Method and apparatus performed by network node

Abstract

The disclosure relates to a 5G or 6G communication system for supporting a higher data transmission rate. A method performed by a base station in a wireless communication system is provided. The method comprises transmitting, to a distributed unit (DU) of the base station, a first message including first information for requesting a reference configuration for a layer 1 / layer 2 triggered mobility (LTM), and second information for requesting synchronization information for the LTM by a central unit (CU) of the base station, receiving, from the DU, a second message as a response to the first message by the CU, wherein the second message includes the reference configuration, and the synchronization information, and transmitting, to a user equipment (UE) associated with the LTM, a third message including information on a LTM configuration associated with a candidate configuration.

Description

METHOD AND APPARATUS PERFORMED BY NETWORK NODE

[0001] The present disclosure relates generally to a wireless communication system, and more specially a method and an apparatus performed by a network node.

[0002] 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.

[0003] 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.

[0004] 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.

[0005] 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.

[0006] 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.

[0007] Furthermore, such development of 5G mobile communication systems will serve as a basis for developing not only new waveforms for providing coverage in terahertz bands of 6G mobile communication technologies, multi-antenna transmission technologies such as Full Dimensional MIMO (FD-MIMO), array antennas and large-scale antennas, metamaterial-based lenses and antennas for improving coverage of terahertz band signals, high-dimensional space multiplexing technology using OAM (Orbital Angular Momentum), and RIS (Reconfigurable Intelligent Surface), but also full-duplex technology for increasing frequency efficiency of 6G mobile communication technologies and improving system networks, AI-based communication technology for implementing system optimization by utilizing satellites and AI (Artificial Intelligence) from the design stage and internalizing end-to-end AI support functions, and next-generation distributed computing technology for implementing services at levels of complexity exceeding the limit of UE operation capability by utilizing ultra-high-performance communication and computing resources.

[0008] A method performed by a base station in a wireless communication system is provided. The method comprises transmitting, to a distributed unit (DU) of the base station, a first message including first information for requesting a reference configuration for a layer 1 / layer 2 triggered mobility (LTM), and second information for requesting synchronization information for the LTM by a central unit (CU) of the base station, receiving, from the DU, a second message as a response to the first message by the CU, wherein the second message includes the reference configuration, and the synchronization information, and transmitting, to a user equipment (UE) associated with the LTM, a third message including information on a LTM configuration associated with a candidate configuration.

[0009] A base station in a wireless communication system is provided. The base station comprises a transceiver and a controller coupled with the transceiver and configured to transmit, to a distributed unit (DU) of the base station, a first message including first information for requesting a reference configuration for a layer 1 / layer 2 triggered mobility (LTM), and second information for requesting synchronization information for the LTM by a central unit (CU) of the base station, receive, from the DU, a second message as a response to the first message by the CU, wherein the second message includes the reference configuration, and the synchronization information, and transmit, to a user equipment (UE) associated with the LTM, a third message including information on a LTM configuration associated with a candidate configuration.

[0010] A method performed by a base station in a wireless communication system is provided. The method comprises receiving, from a central unit (CU) of the base station, a first message including first information for requesting a reference configuration for a layer 1 / layer 2 triggered mobility (LTM), and second information for requesting synchronization information for the LTM by a distributed unit (DU) of the base station, transmitting, to the CU, a second message as a response to the first message by the DU, wherein the second message includes the reference configuration, and the synchronization information, and transmitting, to a user equipment (UE) associated with the LTM, a third message including information on a LTM configuration associated with a candidate configuration.

[0011] A base station in a wireless communication system is provided. The base station comprises a transceiver and a controller coupled with the transceiver and configured to receive, from a central unit (CU) of the base station, a first message including first information for requesting a reference configuration for a layer 1 / layer 2 triggered mobility (LTM), and second information for requesting synchronization information for the LTM by a distributed unit (DU) of the base station, transmit, to the CU, a second message as a response to the first message by the DU, wherein the second message includes the reference configuration, and the synchronization information, and transmit, to a user equipment (UE) associated with the LTM, a third message including information on a LTM configuration associated with a candidate configuration.

[0012] FIG. 1 illustrates an exemplary system architecture of system architecture evolution (SAE).

[0013] FIG. 2 illustrates an exemplary system architecture according to various embodiments of the present disclosure.

[0014] FIG. 3 illustrates a first example flow according to an example embodiment of the present disclosure.

[0015] FIG. 4A illustrates an example synchronization information acquisition flow and / or an example uplink resource acquisition flow according to a first implementation of the present disclosure.

[0016] FIG. 4B illustrates an example synchronization information acquisition flow and / or an example uplink resource acquisition flow according to a second implementation of the present disclosure.

[0017] FIG. 4C illustrates an example synchronization information acquisition flow and / or an example uplink resource acquisition flow according to a third implementation of the present disclosure.

[0018] FIG. 4D illustrates an example synchronization information acquisition flow and / or an example uplink resource acquisition flow according to a fourth implementation of the present disclosure.

[0019] FIG. 5 illustrates a block diagram of a node (network node) according to an example embodiment of the present disclosure.

[0020] FIG. 6 illustrates a block diagram of user equipment according to an example embodiment of the present disclosure.

[0021] The following description with reference to the accompanying drawings is provided to facilitate a comprehensive understanding of various embodiments of the present disclosure defined by the claims and their equivalents. This description includes various specific details to facilitate understanding but should only be considered exemplary. Therefore, those of ordinary skill in the art will recognize that various changes and modifications can be made to the various embodiments described herein without departing from the scope and spirit of the present disclosure. In addition, for the sake of clarity and conciseness, descriptions of well-known functions and structures may be omitted.

[0022] The terms and phrases used in the following specification and claims are not limited to their dictionary meanings, but are used only by the inventors to enable a clear and consistent understanding of the present disclosure. Therefore, it should be apparent to those skilled in the art that the following description of the various embodiments of the present disclosure is provided for illustration only and not for the purpose of limiting the present disclosure as defined by the appended claims and their equivalents.

[0023] It should be understood that the singular forms “a”, “an”, and “the” include plural referents unless the context clearly dictates otherwise. Thus, for example, a reference to a “component surface” includes a reference to one or more such surfaces.

[0024] The terms “comprising” or “may comprise” refer to the presence of respective disclosed functions, operations, or components that may be used in various embodiments of the present disclosure, and do not limit the presence of one or more additional functions, operations, or features. In addition, the terms “comprising” or “having” can be interpreted as indicating certain characteristics, numbers, steps, operations, constituent elements, components or combinations thereof, but should not be interpreted as excluding the possibility of presence of one or more other characteristics, numbers, steps, operations, constituent elements, components or combinations thereof.

[0025] The term “or” used in various embodiments of the present disclosure includes any of the listed terms and all combinations thereof. For example, “A or B” may include A, may include B, or may include both A and B.

[0026] Unless defined differently, all terms (including technical terms or scientific terms) used in the present disclosure have the same meaning as those understood by those skilled in the art to which the present disclosure belongs. General terms as defined in dictionaries are to be interpreted as having a meaning that is consistent with their context in the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.

[0027] 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”.

[0028] Wireless communication is one of the most successful innovations in modern history. Recently, a 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.

[0029] According to an aspect of the present disclosure, there is provided a method performed by a first network node in a wireless communication system. The method may include: transmitting a first message to a second network node; and transmitting a third message to a first node, wherein, the first message may include at least one of the following information: first synchronization request information comprising synchronization information feedback time indication information, first uplink resource request information comprising first synchronization mode indication information and / or assistant information for uplink resource allocation, first user equipment configuration request information comprising associated configuration indication information, and first reference configuration request information comprising reference configuration indication information.

[0030] In some implementations, in the method performed by the first network node, the third message may include at least one of the following information: synchronization signal configuration information comprising signal transmission valid time information, candidate cell configuration information comprising Serving Cell as Candidate indication, uplink resource information, and second reference configuration information.

[0031] In some implementations, the method performed by the first network node may further include: receiving a second message from the second network node, wherein the second message is used to provide a configuration required for the first node to access a candidate cell.

[0032] In some implementations, in the method performed by the first network node, the first message may further include: first configuration notification information for notifying the second network node of configuration information about the first node.

[0033] In some implementations, in the method performed by the first network node, the first synchronization request information may further include at least one of the following information: first node identity information, cell identity information, identity information of a third network node, synchronization configuration indication information for indicating a configuration used by the first node for synchronization, system frame number information, preamble configuration information, beam configuration information and resource configuration information.

[0034] In some implementations, in the method performed by the first network node, the first user equipment configuration request information may further include at least one of the following information: first configuration reservation indication information for indicating a configuration that the second network node needs to reserve, first bearer related information, first cell related information, second synchronization mode indication information, first reference configuration information for indicating a configuration referenced in generating first configuration information, and first reference configuration indication information for indicating that a configuration generated based on the first user equipment configuration request information is a reference configuration.

[0035] In some implementations, in the method performed by the first network node, the first reference configuration request information may further include at least one of the following information: reference bearer related information, reference cell related information, modification indication information, and release indication information.

[0036] In some implementations, in the method performed by the first network node, the first configuration notification information may include at least one of the following information: first synchronization information for indicating synchronization information used by the first node to access the candidate cell in a mobile process, and first uplink resource information for indicating uplink resources allocated to the first node.

[0037] In some implementations, in the method performed by the first network node, the synchronization signal configuration information may further include at least one of the following information: start time allowing signal transmission, end time allowing signal transmission, cell identity information, preamble configuration information, beam configuration information and resource configuration information.

[0038] In some implementations, in the method performed by the first network node, the candidate cell configuration information may further include at least one of the following information: cell identity information, configuration identity information, and first user equipment configuration information.

[0039] In some implementations, in the method performed by the first network node, the second message may include at least one of the following information: first synchronization response information for providing synchronization information used by the first node to access the candidate cell, first uplink resource response information for providing uplink resources for the first node, first configuration information including synchronization signal configuration information comprising signal transmission valid time information, and first reference configuration response information comprising a reference configuration generated by the second network node.

[0040] In some implementations, in the method performed by the first network node, the assistant information for uplink resource allocation may include at least one of the following information: indication information of an uplink resource allocation mode, beam indication information, and valid time information of the uplink resources.

[0041] In some implementations, in the method performed by the first network node, the associated configuration indication information may be used to indicate information required by the second network node in generating first configuration information of the first node, and the associated configuration indication information may include at least one of the following information: first node identity information, configuration identity information, and associated cell identity information.

[0042] According to another aspect of the present disclosure, there is also provided a method performed by a second network node in a wireless communication system. The method may include: receiving a first message from a first network node; and transmitting a second message to the first network node, wherein, the first message may include at least one of the following information: first synchronization request information comprising synchronization information feedback time indication information, first uplink resource request information comprising first synchronization mode indication information and / or assistant information for uplink resource allocation, first user equipment configuration request information comprising associated configuration indication information, and first reference configuration request information comprising reference configuration indication information. The second message may be used to provide a configuration required for the first node to access the candidate cell.

[0043] In some implementations, in the method performed by the second network node, the second message may include at least one of the following information: first synchronization response information for providing synchronization information used by the first node to access the candidate cell, first uplink resource response information for providing uplink resources for the first node, first configuration information including synchronization signal configuration information comprising signal transmission valid time information, and first reference configuration response information comprising a reference configuration generated by the second network node.

[0044] According to yet another aspect of the present disclosure, there is also provided a method performed by a first node in a wireless communication system. The method may include: receiving a third message from a first network node; and accessing a candidate cell served by a second network node based on the third message, wherein, the third message may include at least one of the following information: synchronization signal configuration information comprising signal transmission valid time information, candidate cell configuration information comprising Serving Cell as Candidate indication, uplink synchronization information, uplink resource information, and second reference configuration information.

[0045] In some implementations, the method performed by the first node further comprises: starting a first timer for assisting a user of the first node in determining whether a cell handover or cell switch is completed, and / or starting a second timer for assisting the first node in determining whether the uplink synchronization information is valid; and triggering a random access process or stopping the first timer when the second timer expires before the first timer.

[0046] In some implementations, the method performed by the first node further comprises: determining that a process of the cell handover or cell switch is successful, if the random access process is triggered and after the random access process is completed successfully; or starting a failure recovery process if the first timer is stopped.

[0047] According to yet another aspect of the present disclosure, there is provided a first network node. The first network node may include: a transceiver for transmitting and receiving signals; and a controller coupled with the transceiver and configured to perform the method performed by the first network node as described above.

[0048] According to yet another aspect of the present disclosure, there is provided a second network node. The second network node may include: a transceiver for transmitting and receiving signals; and a controller coupled with the transceiver and configured to perform the method performed by the second network node as described above.

[0049] According to yet another aspect of the present disclosure, there is provided a first node. The first node may include: a transceiver for transmitting and receiving signals; and a controller coupled with the transceiver and configured to perform the method performed by the first node as described above.

[0050] According to another aspect of the present disclosure, there is provided a non-transitory computer-readable medium, having stored thereon instructions, which, when executed by one or more controllers, cause the one or more controllers to perform the methods performed by the first network node and / or the second network node and / or the first node as described above.

[0051] FIGS. 1 to 6 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.

[0052] Exemplary embodiments of the present disclosure are further described below with reference to the accompanying drawings.

[0053] 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.

[0054] FIG. 1 illustrates an exemplary system architecture 100 of system architecture evolution (SAE). Referring to FIG. 1, 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.

[0055] FIG. 2 illustrates 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.

[0056] Referring to FIG. 2, 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-gNB) 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.

[0057] In a mobile network, a user equipment may perform handover between different cells. A main problem caused by the handover is that the user equipment undergoes communication interruption during this process. The user equipment may in a mobile process initiate a handover (a cell switch) according to signaling from a network side. In order to speed up a handover flow of the user equipment, the signaling from the network side may be signaling from a lower layer (signaling at a layer 1, such as signaling at a physical layer, a downlink control information (DCI); signaling at a layer 2, such as signaling at a medium access control (MAC) layer, an MAC control element (MAC CE)). When the user equipment receives the order, the user equipment may access a target cell.

[0058] In this process, there is at least one problem as follows:

[0059] Before handover, the network side needs to carry out signaling interaction between different nodes to determine the target cell and a configuration of the target cell, and then transmits a handover command to the user equipment, and in this process, signaling overhead is relatively large.

[0060] The user equipment also needs to perform uplink and downlink synchronization with the network, and in this process, the time required for the user equipment to switch cells is relatively long, which may cause communication interruption, further affecting the performance of the user equipment in the mobile process.

[0061] Before introducing specific contents, some assumptions and some definitions of the present disclosure are given below.

[0062] Message names in the present disclosure are only examples, and other message names can also be used.

[0063] The “first” and “second” and so on included in the message names of the present disclosure are only used to distinguish one message from another, and do not represent an execution order.

[0064] Detailed description of steps irrelevant to the present disclosure is omitted in the present disclosure.

[0065] In the present disclosure, the steps in each flow may be executed in combination with each other or independently. The execution steps of each flow are only examples, and other possible execution steps and / or orders are not excluded.

[0066] In the present disclosure, the base station may be a 6G base station, a 5G base station (such as a gNB and a ng-eNB), a 4G base station (such as an eNB) or other types of access nodes.

[0067] In the present disclosure, when a cell accessed by the user equipment switches from one cell to another cell, this behavior may be called a handover or a cell switch. In the following description, the handover and the cell switch have the same meaning.

[0068] In the present disclosure, user equipment, a user terminal and user terminal device are equivalent and can be used interchangeably with one another.

[0069] In the present disclosure, synchronization information includes at least one of the following information:

[0070] ■ downlink synchronization information

[0071] ■ uplink synchronization information, such as timing advance (TA) information

[0072] The nodes involved in the present disclosure may include:

[0073] ■ a first node: a user terminal device, which may be a mobile phone or a relay node

[0074] ■ a second node: a central unit of a base station, or a control plane portion of a centralized unit of a base station, or a base station, in one example, the base station may be a source base station or a source master base station in a mobile process of a user terminal, and in another example, the base station may be a source secondary base station in the mobile process of the user terminal

[0075] ■ a third node: a distributed unit of a base station, which may be a distributed unit where a source cell is located in the mobile process of the user terminal, the source cell is a special cell (SpCell), in one example, the special cell may be a SpCell of a master cell group or a primary cell (PCell), and in another example, the special cell may be a SpCell of a secondary cell group or a primary secondary cell (PSCell: source primary secondary cell group cell)

[0076] ■ a fourth node: a central unit of a base station, or a control plane portion of a central unit of a base station, or a base station which may be a target base station in the mobile process of the user terminal, in one example, the base station may be a target base station or a target master base station in the mobile process of the user terminal, and in another example, the base station may be a target secondary base station in the mobile process of the user terminal

[0077] ■ a fifth node: a distributed unit of a base station, which may be a distributed unit where a target cell is located in the mobile process of the user terminal, the target cell is a special cell (SpCell), in one example, the special cell may be a SpCell of a master cell group or a primary cell (PCell), and in another example, the special cell may be a SpCell of a secondary cell group or a primary secondary cell (PSCell: source primary secondary cell group cell).

[0078] The cell involved in the present disclosure may be at least one of the following cell types:

[0079] ■ a special cell (SpCell)

[0080] ■ a primary cell (PCell) or a SpCell of a master cell group

[0081] ■ a primary cell of a secondary cell group (PSCell) or a SpCell of a secondary cell group

[0082] ■ a secondary cell (SCell)

[0083] The base station involved in the above second node / third node / fourth node / fifth node may be one of the following types (without excluding other types that may be used for user terminal access):

[0084] ■ a long term evolution (LTE) base station

[0085] ■ a 5G base station

[0086] ■ a 6G base station

[0087] ■ a non-terrestrial network (NTN) base station

[0088] ■ a high altitude platform station (HAPS) base station

[0089] ■ a drone base station

[0090] ■ a WIFI access point

[0091] On one hand, before receiving a handover command, the user equipment acquires information related to data transmission, and the network side pre-configures a configuration of a target cell to the user equipment before the user equipment hands over to the target cell. Through this process, signaling overhead is effectively reduced. On the other hand, before receiving the handover command, the user equipment first synchronizes with the target cell and acquires information related to synchronization, so that the time required for the user equipment to switch cells is shortened, the possibility of communication interruption is reduced, and the performance of the user equipment in the mobile process is improved. These means facilitate reducing the interruption of data communication in the handover process of the user equipment, so as to implement rapid handover of the user equipment and improve the performance of the user equipment in the mobile process.

[0092] Numbers of the following steps do not represent the execution order of the steps, and the following steps may be executed separately or in combination with each other.

[0093] In order to access one cell, the user equipment needs to acquire synchronization information (such as uplink synchronization information, like a timing advance of uplink synchronization) in the cell. In the present disclosure, the user equipment may acquire synchronization information by employing the following two methods.

[0094] Method 1 (a RACH-based synchronization, which may also be called a RACH-based TA acquisition or a RACH-based UL synchronization): the user equipment needs to acquire the synchronization information through a random access process.

[0095] Method 2 (a RACH-less synchronization, also known as a RACH-less TA acquisition, or a RACH-less UL synchronization, or an early UL synchronization): the user equipment does not need to acquire the synchronization information through the random access process, but may obtain the synchronization information in the handover command or before receiving the handover command.

[0096] In order to help the user equipment perform rapid handover, the network side needs to configure the user equipment. This configuration may include the following steps, as shown in Fig. 3:

[0097] Step 1-1: a first network node transmits a first message to a second network node. In one embodiment, the first message may be, for example, a first request message. Further, the first request message may be, for example, a first configuration request message. The function of the message includes at least one of: 1) acquiring synchronization information and / or uplink resource information used by the user equipment to access a candidate cell in the mobile process, 2) requesting the second network node to generate first configuration information of the user terminal (the first node) based on a reference configuration, and 3) helping the second network node generate / modify / release the reference configuration. Hereinafter, the first configuration request message is taken as an example to explain the first message, and those skilled in the art should understand that the name of the first message is not limited to the first configuration request message. The first configuration request message may include at least one of the following information:

[0098] ■ first synchronization request information, for acquiring synchronization information used by the user terminal to access the candidate cell in the mobile process, and / or for indicating configuration information used by the user equipment for synchronization, while the synchronization information is acquired by the second network node. In one example, the acquired synchronization information is uplink synchronization information (such as timing advance information and valid time information), and configuration information indicated by this information is configuration information of uplink synchronization related signals (such as a random access preamble) transmitted by the user equipment. Further, the uplink synchronization is the uplink synchronization between the user equipment and a cell served by the second network node, and the uplink synchronization is performed before the user equipment accesses the cell served by the second network node (such as before a cell handover indication for accessing the second network node is received). This information has the beneficial effects of helping the network node serving the user terminal acquire the synchronization information used by the user terminal to access the candidate cell in the mobile process, and / or indicating configuration information used by the user terminal for synchronization, thereby assisting the user terminal in completing synchronization and reducing service interruption in the synchronization process. This information may include at least one of the following information:

[0099] ● user equipment identity information, or first node identity information, such as a CU / DU F1AP UE ID, a XnAP UE ID, a cell-radio network temporary identifier (C-RNTI), etc.

[0100] ● cell identity information, such as a physical cell identity (PCI), a new radio (NR) cell global identity (CGI), a cell index, etc., which indicates the cell performing synchronization with the user terminal, in one example, this cell is a candidate target cell in the mobile process of the user equipment

[0101] ● node identity information, or identity information of a third network node, such as a base station ID, a distributed unit DU ID, etc., a node identified by this information is a node that triggers the user terminal to perform synchronization

[0102] ● synchronization configuration indication information, such as a configuration index, which indicates a configuration used by the user equipment for synchronization. In one example, this information indicates a configuration used for a uplink synchronization that is performed before the user equipment accesses the cell, such as a configuration index for early UL synchronization; specifically, a serving node of a current serving cell of the user terminal may transmit trigger information to the user terminal to trigger the user terminal to transmit synchronization information to a non-serving cell (such as a candidate target cell), then a configuration indicated by this information is a configuration of a synchronization signal transmitted by the user terminal to the non-serving cell; further, the indicated configuration may include at least one of the following configurations: preamble configuration information (e.g., a preamble index), beam configuration information (e.g., a synchronization signal block (SSB) / a physical broadcast channel (PBCH) index), and resource configuration information (e.g., a random access occasion indication, an random access channel occasion index (RACH occasion index)), carrier configuration information

[0103] ● system frame number information, which indicates a system frame number when the user terminal transmits an uplink synchronization related signal (such as a preamble), and which can help the second network node determine the time when the user terminal transmits a synchronization signal

[0104] ● synchronization information feedback time indication information, which indicates waiting time needed for the second network node to provide synchronization information, in other words, after receiving the “first synchronization request information”, the second network node may provide its obtained synchronization information to the first network node after or within the time indicated by the “synchronization information feedback time indication information”; in one example, after the second network node receives the first configuration request message, the second network node may start a timer whose length is a time length indicated by the “synchronization information feedback time indication information”, only after the timer expires, the second network node feeds back synchronization information to the first network node, or before the timer expires, the second network node needs to feed back the synchronization information to the first network node

[0105] ● preamble configuration information, the preamble is a preamble used by the user equipment to perform a random access process, such as a preamble index and a random access preamble identifier (RAPID)

[0106] ● beam configuration information, such as a SSB / PBCH index

[0107] ● resource configuration information, the resource is a resource used by the user equipment for synchronization; in one example, this resource is a resource used by the user equipment for random access (or transmitting the random access preamble), such as an RACH occasion. This information may include at least one of the following information:

[0108] ◆resource indication information, such as a random access-radio network temporary identifier (RA-RNTI), that is, a resource associated with a RA-RNTI

[0109] ◆an index of a resource start symbol

[0110] ◆an index of a resource start slot, the slot is a slot in a system frame

[0111] ◆a frequency domain index of a resource

[0112] ◆an indication of a carrier where a resource is located, such as a common uplink carrier and a supplementary uplink carrier

[0113] ■ first uplink resource request information, which is used to request a resource used for uplink data transmission, the resource being a resource of a cell served by the second network node. The cell served by the second network node may be a candidate target cell of the user equipment. When the user equipment prepares to access the cell served by the second network node, the second network node may prepare some uplink resources for the user equipment to quickly perform uplink data transmission. This information has the beneficial effects of determining a configuration of uplink resources used by the user equipment after accessing the cell, helping the user equipment quickly initiate data transmission, and reducing the possibility of interruption of data transmission caused by cell switch. This information may include at least one of the following information:

[0114] ● first synchronization mode indication information, which indicates a synchronization mode used when the user equipment accesses the cell served by the second network node. In one example, the synchronization is uplink synchronization. Further, the synchronization mode indicated by this indication information may be RACH-based synchronization or RACH-less synchronization. The second network node may determine how to allocate uplink resources based on this information. If the synchronization mode indicated by this indication information is RACH-based synchronization, then the second network node does not need to allocate uplink resources for the user equipment, and the user equipment may obtain uplink resources through the random access process, that is, information of allocated uplink resources does not need to be included in the following step 1-2; if the synchronization mode indicated by this indication information is RACH-less synchronization, then the second network node may allocate uplink resources for the user equipment. Further, the following step 1-2 may include information of uplink resources allocated for the user equipment. If the second network node allocates resources for RACH-based synchronization, then the second network node may release these resources. This information has the beneficial effects of helping the second network node release resources in time, and allocating appropriate uplink resources for the user equipment, thus improving the utilization efficiency of resources

[0115] ● assistant information for uplink resource allocation, which helps the second network node perform uplink resource allocation. Further, the second network node may provide the allocated uplink resources to the first network node through the following Step 1-2. This information may include one of the following information:

[0116] ◆ indication information of an uplink resource allocation mode, which indicates the mode on how to allocate uplink resources for the user equipment. In one example, one mode indicated by this information is a pre-allocated uplink resource (such as a configured grant). In this mode, the second network node may pre-allocate some uplink resources for the user equipment, and the configuration information of these resources may be provided to the first network node through the following Step 1-2, and then the resources are pre-configured to the user equipment. After the user equipment accesses the cell served by the second network node, the user equipment may use these resources to perform uplink data transmission. This mode requires the second network node to reserve some resources, which can speed up uplink data transmission of the user equipment, but may lead to waste of resources (because an occasion where the user equipment accesses the cell is uncertain, resulting in that not all these reserved resources may be used by the user equipment). In another example, one mode indicated by this information is a dynamic grant. In this mode, the second network node may dynamically allocate uplink resources for the user equipment after the user equipment accesses the cell (such as indicating the allocated uplink resources through a physical downlink control channel (PDCCH)). This mode does not need to reserve resources, which reduces the waste of resources, but may lead to a delay of the uplink data transmission of the user equipment (because the second network node cannot know the specific time when the user equipment starts to perform uplink data transmission). This information has the beneficial effects of helping the second network node select the appropriate uplink resources for allocation, reducing the waste of resources and accelerating the uplink data transmission of the user equipment

[0117] ◆ beam indication information, such as a transmission configuration indication (TCI) status, an SSB / PBCH index, etc., which indicates beam information used by the user equipment for uplink data transmission. After receiving this information, the second network node may determine a beam used to receive uplink data transmission by the user equipment. This information has the beneficial effects of helping the second network node determine the beam used to receive uplink data, and improving the efficiency of uplink data transmission. This information may only be applied to the configured grant mode, or the dynamic grant mode, or both

[0118] ◆ valid time information of uplink resources, such as time length information, start time information, end time information, etc. This information indicates the valid time of the allocated uplink resource, that is, the uplink resources allocated for the user equipment may only be used within this valid time. This information has the beneficial effects of reducing the allocation of unnecessary uplink resources and improving the utilization efficiency of resources

[0119] ■ first user equipment configuration request information, which is used to request the second network node to generate first configuration information of the user terminal. In one example, the requested generated first configuration information is used to configure candidate cells in the mobile process of the user equipment. This information may include at least one of the following information:

[0120] ● associated configuration indication information, which indicates information required by the second network node in generating the first configuration information of the user terminal or helps the second network node acquire the information required in generating the first configuration information of the user terminal. The information required in generating the first configuration information of the user terminal includes, for example, bearer related information (see “first bearer related information” below), cell related information (see “first cell related information” below), reference configuration information (see “first reference configuration information” below), etc., which are not provided to the second network node through the first configuration request message in Step 1-1, but are provided to the second network node in advance by the first network node through another flow (for example, being provided to the second network node when configuring the candidate cell for user terminal device), and the second network node may acquire the above-mentioned “information required in generating the first configuration information of the user terminal” provided through the other flow based on the “associated configuration indication information”. This information has the beneficial effects of helping the second network node reuse the information required in generating the first configuration information of the user terminal, and the second network node is able to directly acquire “information required in generating the first configuration information of the user terminal” based on associated configuration indication information, so that the first configuration information of the user terminal is generated, the repeated transmission of “information required in generating the first configuration information of the user terminal” is avoided and the signaling overhead is reduced. For example, if the above “first user equipment configuration request information” includes the “associated configuration indication information”, then the “first user equipment configuration request information” does not need to include the following “first bearer related information” and / or “first cell related information” and / or “first reference configuration information”. This associated configuration indication information may include at least one of the following information:

[0121] ◆user equipment identity information, such as a CU / DU F1AP UE ID, a XnAP UE ID, a C-RNTI, etc. Specifically, the first network node and the second network node use this information in other flows (such as a first flow) for generating the first configuration information of the user terminal, and after the second network node receives this information in step 1-1, it can refer to the configuration information in the first flow

[0122] ◆ configuration identity information, such as a candidate ID, a configuration ID, etc. The first network node and the second network node use this information in other flows (such as a first flow) for generating the first configuration information of the user terminal, and after the second network node receives this information in Step 1-1, it can refer to the configuration information in the first flow

[0123] ◆ associated cell identity information, the second network node may refer to information used in the flow (such as the first flow) for generating the first configuration information of the user terminal of a cell identified by this identity information

[0124] ■first configuration reservation indication information, indicating a configuration that the second network node needs to reserve, which may be a configuration (such as first configuration information) generated by the second network node based on other information in the above “first user equipment configuration request information”. In one example, if the user terminal leaves the cell (such as the current serving cell) indicated by the “first cell related information” below, then the second network node needs to continue to reserve the first configuration information related to the cell (e.g. the current serving cell) indicated by the “first cell related information” described below. This information has the beneficial effects of helping the second network node reserve the configuration of the user equipment and reducing the signaling overhead when the user equipment accesses the second network node again (the second network node may reuse the reserved configuration without signaling interaction between the first network node and the second network node, and then generate the first configuration information again). In one example, the configuration required to be reserved indicated by this indication information may be a configuration used by the user equipment in the current serving cell. Further, the indication information may also include one configuration identity information which may be used to identify the configuration required to be reserved, so that this identity information may be used to indicate the configuration required to serve the user equipment when the user equipment moves

[0125] ●first bearer related information, which indicates bearer information of the user terminal, such as bearer identity information, bearer quality of service (QoS) information, bearer uplink tunnel information, etc.

[0126] ●first cell related information, which indicates information of a cell (such as an SpCell, a SCell, etc.) that is requested to be configured for the user equipment, such as cell identity information, cell uplink configuration information, etc. In one example, the cell is a candidate target cell in the mobile process of the user equipment

[0127] ●second synchronization mode indication information, which indicates a synchronization mode used when the user equipment accesses the cell served by the second network node. In one example, the synchronization is uplink synchronization. Further, the synchronization mode indicated by this indication information may be RACH-based synchronization, or RACH-less synchronization, or both. Based on this indication information, the second network node may determine how to allocate resources randomly accessed by the user equipment for the user equipment. In one example, if the synchronization mode indicated by this indication information is RACH-based synchronization, then the second network node needs to allocate resources for the mode (such as resources for contention-free random access (CFRA)) for the user equipment, and include the configuration of the resources in “first configuration information” in the following Step 1-2, and after receiving a handover command, the user equipment needs to perform random access according to the resources; further, when the synchronization mode is RACH-based synchronization, the second network node will not allocate resources (such as early UL synchronization resources) for RACH-less synchronization for the user equipment, and will not provide the configuration of the resources in the following Step 1-2. In another example, if the synchronization mode indicated by the indication information is RACH-less synchronization, then the second network node needs to allocate resources supporting the synchronization mode (such as early UL synchronization resources), and include the configuration of the resources in the “first configuration information” in the following Step 1-2, and the user equipment uses the configuration of the resources to transmit a random access signal before receiving the handover command; further, when the synchronization mode is RACH-less synchronization, the second network node will not allocate resources (such as CFRA resources) for RACH-based synchronization for the user equipment, and will not provide the configuration of the resources in the following Step 1-2. In another example, if the synchronization mode indicated by this indication information includes RACH-based synchronization and RACH-less synchronization, then the second network node will allocate resources for these two modes respectively, and provides the configuration of these resources in the following Step 1-2. This information has the beneficial effects of helping the second network node allocate resources for synchronization, and improving the utilization efficiency of resources

[0128] ● first reference configuration information, which indicates a configuration referenced in generating the first configuration information. The generated first configuration information in turn will be a differential configuration (or a delta configuration) based on the first reference configuration information. This configuration information may include at least one of the following information: radio bearer configuration (such as a packet data convergence protocol (PDCP) configuration, a service data adaptation protocol (SDAP) configuration), a radio link control (RLC) bearer configuration (such as an RLC configuration and a logical channel configuration) and a cell group configuration (such as an MAC layer configuration, a physical layer configuration, a cell configuration, etc.)

[0129] ● first reference configuration indication information, which indicates that the configuration generated based on the above “first user equipment configuration request information” is a reference configuration. In one example, if the above “first user equipment configuration request information” is a configuration requested for a serving cell of the user equipment, then the configuration used by the user equipment in the current serving cell may be used as a reference configuration. In another example, if the above “first user equipment configuration request information” is a configuration requested for a candidate cell of the user equipment, then the configuration used by the user equipment in the candidate cell may serve as a reference configuration. Further, this indication information may also include configuration identity information for identifying the configuration. After receiving this indication information, the second network node may take the configuration used by the user equipment in the current serving cell or the configuration of the candidate cell as a reference configuration and reverses the configuration

[0130] ■ first reference configuration request information, which is used to help the second network node generate / modify / release the reference configuration. Further, the reference configuration may be a configuration of a cell group, such as a master cell group (MCG) configuration, a secondary cell group (SCG) configuration or it may be a reference configuration that includes configurations of multiple cell groups. This information may include at least one of the following information:

[0131] ● reference configuration indication information, which indicates that a configuration required to be generated by the second network node is a reference configuration. After receiving this information, the second network node may generate the reference configuration according to other information included in the above “first reference configuration request information”. Further, after receiving this indication information, the second network node does not reserve resources (such as resources of an air interface) for the generated configuration in a configuration generating process. This information has the beneficial effects of reducing unnecessary resource reservation and saving the resources of the second network node

[0132] ● reference bearer related information, which indicates bearer information required to be considered in the generated reference configuration, such as bearer identity information, bearer QoS information, bearer uplink tunnel information, etc.

[0133] ● reference cell related information, which indicates cell information required to be considered in the generated reference configuration, such as cell identity information, cell uplink configuration information, etc. Further, the reference cell may include one cell or multiple cells (such as a master cell and at least one secondary cell)

[0134] ● modification indication information, which is used to instruct the second network node to modify the reference configuration, and which may be explicit indication information or an implicit indication information

[0135] ● release indication information, which is used to instruct the second network node to release reference configuration, and which may be explicit indication information or an implicit indication information

[0136] ■ first configuration notification information, which is used to notify the second network node of configuration information about the user equipment, and which may include at least one of the following information:

[0137] ● first synchronization information, which indicates synchronization information used by the user equipment to access the candidate cell in the mobile process. Further, the synchronization information may be uplink synchronization information. In one example, the information is used to notify the second network node of synchronization information used by the user equipment to access the candidate cell in the mobile process (the synchronization information may be targeted at one cell or multiple cells), and in another example, the information is used to respond to a request of the second network node and transmit the requested synchronization information to the second network node. After receiving this information, the second network node may transmit the obtained synchronization information to the user equipment to accelerate the user equipment to access the cell. This information has the beneficial effects of helping the second network node acquire synchronization information used by the user equipment to access the candidate cell in the mobile process, and provide the synchronization information to the user equipment to accelerate the user equipment to access a new cell. For one cell, the information may include at least one of the following information:

[0138] ◆user equipment identity information, such as a CU / DU F1AP UE ID, a C-RNTI, etc.

[0139] ◆cell identity information, which indicates a cell related to the synchronization information. In one example, the cell is a candidate target cell accessed by the user equipment

[0140] ◆source cell identity information, which indicates a serving cell where the user equipment is located when transmitting a random access signal

[0141] ◆uplink synchronization information, such as timing advance information

[0142] ◆synchronization valid time information, which indicates valid time of the above “uplink synchronization information”, during such valid time, the above “uplink synchronization information” may be used for uplink synchronization of the user equipment, otherwise, the uplink synchronization of the user equipment cannot be performed using the above “uplink synchronization information”

[0143] ● first uplink resource information, such as UL grant configuration information, which indicates uplink resources allocated for the user equipment. The uplink resources are uplink resources used by the user equipment when accessing the cell. After receiving this information, the second network node may transmit configuration information of uplink resources to the user equipment, so that the user equipment uses the uplink resources to perform uplink data transmission after accessing the cell. This information has the beneficial effects of helping the second network node configure uplink resources to the user equipment, and accelerating uplink data transmission after the user equipment accesses the cell. This information may include at least one of the following information:

[0144] ◆user equipment identity information, such as a CU / DU F1AP UE ID, a XnAP UE ID, a C-RNTI, etc.

[0145] ◆cell identity information, which indicates a cell related to the uplink resource. In one example, the cell is a candidate target cell accessed by the user equipment

[0146] ◆time resource indication information, such as a time length, time starting point information, time end point information, cycle information, etc.

[0147] ◆frequency domain resource indication information, such as bandwidth part (BWP) identity information, frequency domain starting point information, frequency domain bandwidth information (such as a number of physical resource blocks (PRBs) and a size of a bandwidth), frequency domain end point information, etc.

[0148] ◆beam indication information, which indicates a beam used by the user equipment when performing uplink data transmission

[0149] Step 1-2: the second network node transmits a second message to the first network node. In one embodiment, the second message may be a second response message. Further, the second response message may be a first configuration response message, and its function is to transmit the generated configuration information to the first network node and / or provide a configuration required for the first node to access the candidate cell. The second message may include at least one of the following information:

[0150] ■first synchronization response information, which is used to provide the first network node with synchronization information used by the user equipment to access the candidate cell in the mobile process, and which is acquired by the second network node. This information may include at least one of the following information:

[0151] ●user equipment identity information, such as a CU / DU F1AP UE ID, a XnAP UE ID, a C-RNTI, etc.

[0152] ●cell identity information, which indicates a cell related to the synchronization information. In one example, the cell is a candidate target cell accessed by the user equipment

[0153] ●source cell identity information, which indicates a serving cell where the user equipment is located when transmitting a random access signal

[0154] ●uplink synchronization information, such as timing advance information

[0155] ●synchronization valid time information, which indicates valid time of the above “uplink synchronization information”, during such valid time, the above “uplink synchronization information” may be used for uplink synchronization of the user equipment, otherwise, the uplink synchronization of the user equipment cannot be performed using the above “uplink synchronization information”

[0156] ■first uplink resource response information, which is used to provide the first network node with uplink resources of the user equipment, and which may include at least one of the following information:

[0157] ●user equipment identity information, such as a CU / DU F1AP UE ID, a XnAP UE ID, a C-RNTI, etc.

[0158] ●cell identity information, which indicates a cell related to the uplink resource. In one example, the cell is a candidate target cell accessed by the user equipment

[0159] ●time resource indication information, such as a time length, time starting point information, time end point information, cycle information, etc.

[0160] ●frequency domain resource indication information, such as BWP identity information, frequency domain starting point information, frequency domain bandwidth information (such as a number of PRBs and a size of a bandwidth), frequency domain end point information, etc.

[0161] ●beam indication information, which indicates a beam used by the user equipment when performing uplink data transmission

[0162] ■first user configuration response information, also called first configuration information, which includes configuration information generated by the second network node for the user terminal device, and which may include at least one of the following information: accepted bearer information (such as bearer identity information, downlink tunnel information, etc.), accepted cell information (such as cell identity information), an RLC bearer configuration (such as an RLC configuration, a logical channel configuration, etc.), a cell group configuration (such as an MAC layer configuration, a physical layer configuration, a cell configuration, etc.), a resource configuration supporting “RACH-based synchronization” (such as preamble configuration information, beam configuration information, resource configuration information, etc., which can be seen in the description of “first synchronization request information” in Step 1-1 above), and a resource configuration supporting “RACH-less synchronization” (such as preamble configuration information, beam configuration information, resource configuration information, etc., which can be seen in the description of “first synchronization request information” in Step 1-1 above). In addition, this information may also include “synchronization signal configuration information” (for details, see “synchronization signal configuration information” in the following Step 1-3). Further, the information may be generated based on the reference configuration information, for example, the first configuration information is a differential configuration (delta configuration) based on the reference configuration information.

[0163] ■first reference configuration response information, which includes the reference configuration generated by the second network node, and which may include at least one of the following information: accepted bearer information (such as bearer identity information, downlink tunnel information, etc.), accepted cell information (such as cell identity information), a radio bearer configuration (such as a PDCP configuration, an SDAP configuration), an RLC bearer configuration (such as an RLC configuration, a logical channel configuration, etc.), a cell group configuration (such as an MAC layer configuration, a physical layer configuration, a cell configuration, etc.)

[0164] The first network node and the second network node may be the following possible nodes, respectively:

[0165] ●the first network node is the above-mentioned second node, and the second network node is the above-mentioned third node or fifth node

[0166] ●the first network node is the above-mentioned fourth node, and the second network node is the above-mentioned fifth node

[0167] ●the first network node is the above-mentioned second node, and the second network node may be the above-mentioned fourth node

[0168] ●the first network node is the above-mentioned third node, and the second network node is the above-mentioned second node

[0169] ●the first network node is the above-mentioned third node, and the second network node is the above-mentioned fifth node

[0170] Step 1-3: the first network node transmits a third message to the first node. In one embodiment, the third message may be a first user equipment configuration message, which is used to configure a candidate cell for the first node. In one example, the first network node may be the above-mentioned second node, and in another example, the first network node may be the above-mentioned fourth node. The message may include at least one of the following information:

[0171] ■synchronization signal configuration information, which is used to indicate configuration information required by the user equipment to transmit a signal, which may be an uplink synchronization signal (such as a random access preamble signal, a preamble signal). This information may include at least one of the following information:

[0172] ●signal transmission valid time information, which indicates the valid time for the first node to transmit a signal, that is, the first node needs to transmit a signal (such as the preamble) within a time window indicated by the information. Specifically, after the first node receives an order that triggers the first node to transmit a preamble (such as a PDCCH order), the first node needs to transmit the preamble within a time window indicated by the “signal transmission valid time information”, or after the first node receives the order that triggers the transmission of the preamble, the first node needs to wait for a period of time (such as a time period 1) before transmitting the preamble, and needs to transmit the preamble within the time window indicated by the “signal transmission valid time information”

[0173] ●start time allowing signal transmission

[0174] ●end time allowing signal transmission

[0175] ●cell identity information, which indicates a cell where the user equipment transmits a signal or the cell that receives the signal transmitted by the user equipment. In one example, this cell is a candidate cell for the handover

[0176] ●preamble configuration information, referring to the description in “first synchronization request information” in Step 1-1

[0177] ●beam configuration information, referring to the description in “first synchronization request information” in Step 1-1

[0178] ●resource configuration information, referring to the description in “first synchronization request information” in Step 1-1

[0179] ■uplink synchronization information, such as timing advance information

[0180] ■uplink resource information, which includes uplink resources allocated to the first node. The uplink resources may be configured grant resources or dynamic grant resources. This information may include at least one of the following information:

[0181] ●cell identity information, which indicates a cell related to the uplink resource. In one example, the cell is a candidate target cell accessed by the user equipment.

[0182] ●time resource indication information, such as a time length, time starting point information, time end point information, cycle information, etc.

[0183] ●frequency domain resource indication information, such as BWP identity information, frequency domain starting point information, frequency domain bandwidth information (such as a number of PRBs and a size of a bandwidth), frequency domain end point information, etc.

[0184] ●beam indication information, which indicates a beam used by the user equipment when performing uplink data transmission.

[0185] ■second reference configuration information, which includes reference configuration information. The description of this information may refer to the description of “first reference configuration information” in Step 1-1 above. Further, this information may further include second reference configuration indication information (such as a reference indication), which is used to indicate configuration information as a reference configuration. In one example, this indication information may be used to indicate that a configuration used by the user equipment in the current serving cell may be used as a reference configuration, and in another example, this indication information may be used to indicate that a configuration used by a candidate cell of the user equipment may be used as a reference configuration. After receiving the second reference configuration indication information, the user equipment can take the configuration indicated by the information as a reference configuration. This second reference configuration indication information has the beneficial effects of helping the user equipment determine the reference configuration and reducing the signaling overhead caused by transmission of the reference configuration

[0186] ■candidate cell configuration information, which includes a configuration of a candidate cell for handover by the first node, and which may include at least one of the following information:

[0187] ●cell identity information, which indicates a candidate cell

[0188] ●configuration identity information, which identifies a configuration of a candidate cell

[0189] ●first user equipment configuration information, which indicates a configuration used by the user equipment to access the candidate cell. In one example, this configuration may be a differential configuration (a delta configuration) based on the above “first reference configuration information”. This configuration information includes at least one of the following configurations: a radio bearer configuration (such as a PDCP configuration, an SDAP configuration), an RLC bearer configuration (such as an RLC configuration, a logical channel configuration, etc.), a cell group configuration (such as an MAC layer configuration, a physical layer configuration), a cell configuration, a resource configuration supporting “RACH-based synchronization” (see the description in “first user equipment configuration response information” in Step 1-2 above), a resource configuration supporting “RACH-less synchronization” (see the description in “first user equipment configuration response information” in Step 1-2 above), and an uplink resource configuration (the information included in this configuration may refer to the description of “first uplink resource response information” in Step 1-2 above), etc. When the user equipment receives this information, the user equipment needs to combine this information with the above-mentioned “first reference configuration information” to generate a complete configuration that is used after the first user equipment accesses the candidate cell. Therefore, the first node will store the generated complete configuration, for example, in a variable (such as VALTM-UE-config) at the first node side

[0190] ●Serving cell Indication or Serving Cell as Candidate Indication, which indicates that the current serving cell of the first node may also be used as a candidate cell. Further, the “configuration identity information” included in the above “candidate cell configuration information” is allocated to the configuration corresponding to the current serving cell. After receiving this information, the first node may store complete configuration information (such as a configuration included in a radio resource control (RRC) reconfiguration message) corresponding to the current serving cell (for example, the first node stores the complete configuration information in a variable (such as VarLTM-UE-config) at the first node side), so that after the source cell becomes a candidate cell for the handover, the first node can continue to use the stored configuration for data transmission after accessing the cell again in the future. In one example, this information may be explicit indication information, and in another example, this information may be implicit indication information. For example, when a cell indicated by the “cell identity information” included in the above “candidate cell configuration information” is the current serving cell of the first node, the first node may store the complete configuration information corresponding to the current serving cell, or, when the configuration indicated by the “configuration identity information” included in the above “candidate cell configuration information” is the configuration of the current serving cell of the first node, the first node may store the complete configuration information corresponding to the current serving cell. Further, if the above “first user equipment configuration message” includes the “Serving cell Indication” (or Serving Cell as Candidate Indication), the first node may use the “configuration identity information” as identity information allocated to the configuration corresponding to the current serving cell. This information has the beneficial effects of reducing the signaling overhead required to configure the candidate cell and saving the bandwidth of the air interface.

[0191] Combined with the flows above, the present disclosure gives different embodiments according to different scenarios.

[0192] Scenario 1: Synchronization information acquisition

[0193] In this scenario, user equipment performs cell handover, and a network node acquires uplink synchronization information used by the user equipment to access a candidate cell in a handover process. In one example, after the user equipment transmits a random access preamble signal, the network node acquires uplink synchronization information used by the user equipment to access the candidate cell in the handover process. Depending on structures of different network nodes, there may be the following different implementations:

[0194] ■Implementation 1: A current serving cell and a candidate cell of the user equipment belong to different base stations (such as a base station 1 and a base station 2)

[0195] The user equipment transmits an uplink synchronization signal in the candidate cell after receiving a signaling that triggers uplink synchronization signal transmission in the serving cell. In order to acquire uplink synchronization information of the candidate cell, this implementation includes the following flow, as shown in Fig. 4A:

[0196] - Step a-0: the base station 1 (such as the base station where the current serving cell is located) transmits a signaling (such as a PDCCH order) that triggers a random access preamble to the user equipment, and the user equipment transmits the preamble

[0197] - Step a-1: the base station 1 transmits a first configuration request message to the base station 2, this message includes “first synchronization request information”, and information included in this information may refer to the description of “first synchronization request information” in Step 1-1 above

[0198] - Step a-2: the base station 2 transmits a first configuration response message to the base station 1, this message includes “first synchronization response information”, and information included in this information may refer to the description of “first synchronization response information” in Step 1-2 above

[0199] ■ Implementation 2: A current serving cell and a candidate cell of the user equipment belong to different distributed units (such as a distributed unit 1 and a distributed unit 2) of a same base station.

[0200] The user equipment transmits an uplink synchronization signal in the candidate cell after receiving a signaling that triggers uplink synchronization signal transmission in the serving cell. The distributed unit 1 is a distributed unit serving a source cell, the distributed unit 2 is a distributed unit serving a target cell, and the two distributed units are connected to a same central unit. In order to acquire uplink synchronization information of the candidate cell, this implementation includes the following flow, as shown in Fig. 4B:

[0201] - Step b-0: the distributed unit 1 transmits a signaling (such as a PDCCH order) that triggers a random access preamble to the user equipment, and the user equipment transmits the preamble

[0202] - Step b-1: the distributed unit 1 transmits a first configuration request message to the central unit, this message includes “first synchronization request information”, and information included in this information may refer to the description of “first synchronization request information” in Step 1-1 above

[0203] - Step b-2: the central unit transmits a second configuration request message to the distributed unit 2, the message includes “second synchronization request information”, and information included in this information may refer to the description of “first synchronization request information” in Step 1-1 above

[0204] - Step b-3: the distributed unit 2 transmits a second configuration response message to the central unit, which includes “second synchronization response information”, and information included in this information may refer to the description of “first synchronization response information” in Step 1-2 above

[0205] - Step b-4: the central unit transmits a first configuration response message to the distributed unit 1, this message includes “first synchronization response information”, and information included in this information may refer to the description of “first synchronization response information” in Step 1-2 above

[0206] ■ Implementation 3: A current serving cell and a candidate cell of user equipment belong to different base stations (a base station 1 and a base station 2), and each base station includes a central unit and a distributed unit.

[0207] The base station 1 includes a central unit 1 and a distributed unit 1, and the base station 2 includes a central unit 2 and a distributed unit 2. The user equipment transmits an uplink synchronization signal in the candidate cell after receiving a signaling that triggers uplink synchronization signal transmission in the serving cell. In order to acquire uplink synchronization information of the candidate cell, this implementation includes the following flow, as shown in Fig. 4C:

[0208] - Step c-0: the distributed unit 1 transmits a signaling (such as a PDCCH order) that triggers a random access preamble to the user equipment, and the user equipment transmits the preamble

[0209] - Step c-1: the distributed unit 1 transmits a first configuration request message to the central unit 1, this message includes “first synchronization request information”, and information included in this information may refer to the description of “first synchronization request information” in Step 1-1 above

[0210] - Step c-2: the central unit 1 transmits a second configuration request message to the central unit 2, which includes “second synchronization request information”, and information included in this information may refer to the description of “first synchronization request information” in Step 1-1 above

[0211] - Step c-3: the central unit 2 transmits a third configuration request message to the distributed unit 2, which includes “third synchronization request information”, and information included in this information may refer to the description of “first synchronization request information” in Step 1-1 above

[0212] - Step c-4: the distributed unit 2 transmits a third configuration response message to the central unit 2, which includes “third synchronization response information”, and information included in this information may refer to the description of “first synchronization response information” in Step 1-2 above

[0213] - Step c-5: the central unit 2 transmits a second configuration response message to the central unit 1, which includes “second synchronization response information”, and information included in this information may refer to the description of “first synchronization response information” in Step 1-2 above

[0214] - Step c-6: the central unit 1 transmits a first configuration response message to the distributed unit 1, this message includes “first synchronization response information”, and information included in this information may refer to the description of “first synchronization response information” in Step 1-2 above

[0215] ■ Implementation 4: A current serving cell and a candidate cell of the user equipment belong to different distributed units (a distributed unit 1 and a distributed unit 2).

[0216] The user equipment transmits an uplink synchronization signal in the candidate cell after receiving a signaling that triggers uplink synchronization signal transmission in the serving cell. In order to acquire uplink synchronization information of the candidate cell, this implementation includes the following flow, as shown in Fig. 4D:

[0217] - Step d-0: the distributed unit 1 transmits a signaling (such as a PDCCH order) that triggers a random access preamble to the user equipment, and the user equipment transmits the preamble

[0218] - Step d-1: the distributed unit 1 transmits a first configuration request message to the distributed unit 2, this message includes “first synchronization request information”, and information included in this information may refer to the description of “first synchronization request information” in Step 1-1 above

[0219] - Step d-2: the distributed unit 2 transmits a first configuration response message to the distributed unit 1, this message includes “first synchronization response information”, and information included in this information may refer to the description of “first synchronization response information” in Step 1-2 above

[0220] Scenario 2: Uplink resource acquisition

[0221] In this scenario, user equipment performs cell handover, and a network node acquires uplink resources of the user equipment. In one example, the uplink resources may be uplink resources required by the user equipment after transmitting a random access preamble signal. Further, the uplink resources are for the user equipment to transmit an uplink data packet after accessing a candidate cell of the handover. Depending on the structures of different network nodes, there may be the following different implementations:

[0222] ■ Implementation 1: A current serving cell and a candidate cell of user equipment belong to different base stations (such as a base station 1 and a base station 2).

[0223] The base station 1 serves a source cell of the user equipment, and the base station 2 serves a candidate cell of the user equipment. In order to obtain uplink resources of the candidate cell, this implementation includes the following steps, as shown in Fig. 4A:

[0224] - Step a-1: the base station 1 transmits a first configuration request message to the base station 2, this message includes “first uplink resource request information”, and information included in this information may refer to the description of “first uplink resource request information” in Step 1-1 above

[0225] - Step a-2: the base station 2 transmits a first configuration response message to the base station 1, this message includes “first uplink resource response information”, and information included in this information may refer to the description of “first uplink resource response information” in Step 1-2 above

[0226] ■ Implementation 2: A current serving cell and a candidate cell of user equipment belong to different distributed units (such as a distributed unit 1 and a distributed unit 2) of a same base station.

[0227] The distributed unit 1 is a distributed unit serving a source cell, the distributed unit 2 is a distributed unit serving a target cell, and the two distributed units are connected to a same central unit. In order to acquire uplink resources of the candidate cell, this implementation includes the following flow, as shown in Fig. 4B:

[0228] - Step b-1: the distributed unit 1 transmits a first configuration request message to the central unit, this message includes “first uplink resource request information”, and information included in this information may refer to the description of “first uplink resource request information” in Step 1-1 above

[0229] - Step b-2: the central unit transmits a second configuration request message to the distributed unit 2, which includes “second uplink resource request information”, and information included in this information may refer to the description of “first uplink resource request information” in Step 1-1 above

[0230] - Step b-3: the distributed unit 2 transmits a second configuration response message to the central unit, which includes “second uplink resource response information”, and information included in this information may refer to the description of “first uplink resource response information” in Step 1-2 above

[0231] - Step b-4: the central unit transmits a first configuration response message to the distributed unit 1, this message includes “first uplink resource response information”, and information included in this information may refer to the description of “first uplink resource response information” in Step 1-2 above

[0232] ■ Implementation 3: A current serving cell and a candidate cell of user equipment belong to different base stations (a base station 1 and a base station 2), and each base station includes a central unit and a distributed unit.

[0233] The base station 1 includes a central unit 1 and a distributed unit 1, and the base station 2 includes a central unit 2 and a distributed unit 2. In order to acquire uplink resources of the candidate cell, this implementation includes the following flow, as shown in Fig. 4C:

[0234] - Step c-1: the distributed unit 1 transmits a first configuration request message to the central unit 1, this message includes “first uplink resource request information”, and information included in this information may refer to the description of “first uplink resource request information” in Step 1-1 above

[0235] - Step c-2: the central unit 1 transmits a second configuration request message to the central unit 2, which includes “second uplink resource request information”, and information included in this information may refer to the description of “first uplink resource request information” in Step 1-1 above

[0236] - Step c-3: the central unit 2 transmits a third configuration request message to the distributed unit 2, which includes “third uplink resource request information”, and information included in this information may refer to the description of “first uplink resource request information” in Step 1-1 above

[0237] - Step c-4: the distributed unit 2 transmits a third configuration response message to the central unit 2, which includes “third uplink resource response information”, and information included in this information may refer to the description of “first uplink resource response information” in Step 1-2 above

[0238] - Step c-5: the central unit 2 transmits a second configuration response message to the central unit 1, which includes “second uplink resource response information”, and information included in this information may refer to the description of “first uplink resource response information” in Step 1-2 above

[0239] - Step c-6: the central unit 1 transmits a first configuration response message to the distributed unit 1, this message includes “first uplink resource response information”, and information included in this information may refer to the description of “first uplink resource response information” in Step 1-2 above

[0240] ■ Implementation 4: A current serving cell and a candidate cell of user equipment belong to different distributed units (a distributed unit 1 and a distributed unit 2)

[0241] In order to acquire uplink resources of the candidate cell, this implementation includes the following flow, as shown in Fig. 4D:

[0242] - Step d-1: the distributed unit 1 transmits a first configuration request message to the distributed unit 2, this message includes “first uplink resource request information”, and information included in this information may refer to the description of “first uplink resource request information” in Step 1-1 above

[0243] - Step d-2: the distributed unit 2 transmits a first configuration response message to the distributed unit 1, this message includes “first uplink resource response information”, and information included in this information may refer to the description of “first uplink resource response information” in Step 1-2 above

[0244] In the above flows, the first configuration request message and the first configuration response message may respectively be:

[0245] ■a handover request message and a handover request acknowledge message

[0246] ■an SN addition / modification request message and an SN addition / modification ACK message

[0247] ■a UE context setup / modification request message and a UE context setup / modification response message

[0248] ■ a UE context modification required message and a UE context modification confirm message

[0249] They may also be new messages on interfaces between base stations, new messages on interfaces between central units and distributed units of the base stations, or other types of new messages. The first user equipment configuration message may be an RRC reconfiguration message, other messages or new messages.

[0250] In the above flows, the information included in the first configuration request message may be the same as that included in the second configuration request message and / or the third configuration request message.

[0251] The above flows include the following beneficial effects:

[0252] 1) helping the user equipment acquire synchronization information of the candidate cell, and reducing latency of the user equipment accessing the candidate cell

[0253] 2) helping the user equipment acquire uplink resource information of the candidate cell, and accelerating uplink data transmission after the user equipment accesses the candidate cell

[0254] 3) helping the user equipment generate a complete configuration of the candidate cell, and reducing configuration signaling overhead generated for the user equipment configuration in the mobile process of the user equipment

[0255] Another aspect of the present invention is how to acquire valid uplink synchronization information (such as timing advance (TA) information) after a user accesses a target / candidate cell. In order to trigger the user to perform a cell handover or cell switch, a signaling transmitted by a base station or a distribution unit of the base station to the user (such as a MAC CE, a LTM Cell Switch command MAC CE) will contain uplink synchronization information. After receiving the signaling, the user may start at least one of the following timers:

[0256] ■ Timer 1: This timer is used to assist the user in determining whether the cell handover or cell switch has been completed. If the user's cell handover or cell switch process is not completed when the timer expires, it can be considered that the cell handover or cell switch process has failed, and the user will then start a failure recovery process (such as a reestablishment process, a cell selection process, etc.). In one example, the timer is T304

[0257] ■ Timer 2: This timer is used to assist a user in determining whether the uplink synchronization information is valid. When the timer expires, the user can consider that the uplink synchronization information obtained by it is invalid, that is, the user cannot transmit uplink signals or data according to the obtained uplink synchronization information any more. In one example, the timer is a Time Alignment Timer (TAT).

[0258] After the user starts the above timers, timer 2 may expires before timer 1, that is, the uplink synchronization information obtained by the user is invalid, but the user has not yet completed the process of cell handover or cell switch. In order to be able to access a candidate cell (target cell), the user may have at least one of the following behaviors:

[0259] ■ Behavior 1: the user triggers a random access process

[0260] ■Behavior 2: the user triggers a scheduling request process, during which a random access process is triggered

[0261] ■ Behavior 3: the user receives a signaling from a base station or a distribution unit of the base station, thereby triggering a random access process, such as a random access process triggered by the PDCCH order

[0262] ■ Behavior 4: the user stops timer 1 and starts a failure recovery process (in one example, the failure recovery process is the process of connection reestablishment, such as the user selects a cell and performs the process of connection reestablishment within the selected cell, or when the selected cell is a candidate cell configured for the user, accesses the candidate cell according to the candidate cell configuration information)

[0263] The above four behaviors all occur after the user receives a signaling for cell handover or cell switch including uplink synchronization information, and timer 2 expires earlier than timer 1. When the user performs at least one of the above behaviors 1 / 2 / 3, if the random access process is successfully completed, the user can consider the process of cell handover or cell switch (or the execution process of LTM cell switch) to be successful.

[0264] In addition, in order to avoid the above-mentioned behaviors of users (i.e. any one or more of behaviors 1 / 2 / 3 / 4), the network side (such as the base station or distributed unit of the base station where the target / candidate cell is located) may set that a length of the Timer 1 is always smaller than a length of the Timer 2, that is, the Timer 2 is not allowed to expire when the Timer 1 is running.

[0265] Fig. 5 is a block diagram of a node according to an example embodiment of the present disclosure. Here, the node is taken as an example to explain its structure and function, but it should be understood that the shown structure and function can be equally applied to a base station (or a central unit of a base station, or a control plane portion of a central unit of a base station, or a user plane portion of a central unit of a base station, or a distributed unit of a base station, etc.) as well as a network node.

[0266] Referring to Fig. 5, the node 1000 includes a transceiver 1010, a controller 1020 and a memory 1030. Under the control of the controller 1020, which may be implemented as one or more processors, the node 1000 (including the transceiver 1010 and the memory 1030) is configured to perform operations of the node described herein. Although the transceiver 1010, the controller 1020 and the memory 1030 are shown as separate entities, they may be implemented as a single entity, such as a single chip. The transceiver 1010, the controller 1020 and the memory 1030 may be electrically connected or coupled to each other. The transceiver 1010 may transmit and receive signals to and from other network entities, such as another node and / or UE. In one implementation, the transceiver 1010 may be omitted. In this case, the controller 1020 may be configured to perform instructions (including computer programs) stored in the memory 1030 to control an overall operation of the node 1000, thereby implementing the operations of the node described herein.

[0267] Fig. 6 is a block diagram of a user equipment according to an exemplary embodiment of the present disclosure. In the present disclosure, the terms “user equipment”, “user terminal device”, “user terminal” and “terminal device” may be used interchangeably.

[0268] Referring to Fig. 6, the user equipment 1100 includes a transceiver 1110, a controller 1120 and a memory 1130. Under the control of the controller 1120, which may be implemented as one or more processors, the user equipment 1100 (including the transceiver 1110 and the memory 1130) is configured to perform operations of the user equipment described herein. Although the transceiver 1110, the controller 1120 and the memory 1130 are shown as separate entities, they may be implemented as a single entity, such as a single chip. The transceiver 1110, the controller 1120 and the memory 1130 may be electrically connected or coupled to each other. The transceiver 1110 may transmit and receive signals to and from other network entities, such as a node, another UE, and the like. In one implementation, the transceiver 1110 may be omitted. In this case, the controller 1120 may be configured to execute instructions (including computer programs) stored in the memory 1130 to control an overall operation of the user equipment 1100, thereby performing the operations of the user equipment described herein.

[0269] The present application provides network nodes, nodes and methods performed by the same. A method performed by a first network node in a wireless communication system comprises: transmitting a first message to a second network node; and transmitting a third message to a first node, wherein the first message includes at least one of the following information: first synchronization request information comprising synchronization information feedback time indication information, first uplink resource request information comprising first synchronization mode indication information and / or assistant information for uplink resource allocation, first user equipment configuration request information comprising associated configuration indication information, and first reference configuration request information comprising reference configuration indication information.

[0270] Those skilled in the art may recognize that the present disclosure can be implemented in other specific forms without changing the technical idea or basic features of the present disclosure. Therefore, it should be understood that the above-mentioned embodiments are only examples and are not limited. The scope of the present disclosure is defined by the appended claims, rather than the detailed description. Therefore, it should be understood that all modifications or changes derived from the meaning and scope of the appended claims and their equivalents are within the scope of the present disclosure.

[0271] In the above embodiments of the present disclosure, all operations and messages may be selectively executed or may be omitted. In addition, the operations in each embodiment do not need to be executed sequentially, and the order of the operations may be changed. Messages do not need to be transferred in order, and the transfer order of the messages may be changed. Each operation and each message transfer may be executed independently.

[0272] Although the present disclosure has been shown and described with reference to various embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made without departing from the spirit and scope of the present disclosure as defined by the appended claims and their equivalents.

[0273] A method performed by a first network node in a wireless communication system is provided. The method comprises transmitting a first message to a second network node and transmitting a third message to a first node, wherein the first message comprises at least one of the following information: first synchronization request information comprising synchronization information feedback time indication information, first uplink resource request information comprising first synchronization mode indication information and / or assistant information for uplink resource allocation, first user equipment configuration request information comprising associated configuration indication information, and first reference configuration request information comprising reference configuration indication information.

[0274] The third message comprises at least one of the following information: synchronization signal configuration information comprising signal transmission valid time information, candidate cell configuration information comprising Serving Cell as Candidate indication, uplink resource information, and second reference configuration information.

[0275] The method further comprises receiving a second message from the second network node, wherein the second message is used to provide a configuration required for the first node to access a candidate cell.

[0276] The first message further comprises first configuration notification information for notifying the second network node of configuration information about the first node.

[0277] The first synchronization request information further comprises at least one of the following information: first node identity information, cell identity information, identity information of a third network node, synchronization configuration indication information for indicating a configuration used by the first node for synchronization, system frame number information, preamble configuration information, beam configuration information and resource configuration information.

[0278] The first user equipment configuration request information further comprises at least one of the following information: first configuration reservation indication information for indicating a configuration that the second network node needs to reserve, first bearer related information, first cell related information, second synchronization mode indication information, first reference configuration information for indicating a configuration referenced in generating first configuration information, and first reference configuration indication information for indicating that a configuration generated based on the first user equipment configuration request information is a reference configuration; and the first reference configuration request information further comprises at least one of the following information: reference bearer related information, reference cell related information, modification indication information, and release indication information; and the first configuration notification information comprises at least one of the following information: first synchronization information for indicating synchronization information used by the first node to access the candidate cell in a mobile process, and first uplink resource information for indicating uplink resources allocated to the first node.

[0279] The synchronization signal configuration information further comprises at least one of the following information: start time allowing signal transmission, end time allowing signal transmission, cell identity information, preamble configuration information, beam configuration information and resource configuration information; and the candidate cell configuration information further comprises at least one of the following information: cell identity information, configuration identity information, and first user equipment configuration information.

[0280] The second message comprises at least one of the following information: first synchronization response information for providing synchronization information used by the first node to access the candidate cell, first uplink resource response information for providing uplink resources for the first node, first configuration information including synchronization signal configuration information comprising signal transmission valid time information, and first reference configuration response information comprising a reference configuration generated by the second network node.

[0281] The assistant information for uplink resource allocation comprises at least one of the following information: indication information of an uplink resource allocation mode, beam indication information, and valid time information of uplink resources; and the associated configuration indication information is used to indicate information required by the second network node in generating first configuration information of the first node, and the associated configuration indication information comprises at least one of the following information: first node identity information, configuration identity information, and associated cell identity information.

[0282] A method performed by a second network node in a wireless communication system is provided. The method comprises receiving a first message from a first network node; and transmitting a second message to the first network node, wherein the first message comprises at least one of the following information: first synchronization request information comprising synchronization information feedback time indication information, first uplink resource request information comprising first synchronization mode indication information and / or assistant information for uplink resource allocation, first user equipment configuration request information comprising associated configuration indication information, and first reference configuration request information comprising reference configuration indication information, wherein the second message is used to provide a configuration required for the first node to access a candidate cell.

[0283] The second message comprises at least one of the following information: first synchronization response information for providing synchronization information used by the first node to access the candidate cell, first uplink resource response information for providing uplink resources for the first node, first configuration information including synchronization signal configuration information comprising signal transmission valid time information, and first reference configuration response information comprising a reference configuration generated by the second network node.

[0284] A method performed by a first node in a wireless communication system is provide. The method comprises receiving a third message from a first network node; and accessing a candidate cell served by a second network node based on the third message; wherein the third message comprises at least one of the following information: synchronization signal configuration information comprising signal transmission valid time information, candidate cell configuration information comprising Serving Cell as Candidate indication, uplink synchronization information, uplink resource information, and second reference configuration information.

[0285] The method further comprises starting a first timer for assisting a user of the first node in determining whether a cell handover or cell switch is completed, and / or starting a second timer for assisting the first node in determining whether the uplink synchronization information is valid; and triggering a random access process or stopping the first timer when the second timer expires before the first timer.

[0286] The method further comprises determining that a process of the cell handover or cell switch is successful, if the random access process is triggered and after the random access process is completed successfully; or starting a failure recovery process if the first timer is stopped.

[0287] A network node comprising a transceiver for transmitting and receiving signals; and a controller coupled with the transceiver and configured to perform the above method.

Claims

1.A method performed by a base station in a wireless communication system, the method comprising:transmitting, to a distributed unit (DU) of the base station, a first message including first information for requesting a reference configuration for a layer 1 / layer 2 triggered mobility (LTM), and second information for requesting synchronization information for the LTM by a central unit (CU) of the base station;receiving, from the DU, a second message as a response to the first message by the CU, wherein the second message includes the reference configuration, and the synchronization information; andtransmitting, to a user equipment (UE) associated with the LTM, a third message including information on a LTM configuration associated with a candidate configuration.2.The method of claim 1, wherein the first message further includes information on an identity (ID) of the DU,wherein the reference configuration includes cell group configuration information, andwherein the synchronization information includes information on a random access channel (RACH) configuration, and information on preamble indexes.3.The method of claim 1, wherein the information on the LTM configuration includes information on an identity (ID) of the candidate configuration, and information on an ID of a candidate cell.4.The method of claim 1, further comprising:transmitting, to the DU, information on an identity (ID) of a candidate cell, and information on a timing advance (TA) for the LTM by the CU.5.A base station in a wireless communication system, the base station comprising:a transceiver; anda controller coupled with the transceiver and configured to:transmit, to a distributed unit (DU) of the base station, a first message including first information for requesting a reference configuration for a layer 1 / layer 2 triggered mobility (LTM), and second information for requesting synchronization information for the LTM by a central unit (CU) of the base station,receive, from the DU, a second message as a response to the first message by the CU, wherein the second message includes the reference configuration, and the synchronization information, andtransmit, to a user equipment (UE) associated with the LTM, a third message including information on a LTM configuration associated with a candidate configuration.6.The base station of claim 5, wherein the first message further includes information on an identity (ID) of the DU,wherein the reference configuration includes cell group configuration information, andwherein the synchronization information includes information on a random access channel (RACH) configuration, and information on preamble indexes.7.The base station of claim 5, wherein the information on the LTM configuration includes information on an identity (ID) of the candidate configuration, and information on an ID of a candidate cell.8.The base station of claim 5, wherein the controller is further configured to:transmit, to the DU, information on an identity (ID) of a candidate cell, and information on a timing advance (TA) for the LTM by the CU.9.A method performed by a base station in a wireless communication system, the method comprising:receiving, from a central unit (CU) of the base station, a first message including first information for requesting a reference configuration for a layer 1 / layer 2 triggered mobility (LTM), and second information for requesting synchronization information for the LTM by a distributed unit (DU) of the base station;transmitting, to the CU, a second message as a response to the first message by the DU, wherein the second message includes the reference configuration, and the synchronization information; andtransmitting, to a user equipment (UE) associated with the LTM, a third message including information on a LTM configuration associated with a candidate configuration.10.The method of claim 9, wherein the first message further includes information on an identity (ID) of the DU,wherein the reference configuration includes cell group configuration information, andwherein the synchronization information includes information on a random access channel (RACH) configuration, and information on preamble indexes.11.The method of claim 9, wherein the information on the LTM configuration includes information on an identity (ID) of the candidate configuration, and information on an ID of a candidate cell.12.The method of claim 9, further comprising:receiving, from the CU, information on an identity (ID) of a candidate cell, and information on a timing advance (TA) for the LTM by the DU.13.A base station in a wireless communication system, the base station comprising:a transceiver; anda controller coupled with the transceiver and configured to:receive, from a central unit (CU) of the base station, a first message including first information for requesting a reference configuration for a layer 1 / layer 2 triggered mobility (LTM), and second information for requesting synchronization information for the LTM by a distributed unit (DU) of the base station,transmit, to the CU, a second message as a response to the first message by the DU, wherein the second message includes the reference configuration, and the synchronization information, andtransmit, to a user equipment (UE) associated with the LTM, a third message including information on a LTM configuration associated with a candidate configuration.14.The base station of claim 13, wherein the first message further includes information on an identity (ID) of the DU,wherein the reference configuration includes cell group configuration information,wherein the synchronization information includes information on a random access channel (RACH) configuration, and information on preamble indexes, andwherein the information on the LTM configuration includes information on an identity (ID) of the candidate configuration, and information on an ID of a candidate cell.15.The base station of claim 13, wherein the controller is further configured to:receive, from the CU, information on an identity (ID) of a candidate cell, and information on a timing advance (TA) for the LTM by the DU.

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