Managing radio resources and downlink transmission during handover

Abstract

To provide methods and a core network (CN) for managing radio resources and downlink transmission during handover.SOLUTION: A radio access network (RAN) for configuring user equipment (UE) generates (i) a conditional configuration, and (ii) a condition to be satisfied before the UE applies the conditional configuration (1402), receives, from the CN, an interface message indicating configuring the UE (1404), determines that the interface message affects the conditional configuration (1406), generates a message related to the conditional configuration in view of the received interface message (1408), and transmits the message to the UE (1410).SELECTED DRAWING: Figure 14

Description

[Technical Field]

[0001] The present disclosure relates generally to wireless communications, and more particularly to managing radio resources and downlink transmissions during handover preparation and execution procedures. [Background technology]

[0002] This Background Description section is provided for the purpose of generally presenting the context of the present disclosure. The work of the presently named inventors is not admitted, explicitly or implicitly, as prior art to the present disclosure to the extent that the work is described in this Background section, and further, any aspects of the description that may not otherwise qualify as prior art at the time of filing.

[0003] In telecommunications systems, the Packet Data Convergence Protocol (PDCP) sublayer of the radio protocol stack provides services such as user plane data transport, encryption, and integrity protection. For example, the PDCP layer defined for the Evolved Universal Terrestrial Radio Access (EUTRA) air interface (see 3GPP (registered trademark) specification TS 36.323) and New Radio (NR) (see 3GPP specification TS 38.323) provides protocol data unit (PDU) sequencing in the uplink direction (from a user device, also called user equipment (UE), to a base station) and downlink direction (from a base station to a UE). Furthermore, the PDCP sublayer provides signaling radio bearers (SRBs) and data radio bearers (DRBs) to the radio resource control (RRC) sublayer. Generally speaking, the UE and the base station can exchange RRC messages and non-access stratum (NAS) messages using SRBs, and can transport data on the user plane using DRBs.

[0004] A UE can use several types of SRBs and DRBs. When operating in dual connectivity (DC), cells associated with a base station acting as a master node (MN) define a master cell group (MCG), and cells associated with a base station acting as a secondary node (SN) define a secondary cell group (SCG). So-called SRB1 resources carry RRC messages, including NAS messages in some cases on a dedicated control channel (DCCH), while SRB2 resources support RRC messages, including logged measurement information or NAS messages, also on the DCCH but with lower priority than SRB1 resources. More generally, SRB1 and SRB2 resources allow the UE and MN to exchange RRC messages related to the MN and embed RRC messages related to the SN, and may also be referred to as MCG SRBs. SRB3 resources allow the UE and SN to exchange RRC messages related to the SN, and may also be referred to as SCG SRBs. Split SRBs allow the UE to exchange RRC messages directly with the MN via the MN's and SN's lower layer resources. An MCG DRB uses lower layer resources of only the MN, an SCG DRB uses lower layer resources of only the SN, and a split DRB uses lower layer resources of both the MCG and SCG. A DRB that terminates in the MN but uses lower layer resources of only the SN may be referred to as an MN-terminated SCG DRB. A DRB that terminates in the SN but uses lower layer resources of only the MN may be referred to as an SN-terminated MCG DRB.

[0005] In some scenarios, a UE can simultaneously utilize resources from multiple RAN nodes (e.g., base stations or components of a distributed base station) interconnected by a backhaul. When these network nodes support different radio access technologies (RATs), this type of connectivity is referred to as multi-radio dual connectivity (MR-DC). When a UE operates in MR-DC, one base station acts as a mobile node (MN) covering a primary cell (PCell), and the other base station acts as a secondary node (SN) covering a primary secondary cell (PSCell). The UE communicates with the mobile node (via the PCell) and with the secondary node (via the PSCell). In other scenarios, the UE uses resources from one base station at a time. One base station and / or the UE determines that the UE should establish a radio connection with another base station. For example, one base station can decide to hand over the UE to a second base station and initiate a handover procedure.

[0006] 3GPP Technical Specifications (TS) 36.300 and 38.300 (v16.4.0) describe procedures for handover (or called reconfiguration with synchronization) scenarios. When these procedures do not involve conditions that are checked in the UE, they may be referred to as immediate or unconditional handover procedures. When these procedures involve conditions that are checked in the UE, they may be referred to as conditional handover (CHO) procedures.

[0007] 3GPP TS 37.340 (v16.3.0) describes procedures for a UE to change a PSCell in a DC scenario. These procedures involve messaging (e.g., RRC signaling and preparation) between radio access network (RAN) nodes. When these procedures do not involve conditions that are checked in the UE, these procedures may be referred to as immediate or unconditional PSCell change procedures. When these procedures involve conditions that are checked in the UE, these procedures may be referred to as conditional PSCell change (CPC) procedures.

[0008] 3GPP specification TS 37.340 v16.4.0 describes procedures for a UE to add or change an SN in a DC scenario. These procedures involve messaging between RAN nodes (e.g., RRC signaling and preparation). When these procedures do not involve conditions that are checked in the UE, they may be referred to as immediate or unconditional SN addition / change procedures. When these procedures involve conditions that are checked in the UE, they may be referred to as conditional SN addition / change (CSAC) procedures, also known as conditional PSCell addition / change (CPAC) procedures.

[0009] To configure the CHO, CSAC, or CPC procedure, the RAN provides the UE with conditions along with configurations (e.g., a set of random access preambles) that, when the conditions are met, enable the UE to communicate with an appropriate base station or via an appropriate cell. For example, for CHO, the RAN provides the UE with conditions that must be met before the UE can add a candidate base station or candidate PCell, and configurations that enable the UE to communicate with that candidate base station or candidate PCell after the conditions are met. As another example, for CSAC or CPC, the RAN provides the UE with conditions that must be met before the UE can add a candidate base station or candidate PSCell as an SN, and configurations that enable the UE to communicate with that candidate base station or candidate PSCell after the conditions are met. Thus, in each of the CHO, CSAC, or CPC procedures, the UE does not immediately apply the conditional configuration upon receiving it; rather, the UE waits until the conditions are met and then applies the conditional configuration.

[0010] Generally speaking, the RAN performs a CHO, CSAC, or CPC "preparation" procedure, or its respective immediate (as opposed to "conditional") counterpart, to generate and provide an immediate or conditional configuration to the UE. The UE is then said to "perform" the immediate or conditional procedure. For example, for an immediate or conditional HO procedure, the RAN performs the immediate or conditional HO preparation procedure by generating an immediate or conditional HO configuration and providing that configuration to the UE. The UE then performs the immediate or conditional HO procedure, such as by immediately disconnecting from a first RAN node and connecting to a second RAN node according to the immediate HO procedure, or by delaying the disconnection and connection process until a condition is met according to the CHO procedure.

[0011] In some scenarios, while the UE is performing the CHO procedure, the first RAN node receives a request from the Core Network (CN) for a resource management procedure (e.g., an E-RAB Setup procedure, an E-RAB Modify procedure, an E-RAB Release procedure, a PDU Session Resource Setup procedure, a PDU Session Resource Modify procedure, a PDU Session Resource Release procedure, or a downlink NAS transport procedure according to 3GPP specifications 36.413 and 38.413) to be performed by the first RAN node with the UE. When the UE disconnects from the first RAN node according to the CHO procedure, the first RAN node fails to communicate with the UE and therefore fails to perform the resource management procedure with the UE.

[0012] In another scenario, the first RAN node receives a request for a resource management procedure from the CN while performing a CHO preparation procedure, and when the first RAN node prioritizes the CHO preparation procedure over the request, the first RAN node may decide not to interrupt the CHO preparation procedure, thereby failing to perform the resource management procedure according to the request. Summary of the Invention [Means for solving the problem]

[0013] According to the techniques of the present disclosure, the RAN receives a request from the CN to perform a resource management procedure with a UE. In some scenarios, the RAN receives the request when the UE is currently performing a conditional procedure with the RAN in accordance with the conditional configuration received from the RAN. As a result of the UE performing the conditional procedure, the RAN determines that the UE will disconnect from a first RAN node and then connect with the UE via a second RAN node, thereby allowing the RAN to have a radio connection with the UE and perform the resource management procedure in accordance with the request from the CN. In other scenarios, the RAN receives the request from the CN after generating a conditional configuration while performing a conditional preparation procedure for the UE. Because the RAN was unable to consider the request at the time the RAN generated the conditional configuration, the RAN can send a message including appropriate parameters to the UE in accordance with the request. In yet other scenarios, the RAN receives the request from the CN before performing the conditional preparation procedure for the UE. Because the RAN can consider the request when the RAN generates the conditional configuration during the conditional preparation procedure, the RAN can send the conditional configuration to the UE.

[0014] One exemplary embodiment of these techniques is a method in a RAN for configuring a UE. The method may be performed by processing hardware and includes generating (i) a conditional configuration and (ii) a condition to be satisfied before the UE applies the conditional configuration, receiving an interface message from a CN instructing the UE to configure, determining that the interface message affects the conditional configuration, generating a message related to the conditional configuration in consideration of the received interface message, and transmitting the message to the UE. Another embodiment of these techniques is a RAN including processing hardware configured to perform the above method.

[0015] Yet another exemplary embodiment of these techniques is a method implemented in a CN for configuring a UE. The method may be performed by processing hardware and includes sending a first interface message to a first node of a RAN instructing the UE to configure, receiving a response interface message from the RAN instructing the UE to configure in light of the first interface message, receiving a request from the RAN to switch paths to a second node of the RAN, and sending a second interface message to the second node instructing the UE to configure. Yet another exemplary embodiment of these techniques is a CN including processing hardware configured to perform the above method. [Brief explanation of the drawings]

[0016] [Figure 1A] FIG. 1 is a block diagram of an example system in which base stations operating in a RAN, a CN, and a UE may implement techniques for managing handover procedures. [Figure 1B] 1B is a block diagram of an exemplary base station in which the centralized unit (CU) and distributed units (DU) can operate in the system of FIG. 1A. [Figure 2] 1B is a block diagram of an example protocol stack followed by the UE of FIG. 1A when communicating with a base station. [Figure 3] 1B is a messaging diagram of an example scenario in which the RAN of FIG. 1A sends a message to the UE to configure the UE with parameters for setting up, modifying, or releasing radio resources to recover from sending the UE a conditional handover configuration that does not include parameters for setting up, modifying, or releasing radio resources in accordance with an interface message received from the CN. [Figure 4A]FIG. 1B is a messaging diagram of an example scenario in which the base station of FIG. 1A omits sending to the UE a conditional handover configuration that does not include parameters for setting up, modifying, or releasing radio resources according to an interface message received from the CN. [Figure 4B] 1B is a messaging diagram of an example scenario in which the base station of FIG. 1A sends to the UE a conditional handover configuration including parameters for setting up, modifying, or releasing radio resources according to an interface message received from the CN. [Figure 5] 1B is a messaging diagram of an example scenario in which the base station of FIG. 1A forwards to the UE a NAS message received from the CN during a conditional handover preparation procedure for setting up, modifying, or releasing radio resources. [Figure 6] FIG. 1C is a messaging diagram of an example scenario similar to the scenario of FIG. 3, but in which the distributed base station of FIG. 1B sends a message to the UE to configure the UE with parameters for setting up, modifying, or releasing radio resources. [Figure 7A] FIG. 4B is a messaging diagram of an example scenario similar to the scenario of FIG. 4A, but omitting that the distributed base station of FIG. 1B sends a conditional handover configuration that does not include parameters for setting up, modifying, or releasing radio resources. [Figure 7B] FIG. 4B is a messaging diagram of an exemplary scenario similar to that of FIG. 4B, but in which the distributed base station of FIG. 1B sends a conditional handover configuration including parameters to set up, modify, or release radio resources. [Figure 8] 6 is a messaging diagram of an exemplary scenario similar to the scenario of FIG. 5, but in which the distributed base station of FIG. 1B forwards a NAS message to the UE. [Figure 9]1 is a flow diagram of an example method for transmitting a message to a UE to configure the UE with parameters for setting up, modifying, or releasing radio resources to recover from transmitting a conditional handover configuration to the UE that does not include parameters for setting up, modifying, or releasing radio resources according to an interface message received from a CN, which may be implemented in a RAN of the present disclosure. [Figure 10] 10 is a flow chart of an example method similar to that of FIG. 9, but which may be implemented in a distributed base station of the present disclosure. [Figure 11] 1 is a flow diagram of an example method for performing a handover preparation procedure in consideration of receiving a CN-BS interface message for setting up, modifying, or releasing radio resources after deciding to perform the handover preparation procedure or while performing the handover preparation procedure, which may be implemented in a RAN of the present disclosure. [Figure 12] 12 is a flow diagram of an exemplary method similar to the method of FIG. 11, but in which a CN-BS interface message is received before deciding to perform a handover preparation procedure or before performing a handover preparation procedure. [Figure 13] 1 is a flow diagram of an example method for transmitting a follow-up message to a RAN to set up, modify, or release radio resources for a UE in response to receiving an indication from the RAN that a previous attempt to set up, modify, or release radio resources has failed, which may be implemented in a CN of the present disclosure. [Figure 14] 1 is a flow diagram of an example method for configuring a UE, which may be implemented in a RAN of the present disclosure. [Figure 15] 1 is a flow diagram of an example method for configuring a UE, which may be implemented in a CN of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0017] As described in detail below, the RAN generates a conditional configuration for the UE to perform a procedure such as a conditional handover (CHO) procedure. When the RAN receives a request from the CN to set up, modify, or release radio resources for the UE before or after sending the conditional configuration to the UE, the RAN may implement techniques described below to configure the UE to set up, modify, or release radio resources according to the request.

[0018] 1A , an exemplary wireless communication system 100 includes a UE 102, a base station (BS) 104, a base station 106, and a core network (CN) 110. The base stations 104 and 106 may operate in a RAN 105 connected to the same core network (CN) 110. The CN 110 may be implemented, for example, as an evolved packet core (EPC) 111 or a fifth generation (5G) core (5GC) 160.

[0019] Among other components, the EPC 111 may include a Serving Gateway (SGW) 112, a Mobility Management Entity (MME) 114, and a Packet Data Network Gateway (PGW) 116. The SGW 112 is generally configured to forward user plane packets related to voice calls, video calls, Internet traffic, etc., and the MME 114 is configured to manage authentication, registration, paging, and other related functions. The PGW 116 is generally configured to provide connectivity from the UE 102 to one or more external packet data networks, e.g., an Internet network and / or an Internet Protocol (IP) Multimedia Subsystem (IMS) network. The 5GC 160 comprises a User Plane Function (UPF) 162, an Access and Mobility Management (AMF) 164, and / or a Session Management Function (SMF) 166. Generally, the UPF 162 is configured to forward user plane packets related to voice calls, video calls, Internet traffic, etc., the AMF 164 is configured to manage authentication, registration, paging, and other related functions, and the SMF 166 is configured to manage PDU sessions.

[0020] As illustrated in FIG. 1A , base station 104 supports cell 124, and base station 106A supports cell 126. Cells 124 and 126 may partially overlap, allowing UE 102 to handover from cell 124 to cell 126 or vice versa. Base station 104 may additionally support cell 123, which may overlap with cell 124. Base station 106 may additionally support cell 125, which may overlap with cell 126. To directly exchange messages during handover preparation scenarios described below, base stations 104 and 106 may support X2 or Xn interfaces. In general, CN 110 may be connected to any suitable number of base stations supporting NR and / or EUTRA cells.

[0021] The base station 104 is equipped with processing hardware 130, which may include one or more general-purpose processors, such as a CPU, and non-transitory computer-readable memory that stores machine-readable instructions executable on one or more general-purpose processors and / or dedicated processing units. The processing hardware 130 in one exemplary implementation includes a conditional configuration controller 132 that is configured to manage conditional configuration for one or more CHO procedures. The processing hardware 130 also includes an immediate configuration controller 134 that is configured to manage immediate configuration for one or more immediate procedures (e.g., RRC connection re-establishment, RRC reconfiguration, immediate handover procedure).

[0022] The base station 106 is equipped with processing hardware 140, which may include one or more general-purpose processors, such as a CPU, and / or non-transitory computer-readable memory that stores machine-readable instructions executable on the one or more general-purpose processors and / or dedicated processing units. The processing hardware 140 in one exemplary implementation includes a conditional configuration controller 142 configured to manage conditional configuration for one or more CHO procedures. The processing hardware 140 also includes an immediate configuration controller 144 configured to manage immediate configuration for one or more immediate procedures (e.g., RRC connection re-establishment, RRC reconfiguration, measurement configuration, immediate handover procedure).

[0023] 1A , UE 102 is equipped with processing hardware 150, which may comprise one or more general-purpose processors, such as a CPU, and non-transitory computer-readable memory that stores machine-readable instructions executable on one or more general-purpose processors and / or dedicated processing units. Processing hardware 150 in one exemplary implementation comprises a UE conditional configuration controller 152 configured to manage conditional configuration for one or more CHO procedures. Processing hardware 150 also includes an immediate configuration controller 154 configured to manage immediate configuration for one or more immediate procedures (e.g., RRC connection re-establishment, RRC reconfiguration, measurement configuration, immediate handover procedure).

[0024] More specifically, each of the conditional configuration controllers 132, 142, and 152 may implement at least some of the techniques described with reference to the following messaging and flow diagrams for receiving conditional configurations, releasing the conditional configurations in response to particular events, applying the conditional configurations, etc. For example, when the UE 102 determines that a condition associated with the conditional configuration for CHO is satisfied, the UE 102 may apply the conditional configuration. As used herein, the term "condition" may refer to a single, detectable state or event (e.g., a particular signal quality metric exceeds a threshold) or a logical combination of such states or events (e.g., condition A and condition B, or (condition A or condition B) and condition C, etc.).

[0025] In operation, the UE 102 may use a radio bearer (e.g., a DRB or SRB) that terminates at the base station 104 or the base station 106. The UE 102 may apply one or more security keys when communicating on the radio bearer in the uplink (e.g., from the UE 102 to the base station 104 or 106) and / or downlink (e.g., from the base station 104 or 106 to the UE 102) directions. The UE 102 may, in some cases, use a RAT to communicate with the base station 104 or 106. The following examples may specifically reference a particular RAT type, 5G NR or EUTRA, but in general, the techniques of this disclosure may also be applied to other suitable radio access and / or core network technologies (e.g., sixth generation (6G)).

[0026] In some implementations, the CN 110 communicatively connects the UE 102 to an Internet Protocol (IP) Multimedia Subsystem (IMS) network (not shown in FIG. 1A ) via the RAN 105. The IMS network can provide the UE 102 with various IMS services, such as IMS short messages, IMS unstructured supplementary service data (USSD), IMS value-added service data, IMS supplementary service data, IMS voice calls, and IMS video calls. To this end, entities (e.g., servers or server groups) operating within the IMS network support packet exchanges with the UE. The packets can carry signaling (such as Session Initiation Protocol (SIP) messages, IP messages, or other suitable messages) as well as data (“or media”) such as voice or video. While the techniques of this disclosure are described with specific reference to IMS, the CN 110 may generally connect to or include any suitable system that provides packet-based calls.

[0027] In some scenarios, the wireless communication system 100 supports immediate handover between cells. In one scenario, for example, the UE 102 initially connects to the base station 104, which later performs preparation for immediate handover with the base station 106 over an interface (e.g., X2 or Xn). In this scenario, the base stations 104 and 106 act as the source and target base stations, respectively. In preparing for the handover, the source base station 104 sends a Handover Request message to the target base station 106. In response, the target base station 106 includes an immediate handover command message in a Handover Request Acknowledge message and sends the Handover Request Acknowledge message to the source base station 104. The source base station 104 then transmits the handover command message to the UE 102 in response to receiving the Handover Request Acknowledge message.

[0028] Upon receiving the immediate handover command message, the UE 102 immediately reacts to the immediate handover command by attempting to connect to the target base station 106. To connect to the target base station 106, the UE 102 may perform a random access procedure on a cell (e.g., cell 126) with the target base station 106 and then (after gaining access to the channel) transmit a handover complete message to the target base station 106 via the cell of the base station 106 (i.e., in response to the immediate handover command).

[0029] In some implementations, the wireless communication system 100 also supports conditional handover. In one scenario, for example, the UE 102 initially connects to the base station 104, and the base station 104 later performs a conditional handover preparation procedure with the base station 106 over an interface (e.g., X2 or Xn) to prepare for a potential handover of the UE 102 to the base station 106. In this scenario, the base stations 104 and 106 act as a source base station and a candidate base station, respectively. In the conditional handover preparation procedure, the source base station 104 sends a Handover Request message to the candidate base station 106. In response, the candidate base station 106 includes a conditional handover command message in a Handover Request Acknowledge message and sends the Handover Request Acknowledge message to the source base station 104. The source base station 104 then transmits the conditional handover command message to the UE 102 in response to receiving the Handover Request Acknowledge message.

[0030] Upon receiving the conditional handover command message, the UE 102 does not immediately react to the message by attempting to connect to the candidate base station 106. Instead, the UE 102 connects to the candidate base station 106 in accordance with the conditional handover command message only if the UE 102 determines that the conditions for handing over to the candidate cell 126 of the candidate base station 106 are met. In the conditional handover command message, the base station 106 provides a configuration for the candidate cell 126 (i.e., a configuration that the UE 102 can use to connect with the base station 106 via the candidate cell 126).

[0031] Before the condition is met, the UE 102 is not yet connected to the candidate base station 106. In other words, the candidate base station 106 has not yet connected to and provided service to the UE 102. In some implementations, the condition may be that the signal strength / quality, as measured by the UE 102 on the candidate cell 126 of the candidate base station 106, is sufficiently “good” and / or that the signal strength / quality, as measured by the UE 102 on the cell 124 of the source base station 104, is poor. For example, the condition may be met if one or more measurement results obtained by the UE 102 (when performing measurements on the candidate cell 126) exceed a threshold configured by the source base station 104, which may be a predetermined or pre-configured threshold, and / or if one or more measurement results obtained by the UE 102 (when performing measurements on the candidate cell 126) exceed a threshold configured by the source base station 104, which may be a predetermined or pre-configured threshold. In some implementations, the condition may be that the signal strength / quality, as measured by the UE 102 on the candidate cell 126, is better than the signal strength / quality, as measured by the UE 102 on the cell 124, by at least some threshold (e.g., at least an offset). The threshold may be configured by the source base station 104 or may be a predetermined or pre-configured offset. If the UE 102 determines that the condition is met, the candidate base station 106 becomes the target base station 106 for the UE 102, and the UE 102 attempts to connect to the target base station 106. To connect to the target base station 106, the UE 102 may perform a random access procedure on the candidate cell 126 with the target base station 106 and then transmit a handover complete message to the target base station 106 via the candidate cell 126 (after gaining access to the channel). After the UE 102 successfully completes the random access procedure and / or transmits a handover complete message, the target base station 106 becomes the source base station 106 for the UE 102, and the UE 102 begins data communication with the source base station 106.

[0032] The base stations 104 and 106 may be connected to the same CN 110, which may be an Evolved Packet Core (EPC) 111 or a 5th Generation Core (5GC) 160. The base station 104 may be implemented as an eNB supporting an S1 interface for communicating with the EPC 111, an ng-eNB supporting an NG interface for communicating with the 5GC 160, or a base station supporting an NR radio interface as well as an NG interface for communicating with the 5GC 160. The base stations 104 and 106 may support an X2 or Xn interface for directly exchanging messages during the scenarios described below.

[0033] In general, the wireless communication network 100 may include any suitable number of base stations supporting NR and / or EUTRA cells. More specifically, the EPC 111 or 5GC 160 may be connected to any suitable number of base stations supporting NR and / or EUTRA cells. While the following examples refer specifically to particular CN types (EPC, 5GC) and RAT types (5G NR and EUTRA), in general, the techniques of this disclosure may also be applied 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.

[0034] 1B depicts an exemplary distributed or decentralized implementation of any one or more of the base stations 104, 106. In this implementation, the base station 104 or 106 comprises a central unit (CU) 172 and one or more DUs 174. The CU 172 includes processing hardware such as one or more general-purpose processors (e.g., CPUs) and computer-readable memory that stores machine-readable instructions executable on the general-purpose processors and / or dedicated processing units. For example, the CU 172 can comprise the processing hardware 130 or 140 of FIG. 1A.

[0035] Each of the DUs 174 also includes processing hardware that may include one or more general-purpose processors (e.g., CPUs) and computer-readable memory that stores machine-readable instructions executable on the one or more general-purpose processors and / or special-purpose processing units. For example, the processing hardware may include a medium access control (MAC) controller configured to manage or control one or more MAC operations or procedures (e.g., random access procedures) and a radio link control (RLC) controller configured to manage or control one or more RLC operations or procedures. The processing hardware may also include a physical layer controller configured to manage or control one or more physical layer operations or procedures.

[0036] In some implementations, the CU 172 may include a logical node CU-CP 172A that hosts the control plane portion of the Packet Data Convergence Protocol (PDCP) protocol for the CU 172. The CU 172 may also include a logical node CU-UP 172B that hosts the user plane portion of the PDCP protocol and / or the Service Data Adaptation Protocol (SDAP) protocol for the CU 172. The CU-CP 172A may carry control information (e.g., RRC messages, F1 application protocol messages), and the CU-UP 172B may carry data packets (e.g., SDAP PDUs or Internet Protocol packets).

[0037] The CU-CP 172A may be connected to multiple CU-UPs 172B through an E1 interface. The CU-CP 172A selects an appropriate CU-UP 172B for a requested service for the UE 102. In some implementations, a single CU-UP 172B may be connected to multiple CU-CPs 172A through an E1 interface. The CU-CP 172A may be connected to one or more DUs 174 through an F1-C interface. The CU-UP 172B may be connected to one or more DUs 174 through an F1-U interface under the control of the same CU-CP 172A. In some implementations, one DU 174 may be connected to multiple CU-UPs 172B under the control of the same CU-CP 172A. In such implementations, connectivity between the CU-UP 172B and the DU 174 is established by the CU-CP 172A using a bearer context management function.

[0038] FIG. 2 illustrates in a simplified manner an example protocol stack 200 that a UE 102 may follow when communicating with an eNB / ng-eNB or gNB (e.g., one or more of the base stations 104, 106).

[0039] In the example stack 200, the EUTRA physical layer (PHY) 202A provides transport channels to the EUTRA MAC sublayer 204A, which in turn provides logical channels to the EUTRA RLC sublayer 206A. The EUTRA RLC sublayer 206A then provides RLC channels to the EUTRA PDCP sublayer 208 and, in some cases, to the NR PDCP sublayer 210. Similarly, the NR PHY 202B provides transport channels to the NR MAC sublayer 204B, which then provides logical channels to the NR RLC sublayer 206B. The NR RLC sublayer 206B then provides data transfer services to the NR PDCP sublayer 210. The NR PDCP sublayer 210 can then provide data transfer services to an Ethernet protocol layer (not shown in FIG. 2), an Internet Protocol (IP) layer (not shown in FIG. 2), a Service Data Adaptation Protocol (SDAP) 212, and / or a Radio Resource Control (RRC) sublayer (not shown in FIG. 2). The UE 102, in some implementations, supports both EUTRA and NR stacks as shown in FIG. 2 to support handover between EUTRA and NR base stations. Additionally, as illustrated in FIG. 2, the UE 102 can support layering of the NR PDCP 210 over the EUTRA RLC 206A and the SDAP sublayer 212 over the NR PDCP sublayer 210.

[0040] 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 layered directly or indirectly above 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 where the distinction between SDUs and PDUs is relevant, this disclosure will refer to both SDUs and PDUs as "packets" for simplicity.

[0041] On the control plane, the EUTRA PDCP sublayer 208 and the NR PDCP sublayer 210 can provide SRBs for exchanging, 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 can provide DRBs to support data exchange. The data exchanged on the NR PDCP sublayer 210 can be SDAP PDUs, Internet Protocol (IP) packets, or Ethernet packets.

[0042] 3-5 illustrate a conditional handover scenario in which a RAN (e.g., RAN 105) prepares a conditional handover for a UE (e.g., UE 102) from a source base station (S-BS) (e.g., S-BS 104) 174A to a candidate base station (C-BS) (e.g., C-BS 106).

[0043] Referring first to FIG. 3, in scenario 300, base station 104A acts as a source base station (S-BS) and base station 106A acts as a candidate base station (C-BS).

[0044] Initially, the UE 102 communicates 302 data to the S-BS 104 via one or more cells, such as a PCell (e.g., cell 124) and zero, one, or more secondary cells (SCells). More specifically, the UE 102 may communicate 302 data and control signals to the S-BS 104 according to a first base station (BS) configuration. The first BS configuration may include one or more configuration parameters used by the UE 102 to communicate with the S-BS 104. These configuration parameters may configure radio resources for the UE 102 to communicate with the S-BS 104 via the cells described above. The configuration parameters may configure zero, one, or more radio bearers, which may include one or more SRBs (e.g., SRB1 and / or SRB2) and / or one or more DRBs. Data communicated between the UE 102 and the S-BS 104 may include downlink and / or uplink PDUs that the S-BS 104 transmits to and / or receives from the UE 102. Control signals communicated between the UE 102 and the S-BS 104 may include downlink control signals and uplink control signals. Downlink control signals may include channel state information reference signals, tracking reference signals, and / or physical downlink control channel (PDCCH) signals that the S-BS 104 transmits to the UE 102. Uplink control signals may include hybrid automatic repeat request (HARQ) acknowledgments or negative acknowledgments, channel state information, scheduling requests, and / or sounding reference signals that the UE 102 transmits to the S-BS 104.

[0045] Later, the S-BS 104 initiates the CHO preparation procedure by deciding to request a conditional configuration (i.e., a C-BS configuration) from the C-BS 106 to provide the UE 102 for the CHO procedure so that, when conditions are met, the UE 102 can communicate with the C-BS 106 via a candidate cell (e.g., cell 126). The S-BS 104 can make this decision based on one or more measurements received directly from the UE 102 (e.g., via an SRB established between the UE 102 and the S-BS 104 or via a physical control channel) that are above (or below) one or more predetermined thresholds, or from, for example, the S-BS 104 analyzing measurements on signals, control channels, or data channels received from the UE 102, or another suitable event (e.g., the UE 102 is moving toward the C-BS 106).

[0046] In response to this determination, the S-BS 104 transmits a Handover Request message to the C-BS 106, including, for example, a CHO information request 304. In response to the Handover Request message, the C-BS 106 generates a C-BS configuration, including information that enables the UE 102 to communicate with the C-BS 106 via a candidate cell (e.g., cell 126). The C-BS 106 includes the C-BS configuration in a Handover Request Acknowledge message to the UE 102 and then transmits a Handover Request Acknowledge message to the S-BS 104 in response to the Handover Request message 306. In some implementations, instead of including the C-BS configuration in the Handover Request Acknowledge message, the C-BS 106 may include a CHO command in the Handover Request Acknowledge message. In such a case, the C-BS 106 may include the C-BS configuration in the CHO command and include the CHO command in the Handover Request Acknowledge message. In the following description, the C-BS configuration and the CHO command are interchangeable. In some implementations, after receiving the C-BS configuration, the S-BS 104 includes in the RRC reconfiguration message the C-BS configuration and a trigger condition configuration (e.g., a triggerCondition-r16 or condExecutionCond-r16 field) that specifies a condition (or "trigger condition") that the UE 102 may use to determine whether to execute the C-BS configuration or connect to the candidate cell 126. That is, if the UE 102 determines that the condition is met, the UE 102 may connect to the candidate cell 126 using the C-BS configuration. If the UE 102 does not determine that the condition is met, the UE 102 does not connect to the candidate cell 126.

[0047] The S-BS 104 transmits 308 an RRC reconfiguration message to the UE 102, which then transmits 310 an RRC reconfiguration complete message to the S-BS 104 in response to receiving the RRC reconfiguration message. Events 304, 306, and 308 are collectively referred to in FIG. 3 as the CHO preparation procedure.

[0048] In some implementations, the S-BS 104 may include the C-BS configuration in a conditional configuration field or information element (IE) (e.g., CondReconfigToAddMod-r16 IE) of the RRC reconfiguration message. The S-BS 104 may further include a configuration identity / identifier (ID) associated with the C-BS configuration in the conditional configuration field / IE, thereby enabling the UE 102 to identify and store the C-BS configuration.

[0049] Sometime after the CHO preparation procedure (e.g., after transmitting 310 an RRC reconfiguration complete message), the UE 102 may determine 312 that the conditions for connecting to the candidate cell 126 are met, and in response, performs 316 a random access procedure (also referred to as a "random access channel" or "RACH" procedure) on the candidate cell 126 with the C-BS 106, e.g., using a random access configuration included in the C-BS configuration. The UE 102 disconnects 314 from the cell 124 of the S-BS 104 in response to event 312 or 316. In some implementations, the random access procedure at event 316 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.

[0050] The UE 102 transmits 318 an RRC reconfiguration complete message to the C-BS 106 via the candidate cell 126 while or after performing 316 the random access procedure. In some implementations, the UE 102 may include the RRC reconfiguration complete message in "Message 3" of a four-step random access procedure or "Message A" of a two-step random access procedure according to the C-BS configuration.

[0051] After performing the random access procedure 316 or transmitting the RRC reconfiguration complete message 318, the UE 102 communicates with the C-BS 106 by using the C-BS configuration 320. Events 312, 314, 316, 318, and 320 are collectively referred to as the CHO execution procedure in FIG.

[0052] In some implementations, during a CHO execution procedure, the CN 110 may send 322 a first CN-BS interface message to the S-BS 104 to perform a resource management procedure (e.g., an E-RAB Setup procedure, an E-RAB Modify procedure, an E-RAB Release procedure, a PDU Session Resource Setup procedure, a PDU Session Resource Modify procedure, a PDU Session Resource Release procedure, or a downlink NAS transport procedure according to 3GPP specifications 36.413 and 38.413) to request to set up, modify, or release resources (e.g., radio resources) for the UE 102 for various reasons. For example, the CN 110 may send a first CN-BS interface message for an IMS mobile terminating service (e.g., voice call, video call) for the UE 102. As another example, the CN 110 may send a first CN-BS interface message for a multicast or broadcast service (MBS) service for the UE 102. In some implementations, the first CN-BS interface message can be a PDU session Resource message, such as a PDU Session Resource Setup Request message, a PDU Session Resource Modify Request message, or a PDU Session Resource Release Command message. In other implementations, the first CN-BS interface message can be an E-RAB message, such as an E-RAB Setup Request message, an E-RAB Modify Request message, or an E-RAB Release Command message. In yet other implementations, the first CN-BS interface message can be a downlink (DL) NAS Transport message that includes a NAS message.In some implementations, the CN 110 may send NAS messages to set up, modify, or release resources or NAS configurations for the UE 102. In other implementations, the CN 110 may include application data, a Short Message Service (SMS) message, or an LTE Positioning Protocol (LPP) message in the NAS message.

[0053] If, in response to the first CN-BS interface message, the S-BS 104 transmits an RRC message (e.g., an RRC reconfiguration message) to the UE 102 to set up, modify, or release radio resources for the UE 102 when the UE 102 has already disconnected 314 from the S-BS 104 during the CHO execution procedure, the S-BS 104 will fail to transmit the RRC message to the UE 102.

[0054] To ensure that the RAN 105 can properly set up, modify, or release radio resources for the UE 102, the S-BS 104 sends 324 a first BS-CN interface message to the CN 110. In some implementations, the S-BS 104 includes a cause value in the first BS-CN interface message to indicate the reason the S-BS 104 failed to set up, modify, or release radio resources for the UE 102. For example, the cause value can be "Radio connection with UE lost." In some implementations, the first BS-CN interface message can be a PDU session Resource message, such as a PDU Session Resource Setup Response message, a PDU Session Resource Setup Failure message, a PDU Session Resource Modify Response message, a PDU Session Resource Modify Failure message, or a PDU Session Resource Release Response message. In other implementations, the first BS-CN interface message can be an E-RAB message, such as an E-RAB Setup Response message, an E-RAB Modify Response message, or an E-RAB Release Response message. In some implementations, the first BS-CN interface message can be an indication that the S-BS 104 failed to send a NAS message from the CN 110 to the UE 102.

[0055] After performing the random access procedure 316 or receiving the RRC reconfiguration complete message 318, the C-BS 106 may establish a UE-associated signaling connection between the UE 102 and the CN 110 and may send 326 a Path Switch Request message to the CN 110 to request a switch of the downlink termination point of the transport bearer toward the C-BS 106. In response to the Path Switch Request message, the CN 110 performs a path switch for the UE 102 and sends 328 a Path Switch Request Acknowledge message to the C-BS 106. To perform the path switch, the CN 110 may update the downlink path from the S-BS 104 to the UE 102 to the downlink path from the C-BS 106 to the UE 102. Similarly, the CN 110 may update the uplink path from the UE 102 to the S-BS 104 to the uplink path from the UE 102 to the C-BS 106.

[0056] After performing the path switch, the CN 110 transmits 330 to the C-BS 106 a second CN-BS interface message to set up, modify, or release radio resources for the UE 102. In some implementations, the second CN-BS interface message is the same as the first CN-BS interface message. In other implementations, the second CN-BS interface message is similar to the first CN-BS interface message with some differences. For example, the CN 110 may include at least one first UE ID in the first CN-BS interface message and at least one second UE ID in the second CN-BS interface message. The first UE ID and the second UE ID are associated with the UE 102. The first UE ID is different from the second UE ID. For example, the first UE ID includes a first AMF UE NGAP ID and / or a first RAN UE NGAP ID, and the second UE ID includes a second AMF UE NGAP ID and / or a second RAN UE NGAP ID. The first AMF UE NGAP ID may be the same as or different from the second AMF UE NGAP ID. The first RAN UE NGAP ID may be the same as or different from the second RAN UE NGAP ID. In another example, the first UE ID includes a first MME UE S1AP ID and / or a first eNB UE S1AP ID, and the second UE ID includes a second MME UE S1AP ID and / or a second eNB UE S1AP ID. The first MME UE S1AP ID may be the same as or different from the second MME UE S1AP ID. The first eNB UE S1AP ID may be the same as or different from the second eNB UE S1AP ID.

[0057] In some implementations, the CN 110 includes the same PDU Session ID or E-RAB ID in the first CN-BS interface message and the second CN-BS interface message. In other implementations, the CN 110 includes the same network slice information, for example, a Network Slice Selection Assistance Information (NSSAI) or a single NSSAI (S-NSSAI), in the first and second CN-BS interface messages. In yet other implementations, the CN 110 includes the same PDU Session Resource Setup Request Transfer IE in the first and second CN-BS interface messages. In yet other implementations, the CN 110 includes a first PDU Session Resource Setup Request Transfer IE in the first CN-BS interface message and a second PDU Session Resource Setup Request Transfer IE in the second CN-BS interface message. A portion of the first PDU Session Resource Setup Request Transfer IE and a portion of the second PDU Session Resource Setup Request Transfer IE may be the same, and the remaining portions of the first and second PDU Session Resource Setup Request Transfer IEs may be different. In some implementations, the CN 110 includes the same Quality of Service (QoS) parameters (values), transport layer addresses, and / or tunnel endpoint IDs (TEIDs) in the first and second CN-BS interface messages. In other implementations, the CN 110 includes different QoS parameters (values), transport layer addresses, and / or TEIDs in the first and second CN-BS interface messages, respectively.

[0058] In response to receiving the second CN-BS interface message, the C-BS 106 can be configured to set up, modify, or release radio resources for the UE 102 according to the second CN-BS interface message in various manners. When releasing radio resources, the C-BS 106 can release all radio resources configured for the UE 102 (i.e., release the radio connection with the UE 102) or release a portion of the radio resources configured for the UE 102. For example, the C-BS 106 can send an RRC release message to the UE 102 that releases all radio resources configured for the UE 102. In another example, the C-BS 106 can send an RRC reconfiguration message to release a portion of the radio resources configured for the UE 102. In yet another example, the C-BS 106 can send an RRC release message to the UE 102 that releases physical radio resources of the radio resources configured for the UE 102 to suspend the radio connection with the UE 102.

[0059] In some implementations, if the second CN-BS interface message is a DL Transport message that includes a NAS message to set up, modify, or release resources for the UE 102, the C-BS 106 may forward 342 the NAS message to the UE 102. Thus, the RAN 105, via the C-BS 106, may appropriately set up, modify, or release resources for the UE 102.

[0060] In other implementations, if the second CN-BS interface message is a PDU session Resource message or an E-RAB message that includes instructions or information elements to set up, modify, or release radio resources for the UE 102, the C-BS 106 may generate a second BS configuration for setting up, modifying, or releasing radio resources for the UE 102. The C-BS 106 may transmit 332 an RRC reconfiguration message to the UE 102 that includes the second BS configuration, and in response to the RRC reconfiguration message, the UE 102 transmits 334 an RRC reconfiguration complete message to the C-BS 106. After receiving 332 the RRC reconfiguration message from the C-BS 106, the UE 102 communicates 338 with the C-BS 106 using the second BS configuration. The C-BS 106 may not include a random access configuration in the second BS configuration so that the UE 102 does not perform a random access procedure in response to the second BS configuration. Thus, the RAN 105, via the C-BS 106, can appropriately set up, modify, or release radio resources for the UE 102.

[0061] In yet another implementation, if the second CN-BS interface message is either a DL NAS Transport message, a PDU session Resource message, or an E-RAB message for releasing radio resources for the UE 102, the C-BS 106 may send 340 an RRC release message releasing the radio resources. Thus, the RAN 105 may appropriately release the radio resources for the UE 102 via the C-BS 106.

[0062] In some implementations, after the C-BS 106 decides to set up, modify, or release radio resources for the UE 102, the C-BS 106, in response to the second CN-BS interface message, sends 336 a second BS-CN interface message to the CN 110 indicating that the C-BS 106 successfully set up, modify, or release radio resources for the UE 102. In other implementations, after or in response to transmitting 342 an NAS message, transmitting 332 an RRC reconfiguration message, or receiving 334 an RRC reconfiguration complete message, the C-BS 106 sends 336 the second BS-CN interface message to the CN 110. In some implementations, after the C-BS106 decides to release the radio resources for the UE102 or transmits an RRC release message releasing the radio resources 340, the C-BS106 sends a third BS-CN interface message to the CN110 in response to the second CN-BS interface message 341 indicating that the C-BS106 has successfully released the radio resources for the UE102.

[0063] The second or third BS-CN interface message may be a PDU Session Resource Response message, such as a PDU Session Resource Setup Response message, a PDU Session Resource Modify Response message, or a PDU Session Resource Release Response message. In other implementations, the second or third BS-CN interface message may be an E-RAB Setup Response message, an E-RAB Modify Response message, or an E-RAB Release Response message. In some implementations, unlike the first BS-CN interface message, which may include a cause value indicating why the S-BS 104 failed to set up, modify, or release the radio resources for the UE 102, the second or third BS-CN interface message need not include a similar cause value because the C-BS 106 successfully set up, modify, or release the radio resources for the UE 102.

[0064] In an implementation of the scenario 300 described above, the C-BS configuration may include configuration parameters for the UE 102 to communicate with the C-BS 106. These configuration parameters may configure radio resources for the UE 102 to communicate with the C-BS 106 via the candidate cell 126 (i.e., the candidate primary cell (C-PCell)) and zero, one, or more candidate secondary cells (C-SCells) of the C-BS 106. The configuration parameters may configure zero, one, or more radio bearers, where a radio bearer may include one or more SRBs and / or one or more DRBs. The SRBs may include SRB1 and / or SRB2.

[0065] In some implementations, the C-BS configuration generated 306 by the C-BS 106 is a completely self-contained configuration (i.e., a "full" configuration). Within the C-BS configuration, the C-BS 106 may include a full configuration indication (e.g., an IE or field) that indicates that the C-BS configuration is a completely self-contained configuration. The UE 102 can communicate with the C-BS 106 directly using the C-BS configuration without referencing the first BS configuration that the UE 102 previously used.

[0066] In other implementations, the C-BS configuration can include one or more configurations on top of the first BS configuration (i.e., the C-BS configuration is a “delta” configuration). The UE 102 can use this delta C-BS configuration along with at least some of the configuration parameters in the first BS configuration to communicate with the C-BS 106 at event 320. The delta C-BS configuration is not a complete configuration and does not include a full configuration indication. The UE 102 cannot use only the delta C-BS configuration to communicate with the C-BS 106, but instead also references the first BS configuration stored in the UE 102 as shown at event 302. The delta C-BS configuration can include one or more configuration parameters for the UE 102 to communicate with the C-BS 106. These configuration parameters may configure the radio resources for the UE 102 to communicate with the C-BS 106 via the candidate cell 126 (i.e., the C-PCell) and zero, one, or more C-SCells of the C-BS 106. The configuration parameters may configure zero, one, or multiple radio bearers. A radio bearer may include one or multiple SRBs and / or one or multiple DRBs. The configuration parameters may or may not include measurement configuration and / or security configuration.

[0067] If the C-BS configuration is a full configuration, the C-BS 106 may optionally update the C-BS configuration (i.e., configure a new configuration, modify an existing configuration, and / or release an existing configuration in the C-BS configuration) in the second BS configuration. If the C-BS configuration is instead a delta configuration, the C-BS 106 may update the C-BS configuration and / or the first BS configuration (i.e., configure a new configuration, modify an existing configuration, and / or release an existing configuration in the C-BS configuration and / or the first BS configuration) in the second BS configuration.

[0068] In response to the second RRC reconfiguration message, the UE 102 updates the first C-BS configuration and / or the first BS configuration using the second BS configuration, and thus the UE 102 communicates with the C-BS 106 according to the updated first C-BS configuration and / or the updated first BS configuration.

[0069] The C-BS configuration may include a group configuration (CellGroupConfig) IE that configures the C-PCell 126 and may configure zero, one, or multiple C-SCells for the C-BS 106. In some implementations, the C-BS configuration is in an RRCReconfiguration message, an RRCReconfiguration-IE, or a CellGroupConfig IE that conforms to 3GPP specification 38.331. In these implementations, the RRC reconfiguration complete message at event 310 may be an RRCReconfigurationComplete message. In other implementations, the C-BS configuration may include a RadioResourceConfigDedicated IE and / or a MobilityControlInfo IE that configures the C-PCell 126 and may or may not include a SCellToAddModList IE that configures one or more C-SCells for the C-BS 106. In other implementations, the C-BS configuration may be an RRCConnectionReconfiguration message or an RRCConnectionReconfiguration-IE that conforms to 3GPP specification 36.331. In these implementations, the RRC reconfiguration complete message at event 310 may be an RRCConnectionReconfigurationComplete message.

[0070] In some implementations, the first (or second) BS configuration can include a CellGroupConfig IE that configures the PCell 124 (or 126) and zero, one, or more SCells of the S-BS 104 (or C-BS 106). In some implementations, the first (or second) BS configuration is an RRCReconfiguration message, an RRCReconfiguration-IE, or a CellGroupConfig IE that conforms to 3GPP specification 38.331, or includes a configuration within an RRCReconfiguration message, an RRCReconfiguration-IE, or a CellGroupConfig IE. In other implementations, the first (or second) BS configuration can include a RadioResourceConfigDedicated IE and / or a MobilityControlInfo IE that configure the PCell 124 (or 126) and may or may not include a SCellToAddModList IE that configures one or more SCells of the S-BS 104 (or C-BS 106). In still other implementations, the first (or second) BS configuration may include a configuration in a RadioResourceConfigDedicated IE and / or a MobilityControlInfo IE.

[0071] If S-BS104 is implemented as a gNB, the RRC reconfiguration message of event 308 and the RRC reconfiguration complete message of event 310 may be an RRCReconfiguration message and an RRCConnectionReconfigurationComplete message, respectively. If S-BS104 is implemented as an eNB or ng-eNB, the RRC reconfiguration message of event 308 and the RRC reconfiguration complete message of event 310 may be implemented as an RRCReconfiguration message and an RRCConnectionReconfigurationComplete message, respectively.

[0072] If the C-BS 106 is implemented as a gNB, the RRC reconfiguration message of event 332 and the RRC reconfiguration complete message of event 334 may be an RRCReconfiguration message and an RRCConnectionReconfigurationComplete message, respectively. If the C-BS 106 is implemented as an eNB or ng-eNB, the RRC reconfiguration message 332 and the RRC reconfiguration complete message 334 may be implemented as an RRCReconfiguration message and an RRCConnectionReconfigurationComplete message, respectively.

[0073] 4A , at the start of scenario 400A, UE 102 communicates 402 data to and from S-BS 104 via one or more cells (e.g., cell 124), similar to event 302. Also similar to events 304 and 306, S-BS 104 initiates a CHO preparation procedure by transmitting 404 a Handover Request message to C-BS 106, which then transmits 406 a Handover Request Acknowledge message including a C-BS configuration to UE 102. The C-BS configuration may include information that enables UE 102 to communicate with C-BS 106 via a candidate cell (e.g., cell 126).

[0074] While in scenario 300, the CN 110 may send 322 a first CN-BS interface message to the S-BS 104 requesting to set up, modify, or release radio resources for the UE 102 after the S-BS 104 completes the CHO preparation procedure (e.g., after the S-BS 104 sends 308 the C-BS configuration to the UE 102), in scenario 400A, the CN 110 may send 422 a CN-BS interface message to the S-BS 104 requesting to set up, modify, or release radio resources for the UE 102 during the CHO preparation procedure (e.g., after the C-BS 106 receives 404 the Handover Request message and before the C-BS 106 transmits 406 the Handover Request Acknowledge message). In some implementations, the CN-BS interface message may be a PDU session Resource message or an E-RAB message, similar to the messages described above in FIG. 3. Because the S-BS 104 receives 422 the CN-BS interface message after sending 404 the Handover Request message to the C-BS 106, the S-BS 104 cannot notify the C-BS 106 to change the configuration parameters of the C-BS configuration to set up, modify, or release radio resources for the UE 102 in accordance with the CN-BS interface message. Thus, the C-BS 106 sends 406 to the S-BS 104 a C-BS configuration that does not include configuration parameters to set up, modify, or release radio resources in accordance with the CN-BS interface message.

[0075] Thus, the S-BS 104 determines not to send the C-BS configuration to the UE 102 409. In some implementations, the S-BS 104 may release the C-BS configuration. Instead of sending the C-BS configuration to the UE 102, in response to the determination 409, the S-BS 104 generates a second BS configuration for setting up, modifying, or releasing radio resources for the UE 102 when the CN-BS interface message indicates that radio resources be set up, modified, or released, and in some implementations transmits an RRC reconfiguration message including the second BS configuration to the UE 102 432. In this way, the S-BS 104 ensures that the UE 102 can set up, modify, or release radio resources via the second BS configuration. In response to the RRC reconfiguration message, the UE 102 transmits an RRC reconfiguration complete message to the S-BS 104 434.

[0076] In other implementations, in response to the decision 409, the S-BS 104 may generate an RRC release message for the UE 102 to release the radio resources if the CN-BS interface message indicates to release the radio resources. The S-BS 104 may transmit 440 the RRC release message to the UE 102, causing the UE 102 to transition to an idle or inactive state.

[0077] Thus, in the implementations described above, the RAN 105 can appropriately set up, modify, or release radio resources for the UE 102 via the S-BS 104. In some implementations, after event 432, 434, or 440, the S-BS 104 sends 424 a BS-CN interface message to the CN 110 in response to the CN-BS interface message, similar to event 336 or 341, indicating that the S-BS 104 successfully set up, modified, or released radio resources for the UE 102.

[0078] Referring now to FIG. 4B, in scenario 400A, the S-BS 104 decides not to send a C-BS configuration to the UE 102, while in scenario 400B, the S-BS 104 decides to send a C-BS configuration to the UE 102.

[0079] At the start of scenario 400B, similar to scenario 400A, UE 102 communicates data 402 with S-BS 104 via one or more cells (e.g., cell 124), and S-BS 104 initiates a CHO preparation procedure with C-BS 106A at events 404 and 406. However, in contrast to scenario 400A, in which CN 110 sends 422 a CN-BS interface message to S-BS 104 requesting that it set up, modify, or release radio resources for UE 102 during the CHO preparation procedure, CN 110 in scenario 400B sends 423 a CN-BS interface message to S-BS 104 requesting that it set up, modify, or release radio resources for UE 102 before S-BS 104 initiates the CHO preparation procedure. Thus, S-BS 104 can generate the second BS configuration described above in FIG. 4A and include the second BS configuration in the Handover Request message at event 404. Additionally, the S-BS 104 determines the configuration parameters in the format of the interface protocol (e.g., the X2 or Xn application protocol) after considering the CN-BS message requesting that the S-BS 104 set up, modify, or release radio resources. The S-BS 104 then includes the UE capabilities and configuration parameters in a Handover Request message.

[0080] As a result, because the C-BS 106 receives the second BS configuration (and thus knows the configuration parameters for setting up, modifying, or releasing radio resources according to the CN-BS interface message), the C-BS 106 can generate a C-BS configuration on top of the second BS configuration (i.e., the C-BS configuration is a "delta" configuration). Alternatively, the S-BS 104 does not include the second BS configuration in the Handover Request message. In this alternative implementation, the C-BS 106 can generate a full C-BS configuration (i.e., the C-BS configuration is a "full" configuration) according to the UE capabilities and configuration parameters. The C-BS 106 can then include the C-BS configuration in a Handover Request Acknowledge message and then transmit the Handover Request Acknowledge message to the S-BS 104 406.

[0081] The S-BS 104 may then decide to send the C-BS configuration to the UE 102 410, and thereafter transmits an RRC reconfiguration message to the UE 102 433, including the C-BS configuration and the second BS configuration. The S-BS 104 may include a trigger condition configuration in the RRC reconfiguration message, similar to event 308. As a result, the UE 102 can set up, modify, or release radio resources according to at least some of the configuration parameters in the second BS configuration, and further perform a CHO procedure when the conditions according to the C-BS configuration are met, thereby communicating with the C-BS 106 at event 320. In this way, the S-BS 104 ensures that the UE 102 can set up, modify, or release radio resources via the second BS configuration. In response to the RRC reconfiguration message, the UE 102 transmits an RRC reconfiguration complete message to the S-BS 104 434.

[0082] Thus, in the implementations described above, the RAN 105 can appropriately set up, modify, or release radio resources for the UE 102 via the S-BS 104. In some implementations, after event 433 or 434, the S-BS 104 sends 424 a BS-CN interface message to the CN 110 in response to the CN-BS interface message, similar to event 336 or 341, indicating that the S-BS 104 successfully set up, modified, or released radio resources for the UE 102.

[0083] 5, at the start of scenario 500, UE 102 communicates 302 data to and from S-BS 104 via one or more cells (e.g., cell 124), similar to event 302. Also similar to events 304 and 306, S-BS 104 initiates a CHO preparation procedure by transmitting 504 a Handover Request message to C-BS 106, which then transmits 506 a Handover Request Acknowledge message including a C-BS configuration to UE 102. The C-BS configuration may include information that enables UE 102 to communicate with C-BS 106 via a candidate cell (e.g., cell 126).

[0084] While in scenario 300, the CN 110 may send 322 a first CN-BS interface message to the S-BS 104 requesting to set up, modify, or release radio resources for the UE 102 after the S-BS 104 completes the CHO preparation procedure (e.g., after the S-BS 104 sends 308 the C-BS configuration to the UE 102), in scenario 500, for reasons similar to those described in FIG. 3, the CN 110 may send 542 a CN-BS interface message to the S-BS 104 including a NAS message requesting to set up, modify, or release resources for the UE 102 during the CHO preparation procedure (e.g., after the C-BS 106 receives 504 the Handover Request message and before the C-BS 106 transmits 506 the Handover Request Acknowledge message). In some implementations, the first CN-BS interface message may be a downlink (DL) NAS Transport message.

[0085] In response to receiving 542 the CN-BS interface message, the S-BS 104 transmits 544 an RRC message to the UE 102 that includes the NAS message. In some implementations, the RRC message is a DL Information Transfer message. After transmitting 544 the RRC message to the UE 102, the S-BS 104 transmits 508 an RRC reconfiguration message to the UE 102 that includes the C-BS configuration, and the UE 102 then transmits 510 an RRC reconfiguration complete message to the S-BS 104 in response to receiving the RRC reconfiguration message, similar to events 308 and 310, respectively. Alternatively, the S-BS 104 can transmit 544 the RRC message to the UE 102 after transmitting 508 the RRC reconfiguration message.

[0086] Sometime after transmitting the RRC reconfiguration complete message, the UE 102 may determine 512 that the conditions for connecting to the candidate cell 126 are met, and in response, perform 516 a random access procedure with the C-BS 106 to the candidate cell 126, similar to events 312 and 316. The UE 102 disconnects 514 from the S-BS 104's cell 124 in response to event 512 or 516, similar to event 314. Because the S-BS 104 has already transmitted an NAS message to the UE 102 before the UE 102 disconnects 514 from the S-BS 104's cell 124, the S-BS 104 ensures that the UE 102 receives instructions from the CN 110 in time to set up, modify, or release resources or NAS configuration via the NAS message.

[0087] While or after performing 516 the random access procedure, the UE 102 sends 518 an RRC reconfiguration complete message to the C-BS 106 via the candidate cell 126, similar to event 318. After performing 516 the random access procedure or transmitting 518 the RRC reconfiguration complete message, the UE 102 communicates 520 with the C-BS 106 by using a C-BS configuration, similar to event 320. After performing 516 the random access procedure or receiving 518 the RRC reconfiguration complete message, the C-BS 106 may establish 526 a UE-associated signaling connection to the CN 110 and send 526 a Path Switch Request message to the CN 110 requesting a switch of the downlink termination point of the transport bearer towards the C-BS 106, similar to event 326. In response to the Path Switch Request message, the CN 110 performs a path switch for the UE 102 and sends 528 a Path Switch Request Acknowledge message to the C-BS 106, similar to event 328.

[0088] 6-8 illustrate additional conditional handover scenarios. Unlike FIGS. 3-5, FIGS. 6-8 illustrate scenarios in which a distributed base station 104 having a CU 172 and at least two DUs 174 prepares a conditional handover from a source DU (S-DU) 174A to a candidate DU (C-DU) 174B.

[0089] Referring first to FIG. 6, in scenario 600, UE 102 communicates data 602 between S-DU 174A via one or more cells (e.g., cell 124) and CU 172 according to a first BS configuration, similar to event 302.

[0090] Later, the CU 172 initiates the CHO preparation procedure by determining to configure the UE 102 with a conditional configuration for the CHO procedure (i.e., C-DU configuration) such that the UE 102 can communicate with the C-DU 174B via a candidate cell (e.g., cell 126) when a condition is met. The CU 172 can make this determination based on one or more measurement results received directly from the UE 102 (e.g., via an SRB established between the UE 102 and the S-DU 174A or via a physical control channel) that are higher (or lower) than one or more predetermined thresholds, or from, for example, the CU 172 analyzing measurements related to signals, control channels, or data channels received from the UE 102, or another suitable event (e.g., the UE 102 is moving toward the C-DU 174B).

[0091] In response to this determination, the CU 172 transmits a UE Context Setup Request message to the C-DU 174B 604. In response to the UE Context Setup Request message, the C-DU 174B generates a C-DU configuration for the candidate cell (e.g., cell 126) associated with the C-DU 174B. The C-DU 174B includes the C-DU configuration in a UE Context Setup Response message to the UE 102 and then transmits the UE Context Setup Response message to the CU 172 606 in response to the UE Context Setup Request message. The C-DU configuration includes information that enables the UE 102 to communicate with the C-DU 174B via the candidate cell (e.g., cell 126). The C-DU configuration may be a “full” configuration or a “delta” configuration, as described above with reference to FIG. 3, and the configuration parameters may be similar to those described above with reference to FIG. 3.

[0092] The CU 172 transmits 607 an RRC reconfiguration message including the C-DU configuration and trigger condition configuration to the S-DU 174A, similar to event 308. The S-DU 174A then sends 608 an RRC reconfiguration message including the C-DU configuration to the UE 102. The UE 102 responds by transmitting 610 an RRC reconfiguration complete message to the S-DU 174A, and in response, the S-DU 174A sends 611 an RRC reconfiguration complete message to the CU 172. Events 604, 606, 607, and 608 are collectively referred to in FIG. 6 as the CHO preparation procedure.

[0093] Sometime after the CHO preparation procedure (e.g., after transmitting 610 the RRC reconfiguration complete message), the UE 102 may determine 612 that the conditions for connecting to the candidate cell 126 are met, and in response, performs 616 a random access procedure to the candidate cell 126 with the C-DU 174B, similar to events 312 and 316, respectively. The UE 102 disconnects 314 from the S-DU 174A in response to event 312 or 316.

[0094] Similar to event 318, the UE 102 transmits 618 an RRC reconfiguration complete message to the C-DU 174B via the candidate cell 126 while or after performing 616 the random access procedure. The C-DU 174B then transmits 619 the RRC reconfiguration complete message to the CU 172.

[0095] After performing the random access procedure 616 or transmitting the RRC reconfiguration complete message 618, the UE 102 communicates 620 with the C-DU 174B and the CU 172 by using the C-DU configuration. Events 612, 614, 616, 618, 619, and 620 are collectively referred to as the CHO execution procedure in FIG. 6.

[0096] In some implementations, during the CHO execution procedure, the CN 110 may send 622 a CN-BS interface message to the CU 172 requesting that radio resources for the UE 102 be set up, modified, or released, for various reasons, similar to event 322.

[0097] In response to the CN-BS interface message, the CU 172 may optionally generate and transmit 623 to the S-DU 174A a first RRC message (e.g., an RRC reconfiguration message) to set up, modify, or release radio resources for the UE 102. The S-DU 174A may then attempt to transmit the first RRC message to the UE 102. However, if the UE 102 had already disconnected 614 from the S-DU 174A during a CHO execution procedure prior to the time the S-DU 174A transmits the first RRC message, the CU 172 fails to transmit the first RRC message to the UE 102.

[0098] To ensure that the BS 104 can properly set up, modify, or release radio resources for the UE 102, the CU 172 may be configured to set up, modify, or release radio resources for the UE 102 according to CN-BS interface messages in various manners such as those described for the C-BS 106 in FIG. 3 .

[0099] In some implementations, if the CN-BS interface message is a DL NAS Transport message that includes a NAS message to set up, modify, or release resources for the UE 102, the CU 172 may forward 642 the NAS message to the UE 102 by transmitting 642 the NAS message to the C-DU 174B, similar to event 342, which then forwards 643 the NAS message to the UE 102. Thus, the CU 172 may appropriately set up, modify, or release resources (e.g., radio resources) for the UE 102 via the C-DU 174B.

[0100] In another implementation, if the CN-BS interface message is a PDU session Resource message or an E-RAB message containing an instruction or information element to set up, modify, or release radio resources for the UE 102, the CU 172 sends 644 a UE Context Modification Request message to the C-DU 174B. In response, the C-DU 174B generates a second BS configuration for setting up, modifying, or releasing radio resources for the UE 102 according to the CN-BS interface message at event 622. The C-DU 174B can send 646 a UE Context Modification Response message to the CU 172 containing the DU configuration, and the CU 172 then generates a second BS configuration containing the DU configuration. The CU 172 can generate other configuration parameters and include these configuration parameters in the second BS configuration. Events 644 and 646 are collectively referred to in FIG. 6 as a UE Context Modification procedure 650. The CU 172 then sends 631 to the C-DU 174B a second RRC message (e.g., an RRC reconfiguration message) including a second BS configuration that sets up, modifies, or releases radio resources for the UE 102 after the UE 102 completes the CHO execution procedure, e.g., after event 620. In response, the C-DU 174B transmits 632 a second RRC message including the second BS configuration to the UE 102. The UE 102 responds by transmitting 634 an RRC reconfiguration complete message to the C-DU 174B, which then forwards 635 the RRC reconfiguration complete message to the CU 172. After receiving 632 the second RRC message, the UE 102 communicates 638 with the C-DU 174B and the CU 172 by using the second BS configuration. Thus, the CU 172 can appropriately set up, modify, or release radio resources for the UE 102 via the C-DU 174B.

[0101] In yet other implementations, if the second CN-BS interface message is either a DL NAS Transport message, a PDU session Resource message, or an E-RAB message for releasing resources for the UE 102, the CU 172 may transmit 639 an RRC release message to the UE 102 to release the radio resources, similar to event 340, by transmitting 640 an RRC release message to the C-DU 174B, which then forwards 640 the RRC release message to the UE 102. Thus, the CU 172 can properly release the radio resources for the UE 102 via the C-DU 174B. In some implementations, the CU 172 may transmit 639 a UE Context Release Command message to the C-DU 174B to release the radio resources for the UE 102. The CU 172 may include the RRC release message in the UE Context Release Command message. In response to the UE Context Release Command message, the C-DU 174B releases the radio resources for the UE 102 .

[0102] In some implementations, after the CU 172 decides to set up, modify, or release radio resources for the UE 102, the CU 172 sends 636 a first BS-CN interface message to the CN 110 indicating that the CU 172 successfully set up, modify, or release radio resources for the UE 102 in response to the CN-BS interface message, similar to event 336. In other implementations, after transmitting 642 a NAS message, transmitting 631 an RRC reconfiguration message, or receiving 635 an RRC reconfiguration complete message, or in response to receiving 635 an RRC reconfiguration complete message, the CU 172 sends 636 the first BS-CN interface message to the CN 110. In some implementations, after the CU 172 decides to release the radio resources for the UE 102 or transmits an RRC release message releasing the radio resources 639, the CU 172 sends a second BS-CN interface message to the CN 110 in response to the CN-BS interface message, similar to event 341, indicating that the CU 172 has successfully released the radio resources for the UE 102 641.

[0103] 7A , at the start of scenario 700A, UE 102 communicates 702 data with S-DU 174A via one or more cells (e.g., cell 124) and CU 172, similar to event 602. Also similar to events 604 and 606, CU 172 initiates a CHO preparation procedure by transmitting 704 a UE Context Setup Request message to C-DU 174B, which then transmits 706 a UE Context Setup Response message including a C-DU configuration to UE 102. The C-DU configuration may include information that enables UE 102 to communicate with C-DU 174B via a candidate cell (e.g., cell 126).

[0104] In scenario 600, the CN 110 may send 622 a CN-BS interface message to the CU 172 requesting to set up, modify, or release radio resources for the UE 102 after the CU 172 completes the CHO preparation procedure (e.g., after the S-DU 174A sends 608 a C-BU configuration to the UE 102), whereas in scenario 700A, the CN 110 may send 722 a CN-BS interface message to the CU 172 requesting to set up, modify, or release radio resources for the UE 102 during the CHO preparation procedure (e.g., after the C-DU 174B receives 704 a UE Context Setup Request message and before the C-DU 174B transmits 706 a UE Context Setup Response message). In some implementations, the CN-BS interface message may be a PDU session Resource message or an E-RAB message, similar to the messages described above in FIG. 3. Because the CU 172 receives 722 the CN-BS interface message after sending 704 the UE Context Setup Request message to the C-DU 174B, the CU 172 cannot notify the C-DU 174B to change the configuration parameters of the C-DU configuration to set up, modify, or release radio resources for the UE 102 in accordance with the CN-BS interface message. Therefore, the C-DU 174B sends 706 to the CU 172 a C-DU configuration that does not include configuration parameters to set up, modify, or release radio resources in accordance with the CN-BS interface message.

[0105] Thus, the CU 172 determines 709 not to send the C-DU configuration to the UE 102. Instead of sending the C-DU configuration to the UE 102, in response to the decision 709, the CU 172 performs a UE Context Modification procedure 750 with the S-DU 174A, similar to the manner in which the CU 172 performs the UE Context Modification procedure 650 with the C-DU 174B. Thus, the CU 172 receives from the S-DU 174A a second BS configuration for setting up, modifying, or releasing radio resources for the UE 102 when the CN-BS interface message indicates that radio resources are to be set up, modified, or released. The CU 172 transmits 731 an RRC reconfiguration message including the second BS configuration to the S-DU 174A, which, in some implementations, then forwards 732 the RRC reconfiguration message to the UE 102. In this way, the CU 172 ensures that the UE 102 can set up, modify, or release radio resources via the second BS configuration. In response to the RRC reconfiguration message, the UE 102 transmits 734 an RRC reconfiguration complete message to the S-DU 174A, which then forwards 735 the RRC reconfiguration complete message to the CU 172.

[0106] In other implementations, in response to the decision 709, the CU 172 may generate an RRC release message for the UE 102 to release the radio resources if the CN-BS interface message indicates to release the radio resources. The CU 172 may transmit 739 the RRC release message to the S-DU 174A, which may then forward 740 the RRC release message to the UE 102, causing the UE 102 to transition to an idle or inactive state.

[0107] Thus, in the implementations described above, the BS 104 can appropriately set up, modify, or release radio resources for the UE 102 via the CU 172. In some implementations, after event 732, 734, or 740, the CU 172 sends 724 a BS-CN interface message to the CN 110 indicating that the CU 172 successfully set up, modify, or release radio resources for the UE 102 in response to the CN-BS interface message, similar to event 636 or 641.

[0108] Referring now to FIG. 7B, the CU 172 in scenario 700A decides not to send a C-DU configuration to the UE 102, while in scenario 700B the CU 172 decides to send a C-DU configuration to the UE 102.

[0109] At the start of scenario 700B, similar to scenario 700A, UE 102 communicates data 702 with S-DU 174A via one or more cells (e.g., cell 124) and CU 172, and CU 172 initiates a CHO preparation procedure with C-DU 174A at events 704 and 706. However, in contrast to scenario 700A, in which CN 110 sends 722 a CN-BS interface message to CU 172 requesting that radio resources for UE 102 be set up, modified, or released during the CHO preparation procedure, CN 110 in scenario 700B sends 723 a CN-BS interface message to CU 172 requesting that radio resources for UE 102 be set up, modified, or released before CU 172 initiates the CHO preparation procedure. Thus, CU 172 can generate the second BS configuration described above in FIG. 7A and include the second BS configuration in the UE Context Setup Request message at event 704. Additionally, the CU 172 determines the configuration parameters in the format of the interface protocol (e.g., the F1 or W1 application protocol) after considering the CN-BS message requesting that the CU 172 set up, modify, or release radio resources. The CU 172 then includes the UE capabilities and configuration parameters in a UE Context Setup Request message.

[0110] As a result, because the C-DU 174B receives the second BS configuration (and thus knows the configuration parameters for setting up, modifying, or releasing radio resources according to the CN-BS interface message), the C-DU 174B can generate a C-DU configuration on top of the second BS configuration. Alternatively, the CU 172 does not include the second BS configuration in the UE Context Setup Request message. In this alternative implementation, the C-BS 106 can generate a full C-BS configuration (i.e., the C-BS configuration is a "full" configuration) according to the UE capabilities and configuration parameters. The C-DU 174B can then include the C-DU configuration in a UE Context Setup Response message and then transmit 706 the UE Context Setup Response message to the CU 172.

[0111] The CU 172 may then determine 710 to send the C-DU configuration to the UE 102 and subsequently transmit 731 an RRC reconfiguration message including the C-DU configuration over the second BS configuration to the S-DU 174A, which then forwards 733 the RRC reconfiguration message to the UE 102. The CU 172 may include a trigger condition configuration in the RRC reconfiguration message, similar to event 308. In this way, the CU 172 ensures that the UE 102 can set up, modify, or release radio resources via the second BS configuration. In response to the RRC reconfiguration message, the UE 102 transmits 734 an RRC reconfiguration complete message to the S-DU 174A, which then forwards 735 the RRC reconfiguration complete message to the CU 172.

[0112] Thus, in the implementations described above, the BS 104 can appropriately set up, modify, or release radio resources for the UE 102 via the CU 172. In some implementations, after event 731 or 735, the CU 172 sends 724 a BS-CN interface message to the CN 110 indicating that the CU 172 successfully set up, modify, or release radio resources for the UE 102 in response to the CN-BS interface message, similar to event 636 or 641.

[0113] 8, at the start of scenario 800, UE 102 communicates 802 data to and from S-DU 174A via one or more cells (e.g., cell 124) and CU 172, similar to event 602. Also similar to events 604 and 606, CU 172 initiates a CHO preparation procedure by transmitting 804 a UE Context Setup Request message to C-DU 174B, which then transmits 806 a UE Context Setup Response message including a C-DU configuration to UE 102. The C-DU configuration may include information that enables UE 102 to communicate with C-DU 174B via a candidate cell (e.g., cell 126).

[0114] In scenario 600, the CN 110 may send 622 a CN-BS interface message to the CU 172 requesting to set up, modify, or release radio resources for the UE 102 after the CU 172 completes the CHO preparation procedure (e.g., after the S-DU 174A sends 608 a C-BU configuration to the UE 102), whereas in scenario 800, the CN 110 may send 842 a CN-BS interface message to the CU 172 including a NAS message requesting to set up, modify, or release resources for the UE 102 during the CHO preparation procedure (e.g., after the C-DU 174B receives 704 a UE Context Setup Request message and before the C-DU 174B transmits 706 a UE Context Setup Response message). In some implementations, the CN-BS interface message may be a downlink (DL) NAS Transport message.

[0115] In response to receiving 842 the CN-BS interface message, the CU 172 sends 843 an RRC message including the NAS message to the S-DU 174A, which then forwards 844 the RRC message to the UE 102. In some implementations, the RRC message is a DL Information Transfer message. After transmitting the RRC message to the UE 102, the CU 172 sends 807 an RRC reconfiguration message including the C-DU configuration to the S-DU 174A, which then forwards 808 the RRC reconfiguration message to the UE 102. In response, the UE 102 transmits 810 an RRC reconfiguration complete message to the S-DU 174A, which then forwards 811 the RRC reconfiguration complete message to the CU 172. Alternatively, the CU 172 can transmit 843 the RRC message to the S-DU 174A after transmitting 807 the RRC reconfiguration message. Thus, the S-DU 174A may transmit 844 an RRC message after transmitting 808 the RRC reconfiguration message.

[0116] Sometime after transmitting the RRC reconfiguration complete message, the UE 102 may determine 812 that the conditions for connecting to the candidate cell 126 are met, and in response, perform 816 a random access procedure with the C-DU 174B to the candidate cell 126, similar to events 612 and 616. The UE 102 disconnects 814 from the cell 124 of the S-DU 174A in response to event 812 or 816, similar to event 614. Because the CU 172 has already transmitted an NAS message to the UE 102 before the UE 102 disconnects 814 from the cell 124 of the S-DU 174A, the CU 172 ensures that the UE 102 receives in time an instruction from the CN 110 to set up, modify, or release resources or an NAS configuration via the NAS message.

[0117] During or after performing 816 the random access procedure, the UE 102 transmits 818 an RRC reconfiguration complete message to the C-DU 174B via the candidate cell 126, which then forwards 819 the RRC reconfiguration complete message to the CU 172, similar to events 618 and 619, respectively. After performing 816 the random access procedure or transmitting 818 the RRC reconfiguration complete message, the UE 102 communicates 820 with the C-DU 174B and the CU 172 by using the C-DU configuration, similar to 620.

[0118] For further clarity, some exemplary methods that may be implemented by devices operating in the systems of FIGS. 1A and 1B will now be described with reference to FIGS.

[0119] 9, an exemplary method 900 for configuring a UE with parameters for setting up, modifying, or releasing radio resources may be implemented as a set of instructions stored on a computer-readable medium and executable by processing hardware (e.g., one or more processors) in a suitable RAN, such as the RAN 105 of FIG. 1A. For convenience, the method 900 is described below with reference to the RAN 105, the CN 110, and the UE 102.

[0120] The method 900 begins at block 902, where the RAN 105 communicates with the UE 102 via a cell (eg, at event 302).

[0121] At block 904, the RAN 105 transmits to the UE 102 via one of the cells a conditional configuration for a conditional procedure to communicate with the UE 102 via the candidate cell when a condition is met (e.g., at event 308). In some implementations, the conditional configuration is a conditional handover configuration for a conditional handover procedure.

[0122] In block 906, after transmitting the conditional configuration to the UE 102 and before connecting with the UE 102 via the candidate cell, the RAN 105 receives from the CN 110 a first CN-BS interface message (e.g., at event 322) that sets up, modifies, or releases radio resources for the UE 102. In some implementations, the first CN-BS interface message can be a PDU session Resource message, such as a PDU Session Resource Setup Request message, a PDU Session Resource Modify Request message, or a PDU Session Resource Release Command message. In other implementations, the first CN-BS interface message can be an E-RAB message, such as an E-RAB Setup Request message, an E-RAB Modify Request message, or an E-RAB Release Command message. In yet other implementations, the first CN-BS interface message can be a NAS transport message that includes a NAS message.

[0123] At block 908, the RAN 105 disconnects from the UE 102 (e.g., at event 314). In some implementations, the RAN 105 disconnects from the UE 102 because the UE 102 determines that a condition associated with the conditional configuration has been met.

[0124] At block 910, the RAN 105 sends a first BS-CN interface message to the CN 110 indicating a failure to set up, modify, or release radio resources for the UE 102 in response to the first CN-BS interface message (e.g., at event 324). In some implementations, the first BS-CN interface message can be a PDU session Resource message, such as a PDU Session Resource Setup Response message, a PDU Session Resource Setup Failure message, a PDU Session Resource Modify Response message, a PDU Session Resource Modify Failure message, or a PDU Session Resource Release Response message. In other implementations, the first BS-CN interface message can be an E-RAB message, such as an E-RAB Setup Response message, an E-RAB Modify Response message, or an E-RAB Release Response message. In some implementations, the first BS-CN interface message may be an indication that the S-BS 104 failed to send to the UE 102 a NAS message from the CN 110 to set up, modify, or release resources for the UE 102.

[0125] In block 912, the RAN 105, in some implementations, connects to the UE 102 via the candidate cell (eg, at event 316).

[0126] In block 914, the RAN 105, in some implementations, receives an RRC message from the UE 102 via the candidate cell indicating completion of the conditional procedure (eg, at event 318).

[0127] In block 916, after receiving the RRC message, the RAN 105, in some implementations, sends to the CN 110 (e.g., at event 326) a second BS-CN interface message to establish a UE-associated signaling connection between the UE 102 and the CN 110. In some implementations, the second BS-CN interface message can be a Path Switch Request message.

[0128] After transmitting the second BS-CN interface message in block 918, the RAN 105, in some implementations, receives a second CN-BS interface message from the CN 110 (e.g., at event 330) to set up, modify, or release radio resources for the UE 102. In some implementations, the second CN-BS interface message is the same as the first CN-BS interface message. In other implementations, the second CN-BS interface message is similar to the first CN-BS interface message with some differences.

[0129] At block 920, the RAN 105 transmits to the UE 102 via the candidate cell a message to set up, modify, or release radio resources for the UE in response to the second CN-BS interface message (e.g., at events 340, 342, 332). In some implementations, the message is an RRC message, such as an RRC reconfiguration message or an RRC release message. In other implementations, the message is a NAS message.

[0130] 10, an exemplary method 1000 for configuring a UE with parameters for setting up, modifying, or releasing radio resources may be implemented as a set of instructions stored on a computer-readable medium and executable by processing hardware (e.g., one or more processors) in a suitable distributed base station, such as the distributed base station 104 of FIG. 1B. For convenience, the method 1000 is described below with reference to the distributed base station 104, the CN 110, and the UE 102.

[0131] The method 1000 begins at block 1002, where the distributed base station 104 communicates with the UE 102 via a cell (eg, at event 602), similar to block 902.

[0132] In block 1004, the distributed base station 104 transmits to the UE 102 via one of the cells a conditional configuration for a conditional procedure to communicate with the UE 102 via the candidate cell when a condition is met, similar to block 904 (e.g., at events 607, 608).

[0133] In block 1006, after transmitting the conditional configuration to the UE 102 but before connecting with the UE 102 via the candidate cell, the distributed base station 104 receives a CN-BS interface message from the CN 110 (e.g., at event 622) to set up, modify, or release radio resources for the UE 102, similar to block 906.

[0134] In block 1008, the distributed base station 104, in some implementations, fails to transmit to the UE 102 via one of the cells an RRC message to set up, modify, or release radio resources for the UE 102 in response to the CN-BS interface message (e.g., at event 623). In some implementations, the RRC message is an RRC reconfiguration message.

[0135] In block 1010, the distributed base station 104 disconnects from the UE 102 (eg, at event 614), similar to block 908.

[0136] In block 1012, the distributed base station 104 connects to the UE 102 via the candidate cell (eg, at event 616), similar to block 912.

[0137] At block 1014, the distributed base station 104 receives an RRC message from the UE 102 via the candidate cell indicating completion of the conditional procedure (eg, at event 618), similar to block 914.

[0138] At block 1016, the distributed base station 104 transmits a message to the UE 102 via the candidate cell in response to the CN-BS interface message to set up, modify, or release radio resources for the UE 102 (e.g., at events 639, 640, 642, 643, 631, 632). In some implementations, the message is an RRC message, such as an RRC reconfiguration message or an RRC release message. In other implementations, the message is a NAS message.

[0139] In block 1018, the distributed base station 104, in some implementations, in response to the CN-BS interface message, sends a BS-CN interface message to the CN 110 indicating successful setup, modification, or release of radio resources for the UE 102 (e.g., at events 636, 641).

[0140] 11, an exemplary method 1100 for performing a handover preparation procedure in consideration of receiving a CN-BS interface message for setting up, modifying, or releasing radio resources after deciding to perform the handover preparation procedure or while performing the handover preparation procedure may be implemented in a suitable RAN as a set of instructions stored on a computer-readable medium and executable by processing hardware (e.g., one or more processors), such as by the base station 104 of FIG. 1A or 1B operating in the RAN 105. For convenience, the method 1100 is described below with reference to the RAN 105, the CN 110, and the UE 102.

[0141] The method 1100 begins at block 1102, where the RAN 105 communicates with the UE 102 via a cell (eg, at events 302, 402, 602, 702).

[0142] In block 1104, the RAN 105 receives a CN-BS interface message from the CN 110 (e.g., at events 322, 422, 622, 722) requesting the RAN 105 to set up, modify, or release radio resources for the UE 102. In various implementations, the RAN 105 can receive the CN-BS interface message after deciding to perform a handover preparation procedure or while performing the handover preparation procedure.

[0143] If the RAN 105 decides to perform or is currently performing a handover preparation procedure for an immediate handover (i.e., an immediate handover preparation procedure) in block 1106, then in block 1108 the RAN 105 sends a BS-CN interface message to the CN 110 indicating a failure to set up, modify, or release radio resources for the UE 102. In other words, the RAN 105 prioritizes the immediate handover preparation procedure over a request from the CN 110 to set up, modify, or release radio resources for the UE 102. Thereafter, in block 1110, the RAN 105 transmits an (immediate) handover command to the UE 102 as a result of the immediate handover preparation procedure.

[0144] If, in block 1106, the RAN 105 decides to or is currently performing a handover preparation procedure that is not for an immediate handover (e.g., a conditional handover preparation procedure), then, in block 1112, the RAN 105 generates and transmits to the UE 102 a message to set up, modify, or release radio resources for the UE 102 in response to the CN-BS interface message (e.g., at events 332, 340, 342, 440, 432, 631, 632, 639, 640, 642, 643, 739, 740). In other words, the RAN 105 prioritizes a request from the CN 110 to set up, modify, or release radio resources for the UE 102 over a conditional handover preparation procedure. In various implementations, the message can be an RRC message or an NAS message. Thereafter, in block 1114, the RAN 105 may, in response to the CN-BS interface message received in block 1104, send a BS-CN interface message to the CN 110 indicating that the RAN 105 has successfully set up, modified, or released radio resources for the UE 102 (e.g., at events 336, 341, 424, 636, 641, 724).

[0145] Referring now to FIG. 12, while the example method 1100 of FIG. 11 includes receiving a CN-BS interface message to set up, modify, or release radio resources for the UE 102 after deciding to perform a handover preparation procedure or while performing the handover preparation procedure, the example method 1200 of FIG. 12 includes receiving a CN-BS interface message before deciding to perform the handover preparation procedure.

[0146] The method 1200 begins at block 1202, where the RAN 105 communicates with the UE 102 via a cell (eg, at event 502), similar to block 1102.

[0147] In block 1204, the RAN 105 receives from the CN 110 a CN-BS interface message (e.g., at events 506, 806) that includes a NAS message for the UE 102. In various implementations, the RAN 105 can receive the CN-BS interface message before deciding to perform a handover preparation procedure or before performing a handover preparation procedure.

[0148] If, in block 1206, the RAN 105 decides to perform a handover preparation procedure for an immediate handover (i.e., an immediate handover preparation procedure), in block 1208, the RAN 105 sends a BS-CN interface message to the CN 110 indicating a failure to send the NAS message to the UE 102. In other words, the RAN 105 prioritizes the immediate handover preparation procedure over a request from the CN 110 to set up, modify, or release radio resources for the UE 102. Thereafter, in block 1210, the RAN 105 transmits an (immediate) handover command to the UE 102 as a result of the immediate handover preparation procedure, similar to block 1110.

[0149] If, in block 1206, the RAN 105 determines to perform a handover preparation procedure that is not for an immediate handover (e.g., a conditional handover preparation procedure), in block 1212, the RAN 105 transmits (e.g., forwards) to the UE 102 an NAS message to set up, modify, or release resources for the UE 102 (e.g., at events 544, 844). In other words, the RAN 105 prioritizes a request from the CN 110 to set up, modify, or release resources for the UE 102 over the conditional handover preparation procedure. Thereafter, in block 1214, the RAN 105 may send to the UE 102 an RRC message including a conditional configuration as a result of the conditional handover preparation procedure (e.g., at events 508, 808).

[0150] 13, an exemplary method 1300 for transmitting a follow-up message to a RAN to set up, modify, or release radio resources for a UE in response to receiving an indication from the RAN that it has previously failed to set up, modify, or release radio resources may be implemented as a set of instructions stored on a computer-readable medium and executable by processing hardware (e.g., one or more processors) in a suitable CN, such as the CN 110 of FIG. 1A. For convenience, the method 1300 is described below with reference to the CN 110, the RAN 105, and the UE 102.

[0151] The method 1300 begins at block 1302, where the CN 110 communicates with the UE 102 via the RAN 105 (eg, at event 302).

[0152] In block 1304, the CN 110 sends a first CN-BS interface message to the RAN 105 to request the RAN 105 to set up, modify, or release radio resources for the UE 102, similar to block 906 (e.g., at event 322).

[0153] In block 1306, the CN 110 receives a first BS-CN interface message from the RAN 105 indicating a failure to set up, modify, or release radio resources for the UE 102 in response to the first CN-BS interface message (e.g., at event 324), similar to block 910.

[0154] In block 1308, the CN 110 receives a request message from the RAN 105 to establish a UE-associated signaling connection for the UE 102 (eg, at event 326), similar to block 916.

[0155] In block 1310, the CN 110 sends a second CN-BS interface message to the RAN 105 requesting the RAN 105 to set up, modify, or release radio resources for the UE 102 in response to the request message, similar to block 918 (e.g., at event 330).

[0156] In block 1312, the CN 110, in some implementations, receives a second BS-CN interface message from the RAN to confirm that the RAN 105 has successfully set up, modified, or released radio resources for the UE 102, similar to block 1114 (e.g., at events 336, 341).

[0157] 14, an example method 1400 for configuring a UE may be implemented as a set of instructions stored on a computer-readable medium and executable by processing hardware (e.g., one or more processors) in a suitable RAN, such as the RAN 105 of FIG. 1A. For convenience, the method 1400 is described below with reference to the RAN 105, the CN 110, and the UE 102.

[0158] The method 1400 begins at block 1402, where the RAN 105 generates a conditional configuration and a condition to be met before the UE 102 applies the conditional configuration (e.g., at events 306, 406, 506, 606, 706, 806). In some implementations, the conditional configuration is a conditional handover configuration for the UE 102 to handover from a source base station (e.g., S-BS 104) to a candidate base station (e.g., C-BS 106). In other implementations, the conditional configuration is a conditional handover configuration for the UE 102 to handover from a source DU (e.g., S-DU 174A) to a candidate DU (e.g., C-DU 174B).

[0159] In block 1404, the RAN 105 receives an interface message from the CN 110 instructing it to configure the UE 102, similar to block 906 (e.g., at events 322, 422, 423, 542, 622, 722, 723, 842).

[0160] In block 1406, the RAN 105 determines that the interface message affects the conditional configuration. In some implementations, the RAN 105 determines that the interface message affects the conditional configuration because a node included in the RAN 105 cannot deliver the interface message to the UE 102 as a result of the UE 102 being disconnected from the node in accordance with the conditional configuration (e.g., at events 314, 614). In other implementations, the RAN 105 determines that the conditional configuration does not include configuration parameters for configuring the UE 102 in accordance with the interface message when the RAN 105 receives the interface message after already generating the conditional configuration (e.g., at events 422, 406, 722, 706, 542, 506, 842, 806). In yet another implementation, the RAN 105 receives the interface message before generating the conditional configuration, and when the RAN 105 takes the interface message into account when generating the conditional configuration, the RAN 105 determines (e.g., at events 423, 723) that the conditional configuration includes configuration parameters for configuring the UE 102 in accordance with the interface message.

[0161] At block 1408, the RAN 105 generates a message related to the conditional configuration in consideration of the received interface message. In some implementations, as a result of the UE 102 being disconnected from a first node of the RAN 105 and connected to a second node of the RAN 105 according to the conditional configuration, the second node generates a message in consideration of the received interface message (e.g., at events 340, 342, 332, 640, 643, 632). In other implementations, as a result of the RAN 105 determining that the conditional configuration does not include configuration parameters for configuring the UE 102 according to the interface message, the RAN 105 generates a message in consideration of the received interface message (e.g., at events 440, 432, 740, 732, 544, 844). In yet other implementations, as a result of the RAN 105 determining that the conditional configuration includes configuration parameters for configuring the UE 102 according to the interface message, the RAN 105 generates a message in consideration of the received interface message (e.g., at events 433, 733).

[0162] In block 1410, the RAN 105 transmits a message to the UE 102 (e.g., at events 340, 342, 332, 440, 432, 433, 544, 640, 643, 632, 740, 732, 733, 844), similar to block 920.

[0163] 15, an exemplary method 1500 for configuring a UE may be implemented as a set of instructions stored on a computer-readable medium and executable by processing hardware (e.g., one or more processors) in a suitable CN, such as the CN 110 of FIG. 1A. For convenience, the method 1500 is described below with reference to the CN 110, the RAN 105, and the UE 102.

[0164] The method 1500 begins at block 1502, where the CN 110 sends a first interface message to a first node of the RAN 105 instructing it to configure the UE 102 (e.g., at event 322), similar to block 1304.

[0165] In block 1504, the CN 110 receives a response interface message from the RAN 105 indicating a failure to configure the UE in light of the first interface message, similar to block 1306 (e.g., at event 324).

[0166] In block 1506, the CN 110 receives a request from the RAN 105 to switch the path to a second node in the RAN 105 (eg, at event 326), similar to block 1308.

[0167] In block 1508, the CN 110 sends a second interface message to the second node instructing it to configure the UE 102, similar to block 1310 (eg, at event 330).

[0168] The following explanation may be applied to the above explanation.

[0169] In some implementations, "message" is used, but this can be replaced with "information element (IE)." In some implementations, "IE" is used, but this can be replaced with "field." In some implementations, "configuration" can be replaced with "multiple configurations" or configuration parameters included in the MN or SN configuration described above. For example, "configuration" can be replaced with "several configurations" or "configuration parameters." The MN or SN configuration can be replaced with cell group configuration and / or radio bearer configuration.

[0170] A user device (e.g., UE 102) in which the techniques of this disclosure may be implemented may be any suitable device capable of wireless communication, such as a smartphone, a tablet computer, a laptop computer, a mobile gaming console, 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 smartwatch, a wireless hotspot, a femtocell, or a broadband router. Furthermore, a user device may, in some cases, be integrated into an electronic system such as a vehicle head unit or an advanced driver assistance system (ADAS). Still further, a user device may operate as an Internet of Things (IoT) device or a mobile / internet device (MID). Depending on the type, a user device may include one or more general-purpose processors, computer-readable memory, a user interface, one or more network interfaces, one or more sensors, etc.

[0171] Some embodiments are described in this disclosure as including logic or multiple components or modules. A module may 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 may be configured or arranged in a particular way. A hardware module may comprise dedicated circuitry or logic permanently configured to perform certain operations (e.g., as a field programmable gate array (FPGA) or application-specific integrated circuit (ASIC), dedicated processor such as a digital signal processor (DSP)) . A hardware module may also comprise programmable logic or circuitry (e.g., as contained within a general-purpose processor or other programmable processor) temporarily configured by software to perform certain operations. The decision whether to implement a hardware module with dedicated, permanently configured circuitry or temporarily configured circuitry (e.g., configured by software) may be driven by cost and time considerations.

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

[0173] Those skilled in the art will, after reading this disclosure, recognize still additional alternative structural and functional designs for managing configurations through the principles disclosed herein. Thus, while particular embodiments and applications have been illustrated and described, it should be understood that the disclosed embodiments are not limited to the exact structure and components disclosed herein. Various other modifications, changes, and variations, which will be apparent to those skilled in the art, may be made in the arrangement, operation, and details of the methods and apparatus disclosed herein without departing from the spirit and scope, as defined in the appended claims. [Example]

[0174] A method in a radio access network (RAN) for configuring a user equipment (UE), the method comprising: generating, by processing hardware, (i) a conditional configuration and (ii) a condition to be met before the UE applies the conditional configuration; receiving, by the processing hardware, an interface message from a core network (CN) instructing the UE to configure; determining, by the processing hardware, that the interface message affects the conditional configuration; generating, by the processing hardware, a message related to the conditional configuration taking into account the received interface message; and transmitting, by the processing hardware, the message to the UE. [Example]

[0175] 2. The method of embodiment 1, further comprising: transmitting, by the first node of the RAN, a conditional configuration to the UE before receiving the interface message from the CN. [Example]

[0176] 3. The method of embodiment 2, further comprising: determining that a wireless connection between the UE and the first node is suspended; and transmitting the message to the UE comprises transmitting the message via a second node in the RAN after the UE connects to the second node. [Example]

[0177] The method of example 3, wherein the interface message is a first interface message, and the method further includes, in response to determining that the wireless connection is suspended, sending, by the first node to the CN, an indication that the resource setup, modification, or release has failed, and receiving, by the second node from the CN, a second interface message that sets up, modifies, or releases the resource. [Example]

[0178] 5. The method of embodiment 4, wherein transmitting the message to the UE includes transmitting, by the second node, the message to the UE in response to receiving the second interface message. [Example]

[0179] The method of example 3, wherein receiving the interface message includes receiving the interface message by the first node, and transmitting the message to the UE includes transmitting the message to the UE by the first node via the second node in response to receiving the interface message. [Example]

[0180] 2. The method of claim 1, wherein generating the conditional configuration includes, by a second node of the RAN, generating the conditional configuration, and the method further includes, by a first node of the RAN, determining that the conditional configuration omits one or more parameters for setting up, modifying, or releasing resources; and preventing, by the first node, transmission of the conditional configuration to the UE. [Example]

[0181] 2. The method of claim 1, wherein generating the conditional configuration includes, by a second node of the RAN, generating the conditional configuration, and the method further includes, by a first node of the RAN, determining that the conditional configuration includes one or more parameters for setting up, modifying, or releasing resources; and transmitting, by the first node of the RAN, the conditional configuration to the UE. [Example]

[0182] 9. The method according to any one of embodiments 1 to 8, wherein the message is a first message, and the method further includes, after transmitting the first message to the UE, sending a second message to the CN indicating that the RAN has configured the UE. [Example]

[0183] 2. The method of claim 1, wherein generating the conditional configuration includes generating the conditional configuration by a second node of the RAN, and the method further includes transmitting, by the first node of the RAN, the conditional configuration to the UE after transmitting the message. [Example]

[0184] 11. The method of embodiment 10, wherein the interface message comprises a non-access stratum (NAS) message, and the message comprises a NAS message. [Example]

[0185] 12. The method according to any one of embodiments 2 to 5 and 7 to 11, wherein the first node is a source base station (S-BS) included in the RAN, and the second node is a candidate base station (C-BS) included in the RAN. [Example]

[0186] The method according to any one of Examples 2 to 3 and 9 to 11, wherein the first node is a source distributed unit (S-DU) in a distributed base station included in the RAN, and the second node is a candidate DU (C-DU) in the distributed base station. [Example]

[0187] 9. The method according to any one of embodiments 6 to 8, wherein the first node is a central unit (CU) in a distributed base station included in a RAN, and the second node is a C-DU included in the distributed base station. [Example]

[0188] 15. The method of any one of examples 1 to 14, wherein the conditional configuration is a configuration for a conditional handover (CHO) procedure. [Example]

[0189] 16. The method of any one of embodiments 1 to 15, wherein the generating is performed at a first instance, and the method further includes, at a second instance, generating an immediate configuration for an immediate handover procedure and sending a response interface message to the CN, indicating that the RAN failed to configure the UE. [Example]

[0190] One or more base stations comprising processing hardware and configured to implement the method according to any one of Examples 1 to 16. [Example]

[0191] 1. A method in a core network (CN) for configuring a user equipment (UE), the method comprising: sending, by processing hardware, a first interface message to a first node of a radio access network (RAN) instructing the UE to be configured; receiving, by the processing hardware, a response interface message from the RAN instructing that configuring the UE has failed in light of the first interface message; receiving, by the processing hardware, a request from the RAN to switch paths to a second node of the RAN; and sending, by the processing hardware, a second interface message to the second node instructing the UE to be configured. [Example]

[0192] 19. The method of embodiment 18, wherein the request further includes an instruction to establish a connection between the UE and the CN. [Example]

[0193] 20. The method of embodiment 18 or 19, wherein the response interface message is a first response interface message, and the method further includes receiving, by the processing hardware, a second response interface message from the RAN indicating that the RAN has configured the UE. [Example]

[0194] A method according to any one of embodiments 18 to 20, wherein receiving a response interface message includes receiving an indication from the first node that the resource has failed to be set up, modified, or released, and sending a second interface message includes sending an indication to the second node that the resource has been set up, modified, or released. [Example]

[0195] 22. The method according to any one of embodiments 18 to 21, wherein the first node is a source base station (S-BS) included in the RAN, and the second node is a candidate base station (C-BS) included in the RAN. [Example]

[0196] A CN comprising processing hardware and configured to implement the method according to any one of Examples 18 to 22. [Explanation of symbols]

[0197] 100 Wireless Communication System 102UE 104 Base station (BS) 106 Base Station 106A base station 110 Core Network (CN) 111 Evolved Packet Core (EPC) 112 Serving Gateway (SGW) 114 Mobility Management Entity (MME) 116 Packet Data Network Gateway (PGW) 124 cells 125 cells 126 cells 130 Processing Hardware 132 Controller 134 Instant Configuration Controller 140 Processing Hardware 142 Conditional Configuration Controller 144 Instant Configuration Controller 150 Processing Hardware 152 UE Conditional Configuration Controller 154 Instant Configuration Controller 160 5th Generation (5G) Core (5GC) 162 User Plane Function (UPF) 164 Access and Mobility Management (AMF) 166 Session Management Facility (SMF) 172 Central Unit (CU) 172A Logical Node CU-CP 172B Logical node CU-UP 174 DU 174A Source DU (S-DU) 174B Candidate DU (C-DU) 200 Protocol Stack 202A Physical layer (PHY) 202B NR PHY 204A EUTRA MAC sublayer 204B NR MAC sublayer 206A EUTRA RLC sublayer 206B NR RLC sublayer 208 EUTRA PDCP sublayer 210 NR PDCP sublayer 212 SDAP Sublayer 300 Scenarios 302, 402, 602, 702 Events 306, 406, 506, 606, 706, 806 Events 312, 314, 316, 318, 320 Events 322, 422, 423, 542, 622, 722, 723, 842 events 324 Events 326 Events 330 Events 332, 340, 342, 440, 432, 631, 632, 639, 640, 642, 643, 739, 740 Events 336, 341, 424, 636, 641, 724 events 340, 342, 332 Events 400A Scenario 400B Scenario 409 decision 422, 406, 722, 706, 542, 506, 842, 806 events 423, 723 Events 433, 733 Events 500 Scenarios 506, 806 Events 508, 808 Events 544, 844 events 600 scenarios 604, 606, 607, 608 Events 612, 614, 616, 618, 619, 620 Events 636, 641 Events 639, 640, 642, 643, 631, 632 Events 644, 646 Events 650 UE Context Modification Procedure 700A Scenario 700B Scenario 704 Events 709 decision 750 UE Context Modification Procedure 800 Scenarios 900 ways 1000 ways 1100 methods 1200 methods 1300 methods 1400 methods 1500 ways

Claims

1. 1. A method in a Radio Access Network (RAN) for configuring a user equipment (UE), comprising: generating, by processing hardware, (i) a conditional configuration and (ii) a condition that must be satisfied before the UE applies the conditional configuration; receiving, by the processing hardware, an interface message from a core network (CN) instructing to configure the UE; determining, by the processing hardware, that the interface message affects the conditional configuration; generating, by said processing hardware, a message relating to said conditional configuration taking into account said received interface message; transmitting, by the processing hardware, the message to the UE; A method comprising:

2. before receiving the interface message from the CN; The method of claim 1 , further comprising transmitting, by a first node of the RAN, the conditional configuration to the UE.

3. determining that a radio connection between the UE and the first node is suspended; 3. The method of claim 2, wherein transmitting the message to the UE comprises transmitting the message via a second node of the RAN after the UE connects to the second node.

4. The step of generating the conditional configuration includes generating the conditional configuration by a second node of the RAN, the method comprising: determining, by a first node of the RAN, that the conditional configuration omits one or more parameters for setting up, modifying, or releasing resources; preventing transmission of the conditional configuration to the UE by the first node; The method of claim 1 further comprising:

5. The step of generating the conditional configuration includes generating the conditional configuration by a second node of the RAN, the method comprising: determining, by a first node of the RAN, that the conditional configuration includes one or more parameters for setting up, modifying, or releasing resources; transmitting, by the first node of the RAN, the conditional configuration to the UE; The method of claim 1 further comprising:

6. The step of generating the conditional configuration includes generating the conditional configuration by a second node of the RAN, the method comprising:

2. The method of claim 1, further comprising transmitting, by a first node of the RAN, the conditional configuration to the UE after transmitting the message.

7. 7. The method of claim 1, wherein the conditional configuration is a configuration for a conditional handover (CHO) procedure.

8. The generating step is performed in a first instance, and the method is performed in a second instance by: generating an immediate configuration for an immediate handover procedure; sending a response interface message to the CN indicating that the RAN has failed to configure the UE; The method of any one of claims 1 to 7, further comprising:

9. One or more base stations comprising processing hardware and configured to implement the method according to any one of claims 1 to 8.

10. 1. A method in a core network (CN) for configuring a user equipment (UE), comprising: sending, by processing hardware, a first interface message to a first node in a Radio Access Network (RAN) instructing the UE to configure; receiving, by the processing hardware, a response interface message from the RAN indicating a failure to configure the UE in light of the first interface message; receiving, by the processing hardware, a request from the RAN to switch paths to a second node of the RAN; sending, by the processing hardware, a second interface message to the second node instructing the second node to configure the UE; A method comprising:

11. The method of claim 10, wherein the request further includes an instruction to establish a connection between the UE and the CN.

12. the response interface message is a first response interface message, and the method comprises:

12. The method of claim 10 or 11, further comprising receiving, by the processing hardware, a second response interface message from the RAN indicating that the RAN has configured the UE.

13. receiving the response interface message includes receiving an indication from the first node that there was a failure to set up, modify, or release a resource; The step of transmitting the second interface message includes transmitting an instruction to the second node to set up, modify, or release the resource.

13. The method according to any one of claims 10 to 12.

14. the first node is a source base station (S-BS) included in the RAN; The second node is a candidate base station (C-BS) included in the RAN.

14. The method according to any one of claims 10 to 13.

15. 15. A CN comprising processing hardware and configured to implement the method of any one of claims 10 to 14.

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