Route Adaptation in Multi-hop Relay Networks

Abstract

Systems, methods, and apparatus for recovering from backhaul failures in an integrated access and backhaul (IAB) communication system with multi-hop routing.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This patent application claims the benefit of U.S. Provisional Patent Application No. 62 / 739,065, filed September 28, 2018, which is hereby incorporated by reference in its entirety. Technical Field

[0003] The present application relates generally to wireless communication systems, and more particularly to integrated access and backhaul (IAB). Background Art

[0004] Wireless mobile communication technologies use various standards and protocols to transmit data between base stations and wireless mobile devices. Wireless communication system standards and protocols may include: the Third Generation Partnership Project (3GPP) Long Term Evolution (LTE); the Institute of Electrical and Electronics Engineers (IEEE) 802.16 standard, commonly referred to by industry organizations as Worldwide Interoperability for Microwave Access (WiMAX); and the IEEE 802.11 standard for wireless local area networks (WLANs), commonly referred to by industry organizations as Wi-Fi. In the 3GPP radio access network (RAN) in an LTE system, a base station may include a RAN node such as an Evolved Universal Terrestrial Radio Access Network (E-UTRAN) Node B (also commonly referred to as an evolved Node B, enhanced Node B, eNodeB, or eNB) and / or a radio network controller (RNC) in the E-UTRAN, which communicates with wireless communication devices called user equipment (UE). In the fifth generation (5G) wireless RAN, RAN nodes may include 5G nodes, new radio (NR) nodes, or gNode Bs (gNBs). BRIEF DESCRIPTION OF THE DRAWINGS

[0005] Figure 1 An exemplary IAB network is shown.

[0006] Figure 2 An exemplary protocol architecture for IAB is shown.

[0007] Figure 3 An exemplary IAB network configured according to one embodiment is schematically illustrated.

[0008] Figure 4 According to one embodiment, Figure 3 Additional details of a portion of the IAB network are shown.

[0009] Figure 5 is a flow chart of a method for timer-based sequencing according to one embodiment.

[0010] Figure 6A system according to one embodiment is shown.

[0011] Figure 7 An NG-RAN architecture according to one embodiment is shown.

[0012] Figure 8 An apparatus according to one embodiment is shown.

[0013] Figure 9 An exemplary interface according to one embodiment is shown.

[0014] Figure 10 Components according to one embodiment are shown. DETAILED DESCRIPTION

[0015] Integrated Access and Backhaul (IAB) is a feature designed in 3GPP to enable multi-hop routing. IAB nodes act as both access nodes for connecting UEs and provide backhaul links to other IAB nodes. The implementation presented here enables the system to recover from backhaul failures while providing a topologically valid network with configured routing.

[0016] Exemplary IAB Network Architecture

[0017] By way of example, Figure 1 An exemplary IAB network 100 according to certain embodiments is shown. The exemplary IAB network 100 includes a core network (shown as CN 102), an IAB donor node (shown as IAB donor 104), a plurality of IAB nodes (shown as five IAB nodes, namely IAB node 116, IAB node 118, IAB node 120, IAB node 124, and IAB node 126), and a plurality of UEs (shown as three UEs, namely UE 122, UE 128, and UE 130). The IAB donor 104 may include a centralized unit-control plane (CU-CP, shown as CU-CP 106), a centralized unit-user plane (CU-UP, shown as CU-UP 108), one or more distributed units (DUs, shown as two DUs, namely DU 110 and DU 112), and other functions 114. Components within IAB donor 104 may connect to each other and to CN 102 using wired IP links (wired links), while wireless backhaul links (e.g., wireless backhaul link 132, wireless backhaul link 134, and wireless backhaul link 136) are used for IAB nodes to communicate with each other, with UEs, and with IAB donor 104.

[0018] Each IAB node is a network node in an IAB deployment that has (at least a portion of) the functionality of a UE and a gNB unit. As shown, some IAB nodes access other IAB nodes, while some IAB nodes access an IAB donor 104. An IAB donor node (or IAB donor, also referred to as an "anchor node," etc.) is a network node in an IAB deployment that terminates the NG interface via a wired connection. The IAB donor can be a RAN node that provides a UE interface to the core network (shown as 5GC 102) and wireless backhaul functionality to the IAB node. An IAB node is a relay node and / or RAN node that supports wireless access to UEs and wireless backhaul access traffic.

[0019] The IAB nodes in the IAB network support the attachment of UEs and other IAB nodes. However, the IAB nodes do not have full-function base station (gNB) capabilities. The IAB network utilizes a CU-DU split architecture. The radio resource control (RRC) function is placed in the CU (e.g., CU-CP 106 and / or CU-UP 108) of the IAB donor 104. Each IAB node can act as a DU. The IAB node is controlled by the IAB donor 104 in a manner similar to the way the CU controls the DU. Specifically, the F1 control plane protocol between the CU and the DU is modified to support transmission over multiple hops; the modified F1 protocol enables the IAB donor 104 to control the IAB node.

[0020] The backhaul link not only carries data for UEs attached to an IAB node and its descendant IAB nodes, but also supports the control plane connection between the IAB node and the IAB donor 104. Unlike traditional fixed backhaul links, IAB backhaul links are subject to various impairments that can render the link unusable. For example, if millimeter wave spectrum is used, the backhaul link can be blocked by structures or moving objects (such as the media). Even seasonal changes in foliage can cause signal obstruction. The impact of a backhaul link failure on an IAB network can be much more significant than a link failure between a base station and a UE. This is because not only do all UEs connected to the IAB node experiencing the backhaul failure lose connectivity, but all descendant IAB nodes connected via the IAB node, as well as UEs connected to the descendant IAB nodes, also lose connectivity. Therefore, when backhaul failures do occur, even in a well-designed network where backhaul failures are rare, their impact can be severe. This loss of connectivity assumes the existence of a single route from the IAB node to the IAB donor. Based on appropriate standardization, configurations are possible where an IAB node supports "multi-connectivity" and has routes to the IAB donor via more than one parent node. However, ensuring that there are dual or multiple parent nodes for each IAB node can be extremely difficult.Even for IAB nodes with dual or multiple connections, the loss of one route can severely impact performance, so establishing alternative routes can be very useful.

[0021] Given that such backhaul failures may occur, embodiments herein define schemes for identifying alternative routes.Certain embodiments provide for fast and efficient recovery from backhaul failures, which provides useful functionality in IAB networks.

[0022] Exemplary control plane protocol architecture for multi-hop IAB networks

[0023] Figure 2 An exemplary protocol architecture for IAB 200 according to one embodiment is shown. Specifically, Figure 2 An exemplary protocol architecture for an RRC connection between a UE 202 and an IAB donor 208 is shown. The exemplary protocol architecture for the IAB 200 illustrates various protocol layers of the UE 202, a first IAB node 204 (IAB Node 1), a second IAB node 206 (IAB Node 2), and the IAB donor 208. The various layers may correspond to mobile terminal (MT), distributed unit (DU), or centralized unit (CU)-user plane (UP) entities. The DU and CU-CP of the IAB donor 208 may communicate via an intra-donor F1-C interface. In this example, the UE 202 wirelessly communicates with the second IAB node 206 via the UE's signaling radio bearer (SRB), and the second IAB node 206 wirelessly relays uplink traffic to the first IAB node 204 via a backhaul (BH) radio link control (RLC) channel. The protocol layers include, for example, RLC, Packet Data Convergence Protocol (PDCP), RRC, Stream Control Transmission Protocol (SCTP), Datagram Transport Layer Security (DTLS), Internet Protocol (IP), and F1 Application Protocol (F1-AP).

[0024] The exemplary protocol architecture for IAB 200 also includes a Backhaul Adaptation Protocol (BAP) layer, which may also be referred to as an "adaptation" layer (or simply, the adaptation layer). The BAP layer provides functionality for routing data through the network using different routes for different UE bearers. This is accomplished by including an adaptation layer header that includes information identifying the bearer. This routing includes mapping incoming data to outgoing links based on the bearer identifier.

[0025] Each IAB node operates as a combination of DU (serving the next hop) and MT (providing connectivity with the parent node). The Mobile Terminal (MT) of an IAB node embodies the UE functionality that enables connectivity with the parent node.

[0026] Figure 3An exemplary IAB network 300 configured according to certain embodiments is schematically illustrated. The IAB network 300 includes an IAB donor 302, a first IAB node 304 (IAB Node 1), a second IAB node 306 (IAB Node 2), a third IAB node 308 (IAB Node 3), a fourth IAB node 310 (IAB Node 4), a fifth IAB node 312 (IAB Node 5), a sixth IAB node 314 (IAB Node 6), a seventh IAB node 316 (IAB Node 7), and an eighth IAB node 318 (IAB Node 8). Each of the IAB nodes may include an MT and a DU (e.g., see Figure 4 ).

[0027] An IAB node can receive uplink traffic from a descendant or child relay node (or from a UE) and provide the uplink traffic to a parent relay node. Uplink traffic from six UEs (a first UE 320 (UE1), a second UE 322 (UE2), a third UE 324 (UE3), a fourth UE 326 (UE4), a fifth UE 328 (UE5), and a sixth UE 330 (UE6)) is routed through the exemplary IAB network 300. Both uplink and downlink traffic flows along the established links.

[0028] Different UEs are configured with different routes to the IAB donor 302. For example, the route from the IAB donor 302 to the first IAB node 304 to the fourth IAB node 310 to the sixth IAB node 314 to the eighth IAB node 318 serves the fourth UE 326, the fifth UE 328, and the sixth UE 330. For another example, the route from the IAB donor 302 to the second IAB node 306 to the fifth IAB node 312 serves the third UE 324.

[0029] If the link between an IAB node and its parent node fails, the MT for that IAB node may follow standard NR UE procedures when a radio link problem is detected. If the radio link problem is not resolved within a predetermined time period, the MT may declare a radio link failure (RLF). The MT then attempts to identify an alternative node to connect to, which may involve performing signal measurements of candidate nodes and identifying a suitable candidate node.

[0030] However, MT may not be able to identify suitable candidate nodes. Figure 3In the example shown, a link 332 between the first IAB node 304 and the fourth IAB node 310 fails. Due to signal blockage 334, the fourth IAB node 310 cannot connect to the third IAB node 308, and the signal quality from the second IAB node 306 and the seventh IAB node 316 is not good enough. Therefore, the fourth IAB node 310 cannot find an alternative parent node, and this makes the fourth IAB node 310, the sixth IAB node 314, the eighth IAB node 318, the second UE 322, the fourth UE 326, the fifth UE 328, and the sixth UE 330 inaccessible.

[0031] In this case, sixth IAB node 314, eighth IAB node 318, second UE 322, fourth UE 326, fifth UE 328, and sixth UE 330 may independently attempt to identify their own alternative routes to IAB donor 302. Having a well-defined process to accomplish this is helpful. Specifically, if all newly disconnected nodes and UEs are notified of the backhaul failure along that route, they may independently attempt to simultaneously identify alternative connection points. This can lead to topologically inefficient, or even unhelpful, arrangements.

[0032] For example, the second UE 322 may attempt to connect to the fourth IAB node 310, which does not resolve the issue. The eighth IAB node 318 may connect to the seventh IAB node 316, which will replace the seventh IAB node 316 as the parent node of the eighth IAB node 318. Then, if the sixth IAB node 314 is also connected to the seventh IAB node 316, the eighth IAB node 318 may receive better service (better signal quality and throughput) when connected to the sixth IAB node 314. Therefore, for efficiency reasons, the eighth IAB node 318 may need to switch its backhaul link back to the sixth IAB node 314. In addition, the fourth UE 326, the fifth UE 328, and the sixth UE 330 may identify other parent nodes and switch their access links. At the same time, the sixth IAB node 314 may be able to reestablish a connection through the seventh IAB node 316. Moreover, identifying a parent IAB node does not guarantee that the IAB node can support the necessary traffic requirements.

[0033] Thus, various embodiments are disclosed herein for quickly and efficiently recovering from backhaul failures.

[0034] Sequencing the RLF recovery process

[0035] In one embodiment, the following sequence provides a systematic and clear recovery from a backhaul failure. Specifically, when the fourth IAB node 310 experiences a radio link problem and declares a radio link failure (RLF), the fourth IAB node 310 attempts to identify an alternative parent node. Among the near-side nodes, the signal from the third IAB node 308 is blocked, and the signals from the second IAB node 306 and the seventh IAB node 316 are too weak. Therefore, the fourth IAB node 310 is unable to find an alternative parent node.

[0036] In response to being unable to find an alternative parent node, the fourth IAB node 310 sends a "Backhaul RLF" indication to all direct descendant nodes (i.e., nodes attached to the DU of the fourth IAB node 310) and all UEs attached to the fourth IAB node 310 (if any). This indication identifies the node that has not yet been able to identify the alternative parent node (i.e., the fourth IAB node 310). In this example, the sixth IAB node 314 receives the Backhaul RLF indication and, in response, attempts to identify an alternative parent node. The sixth IAB node 314 explicitly does not consider the fourth IAB node 310 as a candidate node for recovery.

[0037] If the sixth IAB node 314 attaches to the seventh IAB node 316 and restores its connection, routes to the second UE 322 , the fourth UE 326 , the fifth UE 328 , and the sixth UE 330 are reestablished through the seventh IAB node 316 , the sixth IAB node 314 , and the eighth IAB node 318 .

[0038] However, if the sixth IAB node 314 is unable to identify an alternative parent node, the sixth IAB node 314 sends a backhaul RLF indication to the eighth IAB node 318 and the second UE 322. This indication identifies the fourth IAB node 310 and the sixth IAB node 314 as nodes that have not yet been able to identify an alternative parent node. In response, the second UE 322 searches for alternative access nodes and explicitly avoids considering the sixth IAB node 314 and the fourth IAB node 310 as candidate nodes. In this example, the second UE 322 identifies the third IAB node 308 as a suitable candidate node and attaches to it. The network then updates the route to the second UE 322 accordingly.

[0039] The eighth IAB node 318 also attempts to perform a search for an alternative parent node and explicitly avoids considering the sixth IAB node 314 and the fourth IAB node 310 as candidate nodes. The eighth IAB node 318 identifies the seventh IAB node 316 as a suitable candidate node and attaches to the seventh IAB node 316. The network then updates the routes to the fourth UE 326, the fifth UE 328, and the sixth UE 330 accordingly.

[0040] Similarly, if the eighth IAB node 318 also fails to identify a suitable parent node, the eighth IAB node 318 sends an RLF indication to the fourth UE 326, the fifth UE 328, and the sixth UE 330, which enables the fourth UE, the fifth UE, and the sixth UE to identify an alternative access node (while explicitly avoiding the fourth IAB node 310, the sixth IAB node 314, and the eighth IAB node 318).

[0041] Example Return RLF Message

[0042] In one embodiment, a backhaul RLF indication is sent from an IAB node to its direct descendant IAB nodes and UEs attached to the IAB node. The backhaul RLF indication may be a broadcast downstream message, i.e., it is transmitted on all downstream outbound links from the node. For example, Figure 4 According to one embodiment, Figure 3 Additional details 400 of a portion of the IAB network 300 are shown. When an IAB node's MT declares an RLF, the IAB node attempts to identify an alternative parent node. If the search fails, the MT indicates to the IAB node's DU that a backhaul RLF indication is required. The DU transmits the backhaul RLF indication to all nodes and UEs attached to the DU.

[0043] In response to receiving the backhaul RLF indication, the MT or UE searches for a suitable parent node or access node, while excluding nodes for which an alternative parent node was indicated as not being found in the backhaul RLF. If successful, the MT or UE performs a handover of its backhaul or access link and transmits a request to the identified node to reestablish a connection and establish an alternative route.

[0044] For example, reference Figure 3 and Figure 4 When the fourth IAB node 310 experiences a radio link problem and declares a radio link failure (RLF) on link 332, the MT of the fourth IAB node 310 performs a candidate parent search 402 to identify an alternative parent node. Among the near-side nodes, the signal from the third IAB node 308 is blocked, and the signals from the second IAB node 306 and the seventh IAB node 316 are too weak. Therefore, the candidate parent search 402 fails, and the fourth IAB node 310 cannot find an alternative parent node.

[0045] In response to being unable to find an alternative parent node, the MT of the fourth IAB node 310 sends a signal to the DU of the fourth IAB node 310 to trigger a return RLF indication. The DU of the fourth IAB node 310 sends a return RLF indication to the MT of the sixth IAB node 314. In response, the MT of the sixth IAB node 314 performs a candidate parent search 404 to attempt to identify an alternative parent node. The candidate parent search 404 explicitly does not consider the fourth IAB node 310 as a candidate node for recovery.

[0046] exist Figure 4 In the example shown, candidate parent search 404 fails, and the mobile operator (MT) of the sixth IAB node 314 is unable to identify an alternative parent node. Therefore, the MT of the sixth IAB node 314 signals the DU of the sixth IAB node 314 to initiate a backhaul RLF indication. The DU of the sixth IAB node 314 then sends a backhaul RLF indication to the MT of the eighth IAB node 318 and to the second UE 322. This indication identifies the fourth IAB node 310 and the sixth IAB node 314 as nodes that have not yet identified an alternative parent node. In response, the second UE 322 performs a candidate access node search 406, which explicitly avoids the sixth IAB node 314 and the fourth IAB node 310 as candidate nodes. In this example, candidate access node search 406 succeeds, and the second UE 322 identifies the third IAB node 308 as a suitable candidate node. It then sends a request to the DU of the third IAB node 308 to reestablish a connection and reroute the second UE 322 to the IAB donor 302. The network then updates the routing to the second UE 322 accordingly.

[0047] In addition, the MT of the eighth IAB node 318 performs a candidate parent search 408 for alternative parent nodes, which explicitly avoids the sixth IAB node 314 and the fourth IAB node 310 as candidate nodes. In this example, the candidate parent search 408 is successful, and the MT of the eighth IAB node 318 identifies the seventh IAB node 316 as a suitable candidate node. The MT of the eighth IAB node 318 sends a request to the seventh IAB node 316 to reestablish a connection and change the route of the eighth IAB node 318. The network then updates the routes to the fourth UE 326, the fifth UE 328, and the sixth UE 330 accordingly.

[0048] In one embodiment, a request from an MT of an IAB node to establish an alternative route may include information about the following: UEs attached to the IAB node; descendant nodes connected to the IAB node directly or through other nodes; UEs attached to these descendant nodes; and / or a cause value for re-establishment (potentially, for this cause value, the requesting IAB node may be able to process re-establishment requests from downstream IAB nodes or UEs with lost backhaul links with high priority). Thus, the information in the request allows re-establishment of routes for all affected UEs and nodes.

[0049] The backhaul RLF indication may be a MAC message (such as a MAC control element) or an RLC message (i.e., an RLC control protocol data unit (PDU)). Since the message is transmitted to all nodes and UEs attached to the DU of the IAB node, it may not need to be routed through the adaptation layer (i.e., no significant routing decisions are required), and an adaptation layer header may not be required. However, to facilitate protocol processing, the backhaul RLF indication may be defined as an RLC message.

[0050] Parallelized Sequencing

[0051] In some specific implementations of the RLF recovery process described above, downstream nodes do not initiate their search for an alternative parent node until the upstream node has attempted and failed to do so. Since this step involves scanning for alternative nodes, the entire process can be very time-consuming at each intermediate node, and the disruption experienced by the UE can be significant. Therefore, some implementations use parallel sequencing to mitigate the latency involved.

[0052] For example, when the fourth IAB node 310 experiences a radio link problem and declares a radio link failure, the fourth IAB node 310 may transmit a "Preliminary Backhaul RLF" indication to all direct descendant nodes and all UEs attached to the fourth IAB node 310. The Preliminary Backhaul RLF indication identifies the identity of a node that should not be considered as a candidate alternative parent node (i.e., the fourth IAB node 310).

[0053] Sixth IAB node 314 receives the preliminary backhaul RLF indication and, in response, attempts to identify an alternative parent node. Sixth IAB node 314 explicitly does not consider fourth IAB node 310 as a candidate node for recovery. In this example, sixth IAB node 314 is able to identify seventh IAB node 316 as an alternative candidate node for recovery. Meanwhile, fourth IAB node 310 attempts to identify an alternative parent node. In the near-side node, the signal from third IAB node 308 is blocked, and the signals from second IAB node 306 and seventh IAB node 316 are too weak. Therefore, fourth IAB node 310 is unable to find an alternative parent node. In response to being unable to find an alternative parent node, fourth IAB node 310 sends a "final backhaul RLF" indication to all direct descendant nodes (i.e., nodes attached to the DU of fourth IAB node 310) and all UEs (if any) attached to fourth IAB node 310. The sixth IAB node 314 receives the final backhaul RLF indication and responsively restores its connection by attaching to the seventh IAB node 316. Routes to the second UE 322, the fourth UE 326, the fifth UE 328, and the sixth UE 330 are reestablished through the seventh IAB node 316, the sixth IAB node 314, and the eighth IAB node 318.

[0054] and Figure 4 The scheme for backhaul RLF indication is similar, with both the preliminary and final backhaul RLF indications transmitted downstream. In response to the preliminary backhaul RLF indication, the MT or UE attempts to identify candidate nodes for recovery (while excluding nodes identified in the preliminary backhaul RLF indication as not considered for recovery). In response to the final backhaul RLF indication, the MT or UE attempts to perform connection recovery by attaching to a node identified as a candidate node (if such a node is identified). If the MT of the IAB node does not identify the node as a candidate node, the MT indicates to the DU of the IAB node that a final backhaul RLF indication needs to be transmitted.

[0055] Timer-based sequencing

[0056] In one embodiment, a timer-based process can be defined instead of two separate indications (i.e., both preliminary and final backhaul RLF indications). For example, after the fourth IAB node 310 experiences a radio link problem, declares a radio link failure, and transmits a "backhaul RLF" indication to all direct descendant nodes and all UEs attached to node 4, the sixth IAB node 314 receives the backhaul RLF indication and, in response, starts a recovery timer. The sixth IAB node 314 transmits the backhaul RLF indication to all direct descendant nodes and UEs attached to the sixth IAB node. This indication identifies the identities of nodes that should not be considered as candidate alternative parent nodes (i.e., the fourth IAB node 310 and the sixth IAB node 314). Simultaneously, the fourth IAB node 310 attempts to identify an alternative parent node.

[0057] If the fourth IAB node 310 successfully identifies a suitable alternative parent node, the fourth IAB node 310 transmits a "backhaul recovery success" indication. If a descendant node of the fourth IAB node 310 or a UE attached to the fourth IAB node 310 receives the "backhaul recovery success" indication, the descendant node cancels the recovery process and remains attached to the fourth IAB node 310. The descendant node may also send a backhaul recovery success indication downstream.

[0058] The sixth IAB node 314 also attempts to identify an alternative parent node. The sixth IAB node explicitly does not consider the fourth IAB node 310 as a candidate node for recovery.

[0059] If the sixth IAB node 314 receives a backhaul resumption success indication from its parent node, or if the sixth IAB node is able to identify an alternative candidate parent node (eg, the seventh IAB node 316), the sixth IAB node 314 transmits the backhaul resumption success indication to its direct descendant nodes and attached UEs.

[0060] Assuming that the fourth IAB node 310 is unable to identify an alternative parent node (in this case, the sixth IAB node 314 does not receive a backhaul recovery success indication), the recovery timer at the sixth IAB node 314 expires. In response to the expiration of the timer, the sixth IAB node 314 attaches to the seventh IAB node 316 and restores its connection. Routes to the second UE 322, the fourth UE 326, the fifth UE 328, and the sixth UE 330 are reestablished through the seventh IAB node 316, the sixth IAB node 314, and the eighth IAB node 318.

[0061] The Backhaul RLF Indication is used to trigger a search for candidate parent nodes or candidate access nodes at the UE and the MT of the IAB node. An IAB node MT or UE that receives the Backhaul RLF Indication also starts a recovery timer that controls whether the MT or UE switches its parent node. The Backhaul Recovery Success Indication is used to cancel the recovery process initiated at the IAB node or UE due to the previous Backhaul RLF Indication. If the recovery timer at the IAB node or UE expires before it receives the Backhaul Recovery Success Indication, the IAB node MT or UE attempts to perform recovery by attaching to a candidate parent node.

[0062] In some embodiments, the resumption timer duration may be different for different nodes and UEs. For example, the resumption timer duration at the sixth IAB node 314 may be longer than the resumption timer duration at the fourth IAB node 310.

[0063] Figure 5 5 is a flow chart of a method 500 for timer-based sequencing according to one embodiment. The method 500 may be performed by an IAB node in an IAB network. The method 500 may begin at block 502 when an upstream node experiences RLF, and at block 504, the IAB node receives a first backhaul RLF indication from the upstream node. The first backhaul RLF indication may identify nodes that should not be considered as alternative parent nodes, including the parent node that experienced the RLF failure. In response to receiving the backhaul RLF indication, at block 506, the IAB node starts a backhaul recovery timer. At block 508, the IAB node transmits a second backhaul RLF indication to direct descendant nodes and any UEs attached to the IAB node. The second backhaul RLF indication identifies nodes that should not be considered as candidate alternative parent nodes, including the IAB node that experienced the RLF failure and the parent node.

[0064] At block 510, the IAB node attempts to identify an alternative parent node. Based on the first backhaul RLF indication, the IAB node does not consider the parent node as a candidate node for recovery. At decision block 516, the IAB node determines whether a candidate alternative parent node has been identified. If a candidate alternative parent node has not been identified, at decision block 512, the IAB node determines whether a first backhaul recovery success indication has been received from the parent node. If the first backhaul recovery success indication has been received, at block 514, method 500 ends. The IAB node may also send a second backhaul recovery success indication to its direct descendant nodes and any attached UEs before terminating.

[0065] However, if the first backhaul recovery success indication has not been received, the method 500 returns to block 510 to continue trying to identify an alternative parent node. When the IAB node determines that a candidate alternative parent node has been identified, at block 518, the IAB node transmits a second backhaul recovery success indication to its direct descendant nodes and any attached UEs.

[0066] At decision block 520, the IAB node determines whether a first backhaul recovery success indication has been received from the parent node. If a first backhaul recovery success indication has been received, method 500 ends at 514. The IAB node may also send a second backhaul recovery success indication to its direct descendant nodes and any attached UEs before ending.

[0067] If the first backhaul recovery success indication has not been received from the parent node, then at decision block 522, the IAB node determines whether the backhaul recovery timer has expired. If the backhaul recovery timer has not expired, then method 500 returns to block 510. However, if the backhaul recovery timer has expired, then at block 524, the IAB node connects to the identified candidate alternative parent node and reestablishes its own routing as well as the routing of its downstream nodes and any attached UEs.

[0068] System information based recovery

[0069] In one embodiment, system information broadcast by the IAB node may be used instead of returning the RLF message. Figure 3 and Figure 4 When the fourth IAB node 310 experiences a radio link problem and declares a radio link failure, the fourth IAB node 310 attempts to identify an alternative parent node. In the near-side node, the signal from the third IAB node 308 may be blocked, and the signals from the second IAB node 306 and the seventh IAB node 316 may be too weak. Therefore, the fourth IAB node 310 may be unable to find an alternative parent node. In response to being unable to find an alternative parent node, the fourth IAB node 310 updates its system information to signal that it is barred. The system information may also indicate which nodes should not be used as candidate nodes for recovery (i.e., the fourth IAB node 310). Specifically, the fourth IAB node 310 may update information in its master information block (MIB) or first system information block (SIB1) to indicate restrictions and additional information.

[0070] In this example, sixth IAB node 314 may obtain modified system information from fourth IAB node 310 and identify an alternative parent node in response to the restriction attempt. Sixth IAB node 314 explicitly does not consider fourth IAB node 310 as a candidate node for recovery. Sixth IAB node 314 attaches to seventh IAB node 316 and restores its connection. Routes to second UE 322, fourth UE 326, fifth UE 328, and sixth UE 330 are reestablished via seventh IAB node 316, sixth IAB node 314, and eighth IAB node 318.

[0071] However, if the sixth IAB node 314 is also unable to identify an alternative parent node, the sixth IAB node 314 updates its system information to signal that it is barred. The system information may also indicate which nodes should not be used as candidate nodes for restoration (i.e., the fourth IAB node 310 and the sixth IAB node 314). The second UE 322 may perform a search for alternative access nodes and may explicitly avoid considering the sixth IAB node 314 and the fourth IAB node 310 as candidate nodes. The second UE 322 may identify the third IAB node 308 as a suitable candidate node and attach to it. The network may then update the route to the second UE 322 accordingly.

[0072] The eighth IAB node 318 may also attempt to perform a search for an alternative parent node and may explicitly avoid considering the sixth IAB node 314 and the fourth IAB node 310 as candidate nodes. The eighth IAB node 318 may identify the seventh IAB node 316 as a suitable candidate node and may attach to the seventh IAB node 316. The network then updates the routes to the fourth UE 326, the fifth UE 328, and the sixth UE 330 accordingly.

[0073] Example Alternatives for Delivering Backhaul RLF Indications

[0074] In one embodiment, the backhaul RLF indication may also be transmitted via a physical layer message. For example, a backhaul RLF physical downlink control channel (PDCCH) may be designed so that when an IAB node MT experiences a backhaul failure, the IAB node transmits a backhaul RLF PDCCH on the downlink from its DU.

[0075] In another embodiment, a group common PDCCH (GC-PDCCH) may be used, enabling transmission of broadcast physical layer control messages that may be received by all direct descendant IAB nodes and UEs.

[0076] Exemplary Systems and Apparatus

[0077] Figure 6The architecture of a system 600 of a network according to some embodiments is shown. The system 600 is shown to include: a UE 602; a 5G access node or RAN node (shown as (R)AN node 608); a user plane function (shown as UPF 604); a data network (DN 606), which can be, for example, an operator service, internet access, or a third-party service; and a 5G core network (5GC) (shown as CN 610).

[0078] The CN 610 may include an authentication server function (AUSF 614); a core access and mobility management function (AMF 612); a session management function (SMF 618); a network exposure function (NEF 616); a policy control function (PCF 622); a network function (NF) repository function (NRF 620); a unified data management (UDM 624); and an application function (AF 626). The CN 610 may also include other elements not shown, such as a structured data storage network function (SDSF), an unstructured data storage network function (UDSF), and the like.

[0079] The UPF 604 can serve as an anchor point for intra-RAT and inter-RAT mobility, an external PDU session point interconnected with the DN 606, and a branch point to support multi-homed PDU sessions. The UPF 604 can also perform packet routing and forwarding, packet inspection, enforce the user plane portion of policy rules, lawful interception of packets (UP collection); traffic usage reporting, perform QoS processing on the user plane (e.g., packet filtering, gating, UL / DL rate enforcement), perform uplink traffic validation (e.g., SDF to QoS flow mapping), transport level packet marking in the uplink and downlink, and downlink packet buffering and downlink data notification triggering. The UPF 604 may include an uplink classifier to support routing of traffic flows to the data network. The DN 606 may represent various network operator services, Internet access, or third-party services.

[0080] The AUSF 614 may store data and handle functions related to authenticating the UE 602. The AUSF 614 may facilitate a common authentication framework for various access types.

[0081] The AMF 612 may be responsible for registration management (e.g., registering the UE 602), connection management, reachability management, mobility management, and lawful interception of AMF-related events, as well as access authentication and authorization. The AMF 612 may provide transport for SM messages destined for the SMF 618 and act as a transparent proxy for routing SM messages. The AMF 612 may also provide communication between the UE 602 and the SMS Function (SMSF) ( Figure 6The AMF 612 may provide for the transfer of short message service (SMS) messages between the AUSF 614 and the UE 602 (not shown). The AMF 612 may act as a security anchor function (SEA), which may include interaction with the AUSF 614 and the UE 602, and receiving intermediate keys established as a result of the UE 602 authentication process. In the case of using USIM-based authentication, the AMF 612 may retrieve security information from the AUSF 614. The AMF 612 may also include a secure content management (SCM) function that receives keys for deriving access network-specific keys from the SEA. In addition, the AMF 612 may be the termination point for the RAN CP interface (N2 reference point), the termination point for NAS (NI) signaling, and perform NAS encryption and integrity protection.

[0082] The AMF 612 may also support NAS signaling with the UE 602 via the N3 Interworking Function (IWF) interface. The N3 IWF may be used to provide access to untrusted entities. The N3 IWF may be an endpoint of the N2 and N3 interfaces for the control plane and user plane, respectively, and may therefore handle N2 signaling for PDU sessions and QoS from the SMF and AMF, encapsulate / decapsulate packets for IPSec and N3 tunnels, mark N3 user plane packets in the uplink, and enforce QoS corresponding to the N3 packet markings, taking into account the QoS requirements associated with such markings received via N2. The N3 IWF may also relay uplink and downlink control plane NAS (NI) signaling between the UE 602 and the AMF 612, and relay uplink and downlink user plane packets between the UE 602 and the UPF 604. The N3 IWF also provides a mechanism for establishing an IPsec tunnel with the UE 602.

[0083] The SMF 618 may be responsible for session management (e.g., session establishment, modification, and release, including tunnel maintenance between the UPF and AN nodes); UE IP address allocation & management (including optional authorization); selection and control of UP functions; configuring traffic steering at the UPF to route traffic to the correct destination; terminating the interface towards the policy control function; control part of policy enforcement and QoS; lawful interception (for SM events and interface with the LI system); terminating the SM part of the NAS message; downlink data notification; initiator of AN-specific SM information sent to the AN via the AMF over N2; determining the SSC mode of the session. The SMF 618 may include the following roaming functions: handling local execution to apply QoS SLA (VPLMN); charging data collection and charging interface (VPLMN); lawful interception (for SM events and interface with the LI system, in the VPLMN); supporting interaction with external DNs to transport signaling for PDU session authorization / authentication over the external DN.

[0084] The NEF 616 may provide components for securely exposing services and capabilities provided by 3GPP network functions to third parties, internal exposure / re-exposure, application functions (e.g., AF 626), edge computing or fog computing systems, and the like. In such embodiments, the NEF 616 may authenticate, authorize, and / or restrict the AF. The NEF 616 may also convert information exchanged with the AF 626 and information exchanged with internal network functions. For example, the NEF 616 may convert between AF service identifiers and internal 5GC information. The NEF 616 may also receive information from other network functions (NFs) based on their exposed capabilities. This information may be stored at the NEF 616 as structured data or at a data storage NF using standardized interfaces. The stored information may then be re-exposed by the NEF 616 to other NFs and AFs and / or used for other purposes such as analysis.

[0085] The NRF 620 may support service discovery functionality, receive NF discovery requests from NF instances, and provide information about the discovered NF instances to the NF instances. The NRF 620 also maintains information about available NF instances and the services supported by these instances.

[0086] PCF 622 can provide policy rules for control plane functions to perform these functions and can also support a unified policy framework for managing network behavior. PCF 622 can also implement a front end (FE) to access subscription information related to policy decisions in the UDR of UDM 624.

[0087] The UDM 624 can process subscription-related information to support network entities' handling of communication sessions and can store subscription data for the UE 602. The UDM 624 can include two parts: an application FE and a user data repository (UDR). The UDM can include a UDM FE, which is responsible for handling credentials, location management, subscription management, etc. In different transactions, several different front ends can serve the same user. The UDM-FE accesses subscription information stored in the UDR and performs authentication credential processing; user identity processing; access authorization; registration / mobility management; and subscription management. The UDR can interact with the PCF 622. The UDM 624 can also support SMS management, where the SMS-FE implements similar application logic discussed previously.

[0088] AF 626 can provide application influence on traffic routing, access network capability exposure (NCE), and interact with the policy framework for policy control. NCE can be a mechanism that allows 5GC and AF 626 to provide information to each other via NEF 616, which can be used for edge computing implementations. In such implementations, network operators and third-party services can be hosted near the UE 602 access point to achieve efficient service delivery with reduced end-to-end latency and load on the transport network. For edge computing implementations, the 5GC can select a UPF 604 near the UE 602 and perform traffic steering from the UPF 604 to the DN 606 via the N6 interface. This can be based on UE subscription data, UE location, and information provided by AF 626. In this way, AF 626 can influence UPF (re)selection and traffic routing. Based on operator deployment, when AF 626 is considered a trusted entity, the network operator can allow AF 626 to interact directly with the relevant NF.

[0089] As previously discussed, CN 610 may include an SMSF that may be responsible for SMS subscription checking and verification, and relaying SM messages to / from UE 602 from / to other entities, such as SMS-GMSC / IWMSC / SMS routers. The SMS may also interact with AMF 612 and UDM 624 for notification procedures to make UE 602 available for SMS transmission (e.g., setting a UE unreachable flag and notifying UDM 624 when UE 602 is available for SMS).

[0090] System 600 may include the following service-based interfaces: Namf: a service-based interface presented by AMF; Nsmf: a service-based interface presented by SMF; Nnef: a service-based interface presented by NEF; Npcf: a service-based interface presented by PCF; Nudm: a service-based interface presented by UDM; Naf: a service-based interface presented by AF; Nnrf: a service-based interface presented by NRF; and Nausf: a service-based interface presented by AUSF.

[0091] System 600 may include the following reference points: N1: a reference point between the UE and the AMF; N2: a reference point between the (R)AN and the AMF; N3: a reference point between the (R)AN and the UPF; N4: a reference point between the SMF and the UPF; and N6: a reference point between the UPF and the data network. Additional reference points and / or service-based interfaces may exist between NF services within these NFs; however, these interfaces and reference points are omitted for clarity. For example, the NS reference point may be between the PCF and the AF; the N7 reference point may be between the PCF and the SMF; the N11 reference point may be between the AMF and the SMF, etc. In some embodiments, the CN 610 may include an Nx interface, which is an inter-CN interface between the MME and the AMF 612, to enable interworking between the CN 610 and the LTE core network.

[0092] although Figure 6 Not shown, the system 600 may include multiple RAN nodes (such as (R)AN node 608), where the Xn interface is defined between two or more (R)AN nodes 608 (e.g., gNBs, etc.) connected to the 5GC 410, between a node 608 (e.g., a gNB) connected to the CN 610 and an eNB, and / or between two eNBs connected to the CN 610.

[0093] In some implementations, the Xn interface may include an Xn user plane (Xn-U) interface and an Xn control plane (Xn-C) interface. The Xn-U may provide non-guaranteed delivery of user plane PDUs and support / provide data forwarding and flow control functions. The Xn-C may provide management and error handling functions for managing the functions of the Xn-C interface; mobility support for UE 602 in connected mode (e.g., CM connection) includes the function of managing UE mobility in connected mode between one or more (R)AN nodes 608. Mobility support may include context transfer from an old (source) serving (R)AN node 608 to a new (target) serving (R)AN node 608; and control of a user plane tunnel between the old (source) serving (R)AN node 608 and the new (target) serving (R)AN node 608.

[0094] The protocol stack of Xn-U may include a transport network layer built on the Internet Protocol (IP) transport layer, and a GTP-U layer on top of the UDP and / or IP layer for carrying user plane PDUs. The Xn-C protocol stack may include an application layer signaling protocol (referred to as the Xn Application Protocol (Xn-AP)) and a transport network layer built on the SCTP layer. The SCTP layer may be located on top of the IP layer. The SCTP layer provides guaranteed delivery of application layer messages. In the transport IP layer, point-to-point transport is used to deliver signaling PDUs. In other specific implementations, the Xn-U protocol stack and / or the Xn-C protocol stack may be the same as or similar to the user plane and / or control plane protocol stacks shown and described herein.

[0095] Figure 7 An NG-RAN architecture 700 is shown according to one embodiment, including a 5GC 702 and an NG-RAN 704. The NG-RAN 704 includes multiple gNBs (two gNBs shown are gNB 706 and gNB 708) connected to the 5GC 702 via an NG interface. gNB 706 and gNB 708 can support FDD mode, TDD mode, or dual mode operation and are connected to each other via an Xn-C interface. As shown, gNB 708 includes a gNB-CU 710 connected to gNB-DU 712 and gNB-DU 714 via an F1 interface. gNB 708 can include only a single gNB-DU or more than the two gNB-DUs shown. The NG interface, Xn-C interface, and F1 interface are logical interfaces.

[0096] Figure 8 Example components of a device 800 according to some embodiments are shown. In some embodiments, the device 800 may include application circuitry 802, baseband circuitry 804, radio frequency (RF) circuitry (shown as RF circuitry 820), front-end module (FEM) circuitry (shown as FEM circuitry 830), one or more antennas 832, and power management circuitry (PMC) (shown as PMC 834) (coupled together at least as shown). The components of the illustrated device 800 may be included in a UE or a RAN node. In some embodiments, the device 800 may include fewer components (e.g., a RAN node may not utilize application circuitry 802 but instead include a processor / controller to process IP data received from an EPC). In some embodiments, the device 800 may include additional components such as memory / storage, a display, a camera, sensors, or input / output (I / O) interfaces. In other embodiments, the components described below may be included in more than one device (e.g., the circuitry may be included separately in more than one device for a Cloud-RAN (C-RAN) implementation).

[0097] The application circuitry 802 may include one or more application processors. For example, the application circuitry 802 may include circuitry such as, but not limited to, one or more single-core or multi-core processors. The one or more processors may include any combination of general-purpose processors and specialized processors (e.g., graphics processors, application processors, etc.). These processors may be coupled to or include memory / storage and may be configured to execute instructions stored in the memory / storage to enable various applications or operating systems to run on the device 800. In some embodiments, the processors of the application circuitry 802 may process IP data packets received from the EPC.

[0098] The baseband circuitry 804 may include circuitry such as, but not limited to, one or more single-core or multi-core processors. The baseband circuitry 804 may include one or more baseband processors or control logic components for processing baseband signals received from the receive signal path of the RF circuitry 820 and generating baseband signals for the transmit signal path of the RF circuitry 820. The baseband circuitry 804 may interact with the application circuitry 802 to generate and process baseband signals and control the operation of the RF circuitry 820. For example, in some embodiments, the baseband circuitry 804 may include a third generation (3G) baseband processor (3G baseband processor 806), a fourth generation (4G) baseband processor (4G baseband processor 808), a fifth generation (5G) baseband processor (5G baseband processor 810), or other baseband processors 812 of other existing generations, generations under development, or generations to be developed in the future (e.g., second generation (2G), sixth generation (6G), etc.). The baseband circuitry 804 (e.g., one or more processors within the baseband processor) may handle various radio control functions that enable communication with one or more radio networks via the RF circuitry 820. In other embodiments, some or all of the functions of the illustrated baseband processor may be included in modules stored in the memory 818 and executed via the central processing unit (CPU 814). Radio control functions may include, but are not limited to, signal modulation / demodulation, encoding / decoding, radio frequency shifting, and the like. In some embodiments, the modulation / demodulation circuitry of the baseband circuitry 804 may include fast Fourier transform (FFT), precoding, or constellation mapping / demapping functions. In some embodiments, the encoding / decoding circuitry of the baseband circuitry 804 may include convolution, tail-biting convolution, turbo, Viterbi, or low-density parity check (LDPC) encoder / decoder functions. The implementation of the modulation / demodulation and encoder / decoder functions is not limited to these examples and may include other suitable functions in other embodiments.

[0099] In some embodiments, the baseband circuitry 804 may include a digital signal processor (DSP), such as one or more audio DSPs 816. The audio DSP 816 may include elements for compression / decompression and echo cancellation, and in other embodiments may include other suitable processing elements. In some embodiments, the components of the baseband circuitry may be appropriately combined in a single chip, a single chipset, or disposed on the same circuit board. In some embodiments, some or all of the components of the baseband circuitry 804 and the application circuitry 802 may be implemented together, such as on a system on a chip (SOC).

[0100] In some embodiments, the baseband circuitry 804 can provide communications compatible with one or more radio technologies. For example, in some embodiments, the baseband circuitry 804 can support communications with the Evolved Universal Terrestrial Radio Access Network (EUTRAN) or other wireless metropolitan area networks (WMANs), wireless local area networks (WLANs), and wireless personal area networks (WPANs). Embodiments in which the baseband circuitry 804 is configured to support radio communications using more than one wireless protocol may be referred to as multi-mode baseband circuitry.

[0101] The RF circuitry 820 can communicate with a wireless network using modulated electromagnetic radiation through a non-solid medium. In various embodiments, the RF circuitry 820 can include switches, filters, amplifiers, and the like for facilitating communication with the wireless network. The RF circuitry 820 can include a receive signal path that can include circuitry for down-converting RF signals received from the FEM circuitry 830 and providing baseband signals to the baseband circuitry 804. The RF circuitry 820 can also include a transmit signal path that can include circuitry for up-converting baseband signals provided by the baseband circuitry 804 and providing an RF output signal to the FEM circuitry 830 for transmission.

[0102] In some embodiments, the receive signal path of RF circuitry 820 may include mixer circuitry 822, amplifier circuitry 824, and filter circuitry 826. In some embodiments, the transmit signal path of RF circuitry 820 may include filter circuitry 826 and mixer circuitry 822. RF circuitry 820 may also include synthesizer circuitry 828 for synthesizing frequencies for use by mixer circuitry 822 in the receive and transmit signal paths. In some embodiments, mixer circuitry 822 in the receive signal path may be configured to downconvert the RF signal received from FEM circuitry 830 based on the synthesized frequency provided by synthesizer circuitry 828. Amplifier circuitry 824 may be configured to amplify the downconverted signal, and filter circuitry 826 may be a low-pass filter (LPF) or a band-pass filter (BPF) configured to remove unwanted signals from the downconverted signal to generate an output baseband signal. The output baseband signal may be provided to baseband circuitry 804 for further processing. In some embodiments, the output baseband signal may be a zero-frequency baseband signal, although this is not required. In some embodiments, mixer circuit 822 of the receive signal path may include a passive mixer, although the scope of the embodiments is not limited in this respect.

[0103] In some embodiments, mixer circuitry 822 of the transmit signal path can be configured to upconvert an input baseband signal based on a synthesized frequency provided by synthesizer circuitry 828 to generate an RF output signal for FEM circuitry 830. The baseband signal can be provided by baseband circuitry 804 and can be filtered by filter circuitry 826.

[0104] In some embodiments, the mixer circuit 822 of the receive signal path and the mixer circuit 822 of the transmit signal path may include two or more mixers and may be arranged for quadrature down-conversion and up-conversion, respectively. In some embodiments, the mixer circuit 822 of the receive signal path and the mixer circuit 822 of the transmit signal path may include two or more mixers and may be arranged for image rejection (e.g., Hartley image rejection). In some embodiments, the mixer circuit 822 of the receive signal path and the mixer circuit 822 may be arranged for direct down-conversion and direct up-conversion, respectively. In some embodiments, the mixer circuit 822 of the receive signal path and the mixer circuit 822 of the transmit signal path may be configured for superheterodyne operation.

[0105] In some embodiments, the output baseband signal and the input baseband signal may be analog baseband signals, although the scope of the embodiments is not limited in this respect. In some alternative embodiments, the output baseband signal and the input baseband signal may be digital baseband signals. In these alternative embodiments, RF circuitry 820 may include analog-to-digital converter (ADC) and digital-to-analog converter (DAC) circuitry, and baseband circuitry 804 may include a digital baseband interface to communicate with RF circuitry 820.

[0106] In some dual-mode embodiments, separate radio IC circuits may be provided to process signals for each spectrum, although the scope of the embodiments is not limited in this respect.

[0107] In some embodiments, synthesizer circuit 828 may be a fractional-N synthesizer or a fractional N / N+1 synthesizer, but the scope of the embodiments is not limited in this respect, as other types of frequency synthesizers may also be suitable. For example, synthesizer circuit 828 may be a delta-sigma synthesizer, a frequency multiplier, or a synthesizer including a phase-locked loop with a frequency divider.

[0108] Synthesizer circuit 828 may be configured to synthesize an output frequency based on a frequency input and a divider control input for use by mixer circuit 822 of RF circuit 820. In some embodiments, synthesizer circuit 828 may be a fractional-N / N+1 synthesizer.

[0109] In some embodiments, the frequency input may be provided by a voltage controlled oscillator (VCO), although this is not required. The divider control input may be provided by baseband circuitry 804 or application circuitry 802 (such as an application processor) based on the desired output frequency. In some embodiments, the divider control input (e.g., N) may be determined from a lookup table based on the channel indicated by application circuitry 802.

[0110] The synthesizer circuit 828 of the RF circuit 820 may include a frequency divider, a delay-locked loop (DLL), a multiplexer, and a phase accumulator. In some embodiments, the frequency divider may be a dual-mode frequency divider (DMD), and the phase accumulator may be a digital phase accumulator (DPA). In some embodiments, the DMD may be configured to divide the input signal by N or N+1 (e.g., based on a carry) to provide a fractional division ratio. In some example embodiments, the DLL may include a cascaded, tunable delay element, a phase detector, a charge pump, and a set of D-type flip-flops. In these embodiments, the delay element may be configured to divide the VCO cycle into Nd equal phase groups, where Nd is the number of delay elements in the delay line. In this way, the DLL provides negative feedback to help ensure that the total delay through the delay line is one VCO cycle.

[0111] In some embodiments, the synthesizer circuit 828 can be configured to generate a carrier frequency as the output frequency, while in other embodiments, the output frequency can be a multiple of the carrier frequency (e.g., twice the carrier frequency, four times the carrier frequency) and can be used with a quadrature generator and divider circuit to generate multiple signals at the carrier frequency with multiple different phases relative to each other. In some embodiments, the output frequency can be the LO frequency (fLO). In some embodiments, the RF circuit 820 can include an IQ / polarity converter.

[0112] The FEM circuitry 830 may include a receive signal path that may include circuitry configured to operate on RF signals received from one or more antennas 832, amplify the received signals, and provide an amplified version of the received signals to the RF circuitry 820 for further processing. The FEM circuitry 830 may also include a transmit signal path that may include circuitry configured to amplify transmit signals provided by the RF circuitry 820 for transmission via one or more of the one or more antennas 832. In various embodiments, amplification by either the transmit or receive signal path may be performed only in the RF circuitry 820, only in the FEM circuitry 830, or in both the RF circuitry 820 and the FEM circuitry 830.

[0113] In some embodiments, the FEM circuit 830 may include a TX / RX switch to switch between transmit and receive modes of operation. The FEM circuit 830 may include a receive signal path and a transmit signal path. The receive signal path of the FEM circuit 830 may include an LNA to amplify a received RF signal and provide the amplified received RF signal as an output (e.g., to the RF circuit 820). The transmit signal path of the FEM circuit 830 may include a power amplifier (PA) to amplify an input RF signal (e.g., provided by the RF circuit 820), and one or more filters to generate an RF signal for subsequent transmission (e.g., via one or more of the one or more antennas 832).

[0114] In some embodiments, the PMC 834 can manage the power provided to the baseband circuitry 804. Specifically, the PMC 834 can control power source selection, voltage scaling, battery charging, or DC-DC conversion. When the device 800 is capable of being powered by a battery, for example, when the device 800 is included in a UE, the PMC 834 is typically included. The PMC 834 can improve power conversion efficiency while providing the desired implementation size and heat dissipation characteristics.

[0115] Figure 8PMC 834 is shown coupled only to baseband circuitry 804. However, in other embodiments, PMC 834 may additionally or alternatively be coupled to other components (such as, but not limited to, application circuitry 802, RF circuitry 820, or FEM circuitry 830) and perform similar power management operations for these components.

[0116] In some embodiments, the PMC 834 can control or otherwise be part of various power saving mechanisms of the device 800. For example, if the device 800 is in the RRC_Connected state, where the device is still connected to the RAN node because it expects to receive traffic immediately, then after a period of inactivity, the device can enter a state known as discontinuous reception mode (DRX). During this state, the device 800 can be powered down for short intervals, thereby saving power.

[0117] If there is no data traffic activity for an extended period of time, the device 800 may transition to the RRC_Idle state, in which the device is disconnected from the network and does not perform operations such as channel quality feedback, handovers, etc. The device 800 enters a very low power state and performs paging, in which the device periodically wakes up again to listen to the network and then powers down again. The device 800 cannot receive data in this state and must transition back to the RRC_Connected state in order to receive data.

[0118] An additional power saving mode can disable the device from using the network for periods exceeding the paging interval (ranging from a few seconds to several hours). During this period, the device is completely unable to connect to the network and can be completely powered down. Any data sent during this period will incur significant latency, assuming that latency is acceptable.

[0119] The processor of the application circuitry 802 and the processor of the baseband circuitry 804 can be used to execute elements of one or more instances of the protocol stack. For example, the processor of the baseband circuitry 804 can be used, alone or in combination, to perform layer 3, layer 2, or layer 1 functions, while the processor of the application circuitry 802 can utilize data received from these layers (e.g., packet data) and further perform layer 4 functions (e.g., transport communication protocol (TCP) and user datagram protocol (UDP) layers). As mentioned herein, layer 3 may include a radio resource control (RRC) layer, which is described in further detail below. As mentioned herein, layer 2 may include a medium access control (MAC) layer, a radio link control (RLC) layer, and a packet data convergence protocol (PDCP) layer, which are described in further detail below. As mentioned herein, layer 1 may include a physical (PHY) layer of a UE / RAN node, which is described in further detail below.

[0120] Figure 9900 shows an exemplary interface of a baseband circuit according to some embodiments. As described above, Figure 8 The baseband circuit 804 may include a 3G baseband processor 806, a 4G baseband processor 808, a 5G baseband processor 810, other baseband processors 812, a CPU 814, and a memory 818 used by the processors. As shown, each of these processors may include a corresponding memory interface 902 for sending / receiving data to / from the memory 818.

[0121] The baseband circuit 804 may also include one or more interfaces for communicatively coupling to other circuits / devices, such as a memory interface 904 (e.g., an interface for sending / receiving data to / from a memory external to the baseband circuit 804); an application circuit interface 906 (e.g., an interface for sending / receiving data to / from a memory external to the baseband circuit 804); Figure 8 RF circuit interface 908 (for example, for sending / receiving data to / from the application circuit 802); Figure 8 an interface for transmitting / receiving data to / from a RF circuit 820); a wireless hardware connection interface 910 (e.g., for transmitting / receiving data to / from a near field communication (NFC) component, Components (e.g. Low power consumption), components and other communication components to send / receive data); and a power management interface 912 (eg, an interface for sending / receiving power or control signals to / from the PMC 834).

[0122] Figure 10 is a block diagram illustrating a component 1000 capable of reading instructions from a machine-readable or computer-readable medium (e.g., a non-transitory machine-readable storage medium) and capable of performing any one or more of the methods discussed herein, according to some example embodiments. Specifically, Figure 10 A diagrammatic representation of hardware resources 1002 is shown including one or more processors 1012 (or processor cores), one or more memory / storage devices 1018, and one or more communication resources 1020, each of which may be communicatively coupled via a bus 1022. For embodiments in which node virtualization (e.g., NFV) is utilized, a hypervisor 1004 may be executed to provide an execution environment for one or more network slices / sub-slices to utilize the hardware resources 1002.

[0123] Processor 1012 (e.g., a central processing unit (CPU), a reduced instruction set computing (RISC) processor, a complex instruction set computing (CISC) processor, a graphics processing unit (GPU), a digital signal processor (DSP) (such as a baseband processor), an application-specific integrated circuit (ASIC), a radio frequency integrated circuit (RFIC), another processor, or any suitable combination thereof) may include, for example, processor 1014 and processor 1016.

[0124] The memory / storage device 1018 may include main memory, disk storage, or any suitable combination thereof. The memory / storage device 1018 may include, but is not limited to, any type of volatile or non-volatile memory, such as dynamic random access memory (DRAM), static random access memory (SRAM), erasable programmable read-only memory (EPROM), electrically erasable programmable read-only memory (EEPROM), flash memory, solid-state storage, etc.

[0125] The communication resources 1020 may include interconnect means or network interface components or other suitable devices to communicate with one or more peripheral devices 1006 or one or more databases 1008 via the network 1010. For example, the communication resources 1020 may include wired communication components (e.g., for coupling via a universal serial bus (USB)), cellular communication components, NFC components, Components (e.g. Low power consumption), components and other communication components.

[0126] The instructions 1024 may include software, programs, applications, applets, applications, or other executable code for causing at least one of the processors 1012 to perform any one or more of the methodologies discussed herein. The instructions 1024 may reside, in whole or in part, within at least one of the processors 1012 (e.g., within a cache memory of the processor), the memory / storage device 1018, or any suitable combination thereof. Furthermore, any portion of the instructions 1024 may be transferred to the hardware resources 1002 from any combination of the peripheral device 1006 or the database 1008. Thus, the memory of the processor 1012, the memory / storage device 1018, the peripheral device 1006, and the database 1008 are examples of computer-readable and machine-readable media.

[0127] For one or more embodiments, at least one of the components shown in one or more of the foregoing figures may be configured to perform one or more operations, techniques, processes, and / or methods described in the Examples section below. For example, the baseband circuitry described above in conjunction with one or more of the foregoing figures may be configured to operate according to one or more of the embodiments described below. For another example, circuitry associated with the UE, base station, network element, etc. described above in conjunction with one or more of the foregoing figures may be configured to operate according to one or more of the embodiments described below in the Examples section.

[0128] Examples

[0129] The following examples relate to additional embodiments.

[0130] Embodiment 1 is a non-transitory computer-readable storage medium. The computer-readable storage medium includes instructions that, when executed by a processor of an integrated access and backhaul (IAB) node in a wireless network, cause the processor to: detect a radio link failure (RLF) associated with a parent node in the wireless network; attempt to identify one or more alternative parent nodes in response to the radio link failure; and generate a first backhaul RLF message to one or more descendant nodes of the IAB node, the first backhaul RLF message indicating that at least the IAB node is not a candidate node for the one or more descendant nodes.

[0131] Embodiment 2 is the computer-readable storage medium of embodiment 1, wherein detecting the RLF comprises losing communication with the parent node.

[0132] Embodiment 3 is a computer-readable storage medium according to embodiment 1, wherein detecting the RLF comprises receiving a second RLF message from the parent node, the second RLF message indicating that the parent node has experienced the RLF.

[0133] Embodiment 4 is the computer-readable storage medium of embodiment 3, wherein the second RLF message further indicates that the parent node is not a candidate parent node among the one or more alternative parent nodes.

[0134] Embodiment 5 is a computer-readable storage medium according to embodiment 3, wherein the first return RLF message further indicates that the parent node is not a candidate node for the one or more descendant nodes.

[0135] Embodiment 6 is the computer-readable storage medium of embodiment 3, wherein attempting to identify the one or more alternative parent nodes comprises searching a set of IAB nodes that does not include the parent node.

[0136] Embodiment 7 is a computer-readable storage medium according to embodiment 3, wherein the instructions further configure the processor to: in response to receiving the second RLF message, start a recovery timer and generate the first backhaul RLF message; if the recovery timer has not expired before the IAB node is able to identify a candidate parent node from the one or more alternative parent nodes, or if the IAB node receives a first backhaul recovery success indication from the parent node, generate a second backhaul recovery success indication to transmit to the one or more descendant nodes of the IAB node and reestablish a connection with the parent node; and if the recovery timer expires before the IAB node receives the first backhaul recovery success indication from the parent node and the IAB node is able to identify the candidate parent node from the one or more alternative parent nodes, attach to the candidate parent node to establish a new route between the IAB node and the one or more descendant nodes of the IAB node.

[0137] Embodiment 8 is a computer-readable storage medium according to embodiment 3, wherein the instructions further configure the processor to: if the recovery timer expires before the IAB node receives the first backhaul recovery success indication from the parent node, and the IAB node cannot identify a candidate parent node from the one or more alternative parent nodes, generate the first backhaul RLF message and transmit it to one or more descendant nodes of the IAB node.

[0138] Embodiment 9 is a computer-readable storage medium according to embodiment 1, wherein the one or more descendant nodes of the IAB node include at least one of: a descendant IAB node and a user equipment (UE) attached to the IAB node.

[0139] Embodiment 10 is a computer-readable storage medium according to embodiment 1, wherein the instructions further configure the processor to: in response to an inability to identify the one or more alternative parent nodes, generate a signal from a mobile terminal (MT) of the IAB node to a distributed unit (DU) of the IAB node to transmit the first backhaul RLF message; and transmit the first backhaul RLF message from the DU of the IAB node.

[0140] Embodiment 11 is the computer-readable storage medium of embodiment 10, wherein transmitting the first backhaul RLF message comprises transmitting one of: a Backhaul Adaptation Protocol (BAP) message, a Medium Access Control (MAC) message, or a Radio Link Control (RLC) message.

[0141] Embodiment 12 is a computer-readable storage medium according to embodiment 10, wherein transmitting the first backhaul RLF message comprises transmitting one of: an RLF physical downlink control channel (PDCCH) on a downlink from the DU of the IAB node, or a group common PDCCH (GC-PDCCH) broadcast to the one or more descendant nodes of the IAB node.

[0142] Embodiment 13 is a computer-readable storage medium according to embodiment 1, wherein the first RLF message includes one or more of the following: a first identifier of one or more user equipment (UE) attached to the IAB, a second identifier of one or more descendant IAB nodes directly or indirectly attached to the IAB node, a third identifier of one or more UEs attached to the one or more descendant IAB nodes, and a cause value for re-establishment.

[0143] Embodiment 14 is a computer-readable storage medium according to embodiment 1, wherein the first return RLF message includes a preliminary return RLF indication, and wherein the instructions further configure the processor to: in response to being unable to identify the one or more alternative parent nodes, generate a second return RLF message including a final return indication.

[0144] Embodiment 15 is a method for an integrated access and backhaul (IAB) node in a wireless network. The method includes: determining a radio link failure (RLF) associated with a parent IAB node; in response to the RLF, attempting to identify one or more alternative parent nodes; and in response to failing to identify the one or more alternative parent nodes, updating first system information of the IAB node to indicate that the IAB node is barred, the first system information indicating at least that the IAB node is not a candidate node.

[0145] Embodiment 16 is a method according to embodiment 15, wherein determining the RLF associated with the parent node includes processing second system information associated with the parent node, the second system information indicating that the parent node is barred and is not a candidate parent node among the one or more alternative parent nodes.

[0146] Embodiment 17 is the method of embodiment 16, wherein the first system information further indicates that the parent node is not the candidate node for one or more descendant nodes of the IAB node.

[0147] Embodiment 18 is the method of embodiment 17, wherein the one or more descendant nodes include at least one of: a descendant IAB node and a user equipment (UE) attached to the IAB node.

[0148] Embodiment 19 is a method according to embodiment 16, wherein attempting to identify the one or more alternative parent nodes comprises searching a set of IAB nodes that does not include the parent node.

[0149] Embodiment 20 is the method of embodiment 15, wherein updating the first system information of the IAB node comprises updating one of: a master information block (MIB) or a first system information block (SIB1).

[0150] Embodiment 21 is an apparatus for user equipment. The apparatus includes a memory interface and a baseband processor. The memory interface is configured to send data corresponding to a backhaul radio link failure (RLF) indication to or from a memory device. The baseband processor is configured to: process the backhaul RLF indication, the backhaul RLF indication including a list of one or more integrated access and backhaul (IAB) nodes that cannot identify an alternative parent node; and, in response to the backhaul RLF indication, search for an alternative access node without considering the one or more IAB nodes in the list.

[0151] Embodiment 22 is an apparatus according to embodiment 21, wherein the baseband processor is further configured to: start a recovery timer in response to the backhaul RLF indication; if the recovery timer does not expire before receiving a backhaul recovery success indication from a parent IAB node, cancel the recovery process and remain attached to the parent IAB node; and if the recovery timer expires before receiving the backhaul recovery success indication, continue the recovery process and attach to the alternative access node.

[0152] Embodiment 23 is an apparatus according to embodiment 21, wherein the return RLF indication includes a preliminary return RLF indication, and wherein the baseband processor is further configured to: in response to the preliminary RLF indication, start searching for the alternative access node without considering the one or more IAB nodes in the list; receive a final return RLF indication; and in response to receiving the final return RLF indication, attach to the alternative access node.

[0153] Unless expressly stated otherwise, any of the above embodiments may be combined with any other embodiment (or combination of embodiments). The foregoing description of one or more specific implementations provides illustration and description, but is not intended to be exhaustive or to limit the scope of the embodiments to the precise forms disclosed. Modifications and variations are possible in light of the above teachings or may be acquired from practice of the various embodiments.

[0154] Embodiments and implementations of the systems and methods described herein may include various operations that may be embodied in machine-executable instructions to be executed by a computer system. A computer system may include one or more general-purpose or special-purpose computers (or other electronic devices). A computer system may include hardware components that include specific logic components for performing the operations, or may include a combination of hardware, software, and / or firmware.

[0155] The computer system and the computers in the computer system can be connected via a network. Suitable networks for configuration and / or use include, as described herein, one or more local area networks, wide area networks, metropolitan area networks, and / or the Internet or IP networks, such as the World Wide Web, private Internet, secure Internet, value-added network, virtual private network, extranet, intranet, or even a standalone machine that communicates with other machines through physical transmission of media. Specifically, a suitable network can be composed of parts or whole of two or more other networks, including networks that use different hardware and network communication technologies.

[0156] One suitable network includes a server and one or more clients; other suitable networks may include other combinations of servers, clients, and / or peer nodes, and a given computer system may act as both a client and a server. Each network includes at least two computers or computer systems, such as servers and / or clients. The computer systems may include workstations, laptops, disconnectable mobile computers, servers, mainframes, clusters, so-called "network computers" or "thin clients," tablet computers, smartphones, personal digital assistants or other handheld computing devices, "smart" consumer electronic devices or appliances, medical devices, or combinations thereof.

[0157] Suitable networks may include communication or networking software, such as that available from and other vendors, and may operate using TCP / IP, SPX, IPX, and other protocols over twisted pair, coaxial or fiber optic cable, telephone line, radio waves, satellite, microwave repeaters, modulated AC power line, physical media transmission, and / or other data transmission "wires" known to those skilled in the art. The network may include smaller networks and / or be connectable to other networks through gateways or similar mechanisms.

[0158] The various techniques or aspects or portions thereof may take the form of program code (i.e., instructions) embodied in a tangible medium such as a floppy disk, CD-ROM, hard drive, magnetic or optical card, solid-state storage device, non-transitory computer-readable storage medium, or any other machine-readable storage medium, wherein when the program code is loaded into a machine (such as a computer) and executed by the machine, the machine becomes an apparatus for practicing the various techniques. In the case of program code execution on a programmable computer, the computing device may include a processor, a storage medium readable by the processor (including volatile and non-volatile memory and / or storage elements), at least one input device, and at least one output device. The volatile and non-volatile memory and / or storage elements may be RAM, EPROM, flash drive, optical drive, magnetic hard drive, or other medium for storing electronic data. The eNB (or other base station) and UE (or other mobile station) may also include a transceiver component, a counter component, a processing component, and / or a clock component or timer component. One or more programs that may implement or utilize the various techniques described herein may use an application programming interface (API), reusable controls, and the like. Such programs may be implemented in a high-level procedural or object-oriented programming language to communicate with a computer system. However, if desired, one or more programs can be implemented in assembly language or machine language. In any case, the language can be a compiled or interpreted language and combined with a hardware implementation.

[0159] Each computer system includes one or more processors and / or memory; the computer system may also include various input devices and / or output devices. The processor may include general-purpose devices such as or other "off-the-shelf" microprocessor. The processor may include a dedicated processor device such as an ASIC, SoC, SiP, FPGA, PAL, PLA, FPLA, PLD, or other custom or programmable device. The memory may include static RAM, dynamic RAM, flash memory, one or more flip-flops, ROM, CD-ROM, DVD, disk, tape, or magnetic, optical or other computer storage media. The one or more input devices may include a keyboard, mouse, touch screen, light pen, tablet computer, microphone, sensor, or other hardware with accompanying firmware and / or software. The output device may include a monitor or other display, printer, speech or text synthesizer, switch, signal line, or other hardware with accompanying firmware and / or software.

[0160] It should be understood that many of the functional units described in this specification can be implemented as one or more components, a term used to more specifically emphasize their implementation independence. For example, a component can be implemented as a hardware circuit comprising custom very large scale integrated (VLSI) circuits or gate arrays, or off-the-shelf semiconductors (such as logic chips, transistors), or other discrete components. A component can also be implemented in a programmable hardware device (such as a field programmable gate array, programmable array logic, programmable logic device, etc.).

[0161] Components may also be implemented in software for execution by various types of processors. An identified component of executable code may, for example, include one or more physical or logical blocks of computer instructions that may be organized, for example, as objects, procedures, or functions. However, the executables of an identified component need not be physically located together, but may include different instructions stored in different locations that, when logically joined together, comprise the component and achieve the intended purpose of the component.

[0162] In practice, a component of executable code can be a single instruction or many instructions, and can even be distributed across multiple different code segments, between different programs, and across multiple storage devices. Similarly, operational data can be identified and illustrated herein within a component and can be embodied in any suitable form and organized within any suitable type of data structure. The operational data can be collected as a single data set, or can be distributed across different locations, including across different storage devices, and the operational data can exist, at least in part, only as electronic signals on a system or network. Components can be passive or active, including agents operable to perform desired functions.

[0163] Aspects of the embodiments will be shown as software modules or components. As used herein, software modules or components may comprise any type of computer instruction or computer executable code that may be located in a storage device. A software module may, for example, comprise one or more physical or logical blocks of a computer instruction that may be organized into routines, programs, objects, parts, data structures, etc. that perform one or more tasks or realize a particular data type. It should be understood that software modules may replace software or may be implemented in hardware and / or firmware in addition to software. One or more functional modules in the functional module described herein may be divided into submodules and / or combined into a single or smaller number of modules.

[0164] In certain embodiments, a specific software module may include different instructions stored in different locations, different storage devices, or different computers in a storage device, and these instructions together implement the functions of the module. In fact, a module may include a single instruction or many instructions and may be distributed on multiple different code segments, between different programs, and on multiple storage devices. Some embodiments may be put into practice in a distributed computing environment, wherein tasks are performed by a remote processing device linked by a communication network. In a distributed computing environment, a software module may be located in a local memory storage device and / or a remote memory storage device. In addition, the data that are bound or presented together in a database record may reside in the same storage device, may reside on multiple storage devices, and may be linked together in a record field in a database on a network.

[0165] References throughout this specification to "one embodiment" mean that a particular feature, structure, or characteristic described in conjunction with the embodiment is included in at least one embodiment. Therefore, the phrases "in one embodiment" appearing in various places throughout this specification are not necessarily referring to the same embodiment.

[0166] As used herein, for convenience, multiple items, structural elements, constituent elements and / or materials may be presented in a common list. However, these lists should be understood to mean that each member of the list is identified as a separate and unique member. Therefore, any individual member in such a list should not be understood to be equivalent to any other member in the same list simply based on being presented in a common group in the absence of an indication to the contrary. In addition, various embodiments and examples may be cited herein together with alternatives to their various components. It should be understood that these embodiments, examples and alternatives should not be understood to be equivalents to each other in fact, but should be considered as separate and autonomous representations.

[0167] In addition, the features, structures, or characteristics may be combined in any suitable manner in one or more embodiments. In the following description, numerous specific details are provided, such as examples of materials, frequencies, sizes, lengths, widths, shapes, etc., to provide a thorough understanding of the embodiments. However, those skilled in the relevant art will recognize that these embodiments may be practiced without one or more of the specific details or with other methods, components, materials, etc. In other cases, well-known structures, materials, or operations are not shown or described in detail to avoid obscuring various aspects of the embodiments.

[0168] It should be understood that the systems described herein include descriptions of specific embodiments. These embodiments can be combined into a single system, partially integrated into other systems, separated into multiple systems, or otherwise divided or combined. In addition, it is contemplated that parameters, attributes, aspects, etc. of one embodiment can be used in another embodiment. For clarity, these parameters, attributes, aspects, etc. are described only in one or more embodiments, and it should be understood that unless otherwise stated herein, these parameters, attributes, aspects, etc. can be combined with or substituted for parameters, attributes, etc. of another embodiment.

[0169] Although the foregoing has been described in considerable detail for purposes of clarity, it will be apparent that certain changes and modifications may be made without departing from the principles of the invention. It should be noted that there are many alternative ways of implementing both the processes and the apparatus described herein. The embodiments of the present invention are therefore to be considered illustrative and not restrictive, and the description is not to be limited to the details given herein, but may be modified within the scope and equivalents of the appended claims.

Claims

1. A computer-readable storage medium comprising instructions, which, when executed by a processor of an integrated access and backhaul IAB node in a wireless network, causes the IAB node to perform the following operations: detecting a radio link failure (RLF) associated with a parent node in the wireless network; and In response to detecting the RLF associated with a parent node in the wireless network: Transmitting a first backhaul RLF indication message to one or more descendant nodes of the IAB node, the first backhaul RLF indication message including identities of one or more nodes that should not be considered as candidate nodes for the one or more descendant nodes, the one or more nodes including the parent node; After transmitting the first backhaul RLF indication message, attempting to identify one or more alternative parent nodes of the IAB node; and In response to being unable to identify the one or more alternative parent nodes, transmitting a second return RLF indication message to the one or more descendant nodes of the IAB node, the second return RLF indication message indicating that the IAB node should also not be considered as a candidate node for the one or more descendant nodes.

2. The computer-readable storage medium of claim 1, wherein detecting the RLF comprises losing communication with the parent node.

3. The computer-readable storage medium of claim 1, wherein detecting the RLF comprises receiving a RLF message from the parent node, the RLF message indicating that the parent node has experienced the RLF. 4 . The computer-readable storage medium of claim 3 , wherein the RLF message further indicates that the parent node is not a candidate parent node among the one or more alternative parent nodes.

5. The computer-readable storage medium of claim 3, wherein attempting to identify the one or more alternative parent nodes comprises searching a set of IAB nodes that does not include the parent node.

6. The computer-readable storage medium of claim 3, wherein the instructions further configure the IAB node to: In response to receiving the RLF message, starting a recovery timer and generating the first backhaul RLF indication message; If the recovery timer does not expire before the IAB node is able to identify a candidate parent node from the one or more alternative parent nodes, or if the IAB node receives a first backhaul recovery success indication from the parent node, generating a second backhaul recovery success indication to transmit to the one or more descendant nodes of the IAB node and reestablishing a connection with the parent node; and If the recovery timer expires before the IAB node receives the first backhaul recovery success indication from the parent node and the IAB node is able to identify the candidate parent node from the one or more alternative parent nodes, attach to the candidate parent node to establish a new route between the IAB node and the one or more descendant nodes of the IAB node.

7. The computer-readable storage medium of claim 6, wherein the instructions further configure the IAB node to: If the recovery timer expires before the IAB node receives the first backhaul recovery success indication from the parent node and the IAB node cannot identify a candidate parent node from the one or more alternative parent nodes, the first backhaul RLF indication message is transmitted to one or more descendant nodes of the IAB node.

8. The computer-readable storage medium of claim 1, wherein the one or more descendant nodes of the IAB node include at least one of a descendant IAB node and a user equipment (UE) attached to the IAB node.

9. The computer-readable storage medium of claim 1, wherein the instructions further configure the IAB node to: In response to being unable to identify the one or more alternative parent nodes, generating a signal from the mobile terminal MT of the IAB node to the distributed unit DU of the IAB node to transmit the first backhaul RLF indication message; and The first backhaul RLF indication message is transmitted from the DU of the IAB node.

10. The computer-readable storage medium of claim 1, wherein the first backhaul RLF indication message comprises one or more of the following: a first identifier of one or more user equipment UEs attached to the IAB node, a second identifier of one or more descendant IAB nodes directly or indirectly attached to the IAB node, a third identifier of one or more UEs attached to the one or more descendant IAB nodes, and a cause value for re-establishment.

11. A method for an integrated access and backhaul IAB node in a wireless network, the method comprising: detecting a radio link failure (RLF) associated with a parent node in the wireless network; as well as In response to detecting the RLF associated with a parent node in the wireless network: Transmitting a first backhaul RLF indication message to one or more descendant nodes of the IAB node, the first backhaul RLF indication message including identities of one or more nodes that should not be considered as candidate nodes for the one or more descendant nodes, the one or more nodes including the parent node; After transmitting the first backhaul RLF indication message, attempting to identify one or more alternative parent nodes of the IAB node; as well as In response to being unable to identify the one or more alternative parent nodes, transmitting a second return RLF indication message to the one or more descendant nodes of the IAB node, the second return RLF indication message indicating that the IAB node should also not be considered as a candidate node for the one or more descendant nodes.

12. The method of claim 11, wherein detecting the RLF comprises losing communication with the parent node.

13. The method of claim 11, wherein detecting the RLF comprises receiving a RLF message from the parent node, the RLF message indicating that the parent node has experienced the RLF. 14 . The method of claim 13 , wherein the RLF message further indicates that the parent node is not a candidate parent node among the one or more alternative parent nodes.

15. The method of claim 13, wherein attempting to identify the one or more alternative parent nodes comprises searching a set of IAB nodes that does not include the parent node.

16. The method according to claim 13, further comprising: In response to receiving the RLF message, starting a recovery timer and generating the first backhaul RLF indication message; If the recovery timer does not expire before the IAB node is able to identify a candidate parent node from the one or more alternative parent nodes, or if the IAB node receives a first backhaul recovery success indication from the parent node, generating a second backhaul recovery success indication to transmit to the one or more descendant nodes of the IAB node and reestablishing a connection with the parent node; as well as If the recovery timer expires before the IAB node receives the first backhaul recovery success indication from the parent node and the IAB node is able to identify the candidate parent node from the one or more alternative parent nodes, attach to the candidate parent node to establish a new route between the IAB node and the one or more descendant nodes of the IAB node.

17. The method according to claim 16, further comprising: If the recovery timer expires before the IAB node receives the first backhaul recovery success indication from the parent node and the IAB node cannot identify a candidate parent node from the one or more alternative parent nodes, the first backhaul RLF indication message is transmitted to one or more descendant nodes of the IAB node.

18. The method of claim 11, wherein the one or more descendant nodes of the IAB node include at least one of a descendant IAB node and a user equipment (UE) attached to the IAB node.

19. The method according to claim 11, further comprising: In response to being unable to identify the one or more alternative parent nodes, generating a signal from the mobile terminal MT of the IAB node to the distributed unit DU of the IAB node to transmit the first backhaul RLF indication message; as well as The first backhaul RLF indication message is transmitted from the DU of the IAB node.

20. The method according to claim 11, wherein the first backhaul RLF indication message includes one or more of the following: a first identifier of one or more user equipment UEs attached to the IAB node, a second identifier of one or more descendant IAB nodes directly or indirectly attached to the IAB node, a third identifier of one or more UEs attached to the one or more descendant IAB nodes, and a cause value for re-establishment.

21. An apparatus for wireless communication, the apparatus comprising: A baseband processor, the baseband processor is used for: detecting a radio link failure RLF associated with a parent node in a wireless network; as well as In response to detecting the RLF associated with a parent node in the wireless network: Transmitting a first backhaul RLF indication message to one or more descendant nodes of the IAB node, the first backhaul RLF indication message including identities of one or more nodes that should not be considered as candidate nodes for the one or more descendant nodes, the one or more nodes including the parent node; After transmitting the first backhaul RLF indication message, attempting to identify one or more alternative parent nodes of the IAB node; as well as In response to being unable to identify the one or more alternative parent nodes, transmitting a second return RLF indication message to the one or more descendant nodes of the IAB node, the second return RLF indication message indicating that the IAB node should also not be considered as a candidate node for the one or more descendant nodes.

22. The apparatus of claim 21, wherein detecting the RLF comprises losing communication with the parent node.

23. The apparatus of claim 21, wherein detecting the RLF comprises receiving a RLF message from the parent node, the RLF message indicating that the parent node has experienced the RLF.

24. The apparatus of claim 23, wherein the RLF message further indicates that the parent node is not a candidate parent node among the one or more alternative parent nodes.

25. The apparatus of claim 23, wherein attempting to identify the one or more alternative parent nodes comprises searching a set of IAB nodes that does not include the parent node.

26. The apparatus of claim 23, wherein the baseband processor is further configured to: In response to receiving the RLF message, starting a recovery timer and generating the first backhaul RLF indication message; If the recovery timer does not expire before the IAB node is able to identify a candidate parent node from the one or more alternative parent nodes, or if the IAB node receives a first backhaul recovery success indication from the parent node, generating a second backhaul recovery success indication to transmit to the one or more descendant nodes of the IAB node and reestablishing a connection with the parent node; and If the recovery timer expires before the IAB node receives the first backhaul recovery success indication from the parent node and the IAB node is able to identify the candidate parent node from the one or more alternative parent nodes, attach to the candidate parent node to establish a new route between the IAB node and the one or more descendant nodes of the IAB node.

27. The apparatus of claim 26, wherein the baseband processor is further configured to: If the recovery timer expires before the IAB node receives the first backhaul recovery success indication from the parent node and the IAB node cannot identify a candidate parent node from the one or more alternative parent nodes, the first backhaul RLF indication message is transmitted to one or more descendant nodes of the IAB node.

28. The apparatus of claim 21, wherein the one or more descendant nodes of the IAB node include at least one of a descendant IAB node and a user equipment (UE) attached to the IAB node.

29. The apparatus of claim 21, wherein the baseband processor is further configured to: In response to being unable to identify the one or more alternative parent nodes, generating a signal from the mobile terminal MT of the IAB node to the distributed unit DU of the IAB node to transmit the first backhaul RLF indication message; and The first backhaul RLF indication message is transmitted from the DU of the IAB node.

30. The apparatus of claim 21, wherein the first backhaul RLF indication message comprises one or more of: a first identifier of one or more user equipment UEs attached to the IAB node, a second identifier of one or more descendant IAB nodes directly or indirectly attached to the IAB node, a third identifier of one or more UEs attached to the one or more descendant IAB nodes, and a cause value for re-establishment.

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