WO2023213401A1

WO2023213401A1 - Xn connections management in integrated access and backhaul network

Info

Publication number: WO2023213401A1
Application number: PCT/EP2022/062159
Authority: WO
Inventors: Ilkka Antero Keskitalo; György Tamás Wolfner; Henri Markus Koskinen; Alessio Casati; Ömer BULAKCI
Original assignee: Nokia Solutions And Networks Oy
Priority date: 2022-05-05
Filing date: 2022-05-05
Publication date: 2023-11-09

Abstract

Various example embodiments relate to apparatuses and methods for Xn connections management in Integrated Access and Backhaul (IAB) networks. An integrated access and backhaul node may establish a first connection between a mobile termination component in the integrated access and backhaul node and a cell serviced by a serving node, establish a second connection between a distributed unit in the integrated access and backhaul node and a central unit for controlling the integrated access and backhaul node, and transmit cell information to the central unit during and/or after establishing the second connection. The cell information indicates at least one of a serving cell and one or more neighboring cells for the integrated access and backhaul node.

Description

XN CONNECTIONS MANAGEMENT IN INTEGRATED ACCESS AND

BACKHAUL NETWORK

TECHNICAL FIELD

[0001] Various example embodiments described herein generally relate to communication technologies, and more particularly, to apparatuses and methods for Xn connections management in Integrated Access and Backhaul (IAB) networks.

BACKGROUND

[0002] Certain abbreviations that may be found in the description and/or in the figures are herewith defined as follows:

AMF Access and Mobility Management function

ANR Automatic Neighbor Relation

CU Central Unit

CP Control Plane

DU Distributed Unit gNB next generation Node-B

HO Handover

IAB Integrated Access and Backhaul

MT Mobile Termination

NR New Radio

0AM Operation Administration Maintenance

RAN Radio Access Network

RRC Radio Resource Control

UE User Equipment

UP User Plane

UPF User Plane Function i [0003] Vehicle mounted relays (VMRs) can provide high-quality communication services to onboard and/or surrounding user equipments (UEs). 5G New Radio (NR) provides support for VMR scenarios in Integrated Access and Backhaul (IAB) networks where a moving VMR may be implemented as an IAB node which enables wireless relaying for NR access via wireless backhauling. On the network side the wireless backhauling terminates at a base station known as IAB donor which provides NR access to the network for one or more IAB nodes and UEs connected to the IAB nodes.

SUMMARY

[0004] A brief summary of example embodiments is provided below to provide basic understanding of some aspects of various embodiments. It should be noted that this summary is not intended to identify key features of essential elements or define scopes of the embodiments, and its sole purpose is to introduce some concepts in a simplified form as a preamble for a more detailed description provided below.

[0005] In a first aspect, an example embodiment of an integrated access and backhaul node is provided. The integrated access and backhaul node may comprise at least one processor and at least one memory including computer program code. The at least one memory and the computer program code may be configured to, with the at least one processor, cause the integrated access and backhaul node at least to establish a first connection between a mobile termination component in the integrated access and backhaul node and a cell serviced by a serving node, establish a second connection between a distributed unit in the integrated access and backhaul node and a central unit for controlling the integrated access and backhaul node, and transmit cell information to the central unit during and/or after establishing the second connection. The cell information is indicative of at least one of a serving cell and one or more neighboring cells for the integrated access and backhaul node.

[0006] In a second aspect, an example embodiment of a central unit for controlling one or more integrated access and backhaul nodes is provided. The central unit may comprise at least one processor and at least one memory including computer program code. The at least one memory and the computer program code may be configured to, with the at least one processor, cause the central unit at least to establish a second connection between a distributed unit in an integrated access and backhaul node and the central unit, receive cell information from the integrated access and backhaul node during and/or after establishing the second connection, the cell information indicative of at least one of a serving cell and one or more neighboring cells for the integrated access and backhaul node, and establish a third connection between the central unit and one or more base stations serving the at least one of the serving cell and the one or more neighboring cells.

[0007] In a third aspect, an example embodiment of an integrated access and backhaul node is provided. The integrated access and backhaul node may comprise at least one processor and at least one memory including computer program code. The at least one memory and the computer program code may be configured to, with the at least one processor, cause the integrated access and backhaul node at least to establish a first connection between a mobile termination component in the integrated access and backhaul node and a cell serviced by a serving node, establish a second connection between a distributed unit in the integrated access and backhaul node and a central unit for controlling the integrated access and backhaul node, and transmit cell information to the serving node. The cell information is indicative of a cell serviced by the distributed unit in the integrated access and backhaul node.

[0008] In a fourth aspect, an example embodiment of a radio access network node is provided. The radio access network node may comprise at least one processor and at least one memory including computer program code. The at least one memory and the computer program code may be configured to, with the at least one processor, cause the radio access network node at least to receive cell information from a mobile termination component in an integrated access and backhaul node, the cell information indicative of a cell serviced by a distributed unit in the integrated access and backhaul node, and to establish a third connection between the radio access network node and a central unit for controlling the integrated access and backhaul node based on the received cell information. The central unit may have a second connection with the distributed unit in the integrated access and backhaul node.

[0009] In a fifth aspect, an example embodiment of a central unit for controlling one or more integrated access and backhaul nodes is provided. The central unit may comprise at least one processor and at least one memory including computer program code. The at least one memory and the computer program code may be configured to, with the at least one processor, cause the central unit at least to establish a third connection between the central unit and a radio access network node, receive neighboring cell information from the radio access network node during and/or after establishing the third connection between the central unit and the radio access network node, the neighboring cell information indicative of one or more neighboring cells for an integrated access and backhaul node under the control of the central unit, and establish a third connection between the central unit and one or more neighboring base stations supporting the one or more neighboring cells indicated in the neighboring cell information.

[0010] Example embodiments of methods, apparatus and computer program products are also provided. Such example embodiments generally correspond to the above example embodiments, and a repetitive description thereof is omitted here for convenience.

[0011] Other features and advantages of the example embodiments of the present disclosure will also be apparent from the following description of specific embodiments when read in conjunction with the accompanying drawings, which illustrate, by way of example, the principles of example embodiments of the present disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Some example embodiments will now be described, by way of nonlimiting examples, with reference to the accompanying drawings.

[0013] Fig. 1A and Fig. IB are schematic diagrams illustrating an IAB network architecture in which example embodiments of the present disclosure can be implemented.

[0014] Fig. 2 is a schematic diagram illustrating inter-donor mobility of an lAB-node according to an example embodiment of the present disclosure.

[0015] Fig. 3 is a high-level message sequence chart illustrating a procedure to establish Xn connections according to an example embodiment of the present disclosure.

[0016] Fig. 4 is a schematic message sequence chart illustrating a procedure to establish an Xn connection between an lAB-donor and a mobile central unit (m-CU) in an IAB node integration scenario according to an example embodiment of the present disclosure.

[0017] Fig. 5 is a schematic message sequence chart illustrating an Xn connection establishment procedure according to an example embodiment of the present disclosure.

[0018] Fig. 6 is a schematic message sequence chart illustrating a procedure to establish Xn connections between an m-CU and neighboring base stations in an IAB node handover scenario according to an example embodiment of the present disclosure.

[0019] Fig. 7 is a high-level message sequence chart illustrating a procedure to establish Xn connections according to an example embodiment of the present disclosure.

[0020] Fig. 8 is a schematic message sequence chart illustrating a procedure to establish Xn connections initiated at an IAB donor according to an example embodiment of the present disclosure.

[0021] Fig. 9 is a schematic message sequence chart illustrating a procedure to establish Xn connections between an m-CU and neighboring base stations according to an example embodiment of the present disclosure.

[0022] Fig. 10 is a schematic structure block diagram illustrating devices in a communication system in which example embodiments of the present disclosure can be implemented.

[0023] Throughout the drawings, same or similar reference numerals indicate same or similar elements. A repetitive description on the same elements would be omitted.

DETAILED DESCRIPTION

[0024] Herein below, some example embodiments are described in detail with reference to the accompanying drawings. The following description includes specific details for the purpose of providing a thorough understanding of various concepts. However, it will be apparent to those skilled in the art that these concepts may be practiced without these specific details. In some instances, well known circuits, techniques and components are shown in block diagram form to avoid obscuring the described concepts and features.

[0025] As used herein, the term “network device” refers to any suitable devices or entities that can provide cells or coverage, through which terminal devices can access the network or receive services. The network device may be commonly referred to as a base transceiver station (BTS), a base station (BS), or some other suitable terminology. The term “base station” or “base transceiver station” used herein can represent a node B (NodeB or NB), an evolved node B (eNodeB or eNB), a next generation Node B (gNB), or a next generation enhanced Node B (ng-eNB). The base station may be embodied as a macro base station, a relay node, or a low power node such as a pico base station or a femto base station. The base station may also include or may be referred to as a RAN (radio access network) node, and may consist of several distributed network units, such as a central unit (CU), one or more distributed units (DUs), one or more remote radio heads (RRHs) or remote radio units (RRUs). The number and functions of these distributed units depend on the selected split RAN architecture.

[0026] As used herein, the term “terminal device” or “user equipment” (UE) refers to any devices or entities that can wirelessly communicate with the network devices or with each other. Examples of the terminal device can include a mobile phone, a mobile terminal, a mobile station (MS), a subscriber station, a portable subscriber station, an access terminal, a personal digital assistant (PDA), a computer, a wearable device, an on-vehicle communication device, a machine type communication (MTC) device, a D2D communication device, a V2X communication device, a sensor and the like. The term “terminal device” can be used interchangeably with UE, a user terminal, a mobile terminal, a mobile station, or a wireless device.

[0027] In a 5G communication network, New Radio (NR) cells may be deployed in a varying range of frequency spectrum, which comprises a frequency range 1 (FR1) occupying frequencies less than 6 GHz and a frequency range 2 (FR2) occupying frequencies greater than 6 GHz. At higher frequencies, the coverage of the NR cells is relatively small. As a result, densification via the deployment of more and more base stations is one of the mechanisms that can be employed to satisfy the increasing demand of capacity while providing a full coverage area in wireless networks. In such a deployment, various forms of wireless connectivity that uses integrated access and backhaul (IAB) nodes between base stations and User Equipments (UEs) are supported in 5G NR systems. The IAB nodes can support wireless access and backhaul in both FR1 and FR2 spectrum. NR UEs can transparently connect to an IAB- node via NR. Further, legacy Long Term Evolution (LTE) UEs can transparently connect to an IAB node via LTE in case the IAB node supports backhauling of LTE access.

[0028] IAB nodes can be used in a diverse range of deployment scenarios, including support for outdoor small cell deployments, indoor deployments, or even vehicle mounted relays (VMRs). For example, VMR utilizes mobile IAB nodes mounted in a vehicle (e.g., train, bus, tram, subway, etc.) to increase data rate and reliability for UEs either within the vehicle or in the surrounding.

[0029] In such mobile deployment scenarios, it may be desirable that full migration of an IAB -node would be supported in order to have sufficient capabilities. For example, when a mobile IAB node deployed on a high speed train, to which UEs are wirelessly connected, migrates from a source IAB donor base station to a target IAB donor base station, the communication and signaling interfaces with the source IAB donor need to be released completely, and new interfaces need to be established for the target IAB donor base station. [0030] Fig. 1 A illustrates a schematic diagram of an IAB network architecture with single hop backhauling, in which example embodiments of the present disclosure can be implemented. As shown in Fig. 1A, an IAB node 110 may connect to a core network 140 via an IAB donor 120, and a central unit 130 is provided for controlling one or more mobile IAB nodes including the IAB node 110. Hereinafter the central unit 130 for controlling the mobile IAB nodes may be referred to as mobile CU (m-CU). The m-CU 130 may connect to a mobile IAB specific user plane function (UPF) 142, which may be referred to as mobile UPF (m-UPF) hereinafter. The IAB network shown in Fig. lAmay be a part of a larger cellular communication system such as a 5G system (5GS).

[0031] The IAB donor 120 may be a Radio Access Network (RAN) node e.g. a base station that has backhaul connectivity to the core network 140. The IAB donor 120 may be treated as a single logical node that comprises a set of functions such as a Central Unit (CU) 124, one or more Distributed Units (DUs) 122, and potentially other functions. In some deployments, the IAB donor 120 can be split according to these functions, which can all be either collocated or non-collocated as allowed by 3GPP NG-RAN architecture. Also, some of the functions presently associated with the IAB donor 120 may be moved outside of the donor in case those functions do not perform lAB-specific tasks. In an example deployment, the CU 124 may be deployed at a central office, and the DUs 122 may be deployed at respective cell sites. In another example where the RAN has a cloud-based architecture, the CU 124 may be deployed in the cloud.

[0032] The donor CU 124 and the donor DU 122 are connected via Fl interface, and the operations of the donor DU 122 may be partly controlled by the donor CU 124. Although one donor DU 122 is illustrated for convenience in Fig. 1A, any suitable number of DUs can be interfaced to the donor CU 124 of the IAB donor 120. The donor DU 122 may serve one or more cells, and a cell is supported by only one donor DU 122.

[0033] In the 5G NR context, the core network 140 may be NextGen Core (NGC). The NGC 140 may include various entities and network functions (not shown), such as an Access and Mobility Management function (AMF), a Session Management Function (SMF), a User Plane Function (UPF), a non- 3GPP Interworking Function (N3IWF) and so on.

[0034] The IAB node 110 may hold a Distributed Unit (DU) part 112 and Mobile Termination (MT) part 114. The MT part 114 is a component of mobile equipment that offers a function residing on the IAB node 110 that terminates the radio interface layers of the backhaul Uu interface toward the corresponding DU 122 of the IAB donor 120. The MT 114 enables the IAB node 110 to act as a normal UE towards the IAB donor 120. For example, the MT 114 can select the best cell served by the donor DU 122 and establish a radio resource control (RRC) connection with the donor CU 124 in association with the donor DU 122.

[0035] The IAB DU 112 may host one or more transmit/receive points (TRPs) and serve one or more cells the same way as the donor DU 122. For example, the IAB DU cells may broadcast control signaling like synchronization signal blocks (SSBs) and system information (SI). From the UE point of view, the IAB DU cell may be seen as a normal cell like a donor DU cell. The IAB DU 112 may have an Fl connection to the m-CU 130, and from the NGC 140 point of view, the IAB DU 112 and the m-CU 130 may be seen as a base station. The Fl connection and other backhaul connections may be carried via a PDU session established through the access RAN. During the PDU session establishment, the NGC 140 can select an appropriate m-UPF 142, e.g., in the same local edge cloud as the donor CU 124. The PDU session serves as a point- to-point link between the IAB MT 114 and the m-UPF 142, and bearer layers are configured for the PDU session between the IAB MT 114 and the donor CU 124.

[0036] Physical location of the m-CU 130 and the m-UPF 142 may be flexibly determined depending on the network physical architecture. In one example, the m-CU 130 and the m-UPF 142 may reside on the IAB donor 120 as part of functions of the IAB donor 120. In another example where the access RAN has a cloud-based architecture, the m-CU 130 and the m-UPF 142 may be placed in a cloud infrastructure. Depending on the use cases and moving range of the mobile IAB node 110, the m-CU 130 and the m-UPF 142 can be placed within a RAN local cloud, e.g. hosted by the IAB donor 120 or another donor node. An advantage of the cloud-based architecture is that it can provide flexibility to serve relatively large areas with dedicated mobile functions serving the mobile IAB node 110. In some example embodiments, the m-CU 130 and the m-UPF 142 may be a part of a specific slice serving mobile IAB nodes.

[0037] In general, the illustrated mobile IAB network architecture reuses existing functions and interfaces defined in NR. In particular, the mobile IAB node 110 reuses the MT plus DU structure of current fixed IAB nodes, which can minimize changes to IAB node hardware and software. IAB MT, IAB DU, donor DU, donor CU, UPF, AMF and SMF as well as the corresponding interfaces NR Uu (between MT and IAB donor), Fl, NG, X2 and N4 may be used as baseline for the IAB architectures. Therefore, the mobile IAB architecture can serve legacy UEs with minimum or no impact to the access network. Enhancements to the IAB network may be implemented in the dedicated functions or entities, i.e. the m-CU 130, the m-UPF 142 and the mobile IAB node 110. The IAB nodes are almost transparent to the access RAN, which provides flexibility to apply the architecture for a variety of use cases and network deployment scenarios.

[0038] With the single-hop IAB network architecture shown in Fig. 1A, backhaul routing to the mobile IAB node 110 is carried via the PDU session established between the IAB MT 114 and the m-UPF 142 through the access RAN, and there is no need to include a Backhaul Adaption Protocol (BAP) layer for backhaul routing.

[0039] A further advantage according to the IAB network architecture shown in Fig. 1A is that the RAN node which provides network access for the IAB node 110 may be an lAB-capable RAN node such as the IAB donor 120 or a non-IAB capable RAN node such as a legacy gNB. It enables the IAB node 110 to connect to any NR RAN gNB, and the operator does not need to upgrade a large number of legacy gNBs which normally do not need wireless backhaul for TAB support. This is especially useful in scenarios where the mobile vehicle carrying the TAB node 110 travels a long distance and the IAB node 110 connects to many different gNBs deployed along the distance.

[0040] In an example embodiment, the mobile IAB node 110 may also connect to the RAN node via one or more intermediate IAB nodes, of which an example is shown in Fig. IB. Referring to Fig. IB, the mobile IAB node 110 may connect to a stationary/fixed IAB node 118, which may be the last (the most downstream) IAB node in a possible multi-hop chain serving access UEs. The IAB node 118 may include an IAB DU 117 which sustains a Uu interface with the IAB MT 114 in the mobile IAB node 110 and an IAB MT 119 which sustains a Uu interface with the IAB donor DU 122 in the IAB donor 120. The IAB DU 117 may also have an Fl connection to the IAB donor CU 124 of the IAB donor 120, and the Fl connection may be carried via a PDU session or a backhaul adaption protocol (BAP) layer (not shown).

[0041] Similar to the architecture shown in Fig. 1A, the wireless backhaul of the mobile IAB node 110 is carried via the PDU session, and the radio bearer for the PDU session goes transparently through the stationary IAB node 118. Therefore, the mobile IAB node 110 is regarded as a normal UE connected to the stationary IAB node 118, and the BAP routing may be terminated at the access IAB node 118. Other aspects of the example shown in Fig. IB are similar to the example shown in Fig. 1 A and a repetitive description is omitted here for convenience.

[0042] Fig. 2 is a schematic diagram illustrating inter-donor mobility of an lAB-node according to an example embodiment of the present disclosure. The mobile IAB node 110 deployed on a vehicle (e.g., bus, train) may move with the vehicle. Initially, it may be assumed that the IAB node 110 is connected to the source donor 120 or a stationary IAB node (not shown) connected to the source donor 120. As the vehicle moves away from the source donor 120 towards a target donor 121, the quality of the wireless link between the IAB MT 114 and the source donor 120 or the stationary IAB node connected to the source donor 120 may deteriorate and the quality of the wireless link between the IAB MT 114 and the target donor 121 or a stationary IAB node (not shown) connected to the target donor 121 may become better. When a certain threshold or condition is satisfied, the IAB node 110 may migrate from the topology of the source donor 120 or the stationary IAB node connected to the source donor

120 to the topology of the target donor 121 or the stationary IAB node connected to the target donor 121.

[0043] By way of example, Fig. 2 shows a migration of the IAB node 110 from the source donor 120 to the target donor 121. Similar to the source donor 120, the target donor 121 may also include a Central Unit (CU) 125 and one or more Distributed Units (DUs) 123. An Xn connection may be established between the source donor CU 124 and the target donor CU 125. For example, the Xn connection may be established by keeping the neighboring cell lists updated. Automatic neighbor relation (ANR) update/maintenance may be carried out by utilizing UE measurement reporting of detected cells. Once a new cell/gNB has been detected, Xn connection can be established between the CUs. The IAB MT 114 may change its access and backhaul connections to the target donor

121 in a normal handover procedure. Similarly, the CU user plane (UP) connection to the m-UPF 142 may be changed from the source donor CU 124 to a target donor CU 125 through a normal path switch procedure.

[0044] However, such a neighbor cell update procedure cannot be used between the donor CU 124/125 and the m-CU 130. The m-CU 130 can collect UE measurements from the IAB node cell(s) but those are not relevant for the backhaul link which is between the IAB MT 114 and the donor. The m-CU 130 does not know which cells/nodes are candidates for the IAB MT 114 handover and therefore to which the m-CU 130 should establish the Xn connection. Because the Fl connection from the mobile IAB node 110 to the m-CU 130 is transparent to the access RAN, the m-CU 130 does not know the donor cell/node to which the IAB MT 114 is connected to, or to which the handover has been executed.

[0045] Hereinafter, various example embodiments of apparatuses and methods for Xn connections management will be described in detail with reference to the accompanying drawings. The example embodiments can be implemented to enable Xn establishment between a central unit capable of or dedicated to controlling mobile IAB nodes (e.g., the m-CU 130) and an RAN node (e.g., the IAB donor 120 or a non-IAB RAN node) providing network access for the mobile IAB nodes. The example embodiments can also be implemented to enable Xn establishment between the central unit capable of or dedicated to controlling the mobile IAB nodes and one or more neighboring base stations (e.g., the target donor 121) of the mobile IAB node which may include a target base station for handover of the mobile IAB node. The example embodiments can facilitate Xn connection establishment between the CU for controlling mobile IAB nodes and relevant RAN nodes with minimal impact to current F1AP and XnAP specifications. Though some example embodiments are described in the context of a 5G system, it would be appreciated that various example embodiments described herein can also be applicable to a beyond 5G system, e.g., a 6G system (6GS).

[0046] Fig. 3 is a high-level message sequence chart illustrating a procedure 200 to establish Xn connections according to an example embodiment. The operations shown in Fig. 3 may be performed by a mobile IAB node, a serving node supporting a serving cell to which the IAB node is connected, one or more neighbor base stations including for example an IAB target donor, and an m- CU for controlling mobile IAB nodes. Fig. 3 shows the IAB donor 120 as an example of the serving node, though the serving node may also be a non-IAB RAN node e.g. a legacy gNB, or a stationary IAB node. The above mentioned network and terminal nodes may include a plurality of means, modules, components or elements for performing the operations discussed below with reference to Fig. 3. The means, modules, components or elements may be implemented in various manners, including but not limited to software, hardware, firmware, or any combination thereof.

[0047] Referring to Fig. 3, at 210, the IAB node 110 may establish an RRC connection between the IAB node 110 and the IAB donor 120. In some example embodiments, the IAB node 110 may establish the RRC connection between the IAB node 110 and the IAB donor 120 by a random access procedure when it is powered on and initially registers to the network. For example, the IAB node 110 may detect a cell supported by the IAB donor 120 as the best cell and initiates the random access procedure to the cell. In some other example embodiments, the IAB node 110 may establish the RRC connection between the IAB node 110 and the IAB donor 120 in a handover procedure by which the IAB node 110 migrates from a former IAB donor to the current IAB donor 120.

[0048] When the IAB node 110 initially connects to the network, the IAB node 110 may also establish an Fl connection to the m-CU 130 at an operation 212. As discussed above with respect to Fig. 1, the Fl connection is established between the distributed unit 112 and the m-CU 130 that functions to control the IAB node 110. The Fl connection may be carried by a PDU session established through the IAB donor 120.

[0049] At 220, the IAB node 110 may transmit cell information to the m-CU 130. The cell information may be transmitted via an Fl application protocol (F1AP) message during and/or after establishing the Fl connection at the operation 212, and it may comprise at least one of a serving cell and one or more neighboring cells for the TAB node 110. It would be appreciated that the TAB node 110 may have multiple serving cells including a primary cell and one or more secondary cells in case of Carrier Aggregation (CA). Since the multiple serving cells are operated by one base station (e.g., the IAB donor 120), the cell information may indicate any one of the multiple serving cells of the IAB node 110. The one or more neighboring cells may be supported by one or more neighboring base stations 150.

[0050] In an example embodiment, the IAB node 110 may transmit the serving cell information to the m-CU 130 after the IAB node 110 connects to the network.

[0051] In an example embodiment, the IAB node 110 may transmit the information of one or more neighboring cells to the m-CU 130 when the IAB node 110 sends a measurement report to the IAB donor 120. The one or more neighboring cells may be indicated in the measurement report as candidate target cells. Alternatively or additionally, the IAB node 110 may transmit the information of one or more neighboring cells to the m-CU 130 when the one or more neighboring cells have a signal level above a certain threshold which indicates that the one or more neighboring cells are potential handover candidates for the IAB node 110.

[0052] When the m-CU 130 receives the cell information, the m-CU 130 may initiate an Xn setup procedure to establish Xn connections between the m-CU 130 and one or more base stations supporting the cells indicated in the received cell information at 230.

[0053] As shown in Fig. 3, when the received cell information indicates the serving cell serviced by the IAB donor 120 (or by the IAB node 118 connected to the IAB donor 120), the m-CU 130 may establish an Xn connection between the m-CU 130 and the IAB donor 120 which is indicated in the serving cell information. Alternatively or additionally, when the received cell information indicates one or more neighboring cells, the m-CU 130 may establish an Xn connection(s) between the m-CU 130 and one or more neighboring base stations 150 supporting the one or more neighboring cells.

[0054] Fig. 4 is a schematic message sequence chart illustrating a procedure 300 to establish an Xn connection between the lAB-donor 120 and the m-CU 130 in an IAB node integration scenario according to an example embodiment of the present disclosure. It would be appreciated that the operations shown in Fig. 4 represent a specific example of the procedure 200 discussed above with reference to Fig. 3 and can be incorporated into the procedure shown in Fig. 3. [0055] Referring to Fig. 4, at 310, the IAB MT component 114 of the IAB node 110 may establish a radio resource control (RRC) connection with the donor CU 124 of the IAB donor 120. As discussed above, the IAB MT 114 may establish the RRC connection to the donor CU 124 via a random access procedure or a handover procedure. With the IAB network architecture as shown in Fig. 1, the IAB MT 114 may connect to the donor CU 124 regardless of whether the IAB donor 120 supports IAB or not.

[0056] In an example embodiment, for the backhaul connection of the IAB node 110, the IAB MT 114 may also establish a PDU session to the m-UPF 142 (Fig. 1) at 310. During the initial RRC connection setup, the IAB MT 114 may indicate to the network that the IAB node 110 is a mobile IAB node, and the NGC 140 may select a central unit capable of or dedicated to controlling mobile IAB nodes and select a mobile lAB-specific user plane function (UPF) for the IAB node 110. For example, an Access and Mobility Management Function (AMF) in the NGC 140 may have information about m-CU in the proximity of the IAB node 110 and it may select the m-CU 130 for the IAB node 110. A Service Management Function (SMF) in the NGC 140 may select the m-UPF 142 in the same local edge cloud as the donor CU 124 for the IAB MT 114. The PDU session between the IAB MT 114 and the m-UPF 142 may serve as a transport layer for the Fl interface to be established between the IAB DU 112 and the m-CU 130, which will be described in more detail below.

[0057] In another example embodiment, the IAB node 110 may receive information of the m-CU 130 from an Operation Administration and Maintenance (0AM) server (not shown). For example, the IAB MT 114 may establish a PDU session with the 0AM server, indicate the serving cell information to the 0AM server and obtain the configuration information on the m-CU 130. The configuration information of the m-CU 130 may include for example transport network layer (TNL) association information. In another example, the IAB DU 112 may be pre-configured by the 0AM server with regards to the m-CU information, e.g., the TNL association information. This may be applicable for a scenario for example where the m-CU 130 covers the movement region of the mobile IAB node 110. The TNL association information may include for example tunnel endpoint identifier (TEID), transport layer address and optionally other information for setting up an Fl connection.

[0058] At 320, the IAB MT 114 may transmit the serving cell information to the IAB DU 112 of IAB node 110. In an example, the serving cell information may include for example physical cell ID (PCI), cell global ID (CGI), tracking area code (TAC), frequency information and other information of the serving cell.

[0059] At 330, the IAB DU 112 of IAB node 110 may establish an Fl connection/interface to the m-CU 130. As discussed above, information of the m-CU 130 may be obtained during the connection setup procedure at the operation 310. The Fl interface may be used to exchange application level data between the IAB DU 112 and the m-CU 130. In an example embodiment, the operation 330 may include a step 332 of sending an Fl SETUP REQUEST message from the IAB DU 112 to the m-CU 130. The message may be transmitted to the m-CU 130 transparently via the PDU session established between the IAB MT 114 and the m-UPF 142 through the access RAN.

[0060] The Fl SETUP REQUEST message may include ID of the IAB DU 112 and information of one or more cells served by the IAB DU 112. For example, the Fl SETUP REQUEST may include an information element “served cell information”. In an example embodiment, the Fl SETUP REQUEST message may further include the serving cell information received at 320 which indicates the serving cell supported by the donor DU 124 to which the IAB node 110 is connected. For example, the Fl SETUP REQUEST message may be extended with a new information element (IE) “neighbor cell information” which refers to the serving cell of the donor DU 122 to which the IAB MT 114 is connected. The “neighbor cell information” IE may re-use the IE in the 3GPP F1AP or XnAP specification and it would minimize the impact on the existing specifications.

[0061] In response to receiving the Fl SETUP REQUEST message, at 334, the m-CU 130 may transmit an Fl SETUP RESPONSE message to the IAB DU 112.

[0062] When the Fl Setup procedure is finished, the Fl interface is operational and other F1AP messages may be exchanged between the IAB DU 112 and the m-CU 130. In an example embodiment, instead of using the Fl SETUP REQUEST message, the IAB DU 112 may transmit the serving cell information to the m-CU 130 via another F1AP message after the Fl connection is set up. For example, the serving cell information may be transmitted to the m-CU 130 in a gNB-DU configuration update procedure at 340.

[0063] As shown in Fig. 4, at 342, the IAB DU 112 may send a GNB-DU CONFIGURATION UPDATE message to the m-CU 130, which may be extended with the IE “neighbor cell information” including the serving cell information. At 344, the m-CU 130 may respond to the IAB DU 112 with a GNB-DU CONFIGURATION UPDATE ACKNOWLEDGE message to acknowledge successful receipt of the serving cell information.

[0064] At 350, with the serving cell information provided by the IAB DU 112 of the IAB node 110, the m-CU 130 may establish an Xn connection between the m-CU 130 and the IAB donor 120 that supports the serving cell. In an example embodiment, the m-CU 130 may reuse the legacy Xn setup procedure at 350.

[0065] In the example embodiment shown in Fig. 4, the IAB node 110 sends the serving cell information to the m-CU 130, and then the m-CU 130 initiates the Xn connection setup procedure to establish an Xn connection between the m-CU 130 and the IAB donor 120 supporting the serving cell.

[0066] In an example embodiment, the m-CU 130 may further receive from the IAB donor 120 neighboring cell information of the IAB node 110 during or after the Xn setup procedure at 350, and establish an Xn connection between the m-CU 130 and one or more neighboring base stations, an example of which is shown in Fig. 5.

[0067] Referring to Fig. 5, at 351, the m-CU 130 may send an XN SETUP REQUEST message to the IAB donor 120, e.g., in response to receiving the serving cell information from the IAB DU 112. Then at 352, the IAB donor 120 may respond to the m-CU 130 with an XN SETUP RESPONSE message. In an example embodiment, the XN SETUP RESPONSE message may be extended with the “neighbor cell information” IE which refers to one or more neighboring cells for the IAB node 110. The IAB donor 120 may receive the neighboring cell information from the IAB MT 114 e.g. via a measurement report. In an example embodiment, the IAB donor 120 may maintain a neighboring cell list for the IAB node 110 by e.g. an automatic neighbor relation (ANR) procedure. [0068] When the Xn Setup procedure is finished, an Xn interface is established between the IAB donor 120 and the m-CU 130, and other messages may be transmitted on the Xn interface. In an example embodiment, instead of using the XN SETUP RESPONSE message, the IAB donor 120 may utilize a NG- RAN node Configuration Update procedure to transmit the neighboring cell information to the m-CU 130. For example, at 353, the IAB donor 120 may send a NG-RAN NODE CONFIGURATION UPDATE message to the m-CU 130. The NG-RAN NODE CONFIGURATION UPDATE message may be extended with the “neighbor cell information” IE which refers to one or more neighboring cells for the IAB node 110. At 354, the m-CU 130 may respond to the IAB donor 120 with a NG-RAN NODE CONFIGURATION UPDATE ACKNOWLEDGE message to acknowledge that it has successfully received the neighboring cell information.

[0069] In response to the neighboring cell information received from the IAB donor 120 at 352 or 354, the m-CU 130 may establish an Xn connection between the m-CU 130 and one or more neighboring base stations supporting the neighboring cells. For example, at 362, the m-CU 130 may send an XN SETUP REQUEST message to the neighboring base stations 150. At 364, the neighbor base stations 150 may send an XN SETUP RESPONSE message to the m-CU 130 to complete the Xn setup procedure.

[0070] Fig. 6 is a schematic message sequence chart illustrating a procedure to establish Xn connections between an m-CU and one or more neighboring base stations in an IAB node handover scenario according to an example embodiment of the present disclosure.

[0071] Referring to Fig. 6, the MT 114 of the IAB node 110 may establish an RRC connection to the donor CU 124 of the IAB donor 120 at 410. Further, the IAB DU 112 of the IAB node 110 may establish an Fl connection to the m-CU 130 at 420. Details of the operation 410 and the operation 420 may refer to the operation 310 and operation 330 discussed above with respect to Fig. 4, and a repetitive description thereof is omitted here.

[0072] At 430, the IAB MT 114 may indicate the TAB DU 112 about one or more neighboring cells detected at the IAB MT 114. The IAB MT 114 may indicate the neighboring cells to the IAB DU 112 when it transmits a measurement report (e.g., a measurement report triggered by mobility Event A3 or A4) to the IAB donor 120, or when the neighboring cells have a signal level above a certain threshold. When the IAB donor 120 receives the measurement report from the IAB node 110, the IAB donor 120 may decide to handover the IAB node 110 to a target cell, e.g. the best one of the neighboring cells. A legacy inter-CU handover procedure may be performed to move the access and backhaul connections of the IAB node 110 from the source donor 120 to the target donor, as discussed above with respect to Fig. 2.

[0073] In response to receiving the neighboring cell information at 430, the IAB DU 112 of the IAB node 110 may transmit the neighboring cell information to the m-CU 130 at 440. In an example embodiment, the neighboring cell information may be transmitted in a gNB-DU Configuration Update procedure. For example, the IAB DU 112 may send a GNB-DU CONFIGURATION UPDATE message to the m-CU 130, which may be extended with the “neighbor cell information” IE that refers to the neighbor cells.

[0074] At 450, with the neighboring cell information received from the IAB DU 112 of the IAB node 110, the m-CU 130 may establish an Xn connection between the m-CU 130 and one or more neighboring base stations 150 supporting the neighboring cells. In an example embodiment, the Xn setup procedure may be performed before or in parallel with the handover procedure. Since the handover target cell is included in the neighboring cell information, the Xn connection between the m-CU 130 and the handover target base station can be established in a timely manner at 450 and would not violate the IAB node mobility requirements. Details of the operation 450 has been described above with respect to the operations 362, 364 in Fig. 5, and a repetitive description thereof is omitted here.

[0075] Fig. 7 is a high-level message sequence chart illustrating a procedure 500 to establish Xn connections according to an example embodiment of the present disclosure. Unlike the procedures shown in Figs. 3-6 where the Xn setup procedure is initiated at the m-CU 130, in the procedure 500 the Xn setup procedure may be initiated at an RAN node such as the IAB donor 120 or a non-IAB capable base station.

[0076] Referring to Fig. 7, at 510, the IAB node 110 may establish an RRC connection to the IAB donor 120. When the IAB node 110 is connected to the IAB donor 120, the IAB node 110 may further establish an Fl connection to the m-CU 130 via the access RAN at 512. Details of the RRC connection setup procedure and the Fl connection setup procedure have been discussed above, and a repetitive description thereof is omitted here.

[0077] At 520, the IAB node 110 may transmit cell information to the IAB donor 120. In an example embodiment, the cell information may comprise a cell serviced by the IAB DU 112 in the IAB node 110, hereinafter referred to as “IAB DU cell”. It would be appreciated that in a case where the IAB node 110 connects to the stationary IAB node 118 as shown in Fig. IB, the IAB node 110 may transmit the cell information to the stationary IAB node 118, and the stationary IAB node 118 may send the cell information to the IAB donor 120.

[0078] On the side of IAB donor 120, at 530, the IAB donor 120 may establish an Xn connection between the IAB donor 120 and the m-CU 130 in association with the IAB DU 112 serving the IAB DU cell. At 540, the IAB donor 120 may further transmit neighboring cell information to the m-CU 130. The neighboring cell information may indicate one or more neighboring cells for the IAB node 110, including for example neighboring cells supported by the TAB donor 120 and neighboring cells supported by neighboring base stations, which would be primary target cell candidates for the IAB node 110 when for example the IAB node 110 is moving away from the coverage of the IAB donor 120. In an example embodiment, the IAB donor 120 may maintain a neighboring cell list for the IAB node 110 based on measurement reports received from the IAB node 110.

[0079] On the side of the m-CU 130, in response to receiving the neighboring cell information from the IAB donor 120, the m-CU 130 may establish an Xn connection between the m-CU 130 and one or more neighboring base stations 150 supporting the neighboring cells indicated in the received neighboring cell information.

[0080] Fig. 8 is a schematic message sequence chart illustrating a procedure 600 to establish Xn connections initiated at the IAB donor 120 according to an example embodiment of the present disclosure. It would be appreciated that the operations shown in Fig. 8 represent a specific example of the procedure 500 discussed above with reference to Fig. 7 and can be incorporated into the procedure shown in Fig. 7.

[0081] Referring to Fig. 8, at 610, the IAB MT component 114 of the IAB node 110 may establish a radio resource control (RRC) connection with the donor CU 124 in association with the donor DU 122 in the IAB donor 120. In a cell selection/reselection procedure before establishing the RRC connection to the cell at 610, the IAB MT 114 may receive system information (SI) broadcast by the donor DU 122 of the IAB donor 120. In an example embodiment, the SI may include an indication idleModeMeasurementsNR in System Information Block 1 (SIB1) to indicate that the IAB donor 120 supports idle mode measurement. If the indication is received, the IAB MT 114 may include an indication idleMeasAvailable in the RRC Setup Complete message to indicate that the idle mode measurement report is available at the IAB MT 114.

[0082] When the RRC connection is established between the IAB MT 114 and the IAB donor CU 124, the IAB node 110 may further establish an Fl connection between the IAB DU 112 and the m-CU 130 at 612. Details of the RRC connection setup procedure and the Fl connection setup procedure have been discussed above, and a repetitive description thereof is omitted here.

[0083] At 620, the IAB DU 112 may transmit cell information to the IAB MT 114 of IAB node 110. The cell information may include one or more cells serviced by the IAB DU 112. In a half-duplex mode, the IAB MT 114 cannot detect the cell(s) serviced by the IAB DU 112 and the cell information is provided from the IAB DU 112 to the IAB MT 114.

[0084] At 630, the IAB MT 114 may transmit the cell information of the IAB DU cell to the donor CU 124 of the IAB donor 120. In an example embodiment, when the IAB MT 114 indicates idleMeasAvailable in the RRC Setup Complete message to the donor CU 124, the donor CU 124 may request the IAB DU cell information by a UE information request message UEInformationRequest including an idleModeMeasurementReq IE. Then the IAB MT 114 may transmit the IAB DU cell information to the IAB CU 124 as an idle mode measurement report in a response message UEInformationResponse . Because the IAB MT 114 cannot measure the IAB-DU cell (with the half-duplex assumption), the measurement result in the response message may have a dummy value suitable for the donor CU 124 to recognize the IAB DU cell but not high enough to trigger an immediate handover for the IAB MT 114 to its collocated DU cell. In an example, the cell information may also indicate an identifier of the base station i.e. the m-CU 130 supporting the IAB DU cell.

[0085] At 642, based on the received IAB DU cell information, the IAB donor CU 124 may initiate an Xn setup procedure by sending an XN SETUP REQUEST message to the m-CU 130. In an example embodiment, the XN SETUP REQUEST message may include neighboring cell information indicative of one or more neighboring cells for the IAB node 110. The donor CU 124 may obtain the neighboring cell information from the measurement reports received from the IAB node 110. In an example embodiment, the donor CU 124 may maintain a neighboring cell list for the IAB node 110 by automatic neighbor relation (ANR). The XN SETUP REQUEST message may be extended with the “neighbor cell information” IE which refers to the neighboring cells of the IAB node 110.

[0086] Then at 644, the m-CU 130 may reply with an XN SETUP RESPONSE message to complete the Xn setup procedure.

[0087] When the Xn Setup procedure is finished, the Xn interface is established between the donor CU 124 of the IAB donor 120 and the m-CU 130, and additional Xn application protocol (XnAP) messages may be transmitted via the Xn interface. In an example embodiment, instead of using the XN SETUP REQUEST message, the donor CU 124 may send a NG-RAN NODE CONFIGURATION UPDATE message to the m-CU 130 at 646, which may be extended with the “neighbor cell information” IE that refers to the neighboring cells for the IAB node 110. At 648, the m-CU 130 may respond to the donor CU 124 with a NG-RAN NODE CONFIGURATION UPDATE ACKNOWLEDGE message to acknowledge that it has successfully received the neighboring cell information.

[0088] At 650, with the neighboring cell information received from the donor CU 124, the m-CU 130 may establish an Xn connection between the m-CU 130 and one or more neighboring base stations 150 supporting the one or more neighboring cells indicated in the neighboring cell information received at the operation 642 or 646.

[0089] Fig. 9 is a schematic message sequence chart illustrating a procedure 700 to establish Xn connections between the m-CU 130 and one or more neighboring base stations 150 according to an example embodiment of the present disclosure. It would be appreciated that the procedure 700 may also be applied in Figs. 3, 5-8 to establish the Xn connection between the m-CU 130 and the neighboring base stations 150.

[0090] Referring to Fig. 9, at 710, the m-CU 130 may establish Xn connections in standby state to the neighbor base stations 150 servicing the neighboring cells of the TAB node 110. The standby Xn connections cannot be used to transmit XnAP messages between the m-CU 130 and the neighbor base stations 150.

[0091] At 720, the m-CU 130 may activate one or more of the standby Xn connections. For example, when the TAB donor 120 decides to handover the IAB node 110 to a neighboring cell serviced by a neighboring base station (inter-CU handover), the IAB donor 120 may inform the m-CU 130 of the target neighboring cell e.g. via the operational Xn connection between the IAB donor 120 and the m-CU 130, and then the m-CU 130 can activate the standby Xn connection between the m-CU 130 and the target neighboring base station servicing the target neighboring cell. In a case of conditional handover, the m- CU 130 may activate multiple standby Xn connections to multiple potential target base stations. The other standby Xn connections may remain in the standby state or may be released.

[0092] In the procedure 700, the m-CU 130 can establish standby Xn connections to a number of neighboring base stations of the IAB node 110. When the IAB donor 120 decides the handover target base station or multiple potential target base stations, the IAB donor 120 may inform the m-CU 130 of the target base station or potential target base stations, and then the m-CU 130 may activate the Xn connection to the target base station or the respective potential target base stations. Using the procedure 700, the m-CU 130 can establish an operational Xn connection with the target base station or potential target base stations quickly when handover or conditional handover occurs because standby Xn connections have already been established before the handover is triggered. Therefore, the procedure 700 can minimize delay caused by the Xn setup procedure and meet the I AB -MT mobility requirements.

[0093] Fig. 10 is a schematic structure block diagram illustrating devices in a communication system 800 in which example embodiments of the present disclosure can be implemented. As shown in Fig. 10, the communication system 800 may comprise a first network device 810 which may be implemented as the IAB node 110 discussed above, a second network device 820 which may be implemented as the IAB donor 120 discussed above, and a third network device 830 which may be implemented as the m-CU 130 discussed above.

[0094] Referring to Fig. 10, the first network device 810 may comprise one or more processors 812, one or more memories 814 and one or more transceivers (not shown) interconnected through one or more buses. The one or more buses may be address, data, or control buses, and may include any interconnection mechanism such as series of lines on a motherboard or integrated circuit, fiber, optics or other optical communication equipment, and the like. Each of the one or more transceivers may comprise a receiver and a transmitter, which are connected to one or more antennas. The first network device 810 may wirelessly communicate with the second network device 820 through the one or more antennas. The one or more memories 814 may include computer program code 816. The one or more memories 814 and the computer program code 816 may be configured to, when executed by the one or more processors 812, cause the first network device 810 to perform processes and steps relating to the IAB node 110 as described above.

[0095] The second network device 820 may comprise one or more processors 822, one or more memories 824, one or more transceivers (not shown) and one or more network interfaces (not shown) interconnected through one or more buses. The one or more buses may be address, data, or control buses, and may include any interconnection mechanism such as a series of lines on a motherboard or integrated circuit, fiber, optics or other optical communication equipment, and the like. Each of the one or more transceivers may comprise a receiver and a transmitter, which are connected to one or more antennas. The second network device 820 may wirelessly communicate with the first network device 810 through the one or more antennas. The one or more network interfaces may provide wired or wireless communication links through which the second network device 820 may communicate with other network devices, entities, elements or functions. For example, the second network device 820 may communicate with the third network device 830 via Xn interface. The one or more memories 824 may include computer program code 826. The one or more memories 824 and the computer program code 826 may be configured to, when executed by the one or more processors 822, cause the second network device 820 to perform processes and steps relating to the IAB donor 120 as described above.

[0096] The third network device 830 may comprise one or more processors 832, one or more memories 834, and one or more network interfaces (not shown) interconnected through one or more buses. The one or more buses may be address, data, or control buses, and may include any interconnection mechanism such as a series of lines on a motherboard or integrated circuit, fiber, optics or other optical communication equipment, and the like. The one or more network interfaces may provide wired or wireless communication links through which the third network device 830 may communicate with other network devices, entities, elements or functions. For example, the third network device 830 may communicate with the first network device 810 over the Fl interface and communicate with the second network device 820 via Xn interface. The one or more memories 834 may include computer program code 836. The one or more memories 834 and the computer program code 836 may be configured to, when executed by the one or more processors 832, cause the third network device 830 to perform processes and steps relating to the m-CU 130 as described above.

[0097] The one or more processors 812, 822 and 832 discussed above may be of any appropriate type that is suitable for the local technical network, and may include one or more of general purpose processors, special purpose processor, microprocessors, a digital signal processor (DSP), one or more processors in a processor based multi-core processor architecture, as well as dedicated processors such as those developed based on Field Programmable Gate Array (FPGA) and Application Specific Integrated Circuit (ASIC). The one or more processors 812, 822 and 832 may be configured to control other elements of the network device/network node and operate in cooperation with them to implement the procedures discussed above.

[0098] The one or more memories 814, 824 and 834 may include at least one storage medium in various forms, such as a volatile memory and/or a nonvolatile memory. The volatile memory may include but not limited to for example a random access memory (RAM) or a cache. The non-volatile memory may include but not limited to for example a read only memory (ROM), a hard disk, a flash memory, and the like. Further, the one or more memories 814, 824 and 834 may include but not limited to an electric, a magnetic, an optical, an electromagnetic, an infrared, or a semiconductor system, apparatus, or device or any combination of the above.

[0099] It would be understood that blocks in the drawings may be implemented in various manners, including software, hardware, firmware, or any combination thereof. In some embodiments, one or more blocks may be implemented using software and/or firmware, for example, machine- executable instructions stored in the storage medium. In addition to or instead of machine-executable instructions, parts or all of the blocks in the drawings may be implemented, at least in part, by one or more hardware logic components. For example, and without limitation, illustrative types of hardware logic components that can be used include Field-Programmable Gate Arrays (FPGAs), Application-Specific Integrated Circuits (ASICs), Application- Specific Standard Products (ASSPs), System-on-Chip systems (SOCs), Complex Programmable Logic Devices (CPLDs), etc.

[00100] Some example embodiments further provide computer program code or instructions which, when executed by one or more processors, may cause a device or apparatus to perform the procedures described above. The computer program code for carrying out procedures of the example embodiments may be written in any combination of one or more programming languages. The computer program code may be provided to one or more processors or controllers of a general purpose computer, special purpose computer, or other programmable data processing apparatus, such that the program code, when executed by the processor or controller, cause the functions/operations specified in the flowcharts and/or block diagrams to be implemented. The program code may execute entirely on a machine, partly on the machine, as a stand-alone software package, partly on the machine and partly on a remote machine or entirely on the remote machine or server.

[00101] Some example embodiments further provide a computer program product or a computer readable medium having the computer program code or instructions stored therein. The computer readable medium may be any tangible medium that may contain, or store a program for use by or in connection with an instruction execution system, apparatus, or device. The machine readable medium may be a machine readable signal medium or a machine readable storage medium. A machine readable medium may include but is not limited to an electronic, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus, or device, or any suitable combination of the foregoing. More specific examples of the machine readable storage medium would include an electrical connection having one or more wires, a portable computer diskette, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or Flash memory), an optical fiber, a portable compact disc read-only memory (CD-ROM), an optical storage device, a magnetic storage device, or any suitable combination of the foregoing.

[00102]Further, while operations are depicted in a particular order, this should not be understood as requiring that such operations be performed in the particular order shown or in sequential order, or that all illustrated operations be performed, to achieve desirable results. In certain circumstances, multitasking and parallel processing may be advantageous. Likewise, while several specific implementation details are contained in the above discussions, these should not be construed as limitations on the scope of the present disclosure, but rather as descriptions of features that may be specific to particular embodiments. Certain features that are described in the context of separate embodiments may also be implemented in combination in a single embodiment. Conversely, various features that are described in the context of a single embodiment may also be implemented in multiple embodiments separately or in any suitable sub-combination.

[00103] Although the subject matter has been described in a language that is specific to structural features and/or method actions, it is to be understood the subject matter defined in the appended claims is not limited to the specific features or actions described above. On the contrary, the above-described specific features and actions are disclosed as an example of implementing the claims.

Claims

CLAIMS:

1. An integrated access and backhaul node comprising: at least one processor; and at least one memory including computer program code, the at least one memory and the computer program code being configured to, with the at least one processor, cause the integrated access and backhaul node at least to: establish a first connection between a mobile termination component in the integrated access and backhaul node and a cell serviced by a serving node; establish a second connection between a distributed unit in the integrated access and backhaul node and a central unit for controlling the integrated access and backhaul node; and transmit cell information to the central unit during and/or after establishing the second connection, the cell information indicative of at least one of a serving cell and one or more neighboring cells for the integrated access and backhaul node.

2. The integrated access and backhaul node of Claim 1 wherein the mobile termination component sends the cell information to the distributed unit, and the distributed unit transmits the cell information to the central unit.

3. The integrated access and backhaul node of Claim 1 wherein the first connection between the mobile termination component in the integrated access and backhaul node and the serving node is established during a radio resource control connection setup procedure or during a handover procedure, and the second connection between the distributed unit in the integrated access and backhaul node and the central unit is partially carried via the first connection.

4. The integrated access and backhaul node of Claim 3 wherein the integrated access and backhaul node is preconfigured by an Operation Administration Maintenance server with information of the central unit or receives the information of the central unit from an Operation Administration Maintenance server.

5. The integrated access and backhaul node of Claim 3 wherein the integrated access and backhaul node receives information of the central unit from an Access and Mobility Management Function server.

6. The integrated access and backhaul node of Claim 1 wherein the integrated access and backhaul node transmits the cell information of the one or more neighboring cells when: the integrated access and backhaul node transmits a measurement report to the serving node; and/or the one or more neighboring cells have a signal level above a threshold.

7. The integrated access and backhaul node of Claim 1 wherein the serving node is an integrated access and backhaul donor node, a non-integrated access and backhaul radio access network node, or a stationary integrated access and backhaul node.

8. A central unit for controlling one or more integrated access and backhaul nodes, comprising: at least one processor; and at least one memory including computer program code, the at least one memory and the computer program code being configured to, with the at least one processor, cause the central unit at least to: establish a second connection between a distributed unit in an integrated access and backhaul node and the central unit; receive cell information from the integrated access and backhaul node during and/or after establishing the second connection, the cell information indicative of at least one of a serving cell and one or more neighboring cells for the integrated access and backhaul node; and establish a third connection between the central unit and one or more base stations serving the at least one of the serving cell and the one or more neighboring cells.

9. The central unit of Claim 8 wherein the cell information received from the integrated access and backhaul node indicates said serving cell of the integrated access and backhaul node, and the at least one memory and the computer program code are further configured to, with the at least one processor, cause the central unit at least to: receive neighboring cell information from a serving base station supporting said serving cell during and/or after establishing the third connection between the central unit and the serving base station, the neighboring cell information indicative of one or more neighboring cells for the integrated access and backhaul node; and establish a third connection between the central unit and one or more neighboring base stations supporting the one or more neighboring cells.

10. An integrated access and backhaul node comprising: at least one processor; and at least one memory including computer program code, the at least one memory and the computer program code being configured to, with the at least one processor, cause the integrated access and backhaul node at least to: establish a first connection between a mobile termination component in the integrated access and backhaul node and a cell serviced by a serving node; establish a second connection between a distributed unit in the integrated access and backhaul node and a central unit for controlling the integrated access and backhaul node; and transmit cell information to the serving node, the cell information indicative of a cell serviced by the distributed unit in the integrated access and backhaul node.

11. The integrated access and backhaul node of Claim 10 wherein the serving node is an integrated access and backhaul donor node, a non-integrated access and backhaul radio access network node, or a stationary integrated access and backhaul node.

12. A radio access network node comprising: at least one processor; and at least one memory including computer program code, the at least one memory and the computer program code being configured to, with the at least one processor, cause the radio access network node at least to: receive cell information from a mobile termination component in an integrated access and backhaul node, the cell information indicative of a cell serviced by a distributed unit in the integrated access and backhaul node; and establish a third connection between the radio access network node and a central unit for controlling the integrated access and backhaul node based on the received cell information, the central unit having a second connection with the distributed unit in the integrated access and backhaul node.

13. The radio access network node of Claim 12 wherein the radio access network node is an integrated access and backhaul donor node or a nonintegrated access and backhaul radio access network node.

14. The radio access network node of Claim 12 wherein the at least one memory and the computer program code are further configured to, with the at least one processor, cause the radio access network node at least to: transmit neighboring cell information to the central unit for controlling the integrated access and backhaul node during and/or after establishing the third connection between the radio access network node and the central unit, the neighboring cell information indicative of one or more neighboring cells for the integrated access and backhaul node.

15. A central unit for controlling one or more integrated access and backhaul nodes, comprising: at least one processor; and at least one memory including computer program code, the at least one memory and the computer program code being configured to, with the at least one processor, cause the central unit at least to: establish a third connection between the central unit and a radio access network node; receive neighboring cell information from the radio access network node during and/or after establishing the third connection between the central unit and the radio access network node, the neighboring cell information indicative of one or more neighboring cells for an integrated access and backhaul node under the control of the central unit; and establish a third connection between the central unit and one or more neighboring base stations supporting the one or more neighboring cells indicated in the neighboring cell information.

16. The central unit of Claim 15 wherein the radio access network node is an integrated access and backhaul donor node or a non-integrated access and backhaul radio access network node which provides network access for the integrated access and backhaul node.

17. A method implemented at an integrated access and backhaul node comprising: establishing a first connection between a mobile termination component in the integrated access and backhaul node and a cell serviced by a serving node; establishing a second connection between a distributed unit in the integrated access and backhaul node and a central unit for controlling the integrated access and backhaul node; and transmitting cell information to the central unit during and/or after establishing the second connection, the cell information indicative of at least one of a serving cell and one or more neighboring cells for the integrated access and backhaul node.

18. The method of Claim 17 wherein the mobile termination component sends the cell information to the distributed unit, and the distributed unit transmits the cell information to the central unit.

19. The method of Claim 17 wherein the first connection between the mobile termination component in the integrated access and backhaul node and the serving node is established during a radio resource control connection setup procedure or during a handover procedure, and the second connection between the distributed unit in the integrated access and backhaul node and the central unit is partially carried via the first connection.

20. The method of Claim 19 wherein the integrated access and backhaul node is preconfigured by an Operation Administration Maintenance server with information of the central unit or receives the information of the central unit from an Operation Administration Maintenance server.

21. The method of Claim 19 wherein the integrated access and backhaul node receives information of the central unit from an Access and Mobility Management Function server.

22. The method of Claim 17 wherein the integrated access and backhaul node transmits the cell information of the one or more neighboring cells when: the integrated access and backhaul node transmits a measurement report to the serving node; and/or the one or more neighboring cells have a signal level above a threshold.

23. The method of Claim 17 wherein the serving node is an integrated access and backhaul donor node, a non-integrated access and backhaul radio access network node, or a stationary integrated access and backhaul node.

24. A method implemented at a central unit controlling one or more integrated access and backhaul nodes, comprising: establishing a second connection between a distributed unit in an integrated access and backhaul node and the central unit; receiving cell information from the integrated access and backhaul node during and/or after establishing the second connection, the cell information indicative of at least one of a serving cell and one or more neighboring cells for the integrated access and backhaul node; and establishing a third connection between the central unit and one or more base stations serving the at least one of the serving cell and the one or more neighboring cells.

25. The method of Claim 24 wherein the cell information received from the integrated access and backhaul node indicates said serving cell of the integrated access and backhaul node, and the method further comprises: receiving neighboring cell information from a serving base station supporting said serving cell during and/or after establishing the third connection between the central unit and the serving base station, the neighboring cell information indicative of one or more neighboring cells of the integrated access and backhaul node; and establishing a third connection between the central unit and one or more neighboring base stations supporting the one or more neighboring cells.

26. A method implemented at an integrated access and backhaul node comprising: establishing a first connection between a mobile termination component in the integrated access and backhaul node and a cell serviced by a serving node; establishing a second connection between a distributed unit in the integrated access and backhaul node and a central unit for controlling the integrated access and backhaul node; and transmitting cell information to the serving node, the cell information indicative of a cell serviced by the distributed unit in the integrated access and backhaul node.

27. The method of Claim 26 wherein the serving node is an integrated access and backhaul donor node, a non-integrated access and backhaul radio access network node, or a stationary integrated access and backhaul node.

28. A method implemented at a radio access network node comprising: receiving cell information from a mobile termination component in an integrated access and backhaul node, the cell information indicative of a cell serviced by a distributed unit in the integrated access and backhaul node; and establishing a third connection between the radio access network node and a central unit for controlling the integrated access and backhaul node based on the received cell information, the central unit having a second connection with the distributed unit in the integrated access and backhaul node.

29. The method of Claim 28 wherein the radio access network node is an integrated access and backhaul donor node or a non-integrated access and backhaul radio access network node.

30. The method Claim 28 further comprising:

Transmitting neighboring cell information to the central unit for controlling the integrated access and backhaul node during and/or after establishing the third connection between the radio access network node and the central unit, the neighboring cell information indicative of one or more neighboring cells for the integrated access and backhaul node.

31. A method implemented at a central unit controlling one or more integrated access and backhaul nodes, comprising: establishing a third connection between the central unit and a radio access network node; receiving neighboring cell information from the radio access network node during and/or after establishing the third connection between the central unit and the radio access network node, the neighboring cell information indicative of one or more neighboring cells for an integrated access and backhaul node under the control of the central unit; and establishing a third connection between the central unit and one or more neighboring base stations supporting the one or more neighboring cells indicated in the neighboring cell information.

32. The method of Claim 31 wherein the radio access network node is an integrated access and backhaul donor node or a non-integrated access and backhaul radio access network node which provides network access for the integrated access and backhaul node.

33. An apparatus comprising: means for establishing a first connection between a mobile termination component in an integrated access and backhaul node and a cell serviced by a serving node; means for establishing a second connection between a distributed unit in the integrated access and backhaul node and a central unit for controlling the integrated access and backhaul node; and means for transmitting cell information from the integrated access and backhaul node to the central unit during and/or after establishing the second connection, the cell information indicative of at least one of a serving cell and one or more neighboring cells for the integrated access and backhaul node.

34. An apparatus comprising: means for establishing a second connection between a distributed unit in an integrated access and backhaul node and a central unit for controlling the integrated access and backhaul node; means for receiving, at the central unit, cell information from the integrated access and backhaul node during and/or after establishing the second connection, the cell information indicative of at least one of a serving cell and one or more neighboring cells for the integrated access and backhaul node; and means for establishing a third connection between the central unit and one or more base stations serving the at least one of the serving cell and the one or more neighboring cells.

35. An apparatus comprising: means for establishing a first connection between a mobile termination component in an integrated access and backhaul node and a cell serviced by a serving node; means for establishing a second connection between a distributed unit in the integrated access and backhaul node and a central unit for controlling the integrated access and backhaul node; and means for transmitting cell information from the integrated access and backhaul node to the serving node, the cell information indicative of a cell serviced by the distributed unit in the integrated access and backhaul node.

36. An apparatus comprising: means for receiving, at a radio access network node, cell information from an integrated access and backhaul node, the cell information indicative of a cell serviced by a distributed unit in the integrated access and backhaul node; and means for establishing a third connection between the radio access network node and a central unit for controlling the integrated access and backhaul node based on the received cell information, the central unit having a second connection with the distributed unit in the integrated access and backhaul node.

37. An apparatus comprising: means for establishing a third connection between a central unit for controlling one or more integrated access and backhaul nodes and a radio access network node; means for receiving, at the central unit, neighboring cell information from the radio access network node during and/or after establishing the third connection between the central unit and the radio access network node, the neighboring cell information indicative of one or more neighboring cells for an integrated access and backhaul node under the control of the central unit; and means for establishing a third connection between the central unit and one or more neighboring base stations supporting the one or more neighboring cells indicated in the neighboring cell information.

38. A computer program product embodied in at least one computer readable medium and comprising instructions, when executed by at least one processor of an integrated access and backhaul node, causing the integrated access and backhaul node at least to: establish a first connection between a mobile termination component in the integrated access and backhaul node and a cell serviced by a serving node; establish a second connection between a distributed unit in the integrated access and backhaul node and a central unit for controlling the integrated access and backhaul node; and transmit cell information from the integrated access and backhaul node to the central unit during and/or after establishing the second connection, the cell information indicative of at least one of a serving cell and one or more neighboring cells for the integrated access and backhaul node.

39. A computer program product embodied in at least one computer readable medium and comprising instructions, when executed by at least one processor of a central unit, causing the central unit at least to: establish a second connection between the central unit and a distributed unit in an integrated access and backhaul node controlled by the central unit; receive cell information from the integrated access and backhaul node during and/or after establishing the second connection, the cell information indicative of at least one of a serving cell and one or more neighboring cells for the integrated access and backhaul node; and establish a third connection between the central unit and one or more base stations serving the at least one of the serving cell and the one or more neighboring cells.

40. A computer program product embodied in at least one computer readable medium and comprising instructions, when executed by at least one processor of an integrated access and backhaul node, causing the integrated access and backhaul node at least to: establish a first connection between a mobile termination component in the integrated access and backhaul node and a cell serviced by a serving node; establish a second connection between a distributed unit in the integrated access and backhaul node and a central unit for controlling the integrated access and backhaul node; and transmit cell information from the integrated access and backhaul node to the serving node, the cell information indicative of a cell serviced by the distributed unit in the integrated access and backhaul node.

41. A computer program product embodied in at least one computer readable medium and comprising instructions, when executed by at least one processor of a radio access network node, causing the radio access network node at least to: receive cell information from an integrated access and backhaul node, the cell information indicative of a cell serviced by a distributed unit in the integrated access and backhaul node; and establish a third connection between the radio access network node and a central unit for controlling the integrated access and backhaul node based on the received cell information, the central unit having a second connection with the distributed unit in the integrated access and backhaul node.

42. A computer program product embodied in at least one computer readable medium and comprising instructions, when executed by at least one processor of a central unit, causing the central unit at least to: establish a third connection between the central unit and a radio access network node,; receive neighboring cell information from the radio access network node during and/or after establishing the third connection between the central unit and the radio access network node, the neighboring cell information indicative of one or more neighboring cells for an integrated access and backhaul node under the control of the central unit; and establish a third connection between the central unit and one or more neighboring base stations supporting the one or more neighboring cells indicated in the neighboring cell information.