EP4666670A1

EP4666670A1 - Conditional handover with candidate secondary cell group enhancements

Info

Publication number: EP4666670A1
Application number: EP23921820.9A
Authority: EP
Inventors: Fangli Xu; Naveen Kumar R PALLE VENKATA; Haijing Hu; Yuqin Chen
Original assignee: Apple Inc
Current assignee: Apple Inc
Priority date: 2023-02-16
Filing date: 2023-02-16
Publication date: 2025-12-24
Also published as: CN120693910A; WO2024168660A1

Abstract

Wireless communication systems implementing conditional handover (CHO) and conditional primary secondary cell (PSCell) addition or change (CPAC) are described herein. A CHO command from a network to a user equipment (UE) includes a CHO condition for a candidate master cell group (MCG) and one or more conditional primary secondary cell (PSCell) addition or change (CPAC) conditions for one or more corresponding candidate secondary cell groups (SCGs). In some cases, the UE is configured to use such information to always perform a PSCell addition or change when a handover (HO) of a CHO procedure occurs. In some cases, the UE is configured to use such information to perform separated CHO and CPAC procedures. In some cases, the UE is configured to use such information to dynamically determine whether a PSCell change of a CPAC procedure is performed in addition to a HO according to a CHO procedure.

Description

CONDITIONAL HANDOVER WITH CANDIDATE SECONDARY CELL GROUP ENHANCEMENTS

TECHNICAL FIELD

This application relates generally to wireless communication systems, including wireless communications systems implementing conditional handover (CHO) and conditional primary secondary cell (PSCell) addition or change (CPAC) .

BACKGROUND

Wireless mobile communication technology uses various standards and protocols to transmit data between a base station and a wireless communication device. Wireless communication system standards and protocols can include, for example, 3rd Generation Partnership Project (3GPP) long term evolution (LTE) (e.g., 4G) , 3GPP new radio (NR) (e.g., 5G) , and Institute of Electrical and Electronics Engineers (IEEE) 802.11 standard for wireless local area networks (WLAN) (commonly known to industry groups as) .
As contemplated by the 3GPP, different wireless communication systems standards and protocols can use various radio access networks (RANs) for communicating between a base station of the RAN (which may also sometimes be referred to generally as a RAN node, a network node, or simply a node) and a wireless communication device known as a user equipment (UE) . 3GPP RANs can include, for example, global system for mobile communications (GSM) , enhanced data rates for GSM evolution (EDGE) RAN (GERAN) , Universal Terrestrial Radio Access Network (UTRAN) , Evolved Universal Terrestrial Radio Access Network (E-UTRAN) , and/or Next-Generation Radio Access Network (NG-RAN) .
Each RAN may use one or more radio access technologies (RATs) to perform communication between the base station and the UE. For example, the GERAN implements GSM and/or EDGE RAT, the UTRAN implements universal mobile telecommunication system (UMTS) RAT or other 3GPP RAT, the E-UTRAN implements LTE RAT (sometimes simply referred to as LTE) , and NG-RAN implements NR RAT (sometimes referred to herein as 5G RAT, 5G NR RAT, or simply NR) . In certain deployments, the E-UTRAN may also implement NR RAT. In certain deployments, NG-RAN may also implement LTE RAT.
A base station used by a RAN may correspond to that RAN. One example of an E-UTRAN base station is an Evolved Universal Terrestrial Radio Access Network (E-UTRAN) Node B (also commonly denoted as evolved Node B, enhanced Node B, eNodeB, or eNB) . One example of an NG-RAN base station is a next generation Node B (also sometimes referred to as a g Node B or gNB) .
A RAN provides its communication services with external entities through its connection to a core network (CN) . For example, E-UTRAN may utilize an Evolved Packet Core (EPC) , while NG-RAN may utilize a 5G Core Network (5GC) .
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS
To easily identify the discussion of any particular element or act, the most significant digit or digits in a reference number refer to the figure number in which that element is first introduced.
FIG. 1A and FIG. 1B together illustrate a flow diagram for conditional handover that may be used in some wireless communications systems.
FIG. 2 illustrates a flow diagram corresponding to a first direction for handling a CHO with corresponding SCG considerations, according to embodiments herein.
FIG. 3A illustrates a flow diagram corresponding to a second direction for handling a CHO with corresponding SCG considerations, according to embodiments herein.
FIG. 3B illustrates a flow diagram corresponding to a second direction for handling a CHO with corresponding SCG considerations, according to embodiments herein.
FIG. 4A illustrates a flow diagram corresponding to a third direction for handling a CHO with corresponding SCG considerations, according to embodiments herein.
FIG. 4B illustrates a flow diagram corresponding to a third direction for handling a CHO with corresponding SCG considerations, according to embodiments herein.
FIG. 5 illustrates a method of a UE, according to embodiments herein.
FIG. 6 illustrates a method of a UE, according to embodiments herein.
FIG. 7 illustrates a method of a UE, according to embodiments herein.
FIG. 8 illustrates a method of a UE, according to embodiments herein.
FIG. 9 illustrates a method of a UE, according to embodiments herein.
FIG. 10 illustrates a method of a RAN, according to embodiments herein.
FIG. 11 illustrates an example architecture of a wireless communication system, according to embodiments disclosed herein.
FIG. 12 illustrates a system for performing signaling between a wireless device and a network device, according to embodiments disclosed herein.

DETAILED DESCRIPTION

Various embodiments are described with regard to a UE. However, reference to a UE is merely provided for illustrative purposes. The example embodiments may be utilized with any electronic component that may establish a connection to a network and is configured with the hardware, software, and/or firmware to exchange information and data with the network. Therefore, the UE as described herein is used to represent any appropriate electronic component.
Conditional handover (CHO) is a feature introduced to improve mobility robustness. In CHO, the UE may be configured with a handover command and an associated condition to be monitored. The UE may execute a corresponding handover when the associated condition (s) from the handover command become true.
Event conditions may include, for example, when a neighbor cell becomes better than a special cell (SpCell) by an offset (i.e., an A3 event condition) or when the SpCell becomes worse than a first threshold and the neighbor cell becomes better than a second threshold (i.e., an A5 event condition. The SpCell is the primary serving cell of either the master cell group (MCG) or secondary cell group (SCG) , and the offset may be either positive or negative.
When more than one candidate target cell satisfies the condition, it may be up to the UE implementation to determine which cell may execute handover (HO) . In certain wireless communication systems (e.g., 3GPP Release 17) , new conditional trigger conditions related to location and time may be defined to help enhance CHO for NR non-terrestrial networks (NTN) .
FIG. 1A and FIG. 1B together illustrate a flow diagram 100 for conditional handover that may be used in some wireless communications systems. The flow diagram 100 illustrates a wireless communication system that includes a UE 102, a source gNB 104, a target gNB 106, other potential target gNB (s) 108, an access and mobility management function (AMF) 110, and one or more user plane functions (UPF (s) ) 112. As can be seen, the flow diagram 100 corresponds to an intra-AMF/UPF case.
As illustrated in FIG. 1A, the flow diagram 100 begins with the handover preparation phase 114. Presently, user data 116 is transported between the UE 102 and the source gNB 104 and between the source gNB 104 and the UPF (s) 112, as illustrated. The AMF 110 provides the source gNB 104 with mobility control information 118. Then, the source gNB 104 configures measurements at the UE 102, and the UE 102 performs measurements and reports measurement results to the source gNB 104, during the measurement control and reports 120. Based on the receipt of the measurement reporting, the source gNB 104 makes a CHO decision 122. Based on the CHO decision 122, the source gNB 104 sends handover requests 124 to other gNBs (in the flow diagram 100, both the target gNB 106 that will ultimately be selected as the target of the handover and other potential target gNB (s) 108 are illustrated as receiving the handover requests 124) .
The other gNBs (e.g., the target gNB 106 and the other potential target gNB (s) 108) each perform admission control 126, and reply to the source gNB 104 with a handover request acknowledgement 128, including configuration of any CHO candidate cell (s) at that gNB.
FIG. 1B continues the flow diagram 100 discussed above in relation to FIG. 1A. The source gNB 104 sends the UE 102 a radio resource control (RRC) reconfiguration message 130 having the configuration for the CHO candidate cells. The UE 102 sends the source gNB 104 an RRC reconfiguration complete message 132.
The flow diagram 100 then enters the handover execution phase 134. The UE 102 evaluates 136 the CHO condition. Further, in some embodiments (e.g., where early data forwarding is used) the target gNB 106 sends the other potential target gNB (s) 108 an early status transfer message 138.
Then, the UE 102 detaches 140 from the old cell and synchronizes to a new cell (e.g., on the target gNB 106) . As part of this process, the UE performs an evaluation of conditions on the candidate cell (s) and determines that the new cell (on the target gNB 106) meets the conditions and that it will accordingly handover to that cell. The configuration for that new cell is then applied at the UE.
Further, user data 142 is transported between the UPF (s) 112 and the target gNB 106 and/or the other potential target gNB (s) 108 via the source gNB 104. The CHO handover completion 144 occurs once the UE 102 becomes associated with the new cell on the source gNB 104 (and the UE 102 may send an attendant RRC reconfiguration complete message to the target gNB 106) .
The flow diagram 100 then enters the handover completion phase 146. First, the target gNB 106 sends the source gNB 104 a handover success message 148. Then, the source gNB 104 sends the target gNB 106 a sequence number status transfer 150. User data 152 is transported between the UPF (s) 112 and the target gNB 106 via the source gNB 104. Finally, the source gNB 104 may send the target gNB 106 and/or the other potential target gNB (s) 108 a handover cancel message 154.
In some wireless communication networks, for (e.g., non-conditional) handover (HO) , the network may provide information regarding one or more candidate SCGs together with information regarding a target primary cell (PCell) together in the HO command to the UE. Further, in some wireless communication network, for CHO, the network may provide information regarding a candidate SCG together with information regarding a candidate target PCell in the CHO configuration that is provided to the UE.
In some wireless communication networks, with HO, a UE will execute a HO to a target PCell upon receiving the HO command specifying the target PCell. Further, with CHO, it may be that a UE first analyzes a CHO condition provided as part of the CHO configuration. Then, when the CHO condition is fulfilled, UE will execute a HO to the candidate target PCell.
In some wireless communications networks, when a UE starts to perform HO to target PCell, the UE may also start to access in a target SCG. In such cases, the UE transmits an RRCReconfigurationComplete message corresponding to each of the MCG configuration and the SCG configuration in the same message. For example, an SCG RRCReconfigurationComplete message may be embedded in the MCG RRCReconfigurationComplete message that is sent in the target PCell.
Further, the UE may then start separate T304 timers corresponding to access on each of the MCG and SCG. An expiration of the MCG T304 timer indicates a HO failure, in which case the UE may initiate a UE connection reestablishment procedure. An expiration of the SCG T304 timer indicates a SCG failure, in which case the UE may initiate a SCG failure recovery procedure via the MCG path.
In some wireless communication systems, intra-secondary node (SN) conditional primary secondary cell (PSCell) change (CPC) procedures may be supported. In some such cases, an SN can configure a UE with one or more candidate SCGs and their associated CPC condition (s) via the SCG path, where the CPC conditions describe conditions under which the UE may perform CPC with/to the candidate SCG. Then, the UE performs a CPC condition evaluation on the one or more candidate SCGs using the condition (s) , and executes an SCG change to the candidate SCG if the associated condition is met. In the event that the SCG change is a failure, the UE may declare an SCG failure, during which it may suspend any SCG transmission and/or transmit SCGFailure information to the network via the MCG path or initiate an RRC connection reestablishment procedure. Note that it may be in such cases that an SCG change within the purview of the SN in intra-SN embodiments described here may have no impact on a master node (MN) configuration.
In some wireless communication systems, inter-SN CPC and conditional PSCell addition or change (CPAC) are supported. In some such cases, a conditional SCG/PSCell addition or change may be initiated by either an SN or an MN. Any corresponding CPAC configuration may be coordinated between MN and SN, and then delivered to UE via MCG path.
In such cases, any associated CPAC condition (s) (conditions under which a UE is permitted to perform PSCell addition or change to/with a corresponding SCG/PSCell of the corresponding SCG) can be configured by the MN or by the SN. Upon receiving the configuration, UE may evaluate the CPAC condition (s) against the candidate SN (s) . If a CPAC condition is met, the UE may then initiate an SCG/PSCell addition or change (as the case may be) to the corresponding candidate SCG. In the event that the SCG/PSCell addition or change fails, UE may declare an SCG failure, during which it may suspend any SCG configuration and/or transmit an SCGFailureInformation message to the network via an MCG path or initiate an RRC Connection reestablishment procedure.
It may be that in some wireless communications systems, the simultaneous operation of HO/CHO procedures and CPAC procedures is not supported.
In some cases, it may be beneficial to improve the integration of considerations related to both a candidate CHO and one or more candidate SCGs. For example, it may be beneficial to configure a CHO configuration or command such that it includes both information related to a candidate MCG and one or more candidate SCG (s) for CPAC. In other words, a CHO command may be specified that includes information regarding a candidate MCG and candidate SCG (s) for CPAC (e.g., in new radio-dual connectivity (NR-DC) ) . In such cases, a CHO command may include an identification of and/or HO condition (s) for the target MCG and an identification of and/or PSCell addition or change condition (s) for one or more candidate SCGs.
It may be that some wireless communications systems support CHO procedures that involve a candidate MCG and a candidate SCG as part of the overall CHO procedure. In such cases, CHO configurations referring to or including CPAC configurations (e.g., as intended to be applicable together) may be supported. In some cases, when triggering CHO, a UE may perform or implement a CPAC configuration to start a corresponding CPAC evaluation. In such cases, it may be undefined (e.g., at the UE) whether the CHO evaluation and the CPAC evaluation are concurrent with each other, or if they are handled sequentially.
In some wireless communications systems, it may be that a UE does not execute CPAC unless the CHO condition is fulfilled (regardless of whether evaluation of the CHO and the CPAC occurred concurrently or sequentially) .
In some wireless communication systems that perform HOs or CHOs that also involve (e.g., non-conditional) SCG/PSCell additions or changes, it may be that the UE determines to execute the CHO based (only) on the CHO condition of the candidate target PCell. In other words, radio conditions of the target SCG may not be taken into account at this stage. Then, in some such circumstances, when the HO/CHO is executed, a dual connectivity (DC) mode may be assumed to be enabled, and the UE performs access in the candidate MCG and the candidate SCG. Upon completion, the network receives the HO/CHO complete and the SCG complete messages in a same (single) RRC message via the target PCell/the MCG path.
In some wireless communications systems implementing CHO and CPAC, when a UE selects the a target PCell (e.g., corresponding to the completion of the CHO condition evaluation) , there may be several cases. In a first case, UE has selected a candidate SCG (e.g., in addition to the completion of the CHO condition evaluation, the UE has also completed the CPAC condition evaluation and selected a candidate SCG for the CPAC) . In a second case, the UE has started the CPAC condition evaluation, but there is no SCG that meets the corresponding condition. In a third case, the UE has not started CPAC evaluation at the time of the completion of the CHO condition evaluation.
Corresponding to these cases, note that the UE can complete the HO with an SCG CPAC procedure in the target network in the first case. However, the UE cannot complete the HO with an SCG CPAC procedure in the second and third cases, since UE has not identified an SCG which meets the CPAC condition by the time the HO initiation occurs.
Discussion herein relates to embodiments for CHO with CPAC for a candidate SCG that can be applied across all three of the above cases. Correspondingly, discussion herein relates to enhancements for the CHO with candidate SCG mechanism such that all three of the above cases may be covered.
Accordingly, various embodiments here discuss cases where the UE is configured to perform a CHO and where candidate SCGs are to be considered as part of an overall CHO mechanism.
In a first direction, it may be that a UE performs both HO to a PCell of an MCG and PSCell addition or change on an SCG in a target network, regardless of whether it has found that an SCG meets a corresponding CPAC condition. Under the first direction, new condition (s) may be defined to enable the UE to select a candidate SCG for the PSCell addition or change in the case that a candidate SCG that meets is corresponding CPAC condition has not been found.
In a second direction, the UE may be configured such that it executes separate CHO and CPAC procedures. In such circumstances, the UE may apply a non-dual-connectivity (non-DC) configuration/mode in/with a target PCell of a target MCG after CHO access and before any subsequent SCG/PSCell addition or change. In such cases, the network may provide at least two configurations of the target MCG, one of which corresponds to the non-DC mode and one of which corresponds to a DC mode (which may be provided in anticipation of a potential eventual success of CPAC after the CHO access) .
In a third direction, a HO type selection (e.g., with or without SCG/PSCell addition or change) depends on whether any candidate SCG meets its corresponding CPAC condition (s) when CHO is executed. In such cases, the target network may distinguish a HO type that is performed based on a received UE response message and apply the corresponding MCG configuration. In such cases, the HO type selected depends on whether a candidate SCG meets its CPAC condition (s) when a CHO is executed. In such cases, the network may provide at least two configurations of the target MCG, one of which corresponds to the non-DC mode and one of which corresponds to a DC mode (which may be provided in anticipation of a potential eventual success of CPAC after the CHO access) . In the event that HO type without an SCG/PSCell addition or change is used, whether to subsequently initiate an SCG/PSCell addition or change may depend on a UE capability and/or a network configuration.
CHO First Direction: HOs that Always Use a PSCell Addition or Change in the Target Network
A first direction for CHO corresponds to cases of CHO where a UE will perform HO to a target MCG and a PSCell addition or change to a candidate SCG, regardless of whether the UE can/has identified an SCG that meets its CPAC condition (s) . In such cases, if the UE is configured to perform a CHO with the use/analysis of one or more candidate SCGs, the UE always performs HO together with a PSCell addition or change to a candidate SCG in the target network.
In such cases, it may be that the UE and network work in a DC mode after the initiation of the HO in the network.
UE operation according to the first direction will now be described. A UE may receive a CHO command providing CHO condition (s) for a candidate MCG and CPAC condition (s) for one or more associated candidate SCGs. The UE starts the CHO condition evaluation, and selects the PCell of the candidate MCG/the candidate MCG as a target PCell/target MCG after determining that the candidate MCG meets CHO condition (s) corresponding to the MCG.
Note that in some of these cases, the UE (optionally) simultaneously performs condition evaluations for the one or more SCGs at the same time that is performs the CHO condition evaluation (e.g., the UE uses first radio frequency (RF) resources to perform a CPAC condition evaluation for one of the SCGs at the same time the UE uses second RF resources to perform the CHO condition evaluation) .
Then, when the UE initiates the HO to the target MCG, it will also perform PSCell addition or change with one of the candidate SCGs in the network. The candidate SCG with which the PSCell addition or change is performed can be selected according to one of various options.
In a first option, the selected (target) SCG is an SCG for which the UE has determined that corresponding configured CPAC condition (s) have been met.
In a second option, the selected (target) SCG is an SCG that meets S-criteria (e.g., the PSCell of the selected SCG is better than a predefined or configured threshold value) . In such cases, it may be that the selected SCG does not meet its corresponding configured CPAC condition (s) and/or that the UE has not made a determination whether or not the selected SCG has met its corresponding configured CPAC conditions.
In a third option, the selected (target) SCG is a default SCG. In some cases, the default SCG may have been indicated by the network. In some cases, the default SCG may be selected according to a predefined rule (e.g., the first SCG of the one or more associated candidate SCGs is understood to be the default SCG) This option may be applied in cases where, for example, the UE has not completed or has not started performing CPAC condition evaluation. Further, the UE may fall back to the use of a default SCG as in this third option in cases where it first uses the first option and/or the second option, but fails to identify any SCG that meets its corresponding CPAC condition (s) /the S-criteria, as the case may be.
Then, as part of the HO/PSCell addition or change with the network, the UE may embed an SCG complete message in an RRC reconfiguration complete message (e.g., that also includes a HO complete message) . Then, the UE may start separate (individual) T304 timers corresponding to each of the MCG and the SCG.
After the HO/PSCell addition or change is complete, the UE may release the one or more candidate SCGs autonomously. Alternatively, this release may be based on some condition. For example, the one or more candidate SCGs may be released in the case that the UE does not support a subsequent SCG/PSCell addition or change, and/or in the case where the network is configured to explicitly indicate whether to keep or release the one or more candidate SCGs and makes the indication to release the one or more candidate SCGs.
Under the first direction, the network, upon receiving a HO complete message from the UE, operates with the UE in a DC mode.
FIG. 2 illustrates a flow diagram 200 corresponding to a first direction for handling a CHO with corresponding SCG considerations, according to embodiments herein. The flow diagram 200 illustrates a wireless communication system that includes a UE 202, a source MN 204 (labelled “S-MN” in FIG. 2) , a source SN 206 (labelled “S- SN” in FIG. 2) , a candidate MN 208 (labelled “C-MN” in FIG. 2) , a first candidate SN 210 (labelled “C-SN1” in FIG. 2) and a second candidate SN 212 (labelled “C-SN2” in FIG. 2) .
The start condition for the flow diagram 200 is that the UE 202 is served by the source MN 204. The source MN 204 then sends the UE 202 a CHO command 214. The CHO command 214 includes one or more configurations for a candidate MCG (referred to as “C-MCG” in FIG. 2) associated with the candidate MN 208, along with one or more CHO condition (s) for performing HO to the candidate MN 208. In some cases, the one or more configurations for the candidate MN 408 may include a first configuration for the UE to operate on the candidate MN 208 in a DC mode and a second configuration for the UE to operate on the candidate MN 208 in a non-DC mode.
Further, the CHO command 214 includes a configuration for a first candidate SCG (referred to as “C-SCG1” in FIG. 2) associated with the first candidate SN 210, along with one or more CPAC condition (s) for performing a PSCell addition or change to the first candidate SCG. Finally, the CHO command 214 includes the CHO command 214 includes a configuration for a second candidate SCG (referred to as “C-SCG2” in FIG. 2) associated with the second candidate SN 212, along with one or more CPAC condition (s) for performing a PSCell addition or change to the second candidate SCG. Note that the use a configuration and condition (s) for two SCGs is given by way of example and not by way of limitation. In embodiments alternative to that illustrated in FIG. 2, this information may be provided for fewer or more than two SCGs.
After receiving the CHO command 214, the UE 202 evaluates 216 whether the candidate MCG meets its corresponding one or more CHO condition (s) during the illustrated time period. Optionally, it may be that the UE also evaluates 216 whether either of the first candidate SCG and the second candidate SCG meets their respective one or more CPAC condition (s) during the illustrated time period. In some such cases, it may be that the evaluation of the candidate MCG, the evaluation of the first candidate SCG, and the evaluation of the second candidate SCG are performed simultaneously.
The flow diagram 200 corresponds to a case where the UE 202 ultimately evaluates 216 that the candidate MCG meets its corresponding CHO conditions and determines that a corresponding HO to the candidate MCG on the candidate MN 208 is to be performed. In such a case, the UE 202 then proceeds to select one of the first candidate SCG and the second candidate SCG with which to perform PSCell addition or change (e.g., in addition to the handover to the candidate MCG) . Note that, corresponding to FIG. 2, the process of selecting a candidate SCG with which to perform PSCell addition or change may be referred to as, for example, selecting a “target SCG. ”
The flow diagram 200 corresponds to the case where the selected (target) candidate SCG with which to perform PSCell addition or change is the first candidate SCG corresponding to the first candidate SN 210. The selection of the first candidate SCG may occur according to multiple options.
In a first option, the UE 202 selects the first candidate SCG because it has determined that CPAC condition (s) for the first candidate SCG (e.g., as received in the CHO command 214) have been met.
In a second option, the UE 202 selects the first candidate SCG because it has determined that the first candidate SCG has met corresponding S-criteria. In such cases, it may be that the first candidate SCG does not meet its corresponding CPAC condition (s) from the CHO command 214, and/or that the UE 202 has not made a determination that the first candidate SCG has met such CPAC condition (s) .
In a third option, the UE 202 selects the first candidate SCG because the first candidate SCG has been explicitly indicated by the network for this use. This option may be applied in cases where, for example, the UE 202 has not completed or has not started performing CPAC condition evaluation prior to the time of the HO on the MCG.
The UE performs the UE-side functions related to the HO and the PSCell addition or change. After performing the UE-side functions of the HO to the candidate MCG and the PSCell addition or change to the first candidate SCG, the UE 202 delivers 220 a HO complete message and an SCG complete message (labelled “SN1 complete” in FIG. 2) to the candidate MN 208 on the (new) MCG path. These messages may be delivered as part of a (same) RRC reconfiguration complete message 222, as illustrated.
These messages inform the candidate MN 208 that UE-side functions of the HO to the candidate MCG and the PSCell addition or change to the first candidate SCG have been completed by the UE. The candidate MN 208 forwards 224 the SCG complete message to the first candidate SN 210, which informs the first candidate SN 210 that the UE-side functions of the PSCell addition or change to the first candidate SCG are completed. Accordingly, the candidate MN 208 and the first candidate SN 210 are enabled to operate with the UE 202 using, respectively, the candidate MCG and the first candidate SCG. Note that, as illustrated, the configuration used by the candidate MN 208 and the UE 202 is a DC mode 226, corresponding to the use by the UE 202 of both the candidate MN 208 and the first candidate SN 210 (e.g., as such configuration was provided in the CHO command 314) .
Finally, it is noted that while the first direction has been described in relation to a CHO command providing CHO condition (s) for a candidate MCG and CPAC condition (s) for one or more associated candidate SCGs, it is contemplated that functionalities of the first direction could be implemented in relation to a HO command having a configuration to simply perform a (non-conditional) HO to an MCG along with CPAC condition (s) for use relative to one or more associated candidate SCGs. In such a case, it may be that the UE treats this strict HO case equivalently as CHO cases that have been described for the first direction where the UE has determined that a CHO condition for a candidate MCG has been fulfilled (and thus is performing HO) .
CHO Second Direction: UE Uses Separate CHO and CPAC Procedures
A second direction for CHO corresponds to cases of CHO where the CHO procedure and a corresponding CPAC procedure are separately handled. In such cases, a UE performs a CHO procedure first, and after CHO procedure is complete, the UE performs a corresponding CPAC procedure. In such cases, it may be that the UE may start evaluation (s) on one or more candidate SCGs after a target PCell/atarget candidate MCG is selected.
UE operation according to the second direction will now be discussed. A UE may receive a CHO command providing CHO condition (s) for a candidate MCG and CPAC condition (s) for one or more associated candidate SCGs. The UE starts the CHO condition evaluation, and selects the PCell of the candidate MCG/the candidate MCG as a target PCell/target MCG after determining that the candidate MCG meets CHO condition (s) corresponding to the MCG.
Note that in some of these cases, the UE (optionally) simultaneously performs condition evaluations for the one or more SCGs at the same time that it performs the CHO condition evaluation (e.g., the UE uses first RF resources to perform a CPAC condition evaluation for one of the SCGs at the same time the UE uses second RF resources to perform a CHO condition evaluation) .
Upon selecting the candidate MCG, the UE initiates CHO without targeting an SCG of a PSCell addition or change in the target network. Upon finalizing the UE-side functions of this HO, the UE communicates with the network on the candidate MCG in a non-DC mode.
Then, after the HO, the UE performs (e.g., continues to perform) CPAC condition evaluation for the one or more candidate SCGs. As a result, the UE may select a target SCG from within the candidate SCGs (in the case that the target SCG meets its corresponding CPAC condition (s) ) .
It may be that such a selection may be configured to occur within a time period T. In such a case, if a candidate SCG is successfully selected within the time period T, the UE may execute a PSCell addition procedure (including an update of the MCG configuration being used from, for example, a non-DC configuration to a DC configuration) , and then proceed to deliver an SCG complete message to the network (e.g., on either of the MCG or the SCG) .
However, if no candidate SCG is selected during time period T (due to no candidate SCG meeting its corresponding CPAC condition (s) during the time period T) , the UE may discard the one or more candidate SCG configurations and/or stop the CPAC condition evaluation corresponding to the one or more SCG configuration. In such a case, the UE would remain in the non-DC mode going forward.
In other cases, it may be that no time period T is used, and that the UE continues to evaluate CPAC conditions going forward.
Under the second direction, upon receiving a HO complete message, the network may understand that the UE will enable an MCG configuration for non-DC use.
Further, upon receiving an SCG complete message (e.g., subsequent to the prior receipt of an HO complete message) , the network may understand that the UE will enable an MCG configuration for DC use and that the UE will further coordinate with the selected SCG to complete the DC procedure.
Finally, in some cases under the second direction, it may be that the UE and/or the network retain configurations for the one or more candidate SCGs, such that a subsequent CPAC procedure based on these configurations can be executed at a later time.
FIG. 3A illustrates a flow diagram 300 corresponding to a second direction for handling a CHO with corresponding SCG considerations, according to embodiments herein. The flow diagram 300 illustrates a wireless communication system that includes a UE 302, a source MN 304 (labelled “S-MN” in FIG. 3A) , a source SN 306 (labelled “S-SN” in FIG. 3A) , a candidate MN 308 (labelled “C-MN” in FIG. 3A) , a first candidate SN 310 (labelled “C-SN1” in FIG. 3A) and a second candidate SN 312 (labelled “C-SN2” in FIG. 3A) .
The start condition for the flow diagram 300 is that the UE 302 is served by the source MN 304. The source MN 304 then sends the UE 302 a CHO command 314. The CHO command 314 includes one or more configurations for a candidate MCG (referred to as “C-MCG” in FIG. 3A) associated with the candidate MN 308, along with one or more CHO condition (s) for performing HO to the candidate MN 308. In some cases, the one or more configurations may include a first configuration for the UE to operate on the candidate MN 308 in a DC mode and a second configuration for the UE to operate on the candidate MN 308 in a non-DC mode.
Further, the CHO command 314 includes a configuration for a first candidate SCG (referred to as “C-SCG1” in FIG. 3A) associated with the first candidate SN 310, along with one or more CPAC condition (s) for performing a PSCell addition or change to the first candidate SCG. Finally, the CHO command 314 includes a configuration for a second candidate SCG (referred to as “C-SCG2” in FIG. 3A) associated with the second candidate SN 312, along with one or more CPAC condition (s) for performing a PSCell addition or change to the second candidate SCG. Note that the use a configuration and condition (s) for two SCGs is given by way of example and not by way of limitation. In embodiments alternative to that illustrated in FIG. 3A, this information may be provided for fewer or more than two SCGs.
After receiving the CHO command 314, the UE 202 evaluates 316 whether the candidate MCG meets its corresponding one or more CHO condition (s) during the illustrated time period. Optionally, it may be that the UE also evaluates 316 whether either of the first candidate SCG and the second candidate SCG meets their respective one or more CPAC condition (s) during the illustrated time period. In some such cases, it may be that the evaluation of the candidate MCG, the evaluation of the first candidate SCG, and the evaluation of the second candidate SCG are performed simultaneously.
The flow diagram 300 corresponds to a case where the UE 302 ultimately evaluates 316 that the candidate MCG meets its corresponding CHO conditions and accordingly determines that a corresponding HO to the candidate MCG on the candidate MN 308 is to be performed. In such a case, the UE 302 performs UE-side functions of the HO to the candidate MCG, and begins operating on the candidate MCG according to a non-DC configuration for the candidate MCG (e.g., as was provided in the CHO command 314) .
The UE 302 then delivers 318 a first RRC reconfiguration complete message 320 including a HO complete message to the candidate MN 308. This HO complete message informs the candidate MN 308 that UE-side functions of the HO to the candidate MCG have been completed by the UE. This causes the candidate MN 308 to begin operation with the UE 302 in a non-DC mode 322.
After sending the first RRC reconfiguration complete message 320, the UE then evaluates 324 whether any of the one or more candidate SCGs meet their corresponding CPAC condition (s) . The case of the flow diagram 300 of FIG. 3A corresponds to a case where the UE 302 determines that the first candidate SCG corresponding to the first candidate SN 310 has met its corresponding CPAC condition (s) . This determination may be made within a time period T 326 that occurs after the HO to the candidate MN 308 is performed by the UE.
In response to determining that the first candidate SCG has met its corresponding CPAC condition (s) , the UE 302 performs UE-side function of a PSCell addition procedure with the first candidate SCG. The UE 302 then delivers 318 a second RRC reconfiguration complete message 330 including an SCG complete message (labelled “SN1 complete” in FIG. 3A) to the candidate MN 308. The candidate MN 308 then forwards 332 this SCG complete message to the first candidate SN 310. Alternatively, the UE 302 could instead send the SCG complete message directly to the first candidate SN 310. This SCG complete message informs the first candidate SN 310 that UE-side functions of the PSCell addition with respect to the first candidate SCG have been completed by the UE. This causes the first candidate SN 310 to begin operation with the UE 302.
As noted, at this juncture, the network and the UE 302 each switch from operating in the non-DC mode 322 (that was previously used after the non-DC mode 322) to a DC mode 334 (corresponding to the use by the UE 302 of both the candidate MN 308 and the first candidate SN 310) . As part of this process, the UE 302 may switch from the use of a first configuration for the candidate MCG corresponding to a non-DC use of the MCG to a second configuration for the candidate MCG corresponding to a DC use of the MCG (e.g., as these configurations were provided in the CHO command 314) .
FIG. 3B illustrates a flow diagram 336 corresponding to a second direction for handling a CHO with corresponding SCG considerations, according to embodiments herein.
The flow diagram 336 illustrates the UE 302, the source MN 304 (labelled “S-MN”in FIG. 3B) , the source SN 306 (labelled “S-SN” in FIG. 3B) , the candidate MN 308 (labelled “C-MN” in FIG. 3B) , the first candidate SN 310 (labelled “C-SN1” in FIG. 3B) and the second candidate SN 312 (labelled “C-SN2” in FIG. 3B) that were discussed in relation to FIG. 3A. Further, the operations of the flow diagram 336 match the operations as described in relation to the flow diagram 300 up to the point that the UE 302 evaluates 324 whether any of the one or more candidate SCGs meet their corresponding CPAC condition (s) .
However, differently than the case of the flow diagram 300 of FIG. 3A, the case of the flow diagram 336 of FIG. 3B corresponds to a case where the UE 302 determines that the no candidate SCG (e.g., neither of the first candidate SCG corresponding to the first candidate SN 310 nor the second candidate SCG corresponding to the second candidate SN 312) meets its corresponding CPAC condition (s) within the time period T 326.
As illustrated, in such a case, it may be that the UE 302 stops 338 evaluating the one or more SCGs (e.g., stop evaluating the first candidate SN 310 and the second candidate SN 312) . Further, as illustrated, the UE 302 and the network may use the non-DC mode 322 going forward after this period (rather than using a DC mode such as the DC mode 334 described in the flow diagram 300 of FIG. 3A) .
Finally, it is noted that while the second direction has been described in relation to a CHO command providing CHO condition (s) for a candidate MCG and CPAC condition (s) for one or more associated candidate SCGs, it is contemplated that functionalities of the second direction could be implemented in relation to a HO command having a configuration to simply perform a (non-conditional) HO to an MCG along with CPAC condition (s) for use relative to one or more associated candidate SCGs. In such a case, it may be that the UE treats this strict HO case equivalently as CHO cases that have been described for the second direction where the UE has determined that a CHO condition for a candidate MCG has been fulfilled (and thus is performing HO) .
CHO Third Direction: UE Performs HO Type Selection based on SCG Selection Situation
A third direction for CHO corresponds to cases of CHO where the UE determines whether or not to perform PSCell addition or change with a HO. Note that herein, the use of “HO type” refers to the notion that one type of HO is performed along with a corresponding PSCell addition or change, while another type of HO is performed without any corresponding PSCell addition or change also being performed.
Under the third direction, a choice of whether to initiate a HO with or without a corresponding SCG/PCell addition or change depends on whether any of one or more configured candidate SCGs meets their corresponding CPAC condition (s) .
UE operation according to the third direction will now be described. A UE may receive a CHO command providing CHO condition (s) for a candidate MCG and CPAC condition (s) for one or more associated candidate SCGs. The UE starts the CHO condition evaluation, and selects the PCell of the candidate MCG/the candidate MCG as a target PCell/target MCG after determining that the candidate MCG meets CHO condition (s) corresponding to the MCG.
Note that in some of these cases, the UE (optionally) simultaneously performs condition evaluations for the one or more SCGs at the same time that is performs the CHO condition evaluation (e.g., the UE uses first RF resources to perform a CPAC condition evaluation for one of the SCGs at the same time the UE uses second RF resources to perform a CHO condition evaluation) .
Then, when the UE initiates the HO to the target MCG, the operation of the UE may be according to one of multiple cases.
In a first case, at the time of the HO, the UE has been able to identify that (at least) one candidate SCG has met its corresponding CPAC condition (s) . In this case, the UE initiates a HO to the UE that has a corresponding SCG/PSCell addition or change to the candidate SCG. In other words, the UE performs both the HO to the candidate MCG and the PSCell addition or change with/to the SCG.
In a second case, at the time of the HO, the UE has not identified that any candidate SCG has met its corresponding CPAC condition (s) . In such a case, the UE initiates the HO with the MCG without also performing a corresponding SCG/PSCell addition or change. In such a case, the UE uses a non-DC MCG configuration for communicating with the MCG. Further the UE delivers (only) a HO complete message to the network via the PCell of the MCG (no additional SN complete/SCG complete message is sent by the UE) .
Note that in some embodiments of this second case that, after the HO, the UE may continue to evaluate the candidate SCGs (e.g., as is described herein in relation to the second direction) and may be allowed to perform a PSCell addition or change with a candidate SCG that meets its corresponding CPAC condition within a time period T.
After the HO and PSCell addition or change (if any) are complete, the UE may release the one or more candidate SCGs autonomously. Alternatively, this release may be based on some condition. For example, the one or more candidate SCGs may be released in the case that the UE does not support a subsequent SCG/PSCell change, and/or in the case where the network is configured to explicitly indicate whether to keep or release the one or more candidate SCGs and makes the indication to release the one or more candidate SCGs.
Under the third direction, the network determines whether or not to enable a first MCG configuration for a multiple-RAT dual connectivity (MR-DC) mode (a DC mode) or a second MCG configuration for a non-DC mode based on whether or not an SN complete message/SCG complete message is received with a HO complete message sent by the UE. For the case where HO without a corresponding SCG/PSCell addition or change is performed, the network may simply apply the second MCG configuration for the non-DC mode for communicating with the UE.
FIG. 4A illustrates a flow diagram 400 corresponding to a third direction for handling a CHO with corresponding SCG considerations, according to embodiments herein. The flow diagram 400 illustrates a wireless communication system that includes a UE 402, a source MN 404 (labelled “S-MN” in FIG. 4A) , a source SN 406 (labelled “S-SN” in FIG. 4A) , a candidate MN 408 (labelled “C-MN” in FIG. 4A) , a first candidate SN 410 (labelled “C-SN1” in FIG. 4A) and a second candidate SN 412 (labelled “C-SN2” in FIG. 4A) .
The start condition for the flow diagram 400 is that the UE 402 is served by the source MN 404. The source MN 404 then sends the UE 302 a CHO command 414. The CHO command 414 includes one or more configurations for a candidate MCG (referred to as “C-MCG” in FIG. 4A) associated with the candidate MN 408, along with one or more CHO condition (s) for performing HO to the candidate MN 408. In some cases, the one or more configurations may include a first configuration for the UE to operate on the candidate MN 408 in a DC mode and a second configuration for the UE to operate on the candidate MN 408 in a non-DC mode.
Further, the CHO command 414 includes a configuration for a first candidate SCG (referred to as “C-SCG1” in FIG. 4A) associated with the first candidate SN 410, along with one or more CPAC condition (s) for performing a PSCell addition or change to the first candidate SCG. Finally, the CHO command 414 includes a configuration for a second candidate SCG (referred to as “C-SCG2” in FIG. 4A) associated with the second candidate SN 412, along with one or more CPAC condition (s) for performing a PSCell addition or change to the second candidate SCG. Note that the use a configuration and condition (s) for two SCGs is given by way of example and not by way of limitation. In embodiments alternative to that illustrated in FIG. 4A, this information may be provided for fewer or more than two SCGs.
After receiving the CHO command 414, the UE 402 evaluates 416 whether the candidate MCG meets its corresponding one or more CHO condition (s) during the illustrated time period, and whether either of the first candidate SCG and the second candidate SCG meets their respective one or more CPAC condition (s) during the illustrated time period. In some such cases, it may be that the evaluation of the candidate MCG, the evaluation of the first candidate SCG, and the evaluation of the second candidate SCG are performed simultaneously.
The flow diagram 400 corresponds to a case where the UE 402 ultimately evaluates 416 that the candidate MCG meets its corresponding CHO conditions and determines that a corresponding HO to the candidate MCG on the candidate MN 408 is to be performed, and where the UE 402 further evaluates 416 that the first candidate SCG meets its corresponding CPAC condition (s) and determines that a corresponding PSCell addition or change is to be performed.
The UE performs the UE-side functions related to the HO and the PSCell addition or change. After performing the UE-side functions of the HO to the candidate MCG and the PSCell addition or change to the first candidate SCG, the UE 402 delivers 418 a HO complete message and an SCG complete message (labelled “SN1 complete” in FIG. 4A) to the candidate MN 408 on the (new) MCG path. These messages may be delivered as part of a (same) RRC reconfiguration complete message 420, as illustrated.
These messages inform the candidate MN 408 that UE-side functions of the HO to the candidate MCG and the PSCell addition or change to the first candidate SCG have been completed by the UE. The candidate MN 408 forwards 422 the SCG complete message to the first candidate SN 410, which informs the first candidate SN 410 that the UE-side functions of the PSCell addition or change to the first candidate SCG are completed. Accordingly, the candidate MN 408 and the first candidate SN 410 are enabled to operate with the UE 402 using, respectively, the candidate MCG and the first candidate SCG. Note that, as illustrated, the configuration used by the candidate MN 408 and the UE 402 is a DC mode 424 corresponding to the use by the UE 402 of both the candidate MN 408 and the first candidate SN 410 (e.g., as this configuration was provided in the CHO command 414) .
FIG. 4B illustrates a flow diagram 426 corresponding to a third direction for handling a CHO with corresponding SCG considerations, according to embodiments herein.
The flow diagram 426 illustrates the UE 402, the source MN 404 (labelled “S-MN” in FIG. 4B) , the source SN 406 (labelled “S-SN” in FIG. 4B) , the candidate MN 408 (labelled “C-MN” in FIG. 4B) , the first candidate SN 410 (labelled “C-SN1” in FIG. 4B and the second candidate SN 412 (labelled “C-SN2” in FIG. 4B) that were discussed in relation to FIG. 4A. Further, the operations of the flow diagram 426 match the operations as described in relation to the flow diagram 400 up to the point that the UE 402 evaluates 416 whether the candidate MCG meets is corresponding CHO condition (s) and whether any of the one or more candidate SCGs meet their corresponding CPAC condition (s) .
However, differently than the case of the flow diagram 400 of FIG. 4A, the case of the flow diagram 426 of FIG. 4B corresponds to a case where the UE 402 determines that the no candidate SCG (e.g., neither of the first candidate SCG corresponding to the first candidate SN 410 nor the second candidate SCG corresponding to the second candidate SN 412) meets its corresponding CPAC condition (s) .
As illustrated, in such a case, it may be that the UE 402 does not select/use an SCG for a PSCell addition or change (no PSCell addition or change is performed) . Further, as illustrated, the UE 402 and the network may use the non-DC mode 432 going forward after this period rather than using a DC mode such as the DC mode 424 described in the flow diagram 400 of FIG. 4A (e.g., according to the non-DC configuration for the candidate MN 408 that was provided in the CHO command 414) .
Finally, it is noted that while the third direction has been described in relation to a CHO command providing CHO condition (s) for a candidate MCG and CPAC condition (s) for one or more associated candidate SCGs, it is contemplated that functionalities of the third direction could be implemented in relation to a HO command having a configuration to simply perform a (non-conditional) HO to an MCG along with CPAC condition (s) for use relative to one or more associated candidate SCGs. In such a case, it may be that the UE treats this strict HO case equivalently as CHO cases that have been described for the third direction where the UE has determined that a CHO condition for a candidate MCG has been fulfilled (and thus is performing HO) .
FIG. 5 illustrates a method 500 of a UE, according to embodiments herein. The method 500 includes receiving 502, from a network, a CHO command comprising a CHO condition for a candidate MCG and a first CPAC condition for a first candidate SCG.
The method 500 further includes evaluating 504 that the candidate MCG meets the CHO condition and that the first candidate SCG meets the first CPAC condition.
The method 500 further includes performing 506 a HO to the candidate MCG and a PSCell addition or change to the first candidate SCG based on the evaluation that the candidate MCG meets the CHO condition and that the first candidate SCG meets the first CPAC condition, such that the UE operates in a DC mode.
In some embodiments of the method 500, the CHO command further comprises a second CPAC condition for a second candidate SCG.
In some embodiments of the method 500, the evaluation that the candidate MCG meets the CHO condition and the evaluation that the first candidate SCG meets the first CPAC condition occur simultaneously.
In some embodiments, the method 500 further includes transmitting, to a master node (MN) of the candidate MCG, an RRC reconfiguration complete message comprising each of a HO complete message and an SCG complete message.
FIG. 6 illustrates a method 600 of a UE, according to embodiments herein. The method 600 includes receiving 602, from a network, a CHO command comprising a CHO condition for a candidate MCG and a first CPAC condition for a first candidate SCG.
The method 600 further includes evaluating 604 that the candidate MCG meets the CHO condition.
The method 600 further includes evaluating 606 that the first candidate SCG meets S-criteria.
The method 600 further includes performing 608 a HO to the candidate MCG and a PSCell change to the first candidate SCG based on the evaluation that the candidate MCG meets the CHO condition and the evaluation that the first candidate SCG meets the S-criteria, such that the UE operates in a DC mode.
In some embodiments of the method 600, the CHO command further comprises a second CPAC condition for a second candidate SCG.
In some embodiments of the method 600, the evaluation that the candidate MCG meets the CHO condition and the evaluation that the first candidate SCG meets the S-criteria occur simultaneously.
In some embodiments, the method 600 further includes transmitting, to a master node (MN) of the candidate MCG, a RRC reconfiguration complete message comprising each of a HO complete message and an SCG complete message.
FIG. 7 illustrates a method 700 of a UE, according to embodiments herein. The method 700 includes receiving 702, from a network, a CHO command comprising a CHO condition for a candidate MCG and a first conditional CPAC condition for a first candidate SCG.
The method 700 further includes identifying 704 that the first candidate SCG is a default SCG.
The method 700 further includes evaluating 706 that the candidate MCG meets the CHO condition.
The method 700 further includes performing 708 a HO to the candidate MCG and a PSCell change to the first candidate SCG based on the evaluation that the candidate MCG meets the CHO condition and the identifying that the first candidate SCG is the default SCG, such that the UE operates in a DC mode.
In some embodiments of the method 700, the identifying that the first candidate SCG is the default SCG is based on a network indication that the first candidate SCG is the default SCG.
In some embodiments of the method 700, the identifying that the first candidate SCG is the default SCG is based on a preconfigured rule.
In some embodiments of the method 700, the CHO command further comprises a second CPAC condition for a second candidate SCG.
In some embodiments, the method 700 further includes transmitting, to a master node (MN) of the candidate MCG, a RRC reconfiguration complete message comprising each of a HO complete message and an SCG complete message.
FIG. 8 illustrates a method 800 of a UE, according to embodiments herein. The method 800 includes receiving 802, from a network, a CHO command comprising a CHO condition for a candidate MCG and one or more conditional CPAC conditions for one or more corresponding candidate SCGs.
The method 800 further includes evaluating 804 that the candidate MCG meets the CHO condition.
The method 800 further includes performing 806 a HO to the candidate MCG based on the evaluation that the candidate MCG meets the CHO condition, such that the UE operates in a non-DC mode.
The method 800 further includes transmitting 808, to an MN of the candidate MCG, a first RRC reconfiguration complete message comprising a HO complete message.
The method 800 further includes evaluating 810, after the HO to the candidate MCG, whether any of the one or more SCGs meets its corresponding CPAC condition.
In some embodiments of the method 800, the evaluating whether any of the one or more SCGs meets its corresponding CPAC condition comprises evaluating that a first candidate SCG of the one or more candidate SCG meets a corresponding first CPAC condition of the one or more CPAC conditions, and the method 800 further includes performing a PSCell addition with the first candidate SCG based on the evaluating that the first candidate SCG meets the first CPAC condition, such that the UE operates in a DC mode, and transmitting, to the network, a second RRC reconfiguration complete message comprising an SCG complete message.
In some embodiments of the method 800, the evaluating whether any of the one or more SCGs meets its corresponding CPAC condition comprises determining, at the end of a time period T that begins after the HO to the candidate MCG, that no SCG met its corresponding CPAC condition during the time period T, and the UE, after the time period T, stops the evaluating whether any of the one or more SCGs meets its corresponding CPAC condition and remains in the non-DC mode.
FIG. 9 illustrates a method 900 of a UE, according to embodiments herein. The method 900 includes receiving 902, from a network, a CHO command comprising a CHO condition for a candidate MCG and one or more CPAC conditions for one or more corresponding candidate SCGs.
The method 900 further includes evaluating 904 that the candidate MCG meets the CHO condition.
The method 900 further includes evaluating 906, prior to a HO to the candidate MCG, that none of the one or more candidate SCGs meets its corresponding CPAC condition.
The method 900 further includes performing 908 the HO to the candidate MCG based on the evaluation that the candidate MCG meets the CHO condition, such that the UE operates in a non-DC mode.
The method 900 further includes transmitting 910, to an MN of the candidate MCG, a first RRC reconfiguration complete message comprising a HO complete message.
In some embodiments, the method 900 further includes evaluating, within a time period T that begins after the HO to the candidate MCG, that a first candidate SCG of the one or more SCGs meets a corresponding first CPAC condition of the one or more CPAC conditions, performing a PSCell addition with the first candidate SCG based on the evaluating that the first SCG meets the first CPAC condition, such that the UE operates in a DC mode, and transmitting, to the MN of the candidate MCG, a second RRC reconfiguration complete message comprising an SCG complete message.
In some embodiments, the method 900 further includes releasing the one or more candidate SCGs based on a determination that the UE does not support a use of the one or more candidate SCGs subsequent to the HO.
In some embodiments, the method 900 further includes receiving a network indication to release the one or more candidate SCGs after the HO, and releasing the one or more candidate SCGs after the HO based on the network indication.
FIG. 10 illustrates a method 1000 of a RAN, according to embodiments herein. The method 1000 includes sending 1002, to a UE, a CHO command comprising a CHO condition for a candidate MCG and one or more CPAC conditions for one or more corresponding candidate SCGs.
The method 1000 further includes receiving 1004, from the UE, an RRC reconfiguration complete message that is responsive to the CHO command.
The method 1000 further includes operating 1006 with the UE in one of a non-DC mode and a DC mode based on contents of the RRC reconfiguration complete message.
In some embodiments of the method 1000, the RAN operates with the UE in the non-DC mode when the RRC reconfiguration message does not include an SCG complete message.
In some embodiments of the method 1000, the RAN operates with the UE in the DC mode when the RRC reconfiguration message includes an SCG complete message.
FIG. 11 illustrates an example architecture of a wireless communication system 1100, according to embodiments disclosed herein. The following description is provided for an example wireless communication system 1100 that operates in conjunction with the LTE system standards and/or 5G or NR system standards as provided by 3GPP technical specifications.
As shown by FIG. 11, the wireless communication system 1100 includes UE 1102 and UE 1104 (although any number of UEs may be used) . In this example, the UE 1102 and the UE 1104 are illustrated as smartphones (e.g., handheld touchscreen mobile computing devices connectable to one or more cellular networks) , but may also comprise any mobile or non-mobile computing device configured for wireless communication.
The UE 1102 and UE 1104 may be configured to communicatively couple with a RAN 1106. In embodiments, the RAN 1106 may be NG-RAN, E-UTRAN, etc. The UE 1102 and UE 1104 utilize connections (or channels) (shown as connection 1108 and connection 1110, respectively) with the RAN 1106, each of which comprises a physical communications interface. The RAN 1106 can include one or more base stations (such as base station 1112 and base station 1114) that enable the connection 1108 and connection 1110.
In this example, the connection 1108 and connection 1110 are air interfaces to enable such communicative coupling, and may be consistent with RAT (s) used by the RAN 1106, such as, for example, an LTE and/or NR.
In some embodiments, the UE 1102 and UE 1104 may also directly exchange communication data via a sidelink interface 1116. The UE 1104 is shown to be configured to access an access point (shown as AP 1118) via connection 1120. By way of example, the connection 1120 can comprise a local wireless connection, such as a connection consistent with any IEEE 802.11 protocol, wherein the AP 1118 may comprise arouter. In this example, the AP 1118 may be connected to another network (for example, the Internet) without going through a CN 1124.
In embodiments, the UE 1102 and UE 1104 can be configured to communicate using orthogonal frequency division multiplexing (OFDM) communication signals with each other or with the base station 1112 and/or the base station 1114 over a multicarrier communication channel in accordance with various communication techniques, such as, but not limited to, an orthogonal frequency division multiple access (OFDMA) communication technique (e.g., for downlink communications) or a single carrier frequency division multiple access (SC-FDMA) communication technique (e.g., for uplink and ProSe or sidelink communications) , although the scope of the embodiments is not limited in this respect. The OFDM signals can comprise a plurality of orthogonal subcarriers.
In some embodiments, all or parts of the base station 1112 or base station 1114 may be implemented as one or more software entities running on server computers as part of a virtual network. In addition, or in other embodiments, the base station 1112 or base station 1114 may be configured to communicate with one another via interface 1122. In embodiments where the wireless communication system 1100 is an LTE system (e.g., when the CN 1124 is an EPC) , the interface 1122 may be an X2 interface. The X2 interface may be defined between two or more base stations (e.g., two or more eNBs and the like) that connect to an EPC, and/or between two eNBs connecting to the EPC. In embodiments where the wireless communication system 1100 is an NR system (e.g., when CN 1124 is a 5GC) , the interface 1122 may be an Xn interface. The Xn interface is defined between two or more base stations (e.g., two or more gNBs and the like) that connect to 5GC, between a base station 1112 (e.g., a gNB) connecting to 5GC and an eNB, and/or between two eNBs connecting to 5GC (e.g., CN 1124) .
The RAN 1106 is shown to be communicatively coupled to the CN 1124. The CN 1124 may comprise one or more network elements 1126, which are configured to offer various data and telecommunications services to customers/subscribers (e.g., users of UE 1102 and UE 1104) who are connected to the CN 1124 via the RAN 1106. The components of the CN 1124 may be implemented in one physical device or separate physical devices including components to read and execute instructions from a machine-readable or computer-readable medium (e.g., a non-transitory machine-readable storage medium) .
In embodiments, the CN 1124 may be an EPC, and the RAN 1106 may be connected with the CN 1124 via an S1 interface 1128. In embodiments, the S1 interface 1128 may be split into two parts, an S1 user plane (S1-U) interface, which carries traffic data between the base station 1112 or base station 1114 and a serving gateway (S-GW) , and the S1-MME interface, which is a signaling interface between the base station 1112 or base station 1114 and mobility management entities (MMEs) .
In embodiments, the CN 1124 may be a 5GC, and the RAN 1106 may be connected with the CN 1124 via an NG interface 1128. In embodiments, the NG interface 1128 may be split into two parts, an NG user plane (NG-U) interface, which carries traffic data between the base station 1112 or base station 1114 and a user plane function (UPF) , and the S1 control plane (NG-C) interface, which is a signaling interface between the base station 1112 or base station 1114 and access and mobility management functions (AMFs) .
Generally, an application server 1130 may be an element offering applications that use internet protocol (IP) bearer resources with the CN 1124 (e.g., packet switched data services) . The application server 1130 can also be configured to support one or more communication services (e.g., VoIP sessions, group communication sessions, etc. ) for the UE 1102 and UE 1104 via the CN 1124. The application server 1130 may communicate with the CN 1124 through an IP communications interface 1132.
FIG. 12 illustrates a system 1200 for performing signaling 1234 between a wireless device 1202 and a network device 1218, according to embodiments disclosed herein. The system 1200 may be a portion of a wireless communications system as herein described. The wireless device 1202 may be, for example, a UE of a wireless communication system. The network device 1218 may be, for example, a base station (e.g., an eNB or a gNB) of a wireless communication system.
The wireless device 1202 may include one or more processor (s) 1204. The processor (s) 1204 may execute instructions such that various operations of the wireless device 1202 are performed, as described herein. The processor (s) 1204 may include one or more baseband processors implemented using, for example, a central processing unit (CPU) , a digital signal processor (DSP) , an application specific integrated circuit (ASIC) , a controller, a field programmable gate array (FPGA) device, another hardware device, a firmware device, or any combination thereof configured to perform the operations described herein.
The wireless device 1202 may include a memory 1206. The memory 1206 may be a non-transitory computer-readable storage medium that stores instructions 1208 (which may include, for example, the instructions being executed by the processor (s) 1204) . The instructions 1208 may also be referred to as program code or a computer program. The memory 1206 may also store data used by, and results computed by, the processor (s) 1204.
The wireless device 1202 may include one or more transceiver (s) 1210 that may include radio frequency (RF) transmitter and/or receiver circuitry that use the antenna (s) 1212 of the wireless device 1202 to facilitate signaling (e.g., the signaling 1234) to and/or from the wireless device 1202 with other devices (e.g., the network device 1218) according to corresponding RATs.
The wireless device 1202 may include one or more antenna (s) 1212 (e.g., one, two, four, or more) . For embodiments with multiple antenna (s) 1212, the wireless device 1202 may leverage the spatial diversity of such multiple antenna (s) 1212 to send and/or receive multiple different data streams on the same time and frequency resources. This behavior may be referred to as, for example, multiple input multiple output (MIMO) behavior (referring to the multiple antennas used at each of a transmitting device and a receiving device that enable this aspect) . MIMO transmissions by the wireless device 1202 may be accomplished according to precoding (or digital beamforming) that is applied at the wireless device 1202 that multiplexes the data streams across the antenna (s) 1212 according to known or assumed channel characteristics such that each data stream is received with an appropriate signal strength relative to other streams and at a desired location in the spatial domain (e.g., the location of a receiver associated with that data stream) . Certain embodiments may use single user MIMO (SU-MIMO) methods (where the data streams are all directed to a single receiver) and/or multi user MIMO (MU-MIMO) methods (where individual data streams may be directed to individual (different) receivers in different locations in the spatial domain) .
In certain embodiments having multiple antennas, the wireless device 1202 may implement analog beamforming techniques, whereby phases of the signals sent by the antenna (s) 1212 are relatively adjusted such that the (joint) transmission of the antenna (s) 1212 can be directed (this is sometimes referred to as beam steering) .
The wireless device 1202 may include one or more interface (s) 1214. The interface (s) 1214 may be used to provide input to or output from the wireless device 1202. For example, a wireless device 1202 that is a UE may include interface (s) 1214 such as microphones, speakers, a touchscreen, buttons, and the like in order to allow for input and/or output to the UE by a user of the UE. Other interfaces of such a UE may be made up of made up of transmitters, receivers, and other circuitry (e.g., other than the transceiver (s) 1210/antenna (s) 1212 already described) that allow for communication between the UE and other devices and may operate according to known protocols (e.g., and the like) .
The wireless device 1202 may include a CHO module 1216. The CHO module 1216 may be implemented via hardware, software, or combinations thereof. For example, the CHO module 1216 may be implemented as a processor, circuit, and/or instructions 1208 stored in the memory 1206 and executed by the processor (s) 1204. In some examples, the CHO module 1216 may be integrated within the processor (s) 1204 and/or the transceiver (s) 1210. For example, the CHO module 1216 may be implemented by a combination of software components (e.g., executed by a DSP or a general processor) and hardware components (e.g., logic gates and circuitry) within the processor (s) 1204 or the transceiver (s) 1210.
The CHO module 1216 may be used for various aspects of the present disclosure, for example, aspects of FIG. 1A through FIG. 10. The CHO module 1216 may configure the wireless device 1202 to operate according to CHO mechanisms that include CPAC mechanisms, in the manner described herein.
The network device 1218 may include one or more processor (s) 1220. The processor (s) 1220 may execute instructions such that various operations of the network device 1218 are performed, as described herein. The processor (s) 1220 may include one or more baseband processors implemented using, for example, a CPU, a DSP, an ASIC, a controller, an FPGA device, another hardware device, a firmware device, or any combination thereof configured to perform the operations described herein.
The network device 1218 may include a memory 1222. The memory 1222 may be a non-transitory computer-readable storage medium that stores instructions 1224 (which may include, for example, the instructions being executed by the processor (s) 1220) . The instructions 1224 may also be referred to as program code or a computer program. The memory 1222 may also store data used by, and results computed by, the processor (s) 1220.
The network device 1218 may include one or more transceiver (s) 1226 that may include RF transmitter and/or receiver circuitry that use the antenna (s) 1228 of the network device 1218 to facilitate signaling (e.g., the signaling 1234) to and/or from the network device 1218 with other devices (e.g., the wireless device 1202) according to corresponding RATs.
The network device 1218 may include one or more antenna (s) 1228 (e.g., one, two, four, or more) . In embodiments having multiple antenna (s) 1228, the network device 1218 may perform MIMO, digital beamforming, analog beamforming, beam steering, etc., as has been described.
The network device 1218 may include one or more interface (s) 1230. The interface (s) 1230 may be used to provide input to or output from the network device 1218. For example, a network device 1218 that is a base station may include interface (s) 1230 made up of transmitters, receivers, and other circuitry (e.g., other than the transceiver (s) 1226/antenna (s) 1228 already described) that enables the base station to communicate with other equipment in a core network, and/or that enables the base station to communicate with external networks, computers, databases, and the like for purposes of operations, administration, and maintenance of the base station or other equipment operably connected thereto.
The network device 1218 may include a CHO module 1232. The CHO module 1232 may be implemented via hardware, software, or combinations thereof. For example, the CHO module 1232 may be implemented as a processor, circuit, and/or instructions 1224 stored in the memory 1222 and executed by the processor (s) 1220. In some examples, the CHO module 1232 may be integrated within the processor (s) 1220 and/or the transceiver (s) 1226. For example, the CHO module 1232 may be implemented by a combination of software components (e.g., executed by a DSP or a general processor) and hardware components (e.g., logic gates and circuitry) within the processor (s) 1220 or the transceiver (s) 1226.
The CHO module 1232 may be used for various aspects of the present disclosure, for example, aspects of FIG. 1A through FIG. 10. For example, the CHO module 1232 may configure the network device 1218 to operate with a wireless device 1202 that uses CHO mechanisms that include CPAC mechanisms, in the manner described herein.
Embodiments contemplated herein include an apparatus comprising means to perform one or more elements of any one of the method 500, the method 600, the method 700, the method 800, and/or the method 900. This apparatus may be, for example, an apparatus of a UE (such as a wireless device 1202 that is a UE, as described herein) .
Embodiments contemplated herein include one or more non-transitory computer-readable media comprising instructions to cause an electronic device, upon execution of the instructions by one or more processors of the electronic device, to perform one or more elements of any one of the method 500, the method 600, the method 700, the method 800, and/or the method 900. This non-transitory computer-readable media may be, for example, a memory of a UE (such as a memory 1206 of a wireless device 1202 that is a UE, as described herein) .
Embodiments contemplated herein include an apparatus comprising logic, modules, or circuitry to perform one or more elements of any one of the method 500, the method 600, the method 700, the method 800, and/or the method 900. This apparatus may be, for example, an apparatus of a UE (such as a wireless device 1202 that is a UE, as described herein) .
Embodiments contemplated herein include an apparatus comprising: one or more processors and one or more computer-readable media comprising instructions that, when executed by the one or more processors, cause the one or more processors to perform one or more elements of any one of the method 500, the method 600, the method 700, the method 800, and/or the method 900. This apparatus may be, for example, an apparatus of a UE (such as a wireless device 1202 that is a UE, as described herein) .
Embodiments contemplated herein include a signal as described in or related to one or more elements of any one of the method 500, the method 600, the method 700, the method 800, and/or the method 900.
Embodiments contemplated herein include a computer program or computer program product comprising instructions, wherein execution of the program by a processor is to cause the processor to carry out one or more elements of any one of the method 500, the method 600, the method 700, the method 800, and/or the method 900. The processor may be a processor of a UE (such as a processor (s) 1204 of a wireless device 1202 that is a UE, as described herein) . These instructions may be, for example, located in the processor and/or on a memory of the UE (such as a memory 1206 of a wireless device 1202 that is a UE, as described herein) .
Embodiments contemplated herein include an apparatus comprising means to perform one or more elements of the method 1000. This apparatus may be, for example, an apparatus of a base station (such as a network device 1218 that is a base station, as described herein) .
Embodiments contemplated herein include one or more non-transitory computer-readable media comprising instructions to cause an electronic device, upon execution of the instructions by one or more processors of the electronic device, to perform one or more elements of the method 1000. This non-transitory computer-readable media may be, for example, a memory of a base station (such as a memory 1222 of a network device 1218 that is a base station, as described herein) .
Embodiments contemplated herein include an apparatus comprising logic, modules, or circuitry to perform one or more elements of the method 1000. This apparatus may be, for example, an apparatus of a base station (such as a network device 1218 that is a base station, as described herein) .
Embodiments contemplated herein include an apparatus comprising: one or more processors and one or more computer-readable media comprising instructions that, when executed by the one or more processors, cause the one or more processors to perform one or more elements of the method 1000. This apparatus may be, for example, an apparatus of a base station (such as a network device 1218 that is a base station, as described herein) .
Embodiments contemplated herein include a signal as described in or related to one or more elements of the method 1000.
Embodiments contemplated herein include a computer program or computer program product comprising instructions, wherein execution of the program by a processing element is to cause the processing element to carry out one or more elements of the method 1000. The processor may be a processor of a base station (such as a processor (s) 1220 of a network device 1218 that is a base station, as described herein) . These instructions may be, for example, located in the processor and/or on a memory of the base station (such as a memory 1222 of a network device 1218 that is a base station, as described herein) .
For one or more embodiments, at least one of the components set forth in one or more of the preceding figures may be configured to perform one or more operations, techniques, processes, and/or methods as set forth herein. For example, a baseband processor as described herein in connection with one or more of the preceding figures may be configured to operate in accordance with one or more of the examples set forth herein. For another example, circuitry associated with a UE, base station, network element, etc. as described above in connection with one or more of the preceding figures may be configured to operate in accordance with one or more of the examples set forth herein.
Any of the above described embodiments may be combined with any other embodiment (or combination of embodiments) , unless explicitly stated otherwise. The foregoing description of one or more implementations provides illustration and description, but is not intended to be exhaustive or to limit the scope of embodiments to the precise form disclosed. Modifications and variations are possible in light of the above teachings or may be acquired from practice of various embodiments.
Embodiments and implementations of the systems and methods described herein may include various operations, which may be embodied in machine-executable instructions to be executed by a computer system. A computer system may include one or more general-purpose or special-purpose computers (or other electronic devices) . The computer system may include hardware components that include specific logic for performing the operations or may include a combination of hardware, software, and/or firmware.
It should be recognized that the systems described herein include descriptions of specific embodiments. These embodiments can be combined into single systems, partially combined into other systems, split into multiple systems or divided or combined in other ways. In addition, it is contemplated that parameters, attributes, aspects, etc. of one embodiment can be used in another embodiment. The parameters, attributes, aspects, etc. are merely described in one or more embodiments for clarity, and it is recognized that the parameters, attributes, aspects, etc. can be combined with or substituted for parameters, attributes, aspects, etc. of another embodiment unless specifically disclaimed herein.
It is well understood that the use of personally identifiable information should follow privacy policies and practices that are generally recognized as meeting or exceeding industry or governmental requirements for maintaining the privacy of users. In particular, personally identifiable information data should be managed and handled so as to minimize risks of unintentional or unauthorized access or use, and the nature of authorized use should be clearly indicated to users.
Although the foregoing has been described in some detail for purposes of clarity, it will be apparent that certain changes and modifications may be made without departing from the principles thereof. It should be noted that there are many alternative ways of implementing both the processes and apparatuses described herein. Accordingly, the present embodiments are to be considered illustrative and not restrictive, and the description is not to be limited to the details given herein, but may be modified within the scope and equivalents of the appended claims.

Claims

A method of a user equipment (UE) , comprising:

receiving, from a network, a conditional handover (CHO) command comprising a CHO condition for a candidate master cell group (MCG) and a first conditional primary secondary cell (PSCell) addition or change (CPAC) condition for a first candidate secondary cell group (SCG) ;

evaluating that the candidate MCG meets the CHO condition and that the first candidate SCG meets the first CPAC condition; and

performing a handover (HO) to the candidate MCG and a PSCell addition or change to the first candidate SCG based on the evaluation that the candidate MCG meets the CHO condition and that the first candidate SCG meets the first CPAC condition, such that the UE operates in a dual connectivity (DC) mode.
The method of claim 1, wherein the CHO command further comprises a second CPAC condition for a second candidate SCG.
The method of claim 1, wherein the evaluation that the candidate MCG meets the CHO condition and the evaluation that the first candidate SCG meets the first CPAC condition occur simultaneously.
The method of claim 1, further comprising transmitting, to a master node (MN) of the candidate MCG, a radio resource control (RRC) reconfiguration complete message comprising each of a HO complete message and an SCG complete message.
A method of a user equipment (UE) , comprising:

receiving, from a network, a conditional handover (CHO) command comprising a CHO condition for a candidate master cell group (MCG) and a first conditional primary secondary cell (PSCell) addition or change (CPAC) condition for a first candidate secondary cell group (SCG) ;

evaluating that the candidate MCG meets the CHO condition;

evaluating that the first candidate SCG meets S-criteria;

performing a handover (HO) to the candidate MCG and a PSCell change to the first candidate SCG based on the evaluation that the candidate MCG meets the CHO condition and the evaluation that the first candidate SCG meets the S-criteria, such that the UE operates in a dual connectivity (DC) mode.
The method of claim 5, wherein the CHO command further comprises a second CPAC condition for a second candidate SCG.
The method of claim 5, wherein the evaluation that the candidate MCG meets the CHO condition and the evaluation that the first candidate SCG meets the S-criteria occur simultaneously.
The method of claim 5, further comprising transmitting, to a master node (MN) of the candidate MCG, a radio resource control (RRC) reconfiguration complete message comprising each of a HO complete message and an SCG complete message.
A method of a user equipment (UE) , comprising:

receiving, from a network, a conditional handover (CHO) command comprising a CHO condition for a candidate master cell group (MCG) and a first conditional primary secondary cell (PSCell) addition or change (CPAC) condition for a first candidate secondary cell group (SCG) ;

identifying that the first candidate SCG is a default SCG;

evaluating that the candidate MCG meets the CHO condition; and

performing a handover (HO) to the candidate MCG and a PSCell change to the first candidate SCG based on the evaluation that the candidate MCG meets the CHO condition and the identifying that the first candidate SCG is the default SCG, such that the UE operates in a dual connectivity (DC) mode.
The method of claim 9, wherein the identifying that the first candidate SCG is the default SCG is based on a network indication that the first candidate SCG is the default SCG.
The method of claim 9, wherein the identifying that the first candidate SCG is the default SCG is based on a preconfigured rule.
The method of claim 9, wherein the CHO command further comprises a second CPAC condition for a second candidate SCG.
The method of claim 9, further comprising transmitting, to a master node (MN) of the candidate MCG, a radio resource control (RRC) reconfiguration complete message comprising each of a HO complete message and an SCG complete message.
A method of a user equipment (UE) , comprising:

receiving, from a network, a conditional handover (CHO) command comprising a CHO condition for a candidate master cell group (MCG) and one or more conditional primary secondary cell (PSCell) addition or change (CPAC) conditions for one or more corresponding candidate secondary cell groups (SCGs) ;

evaluating that the candidate MCG meets the CHO condition;

performing a handover (HO) to the candidate MCG based on the evaluation that the candidate MCG meets the CHO condition, such that the UE operates in a non-dual connectivity (DC) mode;

transmitting, to a master node (MN) of the candidate MCG, a first radio resource control (RRC) reconfiguration complete message comprising a HO complete message; and

evaluating, after the HO to the candidate MCG, whether any of the one or more SCGs meets its corresponding CPAC condition.
The method of claim 14, wherein the evaluating whether any of the one or more SCGs meets its corresponding CPAC condition comprises evaluating that a first candidate SCG of the one or more candidate SCG meets a corresponding first CPAC condition of the one or more CPAC conditions; and further comprising:

performing a PSCell addition with the first candidate SCG based on the evaluating that the first candidate SCG meets the first CPAC condition, such that the UE operates in a dual connectivity (DC) mode; and

transmitting, to the network, a second RRC reconfiguration complete message comprising an SCG complete message.
The method of claim 14, wherein:

the evaluating whether any of the one or more SCGs meets its corresponding CPAC condition comprises determining, at the end of a time period T that begins after the HO to the candidate MCG, that no SCG met its corresponding CPAC condition during the time period T;

the UE, after the time period T, stops the evaluating whether any of the one or more SCGs meets its corresponding CPAC condition and remains in the non-DC mode.
A method of a user equipment (UE) , comprising:

receiving, from a network, a conditional handover (CHO) command comprising a CHO condition for a candidate master cell group (MCG) and one or more conditional primary secondary cell (PSCell) addition or change (CPAC) conditions for one or more corresponding candidate secondary cell groups (SCGs) ;

evaluating that the candidate MCG meets the CHO condition;

evaluating, prior to a handover (HO) to the candidate MCG, that none of the one or more candidate SCGs meets its corresponding CPAC condition;

performing the HO to the candidate MCG based on the evaluation that the candidate MCG meets the CHO condition, such that the UE operates in a non-dual connectivity (DC) mode; and

transmitting, to a master node (MN) of the candidate MCG, a first radio resource control (RRC) reconfiguration complete message comprising a HO complete message.
The method of claim 17, further comprising:

evaluating, within a time period T that begins after the HO to the candidate MCG, that a first candidate SCG of the one or more SCGs meets a corresponding first CPAC condition of the one or more CPAC conditions;

performing a PSCell addition with the first candidate SCG based on the evaluating that the first SCG meets the first CPAC condition, such that the UE operates in a dual connectivity (DC) mode; and

transmitting, to the MN of the candidate MCG, a second RRC reconfiguration complete message comprising an SCG complete message.
The method of claim 17, further comprising releasing the one or more candidate SCGs based on a determination that the UE does not support a use of the one or more candidate SCGs subsequent to the HO.
The method of claim 17, further comprising:

receiving a network indication to release the one or more candidate SCGs after the HO; and

releasing the one or more candidate SCGs after the HO based on the network indication.
A method of a radio access network (RAN) , comprising:

sending, to a user equipment (UE) , a conditional handover (CHO) command comprising a CHO condition for a candidate master cell group (MCG) and one or more conditional primary secondary cell (PSCell) addition or change (CPAC) conditions for one or more corresponding candidate secondary cell groups (SCGs) ;

receiving, from the UE, an RRC reconfiguration complete message that is responsive to the CHO command; and

operating with the UE in one of a non-dual connectivity (DC) mode and a DC mode based on contents of the RRC reconfiguration complete message.
The method of claim 21, wherein the RAN operates with the UE in the non-DC mode when the RRC reconfiguration message does not include an SCG complete message.
The method of claim 21, wherein the RAN operates with the UE in the DC mode when the RRC reconfiguration message includes an SCG complete message.
An apparatus comprising means to perform the method of any of claim 1 to claim 23.
A computer-readable media comprising instructions to cause an electronic device, upon execution of the instructions by one or more processors of the electronic device, to perform the method of any of claim 1 to claim 23.
An apparatus comprising logic, modules, or circuitry to perform the method of any of claim 1 to claim 23.