First node, second node or third node, and methods thereof.

Abstract

The disclosure relates to a 5G or 6G communication system for supporting a higher data transmission rate. The disclosure relates to a method performed by a central unit (CU) of a base station in a wireless communication system, the method comprises transmitting, to a distributed unit (DU) of the base station, a user equipment (UE) context modification request message including first information on a serving cell and second information on a layer1 / layer2 triggered mobility (LTM) candidate cell, receiving, from the DU of the base station, a UE context modification response message and transmitting, to a UE, a radio resource control (RRC) reconfiguration message including an LTM configuration, wherein the first information includes a UE based timing advance (TA) measurement configuration for the serving cell and the second information includes a UE based TA measurement configuration for the LTM candidate cell.

Description

FIRST NODE, SECOND NODE OR THIRD NODE, AND METHODS THEREOF.

[0001] The present disclosure relates to the field of communication, and more specifically, to a method performed by a first node, a method performed by a second node, a method performed by a third node, a first node, a second node, and a third node.

[0002] Fifth generation (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 6 gigahertz (GHz)" bands such as 3.5GHz, but also in "Above 6GHz" bands referred to as millimeter wave (mmWave) including 28GHz and 39GHz. In addition, it has been considered to implement sixth generation (6G) mobile communication technologies (referred to as Beyond 5G systems) in terahertz (THz) 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 multi input multi output (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 BandWidth Part (BWP), new channel coding methods such as a Low Density Parity Check (LDPC) 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 Vehicle-to-everything (V2X) 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, New Radio Unlicensed (NR-U) aimed at system operations conforming to various regulation-related requirements in unlicensed bands, new radio (NR) user equipment (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, Integrated Access and Backhaul (IAB) 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 Dual Active Protocol Stack (DAPS) handover, and two-step random access for simplifying random access procedures (2-step random access channel (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 Augmented Reality (AR), Virtual Reality (VR), Mixed Reality (MR) 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 Orbital Angular Momentum (OAM), and Reconfigurable Intelligent Surface (RIS), 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 Artificial Intelligence (AI) 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] 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".

[0009] 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.

[0010] The present disclosure aims to provide a method for an efficient communication.

[0011] Also, the present disclosure aims to provide a method of an improved LTM-based handover.

[0012] According to an aspect of the present disclosure, a method performed by a central unit (CU) of a base station in a wireless communication system is provided. The method comprises transmitting, to a distributed unit (DU) of the base station, a user equipment (UE) context modification request message including first information on a serving cell and second information on a layer1 / layer2 triggered mobility (LTM) candidate cell, receiving, from the DU of the base station, a UE context modification response message and transmitting, to a UE, a radio resource control (RRC) reconfiguration message including an LTM configuration, wherein the first information includes a UE based timing advance (TA) measurement configuration for the serving cell, and the second information includes a UE based TA measurement configuration for the LTM candidate cell.

[0013] According to an aspect of the present disclosure, a method performed by a user equipment (UE) in a wireless communication system is provided. The method comprises receiving, from a base station, a radio resource control (RRC) reconfiguration message including a layer1 / layer2 triggered mobility (LTM) configuration, the LTM configuration including a no reset identity for a serving cell and a no reset identity for an LTM candidate cell, triggering an LTM cell switch execution and re-establishing a radio link control (RLC) entity for a backhaul (BH) logical channel identity after the LTM cell switch procedure, in case that the no reset identity for the serving cell is not equal to the no reset identity for the LTM candidate cell.

[0014] According to an aspect of the present disclosure, a central unit (CU) of a base station in a wireless communication system is provided. The CU comprises a transceiver and at least one processor coupled with the transceiver and configured to transmit, to a distributed unit (DU) of the base station, a user equipment (UE) context modification request message including first information on a serving cell and second information on a layer1 / layer2 triggered mobility (LTM) candidate cell, to receive, from the DU of the base station, a UE context modification response message, and to transmit, to a UE, a radio resource control (RRC) reconfiguration message including an LTM configuration, wherein the first information includes a UE based timing advance (TA) measurement configuration for the serving cell, and the second information includes a UE based TA measurement configuration for the LTM candidate cell.

[0015] According to an aspect of the present disclosure, a user equipment (UE) in a wireless communication system is provided. the UE comprises a transceiver and at least one processor coupled with the transceiver, and configured to receive, from a base station, a radio resource control (RRC) reconfiguration message including a layer1 / layer2 triggered mobility (LTM) configuration, the LTM configuration including a no reset identity for a serving cell and a no reset identity for an LTM candidate cell, to trigger an LTM cell switch execution, and to re-establish a radio link control (RLC) entity for a backhaul (BH) logical channel identity after the LTM cell switch procedure, in case that the no reset identity for the serving cell is not equal to the no reset identity for the LTM candidate cell.

[0016] According to an aspect of the present disclosure, there is provided a method performed by a second node in a communication system, the method comprising: sending a first message to a third node or receiving a third message from the third node, wherein the first message includes first information related to protocol layer reset and / or second information related to timing advance (TA) measurement, and the third message includes fifth information related to protocol layer reset and / or sixth information related to timing advance (TA) measurement; sending a second message to a first node, wherein the second message includes third information related to protocol layer reset and / or fourth information related to timing advance (TA) measurement; wherein the first information or the third information or the fifth information is used for determining a protocol layer reset operation associated with a first cell; wherein the second information or the fourth information or the sixth information is used for determining a measurement behaviour associated with the first cell; wherein the first cell includes at least one of a serving cell, a target cell and a candidate cell.

[0017] According to the method performed by the second node provided by the present disclosure, wherein the first information, the third information, or the fifth information further comprises at least one of: a cell identification for indicating a cell associated with the first cell and not requiring to perform protocol layer reset; a cell identification for indicating a cell associated with the first cell and requiring to perform protocol layer reset.

[0018] According to the method performed by the second node provided by the present disclosure, wherein the second information, the fourth information, or the sixth information further comprises at least one of: a cell identification for indicating a cell associated with the first cell and not requiring to perform TA measurement; cell identification for indicating a cell associated with the first cell and requiring to perform TA measurement.

[0019] According to the method performed by the second node provided by the present disclosure, wherein the first message further comprises at least one of: indication information for indicating configuration that the third node needs to reserve (keep) or release; configuration information associated with synchronization, which is used for the third node to trigger the first node to acquire synchronization information of a target cell or a candidate cell in advance; configuration information associated with a reference signal, which is used for the third node to configure measurement of a reference signal; reference configuration information, which is used for the third node to generate configuration information of a candidate cell; indication information for indicating whether the third node needs to perform protocol layer reset, indication information for indicating whether the first node needs to perform TA measurement; configuration information of a source cell, including configuration information of the first node in the source cell; first default configuration information, including configuration information used by the third node when it is uncertain whether needs to perform protocol layer reset.

[0020] According to the method performed by the second node provided by the present disclosure, wherein the configuration information associated with synchronization includes at least one of: first synchronization configuration information, including configuration information related to synchronization information of a target cell or a candidate cell acquired by the first node in advance; second synchronization configuration information, including configuration information related to synchronization information of a target cell or a candidate cell acquired by the first node through a random access procedure; configuration information associated with a beam for indicating a beam used by the first node when sending a signal.

[0021] According to the method performed by the second node provided by the present disclosure, wherein the first synchronization configuration information or the second synchronization configuration information includes at least one of: indication information of frequency domain, which is used for indicating frequency domain information on which the first node transmits a random access signal; sequence related information for indicating a sequence used for the transmitted random access signal, a time alignment timer for indicating effective time of the time advance; generic configuration of a random access channel (RACH) for indicating generic configuration information for transmitting a random access signal; RACH dedicated configuration for indicating dedicated configuration information for transmitting a random access signal.

[0022] According to the method performed by the second node provided by the present disclosure, wherein the configuration information associated with the reference signal comprises at least one of: first signal configuration identification information for identifying configuration of a signal measured by the first node; first resource information for indicating resources used by a measured signal; configuration information of synchronization signal block measurement timing configuration (SMTC), which is used to indicate configuration information of synchronization signal block (SSB) of a cell.

[0023] According to the method performed by the second node provided by the present disclosure, wherein the second message further comprises at least one of: information for indicating configuration that the first node needs to reserve (keep) or release; second default configuration information, including configuration information used by the first node when it is uncertain whether needs to perform protocol layer reset; configuration information of L1 / L2 triggered mobility (LTM), including configuration information of an LTM candidate cell.

[0024] According to the method performed by the second node provided by the present disclosure, wherein the third message further comprises at least one of: third default configuration information, including configuration information used by the first node when it is uncertain whether needs to perform protocol layer reset.

[0025] According to an aspect of the present disclosure, there is provided a method performed by a third node, the method comprising: receiving a first message from a second node, and based on the first message, determining whether to perform protocol layer reset and / or determining whether the first node performs TA measurement; or sending a third message to the second node, wherein the first message includes first information related to protocol layer reset and / or second information related to timing advance (TA) measurement, wherein the third message includes fifth information related to protocol layer reset and / or sixth information related to timing advance (TA) measurement; wherein the first information or the fifth information is used for determining a protocol layer reset operation associated with a first cell; wherein the second information or the sixth information is used for determining a measurement behaviour associated with the first cell; wherein the first cell includes at least one of a serving cell, a target cell and a candidate cell.

[0026] According to the method performed by the third node provided by the present disclosure, wherein the first information or the fifth information further comprises at least one of: a cell identification for indicating a cell associated with the first cell and not requiring to perform protocol layer reset; a cell identification for indicating a cell associated with the first cell and requiring to perform protocol layer reset.

[0027] According to the method performed by the third node provided by the present disclosure, wherein the second information or the fourth information further comprises at least one of: a cell identification for indicating a cell associated with the first cell and not requiring to perform TA measurement; a cell identification for indicating a cell associated with the first cell and requiring to perform TA measurement.

[0028] According to the method performed by the third node provided by the present disclosure, wherein the first message further comprises: indication information for indicating configuration that the third node needs to reserve (keep) or release; configuration information associated with synchronization, which is used for the third node to trigger the first node to acquire synchronization information of a target cell or a candidate cell in advance; configuration information associated with a reference signal, which is used for the third node to configure measurement of a reference signal; reference configuration information, which is used for the third node to generate configuration information of a candidate cell; indication information for indicating whether the third node needs to perform protocol layer reset, indication information for indicating whether the first node needs to perform TA measurement; configuration information of a source cell, including configuration information of the first node in the source cell; first default configuration information, including configuration information used by the third node when it is uncertain whether needs to perform protocol layer reset.

[0029] According to the method performed by the third node provided by the present disclosure, wherein determining whether to perform protocol layer reset based on the first message comprises at least one of: when a cell accessed by the first node changes, determining whether to perform protocol layer reset according to related information for indicating a protocol layer reset operation of a first node associated with a serving cell and related information for indicating a protocol layer reset operation of a first node associated with a candidate cell; when a cell accessed by the first node changes, determining whether to perform protocol layer reset according to related information for indicating a protocol layer reset operation of a first node associated with a target cell and related information for indicating a protocol layer reset operation of a first node associated with a candidate cell; when a cell accessed by the first node changes, determining whether to perform protocol layer reset according to related information for indicating a protocol layer reset operation of a first node associated with a first candidate cell and related information for indicating a protocol layer reset operation of a first node associated with a second candidate cell; determining whether to perform protocol layer reset according to indication information indicating whether the third node needs to perform protocol layer reset; determining whether to perform protocol layer reset according to the cell identification included in the first information.

[0030] According to the method performed by the third node provided by the present disclosure, wherein determining whether the first node performs TA measurement based on the first message comprises at least one of: when a cell accessed by the first node changes, determining whether the first node performs TA measurement related information for indicating a measurement behaviour of a first node associated with a serving cell and related information for indicating a measurement behaviour of a first node associated with a candidate cell; when a cell accessed by the first node changes, determining whether the first node performs TA measurement related information for indicating a measurement behaviour of a first node associated with a target cell and related information for indicating a measurement behaviour of a first node associated with a candidate cell; when a cell accessed by the first node changes, determining whether the first node performs TA measurement related information for indicating a measurement behaviour of a first node associated with a first candidate cell and related information for indicating a measurement behaviour of a first node associated with a second candidate cell; determining whether the first node needs to perform TA measurement according to indication information indicating whether the first node needs to perform TA measurement; determining whether the first node performs TA measurement according to the cell identification included in the second information.

[0031] According to an aspect of the present disclosure, there is provided a method performed by a first node, the method comprising: receiving a second message from a second node, wherein the second message includes third information related to protocol layer reset and / or fourth information related to timing advance (TA) measurement; based on the second message, determining whether the first node performs protocol layer reset and / or determining whether the first node performs TA measurement; wherein the third information is used for determining a protocol layer reset operation associated with a first cell; wherein the fourth information is used for determining a measurement behaviour associated with the first cell; wherein the first cell includes at least one of a serving cell, a target cell and a candidate cell.

[0032] According to the method performed by the first node provided by the present disclosure, wherein the third information further comprises at least one of: a cell identification for indicating a cell associated with the first cell and not requiring to perform protocol layer reset; a cell identification for indicating a cell associated with the first cell and requiring to perform protocol layer reset.

[0033] According to the method performed by the first node provided by the present disclosure, wherein the fourth information further comprises at least one of: a cell identification for indicating a cell associated with the first cell and not requiring to perform TA measurement; a cell identification for indicating a cell associated with the first cell and requiring to perform TA measurement.

[0034] According to the method performed by the first node provided by the present disclosure, wherein the second message further comprises at least one of: information for indicating configuration that the first node needs to reserve (keep)or release; second default configuration information, including configuration information used by the first node when it is uncertain whether needs to perform protocol layer reset; configuration information of L1 / L2 triggered mobility (LTM), including configuration information of an LTM candidate cell.

[0035] According to the method performed by the first node provided by the present disclosure, wherein the protocol layer reset comprises: when the first node is an integrated access and backhaul node, radio link control layer reset corresponding to a backhaul radio link control channel is performed.

[0036] According to another aspect of the present disclosure, there is provided a first node comprising: a transceiver configured to transmit and receive signals with the outside; and a controller configured to control the transceiver to perform the above method performed by the first node.

[0037] According to another aspect of the present disclosure, there is provided a second node comprising: a transceiver configured to transmit and receive signals with the outside; and a controller configured to control the transceiver to perform the above method performed by the second node.

[0038] According to another aspect of the present disclosure, there is provided a third node comprising: a transceiver configured to transmit and receive signals with the outside; and a controller configured to control the transceiver to perform the above method performed by the third node.

[0039] According to another aspect of the present disclosure, there is provided a non-transitory computer-readable recording medium having stored thereon a program which, when being executed by a computer, performs any of the above methods.

[0040] According to the present disclosure, a method for an efficient communication may be provided.

[0041] Also, according to the present disclosure, a method of an LTM-based handover may be provided.

[0042] Fig. 1 is an exemplary system architecture of System Architecture Evolution (SAE).

[0043] Fig. 2 is an exemplary system architecture according to various embodiments of the present disclosure.

[0044] Fig. 3 is a schematic diagram of interaction among a first node, a second node and a third node according to an embodiment of the present disclosure.

[0045] Fig. 4 is a block diagram illustrating a structure of a first node according to an embodiment of the present disclosure.

[0046] Fig. 5 is a block diagram illustrating a structure of a second node according to an embodiment of the present disclosure.

[0047] Fig. 6 is a block diagram illustrating a structure of a third node according to an embodiment of the present disclosure.

[0048] 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 as exemplary. Therefore, those skilled 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.

[0049] The terms and expressions used in the following specification and claims are not limited to their dictionary meanings, but are only used by the inventors to enable a clear and consistent understanding of the present disclosure. Therefore, it should be obvious to those skilled in the art that the following descriptions of various embodiments of the present disclosure are provided for illustration purposes only and are not intended to limit the purposes of the present disclosure as defined in the appended claims and their equivalents.

[0050] It should be understood that singular forms of "a", "an" and "the" include plural referents unless the context clearly indicates otherwise. Thus, for example, a reference to a "component surface" includes a reference to one or more such surfaces.

[0051] The terms "include" or "may include" refer to the existence of a corresponding disclosed function, operation or component that can be used in various embodiments of the present disclosure, and do not limit the existence of one or more additional functions, operations or features. In addition, the terms "including" 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 the existence of one or more other characteristics, numbers, steps, operations, constituent elements, components or combinations thereof.

[0052] 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.

[0053] Unless defined differently, all terms (including technical terms or scientific terms) used in this disclosure have the same meaning as those understood by those skilled in the art in this disclosure. Common terms, as defined in dictionaries, are interpreted as having meanings consistent with the context in the relevant technical fields, and should not be interpreted in an idealized or overly formal way unless explicitly defined in this disclosure.

[0054] 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.

[0055] Fig. 1 is an exemplary system architecture 100 of system architecture evolution (SAE). User equipment (UE) 101 is a terminal device for receiving data. An evolved universal terrestrial radio access network (E-UTRAN) 102 is a radio access network, which includes a macro base station (eNodeB / NodeB) that provides UE with interfaces to access the radio network. A mobility management entity (MME) 103 is responsible for managing mobility context, session context and security information of the UE. A serving gateway (SGW) 104 mainly provides functions of user plane, and the MME 103 and the SGW 104 may be in the same physical entity. A packet data network gateway (PGW) 105 is responsible for functions of charging, lawful interception, etc., and may be in the same physical entity as the SGW 104. A policy and charging rules function entity (PCRF) 106 provides quality of service (QoS) policies and charging criteria. A general packet radio service support node (SGSN) 108 is a network node device that provides routing for data transmission in a universal mobile telecommunications system (UMTS). A home subscriber server (HSS)109 is a home subsystem of the UE, and is responsible for protecting user information including a current location of the user equipment, an address of a serving node, user security information, and packet data context of the user equipment, etc.

[0056] Fig. 2 is an exemplary system architecture 200 according to various embodiments of the present disclosure. Other embodiments of the system architecture 200 can be used without departing from the scope of the present disclosure.

[0057] 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.

[0058] The text and drawings are provided as examples only to help understand the present disclosure. They should not be construed 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 is obvious to those skilled in the art that changes can be made to the illustrated embodiments and examples without departing from the scope of this disclosure.

[0059] Before introducing the specific content, some assumptions and some definitions of the present invention are given below.

[0060] - The message names in the present invention are only examples, and other message names can be used.

[0061] - The "first" and "second", etc., included in the message name of the present invention are only examples of messages and do not represent the execution order.

[0062] - Detailed description of steps irrelevant to the present invention is omitted in the present invention.

[0063] - In the present invention, the steps in each flow can be executed in combination with each other or independently. The execution steps of each process are only examples, and other possible execution orders are not excluded.

[0064] - In the present invention, the base station may be a 6G base station, a 5G base station (such as gNB and ng-eNB), a 4G base station (such as eNB) or other types of access nodes.

[0065] - In the present invention, when the cell accessed by the user equipment changes from one cell to another, this behaviour can be called handover or Cell switch. In the following description, handover and cell switch have the same meaning.

[0066] - In the invention, the user, the user terminal and the user terminal device are equivalent.

[0067] - In the present invention, the synchronization information may include at least one of the following information:

[0068] downlink synchronization information;

[0069] uplink synchronization information such as timing advance information.

[0070] The nodes involved in the invention are:

[0071] - The first node: User equipment (UE), which can be a mobile phone, or the Mobile terminal part (IAB-MT) of the IAB node in the Integrated Access and Backhaul (IAB) network;

[0072] - The second node: the centralized unit (CU) of the base station, or the control plane part of the centralized unit of the base station or the base station;

[0073] - The third node: the distribution unit (DU) of the base station, which can be the distribution unit where the source cell is located, or the distribution unit where the target cell is located, or the distribution unit where the handover candidate target cell is located, during the movement of the user terminal. The source cell or 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, and in another example, the special cell may be a special cell of an secondary cell group or a primary secondary cell (PSCell).

[0074] The base station involved in the second / third node can be one of the following types (other types that can be used for user terminal access are not excluded):

[0075] - LTE base station

[0076] - 5G base station

[0077] - 6G base station

[0078] - NTN base station

[0079] - HAPS base station

[0080] - Drone base station

[0081] - WIFI access point

[0082] Reset related operations (or protocol layer reset related operations)

[0083] In the present invention, nodes (such as the first node, the second node, or the third node) will perform reset related behaviours, which include "Layer 2 reset" (or protocol layer reset) or "No L2 reset" (or No protocol layer reset). In one example, "Layer 2 reset" and "No L2 reset" respectively include the following behaviours:

[0084] - Layer L2 reset may include at least one of the following possible behaviours:

[0085] -> Re-establish RLC entity. In one example, the RLC entity is the RLC entity corresponding to the configured logical channel. In another example, the RLC entity is an RLC entity corresponding to the backhaul logical channel of the backhaul RLC channel configured for the IAB-MT;

[0086] -> Reset MAC entity;

[0087] -> PDCP re-establishment. In one example, the PDCP entity is the PDCP entity corresponding to the configured bearer.

[0088] -> PDCP entity data recovery. In one example, the PDCP entity is the PDCP entity corresponding to the configured bearer.

[0089] - No L2 reset may include at least one of the following possible behaviours:

[0090] -> Continue to use the current RLC entity. In one example, the RLC entity is the RLC entity corresponding to the configured logical channel. In another example, the RLC entity is an RLC entity corresponding to the backhaul logical channel of the backhaul RLC channel configured for the IAB-MT;

[0091] -> Continue to use the current MAC entity;

[0092] -> Continue to use the current PDCP entity. In one example, the PDCP entity is the PDCP entity corresponding to the configured bearer.

[0093] The above-mentioned behaviour of "Layer 2 reset" or "No L2 reset" can be performed by the user terminal (the first node), the base station or the centralized unit of the base station (the second node), or the distributed unit of the base station (the third node). Before performing "Layer 2 reset" or "No L2 reset", the above nodes need to determine whether to perform Layer 2 reset. In one example, when the user terminal (first node) performs cell handover (such as LTM cell switch), the first node / second node / third node needs to determine whether to perform a Layer 2 reset. In another example, after the user terminal (first node) selects a new cell (such as selecting a new cell after a failure and performing LTM cell switch in the new cell), the first node / second node / third node needs to determine whether to perform a Layer 2 reset.

[0094] - The number of steps used in the description of the embodiment of the present disclosure does not represent the order in which the steps are executed, and the following steps can be executed separately or in combination with each other.

[0095] In the mobile network, user equipment will handover between different cells. The main problem caused by handover is that the user equipment will have communication interruption during this process. The main reason for the interruption is that the user equipment needs to measure for a long time. Before the handover, the network side needs to conduct signaling interaction between different nodes to determine the target cell and the configuration of the target cell, and then send a handover command to the user equipment. After that, the user equipment needs to perform uplink and downlink synchronization with the network side. In this process, it takes a long time for the user equipment to switch cells, which further affects the user's performance during the mobile process.

[0096] Whether it is necessary to performs Layer 2 reset and / or whether it is necessary to perform the time advance measurement required for uplink synchronization are the factors that affect the time delay when the user equipment is handed over. When performing handover, the user terminal needs to determine whether it is necessary to performs Layer 2 reset or whether it can perform the time advance measurement required for uplink synchronization. However, in the actual handover process, the network side (for example, the distribution unit of the base station) cannot know whether the user terminal needs to be reset or whether it can perform the time advance measurement. This situation will cause the network side and the user terminal side to adopt different configurations for data transmission, resulting in data transmission errors or waste of resources.

[0097] Various embodiments of the present disclosure propose a method performed by a second node in a communication system, the method comprising: sending a first message to a third node, wherein the first message includes first information related to the reset of the first node and / or second information related to the timing advance (TA) measurement of the first node, and sending a second message to the first node, wherein the second message includes third information related to the reset of the first node and / or related to the timing advance (TA) measurement of the first node. Herein the first information or the third information includes reset indication information for indicating information related to the reset operation of the first node associated with the serving cell and / or the target cell and / or the candidate cell. Herein the second information or the fourth information includes TA indication information for indicating information related to the measurement behaviour of the first node associated with the serving cell and / or the target cell and / or the candidate cell.

[0098] In the embodiment provided by the present disclosure, operations related to reset of user terminal or information related to TA measurement are determined through signaling interaction between network nodes and between the network node and the user terminal and acquisition of user terminal cell switch information. For example, by a second node (e.g., a centralized unit of a base station) sending a first message to a third node (e.g., a distributed unit of a base station), wherein the first message includes first information related to the reset of the first node and / or second information related to the timing advance (TA) measurement of the first node and sending a second message to the first node (e.g., a user terminal), wherein the first message or second message includes information related to the reset of the first node and / or information related to the timing advance (TA) measurement of the first node, the third node and the first node can determine whether to reset and / or determine whether to perform TA measurement based on the first message and the second message, respectively, so that the network side (for example, it can be the distribution unit of the base station) and the user terminal side adopt the same configuration (for example, the configuration of layer 2 and the configuration of the user terminal for TA measurement) for data transmission, thereby further avoiding or improving the error of data transmission or reducing the waste of resources.

[0099] In the embodiment provided by the present disclosure, the user terminal can perform the time advance (TA) measurement, such as UE-based TA measurement. Specifically, before the user terminal accesses the target cell, it can obtain the time advance required for accessing the target cell through measurement. After obtaining this information, the user terminal can avoid the random access process when accessing the target cell, thus reducing the time delay or communication interruption of the user terminal accessing the target cell.

[0100] In addition, in order to reduce the time delay or communication interruption of user terminals during handover, a cell handover method based on Layer 1 / Layer 2 signaling is proposed, namely L1 / L2 triggered mobility (LTM). Specifically, in the process of LTM cell switch, the network side will trigger the user terminal to hand over through layer 1 or layer 2 signaling (such as MAC CE). Furthermore, before triggering the user terminal to hand over, the user terminal can also obtain the information of the time advance required to access the target cell in advance, such as through the measurement of the user terminal, or sending a random access signal in advance.

[0101] Various embodiments of the present disclosure will be described in detail with reference to Fig. 3. Please refer to Fig. 3, which is a schematic diagram of interaction among a first node, a second node and a third node according to an embodiment of the present disclosure. Embodiments of the present disclosure may include at least one step from step 1-1 to step 1-3, and the execution order of each step is not limited. In the embodiment of the present disclosure, it can be ensured that the network side and the user terminal side can adopt the same configuration information (such as the configuration of Layer 2 and the configuration of the user terminal for TA measurement) during the LTM cell switch.

[0102] Step 1-1: The second node sends a first configuration request message (for example, it can also be called the first message, and the name of the message is not limited in this disclosure) to the third node. The message is used to configure a cell of the first node (user terminal). The cell can be the current serving cell of the first node, a target cell of handover or a candidate cell of handover (such as LTM). After receiving the message, the third node will generate the relevant configuration of the cell, thus helping to configure the first node. In addition, the third node will determine its own behaviour (such as layer 2 reset, triggering the first node to acquire the time advance in advance, triggering the first node to perform Early uplink synchronization, etc.), according to the message and the cell switch of the first node. The message may include at least one of the following information:

[0103] - The first configuration request information of the serving cell, the function of the information is to provide the third node with configuration information related to the current serving cell of the first node. In one example, the serving cell is one candidate cell of LTM, and in another example, the serving cell is not a candidate cell of LTM. The information includes at least one of the following information:

[0104] -> The first reset related configuration information, which is used to help the third node determine the reset related operations that the third node needs to perform when the cell of the first node switches (such as the LTM cell switch or selecting a new cell to perform LTM). Further, the reset related operation is used in case of cell switch within the third node (Intra-DU cell switch) or cell handover within the third node (Intra-DU handover). The information may include at least one of the following information:

[0105] ->> First indication information (or first reset indication information) identifying that the serving cell is not reset, such as Serving Cell No Reset ID, which indicates information of reset operation associated with the current serving cell. In one example, the information is used to determine whether a Layer 2 reset is required when a first node triggers or performs a process of cell switch (such as LTM cell switch) for one candidate cell (such as a third node triggers or performs the process, or the first node triggers or performs the process on a selected cell). After receiving this information, the third node will determine whether it is necessary to perform a reset operation (such as whether to perform a Layer 2 reset) according to the cell switch of the first node (such as changing from a serving cell to another cell, or changing from another cell to a serving cell, in one example, the another cell is a candidate cell of the LTM) and the indication information. Further, the reset related operation is used in case of cell switch within the third node (Intra-DU cell switch) or cell handover within the third node (Intra-DU handover), so this information can also be named Intra-DU L2 reset configuration. If the third node receives this information, it will decide the Layer 2 reset (such as the reconstruction of an RLC entity) according to this information during the Intra-DU switch or handover. The beneficial effect of this information is to help the third node know whether the first node has perform the Layer 2 reset, and determine whether it needs to perform the Layer 2 reset, so as to achieve the same behaviour as the first node, and reduce the time delay of the cell switch of the first node without performing the Layer 2 reset.

[0106] ->> Identification Information of first cell for no reset. The cell indicated by the information is a cell which does not need to perform Layer 2 reset when the first node performs the cell switch. In one embodiment, this cell is a candidate cell of LTM. In one example, if the cell of the first node changes from the cell indicated by the "Identification Information of first cell for no reset" to the current serving cell, the third node does not need to perform layer 2 reset. In another example, if the cell of the first node changes from the current serving cell to the cell indicated by the "Identification Information of first cell for no reset", the third node does not need to perform Layer 2 reset. Further, the reset related operation is used in case of cell switch within the third node (Intra-DU cell switch) or cell handover within the third node (Intra-DU handover), so the cell indicated by the "Identification Information of first cell for no reset" belongs to the same third node as the current serving cell. If the third node receives this information, it will decide the Layer 2 reset (such as the reconstruction of an RLC entity) according to this information during the Intra-DU switch or handover.

[0107] ->> Identification Information of first cell for reset. The cell indicated by the information is a cell which needs to perform Layer 2 reset when the first node performs the cell switch. In one embodiment, this cell is a candidate cell of LTM. In one example, this cell is a candidate cell of LTM. In one example, if the cell of the first node changes from the cell indicated by the "Identification Information of first cell for reset" to the current serving cell, the third node needs to perform layer 2 reset. In another example, if the cell of the first node changes from the current serving cell to the cell indicated by the " Identification Information of first cell for reset", the third node needs to perform Layer 2 reset.

[0108] -> Configuration information related to the first TA measurement. In one example, the configuration information is used to indicate the UE to perform the time advance measurement, such as UE-based TA measurement, which can help the UE to obtain the uplink time advance of the cell. The function of this information is to help the third node determine whether the first node can perform the time advance measurement when the cell of the first node switches (such as the LTM cell switch, or a new cell is selected to perform LTM), so as to help the third node decide whether it is necessary to trigger the first node to acquire TA in advance (such as early uplink synchronization, such as triggering the first node to send a random access signal to the candidate cell). The information includes at least one of the following information:

[0109] ->> The first indication information (or the first TA measurement indication information) identifying the TA measurement of the serving cell, such as the Serving Cell UE-Measured TA ID. The information indicates the measurement behaviour of the first node related to the current serving cell (such as UE-based TA measurement). In one example, the information is used to determine whether it is necessary to perform the UE-based TA measurement when or before the first node triggers or performs the process of cell switch (such as LTM cell switch) for one candidate cell (such as the third node triggers or performs the process or the first node triggers or performs the process on the selected cell). After the third node receives this information, it will determine whether the first node will perform the UE-based TA measurement according to the cell of the first node switches to other cell (such as changing from the serving cell to other cell, or changing from other cell to the serving cell, in one example, the other cell is one candidate cell of LTM) and the indication information, and further, it can decide whether the third node will trigger the first node to obtain the time advance in advance. The information has the beneficial effects of helping the third node to know whether the first node has performed the UE-based TA measurement, thereby optimizing the resource allocation and avoiding the trigger of unnecessary acquisition (or early uplink synchronization) of the time advance in advance.

[0110] ->> Identification information of first cell for no TA measurement. The cell indicated by the information is the cell on which the first node does not perform the UE-based TA measurement when the first node occurs the cell switch. In one example, if the cell of the first node is changed from the cell indicated by the "Identification information of first cell for no TA measurement" to the current serving cell, the first node does not perform the UE-based TA measurement. In another example, if the cell of the first node changes from the current serving cell to the cell indicated by the "Identification information of first cell for no TA measurement", the first node does not perform the UE-based TA measurement.

[0111] ->> Identification information of first cell for TA measurement. The cell indicated by the information is the cell on which the first node needs to perform the UE-based TA measurement when the first node occurs the cell switch. In one example, if the cell of the first node is changed from the cell indicated by the "Identification information of first cell for TA measurement" to the current serving cell, the first node needs to perform the UE-based TA measurement. In another example, if the cell of the first node changes from the current serving cell to the cell indicated by the "Identification information of first cell for TA measurement", the first node needs to perform the UE-based TA measurement.

[0112] - The first configuration request information of the target cell, which is used to provide the third node with the information of the target cell, so that the third node can generate the configuration of the target cell, therefore helping the first node to perform the cell handover. In one example, the target cell is the target cell selected when performing Layer 3 handover (such as the handover is the handover performed after the user terminal receives an RRC handover command sent by the network side, the RRC handover command is an RRC RRCReconfiguration message containing reconfiguration information element with synchronization information (ReconfigurationWithSync IE)). In one example, the target cell is one candidate cell of LTM, and in another example, the target cell is not a candidate cell of LTM. The information includes at least one of the following information:

[0113] -> identification information of the target cell, such as Cell ID, NR CGI, PCI, etc.

[0114] -> Second reset related configuration information, which is used to help the third node determine the reset related operations that the third node needs to perform when the cell of the first node switches (such as the LTM cell switch or selecting a new cell to perform LTM), after accessing the target cell. Further, the reset related operation is used in case of cell switch within the third node (Intra-DU cell switch) or cell handover within the third node (Intra-DU handover). The information may include at least one of the following information:

[0115] ->> Second indication information (or second reset indication information) identifying that the serving cell is not reset, such as Serving Cell No Reset ID, which indicates information of reset operation associated with the cell indicated by the "identification information of the target cell". In one example, the information is used to determine whether needs to perform the Layer 2 reset when a first node triggers or executes a process of cell switch (such as LTM cell switch) for one candidate cell (such as LTM cell) (such as a third node triggers or executes the process, or the first node triggers or executes the process on a selected cell). After receiving this information, the third node will determine whether it is necessary to perform a reset operation (such as whether to perform a Layer 2 reset) according to the cell switch of the first node (such as changing from the cell indicated by the "identification information of the target cell" to another cell, or changing from another cell to the cell indicated by the "identification information of the target cell", in one example, another cell is one candidate cell of the LTM) and the indication information. Further, the reset related operation is used in case of cell switch within the third node (Intra-DU cell switch) or cell handover within the third node (Intra-DU handover), so this information can also be named Intra-DU L2 reset configuration. If the third node receives this information, it will decide the Layer 2 reset (such as the reconstruction of an RLC entity) according to this information during the Intra-DU switch or handover. The beneficial effect of this information is to help the third node know whether the first node has perform the Layer 2 reset, so as to achieve the same behaviour as the first node, and determine whether it needs to perform the Layer 2 reset, and reduce the time delay of the cell switch of the first node without performing the Layer 2 reset.

[0116] ->> Identification Information of second cell for no reset. The cell indicated by the information is a cell which does not need to perform Layer 2 reset when the first node occurs the cell switch. In one embodiment, this cell is a candidate cell of LTM. In one example, if the cell of the first node changes from the cell indicated by the "Identification Information of second cell for no reset" to the cell indicated by the "identification information of the target cell", the third node does not need to perform layer 2 reset. In another example, if the cell of the first node changes from the cell indicated by the "identification information of the target cell" to the cell indicated by the "Identification Information of second cell for no reset", the third node does not need to perform Layer 2 reset. Further, the reset related operation is used in case of cell switch within the third node (Intra-DU cell switch) or cell handover within the third node (Intra-DU handover), so the cell indicated by the " Identification Information of second cell for no reset" belongs to the same third node as the current serving cell. If the third node receives this information, it will decide the Layer 2 reset (such as the reconstruction of an RLC entity) according to this information during the Intra-DU switch or handover.

[0117] ->> Identification Information of second cell for reset. The cell indicated by the information is a cell which needs to perform Layer 2 reset when the first node occurs the cell switch. In one embodiment, this cell is a candidate cell of LTM. In one example, if the cell of the first node changes from the cell indicated by the "Identification Information of second cell for reset" to the cell indicated by the "identification information of the target cell", the third node needs to perform layer 2 reset. In another example, if the cell of the first node changes from the cell indicated by the "identification information of the target cell" to the cell indicated by the "Identification Information of second cell for reset", the third node needs to perform Layer 2 reset.

[0118] -> Configuration information related to the second TA measurement. In one example, the configuration information is used to indicate the UE to perform the time advance measurement, such as UE-based TA measurement, which can help the UE to obtain the uplink time advance of the cell. The function of this information is to help the third node determine whether the first node can perform the time advance measurement when the cell of the first node switches (such as the LTM cell switch, or a new cell is selected to perform LTM), after the first node accessing the target cell, so as to help the third node decide whether it is necessary to trigger the first node to acquire TA in advance (such as early uplink synchronization, such as triggering the first node to send a random access signal to the candidate cell). The information includes at least one of the following information:

[0119] ->> The second indication information (or the second TA measurement indication information) identifying the TA measurement of the serving cell, such as the Serving Cell UE-Measured TA ID. The information indicates the measurement behaviour of the first node related to the cell indicated by the "identification information of the target cell" (such as UE-based TA measurement). In one example, the information is used to determine whether it is necessary to perform the UE-based TA measurement when or before the first node triggers or performs the process of cell switch (such as LTM cell switch) for one candidate cell (such as LTM cell) (such as the third node triggers or performs the process or the first node triggers or performs the process on the selected cell). After the third node receives this information, it will determine whether the first node will perform the UE-based TA measurement according to the cell switch of the first node (such as changing from the cell indicated by the "identification information of the target cell" to other cell, or changing from other cell to the cell indicated by the "identification information of the target cell", in one example, the other cell is one candidate cell of LTM) and the indication information, and further, it can decide whether the third node will trigger the first node to obtain the time advance in advance. The information has the beneficial effects of helping the third node to know whether the first node has performed the UE-based TA measurement, thereby optimizing the resource allocation and avoiding the trigger of unnecessary acquisition (or early uplink synchronization) of the time advance in advance.

[0120] ->> Identification information of second cell for no TA measurement. The cell indicated by the information is the cell on which the first node does not perform the UE-based TA measurement when the first node occurs the cell switch. In one example, if the cell of the first node is changed from the cell indicated by the "Identification information of second cell for no TA measurement" to the cell indicated by the "identification information of the target cell", the first node does not perform the UE-based TA measurement. In another example, if the cell of the first node changes from the cell indicated by the "identification information of the target cell" to the cell indicated by the "Identification information of second cell for no TA measurement", the first node does not perform the UE-based TA measurement.

[0121] ->> Identification information of second cell for TA measurement. The cell indicated by the information is the cell on which the first node needs to perform the UE-based TA measurement when the first node occurs the cell switch. In one example, if the cell of the first node is changed from the cell indicated by the "Identification information of second cell for TA measurement" to the cell indicated by the "identification information of the target cell", the first node needs to perform the UE-based TA measurement. In another example, if the cell of the first node changes from the cell indicated by the "identification information of the target cell" to the cell indicated by the "Identification information of second cell for TA measurement", the first node needs to perform the UE-based TA measurement.

[0122] -> The first configuration reservation (keeping) indication information, which indicates the configuration that the third node needs to reserve (keep). In one example, the configuration that the third node needs to reserve (keep) is the configuration on LTM (LTM-config), in another example, the configuration that the third node needs to reserve (keep) is the configuration of the source cell, and in another example, the configuration that the third node needs to reserve (keep) is configuration on LTM in the configuration of the source cell. In one embodiment, the configuration that needs to reserve (keep) which is indicated by this information is the configuration used in the source cell, and further, these configurations to be reserved may be the information contained in the following "Configuration Information of Source Cell". The information includes at least one of the following information:

[0123] ->> First indication information of reserved configuration, which indicates the configuration that the third node needs to reserve. In one example, for LTM, this information indicates that the third node needs to reserve (keep) the configuration of LTM (such as the configuration of LTM included in "Configuration Information of Source Cell" below, LTM-config). Further, this information also includes at least one of the following information:

[0124] ->>> Identification information of the reserved (kept) configuration. In one example, for the LTM, the information is identification information of candidate configurations of the LTM, and indicates an LTM candidate configuration.

[0125] ->>> The identification information of the cell corresponding to the reserved (kept) configuration. In one example, for LTM, the information is the identification information of the candidate cell of LTM.

[0126] ->> First indication information of the release configuration. The information indicates the configuration to be released, and the information includes at least one of the following information:

[0127] ->>> The identification information of the released configuration. In one example, for LTM, the information is the identification information of the candidate configuration of LTM, and indicates an LTM candidate configuration.

[0128] ->>> The identification information of the cell corresponding to the released configuration. In one example, for LTM, the information is the identification information of the candidate cell of LTM.

[0129] - First configuration information of a candidate cell. The candidate cell is a candidate cell for handover prepared by the second node for the first node. In one example, the handover may be a Layer 3 handover, and in another example, the handover is an LTM cell switch. In one example, the first configuration information of the candidate cell is provided to a third node (the third node is the node of the target cell of the service layer 3 handover) during the configuration of the layer 3 handover. In another example, the first configuration information of the candidate cell is provided to the third node when the serving cell of the current first node is reconfigured. In another example, the first configuration information of the candidate cell is provided to the third node when configuring other candidate cells (such as preparing other candidate cells). The information includes configuration information of one or more candidate cells, and for one candidate cell, the information includes at least one of the following information:

[0130] -> identification information of the candidate cell, such as Cell ID, NR CGI, PCI, etc.

[0131] -> Third reset related configuration information, which is used to help the third node determine the reset related operations that the third node needs to perform when the cell of the first node switches (such as the LTM cell switch or selecting a new cell to perform LTM). In one embodiment, the reset related operation is used in case of cell switch within the third node (Intra-DU cell switch) or cell handover within the third node (Intra-DU handover). Further, when the "identification information of the candidate cell" belongs to the third node, it may include this information to indicate the reset related operation. The information may include at least one of the following information:

[0132] ->> Third indication information (or third reset indication information) identifying no reset, such as No Reset ID, which indicates information of reset operation associated with the cell indicated by the "identification information of the candidate cell". In one example, the information is used to determine whether needs to perform the Layer 2 reset when a first node triggers or executes a process of cell switch (such as LTM cell switch) for one candidate cell (such as LTM cell) (such as a third node triggers or executes the process, or the first node triggers or executes the process on a selected cell). After receiving this information, the third node will determine whether it is necessary to perform a reset operation (such as whether to perform a Layer 2 reset) according to the cell switch of the first node (such as changing from the cell indicated by the "identification information of the candidate cell" to another cell, or changing from another cell to the cell indicated by the "identification information of the candidate cell", in one example, another cell is one candidate cell of the LTM, in another example, another cell is not one candidate cell of the LTM) and the indication information. Further, the reset related operation is used in case of cell switch within the third node (Intra-DU cell switch) or cell handover within the third node (Intra-DU handover), so this information can also be named Intra-DU L2 reset configuration. If the third node receives this information, it will decide the Layer 2 reset (such as the reconstruction of an RLC entity) according to this information during the Intra-DU switch or handover. The beneficial effect of this information is to help the third node know whether the first node has perform the Layer 2 reset, and determine whether it needs to perform the Layer 2 reset, so as to achieve the same behaviour as the first node, and reduce the time delay of the cell switch of the first node without performing the Layer 2 reset.

[0133] ->> Identification Information of third cell for no reset. The cell indicated by the information is a cell which does not need to perform Layer 2 reset when the first node occurs the cell switch. In one embodiment, this cell is a candidate cell of LTM. In one example, if the cell of the first node changes from the cell indicated by the "Identification Information of third cell for no reset" to the cell indicated by the "identification information of the candidate cell", the third node does not need to perform layer 2 reset. In another example, if the cell of the first node changes from the cell indicated by the "identification information of the candidate cell" to the cell indicated by the "Identification Information of third cell for no reset", the third node does not need to perform Layer 2 reset. Further, the reset related operation is used in case of cell switch within the third node (Intra-DU cell switch) or cell handover within the third node (Intra-DU handover), so the cell indicated by the " Identification Information of third cell for no reset" belongs to the same third node as the current serving cell. If the third node receives this information, it will decide the Layer 2 reset (such as the reconstruction of an RLC entity) according to this information during the Intra-DU switch or handover.

[0134] ->> Identification Information of third cell for reset. The cell indicated by the information is a cell which needs to perform Layer 2 reset when the first node occurs the cell switch. In one embodiment, this cell is a candidate cell of LTM. In one example, this cell is a candidate cell of LTM. In one example, if the cell of the first node changes from the cell indicated by the "Identification Information of third cell for reset" to the cell indicated by the "identification information of the candidate cell", the third node needs to perform layer 2 reset. In another example, if the cell of the first node changes from the cell indicated by the "identification information of the candidate cell" to the cell indicated by the "Identification Information of third cell for reset", the third node needs to perform Layer 2 reset.

[0135] -> Configuration information related to the third TA measurement. In one example, the configuration information is used to indicate the UE to perform the time advance measurement, such as UE-based TA measurement, which can help the UE to obtain the uplink time advance of the cell. The function of this information is to help the third node determine whether the first node can perform the time advance measurement when the cell of the first node switches (such as the LTM cell switch, or a new cell is selected to perform LTM) , so as to help the third node decide whether it is necessary to trigger the first node to acquire TA in advance (such as early uplink synchronization, such as triggering the first node to send a random access signal to the candidate cell). The information includes at least one of the following information:

[0136] ->> Third indication information (or the third TA measurement indication information) identifying the TA measurement, such as the UE-Measured TA ID. The information indicates the measurement behaviour of the first node related to the cell indicated by the "identification information of the candidate cell" (such as UE-based TA measurement). In one example, the information is used to determine whether it is necessary to perform the UE-based TA measurement when or before the first node triggers or performs the process of cell switch (such as LTM cell switch) for one candidate cell (such as LTM cell) (such as the third node triggers or performs the process or the first node triggers or performs the process on the selected cell). After the third node receives this information, it will determine whether the first node will perform the UE-based TA measurement according to the cell switch of the first node (such as changing from the cell indicated by the "identification information of the candidate cell" to other cell, or changing from other cell to the cell indicated by the "identification information of the candidate cell", in one example, the other cell is one candidate cell of LTM, in another example, the other cell is not one candidate cell of LTM) and the indication information, and further, it can decide whether the third node will trigger the first node to obtain the time advance in advance. The information has the beneficial effects of helping the third node to know whether the first node has performed the UE-based TA measurement, thereby optimizing the resource allocation and avoiding the trigger of unnecessary acquisition (or early uplink synchronization) of the time advance in advance.

[0137] ->> Identification information of third cell for no TA measurement. The cell indicated by the information is the cell on which the first node does not perform the UE-based TA measurement when the first node occurs the cell switch. In one example, if the cell of the first node is changed from the cell indicated by the "Identification information of third cell for no TA measurement" to the cell indicated by the "identification information of the candidate cell", the first node does not perform the UE-based TA measurement. In another example, if the cell of the first node changes from the cell indicated by the "identification information of the candidate cell" to the cell indicated by the "Identification information of third cell for no TA measurement", the first node does not perform the UE-based TA measurement.

[0138] ->> Identification information of third cell for TA measurement. The cell indicated by the information is the cell on which the first node needs to perform the UE-based TA measurement when the first node occurs the cell switch. In one example, if the cell of the first node is changed from the cell indicated by the "Identification information of third cell for TA measurement" to the cell indicated by the "identification information of the candidate cell", the first node needs to perform the UE-based TA measurement. In another example, if the cell of the first node changes from the cell indicated by the "identification information of the candidate cell" to the cell indicated by the "Identification information of third cell for TA measurement", the first node needs to perform the UE-based TA measurement.

[0139] -> synchronization configuration information. In one example, the information is used by the third node to trigger the user terminal to obtain synchronization information (such as time advance information) of the target cell or the candidate cell in advance (early), such as triggering the user terminal to send a random access signal to the target cell or the candidate cell, which includes at least one of the following information:

[0140] ->> The configuration of the RACH required for advance (early) synchronization, or the configuration of the RACH for RACH-less, or the Early UL synchronization configuration. The configuration information is used for the first node to acquire synchronization information of the target cell or candidate cell (or send a random access signal to the target cell or candidate cell) before receiving a handover command (such as a command for triggering the user to perform the LTM cell switch, LTM MAC Control Element), which includes at least one of the following information:

[0141] ->>> Frequency domain indication information, which indicates the frequency domain information of a random access signal (such as a random access pilot signal preamble) sent by the first node, such as frequency points of common uplink carriers, frequency points of supplementary uplink carriers, and configuration information of bandwidth part (BWP) (such as BWP ID, BWP range, etc.).

[0142] ->>> Sequence related information, which indicates the sequence used for the transmitted random access signal, such as prach-RootSequenceIndex.

[0143] ->>> Time alignment timer, which indicates the effective time of time advance, such as time advance timer.

[0144] ->>> RACH generic configuration, which indicates generic configuration information for transmitting random access signals, including at least one of the following information: random access channel configuration index information (prach-configurationIndex), the target power that the network receiver side receives the preamble (preambleReceivedTargetPower), the maximum number of times to transmit the preamble (premableTransMax), the Ramping step size of the transmission power of the preamble (powerRampingSetp), the size of the random access response window (ra-ResponseWindow), and so on.

[0145] ->>> RACH dedicated configuration, which indicates dedicated configuration information for transmitting random access signals. The information may be different for different users, and includes at least one of the following information: RACH occasion information (which indicates resources for transmitting random access signals), the number of SSBs corresponding to each RACH occasion (ssb-perRACH-occasion), the configuration information of resources (such as mask index used for random access resource selection (physical random access channel mask index)), the index of the corresponding SSB or CSI-RS(SSB / CSI-RS index), and the index of preamble (ra-PreambleIndex).

[0146] ->> Configuration information related to contention free random access, or configuration information of RACH for RACH-based. The configuration information is used for the first node to obtain synchronization information of the target cell or candidate cell (or send random access signals to the target cell or candidate cell) when receiving a handover command (such as a command for triggering the user to perform the LTM cell switch, LTM MAC Control Element). In one example, when the first node receives a handover command (such as a command of LTM cell switch), the first node will send a random access signal according to the information in the handover command, and then acquire synchronization information (such as time advance) of the target cell or candidate cell. The handover command may include at least one of the following information: preamble index, indication information of uplink carrier (such as indicating supplementary UL or indicating normal UL, etc.), SSB (Synchronization signal block) index information, physical random access channel mask index, etc. The information includes at least one of the following information:

[0147] ->>> Frequency domain indication information

[0148] ->>> Sequence related information

[0149] ->>> Time alignment timer

[0150] ->>> RACH generic configuration

[0151] ->>> RACH dedicated configuration

[0152] For the detailed description of the above information, please refer to the description of each information in the above "Configuration of RACH Required for Advance (early) Synchronization".

[0153] ->> Configuration information of the beam, which indicates the beam used by the first node when sending signals (such as random access signals). The information includes at least one of the following information:

[0154] ->>> Indication information of downlink beam, such as transmission configuration indication (TCI) state index (TCI state index).

[0155] ->>> Indication information of uplink beam, such as TCI state index.

[0156] ->>> Indication information of uplink and downlink beams, such as TCI state index.

[0157] -> Configuration information of the reference signal, which can be used for the third node to configure the measurement of the reference signal, so as to help the first node to measure the candidate cell. In one example, the reference signal may be a CSI-RS signal, such as CSI resource configuration information, and in another example, the reference signal may be a downlink synchronization signal (such as SSB), such as SSB configuration information. The information includes at least one of the following information:

[0158] ->> The first signal configuration identification information, which identifies a set of configurations of signals measured by the first node.

[0159] ->> First resource information, which indicates the resources used by the measured signal, and may include at least one of the following information:

[0160] ->>> First frequency domain resource information, which indicates the location of the frequency domain where the signal is located. In one embodiment, the location can be indicated by frequency point. In one embodiment, the location can be indicated by frequency point and bandwidth. In another embodiment, the location can be indicated by identification of frequency domain resources, such as identification of the range of frequency domain resources. In another embodiment, the location can be indicated by identification of frequency band, such as the identification of bandwidth part (BWP) and the identification of sub-band. In another embodiment, the frequency domain resource can be given by the configuration information of BWP. Further, the user equipment should be able to measure the signals of non-serving cells (such as synchronization signal block (SSB)) within the configured BWP.

[0161] ->>> Sub-carrier interval information

[0162] ->>> First time domain resource information, which indicates the position of the signal in the time domain. In order to indicate the position, the information may include at least one of the following information:

[0163] ->>>> period

[0164] ->>>> offset

[0165] ->>>> The number of the time unit (e.g. the number of time slot, the number of symbol).

[0166] ->>>> The length of time

[0167] ->>>> Start time, which indicates the time to start measuring signals.

[0168] ->>>> Position indication information of SSB, such as SSB position in burst.

[0169] ->> configuration information of SSB measurement timing configuration (SMTC), which gives the configuration information of SSB of the cell, such as period, offset, measurement duration, indication information of Physical cell identity (PCI), location information of SSB, etc.

[0170] -> Reference configuration information, which is used by the third node to generate configuration information of candidate cells. In one embodiment, the configuration information of candidate cell is a Delta configuration generated based on the reference configuration information. The configuration information includes at least one of configuration information of bearer, configuration information of SDAP, configuration information of PDCP, configuration information of RLC, configuration information of MAC and configuration information of physical layer. In one example, the configuration information contains the contents of RRC Reconfiguration message. In another example, the configuration information contains the contents of Cell Group Configuration (CellGroupConfig).

[0171] - First indication information (or first reset information) of reset, which indicates whether to perform reset, such as indicating to perform the above-mentioned "Layer 2 reset", such as indicating to perform the above-mentioned "No L2 reset". After the third node receives the information, the third node performs the Layer 2 reset according to the indication information, or does not perform the Layer 2 reset. In one example, before step 1-1, the second node knows the cell to which the first node will access (such as informing the second node through the third node), and then the second node determines the " First indication information of reset " according to the cell accessed by the first node;

[0172] - The first indication information of TA measurement (or the first TA measurement information), which indicates the measurement behaviour of the first node (such as performing UE-based TA measurement), for example, the first node needs to perform the UE-based TA measurement. After receiving the information, the third node determines whether the first node performs the UE-based TA measurement. In one example, if the first node performs the UE-based TA measurement, the third node will not configure the first node to acquire the time advance. In one example, before step 1-1, the second node knows the cell to which the first node will access (such as informing the second node through the third node), and then the second node determines the "first indication information of TA measurement" according to the cell accessed by the first node;

[0173] - Configuration information of the source cell, which includes the configuration information of the user terminal (the first node) in the source cell, such as the configuration information of the bearer, the configuration information of SDAP / PDCP / RLC / MAC / PHY. Further, the information may also be included in the configuration information (LTM-Config) of the LTM in the source cell.

[0174] - Default Layer 2 configuration information, which is the configuration information used by the third node when it is uncertain whether it is necessary to performs Layer 2 reset (for example, when the first node sends a first RRC message to the third node). This configuration information can be used for data transmission with the first node. The information includes at least one of the following configuration information: configuration information of RLC layer, configuration information of logical channel, configuration information of MAC layer, and configuration information of physical layer.

[0175] After receiving the above-mentioned first configuration request message, the third node will determine its own behaviour according to the subsequent cell switches made by the first node, such as determine whether to perform the Layer 2 reset or whether the first node performs the UE-based TA measurement, and then determine whether the third node triggers the first node to acquire the time advance in advance or early uplink synchronization. The cell switch of the first node will have different implementations:

[0176] - Embodiment 1: The cell of the first node switches by triggering the LTM cell switch process, such as handing over from cell 1 to cell 2, wherein cell may or may not be a candidate cell of LTM, and cell 2 is a candidate cell of LTM. When cell 1 is not a candidate cell for LTM, in one example, cell 1 is the current serving cell, and in another example, cell 1 is the target cell for handover (such as the target cell for L3 handover). In this embodiment, the third node can judge whether the first node has performed a cell switch according to whether the third node has sent a cell switch command to the first node.

[0177] - Embodiment 2: A new cell is selected through the cell selection process, which causes the cell of the first node to change. Further, the first node will perform the LTM cell switch process in the selected cell. In one example, the cell selection made by the first node is because the first node has a link failure (such as radio link failure, handover failure, reconfiguration failure, etc.). For example, the new cell selected by the first node is cell 2, and the cell accessed by the first node before cell selection (such as the cell accessed before link failure) is cell 1. This cell 1 may or may not be a candidate cell of LTM, and cell 2 is a candidate cell of LTM. When cell 1 is not a candidate cell for LTM, in one example, cell 1 is the current serving cell, and in another example, cell 1 is the target cell for handover (such as the target cell for L3 handover). In this embodiment, the third node can judge whether the cell of the first node has switched according to the information received by the third node from the first node (such as the identification of the cell selected by the first node, the identification of the source cell where the first node hands over or performs the LTM cell switch, the random access signal sent by the first node, etc.)

[0178] The third node determines whether to perform Layer 2 reset:

[0179] When the cell of the first node hands over (for example, it is changed from cell 1 to cell 2 according to the above-mentioned embodiment, and in one embodiment, the cell switch is judged by the third node), the third node will determine whether to perform Layer 2 reset based on at least one of the following methods according to the above-mentioned "First indication information identifying that the serving cell is not reset" or "second indication information identifying that the serving cell is not reset" or "third indication information identifying that the serving cell is not reset" (or a variable maintained by the third node, such as a variable identifying that the serving cell is not reset, this variable is stored at the third node):

[0180] - Method 1: When the cell switch of the first node is from the current serving cell (cell 1) to one of the candidate cells (cell 2), it is determined according to the above-mentioned "First indication information identifying that the serving cell is not reset" of the serving cell (cell 1) and the above-mentioned "third indication information identifying that the serving cell is not reset" of the candidate cell (cell 2). When the above-mentioned "First indication information identifying that the serving cell is not reset" (or a variable maintained by the third node, such as the variable information indicating that the serving cell is not reset) is the same as (equal to) the above-mentioned "third indication information indicating that is not reset" of the candidate cell, the Layer 2 reset will not be performed, such as performing the above-mentioned "No L2 reset" behaviour. When the above-mentioned " First indication information identifying that the serving cell is not reset " (or a variable maintained by the third node, such as the variable information indicating that the serving cell is not reset) of the serving cell is different from (unequal to) the above-mentioned "third indication information indicating that is not reset" of the candidate cell, a layer 2 reset is performed, such as performing the above-mentioned "layer 2 reset" behaviour. Further, after the first node accesses the cell 2 and the cell 2 becomes a new serving cell, the above-mentioned "First indication information identifying that the serving cell is not reset" (or a variable maintained by the third node, such as variable information indicating that the serving cell is not reset) of the service cell is updated to the above-mentioned "third indication information indicating that is not reset" of the cell 2, so as to determine whether to perform layer 2 reset in the subsequent cell switch process of the first node.

[0181] - Method 2: After the first node accesses the target cell in the handover process, when the cell switch of the first node is from the target cell (cell 1) to one of the candidate cells (cell 2), it is determined according to the above-mentioned "second indication information identifying that the serving cell is not reset" (or a variable maintained by the third node, such as variable information indicating that the serving cell is not reset) of the target cell (cell 1) and the above-mentioned "third indication information identifying that is not reset" of the candidate cell (cell 2). When the above-mentioned "second indication information identifying that the serving cell is not reset" (or a variable maintained by the third node, such as variable information indicating that the serving cell is not reset) of the target cell is the same as (equal to) the above-mentioned "third indication information indicating that is not reset" of the candidate cell, the Layer 2 reset will not be performed, such as performing the above-mentioned "No L2 reset" behaviour. When the above-mentioned "second indication information identifying that the serving cell is not reset" (or a variable maintained by the third node, such as variable information indicating that the serving cell is not reset) of the target cell is different from (unequal to) the above-mentioned "third indication information indicating that is not reset" of the candidate cell, a layer 2 reset is performed, such as performing the above-mentioned "layer 2 reset" behaviour. Further, after the first node accesses the cell 2 and the cell 2 becomes a new serving cell, the above-mentioned "First indication information identifying that the serving cell is not reset" (or a variable maintained by the third node, such as variable information indicating that the serving cell is not reset) of the service cell is updated to the above-mentioned "third indication information indicating that is not reset" of the cell 2, so as to determine whether to perform layer 2 reset in the subsequent cell switch process of the first node.

[0182] - Method 3: When the cell switch of the first node is from one candidate cell (cell 1) to another candidate cells (cell 2), it is determined according to the above-mentioned "third indication information identifying that is not reset"(or a variable maintained by the third node, such as variable information indicating that the serving cell is not reset) of the cell 1 and the above-mentioned "third indication information identifying that is not reset" of the cell 2. When the above-mentioned "third indication information identifying that is not reset"(or a variable maintained by the third node, such as variable information indicating that the serving cell is not reset) of the cell 1 is the same as (equal to) the above-mentioned "third indication information identifying that is not reset" of the cell 2, the Layer 2 reset will not be performed, such as performing the above-mentioned "No L2 reset" behaviour. When the above-mentioned "third indication information identifying that is not reset"(or a variable maintained by the third node, such as variable information indicating that the serving cell is not reset) of the cell 1 is different from (unequal to) the above-mentioned "third indication information identifying that is not reset" of the cell 2, a layer 2 reset is performed, such as performing the above-mentioned "layer 2 reset" behaviour. Further, after the first node accesses the cell 2 and the cell 2 becomes a new serving cell, the above-mentioned "First indication information identifying that the serving cell is not reset" (or a variable maintained by the third node, such as variable information indicating that the serving cell is not reset) of the service cell is updated to the above-mentioned "third indication information identifying that is not reset" of the cell 2, so as to determine whether to perform layer 2 reset in the subsequent cell switch process of the first node.

[0183] - Method 4: The third node directly determines according to the "First indication information of reset" contained in the first configuration request message. For specific methods, please refer to the above description about "First indication information of reset".

[0184] - Method 5: It is determined according to "Identification Information of first cell for no reset", "Identification Information of second cell for no reset", "Identification Information of third cell for no reset", "Identification Information of first cell for reset", "Identification Information of second cell for reset", "Identification Information of third cell for reset" contained in the first configuration request message. For specific methods, please refer to the above description about the above identification information.

[0185] - Method 6: The first node directly informs the third node whether to performs Layer 2 reset through signaling.

[0186] The third node determines the way for the first node to perform the UE-based TA measurement:

[0187] When the cell of the first node switches (e.g., it changes from cell 1 to cell 2 according to the above embodiment, and in one embodiment, the cell switch is judged by the third node), the third node will determine the first node to perform UE-based TA measurement based on at least one of the following methods according to the above-mentioned "First indication information identifying the TA measurement of the serving cell" or "Second indication information identifying the TA measurement of the serving cell" or "Third indication information identifying the TA measurement" (or a variable maintained by the third node, such as a variable identifying the TA measurement, this variable is stored at the third node):

[0188] - Method 1: When the cell switch of the first node is from the current serving cell (cell 1) to one of the candidate cells (cell 2), it is determined according to the above-mentioned "First indication information identifying the TA measurement of the serving cell" of the serving cell (cell 1) (or a variable maintained by the third node, such as a variable identifying the TA measurement, this variable is stored at the third node) and the above-mentioned "Third indication information identifying the TA measurement" of the candidate cell (cell 2). When "First indication information identifying the TA measurement of the serving cell" of the serving cell (or a variable maintained by the third node, such as a variable identifying the TA measurement, this variable is stored at the third node) is the same as (equal to) the above-mentioned " Third indication information identifying the TA measurement" of the candidate cell, the first node performs UE-based TA measurement. When "First indication information identifying the TA measurement of the serving cell" of the serving cell (or a variable maintained by the third node, such as a variable identifying the TA measurement, this variable is stored at the third node) is different from (unequal to) the above-mentioned "Third indication information identifying the TA measurement" of the candidate cell, the first node does not perform UE-based TA measurement. Further, after the first node accesses the cell 2 and the cell 2 becomes a new serving cell, "First indication information identifying the TA measurement of the serving cell" of the serving cell (or a variable maintained by the third node, such as a variable identifying the TA measurement, this variable is stored at the third node) is updated to the above-mentioned "Third indication information identifying the TA measurement " of the cell 2, so as to determine whether to perform UE-based TA measurement in the subsequent cell switch process of the first node.

[0189] - Method 2: After the first node accesses the target cell in the handover process, when the cell switch of the first node is from the target cell (cell 1) to one of the candidate cells (cell 2), it is determined according to the above-mentioned "Second indication information identifying the TA measurement of the serving cell" of the target cell (cell 1) (or a variable maintained by the third node, such as a variable identifying the TA measurement, this variable is stored at the third node) and the above-mentioned "Third indication information identifying the TA measurement" of the candidate cell (cell 2). When "Second indication information identifying the TA measurement of the serving cell" of the target cell (or a variable maintained by the third node, such as a variable identifying the TA measurement, this variable is stored at the third node) is the same as (equal to) the above-mentioned "Third indication information identifying the TA measurement" of the candidate cell, the first node performs UE-based TA measurement. When the above-mentioned "Second indication information identifying the TA measurement of the serving cell" of the target cell (or a variable maintained by the third node, such as a variable identifying the TA measurement, this variable is stored at the third node) is different from (unequal to) the above-mentioned "Third indication information identifying the TA measurement" of the candidate cell, the first node does not perform UE-based TA measurement. Further, after the first node accesses the cell 2 and the cell 2 becomes a new serving cell, the above-mentioned " First indication information identifying the TA measurement of the serving cell" of the serving cell (or a variable maintained by the third node, such as a variable identifying the TA measurement, this variable is stored at the third node) is updated to the above-mentioned "Third indication information identifying the TA measurement " of the cell 2, so as to determine whether to perform UE-based TA measurement in the subsequent cell switch process of the first node.

[0190] - Method 3: When the cell switch of the first node is from one candidate cell (cell 1) to another candidate cells (cell 2), it is determined according to the above-mentioned " Third indication information identifying the TA measurement" of the cell 1 (or a variable maintained by the third node, such as a variable identifying the TA measurement, this variable is stored at the third node) and the above-mentioned "Third indication information identifying the TA measurement" of cell 2. When " the above-mentioned " Third indication information identifying the TA measurement" of the cell 1 (or a variable maintained by the third node, such as a variable identifying the TA measurement, this variable is stored at the third node) is the same as (equal to) the above-mentioned "Third indication information identifying the TA measurement" of cell 2, the first node performs UE-based TA measurement. When the above-mentioned " Third indication information identifying the TA measurement" of the cell 1 (or a variable maintained by the third node, such as a variable identifying the TA measurement, this variable is stored at the third node) is different from (unequal to) the above-mentioned "Third indication information identifying the TA measurement" of cell 2, the first node does not perform UE-based TA measurement. Further, after the first node accesses the cell 2 and the cell 2 becomes a new serving cell, "First indication information identifying the TA measurement of the serving cell" of the serving cell (or a variable maintained by the third node, such as a variable identifying the TA measurement, this variable is stored at the third node) is updated to the above-mentioned "Third indication information identifying the TA measurement" of the cell 2, so as to determine whether to perform UE-based TA measurement in the subsequent cell switch process of the first node.

[0191] - Method 4: The third node directly determines according to the "first indication information of TA measurement" contained in the first configuration request message. For specific methods, please refer to the above description about "the first indication information of TA measurement".

[0192] - Method 5: It is determined according to "Identification information of first cell for no TA measurement", "Identification information of second cell for no TA measurement", "Identification information of third node for no TA measurement", "Identification information of first cell for TA measurement", "Identification information of second cell for TA measurement", "Identification information of third node for TA measurement" contained in the first configuration request message. For specific methods, please refer to the above description about the above identification information.

[0193] - Method 6: The first node directly informs the third node whether to perform the UE-based TA measurement through signaling.

[0194] Step 1-2: The third node sends a first configuration response message (for example, it can also be called a third message, and the name of the message is not limited in this disclosure) to the second node, which includes at least one of the following information:

[0195] - First configuration response information of the serving cell, which includes at least one of the following information:

[0196] -> Configuration information of the service cell, such as cell group configuration information, CellGroupConfig, which includes at least one of the following configurations of the service cell: configuration information of bearer, configuration information of RLC, configuration information of MAC layer, configuration information of physical layer and configuration information of measurement.

[0197] -> Fourth reset related configuration information, which includes at least one of the following information:

[0198] ->> The fourth indication information (or fourth reset indication information) identifying that the serving cell is not reset, refer to the description of the above-mentioned "First indication information identifying that the serving cell is not reset".

[0199] ->> Identification Information of fourth cell for no reset, please refer to the description of " Identification Information of first cell for no reset".

[0200] ->> Identification Information of fourth cell for reset, please refer to the description of " Identification Information of first cell for reset".

[0201] After receiving the above information, the second node will determine whether the third node needs to perform a reset operation (such as whether to perform a Layer 2 reset) according to the cell switch of the first node (such as changing from a serving cell to another cell, or changing from another cell to a serving cell, in one example, the other cell is one candidate cell of the LTM) and the above information. For specific methods, please refer to the descriptions in Method 1 to Method 6 for determining whether to perform a Layer 2 reset.

[0202] -> Configuration information related to the fourth TA measurement, which includes at least one of the following information:

[0203] ->> The fourth indication information (or the fourth TA measurement indication information) identifying the TA measurement of the serving cell , refer to the description of " The first indication information identifying the TA measurement of the serving cell" above.

[0204] ->> Identification information of fourth cell for no TA measurement, please refer to the description of "Identification information of first cell for no TA measurement" above.

[0205] ->> Identification information of fourth cell for TA measurement, please refer to the description of "Identification information of first cell for TA measurement" above.

[0206] After receiving the above information, the second node will determine whether the first node needs to perform the UE-based TA measurement according to the cell switch of the first node (for example, from the serving cell to the other cell, or from the other cell to the serving cell, in one example, the other cell is a candidate cell of LTM) and the above information. For specific methods, please refer to the descriptions in Method 1 to Method 6 above about determining to perform the UE-based TA measurement.

[0207] In one example, the above-mentioned "Fourth reset related configuration information" (or "Configuration information related to the TA fourth measurement") and the above-mentioned "First reset related configuration information" (or "Configuration information related to the first TA measurement") will not appear in the first configuration request message and the first configuration response message respectively at the same time. If it is decided by the second node, only the "First reset related configuration information" (or "Configuration information related to the first TA measurement") will be included in the first configuration request message, and if it is decided by the third node, only the "Fourth reset related configuration information" (or "Configuration information related to the fourth TA measurement") will be included in the first configuration response message.

[0208] - First configuration response information of the target cell, which includes at least one of the following information:

[0209] -> Configuration information of the target cell, such as cell group configuration information, CellGroupConfig, which includes at least one of the following configurations of the target cell: configuration information of bearer, configuration information of RLC, configuration information of MAC layer, configuration information of physical layer and configuration information of measurement.

[0210] -> Fifth reset related configuration information, which includes at least one of the following information:

[0211] ->> The Fifth indication information (or Fifth reset indication information) identifying that the serving cell is not reset, refer to the description of the above-mentioned "second indication information identifying that the serving cell is not reset".

[0212] ->> Identification Information of fifth cell for no reset, please refer to the description of " Identification Information of second cell for no reset".

[0213] ->> Identification Information of fifth cell for reset, please refer to the description of "Identification Information of second cell for reset".

[0214] After receiving the above information, the second node will determine whether the third node needs to perform a reset operation (such as whether to perform a Layer 2 reset) according to the cell switch of the first node (such as changing from a serving cell to another cell, or changing from another cell to a serving cell, in one example, the other cell is one candidate cell of the LTM) and the above information. For specific methods, please refer to the descriptions in Method 1 to Method 6 for determining whether to perform a Layer 2 reset.

[0215] -> Configuration information related to the Fifth measurement, which includes at least one of the following information:

[0216] ->> The Fifth indication information (or the Fifth TA measurement indication information) identifying the TA measurement of the serving cell , refer to the description of " The second indication information identifying the TA measurement of the serving cell" above.

[0217] ->> Identification information of fifth cell for no TA measurement, please refer to the description of " identification information of second cell for no TA measurement" above.

[0218] ->> Identification information of fifth cell for TA measurement, please refer to the description of " identification information of second cell for TA measurement" above.

[0219] After receiving the above information, the second node will determine whether the first node needs to perform the UE-based TA measurement according to the cell switch of the first node (for example, from the serving cell to the other cell, or from the other cell to the serving cell, in one example, the other cell is one candidate cell of LTM) and the above information. For specific methods, please refer to the descriptions in Method 1 to Method 6 above about determining to perform the UE-based TA measurement.

[0220] In one example, the above-mentioned "Fifth reset related configuration information" (or "Configuration information related to the Fifth measurement") and the above-mentioned "second reset related configuration information" (or "Configuration information related to the second TA measurement") will not appear in the first configuration request message and the first configuration response message respectively at the same time. If it is decided by the second node, only the "second reset related configuration information" (or "Configuration information related to the second TA measurement") will be included in the first configuration request message, and if it is decided by the third node, only the "Fifth reset related configuration information" (or "Configuration information related to the Fifth measurement") will be included in the first configuration response message.

[0221] -> First configuration response information of the candidate cell, which includes at least one of the following information:

[0222] -> Sixth reset related configuration information, which includes at least one of the following information :

[0223] ->> The sixth indication information (or sixth reset indication information) identifying that is not reset, refer to the description of the above-mentioned "Third indication information identifying that is not reset".

[0224] ->> Identification Information of sixth cell for no reset, please refer to the description of " Identification Information of third cell for no reset".

[0225] ->> Identification Information of sixth cell for reset, please refer to the description of " Identification Information of third cell for reset.

[0226] After receiving the above information, the second node will determine whether the third node needs to perform a reset operation (such as whether to perform a Layer 2 reset) according to the cell switch of the first node (such as changing from a serving cell to another cell, or changing from another cell to a serving cell, in one example, the other cell is one candidate cell of the LTM) and the above information. For specific methods, please refer to the descriptions in Method 1 to Method 6 for determining whether to perform a Layer 2 reset.

[0227] -> Configuration information related to the Sixth TA measurement, which includes at least one of the following information:

[0228] ->> The Sixth indication information (or the Sixth TA measurement indication information) identifying the TA measurement, refer to the description of "The third indication information identifying the TA measurement" above.

[0229] ->> Identification information of sixth cell for no TA measurement, please refer to the description of "identification information of third cell for no TA measurement" above.

[0230] ->> Identification information of sixth cell for TA measurement, please refer to the description of "identification information of third cell for TA measurement" above.

[0231] After receiving the above information, the second node will determine whether the first node needs to perform the UE-based TA measurement according to the cell switch of the first node (for example, from the serving cell to the other cell, or from the other cell to the serving cell, in one example, the other cell is a candidate cell of LTM) and the above information. For specific methods, please refer to the descriptions in Method 1 to Method 6 above about determining to perform the UE-based TA measurement.

[0232] In one example, the above-mentioned "Sixth reset related configuration information" (or "Configuration information related to the TA Sixth measurement") and the above-mentioned "Third reset related configuration information" (or "Configuration information related to the Third TA measurement") will not appear in the first configuration request message and the first configuration response message respectively at the same time. If it is decided by the second node, only the "Third reset related configuration information" (or "Configuration information related to the Third TA measurement") will be included in the first configuration request message, and if it is decided by the third node, only the "Sixth reset related configuration information" (or "Configuration information related to the Sixth TA measurement") will be included in the first configuration response message.

[0233] -> Default Layer 2 configuration information, which is the configuration information used by the first node when it is uncertain whether it is necessary to perform Layer 2 reset (such as when the first node sends the first RRC message to the third node), which can be used for data transmission between the third node and the first node. The information includes at least one of the following configuration information: configuration information of RLC, configuration information of logical channel, configuration information of MAC layer, configuration information of physical layer.

[0234] Step 1-3: The second node sends a first configuration message (for example, it can also be called a second message, and the name of the message is not limited in this disclosure) to the first node, which is used to provide the user terminal with configuration information related to cell handover. In one example, the cell handover may be a Layer 3 handover, and in another example, the cell handover is an LTM. The message includes at least one of the following information:

[0235] -> Second configuration information of the target cell. In one example, the target cell is the target cell selected when performing Layer 3 handover (such as the handover is the handover performed after the user terminal receives an RRC handover command sent by the network side, the RRC handover command is an RRC RRCReconfiguration message containing ReconfigurationWithSync IE, for example, the first configuration message as mentioned above is the RRC handover command). The information includes at least one of the following information:

[0236] -> Identification information of the target cell

[0237] -> Seventh reset related configuration information, which is used to help the first node determine the reset related operation that the first node needs to perform when the cell of the first node changes after accessing the target cell indicated by the "identification information of the target cell". In one example, when the above-mentioned first configuration message is a message for triggering Layer 3 handover (such as RRC Reconfiguration message containing ReconfigurationWithSync IE, such as handover command message) and / or variable of the first node (such as variables storing LTM candidate configurations, LTM-config variable) contains at least one candidate configuration of LTM, the first configuration message may contain the " Seventh reset related configuration information" or the following " Seventh indication information identifying that the serving cell is not reset". The information includes at least one of the following information:

[0238] ->> Seventh indication information (or Seventh reset indication information) identifying that the serving cell is not reset, such as Serving Cell No Reset ID, which indicates information of reset operation associated with the cell indicated by the "identification information of the target cell". In one example, the information is used to determine whether needs to perform the Layer 2 reset when a first node triggers or executes a process of cell switch (such as LTM cell switch) for one candidate cell (such as LTM cell) (such as a third node triggers or executes the process, or the first node triggers or executes the process on a selected cell). After receiving this information, the third node will determine whether it is necessary to perform a reset operation (such as whether to perform a Layer 2 reset) according to the cell switch of the first node (such as changing from the cell indicated by the "identification information of the target cell" to another cell, or changing from another cell to the cell indicated by the "identification information of the target cell", in one example, another cell is one candidate cell of the LTM) and the indication information. The beneficial effect of this information is to help the first node know whether to perform the Layer 2 reset, and reduce the time delay of the cell switch of the first node without performing the Layer 2 reset. In an example, after the first node receives the information, the first node can maintain a second variable information identifying that the serving cell is not reset, and it can update the variable with the "Seventh indication information identifying that the serving cell is not reset".

[0239] ->> Identification Information of seventh cell for no reset. The cell indicated by the information is a cell which does not need to perform Layer 2 reset when the first node occurs the cell switch. In one embodiment, this cell is a candidate cell of LTM. In one example, if the cell of the first node changes from the cell indicated by the " Identification Information of seventh cell for no reset" to the cell indicated by the "identification information of the target cell", the third node does not need to perform layer 2 reset. In another example, if the cell of the first node changes from the cell indicated by the "identification information of the target cell" to the cell indicated by the " Identification Information of seventh cell for no reset", the third node does not need to perform Layer 2 reset.

[0240] ->> Identification Information of seventh cell for reset. The cell indicated by the information is a cell which needs to perform Layer 2 reset when the first node occurs the cell switch. In one embodiment, this cell is a candidate cell of LTM. In one example, if the cell of the first node changes from the cell indicated by the " Identification Information of seventh cell for reset" to the cell indicated by the "identification information of the target cell", the third node needs to perform layer 2 reset. In another example, if the cell of the first node changes from the cell indicated by the "identification information of the target cell" to the cell indicated by the " Identification Information of seventh cell for reset", the third node needs to perform Layer 2 reset.

[0241] -> Configuration information related to the Seventh TA measurement. In one example, the configuration information is used to indicate the UE to perform the time advance measurement, such as UE-based TA measurement. The function of this information is to help the first node determine whether to perform the time advance measurement when the cell of the first node switches (such as the LTM cell switch, or a new cell is selected to perform LTM), after the first node accessing the target cell, so as to help the third node decide whether it is necessary to trigger the first node to acquire TA in advance (such as early uplink synchronization, such as triggering the first node to send a random access signal to the candidate cell). In one example, when the above-mentioned first configuration message is a message for triggering Layer 3 handover (such as RRC Reconfiguration message containing ReconfigurationWithSync IE, such as a handover command message) and / or variable of the first node (such as variables storing LTM candidate configurations, LTM-config variable) contains at least one candidate configuration of LTM, the first configuration message may contain the "Configuration information related to the Seventh TA measurement" or the following "Seventh indication information identifying the TA measurement of the serving cell". The information includes at least one of the following information:

[0242] ->> Seventh indication information (or the Seventh TA measurement indication information) identifying the TA measurement of the serving cell, such as the Serving Cell UE-Measured TA ID. The information indicates the measurement behaviour of the first node related to the cell indicated by the "identification information of the target cell" (such as UE-based TA measurement). In one example, the information is used to determine whether it is necessary to perform the UE-based TA measurement when or before the first node triggers or performs the process of cell switch (such as LTM cell switch) for one candidate cell (such as LTM cell) (such as the third node triggers or performs the process or the first node triggers or performs the process on the selected cell). After the first node receives this information, it will determine whether the first node will perform the UE-based TA measurement according to the cell switch of the first node (such as changing from the cell indicated by the "identification information of the target cell" to other cell, or changing from other cell to the cell indicated by the "identification information of the target cell", in one example, the other cell is one candidate cell of LTM) and the indication information. The first node can maintain a second variable information identifying the TA measurement, and it can update the variable with the "Seventh indication information identifying the TA measurement of the serving cell". The information has the beneficial effects of helping the first node to know whether to perform the UE-based TA measurement, thereby reducing the interruption delay in the handover process.

[0243] ->> Identification information of seventh cell for no TA measurement. The cell indicated by the information is the cell on which the first node does not perform the UE-based TA measurement when the first node occurs the cell switch. In one example, if the cell of the first node is changed from the cell indicated by the " identification information of seventh cell for no TA measurement" to the cell indicated by the "identification information of the target cell", the first node does not perform the UE-based TA measurement. In another example, if the cell of the first node changes from the cell indicated by the "identification information of the target cell" to the cell indicated by the " identification information of seventh cell for no TA measurement", the first node does not perform the UE-based TA measurement.

[0244] ->> Identification information of seventh cell for TA measurement. The cell indicated by the information is the cell on which the first node needs to perform the UE-based TA measurement when the first node occurs the cell switch. In one example, if the cell of the first node is changed from the cell indicated by the "identification information of seventh cell for TA measurement" to the cell indicated by the "identification information of the target cell", the first node needs to perform the UE-based TA measurement. In another example, if the cell of the first node changes from the cell indicated by the "identification information of the target cell" to the cell indicated by the "identification information of seventh cell for TA measurement", the first node needs to perform the UE-based TA measurement.

[0245] -> The second configuration reservation (keeping) indication information, which indicates the configuration that the first node needs to reserve (keep). In one example, the configuration that the first node needs to reserve (keep) is the configuration on LTM (LTM-config), in another example, the configuration that the first node needs to reserve (keep) is the configuration of the source cell, and in another example, the configuration that the first node needs to reserve (keep) is configuration on LTM in the configuration of the source cell. The information includes at least one of the following information:

[0246] ->> second indication information of reserved (kept) configuration, which indicates the configuration that the first node needs to reserve. In one example, for LTM, this information indicates that the first node needs to reserve (keep) the configuration of LTM (such as the configuration of LTM included in "Configuration Information of Source Cell" below, LTM-config). Further, this information also includes at least one of the following information:

[0247] ->>> Identification information of the reserved (kept) configuration. In one example, for the LTM, the information is identification information of candidate configurations of the LTM, and indicates an LTM candidate configuration.

[0248] ->>> The identification information of the reserved (kept) cell. In one example, for LTM, the information is the identification information of the candidate cell of LTM .

[0249] ->> second indication information of the release configuration. The information indicates the configuration to be released, and the information includes at least one of the following information:

[0250] ->>> The identification information of the released configuration. In one example, for LTM, the information is the identification information of the candidate configuration of LTM, and indicates an LTM candidate configuration.

[0251] ->>> The identification information of the released cell. In one example, for LTM, the information is the identification information of the candidate cell of LTM.

[0252] -> Default Layer 2 configuration information, which is the configuration information used by the first node when it is uncertain whether it is necessary to performs Layer 2 reset (for example, when the first node sends a first RRC message to the third node). This configuration information can be used for data transmission with the first node. The information includes at least one of the following configuration information: configuration information of RLC layer, configuration information of logical channel, configuration information of MAC layer, and configuration information of physical layer.

[0253] -> Configuration information of the LTM, which includes the configuration information of the LTM candidate cell, such as the information contained in the RRCReconfiguration message of the candidate cell.

[0254] In the above flow, the first configuration request message may be a UE Context Setup Request message or a UE Context Modification Request message. The first configuration response message may be a UE Context Setup Response message or a UE Context Modification Response message. The first configuration message may be an RRC reconfiguration message. The above message can also be other messages.

[0255] In the above-mentioned embodiment provided by the present disclosure, the reset operation related to the user terminal or the information related to the TA measurement are determined by signaling interaction between network nodes and between the network node and the user terminal and the acquisition of the user terminal's cell switch information, so that the network side (for example, it can be the distribution unit of the base station) and the user terminal side adopt the same configuration (for example, the configuration of layer 2 and the configuration of the user terminal for TA measurement) for data transmission, thereby further avoiding or improving the error of data transmission.

[0256] In the flow of the following embodiment, the specific description of the information contained in each message can refer to the description in the above step 1-1 / 1-2 / 1-3.

[0257] Embodiment 1: Configure the target cell of Layer 3 handover (the third node is the distribution unit where the target cell is located).

[0258] In this embodiment, the first node is configured to perform Layer 3 handover, and the first node is configured with relevant configuration information of LTM in the source cell. When the first node receives the handover command of Layer 3 or accesses the target cell, the first node may keep at least part of the configuration information of the LTM.

[0259] This embodiment includes the following processes:

[0260] Step a-1: The second node sends a first configuration request message (such as UE context setup request) to the third node, which is the node serving the target cell. The first configuration request message is used to prepare the target cell of the first node. The first configuration request message may include at least one of the following information:

[0261] - First configuration request information of the target cell, which includes at least one of the following information:

[0262] -> Identification information of the target cell

[0263] -> Second reset related configuration information

[0264] -> Configuration information related to the second TA measurement

[0265] -> The first configuration reservation (keeping) indication information.

[0266] - First configuration information of a candidate cell, which includes configuration information of one or more candidate cells, and for a candidate cell, the information includes at least one of the following information:

[0267] -> Identification information of a candidate cell

[0268] -> Third reset related configuration information

[0269] -> Configuration information related to the third TA measurement

[0270] -> synchronization configuration information

[0271] -> Configuration information of reference signal

[0272] -> Reference configuration information

[0273] -> Configuration information of source cell

[0274] Step a-2: The third node sends a first configuration response message (such as UE context setup response) to the second node, which provides the configuration information of the target cell, and the information contained in this message can be referred to the above step 1-2.

[0275] Step a-3: The second node sends a first configuration message (such as RRCReconfiguration) to the first node, which may be sent by the third node or other nodes (such as the distribution unit of the source cell serving the first node). The message is a message to configure the first node to perform Layer 3 handover, such as an RRC Reconfiguration message containing reconfiguration with synchronization IE. After receiving this message, the first node will perform Layer 3 handover. The message includes the following information. Please refer to the description in Step 1-3 above. If the first node continues to reserve (keep) the configuration information of the LTM when performing the Layer 3 handover, the deletion of the configuration information of the LTM will not be indicated in the first configuration message. In one example, in order to ensure that the first node can continue to perform the LTM cell switch, the first configuration message will include the above-mentioned "seventh reset related configuration information" and / or the above-mentioned "seventh indication information identifying that the serving cell is not reset" and / or the above-mentioned "configuration information related to the seventh TA measurement" and / or the above-mentioned "seventh indication information identifying the TA measurement of the serving cell". Further, after receiving the information, the first node will use this information to update the corresponding variables.

[0276] The above process has the advantages that after the first node performs Layer 3 handover, the configuration information of the LTM is still maintained, and the candidate LTM cell switch can be performed, thus reducing the time delay and communication interruption in the cell switch process.

[0277] Embodiment 2: Configure the serving cell or LTM candidate cell of the first node (the third node is the distribution unit where the source cell is located or the distribution unit where the candidate cell is located).

[0278] Example 1: the reset related configuration and / or the configuration related to TA measurement is determined by CU.

[0279] This example includes the following process:

[0280] Step b-1: The second node sends a first configuration request message to a third node, which is the node serving the current serving cell of the first node. The first configuration request message includes at least one of the following information:

[0281] - First configuration request information of the serving cell, which includes at least one of the following information:

[0282] -> First reset related configuration information

[0283] -> Configuration information related to the first TA measurement

[0284] - First configuration information of a candidate cell, which includes configuration information of one or more candidate cells, and for a candidate cell, the information includes at least one of the following information:

[0285] -> Identification information of candidate cells

[0286] -> Third reset related configuration information

[0287] -> Configuration information related to the third TA measurement

[0288] -> Synchronization configuration information

[0289] -> Configuration information of reference signal

[0290] -> Reference configuration information

[0291] Step b-2: The third node sends a first configuration response message to the second node, which provides the configuration information of the target cell, and the information contained in this message can be referred to the above step 1-2.

[0292] Step b-3: The second node sends the first configuration message to the first node, which may be sent through the third node. The message is to reconfigure the current serving cell of the first node, such as RRCReconfiguration message, and further, the message may also include information about reconfiguring the LTM. The information contained in this message can be referred to the above steps 1-3.

[0293] When the first node accesses a new cell, the third node will determine whether to performs Layer 2 reset or whether the first node performs the UE-based TA measurement. In one example, the third node will determine according to the cell where the information of the first node is received. In another example, the third node will determine according to the information sent by the first node to the third node, and the information sent by the third node to the first node includes at least one of the following information: the identification information of the source cell (which is the source cell of the LTM cell switch or the cell connected by the first node before the cell selection), the configuration information related to the reset of the source cell (please refer to the above-mentioned " First Reset Related Configuration Information" for details), configuration information related to the TA measurement of the source cell (for details, please refer to the above-mentioned "Configuration Information Related to the First TA Measurement"), indication information of Layer 2 reset (such as whether it is necessary to perform Layer 2 reset), and indication information of TA measurement (used to indicate whether the first node performs UE-based TA measurement). In another example, it is determined by the third node according to the information sent by the second node, such as "Reset first indication information" and / or "TA measurement first indication information" in the first configuration request message. Optionally, the information sent by the second node is determined based on the information received from the first node, which (in one example, the information is forwarded to the first node through the third node) including at least one of the following information: identification information of the source cell (the source cell is the source cell of the LTM cell switch, or the cell connected by the first node before cell selection), configuration information related to the reset of the source cell (please refer to the above-mentioned "First Reset Related Configuration Information" for details), configuration information related to the TA measurement of the source cell (for details, please refer to the above-mentioned "Configuration Information Related to the First TA Measurement"), indication information of Layer 2 reset (such as whether it is necessary to perform Layer 2 reset), and indication information of TA measurement (used to indicate whether the first node performs UE-based TA measurement).

[0294] The beneficial effects of this embodiment are that the CU can determine appropriate parameters for layer 2 reset and / or parameters for TA measurement according to the capabilities of the user terminal and the accessed cell, thus reducing communication interruption and resource waste during the cell switch of the user terminal.

[0295] Example 2: the reset related configuration and / or the configuration related to TA measurement is determined by DU.

[0296] This example includes the following process:

[0297] Step c-1: The second node sends a first configuration request message to a third node, which is the node serving the current serving cell of the first node. The message does not contain the reset related configuration and / or the configuration related to TA measurement. The first configuration request message includes at least one of the following information:

[0298] - First configuration request information of the serving cell

[0299] - First configuration information of a candidate cell, which includes configuration information of one or more candidate cells, and for a candidate cell, the information includes at least one of the following information:

[0300] -> Identification information of a candidate cell

[0301] -> Synchronization configuration information

[0302] -> Configuration information of a reference signal

[0303] -> Reference configuration information

[0304] Step c-2: The third node sends a first configuration response message to the second node, the first configuration response message provides the configuration information of the target cell, and the information contained in this message can be referred to the above step 1-2. The message includes at least one of the following information:

[0305] - First configuration response information of the serving cell, which includes at least one of the following information:

[0306] -> Configuration information of a service cell

[0307] -> Fourth reset related configuration information.

[0308] -> Configuration information related to the fourth TA measurement

[0309] - First configuration response information of the target cell, which includes at least one of the following information:

[0310] -> Configuration information of a target cell

[0311] -> Fifth reset related configuration information.

[0312] -> Configuration information related to the fifth TA measurement

[0313] -> First configuration response information of the candidate cell, which includes at least one of the following information:

[0314] -> Sixth reset related configuration information

[0315] -> Configuration information related to the sixth TA measurement

[0316] -> Default Layer 2 Configuration Information

[0317] Step c-3: The second node sends the first configuration message to the first node, which may be sent through the third node. The message is to reconfigure the current serving cell of the first node, such as RRCReconfiguration message, and further, the message may also include information about reconfiguring the LTM. The information contained in this message can be referred to the above steps 1-3.

[0318] The beneficial effects of this embodiment are that the DU can determine appropriate parameters for layer 2 reset and / or parameters for TA measurement according to the capabilities of the user terminal, the accessed cell and its own resource status, so as to ensure the consistent parameter configuration with the user terminal and reduce communication interruption and resource waste during the cell switch of the user terminal.

[0319] In another embodiment, when the first node is an IAB node, the first node will determine whether to re-establish the RLC entity corresponding to the backhaul RLC channel according to the configuration information related to LTM and the configuration when the first node performs the LTM cell switch or L3 handover. Specifically, the second node sends a first configuration message to the first node, the information includes the configuration information of the target cell for L3 handover or the configuration information of the LTM candidate cell, for example, at least one of the following information:

[0320] - Reset configuration information of the serving cell, which indicates the reset configuration of the serving cell of the first node or the target cell of L3 handover, such as Serving Cell No Reset ID.

[0321] - Identification information of the candidate cell, which indicates the identification of the LTM candidate cell of the first node;

[0322] - Reset configuration information of the candidate cell, which indicates the reset configuration of the LTM candidate cell of the first node, such as No Reset ID.

[0323] When the first node performs a cell switch (such as L3 handover or LTM cell switch), the first node will have at least one of the following behaviours:

[0324] - Reserving (keeping) backhaul logical channel identification information of backhaul RLC channel, and corresponding RLC entity, state variable, buffer and timer;

[0325] - If the handover target cell (such as the candidate cell of LTM or the target cell of L3 handover) is not configured with the "reset configuration information of the service cell" and / or the first node does not store the "reset configuration information of the service cell", the RLC entity corresponding to the backhaul logical channel identification is re-established after the first node performs the handover (performs the configuration of the candidate cell of LTM).

[0326] - If the serving cell is configured with "Reset Configuration Information of the Serving Cell" and the target cell for handover (such as the candidate cell for LTM or the target cell for L3 handover) is configured with "Reset Configuration Information of the Candidate Cell", and they are different, the RLC entity corresponding to the backhaul logical channel identification is re-established after the first node performs the handover (performs the configuration of the candidate cell of LTM)..

[0327] In addition, it can be understood that the contents contained in each message in the above-mentioned embodiment are only examples of this disclosure, and the contents contained in various similar or identical messages can be replaced with each other, or named with different names, or some items can be added or deleted according to the situation, and for the sake of brevity, the meanings of similar content items can be mutually explained according to the context without being repeated, and the modified and explained embodiments still belong to the scope of protection of the present invention.

[0328] Fig. 4 is a block diagram illustrating the structure of a first node 400 according to an embodiment of the present disclosure.

[0329] Referring to Fig. 4, the first node 400 includes a transceiver 401 and a controller 402. The transceiver 401 is configured to transmit and receive signals to and from the outside. The controller 402 is configured to perform the above-described method performed by the first node. The first node 400 may be implemented in the form of hardware, software, or a combination of hardware and software, so that it can perform the method performed by the first node described in the present disclosure.

[0330] Fig. 5 is a block diagram illustrating the structure of a second node 500 according to an embodiment of the present disclosure.

[0331] Referring to Fig. 5, the second node 500 includes a transceiver 501 and a controller 502. The transceiver 501 is configured to transmit and receive signals to and from the outside. The controller 502 is configured to perform a method performed by the second node. The second node 500 may be implemented in the form of hardware, software, or a combination of hardware and software, so that it can perform the method performed by the second node described in the present disclosure.

[0332] Fig. 6 is a block diagram illustrating the structure of a third node 600 according to an embodiment of the present disclosure.

[0333] Referring to Fig. 6, the third node 600 includes a transceiver 601 and a controller 602. The transceiver 601 is configured to transmit and receive signals to and from the outside. The controller 602 is configured to perform a method performed by a third node. The third node 600 may be implemented in the form of hardware, software, or a combination of hardware and software, so that it can perform the method performed by the third node described in the present disclosure.

[0334] At least one embodiment of the present disclosure also provides a non-transitory computer-readable recording medium, on which a program for executing the above method when a computer runs has been stored.

[0335] Various embodiments of the present disclosure can be realized as computer-readable codes embodied on a computer-readable recording medium from a specific perspective. A computer-readable recording medium is any data storage device that can store data readable by a computer system. Examples of computer-readable recording media may include read-only memory (ROM), random access memory (RAM), compact disk read-only memory (CD-ROM), magnetic tape, floppy disk, optical data storage device, carrier wave (for example, data transmission via the Internet), and the like. Computer-readable recording media can be distributed through computer systems connected via a network, and thus computer-readable codes can be stored and executed in a distributed manner. Moreover, functional programs, codes and code segments for implementing various embodiments of the present disclosure can be easily interpreted by those skilled in the art to which the embodiments of the present disclosure are applied.

[0336] It will be understood that the embodiments of the present disclosure can be implemented in the form of hardware, software, or a combination of hardware and software. The software can be stored as program instructions or computer-readable code executable on a controller on a non-transient computer-readable medium. Examples of non-transient computer-readable recording media include magnetic storage media (e.g., ROM, floppy disk, hard disk, etc.) and optical recording media (e.g., CD-ROM, digital video disk (DVD), etc.). Non-transient computer-readable recording media can also be distributed on network-coupled computer systems, so that computer-readable codes are stored and executed in a distributed manner. The medium can be read by a computer, stored in a memory, and executed by a controller. Various embodiments may be implemented by a computer or a portable terminal including a controller and a memory, and the memory may be an example of a non-transitory computer-readable recording medium suitable for storing program (s) having instructions for implementing embodiments of the present disclosure. The present disclosure can be realized by a program having codes for concretely implementing the apparatus and method described in the claims, which is stored in a machine (or computer) readable storage medium. The program may be electronically carried on any medium, such as a communication signal transmitted via a wired or wireless connection, and this disclosure suitably includes its equivalents.

[0337] What has been described above is only the specific implementation of this disclosure, but the protection scope of this disclosure is not limited to this. Any person familiar with this technical field can make various changes or substitutions within the technical scope disclosed in this disclosure, and these changes or substitutions should be included in the protection scope of this disclosure. Therefore, the scope of protection of this disclosure should be based on the scope of protection of the claims.

Claims

1.A method performed by a central unit (CU) of a base station in a wireless communication system, the method comprising:transmitting, to a distributed unit (DU) of the base station, a user equipment (UE) context modification request message including first information on a serving cell and second information on a layer1 / layer2 triggered mobility (LTM) candidate cell;receiving, from the DU of the base station, a UE context modification response message; andtransmitting, to a UE, a radio resource control (RRC) reconfiguration message including an LTM configuration,wherein the first information includes a UE based timing advance (TA) measurement configuration for the serving cell, and the second information includes a UE based TA measurement configuration for the LTM candidate cell.2.The method of claim 1,wherein the LTM configuration includes a no reset identity for the serving cell and a no reset identity for the LTM candidate cell.3.The method of claim 2,wherein, in case that an LTM cell switch procedure is triggered and the no reset identity for the serving cell is not equal to the no reset identity for the LTM candidate cell, a radio link control (RLC) entity for a backhaul (BH) logical channel identity is re-established after the LTM cell switch procedure.4.The method of claim 1,wherein the UE context modification request message further includes reset information for the serving cell, reset information for the LTM candidate cell, and identification information of the LTM candidate cell,wherein the reset information for the serving cell includes a no reset identity for the serving cell,wherein the reset information for the LTM candidate cell includes a no reset identity for the LTM candidate cell, andwherein the UE based TA measurement configuration for the serving cell includes a UE-measured TA identity for the serving cell, and the UE based TA measurement configuration for the LTM candidate cell includes a UE-measured TA identity for the LTM candidate cell.5.A method performed by a user equipment (UE) in a wireless communication system, the method comprising:receiving, from a base station, a radio resource control (RRC) reconfiguration message including a layer1 / layer2 triggered mobility (LTM) configuration, the LTM configuration including a no reset identity for a serving cell and a no reset identity for an LTM candidate cell;triggering an LTM cell switch execution; andre-establishing a radio link control (RLC) entity for a backhaul (BH) logical channel identity after the LTM cell switch procedure, in case that the no reset identity for the serving cell is not equal to the no reset identity for the LTM candidate cell.6.The method of claim 5,wherein a UE context modification request message including first information on a serving cell and second information on the LTM candidate cell is transmitted from a central unit (CU) of the base station to a distributed unit (DU) of the base station, andwherein the first information includes a UE based timing advance (TA) measurement configuration for the serving cell, and the second information includes a UE based TA measurement configuration for the LTM candidate cell.7.The method of claim 6,wherein the UE based TA measurement configuration for the serving cell includes a UE-measured TA identity for the serving cell and the UE based TA measurement configuration for the LTM candidate cell includes a UE-measured TA identity for the LTM candidate cell.8.The method of claim 6,wherein the UE context modification request message further includes reset information for the serving cell, reset information for the LTM candidate cell, and identification information of the LTM candidate cell,wherein the reset information for the serving cell includes a no reset identity for the serving cell, andwherein the reset information for the LTM candidate cell includes a no reset identity for the LTM candidate cell.9.A central unit (CU) of a base station in a wireless communication system, the CU comprising:a transceiver; andat least one processor coupled with the transceiver and configured to:transmit, to a distributed unit (DU) of the base station, a user equipment (UE) context modification request message including first information on a serving cell and second information on a layer1 / layer2 triggered mobility (LTM) candidate cell,receive, from the DU of the base station, a UE context modification response message, andtransmit, to a UE, a radio resource control (RRC) reconfiguration message including an LTM configuration,wherein the first information includes a UE based timing advance (TA) measurement configuration for the serving cell, and the second information includes a UE based TA measurement configuration for the LTM candidate cell.10.The CU of claim 9,wherein the LTM configuration includes a no reset identity for the serving cell and a no reset identity for the LTM candidate cell.11.The CU of claim 10,wherein, in case that an LTM cell switch procedure is triggered and the no reset identity for the serving cell is not equal to the no reset identity for the LTM candidate cell, a radio link control (RLC) entity for a backhaul (BH) logical channel identity is re-established after the LTM cell switch procedure.12.The CU of claim 9,wherein the UE context modification request message further includes reset information for the serving cell, reset information for the LTM candidate cell, and identification information of the LTM candidate cell,wherein the reset information for the serving cell includes a no reset identity for the serving cell,wherein the reset information for the LTM candidate cell includes a no reset identity for the LTM candidate cell, andwherein the UE based TA measurement configuration for the serving cell includes a UE-measured TA identity for the serving cell, and the UE based TA measurement configuration for the LTM candidate cell includes a UE-measured TA identity for the LTM candidate cell.13.A user equipment (UE) in a wireless communication system, the UE comprising:a transceiver; andat least one processor coupled with the transceiver, and configured to:receive, from a base station, a radio resource control (RRC) reconfiguration message including a layer1 / layer2 triggered mobility (LTM) configuration, the LTM configuration including a no reset identity for a serving cell and a no reset identity for an LTM candidate cell,trigger an LTM cell switch execution, andre-establish a radio link control (RLC) entity for a backhaul (BH) logical channel identity after the LTM cell switch procedure, in case that the no reset identity for the serving cell is not equal to the no reset identity for the LTM candidate cell.14.The method of claim 13,wherein a UE context modification request message including first information on a serving cell and second information on the LTM candidate cell is transmitted from a central unit (CU) of the base station to a distributed unit (DU) of the base station, andwherein the first information includes a UE based timing advance (TA) measurement configuration for the serving cell, and the second information includes a UE based TA measurement configuration for the LTM candidate cell.15.The method of claim 14,wherein the UE based TA measurement configuration for the serving cell includes a UE-measured TA identity for the serving cell and the UE based TA measurement configuration for the LTM candidate cell includes a UE-measured TA identity for the LTM candidate cell,wherein the UE context modification request message further includes reset information for the serving cell, reset information for the LTM candidate cell, and identification information of the LTM candidate cell,wherein the reset information for the serving cell includes a no reset identity for the serving cell, andwherein the reset information for the LTM candidate cell includes a no reset identity for the LTM candidate cell.

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