Method and apparatus for CHO with candidate SCG for CPC / CPA procedures

Abstract

Embodiments of the present application relate to a method and apparatus for a conditional handover (CHO) with a candidate secondary cell group (SCG) for a conditional primary / secondary cell group (PSCell) change (CPC) / conditional PSCell addition (CPA) procedure. According to embodiments of the present application, a user device (UE) includes a transceiver and a processor coupled to the transceiver, the processor configured to cause the UE to receive radio resource control (RRC) configuration information for a CHO with a candidate secondary cell group (SCG) for a conditional primary / secondary cell group (PSCell) change (CPC) / conditional PSCell addition (CPA) procedure, and to access a candidate PCell based on the RRC configuration information.

Description

Technical Field

[0001] Embodiments of the present application generally relate to wireless communication technologies, and more particularly, to methods and apparatuses for conditional handover (CHO) with a candidate secondary cell group (SCG) for conditional primary-secondary cell group (PSCell) change (CPC) / conditional PSCell addition (CPA) procedures.

Background Art

[0002] In a plurality of wireless dual connectivity (MR-DC) scenarios, a UE having a plurality of transceivers may be configured to use resources provided by two different nodes connected via a non-ideal backhaul. One node may provide new radio (NR) access, and the other node may provide either evolved universal mobile telecommunications system (UMTS) terrestrial radio access (UTRA) (E-UTRA) or NR access. One node may act as a master node (MN), and the other node may act as a secondary node (SN). The MN and the SN are connected via a network interface (e.g., the Xn or X2 interface defined in 3rd Generation Partnership Project (3GPP (registered trademark)) standard documents), and at least the MN is connected to the core network.

[0003] Currently, Conditional PSCell Addition (CPA) procedures and Conditional PSCell Modification (CPC) procedures are supported. A CPAC procedure may be either a CPA procedure or a CPC procedure. According to the agreements in the 3GPP standard document, a CPAC procedure is defined as a PSCell Addition or PSCell Modification performed by the UE when the configured CPAC execution conditions are met or achieved. When the UE receives CPAC-related configuration information, it begins evaluating the CPAC execution conditions, and when a PSCell Addition and / or Modification procedure is triggered or executed, it stops evaluating the CPAC execution conditions. The triggering or execution of a PSCell Addition and / or Modification procedure means that when the CPAC execution conditions for a candidate PSCell are met or achieved (the "candidate PSCell" may also be referred to as the "CPAC candidate PSCell"), the UE determines the candidate PSCell to be the target PSCell and executes a PSCell Addition or Modification procedure with the target PSCell, for example, the UE executes an RA procedure to the target PSCell.

[0004] A CHO with a candidate SCG for a CPC / CPA procedure may also be referred to as a "CHO ​​procedure with a candidate SCG," or "CHO ​​including a target MCG and a candidate SCG for a CPC / CPA procedure," or "CHO ​​including a target MCG and a candidate SCG for a CPA / CPC procedure," or "CHO ​​procedure with a candidate SCG," or "CHO ​​procedure including a target MCG and a candidate SCG," or "CHO ​​procedure including a candidate target MCG and a candidate target SCG for a CPC / CPA procedure," or "CHO ​​procedure including a candidate target MCG and a candidate target SCG."

[0005] In a CHO with a candidate SCG for a CPC / CPA procedure, when the UE receives a configuration for the CHO (i.e., a CHO configuration that references or includes a CPC or CPA configuration, or a configuration for a CHO procedure with a candidate SCG) that includes the target MCG and candidate SCG for the CPC / CPA procedure, for example, when the UE receives a configuration for a CHO candidate (target) PCell, CHO execution conditions, a configuration for a CPAC candidate (target) PSCell, and CPAC execution conditions, the CHO evaluation and the CPC or CPA evaluation may be in parallel. For example, the UE begins evaluating the CHO execution conditions for a candidate (target) PCell and the CPAC execution conditions for a candidate (target) PSCell at the same time (when it receives the configuration for a CHO procedure with a candidate SCG). The UE does not execute either CPC or CPA until the CHO execution conditions for the CHO candidate PCell are met.

[0006] At present, details regarding the concurrent execution of PCell / PSCell changes and the MRO mechanism for CHO with candidate SCGs for CPC / CPA procedures (i.e., CHO procedures with candidate SCGs) have not yet been discussed. [Overview of the project] [Means for solving the problem]

[0007] Some embodiments of this application provide a user device (UE). The UE includes a transceiver and a processor coupled to the transceiver, the processor configured to cause the UE to receive first radio resource control (RRC) configuration information for a CHO with a candidate secondary cell group (SCG) for a conditional primary / secondary cell group (PSCell) change (CPC) / conditional PSCell addition (CPA) procedure, and to access the candidate PCell based on the first RRC configuration information.

[0008] In some embodiments, the first RRC configuration information includes a first CHO configuration associated with a candidate primary cell (PCell), a first CHO execution condition for the candidate PCell, configuration information for one or more candidate SCGs associated with one or more candidate PSCells, and a set of execution conditions for one or more candidate SCGs.

[0009] In some embodiments, the processor is configured to cause the UE to receive second RRC configuration information for a second CHO configuration without a candidate SCG.

[0010] In some embodiments, the second CHO execution conditions are configured for the second CHO configuration.

[0011] In some embodiments, the second RRC configuration information includes a first instruction indicating the relationship between the second CHO configuration and the first CHO configuration.

[0012] In some embodiments, in response to receiving a first instruction, the processor is configured to cause the UE to consider that the second CHO execution condition for the second CHO configuration is the same as the first CHO execution condition for the candidate PCell.

[0013] In some embodiments, in response to the fulfillment of both a second CHO execution condition for a second CHO configuration and a first CHO execution condition for a first CHO configuration, the processor is configured to cause the UE to perform a CHO on both a candidate PCell and a candidate PSCell associated with a candidate SCG, based on the first CHO configuration, in response to the fulfillment of a set of execution conditions for one candidate SCG among one or more candidate SCGs, or to perform a CHO on a candidate PCell, based on the second CHO configuration, in response to the failure to fulfill a set of execution conditions for one or more candidate SCGs.

[0014] In some embodiments, the processor is configured to cause the UE to receive a second instruction indicating that the UE is permitted to perform the CHO based on a second CHO configuration without a candidate SCG, or a third instruction indicating that the second CHO configuration without a candidate SCG associated with a candidate PCell is the same as the first CHO configuration associated with a candidate PCell.

[0015] In some embodiments, in response to receiving a second or third instruction, the processor is configured to cause the UE to consider the second CHO configuration to be the same as the first CHO configuration.

[0016] In some embodiments, in response to the failure to meet a set of execution conditions for one or more candidate SCGs and the fulfillment of a first CHO execution condition, the processor is configured to cause the UE to access a candidate PCell based on a second CHO configuration.

[0017] In some embodiments, after successfully accessing a candidate PCell based on a second CHO configuration, the processor is configured to cause the UE to release one or more SCG bearers configured in one or more candidate SCGs, or to remap one or more SCG bearers to master cell group (MCG) bearers configured in the candidate PCell.

[0018] In some embodiments, the processor is configured to cause the UE to perform a CHO based on a first or second CHO configuration and, after successfully accessing the candidate PCell, send an RRC reconfiguration complete message to the candidate PCell.

[0019] In some embodiments, the RRC reconfiguration complete message includes an instruction indicating that the UE performed a CHO based on either a first CHO configuration or a second CHO configuration.

[0020] In some embodiments, the RRC reconstruction completion message includes at least one of the identifier (ID) of the candidate PCell accessed by the UE, or the ID of the candidate PSCell accessed by the UE.

[0021] In some embodiments, in response to the fulfillment of a trigger condition, the processor is configured to cause the UE to send both a successful handover report (SHR) and a successful PSCell change report (SPCR) to the target network node.

[0022] In some embodiments, the processor is configured to cause the UE to receive thresholds from the source network node related to trigger conditions, where the thresholds are a first threshold associated with a timer for initiating failure recovery based on the triggering of the measurement report, a second threshold associated with a physical layer problem timer, or a third threshold associated with a handover timer.

[0023] In some embodiments, the threshold is a percentage of the timer length.

[0024] In some embodiments, the trigger condition includes at least one of the following: the elapsed time duration of the timer for initiating failure recovery based on the triggering of the measurement report exceeds a first threshold multiplied by the length of the timer for initiating failure recovery based on the triggering of the measurement report; the elapsed time duration of the physical layer problem timer exceeds a second threshold multiplied by the length of the physical layer problem timer; or the elapsed time duration of the handover timer exceeds a third threshold multiplied by the length of the handover timer.

[0025] In some embodiments, the SHR and SPCR are included in the UE information response message.

[0026] In some embodiments, in response to the achievement of the set of execution conditions of a plurality of SCGs within one or more candidate SCGs, the UE information response message further includes the ID information of other SCGs within the plurality of SCGs, excluding one SCG accessed by the UE.

[0027] Some embodiments of the present application provide a source network node. The source network node includes a transceiver and a processor coupled to the transceiver. The processor is configured to cause the source network node to send a handover request for CHO and receive a response from a candidate network node. The response includes a first CHO configuration related to a candidate primary cell (PCell) and configuration information about one or more candidate SCGs associated with one or more candidate PSCs.

[0028] In some embodiments, the response includes a set of execution conditions related to one or more candidate SCGs.

[0029] In some embodiments, the processor is configured to cause the source network node to receive an instruction from a candidate network node. The instruction indicates that a second CHO configuration related to the candidate PCell is the same as the first CHO configuration related to the candidate PCell.

[0030] In some embodiments, the instruction is included in a handover request reception confirmation message.

[0031] In some embodiments, the processor is configured to cause the source network node to send the instruction to the UE.

[0032] In some embodiments, the processor is configured to cause the source network node to send a threshold related to a trigger condition to a user equipment (UE). The trigger condition is for triggering the simultaneous transmission of both a successful handover report (SHR) and a successful PSCell change report (SPCR).

[0033] In some embodiments, the threshold is a percentage of the timer length.

[0034] In some embodiments, the threshold is a first threshold associated with a timer for initiating failure recovery based on the triggering of a measurement report, or a second threshold associated with a physical layer problem timer, or a third threshold associated with a handover timer.

[0035] In some embodiments, the trigger condition includes at least one of the following: the elapsed duration of the timer for initiating failure recovery based on the triggering of the measurement report exceeds a first threshold multiplied by the length of the timer for initiating failure recovery based on the triggering of the measurement report; the elapsed duration of the physical layer problem timer exceeds a second threshold multiplied by the length of the physical layer problem timer; or the elapsed duration of the handover timer exceeds a third threshold multiplied by the length of the handover timer.

[0036] Some embodiments of this application provide candidate network nodes. The candidate network node includes a transceiver and a processor coupled to the transceiver, the processor configured to cause the candidate network node to receive a handover request for CHO from a source network node and to send a response to the source network node, the response including a first CHO configuration associated with a candidate primary cell (PCell) and configuration information for one or more candidate SCGs associated with one or more candidate PSCells.

[0037] In some embodiments, the response includes a set of execution conditions relating to one or more candidate SCGs.

[0038] In some embodiments, the processor is configured to cause a candidate network node to send an instruction to a source network node, which indicates that a second CHO configuration associated with the candidate PCell is the same as a first CHO configuration associated with the candidate PCell.

[0039] In some embodiments, the processor is configured to cause candidate network nodes to receive both a successful handover report (SHR) and a successful PSCell change report (SPCR) from the user equipment (UE), and the SHR and SPCR are sent simultaneously by the UE in response to the fulfillment of a trigger condition.

[0040] In some embodiments, the trigger condition includes at least one of the following: the elapsed duration of the timer for initiating failure recovery based on the triggering of the measurement report exceeds a first threshold multiplied by the length of the timer for initiating failure recovery based on the triggering of the measurement report; the elapsed duration of the physical layer problem timer exceeds a second threshold multiplied by the length of the physical layer problem timer; or the elapsed duration of the handover timer exceeds a third threshold multiplied by the length of the handover timer.

[0041] In some embodiments, the first threshold, the second threshold, and the third threshold are each a percentage of the timer length.

[0042] In some embodiments, the SHR and SPCR are included in the UE information response message.

[0043] In some embodiments, in response to the fulfillment of a set of execution conditions for multiple SCGs within one or more candidate SCGs, the UE information response message further includes identifier (ID) information for the other SCGs within the multiple SCGs, excluding the one SCG accessed by the UE.

[0044] Some embodiments of this application provide a method that can be implemented by a UE. This method includes the steps of receiving first radio resource control (RRC) configuration information for a CHO with a candidate secondary cell group (SCG) for a conditional primary / secondary cell group (PSCell) change (CPC) / conditional PSCell addition (CPA) procedure, and accessing a candidate PCell based on the first RRC configuration information.

[0045] Some embodiments of this application provide a method that can be implemented by a source network node. The method includes the steps of sending a handover request for a CHO and receiving a response from a candidate network node, the response including a first CHO configuration associated with a candidate primary cell (PCell) and configuration information for one or more candidate SCGs associated with one or more candidate PSCells.

[0046] Some embodiments of this application provide a method that can be implemented by a candidate network node. The method includes the steps of receiving a handover request for a CHO from a source network node and sending a response to the source network node, the response including a first CHO configuration associated with a candidate primary cell (PCell) and configuration information for one or more candidate SCGs associated with one or more candidate PSCells.

[0047] Some embodiments of this application also provide a device for wireless communication. The device includes a non-temporary computer-readable medium storing computer-executable instructions, a receiving circuit, a transmitting circuit, and a processor coupled to the non-temporary computer-readable medium, the receiving circuit, and the transmitting circuit, wherein the computer-executable instructions cause the processor to implement any of the above methods, which are carried out by a UE, a source network node, or a candidate network node.

[0048] Details of one or more examples are described in the accompanying drawings and the following description. Other features, purposes, and advantages will become apparent from the description and drawings, as well as from the claims.

[0049] To describe the forms in which the advantages and features of this application may be obtained, the description of this application is made by reference to specific embodiments shown in the accompanying drawings. These drawings illustrate only exemplary embodiments of this disclosure and should therefore not be considered to limit the scope of this application. [Brief explanation of the drawing]

[0050] [Figure 1] This figure shows a schematic diagram of a wireless communication system according to several embodiments of this application. [Figure 2] This figure shows an exemplary UE information procedure according to several embodiments of this application. [Figure 3] This is an illustrative flowchart of access to a candidate PCell according to some embodiments of this application. [Figure 4] This is an illustrative flowchart of sending a handover request according to some embodiments of the present application. [Figure 5] This is an illustrative flowchart of receiving a handover request according to some embodiments of the present application. [Figure 6] This is an exemplary flowchart relating to a candidate SCG-containing CHO procedure according to several embodiments of this application. [Figure 7] This is an exemplary flowchart relating to a candidate SCG-containing CHO procedure according to several embodiments of this application. [Figure 8] This is an exemplary flowchart relating to a candidate SCG-containing CHO procedure according to several embodiments of this application. [Figure 9] This is an exemplary block diagram of a device according to several embodiments of this application. [Modes for carrying out the invention]

[0051] The detailed description of the attached drawings illustrates preferred embodiments of this application and does not represent the only possible forms in which this application may be carried out. It should be understood that the same or equivalent functions may be performed by different embodiments intended to be included within the spirit and scope of this application.

[0052] Herein, references to several embodiments of this application are made in detail, and examples of embodiments are shown in the accompanying drawings. For ease of understanding, embodiments are provided under specific network architectures and novel service scenarios, such as 3GPP 5G and 3GPP LTE Release 8. As network architectures and novel service scenarios develop, it is intended that all embodiments of this application are applicable to similar technical problems, and furthermore, the terminology expressed herein may change, but this does not affect the principles of this application.

[0053] Figure 1 shows a schematic diagram of a wireless communication system according to several embodiments of this application.

[0054] As illustrated and shown in Figure 1, the wireless communication system 100 includes at least one UE101 and at least one BS102. Specifically, for illustrative purposes, the wireless communication system 100 includes one UE101 (e.g., UE101a) and three BS102s (e.g., BS102a, BS102b, and BS102c). While a specific number of UE101s and BS102s are shown in Figure 1, it is intended that any number of UE101s and BS102s may be included in the wireless communication system 100.

[0055] UE101 may include computing devices such as desktop computers, laptop computers, personal digital assistants (PDAs), tablet computers, smart televisions (e.g., Internet-connected televisions), set-top boxes, game consoles, security systems (including security cameras), in-vehicle computers, network devices (e.g., routers, switches, and modems), and Internet of Things (IoT) devices. According to some embodiments of this application, UE101 may include portable wireless communication devices, smartphones, cellular phones, flip phones, devices having subscriber identification modules, personal computers, selective call receivers, or any other devices capable of transmitting and receiving communication signals over a wireless network. In some embodiments of this application, UE101 includes wearable devices such as smartwatches, fitness bands, and optical head-mounted displays. Furthermore, UE101 may be referred to as subscriber units, mobile, mobile stations, users, terminals, mobile terminals, wireless terminals, fixed terminals, subscriber stations, user terminals, or devices, or described using other terms used in the art. UE101 can communicate directly with BS102 via uplink (UL) communication signals.

[0056] In some embodiments of this application, each of the UE101 may be deployed as an IoT application, an eMBB application, and / or a URLLC application. The specific types of applications deployed in the UE101 are diverse and not limited to them.

[0057] BS102 may be distributed across geographical areas. In some embodiments of this application, each of BS102 may also be referred to as an access point, access terminal, base, base unit, macrocell, node B, advanced node B (eNB), gNB, NG-RAN (next-generation radio access network) node, home node B, relay node, or device, or may be described using other terms used in the art. Generally, BS102 is part of a radio access network which may include one or more controllers communically coupled to one or more corresponding BS102.

[0058] The wireless communication system 100 can be compatible with any type of network capable of transmitting and receiving wireless communication signals. For example, the wireless communication system 100 is compatible with wireless communication networks, cellular telephone networks, time division multiple access (TDMA) based networks, code division multiple access (CDMA) based networks, orthogonal frequency division multiple access (OFDMA) based networks, LTE networks, 3GPP based networks, 3GPP 5G networks, satellite communication networks, high-altitude platform networks, and / or other communication networks.

[0059] In some embodiments of this application, the wireless communication system 100 conforms to the 3GPP protocol 5G, with BS102 transmitting data on the downlink (DL) using an OFDM modulation scheme, and UE101 transmitting data on the UL using a single-carrier frequency division multiple access (SC-FDMA) or OFDM scheme. More generally, however, the wireless communication system 100 may implement several other open or proprietary communication protocols, such as WiMAX, among others.

[0060] In some embodiments of this application, BS102 may communicate using other communication protocols, such as the IEEE 802.11 family of wireless communication protocols. Furthermore, in some embodiments of this application, BS102 may communicate over licensed spectrum, and in other embodiments, BS102 may communicate over unlicensed spectrum. This application is not intended to be limited to any particular wireless communication system architecture or protocol implementation. In several further embodiments of this application, BS102 may communicate with UE101 using the 3GPP 5G protocol.

[0061] Each BS102 may contain one or more cells. Each UE101 may perform a cell section procedure between different cells of different BSs. Each UE101 may hand over from a serving cell of a source BS to a target cell of a target BS. For example, in the wireless communication system 100 illustrated and shown in Figure 1, BS102a may function as a source BS, and BS102b and BS102c may each function as a target BS. If a handover is necessary, UE101a, illustrated and shown in Figure 1, may perform a handover procedure from the serving cell of BS102a to the target cell of BS102b or the target cell of BS102c, which depends on the result of a cell selection procedure. The handover procedure performed by UE101a may be a CHO procedure.

[0062] As defined in the 3GPP standard document, a CHO is defined as a handover performed by a user device (UE) when one or more CHO execution conditions are met. Upon receiving CHO-related configuration information (including, for example, one or more configurations associated with a candidate PCell and one or more CHO execution conditions), the UE begins evaluating one or more CHO execution conditions and stops evaluating them during CHO execution, or when one or more CHO execution conditions are met or achieved. CHO execution means that when the CHO execution conditions of a candidate PCell are satisfied or achieved (the "candidate PCell" may also be referred to as the "CHO ​​candidate PCell"), the UE determines the candidate PCell as a target PCell and performs a PCell change or handover procedure with the target PCell, for example, the UE performs an RA procedure to the target PCell.

[0063] Mobility Robustness Optimization (MRO) is the detection of connection failures caused by Too Early Handover, Too Late Handover, or Handover to Wrong Cell. A common procedure is that after an RLF / HO failure occurs, the UE accesses a new cell through re-establishment or connection setup. Once the UE enters a connected state, it sends RLF and RACH reports to the serving cell. The serving cell sends a failure instruction, including an RLF report, to the last serving cell. Ultimately, the information is used to optimize mobility. One of the functions of Mobility Robustness Optimization is the detection of connection failures caused by Too Early Handover, Too Late Handover, or Handover to Wrong Cell.

[0064] Generally, in the UE information procedure, after an RLF or HO failure occurs, the UE may execute the RRC re-establishment procedure within the cell. The UE stores any information related to the RLF failure and / or HO failure. The UE stores the most recent RLF report, including both LTE and NR RLF reports, for 48 hours after the RLF report is fetched by the network or the connection failure is detected. For analysis of the connection failure, the UE makes the RLF report available to the network.

[0065] Figure 2 shows an exemplary UE information procedure according to several embodiments of the present application. The embodiments in Figure 2 show a procedure in which a UE (e.g., UE210) communicates with a BS (e.g., BS220). In some examples, UE210 may function as UE101a in Figure 1. BS220 may function as BS102a, BS102b, or BS102c in Figure 1.

[0066] As shown in Figure 2, in operation 201, BS220 (for example, BS102a illustrated and shown in Figure 1) sends a UE Information Request message to UE210 (for example, UE101a illustrated and shown in Figure 1). BS220 may be a source BS controlling the serving cell of UE210. In operation 202, US210 sends a UE Information Response message containing an RLF report to BS220. Based on the response sent from UE210, BS220 can optimize mobility issues.

[0067] 3GPP Release 17 introduces Successful Handover Reports (SHRs) for MRO of PCell change procedures. A PCell change can be a legacy PCell change or handover, or a conditional PCell change or conditional handover (CHO). In particular, the MRO functionality in NR can be enhanced to provide more robust mobility by reporting failure events observed during a successful handover from the source NG-RAN to the target NG-RAN via SHRs. An SHR is a report associated with a successful handover, including a set of measurements collected during the handover phase, i.e., measurements at the handover trigger, measurements at the end of the handover execution, or measurements after the handover execution. For example, when at least one of the following trigger conditions is met and / or the RA to the PCell is successful, the UE may also store successful PCell change-related information or generate a VarSuccessHO-Report / SHR. (1) The ratio between the elapsed time value of Timer T310 on the source PCell while the UE was connected to the source PCell before the last PCell change / HO procedure was executed, and the configured value of Timer T310 configured for the source PCell, is greater than the configured threshold (for example, thresholdPercentageT310 configured by the source PCell before the last PCell change / HO procedure was executed). (2) If the T312 associated with the target PCell's measurement identity was running at the start of the execution of the PCell change / HO procedure, and the ratio between the elapsed time value of timer T312 and the configured value of timer T312 (configured while the UE was connected to the source PCell before the last PCell change / HO procedure was executed) is greater than the configured threshold (e.g., thresholdPercentageT312 configured by the source PCell before the last PCell change / HO procedure was executed). (3) If the ratio between the elapsed time value of the target PCell's elapsed timer T304 and the configured value of timer T304 (i.e., included in the last applied RRCReconfiguration message, including reconfigurationWithSync for the PCell change / HO procedure) is greater than the configured threshold (e.g., thresholdPercentageT304 configured by the target PCell before the last PCell change / HO procedure was executed).

[0068] The SHR includes at least one of the following: successful PCell change-related information, such as the cell information of the source PCell, the cell information of the target PCell, cause values ​​for the SHR (e.g., t304-cause, t310-cause, or t312-cause), measurement results of the source PCell and / or target PCell when the HO is performed or successful, and RA information (e.g., RACH configuration for the target PCell). Generally, cell information includes the cell's global cell identity and tracking area code, or PCI and frequency information (e.g., ARFCN).

[0069] The availability of the SHR can be indicated by a handover completion message (RRCReconfigurationComplete) sent from the UE to the target NG-RAN node via the RRC. The target NG-RAN node may fetch information about the successful handover report via the UE Information Request / Response mechanism. Furthermore, the target NG-RAN node may then forward the SHR to the source NR-RAN node to indicate any failures that occurred during the successful handover event.

[0070] Upon receiving an SHR, the receiving node can analyze whether its mobility configuration requires adjustment. Such adjustments may result in changes to the mobility configuration, such as changes to the RLM configuration or changes to the mobility threshold between the source and target. Furthermore, the target NG-RAN node may further optimize its dedicated RACH resources during the handover, based on the measurements reported when the handover was successful.

[0071] 3GPP Release 18 will introduce Successful PSCell Change Reports (SPCRs) to optimize PSCell changes or CPAC-related parameters, for example, if a physical layer problem is detected by the UE during an ongoing legacy PSCell change procedure or CPAC procedure. To report an SPCR, the UE will log or generate an SPCR (e.g., successPSCellChange-Config IE(information element)) via an RRCReconfiguration message, which will include, for example, timer T304 related thresholds (thresholdPercentageT304 generated by the target PSCell), timer T310 related thresholds (thresholdPercentageT310 generated by the source PSCell or source PCell), or timer T312 related thresholds (thresholdPercentageT312 generated by the source PSCell or source PCell). Based on the network configuration, the UE should log or generate successful PSCell change-related parameters when at least one trigger condition is met. It can generate and report to the network an SPCR containing the source PSCell's Cell Global Identifier (CGI) information, the target PSCell's CGI information, cause values ​​for the successful PSCell change report (e.g., t304-cause, t310-cause, or t312-cause), and measurement results.

[0072] A CHO without a candidate SCG may also be referred to as "CHO-only." At present, the following two scenarios are possible: (1) Use case #1: The CHO configuration for a CHO procedure with a candidate SCG and the CHO configuration for a CHO without a candidate SCG (i.e., CHO-only) are configured separately. In this scenario, the CHO execution conditions for the CHO procedure with a candidate SCG and the CHO-only may be the same or different. (2) Usage example #2: The CHO configuration of a CHO without a candidate SCG (i.e., CHO-only) is the same as the CHO configuration from a CHO procedure with a candidate SCG (i.e., the CHO part).

[0073] However, the following issues need to be resolved: how to ensure that candidate SCG-containing CHO procedures can be executed preferentially in use case #1; how to implement use case #2; how to implement some enhancements to use case #2; what are the enhanced trigger conditions for CHO and CPC procedure success; and what additional information should be reported in the case of candidate SCG-containing CHO procedures.

[0074] The embodiments of this application aim to solve the above-mentioned problems. For example, some embodiments of this application provide mechanisms for use cases #1 and #2. Some embodiments of this application provide mechanisms for the simultaneous execution of PCell / PSCell changes in a candidate SCG-enabled CHO procedure. Some embodiments of this application provide MRO mechanisms for a candidate SCG-enabled CHO procedure. Further details are shown in the following text in combination with the accompanying drawings.

[0075] Figure 3 shows an exemplary flowchart of access to a candidate PCell according to several embodiments of this application. The exemplary flowchart 300 may be performed by a UE (for example, UE101, UE601, UE701, or UE801 shown and illustrated in Figures 1 and any of Figures 6-8). While described in relation to a UE, it should be understood that other devices may be configured to perform the exemplary flowchart shown and illustrated in Figure 3.

[0076] In the exemplary flowchart 300 shown in Figure 3, in operation 301, the UE may receive RRC configuration information for a candidate SCG-enabled CHO (i.e., a candidate SCG-enabled CHO procedure) for a CPC / CPA procedure. In operation 302, the UE may access a candidate PCell based on the RRC configuration information.

[0077] For example, RRC configuration information may be included in the RRC reconfiguration message. In some embodiments, the RRC configuration information may include the following: (1) CHO configuration related to candidate PCell (referred to as CHO configuration #1 for simplicity), (2) CHO execution conditions for candidate PCell (referred to as CHO execution condition #1), (3) Configuration information for one or more candidate SCGs associated with one or more candidate PSCells, and (4) A set of execution conditions for one or more candidate SCGs.

[0078] In some embodiments of the exemplary flowchart 300, for example, in use case #1, the UE may receive additional RRC configuration information for a CHO configuration without a candidate SCG (i.e., a CHO-only CHO configuration, designated as CHO configuration #2). For example, the additional RRC configuration information and the RRC configuration information in operation 301 may be included in the same RRC reconfiguration message or in different RRC reconfiguration messages.

[0079] In one embodiment, a CHO execution condition (denoted as CHO execution condition #2) may be configured for CHO configuration #2. For example, the trigger time (TTT) for CHO execution condition #2 may be greater than the TTT for CHO execution condition #1.

[0080] In one embodiment, the additional RRC configuration information includes an instruction (denoted as instruction #1) indicating the association between CHO configuration #2 and CHO configuration #1. For example, instruction #1 may indicate that CHO configuration #2 is a supplement to CHO configuration #1. A specific example is shown in the embodiment of Figure 6.

[0081] In some embodiments of the exemplary flowchart 300, when instruction #1 is received, the UE may assume that CHO execution condition #2 for CHO configuration #2 is the same as CHO execution condition #1 for candidate PCell. Thus, a specific configuration of CHO execution condition #2 can be avoided.

[0082] In some embodiments of the exemplary flowchart 300, if both CHO execution condition #2 for CHO configuration #2 (e.g., for CHO-only) and CHO execution condition #1 for CHO configuration #1 (e.g., for CHO procedures with candidate SCG) are met, the UE will: (1) If a set of execution conditions for one candidate SCG within one or more candidate SCGs is met, execute a CHO based on CHO configuration #1 on both the "candidate PCell" and the "candidate PSCell associated with one candidate SCG", or (2) If one or more sets of execution conditions for candidate SCG are not met, a CHO based on CHO configuration #2 may be executed on the candidate PCell.

[0083] In some embodiments of the exemplary flowchart 300, for example, in use case #2, the UE may receive an instruction (denoted as instruction #2) indicating that the CHO is permitted to be performed by the UE based on a CHO configuration without a candidate SCG (e.g., CHO configuration #2). In some embodiments, the UE may receive an instruction (denoted as instruction #3) indicating that a CHO configuration without a candidate SCG associated with a candidate PCell (e.g., CHO configuration #2) is the same as CHO configuration #1 associated with a candidate PCell. In some embodiments, the UE may receive both instruction #2 and instruction #3.

[0084] In one embodiment, if instruction #2 and / or instruction #3 are received, for example, via the Uu interface, the UE may consider the candidate SCG-less CHO configuration (e.g., CHO configuration #2) to be the same as the candidate PCell-associated CHO configuration #1 (e.g., for the candidate SCG-inclusive CHO procedure).

[0085] In one embodiment, if a set of execution conditions for one or more candidate SCGs is not met and CHO execution condition #1 is met, the UE may access a candidate PCell based on CHO configuration #2. After successfully accessing a candidate PCell (i.e., a target PCell) based on CHO configuration #2, the UE may release one or more SCG bearers configured in one or more candidate SCGs, or the UE may remap one or more SCG bearers to MCG bearers configured in the candidate PCell.

[0086] According to some embodiments of the exemplary flowchart 300, the UE may perform a CHO based on CHO configuration #1 or CHO configuration #2. After successfully accessing a candidate PCell (i.e., a target PCell), the UE may send an RRC reconfiguration complete message to the candidate PCell. In one embodiment, the RRC reconfiguration complete message includes an indication that the UE performed a CHO based on either CHO configuration #1 or CHO configuration #2.

[0087] In one embodiment, the RRC reconfiguration completion message includes at least one of the IDs of the candidate PCell accessed by the UE, or the ID of the candidate PSCell accessed by the UE. For example, if the UE performs a CHO based on CHO configuration #2, the RRC reconfiguration completion message may include the ID of the candidate PCell. If the UE performs a CHO based on CHO configuration #1, the RRC reconfiguration completion message may include both the ID of the candidate PCell and the ID of the candidate PSCell. A specific example is shown in the embodiment of Figure 7.

[0088] In some embodiments of the exemplary flowchart 300, in response to the fulfillment of trigger conditions, the UE may send both a Success Handover Report (SHR) and a Success PSCell Change Report (SPCR) to the target network node. In some embodiments, the SHR and SPCR are included in the UE information response message. For example, if a set of execution conditions for multiple SCGs within one or more candidate SCGs is met, the UE may select one SCG from the multiple SCGs and execute a CHO with candidate SCGs for a CPC / CPA procedure to access that one SCG. If a set of execution conditions for multiple SCGs is met, the UE information response message may also include ID information for the other SCGs within the multiple SCGs, excluding the one SCG accessed by the UE. A specific example is shown in the embodiment of Figure 8.

[0089] In one embodiment, the UE may receive a threshold related to the trigger condition from the source network node. The threshold may be a percentage of the timer length. For example, the threshold is: (1) Based on the triggering of the measurement report, a threshold (designated as threshold #1) associated with a timer (e.g., timer T312) for initiating failure recovery, or (2) A threshold associated with a physical layer problem timer (e.g., timer T310) (denoted as threshold #2), or (3) A threshold associated with a handover timer (for example, timer T304) (denoted as threshold #3).

[0090] In some embodiments, the trigger condition includes at least one of the following: (1) The elapsed duration of the timer for initiating failure recovery based on the triggering of the measurement report (e.g., Timer T312) exceeds the threshold #1 multiplied by the length of the timer for initiating failure recovery based on the triggering of the measurement report (e.g., Timer T312). (2) The elapsed duration of the physical layer problem timer (e.g., Timer T310) exceeds the threshold #2 multiplied by the length of the physical layer problem timer (e.g., Timer T310), or (3) The elapsed duration of the handover timer (e.g., Timer T304) exceeds the threshold #3 multiplied by the length of the handover timer (e.g., Timer T304).

[0091] Figure 4 shows an exemplary flowchart of sending a handover request according to several embodiments of the present application. The exemplary flowchart 400 may be implemented by a source network node (for example, source gNB, source BS602, source BS702, or source BS802 shown and illustrated in Figures 1 and any of Figures 6-8). While described in relation to a source network node, it should be understood that other devices may be configured to implement the exemplary flowchart shown and illustrated in Figure 4.

[0092] In the exemplary flowchart 400 shown in Figure 4, in operation 401, the source network node may send a handover request for the CHO. In operation 402, the source network node may receive a response from a candidate network node (e.g., a candidate gNB or a target gNB). The response may include at least one of the following: (1) CHO configuration associated with candidate PCell (for example, CHO configuration #1 as shown in the example flowchart 300), (2) Configuration information for one or more candidate SCGs associated with one or more candidate PSCells, or (3) A set of execution conditions for one or more candidate SCGs.

[0093] In some embodiments of the exemplary flowchart 400, a source network node may receive an instruction (denoted as instruction #4) from a candidate network node, for example, via the Xn interface. Instruction #4 may indicate that another CHO configuration associated with the candidate PCell (for example, CHO configuration #2 as described in exemplary flowchart 300) is the same as the CHO configuration associated with the candidate PCell in operation 402, or that a CHO-only configuration can be performed from a CHO configuration with candidate SCG. In some embodiments, instruction #4 is included in a handover request acknowledgment message. For example, the source network node may further send a similar instruction (for example, instruction #3 as described in exemplary flowchart 300) to the UE. A specific example is described in the embodiment of Figure 7.

[0094] In some embodiments of the exemplary flowchart 400, a source network node may send a threshold related to a trigger condition to a UE (e.g., UE101, UE601, UE701, or UE801 shown and illustrated in Figures 1 and any of Figures 6-8). The trigger condition is to trigger simultaneous transmission of both SHR and SPCR. The threshold may be a percentage of the timer length. A specific example is shown in the embodiment of Figure 8.

[0095] According to some embodiments, the threshold is (1) A threshold associated with a timer (e.g., Timer T312) to initiate failure recovery based on the triggering of the measurement report (e.g., threshold #1 as shown in the exemplary flowchart 300), or (2) A threshold associated with a physical layer problem timer (e.g., timer T310) (e.g., threshold #2 as shown in the exemplary flowchart 300), or (3) A threshold associated with the handover timer (e.g., timer T304) (e.g., threshold #3 as shown in the exemplary flowchart 300).

[0096] According to some embodiments, the trigger condition includes at least one of the following: (1) The elapsed duration of the timer for initiating failure recovery based on the triggering of the measurement report (e.g., Timer T312) exceeds the threshold #1 multiplied by the length of the timer for initiating failure recovery based on the triggering of the measurement report (e.g., Timer T312). (2) The elapsed duration of the physical layer problem timer (e.g., Timer T310) exceeds the threshold #2 multiplied by the length of the physical layer problem timer (e.g., Timer T310), or (3) The elapsed duration of the handover timer (e.g., Timer T304) exceeds the threshold #3 multiplied by the length of the handover timer (e.g., Timer T304).

[0097] Figure 5 shows an exemplary flowchart of receiving a handover request according to several embodiments of the present application. The exemplary flowchart 500 may be implemented by a candidate network node (for example, candidate gNB, candidate BS603, candidate BS703, or candidate BS803 shown and illustrated in Figures 1 and any of Figures 6-8). While described in relation to a candidate network node, it should be understood that other devices may be configured to implement the exemplary flowchart shown and illustrated in Figure 5.

[0098] In the exemplary flowchart 500 shown in Figure 5, in operation 501, the candidate network node may receive a handover request for CHO from the source network node. In operation 502, the candidate network node may send a response to the source network node. The response may include at least one of the following: (1) CHO configuration associated with candidate PCell (for example, CHO configuration #1 as shown in the example flowchart 300), (2) Configuration information for one or more candidate SCGs associated with one or more candidate PSCells, and (3) A set of execution conditions for one or more candidate SCGs.

[0099] In some embodiments of the exemplary flowchart 500, a candidate network node sends an instruction to a source network node, for example, via the Xn interface. This instruction indicates that another CHO configuration associated with the candidate PCell (for example, CHO configuration #2 described in the exemplary flowchart 300) is the same as the CHO configuration associated with the candidate PCell in operation 502.

[0100] In some embodiments of the exemplary flowchart 500, a candidate network node may receive both an SHR and an SPCR from the UE. The SHR and SPCR may be sent simultaneously by the UE in response to the fulfillment of a trigger condition. In some embodiments, the SHR and SPCR are included in the UE information response message. In some embodiments, in response to the fulfillment of a set of execution conditions for multiple SCGs within one or more candidate SCGs, the UE information response message further includes ID information for the other SCGs within the multiple SCGs, excluding one SCG accessed by the UE.

[0101] For example, the trigger condition includes at least one of the following: (1) Based on the triggering of the measurement report, the elapsed duration of the timer for initiating failure recovery (e.g., Timer T312) exceeds the threshold (e.g., threshold #1 as shown in Exemplary Flowchart 300) multiplied by the length of the timer for initiating failure recovery based on the triggering of the measurement report (e.g., Timer T312). (2) If the elapsed duration of the physical layer problem timer (e.g., Timer T310) exceeds the value obtained by multiplying the threshold (e.g., threshold #2 as shown in Exemplary Flowchart 300) by the length of the physical layer problem timer (e.g., Timer T310), (3) The elapsed duration of the handover timer (e.g., Timer T304) exceeds the value obtained by multiplying the threshold (e.g., threshold #3 as shown in Exemplary Flowchart 300) by the length of the handover timer (e.g., Timer T304).

[0102] In one embodiment, threshold #1, threshold #2, and threshold #3 are each a percentage of the timer length. A specific example is shown in the embodiment of Figure 8.

[0103] Details described in all other embodiments of this application are applicable to the embodiments shown in Figures 3 to 5. Furthermore, details described in the embodiments shown in Figures 3 to 5 are applicable to all embodiments shown in Figures 1 to 4 and Figures 6 to 9.

[0104] The following text describes a specific embodiment shown and illustrated in Figures 3 to 5, in which the UE and network nodes (e.g., a source base station (BS) and a candidate BS) perform the following operations. Those skilled in the art will understand that the sequence of operations in any of the exemplary flowcharts 600, 700, and 800 in Figures 6 to 8 may be modified without departing from the spirit and scope of this disclosure, and that some of the operations in any of the exemplary flowcharts 600 to 800 in Figures 6 to 8 may be deleted or modified.

[0105] Figure 6 shows an exemplary flowchart relating to a candidate SCG-enabled CHO procedure according to several embodiments of the present application. Details described in all other embodiments of the present application are applicable to the embodiments shown in Figure 6. The embodiment in Figure 6 refers to Use Case #1.

[0106] In the exemplary flowchart 600 shown in Figure 6, in operation 611, UE601, which is in an RRC connection state, accesses its serving BS (i.e., serving gNB, e.g., source BS602). For example, dual connectivity (DC) may be configured for UE601. In some embodiments, UE601 may report measurement results to source BS602 (e.g., source MN602).

[0107] In operation 612, based on the measurement results, source BS602 may determine, by CHO, to switch UE601 to candidate BS603.

[0108] In operation 613, source BS602 may send a handover request message to candidate BS603. For example, source BS602 may instruct candidate BS603 to prepare a CHO configuration with or without candidate SCG.

[0109] In operation 614, if candidate BS603 (i.e., target MN603) decides to prepare candidate SCG after receiving a handover request message from source BS602, candidate BS603 (as target MN) may send a request (e.g., an SgNB addition request message or an SN modification request message) to candidate SN604 via the Xn interface.

[0110] In operation 615, candidate SN604 may send an acknowledgment message (for example, an acknowledgment of an SgNB addition request or an acknowledgment of an SgNB modification request) to target MN603. One or more CHO configurations for candidate SCGs are included in the acknowledgment message.

[0111] In operation 616, after receiving an acknowledgment message from candidate SN604, target MN603 sends a handover request acknowledgment message (i.e., an Xn message) containing CHO configurations for one or more candidate SCGs to source BS602 via the Xn interface. For example, a CHO configuration without a candidate SCG may be included in the same Xn message or in a separate Xn message. Execution conditions for each candidate SCG may be generated by target MN603.

[0112] In operation 617, after receiving a handover request acknowledgment message from target MN603, source BS602 sends an RRC reconfiguration message to UE601 that includes a CHO configuration for one or more candidate SCGs. For example, a corresponding CHO configuration without a candidate SCG may be sent to UE601 in the same RRC reconfiguration message or a different RRC reconfiguration message. The corresponding CHO configuration without a candidate SCG may include the same target PCell ID information as the target PCell ID information included in the CHO configuration with one or more candidate SCGs.

[0113] In various embodiments of this application, there may be two options, namely Option 1 and Option 2.

[0114] Option 1: The same execution conditions may be configured for CHO configurations without candidate SCGs and CHO configurations with candidate SCGs.

[0115] For example, in Option 1, in operation 617, UE601 may receive an instruction (e.g., instruction #1 as shown in Exemplary Flowchart 300) indicating an association (e.g., a complement relationship) between a CHO configuration without a candidate SCG and a CHO configuration with a candidate SCG. UE601 may then assume that the execution conditions for the CHO configuration without a candidate SCG are the same as the execution conditions for the candidate PCell of the CHO configuration with a candidate SCG.

[0116] In one embodiment, the RRC information element (IE) may be as follows, and include the above instruction (for example, associatedCondReconfigId as shown below) and the above configuration and execution conditions. CondReconfigToAddModList information element (IE) [Table 1]

[0117] Option 2: Different execution conditions may be configured for CHO configurations without candidate SCGs and CHO configurations with candidate SCGs, and this depends on the network implementation.

[0118] Referring again to Figure 6, in operation 618, after receiving an RRC reconstruction message from source BS602 for a CHO configuration with or without a candidate SCG, UE601 sends an RRC reconstruction complete message to source BS602.

[0119] In operation 619, UE601 begins evaluating the execution conditions for the CHO configuration with a candidate SCG and the execution conditions for the CHO configuration without a candidate SCG. (1) For example, if UE601 receives an instruction (e.g., instruction #1) in operation 617 that indicates an association between a CHO configuration without a candidate SCG and a CHO configuration with a candidate SCG, the execution conditions for the CHO configuration with a candidate SCG may be the same as, or associated with, the execution conditions for the CHO configuration without a candidate SCG. (2) If the execution conditions for both a CHO with a candidate SCG and a CHO without a candidate SCG related to the same candidate PCell are met, the CHO procedure with a candidate SCG can be executed when the execution conditions for the candidate SCG are met. (3) If the execution conditions for both a CHO with a candidate SCG and a CHO without a candidate SCG, associated with the same target PCell, are met, the CHO without a candidate SCG (i.e., CHO-only) may be executed if none of the execution conditions for the candidate SCG are met.

[0120] In the exemplary flowchart 600, in some embodiments, when a CHO without a candidate SCG is configured for UE601, the execution conditions for candidate PCells from both the CHO without a candidate SCG and the CHO with a candidate SCG are met at the same time. In this case, if the execution conditions for the candidate SCG are also met, UE601 may prioritize executing the CHO with a candidate SCG. If the execution conditions for candidate PCells from both the CHO without a candidate SCG and the CHO with a candidate SCG are met, but the execution conditions for the candidate SCG are not yet met, UE601 does not have to immediately execute the CHO-only. Alternatively, a time offset can be configured for the CHO without a candidate SCG for UE601. That is, if the execution conditions for candidate PCells from both the CHO without a candidate SCG and the CHO with a candidate SCG are met at the same time, but the execution conditions for the candidate SCG are not yet met, UE601 must wait for a certain period of time. If the execution conditions for the candidate SCG are still not met after that period, UE601 is permitted to perform CHO-only.

[0121] Figure 7 shows an exemplary flowchart relating to a candidate SCG-enabled CHO procedure according to several embodiments of this application. Details described in all other embodiments of this application are applicable to the embodiments shown in Figure 7. The embodiment in Figure 7 refers to Use Case #2.

[0122] In the exemplary flowchart 700 shown in Figure 7, in operation 711, UE701, which is in an RRC connection state, accesses its serving BS (i.e., serving gNB, e.g., source BS702). For example, dual connectivity (DC) may be configured for UE701. In some embodiments, UE701 may report measurement results to source BS702 (e.g., source MN702).

[0123] In operation 712, based on the measurement results, source BS702 may determine, by CHO, to switch UE701 to candidate BS703.

[0124] In operation 713, source BS702 may send a handover request message to candidate BS703. For example, source BS702 may instruct candidate BS703 to prepare a CHO configuration with or without candidate SCG.

[0125] In operation 714, if candidate BS703 (i.e., target MN703) decides to prepare candidate SCG after receiving a handover request message from source BS702, candidate BS703 (as target MN) may send a request (e.g., an SgNB addition request message or an SN modification request message) to candidate SN704 via the Xn interface.

[0126] In operation 715, candidate SN704 may send an acknowledgment message (for example, an acknowledgment of an SgNB addition request or an acknowledgment of an SgNB modification request) to target MN703. One or more CHO configurations for candidate SCGs are included in the acknowledgment message.

[0127] In operation 716, after receiving an acknowledgment message from candidate SN704, target MN703 sends a handover request acknowledgment message (i.e., an Xn message) containing CHO configurations for one or more candidate SCGs to source BS702 via the Xn interface.

[0128] In one embodiment, the handover request acknowledgment message includes an instruction (for example, instruction #4 as shown in illustrative flowchart 400) which is used to indicate that a CHO configuration without a candidate SCG associated with a candidate PCell is the same as a CHO configuration from a CHO configuration with a candidate SCG (i.e., a CHO-only configuration), or that a CHO-only configuration from a CHO configuration with a candidate SCG can be performed. More specifically, a CHO-only configuration from a CHO configuration with a candidate SCG can be performed if the execution conditions for the candidate SCG are not met.

[0129] In operation 717, after receiving a handover request acknowledgment message from target MN703, source BS702 sends an RRC reconfiguration message to UE701, which includes the CHO configuration for the candidate SCG.

[0130] In one embodiment, the RRC reconfiguration message includes an instruction (for example, instruction #2 as shown in exemplary flowchart 300) used to indicate that the CHO is permitted to be executed by UE701 based on a CHO configuration without a candidate SCG. Upon receiving this instruction, UE701 may assume that a CHO-only configuration associated with a candidate PCell may be the same as a CHO configuration associated with a candidate PCell for a CHO procedure with a candidate SCG. Thus, in this case, a separate configuration for CHO-only can be avoided. This instruction may be referred to as a CHO-only instruction, etc. UE701 may execute the CHO-only based on the CHO-only configuration.

[0131] In further embodiments, the RRC reconfiguration message may include an instruction (for example, instruction #3 as shown in the exemplary flowchart 300) that indicates that a CHO configuration without a candidate SCG associated with a candidate PCell is the same as a CHO configuration from a CHO configuration with a candidate SCG (i.e., a CHO-only configuration), or that a CHO-only configuration from a CHO configuration with a candidate SCG can be performed. More specifically, UE701 may perform a CHO-only configuration from a CHO configuration with a candidate SCG if the execution conditions for the candidate SCG are not met. In some examples, the RRC reconfiguration message may include both instruction #2 and instruction #3.

[0132] In another embodiment, UE701 may also receive a CHO-only configuration separate from the CHO configuration from the candidate SCG-enabled CHO, and then perform CHO-only based on the CHO-only configuration.

[0133] In one embodiment, the RRC IE is as follows, and includes the above instructions (for example, CHOonlyallowed as shown below) and the above configuration and execution conditions. CondReconfigToAddModList information element [Table 2]

[0134] If CHO-only is implemented, different embodiments may exist regarding how to handle SCG bearers configured in the candidate SCG. In one embodiment, UE701 can release such SCG bearers. In another embodiment, UE701 can remap such SCG bearers to MCG bearers.

[0135] In operation 718, UE701 begins evaluating the execution conditions for a CHO configuration with a candidate SCG and a CHO configuration without a candidate SCG (i.e., a CHO-only configuration).

[0136] In operation 719, UE701 may perform a CHO procedure with a candidate SCG or a CHO-only procedure (i.e., a CHO without a candidate SCG).

[0137] In operation 720, UE701 may send an RRC reconstruction complete message to target MN703. In various embodiments, there may be two options, namely option A and option B.

[0138] Option A: The RRC Reconfiguration Complete message may include instructions to indicate that UE701 performed the CHO based on either configuration, i.e., a CHO-only configuration or a CHO configuration for a CHO with a candidate SCG procedure.

[0139] Option B: The RRC Reconfiguration Complete message includes the target PCell ID and / or target PSCell ID, which can be used to indicate whether UE701 performed CHO or CPC. For example, if only the target PCell ID is included in the RRC Reconfiguration Complete message, it means that UE701 performed CHO-only to the target PCell. If both the target PCell ID and target PSCell ID are included in the RRC Reconfiguration Complete message, it means that UE701 performed both CHO to the target PCell and CPC / CPA to the target PSCell.

[0140] Figure 8 shows an exemplary flowchart relating to a candidate SCG-enabled CHO procedure according to several embodiments of the present application. Details described in all other embodiments of the present application are applicable to the embodiments shown in Figure 8.

[0141] In the exemplary flowchart 800 shown in Figure 8, in operation 811, UE801, which is in an RRC connection state, accesses its serving BS (i.e., serving gNB, e.g., source BS802). For example, dual connectivity (DC) may be configured for UE801. In some embodiments, UE801 may report measurement results to source BS802 (e.g., source MN802).

[0142] In operation 812, based on the measurement results, source BS802 may determine, by CHO, to switch UE801 to candidate BS803.

[0143] In operation 813, source BS802 may send a handover request message to candidate BS803. For example, source BS802 may instruct candidate BS803 to prepare a CHO configuration with or without candidate SCG.

[0144] In operation 814, candidate BS803 sends a handover request acknowledgment message (i.e., an Xn message) containing CHO configurations for one or more candidate SCGs to source BS802 via the Xn interface. For example, a CHO configuration without a candidate SCG may be included in the same Xn message or in a separate Xn message. Execution conditions for each candidate SCG may be generated by candidate BS803 (which may also be referred to as target MN803).

[0145] In operation 815, after receiving a handover request acknowledgment message from candidate BS803, source BS802 sends an RRC reconfiguration message to UE801 that includes a CHO configuration for one or more candidate SCGs. For example, a corresponding CHO configuration without a candidate SCG may be sent to UE801 in the same RRC reconfiguration message or a different RRC reconfiguration message. The corresponding CHO configuration without a candidate SCG may have the same target PCell ID information as the target PCell ID information included in the CHO configuration with one or more candidate SCGs.

[0146] In one embodiment, the RRC reconfiguration message includes a trigger condition to trigger the simultaneous transmission of both CHO-related information and CPC-related information (e.g., SHR and SPCR). For example, a new single threshold for timers T312, T311, or T304 for both PCell and PSCell may be included in the RRC reconfiguration message. The threshold may be threshold #1, threshold #2, or threshold #3 as shown in the exemplary flowchart 300. The threshold may be a percentage of the timer length. In one example, the threshold can be applied to both PCell and PSCell changes performed by UE801. When the threshold is triggered for a PCell or PSCell change, both CHO-related information and CPC-related information (e.g., SHR and SPCR) may be reported by UE801.

[0147] In operation 816, after receiving an RRC reconstruction message from source BS802 for a CHO configuration with or without a candidate SCG, UE801 sends an RRC reconstruction complete message to source BS802.

[0148] In operation 817, UE801 begins evaluating the execution conditions for the CHO configuration and the candidate SCG.

[0149] In operation 818, UE801 performs a CHO with one candidate SCG, i.e., both a PCell change and a PSCell change. After UE801 successfully accesses the target PCell and target PSCell, SHR and SPCR may be triggered based on the following conditions. (1) The elapsed duration of T312 exceeds the value obtained by multiplying the threshold (e.g., threshold #1) by the length of T312. (2) The elapsed duration of T310 exceeds the value obtained by multiplying the threshold (e.g., threshold #2) by the length of T310, or (3) The elapsed duration of T304 exceeds the value obtained by multiplying the threshold (e.g., threshold #3) by the length of T304.

[0150] In operation 819, UE801 sends an RRC message to candidate BS803 (i.e., target MN803) that includes an instruction (e.g., an available instruction) to indicate that the SHR and / or SPCR are available.

[0151] In operation 820, target MN803 may send a UE information request message to UE801 based on the availability indication. The UE information request message may include an SHR and / or SPCR.

[0152] In operation 821, UE801 sends a UE information response message to target MN803. For example, the UE information response message may include SHR and SPCR. Furthermore, in one embodiment, UE801 selects one SCG from among several suitable SCGs and executes a CHO with the selected SCG. Thus, it can report whether the execution conditions of the other SCGs among the several suitable SCGs are met. Therefore, the UE information response message may further include whether the execution conditions of the other SCGs among the several suitable SCGs are met, excluding the selected SCG.

[0153] In operation 822, target MN803 forwards the report received from UE801 to source MN802.

[0154] Figure 9 shows an exemplary block diagram of an apparatus according to several embodiments of the present application. As shown in Figure 9, the apparatus 900 may include at least one processor 904 and at least one transceiver 902 coupled to the processor 904. The apparatus 900 may be a UE or a network node (for example, a source network node or a candidate network node).

[0155] In this figure, elements such as at least one transceiver 902 and processor 904 are described singly, but unless otherwise specified, multiple transceivers are also intended. In some embodiments of this application, the transceiver 902 may be divided into two devices, such as a receiving circuit and a transmitting circuit. In some embodiments of this application, the apparatus 900 may further include an input device, memory, and / or other components.

[0156] In some embodiments of this application, the apparatus 900 may further include at least one non-temporary computer-readable medium. In some embodiments of this disclosure, the non-temporary computer-readable medium may store computer-executable instructions for a processor to implement the methods relating to the UE or network node (e.g., a source BS or a candidate BS) as described above. For example, the computer-executable instructions, when executed, cause a processor 904 interacting with a transceiver 902 to perform an operation of the method as described, for example, with reference to any of Figures 3 to 8.

[0157] While this disclosure has been described with respect to specific embodiments, it is evident that many alternative, modified, and altered forms may be apparent to those skilled in the art. For example, various components of an embodiment may be replaced, added, or substituted in other embodiments. Furthermore, not all elements in each figure are necessary for the operation of the disclosed embodiment. For example, a person skilled in the art could perform and use the teachings of this disclosure simply by utilizing the elements of an independent claim. Therefore, the embodiments of this disclosure described herein are intended to be illustrative, not limiting. Various modifications may be made without departing from the spirit and scope of this disclosure.

[0158] In this document, the terms “includes,” “including,” or any other variation thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus containing a list of elements does not exclude only those elements, but may also include other elements that are not explicitly enumerated or that are inherent to such process, method, article, or apparatus. Elements preceded by “a,” “an,” etc., do not, without further constraint, exclude the existence of additional identical elements in a process, method, article, or apparatus containing that element. The term “another” is defined as at least second or subsequent. As used herein, terms such as “have” are defined as “include.” Expressions such as “A and / or B” or “at least one of A and B” may include any combination of the words enumerated with the expression. For example, the expression “A and / or B” or “at least one of A and B” may include A, B, or both A and B. Words such as “first,” “second,” etc., are used solely to definitively describe embodiments of this application and not to limit the nature of this application. [Explanation of symbols]

[0159] 100 Wireless Communication Systems 101 UE 102 BS 210 UE 220 BS 601 UE 602 Source BS, Source MN 603 Candidate BS, Target MN 604 Candidate SN 701 UE 702 Source BS, Source MN 703 Candidate BS, Target MN 801 UE 802 Source BS, Source MN 803 Candidate BS, Target MN 900 equipment 902 Transceiver 904 Processor

Claims

1. Transceiver and, A user device (UE) comprising a processor coupled to the transceiver, wherein the processor is connected to the UE, Receiving first Radio Resource Control (RRC) configuration information for a CHO with a candidate secondary cell group (SCG) for the Conditional Primary / Secondary Cell Group (PSCell) Change (CPC) / Conditional PSCell Addition (CPA) procedure, Accessing candidate PCells based on the first RRC configuration information and A UE configured to perform the following actions.

2. The first RRC configuration information described above is: The first CHO configuration associated with the candidate primary cell (PCell), The first CHO execution conditions for the candidate PCell, Configuration information for one or more candidate SCGs associated with one or more candidate PSCells, A set of execution conditions for the aforementioned one or more candidate SCGs and The UE according to claim 1, including the following:

3. The UE according to claim 1 or 2, wherein the processor is configured to cause the UE to receive second RRC configuration information for a second CHO configuration without candidate SCG.

4. The UE according to claim 3, wherein the second CHO execution condition is configured for the second CHO configuration.

5. The UE according to claim 3, wherein the second RRC configuration information includes a first instruction indicating an association relationship between the second CHO configuration and the first CHO configuration.

6. The UE according to claim 5, wherein, in response to receiving the first instruction, the processor is configured to cause the UE to consider that the second CHO execution condition relating to the second CHO configuration is the same as the first CHO execution condition relating to the candidate PCell.

7. In response to the fulfillment of both the second CHO execution condition for the second CHO configuration and the first CHO execution condition for the first CHO configuration, the processor provides the UE with: In response to the fulfillment of the set of execution conditions for one of the one or more candidate SCGs, a CHO is performed on both the candidate PCell and the candidate PSCell associated with the one candidate SCG, based on the first CHO configuration, or In response to the failure to meet the set of execution conditions for one or more candidate SCGs, execute a CHO on the candidate PCell based on the second CHO configuration. The UE according to claim 6, configured to perform the following.

8. The aforementioned processor provides the UE with, A second instruction indicating that the UE is permitted to perform the CHO based on a second CHO configuration without a candidate SCG, or A third instruction indicating that the second CHO configuration without candidate SCG associated with candidate PCell is the same as the first CHO configuration associated with candidate PCell. The UE according to claim 2, configured to receive at least one of the following.

9. The UE according to claim 8, wherein, in response to receiving at least one of the second or third instructions, the processor is configured to cause the UE to consider the second CHO configuration to be the same as the first CHO configuration.

10. The UE according to claim 8 or 9, wherein, in response to the failure to fulfill the set of execution conditions relating to one or more candidate SCGs and the fulfillment of the first CHO execution condition, the processor is configured to cause the UE to access the candidate PCell based on the second CHO configuration.

11. After successfully accessing the candidate PCell based on the second CHO configuration, the processor provides the UE with: Releasing one or more SCG bearers configured in the aforementioned one or more candidate SCGs, or Remapping one or more SCG bearers to master cell group (MCG) bearers configured within the candidate PCell. The UE according to claim 10, configured to perform the following.

12. The aforementioned processor provides the UE with, Performing a CHO based on the first CHO configuration or the second CHO configuration, After successfully accessing the candidate PCell, send an RRC reconstruction completion message to the candidate PCell. A UE according to claim 1 or 9, configured to perform the following:

13. The UE according to claim 12, wherein the RRC reconstruction completion message includes an instruction indicating that the UE performed a CHO based on either the first CHO configuration or the second CHO configuration.

14. Transceiver and, A source network node comprising a processor coupled to the transceiver, wherein the processor is provided to the source network node, Sending a handover request for CHO, Receiving a response from a candidate network node and It is configured to cause the following to occur, and the response is, The first CHO configuration associated with the candidate primary cell (PCell), Configuration information for one or more candidate SCGs associated with one or more candidate PSCells and Source network nodes, including those mentioned above.

15. Transceiver and, A candidate network node comprising a processor coupled to the transceiver, wherein the processor is provided to the candidate network node, Receiving a handover request for CHO from the source network node, To send a response to the aforementioned source network node It is configured to cause the following to occur, and the response is, The first CHO configuration associated with the candidate primary cell (PCell), Configuration information for one or more candidate SCGs associated with one or more candidate PSCells and Candidate network nodes, including those mentioned above.

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