WO2024207145A1

WO2024207145A1 - Optimization in integrated access and backhaul network

Info

Publication number: WO2024207145A1
Application number: PCT/CN2023/085936
Authority: WO
Inventors: Xiang Xu; Ilkka Antero Keskitalo; Matti Einari Laitila; Andrew LAPPALAINEN; Alessio Casati
Original assignee: Nokia Shanghai Bell Co Ltd; Nokia Solutions and Networks Oy; Nokia Technologies Oy
Current assignee: Nokia Shanghai Bell Co Ltd; Nokia Solutions and Networks Oy; Nokia Technologies Oy
Priority date: 2023-04-03
Filing date: 2023-04-03
Publication date: 2024-10-10
Anticipated expiration: 2025-10-03
Also published as: CN120898488A

Abstract

Embodiments of the present disclosure relate to support of paging optimization in an integrated access and backhaul (IAB) network. An IAB node performs a migration from a first IAB donor to a second IAB donor. The IAB node transmits, to a network device, a message comprising a first set of identifiers associated with a connection between the IAB node and the first IAB donor and a second set of identifiers associated with a connection between the IAB node and the second IAB donor. In this way, reliability of the IAB communication may be improved.

Description

OPTIMIZATION IN INTEGRATED ACCESS AND BACKHAUL NETWORK

FIELD

Example embodiments of the present disclosure generally relate to the field of telecommunication, and in particular, to an integrated access backhaul (IAB) node, network devices, methods, apparatuses and a computer readable storage medium for optimizing an IAB network.

BACKGROUND

A communication system may include one or more IAB nodes to enable fast and cost-efficient deployments. IAB nodes may use the same Uu air interface for access and backhaul, creating a hierarchical wireless multi-hop network between sites. The hops may terminate at an IAB donor that is connected by means of a conventional backhaul to a core network (CN) . An IAB donor may include a central unit (CU) part and a distributed unit (DU) part. An IAB node may include a mobile terminal (MT) part that may operate like a UE toward the parent IAB node or an IAB donor, and a DU part that may operate like a base station towards the terminal device or a mobile terminal of the child IAB node. On the access links, the IAB nodes may operate like ordinary base stations, providing the NR radio interface for user equipments (UEs) in their coverage areas. The DU part of an IAB node may provide one or more cells to serve UEs.

Due to possible failures on the backhaul (BH) connections or changes in the IAB topology or IAB mobility, an IAB node may need to change its serving node which can be under the same or different IAB donor (s) .

SUMMARY

In general, example embodiments of the present disclosure provide a solution for optimizing an IAB network, especially for supporting paging optimization in an IAB network.

In a first aspect, there is provided an integrated access backhaul (IAB) node. The IAB node comprises at least one processor and at least one memory storing instructions. The instructions, when executed by the at least one processor, cause the IAB node at least to: perform a migration from a first IAB donor to a second IAB donor; and transmit, to a network device, a message comprising a first set of identifiers associated with a connection between the IAB node and the first IAB donor and a second set of identifiers associated with a connection between the IAB node and the second IAB donor.

In a second aspect, there is provided a first network device. The first network device comprises at least one processor; and at least one memory storing instructions. The instructions, when executed by the at least one processor, cause the first network device at least to: obtain a first set of identifiers associated with a connection between an integrated access backhaul (IAB) node and a first IAB donor and a second set of identifiers associated with a connection between the IAB node and a second IAB donor; and transmit, to a second network device, a message comprising the first set of identifiers and the second set of identifiers.

In a third aspect, there is provided a second network device. The second network device comprises at least one processor; and at least one memory storing instructions. The instructions, when executed by the at least one processor, cause the second network device at least to: receive, from an integrated access backhaul (IAB) node or a first network device, a message comprising a first set of identifiers associated with a connection between the IAB node and a first IAB donor and a second set of identifiers associated with a connection between the IAB node and a second IAB donor; and based on determining that context information of at least one terminal device comprises the first set of identifiers, store the second set of identifiers in the context information of the at least one terminal device, the at least one terminal device being in an idle state.

In a fourth aspect, there is provided a method. The method comprises: performing, at an integrated access backhaul (IAB) node, a migration from a first IAB donor to a second IAB donor; and transmitting, to a network device, a message comprising a first set of identifiers associated with a connection between the IAB node and the first IAB donor and a second set of identifiers associated with a connection between the IAB node and the second IAB donor.

In a fifth aspect, there is provided a method. The method comprises: obtaining, at a first network device, a first set of identifiers associated with a connection between an integrated access backhaul (IAB) node and a first IAB donor and a second set of identifiers associated with a connection between the IAB node and a second IAB donor; and transmitting, to a second network device, a message comprising the first set of identifiers and the second set of identifiers.

In a sixth aspect, there is provided a method. The method comprises: receiving, at a second network device and from an integrated access backhaul (IAB) node or a first network device, a message comprising a first set of identifiers associated with a connection between the IAB node and a first IAB donor and a second set of identifiers associated with a connection between the IAB node and the second IAB donor; and based on determining that context information of at least one terminal device comprises the first set of identifiers, storing the second set of identifiers in the context information of the at least one terminal device, the at least one terminal device being in an idle state.

In a seventh aspect, there is provided an apparatus. The apparatus comprises means for performing, at an integrated access backhaul (IAB) node, a migration from a first IAB donor to a second IAB donor; and means for transmitting, to a network device, a message comprising a first set of identifiers associated with a connection between the IAB node and the first IAB donor and a second set of identifiers associated with a connection between the IAB node and the second IAB donor.

In an eighth aspect, there is provided an apparatus. The apparatus comprises means for obtaining, at a first network device, a first set of identifiers associated with a connection between an integrated access backhaul (IAB) node and a first IAB donor and a second set of identifiers associated with a connection between the IAB node and a second IAB donor; and means for transmitting, to a second network device, a message comprising the first set of identifiers and the second set of identifiers.

In a ninth aspect, there is provided an apparatus. The apparatus comprises means for receiving, at a second network device and from an integrated access backhaul (IAB) node or a first network device, a message comprising a first set of identifiers associated with a connection between the IAB node and a first IAB donor and a second set of identifiers associated with a connection between the IAB node and the second IAB donor; and means for based on determining that context information of at least one terminal device comprises the first set of identifiers, storing the second set of identifiers in the context information of the at least one terminal device, the at least one terminal device being in an idle state.

In a tenth aspect, there is provided an apparatus. The apparatus comprises performing circuitry configured to perform, at an integrated access backhaul (IAB) node, a migration from a first IAB donor to a second IAB donor; and transmitting circuitry configured to transmit, to a network device, a message comprising a first set of identifiers associated with a connection between the IAB node and the first IAB donor and a second set of identifiers associated with a connection between the IAB node and the second IAB donor.

In an eleventh aspect, there is provided an apparatus. The apparatus comprises obtaining circuitry configured to obtain, at a first network device, a first set of identifiers associated with a connection between an integrated access backhaul (IAB) node and a first IAB donor and a second set of identifiers associated with a connection between the IAB node and a second IAB donor; and transmitting circuitry configured to transmit, to a second network device, a message comprising the first set of identifiers and the second set of identifiers.

In a twelfth aspect, there is provided an apparatus. The apparatus comprises receiving circuitry configured to receive, at a second network device and from an integrated access backhaul (IAB) node or a first network device, a message comprising a first set of identifiers associated with a connection between the IAB node and a first IAB donor and a second set of identifiers associated with a connection between the IAB node and the second IAB donor; and storing circuitry configured to store the second set of identifiers in context information of at least one terminal device based on determining that the context information of the at least one terminal device comprises the first set of identifiers, the at least one terminal device being in an idle state.

In a thirteenth aspect, there is provided a non-transitory computer readable medium comprising program instructions for causing an apparatus to perform at least the method according to any one of the above fourth to sixth aspect.

In a fourteenth aspect, there is provided a computer program comprising instructions, which, when executed by an apparatus, cause the apparatus at least to perform at least the method according to any one of the above fourth to sixth aspect.

It is to be understood that the summary section is not intended to identify key or essential features of embodiments of the present disclosure, nor is it intended to be used to limit the scope of the present disclosure. Other features of the present disclosure will become easily comprehensible through the following description.

BRIEF DESCRIPTION OF THE DRAWINGS

Some example embodiments will now be described with reference to the accompanying drawings, in which:

Fig. 1A illustrates an example communication network in which embodiments of the present disclosure may be implemented;

Figs. 1B and 1C show the Recommended RAN Nodes for Paging IE and the Recommended Cells for Paging IE, respectively.

Fig. 2 illustrates a flowchart illustrating a communication process in accordance with some example embodiments of the present disclosure;

Fig. 3 illustrates a flowchart illustrating a communication process in accordance with some further example embodiment of the present disclosure;

Figs. 4A and 4B illustrates examples of communication processes in accordance with some example embodiments of the present disclosure;

Fig. 5 illustrates a flowchart of a method implemented at an IAB node according to some embodiments of the present disclosure;

Fig. 6 illustrates a flowchart of a method implemented at a first network device according to some embodiments of the present disclosure;

Fig. 7 illustrates a flowchart of a method implemented at a second network device according to some other embodiments of the present disclosure;

Fig. 8 illustrates a simplified block diagram of an apparatus that is suitable for implementing embodiments of the present disclosure; and

Fig. 9 illustrates a block diagram of an example computer readable medium in accordance with some embodiments of the present disclosure.

Throughout the drawings, the same or similar reference numerals represent the same or similar element.

DETAILED DESCRIPTION

Principle of the present disclosure will now be described with reference to some example embodiments. It is to be understood that these embodiments are described only for the purpose of illustration and help those skilled in the art to understand and implement the present disclosure, without suggesting any limitation as to the scope of the disclosure. The disclosure described herein can be implemented in various manners other than the ones described below.

In the following description and claims, unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skills in the art to which this disclosure belongs.

References in the present disclosure to “one embodiment, ” “an embodiment, ” “an example embodiment, ” and the like indicate that the embodiment described may include a particular feature, structure, or characteristic, but it is not necessary that every embodiment includes the particular feature, structure, or characteristic. Moreover, such phrases are not necessarily referring to the same embodiment. Further, when a particular feature, structure, or characteristic is described in connection with an embodiment, it is submitted that it is within the knowledge of one skilled in the art to affect such feature, structure, or characteristic in connection with other embodiments whether or not explicitly described.

It shall be understood that although the terms “first” and “second” etc. may be used herein to describe various elements, these elements should not be limited by these terms. These terms are only used to distinguish one element from another. For example, a first element could be termed a second element, and similarly, a second element could be termed a first element, without departing from the scope of example embodiments. As used herein, the term “and/or” includes any and all combinations of one or more of the listed terms.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of example embodiments. As used herein, the singular forms “a” , “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises” , “comprising” , “has” , “having” , “includes” and/or “including” , when used herein, specify the presence of stated features, elements, and/or components etc., but do not preclude the presence or addition of one or more other features, elements, components and/or combinations thereof. As used herein, “at least one of the following: <a list of two or more elements>” and “at least one of <a list of two or more elements>” and similar wording, where the list of two or more elements are joined by “and” or “or” , mean at least any one of the elements, or at least any two or more of the elements, or at least all the elements.

As used in this application, the term “circuitry” may refer to one or more or all of the following:

(a) hardware-only circuit implementations (such as implementations in only analog and/or digital circuitry) and

(b) combinations of hardware circuits and software, such as (as applicable) :

(i) a combination of analog and/or digital hardware circuit (s) with software/firmware and

(ii) any portions of hardware processor (s) with software (including digital signal processor (s) ) , software, and memory (ies) that work together to cause an apparatus, such as a mobile phone or server, to perform various functions) and

(c) hardware circuit (s) and or processor (s) , such as a microprocessor (s) or a portion of a microprocessor (s) , that requires software (e.g., firmware) for operation, but the software may not be present when it is not needed for operation.

This definition of circuitry applies to all uses of this term in this application, including in any claims. As a further example, as used in this application, the term circuitry also covers an implementation of merely a hardware circuit or processor (or multiple processors) or portion of a hardware circuit or processor and its (or their) accompanying software and/or firmware. The term circuitry also covers, for example and if applicable to the particular claim element, a baseband integrated circuit or processor integrated circuit for a mobile device or a similar integrated circuit in server, a cellular network device, or other computing or network device.

As used herein, the term “communication network” refers to a network following any suitable communication standards, such as Long Term Evolution (LTE) , LTE-Advanced (LTE-A) , Wideband Code Division Multiple Access (WCDMA) , High-Speed Packet Access (HSPA) , Narrow Band Internet of Things (NB-IoT) and so on. Furthermore, the communications between a terminal device and a network device in the communication network may be performed according to any suitable generation communication protocols, including, but not limited to, the first generation (1G) , the second generation (2G) , 2.5G, 2.75G, the third generation (3G) , the fourth generation (4G) , 4.5G, the future fifth generation (5G) communication protocols, and/or any other protocols either currently known or to be developed in the future. Embodiments of the present disclosure may be applied in various communication systems. Given the rapid development in communications, there will of course also be future type communication technologies and systems with which the present disclosure may be embodied. It should not be seen as limiting the scope of the present disclosure to only the aforementioned system.

As used herein, the term “network device” refers to a node in a communication network via which a terminal device accesses the network and receives services therefrom. The network device may refer to a base station (BS) or an access point (AP) , for example, a node B (NodeB or NB) , an evolved NodeB (eNodeB or eNB) , a NR NB (also referred to as a gNB) , a gNB distributed unit (gNB-DU) , a gNB central unit (gNB-CU) , a Remote Radio Unit (RRU) , a radio header (RH) , a remote radio head (RRH) , a relay, a low power node such as a femto, a pico, and so forth, depending on the applied terminology and technology.

The term “terminal device” refers to any end device that may be capable of wireless communication. By way of example rather than limitation, a terminal device may also be referred to as a communication device, user equipment (UE) , a Subscriber Station (SS) , a Portable Subscriber Station, a Mobile Station (MS) , or an Access Terminal (AT) . The terminal device may include, but not limited to, a mobile phone, a cellular phone, a smart phone, voice over IP (VoIP) phones, wireless local loop phones, a tablet, a wearable terminal device, a personal digital assistant (PDA) , portable computers, desktop computer, image capture terminal devices such as digital cameras, gaming terminal devices, music storage and playback appliances, vehicle-mounted wireless terminal devices, wireless endpoints, mobile stations, laptop-embedded equipment (LEE) , laptop-mounted equipment (LME) , USB dongles, smart devices, wireless customer-premises equipment (CPE) , an Internet of Things (loT) device, a watch or other wearable, a head-mounted display (HMD) , a vehicle, a drone, a medical device and applications (e.g., remote surgery) , an industrial device and applications (e.g., a robot and/or other wireless devices operating in an industrial and/or an automated processing chain contexts) , a consumer electronics device, a device operating on commercial and/or industrial wireless networks, and the like. In the following description, the terms “terminal device” , “communication device” , “terminal” , “user equipment” and “UE” may be used interchangeably.

Example embodiments of the present disclosure are directed to a radio access network with wireless backhaul of the access points. The backhaul can be multi-hop or meshed. An important application of embodiments of the present disclosure is for IAB communication in a 3GPP IAB network with terminal devices, IAB nodes and IAB donor nodes. In the following, embodiments of the present disclosure will be described with reference to the 3GPP IAB network. It is to be understood that embodiments of the present disclosure may also be applied to any other network with wireless backhaul.

Fig. 1A shows an example communication network 100 in which example embodiments of the present disclosure can be implemented. As shown in Fig. 1A, the communication network 100 includes a core network (CN) 110, a first IAB donor 120-1 and a second IAB donor 120-2 (collectively referred to as “IAB donors 120” or individually referred to as “IAB donor 120” ) , an IAB node 130, and a terminal device 150. As used herein, the terms “IAB node” , “IAB-node” and “IAB device” can be used interchangeably. The terms “IAB donor node” , “IAB donor” , “IAB-donor” and “IAB donor device” can be used interchangeably.

In the example architecture of Fig. 1A, the IAB donors 120 are in communication with the CN 110. The IAB node 130 is connected to one of the IAB donors 120. The terminal device 150 accesses the communication network 100 via the IAB node 130. In some embodiments, the IAB node 130 may be connected to one of the IAB donors 120 directly. Alternatively, the IAB node 130 may be connected to one of the IAB donors 120 via one or more parent IAB nodes that are chained over multiple wireless backhaul hops (not shown) . The IAB donor 120 may also serve terminal devices directly connected thereto (not shown) .

The CN 110 may include one or more core network elements that provide different network functions, for example, Mobility Management Entity (MME) , Network Slice Selection Function (NSSF) , Unified Data Repository (UDM) , Access and Mobility Management Function (AMF) , Operation Administration and Maintenance (OAM) , Network Repository Function (NRF) , Session Management Function (SMF) , Policy Control Function (PCF) , Network Exposure Function (NEF) and so on. IAB-donors may communicate with core network elements (such as one or more AMFs) in the CN 110.

In the example communication network 100, the CN interfaces are terminated at the IAB donors 120 and therefore the relaying is radio access network (RAN) functionality. The architecture leverages a split gNB architecture for the CU and DU so that the CU functions are at the IAB donor 120 and the DU functions are at the IAB donor 120 or at the IAB node 130. For the connection setup and communication with the parent node (which can be another IAB node or the IAB donor) , the IAB node 130 hosts the MT function corresponding to UE operation or a part of the UE operation.

The first IAB donor 120-1 may include an IAB-donor-CU 121-1 and an IAB-donor-DU 122-1. The first IAB donor 120-1 may include multiple IAB-donor-DUs. It is to be understood that the IAB-donor-CU 121-1 and the IAB-donor-DU 122-1 may be implemented in the same device, or in different devices. The IAB-donor-CU 121-1 may further include a CU-Control Plane (CU-CP) and one or more CU-User Plane (CU-UP) . It is to be understood that the CU-CP and CU-UP may be implemented in the same device, or in different devices. Similarly, the second IAB donor 120-2 may include an IAB-donor-CU 121-2 and an IAB-donor-DU 122-2. The second IAB donor 120-2 may include multiple IAB-donor-DUs. The IAB-donor-CU 121-1 and 121-2 may be collectively referred to as “IAB-donor-CUs 121” or individually referred to as “IAB-donor-CU 121” . The IAB-donor-DU 122-1 and 122-2 may be collectively referred to as “IAB-donor-DUs 122” or individually referred to as “IAB-donor-DU 122” . The IAB-donor-CU 121-1 and the IAB-donor-CU 121-2 may communicate with each other via an Xn interface. It should be appreciated that the Xn interface is just an example; any appropriate communication interface may be used between the first IAB donor 120-1 and the second IAB donor 120-2.

The IAB node 130 may include a MT part 131 (also referred to as “IAB-UE 131” ) and a DU part 132 (also referred to as “gNB-DU 132” or “IAB-DU 132” ) . The MT part of an IAB node maintains connectivity with one or more upstream nodes (using for example, dual connectivity) . The IAB node 130 may include one or multiple IAB-DUs.

A CU (e.g., an IAB-donor-CU 121) may be a logical node which may include the functions (for example, gNB functions) such as transfer of user data, mobility control, radio access network sharing, positioning, session management etc., except those functions allocated exclusively to DUs. A CU terminates the radio resource control (RRC) connection of an IAB-UE via Uu interface. The CU may control the operation of the DUs over a front-haul (F1) interface, i.e. the CU terminates the F1 connection of the IAB-DU. A DU (e.g., an IAB-donor-DU 122 or a IAB-DU 132) is a logical node which may include a subset of the functions (for example, gNB functions) . It can be different CU that terminates the IAB-UE’s RRC connection, and terminates the co-located IAB-DU’s F1 connection. For example, at IAB integration phase, it may be same CU that terminates the RRC connection of the IAB-UE and the F1 connection of the co-located IAB-DU. Then the IAB performs partial migration and sets up RRC connection with a different CU, while the co-located IAB-DU’s F1 connections remains terminated at the previous CU.

Backhaul radio link control (RLC) channel (s) can be set up between the IAB-UE 131 and a DU of the parent node and an adaptation layer called a Backhaul Adaptation Protocol (BAP) is agreed to be on top of a RLC layer. The IAB-DU 132 connects to the IAB-donor-CU 121 with an F1 interface which supports IAB functions. For example, when the IAB node 130 is connected to the first IAB donor 120-1, the IAB-DU 132 sets up a F1 connection 161 with the IAB-donor-CU 121-1; and when the IAB node 130 is connected to the second IAB donor 120-2, the IAB-DU 132 sets up a F1 interface/connection 162 with the IAB-donor-CU 121-2. The F1 interface/connection may include a F1-C interface/connection and a F1-U interface/connection, via which the IAB-DU connects to the IAB-donor-CU-CP and to the IAB-donor-CU-UP, respectively. It is also possible that the IAB node 130 connects with a different IAB donor (for example IAB donor 120-3 not shown in the figure) , and the IAB-DU 132 sets up a F1 connection 161 with the IAB-donor-CU 121-1 or the IAB-DU 132 sets up a F1 connection 162 with the IAB-donor-CU 121-2. In other words, it may be same or different IAB-donor-CU that terminates the RRC connection of the IAB-UE 131, and terminates the F1 connection of the IAB-DU 132.

The IAB-node may support a NR Uu radio interface, referred to as MT functionality, to connect to the DU of a parent IAB-node or the IAB-donor, and to connect to the gNB-CU on the IAB-donor via radio resource control (RRC) signaling. Similar to a conventional user equipment, the IAB node may use RRC signaling to supply radio link measurements of alternative upstream nodes to its current serving CU. A migration of the IAB node may be performed. For example, a handover is performed for the IAB-UE based on signal strength, signal quality and other factors. Hence, the IAB topology, such as the one as shown in Fig. 1A, may be non-static. As a result of the migration, the IAB node 130 may change the parent node from a source parent node device (e.g., the first IAB donor 120-1) to a target parent node device (e.g., the second IAB donor 120-2) after the migration. The IAB topology may change over time as radio conditions fluctuate and as the IAB nodes move or are added or removed. Accordingly, the IAB node 130 may be configured with a new cell identifier. The cell identifier may be used by the IAB node 130 operating as a RAN node to facilitate the terminal device 150 and/or other child IAB nodes camping on and utilizing services.

For example, the cell identifier may be a radio cell global identifier (NR CGI) . The NR CGI information element (IE) is related to the gNB identity (ID) and may be used to globally identify an NR cell. The gNB ID is also referred as Global NG-RAN Node ID. The NR CGI IE may include a public land mobile network (PLMN) identity IE and a NR cell identity IE. The leftmost bits of the NR cell identity IE corresponds to the gNB ID.

Each of the IAB-DU 132 and IAB-donor-DUs 122 can provide one or more cells to serve terminal devices and/or IAB-UEs. For example, as shown in Fig. 1A, at T1, the IAB node 130 may be connected to the first IAB donor 120-1, and the IAB-UE 131 may be served by the IAB-donor-DU 122-1. The IAB-DU 132 may be configured/associated with a cell identifier NR CGI #X. The IAB-DU 132 uses NR CGI #X when it sets up F1 connection with IAB-donor-CU 121-1. The IAB-DU 132 broadcast NR CGI #X over the Uu interface and the terminal device 150 and other child IAB nodes may access the cell 141 provided by the IAB-DU 132. At T2, the IAB node 130 may be disconnected from the first IAB donor 120-1 and connected to the second IAB donor 120-2, and the IAB-UE 131 may be served by the IAB-donor-DU 122-2. The IAB-DU 132 may be configured/associated with a new cell identifier NR CGI #Y, and uses it during the F1 setup with IAB-donor-CU 121-2. The IAB-DU 132 broadcasts NR CGI #Y over the Uu interface and the terminal device 150 and other child IAB nodes may access the cell 142 provided by the IAB-DU 132.

It is to be understood that the architecture of the network 100 shown in Fig. 1A is described only for the purpose of illustration without suggesting any limitation. In addition, it is to be understood that the numbers of IAB donors, IAB nodes and terminal devices and their connections shown in Fig. 1A are only for the purpose of illustration without suggesting any limitations. The network 100 may include any suitable number of IAB donors, IAB nodes, terminal devices and other devices adapted for implementing example embodiments of the present disclosure. Although not shown, it would be appreciated that one or more additional devices may be deployed in the network 100.

Communications in the communication system 100 may be implemented according to any proper communication protocol (s) , comprising, but not limited to, cellular communication protocols of the first generation (1G) , the second generation (2G) , the third generation (3G) , the fourth generation (4G) and the fifth generation (5G) and on the like, wireless local network communication protocols such as Institute for Electrical and Electronics Engineers (IEEE) 802.11 and the like, and/or any other protocols currently known or to be developed in the future. Moreover, the communication may utilize any proper wireless communication technology, comprising but not limited to: Code Division Multiple Access (CDMA) , Frequency Division Multiple Access (FDMA) , Time Division Multiple Access (TDMA) , Frequency Division Duplex (FDD) , Time Division Duplex (TDD) , Multiple-Input Multiple-Output (MIMO) , Orthogonal Frequency Division Multiple (OFDM) , Discrete Fourier Transform spread OFDM (DFT-s-OFDM) and/or any other technologies currently known or to be developed in the future.

Mobile IAB technology is a Rel-18 work item (WI) in 3GPP. As a mobile IAB relay base station, when installed on a vehicle (such as high-speed railway, bus, or ship) , the mobile IAB node can provide a high-quality instant communication service for passenger users. The trajectory of the mobile IAB node may be predefined or randomly dynamic. For example, the IAB node 130 in Fig. 1A may be a mobile IAB node, e.g., installed on a vehicle, and may migrate from the first IAB donor 120-1 to the second IAB donor 120-2 when the vehicle moves. During the migration or before the migration, the terminal device on board the vehicle may transition to a RRC idle state. After the migration, a downlink data may need to be transmitted to the terminal device. Since the terminal device has transitioned to a RRC idle state, the terminal device needs to be paged.

A paging optimization procedure is defined in TS23.502. The AMF and the (R)AN may support further paging optimizations in order to reduce the signaling load and the network resources used to successfully page a UE by one or several of the following means:

- by the AMF implementing specific paging strategies (e.g. the N2 paging message is sent to the (R) AN nodes that served the UE last) ;

- by the AMF considering Information On Recommended Cells And NG-RAN nodes provided by the (R) AN at transition to CM-IDLE state. The AMF takes the (R) AN nodes related part of this information into account to determine the (R) AN nodes to be paged and provides the information on recommended cells within the N2 paging message to each of these (R) AN nodes;

- by the (R) AN considering the Paging Attempt Count Information provided by the AMF at paging.

An NGAP UE CONTEXT RELEASE COMPLETE message may be transmitted to an AMF indicating that the release of a connection between the terminal device and the gNB is completed. The NGAP UE CONTEXT RELEASE COMPLETE message includes Information on Recommended Cells and RAN Nodes for Paging IE. The Information on Recommended Cells and RAN Nodes for Paging IE provides information on recommended cells and NG-RAN nodes for paging. Figs. 1B and 1C show the Recommended RAN Nodes for Paging IE and the Recommended Cells for Paging IE in the Information on Recommended Cells and RAN Nodes for Paging IE, respectively. The AMF may save the received information in UE context of the terminal device, and use it later when need to transmit a NGAP paging message to page the terminal device based on the UE context. The NGAP paging message includes Assistance Data for Paging IE, which further includes Recommended Cells for Paging IE. For example, the AMF may send the NGAP paging message to the recommended RAN nodes and request the RAN node to perform paging in the recommended cells, thus avoid sending the NGAP paging message (s) to all RAN node (s) , and RAN node paging the UE in all cell (s) belonging to the UE’s registration area. However, the paging optimization procedure doesn’ t work in the mobile IAB network.

As described above with reference to Fig. 1A, at T1, when the IAB-DU 132 is connected with the first IAB donor 120-1, the IAB-DU 132 uses an identifier NR CGI #X, which is related to a gNB ID of the first IAB donor 120-1. The terminal device 150 on board the vehicle may then transition to a RRC idle state. When the terminal device 150 transitions to the RRC idle state, the first IAB donor 120-1 may transmit a UE CONTEXT RELEASE COMPLETE message to an AMF in the CN 110 indicating that the release of a connection between the terminal device 150 and the first IAB donor 120-1 is completed. The UE CONTEXT RELEASE COMPLETE message may include the Recommended Cell NR CGI#X, and Recommended RAN node ID for the first IAB donor 120-1 indicating that the last visited NG-RAN node is the first IAB donor 120-1. The AMF save the received information in UE context of the terminal device 150.

The first IAB donor 120-1 may also include the non-visited NG-RAN nodes/cells.

At T2, the IAB node 130 is full migrated to the second IAB donor 120-2. The terminal device 150 on board the vehicle may move with the IAB node 130. When a full migration is performed, the IAB-DU needs to change the NR CGI to align with the target IAB donor. The IAB-DU 132 thus stops to use the NR CGI#X, then uses a new NR CGI #Y, which is related to a gNB ID of the second IAB donor 120-2. For example, the IAB-DU 132 may initiate a F1 Removal procedure to deactivate the cell 141 or a gNB-DU Configuration Update procedure to delete the cell 141. The IAB-DU 132 uses the new NR CGI #Y when setting up a F1 connection with IAB-donor-CU 121-2.

At T3, a downlink data may need to be transmitted to the terminal device 150. Since the terminal device 150 is in a RRC idle state, the terminal device 150 needs to be paged. For example, the AMF in the CN 110 may initiate a network triggered service request. In the network triggered service request, the AMF may send a paging message to eNB(s) or gNB (s) to page the terminal device 150. The AMF may check the stored UE context for the terminal device 150. Since the recommended RAN node ID is the gNB ID of the first IAB donor 120-1, the AMF may send a paging message to the first IAB donor 120-1. Since the recommended cell is NR CGI#X, the paging message may include NR CGI#X.

However, the paging message should not be sent to the first IAB donor 120-1, since the terminal device 150 moves with the IAB node 130 and the IAB node 130 is now connected with the second IAB donor 120-2. The paging message should be sent to the second IAB donor 120-2. In addition, even if the first IAB donor 120-1 receives the paging message, the first IAB donor 120-1 would not be able to transmit the paging message to the IAB-DU 132 to perform the paging, since the IAB-DU 132 is migrated to the second IAB donor 120-2, and NR CGI#X is deactivated after the IAB node 130 migrated to the second IAB donor 120-2. Even if the first IAB donor 120-1 transmits the paging message to all cells, the paging will probably fail, since the terminal device 150 has already left. A solution is needed to support the paging optimization when the terminal device moves with the IAB node and the IAB node has performed a full migration to a different IAB-donor.

The tracking area code (TAC) of the IAB-DU may or may not be changed depending on configuration. In some embodiments of the present disclosure, it is assumed the IAB-DU’s TAC remains unchanged. Principle and embodiments of the present disclosure will be described in detail below with reference to the accompanying drawings.

Reference is now made to Fig. 2, which shows a communication process 200 according to an embodiment of the present disclosure. For the purpose of discussion, the process 200 will be described with reference to Fig. 1A. The process 200 may involve the IAB node 130 as illustrated in Fig. 1A. In some embodiments, the process 200 may also involve the first IAB donor 120-1, the second IAB donor 120-2 or the CN 110 as illustrated in Fig. 1A. The network device 210 may correspond to one of the first IAB donor 120-1, the second IAB donor 120-2 or the CN 110. It would be appreciated that although the process 200 has been described in the communication system 100 of Fig. 1A, this process may be likewise applied to other communication scenarios.

In the process 200, the IAB node 130 performs a migration (202) from the first IAB donor 120-1 to the second IAB donor 120-2. The IAB node 130 transmits (204) , to the network device 210, a message 206 comprising a first set of identifiers associated with a connection between the IAB node 130 and the first IAB donor 120-1 and a second set of identifiers associated with a connection between the IAB node 130 and the second IAB donor 120-2. The network device 210 receives (208) the message. In this way, when a migration of the IAB node happens, both the original (or old) identifier (s) associated with the original connection (or old connection) and the new identifier (s) associated with the connection after migration may be reported to the network device, which may improve the reliability of the IAB communication, especially for mobile IAB networks.

In some embodiments, the first set of identifiers may comprise an identifier of a cell associated with the connection between the IAB node 130 and the first IAB donor 120-1, for example, a cell identifier associated with the F1 connection between the IAB-DU 132 and the first IAB-donor-CU 121-1. In one example, it is the cell identifier provided by the IAB-DU 132 to the first IAB-donor-CU 121-1 during the F1 setup procedure, or F1 gNB-DU configuration update procedure. Alternatively or additionally, the first set of identifiers may comprise an identifier of the first IAB donor 120-1, for example, a Global NG-RAN Node ID of the first IAB donor 120-1. In other words, the first set of identifiers is the original identifier (s) which may correspond to the last visited RAN nodes and/or cells of the terminal device. In some embodiments, the second set of identifiers may comprise an identifier of a cell associated with the connection between the IAB node 130 and the second IAB donor 120-2, for example, a cell identifier associated with the F1 connection between the IAB-DU 132 and the first IAB donor-CU 121-2. In one example, it is the cell identifier provided by the IAB-DU 132 to the second IAB-donor-CU 121-2 during the F1 setup procedure, or F1 gNB-DU configuration update procedure. Alternatively or additionally, the second set of identifiers may comprise an identifier of the second IAB donor 120-2, for example, a Global NG-RAN Node ID of the first IAB donor 120-2. In other words, the second set of identifiers is the new identifier (s) which may correspond to the RAN nodes and/or cells currently associated with the IAB node. In this way, when a migration of the IAB node happens, both the original identifier (s) and the new identifier (s) may be reported, which facilitates updating the recommended RAN nodes and/or cells for the terminal device.

In some embodiments, the network device 210 may be the first IAB donor 120-1. Alternatively, the network device 210 may be the second IAB donor 120-2. Alternatively, the network device 210 may be an AMF in the CN 110. In some embodiments, the AMF may be associated with the IAB node 130. In some embodiments, the message may be a request message for updating context information of terminal devices.

Fig. 3 illustrates an example of a communication process 300 according to an embodiment of the present disclosure. For the purpose of discussion, the process 300 will be described with reference to Fig. 1A. The process 300 may involve at least one of the IAB node 130, the first IAB donor 120-1, the second IAB donor 120-2 or the CN 110 as illustrated in Fig. 1A. The first network device 310 may correspond to one of the first IAB donor 120-1 or the second IAB donor 120-2. Alternatively, the first network device 310 may correspond to the CN 110, e.g., an AMF serving the IAB-UE 130 in the CN 110. The second network device 320 may correspond to the CN 110, e.g., an AMF that maintains context for a terminal device in the CN 110. It would be appreciated that although the process 300 has been described in the communication system 100 of Fig. 1A, this process may be likewise applied to other communication scenarios.

In the process 300, the first network device 310 obtains (302) a first set of identifiers associated with a connection between an integrated access backhaul (IAB) node and a first IAB donor 120-1 and a second set of identifiers associated with a connection between the IAB node 130 and a second IAB donor 120-2. The first network device 310 transmits (304) , to the second network device 320, a message 306 comprising the first set of identifiers and the second set of identifiers. The second network device 320 receives (308) the message 306 from the first network device 310. The second network device 320 determines (312) that context information of at least one terminal device comprises the first set of identifiers. Based on determining that context information of at least one terminal device comprises the first set of identifiers, the second network device 320 stores (314) the second set of identifiers in the context information of the at least one terminal device. The at least one terminal device is in an idle state. In some embodiments, the idle state may also referred as radio resource control (RRC) idle state, or connection management (CM) idle state, or 5GS mobility management (5GMM) IDLE mode or state. In this way, the network device may be aware of the new identifier (s) associated with the connection after migration and its mapping relation with the original identifier (s) associated with the original connection. Thus, the new identifiers may be stored in the context information of the terminal devices in an idle state, which may improve the reliability of the IAB communication, especially for mobile IAB networks.

In some embodiments, the first set of identifiers may comprise an identifier of a cell associated with the connection between the IAB node 130 and the first IAB donor 120-1, for example, a cell identifier associated with the F1 connection between the IAB-DU 132 and the first IAB-donor-CU 121-1. Alternatively or additionally, the first set of identifiers may comprise an identifier of the first IAB donor 120-1, for example, a Global NG-RAN Node ID of the first IAB donor 120-1. In other words, the first set of identifiers is the original identifier (s) which may correspond to the last visited RAN nodes and/or cells of the terminal device. In some embodiments, the second set of identifiers may comprise an identifier of a cell associated with the connection between the IAB node 130 and the second IAB donor 120-2, for example, a cell identifier associated with the F1 connection between the IAB-DU 132 and the first IAB donor-CU 121-2. Alternatively or additionally, the second set of identifiers may comprise an identifier of the second IAB donor 120-2, for example, a Global NG-RAN Node ID of the second IAB donor 120-2. In other words, the second set of identifiers is the new identifier (s) which may correspond to the RAN nodes and/or cells currently associated with the IAB node. In this way, when a migration of the IAB node happens, both the original identifier (s) and the new identifier (s) may be reported, which facilitates updating the recommended RAN nodes and/or cells for the terminal device.

In some embodiments, the first network device 310 may be the first IAB donor 120-1. The message may be a first message. In order to obtain the first set of identifiers and the second set of identifiers, the first IAB donor 120-1 may receive a second message comprising the first set of identifiers and the second set of identifiers from the IAB node 130.

In some embodiments, the first network device 310 may be the second IAB donor 120-2. The message may be a first message. In order to obtain the first set of identifiers and the second set of identifiers, the second IAB donor 120-2 may receive the first set of identifiers from the first IAB donor 120-1 and receive a second message comprising the second set of identifiers from the IAB node 130.

In some embodiments, the first network device 310 may be the second IAB donor 120-2. The message may be a first message. In order to obtain the first set of identifiers and the second set of identifiers, the second IAB donor 120-2 may receive a second message comprising the first set of identifiers and the second set of identifiers from the IAB node 130 or the first IAB donor 120-1.

In some embodiments, the first network device 310 may be an AMF in the CN 110. In some embodiments, the AMF may be associated with the IAB node 130, for example, the AMF serving the IAB-UE 131. In some embodiments, the message may be a first message. In order to obtain the first set of identifiers and the second set of identifiers, the AMF may receive a second message comprising the first set of identifiers and the second set of identifiers from the IAB node 130, or from the first IAB donor 120-1, or from the second IAB donor 120-2.

In some embodiments, the first message may be transmitted to the second network device 320 based on the second message received from the IAB node 130. In some embodiments, the first message may be transmitted to the second network device 320 based on the first network device 310’s decision. In some embodiments, the second message received from the IAB node 130 may be a request message for updating context information of terminal devices.

In some embodiments, the first network device may be the first IAB donor 120-1. In some embodiments, the second network device 320 may comprise at least one AMF in the CN 110. In some embodiments, the second network device 320 may transmit a paging message for the at least one terminal device based on the context information.

In some embodiments, in order to store the second set of identifiers in the context information, the second network device 320 may store, in addition to the first set of identifiers, the second set of identifiers in the context information of the at least one terminal device. In this way, both the original identifier (s) corresponding to the last visited RAN nodes and/or cells of the terminal device and the new identifier (s) corresponding to the RAN nodes and/or cells currently associated with the IAB node may be stored in the context information of the terminal device. Thus, paging messages for the terminal device may be transmitted to the RAN nodes and/or cells currently associated with the IAB node, or both the last visited RAN nodes and/or cells of the terminal device and the RAN nodes and/or cells currently associated with the IAB node, which improves the reliability of the IAB communication.

In some embodiments, in order to store the second set of identifiers in the context information, the second network device 320 may store the second set of identifiers to replace the first set of identifiers in the context information of the at least one terminal device. In this way, the original identifier (s) may be replaced with the new identifier (s) in the context information of the terminal device. Thus, paging messages for the terminal device may be transmitted to the RAN nodes and/or cells currently associated with the IAB node without transmission to the RAN nodes and/or cells associated with the IAB node prior to the IAB migration, which improves the reliability of the IAB communication with reduced resource cost.

Fig. 4A illustrates an example implementation of a process 400A for communication according to embodiments of the present disclosure. It is noted that the process 400A can be considered as a more specific example of the process 200 of Fig. 2 and the process 300 of Fig. 3 applied into an IAB network. The example implementation of Fig. 4A is depicted and will be described from perspectives of a UE1 450, an IAB node 430, an IAB donor (IAB-donor1) 420-1, an IAB donor (IAB-donor2) 420-2, and a CN device (AMF (UE) ) 410-1. More particularly, the IAB node 430 may be a mobile IAB node. The UE1 450 may be on board of a vehicle on which the IAB node 430 is mounted. The AMF (UE) 410-1 is an AMF node that terminates the NAS procedure of the UE (for example, the UE1 450) . It should be understood that the UE1 450, the IAB node 430, the IAB-donor1 420-1, the IAB-donor2 420-2 and the AMF (UE) 410-1 may correspond to the terminal device 150, the IAB node 130, the first IAB donor 120-1, the second IAB donor 120-2 and the CN 110 in Fig. 1A, respectively. The AMF (UE) 410-1 may be the AMF associated with the UE1 450. It is to be understood that process 400A may further include additional blocks not shown and/or omit some shown blocks, and the scope of the present disclosure is not limited in this regard.

In the process flow 400A, at 404, the IAB-DU of the IAB node 430 may set up a F1 interface/connection 402 with the IAB-donor1 420-1. A F1 SETUP REQUEST message may include a cell ID of the IAB-DU of the IAB node 430. The cell ID of the IAB-DU of the IAB node 430 may be NR CGI #X that is related to the IAB-donor1 420-1. At 406, the UE1 450 may be connected to the IAB node 430. The IAB-DU of the IAB node 430 may start to serve the UE1 450 using the cell ID NR CGI #X. At 408, the UE1 450 may transition to a RRC idle state. At 414, as part of the UE context release procedure, the IAB-donor1 420-1 may send a UE CONTEXT RELEASE COMPLETE message 412 to the AMF (UE) 410-1. The UE CONTEXT RELEASE COMPLETE message 412 may include information indicating that the recommended NG-RAN node is the IAB-donor1 420-1, and recommend cell is NR CGI #X. The AMF (UE) 410-1 may save such information for the UE1 450. In particular, the AMF (UE) 410-1 may save the following context for the UE1 450: recommended NG-RAN node is the IAB-donor1 420-1; and recommended cell is NR CGI#X.

At 416, the IAB node 430 may perform a full migration from the IAB-donor1 420-1 to the IAB-donor2 420-2. At 418, the IAB-DU 132 may set up a F1 interface/connection with the IAB-donor2 420-2. The F1 SETUP REQUEST message 422 may include a cell ID of the IAB-DU of the IAB node 430. The cell ID of the IAB-DU of the IAB node 430 may be NR CGI #Y that is related to the IAB-donor2 420-2. During the migration, the UE1 450 may stay in the vehicle. In some embodiments, the cell ID of the IAB-DU of the IAB node 430 may be configured by OAM in the CN or by some other method, so that the IAB-donor2 is aware of the NR CGI #Y during the F1 setup between IAB node 430 and IAB-donor2 420-2.

At 426, the IAB node 430 may initiate a first request procedure via RRC or F1 interface to update the context for UE (s) in an idle state. The first request message 424 may include old NR CGI, old IAB-donor ID, new NR CGI and new IAB-donor ID of the IAB node 430. The old NR CGI of the IAB node 430 may include the NR CGI #X used by the IAB node 430 for F1 setup with the IAB-donor1 420-1. The old IAB-donor ID of the IAB node 430 may include gNB ID of the IAB-donor1 420-1. The new NR CGI of the IAB node 430 may include the NR CGI #Y used by the IAB node 430 for F1 setup with the IAB-donor2 420-2. The new IAB-donor ID may include gNB ID of the IAB-donor2 420-2.

In some embodiments, the IAB node 430 does not maintain any context for UE (s) in an idle state. The IAB node 430 initiates the first request procedure irrespective of the number of UE (s) in an idle state. In other words, the first request procedure is not UE specific. The first request procedure may be performed via non-UE associated signaling. The first request message 424 does not contain any UE ID.

At 432, the IAB-donor2 420-2 may initiate a second request procedure to a connected AMF, e.g., the AMF (UE) 410-1. The second request message 428 may include old NR CGI (i.e. #X) , old IAB-donor ID (i.e., gNB ID of the IAB-donor1 420-1) , new NR CGI (i.e. #Y) , new IAB-donor ID (i.e., gNB ID of the IAB-donor2 420-2) of the IAB node 430.

In some embodiments, it is assumed the AMF of the UE1 450 remains unchanged during the full migration of the IAB node 430. In some embodiments, if the UE1 450 is out of the service area of its previous AMF, the UE1 450 may first perform a registration update procedure.

In some embodiments, the IAB-donor2 420-2 may initiate the second request procedure either based on its own decision, or based on the first request message 424 received from the IAB node 430. In some embodiments, the IAB-donor2 420-2 may obtain the old NR CGI and old IAB-donor ID via other means (e.g. the IAB-donor1 420-1 provides the related information to the IAB-donor2 420-2 via an Xn interface) and perform the second request procedure based on its own decision.

In some embodiments, the IAB-donor does not maintain any context for UEs in an idle state. The IAB-donor2 420-2 may initiate second request procedure irrespective of the number of UE (s) in an idle state. In other words, the second request procedure is not UE specific. The second request procedure may be performed via non-UE associated signaling. The second request message 428 does not contain any UE ID.

In some embodiments, the IAB node may transmit the first request message 424 to the IAB-donor1 420-1, and the IAB-donor1 420-1 may then initiate a request procedure to the AMF (UE) 410-1.

At 434, upon the reception of the second request message 428, the AMF (UE) 410-1 may update the context for (any) UEs. In some embodiments, if the context of a UE includes a recommended cell associated with NR CGI #X, the AMF (UE) 410-1 may replace the NR CGI #X with the new NR CGI#Y in the UE context. The AMF (UE) 410-1 may also update the recommended NG-RAN node information with the gNB ID of the IAB-donor2 420-2. For example, the AMF (UE) 410-1 may then store following updated context for the UE1 450: recommended NG-RAN node is the IAB-donor2 420-2; and recommended cell is NR CGI#Y.

In some embodiments, the AMF (UE) 410-1 may save the identifiers of the new recommended NG-RAN node/recommended cell as additional recommended NG-RAN node/cell information. In other words, the AMF (UE) 410-1 may store following updated context for the UE1 450: recommended NG-RAN nodes are the IAB-donor2 420-2 and the IAB-donor1 420-1; and recommended cells are NR CGI #Y and #X.

In some embodiments, the second request message 428 may be transmitted to multiple AMFs connected to the IAB-donor2 420-2, e.g. in case of network sharing, or in case that the IAB-donor2 420-2 is connected to all AMFs of AMF set (s) within an AMF region. For example, the contexts of different UEs in idle state may be maintained in different AMFs. The IAB-donor2 420-2 may initiate the second request procedure towards all connected AMFs.

In some embodiments, the IAB node 430 may further full migrate to another IAB donor (e.g., IAB-donor3) , steps similar to steps 416, 418, 426, 432 and 434 may be performed. The UE context stored in the AMF (e.g. recommended NG-RAN node (s) and recommended cell (s) of the UE1 450) may be updated accordingly.

At 436, the AMF (UE) 410-1 may determine that there is a need to page the UE1 450, e.g. due to a network triggered service request. At 438, based on the updated recommended NG-RAN node information and recommended cell information, the AMF (UE) 410-1 may transmit a paging message 442 including the recommended cell NR CGI#Y to the IAB-donor2 420-2. In some embodiments, a legacy paging procedure may be performed. For example, at 446, based on the recommended cell NR CGI#Y in the paging message 442, the IAB-donor2 420-2 may transmit a paging message 444 including the recommended cell NR CGI#Y to the IAB node 430. At 452, based on the recommended cell NR CGI#Y in the paging message 444, the IAB node 430 may transmit a paging message 448 to page the UE1 450. Thus, the paging of the UE1 450 may be successfully performed via the IAB-donor2 420-2 and the IAB node 430.

Through the process 400A, the UE context for an UE in idle state previously connected to an IAB node may be updated from reflecting the NG-RAN node of the IAB-donor who served the IAB node before IAB migration to (also) reflecting the updated cell ID of the IAB-node and the NG-RAN node of IAB-donor currently connected to the IAB-node. Paging of the UE may thus be successfully performed based on the updated UE context. In this way, the paging optimization may be reused for a mobile IAB network and the current standard may be reused with very limited changes.

Fig. 4B illustrates another example implementation of a process 400B for communication according to embodiments of the present disclosure. It is noted that the process 400B can be considered as a more specific example of the process 200 of Fig. 2 and the process 300 of Fig. 3 applied into an IAB network. The example implementation of Fig. 4B is depicted and will be described from perspectives of a UE1 450, an IAB node 430, an IAB donor (IAB-donor1) 420-1, an IAB donor (IAB-donor2) 420-2, a CN device (AMF (UE) ) 410-1 and a CN device (AMF (IAB) ) 410-2. More particularly, the IAB node 430 may be a mobile IAB node. The UE1 450 may be on board of a vehicle on which the IAB node 430 is mounted. The AMF (IAB) 410-2 is an AMF node that terminates the NAS procedure of the IAB-MT (for example, the IAB-UE of the IAB node 430) . The AMF (UE) 410-1 is an AMF node that terminates the NAS procedure of the UE (for example, the UE1 450) . The AMF (IAB) and AMF (UE) may be the same AMF node or different AMF nodes. It should be understood that the UE1 450, the IAB node 430, the IAB-donor1 420-1, the IAB-donor2 420-2 may correspond to the terminal device 150, the IAB node 130, the first IAB donor 120-1 and the second IAB donor 120-2 in Fig. 1A, respectively. The AMF (UE) 410-1 and the AMF (IAB) 410-2 may be AMFs associated with the UE1 450 and the IAB node 430, respectively, in the CN 110 in Fig. 1A. Similar reference numerals are used to denote the steps or components described in Fig. 4B having the same operations as the steps or components described in Fig. 4A, and detailed description thereof will be omitted. It is to be understood that process 400B may further include additional blocks not shown and/or omit some shown blocks, and the scope of the present disclosure is not limited in this regard.

In the process 400B, at 426’ , the IAB node 430 may transmit the first request message 424 to the AMF (IAB) 410-2 via non-access stratum (NAS) signaling. At 432’ , the AMF (IAB) 410-2 may inform the AMF (UE) 410-1 about the request message. In some embodiments, the AMF (IAB) 410-2 may be aware of the address of the AMF (UE) 410-1. In some embodiments, the AMF (UE) 410-1 and the AMF (IAB) 410-2 may be the same AMF and the step 432’ may thus be omitted.

Fig. 5 shows a flowchart of an example method 500 implemented at an IAB node in accordance with some embodiments of the present disclosure. For the purpose of discussion, the method 500 will be described from the perspective of the IAB node 130 with reference to Fig. 1A.

At block 510, the IAB node 130 performs a migration from a first IAB donor to a second IAB donor. At block 520, the IAB node 130 transmits, to a network device, a message comprising a first set of identifiers associated with a connection between the IAB node 130 and the first IAB donor and a second set of identifiers associated with a connection between the IAB node 130 and the second IAB donor.

In some embodiments, the first set of identifiers may comprise an identifier of a cell associated with the connection between the IAB node 130 and the first IAB donor. Alternatively or additionally, the first set of identifiers may comprise an identifier of the first IAB donor. In some embodiments, the second set of identifiers may comprise an identifier of a cell associated with the connection between the IAB node 130 and the second IAB donor. Alternatively or additionally, the second set of identifiers may comprise an identifier of the second IAB donor.

In some embodiments, the network device may be the first IAB donor. Alternatively, the network device may be the second IAB donor. Alternatively, the network device may be an access and mobility management function (AMF) . In some embodiments, the message may be a request message for updating context information of terminal devices.

Fig. 6 shows a flowchart of an example method 600 implemented at a first network device in accordance with some embodiments of the present disclosure. For the purpose of discussion, the method 600 will be described from the perspective of the first IAB donor 120-1, the second IAB donor 120-2 or the CN 110 with reference to Fig. 1A.

At block 610, the first network device obtains a first set of identifiers associated with a connection between an integrated access backhaul (IAB) node and a first IAB donor and a second set of identifiers associated with a connection between the IAB node and a second IAB donor. At block 620, the first network device transmits, to a second network device, a message comprising the first set of identifiers and the second set of identifiers.

In some embodiments, the first set of identifiers may comprise an identifier of a cell associated with the connection between the IAB node and the first IAB donor. Alternatively or additionally, the first set of identifiers may comprise an identifier of the first IAB donor. In some embodiments, the second set of identifiers may comprise an identifier of a cell associated with the connection between the IAB node and the second IAB donor. Alternatively or additionally, the second set of identifiers may comprise an identifier of the second IAB donor.

In some embodiments, the first network device may be the first IAB donor. The message may be a first message. In order to obtain the first set of identifiers and the second set of identifiers, the first IAB donor may receive a second message comprising the first set of identifiers and the second set of identifiers from the IAB node.

In some embodiments, the first network device may be the second IAB donor. In order to obtain the first set of identifiers and the second set of identifiers, the second IAB donor may receive the first set of identifiers from the first IAB donor and receive a message comprising the second set of identifiers from the IAB node.

In some embodiments, the first network device may be the second IAB donor and the message may be a first message. In order to obtain the first set of identifiers and the second set of identifiers, the second IAB donor may receive, from the IAB node or the first IAB donor, a second message comprising the first set of identifiers and the second set of identifiers.

In some embodiments, the first network device may be an access and mobility management function (AMF) . In some embodiments, the message may be a first message. In order to obtain the first set of identifiers and the second set of identifiers, the AMF may receive, from the IAB node or the first IAB donor or the second IAB donor, a second message comprising the first set of identifiers and the second set of identifiers.

In some embodiments, the first message may be transmitted to the second network device based on the second message received from the IAB node. In some embodiments, the second message received from the IAB node may be a request message for updating context information of terminal devices. In some embodiments, the second network device may comprise at least one AMF.

Fig. 7 shows a flowchart of an example method 700 implemented at a second network device in accordance with some embodiments of the present disclosure. For the purpose of discussion, the method 700 will be described from the perspective of the CN 110 with reference to Fig. 1A.

At block 710, the second network device receives, from an IAB node or a first network device, a message comprising a first set of identifiers associated with a connection between the IAB node and a first IAB donor and a second set of identifiers associated with a connection between the IAB node and a second IAB donor. At block 720, the second network device determines whether context information of at least one terminal device comprises the first set of identifiers. If yes, the process proceeds to block 730. At block 730, the second network device stores the second set of identifiers in the context information of the at least one terminal device, the at least one terminal device being in an idle state. In some embodiments, the second network device may be the CN 110 in Fig. 1A or an AMF in the CN 110. For example, the CN 110 receives, from an IAB node or a first network device, a message comprising a first set of identifiers associated with a connection between the IAB node and a first IAB donor and a second set of identifiers associated with a connection between the IAB node and a second IAB donor and determines whether context information of at least one terminal device comprises the first set of identifiers. If yes, the CN 110 stores the second set of identifiers in the context information of the at least one terminal device, the at least one terminal device being in an idle state.

In some embodiments, the first network device may be the first IAB donor. Alternatively, the first network device may be the second IAB donor. Alternatively, the first network device may be an access and mobility management function (AMF) .

In some embodiments, in order to store the second set of identifiers in the context information, the CN 110 may store, in addition to the first set of identifiers, the second set of identifiers in the context information of the at least one terminal device.

In some embodiments, in order to store the second set of identifiers in the context information, the CN 110 may store the second set of identifiers to replace the first set of identifiers in the context information of the at least one terminal device. In some embodiments, the CN 110 may further transmit a paging message for the at least one terminal device based on the context information.

In some example embodiments, an apparatus capable of performing the method 500 (for example, the IAB node 130) may comprise means for performing the respective steps of the method 500. The means may be implemented in any suitable form. For example, the means may be implemented in a circuitry or software module.

In some example embodiments, the apparatus comprises: means for performing a migration from a first IAB donor to a second IAB donor; and means for transmitting, to a network device, a message comprising a first set of identifiers associated with a connection between the apparatus and the first IAB donor and a second set of identifiers associated with a connection between the apparatus and the second IAB donor.

In some embodiments, the first set of identifiers may comprise an identifier of a cell associated with the connection between the apparatus and the first IAB donor. Alternatively or additionally, the first set of identifiers may comprise an identifier of the first IAB donor. In some embodiments, the second set of identifiers may comprise an identifier of a cell associated with the connection between the apparatus and the second IAB donor. Alternatively or additionally, the second set of identifiers may comprise an identifier of the second IAB donor.

In some example embodiments, the apparatus further comprises means for performing other steps in some example embodiments of the method 500. In some example embodiments, the means comprises at least one processor and at least one memory including computer program code. The at least one memory and the computer program code are configured to, with the at least one processor, cause the performance of the apparatus.

In some example embodiments, an apparatus capable of performing the method 600 (for example, the first IAB donor 120-1, the second IAB donor 120-2 or the CN 110) may comprise means for performing the respective steps of the method 600. The means may be implemented in any suitable form. For example, the means may be implemented in a circuitry or software module.

In some example embodiments, the apparatus comprises: means for obtaining a first set of identifiers associated with a connection between an integrated access backhaul (IAB) node and a first IAB donor and a second set of identifiers associated with a connection between the IAB node and a second IAB donor; and means for transmitting, to a second network device, a message comprising the first set of identifiers and the second set of identifiers.

In some embodiments, the apparatus may be the first IAB donor. The message may be a first message. The means for obtaining the first set of identifiers and the second set of identifiers may comprise means for receiving a second message comprising the first set of identifiers and the second set of identifiers from the IAB node.

In some embodiments, the apparatus may be the second IAB donor. The means for obtaining the first set of identifiers and the second set of identifiers may comprise means for receiving the first set of identifiers from the first IAB donor and means for receiving a message comprising the second set of identifiers from the IAB node.

In some embodiments, the apparatus may be the second IAB donor and the message may be a first message. The means for obtaining the first set of identifiers and the second set of identifiers may comprise means for receiving, from the IAB node or the first IAB donor, a second message comprising the first set of identifiers and the second set of identifiers.

In some embodiments, the apparatus may be an access and mobility management function (AMF) . In some embodiments, the message may be a first message. The means for obtaining the first set of identifiers and the second set of identifiers may comprise means for receiving, from the IAB node or the first IAB donor or the second IAB donor, a second message comprising the first set of identifiers and the second set of identifiers.

In some example embodiments, the apparatus further comprises means for performing other steps in some example embodiments of the method 600. In some example embodiments, the means comprises at least one processor and at least one memory including computer program code. The at least one memory and the computer program code are configured to, with the at least one processor, cause the performance of the apparatus.

In some example embodiments, an apparatus capable of performing the method 700 (for example, the CN 110) may comprise means for performing the respective steps of the method 700. The means may be implemented in any suitable form. For example, the means may be implemented in a circuitry or software module.

In some example embodiments, the apparatus comprises: means for receiving from an integrated access backhaul (IAB) node or a first network device, a message comprising a first set of identifiers associated with a connection between the IAB node and a first IAB donor and a second set of identifiers associated with a connection between the IAB node and the second IAB donor; and means for based on determining that context information of at least one terminal device comprises the first set of identifiers, storing the second set of identifiers in the context information of the at least one terminal device, the at least one terminal device being in an idle state.

In some embodiments, the second network device may be a first access and mobility management function (AMF) . In some embodiments, the first network device may be the first IAB donor. Alternatively, the first network device may be the second IAB donor. Alternatively, the first network device may be a second AMF.

In some embodiments, means for storing the second set of identifiers in the context information may comprise means for storing, in addition to the first set of identifiers, the second set of identifiers in the context information of the at least one terminal device.

In some embodiments, means for storing the second set of identifiers in the context information may comprise means for storing the second set of identifiers to replace the first set of identifiers in the context information of the at least one terminal device. In some embodiments, the apparatus may further comprise means for transmitting a paging message for the at least one terminal device based on the context information.

In some example embodiments, the apparatus further comprises means for performing other steps in some example embodiments of the method 700. In some example embodiments, the means comprises at least one processor and at least one memory including computer program code. The at least one memory and the computer program code are configured to, with the at least one processor, cause the performance of the apparatus.

Fig. 8 is a simplified block diagram of a device 800 that is suitable for implementing embodiments of the present disclosure. The device 800 may be provided to implement the communication device, for example the CN 110, the first IAB donor 120-1, the second IAB donor 120-2 and the IAB node 130 as shown in Fig. 1A. As shown, the device 800 includes one or more processors 810, one or more memories 820 coupled to the processor 810, and one or more communication modules 840 coupled to the processor 810.

The communication module 840 is for bidirectional communications. The communication module 840 has at least one antenna to facilitate communication. The communication interface may represent any interface that is necessary for communication with other network elements.

The processor 810 may be of any type suitable to the local technical network and may include one or more of the following: general purpose computers, special purpose computers, microprocessors, digital signal processors (DSPs) and processors based on multicore processor architecture, as non-limiting examples. The device 800 may have multiple processors, such as an application specific integrated circuit chip that is slaved in time to a clock which synchronizes the main processor.

The memory 820 may include one or more non-volatile memories and one or more volatile memories. Examples of the non-volatile memories include, but are not limited to, a Read Only Memory (ROM) 824, an electrically programmable read only memory (EPROM) , a flash memory, a hard disk, a compact disc (CD) , a digital video disk (DVD) , and other magnetic storage and/or optical storage. Examples of the volatile memories include, but are not limited to, a random access memory (RAM) 822 and other volatile memories that will not last in the power-down duration.

A computer program 830 includes computer executable instructions that are executed by the associated processor 810. The program 830 may be stored in the ROM 824. The processor 810 may perform any suitable actions and processing by loading the program 830 into the RAM 822.

The embodiments of the present disclosure may be implemented by means of the program 830 so that the device 800 may perform any process of the disclosure as discussed with reference to Figs. 2-7. The embodiments of the present disclosure may also be implemented by hardware or by a combination of software and hardware.

In some embodiments, the program 830 may be tangibly contained in a computer readable medium which may be included in the device 800 (such as in the memory 820) or other storage devices that are accessible by the device 800. The device 800 may load the program 830 from the computer readable medium to the RAM 822 for execution. The computer readable medium may include any types of tangible non-volatile storage, such as ROM, EPROM, a flash memory, a hard disk, CD, DVD, and the like. Fig. 9 shows an example of the computer readable medium 900 in form of CD or DVD. The computer readable medium has the program 830 stored thereon.

Generally, various embodiments of the present disclosure may be implemented in hardware or special purpose circuits, software, logic or any combination thereof. Some aspects may be implemented in hardware, while other aspects may be implemented in firmware or software which may be executed by a controller, microprocessor or other computing device. While various aspects of embodiments of the present disclosure are illustrated and described as block diagrams, flowcharts, or using some other pictorial representations, it is to be understood that the block, apparatus, system, technique or method described herein may be implemented in, as non-limiting examples, hardware, software, firmware, special purpose circuits or logic, general purpose hardware or controller or other computing devices, or some combination thereof.

The present disclosure also provides at least one computer program product tangibly stored on a non-transitory computer readable storage medium. The computer program product includes computer-executable instructions, such as those included in program modules, being executed in a device on a target real or virtual processor, to carry out the methods as described above with reference to Figs. 2-7. Generally, program modules include routines, programs, libraries, objects, classes, components, data structures, or the like that perform particular tasks or implement particular abstract data types. The functionality of the program modules may be combined or split between program modules as desired in various embodiments. Machine-executable instructions for program modules may be executed within a local or distributed device. In a distributed device, program modules may be located in both local and remote storage media.

Program code for carrying out methods of the present disclosure may be written in any combination of one or more programming languages. These program codes may be provided to a processor or controller of a general purpose computer, special purpose computer, or other programmable data processing apparatus, such that the program codes, 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.

In the context of the present disclosure, the computer program codes or related data may be carried by any suitable carrier to enable the device, apparatus or processor to perform various processes and operations as described above. Examples of the carrier include a signal, computer readable medium, and the like.

The computer readable medium may be a computer readable signal medium or a computer readable storage medium. A computer readable medium may include but 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 computer 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. The term “non-transitory, ” as used herein, is a limitation of the medium itself (i.e., tangible, not a signal) as opposed to a limitation on data storage persistency (e.g., RAM vs. ROM) .

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.

Although the present disclosure has been described in languages specific to structural features and/or methodological acts, it is to be understood that the present disclosure defined in the appended claims is not necessarily limited to the specific features or acts described above. Rather, the specific features and acts described above are disclosed as example forms of implementing the claims.

Claims

An integrated access backhaul (IAB) node comprising:

at least one processor; and

at least one memory storing instructions that, when executed by the at least one processor, cause the IAB node at least to:

perform a migration from a first IAB donor to a second IAB donor; and

transmit, to a network device, a message comprising a first set of identifiers associated with a connection between the IAB node and the first IAB donor and a second set of identifiers associated with a connection between the IAB node and the second IAB donor.
The IAB node of claim 1, wherein the first set of identifiers comprises at least one of an identifier of a cell associated with the connection between the IAB node and the first IAB donor or an identifier of the first IAB donor.
The IAB node of claim 1 or 2, wherein the second set of identifiers comprises at least one of an identifier of a cell associated with the connection between the IAB node and the second IAB donor or an identifier of the second IAB donor.
The IAB node of any of claims 1-3, wherein the network device is one of the following:

the first IAB donor;

the second IAB donor; or

an access and mobility management function (AMF) .
The IAB node of any of claims 1-4, wherein the message is a request message for updating context information of terminal devices.
A first network device comprising:

at least one processor; and

at least one memory storing instructions that, when executed by the at least one processor, cause the first network device at least to:

obtain a first set of identifiers associated with a connection between an integrated access backhaul (IAB) node and a first IAB donor and a second set of identifiers associated with a connection between the IAB node and a second IAB donor; and

transmit, to a second network device, a message comprising the first set of identifiers and the second set of identifiers.
The first network device of claim 6, wherein the first set of identifiers comprises at least one of an identifier of a cell associated with the connection between the IAB node and the first IAB donor or an identifier of the first IAB donor.
The first network device of claim 6 or 7, wherein the second set of identifiers comprises at least one of an identifier of a cell associated with the connection between the IAB node and the second IAB donor or an identifier of the second IAB donor.
The first network device of any of claims 6-8, wherein the first network device is the first IAB donor, the message is a first message, and wherein the first IAB donor is caused to obtain the first set of identifiers and the second set of identifiers by:

receiving, from the IAB node, a second message comprising the first set of identifiers and the second set of identifiers.
The first network device of any of claims 6-8, wherein the first network device is the second IAB donor, and the second IAB donor is caused to obtain the first set of identifiers and the second set of identifiers by:

receiving the first set of identifiers from the first IAB donor; and

receiving, from the IAB node, a message comprising the second set of identifiers.
The first network device of any of claims 6-8, wherein the first network device is the second IAB donor, the message is a first message, and the second IAB donor is caused to obtain the first set of identifiers and the second set of identifiers by:

receiving, from the IAB node or the first IAB donor, a second message comprising the first set of identifiers and the second set of identifiers.
The first network device of any of claims 6-8, wherein the first network device is an access and mobility management function (AMF) .
The first network device of claim 12, wherein the message is a first message, and the AMF is caused to obtain the first set of identifiers and the second set of identifiers by:

receiving, from the IAB node or the first IAB donor or the second IAB donor, a second message comprising the first set of identifiers and the second set of identifiers.
The first network device of claim 11 or 13, wherein the first message is transmitted to the second network device based on the second message received from the IAB node or the first IAB donor or the second IAB donor.
The first network device of any of claims 11, 13 or 14, wherein the second message received from the IAB node is a request message for updating context information of terminal devices.
The first network device of any of claims 6-15, wherein the second network device comprises at least one AMF.
A second network device comprising:

at least one processor; and

at least one memory storing instructions that, when executed by the at least one processor, cause the second network device at least to:

receive, from an integrated access backhaul (IAB) node or a first network device, a message comprising a first set of identifiers associated with a connection between the IAB node and a first IAB donor and a second set of identifiers associated with a connection between the IAB node and a second IAB donor; and

based on determining that context information of at least one terminal device comprises the first set of identifiers, store the second set of identifiers in the context information of the at least one terminal device, the at least one terminal device being in an idle state.
The second network device of claim 17, wherein the first set of identifiers comprises at least one of an identifier of a cell associated with the connection between the IAB node and the first IAB donor or an identifier of the first IAB donor.
The second network device of claim 17 or 18, wherein the second set of identifiers comprises at least one of an identifier of a cell associated with the connection between the IAB node and the second IAB donor or an identifier of the second IAB donor.
The second network device of any of claims 17-19, wherein the second network device is a first access and mobility management function (AMF) , and the first network device is one of the following:

the first IAB donor;

the second IAB donor; or

a second AMF.
The second network device of any of claims 17-20, wherein the second network device is caused to store the second set of identifiers in the context information by:

storing, in addition to the first set of identifiers, the second set of identifiers in the context information of the at least one terminal device.
The second network device of any of claims 17-20, wherein the second network device is caused to store the second set of identifiers in the context information by:

storing the second set of identifiers to replace the first set of identifiers in the context information of the at least one terminal device.
The second network device of any of claims 17-22, wherein the second network device is further caused to:

transmit, based on the context information, a paging message for the at least one terminal device.
A method comprising:

performing, at an integrated access backhaul (IAB) node, a migration from a first IAB donor to a second IAB donor; and

transmitting, to a network device, a message comprising a first set of identifiers associated with a connection between the IAB node and the first IAB donor and a second set of identifiers associated with a connection between the IAB node and the second IAB donor.
A method comprising:

obtaining, at a first network device, a first set of identifiers associated with a connection between an integrated access backhaul (IAB) node and a first IAB donor and a second set of identifiers associated with a connection between the IAB node and a second IAB donor; and

transmitting, to a second network device, a message comprising the first set of identifiers and the second set of identifiers.
A method comprising:

receiving, at a second network device and from an integrated access backhaul (IAB) node or a first network device, a message comprising a first set of identifiers associated with a connection between the IAB node and a first IAB donor and a second set of identifiers associated with a connection between the IAB node and the second IAB donor; and

based on determining that context information of at least one terminal device comprises the first set of identifiers, storing the second set of identifiers in the context information of the at least one terminal device, the at least one terminal device being in an idle state.
An apparatus, comprising:

means for performing, at an integrated access backhaul (IAB) node, a migration from a first IAB donor to a second IAB donor; and

means for transmitting, to a network device, a message comprising a first set of identifiers associated with a connection between the IAB node and the first IAB donor and a second set of identifiers associated with a connection between the IAB node and the second IAB donor.
An apparatus, comprising:

means for obtaining, at a first network device, a first set of identifiers associated with a connection between an integrated access backhaul (IAB) node and a first IAB donor and a second set of identifiers associated with a connection between the IAB node and a second IAB donor; and

means for transmitting, to a second network device, a message comprising the first set of identifiers and the second set of identifiers.
An apparatus, comprising:

means for receiving, at a second network device and from an integrated access backhaul (IAB) node or a first network device, a message comprising a first set of identifiers associated with a connection between the IAB node and a first IAB donor and a second set of identifiers associated with a connection between the IAB node and the second IAB donor; and

means for based on determining that context information of at least one terminal device comprises the first set of identifiers, storing the second set of identifiers in the context information of the at least one terminal device, the at least one terminal device being in an idle state.
A non-transitory computer readable medium comprising program instructions that, when executed by an apparatus, cause the apparatus to perform at least the method of any of claims 24 to 26.