Managing wireless resources and downlink transmissions 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 specifically to managing radio resources and downlink transmission during handover preparation and execution procedures. [Background Art]

[0002] This section in the description of the background art is provided for the purpose of generally presenting the context of the present disclosure. To the extent that the study of the presently named inventors is described in this Background section, and in particular, any aspects of the description that may not otherwise qualify as prior art as of the filing date of the application are not admitted, expressly or impliedly, to be prior art to the present disclosure.

[0003] In a telecommunication system, the Packet Data Convergence Protocol (PDCP) sublayer of a wireless protocol stack provides services such as user plane data forwarding, encryption and integrity protection. For example, PDCP layers defined for Evolved Universal Terrestrial Radio Access (EUTRA) air interface (see 3GPP (registered trademark, the same applies hereinafter) specification TS 36.323) and New Radio (NR) (see 3GPP specification TS 38.323) provide ordering of protocol data units (PDUs) in the uplink direction (from a user device, also called user equipment (UE), to a base station) and also in the 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, a UE and a base station may use SRBs to exchange RRC messages and also non-access stratum (NAS) messages, and may use DRBs to transport data on the user plane.

[0004] A UE can use several types of SRBs and DRBs. When operating in dual connectivity (DC), a cell associated with a base station acting as a master node (MN) defines a master cell group (MCG), and a cell associated with a base station acting as a secondary node (SN) defines a secondary cell group (SCG). The so-called SRB1 resource carries RRC messages, including NAS messages, over a separate control channel (DCCH) in some cases, while the SRB2 resource supports RRC messages, including logged measurement information or NAS messages, also over the DCCH but with lower priority than the SRB1 resource. 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. The SRB3 resource allows the UE and SN to exchange RRC messages related to the SN, and may be referred to as SCG SRBs. Split SRBs allow the UE to directly exchange RRC messages with the MN via lower-layer resources of the MN and SN. MCG DRBs use only MN lower-layer resources, SCG DRBs use only SN lower-layer resources, and split DRBs use both MCG and SCG lower-layer resources. A DRB that terminates at MN but uses only SN lower-layer resources may be called an MN-terminated SCG DRB. A DRB that terminates at SN but uses only MN lower-layer resources may be called an SN-terminated MCG DRB.

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

[0006] 3GPP Technical Specifications (TS) 36.300 and 38.300 (v16.4.0) describe procedures for handover (or reconfiguration with synchronization) scenarios. When these procedures do not involve conditions that are checked at the UE, they may be referred to as immediate or unconditional handover procedures. When these procedures involve conditions that are checked at 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 modify a PSCell in a DC scenario. These procedures involve messaging between radio access network (RAN) nodes (e.g., RRC signaling and preparation). When these procedures do not involve conditions checked by the UE, they may be referred to as immediate or unconditional PSCell modification procedures. When these procedures involve conditions checked by the UE, they may be referred to as conditional PSCell modification (CPC) procedures.

[0008] The 3GPP specification TS 37.340 v16.4.0 describes procedures for a UE to add or modify a 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 checked by the UE, they may be referred to as immediate or unconditional SN add / modify procedures. When these procedures involve conditions checked by the UE, they may be referred to as conditional SN add / modify (CSAC) procedures, also known as conditional PSCell add / modify (CPAC) procedures.

[0009] To configure a CHO, CSAC, or CPC procedure, the RAN provides the UE with conditions, along with a configuration (e.g., a set of random access preambles) that enables the UE to communicate with the appropriate base station or via the appropriate cell when the conditions are met. For example, for a 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 a configuration that enables the UE to communicate with that candidate base station or candidate PCell after the conditions are met. As another example, for a 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 a configuration that enables 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, but rather waits until the conditions are met before applying the conditional configuration.

[0010] Generally speaking, a RAN generates an immediate or conditional configuration and provides it to the UE by performing the CHO, CSAC, or CPC “preparation” procedure, or the corresponding immediate (not “conditional”) procedure of each. The UE is then said to “execute” 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 executes the immediate or conditional HO procedure, for example, by immediately disconnecting from the first RAN node and connecting to the second RAN node according to the immediate HO procedure, or by delaying the disconnect and connect process until the conditions are met according to the CHO procedure.

[0011] In some scenarios, while the UE is performing a CHO procedure, the first RAN node receives requests from the core network (CN) for resource management procedures performed by the UE on the first RAN node (e.g., E-RAB Setup, E-RAB Modify, E-RAB Release, PDU Session Resource Setup, PDU Session Resource Modify, PDU Session Resource Release, or Downlink NAS Transport procedures according to 3GPP specifications 36.413 and 38.413). When the UE disconnects from the first RAN node in accordance with the CHO procedure, the first RAN node fails to communicate with the UE and therefore fails to perform resource management procedures with the UE.

[0012] In other scenarios, the first RAN node receives a request for a resource management procedure from the CN while it is performing the CHO preparation procedure. When the first RAN node prioritizes the CHO preparation procedure over the request, it may decide not to interrupt the CHO preparation procedure, and thereby fail to perform the resource management procedure in accordance with the request. [Overview of the project] [Means for solving the problem]

[0013] According to the technology of this disclosure, the RAN receives a request from the CN to perform a resource management procedure with the UE. In some scenarios, the RAN receives a request when the UE is currently performing a conditional procedure with the RAN according to a conditional configuration received from the RAN. As a result of the UE performing the conditional procedure, the RAN decides that the UE disconnects from the first RAN node and then connects with the UE via the second RAN node, thereby giving the RAN a wireless connection with the UE and allowing it to perform the resource management procedure according to the request from the CN. In other scenarios, the RAN receives a request from the CN after generating a conditional configuration while performing a conditional preparation procedure for the UE. Since the RAN could not consider the request at the time the conditional configuration was generated, the RAN can send a message to the UE containing the appropriate parameters according to the request. In yet another scenario, the RAN receives a request from the CN before performing a conditional preparation procedure for the UE. Since the RAN can consider the request at the time the conditional configuration is generated during the execution of the conditional preparation procedure, the RAN can send the conditional configuration to the UE.

[0014] An exemplary embodiment of these techniques is a method in a RAN for configuring a UE. This method may be performed by processing hardware and includes: (i) generating a conditional configuration and (ii) conditions that must be met 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 relating to the conditional configuration, taking into account 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 method described above.

[0015] A yet another exemplary embodiment of these techniques is a method implemented in a CN for configuring a UE. This method may be performed by processing hardware and includes sending a first interface message to a first node of a RAN instructing it to configure the UE; receiving a response interface message from the RAN indicating that it failed to configure the UE in consideration of the first interface message; receiving a request from the RAN to switch the route to a second node of the RAN; and sending a second interface message to the second node instructing it to configure the UE. Yet another exemplary embodiment of these techniques is a CN including processing hardware configured to perform the above method. [Brief explanation of the drawing]

[0016] [Figure 1A] This is a block diagram of an exemplary system in which base stations operating in RAN, CN, and UE can implement techniques for managing handover procedures. [Figure 1B] Figure 1A is a block diagram of an exemplary base station in which a centralized unit (CU) and a distributed unit (DU) can operate. [Figure 2] Figure 1A is a block diagram of an exemplary protocol stack that the UE follows when communicating with the base station. [Figure 3] Figure 1A is a messaging diagram of an exemplary scenario in which the RAN sends a message to the UE to configure the UE with parameters to set up, modify, or release radio resources, in order to recover from sending the UE a conditional handover configuration that does not include parameters to set up, modify, or release radio resources according to the interface message received from the CN. [Figure 4A]Figure 1A is a messaging diagram of an exemplary scenario in which the base station omits sending a conditional handover configuration to the UE that does not include parameters for setting up, modifying, or releasing radio resources according to the interface message received from the CN. [Figure 4B] Figure 1A is a messaging diagram of an exemplary scenario in which the base station sends a conditional handover configuration to the UE, containing parameters for setting up, modifying, or releasing radio resources according to the interface message received from the CN. [Figure 5] Figure 1A is a messaging diagram illustrating an exemplary scenario in which the base station forwards NAS messages received from the CN to the UE while a conditional handover preparation procedure is being performed to set up, modify, or release radio resources. [Figure 6] Similar to the scenario in Figure 3, but in an illustrative scenario, Figure 1B shows a messaging diagram of a distributed base station sending a message to the UE that configures the UE with parameters to set up, modify, or release radio resources. [Figure 7A] This is a messaging diagram for an exemplary scenario, similar to the scenario in Figure 4A, but where the distributed base stations in Figure 1B omit sending a conditional handover configuration that does not include parameters for setting up, modifying, or releasing radio resources. [Figure 7B] This is a messaging diagram for an exemplary scenario, similar to the scenario in Figure 4B, but where the distributed base stations in Figure 1B send a conditional handover configuration that includes parameters for setting up, modifying, or releasing radio resources. [Figure 8] This is a messaging diagram for an exemplary scenario, similar to the scenario in Figure 5, but where the distributed base stations in Figure 1B forward NAS messages to the UE. [Figure 9]It is a flow diagram of an exemplary method for transmitting, to a UE, a message configuring the UE with parameters for setting up, modifying, or releasing radio resources to recover from transmitting, to 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 a CN, which may be implemented in the RAN of the present disclosure. [Figure 10] It is a flow diagram of an exemplary method similar to the method of Figure 9, but the method may be implemented in a distributed base station of the present disclosure. [Figure 11] It is a flow diagram of an exemplary 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 determining to perform the handover preparation procedure or while performing the handover preparation procedure, which may be implemented in the RAN of the present disclosure. [Figure 12] It is a flow diagram of an exemplary method similar to the method of Figure 11, but the CN-BS interface message is received before determining to perform the handover preparation procedure or before performing the handover preparation procedure. [Figure 13] It is a flow diagram of an exemplary method for transmitting, to a RAN, a follow-up message for setting up, modifying, or releasing radio resources for a UE in response to receiving, from the RAN, an indication that setting up, modifying, or releasing radio resources has failed previously, which may be implemented in the CN of the present disclosure. [Figure 14] It is a flow diagram of an exemplary method for configuring a UE, which may be implemented in the RAN of the present disclosure. [Figure 15] It is a flow diagram of an exemplary method for configuring a UE, which may be implemented in the CN of the present disclosure. Mode for Carrying Out the Invention

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

[0018] Referring first to Figure 1A, the exemplary wireless communication system 100 includes a UE 102, a base station (BS) 104, a base station 106, and a core network (CN) 110. 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] While there are other components, the EPC111 may include, among others, a Serving Gateway (SGW) 112, a Mobility Management Entity (MME) 114, and a Packet Data Network Gateway (PGW) 116. The SGW 112 is typically 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 relational functions. The PGW 116 is typically configured to provide connectivity from the UE 102 to one or more external packet data networks, such as the Internet network and / or an Internet Protocol (IP) Multimedia Subsystem (IMS) network. The 5GC160 includes a User Plane Function (UPF) 162, Access and Mobility Management (AMF) 164, and / or Session Management Function (SMF) 166. Generally, UPF162 is configured to forward user plane packets related to voice calls, video calls, and internet traffic; AMF164 is configured to manage authentication, registration, paging, and other relational functions; and SMF166 is configured to manage PDU sessions.

[0020] As illustrated in Figure 1A, base station 104 supports cell 124, and base station 106A supports cell 126. Cells 124 and 126 can partially overlap, thereby allowing UE 102 to hand over from cell 124 to cell 126 or vice versa. In addition, base station 104 can support cell 123, which can overlap with cell 124. In addition, base station 106 can support cell 125, which can overlap with cell 126. To directly exchange messages during the execution of the handover preparation scenario described below, base stations 104 and 106 can support X2 or Xn interfaces. In general, CN 110 can be connected to any number of suitable base stations that support NR cells 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-temporary computer-readable memory for storing machine-readable instructions executable on one or more general-purpose processors and / or dedicated processing units. In one exemplary implementation, the processing hardware 130 includes a conditional configuration controller 132 configured to manage conditional configurations for one or more CHO procedures. The processing hardware 130 also includes an immediate configuration controller 134 configured to manage immediate configurations for one or more immediate procedures (e.g., RRC connection re-establishment, RRC reconfiguration, immediate handover procedures).

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

[0023] Referring again to Figure 1A, the UE102 is equipped with processing hardware 150 which may include one or more general-purpose processors such as a CPU, and non-temporary computer-readable memory for storing machine-readable instructions that can be executed on one or more general-purpose processors and / or dedicated processing units. In one exemplary implementation, the processing hardware 150 includes a UE conditional configuration controller 152 configured to manage conditional configurations for one or more CHO procedures. The processing hardware 150 also includes an immediate configuration controller 154 configured to manage immediate configurations 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 messaging diagrams and flowcharts below for receiving conditional configurations, releasing conditional configurations in response to specific events, and applying conditional configurations. For example, UE 102 may apply a conditional configuration when it determines that the conditions associated with a conditional configuration for a CHO are met. As used herein, the term “condition” may refer to a single, detectable state or event (e.g., a specific 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] During operation, UE102 may use a radio bearer (e.g., DRB or SRB) that terminates at base station 104 or base station 106. UE102 may apply one or more security keys when communicating on the radio bearer in the uplink (e.g., from UE102 to base station 104 or 106) and / or downlink (e.g., from base station 104 or 106 to UE102). In some cases, UE102 may use a RAT to communicate with base station 104 or 106. The following examples may specifically refer to a particular RAT type, 5G NR or EUTRA, but generally, the technology of this disclosure can also be applied to other suitable radio access and / or core network technologies (e.g., sixth-generation (6G)).

[0026] In some implementations, the CN110 connects the UE102 to an Internet Protocol (IP) Multimedia Subsystem (IMS) network (not shown in Figure 1A) via the RAN105. The IMS network can provide the UE102 with a variety of IMS services, including IMS short messages, IMS unstructured supplementary service data (USSD), IMS value-added service data, IMS additional service data, IMS voice calls, and IMS video calls. For this purpose, entities operating within the IMS network (e.g., servers or groups of servers) support packet exchange with the UE. Packets can transmit signaling (such as Session Initiation Protocol (SIP) messages, IP messages, or other preferred messages) as well as data ("or media") such as voice or video. Although the technology of this disclosure is described with specific reference to IMS, the CN110 can generally connect to or include any preferred system that provides packet-based calling.

[0027] In several scenarios, the wireless communication system 100 supports instantaneous handover between cells. In one scenario, for example, UE 102 first connects to base station 104, and base station 104 subsequently prepares for instantaneous handover with base station 106 via an interface (e.g., X2 or Xn). In this scenario, base stations 104 and 106 act as the source base station and target base station, respectively. In preparing for the handover, source base station 104 sends a Handover Request message to target base station 106. In response, target base station 106 includes an instantaneous handover command message in a Handover Request Acknowledge message and sends the Handover Request Acknowledge message to source base station 104. Then, in response to receiving the Handover Request Acknowledge message, source base station 104 transmits a handover command message to UE 102.

[0028] Upon receiving an immediate handover command message, UE102 immediately responds to the immediate handover command by attempting to connect to the target base station 106. To connect to the target base station 106, UE102 may perform a random access procedure on a cell (e.g., cell 126) with the target base station 106, and then (after obtaining access to the channel) transmit a handover completion message to the target base station 106 via the cell of 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, UE 102 initially connects to base station 104, and base station 104 later performs a conditional handover preparation procedure with base station 106 via an interface (e.g., X2 or Xn) to prepare for a potential handover of UE 102 to base station 106. In this scenario, base stations 104 and 106 act as source base station and candidate base station, respectively. In the conditional handover preparation procedure, source base station 104 sends a Handover Request message to candidate base station 106. In response, candidate base station 106 includes a conditional handover command message in a Handover Request Acknowledge message and sends the Handover Request Acknowledge message to source base station 104. Source base station 104 then, in response to receiving the Handover Request Acknowledge message, transmits the conditional handover command message to UE 102.

[0030] Upon receiving a conditional handover command message, UE102 does not immediately respond to the message by attempting to connect to candidate base station 106. Instead, UE102 connects to candidate base station 106 in accordance with the conditional handover command message only if UE102 determines that the conditions for handing over to candidate cell 126 of candidate base station 106 are met. In the conditional handover command message, base station 106 provides a configuration for candidate cell 126 (i.e., a configuration that UE102 can use to connect to base station 106 via candidate cell 126).

[0031] Before the condition is met, UE102 is not yet connected to candidate base station 106. In other words, candidate base station 106 has not yet connected to UE102 and provided services. In some implementations, the condition may be that the signal strength / quality is sufficiently "good" as measured by UE102 on candidate cell 126 of candidate base station 106, and / or that the signal strength / quality is poor as measured by UE102 on cell 124 of source base station 104. For example, this condition may be met if one or more measurement results obtained by UE102 (when performing measurements on candidate cell 126) exceed a threshold configured by source base station 104, which may be a predetermined or pre-configured threshold, and / or if one or more measurement results obtained by UE102 (when performing measurements on candidate cell 126) exceed a threshold configured by 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 measured by UE102 on candidate cell 126 is at least a threshold (e.g., at least an offset) better than the signal strength / quality measured by UE102 on cell 124. The threshold may be configured by source base station 104, or it may be a predetermined or preconfigured offset. If UE102 determines that the condition is met, candidate base station 106 becomes the target base station 106 for UE102, and UE102 attempts to connect to the target base station 106. To connect to the target base station 106, UE102 may perform a random access procedure on candidate cell 126 together with the target base station 106, and then (after obtaining access to the channel) transmit a handover completion message to the target base station 106 via candidate cell 126. After UE102 successfully completes the random access procedure and / or transmits a handover completion message, the target base station 106 becomes the source base station 106 for UE102, and UE102 initiates data communication with the source base station 106.

[0032] Base stations 104 and 106 can be connected to the same CN110, which may be an evolved packet core (EPC) 111 or a fifth-generation core (5GC) 160. Base station 104 may be implemented as an eNB supporting the S1 interface for communicating with the EPC 111, an ng-eNB supporting the NG interface for communicating with the 5GC 160, or an NR radio interface, or even an NG interface for communicating with the 5GC 160. Base stations 104 and 106 may support the X2 or Xn interface to directly exchange messages during the execution of the scenarios described below.

[0033] Generally, the wireless communication network 100 may include any suitable number of base stations that support NR cells and / or EUTRA cells. More specifically, an EPC 111 or 5GC 160 may be connected to any suitable number of base stations that support NR cells and / or EUTRA cells. The following examples specifically refer to certain CN types (EPC, 5GC) and RAT types (5G NR and EUTRA), but generally, the technology of this disclosure can also be applied to other suitable radio access and / or core network technologies such as sixth-generation (6G) radio access and / or 6G core networks or 5G NR-6G DC.

[0034] Figure 1B depicts an exemplary distributed or non-aggregated implementation of one or more of the base stations 104 and 106. In this implementation, 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 for storing machine-readable instructions executable on the general-purpose processors and / or dedicated processing units. For example, the CU 172 may comprise the processing hardware 130 or 140 in Figure 1A.

[0035] Each DU174 also includes processing hardware which may comprise one or more general-purpose processors (e.g., CPUs) and computer-readable memory for storing machine-readable instructions executable on one or more general-purpose processors and / or dedicated processing units. For example, the processing hardware may comprise a media 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 process 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, CU172 may include a logical node CU-CP172A that hosts the control plane portion of the CU172's Packet Data Convergence Protocol (PDCP) protocol. CU172 may also include a logical node CU-UP172B that hosts the user plane portion of the CU172's PDCP protocol and / or Service Data Adaptation Protocol (SDAP) protocol. CU-CP172A can transmit control information (e.g., RRC messages, F1 application protocol messages), and CU-UP172B can transmit data packets (e.g., SDAP PDUs or Internet Protocol packets).

[0037] A CU-CP172A can be connected to multiple CU-UP172Bs through the E1 interface. The CU-CP172A selects the appropriate CU-UP172B for the requested service to the UE102. In some implementations, a single CU-UP172B can be connected to multiple CU-CP172As through the E1 interface. A CU-CP172A can be connected to one or more DU174s through the F1-C interface. A CU-UP172B can be connected to one or more DU174s through the F1-U interface under the control of the same CU-CP172A. In some implementations, a single DU174 can be connected to multiple CU-UP172Bs under the control of the same CU-CP172A. In such implementations, connectivity between the CU-UP172B and DU174 is established by the CU-CP172A using bearer context management functionality.

[0038] Figure 2 illustrates, in a simplified manner, an exemplary protocol stack 200 that UE102 may follow when communicating with an eNB / ng-eNB or gNB (for example, one or more of base stations 104, 106).

[0039] In an exemplary stack 200, the EUTRA physical layer (PHY) 202A provides a transport channel to the EUTRA MAC sublayer 204A, which in turn provides a logical channel to the EUTRA RLC sublayer 206A. The EUTRA RLC sublayer 206A then provides an RLC channel to the EUTRA PDCP sublayer 208, and in some cases, to the NR PDCP sublayer 210. Similarly, the NR PHY 202B provides a transport channel to the NR MAC sublayer 204B, which in turn provides a logical channel to the NR RLC sublayer 206B. The NR RLC sublayer 206B then provides data transfer services to the NR PDCP sublayer 210. The NR PDCP sublayer 210 can then provide data transfer services to the Ethernet protocol layer (not shown in Figure 2), the Internet Protocol (IP) layer (not shown in Figure 2), the Service Data Adaptation Protocol (SDAP) 212, and / or the Radio Resource Control (RRC) sublayer (not shown in Figure 2). In several implementations, the UE102 supports both the EUTRA and NR stacks as shown in Figure 2 to support handover between EUTRA and NR base stations. Furthermore, as illustrated in Figure 2, the UE102 can support layering of the NR PDCP 210 on the EUTRA RLC 206A and the SDAP sublayer 212 on the NR PDCP sublayer 210.

[0040] EUTRA PDCP sublayer 208 and NR PDCP sublayer 210 receive packets that may be referred to as Service Data Units (SDUs) (for example, from the Internet Protocol (IP) layer layered directly or indirectly on top of PDCP layer 208 or 210) and output packets that may be referred to as Protocol Data Units (PDUs) (for example, to RLC layer 206A or 206B). Unless the difference between SDUs and PDUs is relevant, for simplicity's sake, both SDUs and PDUs are referred to as “packets” in this disclosure.

[0041] On the control plane, EUTRA PDCP sublayer 208 and NR PDCP sublayer 210 can provide an SRB for exchanging, for example, RRC messages or Non-Access Stratum (NAS) messages. On the user plane, EUTRA PDCP sublayer 208 and NR PDCP sublayer 210 can provide a DRB to support data exchange. The data exchanged on NR PDCP sublayer 210 may be SDAP PDUs, Internet Protocol (IP) packets, or Ethernet packets.

[0042] Figures 3 to 5 illustrate a conditional handover scenario in which a RAN (e.g., RAN105) prepares for a conditional handover from a source base station (S-BS) (e.g., S-BS104) 174A to a candidate base station (C-BS) (e.g., C-BS106) to a UE (e.g., UE102).

[0043] Referring first to Figure 3, in Scenario 300, base station 104A operates as the source base station (S-BS), and base station 106A operates as the candidate base station (C-BS).

[0044] First, UE102 transmits data to S-BS104 via one or more cells, such as a PCell (e.g., cell 124) and zero, one, or more secondary cells (SCells). More specifically, UE102 can transmit data and control signals to S-BS104 according to a first base station (BS) configuration. The first BS configuration may include one or more configuration parameters that UE102 uses to communicate with S-BS104. These configuration parameters may constitute radio resources for UE102 to communicate with S-BS104 via the cells described above. The configuration parameters may constitute 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. The data transmitted between UE102 and S-BS104 may include downlink and / or uplink PDUs transmitted by S-BS104 to and / or received from UE102. The control signals transmitted between UE102 and S-BS104 may include downlink and uplink control signals. The downlink control signal may include a channel status information reference signal, a tracking reference signal, and / or a physical downlink control channel (PDCCH) transmitted by S-BS104 to UE102. The uplink control signal may include a hybrid automatic retransmission request (HARQ) acknowledgment or denial, channel status information, a scheduling request, and / or a sounding reference signal transmitted by UE102 to S-BS104.

[0045] Later, S-BS104 initiates the CHO preparation procedure by deciding to request C-BS106 to provide UE102 with a conditional configuration (i.e., a C-BS configuration) for the CHO procedure, which UE102 will provide to C-BS106 for when the conditions are met, enabling UE102 to communicate with C-BS106 via a candidate cell (e.g., cell 126). S-BS104 may make this decision based on one or more measurements received directly from UE102 (e.g., via an SRB established between UE102 and S-BS104, or via a physical control channel) that are above (or below) one or more predetermined thresholds, or from, for example, S-BS104 analyzing measurements of a signal, control channel, or data channel received from UE102, or from another appropriate event (e.g., UE102 is moving toward C-BS106).

[0046] In response to this decision, S-BS104 transmits a Handover Request message to C-BS106, for example, containing a CHO information request.304 In response to the Handover Request message, C-BS106 generates a C-BS configuration containing information that enables UE102 to communicate with C-BS106 via a candidate cell (e.g., cell 126). C-BS106 includes the C-BS configuration in a Handover Request Acknowledge message to UE102 and then transmits a Handover Request Acknowledge message to S-BS104 in response to the Handover Request message.306 In some implementations, instead of including the C-BS configuration in the Handover Request Acknowledge message, C-BS106 may include a CHO command in the Handover Request Acknowledge message. In such a case, C-BS106 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 CHO command are interchangeable. In some implementations, after receiving the C-BS configuration, S-BS104 includes in the RRC reconfiguration message the C-BS configuration and a trigger condition configuration (e.g., the triggerCondition-r16 or condExecutionCond-r16 field) that specifies conditions (or "trigger conditions") that UE102 may use to determine whether to execute the C-BS configuration or connect to candidate cell 126. That is, if UE102 determines that the conditions are met, UE102 may connect to candidate cell 126 using the C-BS configuration. If UE102 does not determine that the conditions are met, UE102 will not connect to candidate cell 126.

[0047] S-BS104 transmits an RRC reconstruction message to UE102 308, and UE102, in response to receiving the RRC reconstruction message, transmits an RRC reconstruction complete message to S-BS104 310. Events 304, 306, and 308 are collectively referred to as the CHO preparation procedure in Figure 3.

[0048] In some implementations, the S-BS104 can include the C-BS configuration in a conditional configuration field or information element (IE) of the RRC reconfiguration message (for example, the CondReconfigToAddMod-r16 IE). The S-BS104 can further include a configuration identity / identifier (ID) associated with the C-BS configuration in the conditional configuration field / IE, thereby allowing the UE102 to identify and store the C-BS configuration.

[0049] After the CHO preparation procedure (for example, after transmitting the RRC reconfiguration complete message 310), after some time, UE 102 may determine that the conditions for connecting to candidate cell 126 have been met 312, and in response to this, execute a random access procedure (also called a “random access channel” or “RACH” procedure) on candidate cell 126 together with C-BS 106, for example, using the random access configuration included in the C-BS configuration 316. UE 102 disconnects the S-BS 104 from cell 124 in response to event 312 or 316 314. In some implementations, the random access procedure in event 316 may be a four-step random access procedure or a two-step random access procedure. In other implementations, the random access procedure may be a contention-based random access procedure or a contention-free random access procedure.

[0050] UE102 sends an RRC reconstruction complete message to C-BS106 via candidate cell 126 during or after the execution of the random access procedure 316 318. In some implementations, UE102 may include the RRC reconstruction complete message in "Message 3" for a four-step random access procedure or "Message A" for a two-step random access procedure, according to the C-BS configuration.

[0051] After 316 has performed the random access procedure, or 318 has transmitted the RRC reconfiguration complete message, UE102 communicates with C-BS106 by using the C-BS configuration 320. Events 312, 314, 316, 318, and 320 are collectively referred to as the CHO execution procedure in Figure 3.

[0052] In some implementations, during the CHO execution procedure, CN110 may send a first CN-BS interface message to S-BS104 to execute resource management procedures (e.g., E-RAB Setup procedure, E-RAB Modify procedure, E-RAB Release procedure, PDU Session Resource Setup procedure, PDU Session Resource Modify procedure, PDU Session Resource Release procedure, or downlink NAS transport procedures according to 3GPP specifications 36.413 and 38.413) and request that resources (e.g., radio resources) be set up, modified, or released for UE102 for various reasons. For example, CN110 may send a first CN-BS interface message for IMS mobile terminating services (e.g., voice calls, video calls) to UE102. As another example, CN110 may send a first CN-BS interface message for multicast or broadcast service (MBS) services to UE102. In some implementations, the first CN-BS interface message may 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 may 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 another implementation, the first CN-BS interface message may be a downlink (DL) NAS Transport message containing a NAS message.In some implementations, the CN110 can send NAS messages to set up, modify, or release resources or NAS configurations for the UE102. In other implementations, the CN110 can include application data, Short Message Service (SMS) messages, or LTE Positioning Protocol (LPP) messages in the NAS messages.

[0053] If, in response to a first CN-BS interface message, UE102 has already disconnected from S-BS104 during the CHO execution procedure, and S-BS104 transmits an RRC message (e.g., an RRC reconfiguration message) to UE102 to set up, correct, or release radio resources to UE102, S-BS104 will fail to transmit the RRC message to UE102.

[0054] To ensure that RAN105 can properly set up, modify, or release radio resources for UE102, S-BS104 sends a first BS-CN interface message to CN110.324 In some implementations, S-BS104 includes a cause value in the first BS-CN interface message to indicate why S-BS104 failed to set up, modify, or release radio resources for UE102. For example, the cause value could be "Radio connection with UE lost". In some implementations, the first BS-CN interface message may 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 instruction from S-BS104 to UE102 that it failed to send a NAS message from CN110.

[0055] After executing the random access procedure 316, or after receiving the RRC reconfiguration complete message 318, C-BS106 may establish a UE-related signaling connection between UE102 and CN110 and send a Path Switch Request message to CN110 requesting a switch of the downlink termination point of the transport bearer directed to C-BS106 326. In response to the Path Switch Request message, CN110 performs a route switch for UE102 and sends a Path Switch Request Acknowledge message to C-BS106 328. To perform the route switch, CN110 may update the downlink route from S-BS104 to UE102 to a downlink route from C-BS106 to UE102. Similarly, CN110 may update the uplink route from UE102 to S-BS104 to an uplink route from UE102 to C-BS106.

[0056] After performing a route switch, CN110 sends a second CN-BS interface message to C-BS106 to set up, modify, or release the radio resources of UE102.330 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, but with some differences. For example, CN110 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 and second UE IDs are associated with UE102. The first UE ID is different from the second UE ID. For example, the first UE ID includes the first AMF UE NGAP ID and / or the first RAN UE NGAP ID, and the second UE ID includes the second AMF UE NGAP ID and / or the second RAN UE NGAP ID. The first AMF UE NGAP ID may or may not be the same as the second AMF UE NGAP ID. The first RAN UE NGAP ID may or may not be the same as the second RAN UE NGAP ID. In another example, the first UE ID includes the first MME UE S1AP ID and / or the first eNB UE S1AP ID, and the second UE ID includes the second MME UE S1AP ID and / or the second eNB UE S1AP ID. The first MME UE S1AP ID may or may not be the same as the second MME UE S1AP ID. The first eNB UE S1AP ID may or may not be the same as the second eNB UE S1AP ID.

[0057] In some implementations, CN110 includes the same PDU Session ID or E-RAB ID in the first and second CN-BS interface messages. In other implementations, CN110 includes the same network slice information, such as Network Slice Selection Assistance Information (NSSAI) or Single NSSAI (S-NSSAI), in the first and second CN-BS interface messages. In yet another implementation, CN110 includes the same PDU Session Resource Setup Request Transfer IE in the first and second CN-BS interface messages. In yet another implementation, CN110 includes the first PDU Session Resource Setup Request Transfer IE in the first CN-BS interface message and the second PDU Session Resource Setup Request Transfer IE in the second CN-BS interface message. Parts of the first PDU Session Resource Setup Request Transfer IE and parts of the second PDU Session Resource Setup Request Transfer IE may be the same, while the remaining parts of the first and second PDU Session Resource Setup Request Transfer IEs may be different. In some implementations, CN110 includes the same Quality of Service (QoS) parameters (values), transport layer address, and / or tunnel endpoint ID (TEID) in the first and second CN-BS interface messages. In other implementations, CN110 includes different QoS parameters (values), transport layer address, and / or TEID in the first and second CN-BS interface messages, respectively.

[0058] In response to receiving a second CN-BS interface message, C-BS106 can be configured in various ways to set up, modify, or release radio resources to UE102 in accordance with the second CN-BS interface message. When releasing radio resources, C-BS106 can release all radio resources configured for UE102 (i.e., release the radio connection to UE102) or release some of the radio resources configured for UE102. For example, C-BS106 may send an RRC release message to UE102 to release all radio resources configured for UE102. In another example, C-BS106 may send an RRC reconfiguration message to release some of the radio resources configured for UE102. In yet another example, C-BS106 may suspend the radio connection to UE102 by sending an RRC release message to UE102 to release the physical radio resources of the radio resources configured for UE102.

[0059] In some implementations, if the second CN-BS interface message is a DL Transport message containing a NAS message to set up, modify, or release resources for UE102, C-BS106 can forward the NAS message to UE102. Thus, RAN105 can properly set up, modify, or release resources for UE102 via C-BS106.

[0060] In other implementations, if the second CN-BS interface message is a PDU session Resource message or E-RAB message containing instructions or informational elements for setting up, modifying, or releasing radio resources for UE102, C-BS106 can generate a second BS configuration for setting up, modifying, or releasing radio resources for UE102. C-BS106 can transmit an RRC reconfiguration message containing the second BS configuration to UE102 332, and in response to the RRC reconfiguration message, UE102 transmits an RRC reconfiguration complete message to C-BS106 334. After receiving the RRC reconfiguration message from C-BS106 332, UE102 communicates with C-BS106 using the second BS configuration 338. C-BS106 may omit a random access configuration in the second BS configuration so that UE102 does not perform a random access procedure in response to the second BS configuration. Therefore, RAN105 can properly set up, modify, or release wireless resources for UE102 via C-BS106.

[0061] In other implementations, if the second CN-BS interface message is a DL NAS Transport message, a PDU session Resource message, or an E-RAB message to release radio resources to UE102, C-BS106 can send an RRC release message to release the radio resources. Thus, RAN105 can properly release radio resources to UE102 via C-BS106.

[0062] In some implementations, after C-BS106 decides to set up, modify, or release radio resources for UE102, C-BS106 sends a second BS-CN interface message to CN110 in response to a second CN-BS interface message indicating that C-BS106 has successfully set up, modified, or released radio resources for UE102 336. In other implementations, after or in response to having transmitted a NAS message 342, transmitted an RRC reconfiguration message 332, or received an RRC reconfiguration complete message 334, C-BS106 sends a second BS-CN interface message to CN110 336. In some implementations, after C-BS106 decides to release radio resources to UE102 or transmits an RRC release message to release radio resources 340, C-BS106 responds to a second CN-BS interface message by sending a third BS-CN interface message to CN110 indicating that C-BS106 has successfully released radio resources to UE102 341.

[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. Unlike the first BS-CN interface message, which in some implementations may contain a cause value indicating why S-BS104 failed to set up, modify, or release the radio resources for UE102, C-BS106 succeeded in setting up, modifying, or releasing the radio resources for UE102, and therefore the second or third BS-CN interface message does not need to contain a similar cause value.

[0064] In the implementation of Scenario 300 described above, the C-BS configuration may include several configuration parameters for UE102 to communicate with C-BS106. These configuration parameters may constitute radio resources for UE102 to communicate with C-BS106 via candidate cell 126 (i.e., candidate primary cell (C-PCell)) and zero, one, or more candidate secondary cells (C-SCell) of C-BS106. The multiple configuration parameters may constitute zero, one, or more radio bearers, each of which may include one or more SRBs and / or one or more DRBs. An SRB may include SRB1 and / or SRB2.

[0065] In some implementations, the C-BS configuration generated by C-BS106 is a complete self-contained configuration (i.e., a "full" configuration). Within the C-BS configuration, C-BS106 may include a full configuration instruction (e.g., an IE or field) indicating that the C-BS configuration is a complete self-contained configuration. UE102 can communicate with C-BS106 using the C-BS configuration directly without referring to a first BS configuration previously used by UE102.

[0066] In other implementations, the C-BS configuration may include one or more configurations on top of the first BS configuration (i.e., the C-BS configuration is a "delta" configuration). UE102 can use this delta C-BS configuration, along with at least some of the configuration parameters in the first BS configuration, to communicate with C-BS106 in event 320. The delta C-BS configuration is not a complete configuration and does not include a full configuration display. UE102 cannot use only the delta C-BS configuration to communicate with C-BS106; instead, it also refers to the first BS configuration stored in UE102, as shown in event 302. The delta C-BS configuration may include one or more configuration parameters for UE102 to communicate with C-BS106. These configuration parameters may constitute the radio resources for UE102 to communicate with C-BS106 via candidate cell 126 (i.e., C-PCell) and C-BS106 via zero, one, or more C-SCells. The configuration parameters can constitute zero, one, or more wireless bearers. A wireless bearer can include one or more SRBs and / or one or more DRBs. The configuration parameters may or may not include measurement configurations and / or security configurations.

[0067] If the C-BS configuration is a full configuration, C-BS106 may optionally update the C-BS configuration in the second BS configuration (i.e., configure a new configuration in the C-BS configuration, modify an existing configuration, and / or release an existing configuration). If the C-BS configuration is instead a delta configuration, C-BS106 may update the C-BS configuration and / or the first BS configuration in the second BS configuration (i.e., configure a new configuration in the C-BS configuration and / or the first BS configuration, modify an existing configuration, and / or release an existing configuration).

[0068] In response to the second RRC reconfiguration message, UE102 updates the first C-BS configuration and / or the first BS configuration using the second BS configuration. Thus, UE102 communicates with C-BS106 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 constitutes a C-PCell126, and may constitute zero, one, or more C-SCells of C-BS106. In some implementations, the C-BS configuration is contained within an RRCReconfiguration message, an RRCReconfiguration-IE, or a CellGroupConfig IE compliant with 3GPP specification 38.331. In these implementations, the RRC reconfiguration completion message in 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 constitutes a C-PCell126, and may or may not include a SCellToAddModList IE that constitutes one or more C-SCells of C-BS106. In other implementations, the C-BS configuration may be an RRCConnectionReconfiguration message or an RRCConnectionReconfiguration-IE compliant with 3GPP specification 36.331. In these implementations, the RRC reconfiguration completion message in event 310 can be an RRCConnectionReconfigurationComplete message.

[0070] In some implementations, the first (or second) BS configuration may include a CellGroupConfig IE that configures zero, one, or more SCells of PCell124 (or 126) and S-BS104 (or C-BS106). In some implementations, the first (or second) BS configuration may be an RRCReconfiguration message, RRCReconfiguration-IE, or CellGroupConfig IE compliant with 3GPP specification 38.331, or may include a configuration within an RRCReconfiguration message, RRCReconfiguration-IE, or CellGroupConfig IE. In other implementations, the first (or second) BS configuration may include a RadioResourceConfigDedicated IE and / or MobilityControlInfo IE that configures PCell124 (or 126), and may or may not include a SCellToAddModList IE that configures one or more SCells of S-BS104 (or C-BS106). In other implementations, the first (or second) BS configuration may include configurations within the RadioResourceConfigDedicated IE and / or MobilityControlInfo IE.

[0071] When S-BS104 is implemented as a gNB, the RRC reconfiguration message in event 308 and the RRC reconfiguration completion message in event 310 can be the RRCReconfiguration message and the RRCConnectionReconfigurationComplete message, respectively. When S-BS104 is implemented as an eNB or ng-eNB, the RRC reconfiguration message in event 308 and the RRC reconfiguration completion message in event 310 can be implemented as the RRCReconfiguration message and the RRCConnectionReconfigurationComplete message, respectively.

[0072] When C-BS106 is implemented as a gNB, the RRC reconfiguration message in event 332 and the RRC reconfiguration completion message in event 334 can be the RRCReconfiguration message and the RRCConnectionReconfigurationComplete message, respectively. When C-BS106 is implemented as an eNB or ng-eNB, the RRC reconfiguration message 332 and the RRC reconfiguration completion message 334 can be implemented as the RRCReconfiguration message and the RRCConnectionReconfigurationComplete message, respectively.

[0073] Next, referring to Figure 4A, at the start of scenario 400A, UE102 transmits data to S-BS104 via one or more cells (e.g., cell 124), similar to event 302. Also, similar to events 304 and 306, S-BS104 initiates the CHO preparation procedure by transmitting a Handover Request message to C-BS106, which then transmits a Handover Request Acknowledge message to UE102, including the C-BS configuration. The C-BS configuration may include information that allows UE102 to communicate with C-BS106 via a candidate cell (e.g., cell 126).

[0074] In Scenario 300, CN110 may send a first CN-BS interface message to S-BS104 requesting that S-BS104 set up, modify, or release radio resources to UE102 after S-BS104 has completed the CHO preparation procedure (for example, after S-BS104 has sent the C-BS configuration to UE102 308). In Scenario 400A, CN110 may send a CN-BS interface message to S-BS104 requesting that S-BS106 set up, modify, or release radio resources to UE102 during the CHO preparation procedure (for example, from after C-BS106 has received the Handover Request message 404 until before C-BS106 has transmitted the Handover Request Acknowledge message 406). In some implementations, the CN-BS interface message may be a PDU session resource message or an E-RAB message, similar to the message described above in Figure 3. Since S-BS104 receives a CN-BS interface message 422 after sending a Handover Request message 404 to C-BS106, S-BS104 cannot notify C-BS106 to change the configuration parameters of the C-BS configuration in order to set up, modify, or release radio resources for UE102 according to the CN-BS interface message. Therefore, C-BS106 sends S-BS104 a C-BS configuration that does not include the configuration parameters for setting up, modifying, or releasing radio resources according to the CN-BS interface message 406.

[0075] Therefore, S-BS104 decides not to transmit the C-BS configuration to UE102 409. In some implementations, S-BS104 may release the C-BS configuration. Instead of transmitting the C-BS configuration to UE102, in response to decision 409, S-BS104 generates a second BS configuration for UE102 to set up, modify, or release radio resources if the CN-BS interface message instructs UE102 to set up, modify, or release radio resources, and in some implementations, transmits an RRC reconfiguration message to UE102 containing the second BS configuration 432. In this way, S-BS104 ensures that UE102 can set up, modify, or release radio resources via the second BS configuration. In response to the RRC reconfiguration message, UE102 transmits an RRC reconfiguration complete message to S-BS104 434.

[0076] In other implementations, in response to decision 409, S-BS104 may generate an RRC release message for UE102 to release radio resources if the CN-BS interface message instructs UE102 to release radio resources. S-BS104 may transmit the RRC release message to UE102 440, causing UE102 to transition to an idle or inactive state.

[0077] Therefore, in the implementations described above, RAN105 can properly set up, modify, or release radio resources for UE102 via S-BS104. In some implementations, after events 432, 434, or 440, S-BS104, in response to a CN-BS interface message, as with events 336 or 341, sends a BS-CN interface message to CN110 indicating that S-BS104 has successfully set up, modified, or released radio resources for UE102 424.

[0078] Next, referring to Figure 4B, in Scenario 400A, S-BS104 decides not to send the C-BS configuration to UE102, but in Scenario 400B, S-BS104 decides to send the C-BS configuration to UE102.

[0079] At the start of Scenario 400B, as in Scenario 400A, UE102 transmits data to S-BS104 via one or more cells (e.g., cell 124) 402, and S-BS104 initiates the CHO preparation procedure with C-BS106A in events 404 and 406. However, in contrast to Scenario 400A, in Scenario 400B, CN110 sends a CN-BS interface message to S-BS104 requesting that CN110 set up, modify, or release radio resources for UE102 during the CHO preparation procedure 422, whereas in Scenario 400B, CN110 sends a CN-BS interface message to S-BS104 requesting that S-BS104 set up, modify, or release radio resources for UE102 before S-BS104 initiates the CHO preparation procedure 423. Thus, S-BS104 can generate the second BS configuration described above in Figure 4A and include the second BS configuration in the Handover Request message in event 404. In addition, S-BS104 determines the configuration parameters of the interface protocol format (e.g., X2 or Xn application protocol) after considering CN-BS messages requesting that S-BS104 set up, modify, or release radio resources. S-BS104 then includes the UE capabilities and configuration parameters within the Handover Request message.

[0080] As a result, C-BS106 receives the second BS configuration (and therefore is aware of the configuration parameters to set up, modify, or release radio resources according to the CN-BS interface message), so C-BS106 can generate a C-BS configuration on top of the second BS configuration (i.e., the C-BS configuration is a "delta" configuration). Alternatively, S-BS104 does not include the second BS configuration in the Handover Request message. In this alternative implementation, C-BS106 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. C-BS106 can then include the C-BS configuration in the Handover Request Acknowledge message and subsequently transmit the Handover Request Acknowledge message to S-BS104.

[0081] Next, S-BS104 may decide to send the C-BS configuration to UE102 410, and then transmit an RRC reconfiguration message to UE102, including the C-BS configuration and the second BS configuration 433. S-BS104 may include a trigger condition configuration in the RRC reconfiguration message, as with event 308. As a result, UE102 can set up, modify, or release the radio resources according to at least some of the configuration parameters in the second BS configuration, and even perform a CHO procedure when the conditions by the C-BS configuration are met, thereby communicating with C-BS106 in event 320. In this way, S-BS104 ensures that UE102 can set up, modify, or release the radio resources via the second BS configuration. In response to the RRC reconfiguration message, UE102 transmits an RRC reconfiguration complete message to S-BS104 434.

[0082] Therefore, in the implementations described above, RAN105 can properly set up, modify, or release radio resources to UE102 via S-BS104. In some implementations, after event 433 or 434, S-BS104, in response to a CN-BS interface message, as with event 336 or 341, sends a BS-CN interface message to CN110 indicating that S-BS104 has successfully set up, modified, or released radio resources to UE102 424.

[0083] Next, referring to Figure 5, at the start of scenario 500, UE102 transmits data to S-BS104 via one or more cells (e.g., cell 124), similar to event 302. Also, similar to events 304 and 306, S-BS104 initiates the CHO preparation procedure by transmitting a Handover Request message to C-BS106, 504 and C-BS106 then transmits a Handover Request Acknowledge message to UE102, 506 containing the C-BS configuration. The C-BS configuration may include information that allows UE102 to communicate with C-BS106 via a candidate cell (e.g., cell 126).

[0084] In Scenario 300, CN110 may send a first CN-BS interface message to S-BS104 requesting that S-BS104 set up, modify, or release radio resources to UE102 after S-BS104 has completed the CHO preparation procedure (for example, after S-BS104 has sent the C-BS configuration to UE102 308). However, in Scenario 500, for reasons similar to those described in Figure 3, CN110 may send a CN-BS interface message to S-BS104 containing a NAS message requesting that S-BS106 set up, modify, or release resources to UE102 during the CHO preparation procedure (for example, from after C-BS106 has received the Handover Request message 504 until before C-BS106 has transmitted the Handover Request Acknowledge message 506). In some implementations, the first CN-BS interface message may be a Downlink (DL) NAS Transport message.

[0085] In response to receiving the CN-BS interface message 542, S-BS104 transmits an RRC message containing the NAS message to UE102 544. In some implementations, the RRC message is a DL Information Transfer message. After transmitting the RRC message to UE102 544, S-BS104 transmits an RRC reconfiguration message containing the C-BS configuration to UE102 508, and UE102 then transmits an RRC reconfiguration complete message to S-BS104 in response to receiving the RRC reconfiguration message, as well as events 308 and 310, respectively 510. Alternatively, S-BS104 may transmit an RRC message to UE102 544 after transmitting the RRC reconfiguration message 508.

[0086] Some time after transmitting the RRC Reconfiguration Complete message, UE102 may determine that the conditions for connecting to candidate cell 126 have been met, and in response, perform a random access procedure to candidate cell 126 together with C-BS106, as with events 312 and 316. UE102 disconnects from cell 124 of S-BS104 in response to events 512 or 516, as with event 314. Since S-BS104 has already transmitted a NAS message to UE102 before UE102 disconnects from cell 124 of S-BS104, S-BS104 ensures that UE102 receives a timely command from CN110 to set up, modify, or release a resource or NAS configuration via a NAS message.

[0087] During or after the execution of the random access procedure 516, UE102 sends an RRC reconfiguration complete message to C-BS106 via candidate cell 126, similar to event 318 518. After the random access procedure has been executed 516, or after the RRC reconfiguration complete message has been transmitted 518, UE102 communicates with C-BS106 by using the C-BS configuration, similar to event 520 520. After the random access procedure has been executed 516, or after the RRC reconfiguration complete message has been received 518, C-BS106 may establish a UE-related signaling connection to CN110 and send a Path Switch Request message to CN110 requesting a switch of the downlink termination point of the transport bearer directed to C-BS106, similar to event 326 526. In response to the Path Switch Request message, CN110 performs a route switch for UE102 and sends a Path Switch Request Acknowledge message to C-BS106, similar to event 328 528.

[0088] Figures 6-8 illustrate additional conditional handover scenarios. Unlike Figures 3-5, Figures 6-8 show a scenario in which a distributed base station 104, having CU172 and at least two DU174, prepares for a conditional handover from source DU(S-DU)174A to candidate DU(C-DU)174B.

[0089] Referring first to Figure 6, in scenario 600, UE102, like event 302, transmits data to S-DU174A via one or more cells (e.g., cell 124) and CU172 according to the first BS configuration.

[0090] Later, CU172 initiates the CHO preparation procedure by deciding to configure UE102 by a conditional configuration for the CHO procedure (i.e., a C-DU configuration) so that UE102 can communicate with C-DU174B via a candidate cell (e.g., cell 126) when the conditions are met. CU172 may make this decision based on one or more measurements received directly from UE102 (e.g., via an SRB established between UE102 and S-DU174A, or via a physical control channel) that are above (or below) one or more predetermined thresholds, or from, for example, CU172 analyzing measurements of signals, control channels, or data channels received from UE102, or from another appropriate event (e.g., UE102 is moving toward C-DU174B).

[0091] In response to this decision, CU172 transmits a UE Context Setup Request message to C-DU174B604. In response to the UE Context Setup Request message, C-DU174B generates a C-DU configuration for the candidate cell associated with C-DU174B (e.g., cell 126). C-DU174B includes the C-DU configuration in a UE Context Setup Response message to UE102, and then transmits a UE Context Setup Response message to CU172606 in response to the UE Context Setup Request message. The C-DU configuration contains information that enables UE102 to communicate with C-DU174B 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 Figure 3, and the configuration parameters may be similar to those described above with reference to Figure 3.

[0092] CU172 transmits an RRC reconfiguration message to S-DU174A, including the C-DU configuration and trigger condition configuration, similar to event 308.607 S-DU174A then transmits an RRC reconfiguration message to UE102, including the C-DU configuration.608 UE102 responds by transmitting an RRC reconfiguration complete message to S-DU174A,610 and in response, S-DU174A transmits an RRC reconfiguration complete message to CU172.611 Events 604, 606, 607, and 608 are collectively referred to as the CHO preparation procedure in Figure 6.

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

[0094] Similar to event 318, UE102 sends an RRC reconstruction complete message to C-DU174B via candidate cell 126 during or after the random access procedure 616 is being performed 618. C-DU174B then transmits the RRC reconstruction complete message to CU172 619.

[0095] After 616 has executed the random access procedure, or 618 has transmitted the RRC reconfiguration complete message, UE102 communicates with C-DU174B and CU172 using the C-DU configuration 620. Events 612, 614, 616, 618, 619, and 620 are collectively referred to as the CHO execution procedure in Figure 6.

[0096] In some implementations, during the CHO execution procedure, CN110 may send a CN-BS interface message to CU172 requesting, for various reasons, to set up, modify, or release radio resources to UE102, similar to event 322.

[0097] In response to a CN-BS interface message, CU172 may optionally generate and transmit to S-DU174A a first RRC message (e.g., an RRC reconfiguration message) to set up, modify, or release radio resources for UE102.623 S-DU174A may then attempt to transmit the first RRC message to UE102. However, if UE102 had already disconnected from S-DU174A during a CHO execution procedure prior to when S-DU174A transmits the first RRC message,614 CU172 will fail to transmit the first RRC message to UE102.

[0098] To ensure that BS104 can properly set up, modify, or release radio resources to UE102, CU172 can be configured to set up, modify, or release radio resources to UE102 in accordance with CN-BS interface messages in various ways, such as described for C-BS106 in Figure 3.

[0099] In some implementations, if the CN-BS interface message is a DL NAS Transport message containing a NAS message to set up, modify, or release resources for UE102, CU172 can forward the NAS message to UE102 by transmitting the NAS message to C-DU174B, as well as event 342, and C-DU174B then forwards the NAS message to UE102. Thus, CU172 can properly set up, modify, or release resources (e.g., wireless resources) for UE102 via C-DU174B.

[0100] In other implementations, if the CN-BS interface message is a PDU session Resource message or E-RAB message containing instructions or information elements to set up, modify, or release radio resources for UE102, CU172 sends a UE Context Modification Request message to C-DU174B.644 In response, C-DU174B generates a second BS configuration to set up, modify, or release radio resources for UE102 according to the CN-BS interface message in event 622. C-DU174B may send a UE Context Modification Response message to CU172 containing the DU configuration,646 which then generates a second BS configuration containing the DU configuration. CU172 may generate other configuration parameters and include these configuration parameters in the second BS configuration. Events 644 and 646 are collectively referred to as the UE Context Modification procedure 650 in Figure 6. Next, CU172 sends a second RRC message (e.g., an RRC reconfiguration message) to C-DU174B containing a second BS configuration to set up, modify, or release radio resources for UE102 after UE102 has completed the CHO execution procedure, for example after event 620 631. In response, C-DU174B transmits a second RRC message containing a second BS configuration to UE102 632. UE102 responds by transmitting an RRC reconfiguration complete message to C-DU174B 634, and C-DU174B then forwards the RRC reconfiguration complete message to CU172 635. After receiving the second RRC message 632, UE102 communicates with C-DU174B and CU172 by using the second BS configuration 638. Therefore, CU172 can properly set up, modify, or release radio resources for UE102 via C-DU174B.

[0101] In further 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 to release resources to UE102, CU172 can send an RRC release message to UE102 to release the radio resources, similar to event 340, by transmitting the RRC release message to C-DU174B 639, which then forwards the RRC release message to UE102 640. Thus, CU172 can properly release radio resources to UE102 via C-DU174B. In some implementations, CU172 can send a UE Context Release Command message to C-DU174B to release radio resources to UE102 in event 639. CU172 can include the RRC release message within the UE Context Release Command message. In response to the UE Context Release Command message, the C-DU174B releases radio resources to the UE102.

[0102] In some implementations, after CU172 decides to set up, modify, or release radio resources for UE102, CU172 sends a first BS-CN interface message to CN110, as well as event 336, indicating that CU172 has successfully set up, modified, or released radio resources for UE102 in response to a CN-BS interface message 636. In other implementations, after or in response to having transmitted a NAS message 642, transmitted an RRC reconfiguration message 631, or received an RRC reconfiguration complete message 635, CU172 sends a first BS-CN interface message to CN110 636. In some implementations, after CU172 decides to release the radio resources to UE102 or transmits an RRC release message to release the radio resources 639, CU172, in response to the CN-BS interface message as in event 341, sends a second BS-CN interface message to CN110 indicating that CU172 has successfully released the radio resources to UE102 641.

[0103] Next, referring to Figure 7A, at the start of scenario 700A, UE102, similar to event 602, transmits data to S-DU174A via one or more cells (e.g., cell 124) and CU172. Also, similar to events 604 and 606, CU172 initiates the CHO preparation procedure by transmitting a UE Context Setup Request message to C-DU174B, 704 and C-DU174B then transmits a UE Context Setup Response message containing the C-DU configuration to UE102. 706 The C-DU configuration may include information that allows UE102 to communicate with C-DU174B via a candidate cell (e.g., cell 126).

[0104] In Scenario 600, CN110 may send a CN-BS interface message to CU172 requesting that it set up, modify, or release radio resources for UE102 after CU172 has completed the CHO preparation procedure (for example, after S-DU174A has sent the C-BU configuration to UE102 608). However, in Scenario 700A, CN110 may send a CN-BS interface message to CU172 requesting that it set up, modify, or release radio resources for UE102 during the CHO preparation procedure (for example, from after C-DU174B has received the UE Context Setup Request message 704 until before C-DU174B has transmitted the UE Context Setup Response message 706). In some implementations, the CN-BS interface message may be a PDU session resource message or an E-RAB message, similar to the message described above in Figure 3. CU172 receives a CN-BS interface message 722 after sending a UE Context Setup Request message 704 to C-DU174B, so CU172 cannot notify C-DU174B to change the configuration parameters of the C-DU configuration in order to set up, modify, or release radio resources for UE102 according to the CN-BS interface message. Therefore, C-DU174B sends CU172 a C-DU configuration 706 that does not include the configuration parameters for setting up, modifying, or releasing radio resources according to the CN-BS interface message.

[0105] Therefore, CU172 decides not to send the C-DU configuration to UE102 709. Instead of sending the C-DU configuration to UE102, in response to the decision 709, CU172 performs the UE Context Modification procedure 750 with S-DU174A in the same manner that CU172 performs the UE Context Modification procedure 650 with C-DU174B. Therefore, CU172 receives from S-DU174A a second BS configuration to set up, modify, or release radio resources to UE102, in which case the CN-BS interface message instructs to set up, modify, or release radio resources. CU172 transmits an RRC reconfiguration message containing the second BS configuration to S-DU174A 731, and S-DU174A then forwards the RRC reconfiguration message to UE102 in some implementations 732. In this way, CU172 ensures that UE102 can set up, modify, or release radio resources via the second BS configuration. In response to the RRC reconfiguration message, UE102 transmits an RRC reconfiguration complete message to S-DU174A 734, which then forwards the RRC reconfiguration complete message to CU172 735.

[0106] In other implementations, in response to decision 709, CU172 may generate an RRC release message for UE102 to release radio resources if the CN-BS interface message instructs UE102 to release radio resources. CU172 transmits the RRC release message to S-DU174A 739, S-DU174A then transmits the RRC release message to UE102 740, which may cause UE102 to transition to an idle or inactive state.

[0107] Therefore, in the implementations described above, BS104 can properly set up, modify, or release radio resources to UE102 via CU172. In some implementations, after events 732, 734, or 740, CU172 sends a BS-CN interface message to CN110 indicating that CU172 has successfully set up, modified, or released radio resources to UE102 in response to a CN-BS interface message, similar to events 636 or 641 724.

[0108] Next, referring to Figure 7B, in scenario 700A, CU172 decides not to send the C-DU configuration to UE102, but in scenario 700B, CU172 decides to send the C-DU configuration to UE102.

[0109] At the start of Scenario 700B, similar to Scenario 700A, UE102 transmits data to S-DU174A via one or more cells (e.g., cell 124) and CU172 702, and CU172, along with C-DU174BA, initiates the CHO preparation procedure in events 704 and 706. However, in contrast to Scenario 700A, in Scenario 700B, CN110 sends a CN-BS interface message to CU172 requesting that CN110 set up, modify, or release radio resources for UE102 during the CHO preparation procedure 722, whereas in Scenario 700B, CN110 sends a CN-BS interface message to CU172 requesting that CU172 set up, modify, or release radio resources for UE102 before initiating the CHO preparation procedure 723. Thus, CU172 can generate the second BS configuration described above in Figure 7A and include the second BS configuration within the UE Context Setup Request message in event 704. In addition, CU172 determines the configuration parameters for the interface protocol format (e.g., F1 or W1 application protocol) after considering a CN-BS message requesting CU172 to set up, modify, or release radio resources. CU172 then includes the UE capabilities and configuration parameters within the UE Context Setup Request message.

[0110] As a result, C-DU174B receives the second BS configuration (and therefore is aware of the configuration parameters to set up, modify, or release radio resources according to the CN-BS interface message), so C-DU174B can generate the C-DU configuration on top of the second BS configuration. Alternatively, CU172 does not include the second BS configuration in the UE Context Setup Request message. In this alternative implementation, C-BS106 can generate the full C-BS configuration (i.e., the C-BS configuration is the "full" configuration) according to the UE capabilities and configuration parameters. C-DU174B can then include the C-DU configuration in the UE Context Setup Response message and subsequently transmit the UE Context Setup Response message to CU172.

[0111] Next, CU172 may decide to send the C-DU configuration to UE102 710, and then transmit an RRC reconfiguration message to S-DU174A containing the C-DU configuration on top of the second BS configuration 731, S-DU174A then forwards the RRC reconfiguration message to UE102 733. CU172 may include a trigger condition configuration within the RRC reconfiguration message, as with event 308. In this way, CU172 ensures that UE102 can set up, modify, or release radio resources via the second BS configuration. In response to the RRC reconfiguration message, UE102 transmits an RRC reconfiguration complete message to S-DU174A 734, S-DU174A then forwards the RRC reconfiguration complete message to CU172 735.

[0112] Therefore, in the implementations described above, BS104 can properly set up, modify, or release radio resources to UE102 via CU172. In some implementations, after event 731 or 735, CU172 sends a BS-CN interface message to CN110 indicating that CU172 has successfully set up, modified, or released radio resources to UE102 in response to a CN-BS interface message, as well as event 636 or 641 724.

[0113] Next, referring to Figure 8, at the start of scenario 800, UE102, similar to event 602, transmits data to S-DU174A via one or more cells (e.g., cell 124) and CU172. Also, similar to events 604 and 606, CU172 initiates the CHO preparation procedure by transmitting a UE Context Setup Request message to C-DU174B, 804 and C-DU174B then transmits a UE Context Setup Response message containing the C-DU configuration to UE102.806 The C-DU configuration may include information that allows UE102 to communicate with C-DU174B via a candidate cell (e.g., cell 126).

[0114] In Scenario 600, CN110 may send a CN-BS interface message to CU172 requesting that CU172 set up, modify, or release radio resources for UE102 after CU172 has completed the CHO preparation procedure (for example, after S-DU174A has sent the C-BU configuration to UE102 608). However, in Scenario 800, CN110 may send a CN-BS interface message to CU172 containing a NAS message requesting that UE102 set up, modify, or release resources for UE102 during the CHO preparation procedure (for example, from after C-DU174B has received the UE Context Setup Request message 704 until before C-DU174B has transmitted the UE Context Setup Response message 706). In some implementations, the CN-BS interface message may be a Downlink (DL) NAS Transport message.

[0115] In response to receiving the CN-BS interface message 842, CU172 sends an RRC message containing the NAS message to S-DU174A 843, and S-DU174A then forwards the RRC message to UE102 844. In some implementations, the RRC message is a DL Information Transfer message. After transmitting the RRC message to UE102, CU172 sends an RRC reconfiguration message containing the C-DU configuration to S-DU174A 807, and S-DU174A then forwards the RRC reconfiguration message to UE102 808. In response, UE102 transmits an RRC reconfiguration complete message to S-DU174A 810, and S-DU174A then forwards the RRC reconfiguration complete message to CU172 811. Alternatively, CU172 may transmit the RRC message to S-DU174A 843 after transmitting the RRC reconfiguration message 807. Therefore, S-DU174A can transmit an RRC message after transmitting an RRC reconstruction message.

[0116] Some time after transmitting the RRC Reconfiguration Complete message, UE102 may determine that the conditions for connecting to candidate cell 126 have been met, and in response, perform a random access procedure to candidate cell 126 with C-DU174B, as with events 612 and 616. UE102 disconnects from cell 124 of S-DU174A in response to event 812 or 816, as with event 614. Since CU172 has already transmitted the NAS message to UE102 before UE102 disconnects from cell 124 of S-DU174A, CU172 ensures that UE102 receives a timely command from CN110 to set up, modify, or release a resource or NAS configuration via the NAS message.

[0117] During or after the random access procedure is being performed, UE102 sends an RRC reconfiguration complete message to C-DU174B via candidate cell 126, 818 and then C-DU174B forwards the RRC reconfiguration complete message to CU172, 819, as well as events 618 and 619, respectively. After the random access procedure has been performed, 816, or after the RRC reconfiguration complete message has been transmitted, 818, UE102 communicates with C-DU174B and CU172 by using the C-DU configuration, 820, as well as 620.

[0118] To further clarify, several exemplary methods by which devices operating in the systems shown in Figures 1A and 1B can be implemented are described below with reference to Figures 9 to 15.

[0119] Referring first to Figure 9, an exemplary method 900 for configuring a UE with parameters for setting up, modifying, or releasing wireless 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 preferred RAN such as RAN 105 in Figure 1A. For convenience, method 900 will be described below with reference to RAN 105, CN 110, and UE 102.

[0120] Method 900 begins in block 902, where RAN105 communicates with UE102 via the cell (for example, in event 302).

[0121] In block 904, RAN105 transmits a conditional configuration to UE102 via one of the cells for a conditional procedure that communicates with UE102 via a candidate cell when a condition is met (for example, in event 308). In some implementations, the conditional configuration is a conditional handover configuration for a conditional handover procedure.

[0122] In block 906, between the transmission of the conditional configuration to UE102 and the connection to UE102 via the candidate cell, RAN105 receives a first CN-BS interface message from CN110 to set up, modify, or release radio resources for UE102 (for example, in event 322). In some implementations, the first CN-BS interface message may 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 may 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 another implementation, the first CN-BS interface message may be a NAS transport message, including a NAS message.

[0123] In block 908, RAN105 disconnects from UE102 (for example, in event 314). In some implementations, RAN105 disconnects from UE102 because it determines that the conditions associated with the conditional configuration have been met.

[0124] In block 910, RAN105 sends a first BS-CN interface message to CN110 indicating that it failed to set up, modify, or release the radio resources for UE102 in response to a first CN-BS interface message (for example, in event 324). In some implementations, the first BS-CN interface message may 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 may 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 instruction that S-BS104 failed to send a NAS message from CN110 to UE102 to set up, modify, or release resources for UE102.

[0125] In block 912, RAN105 connects to UE102 via a candidate cell in several implementations (for example, in event 316).

[0126] In block 914, RAN105 receives an RRC message from UE102 via a candidate cell instructing the completion of a conditional procedure (for example, in event 318), in some implementations.

[0127] In block 916, after receiving the RRC message, RAN105, in some implementations, sends a second BS-CN interface message to CN110 to establish a UE-related signaling connection between UE102 and CN110 (for example, in event 326). In some implementations, the second BS-CN interface message can be a Path Switch Request message.

[0128] In block 918, after sending the second BS-CN interface message, RAN105, in some implementations, receives a second CN-BS interface message from CN110 to set up, modify, or release radio resources for UE102 (for example, in event 330). In some implementations, the second CN-BS interface message is identical to 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] In block 920, RAN105 transmits a message to UE102 via the candidate cell in response to a second CN-BS interface message, to set up, modify, or release radio resources for the UE (for example, in events 340, 342, and 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] Referring next to Figure 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 preferred distributed base station such as the distributed base station 104 in Figure 1B. For convenience, method 1000 will be described below with reference to the distributed base station 104, CN110, and UE102.

[0131] Method 1000 begins in block 1002, where the distributed base station 104 communicates with UE 102 via the cell, similar to block 902 (for example, in event 602).

[0132] In block 1004, the distributed base station 104 transmits a conditional configuration to the UE 102 via one of the cells, similar to block 904, for a conditional procedure to communicate with the UE 102 via a candidate cell when the conditions are met (for example, in events 607 and 608).

[0133] In block 1006, between the time the conditional configuration is transmitted to UE102 and the time the distributed base station 104 connects to UE102 via the candidate cell, the distributed base station 104, as in block 906, receives CN-BS interface messages from CN110 to set up, modify, or release radio resources for UE102 (for example, in event 622).

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

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

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

[0137] In block 1014, the distributed base station 104, as in block 914, receives an RRC message from UE 102 via a candidate cell instructing the completion of a conditional procedure (for example, in event 618).

[0138] In 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 (for example, in events 639, 640, 642, 643, 631, and 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, in some implementations, the distributed base station 104 sends a BS-CN interface message to CN 110 in response to a CN-BS interface message indicating that it has successfully set up, modified, or released radio resources for UE 102 (for example, in events 636 and 641).

[0140] Referring next to Figure 11, an exemplary method 1100 for performing a handover preparation procedure, taking into account that a CN-BS interface message has been received to set up, modify, or release radio resources after deciding to perform the handover preparation procedure or while performing the handover preparation procedure, may be implemented in a preferred RAN, such as by a base station 104 in Figure 1A or Figure 1B operating in RAN 105, as a set of instructions stored in a computer-readable medium and executable by processing hardware (e.g., one or more processors). For convenience, method 1100 will be described below with reference to RAN 105, CN 110, and UE 102.

[0141] Method 1100 begins in block 1102, where RAN 105 communicates with UE 102 via the cell (for example, in events 302, 402, 602, and 702).

[0142] In block 1104, RAN105 receives CN-BS interface messages from CN110 requesting RAN105 to set up, modify, or release radio resources for UE102 (for example, in events 322, 422, 622, and 722). In various implementations, RAN105 may receive CN-BS interface messages after deciding to perform handover preparation procedures or while performing handover preparation procedures.

[0143] If in block 1106 RAN105 decides to perform, or is currently performing, a handover preparation procedure for an immediate handover (i.e., an immediate handover preparation procedure), then in block 1108 RAN105 sends a BS-CN interface message to CN110 indicating that it failed to set up, modify, or release radio resources for UE102. In other words, RAN105 prioritizes the immediate handover preparation procedure over requests from CN110 to set up, modify, or release radio resources for UE102. Subsequently, in block 1110 RAN105 transmits an (immediate) handover command to UE102 as a result of the immediate handover preparation procedure.

[0144] In block 1106, if RAN105 decides to perform, 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, RAN105 generates and transmits a message to UE102 to set up, modify, or release radio resources to UE102 in response to a CN-BS interface message (e.g., in events 332, 340, 342, 440, 432, 631, 632, 639, 640, 642, 643, 739, 740). In other words, RAN105 takes precedence over conditional handover preparation procedures over requests from CN110 to set up, modify, or release radio resources to UE102. In several different implementations, the message can be an RRC message or a NAS message. Subsequently, in block 1114, RAN105 may, in response to the CN-BS interface message received in block 1104, send a BS-CN interface message to CN110 indicating that RAN105 has successfully set up, modified, or released radio resources for UE102 (for example, in events 336, 341, 424, 636, 641, and 724).

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

[0146] Method 1200 begins in block 1202, where RAN 105 communicates with UE 102 via the cell, similar to block 1102 (for example, in event 502).

[0147] In block 1204, RAN105 receives CN-BS interface messages from CN110, including NAS messages for UE102 (for example, in events 506 and 806). In various implementations, RAN105 may receive CN-BS interface messages before deciding to perform handover preparation procedures, or before performing handover preparation procedures.

[0148] If in block 1206 RAN105 decides to perform a handover preparation procedure for an immediate handover (i.e., an immediate handover preparation procedure), then in block 1208 RAN105 sends a BS-CN interface message to CN110 indicating that it failed to send a NAS message to UE102. In other words, RAN105 prioritizes the immediate handover preparation procedure over any request from CN110 to set up, modify, or release radio resources for UE102. Then, in block 1210 RAN105 transmits an (immediate) handover command to UE102 as a result of the immediate handover preparation procedure, similar to block 1110.

[0149] If in block 1206 RAN105 decides to perform a handover preparation procedure that is not for immediate handover (e.g., a conditional handover preparation procedure), then in block 1212 RAN105 transmits (e.g., forwards) a NAS message to UE102 to set up, modify, or release resources for UE102 (e.g., in events 544, 844). In other words, RAN105 takes precedence over the conditional handover preparation procedure over the request from CN110 to set up, modify, or release resources for UE102. Then, in block 1214 RAN105 may send an RRC message to UE102 containing the conditional configuration as a result of the conditional handover preparation procedure (e.g., in events 508, 808).

[0150] Next, referring to Figure 13, an exemplary method 1300 for sending a follow-up message to the RAN to set up, modify, or release a radio resource in response to receiving an instruction from the RAN that it had previously failed to set up, modify, or release a radio resource may be implemented as a set of instructions stored in a computer-readable medium and executable by processing hardware (e.g., one or more processors), such as CN110 in Figure 1A. For convenience, method 1300 will be described below with reference to CN110, RAN105, and UE102.

[0151] Method 1300 begins in block 1302, where CN110 communicates with UE102 via RAN105 (for example, in event 302).

[0152] In block 1304, CN110, as in block 906, sends a first CN-BS interface message to RAN105 requesting RAN105 to set up, modify, or release radio resources for UE102 (for example, in event 322).

[0153] In block 1306, CN110, as in block 910, receives a first BS-CN interface message from RAN105 indicating that it failed to set up, modify, or release radio resources for UE102 in response to a first CN-BS interface message (for example, in event 324).

[0154] In block 1308, CN110 receives a request message from RAN105 to establish a UE-related signaling connection to UE102, similar to block 916 (for example, in event 326).

[0155] In block 1310, CN110, similar to block 918, sends a second CN-BS interface message to RAN105 requesting that RAN105 set up, modify, or release radio resources for UE102 in response to the request message (for example, in event 330).

[0156] In block 1312, CN110 receives a second BS-CN interface message from RAN, as in block 1114, confirming that RAN105 has successfully set up, modified, or released radio resources for UE102 (for example, in events 336, 341).

[0157] Referring next to Figure 14, an exemplary 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 preferred RAN such as RAN 105 in Figure 1A. For convenience, method 1400 will be described below with reference to RAN 105, CN 110, and UE 102.

[0158] Method 1400 begins in block 1402, where RAN 105 generates a conditional configuration and conditions that must be met before UE 102 applies the conditional configuration (e.g., in events 306, 406, 506, 606, 706, and 806). In some implementations, the conditional configuration is a conditional handover configuration for UE 102 to hand over from a source base station (e.g., S-BS104) to a candidate base station (e.g., C-BS106). In other implementations, the conditional configuration is a conditional handover configuration for UE 102 to hand over from a source DU (e.g., S-DU174A) to a candidate DU (e.g., C-DU174B).

[0159] In block 1404, RAN105 receives interface messages from CN110 instructing it to configure UE102, similar to block 906 (for example, in events 322, 422, 423, 542, 622, 722, 723, and 842).

[0160] In block 1406, RAN105 determines that the interface message affects the conditional configuration. In some implementations, RAN105 determines that the interface message affects the conditional configuration because the nodes included in RAN105 are unable to deliver the interface message to UE102 as a result of UE102 being disconnected from the node according to the conditional configuration (e.g., in events 314 and 614). In other implementations, RAN105 determines that the conditional configuration does not contain the configuration parameters necessary to configure UE102 according to the interface message when RAN105 receives the interface message after the conditional configuration has already been generated (e.g., in events 422, 406, 722, 706, 542, 506, 842, and 806). In other implementations, RAN105 receives an interface message before generating a conditional configuration, and when considering the interface message when generating the conditional configuration, it determines that the conditional configuration will include configuration parameters to configure UE102 according to the interface message (for example, in events 423 and 723).

[0161] In block 1408, RAN105 generates messages related to the conditional configuration, taking into account the received interface message. In some implementations, UE102 is disconnected from the first node of RAN105 and connected to the second node of RAN105 according to the conditional configuration, and as a result, the second node generates a message, taking into account the received interface message (for example, in events 340, 342, 332, 640, 643, and 632). In other implementations, RAN105 generates a message, taking into account the received interface message, as a result of RAN105 determining that the conditional configuration does not include configuration parameters for configuring UE102 according to the interface message (for example, in events 440, 432, 740, 732, 544, and 844). In yet another implementation, RAN105 generates a message, taking into account the received interface message, as a result of RAN105 determining that the conditional configuration includes configuration parameters for configuring UE102 according to the interface message (for example, in events 433 and 733).

[0162] In block 1410, RAN105 transmits a message to UE102, similar to block 920 (for example, in events 340, 342, 332, 440, 432, 433, 544, 640, 643, 632, 740, 732, 733, and 844).

[0163] Referring next to Figure 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), such as in a preferred CN, such as CN110 in Figure 1A. For convenience, method 1500 will be described below with reference to CN110, RAN105, and UE102.

[0164] Method 1500 begins in block 1502, where CN110, as in block 1304, sends a first interface message to the first node of RAN105 instructing it to configure UE102 (for example, in event 322).

[0165] In block 1504, CN110 receives a response interface message from RAN105, similar to block 1306, indicating that it failed to configure the UE considering the first interface message (for example, in event 324).

[0166] In block 1506, CN110 receives a request from RAN105 to switch the route to the second node of RAN105, similar to block 1308 (for example, in event 326).

[0167] In block 1508, CN110, as in block 1310, sends a second interface message to the second node instructing it to configure UE102 (for example, in event 330).

[0168] The following explanation may apply to the explanation above.

[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". MN or SN configurations can be replaced with cell group configurations and / or wireless bearer configurations.

[0170] A user device (e.g., UE102) on which the techniques of this disclosure may be implemented may be a smartphone, tablet computer, laptop computer, mobile game console, point-of-sale (POS) terminal, health monitoring device, drone, camera, media streaming dongle or other personal media device, wearable device such as a smartwatch, wireless hotspot, femtocell, or any suitable wireless communication device such as a broadband router. Furthermore, in some cases, the user device may be integrated into an electronic system such as a vehicle head unit or advanced driver-assistance system (ADAS). Moreover, the user device may operate as an Internet of Things (IoT) device or a mobile / internet device (MID). Depending on the type, the 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 described herein include logic or a number of components or modules. A module may be a software module (e.g., code or machine-readable instructions stored in a non-temporary machine-readable medium) or a hardware module. A hardware module is a tangible unit capable of performing several operations and may be configured or arranged in a particular manner. A hardware module may comprise dedicated circuitry or logic permanently configured to perform several operations (e.g., as a dedicated processor such as a field-programmable gate array (FPGA) or application-specific integrated circuit (ASIC), or digital signal processor (DSP)). A hardware module may also comprise programmable logic or circuitry temporarily configured by software to perform several operations (e.g., contained within a general-purpose processor or other programmable processor). The decision of whether to implement a hardware module with dedicated, permanently configured circuitry or with temporarily configured circuitry (e.g., configured by software) may be made by considering cost and time.

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

[0173] Those skilled in the art, after reading this disclosure, will understand additional alternative structural and functional designs for controlling the configuration through the principles disclosed herein. Therefore, it should be understood that while specific embodiments and applications are illustrated and described, the disclosed embodiments are not limited to the exact structures and components disclosed herein. Various other modifications, changes, and alterations, 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 defined in the accompanying claims. [Examples]

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

[0175] The method according to Embodiment 1, further comprising transmitting a conditional configuration to the UE by a first node of the RAN before receiving an interface message from the CN. [Examples]

[0176] The method of Embodiment 2, further comprising deciding to suspend the wireless connection between the UE and the first node, and transmitting a message to the UE via a second node of the RAN, after the UE has connected to the second node. [Examples]

[0177] The method according to Embodiment 3, wherein the interface message is a first interface message, and the method further comprises the first node sending an instruction to the CN that it failed to set up, modify or release a resource in response to a decision that the wireless connection is to be suspended, and the second node receiving a second interface message from the CN to set up, modify or release a resource. [Examples]

[0178] The method according to Embodiment 4, wherein transmitting a message to the UE is performed by a second node in response to the receipt of a second interface message. [Examples]

[0179] The method according to Embodiment 3, wherein receiving an interface message includes receiving an interface message by a first node, and transmitting a message to a UE includes transmitting a message to a UE via a second node by the first node in response to receiving an interface message. [Examples]

[0180] The method according to Embodiment 1, wherein generating a conditional configuration comprises generating a conditional configuration by a second node of the RAN, the method further comprising a first node of the RAN deciding that the conditional configuration omits one or more parameters for setting up, modifying, or releasing resources, and the first node preventing the transmission of the conditional configuration to the UE. [Examples]

[0181] The method according to Embodiment 1, further comprising generating a conditional configuration by a second node of the RAN, the method being to determine by a first node of the RAN that the conditional configuration includes one or more parameters for setting up, modifying, or releasing resources, and the first node of the RAN transmitting the conditional configuration to the UE. [Examples]

[0182] The method according to any one of Embodiments 1 to 8, wherein the message is a first message, and the method further comprises transmitting the first message to the UE and then transmitting a second message to the CN indicating that the RAN has configured the UE. [Examples]

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

[0184] The method according to Example 10, wherein the interface message includes a non-access stratum (NAS) message, and the message includes a NAS message. [Examples]

[0185] The method according to any one of Examples 2-5 and 7-11, 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. [Examples]

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

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

[0188] A conditional configuration is a configuration for a conditional handover (CHO) procedure as described in any one of Examples 1 to 14. [Examples]

[0189] The method according to any one of Examples 1 to 15, wherein the generation is performed in the first instance, and the method further comprises, in the 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. [Examples]

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

[0191] A method in a core network (CN) for configuring a user device (UE), comprising: processing hardware sending a first interface message to a first node of a radio access network (RAN) instructing it to configure the UE; processing hardware receiving a response interface message from the RAN indicating that it failed to configure the UE in consideration of the first interface message; processing hardware receiving a request from the RAN to reroute to a second node of the RAN; and processing hardware sending a second interface message to the second node instructing it to configure the UE. [Examples]

[0192] The request is the method of Embodiment 18, which further includes instructions for establishing a connection between the UE and the CN. [Examples]

[0193] The method according to Embodiment 18 or 19, wherein the response interface message is a first response interface message, and the method further comprises processing hardware receiving a second response interface message from the RAN indicating that the RAN has configured the UE. [Examples]

[0194] The method according to any one of Examples 18 to 20, wherein receiving a response interface message includes receiving an instruction from the first node that it failed to set up, modify, or release a resource, and sending a second interface message includes sending an instruction to the second node to set up, modify, or release a resource. [Examples]

[0195] The method according to any one of Examples 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. [Examples]

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

[0197] 100 Wireless Communication Systems 102 UE 104 Base station (BS) 106 Base Station 106A base station 110 Core Network (CN) 111 Evolutionary 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 Controllers 134 Instant Configuration Controller 140 Processing Hardware 142 Conditional Configuration Controller 144 Instant Configuration Controllers 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 Function (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 stacks 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 Events 302, 402, 602, 702 Events 306, 406, 506, 606, 706, 806 Events 312, 314, 316, 318, and 320 Events 322, 422, 423, 542, 622, 722, 723, 842 324 Events 326 Events 330 events 332, 340, 342, 440, 432, 631, 632, 639, 640, 642, 643, 739, 740 Events Events 336, 341, 424, 636, 641, 724 Events 340, 342, and 332 Scenario 400A 400B Scenario 409 decision Events 422, 406, 722, 706, 542, 506, 842, 806 423, 723 events 433, 733 Events 500 Scenarios 506, 806 Events 508, 808 Events 544, 844 events 600 Scenarios Events 604, 606, 607, 608 Events 612, 614, 616, 618, 619, 620 636, 641 Events Events 639, 640, 642, 643, 631, 632 644, 646 events 650 UE Context Modification Procedure 700A Scenario 700B Scenario 704 Event 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. A method performed by a computer in a radio access network (RAN) for configuring user equipment (UE), The steps include: after deciding to perform a handover preparation procedure, or while performing a handover preparation procedure, receiving an interface message from the core network (CN) to a node in the RAN requesting the setup, modification, or release of radio resources for the UE; In response to the aforementioned reception, When the handover preparation procedure is for an immediate handover, the node transmits an immediate handover command to the UE, When the handover preparation procedure is not for an immediate handover, the node transmits a message to the UE to set up, modify, or release radio resources. Methods that include...

2. The method according to claim 1, wherein the interface message is a first interface message, and the method further includes the step of the node sending a second interface message to the CN indicating that it has failed to set up, modify or release the radio resources for the UE, when the handover preparation procedure is for an immediate handover.

3. The method according to claim 1, wherein the handover preparation procedure is for a conditional handover.

4. The method according to claim 3, further comprising the step of the node prioritizing setting up, modifying or releasing the radio resource to the UE over the conditional handover, wherein the prioritizing step includes transmitting the message to the UE to set up, modify or release the radio resource.

5. The method of claim 3, wherein the interface message is a first interface message, and the method further comprises the step of the node sending a second interface message to the CN indicating that the radio resource for the UE is set up, modified or released.

6. The method according to any one of claims 3 to 5, wherein the message to the UE is a radio resource control (RRC) message.

7. The method according to any one of claims 3 to 5, wherein the message is a non-access stratum (NAS) message.

8. A base station comprising processing hardware and configured to implement the method according to any one of claims 1 to 5.

9. A wireless access network (RAN) comprising processing hardware and configured to implement the method according to any one of claims 1 to 5.

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