Communication method and device

Abstract

The embodiments of the present application disclose a communication method and apparatus for improving stability and reliability of data transmission in an Integrated Access and Backhaul (IAB) network. A first node is served by a first Master Cell Group (MCG) and a first Secondary Cell Group (SCG), and a child node of the first node is a second node. The method is for the first SCG to transmit F1 interface user plane services, and includes the first node sending an RLF indication information to the second node when no Radio Link Failure (RLF) occurs in the first MCG and an RLF occurs in the first SCG.

Description

[Technical Field]

[0001]

[0001] This application claims priority to Chinese Patent Application No. 202210014284.4, entitled "Communication Method and Apparatus," filed with the State Intellectual Property Office of the People's Republic of China on January 6, 2022, the entire contents of which are incorporated herein by reference.

[0002]

[0002] This application relates to communications technology, and more particularly to communications methods and devices. [Background technology]

[0003] To support enhanced mobile broadband (eMBB) and ultra-reliable and low-latency communication (URLLC) service scenarios, the 5th generation (5G) New radio (NR) protocol standard utilizes higher frequency bands, including the sub-6 gigahertz (GHz) frequency band and millimeter-wave frequency band, to obtain more bandwidth resources. High-frequency signals have poor propagation characteristics, short wavelengths, limited signal coverage, and are severely attenuated by obstacles. This necessitates the dense deployment of a large number of small base stations. However, providing optical fiber backhaul to a large number of densely deployed small base stations is costly and difficult to implement. Therefore, a cost-effective and convenient backhaul solution is required. Furthermore, providing network coverage to some remote areas to meet wide-area coverage requirements requires the deployment of optical fiber, which is difficult and costly. Therefore, it is necessary to design flexible and convenient access and backhaul solutions. Wireless transmission solutions are used for the access link and backhaul link in the Integrated Access and Backhaul (IAB) technology. This reduces the amount of optical fiber that needs to be deployed. In this way, NR cells can be deployed flexibly and densely, and there is no need to deploy wired transmission networks at a proportionally high density. IAB technology can support various deployment scenarios, including outdoor small base station deployments, indoor small base station deployments, and even mobile relaying, for example, on buses and trains.

[0004]

[0004] The coverage of high-band signals is small. To ensure network coverage, IAB supports multi-hop networking and flexible scalability. Between a user equipment (UE) served by an IAB node and an IAB donor, there exists at least one transmission path formed by multiple links. Each transmission path may include a UE, one or more IAB nodes, an IAB donor distributed unit (IAB-donor-DU), and an IAB donor central unit (IAB-donor-CU). Each IAB node considers its neighboring nodes, which provide access and backhaul services to it, as parent nodes. Accordingly, each IAB node can be considered a child node of its parent node.

[0005]

[0005] To improve the reliability of service transmission, an IAB node may support dual connectivity (DC) to deal with possible exceptions of the backhaul link, such as link blockage and load fluctuation. Therefore, how to notify a radio link failure of an IAB node with dual connectivity, perform radio link recovery, and ensure stable data transmission between a UE and an IAB donor becomes an urgent technical problem to be solved. Summary of the Invention

[0006]

[0006] The present application provides a communication method and apparatus that improves the stability and reliability of data transmission in an IAB network and helps alleviate problems of data packet stacking, link congestion, and excessively long latency at IAB nodes.

[0007] According to a first aspect, a first node may send a first RLF indication to a second node, A Radio Link Failure (RLF) occurs in the backhaul link of one of the two cell groups that is intended to carry FI Interface User Plane (F1-U) services; or When RLF occurs in the backhaul link of one of the two cell groups that is intended to carry F1-U services and link recovery is performed, or If RLF occurs on the backhaul link of one of the two cell groups that is configured to carry F1 interface services based on a backhaul adaptation protocol (BAP) layer, or When an RLF occurs in a backhaul link of one of two cell groups, the cell group being configured to carry F1 interface services based on the BAP layer, and link recovery is performed, a first node is served by the two cell groups, and the child node of the first node is the second node.

[0008]

[0008] Transmitting F1 interface services based on the BAP layer includes transmitting F1-U services and / or F1 interface control plane (F1-C) services based on the BAP layer. In a control plane-user plane (CP-UP) separation scenario in a DC scenario, transmitting F1 interface services based on the BAP layer may include transmitting F1-U services based on the BAP layer. F1-C services may be transmitted based on the RRC layer (i.e., F1-C services via RRC). In a non-CP-UP separation scenario in a DC scenario, transmitting F1 interface services based on the BAP layer includes transmitting F1-U services and F1-C services based on the BAP layer.

[0009]

[0009] A first node with dual connectivity has two parent nodes, each of which provides a cell group to the first node. In this application, a backhaul link in a cell group is a connection channel established between a mobile terminal (MT) of the first node and a distributed unit (DU) of the parent node based on a cell group configured for some parent node of the first node, for backhaul transmission or forward transmission of data packets.

[0010]

[0010] Thus, the first node triggers the transmission of a first RLF indication by detecting an RLF occurrence in a backhaul link of a cell group for transmitting F1-U services or a backhaul link of a cell group configured to transmit F1-interface services based on a BAP, thereby improving the stability and reliability of data transmission in an IAB network. In some scenarios, problems such as data packet stacking, link congestion, and excessively long delays at the second node caused by unnecessary RLF indications can be alleviated. For example, in a CP-UP separation scenario in a DC scenario, if a cell group for transmitting F1-interface control plane (F1-C) services is an MCG and an RLF occurs, and a cell group for transmitting F1-U services is an SCG and an RLF does not occur, the first node does not promptly transmit the first RLF indication to the second node based on the triggering method of the first RLF indication. In this way, the impact on the normal operation of the SCG for transmitting F1-U services can be reduced. Furthermore, the second node can continue to route data to the first node. This helps to mitigate the problems of data packet stacking, link congestion, and excessively long latency on the second node.

[0011]

[0011] Furthermore, in some scenarios, the RLF indication can be sent in a timely manner, which can trigger the second node to stop sending data packets to the first node, or the second node to trigger a rerouting operation of data packets routed by the first node. This helps to alleviate problems of data packet stacking, link congestion, and excessively long latency of the first node. For example, if the cell group for transmitting the F1-U service is an SCG and RLF occurs only in the SCG, the first node can send the first RLF indication to the second node based on the triggering method of the first RLF indication, which can trigger the second node to stop sending data packets to the first node, or the second node can trigger a rerouting operation of data packets routed by the first node. In this way, the problems of data packet stacking, link congestion, and excessively long latency at the first node can be alleviated.

[0012]

[0012] When an RLF occurrence is detected in a backhaul link in a cell group configured to transmit an F1 interface service based on the BAP, transmission of a first RLF indication information is triggered. When an RLF occurrence is detected in the backhaul links in all cell groups configured to transmit an F1 interface service based on the BAP, the first RLF indication information indicates that an RLF occurrence has occurred in a node-granularity link between the first node and the second node, i.e., that an RLF has occurred across the entire backhaul link between the first node and the second node.

[0013]

[0013] According to a second aspect, an embodiment of the present application provides a communication method, wherein a first node is served by a first Master Cell Group (MCG) and a first Secondary Cell Group (SCG), and a child node of the first node is a second node, and the method may include: the first SCG is for transmitting F1 interface user plane services, and when RLF has not occurred in the first MCG and RLF has occurred in the first SCG, the first node sends first RLF indication information to the second node.

[0014]

[0014] In a possible design, when the first SCG is for carrying F1 interface user plane services, RLF does not occur in the first MCG, and RLF occurs in the first SCG, the first node sending first RLF indication information to the second node includes: The first SCG may be for carrying F1 interface user plane services, and may include the first node sending RLF indication information to the second node when an RLF has not occurred in the first MCG, an RLF has occurred in the first SCG, and link recovery is performed.

[0015]

[0015] In a possible design, the first SCG being for transmitting F1 interface user plane services may include: the first SCG being for transmitting F1 interface user plane services based on a backhaul adaptation protocol (BAP).

[0016] In a possible design, the first MCG is only for carrying F1 interface control plane services, and the RLF indication information indicates that an RLF has occurred on a node-granular link between the first node and the second node, which means that the entire BH link between the first node and the second node is unavailable.

[0017] In a possible design, the RLF indication information may indicate that RLF is occurring on a node granular link between a first node and a second node by: The RLF indication information may include indicating that an RLF has occurred on a node granular link between the first node and the second node and that link recovery is to be performed.

[0018]

[0018] In a possible design, the first MCG is also for transmitting F1 interface user plane services, and the RLF indication information includes a first BAP address, a first routing identifier (routing ID), or a first path identifier (path ID).

[0019]

[0019] In a possible design, the first node determines that all routes through the first node to the destination node are unavailable, and the RLF indication information includes a first BAP address, where the first BAP address is the BAP address of the destination node; the first node determines that a route with a first route ID is unavailable on all routes through the first node to the destination node, and the RLF indication information includes the first route ID; or the first node determines that a route with a first routing ID is unavailable on all routes through the first node to the destination node, and the RLF indication information includes the first routing ID.

[0020]

[0020] According to a third aspect, an embodiment of the present application provides a communication method, wherein a first node is served by a first MCG and a first SCG, and a child node of the first node is a second node, and the method may include: the first MCG is for transmitting F1 interface user plane services, and when an RLF occurs in the first MCG and link recovery is performed, the first node sends RLF indication information to the second node.

[0021]

[0021] In a possible design, the first MCG is for transmitting F1 interface user plane services may include: the first MCG is for transmitting F1 interface user plane services based on a BAP.

[0022]

[0022] In a possible design, the first SCG is only for transmitting F1 interface control plane services, and the RLF indication information indicates that RLF is occurring on the node granular link between the first node and the second node.

[0023]

[0023] In a possible design, the first SCG is also for transmitting F1 interface user plane services, no RLF occurs in the first SCG, and the first RLF indication information includes a first BAP address, a first routing identifier (routing ID), or a first path identifier (path ID).

[0024]

[0024] In a possible design, the first node determines that all routes through the first node to the destination node are unavailable, and the RLF indication information includes a first BAP address, where the first BAP address is the BAP address of the destination node; the first node determines that a route with a first route ID is unavailable on all routes through the first node to the destination node, and the RLF indication information includes the first route ID; or the first node determines that a route with a first routing ID is unavailable on all routes through the first node to the destination node, and the RLF indication information includes the first routing ID.

[0025]

[0025] According to a fourth aspect, an embodiment of the present application provides a communication method, wherein a first node is served by a first MCG and a first SCG, and a child node of the first node is a second node, the method comprising the steps of:

[0026] a second node receiving first RLF indication information sent by the first node, the first RLF indication information including a first backhaul adaptation protocol (BAP) layer address, or a first routing identifier (Routing ID), or a first path identifier (Path ID); The method may include a step in which the second node skips sending the first data packet to the first node based on the first RLF indication information, and the routing identifier carried in the first data packet is the first routing ID, or the path identifier in the routing identifier carried in the first data packet is the first path ID, or the BAP address in the routing identifier carried in the first data packet is the first BAP address.

[0026]

[0027] According to a fifth aspect, the present application provides a communication device including at least one processor and an interface, the interface being configured to input and / or output signals. For example, the interface is configured to receive signals from a communication device other than the communication device and send the signals to the processor, and / or to transmit signals from the processor to a communication device other than the communication device. The processor is configured to enable the communication device to perform the aforementioned method. For example, the processor implements any of the methods of the first, second, or third aspects by using logic circuitry and / or executing program instructions.

[0027]

[0028] Optionally, the device may be a chip or integrated circuit within a node in the first, second or third aspect.

[0028]

[0029] Optionally, the communication device may further include at least one memory, the memory storing program instructions, and a processor coupled to the at least one memory and configured to execute the program to implement the method design described above.

[0029]

[0030] According to a sixth aspect, the present application provides a communications device. The device has components, modules, units, or means for implementing any one of the methods of the first, second, or third aspects, and any design thereof. The device can be implemented using hardware, software, firmware, or any combination thereof. For example, the device may be implemented by hardware executing corresponding software. The hardware or software includes one or more corresponding units (modules) configured to implement the aforementioned method design, such as a transceiver unit and a processing unit.

[0030]

[0031] According to a seventh aspect, the present application provides a computer-readable storage medium, the computer-readable storage medium storing program instructions which, when executed by a processor, perform any of the methods of the first aspect, the second aspect or the third aspect, and any design thereof.

[0031]

[0032] According to an eighth aspect, the present application provides a computer program product, the computer program product comprising program instructions which, when executed by a processor, perform any of the methods of the first aspect, the second aspect or the third aspect, and any design thereof.

[0032]

[0033] According to a ninth aspect, the present application further provides a chip, the chip configured to implement any of the methods of the first aspect, the second aspect or the third aspect, and any design thereof.

[0033]

[0034] It should be understood that the technical solutions of the fourth to eighth aspects of the present application are consistent with the technical solutions of the first to third aspects of the present application, and the beneficial effects achieved by these aspects and corresponding possible implementations are similar, and the details will not be described again. [Brief explanation of the drawings]

[0034]

[0035] The solutions provided in the present application will be described in detail below with reference to the accompanying drawings. Features or contents indicated by dashed lines in the drawings may be understood as optional processes or optional structures in the embodiments of the present application. [Figure 1]

[0036] FIG. 1 is a diagram of an IAB network communication system. [Figure 2]

[0037] Figure 2 shows the control plane protocol stack of the IAB network. [Figure 3]

[0038] Figure 3 is a diagram of the IAB network user plane protocol stack. [Figure 4]

[0039] FIG. 4 is a diagram of a communication scenario. [Figure 5]

[0040] FIG. 5 is a diagram of a dual connectivity communication scenario. [Figure 6]

[0041] FIG. 6 is a diagram of a communications architecture. [Figure 7]

[0042] FIG. 7 is a diagram of a communication scenario. [Figure 8]

[0043] Figure 8 is a diagram of the cross-donor base station handover process. [Figure 9]

[0044] FIG. 9 is a diagram of a radio link failure indication method. [Figure 10]

[0045] Figure 10 is a diagram of the CP-UP separation scenario in the EN-DC scenario. [Figure 11]

[0046] Figure 11 is a diagram of the CP-UP separation scenario in the NR-DC scenario. [Figure 12]

[0047] FIG. 12 is a diagram of an IAB network communication system in the EN-DC form of networking. [Figure 13]

[0048] FIG. 13 is a diagram of an IAB network communication system in the NR-DC form of networking. [Figure 14]

[0049] FIG. 14 is a flow chart of a radio link failure indication method. [Figure 15]

[0050] FIG. 15 is a flow chart of a radio link failure indication method. [Figure 16]

[0051] FIG. 16 is a flow chart of a radio link failure indication method. [Figure 17A]

[0052] FIG. 17A is a diagram of an RLF scenario. [Figure 17B]

[0053] FIG. 17B is a diagram of an RLF scenario. [Figure 18]

[0054] FIG. 18 is a flow chart of a radio link failure indication method. [Figure 19A]

[0055] FIG. 19A is a diagram of an RLF scenario. [Figure 19B]

[0056] FIG. 19B is a diagram of an RLF scenario. [Figure 20]

[0057] FIG. 20 is a flow chart of a radio link failure indication method. [Figure 21]

[0058] FIG. 21 is a block diagram of a communication device 2100. [Figure 22]

[0059] FIG. 22 is a block diagram of a communication device 2200. DETAILED DESCRIPTION OF THE INVENTION

[0035]

[0060] FIG. 1 is a diagram of an IAB network communication system according to the present application. The communication system includes a terminal, an IAB node, and a donor base station. In the present application, the term "IAB network" is merely an example and may be replaced with a "wireless backhaul network" or a "relay network." The term "IAB node" is also merely an example and may be replaced with a "wireless backhaul device" or a "relay node."

[0036]

[0061] A donor base station may function as a donor node for an IAB node. In this application, a donor base station may include, but is not limited to, a next generation base station (gNB), an evolved NodeB (eNB), a radio network controller (RNC), a NodeB (NB), a base station controller (BSC), a base transceiver station (BTS), a home evolved NodeB (or home NodeB), a transmission and reception point (transmission point), a road side unit (RSU) with base station functionality, a baseband unit (BBU), a remote radio unit (RRU), an active antenna unit (AAU), one or a group of antenna panels, a node with base station functionality in a subsequent evolved system, or the like. The donor base station may be an entity and may further include a central unit (CU) entity and at least one distributed unit (DU) entity. The interface between the CU and the DU may be referred to as an F1 interface. The two ends of the F1 interface are the CU and the DU. The peer end of the F1 interface of the CU is the DU, and the peer end of the F1 interface of the DU is the CU. The F1 interface may further include a control plane F1 interface (F1-C) and a user plane F1 interface (F1-U). In this application, the CU of the donor base station may be abbreviated as a donor CU, and the DU of the donor base station may be abbreviated as a donor DU.

[0037]

[0062] In this application, a terminal may also be referred to as user equipment (UE), mobile station, terminal device, etc. Terminals may be widely used in various scenarios, such as device-to-device (D2D), vehicle-to-everything (V2X) communication, machine-type communication (MTC), internet of things (IoT), virtual reality, augmented reality, industrial control, autonomous driving, telemedicine, smart grid, smart furniture, smart office, smart wearable device, smart transportation, and smart city. Terminals may be mobile phones, tablet computers, computers with wireless transceiver capabilities, wearable devices, vehicles, unmanned aerial vehicles, helicopters, airplanes, ships, robots, robotic arms, smart home devices, etc. The terminal may include, but is not limited to, a user equipment (UE), a mobile station, a mobile device, a terminal device, a user agent, a mobile phone, a cordless phone, a session initiation protocol (SIP) phone, a wireless local loop (WLL) station, a personal digital assistant (PDA), a handheld device with wireless communication capabilities, a computing device, or other processing device connected to a wireless modem, an in-vehicle device, a wearable device (e.g., a smart watch, a smart band, or smart glasses), smart furniture or appliances, a vehicle device in a vehicle-to-everything (V2X) system, a terminal device with relay capabilities, a customer premises equipment (CPE), an IAB node (specifically, an IAB node functioning as a MT or terminal for an IAB node), etc. The specific name and implementation of the terminal are not limited by this application.

[0038]

[0063] In the present application, an IAB node may include at least one mobile terminal (MT) and at least one distributed unit (DU). An IAB node may be an entity. For example, an IAB node may include at least one MT function and at least one DU function. Alternatively, an IAB node may include multiple entities. For example, an IAB node may include at least one MT entity and at least one DU entity. The MT entity and the DU entity may communicate with each other, for example, by using a network cable. When an IAB node is directed to its parent node (where the parent node may be a donor base station or another IAB node), the IAB node may, for example, serve as a terminal used in various scenarios in which the aforementioned terminal is used, i.e., a terminal of the IAB node. In this case, the MT function or MT entity provides the functionality of the terminal of the IAB node. When an IAB node is oriented toward a child node of the IAB node (where the child node may be another IAB node or a terminal), the IAB node may act as a network device, i.e., a network device for the IAB node. In this case, the DU function or DU entity provides the IAB node with the functionality of a network device. In this application, the MT of an IAB node may be referred to as IAB-MT for short, and the DU of an IAB node may be referred to as IAB-DU for short. An IAB node may be connected to a donor base station or may be connected to a donor base station via another IAB node.

[0039]

[0064] The IAB network supports multi-hop networking and multi-connection networking to ensure the reliability of service transmission. An IAB node considers an IAB node that provides backhaul services to the IAB node as a parent node. Accordingly, an IAB node can consider a child node of its parent node. Alternatively, a terminal can consider an IAB node accessed by the terminal as a parent node. Accordingly, an IAB node can also consider a terminal accessed by the IAB node as a child node. An IAB node can consider a donor base station accessed by the IAB node as a parent node. Accordingly, a donor base station can alternatively consider an IAB node accessed by the donor base station as a child node.

[0040] As shown in FIG. 1, the parent node of IAB node 1 includes a donor base station. IAB node 1 is also the parent node of IAB node 2 or IAB node 3. The parent node of terminal 1 includes IAB node 4. The child node of IAB node 4 includes terminal 1 or terminal 2. An IAB node directly accessed by a terminal may be called an access IAB node. IAB node 4 in FIG. 1 is the access IAB node of terminal 1 and terminal 2. IAB node 5 is the access IAB node of terminal 2.

[0041] A node on the upstream transmission path from an IAB node to a donor base station may be referred to as the upstream node of the IAB node. An upstream node may include a parent node, a parent node of a parent node (also called a grandparent node), etc. For example, IAB node 1 and IAB node 2 in Figure 1 may be referred to as upstream nodes of IAB node 5.

[0042] A node on the downstream transmission path from an IAB node to a terminal may be referred to as a downstream node or descendant node of the IAB node. A downstream node or descendant node may include a child node, a child node of a child node (also called a grandchild node), a terminal, etc. For example, terminal 1, terminal 2, IAB node 2, IAB node 3, IAB node 4, or IAB node 5 in FIG. 1 may be referred to as a downstream node or descendant node of IAB node 1. As another example, IAB node 4 and IAB node 5 in FIG. 1 may be referred to as a downstream node or descendant node of IAB node 2. Terminal 1 in FIG. 1 may be referred to as a downstream node or descendant node of IAB node 4.

[0043] Each IAB node needs to maintain a backhaul link (BL) toward its parent node. If the child node of the IAB node is a terminal, the IAB node also needs to maintain an access link (AL) between the IAB node and the terminal. As shown in Figure 1, the link between IAB node 4 and terminal 1 or terminal 2 includes an AL. The link between IAB node 4 and IAB node 2 or IAB node 3 includes a BL.

[0044]

[0065] An upstream data packet transmitted by a terminal to a donor base station may be transmitted to the donor base station via one or more IAB nodes. Specifically, the target node of the upstream data between the terminal and the donor base station may be the donor base station. A downstream data packet transmitted by the donor base station to the terminal may be transmitted to the access IAB node of the terminal via one or more IAB nodes, and then the downstream data packet is transmitted to the terminal by the access IAB node. Specifically, the target node of the downstream data between the terminal and the donor base station is the access IAB node. For example, there are two available paths for data transmission between terminal 1 and the donor base station: Route 1: Terminal 1 ←→ IAB node 4 ←→ IAB node 3 ←→ IAB node 1 ←→ donor base station, and Route 2: Terminal 1 ←→ IAB node 4 ←→ IAB node 2 ←→ IAB node 1 ←→ Donor base station For data transmission between terminal 21 and the donor base station, there are three possible paths: Route 1: Terminal 2 ←→ IAB node 4 ←→ IAB node 3 ←→ IAB node 1 ←→ donor base station, Route 2: Terminal 2 ←→ IAB node 4 ←→ IAB node 2 ←→ IAB node 1 ←→ donor base station, and Route 3: Terminal 2 ←→ IAB node 5 ←→ IAB node 2 ←→ IAB node 1 ←→ Donor base station In an IAB network, it can be understood that one transmission path between a terminal and a donor base station may include one or more IAB nodes. Each IAB node must maintain a wireless backhaul link (BL) toward its parent node. If the child node of an IAB node is a terminal, a wireless access link (AL) exists between the IAB node and the terminal. As shown in Figure 1, in path 1 between terminal 1 and a donor base station, terminal 1 accesses IAB node 4 via an AL, IAB node 4 is connected to IAB node 3 via a BL, IAB node 3 is connected to IAB node 1 via a BL, and IAB node 1 is connected to the donor base station via a BL.

[0045]

[0066] 2 and 3 are diagrams of a control plane protocol stack and a user plane protocol stack, respectively, of an IAB network according to an embodiment of the present application. The donor base station in FIGS. 2 and 3 may include a donor CU function and a donor DU function (in this case, the donor base station is a single entity), or may include a donor CU entity and a donor DU entity function (in this case, the donor base station is divided into two entities). As shown in FIGS. 2 and 3, the peer protocol layers between the donor DU and the donor CU include the IP layer, Layer 2 (L2), and Layer 1 (L1). L1 and L2 may be referred to as protocol stack layers in a wired transmission (e.g., optical fiber transmission) network. For example, L1 may be the physical layer, and L2 may be the data link layer. Backhaul links (BL) are established between IAB node 4 and IAB node 3, between IAB node 3 and IAB node 1, and between IAB node 1 and the donor DU. The peer protocol stacks at both ends of the BL may include a backhaul adaptation protocol (BAP) layer, a radio link control (RLC) layer, a media access control (MAC) layer, and a physical (PHY) layer.

[0046]

[0067] As shown in Figure 2, an interface exists between the terminal and the donor base station, and the interface is sometimes referred to as an air interface. For example, the air interface is sometimes referred to as a Uu interface. One end of the Uu interface is located in the terminal, and the other end is located in the donor base station. The peer control plane protocol stack at each end of the Uu interface includes a radio resource control (RRC) layer, a packet data convergence protocol (PDCP) layer, an RLC layer, a MAC layer, and a PHY layer. The protocol layers included in the Uu interface control plane protocol stack are sometimes referred to as a control plane access stratum (AS). If the donor base station includes a donor CU entity and a donor DU entity, the control plane protocol stack of the Uu interface at the donor base station may be located separately in the donor DU and donor CU. For example, the PHY layer, MAC layer, and RLC layer are located in the donor DU, and the RRC layer and PDCP layer are located in the donor CU.

[0047]

[0068] An interface, for example, called an F1 interface, exists between the DU of the IAB node (i.e., IAB node 4 in FIG. 2) accessed by the terminal and the donor base station. One end of the F1 interface is located at IAB node 4, and the other end is located at the donor base station. The peer end of the F1 interface of the donor base station (e.g., which may be a donor CU) is the IAB node (specifically, which may be a DU of the IAB node), and the peer end of the F1 interface of the IAB node (specifically, which may be a DU of the IAB node) is the donor base station (specifically, which may be a donor CU). The peer control plane protocol stacks at both ends of the F1 interface include an F1 application protocol (F1AP) layer, a stream control transmission protocol (SCTP) layer, and an IP layer. The donor base station may include a donor CU entity and a donor DU entity. The control plane protocol stack of the F1 interface at the donor base station end may be located in the donor CU. For example, the donor CU includes an F1AP layer, an SCTP layer, and an IP layer. Alternatively, the control plane protocol stack of the F1 interface on the donor base station side may be separately located in the donor CU and the donor DU. For example, the donor CU includes an F1AP layer and an SCTP layer, and the donor DU includes an IP layer.

[0048] As shown in Figure 3, the peer user plane protocol stack at both ends of the Uu interface between the terminal and the donor base station includes a service data adaptation protocol (SDAP) layer, a PDCP layer, an RLC layer, a MAC layer, and a PHY layer. The protocol layers included in the user plane protocol stack of the Uu interface are sometimes referred to as the user plane access stratum (AS). If the donor base station includes a donor CU entity and a donor DU entity, the user plane protocol stack of the Uu interface at the donor base station side may be located separately in the donor DU and donor CU. For example, the PHY layer, MAC layer, and RLC layer are located in the donor DU, and the SDAP layer and PDCP layer are located in the donor CU.

[0049]

[0069] The peer user plane protocol layers at both ends of the F1 interface between the DU of IAB node 4 and the donor base station include a general packet radio service tunneling protocol for the user plane (GTP-U) layer, a user datagram protocol (UDP) layer, and an IP layer. The donor base station may include a donor CU entity and a donor DU entity. The user plane protocol stack of the F1 interface on the donor base station side may be located in the donor CU. For example, the donor CU includes the GTP-U layer, the UDP layer, and the IP layer. Alternatively, the user plane protocol stack of the F1 interface on the donor base station side may be located separately in the donor CU and the donor DU. For example, the donor CU includes the GTP-U layer and the UDP layer, and the donor DU includes the IP layer.

[0050]

[0070] In the control plane, the terminal's RRC messages are encapsulated in F1AP messages by the access IAB node for transmission. Specifically, in the upstream direction, the terminal encapsulates the RRC messages into PDCP protocol data units (PDUs) and sends the PDCP protocol data units to the DUs of the IAB node after sequential processing in the RLC layer, MAC layer, and PHY layer.

[0051] The DU of IAB node 4 obtains the PDCP PDU after sequential processing at the PHY layer, MAC layer, and RLC layer, encapsulates it into an F1AP message, and obtains an IP packet after sequential processing at the SCTP layer and IP layer. The DU of IAB node 4 transmits the IP packet to the MT of IAB node 4 via the internal interface. The MT of IAB node 4 transmits the IP packet to the DU of IAB node 3 after sequential processing at the BAP layer, RLC layer, MAC layer, and PHY layer.

[0052] The DU of IAB node 3 obtains the IP packet after sequential processing is performed at the PHY layer, MAC layer, RLC layer, and BAP layer. The DU of IAB node 3 sends the IP packet to the MT of IAB node 3 via the internal interface, and then the MT of IAB node 3 sends the IP packet to the DU of IAB node 1 by using the same operation as the MT of IAB node 4.

[0053] Then, the DU of IAB node 1 sends the IP packet to the MT of IAB node 1 by using the same operation as the DU of IAB node 3. Similarly, the MT of IAB node 1 sends the IP packet to the donor DU.

[0054] The donor DU obtains the IP packet through analysis and then sends it to the donor CU. The donor CU processes the IP packet sequentially through the SCTP layer, F1AP layer, and PDCP layer, and then obtains the RRC message of the terminal. The downstream operation is similar. The details will not be described again here.

[0055]

[0071] In the user plane, the terminal's data packets are encapsulated in PDCP PDUs and sent to the access IAB node after sequential processing in the RLC layer, MAC layer, and PHY layer. The access IAB node encapsulates the received PDCP PDUs in a GTP-U tunnel between the access IAB node and the donor CU for transmission. The GTP-U tunnel is established on the F1-U interface. For the specific process of forwarding terminal data packets, refer to the aforementioned process of forwarding RRC messages in the control plane.

[0056]

[0072] Also, in Figures 2 and 3, when a terminal accesses a donor DU, the interface between the donor DU and the donor CU may also include an F1 interface. The peer control plane protocol stacks on both ends of the F1 interface include an F1AP layer, an SCTP layer, and an IP layer. The peer user plane protocol stacks on both ends of the F1 interface include a GTP-U layer, a UDP layer, and an IP layer. When a terminal accesses IAB node 1 or IAB node 3, an F1 interface may also be included between IAB node 1 or IAB node 3 and the donor base station. For a description of the F1 interface, refer to the description of the F1 interface between the DU of IAB node 4 and the donor base station.

[0057]

[0073] When "terminal" refers to an MT function or MT entity of an IAB node, or an IAB node acting as a terminal, the protocol stack of the terminal shown in Figure 2 or Figure 3 is the protocol stack of the MT function or MT entity of the IAB node, or the protocol stack of the IAB node when it acts as a terminal.

[0058]

[0074] When accessing an IAB network, an IAB node can function as a terminal. In this case, the MT of the IAB node has a terminal protocol stack. An air interface (Uu interface) protocol stack exists between the IAB node and the donor base station. The terminal protocol stack in Figures 2 and 3 includes an RRC layer or SDAP layer, a PDCP layer, an RLC layer, a MAC layer, and a PHY layer. In the control plane, the IAB node's RRC messages are encapsulated in F1AP messages by the IAB node's parent node for transmission. In the user plane, the IAB node's data packets are encapsulated in PDCP protocol data units (PDUs) and sent to the IAB node's parent node. The IAB node's parent node encapsulates the received PDCP PDUs in a GTP-U tunnel on the F1 interface between the IAB node's parent node and the donor CU for transmission. Also, after an IAB node accesses an IAB network, the IAB node may still function as a common terminal. For example, the IAB node may transmit its data packets, such as operations, administration and maintenance (OAM) network element data packets and measurement reports, to the donor base station.

[0059]

[0075] It should be noted that an IAB node may have more than one role in the IAB network. For example, an IAB node may function as a terminal, an access IAB node (e.g., the protocol stack of IAB node 4 in Figures 2 and 3), or an intermediate IAB node (e.g., the protocol stack of IAB node 1 or IAB node 3 in Figures 2 and 3). An IAB node may use different protocol stacks for different roles. If an IAB node has multiple roles in the IAB network, it may have multiple protocol stacks at the same time. The protocol stacks may share some of the same protocol layers, for example, the same RLC layer, the same MAC layer, and the same PHY layer.

[0060]

[0076] FIG. 4 is a diagram of a communication scenario. As shown in FIG. 4, a donor base station and an IAB node are included. The donor base station may include a donor CU and at least one donor DU. The communication interface between the donor base station and the IAB node may include an air interface (Uu interface) and an F1 interface. For example, an air interface (Uu interface) exists between a MT of the IAB node and the donor base station, and an F1 interface exists between a DU of the IAB node and the donor base station.

[0061]

[0077] The IP addresses of the IAB nodes are assigned to the IAB nodes by the donor DU or a network management device. The IP addresses of the donor CUs may also be assigned by a network management device. In this application, a network management device may include an operations, administration, and maintenance (OAM) network element, an element management system (EMS), a network management system (NMS), etc.

[0062]

[0078] Figure 5 is a diagram of a dual connectivity communication scenario. As shown in Figure 5, a master base station, a secondary base station, and an IAB node are included. The donor base station of the IAB node is the secondary base station. The communication interface between the master base station and the IAB node includes an air interface (Uu interface). The communication interface between the secondary base station and the IAB node includes a Uu interface and an F1 interface.

[0063]

[0079] FIG. 6 is a diagram of a communication architecture. As shown in FIG. 6, donor base station 1 includes donor CU1 and donor DU1. Donor base station 2 includes donor CU2 and donor DU2. A communication interface exists between the IAB node and donor base station 1 or donor base station 2. For example, the communication interface between the IAB node and donor base station 1 or donor base station 2 may include a Uu interface and / or an F1 interface. A communication interface also exists between donor base station 1 and donor base station 2. Donor CU1 and donor CU2 may communicate with each other, for example, via an X2 or Xn interface. Donor CU1 and donor DU2, and donor CU2 and donor DU1 may also communicate with each other, for example, by using an IP network. It can be understood that the communication architecture shown in FIG. 6 may further include downstream or descendant nodes of the IAB node. An upstream node of the IAB node may also be included between the IAB node and the donor base station.

[0064]

[0080] FIG. 7 is a diagram of possible communication scenarios. As shown in FIG. 7, the IAB node includes an MT and DU portion (in this case, the IAB node is split into two entities) or an MT and DU function (in this case, the IAB node is one entity). The donor base station includes a donor CU entity and a donor DU entity (in this case, the donor base station is split into two entities) or a donor CU and donor DU function (in this case, the donor base station is still one whole). An upstream node, IAB node 2 (i.e., the parent node of IAB node 3), also exists between IAB node 3 and the donor base station. In FIG. 7, the thick curves indicate possible paths of communication over the F1 interface between the IAB node and donor base station 1 or donor base station 2 in each scenario. It can be seen from FIG. 7 that another upstream node from IAB node 3 may also be included between IAB node 3 and IAB node 2 or between IAB node 3 and IAB node 1. In Figure 7, another downstream node or descendant node of IAB node 3 may be further included. In Figure 7, IAB node 1 may not exist. Specifically, IAB node 3 may be directly connected to donor base station 1. Alternatively, IAB node 2 may not exist. Specifically, IAB node 3 may be directly connected to donor base station 2. Several communication scenarios shown in Figure 7 will be described below.

[0065]

[0081] Communication Scenario A: 7 is donor base station 1 (specifically, the donor CU is donor CU1 and the donor DU is donor DU1), there are a Uu interface and an F1 interface between IAB node 3 and donor base station 1. Communication on the F1 interface between IAB node 3 and donor base station 1 needs to go through donor DU1.

[0066]

[0082] 7 is donor base station 2 (the donor CU is donor CU2 and the donor DU is donor DU2), there are a Uu interface and an F1 interface between IAB node 3 and donor base station 2. Communication on the F1 interface between IAB node 3 and donor base station 2 needs to go through donor DU2.

[0067]

[0083] Communication Scenario B: A Uu interface exists between the IAB node 3 and the donor base station 2 (including the donor CU2 and donor DU2), and an F1 interface exists between the IAB node 3 and the donor base station 1. Communication on the F1 interface between the IAB node 3 and the donor base station 1 needs to go through the donor DU2.

[0068]

[0084] Communication Scenario C: A Uu interface exists between the IAB node 3 and the donor base station 1 (including donor CU1 and donor DU1), and an F1 interface exists between the IAB node 3 and the donor base station 2. In communication scenario C, the F1 interface may exist between the IAB node 3 and the donor base station 1, or may not exist (it can also be said that the F1 interface is not established between the IAB node 3 and the donor base station 1). Communication on the F1 interface between the IAB node and the donor base station 2 needs to go through the donor DU1.

[0069]

[0085] Communication Scenario D (also called dual connectivity scenario): A Uu interface exists between the IAB node 3 and donor base station 1 (including donor CU1 and donor DU1), and a Uu interface exists between the IAB node 3 and donor base station 2. An F1 interface exists between the IAB node 3 and donor base station 1. Communication on the F1 interface between the IAB node 3 and donor base station 1 may go through donor DU1 or donor DU2. In other words, donor base station 1 may choose to perform communication on the F1 interface with IAB node 3 via donor DU1 and / or donor DU.

[0070]

[0086] Communication scenarios A, B, C, and D in IAB node 3 may be converted to each other. For example, a process in which cross-donor base station handover is performed in IAB node 3 may involve switching from communication scenario A to communication scenario B or from communication scenario A to communication scenario C. In this case, donor base station 1 may be referred to as a source donor base station (S-donor) (S-donor), and donor base station 2 may be referred to as a target donor base station (T-donor) (T-donor). The S-donor may further include an S-donor CU1 and an S-donor DU1. The T-donor may further include a T-donor CU2 and a T-donor DU2. A process in which cross-donor base station handover is performed in an IAB node may be as shown in FIG. 8.

[0071]

[0087] Figure 8 is a diagram of the cross-donor base station handover process. Before performing the cross-donor base station handover, IAB node 3 may be in an initial stage. For a description of the initial stage, see the previous description of communication scenario A.

[0072]

[0088] A possible cross-donor base station handover process includes the following: after IAB node 3 receives a message from donor base station 1 instructing IAB node 3 to be handed over from donor base station 1 to donor base station 2, first, the MT of IAB node 3 is handed over to donor base station 2 (i.e., the air interface is handed over from donor base station 1 to donor base station 2), and the DU of IAB node 3 still maintains the F1 interface between IAB node 3 and donor base station 1 (i.e., the F1 interface has not been handed over). In this case, the IAB node is in intermediate stage 1. For communication between IAB node 3 and donor base station 1 or donor base station 2 in intermediate stage 1, please refer to the above description of communication scenario B. Optionally, IAB node 3 in intermediate stage 1 can continue to hand over the F1 interface to donor base station 2 (specifically, disconnect the F1 interface between IAB node 3 and donor base station 1 and establish the F1 interface between IAB node 3 and donor base station 2). In this case, the IAB node enters the final stage.

[0073]

[0089] Another possible cross-donor base station handover process includes the following: IAB node 3 establishes an F1 interface with donor base station 2 based on the received instruction information, and the MT of IAB node 3 still maintains the Uu interface between IAB node 3 and donor base station 1 (i.e., the Uu interface has not been handed over). In this case, the IAB node is in intermediate stage 2. The instruction information may be from donor base station 1 and instructs IAB node 3 (specifically, the DU of IAB node 3) to establish an F1 interface with donor base station 2. For example, the instruction information carries the IP address of donor CU2. For communication between IAB node 3 and donor base station 1 or donor base station 2 in intermediate stage 2, please refer to the above description of communication scenario C. Optionally, after the IAB node 3 receives a message from the donor base station 1 indicating that it is to be handed over from the donor base station 1 to the donor base station 2, the IAB node 3 in the intermediate stage 2 can continue to hand over the Uu interface to the donor base station 2 (specifically, disconnect the Uu interface between the MT of the IAB node 3 and the donor base station 1, and establish the Uu interface between the MT of the IAB node 3 and the donor base station 1). If an F1 interface exists between the IAB node 3 and the donor base station 1 in the communication scenario C or the intermediate stage 2, in this case, the F1 interface between the IAB node 3 and the donor base station 1 may be disconnected. In this case, the IAB node enters the final stage.

[0074]

[0090] In the present application, establishing an interface may include establishing a connection and / or a bearer in the interface. For example, establishing a Uu interface may include at least one of establishing an RRC connection, establishing an SRB, and establishing a DRB. Establishing an F1 interface may include establishing an F1 connection.

[0075] Disconnecting the interface may include disconnecting connections and / or bearers in the interface. For example, disconnecting the Uu interface may include at least one of disconnecting an RRC connection, disconnecting an SRB, and disconnecting a DRB. Disconnecting the F1 interface may include disconnecting an F1 connection.

[0076]

[0091] As another example, IAB node 3 may further switch from communication scenario A or communication scenario B to a dual connectivity communication scenario (communication scenario D). In this case, donor base station 1 may be referred to as a master donor base station (M-donor), and donor base station 2 may be referred to as a secondary donor base station (S-donor). The M-donor may further include an M-donor CU1 and an M-donor DU1. The S-donor may further include an S-donor CU2 and an S-donor DU2.

[0077]

[0092] To ensure stable data transmission between a UE and an IAB-donor, a radio link recovery mechanism is introduced. Specifically, after a radio link failure (RLF) occurs between two IAB nodes, an attempt may be made to restore the radio link between the two IAB nodes. If an IAB node discovers that an RLF has occurred on the link between the IAB node and its parent node and that RLF recovery has failed (e.g., RRC re-establishment has failed), the IAB node sends an RLF indication to its child node, which then triggers the link recovery procedure. For example, as shown in Figure 9, if an RLF has occurred on the link between the IAB node and its parent node and that RLF recovery has failed, the IAB node sends an RLF indication to its child node.

[0078]

[0093] However, for an IAB node with dual connectivity, the IAB node accesses two parent nodes in a dual connectivity manner. One of the two parent nodes serves as the IAB node's master node (Master Node, MN), and the other parent node serves as the IAB node's secondary node (Secondary Node, SN). The cell group (CG) configured on the MN side is the master cell group (MCG), and the cell group (Secondary Cell Group, SCG) configured on the SN side is the secondary cell group. In other words, the IAB node is served by both the MCG and the SCG.

[0079]

[0094] The condition for triggering an IAB node having dual connectivity to send RLF indication information to its child nodes is that the IAB node initiates RRC re-establishment, where the cause of the RRC re-establishment is: RLF occurs on backhaul links (BLs) within two cell groups (CGs) of an IAB node, or RLF occurs on the backhaul link within the master cell group and master cell group fast recovery is not performed (no MCG fast recovery).

[0080] This RLF indication method cannot guarantee stable data transmission. In particular, problems such as data packet stacking, link congestion, and excessively long latency may occur in some scenarios. These scenarios may include, but are not limited to, a CP-UP separation scenario in a DC scenario of an IAB node. CP-UP separation means that the F1-U (F1 interface user plane) service and the F1-C (F1 interface control plane) service of an IAB node with dual connectivity do not reach the IAB donor via the same route.

[0081]

[0095] The IAB-MT encapsulates F1 interface user plane (F1-U) services in BAP layer data packets (e.g., BAP PDUs) and then forwards the packets to the IAB donor over the backhaul link (via at least one intermediate IAB node) based on the BAP layer routing and backhaul link RLC channel mapping protocol. This transmission mode may be called "F1 over BAP." "F1 over BAP" is also applicable to F1-C services in general DC scenarios without CP-UP separation.

[0082]

[0096] F1 interface control plane (F1-C) services are encapsulated by the IAB-MT in IAB-MT RRC messages and reach the MN or SN via the Uu interface of the non-F1 terminating node, and then reach the IAB donor via the inter-base station Xn interface or X2 interface. This transmission mode may be called "F1 over RRC." "F1 over RRC" applies to F1-C services.

[0083]

[0097] A non-F1 terminating node is a node that does not have an F1 interface with an IAB node in dual-connection mode. For an IAB node in dual-connection mode, if the IAB node transmits its F1-C services to an eNB or gNB connected to the IAB node via an LTE Uu interface or an NR Uu interface (instead of the F1 interface) by using the MT portion of the IAB node, the eNB or gNB may be referred to as a non-F1 terminating node. For example, in EN-DC networking, the non-F1 terminating node may be an MeNB. In NR-DC networking, the non-F1 terminating node may be an MgNB or SgNB. The F1 terminating node is an IAB donor node. Specifically, F1-U services and / or F1-C services (both / either) are transmitted between the IAB node and the donor node via the F1 interface.

[0084]

[0098] The DC scenario of the IAB node in Figures 10 and 11 is used as an example. Figure 10 is a diagram of a CP-UP separation scenario in an EN-DC scenario according to an embodiment of the present application. Figure 11 is a diagram of a CP-UP separation scenario in an NR-DC scenario according to an embodiment of the present application. As shown in Figure 10, an IAB node (e.g., IAB node 2 or IAB node 1 in Figure 10) supports dual connectivity of 4G and 5G networks, i.e., E-UTRAN NR Dual Connectivity (EN-DC) mode. The LTE base station eNB is a master base station (MeNB), which provides LTE air interface (LTE Uu) connection to the IAB node and establishes an S1 interface with a 4G Evolved Packet Core Network (EPC) to perform user plane and control plane transmission. The LTE-side CG is the MCG. The IAB donor (e.g., gNB) is a secondary base station that provides NR air interface (NR Uu) connectivity to the IAB node and establishes an S1 interface with the core network EPC for user plane transmission. The CG on the NR side is the SCG. The F1-C and F1-U services of an IAB node (e.g., IAB node 2 or IAB node 1 in Figure 10) reach the IAB donor (e.g., gNB) separately via different routes. As shown in Figure 11, IAB node 2 establishes a connection to the network only through the New Radio (NR) air interface. In other words, IAB node 2 is connected to two parent nodes in an NR-DC format. The two parent nodes can function as the master node (MN) or secondary node (SN) of IAB node 2, respectively. The CG configured on the MN side is the MCG, and the CG configured on the SN side is the SCG. The F1-C and F1-U services of IAB Node 2 reach the IAB donor (gNB) separately via different routes.

[0085]

[0099] Regardless of the CP-UP separation scenario in the EN-DC scenario shown in Figure 10 or the CP-UP separation scenario in the NR-DC scenario shown in Figure 11, if the CG for transmitting F1-C services of an IAB node is an MCG and a link RLF occurs, the normal operation of the SCG for transmitting F1-U services is not immediately affected, and accordingly, the F1-U services of child nodes forwarded by the IAB node are not immediately affected. In this case, based on the aforementioned trigger condition "RLF occurs in the backhaul link of the master cell group, and fast recovery of the master cell group is not performed (no MCG fast recovery), causing the IAB node to initiate RRC re-establishment," the IAB node sends RLF indication information to its child nodes. As a result, the child nodes stop routing data to the IAB nodes, causing data packet stacking, link congestion, and excessively long latencies for the child nodes (in which case the amount of data traffic associated with the user plane is usually much higher than the amount of data traffic in the control plane).

[0086] Furthermore, if the cell group carrying the F1-U service is an SCG and the link RLF occurs only in the SCG, based on the aforementioned trigger condition that "RLF occurs in the backhaul links (BLs) of two cell groups (CGs) of the IAB node, causing the IAB node to initiate RRC re-establishment," the IAB node will not send RLF indication information to the child node, and the child node will continue to schedule data to the IAB node normally, which will result in data packet stacking, link congestion, and excessively long latency for the IAB node.

[0087]

[0100] Therefore, the present application provides a radio link failure indication method according to the following embodiments, which helps improve the stability and reliability of data transmission in an IAB network and alleviate the problems of data packet stacking, link congestion, and excessively long latency of an IAB node. Below, the radio link failure indication method in the present application is described in detail using several embodiments.

[0088]

[0101] First, a communication system architecture to which the radio link failure indication method of the present application is applied will be described. The radio link failure indication method of the present application is mainly for an IAB network communication system in DC type networking, such as an IAB network communication system in EN-DC type networking shown in Fig. 12 or an IAB network communication system in NR-DC type networking shown in Fig. 13.

[0089]

[0102] For example, Figure 12 is a diagram of an IAB network communication system in EN-DC type networking according to the present application. As shown in Figure 12, the IAB network communication system may include a UE, an IAB node 1, an IAB node 2, an MeNB, an IAB donor 1, an IAB donor 2, and an EPC.

[0090]

[0103] A UE can communicate with IAB Donor 1 or IAB Donor 2 via IAB Node 2 and IAB Node 1. IAB Node 2 is for providing access and backhaul services to the UE. IAB Node 2 may be configured with IAB Node DU (abbreviated as IAB-DU) and IAB Node MT (abbreviated as IAB-MT). IAB Node 1 is for providing access and backhaul services to a child node (here, IAB Node 2). IAB Node 1 may be configured with IAB Node DU (abbreviated as IAB-DU) and IAB Node MT (abbreviated as IAB-MT).

[0091]

[0104] The IAB-DU is a distributed unit part of the IAB node (here, IAB node 1 or IAB node 2) and has the same functions as the gNB-DU. An F1 interface is established between the IAB-DU and the IAB donor CU, and it provides access services to UEs or child nodes of the IAB-DU.

[0092]

[0105] The IAB-MT is the mobile terminal part of the IAB node (here, IAB node 1 or IAB node 2), has UE functionality, and provides data backhaul services to the child nodes of the IAB-MT.

[0093]

[0106] An IAB donor (here, IAB Donor 1 or IAB Donor 2) is a donor base station that supports an IAB node and may include an IAB Donor CU and at least one IAB Donor DU. The IAB Donor CU portion may include one IAB Donor CU-CP (responsible for control plane services) and at least one IAB Donor CU-UP (responsible for user plane services).

[0094]

[0107] The IAB Donor DU is a distributed unit part of the IAB donor (here, IAB Donor 1 or IAB Donor 2) and has similar functions to the gNB-DU, mainly implementing the L1 and L2 protocol stack functions, including the PHY layer, MAC layer, and RLC layer functions.

[0095]

[0108] The IAB donor CU is the central unit of the IAB donor (here, IAB donor 1 or IAB donor 2), and has the same functions as the gNB-CU, mainly performing the functions of the PDCP layer, SDAP layer, and RRC layer. An F1-C interface is established between the IAB donor CU-CP and the IAB-DU, and an F1-U interface is established between the IAB donor CU-UP and the IAB-DU.

[0096]

[0109] The MeNB is an LTE base station in the EN-DC networking mode. For a UE or an IAB node (here, IAB node 1 or IAB node 2), the MeNB is the master base station (Master eNB, MeNB).

[0097]

[0110] BH is used to represent a backhaul link. For example, the NR BH shown in Figure 12 is specifically a connection channel between the MT part of an IAB node (here, IAB node 1 or IAB node 2) and the DU part of the IAB node's parent node, and is used to backhaul UE data packets or forward IAB donor data packets.

[0098]

[0111] As shown in FIG. 12, the IAB node (here, IAB node 1 or IAB node 2) supports 4G and 5G network dual connectivity, i.e., EN-DC mode. The LTE base station eNB is an MeNB, which provides the IAB node with an LTE air interface (LTE Uu) connection and establishes an S1 interface with the EPC for user plane and control plane transmission. The CG on the LTE side is the MCG. The NR base station gNB is a secondary base station, which provides the IAB node with an NR air interface (NR Uu) connection and establishes an S1 interface with the core network EPC for user plane transmission. The CG on the NR side is the SCG. Similarly, the UE also supports EN-DC. The UE is connected to the master base station eNB via the LTE Uu interface and to the secondary base station IAB node 2 via the NR Uu interface. In some embodiments, the UE's secondary base station may be IAB donor 1 or IAB donor 2. As shown in FIG. 12, the EN-DC scenario of the IAB network may support multi-hop IAB networking. Specifically, an IAB node may be connected to IAB Donor 1 or IAB Donor 2 by using a multi-hop wireless backhaul link.

[0099]

[0112] Optionally, the EN-DC scenario of the IAB network may include a CP-UP separation scenario and a non-CP-UP separation scenario. In the CP-UP separation scenario of the EN-DC scenario, the F1-C service of the IAB node (here, IAB Node 1 or IAB Node 2) reaches the non-F1 terminating node (i.e., MeNB) via the LTE Uu interface channel, and then the non-F1 terminating node transmits the F1-C service to the IAB donor (here, IAB Donor 1 or IAB Donor 2) via the base station-to-base station interface X2, where the IAB donor may be called the F1-terminating node of the IAB node. The F1-U service of the IAB node (here, IAB Node 1 or IAB Node 2) is multi-hop forwarded by the IAB node to the IAB donor (here, IAB Donor 1 or IAB Donor 2) by using a backhaul link based on the BAP layer protocol.

[0100]

[0113] It should be noted that the communication system architecture shown in Figure 12 is described using two IAB nodes as an example. The communication system architecture can be described using more IAB nodes, for example, three, four, or more IAB nodes, or can be described using fewer IAB nodes, for example, one IAB node. The present application is not limited to the system architecture shown in Figure 12.

[0101]

[0114] 13 is a diagram of an IAB network communication system in NR-DC type networking according to the present application. As shown in FIG. 13, the IAB network communication system may include a UE, IAB node 1, IAB node 2, a gNB, IAB donor 1, IAB donor 2, and a 5GC.

[0102]

[0115] For descriptions of the UE, IAB Node 1, IAB Node 2, IAB-DU, IAB-MT, IAB donor, IAB donor DU, and IAB donor CU, please refer to the related descriptions in Figure 12. The details will not be described again here.

[0103]

[0116] A gNB is a 5G base station. With respect to a UE or an IAB node (here, IAB node 1 or IAB node 2), the gNB may be a master node (i.e., MN or MgNB) or a secondary node (i.e., SN or SgNB) of the IAB node or UE in DC mode.

[0104]

[0117] Unlike the IAB network communication system in the EN-DC networking shown in Figure 12, in the IAB network communication system of this embodiment, both the IAB node and the UE establish a connection to the network only via the NR air interface. IAB node 2 is connected to two parent nodes, IAB node 1 and a gNB, in the NR-DC networking. The two parent nodes can function as the MN or SN of IAB node 2, respectively. The CG configured on the MN side is the MCG, and the CG configured on the SN side is the SCG.

[0105]

[0118] Optionally, the NR-DC scenario for IAB networks may include a CP-UP separation scenario and a non-CP-UP separation scenario. In the CP-UP separation scenario of the NR-DC scenario, the F1-C service of an IAB node (here, IAB Node 1 or IAB Node 2) can reach a non-F1 terminating node via the NR Uu interface channel, and the non-F1 terminating node then transmits the F1-C service to an IAB donor (here, IAB Donor 1 or IAB Donor 2) via the base station-to-base station interface Xn, where the IAB donor may be called the F1-terminating node of the IAB node. The F1-U service of the IAB node (here, IAB Node 1 or IAB Node 2) is multi-hop forwarded by the IAB node to the IAB donor (here, IAB Donor 1 or IAB Donor 2) using a backhaul link based on the BAP layer protocol.

[0106]

[0119] In NR-DC networking, the non-F1 terminal node may be an MgNB and the F1 terminal node may be an SgNB; or, the non-F1 terminal node may be an SgNB and the F1 terminal node may be an MgNB.

[0107]

[0120] It should be noted that the communication system architecture shown in Figure 13 is described using two IAB nodes as an example. The communication system architecture can be described using more IAB nodes, for example, three, four, or more IAB nodes, or can be described using fewer IAB nodes, for example, one IAB node. The present application is not limited to the system architecture shown in Figure 13.

[0108]

[0121] It should be further noted that the name of the F1 interface is merely an example and does not constitute any limitation on the functionality of the F1 interface. In 5G networks and other future networks, the F1 interface may alternatively have another name, which is not particularly limited in this embodiment of the present application. Furthermore, it should be understood that the names of the messages (or signaling) transmitted between the aforementioned network elements are merely an example and do not constitute any limitation on the functionality of the messages.

[0109]

[0122] According to the radio link failure indication method in the present application, a first node sends a first RLF indication information to a second node, If RLF occurs in the backhaul link of one of the two cell groups that is intended to carry FI Interface User Plane (F1-U) services, or When RLF occurs in the backhaul link of one of the two cell groups that is intended to carry F1-U services and link recovery is performed, or If an RLF occurs in the backhaul link of one of the two cell groups that is configured to carry F1 interface services based on the BAP layer, or When an RLF occurs in a backhaul link of one of two cell groups, the cell group being configured to carry F1 interface services based on the BAP layer, and link recovery is performed, the first node is served by the two cell groups, and the child node of the first node is the second node.

[0110] Therefore, the first node triggers the transmission of the first RLF indication upon detecting the occurrence of RLF on the backhaul link in the cell group for transmitting F1-U services, thereby improving the stability and reliability of data transmission in the IAB network. In the CP-UP separation scenario in the DC scenario, if the cell group for transmitting F1-C services is an MCG and RLF occurs, and the cell group for transmitting F1-U services is an SCG and RLF does not occur, the first node does not immediately transmit the first RLF indication to the second node based on the triggering method of the first RLF indication. In this way, the impact on the normal operation of the SCG for transmitting F1-U services can be reduced. The second node can continue to route data to the first node. This helps to reduce problems of data packet stacking, link congestion, and excessively long latency at the second node. In addition, when the cell group for transmitting the F1-U service is an SCG and the RLF occurs only in the SCG, the first node sends the first RLF indication information to the second node according to the triggering manner of the first RLF indication information, and the second node can trigger the stop of transmitting data packets to the first node, or the second node can trigger the rerouting operation of the data packets routed by the first node. In this way, the problems of data packet stacking, link congestion, and excessively long latency of the first node can be alleviated.

[0111]

[0123] Transmitting F1 interface services based on the BAP layer may include transmitting F1-U services and / or F1 interface control plane (F1-C) services based on the BAP layer. In a control plane-user plane (CP-UP) separation scenario in a DC scenario, transmitting F1 interface services based on the BAP layer may include transmitting F1-U services based on the BAP layer, and F1-C services may be transmitted based on the RRC layer (i.e., F1-C services in RRC). In a non-CP-UP separation scenario in a DC scenario, transmitting F1 interface services based on the BAP layer may include transmitting F1-U services and F1-C services based on the BAP layer.

[0112]

[0124] When an RLF is detected on a backhaul link in a cell group configured to carry an F1 interface service based on the BAP, transmission of a first RLF indication is triggered. When an RLF is detected on backhaul links in all cell groups configured to carry an F1 interface service based on the BAP, the first RLF indication indicates that an RLF has occurred on a node-granularity link between the first node and the second node, i.e., indicates that an RLF has occurred across the entire backhaul link between the first node and the second node.

[0113]

[0125] In some cases, the occurrence of an RLF on a backhaul link in a cell group for transmitting F1-U services may be understood as the cell group for transmitting F1-U services failing. The occurrence of an RLF on a backhaul link in a cell group for transmitting F1-U services and link recovery being performed may be understood as the cell group for transmitting F1-U services failing and link recovery being performed. Link recovery in this embodiment of the present application may include fast recovery.

[0114]

[0126] For example, in the case of the IAB network communication system shown in FIG. 12 or FIG. 13, the first node in this embodiment of the present application may be IAB node 1 in FIG. 12 or FIG. 13, and the second node may be IAB node 2 in FIG. 12 or FIG. 13.

[0115]

[0127] The two cell groups may include an MCG and an SCG, the first node is served by the MCG and the SCG, and the child node of the first node is the second node. The communication method in the present application may include multiple different implementations. The multiple different implementations will be described below with reference to the accompanying drawings.

[0116]

[0128] Implementation 1: When the SCG is for transmitting an F1-U service, an RLF does not occur in the MCG, and an RLF occurs in the SCG, the first node sends first RLF indication information to the second node.

[0117]

[0129] Referring to Figure 14, implementation 1 of the radio link failure indication method in the present application will be described. Figure 14 is a flowchart of the radio link failure indication method according to the present application. As shown in Figure 14, the indication method may include the following steps:

[0130] S1401: A first node determines that a first trigger condition is satisfied, where the first trigger condition includes: an SCG is for transmitting an F1-U service, an RLF is not occurring in an MCG, and an RLF is occurring in an SCG.

[0118]

[0131] For example, the first node may be IAB node 1 in Figure 12, and the second node may be IAB node 2 in Figure 12. The MeNB configures the MCG of the first node, and the IAB Donor 1 configures the SCG of the first node.

[0119]

[0132] For example, the first node may be IAB node 1 in Figure 13, and the second node may be IAB node 2 in Figure 13. The gNB configures the MCG for the first node, and IAB Donor 1 configures the SCG for the first node. Alternatively, the gNB configures the SCG for the first node, and IAB Donor 1 configures the MCG for the first node.

[0120]

[0133] No RLF at the MCG means that no RLF occurs on the backhaul link of the MCG. RLF at the SCG means that RLF occurs on the backhaul link of the SCG, which may also be referred to as an SCG failure.

[0121]

[0134] The occurrence of an RLF in an SCG in the first trigger condition may specifically include: an RLF occurs in an SCG and link recovery is performed.

[0122]

[0135] In the first trigger condition, the SCG is for transmitting the F1-U service may specifically include the SCG is for transmitting the F1-U service based on the BAP, in other words, the F1-U service is transmitted in the SCG in an F1 over BAP transmission mode.

[0123]

[0136] S1402: The first node sends a first RLF indication to the second node.

[0124]

[0137] The first node having the dual connection sends a first RLF indication to the second node by determining that a first trigger condition is satisfied, and the first RLF indication may be a Type-2 RLF indication.

[0125]

[0138] The MCG may be used to carry F1-C services or may be used to transmit F1-U services.

[0126]

[0139] In this implementation, the MCG is only for transmitting F1-C services, and the first RLF indication information indicates that an RLF has occurred in a node-granular link between a first node and a second node. The occurrence of an RLF in a node-granular link means that the entire BH link between the first node and the second node is unavailable. The unavailability of the entire BH link between the first node and the second node specifically means that data packets of the second node cannot be transmitted via the first node.

[0127]

[0140] The first RLF indication information indicating that an RLF has occurred on a node granular link between the first node and the second node may include: The first RLF indication information indicates that an RLF has occurred on a node-granular link between the first node and the second node, and that link recovery is to be performed.

[0128]

[0141] In some embodiments, the second node receives a first RLF indication, the first RLF indication indicating that an RLF has occurred on a node granular link between the first node and the second node, or that an RLF has occurred on a node granular link between the first node and the second node and link recovery is to be performed, and the second node may trigger a cessation of transmitting data packets to the first node based on the first RLF indication.

[0129]

[0142] In another possible implementation, the MCG is also for transmitting F1-U services, and the first RLF indication information may include a first BAP address, a first routing ID, or a first path ID. The first routing ID may be formed by the first BAP address and the first path ID. The first node may determine the content included in the first RLF indication information based on various cases.

[0130]

[0143] If the first RLF indication information includes a first BAP address, a first routing ID, or a first path ID, different from indicating that the entire backhaul link between the first node and the second node is unavailable, the first data packet of the second node cannot be transmitted through the first node, wherein: the routing identifier carried in the first data packet is a first routing ID, or a route identifier within a routing identifier carried in the first data packet is the first route ID, or The BAP address in the routing identifier carried in the first data packet is the first BAP address.

[0131]

[0144] For example, the first node determines that all paths through the first node to the destination node are unavailable. The first RLF indication information may include a first BAP address, where the first BAP address is a BAP address of the destination node.

[0132]

[0145] For example, the first node determines that a route with a first route ID is unavailable for all routes through the first node to the destination node. The first RLF indication information may include the first route ID.

[0133]

[0146] For example, the first node determines that a route having a first routing ID is unavailable for all routes passing through the first node to the destination node, and the first RLF indication information may include the first routing ID.

[0134]

[0147] After receiving the first RLF indication information, the second node may skip sending the first data packet to the first node, in which case: the routing identifier carried in the first data packet is a first routing ID, or a route identifier within a routing identifier carried in the first data packet is the first route ID, or The BAP address in the routing identifier carried in the first data packet is the first BAP address. For example, the second node may trigger a rerouting operation of the data packet routed by the first node to skip transmitting the first data packet to the first node.

[0135]

[0148] In this embodiment, when the SCG is for transmitting F1-U services, and RLF does not occur in the MCG and RLF occurs in the SCG, the first node sends first RLF indication information to the second node to improve the stability and reliability of data transmission in the IAB network.

[0136] In the case of a CP-UP separation scenario in a DC scenario, if the cell group for transmitting F1-C services is an MCG and RLF occurs, and the cell group for transmitting F1-U services is an SCG and RLF does not occur, the first node does not immediately send the first RLF indication information to the second node based on the triggering method of the first RLF indication information. In this way, the impact on the normal operation of the SCG for transmitting F1-U services can be reduced. The second node can further continue routing data to the first node. This can reduce the problems of data packet stacking, link congestion, and excessively long latency of the second node.

[0137] Furthermore, when the cell group for transmitting the F1-U service is an SCG, and the RLF only occurs in the SCG, the first node sends first RLF indication information to the second node according to a triggering method of the first RLF indication information; The second node may trigger a cessation of sending data packets to the first node, or The second node can trigger a rerouting operation of the data packets routed by the first node, thus alleviating the problems of data packet stacking, link congestion, and excessively long latency of the first node.

[0138]

[0149] Implementation 2: When the MCG is for transmitting F1-U services, an RLF occurs in the MCG, and a link recovery is performed, the first node sends first RLF indication information to the second node.

[0139]

[0150] Referring to Figure 15, implementation 2 of the wireless link failure indication method in the present application will be described. Figure 15 is a flowchart of the wireless link failure indication method in the present application. As shown in Figure 15, the indication method may include the following steps:

[0151] S1501: A first node determines that a second trigger condition is satisfied, where the second trigger condition includes: an MCG is for transmitting an F1-U service, an RLF occurs in the MCG, and link recovery is performed.

[0140]

[0152] For example, the first node may be IAB node 1 in Figure 13, and the second node may be IAB node 2 in Figure 13. The gNB configures the MCG for the first node, and IAB Donor 1 configures the SCG for the first node. Alternatively, the gNB configures the SCG for the first node, and IAB Donor 1 configures the MCG for the first node.

[0141]

[0153] RLF occurring in the MCG means that RLF is occurring in the backhaul link of the SCG, which may also be referred to as an SCG failure.

[0142]

[0154] In the second triggering condition, the MCG is for transmitting the F1-U service, specifically, the MCG is for transmitting the F1-U service based on the BAP, in other words, the F1-U service is transmitted in the MCG in an F1 over BAP transmission mode.

[0143]

[0155] S1502: The first node sends a first RLF indication to the second node.

[0144]

[0156] The first node having the dual connection sends a second RLF indication to the second node by determining that the second trigger condition is satisfied. The first RLF indication may be a Type-2 RLF indication.

[0145]

[0157] The SCG may be used to carry F1-C services or may be used to transmit F1-U services.

[0146]

[0158] In this implementation, the SCG is only for transmitting F1-C services, and the first RLF indication information indicates that an RLF has occurred in a node-granular link between the first node and the second node, which means that the entire BH link between the first node and the second node is unavailable.

[0147]

[0159] The first RLF indication information indicating that an RLF has occurred on a node granular link between the first node and the second node may include: The first RLF indication information indicates that an RLF has occurred on a node-granular link between the first node and the second node, and that link recovery is to be performed.

[0148]

[0160] In some embodiments, the second node receives a first RLF indication, the first RLF indication indicating that an RLF has occurred on a node granular link between the first node and the second node, or that an RLF has occurred on a node granular link between the first node and the second node and link recovery is to be performed, and the second node may trigger a cessation of transmitting data packets to the first node based on the first RLF indication.

[0149]

[0161] In another possible implementation, the SCG is also for transmitting F1-U services, and no RLF occurs in the SCG. The first RLF indication information may include a first BAP address, a first routing ID, or a first path ID. The first routing ID may be formed by the first BAP address and the first path ID. The first node may determine the content included in the first RLF indication information based on various cases.

[0150]

[0162] For example, the first node determines that all paths through the first node to the destination node are unavailable. The first RLF indication information may include a first BAP address, where the first BAP address is a BAP address of the destination node.

[0151]

[0163] For example, the first node determines that a route with a first route ID is unavailable for all routes through the first node to the destination node. The first RLF indication information may include the first route ID.

[0152]

[0164] For example, the first node determines that a route having a first routing ID is unavailable for all routes through the first node to the destination node, and the first RLF indication information may include the first routing ID.

[0153]

[0165] After receiving the first RLF indication information, the second node may skip sending the first data packet to the first node, in which case: the routing identifier carried in the first data packet is a first routing ID, or a route identifier within a routing identifier carried in the first data packet is the first route ID, or The BAP address in the routing identifier carried in the first data packet is the first BAP address. For example, the second node may trigger a rerouting operation of the data packet routed by the first node to skip transmitting the first data packet to the first node.

[0154]

[0166] In this embodiment, the MCG is for transmitting F1-U services, and when an RLF occurs in the MCG and link recovery is performed, the first node sends a first RLF indication to the second node to improve the stability and reliability of data transmission in the IAB network. Compared with the case where an RLF indication is triggered when an RLF occurs in the MCG and fast recovery is not performed, in the present application, an RLF indication is triggered by using a second trigger condition, so that the second node can receive the indication in advance, thereby reducing the problems of data packet stacking, link congestion, and excessively long latency of the first node or the second node.

[0155]

[0167] In the case of a CP-UP separation scenario in a DC scenario, if the cell group for transmitting F1-C services is an MCG and RLF occurs, and the cell group for transmitting F1-U services is an SCG and RLF does not occur, the first node does not immediately send the first RLF indication information to the second node based on the triggering method of the first RLF indication information. In this way, the impact on the normal operation of the SCG for transmitting F1-U services can be reduced. The second node can further continue routing data to the first node. This can reduce the problems of data packet stacking, link congestion, and excessively long latency of the second node.

[0156]

[0168] In some embodiments, the first node may be configured with a first trigger condition and a second trigger condition and may send a first RLF indication to the second node if either the first trigger condition or the second trigger condition is satisfied.

[0157]

[0169] Implementations 1 and 2 of the radio link failure indication method in this application are applied to a CP-UP separation scenario in an EN-DC scenario of an IAB network shown in Figure 12. IAB node 1 in Figure 12 functions as a first node, and IAB node 2 in Figure 12 functions as a second node. The MeNB configures an MCG, and the IAB donor 1 configures an SCG, where the MCG is for transmitting F1-C services and the SCG is for transmitting F1-U services. For specific implementations, please refer to the description of the embodiment of the method shown in Figure 16.

[0158]

[0170] 16 is a flowchart of a wireless link failure indication method according to the present application. As shown in FIG. 16, the indication method may include the following steps:

[0159]

[0171] S1601: If IAB node 1 detects that RLF occurs in the MCG and that RLF does not occur in the SCG, the first IAB node does not send first RLF indication information to IAB node 2 during the first period.

[0160]

[0172] For example, FIG. 17A is a diagram of an RLF scenario according to the present application. As shown in FIG. 17A , in the RLF scenario, an RLF occurs in the backhaul link between IAB node 1 and MeNB. Specifically, an RLF occurs in the backhaul link of the MCG, but an RLF does not occur in the backhaul link between IAB node 1 and IAB donor 1. That is, an RLF does not occur in the backhaul link of the SCG. Therefore, the current RLF scenario does not satisfy the first or second trigger condition, and IAB node 1 does not immediately send a first RLF indication to IAB node 2. For example, IAB node 1 does not send a first RLF indication to IAB node 2 during a first period. The first period can be flexibly configured based on requirements.

[0161]

[0173] Therefore, when an RLF occurs on a link to the MeNB or an RLF occurs on an MCG for transmitting an F1-C service, the IAB node 1 does not immediately transmit the first RLF indication information to the IAB node 2. The link to the MeNB may be understood as a link where an LTE Uu interface is located, an LTE leg link, or a link to a non-F1 terminating node. The MCG for transmitting an F1-C service may include an MCG for transmitting an F1-C service based on an RRC protocol layer.

[0162]

[0174] S1602: IAB node 1 detects that an RLF has occurred in the SCG and an RLF has not occurred in the MCG, and IAB node 1 sends a first RLF indication information to IAB node 2.

[0163]

[0175] For example, Figure 17B is a diagram of an RLF scenario according to the present application. As shown in Figure 17B, in the RLF scenario, an RLF occurs in the backhaul link between IAB node 1 and IAB donor 1. Specifically, an RLF occurs in the backhaul link of the SCG, and an RLF does not occur in the backhaul link between IAB node 1 and MeNB. That is, an RLF does not occur in the backhaul link of the MCG. Therefore, the current RLF scenario satisfies the first trigger condition described above, and IAB node 1 sends a first RLF indication to IAB node 2.

[0164]

[0176] For a specific description of the first RLF indication information, please refer to the description of S1402 in Fig. 14. The details will not be described again here.

[0165]

[0177] In this embodiment, when the cell group transmitting the F1-C service is an MCG and an RLF occurs, and when the cell group transmitting the F1-U service is an SCG and an RLF does not occur, the first node does not immediately send the first RLF indication information to the second node based on the triggering method of the first RLF indication information. In this way, the impact on the normal operation of the SCG transmitting the F1-U service can be reduced. The second node can further continue to route data to the first node. This can reduce the problems of data packet stacking, link congestion, and excessively long latency of the second node.

[0166] When the cell group for transmitting the F1-U service is an SCG, and the RLF only occurs in the SCG, the first node sends first RLF indication information to the second node according to a triggering method of the first RLF indication information; The second node may trigger a cessation of sending data packets to the first node, or The second node can trigger a rerouting operation of the data packets routed by the first node, thus alleviating the problems of data packet stacking, link congestion, and excessively long latency of the first node.

[0167]

[0178] Implementation 1 and Implementation 2 of the radio link failure indication method in this application are applied to the NR-DC scenario of the IAB network shown in Figure 13. IAB node 1 in Figure 13 functions as the first node, and IAB node 2 in Figure 13 functions as the second node. The gNB configures the MCG, and IAB donor 1 configures the SCG. Alternatively, the gNB configures the SCG, and IAB donor 1 configures the MCG. This embodiment is described using an example in which the gNB configures the SCG, and IAB donor 1 configures the MCG. For specific implementation details, please refer to the description of the method embodiment shown in Figure 18.

[0168]

[0179] 18 is a flowchart of a wireless link failure indication method according to the present application. As shown in FIG. 18, the indication method may include the following steps:

[0169]

[0180] S1801: If IAB node 1 detects that the SCG is for transmitting F1-C services, and RLF occurs in the SCG, but RLF does not occur in the MCG, the first IAB node does not send first RLF indication information to IAB node 2 during the first period.

[0170]

[0181] For example, FIG. 19A is a diagram of an RLF scenario according to the present application. As shown in FIG. 19A , in the RLF scenario, an RLF occurs in the backhaul link between IAB node 1 and a gNB. Specifically, an RLF occurs in the backhaul link of the SCG, but an RLF does not occur in the backhaul link between IAB node 1 and IAB donor 1. That is, an RLF does not occur in the backhaul link of the MCG. Therefore, the current RLF scenario does not satisfy the first or second trigger condition, and IAB node 1 does not immediately transmit a first RLF indication to IAB node 2. For example, IAB node 1 does not transmit a first RLF indication to IAB node 2 during a first period. The first period can be flexibly configured based on requirements.

[0171]

[0182] Therefore, when an RLF occurs on a link to a non-F1 terminating node (e.g., a gNB here) or an RLF occurs in a CG for transmitting F1-C services (e.g., an SCG here), IAB node 1 does not immediately send the first RLF indication information to IAB node 2. The CG for transmitting F1-C services may include a CG configured to transmit F1-C services based on the RRC protocol layer.

[0172]

[0183] S1802: When IAB node 1 detects that the MCG is for transmitting F1-U service and an RLF occurs in the MCG and link recovery is performed, IAB node 1 sends first RLF indication information to IAB node 2.

[0173]

[0184] For example, Figure 19B is a diagram of an RLF scenario according to the present application. As shown in Figure 19B, in the RLF scenario, an RLF occurs in the backhaul link between IAB node 1 and IAB donor 1. That is, an RLF does not occur in the backhaul link of the MCG. Therefore, the current RLF scenario satisfies the second trigger condition described above, and IAB node 1 sends a first RLF indication to IAB node 2.

[0174]

[0185] For a specific description of the first RLF indication information, please refer to the description of S1502 in Fig. 15. The details will not be described again here.

[0175]

[0186] In this embodiment, when the cell group transmitting the F1-C service is an MCG and an RLF occurs, and when the cell group transmitting the F1-U service is an SCG and an RLF does not occur, the first node does not immediately send the first RLF indication information to the second node based on the triggering method of the first RLF indication information. In this way, the impact on the normal operation of the SCG transmitting the F1-U service can be reduced. The second node can further continue to route data to the first node. This helps to reduce the problems of data packet stacking, link congestion, and excessively long latency of the second node.

[0176] When the cell group for transmitting the F1-U service is an MCG, and an RLF occurs in the MCG and a link recovery is performed, the first node sends first RLF indication information to the second node according to a triggering method of the first RLF indication information; The second node may trigger a cessation of sending data packets to the first node, or The second node can trigger a rerouting operation of the data packets routed by the first node, thus alleviating the problems of data packet stacking, link congestion, and excessively long latency of the first node.

[0177]

[0187] In the above embodiment, the first node sends a first RLF indication to the second node by detecting a first trigger condition and / or a second trigger condition. Based on the first RLF indication, the second node can trigger to stop sending data packets to the first node or trigger a rerouting operation of the data packets routed by the first node to alleviate problems of data packet stacking, link congestion, and excessively long latency. Different from the above embodiment, the present application further provides the following radio link failure indication method: RLF link information or routing information is carried in the second RLF indication, so that the second node performs corresponding operations based on the RLF link information or routing information to alleviate problems of data packet stacking, link congestion, and excessively long latency.

[0178]

[0188] 20 is a flowchart of a radio link failure indication method according to an embodiment of the present application. Similar to the previous embodiment, a first node is served by an SCG and an MCG, and a second node is a child node of the first node. As shown in FIG. 20, the indication method may include the following steps:

[0179]

[0189] S2001: The first node sends a second RLF indication to the second node.

[0180]

[0190] For example, the first node may be IAB node 1 in Figure 12, and the second node may be IAB node 2 in Figure 12. The MeNB configures an MCG for the first node, and IAB Donor 1 configures an SCG for the first node.

[0181]

[0191] For example, the first node may be IAB node 1 in Figure 13, and the second node may be IAB node 2 in Figure 13. The gNB configures the MCG for the first node, and IAB Donor 1 configures the SCG for the first node. Alternatively, the gNB configures the SCG for the first node, and IAB Donor 1 configures the MCG for the first node.

[0182]

[0192] The second RLF indication information may be a Type-1 RLF indication, a Type-2 RLF indication, a Type-3 RLF indication, or a Type-4 RLF indication.

[0183]

[0193] A Type-1 RLF indication is an indication triggered when an RLF event is detected on a backhaul link. Specifically, when a first node discovers that an RLF event has occurred on a backhaul link, the first node sends a Type-1 RLF indication to a second node.

[0184] A Type-2 RLF indication is an indication triggered when an RLF occurs on a backhaul link and link recovery is detected. Specifically, when a first node detects that an RLF occurs on a backhaul link and prepares to perform link recovery, the first node sends a Type-2 RLF indication to a second node.

[0185] A Type-3 RLF indication is an indication triggered during link recovery. Specifically, when a link of a first node recovers, the first node sends a Type-3 RLF indication to a second node.

[0186] A Type-4 RLF indication is an indication triggered when a RLF occurs on a backhaul link and link recovery fails. Specifically, when a first node detects that an RLF occurs on a backhaul link, performs link recovery, and fails to recover, the first node sends a Type-4 RLF indication to a second node.

[0187]

[0194] In some implementations, the second RLF indication information may include RLF link information. The RLF link information may be backhaul link information to a non-F1 termination node, LTE-Uu interface link information (as in the aforementioned EN-DC scenario), backhaul link information for transmitting F1-C services, or cell group identifier information for transmitting F1-C services based on the RRC protocol layer. In the EN-DC scenario, the cell group identifier information for transmitting F1-C services based on the RRC protocol layer may be MCG identifier information for transmitting F1-C services based on the RRC protocol layer. In the NR-DC scenario, the cell group identifier information for transmitting F1-C services based on the RRC protocol layer may be MCG or SCG identifier information for transmitting F1-C services based on the RRC protocol layer.

[0188]

[0195] For example, if a first node detects the RLF scenario shown in FIG. 17A, the second RLF indication information sent by the first node to the second node may include RLF link information.

[0189]

[0196] In another possible implementation, the second RLF indication information may include routing information, which may include a first BAP address, a first routing ID, or a first path ID.

[0190]

[0197] For example, if a first node detects the RLF scenario shown in FIG. 17B, the second RLF indication information sent by the first node to the second node may include routing information.

[0191]

[0198] 2002: The second node does not trigger a scheduling stop and / or a rerouting operation of the upstream data packet based on the RLF link information, or the second node triggers a rerouting operation of the upstream data packet based on the routing information.

[0192]

[0199] For example, if the second RLF indication information received by the second node includes RLF link information, the second node does not trigger scheduling stop and / or rerouting operations of upstream data packets based on the RLF link information. Optionally, if the second RLF indication information is a Type-3 RLF indication, the second node does not stop rerouting of upstream data packets caused by an RLF occurring on another link.

[0193]

[0200] For example, if the second RLF indication information received by the second node includes routing information, the second node triggers a rerouting operation of the upstream data packet based on the routing information, for example, rewriting the BAP routing ID in the upstream data packet.

[0194]

[0201] In this embodiment, the first node sends second RLF indication information to the second node, and if the second RLF indication information includes RLF link information, the second node does not trigger scheduling stop and / or rerouting operations of upstream data packets based on the RLF link information, thereby alleviating problems of data packet stacking, link congestion, and excessively long latency of the second node caused by unnecessary RLF indications. If the second RLF indication information includes routing information, the second node triggers rerouting operations of upstream data packets based on the routing information, thereby alleviating problems of data packet stacking, link congestion, and excessively long latency of the first node.

[0195]

[0202] Based on the same technical concept as above, an embodiment of the present application provides a communication device. The communication device may be a first node or a second node in any possible design solution of the method of the above embodiment. The communication device includes at least one corresponding unit configured to perform a method step, process, or operation performed by the first node or the second node in the above communication method. The at least one unit may be arranged in one-to-one correspondence with the method step, process, or operation performed by the first node or the second node. These units may be implemented using a computer program, a hardware circuit, or a combination of a computer program and a hardware circuit.

[0196]

[0203] According to the foregoing method, FIG. 21 is a diagram of a communication device 2100 according to an embodiment of the present application.

[0197]

[0204] The device 2100 may be a relay forwarding node having access and backhaul functions, or may be a chip or circuit, for example a chip or circuit capable of being disposed in a relay forwarding node having access and backhaul functions.

[0198]

[0205] The apparatus 2100 may include a processing unit 2110 (eg, including a processor or a communication processor) and a transceiver unit 2130 .

[0199]

[0206] Optionally, the transceiver unit 2130 may be implemented using a transceiver, transceiver-related circuitry, or interface circuitry.

[0200]

[0207] In some embodiments, the apparatus 2100 is used as a first node, the first node being served by a first master cell group (MCG) and a first secondary cell group (SCG), a child node of the first node being a second node, and the processing unit 2110 is configured to: send RLF indication information to the second node via the transceiver unit when the first SCG is for carrying F1 interface user plane services, and when a radio link failure (RLF) has not occurred in the first MCG and an RLF has occurred in the first SCG.

[0201]

[0208] Optionally, the processing unit 2110 is configured to send RLF indication information to the second node via the transceiver unit 2130 when the first SCG is for carrying F1 interface user plane services, a radio link failure RLF has not occurred in the first MCG, and an RLF has occurred in the first SCG, including: the processing unit 2110 is configured to send RLF indication information to the second node via the transceiver unit 2130 when the first SCG is for carrying F1 interface user plane services, a radio link failure RLF has not occurred in the first MCG, an RLF has occurred in the first SCG, and link recovery is performed.

[0202]

[0209] Optionally, the first SCG is intended to carry F1 interface user plane services: The first SCG includes being configured to carry F1 interface user plane services based on a backhaul adaptation protocol (BAP) layer.

[0203]

[0210] Optionally, the first MCG is solely for carrying F1 interface control plane services, and the RLF indication information indicates that RLF is occurring on the node-granular link between the first node and the second node.

[0204]

[0211] Optionally, the RLF indication information may indicate that RLF is occurring on a node-granularity link between a first node and a second node: The RLF indication information indicates that an RLF has occurred on a node-granular link between a first node and a second node, and that link recovery is to be performed.

[0205]

[0212] Optionally, the first MCG is also for transmitting F1 interface user plane services, and the RLF indication information includes a first BAP address, a first routing identifier (routing ID), or a first path identifier (path ID).

[0206]

[0213] Optionally, the processing unit 2110 is configured to determine that all routes through the first node to the destination node are unavailable, and the RLF indication information includes a first BAP address, which is the BAP address of the destination node; the processing unit 2110 is configured to determine that all routes through the first node to the destination node are unavailable, and the RLF indication information includes a first route ID; or the processing unit 2110 is configured to determine that all routes through the first node to the destination node are unavailable, and the RLF indication information includes a first routing ID.

[0207]

[0214] In some embodiments, the apparatus 2100 is used as a first node, the first node being served by a first master cell group (MCG) and a first secondary cell group (SCG), a child node of the first node being a second node, and the processing unit 2110 is configured to: send RLF indication information to the second node via the transceiver unit 2130 when the first MCG is for transmitting F1 interface user plane services, a radio link failure (RLF) occurs in the first MCG, and link recovery is to be performed.

[0208]

[0215] Optionally, the first MCG is intended to carry F1 interface user plane services: The first MCG includes being configured to carry F1 interface user plane services based on a backhaul adaptation protocol (BAP) layer.

[0209]

[0216] Optionally, the first SCG is solely for carrying F1 interface control plane services, and the RLF indication information indicates that RLF is occurring on the node granular link between the first node and the second node.

[0210]

[0217] Optionally, the first SCG is also for carrying F1 interface user plane services, and no RLF occurs in the first SCG, and the RLF indication information includes a first BAP address, a first routing ID, or a first path ID.

[0211]

[0218] Optionally, the processing unit 2110 is configured to determine that all routes through the first node to the destination node are unavailable, and the RLF indication information includes a first BAP address, which is the BAP address of the destination node; the processing unit 2110 is configured to determine that all routes through the first node to the destination node are unavailable, and the RLF indication information includes a first route ID; or the processing unit 2110 is configured to determine that all routes through the first node to the destination node are unavailable, and the RLF indication information includes a first routing ID.

[0212]

[0219] The units in the above embodiments may be called modules, circuits, or components.

[0213]

[0220] For the concept, description, detailed description and other steps of the device 2100 related to the technical solutions provided in the embodiments of the present application, please refer to the description of the content of the aforementioned method or other embodiments, and the details will not be described again here.

[0214]

[0221] FIG. 22 is a structural diagram of a communication device 2200 according to an embodiment of the present application. The communication device 2200 may be configured to implement the functionality of a relay node (e.g., a first node) having access and backhaul functions in the aforementioned method. As shown in FIG. 22, the communication device 2200 includes one or more processors 2201 and optionally further includes an interface 2202. When associated program instructions are executed in the at least one processor 2201, the device 2200 can realize the radio link failure indication method and any possible design of the radio link failure indication method provided in any of the aforementioned embodiments. Alternatively, the processor 2201 is configured to realize the radio link failure indication method and any possible design of the radio link failure indication method provided in any of the aforementioned embodiments using logic circuits or by executing code instructions. The interface 2202 may be configured to receive and transmit program instructions to the processor, or may be used by the device 2200 to communicate and interact with another communication device, for example, to exchange control signaling and / or service data. For example, the interface 2202 may be configured to receive and transmit signals from a device other than the device 2200 to the processor 2201, or to transmit signals from the processor 2201 to a communication device other than the device 2200. The interface 2202 may be a code and / or data read / write interface circuit, or may be a signal transmission interface circuit or chip pin between a communication processor and a transceiver. Optionally, the communication device 2200 may further include at least one memory 2203, which may be configured to store relevant program instructions and / or data as needed. Optionally, the device 2200 may further include a power supply circuit 2204. The power supply circuit 2204 can be configured to provide power to the processor 2201 .The power supply circuit 2204 and the processor 2201 may be located on the same chip, or the power supply circuit 2204 may be located on a chip separate from the chip on which the processor 2201 is located. Optionally, the device 2200 may further include a bus 2205, and parts within the device 2200 may be interconnected via the bus 2205.

[0215]

[0222] It should be understood that the processor in embodiments of the present application may be a central processing unit (CPU), or the processor may be another general-purpose processor, a digital signal processor (DSP), an application-specific integrated circuit (ASIC), a field programmable gate array (FPGA) or other programmable logic device, a discrete gate or transistor logic device, a discrete hardware component, etc. The general-purpose processor may be a microprocessor, or the processor may be any conventional processor, etc.

[0216]

[0223] It should be further understood that the memory in the embodiments of the present application may be volatile or nonvolatile, or may include both volatile and nonvolatile memory. Nonvolatile memory may be read-only memory (ROM), programmable read-only memory (PROM), erasable programmable read-only memory (EPROM), electrically erasable programmable read-only memory (EEPROM), or flash memory. Volatile memory may be random access memory (RAM) used as an external cache. By way of example, and not limitation, many forms of random access memory (RAM) are available, such as static random access memory (SRAM), dynamic random access memory (DRAM), synchronous dynamic random access memory (SDRAM), double data rate synchronous dynamic random access memory (DDR SDRAM), enhanced synchronous dynamic random access memory (ESDRAM), synchronous link dynamic random access memory (synchlink DRAM, SLDRAM), or direct Rambus random access memory (DR RAM).

[0217]

[0224] The power supply circuit in the embodiments of the present application includes, but is not limited to, at least one of a power supply line, a power subsystem, a power management chip, a power consumption management processor, or a power consumption management control circuit.

[0218]

[0225] The transceiver device, interface, or transceiver in the embodiments of the present application may include a separate transmitter and / or a separate receiver, or the transmitter and receiver may be integrated. The transceiver device, interface, or transceiver may operate under the direction of a corresponding processor. Optionally, the transmitter may correspond to a transmitter machine in a physical device, and the receiver may correspond to a receiver machine in a physical device.

[0219]

[0226] It will be clearly understood by those skilled in the art that for convenience and concise description, the division of the above functional modules is used as an example for explanation. In actual applications, the above functions can be allocated and implemented in various functional modules according to requirements, that is, the internal structure of the device is divided into various functional modules to implement all or part of the above functions. For detailed operation processes of the above systems, devices, and units, please refer to the corresponding processes in the above method embodiments. The details will not be described again here.

[0220]

[0227] In the embodiments of the present application, it should be understood that the disclosed system, device, and method may be implemented in other ways. For example, the described device embodiment is merely an example. For example, the division into multiple modules or units is merely a logical division of functions, and other divisions may be used in actual implementation. For example, multiple units or components may be combined or integrated into another system, and some functions may be ignored or not performed. Furthermore, the illustrated or described mutual couplings or direct couplings or communication connections may be implemented via some interface. Indirect couplings or communication connections between devices or units may be implemented electrically, mechanically, or in other forms.

[0221]

[0228] Those skilled in the art will recognize that in combination with the examples described in the embodiments disclosed herein, the unit or algorithm processing may be implemented by hardware, software, or a combination of software and hardware. Whether a function is performed by hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art may use various methods to implement the described functions for each specific application, but such implementation should not be considered to go beyond the scope of the present application.

[0222]

[0229] In this application, "implemented by software" may mean that a processor reads and executes program instructions stored in a memory to realize the functions corresponding to the aforementioned modules or units. A processor is a processing circuit capable of executing program instructions, including, but not limited to, at least one of the following types of processing circuits capable of executing program instructions: a central processing unit (CPU), a microprocessor, a digital signal processor (DSP), a microcontroller unit (MCU), or an artificial intelligence processor. In some other embodiments, the processor may further include circuits having other processing functions (e.g., hardware circuits used for hardware acceleration, buses, and interface circuits). The processor may be provided in the form of an integrated chip. For example, the processor may be provided in the form of an integrated chip whose processing function only includes the function of executing software instructions; or the processor may be provided in the form of a system-on-a-chip (SoC). Specifically, in a chip, in addition to a processing circuit (usually called a "core") capable of executing program instructions, another hardware circuit configured to perform a specific function is further included (of course, the hardware circuit may be implemented independently based on an ASIC or FPGA). Accordingly, the processing function may further include various hardware acceleration functions (such as AI calculations, encoding and decoding, compression and decompression, etc.) in addition to the function of executing software instructions.

[0223]

[0230] In this application, "implemented by hardware" means that the functions of the aforementioned modules or units are implemented by a hardware processing circuit that does not have the function of processing program instructions. The hardware processing circuit may include discrete hardware components or may be an integrated circuit. To reduce power consumption and size, integrated circuits are usually used for implementation. The hardware processing circuit may include an ASIC or a programmable logic device (PLD). A PLD may further include an FPGA, a complex programmable logic device (CPLD), etc. These hardware processing circuits may be independently packaged semiconductor chips (e.g., packaged in an ASIC) or may be integrated with other circuits (such as a CPU or DSP) and then packaged in a semiconductor chip. For example, multiple hardware circuits and a CPU may be formed on a single silicon base and packaged separately into a chip, in which case the chip may also be called an SoC; or, circuits configured to implement FPGA functionality and a CPU may be formed on a silicon base and packaged separately into a chip, in which case the chip may also be called a system-on-a-programmable-chip (SoPC).

[0224]

[0231] When the present application is implemented using software, hardware, or a combination of software and hardware, the present application may be implemented by using various software and hardware and is not limited to only one type of software or hardware. For example, one of the modules or units may be implemented by a CPU, and another module or unit may be implemented by a DSP. Similarly, when hardware is used for implementation, one of the modules or units may be implemented by an ASIC, and another module or unit may be implemented by an FPGA. Of course, some or all of the modules or units are not limited to being implemented by using the same type of software (e.g., via a CPU) or the same type of hardware (e.g., via an ASIC). Furthermore, those skilled in the art will know that software is usually more flexible but has lower performance than hardware, and the opposite is true for hardware. Therefore, those skilled in the art can select software, hardware, or a combination thereof for implementation based on actual requirements.

[0225]

[0232] In the above embodiments, the description of each embodiment has its own focus. For parts not described in detail in an embodiment, reference can be made to the relevant descriptions of other embodiments. The embodiments of the present application can be combined, or some technical features of the embodiments can be separated from a specific embodiment or combined with prior art to solve the technical problems in the embodiments of the present application.

[0226]

[0233] In the embodiments of the present application, units described as separate components may or may not be physically separate, and components illustrated as units may or may not be physical units, and may be located in one place or distributed across multiple network units. Some or all of the units may be selected according to actual requirements to achieve the objectives of the solutions of the embodiments of the present application.

[0227]

[0234] Furthermore, the functional units in the embodiments of the present application may be integrated into one processing unit, each unit may exist physically independently, or two or more units may be integrated into one unit. The integrated unit may be implemented in the form of hardware or in the form of a software functional unit.

[0228]

[0235] If the integrated unit is implemented in the form of a software functional unit and sold or used as an independent product, the integrated unit may be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present application may essentially, or a portion that contributes to the prior art, or all or part of the technical solution may be embodied in the form of a software product. A computer software product may be stored in a storage medium and include several instructions for instructing a computer device, such as a personal computer, server, or network device, or a processor, to perform all or part of the operations of the methods described in the embodiments of the present application. The storage medium may include any medium or computer-readable storage medium capable of storing program code, such as a USB flash drive, a removable hard disk, a read-only memory (ROM), a random access memory (RAM), a magnetic disk, or an optical disk.

[0229]

[0236] In the description of this application, terms such as "first", "second", "S101", "S102", etc. are used merely for the purpose of distinction and explanation, and to facilitate the organization of this document. Different sequences or numbers do not have any specific technical meaning and cannot be understood as indicating or implying relative importance or the execution sequence of operations.

[0230]

[0237] The term "and / or" in this application only describes the associative relationship of related objects and indicates that three relationships may exist. For example, "A and / or B" may indicate three cases: only A exists; or both A and B exist; or only B exists. A and B may be singular or plural. Furthermore, the character " / " in this specification indicates an "or" relationship between related objects.

[0231]

[0238] In this application, "transmission" may include three cases: data transmission, data reception, or data transmission and data reception. In this application, "data" may include service data and / or signaling data.

[0232]

[0239] In this application, the terms "comprises" or "having" and any variations thereof are intended to cover a non-exclusive inclusion. For example, a process / method including a series of steps or a system / product / device including a series of units is not necessarily limited to the explicitly listed steps or units, but may include other steps or units not explicitly listed or inherent to those processes / methods / products / devices.

[0233]

[0240] In the description of this application, unless otherwise specified, noun quantities refer to "singular or plural," i.e., "one or more." "At least one" refers to one or more. "Comprising at least one of A, B, and C" may refer to including A, including B, including C, including A and B, including A and C, including B and C, or including A, B, and C, where A, B, and C may be singular or plural.

[0234]

[0241] The above description is only a specific implementation of the present application and is not intended to limit the scope of protection of the present application. Any modifications or replacements that can be easily understood by those skilled in the art within the technical scope disclosed in the present application shall be included in the scope of protection of the present application.

Claims

1. 1. A method of communication, wherein a first node is served by a first master cell group (MCG) and a first secondary cell group (SCG), the method comprising: the first SCG is for transmitting an F1 interface user plane service, and when a radio link failure (RLF) does not occur in the first MCG and an RLF occurs in the first SCG, the first node sends an RLF indication information to a second node, the second node being a child node of the first node; wherein the first node transmitting RLF indication information to the second node includes the first node determining that a path through the first node to a destination node is unavailable.

2. 2. The method of claim 1, wherein the first SCG is for transmitting an F1 interface user plane service, and when a radio link failure (RLF) does not occur in the first MCG and an RLF occurs in the first SCG, the step of the first node sending an RLF indication information to a second node comprises: When the first SCG is for transmitting an F1 interface user plane service, a radio link failure (RLF) does not occur in the first MCG, an RLF occurs in the first SCG, and link recovery is performed, the first node sends an RLF indication information to the second node; A method comprising:

3. 2. The method of claim 1, wherein the first SCG is for transmitting F1 interface user plane services, comprising: The method includes the first SCG being for transmitting the F1 interface user plane service based on a Backhaul Adaptation Protocol (BAP) layer.

4. 2. The method of claim 1, wherein the first MCG is only for carrying F1 interface control plane services, and the RLF indication information indicates that RLF is occurring on a node granular link between the first node and the second node.

5. 5. The method of claim 4, wherein the RLF indication information indicates that RLF is occurring on a node granular link between the first node and the second node by: The method, wherein the RLF indication information indicates that an RLF has occurred on a node-granular link between the first node and the second node and that link recovery is to be performed.

6. 2. The method of claim 1, wherein the first MCG is also for transmitting the F1 interface user plane service, and the RLF indication information includes a first BAP address, a first routing identifier (ID), or a first path identifier (path ID).

7. 7. The method of claim 6, wherein the step of determining by the first node that a path through the first node to a destination node is unavailable comprises: determining by the first node that all paths through the first node to a destination node are unavailable, the RLF indication information including the first BAP address, the first BAP address being a BAP address of the destination node; determining by the first node that a route having the first route ID is unavailable among all routes passing through the first node to a destination node, the RLF indication information including the first route ID; or determining by the first node that a route having the first routing ID is unavailable in all routes passing through the first node to a destination node, the RLF indication information including the first routing ID; A method comprising:

8. 1. A method of communication, wherein a first node is served by a first master cell group (MCG) and a first secondary cell group (SCG), the method comprising: the first MCG is for transmitting an F1 interface user plane service, and when a radio link failure (RLF) occurs in the first MCG and link recovery is performed, the first node sends an RLF indication information to a second node, the second node being a child node of the first node; wherein the first node transmitting RLF indication information to the second node includes the first node determining that a path through the first node to a destination node is unavailable.

9. 9. The method of claim 8, wherein the first MCG is for transmitting an F1 interface user plane service, comprising: The method includes the first MCG being for transmitting the F1 interface user plane service based on a Backhaul Adaptation Protocol (BAP) layer.

10. 9. The method of claim 8, wherein the first SCG is only for carrying F1 interface control plane services, and the RLF indication information indicates that RLF is occurring on a node granular link between the first node and the second node.

11. 9. The method of claim 8, wherein the first SCG is also for carrying the F1 interface user plane service, no RLF occurs in the first SCG, and the RLF indication information includes a first BAP address, a first routing identifier (ID), or a first path identifier (path ID).

12. 12. The method of claim 11, wherein the step of determining by the first node that a path through the first node to a destination node is unavailable comprises: determining by the first node that all paths through the first node to a destination node are unavailable, the RLF indication information including the first BAP address, the first BAP address being a BAP address of the destination node; determining by the first node that a route having the first route ID is unavailable among all routes passing through the first node to a destination node, the RLF indication information including the first route ID; or determining by the first node that a route having the first routing ID is unavailable in all routes passing through the first node to a destination node, the RLF indication information including the first routing ID; A method comprising:

13. 13. A communications device comprising at least one processor and an interface, wherein the at least one processor is configured to call instructions from the interface and execute the instructions, and wherein execution of the instructions by the at least one processor performs the method of any one of claims 1 to 12.

14. 13. A computer-readable storage medium containing computer instructions that, when executed on a first node, enable the first node to perform the method of any one of claims 1 to 12.

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