Message sending method, device and system

Abstract

In an embodiment of the present invention, a message transmission method, an apparatus and a system are provided, which include: a first IAB node (IAB-node) receives a second Radio Resource Control (RRC) reconfiguration message for a path transition of a second IAB-node from a donor aggregation unit (Donor-CU), the second IAB-node being a downstream child node of the first IAB-node; the first IAB-node receives a first RRC reconfiguration message for a path transition of the first IAB-node from the Donor-CU; and the first IAB-node forwards the second RRC reconfiguration message to the second IAB-node upon successful random access.

Description

[Technical Field]

[0001] The present invention relates to the field of communications. [Background technology]

[0002] When deploying future seamless cellular networks, highly flexible and ultra-dense NR cell deployment is required. Ultra-dense networks are one of the goals of 5G, and the deployment of new radio (NR) networks that do not require wired backhaul is crucial to realizing 5G ultra-dense networks. As 5G mmWave reduces cell coverage, wireless cell backhaul systems require multi-hop to meet deployment requirements. 5G's high bandwidth, massive multiple-input multiple-output MIMO, and beam systems make it easier to develop wireless cell backhaul systems for 5G ultra-dense NR cells than LTE. Such wireless cells Backhaul In order to develop a multi-hop system with LTE, 3GPP (registered trademark) started research and standardization of IAB (Integrated access and backhaul) in R16.

[0003] An IAB system is shown in Figure 1. As shown in Figure 1, in an IAB system, a relay node simultaneously supports access and backhaul functions, and the wireless transmission link of the relay node multiplexes the access link and the backhaul link in the time domain, frequency domain, or spatial domain, and the access link and the backhaul link can use the same or different frequency bands.

[0004] In the IAB network architecture, the relay node refers to the IAB-node, which can simultaneously support access and backhaul functions. The last one-hop access node on the network side is called the IAB-donor, which supports gNB functions and also supports IAB-node access. All UE data can be backhauled to the IAB-donor via the IAB-node via a single hop or multi-hop.

[0005] The IAB-node functions can be divided into two parts: one part is the gNB-DU function and is called the IAB-DU (Distributed Unit), and the other part is the UE function and is called the IAB-MT (Mobile Terminal). The IAB-DU implements network side device functions, connects to downstream child IAB-nodes, provides NR air interface access for UEs and downstream child IAB-nodes, and establishes an F1 connection with the IAB Donor-CU. The IAB-MT implements some terminal device functions and connects to the upstream parent IAB-node or IAB-Donor DU. The IAB-MT includes physical layer, Layer 2, RRC (Radio Resource Control), and NAS (Non-Access Stratum) layer functions, and is indirectly connected to the IAB Donor-CU and the core network (CN).

[0006] In the IAB system, an IAB-node can access the network in either standalone (SA) mode or non-standalone (EN-DC, E-UTRA-NR Dual Connectivity) mode. Figure 2 shows the IAB architecture in SA mode. Figure 3 shows the IAB architecture in EN-DC mode.

[0007] Figure 4 shows one IAB node (IAB-node), its parent node (parent IAB-node), and its child node (child IAB-node). As shown in Figure 4, the IAB node's IAB-DU is connected to the child node IAB-MT as the network side, and the IAB node's IAB-MT is connected to the parent node IAB-DU as the terminal side.

[0008] Figure 5 shows the F1 user plane (F1-U) protocol stack between the IAB-DU and IAB-Donor CU. Figure 6 shows the F1 control plane (F1-C) protocol stack between the IAB-DU and IAB-Donor CU.

[0009] As shown in Figures 5 and 6, F1-U and F1-C are established on the transport (IP) layer between the IAB-DU and IAB-Donor-CU, which in Figures 5 and 6 traverse two hops of wireless backhaul and one hop of wired backhaul. In the backhaul link, the transport (IP) layer is carried to the Backhaul Adaptation Protocol (BAP) sublayer. The BAP entity in the IAB-node implements the routing function of the IAB system, and the IAB-Donor CU provides the routing table. BAP PDUs (Protocol Data Units) are transmitted over the RLC (Radio Link Control) channel of the backhaul link. Multiple RLC channels of the backhaul link are configured by the IAB-Donor to carry services with different priorities and QoS (Quality of Service). The BAP entity maps the BAP PDUs to different backhaul RLC channels.

[0010] It should be noted that the introduction of the above background art is intended to clearly and completely explain the technical solutions of the present invention and to facilitate understanding by those skilled in the art, and these technical solutions described in the background art of the present invention should not be construed as being known to those skilled in the art. Summary of the Invention [Problem to be solved by the invention]

[0011] In R16, the IAB system already supports adaptive changes in topology and routing that occur when an IAB-node moves between different DUs under the same Donor-CU. When an IAB-node moves under the same Donor-CU (at this time, the IAB-node is called a Migrating IAB-node), it still maintains its topology relationship with downstream child IAB-nodes and UEs. However, if the IAB-node disconnects from its original parent IAB-node and connects to a new parent IAB-node during the movement process, this may result in a change in the transmission path from the IAB-node and its child nodes to the Donor-CU, i.e., a change in network topology. For example, this change in network topology occurs when the IAB-node switches to a new parent node or establishes a dual connection with the new parent node.

[0012] Figure 7 shows the change in network topology caused by the movement of IAB-node. As shown in Figure 7, after IAB-node 5 switches from the cell under IAB-node 3 to the cell under IAB-node 4, the transmission path from IAB-node 5 and its downstream child node IAB-node 6 to Donor-CU changes from passing through IAB-node 1 and IAB-node 2 to passing through IAB-node 2 and IAB-node 4, that is, a change occurs in the network topology.

[0013] For now, when an IAB-node moves under the same Donor-CU, the process of updating the network topology is as follows: when the IAB-node changes its parent node, the Donor-CU can use an RRC reconfiguration message to configure the IAB-node with configuration information related to network topology updates, where the routing indicator (ID) implicitly includes the BAP address and route ID of the target Donor-DU. After the IAB-node switches to a new parent node, the IAB-node starts applying the above configuration information. The downstream child nodes of the IAB-node can also be configured with the same method for network topology updates.

[0014] The inventors have discovered the following: In other words, the existing method does not allow the IAB-node that has switched to a new parent node and its child nodes to simultaneously perform F1 path transition, which can result in a relatively long service interruption during the IAB-node's path transition process. Currently, the network topology update for the child node is performed after the IAB-node has completed accessing the new parent node, and the child node updates its network topology after the IAB-node. After the topology update, the Donor-DU (parent node) changes, and the address carried in the uplink data generated by the child node based on the original path configuration is the address of the original Donor-DU, which is different from the address of the new Donor-DU. This uplink data is dropped by the new Donor-DU, which prevents the child node from transmitting the uplink data generated based on the original path configuration to the CU. Furthermore, the dropped uplink data may be retransmitted by the UE, which can result in a relatively long data transmission delay and service interruption.

[0015] In addition, in the process of updating the network topology (topology adaptation) due to the movement of the IAB-node, the Donor-CU needs to send a configuration message related to updating the network topology to the IAB-node and each of its downstream child nodes. However, since the configuration message of each node needs to be sent independently, this may result in a large amount of signaling message overhead and may also cause a relatively long service interruption time.

[0016] SUMMARY OF THE INVENTION To address at least one of the above-mentioned problems or other similar problems, embodiments of the present invention provide a method, apparatus and system for sending messages. [Means for solving the problem]

[0017] According to one aspect of an embodiment of the present invention, there is provided a message sending device for use in a first IAB node, the device comprising: a first receiving unit for receiving a second radio resource control (RRC) reconfiguration message for a path transition of a second IAB-node from a donor aggregation unit (Donor-CU), wherein the second IAB-node is a downstream child node of the first IAB-node; A second receiving unit for receiving a first RRC reconfiguration message for a path transition of the first IAB-node from the Donor-CU; and The first transmitting unit transmits the second RRC reconfiguration message to the second IAB-node when the random access of the first IAB-node is successful.

[0018] According to one aspect of an embodiment of the present invention, there is provided a message sending device for use in a second IAB node, the device comprising: A fourth receiving unit for receiving a third RRC reconfiguration message for a path transition of the third IAB-node from the Donor-CU; and a third transmitting unit, which, upon receiving a second RRC Reconfiguration message sent by the Donor-CU and forwarded by a first IAB-node, forwards the third RRC Reconfiguration message to the third IAB-node, wherein the second RRC Reconfiguration message is used for path transition of the second IAB-node; Among them, the third IAB-node is a downstream child node of the second IAB-node, and the second IAB-node is a downstream child node of the first IAB-node.

[0019] According to one aspect of an embodiment of the present invention, there is provided a message sending device for use in a second IAB node, the device comprising: a sixth receiving unit for receiving a third RRC reconfiguration message for a path transition of the third IAB-node from the Donor-CU; A seventh receiving unit for receiving route transition failure indication information sent by the first IAB-node when the random access fails; and a second processing unit for triggering an RRC re-establishment procedure or falling back to an original path configuration; Among them, the third IAB-node is a downstream child node of the second IAB-node, and the second IAB-node is a downstream child node of the first IAB-node. [Effects of the Invention]

[0020] One of the advantageous effects of the embodiment of the present invention is as follows: before the IAB-node switches to a new parent node, information about the network topology update set for its child node is sent to the IAB-node by the Donor-CU and cached in the IAB-node; when the random access for the IAB-node to switch to a new parent node is successful, the IAB-node transfers to its child node the information about the network topology update set for its child node by the Donor-CU; in this way, the IAB-node and its child node can update the network topology almost simultaneously, thereby reducing the service interruption time due to node migration.

[0021] The following description and reference to the drawings disclose in detail particular embodiments of the present invention, illustrating ways in which the principles of the present invention may be employed, but the scope of the present invention is not limited thereto, and various changes, modifications, and alternatives may be included within the scope of the appended claims.

[0022] Additionally, features described and / or illustrated with respect to one embodiment may be used in the same or similar manner in one or more other embodiments, may be combined with features in the other embodiments, or may be substituted for features in the other embodiments.

[0023] It should be noted that terms such as "comprise / have" when used in this specification refer to the presence of a feature, element, step or assembly, but do not exclude the presence or addition of one or more other features, elements, steps or assemblies. [Brief explanation of the drawings]

[0024] Elements and features described in one drawing or one embodiment of the invention may be combined with elements and features shown in one or more other drawings or embodiments, and in the drawings, like reference numerals are used to indicate corresponding parts in several drawings and to indicate corresponding parts used in several embodiments.

[0025] The included drawings are used to provide a further understanding of the embodiments of the present invention, and these drawings constitute a part of this specification, illustrate embodiments of the present invention, and together with the written description, serve to explain the principles of the present invention. Also, it is apparent that the drawings described below are only for illustrating some embodiments of the present invention, and those skilled in the art can derive other drawings based on these drawings without any creative effort. [Figure 1] FIG. 1 illustrates an IAB system. [Figure 2] FIG. 1 illustrates the IAB architecture in SA mode. [Figure 3] FIG. 1 illustrates an IAB architecture in EN-DC mode. [Figure 4] FIG. 1 is a diagram showing a parent node (parent IAB-node) and a child node (child IAB-node). [Figure 5] FIG. 1 illustrates the F1-U protocol stack of the IAB system. [Figure 6] FIG. 1 illustrates the F1-C protocol stack of the IAB system. [Figure 7] FIG. 10 illustrates how an IAB node moves between different DUs under the same Donor. [Figure 8] FIG. 1 illustrates a method for sending a message in an embodiment of the present invention. [Figure 9] FIG. 1 illustrates a method for sending a message in an embodiment of the present invention. [Figure 10] FIG. 1 illustrates a method for sending a message in an embodiment of the present invention. [Figure 11] FIG. 1 illustrates a method for sending a message in an embodiment of the present invention. [Figure 12] FIG. 1 illustrates a method for sending a message in an embodiment of the present invention. [Figure 13] FIG. 1 is a diagram (part 1) showing one scenario of a message transmission method according to an embodiment of the present invention. [Figure 14]FIG. 2 is a diagram (part 2) showing one scenario of a message transmission method in an embodiment of the present invention. [Figure 15] FIG. 3 is a diagram (part 3) showing one scenario of a message transmission method in an embodiment of the present invention. [Figure 16] FIG. 10 is a diagram (part 1) showing another scenario of a message transmission method according to an embodiment of the present invention. [Figure 17] FIG. 2 is a diagram (part 2) showing another scenario of the message transmission method according to the embodiment of the present invention. [Figure 18] FIG. 10 illustrates yet another scenario of a message sending method in an embodiment of the present invention. [Figure 19A] A diagram showing the structure of a downlink message in an embodiment of the present invention. [Figure 19B] A diagram showing the structure of an uplink message in an embodiment of the present invention. [Figure 20A] A diagram showing the structure of a downlink message in an embodiment of the present invention. [Figure 20B] A diagram showing the structure of an uplink message in an embodiment of the present invention. [Figure 21] FIG. 1 illustrates a message sending device according to an embodiment of the present invention. [Figure 22] FIG. 10 is another diagram illustrating a message sending device in an embodiment of the present invention. [Figure 23] FIG. 10 is yet another diagram showing a message sending device in an embodiment of the present invention. [Figure 24] FIG. 10 is another diagram illustrating a message sending device according to an embodiment of the present invention. [Figure 25] 1 is a diagram illustrating a communication system according to an embodiment of the present invention. [Figure 26] FIG. 2 is a diagram illustrating an IAB node in an embodiment of the present invention. [Figure 27] 1 is a diagram showing a donor device according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0026] The foregoing and other features of the present invention will become more apparent from the following detailed description and the accompanying drawings, in which: While the specification and drawings disclose particular embodiments of the present invention, these illustrate only some of the embodiments which may employ the principles of the present invention, and it is to be understood that the present invention is not limited to the described embodiments, but rather includes all modifications, variations, and alternatives which fall within the scope of the appended claims.

[0027] In embodiments of the present invention, the term "communication network" or "wireless communication network" may refer to a network conforming to any communication standard, such as LTE (Long Term Evolution), LTE-A (LTE-Advanced), WCDMA (Wideband Code Division Multiple Access), HSPA (High-Speed ​​Packet Access), etc.

[0028] Additionally, communications between devices in a communications system may be performed according to any level of communications protocol, including, but not limited to, 1G (generation), 2G, 2.5G, 2.75G, 3G, 4G, 4.5G, 5G, New Radio (NR), and / or other conventional or future-developed communications protocols.

[0029] In the embodiments of the present invention, the term "network device" refers to a device that connects a terminal device to a communication network and provides services to the terminal device in a communication system, for example, a network device may include, but is not limited to, a base station (BS), an access point (AP), a transmission reception point (TRP), a broadcast transmitter, a mobile management entity (MME), a network gateway, a server, a radio network controller (RNC), a base station controller (BSC), etc.

[0030] The base station may include, but is not limited to, a Node B (NodeB or NB), an evolved Node B (eNodeB or eNB), a 5G base station (gNB), etc., and may further include a Remote Radio Head (RRH), a Remote Radio Unit (RRU), a relay, or a low-power node (e.g., femto, pico, etc.). The term "base station" may include some or all of the functions thereof, and each base station can provide communication coverage for a specific geographic area. The term "cell" may refer to a base station and / or the area it covers, depending on the context of the term.

[0031] In embodiments of the present invention, the term "User Equipment" (UE) or "Terminal Equipment" (TE) refers to a device that accesses a communication network and receives services from the network, for example, via a network device. A User Equipment may be fixed or mobile, and may also be referred to as a Mobile Station (MS), a terminal, a Subscriber Station (SS), an Access Terminal (AT), a station, etc.

[0032] Among these, user devices may include, but are not limited to, cellular phones, personal digital assistants (PDAs), wireless modems, wireless communication devices, handheld devices, machine-type communication devices, laptop computers, cordless phones, smartphones, smart watches, digital cameras, etc.

[0033] Furthermore, for example, in a scenario such as the Internet of Things (IoT), the user equipment may also be a monitoring or measuring device or apparatus, including, but not limited to, a Machine Type Communication (MTC) terminal, an in-vehicle communication terminal, a Device to Device (D2D) terminal, a Machine to Machine (M2M) terminal, etc.

[0034] For example, in the above-mentioned Figure 7, IAB-node3 is the parent node of IAB-node4, and IAB-node4 is the parent node of IAB-node5. After IAB-node3 switches to its new parent node IAB-node2, a change occurs in the network topology, i.e., the transmission paths between IAB-node3, IAB-node4, and IAB-node5 and Donor-CU are changed. Donor CU sends a configuration message for network topology update to IAB-node3, IAB-node4, and IAB-node5, causing the F1 transmission path to be switched from the original path to the new path. The network topology update for IAB-node4 and IAB-node5 is performed after IAB-node3 completes access to the new parent node, i.e., IAB-node4 and IAB-node5 perform the network topology update after IAB-node3. As a result, the uplink data transmitted by IAB-node4 and IAB-node5 based on the original configuration may be dropped by Donor-DU2, resulting in a relatively long transmission delay and service interruption time.

[0035] Furthermore, in the prior art, Donor-Cu needs to send one downlink F1AP message (F1 Application Protocol) carrying configuration information for updating the network topology, i.e., DL F1AP MESSAGE, to each parent node of IAB-node3 and each of its child nodes (see messages A, B, and C in FIG. 7), for IAB-node3 and each of its child nodes. Message B can be sent only after the path transition of IAB-node3 is successful, and message C can be sent only after the path transition of IAB-node4 is successful. This can result in a large amount of signaling message overhead and a relatively long service interruption time.

[0036] In the present invention, before the IAB-node switches to a new parent node, information regarding the network topology update set for its child node is sent to the IAB-node by the Donor-CU and cached in the IAB-node. When the random access by which the IAB-node switches to a new parent node is successful, the IAB-node transfers to its child node the information regarding the network topology update set for its child node by the Donor-CU. In this way, the IAB-node and its child node can update the network topology almost simultaneously, thereby reducing the service interruption time due to node migration.

[0037] Although the present invention will be described taking the example of an IAB-node switching to a new parent node, embodiments of the present invention are not limited thereto, and the present invention can also be applied to changes in network topology that occur when an IAB-node establishes a dual connection with a new parent node.

[0038] Various embodiments of the present invention will be described below in conjunction with the drawings, but these embodiments are merely illustrative and are not intended to limit the present invention.

[0039] For example, in each embodiment of the present invention, the first IAB-node is a transition node (e.g., IAB-node3 shown in FIG. 7 ) and is an IAB node under the control of Donor-CU. The first IAB-node transitions (switches) from a first parent node (e.g., IAB-node1 shown in FIG. 7 ) to a second parent node (e.g., IAB-node2 shown in FIG. 7 ). The second IAB-node (e.g., IAB-node4 shown in FIG. 7 ) is a downstream child node of the first IAB-node, and the third IAB-node (e.g., IAB-node5 shown in FIG. 7 ) is a downstream child node of the second IAB-node. Note that the number of the second IAB-node or the third IAB-node may be one or at least two, and the third IAB-node may further have other child nodes; however, the embodiments of the present invention are not limited thereto. For convenience of explanation, the following description will be given taking as an example a case where IAB-node4 in FIG. 7 is the second IAB-node, IAB-node5 is the third IAB-node, and IAB-node5 has no other child nodes.

[0040] <Example of the first aspect> In the embodiment of the present invention, a message sending method is provided, which will be explained from the first IAB-node side.

[0041] This method is applied when the first IAB-node and its child nodes perform path transition due to the first IAB-node switching to a new parent node. Figure 8 shows a diagram of a message transmission method in this embodiment. As shown in Figure 8, the method includes the following steps (operations):

[0042] 801: A first IAB-node receives a second radio resource control (RRC) reconfiguration message for a route transition of a second IAB-node from a Donor-CU; 802: The first IAB-node receives a first RRC reconfiguration message for a path transition of the first IAB-node from the Donor-CU; and 803: When the first IAB-node has successfully completed the random access, it forwards the second RRC reconfiguration message to the second IAB-node.

[0043] In some embodiments, in 801 and 802, the first RRC reconfiguration message and the second RRC reconfiguration message are both configured and generated by the Donor-CU, and the first or second RRC reconfiguration message from the Donor-CU may be sent directly to the first IAB-node by the Donor-CU, or may be sent to the first parent node by the Donor-CU and forwarded to the first IAB-node by the first parent node, but embodiments of the present invention are not limited thereto.

[0044] In some embodiments, in 803, the first IAB-node forwards the second RRC reconfiguration message to the second IAB-node when it determines that the first RRC reconfiguration message is for a path transition of the first IAB-node. The first IAB-node can determine that the first RRC reconfiguration message is for a path transition of the first IAB-node when the first RRC reconfiguration message includes first parameters configured for a change in the transmission path of the first IAB-node. The first parameters include a default backhaul radio link control (BH RLC) channel, a default backhaul adaptation protocol (BAP) routing, or an Internet Protocol (IP) address configured for the first IAB-node. Wherein, the default BH RLC channel may be a BH RLC channel used by uplink F1-C and non-F1 data, and the default BAP routing may be a routing used by uplink F1-C and non-F1 data, and includes a route identifier (ID) and a destination BAP address, and the IP address represents an IP address that can be routed to a new Donor-DU (e.g., Donor-DU2 in Figure 7) after switching to the second parent node. When the first IAB-node receives a first RRC reconfiguration message including the above-mentioned first parameter, it can determine that the first RRC reconfiguration message is a configuration message for route transition.

[0045] In some embodiments, the first IAB-node determines that the first RRC reconfiguration message is a configuration message for path transition because the first RRC reconfiguration message includes first path transition indication information. If the first RRC reconfiguration message includes parameters configured for the above-mentioned transmission path change, the RRC message may not be for path transition. Therefore, it is necessary to explicitly instruct the first IAB-node to perform RRC reconfiguration for path transition, where the first path transition indication information is used to indicate that the first RRC reconfiguration message is a reconfiguration message for path transition of the first IAB-node.

[0046] In some embodiments, the method is applied when the first IAB-node performs a path transition between different Donor-DUs (the Donor-DU has changed after switching to a new parent node), and in this case, the first RRC reconfiguration message is for a path transition between Donor-DUs of the first IAB-node. The first path transition indication information is used to instruct the first IAB-node to perform a path transition between Donor-DUs, that is, when the first RRC message includes the first path transition indication information, it indicates that the first RRC reconfiguration message is a reconfiguration message for a path transition between different Donor-DUs of the first IAB-node.

[0047] In some embodiments, in 801 and 802, the first RRC reconfiguration message and the second RRC reconfiguration message may be carried by one downlink message, i.e., the first IAB-node receives the first RRC reconfiguration message and the second RRC reconfiguration message simultaneously, or may be carried by two downlink messages, i.e., the first IAB-node receives the second RRC reconfiguration message and the first RRC reconfiguration message sequentially, as will be described below.

[0048] In some embodiments, in step 803, the first IAB node performs a path transition by switching to the second parent node. The first IAB node must perform a random access to switch to the second parent node. The first RRC reconfiguration message includes information about the first IAB node's switching to the second parent node. The random access procedure can refer to the random access of an IAB node in the prior art, and a detailed description thereof is omitted here. Only if the random access is successful, the first IAB node triggers transmission of the cached second RRC reconfiguration message. If the random access fails, the first IAB node triggers RRC reestablishment. The RRC reestablishment procedure can refer to the RRC reestablishment of an IAB node in the prior art, and a detailed description thereof is omitted here. The first IAB node must also send a path transition failure indication to its child node, and may optionally further forward the second RRC reconfiguration message to its child node or clear the second RRC reconfiguration message. The behavior of the child node when random access fails will be explained in the embodiment of the second aspect below.

[0049] In some embodiments, in 803, upon successful random access, the method may further include: the first IAB-node sending a first RRC reconfiguration complete message to the Donor-CU, and the first IAB-node may further receive a second RRC reconfiguration complete message sent by the second IAB-node, and optionally forward the second RRC reconfiguration complete message to the Donor-CU, where the first RRC reconfiguration complete message and the second RRC reconfiguration complete message may be carried by one uplink message or two uplink messages respectively, and the above-mentioned transmission to the Donor-CU may be sent directly to the Donor-CU or forwarded to the Donor-CU by a second parent node, as will be described later.

[0050] As a result, before the IAB-node switches to a new parent node, information regarding the network topology update set for its child node is sent to the IAB-node by the Donor-CU and cached in the IAB-node, and when the random access for the IAB-node to switch to a new parent node is successful, the IAB-node transfers to its child node information regarding the network topology update set for its child node by the Donor-CU.In this way, the IAB-node and its child node can update the network topology almost simultaneously, thereby reducing the service interruption time due to node migration.

[0051] <Example of the second aspect> In the embodiment of the present invention, a message transmission method is provided, which is described from the second IAB-node side, and the actions of the third IAB-node side are the same as those of the second IAB-node side, so detailed description thereof is omitted here.

[0052] In some embodiments, the second IAB-node receives a third RRC reconfiguration message from the Donor-CU for a route transition of the third IAB-node.

[0053] In some embodiments, the third RRC reconfiguration message is configured and generated by the Donor-CU, and the third RRC reconfiguration message from the Donor-CU may be sent directly to the second IAB-node by the Donor-CU, may be sent to the first IAB-node by the Donor-CU and forwarded to the second IAB-node by the first IAB-node, or may be sent to the first parent node by the Donor-CU, forwarded to the first IAB-node by the first parent node, and then forwarded to the second IAB-node by the first IAB-node, although embodiments of the present invention are not limited thereto.

[0054] In some embodiments, when the random access of the first IAB-node is successful (random access is completed), the second IAB-node receives a second RRC reconfiguration message forwarded by the first IAB-node, and upon receiving the second RRC reconfiguration message, forwards the third RRC reconfiguration message to the third IAB-node. Also, when the random access of the first IAB-node fails (random access is not completed, or cannot be completed or cannot be completed correctly), the second IAB-node receives path transition failure indication information sent by the first IAB-node, and triggers an RRC re-establishment procedure or falls back to the original path configuration. Each of these will be described below.

[0055] 9 is a diagram showing a message transmission method on the side of the second IAB-node when the random access of the first IAB-node is successful. As shown in FIG. 9, the method includes the following steps (operations):

[0056] 901: The second IAB-node receives a third RRC reconfiguration message for a route transition of the third IAB-node from the Donor-CU; and 902: When the second IAB-node receives a second RRC reconfiguration message sent by the Donor-CU and forwarded by the first IAB-node, it forwards the third RRC reconfiguration message to the third IAB-node, and the second RRC reconfiguration message is used for the path transition of the second IAB-node.

[0057] In some embodiments, before 902, the method may further include the following step (not shown): the second IAB-node receives a second RRC reconfiguration message sent by the Donor-CU and forwarded by the first IAB-node, the implementation manner of the second RRC reconfiguration message has been described above and will not be described in detail here, the second RRC reconfiguration message and the third RRC reconfiguration message may be carried by one downlink message or two downlink messages respectively, as will be described in detail below.

[0058] In some embodiments, at 902, upon receiving the second RRC Reconfiguration message, the second IAB-node performs a route transition and triggers the second IAB-node to forward the cached third RRC Reconfiguration message to the third IAB-node. Because the second IAB-node does not change its parent node (the parent node is still the first IAB-node) and the second RRC Reconfiguration message does not contain switching information, the second IAB-node does not need to perform a random access procedure.

[0059] In some embodiments, in 902, when the second IAB-node determines that the second RRC reconfiguration message is a configuration message for path transition of the second IAB-node, it forwards the third RRC reconfiguration message to the third IAB-node. The second RRC reconfiguration message can be determined to be for path transition of the second IAB-node in two ways: for example, the second RRC reconfiguration message includes a second parameter configured for the second IAB-node to change its transmission path, or includes second path transition indication information. The implementation manner of the second parameter and the second path transition indication information is the same as the implementation manner of the first parameter and the first path transition indication information described above, and detailed description thereof will be omitted here.

[0060] Furthermore, upon receiving the second RRC reconfiguration message, the method may further include the following steps (not shown): the second IAB-node sends a second RRC reconfiguration complete message to the first IAB-node, and the second IAB-node receives a third RRC reconfiguration complete message sent by the third IAB-node. Optionally, the third RRC reconfiguration complete message may be further forwarded to the Donor-CU, where the second RRC reconfiguration complete message and the third RRC reconfiguration complete message may be carried by one uplink message or by two uplink messages respectively. The above-mentioned transmission to the Donor-CU may be directly sent to the Donor-CU or may be forwarded to the Donor-CU via the first IAB node and / or the second parent node, as will be described in detail below.

[0061] As a result, before the IAB-node switches to a new parent node, information regarding the network topology update set for its child node is sent to the IAB-node by the Donor-CU and cached in the IAB-node; when the random access by which the IAB-node switches to a new parent node is successful, the IAB-node forwards to its child node the information regarding the network topology update set for its child node by the Donor-CU; and when the child node receives the information regarding the network topology update, it further forwards to its child node the information regarding the network topology update set for its child node by the Donor-CU; in this way, the IAB-node and its child node can perform network topology updates almost simultaneously, thereby reducing the service interruption time due to node migration.

[0062] 10 is a diagram showing a method for sending a message from a second IAB-node when the first IAB-node fails to randomly access the first IAB-node. As shown in FIG. 10, the method includes the following steps (operations):

[0063] 1001: The second IAB-node receives a third RRC reconfiguration message for a route transition of the third IAB-node from the Donor-CU; 1002: The second IAB-node receives the route transition failure indication information sent by the first IAB-node when the random access fails; and 1003: The second IAB-node triggers an RRC re-establishment procedure.

[0064] In some embodiments, the implementation of 1001 is as described above, and a detailed description thereof will be omitted here.

[0065] In some embodiments, in 1002, if the T304 timer expires, it indicates that the random access of the first IAB-node has failed (random access has not been completed, or cannot be completed or cannot be completed correctly), and the first IAB-node sends a path transition failure indication to the second IAB-node, causing the second IAB-node to perform an RRC re-establishment procedure, and the first IAB-node may further forward the second RRC reconfiguration message to the second IAB-node or may clear the second RRC reconfiguration message. Correspondingly, in 1002, the method may further include: the second IAB-node receives a second RRC reconfiguration message for path transition of the second IAB-node, which is sent by the Donor-CU to the first IAB-node and forwarded by the first IAB-node.

[0066] In some embodiments, the method may further include the following step (not shown): the second IAB-node forwards the path transition failure indication information received in 1002 to a third IAB-node, thereby triggering the third IAB-node to perform RRC re-establishment.

[0067] In some embodiments, the method may further include the following step (not shown): the second IAB-node forwards the third RRC reconfiguration message to the third IAB-node, or clears the third RRC reconfiguration message, the specific implementation of which can be referred to in the first IAB-node, and the detailed description thereof will be omitted here.

[0068] In some embodiments, in 1003, the second IAB-node triggers an RRC re-establishment procedure, which can refer to the RRC re-establishment of an IAB-node in the prior art, and a detailed description thereof will be omitted here.

[0069] As a result, when the IAB-node fails in random access to switch to a new parent node, it triggers RRC re-establishment and instructs its child node of a path transition failure, and the child node also triggers RRC re-establishment. In this way, when the IAB-node transition fails, the IAB-node and its child node can perform RRC re-establishment almost simultaneously, thereby reducing the service interruption time due to a path transition failure.

[0070] 11 is a diagram illustrating another method for sending a message from the second IAB-node when the first IAB-node fails to randomly access the first IAB-node. As shown in FIG. 11, the method includes the following steps (operations):

[0071] 1101: The second IAB-node receives a third RRC reconfiguration message for a route transition of the third IAB-node from the Donor-CU; 1102: The second IAB-node receives a second RRC reconfiguration message for path transition of the second IAB-node, which is sent by the Donor-CU to the first IAB-node and forwarded by the first IAB-node; 1103: The second IAB-node receives the route transition failure indication information sent by the first IAB-node when the random access fails; and 1104: The second IAB-node falls back to the original route setting.

[0072] In some embodiments, the implementation manners of 1101 and 1103 are the same as those described above, and detailed description thereof will be omitted here.

[0073] In some embodiments, the first IAB-node sends the path change failure indication and a second RRC reconfiguration message to the second IAB-node, causing the second IAB-node to fall back to the original path configuration. The difference from the above-mentioned Figure 10 is that the second IAB-node does not perform RRC re-establishment, i.e., it receives the second RRC reconfiguration message but does not perform the reconfiguration, and only performs fallback to the original path configuration. Therefore, it is not optional for the first IAB-node to forward the second RRC reconfiguration message to the second IAB-node, but it must forward it. In other words, step 1102 is a required step; otherwise, the Packet Data Convergence Protocol (PDCP) of the second IAB-node may experience an abnormality due to not receiving the second RRC reconfiguration message.

[0074] In some embodiments, the method further includes the following step (not shown): the second IAB-node forwards the third RRC reconfiguration message to the third IAB-node, and the second IAB-node forwards the path transition failure indication information received in 1103 to the third IAB-node, so that the third IAB-node falls back to the original path configuration. Note that the specific implementation manner can be referred to in the first IAB-node, and the detailed description thereof will be omitted here.

[0075] Thus, when an IAB-node fails in random access to switch to a new parent node, it triggers RRC re-establishment, forwards the RRC reconfiguration of its child node to the child node, and instructs the child node of a path transition failure, causing the child node to fall back to the original path configuration. In this way, when the IAB-node's path transition fails, the IAB-node and its child node can simultaneously fall back to the original path configuration. Otherwise, when the child node performs a path transition and generates uplink data according to the new path configuration, the uplink data will be subsequently dropped and retransmitted by the UE, increasing the delay in uplink data transmission. This method can avoid an increase in data transmission time due to a path transition failure.

[0076] <Example of the third aspect> In the embodiment of the present invention, a message sending method is provided and explained from the Donor-CU side.

[0077] FIG. 12 is a diagram showing the message sending method. As shown in FIG. 12, the method includes the following steps (operations):

[0078] 1201: A Donor-CU sends a second radio resource control (RRC) reconfiguration message for a route transition of a second IAB-node to a first IAB-node, and causes the first IAB-node to forward the second RRC reconfiguration message to the second IAB-node upon successful random access; and 1202: The Donor-CU sends a first Radio Resource Control (RRC) reconfiguration message for the path transition of the first IAB-node to the first IAB-node.

[0079] In some embodiments, when the second IAB-node has further child nodes, the method may further include the following steps:

[0080] 1203: The Donor-CU sends a third RRC reconfiguration message to the second IAB-node for path transition of the third IAB-node.

[0081] In some embodiments, the Donor-CU generates the first RRC Reconfiguration message, the second RRC Reconfiguration message, the third RRC Reconfiguration message, the first RRC Reconfiguration message, and the second RRC Reconfiguration message. The contents and structure of the third RRC Reconfiguration message and the manner of carrying them can refer to the embodiments of the first and second aspects. For example, in 1201 to 1203, the first RRC Reconfiguration message, the second RRC Reconfiguration message, and the third RRC Reconfiguration message can be carried by one downlink message, that is, the Donor-CU simultaneously transmits the first RRC Reconfiguration message, the second RRC Reconfiguration message, and the third RRC Reconfiguration message, or can be carried by three downlink messages, that is, the Donor-CU sequentially transmits the third RRC Reconfiguration message, the second RRC Reconfiguration message, and the first RRC Reconfiguration message. Details will be described later.

[0082] In some embodiments, the act of Donor-CU sending to the first IAB-node may be sent directly to the first IAB-node without going through other relay nodes, or may be forwarded to the first IAB-node via the first parent node, and the act of Donor-CU sending to the second IAB-node may be sent directly to the second IAB-node without going through other relay nodes, or may be forwarded to the first IAB-node via the first parent node, and then forwarded by the first IAB-node to the second IAB-node, but this embodiment is not limited to these.

[0083] In some embodiments, the method may further include the following steps:

[0084] 1204: The Donor-CU receives a first RRC reconfiguration complete message from the first IAB-node. Optionally, the Donor-CU may further receive a second RRC reconfiguration complete message from the second IAB-node, and a third RRC reconfiguration complete message, the first RRC reconfiguration complete message, and the second RRC reconfiguration complete message from the third IAB-node. For the content and structure contained in the third RRC reconfiguration complete message and the implementation manner of carrying them, reference may be made to the embodiments of the first and second aspects. For example, the first RRC reconfiguration complete message, the second RRC reconfiguration complete message, and the third RRC reconfiguration complete message may be carried by one uplink message, i.e., the Donor-CU receives the first RRC reconfiguration complete message, the second RRC reconfiguration complete message, and the third RRC reconfiguration complete message simultaneously, or they may be carried by three downlink messages, i.e., the Donor-CU receives the third RRC reconfiguration complete message, the second RRC reconfiguration complete message, and the first RRC reconfiguration complete message sequentially. The Donor-CU may receive the RRC reconfiguration complete message directly transmitted by the first IAB-node, the second IAB-node, or the third IAB-node, or may receive the RRC reconfiguration complete message transmitted by the first IAB-node, the second IAB-node, or the third IAB-node and forwarded via a node, as will be described in detail later.

[0085] The message transmission method according to the embodiment of the present invention has been described above with reference to the first to third aspects. To make the method according to the embodiment of the present invention easier to understand, the method according to the embodiment of the present invention will be described below based on the interaction flow.

[0086] As mentioned above, the first RRC reconfiguration message and the second RRC reconfiguration message may be carried by one downlink message, or may be carried by two downlink messages, respectively.

[0087] Implementation Scenario 1: The above-mentioned RRC Reconfiguration messages are each carried by two downlink messages, and the difference from the existing method is that the signaling carrying the second RRC Reconfiguration message is transmitted before the signaling carrying the first RRC Reconfiguration message. In this way, before the first IAB-node receives the first RRC Reconfiguration message and switches to the second parent node, the RRC Reconfiguration message sent by the Donor-CU for its child node has already been transmitted to the first IAB-node and cached by the first IAB-node, and can be transmitted when the first IAB-node switches to the second parent node. This allows the first IAB-node and its child node to simultaneously update the network topology.

[0088] FIG. 13 shows the message sending method. As shown in FIG. 13, the method includes the following steps:

[0089] 1301: The Donor-CU sends a second radio resource control (RRC) reconfiguration message for a path transition of the second IAB-node to the first IAB-node; 1302: The Donor-CU sends a first Radio Resource Control (RRC) reconfiguration message for a path transition of the first IAB-node to the first parent node; 1303: The first parent node forwards the first RRC reconfiguration message to the first IAB-node; 1304: The first IAB-node performs random access to the second parent node; and 1305: Upon successful random access, the first IAB-node forwards the second RRC reconfiguration message to the second IAB-node.

[0090] Optionally, when the second IAB-node has a further child node, ie, a third IAB-node, the method may further include the following steps:

[0091] 1300: The Donor-CU sends a third RRC reconfiguration message to the second IAB-node for the path transition of the third IAB-node; and 1306: When the second IAB-node receives the second RRC reconfiguration message, forward the third RRC reconfiguration message to the third IAB-node.

[0092] In some embodiments, in 1301, the second RRC Reconfiguration message is carried by a first downlink F1AP message, and a distributed unit (DU) of the first IAB-node receives the first downlink F1AP message sent by the Donor-CU, thereby receiving the second RRC Reconfiguration message carried by the first downlink F1AP message, for example, the first downlink F1AP message further includes first cache indication information, which is used to instruct the first IAB-node to cache the second RRC Reconfiguration message and release it after receiving first indication information described below. As an example, the first downlink F1AP message may be a UE context modification request message.

[0093] In some embodiments, in steps 1302-1303, the first RRC reconfiguration message is forwarded by the Donor-CU to a downlink F1AP message of the first parent node, and then the first parent node forwards the first RRC reconfiguration message in the downlink F1AP message to the first IAB-node. For example, the F1AP message may be a UE context modification request message. The downlink F1AP message may further include the first context identifier (ID) of the UE. For specific details, please refer to the prior art, and detailed descriptions thereof will be omitted here.

[0094] In some embodiments, the first IAB-node performs a random access procedure in 1304. The implementation method can be referred to in the prior art and will not be described in detail here. Upon successful random access, i.e., after the MT (MAC layer) of the first IAB-node completes random access to the second parent node, the first IAB-node transmits the second RRC reconfiguration message to the second IAB-node in 1305. Specifically, upon successful random access, the mobile terminal (MT) of the first IAB-node transmits first indication information to the distributed unit (DU) of the first IAB-node, and upon receiving the first indication information, the distributed unit (DU) of the first IAB-node transmits the second RRC reconfiguration message to the second IAB-node. Wherein, when the first RRC reconfiguration message includes a first parameter set for changing the transmission path of the first IAB-node and / or includes first path transition indication information, the first RRC reconfiguration message indicates that it is for path transition of the first IAB-node, and the MT of the first IAB-node sends first indication information to the DU of the first IAB-node. Note that for the meaning of the first parameter and / or the first path transition indication information, reference may be made to the embodiments of the first aspect, and detailed description thereof will be omitted here.

[0095] In some embodiments, the first RRC reconfiguration message further includes configuration information of first indication information, which is used to instruct the MT of the first IAB-node to send first indication information to a distributed unit (DU) of the first IAB-node upon successful random access. When the first RRC reconfiguration message includes the configuration information of the first indication information, the MT of the first IAB-node sends the first indication information to the DU of the first IAB-node. Alternatively, when the first RRC reconfiguration message includes the first parameter and / or first path transition indication information and includes the configuration information of the first indication information, the MT of the first IAB-node sends the first indication information to the DU of the first IAB-node.

[0096] In some embodiments, when the first downlink F1AP message further includes the aforementioned first cache indication information, in 1305, the DU of the first IAB-node forwards the second RRC reconfiguration message to the second IAB-node upon receiving the first indication information.

[0097] The first instruction information, first instruction information setting information, first cache instruction information, first path transition instruction information, etc., as described above, may be information elements IEs that are added (newly added) to the message, and their values ​​may be default values, but embodiments of the present invention are not limited to this.

[0098] In some embodiments, in 1300, in some embodiments, in 1301, the third RRC reconfiguration message is carried by a second downlink F1AP message, and a distributed unit (DU) of the second IAB-node receives the second downlink F1AP message sent by the Donor-CU, thereby receiving the third RRC reconfiguration message carried in the second downlink F1AP message, for example, the second downlink F1AP message further includes second cache indication information, and the second cache indication information is used to instruct the second IAB-node to cache the third RRC reconfiguration message and release it after receiving the above-mentioned second indication information.

[0099] In some embodiments, when the second IAB-node receives the second RRC Reconfiguration message forwarded by the first IAB-node in 1306, the second IAB-node forwards the third RRC Reconfiguration message to a third IAB-node. Specifically, when a mobile terminal (MT) of the second IAB-node receives the second RRC Reconfiguration message, it sends second indication information to a distribution unit (DU) of the second IAB-node, and when the distribution unit (DU) of the second IAB-node receives the second indication information, it forwards the third RRC Reconfiguration message to the third IAB-node. Wherein, when the second RRC Reconfiguration message includes second parameters configured for changing the transmission path of the second IAB-node and / or includes second path transition indication information, this indicates that the second RRC Reconfiguration message is for path transition of the second IAB-node, and the MT of the second IAB-node sends second indication information to the DU of the second IAB-node. For the meaning of the second parameter and / or the second path transition instruction information, reference can be made to the examples of the second aspect, and for the structure and content of the third RRC reconfiguration message, reference can be made to the examples of the second aspect, and detailed explanations thereof will be omitted here.

[0100] In some embodiments, the second RRC reconfiguration message further includes configuration information of second indication information, which is used to instruct the second IAB-node to send second indication information to a distributed unit (DU) of the second IAB-node when the second RRC reconfiguration message receives the second RRC reconfiguration message. When the second RRC reconfiguration message includes the configuration information of the second indication information, the MT of the second IAB-node sends the second indication information to the DU of the second IAB-node. Or, when the second RRC reconfiguration message includes the second parameter and / or second path transition indication information and includes the configuration information of the second indication information, the MT of the second IAB-node sends the second indication information to the DU of the second IAB-node.

[0101] In some embodiments, when the second downlink F1AP message further includes the second cache indication information, in 1306, the DU of the second IAB-node forwards the third RRC reconfiguration message to the third IAB-node upon receiving the second indication information.

[0102] The second instruction information, second instruction information setting information, second cache instruction information, second path transition instruction information, etc., as described above, may be an information element IE added to the message, and its value may be a default value, but embodiments of the present invention are not limited to this.

[0103] In some embodiments, when the random access of the first IAB-node is successful, the method further includes the following steps:

[0104] 1307: The first IAB-node sends a first RRC reconfiguration complete message to the Donor-CU; 1308: The first IAB-node receives a second RRC reconfiguration completion message sent by the second IAB-node; 1309: The first IAB-node forwards the second RRC reconfiguration complete message to the Donor-CU; 1310: The second IAB-node receives a third RRC reconfiguration complete message sent by the third IAB-node; and 1311: The second IAB-node forwards the third RRC reconfiguration complete message to the Donor-CU.

[0105] In some embodiments, in 1307, after the first IAB-node completes the reconfiguration, the first IAB-node sends the first RRC reconfiguration complete message to the second parent node, and the second parent node forwards the first RRC reconfiguration complete message to the Donor-CU, where the second parent node may send an uplink F1AP message to the Donor-CU, carrying the first RRC reconfiguration complete message. For details, see the prior art.

[0106] In some embodiments, in 1308 and 1309, after the reconfiguration of the second IAB-node is completed, the second IAB-node sends the second RRC reconfiguration complete message to the first IAB-node, and the first IAB-node forwards the second RRC reconfiguration complete message to the Donor-CU, wherein the first IAB-node may send a first uplink F1AP message to the Donor-CU and carry the second RRC reconfiguration complete message in the first uplink F1AP message.

[0107] In some embodiments, in 1310 and 1311, after the reconfiguration of the third IAB-node is completed, the third IAB-node sends the third RRC reconfiguration complete message to the second IAB-node, and the second IAB-node forwards the third RRC reconfiguration complete message to the Donor-CU, wherein the second IAB-node may send a second uplink F1AP message to the Donor-CU, and the second uplink F1AP message may carry the third RRC reconfiguration complete message.

[0108] FIG. 14 shows the message sending method. As shown in FIG. 14, the method includes the following steps:

[0109] 1400: The Donor-CU sends a third RRC reconfiguration message to the second IAB-node for route transition of the third IAB-node; 1401: The Donor-CU sends a second wireless RRC reconfiguration message to the first IAB-node for route transition of the second IAB-node; 1402: The Donor-CU sends a first wireless RRC reconfiguration message for a route transition of the first IAB-node to the first parent node; 1403: The first parent node forwards the first RRC reconfiguration message to the first IAB-node; and 1404: The first IAB-node performs random access to the second parent node.

[0110] Among them, the implementation method of 1400-1404 is the same as the implementation method of 1300-1304, and detailed explanation is omitted here.

[0111] In some embodiments, the method may further include the following steps:

[0112] 1405: When the random access of the first IAB-node fails, the first IAB-node triggers an RRC re-establishment procedure; 1406: The first IAB-node sends a path transition failure indication to the second IAB-node; 1407: The first IAB-node forwards the second RRC reconfiguration message to the second IAB-node or clears the second RRC reconfiguration message; and 1408: The second IAB-node triggers an RRC re-establishment procedure when it receives the path change failure indication information.

[0113] Optionally, the method may further comprise the steps of:

[0114] 1409: The second IAB-node forwards the path transition failure indication information to the third IAB-node; 1410: triggering an RRC re-establishment procedure when the third IAB-node receives the path transition failure indication information; and 1411: The second IAB-node forwards the third RRC reconfiguration message to the third IAB-node, or clears the third RRC reconfiguration message.

[0115] In some embodiments, when T304 expires, it means that random access has failed, is not completed, or is not successful in 1405 and 1408. The RRC re-establishment process can refer to the prior art, and the implementation manner of 1406 can refer to 1002 in the second aspect embodiment, and detailed description thereof will be omitted here.

[0116] In some embodiments, at 1406, when the first RRC reconfiguration message includes first parameters and / or first path transition indication information configured for a change of the transmission path of the first IAB-node, the first IAB-node transmits the path transition failure indication information to the second IAB-node.

[0117] In some embodiments, the first RRC reconfiguration message further includes configuration information for path transition failure indication, which is used to instruct the first IAB-node to transmit path transition failure indication to the second IAB-node upon a random access failure. For example, upon a random access failure of the first IAB-node, if the first RRC reconfiguration message includes configuration information for path transition failure indication, the first IAB-node transmits the path transition failure indication to the second IAB-node; or, if the first RRC reconfiguration message includes configuration information for the first parameter and / or the first path transition indication and the path transition failure indication, the first IAB-node transmits the path transition failure indication to the second IAB-node.

[0118] In some embodiments, in 1407, the first IAB-node forwards the second RRC reconfiguration message to the second IAB-node or clears the second RRC reconfiguration message. This step is optional, and embodiments of the present invention are not limited thereto. In addition, the implementation manners of 1409-1411 are the same as those of 1406-1408, and detailed descriptions thereof are omitted here.

[0119] FIG. 15 is a diagram showing the message sending method, and as shown in FIG. 15, the method includes the following steps:

[0120] 1500: The Donor-CU sends a third RRC reconfiguration message to the second IAB-node for route transition of the third IAB-node; 1501: The Donor-CU sends a second RRC reconfiguration message to the first IAB-node for route transition of the second IAB-node; 1502: The Donor-CU sends a first RRC reconfiguration message for a path transition of the first IAB-node to the first parent node; 1503: The first parent node forwards the first RRC reconfiguration message to the first IAB-node; 1504: The first IAB-node performs random access to the second parent node; 1505: When the random access of the first IAB-node fails, the first IAB-node triggers an RRC re-establishment procedure; 1506: The first IAB-node sends a path change failure indication to the second IAB-node.

[0121] Among them, the implementation method of 1500-1506 is the same as the implementation method of 1400-1406, so detailed explanation is omitted here.

[0122] 1507: The first IAB-node forwards the second RRC reconfiguration message to the second IAB-node; 1508: When the second IAB-node receives the path transition failure indication information and the second RRC reconfiguration message, it does not perform an RRC re-establishment procedure and falls back to the original path configuration; 1509: The second IAB-node forwards the path transition failure indication information to the third IAB-node; 1510: The second IAB-node forwards the third RRC reconfiguration message to the third IAB-node; and 1511: When the third IAB-node receives the path change failure indication information and the third RRC reconfiguration message, it does not perform an RRC re-establishment procedure and falls back to the original path configuration.

[0123] 14 , in some embodiments, the first IAB-node forwarding the second RRC reconfiguration message to the second IAB-node is not optional but mandatory, i.e., 1507 is a mandatory step, otherwise the Packet Data Convergence Protocol (PDCP) of the second IAB-node may malfunction. Regarding how the first IAB-node forwards the second RRC reconfiguration message, please refer to 1305 above, and the detailed description thereof will be omitted here.

[0124] The implementation of 1508 can be referred to as 1104 in the second embodiment, and the implementation of 1509-1511 is the same as 1506-1508, so detailed description thereof will be omitted here.

[0125] Implementation Scenario 2: The difference from Implementation Scenario 1 is that each of the above-mentioned RRC reconfiguration messages is carried by one downlink message, which not only reduces the service interruption time but also saves signaling overhead.

[0126] 16 is a diagram showing the message sending method. As shown in FIG. 16, the method includes the following steps:

[0127] 1601: The Donor-CU sends a first RRC reconfiguration message for a path transition of the first IAB-node and a second RRC reconfiguration message for a path transition of the second IAB-node to the first parent node; 1602: The first parent node forwards the first RRC reconfiguration message and the second RRC reconfiguration message to the first IAB-node; 1603: The first IAB-node performs random access to the second parent node; and 1604: Upon successful random access, the first IAB-node forwards the second RRC reconfiguration message to the second IAB-node.

[0128] Optionally, when the second IAB-node has a further child node, ie, a third IAB-node, the method may further include the following steps:

[0129] In 1601, the Donor-CU sends a third RRC reconfiguration message to the first parent node for path transition of the third IAB-node, in 1602, the first parent node further forwards the third RRC reconfiguration message to the first IAB-node, in 1604, the first IAB-node further forwards the third RRC reconfiguration message to the second IAB-node, and in 1605, when the second IAB-node receives the second RRC reconfiguration message and the third RRC reconfiguration message, it forwards the third RRC reconfiguration message to the third IAB-node.

[0130] In some embodiments, the second RRC reconfiguration message is carried by the first RRC reconfiguration message, and the third RRC reconfiguration message is included in the second RRC reconfiguration message. The contents of the information elements included in each RRC reconfiguration message have been described above, and detailed descriptions thereof will be omitted here.

[0131] In 1601, the Donor-CU carries the above-mentioned first RRC reconfiguration message, second RRC reconfiguration message, and third RRC reconfiguration message in one downlink F1AP message. For example, the downlink F1AP message may be a UE context change request message (UE CONTEXT SETUP REQUEST). The above-mentioned UE CONTEXT SETUP REQUEST may further include the above-mentioned first context indicator of the UE, etc. For specific details, please refer to the prior art, and detailed description thereof will be omitted here.

[0132] 19A is a diagram showing the structure of the downlink F1AP message. As shown in FIG. 19A, the first RRC reconfiguration message is sent by the Donor-CU to the first parent node in the downlink F1AP message for carrying, the second RRC reconfiguration message is included in the first RRC reconfiguration message, and the third RRC reconfiguration message is included in the second RRC reconfiguration message.

[0133] In addition, to allow the first IAB-node to identify the second RRC reconfiguration message sent to the second IAB-node, the first RRC reconfiguration message further includes indicator information of the second IAB-node, which is a parent node cell indicator of the second IAB-node (e.g., a DU cell indicator of the first IAB-node) and a Cell Radio Network Temporary Indicator C-RNTI in the parent node cell of the second IAB-node (e.g., a CNTI in the DU cell of the first IAB-node of the MT of the second IAB-node), or the indicator information is a UE F1AP indicator of the second IAB-node in its parent node (e.g., a DU UE F1AP ID in the DU of the first IAB-node of the MT of the second IAB-node). Similarly, the second RRC reconfiguration message further includes indicator information of the third IAB-node, where the indicator information is a parent node cell indicator of the third IAB-node (e.g., a DU cell indicator of the second IAB-node) and a cell radio network temporary indicator C-RNTI in the parent node cell of the third IAB-node (e.g., a CNTI in the DU cell of the second IAB-node of the MT of the third IAB-node), or the indicator information is a UE F1AP indicator in its parent node of the third IAB-node (e.g., a DU UE F1AP ID in the DU of the second IAB-node of the MT of the third IAB-node).

[0134] In some embodiments, after receiving the F1AP message, the first parent node sends a first RRC Reconfiguration message therefrom to the first IAB-node. In 1604 and 1605, the first IAB-node extracts a second RRC Reconfiguration message from the first RRC Reconfiguration message and forwards it to the second IAB-node. After receiving the second RRC Reconfiguration message, the second IAB-node extracts a third RRC Reconfiguration message therefrom and forwards it to the third IAB-node. Specifically, upon successful random access, the mobile terminal (MT) of the first IAB-node sends the second RRC Reconfiguration message to the DU of the first IAB-node, which then forwards it to the second IAB-node. When the first RRC Reconfiguration message includes first parameters configured for a change in the transmission path of the first IAB-node and / or includes first path transition indication information, this indicates that the first RRC Reconfiguration message is for a path transition of the first IAB-node, and the MT of the first IAB-node sends a second RRC Reconfiguration message to the DU of the first IAB-node. For the meaning of the first parameter and / or the first path transition instruction information, please refer to the embodiments of the first aspect, and detailed description thereof will be omitted here. When the mobile terminal (MT) of the second IAB-node receives the second RRC reconfiguration message, it transmits a third RRC reconfiguration message to the DU of the second IAB-node, and then forwards it to the third IAB-node. When the second RRC reconfiguration message includes a second parameter set for changing the transmission path of the second IAB-node and / or includes second path transition instruction information, this indicates that the second RRC reconfiguration message is for path transition of the second IAB-node, and the MT of the second IAB-node transmits a third RRC reconfiguration message to the DU of the second IAB-node. For the meaning of the second parameter and / or the second path transition instruction information, please refer to the embodiments of the second aspect, and detailed description thereof will be omitted here.

[0135] Furthermore, since the third RRC reconfiguration message is for the path transition of the third IAB-node, the third RRC reconfiguration message includes a third parameter that is set for changing the transmission path of the third IAB-node, and the third IAB-node can perform path transition after receiving the third RRC reconfiguration message. For the operation of path transition, reference can be made to the prior art, and the meaning of the third parameter is the same as that of the first parameter, and detailed explanation thereof will be omitted here.

[0136] In some embodiments, when the third IAB-node has another child node, the third RRC reconfiguration message may further include a fourth RRC reconfiguration message for the path transition of the child node, and the third IAB-node may forward the fourth RRC reconfiguration message to the child node upon receiving the third RRC reconfiguration message, wherein the specific manner of forwarding is the same as that of the second IAB-node, and therefore a detailed description thereof is omitted here.

[0137] In this way, the Donor-CU does not need to send one downlink F1AP message to each of the first IAB-node, the second IAB-node, and the third IAB-node, thereby saving signaling overhead. Furthermore, layer-by-layer message transmission allows the first IAB-node, the second IAB-node, and the third IAB-node to receive their respective RRC reconfiguration messages almost simultaneously. Furthermore, the first IAB-node transmits a message when its random access to the second parent node is successful, allowing the first IAB-node, the second IAB-node, and the third IAB-node to simultaneously update the network topology, thereby reducing service interruption time.

[0138] In some embodiments, upon successful random access of the first IAB-node, the method may further include the following steps:

[0139] 1606: The first IAB-node sends a first RRC reconfiguration complete message to the Donor-CU; 1607: The first IAB-node receives a second RRC reconfiguration complete message sent by the second IAB-node; 1608: The first IAB-node forwards the second RRC reconfiguration complete message to the Donor-CU; 1609: The second IAB-node receives a third RRC reconfiguration complete message sent by the third IAB-node; and 1610: The second IAB-node forwards the third RRC reconfiguration complete message to the Donor-CU.

[0140] In some embodiments, the implementation methods of the above 1606-1610 can be referred to 1307-1311 in Implementation Scenario 1, and detailed descriptions thereof will be omitted here.

[0141] Figure 17 is another diagram showing a message transmission method, which differs from Figure 16 in that the RRC reconfiguration complete messages of each IAB-node are not transmitted by different uplink messages, but are carried by the second parent node using the same uplink F1AP message and transmitted to the Donor-CU, thereby further reducing signaling overhead. As shown in Figure 17, the method includes operations 1701-1705, which are the same as operations 1601-1605 in Figure 16, and may further include the following steps:

[0142] 1706: The second IAB-node receives a third RRC reconfiguration completion message sent by the third IAB-node; 1707: The first IAB-node receives a second RRC reconfiguration completion message sent by the second IAB-node; 1708: The first IAB-node sends a first RRC reconfiguration complete message to the second parent node; and 1709: The second parent node forwards the first RRC reconfiguration complete message to Donor-CU.

[0143] In some embodiments, in 1707-1709, the second IAB-node sends the third RRC reconfiguration complete message in the second RRC reconfiguration complete message to the first IAB-node, the first IAB-node sends the second RRC reconfiguration complete message in the first RRC reconfiguration complete message to the second parent node, and the second parent node sends an uplink F1AP message to the Donor-CU, carrying the first RRC reconfiguration complete message in the uplink F1AP message.

[0144] Figure 19B is a structure diagram of the uplink F1AP message. As shown in Figure 19B, the first RRC reconfiguration completion message is sent by the second parent node to the uplink F1AP message of Donor-CU and carried, the second RRC reconfiguration completion message is included in the first RRC reconfiguration completion message, and the third RRC reconfiguration completion message is included in the second RRC reconfiguration completion message.

[0145] In addition, the first RRC reconfiguration complete message further includes identification information of the second IAB-node, so that the Donor-CU can identify the second RRC reconfiguration complete message from the second IAB-node. Similarly, the second RRC reconfiguration complete message further includes identification information of the third IAB-node, which has been described above and will not be described in detail here.

[0146] In some embodiments, in 1706-1709, the third IAB-node completes the RRC reconfiguration and sends a third RRC reconfiguration complete message to the second IAB-node, and also performs an F1 transmission path transition; the second IAB-node receives the third RRC reconfiguration complete message, completes its own RRC reconfiguration, includes the third RRC reconfiguration complete message in a second RRC reconfiguration complete message and sends it to the first IAB-node, and also realizes an F1 transmission path transition; the first IAB-node receives the second RRC reconfiguration complete message, completes its own RRC reconfiguration, includes the second RRC reconfiguration complete message in a first RRC reconfiguration complete message and sends it to its second parent node, and also realizes an F1 transmission path transition; and the second parent node carries the first RRC reconfiguration complete message in an uplink F1AP message and sends it to Donor-CU.

[0147] Currently, the uplink RRC message of the child node of the IAB-node is carried by the F1AP and transmitted through the backhaul RLC channel (i.e., BAP layer transmission), so there is no need to send its own RRC reconfiguration complete message after receiving the RRC reconfiguration complete message of the child node. Therefore, to allow one uplink F1AP message to carry the RRC reconfiguration complete messages of each IAB node, the first RRC reconfiguration message may further include completion message transmission timing configuration information, which is used to instruct the first IAB-node to send its own RRC reconfiguration complete message after receiving the RRC reconfiguration complete message sent by the child node. In some embodiments, the first IAB-node transmits the first RRC reconfiguration complete message as the first uplink data using the new F1 transmission path. However, because the first IAB-node can transmit the first RRC reconfiguration complete message after receiving the second RRC reconfiguration complete message, the first IAB-node should not transmit other uplink data using the new F1 transmission path during the period from receiving the first RRC reconfiguration message to transmitting the first RRC reconfiguration complete message. In 1702, the first IAB-node suspends all uplink transmissions (including scheduling requests and buffer status reports) including transmissions of data radio bearers and BH RLC channels when it receives the first RRC reconfiguration message, and resumes transmissions of data radio bearers and BH RLC channels after it transmits the first RRC reconfiguration complete message, or resumes uplink transmissions after it receives the second RRC reconfiguration complete message. At this time, since the priority of the RRC signaling message is higher than the priority of the data, it can ensure that the first RRC reconfiguration complete message is sent preferentially after the uplink transmission is restored.

[0148] 16 and 17 show the information exchange between each IAB-node when the random access of the first IAB-node is successful. When the random access of the first IAB-node is unsuccessful, the method may further include steps 1405-1411 or 1505-1511 in the first implementation scenario, but detailed description thereof will be omitted here.

[0149] Implementation Scenario 3: Implementation Scenario 3 differs from Implementation Scenario 2 in that the message configuration of the downlink F1AP message sent by the Donor-CU to the first parent node is different.

[0150] The structure of the downlink message will be described below. Figure 20A is a diagram showing the structure of the downlink F1AP message. As shown in Figure 20A, the downlink F1AP message carries the first RRC reconfiguration message, which includes a third downlink F1AP message sent by the Donor-CU to the first IAB-node. The second RRC reconfiguration message is carried by the third downlink F1AP message, which includes a fourth downlink F1AP message sent by the Donor-CU to the second IAB-node. The third downlink F1AP message further includes identification information of the second IAB-node (e.g., the DU UE F1AP ID of the second IAB-node), and the fourth downlink F1AP message further includes identification information of the third IAB-node (e.g., the DU UE F1AP ID of the third IAB-node).

[0151] 18 is a diagram showing the message sending method. As shown in FIG. 18, the method includes the following steps:

[0152] 1801: The Donor-CU sends a downlink F1AP message having the configuration shown in FIG. 20A to the first parent node; 1802: The first parent node extracts and forwards the first RRC reconfiguration message to the MT of the first IAB-node; 1803: The first IAB-node performs random access to the second parent node; 1804: When the random access is successful, the MT of the first IAB-node extracts a third downlink F1AP message from the first RRC reconfiguration message, and sends the third downlink F1AP message to the DU of the first IAB-node; 1805: The DU of the first IAB-node forwards a second RRC reconfiguration message in a third downlink F1AP message to the MT of the second IAB-node; 1806: The MT of the second IAB-node extracts a fourth downlink F1AP message from the second RRC reconfiguration message and sends the fourth downlink F1AP message to the DU of the second IAB-node; and 1807: The DU of the second IAB-node forwards the third RRC reconfiguration message in the fourth downlink F1AP message to the MT of the third IAB-node.

[0153] In some embodiments, in 1804, when the first RRC reconfiguration message includes a first parameter configured for changing the transmission path of the first IAB-node and / or includes first path transition indication information, it indicates that the first RRC reconfiguration message is for path transition of the first IAB-node, and the MT of the first IAB-node extracts a third downlink F1AP message from the first RRC reconfiguration message and transmits the third downlink F1AP message to the DU of the first IAB-node. Note that the meaning of the first parameter and / or the first path transition indication information can be referred to in the embodiments of the first aspect, and detailed description thereof will be omitted here. In 1806, when the second RRC reconfiguration message includes a second parameter set to change the transmission path of the second IAB-node and / or includes second path transition indication information, it indicates that the second RRC reconfiguration message is for path transition of the second IAB-node, and the MT of the second IAB-node extracts a fourth downlink F1AP message from the second RRC reconfiguration message and transmits the fourth downlink F1AP message to the DU of the second IAB-node. Note that the meaning of the second parameter and / or the second path transition indication information can be referred to in the embodiments of the second aspect, and detailed description thereof will be omitted here.

[0154] Furthermore, since the third RRC reconfiguration message is for the path transition of the third IAB-node, the third RRC reconfiguration message includes a third parameter that is set for changing the transmission path of the third IAB-node, and the third IAB-node can perform path transition after receiving the third RRC reconfiguration message. For the operation of path transition, reference can be made to the prior art, and the meaning of the third parameter is the same as that of the first parameter, and detailed explanation thereof will be omitted here.

[0155] In some embodiments, when the third IAB-node has a child node, the third RRC Reconfiguration message may further include a fifth downlink F1AP message, which includes a fourth RRC Reconfiguration message for path transition of the child node. Upon receiving the third RRC Reconfiguration message, the third IAB-node forwards the fourth RRC Reconfiguration message to the child node. Note that the specific forwarding implementation manner is the same as that of the second IAB-node, and a detailed description thereof is omitted here. When the third IAB-node has no child node, the third IAB-node performs path transition after receiving the third RRC Reconfiguration message, and does not need to perform a forwarding operation. Note that the prior art can be referred to for specific details, and a detailed description thereof is omitted here.

[0156] In this way, the Donor-CU does not need to send one downlink F1AP message to each of the first IAB-node, the second IAB-node, and the third IAB-node, respectively, thereby saving signaling overhead, and the layer-by-layer message forwarding allows the first IAB-node, the second IAB-node, and the third IAB-node to receive their respective RRC reconfiguration messages almost simultaneously. Furthermore, the first IAB-node forwards the message when it successfully accesses the second parent node, allowing the first IAB-node, the second IAB-node, and the third IAB-node to simultaneously update the network topology, thereby reducing service interruption time.

[0157] In some embodiments, the downlink F1AP message in Figure 20A may be a UE context modification request message (UE CONTEXT SETUP REQUEST). The above-mentioned UE CONTEXT SETUP REQUEST may further include reconfiguration information regarding a topology to be reconfigured for a backhaul RLC channel of the first IAB-node, where the reconfiguration information includes backhaul RLC channel mapping relationship reconfiguration information and / or backhaul RLC channel modification information between the first IAB-node and its child nodes.

[0158] For example, the backhaul RLC channel mapping relationship reconfiguration information refers to the mapping relationship between the BH RLC channel between the first IAB-node and the second IAB-node and the BH RLC channel between the first IAB-node and the second parent node, and the backhaul RLC channel modification information refers to the addition, modification, and deletion of related information of the BH RLC channel between the first IAB-node and the second IAB-node, for example, the modification of the related information includes a modification of the quality of service (QoS) parameters of the BH RLC channel.

[0159] Another difference between this embodiment and the second implementation scenario is that the message configuration of the uplink F1AP message sent by the second parent node to Donor-CU is different.

[0160] The uplink message structure will be described below. The above-mentioned first RRC Reconfiguration Complete message, second RRC Reconfiguration Complete message, and third RRC Reconfiguration Complete message are all carried by one uplink F1AP message. Figure 20B is a structure diagram of the uplink F1AP message. As shown in Figure 20B, the third RRC Reconfiguration Complete message is carried by the fourth uplink F1AP message of the second IAB-node, the fourth uplink F1AP message is carried by the second RRC Reconfiguration Complete message, the second RRC Reconfiguration Complete message is carried by the third uplink F1AP message of the first IAB-node, the third uplink F1AP message is carried by the first RRC Reconfiguration Complete message, and the first RRC Reconfiguration Complete message is included in the uplink F1AP message (e.g., UL RRC MESSAGE TRNASFOR) sent by the second parent node to Donor-CU. The third uplink F1AP message includes the identification information of the second IAB-node, and the fourth uplink F1AP message includes the identification information of the third IAB-node. The implementation manner of the identification information is the same as the identification information in the downlink F1AP message, and detailed explanations thereof are omitted here.

[0161] In some embodiments, upon successful random access, the method may further include the following steps:

[0162] 1808: The DU of the second IAB-node receives the third RRC reconfiguration completion message transmitted by the MT of the third IAB-node; 1809: The DU of the second IAB-node sends the third RRC reconfiguration complete message in a fourth uplink F1AP message to the MT of the second IAB-node; 1810: The MT of the second IAB-node sends the fourth uplink F1AP message in the second RRC reconfiguration complete message to the DU of the first IAB-node; 1811: The DU of the first IAB-node sends the second RRC reconfiguration complete message in a third uplink F1AP message to the MT of the first IAB-node; 1812: The MT of the first IAB-node sends the third uplink F1AP message in the first RRC reconfiguration complete message to the second parent node; and 1813: The second parent node sends an uplink F1AP message (eg, UL RRC MESSAGE TRNASFOR) to the Donor-CU, where the uplink F1AP message includes a first RRC reconfiguration complete message.

[0163] In some embodiments, in 1808-1813, the third IAB-node completes the RRC reconfiguration and sends a third RRC reconfiguration complete message to the second IAB-node, and performs an F1 transmission path transition; the second IAB-node receives the third RRC reconfiguration complete message, completes its own RRC reconfiguration, includes the third RRC reconfiguration complete message in a fourth uplink F1AP message, and sends the fourth F1AP message in a second RRC reconfiguration complete message to the first IAB-node, and also achieves an F1 transmission path transition; the first IAB-node receives the second RRC reconfiguration complete message, completes its own RRC reconfiguration, includes the second RRC reconfiguration complete message in a third uplink F1AP message, and sends the third F1AP message in a first RRC reconfiguration complete message to its second parent node, and also achieves an F1 transmission path transition; and the second parent node carries the first RRC reconfiguration complete message in one uplink F1AP message and sends it to Donor-CU.

[0164] Currently, the uplink RRC messages of the child nodes of the IAB-node are carried by the F1AP and transmitted over the backhaul RLC channel (i.e., BAP layer transmission), so there is no need for the first IAB-node to transmit its own RRC reconfiguration complete message after receiving the child node's RRC reconfiguration complete message. Therefore, to allow one uplink F1AP message to carry the RRC reconfiguration complete messages of each IAB node, the first RRC reconfiguration message may further include a complete message transmission timing configuration message, which is used to instruct the first IAB-node to transmit its own RRC reconfiguration complete message after receiving the RRC reconfiguration complete message sent by the child node.

[0165] In some embodiments, the first IAB-node transmits the first RRC reconfiguration complete message as the first uplink data using the new F1 transmission path. However, since the first IAB-node can transmit the first RRC reconfiguration complete message after receiving the second RRC reconfiguration complete message, the first IAB-node should not transmit other uplink data using the new F1 transmission path during the period from receiving the first RRC reconfiguration message to transmitting the first RRC reconfiguration complete message. In 1802, when the first IAB-node receives the first RRC reconfiguration message, it suspends all uplink transmissions (including scheduling requests and buffer status reports) including transmissions of the data radio bearer and BH RLC channel, and resumes transmissions of the data radio bearer and BH RLC channel after sending a first RRC reconfiguration complete message, or resumes uplink transmissions after receiving a second RRC reconfiguration complete message, and at this time, since the priority of the RRC signaling message is higher than the data priority, it can ensure that the first RRC reconfiguration complete message is sent preferentially after resuming uplink transmission.

[0166] 18 shows the exchange of information between each IAB-node when the random access of the first IAB-node is successful. When the random access of the first IAB-node is unsuccessful, the method may further include steps 1405-1411 or 1505-1511 in the first implementation scenario, but detailed description thereof will be omitted here.

[0167] 8-18 are merely illustrative of embodiments of the present invention, and the present invention is not limited thereto. For example, the execution order of each operation may be appropriately adjusted, or some operations may be added or removed. Those skilled in the art are not limited to the descriptions of the above-described FIGS. 8-18, and may make appropriate modifications based on the above content.

[0168] Furthermore, although the above-described embodiments are provided to exemplify the present invention, the present invention is not limited to these, and appropriate modifications may be made based on the above-described embodiments. For example, each of the above-described embodiments may be used alone, or a plurality of the above-described embodiments may be combined.

[0169] <Example of the fourth aspect> An embodiment of the present invention provides a message sending device.

[0170] 21 is a diagram illustrating a message transmission device in an embodiment of the present invention. The device may be, for example, an IAB node in an IAB system, or one or more components or assemblies disposed in the IAB node. The IAB system includes a Donor device and an IAB node, and the embodiment of the present invention will be described from the perspective of the first IAB node. The implementation principle of the message transmission device in the embodiment of the present invention is the same as that of the embodiment of the first aspect, and repeated descriptions of the same content will be omitted.

[0171] As shown in FIG. 21, a message sending device 2100 in an embodiment of the present invention includes:

[0172] A first receiving unit 2101: receives a second radio resource control (RRC) reconfiguration message for a path transition of a second IAB-node from a donor aggregation unit (Donor-CU), where the second IAB-node is a downstream child node of the first IAB-node; A second receiving unit 2102: receives a first RRC reconfiguration message of a path transition for the first IAB-node from the Donor-CU; and A first sending unit 2103: forwards the second RRC reconfiguration message to the second IAB-node when the first IAB-node has successfully completed random access.

[0173] In some embodiments, the implementation manner of the first receiving unit 2101, the second receiving unit 2102 and the first transmitting unit 2103 can refer to 801-803 in the first aspect embodiment and the implementation manner of the first IAB-node in implementation scenarios 1 to 3, and detailed description thereof will be omitted here.

[0174] In some embodiments, the second RRC reconfiguration message is carried by the first downlink F1AP message transmitted by the Donor-CU.

[0175] In some embodiments, the first transmitting unit 2103 includes a first transmitting module and a second transmitting module (not shown), and when the random access of the mobile terminal (MT) of the first IAB-node is successful, the first transmitting module transmits first indication information to the distributed unit (DU) of the first IAB-node, and when the distributed unit (DU) of the first IAB-node receives the first indication information, the second transmitting module forwards the second RRC reconfiguration message to the second IAB-node.

[0176] In some embodiments, when the first RRC reconfiguration message includes a first parameter set for changing the transmission path of the first IAB-node, a first sending module in the MT of the first IAB-node sends first indication information to the DU of the first IAB-node.

[0177] In some embodiments, the first parameter set for changing the transmission path of the first IAB-node includes a default backhaul RLC channel, a default BAP routing (route), or an IP address set for the first IAB-node.

[0178] In some embodiments, when the first RRC reconfiguration message includes first path transition indication information, a first sending module in the MT of the first IAB-node sends first indication information to the DU of the first IAB-node, and the first path transition indication information is used to indicate that the first RRC reconfiguration message is a reconfiguration message for path transition of the first IAB-node.

[0179] In some embodiments, the first RRC reconfiguration message further includes configuration information of first indication information, which is used to instruct a first sending module to send first indication information to a distributed unit (DU) of the first IAB-node when the random access of the MT of the first IAB-node is successful.

[0180] In some embodiments, the first downlink F1AP message further indicates first cache indication information, which is used to instruct the first IAB-node to cache the second RRC reconfiguration message and release it after receiving the first indication information.

[0181] In some embodiments, the second RRC reconfiguration message is carried by the first RRC reconfiguration message.

[0182] In some embodiments, the first RRC reconfiguration message further includes identification information of the second IAB-node.

[0183] In some embodiments, the second RRC reconfiguration message is carried by a third downlink F1AP message from the Donor-CU, and the third downlink F1AP message is carried by the first RRC reconfiguration message.

[0184] In some embodiments, the third downlink F1AP message further includes identification information of the second IAB-node.

[0185] In some embodiments, the first transmitting unit 2103 includes a third transmitting module and a fourth transmitting module (not shown), and when the random access of the MT of the first IAB-node is successful, the third transmitting module transmits the third downlink F1AP message to the DU of the first IAB-node, and when the DU of the first IAB-node receives the third downlink F1AP message, the fourth transmitting module forwards the second RRC reconfiguration message in the third downlink F1AP message to the second IAB-node.

[0186] In some embodiments, when the random access of the first IAB-node fails, the first sending unit 2103 further sends a path transition failure indication to the second IAB-node.

[0187] In some embodiments, the device further includes a first processing unit (not shown), which is used to forward the second RRC reconfiguration message to the second IAB-node or clear the second RRC reconfiguration message.

[0188] In some embodiments, when the first RRC reconfiguration message includes first parameters and / or first path transition indication information set for changing the transmission path of the first IAB-node, the first transmitting unit 2103 transmits the path transition failure indication information to the second IAB-node.

[0189] In some embodiments, the first RRC reconfiguration message further includes configuration information for path transition failure indication information, which is used by the first IAB-node to instruct the second IAB-node to send path transition failure indication information when random access fails.

[0190] In some embodiments, when the random access of the first IAB-node is successful, the device further includes a second transmitting unit 2104 and a third receiving unit 2105 (optional), wherein the second transmitting unit 2104 transmits a first RRC reconfiguration complete message to the Donor-CU, and the third receiving unit 2105 receives a second RRC reconfiguration complete message transmitted by the second IAB-node.

[0191] In some embodiments, the second transmitting unit 2104 forwards the second RRC reconfiguration complete message to the Donor-CU, and the second RRC reconfiguration complete message is carried by a first uplink F1AP message.

[0192] In some embodiments, the second transmitting unit 2104 includes the second RRC reconfiguration complete message in the first RRC reconfiguration complete message and forwards it to the Donor-CU.

[0193] In some embodiments, the second transmitting unit 2104 includes a first receiving module, a fifth transmitting module, and a sixth transmitting module (not shown), wherein the first receiving module on the DU of the first IAB-node receives the second RRC reconfiguration complete message transmitted by the second IAB-node, the fifth transmitting module on the DU of the first IAB-node transmits a third uplink F1AP message including the second RRC reconfiguration complete message to the MT of the first IAB-node, and the sixth transmitting module in the MT of the first IAB-node includes the third uplink F1AP message in the first RRC reconfiguration complete message and forwards it to the Donor-CU.

[0194] Although the components or modules related to the present invention have been described above, the present invention is not limited to these. Furthermore, the message sending device 2100 in the embodiment of the present invention may further include other components or modules, and the specific contents of these components or modules can be found in the related art.

[0195] 21 shows only the connection relationships or signal directions between the components or modules for convenience, but as will be understood by those skilled in the art, various related technologies such as a bus connection may be employed. Furthermore, the above-described components or modules may be realized by hardware such as a processor, a memory, a transmitter, a receiver, etc., but the implementation of the present invention is not limited thereto.

[0196] As a result, before the IAB-node switches to a new parent node, information regarding the network topology update set for its child node is sent to the IAB-node by the Donor-CU and cached in the IAB-node, and when the random access for the IAB-node to switch to a new parent node is successful, the IAB-node transfers to its child node information regarding the network topology update set for its child node by the Donor-CU.In this way, the IAB-node and its child node can update the network topology almost simultaneously, thereby reducing the service interruption time due to node migration.

[0197] <Example of the fifth aspect> An embodiment of the present invention provides a message sending device.

[0198] 22 is a diagram illustrating a message transmission device in an embodiment of the present invention. The device may be, for example, an IAB node in an IAB system, or one or more components or assemblies disposed in the IAB node. The IAB system includes a Donor device and an IAB node, and the embodiment of the present invention will be described from the perspective of the second IAB node. The implementation principle of the message transmission device in the embodiment of the present invention is the same as that of the embodiment of the second aspect, and repeated descriptions of the same content will be omitted.

[0199] As shown in FIG. 22, a message sending device 2200 in an embodiment of the present invention includes:

[0200] A fourth receiving unit 2201: receives a third RRC reconfiguration message for a path transition of a third IAB node from a Donor-CU; and A third transmitting unit 2202: upon receiving a second RRC reconfiguration message sent by the Donor-CU and forwarded by the first IAB-node, forwards the third RRC reconfiguration message to the third IAB-node, and the second RRC reconfiguration message is used for path transition of the second IAB-node.

[0201] Among them, the third IAB-node is a downstream child node of the second IAB-node, and the second IAB-node is a downstream child node of the first IAB-node.

[0202] In some embodiments, the third RRC reconfiguration message is carried by the second downlink F1AP message sent by the Donor-CU.

[0203] In some embodiments, the third transmitting unit 2202 includes a seventh transmitting module and an eighth transmitting module (not shown), and when the MT of the second IAB-node receives the second RRC reconfiguration message, the seventh transmitting module transmits second indication information to the DU of the second IAB-node, and when the DU of the second IAB-node receives the second indication information, the eighth transmitting module forwards the third RRC reconfiguration message to the third IAB-node.

[0204] In some embodiments, when the second RRC reconfiguration message includes a second parameter set to change the transmission path of the second IAB-node, a seventh sending module in the MT of the second IAB-node sends second indication information to the DU of the second IAB-node.

[0205] In some embodiments, the second parameters configured for the second IAB-node to change the transmission path include a default backhaul RLC channel, a default BAP routing, or an IP address configured for the second IAB-node.

[0206] In some embodiments, when the second RRC reconfiguration message includes second path transition indication information, a seventh sending module in the MT of the second IAB-node sends second indication information to the DU of the first IAB-node, and the second path transition indication information is used to indicate that the second RRC reconfiguration message is a reconfiguration message for path transition of the second IAB-node.

[0207] In some embodiments, the apparatus is applied when the Donor-DU changes after the first IAB-node switches to a new parent node, and at this time, the second RRC reconfiguration message is used for the second IAB-node to perform path transition between Donor-DUs. The second path transition indication information is used to instruct the second IAB-node to perform path transition between Donor-DUs, that is, when the second RRC message includes the second path transition indication information, it means that the second RRC reconfiguration message is a reconfiguration message for the second IAB-node to perform path transition between different Donor-DUs.

[0208] In some embodiments, the second RRC reconfiguration message further includes configuration information of second indication information, which is used to instruct the MT of the second IAB-node to send the second indication information to the distributed unit (DU) of the second IAB-node when the MT of the second IAB-node receives the second RRC reconfiguration message.

[0209] In some embodiments, the second downlink F1AP message further includes second cache indication information, which is used to instruct the second IAB-node to cache the third RRC reconfiguration message and release it after receiving the second indication information.

[0210] In some embodiments, the third RRC reconfiguration message is included in the second RRC reconfiguration message sent by the Donor-CU and forwarded by the first IAB-node.

[0211] In some embodiments, the second RRC reconfiguration message further includes identification information of the third IAB-node.

[0212] In some embodiments, the third RRC reconfiguration message is carried by a fourth downlink F1AP message transmitted by the Donor-CU, and the fourth downlink F1AP message is carried by the third RRC reconfiguration message.

[0213] In some embodiments, the fourth downlink F1AP message further includes identification information of the third IAB-node.

[0214] In some embodiments, the third transmitting unit 2202 includes a ninth transmitting module and a tenth transmitting module (not shown), where when the MT of the second IAB-node receives the second RRC Reconfiguration message sent by the Donor-CU and forwarded by the first IAB-node, the ninth transmitting module transmits the fourth downlink F1AP message to the DU of the second IAB-node. When the DU of the second IAB-node receives the fourth downlink F1AP message, the tenth transmitting module forwards the third RRC Reconfiguration message in the fourth downlink F1AP message to the third IAB-node.

[0215] In some embodiments, when the second IAB-node receives the second RRC reconfiguration message, the device further includes a fourth transmitting unit 2203 and a fifth receiving unit 2204 (optional), wherein the fourth transmitting unit 2203 transmits a second RRC reconfiguration complete message to the first IAB-node, and the fifth receiving unit 2204 receives a third RRC reconfiguration complete message transmitted by the third IAB-node.

[0216] In some embodiments, the fourth transmitting unit 2203 is further used to forward the third RRC reconfiguration complete message to the Donor-CU, and the third RRC reconfiguration complete message is carried by a second uplink F1AP message.

[0217] In some embodiments, the fourth sending unit 2203 is further used for including the third RRC reconfiguration complete message in the second RRC reconfiguration complete message and forwarding it to the Donor-CU.

[0218] In some embodiments, the fourth transmitting unit 2203 further includes a second receiving module, an eleventh transmitting module, and a twelfth transmitting module (not shown), wherein the second receiving module on the DU of the second IAB-node receives the third RRC reconfiguration complete message transmitted by the third IAB-node, the eleventh transmitting module on the DU of the second IAB-node transmits a fourth uplink F1AP message including the third RRC reconfiguration complete message to the MT of the second IAB-node, and the twelfth transmitting module in the MT of the second IAB-node includes the fourth uplink F1AP message in the second RRC reconfiguration complete message and forwards it to the Donor-CU.

[0219] As a result, before the IAB-node switches to a new parent node, information regarding the network topology update set for its child node is sent to the IAB-node by the Donor-CU and cached in the IAB-node; when the random access for the IAB-node to switch to a new parent node is successful, the IAB-node transfers to its child node the information regarding the network topology update set for its child node by the Donor-CU; and when the child node receives the relevant information, it transfers to its child node the information regarding the network topology update set for its child node by the Donor-CU; in this way, the IAB-node and its child node can perform network topology updates almost simultaneously, thereby reducing the service interruption time due to node migration.

[0220] 23 is a diagram illustrating a message transmission device in an embodiment of the present invention. The device may be, for example, an IAB node in an IAB system, or may be one or more components or assemblies disposed in the IAB node. The IAB system includes a Donor device and an IAB node, and the embodiment of the present invention will be described from the perspective of the second IAB node. The implementation principle of the message transmission device in the embodiment of the present invention is the same as that of the embodiment of the second aspect, and repeated descriptions of the same content will be omitted.

[0221] As shown in FIG. 23, a message sending device 2300 in an embodiment of the present invention includes:

[0222] A sixth receiving unit 2301: receives a third RRC reconfiguration message for a route transition of a third IAB-node from a Donor-CU; A seventh receiving unit 2302: receives route transition failure indication information sent by the first IAB-node when the random access fails; and Second processing unit 2303: Triggering the RRC re-establishment procedure or falling back to the original route configuration.

[0223] Among them, the third IAB-node is a downstream child node of the second IAB-node, and the second IAB-node is a downstream child node of the first IAB-node.

[0224] In some embodiments, the apparatus further includes a fifth sending unit 2304, which forwards the path transition failure indication information to the third IAB-node.

[0225] In some embodiments, the second processing unit 2303 is further used to forward the third RRC reconfiguration message to the third IAB-node or clear the third RRC reconfiguration message.

[0226] In some embodiments, the third RRC reconfiguration message is carried by a second downlink F1AP message sent by the Donor-CU, and the second processing unit 2303 further includes a thirteenth sending module and a fourteenth sending module, wherein the thirteenth sending module in the MT of the second IAB-node sends second indication information to the DU of the second IAB-node, and when the DU of the second IAB-node receives the second indication information, the fourteenth sending module forwards the third RRC reconfiguration message carried by the second downlink F1AP message to the third IAB-node.

[0227] In some embodiments, the sixth receiving unit 2301 is further used to receive a second RRC reconfiguration message for the path transition of the second IAB-node, which is sent by the Donor-CU to the first IAB-node and forwarded by the first IAB-node.

[0228] As a result, when the IAB-node fails in random access to switch to a new parent node, it triggers RRC re-establishment and instructs its child node of a path transition failure, and the child node also triggers RRC re-establishment.In this way, when the IAB-node transition fails, the IAB-node and its child node can perform RRC re-establishment almost simultaneously, thereby reducing the service interruption time due to a path transition failure.

[0229] Alternatively, when the IAB node fails in random access to switch to a new parent node, it triggers RRC reestablishment, forwards the RRC reconfiguration of its child node to the child node, and causes the child node to fail a route transition, causing the child node to fall back to the original route configuration. In this way, when the IAB node's transition fails, the IAB node and its child node can simultaneously fall back to the original route configuration. Otherwise, when the child node performs a route transition and generates uplink data according to the new route configuration, the uplink data may be subsequently dropped and retransmitted by the UE, increasing the delay of uplink data transmission. This method can avoid an increase in data transmission time due to a route transition failure.

[0230] Although the components and modules related to the present invention have been described above, the present invention is not limited thereto. The message transmission devices 2200-2300 in the embodiments of the present invention may further include other components or modules. For details of these components or modules, please refer to the related art.

[0231] 22 and 23 show the connection relationships or signal directions between the components or modules for convenience, but as will be understood by those skilled in the art, various related technologies such as bus connections may be employed. Furthermore, the above-described components or modules may be realized by hardware such as a processor, a memory, a transmitter, a receiver, etc., but the implementation of the present invention is not limited thereto.

[0232] <Example of the sixth aspect> An embodiment of the present invention provides a message sending device.

[0233] 24 is a diagram illustrating a message sending device in an embodiment of the present invention. The device may be, for example, a Donor device in an IAB system, or one or more components or assemblies installed in the Donor device. The IAB system includes a Donor device and an IAB node, and the embodiment of the present invention will be described from the Donor-CU side. The implementation principle of the message sending device in the embodiment of the present invention is the same as the embodiment of the third aspect, and repeated explanations of the same content will be omitted.

[0234] 24 is a diagram showing a message sending device in an embodiment of the present invention. As shown in FIG. 24, a message sending device 2400 in an embodiment of the present invention includes:

[0235] A sixth sending unit 2401: sending a second radio resource control (RRC) reconfiguration message for a route transition of a second IAB-node to a first IAB-node, so that the first IAB-node forwards the second RRC reconfiguration message to the second IAB-node upon successful random access; and A seventh sending unit 2402: sends a first Radio Resource Control (RRC) reconfiguration message for the path transition of the first IAB-node to the first IAB-node.

[0236] In some embodiments, the second RRC reconfiguration message is carried by the first downlink F1AP message sent by the Donor-CU.

[0237] In some embodiments, the first RRC reconfiguration message includes a first parameter configured for changing the transmission path of the first IAB-node.

[0238] In some embodiments, the first parameter includes a default backhaul RLC channel, a default BAP routing, or an IP address configured for the first IAB-node.

[0239] In some embodiments, the first RRC reconfiguration message further includes first path transition indication information, which is used to indicate that the first RRC reconfiguration message is a reconfiguration message for path transition of the first IAB-node.

[0240] In some embodiments, the first RRC reconfiguration message further includes configuration information of first indication information, which is used to instruct the MT of the first IAB-node to send the first indication information to the distributed unit (DU) of the first IAB-node upon successful random access.

[0241] In some embodiments, the first downlink F1AP message further includes first cache indication information, which is used to instruct the first IAB-node to cache the second RRC reconfiguration message and release it after receiving the first indication information.

[0242] In some embodiments, the second RRC reconfiguration message is carried by the first RRC reconfiguration message.

[0243] In some embodiments, the first RRC reconfiguration message further includes identification information of the second IAB-node.

[0244] In some embodiments, the second RRC reconfiguration message is carried by the third downlink F1AP message, and the third downlink F1AP message is carried by the first RRC reconfiguration message.

[0245] In some embodiments, the third downlink F1AP message further includes identification information of the second IAB-node.

[0246] In some embodiments, the first RRC reconfiguration message further includes configuration information for path transition failure indication information, which is used by the first IAB-node to instruct the second IAB-node to send path transition failure indication information when random access fails.

[0247] In some embodiments, the second RRC reconfiguration message includes a second parameter configured for the second IAB-node to change the transmission path.

[0248] In some embodiments, the second parameter includes a default backhaul RLC channel, a default BAP routing, or an IP address configured for the second IAB-node.

[0249] In some embodiments, the second RRC reconfiguration message further includes second path transition indication information, which is used to indicate that the second RRC reconfiguration message is a reconfiguration message for a path transition of the second IAB-node.

[0250] In some embodiments, the second RRC reconfiguration message further includes configuration information of second indication information, which is used to instruct the MT of the second IAB-node to send the second indication information to the DU of the second IAB-node when the MT of the second IAB-node receives the second RRC reconfiguration message.

[0251] In some embodiments, the device further includes an eighth transmitting unit 2403 (optional), which is used to transmit a third RRC reconfiguration message for a path transition of a third IAB-node to the second IAB-node.

[0252] In some embodiments, the third RRC reconfiguration message is carried by a second downlink F1AP message sent by the Donor-CU.

[0253] In some embodiments, the second downlink F1AP message further includes second cache indication information, which is used to instruct the second IAB-node to cache the third RRC reconfiguration message and release it after receiving the second indication information.

[0254] In some embodiments, the third RRC reconfiguration message is included in the second RRC reconfiguration message sent by the Donor-CU and forwarded by the first IAB-node.

[0255] In some embodiments, the second RRC reconfiguration message further includes identification information of the third IAB-node.

[0256] In some embodiments, the third RRC reconfiguration message is carried by a fourth downlink F1AP message, and the fourth downlink F1AP message is carried by the second RRC reconfiguration message.

[0257] In some embodiments, the fourth downlink F1AP message further includes identification information of the third IAB-node.

[0258] In some embodiments, the feature is as follows: the device further includes an eighth receiving unit (optional; not shown), which receives the first RRC reconfiguration complete message sent by the first IAB-node.

[0259] In some embodiments, the eighth receiving unit is further used to receive a second RRC reconfiguration complete message transmitted by the second IAB-node, and the second RRC reconfiguration complete message is carried by a first uplink F1AP message transmitted by the first IAB-node.

[0260] In some embodiments, the first RRC reconfiguration complete message further includes a third uplink F1AP message, and the third uplink F1AP message includes a second RRC reconfiguration complete message.

[0261] In some embodiments, the feature is as follows: the first RRC reconfiguration complete message further includes a second RRC reconfiguration message.

[0262] Although the components and modules related to the present invention have been described above, the present invention is not limited thereto. The message sending device 2400 according to the embodiment of the present invention may further include other components or modules. For details of these components or modules, please refer to the related art.

[0263] 24 shows only the connection relationships or signal directions between the components or modules for convenience, but various related technologies such as bus connections may be adopted, as will be understood by those skilled in the art. Each of the components or modules described above may be realized by hardware such as a processor, a memory, a transmitter, a receiver, etc., but the implementation of the present invention is not limited thereto.

[0264] <Example of the seventh aspect> In an embodiment of the present invention, a communication system is provided. Figure 25 is a diagram showing the communication system 2500. As shown in Figure 25, the communication system 2500 includes a Donor device 2500 and IAB nodes 2501, 2502, 2503, 2504, and 2505, of which the IAB node 2503 is a transition IAB node (first IAB-node), the IAB node 2501 is the source node (first parent node) of the IAB node 2503, the IAB node 2502 is the target node (second parent node) of the IAB node 2503, the Donor device 2500 is a Donor-CU, the IAB node 2504 is a downstream child node of the IAB node 2503, and the IAB node 2505 is a downstream child node of the IAB node 2504.

[0265] For convenience, the explanation in Fig. 25 is given using the above-mentioned Donor device and IAB node as an example, but the embodiment of the present invention is not limited thereto. For the network architecture of the Donor device and IAB node, reference can be made to the related art, and detailed explanations thereof will be omitted here.

[0266] In some embodiments, IAB node 2503 is configured to perform the method performed by the first IAB-node in the embodiments of the first aspect and may include the device of Fig. 21. In some embodiments, IAB node 2504 is configured to perform the method performed by the second IAB-node in the embodiments of the second aspect and may include the device of Fig. 22 or 23. In some embodiments, Donor device 2500 is configured to perform the method performed by the Donor-CU in the embodiments of the third aspect and may include the device of Fig. 24. Note that the relevant contents of Donor device 2500 and each IAB node can be referred to in the embodiments of the first to third aspects, and detailed description thereof will be omitted here.

[0267] In some embodiments, IAB node 2501 corresponds to a first parent node, which receives a downlink F1AP message including a first RRC reconfiguration message in a first aspect embodiment of a Donor-CU transmission, or is used to receive a downlink F1AP message, the configuration of which is as shown in FIG. 19A or FIG. 20A, which is further used to forward the first RRC reconfiguration message in the F1AP message to IAB node 2503.

[0268] In some embodiments, IAB node 2502 corresponds to a second parent node, which is used to receive the first RRC reconfiguration complete message sent by IAB node 2503 and include the first RRC reconfiguration complete message in an uplink F1AP message and send it to Donor-CU, and the structure of the uplink F1AP message is as shown in Figure 19B or Figure 20B.

[0269] An embodiment of the present invention further provides an IAB node.

[0270] 26 is a diagram illustrating an IAB node according to an embodiment of the present invention. As shown in FIG. 26, the IAB node 2600 may include a processor 2601 and a memory 2602, where the memory 2602 stores data and programs and is connected to the processor 2601. Note that this diagram is merely an example, and other types of components may be used to supplement or replace the components to achieve telecommunications or other functions.

[0271] For example, the processor 2601 may be configured to execute a program to implement the method performed by the IAB-node, the first parent node, or the second parent node in the first or second aspect of the embodiment.

[0272] As shown in Fig. 26, the IAB node 2600 may further include a communication module 2603, an input unit 2604, a display 2605, a power supply 2606, etc. The functions of these components are the same as those of the prior art, and detailed descriptions thereof will be omitted here. Note that the IAB node 2600 does not need to include all the components shown in Fig. 26, and these components are not essential. In addition, the IAB node 2600 may further include components not shown in Fig. 26, and reference can be made to the prior art for such components.

[0273] In a further embodiment of the present invention, a Donor device is provided.

[0274] 27 is a diagram illustrating a Donor device according to an embodiment of the present invention. As shown in FIG. 27, the Donor device 2700 may include a processor (e.g., a central processing unit (CPU)) 2701 and a memory 2702, and the memory 2702 is connected to the processor 2701. The memory 2702 can store various data and can also store programs for information processing and execute the programs under the control of the central processing unit 2701.

[0275] For example, the processor 2701 may be configured to execute a program to implement the method in the embodiment of the third aspect.

[0276] 27, the Donor device 2700 may further include a transceiver 2703, an antenna 2704, etc., the functions of which are the same as those of the prior art, and detailed descriptions thereof will be omitted here. The Donor device 2700 does not need to include all the components shown in FIG. 27. The Donor device 2700 may further include components not shown in FIG. 27, and reference can be made to the prior art for such components.

[0277] An embodiment of the present invention further provides a computer-readable program, which, when executed by an IAB node, causes a computer to perform a method in an embodiment of the first or second aspect at the IAB node.

[0278] An embodiment of the present invention further provides a storage medium storing a computer-readable program, wherein the computer-readable program causes a computer to perform the method in the embodiment of the first or second aspect at an IAB node.

[0279] An embodiment of the present invention further provides a computer-readable program, which, when executed on a Donor device, causes a computer to perform the method in the embodiment of the third aspect on the Donor device.

[0280] An embodiment of the present invention further provides a storage medium storing a computer-readable program, wherein the computer-readable program causes a computer to perform the method in the embodiment of the third aspect on a Donor device.

[0281] The above-described apparatus and methods may be realized by software or hardware, or by a combination of hardware and software. The present invention also relates to a computer-readable program as described below, which, when executed by a logic component, causes the logic component to realize the above-described apparatus or component, or to perform the various methods or steps described above. The logic component may be, for example, an FPGA (Field Programmable Gate Array), a microprocessor, or a processing unit used in a computer. The present invention also relates to a storage medium, such as a hard disk, magnetic disk, optical hard disk, DVD, or flash memory, that stores the above-described program.

[0282] Furthermore, one or more combinations of the functional blocks illustrated in the figures and / or one or more combinations of the functional blocks may be implemented as a general purpose processor, a digital signal processor (DSP), an application specific integrated circuit (ASIC), a field programmable gate array (FPGA) or other programmable logic component, a discrete gate or transistor logic component, a discrete hardware assembly, or any other suitable combination for performing the functions described herein. Also, one or more combinations of the functional blocks illustrated in the figures and / or one or more combinations of the functional blocks may be further implemented as a combination of computing devices, such as a combination of a DSP and a microprocessor, multiple microprocessors, one or more microprocessors communicatively coupled with a DSP, or any other configuration.

[0283] Although the preferred embodiments of the present invention have been described above, the present invention is not limited to these embodiments, and any modifications to the present invention that do not depart from the spirit of the present invention fall within the technical scope of the present invention.

[0284] Furthermore, the following additional notes are disclosed regarding the above-described embodiments.

[0285] (Addendum) 1. A method for sending a message, comprising: A first IAB node (IAB-node) receives a second radio resource control (RRC) reconfiguration message for a path transition of a second IAB-node from a donor aggregation unit (Donor-CU), where the second IAB-node is a downstream child node of the first IAB-node; The first IAB-node receives a first RRC reconfiguration message for a path transition of the first IAB-node from the Donor-CU; and The method includes the first IAB-node forwarding the second RRC reconfiguration message to the second IAB-node upon successful random access.

[0286] (Appendix 2) 2. The method of claim 1, comprising: A method in which the second RRC reconfiguration message is carried by a first downlink F1AP message transmitted by the Donor-CU.

[0287] (Appendix 3) 10. The method of claim 2, The step of the first IAB-node transmitting the second RRC reconfiguration message to the second IAB-node when the random access is successful, When the random access of the mobile terminal (MT) of the first IAB-node is successful, sending first indication information to the distributed unit (DU) of the first IAB-node; and a distributed unit (DU) of the first IAB-node forwarding the second RRC reconfiguration message to the second IAB-node when the distributed unit (DU) of the first IAB-node receives the first indication information.

[0288] (Appendix 4) 4. The method of claim 3, A method in which, when the first RRC reconfiguration message includes a first parameter set for changing the transmission path of the first IAB-node, an MT of the first IAB-node sends first indication information to a DU of the first IAB-node.

[0289] (Appendix 5) 5. The method of claim 4, The method, wherein the first parameters set for changing the transmission path of the first IAB-node include a default backhaul RLC channel, a default BAP routing, or an IP address set for the first IAB-node.

[0290] (Appendix 6) 4. The method of claim 3, When the first RRC reconfiguration message includes first path transition indication information, an MT of the first IAB-node transmits the first indication information to a DU of the second IAB-node, and the first path transition indication information is used to indicate that the first RRC reconfiguration message is a reconfiguration message for a path transition of the first IAB-node.

[0291] (Appendix 7) 4. The method of claim 3, The method, wherein the first RRC reconfiguration message further includes configuration information of first instruction information, and the configuration information of the first instruction information is used to instruct an MT of the first IAB-node to send first instruction information to a distributed unit (DU) of the first IAB-node when random access is successful.

[0292] (Appendix 8) 5. The method of claim 4, the first downlink F1AP message further includes first cache indication information; The method, wherein the first cache indication information is used to instruct the first IAB-node to cache the second RRC reconfiguration message and release it after receiving the first indication information.

[0293] (Appendix 9) 2. The method of claim 1, comprising: The second RRC reconfiguration message is carried by the first RRC reconfiguration message.

[0294] (Appendix 10) 10. The method of claim 9, The first RRC reconfiguration message further includes identification information of the second IAB-node.

[0295] (Appendix 11) 2. The method of claim 1, comprising: The method, wherein the second RRC reconfiguration message is carried by a third downlink F1AP message from the Donor-CU, and the third downlink F1AP message is carried by the first RRC reconfiguration message.

[0296] (Appendix 12) 12. The method of claim 11, The third downlink F1AP message further includes identification information of the second IAB-node.

[0297] (Appendix 13) 12. The method of claim 11, The step of the first IAB-node transmitting the second RRC reconfiguration message to the second IAB-node when the random access is successful, When the MT of the first IAB-node succeeds in random access, the MT sends the third downlink F1AP message to the DU of the first IAB-node; and The method includes, when a DU of the first IAB-node receives the third downlink F1AP message, forwarding the second RRC reconfiguration message in the third downlink F1AP message to the second IAB-node.

[0298] (Appendix 14) The method of claim 1, further comprising: The method includes, upon a random access failure of the first IAB-node, sending a route transition failure indication information to the second IAB-node.

[0299] (Appendix 15) 15. The method of claim 14, further comprising: The method includes the first IAB-node forwarding the second RRC reconfiguration message to the second IAB-node or clearing the second RRC reconfiguration message.

[0300] (Appendix 16) 15. The method of claim 14, A method for transmitting the path transition failure indication information to the second IAB-node when the first RRC reconfiguration message includes first parameters and / or first path transition indication information that are set for changing the transmission path of the first IAB-node.

[0301] (Appendix 17) 15. The method of claim 14, The method, wherein the first RRC reconfiguration message further includes configuration information for path transition failure indication information, and the configuration information for path transition failure indication information is used by the first IAB-node to instruct the second IAB-node to send path transition failure indication information when random access fails.

[0302] (Appendix 18) 2. The method of claim 1, comprising: When the random access of the first IAB-node is successful, the method further comprises: The first IAB-node sends a first RRC reconfiguration complete message to the Donor-CU; and The method includes receiving, by the first IAB-node, a second RRC reconfiguration complete message transmitted by the second IAB-node.

[0303] (Appendix 19) 19. The method of claim 18, further comprising: The method includes the first IAB-node forwarding the second RRC reconfiguration complete message to the Donor-CU, and the second RRC reconfiguration complete message is carried by a first uplink F1AP message.

[0304] (Appendix 20) 19. The method of claim 18, further comprising: The method includes the first IAB-node including the second RRC reconfiguration complete message in the first RRC reconfiguration complete message and forwarding it to the Donor-CU.

[0305] (Appendix 21) 19. The method of claim 18, further comprising: a DU of the first IAB-node receiving the second RRC reconfiguration complete message sent by the second IAB-node; The DU of the first IAB-node sends a third uplink F1AP message including the second RRC reconfiguration complete message to the MT of the first IAB-node; and The method includes an MT of the first IAB-node including the third uplink F1AP message in the first RRC reconfiguration complete message and forwarding the message to the Donor-CU.

[0306] (Appendix 22) 1. A method for sending a message, comprising: receiving a third RRC reconfiguration message for a route transition of a third IAB-node from a second IAB-nodeDonor-CU; and When the second IAB-node receives a second RRC Reconfiguration message sent by the Donor-CU and forwarded by the first IAB-node, the second IAB-node forwards the third RRC Reconfiguration message to the third IAB-node, and the second RRC Reconfiguration message is used for path transition of the second IAB-node; wherein the third IAB-node is a downstream child node of the second IAB-node, and the second IAB-node is a downstream child node of the first IAB-node.

[0307] (Appendix 23) 23. The method of claim 22, A method in which the third RRC reconfiguration message is carried by a second downlink F1AP message transmitted by the Donor-CU.

[0308] (Appendix 24) 23. The method of claim 22, and forwarding the third RRC Reconfiguration message to the third IAB-node when the second IAB-node receives the second RRC Reconfiguration message sent by the Donor-CU and forwarded by the first IAB-node, the step of: When the MT of the second IAB-node receives the second RRC reconfiguration message, sending second indication information to the DU of the second IAB-node; and a DU of the second IAB-node forwarding the third RRC reconfiguration message to the third IAB-node when the DU of the second IAB-node receives the second indication information.

[0309] (Appendix 25) 25. The method of claim 24, When the second RRC reconfiguration message includes a second parameter set for changing the transmission path of the second IAB-node, the MT of the second IAB-node sends second indication information to the DU of the second IAB-node.

[0310] (Appendix 26) 26. The method of claim 25, The second parameter set for changing the transmission path of the second IAB-node includes a default backhaul RLC channel, a default BAP routing, or an IP address set for the second IAB-node.

[0311] (Appendix 27) 25. The method of claim 24, When the second RRC reconfiguration message includes second path transition indication information, an MT of the second IAB-node transmits the second indication information to a DU of the second IAB-node, and the second path transition indication information is used to indicate that the second RRC reconfiguration message is a reconfiguration message for a path transition of the second IAB-node.

[0312] (Appendix 28) 25. The method of claim 24, The second RRC reconfiguration message further includes configuration information of second indication information, and the configuration information of the second indication information is used to instruct a distributed unit (DU) of the second IAB-node to send second indication information when an MT of the second IAB-node receives the second RRC reconfiguration message.

[0313] (Appendix 29) 24. The method of claim 23, The second downlink F1AP message further includes second cache indication information, and the second cache indication information is used to instruct the second IAB-node to cache the third RRC reconfiguration message and release it after receiving the second indication information.

[0314] (Appendix 30) 23. The method of claim 22, The third RRC reconfiguration message is included in the second RRC reconfiguration message sent by the Donor-CU and forwarded by the first IAB-node.

[0315] (Appendix 31) 31. The method of claim 30, The second RRC reconfiguration message further includes indicator information of the third IAB-node.

[0316] (Appendix 32) 23. The method of claim 22, A method in which the third RRC reconfiguration message is carried by a fourth downlink F1AP message transmitted by the Donor-CU, and the fourth downlink F1AP message is carried by the third RRC reconfiguration message.

[0317] (Appendix 33) 33. The method of claim 32, The fourth downlink F1AP message further includes indicator information of the third IAB-node.

[0318] (Appendix 34) 33. The method of claim 32, and forwarding the third RRC Reconfiguration message to the third IAB-node when the second IAB-node receives the second RRC Reconfiguration message sent by the Donor-CU and forwarded by the first IAB-node, the step of: When the MT of the second IAB-node receives the second RRC reconfiguration message sent by the Donor-CU and forwarded by the first IAB-node, sending the fourth downlink F1AP message to the DU of the second IAB-node; and A method comprising, when a DU of the second IAB-node receives the fourth downlink F1AP message, forwarding the third RRC reconfiguration message in the fourth downlink F1AP message to the third IAB-node.

[0319] (Appendix 35) 23. The method of claim 22, When the second IAB-node receives the second RRC reconfiguration message, the method further comprises: the second IAB-node sending a second RRC reconfiguration complete message to the first IAB-node; and The method includes receiving, by the second IAB-node, a third RRC reconfiguration complete message transmitted by the third IAB-node.

[0320] (Appendix 36) 36. The method of claim 35, further comprising: The method includes the second IAB-node forwarding the third RRC reconfiguration complete message to the Donor-CU, and the third RRC reconfiguration complete message being carried by a second uplink F1AP message.

[0321] (Appendix 37) 37. The method of claim 36, further comprising: The method includes the second IAB-node including the third RRC reconfiguration complete message in the second RRC reconfiguration complete message and forwarding it to the Donor-CU.

[0322] (Appendix 38) 36. The method of claim 35, further comprising: a DU of the second IAB-node receiving the third RRC reconfiguration complete message sent by the third IAB-node; The DU of the second IAB-node sends a fourth uplink F1AP message including the third RRC reconfiguration complete message to the MT of the second IAB-node; and The method includes an MT of the second IAB-node including the fourth uplink F1AP message in the second RRC reconfiguration complete message and forwarding the message to the Donor-CU.

[0323] (Appendix 39) 1. A method for sending a message, comprising: The second IAB-node receives a third RRC reconfiguration message from the Donor-CU for route transition of the third IAB-node; The second IAB-node receives the route transition failure indication information sent by the first IAB-node when the random access fails; and The second IAB-node triggers an RRC re-establishment procedure or falls back to the original route setup; wherein the third IAB-node is a downstream child node of the second IAB-node, and the second IAB-node is a downstream child node of the first IAB-node.

[0324] (Appendix 40) 39. The method of claim 39, further comprising: The second IAB-node forwards the path transition failure indication information to the third IAB-node.

[0325] (Appendix 41) 39. The method of claim 39, further comprising: The method includes the second IAB-node forwarding the third RRC reconfiguration message to the third IAB-node or clearing the third RRC reconfiguration message.

[0326] (Appendix 42) 42. The method of claim 41, The third RRC reconfiguration message is carried by a second downlink F1AP message transmitted by the Donor-CU, and the step of forwarding the third RRC reconfiguration message includes: The MT of the second IAB-node sends second indication information to the DU of the second IAB-node; and The method includes, when a DU of the second IAB-node receives the second indication information, forwarding a third RRC reconfiguration message carried by the second downlink F1AP message to the third IAB-node.

[0327] (Appendix 43) 39. The method of claim 39, further comprising: The method includes the second IAB-node receiving a second RRC reconfiguration message for a path transition of the second IAB-node, the second RRC reconfiguration message being sent by the Donor-CU to the first IAB-node and forwarded by the first IAB-node.

[0328] (Appendix 44) 1. A method for sending a message, comprising: The Donor-CU sends a second Radio Resource Control (RRC) reconfiguration message for the route transition of the second IAB-node to the first IAB-node, so that the first IAB-node forwards the second RRC reconfiguration message to the second IAB-node upon successful random access; and The method includes the Donor-CU sending a first radio resource control (RRC) reconfiguration message for a path transition of the first IAB-node to the first IAB-node.

[0329] (Appendix 45) 45. The method of claim 44, A method in which the second RRC reconfiguration message is carried by a first downlink F1AP message transmitted by the Donor-CU.

[0330] (Appendix 46) 46. ​​The method of claim 45, The method, wherein the first RRC reconfiguration message includes a first parameter that is set for changing a transmission path of the first IAB-node.

[0331] (Appendix 47) 47. The method of claim 46, The method, wherein the first parameter includes a default backhaul RLC channel, a default BAP routing, or an IP address configured for the first IAB-node.

[0332] (Appendix 48) 46. ​​The method of claim 45, A method in which the first RRC reconfiguration message includes first path transition indication information, and the first path transition indication information is used to indicate that the first RRC reconfiguration message is a reconfiguration message for path transition of a first IAB-node.

[0333] (Appendix 49) 46. ​​The method of claim 45, The first RRC reconfiguration message further includes configuration information of first indication information, and the configuration information of the first indication information is used to instruct an MT of the first IAB-node to send first indication information to a distributed unit (DU) of the first IAB-node when random access is successful.

[0334] (Appendix 50) 46. ​​The method of claim 45, The first downlink F1AP message further includes first cache indication information, and the first cache indication information is used to instruct the first IAB-node to cache the second RRC reconfiguration message and release it after receiving the first indication information.

[0335] (Appendix 51) 45. The method of claim 44, The second RRC reconfiguration message is carried by the first RRC reconfiguration message.

[0336] (Appendix 52) 52. The method of claim 51, The first RRC reconfiguration message further includes identification information of the second IAB-node.

[0337] (Appendix 53) 45. The method of claim 44, The method, wherein the second RRC reconfiguration message is carried by the third downlink F1AP message, and the third downlink F1AP message is carried by the first RRC reconfiguration message.

[0338] (Appendix 54) 54. The method of claim 53, The third downlink F1AP message further includes identification information of the second IAB-node.

[0339] (Appendix 55) 45. The method of claim 44, The method, wherein the first RRC reconfiguration message further includes configuration information for path transition failure indication information, and the configuration information for path transition failure indication information is used by the first IAB-node to instruct the second IAB-node to send path transition failure indication information when random access fails.

[0340] (Appendix 56) 45. The method of claim 44, The second RRC reconfiguration message includes a second parameter that is set for changing the transmission path of the second IAB-node.

[0341] (Appendix 57) 57. The method of claim 56, The second parameter includes a default backhaul RLC channel, a default BAP routing, or an IP address configured for the second IAB-node.

[0342] (Appendix 58) 56. The method of claim 55, A method in which the second RRC reconfiguration message includes second path transition indication information, and the second path transition indication information is used to indicate that the second RRC reconfiguration message is a reconfiguration message for path transition of a second IAB-node.

[0343] (Appendix 59) 57. The method of claim 56, The second RRC reconfiguration message further includes configuration information of second indication information, and the configuration information of the second indication information is used by an MT of the second IAB-node to instruct a DU of the second IAB-node to send second indication information upon receiving the second RRC reconfiguration message.

[0344] (Appendix 60) 45. The method of claim 44, further comprising: The method includes the Donor-CU sending a third RRC reconfiguration message for a path transition of a third IAB-node to the second IAB-node.

[0345] (Appendix 61) 61. The method of claim 60, A method in which the third RRC reconfiguration message is carried by a second downlink F1AP message transmitted by the Donor-CU.

[0346] (Appendix 62) 62. The method of claim 61, The second downlink F1AP message further includes second cache indication information, and the second cache indication information is used to instruct the second IAB-node to cache the third RRC reconfiguration message and release it after receiving the second indication information.

[0347] (Appendix 63) 61. The method of claim 60, The third RRC reconfiguration message is included in the second RRC reconfiguration message sent by the Donor-CU and forwarded by the first IAB-node.

[0348] (Appendix 64) 64. The method of claim 63, The second RRC reconfiguration message further includes indication information of the third IAB-node.

[0349] (Appendix 65) 61. The method of claim 60, The third RRC reconfiguration message is carried by a fourth downlink F1AP message, and the fourth downlink F1AP message is carried by the second RRC reconfiguration message.

[0350] (Appendix 66) 66. The method of claim 65, The fourth downlink F1AP message further includes identification information of the third IAB-node.

[0351] (Appendix 67) 45. The method of claim 44, further comprising: The method includes the Donor-CU receiving a first RRC reconfiguration complete message transmitted by the first IAB-node.

[0352] (Appendix 68) 68. The method of claim 67, further comprising: The method includes the Donor-CU receiving a second RRC reconfiguration complete message transmitted by the second IAB-node, the second RRC reconfiguration complete message being carried by a first uplink F1AP message transmitted by the first IAB-node.

[0353] (Appendix 69) 68. The method of claim 67, The method, wherein the first RRC reconfiguration complete message further includes a third uplink F1AP message, and the third uplink F1AP message includes a second RRC reconfiguration complete message.

[0354] (Appendix 70) 68. The method of claim 67, The method, wherein the first RRC reconfiguration complete message further includes a second RRC reconfiguration message.

[0355] (Appendix 71) A Donor device, a memory and a processor; The storage device stores a computer program, wherein the processor is configured to execute the computer program to perform the method according to any one of claims 44 to 70.

[0356] (Appendix 72) An IAB-node, a memory and a processor; The storage device stores a computer program, The processor executes the computer program to perform the method of any one of claims 1 to 43.

[0357] (Appendix 73) 1. A communication system comprising: a donor device, including a first IAB-node and a second IAB-node; 10. A communication system, wherein the Donor device is configured to perform the method according to any one of Supplementary Notes 44 to 70, the first IAB-node is configured to perform the method according to any one of Supplementary Notes 1 to 21, and the second IAB-node is configured to perform the method according to any one of Supplementary Notes 22 to 43.

Claims

1. A message transmitting device, applied to a first IAB node (IAB-node), comprising: A receiver and a transmitter are included. The receiver includes: receiving a second radio resource control (RRC) reconfiguration message for a path transition of a second IAB-node when the first IAB-node is connected to a source parent node, the second RRC reconfiguration message being sent by a donor aggregation unit (Donor-CU), and the second IAB-node being a downstream child node of the first IAB-node; and receiving a first RRC reconfiguration message for a path transition of the first IAB-node, the first RRC reconfiguration message being sent by the Donor-CU; The transmitter forwards the cached second RRC reconfiguration message to the second IAB-node when the random access of the first IAB-node is successful; The second RRC reconfiguration message is carried by a first downlink F1AP message transmitted by the Donor-CU; The first RRC reconfiguration message includes a first parameter that is set to change a transmission path of the first IAB-node, The first parameter includes a default backhaul RLC channel, a default BAP routing, or an IP address configured for the first IAB-node.

2. 2. The apparatus of claim 1, The first downlink F1AP message further includes first cache indication information, the first cache indication information being used to instruct the first IAB-node to cache the second RRC reconfiguration message.

3. 2. The apparatus of claim 1, The transmitter is further used for transmitting route transition failure indication information to the second IAB-node when random access of the first IAB-node fails.

4. 2. The apparatus of claim 1, The first RRC reconfiguration message includes a first parameter or first path transition instruction information that is set for the first IAB-node to change a transmission path, The transmitter is further used for transmitting a route transition failure indication information to the second IAB-node.

5. 2. The apparatus of claim 1, The transmitter is further used for sending a first RRC reconfiguration completion message to the Donor-CU when the random access of the first IAB-node is successful; The receiver is further used for receiving a second RRC reconfiguration complete message transmitted by the second IAB-node.

6. 6. The apparatus of claim 5, The transmitter further transmits the first RRC reconfiguration complete message to the Donor-CU, wherein the first RRC reconfiguration complete message includes the second RRC reconfiguration complete message.

7. 7. The apparatus of claim 6, The receiver further receives the second RRC reconfiguration complete message transmitted by the second IAB-node; The transmitter further transmits a third uplink F1AP message including the second RRC reconfiguration complete message to a mobile terminal (MT) of the first IAB-node.

8. A message transmitting device, applied to a second IAB node (IAB-node), comprising: A receiver and a transmitter are included. The receiver receives a third RRC reconfiguration message for a path transition of a third IAB-node from a Donor-CU when the first IAB-node is connected to a source parent node; When the transmitter receives a second RRC reconfiguration message transmitted by the Donor-CU and forwarded by the first IAB-node, the transmitter caches the third RRC reconfiguration message until forwarding the third RRC reconfiguration message to the third IAB-node, and the second RRC reconfiguration message is used for a path transition of the second IAB-node; the third IAB-node is a downstream child node of the second IAB-node, the second IAB-node is a downstream child node of the first IAB-node, The third RRC reconfiguration message is carried by a second downlink F1AP message transmitted by the Donor-CU; The second RRC reconfiguration message includes a second parameter that is set so that the second IAB-node changes a transmission path, The second parameters include a default RLC channel, a default BAP routing, or an IP address configured for the second IAB-node.

9. 9. The apparatus of claim 8, When the second RRC reconfiguration message includes second path transition indication information, the transmitter transmits second indication information to the DU of the second IAB-node; The second path transition indication information is used to indicate that the second RRC reconfiguration message is a reconfiguration message for a path transition of the second IAB-node.

10. 9. The apparatus of claim 8, The second downlink F1AP message further includes second cache indication information, the second cache indication information being used to instruct the second IAB-node to cache the third RRC reconfiguration message.

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