Method and apparatus for CHO with candidate SCG mechanism

Abstract

Embodiments of the present application relate to methods and apparatus for conditional handover (CHO) with a candidate secondary cell group (SCG) mechanism. In accordance with an embodiment of the present application, a user equipment (UE) comprises: a transceiver; and a processor coupled to the transceiver; and the processor is configured to receive, via the transceiver, a radio resource control (RRC) configuration and another RRC configuration, where the RRC configuration includes conditional handover (CHO) configuration information for a candidate primary cell group (MCG) and a CHO execution condition, the other RRC configuration comprises configuration information of one or more candidate secondary cell groups (SCGs) and a group of execution conditions of the one or more candidate SCGs; and evaluating the CHO execution condition of the candidate MCG after receiving the RRC configuration.

Description

Technical Field

[0001] Embodiments of the present application generally relate to wireless communication technologies, and in particular, to methods and devices for conditional handover (CHO) with a candidate secondary cell group (SCG) mechanism. Background Art

[0002] CHO is defined as a handover performed by a user equipment (UE) when one or more handover execution conditions are met. The UE starts evaluating one or more handover execution conditions after receiving one or more CHO configurations and one or more CHO execution conditions, and stops evaluating the one or more CHO execution conditions during CHO execution once the one or more CHO execution conditions are met.

[0003] The next-generation radio access network (NG-RAN) supports the multi-radio dual-connectivity (MR-DC) scenario. In the MR-DC scenario, a UE with multiple transceivers can be configured to utilize resources provided by two different nodes connected via a non-ideal backhaul connection. One of the nodes can provide New Radio (NR) access, while the other node can provide Evolved Universal Mobile Telecommunications System (UMTS) Terrestrial Radio Access (UTRA) (E-UTRA) or NR access. One node can act as a master node (MN) and the other node can act as a secondary node (SN). The MN and the SN are connected via a network interface (e.g., the Xn interface specified in the 3rd Generation Partnership Project (3GPP) standard document), and at least the MN is connected to the core network. Currently, details regarding CHO with a candidate SCG mechanism in the MR-DC scenario have not been discussed. Summary of the Invention

[0004] Some embodiments of the present application provide a user equipment (UE). The UE includes: a transceiver; and a processor coupled to the transceiver; and the processor is configured to: receive a first Radio Resource Control (RRC) configuration and a second RRC configuration via the transceiver, where the first RRC configuration includes conditional handover (CHO) configuration information and CHO execution conditions of a candidate master cell group (MCG), and the second RRC configuration includes configuration information of one or more candidate secondary cell groups (SCGs) and a set of execution conditions of the one or more candidate SCGs; and evaluate the CHO execution conditions of the candidate MCG after receiving the first RRC configuration.

[0005] In some embodiments, the first RRC configuration and the second RRC configuration are received via separate messages or via the same message.

[0006] In some embodiments, the configuration information of the one or more candidate SCGs and the set of execution conditions of the one or more candidate SCGs include: the conditional primary secondary cell group (PSCell) addition (CPA) configuration information of the one or more candidate SCGs and a set of CPA execution conditions; or the conditional PSCell change (CPC) configuration information of the one or more candidate SCGs and a set of CPC execution conditions.

[0007] In some embodiments, the processor of the UE is further configured to: evaluate the set of CPA execution conditions after receiving the second RRC configuration for CPA; or evaluate the set of CPC execution conditions after receiving the second RRC configuration for CPC.

[0008] In some embodiments, the processor of the UE is further configured to: start evaluating the set of CPA execution conditions in response to satisfaction of the CHO execution conditions of the candidate MCG; or start evaluating the set of CPC execution conditions in response to the satisfaction of the CHO execution conditions of the candidate MCG.

[0009] In some embodiments, the processor of the UE is further configured to: stop evaluating the set of CPA execution conditions of the other one or more candidate SCGs within the one or more candidate SCGs in response to satisfaction of the set of CPA execution conditions of one candidate SCG within the one or more candidate SCGs; or stop evaluating the set of CPC execution conditions of the other one or more candidate SCGs within the one or more candidate SCGs in response to satisfaction of the set of CPC execution conditions of one candidate SCG within the one or more candidate SCGs.

[0010] In some embodiments, the processor of the UE is configured to release the second RRC configuration in response to: the set of execution conditions of each candidate SCG within the one or more candidate SCGs not being satisfied when the UE completes the random access (RA) procedure to the candidate MCG; the set of execution conditions of each candidate SCG not being satisfied when the handover timer of the candidate MCG stops; the set of execution conditions of each candidate SCG not being satisfied after a first period since the UE completes the RA procedure to the candidate MCG; the set of execution conditions of each candidate SCG not being satisfied when the CHO execution conditions of the candidate MCG are satisfied; or the set of execution conditions of each candidate SCG not being satisfied after a second period since the CHO execution conditions of the candidate MCG are satisfied.

[0011] In some embodiments, in response to the CHO execution condition of the candidate MCG being satisfied, the processor of the UE is further configured to stop evaluating the set of execution conditions of the one or more candidate SCGs in response to: the set of execution conditions of each candidate SCG within the one or more candidate SCGs not being satisfied when the UE completes a random access (RA) procedure to the candidate MCG; the set of execution conditions of each candidate SCG not being satisfied when the handover timer of the candidate MCG stops; the set of execution conditions of each candidate SCG not being satisfied after a first period since the UE completed the RA procedure to the candidate MCG; the set of execution conditions of each candidate SCG not being satisfied when the CHO execution condition of the candidate MCG is satisfied; or the set of execution conditions of each candidate SCG not being satisfied after a second period since the satisfaction of the CHO execution condition of the candidate MCG.

[0012] In some embodiments, the processor of the UE is further configured to release the set of execution conditions of the candidate SCG after stopping evaluating the set of execution conditions of the candidate SCG.

[0013] In some embodiments, in response to the CHO execution condition of the candidate MCG being satisfied, the processor of the UE is configured to: perform a random access (RA) procedure to the candidate MCG based on the first RRC configuration; and transmit an RRC reconfiguration complete message to a candidate MN associated with the candidate MCG.

[0014] In some embodiments, the processor of the UE is configured to: in response to the set of CPA execution conditions of one candidate SCG within the one or more SCGs being satisfied and the UE completing the RA procedure to the candidate MCG, transmit, via the transceiver, a first indication to a candidate MN associated with the candidate MCG indicating selection of the one candidate SCG for cell addition; or in response to the set of CPC execution conditions of the one candidate SCG being satisfied and the UE completing the RA procedure to the candidate MCG, transmit, via the transceiver, a second indication to the candidate MN indicating selection of the one candidate SCG for cell handover.

[0015] In some embodiments, the processor of the UE is configured to: in response to the execution conditions of the set of CPAs for each candidate SCG within the one or more candidate SCGs not being met and the UE completing the RA procedure to the candidate MCG, transmit, via the transceiver, a third indication to a candidate MN associated with the candidate MCG indicating that a candidate SCG within the one or more SCGs is not selected for cell addition; or in response to the execution conditions of the set of CPCs for each candidate SCG not being met and the UE completing the RA procedure to the candidate MCG, transmit, via the transceiver, a fourth indication to the candidate MN indicating that a candidate SCG within the one or more SCGs is not selected for cell handover.

[0016] In some embodiments, in response to the UE failing to execute the CHO procedure to the candidate MCG, the processor of the UE is configured to execute a CHO recovery procedure to the candidate MCG.

[0017] In some embodiments, the processor of the UE is further configured to transmit, via the transceiver, a fifth indication to a candidate MN associated with the candidate MCG indicating that a procedure to a candidate SCG is not allowed during the CHO recovery procedure.

[0018] In some embodiments, at least one of the first indication, the second indication, the third indication, the fourth indication, or the fifth indication is included in an SNRRC reconfiguration complete message embodied in an RRC reconfiguration complete message to the candidate MN.

[0019] In some embodiments, in response to the SNRRC reconfiguration complete message including at least one of the first indication or the second indication, the SNRRC reconfiguration complete message further includes an identifier (ID) of the one candidate SCG.

[0020] In some embodiments, in response to completing the CHO recovery procedure, the processor of the UE is configured to transmit, via the transceiver, an indication to the candidate MN indicating at least one of the following: the CHO recovery procedure; or the second RRC configuration of the one or more candidate SCGs is released due to the CHO recovery procedure.

[0021] In some embodiments, in response to the CHO execution condition of the candidate MCG being satisfied, the processor of the UE is configured to consider the set of CPA execution conditions or the set of CPC execution conditions of the candidate SCG within the one or more candidate SCGs as satisfied in response to the following: once the entry condition of the candidate SCG is satisfied while the handover timer of the candidate MCG is running; or when the handover timer is running, the channel quality of the primary secondary cell (PSCell) of the candidate SCG is greater than or equal to a threshold.

[0022] In some embodiments, the processor of the UE is configured to receive an information element (IE) from a source MN via the transceiver, and the IE indicates permission to perform a CHO recovery procedure to the candidate MCG and permission to perform a CPC procedure to one or more candidate SCGs during the CHO recovery procedure of the candidate MCG.

[0023] In some embodiments, the IE is a conditional reconfiguration IE included in the second RRC configuration.

[0024] In some embodiments, in response to permission to perform the CPA procedure or the CPC procedure to the one or more candidate SCGs, the processor of the UE is configured to perform the CPA procedure or the CPC procedure to the candidate SCG within the one or more candidate SCGs during the CHO recovery procedure to the candidate MCG in response to the channel quality of the primary secondary cell (PSCell) of the candidate SCG being greater than or equal to a threshold.

[0025] Some embodiments of the present application further provide a candidate master node (MN). The candidate MN includes: a transceiver; and a processor coupled to the transceiver; and the processor of the UE is configured to: receive a radio resource control (RRC) reconfiguration complete message from a user equipment (UE) via the transceiver; and transmit an indication associated with a candidate secondary cell group (SCG) to a candidate SN via the transceiver.

[0026] In some embodiments, the indication indicates at least one of the following: selecting the candidate SCG for cell addition; selecting the candidate SCG for cell handover; not selecting the candidate SCG for cell addition; not selecting the candidate SCG for cell handover; not choosing the candidate SCG for cell addition; not choosing the candidate SCG for cell handover; during a conditional handover (CHO) recovery procedure to a candidate master cell group (MCG), not allowing execution of a conditional primary secondary cell group (PSCell) addition (CPA) procedure to a candidate SCG; during the CHO recovery procedure, not allowing execution of a conditional PSCell change (CPC) procedure to a candidate SCG; a user equipment (UE) accessing the candidate MCG via a CHO procedure; the UE accessing the candidate MCG via the CHO recovery procedure; or the UE releasing the RRC configuration of the candidate SCG due to the CHO recovery procedure.

[0027] In some embodiments, the indication associated with the candidate SCG is carried in an SN RRC reconfiguration complete message.

[0028] In some embodiments, the SN RRC reconfiguration complete message is included in the RRC reconfiguration complete message and includes an identifier (ID) of the candidate SCG belonging to the candidate SN.

[0029] In some embodiments, the processor of the candidate MN is configured to: receive the indication from the UE via the transceiver; or generate the indication based on the RRC reconfiguration complete message.

[0030] In some embodiments, the processor of the candidate MN is further configured to: transmit an information element (IE) to the UE via the transceiver, and the IE indicates that execution of a CHO recovery procedure to the candidate MCG is allowed and execution of a CPC procedure to one or more candidate SCGs is allowed during the CHO recovery procedure.

[0031] In some embodiments, the IE is a trial conditional reconfiguration IE included in an RRC configuration.

[0032] In some embodiments, the processor of the candidate MN is configured to transmit, via the transceiver, an RRC configuration including conditional handover (CHO) configuration information of a candidate master cell group (MCG) and CHO execution conditions to a source MN.

[0033] Some embodiments of the present application also provide a candidate secondary node (SN). The candidate SN includes: a transceiver; and a processor coupled to the transceiver; and the processor is configured to: transmit, via the transceiver, radio resource control (RRC) configuration including configuration information of one or more candidate secondary cell groups (SCGs) and a set of execution conditions for the one or more candidate SCGs to a candidate master node (MN); and receive, via the transceiver, an indication associated with the one or more candidate SCGs from the candidate MN.

[0034] In some embodiments, the configuration information of the one or more candidate SCGs and the set of execution conditions for the one or more candidate SCGs include: conditional primary secondary cell group (PSCell) addition (CPA) configuration information of the one or more candidate SCGs and a set of CPA execution conditions; or conditional PSCell change (CPC) configuration information of the one or more candidate SCGs and a set of CPC execution conditions.

[0035] In some embodiments, the indication indicates at least one of the following: select the candidate SCG for cell addition; select the candidate SCG for cell handover; do not select the candidate SCG for cell addition; do not select the candidate SCG for cell handover; do not select the candidate SCG for cell addition; do not select the candidate SCG for cell handover; during a conditional handover (CHO) recovery procedure to a candidate master cell group (MCG), do not allow execution of a conditional primary secondary cell group (PSCell) addition (CPA) procedure to the candidate SCG; during the CHO recovery procedure, do not allow execution of a conditional PSCell change (CPC) procedure to the candidate SCG; a user equipment (UE) accesses the candidate MCG via a CHO procedure; the UE accesses the candidate MCG via the CHO recovery procedure; or the UE releases the RRC configuration of the candidate SCG due to the CHO recovery procedure.

[0036] In some embodiments, the processor of the candidate SN is further configured to release resources of the candidate SCG in response to the indication indicating: do not select the candidate SCG for cell addition; do not select the candidate SCG for cell handover; do not select the candidate SCG for cell addition; or do not select the candidate SCG for cell handover.

[0037] Some embodiments of the present application provide a method performed by a UE. The method includes: receiving a first Radio Resource Control (RRC) configuration and a second RRC configuration, where the first RRC configuration includes conditional handover (CHO) configuration information and a CHO execution condition of a candidate master cell group (MCG), and the second RRC configuration includes configuration information of one or more candidate secondary cell groups (SCGs) and a set of execution conditions of the one or more candidate SCGs; and evaluating the CHO execution condition of the candidate MCG after receiving the first RRC configuration.

[0038] Some embodiments of the present application provide a method performed by a candidate MN. The method includes: receiving a Radio Resource Control (RRC) reconfiguration complete message from a user equipment (UE); and transmitting an indication associated with a candidate secondary cell group (SCG) to a candidate SN.

[0039] Some embodiments of the present application provide a method performed by a candidate SN. The method includes: transmitting a Radio Resource Control (RRC) configuration including configuration information of one or more candidate secondary cell groups (SCGs) and a set of execution conditions of the one or more candidate SCGs to a candidate master node (MN); and receiving an indication associated with the one or more candidate SCGs from the candidate MN.

[0040] Some embodiments of the present application provide a wireless communication device. The device includes: a non-transitory computer-readable medium having computer-executable instructions stored thereon; receiving circuitry; transmitting circuitry; and a processor coupled to the non-transitory computer-readable medium, the receiving circuitry, and the transmitting circuitry, where the computer-executable instructions cause the processor to implement the methods performed by the UE or a network node (source MN, target MN, candidate MN, source SN, target SN, or candidate SN) mentioned above.

[0041] The details of one or more examples are set forth in the accompanying drawings and the description below. Other features, objects, and advantages will be apparent from the description and drawings, and from the claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] To describe the manner in which the advantages and features of the present application can be obtained, a description of the present application is presented by reference to specific embodiments of the present application illustrated in the accompanying drawings. These drawings only depict example embodiments of the present application and should not be considered as limiting its scope.

[0043] Figure 1 A schematic diagram illustrating a wireless communication system according to some embodiments of the present application.

[0044] Figure 2Exemplary flowchart of a CHO with a candidate SCG mechanism according to some embodiments of the present application.

[0045] Figure 3 Exemplary flowchart of transmitting an indication associated with a candidate SCG according to some embodiments of the present application.

[0046] Figure 4 Exemplary flowchart of receiving an indication associated with a candidate SCG according to some embodiments of the present application.

[0047] Figures 5 to 8 Exemplary flowchart of a CHO with a candidate SCG mechanism according to some embodiments of the present application.

[0048] Figure 9 Block diagram of an exemplary device according to some embodiments of the present disclosure. Detailed Description

[0049] The detailed description of the drawings is intended to be a description of the preferred embodiments of the present application and is not intended to represent the only form in which the present application can be practiced. It should be understood that the same or equivalent functions can be achieved by different embodiments that are intended to be covered by the spirit and scope of the present application.

[0050] Reference will now be made in detail to some embodiments of the present application, examples of which are illustrated in the accompanying drawings. For the sake of promoting understanding, the embodiments are provided in the context of a specific network architecture and new service scenarios (such as 3GPP 5G, 3GPP LTE Release 8, etc.). It is contemplated that as the network architecture and new service scenarios evolve, all embodiments in the present application are also applicable to similar technical problems; and furthermore, the terms cited in the present application may change, which should not affect the principles of the present application.

[0051] Figure 1 Schematic diagram of a wireless communication system according to some embodiments of the present application.

[0052] As Figure 1 shown, the wireless communication system 100 may be a dual-connection system 100 including at least one UE 101, at least one MN 102, and at least one SN 103. Specifically, for illustrative purposes, Figure 1 the dual-connection system 100 in Figure 1 includes one shown UE 101, one shown MN 102, and one shown SN 103. Although a specific number of UEs 101, MNs 102, and SNs 103 are depicted in

[0053] Reference Figure 1, the UE 101 can be connected to the MN 102 and the SN 103 via a network interface (e.g., the Uu interface as specified in the 3GPP standard document). The MN 102 and the SN 103 can be connected to each other via a network interface (e.g., the Xn interface specified for NR-NR DC or NGEN-DC or NE-DC in the 3GPP standard document or the X2 interface specified for EN-DC in the 3GPP standard document). The MN 102 can be connected to the core network via a network interface ( Figure 1 not shown in). The UE 102 can be configured to perform data transmission by using the resources provided by the MN 102 and the SN 103.

[0054] The MN 102 can refer to a radio access node that provides a control plane connection to the core network. In an embodiment of the present application, in an E-UTRA-NR dual-connection (EN-DC) scenario, the MN 102 can be an eNB. In another embodiment of the present application, in a next-generation E-UTRA-NR dual-connection (NGEN-DC) scenario, the MN 102 can be an ng-eNB. In yet another embodiment of the present application, in an NR-E-UTRA dual-connection (NE-DC) scenario or an NR-NR dual-connection (NR-DC) scenario, the MN 102 can be a gNB.

[0055] The MN 102 can be associated with a master cell group (MCG). The MCG can refer to a set of serving cells associated with the MN 102, and can include a primary cell (PCell) and optionally one or more secondary cells (SCells) of the MCG. The PCell can provide a control plane connection to the UE 101.

[0056] The SN 103 can refer to a radio access node that does not have a control plane connection to the core network but provides additional resources to the UE 101. In an embodiment of the present application, in an EN-DC scenario, the SN 103 can be an en-gNB. In another embodiment of the present application, in a NE-DC scenario, the SN 103 can be an ng-eNB. In yet another embodiment of the present application, in an NR-DC scenario or an NGEN-DC scenario, the SN 103 can be a gNB.

[0057] The SN 103 can be associated with a secondary cell group (SCG). The SCG can refer to a set of serving cells associated with the SN 103, and can include a primary secondary cell (PSCell) and optionally one or more secondary cells (SCells). The PCell of the MCG and the PSCell of the SCG can also be referred to as special cells (SpCell).

[0058] In some embodiments of the present application, the UE 101 may include a computing device, such as a desktop computer, a laptop computer, a personal digital assistant (PDA), a tablet computer, a smart TV (e.g., a TV connected to the Internet), a set-top box, a gaming console, a security system (including security cameras), an in-vehicle computer, a network device (e.g., a router, a switch, and a modem), or the like. In some other embodiments of the present application, the UE 101 may include a portable wireless communication device, a smart phone, a cellular phone, a flip phone, a device with a subscriber identity module, a personal computer, a selective call receiving circuitry, or any other device capable of transmitting and receiving communication signals over a wireless network.

[0059] In some other embodiments of the present application, the UE 101 may include a wearable device, such as a smart watch, a fitness bracelet, an optical head-mounted display, or the like. Additionally, the UE 101 may be referred to as a user unit, a mobile device, a mobile station, a user, a terminal, a mobile terminal, a wireless terminal, a fixed terminal, a user station, a user terminal, or a device, or other terms used in the art to describe.

[0060] Generally, CHO is performed by the UE when one or more handover execution conditions are met. The UE starts evaluating the execution conditions after receiving the CHO configuration, and once the execution conditions are met, it stops evaluating the execution conditions during the CHO execution. The CHO configuration contains the configuration of the CHO candidate cells generated by the candidate BS and the execution conditions generated by the source BS.

[0061] As in the NR intra-RAN handover or in the NR radio access network (RAN) CHO, the preparation and execution phases of the CHO procedure are performed without involving the 5G core network (5GC); that is, the preparation messages are directly exchanged between the BSs. The release of resources at the source BS during the conditional handover completion phase is triggered by the candidate BS, where both the access and mobility management function (AMF) and the user plane function UPF remain unchanged.

[0062] Generally, inter-MN handover with or without SN change initiated by the MN is used to transfer UE context data from the source MN to the candidate MN, while the UE context at the SN is either maintained or moved to another SN. During the inter-MN handover, the candidate MN decides whether to maintain or change the SN (or release the SN). Only RAT-internal (intra-RAT) inter-MN handover with or without SN change is supported.

[0063] Currently, there is no mechanism for the CHO scenario with one or more candidate SCGs. Embodiments of the present disclosure aim to solve this problem. Specifically, some embodiments of the present disclosure design a mechanism to support the simultaneous execution of both CHO and candidate SCGs. In some embodiments of the present disclosure, after the UE performs CHO with or without a candidate SCG within one or more candidate SCGs, information (e.g., included in the RRC reconfiguration complete message) is transmitted to the candidate node or the target node. Some embodiments of the present disclosure design relaxed execution conditions for the candidate SCG when the CHO execution conditions are met. Some embodiments of the present disclosure introduce an enhanced mechanism for CHO recovery in the CHO scenario with a candidate SCG.

[0064] In some embodiments of the present disclosure, during a cell handover (e.g., the CHO procedure) from the source SN, the candidate MN may also be referred to as the target MN or the target candidate MN or the like. During cell addition or cell handover (e.g., the CPA or CPC procedure), the candidate SN may also be referred to as the target SN or the target candidate SN or the like. During cell addition or cell handover, the candidate cell may also be referred to as the target cell or the target candidate cell or the like. In other words, from the perspective of the UE, the same MN may be referred to as the candidate MN or the target MN in different scenarios, the same SN may be referred to as the candidate SN or the target SN in different scenarios, and the same cell may be referred to as the candidate cell or the target cell in different scenarios, without departing from the spirit and scope of the present disclosure.

[0065] More details regarding embodiments of the present application will be described below in conjunction with the drawings.

[0066] Figure 2 Illustrate an exemplary flowchart of CHO with a candidate SCG mechanism according to some embodiments of the present application. Figure 2 The exemplary procedure 200 in the embodiments of Figure 1 and 5 can be executed by a UE (e.g., the UE 101, UE701, UE 801, UE 901, or UE 1001 shown in any of Figure 2 to 8). Although described with respect to the UE, it should be understood that other devices may be configured to execute methods similar to the

[0067] In Figure 2In the exemplary procedure 200 shown, in operation 201, the UE may receive an RRC configuration (simply denoted as RRC configuration #1) and another RRC configuration (denoted as RRC configuration #2). The RRC configuration #1 includes CHO configuration information and CHO execution conditions of a candidate MCG. The CHO execution conditions of the candidate MCG may include one or more execution conditions of the candidate MCG, such as entry conditions and / or exit conditions. The RRC configuration #2 includes configuration information of one or more candidate SCGs and a set of execution conditions of one or more candidate SCGs.

[0068] The RRC configuration #1 and the RRC configuration #2 may be received via separate messages or via the same message. For example, a candidate MN (such as candidate MN 705) may generate a configuration for its corresponding candidate MCG and transmit the configuration of the corresponding candidate MCG (i.e., RRC configuration #1) to the source MN (such as source MN 702). A candidate SN (such as candidate SN 704) of the candidate MN may generate a configuration for its corresponding candidate SCG and transmit the configuration of the corresponding candidate SCG to the candidate MN. The candidate MN may transmit the configurations of all candidate SCGs received from one or more candidate SNs (i.e., RRC configuration #2) to the source MN. Then, in some embodiments, the source MN may transmit an RRC reconfiguration message containing both the RRC configuration #1 and the RRC configuration #2 to the UE (such as UE 701). In some other embodiments, the source MN may transmit an RRC reconfiguration message containing the RRC configuration #1 to the UE and transmit another RRC reconfiguration message containing the RRC configuration #2.

[0069] In operation 202, the UE may evaluate the CHO execution conditions of the candidate MCG after receiving the RRC configuration #1.

[0070] In some embodiments, the set of execution conditions of one or more candidate SCGs in the RRC configuration #2 may be conditional PSCell addition or change (CPAC) execution conditions of one or more candidate SCGs. In some embodiments, in the RRC configuration #2, the configuration information of one or more candidate SCGs and the set of execution conditions of one or more candidate SCGs include:

[0071] (1) CPA configuration information and a set of CPA execution conditions of one or more candidate SCGs; or

[0072] (2) CPC configuration information and a set of CPC execution conditions of one or more candidate SCGs.

[0073] In some embodiments, the UE may concurrently evaluate the CHO execution conditions of a candidate MCG and evaluate the set of CPA or CPC execution conditions of a candidate SCG. In an embodiment, the UE may evaluate the set of CPA execution conditions after receiving RRC configuration #2 for the CPA. In another embodiment, the UE may evaluate the set of CPC execution conditions after receiving RRC configuration #2 for the CPC.

[0074] In some other embodiments, the UE may sequentially evaluate the CHO execution conditions of a candidate MCG and evaluate the set of CPA or CPC execution conditions of a candidate SCG. For some cases, the UE may first evaluate the CHO execution conditions of the candidate MCG, and then, after the CHO execution conditions of the candidate MCG are satisfied, start to evaluate the set of CPA or CPC execution conditions of the candidate SCG. In an embodiment, the UE starts to evaluate the set of CPA execution conditions in response to the CHO execution conditions of the candidate MCG being satisfied. In another embodiment, the UE starts to evaluate the set of CPC execution conditions in response to the CHO execution conditions of the candidate MCG being satisfied.

[0075] For some other cases, the UE may first evaluate the set of CPA or CPC execution conditions of the candidate SCG, and then, after the set of CPA or CPC execution conditions of the candidate SCG are satisfied, start to evaluate the CHO execution conditions of the candidate MCG. In such cases, the CHO with the candidate SCG is only executed when the execution conditions of both the candidate MCG and the candidate SCG are satisfied. If only the CHO execution conditions of the candidate MCG are satisfied but the set of CPA or CPC execution conditions of the candidate SCG are not met, then the CHO with the candidate SCG is not applied. Specific examples are described below in Embodiment 3 of the embodiments in Figure 5 as follows.

[0076] In some embodiments, if the set of CPA execution conditions of a candidate SCG (denoted as candidate SCG#1) within the candidate SCG are satisfied, then the UE may stop evaluating the set of CPA execution conditions of other candidate SCGs within the candidate SCG. In some other embodiments, if the set of CPC execution conditions of a candidate SCG (such as candidate SCG#1) within the candidate SCG are satisfied, then the UE may stop evaluating the set of CPC execution conditions of other candidate SCGs within the candidate SCG. Specific examples are described below in Embodiment 2 of the embodiments in Figure 5 as follows.

[0077] In some embodiments, when the UE "concurrently evaluates" or "sequentially evaluates" the CHO execution conditions of the candidate MCG and the set of CPA or CPC execution conditions of the candidate SCG as described above, the UE may release RRC configuration #2 in response to the following:

[0078] (1) The set of execution conditions for each candidate SCG within the candidate SCG is not satisfied when the UE completes the RA procedure to the candidate MCG;

[0079] (2) The set of execution conditions for each candidate SCG is not satisfied when the handover timer of the candidate MCG (e.g., timer T304 described in the 3GPP standard document) stops;

[0080] (3) The set of execution conditions for each candidate SCG is not satisfied after a period (denoted as period #1) since the UE completed the RA procedure to the candidate MCG;

[0081] (4) The set of execution conditions for each candidate SCG is not satisfied when the CHO execution conditions of the candidate MCG are satisfied; or

[0082] (5) The set of execution conditions for each candidate SCG is not satisfied after a period (denoted as period #2) since the CHO execution conditions of the candidate MCG are satisfied.

[0083] In an embodiment, the UE may release RRC configuration #2 in response to the following:

[0084] (1) The set of execution conditions for each candidate SCG within one or more candidate SCGs is not satisfied when the UE completes the random access (RA) procedure to the candidate MCG;

[0085] (2) The set of CPA execution conditions for each candidate SCG is not satisfied when the handover timer of the candidate MCG (e.g., timer T304) stops;

[0086] (3) The set of CPA execution conditions for each candidate SCG is not satisfied after period #1;

[0087] (4) The set of CPA execution conditions for each candidate SCG is not satisfied when the CHO execution conditions of the candidate MCG are satisfied; or

[0088] (5) The set of CPA execution conditions for each candidate SCG is not satisfied after period #2.

[0089] In another embodiment, the UE may release RRC configuration #2 in response to the following:

[0090] (1) The set of execution conditions for each candidate SCG is not satisfied when the UE completes the RA procedure to the candidate MCG;

[0091] (2) The set of CPC execution conditions for each candidate SCG is not satisfied when the handover timer of the candidate MCG (e.g., timer T304) stops;

[0092] (3) The set of CPC execution conditions for each candidate SCG is not satisfied after time period #1;

[0093] (4) The set of CPC execution conditions for each candidate SCG is not satisfied when the CHO execution condition of the candidate MCG is satisfied; or

[0094] (5) The set of CPC execution conditions for each candidate SCG is not satisfied after time period #2.

[0095] In some embodiments, if the CHO execution condition of the candidate MCG is satisfied, the UE may stop evaluating the set of execution conditions of the candidate SCG in response to the following:

[0096] (1) The set of execution conditions for each candidate SCG within the candidate SCG is not satisfied when the UE completes the RA procedure to the candidate MCG;

[0097] (2) The set of execution conditions for each candidate SCG is not satisfied when the handover timer of the candidate MCG (e.g., timer T304) stops;

[0098] (3) The set of execution conditions for each candidate SCG is not satisfied after time period #1;

[0099] (4) The set of execution conditions for each candidate SCG is not satisfied when the CHO execution condition of the candidate MCG is satisfied; or

[0100] (5) The set of execution conditions for each candidate SCG is not satisfied after time period #2.

[0101] In an embodiment, if the CHO execution condition of the candidate MCG is satisfied, the UE may stop evaluating the set of CPA execution conditions of the candidate SCG in response to the following:

[0102] (1) The set of CPA execution conditions for each candidate SCG within the candidate SCG is not satisfied when the UE completes the RA procedure to the candidate MCG;

[0103] (2) The set of CPA execution conditions for each candidate SCG is not satisfied when the handover timer of the candidate MCG (e.g., timer T304) stops;

[0104] (3) The set of CPA execution conditions for each candidate SCG is not satisfied after time period #1;

[0105] (4) The set of CPA execution conditions for each candidate SCG is not satisfied when the CHO execution condition of the candidate MCG is satisfied; or

[0106] (5) The set of CPA execution conditions for each candidate SCG is not satisfied after time period #2.

[0107] In another embodiment, if the CHO execution condition of the candidate MCG is satisfied, the UE may stop evaluating the set of CPC execution conditions of the candidate SCG in response to the following:

[0108] (1) The set of CPC execution conditions of each candidate SCG within the candidate SCG is not satisfied when the UE completes the RA procedure to the candidate MCG;

[0109] (2) The set of CPC execution conditions of each candidate SCG is not satisfied when the handover timer (e.g., timer T304) of the candidate MCG stops;

[0110] (3) The set of CPC execution conditions of each candidate SCG is not satisfied after time period #1;

[0111] (4) The set of CPC execution conditions of each candidate SCG is not satisfied when the CHO execution condition of the candidate MCG is satisfied; or

[0112] (5) The set of CPC execution conditions of each candidate SCG is not satisfied after time period #2.

[0113] In some embodiments, the UE may release the set of execution conditions of the candidate SCG after stopping evaluating the set of execution conditions of the candidate SCG. A specific example is described as follows in Embodiment 1 of the embodiment in Figure 5 .

[0114] In some embodiments, if the CHO execution condition of the candidate MCG is satisfied, the UE may perform the RA procedure to the candidate MCG based on the first RRC configuration; and transmit an RRC reconfiguration complete message to the candidate MN associated with the candidate MCG.

[0115] In some embodiments, if the set of CPA execution conditions of a candidate SCG (e.g., candidate SCG #1) within the candidate SCG is satisfied and the UE completes the RA procedure to the candidate MCG, the UE may transmit an indication (denoted as indication #1) indicating the selection of candidate SCG #1 for cell addition to the candidate MN associated with the candidate MCG.

[0116] In some other embodiments, if the set of CPC execution conditions of a candidate SCG (e.g., candidate SCG #1) is satisfied and the UE completes the RA procedure to the candidate MCG, the UE may transmit an indication (denoted as indication #2) indicating the selection of candidate SCG #1 for cell handover to the candidate MN.

[0117] In some embodiments, if the set of CPA execution conditions for a subset of candidate SCGs is not satisfied and the UE completes the RA procedure to the candidate MCG, the UE may transmit an indication (referred to as indication #3) to the candidate MN associated with the candidate MCG indicating the subset of candidate SCGs that are not selected from the candidate SCGs for cell addition. For example, indication #3 includes the ID information of each SCG in the subset of candidate SCGs.

[0118] In some other embodiments, if the set of CPC execution conditions for a subset of candidate SCGs is not satisfied and the UE completes the RA procedure to the candidate MCG, the UE may transmit an indication (referred to as indication #4) to the candidate MN indicating the subset of candidate SCGs that are not selected from the candidate SCGs for cell handover. For example, indication #4 includes the ID information of each SCG in the subset of candidate SCGs.

[0119] In some embodiments, if the set of CPA execution conditions for each candidate SCG is not satisfied and the UE completes the RA procedure to the candidate MCG, the UE may transmit an indication (referred to as indication #5) to the candidate MN associated with the candidate MCG indicating that the candidate SCGs within the candidate SCGs are not selected for cell addition.

[0120] In some other embodiments, if the set of CPC execution conditions for each candidate SCG is not satisfied and the UE completes the RA procedure to the candidate MCG, the UE may transmit an indication (referred to as indication #6) to the candidate MN indicating that the candidate SCGs within the candidate SCGs are not selected for cell handover.

[0121] In some embodiments, in response to the UE failing to execute the CHO procedure to the candidate MCG, the UE may execute the CHO recovery procedure to the candidate MCG.

[0122] In some embodiments, the UE may transmit an indication (referred to as indication #7) to the candidate MN associated with the candidate MCG indicating that procedures to the candidate SCG (e.g., the CPA procedure or the CPC procedure) are not allowed during the CHO recovery procedure.

[0123] In some embodiments, indication #1, indication #2, indication #3, indication #4, indication #5, indication #6, and / or indication #7 are included in the SN RRC reconfiguration complete message embodied in the RRC reconfiguration complete message to the candidate MN.

[0124] In some embodiments, if the SN RRC reconfiguration complete message includes indication #1 and / or indication #2, the SN RRC reconfiguration complete message further includes the identity (ID) of one candidate SCG associated with indication #1 or indication #2 (e.g., candidate SCG #1).

[0125] In some embodiments, in response to completion of a CHO recovery procedure to a candidate MCG, the UE may transmit at least one of the following indications to the candidate MN:

[0126] (1) An indication of the CHO recovery procedure (denoted as indication #8); or

[0127] (2) An indication that the RRC configuration #2 of the candidate SCG has been released due to the CHO recovery procedure (denoted as indication

[0128] #9). Specific instances are described below in the embodiments of Figures 6 to 8 .

[0129] In some embodiments, if the CHO execution conditions of the candidate MCG are met, then the CPA or CPA execution conditions may be relaxed. For example, if the CHO execution conditions of the candidate MCG are met, then the UE may consider the set of CPA execution conditions or the set of CPC execution conditions of the candidate SCG within the candidate SCG to be satisfied in response to the following:

[0130] (1) Once the entry conditions of the candidate SCG (e.g., the entry conditions of the CPA or CPC) are met while the handover timer of the candidate MCG (e.g., T304) is running; or

[0131] (2) When the handover timer (e.g., T304) is running, the channel quality of the PSCell of the candidate SCG is greater than or equal to a threshold (e.g., when the S-criterion described in the 3GPP standard document is satisfied).

[0132] In some embodiments, the UE may receive an information element (IE) from the source MN. The IE may indicate that execution of the CHO recovery procedure to the candidate MCG is permitted. The IE may indicate that execution of the CPA procedure or CPC procedure to the candidate SCG is permitted during the CHO recovery procedure to the candidate MCG. In an embodiment, the IE is a conditional reconfiguration attempt IE (e.g., attemptCondReconfig IE) included in the RRC configuration #1.

[0133] In some embodiments, if execution of the CPA procedure or CPC procedure to the candidate SCG is permitted, then the UE may execute the CPA procedure or CPC procedure of the candidate SCG within the candidate SCG during the CHO recovery procedure to the candidate MCG in response to the channel quality of the PSCell of the candidate SCG being greater than or equal to a threshold (e.g., when the S-criterion is satisfied). Specific instances are described below in the embodiments of Figure 8 .

[0134] Figure 3 Exemplary flowchart illustrating transmission of an indication associated with a candidate SCG according to some embodiments of the present application.Figure 3 The exemplary procedure 300 in the embodiment of Figure 1 and 5 can be executed by a target MN or a candidate MN (e.g., Figure 3 MN 102, candidate MN 705, candidate MN 805, candidate MN 905, or candidate MN 1005 shown in any of

[0135] In Figure 3 the exemplary procedure 300 shown in Figure 1 in operation 301, the candidate MN can receive an RRC reconfiguration complete message from a UE (e.g., Figure 1 UE 101 shown in Figure 1 ). In operation 302, the candidate MN can transmit an indication associated with a candidate SCG to a candidate SN (e.g.,

[0136] In some embodiments, the indication associated with the candidate SCG is carried in an SN RRC reconfiguration complete message. In an embodiment, the SN RRC reconfiguration complete message is included in the RRC reconfiguration complete message in operation 301. The SN RRC reconfiguration complete message may include an identity (ID) of a candidate SCG belonging to the candidate SN. In some other embodiments, the candidate MN can receive an indication from the UE. In some additional embodiments, the candidate MN can generate an indication based on the RRC reconfiguration complete message in operation 301.

[0137] In some embodiments, the indication transmitted by the candidate MN to the candidate SN in operation 302 indicates at least one of the following:

[0138] (1) Selecting the candidate SCG for cell addition, e.g., Figure 2 indication #1 described in the embodiment of

[0139] (2) Selecting the candidate SCG for cell handover, e.g., Figure 2 indication #2 described in the embodiment of

[0140] (3) Not selecting the candidate SCG for cell addition, e.g., Figure 2 indication #3 described in the embodiment of

[0141] (4) Not selecting the candidate SCG for cell handover, e.g., Figure 2 indication #4 described in the embodiment of

[0142] (5) Not choosing the candidate SCG for cell addition, e.g., Figure 2The indication #5 described in the embodiment of;

[0143] (6) Do not select a candidate SCG for cell handover, for example Figure 2 The indication #6 described in the embodiment of;

[0144] (7) Do not allow the execution of the CPA procedure to the candidate SCG during the CHO recovery procedure to the candidate MCG, for example Figure 2 The indication #7 described in the embodiment of;

[0145] (8) Do not allow the execution of the CPC procedure to the candidate SCG during the CHO recovery procedure, for example Figure 2 The indication #7 described in the embodiment of; or

[0146] (9) The UE accesses the candidate MCG via the CHO procedure;

[0147] (10) The UE accesses the candidate MCG via the CHO recovery procedure, for example Figure 2 The indication #8 described in the embodiment of;

[0148] Or

[0149] (11) The UE releases the RRC configuration of the candidate SCG due to the CHO recovery procedure, for example Figure 2 The indication #9 described in the embodiment of.

[0150] In some embodiments, the candidate MN may transmit an IE to the UE. The IE may indicate that the execution of the CHO recovery procedure to the candidate MCG is allowed. The IE may indicate that the execution of the CPA procedure or the CPC procedure to one or more candidate SCGs is allowed during the CHO recovery procedure. In an embodiment, the IE is an attempt conditional reconfiguration IE (such as attemptCondReconfigIE) included in the RRC configuration.

[0151] In some embodiments, the candidate MN may transmit an RRC configuration including the CHO configuration information and the CHO execution conditions of the candidate MCG to the source MN. For example, the attemptCondReconfigIE is included in the RRC configuration. A specific instance is described as follows in the Figure 8 embodiment of.

[0152] Figure 4 Illustrative flowchart showing the reception of an indication associated with a candidate SCG according to some embodiments of the present application. Figure 4 The illustrative procedure 400 in the embodiment of may be performed by the target SN or the candidate SN (such as Figure 1 And 5performed on SN103, candidate SN 704, candidate SN 804, candidate SN 806, candidate SN 904, candidate SN 906, candidate SN 1004, or candidate SN 1006 shown in FIGS. 0 to 8. Although described with respect to a target SN or candidate SN, it should be understood that other devices may be configured to perform methods similar to those of Figure 4 the method.

[0153] In Figure 4 exemplary procedure 400 shown in, in operation 401, a candidate SN may transmit an RRC configuration to a candidate MN that includes configuration information of a candidate SCG and a set of execution conditions of the candidate SCG. In some embodiments, the set of execution conditions of the candidate SCG may be the CPAC execution conditions of the candidate SCG. In some embodiments, the configuration information of the candidate SCG and the set of execution conditions of the candidate SCG include:

[0154] (1) the CPA configuration information of the candidate SCG and a set of CPA execution conditions; or

[0155] (2) the CPC configuration information of the candidate SCG and a set of CPC execution conditions.

[0156] In operation 402, the candidate SN may receive an indication associated with the candidate SCG from the candidate MN. In some embodiments, the indication indicates at least one of the following:

[0157] (1) selecting the candidate SCG or a subset within the candidate SCG for cell addition, e.g., Figure 2 indication #1 described in the embodiments of

[0158] (2) selecting the candidate SCG or a subset within the candidate SCG for cell handover, e.g., Figure 2 indication #2 described in the embodiments of

[0159] (3) not selecting the candidate SCG for cell addition, e.g., Figure 2 indication #3 described in the embodiments of

[0160] (4) not selecting the candidate SCG for cell handover, e.g., Figure 2 indication #4 described in the embodiments of

[0161] (5) not choosing the candidate SCG for cell addition, e.g., Figure 2 indication #5 described in the embodiments of

[0162] (6) not choosing the candidate SCG for cell handover, e.g., Figure 2 indication #6 described in the embodiments of

[0163] (7) During the CHO recovery procedure to the candidate MCG, execution of the CPA procedure to the candidate SCG is not allowed, such as Figure 2 Indication #7 described in the embodiment of

[0164] (8) During the CHO recovery procedure, execution of the CPC procedure to the candidate SCG is not allowed, such as Figure 2 Indication #7 described in the embodiment of

[0165] (9) The UE accesses the candidate MCG via the CHO procedure;

[0166] (10) The UE accesses the candidate MCG via the CHO recovery procedure, such as Figure 2 Indication #8 described in the embodiment of

[0167] Or

[0168] (11) The UE releases the RRC configuration of the candidate SCG due to the CHO recovery procedure, such as Figure 2 Indication #9 described in the embodiment of

[0169] In some embodiments, the candidate SN may release the resources of the candidate SCG in response to an indication indicating the following:

[0170] (1) The candidate SCG is not selected for cell addition, such as Figure 2 Indication #3 described in the embodiment of

[0171] (2) The candidate SCG is not selected for cell handover, such as Figure 2 Indication #4 described in the embodiment of

[0172] (3) The candidate SCG is not selected for cell addition, such as Figure 2 Indication #5 described in the embodiment of

[0173] (4) The candidate SCG is not selected for cell handover, such as Figure 2 Indication #6 described in the embodiment of

[0174] (5) During the CHO recovery procedure to the candidate MCG, execution of the CPA procedure to the candidate SCG is not allowed, such as Figure 2 Indication #7 described in the embodiment of

[0175] (6) During the CHO recovery procedure, execution of the CPC procedure to the candidate SCG is not allowed, such as Figure 2 Indication #7 described in the embodiment of

[0176] (7) The UE accesses the candidate MCG via the CHO recovery procedure, such as Figure 2 Indication #8 described in the embodiment of; or

[0177] (8) The UE releases the RRC configuration of the candidate SCG due to the CHO recovery procedure, such as Figure 2 the indication #9 described in the embodiment of Figures 6 to 8 as described below in the embodiment of

[0178] The details described in all other embodiments of this application apply to Figures 2 to 4 the embodiments shown in any of Figures 2 to 4 The sequence of operations in any of the exemplary procedures 200, 300, and 400 in Figures 2 to 4 can be changed and some operations in any of the exemplary procedures 200 to 400 in

[0179] are described below Figures 2 to 4 The specific embodiments shown and described in where the UE and network nodes (such as source MN, target MN, candidate MN, source SN, target SN, and / or candidate SN) perform the following operations. Those skilled in the art should understand that Figures 5 to 8 The sequence of operations in any of the exemplary procedures 700, 800, 900, and 1000 in Figures 5 to 8 can be changed and some operations in any of the exemplary procedures 700 to 1000 in

[0180] Figure 5 Exemplary flowcharts of CHO with a candidate SCG mechanism according to some embodiments of this application are described. The details described in all other embodiments of this application apply to Figure 5 the embodiments shown in

[0181] In Figure 5 the exemplary flowchart 700 shown in, in operation 711, the UE 701 in the RRC connected state accesses its serving BS, i.e., the source MN 702. For example, DC (Dual Connectivity) may be configured for the UE 701. In some embodiments, the UE 701 may report measurement results to the source MN 702.

[0182] In operation 712, based on the measurement results, the source MN 702 may determine to switch the UE 701 to the candidate MN 705 via the CHO procedure.

[0183] In operation 713, the source MN 702 may send a handover request to the candidate MN 705. For example, the source MN 702 may instruct the candidate MN 705 to prepare the candidate SCG.

[0184] In operation 714, after the candidate MN 705 receives a handover request from the source MN 702, the candidate MN 705 may transmit a request (e.g., an SgNB addition request message or an SN modification request message) to the candidate SN 704 via the Xn interface.

[0185] In operation 715, the candidate SN 704 may transmit an acknowledgment message (e.g., an SgNB addition request acknowledgment message or an SgNB modification request acknowledgment message) to the candidate MN 705. The configuration of the candidate SCG of the candidate SN 704 may be included in the acknowledgment message.

[0186] In operation 716, after receiving the acknowledgment message from the candidate SN 704, the candidate MN 705 transmits a handover request acknowledgment message to the source MN 702 that includes the RRC configuration of the candidate MCG (e.g., RRC configuration #1 described in the embodiment of Figure 2 and / or the RRC configuration of the candidate SCG (e.g., RRC configuration #2 described in the embodiment of Figure 2 .

[0187] In some embodiments, the RRC configuration of the candidate MCG may include the CHO configuration of the candidate MCG and the CHO execution conditions of the candidate MCG. In some embodiments, the RRC configuration of the candidate SCG may include: (1) the CPA configuration of the candidate SCG and the CPA execution conditions; or (2) the CPC configuration of the candidate SCG and a set of CPC execution conditions.

[0188] In operation 717, after receiving the handover request acknowledgment message from the candidate MN 705, the source MN 702 transmits an RRC reconfiguration message to the UE 701 that includes the RRC configuration of the candidate MCG and / or the RRC configuration of the candidate SCG.

[0189] In operation 718, after receiving the RRC reconfiguration message from the source MN 702, the UE 701 transmits an RRC reconfiguration complete message to the source MN 702.

[0190] In operation 719, different embodiments may exist in different scenarios, namely, Embodiment 1, Embodiment 2, and Embodiment 3 as follows.

[0191] Embodiment 1

[0192] In operation 719, the UE 701 starts to "concurrently evaluate" or "sequentially evaluate" the CHO execution conditions of the candidate MCG and / or the execution conditions of the candidate SCG (e.g., CPA or CPC execution conditions).

[0193] In some embodiments of "concurrent evaluation", after the UE 701 receives the RRC configuration of the candidate MCG in the RRC reconfiguration message, it starts to evaluate the CHO execution conditions of the candidate MCG, and after receiving the RRC configuration of the candidate SCG in the RRC reconfiguration message, it starts to evaluate the CPA or CPC execution conditions.

[0194] In some embodiments of "sequential evaluation", when the UE 701 receives the RRC configuration of the candidate MCG in the RRC reconfiguration message, it starts to evaluate the CHO execution conditions of the candidate MCG. The UE starts to evaluate the CPA or CPC execution conditions after the CHO execution conditions of the candidate MCG are satisfied.

[0195] In operation 719 of embodiment 1, in different embodiments, there may be the following two options, namely, option 1 and option 2 as follows.

[0196] Option 1: The UE 701 may release the RRC configuration associated with the candidate SCG in response to the following:

[0197] (1) The CPA or CPC execution conditions of each candidate SCG within the candidate SCG are not satisfied when the UE completes the RA procedure to the candidate MCG;

[0198] (2) The CPA or CPC execution conditions of each candidate SCG are not satisfied when the handover timer (e.g., timer T304) of the candidate MCG stops;

[0199] (3) The CPA or CPC execution conditions of each candidate SCG are not satisfied after a period (e.g., Figure 2 the period #1 described in the embodiment of

[0200] (4) The CPA or CPC execution conditions of each candidate SCG are not satisfied when the CHO execution conditions of the candidate MCG are satisfied; or

[0201] (5) The CPA or CPC execution conditions of each candidate SCG are not satisfied after a period (e.g., Figure 2 the period #2 described in the embodiment of

[0202] Option 2: The UE 701 may stop evaluating the execution conditions of the candidate SCG in response to the following:

[0203] (1) The CPA or CPC execution conditions of each candidate SCG within the candidate SCG are not satisfied when the UE completes the RA procedure to the candidate MCG;

[0204] (2) The execution conditions of CPA or CPC for each candidate SCG are not satisfied when the handover timer (e.g., timer T304) of the candidate MCG stops;

[0205] (3) The execution conditions of CPA or CPC for each candidate SCG are not satisfied after a period (e.g., Figure 2 the period #1 described in the embodiment of

[0206] (4) The execution conditions of CPA or CPC for each candidate SCG are not satisfied when the CHO execution conditions of the candidate MCG are satisfied; or

[0207] (5) The execution conditions of CPA or CPC for each candidate SCG are not satisfied after a period (e.g., Figure 2 the period #2 described in the embodiment of

[0208] Embodiment 2

[0209] In operation 719, the UE 701 starts to evaluate the CHO execution conditions of the candidate MCG. After the CHO execution conditions of the candidate MCG are satisfied, the UE 701 starts to evaluate the execution conditions (e.g., CPA or CPC execution conditions) of the candidate SCG. In some embodiments, if the CPA or CPC execution conditions of a candidate SCG (e.g., Figure 2 the candidate SCG#1 described in the embodiment of

[0210] Embodiment 3

[0211] In operation 719, the UE 701 may first evaluate the CPA or CPC execution conditions of the candidate SCG, and then, after the CPA or CPC execution conditions of the candidate SCG are satisfied, start to evaluate the CHO execution conditions of the candidate MCG. In Embodiment 3, the CHO with the candidate SCG is executed only when the execution conditions of both the candidate MCG and the candidate SCG are satisfied (e.g., the UE 701 accesses the candidate MN 705 based on the CHO configuration of the candidate MCG and accesses the candidate SN 704 based on the configuration of the candidate SCG). In the case where only the CHO execution conditions of the candidate MCG are satisfied but the set of CPA or CPC execution conditions of the candidate SCG are not met, the CHO with the candidate SCG is not applied.

[0212] Figure 6 Another exemplary flowchart of a CHO with a candidate SCG mechanism according to some embodiments of the present application. Details described in all other embodiments of the present application apply to Figure 6 the embodiments shown in

[0213] In Figure 6 the exemplary flowchart 800 shown in, in operation 811, a UE 801 in the RRC connected state accesses its serving BS, i.e., the source MN 802. For example, DC (Dual Connectivity) may be configured for the UE 801. In some embodiments, the UE 801 may report measurement results to the source MN 802.

[0214] In operation 812, based on the measurement results, the source MN 802 may determine to switch the UE 801 to a candidate MN 805 via a CHO procedure.

[0215] In operation 813, the source MN 802 may transmit a handover request to the candidate MN 805. For example, the source MN 802 may instruct the candidate MN 805 to prepare a candidate SCG.

[0216] In operation 814, after the candidate MN 805 receives the handover request from the source MN 802, the candidate MN 805 may transmit a request (such as an SgNB addition request message or an SN modification request message) to the candidate SN 804 via the Xn interface.

[0217] In operation 815, the candidate SN 804 may transmit an acknowledgment message (such as an SgNB addition request acknowledgment message or an SgNB modification request acknowledgment message) to the candidate MN 805. The configuration of the candidate SCG of the candidate SN 804 may be included in the acknowledgment message.

[0218] In operation 816, after receiving the acknowledgment message from the candidate SN 804, the candidate MN 805 transmits a handover request acknowledgment message to the source MN 802 that includes the RRC configuration associated with the candidate MCG (such as Figure 2 the RRC configuration #1 described in the embodiments of Figure 2 and / or the RRC configuration of the candidate SCG (such as

[0219] In some embodiments, the RRC configuration associated with a candidate MCG may include the CHO configuration of the candidate MCG and the CHO execution conditions of the candidate MCG, and may be referred to as the "CHO configuration associated with the candidate MCG" or the like. In some embodiments, the RRC configuration associated with a candidate SCG may include: (1) the CPA configuration of the candidate SCG and the CPA execution conditions; or (2) the CPC configuration of the candidate SCG and a set of CPC execution conditions.

[0220] In operation 817, after receiving a handover request confirmation message from candidate MN 805, source MN 802 transmits an RRC reconfiguration message to UE 801 that includes the CHO configuration associated with the candidate MCG and / or the configuration of the candidate SCG.

[0221] In operation 818, after receiving the RRC reconfiguration message from source MN 802, UE 801 transmits an RRC reconfiguration complete message to source MN 802.

[0222] In operation 819, UE 801 begins "concurrent evaluation" or "sequential evaluation" of the CHO execution conditions of the candidate MCG and / or the CPA or CPC execution conditions of the candidate SCG.

[0223] In some embodiments of "concurrent evaluation", UE 801 begins evaluating the CHO execution conditions of the candidate MCG after receiving the RRC configuration of the candidate MCG in the RRC reconfiguration message, and begins evaluating the CPA or CPC execution conditions after receiving the RRC configuration of the candidate SCG in the RRC reconfiguration message.

[0224] In some embodiments of "sequential evaluation", UE 801 begins evaluating the CHO execution conditions of the candidate MCG when it receives the RRC configuration of the candidate MCG in the RRC reconfiguration message. The UE begins evaluating the CPA or CPC execution conditions after the CHO execution conditions of the candidate MCG are met.

[0225] In some embodiments, after the CHO execution conditions of the candidate MCG are met in operation 819, the execution conditions of the candidate SCG may be relaxed. For example, in operation 820, UE 801 considers the CPA or CPC execution conditions of the candidate SCG to be met in response to the following two options in different embodiments (in Option A and Option B below).

[0226] (1) Option A: Once the CPA or CPC entry condition of the candidate SCG within the candidate SCG is met while the timer T304 of the candidate MCG is running, UE 801 considers the CPA or CPC execution conditions of the candidate SCG to be met.

[0227] (2) Option B: Once the channel quality of the PSCell of a candidate SCG within a candidate SCG is greater than or equal to a configured or pre-configured threshold (e.g., when the S-criterion is met) while the timer T304 of the candidate MCG is running, the UE

[0228] 801 regards the execution condition of the CPA or CPC of the candidate SCG as being satisfied.

[0229] In some embodiments, in operations 821A and 821B, after the UE 801 determines that the execution condition of the CPA or CPC of the candidate SCG has been met, the UE 801 accesses the candidate MN 805 based on the CHO configuration of the candidate MCG and accesses the candidate SN 804 based on the CPA or CPC configuration of the candidate SCG in the RRC reconfiguration message received in operation 817. The sequence of operations 821A and 821B is not fixed and may vary in different embodiments.

[0230] In some other embodiments, operation 821B is performed before operation 820. That is, in operation 821B, after the UE 801 meets the CHO execution condition of the candidate MCG in operation 819, the UE 801 accesses the candidate MN 805 based on the CHO configuration of the candidate MCG. Then, in operation 821A, after the UE 801 determines that the execution condition of the CPA or CPC of the candidate SCG has been met in operation 820, the UE 801 accesses the candidate SN 804 based on the CPA or CPC configuration of the candidate SCG.

[0231] In operation 822, the UE 801 transmits an RRC reconfiguration complete message to the candidate MN 805. In some embodiments, the RRC reconfiguration complete message includes an SN RRC reconfiguration complete message. In an embodiment, which candidate SCG among multiple candidate SCGs should be indicated in the SN RRC reconfiguration complete message of the candidate SN 804. For example, the SN RRC reconfiguration complete message includes the ID of the candidate SCG belonging to the candidate SN 804.

[0232] In some embodiments, the RRC reconfiguration complete message in operation 822 includes at least one of the following indications. In an embodiment, at least one of the following indications is included in the SN RRC reconfiguration complete message embodied in the RRC reconfiguration complete message.

[0233] (1) An indication (e.g., indication #1) indicating the selection of a candidate SCG (e.g., candidate SCG #1) associated with the candidate SN 804 for cell addition;

[0234] (2) An indication (e.g., indication #2) indicating the selection of a candidate SCG (e.g., candidate SCG #1) associated with the candidate SN 804 for cell handover;

[0235] (3) An indication indicating a subset of candidate SCGs that are not selected from all candidate SCGs for cell addition (e.g., indication #3); or

[0236] (4) An indication indicating a subset of candidate SCGs that are not selected from all candidate SCGs for cell handover (e.g., indication #4).

[0237] In some embodiments, in operation 823A, the candidate MN 805 transmits an SN RRC reconfiguration complete message and indication #1 or indication #2 to the candidate SN 804. In an embodiment, indication #1 or indication #2 is included in the SN RRC reconfiguration complete message. In another embodiment, indication #1 or indication #2 is included in another RRC message via the Xn interface to the candidate SN 804.

[0238] In operation 823B (optional), the candidate MN 805 transmits indication #3 and / or indication #4 to the candidate SN 806 in an RRC message via the Xn interface, for example, to indicate to the candidate SN 904 that is not selected for cell addition or cell handover. Then, the candidate SN 806 may release or cancel the resources reserved for the UE 801.

[0239] Figure 7 Another exemplary flowchart of a CHO with a candidate SCG mechanism according to some embodiments of the present application. Details described in all other embodiments of the present application apply to Figure 7 the embodiments shown in

[0240] In Figure 7 In the exemplary flowchart 900 shown in, in operation 911, the UE 901 in the RRC connected state accesses its serving BS, i.e., the source MN 902. For example, DC (Dual Connectivity) may be configured for the UE 901. In some embodiments, the UE 901 may report measurement results to the source MN 902.

[0241] In operation 912, based on the measurement results, the source MN 902 may determine to hand over the UE 901 to the candidate MN 905 via the CHO procedure.

[0242] In operation 913, the source MN 902 may transmit a handover request to the candidate MN 905. For example, the source MN 902 may instruct the candidate MN 905 to prepare a candidate SCG.

[0243] In operation 914, after the candidate MN 905 receives the handover request from the source MN 902, the candidate MN 905 may transmit a request (e.g., an SgNB addition request message or an SN modification request message) to the candidate SN 904 via the Xn interface.

[0244] In operation 915, the candidate SN 904 may transmit a confirmation message (e.g., an SgNB addition request confirmation message or an SgNB modification request confirmation message) to the candidate MN 905. The configuration of the candidate SCG of the candidate SN 904 may be included in the confirmation message.

[0245] In operation 916, after receiving the confirmation message from the candidate SN 904, the candidate MN 905 transmits a handover request confirmation message to the source MN 902 that includes the RRC configuration associated with the candidate MCG (e.g., Figure 2 RRC configuration #1 described in the embodiments of Figure 2 and / or the RRC configuration of the candidate SCG (e.g.,

[0246] RRC configuration #2 described in the embodiments of

[0247] In some embodiments, the RRC configuration associated with the candidate MCG may include the CHO configuration of the candidate MCG and the CHO execution conditions of the candidate MCG, and may be referred to as the "CHO configuration associated with the candidate MCG" or the like. In some embodiments, the RRC configuration associated with the candidate SCG may include: (1) the CPA configuration of the candidate SCG and the CPA execution conditions; or (2) the CPC configuration of the candidate SCG and a set of CPC execution conditions.

[0248] In operation 917, after receiving the handover request confirmation message from the candidate MN 905, the source MN 902 transmits an RRC reconfiguration message to the UE 901 that includes the CHO configuration associated with the candidate MCG and / or the configuration of the candidate SCG.

[0249] In operation 918, after receiving the RRC reconfiguration message from the source MN 902, the UE 901 transmits an RRC reconfiguration complete message to the source MN 902.

[0250] In some embodiments of "concurrent evaluation", the UE 901 starts evaluating the CHO execution conditions of the candidate MCG after receiving the RRC configuration of the candidate MCG in the RRC reconfiguration message, and starts evaluating the CPA or CPC execution conditions after receiving the RRC configuration of the candidate SCG in the RRC reconfiguration message.

[0251] In some embodiments of "sequential evaluation", the UE 901 starts evaluating the CHO execution conditions of a candidate MCG when it receives the RRC configuration of the candidate MCG in an RRC reconfiguration message. The UE starts evaluating the CPA or CPC execution conditions after meeting the CHO execution conditions of the candidate MCG.

[0252] In some embodiments, in operation 920, the CPA or CPC execution conditions of all candidate SCGs are not met. In operation 921, the UE 901 accesses the candidate MN 905 based on the CHO configuration of the candidate MCG in the RRC reconfiguration message received in operation 917.

[0253] The sequence of operations 920 and 921 is not fixed and may vary in different embodiments. In some other embodiments, operation 921 is performed before operation 920. That is, in operation 921, after meeting the CHO execution conditions of the candidate MCG in operation 919, the UE 901 accesses the candidate MN 905 based on the CHO configuration of the candidate MCG. Then, the UE 901 determines that the CPA or CPC execution conditions of the candidate SCG are not met in operation 920.

[0254] In some embodiments, in operation 922, the UE 901 transmits an RRC reconfiguration complete message to the candidate MN 905. For example, the RRC reconfiguration complete message includes at least one of the following indications. In some other embodiments, at least one of the following indications is included in the RRC message to the candidate MN 905 via the Xn interface that may be transmitted in operation 922.

[0255] (1) An indication indicating not to select a candidate SCG within the candidate SCG for cell addition (e.g., indication #5); or

[0256] (2) An indication indicating not to select a candidate SCG within the candidate SCG for cell handover (e.g., indication #6).

[0257] In some embodiments, in operation 923A, the candidate MN 905 transmits indication #5 and / or indication #6 to the candidate SN 904 in an RRC message via the Xn interface, for example, to indicate to the candidate SN 904 not to add the candidate SCG for cell addition or cell handover. Then, the candidate SN 904 may release or cancel the resources reserved for the UE 901.

[0258] In operation 923B (optional), the candidate MN 905 transmits indication #5 and / or indication #6 to the candidate SN906 in an RRC message via the Xn interface, for example, to indicate to the candidate SN not to add the candidate SCG for cell addition or cell handover. Then, the candidate SN 906 may release or cancel the resources reserved for the UE 901.

[0259] Figure 8 Another exemplary flowchart of a CHO with a candidate SCG mechanism according to some embodiments of the present application. Details described in all other embodiments of the present application apply to Figure 8 the embodiments shown in

[0260] In Figure 8 the exemplary flowchart 1000 shown in, in operation 1011, a UE 1001 in the RRC connected state accesses its serving BS, i.e., the source MN 1002. For example, DC (Dual Connectivity) may be configured for the UE 1001. In some embodiments, the UE1001 may report measurement results to the source MN 1002.

[0261] In operation 1012, based on the measurement results, the source MN 1002 may determine to switch the UE 1001 to the candidate MN 1005 via the CHO procedure.

[0262] In operation 1013, the source MN 1002 may transmit a handover request to the candidate MN 1005. For example, the source MN 1002 may instruct the candidate MN 1005 to prepare the candidate SCG.

[0263] In operation 1014, after the candidate MN 1005 receives the handover request from the source MN 1002, the candidate MN 1005 may transmit a request (such as an SgNB addition request message or an SN modification request message) to the candidate SN 1004 via the Xn interface.

[0264] In operation 1015, the candidate SN 1004 may transmit an acknowledgment message (such as an SgNB addition request acknowledgment message or an SgNB modification request acknowledgment message) to the candidate MN 1005. The configuration of the candidate SCG of the candidate SN 1004 may be included in the acknowledgment message.

[0265] In operation 1016, after receiving the acknowledgment message from the candidate SN 1004, the candidate MN 1005 transmits a handover request acknowledgment message to the source MN 1002 that includes the RRC configuration associated with the candidate MCG (such as Figure 2 the RRC configuration #1 described in the embodiments of Figure 2 and / or the RRC configuration of the candidate SCG (such as

[0266] In some embodiments, the RRC configuration associated with a candidate MCG may include the CHO configuration of the candidate MCG and the CHO execution conditions of the candidate MCG, and may be referred to as the "CHO configuration associated with the candidate MCG" or the like. In an embodiment, the RRC configuration associated with a candidate MCG includes an attemptCondReconfig IE, which is configured to indicate whether execution of CHO recovery is allowed. If the attemptCondReconfig IE is configured, then this IE may also imply that CHO with a candidate SCG is allowed. For example, the IE indicates that execution of a CPA procedure or a CPC procedure to one or more candidate SCGs is allowed during a CHO recovery procedure.

[0267] In some embodiments, the RRC configuration associated with a candidate SCG may include: (1) the CPA configuration of the candidate SCG and the CPA execution conditions; or (2) the CPC configuration of the candidate SCG and a set of CPC execution conditions.

[0268] In operation 1017, after receiving a handover request confirmation message from candidate MN 1005, source MN 1002 transmits an RRC reconfiguration message to UE 1001 that includes the CHO configuration associated with the candidate MCG and / or the configuration of the candidate SCG.

[0269] In operation 1018, after receiving the RRC reconfiguration message from source MN 1002, UE 1001 transmits an RRC reconfiguration complete message to source MN 1002.

[0270] In operation 1019, UE 1001 begins "concurrent evaluation" or "sequential evaluation" of the CHO execution conditions of the candidate MCG and / or the CPA or CPC execution conditions of the candidate SCG.

[0271] In some embodiments of "concurrent evaluation", UE 1001 begins evaluating the CHO execution conditions of the candidate MCG after receiving the RRC configuration of the candidate MCG in the RRC reconfiguration message, and begins evaluating the CPA or CPC execution conditions after receiving the RRC configuration of the candidate SCG in the RRC reconfiguration message.

[0272] In some embodiments of "sequential evaluation", UE 1001 begins evaluating the CHO execution conditions of the candidate MCG when receiving the RRC configuration of the candidate MCG in the RRC reconfiguration message. The UE begins evaluating the CPA or CPC execution conditions after satisfying the CHO execution conditions of the candidate MCG.

[0273] In operation 1020, a failure occurs, such as an RLF, handover failure, or CHO failure on the source MCG associated with the source MN 1002. In some embodiments, if the attemptCondReconfig IE is configured in the RRC configuration associated with the candidate MCG in operation 1017, then after the failure occurs, the UE 1001 starts an RRC reestablishment procedure in operation 1020.

[0274] In operation 1021, the UE 1001 selects a candidate cell among the CHO candidate PCells. Then, the UE 1001 may perform a CHO procedure to the selected candidate cell. That is, the UE 1001 performs a CHO recovery procedure in operation 1021.

[0275] Next, in different embodiments, there may be the following two options, namely, option M, option N, and option L as follows.

[0276] Option M: If the channel quality of the PSCell of the candidate SCG (e.g., candidate SN 1004) within the candidate SCG is greater than a threshold (e.g., the candidate PSCell meets the S-criterion), then the UE 1001 may perform a CPA or CPC procedure associated with the candidate SCG together with the CHO recovery procedure in operation 1021. Then, the UE 1001 transmits an RRC reconfiguration complete message to the candidate MN 1005.

[0277] Option N: When performing the CHO recovery procedure in operation 1021, do not perform a CPA or CPC procedure associated with the candidate SCG. Specifically, after the UE 1001 performs the CHO recovery procedure in operation 1021, operations 1022, 1023A, and 1023B may be performed.

[0278] (1) In operation 1022, the UE 1001 transmits at least one of the following indications to the candidate MN 1005, for example, in an RRC message or an RRC reconfiguration complete message via the Xn interface. In some embodiments, the candidate MN

[0279] 1005 may perform bearer remapping to the candidate SCG based on the RRC message or the RRC reconfiguration complete message in operation 1022.

[0280] (a) An indication (e.g., indication #7) that prohibits performing a CPA procedure or a CPC procedure to the candidate SCG during the CHO recovery procedure.

[0281] (b) An indication (e.g., indication #8) of the CHO recovery procedure.

[0282] (c) An indication (e.g., indication

[0283] #9).

[0284] (2) In operation 1023A (optional), the candidate MN 1005 transmits indication #7, indication #8, and / or indication #9 to the candidate SN 1004 in an RRC message via, for example, the Xn interface, to indicate to the candidate SN 1004 not to add the candidate SCG for cell addition or cell handover. Then, the candidate SN 1004 may release or cancel the resources reserved for the UE 1001.

[0285] (3) In operation 1023B (optional), the candidate MN 1005 transmits indication #7, indication #8, and / or indication #9 to the candidate SN 1006 in an RRC message via, for example, the Xn interface, to indicate to the candidate SN not to add the candidate SCG for cell addition or cell handover. Then, the candidate SN 1006 may release or cancel the resources reserved for the UE 1001.

[0286] The details described in all other embodiments of the present disclosure apply to Figures 5 to 8 any of the embodiments shown in Figures 5 to 8 Those skilled in the art should understand that the sequence of operations in any of the exemplary procedures 700 to 1000 in Figures 5 to 8 any of the exemplary procedures 700 to 1000 in

[0287] Figure 9 A block diagram of an exemplary device 1100 according to some embodiments of the present disclosure is illustrated. As Figure 9 shown, the device 1100 may include at least one processor 1106 and at least one transceiver 1102 coupled to the processor 1106.

[0288] Although the elements are described in the singular in this figure, such as at least one transceiver 1102 and processor 1106, the plural form is contemplated unless explicitly stated to be limited to the singular form. In some embodiments of the present application, the transceiver 1102 may be divided into two devices, such as a receiving circuit system and a transmitting circuit system. In some embodiments of the present application, the device 1100 may further include an input device, a memory, and / or other components.

[0289] In some embodiments of the present application, the device 1100 may be a UE, a target MN, a candidate MN, a source MN, a target SN, a candidate SN, or a source SN. The transceiver 1102 and the processor 1106 may interact with each other to perform the above, for example, in Figures 1 to 8The operations described for the UE, target MN, candidate MN, source MN, target SN, candidate SN, or source SN in any of them.

[0290] In some embodiments of the present application, device 1100 may further include at least one non-transitory computer-readable medium. For example, in some embodiments of the present disclosure, computer-executable instructions may be stored on the non-transitory computer-readable medium that cause processor 1106 to implement the methods described above for the UE. For example, when executed, the computer-executable instructions cause processor 1106 to interact with transceiver 1102 to perform the operations Figures 1 to 8 described for the UE, target MN, candidate MN, source MN, target SN, candidate SN, or source SN in.

[0291] Those of ordinary skill in the art will understand that the operations or steps of the methods described in connection with the aspects disclosed herein may be embodied directly in hardware, in software modules executed by a processor, or in a combination of both. The software modules may reside in RAM memory, flash memory, ROM memory, EPROM memory, EEPROM memory, registers, a hard disk, a removable disk, a CD-ROM, or any other form of storage medium known in the art. Additionally, in some aspects, the operations or steps of the methods may reside on a non-transitory computer-readable medium as one or any combination or set of code and / or instructions, which may be incorporated into a computer program product.

[0292] Although the present disclosure has been described with reference to specific embodiments of the present disclosure, it is apparent that many alternatives, modifications, and variations will be apparent to those skilled in the art. For example, the various components of the embodiments may be interchanged, added, or substituted in other embodiments. Moreover, all elements of each figure are not necessary for the operation of the disclosed embodiments. For example, it will enable those of ordinary skill in the art of the disclosed embodiments to make and use the teachings of the present disclosure by simply employing the elements of the independent claims. Therefore, the embodiments of the present disclosure set forth herein are intended to be illustrative and not restrictive. Various changes may be made without departing from the spirit and scope of the present disclosure.

[0293] In this document, the term "comprising" or any other variation thereof is intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a series of elements does not include only those elements but may include other elements not expressly listed or inherent to the process, method, article, or apparatus. An element that begins with "a" or the like does not, without further limitation, preclude the presence of additional identical elements in the process, method, article, or apparatus that includes that element. Also, the term "another" is defined as at least a second or more. As used herein, the terms "having" and the like are defined as "comprising". For example, an expression such as "A and / or B" or "at least one of A and B" can include any and all combinations of the words listed together with the expression. For example, the expression "A and / or B" or "at least one of A and B" can include A, B, or both A and B. The terms "first", "second", or the like are used only for clarity in describing embodiments of the present application and are not intended to limit the substance of the present application.

Claims

1. A user equipment (UE) comprising: a transceiver; and a processor coupled to the transceiver and configured to: receive a first radio resource control (RRC) configuration and a second RRC configuration via the transceiver, wherein the first RRC configuration includes conditional handover (CHO) configuration information and CHO execution conditions of a candidate primary cell group (MCG), and the second RRC configuration includes configuration information of one or more candidate secondary cell groups (SCGs) and a set of execution conditions of the one or more candidate SCGs; and evaluate the CHO execution conditions of the candidate MCG after receiving the first RRC configuration.

2. The UE according to claim 1, wherein the first RRC configuration and the second RRC configuration are received via separate messages or via the same message.

3. The UE according to claim 1, wherein the configuration information of the one or more candidate SCGs and the set of execution conditions of the one or more candidate SCGs include: conditional primary secondary cell group (PSCell) addition (CPA) configuration information and a set of CPA execution conditions of the one or more candidate SCGs; or conditional PSCell change (CPC) configuration information and a set of CPC execution conditions of the one or more candidate SCGs.

4. The UE according to claim 3, wherein the processor of the UE is further configured to: evaluate the set of CPA execution conditions after receiving the second RRC configuration of CPA; or evaluate the set of CPC execution conditions after receiving the second RRC configuration of CPC.

5. The UE according to claim 3, wherein the processor of the UE is further configured to: start evaluating the set of CPA execution conditions in response to satisfaction of the CHO execution conditions of the candidate MCG; or start evaluating the set of CPC execution conditions in response to the satisfaction of the CHO execution conditions of the candidate MCG.

6. The UE according to claim 5, wherein the processor of the UE is further configured to: stop evaluating the set of CPA execution conditions of the other one or more candidate SCGs within the one or more candidate SCGs in response to satisfaction of the set of CPA execution conditions of one candidate SCG within the one or more candidate SCGs; or stop evaluating the set of CPC execution conditions of the other one or more candidate SCGs within the one or more candidate SCGs in response to satisfaction of the set of CPC execution conditions of one candidate SCG within the one or more candidate SCGs.

7. The UE according to claim 1, wherein the processor of the UE is configured to release the second RRC configuration in response to: the set of execution conditions of each candidate SCG within the one or more candidate SCGs not being satisfied when the UE completes a random access (RA) procedure to the candidate MCG; the set of execution conditions of each candidate SCG not being satisfied when a handover timer of the candidate MCG stops; The set of execution conditions for each candidate SCG is not satisfied after a first period since the UE completes the RA procedure to the candidate MCG; The set of execution conditions for each candidate SCG is not satisfied when the CHO execution conditions of the candidate MCG are satisfied; or The set of execution conditions for each candidate SCG is not satisfied after a second period since the CHO execution conditions of the candidate MCG are satisfied.

8. The UE according to claim 1, wherein in response to the CHO execution conditions of the candidate MCG being satisfied, the processor of the UE is further configured to stop evaluating the set of execution conditions for the one or more candidate SCGs in response to: The set of execution conditions for each candidate SCG within the one or more candidate SCGs is not satisfied when the UE completes the random access RA procedure to the candidate MCG; The set of execution conditions for each candidate SCG is not satisfied when the handover timer of the candidate MCG stops; The set of execution conditions for each candidate SCG is not satisfied after a first period since the UE completes the RA procedure to the candidate MCG; The set of execution conditions for each candidate SCG is not satisfied when the CHO execution conditions of the candidate MCG are satisfied; or The set of execution conditions for each candidate SCG is not satisfied after a second period since the satisfaction of the CHO execution conditions of the candidate MCG.

9. The UE according to claim 8, wherein the processor of the UE is further configured to release the set of execution conditions for the candidate SCG after stopping evaluating the set of execution conditions for the candidate SCG.

10. The UE according to claim 1 or claim 3, wherein in response to the CHO execution conditions of the candidate MCG being satisfied, the processor of the UE is configured to: Perform a random access RA procedure to the candidate MCG based on the first RRC configuration; and Transmit an RRC reconfiguration complete message to a candidate MN associated with the candidate MCG.

11. A candidate master node MN, comprising: A transceiver; And A processor, coupled to the transceiver and configured to: Receive a radio resource control RRC reconfiguration complete message from a user equipment UE via the transceiver; and Transmit an indication associated with a candidate secondary cell group SCG to a candidate SN via the transceiver.

12. The candidate MN according to claim 11, wherein the indication indicates at least one of the following: Select the candidate SCG for cell addition; Select the candidate SCG for cell handover; Do not select the candidate SCG for cell addition; Do not select the candidate SCG for cell handover; Do not select a candidate SCG for cell addition; Do not select a candidate SCG for cell handover; During the conditional handover (CHO) recovery procedure to a candidate master cell group (MCG), execution of the conditional primary secondary cell group (PSCell) addition (CPA) procedure to a candidate secondary cell group (SCG) is not allowed; During the CHO recovery procedure, execution of the conditional PSCell change (CPC) procedure to a candidate SCG is not allowed; A user equipment (UE) accesses the candidate MCG via a CHO procedure; The UE accesses the candidate MCG via the CHO recovery procedure; Or The UE releases the radio resource control (RRC) configuration of the candidate SCG due to the CHO recovery procedure.

13. A candidate secondary node (SN), comprising: A transceiver; And A processor coupled to the transceiver and configured to: Transmit, via the transceiver, a radio resource control (RRC) configuration including configuration information of a candidate secondary cell group (SCG) and a set of execution conditions for the candidate SCG to a candidate master node (MN); And Receive, via the transceiver, an indication associated with the candidate SCG from the candidate MN.

14. The candidate SN according to claim 13, wherein the configuration information of the candidate SCG and the set of execution conditions for the candidate SCG include: The conditional PSCell addition (CPA) configuration information of the candidate SCG and a set of CPA execution conditions; or The conditional PSCell change (CPC) configuration information of the candidate SCG and a set of CPC execution conditions.

15. The candidate SN according to claim 13, wherein the indication indicates at least one of the following: Selecting the candidate SCG for cell addition; Selecting the candidate SCG for cell handover; Not selecting the candidate SCG for cell addition; Not selecting the candidate SCG for cell handover; Not choosing the candidate SCG for cell addition; Not choosing the candidate SCG for cell handover; During the conditional handover (CHO) recovery procedure to a candidate master cell group (MCG), execution of the conditional primary secondary cell group (PSCell) addition (CPA) procedure to a candidate secondary cell group (SCG) is not allowed; During the CHO recovery procedure, execution of the conditional PSCell change (CPC) procedure to a candidate SCG is not allowed; A user equipment (UE) accesses the candidate MCG via a CHO procedure; The UE accesses the candidate MCG via the CHO recovery procedure; Or The UE releases the radio resource control (RRC) configuration of the candidate SCG due to the CHO recovery procedure.

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