Method and equipment for IAB node migration

Abstract

The embodiment of the invention relates to a method and equipment for integrated access and backhaul (IAB) node migration. In accordance with some embodiments of the present disclosure, a base station (BS) may determine whether there is an Internet Protocol (IP) connection between a second BS and a third BS, where one of a first BS and the second BS has a Radio Resource Control (RRC) connection to a Mobile Terminal (MT) of a wireless network node, and the other one of the first BS and the second BS has an F1 connection to a distributed unit (DU) of the wireless network node; and initiating a migration of the MT of the wireless network node to the third BS or a migration of the DU of the wireless network node to the third BS based on the determination.

Description

Technical Field

[0001] Embodiments of the present disclosure generally relate to communication technologies, and more particularly to integrated access and backhaul (IAB) node migration. Background Art

[0002] Wireless communication systems have been widely deployed to provide various telecommunication services such as telephony, video, data, messaging, broadcasting, and so on. A wireless communication system may employ a multiple access technology capable of supporting communication with multiple users by sharing available system resources such as time, frequency, and power. Examples of wireless communication systems may include fourth generation (4G) systems (such as Long Term Evolution (LTE) systems, Advanced LTE (LTE-A) systems, or LTE-A Pro systems) and fifth generation (5G) systems (which may also be referred to as New Radio (NR) systems).

[0003] To extend the coverage and availability of wireless communication systems (such as 5G systems), the Third Generation Partnership Project (3GPP) envisions an integrated access and backhaul (IAB) architecture for supporting multi-hop relaying. In an IAB network, an IAB node may skip one or more IAB nodes (also referred to as an "IAB donor" or "donor node") before reaching a base station. A single hop can be regarded as a special case of multi-hop. Multi-hop backhaul is beneficial because it provides a relatively large coverage extension compared to single-hop backhaul. In a relatively high-frequency radio communication system (such as a radio signal transmitted in a band above 6 GHz), a relatively narrow or small signal coverage area may benefit from multi-hop backhaul technology.

[0004] The industry needs technologies to facilitate communication in IAB networks. Summary of the Invention

[0005] Some embodiments of the present disclosure provide a first base station (BS). The first BS may include: a transceiver; and a processor coupled to the transceiver. The processor may be configured to: determine whether there is an Internet Protocol (IP) connection between a second BS and a third BS, wherein one of the first BS and the second BS has a Radio Resource Control (RRC) connection to a mobile terminal (MT) of a wireless network node, and the other of the first BS and the second BS has an F1 connection to a Distributed Unit (DU) of the wireless network node; and based on the determination, initiate migration of the MT of the wireless network node to the third BS or migration of the DU of the wireless network node to the third BS.

[0006] Some embodiments of the present disclosure provide a second BS. The second BS may include: a processor; and a transceiver coupled to the processor. The transceiver may be configured to: receive, from a first BS, second information regarding IP connectivity to the first BS or an inquiry regarding IP connectivity of the second BS, wherein one of the first BS and the second BS has an RRC connection to an MT of a radio network node, and the other of the first BS and the second BS has an F1 connection to a DU of the radio network node; and transmit, to the first BS, first information regarding IP connectivity to the second BS.

[0007] In some embodiments of the present disclosure, the first information includes a first BS list and each BS in the first BS list has an IP connection to the second BS. In some embodiments of the present disclosure, the second information includes a second BS list and each BS in the second BS list has an IP connection to the first BS.

[0008] Some embodiments of the present disclosure provide a third BS. The third BS may include: a processor; and a transceiver coupled to the processor. The transceiver may be configured to: receive, from a first BS, an inquiry regarding whether there is an IP connection between the third BS and a second BS, wherein one of the first BS and the second BS has an RRC connection to an MT of a radio network node, and the other of the first BS and the second BS has an F1 connection to a DU of the radio network node; and transmit, to the first BS, a response to the inquiry.

[0009] In some embodiments of the present disclosure, in response to the response indicating that there is an IP connection between the third BS and the second BS, the transceiver is further configured to: receive, from one of the first BS and the second BS, a request to migrate the MT of the radio network node to the third BS; or receive, from the other of the first BS and the second BS or the radio network node, a request to migrate the DU of the radio network node to the third BS.

[0010] Some embodiments of the present disclosure provide a first BS. The first BS may include: a processor; and a transceiver coupled to the processor. The transceiver may be configured to: transmit, to a third BS, a request to migrate one of an MT and a DU of a radio network node to the third BS, wherein the first BS is connected to one of the MT and the DU of the radio network node, and the request includes information associated with a second BS connected to the other of the MT and the DU of the radio network node; and receive, from the third BS, a response to the request.

[0011] In some embodiments of the present disclosure, the response indicates that the relocation is rejected due to the absence of an IP connection between the second BS and the third BS.

[0012] In some embodiments of the present disclosure, the information associated with the second BS includes an identifier of the second BS.

[0013] Some embodiments of the present disclosure provide a wireless network node. The wireless network node may include: a processor; and a transceiver coupled to the processor. The transceiver may be configured to: transmit a request to a third BS to trigger a relocation of a DU of the wireless network node from a first BS to the third BS, wherein an MT of the wireless network node has an RRC connection to a second BS; and receive a response to the request.

[0014] Some embodiments of the present disclosure provide a method performed by a first BS. The method may include: determining whether there is an IP connection between a second BS and a third BS, wherein one of the first BS and the second BS has an RRC connection to an MT of a wireless network node, and the other of the first BS and the second BS has an F1 connection to a DU of the wireless network node; and based on the determination, initiating a relocation of the MT of the wireless network node to the third BS or a relocation of the DU of the wireless network node to the third BS.

[0015] Some embodiments of the present disclosure provide a method performed by a second BS. The method may include: receiving, from a first BS, second information regarding IP connectivity to the first BS or an inquiry regarding IP connectivity of the second BS, wherein one of the first BS and the second BS has an RRC connection to an MT of a wireless network node, and the other of the first BS and the second BS has an F1 connection to a DU of the wireless network node; and transmitting, to the first BS, first information regarding IP connectivity to the second BS.

[0016] Some embodiments of the present disclosure provide a method performed by a third BS. The method may include: receiving, from a first BS, an inquiry regarding whether there is an IP connection between the third BS and a second BS, wherein one of the first BS and the second BS has an RRC connection to an MT of a wireless network node, and the other of the first BS and the second BS has an F1 connection to a DU of the wireless network node; and transmitting, to the first BS, a response to the inquiry.

[0017] Some embodiments of the present disclosure provide a method performed by a first BS. The method may include: transmitting to a third BS a request to migrate one of an MT and a DU of a wireless network node to the third BS, wherein the first BS is connected to one of the MT and the DU of the wireless network node, and the request includes information associated with a second BS connected to the other of the MT and the DU of the wireless network node; and receiving, from the third BS, a response to the request.

[0018] Some embodiments of the present disclosure provide a method performed by a wireless network node. The method may include: transmitting to a third BS a request to trigger migration of a DU of the wireless network node from a first BS to the third BS, wherein an MT of the wireless network node has an RRC connection to a second BS; and receiving a response in response to the request.

[0019] 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-transitory computer-readable medium having computer-executable instructions stored thereon; at least one receiving circuit system; at least one transmitting circuit system; and at least one processor coupled to the at least one non-transitory computer-readable medium, the at least one receiving circuit system, and the at least one transmitting circuit system, wherein the at least one non-transitory computer-readable medium and the computer-executable instructions may be configured to, together with the at least one processor, cause the apparatus to perform a method according to some embodiments of the present disclosure.

[0020] Embodiments of the present disclosure provide technical solutions for facilitating and improving implementations of various communication technologies (such as 5G NR). BRIEF DESCRIPTION OF THE DRAWINGS

[0021] To describe the manner in which the advantages and features of the present disclosure can be obtained, a description of the present disclosure is presented by reference to specific embodiments of the present disclosure illustrated in the drawings. These drawings only depict exemplary embodiments of the present disclosure and should not be considered as limiting its scope.

[0022] Figure 1 A schematic diagram illustrating a wireless communication system according to some embodiments of the present disclosure;

[0023] Figure 2 and 3 An example block diagram illustrating a protocol stack for an IAB network according to some embodiments of the present disclosure;

[0024] Figure 4 and 5 A schematic diagram illustrating IAB node migration according to some embodiments of the present disclosure;

[0025] Figures 6 to 16 A flowchart illustrating an exemplary procedure for wireless communication according to some embodiments of the present disclosure; and

[0026] Figure 17 A block diagram illustrating an exemplary device according to some embodiments of the present disclosure. Detailed Description of the Embodiments

[0027] The detailed description of the drawings is intended as a description of the preferred embodiments of the present disclosure and is not intended to represent the only form in which the present disclosure can be practiced. It should be understood that the same or equivalent functions can be accomplished by different embodiments that are intended to be covered within the spirit and scope of the present disclosure.

[0028] Reference will now be made in detail to some embodiments of the present disclosure, examples of which are illustrated in the accompanying drawings. For the sake of promoting understanding, the embodiments are provided under a specific network architecture and new service scenarios (such as 3rd Generation Partnership Project (3GPP) 5G (NR), 3GPP Long Term Evolution (LTE) Release 8, etc.). It is considered that with the development of the network architecture and new service scenarios, all the embodiments in the present disclosure are also applicable to similar technical problems; and in addition, the terms described in the present disclosure may change, which should not affect the principles of the present disclosure.

[0029] Compared with 4G communication systems, 5G communication systems have put forward more stringent requirements for various network performance metrics, such as a 1000-fold increase in capacity, a wider coverage range requirement, ultra-high reliability, ultra-low latency, etc. Considering the rich frequency resources of high-frequency carriers, it has become increasingly popular to deploy high-frequency small cells in hot spots in order to meet the 5G ultra-high capacity requirements. However, the propagation characteristics of high-frequency carriers are poor, severely attenuated due to obstacles, and the coverage range is limited. Therefore, it is necessary to deploy small cells densely. In addition, for these small cells, the deployment of optical fibers may be both difficult and expensive. Therefore, an economical and convenient backhaul solution is needed. The integrated access and backhaul (IAB) technology that can use wireless transmission solutions for both the access link and the backhaul link provides an idea for solving the above problems.

[0030] In an IAB network, a wireless network node, such as a relay node (RN) or an IAB node or a wireless backhaul node / device, can provide wireless access services for a UE. For example, a UE can be connected to an IAB donor relayed by one or more IAB nodes. The IAB donor can also be referred to as a donor node or a donor base station (e.g., DgNB, donor gNodeB). In addition, the wireless link between the IAB donor and the IAB node, or the wireless link between different IAB nodes, can be referred to as a "backhaul link". The wireless network nodes in the IAB network can be fixed or mobile. The embodiments of the present disclosure can be applied to wireless network nodes regardless of whether they are fixed or mobile.

[0031] The IAB node may include an IAB mobile terminal (MT) part and an IAB distributed unit (DU) part. When the IAB node is connected to its parent node (which may be another IAB node or an IAB donor), it can be regarded as a UE, that is, the role of the MT. When the IAB node provides services to its child nodes (which may be another IAB node or a UE), it can be regarded as a network device, that is, the role of the DU.

[0032] The IAB donor may be an access network element with complete base station functions, or an access network element with a separate form of a centralized unit (CU) and a distributed unit (DU). The IAB donor can be connected to the core network (for example, connected to a 5G core (5GC) network), and provide a wireless backhaul function for the IAB node. The CU of the IAB donor may be referred to as "IAB donor-CU" (or directly as "CU"), and the DU of the IAB donor may be referred to as "IAB donor-DU". The IAB donor-CU can be divided into a control plane (CP) and a user plane (UP). For example, the CU may include a CU-CP and one or more CU-UPs.

[0033] Considering the limited coverage of the high-frequency band and to ensure the coverage performance of the network, multi-hop networking can be adopted in the IAB network. Considering the requirements of service transmission reliability, the IAB node can support dual connectivity (DC) or multi-connectivity to improve transmission reliability in order to handle abnormal situations that may occur on the backhaul (BH) link, such as radio link failure (RLF) or blockage, load fluctuation, etc.

[0034] In the case where the IAB network supports multi-hop and dual-connectivity networking, there may be multiple transmission paths between the UE and the IAB donor. The transmission path may include multiple nodes, such as a UE, one or more IAB nodes, and an IAB donor (if the IAB donor is in the form of a separate CU and DU, then it may also include an IAB donor-DU and an IAB donor-CU). Each IAB node may regard the adjacent node providing backhaul services for it as the parent node (or parent IAB node), and each IAB node may be regarded as the child node (or child IAB node) of its parent node.

[0035] Figure 1 Schematic diagram of a wireless communication system 100 according to some embodiments of the present disclosure.

[0036] As Figure 1 shown, the wireless communication system 100 may include some base stations (for example, IAB donor 110A and IAB donor 110B), some IAB nodes (for example, IAB node 120A, IAB node 120B, and IAB node 120C), and some UEs (for example, UE130A and UE 130B). Although in Figure 1depicts a specific number of UEs, IAB nodes, and IAB donors, but it is contemplated that any number of UEs, IAB nodes, and IAB donors may be included in the wireless communication system 100.

[0037] According to some other embodiments of the present disclosure, each of IAB donors 110A, 110B, IAB nodes 120A, 120B, and 120C may be directly connected to one or more IAB nodes. According to some other embodiments of the present disclosure, each of IAB donors 110A, 110B, IAB nodes 120A, 120B, and 120C may be directly connected to one or more UEs.

[0038] UEs 130A and 130B may be any type of device configured to operate and / or communicate in a wireless environment. For example, UEs 130A and 130B may include computing devices such as desktop computers, laptop computers, personal digital assistants (PDAs), tablet computers, smart TVs (e.g., TVs connected to the Internet), set-top boxes, gaming consoles, security systems (including security cameras), in-vehicle computers, network devices (e.g., routers, switches, and modems), or the like. According to some embodiments of the present disclosure, UEs 130A and 130B may include portable wireless communication devices, smartphones, cellular phones, flip phones, devices with subscriber identity modules, personal computers, paging receivers, or any other device capable of transmitting and receiving communication signals over a wireless network. In some embodiments of the present disclosure, UEs 130A and 130B may include wearable devices such as smartwatches, fitness bands, optical head-mounted displays, Internet of Things (IoT) devices, or the like. Additionally, UEs 130A and 130B may be referred to as subscriber units, mobile devices, 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.

[0039] IAB donors 110A and 110B may communicate with a core network ( Figure 1 not shown). The core network (CN) may include multiple core network components such as a mobility management entity (MME) ( Figure 1 not shown) or an access and mobility management function (AMF) ( Figure 1 not shown). The CN may act as a gateway for the UEs to access the public switched telephone network (PSTN) and / or other networks ( Figure 1 not shown).

[0040] 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.

[0041] In some embodiments of the present disclosure, the wireless communication system 100 is compatible with 5G NR of the 3GPP protocol. For example, the IAB donors 110A and 110B may transmit data on the DL using an orthogonal frequency division multiple access (OFDM) modulation scheme. The UEs 130A and 130B may transmit data on the UL using a discrete Fourier transform-spread-orthogonal frequency division multiplexing (DFT-S-OFDM) or cyclic prefix-OFDM (CP-OFDM) scheme. However, more generally, the wireless communication system 100 may implement some other open or proprietary communication protocols, such as WiMAX and other protocols.

[0042] Those skilled in the art should understand that as technology develops and progresses, the terms described in the present disclosure may change, but should not affect or limit the principles and spirit of the present disclosure.

[0043] Referring Figure 1 , the IAB node 120A may be directly connected to the IAB donors 110A and 110B, and the IAB node 120B may be directly connected to the IAB donor 110A. The IAB donors 110A and 110B are the parent nodes of the IAB node 120A, and the IAB donor 110A is the parent node of the IAB node 120B. In other words, the IAB nodes 120A and 120B are the child IAB nodes of the IAB donor 110A, and the IAB node 120A is also the child IAB node of the IAB donor 110B. The IAB node 120C may reach the IAB donor 110A by skipping the IAB node 120B. The IAB node 120B is the parent IAB node of the IAB node 120C. In other words, the IAB node 120C is the child IAB node of the IAB node 120B.

[0044] In some other embodiments of the present disclosure, an IAB node may be connected to the IAB node 120C, so that it may reach the IAB donor 110A by skipping the IAB node 120C and the IAB node 120B. This IAB node and the IAB node 120C may be referred to as the descendant IAB nodes of the IAB node 120B.

[0045] UEs 130A and 130B can be connected to IAB nodes 120A and 120C respectively. The IAB nodes 120A and 120C can thus be referred to as access IAB nodes. Uplink (UL) packets (e.g., data or signaling) from UE 130A or UE 130B can be transmitted via one or more IAB nodes to an IAB donor (e.g., IAB donor 110A or 110B), and then be transmitted by the IAB donor to a mobile gateway device (e.g., a user plane function (UPF) in 5GC). Downlink (DL) packets (e.g., data or signaling) can be transmitted from an IAB donor (e.g., IAB donor 110A or 110B) after being received by the gateway device, and then be transmitted through one or more IAB nodes to UE 130A or 130B.

[0046] For example, referring to Figure 1 , UE 130A can transmit UL data to or receive DL data from IAB donor 110A or 110B via IAB node 120A. UE 130B can transmit UL data to or receive DL data from IAB donor 110A via IAB node 120C and IAB node 120B.

[0047] In an IAB deployment (e.g., wireless communication system 100), the radio link between an IAB donor (e.g., Figure 1 IAB donor 110A or 110B in Figure 1 ) and an IAB node or between two IAB nodes can be referred to as a backhaul link (BL). The radio link between an IAB donor (e.g., Figure 1 ) and a UE or between an IAB node and a UE can be referred to as an access link (AL). For example, in

[0048] , radio links 140A to 140D are BLs and radio links 150A and 150B are ALs.

[0048] A protocol layer (backhaul adaptation protocol (BAP)) layer located above the radio link control (RLC) layer is introduced into the IAB system and can be used to implement packet routing, bearer mapping, and traffic control on the wireless backhaul link.

[0049] An F1 interface can be established between an IAB node (e.g., the DU part of the IAB node) and an IAB donor (e.g., the IAB donor-CU). The F1 interface can support both the user plane protocol (e.g., F1-U) and the control plane protocol (e.g., F1-C). The user plane protocol of the F1 interface can include one or more of General Packet Radio Service (GPRS) Tunneling Protocol User Plane (GTP-U), User Datagram Protocol (UDP), Internet Protocol (IP), and other protocols. The control plane protocol of the F1 interface can include one or more of F1 Application Protocol (F1AP), Stream Control Transmission Protocol (SCTP), IP, and other protocols.

[0050] Through the control plane of the F1 interface, the IAB node and the IAB donor can perform, for example, interface management, IAB-DU management, and UE context-related configuration. Through the user plane of the F1 interface, the IAB node and the IAB donor can perform, for example, user plane data transmission and downlink transmission status feedback functions.

[0051] Figure 2 An example block diagram of a user plane (UP) protocol stack 200 for an IAB network according to some embodiments of the present disclosure is illustrated. Figure 3 An example block diagram of a control plane (CP) protocol stack 300 for an IAB network according to some embodiments of the present disclosure is illustrated. In Figure 2 and 3 the UE can be connected to the IAB donor via IAB node 2 and IAB node 1. In some other embodiments of the present disclosure, the UE can be connected to the IAB donor via more or fewer IAB nodes.

[0052] Referring to Figure 2 , the UP protocol stack of the UE can include a Service Data Adaptation Protocol (SDAP) layer, a Packet Data Convergence Protocol (PDCP) layer, a Radio Link Control (RLC) layer, a Media Access Control (MAC) layer, and a Physical (PHY) layer. The UP protocol stack of the DU of IAB node 2 can include a GTP-U layer, a UDP layer, an IP layer, an RLC layer, a MAC layer, and a PHY layer. The UP protocol stack of the MT of IAB node 2 or the DU or MT of IAB node 1 can include a BAP layer, an RLC layer, a MAC layer, and a PHY layer. The UP protocol stack of the DU of the IAB donor can include an IP layer, a BAP layer, an RLC layer, a MAC layer, and a PHY layer, where the PHY layer belongs to layer 1 (L1), and the BAP layer, RLC layer, and MAC layer belong to layer 2 (L2). The protocol stack of the CU-UP of the IAB donor can include a GTP-U layer, a UDP layer, an IP layer, an SDAP layer, a PDCP layer, (several) L2 layers, and an L1 layer.

[0053] Referring to Figure 3, the CP protocol stack of the UE may include a Radio Resource Control (RRC) layer, a Packet Data Convergence Protocol (PDCP) layer, a Radio Link Control (RLC) layer, a Medium Access Control (MAC) layer, and a Physical (PHY) layer. The CP protocol stack of the DU of IAB Node 2 may include an F1 Application Part (F1AP) layer, a Stream Control Transmission Protocol (SCTP) layer, an Internet Protocol (IP) layer, an RLC layer, a MAC layer, and a PHY layer. The CP protocol stack of the MT of IAB Node 2 or the DU or MT of IAB Node 1 may include a Backhaul Application Part (BAP) layer, an RLC layer, a MAC layer, and a PHY layer. The CP protocol stack of the DU of the IAB donor may include an IP layer, a BAP layer, an RLC layer, a MAC layer, and a PHY layer, where the PHY layer belongs to L1, and the BAP layer, the RLC layer, and the MAC layer belong to L2. The protocol stack of the CU-CP of the IAB donor may include an RRC layer, a PDCP layer, an F1AP layer, an SCTP layer, an IP layer, (several) L2 layers, and an L1 layer.

[0054] Figure 2 and 3 The protocol stacks shown in Figure 2 and 3 are for illustrative purposes only. For example, for illustrative purposes, the sequence of some protocol layers in the protocol stack of Figure 2 can be rearranged. For example, although the Service Data Adaptation Protocol (SDAP) and PDCP layers belong to L2, they are shown above the GTP-U layer, UDP layer, and IP layer in the protocol stack of the CU-UP of the IAB donor in

[0055] The signals between each node in the IAB network may include, for example, the following and can be applied to the present disclosure:

[0056] - IAB donor CU and IAB donor DU: F1AP messages;

[0057] - IAB donor CU and IAB node: F1AP messages between the CU and the IAB-DU or RRC messages between the CU and the IAB-MT;

[0058] - IAB donor-CU and UE: RRC messages;

[0059] - Access IAB node and UE: L2 control PDUs, such as MAC control elements (CEs) or RLC control PDUs; and

[0060] - IAB node and another child or parent IAB node: L2 control PDUs, such as MAC CEs, RLC control PDUs, or BAP control PDUs.

[0061] As the demand for improved cellular coverage and connectivity continues to increase, communication in outdoor and mobile scenarios may face more challenges. In some embodiments of the present disclosure, a mobile radio network node acting as a repeater between a UE and a 3GPP communication network (e.g., 5G) can be used to facilitate communication in such scenarios. The mobile radio network node can provide, for example, an access link to the UE and be wirelessly connected (e.g., using NR) to the core network via a BS (e.g., a donor next-generation radio access network (NG-RAN)). In some instances, this mobile radio network node can also be referred to as a mobile base station repeater or a mobile repeater. The above description regarding radio network nodes and IAB nodes can be applied to mobile base station repeaters. That is, a mobile base station repeater can be a mobile IAB node.

[0062] In some instances, a mobile base station repeater can be installed on a vehicle. The mobile base station repeater can serve UEs located inside or outside the vehicle, or UEs entering or leaving the vehicle. In the context of the present disclosure, the inside or outside of the mobile base station repeater can mean the inside or outside of the vehicle or other device(s) on which the mobile radio network node is installed.

[0063] In some instances, the radio links used between the mobile base station repeater and the served UE and between the mobile base station repeater and the BS can be Uu links (e.g., NR-Uu), which are different from UE repeaters that use PC5-based links to provide, for example, an indirect connection to a remote UE. In some instances, there can be at least one hop between the UE and the mobile base station repeater. In some instances, there can be at least one hop between the mobile base station repeater and the BS.

[0064] Employing this mobile radio network node is advantageous in various aspects and can be applied to various scenarios. For example, in some outdoor environments, the availability of vehicles equipped with mobile base station repeaters, whether following a certain known / predictable itinerary (e.g., buses, trams, etc.) or located in a convenient location (e.g., outside a stadium, a hot spot area, or an emergency location), can provide a very opportunistic boost to cellular coverage and capacity when needed or in the event of a need. These repeaters can use, for example, 5G wireless backhaul towards the macro network and thus can provide better coverage and connectivity to adjacent UEs. Mobile repeaters are also well-suited to improving the connectivity of users or devices inside the vehicle on which the mobile repeater is installed in different environments (e.g., passengers, casual / professional personnel, or equipment in buses, cars / taxis, or trains). This mobile radio network node can also be used to reach users or devices that originally had no macro coverage or very poor macro coverage. For example, in the case where a first responder is in an indoor building / area and has no signal, a repeater placed near or outside the vehicle can be used to obtain the required coverage and connectivity.

[0065] The technical advantages of using such a mobile radio network node further include, for example, the ability to obtain better macro coverage than nearby UEs by leveraging better radio frequency, antenna, and power capabilities, etc. Additionally, in addition to the value to network operators and end users, valuable incentives can also be found for other parties (such as vehicle manufacturers, and vehicle and fleet owners or providers) to install and operate repeaters in their vehicles.

[0066] Due to the mobility of a radio network node (such as an IAB node), the radio network node may need to migrate (or handover) from one IAB donor to another IAB donor.

[0067] In some embodiments, the MT of a radio network node may migrate from an initial (source) IAB donor to a new (target) IAB donor. For example, the MT of a radio network node may migrate to a different parent node under a different CU of an IAB donor. For example, referring again to Figure 1 , the MT of IAB node 120C or IAB node 120B may migrate from IAB donor 110A to IAB donor 110B. In such a scenario, the DU of the radio network node and the DUs of the (several) descendant nodes of the radio network node may maintain F1 connectivity with the source IAB donor (such as the CU of the source IAB donor). Such a migration may be referred to as an inter-donor partial migration. The radio network node whose MT migrates to the target IAB donor (such as the CU of the target IAB donor) may be referred to as a border radio network node. After the inter-donor partial migration, the F1 traffic of the DU of the radio network node and the DUs of the (several) descendant nodes of the radio network node may be routed via, for example, the BAP layer of the IAB topology to which the MT of the radio network node has migrated.

[0068] In some embodiments, the DU of a radio network node may migrate from an initial (source) IAB donor to a new (target) IAB donor. Such a migration may be referred to as an inter-donor IAB-DU migration. In some embodiments, in order to perform a handover of a UE served by a radio network node (such as its DU), the radio network node may concurrently support two logical DUs (such as DU#1 and DU#2), and the two logical DUs may have F1AP associations with the source IAB donor (such as the CU of the source IAB donor) and the target IAB donor (such as the CU of the target IAB donor), respectively. The UE connected to the radio network node may handover from the cell of DU#1 (i.e., the source DU of the radio network node) that has an F1AP association with the source CU (i.e., the CU of the source IAB donor) to the cell of DU#2 (i.e., the target DU of the radio network node) that has an F1AP association with the target CU (i.e., the CU of the target IAB donor). After the migration of the DU of the radio network node, the F1 interface between DU#1 and the source IAB donor may be released.

[0069] In some embodiments of the present disclosure, the migration of the DU of a wireless network node can be performed independently of the migration of the MT of the wireless network node. For example, the DU and MT of a wireless network node can migrate (or switch) to different IAB donors (e.g., donor CUs).

[0070] For example, Figure 4 and 5 shows a schematic diagram of IAB node migration according to some embodiments of the present disclosure. In Figure 4 example, the MT of the wireless network node migrates from BS to another BS, while the DU of the wireless network node is connected to yet another BS (hereinafter referred to as "Scenario 1"). In Figure 5 example, the DU of the wireless network node migrates from BS to another BS, while the MT of the wireless network node is connected to yet another BS (hereinafter referred to as "Scenario 2"). All the details described in all the foregoing embodiments of the present disclosure apply to Figure 4 and 5 the embodiments shown in.

[0071] Referring to Figure 4 , the IAB donor 410A may include a CU 475 and a DU 465, the IAB donor 410B may include a CU 476 and a DU 466, and the IAB donor 410C may include a CU 477 and a DU 467. The IAB node 420A may be directly connected to the IAB donor 410A and may include an MT 451 and a DU 461. The IAB node 420B may be directly connected to the IAB donor 410B and may include an MT 452 and a DU 462. The IAB node 420C may be directly connected to the IAB donor 410C and may include an MT 453 and a DU 463. The IAB node 420D may include an MT 454 and a DU 464, and the UE 430 may be connected to the IAB node 420D. The IAB node 420D may be referred to as the access IAB node of the UE 430.

[0072] The DU 464 of the IAB node 420D may be anchored at the IAB donor 410C (e.g., CU 477). The MT 454 of the IAB node 420D may migrate (or switch) from the IAB donor 410A to the IAB donor 410B. During the migration of the MT 454, the F1 transmission between the DU 464 and the IAB donor 410C switches from the topology of the IAB donor 410A (e.g., represented by the signaling flow 440A) to the topology of the IAB donor 410B (e.g., represented by the signaling flow 440B).

[0073] Referring to Figure 5, the IAB donor 510A may include a CU 575 and a DU 565, the IAB donor 510B may include a CU 576 and a DU 566, and the IAB donor 510C may include a CU 577 and a DU 567. The IAB node 520A may be directly connected to the IAB donor 510A and may include an MT 551 and a DU 561. The IAB node 520B may be directly connected to the IAB donor 510B and may include an MT 552 and a DU 562. The IAB node 520C may be directly connected to the IAB donor 510C and may include an MT 553 and a DU 563. The IAB node 520D may include an MT 554 and two DUs (DU 564a and DU 564b), and the UE 530 may be connected to the IAB node 520D. The IAB node 520D may be referred to as the access IAB node of the UE 530.

[0074] The MT 554 of the IAB node 520D may be anchored at the IAB donor 510B (e.g., CU 576). The DU of the IAB node 520D may migrate from the IAB donor 510A (i.e., the source IAB donor) to the IAB donor 510C (i.e., the target IAB donor). Before the DU migration, only the DU 564a of the IAB node 520D has an F1 connection to the IAB donor 510A (e.g., represented by the signaling flow 540A). During the DU migration, the IAB node 520D may have two DUs (e.g., DU 564a and DU 564b as shown Figure 5 ). The DU 564a may have an F1 connection to the IAB donor 510A and the DU 564b may have an F1 connection to the IAB donor 510C (e.g., represented by the signaling flow 540B). And after the DU migration, only the DU 564b of the IAB node 520D has an F1 connection to the IAB donor 510C. The two F1 connections are transmitted via the topology of the IAB donor 510B.

[0075] Figure 4 and 5 The DU migration and MT migration shown in are for illustrative purposes only. For example, in some other embodiments, the MT and DU of a radio network node may be anchored at the same BS (e.g., an IAB donor) and the MT or DU of a radio network node may migrate from a source BS to a target BS (e.g., an IAB donor). For example, in some other embodiments, a radio network node may skip one or more radio network nodes (e.g., IAB nodes) before reaching the source or target BS, or may be directly connected to the source or target BS.

[0076] It should be noted that although the embodiments of the present disclosure are discussed under a specific network architecture (e.g., IAB architecture) and based on certain specific components (e.g., IAB donor or mobile IAB node), the embodiments of the present disclosure are also applicable to other similar network architectures and new service scenarios.

[0077] During the migration of a wireless network node (e.g., DU or MT migration), several issues may need to be addressed.

[0078] For example, in both Scenario 1 (e.g., as shown in Figure 4 ) and Scenario 2 (e.g., as shown in Figure 5 ), the MT and DU of the wireless network node will terminate at different BSs after migration. As a prerequisite for achieving this, there should be an IP connection between the two BSs so that the MT and DU of the wireless network node can terminate at them. Therefore, the problem to be solved is whether this IP connectivity information should be obtained before migration to ensure the success of the migration. For example, referring to Figure 4 , should the IAB donor 410A know whether there is an IP connection between the IAB donor 410B and the IAB donor 410C before the migration of the MT 454 of the IAB node 420D. For example, referring to Figure 5 , should the IAB donor 510A know whether there is an IP connection between the IAB donor 510B and the IAB donor 510C before the migration of the DU of the IAB node 520D. In addition, it may be necessary to solve how to obtain this information.

[0079] For example, the MT and DU of the wireless network node terminate at different BSs and the F1-terminating BS to which the DU of the wireless network node is connected may trigger the migration of the DU of the wireless network node. The problem to be solved is how the F1-terminating BS can determine whether to perform the migration of the DU of the wireless network node to another BS. For example, referring to Figure 5 , how should the IAB donor 510A determine whether to trigger the migration of the DU of the IAB node 520D.

[0080] For example, the MT and DU of the wireless network node terminate at different BSs and the migration of the DU of the wireless network node may not be triggered by the F1-terminating BS to which the DU of the wireless network node is connected. The problem to be solved is how the F1-terminating BS can know the completion of the DU migration and the target BS of the migration, so that the F1-terminating BS may trigger the handover of the UE served by the wireless network node to the target BS. For example, referring to Figure 5 , how can the IAB donor 510A know the completion of the migration of the DU of the IAB node 520D and the IAB donor 510C.

[0081] Embodiments of the present disclosure provide solutions for enhancing the migration of wireless network nodes, which can at least solve the above problems. More details regarding the embodiments of the present disclosure will be described below with reference to the accompanying drawings.

[0082] In some embodiments of the present disclosure, the DU of a network node may perform a migration from a BS (i.e., the source F1-terminated BS) to another BS (i.e., the target F1-terminated BS). The MT of the network node may be connected to yet another BS (i.e., the RRC-terminated BS). As described above, during this migration, the network node may have two logical DUs, and the two logical DUs respectively have F1 connections to the source and target F1-terminated BSs, and the two F1 connections need to be transmitted via the topology of the RRC-terminated BS. However, an error situation may occur when the DU migration is triggered by the source F1-terminated BS, and the source F1-terminated BS does not know whether there is an IP connection between the RRC-terminated BS and the target F1-terminated BS (or whether there is an IP connection between the DU of the RRC-terminated BS and the CU of the target F1-terminated BS). To solve this problem, the source F1-terminated BS may query the RRC-terminated BS or the target F1-terminated BS before triggering the DU migration. Additionally, the source F1-terminated BS may obtain information to assist it in initiating the migration of the DU of the network node.

[0083] For example, Figure 6 A flowchart of an exemplary procedure 600 for wireless communication according to some embodiments of the present disclosure is illustrated.

[0084] The details described in all of the foregoing embodiments of the present disclosure are applicable to Figure 6 the embodiments shown in. For example, BSs 610A to 610C may be used as IAB donors as described above and may include a CU and at least one DU. The network node 620 may be used as an IAB node as described above and may include an MT and at least one DU (e.g., one DU before and after the DU migration or two DUs during the DU migration).

[0085] The network node 620 (e.g., the DU of the network node 620) may have an F1 connection with BS 610A (e.g., the CU of BS 610A). The network node 620 (e.g., the MT of the network node 620) may have an RRC connection with BS 610B (e.g., the CU of BS 610B). BS 610A and BS 610B may be referred to as the F1-terminated BS and the RRC-terminated BS, respectively.

[0086] In some embodiments, the DU of network node 620 can perform a migration from BS 610A (i.e., the source F1-terminated BS) to the target BS (i.e., the target F1-terminated BS, such as BS 610C), while the MT of network node 620 maintains its connection with BS 610B. For example, BS 610A, BS 610B, BS 610C, and network node 620 can be used as Figure 5 the IAB donors 510A, IAB donors 510B, IAB donors 510C, and the IAB node 520D in

[0087] In some embodiments, before initiating the migration of the DU of network node 620 to BS 610C, BS 610A can determine whether there is an IP connection between BS 610B and BS 610C. As will be described in detail below, the determination can be based on an inquiry initiated by BS610A to BS 610B or BS 610C.

[0088] In some embodiments of the present disclosure, to assist BS 610A in determining whether to migrate the DU of network node 620, BS610A may need to know the location of the MT of network node 620. For example, to assist BS 610A in initiating the migration of the DU of network node 620, network node 620 can transmit the location information of the MT of network node 620 to BS 610A in operation 611a. The information can be transmitted via the F1 interface between the DU of network node 620 and BS 610A. In some embodiments, in addition to or instead of operation 611a, BS 610B (i.e., the RRC-terminated BS) can also transmit the location information of the MT of network node 620 to BS 610A in operation 611b. The information can be transmitted via the Xn interface between BS 610A and BS 610B.

[0089] In some embodiments of the present disclosure, in operation 613a, BS 610A can transmit an inquiry about the IP connectivity of BS 610B (e.g., an inquiry about whether there is an IP connection between BS 610B and BS 610C) to BS 610B. In some embodiments of the present disclosure, in addition to or instead of operation 613a, BS 610A can also transmit an inquiry about the IP connectivity of BS 610C (e.g., an inquiry about whether there is an IP connection between BS 610B and BS 610C) to BS610C in operation 613b. The above inquiries can be transmitted via the Xn interface between BS 610A and BS 610B or between BS 610A and BS 610C.

[0090] In the case of performing operation 613a, BS 610B may transmit a response to the query to BS 610A in operation 615a. In the case of performing operation 613b, BS 610C may transmit a response to the query to BS 610A in operation 615b. BS 610A may then determine whether to trigger the migration of the DU of network node 620 from BS 610A to BS 610C based on the response. For example, in the case where the response indicates that there is an IP connection between BS 610B and BS 610C (i.e., positive feedback), BS 610A may initiate the migration of the DU of network node 620 to BS 610C. Otherwise, in the case where the response indicates that there is no IP connection between BS 610B and BS 610C (i.e., negative feedback), BS 610A may not initiate the migration of the DU of network node 620 to BS 610C.

[0091] In some embodiments, to initiate the migration of the DU of network node 620 to BS 610C, BS 610A may transmit a migration command to network node 620 ( Figure 6 not shown in the figure). Network node 620 may have two logical DUs (denoted as DU#A1 and DU#A2), where DU#A1 has an F1 connection to BS 610A, and DU#A2 may set up an F1 connection to BS 610C via the BH link under BS 610B. After the cell of DU#A2 has been activated, all UEs connected to DU#A1 may perform a handover from the cell(s) of DU#A1 to the cell(s) of DU#A2.

[0092] In some other embodiments, BS 610A may transmit a migration command (e.g., a DU or F1 migration request) to BS 610C to initiate the migration of the DU of network node 620 to BS 610C.

[0093] Those skilled in the art should understand that, without departing from the spirit and scope of the present disclosure, the operation sequence in the exemplary procedure 600 may be changed and some operations in the exemplary procedure 600 may be eliminated or modified.

[0094] In some embodiments of the present disclosure, the MT of a network node may perform a migration from a BS (i.e., a source RRC-terminating BS) to another BS (i.e., a target RRC-terminating BS). The DU of the network node may be connected to yet another BS (i.e., an F1-terminating BS). As described above, during this migration, the F1 transmission between the DU of the network node and the F1-terminating BS switches from the topology of the source RRC-terminating BS to the topology of the target RRC-terminating BS. However, an error situation may occur in the case where the MT migration is triggered by the source RRC-terminating BS, which does not know whether there is an IP connection between the target RRC-terminating BS and the F1-terminating BS (or whether there is an IP connection between the DU of the target RRC-terminating BS and the CU of the F1-terminating BS). To solve this problem, the source RRC-terminating BS may inquire about the IP connectivity with the target RRC-terminating BS or the F1-terminating BS before triggering the MT migration.

[0095] For example, Figure 7 A flowchart illustrating an exemplary procedure 700 for wireless communication according to some embodiments of the present disclosure.

[0096] The details described in all the foregoing embodiments of the present disclosure apply to Figure 7 the embodiments shown in. For example, BSs 710A to 710C may be used as IAB donors as described above and may include a CU and at least one DU. The network node 720 may be used as an IAB node as described above and may include an MT and at least one DU (e.g., one DU before and after the DU migration or two DUs during the DU migration).

[0097] The network node 720 (e.g., the DU of the network node 720) may have an F1 connection with BS 710C (e.g., the CU of BS 710C). The network node 720 (e.g., the MT of the network node 720) may have an RRC connection with BS 710A (e.g., the CU of BS 710A). BS 710C and BS 710A may be referred to as the F1-terminating BS and the RRC-terminating BS, respectively.

[0098] In some embodiments, the MT of the network node 720 may perform a migration from BS 710A (i.e., the source RRC-terminating BS) to a target BS (i.e., the target RRC-terminating BS, e.g., BS 710B), while the DU of the network node 720 maintains its connection with BS 710C. For example, BSs 710A, 710B, 710C, and the network node 720 may be used as Figure 4 the IAB donors 410A, 410B, 410C, and the IAB node 420D in.

[0099] In some embodiments, BS 710A may trigger the migration of the MT of network node 720 (e.g., to BS 710B) based on the measurement report of the MT from network node 720. Before initiating the migration of the MT of network node 720 to BS 710B, BS 710A may determine whether there is an IP connection between BS 710B and BS 710C. As will be described in detail below, the determination may be based on an inquiry initiated by BS 710A to BS 710B or BS 710C.

[0100] In some embodiments of the present disclosure, in operation 713a, BS 710A may transmit an inquiry regarding the IP connectivity of BS 710B (e.g., an inquiry regarding whether there is an IP connection between BS 710B and BS 710C) to BS 710B. In some embodiments of the present disclosure, in addition to or instead of operation 713a, BS 710A may also transmit an inquiry regarding the IP connectivity of BS 710C (e.g., an inquiry regarding whether there is an IP connection between BS 710B and BS 710C) to BS 710C in operation 713b. The above inquiries may be transmitted via the Xn interface between BS 710A and BS 710B or between BS 710A and BS 710C.

[0101] In the case of performing operation 713a, BS 710B may transmit a response to the inquiry to BS 710A in operation 715a. In the case of performing operation 713b, BS 710C may transmit a response to the inquiry to BS 710A in operation 715b. BS 710A may then determine whether to trigger the migration of the MT of network node 720 from BS 710A to BS 710B based on the response. For example, in the case where the response indicates that there is an IP connection between BS 710B and BS 710C (i.e., positive feedback), BS 710A may initiate the migration of the MT of network node 720 to BS 710B. Otherwise, in the case where the response indicates that there is no IP connection between BS 710B and BS 710C (i.e., negative feedback), BS 710A may not initiate the migration of the MT of network node 720 to BS 710B.

[0102] In some embodiments, in order to initiate the migration of the MT of network node 720 to BS 710B, BS 710A may transmit a migration command (e.g., a handover command) to BS 710B ( Figure 7 not shown). The MT of network node 720 may perform the migration (or handover) from BS 710A to BS 710B as a UE. The F1 transmission between the DU of network node 720 and BS 710C switches from the topology of BS 710A to the topology of BS 710B.

[0103] Those skilled in the art will appreciate that the order of operations in exemplary procedure 700 may be changed and some operations in exemplary procedure 700 may be eliminated or modified without departing from the spirit and scope of the present disclosure.

[0104] In some embodiments of the present disclosure, a procedure between two BSs is introduced to exchange IP connectivity information of the two BSs. For example, the F1-terminated BS and the RRC-terminated BS of a network node may exchange this information via the Xn interface therebetween. This procedure may be triggered by either the F1-terminated BS or the RRC-terminated BS. The F1-terminated BS or the RRC-terminated BS may use the exchanged information to determine whether to initiate or perform a DU or MT migration of the network node to a different BS.

[0105] For example, Figure 8A and 8B Flowcharts illustrating exemplary procedures 800A and 800B for wireless communication according to some embodiments of the present disclosure. Exemplary procedures 800A and 800B may be used to exchange IP connectivity information of two BSs.

[0106] The details described in all of the foregoing embodiments of the present disclosure apply to Figure 8A and 8B the embodiments shown in. For example, BSs 810A and 810B may be used as IAB donors as described above and may include a CU and at least one DU.

[0107] In some embodiments of the present disclosure, BSs 810A and 810B may be the F1-terminated BS and the RRC-terminated BS of a network node (not shown in FIG. 8). That is, a network node (e.g., the DU of a network node) may have an F1 connection with BS 810A (e.g., the CU of BS 810A); and a network node (e.g., the MT of a network node) may have an RRC connection with BS 810B (e.g., the CU of BS 810B).

[0108] Referring to Figure 8A , BS 810A may transmit information regarding the IP connectivity to BS 810A (denoted as information #A1) to BS 810B in operation 811. In some embodiments, information #A1 may include a list of BSs, and each BS in this list has an IP connection to BS 810A. In response to the reception of information #A1, BS 810B may transmit information regarding the IP connectivity to BS 810B (denoted as information #A2) to BS 810A in operation 813. In some embodiments, information #A2 may include a list of BSs, and each BS in this list has an IP connection to BS 810B.

[0109] Referring to Figure 8B, BS 810B may transmit information regarding the IP connectivity to BS 810B (represented as Information #B1) to BS 810A in operation 821. In some embodiments, Information #B1 may include a list of BSs, and each BS in this list has an IP connection to BS 810B. In response to the reception of Information #B1, BS 810A may transmit information regarding the IP connectivity to BS 810A (represented as Information #B2) to BS 810B in operation 823. In some embodiments, Information #B2 may include a list of BSs, and each BS in this list has an IP connection to BS 810A.

[0110] In some embodiments of the present disclosure, BS 810A may use the IP connectivity information to BS 810B (e.g., Information #A2 or Information #B1) to determine whether to initiate the DU migration of a network node to a BS (represented as BS#C1) different from both BS 810A and BS 810B. For example, BS 810A may determine whether there is an IP connection between BS 810B and BS#C1 based on the IP connectivity information to BS 810B, and if it is determined that BS 810B and BS#C1 have an IP connection, then the DU of the wireless network node to BS#C1 may be initiated.

[0111] In some embodiments of the present disclosure, BS 810B may use the IP connectivity information to BS 810A (e.g., Information #A1 or Information #B2) to determine whether to initiate the MT migration of a network node to a BS (represented as BS#C2) different from both BS 810A and BS 810B. For example, BS 810B may determine whether there is an IP connection between BS 810B and BS#C2 based on the IP connectivity information to BS 810A, and if it is determined that BS 810B and BS#C2 have an IP connection, then the MT of the wireless network node to BS#C2 may be initiated.

[0112] Those skilled in the art should understand that, without departing from the spirit and scope of the present disclosure, the operation sequences in exemplary procedures 800A and 800B may be changed and some operations in exemplary procedures 800A and 800B may be eliminated or modified.

[0113] As described above, the IP connectivity information may be obtained before performing the MT or DU migration of the network node. For example, the MT or DU migration of the network node is only performed when the source RRC-terminating BS or the source F1-terminating BS obtains the information that the target RRC-terminating BS or the target F1-terminating BS has an IP connection to the F1-terminating BS or the RRC-terminating BS. However, in some other embodiments of the present disclosure, this information may not necessarily be obtained before the MT or DU migration of the network node.

[0114] For example, Figure 9 FIG. 900 is a flowchart illustrating an exemplary procedure for wireless communication according to some embodiments of the present disclosure.

[0115] The details described in all of the foregoing embodiments of the present disclosure apply to Figure 9 the embodiments shown in. For example, BSs 910A and 910B can be used as IAB donors as described above and can include a CU and at least one DU.

[0116] In some embodiments of the present disclosure, BS 910A can be an RRC-terminating BS of a network node ( Figure 9 not shown in). That is, a network node (e.g., the MT of the network node) can have an RRC connection with BS 910A (e.g., the CU of BS 910A). A network node (e.g., the DU of the network node) can have an F1 connection with another BS (not shown for clarity Figure 9 and denoted as BS#C3).

[0117] Referring to Figure 9 , BS 910A (i.e., the source RRC-terminating BS) can transmit a handover request to BS 910B (i.e., the target RRC-terminating BS) in operation 911 to hand over the MT of the network node to BS 910B. For example, BSs 910A and 910B can be used as Figure 4 IAB donors 410A and 410B in. In some embodiments, the handover request can include information associated with BS#C3 that has an F1 connection to the network node. For example, the information can indicate the identifier of BS#C3.

[0118] In some embodiments of the present disclosure, if BS 910B has an IP connection to BS#C3, then BS 910B can accept the handover in operation 913 and can transmit a response to the handover request (e.g., positive feedback, such as a handover request confirmation message) to BS 910A in operation 915.

[0119] In some embodiments of the present disclosure, if BS 910B does not have an IP connection to BS#C3, then BS 910B can reject the handover in operation 913 and can transmit a response to the handover request (e.g., negative feedback, such as a handover preparation failure message) to BS 910A. In some embodiments, the response can indicate that the handover (or migration) was rejected due to the absence of an IP connection between BS#C3 and BS 910B. For example, the handover preparation failure message can include a cause value for the absence of an IP connection.

[0120] In some embodiments of the present disclosure, the BS 910A may be an F1 terminated BS of a network node ( Figure 9 not shown in). That is, a network node (e.g., the DU of the network node) may have an F1 connection with the BS 910A (e.g., the CU of the BS 910A). A network node (e.g., the MT of the network node) may have an RRC connection with another BS (not shown for clarity and denoted as BS#C4 in Figure 9 ).

[0121] Reference Figure 9 , the BS 910A (i.e., the source F1 terminated BS) may, in operation 911, transmit a request (e.g., a DU or F1 migration request) to the BS 910B (i.e., the target F1 terminated BS) to migrate the DU of the network node to the BS 910B. For example, the BS 910A and the BS 910B may act as Figure 5 the IAB donors 510A and 510C in. In some embodiments, the request may include information associated with the BS#C4 having an RRC connection to the network node. For example, the information may indicate the identifier of the BS#C4.

[0122] In some embodiments of the present disclosure, if the BS 910B has an IP connection to the BS#C4, then the BS 910B may accept the request in operation 913 and may transmit a response (e.g., positive feedback) to the BS 910A in operation 915.

[0123] In some embodiments of the present disclosure, if the BS 910B does not have an IP connection to the BS#C4, then the BS 910B may reject the request in operation 913 and may transmit a response (e.g., negative feedback) to the BS 910A in operation 915. In some embodiments, the response may indicate that the migration is rejected due to the absence of an IP connection between the BS#C4 and the BS 910B. For example, the response message may indicate the cause value of the absence of the IP connection.

[0124] Those skilled in the art will appreciate that, without departing from the spirit and scope of the present disclosure, the order of operations in the exemplary procedure 900 may be changed and some operations in the exemplary procedure 900 may be eliminated or modified.

[0125] For example, Figure 10 FIG. 1000 is a flowchart illustrating an exemplary procedure for wireless communication according to some embodiments of the present disclosure.

[0126] All of the details described in the foregoing embodiments of the present disclosure apply to Figure 10The embodiments shown therein. For example, BS1010A and 1010B can be used as the IAB donors as described above and can include a CU and at least one DU. The network node 1020 can be used as the IAB node as described above and can include an MT and at least one DU (e.g., one DU before and after DU migration or two DUs during DU migration).

[0127] The network node 1020 (e.g., the DU of the network node 1020) can have an F1 connection with BS1010A (e.g., the CU of BS1010A). The network node 1020 (e.g., the MT of the network node 1020) can have an RRC connection with BS1010B (e.g., the CU of BS 1010B). BS1010A and BS1010B can be referred to as the F1-terminating BS and the RRC-terminating BS, respectively.

[0128] In some embodiments, the DU of the network node 1020 can perform a migration from BS1010A (i.e., the source F1-terminating BS) to a target BS (i.e., the target F1-terminating BS, which is not shown in Figure 10 and is denoted as BS#C5 for clarity), while the MT of the network node 1020 maintains its connection with BS1010B. For example, BS1010A, BS1010B, and the network node 1020 can be used as Figure 5 the IAB donors 510A, IAB donors 510B, and the IAB node 520D in

[0129] In some embodiments, the migration of the DU of the network node 1020 can be triggered by the F1-terminating BS of the network node 1020 (e.g., BS1010A). In some embodiments, the migration of the DU of the network node 1020 may not be triggered by the F1-terminating BS of the network node 1020 (e.g., BS1010A). For example, the migration can be triggered by the network node 1020 itself or by an operation, administration, and maintenance (OAM) entity.

[0130] For example, in some embodiments, BS1010A may trigger DU migration and may transmit a migration command to network node 1020 to migrate its DU from BS1010A to BS #C5. In some embodiments, to assist BS1010A in determining whether to migrate the DU of network node 1020, BS1010A may need to know the location of the MT of network node 1020. For example, to assist BS1010A in initiating the migration of the DU of network node 1020, BS1010A may obtain the location information of the MT of network node 1020 from network node 1020, BS1010B, or both. For example, the location information may be obtained via the F1 interface between the DU of network node 1020 and BS1010A. For example, the location information may be obtained via the Xn interface between BS 1010A and BS1010B.

[0131] During the migration of the DU of network node 1020, network node 1020 may have two logical DUs (represented as DU #B1 and DU #B2), where DU #B1 has an F1 connection to BS1010A, and network node 1020 (e.g., DU #B2) may need to establish an F1 connection to BS #C5. In response to initiating or triggering DU migration (e.g., receiving a migration command from BS1010A or network node 1020 itself triggering DU migration), network node 1020 (e.g., DU #B2) may attempt to transmit an F1 setup request to BS #C5 (e.g., the CU of BS #C5). For example, DU #B2 may attempt to transmit an F1 setup request message to BS #C5 via BS1010B. For example, in operation 1011, BS1010B (e.g., the DU of BS1010B) may receive an F1 setup request message from network node 1020.

[0132] In some embodiments, BS1010B (e.g., the DU of BS1010B) cannot transmit an F1 setup request message to BS #C5 (e.g., the CU of BS #C5) because there is no IP connection between BS1010B (e.g., the DU of BS1010B) and BS #C5 (e.g., the CU of BS #C5). In this case, the DU of BS1010B may notify the CU of BS1010B in operation 1013 that "(some) UL packets for the F1 setup request message are not IP-routable" (which may be identified by the source / destination IP addresses).

[0133] Next, in operation 1015, BS1010B (e.g., the CU of BS1010B) may notify network node 1020 (e.g., the MT of network node 1020) about the failure of (a) UL packet(s) for delivering an F1 setup request message to BS#C5 (which is identified by the destination IP address). In some embodiments, the cause of the failure (i.e., there is no IP connection between BS#C5 and BS 1010B) may also be notified to network node 1020. For example, the message transmitted in operation 1015 may indicate the cause value of no IP connection.

[0134] In the case where the DU migration is triggered by network node 1020, in response to receiving the information in operation 1015, network node 1020 may cancel the DU migration to BS#C5 in operation 1017a.

[0135] In the case where the DU migration is triggered by BS1010A, in response to receiving the information in operation 1015, network node 1020 (e.g., DU#B1) may notify BS1010A (e.g., the CU of BS1010A) about the failure of F1 setup in operation 1017b. In some embodiments, the cause of the failure (i.e., there is no IP connection between BS#C5 and BS1010B) may also be transmitted to BS1010A. For example, the message transmitted in operation 1017b may indicate the cause value of no IP connection. Based on the information received in operation 1017b, BS1010A may cancel the DU migration to BS#C5.

[0136] Those skilled in the art will appreciate that, without departing from the spirit and scope of the present disclosure, the operation sequence in the exemplary procedure 1000 may be changed and some operations in the exemplary procedure 1000 may be eliminated or modified.

[0137] For example, Figure 11 A flowchart illustrating an exemplary procedure 1100 for wireless communication according to some embodiments of the present disclosure.

[0138] The details described in all the foregoing embodiments of the present disclosure apply to Figure 11 the embodiments shown in. For example, BS1110A to 1110C may be used as IAB donors as described above and may include a CU and at least one DU. Network node 1120 may be used as an IAB node as described above and may include an MT and at least one DU (e.g., one DU before and after the DU migration or two DUs during the DU migration).

[0139] The network node 1120 (e.g., the DU of the network node 1120) may have an F1 connection with BS1110A (e.g., the CU of BS1110A). The network node 1120 (e.g., the MT of the network node 1120) may have an RRC connection with BS1110B (e.g., the CU of BS1110B). BS1110A and BS1110B may be referred to as the F1-terminating BS and the RRC-terminating BS, respectively.

[0140] In some embodiments, the DU of the network node 1120 may perform a migration from BS1110A (i.e., the source F1-terminating BS) to a target BS (i.e., the target F1-terminating BS, e.g., BS1110C), while the MT of the network node 1120 maintains its connection with BS1110B. For example, BS1110A, BS1110B, BS1110C, and the network node 1120 may be used as Figure 5 the IAB donor 510A, the IAB donor 510B, the IAB donor 510C, and the IAB node 520D in

[0141] In some embodiments, the migration of the DU of the network node 1120 may not be triggered by the F1-terminating BS (e.g., BS1110A) of the network node 1120. For example, the migration may be triggered by the network node 1120 itself or by an OAM entity.

[0142] During the migration of the DU of the network node 1120, the network node 1120 may have two logical DUs (denoted as DU#C1 and DU#C2), where DU#C1 has an F1 connection to BS1110A, and the network node 1120 (e.g., DU#C2) may need to establish an F1 connection to BS1110C. In response to initiating or triggering the DU migration, the network node 1120 (e.g., DU#C2) may attempt to send an F1 setup request to BS1110C (e.g., the CU of BS1110C). For example, DU#C2 may attempt to send an F1 setup request message to BS1110C via BS1110B. For example, in operation 1111, BS1110B (e.g., the DU of BS1110B) may receive an F1 setup request message from the network node 1120.

[0143] In some embodiments, the F1 setup request in the context of the present disclosure may also be referred to as a request for DU migration, a request to trigger DU migration, or other similar names.

[0144] In operation 1113, BS1110B may transmit an F1 setup request message to BS1110C, and network node 1120 (e.g., DU#C2) may set up an F1 connection to BS1110C (e.g., the CU of BS1110C) after receiving an F1 setup response message from BS1110C. For example, network node 1120 may receive positive feedback as a response to the F1 setup request (i.e., the F1 setup response message). After the F1 setup, the cell on DU#C2 has been activated to serve the UE.

[0145] It is necessary to notify BS1110A of the completion of the F1 setup in order to migrate the UE(s) served by the cell(s) of DU#C1 to the cell(s) of DU#C2 (or in other words, from BS1110A to BS1110C).

[0146] In some embodiments of the present disclosure, in response to receiving a response in operation 1113, network node 1120 may transmit, in operation 1115, a message to BS1110A indicating the completion of the F1 interface setup between network node 1120 and BS1110C (e.g., the CU of BS1110C). For example, DU#C1 may notify the CU of BS1110A that DU#C2 has set up the F1 interface to BS1110C. In some embodiments, the message may include an identifier of BS1110C (e.g., the ID of the CU of BS1110C).

[0147] BS1110A may then trigger a handover of the UE(s) served by network node 1120 (e.g., DU#C1). For example, BS1110A may transmit at least one handover request to BS1110C (e.g., the CU of BS1110C) based on the identifier of BS1110C. The handover request may be transmitted for each served UE or may be a group-based handover request for all served UEs.

[0148] In some other embodiments of the present disclosure, BS1110A (e.g., the CU of BS1110A) may receive an F1 interface setup completion indication from BS1110C (e.g., the CU of BS1110C). To achieve this, network node 1120 may include the identifier of BS1110A (e.g., the ID of the CU of BS1110A) in the F1 setup request (e.g., in operation 1111), such that BS1110C (e.g., the CU of BS1110C) may transmit an F1 interface setup completion indication to BS1110A (e.g., the CU of BS1110A) Figure 11(not shown in the figure). The F1 interface setup completion indication may include information for identifying network node 1120 (e.g., the gNB-DU ID of network node 1120). In response to receiving the indication, BS1110A may trigger a handover of the UEs served by network node 1120 (e.g., DU#C1), as described above. In these embodiments, operation 1115 may be omitted.

[0149] Those skilled in the art will appreciate that, without departing from the spirit and scope of the present disclosure, the order of operations in the exemplary procedure 1100 may be changed and some operations in the exemplary procedure 1100 may be eliminated or modified.

[0150] In some embodiments of the present disclosure, in response to a migration of the DU of a network node (e.g., to a target F1 terminated BS, which is denoted as BS#C6 for clarity) being triggered, the network node may determine whether there is an IP connection between the RRC terminated BS of the network node (denoted as BS#B6 for clarity) and BS#C6 before transmitting an F1 setup request. In these embodiments, the network node may terminate its F1 connection to BS#B6 or another BS. For example, the network node may transmit an inquiry to BS#B6 regarding whether there is an IP connection between BS#B6 and BS#C6. The transmission of the F1 setup request may be based on the response from BS#B6. For example, in the case where the response indicates that there is no IP connection between BS#B6 and BS#C6 (e.g., negative feedback), the migration of the DU of the network node may be cancelled. For example, in the case where the response indicates that there is an IP connection between BS#B6 and BS#C6 (e.g., positive feedback), the network node may transmit an F1 setup request to BS#B6.

[0151] The foregoing procedure used by the network node to obtain IP connectivity information may be applied to the foregoing embodiments of the present disclosure. For example, in the exemplary procedure 1000, network node 1020 may obtain this IP connectivity information before operation 1011. When negative feedback is obtained, operations 1011 to 1015 may be omitted. For example, in the exemplary procedure 1100, network node 1120 may obtain this IP connectivity information before operation 1111. When positive feedback is obtained, network node 1120 may perform operation 1111.

[0152] It should be noted that the foregoing procedure used by the network node to obtain IP connectivity information may be applied not only to Scenario 1 and Scenario 2, but also to all cases when a migration of the DU of the network node is triggered.

[0153] Figure 12 A flowchart illustrating an exemplary procedure 1200 for wireless communication according to some embodiments of the present disclosure. The details described in all the foregoing embodiments of the present disclosure apply toFigure 12 The embodiments shown in

[0154] Refer to Figure 12 , in operation 1211, the BS (represented as the first BS) may determine whether there is an IP connection between another BS (represented as the second BS) and yet another BS (represented as the third BS), where one of the first BS and the second BS has an RRC connection to the MT of the radio network node, and the other of the first BS and the second BS has an F1 connection to the DU of the radio network node. In some instances, the radio network node may be an IAB node. In some instances, the first, second, and third BSs may be IAB donors.

[0155] In operation 1213, the first BS may initiate the migration of the MT of the radio network node to the third BS or the migration of the DU of the radio network node to the third BS based on the determination.

[0156] For example, the first BS is the (source) RRC terminating BS of the radio network node, and the second BS is the F1 terminating BS of the radio network node, and the first BS may initiate the migration of the MT of the radio network node to the third BS (i.e., the target RRC terminating BS). For example, the second BS is the RRC terminating BS of the radio network node, and the first BS is the (source) F1 terminating BS of the radio network node, and the first BS may initiate the migration of the DU of the radio network node to the third BS (i.e., the target F1 terminating BS).

[0157] In some embodiments of the present disclosure, to determine whether there is an IP connection between the second BS and the third BS, the first BS may: initiate an inquiry regarding whether there is an IP connection between the second BS and the third BS to the second BS, the third BS, or both; and determine whether there is an IP connection between the second BS and the third BS based on the response to the inquiry from the second BS, the third BS, or both.

[0158] In some embodiments of the present disclosure, the first BS may receive the location information of the MT of the radio network node from the radio network node or the second BS to assist the first BS in initiating the migration of the DU of the radio network node.

[0159] In some embodiments of the present disclosure, the first BS may receive first information regarding the IP connectivity to the second BS from the second BS. The determination of whether there is an IP connection between the second BS and the third BS is based on the first information.

[0160] In some embodiments of the present disclosure, the first BS may transmit second information regarding the IP connectivity to the first BS to the second BS. In some instances, the second information is transmitted in response to the reception of the first information. In some instances, the first information is received in response to the transmission of the second information.

[0161] In some embodiments of the present disclosure, the first information includes a list of first BSs and each BS in the list of first BSs has an IP connection to the second BS, and the second information includes a list of second BSs and each BS in the list of second BSs has an IP connection to the first BS.

[0162] Those skilled in the art will appreciate that, without departing from the spirit and scope of the present disclosure, the order of operations in exemplary procedure 1200 may be changed and some operations in exemplary procedure 1200 may be eliminated or modified.

[0163] Figure 13 A flowchart of an exemplary procedure 1300 for wireless communication according to some embodiments of the present disclosure is illustrated. The details described in all of the foregoing embodiments of the present disclosure apply to Figure 13 the embodiments shown therein. Exemplary procedure 1300 may be performed by a BS (e.g., an IAB donor).

[0164] Refer to Figure 13 , in operation 1311, a BS (represented as the second BS) may receive second information regarding the IP connectivity to the first BS or an inquiry regarding the IP connectivity of the second BS from another BS (represented as the first BS), where one of the first BS and the second BS has an RRC connection to the MT of a wireless network node, and the other of the first BS and the second BS has an F1 connection to the DU of the wireless network node. In some instances, the wireless network node may be an IAB node.

[0165] In operation 1313, the second BS may transmit first information regarding the IP connectivity to the second BS to the first BS.

[0166] In some embodiments of the present disclosure, the first information is transmitted in response to the inquiry, which is regarding whether there is an IP connection between the second BS and yet another BS (represented as the third BS), and the first information indicates the IP connectivity between the second BS and the third BS. In some instances, the first, second, and third BSs may be IAB donors.

[0167] In some embodiments of the present disclosure, in the case where the second BS has an RRC connection to the MT of the wireless network node, the second BS may transmit the location information of the MT of the wireless network node to the first BS.

[0168] In some embodiments of the present disclosure, the first information is transmitted in response to the reception of the second information. In some embodiments of the present disclosure, the second information is received in response to the transmission of the first information.

[0169] In some embodiments of the present disclosure, the first information includes a first BS list, and each BS in the first BS list has an IP connection to the second BS. In some embodiments of the present disclosure, the second information includes a second BS list, and each BS in the second BS list has an IP connection to the first BS.

[0170] Those skilled in the art should understand that, without departing from the spirit and scope of the present disclosure, the operation sequence in the exemplary procedure 1300 can be changed and some operations in the exemplary procedure 1300 can be eliminated or modified.

[0171] Figure 14 A flowchart illustrating an exemplary procedure 1400 for wireless communication according to some embodiments of the present disclosure. The details described in all the foregoing embodiments of the present disclosure apply to Figure 14 the embodiments shown therein. The exemplary procedure 1400 can be executed by a BS (e.g., an IAB donor).

[0172] Referring to Figure 14 , in operation 1411, a BS (represented as the third BS) may receive an inquiry from another BS (represented as the first BS) regarding whether there is an IP connection between the third BS and yet another BS (represented as the second BS), where one of the first BS and the second BS has an RRC connection to the MT of the wireless network node, and the other of the first BS and the second BS has an F1 connection to the DU of the wireless network node. In some instances, the wireless network node may be an IAB node. In some instances, the first, second, and third BSs may be IAB donors.

[0173] In operation 1413, the third BS may transmit a response to the inquiry to the first BS.

[0174] In some embodiments of the present disclosure, in response to the response indicating that there is an IP connection between the third BS and the second BS, the third BS may: receive a request to migrate the MT of the wireless network node to the third BS from one of the first BS and the second BS; or receive a request to migrate the DU of the wireless network node to the third BS from the other of the first BS and the second BS or the wireless network node.

[0175] Those skilled in the art should understand that, without departing from the spirit and scope of the present disclosure, the operation sequence in the exemplary procedure 1400 can be changed and some operations in the exemplary procedure 1400 can be eliminated or modified.

[0176] Figure 15 FIG. 1500 is a flowchart illustrating an exemplary procedure for wireless communication according to some embodiments of the present disclosure. The details described in all of the foregoing embodiments of the present disclosure apply to the embodiments shown in Figure 15 FIG. 1500. The exemplary procedure 1500 may be performed by a BS (e.g., an IAB donor).

[0177] Referring to Figure 15 FIG. 1500, in operation 1511, a BS (represented as a first BS) may transmit a request to another BS (represented as a third BS) to migrate one of an MT and a DU of a wireless network node to the third BS, where the first BS is connected to one of the MT and the DU of the wireless network node, and the request includes information associated with yet another BS (represented as a second BS) connected to the other of the MT and the DU of the wireless network node. In some instances, the wireless network node may be an IAB node. In some instances, the first, second, and third BSs may be IAB donors.

[0178] In operation 1513, the first BS may receive a response to the request from the third BS.

[0179] In some embodiments of the present disclosure, the response indicates that the migration is rejected due to no IP connection between the second BS and the third BS. For example, the response may indicate a cause value for the no IP connection.

[0180] In some embodiments of the present disclosure, the information associated with the second BS includes an identifier of the second BS. For example, the identifier may be an identifier of a CU of the second BS.

[0181] Those skilled in the art will appreciate that, without departing from the spirit and scope of the present disclosure, the order of operations in the exemplary procedure 1500 may be changed and some operations in the exemplary procedure 1500 may be eliminated or modified.

[0182] Figure 16 FIG. 1600 is a flowchart illustrating an exemplary procedure for wireless communication according to some embodiments of the present disclosure. The details described in all of the foregoing embodiments of the present disclosure apply to the embodiments shown in Figure 16 FIG. 1600. The exemplary procedure 1600 may be performed by a network node (e.g., an IAB node).

[0183] Referring to Figure 16 FIG. 1600, in operation 1611, a network node may transmit a request to a BS (represented as a third BS) to trigger migration of a DU of a wireless network node from another BS (represented as a first BS) to the third BS, where the MT of the wireless network node has an RRC connection to yet another BS (represented as a second BS).

[0184] In operation 1613, the network node may receive a response in response to a request.

[0185] In some embodiments of the present disclosure, in the case where the response acknowledges the request, the wireless network node may: in response to the reception of the response, transmit a message indicating the completion of the F1 interface setup between the wireless network node and the third BS to the first BS. In some embodiments of the present disclosure, the message includes an identifier of the third BS.

[0186] In some embodiments of the present disclosure, the request includes an identifier of the first BS.

[0187] In some embodiments of the present disclosure, the wireless network node may transmit an inquiry to the second BS regarding whether there is an IP connection between the second BS and the third BS; and wherein the transmission of the request is based on the response to the inquiry from the second BS.

[0188] Those skilled in the art will appreciate that, without departing from the spirit and scope of the present disclosure, the order of operations in the exemplary procedure 1600 may be changed and some operations in the exemplary procedure 1600 may be eliminated or modified.

[0189] Figure 17 A block diagram of an exemplary device 1700 according to some embodiments of the present disclosure is illustrated.

[0190] As Figure 17 shown, the device 1700 may include at least one processor 1706 and at least one transceiver 1702 coupled to the processor 1706. The device 1700 may be a 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. In the case where the device 1700 is a BS, the device 1700 may further include a CU and at least one DU coupled to the CU. The CU and the DU may be co-located or separately located. The CU and the DU may be coupled to the processor 1706. In the case where the device 1700 is a network node, the device 1700 may further include an MT and a DU coupled to the MT. The MT and the DU may be coupled to the processor 1706.

[0191] Although in this figure, elements such as at least one transceiver 1702 and processor 1706 are described in the singular form, the plural form is also contemplated unless explicitly stated to be limited to the singular form. In some embodiments of the present application, the transceiver 1702 may be divided into two devices, such as a receiving circuit system and a transmitting circuit system. In some embodiments of the present application, the device 1700 may further include an input device, a memory, and / or other components.

[0192] In some embodiments of the present application, the device 1700 may be a BS. The processor 1706 may interact with other element(s) of the device 1700 (such as the transceiver 1702, DU, or CU) to perform Figures 1 to 16 the operations described in Figures 1 to 16 for a BS, IAB donor, IAB donor-CU, or IAB donor-DU. In some embodiments of the present application, the device 1700 may be a network node. The transceiver 1702 and the processor 1706 may interact with each other to perform

[0193] the operations described in

[0194] for a network node or IAB node (mobile or fixed). Figures 1 to 16 In some embodiments of the present application, the device 1700 may further include at least one non-transitory computer-readable medium.

[0195] In some embodiments of the present disclosure, the non-transitory computer-readable medium may store computer-executable instructions thereon to cause the processor 1706 to implement the methods for a BS, IAB donor, IAB donor-CU, or IAB donor-DU as described above. For example, when the computer-executable instructions are executed, they cause the processor 1706, which interacts with, for example, the transceiver 1702, to perform Figures 1 to 16 the operations described in

[0196] for a BS, IAB donor, IAB donor-CU, or IAB donor-DU. For example, in some embodiments of the present disclosure, the non-transitory computer-readable medium may store computer-executable instructions thereon to cause the processor 1706 to implement the methods for a network node or IAB node (mobile or fixed) as described above. For example, when the computer-executable instructions are executed, they cause the processor 1706, which interacts with the transceiver 1702, to perform

[0197] Although the present disclosure has been described in terms of its specific embodiments, it will be apparent that many alternatives, modifications, and variations will be obvious to those skilled in the art. For example, the various components of the embodiments may be interchanged, added, or replaced in other embodiments. Also, all elements of each figure are not necessary for the operation of the disclosed embodiments. For example, the teachings of the present disclosure will enable one of ordinary skill in the art of the disclosed embodiments to make and use the present disclosure by only employing the elements of the independent claims. Thus, the embodiments of the present disclosure as set forth herein are intended to be illustrative and not restrictive. Various changes may be made without departing from the spirit and scope of the present disclosure.

[0198] In this document, the terms "switching", "path switching", and "migration" may be used interchangeably. The term "includes", "including", or any other variant thereof is intended to cover a non-exclusive inclusion such that a process, method, article, or apparatus that includes a series of elements includes not only those elements but also other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element preceded by "a", "an", or the like does not preclude the existence of additional identical elements in the process, method, article, or apparatus that includes the element. Also, the term "another" is defined as at least a second or more. As used herein, the terms "having" and the like are defined as "including". For example, the expression "A and / or B" or "at least one of A and B" may include any and all combinations of the words enumerated together with such 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. The terms "first", "second", or the like are used only to clearly illustrate the embodiments of the present application and not to limit the substance of the present application.

Claims

1. A first base station BS, comprising: A transceiver; And A processor coupled to the transceiver, wherein the processor is configured to: Determine whether there is an Internet Protocol IP connection between a second BS and a third BS, wherein one of the first BS and the second BS has a Radio Resource Control RRC connection to a mobile terminal MT of a radio network node, and the other of the first BS and the second BS has an F1 connection to a distributed unit DU of the radio network node; and Based on the determination, initiate a migration of the MT of the radio network node to the third BS or a migration of the DU of the radio network node to the third BS.

2. The first BS according to claim 1, wherein, in order to determine whether there is an IP connection between the second BS and the third BS, the processor is configured to: Initiate an inquiry to the second BS, the third BS, or both regarding whether there is an IP connection between the second BS and the third BS; and Based on a response to the inquiry from the second BS, the third BS, or both, determine whether there is an IP connection between the second BS and the third BS.

3. The first BS according to claim 1, wherein the transceiver is configured to receive location information of the MT of the radio network node from the radio network node or the second BS to assist the first BS in initiating the migration of the DU of the radio network node.

4. The first BS according to claim 1, wherein the transceiver is configured to receive first information regarding IP connectivity to the second BS from the second BS; and Wherein the determination of whether there is an IP connection between the second BS and the third BS is based on the first information.

5. The first BS according to claim 4, wherein the transceiver is configured to transmit second information regarding IP connectivity to the first BS to the second BS; and Wherein the second information is transmitted in response to the reception of the first information or the first information is received in response to the transmission of the second information.

6. The first BS according to claim 5, wherein the first information includes a first BS list and each BS in the first BS list has an IP connection to the second BS, and the second information includes a second BS list and each BS in the second BS list has an IP connection to the first BS.

7. A second base station BS, comprising: A processor; And A transceiver coupled to the processor, wherein the transceiver is configured to: Receive second information regarding Internet Protocol IP connectivity to the first BS from the first BS or an inquiry regarding the IP connectivity of the second BS, wherein one of the first BS and the second BS has a Radio Resource Control RRC connection to a mobile terminal MT of a radio network node, and the other of the first BS and the second BS has an F1 connection to a distributed unit DU of the radio network node; and Transmit first information regarding the IP connectivity to the second BS to the first BS.

8. The second BS according to claim 7, wherein the first information is transmitted in response to the inquiry, the inquiry being regarding whether there is an IP connection between the second BS and a third BS, and the first information indicating the IP connectivity between the second BS and the third BS.

9. The second BS according to claim 7, wherein the transceiver is further configured to transmit the location information of the MT of the radio network node to the first BS when the second BS has an RRC connection to the MT of the radio network node.

10. The second BS according to claim 7, wherein the first information is transmitted in response to the reception of the second information or the second information is received in response to the transmission of the first information.

11. A radio network node, comprising: a processor; and a transceiver coupled to the processor, wherein the transceiver is configured to: transmit a request to a third base station BS to trigger the migration of the distributed unit DU of the radio network node from the first BS to the third BS, wherein a mobile terminal MT of the radio network node has a radio resource control RRC connection to the second BS; and receive a response in response to the request.

12. The radio network node according to claim 11, wherein when the response confirms the request, the transceiver is configured to: in response to the reception of the response, transmit a message to the first BS indicating the completion of the F1 interface setup between the radio network node and the third BS.

13. The radio network node according to claim 12, wherein the message includes an identifier of the third BS.

14. The radio network node according to claim 11, wherein the request includes an identifier of the first BS.

15. The radio network node according to claim 11, wherein the transceiver is further configured to transmit an inquiry to the second BS regarding whether there is an Internet Protocol IP connection between the second BS and the third BS; and wherein the transmission of the request is based on a response from the second BS to the inquiry.

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