Managing master node communications in conditional dual connectivity

Abstract

A central unit (CU) of a distributed base station further comprising a distributed unit (DU) sends (1402) to the DU a context modification request for the UE, the context modification request comprising (i) a first indication that the context modification request is related to a condition addition or change of a primary-secondary cell (PSCell), and (ii) a second indication that whether a preparation has been performed for the condition addition or change; and receiving (1408) a context modification response for the UE from the DU.

Description

[0001] Cross - Reference to Related Applications

[0002] This application claims the benefit and priority of the filing dates of U.S. Provisional Patent Application No. 63 / 420,583, filed on October 29, 2022, entitled "Managing Master Node Communication in Conditional Dual Connectivity", and U.S. Provisional Patent Application No. 63 / 383,916, filed on November 15, 2022, entitled "Managing Master Node Communication in Conditional Dual Connectivity". The entire contents of these provisional applications are hereby incorporated by reference in their entirety. Field of the Invention

[0003] The present disclosure generally relates to wireless communication, and more particularly, to managing master node communication in dual connectivity for conditional configuration of multi - connectivity, such as for secondary node addition or change procedures. Background Art

[0004] This background description is provided for the purpose of generally presenting the context of the present disclosure. The work of the currently named inventors (to the extent it is described in this background section) and aspects of the specification that may not have been prior art at the time of filing are neither expressly nor impliedly admitted to be prior art of the present disclosure.

[0005] In a telecommunications system, a user equipment (UE) can sometimes concurrently utilize the resources of multiple radio access network (RAN) nodes (such as base stations, or components of a split base station (also known as a distributed base station)) interconnected by a backhaul. When these network nodes support different radio access technologies (RATs), this type of connection is called multi - radio dual connectivity (MR - DC). When the UE operates in MR - DC, one base station operates as a master node (MN) covering a primary cell (PCell), and another base station operates as a secondary node (SN) covering a primary secondary cell (PSCell). The UE communicates with the MN (via the PCell) and the SN (via the PSCell). In other scenarios, the UE transfers a wireless connection from one base station to another. For example, the serving base station can determine to hand over the UE to a target base station and initiate a handover procedure.

[0006] 3GPP specification TS 37.340 v16.6.0 describes the procedures for a UE to add or change a SN in a DC scenario. These procedures involve message passing between radio access network (RAN) nodes (e.g., RRC signaling and preparation). Such message passing generally results in latency, which in turn increases the probability that the SN addition or SN change procedure will fail. These legacy procedures that do not involve conditions checked at the UE can be referred to as "immediate" SN addition and SN change procedures.

[0007] Recently, "conditional" procedures (i.e., conditional SN or PSCell addition / change) have been considered for both SN or PSCell addition / change. Different from the "immediate" procedures discussed above, these procedures do not add or change the SN or PSCell, or perform a handover, until the UE determines that the conditions are met. As used herein, the term "condition" can refer to a single detectable state or event (e.g., a specific signal quality metric exceeds a threshold), or to 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.).

[0008] To configure a conditional procedure, the RAN provides the UE with the conditions and the configuration (e.g., one or more random access preambles, etc.) that will enable the UE to communicate with the appropriate base station or via the appropriate cell when the conditions are met. For conditional addition of a base station as a SN or a candidate cell as a PSCell, for example, the RAN provides the UE with the conditions to be met before the UE can add that base station as a SN or that candidate cell as a PSCell and the configuration that enables the UE to communicate with that base station or PSCell after the conditions have been met.

[0009] As part of the immediate PSCell addition or change procedure, the RAN (i.e., the MN or SN) sends an RRC reconfiguration message to the UE that includes multiple configuration parameters, 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 by using the multiple configuration parameters and a security key associated with the PSCell and derived from one or more security configuration parameters in the RRC reconfiguration message. The SN also derives a security key that matches the security key derived from the UE. After the UE successfully connects to the PSCell, the RAN (e.g., the SN) communicates data with the UE by using the matching security key and the multiple configuration parameters.

[0010] In some cases, when there are multiple candidate PSCs available, for example, a candidate SN (C-SN) may provide multiple candidate configurations. When the MN finishes preparing for a conditional SN procedure (e.g., conditional SN addition or conditional SN cell change), the MN cannot determine at this time which candidate secondary cell the UE will connect to in the future. In addition, since the UE connects to a secondary cell only when one or more conditions are met, the MN cannot determine whether the UE will even connect to any of the candidate cells in the future.

[0011] The conditional SN procedure poses certain challenges for coordinating the use of radio resources between the MN and the SN in a correct and timely manner. The coordination may involve, for example, selecting power or discontinuous reception (DRX) parameters at the MN in view of the SN, or restricting the uplink power of the UE when transmitting to the MN in view of any overlapping uplink transmissions to the SN. In addition, when the MN includes a central unit (CU) and a distributed unit (DU), it is unknown how the CU controls the DU to select power or DRX parameters.

[0012] Given that the MCG configuration is also conditional and that when the network prepares multiple candidate PSCs, the candidate SN provides the CG-CandidateList information element (IE) to the MN instead of a single CG-Config IE, it is unclear how a distributed MN can generate a conditional RRC reconfiguration message including the MCG configuration for CPAC. It is also unclear how the MN-DU (such as gNB-DU) can determine that the UE has selected a certain candidate PSC and how the MN-DU can apply the corresponding MCG L1 / L2 configuration when CPAC is executed. Additionally, it is unclear how the MN-DU can obtain MN restriction information (e.g., powerCoordination-FR1, powerCoordination-FR2, or p-maxNR-FR1-MCG). SUMMARY

[0013] An example embodiment of the technology of the present disclosure is a configuration method implemented in a CU of a distributed base station that also includes a DU. The method includes: sending a context modification request for a UE to the DU, the context modification request including (i) a first indication that the context modification request is related to a conditional addition or change of a primary secondary cell (PSCell), and (ii) a second indication of whether preparation for the conditional addition or change has been performed; and receiving a context modification response for the UE from the DU.

[0014] Another exemplary embodiment of these techniques is a configuration method implemented in a distributed unit (DU) of a distributed base station that also includes a central unit (CU). The method includes: receiving, from the DU, a context modification request for a user equipment (UE), the context modification request including a first indication related to adding or changing a condition of the context modification request with respect to a primary secondary cell (PSCell); and determining, based on a second indication included in the context modification request, whether preparation for the addition or change of the condition has been performed.

[0015] Another exemplary embodiment of these techniques is a radio access network (RAN) node, the RAN node including: a transceiver; and processing hardware configured to implement one of the above methods.

[0016] Another exemplary embodiment of these techniques is a method for managing conditional cell change in the CU of a distributed base station including a central unit (CU) and a distributed unit (DU), the method including: obtaining, by the CU, a cell group (CG) configuration of one or more candidate secondary cells (SCs) for a candidate secondary node (SN) to support dual connectivity (DC) between the UE, the DU operating as a master node (MN), and the candidate SN; sending, from the CU to the DU, the CG configuration; receiving, at the CU, a DU configuration corresponding to the CG configuration from the DU; and sending, via the DU, from the CU to the UE (i) a conditional SN configuration corresponding to the CG configuration, (ii) at least one condition to be satisfied before the UE initiates a process of connecting to the candidate node according to the conditional SN configuration, and (iii) the DU configuration.

[0017] Another exemplary embodiment of these techniques is a base station, the base station including processing hardware and configured to implement the above method. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1A is a block diagram of an exemplary system in which a base station and / or a user equipment (UE) may implement the techniques of the present disclosure for managing conditional processes related to a master node (MN) or a secondary node (SN);

[0019] Figure 1B is another block diagram of an exemplary system in which a radio access network (RAN) and a user device may implement the techniques of the present disclosure for managing conditional processes related to an MN or an SN;

[0020] Figure 1C is a block diagram of an exemplary base station including a central unit (CU) and a distributed unit (DU), the CU and the DU may operate in Figure 1A or Figure 1B the system of;

[0021] Figure 2A It is a block diagram of an example protocol stack, Figures 1A to 1B and the UE of

[0022] Figure 2B It is a block diagram of an example protocol stack, Figure 1A and the UE of

[0023] Figure 3A It is a message passing diagram of an example scenario, where the MN receives and processes one or more SN configurations from the C-SN during the conditional SN addition process;

[0024] Figure 3B It is a message passing diagram of an example scenario, where the MN receives and processes one or more SN configurations from the C-SN during the MN-initiated conditional SN change process;

[0025] Figure 3C It is a message passing diagram of an example scenario, where the MN receives and processes one or more SN configurations from the C-SN during the SN-initiated conditional SN change scenario;

[0026] Figure 3D It is a message passing diagram of an example scenario, where the C-MN receives a conditional handover request and receives and processes one or more SN configurations from the C-SN during the conditional handover scenario with CPAC;

[0027] Figure 3E It is a message passing diagram of an example scenario, where the C-MN receives a conditional handover request and receives and processes the SN configuration from the C-SN during the conditional handover scenario with SCG configuration;

[0028] Figure 4 is similar to Figures 3A to 3C the message passing diagram of an example scenario of

[0029] Figure 5 It is a flowchart of an example method, where the CU of the MN receives a conditional configuration during the conditional process with the C-SN and then sends multi-connection coordination information to the DU;

[0030] Figure 6 is similar to Figure 5 the flowchart of an example method of

[0031] Figure 7It is a flowchart of an example method, where the CU of the MN that executes the SN process determines when to send multi-connection coordination information to the DU based on whether the SN process is a conditional SN process or an immediate SN process;

[0032] Figures 8 to 10 Similar to Figures 5 to 7 the method, except that a single base station operates as the MN and the SN;

[0033] Figure 11 It is a flowchart of an example method, where the CU of the C-MN notifies the DU of the C-MN to perform conditional preparation for handover and one or more conditional preparations for multi-connection coordination for the RAN node and then instructs the DU to apply the prepared handover and multi-connection coordination;

[0034] Figure 12 It is a flowchart of an example method, where the CU of the C-MN notifies the DU of the C-MN to perform conditional preparation for handover and conditional preparation for multi-connection coordination for the RAN node and then instructs the DU to apply the prepared handover and multi-connection coordination;

[0035] Figure 13 It is a flowchart of an example method, where the CU of the C-MN notifies the DU of the C-MN to perform conditional preparation for handover and conditional preparation for multi-connection coordination for the RAN node; and

[0036] Figure 14 It is a flowchart of an example method for preparing one or more configurations for multi-connection coordination and applying a specific prepared configuration when notified by the CU, and the method can be implemented in the DU. Detailed implementation

[0037] As discussed in detail below, the UE and / or one or more base stations can use the techniques of the present disclosure to manage conditional processes, such as conditional PSCell addition or change (CPAC). The present disclosure can also separately use the acronyms CPA and CPC to separately refer to the conditional PSCell addition process and the conditional PSCell change process. Additionally, the base station can use the techniques of the present disclosure to manage multi-connection coordination information to support multi-connection. This multi-connection coordination information can include parameters for coordinating frequency bands, transmission timing, power control, signal directionality, and other aspects of wireless communication between the MN and the SN. The multi-connection coordination information can additionally or alternatively include restriction information, such as to limit the maximum power level of uplink power control at the connected RAN node.

[0038] The CU of a distributed base station obtains configuration information of one or more candidate secondary cells for a candidate SN during a process for adding or changing the SN. When the CU and the candidate SN are implemented in different base stations, the CU receives a message via an inter-base station interface. When the CU and the candidate SN are implemented in the same base station (e.g., when the candidate node is another DU of the distributed base station), the CU can directly retrieve the configuration information from a memory. The CU obtains a DU configuration corresponding to the configuration information of the SN and then provides the SN configuration, the DU configuration, and conditions to be specified before the UE applies the SN configuration to the UE.

[0039] First, referring to Figure 1A , example wireless communication system 100 includes a UE 102, a base station (BS) 104A, a base station 106A, and a core network (CN) 110. Base stations 104A and 106A may operate in a radio access network (RAN) 105 connected to the same core network (CN) 110. For example, CN 110 may be implemented as an evolved packet core (EPC) 111 or a fifth-generation (5G) core (5GC) 160.

[0040] Among other components, EPC 111 may include a serving gateway (SGW) 112, a mobility management entity (MME) 114, and a packet data network gateway (PGW) 116. SGW 112 is generally configured to forward user plane packets related to audio calls, video calls, Internet services, etc., and MME 114 is configured to manage authentication, registration, paging, and other related functions. PGW 116 provides a connection from the UE to one or more external packet data networks (e.g., the Internet network and / or the Internet Protocol (IP) Multimedia Subsystem (IMS) network). 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, UPF 162 is configured to forward user plane packets related to audio calls, video calls, Internet services, etc.; AMF 164 is configured to manage authentication, registration, paging, and other related functions; and SMF 166 is configured to manage PDU sessions.

[0041] As Figure 1AAs shown, base station 104A supports cell 124A, and base station 106A supports cell 126A. Additionally, each of base stations 104A and 106A may support more than one cell. For example, base station 106A may also support cell 126C. Cells 124A and 126A may partially overlap such that UE 102 may communicate with base stations 104A and 106A operating as a master node (MN) and a secondary node (SN), respectively, in DC communication. To directly exchange messages during the DC scenario and other scenarios discussed below, MN 104A and SN 106A may support the X2 or Xn interface. Generally, CN 110 may be connected to any suitable number of base stations that support NR cells and / or EUTRA cells. The following references Figure 1B discuss an example configuration in which EPC 110 is connected to additional base stations.

[0042] Base station 104A is equipped with processing hardware 130, which may include one or more general-purpose processors (such as a CPU) and a non-transitory computer-readable memory storing machine-readable instructions executable on one or more general-purpose processors, and / or a dedicated processing unit. In an example implementation, processing hardware 130 includes a conditional configuration controller 132 configured to manage conditional configurations for one or more conditional procedures (such as conditional handover (CHO), conditional PSCell addition or change (CPAC), or conditional SN addition or change (CSAC)) when base station 104A operates as an MN.

[0043] Base station 106A is equipped with processing hardware 140, which may also include one or more general-purpose processors (such as a CPU) and a non-transitory computer-readable memory storing machine-readable instructions executable on one or more general-purpose processors, and / or a dedicated processing unit. In an example implementation, processing hardware 140 includes a conditional configuration controller 142 configured to manage conditional configurations for one or more conditional procedures (such as CHO, CPAC, or CSAC) when base station 106A operates as an SN.

[0044] Still referring to Figure 1A , UE 102 is equipped with processing hardware 150, which may include one or more general-purpose processors (such as a CPU) and a non-transitory computer-readable memory storing machine-readable instructions executable on one or more general-purpose processors, and / or a dedicated processing unit. In an example implementation, processing hardware 150 includes a UE conditional configuration controller 152 configured to manage conditional configurations for one or more conditional procedures.

[0045] More particularly, the conditional configuration controllers 132, 142, and 152 may implement at least some of the techniques discussed below with reference to messaging and flowcharts. Although Figure 1A the conditional configuration controllers 132 and 142 are shown as separate components, in at least some scenarios, the base stations 104A and 106A may have a similar implementation and operate as MN or SN nodes in different scenarios. In these implementations, each of the base stations 104A and 106A may implement both the conditional configuration controller 132 and the conditional configuration controller 142 to support MN and SN functions, respectively.

[0046] In operation, the UE 102 may use radio bearers (e.g., DRB or SRB) that terminate at the MN 104A or the SN 106A at different times. When communicating on a radio bearer in the uplink (from the UE 102 to the BS) and / or downlink (from the base station to the UE 102) direction, the UE 102 may apply one or more security keys. In some cases, the UE may use different RATs to communicate with the base stations 104A and 106A. Although the examples below may specifically relate to a particular RAT type (5G NR or EUTRA), generally, the techniques of the present disclosure may also be applicable to other suitable radio access and / or core network technologies.

[0047] Figure 1B Additional base stations 104B and 106B that may be included in the wireless communication system 100 are depicted. The UE 102 is initially connected to the base station 104A. BS104B and 106B may have similar processing hardware to the base station 106A. The UE 102 is initially connected to the base station 104A.

[0048] In some scenarios, the base station 104A may perform an immediate SN addition to configure the UE 102 to operate in dual connectivity (DC) with the base station 104A (via the PCell) and the base station 106A (via a PSCell other than cell 126A). The base stations 104A and 106A operate as the MN and SN of the UE 102, respectively. In some cases, the UE 102 may operate in the MR-DC connection mode, e.g., communicate with the base station 104A using 5G NR and communicate with the base station 106A using EUTRA, or communicate with the base station 104A using EUTRA and communicate with the base station 106A using 5G NR. Multi-connection coordination may help the two base stations coordinate the shared UE capabilities, including operating frequency (e.g., band combination, frequency range), UE measurement and reporting (e.g., intra-frequency measurement, inter-frequency measurement, inter-RAT measurement, measurement gap), reception timing (e.g., DRX configuration, offset timing), and uplink power control (e.g., power headroom, maximum transmit power).

[0049] At a certain point in time, when the UE 102 is communicating with the MN 104A and the S-SN 106A in DC, 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"). 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 implementation, the SN 106A can send a configuration to change the PSCell to the cell 126A to the UE 102 via a signaling radio bearer (SRB) (e.g., SRB3) for an immediate PSCell change. In another implementation, the SN 106A can send a configuration to change the PSCell to the cell 126A to the UE 102 via the MN 104A for an immediate PSCell change. The MN 104A can send a configuration to immediately change the PSCell to the cell 126A to the UE 102 via SRB1. Extended multi-connection coordination can help the newly added base stations coordinate the shared UE capabilities.

[0050] In other scenarios, the base station 104A can perform a conditional SN addition procedure to first configure the base station 106B as the C-SN of the UE 102, i.e., conditional SN addition or change (CSAC). At this time, the UE 102 can be in single connection (SC) with the base station 104A, or in DC with the base station 104A and the base station 106A. If the UE 102 is in DC with the base station 104A and the base station 106A, the MN 104A can determine 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 (e.g., extracted from the UE measurement report) or obtained by the MN 104A based on the measurement of the signals received from the UE 102 (e.g., sounding reference signal (SRS) or uplink demodulation reference signal (DMRS)). Contrary to the immediate SN addition case discussed above, the UE 102 does not immediately attempt to connect to the C-SN 106B. In this scenario, the base station 104A operates as an MN again, but the base station 106B initially operates as a C-SN rather than an SN.

[0051] More specifically, when UE 102 receives a configuration for C-SN 106B, UE 102 does not connect to C-SN 106B until UE 102 has determined that a certain condition is met (in some cases, UE 102 may consider multiple conditions, but for the sake of convenience, the discussion below only refers to a single condition). Before the condition is met, multi-connection coordination is not required; however, once the C-SN becomes connected, it will be helpful. When UE 102 determines that the condition has been met, UE 102 connects to C-SN 106B such that C-SN 106B begins to operate as SN 106B of UE 102. Thus, although base station 106B operates as a C-SN rather than an SN, base station 106B has not been connected to UE 102 and has thus not served UE 102. In some implementations, UE 102 may disconnect from SN 106A to connect to C-SN 106B.

[0052] In yet other scenarios, UE 102 is in DC with MN 104A (via the PCell) and SN 106A (via a PSCell other than cell 126A and Figure 1A not shown in the figure). SN 106A may perform a conditional PSCell addition or change (CPAC) to configure a candidate PSCell (C-PSCell) 126A for UE 102. If UE 102 is configured with a signaling radio bearer (SRB) (e.g., SRB3) to exchange RRC messages with SN 106A, then SN 106A may send a configuration for C-PSCell 126A to UE 102 via the SRB in response to one or more measurement results, where the one or more measurement results may be received from UE 102 via the SRB or via MN 104A or may be obtained by SN 106A based on measurements of signals received from UE 102. In the case via MN 104A, MN 104A receives the configuration for C-PSCell 126A. Contrary to the immediate PSCell change case discussed above, UE 102 does not immediately disconnect from the PSCell and attempt to connect to C-PSCell 126A.

[0053] More particularly, when the UE 102 receives the configuration for the C-PSCell 126A, the UE 102 does not connect to the C-PSCell 126A until the UE 102 has determined that a certain condition is met (in some cases, the UE 102 may consider multiple conditions, but for the sake of convenience, the discussion below only refers to a single condition). When the UE 102 determines that the condition has been met, the UE 102 connects to the C-PSCell 126A, such that the C-PSCell 126A begins to operate as the C-PSCell 126A of the UE 102. Thus, although 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.

[0054] In some scenarios, the condition associated with CSAC or CPAC can be that the signal strength / quality detected by UE 102 on C-PSCell126A of SN 106A or on C-PSCell 126B of C-SN 106B exceeds a certain threshold or otherwise corresponds to an acceptable measurement. For example, when one or more measurement results obtained by UE 102 on C-PSCell 126A are higher than the threshold configured by MN 104A or SN 106A or higher than a predetermined or pre-configured threshold, UE 102 determines that the condition is satisfied. When UE 102 determines that the signal strength / quality on C-PSCell 126A of SN 106A is good enough (similarly, measured relative to one or more quantitative thresholds or other quantitative metrics), UE 102 can perform a random access procedure on C-PSCell 126A with SN 106A to connect to SN 106A. After UE 102 successfully completes the random access procedure on C-PSCell 126A, C-PSCell 126A becomes PSCell 126A of UE 102. Then, SN 106A can start communicating data (user plane data or control plane data) with UE 102 through PSCell126A. In another example, when one or more measurement results obtained by UE 102 on C-PSCell 126B are higher than the threshold configured by MN 104A or C-SN 106B or higher than a predetermined or pre-configured threshold, UE 102 determines that the condition is satisfied. When UE 102 determines that the signal strength / quality on C-PSCell 126B of C-SN 106B is good enough (similarly, measured relative to one or more quantitative thresholds or other quantitative metrics), UE 102 can perform a random access procedure on C-PSCell 126B with C-SN 106B to connect to C-SN 106B. After UE 102 successfully completes the random access procedure on C-PSCell 126B, C-PSCell 126B becomes PSCell 126B of UE 102 and C-SN 106B becomes SN 106B. Then, SN 106B can start communicating data (user plane data or control plane data) with UE102 through PSCell 126B.

[0055] In various configurations of the wireless communication system 100, base station 104A may be implemented as a master eNB (MeNB) or a master gNB (MgNB), and base stations 106A or 106B may be implemented as secondary gNBs (SgNBs) or candidate SgNBs (C-SgNBs). UE 102 may communicate with base station 104A and base stations 106A or 106B (106A / B) via the same RAT (such as EUTRA or NR) or different RATs. When base station 104A is a MeNB and base station 106A is an SgNB, UE 102 may be in EUTRA-NR DC (EN-DC) with the MeNB and the SgNB. In this scenario, MeNB 104A may or may not configure base station 106B as a C-SgNB for UE 102. In this scenario, SgNB 106A may configure cell 126A as a C-PSCell for UE 102. When base station 104A is a MeNB and base station 106A is a C-SgNB for UE 102, UE 102 may be in SC with the MeNB. In this scenario, MeNB 104A may or may not configure base station 106B as another C-SgNB for UE 102.

[0056] In some cases, a MeNB, a SeNB, or a C-SgNB is implemented as an ng-eNB instead of an eNB. When base station 104A is a master ng-eNB (Mng-eNB) and base station 106A is an SgNB, UE 102 may be in next generation (NG) EUTRA-NR DC (NGEN-DC) with the Mng-eNB and the SgNB. In this scenario, MeNB 104A may or may not configure base station 106B as a C-SgNB for UE102. In this scenario, SgNB 106A may configure cell 126A as a C-PSCell for UE 102. When base station 104A is a Mng-NB and base station 106A is a C-SgNB for UE 102, UE 102 may be in SC with the Mng-NB. In this scenario, Mng-eNB 104A may or may not configure base station 106B as another C-SgNB for UE 102.

[0057] When base station 104A is a MgNB and base stations 106A / B are SgNBs, UE 102 can be in NR-NR DC (NR-DC) with the MgNB and the SgNBs. In this scenario, MeNB 104A may or may not configure base station 106B as a C-SgNB for UE 102. In this scenario, SgNB 106A can configure cell 126A as a C-PSCell for UE 102. When base station 104A is a MgNB and base station 106A is a C-SgNB for UE 102, UE 102 can be in SC with the MgNB. In this scenario, MgNB 104A may or may not configure base station 106B as another C-SgNB for UE 102.

[0058] When base station 104A is a MgNB and base stations 106A / B are secondary ng-eNBs (Sng-eNBs), UE 102 can be in NR-EUTRA DC (NE-DC) with the MgNB and the Sng-eNBs. In this scenario, MgNB 104A may or may not configure base station 106B as a C-Sng-eNB for UE 102. In this scenario, Sng-eNB 106A can configure cell 126A as a C-PSCell for UE 102. When base station 104A is a MgNB and base station 106A is a candidate Sng-eNB (C-Sng-eNB) for UE 102, UE 102 can be in SC with the MgNB. In this scenario, MgNB 104A may or may not configure base station 106B as another C-Sng-eNB for UE 102.

[0059] Base stations 104A, 106A, and 106B can be connected to the same core network (CN) 110, which can be an evolved packet core (EPC) 111 or a fifth-generation core (5GC) 160. Base station 104A can be implemented as an eNB supporting the S1 interface for communication with the EPC 111, an ng-eNB supporting the NG interface for communication with the 5GC 160, or a base station supporting the NR radio interface and the NG interface for communication with the 5GC 160. Base station 106A can be implemented as an EN-DC gNB (en-gNB) with an S1 interface to the EPC 111, an en-gNB not connected to the EPC 111, a gNB supporting the NR radio interface and the NG interface to the 5GC 160, or an ng-eNB supporting the EUTRA radio interface and the NG interface to the 5GC 160. To directly exchange messages during the scenarios discussed below, base stations 104A, 106A, and 106B can support the X2 or Xn interface.

[0060] As Figure 1BAs shown, base station 104A supports cell 124A, base station 104B supports cell 124B, base station 106A supports cell 126A, and base station 106B supports cell 126B. Cell 124A and 126A may partially overlap, and cell 124A and 124B may also partially overlap, such that UE 102 can communicate with base station 104A (operating as an MN) and base station 106A (operating as an SN) in DC, and after completing an SN change, communicate with base station 104A (operating as an MN) and SN 104B in DC. More particularly, when UE 102 operates in DC with base station 104A and base station 106A, base station 104A operates as a MeNB, Mng-eNB, or MgNB, and base station 106A operates as an SgNB or Sng-eNB. Cell 124A and 126B may partially overlap. When UE 102 is in SC with base station 104A, base station 104A operates as a MeNB, Mng-eNB, or MgNB, and base station 106B operates as a C-SgNB or C-Sng-eNB. When UE 102 operates in DC with base station 104A and base station 106A, base station 104A operates as a MeNB, Mng-eNB, or MgNB, base station 106A operates as an SgNB or Sng-eNB, and base station 106B operates as a C-SgNB or C-Sng-eNB.

[0061] Generally, wireless communication network 100 may include any suitable number of base stations that support NR cells and / or EUTRA cells. More particularly, EPC 111 or 5GC 160 may be connected to any suitable number of base stations that support NR cells and / or EUTRA cells. Although the examples below specifically relate to particular CN types (EPC, 5GC) and RAT types (5G NR and EUTRA), generally, the techniques of the present disclosure may also be applicable to other suitable radio access and / or core network technologies, such as sixth generation (6G) radio access and / or 6G core network or 5G NR-6G DC.

[0062] Figure 1CDepicts an example distributed implementation of a base station such as base stations 104A, 104B, 106A, or 106B. In this implementation, a base station may include a Central Unit (CU) 172 and one or more Distributed Units (DUs) 174. The CU 172 is equipped with processing hardware, which may include one or more general-purpose processors (such as a CPU) and a non-transitory computer-readable memory storing machine-readable instructions executable on one or more general-purpose processors, and / or a dedicated processing unit. In one example, the CU 172 is equipped with processing hardware 130. In another example, the CU 172 is equipped with processing hardware 140. In an example implementation, the processing hardware 140 includes a (C-)SN RRC controller, which is configured to manage or control one or more RRC configurations and / or RRC procedures when the base station 106A operates as an SN or a candidate SN (C-SN). The base station 106B may have the same or similar hardware as the base station 106A. The DU 174 is also equipped with processing hardware, which may include one or more general-purpose processors (such as a CPU) and a non-transitory computer-readable memory storing machine-readable instructions executable on one or more general-purpose processors, and / or a dedicated processing unit. In some examples, in an example implementation, the processing hardware includes: a Medium Access Control (MAC) controller, which is configured to manage or control one or more MAC operations or procedures (e.g., random access procedures); and a Radio Link Control (RLC) controller, which is configured to manage or control one or more RLC operations or procedures when the base station 106A operates as an MN, SN, or candidate SN (C-SN). The processing hardware may further include a physical layer controller, which is configured to manage or control one or more physical layer operations or procedures.

[0063] Figure 2A An example protocol stack 200 is shown in a simplified manner, according to which the UE 102 may communicate with an eNB / ng-eNB or gNB (e.g., one or more of the base stations 104, 106).

[0064] In example stack 200, the physical layer (PHY) 202A of EUTRA provides a transport channel to the EUTRA MAC sublayer 204A, which in turn provides a logical channel to the EUTRA RLC sublayer 206A. The EUTRA RLC sublayer 206A in turn provides an RLC channel to the EUTRA PDCP sublayer 208 and in some cases to the NR PDCP sublayer 210. Similarly, the NR PHY 202B provides a transport channel to the NR MAC sublayer 204B, which in turn provides a logical channel to the NR RLC sublayer 206B. The NR RLC sublayer 206B in turn provides a data transfer service to the NR PDCP sublayer 210. The NR PDCP sublayer 210 in turn may provide a data transfer service to the service data adaptation protocol (SDAP) 212 or the radio resource control (RRC) sublayer (not shown in FIG. 2). In some implementations, the UE 102 supports both the EUTRA and NR stacks, as shown in FIG. 2, to support handover between EUTRA and NR base stations and / or to support DC over EUTRA and NR interfaces. Additionally, as shown in FIG. 2, the UE 102 may support the NR PDCP 210 to be layered on the EUTRA RLC 206A, and the SDAP sublayer 212 to be layered on the NR PDCP sublayer 210.

[0065] The EUTRA PDCP sublayer 208 and the NR PDCP sublayer 210 receive packets that may be referred to as service data units (SDUs) (e.g., from an Internet protocol (IP) layer that is directly or indirectly layered on the PDCP layer 208 or 210), and output packets that may be referred to as protocol data units (PDUs) (e.g., to the RLC layer 206A or 206B). Except in cases related to the differences between SDUs and PDUs, for simplicity, this disclosure refers to both SDUs and PDUs as "packets".

[0066] On the control plane, the EUTRA PDCP sublayer 208 and the NR PDCP sublayer 210 may provide a signaling radio bearer (SRB) or the 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 208 and the NR PDCP sublayer 210 may provide a data radio bearer (DRB) to support data exchange. The data exchanged on the NR PDCP sublayer 210 may be SDAP PDUs, Internet protocol (IP) packets, or Ethernet packets.

[0067] Figure 2B An example protocol stack 250 is shown in a simplified manner, which the UE 102 may use to communicate with a DU (e.g., DU 174) and a CU (e.g., CU 172).Figure 2A The radio protocol stack 200 is functionally split, as shown by Figure 2B the radio protocol stack 250 in

[0068] Next, referring to Figures 3A to 3E and Figure 4 several example scenarios are discussed in which the UE and / or the RAN perform the techniques of the present disclosure for supporting conditional procedures. Generally speaking, Figures 3A to 3E and Figure 4 similar events in

[0069] First, referring to Figure 3A , in scenario 300A, the MN receives and processes one or more SN configurations from the C-SN during the conditional SN addition procedure. In scenario 300A, base station 104A operates as the MN, and base station 106A operates as the C-SN. The MN 104A also includes a CU 172 and one or more DUs 174.

[0070] Initially, UE 102 operates with MN 104A in a single connection (SC) 302. When in SC, UE 102 exchanges UL PDUs and / or DL PDUs with MN 104A according to the MN configuration (e.g., via the PCell served by DU 174). In some implementations, the MN configuration includes a first DU configuration that UE 102 previously received from MN 104A. For example, MN 104 may send the first DU configuration as a CellGroupConfig IE or include the configuration parameters in the CellGroupConfig IE defined in 3GPP specification 38.331. In some implementations, DU 174 generates the first DU configuration and sends the first DU configuration to CU 172, and CU 172 sends an RRC reconfiguration message including the first DU configuration to UE 102 via DU 174. CU 172 receives an RRC reconfiguration complete message from UE 102 via DU 174 in response to the RRC reconfiguration message (e.g., similar to events 310, 312, 314, 316 discussed in more detail below). After receiving the RRC reconfiguration complete message, CU 172 sends a CU-to-DU message (e.g., UE context modification request message) to DU 174 including an immediate indication (e.g., RRC reconfiguration complete indicator IE) indicating that UE 102 has received and / or applied the first DU configuration. For example, CU 172 may set the RRC reconfiguration complete indicator IE to a specific value (e.g., "true") to indicate that UE 102 has received and / or applied the first DU configuration. According to or in response to the immediate indication, DU 174 applies the first DU configuration to communicate with UE 102.

[0071] MN 104A (the CU 172 of MN 104A in this scenario) then determines to configure base station 106A as a C-SN for conditional PSCell addition (CPA). For example, MN 104A may make this determination based on measurement results from UE 102. In some implementations, MN 104A may detect or estimate that UE 102 is moving towards the coverage area (i.e., one or more cells) of base station 106A based on the uplink signal received from UE 102 or the positioning measurement results received from UE 102. In response to the determination, MN 104A (or the CU 172 of MN 104A) sends a SN addition request message 304 to C-SN 106A that includes a conditional PSCell addition information request IE. In some implementations, the conditional PSCell addition information request IE also includes a CPAC indicator for indicating CPAC-initiation and a maximum number IE / field of PSCs to be prepared. MN104A may generate candidate cell information including measurement results of one or more cells and include the candidate cell information in the SN addition request message. In addition, MN 104A (or the CU 172 of MN 104A) may determine SN restriction information for restricting the (value of) configuration parameters that C-SN 106A can configure for UE 102. MN 104A may include the SN restriction information in the SN addition request message. When determining the SN restriction information, MN 104A (or the CU 172 of MN 104A) may determine MN restriction information for restricting the (value of) configuration parameters that MN 104A can configure for UE 102. In some implementations, the MN restriction information and / or the SN restriction information are included in at least one of the fields shown in Table 1 below.

[0072]

[0073] Table 1: Example fields in MN and / or SN restriction information

[0074] In some implementations, the MN 104A (or the CU 172 of the MN 104A) may determine MN restriction information and SN restriction information according to the capabilities of the UE 102. More specifically, the MN 104A determines the MN restriction information and the SN restriction information such that when the UE 102 communicates with the MN 104A and the C-SN 106A simultaneously, the communications with the MN 104A and the C-SN 106A do not exceed the capabilities of the UE 102. For example, the MN 104A may determine, in the MN restriction information, the maximum uplink power that the MN 104A allows the UE 102 to transmit in the communication with the MN 104A, and the MN 104A may determine, in the SN restriction information, the maximum uplink power that the C-SN 106A allows the UE 102 to transmit in the communication with the C-SN 106A.

[0075] In response to receiving a SN addition request message 304, C-SN 106A determines 306 one or more C-PSCells (C-PSCells) and generates one or more C-SN configurations (C-SN configurations) for UE 102, where each C-SN configuration is associated with a specific C-PSCell among the C-PSCells. For example, the C-PSCells may be cell 126A and cell 126C. In some implementations, C-SN 106A determines the C-PSCells and C-SN configurations at least partially based on candidate cell information and SN restriction information. C-SN 106A generates an inter-node RRC message CG-CandidateList to include a list of CG-CandidateInfo elements such that each CG-CandidateInfo corresponds to a C-PSCell and includes C-PSCell information, such as C-PSC ellID (e.g., SSB frequency / ARFCN-ValueNR and physical cell ID), and a CG-Config IE (e.g., the inter-node RRC message CG-Config defined in 3GPP TS38.331), to include the C-SN configuration and parameters for MN 104A to prepare conditional configurations. In some implementations, each CG-CandidateInfo IE is included in a specific CG-CandidateToAddModList within the CG-Candidate List. C-SN 106A sends 308 a SN addition request acknowledgment message including the CG-CandidateList to MN 104A (or the CU 172 of MN 104A). In additional implementations, C-SN106A may generate coordination information and include the coordination information in the SN addition request acknowledgment message. In some implementations, the coordination information includes one or more coordination parameters. In some implementations, C-SN 106A may include one or more coordination parameters in the corresponding CG-Config in the CG-Candida teList and / or in IEs other than the SN-to-MN container (e.g., S-NG-RAN node-to-M-NG RAN node container or SgNB-to-MeNB container) in the SN addition request acknowledgment message. For example, the coordination information may include coordination parameters such as a resource coordination information IE associated with a specific C-PSCell (e.g., SgNB resource coordination information IE or MR-DC resource coordination information IE), one or more power coordination parameters (e.g., powerCoordination-FR1 and / or powerCoordination-FR2), or a discontinuous reception (DRX) configuration (e.g., DRX-Info or DRX-Info2).The coordination information may include coordination information for each of the C-PSCells. As another example, the coordination parameters may include one or more coordination parameters as shown in Table 2 below.

[0076]

[0077]

[0078] Table 2: Example coordination parameters

[0079] In some implementations, C-SN 106A includes SN restriction information in the SN addition request confirmation message, and MN104A may use the SN restriction information to determine MN restriction information.

[0080] After receiving 308 the CG-CandidateList including the CG-Config IE and before determining which of the candidate cells the UE 102 has connected to, the CU 172 sends 307 a CU-to-DU message including the CG-CandidateList to the DU 174. In some implementations, in response to the CU-to-DU message including the CG-CandidateList IE and / or the condition indication, the DU 174 may send 309 a single DU-to-CU message, and the single DU-to-CU message may include a list of DU configurations corresponding to each of the CG-Config IEs in the CG-CandidateList IE (e.g., a list of CellGroupConfig). Alternatively, the CU 172 retrieves the CG-Config IE from the CG-CandidateList, and for each of the CG-Config IEs, the CU 172 sends 307 a CU-to-DU message including the CG-Config IE to the DU 174. If the CU 172 receives 308 the restriction and / or coordination information, the CU 172 may include the restriction and / or coordination information in the CU-to-DU message that the CU 172 sends 307. In some implementations, the CU-to-DU message is a UE context modification request message. In response to each of the CU-to-DU messages of event 307, the DU 174 may send 309 a DU-to-CU message to the CU 172. In some implementations, the DU-to-CU message is a UE context modification response message.

[0081] In some implementations, for each CG-Config IE, DU 174 determines whether to prepare a DU configuration for UE 102 based on each CG-Config IE. For each CG-Config IE, if DU 174 determines that the CG-Config IE or the C-SN configuration in the CG-Config IE affects the first DU configuration, DU 174 may prepare a DU configuration (e.g., CellGroupConfig) to update the first DU configuration. For example, DU 174 determines that applying both the first DU configuration and the C-SN configuration exceeds the capabilities of UE 102. In another example, DU 174 determines that the first DU configuration conflicts with or is incompatible with the CG-Config IE or the C-SN configuration. Through these examples, DU 174 determines that the CG-Config IE or the C-SN configuration affects the first DU configuration. Otherwise, if DU 174 determines that the CG-Config IE or the C-SN configuration does not affect the first DU configuration, DU 174 may not prepare a DU configuration to update the first DU configuration. In some implementations, DU 174 generates DU configurations 1, …, N for CG-Config IEs 1, …, N in the CG-Config IE respectively to update the first DU configuration. N is an integer greater than zero. In some implementations, DU 174 may store the CG-Config IE and associate the DU configuration with CG-Config IEs 1, …, N. In other implementations, DU 174 stores C-SN configurations 1, …, N in CG-Config IEs 1, …, N respectively and associates DU configurations 1, …, N with C-SN configurations 1, …, N respectively. In still other implementations, DU 174 stores C-PSCell information 1, …, N in CG-Config IEs 1, …, N respectively and associates DU configurations 1, …, N with C-PSCell information 1, …, N respectively. In some implementations, for each of the CG-Config IEs, CU 172 may include a condition indication in the corresponding CU-to-DU message of event 307. The condition indication indicates the corresponding CG-Config IE for CPA or CPC. Based on the condition indication, DU 174 may avoid applying DU configurations 1, …, N. In some implementations, the condition indication is a conditional MCG information IE in which the CPAC trigger field is set to CPAC-initiation. In some implementations, DU 174 generates DU configurations 1, ..., N (e.g., CellGroupConfig) without including the reconfigurationWithSync IE / field in each of the DU configurations.In some implementations, due to the specific condition indication IE in the CU-to-DU message of event 307, DU 174 does not include the reconfigurationWithSync IE / field in the DU configuration. In other implementations, the DU does not include the reconfigurationWithSync IE / field in the DU configuration because the CU-to-DU message of event 307 does not include the SpCell ID IE.

[0082] After receiving 308 the CG-Candidate List, for each entry in the CG-Candidate List, the CU 172 of MN104A retrieves the C-PSCell ID and C-SN configuration and correlates them, and can use the C-PSCell ID and / or C-SN ID (e.g., global en-gNB ID or global NG-RAN node ID) to distinguish and manage the C-SN configuration to prepare for conditional configuration. The CU 172 can assign a specific configuration ID (e.g., condReconfigId or CondReconfigurationId) to each of the C-SN configurations. The CU 172 can generate a trigger condition configuration (e.g., condExecutionCond or triggerCondition) for each of the C-SN configurations. Each of the trigger condition configurations can be linked to one or more measurement configurations that trigger the UE 102 to connect to the C-SN 106A via a specific C-PSCell configured in a specific C-SN configuration. In some implementations, the CU 172 can generate a conditional (re)configuration IE (e.g., ConditionalReconfiguration) to include a list of C-SN configurations with corresponding configuration IDs and trigger condition configurations. The CU 172 includes the conditional (re)configuration IE in an RRC reconfiguration message (e.g., RRCConnectionReconfiguration message or RRCReconfiguration message). In some implementations, if the CU172 receives the DU configurations 1, …, N from the DU 174 as described above, the CU 172 includes each of the DU configurations 1, …, N together with the corresponding C-SN configuration in the conditional (re)configuration IE. The CU 172 can send the 310 RRC reconfiguration message to the DU 174 in a CU-to-DU message (e.g., DL RRC message transfer or UE context modification request message). The DU 174 sends the 312 RRC reconfiguration message including the conditional (re)configuration field / IE to the UE 102. The UE 102 applies the RRC reconfiguration and replies with a 314 RRC reconfiguration complete message (e.g., RRCConnectionReconfigurationComplete message or RRCReconfigurationComplete message) to the DU 174. The DU 174 then sends the 316 RRC reconfiguration complete message to the CU 172 in a DU-to-CU message (e.g., UL RRC message transfer message or UE context modification response message).Events 304, 306, 307, 309, 308, 310, 312, 314, and 316 can be collectively referred to as MN-initiated conditional SN addition preparation 390. Events 304, 306, 308 can also be collectively referred to as conditional SN addition preparation 392, while events 307, 309, 310, 312, 314, and 316 can be collectively referred to as RRC reconfiguration procedure 394. After receiving 316 the RRC reconfiguration complete message or an acknowledgment (e.g., RLC acknowledgment or hybrid automatic repeat request (HARQ) acknowledgment) of a PDU (e.g., RLC PDU or MAC PDU) including the RRC reconfiguration message, the CU 172 of MN 104A can send 318 an early status transfer message to C-SN 106A to convey the COUNT value of the first downlink SDU forwarded by MN 104A to C-SN 106A or the COUNT value of the already forwarded downlink SDUs for each of the DRBs of UE 102 to be discarded. The early status transfer message may be an early sequence number (SN) status transfer message, where "SN" in this context refers to the sequence number rather than the secondary node. In some implementations, MN 104A can send 318 the early status transfer message without receiving an interface message indicating that UE 102 is connected to C-SN 106A.

[0083] In some implementations, before the UE detects that the conditions for connecting to the C-PSCell are met, the MN 104A may perform an MN-initiated SN modification procedure with the C-SN 106A and obtain the (updated) CG-Config IE or the (updated) CG-CandidateList IE from the C-SN 106A in the SN modification request confirmation message, similar to event 392. In other implementations, before the UE detects that the conditions for connecting to the C-PSCell are met, the C-SN 106A may perform an SN-initiated SN modification procedure with the MN 104A and provide the (updated) CG-Config IE or the (updated) CG-CandidateList IE to the MN 104A in the SN modification requirement message, similar to event 392. Therefore, the CU 172 may perform another RRC reconfiguration procedure similar to event 394 with the DU 174 and the UE 102, as described above, to update the DU configuration and the UE configuration accordingly. In some implementations, the condition indication for updating the RRC reconfiguration procedure in event 307 is the conditional MCG information IE in which the CPAC trigger field is set to CPAC-initiation or CPAC-replace, and the DU 174 replaces the existing prepared conditional configuration identified by the gNB-DU UE F1APID IE. In other implementations, the condition indication for updating the RRC reconfiguration procedure in event 307 is the conditional MCG information IE in which the CPAC trigger is set to CPAC-cancel, and the DU 174 assumes that the CU 172 is about to remove any reference to any resources previously reserved for coordinating with the C-PSCell associated with the signaling associated with the UE identified by both the gNB-CU UE F1AP ID IE and the gNB-DU UE F1AP ID IE and release the resources. If the candidate cell list IE to be cancelled is also included in the UE context modification request message, the DU 174 shall assume that only the resources reserved for coordinating with the C-PSCell identified by the included cell ID (e.g., NR CGI) are about to be released by the CU 172.

[0084] At a later time, if the UE 102 detects 320 that the conditions for connecting to the C-PSCell are 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 perform C-SN configuration regarding the C-PSCell. In response to the detection, the UE 102 initiates a random access procedure on the C-PSCell. In response to the initiation, the UE 102 performs 322 a random access procedure with the C-SN 106A via the identified C-PSCell. In response to the detection or initiation 320, the UE 102 sends 324 an RRC reconfiguration complete message to the MN 104A via the DU 174. The DU 174 sends 326 the RRC reconfiguration complete message to the CU 172 in a DU-to-CU message (e.g., UL RRC message transfer message). The UE 102 may send 324 the RRC reconfiguration complete message before, during, or after the random access procedure.

[0085] In some implementations, the UE 102 may indicate in the RRC reconfiguration complete message that the UE 102 has performed a specific C-SN configuration by including a configuration ID corresponding to one of the C-SN configurations. If the MN 104A performs multiple CPA procedures with different C-SNs, the CU 172 of the MN 104A may 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.

[0086] In response to receiving 326 the RRC reconfiguration complete message or after receiving 326 the RRC reconfiguration complete message, the CU 172 of the MN 104A may send 328 an SN message to the C-SN 106A. In some implementations, the SN message may be an SgNB reconfiguration complete or S-Node reconfiguration complete message. In other implementations, the SN message may be an RRC transfer message. In still other implementations, the SN message may be a new interface message defined in 3GPP 38.423 or 36.423 version 17 or future specifications (e.g., an XnAP or X2AP message). In some implementations, the UE 102 may include an SN RRC message (e.g., an RRCConnectionReconfigurationComplete or RRCReconfigurationCompl ete message) in the RRC reconfiguration complete message sent by the UE 102 at event 324. In such cases, the MN 104A may include the SN RRC message in the SN message.

[0087] In some implementations, the random access procedure can be a four-step random access procedure or a two-step random access procedure. In other implementations, the random access procedure can be a contention-based random access procedure or a contention-free random access procedure. For example, UE 102 can include the RRC reconfiguration complete message in Message 3 of the four-step random access procedure or in Message A of the two-step random access procedure.

[0088] After the C-SN 106A and the UE 102 successfully complete the random access procedure, the C-SN 106A can send a 332 interface message (e.g., an SN modification request message, an NG-RAN node configuration update message, an E-UTRA–NR cell resource coordination request message, or a success indication message) to the CU 172 of the MN 104A. The interface message can include PSCell information (e.g., Cell 126A) of the PSCell and / or the corresponding CG-Config IE for the performed C-SN configuration and / or coordination information for physical resource block (PRB) coordination (e.g., SgNB resource coordination information IE or MR-DC resource coordination information IE). The PSCell information can include the cell global identity (CGI), the physical cell identity (PCI), and / or the absolute radio frequency channel number (ARFCN) identifying the DL carrier frequency of the PSCell 126A. In some implementations, in response to receiving an SN message or performing the 322 random access procedure or after receiving an SN message or performing the 322 random access procedure, the C-SN 106A can send a 332 interface message. In some implementations, the interface message further includes SN restriction information. The MN 104A (CU 172 and / or DU 174) can use the SN restriction information to determine the MN restriction information.

[0089] In some implementations, in response to receiving the 326 RRC reconfiguration or after receiving the 326 RRC reconfiguration, the CU 172 of the MN 104A can also use the configuration ID to determine (e.g., identify or select) the CG-Config corresponding to the C-PSCell from the CG-CandidateList received in event 308. In such cases, the C-SN 106A may not include the CG-Config in the interface message at event 332, or the C-SN 106A may not send a 332 interface message (e.g., if the C-SN 106A previously sent coordination information to the MN 104A at event 308).

[0090] The CU 172 of MN 104A may send a 334 CU-to-DU message (e.g., UE context modification request message) to the DU 174 of MN 104A after or in response to event 326 or event 332 (i.e., after identifying, based on event 326 or event 332, the C-PSCell to which the UE is connected), and the CU-to-DU message may include CG-ConfigInfo (e.g., the inter-node RRC message CG-ConfigInfo defined in 3GPP TS 38.331) and / or CG-Config and / or the C-PSCell ID corresponding to the C-PSCell to which the UE is connected and / or coordination information. The CU 172 may send coordination information corresponding to the C-PSCell to which the UE is connected. In some implementations, the CG-ConfigInfo may include MN restriction information. After receiving the 334 CU-to-DU message, the DU 174 of MN 104A applies the 336 specific DU configuration and / or coordination information. For other candidate cells not connected to the UE 102, the DU 174 may then discard (i.e., release or stop applying) the CG-Config IE and / or the CG-ConfigInfo IE and / or the coordination information.

[0091] In some implementations, the DU 174 may identify a specific DU configuration corresponding to the CG-Config included in the CU-to-DU message of event 334 in the DU configuration. The DU 174 may identify the specific DU configuration based on the association between the specific DU configuration and the CG-Config, the C-SN configuration in the CG-Config, or the C-PSCell information in the CG-Config. In some implementations, the CU 172 includes a conditional execution indication in the CU-to-DU message of event 334. The conditional execution indication indicates that the C-SN configuration in the CG-Config is to be executed or applied by the UE 102. In response to the conditional execution indication, the DU 174 applies the identified DU configuration to communicate with the UE 102. In some implementations, the conditional execution indication is a conditional MCG information IE in which the CPAC trigger is set to CPAC-execution. In other implementations, the CU 172 includes an RRC reconfiguration complete indicator IE in the CU-to-DU message of event 334. The RRC reconfiguration complete indicator IE indicates that the C-SN configuration in the CG-Config is to be executed or applied by the UE 102. In response to the RRC reconfiguration complete indicator IE, the DU 174 applies the identified DU configuration to communicate with the UE 102. In some implementations, the CU 172 may include both the RRC reconfiguration complete indicator IE and the conditional execution indication in the CU-to-DU message of event 334.

[0092] In some implementations, DU 174 releases the remainder of DU configurations 1, …, N in response to a CU-to-DU message for event 334. In some implementations, DU 174 releases the stored CG-Config IE, C-SN configuration, and / or C-PSCell information in response to a CU-to-DU message for event 334.

[0093] In some implementations, applying the MN restriction information and / or coordination information means that, for example, DU 174 configures the uplink power value (e.g., p-maxNR-FR1-MCG) within the maximum power allowed for MCG, also taking into account the requested maximum power of SCG (e.g., requested-MaxFR1) and / or UE capabilities (e.g., p-maxUE-FR1). As another example, DU 174 may configure the PRBs of MCG not to overlap with the PRBs used or configured by SCG (e.g., as indicated in the UL coordination information or DL coordination information field / IE). DU 174 may send a 338 DU-to-CU message (e.g., UE context modification response message) to CU 172. In response to applying the 336 MN restriction information and / or coordination information, if the MN restriction information and / or coordination information has not been conditionally configured to UE 102 in steps 310 to 312, MN 104A may decide to send an RRC reconfiguration message including configuration parameters to UE 102. Accordingly, CU 172 sends a 340 RRC reconfiguration message to DU 174 in a CU-to-DU message (e.g., DL RRC message transfer or UE context modification request message), and DU 174 sends a 342 RRC reconfiguration message to UE 102. In some implementations, the configuration parameter 342 may reconfigure or release the configuration parameter (value) that UE 102 uses to communicate with MN 104A. In other implementations, the configuration parameter 342 may be a new configuration parameter for configuring UE 102 to communicate with MN 104A. In response to the RRC reconfiguration message 342, UE 102 may send a 344 RRC reconfiguration complete message to DU 174, and DU 174 sends a 346 RRC reconfiguration complete message to CU 172 in a DU-to-CU message (e.g., UL RRC message transfer or UE context modification request message). In response, the CU 102 of MN 104A may send a 348 SN modification confirm message (e.g., SgNB modification confirm or S-Node modification confirm message). Events 322, 324, 326, 328, 330, 332, 334, 336, 338, 340, 342, 344, 346, 348 may be collectively referred to as the conditional SN addition execution procedure 396.

[0094] In response to receiving the RRC reconfiguration complete message 326 or the interface message 332, or after receiving the RRC reconfiguration complete message 326 or the interface message 332, the MN 104A may send the SN status transfer message 330 to transfer the uplink PDCP SN and HFN receiver status and / or the downlink PDCP SN and HFN transmitter status of each of the DRBs of the UE 102. Contrary to event 318, the MN 104A sends the 330 (non-early) SN status transfer message.

[0095] After the UE 102 successfully completes the random access procedure 322, the UE 102 communicates 350 with the MN and the C-SN via the C-PSCell according to the (updated) MN configuration and the C-SN configuration, respectively.

[0096] Continuing to refer Figure 3A , in some implementations, the C-SN configuration may be a complete and independent configuration (i.e., full configuration). The C-SN configuration may include a full configuration indication (information element (IE) or field) that identifies the C-SN configuration as a full configuration. In this case, the UE 102 may use the C-SN configuration to communicate with the SN 106A without relying on the SN configuration. On the other hand, in other cases, the C-SN configuration may include an "incremental" configuration or one or more configurations that augment the previously received SN configuration. In these cases, the UE 102 may use the incremental C-SN configuration together with the SN configuration to communicate with the C-SN 106A.

[0097] The C-SN configuration may include a plurality of configuration parameters for the UE 102 to apply when communicating with the C-SN 106A via the C-PSCell. The plurality of configuration parameters may configure the C-PSCell of the C-SN 106A and zero, one, or more candidate secondary cells (C-SCells) for the UE 102. The plurality of configuration parameters may configure radio resources for the UE 102 to communicate with the C-SN 106A via the C-PSCell of the C-SN 106A and zero, one, or more C-SCells. The plurality of configuration parameters may configure zero, one, or more radio bearers. One or more radio bearers may include an SRB and / or one or more DRBs.

[0098] In some implementations, the C-SN configuration may include a CellGroupConfig IE that configures the C-PSCell of C-SN 106A and a group of zero, one, or more C-SCells. In one implementation, the C-SN configuration includes a radio bearer configuration. In another implementation, the C-SN configuration does not include a radio bearer configuration. For example, the radio bearer configuration may be a RadioBearerConfig IE, a DRB-ToAddModList IE, or an SRB-ToAddModList IE, a DRB-ToAddMod IE, or an SRB-ToAddMod IE. In various implementations, the C-SN configuration may be an RRCReconfiguration message, an RRCReconfiguration-IE, or a CellGroupConfig IE that complies with 3GPP TS 38.331. The full configuration indication may be a field or an IE that complies with 3GPP TS 38.331. In other implementations, the C-SN configuration may include an SCG-ConfigPartSCG-r12 IE that configures the C-PSCell of C-SN 106A and zero, one, or more C-SCells. In some implementations, the C-SN configuration is an RRCConnectionReconfiguration message, an RRCConnectionReconfiguration-IE, or a ConfigPartSCG-r12 IE that complies with 3GPP TS 36.331. The full configuration indication may be a field or an IE that complies with 3GPP TS 36.331.

[0099] Still referring to Figure 3A , in some cases, the base station 106A (i.e., the C-SN) may also include a CU 172 and one or more DUs 174, as Figure 1C shown. For each of the C-SN configurations, one or more DUs 174 may generate the C-SN configuration. Alternatively, for each of the C-SN configurations, one or more DUs 174 may generate a part of the C-SN configuration, and the CU 172 may generate the remaining part of the C-SN configuration. For example, the UE 102 performs a random access procedure 322 with the first DU 174A that operates the (C-)PSCell, and the first DU 174A may identify the UE 102 during the random access procedure. In this case, the UE 102 communicates with the SN 106A via the first DU 174A 350.

[0100] The first DU 174A of the C-SN 106A operating on the C-PSCell may generate a C-SN configuration for configuring the C-PSCell or a part of the C-SN configuration and send the C-SN configuration or the part of the C-SN configuration to the CU 172. In the case of generating a part of the C-SN configuration, the CU 172 generates the remaining part of the C-SN configuration. In some scenarios or implementations, the first DU 174A generates each of the other C-SN configurations. Alternatively, for each of the other C-SN configurations, the first DU 174A generates a part of the C-SN configuration, and the CU 172 generates the remaining part of the C-SN configuration. In other scenarios or implementations, the first DU 174A generates at least one first C-SN configuration in the C-SN configuration. Alternatively, for each of the at least one first C-SN configurations, the first DU 174A generates a part of the C-SN configuration, and the CU 172 generates the remaining part of the C-SN configuration. The second DU 174B of the C-SN 106A generates at least one second C-SN configuration in the C-SN configuration. Alternatively, for each of the at least one second C-SN configurations, the second DU 174B generates a part of the C-SN configuration, and the CU 172 generates the remaining part of the C-SN configuration.

[0101] Next, referring to Figure 3B , scenario 300B is similar to scenario 300A. However, in scenario 300B, the MN 104A initially operates in DC with the source SN (S-SN) 106B to connect to the UE 102 and later decides to perform a conditional SN change procedure. The interaction between the MN 104A and the C-SN 106A is similar to Figure 3A the interactions described in Figure 3B The differences between Figure 3A are further described below.

[0102] 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 the PSCell according to the S-SN configuration. At a later time, the MN 104A, the C-SN 106A, and the UE 102 perform a conditional SN addition preparation procedure 390. In the case where early data forwarding is required, the MN 104A may send a 352 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 sends a 354 early state transfer message to the MN 104A, and the MN 104A sends a 356 early state transfer message to the C-SN 106A. Events 390, 352, 354, and 356 may be collectively referred to as event 391 for MN-initiated conditional SN change preparation.

[0103] Similar to Figure 3A , UE 102 later detects 320 that the conditions for connecting to the C-PSCell are met, and in response to the detection, performs a random access procedure with C-SN 106A on the C-PSCell. UE 102, MN 104A, and C-SN 106A perform conditional SN addition execution 396. MN 104A sends 358 an SN release request message (e.g., SgNB release request or S-Node release request message) to S-SN 106B. In response, S-SN 106B sends 360 an SN release request confirmation message (e.g., SgNB release request confirmation or S-Node release request confirmation message). In cases where data forwarding is required, MN 104A may send 362 an interface message (e.g., Xn-U address indication or data address indication message) to S-SN 106B to signal the forwarding address information of the user plane data. S-SN 106B may then send 364 an SN status transfer message to MN 104A, and MN 104A may then send 366 an SN status transfer message to C-SN 106A. MN 104A sends 368 a UE context release message to S-SN 106B. Events 358, 360, 362, 364, 366, and 368 may be collectively referred to as the SN release and SN status transfer process 398.

[0104] After UE 102 successfully completes 322 the random access procedure, UE 102 communicates 350 with the MN and C-SN via the C-PSCell according to the C-SN configuration.

[0105] Next, referring to Figure 3C , scenario 300C depicts an SN-initiated conditional SN change scenario, where MN 104A is initially connected to 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 Figure 3A or Figure 3B described therein. The differences between Figure 3C and Figure 3A and Figure 3B are described below.

[0106] At a certain point in time, S-SN 106B decides to initiate a conditional SN change procedure and sends a 303 SN change request message (e.g., an SgNB change request or an S-Node change request message defined in 3GPP TS 36.423 and 38.423, respectively) to MN 104A. The SN change request message includes a candidate / target SN ID (e.g., a global en-gNB ID or a global NG-RAN node ID, which refers to C-SN 106A, for example) and a CG-Config IE. The CG-Config IE also includes proposed candidate cell information (e.g., a physical cell ID and / or related cell measurement results) and a trigger condition for the corresponding candidate cell (e.g., a condExecution Cond-SCG IE, which may include a measurement ID referring to a configured S-SN measurement). MN 104A and C-SN 106A perform a conditional SN addition preparation procedure 392 with the proposed candidate cell information from S-SN 106B. MN 104A may send a 370 SN request message (e.g., an SgNB modification request or an S-Node modification request message) to S-SN 106B to provide a candidate PSCell accepted by C-SN 106A. In response, S-SN 106B may send a 372 SN request confirmation message (e.g., an SgNB modification request confirmation or an S-Node modification request confirmation message) to provide an updated measurement configuration and / or trigger condition. MN 104A performs a 394 RRC reconfiguration procedure with UE 102. MN 104A sends a 309 SN change confirmation message (e.g., an SgNB change confirmation or an S-Node change confirmation message) to S-SN 106B. Events 303, 392, 370, 372, 394, and 309 may be collectively referred to as an SN-initiated conditional SN change preparation procedure 393.

[0107] If UE 102 later detects 320 that the conditions for connecting to the C-PSCell are met, then similarly, UE 102 performs a random access procedure via the C-PSCell with C-SN 106A, a conditional SN addition execution procedure 396, and an SN release and SN state transfer procedure 398. However, different from scenario 300B, MN 104A may not send a 344 SN release request message, and thus, S-SN 106B may not send a 346 SN release request confirmation message.

[0108] Next, refer to Figure 3D, Scenario 300D depicts a conditional handover scenario with conditional SN addition or change, where S-MN 104B is initially connected to UE 102 and later initiates a CHO to C-MN 104A, and the C-MN further performs a CPA process with C-SN106A. The interaction between MN 104A and C-SN 106A is similar to Figures 3A to 3C those described in Figure 3D and Figures 3A to 3C the differences between

[0109] Initially, UE 102 operates in a single connection (SC) with S-MN 104B at operation 302 or in a dual connection with S-MN 104B and S-SN 106B at operation 301 (not shown in the figure), and communicates with S-SN 106B via the PSCell according to the S-SN configuration. At a later time, S-MN 104B decides to perform a conditional handover procedure for UE 102 and sends 382 a handover request message including the target cell ID, a CHO indication (e.g., conditional handover information request IE including a CHO trigger IE indicating "CHO-initiation"), HandoverPreparationInformation IE, and / or measurement results from UE 102 to C-MN 104A. The measurement results may include some candidate cell information for C-MN 104A to consider whether to trigger an SN addition process. In some implementations, C-MN 104A may consider whether to trigger an SN addition process based on other parameters (such as the expected UE movement trajectory, UE identity, UE mobility history) or even blindly consider whether to trigger an SN addition process without receiving the measurement results. The CU 172 of C-MN 104A decides to perform a CHO process with CPAC to prepare multiple C-PSCells and a conditional handover. The CU 172 sends 342 a UE context setup request message to DU 174 and includes a condition indication (e.g., conditional DU-to-DU mobility information indicating CHO-initiation) and HandoverPreparationInformation IE. In response, DU 174 sends 344 a UE context setup response message including a first DU configuration to CU 172. In some implementations, DU 174 considers the received HandoverPreparationInformation IE and generates a CellGroupConfig IE to include the first DU configuration. In some implementations, the first DU configuration further includes a reconfigurationWithSync IE / field. The CU 172 performs 392 a conditional SN addition preparation process with C-SN 106A, obtains a CG-CandidateList IE from an SN addition request confirmation message, and sends 307 one or more UE context modification request messages to DU 174, each UE context modification request message including a CG-Config IE retrieved from the CG-CandidateList, as Figure 3AAs described in. CU 172 receives a UE context modification response message from DU 174 in response to a UE context modification request message. In some implementations, the UE context modification request message may include a second DU configuration, which may update the first DU configuration when dual connectivity is in effect. CU172 then generates an RRC reconfiguration message that includes the first DU configuration and one or more conditional (re)configuration IEs (e.g., CondRe configurationToAddMod IE or CondReconfigToAddMod IE), and the one or more conditional (re)configuration IEs include one or more C-SN configurations and / or the corresponding second DU configuration, as Figure 3A As described in. CU 172 sends a handover request confirmation message including the RR C reconfiguration message to S-MN 104B. S-MN 104B generates an RRC reconfiguration * message and sends the 386 RRC reconfiguration * message to UE 102. The RRC reconfiguration * message includes one or more conditional (re)configuration IEs (e.g., CondReconfigurationToA ddMod IE or CondReconfigToAddModIE), and the one or more conditional (re)configuration IEs include one or more RRC reconfiguration messages. In response, UE 102 sends a 388 RRC reconfiguration complete message to S-MN 104B.

[0110] At a later time, UE 102 detects 321 that the conditions for connecting to the C-PCell for conditional handover are met and initiates a random access procedure on the C-PCell. UE performs a 323 random access procedure with C-MN 104A via the C-PCell in DU 174. UE 102 also sends a 374 RRC reconfiguration complete message to DU 174, and DU 174 forwards the 376 RRC reconfiguration complete message to CU 172 in a DU-to-CU message (e.g., ULRRC message transfer message). DU 174 also sends a 339 access success message to CU 172 after the random access procedure. UE 102 communicates 350 with C-MN 104A using the MN configuration that includes the first DU configuration. CU 172 sends a 378 handover success message to S-MN 104B. CU 172 may send a UE context release message to S-MN 104B.

[0111] At a later time, UE 102 detects 320 that the conditions for connecting to the C-PSCell are met and initiates a random access procedure on the C-PSCell. UE 102, DU 174, CU 172, and C-SN 106A perform a 396 conditional SN addition execution procedure via the C-PSCell, similar toFigure 3A The UE 102 communicates with the C-MN 104A and the C-SN 106A using the MN configuration and the C-SN configuration respectively. The MN configuration may include a second DU configuration if the second DU configuration is provided to the CU 172 in event 309.

[0112] Next, referring to Figure 3E , scenario 300E depicts a conditional handover scenario with an SCG configuration, where the S-MN 104B is initially connected to the UE 102 and later initiates a CHO to the C-MN 104A, and the C-MN further performs a CPA process with the C-SN 106A. The interaction between the C-MN 104A and the C-SN 106A is similar to Figures 3A to 3D those described in Figure 3E and Figures 3A to 3D the differences between

[0113] After receiving the handover request message 382, different from scenario 300D, the CU 172 decides to perform a CHO procedure with an SCG configuration to prepare only one C-PSCell and a conditional handover. The CU 172 sends a SN addition request message 303 including a CHO indication (e.g., CHO information SN addition IE) to the C-SN 106A, such that the C-SN 106A generates a single C-SN configuration 306. The C-SN 106A sends a SN addition request confirmation message 305 including a CG-Config IE to the CU 172, where the CG-Config IE includes the single C-SN configuration. The CU 172 sends a UE context setup request message 341 including a conditional indication, a HandoverPreparationInformation IE, and a CG-Config IE to the DU 174. In some implementations, the conditional indication is a conditional inter-DU mobility information IE indicating CHO-initiation and / or a conditional MCG information IE indicating CPAC-initiation. In response, the DU 174 sends a UE context setup response message 343 including a (first) DU configuration to the CU 172. In some implementations, the DU 174 considers the received HandoverPreparationInformation IE and CG-Config IE and generates a CellGroupConfig IE to include the (first) DU configuration. In some implementations, the (first) DU configuration further includes a reconfigurationWithSync IE / field. The CU 172 then generates an RRC reconfiguration message including the (first) DU configuration and the C-SN configuration retrieved from the CG-Config IE. The CU 172 sends a handover request confirmation message 385 including the RRC reconfiguration message to the S-MN 104B. The S-MN 104B generates an RRC reconfiguration* message and sends an RRC reconfiguration* message 386 to the UE 102, where the RRC reconfiguration* message includes one or more conditional (re)configuration IEs (e.g., CondReconfigurationToAddMod IE or CondReconfigToAddMod IE), and the one or more conditional (re)configuration IEs include one or more RRC reconfiguration messages. In response, the UE 102 sends an RRC reconfiguration complete message 388 to the S-MN 104B.

[0114] At a later time, the UE 102 detects 321 that the conditions for connecting to the C-PCell for conditional handover are met, and initiates a random access procedure not only on the C-PCell but also additionally on the C-PSCell compared to scenario 300D. The UE performs 323 the random access procedure with the C-MN 104A via the C-PCell in the DU174. The DU 174 also sends 339 an access success message to the CU172 after the random access procedure. The CU 172 sends 378 a handover success message to the S-MN 104B. The CU 172 may send a UE context release message to the S-MN104B. The UE also performs 322 the random access procedure with the C-SN 106A via the C-PSCell. The UE102 sends 374 an RRC reconfiguration complete message to the DU 174, and the DU 174 forwards 376 the RRC reconfiguration complete message to the CU 172 in a DU-to-CU message (e.g., UL RRC message transfer message). The CU 172 then sends 328 an SN reconfiguration complete message to the C-SN 106A. The C-SN 106A may send 332 an interface message (e.g., SN modification request message) including coordination information (e.g., MR-DC resource coordination information IE) to the CU 172. After the 374 RRC reconfiguration complete message or in response to the 374 RRC reconfiguration complete message, the CU 172 may send 335 a CU-to-DU message (e.g., UE context modification request message) to the DU 174, and the CU-to-DU message may include an RRC reconfiguration complete indicator for indicating that the UE 102 has successfully applied the (first) DU configuration and / or coordination information (e.g., resource coordination transfer container IE) (if received from the C-SN 106A). In some implementations, the CU-to-DU message in event 335 does not include the CG-Config IE because only one C-SN configuration is prepared. In some implementations, the CU-to-DU message in event 335 and the UE context setup request message in event 341 contain the same gNB-CU UE F1AP ID and / or gNB-DU UE F1AP ID, so that the DU 174 can identify the UE 102 and the corresponding (first) DU configuration. The DU 174 will apply 336 the (first) DU configuration and / or coordination information (if received). The DU174 sends 338 a DU-to-CU message (e.g., UE context modification response message) to the CU 172. The CU 172 may send 348 an SN modification confirmation message in response to the interface message at event 332. The UE 102 communicates with the C-MN104A and the C-SN 106A using the MN configuration and the C-SN configuration respectively. The MN configuration including the (first) DU configuration and the (first) DU configuration have been adapted to the MR-DC resource coordination.

[0115] Next, Figure 4 Scenario 400 is shown where UE 102 is connected to a single base station (e.g., MN 104A), and the base station later acts as both an MN and an SN and configures both the MCG and the SCG. Scenario 400 is similar to Scenarios 300A to 300C, and the same actions and events are labeled with the same reference numerals. Differences from Figure 4 and Figures 3A to 3C are further described below.

[0116] UE 102 initially operates in SC with M-DU 174A and communicates with CU 172 via M-DU 174A, or operates in DC with M-DU 174A and an S-DU (e.g., DU 174C, not shown in this figure) and communicates with CU 172 via M-DU 174A and the S-DU.

[0117] CU 172 later sends 403 to C-DU 174B one or more UE context setup request messages including a condition indication. In response, C-DU 174B sends 405 to CU 172 one or more UE context setup response messages including C-DU configuration and / or corresponding coordination information. CU 172 may generate 406 a C-SN configuration based on the C-DU configuration. CU 172 may generate 433 a CG-Config IE including the C-SN configuration and / or other coordination parameters. CU 172 may also generate a CG-ConfigInfo IE including MN restriction information. CU 172, M-DU 174A, and UE 102 perform 494 an RRC reconfiguration process similar to process 394. Events 403, 405, and 406 may be collectively referred to as event 492. Events 492 and 494 may also be collectively referred to as process 490 for conditional SN addition preparation in a single base station.

[0118] The UE 102 may later detect that 420 it meets the conditions for connecting to the C-PSCell and initiate a random access procedure on the identified C-PSCell in response to the detection. In response to the initiation, the UE 102 performs 422 a random access procedure with the C-DU 174B via the identified C-PSCell. In response to the detection or initiation 420, the UE 102 sends 424 an RRC reconfiguration complete message including a configuration ID corresponding to the C-PSCell to the CU 172 via the M-DU 174A. The M-DU 174A sends 426 the RRC reconfiguration complete message to the CU 172 in a DU-to-CU message (e.g., UL RRC message transfer message). The UE 102 may send 424 the RRC reconfiguration complete message before, during, or after the random access procedure. The C-DU 174B may send 431 a DU-to-CU message (e.g., access success or UE context modification request message) including PSCell information (e.g., CGI) and / or C-DU configuration and / or corresponding coordination information. The CU 172 may send 434 a CU-to-DU message (e.g., UE context modification request message) to the M-DU 174A, and the CU-to-DU message may include CG-ConfigInfo and / or CG-Config and / or a C-PSCellID corresponding to the C-PSCell to which the UE has connected and / or coordination information, similar to event 334. The M-DU 174A applies 436 a specific DU configuration (i.e., (updated) M-DU configuration) and / or coordination information, similar to event 336. The M-DU 174A may send 438 a DU-to-CU message (e.g., UE context modification response message) to the CU 172. Events 422, 424, 426, 431, 434, 436, 438 may be collectively referred to as the conditional SN addition execution process in a single base station 496. The UE communicates 450 with the M-DU 174A and the C-DU 174B according to the M-DU configuration and the C-SN configuration, respectively.

[0119] In some implementations, if the above events involve an SN change (initiated by the MN or SN), the CU 172 may send a UE context release command message to the S-DU after the successful execution of the C-SN configuration.

[0120] In some implementations, the CU 172 and a single DU 174 serve both the MCG and the SCG in different cells. In such cases, for example, events 403 and 405 may be a UE context modification request and a UE context modification response message between the CU 172 and the M-DU 174A, respectively. Similarly, for example, events 431 and 434 may also occur between the M-DU 174A and the CU 172.

[0121] Figures 5 to 13 is a flowchart depicting an example method according to the techniques of the present disclosure, which may be implemented by a base station CU (e.g., the CU 172 of base station 104A) to support conditional procedures. As indicated throughout the present disclosure, Figures 5 to 13 the example method depicted in Figures 5 to 7 may be implemented during scenarios 300A to 300E and 400 described above. In particular, Figures 8 to 10 illustrates a conditional procedure that may be performed by two base stations (i.e., an inter-base-station conditional procedure, such as in scenarios 300A to 300C), and Figures 11 to 13 illustrates a similar conditional procedure that may be performed by a single base station (i.e., an intra-base-station conditional procedure, such as in scenario 400).

[0122] Referring to Figure 5 , method 500 is described, in which an MN-CU (e.g., the CU 172 of MN 104A) performs a conditional SN procedure for a UE (e.g., UE102) with a candidate SN (e.g., C-SN 106A).

[0123] During method 500, at block 502, the CU communicates with the UE via the DU. At block 504, the CU performs a conditional procedure (e.g., CPA or CPC) with a candidate SN for the UE and receives a CG-ConfigIE (e.g., event 308) from the candidate SN in the SN message of the procedure. At block 506, the CU sends a first CU-to-DU message (e.g., event 307) to the DU, including a conditional indication and the CG-Config IE. In some implementations, the first CU-to-DU message also includes a CG-ConfigInfo IE. In some implementations, the conditional indication is a conditional MCG information IE indicating CPAC-initiation. At block 508, the CU receives a first DU-to-CU message (e.g., event 309) from the DU in response to the first CU-to-DU message. In some implementations, the DU-to-CU message may include a DU configuration (i.e., MCG configuration). At block 510, the CU retrieves an RRC message (i.e., SN RRC message) from the CG-Config IE. In some implementations, the RRC message is or includes the C-SN configuration described above. At block 512, the CU sends an RRC reconfiguration message (e.g., events 310 and 312) to the UE via the DU, including the RRC message and / or the DU configuration (if received). In some implementations, if the CU receives a DU configuration, the CU includes the DU configuration and the SN RRC message in the conditional (re)configuration IE in the RRC reconfiguration message at block 512. In some implementations, the CU may generate an MN RRC message including the DU configuration and the SN RRC message and include the MN RRC message in the conditional (re)configuration IE. At block 514, the CU receives a first RRC reconfiguration complete message (e.g., events 314 and 316) from the UE via the DU in response to the RRC reconfiguration message. At block 516, the CU receives a second RRC reconfiguration complete message (e.g., events 324 and 326) from the UE via the DU, including a configuration ID. At block 518, the CU may send a second CU-to-DU message to indicate that the UE has executed the RRC message (e.g., event 334). In some implementations, the second CU-to-DU message includes a CG-Config and / or a C-PSCellID corresponding to the C-PSCell to which the UE has connected. In some implementations, the second CU-to-DU message includes a conditional execution indication. In other implementations, the second CU-to-DU message includes an RRC reconfiguration complete indicator IE. In some implementations, the second CU-to-DU message includes an RRC reconfiguration complete indicator IE and a conditional execution indication.

[0124] In some implementations, the CU may send a second CU-to-DU message to the DU after receiving or in response to receiving the second RRC reconfiguration complete message to indicate to the DU that the UE has executed the SN RRC message. After receiving the indication or the second CU-to-DU message from the CU or in response to receiving the indication or the second CU-to-DU message from the CU, the DU applies the DU configuration to communicate with the UE.

[0125] In some implementations, the CU may include the MN restriction information in the CG-Config Info IE and include the CG-ConfigInfo IE in the first CU-to-DU message and / or the second CU-to-DU message.

[0126] In some implementations, the CU receives the CG-Config IE and / or coordination information from a candidate SN in the SN message of the conditional procedure. The CG-Config IE includes the SN restriction information. The CU may include the CG-Config IE in the first CU-to-DU message to send the SN restriction information to the DU.

[0127] Go to Figure 6 , method 600 is described, where the MN-CU (e.g., the CU 172 of the MN 104A) performs a conditional SN procedure for the UE (e.g., UE102) with a candidate SN (e.g., C-SN 106A). Method 600 is similar to method 500, except that the MN-CU receives multiple CG-Config IEs and multiple SN restriction information.

[0128] Method 600 begins at block 602, where the CU communicates with the UE via the DU. At block 604, the CU performs at least one conditional procedure (e.g., CPA or CPC) (e.g., event 304) for the UE with a candidate SN. At block 606, the CU receives, in at least one SN message of the at least one conditional SN procedure, multiple CG-ConfigIEs from the candidate SN (e.g., event 308). At block 608, for each of the CG-Config IEs, the CU sends a first CU-to-DU message to the DU that includes a conditional indication and the CG-Config IE (e.g., event 307). In some implementations, the first CU-to-DU message also includes a CG-ConfigInfo IE. In some implementations, the conditional indication is a conditional MCG information IE that indicates CPAC-initiation. At block 610, the CU receives a first DU-to-CU message from the DU in response to each first CU-to-DU message (e.g., event 309). In some implementations, the first DU-to-CU message may include a DU configuration (i.e., MCG configuration). At block 612, the CU retrieves an RRC message (i.e., SN RRC message) from each of the multiple CG-Config IEs, generates a conditional configuration that includes the RRC message and / or the corresponding DU configuration, and assigns a configuration ID to each of the conditional configurations. In some implementations, the RRC message is or includes the C-SN configuration described above. At block 614, the CU sends at least one RRC reconfiguration message that includes the conditional configuration and the configuration ID to the UE via the DU (e.g., events 310 and 312). In some implementations, if the CU receives a DU configuration at block 610, the CU includes the DU configuration and the SN RRC message in a conditional (re)configuration IE in the RRC reconfiguration message at block 614. In some implementations, the CU may generate an MN RRC message that includes the DU configuration and the SN RRC message and include the MN RRC message in the conditional (re)configuration IE. At block 616, the CU receives at least one RRC reconfiguration complete message from the UE via the DU in response to the at least one RRC reconfiguration message (e.g., events 314 and 316). At block 618, the CU receives a first RRC reconfiguration complete message that includes a first configuration ID from the UE via the DU (e.g., events 324 and 326). At block 620, the CU determines (e.g., identifies or selects) a CG-Config and / or a PSCellID from the multiple CG-Config IEs according to the first configuration ID. At block 622, the CU may send a second CU-to-DU message to the DU to indicate that the UE has executed the RRC message (e.g., event 334). In some implementations, the second CU-to-DU message includes a CG-Config and / or a C-PSCell ID corresponding to the C-PSCell to which the UE has connected.In some implementations, the second CU-to-DU message includes a conditional execution indication. In other implementations, the second CU-to-DU message includes an RRC reconfiguration complete indicator IE. In some implementations, the second CU-to-DU message includes an RRC reconfiguration complete indicator IE and a conditional execution indication.

[0129] In some implementations, at block 608, the CU may include MN restriction information in the CG-ConfigInfo IE in the first CU-to-DU message.

[0130] Go to Figure 7 , method 700 is described, where the MN-CU (e.g., the CU 172 of the MN 104A) performs a conditional SN procedure for a UE (e.g., UE 102) with a candidate SN (e.g., C-SN 106A). During method 700, the MN-CU determines how to handle multi-connection coordination based on whether the SN procedure is conditional or immediate.

[0131] Method 700 begins at block 702, where the CU communicates with the UE via the DU. At block 704, the CU performs an SN procedure (e.g., an SN addition procedure or an SN modification procedure) for the UE with the SN and receives a CG-Config IE (e.g., event 308) from the SN in the SN message of the SN procedure. At block 706, the CU determines whether the SN procedure is for an immediate SN procedure or a conditional SN procedure. If the SN procedure is for an immediate SN procedure, the process proceeds to block 708, where the CU sends a CU-to-DU message including the CG-Config IE to the DU in response to receiving the SN message. If the SN procedure is for a conditional SN procedure, the process proceeds to block 710, where the CU sends a first CU-to-DU message including a conditional indication and the CG-Config IE to the DU in response to receiving the SN message (e.g., event 307). In some implementations, the first CU-to-DU message also includes a CG-ConfigInfo IE for MN restriction information. The process then proceeds to block 712, where the CU receives a first DU-to-CU message (e.g., event 309) from the DU in response to the first CU-to-DU message. In some implementations, the first DU-to-CU message may include DU configuration (i.e., MCG configuration). In some implementations, the CU retrieves an RRC message (i.e., an SN RRC message) from the CG-Config IE. In some implementations, the RRC message is or includes the C-SN configuration described above. If the CU receives a DU configuration at block 712, the CU includes the DU configuration and the SN RRC message in a conditional (re)configuration IE in the RRC reconfiguration message for the UE (e.g., event 310). In some implementations, the CU may generate an MN RRC message including the DU configuration and the SN RRC message and include the MN RRC message in the conditional (re)configuration IE. The process proceeds to block 714, where the CU receives an RRC reconfiguration complete message indicating that the UE has connected to the SN from the UE via the DU (e.g., event 326). In response to block 714 or after block 714, at block 716, the CU may send a second CU-to-DU message to the DU after receiving the RRC reconfiguration complete message or in response to receiving the RRC reconfiguration complete message to indicate to the DU to apply the DU configuration (e.g., event 334).

[0132] In some implementations, the second CU-to-DU message includes a CG-Config and / or a C-PSCell ID corresponding to the C-PSCell to which the UE has connected. In some implementations, the second CU-to-DU message includes a conditional execution indication. In other implementations, the second CU-to-DU message includes an RRC reconfiguration complete indicator IE. In some implementations, the second CU-to-DU message includes an RRC reconfiguration complete indicator IE and a conditional execution indication.

[0133] Next, referring to Figure 8 , method 800 is described, in which a CU (e.g., CU 172 of MN 104A) performs a conditional procedure for a UE (e.g., UE 102) with a candidate DU (e.g., C-DU 174B). Method 800 is similar to method 500, except that the conditional procedure is performed within the same base station operating as both an MN and a C-SN.

[0134] Method 800 begins at block 802, where the CU communicates with the UE via a first DU (i.e., M-DU). At block 804, the CU performs a conditional procedure (e.g., CPA or CPC) for the UE with a second DU (i.e., C-DU) and receives from the second DU a DU configuration (i.e., C-DU configuration) and / or SN restriction information (e.g., events 403 and 405) in the DU-to-CU message of the procedure. In some implementations, the CU may generate a CG-Config IE including the C-DU configuration and / or SN restriction information. In some implementations, the CU may generate a CG-ConfigInfo IE including the C-DU configuration and / or SN restriction information and / or MN restriction information. At block 806, the CU sends a first CU-to-DU message to the first DU for the UE, the first CU-to-DU message including a conditional indication and a CG-Config IE and / or a CG-ConfigInfo IE corresponding to the C-DU configuration (e.g., an event similar to 307). At block 808, the CU receives a first DU-to-CU message from the first DU in response to the first CU-to-DU message (e.g., an event similar to 309). In some implementations, the first DU-to-CU message may include an M-DU configuration (i.e., MCG configuration). At block 810, the CU generates an RRC message including the C-DU configuration (e.g., an SN RRC message). At block 812, the CU sends an RRC reconfiguration message including the RRC message and / or the M-DU configuration to the UE via the first DU (e.g., events 310 and 312 or 494). In some implementations, if the CU receives an M-DU configuration at block 808, the CU includes the M-DU configuration and the SN RRC message in a conditional (re)configuration IE and includes the conditional (re)configuration IE in the RRC reconfiguration message at block 812. In some implementations, the CU may generate an MN RRC message including the M-DU configuration and the SN RRC message and include the MN RRC message in the conditional (re)configuration IE. At block 814, the CU receives a first RRC reconfiguration complete message from the UE via the DU in response to the RRC reconfiguration message (e.g., events 314 and 316 or 494). At block 816, the CU receives a second RRC reconfiguration complete message including a configuration ID from the UE via the first DU (e.g., events 324 and 326 or 424 and 426). The flow may then proceed to block 818, where the CU may send a second CU-to-DU message to the first DU after receiving or in response to receiving the second RRC reconfiguration complete message to indicate that the UE has executed the RRC message (e.g., event 434). In some implementations, the second CU-to-DU message includes a CG-Config and / or a C-PSCell ID corresponding to the C-PSCell to which the UE has connected.In some implementations, the second CU-to-DU message includes a conditional execution indication. In other implementations, the second CU-to-DU message includes an RRC reconfiguration complete indicator IE. In some implementations, the second CU-to-DU message includes an RRC reconfiguration complete indicator IE and a conditional execution indication.

[0135] Next, referring to Figure 9 , method 900 is described, where a CU (e.g., CU 172 of MN 104A) performs a conditional procedure for a UE (e.g., UE 102) with a candidate DU (e.g., C-DU 174B). Method 900 is similar to method 600, except that the conditional procedure is performed within the same base station operating as both an MN and a C-SN.

[0136] Method 900 begins at block 902, where the CU communicates with the UE via a first DU (i.e., M-DU). At block 904, the CU performs at least one conditional procedure (e.g., CPA or CPC) (e.g., event 403) for the UE with a second DU (i.e., C-DU). At block 906, the CU receives, in at least one DU-to-CU message of the at least one conditional procedure, multiple C-DU configurations and multiple SN restriction information (e.g., event 405) from the second DU. At block 908, the CU generates a CG-Config IE for the C-DU configuration, and for each of the CG-Config IEs, sends a first CU-to-DU message including a conditional indication and the CG-Config IE to the first DU (e.g., an event similar to 307). In some implementations, for each of the multiple DU configurations (i.e., C-DU configurations), the CU may generate a CG-Config IE including the C-DU configuration and / or SN restriction information. In some implementations, for each of the multiple DU configurations (i.e., C-DU configurations), the CU may generate a CG-ConfigInfo IE including the C-DU configuration and / or MN restriction information and include the CG-ConfigInfo in the first CU-to-DU message. At block 910, the CU receives a first DU-to-CU message from the first DU in response to the first CU-to-DU message (e.g., an event similar to 309). In some implementations, the first DU-to-CU message may include an M-DU configuration (i.e., MCG configuration). For each of the multiple DU configurations, at block 912, the CU generates an RRC message including the C-DU configuration (e.g., an SN RRC message) and generates a conditional configuration (e.g., a conditional (re)configuration IE) including the RRC message and / or the M-DU configuration, and assigns a configuration ID to each of the conditional configurations. If the CU receives an M-DU configuration, the CU may include the M-DU configuration and the SN RRC message in the conditional configuration of block 912. At block 914, the CU sends at least one RRC reconfiguration message including the conditional configuration and the configuration ID to the UE via the first DU (e.g., events 310 and 312 or 494). In some implementations, the CU may generate an MN RRC message including the M-DU configuration and the SN RRC message (which includes the C-DU configuration) and include the MN RRC message in the conditional configuration of block 914. At block 916, the CU receives at least one RRC reconfiguration complete message from the UE via the first DU in response to the at least one RRC reconfiguration message (e.g., events 314 and 316 or 494). At block 918, the CU receives a first RRC reconfiguration complete message including a first configuration ID from the UE via the first DU (e.g., events 424 and 426).At block 920, the CU determines (e.g., identifies or selects) the CG-Config and / or the PSCell ID from among multiple CG-Config IEs according to a first configuration ID. In response to or after block 920, the CU may send 922 a second CU-to-DU message to the first DU to indicate that the UE has executed an RRC message (e.g., event 434). In some implementations, the second CU-to-DU message includes the CG-Config and / or the C-PSCell ID corresponding to the C-PSCell to which the UE has connected. In some implementations, the second CU-to-DU message includes a conditional execution indication. In other implementations, the second CU-to-DU message includes an RRC reconfiguration complete indicator IE. In some implementations, the second CU-to-DU message includes an RRC reconfiguration complete indicator IE and a conditional execution indication.

[0137] In some implementations, at block 908, the CU may include a CG-ConfigInfo IE in the first CU-to-DU message.

[0138] Go to Figure 10 , method 1000 is described, where the CU (e.g., the CU 172 of the MN 104A) performs a conditional procedure for a UE (e.g., UE 102) with a candidate DU (e.g., C-DU 174B). Method 1000 is similar to method 700, except that the conditional procedure is performed within the same base station operating as both the MN and the C-SN.

[0139] Method 1000 begins at block 1002, where the CU communicates with the UE via a first DU (i.e., M-DU). At block 1004, the CU performs a UE context procedure (e.g., UE context setup procedure or UE context modification procedure) for the UE with a second DU (i.e., C-DU) and receives a DU configuration (e.g., event 405) from the second DU in the DU-to-CU message of the UE context procedure. At block 1006, the CU determines whether the UE context procedure is for an immediate UE context procedure or a conditional UE context procedure. If the UE context procedure is for an immediate UE context procedure, the flow proceeds to block 1008, where the CU sends a CU-to-DU message including a CG-Config IE to the first DU in response to receiving the DU-to-CU message. If the UE context procedure is for a conditional UE context procedure, the flow proceeds to block 1010, where the CU sends a first CU-to-DU message including a conditional indication and a CG-Config IE and / or a CG-ConfigInfo IE (e.g., an event similar to 307) to the first DU in response to receiving an SN message. In some implementations, the CG-Config IE includes a DU configuration (i.e., C-DU configuration). In some implementations, the CG-ConfigInfo IE includes a C-DU configuration. In some implementations, if the UE context procedure is for a conditional UE context procedure, the CU generates an RRC message (e.g., an SN RRC message) including a DU configuration (e.g., C-DU configuration). At block 1012, the CU receives a first DU-to-CU message (e.g., an event similar to 309) from the first DU in response to the first CU-to-DU message. In some implementations, the first DU-to-CU message may include an M-DU configuration. If the CU receives an M-DU configuration, the CU includes the M-DU configuration and the SN RRC message in a conditional (re)configuration IE, includes the conditional (re)configuration IE in an RRC reconfiguration message, and sends the RRC reconfiguration message to the UE via the first DU (e.g., an event similar to 310). In some implementations, the CU may generate an MN RRC message including the first DU configuration and the SN RRC message (which includes the second DU configuration) and include the MN RRC message in the conditional (re)configuration IE. At block 1014, the CU receives an RRC reconfiguration complete message (e.g., events 424 and 426) from the UE via the first DU indicating that the UE has connected to the second DU. At block 1016, the CU may send a second CU-to-DU message to the first DU after receiving the RRC reconfiguration complete message or in response to receiving the RRC reconfiguration complete message to indicate to the first DU to apply the M-DU configuration (e.g., event 434).In some implementations, the second CU-to-DU message includes a CG-Config and / or a C-PSCell ID corresponding to the C-PSCell to which the UE is already connected. In some implementations, the second CU-to-DU message includes a conditional execution indication. In other implementations, the second CU-to-DU message includes an RRC reconfiguration complete indicator IE. In some implementations, the second CU-to-DU message includes an RRC reconfiguration complete indicator IE and a conditional execution indication.

[0140] Go to Figure 11 , method 1100 is described, where a CU (e.g., CU 172 of C-MN 104A) receives a conditional handover request from a source MN (e.g., S-MN 104B) and performs a conditional procedure with a candidate SN (e.g., C-SN 106A) for a UE (e.g., UE 102). Method 1100 is similar to methods 500 to 700, except that the conditional procedure is performed after the requesting CU prepares for the conditional handover.

[0141] Method 1100 starts at block 1102, where the CU receives a handover request message (e.g., event 382) from the S-MN that includes a condition indication (e.g., a conditional handover information request IE indicating CHO-initiation) and a HandoverPreparationInformation IE. In some implementations, the handover request message also includes a measurement report for the CU to consider for subsequent SN addition operations. At block 1104, the CU sends a UE context setup request message (e.g., event 342) to the DU that includes the condition indication and the HandoverPreparationInformation IE. In some implementations, the condition indication is a conditional inter-DU mobility information IE indicating CHO-initiation. At block 1106, the CU receives a UE context setup response message (e.g., event 344) from the DU that includes a first DU configuration. In some implementations, the first DU configuration includes a reconfigurationWithSync IE / field. At block 1108, the CU performs a conditional procedure with a candidate SN for the UE and receives one or more CG-Config IEs (e.g., event 392) from the candidate SN in the SN message of the procedure. At block 1110, for each of the CG-Config IEs, the CU sends a first UE context modification request message to the DU that includes the condition indication and the CG-Config IE. In some implementations, the condition indication is a conditional MCG information IE indicating CPAC-initiation. At block 1112, the CU receives a first UE context modification response message from the DU. In some implementations, the UE context modification response message may include a second DU configuration. In some implementations, the second DU configuration does not include a reconfigurationWithSync IE / field. At block 1114, the CU generates an RRC reconfiguration message that includes a list of the first DU configuration and the conditional configuration, the list of the conditional configuration including a C-SN configuration and the second DU configuration (if received from the DU in the UE context modification response message). At block 1116, the CU sends a handover request confirmation message (e.g., event 384) to the S-MN that includes the RRC reconfiguration message. At block 1118, the CU receives a first RRC reconfiguration complete message from the UE via the DU in response to the RRC reconfiguration message. At block 1120, the CU receives a second RRC reconfiguration complete message from the UE via the DU that includes a configuration ID. At block 1122, the CU may send a second UE context modification request message to the DU to indicate that the UE has performed the C-SN configuration identified by the configuration ID (e.g., event 334).In some implementations, the second UE context modification request message includes CG-Config and / or a C-PSCell ID corresponding to the C-PSCell to which the UE is already connected. In some implementations, the second UE context modification request message includes a conditional execution indication. In other implementations, the second UE context modification request message includes an RRC reconfiguration complete indicator IE. In some implementations, the second UE context modification request message includes an RRC reconfiguration complete indicator IE and a conditional execution indication.

[0142] Go to Figure 12 , describes method 1200, where a CU (e.g., the CU 172 of the C-MN 104A) receives a conditional handover request from a source MN (e.g., the S-MN 104B) and performs a conditional procedure for a UE (e.g., the UE 102) with a candidate SN (e.g., the C-SN 106A). Method 1200 is similar to methods 500 to 700 and 1100, except that the conditional procedure is performed after the requesting CU prepares for a conditional handover and the conditional procedure only obtains one C-SN configuration, which will be applied together with the configuration for the handover.

[0143] Method 1200 starts at block 1202, where the CU receives a handover request message (e.g., event 382) for the UE from the S-MN, which includes a condition indication (e.g., a conditional handover information request IE indicating CHO-initiation) and a HandoverPreparationInformation IE. In some implementations, the handover request message also includes a measurement report for the CU to consider subsequent SN addition operations. At block 1204, the CU performs a conditional process for the UE with a candidate SN indicating a CHO with an SCG and receives a CG-Config IE (e.g., events 303 and 305) from the candidate SN in the SN message of the process. In some implementations, the CHO indication with an SCG is a CHO information SN addition IE included in the SN addition request message. At block 1206, the CU sends a UE context setup request message including the condition indication, HandoverPreparationInformation IE, and CG-Config IE to the DU (e.g., event 341). In some implementations, the condition indication may include a conditional inter-DU mobility information IE indicating CHO-initiation and / or a conditional MCG information IE indicating CPAC-initiation. At block 1208, the CU receives a UE context setup response message including the DU configuration from the DU (e.g., event 343). In some implementations, the DU configuration includes a reconfigurationWithSync IE / field. In some implementations, the DU generates the DU configuration based on the received HandoverPreparationInformation IE, CG-Config IE, and / or CG-ConfigInfo IE. At block 1210, the CU retrieves the C-SN configuration from the CG-Config IE. At block 1212, the CU generates an RRC reconfiguration message including the DU configuration and the C-SN configuration. At block 1214, the CU sends a handover request confirmation message including the RRC reconfiguration message to the S-MN (e.g., event 385). At block 1216, the CU receives an RRC reconfiguration complete message from the UE via the DU in response to the RRC reconfiguration message. At block 1218, the CU sends a UE context modification request message to the DU to indicate that the UE has performed the C-SN configuration (e.g., event 335). In some implementations, the UE context modification request message does not include the CG-Config and / or the C-PSCell ID corresponding to the C-PSCell to which the UE has connected because only the C-PSCell is prepared. In some implementations, the UE context modification request message includes a conditional execution indication. In other implementations, a second UE context modification request message includes an RRC reconfiguration complete indicator IE.In some implementations, the second UE context modification request message includes an RRC reconfiguration complete indicator IE and a conditional execution indication.

[0144] Next, refer to Figure 13 , Figure 13 FIG. 1300 shows a method for managing conditional handover requests and multi-connection information, which can be implemented in the CU of a distributed base station (e.g., candidate primary base station 104A) including a CU (e.g., CU 172) and a DU (e.g., DU 174).

[0145] At block 1302, the CU receives a handover request message (e.g., event 382) including a conditional indication and a Handover Preparation Information IE from the S-MN. At block 1304, the CU decides to perform a conditional procedure for the UE with the candidate SN. At block 1306, the CU determines whether the conditional procedure is for a CHO with an SCG or a CHO with a CPAC. In some implementations, the CU makes the determination based on the measurement report received in the handover request message and / or other auxiliary information or pre-configuration at the CU. If the CU decides to perform a CHO with an SCG, the process proceeds to block 1308, where the CU performs blocks 1204 to 1218 as Figure 12 described. Alternatively, if the CU decides to perform a CHO with a CPAC, the process proceeds to block 1310, where the CU performs blocks 1104 to 1122 as Figure 11 described.

[0146] Next, refer to Figure 14 , Figure 14 FIG. 1400 shows a method for managing multi-connection information, which can be implemented in the DU of a distributed base station (e.g., candidate primary base station 104A) including a CU (e.g., CU 172) and a DU (e.g., DU 174).

[0147] At block 1402, the DU receives a first CU-to-DU message (e.g., event 307) from the CU that includes a condition indication and a CG-Config IE and / or a CG-ConfigInfo IE. In some implementations, the first CU-to-DU message is a UE context modification request message. In some implementations, the condition indication is a conditional MCG information IE that indicates CPAC-initiation. At block 1404, the DU determines whether an (updated) DU configuration corresponding to the CG-Config IE needs to be generated. In some implementations, the DU makes the determination by checking whether applying both the original DU configuration and the C-SN configuration exceeds the UE's capabilities; if it exceeds the UE capabilities, an updated DU configuration is needed. If the DU decides not to generate an (updated) DU configuration, the process proceeds to block 1406, where the DU sends a first DU-to-CU message that does not include an (updated) DU configuration (e.g., event 309) in response to the first CU-to-DU message. Alternatively, if the DU decides to generate an (updated) DU configuration, the process proceeds to block 1408, where the DU sends a first DU-to-CU message that includes an (updated) DU configuration (e.g., event 309) in response to the first CU-to-DU message. At block 1410, the DU receives a second CU-to-DU message from the CU to indicate the application of the DU configuration (e.g., event 334). In some implementations, the second CU-to-DU message includes a CG-Config and / or a C-PSCell ID corresponding to the C-PSCell to which the UE has connected. In some implementations, the CU-to-DU message includes a conditional execution indication. In other implementations, the second CU-to-DU message includes an RRC reconfiguration complete indicator IE. In some implementations, the second CU-to-DU message includes an RRC reconfiguration complete indicator IE and a conditional execution indication. In some implementations, the second CU-to-DU message is a UE context modification request message.

[0148] Generally referring to the above scenario, for (instantaneous) DC operation, the MN (e.g., MN 104A) can reconfigure / update the MCG configuration based on the SCG configuration / information, and the CU can include a CG-Config IE in the CU-to-DU RRC information for lower layer parameter coordination in a split MN. For CPAC, the MN can send an RRC reconfiguration message to the UE, the RRC reconfiguration message including a list of RRC reconfiguration messages that include both MCG and SCG configurations (e.g., RRC reconfiguration) to be applied together when CPAC is executed.

[0149] Since it is not clear how the decomposition MN generates a conditional RRC reconfiguration message including the MCG configuration for CPAC, or how the MN gNB-DU can determine that the UE has selected a candidate PSCell and the corresponding MCG L1 / L2 configuration will apply, or how the MN-DU can obtain MN restriction information, the network of the present disclosure adds a conditional indicator, in particular a conditional MCG information IE, during the UE context modification request procedure for MN purposes in CPAC. The gNB-CU provides the CG-Config IE and / or CG-ConfigInfo IE corresponding to the candidate PSCell to the gNB-DU and obtains the MCG configuration at the initiation of CPAC. Additionally, the gNB-CU provides the CG-Config IE corresponding to the selected candidate PSCell to the gNB-DU, and the gNB-DU applies the MCG configuration during the execution of CPAC. The CU may include the conditional indicator in the UE context modification request message.

[0150] More particularly, the MN-CU (e.g., CU 172) may include the conditional MCG information IE in the UE context modification request message and set the CPAC trigger indicator "CPAC-initiation", and set the UE context modification request message to the gNB-DU, which may operate as the MN-DU (e.g., DU 174). If the MN-DU supports CPAC, the gNB-DU considers the request to involve a conditional PSCell addition or a conditional PSCell change, considers the CG-Config IE and / or CG-ConfigInfo IE included in the UE context modification request message, and provides the corresponding CellGroupConfig IE to the gNB-CU in the UE context modification response message for MCG configuration preparation.

[0151] On the other hand, if the MN-CU includes the conditional MCG information IE and the CPAC trigger set to "CPAC-execution" in the UE context modification request message, and if the gNB-DU supports CPAC, the gNB-DU considers that the UE has successfully executed CPAC preparation for the CG-Config IE included in the UE context modification request message and corresponding to the selected PSCell. The gNB-DU can then apply the corresponding CellGroupConfig IE of the MCG configuration at the gNB-DU. If the UE context modification request message includes the conditional intra-DU mobility information IE and the CHO trigger is set to "CHO-initiation", the gNB-DU considers that the request involves a conditional handover or a conditional PSCell addition or a conditional PSCell change for the included SpCell ID IE, and includes the SpCell as the requested target cell ID IE in the UE context modification response message. The gNB-DU regards this UE context modification request message as including a synchronous reconfiguration.

[0152] The definition of the UE context modification request message may include a ConditionalMCGInformation field in addition to the elements listed in the previous version of TS 38.473, for example:

[0153]

[0154] The definition of the IE may include the following example definitions:

[0155]

[0156] The present disclosure contemplates at least the following examples:

[0157] Example 1. A method for managing conditional cell change in a central unit (CU) of a distributed base station including a CU and a distributed unit (DU), the method comprising: obtaining, by the CU, cell group (CG) configurations for one or more candidate secondary cells of a candidate secondary node (SN) to support dual connectivity (DC) between a DU operating as a master node (MN) and the candidate SN for a UE; sending the CG configurations from the CU to the DU; receiving, at the CU, a DU configuration corresponding to the CG configurations from the DU; and sending, via the DU, from the CU to the UE (i) a conditional SN configuration corresponding to the CG configurations, (ii) at least one condition to be satisfied before the UE initiates a process of connecting to the candidate node according to the conditional SN configuration, and (iii) the DU configuration.

[0158] Example 2. The method as described in Example 1, wherein the obtaining of the CG configuration includes receiving the CG configuration from the candidate SN, and the CU and the candidate node are implemented in different base stations.

[0159] Example 3. The method as described in Example 1, wherein the obtaining of the CG configuration includes generating the CG configuration at the CU, and the candidate SN is implemented in a second DU of the distributed base station.

[0160] Example 4. The method as described in any of the foregoing examples, wherein the sending of the CG configuration to the DU includes sending a single CU-to-DU message, and the single CU-to-DU message includes a list of two or more elements, and each of the elements corresponds to a different respective candidate secondary cell.

[0161] Example 5. The method as described in any of Examples 1 to 3, wherein the sending of the CG configuration to the DU includes sending a plurality of CU-to-DU messages, and each of the CU-to-DU message information corresponds to a different respective candidate secondary cell.

[0162] Example 6. The method as described in Example 4 or 5, wherein each CU-to-DU message is a UE context modification request message.

[0163] Example 7. The method as described in any of the foregoing examples, further comprising, after the sending of the SN configuration to the UE: receiving, via the DU, an indication from the UE that the UE has completed reconfiguration of the radio link according to the DU configuration; and sending an indication to the DU that the UE has completed the reconfiguration.

[0164] Example 8. The method as described in Example 7, wherein: the sending of the SN configuration to the UE includes sending a configuration identifier; and the receiving of the indication from the UE includes receiving the configuration identifier.

[0165] Example 9. The method as described in any of the foregoing examples, wherein obtaining the CG configuration includes obtaining SN restriction information.

[0166] Example 10. The method as described in Example 9, further comprising: sending the SN restriction information from the CU to the DU.

[0167] Example 11. A base station, including processing hardware and configured to implement the method as described in any of the foregoing examples.

[0168] The following description can be applied to the above description.

[0169] Generally speaking, the description for one of the above figures can be applied to the other one of the above figures. If there is no conflict, the examples, implementation manners, and methods described above can be combined. The events or boxes described above can be optional or omitted. For example, the events or boxes with dashed lines in the figures can be optional. In some implementation manners, "message" is used and "information element (IE)" can be used instead of "message". In some implementation manners, "IE" is used and "field" can be used instead of "IE". In some implementation manners, "configurations" or configuration parameters can be used instead of "configuration".

[0170] The user equipment (e.g., UE 102) in which the technology of the present disclosure can be implemented can be any suitable device capable of performing wireless communication, such as a smart phone, a tablet computer, a laptop computer, a mobile gaming machine, a point-of-sale (POS) terminal, a health monitoring 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. Additionally, in some cases, the user equipment can be embedded in an electronic system (such as the host unit of a vehicle or an advanced driver assistance system (ADAS)). Further still, the user equipment can operate as an Internet of Things (IoT) device or a mobile Internet device (MID). Depending on the type, the user equipment can include one or more general-purpose processors, a computer-readable memory, a user interface, one or more network interfaces, one or more sensors, etc.

[0171] Certain embodiments in the present disclosure are described as including logic or multiple components or modules. A module can be a software module (e.g., code or machine-readable instructions stored on a non-transitory machine-readable medium) or a hardware module. A hardware module is a tangible unit capable of performing certain operations and can be configured or arranged in a certain way. A hardware module can include dedicated circuitry or logic that is persistently configured (e.g., as a dedicated processor, such as a field-programmable gate array (FPGA) or an application-specific integrated circuit (ASIC), a digital signal processor (DSP), etc.) to perform certain operations. A hardware module can also include programmable logic or circuitry (e.g., as included in a general-purpose processor or other programmable processor) that is temporarily configured by software to perform certain operations. The decision to implement a hardware module in dedicated and persistently configured circuitry or in temporarily configured circuitry (e.g., configured by software) may be driven by cost and time considerations.

[0172] When implemented in software, the technology can be provided as part of an operating system, a library used by multiple applications, a specific software application, etc. The software can be executed by one or more general-purpose processors or one or more special-purpose processors.

Claims

1. A configuration method implemented in a central unit (CU) of a distributed base station that further includes a distributed unit (DU), the method comprising: Sending a context modification request for a UE to the DU, the context modification request including (i) a first indication related to adding or changing a condition of the context modification request with respect to a primary secondary cell (PSCell), and (ii) a second indication of whether preparation for adding or changing the condition has been performed; and Receiving a context modification response for the UE from the DU.

2. The method according to claim 1, wherein: The second indication indicates that the preparation for adding or changing the condition of the PSCell has not been performed, and The context modification response includes cell group configuration information.

3. The method according to claim 2, wherein the cell group configuration information is a CG-ConfigInfo information element (IE).

4. The method according to claim 2 or 3, further comprising: Using the cell group configuration information in the master cell group (MCG) configuration preparation.

5. The method according to any one of claims 2 to 4, wherein: The context modification request includes a PSCell identifier; and The context modification response includes a requested target cell identifier corresponding to the PSCell identifier.

6. The method according to claim 1, wherein: The second indication indicates that the preparation for adding or changing the condition of the PSCell has been performed, and The context modification request includes a PSCell identifier identifying a selected PSCell.

7. The method according to any one of the preceding claims, further comprising: Sending a radio resource control (RRC) reconfiguration message including a master cell group (MCG) configuration and a secondary cell group (SCG) configuration to the UE via the DU.

8. The method according to any one of the preceding claims, further comprising: Sending a CU-to-DU message including the context modification request and MN restriction information to the DU.

9. A configuration method implemented in a distributed unit (DU) of a distributed base station that further includes a central unit (CU), the method comprising: Receiving a context modification request for a UE from the DU, the context modification request including a first indication related to adding or changing a condition of the context modification request with respect to a primary secondary cell (PSCell); And Determining whether preparation for adding or changing the condition has been performed based on a second indication included in the context modification request.

10. The method according to claim 9, further comprising: When the second indication indicates that the preparation has not been performed: Using a CG-Config information element (IE) included in the context modification request to generate a CellGroupConfig IE for master cell group (MCG) preparation, and Sending the CellGroupConfig IE to the CU in a context modification response.

11. The method according to claim 10, wherein: The context modification request includes a PSCell identifier; and The context modification response includes the requested target cell identifier corresponding to the PSCell identifier.

12. The method according to claim 9, further comprising: When the second indication indicates that the preparation has been performed: Determine that the UE has successfully performed the preparation for the cell identified by the PSCell identifier included in the context modification request.

13. The method according to claim 12, further comprising: Apply the cell group configuration corresponding to the identified cell to the MCG configuration.

14. The method according to any one of claims 9 to 13, further comprising: Receive a CU-to-DU message including the context modification request and the MN restriction information from the CU.

15. A radio access network (RAN) node, comprising: A transceiver; And Processing hardware configured to implement the method according to any one of the preceding claims.

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