donor in response to an increase or decrease in the number of IAB nodes according to the first embodiment. The process shown in Fig. 5 is executed at predetermined time intervals.

[0037] In S501, the IAB donor 101 detects an increase or decrease in the number of IAB nodes in the IAB network 100. Subsequently, in S502, the IAB donor 101 checks the number of IAB nodes (N) in the IAB network 100.

[0038] In S503, it is confirmed whether or not there has been a change in the number of IAB nodes in the IAB network 100. If there has been a change (Yes in S503), it is confirmed in S504 whether or not the number of IAB nodes N exceeds 1. If there has been no change in the number of nodes N in S502 (No in S503), or if the number of IAB nodes N exceeds 1 in S504 (Yes in S504), the buffer thresholds for the IAB nodes 102 to 105 are determined in S505. If the number of IAB nodes N does not exceed 1 in S504 (No in S504), the process ends.

[0039] In S506, the determined buffer threshold is notified to the IAB nodes 102 to 105, and the process ends. Details of the process in S505 may be determined for each of the IAB nodes 102 to 105 according to the number of IAB nodes connected to the IAB donor 101 via the IAB nodes 102 to 105, as shown in FIG.

[0040] Figure 6 is a sequence diagram showing the method for resetting the buffer threshold of an IAB node, the notification method, and the processing when the threshold is exceeded when the IAB donor detects an increase or decrease in the number of IAB nodes. Here, we will explain the processing for detecting an increase or decrease in the number of nodes, recalculating the buffer thresholds of all IAB nodes in the IAB network 100, notifying the buffer thresholds, and receiving a notification from the IAB node that triggers the execution of flow control processing when the threshold is exceeded. In the example of Figure 6, we will explain the processing for detecting an increase or decrease in the number of IAB ...

[0041] In S601, the IAB node 104 connects to the IAB network 100 by sending a notification such as a connection request to the IAB donor 101. In S602, the IAB node 101 receives a notification from the IAB node 104 and detects that the IAB node 104 has been added to the IAB network 100.

[0042] In S603, the IAB donor 101 recalculates and determines the buffer threshold to be set for each IAB node 102 to 105 in the IAB network 100 in response to a change in the number of IAB nodes connected to the IAB donor 101. The processing of S603 has been explained with reference to Fig. 4, so details thereof will be omitted. In S604, the IAB node 101 notifies the IAB nodes 102 to 105 of the determined buffer threshold.

[0043] In S605, S607, S609, and S611, each IAB node 102-105 receives a buffer threshold change notification. In S606, S608, S610, and S612, each IAB node 102-105 applies the received buffer threshold as its own buffer threshold. Next, in S613-S626, processing when the buffer threshold is exceeded at an IAB node will be described. In S613-S626, the description will be made assuming that the IAB node 103 detects that the buffer threshold has been exceeded.

[0044] In S613 and S614, the IAB node 103 recognizes that the buffer threshold has been exceeded and notifies the IAB node 102 of the exceedance of the buffer threshold. The notification in S613 is notified by a BAP message, which is a message that triggers the execution of flow control processing according to this embodiment. In S614, the IAB node 102 detects that the IAB node 103 connected to the IAB donor 101 via the IAB node 102 has exceeded its threshold. In S615 and S616, the IAB donor 101 receives a notification from the IAB node 102 indicating that the IAB node 103 has exceeded its buffer threshold, and thereby detects that the IAB node 103 has exceeded its buffer threshold. This triggers the execution of flow control processing in the IAB network 100.

[0045] In S617, the IAB donor 101 transmits an instruction to the IAB node 102 to execute the flow control process, and in S618, the IAB node 102 executes the flow control process.

[0046] In S619, the IAB node 102 transmits an instruction to execute a flow control process to the IAB node 103, and in S620, the IAB node 103 identifies the flow control process and executes the flow control process in S621. In S621, the IAB node 103 executes the flow control process.

[0047] Next, in S622, the IAB node 103 notifies the IAB nodes 104 and 105 of flow control. In S623 and S625, the IAB nodes 104 and 105 detect an instruction to execute flow control processing. In S624 and S626, the IAB nodes 104 and 105 execute flow control.

[0048] The flow control process instructed in S617 may perform different flow control processes depending on the location relative to the IAB node where the downlink buffer threshold has been exceeded.

[0049] For example, an IAB node 102, which is a node through which an IAB node 103 whose amount of data buffered in its downlink buffer exceeds a threshold connects to an IAB donor 101, may reduce the amount of downlink data it transfers to the IAB node 103. This allows the IAB node 103 to operate to reduce the amount of data buffered in its downlink buffer.

[0050] Furthermore, when the amount of data buffered in the downlink buffer exceeds a threshold, the IAB node 103 may change its data transmission policy to preferentially transmit data to nodes or user devices with high communication quality, such as a low packet loss rate, thereby reducing the amount of data buffered in the downlink buffer.

[0051] Additionally, IAB nodes 104 and 105, which connect to IAB donor 101 via IAB node 103, may change their communication scheduling to prioritize receiving downlink transmissions from IAB node 103. This allows the amount of data buffered in the downlink buffer of IAB node 103 to be reduced with priority.

[0052] Furthermore, if there is a communication path that does not pass through IAB node 103, IAB donor 101 may perform a route control process, such as transmitting downlink data to IAB nodes 104 and 105 without passing through IAB node 103. In one example, IAB donor 101 may instruct at least one of IAB nodes 104 and 105 to switch the connection to IAB donor 101 or IAB node 102. This allows communication to be performed using a path that does not pass through a node whose amount of data buffered in a downlink buffer exceeds a threshold when IAB network 100 is capable of communication via multiple paths.

[0053] The flow control process to be executed by the IAB nodes 102 to 105 may be instructed by the IAB donor 101 via a notification in S617. Alternatively, the IAB donor 101 may instruct only the execution of the flow control process, with each IAB node deciding which process to execute. For example, the IAB donor 101 may determine which IAB node to cause to execute the flow control process based on the number of times the IAB donor 101 instructs the execution of the flow control process within a predetermined period. For example, when the flow control process is executed the first time within a predetermined period, the flow control process may be executed only by an IAB node whose amount of data buffered in its downlink buffer exceeds a threshold. Subsequently, when the flow control process is executed the second time within the predetermined period, the flow control process may also be executed by a node closer to the IAB donor 101 than the IAB node whose amount of data buffered in its downlink buffer exceeds the threshold. This allows the amount of data buffered in the downlink buffer to be reduced in more IAB nodes when the flow control process is executed frequently.

[0054] As described above, when detecting an increase or decrease in the number of IAB nodes, it is possible to determine an appropriate buffer threshold for each IAB node by determining the buffer threshold for each IAB node according to the number of IAB nodes in the IAB network 100.

[0055] Second Embodiment In the first embodiment, a method was described in which an IAB donor determines a threshold for the amount of data buffered in a downlink buffer of an IAB node depending on the number of IAB nodes connected to the IAB donor via the IAB node. In the second embodiment, a method is described in which a buffer threshold is determined depending on the number of communication devices connected to the IAB network (the total number of IAB nodes and UEs). Note that the same reference numerals are used for configurations, functions, and processes as in the first embodiment, and descriptions thereof will be omitted.

[0056] FIG. 7 shows the configuration of an IAB network 100 according to the second embodiment and a method for determining a buffer threshold for an IAB node.

[0057] If the number of devices connected in the IAB network 100 is N2, the IAB donor 101 distributes network resources equally to each device. The backhaul link between the IAB donor 101 and the IAB node 102 is L1, and the backhaul links with the subordinate IAB nodes are L2 to L4. In this case, the number of UEs is 9 (UEs 110 to 118), and the number of IAB nodes is 4 (IAB nodes 102 to 105), so the number of connected devices is N2=13.

[0058] Here, if the number of connections per IAB node is n, then the number of devices n connected to IAB donor 101 via IAB node 102 is 11. Similarly, the number of connections n for IAB node 103 is 8, and the number of connections n for IAB nodes 104 and 105 is 2. Therefore, the buffer threshold for each IAB node can also be calculated as n / N2 for backhaul link buffers L1 to L4. In this case, if the buffer thresholds set in each IAB node for L1 to L4 are Bi (i=1 to 4), then they can be calculated according to the following formula (3).

[0059] Bi = Li × n / N2(3) In this way, the buffer threshold of an IAB node with a small number of connected devices is set low, and the timing of triggering the execution of flow control processing is made earlier, which makes it possible to reduce the impact on communications to IAB nodes and UEs that are closer to the IAB donor 101 in terms of the network than the IAB node in question.

[0060] FIG. 8 is a flowchart showing a threshold determination process executed by the IAB donor 101 in response to an increase or decrease in the number of IAB nodes or UEs in the second embodiment.

[0061] In S801, the IAB donor 101 detects whether the number of connections of IAB nodes and UEs connected to the IAB donor 101 has increased or decreased (changed) by a predetermined number or more within a predetermined time. For example, an increase in the number of connections of IAB nodes and UEs can be detected when a connection request or a handover request is received from either the IAB node or the UE.

[0062] In S802, the IAB donor 101 checks the number of connections (N2) of IAB nodes and UEs connected to the IAB donor 101. In S803, it is checked whether there has been a change in the number of connections N2 of IAB nodes and UEs connected to the IAB donor 101. If there has been a change (Yes in S803), the IAB donor 101 proceeds to processing in S804 and checks whether the number of connections N2 of IAB nodes and UEs exceeds 1.

[0063] If there is no change in the number of connections N2 in S803 (No in S803), the IAB donor 101 proceeds to S805, where the IAB donor 101 determines the buffer thresholds for the IAB nodes 102 to 105. If the number of connections N2 for the IAB nodes and UEs does not exceed 1 in S804 (No in S804), the IAB donor 101 ends the processing. In S806, the IAB nodes 102 to 105 are notified of the determined buffer thresholds, and the processing ends.

[0064] Next, FIG. 9 is a sequence diagram showing a buffer threshold determination process executed by the IAB donor 101 when a UE connects to an IAB node 104 in the IAB network 100.

[0065] In S601, the IAB node 104 was connected to the IAB network 100 and transmitted a signal for node addition, but in S901, the IAB node 104 transmits a signal such as a connection request from the UE to the IAB donor 101. The subsequent processing sequence is the same as in Fig. 6, so detailed description will be omitted.

[0066] As described above, when the IAB donor detects that the number of IAB nodes and UEs connected to the IAB donor has changed by a predetermined value within a predetermined time, the IAB donor determines a buffer threshold for each IAB node according to the number of IAB nodes and the number of UEs. This makes it possible to determine an appropriate threshold for triggering the execution of flow control processing for each IAB node even if the number of UEs connected to each IAB node varies greatly, such as when a large number of UEs are connected to a specific IAB node. Furthermore, it becomes possible to allocate the amount of data buffered in the downlink buffer equally to IAB nodes and UEs.

[0067] In this embodiment, the data volume is allocated uniformly between the IAB node and the UE, but weighting may be applied to the IAB node and the UE. For example, the IAB node may be allocated a larger data volume than the UE, such as 10 times. In the example of FIG. 7, the total number of connections N2 may be set to 49 UEs. This allows a larger margin to be secured for the backhaul link.

[0068] <Other embodiments> In the first and second embodiments, a given IAB node has only one parent node. However, in a multipath IAB network, one IAB node may have multiple parent nodes. In such a case, the IAB donor 101 may determine, for each path ID, a condition regarding the amount of data buffered in the downlink buffer for each path.

[0069] 10, there are a path P1 passing through IAB nodes 102, 103, and 104, a path P2 passing through IAB nodes 102, 103, and 105, and a path P3 passing through IAB nodes 102, 106, and 105. In this IAB network 1000, a case will be described in which resources are allocated equally to each path, assuming that the upper limit of the buffer threshold is 90%.

[0070] The buffer size allocated to path P1 is B P1 Then, IAB node 102 receives 0.9B P1 , 0.6B at IAB node 103 P1 , and 0.3B to IAB node 104 P1 Similarly, the buffer size allocated to path P2 is set to B P2 Then, IAB node 102 receives 0.9B P2 , 0.6B at IAB node 103 P2 , and 0.3B to IAB node 105 P2 The buffer size allocated to path P3 is B P3 Then, IAB node 102 receives 0.9B P3 , 0.6B at IAB node 106 P3 , and 0.3B to IAB node 105 P3 A buffer threshold of

[0071] Next, the IAB donor 101 adds the buffer thresholds of the IAB nodes through which multiple paths pass. For example, the IAB node 102 has a buffer threshold of 0.9(B P1 +B P2 +B P3 ) buffer threshold is assigned to IAB node 103, and 0.6(B P1 +B P2 ) buffer threshold is assigned. Therefore, 90% of the downlink buffer size of the IAB node 102 is 0.9(B P1 +B P2 +B P3 ) so that B P1 , B P2 , B P3 By determining the buffer size of each IAB node, we can determine the P1 , B P2 , B P3 For example, for each path, P1 =B P2 =B P3) or the buffer may be allocated to correspond to the path length (number of hops). Also, the buffer may be allocated to correspond to the number of UEs connected to each path. Then, the buffer size of each IAB node is allocated to B P1 , B P2 , B P3 can be identified to determine the threshold amount of data buffered in the downlink buffer for each IAB node described above.

[0072] In the first embodiment, the buffer threshold set in an IAB node is described as being set according to the number of IAB nodes connecting to the IAB donor via the IAB node. In the second embodiment, a control method is described in which the buffer threshold set in an IAB node is set according to the number of IAB nodes and UEs connecting to the IAB donor via the IAB node. Alternatively, the buffer threshold set in an IAB node may be determined according to the number of IAB nodes (number of hops) through which the IAB node passes before connecting to the IAB donor. For example, if the number of hops to the IAB donor is H and the maximum value of the buffer threshold is B, then the buffer threshold may be set as B / H. This allows a larger buffer threshold to be assigned to an IAB node with a smaller number of hops to the IAB donor, i.e., closer to the IAB donor in terms of the network, and a smaller buffer threshold to an IAB node with a larger number of hops to the IAB donor. In a multipath IAB network or other situation where there are multiple patterns for the number of hops to the IAB donor, the buffer threshold may be determined based on the smallest number of hops.

[0073] According to this method, a threshold for the amount of data buffered in the downlink buffer of an IAB node far from the IAB donor is set low to trigger the execution of flow control, thereby minimizing the impact of an IAB node farther from the IAB donor in a cascaded IAB network on a closer IAB node and on UEs connected to the IAB node.

[0074] In this embodiment, the IAB node notifies the IAB donor when the amount of data buffered in the downlink buffer exceeds a threshold. However, in one example, the IAB node may send a notification to the IAB donor in response to an event related to the amount of data buffered in the downlink buffer, such as when the amount of data buffered in the downlink buffer increases or decreases by more than a predetermined value within a predetermined period. In other words, the IAB node may trigger the execution of a flow control process when the amount of data buffered in the downlink buffer meets a predetermined condition. [Explanation of symbols]

[0075] 100 IAB network, 101 IAB donor, 102 to 105 IAB nodes, 110 to 118 UE, 201 control unit, 202 memory unit, 203 wireless communication unit, 204 antenna control unit, 301 signal transmission / reception unit, 302 data memory unit, 303 connection control unit, 304 buffer threshold management unit, 305 session management unit, 306 buffer status management unit

Claims

1. A control device for an IAB (Integrated Access and Backhaul) network, comprising: a determining means for determining, for each one or more IAB nodes of the IAB network based on a network configuration of the IAB network, a condition for the amount of data buffered in a downlink buffer of the IAB node, which is used to trigger execution of flow control processing of downlink traffic in a path including the IAB node by the IAB node relaying a connection between an IAB donor and a user equipment via a backhaul link; a notification means for notifying each of the one or more IAB nodes of the condition determined by the determination means; A control device comprising:

2. The control device of claim 1 , wherein the condition indicates a threshold amount of data buffered in a downlink buffer of each of the one or more IAB nodes.

3. 3. The control device according to claim 2, wherein the determining means determines the threshold of each of the one or more IAB nodes to be smaller than the threshold of an IAB node through which each of the one or more IAB nodes connects to the IAB donor.

4. 4. The control device according to claim 2, wherein the determining means determines the condition depending on the number of IAB nodes through which a connection to the IAB donor is made.

5. 5. The control device according to claim 2, wherein the determining means determines the condition of each of the one or more IAB nodes according to the number of IAB nodes that pass through each of the one or more IAB nodes when connecting to the IAB donor.

6. 6. The control device according to claim 2, wherein the determining means determines the condition based on the number of user devices connecting to the IAB donor via each of the one or more IAB nodes.

7. 7. The control device according to claim 2, further comprising: receiving means for receiving a notification indicating that the amount of data buffered in a downlink buffer of a first IAB node of the one or more IAB nodes has exceeded the threshold.

8. 8. The control device according to claim 7, further comprising a transmitting means for transmitting an instruction to reduce the amount of downlink data to be transferred to the first IAB node from an IAB node through which the first IAB node connects to the IAB donor.

9. 8. The control device according to claim 7, further comprising a route control means for changing a communication route of a data packet so as to reduce an amount of downlink data transferred to the first IAB node.

10. 2. The control device according to claim 1, wherein the condition includes that the amount of data buffered in the downlink buffer of each of the one or more IAB nodes has increased or decreased by more than a predetermined value within a predetermined period of time.

11. a detection means for detecting that an IAB node and a user device connected to the IAB donor have changed within a predetermined time; 11. The control device according to claim 1, wherein the determining means determines the condition when the detecting means detects that an IAB node and a user device have changed within the predetermined time.

12. An IAB (Integrated Access and Backhaul) node connected to an IAB donor of an IAB network via a backhaul link, receiving means for receiving, from a control device of the IAB network, a condition of the amount of data buffered in a downlink buffer of the IAB node, for triggering execution of a flow control process for downlink traffic on a path including the IAB node; a storage means for storing the conditions received by the receiving means; a notification means for notifying an upper IAB node of a message that triggers the execution of a flow control process using a BAP (Backhaul Adaptation Protocol) message when the condition stored in the storage means is satisfied; an update means for updating the data amount condition stored in the storage means to a condition corresponding to the notification of the change when a notification of a change to the data amount condition is newly received from the control device; Equipped with The notification of change is a notification sent to the IAB node when the control device performs a recalculation taking into account changes in the communication conditions within the IAB network.

13. A control method executed by a control device of an IAB (Integrated Access and Backhaul) network, comprising: a determining step of determining, for each one or more IAB nodes of the IAB network based on a network configuration of the IAB network, a condition for the amount of data buffered in a downlink buffer of the IAB node that is used by the IAB node relaying a connection between an IAB donor and a user equipment via a backhaul link to trigger execution of a flow control process for downlink traffic on a path including the IAB node; a notification step of notifying each of the one or more IAB nodes of the determined condition; A control method comprising:

14. A control method executed by an IAB (Integrated Access and Backhaul) node connected to an IAB donor in an IAB network via a backhaul link, comprising: receiving, from a control device of the IAB network, a condition of the amount of data buffered in a downlink buffer of the IAB node, for triggering execution of a flow control process for downlink traffic on a path including the IAB node; a control step of controlling the IAB node to store the data amount condition received in the receiving step in a predetermined storage area; a notification step of notifying an upper IAB node of a message that triggers execution of a flow control process using a BAP (Backhaul Adaptation Protocol) message when the condition stored in the predetermined storage area is satisfied; an updating step of updating, when a notification to change a data amount condition is newly received from the control device, the data amount condition stored in the predetermined storage area to a condition corresponding to the notification to change the data amount condition; Including, A control method characterized in that the notification of change is a notification sent to the IAB node when a recalculation is performed in the control device taking into account changes in communication conditions within the IAB network.

15. A program executed by a control device of an IAB (Integrated Access and Backhaul) network, a determining step of determining, for each one or more IAB nodes of the IAB network based on a network configuration of the IAB network, a condition for the amount of data buffered in a downlink buffer of the IAB node that is used by the IAB node relaying a connection between an IAB donor and a user equipment via a backhaul link to trigger execution of a flow control process for downlink traffic on a path including the IAB node; a notification step of notifying each of the one or more IAB nodes of the condition determined in the determination step; A program comprising:

16. A program executed by an Integrated Access and Backhaul (IAB) node connected to an IAB donor of an IAB network via a backhaul link, comprising: receiving, from a control device of the IAB network, a condition of the amount of data buffered in a downlink buffer of the IAB node, for triggering execution of a flow control process for downlink traffic on a path including the IAB node; a control step of controlling the IAB node to store the data amount condition received in the receiving step in a predetermined storage area; a notification step of notifying an upper IAB node of a message that triggers execution of a flow control process using a BAP (Backhaul Adaptation Protocol) message when the condition stored in the predetermined storage area is satisfied; an updating step of updating, when a notification to change a data amount condition is newly received from the control device, the data amount condition stored in the predetermined storage area to a condition corresponding to the notification to change the data amount condition; Including, The program is characterized in that the notification of change is a notification sent to the IAB node when a recalculation is performed in the control device taking into account changes in communication conditions within the IAB network.

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