User equipment, node device, and method performed thereby

Abstract

Various embodiments of the present disclosure provide a method executed by a user equipment (UE) in a communication system, the method comprising: sending a preamble to a second node where a candidate cell is located; and receiving timing advance (TA) information of the candidate cell from the first node, where the TA information is used to perform conditional layer 1 or layer 2 triggered mobility (LTM).

Description

Technical Field

[0001] The present disclosure relates to the field of communications, and more particularly, to methods performed by a user equipment, methods performed by a first node, methods performed by a second node, a user equipment, a first node, and a second node. Background Art

[0002] In order to meet the increasing demand for wireless data communication services since the deployment of 4G communication systems, efforts have been made to develop improved 5G or pre-5G communication systems. Therefore, 5G or pre-5G communication systems are also referred to as "super 4G networks" or "post-LTE systems".

[0003] Wireless communication is one of the most successful innovations in modern history. Recently, the number of subscribers to wireless communication services has exceeded 5 billion and is continuing to grow rapidly. Due to the increasing popularity of smart phones and other mobile data devices (e.g., tablet computers, laptop computers, netbooks, e-book readers, and machine type devices) among consumers and enterprises, the demand for wireless data services is growing rapidly. In order to meet the high growth of mobile data services and support new applications and deployments, it is crucial to improve the efficiency and coverage of wireless interfaces. Summary of the Invention

[0004] According to one aspect of the present disclosure, there is provided a method performed by a user equipment (UE) in a communication system, the method comprising: sending a preamble to a second node where a candidate cell is located; and receiving timing advance (TA) information of the candidate cell from a first node, wherein the TA information is used to perform conditional layer 1 or layer 2 triggered mobility (LTM).

[0005] According to the method performed by a user equipment (UE) in a communication system provided by the present disclosure, wherein, the sending the preamble to the second node includes: the UE selects a first random access (RA) resource for performing an uplink synchronization process in advance from among the RA resources assigned by the candidate cell to the first node for performing an uplink synchronization process in advance, and sends a first preamble, wherein the first preamble is selected by the UE; and the RA resources assigned by the candidate cell to the first node for performing an uplink synchronization process in advance are sent by the candidate cell to the UE through a third node and the first node.

[0006] A method performed by a user equipment (UE) in a communication system according to the present disclosure, wherein receiving a TA includes: monitoring a physical downlink control channel (PDCCH) transmitted by a first node, including: the UE monitoring the PDCCH using a first radio network temporary identity (RNTI), the PDCCH including transmission resources for transmitting a media access control protocol data unit (MAC PDU) containing TA information including the candidate cell, wherein the TA information includes one or more TA information for one or more UEs.

[0007] A method performed by a user equipment (UE) in a communication system according to the present disclosure, wherein the first RNTI is an RNTI assigned by the first node and related to the MAC PDU including the TA information of the candidate cell.

[0008] A method performed by a user equipment (UE) in a communication system according to the present disclosure, wherein transmitting a preamble to a second node includes: the UE transmitting a second preamble on a second random access channel (RACH) resource assigned to the UE by the candidate cell for performing an uplink synchronization process in advance, wherein the second preamble is the preamble assigned to the UE by the candidate cell.

[0009] A method performed by a user equipment (UE) in a communication system according to the present disclosure, wherein the method further includes: the UE transmitting a first message to the first node, the first message including a candidate cell selected by the UE and / or candidate cell measurement results; and the UE receiving a second message transmitted by the first node, the second message instructing the UE to perform an uplink synchronization process in advance with the candidate cell; wherein the second message includes at least one of the following: a candidate cell identifier, a fourth random access (RA) resource for performing an uplink synchronization process in advance, and a fourth preamble; wherein the fourth RA resource and the fourth preamble are selected by the first node from the RA resources assigned to the first node by the candidate cell for performing an uplink synchronization process in advance; wherein the RA resources assigned to the first node by the candidate cell for performing an uplink synchronization process in advance are transmitted by the candidate cell to the first node through a third node.

[0010] A method performed by a user equipment (UE) in a communication system according to the present disclosure, wherein monitoring the PDCCH transmitted by the first node includes: the UE monitoring the PDCCH using a cell radio network temporary identity (C-RNTI) assigned to the UE by the first node, the PDCCH including resources for transmitting a MAC PDU including the TA information of the candidate cell, wherein the MAC PDU includes one or more media access control control elements (MAC CEs), and the TA information is included in the MAC CE.

[0011] A method performed by a user equipment (UE) in a communication system according to the present disclosure, wherein a MAC CE including the TA information is identified by a logical channel identifier.

[0012] A method performed by a user equipment (UE) in a communication system according to the present disclosure, wherein the TA information includes at least one of the following: a candidate configuration identifier; a TA value, where the TA value is determined by a detected preamble of the candidate cell; a random access radio network temporary identifier (RA-RNTI) value, where the RA-RNTI value is determined by the candidate cell according to a resource where the preamble is detected; RA resource information where the preamble is detected.

[0013] A method performed by a user equipment (UE) in a communication system according to the present disclosure, wherein the method further includes: when the UE receives the TA value of the candidate cell, starting or restarting a timer, where the TA value is valid before the timer expires.

[0014] A method performed by a user equipment (UE) in a communication system according to the present disclosure, wherein the TA information is used to perform conditional LTM, including: if the TA value of the target cell is valid, the UE sends a scheduling request to a second node on a first resource or sends uplink data to the second node on a second resource; where the first resource is a resource allocated by the target cell for the UE to send a scheduling request, and the second resource is a resource allocated by the target cell for the UE to send uplink data; if the scheduling request or the uplink data is successfully received by the second node, the UE considers that the conditional LTM is successfully executed.

[0015] A method performed by a user equipment (UE) in a communication system according to the present disclosure, wherein the TA information is used to perform conditional LTM, including: if the TA value of the target cell is valid, the UE sends a conditional LTM indication to a first node, where the conditional LTM indication is used to indicate that the UE will perform conditional LTM; receiving resource scheduling information sent by the target cell; and performing uplink transmission on the resource; where the resource scheduling information is sent by PDCCH.

[0016] A method performed by a user equipment (UE) in a communication system according to the present disclosure, wherein the method further includes: the UE evaluating, according to layer 1 measurement results, the execution conditions of long term measurement (LTM) for candidate cells, and when there is a candidate cell that meets the LTM execution conditions, selecting one candidate cell as a target cell and executing mobility LTM triggered by layer 1 or layer 2 conditions. According to an aspect of the present disclosure, a method performed by a first node in a communication system is provided, the method including: receiving, from a third node, timing advance (TA) information of candidate cells, wherein the TA information of the candidate cells is sent by a second node to the third node after receiving a preamble sent by the UE; and sending the TA information of the candidate cells to the user equipment UE, wherein the TA information is used to execute mobility LTM triggered by layer 1 or layer 2 conditions.

[0017] A method performed by a first node in a communication system according to the present disclosure, wherein the method further includes: sending a physical downlink control channel (PDCCH) to the UE, the PDCCH including resources for sending a media access control protocol data unit (MAC PDU) including the TA information of the candidate cells.

[0018] A method performed by a first node in a communication system according to the present disclosure, wherein the MAC PDU includes one or more media access control control elements (MAC CE), and the TA information is included in the MAC CE.

[0019] A method performed by a first node in a communication system according to the present disclosure, wherein the PDCCH is scrambled by a first radio network temporary identifier (RNTI) or by a cell radio network temporary identifier (C-RNTI) of the UE, wherein the first RNTI is assigned by the first node to the UE in the first node for receiving the MAC PDU including the TA information.

[0020] According to an aspect of the present disclosure, a method performed by a second node in a communication system is provided, the method including: receiving a preamble sent by a user equipment UE; and sending timing advance (TA) information of candidate cells to a third node, wherein the TA information is used to execute mobility LTM triggered by layer 1 or layer 2 conditions.

[0021] According to another aspect of the present disclosure, a user equipment UE is provided, the user equipment UE including: a transceiver configured to transmit and receive signals to and from the outside; and a controller configured to control the transceiver to execute the above method performed by the user equipment UE.

[0022] According to another aspect of the present disclosure, there is provided a first node, the first node comprising: a transceiver configured to transmit and receive signals to and from the outside; and a controller configured to control the transceiver to perform the method performed by the first node as described above.

[0023] According to another aspect of the present disclosure, there is provided a second node, the second node comprising: a transceiver configured to transmit and receive signals to and from the outside; and a controller configured to control the transceiver to perform the method performed by the second node as described above.

[0024] According to another aspect of the present disclosure, there is provided a non-transitory computer-readable recording medium having stored thereon a program for performing any of the methods as described above when run by a computer. Description of the Drawings

[0025] Figure 1 is an exemplary system architecture of System Architecture Evolution (SAE).

[0026] Figure 2 is an exemplary system architecture according to various embodiments of the present disclosure.

[0027] Figure 3 is a schematic diagram of interactions among a user equipment, a first node, a second node, and a third node according to various embodiments of the present disclosure.

[0028] Figure 4a is another schematic diagram of interactions among a user equipment, a first node, a second node, and a third node according to various embodiments of the present disclosure.

[0029] Figure 4b is an example of a MAC PDU structure according to various embodiments of the present disclosure.

[0030] Figure 4c is an example of a timing advance command MAC control unit for obtaining TA values in advance according to various embodiments of the present disclosure.

[0031] Figure 5a is another schematic diagram of interactions among a user equipment, a first node, a second node, and a third node according to various embodiments of the present disclosure.

[0032] Figure 5b is an example of a MAC PDU for obtaining a timing advance command in advance according to various embodiments of the present disclosure.

[0033] Figure 5c is an example of a TA command according to various embodiments of the present disclosure.

[0034] Figure 6It is a schematic diagram of the interaction among a user equipment, a first node, a second node, and a third node according to various embodiments of the present disclosure.

[0035] Figure 7 It is an interaction schematic diagram of a method for executing conditional LTM according to various embodiments of the present disclosure.

[0036] Figure 8 It is an interaction schematic diagram of another method for executing conditional LTM according to various embodiments of the present disclosure.

[0037] Figure 9 It is an interaction schematic diagram of yet another method for executing conditional LTM according to various embodiments of the present disclosure.

[0038] Figure 10 It is a block diagram showing the structure of a user equipment according to an embodiment of the present disclosure.

[0039] Figure 11 It is a block diagram showing the structure of a first node according to an embodiment of the present disclosure.

[0040] Figure 12 It is a block diagram showing the structure of a second node according to an embodiment of the present disclosure.

[0041] Figure 13 It is a block diagram showing the structure of a third node according to an embodiment of the present disclosure. Detailed implementation manners

[0042] The following description with reference to the accompanying drawings is provided to facilitate a comprehensive understanding of various embodiments of the present disclosure defined by the claims and their equivalents. This description includes various specific details to facilitate understanding but should only be considered exemplary. Therefore, those of ordinary skill in the art will recognize that various changes and modifications can be made to the various embodiments described herein without departing from the scope and spirit of the present disclosure. In addition, descriptions of well-known functions and structures may be omitted for clarity and conciseness.

[0043] The terms and phrases used in the following specification and claims are not limited to their dictionary meanings but are merely used by the inventor to enable a clear and consistent understanding of the present disclosure. Therefore, it should be apparent to those skilled in the art that the following description of the various embodiments of the present disclosure is provided only for the purpose of illustration and not for the purpose of limiting the present disclosure as defined by the appended claims and their equivalents.

[0044] It should be understood that the singular forms "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.

[0045] The term "comprises" or "may comprise" refers to the presence of the corresponding disclosed function, operation, or component that can be used in various embodiments of the present disclosure, and does not limit the presence of one or more additional functions, operations, or features. In addition, the term "comprises" or "has" may be interpreted to mean that certain characteristics, numbers, steps, operations, components, components, or combinations thereof are present, but should not be construed as excluding the possibility of the presence of one or more other characteristics, numbers, steps, operations, components, components, or combinations thereof.

[0046] 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.

[0047] Unless differently defined, all terms (including technical or scientific terms) used in the present disclosure have the same meaning as understood by those skilled in the art described in the present disclosure. As commonly defined in a dictionary, a general term is interpreted to have a meaning consistent with the context in the relevant technical field, and should not be interpreted idealistically or overly formally unless explicitly defined as such in the present disclosure.

[0048] The following discussion Figures 1 to 13 and various embodiments for describing the principles of the present disclosure in this patent document are for illustration only and should not be construed in any way as limiting the scope of the present disclosure. Those skilled in the art will understand that the principles of the present disclosure can be implemented in any appropriately arranged system or device.

[0049] Figure 1It is an exemplary system architecture 100 of System Architecture Evolution (SAE). The User Equipment (UE) 101 is a terminal device for receiving data. The Evolved Universal Terrestrial Radio Access Network (E-UTRAN) 102 is a radio access network, which includes macro base stations (eNodeB / NodeB) that provide access to the wireless network interface for the UE. The Mobility Management Entity (MME) 103 is responsible for managing the mobility context, session context, and security information of the UE. The Serving Gateway (SGW) 104 mainly provides user plane functions, and the MME 103 and SGW 104 may be in the same physical entity. The Packet Data Network Gateway (PGW) 105 is responsible for functions such as charging and lawful interception, and may also be in the same physical entity as the SGW 104. The Policy and Charging Rules Function (PCRF) 106 provides Quality of Service (QoS) policies and charging guidelines. The Serving GPRS Support Node (SGSN) 108 is a network node device in the Universal Mobile Telecommunications System (UMTS) that provides routing for data transmission. The Home Subscriber Server (HSS) 109 is the home home subsystem of the UE, responsible for protecting user information including the current location of the user equipment, the address of the serving node, the user's security information, and the packet data context of the user equipment.

[0050] Figure 2 It 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.

[0051] The User Equipment (UE) 201 is a terminal device for receiving data. The Next Generation Radio Access Network (NG-RAN) 202 is a radio access network, which includes base stations (gNB or eNB connected to the 5G Core Network 5GC, and the eNB connected to the 5GC is also called ng-gNB) that provide access to the wireless network interface for the UE. The Access and Mobility Management Function (AMF) 203 is responsible for managing the mobility context and security information of the UE. The User Plane Function (UPF) 204 mainly provides user plane functions. The Session Management Function (SMF) 205 is responsible for session management. The Data Network (DN) 206 includes services such as those of the operator, access to the Internet, and third-party services.

[0052] The text and drawings are provided only as examples to assist in understanding 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, it will be apparent to those skilled in the art based on the content disclosed herein that changes can be made to the illustrated embodiments and examples without departing from the scope of the present disclosure.

[0053] Details of steps unrelated to the present invention are omitted in the present disclosure. In the following embodiments, a 5G system is taken as an example, the central unit of the access network is taken as an example of CU, and the distributed unit is taken as an example of DU for description. The method is also applicable to corresponding entities in other systems.

[0054] The LTM (L1 / L2-triggered mobility) handover mode, also known as layer 1 / layer 2 handover (L1 / L2 handover), also known as LTM cell switch, also known as LTM cell handover, or L1 / L2 mobility. The base station or gNB-DU sends an LTM cell switch command to the UE through the MAC CE (MAC Control Element, media access control control unit) of the MAC layer (L2, Layer 2) to instruct the UE to change the serving cell.

[0055] Conditional LTM cell handover, also known as conditional LTM handover, also known as conditional LTM cell switch, or conditional LTM.

[0056] In the present disclosure, the LTM candidate cell can be called a candidate cell or a target candidate cell. The target cell can be called a target candidate cell, or an LTM target candidate cell, or an LTM target cell.

[0057] In the present disclosure, the content is applicable to the master base station / master node MN (Master Node) in the dual-connectivity DC (Dual Connectivity) system to perform MCG LTM (or MN changes the PCell through LTM), and is also applicable to the secondary base station / secondary node SN (Secondary Node) to perform SCG LTM (or SN changes the PSCell through LTM). Therefore, the LTM candidate cell described in the present disclosure can be the LTM candidate cell of the PCell or the candidate cell of the PSCell of the LTM.

[0058] In LTM, the network selects a target cell for the UE according to the measurement results reported by the user equipment UE, and instructs the UE to perform cell switching by sending a cell switch command. The delay of signaling transmission between the network and the UE may cause handover failure due to changes in the radio link state.

[0059] Various embodiments of the present disclosure provide a method performed by a user equipment (UE) in a communication system. The method includes: sending a preamble to a second node where a candidate cell is located (for example, it can be a target gNB-DU / candidate gNB-DU); and receiving timing advance (TA) information of the candidate cell from a first node (for example, it can be a source gNB-DU), where the TA information is used to perform conditional layer 1 or layer 2 triggered mobility (LTM).

[0060] In the method performed by a user equipment (UE) in a communication system provided by various embodiments of the present disclosure, the condition for conditional LTM switching is configured through network configuration. When the execution condition is met, the UE actively performs LTM for cell switching without waiting for a handover command sent by the source node. This can reduce the signaling interaction between the UE and the network, and also avoid the situation of UE handover failure caused by changes in the radio link state during the time of signaling interaction between the UE and the network, thus improving the robustness of the handover. Moreover, before performing conditional LTM, the UE performs an uplink synchronization process with the candidate cell (including the target cell) in advance to obtain (or acquire) the TA value of the candidate cell (including the target cell) in advance (which can also be referred to as obtaining the TA value in advance). This process can also be referred to as the process of early acquisition (or obtaining) of TA (Early TA Acquisition), or the process of early acquisition of the TA of the candidate cell, or the process of the UE performing uplink synchronization with the candidate cell in advance. By performing the uplink synchronization process with the candidate cell in advance, the UE avoids performing uplink synchronization with the target cell during the handover execution process, thereby reducing the handover latency.

[0061] In the present disclosure, the TA value of the UE in the candidate cell can also be referred to as the Early TA value of the UE in the candidate cell, or simply the Early TA value, or the TA value of the candidate cell. The TA information is the information containing the TA value. The TA information of the UE in the candidate cell can also be referred to as the Early TA information of the UE in the candidate cell, or simply the Early TA information, or the TA information of the candidate cell.

[0062] Various embodiments of the present disclosure involve: the configuration method and execution process of conditional LTM, the method for the UE to obtain the TA value of the target cell (candidate cell) in advance, and the execution method of conditional LTM. The following will be described in detail in conjunction with Figures 3 to 9 For details.

[0063] Example 1: Configuration Method and Execution Process of Conditional LTM

[0064] Please refer to Figure 3 , Figure 3 which is a schematic diagram of the interaction among a user equipment, a first node, a second node, and a third node according to various embodiments of the present disclosure.Figure 3 The method shown may include one or more of steps S300a to step S318:

[0065] Step 300a, the UE sends a message to the source gNB-DU (which may also be referred to as the first node), and the message contains L3 measurement results. Optionally, the message may be a Measurement Report, or other messages. The measurement results include neighbor cell measurement results.

[0066] Step 300b, the source gNB-DU sends a message to the gNB-CU (which may also be referred to as the third node), and sends the received measurement report to the gNB-CU. Optionally, the message may be an UL RRC MESSAGE TRANSFER message, or other messages.

[0067] Step 301, the gNB-CU decides to trigger conditional LTM configuration. The gNB-CU selects an LTM candidate cell for the UE.

[0068] Step 302a, the gNB-CU sends a message to the candidate gNB-DU (which may also be referred to as the second node), requesting configuration of the LTM candidate cell. Optionally, the message may be a UE CONTEXT SETUP REQUEST message, or other messages.

[0069] The message contains at least one of the following information:

[0070] (1) Identification information of the UE at the gNB-CU, which is the identification assigned by the gNB-CU for the UE, and may be the gNB-CU UE F1AP ID, or other identifications,

[0071] (2) Conditional LTM indication, used to indicate that the request is a conditional LTM candidate cell request. The candidate gNB-DU provides the execution conditions for conditional LTM.

[0072] (3) Candidate cell identification, the identification of the requested LTM candidate cell, and the cell identification may be CGI, or other identifications.

[0073] (4) LTM configuration identification. The LTM configuration identification corresponds (or is associated) with the candidate cell identification, that is, each LTM candidate cell has a corresponding LTM configuration identification.

[0074] (5) LTM configuration ID mapping list. It contains the cell identifications of all LTM candidate cells, as well as the LTM configuration identifications.

[0075] (6) CSI resource configuration

[0076] Step 302b, the candidate gNB-DU sends a message to the gNB-CU. If the candidate gNB-DU receives the requested LTM configuration, it sends the said message for feedback, providing the RRC configuration information of the candidate cell that accepts the request.

[0077] Optionally, the said message can be a UE CONTEXT SETUP RESPONSE, or other messages.

[0078] The said message contains at least one of the following information:

[0079] (1) The identification information of the UE in the gNB-CU, which is the identification assigned by the gNB-CU to the UE, and can be the gNB-CU UE F1APID, or other identifications, that is, the identification assigned by the gNB-CU to the UE in step 302a.

[0080] (2) The identification information of the UE in the gNB-DU, which is the identification assigned by the candidate gNB-DU to the UE, and can be the gNB-DU UEF1AP ID, or other identifications.

[0081] (3) The cell identification, indicating the requested candidate cell identification, that is, the candidate cell identification requested in step 302a. The said cell identification can be CGI (Cell Global ID), or other identifications.

[0082] (4) The LTM configuration information, indicating the configuration information of the cell indicated by the said cell identification. It contains at least one of the following information:

[0083] - SSB (Synchronization Signal Block) configuration information, indicating the time and frequency information of the SSB of the cell indicated by the said cell identification. The said frequency information is the ARFCN. SSB is also the Synchronization Signal / Physical Broadcast Channel Block (SS / PBCH Block).

[0084] - Physical cell ID (PCI), indicating the physical cell identification of the cell indicated by the said cell identification.

[0085] (5) TCI (Transmission Configuration Indicator) status configuration list.

[0086] (6) RACH (Random Access Channel) configuration information list, including one or more RACH configuration information, and the RACH configuration information includes at least one of the following information:

[0087] - The first RACH configuration (which can also be called the first resource configuration, or other names, and the present invention is not limited thereto), including the random access resources (Random Access, RA) configured (or allocated) by the candidate cell for the uplink synchronization process in advance, that is, the RA resources for obtaining the TA value of the candidate cell in advance. Among them, the RA resources can also be called RACH resources. The first RACH configuration is the RA resources allocated by the candidate cell to other gNB-DUs for the UEs in the other gNB-DUs to obtain the TA value of the candidate cell in advance.

[0088] - gNB-DU ID, the identifier of the gNB-DU, that is, the identifier of the gNB-DU using the RA resources of the first RACH configuration.

[0089] (7) CSI reporting configuration.

[0090] (8) The second RACH configuration (which can also be called the second resource configuration, or other names, and the present invention is not limited thereto), including the dedicated RA resources configured (or allocated) by the candidate cell to the UE for the uplink synchronization process in advance, that is, the dedicated RA resources for obtaining the TA value of the candidate cell in advance. Among them, the RA resources can also be called RACH resources.

[0091] (9) The third RACH configuration (which can also be called the third resource configuration, or other names, and the present invention is not limited thereto), the RA resources configured (or allocated) by the candidate cell for performing RACH-based LTM, that is, the RA resources used for random access when the candidate cell is selected as the target cell. Among them, the RA resources can also be called RACH resources.

[0092] (10) Dedicated uplink resources, the dedicated uplink resources configured (or allocated) by the candidate cell for the UE, that is, the configured grant. Used for the UE to perform uplink transmission in the target cell when performing LTM.

[0093] (11) LTM execution condition (which can also be referred to as the second LTM execution condition, or other names, and the present invention is not limited thereto), the LTM execution condition provided by the candidate cell (which can also be referred to as the conditional LTM execution condition). Among them, the LTM execution condition is related to Layer 1 (L1) measurement. When the UE selects the candidate cell as the target cell for access, the UE monitors the candidate cell. According to the L1 measurement result, when one or more cells meet the LTM execution condition, one of them is selected as the new target cell, and the conditional LTM is executed, that is, the cell handover is triggered to access the new target cell.

[0094] (12) C-RNTI (Cell Radio Network Temmporary Identify), the C-RNTI value assigned by the candidate cell to the UE, which serves as the identifier of the UE in the candidate cell.

[0095] (13) RNTI (Radio Network Temporary Identifier), the RNTI value assigned (or configured) by the candidate cell. After the candidate cell becomes the target cell (serving cell), the UE receives the RNTI for obtaining the TA information in advance in the target cell. Optionally, the RNTI can be a dedicated RA-RNTI (RandomAccess RNTI) (which can also be referred to as the second RA-RNTI, or other names, and the present invention is not limited thereto), or other RNTIs.

[0096] (14) Physical Uplink Control Channel (PUCCH) resource information, the PUCCH resource information assigned (or configured) by the candidate cell to the UE.

[0097] At least one of the following information is included in the first RACH configuration and the third RACH configuration:

[0098] - Uplink frequency information, which includes the carrier bandwidth, subcarrier spacing, and carrier offset value (offsetToCarrier). The carrier offset value indicates the starting point of the PRB actually and effectively used by the carrier.

[0099] - RACH parameters, which are used for the RACH in the random access process in the candidate cell (execution).

[0100] For example, the general RACH configuration (Rach Config Generic)

[0101] can be used to represent.

[0102] - BWP (Bandwidth Part, bandwidth portion) information, indicating the frequency domain position of the BWP (indicating the starting point of the BWP) and the bandwidth.

[0103] - The number of SSBs, indicating the number of SSBs on the RACH occasion (RACH Occasion). The RACH occasion can also be referred to as the RACH opportunity.

[0104] - PRACH root sequence index (PRACH Root Sequence Index).

[0105] - PRACH subcarrier spacing, indicating the subcarrier spacing of the PRACH used for LTM (which can be represented by ltm prachSubcarrier Spacing).

[0106] - Timing advance offset value, the timing advance offset value (TimingAdvance Offset) for all uplink transmissions on the candidate cell.

[0107] The second RACH configuration includes at least one of the following information:

[0108] - RACH common configuration information, the information included in the RACH common configuration information is the same as the information included in the first RACH configuration, which will not be elaborated here.

[0109] - Random access preamble index, indicating the index of the preamble (Preamble code) used for the uplink synchronization process.

[0110] - SS / PBCH index, indicating the SS / PBCH used to determine the RACH occasion for PRACH transmission.

[0111] - PRACH mask index (PRACH Mask Index), indicating the RACH occasion related to the SS / PBCH for PRACH transmission, and the SS / PBCH is the SS / PBCH indicated by the SS / PBCH index.

[0112] If the candidate cell belongs to the source gNB-DU, then the configuration of the candidate cell is completed through steps 303a - 303b. Among them

[0113] 303a, the gNB-CU sends a message to the source gNB-DU.

[0114] Optionally, the message can be a UE context modification request (UE CONTEXT MODIFICATION REQUEST) message, or other messages.

[0115] The information contained in the message can be referred to in step 302a and will not be elaborated here.

[0116] 303b, the source gNB-DU sends a message to the gNB-CU.

[0117] Optionally, the message can be a UE context modification response (UE CONTEXT MODIFICATION RESPONSE) message, or other messages.

[0118] The information contained in the message can be referred to in step 302b and will not be elaborated here.

[0119] Step 304, the gNB-CU sends a message to the source gNB-DU.

[0120] Optionally, the message can be a UE context modification request (UE CONTEXT MODIFICATION REQUEST) message, or other messages.

[0121] The message contains at least one of the following information:

[0122] (1) Candidate cell information. The candidate cell information contains one or more candidate cell information, and the candidate cell information contains at least one of the following information:

[0123] - LTM cell identifier (LTM Cell ID), indicating the identifier of the LTM candidate cell. The LTM cell identifier can be CGI (Cell Global ID), or other identifiers.

[0124] - LTM configuration identifier (LTM Configuration ID), corresponding to the LTM candidate identifier (LTM Candidate Id). The LTM candidate identifier indicates the LTM candidate configuration, which is related to the LTM candidate cell.

[0125] - gNB identifier (gNB ID), indicating the identifier of the gNB to which the cell indicated by the LTM cell identifier belongs.

[0126] - TCI status configuration list.

[0127] - The first RACH configuration (which can also be called the first resource configuration, or other names, and the present invention is not limited thereto), including the RA resources configured for the candidate cell to perform the uplink synchronization process in advance.

[0128] - The second RACH configuration (which may also be referred to as the second resource configuration, or other names, and the present invention is not limited thereto) includes dedicated RA resources configured by the candidate cell for the UE to perform the uplink synchronization process in advance.

[0129] - The third RACH configuration (which may also be referred to as the third resource configuration, or other names, and the present invention is not limited thereto) includes RA resources configured by the candidate cell for performing RACH-based LTM. When the candidate cell is selected as the target cell, the RA resources used for random access.

[0130] - CSI reporting configuration (which may also be referred to as the second CSI reporting configuration, or other names, and the present invention is not limited thereto).

[0131] - Dedicated uplink resources, dedicated uplink resources configured (or allocated) by the candidate cell for the UE, that is, configured grant. Used for the UE to perform uplink transmission in the target cell when performing LTM.

[0132] - LTM execution conditions (which may also be referred to as the second LTM execution conditions, or other names, and the present invention is not limited thereto), LTM execution conditions provided by the candidate cell.

[0133] - C-RNTI, the C-RNTI value allocated by the candidate cell for the UE, used as the identifier of the UE in the candidate cell.

[0134] (2) LTM configuration ID mapping list. It includes the cell identifiers of all LTM candidate cells and the LTM configuration identifiers.

[0135] Step 305, the source gNB-DU sends a message to the gNB-CU.

[0136] The message may be a UE CONTEXT MODIFICATION RESPONSE message, or other messages.

[0137] The message includes at least one of the following information:

[0138] (1) CSI reporting configuration, the CSI reporting configuration provided by the source cell.

[0139] (2) LTM execution condition (which can also be referred to as the first LTM execution condition, or other names, and the present invention is not limited thereto), the LTM execution condition provided by the source cell. Among them, the LTM execution condition is related to layer 1 (Layer1, L1) measurement. The UE monitors candidate cells. According to the L1 measurement results, when one or more cells meet the LTM execution condition, one of them is selected as the target cell, and the conditional LTM is executed, that is, cell switching is triggered to access the target cell.

[0140] (3) RNTI, the RNTI value allocated (or configured) by the source cell. It is used for the UE to receive the RNTI for obtaining TA information in advance on the source cell. Optionally, the RNTI can be a dedicated RA-RNTI (Random Access RNTI) (which can also be referred to as the first RA-RNTI, or other names, and the present invention is not limited thereto), or other RNTI.

[0141] Steps 306 - 307, if there is an update of candidate cells, all the finally determined candidate cell information is sent to each candidate cell through steps 306 - 307.

[0142] Step 306, the gNB-CU sends a message to the candidate gNB-DU. Optionally, the message can be a UE context modification request message (UE CONTEXT MODIFICATION REQUEST), or other messages. For specific content, refer to step 304.

[0143] Step 307, the candidate gNB-DU sends a message as feedback to the gNB-CU. Optionally, the message can be a UE context modification response message (UE CONTEXT MODIFICATION RESPONSE), or other messages.

[0144] Step 308, the gNB-CU sends a message to the source gNB-DU. The message contains the RRC reconfiguration message sent to the UE.

[0145] Optionally, the message can be a downlink RRC message transfer (DL RRC MESSAGE TRANSFER) message, or other messages.

[0146] The message contains at least one of the following information:

[0147] (1) RRC reconfiguration message, the RRC reconfiguration (RRCReconfiguration) message sent to the UE.

[0148] Step 309, the source gNB-DU sends a message to the UE. The source gNB-DU forwards the RRC reconfiguration message received in step 308 to the UE.

[0149] Optionally, the message is an RRC reconfiguration (RRCReconfiguration) message, or other messages.

[0150] The message contains at least one of the following information:

[0151] (1) Information related to the LTM candidate configuration of one or more LTM candidate cells. The information related to the LTM candidate configuration contains at least one of the following information:

[0152] - LTM Candidate Id, corresponding to the LTM configuration Id, and associated (or corresponding) with the LTM candidate cell.

[0153] - LTM candidate physical cell identifier (LTM candidate PCI), indicating the physical cell identifier of the candidate cell corresponding (or associated) with the LTM candidate identifier.

[0154] - SSB configuration information of LTM, indicating the time and frequency information of the SSB of the candidate cell corresponding (or associated) with the LTM candidate identifier. The frequency information includes the ARFCN of the SSB, that is, the ARFCN of the candidate cell.

[0155] - LTM candidate configuration information, including cell group (Cell Group) configuration information, radio bearer (RadioBearer, RB) configuration information, etc.

[0156] - First LTM RACH resource configuration (which can also be called the first resource configuration, or other names, and the present invention is not limited thereto) (which can also be called LTM early uplink synchronization configuration, ltm Early ULSync Config), including the RA (RandomAccess) resources configured for the candidate cell for the early uplink synchronization process. That is, the RACH configuration received by the gNB-CU in step 302b and / or 303b. Among them, the RA resource can also be called the RACH resource.

[0157] - LTM execution condition, the LTM execution condition provided by the candidate cell.

[0158] - The first LTM RACH resource configuration (which can also be called the first resource configuration, or other names, and the present invention is not limited thereto) (which can also be called the LTM early uplink synchronization configuration, ltm Early ULSync Config), including the RA (RandomAccess) resources configured for the candidate cell for the early uplink synchronization process. That is, the RACH configuration received by the gNB-CU in step 302b and / or 303b. Among them, the RA resource can also be called the RACH resource.

[0159] - The first LTM RACH resource configuration (which can also be called the first resource configuration, or other names, and the present invention is not limited thereto) (which can also be called the LTM early uplink synchronization configuration, ltm Early ULSync Config), including the RA (RandomAccess) resources configured for the candidate cell for the early uplink synchronization process. That is, the RACH configuration received by the gNB-CU in step 302b and / or 303b. Among them, the RA resource can also be called the RACH resource.

[0160] - LTM execution condition, the LTM execution condition provided by the candidate cell.

[0161] - The second LTM RACH resource configuration (which can also be referred to as dedicated ltmEarly UL Sync Config, or dedicated LTM early uplink synchronization configuration) (which can also be referred to as the second resource configuration, or other names, and the present invention is not limited thereto), includes the dedicated RA resources configured by the candidate cell for the UE to perform the uplink synchronization process in advance. That is, the second RACH configuration received by the gNB-CU in step 302b and / or 303b. Among them, the RA resource can also be referred to as the RACH resource.

[0162] - Dedicated uplink resources, the dedicated uplink resources configured (or allocated) by the candidate cell for the UE, that is, Configured Grant. It is used for the UE to perform uplink transmission in the target cell when executing LTM.

[0163] - The third RACH resource configuration (which can also be referred to as the third resource configuration, or other names, and the present invention is not limited thereto), includes the RA resources configured by the candidate cell for performing RACH-based LTM. When the candidate cell is selected as the target cell, the RA resources used for random access. That is, the third RACH configuration received by the gNB-CU in step 302b and / or 303b. Among them, the RA resource can also be referred to as the RACH resource.

[0164] - RNTI, the RNTI value configured (allocated) by the candidate cell. It is used for the UE to receive the RNTI of the TA information obtained in advance in the target cell after the candidate cell becomes the target cell (serving cell). Optionally, the RNTI can be a dedicated RA-RNTI (Random Access RNTI) (which can also be referred to as the second RA-RNTI, or other names, and the present invention is not limited thereto), or other RNTI.

[0165] - PUCCH resource information, the PUCCH resource information allocated (or configured) by the candidate cell for the UE.

[0166] (2) LTM execution conditions (which can also be referred to as the first LTM execution conditions, or other names, and the present invention is not limited thereto), the LTM execution conditions provided by the source cell. Among them, the LTM execution conditions are related to layer 1 (L1) measurements. The UE monitors the candidate cells. According to the L1 measurement results, when one or more cells meet the LTM execution conditions, one of them is selected as the target cell, and the LTM is executed, that is, the cell handover is triggered, and the UE accesses the target cell.

[0167] (3) RNTI, the RNTI value configured (assigned) by the source cell. It is used for the UE to receive the RNTI for obtaining the TA information in advance on the source cell. Optionally, the RNTI may be a dedicated RA-RNTI (Random Access RNTI) (which may also be referred to as the first RA-RNTI, or other names, and the present invention is not limited thereto), or other RNTIs.

[0168] (4) C-RNTI, the C-RNTI assigned by the source cell to the UE, serving as the identifier of the UE on the source cell.

[0169] Step 310, the UE sends an RRC Reconfiguration Complete message to the source gNB-DU.

[0170] Step 311, the source gNB-DU sends an UL RRC MESSAGE TRANSFER message to the source gNB-CU. The source gNB-DU forwards the RRC Reconfiguration Complete message received in Step 310 to the source gNB-CU.

[0171] Step 312, the UE performs LTM execution condition evaluation (or monitoring) according to the information received in Step 309, and evaluates whether the candidate cell meets the LTM execution conditions.

[0172] Based on the L1 measurement results, when one or more cells meet the LTM execution conditions, the UE selects one of them as the target cell and triggers cell switching.

[0173] Step 313, the UE performs the process of Early TA Acquisition.

[0174] If RACH-less (without random access) condition LTM switching is supported, if the UE does not have a valid TA value in the candidate cell, the UE will perform the process of Early TA Acquisition to obtain the TA value of the candidate cell in advance, that is, the Early TA value. Among them, there are the following two ways to obtain the TA value in advance:

[0175] - The UE obtains the TA value of the candidate cell in advance by means of UE-based TA measurement.

[0176] - The UE can obtain the TA value of the candidate cell in advance through the random access process. Among them, there are three methods to obtain the TA value of the candidate cell in advance through the random access process. For details, see the descriptions in Embodiments 2, 3, and 4.

[0177] When performing LTM execution condition evaluation (or monitoring), when one or more cells meet the LTM execution conditions, the UE selects one of them as the target cell, executes conditional LTM, and performs cell switching.

[0178] Step 314, Conditional LTM execution. The UE executes conditional LTM and accesses the target cell, that is, the target cell (target gNB-DU) detects the UE's access. There are three methods for conditional LTM execution. For details, refer to Embodiments Five, Six, and Seven. Among them:

[0179] - If the UE has a valid TA value in the target cell, it will perform a RACH-Less conditional LTM handover to achieve cell switching. In the RACH-less conditional LTM handover, when the first uplink transmission is correctly received, the UE and the network consider that the conditional LTM handover is successfully executed (or the conditional LTM execution is successful), that is, the UE accesses the target cell.

[0180] - If the UE does not have a valid TA value in the target cell, it will perform a RACH-based

[0181] (random access based) conditional LTM handover to achieve cell switching. If the network configures dedicated RACH resources for the UE, then it will perform the CFRA (Contention Free Random Access, contention-free random access) process, otherwise it will perform the CBRA (Contention Based, contention-based random access) process. If the random access process is successfully completed, the UE and the network consider that the conditional LTM handover is successfully executed, that is, the UE accesses the target cell.

[0182] Step 315, The target gNB-DU sends a message to the gNB-CU.

[0183] When the target gNB-DU detects that the UE accesses the target cell, it considers that the conditional LTM handover is successfully executed and will send a message to the gNB-CU to indicate that the UE has successfully accessed the target cell.

[0184] Optionally, the message can be an ACCESS SUCCESS message, or other messages.

[0185] The message contains at least one of the following information:

[0186] (1) Cell identifier, indicating the identifier of the target cell, which can be CGI, or other cell identifiers.

[0187] If the source gNB-DU contains LTM candidate cells, then step 316 will be executed, otherwise steps 317 and 318 will be executed.

[0188] Step 316, the gNB-CU sends a message to the source gNB-DU, indicating that the UE has accessed the target cell, the source cell stops sending data to the UE, and reserves the candidate cell resources configured for the UE.

[0189] Optionally, the message may be an LTM cell switch success (LTM CELL SWITCH SUCCESS) message, or other messages.

[0190] The message includes at least one of the following information:

[0191] (1) Cell identifier, indicating the identifier of the target cell to which the UE has accessed, which may be CGI, or other cell identifiers.

[0192] Step 317, the gNB-CU sends a message to the source gNB-DU, indicating that the UE has accessed the target cell, the source cell stops sending data to the UE, and releases the configured cell resources. Optionally, the message may be a UE context release command (UECONTEXT RELEASE COMMAND) message, or other messages.

[0193] The message includes at least one of the following information:

[0194] (1) Cell identifier, indicating the identifier of the target cell to which the UE has accessed, which may be CGI, or other cell identifiers.

[0195] Step 318, the source gNB-DU sends a message to the gNB-CU as a response. Optionally, the message may be a UE context release complete (UE CONTEXT RELEASE COMPLETE) message, or other messages.

[0196] Through the above process, the network configuration execution condition is used for conditional LTM switching. When the execution condition is met, the UE actively performs LTM for cell switching without waiting for the network to send a switching command. This can reduce the signaling interaction between the UE and the network, and also avoid the situation of UE switching failure caused by the change of the radio link state during the signaling interaction between the UE and the network, thereby improving the robustness of the switching.

[0197] Example 2: A Method for Obtaining TA Values of Candidate Cells in Advance

[0198] Please refer to Figure 4a , Figure 4a is another schematic diagram of the interaction between a user equipment, a first node, a second node, and a third node according to various embodiments of the present disclosure. Figure 4a The method shown may include one or more of steps S400a to step S417:

[0199] In the second embodiment, if the candidate cell allocates dedicated RACH resources for the UE to obtain the TA value in advance in the candidate cell. The process is shown in Figure 4a , and the specific description is as follows.

[0200] Steps 400a - 411, candidate cell configuration process. The specific process is the same as steps 300a - 311.

[0201] In steps 400a - 411, after the candidate cell configuration is completed, the candidate cell allocates RACH resources for the UE to obtain the TA value in advance, and the network sends the candidate cell information and the allocated RACH resource information to the UE, that is, the information included in step 409 contains the dedicated LTM RACH resource configuration information allocated to the UE, and the dedicated LTM RACH resource is used to obtain the TA value of the candidate cell in advance.

[0202] When the UE decides to trigger the uplink synchronization process with the candidate cell in advance (that is, the process of obtaining the TA value of the candidate cell in advance), it will select the candidate cell and send a dedicated preamble (Preamble code) on the RACH resources allocated by the candidate cell for the uplink synchronization process in advance, or it can be called the uplink synchronization code, or the random access code, or the random access preamble.

[0203] Steps 400a - step 402a are the same as steps 300a - 302a. For the specific description, please refer to the first embodiment and will not be elaborated here.

[0204] Step 402b, the candidate gNB-DU sends a message to the gNB-CU. If the candidate gNB-DU receives the requested LTM configuration, it sends the message for feedback and provides the RRC configuration information of the candidate cell that accepts the request.

[0205] Optionally, the message can be a UE context setup response (UE CONTEXT SETUP RESPONSE), or other messages.

[0206] The message contains at least one of the following information:

[0207] (1) The identification information of the UE in the gNB-CU, which is the identification allocated by the gNB-CU for the UE, can be the gNB-CU UE F1APID, or other identifications, that is, the identification allocated by the gNB-CU for the UE in step 402a.

[0208] (2) The identification information of the UE in the gNB-DU, which is the identification allocated by the candidate gNB-DU for the UE, can be the gNB-DU UEF1AP ID, or other identifications.

[0209] (3) Cell identifier, indicating the candidate cell identifier requested, which is the candidate cell identifier requested in step 402a. The cell identifier may be CGI (Cell Global ID), or other identifiers.

[0210] (4) LTM configuration information, indicating the configuration information of the cell indicated by the cell identifier. It includes at least one of the following information:

[0211] - SSB configuration information, indicating the time and frequency information of the SSB of the cell indicated by the cell identifier. The frequency information is the ARFCN.

[0212] - Physical cell identifier (physical cell ID, PCI), indicating the physical cell identifier of the cell indicated by the cell identifier.

[0213] (5) TCI state configuration list.

[0214] (6) CSI report configuration (CSI reporting configuration).

[0215] (7) First RACH configuration, including the RA resources for the uplink synchronization process in advance configured (or allocated) for the candidate cell.

[0216] (8) Second RACH configuration, including the dedicated RA resources configured (or allocated) to the UE by the candidate cell for the uplink synchronization process in advance.

[0217] (9) Third RACH configuration, including the RA resources for performing RACH-based LTM configured (or allocated) for the candidate cell. When the candidate cell is selected as the target cell, the RA resources used for random access.

[0218] (10) Dedicated uplink resources, the dedicated uplink resources configured (or allocated) for the UE by the candidate cell, that is, configured grant. Used for the UE to perform uplink transmission in the target cell when executing LTM.

[0219] (11) LTM execution condition, the LTM execution condition provided by the candidate cell. Among them, the LTM execution condition is related to layer 1 (Layer1, L1) measurement. When the UE selects the candidate cell as the target cell to access, the UE monitors other candidate cells. According to the L1 measurement results, when one or more cells meet the LTM execution condition, one of them is selected as the new target cell, and the conditional LTM is executed, that is, the cell switch is triggered and access to the new target cell is performed.

[0220] (12) C-RNTI, the C-RNTI value assigned to the UE by the candidate cell, serves as the identifier of the UE in the candidate cell.

[0221] (13) PUCCH resource information, the PUCCH resource information assigned (or configured) to the UE by the candidate cell.

[0222] If the candidate cell belongs to the source gNB-DU, then the configuration of the candidate cell is completed through steps 403a - 403b.

[0223] Steps 403a - 403b are the same as steps 303a - 303b. For the specific description, please refer to Embodiment 1 and will not be elaborated here.

[0224] Steps 404 - 405, the gNB-CU provides all candidate cell information to the source cell (source gNB-DU), and the source cell provides CSI report configuration and LTM execution conditions to the gNB-CU. Steps 404 - 405 are the same as steps 304 - 305. For the specific description, please refer to Embodiment 1 and will not be elaborated here.

[0225] Steps 406 - 408 are the same as steps 306 - 308. For the specific description, please refer to Embodiment 1 and will not be elaborated here.

[0226] Step 409, the source gNB-DU sends a message to the UE.

[0227] Optionally, the message is an RRC reconfiguration (RRCReconfiguration) message or other messages.

[0228] The message contains at least one of the following information:

[0229] (1) Information related to the LTM candidate configuration (LTMcandidate configuration) of one or more LTM candidate cells. The information related to the LTM candidate configuration contains at least one of the following information:

[0230] - LTM candidate identifier (LTM Candidate Id), corresponding to the LTM configuration identifier, associated (or corresponding) with the LTM candidate cell.

[0231] - LTM candidate physical cell identifier (LTM candidate PCI), indicating the physical cell identifier of the candidate cell corresponding (or associated) with the LTM candidate identifier.

[0232] - SSB configuration information of LTM, indicating the time and frequency information of the SSB of the candidate cell corresponding (or associated) with the LTM candidate identifier. The frequency information includes the ARFCN of the SSB, that is, the ARFCN of the candidate cell.

[0233] -LTM candidate configuration information, including cell group configuration information, radio bearer (RB) configuration information, etc.

[0234] -LTM execution conditions, LTM execution conditions provided by the candidate cell.

[0235] -The first LTM RACH resource configuration (ltm Early UL Sync Config), including the RA resources configured (or allocated) by the candidate cell for the early uplink synchronization process. That is, the first RACH configuration received by the gNB-CU in step 402b and / or 403b.

[0236] -The second LTM RACH resource configuration (which can also be called the second resource configuration, or other names, the present invention is not limited thereto) (dedicate ltm Early UL Sync Config), the dedicated RA resources configured (or allocated) by the candidate cell for the UE for the early uplink synchronization process. That is, the second RACH configuration received by the gNB-CU in step 402b and / or 403b.

[0237] -Dedicated uplink resources, dedicated uplink resources configured (or allocated) by the candidate cell for the UE, that is, configured grant. Used for the UE to perform uplink transmission in the target cell when executing LTM.

[0238] -The third RACH resource configuration (which can also be called the third resource configuration, or other names, the present invention is not limited thereto), the RA resources configured (or allocated) by the candidate cell for performing RACH-based LTM. When the candidate cell is selected as the target cell, the RA resources used for random access. That is, the third RACH configuration received by the gNB-CU in step 402b and / or 403b.

[0239] -C-RNTI, the C-RNTI value allocated by the candidate cell for the UE, used as the identifier of the UE in the candidate cell.

[0240] -PUCCH resource information, PUCCH resource information allocated (or configured) by the candidate cell for the UE.

[0241] (2) LTM execution conditions (which can also be referred to as the first LTM execution conditions, or other names, and the present invention is not limited thereto), the execution conditions provided by the source cell. Among them, the LTM execution conditions are related to Layer 1 (L1) measurements. The UE monitors candidate cells, and according to the L1 measurement results, when one or more cells meet the LTM execution conditions, one of them is selected as the target cell, and the LTM of the execution conditions is performed, that is, cell switching is triggered,

[0242] and access the target cell.

[0243] Steps 410 - 411 are the same as steps 310 - 311. For specific descriptions, refer to Embodiment 1 and will not be elaborated here.

[0244] Step 412, the UE sends a preamble (also referred to as the second preamble) to the candidate gNB-DU (candidate cell). The UE uses the dedicated RACH resource (also referred to as the second RA resource) allocated to the UE by the candidate cell to send a preamble (Preamble code) to the candidate cell. The candidate cell is selected by the UE. Optionally, the selection of the candidate cell can be based on the measurement results or other information.

[0245] Step 413, the candidate gNB-DU sends a message to the gNB-CU. The candidate cell detects the Preamble code on the RACH resource used for the uplink synchronization process in advance, and determines the TA value. The candidate gNB-DU can determine the UE corresponding to the TA value according to the received Preamble code and the RACH resource. The candidate gNB-DU sends the TA value to the gNB-CU, and the gNB-CU sends the TA value to the UE through the source gNB-DU.

[0246] Optionally, the message can be a DU-to-CU TA information transfer (DU-CU TA INFORMATION TRANSFER) message or other messages. The message can include one or more TA information. The TA information is the TA information of the candidate cell and includes the TA value of the candidate cell.

[0247] The TA information includes at least one of the following information:

[0248] (1) Candidate cell identifier, the candidate cell identifier where the Preamble code is detected. The candidate cell identifier can be a CGI or other identifiers.

[0249] (2) Preamble index, that is, the random access code index. The index of the Preamble code detected by the candidate cell on the allocated RACH resource used for the uplink synchronization process in advance.

[0250] (3) The Timing Advance (TA) value, which can also be referred to as the TA value. The Timing Advance value is the TA value determined by the candidate cell based on the detected Preamble code.

[0251] (4) The RA-RNTI (which can also be referred to as the third RA-RNTI, or other names, and the present invention is not limited thereto), the RA-RNTI value determined based on the resource-related information of the detected preamble code according to formula (1).

[0252] (5) The gNB-DU identifier (which can also be referred to as the first node identifier information, or other names, and the present invention is not limited thereto), the gNB-DU where the UE to which the TA value belongs is located.

[0253] (6) The UE identifier, which can be the identifier of the UE in the candidate gNB-DU (gNB-DU UE F1AP ID), or the identifier of the UE in the gNB-CU (gNB-CU UEF1AP ID), or the C-RNTI, or other identifiers. Among them,

[0254] - If it is the identifier of the UE in the gNB-CU, it is the identifier assigned by the gNB-CU to the UE during the candidate cell configuration process in step 400. Refer to step 302a.

[0255] - If it is the identifier of the UE in the gNB-DU, it is the identifier assigned by the candidate gNB-DU to the UE during the candidate cell configuration process in step 400. Refer to step 302b.

[0256] - If it is the C-RNTI identifier, it can be the C-RNTI value assigned by the candidate cell to the UE.

[0257] The gNB-CU can determine the identifier of the UE in the source gNB-DU according to the UE identifier. During the candidate cell configuration process in steps 402a - 402b, the gNB-CU can obtain the UE identifier, and thus can be associated with the identifier assigned by the source gNB-DU (source cell) to the UE. The identifier assigned by the source gNB-DU (source cell) to the UE can be the gNB-DU UEF1AP ID of the UE in the source gNB-DU, or the C-RNTI of the UE in the source cell.

[0258] Step 414, the gNB-CU sends a message to the source gNB-DU. The gNB-CU sends the TA information belonging to the source gNB-DU in the TA information obtained in step 413 to the source gNB-DU.

[0259] Optionally, the message may be a CU-to-DU TA information transfer (CU-DU TA INFORMATION TRANSFER) message, or other messages. The message may contain one or more TA information. The multiple TA information may be of the same UE or different UEs.

[0260] The TA information contains at least one of the following information:

[0261] (1) Candidate cell identifier, the candidate cell identifier where the Preamble code is detected. The candidate cell identifier may be a CGI, or other identifiers.

[0262] (2) Timing Advance (TA) value, which may also be referred to as the TA value. The TA value is the TA value determined by the candidate cell based on the detected Preamble code.

[0263] (3) Preamble Index, which is also the random access code index. The index of the Preamble code detected on the candidate cell.

[0264] (4) RA-RNTI (which may also be referred to as the third RA-RNTI, or other names, the present invention is not limited thereto), the RA-RNTI value determined based on formula (1) by detecting the resource-related information of the Preamble code.

[0265] (5) gNB-DU identifier (which may also be referred to as the first node identifier information, or other names, the present invention is not limited thereto), the gNB-DU where the UE to which the TA value belongs is located.

[0266] (6) UE identifier, the UE identifier is the identifier of the UE in the source gNB-DU (serving gNB-DU) (gNB-DU UE F1AP ID), or the C-RNTI in the source cell (serving cell), or other identifiers.

[0267] Step 415, the source gNB-DU sends a message to the UE, sending the TA value of the UE in the candidate cell (contained in the TA information) to the UE. The source gNB-DU sends the TA information received in step 414 that belongs to the same UE to the UE. The TA information is the TA information provided by the candidate cell, that is, the Early TA information of the UE in the candidate cell.

[0268] The message may contain the TA information of one or more candidate cells.

[0269] The TA information contains at least one of the following information:

[0270] (1) LTM configuration identifier, that is, the LTM configuration identifier associated (or corresponding) with the candidate cell. It indicates the LTM configuration identifier corresponding to the candidate cell that detects the Preamble code. The value range of the LTM configuration identifier is 0 - 7. The LTM configuration identifier corresponds to the LTM candidate identifier (LTM Candidate Id).

[0271] (2) Timing Advance (TA) value, which can also be called the TA value. The TA value is the TA value determined by the candidate cell according to the detected Preamble code.

[0272] (3) Random Access Preamble Index, that is, the preamble index or the preamble identifier (Preamble Identifier). It is the index or identifier of the Preamble code detected on the candidate cell.

[0273] (4) RA - RNTI (which can also be called the third RA - RNTI, or other names, the present invention is not limited thereto), the RA - RNTI value determined based on formula (1) by detecting the resource - related information of the preamble code.

[0274] Optionally, the TA information transmission can use the MAC control element (MAC CE), which is included in the MAC PDU and sent to the UE through the PDSCH. Or the TA information is sent to the UE through other messages or methods. The MAC CE for transmitting the TA information can be called the Timing Advance Command for Early TA acquisition MAC CE, or the Early TA command MAC CE, or the candidate TA information MAC CE, or the Random Access Response for Early TA acquisition MAC CE (RAR for Early TA Acquisition MAC CE).

[0275] The MAC PDU is a bit string with a length aligned by bytes (i.e., a multiple of 8 bits). The MAC CE is a bit string with a length aligned by bytes (i.e., a multiple of 8 bits). The MAC sub - header is a bit string with a length aligned by bytes (i.e., a multiple of 8 bits).

[0276] The MAC PDU consists of one or more MAC sub-PDUs. Among them, the MAC sub-PDU contains a MAC sub-header (hereinafter referred to as the sub-header) and a MAC CE, or contains a sub-header and a MAC SDU (the MAC SDU contains the data of the RLC layer). Among them, the lengths of the MAC PDU, the MAC CE, and the MAC sub-header are all bit strings aligned by bytes (i.e., multiples of 8 bits). Figure 4b A MAC PDU structure example is given in. The MAC PDU will be sent to the UE through the PDSCH. Optionally, the timing advance command MAC control unit for obtaining the TA value in advance can be included in the MAC sub-PDU of the MAC PDU and transmitted to the UE. The network will allocate a logical channel identifier (Logical Channel ID, LCID), and by setting the value of the logical channel, it can be used to identify (or indicate) that the MAC CE is a timing advance command MAC control unit for obtaining the TA value in advance. The logical channel identifier will be included in the MAC sub-header.

[0277] Among them, the sub-header contains at least one of the following information:

[0278] - Reservation (R): Reserved bit (Reserved bit);

[0279] - Logical channel identifier: The logical channel identifier of the timing advance command MAC control unit for obtaining the TA value in advance. By setting the value of the logical channel identifier, the MAC CE is identified.

[0280] Figure 4c An example of a timing advance command MAC control unit (Early TA command MAC CE) for obtaining the TA value in advance is given in. The MAC CE contains TA information, and the TA information is the Early TA information. The Early TA command MAC CE contains at least one of the following information:

[0281] - Reservation (R): Reserved bit (Reserved bit).

[0282] - LTM configuration identifier, that is, the LTM configuration identifier associated with (or corresponding to) the candidate cell. Corresponding to the LTM candidate identifier and corresponding to the candidate cell.

[0283] - Timing advance command, which is the TA value of the candidate cell.

[0284] - Random access code index, indicating that the TA value is determined by detecting the random access code.

[0285] -RA-RNTI, the RA-RNTI value determined based on formula (1) by detecting the resource-related information of the random access code.

[0286] The UE receives (or monitors) the Physical Downlink Control Channel (PDCCH). If the received PDCCH is scrambled with the C-RNTI assigned by the source cell to the UE, then the UE obtains radio resource information (or scheduling resource information, or dynamic scheduling information) from the PDCCH and receives the PDSCH for transmitting the MAC PDU from the resource. The UE determines the timing advance command MAC control unit for obtaining the TA value in advance according to the logical channel identifier, so as to obtain the TA value of the candidate cell. The C-RNTI is the C-RNTI assigned by the source cell (serving cell) to the UE and serves as the identifier of the UE in the source cell. When the UE selects a candidate cell as the target cell (that is, the serving cell of the UE) and accesses the target cell, then the C-RNTI is the C-RNTI assigned by the candidate cell to the UE. The C-RNTI assigned by the source cell to the UE is obtained when the UE establishes an RRC connection (RRC connection establishment) with the network through the source cell.

[0287] Step 416, start or restart timer T. After the UE receives the TA information of the candidate cell through step 415, it can determine whether the TA value is sent to itself according to the RA-RNTI and the random access code index. Each candidate cell corresponds to a timer. If it is determined that the TA value is for the candidate cell sent to the UE, then the UE starts or restarts the timer T corresponding to the candidate cell. Before the timer corresponding to the candidate cell expires, the TA value of the candidate cell is considered valid; otherwise, if the timer expires, the TA value of the candidate cell is considered invalid.

[0288] The UE performs candidate cell execution condition evaluation (or monitoring) according to the L1 measurement results. If one or more candidate cells meet the execution conditions, the UE selects one of them as the target cell, executes the condition LTM, performs cell switching, accesses the target cell, and executes step 417. There are three methods for executing the condition LTM, which are respectively referred to in Embodiments Five, Six and Seven.

[0289] In the above method, the network configuration execution condition is used for conditional LTM handover. When the execution condition is met, the UE actively performs LTM for cell switching without waiting for the network to send a handover command. This can reduce the signaling interaction between the UE and the network, and also avoid the situation of UE handover failure caused by changes in the radio link state during the signaling interaction time between the UE and the network, thereby improving the robustness of the handover. Moreover, before performing the conditional LTM, the UE performs an uplink synchronization process with candidate cells (including the target cell) in advance to obtain (or acquire) the TA value of the candidate cells (including the target cell) in advance. This process can also be called the process of acquiring TA (Early TAAcquisition) in advance, or the process of acquiring the TA of candidate cells in advance, or the process of the UE performing uplink synchronization with candidate cells in advance. By performing the uplink synchronization process between the UE and candidate cells in advance, it is avoided that the UE needs to perform uplink synchronization with the target cell during the handover execution process, thereby reducing the handover delay. Therefore, the present invention improves the robustness of LTM handover while reducing the handover delay, improving the performance of the handover, and also reducing the signaling overhead.

[0290] Example 3: Another Method for Obtaining TA Values of Candidate Cells in Advance

[0291] Please refer to Figure 5a , Figure 5a FIG. is a schematic diagram of the interaction of a user equipment, a first node, a second node, and a third node according to various embodiments of the present disclosure. Figure 5a The method shown may include one or more of steps S500a to step S517.

[0292] In the third embodiment, the candidate cell allocates RACH resources for each gNB-DU to enable the UE in each gNB-DU to perform uplink synchronization with the candidate cell in advance, that is, to obtain the TA value in the candidate cell in advance. The process is shown in Figure 5a , and is specifically described as follows.

[0293] Steps 500a-511, candidate cell configuration process. The specific process is basically the same as steps 300a-311.

[0294] In steps 500a-511, after the candidate cell configuration is completed, the candidate cell allocates RACH resources for the gNB-DU where the UE is located to obtain the TA value in advance. The RACH resources are the RACH resources shared by the UE served by the source gNB-DU. The network sends the candidate cell information and the allocated RACH resource information to the UE, that is, the LTM RACH resource configuration information is included in step 509, and the LTM RACH resources are used to obtain the TA value in advance.

[0295] When the UE decides to trigger the uplink synchronization process with a candidate cell (i.e., the process of obtaining the TA value of the candidate cell in advance), it will select the candidate cell and select a preamble code, select from the RACH resources allocated to the candidate cell for the uplink synchronization process in advance, and send the selected preamble code on the selected RACH resource. The UE calculates the RA-RNTI value related to the candidate cell according to the RACH resource information of the selected candidate cell.

[0296] Steps 500a - 502a are the same as steps 300a - 302a. For specific descriptions, refer to Embodiment 1 and will not be elaborated here.

[0297] Step 502b, the candidate gNB-DU sends a message to the gNB-CU. If the candidate gNB-DU has received the requested LTM configuration, it sends the message for feedback, providing the RRC configuration information of the candidate cell that accepts the request.

[0298] Optionally, the message can be a UE context setup response (UE CONTEXT SETUP RESPONSE), or other messages.

[0299] The message contains at least one of the following information:

[0300] (1) The identification information of the UE in the gNB-CU, which is the identification allocated by the gNB-CU for the UE, can be the gNB-CU UE F1APID, or other identifications, that is, the identification allocated by the gNB-CU for the UE in step 502a.

[0301] (2) The identification information of the UE in the gNB-DU, which is the identification allocated by the candidate gNB-DU for the UE, can be the gNB-DU UEF1AP ID, or other identifications.

[0302] (3) The cell identification, indicating the requested candidate cell identification, that is, the candidate cell identification requested in step 502a. The cell identification can be the CGI (Cell Global ID), or other identifications.

[0303] (4) The LTM configuration information, indicating the configuration information of the cell indicated by the cell identification. It contains at least one of the following information:

[0304] - The SSB configuration information, indicating the time and frequency information of the SSB of the cell indicated by the cell identification. The frequency information is the ARFCN.

[0305] - The physical cell identification (physical cell ID, PCI), indicating the physical cell identification of the cell indicated by the cell identification.

[0306] (5) TCI status configuration list.

[0307] (6) RACH configuration information list, including one or more RACH configuration information, and the RACH configuration information includes at least one of the following information:

[0308] - The first RACH configuration, including the RA resources configured (or allocated) by the candidate cell for the uplink synchronization process in advance.

[0309] - gNB-DU ID, the identifier of the candidate gNB-DU, that is, the identifier of the gNB-DU using the RA resources of the first RACH configuration.

[0310] (7) CSI reporting configuration.

[0311] (8) The second RACH configuration, including the candidate cell configuration (or allocation)

[0312] The dedicated RA resources for the UE to perform the uplink synchronization process in advance.

[0313] (9) The third RACH configuration, including the RA resources for performing RACH-based LTM when the candidate cell is selected as the target cell, and the RA resources used for random access when the candidate cell is selected as the target cell.

[0314] (10) Dedicated uplink resources, the dedicated uplink resources configured (or allocated) for the UE by the candidate cell, that is, Configured Grant. Used for the UE to perform uplink transmission in the target cell when performing LTM.

[0315] (11) LTM execution condition, the LTM execution condition provided by the candidate cell. Among them, the LTM execution condition is related to layer 1 (Layer1, L1) measurement. When the UE selects the candidate cell as the target cell for access, the UE monitors the candidate cell. According to the L1 measurement results, when one or more cells meet the LTM execution condition, one of them is selected as the new target cell, and the conditional LTM is executed, that is, the cell swap is triggered and the UE accesses the new target cell.

[0316] (12) C-RNTI, the C-RNTI value allocated for the UE by the candidate cell, used as the identifier of the UE in the candidate cell.

[0317] (13) RNTI, the RNTI value assigned (or configured) for the candidate cell. It is used for the UE to receive the TA information obtained in advance in the target cell after the candidate cell becomes the target cell (serving cell). Optionally, the RNTI may be a dedicated RA-RNTI

[0318] (Random Access RNTI, random access RNTI), or other RNTIs.

[0319] (14) PUCCH resource information, the PUCCH resource information assigned (or configured) for the UE by the candidate cell.

[0320] If the candidate cell belongs to the source gNB-DU, the configuration of the candidate cell is completed through steps 503a - 503b.

[0321] Steps 503a - 503b are the same as steps 303a - 303b. For the specific description, refer to Embodiment 1 and will not be elaborated here.

[0322] Steps 504 - 505, the gNB-CU provides all candidate cell information to the source cell (source gNB-DU), and the source cell provides the CSI report configuration and LTM execution conditions to the gNB-CU. Steps 504 - 505 are the same as steps 304 - 305. For the specific description, refer to Embodiment 1 and will not be elaborated here.

[0323] Steps 506 - 508 are the same as steps 306 - 308. For the specific description, refer to Embodiment 1 and will not be elaborated here.

[0324] Step 509, the source gNB-DU sends a message to the UE.

[0325] Optionally, the message is an RRC reconfiguration (RRCReconfiguration) message, or other messages.

[0326] The message contains at least one of the following information:

[0327] (1) Information related to the LTM candidate configuration (LTMcandidate configuration) of one or more LTM candidate cells. The information related to the LTM candidate configuration contains at least one of the following information:

[0328] - LTM candidate identifier (LTM Candidate Id), corresponding to the LTM configuration identifier and associated (or corresponding) with the LTM candidate cell.

[0329] - LTM candidate physical cell identifier (LTM candidate PCI), indicating the physical cell identifier of the candidate cell corresponding to (or associated with) the LTM candidate identifier.

[0330] - LTM's SSB configuration information, indicating the time and frequency information of the SSB of the candidate cell corresponding to (or associated with) the LTM candidate identifier. The frequency information includes the ARFCN of the SSB, which is also the ARFCN of the candidate cell.

[0331] - LTM candidate configuration information, including cell group (Cell Group) configuration information, radio bearer (RadioBearer, RB) configuration information, etc.

[0332] - First LTM RACH resource configuration (ltm-EarlyUL-SyncConfig) (which can also be called the first resource configuration, or other names, and the present invention is not limited thereto), including the RA resources configured (or allocated) for the candidate cell for the early uplink synchronization process. That is, the first RACH configuration received by the gNB-CU in steps 502b and / or 503b.

[0333] - LTM execution condition (which can also be called the second LTM execution condition, or other names, and the present invention is not limited thereto), the LTM execution condition provided by the candidate cell.

[0334] - Dedicated uplink resource, the dedicated uplink resource configured (or allocated) for the UE by the candidate cell, which is the configured grant. It is used for the UE to perform uplink transmission in the target cell when executing LTM.

[0335] - Third RACH resource configuration (which can also be called the third resource configuration, or other names, and the present invention is not limited thereto), including the RA resources configured (or allocated) for the candidate cell for performing RACH-based LTM. When the candidate cell is selected as the target cell, the RA resources used for random access. That is, the third RACH configuration received by the gNB-CU in steps 502b and / or 503b.

[0336] - RNTI, the RNTI value allocated (or configured) for the candidate cell. After the candidate cell becomes the target cell (serving cell), the UE uses this RNTI to receive the TA information in advance in the target cell. Optionally, the RNTI can be a dedicated RA-RNTI

[0337] (Random Access RNTI, random access RNTI) (which may also be referred to as the second RA-RNTI, or other names, the present invention is not limited thereto), or other RNTIs.

[0338] -PUCCH resource information, the PUCCH resource information allocated (or configured) by the candidate cell for the UE.

[0339] (2) LTM execution condition (which may also be referred to as the first LTM execution condition, or other names, the present invention is not limited thereto), the execution condition provided by the source cell. Among them, the LTM execution condition is related to layer 1 (Layer1, L1) measurement. The UE monitors the candidate cells. According to the L1 measurement results, when one or more cells meet the LTM execution condition, one of them is selected as the target cell, and the LTM is executed, that is, the cell handover is triggered and access to the target cell is performed.

[0340] (3) RNTI, the RNTI value allocated (or configured) by the source cell. It is used for the UE to receive the RA-RNTI for obtaining the TA information in advance on the source cell. Optionally, the RNTI may be a dedicated RA-RNTI (Random Access RNTI, random access RNTI) (which may also be referred to as the first RA-RNTI, or other names, the present invention is not limited thereto), or other RNTIs.

[0341] Steps 510 - 511 are the same as steps 310 - 311. For the specific description, refer to Embodiment 1 and will not be elaborated here.

[0342] Step 512a, select a candidate cell. When the UE decides to trigger the uplink synchronization process with the candidate cell, it will select a candidate cell, and select a RACH resource (also referred to as the first RA resource) and a preamble (Preamble code, also referred to as the first preamble).

[0343] Step 512, the UE sends a preamble to the candidate cell.

[0344] Step 513, the candidate gNB-DU sends a message to the gNB-CU. The candidate cell detects a Preamble on the RACH resource for the early uplink synchronization process and determines the TA value. Since in step 502b, the candidate cell of the candidate gNB-DU sent its RACH resource information to other gNB-DUs for the UEs under other gNB-DUs to obtain the TA value of the candidate cell in advance. Optionally, the RACH resources provided to other gNB-DUs are different. Therefore, the candidate gNB-DU can determine the serving gNB-DU of the UE to which the detected TA value belongs (that is, the gNB-DU to which the serving cell of the UE belongs) based on the detected Preamble code and the RACH resource. The candidate gNB-DU sends the TA value to the gNB-CU, which forwards it to the corresponding gNB-DU.

[0345] Optionally, the message can be a DU-to-CU TA information transfer (DU-CU TA INFORMATION TRANSFER) message or other messages. The message can contain one or more TA information.

[0346] The TA information contains at least one of the following information:

[0347] (1) Candidate cell identifier, the identifier of the candidate cell where the Preamble code is detected. The candidate cell identifier can be CGI or other identifiers.

[0348] (2) Preamble Index, that is, the random access code index. The index of the Preamble code detected by the candidate cell on the allocated RACH resource for the early uplink synchronization process.

[0349] (3) Timing Advance (TA) value, which can also be called the TA value. The TA value is the TA value determined by the candidate cell according to the detected Preamle code.

[0350] (4) RA-RNTI (which can also be called the third RA-RNTI or other names, and the present invention is not limited thereto). The RA-RNTI value determined by the candidate cell based on formula (1) through the resource-related information of the detected preamble.

[0351] (5) gNB-DU identifier (which can also be called the first node identifier information or other names, and the present invention is not limited thereto), the gNB-DU where the UE to which the TA value belongs is located.

[0352] If the candidate gNB-DU determines that the serving gNB-DU of the UE is the source gNB-DU,

[0353] Then the gNB-DU is the identifier of the source gNB-DU.

[0354] Based on the gNB-DU identifier, the gNB-CU can determine which gNB-DU to send the received TA information to.

[0355] Step 514, the gNB-CU sends a message to the source gNB-DU.

[0356] If the gNB-DU identifier in step 513 is the source gNB-DU identifier, then the gNB-CU sends the corresponding TA information to the source gNB-DU.

[0357] Optionally, the message can be a CU-to-DU TA information transfer (CU-DU TA INFORMATION TRANSFER) message, or other messages. The message can contain one or more TA information. The TA information may be for the same UE or different UEs.

[0358] The TA information contains at least one of the following information:

[0359] (1) Candidate cell identifier, the candidate cell identifier where the Preamble code is detected. The candidate cell identifier can be CGI, or PCI, or other identifiers.

[0360] (2) Timing Advance (TA) value, which can also be referred to as the TA value. The TA value is the TA value determined by the candidate cell based on the detected Preamble code.

[0361] (3) Preamble Index, which is also the random access code index. The index of the Preamble code detected on the candidate cell.

[0362] (4) RA-RNTI (which can also be referred to as the third RA-RNTI, or other names, and the present invention is not limited thereto), the RA-RNTI value determined by the candidate cell based on formula (1) through the resource-related information of the detected Preamble code.

[0363] Step 515, the source gNB-DU sends a message to the UE. The source gNB-DU sends the TA information received in step 514 to the UE. The TA information is the TA information provided by the candidate cell, that is, the Early TA information determined on the candidate cell. Since the UE has selected RACH resources to perform uplink synchronization with the candidate cell in advance, the source gNB-DU cannot determine which UE the TA information obtained from step 514 belongs to. Therefore, the TA information of the received candidate cell is sent to all UEs in the cell and sent to the UE in the manner of common information, for example, broadcast or multicast.

[0364] Optionally, the message can be a MAC PDU, which is sent to the UE through PDSCH, or sent to the UE through other messages or methods. The TA information of the candidate cell can be included in the MAC PDU. The MAC PDU can be called a MAC PDU for Early Timing Advanced Command (MAC PDU for Early Timing Advanced Command), or a MAC PDU for obtaining Early TA information or a MAC PDU for obtaining TA information in advance (MAC PDU for Ealry TA acquisition), or a MAC PDU of the candidate cell TA information (MAC PDU TA information of candidate cell).

[0365] The MAC PDU is sent to the UE through PDSCH. The resources used to send the PDSCH are included in the PDCCH sent by the source cell to the UE. The PDCCH is scrambled with the RNTI allocated by the source cell or scrambled with the RA-RNTI received from step 514, so as to indicate that the resources in the PDCCH received by the UE are for transmitting the MAC PDU of the Early Timing Advanced Command. Among them:

[0366] - If the RNTI value allocated by the source cell is included in step 509, the UE monitors the PDCCH. If the received PDCCH is scrambled with the said RNTI, then the scheduling resource (or radio resource) information obtained by the UE from the PDCCH is used to receive the PDSCH from the said resource. The MAC PDU (or the MAC PDU of the candidate cell TA information) with the timing advance command obtained in advance is transmitted on the PDSCH. Among them, the RNTI allocated by the source cell is the MAC PDU for the candidate cell TA information, or is related (or corresponding) to the MAC PDU of the candidate cell TA information. When the candidate cell becomes the target cell (serving cell), the RNTI allocated by the candidate cell is the MAC PDU for the candidate cell TA information, or is related (or corresponding) to the MAC PDU of the candidate cell TA information.

[0367] - If the RNTI value allocated by the source cell is not included in step 509, then the UE calculates the RA-RNTI based on the resource information of the Preamble sent. Optionally, the RA-RNTI value can be calculated according to formula (1). If the received PDCCH is scrambled with the calculated RA-RNTI, then the UE receives the PDSCH from the scheduling resource obtained from the PDCCH. The MAC PDU (or the MAC PDU of the candidate cell TA information) with the timing advance command obtained in advance is transmitted on the PDSCH.

[0368] RA-RNTI = 1 + s_id + 14×t_id + 14×80×f_id + 14×80×8×ul_carrier_id Formula (1)

[0369] Among them,

[0370] - s_id: Indicates the PRACH occasion, or the index of the first OFDM symbol of the PRACH opportunity;

[0371] - t_id: Indicates the index of the first time slot of the PRACH occasion in a system frame;

[0372] - f_id: Indicates the index of the PRACH occasion in the frequency domain;

[0373] - ul_carrier_id: Indicates the uplink carrier identifier for transmitting the random access code (preamble).

[0374] The MAC PDU with the timing advance command obtained in advance may contain the TA information of one or more candidate cells.

[0375] The TA information includes at least one of the following information:

[0376] (1) Candidate cell identifier, the candidate cell identifier where the Preamble code is detected, and the candidate cell identifier may be a CGI or other identifier.

[0377] (2) Timing Advance (TA) value, which can also be referred to as the TA value. The TA value is the TA value determined by the candidate cell based on the detected Preamble code.

[0378] (3) Random Access Preamble Index, which is the preamble index or the preamble identifier (Preamble Identifier). The index or identifier of the Preamble code detected on the candidate cell.

[0379] (4) RA-RNTI, the RA-RNTI value determined by the candidate cell based on formula (1) by detecting information such as the resources of the random access code.

[0380] (5) RACH resource information, the RACH resource information for the candidate cell to determine the TA value by detecting the Preamble code.

[0381] Among them, the UE can determine whether the TA value included in the TA information is the TA value sent to itself according to the RA-RNTI and the random access code index included in the TA information.

[0382] The UE calculates the RA-RNTI based on formula (1) according to the resource-related information of the preamble sent to the candidate cell. If the RA-RNTI value included in the TA information is equal to the RA-RNTI value calculated by the UE, and the random access code index included in the TA information is the same as the random access code index sent by the UE. Then the TA value included in the TA information is the TA value sent to the UE. The TA value is the TA value of the candidate cell (the candidate cell corresponding to the candidate cell identifier).

[0383] Figure 5b An example of a MAC PDU for obtaining a timing advance command in advance (including one or more TA information) is given. Among them, the MAC PDU includes one or more MAC sub-PDUs (MAC subPDU) and / or one padding. Each MAC sub-PDU includes a MAC sub-header (or MAC sub-header) and a TA command.

[0384] Among them, the sub-header includes at least one of the following information:

[0385] - E: Extension field. It is used to indicate whether the MAC sub-PDU containing this MAC sub-header (or sub-header) is the last MAC sub-PDU in the MAC PDU. The E field is set to 1, indicating that there is at least one more MAC sub-PDU later. The E field is set to 0, indicating that the MAC sub-PDU containing this MAC sub-header is the last MAC sub-PDU in the MAC PDU.

[0386] - Reserved (R): Reserved bit.

[0387] - Random access code index: The index or identifier of the Preamble code detected on the candidate cell.

[0388] The TA command contains TA information, and the TA information includes at least one of the following information:

[0389] - Reserved (R): Reserved bit.

[0390] - Candidate cell identifier. The cell identifier can be PCI, or CGI (Cell Global ID), or other identifiers.

[0391] - Timing advance command, which is the TA value of the candidate cell.

[0392] - RA-RNTI, the RA-RNTI value determined based on the resource-related information of the detected preamble according to formula (1).

[0393] Figure 5c An example of a TA command is given. The candidate cell identifier uses PCI.

[0394] Step 516, the UE starts or restarts timer T. Each candidate cell corresponds to a timer. After receiving the TA information of the candidate cell through step 515, the UE starts or restarts the timer T corresponding to the candidate cell. Before the timer corresponding to the candidate cell expires, the TA value of the candidate cell is considered valid. Otherwise, if the timer expires, the TA value of the candidate cell is considered invalid.

[0395] The UE evaluates (or monitors) the LTM execution conditions based on the L1 measurement results. If one or more candidate cells meet the execution conditions, the UE selects one of them as the target cell, executes conditional LTM, performs cell switching, accesses the target cell, and executes step 517. There are three methods for executing conditional LTM, which are respectively referred to in Embodiments Five, Six and Seven.

[0396] In the above method, the network configuration execution condition is used for conditional LTM handover. When the execution condition is met, the UE actively performs LTM for cell switching without waiting for the network to send a handover command. This can reduce the signaling interaction between the UE and the network and also avoid the situation of UE handover failure caused by changes in the radio link state during the time of signaling interaction between the UE and the network, thereby improving the robustness of the handover. Moreover, before executing the conditional LTM, the UE performs an uplink synchronization process with candidate cells (including the target cell) in advance to obtain (or acquire) the TA value of the candidate cells (including the target cell) in advance (which can also be referred to as obtaining the TA value in advance). This process can also be called the process of obtaining (or acquiring) TA (Early TAAcquisition), or the process of obtaining the TA of candidate cells in advance, or the process of the UE performing uplink synchronization with candidate cells in advance. By performing the uplink synchronization process between the UE and candidate cells in advance, it is avoided that the UE needs to perform uplink synchronization with the target cell during the handover execution process, thereby reducing the handover latency. Therefore, the present invention improves the robustness of LTM handover, reduces the handover latency, improves the performance of the handover, and also reduces the signaling overhead.

[0397] Example 4: Another Method for Obtaining TA Values of Candidate Cells in Advance

[0398] Please refer to Figure 6 , Figure 6 which is a schematic diagram of the interaction between another user equipment, a first node, a second node, and a third node according to various embodiments of the present disclosure. Figure 6 The method shown may include one or more of steps S600 to step S609.

[0399] Step 600, candidate cell configuration process. The specific process is the same as steps 500a - 511 and will not be elaborated here.

[0400] Step 601, the UE sends a message (which can also be referred to as the first message, or other names, and the present invention is not limited thereto) to the source gNB-DU. Optionally, the message may include L1 measurement results. Through the measurement results, the source cell can determine the candidate cells selected by the UE for uplink synchronization in advance. The message may also include candidate cell identifiers for directly indicating the candidate cells selected by the UE for uplink synchronization in advance. The candidate cell identifier may be the LTM configuration identifier corresponding to the candidate cell, or the LTM candidate identifier, or the CGI, or the PCI, or other cell identifiers. The message may be sent through PUCCH or sent through MAC CE on PUSCH.

[0401] Step 602: The source gNB-DU decides to trigger the UE and the candidate cell to perform uplink synchronization in advance. Among them, the source gNB-DU selects a candidate cell for the UE to perform uplink synchronization in advance. Optionally, the selection of the candidate cell can be based on the L1 measurement result obtained in step 601 or the candidate cell identifier.

[0402] Step 603: The source gNB-DU sends a physical layer signaling (which can also be called the second message or other names, and this invention is not limited thereto) to the UE, instructing the UE to send a Preamble code to the candidate cell or instructing the UE to perform an uplink synchronization process with the candidate cell in advance. Optionally, the physical layer signaling can be a PDCCH order or other signaling.

[0403] The signaling contains at least one of the following information:

[0404] (1) LTM candidate identifier, corresponding to the LTM configuration identifier and associated with (or corresponding to) the LTM candidate cell;

[0405] (2) RACH configuration information, which contains the resource information for the UE to send a preamble (Preamble code) to the candidate cell, that is, the RA resource (or RACH resource, which can also be called the fourth RA resource) related information. The RACH configuration information contains at least one of the following information:

[0406] - SS / PBCH index, indicating the SS / PBCH for determining the RACH occasion for PRACH transmission.

[0407] - PRACH mask index, indicating the RACH occasion related to the SS / PBCH for PRACH transmission, and the SS / PBCH is the SS / PBCH indicated by the SS / PBCH index.

[0408] (3) Preamble code index, indicating the index of the preamble that the UE sends on the resources included in the RACH configuration information.

[0409] Step 604: The UE sends a Preamble code (which can also be called the fourth preamble) to the candidate gNB-DU (candidate cell). The UE determines the resource for sending the Preamble according to the RACH configuration information received in step 603 and the first RACH configuration information allocated by the candidate cell obtained in step 600. The sent Preamble code is the Preamble code received in step 603.

[0410] Step 605 is the same as step 513. The candidate gNB-DU sends a message to the gNB-CU. The candidate cell detects a Preamble on the RACH resource for the uplink synchronization process in advance and determines the TA value. Since in step 502b, the candidate cell of the candidate gNB-DU sent its RACH resource information to other gNB-DUs for the UEs under other gNB-DUs to obtain the TA value of the candidate cell in advance. Optionally, the RACH resources provided to other gNB-DUs are different. Therefore, the candidate gNB-DU can determine the serving gNB-DU of the UE to which the detected TA value belongs (i.e., the gNB-DU to which the serving cell of the UE belongs) based on the detected Preamble code and the RACH resource. The candidate gNB-DU sends the TA value to the gNB-CU and forwards it to the corresponding gNB-DU through the gNB-CU.

[0411] Optionally, the message can be a DU-to-CU TA information transfer (DU-CU TA INFORMATION TRANSFER) message or other messages. The message can contain one or more TA information.

[0412] The TA information contains at least one of the following information:

[0413] (1) Candidate cell identifier, the identifier of the candidate cell where the Preamble code is detected. The candidate cell identifier can be a CGI or other identifiers.

[0414] (2) Timing Advance (TA) value, which can also be referred to as the TA value. The TA value is the TA value determined by the candidate cell based on the detected Preamble code.

[0415] (3) Preamble Index, which is the random access code index. The index of the Preamble code detected on the candidate cell.

[0416] (4) RA-RNTI, the RA-RNTI value determined based on formula (1) through the resource-related information of the detected Preamble code.

[0417] (5) gNB-DU identifier, the gNB-DU where the UE to which the TA value belongs is located.

[0418] If the candidate gNB-DU determines that the serving gNB-DU of the UE is the source gNB-DU,

[0419] then the identifier of the gNB-DU is the identifier of the source gNB-DU.

[0420] Based on the gNB-DU identifier, the gNB-CU can determine which gNB-DU to send the received TA information to.

[0421] Step 606 is the same as step 514, and the gNB-CU sends a message to the source gNB-DU.

[0422] If the gNB-DU identifier in step 605 is the source gNB-DU identifier, then the gNB-CU sends the corresponding TA information to the source gNB-DU.

[0423] Optionally, the message can be a CU-to-DU TA information transfer (CU-DU TA INFORMATION TRANSFER) message, or other messages. The message can contain one or more TA information. The TA information may be for the same UE or different UEs.

[0424] The TA information contains at least one of the following information:

[0425] (1) Candidate cell identifier, the candidate cell identifier where the Preamble code is detected. The candidate cell identifier can be CGI, or PCI, or other identifiers.

[0426] (2) Timing Advance (TA) value.

[0427] (3) Preamble index (i.e., Preamble Index), which is the random access code index. The index of the Preamble code detected on the candidate cell.

[0428] (4) RA-RNTI, the RA-RNTI value determined based on formula (1) by detecting the resource-related information of the Preamble code.

[0429] Step 607, the source gNB-DU sends a message to the UE, sending the TA value of the UE in the candidate cell received in step 606 to the UE.

[0430] The message may contain one or more TA information of the candidate cell.

[0431] For the content of the TA information, the content and manner of the message, please refer to step 415 specifically, which will not be elaborated here.

[0432] Steps 608 - 609 are the same as steps 416 - 417. For the specific description, please refer to steps 416 - 417, which will not be elaborated here.

[0433] The UE evaluates (or monitors) the execution conditions of candidate cells based on L1 measurement results. If one or more candidate cells meet the execution conditions, the UE selects one of them as the target cell, executes conditional LTM, and performs cell handover. In conditional LTM, the target cell is selected by the UE from the candidate cells that meet the execution conditions.

[0434] (1) If the UE has a valid TA value in the target cell, then RACH-less conditional LTM will be executed.

[0435] (2) If the UE does not have a valid TA value in the target cell, then RACH-based conditional LTM will be executed. If the network configures dedicated RACH resources for the UE, then the CFRA process will be executed; otherwise, the CBRA process will be executed.

[0436] In the above method, the execution conditions are configured by the network for conditional LTM handover. When the execution conditions are met, the UE actively executes LTM for cell handover without waiting for the network to send a handover command. This can reduce the signaling interaction between the UE and the network and also avoid the situation of UE handover failure caused by changes in the radio link state during the signaling interaction time between the UE and the network, thus improving the robustness of the handover. Moreover, before executing conditional LTM, the UE performs an uplink synchronization process with the candidate cells (including the target cell) in advance, obtains (or acquires) the TA value of the candidate cells (including the target cell) in advance (which can also be called obtaining the TA value in advance), and this process can also be called the process of obtaining TA (Early TAAcquisition) in advance, or the process of obtaining the TA of candidate cells in advance, or the process of the UE performing uplink synchronization with candidate cells in advance. By performing the uplink synchronization process between the UE and the candidate cells in advance, it is avoided that the UE needs to perform uplink synchronization with the target cell during the handover execution process, thus reducing the handover delay. Therefore, the present invention improves the robustness of LTM handover while reducing the handover delay, improving the performance of the handover, and also reducing the signaling overhead.

[0437] Embodiments Five, Six, and Seven respectively give three methods for executing conditional LTM to achieve the detection of the UE's access by the target cell. For specific descriptions, refer to Embodiments Five, Six, and Seven.

[0438] Example 5: A Method for Executing Conditional LTM

[0439] Please refer to Figure 7 , Figure 7 which is an interaction schematic diagram of a method for executing conditional LTM according to various embodiments of the present disclosure. Figure 7 The method shown may include one or more of steps S701 to step S703:

[0440] Step 701, the UE sends uplink data to the target gNB-DU (target cell).

[0441] If the UE has a valid TA value in the target cell, then RACH-less conditional LTM will be performed. If the network configures dedicated uplink resources for the UE in the target cell, that is, configures a configured grant for the UE, then the UE uses the TA value to send uplink data to the target gNB-DU (target cell) on the configured grant. Then the uplink data can be an RRC reconfiguration complete (RRCReconfigurationComplete) message, or other uplink data. Among them, the uplink transmission beam used by the UE to send uplink data is determined by measurement.

[0442] Step 702, the target gNB-DU (target cell) sends a message to the UE. The target cell determines the downlink transmission beam according to the UE's uplink transmission beam, and uses the downlink transmission beam to send a message to the UE. The message is transmitted through PDCCH, which contains dynamic scheduling information and / or ACK feedback for the uplink data. At the same time, the target cell considers that the UE has accessed the target cell through conditional LTM, and sends a message to the gNB-CU, that is, step 703.

[0443] After the UE receives the message sent by the target cell, it considers that the conditional LTM has been successfully executed, that is, the UE has successfully accessed the target cell.

[0444] Step 703, the target gNB-DU sends a message to the gNB-CU. When the target gNB-DU considers that the conditional LTM has been successfully executed, it uses the message to indicate to the gNB-CU that the UE has successfully accessed the target cell.

[0445] Optionally, the message can be an access success (ACCESS SUCCESS) message, or other messages. The message contains at least one of the following information:

[0446] (1) Cell identifier, indicating the identifier of the target cell, which can be CGI, or other cell identifiers.

[0447] If there are candidate cells that meet the execution conditions and the TA value of the target cell selected by the UE is valid, the UE can directly send uplink data (or messages) to the target cell and perform conditional LTM. When the target cell receives the uplink data (or messages) of the UE and determines that the UE has switched to the target cell, it can send resource scheduling information to the UE for data transmission, reducing the UE's handover delay and the data transmission interruption time at the same time.

[0448] Example 6: A Method for Executing Conditional LTM

[0449] Please refer to Figure 8 , Figure 8 which is an interaction diagram of a method for executing conditional LTM according to various embodiments of the present disclosure. Figure 8 The method shown may include one or more of steps S801 to S804:

[0450] Step 801, the UE sends a message to the target gNB-DU (target cell).

[0451] If the UE has a valid TA value in the target cell, then RACH-less conditional LTM will be executed. If the network does not configure dedicated uplink resources for the UE in the target cell but configures PUCCH resources for the UE, then the UE uses the TA value to send a scheduling request (SR) to the target gNB-DU (target cell) on the PUCCH resource, requesting the target cell to provide uplink resources for the UE to perform uplink transmission. Among them, the uplink transmission beam used by the UE to send the message for uplink transmission is determined by measurement.

[0452] Step 802, the target gNB-DU (target cell) sends a message to the UE.

[0453] The target cell determines the downlink transmission beam according to the uplink transmission beam of the UE, and uses the downlink transmission beam to send a message to the UE. The message is transmitted through PDCCH and contains dynamic scheduling information. When the UE receives the message, it means that the uplink transmission in step 801 is successful. Optionally, it can be considered that the conditional LTM execution is successful.

[0454] Step 803, the UE sends a message to the target gNB-DU (target cell).

[0455] The UE uses the resources provided in the dynamic scheduling information received in step 802 to send a message to the target cell. Optionally, the message can be an RRC reconfiguration complete (RRCReconfigurationComplete) message or other messages.

[0456] Step 804, the target gNB-DU sends a message to the gNB-CU. When the target gNB-DU considers that the conditional LTM execution is successful, it uses the message to indicate to the gNB-CU that the UE has successfully accessed the target cell.

[0457] Optionally, the message may be an ACCESS SUCCESS message or other messages. The message contains at least one of the following information:

[0458] (1) Cell identifier, indicating the identifier of the target cell, which may be CGI or other cell identifier.

[0459] Optionally, steps 802 and 804 do not have a strict order requirement.

[0460] If there is a candidate cell meeting the execution condition and the TA value of the target cell selected by the UE is valid, the UE can directly send a message to the target cell to execute the condition LTM. When the target cell receives the message sent by the UE and determines that the UE has switched to the target cell, it can send resource scheduling information to the UE for data transmission, reducing the UE switching delay and the data transmission interruption time at the same time.

[0461] Example 7: A Method for Executing Conditional LTM

[0462] Please refer to Figure 9 , Figure 9 which is an interaction schematic diagram of a method for executing conditional LTM according to various embodiments of the present disclosure. Figure 9 The method shown may include one or more of steps S901 to S907:

[0463] In the seventh embodiment, the UE sends the selected target cell information to the target cell (target gNB-DU) through the source cell (source gNB-DU). For the specific process, see Figure 9 . Among them:

[0464] Step 901, the UE sends a message to the source gNB-DU (source cell), indicating that the UE has selected a target cell and is ready to execute LTM and the selected target cell information.

[0465] Optionally, the target cell information may be transmitted through MAC CE. The MAC CE may be referred to as LTM CELL SWITCH MAC CE. The MAC CE contains at least one of the following information:

[0466] (1) Target cell identifier, which may be the LTM configuration identifier corresponding to the target cell, or the LTM candidate identifier corresponding to the target cell, or other identifiers.

[0467] (2) TCI status identifier, and the TCI status is determined by the UE according to the measurement result.

[0468] Step 902, the source gNB-DU sends a message to the gNB-CU, indicating to the gNB-CU that the UE has selected the target cell and conditional LTM will be performed.

[0469] Optionally, the message may be a DU-to-CU cell switch notification (DU-CU CELL SWITCH NOTIFICATION) message or other message. The message contains at least one of the following information:

[0470] (1) Target cell identifier, indicating the identifier of the target cell selected by the UE. The cell identifier may be CGI or other identifier.

[0471] (2) TCI state identifier, where the TCI state is determined by the UE based on measurement results.

[0472] Step 903, the gNB-CU sends a message to the target gNB-DU, indicating to the target gNB-DU that the UE has selected the target cell and conditional LTM will be performed.

[0473] Optionally, the message may be a CU-to-DU cell switch notification (CU-DU CELL SWITCH NOTIFICATION) message or other message. The message contains at least one of the following information:

[0474] (1) Target cell identifier, indicating the identifier of the target cell selected by the UE. The cell identifier may be CGI, or the LTM configuration identifier corresponding to the target cell, or other identifier.

[0475] (2) TCI state identifier, where the TCI state is determined by the UE based on measurement results.

[0476] If the UE does not have a valid TA value in the target cell, the UE performs RACH-based conditional LTM.

[0477] If the UE has a valid TA value in the target cell, then RACH-less conditional LTM will be performed.

[0478] - If the network configures dedicated uplink resources for the UE in the target cell, that is, configures authorized grant (ConfiguredGrant) for the UE, then the UE uses the TA value to send uplink data to the target gNB-DU (target cell) on the configured grant. That is, directly execute step 905.

[0479] - If the network does not configure dedicated uplink resources for the UE in the target cell, then the UE monitors PDCCH in the target cell. That is, execute steps 904 and 905.

[0480] Step 904, the target gNB-DU (target cell) sends a message to the UE.

[0481] The target cell determines the downlink transmission beam according to the TCI state identifier received in step 903, and uses the downlink transmission beam to send a message to the UE. The message is transmitted through PDCCH, which contains dynamic scheduling information (or resource scheduling information) and provides dynamic resource information. The UE receives (monitors) the PDCCH in the target cell to receive the dynamic scheduling information, and performs uplink transmission on the resources included in the scheduling information.

[0482] Step 905, the UE sends a message to the target gNB-DU (target cell). The UE uses Configured Grant or dynamically scheduled resources to send the message, that is, to perform uplink transmission.

[0483] Optionally, the message can be an RRC Reconfiguration Complete message, or other messages.

[0484] Step 906, the target gNB-DU (target cell) sends a message to the UE. The message is transmitted through PDCCH, which contains dynamic scheduling information (or resource scheduling information) and provides dynamic resources for the UE to perform data transmission. When the UE receives the message, it considers that the condition LTM is successfully executed, that is, the UE successfully accesses the target cell.

[0485] Step 907, the target gNB-DU sends a message to the gNB-CU. When the target gNB-DU considers that the condition LTM is successfully executed, it uses the message to indicate to the gNB-CU that the UE has successfully accessed the target cell.

[0486] Optionally, the message can be an ACCESS SUCCESS message, or other messages. The message contains at least one of the following information:

[0487] (1) Cell identifier, indicating the identifier of the target cell, which can be CGI, or other cell identifiers.

[0488] Among them, optionally, steps 906 and 907 do not have a strict order requirement.

[0489] If there is a candidate cell that meets the execution condition and the TA value of the target cell selected by the UE is valid, the UE executes conditional LTM and receives the scheduling information (resource information) sent by the target cell. When the target cell receives the uplink transmission sent by the UE on the said resource and determines that the UE has switched to the target cell, it can continue to send resource scheduling information to the UE for data transmission, reducing the UE handover delay and the data transmission interruption time at the same time.

[0490] In addition, it can be understood that the content included in each message in the above embodiments is only an example of the present disclosure. The content included in various similar or identical messages can be replaced with each other according to the situation, or named differently, or some items can be added or deleted. And for the sake of brevity, the meanings between similar content items can be mutually explained according to the context and will not be elaborated. The embodiments after modification and explanation still fall within the scope of protection of the present invention.

[0491] Figure 10 is a block diagram showing the structure of a user equipment 1000 according to an embodiment of the present disclosure.

[0492] Reference Figure 10 , the user equipment 1000 includes a transceiver 1001 and a controller 1002. The transceiver 1001 is configured to send signals to the outside and receive signals from the outside. The controller 1002 is configured to execute the method performed by the user equipment as described above. The user equipment 1000 can be implemented in the form of hardware, software, or a combination of hardware and software, so that it can execute the method performed by the user equipment described in the present disclosure.

[0493] Figure 11 is a block diagram showing the structure of a first node 1100 according to an embodiment of the present disclosure.

[0494] Reference Figure 8 , the first node 1100 includes a transceiver 1101 and a controller 1102. The transceiver 1101 is configured to send signals to the outside and receive signals from the outside. The controller 1102 is configured to execute the method performed by the first node. The first node 1100 can be implemented in the form of hardware, software, or a combination of hardware and software, so that it can execute the method performed by the first node described in the present disclosure.

[0495] Figure 12 is a block diagram showing the structure of a second node 1200 according to an embodiment of the present disclosure.

[0496] Reference Figure 12, the second node 1200 includes a transceiver 1201 and a controller 1202. The transceiver 1201 is configured to send signals to the outside and receive signals from the outside. The controller 1202 is configured to execute the method performed by the second node. The second node 1200 can be implemented in the form of hardware, software, or a combination of hardware and software so that it can execute the method performed by the second node described in this disclosure.

[0497] Figure 13 is a block diagram showing the structure of a third node 1300 according to an embodiment of the present disclosure.

[0498] Refer to Figure 13 , the third node 1300 includes a transceiver 1301 and a controller 1302. The transceiver 1301 is configured to send signals to the outside and receive signals from the outside. The controller 1302 is configured to execute the method performed by the third node. The third node 1300 can be implemented in the form of hardware, software, or a combination of hardware and software so that it can execute the method performed by the third node described in this disclosure.

[0499] 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 run by a computer is stored.

[0500] Various embodiments of the present disclosure can be implemented as computer-readable code specifically implemented 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 can include read-only memory (ROM), random access memory (RAM), compact disc read-only memory (CD-ROM), magnetic tape, floppy disk, optical data storage device, carrier wave (e.g., data transmission via the Internet), and so on. The computer-readable recording medium can be distributed by a computer system connected via a network, and thus the computer-readable code can be stored and executed in a distributed manner. Moreover, the functional programs, codes, and code segments for implementing various embodiments of the present disclosure can be easily interpreted by those skilled in the art in the field applying the embodiments of the present disclosure.

[0501] It will be understood that 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 executable on a controller or computer-readable code on a non-transitory computer-readable medium. Examples of non-transitory computer-readable recording media include magnetic storage media (e.g., ROM, floppy disks, hard disks, etc.) and optical recording media (e.g., CD-ROM, digital video disk (DVD), etc.). The non-transitory computer-readable recording media can also be distributed over network-coupled computer systems such that the computer-readable code is 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 can be implemented by a computer or a portable terminal including a controller and a memory, and the memory can be an example of a non-transitory computer-readable recording medium suitable for storing the program(s) having instructions for implementing the embodiments of the present disclosure. The present disclosure can be implemented by a program having code for specifically implementing the devices and methods described in the claims, the program being stored in a machine (or computer) readable storage medium. The program can be electronically carried on any medium, such as a communication signal transmitted via a wired or wireless connection, and the present disclosure suitably includes its equivalents.

[0502] The above are only specific embodiments of the present disclosure, but the protection scope of the present disclosure is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present disclosure can make various changes or substitutions, and these changes or substitutions should all be covered within the protection scope of the present disclosure. Therefore, the protection scope of the present disclosure shall be subject to the protection scope of the claims.

Claims

1. A method performed by a user equipment (UE) in a communication system, the method comprising: Sending a preamble to the second node where the candidate cell is located; as well as Timing advance (TA) information of a candidate cell is received from a first node, wherein the TA information is used to perform conditional layer 1 or layer 2 triggered mobility (LTM).

2. The method according to claim 1, wherein The sending of the preamble to the second node includes: The UE selects, from among the random access RA resources allocated from the candidate cell to the first node for performing an uplink synchronization process in advance, a first RA resource for performing an uplink synchronization process in advance and sends a first preamble, wherein the first preamble is selected by the UE; The RA resources allocated by the candidate cell to the first node for performing an uplink synchronization process in advance are sent by the candidate cell to the UE via the third node and the first node.

3. The method according to claim 1, wherein Receiving TA includes: The UE monitors a physical downlink control channel (PDCCH) using a first radio network temporary identifier (RNTI), where the PDCCH includes resources for transmitting a media access control protocol data unit (MAC PDU) including TA information of the candidate cell, where the TA information includes one or more TA information for one or more UEs.

4. The method according to claim 3, wherein: The first RNTI is an RNTI allocated by the first node and associated with the MAC PDU including the TA information of the candidate cell.

5. The method according to claim 1, wherein The sending of the preamble to the second node includes: The UE sends a second preamble on a second RA resource allocated by the candidate cell to the UE for performing an uplink synchronization process in advance, wherein the second preamble is a preamble allocated by the candidate cell to the UE.

6. The method according to claim 1, further comprising: The UE sends a first message to the first node, where the first message includes a candidate cell selected by the UE and / or a measurement result of the candidate cell; as well as The UE receives a second message sent by the first node, where the second message instructs the UE to perform an uplink synchronization process with the candidate cell in advance; The second message includes at least one of the following: a candidate cell identifier, a fourth RA resource for performing an uplink synchronization process in advance, and a fourth preamble; The fourth RA resource and the fourth preamble are selected by the first node from RA resources allocated to the first node based on the candidate cell for performing an uplink synchronization process in advance; The RA resources allocated by the candidate cell to the first node for performing an uplink synchronization process in advance are sent by the candidate cell to the first node via the third node.

7. The method according to any one of claims 1, 5 and 6, wherein: Monitoring the PDCCH sent by the first node includes: The UE monitors a PDCCH using a cell radio network temporary identity (C-RNTI) allocated to the UE by the first node, where the PDCCH includes resources for sending a MAC PDU including TA information of the candidate cell, wherein the MAC PDU includes one or more medium access control control elements (MAC CEs), and the TA information is included in the MAC CEs.

8. The method according to claim 7, wherein: The MAC CE including the TA information is identified by a logical channel identifier.

9. The method according to claim 1, wherein The TA information includes at least one of the following: Candidate configuration identifier; A TA value, wherein the TA value is determined by the candidate cell through a detected preamble; a value of a random access radio network temporary identifier (RA-RNTI), wherein the RA-RNTI value is determined by the candidate cell based on a resource in which the preamble is detected; RA resource information of the preamble is detected.

10. The method according to any one of claims 3 and 7, wherein: The method further comprises: When the UE receives the TA value of the candidate cell, it starts or restarts the timer. The TA value is valid before the timer times out.

11. The method according to claim 1, wherein The TA information used to execute the conditional LTM includes: If the TA value of the target cell is valid, the UE sends a scheduling request to the second node on a first resource or sends uplink data to the second node on a second resource; wherein the first resource is a resource allocated by the target cell to the UE for sending the scheduling request, and the second resource is a resource allocated by the target cell to the UE for sending uplink data; If the scheduling request or uplink data is successfully received by the second node, the UE considers that the conditional LTM is successfully executed.

12. The method according to claim 1, wherein The TA information used to execute the conditional LTM includes: If the TA value of the target cell is valid, the UE sends a conditional LTM indication to the first node, where the conditional LTM indication is used to indicate that the UE will perform conditional LTM; receiving resource scheduling information sent by the target cell; and performing uplink transmission on the resource; The resource scheduling information is sent via PDCCH.

13. The method according to claim 1, further comprising: The UE evaluates the LTM execution conditions of the candidate cells based on the layer 1 measurement results. When a candidate cell meets the LTM execution conditions, it selects a candidate cell as the target cell and executes the conditional layer 1 or layer 2 to trigger mobility LTM.

14. A method performed by a first node in a communication system, the method comprising: receiving timing advance (TA) information of a candidate cell from a third node, wherein the TA information of the candidate cell is sent to the third node by the second node after receiving a preamble sent by the UE; and The TA information of the candidate cell is sent to a user equipment UE, wherein the TA information is used to perform conditional layer 1 or layer 2 triggered mobility LTM.

15. The method according to claim 14, wherein The method further comprises: A physical downlink control channel (PDCCH) is sent to the UE, where the PDCCH includes resources for sending a medium access control protocol data unit (MAC PDU) including the TA information of the candidate cell.

16. The method according to claim 15, wherein The MAC PDU includes one or more medium access control elements (MAC CEs), and the TA information is included in the MAC CEs.

17. The method according to claim 15, wherein: The PDCCH is scrambled by the first radio network temporary identifier RNTI, or scrambled by the cell radio network temporary identifier C-RNTI of the UE, The first RNTI is allocated by the first node to the UE in the first node and is used to receive the MAC PDU containing TA information.

18. A method performed by a second node in a communication system, the method comprising: Receiving a preamble sent by a user equipment UE; as well as Timing advance TA information of the candidate cell is sent to the third node, wherein the TA information is used to perform conditional layer 1 or layer 2 triggered mobility LTM.

19. A user equipment, comprising: a transceiver configured to transmit and receive signals with the outside; as well as A controller is configured to control the transceiver to perform the method according to any one of claims 1-13.

20. A node device, wherein the user equipment comprises: a transceiver configured to transmit and receive signals with the outside; as well as A controller is configured to control the transceiver to perform the method according to any one of claims 14-18.

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