Managing candidate cell configurations for a conditional preparation procedure - Patents.com

Abstract

Disclosed herein is a method and system for managing candidate cell configurations for a user equipment (UE) initially in communication with at least a first node. The method is implemented in a second node and includes receiving, by the second node, from the first node a request for connection with the second node, the request including a procedure indicator, and transmitting, by the second node to the first node, depending on the procedure indicator, one of a list of two or more conditional configurations or a single conditional configuration to be used, the list of two or more conditional configurations or the single conditional configuration to be used, to the UE.

Description

[Technical field]

[0001] The present disclosure relates generally to wireless communications, and more particularly to managing conditional configurations for multi-connections, such as conditional handover and conditional secondary node addition or modification procedures. [Background technology]

[0002] This Background is provided for the purpose of generally presenting the context of the present disclosure. The work of the inventors identified herein, to the extent that it is described in this Background section, and aspects of the present specification that may not qualify as prior art at the time of filing, are not admitted expressly or impliedly as prior art to the present disclosure.

[0003] In telecommunication systems, a user equipment (UE) can simultaneously utilize resources from multiple Radio Access Network (RAN) nodes, such as base stations or components of distributed base stations interconnected by a backhaul. When the network nodes support different Radio Access Technologies (RATs), the connection type is called Multi-Radio Dual Connectivity (MR-CD). When a UE operates in MR-DC, one base station acts as a Master Node (MN) covering a Primary Cell (PCell) and the other base station acts as a Secondary Node (SN) covering a Primary Secondary Cell (PSCell). The UE communicates with the MN via the PCell and with the SN via the PSCell. In other scenarios, the UE transfers its wireless connection from one base station to another. For example, the serving base station may decide to handover the UE to a target base station and initiate the handover procedure.

[0004] 3GPP (registered trademark, hereinafter the same) specification TS37.340 v16.6.0 describes procedures for a UE to add or change the SN in a dual connectivity (DC) scenario. These procedures involve messaging between RAN nodes (e.g., RRC signaling and preparation). This messaging generally introduces latency, which increases the probability that the SN addition or SN change procedure will fail. These legacy procedures, which do not include the conditions checked in the UE, can be referred to as "immediate" SN addition and "immediate" SN change procedures.

[0005] More recently, conditional procedures (i.e., conditional SN or PSCell addition / modification) have been considered for both SN and PSCell addition / modification. Unlike the immediate procedures discussed above, the conditional procedures do not add or modify an SN or PSCell or perform a handover until the UE determines that a condition is met.

[0006] To configure a conditional procedure, the RAN provides the UE with conditions along with configurations that allow the UE to communicate with an appropriate base station or via an appropriate cell when the conditions are met. For example, in the case of a conditional addition of a base station as an SN or a candidate cell as a PSCell, the RAN provides the UE with conditions to be met before the UE can add that base station as an SN or that candidate cell as a PSCell, and provides the UE with configurations that allow the UE to communicate with that base station or PSCell after the conditions are met.

[0007] In an immediate PSCell addition or immediate PSCell modification procedure, the RAN (i.e., MN or SN) sends an RRC reconfiguration message containing multiple configuration parameters to the UE, and the UE attempts to connect to the (target) PSCell configured by the RRC reconfiguration message. After the UE successfully connects to the SN via the PSCell, the UE communicates with the SN on the PSCell using multiple configuration parameters and security key(s) associated with the PSCell and derived from one or more security configuration parameters in the RRC reconfiguration message. The SN also derives security key(s) that match the security key(s) derived from the UE. After the UE successfully connects to the PSCell, the RAN (e.g., SN) communicates data with the UE using the matching security key(s) and multiple configuration parameters.

[0008] Using this technique, when the MN completes the configuration for a conditional SN procedure (e.g., conditional SN addition or conditional SN cell change), the MN cannot determine which candidate secondary cell the UE will connect to in the future. Furthermore, since the UE connects to a secondary cell only conditional on the satisfaction of one or more conditions, the MN cannot determine whether the UE will connect to any of the candidate cells.

[0009] Conditional procedures present particular challenges for accurate and timely management of candidate configurations such as CHO configuration(s) and / or C-SN configuration(s). Management may include preparing and advancing the candidate configuration(s). For example, during CHO preparation of the UE, the candidate MN may set up a dual connection with the SN for the UE. It is not clear how the candidate MN and SN prepare the dual connection for the UE. In another embodiment, while the MN is initiating the CHO procedure, the MN may receive a request from the SN for a conditional PSCell change. In this case, it is not clear how the MN processes the request. Summary of the Invention

[0010] One exemplary embodiment of these techniques is a method for managing candidate cell configurations for a user equipment (UE) initially in communication with at least a first node, the method being implemented in a second node and including receiving, by the second node and from the first node, a request for connection with the second node, the request including at least a procedure indicator, and transmitting, by the second node to the first node, in response to the procedure indicator, one of a list of two or more conditional configurations or a single conditional configuration, the list of two or more conditional configurations or the single conditional configuration to be used by the UE.

[0011] Another example embodiment of these techniques is a method of managing candidate cell configurations for a user equipment (UE) initially in communication with at least a first node, the method being implemented in the first node and including: transmitting, by the first node to a second node, a request for connection with the second node including an indication of at least one of (i) a conditional handover (CHO), or (ii) an addition or modification of a conditional primary secondary cell (C-PSCell); in response to transmitting the request for connection, receiving, by the first node and from the second node, a response with an information element configured to include a list of two or more conditional configurations or a single conditional configuration based on at least the indication; transmitting, by the first node, a radio resource message based on the at least two or more conditional configurations or the single conditional configuration. [Brief description of the drawings]

[0012] [Figure 1A] FIG. 1 is a block diagram of an example system in which a base station and / or user equipment (UE) can implement the techniques of the present disclosure to manage conditional procedures associated with a master node (MN) or a secondary node (SN). [Figure 1B] FIG. 2 is another block diagram of an example system in which a radio access network (RAN) and user devices can implement the techniques of this disclosure to manage conditional procedures associated with a MN or SN. [Figure 1C] FIG. 2 is a block diagram of an example of a base station including a central unit (CU) and a distributed unit (DU) capable of operating in the system of FIG. 1A or FIG. 1B. [Diagram 2] FIG. 2 is a block diagram of an example protocol stack by the UE of FIGS. 1A-1B that can communicate with a base station. [Figure 3A] An example scenario is shown in which a MN receives and processes one or more SN configurations from a Conditional SN (C-SN) during a C-SN addition procedure. [Figure 3B] A similar scenario to that of FIG. 3A is shown, but the C-SN addition procedure is explicitly initiated by the MN. [Figure 3C] It illustrates a similar scenario to that of FIG. 3A, but the C-SN addition procedure is explicitly initiated by the SN. [Figure 4A] An example scenario is shown in which a MN initiates a conditional handover (CHO) with a conditional MN (C-MN), and the C-MN further performs a C-SN addition procedure for secondary cell group (SCG) configuration. [Figure 4B] 4A , where the C-SN addition procedure is for a Conditional Primary-Secondary Cell (PSCell) Addition or Modification (CPAC) configuration. [Figure 4C] 4B illustrates a scenario similar to that of FIG. 4B, where the handover is an immediate handover (IHO) with a target MN (T-MN) rather than a conditional handover with a C-MN. [Figure 4D] 4B illustrates a scenario similar to that of FIG. 4B, in which the MN initiates a handover cancellation procedure after initiating CHO. [Figure 4E] 4D illustrates a scenario similar to that of FIG. 4D, in which the C-MN initiates a handover cancellation procedure. [Figure 4F] 4D , a scenario similar to that of FIG. 4D is shown, in which the MN initiates a handover cancellation procedure due to a decision to perform an IHO. [Figure 5A]An example of a scenario in which the MN uses the SCG-configured C-SN addition procedure to initiate a CHO procedure between two distributed units in the MN is shown. [Figure 5B] 5A , where the C-SN addition procedure is for a CPAC. [Figure 5C] 5B illustrates a scenario similar to that of FIG. 5A, where the MN cancels handover and / or conditional configuration(s). [Figure 5D] 5C , a scenario similar to that of FIG. 5C is shown, in which the MN initiates a handover cancellation procedure due to a decision to perform an IHO between two distributed units of the MN. [Figure 6] 1 is a flowchart of an example method, implemented in an MN, for performing a conditional SN procedure at a C-SN to determine whether the SN is permitted to generate a single conditional configuration or list of configurations. [Figure 7A] 1 is a flowchart of an example method, implemented in an SN, for performing a conditional SN procedure at an MN and determining whether to generate a single conditional configuration or a list of configurations based on whether an SN request message includes a conditional indicator. [Figure 7B] 7B is a flowchart of an example method, similar to that of FIG. 7A, implemented in an SN, in which the SN makes a decision based on whether the SN request message includes a CHO indicator or a CPAC indicator. [Figure 8] 1 is a flowchart of an example method, implemented in an MN, for the SN to indicate to the C-SN that it will perform a conditional SN procedure with the C-SN and generate at most one conditional configuration. [Figure 9] 1 is a flowchart of an example method, implemented in an MN, for performing a conditional SN procedure in a C-SN and generating an RRC message including a conditional configuration. [Figure 10] 7B is a flowchart of an example method, similar to that of FIG. 7A, implemented in an SN in which the SN generates a conditional configuration or list of configurations based on cells whose measurements exceed a predetermined threshold. [Figure 11A] 1 is a flowchart of an example method, implemented in an MN, for performing a conditional SN procedure at an SN and determining how to recover an RRC message and / or a conditional configuration or list of configurations from an SN response. [Figure 11B] 11B is a flowchart of an example method, similar to that of FIG. 11A, implemented in a MN in which the MN makes a decision based on whether the SN request message includes a CPAC indicator. [Figure 12A] FIG. 13 is a flow diagram of an example method performed at a MN for indicating to a SN not to perform a conditional SN procedure. [Figure 12B] 12B is a flowchart of an example method, similar to that of FIG. 12A, implemented in an MN that prevents the SN from performing a conditional SN procedure in response to the MN receiving a message from an SN. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] As described in more detail below, the UE and / or one or more base stations manage conditional procedures such as a conditional PSCell addition or modification (CPAC). This disclosure may also separately refer to the conditional PSCell addition procedure and the conditional PSCell modification procedure using the acronyms CPA and CPC, respectively.

[0014] According to one embodiment, the network node manages candidate cell configurations for the UE by sending a request for connection with a conditional secondary node to the conditional secondary node. The conditional secondary node responds with an information element (IE) configured to include either a list of configurations or a single conditional configuration depending on the content of the connection request. The connection request may include, for example, a conditional indicator, a conditional handover (CHO) request, a conditional primary-secondary cell (PSCell) addition or change (CPAC) indicator, etc.

[0015] After the network node receives a response from the conditional secondary node and the condition is satisfied, the network node facilitates communication with the UE. As used herein, the term "condition" may refer to a single detectable state or event (e.g., a particular signal quality indicator exceeding a threshold) or a logical combination of such states or events (e.g., "Condition A and Condition B" or "(Condition A or Condition B) and Condition C, etc.)." Alternatively, after receiving a response from the conditional secondary node but before the condition is satisfied, the process may be interrupted by a CHO or Immediate Handover (IHO) event. The network node then decides whether to delay or cancel the candidate cell configuration or handover event.

[0016] 1A, an exemplary wireless communication system 100 includes a UE 102, a base station (BS) 104A, a base station 106A, and a core network (CN) 110. The base stations 104A and 106A may operate within a RAN 105 connected to the same core network (CN) 110. The CN 110 may be implemented as an evolved packet core (EPC) 111 or a fifth generation (5G) core (5GC) 160, for example.

[0017] Among other components, the EPC 111 may include a Serving Gateway (SGW) 112, a Mobility Management Entity (MME) 114, and a Packet Data Network Gateway (PGW) 116. The SGW 112 is generally configured to forward user plane packets related to voice calls, video calls, Internet traffic, etc., and the MME 114 is configured to manage authentication, registration, paging, and other related functions. The PGW 116 provides connectivity from the UE to one or more external packet data networks, such as an Internet network and / or an Internet Protocol (IP) Multimedia Subsystem (IMS) network. The 5GC 160 includes a User Plane Function (UPF) 162, an Access and Mobility Management Function (AMF) 164, and / or a Session Management Function (SMF) 166. Generally speaking, the UPF 162 is configured to forward user plane packets generally related to voice calls, video calls, Internet traffic, etc., the AMF 164 is configured to manage authentication, registration, paging and other related functions, and the SMF 166 is PDU session.

[0018] As shown in FIG. 1A, the base station 104A supports a cell 124A, and the base station 106A supports a cell 126A. Furthermore, each of the base stations 104A, 106A may support multiple cells. The base station 106A may also support, for example, a cell 126C. The cells 124A and 126A may partially overlap, whereby the UE 102 may communicate in DC with the base station 104A and the base station 106A acting as a master node (MN) and a secondary node (SN), respectively. The MN 104A and the SN 106A may support an X2 or Xn interface to directly exchange messages during the DC scenario and other scenarios described below. In general, the CN 110 may be connected to any suitable number of base stations supporting NR and / or EUTRA cells. An exemplary configuration in which the EPC 110 is connected to additional base stations is described below with reference to FIG. 1B.

[0019] The base station 104A comprises processing hardware 130, which may include one or more general-purpose processors, such as a CPU, and non-transitory computer-readable memory storing machine-readable instructions executable by the one or more general-purpose processors, and / or special-purpose processing units. In an exemplary implementation, the processing hardware 130 includes a conditional configuration controller 132 configured to manage conditional configuration of one or more conditional procedures, such as conditional handover (CHO), conditional PSCell addition or change (CPAC), or conditional SN addition or change (CSAC), when the base station 104A operates as a MN.

[0020] The base station 106A includes processing hardware 140, which may also include one or more general-purpose processors, such as a CPU, and non-transitory computer-readable memory storing machine-readable instructions executable by the one or more general-purpose processors, and / or special-purpose processing units. In an exemplary implementation, the processing hardware 140 includes a conditional configuration controller 142 configured to manage conditional configuration of one or more conditional procedures, such as CHO, CPAC, or CSAC, when the base station 106A operates as an SN.

[0021] 1A, UE 102 comprises processing hardware 150, which may include one or more general-purpose processors, such as a CPU, and non-transitory computer-readable memory storing machine-readable instructions executable by the one or more general-purpose processors, and / or special-purpose processing units. In an exemplary implementation, processing hardware 150 includes a UE conditional configuration controller 152 configured to manage one or more conditional procedures.

[0022] More specifically, the conditional configuration controllers 132, 142, and 152 can implement at least some of the techniques described with reference to the messaging and flow charts below. Although FIG. 1A illustrates the conditional configuration controllers 132 and 142 as separate components, in at least some of the scenarios, the base stations 104A and 106A can have similar implementations and, in different scenarios, operate as MN or SN nodes. In these implementations, each of the base stations 104A and 106A can implement both the conditional configuration controller 132 and the conditional configuration controller 142 to support MN and SN functionality, respectively.

[0023] In operation, the UE 102 may use radio bearers (e.g., DRBs or SRBs) that terminate at the MN 104A or the SN 106A at different times. The UE 102 may apply one or more security keys when communicating on the radio bearers in an uplink (UE 102 to BS) direction and / or a downlink (base station to UE 102) direction. The UE may communicate with the base stations 104A and 106A, possibly using different RATs. Although the following examples may specifically reference a particular RAT type, 5G NR or EUTRA, in general, the techniques of this disclosure may be applied to other suitable radio access and / or core network technologies.

[0024] 1B illustrates additional base stations 104B and 106B that may be included in the wireless communication system 100. The UE 102 initially connects to the base station 104A. The BSs 104B and 106B may have similar processing hardware as the base station 106A. The UE 102 initially connects to the base station 104A.

[0025] In some scenarios, the base station 104A may perform instant SN addition to configure the UE 102 to operate in dual connection (DC) with the base station 104A (through a PCell) and the base station 106A (through a PSCell other than the cell 126A). The base stations 104A and 106A operate as the MN and SN of the UE 102, respectively. The UE 102 may possibly operate using an MR-DC connection mode, for example, communicating with the base station 104A using 5G NR and communicating with the base station 106A using EUTRA, or communicating with the base station 104A using EUTRA and communicating with the base station 106A using 5G NR. The multi-connection coordination may help the two base stations to coordinate shared UE functions including operating frequency (e.g., band combination, frequency range), UE measurements and reporting (e.g., intra-frequency measurements, inter-frequency measurements, inter-RAT measurements, gap measurements), receive timing (e.g., DRX configuration, offset timing), and uplink power control (e.g., power headroom, maximum transmit power).

[0026] At some point, the MN 104A can perform an immediate SN change to change the SN of the UE 102 from the base station 106A (source SN, or "S-SN") to the base station 104B (target SN, or "T-SN") while the UE 102 is communicating with the MN 104A and the S-SN 106A in DC. In another scenario, the SN 106A can perform an immediate PSCell change to change the PSCell of the UE 102 to the cell 126A. In one embodiment, the SN 106A can transmit a configuration to change the PSCell to the cell 126A to the UE 102 via a signaling radio bearer (SRB) (e.g., SRB3) for immediate PSCell change. In another embodiment, the SN 106A can transmit a configuration to change the PSCell to the cell 126A to the UE 102 via the MN 104A for immediate PSCell change. The MN 104A can send a configuration to the UE 102 via the SRB1 to immediately change the PSCell to the cell 126A. Extending the multi-connection coordination can help the newly added base station coordinate the capabilities of the shared UEs.

[0027] In another scenario, the base station 104A may perform a conditional SN addition procedure to initially configure the base station 106B as the C-SN of the UE 102, i.e., perform a conditional SN addition or change (CSAC). At this time, the UE 102 may be in a single connection (SC) with the base station 104A, or in a DC with the base station 104A and the base station 106A. When the UE 102 is in a DC with the base station 104A and the base station 106A, the MN 104A may decide to perform the conditional SN addition procedure in response to a request received from the base station 106A, or in response to one or more measurement results received from the UE 102 or obtained by the MN 104A from measurements on signals received from the UE 102. In contrast to the immediate SN addition case described above, the UE 102 does not immediately attempt to connect to the C-SN 106B. In this scenario, the base station 104A again operates as a MN, but the base station 106B initially operates as a C-SN, not an SN.

[0028] More specifically, when the UE 102 receives the configuration of the C-SN 106B, the UE 102 does not connect to the C-SN 106B until the UE 102 determines that a certain condition is met (in some cases, the UE 102 can consider multiple conditions, but for convenience, the following description only refers to a single condition). Before the condition is met, multi-connection coordination is not necessary. However, it is useful as soon as the C-SN is connected. Once the UE 102 determines that the condition is met, the UE 102 connects to the C-SN 106B, and as a result, the C-SN 106B begins to operate as the SN 106B for the UE 102. Thus, the base station 106B operates as a C-SN rather than an SN, but the base station 106B is not yet connected to the UE 102 and therefore is not yet serving the UE 102. In some implementations, the UE 102 can disconnect from the SN 106A to connect to the C-SN 106B.

[0029] In yet another scenario, the UE 102 is in DC with the MN 104A (via a PCell) and with the SN 106A (via a PSCell other than the cell 126A, not shown in FIG. 1A). The SN 106A can perform a Conditional PSCell Addition or Modification (CPAC) to configure a Candidate PSCell (C-PSCell) 126A for the UE 102. When the UE 102 configures a Signaling Radio Bearer (SRB) (e.g., SRB3) to exchange RRC messages with the SN 106A, the SN 106A can transmit a configuration for the C-PSCell 126A to the UE 102 via the SRB, for example, in response to one or more measurement results that may be received from the UE 102 via the SRB or via the MN 104A, or may be obtained by the SN 106A from measurements on signals received from the UE 102. If via the MN 104A, the MN 104A receives the configuration of the C-PSCell 126A. In contrast to the immediate PSCell change case described above, the UE 102 does not immediately disconnect from the PSCell but attempts to connect to the C-PSCell 126A.

[0030] More specifically, when the UE 102 receives the configuration of the C-PSCell 126A, the UE 102 does not connect to the C-PSCell 126A until the UE 102 determines that a certain condition is met (in some cases, the UE 102 can consider multiple conditions, but for convenience, the following description only refers to a single condition). When the UE 102 determines that the condition is met, the UE 102 connects to the C-PSCell 126A, so that the C-PSCell 126A starts to operate as the PSCell 126A for the UE 102. Thus, while the cell 126A operates as a C-PSCell rather than a PSCell, the SN 106A may not yet be connected to the UE 102 via the cell 126A. In some implementations, the UE 102 may disconnect from the PSCell to connect to the C-PSCell 126A.

[0031] In some scenarios, the condition related to CSAC or CPAC may be signal strength / quality, which the UE 102 detects on the C-PSCell 126A of the SN 106A or on the C-PSCell 126B of the C-SN 106B exceeds a certain threshold or otherwise acceptable measurement. For example, if one or more measurement results the UE 102 obtains on the C-PSCell 126A exceed a threshold set by the MN 104A or the SN 106A, or exceed a predetermined or pre-set threshold, the UE 102 determines that the condition is met. If the UE 102 determines that the signal strength / quality on the C-PSCell 126A of the SN 106A is sufficiently good (again, measured against one or more quantitative thresholds or other quantitative indices), the UE 102 may perform a random access procedure on the C-PSCell 126A with the SN 106A to connect to the SN 106A. After the UE 102 successfully completes the random access procedure on the C-PSCell 126A, the C-PSCell 126A becomes the PSCell 126A for the UE 102. The SN 106A can then start communicating data (user plane data or control plane data) with the UE 102 via the PSCell 126A. In another example, if one or more measurement results that the UE 102 obtains on the C-PSCell 126B exceed a threshold set by the MN 104A or the C-SN 106B, or exceed a predetermined or pre-set threshold, the UE 102 determines that the condition is met. If the UE 102 determines that the signal strength / quality on the C-PSCell 126B of the C-SN 106B is sufficiently good (again, measured against one or more quantitative thresholds or other quantitative indices), the UE 102 may perform a random access procedure on the C-PSCell 126B with the C-SN 106B to connect to the C-SN 106B. After the UE 102 successfully completes the random access procedure on the C-PSCell 126B, the C-PSCell 126B becomes the PSCell 126B for the UE 102 and the C-SN 106B becomes the SN 106B.The SN 106B may then begin communicating data (user plane data or control plane data) with the UE 102 via the PSCell 126B.

[0032] In various configurations of the wireless communication system 100, the base station 104A can be implemented as a master eNB (MeNB) or master gNB (MgNB), and the base station 106A or 106B can be implemented as a secondary gNB (SgNB) or candidate SgNB (C-SgNB). The UE 102 can communicate with the base station 104A and the base station 106A or 106B (106A / B) via the same RAT, such as EUTRA or NR, or a different RAT. If the base station 104A is a MeNB and the base station 106A is a SgNB, the UE 102 can be in EUTRA-NR DC (EN-DC) with the MeNB and the SgNB. In this scenario, depending on the implementation, the MeNB 104A may or may not configure the base station 106B as a C-SgNB for the UE 102. In this scenario, the SgNB 106A may configure the cell 126A as a C-PSCell for the UE 102. The UE 102 may be in an MeNB and an SC if the base station 104A is an MeNB and the base station 106A is a C-SgNB for the UE 102. In this scenario, the MeNB 104A may or may not configure the base station 106B as another C-SgNB for the UE 102.

[0033] In some cases, the MeNB, SeNB, or C-SgNB is implemented as a ng-eNB rather than an eNB. When the base station 104A is a master ng-eNB (Mng-eNB) and the base station 106A is a SgNB, the UE 102 can be in a Next Generation (NG) EUTRA-NR DC (NGEN-DC) with the MeNB and the SgNB. In this scenario, the MeNB 104A may or may not configure the base station 106B as a C-SgNB for the UE 102. In this scenario, the SgNB 106A may configure the cell 126A as a C-PSCell to the UE 102. When the base station 104A is a Mng-NB and the base station 106A is a C-SgNB for the UE 102, the UE 102 can be in a SC with the Mng-NB. In this scenario, the Mng-eNB 104A may or may not configure the base station 106B as another C-SgNB to the UE 102.

[0034] When the base station 104A is an MgNB and the base stations 106A / B are SgNBs, the UE 102 may be in NR-NR DC (NR-DC) with the MgNB and SgNB. In this scenario, the MeNB 104A may or may not configure the base station 106B as a C-SgNB for the UE 102. In this scenario, the SgNB 106A may configure the cell 126A as a C-PSCell to the UE 102. When the base station 104A is an MgNB and the base station 106A is a C-SgNB for the UE 102, the UE 102 may be in an SC with the MgNB. In this scenario, the MgNB 104A may or may not configure the base station 106B as another C-SgNB for the UE 102.

[0035] If the base station 104A is an MgNB and the base stations 106A / B are secondary ng-eNBs (Sng-eNBs), the UE 102 may be in an NR-EUTRA DC (NE-DC) with the MgNB and Sng-eNB. In this scenario, the MgNB 104A may or may not configure the base station 106B as a C-Sng-eNB for the UE 102. In this scenario, the Sng-eNB 106A may configure the cell 126A as a C-PSCell to the UE 102. If the base station 104A is an MgNB and the base station 106A is a candidate Sng-eNB (C-Sng-eNB) for the UE 102, the UE 102 may be in an SC with the MgNB. In this scenario, the MgNB 104A may or may not configure the base station 106B as another C-Sng-eNB for the UE 102.

[0036] The base stations 104A, 106A, and 106B may be connected to the same core network (CN) 110, which may be an evolved packet core (EPC) 111 or a fifth generation core (5GC) 160. The base station 104A may be implemented as an eNB supporting an S1 interface for communicating with the EPC 111, an ng-eNB supporting an NG interface for communicating with the 5GC 160, or as a base station supporting an NR radio interface and an NG interface for communicating with the 5GC 160. The base station 106A may also be implemented as an EN-DC gNB (en-gNB) with an S1 interface to the EPC 111, an en-gNB that does not connect to the EPC 111, a gNB supporting an NR radio interface and an NG interface to the 5GC 160, or an ng-eNB supporting a EUTRA radio interface and an NG interface to the 5GC 160. To directly exchange messages during the scenarios described below, the base stations 104A, 106A, and 106B may support an X2 or Xn interface.

[0037] As shown in FIG. 1B, the base station 104A supports the cell 124A, the base station 104B supports the cell 124B, the base station 106A supports the cell 126A, and the base station 106B supports the cell 126B. The cells 124A and 126A may partially overlap as well as the cells 124A and 124B, and as a result, the UE 102 may communicate with the base station 104A (operating as an MN) and the base station 106A (operating as an SN) in DC, and after completing the SN change, may communicate with the base station 104A (operating as an MN) and the SN 104B. More specifically, when the UE 102 operates in DC with the base station 104A and the base station 106A, the base station 104A operates as an MeNB, Mng-eNB, or MgNB, and the base station 106A operates as an SgNB or Sng-eNB. The cells 124A and 126B may partially overlap. When the UE 102 is in SC with the base station 104A, the base station 104A operates as a MeNB, Mng-eNB, or MgNB, and the base station 106A operates as a C-SgNB or C-Sng-eNB. When the UE 102 operates in DC with the base station 104A and the base station 106A, the base station 104A operates as a MeNB, Mng-eNB, or MgNB, the base station 106A operates as a SgNB or Sng-eNB, and the base station 106B operates as a C-SgNB or C-Sng-eNB.

[0038] In general, the wireless communication network 100 may include any suitable number of base stations supporting NR cells and / or EUTRA cells. More specifically, the EPC 111 or 5GC 160 may be connected to any suitable number of base stations supporting NR cells and / or EUTRA cells. Although the following examples refer specifically to a particular CN type (EPC, 5GC) and RAT type (5G NR or EUTRA), in general, the techniques of this disclosure may also be applied to other suitable radio access technologies and / or core network technologies, such as sixth generation (6G) radio access and / or 6G core network or 5G NR-6G DC.

[0039] 1C illustrates an exemplary distributed implementation of a base station 194 (e.g., any of base stations 104A, 104B, 106A, 106B, or similar base stations). The base station of this implementation may include a central unit (CU) 172 and one or more distributed units (DU) 174. The CU 172 comprises processing hardware that may include one or more general-purpose processors, such as a CPU, and non-transitory computer-readable memory that stores machine-readable instructions executable by the one or more general-purpose processors, and / or special-purpose processing units. In one embodiment, the CU 172 comprises processing hardware 130. In another embodiment, the CU 172 comprises processing hardware 140. In an exemplary implementation, the processing hardware 140 includes a (C-)SN RRC controller configured to manage or control one or more RRC configurations and / or RRC procedures when the base station 194 operates as a SN or candidate SN (C-SN). Depending on the implementation, the base station(s) 104A, 104B, 106A, and / or 106B may have the same or similar hardware or functionality as the base station 194. The DU 174 also comprises processing hardware, which may include one or more general-purpose processors, such as a CPU, and non-transitory computer-readable memory that stores machine-readable instructions executable by the one or more general-purpose processors, and / or special-purpose processing units. In some examples, the processing hardware in the exemplary implementation includes a medium access control (MAC) controller configured to manage or control one or more MAC operations or procedures (e.g., random access procedures), and a radio link control (RLC) controller configured to manage or control one or more RLC operations or procedures when the base station 194 operates as a MN, SN, or candidate SN (C-SN). The processing hardware may further include a physical layer controller configured to manage or control one or more physical layer operations or procedures.

[0040] FIG. 2 illustrates, in a simplified manner, an exemplary protocol stack 200 by which a UE 102 may communicate with an eNB / ng-eNB or gNB (e.g., one or more of base stations 294, 296 similar to base stations 104A, 104B, 106A, 106B described above with respect to FIGS. 1A-1C).

[0041] In the exemplary stack 200, a EUTRA physical layer (PHY) 202A (for the UE 102) or 201A (for the base station 294) provides transport channels to a EUTRA MAC sublayer 204A (for the UE 102) or 203A (for the base station 294), which in turn provides logical channels to a EUTRA RLC sublayer 206A (for the UE 102) or 205A (for the base station 294). The EUTRA RLC sublayers 205A / 206A in turn provide RLC channels to a EUTRA PDCP sublayer 208 (for the UE 102) or 207 (for the base station 294), and possibly to a NR PDCP sublayer 210 (for the UE 102) or 209 (for the base station 294). Similarly, the NR PHY 202B (for the UE 102) or 201B (for the base station 296) provides transport channels to the NR MAC sublayer 204B (for the UE 102) or 203B (for the base station 296), which in turn provides logical channels to the NR RLC sublayer 206B (for the UE 102) or 205B (for the base station 296). The NR RLC sublayer 205B / 206B in turn provides data transfer services to the NR PDCP sublayer 210 (for the UE 102) or 211 (for the base station 296). The NR PDCP sublayer 210 may in turn provide data transfer services to a service data adaptation protocol (SDAP) 212 (towards the UE 102), 213 (towards the base station 294), or 214 (towards the base station 296), or a radio resource control (RRC) sublayer (not shown in FIG. 2). The UE 102, in some implementations, may support both EUTRA and NR stacks, support handover between EUTRA and NR base stations, and / or support DC over EUTRA and NR interfaces, as shown in FIG. 2. Additionally, as shown in FIG. 2, the UE 102 may support layering of the NR PDCP 210 over the EUTRA RLC 206A, and the SDAP sublayer 212 over the NR PDCP sublayer 210.

[0042] The EUTRA PDCP sublayers 207 / 208 and NR PDCP sublayers 209 / 210 / 211 receive packets that may be referred to as service data units (SDUs) (e.g., from an Internet Protocol (IP) layer layered directly or indirectly via the PDCP layers 207 / 208 or 209 / 210 / 211) and output packets (e.g., for RLC layers 205A / 206A or 205B / 206B) called protocol data units (PDUs). For simplicity, this disclosure will refer to both SDUs and PDUs as "packets" except where the distinction between SDUs and PDUs is relevant.

[0043] On the control plane, the EUTRA PDCP sublayer 207 / 208 and the NR PDCP sublayer 209 / 210 / 211 can provide a signaling radio bearer (SRB) or an RRC sublayer (not shown in FIG. 2) to exchange, for example, RRC messages or non-access stratum (NAS) messages. On the user plane, the EUTRA PDCP sublayer 207 / 208 and the NR PDCP sublayer 209 / 210 / 211 can provide a data radio bearer (DRB) to support data exchange. The data exchanged on the NR PDCP sublayer 209 / 210 / 211 can be SDAP PDUs, Internet Protocol (IP) packets, or Ethernet packets.

[0044] Next, some example scenarios in which a UE and / or a RAN perform techniques of the present disclosure to support conditional procedures will be described with reference to Figures 3A-3F, 4A-4F, and 5A-5D. Figures 3A-3F, 4A-4F, and 5A-5D illustrate some example scenarios in which a UE and a RAN node perform methods to support conditional procedures. Generally speaking, events similar to those in Figures 3A-3F, 4A-4F, and 5A-5D are labeled with the same reference numerals and will be described below as different, where appropriate. Time flows from top to bottom in these scenario diagrams, i.e., earlier events or actions are depicted above later events or actions.

[0045] 3A, in a scenario 300A, a MN receives and processes one or more SN configurations from an SN during a conditional SN addition procedure. In scenario 300A, base station 104A of scenario 300A operates as a MN, while base station 106A operates as a C-SN. Initially, UE 102 operates 302 in a single connection (SC) with MN 104A. While in the SC, UE 102 transmits UL PDUs and / or DL ​​PDUs with MN 104A (e.g., via PCell 124A) in accordance with the MN configuration.

[0046] The MN 104A then determines to configure the base station 106A as a C-SN for conditional PSCell addition (CPA). The MN 104A may make this determination based on, for example, measurement result(s) from the UE 102. In some implementations, the MN 104A may detect or estimate that the UE 102 is moving toward the coverage (i.e., one or more cells) of the base station 106A based on an uplink signal received from the UE 102 or positioning measurement result(s) received from the UE 102. In response to the determination, the MN 104A may send 304 a connection message to add and / or modify a connection to the C-SN 106A, such as an SN addition request message (e.g., an SgNB addition request or an S-Node addition request message). The connection message may include an information element identifying a type of message, such as a conditional PSCell addition information request IE. In some embodiments, the conditional PSCell additional information request IE further includes a CPAC indicator indicating CPAC initiation and an IE indicating a maximum number of PSCells (e.g., a maximum number of PSCells for which IEs / fields are prepared). The MN 104A can generate candidate cell information including measurement result(s) of one or more cells and can include the candidate cell information in the connection request message. Furthermore, the MN 104A can determine SN restriction information for restricting configuration parameters and / or values ​​of configuration parameters that the C-SN 106A can set for the UE 102. The MN 104A can include the SN restriction information in the connection request message. The MN 104A can determine MN restriction information for restricting configuration parameters and / or values ​​of configuration parameters that the MN 104A can set for the UE 102 when the MN 104A determines the SN control information.

[0047] In response to receiving 304 the connectivity request message with CPAC indication, the C-SN 106A determines 306 one or more C-PSCells (C-PSCell(s)) for the UE 102, where each C-SN configuration is associated with a particular C-PSCell in the C-PSCell(s), and generates an inter-node RRC message candidate list (e.g., CG-CandidateList) to include the one or more C-SN configurations. For example, the C-PSCells may be cell 126A and cell 126C. In some implementations, the C-SN 106A determines the C-PSCell(s) and C-SN configuration(s) taking into account the candidate cell information and the SN restriction information. The candidate list includes an additional list of candidate IEs (e.g., CG-CandidateInfo IE(s)), each of which corresponds to a C-PSCell. Each candidate IE in the additional list includes C-PSCell information of the C-PSCell (e.g., SSB frequency information (e.g., ARFCN-ValueNR) and Physical Cell ID (PCI) or Cell Global ID (CGI)) and an SCG configuration IE (e.g., CG-Config IE). Each configuration IE includes the C-SN configuration of the corresponding C-PSCell and optional parameters for the MN to prepare conditional (re)configuration(s). In some embodiments, each candidate IE includes a candidate ID (e.g., a CG-CandiateInfoID such as cg-CandiateInfoid or CG-CandigateInfoId) that identifies each candidate IE or an SCG configuration IE within each candidate IE.

[0048] In some embodiments, the C-SN 106A and / or the MN 104A use the candidate IE(s) for management of the candidate IE(s) in the addition list. The C-SN 106A transmits 308 a connection request acknowledgement message (e.g., an SgNB addition request acknowledgement or an S-Node addition request acknowledgement message) including the candidate list in a SN to MN container (e.g., an SgNB to MeNB container or an S-NG-RAN node to M-NG-RAN node container) or a CPAC container. The CPAC container is, for example, a separate RRC container included in an acknowledgement IE (e.g., a Conditional PSCell Additional Information Acknowledgement IE) in an acknowledgement message to the MN 104A. In further embodiments, the C-SN 106A generates adjustment information and includes the adjustment information in the connection request acknowledgement message. In some embodiments, the adjustment information includes one or more adjustment parameters.

[0049] In some embodiments, the C-SN 106A may include one or more adjustment parameters in the candidate list and / or SCG configuration(s) in the connection request acknowledgement message. For example, the adjustment information may include adjustment parameters such as resource adjustment IEs associated with a particular C-PSCell (e.g., resource adjustment information IEs such as SgNB resource adjustment information IE or MR-DC resource adjustment information IE), one or more power adjustment parameters (e.g., powerCoordination-FR1 and / or powerCoordination-FR2), discontinuous reception (DRX) configuration (e.g., DRX-Info or DRX-Info2), etc. The adjustment information may include adjustment information for each of the C-PSCell(s). In some embodiments, the C-SN 106A may include SN restriction information in the connection request acknowledgement message, which the MN 104A may use to determine the MN restriction information. Events 304, 306, 308 collectively define a conditional SN addition preparation procedure 392.

[0050] In order to enable the C-SN 106A to configure multiple C-SN configurations as described above, the MN 104A may set the IE indicating the maximum number of PSCells to a value greater than 1. If the MN 104A only enables the C-SN 106A to configure a single C-SN configuration, the MN 104A may set the IE indicating the maximum number of PSCells to a value equal to 1.

[0051] After receiving 308 the connection request acknowledgement message including the candidate list, the MN 104A can assign a specific configuration ID (e.g., CondReconfigId or CondReconfigurationId) to each of the C-SN configuration(s) in the SCG configuration IE(s). For example, if the SCG configuration IE(s) includes C-SN configurations 1, ..., N (N is an integer greater than zero), the MN 104A can assign configuration IDs 1, ..., N for C-SN configurations 1, ..., N, respectively. In such a case, the MN 104A can include configuration IDs 1, ..., N in an RRC reconfiguration message. In some such implementations, the MN 104A can include trigger condition configurations 1, ..., N for C-SN configurations 1, ..., N, respectively, in the RRC reconfiguration. The MN 104A can generate trigger condition configurations. In some embodiments, each of the trigger condition configurations may set one or more conditions that trigger the UE 102 to connect to the C-SN 106A via a particular C-PSCell configured with a particular C-SN configuration. In some embodiments, the MN 104A generates a conditional (re)configuration field / IE (e.g., CondReconfigurationToAddMod IE or CondReconfigToAddMod IE) 1, ..., N including the C-SN configurations 1, ..., N, a configuration ID (e.g., CondReconfigurationId IE or CondReconfigId IE) 1, ..., N, and a trigger condition configuration 1, ..., N, respectively, and transmits 312 an RRC reconfiguration message including the conditional (re)configuration field / IE to the UE 102.In another embodiment, the MN 104A generates RRC container messages (e.g., RRCConnectionReconfiguration message or RRCReconfiguration message) 1, ..., N, respectively, including C-SN configurations 1, ..., N, generates conditional (re)configuration fields / IEs (e.g., CondReconfigurationToAddMod IE1 or CondReconfigToAddMod IE) 1, ..., N, configuration IDs (e.g., CondReconfigurationId IE or CondReconfigId IE) 1, ..., N, and trigger condition settings 1, ..., N, respectively, including the RRC container messages 1, ..., N, and transmits 312 the RRC reconfiguration messages including the conditional (re)configuration fields / IEs to the UE 102.

[0052] The MN 104A may include the C-SN configuration(s) in an RRC reconfiguration message (e.g., an RRCConnectionReconfiguration message or an RRCReconfiguration message) and transmits 312 the RRC reconfiguration message to the UE 102. In response, the UE 102 transmits 314 an RRC reconfiguration complete message (e.g., an RRCConnectionReconfigurationComplete message or an RRCReconfigurationComplete message) to the MN 104A. Events 312 and 314 together define an RRC reconfiguration procedure 310.

[0053] In some embodiments, the MN 104A sends an SN message (e.g., an SN reconfiguration complete message) to the C-SN 106A to indicate that the UE 102 will receive the C-SN configuration(s). Depending on the embodiment, the MN 104A sends the message in response to or after receiving the RRC reconfiguration complete message. In other embodiments, the MN 104A refrains from sending an SN message to the C-SN 106A to indicate that the UE 102 has received the C-SN configuration(s). Events 304, 306, 308, 312, and 314 collectively define a conditional SN addition preparation procedure 390, which includes RRC reconfiguration steps not covered in 392.

[0054] When the MN 104A and / or the C-SN 106A reconfigure the bearer type of the DRB from MN terminated bearer to SN terminated bearer in the conditional SN addition preparation 392, the MN 104A can send 316 a message indicating an initial status (e.g., an early status transfer message) to the C-MN 104A. For example, the C-SN 106A can include a radio bearer configuration (e.g., a RadioBearerConfig IE) in the SCG configuration IE(s) that reconfigures the bearer type of the DRB from MN terminated bearer to SN terminated bearer. The MN 104A obtains the radio bearer configuration from the SCG configuration IE(s) and includes the radio bearer configuration in the RRC container message(s). In the status message, the MN 104A can include a DL COUNT value of the first downlink SDU that the MN 104A transfers to the C-SN 106A, or a DL COUNT value for discarding downlink SDUs already transferred for the DRB of the UE 102. The MN 104A may do so after receiving 314 an acknowledgment (e.g., an RLC acknowledgment or a hybrid automatic repeat request (HARQ) acknowledgment) for a PDU (e.g., an RLC PDU or a MAC PDU) that includes an RRC reconfiguration complete message or an RRC reconfiguration message. In some embodiments, the MN 104A sends 316 the status message without receiving an interface message indicating that the UE 102 connects to the C-SN 106A. If a change in bearer type from MN terminated bearer to SN terminated bearer does not occur and / or is configured in the SCG configuration IE(s), the MN 104A may refrain from sending a status message to the C-SN 106A.

[0055] In some embodiments, the UE 102 uses one or more conditions to determine whether to connect to one of the C-PSCell(s). If the UE 102 detects 318 that a condition for connecting to a C-PSCell is met, the UE 102 connects to the C-PSCell. That is, the condition (or "trigger condition") triggers the UE 102 to connect to the C-PSCell or to perform C-SN configuration for the C-PSCell. In further embodiments, if the UE 102 does not detect that a condition is met, the UE 102 does not connect to the C-PSCell. In response to this detection, the UE 102 initiates a random access procedure on the C-PSCell. In response to this initiation, the UE 102 initiates 320 a random access procedure with the C-SN 106A via the C-PSCell. In response to the detection or initiation 318, the UE 102 transmits 322 an RRC reconfiguration complete message to the MN 104A. Depending on the embodiment, the UE 102 may send 322 an RRC reconfiguration complete message before, during, or after the random access procedure.

[0056] In some embodiments, the UE 102 indicates that the UE 102 has performed one of the C-SN configuration(s) by including a configuration ID corresponding to a particular C-SN configuration in the RRC reconfiguration complete message. The MN 104A can use the configuration ID to identify or determine the ID of the C-PSCell (e.g., the PCI and / or CGI of the C-PSCell) and / or the C-SN if the MN 104A performs multiple CPA procedures with different C-SNs. The MN 104A can also use the configuration ID to identify or determine the C-SN configuration or the SCG configuration that includes the C-SN configuration.

[0057] In response to receiving the RRC reconfiguration complete message or after receiving 322 it, the MN 104A can transmit 324 a SN message to the C-SN 106A. In some embodiments, the SN message can be a reconfiguration complete message, such as an SgNB reconfiguration complete message or an S-Node reconfiguration complete message. In other embodiments, the SN message can be a radio resource message, such as an RRC forwarding message. In still other embodiments, the SN message can be a new interface message (e.g., an XnAP or X2AP message) defined in the 3GPP 38.423 or 36.423 Release 17 specifications. In some embodiments, the UE 102 can include an SN RRC message (e.g., an RRCReconfigurationComplete message) in the RRC reconfiguration complete message that the UE 102 transmits at event 322. In such a case, the MN 104A can include the SN RRC message in the SN message.

[0058] In some implementations, the random access procedure is a four-step random access procedure or a two-step random access procedure. In other implementations, the random access procedure is a contention-based random access procedure or a contention-free random access procedure. For example, the UE 102 may include the RRC reconfiguration complete message in message 3 of a four-step random access procedure or in message A of a two-step random access procedure.

[0059] In some embodiments, after the C-SN 106A successfully completes the random access procedure with the UE 102, the C-SN 106A transmits 326 an interface message (e.g., an SN Modification Required message, an NG-RAN Node Configuration Update message, an E-UTRA-NR Cell Resource Adjustment Request message, or a success indication message) that may include PSCell information of the PSCell and / or adjustment information for the corresponding CG-Config and / or physical resource block (PRB) adjustment (e.g., an SgNB Resource Adjustment Information IE or an MR-DC Resource Adjustment Information IE, etc.) to the MN 104A. The PSCell information may include a Cell Global Identity (CGI), a Physical Cell Identity (PCI), and / or an Absolute Radio Frequency Channel Number (ARFCN) that identifies the DL carrier frequency of the PSCell. In some embodiments, the C-SN 106A transmits 326 the interface message in response to or after receiving or executing 320 the SN message. In some embodiments, the interface message further includes SN restriction information. In some such embodiments, the MN 104A uses the SN restriction information to determine the MN restriction information.

[0060] In response to or after receiving 322 or transmitting 326 the RRC reconfiguration complete message or interface, the MN 104A applies 328 the adjustment information and / or MN restriction information. In response to applying 328 the adjustment information and / or MN restriction information, the MN 104A may transmit 330 an RRC reconfiguration message including configuration parameters to the UE 102. In some embodiments, the configuration parameters 330 reconfigure or release configuration parameters and / or values ​​of configuration parameters that the UE 102 uses to communicate with the MN 104A. In other embodiments, the configuration parameters 330 may be new configuration parameters for configuring the UE 102 to communicate with the MN 104A. In response to the RRC reconfiguration message 330, the UE 102 may transmit 332 an RRC reconfiguration message to the MN 104A. In further embodiments, the MN 104A transmits 334 a message confirming the modification (e.g., an SgNB modification confirmation message or an S-Node modification confirmation message) in response. Events 320, 322, 324, 326, 328, 330, 332, and 334 are collectively referred to as conditional SN addition execution procedure 394 in FIG. 3A.

[0061] In response to or after receiving 322 or transmitting 326 an RRC reconfiguration complete message or interface message, the MN 104A can transmit 336 a status message to transfer uplink PDCP SN and HFN receiver status and / or downlink PDCP SN and HFN transmitter status for each of the DRB(s) of the UE 102. In contrast to event 316, the MN 104A transmits 336 a (non-early) status message (e.g., an SN status transfer message).

[0062] In some embodiments, after the UE 102 successfully completes 320 the random access procedure, the UE 102 communicates 338 with the MN 104A and with the C-SN 106A via the C-PSCell in accordance with the C-SN configuration that configures the C-PSCell.

[0063] With continued reference to FIG. 3A , the C-SN configuration in some embodiments may be a complete and self-contained configuration (i.e., a full configuration). The C-SN configuration may include a full configuration indication (an information element (IE) or field) that identifies the C-SN configuration as a full configuration. The UE 102 uses the C-SN configuration in some cases to communicate with the SN 106A without relying on the SN configuration. In other cases, the C-SN configuration includes a “delta” configuration, or one or more configurations that extend a previously received SN configuration. The UE 102 uses the delta C-SN configuration and the SN configuration together to communicate with the C-SN 106A in some such cases.

[0064] In some embodiments, the C-SN configuration includes configuration parameters for the UE 102 to apply when communicating with the SN 106A via the C-PSCell. The configuration parameters may configure the C-PSCell and zero, one, or more candidate secondary cells (C-SCells) of the SN 106A for the UE 102. The configuration parameters may configure radio resources for the UE 102 to communicate with the C-SN 106A via the C-PSCell and zero, one, or more C-SCells of the SN 106A. The configuration parameters may configure zero, one, or more radio bearers. The one or more radio bearers may include an SRB and / or one or more DRBs.

[0065] In some embodiments, the C-SN configuration includes a group configuration (CellGroupConfig) IE that configures the C-PSCell and zero, one, or more C-SCells of the C-SN 106A. In one embodiment, the C-SN configuration includes a radio bearer configuration. In another embodiment, the C-SN configuration does not include a radio bearer configuration. For example, the radio bearer configuration can be a RadioBearerConfig IE, a DRB-ToAddModList IE or an SRB-ToAddModList IE, or a DRB-ToAddMod IE or an SRB-ToAddMod IE. In some embodiments, the C-SN configuration can be an RRCReconfiguration message, an RRCReconfiguration-IE, or a CellGroupConfig IE in accordance with 3GPP TS 38.331. The full configuration indication can be a field or IE in accordance with 3GPP TS 38.331. In some embodiments, the C-SN configuration may include an SCG-ConfigPartSCG-r12IE that configures the C-PSCell and zero, one, or more C-SCells of the C-SN 106A. In some embodiments, the C-SN configuration may be an RRCConnectionReconfiguration message, an RRCConnectionReconfiguration-IE, or a ConfigPartSCG-r12 IE in accordance with 3GPP TS 36.331. The full configuration indication may be a field or IE in accordance with 3GPP TS 36.331.

[0066] Continuing to refer to FIG. 3A, the base station 106A (i.e., C-SN) may include a CU 172 and one or more DUs 174, as shown in FIG. 1C. For each of the C-SN configuration(s), one or more DUs 174 may generate the C-SN configuration. Alternatively, for each of the C-SN configuration(s), one or more DUs 174 may generate a portion of the C-SN configuration, and the CU 172 may generate the remainder of the C-SN configuration. For example, the UE 102 may perform 320 a random access procedure with a first DU 174A that operates a (C-)PSCell, and the first DU 174A may identify the UE 102 in the random access procedure. In such a case, the UE 102 may communicate 338 with the SN 106A via the first DU 174A.

[0067] The first DU 174A of the C-SN 106A operating the C-PSCell may generate a C-SN configuration or a portion of a C-SN configuration that configures the C-PSCell and transmit the C-SN configuration or the portion of the C-SN configuration to the CU 172. If the first DU 174 generates a portion of the C-SN configuration, the CU 172 generates the remainder of the C-SN configuration. In some implementations, the first DU 174A generates each of the other C-SN configuration(s). Alternatively, for each of the other C-SN configuration(s), the first DU 174 generates a portion of the C-SN configuration and the CU 172 generates the remainder of the respective C-SN configuration. In other implementations, the first DU 174A generates at least one first C-SN configuration of the C-SN configuration(s). Alternatively, for each of the other C-SN configuration(s), the first DU 174 generates a portion of the C-SN configuration and the CU 172 generates the remainder of the C-SN configuration. In some implementations, the second DU 174B of the C-SN 106A generates at least one second C-SN configuration of the C-SN configuration(s). In other implementations, for each of the C-SN configuration(s), the second DU 174B generates a portion of the C-SN configuration and the CU 172 generates the remainder of the C-SN configuration.

[0068] Referring now to Figure 3B, scenario 300B represents a conditional SN change scenario initiated by the MN, where the MN 104A first connects with the S-SN 106B and later performs a conditional change procedure with the C-SN 106A. The interaction between the MN 104A and the C-SN 106A is similar to that described in Figure 3A. The differences between Figure 3B and Figure 3A are described below.

[0069] The UE 102 is initially in a dual connection 301 with the MN 104A and the S-SN 106B and communicates with the S-SN 106B via a PSCell according to the S-SN configuration. The MN 104A, the C-SN 106A, and the UE 102 then perform a conditional SN addition preparation procedure 390. If early data transfer is utilized, the MN 104A may transmit 340 an interface message (e.g., an Xn-U address indication or a data address indication message) to the S-SN 106B. The S-SN 106B then transmits 342 a status message (e.g., an early status transfer message) to the MN 104A, which then transmits 316 a status message to the C-SN 106A.

[0070] Similar to FIG. 3A, in some embodiments, the UE 102 later detects 318 that the conditions for connecting to the C-PSCell are met, and performs a random access procedure on the C-PSCell in response to the detection by the C-SN 106A. The UE 102, the MN 104A, and the C-SN 106A perform a conditional SN addition execution 394. The MN 104A transmits 344 a release request message (e.g., an SgNB release request or an S-Node release request message) to the S-SN 106B. In response, the S-SN 106B transmits 346 a release request acknowledgement message (e.g., an SgNB release request acknowledgement or an S-Node release request acknowledgement message). If data forwarding is utilized, the MN 104A may transmit 347 an interface message (e.g., an Xn-U address indication or a data address indication message) to the S-SN 106B. The S-SN 106B may then send 348 a status message (e.g., an SN status transfer message) to the MN 104A, which may then send 336 a status message to the C-SN 106A. The MN 104A sends 350 a UE context release message to the S-SN 106B. Events 344, 346, 347, 348, 336, 350 may be collectively referred to as an SN release and SN status transfer procedure 396.

[0071] After the UE 102 successfully completes 320 the random access procedure, the UE 102 communicates 338 with the MN and with the SN via the C-PSCell according to the C-SN configuration that configures the C-PSCell.

[0072] Referring now to Fig. 3C, scenario 300C represents a conditional SN change scenario initiated by an SN, where MN 104A first connects with S-SN 106B and is later triggered by S-SN 106B to perform a conditional change procedure with C-SN 106A. The interaction between MN 104A and C-SN 106A is similar to that described in Fig. 3A or Fig. 3B. The differences between Fig. 3C and Fig. 3A and Fig. 3B are described below.

[0073] At some point, the S-SN 106B decides to initiate a conditional SN change procedure and sends a message indicating that an SN change is required (e.g., an SgNB Change Required or S-Node Change Required message defined in 3GPP TS 36.423 and 38.423, respectively) including a candidate target SN ID (e.g., a global en-gNB ID, or a global NG-RAN node ID), and an SCG configuration 303 further including proposed candidate cell information (e.g., physical cell ID and / or related cell measurement results) and trigger condition(s) (e.g., a condExecutionCond-SCG IE that may include measurement ID(s) referencing configured S-SN measurement values) for the corresponding candidate cell(s) to the MN 104A. The MN 104A and the C-SN 106A perform a conditional SN addition preparation procedure 392 with the proposed candidate cell information from the S-SN 106B. The MN 104A may send 352 an SN request message (e.g., an SgNB modification request or an S-Node modification request message) to the S-SN 106B to provide the S-SN 106B with the candidate PSCell(s) accepted by the C-SN 106A. In response, the S-SN 106B may send 354 an SN message (e.g., an SgNB modification request acknowledgement or an S-Node change request acknowledgement message) acknowledging the request to provide the updated measurement configuration and / or trigger condition(s). The MN 104A performs 310 an RRC reconfiguration procedure with the UE 102 to set up the conditional (re)configuration(s). The MN 104A sends 309 an acknowledgement message (e.g., an SgNB change acknowledgement or an S-Node change acknowledgement message) to the S-SN 106B to acknowledge the SN change. Events 303, 392, 352, 354, 310, and 309 may be collectively referred to as SN change preparation with SN initiation condition 393.

[0074] Depending on the embodiment, if the UE 102 later detects 318 that the conditions for connecting to the C-PSCell are met, the UE 102 performs a random access procedure and a conditional SN addition execution procedure 394 with the C-SN 106A via the C-PSCell. The MN 104A, the S-SN 106B, and the C-SN 106A perform an SN release and SN status transfer procedure 396. In some embodiments, unlike scenario 300B, the MN 104A does not send 344 a release request message, and therefore the S-SN 106B may not send 346 a message acknowledging the release request.

[0075] 4A-4F, each of scenarios 400A-400F may include some portions that are similar to any one of scenarios 300A-300C, however, scenarios 400A-400F include a conditional handover with CPAC as described in scenarios 300A-300C or a conditional handover with SCG configuration as described further below.

[0076] Referring first to FIG. 4A, scenario 400A illustrates an example scenario in which a conditional handover with an SCG configuration is described.

[0077] The UE 102 initially operates 402 in single connectivity (SC) with the S-MN 104B or in DC with the S-MN 104B and an S-SN (e.g., C-SN 106A or a different base station 106B) and communicates with the S-SN via a PSCell according to the S-SN configuration. At some point, the S-MN 104B decides to perform a conditional handover and transmits 404 a message requesting a handover (e.g., a handover request message) including a CHO indication (e.g., a conditional handover information request IE including a CHO trigger indicating "CHO-initiation") and / or a measurement result from the UE 102 to the C-MN 104A. The measurement result may include some candidate cell information about the C-MN 104A to consider whether to trigger an SN addition procedure. Then, the C-MN 104A performs 492 a conditional SN addition preparation procedure with the C-SN 106A. In some embodiments, the handover request message includes the SNUE ID of the UE 102 (e.g., SgNB UE X2AP ID or S-NG-RAN node UE XnAP ID), which the C-MN 104A may further include in the connection request message. If the C-SN 106A is also the S-SN of the UE 102, the C-SN 106A may use the SN UE ID to identify the UE context when the C-SN 106A receives a connectivity request message from the C-MN 104A. Thus, the C-SN 106A may decide to keep the UE context and inform the C-MN 104A of the decision in an acknowledgement message for the connection request. The C-MN 104A may provide this "UE context maintenance" decision to the S-MN 104B in a connection request acknowledgement message, which the S-MN 104B may further indicate to the C-SN 106A (e.g., S-SN) and refrain from releasing the UE context in the release request message.

[0078] In some embodiments, the conditional SN addition preparation procedure 492 is the same as procedure 392 of FIG. 3A. The C-MN 104A obtains SCG configuration IE(s) from the candidate list IE that the C-MN 104A received in the conditional SN addition preparation procedure 492, and obtains one or more C-SN configuration(s) from the SCG configuration IE(s). The C-MN 104A then generates a CHO command (e.g., an RRC reconfiguration message) including one or more conditional (re)configuration IE(s) (e.g., CondReconfigurationToAddMod IE or CondReconfigToAddMod IE) including one or more C-SN configuration(s) as described with respect to FIG. 3A. Such an embodiment of procedure 492 may be referred to as a CHO with CPAC.

[0079] In another embodiment, the conditional SN addition preparation procedure 492 is similar to procedure 392, except that the MN 104A includes an IE indicating the maximum number of PSCells in the connection request message, and the MN 104 further sets the IE with a value equal to 1 to restrict the C-SN 106A to configuring a single SCG configuration including a single C-SN configuration.

[0080] In yet another embodiment, the conditional SN addition preparation procedure 492 is similar to procedure 392, except that the MN 104A includes a CHO indication in the connectivity request message instead of a CAPC indication (e.g., another IE indicating "CHO ​​with SCG"). In some embodiments, in response to the CHO indication, the C-SN 106A only includes a single SCG configuration IE including a single C-SN configuration in the connection request acknowledgement message. In one embodiment, instead of wrapping the SCG configuration IE in a candidate list IE and including the candidate list IE in the SN to MN container IE, the C-SN 106A includes the SCG configuration IE directly in the SN to MN container IE in the connection request acknowledgement message. The C-MN 104A obtains the SCG configuration IE from the SN to MN container IE and obtains the C-SN configuration from the SCG configuration IE. Alternatively, the C-SN 106A wraps the SCG configuration IE in a candidate list IE and includes the candidate list IE in the SN to MN container IE. The C-MN 104A obtains a candidate list IE from the MN container IE from the SN, obtains an SCG configuration IE from the candidate list, and obtains a C-SN configuration from the SCG configuration IE. After obtaining the C-SN configuration, the C-MN 104A generates a CHO command (e.g., an RRC reconfiguration message) including the C-SN configuration (e.g., in an nr-SecondaryCellGroupConfig field or an mrdc-SecondaryCellGroupConfig field) without wrapping the C-SN configuration with a conditional (re)configuration IE (e.g., a CondReconfigurationToAddMod IE or a CondReconfigToAddMod IE). In some such embodiments, the procedure 492 is referred to as a CHO with SCG configuration.

[0081] When the C-MN 104A is an eNB or an ng-eNB, the CHO command or the RRC reconfiguration message is a radio connection reconfiguration message (e.g., an RRCConnectionReconfiguration message). When the C-MN 104A is a gNB, the RRC reconfiguration message is an RRCReconfiguration message.

[0082] In response to the handover request message, the C-MN 104A transmits 406 to the S-MN 104B an acknowledgement message for the handover request including the CHO command (e.g., a handover request acknowledgement message). The S-MN 104B transmits 408 to the UE 102 an RRC reconfiguration message including the CHO command. More specifically, the S-MN 104B generates a conditional (re)configuration IE (e.g., a CondReconfigurationToAddMod IE or a CondReconfigToAddMod IE) including the CHO command and the first trigger condition configuration, and includes the conditional (re)configuration IE in the RRC reconfiguration message during event 408.

[0083] The first trigger condition configuration sets a condition that triggers the UE 102 to connect to a candidate PCell (C-PCell) of the C-MN 104A. In response to the RRC reconfiguration message, the UE 102 responds 410 to the S-MN 104B with an RRC reconfiguration complete message. If the S-MN 104B determines that early data transfer is utilized, the S-MN 104B can transmit 412 a status message (e.g., an early status transfer message) to the C-MN 104A. If the MN 104A and / or the C-SN 106A reconfigure the bearer type of the DRB from MN terminated bearer to SN terminated bearer in the conditional SN addition preparation procedure 492, the C-MN 104A can transmit 414 an early status message (e.g., an early status transfer message) to the C-SN 106A. For example, the C-SN 106A may include in the SCG Configuration IE a radio bearer configuration (e.g., a Radio Bearer Config IE) that reconfigures the bearer type of the DRB from the MN terminated bearer to the SN terminated bearer. The C-MN 104A obtains the radio bearer configuration from the SCG Configuration IE and includes the radio bearer configuration in the CHO command. In such a case, the C-MN 104A may obtain the DL COUNT value received from the initial status message 412 and include the DL COUNT value in the initial status message 414.

[0084] In some cases where a change of bearer type from MN terminated bearer to SN terminated bearer is not configured as a result of the conditional SN addition preparation procedure 492, the C-MN 104A refrains from sending an initial status message to the C-SN 106A. In scenario 400A, a CHO with SCG configuration is employed in procedure 492. Events 402, 404, 492, 406, 408, 410, 412, and 414 may be collectively referred to as a procedure 480 involving preparation for a conditional handover with SCG configuration (CHO with SCG).

[0085] In some implementations, after receiving the first conditional configuration, the UE 102 evaluates whether the condition is met to determine whether to connect to the C-PCell. If the UE 102 detects 415 that the condition for connecting to the C-PCell is met, the UE 102 connects to the C-PCell and the C-PSCell in response to the detection. That is, the condition (or "trigger condition") triggers the UE 102 to connect to the C-PCell and the C-PSCell or to execute a CHO command that includes a C-SN configuration for both the C-PCell and the C-PSCell. If the UE 102 does not detect that the condition is met, the UE 102 does not connect to the C-PCell and the C-PSCell.

[0086] In response to the detection, the UE 102 initiates 415 a first random access procedure on the C-PCell and a second random access procedure on the C-PSCell. In response to the initiation, the UE 102 performs 419 a first random access procedure with the C-MN 104A via the C-PCell and performs 420 a second random access procedure with the C-SN 106A via the C-PSCell. In response to the detection or initiation 415, the UE 102 transmits 422 an RRC reconfiguration complete message to the C-MN 104A, the RRC reconfiguration complete message including a SN RRC reconfiguration complete message. The UE 102 may transmit 422 an RRC reconfiguration complete message before, during, or after the first random access procedure. In response to receiving 422 the RRC reconfiguration complete message, or afterwards, the C-MN 104A transmits 424 an SN message (e.g., an SN reconfiguration complete message) including a SN RRC reconfiguration complete message to the C-SN 106A.

[0087] After the UE 102 receives 422 the RRC reconfiguration message and successfully completes the first random access procedure, the C-MN 104A transmits 426 a message indicating the success of the handover (e.g., a handover success message) to the S-MN 104B. If data transfer is utilized, the S-MN 104B may transmit 428 a status message (e.g., an SN status transfer message) to the C-MN 104A. The C-MN 104A may transmit 430 a status message to the C-SN 106A. The C-MN 104A may further transmit 432 a message to release the UE context (e.g., a UE context release message) to the S-MN 104B, which initiates an SN release procedure for the S-SN if the UE 102 was in a DC at event 402. The UE 102 communicates 439 with the C-MN 104A and the C-SN 106A via the C-PCell and C-PSCell, respectively, in accordance with the CHO command and the C-SN configuration. Events 415, 419, 420, 422, 424, 426, 428, 430, 432, and 439 may be collectively referred to as the CHO in the SCG configuration execution procedure 484.

[0088] Referring now to FIG. 4B, scenario 400B is an example scenario similar to scenario 400A, except that a conditional handover is configured with a CPAC instead of the SCG configuration specified in 400A.

[0089] First, the UE 102, the S-MN 104B, the C-MN 104A, and the C-SN 106A perform a CHO and CPAC configuration procedure 481 similar to procedure 480 with differences described below. In particular, in the conditional SN addition preparation procedure in CHO (similar to procedure 492) and the CPAC configuration procedure 481, the C-MN 104A can include a CPAC indication in a connection request message (e.g., an SN addition request message) instead of a CHO indication by the SCG (as described with respect to procedure 480), similar to event 304. Alternatively, the C-MN 104A still includes a CHO indication in a connection request message in addition to a CPAC indication. Depending on the embodiment, the C-MN 104A may or may not limit the C-SN 106A to configuring only one C-SN configuration. If the C-MN 104 enables the C-SN 106A to configure multiple C-SN configurations, the C-SN 106A may configure one or more C-SN configurations as described for Figure 3A. For each of the C-SN configuration(s), the C-MN 104A generates a conditional (re)configuration IE(s) (e.g., a CondReconfigurationToAddMod IE or a CondReconfigToAddMod IE) that includes the conditional (re)configuration field(s) / IE(s) of the CHO command as described for Figure 3A.

[0090] Thereafter, when the UE 102 detects 417 that a condition for connecting to the C-PCell is met according to the first trigger condition configuration, the UE 102 connects to the C-PCell in response to the detection. That is, the condition (or "trigger condition") triggers the UE 102 to connect to the C-PCell or to execute a CHO command for the C-PCell. In response to the detection 417, the UE 102 executes 419 a first random access procedure with the C-MN 104A via the C-PCell. In response to the detection or initiation 419, the UE 102 transmits 429 an RRC reconfiguration complete message to the C-MN 104A. The UE 102 may transmit 429 an RRC reconfiguration complete message before, during, or after the first random access procedure. The C-MN 104A transmits 426 an indication of handover success (e.g., a handover success message) to the S-MN 104B. The S-MN 104B may transmit 428 a status message (e.g., an SN status transfer message) to the C-MN 104A. The C-MN 104A transmits 432 a message to release the UE context (e.g., a UE context release message) to the S-MN 104B. The UE 102 communicates 437 with the C-MN 104A via the C-PCell in accordance with the CHO command. The C-MN 104A may transmit 416 a status message (e.g., an early status transfer message) to the C-MN 106A.

[0091] After executing the CHO command, the UE 102 starts evaluating the trigger condition(s) in the conditional (re)configuration field(s) / IE(s). While evaluating the trigger condition(s), the UE 102 detects 418 that the condition for connecting to the C-PSCell is met, and in response to the detection, initiates a second random access procedure in the C-PSCell. The UE 102 then performs 494 a conditional SN addition execution procedure in the C-MN 104A and the C-SN 106A, similar to the conditional SN addition execution 394. After connecting the C-PSCell, the UE 102 communicates 439 with the C-MN 104A and the C-SN 106A via the C-PCell and the C-PSCell, respectively, according to the CHO command and the C-SN configuration. Events 417 , 419 , 429 , 426 , 428 , 432 , 437 , 418 , 416 , 494 and 439 may be collectively referred to as CHO and CPAC execution procedure 485 .

[0092] Referring now to FIG. 4C, in scenario 400C, an example scenario is described in which an immediate handover with a conditional SN addition preparation procedure is performed.

[0093] The UE 102 initially operates 402 in a single connection (SC) with the S-MN 104B or in DC with the S-MN 104B and an S-SN (e.g., C-SN 106A or a different base station 106B) and communicates with the S-SN via a PSCell according to the S-SN configuration. At some point, the S-MN 104B decides to send 405 a message (e.g., a handover request message) to the target MN (T-MN) 104A requesting a handover including a target PCell. The T-MN 104A performs a conditional SN addition preparation procedure 492 with the C-SN 106A as described with respect to 392 and obtains a candidate list including one or more SCG configuration IE(s). The T-MN 104A generates a handover command (e.g., an RRC reconfiguration message) that also includes a conditional (re)configuration(s) including the C-SN configuration(s) described after event 308. The T-MN 104A sends 407 a handover request acknowledgment (e.g., a handover request acknowledgment message) that includes a handover command. In some cases where the S-SN is also the C-SN 106A, the handover acknowledgment may also include a UE context IE (e.g., a UE context maintenance indicator IE) to indicate that the UE context in the S-SN should be retained after the handover procedure. The S-MN 104B sends 409 a handover command to the UE 102 that includes conditional configuration(s) for the C-SN configuration(s). Events 402, 405, 492, 407 may be collectively referred to as a handover with CPAC preparation procedure 491 (HO).

[0094] In response to receiving 409 the HO command, the UE 102 performs 421 a first random access procedure via the target PCell with the T-MN 104A. The UE 102 transmits 429 an RRC reconfiguration complete message to the T-MN 104A during or after the random access procedure 421. The S-MN 104B may transmit 428 a status message (e.g., an SN status transfer message) to the T-MN 104A. The T-MN 104A may transmit 432 a message (e.g., a UE context release message) to the S-MN 104B to release the context of the UE 102. If the UE 102 was in a DC at event 402, the S-MN 104B may initiate an SN release procedure with the S-SN and indicate the UE context to be maintained if requested by the T-MN 104A. After the handover, the UE 102 communicates 436 with the T-MN 104A via the configured PCell according to the HO command.

[0095] In some embodiments, the UE 102 then detects 418 that the conditions for connecting to the C-PSCell are met and, in response to the detection, initiates a second random access procedure with the C-PSCell. The UE 102, the T-MN 104A, and the C-SN 106A then perform a conditional SN addition execution procedure 494, similar to procedure 394. The UE 102 communicates 438 with the T-MN 104A via the PCell and with the C-SN 106A via the identified C-PSCell, respectively, in accordance with the HO command and the C-SN configuration.

[0096] Referring now to FIG. 4D, in scenario 400D, an example scenario is described in which a handover cancellation procedure is initiated by the S-MN after a CHO with CPAC configuration or a handover (HO) with CPAC configuration.

[0097] The UE 102, the S-MN 104B, the C-MN (or T-MN) 104A, and the C-SN 106A first perform CHO in the SCG configuration procedure 480, the CHO and CPAC configuration procedure 481, or the HO and CPAC configuration procedure 482, respectively, as described in Figures 4A, 4B, and 4C. The S-MN 104B may later send 440 a message to the C-MN 104A to cancel the handover (e.g., a handover cancel message), for example, to cancel the CHO or immediate HO preparation. In some embodiments, the S-MN 104B may do so because it determines that the candidate cell(s) are no longer eligible for CHO or immediate HO. When canceling the CHO preparation, the S-MN 104B also sends 448 an RRC reconfiguration message to the UE 102, which may include a release list (e.g., a condReconfigToRemoveList IE) that lists the configuration IDs of the conditional configuration(s). In response to the RRC reconfiguration message, the UE 102 replies 450 with an RRC reconfiguration complete message. The UE 102 releases the conditional (re)configuration field(s) / IE(s) indicated in the release list. The C-MN (or T-MN) 104A may send 442 an SN release request message (e.g., an SN release request message) to the C-SN 106A. In response, the C-SN 106A sends 444 an acknowledgement response to the request (e.g., an SN release request acknowledgement message) to the C-MN (or T-MN) 104A. The C-MN (or T-MN) 104A sends 446 a message to the C-SN 106A releasing the UE context (e.g., a UE context release message).

[0098] Referring now to FIG. 4E, scenario 400E is an example scenario in which a conditional handover cancellation procedure is initiated by the C-MN after CHO with CPAC configuration.

[0099] UE 102, S-MN 104B, C-MN 104A, and C-SN 106A first perform CHO in SCG configuration procedure 480 or CHO and CPAC configuration procedure 481, respectively, as described in Figures 4A and 4B. C-MN 104A may later transmit 443 a message to cancel handover (e.g., a conditional handover cancel message) to S-MN 104B in response to an SN request message (e.g., an SN modification required or SN change required message) 441 transmitted by C-SN 106A to C-MN 104A to cancel CHO in CPAC preparation because C-MN 104A detects congested traffic or an error. In some embodiments, C-SN 106A transmits 441 an SN required message to C-MN 104A because C-SN 106A detects congested traffic or an error. In response, the S-MN 104B transmits 448 an RRC reconfiguration message to the UE 102, which may include a release list (e.g., a condReconfigToRemoveList IE) that lists the configuration IDs of the conditional configuration(s). The UE 102 returns 450 an RRC reconfiguration complete message in response to the RRC reconfiguration message. In a further embodiment, the C-MN 104A transmits 442 a release request message (e.g., an SN release request message) to the C-SN 106A. In response, the C-SN 106A transmits 444 an acknowledgement response (e.g., an SN release request acknowledgement message) to the C-MN 104A. The C-MN 104A transmits 446 a message to release the UE context (e.g., a UE context release message) to the C-SN 106A.

[0100] Referring now to FIG. 4F, in scenario 400F, an example scenario is illustrated in which the MN first initiates an immediate handover after CHO with a conditional SN addition procedure.

[0101] The UE 102, the S-MN 104B, the C-MN 104A, and the C-SN 106A first perform CHO in the SCG configuration procedure 480 or the CHO and CPAC configuration procedure 481, respectively, as described in FIG. 4A and FIG. 4B. In some embodiments, the UE 102 later changes the moving orbit and provides the measurement result to the S-MN 104B. Thus, the S-MN 104B can determine to perform immediate handover preparation of the UE 102 based on the measurement result, and transmit 452 a message requesting handover without including a CHO indication (e.g., a handover request message) to the C-MN 104A, and initiate immediate handover to the target PCell (T-PCell). In some embodiments, the C-MN 104A determines to perform immediate SN addition with the C-SN 106A during the immediate handover preparation. In response to the determination, the C-MN 104A transmits 455 a connection request message (e.g., an SN addition request message that does not include a conditional indication) to the C-SN 106A. In response, the C-SN 106A transmits 457 an acknowledgement (e.g., an SN addition request acknowledgement message) including an SN configuration (e.g., an SN RRC reconfiguration message) for the PSCell to the C-MN 104A. In response to the message requesting handover, the C-MN 104A can transmit 458 an acknowledgement (e.g., a handover request acknowledgement message) including a handover command message (e.g., an RRC reconfiguration message that may include an SN configuration if received from the C-SN 106A in event 457) to the S-MN 104B.

[0102] In response, the S-MN 104B transmits 460 a handover command message to the UE 102. In response to the handover command message, the UE 102 removes (or discards) the conditional configuration(s) and performs 421 a first random access procedure with the C-MN 104A via the target PCell. If the handover command message includes an SN configuration, the UE 102 performs 420 a second random access procedure with the C-SN 106A via the PSCell in response to the SN configuration. In response to the handover command message, the UE 102 transmits 464 a handover complete message (e.g., an RRC reconfiguration complete message) to the C-MN 104A.

[0103] In some embodiments, the UE 102 transmits 464 a handover complete message before, during, or after the first random access procedure. If the handover complete message includes a SN RRC reconfiguration complete message, the C-MN 104A transmits 466 an SN message (e.g., an SN reconfiguration complete message) including the SN RRC reconfiguration complete message to the C-SN 106A. In some embodiments where data transfer is used, the S-MN 104B transmits 428 a status message (e.g., an SN status transfer message) to the C-MN 104A. Depending on the embodiment, the C-MN 104A may transmit 430 a status message to the C-SN 106A. The C-MN 104A may further transmit 432 a message to release the UE context (e.g., a UE context release message) to the S-MN 104B, which initiates an SN release procedure with the S-SN if the UE 102 was in a DC at event 402. The UE 102 communicates 440 with the C-MN 104A via the target PCell in accordance with the handover command (and, if a C-SN 106A is added during the immediate handover, communicates with the C-SN 106A via the configured PCell in accordance with the SN configuration, respectively).

[0104] In response to or after receiving 452 the handover request message, the C-MN 104A may send 468 a SN request (e.g., SN release request (or SN modification request)) message to the C-SN 106A to request that the C-SN 106A cancel all C-SN configuration(s) of the UE 102. In response, the C-SN 106A sends 470 an acknowledgement (e.g., SN release request acknowledgement (or SN modification request acknowledgement)) message. The SN request message may include the MN UE X2 / XnAP ID and / or SN UE X2 / XnAP ID that were included in the message(s) of the conditional SN addition preparation procedure 492 (e.g., the SN addition request message and / or the SN addition request acknowledgement message). Events 468 and / or 470 may occur before or after events 455, 457, 466, or 430.

[0105] 5A-5D, each of scenarios 500A-500D may include some portions similar to any one of scenarios 300A-300C or 400A-400G, however, scenarios 500A-500D include an intra-base station CHO with CPAC or a CHO with SCG configuration.

[0106] Referring first to FIG. 5A, scenario 500A is an exemplary scenario in which MN 104A, consisting of CU 172 and one or more DU(s) 174B, such as source / serving DU (S-DU) 174A and candidate DU (C-DU), decides to perform intra-MN CHO with conditional SN addition.

[0107] The UE 102 is initially in the SC 502 with the MN 104A via the S-DU 174A, or in the DC with the MN 104A via the S-DU 174A and an S-SN (e.g., the C-SN 106A or another base station, not shown), and communicates with the S-SN via the PSCell according to the S-SN configuration. The CU 172 of the MN 104A decides at some point (e.g., based on some measurement results) to perform a conditional intra-MN handover. The CU 172 transmits 516 a message to the C-DU 174B requesting a context (e.g., a UE context setup request) for the UE 102 including a CHO indication (e.g., a conditional intra-DU mobility information IE including a CHO trigger IE with a value "CHO-initiation"). In response, the C-DU 174B transmits 506 a response to the request (e.g., a UE context setup response) including the C-DU configuration. The CU 172 of the MN 104A performs 592 a conditional SN addition preparation procedure with the C-SN 106A, similar to and as described with respect to the procedure 492 of CHO with SCG configuration of FIG. 4A. The CU 172 generates a CHO command including an SCG configuration for the CHO with SCG configuration. The CU 172 sends 507 an RRC reconfiguration message to the S-DU 174A, including a configuration ID, a trigger condition configuration, and a CHO command. In some embodiments, the RRC reconfiguration message 507 is included in a DL RRC message transfer message. In other embodiments, the RRC reconfiguration message 507 is included in a context modification request (e.g., a UE context modification request message). The S-DU 174A sends 508 an RRC reconfiguration message to the UE 102. The UE 102 replies 510 to the RRC reconfiguration message with an RRC reconfiguration complete message to the S-DU 174A. The S-DU 174A forwards 511 the RRC reconfiguration complete message in an uplink or acknowledgement message (e.g., a UL RRC Message Transfer message or a UE Context Modification Request Acknowledgement message) to the CU 172. Events 502, 516, 506, 592, 507, 508, 510, and 511 may be collectively referred to as an intra-MN CHO with SCG configuration preparation procedure 580.

[0108] After receiving the first conditional configuration, the UE 102 evaluates whether the condition is met to determine whether to connect to the C-PCell. If the UE 102 detects 515 that the condition for connecting to the C-PCell is met, the UE 102 initiates random access procedure(s) on the C-PCell and C-PSCell in response to the detection. That is, the condition (or "trigger condition") triggers the UE 102 to connect to the C-PCell and C-PSCell or to execute a CHO command including a C-SN configuration for both the C-PCell and C-PSCell. If the UE 102 does not detect that the condition is met, the UE 102 does not connect to the C-PCell and C-PSCell.

[0109] In response to the detection, the UE 102 initiates 515 a first random access procedure on the C-PCell and a second random access procedure on the C-PSCell. In response to the initiation, the UE 102 performs 519 a first random access procedure with the C-DU 174B via the C-PCell and performs 520 a second random access procedure with the C-SN 106A via the C-PSCell. In some embodiments, after successfully completing the first random access procedure with the UE 102, the C-DU 174B transmits 521 an indication of success (e.g., an access success message) to the CU 172, including a cell ID of the PCell. In response to the detection or initiation 515, the UE 102 transmits 522 an RRC reconfiguration complete message to the MN 104A via the C-DU 174B, including a SN RRC reconfiguration complete message. The C-DU 174B further forwards 523 the RRC reconfiguration complete message in an uplink message (e.g., a UL RRC message forwarding message). The RRC reconfiguration complete message also includes an SN RRC reconfiguration complete message to the CU 172. The UE 102 may send 522 the RRC reconfiguration complete message before, during, or after the first random access procedure.

[0110] In response to sending 522 the RRC reconfiguration complete message with the embedded SN RRC reconfiguration complete message, the MN 104A (or the CU 172 of the MN 104A) sends 524 an SN message (e.g., an SN reconfiguration complete message) including the SN RRC reconfiguration complete message to the C-SN 106A. In some embodiments where data transfer is utilized, the MN 104A (or the CU 172 of the MN 104A) sends 530 a status message (e.g., an SN status transfer message) to the C-SN 106A. Depending on the embodiment, the CU 172 may further send 532 a context release message (e.g., a UE context release command message) to the S-DU 174A, and in response, the S-DU 174A sends a completion message (e.g., a UE context release complete message). If the UE 102 is in a DC at event 502 and the S-SN is different from the C-SN 106A, the MN 104A may initiate an SN release procedure with the S-SN. The UE 102 communicates 539 with the MN 104A and the C-SN 106A via the C-PCell serving by the C-DU 174B and the C-PSCell according to the C-DU configuration and the C-SN configuration, respectively. Events 515, 519, 520, 521, 522, 523, 524, 530, 532, and 539 may be collectively referred to as an intra-MN CHO with SCG execution procedure 584.

[0111] Referring now to FIG. 5B, scenario 500B is an example scenario similar to scenario 500A, except that conditional handover is configured along with a CPAC configuration instead of an SCG configuration.

[0112] First, the UE 102, the MN 104A (S-DU 174A, C-DU 174B, CU 172), and the C-SN 106A perform an intra-MN CHO and CPAC configuration procedure 581 similar to the procedure 580 described with respect to FIG. 5A above. The differences are described below. In particular, in the conditional SN addition preparation procedure in CHO (similar to procedure 592 or 492) and the CPAC configuration procedure 581, the CU 172 can include a CPAC indication in the connection request message (e.g., SN addition request message) instead of a CHO indication by the SCG (as described with respect to procedure 480 or 580), similar to event 304. Alternatively, the CU 172 still includes a CHO indication in the connection request message in addition to a CPAC indication. Depending on the embodiment, the CU 172 may or may not restrict the C-SN 106A to configure only one C-SN configuration. If CU 172 enables C-SN 106A to configure multiple C-SN configurations, C-SN 106A may configure one or more C-SN configurations as described for Figure 3 A. For each of the C-SN configuration(s), CU 172 generates a conditional (re)configuration IE (e.g., CondReconfigurationToAddMod IE or CondReconfigToAddMod IE) that includes the conditional (re)configuration field(s) / IE(s) of the CHO command as described for Figure 3 A.

[0113] Thereafter, when the UE 102 detects 517 that a condition for connecting to the C-PCell is met according to the first trigger condition configuration, the UE 102 initiates a first random access procedure on the C-PCell in response to the detection. That is, the condition (or "trigger condition") triggers the UE 102 to connect to the C-PCell or to execute a CHO command for the C-PCell. In response to the initiation 517, the UE 102 executes 519 the first random access procedure with the C-DU 174B via the C-PCell. After successfully completing the first random access procedure with the UE 102, the C-DU 174B may transmit 521 an indication of success (e.g., an access success message) to the CU 172, including a cell ID of the PCell. In response to the detection or initiation 517, the UE 102 transmits 529 an RRC reconfiguration complete message to the MN 104A via the C-DU 174B. The C-DU 174B further forwards 531 the RRC reconfiguration complete message to the CU 172 in an uplink radio resource message (e.g., a UL RRC message transfer message). The UE 102 may transmit 529 the RRC reconfiguration complete message before, during, or after the first random access procedure. The CU 172 may further transmit 532 a context release message (e.g., a UE context release command message) to the S-DU 174A, in response to which the S-DU 174A transmits a message confirming completion (e.g., a UE context release complete message). The UE 102 communicates 537 with the MN 104A via the C-DU 174B via the C-PCell according to the C-DU configuration.

[0114] After executing the CHO command (including the C-DU configuration), the UE 102 starts evaluating the trigger condition(s) in the conditional (re)configuration field(s) / IE. While evaluating the trigger condition(s), the UE 102 detects 518 that the condition for connecting to the C-PSCell is met, and in response to the detection, initiates a second random access procedure in the C-PSCell. The UE 102 then performs a conditional SN addition execution procedure 594 in the C-DU 174B, the CU 172, and the C-SN 106A, similar to the conditional SN addition execution procedure 394 in FIG. 3A and procedure 494 in FIG. 4B. The UE 102 communicates 539 with the MN 104A and the C-SN 106A via the C-PCell serving by the C-DU 174B and the C-PSCell, respectively, according to the C-DU configuration and the C-SN configuration. Events 517 , 519 , 521 , 529 , 531 , 532 , 537 , 516 , 518 , 594 , and 539 may be collectively referred to as an intra-MN CHO with CPAC execution procedure 585 .

[0115] Referring now to FIG. 5C, scenario 500C describes an example scenario in which the MN first performs an intra-MN CHO with CPAC configuration preparation and later decides to cancel (some or all of) the conditional configuration preparation(s).

[0116] The UE 102, S-DU 174A, C-DU 174B, CU 172, and C-SN 106A first perform CHO at SCG configuration preparation procedure 580 and CHO at CPAC configuration procedure 581, respectively, as described in Figures 5A and 5B. The CU 172 may later send 512 a UE context request (e.g., a UE context request message) to the C-DU 174B, which may indicate the C-DU configuration(s) to be cancelled. In some embodiments, the CU 172 sends 512 the request because the CU 172 determines that the C-PCell(s) are no longer eligible for CHO. In response, the C-DU 174B sends 514 a response (e.g., a UE context response message) to the CU 172. Depending on the embodiment, the CU 172 may send 542 a request to release the SN (e.g., an SN release request message) to the C-SN 106A. In response, the C-SN 106A sends 544 an acknowledgement (e.g., an SN Release Request Acknowledgement message) to the CU 172. The CU 172 sends 546 a context release message (e.g., a UE Context Release message) to the C-SN 106A. The CU 172 generates an RRC reconfiguration message including a release list (e.g., a condReconfigToRemoveList field or a condReconfigurationToRemoveList field) including the configuration ID(s) of the conditional configuration(s) to be released. The CU 172 sends 547 a CU-to-DU message (e.g., a DL RRC Message Transfer message or a UE Context Modification Request message) including the RRC reconfiguration message to the S-DU 174A. The S-DU 174A retrieves the RRC reconfiguration message from the CU-to-DU message and sends 548 the RRC reconfiguration message to the UE 102. The UE 102 sends 550 an RRC reconfiguration complete message to the S-DU 174A in response to the RRC reconfiguration message. The S-DU 174A sends 551 a DU-to-CU message (eg, a UL RRC message transfer message or a UE context modification response message) including an RRC reconfiguration complete message to the CU 172).

[0117] In some embodiments, the context request response message at events 512 and 514 is a release command (e.g., a UE context release command message) and a completion notification (e.g., a UE context release complete message), respectively. In other embodiments, the UE context request message and the UE context response message at events 512 and 514 are a modification request (e.g., a UE context modification request message) and a response (e.g., a UE context modification response message), respectively.

[0118] Referring now to FIG. 5D, in scenario 500D, an example scenario is described in which the MN first initiates an immediate intra-MN handover after an intra-MN CHO with a conditional SN addition procedure.

[0119] Initially, the UE 102, the S-DU 174A, the C-DU 174B, the CU 172, and the C-SN 106A perform the CHO in SCG configuration preparation procedure 580 and the CHO in CPAC configuration procedure 581, respectively, as described in FIG. 5A and FIG. 5B. In some embodiments, the UE 102 later changes the moving orbit and provides the measurement result to the CU 172. Thus, the CU 172 may determine to perform immediate handover preparation for the UE 102 based on the measurement result, and send 512 a request for UE context (e.g., a UE context setup request message) to the C-DU 174B for immediate handover preparation without including a conditional indication (e.g., a CHO indication). In response, the C-DU 174B sends a response (a UE context response message, such as a UE context setup response message) to the CU 172, including the DU configuration for the target PCell. In some embodiments, the CU 172 determines to perform an immediate SN addition with the C-SN 106A during immediate handover preparation. In response to the determination, the CU 172 sends 554 a connection request (e.g., an SN request message such as an SN addition request message) to the C-SN 106A without including a conditional indication (e.g., a CPAC indication). The C-SN 106A in response sends 556 an acknowledgement (e.g., an SN addition request acknowledgement) to the CU 172 that includes an SN configuration (e.g., an SN RRC reconfiguration message) for the PSCell. The CU 172 can generate a handover command message (e.g., an RRC reconfiguration message) that includes the DU configuration, and may include the SN configuration if received from the C-SN 106A at event 556.

[0120] The CU 172 sends 559 a CU-to-DU message (e.g., DL RRC message transfer message) containing the handover command message to the S-DU 174A. The S-DU 174A retrieves the handover command message from the CU-to-DU message and sends 560 the handover command message to the UE 102. In response to the RRC reconfiguration message, the UE 102 deletes or discards all configured conditional configuration(s) and performs 519 a first random access procedure with the C-DU 174B via the target PCell. If the handover command message also contains a SN configuration, the UE 102 performs 520 a second random access procedure with the C-SN 106A via the PSCell. In response to the handover command message, the UE 102 sends 562 a handover complete message (e.g., RRC reconfiguration complete message) to the C-DU 174B.

[0121] Depending on the embodiment, the UE 102 transmits 562 an RRC reconfiguration complete message before, during, or after the (first) random access procedure. The C-DU 174B transmits the RRC reconfiguration complete message to the CU 172 in an uplink radio resource message (e.g., a UL RRC message transfer message). If the handover complete message includes a SN RRC reconfiguration complete message, the CU 172 transmits 566 an SN message (e.g., an SN reconfiguration complete message) including the SN RRC reconfiguration complete message to the C-SN 106A. In some embodiments where data transfer is used, the CU 172 transmits 530 a status message (e.g., an SN status transfer message) to the C-SN 106A. The CU 172 may further transmit 532 a context release message (e.g., a UE context release command message) to the S-DU 174A, which in response transmits an indication of completion (e.g., a UE context release complete message) to the CU 172. The UE 102 communicates 540 with the C-DU 174B via the target PCell in accordance with the DU configuration (and also communicates with the C-SN 106A via the configured PSCell in accordance with the SN configuration, respectively, if the C-SN 106A is added during the immediate intra-MN handover).

[0122] Depending on the embodiment, the CU 172 may send 568 a SN request message (e.g., a SN release request or a SN change request message) to the C-SN 106A to request the C-SN 106A to cancel all of the C-SN configuration(s). The C-SN 106A may respond by sending 570 an acknowledgement (e.g., a SN release request acknowledgement or a SN modification request acknowledgement message). The SN request message may include the MN UE X2 / XnAP ID and / or the SN UE X2 / XnAP ID that were included in the messages of the conditional SN addition preparation procedure 592 (e.g., the SN addition request message and / or the SN addition request acknowledgement message). Events 568 and / or 570 may occur before or after events 554, 556, 566, or 430.

[0123] 6-12 are flowcharts illustrating example methods that a base station (e.g., base station 104A, 104B, 106A, or 106B) may implement to support conditional procedures in accordance with the techniques of this disclosure. As indicated at various times throughout this disclosure, the example methods illustrated in FIGS. 6-12 may be implemented during scenarios 300A-300C, 400A-400G, and 500A-500E above.

[0124] Referring to FIG. 6, a method 600 is shown in which an MN (e.g., MN 104A or C-MN 104A) performs a conditional SN procedure with a C-SN of a C-SN (e.g., C-SN 106A) for a UE (e.g., UE 102) and determines whether to include a CPAC indicator or a CHO indicator in an SN request message.

[0125] During method 600, at block 602, the MN decides to send an SN request message (e.g., an SN addition request or an SN modification request message) to the C-SN to perform a conditional SN procedure for the UE. At block 604, the MN decides whether a conditional SN procedure is performed during CHO preparation for the UE. If a conditional SN procedure is performed during CHO preparation, the flowchart proceeds to block 614, where the MN includes a CHO indicator in the SN request message. The flowchart may then continue to block 616, where the MN may indicate generating at most one C-SN configuration in the SN request message to the C-SN. At block 618, the MN sends an SN request message to the C-SN (e.g., event 455, 492, 554, or 592). At block 620, the MN receives an acknowledgement message (e.g., an SN addition request acknowledgement or an SN modification request acknowledgement message) from the SN that includes a configuration IE (e.g., event 457, 492, 556, or 592).

[0126] To indicate to the C-SN to generate at most one C-SN configuration at block 616, in some embodiments, the RAN node may include an indication of the maximum number of PSCells (e.g., maximum number of PSCells to prepare IE) with a value equal to one in the SN request message. Alternatively, the RAN node refrains from including an indication in the SN request message. In further embodiments, the RAN node includes a candidate cell information list in the SN request message, where the candidate cell information list indicates only one cell of the C-SN that is eligible to become a C-PSCell. For example, the candidate cell information list includes measurement results that indicate only one cell of the C-SN that is eligible to become a C-PSCell.

[0127] If, at block 604, a conditional SN procedure is not performed during preparation of the CHO, the flowchart proceeds to block 606 where the MN includes a CPAC indicator in the SN request message. At block 608, the MN indicates that it is allowed to generate multiple C-SN configurations in the SN request message to the C-SN. In some implementations of block 608, the RAN node may include an indication of the maximum number of PSCells with a value greater than one. At block 610, the MN sends the SN request message to the C-SN (e.g., Event 304). At block 612, the MN receives an acknowledgement (e.g., SN Addition Request Acknowledgement or SN Modification Request Acknowledgement message) message from the SN that includes one or more configuration IEs (e.g., Event 308).

[0128] Referring now to FIG. 7A, a method 700A is shown in which an SN (e.g., C-SN 106A) performs a conditional SN procedure with a MN (e.g., MN 104A or C-MN 104A) of a UE (e.g., UE 102) to determine whether to generate one or more configuration IE(s).

[0129] During method 700A, the SN at block 702 receives an SN request message (e.g., an SN Add Request or SN Modify Request message) from the MN (e.g., events 304, 492, 455, 554, or 592). At block 704, the SN determines whether the SN request message includes a conditional indicator. If the SN request message includes a conditional indicator, the flowchart proceeds to block 706 where the SN generates one or more configuration IEs (e.g., CG-Config IEs). Then, at block 708, the SN sends an acknowledgement message (e.g., an SN Add Request Acknowledgement or SN Modify Request Acknowledgement message) including the configuration IEs to the MN (e.g., events 308, 492, 457, 556, or 592). If the SN request message does not include a conditional indicator, the flowchart proceeds to block 710 where the SN generates a single configuration IE. Then, at block 712, the SN sends an acknowledgement message including the configuration IE to the MN.

[0130] In some embodiments, the SN request message at block 702 includes a CPAC indicator. In some embodiments, the SN request message at block 702 includes a CHO indicator.

[0131] In some embodiments, the RAN node generates a container that includes one or more configuration IEs at block 706 and includes the container in the acknowledgement message at block 708. In some embodiments, the RAN node refrains from generating a container that includes the configuration IEs at block 710 and includes the configuration IEs directly in the acknowledgement message.

[0132] In some embodiments, the container is a cg-CandidateList field, a cg-CandidateList field-r17, a CG-CandidateList-IEs IE, a CG-CandidateList-r17 IE, a cg-CandidateToAddModList field, a cg-CandidateToAddModList field-r17, a CG-CandidateToAddModList-r17 IE.

[0133] Referring now to FIG. 7B, a method 700B is shown in which an SN (e.g., C-SN 106A) performs a conditional SN procedure with a MN (e.g., MN 104A or C-MN 104A) of a UE (e.g., UE 102) to determine whether to generate one or more configuration IE(s).

[0134] During method 700B, in block 702, the SN receives an SN request message (e.g., an SN Add Request or SN Modify Request message) from the MN (e.g., events 304, 492, 455, 554, or 592). In block 705, the SN determines whether the SN request message includes a CHO indicator or a CPAC indicator. If the SN request message includes a CPAC indicator, the flowchart proceeds to block 706 where the SN generates one or more CG-Config IEs. Thereafter, in block 708, the SN receives an acknowledgement message (e.g., an SN Add Request Acknowledgement or an SN Modify Request Acknowledgement message) including a CG-Config IE to the MN (e.g., event 308). If the SN request message includes a CHO indicator in block 705, the flowchart proceeds to block 710 where the SN generates a single configuration IE. Then, in block 712, the SN sends an acknowledgement message including a configuration IE to the MN (e.g., events 457, 492, 556, 592).

[0135] In some embodiments, the RAN node at block 706 generates a first container including one or more configuration IEs and includes the container in the acknowledgement message at block 708. In some embodiments, the RAN node at block 710 generates a second container including a single configuration IE and includes the container IE in the acknowledgement message at block 712. In other embodiments, the RAN node refrains from generating a container including a configuration IE at block 710 and includes the configuration IE directly in the acknowledgement message.

[0136] In some embodiments, the first container is a cg-CandidateList field, a cg-CandidateList field-r17, a CG-CandidateList-IEs IE, a CG-CandidateList-r17 IE, a cg-CandidateToAddModList field, a cg-CandidateToAddModList field-r17, a CG-CandidateToAddModList-r17 IE. In some embodiments, the second container is a cg-CandidateList field, a cg-CandidateList field-r17, a CG-CandidateList-IEs IE, a CG-CandidateList-r17 IE, a cg-CandidateToAddModList field, a cg-CandidateToAddModList field-r17, a CG-CandidateToAddModList-r17 IE.

[0137] Referring to FIG. 8, a method 800 is shown in which an MN (e.g., MN 104A or C-MN 104A) performs a conditional SN procedure with a C-SN (e.g., C-SN 106A) of a UE (e.g., UE 102) and indicates to the C-SN to generate up to one C-SN configuration.

[0138] During method 800, the MN decides to perform a conditional SN procedure with the C-SN at block 802. At block 804, the MN includes a conditional indicator (e.g., a CPAC indicator or a CHO indicator) in an SN request message (e.g., an SN addition request or an SN modification request message). At block 806, the MN indicates in the SN request message to the C-SN that it will generate at most one C-SN configuration. At block 808, the MN sends an SN request message to the C-SN (e.g., event 304, 455, 492, 554, or 592). At block 810, the MN receives an acknowledgement message (e.g., an SN addition request acknowledgement or an SN modification request acknowledgement message) from the SN that includes a single configuration IE (e.g., event 308, 457, 492, 556, or 592). At block 812, the MN obtains the C-SN configuration from the configuration IE. At block 814, the MN generates an RRC message that includes the C-SN configuration. In block 816, the MN sends an RRC message to the UE (eg, event 312, 406 to 408, 407 to 409, 458 to 460, 507 to 508, or 559 to 560).

[0139] If the RAN node is a CU of the MN, the CU sends an RRC message to the UE via the DU. If the RAN node is a C-MN, the RRC message is a CHO command, and the C-MN sends the CHO command to the UE via the source base station. If the RAN node is a T-MN, the RRC message is a HO command, and the T-MN sends the HO command to the UE via the source base station.

[0140] Referring to FIG. 9, a method 900 is shown in which an MN (e.g., MN 104A or C-MN 104A) determines to perform a conditional SN procedure with a C-SN (e.g., C-SN 106A) of a UE (e.g., UE 102) and generates an RRC message including one C-SN configuration.

[0141] During method 900, at block 902, the MN sends an SN request message (e.g., an SN addition request or an SN modification request message) to the C-SN to perform a conditional SN procedure for the UE (e.g., event 304, 492, 455, 554, or 592). At block 904, the MN receives an acknowledgement message (e.g., an SN addition request acknowledgement or an SN modification request acknowledgement message) from the C-SN (e.g., event 308, 492, 457, 556, or 592). At block 906, the MN determines whether the acknowledgement message includes a single C-SN configuration or multiple C-SN configurations. If the acknowledgement message includes multiple C-SN configurations, the flowchart proceeds to block 908 where the MN selects one of the multiple C-SN configurations. At block 910, the MN generates an RRC message including the C-SN configuration. In block 912, the MN sends an RRC message to the UE (e.g., events 312, 406-408, 407-409, 458-460, 507-508, or 559-560). If the acknowledgement message includes a single C-SN configuration in block 906, the flowchart proceeds to block 910, where the MN generates an RRC message including the C-SN configuration. In block 912, the MN sends an RRC message to the UE (e.g., events 312, 406-408, 407-409, 458-460, 507-508, or 559-560).

[0142] In some embodiments, the SN request message includes a CPAC indicator. In some embodiments, the SN request message includes a CHO indicator.

[0143] If the RAN node is a CU of the MN, the CU sends an RRC message to the UE via the DU. If the RAN node is a C-MN, the RRC message is a CHO command, and the C-MN sends the CHO command to the UE via the source base station. If the RAN node is a T-MN, the RRC message is a HO command, and the T-MN sends the HO command to the UE via the source base station.

[0144] Referring now to FIG. 10, a method 1000 is shown in which an SN (e.g., C-SN 106A) performs a conditional SN procedure with a MN (e.g., MN 104A or C-MN 140A) of a UE (e.g., UE 102) to determine whether to generate one or more configuration IE(s).

[0145] During method 1000, at block 1002, the SN receives an SN request message (e.g., an SN Addition Request or an SN Change Request message) from the MN, the message including one or more cell measurement results (e.g., events 304, 492, 455, 554, or 592). At block 1004, the SN determines whether the SN Request message includes a conditional indicator. If the SN Request message includes a conditional indicator, the flowchart proceeds to block 1006, where the SN determines at least one of the one or more cells, the measurement result(s) of the at least one cell exceed a first threshold. At block 1008, the SN generates a configuration IE (e.g., a CG-Config IE) for each cell. At block 1010, the SN receives an acknowledgement message (e.g., an SN Addition Request Acknowledgement or an SN Modify Request Acknowledgement message) including the at least one configuration IE to the MN (e.g., events 308, 492, 457, 556, or 592). If the SN request message does not include a conditional indicator at block 1004, the flowchart proceeds to block 1012 where the SN determines only one of the one or more cells as a PSCell and the measurement results of the cell exceed a second threshold. At block 1014, the SN generates a configuration IE for the cell. At block 1016, the SN receives an acknowledgement message (e.g., an SN Addition Request Acknowledgement or an SN Modification Request Acknowledgement message) that includes the configuration IE to the MN (e.g., event 308, 492, 456, 556, or 592).

[0146] Referring to FIG. 11A, a method 1100A is shown in which a MN (e.g., a MN or C-MN 104A) determines how to perform a conditional SN procedure with a SN (e.g., C-SN 106A) for a UE (e.g., UE 102) and obtain RRC message(s) from an acknowledgment message.

[0147] During method 1100A, in block 1102, the MN sends an SN request message (e.g., an SN Addition Request or an SN Change Request message) to the SN to perform an SN procedure at a second RAN node for the UE (e.g., event 304, 492, 455, 554, or 592). In block 1104, the MN receives an acknowledgement message (e.g., an SN Addition Request Acknowledgement or an SN Modification Request Acknowledgement message) including an MN container from the SN in response to the SN request message (e.g., event 308, 492, 457, 556, or 592). In block 1106, the MN determines whether the SN procedure is for an immediate SN procedure or a conditional SN procedure. If the SN procedure is an immediate SN procedure, the flowchart proceeds to block 1108, where the MN determines that the MN container from the SN includes a first IE (e.g., a CG-Config IE). In block 1110, the MN retrieves the RRC message from the first IE in response to the determination. At block 1112, the MN sends an RRC message to the UE. If, at 1106, the SN procedure is a conditional SN procedure, the flowchart proceeds to block 1114 where the MN determines that the MN container includes a second IE (e.g., a CG-CandidateList IE) from the SN. At block 1116, the MN obtains one or more configuration IE(s) (e.g., a CG-Config IE(s)) from the second IE in response to the determination. At block 1118, the MN obtains one or more RRC message(s) from the configuration IE(s). The MN sends an RRC message to the UE (e.g., events 312, 406-408, 407-409, 458-460, 507-508, or 559-560) at block 1120. At block 1122, the MN (or the MN's CU) can send one of the configuration IE(s) to the DU.

[0148] Referring to FIG. 11B, a method 1100B is shown in which a MN (e.g., MN 104A or C-MN 104A) determines how to perform a conditional SN procedure with a SN (e.g., C-SN 106A) for a UE (e.g., UE 102) and obtain RRC message(s) from an acknowledgment message.

[0149] During method 1100B, in block 1102, the MN sends an SN request message (e.g., an SN Addition Request or an SN Change Request message) to the SN to perform an SN procedure at a second RAN node for the UE (e.g., event 304, 492, 455, 554, or 592). In block 1104, the MN receives an acknowledgement message (e.g., an SN Addition Request Acknowledgement or an SN Modification Request Acknowledgement message) including an MN container from the SN in response to the SN request message (e.g., event 308, 492, 457, 556, or 592). In block 1107, the MN determines whether a CPAC indicator is included in the SN request message. If a CPAC indicator is not included in the SN request message (i.e., if a CHO indicator is included or if neither a CPAC indicator nor a CHO indicator is included), the flowchart proceeds to block 1108, where the MN determines whether the MN container includes a first IE (e.g., a CG-Config IE) from the SN. At block 1110, the MN retrieves an RRC message from the first IE in response to the determination. At block 1112, the MN sends the RRC message to the UE. If, at block 1107, a CPAC indicator was included in the SN request message, the flowchart proceeds to block 1114, where the MN determines from the SN whether the MN container includes a second IE (e.g., a CG-CandidateList IE). At block 1116, the MN retrieves one or more configuration IE(s) (e.g., a CG-Config IE(s)) from the second IE in response to the determination. At block 1118, the MN retrieves one or more RRC message(s) from the configuration IE(s). The MN sends an RRC message to the UE (e.g., events 312, 406-408, 407-409, 458-460, 507-508, or 559-560) at block 1120. In block 1122, the MN (or the CU of the MN) may send one of the configuration IE(s) to the DU.

[0150] Referring to FIG. 12A, a method 1200A is shown in which a MN (e.g., MN 104A) performs an SN procedure with a SN (e.g., S-SN 106B) for a UE (e.g., UE 102) to prevent the SN from performing a conditional SN procedure.

[0151] During method 1200A, at block 1202, the MN operates with the SN in the DC. At block 1204, the MN may decide to perform a conditional handover procedure with the C-MN. At block 1206, the MN indicates in an SN request message to the SN to avoid conditional configuration (e.g., SN-initiated intra-SN or intra-SN CPC) configuration. At block 1208, the MN sends an SN request message to the SN. At block 1210, the MN receives an acknowledgement message (e.g., an SN request acknowledgement message) from the SN.

[0152] In some embodiments, the SN avoids configuring conditional settings after receiving a SN request message (eg, an SN add request message or an SN modify request message).

[0153] Referring to FIG. 12B, a method 1200B is shown in which a MN (e.g., MN 104A) performs an SN procedure with a SN (e.g., S-SN 106B) for a UE (e.g., UE 102) to prevent the SN from performing a conditional SN procedure.

[0154] During method 1200B, in block 1202, the MN operates with the SN in the DC. In block 1204, the MN may decide to perform a conditional handover procedure with the C-MN. In block 1207, the MN receives an SN Required message (e.g., SN Modification Required or SN Change Required message) from the SN indicating that the SN requests a conditional SN procedure. In block 1209, the MN indicates rejection of the requested action to the SN with an SN message (e.g., SN Modification Reject or SN Change Reject message). In block 1211, the MN sends the SN message to the SN.

[0155] In some embodiments, the SN avoids configuring the conditional configuration after receiving a SN message (eg, an SN modification reject message or an SN change reject message).

[0156] The following list of examples reflects various embodiments expressly contemplated by this disclosure.

[0157] Example 1. A method for managing candidate cell configurations for a user equipment (UE), implemented in a first node, comprising: transmitting to a second node a request for connection with the second node; receiving, in response to transmitting the request for connection, a response from the second node having an information element configured to include a list of configurations or a conditional configuration, the response including at least one of the list of configurations or the conditional configuration; and transmitting a radio resource message based at least on the list of configurations or the conditional configuration.

[0158] Example 2. The method of example 1, wherein the request for connection includes an indication that (i) the second node has permission to generate multiple configurations for the list of configurations in the request for connection, or (ii) the second node will generate at most one conditional configuration, and further wherein the response includes the conditional configuration.

[0159] Example 3. The method of example 2, wherein the request for connection includes the indication that the second node has permission to generate multiple configurations for the list of configurations when the first node does not allow the UE to initiate communication with the second node during preparation for a conditional handover.

[0160] Example 4. The method of example 2, wherein the request for connection includes the indication that the second node generates at most one conditional configuration when the first node causes the UE to initiate communication with the second node during preparation for a conditional handover.

[0161] Example 5. A method according to any of the preceding examples, wherein the response includes an information element and one of an indication of an immediate secondary node procedure or an indication of a conditional secondary node procedure.

[0162] Example 6. The method of Example 5, wherein the response includes the indication for an immediate secondary node procedure, and further includes determining that the information element includes the conditional configuration based on the indication for an immediate secondary node procedure, and generating the radio resource message to be transmitted to the UE from the conditional configuration in response to the determining.

[0163] Example 7. The method of Example 5, wherein the response includes the indication for a conditional secondary node procedure, and further includes determining, based on the indication for a conditional secondary node procedure, that the information element includes the list of configurations, obtaining one or more configurations of the list of configurations from the information element in response to the determining, and generating the radio resource message to be transmitted to the UE from the one or more configurations.

[0164] Example 8. A method according to any of Examples 1 to 4, further comprising: determining, based on a request for the connection not including a CPA indicator, that an information element of the response includes the conditional configuration; and generating, from the conditional configuration, the radio resource message to be transmitted to the UE in response to the determining.

[0165] Example 9. A method according to any of Examples 1 to 4, further comprising: determining, based on the request for connection including a CPA indicator, that an information element of the response includes the list of configurations; obtaining from the information element one or more configurations of the list of configurations in response to the determining; and generating the radio resource message to be transmitted to the UE from the one or more configurations.

[0166] Example 10. A method according to any of the preceding examples, further comprising: receiving from the UE a configuration identifier corresponding to the second node; and using the configuration identifier to identify at least one of: (i) an identity of the second node, (ii) an identity of a radio cell of the second node, or (iii) a configuration of the second node.

[0167] Example 11. The method of example 10, further comprising: sending a message to the second node in response to receiving the configuration identifier; and receiving coordination information from the second node in response to sending the message to the second node.

[0168] Example 12. The method of example 11, further comprising: modifying one or more configuration parameters of the second node using the adjustment information; and transmitting the modified configuration parameters to the UE.

[0169] Example 13. A method as described in any of Examples 1 to 9, further comprising: the UE being dual-connected to the first node and a third node; receiving a request from the third node to forward communications for the UE; and transmitting the request for connection in response to receiving the request to forward the communications.

[0170] Example 14. The method of example 13, further comprising sending a message to the third node based at least on the list of configurations or the conditional configuration.

[0171] Example 15. A method as described in any of Examples 10 to 14, wherein the UE is dual-connected to the first node and a third node, and further comprising sending a command to the third node to release the context of the UE.

[0172] Example 16. The method of any one of Examples 10 to 15, further comprising sending a command to the third node to release radio resources.

[0173] Example 17. The method of example 15 or 16, further comprising: receiving a message from the third node including a status parameter of the third node; and transmitting the status parameter of the third node to the second node.

[0174] Example 18. A method according to any of the preceding examples, further comprising: receiving an indication from a fourth node to the first node to perform a handover; and generating a handover command including the at least one of the list of configurations or the conditional configurations.

[0175] Example 19. The method of example 18, further comprising: sending the handover command to the fourth node; and communicating with the UE according to the handover command.

[0176] Example 20. The method of example 18 or 19, further comprising communicating with the UE and the second node according to the at least one of the commands and the list of configurations or the conditional configuration.

[0177] Example 21. A method according to any of Examples 18 to 20, wherein transmitting the radio resource message based at least on the list of configurations or the conditional configuration includes transmitting to the fourth node the list of configurations or the conditional configuration, and an indication to transmit the list of configurations or the conditional configuration together with the handover command to the UE.

[0178] Example 22. The method according to any one of Examples 18 to 21, wherein the handover is a conditional handover and the handover command is a conditional handover command.

[0179] Example 23. The method according to any one of Examples 18 to 21, wherein the handover is an immediate handover and the handover command is an immediate handover command.

[0180] Example 24. A method according to any of Examples 18 to 23, further comprising: receiving an indication from the fourth node to cancel the handover; and sending an indication to the second node to release the context of the UE.

[0181] Example 25. A method according to any of Examples 18 to 23, further comprising: deciding to cancel the handover; sending an indication to the fourth node to cancel the handover; and sending an indication to the second node to release the context of the UE.

[0182] Example 26. The method of example 22, further comprising: receiving an indication to perform an immediate handover after receiving the indication to perform the conditional handover; and sending an immediate handover command to the fourth node.

[0183] Example 27. The method of example 26, further comprising sending to the second node an indication canceling the request for the connection with the second node.

[0184] Example 28. The method of example 27, further comprising sending an indication to the second node to temporarily suspend the request for the connection with the second node.

[0185] Example 29. The method of example 1, wherein the first node includes a first distributed unit, a second distributed unit, and a central unit.

[0186] Example 30. The method described in Example 29, wherein sending the request for connection is performed from the central unit, receiving the response is performed at the central unit, and sending the radio resource message is performed from the central unit to the first distributed unit.

[0187] Example 31. The method of example 29 or 30, further comprising sending to the second distributed unit an indication to perform a conditional handover, wherein sending the request for connection is in response to receiving the response, and further wherein the radio resource message includes a conditional handover command.

[0188] Example 32. The method of any of Examples 29 to 31, further comprising communicating with the UE and the second node according to the conditional handover command and the at least one of the list of configurations or the conditional configuration.

[0189] Example 33. The method of Example 31 or 32, further comprising sending to the first distributed unit a command to release the context of the UE in response to receiving an indication from the second distributed unit that radio resource reconfiguration is complete.

[0190] Example 34. The method of any of Examples 31, further comprising obtaining a context of the UE from the second distributed unit.

[0191] Example 35. The method of any of Examples 34, further comprising: determining to cancel the conditional handover based on the context of the UE; and sending a command to the first distributed unit to release the conditional configuration or the list of configurations.

[0192] Example 36. The method of Example 34, further including: determining to cancel the conditional handover and perform an immediate handover based on the context of the UE; and sending a command to the first distributed unit for the UE to perform the immediate handover to the second distributed unit.

[0193] Example 37. The method of Example 36, further comprising: receiving an indication from the second distributed unit that the immediate handover is complete; and sending a command to the first distributed unit to release the context of the UE in response to receiving the indication that the immediate handover is complete.

[0194] Example 38. The method of Example 37, further comprising sending to the second node a request for the UE to initiate communication with the second node in the handover procedure, the command for the UE to perform the handover being responsive to receiving a response to the request to add the second node to the handover procedure.

[0195] Example 39. The method of example 37 or 38, further comprising sending to the second node, in response to receiving a first indication that the handover is complete, a second indication that the handover is complete and a status parameter for the second node.

[0196] Example 40. The method of any of the preceding examples, further comprising sending to the second node a request to release radio resources for the second node.

[0197] Example 41. A method according to any of the preceding examples, further comprising the first node operating in a dual connection with the second node for the UE and sending an indication to the second node to avoid configuring a conditional configuration.

[0198] Example 42. A method according to any of Examples 1 to 40, wherein the first node operates in a dual connection with the second node for the UE, and further includes receiving a request for a conditional secondary node procedure from the second node, and sending a rejection of the request for the conditional secondary node procedure to the second node.

[0199] Example 43. A method for managing candidate cell configurations of a user equipment (UE) initially configured to operate in connection with a first node, the method being implemented in a second node and comprising: receiving a request for connection with the second node from the first node; determining, based on the received request for connection, whether the request includes a list of configurations or a conditional configuration; and, in response to the determining, transmitting a response to the first node including at least one of the list of configurations or the conditional configuration.

[0200] Example 44. The method of Example 43, wherein the request for connection with the second node includes candidate cell information, and the determining is based on the candidate cell information.

[0201] Example 45. The method of example 43, wherein the determining is based on whether the request for the connection includes a conditional indicator.

[0202] Example 46. The method of example 45, wherein the request for connection includes the conditional indicator and further includes generating a list of the configurations, and the response includes the list of the configurations.

[0203] Example 47. The method of example 45, wherein the request for the connection does not include the conditional indicator, further comprising generating the conditional configuration, and the response includes the conditional configuration.

[0204] Example 48. The method of example 43, wherein the determining is based on whether the request for connection includes a conditional handover indicator or a conditional primary-secondary cell (PSCell) addition or change (CPAC) indicator.

[0205] Example 49. The method of Example 48, wherein the request for connection includes the CPAC indicator and further includes generating a list of the configurations, and the response includes the list of the configurations.

[0206] Example 50. The method of example 48, wherein the request for connection includes the conditional handover indicator, further including generating the conditional configuration, and the response includes the conditional configuration.

[0207] Example 51. The method of Example 43, further comprising determining whether the request for connection includes measurement results of one or more cells and whether the request for connection includes a conditional indicator.

[0208] Example 52. The method of Example 51, wherein the request for connection includes the conditional indicator, and further includes selecting at least one cell of the one or more cells with a measurement result exceeding a threshold, and generating a list of configurations, the list of configurations including a configuration for each of the at least one cell, and the response including the list of configurations.

[0209] Example 53. The method of Example 51, wherein the request for connection does not include the conditional indicator, and further includes selecting one cell from the one or more cells with a measurement result for the cell that exceeds a pre-set threshold, and generating the conditional configuration based on the one cell, and wherein the response includes the conditional configuration.

[0210] Example 54. A network node including processing hardware and configured to implement any of the preceding examples.

[0211] Example 55. A method of managing candidate cell configurations for a user equipment (UE) initially configured to operate in connection with a first node, the method being implemented in the UE and comprising: receiving a radio resource message from the first node, the radio resource message including an information element that may include either a list of configurations or a conditional configuration, and may include one of the list of configurations or the conditional configurations; detecting that a condition for connecting to a second node is satisfied, the condition for connecting to the second node being in accordance with the list of configurations or one of the conditional configurations; and operating in connection with the second node in response to the detecting.

[0212] Example 56. The method of example 55, wherein the radio resource message includes a handover command.

[0213] Example 57. The method of Example 56, further comprising: detecting that the handover command is a conditional handover command and that a condition for connecting to a third node is met, the condition for connecting to the third node being in accordance with the conditional handover command; and, in response to detecting that the condition for connecting to the third node is met, operating on the connection with the third node; and at least temporarily suspending the connection with the first node.

[0214] Example 58. The method of Example 56, wherein the handover command is an immediate handover command, and further comprising: operating on the connection with the third node in accordance with the immediate handover command; and at least temporarily suspending the connection with the first node.

[0215] Example 59. The method of Example 56, wherein the handover command is a conditional handover command, and further comprising, after receiving the conditional handover command, receiving a command from the first node to cancel the conditional handover before a condition associated with the conditional handover command is satisfied.

[0216] Example 60. The method of example 56, wherein the handover command is a conditional handover command, and further comprising, after receiving the conditional handover command, receiving an immediate handover command before a condition associated with the conditional handover command is satisfied, operating on the connection with the third node in accordance with the immediate handover command, and at least temporarily suspending the connection with the first node.

[0217] Example 61. The method described in any of Examples 56 to 60, wherein the first node is a first distributed unit of a master node, and the third node is a second distributed unit of the master node.

[0218] Example 62. A user device including processing hardware and configured to implement any of Examples 55 to 61.

[0219] The following explanations may be applied to the above explanations.

[0220] In some embodiments, "message" is used and can be replaced with "information element (IE)". In some embodiments, "IE" is used and can be replaced with "field". In some embodiments, "config" is used and can be replaced with "configurations" or configuration parameters. In some embodiments, the action "send" is used and can be replaced with "send".

[0221] A user device (e.g., UE 102) capable of implementing the techniques of this disclosure may be any suitable device capable of wireless communication, such as a smartphone, a tablet computer, a laptop computer, a mobile game console, a point of sale (POS) terminal, a health management device, a drone, a camera, a media streaming dongle or another personal media device, a wearable device such as a smart watch, a wireless hotspot, a femtocell, or a broadband router. Furthermore, a user device may in some cases be embedded in an electronic system such as a vehicle's head unit or an advanced driver assistance system (ADAS). Still further, a user device may operate as an Internet of Things (IoT) device or a Mobile Internet Device (MID). Depending on the type, a user device may include one or more general-purpose processors, computer-readable memory, a user interface, one or more network interfaces, one or more sensors, and the like.

[0222] Certain embodiments are described in this disclosure as including logic, or several components or modules. The modules can be software modules (e.g., code or machine-readable instructions stored on a non-transitory machine-readable medium) or hardware modules. A hardware module is a tangible unit that can perform certain operations and can be configured or arranged in a certain manner. A hardware module can include dedicated circuitry or logic that is permanently configured (e.g., as a special-purpose processor, such as a field programmable gate array (FPGA) or application specific integrated circuit (ASIC), digital signal processor (DSP)) to perform certain operations. A hardware module can also include programmable logic or circuitry that is temporarily configured by software (e.g., contained within a general-purpose processor or other programmable processor) to perform certain operations. The decision to implement a hardware module in dedicated and permanently configured circuitry or in temporarily configured circuitry (e.g., configured by software) can be subject to cost and time considerations.

[0223] If implemented in software, the techniques may be provided as part of an operating system, a library used by multiple applications, a specific software application, etc. The software may be executable by one or more general-purpose processors or one or more special-purpose processors.

Claims

1. 1. A method for managing a candidate cell configuration for a user equipment (UE) initially communicating with at least a first node, the method being implemented in a second node, the method comprising: receiving, by the second node, from the first node, a request for connection with the second node, the request including a procedure indicator; transmitting, by the second node to the first node, one of a list of two or more conditional configurations or a single conditional configuration in dependence on the procedure indicator, wherein the list of two or more conditional configurations or the single conditional configuration is used by the UE; The method comprising:

2. The method of claim 1 , wherein the procedure indicator is a conditional handover (CHO) indicator or a conditional primary-secondary cell (PSCell) addition or change (CPAC) indicator.

3. The method further comprising: The method of claim 2 , further comprising: when the procedure indicator is the CPAC indicator, including a list of the two or more conditional configurations.

4. the request for connection includes the CHO indicator, the method comprising: generating the single conditional configuration; The method of claim 2 , wherein the response includes the single conditional configuration.

5. The method of claim 1 , wherein the request for a connection includes measurements of one or more cells.

6. The method further comprising: selecting at least one cell of the one or more cells with a measurement result exceeding a threshold; generating a list of the two or more conditional configurations, the list of the two or more conditional configurations including a configuration for each cell of the at least one cell; the response including a list of the two or more conditional configurations. The method according to claim 5.

7. 1. A method for managing candidate cell configurations for a user equipment (UE) initially communicating with at least a first node, the method being implemented in the first node, the method comprising: transmitting, by the first node to a second node, a request for connection with the second node, the request including at least one indication of (i) a conditional handover (CHO), or (ii) an addition or change for a conditional primary secondary cell (C-PSCell); receiving, by the first node, from the second node, a response to the request, the response causing the first node to perform a secondary node procedure, the response including an information element conveying a list of two or more conditional configurations or a single conditional configuration according to the indication; transmitting, by the first node, a radio resource message to the UE based at least on the list of two or more conditional configurations or the single conditional configuration; The method comprising:

8. 8. The method of claim 7, wherein the secondary node procedure is one of an immediate secondary node procedure or a conditional secondary node procedure.

9. The method further comprising: determining, when the secondary node procedure is the conditional secondary node procedure, that the information element includes a list of the two or more conditional configurations; obtaining, from the information element, one or more configurations of the list of two or more conditional configurations in response to the determining; generating the radio resource message to be transmitted to the UE based on the one or more configurations; The method of claim 8 , further comprising:

10. The method further comprising: determining that the information element includes the single conditional configuration when the secondary node procedure is the immediate secondary node procedure; generating the radio resource message to be transmitted to the UE based on the single conditional configuration; The method of claim 8 , further comprising:

11. The method further comprising: determining, based on the request for connection including the indication of the addition or modification of the C-PSCell, that the information element includes a list of the two or more conditional configurations; obtaining, from the information element, one or more configurations of the list of two or more conditional configurations in response to the determining; generating the radio resource message from the one or more configurations, the radio resource message being transmitted to the UE; The method of any one of claims 7 to 10, further comprising:

12. A method according to any one of claims 7 to 11, wherein the request for connection includes the indication of the addition or modification of the C-PSCell when the first node does not allow the UE to initiate communication with the second node during preparation for a conditional handover.

13. 12. The method of claim 7, wherein the request for connection includes the indication of CHO when the first node causes the UE to initiate communication with the second node during preparation for a conditional handover.

14. the first node includes a first distributed unit, a second distributed unit, and a central unit; said transmitting a request for connection is effected from said central unit; receiving the response occurs at the central unit; transmitting the radio resource message from the central unit to the first distributed unit; The method according to any one of claims 7 to 13.

15. A network node comprising processing hardware and communication hardware, said network node being configured to implement any one of claims 1 to 14.

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