Methods and devices for CHO organization using candidate SCGs

Abstract

[0003] According to an embodiment of the present application, a user equipment (UE) includes a transceiver and a processor coupled to the transceiver, wherein 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 and a CHO execution condition for a candidate master cell group (MCG), and the another RRC configuration includes configuration information for one or more candidate secondary cell groups (SCGs) and a set of execution conditions for the one or more candidate SCGs; and, upon receiving the RRC configuration, evaluate the CHO execution condition for the candidate MCG.

Description

[Technical Field]

[0001] FIELD Embodiments of the present application generally relate to wireless communication technologies, and more particularly, to a method and apparatus for a conditional handover (CHO) mechanism using candidate secondary cell groups (SCGs). [Background technology]

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

[0003] Next generation radio access networks (NG-RANs) support multi-radio dual connectivity (MR-DC) scenarios. In MR-DC scenarios, a UE with multiple transceivers may be configured to utilize resources provided by two different nodes connected over a non-ideal backhaul. One node may provide new radio (NR) access, and the other node may provide either evolved universal mobile telecommunication system (UMTS) terrestrial radio access (UMTS UTRA) (evolved-UTRA: E-UTRA) or NR access. One node may act as a master node (MN), and the other node may act as a secondary node (SN). The MN and SN are connected via a network interface (e.g., the Xn interface specified in the 3rd Generation Partnership Project (3GPP) standard documents), and at least the MN is connected to the core network. Currently, details regarding the CHO mechanism with candidate SCGs in the MR-DC scenario have not yet been considered. Summary of the Invention [Means for solving the problem]

[0004] Some embodiments of the present application provide a user equipment (UE), the UE including: a transceiver; and a processor coupled to the transceiver, the processor configured to: receive, via the transceiver, a first radio resource control (RRC) configuration and a second RRC configuration, the first RRC configuration including conditional handover (CHO) configuration information and a CHO execution condition for a candidate master cell group (MCG), and the second RRC configuration including configuration information for one or more candidate secondary cell groups (SCGs) and a set of execution conditions for the one or more candidate SCGs; and, upon receiving the first RRC configuration, evaluate the CHO execution condition for the candidate MCG.

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

[0007] In some embodiments, the processor of the UE is further configured to evaluate a set of CPA execution conditions upon reception of a second RRC configuration for CPA, or to evaluate a set of CPC execution conditions upon reception of a second RRC configuration for CPC.

[0008] In some embodiments, the processor of the UE is further configured to initiate evaluation of a set of CPA execution conditions in response to satisfaction of the CHO execution conditions for the candidate MCG, or to initiate evaluation of a set of CPC execution conditions in response to satisfaction of the CHO execution conditions for the candidate MCG.

[0009] In some embodiments, the processor of the UE is further configured to: in response to satisfaction of a set of CPA execution conditions for one candidate SCG in the one or more candidate SCGs, stop evaluating a set of CPA execution conditions for one or more other candidate SCGs in the one or more candidate SCGs; or in response to satisfaction of a set of CPC execution conditions for one candidate SCG in the one or more candidate SCGs, stop evaluating a set of CPC execution conditions for one or more other candidate SCGs in 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: a set of execution conditions for each candidate SCG in one or more candidate SCGs not being satisfied when the UE completes a random access (RA) procedure to the candidate MCG; a set of execution conditions for each candidate SCG not being satisfied when a handover timer for the candidate MCG is stopped; a set of execution conditions for each candidate SCG not being satisfied after a first time period after the UE completes the RA procedure to the candidate MCG; a set of execution conditions for each candidate SCG not being satisfied when a CHO execution condition for the candidate MCG is satisfied; or a set of execution conditions for each candidate SCG not being satisfied after a second time period from the satisfaction of the CHO execution condition for the candidate MCG.

[0011] In some embodiments, in response to satisfaction of the CHO execution conditions for the candidate MCG, 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 in 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 for each candidate SCG not being satisfied when a handover timer for the candidate MCG is stopped; the set of execution conditions for each candidate SCG not being satisfied after a first time period after the UE completes the RA procedure to the candidate MCG; the set of execution conditions for each candidate SCG not being satisfied when the CHO execution conditions for the candidate MCG are satisfied; or the set of execution conditions for each candidate SCG not being satisfied after a second time period from satisfaction of the CHO execution conditions for the candidate MCG.

[0012] In some embodiments, 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.

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

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

[0015] In some embodiments, the processor of the UE is configured to: in response to a set of CPA execution conditions for each candidate SCG in the one or more candidate SCGs not being satisfied and the UE completing an RA procedure to the candidate MCG, send, via the transceiver, a third indication to a candidate MN associated with the candidate MCG indicating that none of the candidate SCGs in the one or more SCGs will be selected for cell addition; or in response to a set of CPC execution conditions for each candidate SCG not being satisfied and the UE completing an RA procedure to the candidate MCG, send, via the transceiver, a fourth indication to the candidate MN indicating that none of the candidate SCGs in the one or more SCGs will be selected for cell switching.

[0016] In some embodiments, in response to the UE failing to perform a CHO procedure to a candidate MCG, a processor of the UE is configured to perform 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 no procedures to any candidate SCG are allowed to be performed 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 SN RRC Reconfiguration Complete message that is embedded in an RRC Reconfiguration Complete message to the candidate MN.

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

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

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

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

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

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

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

[0026] In some embodiments, the indication indicates at least one of the following: a candidate SCG is selected for cell addition; a candidate SCG is selected for cell switching; a candidate SCG is not selected for cell addition; a candidate SCG is not selected for cell switching; none of the candidate SCGs is selected for cell addition; none of the candidate SCGs is selected for cell switching; no conditional primary secondary cell group (PSCell) addition (CPA) procedure to any candidate SCG is allowed to be performed during a conditional handover (CHO) recovery procedure to a candidate master cell group (MCG); no conditional PSCell change (CPC) procedure to any candidate SCG is allowed to be performed during a CHO recovery procedure; a user equipment (UE) accesses the candidate MCG via a CHO procedure; a UE accesses the candidate MCG via a CHO recovery procedure; or an RRC configuration for the candidate SCG is released by the UE for the CHO recovery procedure.

[0027] In some embodiments, an indication associated with the candidate SCG is carried in the 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 the identity (ID) of the candidate SCG belonging to the candidate SN.

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

[0030] In some embodiments, the processor of the candidate MN is further configured to send, via the transceiver, an information element (IE) to the UE, the IE indicating that a CHO recovery procedure to the candidate MCG is enabled to be performed, and that a CPA procedure or a CPC procedure to one or more candidate SCGs is enabled to be performed during the CHO recovery procedure.

[0031] In some embodiments, the IE is a Conditional Reconfiguration Attempt IE included in the RRC configuration.

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

[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, where the processor is configured to: transmit, via the transceiver, to a candidate master node (MN), a radio resource control (RRC) configuration including configuration information for one or more candidate secondary cell groups (SCGs) and a set of execution conditions for the one or more candidate SCGs; and receive, via the transceiver, from the candidate MN, an indication associated with the one or more candidate SCGs.

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

[0035] In some embodiments, the indication indicates at least one of: a candidate SCG is selected for cell addition; a candidate SCG is selected for cell switching; a candidate SCG is not selected for cell addition; a candidate SCG is not selected for cell switching; none of the candidate SCGs is selected for cell addition; none of the candidate SCGs is selected for cell switching; no conditional primary secondary cell group (PSCell) addition (CPA) procedure to any candidate SCG is enabled to be performed during a conditional handover (CHO) recovery procedure to a candidate master cell group (MCG); no conditional PSCell change (CPC) procedure to any candidate SCG is enabled to be performed during a CHO recovery procedure; a user equipment (UE) accesses the candidate MCG via a CHO procedure; a UE accesses the candidate MCG via a CHO recovery procedure; or an RRC configuration for the candidate SCG is released by the UE for the CHO recovery procedure.

[0036] In some embodiments, the processor of the candidate SN is further configured to release resources for the candidate SCG in response to an indication indicating that the candidate SCG is not selected for cell addition, that the candidate SCG is not selected for cell switching, that none of the candidate SCGs is selected for cell addition, or that none of the candidate SCGs is selected for cell switching.

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

[0038] Some embodiments of the present application provide a method performed by a candidate MN, the method including receiving a radio resource control (RRC) reconfiguration complete message from a user equipment (UE) and sending 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 including: transmitting, to a candidate master node (MN), a radio resource control (RRC) configuration including configuration information for one or more candidate secondary cell groups (SCGs) and a set of execution conditions for the one or more candidate SCGs; and receiving, from the candidate MN, an indication associated with the one or more candidate SCGs.

[0040] Some embodiments of the present application provide an apparatus for wireless communication, the apparatus comprising: a non-transitory computer-readable medium storing computer-executable instructions, a receiving circuit, a transmitting circuit, and a processor coupled to the non-transitory computer-readable medium, the receiving circuit, and the transmitting circuit, the computer-executable instructions causing the processor to perform the above-mentioned method performed by a UE or a network node (source MN, target MN, candidate MN, source SN, target SN, or candidate SN).

[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.

[0042] To describe the manner in which the advantages and features of the present application may be obtained, the present application will be described by reference to specific embodiments thereof, which are illustrated in the accompanying drawings. These drawings depict only exemplary embodiments of the present application and are therefore not to be considered limiting of the scope of the present application. [Brief explanation of the drawings]

[0043] [Figure 1] 1 is a schematic diagram of a wireless communication system according to some embodiments of the present application. [Figure 2] 1 is an exemplary flow chart of a CHO mechanism using candidate SCGs, according to some embodiments of the present application. [Figure 3] 10 is an exemplary flowchart for transmitting an indication associated with a candidate SCG according to some embodiments of the present application. [Figure 4] 10 is an exemplary flowchart for receiving an indication associated with a candidate SCG, according to some embodiments of the present application. [Figure 5] 1 is an exemplary flow chart of a CHO mechanism using candidate SCGs, according to some embodiments of the present application. [Figure 6] 1 is an exemplary flow chart of a CHO mechanism using candidate SCGs, according to some embodiments of the present application. [Figure 7] 1 is an exemplary flow chart of a CHO mechanism using candidate SCGs, according to some embodiments of the present application. [Figure 8] 1 is an exemplary flow chart of a CHO mechanism using candidate SCGs, according to some embodiments of the present application. [Figure 9] FIG. 1 is a block diagram of an exemplary apparatus according to some embodiments of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0044] The detailed description of the accompanying drawings is intended as an illustration of a preferred embodiment of the present application and does not represent the only form in which the present application may be practiced. It is to be understood that the same or equivalent function may be accomplished by different embodiments that are encompassed within the spirit and scope of the present application.

[0045] Reference will now be made in detail to several embodiments of the present application, examples of which are illustrated in the accompanying drawings. For ease of understanding, the embodiments are provided under specific network architectures and new service scenarios, such as 3GPP 5G, 3GPP LTE Release 8, etc. With the development of network architectures and new service scenarios, it is contemplated that all embodiments in the present application are also applicable to similar technical problems, and furthermore, the terms described in the present application may be changed, which should not affect the principles of the present application.

[0046] FIG. 1 shows a schematic diagram of a wireless communication system according to some embodiments of the present application.

[0047] 1, the wireless communication system 100 may be a dual connectivity system 100 including at least one UE 101, at least one MN 102, and at least one SN 103. In particular, the dual connectivity system 100 in FIG. 1 includes, for purposes of illustration, one illustrated UE 101, one illustrated MN 102, and one illustrated SN 103. Although a particular number of UEs 101, MNs 102, and SNs 103 are shown in FIG. 1, it is contemplated that any number of UEs 101, MNs 102, and SNs 103 may be included within the wireless communication system 100.

[0048] 1 , the UE 101 may be connected to the MN 102 and the SN 103 via a network interface, for example, a Uu interface specified in a 3GPP standard document. The MN 102 and the SN 103 may be connected to each other via a network interface, for example, an Xn interface specified in a 3GPP standard document in an NR-NR DC, or an NGEN-DC, or an NE-DC, or an X2 interface specified in a 3GPP standard document in an EN-DC. The MN 102 may be connected to a core network (not shown in FIG. 1 ) via the network interface. The UE 101 may be configured to utilize resources provided by the MN 102 and the SN 103 to perform data transmission.

[0049] The MN 102 may refer to a radio access node that provides a control plane connection to a core network. In one embodiment of the present application, in an E-UTRA-NR Dual Connectivity (EN-DC) scenario, the MN 102 may be an eNB. In another embodiment of the present application, in a next generation E-UTRA-NR Dual Connectivity (NGEN-DC) scenario, the MN 102 may be an ng-eNB. In yet another embodiment of the present application, in an NR-E-UTRA Dual Connectivity (NE-DC) scenario or an NR-NR Dual Connectivity (NR-DC) scenario, the MN 102 may be a gNB.

[0050] The MN 102 may be associated with a Master Cell Group (MCG). The MCG may refer to a group of serving cells associated with the MN 102 and may include a primary cell (PCell) and possibly one or more secondary cells (SCells) of the MCG. The PCell may provide a control plane connection to the UE 101.

[0051] The SN 103 may refer to a radio access node without a control plane connection to a core network but providing additional resources to the UE 101. In one embodiment of the present application, in an EN-DC scenario, the SN 103 may be an en-gNB. In another embodiment of the present application, in an NE-DC scenario, the SN 103 may 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 may be a gNB.

[0052] The SN 103 may be associated with a secondary cell group (SCG). An SCG may refer to a group of serving cells associated with the SN 103 and may include a primary secondary cell (PSCell) and possibly one or more secondary cells (SCells). The PCell of the MCG and the PSCell of the SCG may also be referred to as special cells (SpCells).

[0053] 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 television (e.g., a television connected to the Internet), a set-top box, a game console, a security system (including security cameras), a vehicle-mounted computer, a network device (e.g., a router, a switch, and a modem), etc. In some other embodiments of the present application, the UE 101 may include a portable wireless communication device, a smartphone, a cellular telephone, a flip phone, a device with a subscriber identity module, a personal computer, selective call reception circuitry, or any other device capable of sending and receiving communication signals over a wireless network.

[0054] In some other embodiments of the present application, the UE 101 may include a wearable device, such as a smart watch, a fitness band, an optical head-mounted display, etc. Additionally, the UE 101 may be referred to as a subscriber unit, a mobile, a mobile station, a user, a terminal, a mobile terminal, a wireless terminal, a fixed terminal, a subscriber station, a user terminal, or a device, or may be described using other terms used in the art.

[0055] Generally, CHO is performed by a UE when one or more handover execution conditions are satisfied. The UE starts evaluating the execution conditions when it receives a CHO configuration, and stops evaluating the execution conditions during CHO execution when the execution conditions are satisfied. The CHO configuration includes configurations for CHO candidate cells generated by the candidate BS and execution conditions generated by the source BS.

[0056] As in the case of intra-NR RAN handover or intra-NR radio access network (RAN) CHO, the preparation and execution phases of the CHO procedure are performed without the involvement of the 5G Core Network (5GC), i.e., preparation messages are exchanged directly between the BSs. The release of resources at the source BS during the conditional handover completion phase is triggered by the candidate BS, where neither the access and mobility management function (AMF) nor the user plane function (UPF) remains unchanged.

[0057] Generally, an MN initiated inter-MN handover with or without SN change is used to transfer UE context data from a source MN to a candidate MN, while the UE context at the SN is either retained or moved to another SN. During an inter-MN handover, the candidate MN decides whether to retain or change the SN (or release the SN). Only intra radio access technology (intra-RAT) inter-MN handover with or without SN change is supported.

[0058] Currently, there is no mechanism for the case of CHO using one or more candidate SCGs. Embodiments of the present disclosure aim to solve such a problem. In particular, some embodiments of the present disclosure design a mechanism to support that both CHO and candidate SCGs can be executed simultaneously. In some embodiments of the present disclosure, after a UE executes CHO with or without a candidate SCG in one or more candidate SCGs, additional information (e.g., included in an 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 condition is satisfied. Some embodiments of the present disclosure introduce an extended mechanism for CHO recovery in the case of CHO using a candidate SCG.

[0059] In some embodiments of the present disclosure, during a cell switch from a source SN (e.g., a CHO procedure), a candidate MN may also be referred to as a target MN, a target candidate MN, etc. During a cell addition or cell switch (e.g., a CPA or CPC procedure), a candidate SN may also be referred to as a target SN, a target candidate SN, etc. During a cell addition or cell switch, a candidate cell may also be referred to as a target cell, a target candidate cell, etc. In other words, from the UE's perspective, the same MN may be referred to as a candidate MN or a target MN in different scenarios, the same SN may be referred to as a candidate SN or a target SN in different scenarios, and the same cell may be referred to as a candidate cell or a target cell in different scenarios, without departing from the spirit and scope of the present disclosure.

[0060] Further details regarding embodiments of the present application are provided in the following text in combination with the accompanying drawings.

[0061] 2 illustrates an exemplary flowchart of a CHO mechanism using a candidate SCG according to some embodiments of the present application. The exemplary procedure 200 in the embodiment of FIG. 2 may be performed by a UE, such as UE 101, UE 701, UE 801, UE 901, or UE 1001 shown in any of FIGS. 1 and 5-8. While described with respect to a UE, it should be understood that other devices may be configured to perform a method similar to that of FIG. 2.

[0062] In the example procedure 200 shown in FIG. 2, at operation 201, a UE may receive an RRC configuration (for simplicity, denoted as RRC configuration #1) and another RRC configuration (denoted as RRC configuration #2). RRC configuration #1 includes CHO configuration information and CHO execution conditions for candidate MCGs. The CHO execution conditions for the candidate MCGs may include one or more execution conditions for the candidate MCGs, e.g., an entry condition and / or an exit condition. RRC configuration #2 includes configuration information for one or more candidate SCGs and a set of execution conditions for one or more candidate SCGs.

[0063] RRC configuration #1 and RRC configuration #2 may be received via separate messages or via the same message. For example, a candidate MN (e.g., candidate MN 705) may generate a configuration for its corresponding candidate MCG and send the configuration for the corresponding candidate MCG (i.e., RRC configuration #1) to the source MN (e.g., source MN 702). A candidate SN (e.g., candidate SN 704) of the candidate MN may generate a configuration for its corresponding candidate SCG and send the configuration for the corresponding candidate SCG to the candidate MN. The candidate MN may forward the configurations for all candidate SCGs (i.e., RRC configuration #2) received from one or more candidate SNs to the source MN. Then, in some embodiments, the source MN may send one RRC reconfiguration message to the UE (e.g., UE 701) including both RRC configuration #1 and RRC configuration #2. In some other embodiments, the source MN may send one RRC reconfiguration message including RRC configuration #1 and another RRC reconfiguration message including RRC configuration #2 to the UE.

[0064] In operation 202, the UE may evaluate the CHO execution conditions for the candidate MCGs upon receiving RRC configuration #1.

[0065] In some embodiments, the set of execution conditions for one or more candidate SCGs in RRC configuration #2 may be conditional PSCell addition or change (CPAC) execution conditions for one or more candidate SCGs. In some embodiments, the configuration information for one or more candidate SCGs and the set of execution conditions for one or more candidate SCGs in RRC configuration #2 may be: (1) a set of CPA configuration information and CPA execution conditions for one or more candidate SCGs; or (2) A set of CPC configuration information and CPC execution conditions for one or more candidate SCGs. Includes.

[0066] In some embodiments, the UE may evaluate the CHO execution condition for a candidate MCG and evaluate the set of CPA or CPC execution conditions for a candidate SCG in parallel. In one embodiment, the UE may evaluate the set of CPA execution conditions upon reception of RRC configuration #2 for CPA. In another embodiment, the UE may evaluate the set of CPC execution conditions upon reception of RRC configuration #2 for CPC.

[0067] In some other embodiments, the UE may sequentially evaluate the CHO execution conditions for the candidate MCG and evaluate the set of CPA or CPC execution conditions for the candidate SCG. In some cases, the UE may first evaluate the CHO execution conditions for the candidate MCG and then begin evaluating the set of CPA or CPC execution conditions for the candidate SCG after the CHO execution conditions for the candidate MCG are satisfied. In one embodiment, the UE begins evaluating the set of CPA execution conditions in response to satisfaction of the CHO execution conditions for the candidate MCG. In another embodiment, the UE begins evaluating the set of CPC execution conditions in response to satisfaction of the CHO execution conditions for the candidate MCG.

[0068] In some other cases, the UE may first evaluate a set of CPA or CPC execution conditions for the candidate SCG, and then start evaluating the CHO execution conditions for the candidate MCG after the set of CPA or CPC execution conditions for the candidate SCG are satisfied. In such cases, CHO using the candidate SCG is performed only if the execution conditions for the candidate MCG and the candidate SCG are both satisfied. If only the CHO execution conditions for the candidate MCG are satisfied but the set of CPA or CPC execution conditions for the candidate SCG are not satisfied, CHO using the candidate SCG is not applied. A specific example is described in embodiment 3 of the embodiments of Figure 5 as follows.

[0069] In some embodiments, if a set of CPA execution conditions for one candidate SCG (denoted as candidate SCG#1) in the candidate SCG is satisfied, the UE may stop evaluating sets of CPA execution conditions for other candidate SCGs in the candidate SCG. In some other embodiments, if a set of CPC execution conditions for one candidate SCG (e.g., candidate SCG#1) in the candidate SCG is satisfied, the UE may stop evaluating sets of CPC execution conditions for other candidate SCGs in the candidate SCG. A specific example is described in embodiment 2 of the embodiments of FIG. 5 as follows.

[0070] In some embodiments, when the UE “parallelly evaluates” or “serially evaluates” the set of CHO execution conditions for a candidate MCG and CPA or CPC execution conditions for a candidate SCG described above, the UE: (1) When the UE completes the RA procedure to the candidate MCG, a set of execution conditions for each candidate SCG in the candidate MCG is not satisfied; (2) A set of execution conditions for each candidate SCG is not satisfied when a handover timer (e.g., timer T304 described in 3GPP standard documents) for the candidate MCG is stopped; (3) after a time period (denoted as time period #1) since the UE completed the RA procedure to the candidate MCG, the set of execution conditions for each candidate MCG is not satisfied; (4) When the CHO execution condition for the candidate MCG is satisfied, the set of execution conditions for each candidate SCG is not satisfied; or (5) After a time period (denoted as time period #2) from the satisfaction of the CHO execution condition for the candidate MCG, the set of execution conditions for each candidate SCG is not satisfied. In response, the RRC configuration #2 may be released.

[0071] In one embodiment, the UE: (1) when the UE completes a random access (RA) procedure to the candidate MCG, a set of CPA execution conditions for each candidate SCG in one or more candidate SCGs is not satisfied; (2) When the handover timer (e.g., timer T304) for the candidate MCG is stopped, the set of CPA execution conditions for each candidate SCG is not satisfied; (3) after time period #1, the set of CPA execution conditions for each candidate SCG is not satisfied; (4) When the CHO execution condition for the candidate MCG is satisfied, the set of CPA execution conditions for each candidate SCG is not satisfied; or (5) After time period #2, the set of CPA execution conditions for each candidate SCG is not satisfied. In response, the RRC configuration #2 may be released.

[0072] In another embodiment, the UE (1) When the UE completes the RA procedure to the candidate MCG, a set of CPC execution conditions for each candidate SCG is not satisfied; (2) When the handover timer (e.g., timer T304) for the candidate MCG is stopped, the set of CPC execution conditions for each candidate SCG is not satisfied; (3) after time period #1, the set of CPC execution conditions for each candidate SCG is not satisfied; (4) when the CHO execution condition for the candidate MCG is satisfied, the set of CPC execution conditions for each candidate SCG is not satisfied; or (5) After time period #2, the set of CPC execution conditions for each candidate SCG is not satisfied. In response, the RRC configuration #2 may be released.

[0073] In some embodiments, if the CHO execution condition for the candidate MCG is satisfied, the UE: (1) When the UE completes the RA procedure to the candidate MCG, a set of execution conditions for each candidate SCG in the candidate MCG is not satisfied; (2) a set of execution conditions for each candidate SCG is not satisfied when a handover timer (e.g., timer T304) for the candidate MCG is stopped; (3) after time period #1, the set of execution conditions for each candidate SCG is not satisfied; (4) When the CHO execution condition for the candidate MCG is satisfied, the set of execution conditions for each candidate SCG is not satisfied; or (5) After time period #2, the set of execution conditions for each candidate SCG is not satisfied. In response to, the candidate SCG may stop evaluating the set of execution conditions for the candidate SCG.

[0074] In one embodiment, if the CHO execution condition for the candidate MCG is satisfied, the UE: (1) When the UE completes the RA procedure to the candidate MCG, a set of CPA execution conditions for each candidate SCG in the candidate MCG is not satisfied; (2) When the handover timer (e.g., timer T304) for the candidate MCG is stopped, the set of CPA execution conditions for each candidate SCG is not satisfied; (3) after time period #1, the set of CPA execution conditions for each candidate SCG is not satisfied; (4) When the CHO execution condition for the candidate MCG is satisfied, the set of CPA execution conditions for each candidate SCG is not satisfied; or (5) After time period #2, the set of CPA execution conditions for each candidate SCG is not satisfied. In response to, the candidate SCG may stop evaluating the set of CPA execution conditions for the candidate SCG.

[0075] In another embodiment, if the CHO execution condition for the candidate MCG is satisfied, the UE: (1) When the UE completes the RA procedure to the candidate MCG, a set of CPC execution conditions for each candidate SCG in the candidate MCG is not satisfied; (2) When the handover timer (e.g., timer T304) for the candidate MCG is stopped, the set of CPC execution conditions for each candidate SCG is not satisfied; (3) after time period #1, the set of CPC execution conditions for each candidate SCG is not satisfied; (4) when the CHO execution condition for the candidate MCG is satisfied, the set of CPC execution conditions for each candidate SCG is not satisfied; or (5) After time period #2, the set of CPC execution conditions for each candidate SCG is not satisfied. In response to, the candidate SCG may stop evaluating the set of CPC execution conditions for the candidate SCG.

[0076] In some embodiments, the UE may release the set of execution conditions for the candidate SCG after stopping evaluating the set of execution conditions for the candidate SCG. A specific example is described in embodiment 1 of the embodiments of FIG. 5 as follows.

[0077] In some embodiments, if a CHO execution condition for the candidate MCG is satisfied, the UE may perform an RA procedure to the candidate MCG based on the first RRC configuration and send an RRC reconfiguration complete message to the candidate MN associated with the candidate MCG.

[0078] In some embodiments, if a set of CPA execution conditions for one candidate SCG (e.g., candidate SCG#1) within the candidate SCG is satisfied and the UE completes an RA procedure to the candidate MCG, the UE may send an indication (denoted as indication #1) to the candidate MN associated with the candidate MCG indicating that candidate SCG#1 is selected for cell addition.

[0079] In some other embodiments, if a set of CPC execution conditions for one candidate SCG (e.g., candidate SCG#1) is satisfied and the UE completes an RA procedure to the candidate MCG, the UE may send an indication (shown as indication #2) to the candidate MN indicating that candidate SCG#1 is selected for cell switching.

[0080] 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 send an indication (denoted 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 ID information of each SCG in the subset of candidate SCGs.

[0081] 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 send an indication (denoted as indication #4) to the candidate MN indicating the subset of candidate SCGs that are not selected from the candidate SCGs for cell switching. For example, indication #4 includes ID information of each SCG in the subset of candidate SCGs.

[0082] In some embodiments, if the set of CPA execution conditions for each candidate SCG is not satisfied and the UE completes an RA procedure to the candidate MCG, the UE may send an indication (shown as indication #5) to the candidate MN associated with the candidate MCG indicating that none of the candidate SCGs in the candidate SCG is selected for cell addition.

[0083] In some other embodiments, if the set of CPC execution conditions for each candidate SCG is not satisfied and the UE completes an RA procedure to the candidate MCG, the UE may send an indication (shown as indication #6) to the candidate MN indicating that none of the candidate SCGs in the candidate SCGs are selected for cell switching.

[0084] In some embodiments, in response to the UE failing to perform a CHO procedure to a candidate MCG, the UE may perform a CHO recovery procedure to the candidate MCG.

[0085] In some embodiments, the UE may send an indication (shown as indication #7) to a candidate MN associated with a candidate MCG indicating that no procedures (e.g., CPA procedures or CPC procedures) to any candidate SCG are allowed to be performed during the CHO recovery procedure.

[0086] In some embodiments, indication #1, indication #2, indication #3, indication #4, indication #5, indication #6, and / or indication #7 are included in an SN RRC Reconfiguration Complete message that is embedded in an RRC Reconfiguration Complete message to the candidate MN.

[0087] In some embodiments, if the SN RRC reconfiguration complete message includes instruction #1 and / or instruction #2, the SN RRC reconfiguration complete message further includes an identification (ID) of one candidate SCG (e.g., candidate SCG #1) associated with instruction #1 or instruction #2.

[0088] In some embodiments, in response to completing the CHO recovery procedure to the candidate MCG, the UE may send at least one of the following indications to the candidate MN: (1) Instructions showing the CHO recovery procedure (shown as Instruction #8), or (2) An instruction (shown as instruction #9) indicating that RRC configuration #2 for the candidate SCG is released for the CHO recovery procedure. A specific example is described below in the embodiments of FIGS.

[0089] In some embodiments, if the CHO execution condition for the candidate MCG is satisfied, the CPA or CPC execution condition may be relaxed. For example, if the CHO execution condition for the candidate MCG is satisfied, the UE may: (1) After an entry condition for a candidate SCG (e.g., an entry condition for a CPA or CPC) is satisfied when a handover timer (e.g., T304) for the candidate MCG is running, or (2) When a handover timer (e.g., T304) is running, the channel quality of the PSCell of the candidate SCG is equal to or greater than a threshold (e.g., when the S-criteria described in the 3GPP standard document is satisfied). In response to, a set of CPA execution conditions or a set of CPC execution conditions for the candidate SCG in the candidate SCG may be deemed to be satisfied.

[0090] In some embodiments, the UE may receive an information element (IE) from the source MN. The IE may indicate that a CHO recovery procedure to a candidate MCG is allowed to be performed. The IE may indicate that a CPA procedure or a CPC procedure to a candidate SCG is allowed to be performed during the CHO recovery procedure for the candidate MCG. In one embodiment, the IE is a conditional reconfiguration attempt IE (e.g., attemptCondReconfig IE) included in RRC configuration #1.

[0091] In some embodiments, if a CPA procedure or a CPC procedure to a candidate SCG is allowed to be performed, the UE may perform a CPA procedure or a CPC procedure to a candidate SCG in 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 equal to or greater than a threshold (e.g., when the S criterion is satisfied). A specific example is described in the embodiment of FIG. 8 as follows.

[0092] 3 shows an exemplary flowchart for transmitting an instruction associated with a candidate SCG according to some embodiments of the present application. The exemplary procedure 300 in the embodiment of FIG. 3 may be performed by a target MN or a candidate MN, for example, MN 102, candidate MN 705, candidate MN 805, candidate MN 905, or candidate MN 1005 shown in any of FIGS. 1 and 5-8. Although described with respect to a target MN or a candidate MN, it should be understood that other devices may be configured to perform a method similar to the method of FIG. 3.

[0093] In the example procedure 300 shown in Figure 3, in operation 301, a candidate MN may receive an RRC reconfiguration complete message from a UE (e.g., UE 101 shown in Figure 1). In operation 302, the candidate MN may send an indication associated with the candidate SCG to a candidate SN (e.g., SN 103 shown in Figure 1 or a candidate SN not shown in Figure 1).

[0094] In some embodiments, the indication associated with the candidate SCG is carried in an SN RRC reconfiguration complete message. In one 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 identification (ID) of the candidate SCG belonging to the candidate SN. In some other embodiments, the candidate MN may receive the indication from the UE. In some additional embodiments, the candidate MN may generate the indication based on the RRC reconfiguration complete message in operation 301.

[0095] In some embodiments, the indication sent by the candidate MN to the candidate SN in operation 302 is: (1) A candidate SCG is selected for cell addition, e.g., instruction #1 described in the embodiment of FIG. 2; (2) A candidate SCG is selected for cell switching, e.g., instruction #2 described in the embodiment of FIG. 2; (3) The candidate SCG is not selected for cell addition, e.g., instruction #3 described in the embodiment of FIG. 2; (4) The candidate SCG is not selected for cell switching, e.g., instruction #4 described in the embodiment of FIG. 2; (5) No candidate SCG is selected for cell addition, e.g., instruction #5 described in the embodiment of FIG. 2; (6) No candidate SCG is selected for cell switching, e.g., instruction #6 described in the embodiment of FIG. 2; (7) No CPA procedure to any candidate SCG is allowed to be performed during the CHO recovery procedure to the candidate MCG, e.g., instruction #7 described in the embodiment of FIG. 2; (8) No CPC procedure to any candidate SCG is allowed to be performed during the CHO recovery procedure, e.g., instruction #7 described in the embodiment of FIG. 2; or (9) The UE accesses the candidate MCG via a CHO procedure; (10) The UE accesses the candidate MCG via a CHO recovery procedure, for example, instruction #8 described in the embodiment of FIG. 2; or (11) The RRC configuration for the candidate SCG is released by the UE for the CHO recovery procedure, for example, instruction #9 described in the embodiment of FIG. 2 At least one of the following is shown.

[0096] In some embodiments, the candidate MN may send an IE to the UE. The IE may indicate that a CHO recovery procedure to the candidate MCG is allowed to be performed. The IE may indicate that a CPA or CPC procedure to one or more candidate SCGs is allowed to be performed during the CHO recovery procedure. In one embodiment, the IE is a conditional reconfiguration attempt IE (e.g., attemptCondReconfig IE) included in the RRC configuration.

[0097] In some embodiments, the candidate MN may send an RRC configuration including CHO configuration information and a CHO execution condition for the candidate MCG to the source MN. For example, an attemptCondReconfig IE is included in the RRC configuration. A specific example is described in the embodiment of FIG. 8 as follows.

[0098] 4 shows an example flowchart for receiving instructions associated with a candidate SCG according to some embodiments of the present application. The example procedure 400 in the embodiment of FIG. 4 may be performed by a target SN or a candidate SN, for example, SN 103, candidate SN 704, candidate SN 804, candidate SN 806, candidate SN 904, candidate SN 906, candidate SN 1004, or candidate SN 1006 shown in any of FIGS. 1 and 5-8. While described with respect to a target SN or a candidate SN, it should be understood that other devices may be configured to perform a method similar to that of FIG. 4.

[0099] In the example procedure 400 shown in FIG. 4, in operation 401, a candidate SN may send an RRC configuration to a candidate MN, the RRC configuration including configuration information for the candidate SCG and a set of execution conditions for the candidate SCG. In some embodiments, the set of execution conditions for the candidate SCG may be CPAC execution conditions for the candidate SCG. In some embodiments, the configuration information for the candidate SCG and the set of execution conditions for the candidate SCG may be (1) a set of CPA configuration information and CPA execution conditions for a candidate SCG; or (2) A set of CPC configuration information and CPC execution conditions for the candidate SCG. Includes.

[0100] In operation 402, the candidate SN may receive an indication from the candidate MN associated with the candidate SCG. In some embodiments, the indication may include: (1) A candidate SCG or a subset of candidate SCGs is selected for cell addition, e.g., instruction #1 described in the embodiment of FIG. 2; (2) A candidate SCG or a subset of candidate SCGs is selected for cell switching, e.g., instruction #2 described in the embodiment of FIG. 2; (3) The candidate SCG is not selected for cell addition, e.g., instruction #3 described in the embodiment of FIG. 2; (4) The candidate SCG is not selected for cell switching, e.g., instruction #4 described in the embodiment of FIG. 2; (5) No candidate SCG is selected for cell addition, e.g., instruction #5 described in the embodiment of FIG. 2; (6) No candidate SCG is selected for cell switching, e.g., instruction #6 described in the embodiment of FIG. 2; (7) No CPA procedure to any candidate SCG is allowed to be performed during the CHO recovery procedure to the candidate MCG, e.g., instruction #7 described in the embodiment of FIG. 2; (8) No CPC procedure to any candidate SCG is allowed to be performed during the CHO recovery procedure, e.g., instruction #7 described in the embodiment of FIG. 2; (9) The UE accesses the candidate MCG via a CHO procedure; (10) The UE accesses the candidate MCG via a CHO recovery procedure, for example, instruction #8 described in the embodiment of FIG. 2; or (11) The RRC configuration for the candidate SCG is released by the UE for the CHO recovery procedure, for example, instruction #9 described in the embodiment of FIG. 2 At least one of the following is shown.

[0101] In some embodiments, the candidate SN is: (1) The candidate SCG is not selected for cell addition, for example, instruction #3 described in the embodiment of FIG. 2; (2) The candidate SCG is not selected for cell switching, e.g., instruction #4 described in the embodiment of FIG. 2; (3) No candidate SCG is selected for cell addition, e.g., instruction #5 described in the embodiment of FIG. 2; (4) No candidate SCG is selected for cell switching, e.g., instruction #6 described in the embodiment of FIG. 2; (5) No CPA procedure to any candidate SCG is allowed to be performed during the CHO recovery procedure to the candidate MCG, e.g., instruction #7 described in the embodiment of FIG. 2; (6) No CPC procedure to any candidate SCG is allowed to be performed during the CHO recovery procedure, e.g., instruction #7 described in the embodiment of FIG. 2; (7) The UE accesses the candidate MCG via a CHO recovery procedure, for example, instruction #8 described in the embodiment of FIG. 2; or (8) The RRC configuration for the candidate SCG is released by the UE for the CHO recovery procedure, for example, instruction #9 described in the embodiment of FIG. 2 In response to the indication indicating the release of the resource for the candidate SCG, the resource for the candidate SCG may be released. A specific example is described in the embodiments of FIGS.

[0102] Details described in all other embodiments of the present application are applicable to the embodiments shown in any of Figures 2-4. Those skilled in the art will appreciate that the order of the operations in any of the exemplary procedures 200, 300, and 400 in Figures 2-4 may be changed, and some of the operations in any of the exemplary procedures 200-400 in Figures 2-4 may be removed or modified, without departing from the spirit and scope of the present disclosure.

[0103] The following text describes the specific embodiment depicted and illustrated in Figures 2-4, in which the UE and network nodes (e.g., source MN, target MN, candidate MN, source SN, target SN, and / or candidate SN) perform the following operations: Those skilled in the art should appreciate that the order of the operations in any of the exemplary flowcharts 700, 800, 900, and 1000 in Figures 5-8 may be changed, and some of the operations in any of the exemplary flowcharts 700-1000 in Figures 5-8 may be removed or modified, without departing from the spirit and scope of the present disclosure.

[0104] 5 shows an exemplary flow chart of a CHO mechanism using candidate SCGs according to some embodiments of the present application. Details described in all other embodiments of the present application are applicable to the embodiment shown in FIG.

[0105] 5, in operation 711, a UE 701 in an RRC connected state accesses its serving BS, i.e., a 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.

[0106] In operation 712, based on the measurement results, the source MN 702 may decide to switch the UE 701 to the candidate MN 705 via a CHO procedure.

[0107] In operation 713, the source MN 702 may transmit a handover request to the candidate MN 705. For example, the source MN 702 may instruct the candidate MN 705 to prepare a candidate SCG.

[0108] In operation 714, after the candidate MN 705 receives the handover request from the source MN 702, the candidate MN 705 may send a request (eg, an SgNB addition request message or an SN modification request message) to the candidate SN 704 via the Xn interface.

[0109] At operation 715, the candidate SN 704 may send an acknowledgement message (e.g., an SgNB Addition Request Acknowledgement message or an SgNB Modification Request Acknowledgement message) to the candidate MN 705. The configuration for the candidate SCG of the candidate SN 704 may be included in the acknowledgement message.

[0110] In operation 716, after receiving the acknowledgement message from the candidate SN 704, the candidate MN 705 sends a handover request acknowledgement message to the source MN 702, including an RRC configuration for the candidate MCG (e.g., RRC configuration #1 described in the embodiment of FIG. 2) and / or an RRC configuration for the candidate SCG (e.g., RRC configuration #2 described in the embodiment of FIG. 2).

[0111] In some embodiments, the RRC configuration for the candidate MCG may include a CHO configuration for the candidate MCG and a CHO execution condition for the candidate MCG. In some embodiments, the RRC configuration for the candidate SCG may include (1) a CPA configuration and a CPA execution condition for the candidate SCG, or (2) a set of CPC configurations and a CPC execution condition for the candidate SCG.

[0112] In operation 717, after receiving the handover request acknowledgement message from the candidate MN 705, the source MN 702 sends an RRC reconfiguration message to the UE 701, including the RRC configuration for the candidate MCG and / or the RRC configuration for the candidate SCG.

[0113] In operation 718, after receiving the RRC reconfiguration message from the source MN 702, the UE 701 sends an RRC reconfiguration complete message to the source MN 702.

[0114] In operation 719, there may be different embodiments in different scenarios, namely, embodiment 1, embodiment 2, and embodiment 3 as follows.

[0115] Embodiment 1 In operation 719, the UE 701 begins "parallel evaluating" or "serially evaluating" the CHO execution conditions for the candidate MCG and / or the execution conditions (e.g., CPA or CPC execution conditions) for the candidate SCG.

[0116] In some embodiments of "evaluating in parallel," the UE 701 starts evaluating the CHO execution condition for the candidate MCG when it receives the RRC configuration for the candidate MCG in an RRC reconfiguration message, and starts evaluating the CPA or CPC execution condition when it receives the RRC configuration for the candidate SCG in an RRC reconfiguration message.

[0117] In some embodiments of "continuously evaluate," the UE 701 starts evaluating the CHO execution condition for the candidate MCG when it receives an RRC configuration for the candidate MCG in an RRC reconfiguration message. The UE starts evaluating the CPA or CPC execution condition upon satisfaction of the CHO execution condition for the candidate MCG.

[0118] In operation 719 of embodiment 1, there may be two options in different embodiments: option 1 and option 2 as follows:

[0119] Option 1: UE701 is (1) When the UE completes the RA procedure to the candidate MCG, the CPA or CPC execution condition for each candidate SCG in the candidate MCG is not satisfied; (2) When the handover timer (e.g., timer T304) for the candidate MCG is stopped, the CPA or CPC execution condition for each candidate SCG is not satisfied; (3) After the UE completes the RA procedure to the candidate MCG, the CPA or CPC execution condition for each candidate SCG is not satisfied after a time period (e.g., time period #1 described in the embodiment of FIG. 2) since the UE completed the RA procedure to the candidate MCG; (4) When the CHO execution condition for the candidate MCG is satisfied, the CPA or CPC execution condition for each candidate SCG is not satisfied; or (5) After a time period (e.g., time period #2 described in the embodiment of FIG. 2) from the satisfaction of the CHO execution condition for the candidate MCG, the CPA or CPC execution condition for each candidate SCG is not satisfied. In response, the SCG may release the RRC configuration associated with the candidate SCG.

[0120] Option 2: UE701 is (1) When the UE completes the RA procedure to the candidate MCG, the CPA or CPC execution condition for each candidate SCG in the candidate MCG is not satisfied; (2) When the handover timer (e.g., timer T304) for the candidate MCG is stopped, the CPA or CPC execution condition for each candidate SCG is not satisfied; (3) After the UE completes the RA procedure to the candidate MCG, the CPA or CPC execution condition for each candidate SCG is not satisfied after a time period (e.g., time period #1 described in the embodiment of FIG. 2) since the UE completed the RA procedure to the candidate MCG; (4) When the CHO execution condition for the candidate MCG is satisfied, the CPA or CPC execution condition for each candidate SCG is not satisfied; or (5) After a time period (e.g., time period #2 described in the embodiment of FIG. 2) from the satisfaction of the CHO execution condition for the candidate MCG, the CPA or CPC execution condition for each candidate SCG is not satisfied. In response to, the SCG may stop evaluating the execution conditions for the candidate SCG.

[0121] Embodiment 2 At operation 719, the UE 701 starts evaluating the CHO execution condition for the candidate MCG. After the CHO execution condition for the candidate MCG is satisfied, the UE 701 starts evaluating the execution condition (e.g., the CPA or CPC execution condition) for the candidate SCG. In some embodiments, if the CPA or CPC execution condition for a candidate SCG (e.g., candidate SCG#1 described in the embodiment of FIG. 2) within the candidate SCG is satisfied, the UE 701 may stop evaluating the CPA or CPC execution condition for other candidate SCGs within the candidate SCG. In some embodiments, when the CPA or CPC execution condition for a candidate SCG (e.g., candidate SCG#1) is satisfied, the UE 701 may release the RRC configurations for the other candidate SCGs, including, for example, the CPA or CPC configurations and the CPA or CPC execution conditions for these other candidate SCGs.

[0122] Embodiment 3 In operation 719, the UE 701 may first evaluate the CPA or CPC execution condition for the candidate SCG, and then, after the CPA or CPC execution condition for the candidate SCG is satisfied, begin to evaluate the CHO execution condition for the candidate MCG. In embodiment 3, the CHO using the candidate SCG is executed only if the execution conditions for both the candidate MCG and the candidate SCG are both satisfied (e.g., the UE 701 accesses the candidate MN 705 based on the CHO configuration for the candidate MCG and accesses the candidate SN 704 based on the configuration for the candidate SCG). If only the CHO execution condition for the candidate MCG is satisfied, but the set of CPA or CPC execution conditions for the candidate SCG is not satisfied, the CHO using the candidate SCG is not applied.

[0123] 6 shows a further exemplary flow chart of a CHO mechanism using candidate SCGs according to some embodiments of the present application. Details described in all other embodiments of the present application are applicable to the embodiment shown in FIG.

[0124] 6, in operation 811, a UE 801 in an RRC connected state accesses its serving BS, i.e., a 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.

[0125] In operation 812, based on the measurement result, the source MN 802 may decide to switch the UE 801 to the candidate MN 805 via a CHO procedure.

[0126] 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.

[0127] In operation 814, after the candidate MN 805 receives the handover request from the source MN 802, the candidate MN 805 may send a request (eg, an SgNB addition request message or an SN modification request message) to the candidate SN 804 via the Xn interface.

[0128] At operation 815, the candidate SN 804 may send an acknowledgement message (e.g., an SgNB Addition Request Acknowledgement message or an SgNB Modification Request Acknowledgement message) to the candidate MN 805. The configuration for the candidate SCG of the candidate SN 804 may be included in the acknowledgement message.

[0129] In operation 816, after receiving the acknowledgement message from the candidate SN 804, the candidate MN 805 sends a handover request acknowledgement message to the source MN 802, including the RRC configuration associated with the candidate MCG (e.g., RRC configuration #1 described in the embodiment of FIG. 2) and / or the RRC configuration for the candidate SCG (e.g., RRC configuration #2 described in the embodiment of FIG. 2).

[0130] In some embodiments, the RRC configuration associated with the candidate MCG may include a CHO configuration for the candidate MCG and a CHO execution condition for the candidate MCG, and may be referred to as a "CHO ​​configuration associated with the candidate MCG," etc. In some embodiments, the RRC configuration associated with the candidate SCG may include (1) a CPA configuration and a CPA execution condition for the candidate SCG, or (2) a set of CPC configurations and CPC execution conditions for the candidate SCG.

[0131] In operation 817, after receiving the handover request acknowledgement message from the candidate MN 805, the source MN 802 sends an RRC reconfiguration message to the UE 801, including the CHO configuration associated with the candidate MCG and / or the configuration for the candidate SCG.

[0132] In operation 818, after receiving the RRC reconfiguration message from the source MN 802, the UE 801 sends an RRC reconfiguration complete message to the source MN 802.

[0133] In operation 819, the UE 801 begins "parallel evaluating" or "sequentially evaluating" the CHO execution conditions for the candidate MCGs and / or the CPA or CPC execution conditions for the candidate SCGs.

[0134] In some embodiments of "evaluating in parallel," UE801 starts evaluating the CHO execution condition for the candidate MCG when it receives the RRC configuration for the candidate MCG in an RRC reconfiguration message, and starts evaluating the CPA or CPC execution condition when it receives the RRC configuration for the candidate SCG in an RRC reconfiguration message.

[0135] In some embodiments of "continuously evaluate," the UE 801 starts evaluating the CHO execution condition for the candidate MCG when it receives an RRC configuration for the candidate MCG in an RRC reconfiguration message. The UE starts evaluating the CPA or CPC execution condition upon satisfaction of the CHO execution condition for the candidate MCG.

[0136] In some embodiments, the execution condition for the candidate SCG may be relaxed after the CHO execution condition for the candidate MCG is satisfied in operation 819. For example, in operation 820, the UE 801 considers the CPA or CPC execution condition for the candidate SCG to be satisfied in response to the following two options in different embodiments, option A and option B, as follows: (1) Option A: When timer T304 for a candidate MCG is running, if the conditions for entering CPA or CPC for the candidate SCG in the candidate SCG are met, UE801 considers that the CPA or CPC execution conditions for the candidate SCG are satisfied. (2) Option B: When timer T304 for the candidate MCG is running, if the channel quality of the PSCell of the candidate SCG in the candidate SCG is equal to or greater than a configured or preconfigured threshold (e.g., when the S criterion is satisfied), UE801 considers that the CPA or CPC execution condition for the candidate SCG is satisfied.

[0137] In some embodiments, in operations 821A and 821B, after the UE 801 determines that the CPA or CPC execution condition for the candidate SCG is satisfied, the UE 801 accesses the candidate MN 805 based on the CHO configuration for the candidate MCG in the RRC reconfiguration message received in operation 817, and accesses the candidate SN 804 based on the CPA or CPC configuration for the candidate SCG. The order of operations 821A and 821B is not fixed and may be varied in different embodiments.

[0138] In some other embodiments, operation 821B is performed before operation 820. That is, in operation 821B, the UE 801 accesses the candidate MN 805 based on the CHO configuration for the candidate MCG after the CHO execution condition for the candidate MCG is satisfied in operation 819. Then, in operation 820, after the UE 801 determines that the CPA or CPC execution condition for the candidate SCG is satisfied, the UE 801 accesses the candidate SN 804 based on the CPA or CPC configuration for the candidate SCG.

[0139] At 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 one embodiment, which candidate SCG among multiple candidate SCGs is to be indicated in the SN RRC reconfiguration complete message for 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.

[0140] In some embodiments, the RRC reconfiguration complete message in operation 822 includes at least one of the following indications: In one embodiment, at least one of the following indications is included in an SN RRC reconfiguration complete message that is embedded in the RRC reconfiguration complete message. (1) an indication (e.g., indication #1) to indicate that a candidate SCG (e.g., candidate SCG#1) associated with the candidate SN 804 is selected for cell addition; (2) an indication (e.g., indication #2) to indicate that a candidate SCG (e.g., candidate SCG #1) associated with the candidate SN 804 is selected for cell switching; (3) an instruction to indicate a subset of candidate SCGs that are not selected from all candidate SCGs for cell addition (e.g., instruction #3); or (4) An instruction (e.g., instruction #4) to indicate a subset of candidate SCGs that are not selected from all candidate SCGs for cell switching.

[0141] In some embodiments, in operation 823A, the candidate MN 805 sends an SN RRC reconfiguration complete message and either indication #1 or indication #2 to the candidate SN 804. In one 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 to the candidate SN 804 over the Xn interface.

[0142] In operation 823B (optional), the candidate MN 805 sends indication #3 and / or indication #4 to the candidate SN 806, for example, in an RRC message over the Xn interface, to instruct the candidate SN not to be selected for cell addition or cell switching. The candidate SN 806 may then release or cancel the reserved resources for the UE 801.

[0143] 7 shows another exemplary flow chart of a CHO mechanism using candidate SCGs according to some embodiments of the present application. Details described in all other embodiments of the present application are applicable to the embodiment shown in FIG.

[0144] 7, in operation 911, a UE 901 in an RRC connected state accesses its serving BS, i.e., a 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.

[0145] In operation 912, based on the measurement result, the source MN 902 may decide to switch the UE 901 to the candidate MN 905 via the CHO procedure.

[0146] 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.

[0147] In operation 914, after the candidate MN 905 receives the handover request from the source MN 902, the candidate MN 905 may send a request (eg, an SgNB addition request message or an SN modification request message) to the candidate SN 904 via the Xn interface.

[0148] At operation 915, the candidate SN 904 may send an acknowledgement message (e.g., an SgNB Addition Request Acknowledgement message or an SgNB Modification Request Acknowledgement message) to the candidate MN 905. The configuration for the candidate SCG of the candidate SN 904 may be included in the acknowledgement message.

[0149] In operation 916, after receiving the acknowledgement message from the candidate SN 904, the candidate MN 905 sends a handover request acknowledgement message to the source MN 902, including the RRC configuration associated with the candidate MCG (e.g., RRC configuration #1 described in the embodiment of FIG. 2) and / or the RRC configuration for the candidate SCG (e.g., RRC configuration #2 described in the embodiment of FIG. 2).

[0150] In some embodiments, the RRC configuration associated with the candidate MCG may include a CHO configuration for the candidate MCG and a CHO execution condition for the candidate MCG, and may be referred to as a "CHO ​​configuration associated with the candidate MCG," etc. In some embodiments, the RRC configuration associated with the candidate SCG may include (1) a CPA configuration and a CPA execution condition for the candidate SCG, or (2) a set of CPC configurations and CPC execution conditions for the candidate SCG.

[0151] In operation 917, after receiving the handover request acknowledgement message from the candidate MN 905, the source MN 902 transmits to the UE 901 an RRC reconfiguration message including a CHO configuration associated with the candidate MCG and / or a configuration for the candidate SCG.

[0152] 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.

[0153] In operation 919, the UE 901 begins "parallel evaluating" or "sequentially evaluating" the CHO execution conditions for the candidate MCG and / or the CPA or CPC execution conditions for the candidate SCG.

[0154] In some embodiments of "evaluating in parallel," UE901 starts evaluating the CHO execution condition for the candidate MCG when it receives the RRC configuration for the candidate MCG in the RRC reconfiguration message, and starts evaluating the CPA or CPC execution condition when it receives the RRC configuration for the candidate SCG in the RRC reconfiguration message.

[0155] In some embodiments of "continuously evaluate," the UE 901 starts evaluating the CHO execution condition for the candidate MCG when it receives an RRC configuration for the candidate MCG in an RRC reconfiguration message. The UE starts evaluating the CPA or CPC execution condition upon satisfaction of the CHO execution condition for the candidate MCG.

[0156] In some embodiments, the CPA or CPC execution conditions for all candidate SCGs are not met in operation 920. In operation 921, the UE 901 accesses the candidate MN 905 based on the CHO configuration for the candidate MCG in the RRC reconfiguration message received in operation 917.

[0157] The order of operations 920 and 921 is not fixed and may be varied in different embodiments. In some other embodiments, operation 921 is performed before operation 920. That is, in operation 921, the UE 901 accesses the candidate MN 905 based on the CHO configuration for the candidate MCG after the CHO execution condition for the candidate MCG is satisfied in operation 919. Then, the UE 901 determines in operation 920 that the CPA or CPC execution condition for the candidate SCG is not satisfied.

[0158] 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 an RRC message to the candidate MN 905 via the Xn interface, which may be transmitted in operation 922: (1) an instruction to indicate that no candidate SCG in the candidate SCGs is selected for cell addition (e.g., instruction #5); or (2) An indication (e.g., indication #6) to indicate that none of the candidate SCGs in the candidate SCGs is selected for cell switching.

[0159] In some embodiments, in operation 923A, the candidate MN 905 sends indication #5 and / or indication #6 to the candidate SN 904, for example, in an RRC message over the Xn interface, to indicate to the candidate SN 904 that no candidate SCGs will be added for cell addition or cell switching. The candidate SN 904 may then release or cancel the reserved resources for the UE 901.

[0160] In operation 923B (optional), the candidate MN 905 sends indication #5 and / or indication #6 to the candidate SN 906, for example, via the Xn interface in an RRC message, to indicate to the candidate SN that no candidate SCGs will be added for cell addition or cell switching. The candidate SN 906 may then release or cancel the reserved resources for the UE 901.

[0161] 8 shows another exemplary flow chart of a CHO mechanism using candidate SCGs according to some embodiments of the present application. Details described in all other embodiments of the present application are applicable to the embodiment shown in FIG.

[0162] 8, in operation 1011, a UE 1001 in an RRC connected state accesses its serving BS, i.e., a source MN 1002. For example, DC (dual connectivity) may be configured for the UE 1001. In some embodiments, the UE 1001 may report measurement results to the source MN 1002.

[0163] In operation 1012, based on the measurement result, the source MN 1002 may decide to switch the UE 1001 to the candidate MN 1005 via the CHO procedure.

[0164] 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 a candidate SCG.

[0165] In operation 1014, after the candidate MN 1005 receives the handover request from the source MN 1002, the candidate MN 1005 may send a request (eg, an SgNB addition request message or an SN modification request message) to the candidate SN 1004 via the Xn interface.

[0166] At operation 1015, the candidate SN 1004 may send an acknowledgement message (e.g., an SgNB Addition Request Acknowledgement message or an SgNB Modification Request Acknowledgement message) to the candidate MN 1005. The configuration for the candidate SCG of the candidate SN 1004 may be included in the acknowledgement message.

[0167] In operation 1016, after receiving the acknowledgement message from the candidate SN 1004, the candidate MN 1005 sends a handover request acknowledgement message to the source MN 1002, including the RRC configuration associated with the candidate MCG (e.g., RRC configuration #1 described in the embodiment of FIG. 2) and / or the RRC configuration for the candidate SCG (e.g., RRC configuration #2 described in the embodiment of FIG. 2).

[0168] In some embodiments, the RRC configuration associated with the candidate MCG may include a CHO configuration for the candidate MCG and a CHO execution condition for the candidate MCG, and may be referred to as a "CHO ​​configuration associated with the candidate MCG." In one embodiment, the RRC configuration associated with the candidate MCG includes an attemptCondReconfig IE, which is configured to indicate whether CHO recovery is allowed to be performed. If the attemptCondReconfig IE is configured, this IE may also imply that CHO using the candidate SCG is enabled. For example, the IE indicates that a CPA procedure or a CPC procedure to one or more candidate SCGs is allowed to be performed during a CHO recovery procedure.

[0169] In some embodiments, the RRC configuration associated with the candidate SCG may include (1) a CPA configuration and CPA execution conditions for the candidate SCG, or (2) a set of CPC configurations and CPC execution conditions for the candidate SCG.

[0170] In operation 1017, after receiving the handover request acknowledgement message from the candidate MN 1005, the source MN 1002 transmits to the UE 1001 an RRC reconfiguration message including a CHO configuration associated with the candidate MCG and / or a configuration for the candidate SCG.

[0171] In operation 1018, after receiving the RRC reconfiguration message from the source MN 1002, the UE 1001 transmits an RRC reconfiguration complete message to the source MN 1002.

[0172] In operation 1019, the UE 1001 begins "parallel evaluating" or "sequentially evaluating" the CHO execution conditions for the candidate MCG and / or the CPA or CPC execution conditions for the candidate SCG.

[0173] In some embodiments of "evaluating in parallel," UE1001 starts evaluating the CHO execution condition for the candidate MCG when it receives the RRC configuration for the candidate MCG in the RRC reconfiguration message, and starts evaluating the CPA or CPC execution condition when it receives the RRC configuration for the candidate SCG in the RRC reconfiguration message.

[0174] In some embodiments of "continuously evaluate," the UE 1001 starts evaluating the CHO execution condition for the candidate MCG when it receives an RRC configuration for the candidate MCG in an RRC reconfiguration message. The UE starts evaluating the CPA or CPC execution condition upon satisfaction of the CHO execution condition for the candidate MCG.

[0175] In operation 1020, a failure occurs, for example, an RLF, handover failure, or CHO failure on a source MCG associated with the source MN 1002. In some embodiments, after the failure occurs, if an attemptCondReconfig IE is configured in the RRC configuration associated with the candidate MCG in operation 1017, the UE 1001 initiates an RRC re-establishment procedure in operation 1020.

[0176] In operation 1021, the UE 1001 selects a candidate cell from 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.

[0177] Then, there may be two options in different embodiments: Option M, Option N, and Option L as follows:

[0178] Option M: If the channel quality of a PSCell of a candidate SCG (e.g., candidate SN 1004) in the candidate SCG is greater than a threshold (e.g., the S criterion is met for the candidate PSCell), the UE 1001 may perform a CPA or CPC procedure associated with the candidate SCG along with a CHO recovery procedure in operation 1021. The UE 1001 may then send an RRC reconfiguration complete message to the candidate MN 1005.

[0179] Option N: No CPA or CPC procedure associated with the candidate SCG is performed when the CHO recovery procedure is performed in operation 1021. In particular, after the UE 1001 performs the CHO recovery procedure in operation 1021, operations 1022, 1023A, 1023B may be performed. (1) In operation 1022, the UE 1001 sends at least one of the following instructions to the candidate MN 1005, for example, in an RRC message over the Xn interface or an RRC reconfiguration complete message: In some embodiments, the candidate MN 1005 may perform bearer remapping to the candidate SCG based on the RRC message or the RRC reconfiguration complete message in operation 1022. (a) An instruction (e.g., instruction #7) to indicate that no CPA or CPC procedures to any candidate SCG are allowed to be performed during the CHO recovery procedure. (b) Instructions to demonstrate the CHO recovery procedure (e.g., instruction #8). (c) An instruction (e.g., instruction #9) to indicate that the RRC configuration for the candidate SCG is released for the CHO recovery procedure. (2) In operation 1023A (optional), the candidate MN 1005 sends indication #7, indication #8, and / or indication #9 to the candidate SN 1004, for example, in an RRC message via the Xn interface, to indicate to the candidate SN 1004 that no candidate SCGs will be added for cell addition or cell switching. The candidate SN 1004 may then release or cancel the reserved resources for the UE 1001. (3) In operation 1023B (optional), the candidate MN 1005 sends indication #7, indication #8, and / or indication #9 to the candidate SN 1006, for example, in an RRC message over the Xn interface, to indicate to the candidate SN that no candidate SCGs will be added for cell addition or cell switching. The candidate SN 1006 may then release or cancel the reserved resources for the UE 1001.

[0180] Details described in all other embodiments of the present disclosure are applicable to the embodiments shown in any of Figures 5-8. Those skilled in the art will appreciate that the order of the operations in any of the exemplary procedures 700-1000 in Figures 5-8 may be changed, and some of the operations in any of the exemplary procedures 700-1000 in Figures 5-8 may be removed or modified, without departing from the spirit and scope of the present disclosure.

[0181] 9 illustrates a block diagram of an exemplary apparatus 1100 according to some embodiments of the present disclosure. As shown in FIG. 9, the apparatus 1100 may include at least one processor 1106 and at least one transceiver 1102 coupled to the processor 1106.

[0182] In this figure, elements such as at least one transceiver 1102 and processor 1106 are described in the singular, but the plural is contemplated unless limitation to the singular is expressly stated. In some embodiments of the present application, the transceiver 1102 may be divided into two devices, such as a receiving circuit and a transmitting circuit. In some embodiments of the present application, the apparatus 1100 may further include an input device, a memory, and / or other components.

[0183] In some embodiments of the present application, the apparatus 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 operations related to the UE, target MN, candidate MN, source MN, target SN, candidate SN, or source SN described above, for example, in any of FIGS.

[0184] In some embodiments of the present application, the apparatus 1100 may further include at least one non-transitory computer-readable medium. For example, in some embodiments of the present disclosure, the non-transitory computer-readable medium may store computer-executable instructions for causing the processor 1106 to perform the methods related to a UE described above. For example, the computer-executable instructions, when executed, cause the processor 1106 interacting with the transceiver 1102 to perform operations related to a UE, target MN, candidate MN, source MN, target SN, candidate SN, or source SN described in FIGS. 1-8.

[0185] Those skilled 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 the two. A software module 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. Furthermore, in some aspects, the operations or steps of a method may reside as one or any combination or set of codes and / or instructions on a non-transitory computer-readable medium, which may be incorporated into a computer program product.

[0186] While the present disclosure has been described with reference to specific embodiments thereof, it is apparent that numerous alternatives, modifications, and variations may be apparent to those skilled in the art. For example, various components of the embodiments may be exchanged, added, or substituted in other embodiments. Also, not all elements in each figure are necessary for the operation of the disclosed embodiments. For example, one skilled in the art of the disclosed embodiments will be enabled to make and use the teachings of the present disclosure by simply employing the elements of the independent claims. Accordingly, the embodiments of the present disclosure described herein are intended to be illustrative, not limiting. Various changes may be made without departing from the spirit and scope of the present disclosure.

[0187] As used herein, the terms "includes," "including," or any other variations thereof are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that includes a list of elements does not include only those elements, but may include other elements not specifically listed or inherent in such process, method, article, or apparatus. An element preceded by "a," "an," etc., does not, without more constraints, exclude the existence of additional equivalent 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. Terms such as "having," as used herein, are defined as "including." Phrases such as "A and / or B" or "at least one of A and B" may include any and all combinations of the listed words associated with the phrase. For example, the phrase "A and / or B" or "at least one of A and B" may include A, B, or both A and B. The terms "first", "second", etc. are only used to clearly describe the embodiments of the present application, and are not used to limit the contents of the present application. [Explanation of symbols]

[0188] 100 Wireless Communication System, Dual Connectivity System 101, 701, 801, 901, 1001UE 102 MN 103SN 702, 802, 902, 1002 Source MN 703, 803, 903, 1003 Source SN 704, 804, 806, 904, 906, 1004, 1006 Candidate SN 705, 805, 905, 1005 Candidate MN 1100 equipment 1102 Transceiver 1106 processor

Claims

1. A transceiver; a processor coupled to the transceiver; wherein the processor: receiving, via the transceiver, a first radio resource control (RRC) configuration and a second RRC configuration, the first RRC configuration including conditional handover (CHO) configuration information and a CHO execution condition for a candidate master cell group (MCG), and the second RRC configuration including configuration information for one or more candidate secondary cell groups (SCGs) and a set of execution conditions for the one or more candidate SCGs; Upon receiving the first RRC configuration, evaluating the CHO execution condition for the candidate MCG; A user equipment (UE) configured to perform the following:

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

3. the configuration information for the one or more candidate SCGs and the set of execution conditions for the one or more candidate SCGs, a set of conditional Primary Secondary Cell Group (PSCell) Addition (CPA) configuration information and CPA execution conditions for the one or more candidate SCGs; or a set of conditional PSCell change (CPC) configuration information and CPC execution conditions for the one or more candidate SCGs; The UE of claim 1 , comprising:

4. The processor of the UE: evaluating the set of CPA execution conditions upon receipt of the second RRC configuration for CPA; or evaluating the set of CPC execution conditions upon receiving the second RRC configuration for CPC. The UE of claim 3 , further configured to:

5. The processor of the UE: initiating evaluation of the set of CPA execution conditions in response to satisfaction of the CHO execution condition for the candidate MCG; or initiating evaluation of the set of CPC execution conditions in response to the satisfaction of the CHO execution condition for the candidate MCG. The UE of claim 3 , further configured to:

6. The processor of the UE: in response to satisfaction of the set of CPA execution conditions for one candidate SCG in the one or more candidate SCGs, ceasing to evaluate the set of CPA execution conditions for one other candidate SCG or SCGs in the one or more candidate SCGs; or and in response to satisfaction of the set of CPC execution conditions for one candidate SCG among the one or more candidate SCGs, ceasing to evaluate the set of CPC execution conditions for one other candidate SCG among the one or more candidate SCGs. The UE of claim 5, further configured to:

7. The processor of the UE: the set of execution conditions for each candidate SCG in the one or more candidate SCGs is not satisfied when the UE completes a random access (RA) procedure to the candidate MCG; the set of execution conditions for each candidate SCG is not satisfied when a handover timer for the candidate MCG is stopped; the set of execution conditions for each of the candidate SCGs is not satisfied after a first time period after the UE completes the RA procedure to the candidate MCGs; the set of execution conditions for each candidate SCG is not satisfied when the CHO execution condition for the candidate MCG is satisfied; or the set of execution conditions for each of the candidate SCGs is not satisfied after a second time period from the satisfaction of the CHO execution condition for the candidate MCG.

10. The UE of claim 1, configured to release the second RRC configuration in response to:

8. In response to satisfaction of the CHO execution condition for the candidate MCG, the processor of the UE: the set of execution conditions for each candidate SCG in the one or more candidate SCGs is not satisfied when the UE completes a random access (RA) procedure to the candidate MCG; the set of execution conditions for each candidate SCG is not satisfied when a handover timer for the candidate MCG is stopped; the set of execution conditions for each of the candidate SCGs is not satisfied after a first time period after the UE completes the RA procedure to the candidate MCGs; the set of execution conditions for each candidate SCG is not satisfied when the CHO execution condition for the candidate MCG is satisfied; or the set of execution conditions for each of the candidate SCGs is not satisfied after a second time period from the satisfaction of the CHO execution conditions for the candidate MCGs.

10. The UE of claim 1, further configured to: stop evaluating the set of execution conditions for the one or more candidate SCGs in response to:

9. The UE of 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. In response to satisfaction of the CHO execution condition for the candidate MCG, the processor of the UE: performing a random access (RA) procedure to the candidate MCG based on the first RRC configuration; sending an RRC reconfiguration complete message to a candidate MN associated with said candidate MCG; The UE of claim 1 or claim 3, configured to:

11. A candidate master node (MN), A transceiver; a processor coupled to the transceiver; wherein the processor: receiving a radio resource control (RRC) reconfiguration complete message from a user equipment (UE) via the transceiver; transmitting, via the transceiver, to a candidate SN, an indication associated with a candidate secondary cell group (SCG); A candidate master node (MN) configured to perform the following:

12. The instructions are as follows: the candidate SCG is selected for cell addition; the candidate SCG is selected for cell switching; the candidate SCG is not selected for cell addition; the candidate SCG is not selected for cell switching; that no candidate SCG is selected for cell addition; that no candidate SCG is selected for cell switching; A conditional primary secondary cell group (PSCell) addition (CPA) procedure to any candidate SCG is not allowed to be performed during a conditional handover (CHO) recovery procedure to a candidate master cell group (MCG); No conditional PSCell change (CPC) procedure to any candidate SCG is allowed to be performed during said CHO recovery procedure; 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 RRC configuration for the candidate SCG is released by the UE for the CHO recovery procedure. The candidate MN according to claim 11, wherein the candidate MN exhibits at least one of the following:

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

14. The configuration information for the candidate SCG and the set of execution conditions for the candidate SCG are: a set of conditional primary secondary cell group (PSCell) addition (CPA) configuration information and CPA execution conditions for the candidate SCG; or A set of conditional PSCell change (CPC) configuration information and CPC execution conditions for the candidate SCG.

14. The candidate SN of claim 13, comprising:

15. The instructions are as follows: the candidate SCG is selected for cell addition; the candidate SCG is selected for cell switching; the candidate SCG is not selected for cell addition; the candidate SCG is not selected for cell switching; that no candidate SCG is selected for cell addition; that no candidate SCG is selected for cell switching; A conditional primary secondary cell group (PSCell) addition (CPA) procedure to any candidate SCG is not allowed to be performed during a conditional handover (CHO) recovery procedure to a candidate master cell group (MCG); No conditional PSCell change (CPC) procedure to any candidate SCG is allowed to be performed during said CHO recovery procedure; 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 RRC configuration for the candidate SCG is released by the UE for the CHO recovery procedure.

14. The candidate SN of claim 13, wherein the candidate SN exhibits at least one of the following:

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