Node in wireless communication system and method performed by same

Abstract

The disclosure relates to a 5G or 6G communication system for supporting a higher data transmission rate. According to the disclosure, A method performed by a mobile integrated access / backhaul (IAB)-node in a wireless communication system, the method comprising: receiving, from an operation administration and maintenance (OAM), information associated with initiating distributed unit (DU) migration, wherein the information includes a gNodeB(gNB) identifier (ID) of a target F1 terminating donor central unit (CU); transmitting, to the target F1 terminating donor CU, a request message for a connection with the target F1 terminating donor CU based on the gNB ID of the target F1 terminating donor CU; and receiving, from the target F1 terminating donor CU, a response message as a response to the request message.

Description

NODE IN WIRELESS COMMUNICATION SYSTEM AND METHOD PERFORMED BY SAME

[0001] The present disclosure relates to a field of wireless communication technologies, and in particular, to a node in a wireless communication system and methods performed by the same.

[0002] In order to meet an increasing demand for wireless data communication services since a deployment of 4G communication system, efforts have been made to develop an improved 5G or pre-5G communication system. Therefore, the 5G or pre-5G communication system is also called "beyond 4G network" or "post LTE system".

[0003] Wireless communication is one of the most successful innovations in modern history. Recently, the number of subscribers of wireless communication services has exceeded 5 billion, and it continues growing rapidly. With the increasing popularity of smart phones and other mobile data devices (such as tablet computers, notebook computers, netbooks, e-book readers and machine-type devices) in consumers and enterprises, a demand for wireless data services is growing rapidly. In order to meet rapid growth of mobile data services and support new applications and deployments, it is very important to improve efficiency and coverage of wireless interfaces.

[0004] In the 5G communication technology, because of the usage of higher frequency, it has a faster transmission speed than 4G. However, higher frequency will also lead to shorter transmission distance, so more base stations will be deployed in a 5G network to ensure the coverage of the 5G network. But in fact, in some regions, due to environmental or cost reasons, deployment of normal 5G base stations cannot be carried out, so an IAB (Integrated Access and Backhaul) technology is proposed, which makes up for the problem that these regions can not be covered by 5G base stations, and ensures normal communication of users. In the current research on an IAB network, the process of establishing an IAB network, partial migration and transmission of data packets in the IAB network have been determined. Next, the further research will be carried out on mobile IAB nodes and IAB-DU migration.

[0005] 5th generation (5G) or new radio (NR) mobile communications is recently gathering increased momentum with all the worldwide technical activities on the various candidate technologies from industry and academia. The candidate enablers for the 5G / NR mobile communications include massive antenna technologies, from legacy cellular frequency bands up to high frequencies, to provide beamforming gain and support increased capacity, new waveform (e.g., a new radio access technology (RAT)) to flexibly accommodate various services / applications with different requirements, new multiple access schemes to support massive connections, and so on.

[0006] 5G mobile communication technologies define broad frequency bands such that high transmission rates and new services are possible, and can be implemented not only in "Sub 6GHz" bands such as 3.5GHz, but also in "Above 6GHz" bands referred to as mmWave including 28GHz and 39GHz. In addition, it has been considered to implement 6G mobile communication technologies (referred to as Beyond 5G systems) in terahertz bands (for example, 95GHz to 3THz bands) in order to accomplish transmission rates fifty times faster than 5G mobile communication technologies and ultra-low latencies one-tenth of 5G mobile communication technologies.

[0007] At the beginning of the development of 5G mobile communication technologies, in order to support services and to satisfy performance requirements in connection with enhanced Mobile BroadBand (eMBB), Ultra Reliable Low Latency Communications (URLLC), and massive Machine-Type Communications (mMTC), there has been ongoing standardization regarding beamforming and massive MIMO for mitigating radio-wave path loss and increasing radio-wave transmission distances in mmWave, supporting numerologies (for example, operating multiple subcarrier spacings) for efficiently utilizing mmWave resources and dynamic operation of slot formats, initial access technologies for supporting multi-beam transmission and broadbands, definition and operation of BWP (BandWidth Part), new channel coding methods such as a LDPC (Low Density Parity Check) code for large amount of data transmission and a polar code for highly reliable transmission of control information, L2 pre-processing, and network slicing for providing a dedicated network specialized to a specific service.

[0008] Currently, there are ongoing discussions regarding improvement and performance enhancement of initial 5G mobile communication technologies in view of services to be supported by 5G mobile communication technologies, and there has been physical layer standardization regarding technologies such as V2X (Vehicle-to-everything) for aiding driving determination by autonomous vehicles based on information regarding positions and states of vehicles transmitted by the vehicles and for enhancing user convenience, NR-U (New Radio Unlicensed) aimed at system operations conforming to various regulation-related requirements in unlicensed bands, NR UE Power Saving, Non-Terrestrial Network (NTN) which is UE-satellite direct communication for providing coverage in an area in which communication with terrestrial networks is unavailable, and positioning.

[0009] Moreover, there has been ongoing standardization in air interface architecture / protocol regarding technologies such as Industrial Internet of Things (IIoT) for supporting new services through interworking and convergence with other industries, IAB (Integrated Access and Backhaul) for providing a node for network service area expansion by supporting a wireless backhaul link and an access link in an integrated manner, mobility enhancement including conditional handover and DAPS (Dual Active Protocol Stack) handover, and two-step random access for simplifying random access procedures (2-step RACH for NR). There also has been ongoing standardization in system architecture / service regarding a 5G baseline architecture (for example, service based architecture or service based interface) for combining Network Functions Virtualization (NFV) and Software-Defined Networking (SDN) technologies, and Mobile Edge Computing (MEC) for receiving services based on UE positions.

[0010] As 5G mobile communication systems are commercialized, connected devices that have been exponentially increasing will be connected to communication networks, and it is accordingly expected that enhanced functions and performances of 5G mobile communication systems and integrated operations of connected devices will be necessary. To this end, new research is scheduled in connection with eXtended Reality (XR) for efficiently supporting AR (Augmented Reality), VR (Virtual Reality), MR (Mixed Reality) and the like, 5G performance improvement and complexity reduction by utilizing Artificial Intelligence (AI) and Machine Learning (ML), AI service support, metaverse service support, and drone communication.

[0011] A method performed by a mobile integrated access / backhaul (IAB)-node in a wireless communication system, the method comprising: receiving, from an operation administration and maintenance (OAM), information associated with initiating distributed unit (DU) migration, wherein the information includes a gNodeB(gNB) identifier (ID) of a target F1 terminating donor central unit (CU); transmitting, to the target F1 terminating donor CU, a request message for a connection with the target F1 terminating donor CU based on the gNB ID of the target F1 terminating donor CU; and receiving, from the target F1 terminating donor CU, a response message as a response to the request message.

[0012] A method performed by a target F1 terminating donor central unit (CU) in a wireless communication system, the method comprising: receiving, from a mobile integrated access / backhaul (IAB)-node, a request message for a connection, which is associated with distributed unit (DU) migration, with the mobile IAB-node based on a gNodeB(gNB) identifier (ID) of the target F1 terminating donor CU; and transmitting, to the mobile IAB-node, a response message as a response to the request message.

[0013] A mobile integrated access / backhaul (IAB)-node in a wireless communication system, the mobile IAB-node comprising: a transceiver; and a controller coupled with the transceiver and configured to: receive, from an operation administration and maintenance (OAM), information to initiate distributed unit (DU) migration, wherein the information includes a gNodeB(gNB) identifier (ID) of a target F1 terminating donor central unit (CU), transmit, to the target F1 terminating donor CU, a request message for a connection with the target F1 terminating donor CU based on the gNB ID of the target F1 terminating donor CU, and receive, from the target F1 terminating donor CU, a response message as a response to the request message.

[0014] A target F1 terminating donor central unit (CU) in a wireless communication system, the target F1 terminating donor CU comprising: a transceiver; and a controller coupled with the transceiver and configured to: receive, from a mobile integrated access / backhaul (IAB)-node, a request message for a connection, which is associated with distributed unit (DU) migration, with the mobile IAB-node based on a gNodeB(gNB) identifier (ID) of the target F1 terminating donor CU, and transmit, to the mobile IAB-node, a response message as a response to the request message.

[0015] The above and other aspects, features and advantages of certain embodiments of the present disclosure will be more apparent from the following description taken in conjunction with the accompanying drawings, in which:

[0016] FIG. 1 is an exemplary system architecture of system architecture evolution (SAE);

[0017] FIG. 2 is an exemplary system architecture according to various embodiments of the present disclosure;

[0018] FIG. 3A shows an example structure of a base station according to embodiments of the present disclosure;

[0019] FIG. 3B shows an example structure of a base station according to embodiments of the present disclosure;

[0020] FIG. 3C shows an example structure of a base station according to embodiments of the present disclosure;

[0021] FIG. 4A shows an example in which an IAB-MT and an IAB-DU migrate from the same source IAB donor CU to the same target IAB donor CU;

[0022] FIG. 4B shows an example in which an IAB-MT and an IAB-DU migrate from the same source IAB donor CU to different target IAB donor CUs;

[0023] FIG. 4C shows an example in which an IAB-MT and an IAB-DU migrate from different source IAB donor CUs to the same target IAB donor CU;

[0024] FIG. 4D shows an example in which an IAB-MT and an IAB-DU migrate from different source IAB donor CUs to different target IAB donor CUs;

[0025] FIG. 5 shows an example flowchart of a flow that a source F1 terminating donor CU triggers an mIAB node to initiate a DU migration process;

[0026] FIG. 6 shows an example flowchart of a source F1 terminating donor CU changing a target F1 terminating donor CU;

[0027] FIG. 7 shows an example of a DU migration process triggered by OAM;

[0028] FIG. 8 shows an example flowchart of a DU migration process triggered by OAM;

[0029] FIG. 9 shows an example flowchart of a DU migration process triggered by OAM;

[0030] FIG. 10 shows an example flowchart of a DU migration process triggered by OAM;

[0031] FIG. 11 shows an example of signaling enhancement for F1 setup request message;

[0032] FIG. 12 shows an example flowchart for notifying a source F1 terminating donor CU that new F1 connection establishment is successful when a source link lost occurs;

[0033] FIG. 13 shows another example flowchart according to embodiments of the present disclosure;

[0034] FIG. 14 shows another example flowchart according to embodiments of the present disclosure;

[0035] FIG. 15 shows a flowchart of a method performed by a first node in a wireless communication system according to embodiments of the present disclosure;

[0036] FIG. 16 shows a flowchart of a method performed by a second node in a wireless communication system according to embodiments of the present disclosure;

[0037] FIG. 17 shows a flowchart of a method performed by a third node in a wireless communication system according to embodiments of the present disclosure;

[0038] FIG. 18 shows a flowchart of a method performed by a fourth node in a wireless communication system according to embodiments of the present disclosure; and

[0039] FIG. 19 shows a schematic diagram of a node in a wireless communication system according to embodiments of the present disclosure.

[0040] Embodiments of the present disclosure provide a method performed by a first node in a wireless communication system, which includes: transmitting a third message to a third node, wherein the third message includes information about a list of serving cells that the first node expects to activate and an F1 traffic profile; receiving a fourth message from the third node in response to the third message, wherein the fourth message includes an acceptable F1 traffic profile and information of cells to be activated; and transmitting a sixth message to the second node, wherein the sixth message includes information of activated cells and an acceptable F1 traffic profile.

[0041] According to embodiments of the present disclosure, the method further includes receiving a first message from a second node, wherein the first message includes the F1 traffic profile.

[0042] According to embodiments of the present disclosure, the method further includes transmitting a second message to a fourth node, wherein the second message includes at least one of the following: a transport network layer (TNL) address of a second DU of the first node, a node ID and / or IP address of the third node, and information indicating that the first node will perform distributed unit (DU) migration.

[0043] According to embodiments of the present disclosure, the method further includes transmitting a fifth message to a fourth node, wherein the fifth message includes a mobile integrated access and backhaul-mobile terminal (mIAB-MT) ID generated by the third node for the first node.

[0044] According to embodiments of the present disclosure, the method further includes: receiving a seventh message from the second node, wherein the seventh message includes at least one of the following: information indicating cancellation of a successfully established F1 connection between the first node and the third node, node ID and / or IP address of a new target F1 terminating donor CU; transmitting an eighth message to the third node, wherein the eighth message includes at least one of the following: information indicating cancellation of a successfully established F1 connection between the first node and the third node, a cause value for cancellation of the successfully established F1 connection between the first node and the third node; and receiving a ninth message from the third node, wherein the ninth message includes information indicating that the third node agrees to cancel a successfully established F1 connection between the first node and the third node.

[0045] According to embodiments of the present disclosure, the first message is transmitted from the second node in a case that the second node receives a tenth message from an Operation Administration and Maintenance (OAM) node, wherein the tenth message includes at least one of the following: information indicating the first node to perform distributed unit (DU) migration, a node ID and / or IP address of the third node.

[0046] According to embodiments of the present disclosure, the method further includes: receiving an eleventh message from an Operation Administration and Maintenance (OAM) node, wherein the eleventh message includes at least one of the following: information indicating the first node to perform distributed unit (DU) migration, a node ID and / or IP address of the third node; and transmitting a twelfth message to the second node, wherein the twelfth message includes the node ID and / or IP address of the third node.

[0047] According to embodiments of the present disclosure, the first message is transmitted from the second node in a case that the second node agrees to migrate a distributed unit (DU) of the first node to the third node.

[0048] According to embodiments of the present disclosure, the method further includes: receiving an eleventh message from an Operation Administration and Maintenance (OAM) node, wherein the eleventh message includes at least one of the following: information indicating the first node to perform distributed unit (DU) migration, a node ID and / or IP address of the third node; receiving a thirteenth message from the fourth node, wherein the thirteenth message includes at least one of the following: a mobile integrated access and backhaul-mobile terminal (mIAB-MT) ID generated by the fourth node for the first node, a node ID of the fourth node; and transmitting a fifth message to the fourth node, wherein the fifth message includes a mobile integrated access and backhaul-mobile terminal (mIAB-MT) ID generated by the third node for the first node.

[0049] According to embodiments of the present disclosure, the information about a list of serving cells that the first node expects to activate is indicated by one or more of the following: indicated by a first information element in an F1 setup request, wherein the first information element indicates a list of serving cells that the first node expects to activate; indicated by state information corresponding to each serving cell in a serving cell list; or indicated by a second information element in an F1 setup request, wherein the second information element indicates whether all cells in a serving cell list are serving cells that the first node expects to activate.

[0050] According to embodiments of the present disclosure, the method further includes: transmitting a fourteenth message to the third node in a case that transmission of the sixth message fails, wherein the fourteenth message includes at least one of the following: information indicating that a source F1 connection between the first node and the second node is disconnected, information indicating the third node to transmit the sixth message to the second node, and information indicating the third node to inform the second node that the source F1 connection between the first node and the second node is disconnected.

[0051] Embodiments of the present disclosure provide a method performed by a second node in a wireless communication system, which includes: transmitting a first message to a first node, wherein the first message includes an F1 traffic profile; and receiving a sixth message from the first node, wherein the sixth message includes information of activated cells and an acceptable F1 traffic profile.

[0052] According to embodiments of the present disclosure, the method further includes: in a case that the distributed unit (DU) of the first node is agreed to migrate to the third node, performing a user equipment context handover process.

[0053] According to embodiments of the present disclosure, the method further includes: transmitting a seventh message to the first node, wherein the seventh message includes at least one of the following: information indicating cancellation of a successfully established F1 connection between the first node and the third node, a node ID and / or IP address of a new target F1 terminating donor CU.

[0054] According to embodiments of the present disclosure, the method further includes: receiving a tenth message from an Operation Administration and Maintenance (OAM) node, wherein the tenth message includes at least one of the following: information indicating the first node to perform distributed unit (DU) migration, a node ID and / or IP address of a third node, wherein the first message is transmitted to the first node in a case that the second node receives the tenth message.

[0055] According to embodiments of the present disclosure, the method further includes receiving a twelfth message from the first node, wherein the twelfth message includes a node ID and / or IP address of a third node, wherein the node ID and / or IP address of the third node is received by the first node from an Operation Administration and Maintenance (OAM) node.

[0056] According to embodiments of the present disclosure, the first message is transmitted from the second node in a case that the second node agrees to migrate a distributed unit (DU) of the first node to the third node.

[0057] According to embodiments of the present disclosure, the method further includes: receiving a fifteenth message from a third node in a case that reception of the sixth message from the first node fails, wherein the fifteenth message includes at least one of the following: information indicating that an F1 connection between the first node and the third node is successfully established, information indicating that a source F1 connection between the first node and the second node is disconnected, target cell ID, information of activated cells, and an acceptable F1 traffic profile.

[0058] Embodiments of the present disclosure provide a method performed by a third node in a wireless communication system, which includes: receiving a third message from a first node, wherein the third message includes information about a list of serving cells that the first node expects to activate and an F1 traffic profile; and transmitting a fourth message to the first node, wherein the fourth message includes an acceptable F1 traffic profile and information of cells to be activated.

[0059] According to embodiments of the present disclosure, the method further includes: receiving an eighth message from the first node, wherein the eighth message includes at least one of the following: information indicating cancellation of a successfully established F1 connection between the first node and the third node, a cause value for cancellation of the successfully established F1 connection between the first node and the third node; and transmitting a ninth message to the first node, wherein the ninth message includes information indicating that the third node agrees to cancel a successfully established F1 connection between the first node and the third node, wherein the eighth message is transmitted from the first node in a case that the first node receives a seventh message from a second node, wherein the seventh message includes at least one of the following: information indicating cancellation of a successfully established F1 connection between the first node and the third node, node ID and / or IP address of a new target F1 terminating donor CU.

[0060] According to embodiments of the present disclosure, the information about a list of serving cells that the first node expects to activate is indicated by one or more of the following: indicated by a first information element in an F1 setup request, wherein the first information element indicates a list of serving cells that the first node expects to activate; indicated by state information corresponding to each serving cell in a serving cell list; or indicated by a second information element in an F1 setup request, wherein the second information element indicates whether all cells in a serving cell list are serving cells that the first node expects to activate.

[0061] According to embodiments of the present disclosure, the method further includes receiving a fourteenth message from the first node, wherein the fourteenth message includes at least one of the following: information indicating that a source F1 connection between the first node and the second node is disconnected, information indicating the third node to transmit a sixth message to the second node, and information indicating the third node to inform the second node that the source F1 connection between the first node and the second node is disconnected, wherein the fourteenth message is transmitted from the first node in a case that transmission of the sixth message from the first node to the second node fails.

[0062] According to embodiments of the present disclosure, the method further includes transmitting a fifteenth message to the second node, wherein the fifteenth message includes at least one of the following: information indicating that an F1 connection between the first node and the third node is successfully established, information indicating that a source F1 connection between the first node and the second node is disconnected, target cell ID, information of activated cells, and an acceptable F1 traffic profile.

[0063] Embodiments of the present disclosure provide a method performed by a fourth node in a wireless communication system, which includes: receiving a second message from a first node, wherein the second message includes at least one of the following: a transport network layer (TNL) address of a second distributed unit (DU) of the first node, a node ID and / or IP address of a third node, and information indicating that the first node will perform distributed unit (DU) migration; and receiving a fifth message from the first node, wherein the fifth message includes a mobile integrated access and backhaul-mobile terminal (mIAB-MT) ID generated by the third node for the first node.

[0064] According to embodiments of the present disclosure, the method further includes transmitting a thirteenth message to the first node, wherein the thirteenth message includes at least one of the following: a mobile integrated access and backhaul-mobile terminal (mIAB-MT) ID generated by the fourth node for the first node and a node ID of the fourth node.

[0065] Embodiments of the present disclosure provide a node device in a wireless communication system, including a transceiver; and a processor coupled with the transceiver and configured to perform any method performed by a first node and / or a second node and / or a third node and / or a fourth node in a wireless communication system according to embodiments of the present disclosure.

[0066] Embodiments of the present disclosure provide a computer-readable medium on which computer-readable instructions are stored, which, when executed by a processor, implement any method performed by a first node and / or a second node and / or a third node and / or a fourth node in a wireless communication system according to embodiments of the present disclosure.

[0067] Methods implemented by a first node and / or a second node and / or a third node and / or a fourth node in the wireless communication system provided by the present disclosure can realize DU migration of a mobile IAB node.

[0068] The following description with reference to the accompanying drawings is provided to assist in a comprehensive understanding of various embodiments of the present disclosure as defined by the claims and their equivalents. It includes various specific details to assist in that understanding but these are to be regarded as merely exemplary. Accordingly, those of ordinary skill in the art will recognize that various changes and modifications of the various embodiments described herein can be made without departing from the scope and spirit of the present disclosure. In addition, descriptions of well-known functions and constructions may be omitted for clarity and conciseness.

[0069] The terms and words used in the following description and claims are not limited to the bibliographical meanings, but, are merely used by the inventor to enable a clear and consistent understanding of the present disclosure. Accordingly, it should be apparent to those skilled in the art that the following description of various embodiments of the present disclosure is provided for illustration purpose only and not for the purpose of limiting the present disclosure as defined by the appended claims and their equivalents.

[0070] It is to be understood that the singular forms "a," "an," and "the" include plural referents unless the context clearly dictates otherwise. Thus, for example, reference to "a component surface" includes reference to one or more of such surfaces.

[0071] The term "include" or "may include" refers to the existence of a corresponding disclosed function, operation or component which can be used in various embodiments of the present disclosure and does not limit one or more additional functions, operations, or components. Additionally, the terms such as "include" and / or "have" may be construed to denote a certain characteristic, number, step, operation, constituent element, component or a combination thereof, but may not be construed to exclude the existence of or a possibility of addition of one or more other characteristics, numbers, steps, operations, constituent elements, components or combinations thereof.

[0072] The term "or" used in various embodiments of the present disclosure includes any or all of combinations of listed words. For example, the expression "A or B" may include A, may include B, or may include both A and B.

[0073] Unless defined differently, all terms used herein, which include technical terminologies or scientific terminologies, have the same meaning as that understood by a person skilled in the art to which the present disclosure belongs. Such terms as those defined in a generally used dictionary are to be interpreted to have the meanings equal to the contextual meanings in the relevant field of art, and are not to be interpreted to have ideal or excessively formal meanings unless clearly defined in the present disclosure.

[0074] Figures discussed below and various embodiments for describing the principles of the present disclosure in this patent document are only for illustration and should not be interpreted as limiting the scope of the disclosure in any way. Those skilled in the art will understand that the principles of the present disclosure can be implemented in any suitably arranged system or device.

[0075] FIG. 1 is an exemplary system architecture 100 of system architecture evolution (SAE). User equipment (UE) 101 is a terminal device for receiving data. An evolved universal terrestrial radio access network (E-UTRAN) 102 is a radio access network, which includes a macro base station (eNodeB / NodeB) that provides UE with interfaces to access the radio network. A mobility management entity (MME) 103 is responsible for managing mobility context, session context and security information of the UE. A serving gateway (SGW) 104 mainly provides functions of user plane, and the MME 103 and the SGW 104 may be in the same physical entity. A packet data network gateway (PGW) 105 is responsible for functions of charging, lawful interception, etc., and may be in the same physical entity as the SGW 104. A policy and charging rules function entity (PCRF) 106 provides quality of service (QoS) policies and charging criteria. A general packet radio service support node (SGSN) 108 is a network node device that provides routing for data transmission in a universal mobile telecommunications system (UMTS). A home subscriber server (HSS) 109 is a home subsystem of the UE, and is responsible for protecting user information including a current location of the user equipment, an address of a serving node, user security information, and packet data context of the user equipment, etc.

[0076] FIG. 2 is an exemplary system architecture 200 according to various embodiments of the present disclosure. Other embodiments of the system architecture 200 can be used without departing from the scope of the present disclosure.

[0077] User equipment (UE) 201 is a terminal device for receiving data. A next generation radio access network (NG-RAN) 202 is a radio access network, which includes a base station (a gNB or an eNB connected to 5G core network 5GC, and the eNB connected to the 5GC is also called ng-eNB) that provides UE with interfaces to access the radio network. An access control and mobility management function entity (AMF) 203 is responsible for managing mobility context and security information of the UE. A user plane function entity (UPF) 204 mainly provides functions of user plane. A session management function entity SMF 205 is responsible for session management. A data network (DN) 206 includes, for example, services of operators, access of Internet and service of third parties.

[0078] In an NR system, in order to support network function virtualization and more efficient resource management and scheduling, a base station (gNB / ng-eNB) that provides wireless network interfaces for terminals (UEs) may be further divided into a centralized unit (for example, gNB-CU / ng-eNB-CU(gNB central unit / ng-eNB central unit)) and a distributed unit (for example, gNB-DU / ng-eNB-DU(gNB distributed unit / ng-eNB distributed unit)) (abbreviated as CU and DU in the present disclosure), as shown in FIG. 3A. gNB-CU has radio resource control (RRC), Service Data Adaptation Protocol (SDAP) and Packet Data Convergence Protocol (PDCP) protocol layers, while ng-eNB-CU has RRC and PDCP layers. gNB-DU / ng-eNB-DU has Radio Link Control (RLC) protocol, Media Access Control (MAC) and physical (PHY) layers. There is a standardized public interface F1 between gNB-CU and gNB-DU, and a standardized public interface W1 between ng-eNB-CU and ng-eNB-DU. The F1 interface is divided into a control plane F1-C and a user plane F1-U. The transport network layer of F1-C is based on IP transport. In order to transmit signaling more reliably, stream control transmission protocol (SCTP) protocol is added onto IP. The protocol of the application layer is F1 Application Protocol (F1AP). SCTP can provide reliable application layer message transmission. The transport layer of F1-U is UDP / IP, and the GPRS tunneling protocol-user plane (GTP-U) is used to carry the user plane protocol data unit (PDU) above UDP / IP. Further, for a gNB-CU, as shown in FIG. 3B, the gNB-CU may include a gNB-CU-CP (control plane part of a centralized unit of a base station) and a gNB-CU-UP (user plane part of a centralized unit of a base station), a gNB-CU-CP contains functions of a control plane of a base station and has RRC and SDAP protocol layers, and a gNB-CU-UP contains functions of a user plane of a base station and has SDAP and PDCP protocol layers. There is a standardized public interface E1 between gNB-CU-CP and gNB-CU-UP, and the protocol is E1 Application Protocol (E1AP). The interface between the control plane part of the centralized unit of the base station and the distributed unit of the base station is an F1-C interface, that is, the control plane interface of F1, and the interface between the user plane part of the centralized unit of the base station and the distributed unit of the base station is an F1-U interface, that is, the user plane interface of F1. In addition, in the NR system, a base station providing the E-UTRA user plane and control plane which accessed a 5G core network is called ng-eNB. In order to support virtualization, such a base station (ng-eNB) may also be further divided into a centralized unit ng-eNB-CU (gNB central unit / ng-eNB central unit) and a distributed unit ng-eNB-DU (gNB distributed unit / ng-eNB distributed unit) (abbreviated as CU and DU in the present disclosure), as shown in FIG. 3C. ng-eNB-CU has RRC and PDCP layers. gNB-DU / ng-eNB-DU has radio link control (RLC) protocol, media access control (MAC) and physical layer. There is a standardized public interface W1 between ng-eNB-CU and ng-eNB-DU. The W1 interface is divided into a control plane W1-C and a user plane W1-U. The transport network layer of W1-C is based on IP transport. In order to transmit signaling more reliably, SCTP protocol is added onto IP. The protocol of the application layer is W1 Application Protocol (W1AP). The transport layer of W1-U is UDP / IP, and GTP-U is used to carry user plane protocol data unit (PDU) above UDP / IP.

[0079] At present, the research on IAB network mainly determines the process of partial migration (or MT migration). When an IAB node encounters wireless performance degradation, the source IAB donor CU may decide whether to perform partial migration according to the measurement report reported by the IAB node. If partial migration is to be performed, an IAB-MT (that is, an RRC function part) is to be migrated to a target IAB donor CU; however, the current research on IAB network does not consider the mobility of IAB nodes, that is, the IAB nodes studied are considered to be fixed. However, only considering the fixed IAB nodes can not meet people's demand for IAB networks, so it is necessary to study mobile IAB nodes. When IAB nodes are mobile, partial migration may not completely solve the problem of wireless performance degradation, so it is necessary to study the process of DU migration, that is, not only IAB-MT is migrated to the target IAB donor CU, but also IAB-DU (i.e., F1 connection with the donor CU) needs to be migrated, so as to solve the problem of wireless performance degradation caused by mobility of IAB node.

[0080] FIG. 4A shows an example in which an IAB-MT and an IAB-DU migrate from the same source IAB donor CU to the same target IAB donor CU; FIG. 4B shows an example in which an IAB-MT and an IAB-DU migrate from the same source IAB donor CU to different target IAB donor CUs; FIG. 4C shows an example in which an IAB-MT and an IAB-DU migrate from different source IAB donor CUs to the same target IAB donor CU; FIG. 4D shows an example in which an IAB-MT and an IAB-DU migrate from different source IAB donor CUs to different target IAB donor CUs.

[0081] As shown in FIGs. 4A-4D, when a MT (mobile terminal) (mIAB-MT) and a DU (mIAB-DU) of a mobile IAB node (mIAB node) migrate, there may be the following situations:

[0082] ㆍ Case 1: migrating from the same source IAB donor CU to the same target IAB donor CU, as shown in FIG. 4A;

[0083] ㆍ Case 2: migrating from the same source IAB donor CU to different target IAB donor CUs, as shown in FIG. 4B;

[0084] ㆍ Case 3: migrating from different source IAB donor CU to the same target IAB donor CU, as shown in FIG. 4C;

[0085] ㆍ Case 4: migrating from a different source IAB donor CU to different target IAB donor CUs, as shown in FIG. 4D.

[0086] Because MT migration and DU migration are decoupled from each other, in the above situations, only MT migration, only DU migration, MT migration before DU migration and MT migration after DU migration are all possible. For a DU migration process, according to different initial states, that is, whether donor CUs at which the MT and DU are terminated are the same or not, and whether donor CUs at which the MT and DU are terminated after the DU migration is completed are the same or not, there are the following three situations about the DU migration:

[0087] ㆍ Case 1: the initial state is that donor CUs at which the MT and DU are terminated are the same, and when the DU migration is completed, donor CUs at which the MT and DU are terminated are different;

[0088] ㆍ Case 2: the initial state is that donor CUs at which the MT and DU are terminated are different, and when the DU migration is completed, donor CUs at which the MT and DU are terminated are the same;

[0089] ㆍ Case 3: the initial state is that donor CUs at which the MT and DU are terminated are different, and when the DU migration is completed, donor CUs at which the MT and DU are terminated are different.

[0090] One of the technical problems mainly to be solved by the present disclosure is to determine processes of DU migration according to the above three situations of DU migration, and signaling design that needs to be enhanced in the processes.

[0091] Exemplary embodiments of the present disclosure are further described below with reference to the accompanying drawings.

[0092] The text and drawings are provided as examples only to help understand the present disclosure. They should not be interpreted as limiting the scope of the present disclosure in any way. Although certain embodiments and examples have been provided, based on the disclosure herein, it will be apparent to those skilled in the art that changes may be made to the illustrated embodiments and examples without departing from the scope of the present disclosure.

[0093] Before introducing the specific content, some assumptions and some definitions of the present disclosure are given below.

[0094] The message names in the present disclosure are just examples, and other message names may be used.

[0095] The "first" and "second" included in the message names in the present disclosure are only examples of messages and are only used to distinguish messages, and they do not represent an execution order.

[0096] A detailed description of steps irrelevant to the present disclosure is omitted in the present disclosure.

[0097] In the present disclosure, steps in various aspects, methods and processes may be combined with each other or performed independently. Execution steps of each process are only examples, and other possible execution orders are not excluded.

[0098] In the present disclosure, the base station may be a 5G base station (such as gNB, ng-eNB), a 4G base station (such as eNB), a 6G base station, or other types of access nodes.

[0099] In the present disclosure, the transmission of data refers to the reception and / or transmission of data.

[0100] The first aspect: a donor CU triggers DU migration

[0101] According to the four situations shown in FIGs. 4A- 4D, in the present disclosure, a donor CU at which an mIAB-MT and an mIAB-DU are terminated may be represented by the following terms:

[0102] ㆍ Source non-F1 terminating donor CU: that is, the donor CU at which the mIAB-MT is terminated before migration. Herein, it may also be called a fourth node;

[0103] ㆍ Source F1 terminating donor CU: that is, the donor CU at which the mIAB-DU is terminated before migration. Herein, it may also be called a second node;

[0104] ㆍ Target non-F1 terminating donor CU: that is, the donor CU at which the mIAB-MT is terminated after migration;

[0105] ㆍ Target F1 terminating donor CU: that is, the donor CU at which the mIAB-DU is terminated after migration. Herein, it may also be called a third node.

[0106] The initial state of the donor CU at which the mIAB-MT and mIAB-DU are terminated and situations of the migration of mIAB-MT and mIAB-DU may be expressed by the above four donor CUs. For example, if both mIAB-MT and mIAB-DU are terminated at the same donor CU in the initial state, and only the mIAB-DU migrates, then the source non-F1 terminating donor CU and the source F1 terminating donor CU are the same donor CU; because the mIAB-MT has not migrated, the target non-F1 terminating donor CU is also the same donor CU as the source non-F1 terminating donor CU; because only mIAB-DU migration has occurred, the target F1 terminating donor CU is different from the source non-F1 terminating donor CU, the source F1 terminating donor CU and the target non-F1 terminating donor CU. Therefore, in this way, all different situations of mIAB-MT and mIAB-DU migration can be represented by the above four donor CUs.

[0107] FIG. 5 is a schematic flow diagram of an example of DU migration triggered by a source F1 terminating donor CU. Because the present disclosure is mainly aimed at mIAB-DU migration, mIAB-MT migration is not the focus of the present disclosure, a target non-F1 terminating donor CU is omitted in FIG. 5. An example process is as follows:

[0108] 1) In step 501, the source F1 terminating donor CU transmits a first message to the mIAB node, which is used to trigger the mIAB node to initiate an F1 setup procedure or F1 setup request to the target F1 terminating donor CU. For example, the first message may include information for triggering the mIAB node to initiate an F1 setup procedure or F1 setup request to the target F1 terminating donor CU. The first message may be an F1 setup triggering message, or F1 setup triggering signaling, etc., which is not limited here.

[0109] ㆍ The first message may carry one or more of the following: a node ID (for example, a gNB ID, hereinafter, a node ID may be referred to as a gNB ID) and / or IP address of the target F1 terminating donor CU, an mIAB-MT ID (i.e., MT UE XnAP ID) (for example, an mIAB-MT ID generated for the MT of the mIAB node) generated by the source non-F1 terminating donor CU and / or gNB ID of the source non-F1 terminating donor CU, an F1 traffic profile related to the mIAB node, or an indication for the mIAB node to transmit the F1 traffic profile to the target F1 terminating donor CU. The indication may be an F1 traffic profile indication or an F1 traffic profile request, where the message name is not limited. The F1 traffic profile may include at least one of the following: the number of UEs served by the mIAB node, the number of Data Radio Bearers (DRBs) and / or traffic type of each UE, Radio Resource Status, activated cell list, etc. The F1 traffic profile may be at a cell level or at a UE level. When the target F1 terminating donor CU knows the F1 traffic profile related to the mIAB node, it is helpful for it to perform admission control, that is, whether to agree to the request of DU migration.

[0110] 2) In step 502, after the mIAB node receives the first message, mIAB-MT transmits a second message to the source non-F1 terminating donor CU. The second message may be an RRC message, which may be IAB other information or other RRC messages, and is not limited here. When the mIAB node knows that DU migration is to be performed, it will generate a second logical DU (that is, mIAB-DU2), which is used to initiate an F1 setup procedure to the target F1 terminating donor CU. It is the first logical DU (that is, mIAB-DU1) that keeps F1 connection with the source F1 terminating donor CU, and mIAB-DU1 and mIAB-DU2 are on a mIAB-DU entity.

[0111] ㆍ The second message may carry or include at least one of the following: the gNB ID and / or IP address of the target F1 terminating donor CU, and / or indication information (i.e. indication for DU migration) that the mIAB node is going to perform DU migration, so that the source non-F1 terminating donor CU can know that the mIAB node is going to perform DU migration, and which donor CU the target F1 terminating donor CU is. In this case, the source non-F1 terminating donor CU will not trigger mIAB-MT migration, to avoid concurrent mIAB-MT migration and mIAB-DU migration. In an example, the second message may not carry the indication information that the mIAB node is going to perform DU migration. In this case, the indication information that the mIAB node is going to perform DU migration may be implicitly indicated by the gNB ID and / or IP address of the target F1 terminating donor CU. In an example, the second message may carry the indication information that the mIAB node is going to perform DU migration, in which case, the indication information that the mIAB node is going to perform DU migration may be explicitly indicated. When the TNL address (Transport Network Layer address) of mIAB-DU2 is configured by an operation administration and maintenance (OAM), or is one selected by mIAB-DU2 from a TNL address set / list pre-configured by the OAM or source non-F1 terminating donor CU, the second message also needs to carry the TNL address of mIAB-DU2, so that the source non-F1 terminating donor CU can configure BAP configuration (backhaul adaptation protocol configuration) for mIAB-DU2 after knowing it.

[0112] 3) In step 503, mIAB-DU2 transmits a third message to the target F1 terminating donor CU, so as to transmit a request for establishing an F1 connection to the target F1 terminating donor CU, which may be an F1 setup request (or referred to as an F1 connection setup request) or other F1AP messages, which is not limited here. For example, the third message may include the F1 connection setup request to the target F1 terminating donor CU.

[0113] ㆍ The third message may carry or include at least one of the following: the mIAB-MT ID generated by the source non-F1 terminating donor CU and gNB ID of the source non-F1 terminating donor CU, the gNB ID of the source F1 terminating donor CU, the F1 traffic profile related to the mIAB node, the expected or desired activated cell list of the mIAB-DU2, and the cell group configuration (CellGroupConfig) related information of the mIAB-DU1, etc. After the target F1 terminating donor CU knows the gNB ID of the source F1 terminating donor CU, it can know whether there is an Xn interface with the source F1 terminating donor CU, which facilitates the target F1 terminating donor CU to perform admission control. It can also help the target F1 terminating donor CU to perform admission control after knowing the expected or desired activated cell list of mIAB-DU2 and / or the F1 traffic profile related to the mIAB node. After the target F1 terminating donor CU knows the relevant information of the CellGroupConfig of mIAB-DU1, it facilitates the target F1 terminating donor CU to configure the same CellGroupConfig for mIAB-DU2.

[0114] 4) In step 504, after receiving the third message, the target F1 terminating donor CU transmits a fourth message to mIAB-DU2 to inform the mIAB node whether to agree to establish an F1 connection with it. The fourth message may be an F1 setup response or other F1AP messages, which is not limited here.

[0115] ㆍ The fourth message may carry at least one of the following: indication information about whether to accept F1 setup (for example, the above F1 connection setup request), list of cells to be activated (i.e. Cells to be Activated list) on mIAB-DU2, acceptable F1 traffic and / or F1 traffic profile, and the mIAB-MT ID (i.e. MT UE XnAP ID) generated by the target F1 terminating donor CU.

[0116] 5) In step 505, after the mIAB node receives the fourth message, the mIAB-MT transmits a fifth message (for example, an RRC message, such as a UL RRC message) to the source non-F1 terminating donor CU.

[0117] ㆍ The fifth message may be an RRC message, and may carry the mIAB-MT ID generated by the target F1 terminating donor CU (for example, the mIAB-MT ID generated for the MT of the mIAB node). After receiving the fifth message, the source non-F1 terminating donor CU is convenient to accept an IAB transport migration management (IAB TMM) message transmitted by the target F1 terminating donor CU, because the IAB TMM message transmitted by the target F1 terminating donor CU to the source non-F1 terminating donor CU needs to contain the mIAB-MT IDs generated by the target F1 terminating donor CU and the source non-F1 terminating donor CU.

[0118] 6) In step 506, after the successful establishment of the F1 connection between mIAB-DU2 and the target F1 terminating donor CU, mIAB-DU1 transmits a sixth message (Indication for successful F1 setup) to the source F1 terminating donor CU to let the source F1 terminating donor CU know that the F1 connection between mIAB-DU2 and the target F1 terminating donor CU has been successfully established.

[0119] ㆍ The sixth message may be an F1AP message, and in addition to the indication information that the F1 connection between mIAB-DU2 and the target F1 terminating donor CU has been successfully established, it may carry at least one of the following: related information of serving cells activated on mIAB-DU2 (for example, activated serving cell list, activated serving cell ID, and ServCellInfo IE or some information in this IE, such as uplink or downlink carrier frequency, transmission bandwidth, etc.), target cell ID, F1 traffic and / or F1 traffic profile acceptable to the target F1 terminating donor CU, so that the source F1 terminating donor CU can decide whether to change the target F1 terminating donor CU to which the mIAB-DU is to migrate.

[0120] 7) In step 507, after the source F1 terminating donor CU receives the sixth message, if it agrees the mIAB-DU to migrate to the target F1 terminating donor CU, that is to say, it can accept the F1 traffic and / or the F1 traffic profile that the target F1 terminating donor CU can accept, then the source F1 terminating donor CU performs UE context handover (HO) process.

[0121] Specifically, the source F1 terminating donor CU transmits a handover command to the UE, which carries a target cell ID selected from target cell IDs, and the UE performs cell handover. After the handover is completed, the UE transmits an RRC reconfiguration complete message to the target cell.

[0122] In another implementation, after the source F1 terminating donor CU receives the sixth message in FIG. 5, if the migration of mIAB-DU to the target F1 terminating donor CU is not agreed, that is, the F1 traffic and / or the F1 traffic profile acceptable to the target F1 terminating donor CU cannot be accepted, the source F1 terminating donor CU can change the target F1 terminating donor CU to which mIAB-DU is to migrate, and the flow is shown in FIG. 6. An example process is as follows:

[0123] 1) The first six steps in FIG. 6 (namely, F1 setup trigger, RRC message, F1 setup request, F1 setup response, RRC message, and F1 setup success) are the same as the first six steps in FIG. 5, and will not be repeated here.

[0124] 2) In step 601, after the source F1 terminating donor CU receives the sixth message transmitted by mIAB-DU1, if it does not agree with the migration of mIAB-DU to the target F1 terminating donor CU, that is, it cannot accept the F1 traffic and / or the F1 traffic profile that the target F1 terminating donor CU can accept, the source F1 terminating donor CU transmits a seventh message to mIAB-DU1, indicating the mIAB node to cancel (or remove) the newly established F1 connection between mIAB-DU2 and the target F1 terminating donor CU.

[0125] ㆍ The seventh message may be an F1AP message, it may reuse the first message, but the message content it carries is different, and it may also be a newly defined message, which is not limited here. The seventh message may carry or include at least one of the following: information indicating cancellation / removal of the newly established (that is, the above-mentioned successfully established) F1 connection between mIAB-DU2 and the target F1 terminating donor CU, and the gNB ID and / or IP address of the new target F1 terminating donor CU. The seventh message may also carry or include at least one of the following: mIAB-MT ID (i.e. MT UE XnAP ID) generated by the source non-F1 terminating donor CU and / or gNB ID of the source non-F1 terminating donor CU, and the F1 traffic profile related to the mIAB node, and / or information indicating the mIAB node to transmit the F1 traffic profile to the new target F1 terminating donor CU.

[0126] 3) In step 602, after the mIAB node receives the seventh message, mIAB-DU2 transmits an eighth message to the target F1 terminating donor CU, which is used to indicate the cancellation / removal of the newly established F1 connection between mIAB-DU2 and the target F1 terminating donor CU.

[0127] ㆍ The eighth message may be an F1AP message, an F1 removal request message, or other F1AP messages, which is not limited here. The eighth message may include information to indicate cancellation / removal of the newly established (i.e., the above-mentioned successfully established) F1 connection between the mIAB-DU2 and the target F1 terminating donor CU. The eighth message may also carry a new cause value to indicate the reason for the removal of F1 to the target F1 terminating donor CU. The meaning of this value may be that the source F1 terminating donor CU does not agree to the DU migration, or the source F1 terminating donor CU cannot accept the F1 traffic and / or the F1 traffic profile that the target F1 terminating donor CU can accept.

[0128] 4) In step 603, after receiving the eighth message, the target F1 terminating donor CU replies a ninth message to mIAB-DU2, indicating that it agrees to perform an F1 removal process.

[0129] ㆍ The ninth message may also be an F1AP message, an F1 removal response message, or other F1AP messages, which is not limited here. For example, the ninth message may include at least one of the following: information indicating that the target F1 terminating donor CU agrees to cancel / remove the above successfully established F1 connection between the mIAB-DU2 and the target F1 terminating donor CU.

[0130] 5) After the mIAB-DU2 receives the ninth message, it indicates that the newly established F1 connection between mIAB-DU2 and the target F1 terminating donor CU has been cancelled / removed. Then, according to the gNB ID and / or IP address of the new target F1 terminating donor CU in the seventh message transmitted by the source F1 terminating donor CU, an F1 setup procedure (or F1 setup request) is initiated to the new target F1 terminating donor CU, and the subsequent flow is similar to the third message and the flow after the third message in the flow of FIG. 5, so the description will not be repeated here.

[0131] The second aspect: an OAM triggers mIAB-DU migration

[0132] When mIAB-DU is triggered by OAM, it can be divided into three different situations, as shown in FIG. 7:

[0133] ㆍ Case 1: When OAM decides to let mIAB node perform DU migration, it transmits an F1 setup trigger message to mIAB-DU, so that the mIAB-DU can directly initiate an F1 setup procedure to the target F1 terminating donor CU.

[0134] ㆍ Case 2: When OAM decides to let mIAB node perform DU migration, it first transmits an F1 setup trigger message (and / or a DU migration indication message) to mIAB-DU; after receiving this message, mIAB node can know that OAM wants it to perform DU migration. However, the mIAB node does not directly initiate an F1 setup procedure to the target F1 terminating donor CU, but first communicates with the source F1 terminating donor CU, and then initiates an F1 setup procedure to the target F1 terminating donor CU if the source F1 terminating donor CU agrees.

[0135] ㆍ Case 3: When OAM decides to let mIAB node perform DU migration, it first informs the source F1 terminating donor CU. If the source F1 terminating donor CU agrees to perform DU migration, it transmits an F1 setup trigger message to mIAB node to trigger the mIAB node to initiate an F1 setup procedure to the target F1 terminating donor CU.

[0136] ㆍ Therefore, processes in which an OAM triggers mIAB-DU migration need to be given according to the above three different situations.

[0137] FIG. 8 is a flowchart of Case 3. Because the DU migration is triggered by OAM, the target F1 terminating donor CU to which mIAB-DU is to migrate is determined by OAM. An example process is as follows:

[0138] 1) In step 801, when OAM decides to trigger DU migration, OAM transmits a tenth message to the source F1 terminating donor CU.

[0139] ㆍ The tenth message may carry or include at least one of the following: information indicating that mIAB-DU migration is to be performed (for example, information indicating mIAB node to perform DU migration), and / or the gNB ID and / or IP address of the target F1 terminating donor CU, so as to let the source F1 terminating donor CU know to which donor CU the mIAB-DU is to migrate, and whether it agrees to migrate the mIAB-DU to this donor CU. The tenth message may also carry the mIAB-DU ID and / or the mIAB-MT ID generated by the source F1 terminating donor CU, so as to let the source F1 terminating donor CU know which DU or DU of which mIAB node needs to be migrated, since the source F1 terminating donor CU may serve multiple mIAB nodes.

[0140] 2) After the source F1 terminating donor CU receives the tenth message transmitted by OAM, if it agrees to perform DU migration, the source F1 terminating donor CU transmits a first message to mIAB-DU, that is, an F1 setup triggering message, which is used to trigger the mIAB node to initiate an F1 setup procedure to the target F1 terminating donor CU. The following process is the same as that in FIG. 5, and will not be repeated here.

[0141] FIG. 9 is a schematic flowchart of Case 2, and an example is as follows:

[0142] 1) In step 901, when OAM decides to trigger DU migration, OAM transmits an eleventh message to mIAB node, which may include information for indicating mIAB node to perform DU migration.

[0143] ㆍ The eleventh message may carry or include at least one of the following: the gNB ID and / or IP address of the target F1 terminating donor CU, so as to let the mIAB node know to which target donor CU the DU needs to migrate.

[0144] 2) In step 902, after receiving the eleventh message transmitted by OAM, the mIAB node transmits a twelfth message to the source F1 terminating donor CU, which may include information for indicating the source F1 terminating donor CU that mIAB-DU migration is to be performed. The twelfth message may be an F1AP message or other suitable messages.

[0145] ㆍ The twelfth message may carry or include at least one of the following: the gNB ID and / or IP address of the target F1 terminating donor CU, so as to let the source F1 terminating donor CU know to which target donor CU the mIAB-DU is migrated.

[0146] 3) If the source F1 terminating donor CU agrees to the migration of mIAB-DU (that is, agrees to the migration of mIAB-DU to the target F1 terminating donor CU), the source F1 terminating donor CU transmits a first message to the mIAB node for triggering the mIAB node to initiate an F1 setup procedure to the target F1 terminating donor CU. The subsequent flow is as shown in FIG. 5, and will not be repeated here.

[0147] ㆍ Here, the first message may no longer contain the gNB ID and / or IP address of the target F1 terminating donor CU, because the mIAB node has obtained these information from OAM.

[0148] FIG. 10 is a schematic flowchart of Case 1. Because OAM directly triggers mIAB node to perform DU migration, the source F1 terminating donor CU does not know which target donor CU the mIAB-DU has migrated to until the F1 connection between mIAB-DU2 and the target F1 terminating donor CU is successfully established. Therefore, the flowchart of Case 1 is quite different from that of Case 2 and Case 3. An example process is as follows:

[0149] 1) In step 1001, when OAM decides to trigger DU migration, OAM transmits an eleventh message to mIAB node, which may include information for indicating mIAB node to perform DU migration.

[0150] ㆍ The eleventh message may carry or include at least one of the following: the gNB ID and / or IP address of the target F1 terminating donor CU, so as to let the mIAB node know to which target donor CU the DU needs to migrate. It may also carry the TNL address configured by OAM for mIAB-DU2.

[0151] 2) In step 1002, after the mIAB node receives the eleventh message transmitted by OAM and knows that the OAM enables it perform DU migration, the mIAB node generates a second logical DU, namely mIAB-DU2. mIAB-MT transmits a second message to the source non-F1 terminating donor CU.

[0152] ㆍ The content contained in this second message may be the same as that contained in the second message in FIG. 5.

[0153] 3) After receiving the second message, the source non-F1 terminating donor CU knows that mIAB-DU is going to migrate, so the source non-F1 terminating donor CU will no longer trigger MT migration, so as to avoid concurrent MT migration and DU migration. In step 1003, after receiving the second message, the source non-F1 terminating donor CU transmits a thirteenth message to the mIAB-MT, so that the mIAB node may inform the target F1 terminating donor CU of the mIAB-MT ID generated by it.

[0154] ㆍ The thirteenth message may be an RRC message (for example, a DL RRC message), and may carry or include at least one of the following: the mIAB-MT ID generated by the source non-F1 terminating donor CU (for example, the mIAB-MT ID generated for the MT of the mIAB node) and / or the gNB ID of the source non-F1 terminating donor CU.

[0155] 4) In step 1004, after the mIAB node receives the thirteenth message, mIAB-DU2 transmits a third message to the target F1 terminating donor CU, and the content contained in the third message may be the same as that contained in the third message in FIG. 5.

[0156] 5) In step 1005, after receiving the third message, the target F1 terminating donor CU replies to mIAB-DU2 with a fourth message, which may be the same as the fourth message in FIG. 5.

[0157] 6) In step 1006, after receiving the fourth message, the mIAB node transmits a fifth message to the source non-F1 terminating donor CU, and the content contained in the fifth message may be the same as that contained in the fifth message in FIG. 5.

[0158] 7) In step 1007, mIAB-DU1 transmits a sixth message to the source F1 terminating donor CU, informing it that the F1 connection between mIAB-DU2 and the target F1 terminating donor CU has been successfully established.

[0159] ㆍ In addition to the same contents as that contained in the sixth message in FIG. 5, the sixth message also needs to carry the gNB ID and / or IP address of the target F1 terminating donor CU, so that the source F1 terminating donor CU can know to which target donor CU the mIAB-DU has migrated, and let the source F1 terminating donor CU decide whether to agree to migrate the DU to the target F1 terminating donor CU. If the source F1 terminating donor CU agrees to the DU migration, a UE context handover process can be performed; and if the source F1 terminating donor CU disagrees with the DU migration, the flow in FIG. 6 can be performed.

[0160] In some implementations, no matter the DU migration is triggered by a donor CU in the first aspect or is triggered by OAM in the second aspect, mIAB-DU2 needs to inform the target F1 terminating donor CU with a serving cell list that the mIAB-DU2 wants or expects to activate, in order for the target F1 terminating donor CU to perform admission control. For example, the mIAB node or mIAB-DU2 may transmit information about the list of serving cells that the mIAB node or mIAB-DU2 expects to activate to the target F1 terminating donor CU. One aspect of the present disclosure also proposes the following methods for how to do signaling enhancement in F1 setup request:

[0161] Option 1: directly add a new information element (IE) in the F1 setup request (which may be called a first IE herein) to directly indicate a list of serving cells that mIAB-DU2 wants or expects to activate. This IE may be called Preference for activated cells list or other names, and there is no limitation here. FIG. 11 shows an example of this IE.

[0162] Option 2: add status information after the serving cell list, such as preference status, that is, each serving cell ID corresponds to a preference status. The preference status may be "preferred" or "not preferred"; it may also be "true" (indicating "wanted" or "expected") or "false"(indicating "not wanted" or "not expected"); or it may also be that when a serving cell ID has a corresponding preference status, it indicates that it is wanted / expected, and when it does not have, it indicates that it is not wanted / not expected.

[0163] Option 3: add a new IE (it may be called a second IE herein) in the F1 setup request, which indicates that all the cells in the serving cell list are serving cells that the mIAB node wants or expects to activate. This IE may be called Preference for all served cells or other names, and there is no limitation here. An example of this IE is shown in FIG. 11. In an implementation, if this IE exists, it means that all the cells in the serving cell list are serving cells that the mIAB node wants or expects to activate; and if it does not exist, there is no such indication. In another implementation, it may also be represented by 1 bit, which means that all the cells in the serving cell list are serving cells that the mIAB node wants or expects to activate when it is 1; and when it is 0, it means no such indication, and vice versa.

[0164] The third aspect: notification of successful establishment of a new F1 connection when source link lost occurs

[0165] Because of the mobility of mIAB nodes, mIAB-DU1 may lose (or disconnect) the F1 connection with the source F1 terminating donor CU before mIAB-DU migration is completed. This problem is called source link lost. There are many reasons for source link lost. For example, a parent IAB node between the source F1 terminating donor CU and mIAB-DU1 is disconnected from the source F1 terminating donor CU or mIAB-DU1. However, when the F1 connection between mIAB-DU2 and the target F1 terminating donor CU is successfully established, the mIAB node needs to notify the source F1 terminating donor CU the same, and if the source link lost occurs, it cannot be notified to the source F1 terminating donor CU by mIAB-DU1. Therefore, the present disclosure proposes a corresponding solution to this problem. The specific process is shown in FIG. 12. An example of the specific process is as follows:

[0166] 1) When the source link lost occurs, the mIAB-DU1 cannot transmit the sixth message (for example, successful F1 setup) to the source F1 terminating donor CU, and then the mIAB node will know the occurrence of the source link lost.

[0167] 2) In step 1201, mIAB-DU2 transmits a fourteenth message to the target F1 terminating donor CU, which is used to indicate the target F1 terminating donor CU that the source F1 connection is disconnected (that is, the F1 connection between mIAB-DU1 and the source F1 terminating donor CU is disconnected).

[0168] ㆍ The fourteenth message may be an F1AP message, which may reuse the third message or be a new message. In addition to indicating the target F1 terminating donor CU that the source F1 connection is disconnected, it can also indicate the target F1 terminating donor CU to transmit the contents of the sixth message which initially should be transmitted by mIAB-DU1 to the source F1 terminating donor CU. The message may also carry the contents of the sixth message, and optionally, it may not carry the contents of the sixth message that is already known to the target F1 terminating donor CU. The message may also carry indication information to indicate the target F1 terminating donor CU to notify the source F1 terminating donor CU of the source link lost.

[0169] 3) In step 1202, after receiving the fourteenth message, the target F1 terminating donor CU transmits a fifteenth message to the source F1 terminating donor CU, so as to let the source F1 terminating donor CU know that the F1 connection between mIAB-DU2 and the target F1 terminating donor CU has been successfully established.

[0170] ㆍ The fifteenth message may be an XnAP (Xn Application Protocol) message, which may be an Xn setup request message or other XnAP messages, and is not limited here. In addition to the indication information that the F1 connection has been successfully established, the message may also include the indication of source link lost, and some or all of the contents carried in the sixth message in FIG. 5. For example, the fifteenth message may include at least one of the following: information indicating that the F1 connection between mIAB-DU2 and the target F1 terminating donor CU is successfully established, information indicating that the source F1 connection between mIAB-DU1 and the source F1 terminating donor CU is disconnected, and one or more of the contents carried by the sixth message in FIG. 5.

[0171] 4) In step 1203, after receiving the fifteenth message, the source F1 terminating donor CU knows the occurrence of the source link lost, and performs a UE context handover process when the source link lost occurs.

[0172] This embodiment solves the problem of how to inform the source F1 terminating donor CU that the new F1 connection is successfully established when the source link lost occurs.

[0173] The fourth aspect: avoid concurrent MT migration and DU migration

[0174] The present invention mentioned earlier that when the source F1 terminating donor CU triggers the mIAB node to perform DU migration, the mIAB node will transmit a second message to the source non-F1 terminating donor CU, and the source non-F1 terminating donor CU will not trigger the migration of MT after receiving the second message and knowing about the DU migration. In another case, MT migration may occur before DU migration. In this case, it is also necessary to let the source F1 terminating donor CU to know the MT migration, so as not to trigger the DU migration any more. The specific process is as follows:

[0175] 1) The source F1 terminating donor CU transmits a first message to the mIAB node (or mIAB-DU1), which is used to trigger the mIAB node to initiate an F1 setup procedure or F1 setup request (F1 setup procedure or F1 setup request) to the target F1 terminating donor CU. This step is shown as step 501 in FIG. 5.

[0176] 2) mIAB node knows that itself is performing MT migration, and after receiving the first message transmitted by the source F1 terminating donor CU, it replies a sixteenth message to the source F1 terminating donor CU.

[0177] This message is an F1AP message, which may be an F1 setup failure message or other F1AP messages, and there is no restriction here. If the message is an F1 setup failure message, it may carry a new cause value, which indicates the source F1 terminating donor CU the reason why the F1 setup fails, which may be that MT migration is being performed / will be performed. If the message is another F1AP message or a newly defined F1AP message, it may carry indication information, which indicates that MT is being migrated / will be migrated.

[0178] 3) After receiving the sixteenth message, the source F1 terminating donor CU will not trigger the mIAB node to perform DU migration during the MT migration process.

[0179] In another embodiment, when the mIAB node performs MT migration, it may also actively transmit indication information to the source F1 terminating donor, indicating that it is performing MT migration. The specific process is as follows:

[0180] 1) The source non-F1 terminating donor CU transmits the 17th message to the mIAB node (or mIAB-MT), which is used to trigger the mIAB node to perform MT migration.

[0181] The message is an RRC message, which may be an RRC reconfiguration message or other RRC messages, and is not limited here.

[0182] 2) After receiving the seventeenth message, the mIAB node knows that MT migration is to be performed, and transmits an eighteenth message to the source F1 terminating donor CU, indicating that it is performing MT migration / will perform MT migration.

[0183] The eighteenth message is an F1AP message, and the eighteenth message may reuse the sixteenth message or other F1AP messages, which is not limited here.

[0184] 3) After receiving the eighteenth message, the source F1 terminating donor CU will not trigger the mIAB node to perform DU migration during the MT migration.

[0185] In another embodiment, when the source non-F1 terminating donor CU decides to perform MT migration, it may directly inform the same to the source F1 terminating donor CU, and in this case, the source F1 terminating donor CU will not trigger the mIAB node to perform DU migration during MT migration. The flowchart is shown in FIG. 13, and an example is as follows:

[0186] 1) In step 1301, when the source non-F1 terminating donor CU decides to perform MT migration, it transmits a twenty-fifth message to the source F1 terminating donor CU, indicating the source F1 terminating donor CU that mIAB-MT will be migrated / is being migrated.

[0187] The message may be an XnAP message, and besides the above indication information, it may also carry the gNB ID and / or IP address of the target non-F1 terminating donor CU, so as to let the source F1 terminating donor CU know which target IAB donor the mIAB-MT is migrated to. A timer may also be carried, which is used by the source non-F1 terminating donor CU to judge whether a feedback from the source F1 terminating donor CU is received within the duration of the timer.

[0188] 2) In step 1302, after receiving the twenty-fifth message and knowing the target IAB donor to which the mIAB-MT will migrate, the source F1 terminating donor CU judges whether to perform mIAB-DU migration. If the source F1 terminating donor CU decides to perform DU migration and also migrates the mIAB-DU to the target non-F1 terminating donor CU, a twenty-sixth message is transmitted to the source non-F1 terminating donor CU within the duration of the timer, indicating that its mIAB-DU would also be migrated to the target non-F1 terminating donor CU. On the other hand, if it is decided not to perform DU migration, or not to migrate mIAB-DU to the target non-F1 terminating donor CU, the twenty-sixth message is not transmitted. The twenty-sixth message is an XnAP message.

[0189] 3) In step 1303, if the source non-F1 terminating donor CU receives the twenty-sixth message, it carries part or all of the UE context information or all or part of the UE context information of a part of the UEs in the a twenty-seventh message transmitted to the target non-F1 terminating donor CU. On the other hand, if the twenty-sixth message is not received, it does not carry UE context related information in the twenty-seventh message transmitted to the target non-F1 terminating donor CU. The twenty-seventh message is an XnAP message, which may be a handover request message or other messages, and there is no restriction here.

[0190] The fifth aspect: a network integration process of mIAB nodes

[0191] In a network integration process, mIAB-MT and mIAB-DU may also be connected to different IAB donors respectively. The flowchart is shown in FIG. 14, and the specific process is as follows:

[0192] 1) In step 1401, the mIAB-MT initiates a random access procedure to the source non-F1 terminating donor CU to complete the mIAB-MT integration process;

[0193] 2) In step 1402, OAM configures DU-related parameters for mIAB-DU, and allocates a source F1 terminating donor CU for mIAB-DU, that is, OAM transmits a gNB ID and / or IP address of a source F1 terminating donor CU to mIAB-DU;

[0194] 3) In step 1403, after mIAB-DU knows the gNB ID and / or IP address of the source F1 terminating donor CU, mIAB-MT transmits a nineteenth message to the source non-F1 terminating donor CU, and informs the source non-F1 terminating donor CU of the relevant information of the source F1 terminating donor CU;

[0195] The nineteenth message is an RRC message, which may reuse the second message or other RRC messages, and is not limited here. The message may carry the gNB ID and / or IP address of the source F1 terminating donor CU, and the ID and / or IP address of the mIAB-DU;

[0196] 4) In step 1404, after receiving the nineteenth message, the source non-F1 terminating donor CU replies a twentieth message to mIAB-MT, which carries relevant information of BAP configuration.

[0197] The twentieth message is an RRC message, which may be an RRC reconfiguration message or other messages, and is not limited here. In addition to carrying the BAP-related configuration message, it may also carry the mIAB-MT ID generated by the source non-F1 terminating donor CU (for example, the mIAB-MT ID generated for the MT of the mIAB node) and / or the gNB ID of the source non-F1 terminating donor CU. Optionally, if the source non-F1 terminating donor CU triggers the mIAB node to perform an F1 setup procedure in the network integration process, the twentieth message also needs to carry information for triggering the mIAB node to initiate an F1 setup procedure or F1 setup request to the source F1 terminating donor CU. If OAM triggers mIAB node to perform an F1 setup procedure in the network integration process, it is unnecessary for the twentieth message to carry the trigger information.

[0198] 5) In step 1405, after receiving the twentieth message, the mIAB node transmits a twenty-first message to the source F1 terminating donor CU to initiate the F1 setup procedure.

[0199] The twenty-first message is an F1AP message, and it may reuse the third message or be a new message, which is not limited here. The message may carry the mIAB-MT ID generated by the source non-F1 terminating donor CU (for example, the mIAB-MT ID generated for the MT of the mIAB node) and / or the gNB ID of the source non-F1 terminating donor CU.

[0200] 6) In step 1406, the source F1 terminating donor CU replies a twenty-second message to the mIAB-DU to inform the mIAB node whether it agrees to establish an F1 connection with the mIAB node. The twenty-second message may be F1 setup response, which may reuse the fourth message, or may be other F1AP messages, which is not limited here. The content carried by this message may be the same as that of the fourth message.

[0201] 7) In step 1407, the source F1 terminating donor CU transmits a twenty-third message to the source non-F1 terminating donor CU to trigger an IAB TMM process.

[0202] The twenty-third message is an XnAP message, which may be an IAB TMM request or other XnAP messages, which is not limited here. The message may also carry information indicating that F1 is successfully established, which is used to indicate the source non-F1 terminating donor CU that the F1 connection between the mIAB-DU and the source F1 terminating donor CU is successfully established. If the twenty-third message does not carry the information indicating that F1 is successfully established, the mIAB-MT needs to transmit an RRC message to the source non-F1 terminating donor CU to indicate the source non-F1 terminating donor CU that the F1 connection between the mIAB-DU and the source F1 terminating donor CU is successfully established.

[0203] 8) In step 1408, after receiving the twenty-third message, the source non-F1 terminating donor CU replies a twenty-fourth message to the source F1 terminating donor CU. This message is an XnAP message, which may be an IAB TMM response or other XnAP messages, and is not limited here.

[0204] It should be understood that, depending on the application scenario, the various example aspects, methods, steps, processes, etc. shown above in conjunction with the drawings can be combined and implemented in any way, and there is no limitation here.

[0205] Next, FIG. 15 shows a flowchart of a method 1500 performed by a first node in a wireless communication system according to embodiments of the present disclosure.

[0206] As shown in FIG. 15, a method 1500 performed by a first node in a wireless communication system according to embodiments of the present disclosure may include: in step S1501, transmitting a third message to a third node, where the third message includes information about a list of serving cells that the first node expects to activate and an F1 traffic profile; In step S1502, receiving a fourth message from the third node in response to the third message, where the fourth message includes an acceptable F1 traffic profile and information of cells to be activated; and in step S1503, transmitting a sixth message to the second node, where the sixth message includes information of activated cells and an acceptable F1 traffic profile.

[0207] According to embodiments of the present disclosure, the method 1500 may further include receiving a first message from a second node, wherein the first message includes the F1 traffic profile.

[0208] According to embodiments of the present disclosure, the method 1500 may further include transmitting a second message to a fourth node, wherein the second message includes at least one of the following: a transport network layer (TNL) address of a second DU of the first node, a node ID and / or IP address of the third node, and information indicating that the first node will perform distributed unit (DU) migration.

[0209] According to embodiments of the present disclosure, the method 1500 may further include transmitting a fifth message to a fourth node, wherein the fifth message includes a mobile integrated access and backhaul-mobile terminal (mIAB-MT) ID generated by the third node for the first node.

[0210] According to embodiments of the present disclosure, the method 1500 may further include: receiving a seventh message from the second node, wherein the seventh message includes at least one of the following: information indicating cancellation of a successfully established F1 connection between the first node and the third node, node ID and / or IP address of a new target F1 terminating donor CU; transmitting an eighth message to the third node, wherein the eighth message includes at least one of the following: information indicating cancellation of a successfully established F1 connection between the first node and the third node, a cause value for cancellation of the successfully established F1 connection between the first node and the third node; and receiving a ninth message from the third node, wherein the ninth message includes information indicating that the third node agrees to cancel a successfully established F1 connection between the first node and the third node.

[0211] According to embodiments of the present disclosure, the first message is transmitted from the second node in a case that the second node receives a tenth message from an Operation Administration and Maintenance (OAM) node, wherein the tenth message includes at least one of the following: information indicating the first node to perform distributed unit (DU) migration, a node ID and / or IP address of the third node.

[0212] According to embodiments of the present disclosure, the method 1500 may further include: receiving an eleventh message from an Operation Administration and Maintenance (OAM) node, wherein the eleventh message includes at least one of the following: information indicating the first node to perform distributed unit (DU) migration, a node ID and / or IP address of the third node; and transmitting a twelfth message to the second node, wherein the twelfth message includes the node ID and / or IP address of the third node.

[0213] According to embodiments of the present disclosure, the first message is transmitted from the second node in a case that the second node agrees to migrate a distributed unit (DU) of the first node to the third node.

[0214] According to embodiments of the present disclosure, the method 1500 may further include: receiving an eleventh message from an Operation Administration and Maintenance (OAM) node, wherein the eleventh message includes at least one of the following: information indicating the first node to perform distributed unit (DU) migration, a node ID and / or IP address of the third node; receiving a thirteenth message from the fourth node, wherein the thirteenth message includes at least one of the following: a mobile integrated access and backhaul-mobile terminal (mIAB-MT) ID generated by the fourth node for the first node, a node ID of the fourth node; and transmitting a fifth message to the fourth node, wherein the fifth message includes a mobile integrated access and backhaul-mobile terminal (mIAB-MT) ID generated by the third node for the first node.

[0215] According to embodiments of the present disclosure, the information about a list of serving cells that the first node expects to activate is indicated by one or more of the following: indicated by a first information element in an F1 setup request, wherein the first information element indicates a list of serving cells that the first node expects to activate; indicated by state information corresponding to each serving cell in a serving cell list; or indicated by a second information element in an F1 setup request, wherein the second information element indicates whether all cells in a serving cell list are serving cells that the first node expects to activate.

[0216] According to embodiments of the present disclosure, the method 1500 may further include: transmitting a fourteenth message to the third node in a case that transmission of the sixth message fails, wherein the fourteenth message includes at least one of the following: information indicating that a source F1 connection between the first node and the second node is disconnected, information indicating the third node to transmit the sixth message to the second node, and information indicating the third node to inform the second node that the source F1 connection between the first node and the second node is disconnected.

[0217] FIG. 16 shows a flowchart of a method 1600 performed by a second node in a wireless communication system according to embodiments of the present disclosure.

[0218] As shown in FIG. 16, a method 1600 performed by a second node in a wireless communication system according to embodiments of the present disclosure may include: in step S1601, transmitting a first message to a first node, where the first message includes an F1 traffic profile; and in step S1602, receiving a sixth message from the first node, where the sixth message includes information of activated cells and an acceptable F1 traffic profile.

[0219] According to embodiments of the present disclosure, the method further includes: in a case that the distributed unit (DU) of the first node is agreed to migrate to the third node, performing a user equipment context handover process.

[0220] According to embodiments of the present disclosure, the method 1600 may further include: transmitting a seventh message to the first node, wherein the seventh message includes at least one of the following: information indicating cancellation of a successfully established F1 connection between the first node and the third node, a node ID and / or IP address of a new target F1 terminating donor CU.

[0221] According to embodiments of the present disclosure, the method 1600 may further include: receiving a tenth message from an Operation Administration and Maintenance (OAM) node, wherein the tenth message includes at least one of the following: information indicating the first node to perform distributed unit (DU) migration, a node ID and / or IP address of a third node, wherein the first message is transmitted to the first node in a case that the second node receives the tenth message.

[0222] According to embodiments of the present disclosure, the method 1600 may further include receiving a twelfth message from the first node, wherein the twelfth message includes a node ID and / or IP address of a third node, wherein the node ID and / or IP address of the third node is received by the first node from an Operation Administration and Maintenance (OAM) node.

[0223] According to embodiments of the present disclosure, the first message is transmitted from the second node in a case that the second node agrees to migrate a distributed unit (DU) of the first node to the third node.

[0224] According to embodiments of the present disclosure, the method 1600 may further include: receiving a fifteenth message from a third node in a case that reception of the sixth message from the first node fails, wherein the fifteenth message includes at least one of the following: information indicating that an F1 connection between the first node and the third node is successfully established, information indicating that a source F1 connection between the first node and the second node is disconnected, target cell ID, information of activated cells, and an acceptable F1 traffic profile.

[0225] FIG. 17 shows a flowchart of a method 1700 performed by a third node in a wireless communication system according to embodiments of the present disclosure.

[0226] As shown in FIG. 17, a method 1700 performed by a third node in a wireless communication system according to embodiments of the present disclosure may include: in step S1701, receiving a third message from a first node, where the third message includes information about a list of serving cells that the first node expects to activate and an F1 traffic profile; and in step S1702, transmitting a fourth message to the first node, where the fourth message includes an acceptable F1 traffic profile and information of cells to be activated.

[0227] According to embodiments of the present disclosure, the method 1700 may further include: receiving an eighth message from the first node, wherein the eighth message includes at least one of the following: information indicating cancellation of a successfully established F1 connection between the first node and the third node, a cause value for cancellation of the successfully established F1 connection between the first node and the third node; and transmitting a ninth message to the first node, wherein the ninth message includes information indicating that the third node agrees to cancel a successfully established F1 connection between the first node and the third node, wherein the eighth message is transmitted from the first node in a case that the first node receives a seventh message from a second node, wherein the seventh message includes at least one of the following: information indicating cancellation of a successfully established F1 connection between the first node and the third node, node ID and / or IP address of a new target F1 terminating donor CU.

[0228] According to embodiments of the present disclosure, the information about a list of serving cells that the first node expects to activate is indicated by one or more of the following: indicated by a first information element in an F1 setup request, wherein the first information element indicates a list of serving cells that the first node expects to activate; indicated by state information corresponding to each serving cell in a serving cell list; or indicated by a second information element in an F1 setup request, wherein the second information element indicates whether all cells in a serving cell list are serving cells that the first node expects to activate.

[0229] According to embodiments of the present disclosure, the method 1700 may further include receiving a fourteenth message from the first node, wherein the fourteenth message includes at least one of the following: information indicating that a source F1 connection between the first node and the second node is disconnected, information indicating the third node to transmit a sixth message to the second node, and information indicating the third node to inform the second node that the source F1 connection between the first node and the second node is disconnected, wherein the fourteenth message is transmitted from the first node in a case that transmission of the sixth message from the first node to the second node fails.

[0230] According to embodiments of the present disclosure, the method 1700 may further include transmitting a fifteenth message to the second node, wherein the fifteenth message includes at least one of the following: information indicating that an F1 connection between the first node and the third node is successfully established, information indicating that a source F1 connection between the first node and the second node is disconnected, target cell ID, information of activated cells, and an acceptable F1 traffic profile.

[0231] FIG. 18 shows a flowchart of a method 1800 performed by a fourth node in a wireless communication system according to embodiments of the present disclosure.

[0232] As shown in FIG. 18, a method 1800 performed by a fourth node in a wireless communication system according to embodiments of the present disclosure may include: in step S1801, receiving a second message from a first node, where the second message includes at least one of the following: a transport network layer (TNL) address of a second distributed unit (DU) of the first node, a node ID and / or IP address of a third node, and information indicating that the first node will perform distributed unit (DU) migration; and in step S1802, receiving a fifth message from the first node, where the fifth message includes a mobile integrated access and backhaul-mobile terminal (mIAB-MT) ID generated by the third node for the first node.

[0233] According to embodiments of the present disclosure, the method 1800 may further include transmitting a thirteenth message to the first node, wherein the thirteenth message includes at least one of the following: a mobile integrated access and backhaul-mobile terminal (mIAB-MT) ID generated by the fourth node for the first node and a node ID of the fourth node.

[0234] It should be understood that the methods 1500, 1600, 1700 and 1800 according to embodiments of the present disclosure may also include one or more of the methods or steps as described above in connection with any example, aspect or drawing, which are not repeated here.

[0235] Next, FIG. 19 shows a schematic diagram of a node 1900 in a wireless communication system according to embodiments of the present disclosure.

[0236] As shown in FIG. 19, a node 1900 (which may be, for example, a first node (e.g., mIAB node or mIAB-MT or mIAB-DU, etc.), a second node (e.g., a source F1 terminating donor CU), a third node (e.g., a target F1 terminating donor CU), a user equipment, base station or any other network node as described above) may include a transceiver 1910 and a processor 1920. The transceiver 1910 may be configured to transmit and receive signals. The processor 1920 may be coupled with the transceiver 1910 and may be configured to (e.g., control the transceiver 1910 to) perform any method performed by a first node and / or a second node and / or a third node and / or a fourth node in a wireless communication system according to embodiments of the present disclosure.

[0237] Herein, a node may also be called a node device. Herein, a processor may also be called a controller.

[0238] According to an embodiment of the disclosure, a method performed by a first node in a wireless communication system, comprising: transmitting a third message to a third node, wherein the third message includes information about a list of serving cells that the first node expects to activate and an F1 traffic profile; receiving a fourth message from the third node in response to the third message, wherein the fourth message includes an acceptable F1 traffic profile and information of cells to be activated; and transmitting a sixth message to the second node, wherein the sixth message includes information of activated cells and an acceptable F1 traffic profile.

[0239] According to an embodiment of the disclosure, further comprising: receiving a first message from a second node, wherein the first message includes the F1 traffic profile.

[0240] According to an embodiment of the disclosure, further comprising: transmitting a second message to a fourth node, wherein the second message includes at least one of the following: a transport network layer (TNL) address of a second DU of the first node, a node ID and / or IP address of the third node, and information indicating that the first node will perform distributed unit (DU) migration.

[0241] According to an embodiment of the disclosure, further comprising: transmitting a fifth message to a fourth node, wherein the fifth message includes a mobile integrated access and backhaul-mobile terminal (mIAB-MT) ID generated by the third node for the first node.

[0242] According to an embodiment of the disclosure, further comprising: receiving a seventh message from the second node, wherein the seventh message includes at least one of the following: information indicating cancellation of a successfully established F1 connection between the first node and the third node, node ID and / or IP address of a new target F1 terminating donor CU; transmitting an eighth message to the third node, wherein the eighth message includes at least one of the following: information indicating cancellation of a successfully established F1 connection between the first node and the third node, a cause value for cancellation of the successfully established F1 connection between the first node and the third node; and receiving a ninth message from the third node, wherein the ninth message includes information indicating that the third node agrees to cancel a successfully established F1 connection between the first node and the third node.

[0243] According to an embodiment of the disclosure, wherein the first message is transmitted from the second node in a case that the second node receives a tenth message from an Operation Administration and Maintenance (OAM) node, wherein the tenth message includes at least one of the following: information indicating the first node to perform distributed unit (DU) migration, a node ID and / or IP address of the third node.

[0244] According to an embodiment of the disclosure, further comprising: receiving an eleventh message from an Operation Administration and Maintenance (OAM) node, wherein the eleventh message includes at least one of the following: information indicating the first node to perform distributed unit (DU) migration, a node ID and / or IP address of the third node; and transmitting a twelfth message to the second node, wherein the twelfth message includes the node ID and / or IP address of the third node.

[0245] According to an embodiment of the disclosure, wherein the first message is transmitted from the second node in a case that the second node agrees to migrate a distributed unit (DU) of the first node to the third node.

[0246] According to an embodiment of the disclosure, further comprising: receiving an eleventh message from an Operation Administration and Maintenance (OAM) node, wherein the eleventh message includes at least one of the following: information indicating the first node to perform distributed unit (DU) migration, a node ID and / or IP address of the third node; receiving a thirteenth message from the fourth node, wherein the thirteenth message includes at least one of the following: a mobile integrated access and backhaul-mobile terminal (mIAB-MT) ID generated by the fourth node for the first node, a node ID of the fourth node; and transmitting a fifth message to the fourth node, wherein the fifth message includes a mobile integrated access and backhaul-mobile terminal (mIAB-MT) ID generated by the third node for the first node.

[0247] According to an embodiment of the disclosure, wherein the information about a list of serving cells that the first node expects to activate is indicated by one or more of the following: indicated by a first information element in an F1 setup request, wherein the first information element indicates a list of serving cells that the first node expects to activate; indicated by state information corresponding to each serving cell in a serving cell list; or indicated by a second information element in an F1 setup request, wherein the second information element indicates whether all cells in a serving cell list are serving cells that the first node expects to activate.

[0248] According to an embodiment of the disclosure, further comprising: transmitting a fourteenth message to the third node in a case that transmission of the sixth message fails, wherein the fourteenth message includes at least one of the following: information indicating that a source F1 connection between the first node and the second node is disconnected, information indicating the third node to transmit the sixth message to the second node, and information indicating the third node to inform the second node that the source F1 connection between the first node and the second node is disconnected.

[0249] According to an embodiment of the disclosure, a method performed by a second node in a wireless communication system, comprising: transmitting a first message to a first node, wherein the first message includes an F1 traffic profile; and receiving a sixth message from the first node, wherein the sixth message includes information of activated cells and an acceptable F1 traffic profile.

[0250] According to an embodiment of the disclosure, further comprising: in a case that the distributed unit (DU) of the first node is agreed to migrate to the third node, performing a user equipment context handover process.

[0251] According to an embodiment of the disclosure, further comprising: transmitting a seventh message to the first node, wherein the seventh message includes at least one of the following: information indicating cancellation of a successfully established F1 connection between the first node and the third node, a node ID and / or IP address of a new target F1 terminating donor CU.

[0252] According to an embodiment of the disclosure, further comprising: receiving a tenth message from an Operation Administration and Maintenance (OAM) node, wherein the tenth message includes at least one of the following: information indicating the first node to perform distributed unit (DU) migration, a node ID and / or IP address of a third node, wherein the first message is transmitted to the first node in a case that the second node receives the tenth message.

[0253] According to an embodiment of the disclosure, further comprising: receiving a twelfth message from the first node, wherein the twelfth message includes a node ID and / or IP address of a third node, wherein the node ID and / or IP address of the third node is received by the first node from an Operation Administration and Maintenance (OAM) node.

[0254] According to an embodiment of the disclosure, wherein the first message is transmitted from the second node in a case that the second node agrees to migrate a distributed unit (DU) of the first node to the third node.

[0255] According to an embodiment of the disclosure, further comprising: receiving a fifteenth message from a third node in a case that reception of the sixth message from the first node fails, wherein the fifteenth message includes at least one of the following: information indicating that an F1 connection between the first node and the third node is successfully established, information indicating that a source F1 connection between the first node and the second node is disconnected, target cell ID, information of activated cells, and an acceptable F1 traffic profile.

[0256] According to an embodiment of the disclosure, a method performed by a third node in a wireless communication system, comprising: receiving a third message from a first node, wherein the third message includes information about a list of serving cells that the first node expects to activate and an F1 traffic profile; and transmitting a fourth message to the first node, wherein the fourth message includes an acceptable F1 traffic profile and information of cells to be activated.

[0257] According to an embodiment of the disclosure, further comprising: receiving an eighth message from the first node, wherein the eighth message includes at least one of the following: information indicating cancellation of a successfully established F1 connection between the first node and the third node, a cause value for cancellation of the successfully established F1 connection between the first node and the third node; and transmitting a ninth message to the first node, wherein the ninth message includes information indicating that the third node agrees to cancel a successfully established F1 connection between the first node and the third node, wherein the eighth message is transmitted from the first node in a case that the first node receives a seventh message from a second node, wherein the seventh message includes at least one of the following: information indicating cancellation of a successfully established F1 connection between the first node and the third node, node ID and / or IP address of a new target F1 terminating donor CU.

[0258] Various embodiments of the present disclosure may be implemented as computer-readable codes embodied on a computer-readable recording medium from a specific perspective. A computer-readable recording medium is any data storage device that can store data readable by a computer system. Examples of computer-readable recording media may include read-only memory (ROM), random access memory (RAM), compact disk read-only memory (CD-ROM), magnetic tape, floppy disk, optical data storage device, carrier wave (e.g., data transmission via the Internet), etc. Computer-readable recording media can be distributed by computer systems connected via a network, and thus computer-readable codes can be stored and executed in a distributed manner. Furthermore, functional programs, codes and code segments for implementing various embodiments of the present disclosure can be easily explained by those skilled in the art to which embodiments of the present disclosure are applied.

[0259] It will be understood that embodiments of the present disclosure may be implemented in the form of hardware, software, or a combination of hardware and software. The software may be stored as program indications or computer-readable codes executable on a processor on a non-transitory computer-readable medium. Examples of non-transitory computer-readable recording media include magnetic storage media (such as ROM, floppy disk, hard disk, etc.) and optical recording media (such as CD-ROM, digital video disk (DVD), etc.). Non-transitory computer-readable recording media may also be distributed on computer systems coupled to a network, so that computer-readable codes are stored and executed in a distributed manner. The medium can be read by a computer, stored in a memory, and executed by a processor. Various embodiments may be implemented by a computer or a portable terminal including a controller and a memory, and the memory may be an example of a non-transitory computer-readable recording medium suitable for storing program (s) with indications for implementing embodiments of the present disclosure. The present disclosure may be realized by a program with code for concretely implementing the apparatus and method described in the claims, which is stored in a machine (or computer)-readable storage medium. The program may be electronically carried on any medium, such as a communication signal transmitted via a wired or wireless connection, and the present disclosure suitably includes its equivalents.

[0260] What has been described above is only the specific implementation of the present disclosure, but the scope of protection of the present disclosure is not limited thereto. Anyone who is familiar with this technical field may make various changes or substitutions within the technical scope disclosed in the present disclosure, and these changes or substitutions should be covered within the scope of protection of the present disclosure. Therefore, the scope of protection of the present disclosure should be based on the scope of protection of the claims.

Claims

1.A method performed by a mobile integrated access / backhaul (IAB)-node in a wireless communication system, the method comprising:receiving, from an operation administration and maintenance (OAM), information associated with initiating distributed unit (DU) migration, wherein the information includes a gNodeB(gNB) identifier (ID) of a target F1 terminating donor central unit (CU);transmitting, to the target F1 terminating donor CU, a request message for a connection with the target F1 terminating donor CU based on the gNB ID of the target F1 terminating donor CU; andreceiving, from the target F1 terminating donor CU, a response message as a response to the request message.2.The method of claim 1, further comprising:transmitting, to a source F1 terminating donor CU, a notification message indicating that the connection with the target F1 terminating donor CU is configured.3.The method of claim 2, wherein based on the DU migration being triggered by the OAM, the notification message includes the gNB ID of the target F1 terminating donor CU.4.The method of claim 2, wherein the mobile IAB-node includes a source DU and a target DU,wherein the request message is transmitted from the target DU to the target F1 terminating donor CU,wherein the response message is received by the target DU from the target F1 terminating donor CU,wherein the notification message is transmitted from the source DU to the source F1 terminating donor CU, andwherein the connection with the target F1 terminating donor CU is a connection between the target DU and the target F1 terminating donor CU.5.The method of claim 4, wherein a user equipment (UE) served by a source cell of the source DU is handed over from the source cell to a target cell of the target DU by the source F1 terminating donor CU.6.A method performed by a target F1 terminating donor central unit (CU) in a wireless communication system, the method comprising:receiving, from a mobile integrated access / backhaul (IAB)-node, a request message for a connection, which is associated with distributed unit (DU) migration, with the mobile IAB-node based on a gNodeB(gNB) identifier (ID) of the target F1 terminating donor CU; andtransmitting, to the mobile IAB-node, a response message as a response to the request message.7.The method of claim 6, wherein the mobile IAB-node includes a source DU and a target DU,wherein the request message is transmitted from the target DU to the target F1 terminating donor CU,wherein the response message is received by the target DU from the target F1 terminating donor CU, andwherein the connection with the mobile IAB-node is a connection between the target DU and the target F1 terminating donor CU.8.The method of claim 7, wherein a user equipment (UE) served by a source cell of the source DU is handed over from the source cell to a target cell of the target DU by a source F1 terminating donor CU.9.A mobile integrated access / backhaul (IAB)-node in a wireless communication system, the mobile IAB-node comprising:a transceiver; anda controller coupled with the transceiver and configured to:receive, from an operation administration and maintenance (OAM), information to initiate distributed unit (DU) migration, wherein the information includes a gNodeB(gNB) identifier (ID) of a target F1 terminating donor central unit (CU),transmit, to the target F1 terminating donor CU, a request message for a connection with the target F1 terminating donor CU based on the gNB ID of the target F1 terminating donor CU, andreceive, from the target F1 terminating donor CU, a response message as a response to the request message.10.The mobile IAB-node of claim 9, wherein the controller is further configured to:transmit, to a source F1 terminating donor CU, a notification message indicating that the connection with the target F1 terminating donor CU is configured.11.The mobile IAB-node of claim 10, wherein based on the DU migration being triggered by the OAM, the notification message includes the gNB ID of the target F1 terminating donor CU.12.The mobile IAB-node of claim 10, wherein the mobile IAB-node includes a source DU and a target DU,wherein the request message is transmitted from the target DU to the target F1 terminating donor CU,wherein the response message is received by the target DU from the target F1 terminating donor CU,wherein the notification message is transmitted from the source DU to the source F1 terminating donor CU, andwherein the connection with the target F1 terminating donor CU is a connection between the target DU and the target F1 terminating donor CU.13.The mobile IAB-node of claim 12, wherein a user equipment (UE) served by a source cell of the source DU is handed over from the source cell to a target cell of the target DU by the source F1 terminating donor CU.14.A target F1 terminating donor central unit (CU) in a wireless communication system, the target F1 terminating donor CU comprising:a transceiver; anda controller coupled with the transceiver and configured to:receive, from a mobile integrated access / backhaul (IAB)-node, a request message for a connection, which is associated with distributed unit (DU) migration, with the mobile IAB-node based on a gNodeB(gNB) identifier (ID) of the target F1 terminating donor CU, andtransmit, to the mobile IAB-node, a response message as a response to the request message.15.The target F1 terminating donor CU of claim 14, wherein the mobile IAB-node includes a source DU and a target DU,wherein the request message is transmitted from the target DU to the target F1 terminating donor CU,wherein the response message is received by the target DU from the target F1 terminating donor CU, andwherein the connection with the mobile IAB-node is a connection between the target DU and the target F1 terminating donor CU.

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