Method and apparatus for communication in an IAB network

Abstract

Embodiments of the present disclosure relate to methods and apparatus for communication in an Integrated Access and Backhaul (IAB) network. According to some embodiments of the present disclosure, a first base station (BS) may receive a Transport Transfer Management (TMM) request message from a second BS, the TMM request message may include an identifier associated with a wireless network node for the first BS to identify the wireless network node, and in response to receiving the TMM request message, transmit a TMM response message to the second BS, the mobile termination (MT) of the wireless network node handing over from a third BS to the first BS and the distributed unit (DU) of the wireless network node having an F1 connection to the second BS, or the DU of the wireless network node migrates from a fourth BS to the second BS and the MT of the wireless network node has a Radio Resource Control (RRC) connection to the first BS.

Description

Technical Field

[0001] Embodiments of the present disclosure generally relate to communication technologies, and more particularly, to communicating in an integrated access and backhaul (IAB) network.

Background Art

[0002] Wireless communication systems are widely deployed to provide various telecommunication services such as telephony, video, data, messaging, broadcasting, etc. Wireless communication systems may employ multiple access technologies that can support communication with multiple users by sharing available system resources (e.g., time, frequency, and power). Examples of wireless communication systems may include fourth-generation (4G) systems such as Long-Term Evolution (LTE) systems, LTE Advanced (LTE-A) systems, or LTE-A Pro systems, and fifth-generation (5G) systems sometimes referred to as New Radio (NR) systems.

[0003] To expand the coverage and availability of wireless communication systems (e.g., 5G systems), the Third Generation Partnership Project (3GPP (registered trademark)) envisions an integrated access and backhaul (IAB) architecture to support multi-hop relaying. In an IAB network, an IAB node can hop through one or more IAB nodes before reaching a base station (also referred to as an "IAB donor" or "donor node"). A single hop can be considered a special instance of multiple hops. Multi-hop backhauling is beneficial because it provides a relatively large coverage extension compared to single-hop backhauling. In relatively high-frequency wireless communication systems (e.g., wireless signals transmitted in a frequency band above 6 GHz), relatively narrow or small signal coverage can benefit from multi-hop backhauling techniques.

Summary of the Invention

Problems to be Solved by the Invention

[0004] The industry wants technologies to facilitate communication in IAB networks. [Means for solving the problem]

[0005] Some embodiments of the present disclosure provide a first base station (BS). The first BS may include a processor and a transceiver coupled to the processor. The transceiver may be configured to receive a transport transition management (TMM) request message from a second BS, the TMM request message may include an identifier associated with the wireless network node for the first BS to identify the wireless network node, and to transmit a TMM response message to the second BS in response to receiving the TMM request message, such that the mobile terminal (MT) of the wireless network node hands over from a third BS to the first BS and the distributed unit (DU) of the wireless network node has an F1 connection to the second BS, or the DU of the wireless network node moves from a fourth BS to the second BS and the MT of the wireless network node has a radio resource control (RRC) connection to the first BS.

[0006] In some embodiments of the present disclosure, the identifier associated with a wireless network node may include one of the following: the Cell Radio Network Temporary Identifier (C-RNTI) of the MT of the wireless network node, the BS-DU identifier (ID) of the DU of the wireless network node, the Backhaul Adaptive Protocol (BAP) address of the wireless network node, the User Equipment (UE) Xn Application Protocol (XnAP) ID of the MT of the wireless network node, and the BS-DU UE F1 Application Protocol (F1AP) ID of the DU of the wireless network node.

[0007] In some embodiments of the present disclosure, the TMM request message may include an information element (IE) indicating an identifier associated with a wireless network node, the IE being different from a non-F1 terminated BS UE XnAP ID IE in the TMM request message. In some embodiments of the present disclosure, the processor may be configured to ignore the non-F1 terminated BS UE XnAP ID IE in the TMM request message.

[0008] In some embodiments of the present disclosure, the processor may be further configured to, in response to receiving a TMM request message, assign a UE XnAP ID for the MT of a wireless network node which will be used on the Xn interface between a first BS and a second BS, and the TMM response message may include the assigned UE XnAP ID.

[0009] In some embodiments of this disclosure, the identifier associated with the wireless network node may include the UE XnAP ID of the MT of the wireless network node, which will be used on the Xn interface between the first BS and the second BS.

[0010] In some embodiments of this disclosure, the identifier associated with the wireless network node is included in the non-F1 terminated BS UE XnAP ID IE in the TMM request message.

[0011] In some embodiments of the present disclosure, the processor may be configured to assign a UE XnAP ID for the MT of a wireless network node, which will be used on the Xn interface between a first BS and a second BS, and the transceiver may be further configured to transmit the assigned UE XnAP ID to a third BS or wireless network node.

[0012] In some embodiments of the present disclosure, the transceiver may be further configured to receive a request message from a third BS or wireless network node asking for a UE XnAP ID, and assigning a UE XnAP ID may include assigning a UE XnAP ID in response to receiving the request message.

[0013] In some embodiments of this disclosure, the request message is a handover request message from a third BS, and the assigned UE XnAP ID is sent in the handover request confirmation message.

[0014] In some embodiments of the present disclosure, a request message from a third BS may include an identifier for a second BS and an identifier associated with a wireless network node, or a request message from a wireless network node may include an identifier for a second BS.

[0015] In some embodiments of the present disclosure, during the migration of a wireless network node's DU from a fourth BS to a second BS, the wireless network node may include a first DU having an F1 connection to the fourth BS and a second DU having an F1 connection to the second BS. The BS-DU ID of the wireless network node's DU is the BS-DU ID of the first DU of the wireless network node, and the BS-DU UE F1AP ID of the wireless network node's DU is the BS-DU UE F1AP ID of the first DU of the wireless network node.

[0016] Some embodiments of the present disclosure provide a second BS, which may include a processor and a transceiver coupled to the processor. The transceiver may be configured to transmit a TMM request message to a first BS, the TMM request message may include an identifier associated with the wireless network node for the first BS to identify the wireless network node, and to receive a TMM response message from the first BS in response to having transmitted the TMM request message, such that the MT of the wireless network node hands over from a third BS to the first BS and the DU of the wireless network node has an F1 connection to the second BS, or the DU of the wireless network node moves from a fourth BS to the second BS and the MT of the wireless network node has an RRC connection to the first BS.

[0017] In some embodiments of the present disclosure, the transceiver may be further configured to receive an identifier associated with a wireless network node from a third BS. The identifier associated with a wireless network node may include one of the following: the C-RNTI of the MT of the wireless network node, the BS-DU ID of the DU of the wireless network node, the BAP address of the wireless network node, and the UE XnAP ID of the MT of the wireless network node.

[0018] In some embodiments of the present disclosure, the transceiver may be further configured to receive an identifier associated with the wireless network node from the wireless network node. The identifier associated with the wireless network node may include one of the following: the C-RNTI of the MT of the wireless network node, the BS-DU ID of the DU of the wireless network node, the BAP address of the wireless network node, the UE XnAP ID of the MT of the wireless network node, and the BS-DU UE F1AP ID of the DU of the wireless network node.

[0019] In some embodiments of this disclosure, the TMM request message may include an IE indicating an identifier associated with a wireless network node, the IE being different from the non-F1 terminated BS UE XnAP ID IE in the TMM request message.

[0020] In some embodiments of this disclosure, the processor may be configured to set the non-F1 terminated BS UE XnAP ID IE in the TMM request message to be disabled or empty.

[0021] In some embodiments of this disclosure, the TMM response message may include the UE XnAP ID of the MT of the wireless network node, which is assigned by the first BS and will be used on the Xn interface between the first BS and the second BS.

[0022] In some embodiments of the present disclosure, the processor may be further configured to store the UE XnAP ID assigned by the first BS.

[0023] In some embodiments of the present disclosure, the identifier associated with the wireless network node may include the UE XnAP ID of the MT of the wireless network node, which is assigned by the first BS and will be used on the Xn interface between the first BS and the second BS.

[0024] In some embodiments of this disclosure, the identifier associated with the wireless network node is included in the non-F1 terminated BS UE XnAP ID IE in the TMM request message.

[0025] In some embodiments of this disclosure, an identifier associated with a wireless network node is received in the F1 setup request message.

[0026] In some embodiments of the present disclosure, during the transfer of the DU of the wireless network node from the fourth BS to the second BS, the wireless network node may include a first DU having an F1 connection to the fourth BS and a second DU having an F1 connection to the second BS. The BS-DU ID of the DU of the wireless network node is the BS-DU ID of the first DU of the wireless network node, and the BS-DU UE F1AP ID of the DU of the wireless network node is the BS-DU UE F1AP ID of the first DU of the wireless network node.

[0027] Some embodiments of the present disclosure provide a method performed by a first BS. The method may include receiving, from a second BS, a TMM request message, where the TMM request message may include an identifier associated with a wireless network node for the first BS to identify the wireless network node, and transmitting, in response to receiving the TMM request message, a TMM response message to the second BS, where the MT of the wireless network node handovers from a third BS to the first BS, and the DU of the wireless network node has an F1 connection to the second BS, or the DU of the wireless network node transfers from a fourth BS to the second BS, and the MT of the wireless network node has an RRC connection to the first BS.

[0028] Some embodiments of the present disclosure provide a method implemented by a second BS. The method includes transmitting a TMM request message to a first BS, where the TMM request message may include an identifier associated with a wireless network node for the first BS to identify the wireless network node, and receiving a TMM response message from the first BS in response to transmitting the TMM request message. The MT of the wireless network node may handover from a third BS to the first BS, and the DU of the wireless network node has an F1 connection to the second BS, or the DU of the wireless network node migrates from a fourth BS to the second BS, and the MT of the wireless network node has an RRC connection to the first BS.

[0029] Some embodiments of the present disclosure provide an apparatus. According to some embodiments of the present disclosure, the apparatus may include at least one non - transient computer - readable medium storing computer - executable instructions, at least one receiving circuit, at least one transmitting circuit, and at least one processor coupled to the at least one non - transient computer - readable medium, the at least one receiving circuit, and the at least one transmitting circuit. The at least one non - transient computer - readable medium and the computer - executable instructions may be configured to cause the apparatus to implement a method according to some embodiments of the present disclosure using the at least one processor.

[0030] Embodiments of the present disclosure provide technical solutions to facilitate and improve the implementation of various communication technologies such as 5G NR.

[0031] To explain how the advantages and features of the present disclosure can be obtained, the description of the present disclosure is made by referring to its specific embodiments shown in the accompanying drawings. These drawings only illustrate exemplary embodiments of the present disclosure and should not be considered as limiting its scope. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] [Figure 1] This is a schematic diagram of a wireless communication system according to some embodiments of the present disclosure. [Figure 2A] This is an exemplary block diagram of a protocol stack for an IAB network according to some embodiments of the present disclosure. [Figure 2B] This is an exemplary block diagram of a protocol stack for an IAB network according to some embodiments of the present disclosure. [Figure 3] This figure shows exemplary handover cases according to some embodiments of the present disclosure. [Figure 4] This figure shows exemplary handover cases according to some embodiments of the present disclosure. [Figure 5] This figure shows exemplary transition cases according to several embodiments of the present disclosure. [Figure 6] This is a flowchart illustrating exemplary transport transition management (TMM) procedures according to some embodiments of the present disclosure. [Figure 7] This is a flowchart illustrating an exemplary handover procedure according to some embodiments of the present disclosure. [Figure 8] This is a flowchart illustrating an exemplary handover procedure according to some embodiments of the present disclosure. [Figure 9] This is a flowchart illustrating exemplary transition procedures according to some embodiments of the present disclosure. [Figure 10] This is a flowchart illustrating exemplary transition procedures according to some embodiments of the present disclosure. [Figure 11] This is a flowchart illustrating an exemplary procedure for wireless communication according to some embodiments of the present disclosure. [Figure 12] This is a flowchart illustrating an exemplary procedure for wireless communication according to some embodiments of the present disclosure. [Figure 13] This is a block diagram of an exemplary apparatus according to several embodiments of the present disclosure. [Modes for carrying out the invention]

[0033] The detailed description of the accompanying drawings is intended to describe preferred embodiments of this disclosure and is not intended to represent the only forms in which this disclosure may be practiced. It should be understood that the same or equivalent functionality may be achieved by different embodiments that are intended to be included within the spirit and scope of this disclosure.

[0034] Next, several embodiments of this disclosure will be referenced in detail, examples of which are shown in the accompanying drawings. For ease of understanding, the embodiments are provided under specific network architectures and new service scenarios such as the 3rd Generation Partnership Project (3GPP®) 5G(NR) and 3GPP® Long-Term Evolution (LTE) Release 8. As network architectures and new service scenarios evolve, all embodiments in this disclosure are applicable to similar technical challenges, and furthermore, the terms enumerated in this disclosure may change, but this is intended not to affect the principles of this disclosure.

[0035] Compared to 4G communication systems, 5G communication systems have more stringent requirements for various network performance indicators, such as a 1000-fold increase in capacity, wider coverage requirements, ultra-high reliability, and ultra-low latency. Considering the abundant frequency resources of high-frequency carriers, the use of high-frequency small station deployments is becoming increasingly common in hotspot areas to meet the ultra-high capacity needs of 5G. However, high-frequency carriers have poor propagation characteristics, severe attenuation due to obstacles, and limited coverage. Therefore, dense deployment of small stations is required. In addition, the deployment of optical fibers can be difficult and expensive for these small stations. Therefore, an economical and convenient backhaul scheme is needed. Integrated access and backhaul (IAB) technology, where both access links and backhaul links can use wireless transmission solutions to avoid fiber deployment, offers an idea to solve the above challenges.

[0036] In an IAB network, wireless network nodes, such as relay nodes (RNs), IAB nodes, or wireless backhaul nodes / devices, can provide wireless access services for UEs. For example, a UE may connect to an IAB donor relayed by one or more IAB nodes. An IAB donor may also be called a donor node or donor base station (e.g., DgNB, donor gnode B). In addition, wireless links between IAB donors and IAB nodes, or wireless links between different IAB nodes, may be called "backhaul links." Wireless network nodes in an IAB network may be stationary or mobile. Embodiments of this disclosure may apply to wireless network nodes regardless of whether they are stationary or mobile.

[0037] An IAB node may include an IAB Mobile Terminal (MT) portion and an IAB Distributed Unit (DU) portion. When an IAB node connects to its parent node (which may be another IAB node or IAB donor), the IAB node may be considered to be in the role of a UE, i.e., an MT. When an IAB node provides services to its child nodes (which may be another IAB node or UE), the IAB node may be considered to be in the role of a network device, i.e., a DU.

[0038] An IAB donor can be an access network element with full base station functionality, or an access network element having separate forms of centralized units (CUs) and distributed units (DUs). An IAB donor may be connected to a core network (for example, to a 5G core (5GC) network) and provide wireless backhaul functionality for IAB nodes. An IAB donor CU may be called an "IAB donor CU" (or simply called a "CU"), and an IAB donor DU may be called an "IAB donor DU". An IAB donor CU may be divided into a control plane (CP) and a user plane (UP). For example, a CU may include one CU-CP and one or more CU-UPs.

[0039] Considering the limited coverage of the high-frequency bandwidth and to ensure network coverage performance, multi-hop networking may be employed in IAB networks. Taking into account the requirements for service transmission reliability, IAB nodes may support dual connectivity (DC) or multi-connectivity to improve transmission reliability in order to deal with abnormal situations that may occur on the backhaul (BH) link, such as radio link failures (RLF) or interference, load fluctuations, etc.

[0040] If the IAB network supports multi-hop and dual-connection networking, there may be multiple transmission paths between the UE and the IAB donor. A transmission path may include multiple nodes, such as the UE, one or more IAB nodes, and the IAB donor (if the IAB donor is in the form of separate CUs and DUs, the IAB donor may also include the IAB donor DU and IAB donor CU). Each IAB node may treat a neighboring node that provides backhaul services for the IAB node as its parent node (or parent IAB node), and each IAB node may be considered a child node (or child IAB node) of that parent node.

[0041] Figure 1 shows a schematic diagram of a wireless communication system 100 according to several embodiments of the present disclosure.

[0042] As shown in Figure 1, the wireless communication system 100 may include several base stations (e.g., IAB donors 110A and 110B), several IAB nodes (e.g., IAB node 120A, IAB node 120B, and IAB node 120C), and several UEs (e.g., UE130A and UE130B). While a specific number of UEs, IAB nodes, and IAB donors are illustrated in Figure 1, it is intended that any number of UEs, IAB nodes, and IAB donors may be included in the wireless communication system 100.

[0043] Each of IAB donor 110A, IAB donor 110B, IAB node 120A, IAB node 120B, and IAB node 120C may be directly connected to one or more IAB nodes according to some other embodiments of the present disclosure. Each of IAB donor 110A, IAB donor 110B, IAB node 120A, IAB node 120B, and IAB node 120C may be directly connected to one or more UEs according to some other embodiments of the present disclosure.

[0044] UE130A and UE130B may be any type of device configured to operate and / or communicate in a wireless environment. For example, UE130A and UE130B may include computing devices such as desktop computers, laptop computers, personal digital assistants (PDAs), tablet computers, smart televisions (e.g., internet-connected televisions), set-top boxes, game consoles, security systems (including security cameras), in-vehicle computers, and network devices (e.g., routers, switches, and modems). According to some embodiments of the Disclosure, UE130A and UE130B may include portable wireless communication devices, smartphones, cellular phones, flip phones, devices with subscriber identification modules, personal computers, selective call receivers, or any other devices capable of transmitting and receiving communication signals over a wireless network. In some embodiments of the Disclosure, UE130A and UE130B may include wearable devices such as smartwatches, fitness bands, optical head-mounted displays, and Internet of Things (IoT) devices. Furthermore, UE130A and UE130B may be referred to as subscriber units, mobile stations, mobile stations, users, terminals, mobile terminals, wireless terminals, fixed terminals, subscriber stations, user terminals, or devices, or described using other terms used in the art.

[0045] IAB donors 110A and 110B may communicate with a core network (not shown in Figure 1). The core network (CN) may include multiple core network components, such as Mobility Management Entities (MMEs) (not shown in Figure 1) or Access and Mobility Management Functions (AMFs) (not shown in Figure 1). The CN may act as a gateway for UEs to access the Public Switched Telephone Network (PSTN) and / or other networks (not shown in Figure 1).

[0046] The wireless communication system 100 may be compatible with any type of network capable of transmitting and receiving wireless communication signals. For example, the wireless communication system 100 is compatible with wireless communication networks, cellular telephone networks, time division multiple access (TDMA) based networks, code division multiple access (CDMA) based networks, orthogonal frequency division multiple access (OFDMA) based networks, LTE networks, 3GPP® based networks, 3GPP® 5G networks, satellite communication networks, high-altitude platform networks, and / or other communication networks.

[0047] In some embodiments of this disclosure, the wireless communication system 100 is compatible with 5G NR of the 3GPP® protocol. For example, IAB donors 110A and 110B may transmit data using orthogonal frequency division multiplexing (OFDM) modulation over DL. UE 130A and UE 130B may transmit data using discrete Fourier transform spread orthogonal frequency division multiplexing (DFT-S-OFDM) or cyclic prefix OFDM (CP-OFDM) over UL. However, more generally, the wireless communication system 100 may implement several other open or proprietary communication protocols, such as WiMAX among many protocols.

[0048] Those skilled in the art should understand that as the technology develops and progresses, the terms described in this disclosure may change, but this should not affect or limit the principles and intent of this disclosure.

[0049] Referring to Figure 1, IAB node 120A can be directly connected to IAB donors 110A and 110B, and IAB node 120B can be directly connected to IAB donor 110A. IAB donors 110A and 110B are parent nodes of IAB node 120A, and IAB donor 110A is the parent node of IAB node 120B. In other words, IAB nodes 120A and 120B are child IAB nodes of IAB donor 110A, and IAB node 120A is also a child IAB node of IAB donor 110B. IAB node 120C can reach IAB donor 110A by hopping through IAB node 120B. IAB node 120B is the parent IAB node of IAB node 120C. In other words, IAB node 120C is a child IAB node of IAB node 120B.

[0050] In some other embodiments of this disclosure, an IAB node may be connected to an IAB node 120C so that the IAB node can reach an IAB donor 110A by hopping through IAB nodes 120C and 120B. These IAB nodes and 120C may be referred to as descendant IAB nodes of IAB node 120B.

[0051] UE130A and 130B may be connected to IAB nodes 120A and 120C, respectively. Therefore, IAB nodes 120A and 120C are sometimes referred to as access IAB nodes. Uplink (UL) packets (e.g., data or signaling) from UE130A or UE130B may be transmitted to an IAB donor (e.g., IAB donor 110A or 110B) via one or more IAB nodes, and then transmitted by the IAB donor to a mobile gateway device (such as a user plane function (UPF) in 5GC). Downlink (DL) packets (e.g., data or signaling) may be transmitted from the IAB donor (e.g., IAB donor 110A or 110B) after being received by the gateway device, and then transmitted to UE130A or 130B via one or more IAB nodes.

[0052] For example, referring to Figure 1, UE130A can send UL data to IAB donor 110A or 110B via IAB node 120A, or receive DL data from there. UE130B can send UL data to IAB donor 110A via IAB nodes 120C and 120B, or receive DL data from there.

[0053] In an IAB deployment such as wireless communication system 100, the radio link between an IAB donor (for example, IAB donor 110A or 110B in Figure 1) and an IAB node, or between two IAB nodes, is sometimes called a backhaul link (BL). The radio link between an IAB donor (for example, IAB donor 110A or 110B in Figure 1) and an UE, or between an IAB node and an UE, is sometimes called an access link (AL). For example, in Figure 1, radio links 140A through 140D are BLs, and radio links 150A and 150B are ALs.

[0054] A Backhaul Adaptive Protocol (BAP) layer, which is a protocol layer built on top of the Radio Link Control (RLC) layer, can be introduced into the IAB system and used to enable packet routing, bearer mapping, and flow control on wireless backhaul links.

[0055] An F1 interface can be established between an IAB node (e.g., the DU portion of an IAB node) and an IAB donor (e.g., an IAB donor CU). The F1 interface may support both user-plane protocols (e.g., F1-U) and control-plane protocols (e.g., F1-C). The user-plane protocols of the F1 interface may include one or more of the following: General-Package Radio Services (GPRS) Tunneling Protocol User Plane (GTP-U), User Datagram Protocol (UDP), Internet Protocol (IP), and other protocols. The control-plane protocols of the F1 interface may include one or more of the following: F1 Application Protocol (F1AP), Stream Control Transport Protocol (SCTP), IP, and other protocols.

[0056] Through the control plane of the F1 interface, IAB nodes and IAB donors can perform, for example, interface management, IAB-DU management, and UE context-related configurations. Through the user plane of the F1 interface, IAB nodes and IAB donors can perform, for example, user plane data transmission and downlink transmission status feedback functions.

[0057] Figure 2A shows an exemplary block diagram of a user plane (UP) protocol stack 200A for an IAB network according to some embodiments of the present disclosure. Figure 2B shows an exemplary block diagram of a control plane (CP) protocol stack 200B for an IAB network according to some embodiments of the present disclosure. In Figures 2A and 2B, the UE may be connected to the IAB donor via IAB node 2 and IAB node 1. In some other embodiments of the present disclosure, the UE may be connected to the IAB donor via more or fewer IAB nodes.

[0058] Referring to Figure 2A, the UE's UP protocol stack may include the Service Data Adaptive Protocol (SDAP) layer, the Packet Data Convergence Protocol (PDCP) layer, the Radio Link Control (RLC) layer, the Medium Access Control (MAC) layer, and the Physical (PHY) layer. The UP protocol stack of the DU at IAB Node 2 may include the GTP-U layer, UDP layer, IP layer, RLC layer, MAC layer, and PHY layer. The UP protocol stack of the MT at IAB Node 2 or the DU or MT at IAB Node 1 may include the BAP layer, RLC layer, MAC layer, and PHY layer. The UP protocol stack of the DU at an IAB donor may include the IP layer, BAP layer, RLC layer, MAC layer, and PHY layer, with the PHY layer belonging to Layer 1 (L1) and the BAP layer, RLC layer, and MAC layer belonging to Layer 2 (L2). The protocol stack of an IAB donor's CU-UP may include the GTP-U layer, UDP layer, IP layer, SDAP layer, PDCP layer, L2 layer, and L1 layer.

[0059] Referring to Figure 2B, the UE's CP protocol stack may include the Radio Resource Control (RRC) layer, PDCP layer, RLC layer, MAC layer, and Physical (PHY) layer. The CP protocol stack of the DU at IAB Node 2 may include the F1AP layer, SCTP layer, IP layer, RLC layer, MAC layer, and PHY layer. The CP protocol stack of the MT at IAB Node 2 or the DU or MT at IAB Node 1 may include the BAP layer, RLC layer, MAC layer, and PHY layer. The CP protocol stack of the DU at the IAB donor may include the IP layer, BAP layer, RLC layer, MAC layer, and PHY layer, with the PHY layer belonging to L1 and the BAP layer, RLC layer, and MAC layer belonging to L2. The protocol stack of the CU-CP at the IAB donor may include the RRC layer, PDCP layer, F1AP layer, SCTP layer, IP layer, L2 layer, and L1 layer.

[0060] The protocol stacks shown in Figures 2A and 2B are for illustrative purposes only. For example, some sequences of protocol layers in the protocol stacks of Figures 2A and 2B may be rearranged for illustrative purposes. For instance, the SDAP and PDCP layers belong to L2, but these layers are shown above the GTP-U, UDP, and IP layers in the protocol stack of the IAB donor CU-UP in Figure 2A.

[0061] Signals between each node in the IAB network may include, for example, the following, and may be applied to this disclosure: - IAB Donor CU and IAB Donor DU: F1AP message, - IAB donor CU and IAB node: F1AP message between CU and IAB-DU or RRC message between CU and IAB-MT, - IAB donor CU and UE: RRC message, - Access IAB nodes and UE: MAC control element (CE) or L2 control PDU such as RLC control PDU, and - IAB node and other child IAB nodes or parent IAB nodes: L2 control PDUs such as MAC CE, RLC control PDU, or BAP control PDU.

[0062] As the demand for improved cellular coverage and connectivity continues to grow, communications in outdoor and mobility scenarios may face further challenges. In some embodiments of this disclosure, a mobile wireless network node may be employed to facilitate communications in such scenarios, acting as a relay between the UE and a 3GPP® communications network (e.g., 5G). The mobile wireless network node may, for example, provide an access link to the UE and be wirelessly connected to the core network via a BS (e.g., a donor Next Generation Radio Access Network (NG-RAN)) (e.g., using NR). In some examples, such a mobile wireless network node may also be referred to as a mobile base station relay or mobile relay. The above description of wireless network nodes and IAB nodes may apply to mobile base station relays; that is, a mobile base station relay may be a mobile IAB node.

[0063] In some examples, a mobile base station relay may be mounted on a vehicle. The mobile base station relay may serve a UE located inside (in-vehicle) or outside (outside) the vehicle, or a UE entering or leaving the vehicle. In the context of this disclosure, "inside" or "outside" of a mobile base station relay may mean inside or outside a vehicle or other device on which a mobile wireless network node is mounted.

[0064] In some examples, the radio links used between the mobile base station relay and the serviced UE, and between the mobile base station relay and the BS, may be different Uu links (e.g., NR-Uu) from the UE relay (e.g., providing indirect connectivity to the remote UE using a PC5-based link). In some examples, there may be at least one hop between the UE and the mobile base station relay. In some examples, there may be at least one hop between the mobile base station relay and the BS.

[0065] The adoption of such mobile wireless network nodes offers advantages in various aspects and can be applied to a variety of scenarios. For example, in some outdoor environments, having vehicles equipped with mobile base station relays available, following certain known / predictable routes (e.g., buses, trams, etc.) or located in convenient locations (e.g., outdoor sports fields, hotspot areas, or emergency sites), can significantly increase cellular coverage and capabilities on a flexible basis when and where needed. These relays may, for example, use 5G wireless backhaul toward a macro network, and thus can provide better coverage and connectivity to nearby UEs. Mobile relays are also very suitable for improving the connectivity of users or devices inside vehicles equipped with mobile relays in different environments, for example, for passengers in buses, cars / taxis, or trains, or for special / professional personnel or equipment. Such mobile wireless network nodes can also be used to reach users or devices that otherwise have no or very poor macro coverage, for example, in the case of a first responder that has moved into an indoor building / area, using relays placed nearby or in an outdoor vehicle to obtain the necessary coverage and connectivity.

[0066] The technical benefits of using such mobile wireless network nodes include, among many others, the ability to achieve better macro coverage than nearby UEs by leveraging better radio frequencies, antennas, and power capabilities. In addition to the value for network operators and end users, there may also be valuable incentives for other parties, such as vehicle manufacturers, as well as vehicle and fleet owners or providers, to install and operate relays in vehicles.

[0067] In the context of this disclosure, a wireless network node may refer to either a stationary wireless network node or a mobile wireless network node.

[0068] Due to the mobility of wireless network nodes (e.g., IAB nodes), wireless network nodes may need to migrate (or hand over) from one IAB donor to another (i.e., inter-donor migration).

[0069] In some embodiments, the MT of a wireless network node may migrate from the original (source) IAB donor to a new (target) IAB donor. For example, the MT of a wireless network node may migrate to a different parent node under a different CU of the IAB donor. For example, referring back to Figure 1, the MT of IAB node 120C or IAB node 120B may migrate from IAB donor 110A to IAB donor 110B. In this scenario, the DU of the wireless network node and the DU of the descendant nodes of the wireless network node may maintain F1 connectivity with the source IAB donor (e.g., the CU of the source IAB donor). This migration is sometimes called a donor-to-donor partial migration or donor-to-donor IAB-MT handover. The wireless network node performing the donor-to-donor partial migration is sometimes called a perimeter wireless network node. After the donor-to-donor partial migration, the F1 traffic of the DU of the wireless network node and the DU of the descendant nodes of the wireless network node may be routed, for example, through the BAP layer of the IAB topology to which the MT of the wireless network node has migrated.

[0070] In some embodiments, the DU of a wireless network node may migrate from the initial (source) IAB donor to a new (target) IAB donor. This migration is sometimes referred to as an inter-donor IAB-DU migration. In some embodiments, to perform a handover of UEs served by the wireless network node (e.g., its DU), the wireless network node may simultaneously support two logical DUs (e.g., DU #1 and DU #2), each having an F1AP association with a source IAB donor (e.g., the source IAB donor's CU) and a target IAB donor (e.g., the target IAB donor's CU), respectively. UEs connected to the wireless network node may be handed over from the cell of DU #1 (i.e., the source DU of the wireless network node) to the cell of DU #2 (i.e., the target DU of the wireless network node). After the migration of the wireless network node's DU, the F1 interface between DU #1 and the source IAB donor may be released.

[0071] In the context of this disclosure, the terms handover and migration may be used interchangeably. While embodiments of this disclosure may be discussed based on certain specific components (e.g., IAB donors or IAB nodes) under a particular network architecture (e.g., an IAB architecture), it should be noted that embodiments of this disclosure are applicable to other similar network architectures and new service scenarios. In the context of this disclosure, both BS (e.g., an IAB donor) and network nodes (e.g., IAB nodes) may include DUs, but it should be noted that DUs in BS and DUs in network nodes generally function differently.

[0072] For example, Figure 3 shows an exemplary handover case according to several embodiments of the present disclosure. Referring to Figure 3, IAB donor 310A may include IAB donor CU1 and IAB donor DU1, and IAB donor 310B may include IAB donor CU2 and IAB donor DU2. IAB node 321 may be connected to IAB donor 310A and may include IAB-MT 1 and IAB-DU 1, and IAB node 322 may be connected to IAB donor 310B and may include IAB-MT 2 and IAB-DU 2. IAB node 323 may include IAB-MT 3 and IAB-DU 3. Details described in all of the above embodiments of the present disclosure are applicable to Figure 3.

[0073] In the example in Figure 3, the MT (IAB-MT 3) of IAB node 323 can be handed over from IAB donor CU1 to IAB donor CU2. Prior to the handover of IAB node 323, IAB node 323 can reach IAB donor 310A via IAB node 321. Both IAB-MT 3 and IAB-DU 3 can be anchored at IAB donor CU1. During the handover of IAB-MT 3, the F1 transport between IAB-DU 3 and IAB donor 310A (e.g., IAB donor CU1) is switched from a source path (not shown in Figure 3) under the topology of IAB donor 310A (e.g., IAB donor CU1) to a target path (indicated by signaling flow 330) under the topology of IAB donor 310B (e.g., IAB donor CU2).

[0074] Following the handover of IAB node 323, IAB-MT 3 may be handed over from IAB donor 310A to IAB donor 310B, while IAB-DU 3 may still be under the control of IAB donor CU1. That is, after the MT handover, IAB-MT 3 may be anchored at IAB donor CU2, while IAB-DU 3 may still be anchored at IAB donor CU1. IAB donor CU1 is sometimes referred to as the "F1-terminated CU". IAB donor CU2 is sometimes referred to as the "non-F1-terminated CU" or "RRC-terminated CU". IAB donor 310A is sometimes referred to as the "F1-terminated IAB donor" or "F1-terminated BS". IAB donor 310B is sometimes referred to as the "non-F1-terminated IAB donor", "non-F1-terminated BS", or "RRC-terminated BS".

[0075] Figure 4 illustrates an exemplary handover case according to several other embodiments of the present disclosure. In the example in Figure 4, the MT of a wireless network node is handed over from one BS to another, but the DU of the wireless network node connects to yet another BS (hereinafter referred to as "Scenario 1"). Details described in all of the above embodiments of the present disclosure are applicable to Figure 4.

[0076] Referring to Figure 4, IAB donor 410A may include CU475 and DU465, IAB donor 410B may include CU476 and DU466, and IAB donor 410C may include CU477 and DU467. IAB node 420A may be directly connected to IAB donor 410A and may include MT451 and DU461. IAB node 420B may be directly connected to IAB donor 410B and may include MT452 and DU462. IAB node 420C may be directly connected to IAB donor 410C and may include MT453 and DU463. IAB node 420D may include MT454 and DU464, and UE430 may be connected to IAB node 420D. IAB node 420D is sometimes referred to as the access IAB node for UE430.

[0077] DU464 on IAB node 420D may be anchored at IAB donor 410C (e.g., CU477). IAB donor 410C is sometimes referred to as the F1-terminated BS of IAB node 420D. MT454 on IAB node 420D may be handed over (or migrated) from IAB donor 410A (i.e., source non-F1-terminated BS) to IAB donor 410B (i.e., target non-F1-terminated BS). During the handover of MT454, the F1 transport between DU464 and IAB donor 410C is switched from the topology of IAB donor 410A (e.g., indicated by signaling flow 440A) to the topology of IAB donor 410B (e.g., indicated by signaling flow 440B).

[0078] Figure 5 illustrates an exemplary migration case according to several embodiments of the present disclosure. In the example in Figure 5, the DU of a wireless network node migrates from one BS to another, but the MT of the wireless network node connects to yet another BS (hereinafter referred to as "Scenario 2"). Details described in all of the above embodiments of the present disclosure are applicable to Figure 5.

[0079] Referring to Figure 5, IAB donor 510A may include CU575 and DU565, IAB donor 510B may include CU576 and DU566, and IAB donor 510C may include CU577 and DU567. IAB node 520A may be directly connected to IAB donor 510A and may include MT551 and DU561. IAB node 520B may be directly connected to IAB donor 510B and may include MT552 and DU562. IAB node 520C may be directly connected to IAB donor 510C and may include MT553 and DU563. IAB node 520D may include MT554 and two DUs (DU564a and DU564b), and UE530 may be connected to IAB node 520D. IAB node 520D is sometimes referred to as the access IAB node for UE530.

[0080] MT554 of IAB node 520D may be anchored at IAB donor 510B (e.g., CU576). IAB donor 510B is sometimes referred to as the non-F1 terminating BS of IAB node 520D. The DU of IAB node 520D may migrate from IAB donor 510A (i.e., source F1 terminating BS) to IAB donor 510C (i.e., target F1 terminating BS). Before the DU migration, only DU564a of IAB node 520D has an F1 connection to IAB donor 510A (e.g., indicated by signaling flow 540A). During the DU migration, IAB node 520D may have two DUs (e.g., DU564a and DU564b as shown in Figure 5). DU564a may have an F1 connection to IAB donor 510A, and DU564b may have an F1 connection to IAB donor 510C (e.g., indicated by signaling flow 540B). After the DU transition, only DU564b at IAB node 520D will have an F1 connection to IAB donor 510C. Both F1 connections are transported through the topology of IAB donor 510B.

[0081] The MT handover and DU migrations shown in Figures 3 to 5 are for illustrative purposes only. For example, in some other embodiments, the MT and DU of a wireless network node may be anchored at the same BS (e.g., an IAB donor), and the DU of a wireless network node may migrate from a source BS to a target BS (e.g., an IAB donor). For example, in some other embodiments, a wireless network node may hop through one or more wireless network nodes (e.g., IAB nodes) before reaching a source BS or target BS, or it may connect directly to a source BS or target BS.

[0082] Embodiments of this disclosure provide solutions for facilitating the handover or migration of wireless network nodes.

[0083] For example, in Scenario 1, an F1-terminated BS (e.g., IAB donor 410C in Figure 4) may not be aware that a wireless network node has performed an IAB-MT handover to a (target) non-F1-terminated BS (e.g., IAB donor 410B in Figure 4) via a handover or migration procedure, and in Scenario 2, a (target) F1-terminated BS (e.g., IAB donor 510C in Figure 5) may not be aware of which node is the non-F1-terminated BS (e.g., IAB donor 510B in Figure 5). Embodiments of this disclosure provide solutions for notifying an F1-terminated BS (or F1-terminated CU) of the presence of a non-F1-terminated BS (or non-F1-terminated CU), and solutions for associating wireless network nodes between an F1-terminated BS (or F1-terminated CU) and a non-F1-terminated BS (or non-F1-terminated CU).

[0084] For example, as described above, the MT and DU of a wireless network node may be connected to different BS (or CU). In some embodiments of this disclosure, a TMM procedure may be performed between two BS (or CU) to exchange information between the two BS (or CU) and to manage the migration of wireless network node and descendant wireless network node traffic between topologies managed by the two BS (or CU). In the context of IAB networks, the TMM procedure is sometimes referred to as the IAB TMM procedure.

[0085] For example, a TMM procedure may be performed between an F1-terminated BS (e.g., an F1-terminated IAB donor CU) and a non-F1-terminated BS (e.g., a non-F1-terminated IAB donor CU) of a wireless network node (e.g., an IAB node) to exchange information and manage the migration of wireless network node and descendant node traffic between topologies managed by two BSs (e.g., two IAB donor CUs). For example, the procedure may be initiated by the F1-terminated BS (e.g., an F1-terminated IAB donor CU) of the IAB node. For example, the procedure may be used to set up, modify, and release (e.g., for the purpose of reversal) resources under a non-F1-terminated BS (e.g., a non-F1-terminated IAB donor CU) used to service offloaded traffic.

[0086] Figure 6 shows a flowchart of an exemplary TMM procedure 600 according to several embodiments of the present disclosure. Details described in all of the above embodiments of the present disclosure are applicable to the embodiments shown in Figure 6. For example, BS610A and 610B may function as IAB donors as described above and may include a CU and at least one DU.

[0087] BS610A and 610B may be the F1-terminated BS and non-F1-terminated BS of a wireless network node (indicated as node #1 for clarity). For example, the DU of node #1 may have an F1 connection to BS610A, and the MT of node #1 may have an RRC connection to BS610B. In operation 621, BS610A may send a TMM request message (e.g., an IAB TMM request message) to BS610B. In operation 623, BS610B may send a TMM response message (e.g., an IAB TMM response message) to BS610A as a response.

[0088] In some embodiments of this disclosure, the TMM request message and TMM response message may indicate the UE XnAP ID of the MT at node #1 (e.g., the NG-RAN node UE XnAP ID), which will be used on the Xn interface between BS610A and BS610B and is assigned by both BS610A and BS610B. The two UE XnAP IDs may be included in the TMM request message and TMM response message as the F1-terminated BS UE XnAP ID IE and the non-F1-terminated BS UE XnAP ID IE, respectively.

[0089] The UE XnAP ID can be assigned by BS610A and BS610B. For example, the MT of node #1 may be handed over from BS610A to BS610B. For example, node #1 may perform a handover procedure as shown in Figure 3. For example, the MT of node #1 may be handed over from BS610A to BS610B, but the DU of node #1 may still be under the control of BS610A. During the handover of node #1's MT from BS610A to BS610B (for example, during the IAB-MT handover preparation procedure), BS610A (for example, BS610A's CU) may assign a UE XnAP ID for node #1's MT (indicated as "ID #1"), which may be included in the handover request message from BS610A to BS610B. BS610B (for example, BS610B's CU) may feed back the UE XnAP ID of the MT of node #1 (indicated as "ID #2"). For example, BS610B may send a handover request acknowledgment message containing ID #2 to BS610A. The handover request acknowledgment message may also contain ID #1. After the handover preparation procedure, BS610A (for example, BS610A's CU) and BS610B (for example, BS610B's CU) may have the UE XnAP IDs of the MT of node #1 assigned to each other. After the handover of the MT of node #1 from BS610A to BS610B, BS610A (for example, BS610A's CU) may trigger a TMM procedure as shown in Figure 6. The UE XnAP IDs (e.g., ID #1 and ID #2) assigned by BS610A (e.g., the CU of BS610A) and BS610B (e.g., the CU of BS610B) may be included in the TMM request message and TMM response message.

[0090] In scenarios 1 and 2 (for example, Figures 4 and 5), after an MT handover or DU transition, F1 signaling between the F1-terminated BS and the wireless network node (for example, F1 signaling between IAB donor 410C and IAB node 420D in Figure 4 or F1 signaling between IAB donor 510C and IAB node 520D in Figure 5) can be transported over a backhaul link under the topology of a non-F1-terminated BS (for example, IAB donor 410B in Figure 4 or IAB donor 510B in Figure 5). Similarly, the F1-terminated BS (for example, IAB donor 410C in Figure 4 or IAB donor 510C in Figure 5) can trigger a TMM procedure to a non-F1-terminated BS (for example, IAB donor 410B in Figure 4 or IAB donor 510B in Figure 5) to exchange information and manage the transition of traffic between the two BSs (for example, two CUs). However, in scenarios 1 and 2, the F1-terminated BS and the non-F1-terminated BS may not assign and exchange UE XnAP IDs for the Xn interface between the F1-terminated BS and the non-F1-terminated BS. Embodiments of the present disclosure provide a solution for exchanging UE XnAP IDs for the Xn interface between the F1-terminated BS and the non-F1-terminated BS. For example, since such IDs are required for TMM procedures between the F1-terminated BS and the non-F1-terminated BS (for example, the F1-terminated BS may trigger a TMM request to the non-F1-terminated BS that includes the non-F1-terminated BS UE XnAP ID), embodiments of the present disclosure provide a solution for setting the non-F1-terminated BS UE XnAP ID in the TMM request message.

[0091] Further details relating to embodiments of this disclosure are described in the following text in conjunction with the accompanying drawings.

[0092] For example, Figure 7 shows a flowchart of an exemplary handover procedure 700 according to several embodiments of the present disclosure.

[0093] The details described in all of the above embodiments of this disclosure are applicable to the embodiments shown in Figure 7. For example, BS710A-710C may function as IAB donors as described above and may include a CU and at least one DU. Network node 720 may function as an IAB node as described above and may include an MT and a DU.

[0094] Network node 720 (for example, the DU of network node 720) may have an F1 connection with BS710C (for example, the CU of BS710C). Network node 720 (for example, the MT of network node 720) may have an RRC connection with BS710A (for example, the CU of BS710A). BS710C and BS710A are sometimes referred to as F1-terminated BS and non-F1-terminated BS (or RRC-terminated BS), respectively. The CU of BS710C and the CU of BS710A are sometimes referred to as F1-terminated BS-CU and non-F1-terminated BS-CU (or RRC-terminated BS-CU), respectively.

[0095] In some embodiments, the MT of network node 720 may perform a handover from BS710A (i.e., a source non-F1 terminated BS) to a target BS (i.e., a target non-F1 terminated BS such as BS710B), while the DU of network node 720 maintains its connection with BS710C (e.g., the CU of BS710C). For example, BS710A, BS710B, BS710C, and network node 720 may function as IAB donor 410A, IAB donor 410B, IAB donor 410C, and IAB node 420D in Figure 4.

[0096] For example, referring to Figure 7, in operation 711, the handover preparation procedure for network node 720 (e.g., the MT of network node 720) may be performed between BS710A and BS710B. For example, BS710A (e.g., the CU of BS710A) may send a handover request message to BS710B (e.g., the CU of BS710B) in order to hand over network node 720 (e.g., the MT of network node 720). BS710B (e.g., the CU of BS710B) may send a response to the handover request message to BS710A (e.g., positive feedback such as a handover request acknowledgment message or negative feedback such as a handover preparation failure message).

[0097] In some embodiments, operation 711 may further include the following steps: BS710B (e.g., CU of BS710B) sets up a UE context for network node 720 (e.g., MT of network node 720) on the target parent node, performs admission control for network node 720 (e.g., MT of network node 720), and provides RRC reconfiguration (e.g., handover command) as part of a handover request confirmation message.

[0098] In some embodiments, the handover request message may include a UE XnAP ID assigned by BS710A (e.g., the CU of BS710A) (e.g., an NG-RAN node UE XnAP ID shown as ID #7A). The handover request acknowledgment message may include a UE XnAP ID assigned by BS710B (e.g., the CU of BS710B) (e.g., an NG-RAN node UE XnAP ID shown as ID #7B). The handover request acknowledgment message may also include ID #7A. IDs #7A and #7B may be used on the Xn interface between BS710A (e.g., the CU of BS710A) and BS710B (e.g., the CU of BS710B).

[0099] In operation 713, BS710A (e.g., the CU of BS710A) may send a handover command (e.g., RRC reconfiguration) to network node 720 (e.g., the MT of network node 720). In some embodiments, the handover command or RRC reconfiguration may be included in a UE context change request message to the source parent node (e.g., the DU of the source parent node of network node 720). In some examples, assuming that network node 720 functions as IAB node 420D in Figure 4, the source parent node and target parent node of network node 720 may be IAB node 420A and IAB node 420B, respectively. The source parent node (e.g., the DU of the source parent node of network node 720) may forward the received handover command or RRC reconfiguration to the destination node (e.g., the MT of network node 720). In some examples, the source parent node or target parent node of network node 720 may be a BS or an IAB donor.

[0100] In operation 715, network node 720 (for example, the MT of network node 720) may perform a random access procedure with the target parent node (for example, the DU of the target parent node of network node 720) to set up an RRC connection to BS710B (for example, the CU of BS710B).

[0101] In operation 717, BS710A (for example, the CU of BS710A) may send a message to BS710C (for example, the CU of BS710C) indicating that network node 720 (for example, the MT of network node 720) has been handed over to BS710B (for example, the CU of BS710B).

[0102] In some embodiments, the message in operation 717 may include an identifier for BS710B (e.g., the ID of the CU of BS710B) so that BS710C (e.g., the CU of BS710C) can trigger a TMM procedure on the appropriate non-F1 terminating BS (e.g., a non-F1 terminating CU such as the CU of BS710B). For example, the ID of BS710B could be the gNB ID of BS710B, the gNB-CU ID of the CU of BS710B, the IP address of the CU of BS710B, or any ID that can identify BS710B (e.g., the CU of BS710B).

[0103] In some embodiments, the message in operation 717 may include an identifier (ID) associated with the network node 720. As will be described later, the ID associated with the network node 720 may be used by BS710B (e.g., the CU of BS710B) to identify the network node 720. That is, any ID associated with the network node 720 known by BS710B (e.g., the CU of BS710B) may be adopted.

[0104] For example, the ID associated with network node 720 could be the MT ID of network node 720, the DU ID of network node 720, or the ID of network node 720. For example, the ID associated with network node 720 could be the Cell Radio Network Temporary Identifier (C-RNTI) of the MT of network node 720, the BS-DU ID of the DU of network node 720 (e.g., gNB-DU ID), the BAP address of network node 720, or the UE XnAP ID of the MT of network node 720 (e.g., NG-RAN node UE XnAP ID). For example, the ID associated with network node 720 could be the UE XnAP ID of the MT of network node 720 assigned by BS710B (e.g., ID #7B) or BS710A (e.g., ID #7A).

[0105] Next, BS710C (e.g., the CU of BS710C) may exchange information with BS710C (e.g., the CU of BS710C) and BS710B (e.g., the CU of BS710B) on network node 720 and trigger a TMM procedure (e.g., an IAB TMM procedure) to manage the migration of network node 720 and descendant node traffic between topologies managed by the two BSs (e.g., the two CUs). For example, in operation 719, BS710C (e.g., the CU of BS710C) may send a TMM request message to BS710B (e.g., the CU of BS710B).

[0106] In some embodiments, the TMM request message may include an ID associated with the network node 720, as described above with respect to operation 717.

[0107] In some embodiments, the TMM request message may include a non-F1 terminated BS UE XnAP ID IE (e.g., a non-F1 terminated IAB donor UE XnAP ID IE). As described above with respect to Figure 6, the F1 terminated BS (e.g., BS710C) is to include the UE XnAP ID (e.g., NG-RAN node UE XnAP ID) of the MT of the wireless network node (e.g., network node 720) which is assigned by the non-F1 terminated BS (e.g., BS710B) and will be used on the Xn interface between the F1 terminated BS (e.g., BS710C) and the non-F1 terminated BS (e.g., BS710B) in the non-F1 terminated BS UE XnAP ID IE. For example, the value of IE may be the ID, or IE may be set as the ID. However, in the example of Figure 7, BS710C (e.g., the CU of BS710C) does not have information about such a UE XnAP ID in operation 717. BS710C (for example, BS710C's CU) may set the non-F1 terminated BS UE XnAP ID IE in the TMM request message to be invalid or empty. For example, BS710C (for example, BS710C's CU) may use an invalid or empty ID to set the non-F1 terminated BS UE XnAP ID IE.

[0108] In some embodiments, the ID associated with the network node 720 may be included in the IE of the TMM request message, which is different from the non-F1 terminated BS UE XnAP ID IE.

[0109] In some embodiments, the TMM request message may include an F1-terminated BS UE XnAP ID IE (e.g., an F1-terminated IAB donor UE XnAP ID IE) which may include a UE XnAP ID (e.g., an NG-RAN node UE XnAP ID) that is assigned by the BS710C (e.g., the CU of the BS710C) and used on the Xn interface between the BS710C and the BS710B. For example, the value of the F1-terminated BS UE XnAP ID IE may be a UE XnAP ID assigned by the BS710C, or the F1-terminated BS UE XnAP ID IE may be set as a UE XnAP ID assigned by the BS710C.

[0110] In some embodiments, the BS710B (e.g., the CU of the BS710B) can recognize the network node 720 based on the ID associated with the network node 720 in the TMM request message. In some embodiments, the BS710B (e.g., the CU of the BS710B) may ignore the non-F1 terminated BS UE XnAP ID IE in the TMM request message. For example, when the TMM request message includes an ID associated with the network node 720, the BS710B (e.g., the CU of the BS710B) may ignore the non-F1 terminated BS UE XnAP ID IE.

[0111] In some embodiments, BS710B (e.g., the CU of BS710B) may, in response to receiving a TMM request message, assign a UE XnAP ID for the MT of network node 720 (e.g., an NG-RAN node UE XnAP ID) which will be used on the Xn interface between BS710B and BS710C. For example, when the TMM request message includes an ID associated with network node 720, BS710B (e.g., the CU of BS710B) may assign a UE XnAP ID for the MT of network node 720.

[0112] In operation 721, BS710B (e.g., the CU of BS710B) may send a TMM response message to BS710C (e.g., the CU of BS710C) in response to a TMM request message. In some embodiments, the TMM response message may include a UE XnAP ID assigned by BS710B (e.g., the CU of BS710B) that will be used on the Xn interface between an F1-terminated BS (e.g., BS710C) and a non-F1-terminated BS (e.g., BS710B). For example, BS710B (e.g., the CU of BS710B) may set the non-F1-terminated BS UE XnAP ID IE (e.g., the non-F1-terminated IAB donor UE XnAP ID IE) in the TMM response message to be the assigned UE XnAP ID. For example, the value of the non-F1-terminated BS UE XnAP ID IE in the TMM response message is the assigned UE XnAP ID.

[0113] In some embodiments, the TMM response message may also include an F1-terminated BS UE XnAP ID IE (e.g., an F1-terminated IAB donor UE XnAP ID IE) which is set to the same value as the F1-terminated BS UE XnAP ID IE in the TMM request message.

[0114] In some embodiments, BS710C (e.g., the CU of BS710C) may store the UE XnAP ID assigned by BS710B (e.g., the CU of BS710B) in response to receiving a TMM response message. For example, when a TMM request message contains an invalid / empty UE XnAP ID (e.g., the non-F1 terminated BS UE XnAP ID IE in the TMM request message is invalid or empty), BS710C (e.g., the CU of BS710C) may store the UE XnAP ID in the non-F1 terminated BS UE XnAP ID IE in the corresponding TMM response message.

[0115] Following the above operation, BS710B (e.g., the CU of BS710B) and BS710C (e.g., the CU of BS710C) may have UE XnAP IDs assigned to each other for use on the Xn interface between BS710B (e.g., the CU of BS710B) and BS710C (e.g., the CU of BS710C).

[0116] After the TMM procedure, BS710B (e.g., the CU of BS710B) may update the BAP configuration, and F1 traffic between network node 720 and BS710C (e.g., the CU of BS710C) may be transported via the BH link under BS710B (e.g., the CU of BS710B).

[0117] It will be understood by those skilled in the art that, without departing from the spirit and scope of this disclosure, the sequence of operations in the exemplary procedure 700 may be changed, and some of the operations in the exemplary procedure 700 may be deleted or modified.

[0118] For example, Figure 8 shows a flowchart of an exemplary handover procedure 800 according to several embodiments of the present disclosure.

[0119] The details described in all of the above embodiments of this disclosure are applicable to the embodiments shown in Figure 8. For example, BS810A-810C may function as IAB donors as described above and may include a CU and at least one DU. Network node 820 may function as an IAB node as described above and may include an MT and a DU.

[0120] Network node 820 (for example, the DU of network node 820) may have an F1 connection with BS810C (for example, the CU of BS810C). Network node 820 (for example, the MT of network node 820) may have an RRC connection with BS810A (for example, the CU of BS810A). BS810C and BS810A are sometimes referred to as F1-terminated BS and non-F1-terminated BS (or RRC-terminated BS), respectively. The CU of BS810C and the CU of BS810A are sometimes referred to as F1-terminated BS-CU and non-F1-terminated BS-CU (or RRC-terminated BS-CU), respectively.

[0121] In some embodiments, the MT of network node 820 may perform a handover from BS810A (i.e., a source non-F1 terminated BS) to a target BS (i.e., a target non-F1 terminated BS such as BS810B), while the DU of network node 820 maintains its connection with BS810C (e.g., the CU of BS810C). For example, BS810A, BS810B, BS810C, and network node 820 may function as IAB donor 410A, IAB donor 410B, IAB donor 410C, and IAB node 420D in Figure 4.

[0122] For example, referring to Figure 8, in operation 811, the handover preparation procedure for network node 820 (e.g., the MT of network node 820) may be performed between BS810A and BS810B. For example, BS810A (e.g., the CU of BS810A) may send a handover request message to BS810B (e.g., the CU of BS810B) in order to hand over network node 820 (e.g., the MT of network node 820). BS810B (e.g., the CU of BS810B) may send a response to the handover request message to BS810A (e.g., positive feedback such as a handover request acknowledgment message or negative feedback such as a handover preparation failure message).

[0123] In some embodiments, operation 811 may further include the following steps: BS810B (e.g., CU of BS810B) sets up a UE context for network node 820 (e.g., MT of network node 820) on the target parent node, performs admission control for network node 820 (e.g., MT of network node 820), and provides RRC reconfiguration (e.g., handover command) as part of a handover request acknowledgment message.

[0124] In some embodiments, the handover request message may include a UE XnAP ID assigned by BS810A (e.g., the CU of BS810A) (e.g., an NG-RAN node UE XnAP ID shown as ID #8A). The handover request acknowledgment message may include a UE XnAP ID assigned by BS810B (e.g., the CU of BS810B) (e.g., an NG-RAN node UE XnAP ID shown as ID #8B). The handover request acknowledgment message may also include ID #8A. IDs #8A and #8B may be used on the Xn interface between BS810A (e.g., the CU of BS810A) and BS810B (e.g., the CU of BS810B).

[0125] In operation 813, BS810A (e.g., the CU of BS810A) may send a handover command (e.g., RRC reconfiguration) to network node 820 (e.g., the MT of network node 820). In some embodiments, the handover command or RRC reconfiguration may be included in a UE context change request message to the source parent node (e.g., the DU of the source parent node of network node 820). In some examples, assuming that network node 820 functions as IAB node 420D in Figure 4, the source parent node and target parent node of network node 820 may be IAB node 420A and IAB node 420B, respectively. The source parent node (e.g., the DU of the source parent node of network node 820) may forward the received handover command or RRC reconfiguration to the destination node (e.g., the MT of network node 820). In some examples, the source parent node or target parent node of network node 820 may be a BS or an IAB donor.

[0126] In operation 815, network node 820 (for example, the MT of network node 820) may perform a random access procedure with the target parent node (for example, the DU of the target parent node of network node 820) to set up an RRC connection to BS810B (for example, the CU of BS810B).

[0127] In operation 817, BS810A (e.g., the CU of BS810A) may request the UE XnAP ID of the MT of network node 820 (e.g., the NG-RAN node UE XnAP ID) from BS810B (e.g., the CU of BS810B). As will be described later, the requested ID may be used on the Xn interface between BS810B (e.g., the CU of BS810B) and BS810C (e.g., the CU of BS810C).

[0128] For example, BS810A (e.g., the CU of BS810A) may, in operation 817, send a request message to BS810B (e.g., the CU of BS810B). The request message may include the ID of BS810C (e.g., the CU of BS810C) and the ID associated with network node 820. In some examples, the ID of BS810C may include the gNB ID of BS810C or the gNB-CU ID of the CU of BS810C. In some examples, the description of the ID associated with network node 720 may apply to the ID associated with network node 820. For example, the ID associated with network node 820 may be the UE XnAP ID of the MT of network node 820, which is assigned by BS810B (e.g., ID #8B) or BS810A (e.g., ID #8A) and will be used on the Xn interface between BS810A and BS810B.

[0129] In some embodiments, the request message may include an instruction to explicitly request a UE XnAP ID. In some embodiments, such an instruction may be implicitly derived by the ID of BS810C (e.g., the CU of BS810C). That is, when the request message includes the ID of BS810C (e.g., the CU of BS810C), BS810B (e.g., the CU of BS810B) may respond to BS810A (e.g., the CU of BS810A) with the UE XnAP ID of the MT of network node 820 that will be used on the Xn interface between BS810B and BS810C (e.g., the NG-RAN node UE XnAP ID shown as ID #8B'). In other words, in response to receiving the request message, BS810B (e.g., the CU of BS810B) may assign ID #8B' and send a response message containing ID #8B' to BS810A (e.g., the CU of BS810A).

[0130] In some embodiments, the request message may be (or be included in) a handover request message (for example, as described with respect to operation 811). The response message may be (or be included in) a handover request acknowledgment message (for example, as described with respect to operation 811). In some embodiments, the request message may be a separate XnAP message from the handover request message. The response message may be a separate XnAP message from the handover request acknowledgment message. In some embodiments, operation 817 may be performed at any stage that is parallel to or after the handover preparation procedure (for example, operation 811) and before operation 819.

[0131] In operation 819, BS810A (for example, the CU of BS810A) may send a message to BS810C (for example, the CU of BS810C) indicating that network node 820 (for example, the MT of network node 820) has been handed over to BS810B (for example, the CU of BS810B).

[0132] In some embodiments, the message in operation 819 may include an identifier for BS810B (e.g., the ID of the CU of BS810B) so that BS810C (e.g., the CU of BS810C) can trigger a TMM procedure on the appropriate non-F1 terminated BS (e.g., a non-F1 terminated CU such as the CU of BS810B). For example, the ID of BS810B could be the gNB ID of BS810B, the gNB-CU ID of the CU of BS810B, the IP address of the CU of BS810B, or any ID that can identify BS810B (e.g., the CU of BS810B).

[0133] In some embodiments, the message in operation 819 may include an ID associated with network node 820. As will be described later, the ID associated with network node 820 may be used by BS810B (e.g., the CU of BS810B) to identify network node 820. The ID associated with network node 820 may be the UE XnAP ID of the MT of network node 820 (e.g., ID #8B'), which will be used on the Xn interface between BS810B and BS810C and will be assigned by BS810B (e.g., the CU of BS810B).

[0134] Next, BS810C (e.g., the CU of BS810C) may exchange information with BS810C (e.g., the CU of BS810C) and BS810B (e.g., the CU of BS810B) on network node 820 and trigger a TMM procedure (e.g., an IAB TMM procedure) to manage the transition of network node 820 and descendant node traffic between topologies managed by the two BSs (e.g., the two CUs). For example, in operation 821, BS810C (e.g., the CU of BS810C) may send a TMM request message to BS810B (e.g., the CU of BS810B).

[0135] In some embodiments, the TMM request message may include an ID associated with the network node 820 (e.g., ID #8B'), as described above with respect to operation 819. For example, in some embodiments, the TMM request message may include a non-F1 terminated BS UE XnAP ID IE (e.g., a non-F1 terminated IAB donor UE XnAP ID IE). The IE may include an ID associated with the network node 820 (e.g., ID #8B'). For example, the value of IE may be an ID associated with the network node 820 (e.g., ID #8B'), or IE may be set as an ID associated with the network node 820 (e.g., ID #8B').

[0136] In some embodiments, the TMM request message may include an F1-terminated BS UE XnAP ID IE (e.g., an F1-terminated IAB donor UE XnAP ID IE) which may include a UE XnAP ID (e.g., an NG-RAN node UE XnAP ID) that is assigned by the BS810C (e.g., the CU of the BS810C) and used on the Xn interface between the BS810B and the BS810C. For example, the value of the F1-terminated BS UE XnAP ID IE may be a UE XnAP ID assigned by the BS810C, or the F1-terminated BS UE XnAP ID IE may be set as a UE XnAP ID assigned by the BS810C.

[0137] In some embodiments, upon receiving a TMM request message, the BS810B (e.g., the CU of the BS810B) can recognize the network node 820 based on the non-F1 terminated BS UE XnAP ID IE in the TMM request message, since the TMM request message includes an ID assigned by itself (e.g., ID #8B').

[0138] Following the above operation, BS810B (e.g., the CU of BS810B) and BS810C (e.g., the CU of BS810C) may have UE XnAP IDs assigned to each other for use on the Xn interface between BS810B (e.g., the CU of BS810B) and BS810C (e.g., the CU of BS810C).

[0139] In operation 823, BS810B (for example, the CU of BS810B) may send a TMM response message to BS810C (for example, the CU of BS810C) in response to a TMM request message.

[0140] In some embodiments, the TMM response message may include a non-F1 terminated BS UE XnAP ID IE (e.g., a non-F1 terminated IAB donor UE XnAP ID IE) which is set to the same value as the non-F1 terminated BS UE XnAP ID IE in the TMM request message. In some embodiments, the TMM response message may also include an F1 terminated BS UE XnAP ID IE (e.g., an F1 terminated IAB donor UE XnAP ID IE) which is set to the same value as the F1 terminated BS UE XnAP ID IE in the TMM request message.

[0141] After the TMM procedure, BS810B (e.g., the CU of BS810B) may update the BAP configuration, and F1 traffic between network node 820 and BS810C (e.g., the CU of BS810C) may be transported via the BH link under BS810B (e.g., the CU of BS810B).

[0142] Those skilled in the art will understand that, without departing from the spirit and scope of this disclosure, the sequence of operations in the exemplary procedure 800 may be changed, and some of the operations in the exemplary procedure 800 may be deleted or modified.

[0143] For example, Figure 9 shows a flowchart of an exemplary transition procedure 900 according to several embodiments of the present disclosure.

[0144] Details described in all of the above embodiments of the present disclosure are applicable to the embodiments shown in Figure 9. For example, BS910A-910C may function as IAB donors as described above and may include a CU and at least one DU. Network node 920 may function as an IAB node as described above and may include an MT and at least one DU (e.g., one DU before and after a DU transition or two DUs during a DU transition).

[0145] Network node 920 (for example, the DU of network node 920) may have an F1 connection with BS910A (for example, the CU of BS910A). Network node 920 (for example, the MT of network node 920) may have an RRC connection with BS910B (for example, the CU of BS910B). BS910A and BS910B may be referred to as F1-terminated BS and non-F1-terminated BS (or RRC-terminated BS), respectively. The CU of BS910A and the CU of BS910B may be referred to as F1-terminated BS-CU and non-F1-terminated BS-CU (or RRC-terminated BS-CU), respectively.

[0146] In some embodiments, the DU of network node 920 may perform the transition from BS910A (i.e., source F1 termination BS) to target BS (i.e., target F1 termination BS such as BS910C), while the MT of network node 920 maintains its connection with BS910B. For example, BS910A, BS910B, BS910C, and network node 920 may function as IAB donor 510A, IAB donor 510B, IAB donor 510C, and IAB node 520D in Figure 5.

[0147] In some embodiments, a BS910A (e.g., the CU of the BS910A) may trigger a transition of a DU on network node 920. For example, in operation 911 (optionally shown as a dotted arrow), a BS910A (e.g., the CU of the BS910A) may send an F1AP message to instruct network node 920 to trigger a DU transition. For example, network node 920 may include a DU (shown as DU #A1) that has an F1 connection to a BS910A (e.g., the CU of the BS910A). A BS910A (e.g., the CU of the BS910A) may send an F1AP message to DU #A1.

[0148] In some embodiments, the F1AP message may include the ID of the BS910C (e.g., the CU of the BS910C). The ID of the BS910C may be the gNB ID of the BS910C, the gNB-CU ID of the CU of the BS910C, the IP address of the CU of the BS910C, or any ID that can identify the BS910C (e.g., the CU of the BS910C).

[0149] In some other embodiments, the transition may be triggered by an Operations, Administration and Maintenance (OAM) entity or the network node 920 itself (for example, based on pre-configuration on the network node 920). In these embodiments, operation 911 may be omitted.

[0150] During the DU migration of network node 920, network node 920 may have an additional logical DU (indicated as DU #A2) in addition to DU #A1, and network node 920 (e.g., DU #A2) may need to set up an F1 connection to BS910C (e.g., the CU of BS910C). In response to the start or trigger of the DU migration, network node 920 (e.g., DU #A2) may, in operation 921, send an F1 setup request message to BS910C (e.g., the CU of BS910C). For example, the F1 setup request message may first be sent to BS910B (e.g., the DU of BS910B) and then delivered to BS910C (e.g., the CU of BS910C) via IP routing.

[0151] In some embodiments, the F1 setup request message may include the ID of BS910B (e.g., the CU of BS910B) so that BS910C (e.g., the CU of BS910C) can trigger a TMM procedure on the appropriate non-F1 terminating BS (e.g., a non-F1 terminating CU such as the CU of BS910B). The ID of BS910B may be the gNB ID of BS910B, the gNB-CU ID of the CU of BS910B, the IP address of the CU of BS910B, or any ID that can identify BS910B (e.g., the CU of BS910B).

[0152] In some embodiments, the F1 setup request message may include an ID associated with the network node 920. As will be described later, the ID associated with the network node 920 may be used by the BS910B (e.g., the CU of the BS910B) to identify the network node 920. That is, any ID associated with the network node 920 known by the BS910B (e.g., the CU of the BS910B) may be adopted.

[0153] For example, the ID associated with network node 920 could be the ID of the MT of network node 920, the ID of the DU of network node 920 (e.g., DU #A1), or the ID of network node 920. For example, the ID associated with network node 920 could be the C-RNTI of the MT of network node 920, the BS-DU ID of the DU of network node 920 (e.g., DU #A1) (e.g., gNB-DU ID), the BAP address of network node 920, or the BS-DU UE F1AP ID of the DU of network node 920 (e.g., DU #A1) (e.g., gNB-DU UE F1AP ID). For example, the ID associated with network node 920 could be the UE XnAP ID of the MT of network node 920, which will be used on the Xn interface between BS910A and BS910B, assigned by BS910A or BS910B. In this example, network node 920 needs to obtain the UE XnAP ID from BS910A or BS910B beforehand.

[0154] In response to receiving an F1 setup request message, BS910C (e.g., the CU of BS910C) may, in operation 923, send an F1 setup response message to network node 920 (e.g., DU #A2). The F1 setup response message may contain a list of cells that BS910C (e.g., the CU of BS910C) requests network node 920 (e.g., DU #A2) to activate. For example, the F1 setup response message may first be delivered to BS910B (e.g., the DU of BS910B) via IP routing and then sent to network node 920 via BAP routing.

[0155] Next, BS910C (e.g., the CU of BS910C) may exchange information with BS910C (e.g., the CU of BS910C) and BS910B (e.g., the CU of BS910B) on network node 920 and trigger a TMM procedure (e.g., an IAB TMM procedure) to manage the transition of network node 920 and descendant node traffic between topologies managed by the two BSs (e.g., the two CUs). For example, in operation 925, BS910C (e.g., the CU of BS910C) may send a TMM request message to BS910B (e.g., the CU of BS910B).

[0156] In some embodiments, the TMM request message may include an ID associated with the network node 920, as described above with respect to operation 921.

[0157] In some embodiments, the TMM request message may include a non-F1 terminated BS UE XnAP ID IE (e.g., a non-F1 terminated IAB donor UE XnAP ID IE). As described above with respect to Figure 6, the F1 terminated BS (e.g., BS910C) is to include the UE XnAP ID (e.g., NG-RAN node UE XnAP ID) of the MT of the wireless network node (e.g., network node 920) which is assigned by the non-F1 terminated BS (e.g., BS910B) and will be used on the Xn interface between the F1 terminated BS (e.g., BS910C) and the non-F1 terminated BS (e.g., BS910B) in the non-F1 terminated BS UE XnAP ID IE. For example, the value of IE may be the ID, or IE may be set as the ID. However, in the example of Figure 9, BS910C (e.g., the CU of BS910C) does not have information about such a UE XnAP ID in operation 925. BS910C (for example, BS910C's CU) may set the non-F1 terminated BS UE XnAP ID IE in the TMM request message to be disabled or empty.

[0158] In some embodiments, the ID associated with the network node 920 may be included in the IE of the TMM request message, which is different from the non-F1 terminated BS UE XnAP ID IE.

[0159] In some embodiments, the TMM request message may include an F1-terminated BS UE XnAP ID IE (e.g., an F1-terminated IAB donor UE XnAP ID IE) which may include a UE XnAP ID (e.g., an NG-RAN node UE XnAP ID) that is assigned by the BS910C (e.g., the CU of the BS910C) and used on the Xn interface between the BS910C and the BS910B. For example, the value of the F1-terminated BS UE XnAP ID IE may be a UE XnAP ID assigned by the BS910C, or the F1-terminated BS UE XnAP ID IE may be set as a UE XnAP ID assigned by the BS910C.

[0160] In some embodiments, the BS910B (e.g., the CU of the BS910B) can recognize the network node 920 based on the ID associated with the network node 920 in the TMM request message. In some embodiments, the BS910B (e.g., the CU of the BS910B) may ignore the non-F1 terminated BS UE XnAP ID IE in the TMM request message. For example, when the TMM request message includes an ID associated with the network node 920, the BS910B (e.g., the CU of the BS910B) may ignore the non-F1 terminated BS UE XnAP ID IE.

[0161] In some embodiments, BS910B (e.g., the CU of BS910B) may, in response to receiving a TMM request message, assign a UE XnAP ID for the MT of network node 920 (e.g., an NG-RAN node UE XnAP ID) which will be used on the Xn interface between BS910B and BS910C. For example, when the TMM request message includes an ID associated with network node 920, BS910B (e.g., the CU of BS910B) may assign a UE XnAP ID for the MT of network node 920.

[0162] In operation 927, BS910B (e.g., the CU of BS910B) may send a TMM response message to BS910C (e.g., the CU of BS910C) in response to a TMM request message. In some embodiments, the TMM response message may include a UE XnAP ID assigned by BS910B (e.g., the CU of BS910B) that will be used on the Xn interface between an F1-terminated BS (e.g., BS910C) and a non-F1-terminated BS (e.g., BS910B). For example, BS910B (e.g., the CU of BS910B) may set the non-F1-terminated BS UE XnAP ID IE (e.g., the non-F1-terminated IAB donor UE XnAP ID IE) in the TMM response message to be the assigned UE XnAP ID. For example, the value of the non-F1-terminated BS UE XnAP ID IE in the TMM response message is the assigned UE XnAP ID.

[0163] In some embodiments, the TMM response message may also include an F1-terminated BS UE XnAP ID IE (e.g., an F1-terminated IAB donor UE XnAP ID IE) which is set to the same value as the F1-terminated BS UE XnAP ID IE in the TMM request message.

[0164] In some embodiments, BS910C (e.g., the CU of BS910C) may store the UE XnAP ID assigned by BS910B (e.g., the CU of BS910B) in response to receiving a TMM response message. For example, when a TMM request message contains an invalid / empty UE XnAP ID (e.g., the non-F1 terminated BS UE XnAP ID IE in the TMM request message is invalid or empty), BS910C (e.g., the CU of BS910C) may store the UE XnAP ID in the non-F1 terminated BS UE XnAP ID IE in the corresponding TMM response message.

[0165] Following the above operation, BS910B (e.g., the CU of BS910B) and BS910C (e.g., the CU of BS910C) may have UE XnAP IDs assigned to each other for use on the Xn interface between BS910B (e.g., the CU of BS910B) and BS910C (e.g., the CU of BS910C).

[0166] After the TMM procedure, the BS910B (e.g., the CU of the BS910B) may update the BAP configuration, and F1 traffic between network node 920 and the BS910C (e.g., the CU of the BS910C) may be transported via the BH link under the BS910B (e.g., the CU of the BS910B).

[0167] In some embodiments, after the F1 setup between DU #A2 and BS910C (e.g., the CU of BS910C), network node 920 (e.g., DU #A1) may, in operation 931, indicate to BS910A (e.g., the CU of BS910A) that the F1 setup for BS910C (e.g., the CU of BS910C) is complete and notify BS910A (e.g., the CU of BS910A) of a list of cells that BS910C (e.g., the CU of BS910C) requests network node 920 (e.g., DU #A2) to activate.

[0168] In some embodiments, in response to receiving information in operation 931, BS910A (e.g., the CU of BS910A) may trigger in operation 933 a handover of the UE served by network node 920 (e.g., DU #A1) from BS910A (e.g., the CU of BS910A) to BS910C (e.g., the CU of BS910C).

[0169] It will be understood by those skilled in the art that, without departing from the spirit and scope of this disclosure, the sequence of operations in the exemplary procedure 900 may be changed, and some of the operations in the exemplary procedure 900 may be deleted or modified. For example, operations 931 and 933 may be performed in parallel with or before operations 925 and 927.

[0170] For example, Figure 10 shows a flowchart of an exemplary transition procedure 1000 according to some embodiments of the present disclosure.

[0171] Details described in all of the above embodiments of this disclosure are applicable to the embodiments shown in Figure 10. For example, BS1010A-1010C may function as IAB donors as described above and may include a CU and at least one DU. Network node 1020 may function as an IAB node as described above and may include an MT and at least one DU (e.g., one DU before and after a DU transition or two DUs during a DU transition).

[0172] Network node 1020 (for example, the DU of network node 1020) may have an F1 connection with BS1010A (for example, the CU of BS1010A). Network node 1020 (for example, the MT of network node 1020) may have an RRC connection with BS1010B (for example, the CU of BS1010B). BS1010A and BS1010B may be referred to as F1-terminated BS and non-F1-terminated BS (or RRC-terminated BS), respectively. The CU of BS1010A and the CU of BS1010B may be referred to as F1-terminated BS-CU and non-F1-terminated BS-CU (or RRC-terminated BS-CU), respectively.

[0173] In some embodiments, the DU of network node 1020 may perform the transition from BS1010A (i.e., source F1 termination BS) to target BS (i.e., target F1 termination BS such as BS1010C), while the MT of network node 1020 maintains its connection with BS1010B. For example, BS1010A, BS1010B, BS1010C, and network node 1020 may function as IAB donor 510A, IAB donor 510B, IAB donor 510C, and IAB node 520D in Figure 5.

[0174] In some embodiments, BS1010A (e.g., the CU of BS1010A) may trigger a transition of DU at network node 1020. For example, in operation 1011 (optionally shown as a dotted arrow), BS1010A (e.g., the CU of BS1010A) may send an F1AP message to instruct network node 1020 to trigger a DU transition. For example, network node 1020 may include a DU (shown as DU #B1) that has an F1 connection to BS1010A (e.g., the CU of BS1010A). BS1010A (e.g., the CU of BS1010A) may send an F1AP message to DU #B1.

[0175] In some embodiments, the F1AP message may include the ID of BS1010C (e.g., the CU of BS1010C). The ID of BS1010C may be the gNB ID of BS1010C, the gNB-CU ID of the CU of BS1010C, the IP address of the CU of BS1010C, or any ID that can identify BS1010C (e.g., the CU of BS1010C).

[0176] In some other embodiments, the transition may be triggered by the OAM entity or the network node 1020 itself (for example, based on pre-configuration on the network node 1020). In these embodiments, operation 1011 may be omitted.

[0177] In some embodiments, prior to the migration of the DU of network node 1020, network node 1020 may obtain its MT's UE XnAP ID (e.g., an NG-RAN node UE XnAP ID shown as ID #10B'), which will be allocated by network node 1020's non-F1 terminating BS (e.g., BS1010B) and used on the Xn interface between network node 1020's target F1 terminating BS (e.g., BS1010C) and the non-F1 terminating BS (e.g., BS1010B).

[0178] For example, in operation 1013, network node 1020 may send a request message to BS1010B (e.g., CU of BS1010B) requesting the UE XnAP ID of network node 1020's MT (e.g., ID #10B'). As will be described later, the requested ID may be used on the Xn interface between BS1010B (e.g., CU of BS1010B) and BS1010C (e.g., CU of BS1010C).

[0179] In some embodiments, the request message may include the ID of the BS1010C (for example, the CU of the BS1010C). In some examples, the ID of the BS1010C may include the gNB ID of the BS1010C or the gNB-CU ID of the CU of the BS1010C.

[0180] In some embodiments, the request message may include an instruction to explicitly request a UE XnAP ID. In some embodiments, such an instruction may be implicitly derived by the ID of BS1010C (e.g., the CU of BS1010C). That is, when the request message includes the ID of BS1010C (e.g., the CU of BS1010C), BS1010B (e.g., the CU of BS1010B) may respond to network node 1020 with the UE XnAP ID of the MT of network node 1020 that will be used on the Xn interface between BS1010B and BS1010C (e.g., ID #10B'). In other words, in response to receiving the request message, BS1010B (e.g., the CU of BS1010B) may, in operation 1015, assign ID #10B' and send a response message containing ID #10B' to network node 1020.

[0181] In some embodiments, request and response messages may be transmitted via RRC signaling.

[0182] During the DU migration of network node 1020, network node 1020 may have an additional logical DU (indicated as DU #B2) in addition to DU #B1, and network node 1020 (e.g., DU #B2) may need to set up an F1 connection to BS1010C (e.g., the CU of BS1010C). In operation 1021, network node 1020 (e.g., DU #B2) may send an F1 setup request message to BS1010C (e.g., the CU of BS1010C). For example, the F1 setup request message may first be sent to BS1010B (e.g., the DU of BS1010B) and then delivered to BS1010C (e.g., the CU of BS1010C) via IP routing.

[0183] In some embodiments, the F1 setup request message may include the ID of BS1010B (e.g., the CU of BS1010B) so that BS1010C (e.g., the CU of BS1010C) can trigger a TMM procedure on the appropriate non-F1 terminating BS (e.g., a non-F1 terminating CU such as the CU of BS1010B). The ID of BS1010B may be the gNB ID of BS1010B, the gNB-CU ID of the CU of BS1010B, the IP address of the CU of BS1010B, or any ID that can identify BS1010B (e.g., the CU of BS1010B).

[0184] In some embodiments, the F1 setup request message may include an ID associated with network node 1020. As will be described later, the ID associated with network node 1020 may be used by BS1010B (e.g., the CU of BS1010B) to identify network node 1020. The ID associated with network node 1020 may be the UE XnAP ID of the MT of network node 1020 (e.g., ID #10B'), which will be used on the Xn interface between BS1010B and BS1010C and is assigned by BS1010B (e.g., the CU of BS1010B).

[0185] In response to receiving an F1 setup request message, BS1010C (e.g., the CU of BS1010C) may, in operation 1023, send an F1 setup response message to network node 1020 (e.g., DU #B2). The F1 setup response message may include a list of cells that BS1010C (e.g., the CU of BS1010C) requests network node 1020 (e.g., DU #B2) to activate. For example, the F1 setup response message may first be delivered to BS1010B (e.g., the DU of BS1010B) via IP routing and then sent to network node 1020 via BAP routing.

[0186] Next, BS1010C (e.g., the CU of BS1010C) may exchange information with BS1010C (e.g., the CU of BS1010C) and BS1010B (e.g., the CU of BS1010B) on network node 1020 and trigger a TMM procedure (e.g., an IAB TMM procedure) to manage the migration of network node 1020 and descendant node traffic between topologies managed by the two BSs (e.g., the two CUs). For example, in operation 1025, BS1010C (e.g., the CU of BS1010C) may send a TMM request message to BS1010B (e.g., the CU of BS1010B).

[0187] In some embodiments, the TMM request message may include an ID associated with network node 1020 (e.g., ID #10B') as described above with respect to operation 1021. For example, in some embodiments, the TMM request message may include a non-F1 terminated BS UE XnAP ID IE (e.g., a non-F1 terminated IAB donor UE XnAP ID IE). The IE may include an ID associated with network node 1020 (e.g., ID #10B'). For example, the value of IE may be an ID associated with network node 1020 (e.g., ID #10B'), or IE may be set as an ID associated with network node 1020 (e.g., ID #10B').

[0188] In some embodiments, the TMM request message may include an F1-terminated BS UE XnAP ID IE (e.g., an F1-terminated IAB donor UE XnAP ID IE) which may include a UE XnAP ID (e.g., an NG-RAN node UE XnAP ID) that is assigned by BS1010C (e.g., the CU of BS1010C) and used on the Xn interface between BS1010C and BS1010B. For example, the value of the F1-terminated BS UE XnAP ID IE may be a UE XnAP ID assigned by BS1010C, or the F1-terminated BS UE XnAP ID IE may be set as a UE XnAP ID assigned by BS1010C.

[0189] In some embodiments, upon receiving a TMM request message, BS1010B (e.g., CU of BS1010B) can recognize network node 1020 based on the non-F1 terminated BS UE XnAP ID IE in the TMM request message, since the TMM request message includes an ID assigned by itself (e.g., ID #10B').

[0190] Following the above operation, BS1010B (e.g., the CU of BS1010B) and BS1010C (e.g., the CU of BS1010C) may have UE XnAP IDs assigned to each other for use on the Xn interface between BS1010B (e.g., the CU of BS1010B) and BS1010C (e.g., the CU of BS1010C).

[0191] In operation 1027, BS1010B (for example, the CU of BS1010B) may send a TMM response message to BS1010C (for example, the CU of BS1010C) in response to a TMM request message.

[0192] In some embodiments, the TMM response message may include a non-F1 terminated BS UE XnAP ID IE (e.g., a non-F1 terminated IAB donor UE XnAP ID IE) which is set to the same value as the non-F1 terminated BS UE XnAP ID IE in the TMM request message. In some embodiments, the TMM response message may also include an F1 terminated BS UE XnAP ID IE (e.g., an F1 terminated IAB donor UE XnAP ID IE) which is set to the same value as the F1 terminated BS UE XnAP ID IE in the TMM request message.

[0193] After the TMM procedure, BS1010B (e.g., the CU of BS1010B) may update the BAP configuration, and F1 traffic between network node 1020 and BS1010C (e.g., the CU of BS1010C) may be transported via the BH link under BS1010B (e.g., the CU of BS1010B).

[0194] In some embodiments, after the F1 setup between DU #B2 and BS1010C (e.g., the CU of BS1010C), network node 1020 (e.g., DU #B1) may, in operation 1031, indicate to BS1010A (e.g., the CU of BS1010A) that the F1 setup for BS1010C (e.g., the CU of BS1010C) is complete, and notify BS1010A (e.g., the CU of BS1010A) of a list of cells that BS1010C (e.g., the CU of BS1010C) requests network node 1020 (e.g., DU #B2) to activate.

[0195] In some embodiments, in response to receiving information in operation 1031, BS1010A (e.g., the CU of BS1010A) may trigger in operation 1033 a handover of the UE served by network node 1020 (e.g., DU #B1) from BS1010A (e.g., the CU of BS1010A) to BS1010C (e.g., the CU of BS1010C).

[0196] Without departing from the spirit and scope of this disclosure, it will be understood by those skilled in the art that the sequence of operations in exemplary procedure 1000 may be changed, and some of the operations in exemplary procedure 1000 may be deleted or modified. For example, operations 1031 and 1033 may be performed in parallel with or before operations 1025 and 1027.

[0197] Figure 11 shows a flowchart of an exemplary procedure 1100 for wireless communication according to several embodiments of the present disclosure. Details described in all of the above embodiments of the present disclosure are applicable to the embodiments shown in Figure 11. The exemplary procedure 1100 may be performed by a BS (e.g., an IAB donor).

[0198] Referring to Figure 11, in operation 1111, the first BS may receive a TMM request message (e.g., an IAB TMM request message) from the second BS, which may include an identifier associated with the wireless network node for the first BS to identify the wireless network node.

[0199] In operation 1113, the first BS may, in response to receiving a TMM request message, send a TMM response message (e.g., an IAB TMM response message) to the second BS.

[0200] In some embodiments of the present disclosure, the MT of a wireless network node hand over from a third BS to a first BS, and the DU of the wireless network node has an F1 connection to a second BS. In some embodiments of the present disclosure, the DU of the wireless network node migrates from a fourth BS to a second BS, and the MT of the wireless network node has an RRC connection to a first BS.

[0201] In some embodiments of this disclosure, the first BS may function as BS710B in Figure 7, BS810B in Figure 8, BS910B in Figure 9, or BS1010B in Figure 10. In some embodiments of this disclosure, the second BS may function as BS710C in Figure 7, BS810C in Figure 8, BS910C in Figure 9, or BS1010C in Figure 10. In some embodiments of this disclosure, the wireless network node may function as network node 720 in Figure 7, network node 820 in Figure 8, network node 920 in Figure 9, or network node 1020 in Figure 10. In some embodiments of this disclosure, the third BS may function as BS710A in Figure 7 or BS810A in Figure 8. In some embodiments of this disclosure, the fourth BS may function as BS910A in Figure 9 or BS1010A in Figure 10.

[0202] In some embodiments of this disclosure, the identifier associated with a wireless network node may include one of the following: the C-RNTI of the MT of the wireless network node, the BS-DU ID of the DU of the wireless network node (e.g., the gNB-DU ID), the BAP address of the wireless network node, the UE XnAP ID of the MT of the wireless network node (e.g., the NG-RAN node UE XnAP ID), and the BS-DU UE F1AP ID of the DU of the wireless network node (e.g., the gNB-DU UE F1AP ID).

[0203] In some embodiments of this disclosure, the UE XnAP ID may be associated with the Xn interface between a first BS and a third BS. For example, the UE XnAP ID may be ID #7A or ID #7B as described above. In some embodiments of this disclosure, the UE XnAP ID may be associated with the first BS and the second BS. For example, the UE XnAP ID may be ID #8B' or ID #10B' as described above.

[0204] In some embodiments of the present disclosure, during the migration of a wireless network node's DU from a fourth BS to a second BS, the wireless network node may include a first DU having an F1 connection to the fourth BS and a second DU having an F1 connection to the second BS. The BS-DU ID of the wireless network node's DU is the BS-DU ID of the first DU of the wireless network node, and the BS-DU UE F1AP ID of the wireless network node's DU is the BS-DU UE F1AP ID of the first DU of the wireless network node.

[0205] In some embodiments of the present disclosure, the TMM request message may include an IE indicating an identifier associated with a wireless network node, the IE being different from the non-F1 terminated BS UE XnAP ID IE in the TMM request message. In some embodiments of the present disclosure, the first BS may ignore the non-F1 terminated BS UE XnAP ID IE in the TMM request message.

[0206] In some embodiments of the present disclosure, a first BS may, in response to receiving a TMM request message, assign a UE XnAP ID for the MT of a wireless network node, which will be used on the Xn interface between the first BS and the second BS. A TMM response message may include the assigned UE XnAP ID. For example, a TMM response message may include a non-F1 terminated BS UE XnAP ID IE, the value of which may be set as the assigned UE XnAP ID.

[0207] In some embodiments of this disclosure, the identifier associated with a wireless network node may include the UE XnAP ID of the MT of the wireless network node, which will be used on the Xn interface between the first BS and the second BS. In some embodiments of this disclosure, the identifier associated with a wireless network node is included in the non-F1 terminated BS UE XnAP ID IE in the TMM request message. For example, the value of IE is the identifier associated with the wireless network node, or the UE XnAP ID. For example, the value of IE is set as the identifier associated with the wireless network node, or the UE XnAP ID of the MT of the wireless network node, which will be used on the Xn interface between the first BS and the second BS.

[0208] In some embodiments of the present disclosure, a first BS may assign a UE XnAP ID to the MT of a wireless network node, which will be used on the Xn interface between the first BS and the second BS, and the transceiver is further configured to transmit the assigned UE XnAP ID to a third BS or wireless network node. In some embodiments of the present disclosure, the first BS may receive a request message from a third BS or wireless network node asking for a UE XnAP ID, and assigning a UE XnAP ID may include assigning a UE XnAP ID in response to receiving a request message. For example, the description relating to operation 817 in Figure 8 may apply here. For example, the description relating to operations 1013 and 1015 in Figure 10 may apply here.

[0209] For example, in some embodiments of this disclosure, the request message is a handover request message from a third BS, and the assigned UE XnAP ID is sent in the handover request confirmation message.

[0210] For example, in some embodiments of the present disclosure, a request message from a third BS may include an identifier for a second BS and an identifier associated with a wireless network node.

[0211] Those skilled in the art will understand that, without departing from the spirit and scope of this disclosure, the sequence of operations in exemplary procedure 1100 may be changed, and some of the operations in exemplary procedure 1100 may be deleted or modified.

[0212] Figure 12 shows a flowchart of an exemplary procedure 1200 for wireless communication according to several embodiments of the present disclosure. Details described in all of the above embodiments of the present disclosure are applicable to the embodiments shown in Figure 12. The exemplary procedure 1200 may be performed by a BS (e.g., an IAB donor).

[0213] Referring to Figure 12, in operation 1211, the second BS may send a TMM request message (for example, an IAB TMM request message) to the first BS, the TMM request message may include an identifier associated with the wireless network node for the first BS to identify the wireless network node.

[0214] In operation 1213, the second BS may receive a TMM response message (e.g., an IAB TMM response message) from the first BS in response to sending a TMM request message.

[0215] In some embodiments of the present disclosure, the MT of a wireless network node hand over from a third BS to a first BS, and the DU of the wireless network node has an F1 connection to a second BS. In some embodiments of the present disclosure, the DU of the wireless network node migrates from a fourth BS to a second BS, and the MT of the wireless network node has an RRC connection to a first BS.

[0216] In some embodiments of this disclosure, the first BS may function as BS710B in Figure 7, BS810B in Figure 8, BS910B in Figure 9, or BS1010B in Figure 10. In some embodiments of this disclosure, the second BS may function as BS710C in Figure 7, BS810C in Figure 8, BS910C in Figure 9, or BS1010C in Figure 10. In some embodiments of this disclosure, the wireless network node may function as network node 720 in Figure 7, network node 820 in Figure 8, network node 920 in Figure 9, or network node 1020 in Figure 10. In some embodiments of this disclosure, the third BS may function as BS710A in Figure 7 or BS810A in Figure 8. In some embodiments of this disclosure, the fourth BS may function as BS910A in Figure 9 or BS1010A in Figure 10.

[0217] In some embodiments of the present disclosure, a second BS may receive an identifier associated with a wireless network node from a third BS. In some embodiments of the present disclosure, the identifier associated with a wireless network node may include one of the following: the C-RNTI of the MT of the wireless network node, the BS-DU ID of the DU of the wireless network node (e.g., the gNB-DU ID), the BAP address of the wireless network node, and the UE XnAP ID of the MT of the wireless network node (e.g., the NG-RAN node UE XnAP ID).

[0218] In some embodiments of this disclosure, the UE XnAP ID may be associated with the Xn interface between a first BS and a third BS. For example, the UE XnAP ID may be ID #7A or ID #7B as described above. In some embodiments of this disclosure, the UE XnAP ID may be associated with the first BS and the second BS. For example, the UE XnAP ID may be ID #8B' as described above.

[0219] In some embodiments of the present disclosure, a second BS may receive an identifier associated with the wireless network node from the wireless network node. In some embodiments of the present disclosure, the identifier associated with the wireless network node may include one of the following: the C-RNTI of the MT of the wireless network node, the BS-DU ID of the DU of the wireless network node (e.g., gNB-DU ID), the BAP address of the wireless network node, the UE XnAP ID of the MT of the wireless network node (e.g., NG-RAN node UE XnAP ID), and the BS-DU UE F1AP ID of the DU of the wireless network node (e.g., gNB-DU UE F1AP ID). In some embodiments of the present disclosure, the UE XnAP ID may be associated with the first BS and the second BS. For example, the UE XnAP ID may be ID #10B' as described above.

[0220] In some embodiments of the present disclosure, during the migration of a wireless network node's DU from a fourth BS to a second BS, the wireless network node may include a first DU having an F1 connection to the fourth BS and a second DU having an F1 connection to the second BS. The BS-DU ID of the wireless network node's DU is the BS-DU ID of the first DU of the wireless network node, and the BS-DU UE F1AP ID of the wireless network node's DU is the BS-DU UE F1AP ID of the first DU of the wireless network node.

[0221] In some embodiments of the present disclosure, the TMM request message may include an IE indicating an identifier associated with a wireless network node, the IE being different from the non-F1 terminated BS UE XnAP ID IE in the TMM request message. In some embodiments of the present disclosure, a second BS may set the non-F1 terminated BS UE XnAP ID IE in the TMM request message to be invalid or empty.

[0222] In some embodiments of the present disclosure, the TMM response message may include the UE XnAP ID of the MT of the wireless network node, which is assigned by the first BS and will be used on the Xn interface between the first BS and the second BS. For example, the TMM response message may include a non-F1 terminated BS UE XnAP ID IE, the value of which may be set as the UE XnAP ID assigned by the first BS. In some embodiments of the present disclosure, the second BS may store the UE XnAP ID assigned by the first BS.

[0223] In some embodiments of the present disclosure, the identifier associated with a wireless network node may include the UE XnAP ID of the wireless network node's MT, which is assigned by the first BS and will be used on the Xn interface between the first BS and the second BS. In some embodiments of the present disclosure, the identifier associated with a wireless network node is included in the non-F1 terminated BS UE XnAP ID IE in the TMM request message. For example, the value of IE is the identifier associated with the wireless network node, or the UE XnAP ID assigned by the first BS. For example, the value of IE is set as the identifier associated with the wireless network node, or the UE XnAP ID assigned by the first BS.

[0224] In some embodiments of this disclosure, an identifier associated with a wireless network node is received in the F1 setup request message.

[0225] Those skilled in the art will understand that, without departing from the spirit and scope of this disclosure, the sequence of operations in exemplary procedure 1200 may be changed, and some of the operations in exemplary procedure 1200 may be deleted or modified.

[0226] Figure 13 shows a block diagram of an exemplary apparatus 1300 according to some embodiments of the present disclosure.

[0227] As shown in Figure 13, the device 1300 may include at least one processor 1306 and at least one transceiver 1302 coupled to the processor 1306. The device 1300 may be a (wireless) network node (e.g., an IAB node), a BS (e.g., an IAB donor, an IAB donor CU, or an IAB donor DU), a DU of a BS, or a CU of a BS. If the device 1300 is a BS, the device 1300 may further include a CU and at least one DU coupled to the CU. The CU and DU may be co-located or located separately. The CU and DU may be coupled to the processor 1306. If the device 1300 is a (wireless) network node (stationary or mobile), the device 1300 may further include a MT and a DU coupled to the MT. The MT and DU may be coupled to the processor 1306.

[0228] In this figure, elements such as at least one transceiver 1302 and processor 1306 are described singly, but unless explicitly stated otherwise, plural is intended. In some embodiments of this application, the transceiver 1302 may be divided into two devices, such as a receiving circuit and a transmitting circuit. In some embodiments of this application, the apparatus 1300 may further include an input device, memory, and / or other components.

[0229] In some embodiments of this application, the device 1300 may be a BS. The processor 1306 may interact with other elements of the device 1300 (e.g., transceiver 1302, DU, or CU) to perform operations relating to the BS, IAB donor, IAB donor CU, or IAB donor DU as described in Figures 1 to 12. In some embodiments of this application, the device 1300 may be a (wireless) network node. The transceiver 1302 and the processor 1306 may interact with each other to perform operations relating to the network node or IAB node (mobile or stationary) as described in Figures 1 to 12.

[0230] In some embodiments of this application, the apparatus 1300 may further include at least one non-temporary computer-readable medium.

[0231] In some embodiments of the present disclosure, a non-temporary computer-readable medium may store computer-executable instructions causing the processor 1306 to implement methods relating to BS, IAB donors, IAB donor CUs, or IAB donor DUs as described above. For example, when executed, the computer-executable instructions cause the processor 1306, for example, interacting with the transceiver 1302, to perform operations relating to BS, IAB donors, IAB donor CUs, or IAB donor DUs as described in Figures 1 to 12.

[0232] For example, in some embodiments of the present disclosure, a non-temporary computer-readable medium may store computer-executable instructions that cause the processor 1306 to implement methods relating to network nodes or IAB nodes (mobile or stationary) as described above. For example, when executed, the computer-executable instructions cause the processor 1306, which interacts with the transceiver 1302, to perform operations relating to network nodes or IAB nodes (mobile or stationary) as described in Figures 1 to 12.

[0233] Those skilled in the art will understand that the operations or steps of the methods described in relation to the embodiments disclosed herein may be embodied directly in hardware, in software modules executed by a processor, or in a combination of both. The software modules may reside in RAM memory, flash memory, ROM memory, EPROM memory, EEPROM memory, registers, hard disks, removable disks, CD-ROMs, or any other form of storage medium known in the art. In addition, in some embodiments, the operations or steps of the methods may exist as one or any combination or set of code and / or instructions on a non-temporary computer-readable medium that can be incorporated into a computer program product.

[0234] While this disclosure has been described using specific embodiments, it is evident that many alternative, modified, and variant forms may be apparent to those skilled in the art. For example, various components of the embodiments may be replaced, added, or substituted in other embodiments. Furthermore, not all elements in each figure are necessary for the operation of the disclosed embodiments. For example, a person skilled in the art of the disclosed embodiments may be able to create and use the teachings of this disclosure simply by adopting the elements of the independent claims. Accordingly, the embodiments of this disclosure described herein are intended to be illustrative, not limiting. Various modifications may be made without departing from the spirit and scope of this disclosure.

[0235] In this document, the terms “handover,” “path switch,” and “migration” may be used interchangeably. The terms “includes,” “including,” or any other variations thereof are intended to cover non-exclusive inclusion, and as a result, a process, method, article, or apparatus containing a list of elements may include other elements that are not explicitly listed or that are specific to such process, method, article, or apparatus, but do not include only those elements. Elements following “a,” “an,” etc., do not, without further constraint, exclude the presence of additional identical elements in a process, method, article, or apparatus containing that element. Also, the term “another” is defined as at least two or more. Terms such as “having” are defined as “including” when used herein. Expressions such as “A and / or B” or “at least one of A and B” may include any combination of the words enumerated with the expression. For example, the expression "A and / or B" or "at least one of A and B" may include A, B, or both A and B. Phrases such as "first," "second," etc., are used solely to clearly indicate embodiments of this application, but not to limit the scope of this application. [Explanation of Symbols]

[0236] 100 Wireless Communication Systems 110A, 110B IAB donors 120A, 120B, 120C IAB nodes 130A, 130B UE 140A, 140B, 140C, 140D Wireless Link 150A, 150B Wireless Link 200A User Plane (UP) Protocol Stack 200B Control Plane (CP) Protocol Stack 310A, 310B IAB donors 321 IAB nodes 322 IAB nodes 323 IAB nodes 330 Signaling Flow 410A, 410B, 410C IAB donors 420A, 420B, 420C, 420D IAB nodes 430 UE 440A, 440B Signaling Flow 451 MT 452 MT 453 MT 454 MT 461 DU 462 DU 463 DU 464 DU 465 DU 466 DU 467 DU 475 CU 476 CU 477 CU 510A, 510B, 510C IAB donors 520A, 520B, 520C, 520D IAB nodes 530 UE 540A, 540B Signaling Flow 551 MT 552 MT 553 MT 554 MT 561 DU 562 DU 563 DU 564a, 564b DU 565 DU 566 DU 567 DU 575 CU 576 CU 577 CU 600 TMM Procedures 610A, 610B BS 700 steps, handover procedure 710A, 710B, 710C BS 720 network nodes 800 steps, handover procedure 810A, 810B, 810C BS 820 network nodes 900 steps, migration procedure 910A, 910B, 910C BS 920 network nodes 1000 steps 1010A, 1010B, 1010C BS 1020 network nodes 1100 steps 1200 steps 1300 equipment 1302 Transceiver 1306 Processor

Claims

1. The first base station (BS), Processor and The processor comprises a transceiver coupled to the processor, and the transceiver is Receiving a Transport Transition Management (TMM) request message from a second BS, wherein the TMM request message includes an identifier associated with the wireless network node for the first BS to identify the wireless network node. In response to receiving the aforementioned TMM request message, a TMM response message is sent to the aforementioned second BS. It is configured to do the following: The mobile terminal (MT) of the wireless network node hands over from the third BS to the first BS, and the distributed unit (DU) of the wireless network node has an F1 connection to the second BS, or the DU of the wireless network node migrates from the fourth BS to the second BS, and the MT of the wireless network node has a radio resource control (RRC) connection to the first BS. The first BS.

2. The first BS according to claim 1, wherein the identifier associated with the wireless network node includes one of the following: the Cell Radio Network Temporary Identifier (C-RNTI) of the MT of the wireless network node, the BS-DU identifier (ID) of the DU of the wireless network node, the Backhaul Adaptive Protocol (BAP) address of the wireless network node, the User Equipment (UE) Xn Application Protocol (XnAP) ID of the MT of the wireless network node, and the BS-DU UE F1 Application Protocol (F1AP) ID of the DU of the wireless network node.

3. The TMM request message includes an information element (IE) indicating the identifier associated with the wireless network node, wherein the IE is different from the non-F1 terminated BS UE XnAP ID IE in the TMM request message. The processor is configured to ignore the non-F1 terminated BS UE XnAP ID IE in the TMM request message. The first BS according to claim 1 or 2.

4. The first BS according to claim 1 or 2, wherein the identifier associated with the wireless network node includes the UE XnAP ID of the MT of the wireless network node, which will be used on the Xn interface between the first BS and the second BS.

5. The first BS according to claim 4, wherein the processor is configured to assign the UE XnAP ID of the MT of the wireless network node to be used on the Xn interface between the first BS and the second BS, and the transceiver is further configured to transmit the assigned UE XnAP ID to the third BS or the wireless network node.

6. The first BS according to claim 5, wherein the transceiver is further configured to receive a request message from the third BS or the wireless network node for the UE XnAP ID, and assigning the UE XnAP ID includes assigning the UE XnAP ID in response to receiving the request message.

7. The first BS according to claim 6, wherein the request message from the third BS includes an identifier for the second BS and the identifier associated with the wireless network node, or the request message from the wireless network node includes the identifier for the second BS.

8. The second base station (BS), Processor and The processor comprises a transceiver coupled to the processor, and the transceiver is Sending a Transport Transition Management (TMM) request message to a first BS, wherein the TMM request message includes an identifier associated with the wireless network node for the first BS to identify the wireless network node. In response to sending the aforementioned TMM request message, a TMM response message is received from the first BS. It is configured to do the following: The mobile terminal (MT) of the wireless network node hands over from the third BS to the first BS, and the distributed unit (DU) of the wireless network node has an F1 connection to the second BS, or the DU of the wireless network node migrates from the fourth BS to the second BS, and the MT of the wireless network node has a radio resource control (RRC) connection to the first BS. The second BS.

9. The transceiver is further configured to receive the identifier associated with the wireless network node from the third BS, The identifier associated with the wireless network node includes one of the following: the Cell Radio Network Temporary Identifier (C-RNTI) of the MT of the wireless network node, the BS-DU identifier (ID) of the DU of the wireless network node, the Backhaul Adaptive Protocol (BAP) address of the wireless network node, and the User Equipment (UE) Xn Application Protocol (XnAP) ID of the MT of the wireless network node. The second BS according to claim 8.

10. The transceiver is further configured to receive the identifier associated with the wireless network node from the wireless network node, The identifier associated with the wireless network node includes one of the following: the Cell Radio Network Temporary Identifier (C-RNTI) of the MT of the wireless network node, the BS-DU identifier (ID) of the DU of the wireless network node, the Backhaul Adaptive Protocol (BAP) address of the wireless network node, the User Equipment (UE) Xn Application Protocol (XnAP) ID of the MT of the wireless network node, and the BS-DU UE F1 Application Protocol (F1AP) ID of the DU of the wireless network node. The second BS according to claim 8.

11. The second BS according to any one of claims 8 to 10, wherein the TMM request message includes an information element (IE) indicating the identifier associated with the wireless network node, and the IE is different from the non-F1 terminated BS UE XnAP ID IE in the TMM request message.

12. The second BS according to claim 11, wherein the processor is configured to set the non-F1 terminated BS UE XnAP ID IE in the TMM request message to be invalid or empty.

13. The second BS according to claim 11, wherein the TMM response message includes the UE XnAP ID of the MT of the wireless network node, which is assigned by the first BS and will be used on the Xn interface between the first BS and the second BS.

14. The second BS according to any one of claims 8 to 10, wherein the identifier associated with the wireless network node includes the UE XnAP ID of the MT of the wireless network node, which is assigned by the first BS and will be used on the Xn interface between the first BS and the second BS.

15. A method implemented by the first base station (BS), A step of receiving a transport transition management (TMM) request message from a second BS, wherein the TMM request message includes an identifier associated with the wireless network node for the first BS to identify the wireless network node. The steps include: sending a TMM response message to the second BS in response to receiving the TMM request message; Includes, The mobile terminal (MT) of the wireless network node hands over from the third BS to the first BS, and the distributed unit (DU) of the wireless network node has an F1 connection to the second BS, or the DU of the wireless network node migrates from the fourth BS to the second BS, and the MT of the wireless network node has a radio resource control (RRC) connection to the first BS. method.

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