CN117768968A

CN117768968A - Node, user equipment and method for performing the same in wireless communication system

Info

Publication number: CN117768968A
Application number: CN202211364787.0A
Authority: CN
Inventors: 潘瑜; 汪巍崴; 王弘; 许丽香
Original assignee: Samsung Electronics Co Ltd
Current assignee: Samsung Electronics Co Ltd
Priority date: 2022-09-26
Filing date: 2022-11-02
Publication date: 2024-03-26
Also published as: WO2024071768A1

Abstract

The present disclosure provides a node, user equipment and methods performed thereby in a wireless communication system. The method performed by the first node comprises: receiving related information of a first candidate cell; transmitting a first message to the user equipment, wherein the first message comprises synchronization indication information and related information of a second candidate cell, and the second candidate cell is based on grouping information of the first candidate cell; and sending a handover related indication to the user equipment.

Description

Node, user equipment and method for performing the same in wireless communication system

Technical Field

The present disclosure relates to the field of wireless communication technology, and more particularly, to a node, a user equipment and a method performed by the same in a wireless communication system.

Background

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 quasi 5G communication systems. Therefore, a 5G or quasi 5G communication system is also referred to as a "super 4G network" or a "LTE-after-system".

Wireless communication is one of the most successful innovations in modern history. Recently, the number of subscribers to wireless communication services exceeds 50 billion and continues to grow rapidly. As smartphones and other mobile data devices (e.g., tablet computers, notebook computers, netbooks, e-book readers, and machine type devices) become increasingly popular among consumers and businesses, the demand for wireless data services is rapidly growing. To meet the high-speed growth of mobile data services and support new applications and deployments, it is important to improve the efficiency and coverage of the wireless interface.

Disclosure of Invention

Embodiments of the present disclosure provide a method performed by a first node in a wireless communication system, comprising: receiving related information of a first candidate cell; transmitting a first message to the user equipment, wherein the first message comprises synchronization indication information and related information of a second candidate cell, and the second candidate cell is based on grouping information of the first candidate cell; and sending a handover related indication to the user equipment.

According to an embodiment of the present disclosure, the method further comprises: receiving packet information of the first candidate cell from a second node; or grouping based on the related information of the first candidate cell, and determining the grouping information.

According to an embodiment of the present disclosure, sending a handover-related indication to the user equipment comprises one of: transmitting a handover command to the user equipment, wherein the handover command comprises information of a target cell; or sending a reconfiguration message to the user equipment, wherein the reconfiguration message comprises information of the third candidate cell and/or a handover execution condition. In some embodiments, the third candidate cell may be the first candidate cell described above, or may be another candidate cell different from the first candidate cell.

According to an embodiment of the present disclosure, the method further comprises: transmitting a message for a handover execution indication to a second node, wherein the handover execution indication message includes at least one of: information about the changed cell; and the identity of the target cell.

According to an embodiment of the present disclosure, the method further comprises: and sending the synchronous signal and the related information of the second candidate cell to a second node.

According to an embodiment of the present disclosure, the method further comprises: a timing advance value associated with a second candidate cell is received from a second node.

According to an embodiment of the present disclosure, the method further comprises: transmitting the first cell configuration information received from the second node to the user equipment; and transmitting the cell related information which is received from the second node and is used for indicating and/or referencing the first cell configuration information or not to the user equipment.

According to an embodiment of the present disclosure, sending a handover related indication to the user equipment further comprises sending the timing advance value to the user equipment.

According to an embodiment of the present disclosure, the method further comprises: receiving a reconfiguration message from a second node to the user equipment; and sending a response message to the second node, wherein the response message comprises at least one of a reject cause, a target cell for L1/L2 handover, and configuration information of the target cell for L1/L2 handover.

Embodiments of the present disclosure provide a method performed by a user equipment in a wireless communication system, comprising: receiving a first message from a first node, wherein the first message comprises synchronization indication information and related information of a second candidate cell, and the second candidate cell is based on grouping information of the first candidate cell; and receiving a handover related indication from the first node, wherein the related information of the first candidate cell is received by the first node.

According to an embodiment of the present disclosure, receiving a handover-related indication from the first node includes one of: receiving a handover command from the first node, wherein the handover command comprises information of a target cell, and monitoring a PDCCH (physical downlink control channel) based on the information of the target cell; or receiving a reconfiguration message from the first node, wherein the reconfiguration message comprises information of a third candidate cell and/or a handover execution condition; and selecting a target cell based on the information of the third candidate cell and/or the handover execution condition, and monitoring the PDCCH.

According to an embodiment of the present disclosure, receiving a handover related indication from the first node further comprises receiving a timing advance value from the first node.

According to an embodiment of the present disclosure, the method further comprises: transmitting a preamble to the second candidate cell; and receiving a random access response message from the second candidate cell, wherein the random access response message comprises the preamble and a timing advance value corresponding to the uplink preamble.

According to an embodiment of the present disclosure, the method further comprises: receiving first cell configuration information from a first node; and receiving, from a first node, cell related information indicating and/or referencing whether to employ the first cell configuration information.

Embodiments of the present disclosure provide a method performed by a second node in a wireless communication system, comprising: transmitting to the first node related information of the first candidate cell; receiving a response message sent by a first node; the related information of the first candidate cell and the grouping information of the first candidate cell are used for determining a second candidate cell, wherein the related information of the second candidate cell and the synchronization instruction information are used for being sent to user equipment for synchronizing the user equipment with the second candidate cell.

According to an embodiment of the present disclosure, the method further comprises: and sending the grouping information of the first candidate cell to the first node.

According to an embodiment of the present disclosure, the method further comprises: transmitting first cell configuration information to a first node; and transmitting to the first node cell related information whether to employ an indication of said first cell configuration information and/or a reference.

According to an embodiment of the present disclosure, the method further comprises: receiving a message for a handover execution indication from the first node, wherein the handover execution indication message includes at least one of: information about the changed cell; and the identity of the target cell.

According to an embodiment of the present disclosure, the method further comprises: and receiving a synchronization signal and related information of the second candidate cell from the first node.

According to an embodiment of the present disclosure, the method further comprises: a timing advance value associated with a second candidate cell is transmitted to the first node.

Embodiments of the present disclosure provide a node in a wireless communication system, comprising: a transceiver configured to transmit and receive signals; and a controller coupled with the transceiver and configured to perform a method performed by a node in a wireless communication system according to an embodiment of the disclosure.

Embodiments of the present disclosure provide a user equipment in a wireless communication system, comprising: a transceiver configured to transmit and receive signals; and a controller coupled with the transceiver and configured to perform a method performed by a user equipment in a wireless communication system according to an embodiment of the disclosure.

Embodiments of the present disclosure provide a computer readable medium having stored thereon computer readable instructions which, when executed by a processor, may be used to implement any method according to embodiments of the present disclosure.

The method executed by the first node, the second node and/or the user equipment in the wireless communication system can reduce the switching time delay of the UE and ensure the service transmission quality of the UE.

Drawings

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

FIG. 1 is an exemplary system architecture 100 for System Architecture Evolution (SAE);

FIG. 2 is an exemplary system architecture 200 according to various embodiments of the present disclosure;

FIG. 3 illustrates an example signal flow of a method of reducing handoff latency in accordance with an embodiment of the present disclosure;

FIG. 4 illustrates an example signal flow of another method of reducing handoff latency in accordance with an embodiment of the present disclosure;

FIG. 5 illustrates an example signal flow for a cooperative method of L1/L2 handover and L3 handover in accordance with an embodiment of the present disclosure;

FIG. 6 illustrates an example signal flow for another collaborative approach to L1/L2 handover and L3 handover in accordance with an embodiment of the present disclosure;

FIG. 7 illustrates another cooperative approach to L1/L2 handover and L3 handover in accordance with an embodiment of the present disclosure;

fig. 8 illustrates an example signal flow of a method of restoring a service connection when a UE determines that an L1/L2 handover fails according to an embodiment of the present disclosure;

FIG. 9 illustrates an example signal flow of a method of L1/L2 target cell selection in accordance with an embodiment of the disclosure;

fig. 10 illustrates a flowchart of a method performed by a first node in a wireless communication system in accordance with an embodiment of the present disclosure;

fig. 11 shows a flowchart of a method performed by a user equipment in a wireless communication system according to an embodiment of the disclosure;

fig. 12 illustrates a flowchart of a method performed by a second node in a wireless communication system in accordance with an embodiment of the present disclosure;

fig. 13 shows a schematic diagram of a node in a wireless communication system according to an embodiment of the disclosure;

fig. 14 shows a schematic diagram of a user device according to an embodiment of the present disclosure;

FIG. 15 illustrates another cooperative approach to L1/L2 handover and L3 handover in accordance with an embodiment of the present disclosure;

FIG. 16 illustrates another cooperative approach to L1/L2 handover and L3 handover in accordance with an embodiment of the present disclosure;

FIG. 17 illustrates another cooperative approach to L1/L2 handover and L3 handover in accordance with an embodiment of the present disclosure; and is also provided with

Fig. 18 illustrates another cooperative approach to L1/L2 handover and L3 handover according to an embodiment of the present disclosure.

Detailed Description

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

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

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

The terms "comprises" or "comprising" may refer to the presence of a corresponding disclosed function, operation or component that may be used in various embodiments of the present disclosure, rather than to the presence of one or more additional functions, operations or features. Furthermore, the terms "comprises" or "comprising" may be interpreted as referring to certain features, numbers, steps, operations, constituent elements, components, or combinations thereof, but should not be interpreted as excluding the existence of one or more other features, numbers, steps, operations, constituent elements, components, or combinations thereof.

The term "or" as used in the various embodiments of the present disclosure includes any listed term and all combinations thereof. For example, "a or B" may include a, may include B, or may include both a and B.

Unless defined differently, all terms (including technical or scientific terms) used in this disclosure have the same meaning as understood by one of ordinary skill in the art to which this disclosure pertains. The general terms as defined in the dictionary are to be construed to have meanings consistent with the context in the relevant technical field, and should not be interpreted in an idealized or overly formal manner unless expressly so defined in the present disclosure.

Figures 1 through 14, discussed below, and the various embodiments used to describe the principles of the present disclosure in this patent document are by way of illustration only and should not be construed in any way to limit the scope of the disclosure. Those skilled in the art will appreciate that the principles of the present disclosure may be implemented in any suitably arranged system or device.

Fig. 1 is an exemplary system architecture 100 for System Architecture Evolution (SAE). A User Equipment (UE) 101 is a terminal device for receiving data. An evolved universal terrestrial radio access network (E-UTRAN) 102 is a radio access network including macro base stations (enodebs/nodebs) providing an access radio network interface for UEs. The Mobility Management Entity (MME) 103 is responsible for managing the UE's mobility context, session context and security information. Serving Gateway (SGW) 104 mainly provides the functions of the user plane, and MME 103 and SGW 104 may be in the same physical entity. The packet data network gateway (PGW) 105 is responsible for charging, lawful interception, etc. functions, and may also be in the same physical entity as the SGW 104. A Policy and Charging Rules Function (PCRF) 106 provides quality of service (QoS) policies and charging criteria. The general packet radio service support node (SGSN) 108 is a network node device in the Universal Mobile Telecommunications System (UMTS) that provides a route for the transmission of data. A Home Subscriber Server (HSS) 109 is a home subsystem of the UE and is responsible for protecting user information including the current location of the user equipment, the address of the service node, user security information, packet data context of the user equipment, etc.

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

A 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 including base stations (gnbs or enbs connected to a 5G core network 5GC, also called NG-gnbs) providing access radio network interfaces for UEs. An access control and mobility management function (AMF) 203 is responsible for managing the mobility context of the UE, and security information. The User Plane Function (UPF) 204 mainly provides the functions of the user plane. The session management function entity SMF205 is responsible for session management. The Data Network (DN) 206 contains services such as operators, access to the internet, and third party traffic, among others.

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

The text and drawings are provided as examples only to aid in the understanding of the present disclosure. They should not be construed as limiting the scope of the disclosure in any way. While certain embodiments and examples have been provided, it will be apparent to those of ordinary skill in the art from this disclosure that variations can be made to the embodiments and examples shown without departing from the scope of the disclosure.

Detailed descriptions of steps irrelevant to the present disclosure are omitted in the present disclosure. In the following embodiments, a 5G system is taken as an example, an access network concentration unit is taken as an example, a CU is taken as an example, and a distribution unit is taken as an example, a DU is taken as an example. The method is also applicable to the corresponding entities of other systems.

In this disclosure, a node may be a complete base station (e.g., a gNB, or an eNB, or an en-gNB, or a ng-eNB), or may be a base station that includes both a centralized unit and a distributed unit. The gNB may be a single base station, or a primary base station/primary node MN (Master Node) or a secondary base station/secondary node SN (Secondary Node) under dual connectivity DC (Dual Connectivity). The set of cells in the MN that serve the UE is referred to as the primary cell set MCG (Master Cell Group) and the set of cells in the SN that serve the UE is referred to as the secondary (second) cell set SCG (Secondary Cell Group). The MCG primary cell is called PCell (Primary Cell) and the SCG primary cell is called PSCell (Primary SCG Cell). When MCG or SCG adopts carrier aggregation CA (Carrier Aggregation), other cells than PCell and PSCell are referred to as SCell (Secondary Cell).

The candidate cell may be a candidate cell of the PCell, may be a candidate cell of the PSCell, or may be a candidate cell of the SCell. In addition, a node may also refer to a Centralized Unit (CU) or a Distributed Unit (DU).

Under a CU (Central Unit)/Distributed Unit (DU) separation structure, during handover, the source cell and the target cell may be located under the same gNB-DU or may be located under different gNB-DUs.

In this disclosure, message (or information, indication, command, etc.) names are merely examples, and other names may be used to name the message (or information, indication, command, etc.). The sequence number of a message does not represent the order in which the messages are executed, but only the name of the message.

The present disclosure may include the following several example aspects.

Example aspect one, a method of reducing handoff latency

The time delay (or handover interruption) of the layer 3 handover (L3 handover) is the time from when the UE receives a handover command from the source cell to when the UE accesses the target cell to start service transmission. The handoff delay may include the following:

-a first part: the UE receives the layer 3 switching command and analyzes the layer 3 signaling to obtain the processing time delay of the configuration information of the target cell;

-a second part: the UE carries out processing delay of configuration of a physical layer, a media access control (Media Access Control, MAC)/a Radio link control (Radio LinkControl, RLC)/a packet data convergence protocol (Packet Data Convergence Protocol, PDCP) layer according to configuration information of a target cell in layer 3 switching signaling;

-a third part: and the time delay of the downlink and uplink synchronization process is carried out between the UE and the target cell.

The switching delay is relatively large and needs to be further reduced.

A method for reducing handoff latency is described below in connection with examples one and two.

Example one presents a method of reducing handoff latency. The UE establishes downlink and uplink synchronization with the candidate target cell by performing an optimized random access procedure. The specific flow is shown in fig. 3.

And step L1/L2 candidate cell selection, namely finishing the determination and information configuration of the L1/L2 handover candidate cell between the gNB-CU and the gNB-DU where the candidate cell is located.

Step 300, the gNB-CU sends an L1/L2 handover request message to the source gNB-DU, indicating that the gNB-DU can change the serving cell of the UE by adopting an L1/L2 handover mechanism. The serving Cell may be a Primary Cell (PCell), a Primary Secondary Cell (Primary Secondary Cell, PSCell) or a Secondary Cell (Scell). The message contains at least one of the following information:

(1) The first L1/L2 handover indication indicates that the gNB-DU can adjust the serving cell of the UE by adopting an L1/L2 handover mechanism.

(2) The first candidate cell information, which is provided in the form of a list, may include at least one of the following information:

Candidate Cell identity, which may be a Global Cell identity (CGI), or a Physical Cell Identity (PCI).

-a Group identity (Group ID) to which the candidate cell belongs, indicating the Group to which the candidate cell belongs, the candidate cells of the same Group having the same downlink and uplink synchronization relationship with the UE.

-candidate cell index candidatecellndex, indicating the index of candidate cells in all candidate cell list. The range of values is (0-maxchangeateColls-1), where maxchangeateColls refers to the maximum number of candidate cells allocated to the UE.

Dedicated preambles (preamble codes) each candidate cell allocates a dedicated preamble for random access to the UE, which may reduce the time for the UE to complete uplink synchronization with the candidate cells. If the network sends the special preamble to the UE when the L1/L2 switch is triggered, the gNB-DU sends the received special preamble to the UE in the synchronous indication information. If the network sends the dedicated preamble directly to the UE, the dedicated preamble is included in the RRC reconfiguration message sent to the UE.

(3) The RRC reconfiguration message sent to the UE is included in the L1/L2 handover request message in the form of an RRC Container (RRC-Container). The method comprises the following steps:

A timer T for determining whether the L1/L2 handover of the UE is successful during the L1/L2 handover execution. And when the UE receives the L1/L2 switching command and completes the configuration of the target cell, starting a timer T, and starting to monitor the PDCCH in the target cell. If the timer T is overtime, the UE does not monitor the PDCCH sent to the UE by the target cell, the L1/L2 switching is considered to be failed, the UE performs cell selection, and proper cell access is selected. By setting the timer T, when the UE cannot access the target cell, the UE can also select the appropriate cell to access in time, so that the influence of the service quality of the UE due to L1/L2 switching failure is reduced.

Dedicated preamble (preamble) each candidate cell allocates a dedicated preamble for random access to the UE.

-measurement configuration information comprising at least one of the following information:

measurement configuration information for L1/L2 handover

-configuration information of L3 measurements.

(4) Measurement configuration information including measurement configuration information for L1/L2 handover.

The L1/L2 handover request message may be a UE context modification request message UE CONTEXT MODIFICATION REQUEST, or other message.

In step 301a, the source gNB-DU sends a reconfiguration message (RRCRECONfigure) to the UE, including configuration information of the candidate cell. The reconfiguration message is sent by the gNB-CU to the source gNB-DU in the form of an RRC container, and the source gNB-DU is sent to the UE. The message may contain at least one of the following information:

(1) A second L1/L2 switching instruction, which indicates that the UE network will use an L1/L2 switching mechanism to adjust the cell served by the UE so as to ensure the service transmission quality;

(2) First candidate cell information, each candidate cell information is provided in the form of a list, including at least one of the following information:

candidate cell identity, which may be CGI, or PCI.

-a Group ID of said Group of candidate cells, indicating the Group to which the candidate cell belongs, the candidate cells of the same Group having the same downlink and uplink synchronization relationship with the UE. Grouping of the candidate cells can be completed by the gNB-CU, and the grouping information of the candidate cells is sent to the gNB-DU through the step 300, and the gNB-DU is forwarded to the UE; candidate cell grouping may also be accomplished by the gNB-DU and candidate cell grouping information may be sent to the UE.

-candidate cell index candidatecellndex, indicating the index of candidate cells in all candidate cell list. The value range is (0-maxCandida atells-1).

The identity of the UE in the candidate cell may be a C-RNTI, or other user identity information.

-resource information configured by the candidate cell for the UE, physical layer resource information, service configuration information, etc.

A timer T for determining whether the L1/L2 handover of the UE is successful during the L1/L2 handover execution. And when the UE receives the L1/L2 switching command and completes the configuration of the target cell, starting a timer T, and starting to monitor the PDCCH in the target cell. If the timer T is overtime, the UE does not monitor the PDCCH sent to the UE by the target cell, the L1/L2 switching is considered to be failed, the UE performs cell selection, and proper cell access is selected. By setting the timer T, the influence of the service quality of the UE due to the L1/L2 switching failure is reduced. The setting of the timer T may be accomplished by the gNB-CU, and the gNB-DU may be sent to the gNB-DU through step 300, and the gNB-DU may be forwarded to the UE, or may be accomplished by the gNB-DU.

At step 301b, the ue sends a reconfiguration complete to the source gNB-DU (RRCReconfiguration Complete).

Step 302, the source gNB-DU sends an L1/L2 handover request response message to the gNB-CU, indicating that the source gNB-DU accepts the L1/L2 handover request. The message may be a UE context modification response message UE CONTEXT MODIFICATION RESPONSE, or other message.

In step 303a, the ue sends a layer 1 measurement report to the source gNB-DU, and provides the source cell with the candidate cell link quality for the L1/L2 handover.

In step 303b, the source gNB-DU selects a cell list (e.g., a second list) of candidate cells for UE that need downlink and uplink synchronization in different groups according to the measurement result obtained in step 303 a. For example, as previously described, the source gNB-DU selects one candidate cell for the UE in each packet that needs to be downlink and uplink synchronized.

In step 304, the source gNB-DU sends synchronization indication information to the UE, sends cell list information (e.g., a second list) of candidate cells that the UE determined in step 303b needs to perform downlink and uplink synchronization to the UE, and indicates that the UE performs synchronization with the candidate cells in the list, where the information may be sent through a MAC control element MAC CE (MAC Control Element) or physical layer signaling. The synchronization instruction information may include at least one of the following information:

-second candidate cell information, which may be a candidate cell index, or a candidate cell identity;

-synchronization indication information indicating whether the UE performs downlink and/or uplink synchronization with a candidate cell corresponding to the cell index or the candidate cell identity.

-a dedicated preamble (preamble code) for random access by the UE in the candidate cell, thereby reducing the time for the UE to complete uplink synchronization with the candidate cell.

If the MAC CE mode is adopted, the bit of the MAC CE corresponds to the candidate cell index, and if the value of the bit is 1, the UE needs to perform downlink and/or uplink synchronization with the cell indicated by the candidate cell index. If the bit value is 0, it indicates that the UE does not need to perform downlink and/or uplink synchronization with the cell indicated by the candidate cell index.

In step 305, after the UE completes downlink synchronization with the candidate cell according to the cell information obtained in step 304, the UE initiates a random access procedure, and sends an uplink preamble (preamble code), which is also referred to as an uplink synchronization code, to the candidate cell. If the UE obtains the dedicated preamble of the candidate cell in step 301a or step 304, the UE will send the dedicated preamble to the candidate cell.

In step 306, the gNB-DU where the candidate cell is located sends a random access response RAR (Random Access Response) message to the UE, wherein the message contains an uplink preamble and a timing advance TA (Timing Advance) corresponding to the uplink preamble, thus obtaining TA and realizing uplink synchronization with the candidate cell by the UE. Through a grouping mechanism, the UE and one cell in the grouping realize downlink and uplink synchronization, so that the downlink and uplink synchronization of all candidate cells of the grouping to which the cell belongs (for simplifying the description, the UE and the grouping are called as realizing the downlink and uplink synchronization, and the uplink TA of the grouping is obtained), thereby avoiding the UE from needing the downlink and uplink synchronization with all the candidate cells and reducing the energy consumption and processing requirements of the UE.

The ue will thus achieve downlink and uplink synchronization with multiple candidate cells, via steps 305 and 306. The plurality of candidate cells belong to different groups.

Since the candidate cell may be located in the source gNB-DU or other gNB-DU within the gNB-CU, steps 305 and 306 may be transmitted between the UE and the source gNB or other gNB.

In steps 307a and 307b, the source gNB-DU (source cell) selects the target cell for the L1/L2 handover for the UE based on the measurement results provided by the UE.

In step 308a, the source gNB/gNB-DU sends an L1/L2 handover command to the UE, indicating the target cell identity for the UE handover. The handover command may be transmitted using physical layer signaling or MAC CE.

In step 308b, the source gNB-DU sends an L1/L2 handover execution instruction message to the gNB-CU, and instructs the gNB-DU to change the serving cell of the UE in an L1/L2 handover mode. The message contains at least one of the following information:

(1) The changed serving cell information indicates whether the L1/L2 handover adjusts the PCell (or PSCell) or SCell of the UE.

(2) Cell identification. The target cell identity for UE handover may be CGI or other cell identity information. If the inter-gNB-DU cell switching is performed, the gNB-CU needs to determine a target gNB-DU according to the cell identification, and step 308c is executed to inform the target cell of carrying out UE service data transmission.

The message may be a UE context modification required message UE CONTEXT MODIFICATION REQUIRED, or other message.

In step 308c, the gNB-CU sends a third L1/L2 handover indication to the candidate gNB-DU indicating that the UE is to be handed over to a cell belonging to the candidate gNB-DU. And after the candidate gNB-DU receives the indication, resource preparation is about to be carried out, and the UE service data is transmitted. The message may contain at least one of the following information:

-cell identity. The target cell identity for UE handover may be CGI or other cell identity information.

The third L1/L2 handover indication message may be a UE context modification request message UECONTEXT MODIFICATION REQUEST, or other message.

In step 309, the UE receives the L1/L2 handover command, obtains the target cell identifier (e.g., CGI, PCI, etc.) of the handover, and performs configuration update according to the configuration information of the target cell and the configuration information of the candidate cell obtained in step 301 a. Meanwhile, the UE determines the packet to which the target cell belongs according to the packet to which the candidate cell belongs obtained in step 301 a.

Since the UE has achieved downlink synchronization with the target cell or the candidate cell of the group in which the target cell is located in step 305, the UE may directly monitor the physical downlink control channel PDCCH in the target cell.

Step 310, the gNB-DU to which the target cell belongs sends downlink scheduling information or uplink authorization information to the UE through a physical downlink control channel PDCCH.

In step 311, the ue determines an uplink TA of the target cell. When the UE determines the packet to which the target cell belongs according to the packet to which the candidate cell obtained in step 301a belongs, and determines the uplink TA value of the target cell in combination with the TA of the packet obtained in steps 305 and 306. The UE receives the downlink scheduling information and performs downlink PDSCH service data reception in step 310, where the UE needs to perform ACK/NACK feedback (feedback information) on the received downlink data, or when the UE receives uplink grant information and needs to perform uplink data transmission (uplink service data is transmitted on PUSCH), the UE may perform uplink transmission based on the determined uplink TA, without obtaining the TA through a random access procedure, thereby reducing the handover delay of the UE.

In step 312, the ue performs uplink transmission according to the TA value determined in step 311, which may be feedback information (ACK/NACK) or transmission of uplink data (PUSCH). And when the target cell receives uplink transmission from the UE, the feedback information or the uplink data is considered to be successfully accessed to the target cell.

In step 313a, the gNB-DU (target gNB-DU) to which the target cell belongs sends an indication message (ACCESS SUCCESS) to the gNB-CU indicating that the UE completes L1/L2 handover and has successfully accessed the target cell. The message contains at least one of the following information:

(1) And the cell identifier indicates a target cell identifier which is successfully accessed by the UE through an L1/L2 switching mechanism, and the cell identifier can be CGI (Cell Global ID).

In step 313b, the ue transmits a reconfiguration complete message (rrcrecon configuration complete) to the target nb-DU (target nb-DU) to which the target cell belongs, and notifies the CU that the cell handover is completed.

In step 313c, the target gNB-DU sends an uplink RRC message transmission (UL RRC MESSAGE TRANSFER) to the gNB-CU including an RRCRECONfigure complete message sent by the UE to the gNB-CU.

In step 314, the gNB-CU sends an L1/L2 handover complete message of the UE to the gNB-DU (source gNB-DU) to which the source cell belongs. This step is optional if the target cell and the source cell belong to the same gNB-DU. The message contains at least one of the following information:

(2) The candidate cell indication indicates whether the source cell is a candidate cell for a subsequent L1/L2 handover of the UE.

The handover complete message may be a UE context modification request message UE CONTEXT MODIFICATION REQUEST, or other message.

Example two presents another approach to reduce handoff latency. And the UE sends the timing advance information to the source cell after the candidate cell determines the uplink timing by indicating to send signals to the candidate cell. Through the process, the UE and the candidate cell establish downlink and uplink synchronization in advance, so that the switching time delay is reduced. The UE and the candidate cell establish in advance a dedicated preamble or a special signal for uplink synchronization, which may be provided by the source cell or the candidate cell. The candidate cell may provide the dedicated preamble or the special signal in the L1/L2 candidate cell selection stage (the gNB-CU may send the dedicated preamble or the special signal to the UE directly through an RRC message, or may send the dedicated preamble or the special signal to the UE after the source cell is sent to the UE through the gNB-CU, or may provide the dedicated preamble or the special signal to the UE after the source cell is provided to the gNB-CU in a container form through an RRC message), or may provide the dedicated preamble or the special signal to the source cell and send the dedicated preamble or the special signal to the UE by the source cell when the source cell indicates that the UE needs to synchronize with the candidate cell. The specific flow is shown in fig. 4.

Step 400 and step 402 are the same as steps 300 and 302 and are not described in detail herein.

In step 401a, the source gNB-DU sends a reconfiguration message (RRCRECONfigure) to the UE, including configuration information of the candidate cell. The reconfiguration message is sent by the gNB-CU to the source gNB-DU in the form of an RRC container, and the source gNB-DU is sent to the UE. The message contains at least one of the following information:

(1) An L1/L2 switching instruction which instructs the UE network to adjust the cell served by the UE by using an L1/L2 switching mechanism so as to ensure the service transmission quality;

(2) Candidate cell information, each candidate cell information being provided in the form of a list, comprising at least one of the following information:

candidate cell identity, which may be CGI, or PCI.

A timer T for determining whether the L1/L2 handover of the UE is successful during the L1/L2 handover execution. And when the UE receives the L1/L2 switching command and completes the configuration of the target cell, starting a timer T, and starting to monitor the PDCCH in the target cell. If the timer T is overtime, the UE does not monitor the PDCCH sent to the UE by the target cell, the L1/L2 switching is considered to be failed, the UE performs cell selection, and proper cell access is selected. By setting the timer T, the influence of the service quality of the UE due to the L1/L2 switching failure is reduced.

In step 403, the ue sends the measurement result to the source gNB-DU, and provides the candidate cell link quality for the L1/L2 handover to the source cell.

In step 403a, the source gNB-DU selects, for the UE, a candidate cell list to be synchronized in downlink and uplink for different cell groups according to the measurement result obtained in step 403. While the gNB-DU determines a dedicated Preamble code or special signal (e.g., which may be referred to herein as a synchronization signal) for the UE to use for uplink synchronization with the selected candidate cell. The candidate cell can identify the UE through the received dedicated Preamble code sent by the UE, and can also determine the uplink timing advance TA of the UE.

In step 403b, the source gNB-DU sends a first synchronization preparation indication message to the gNB-CU, wherein the first synchronization preparation indication message includes a second synchronization preparation indication message sent by the source gNB-DU to the candidate gNB-DU. The message sent by the source gNB-DU to the gNB-CU may be a UE context modification request message (UE CONTEXT MODIFICATION REQUIRED) or may be other messages, wherein the message contains at least one of the following information:

(1) A synchronization preparation indication container (Synchronization Preparation Container) containing a second synchronization preparation indication message sent by the source gNB-DU to the candidate gNB-DU. The synchronization preparation indication message is used to indicate to the candidate gNB-DU that the UE will send a dedicated preamble or special signal in the candidate cell.

(2) The candidate cell list information includes candidate cell identifiers of the UE which need to perform downlink and uplink synchronization, and the candidate cell identifiers can be CGI or PCI.

In step 403c, the gNB-CU sends a first synchronization preparation indication acknowledgement message to the source gNB-DU indicating that a message sent by the gNB-DU was received. The acknowledgement message may be a UE context modification acknowledgement message (UE CONTEXT MODIFICATION CONFIRM), or other message. Step 403c may also be performed after step 403 e.

In step 403d, the gNB-CU sends a second synchronization preparation indication message to the candidate gNB-DUs, and sends the synchronization indication message received from the source gNB-DUs to the candidate gNB-DUs where each candidate cell obtained in step 403a is located, indicating that the UE will send a dedicated preamble or a special signal in the candidate cell. The message contains at least one of the following information:

(1) Candidate cell information provides each candidate cell identification in the form of a list, and the candidate cell identification can be CGI or PCI.

(2) A dedicated Preamble (Preamble) or a special signal. The UE sends the dedicated preamble or special signal to the candidate cell. By receiving the Preamble code or the special signal, the candidate cell can identify the UE and determine the value of the uplink timing advance TA of the UE in the cell. The same special preamble code can be selected for each candidate cell for the UE, so that the occupation of the preamble code is reduced, the utilization rate of the preamble is improved, and the influence on the access of cell users is reduced.

The message may be a UE context modification request message (UE CONTEXT MODIFICATION REQUEST), or other message.

In step 403e, the candidate gNB-DU sends a second synchronization preparation indication confirmation message to the gNB-CU. The message contains at least one of the following information:

(2) A dedicated preamble (preamble) or a special signal. If the second synchronization preparation indication message in step 403d does not include information of the dedicated preamble or the special signal provided by the source cell, the dedicated preamble or the special signal of each candidate cell w is transmitted to the gNB-CU. By receiving the Preamble code or the special signal, the candidate cell can identify the UE and determine the value of the uplink timing advance TA of the UE in the cell.

The message may be a UE context modification response message (UE CONTEXT MODIFICATION RESPONSE), or other message.

If it is a candidate gNB-DU that provides a dedicated preamble or a special signal, step 403c will be performed after step 403 e. The first synchronization preparation indication confirmation message comprises at least one of the following information:

(1) Candidate cell information provides each candidate cell identification in the form of a list, and the candidate cell identification can be CGI or PCI. Candidate cell information and Source gNB-

The DU is sent to the corresponding gNB-CU.

(2) A dedicated preamble (preamble) or a special signal. By receiving the Preamble code or the special signal, the candidate cell can identify the UE and determine the value of the uplink timing advance TA of the UE in the cell.

In step 404, the source gNB-DU sends synchronization instruction information to the UE, and sends the cell list information determined in step 403a and a dedicated Preamble (Preamble) or a special signal to the UE to instruct the UE to synchronize with the candidate cell. This information may be sent by a MAC control element MAC CE (MAC Control Element) or by physical layer signaling. The information includes at least one of the following information:

candidate cell information, which may be candidate cell index CandidateCellIndex, or candidate cell identity, which may be CGI, or PCI;

Dedicated Preamble (Preamble) or special signal identification

In step 405, the ue sends an uplink preamble or a special signal to the candidate cell after completing downlink synchronization with the candidate cell according to the candidate cell information obtained in step 404.

In step 406a, the candidate cell (located in the source gNB-DU or the candidate gNB-DU) determines the TA value of the UE according to the transmitted preamble or special signal of the UE. The TA value of the UE on the candidate cell is sent to the source gNB-DU. If the candidate cell is located in the candidate gNB-DU, step 406b is needed to be executed, and after the UE sends the gNB-CU at the TA value of the candidate cell, the gNB-CU forwards the gNB-CU to the source gNB-DU.

In step 406b, the candidate gNB-DU sends TA information of the UE to the gNB-CU. The TA information of the UE may include at least one of the following information:

-timing advance TA value, timing advance TA value of UE determined in candidate cell.

The TA information may be sent via a UE context modification required message UE CONTEXT MODIFICATION REQUIRED, or other message.

In step 406c, the gNB-CU forwards the TA information of the UE obtained in step 406b to the source gNB-DU. The source gNB-DU obtains TA values of the UE on the selected candidate cells. The TA value information of the UE may include at least one of the following information:

And the gNB-CU can determine the TA value of the UE on other candidate cells according to the group to which the selected candidate cell belongs.

The TA value information may be sent via a UE context modification request message UE CONTEXT MODIFICATION REQUEST, or other message.

In step 406d, the source gNB-DU sends a message to the gNB-CU indicating that TA information of the UE on the candidate cell has been received. The message may be a UE context modification response message UE CONTEXT MODIFICATION RESPONSE, or other message.

In steps 407a and 407b, the source gNB-DU (source cell) selects the target cell for the L1/L2 handover for the UE according to the measurement result provided by the UE. In step 408a, the source gNB/gNB-DU sends an L1/L2 handover command to the UE, indicating the UE to handover the serving cell. The handover command may be transmitted using physical layer signaling or MAC CE. The handover command may contain at least one of the following information:

the target cell identity, which may be CGI, or PCI.

-TA value indicating the UE's uplink timing advance TA value in the target cell.

In step 408b, the source gNB-DU sends an L1/L2 handover execution instruction message to the gNB-CU, and instructs the source gNB-DU to adjust the serving cell of the UE in an L1/L2 handover mode. The message contains at least one of the following information:

(1) The adjusted serving cell type information indicates whether the L1/L2 handover adjusts the UE to be a PCell (or PSCell) or SCell.

(2) Cell identification. The target cell identity for UE handover may be CGI or other cell identity information. If the inter-gNB-DU cell handover is performed, the gNB-CU needs to determine a target gNB-DU according to the cell identification, and execute step 408c to inform the target cell of carrying out UE service data transmission.

In step 408c, the gNB-CU sends an L1/L2 handover indication to the candidate gNB-DU, indicating that the UE will be handed over to a cell belonging to the candidate gNB-DU. And after the candidate gNB-DU receives the indication, resource preparation is about to be carried out, and the UE service data is transmitted. The message contains at least one of the following information:

In step 409, the UE receives the L1/L2 handover command, obtains the target cell identifier (e.g., CGI, PCI, etc.) of the handover, and performs configuration update according to the configuration information of the target cell and the configuration information of the candidate cell obtained in step 401.

Since the UE has achieved downlink synchronization with the target cell or the candidate cell of the packet in which the target cell is located in step 405, the UE may directly monitor the physical downlink control channel PDCCH in the target cell.

In step 410, the ue monitors the PDCCH channel. And the gNB-DU to which the target cell belongs sends downlink scheduling information or uplink authorization information to the UE through a physical downlink control channel PDCCH.

In step 411, the ue performs uplink transmission according to the TA value of the target cell obtained in step 408a, where the uplink transmission may be transmission of feedback information (ACK/NACK) or uplink data (PUSCH). When the target cell receives uplink transmission, e.g., feedback information or uplink data, from the UE, the UE is considered to be successfully accessed to the target cell.

In step 412a, the gNB-DU (target gNB-DU) to which the target cell belongs sends an indication message (ACCESS SUCCESS) to the gNB-CU indicating that the UE has successfully accessed the target cell by L1/L2 handover. The message contains at least one of the following information:

and the cell identifier indicates a target cell identifier which is successfully accessed by the UE through an L1/L2 switching mechanism, and the cell identifier can be CGI (Cell Global ID).

In step 412b, the ue sends a reconfiguration complete message (rrcrecon configuration complete) to the target nb-DU (target nb-DU) to which the target cell belongs, and notifies the CU that the cell handover is completed.

In step 412c, the target gNB-DU sends an uplink RRC message transmission (UL RRC MESSAGE TRANSFER) to the gNB-CU including an RRCRECONfigure complete message sent by the UE to the gNB-CU.

In step 413, the gNB-CU sends an L1/L2 handover complete message of the UE to the gNB-DU to which the source cell belongs. This step is optional if the target cell and the source cell belong to the same gNB-DU. The message contains at least one of the following information:

Methods for reducing handoff latency in accordance with embodiments of the present disclosure are described above in connection with fig. 3 and 4. As described above, in order to reduce the existing layer 3 handover delay and reduce the influence on UE service transmission in the handover process, the present disclosure selects a plurality of candidate cells for the UE, and sends configuration information of each candidate cell to the UE in advance for storage and processing, so that the UE will not process the configuration information of the target cell after receiving the handover command, thereby reducing the handover delay of the UE. By adopting the layer 1/layer 2 switching (L1/L2 switching, also referred to as L1/L2 Mobility) mode, the switching command is sent to the UE through a control channel of the physical layer (such as a physical downlink control channel PDCCH, physical Downlink Control Channel) or a MAC CE of the MAC layer, so that the processing delay of the UE for layer 3 signaling reception and analysis is reduced. In the L1/L2 switching, the MAC/RLC/PDCP layer is not required to be reconfigured through the reconstruction process of MAC reset, RLC and PDCP, so that the processing time delay of the UE in the switching process is reduced.

In the method, the UE completes the synchronization of the downlink and the uplink with the target cell in advance before executing the L1/L2 switching, and after receiving the L1/L2 switching command, the UE directly receives the downlink scheduling information or the uplink authorization information of the target cell to transmit the service data, thereby further reducing the switching time delay of the UE and the service interruption in the switching process and ensuring the service transmission quality of the UE.

In order to avoid the improvement of processing capability requirements caused by downlink and uplink synchronization of the UE and a plurality of candidate cells, the candidate cells switched by L1/L2 can be grouped through a network, and if any one cell in the UE and the group completes downlink synchronization and uplink synchronization, the UE realizes downlink synchronization and uplink synchronization with all cells in the group. The network groups the candidate cells based on this principle. The network selects a cell for the UE in each group, and indicates the UE to perform downlink and uplink synchronization with the selected cell, and obtains the value of the timing advance TA (Timing Advance) of the uplink synchronization. There are two methods for obtaining the timing advance, which are given in example one and example two above, respectively. The grouping of the candidate cells can be completed by the gNB-CU or by the gNB-DU under the network structure of CU/DU separation.

Example aspect two, coordination of L1/L2 handover with L3 handover

Both L1/L2 handover and L3 handover can be used for inter-cell handover within a gNB-CU (intra-gNB-CU), including inter-cell handover between gNB-DUs (inter-gNB-DUs) within a gNB-CU (intra-gNB-CU), and inter-cell handover within a gNB-DU (intra-gNB-DU), L3 handover can also be used for inter-cell handover between gNB-CUs (inter-gNB-CU). Thus the L1/L2 handover and the L3 handover are configured simultaneously.

If L3 is switched, the configuration information of the candidate cell adopts an incremental configuration (delta) mode, namely, the configuration of the current service cell of the UE is used as a reference, and only configuration items with differences between the candidate cell and the current service cell are provided. Moreover, if both the L1/L2 handover and the L3 handover are triggered, the processing of the UE and the network will be increased. Thus, a cooperative L1/L2 handover and L3 handover is required. If the gNB-CU does not know the change of the serving cell of the UE, the UE cannot obtain the configuration information of the target cell correctly, and the L3 handover fails. The patent proposes seven schemes, realizes the cooperation of L1/L2 switching and L3 switching, and reduces the processing overhead of UE and network while optimizing the switching performance.

Example three gives a synergistic approach to L1/L2 handover and L3 handover.

When the L1/L2 handover preparation is completed, i.e. the L1/L2 candidate cell selection of example one is completed, and steps 301a-302, if the gNB-CU decides to trigger the L3 handover, the source cell already triggers the UE to perform the L1/L2 handover, to perform the serving cell update, and the UE no longer performs data transmission with the source cell. Therefore, after the source gNB-DU receives the L3 handover message sent by the gNB-CU, if the configuration information of the candidate cell in the L3 handover message is found to take the configuration information of the source cell as a reference, the gNB-DU sends an L3 handover reject message to the gNB-CU. Indicating to the gNB-CU that the UE serving cell is updated and that the configuration information for the L3 handover needs to be updated. After receiving the L3 handover reject message, the gNB-CU decides whether an L3 handover request needs to be initiated or not, or updates configuration information of the L3 handover candidate cell sent to the UE.

The specific flow is shown in fig. 5. Wherein:

step L1/L2 handover preparation is the same as the L1/L2 candidate cell selection of example one and steps 301a-302, and will not be repeated here.

Step 500, the gNB-CU selects a candidate cell for L3 handover for the UE and obtains configuration information of the candidate cell.

In step 501, the source gNB-DU sends an L1/L2 handover command to the UE, indicating the target cell identity for UE handover.

In step 502, the gNB-CU sends a handover message to the source gNB-DU, indicating that the UE is to be triggered to perform layer 3 handover, where the handover message includes a reconfiguration message sent to the UE, a configuration mode (incremental configuration or complete configuration) adopted by the target cell configuration, and a reference serving cell identifier.

In step 503, if the source gNB-DU has triggered the UE to perform an L1/L2 handover, an L3 handover reject message will be sent to the gNB-CU. The L3 handover reject message includes a reject reason, which is a change of the serving cell, and L1/L2 handover target cell and target cell configuration information.

Step 505, when the UE handover is completed, the gNB-DU to which the target cell belongs sends a message that the UE access is successful to the gNB-CU, and indicates to the gNB-CU that the UE updates the serving cell through L1/L2 handover. The message at least comprises the following components: target cell identity, handover mode (L1/L2 handover, or conditional handover).

Example four shows another collaborative approach for L1/L2 handover and L3 handover.

When the source cell triggers the UE to perform L1/L2 switching, the gNB-DU to which the source cell belongs sends L1/L2 switching execution information to the gNB-CU, and the UE is indicated to update the service cell. If the gNB-CU prepares to send a layer 3 (L3) handover command, due to the serving cell update, the gNB-CU waits until the UE accesses a new target cell and obtains the configuration information of the target cell, before determining the configuration information setting of the candidate cell for L3 handover.

The specific flow is shown in fig. 6.

Step 600, the source gNB-DU sends an L1/L2 handover command to the UE, indicating the target cell identity for UE handover.

In step 601, when the source cell triggers the UE to perform L1/L2 handover, the gNB-DU to which the source cell belongs will send an L1/L2 handover execution indication message to the gNB-CU, indicating that the UE will update the serving cell. The gNB-CU timely obtains a serving cell to be updated by the UE, so that the influence on the UE to correctly receive a layer 3 switching command caused by the configuration information setting of a target cell for L3 switching by using the configuration of a source cell is avoided. The message contains at least one of the following information:

The adjusted serving cell type information indicates whether the L1/L2 handover adjusts the UE to be a PCell (or PSCell) or SCell.

Example five presents another collaborative approach to L1/L2 handover and L3 handover.

When the gNB-CU is ready to perform L3 handover, a configuration request message is sent to gNB-DU (source gNB-DU) where the UE serving cell is located, and current configuration information of the UE is requested. If the UE is triggered to perform the L1/L2 handover, the configuration information indication fed back to the gNB-CU by the source gNB-DU indicates that the acquisition of the UE configuration information fails, the UE is indicated to be performing the L1/L2 handover, and the serving cell is updated. If the gNB-CU does not obtain the current configuration information of the UE, the triggering of the L3 switching is stopped, or the resources of the candidate target cell are configured for the UE in a complete configuration (full configuration) mode. Therefore, the situation that the UE cannot correctly interpret the switching configuration information due to the fact that the wrong reference cell configuration information is used can be avoided.

The specific flow is shown in fig. 7. Wherein:

the L1/L2 handover preparation is the same as the L1/L2 candidate cell selection of example one and the steps 301a-302, and will not be repeated here.

L3 switching preparation, gNB-CU selects candidate cells for L3 switching for UE, and configuration information of the candidate cells is obtained.

In step 701, a source gNB-DU sends an L1/L2 handover command to the UE, indicating the target cell identity for UE handover.

Step 702, the gNB-CU sends a configuration information acquisition request message to the gNB-DU where the UE serving cell is located, and requests the current configuration information of the UE.

In step 703, the gNB-DU sends a configuration information indication message to the gNB-CU. If the UE is triggered to perform the L1/L2 handover, the gNB-DU feeds back to the gNB-CU that the acquisition of the UE configuration information fails, and indicates that the reason for the failure of the acquisition of the UE configuration information is that the UE is performing the L1/L2 handover. Otherwise, configuration information of the UE is provided to the gNB-CU.

In step 704, the ue accesses to the target cell according to the L1/L2 handover command in step 701. The target cell may be located in the source gNB-DU or in other gNB-DUs.

Step 705, when the UE handover is completed, the gNB-DU to which the target cell belongs sends a message that the UE access is successful to the gNB-CU, and indicates to the CU that the UE updates the serving cell through L1/L2 handover. The message at least comprises: target cell identity, handover mode (L1/L2 handover, or conditional handover).

Wherein example three and example five may each be used in combination with example four.

Example six shows another cooperative approach to L1/L2 handover and L3 handover.

In the layer 3 (L3) handover preparation stage, when the configuration information of the target cell adopts an incremental configuration (delta) mode, when the target cell has completed configuration, the target gNB (also referred to as candidate gNB) has already sent the configuration information of the target cell to the source gNB-CU/gNB, and if the L1/L2 handover causes the serving cell to change at this time, it will cause that the UE cannot correctly obtain the configuration information of the target cell after receiving the L3 handover command. Therefore, the source gNB-CU/gNB can provide a set of cell configuration information as a reference (or referred to as reference cell configuration information) to serve as a reference for incremental configuration of the target cell, and the UE can obtain complete target cell configuration information by combining the incremental configuration information of the target cell based on the reference cell configuration information. The reference cell configuration information may select configuration information of one cell from candidate cells or current serving cells of L1/L2 handover as reference cell configuration information, or may use general reference cell configuration information (or referred to as general cell configuration information or referred to as first cell configuration information), or other cell configuration information as reference cell configuration information. The layer 3 handover command sent to the UE by the source gNB-CU/gNB includes configuration information of the target cell and the referenced configuration indication information, which is used to indicate whether the common reference cell configuration information or other cell configuration information is adopted. The specific flow is shown in fig. 15. Wherein when L3 is switched, the inter-gNB switching is involved, and gNB-CU is a source gNB-CU relative to a target gNB/gNB-CU.

Step L1/L2 handover preparation, between gNB-CU and gNB-DU where candidate cell is located, determination of L1/L2 handover candidate cell and cell information configuration are completed, and the steps are the same as step L1/L2 candidate cell selection in example one and steps 301a-302, and are not repeated here. And the gNB-CU also needs to determine the configuration information of the reference cell, whether to use the general configuration information of the reference cell or the configuration information of a cell selected from the candidate cell or the current service cell of the L1/L2 handover as the configuration information of the reference cell.

In step 1501a, the source gNB-DU sends a first reconfiguration message (RRCReconfiguration) to the UE, including configuration information related to L1/L2 handover and/or reference cell configuration information for L3 handover. The information contained in the first reconfiguration message comprises at least one of the following information:

-information contained in the reconfiguration message in step 301 a;

-reference cell configuration information comprising generic reference cell configuration information.

In step 1501b, the ue sends a reconfiguration complete message to the source gNB-DU (RRCReconfiguration Complete).

In step 1501c, the UE sends a measurement report to the gNB-CU (Measurement Report).

In step 1502a, the gNB-CU sends a HANDOVER REQUEST message (HANDOVER REQUEST) to the target gNB/gNB-CU requesting to HANDOVER the UE to the target cell and configuring resources for the UE. The switching request message comprises at least one of the following information:

Target cell identity, cell CGI (Cell Global ID), or other identity.

-RRC context (RRC context), the gNB-CU being sent to the target gNB/gNB-CU in a container manner in the form of a handover preparation information message (handover preparation information), comprising at least one of the following information:

reference configuration cell identity (or referred to as reference cell identity or referred to as reference configured cell identity), if configuration information of the L1/L2 handover candidate cell or the current serving cell or other cell is used as reference cell configuration information, if the configuration information of the cell is already transmitted to the UE, then the serving cell identity servCellIndex, or cell identity CellIndex, of the cell needs to be provided, and/or cell CGI (Cell Global ID). If the reference configuration cell identity is not included, the target cell considers the provided reference cell configuration information to be common reference cell configuration information.

Reference cell configuration information for resource allocation by the target cell for the UE, configuration information (full configuration or incremental configuration) of the target cell for the UE. Which contains other information than the reference configured cell identity required in the handover preparation information message.

In step 1502b, the target gNB/gNB-CU sends a handover request confirm message (HANDOVER REQUEST ACKNOWLEDGE) to the gNB-CU indicating that resource preparation is complete for the UE to handover to the target cell. The target gNB/gNB-CU sends the configured resources in a container form to the gNB-CU through a handover request acknowledgement message using the format of a handover command message (HandoverCommand message). The handover request confirm message contains at least one of the following information:

-a complete configuration use indication indicating whether the configuration information of the target message adopts a complete configuration fullconfig. If the complete configuration usage indication is "yes" (true), the provided configuration information of the target cell will be complete configuration information, otherwise the provided configuration information of the target cell is incremental configuration information based on the reference cell configuration information.

-a generic reference cell configuration information indication (or referred to as generic cell configuration information indication, or referred to as first cell configuration information indication) for indicating whether the reference cell configuration information is generic reference cell configuration information when the target cell configuration information is configured in increments. If the handover command message does not contain the general reference cell configuration information indication, the UE obtains complete target cell configuration information based on the cell configuration information corresponding to the reference configuration cell identifier. If the handover command message includes the generic reference cell configuration information indication, the UE will obtain complete target cell configuration information based on the generic reference cell configuration information obtained in step 1501 a. Or if the general reference cell configuration information indicates that it is set to "yes" (wire), the UE will obtain the complete target cell configuration based on the general reference cell configuration information obtained in step 1501 a. Otherwise, the UE obtains complete target cell configuration information based on the cell configuration information corresponding to the reference configuration cell identifier.

-reference configured cell identity. And if the configuration information provided by the target cell is incremental configuration information based on reference configuration information, configuring the cell identification by the reference, wherein the reference configuration information is used for indicating the cell identification of the incremental configuration reference. The reference configures a cell identity, which may be a serving cell identity servCellIndex, or a cell identity CellIndex, and/or a cell CGI (Cell Global ID).

-target cell configuration information, which if a complete configuration is employed, will contain complete information of the target cell configuration. If incremental configuration is adopted, the target cell configuration information comprises incremental configuration information based on the reference cell configuration. The target cell configuration information is other information except the complete configuration use indication, the general reference cell configuration information indication and the reference configuration cell identification in the RRCRECONfigure message.

The gNB-CU sends a handover command message obtained from the target gNB to the UE by the source gNB-DU through an RRC message.

In step 1503, the gNB-CU sends a UE context modification request message (UE CONTEXT MODIFICATION REQUEST) to the source gNB-DU, including the RRC message sent to the UE by the gNB-CU.

In step 1504, the source gNB-DU sends a second reconfiguration message (RRC Reconfiguration) to the UE for instructing the UE to conduct inter-gNB cell handover. The second reconfiguration message includes information in the handover command message in step 1502 b.

In step 1505, the source gNB-DU sends a UE context modification response message (UE CONTEXT MODIFICATION RESPONSE) to the gNB-CU indicating that an RRC reconfiguration message has been sent to the UE.

In step 1506, the ue performs a random access procedure to access the target cell.

In step 1507, the ue sends a reconfiguration complete message (RRC Reconfiguration Complete) to the target gNB/gNB-CU, indicating that the configuration of the target cell is complete.

In step 1508, after the UE accesses the target cell, the target gNB/gNB-CU instructs the gNB-CU to perform UE context release. The gNB-CU will instruct the source gNB-DU and the candidate gNB-DU to release the UE context.

Example seven presents another synergistic approach to L1/L2 handover and L3 handover.

When the gNB-CU receives the L1/L2 switching request from the gNB-DU, if the gNB-CU (or RRC layer) prepares to trigger the L3 switching according to the L3 measurement result reported by the UE, the gNB-CU can decide whether to reject the L1/L2 switching request or not according to the quality of the target cell of the L1/L2 switching and the target cell of the L3 switching or other factors, and the serving cell of the UE is changed by adopting the L3 switching. When the gNB-CU receives the L1/L2 switching request from the gNB-DU, if the gNB-CU (or RRC layer) is not ready to trigger the L3 switching, the L1/L2 switching request of the gNB-DU is agreed, namely, the serving cell of the UE is agreed to be changed in an L1/L2 switching mode. The specific flow is shown in fig. 16. Wherein when L3 is switched, the inter-gNB switching is involved, and gNB-CU is a source gNB-CU relative to a target gNB/gNB-CU.

The L1/L2 handover preparation phase includes L1/L2 candidate cell selection of example one, steps 301a-302, and steps 1501a and 1501b of example six (FIG. 15), which are not described here again.

In step 1601, the source gNB-DU sends an L1/L2 handover request message to the gNB-CU requesting to perform an L1/L2 handover to change the serving cell of the UE. The L1/L2 handover request message may be a UE context modification required message (UE CONTEXT MODIFICATION REQUIRED), or other message.

In step 1602, the gNB-CU sends an L1/L2 handover request response message to the source gNB-DU indicating whether to agree to change the serving cell of the UE with L1/L2 handover. If the gNB-CU is not ready to trigger L3 handover at this time, or is ready to trigger L3 handover, but decides that the serving cell of the UE changes to the target cell for L1/L2 handover based on the quality of the target cell for L1/L2 handover and the target cell for L3 handover or other factors, thus agreeing to the L1/L2 handover request of the source gNB-DU and will perform step 1603 (no further steps need to be performed in FIG. 16), and the gNB-CU will cease triggering L3 handover (if there was a ready to trigger L3 handover before), and/or will release the relevant measurement results. Otherwise, if the gNB-CU (or RRC layer) decides to perform the L3 handover, or considers to stop the L1/L2 handover, steps 1604-1610 will be performed, L3 handover preparation and execution will be performed. The L1/L2 handover request response message may contain at least one of the following information:

-an L1/L2 handover indication for indicating whether an L1/L2 handover is agreed to be performed.

-reject reason, if L1/L2 handover is rejected, then reject reason will be provided. For example, an L3 handover is ready to be performed.

When the feedback received by the source gNB-DU is that the L1/L2 handover is not agreed to be executed, the source gNB-DU stops triggering the L1/L2 handover.

The L1/L2 handover request response message may be a UE context modification confirm message (UE CONTEXT MODIFICATION CONFIRM), or other message.

In step 1603, the source gNB-DU sends an L1/L2 handover command to the UE, indicating the UE to handover to the target cell. The L1/L2 handover command may be transmitted using physical layer signaling or MAC CE.

In step 1604, the gNB-CU sends a serving cell configuration information request message to the source gNB-DU, and requests the source gNB-DU for the resource configuration information of the UE in the current serving cell. The serving cell configuration information request message may be a UE context modification request message (UE CONTEXT MODIFICATION REQUEST), or other message.

In step 1605, the source gNB-DU sends a serving cell configuration information response message to the gNB-CU, and provides the resource configuration information of the UE in the current serving cell to the gNB-CU. The serving cell configuration information request message may be a UE context modification response message (UE CONTEXT MODIFICATION RESPONSE), or other message.

In step 1606, the gNB-CU sends a HANDOVER REQUEST (HANDOVER REQUEST) to the target gNB/gNB-CU requesting allocation of resources for the UE to access the target cell. The switching request message comprises at least one of the following information:

target cell identity, cell CGI (Cell Global ID), or other identity.

The RRC context (RRC context), the gNB-CU sends to the target gNB/gNB-CU in the form of a handover preparation information message (handover preparation information) in a container manner, providing the current serving cell configuration information obtained in step 1605.

In step 1607, the target gNB/gNB-CU sends a handover request confirm message (HANDOVER REQUEST ACKNOWLEDGE) to the gNB-CU indicating that resource preparation is complete for the UE to handover to the target cell. The target gNB/gNB-CU sends the configured resources in a container form to the gNB-CU through a handover request acknowledgement message using the format of a handover command message (HandoverCommand message).

In steps 1608-1610, the gNB-CU sends the handover command received in step 1607 to the UE in the form of an RRC message via the source gNB-DU, instructing the UE to perform L3 handover. Wherein the reconfiguration message of step 1609 is a rrcrecon configuration message, or other message; the messages of steps 1608 and 1609 are a UE context modification request message (UE CONTEXT MODIFICATION REQUEST) and a UE context modification response message (UE CONTEXT MODIFICATION RESPONSE), respectively, or other messages.

Example eight shows another collaborative approach for L1/L2 handover and L3 handover.

When the gNB-CU (or RRC layer) prepares to trigger the L3 switching according to the L3 measurement result reported by the UE, an instruction is sent to the gNB-DU, the gNB-CU executes the L3 switching to change the service cell of the UE, and after the gNB-DU receives the instruction, the L1/L2 switching is suspended to trigger. After the gNB-CU obtains the configuration information of the target cell, an RRC message is sent to the UE, and the UE is instructed to perform L3 handover. The specific flow is shown in FIG. 17, where when L3 handover involves inter-gNB handover, gNB-CU is the source gNB-CU with respect to the target gNB/gNB-CU.

In step 1701, the gNB-CU sends a handover preparation request message to the source gNB-DU, sends an indication to the source gNB-DU that the gNB-CU will perform L3 handover to change the serving cell of the UE, and instructs the source gNB-DU to provide the resource configuration information of the UE in the current serving cell. When the source gNB-DU receives the message, the L1/L2 switching is triggered in a suspension mode, and the resource configuration information of the UE in the current service cell is provided. The handover preparation request message may be a UE context modification request message (UE CONTEXT MODIFICATION REQUEST), or other message.

In step 1702, the source gNB-DU sends a handover preparation response message to the gNB-CU, and provides the gNB-CU with the resource configuration information of the UE in the current serving cell. The handover preparation response message may be a UE context modification response message (UE CONTEXT MODIFICATION RESPONSE), or other message.

In steps 1704-1704, the target gNB/gNB-CU completes the target cell resource configuration for the UE and forms an RRC message sent to the UE. The details are the same as in steps 1606-1607 and are not described here in detail.

Steps 1705-1707 are identical to steps 1608-1610 and are not described in detail herein.

Example nine presents another synergistic approach to L1/L2 handover and L3 handover.

If the gNB-DU and gNB-CU (or RRC layer) trigger both the L1/L2 handover and the L3 handover, then an L1/L2 handover command and an RRC reconfiguration message, respectively, may be sent to the UE, which target cell is selected for access by the UE. The specific flow is shown in fig. 18.

The L1/L2 handover preparation phase includes L1/L2 candidate cell selection of example one, steps 301a-302, and steps 1501a and 1501b of example six (FIG. 15), which are not described here again. And will not be described in detail herein.

And the UE performs L1 measurement and L3 measurement according to the measurement configuration information in the L1/L2 switching preparation stage, and respectively sends a first measurement report and a second measurement report to the gNB-CU and the source gNB-DU according to the measurement reporting requirement.

If the gNB-CU decides to trigger L3 handover, through steps 1802a-1802b, the target gNB/gNB-CU completes the target cell resource configuration for the UE and forms an RRC message sent to the UE. The details are the same as those of steps 1502a-1502b and will not be repeated here. And through steps 1803 and 1804a, an RRC reconfiguration message from the gNB-CU is sent to the UE through the gNB-DU, instructing the UE to perform L3 handover for cell change. The details are the same as in steps 1503-1504.

If the gNB-DU decides to trigger an L1/L2 handover, an L1/L2 handover command is sent through step 1804b, instructing the UE to make a cell change.

When the UE receives both the RRC reconfiguration message and the L1/L2 handover command through steps 1804a and 1804b, it will decide which target cell to select for handover. If the cell in the L1/L2 switching command is selected, the L1/L2 switching executing process is carried out, otherwise the L3 switching executing process is carried out.

Method for reducing UE service interruption when L1/L2 handover fails in example aspect III

In the L1/L2 switching process, after the UE receives the L1/L2 switching command, the PDCCH of the target cell is directly monitored to obtain downlink scheduling information or uplink authorization information. If the UE cannot monitor the PDCCH, the service transmission cannot be normally performed, and the service transmission of the UE is affected. In order to avoid that the UE cannot monitor the PDCCH channel for a long time and influence service transmission, the patent sets a timer T for L1/L2 switching, and when the UE receives an L1/L2 switching command, the timer T is started after the UE completes the configuration of a target cell, and the PDCCH is started to be monitored in the target cell. If the timer T is overtime, the UE does not monitor the PDCCH sent to the UE by the target cell, and the L1/L2 handover is considered to be failed. If the UE judges that the L1/L2 switching fails, the UE executes a cell selection process and resumes the connection with the network as soon as possible, thereby ensuring the service transmission.

Example ten shows a method for restoring the service connection when the UE determines that the L1/L2 handover fails. The specific flow is shown in fig. 8. Since this embodiment focuses on how to determine that the L1/L2 handover of the UE fails and how to guarantee the UE to recover and connect to the network, other steps, such as the step of selecting the L1/L2 handover target cell by the network according to the UE measurement result, are described in detail in examples one and two, and are omitted here. Wherein:

step 801 is the same as step 301, and steps 802-802b are the same as steps 308a-308b, and the details are not repeated.

In step 801, a timer T is configured for the UE when the network switches configuration for L1/L2.

In step 803, after receiving the L1/L2 handover command and completing the configuration of the target cell, the ue starts a timer T and starts monitoring the PDCCH in the target cell. If the timer T is overtime, the UE does not monitor the PDCCH sent to the UE by the target cell, and the L1/L2 switching is considered to be failed, and the UE performs cell selection. Wherein the information of the timer T is obtained by the UE through the reconfiguration message of step 800.

-if the UE selects a target cell that is a candidate cell for L1/L2 handover configuration, the UE performs a random access procedure step 804 in the selected target cell. In message 3 (MSG 3) in the random access procedure, the UE transmits the C-RNTI previously allocated to the UE by the target cell to the target cell, and the target cell identifies the UE through the received C-RNTI. If the communication context of the UE is still reserved in the target cell, after completing the random access procedure, the target cell considers that the UE has completed L1/L2 handover, and directly sends downlink scheduling or uplink grant information to the UE, that is, step 805 is executed. After the random access process is completed, the UE also monitors the PDCCH sent to the UE in the target cell. If the PDCCH transmitted to the UE in step 805 is received, the handover is considered to be successful.

-if the cell selected by the UE is not a candidate cell for the L1/L2 handover configuration, the UE triggers an RRC reestablishment procedure, restoring the connection with the network.

In step 804, the ue performs a random access procedure.

In step 805, the target cell sends downlink scheduling/uplink grant information to the UE. Indicating that the UE successfully accesses the target cell.

Step 806, the gNB-DU to which the target cell belongs sends an indication message of successful access of the UE to the gNB-CU, and indicates that the UE completes L1/L2 handover and has successfully accessed the target cell. The message contains at least one of the following information:

And judging whether the target cell accessed by the UE and the target cell provided by the source cell in step 802b are the same according to the received target cell identification by the gNB-CU. If the two target cells are not identical:

if the source cell-selected target cell and the UE-selected target cell are in the same gNB-DU, the gNB-CU need only perform step 807, send an L1/L2 handover complete message to the source gNB-DU. When the source cell judges whether the target cell selected by the UE is the same as the target cell selected by the source cell according to the target cell identification in the L1/L2 handover completion message, if so, the selected target cell is instructed to stop the L1/L2 handover process of the UE and stop the service scheduling of the UE.

If the source cell-selected target cell and the UE-selected target cell are in different gNB-DUs, the gNB-CU still needs to perform step 808 at the same time as step 807. The target cell selected by the source cell is instructed to stop the L1/L2 switching process of the UE, and the service scheduling of the UE is stopped.

In step 807, the gNB-CU sends an L1/L2 handover complete message of the UE to the gNB-DU to which the source cell belongs. The message contains at least one of the following information:

The L1/L2 handover complete message may be a UE context modification request message UE CONTEXT MODIFICATION REQUEST, or other message.

Step 808, the gNB-CU sends an L1/L2 handover stop message to the gNB-DU to which the candidate cell belongs. If the target cell accessed by the UE is different from the target cell selected by the source cell, the gNB-CU sends an L1/L2 handover stop message to the gNB-DU to which the target cell selected by the source cell belongs, and indicates that the UE is accessed to other cells, and service scheduling of the UE is stopped. The message contains at least one of the following information:

The L1/L2 handover stop message may be a UE context modification request message UE CONTEXT MODIFICATION REQUEST, or other message.

Example eleven presents a method of L1/L2 target cell selection. The network does not need to determine a target cell for the UE, and the UE selects a cell meeting the execution condition as the target cell for access according to the candidate cell provided by the network and the execution condition of L1/L2 switching and the measurement result.

The specific flow is shown in fig. 9. Wherein,

and L1/L2 candidate cell selection, and the determination and information configuration of the L1/L2 handover candidate cell are completed between the gNB-CU and the gNB-DU where the candidate cell is located.

Steps 902-906 and steps 909-914 are the same as steps 302-306 and steps 309-314, and are not repeated here.

In step 900, the gNB-CU sends an L1/L2 handover request message to the source gNB-DU, which indicates that the gNB-DU can change the serving cell of the UE by adopting an L1/L2 handover mechanism, and the target cell can be selected by using a conditional reconfiguration mode, namely, the target cell is selected by the UE. The serving cell may be a PCell, a PSCell or a Scell. The message includes the following information in addition to the information of step 300:

(1) The UE selects target cell indication information, and the target cell for indicating the L1/L2 handover is determined by the UE selection. Comprising at least one of the following information:

-L1/L2 handover execution conditions, when the candidate cell measurement results meet the execution conditions, can be used as target cell. If the L1/L2 handover execution condition is not included in the message, the L1/L2 handover execution condition of the candidate cell will be determined by the source gNB-DU (source cell).

-dedicated preambles or special signals for uplink synchronization use when the UE accesses the target cell, or for network identification of the UE. If the special preamble or special signal is not contained in the message, it is determined by the source gNB-DU.

In step 901a, the source gNB-DU sends a reconfiguration message (RRCReconfiguration) to the UE, including the configuration information of the candidate cell. The message may contain the information of step 301a, and may also contain the following information:

-L1/L2 handover execution conditions, when the candidate cell measurement results meet the execution conditions, can be used as target cell.

-a dedicated preamble or special signal for transmission in the target cell when the UE accesses the target cell.

Since the target cell is selected based on the UE itself, after the UE completes synchronization with the candidate cell selected by the network according to the network indication through steps 904-906, the UE will determine whether there is a candidate cell satisfying the L1/L2 handover execution condition according to the measurement result.

When the UE monitors that there are candidate cells satisfying the L1/L2 handover execution condition according to the measurement result, the UE will select one of them as the target cell, execute step 908, and send a dedicated preamble or a special signal to the target cell, where the dedicated preamble or the special signal is obtained in step 901 a.

Through step 908, when the target cell detects that the UE accesses the cell, scheduling and transmission of UE service data begin to be performed, step 910 is performed, and a PDCCH is sent to the UE to perform downlink scheduling or uplink authorization of UE service.

Since the network side does not need to select the target cell for the UE, if the dedicated preamble or special signal used in step 908 is selected by the source gNB-DU, the preamble or special signal determined by the source gNB-DU is sent to the candidate cell, so that when the UE selects the candidate cell as the target cell, the access of the UE can be identified, thereby performing step 910. Steps 907a and 907b need to be performed if the target cell and the source cell are in different gNB-DUs, which need to be forwarded by the gNB-CU. Wherein the source gNB-DU sends a first L1/L2 dedicated preamble and/or special signal information indication to the gNB-CU, the UE context modification required message UE CONTEXT MODIFICATION REQUIRED, or other message transmission, may be used. The source gNB-CU sends the received L1/L2 specific preamble and/or special signal information indication to the candidate gNB-DU via the second L1/L2 specific preamble and/or special signal information indication, which may use the UE context modification request message UE CONTEXT MODIFICATION REQUEST, or other message transmission.

Next, fig. 10 illustrates a flow chart of a method 1000 performed by a first node in a wireless communication system according to an embodiment of the disclosure.

As shown in fig. 10, a method 1000 performed by a first node in a wireless communication system according to an embodiment of the present disclosure may include the following steps. In step S1001, the first node may receive, for example, related information of the first candidate cell from the second node. In step S1002, a first node may send a first message to the user equipment, the first message may include synchronization indication information and related information of a second candidate cell, and the second candidate cell may be based on packet information to which the first candidate cell belongs. In some embodiments, the packet information to which the first candidate cell belongs may be determined by the first node itself, or may be received from another node (e.g., the second node). In step S1003, the first node may send a handover related indication to the user equipment.

Fig. 11 illustrates a flow chart of a method 1100 performed by a user equipment in a wireless communication system according to an embodiment of the disclosure.

As shown in fig. 11, a method 1100 performed by a user equipment in a wireless communication system according to an embodiment of the disclosure may include the following steps. In step S1101, the user equipment may receive a first message from the first node, the first message may include synchronization indication information and related information of a second candidate cell, the second candidate cell being based on packet information to which the first candidate cell belongs. In step S1102, the user equipment may receive a handover related indication from the first node. In some embodiments, the information about the first candidate cell may be received by the first node (e.g., from a second node).

Fig. 12 illustrates a flowchart of a method 1200 performed by a second node in a wireless communication system, according to an embodiment of the disclosure.

As shown in fig. 12, a method 1200 performed by a second node in a wireless communication system according to an embodiment of the disclosure may include: in step S1201, the second node transmits the related information of the first candidate cell to the first node. In step S1202, the second node receives the response message sent by the first node. In some embodiments, the information about the first candidate cell and the grouping information to which the first candidate cell belongs may be used to determine the second candidate cell. In some embodiments, the relevant information and synchronization indication information of the second candidate cell may be used for transmission to a user equipment for synchronization of the user equipment with the second candidate cell.

It should be appreciated that methods 1000, 1100, and 1200 according to embodiments of the present disclosure may also include one or more of the methods or steps as described above in connection with any examples or figures, and are not repeated here.

Next, fig. 13 shows a schematic diagram of a node 1300 in a wireless communication system according to an embodiment of the present disclosure.

As shown in fig. 13, a node 1300 (which may be, for example, a first node, a second node, or any other network node as described above) according to an embodiment of the present disclosure may include a transceiver 1310 and a processor 1320. The transceiver 1310 may be configured to transmit and receive signals. Processor 1320 may be coupled to transceiver 1310 and may be configured (e.g., to control transceiver 1310) to perform any method performed by a node in a wireless communication system in accordance with an embodiment of the disclosure.

Fig. 14 shows a schematic diagram of a user device 1400 according to an embodiment of the disclosure.

As shown in fig. 14, a user device 1400 according to an embodiment of the present disclosure may include a transceiver 1410 and a processor 1420. The transceiver 1410 may be configured to transmit and receive signals. The processor 1420 may be coupled to the transceiver 1410 and may be configured (e.g., to control the transceiver 1410) to perform any method performed by a user equipment according to embodiments of the present disclosure. The processor may also be referred to herein as a controller.

Various embodiments of the present disclosure may be implemented as computer readable code embodied on a computer readable recording medium from a particular perspective. The computer readable recording medium is any data storage device that can store data which can be read by a computer system. Examples of the computer readable recording medium may include a read-only memory (ROM), a random-access memory (RAM), a compact disc read-only memory (CD-ROM), a magnetic tape, a floppy disk, an optical data storage device, a carrier wave (e.g., data transmission via the internet), and so forth. 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, functional programs, codes, and code segments for accomplishing the various embodiments of the present disclosure may be easily construed by one skilled in the art to which the embodiments of the present disclosure are applied.

It will be understood that embodiments of the present disclosure may be implemented in hardware, software, or a combination of hardware and software. The software may be stored as program instructions or computer readable code executable on a processor on a non-transitory computer readable medium. Examples of the non-transitory computer readable recording medium include magnetic storage media (e.g., ROM, floppy disks, hard disks, etc.) and optical recording media (e.g., CD-ROMs, digital Video Disks (DVDs), etc.). The non-transitory computer readable recording medium can also be distributed over network coupled computer systems so that the computer readable code is stored and executed in a distributed fashion. The medium may be readable by a computer, stored in a memory, and executed by a processor. The various embodiments may be implemented by a computer or a portable terminal including a controller and a memory, and the memory may be an example of a non-transitory computer-readable recording medium adapted to store a program(s) having instructions to implement the embodiments of the present disclosure. The present disclosure may be implemented by a program having codes for embodying the apparatus and method described in the claims, the program being stored in a machine (or computer) readable storage medium. The program may be carried electronically on any medium, such as communication signals conveyed via a wired or wireless connection, and the disclosure suitably includes equivalents thereof.

The foregoing is merely a specific embodiment of the present disclosure, but the scope of the present disclosure is not limited thereto, and any person skilled in the art may make various changes or substitutions within the technical scope of the present disclosure, and such changes or substitutions are intended to be included in the 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 first node in a wireless communication system, comprising:

receiving related information of a first candidate cell;

transmitting a first message to the user equipment, wherein the first message comprises synchronization indication information and related information of a second candidate cell, and the second candidate cell is based on grouping information of the first candidate cell; and

and sending a handover related indication to the user equipment.

2. The method of claim 1, further comprising:

receiving packet information of the first candidate cell from a second node; or (b)

And grouping the first candidate cells based on the related information of the first candidate cells, and determining the grouping information.

3. The method of claim 1, wherein transmitting a handover-related indication to the user equipment comprises one of:

Transmitting a handover command to the user equipment, wherein the handover command comprises information of a target cell; or (b)

And sending a reconfiguration message to the user equipment, wherein the reconfiguration message comprises information of the third candidate cell and/or a handover execution condition.

4. The method of claim 1, further comprising:

transmitting the first cell configuration information received from the second node to the user equipment;

and transmitting the cell related information which is received from the second node and is used for indicating and/or referencing the first cell configuration information or not to the user equipment.

5. The method of claim 1, further comprising:

a timing advance value associated with a second candidate cell is received from a second node.

6. The method of claim 5, wherein transmitting a handover related indication to the user equipment further comprises transmitting the timing advance value to the user equipment.

7. The method of claim 1, further comprising:

receiving a reconfiguration message from a second node to the user equipment; and

and sending a response message to the second node, wherein the response message comprises at least one of a reject reason, a target cell for L1/L2 handover and configuration information of the target cell for L1/L2 handover.

8. A method performed by a user equipment in a wireless communication system, comprising:

receiving a first message from a first node, wherein the first message comprises synchronization indication information and related information of a second candidate cell, and the second candidate cell is based on grouping information of the first candidate cell; and

a handover related indication is received from the first node,

wherein the information about the first candidate cell is received by the first node.

9. The method of claim 8, wherein receiving a handover-related indication from the first node comprises one of:

receiving a handover command from the first node, wherein the handover command comprises information of a target cell, and monitoring a PDCCH (physical downlink control channel) based on the information of the target cell; or (b)

Receiving a reconfiguration message from the first node, wherein the reconfiguration message comprises information of a third candidate cell and/or a handover execution condition; and selecting a target cell based on the information of the third candidate cell and/or the handover execution condition, and monitoring the PDCCH.

10. The method of claim 9, receiving a handover related indication from the first node further comprises receiving a timing advance value from the first node.

11. The method of claim 8, further comprising:

receiving first cell configuration information from a first node; and

cell related information is received from a first node indicating whether to employ the first cell configuration information and/or a reference.

12. A method performed by a second node in a wireless communication system, comprising:

transmitting to the first node related information of the first candidate cell;

receiving a response message sent by a first node;

wherein the related information of the first candidate cell and the grouping information of the first candidate cell are used for determining a second candidate cell,

the related information and the synchronization instruction information of the second candidate cell are used for being sent to the user equipment for the user equipment to synchronize with the second candidate cell.

13. A node in a wireless communication system, comprising:

a transceiver configured to transmit and receive signals; and

a controller coupled with the transceiver and configured to perform the method of any of claims 1-7 or 12.

14. A user equipment in a wireless communication system, comprising:

a transceiver configured to transmit and receive signals; and

A controller coupled with the transceiver and configured to perform the method of claims 8-11.

15. A computer readable medium having stored thereon computer readable instructions for implementing the method of any of claims 1-7 or 8-11 or 12 when executed by a processor.