Base Station, User Equipment and Their Methods

Abstract

A method for managing conditional operations related to a user equipment (UE) in a first base station, the method comprising sending conditional connection information to the UE via processing hardware, the conditional connection information including at least one of the following: (i) configuration data related to a second base station for the UE to operate in dual connection with the first base station and the second base station; or (ii) one or more conditions (2202) for connecting to the second base station. The method further comprises, in response to determining via the processing hardware that the UE is to suspend a radio connection with the first base station (2204): causing the UE to suspend the radio connection with the first base station (2206); and causing the second base station to release the conditional connection information (2208).

Description

Technical Field

[0001] The present disclosure generally relates to wireless communication, and more particularly, to conditional processes such as conditional handover and conditional secondary node addition procedures, and conditional operations in the case of a suspended radio connection. Background Art

[0002] This background description is provided for the purpose of generally presenting the background of the present disclosure. To the extent of the description in this background art section, the work of the currently named inventors and aspects that may not qualify as prior art at the time of filing are neither expressly nor implicitly admitted as prior art against the present disclosure.

[0003] In a telecommunication system, the Packet Data Convergence Protocol (PDCP) sublayer of the radio protocol stack provides services such as the transmission, encryption, and integrity protection of user plane data. For example, the PDCP layer defined for the Evolved Universal Terrestrial Radio Access (EUTRA) radio interface (see 3GPP specification TS 36.323) and the New Radio (NR) (see 3GPP specification TS 38.323) provides the sequencing of protocol data units (PDUs) in the uplink direction (from a user device, also known as a user equipment (UE), to a base station) and the downlink direction (from the base station to the UE). In addition, the PDCP sublayer provides signaling radio bearers (SRBs) and data radio bearers (DRBs) to the Radio Resource Control (RRC) sublayer. Generally, the UE and the base station can use the SRB to exchange RRC messages and non-access stratum (NAS) messages, and can use the DRB to transmit data on the user plane.

[0004] A UE can use several types of SRBs and DRBs. When operating in dual connectivity (DC), the cell associated with the base station operating as the master node (MN) defines the master cell group (MCG), and the cell associated with the base station operating as the secondary node (SN) defines the secondary cell group (SCG). The so-called SRB1 resources carry RRC messages, which include NAS messages on the dedicated control channel (DCCH) in some cases. The SRB2 resources support RRC messages including recorded measurement information or NAS messages, which are also on the DCCH but with a lower priority than the SRB1 resources. More generally, the SRB1 and SRB2 resources allow the UE and the MN to exchange RRC messages related to the MN and embed RRC messages related to the SN, and can also be referred to as MCG SRBs. The SRB3 resources allow the UE and the SN to exchange RRC messages related to the SN, and can be referred to as SCG SRBs. The split SRB allows the UE to directly exchange RRC messages with the MN via the lower-layer resources of the MN and the SN. In addition, the DRB terminated at the MN and only using the lower-layer resources of the MN can be referred to as the MCG DRB, the DRB terminated at the SN and only using the lower-layer resources of the SN can be referred to as the SCG DRB, and the DRB terminated at the MCG but using the lower-layer resources of the MN, the SN, or both the MN and the SN can be referred to as the split DRB.

[0005] The 3GPP specification TS 37.340 (v15.7.0) describes the procedures for a UE to add or change an SN in a DC scenario. These procedures involve message passing (e.g., RRC signaling and preparation) between radio access network (RAN) nodes. This message passing usually results in latency, which in turn increases the likelihood that the SN addition or SN change procedure will fail. These procedures do not involve conditions checked at the UE and can be referred to as "immediate" SN addition and SN change procedures.

[0006] In both single connectivity (SC) and DC operations, the UE may also perform a handover procedure to transfer from one cell to another cell. Depending on the scenario, the UE may hand over from a cell of a first base station to a cell of a second base station, or from a cell of a first distributed unit (DU) of a base station to a cell of a second DU of the same base station. 3GPP specifications 36.300 v15.6.0 and 38.300 v15.6.0 describe a handover procedure that includes several steps (RRC signaling and preparation) between RAN nodes, which results in latency in the handover procedure and thus increases the risk of handover failure. This procedure does not involve conditions checked at the UE and can be referred to as an "immediate" handover procedure.

[0007] Recently, for both SN addition / change and handover, "conditional" procedures (i.e., conditional SN addition / change and conditional handover) have been considered. Different from the "immediate" procedures discussed above, these procedures do not add or change the SN or perform a handover until the UE determines that the conditions are met. As used herein, the term "condition" may refer to a single detectable state or event (e.g., a specific signal quality metric exceeding a threshold) or a logical combination of such states or events (e.g., "condition A and condition B" or "(condition A or condition B) and condition C", etc.). Moreover, the term "condition" may be used herein to refer to an abstract condition (e.g., the signal quality being in a specific state) or a condition configuration (e.g., a digital representation / expression of a condition that can be transmitted and stored, etc.).

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

[0009] Currently, after the UE configured for a conditional procedure pauses the radio connection with the base station, the RAN cannot always effectively manage these resources associated with the conditional procedure. As a result, the RAN may prematurely deplete the resource pool that the RAN can allocate to other UEs, or delay resource allocation to other UEs. SUMMARY OF THE INVENTION

[0010] Generally speaking, the base station and / or UE of the present disclosure effectively manage conditional connection information when the UE pauses its radio connection with the base station. The conditional connection information may include configuration data related to a candidate base station and one or more conditions for the UE to connect to the candidate base station. The conditional connection information may relate to a process for conditional secondary node (SN) addition, whereby the base station begins to operate as a master node (MN), and the UE begins to operate in dual connectivity (DC) with the MN and the SN. In another scenario, the conditional connection information may relate to a conditional handover process, whereby the base station operates as a source base station and hands over to a target base station. Both the source base station and the target base station in some implementations operate as MNs with respect to the same or different SNs.

[0011] In some implementations, the base station determines that it should release the conditional connection information when the UE and the base station resume a previously paused radio connection. To this end, the base station may send an appropriate indication to the candidate SN or the candidate target base station. Depending on the specific implementation, in response to a request for the UE to pause the radio connection, receiving a message from the UE requesting to resume the paused radio connection, at the time of requesting the UE to pause the radio connection, in response to receiving a request to retrieve the UE's context, etc., the base station releases the conditional connection information. Further, in various implementations or scenarios, the base station may use an explicit (e.g., a field present in the message) or implicit (e.g., a field omitted from the message) indication to instruct the UE to release or retain the conditional connection information.

[0012] In some implementations, the UE determines that it should retain rather than release the conditional connection information when resuming a previously paused radio connection with the base station. In some cases, the UE relies on the implicit or explicit indication from the base station discussed above. For example, the UE may subsequently use the conditional connection information to connect to the candidate SN or the target MN.

[0013] An embodiment of these techniques is a method for managing conditional operations related to a user equipment (UE) in a first base station. The method includes: sending, via processing hardware, conditional connection information to the UE, the conditional connection information including (i) configuration data related to a second base station for the UE to operate in dual connectivity with the first base station and the second base station, and (ii) one or more conditions for connecting to the second base station; and in response to determining, via the processing hardware, that the UE is to pause its radio connection with the first base station: (i) causing the UE to pause its radio connection with the first base station, and (ii) causing the second base station to release the conditional connection information.

[0014] Another exemplary embodiment of these techniques is a base station including processing hardware and configured to implement the above method.

[0015] Another embodiment of these techniques is a method for managing conditional operations related to a second base station in a UE having a radio connection to a first base station. The method includes: receiving, by processing hardware, conditional connection information from the first base station, the conditional connection information including (i) configuration data related to the second base station for the UE to operate in dual connection with the first base station and the second base station, and (ii) one or more conditions for connecting to the second base station; suspending, in response to a trigger event, the radio connection by the processing hardware; and releasing, in response to the trigger event, the conditional connection information by the processing hardware.

[0016] Yet another embodiment of these techniques is a method for managing conditional operations related to a second base station in a UE having a radio connection to a first base station. The method includes: receiving, by processing hardware, conditional connection information from the first base station, the conditional connection information including at least one of the following: (i) configuration data related to the second base station and (ii) one or more conditions for connecting to the second base station; receiving, by the processing hardware, a suspension indication from the base station indicating that the UE is to suspend the radio connection; receiving, by the processing hardware, a conditional connection indication indicating whether the UE is to release the conditional connection information; and releasing or retaining the conditional connection information according to the conditional connection indication.

[0017] Another embodiment of these techniques is a UE including processing hardware and configured to implement any one of the above two methods. Description of the Drawings

[0018] Figure 1 An exemplary communication system in which techniques for managing conditional handover and / or secondary node (SN) operations can be implemented;

[0019] FIG. 2 is a block diagram of an exemplary protocol stack according to which a UE communicates with a base station; Figure 1 of the UE communicates with the base station according to the exemplary protocol stack;

[0020] FIG. 3 is a message passing diagram of a scenario according to known techniques, in which a MN conditionally adds a candidate SN (C-SN) for dual connection (DC) of a UE;

[0021] FIG. 4 is a message passing diagram of a scenario according to known techniques, in which an SN conditionally configures a cell to which a UE operating in DC with a MN and the SN is to connect, subject to one or more conditions;

[0022] FIG. 5 is a message passing diagram of another scenario according to known techniques, in which an SN conditionally configures a cell for a UE by communicating directly with the UE rather than via the MN;

[0023] FIG. 6 is a messaging diagram of a scenario according to the prior art, in which a source base station configures a conditional handover of a UE to another base station that is subject to one or more conditions;

[0024] Figure 7 is a messaging diagram of the following scenario, in which a base station operating as an MN in a conditional SN management scenario or a source MN (S-MN) in a conditional scenario determines that the UE should suspend the radio connection with the base station and notifies another base station operating as an SN or a target MN, respectively, that it should release the conditional connection information;

[0025] Figure 8 is a messaging diagram of the following scenario, in which the UE receives conditional connection information regarding SN management or handover, suspends the radio connection with the MN or S-MN, and retains the conditional connection information when resuming the radio connection;

[0026] Figure 9 is a messaging diagram of the following scenario, in which the UE receives conditional connection information regarding SN management or handover, suspends the radio connection with the MN or S-MN, and releases the conditional connection information in response to the restoration of the radio connection from the MN or S-MN and an indication to release the conditional connection information;

[0027] Figure 10 is a messaging diagram of the following scenario, in which the UE receives conditional connection information regarding SN management or handover, suspends the radio connection with the MN or S-MN, and releases the conditional connection information in response to the restoration of the radio connection from the (C-)SN or C-MN and an indication to release the conditional connection information;

[0028] Figure 11 is a messaging diagram of the following scenario, in which the UE receives conditional connection information regarding SN management or handover, suspends the radio connection with the MN or S-MN, and releases the conditional connection information in response to an indication from the MN or S-MN to reconfigure the radio connection and to release the conditional connection information;

[0029] Figure 12 is a messaging diagram of the following scenario, in which the UE receives conditional connection information regarding SN management or handover, suspends the radio connection with the MN or S-MN, and releases the conditional connection information in response to a command to release the radio connection, which omits an indication that the conditional connection information should be retained;

[0030] Figure 13It is a message passing diagram of the following scenario, where the UE receives conditional connection information regarding SN management or handover, pauses the radio connection with the MN or S-MN, and releases the conditional connection information in response to a command to release the radio connection, the command including an indication that the conditional connection information should be released;

[0031] Figure 14 It is a message passing diagram of the following scenario, where the base station operating as the MN in the conditional SN management scenario or the source MN (S-MN) in the conditional scenario determines that the UE should pause the radio connection with the base station, and in response to a request from the UE to resume the radio connection, notifies another base station operating as the SN or the target MN respectively that the conditional connection information should be released;

[0032] Figure 15 It is a message passing diagram of the following scenario, where the base station operating as the MN in the conditional SN management scenario or the source MN (S-MN) in the conditional scenario determines that the UE should pause the radio connection with the base station, and in response to a request for the UE's context received from another third base station, notifies another base station operating as the SN or the target MN respectively that the conditional connection information should be released;

[0033] Figure 16 It is Figure 1 a flowchart of an example method for managing conditional connection information that can be implemented in the UE according to an indication received from the MN or S-MN;

[0034] Figure 17 It is Figure 1 a flowchart of an example method for managing conditional connection information at the UE using an indication of whether the UE should retain the conditional connection information that can be implemented in the base station operating as the MN or S-MN;

[0035] Figure 18 It is Figure 1 a flowchart of an example method for managing conditional connection information that can be implemented in the UE according to whether the MN or S-MN has resumed a previously paused radio connection;

[0036] Figure 19 It is Figure 1 a flowchart of an example method for managing conditional connection information at the UE when the UE requests to resume a previously paused radio connection that can be implemented in the base station operating as the MN or S-MN;

[0037] Figure 20 It is Figure 1Flowchart of an example method implemented in a base station for managing conditional connection information at a UE based on measurement results regarding a C-SN or C-MN;

[0038] Figure 21 is a flowchart of an example method that can be implemented in a Figure 1 MN for managing conditional connection information based on whether the conditional connection information is still valid when the UE has resumed a previously suspended radio connection;

[0039] Figure 22 is a flowchart of an example method that can be implemented in a Figure 1 base station for managing conditional operations related to a UE;

[0040] Figure 23 is a flowchart of an example method that can be implemented in a Figure 1 UE for managing conditional operations related to a second base station; and

[0041] Figure 24 is a flowchart of another example method that can be implemented in a Figure 1 UE for managing conditional operations related to a second base station. DETAILED DESCRIPTION

[0042] Figure 1 Depicts an example wireless communication system 100 in which the conditional configuration management techniques of the present disclosure can be implemented when a UE has suspended a radio connection with a base station. As discussed in more detail below, the conditional configuration management techniques can, for example, involve conditional addition of an SN or conditional handover.

[0043] The wireless communication system 100 includes a UE 102 and base stations 104A, 104B, 06A, 106B connected to a core network (CN) 110. For example, the base stations 104A, 106A, 106B can be any suitable type or types of base stations, such as an evolved node B (eNB), a next-generation eNB (ng-eNB), or a 5G node B (gNB). As a more specific example, the base station 104A can be an eNB or a gNB, and the base stations 106A and 106B can be gNBs.

[0044] The base station 104A supports cell 124, the base station 106A supports cell 126A, and the base station 106B supports cell 126B. The base station 104B also supports one or more cells, which are not shown in Figure 1Shown to avoid confusion. Cell 124 partially overlaps both Cell 126A and Cell 126B, such that UE 102 can be within range of communicating with base station 106A while simultaneously being within range of communicating with base station 106A or 106B (or within range of detecting or measuring signals from both base stations 104A and 106A, etc.). For example, the overlap can enable UE 102 to hand over between cells before UE 102 experiences a radio link failure (e.g., from Cell 124 to Cell 126A or 126B, or from Cell 124 to the cell of base station 104B). Moreover, the overlap allows for the various DC scenarios discussed below. For example, UE 102 can communicate with base station 104A (operating as an MN) and base station 106A (operating as an SN) in DC, and upon completion of an SN change, can communicate with base station 104A (operating as an MN) and base station 106B (operating as an SN). More specifically, when UE 102 is in DC with base stations 104A and 106A, base station 104A operates as a MeNB, Mng-eNB, or MgNB, while base station 106A operates as an SgNB or Sng-eNB.

[0045] In an implementation and scenario where UE 102 is in SC with base station 104A but capable of operating in DC, base station 104A operates as a MeNB, Mng-eNB, or MgNB, while base station 106A operates as a candidate SgNB (C-SgNB) or candidate Sng-eNB (C-Sng-eNB).

[0046] In a scenario where UE 102 hands over from base station 104A to base station 104B, base stations 104A and 104B operate as a source base station (S-BS) and a target base station (T-BS), respectively. For example, before the handover, UE 102 can communicate with base stations 104A and 106A in DC, and after the completion of the handover, continue to communicate with base stations 104A and 106A in DC. Assuming the handover is immediate, base stations 104A and 104B operate as a source MN (S-MN) and a target MN (T-MN), respectively, in this case. When the handover is conditional, the base station operates as a conditional T-MN (C-T-MN) or simply a C-MN.

[0047] Although various scenarios are described below where base station 104A operates as an MN and base station 106A (or 106B) operates as an SN or C-SN, in different scenarios, any one of base stations 104A, 104B, 106A, 106B can generally operate as an MN, SN, or C-SN. Thus, in some implementations, base stations 104A, 104B, 106A, and 106B can implement a similar set of functions and each supports MN, SN, and C-SN operations.

[0048] In operation, UE 102 can use radio bearers (e.g., DRBs or SRBs) that terminate at an MN (e.g., base station 104A) or an SN (e.g., base station 106A) at different times. When communicating on a radio bearer in the uplink (from UE 102 to the base station) and / or downlink (from the base station to UE 102) direction, UE 102 can apply one or more security keys.

[0049] Base station 104A includes processing hardware 130, which can include one or more general-purpose processors (e.g., a central processing unit (CPU)) and a computer-readable memory storing machine-readable instructions executable on the (multiple) general-purpose processors and / or dedicated processing units. Figure 1 In an example implementation, processing hardware 130 includes a conditional configuration controller 132 configured to manage or control the conditional configuration techniques of the present disclosure. For example, conditional configuration controller 132 can be configured to support RRC messaging associated with immediate and conditional handover procedures, and / or support operations necessary when base station 104A operates as an MN relative to an SN. Moreover, in some implementations and / or scenarios, conditional configuration controller 132 can be responsible for maintaining the current set of conditional configurations according to the various implementations discussed below (for UE 102 and Figure 1 a plurality of other UEs not shown).

[0050] Base station 106A includes processing hardware 140, which can include one or more general-purpose processors (e.g., a CPU) and a computer-readable memory storing machine-readable instructions executable on the (multiple) general-purpose processors and / or dedicated processing units. Figure 1In an example implementation, the processing hardware 140 includes a conditional configuration controller 142 configured to manage or control RRC procedures and RRC configurations. For example, the conditional configuration controller 142 may be configured to support RRC messaging associated with immediate and conditional handover procedures, and / or support operations necessary when base station 106A operates as a serving node or candidate serving node (C-SN). Moreover, in some implementations and / or scenarios, the conditional configuration controller 142 may be responsible for maintaining the current set of conditional configurations for UE 102 and Figure 1 a plurality of other UEs not shown in the figure. Although Figure 1 not shown in the figure, base station 106B may include processing hardware similar to the processing hardware 140 of base station 106A.

[0051] UE 102 includes processing hardware 150, which may include one or more general-purpose processors (e.g., CPUs) and a computer-readable memory storing machine-readable instructions executable on the (multiple) general-purpose processors and / or dedicated processing units. Figure 1 In an example implementation, the processing hardware 150 includes a conditional configuration controller 152 configured to manage or control RRC procedures and RRC configurations related to conditional configurations. For example, the conditional configuration controller 152 may be configured to support RRC messaging associated with immediate and conditional handovers and / or secondary node addition / modification procedures, and may also be responsible for maintaining the current set of conditional configurations for UE 102 according to any of the implementations discussed below (e.g., adding, releasing, or modifying conditional configurations as needed).

[0052] CN 110 may be an evolved packet core (EPC) 111 or a fifth-generation core (5GC) 160, both depicted in Figure 1 the figure. Base stations 104A and 104B may be eNBs supporting an S1 interface for communicating with EPC 111, ng-eNBs supporting an NG interface for communicating with 5GC 160, or base stations supporting an NR radio interface and an NG interface for communicating with 5GC 160. Base station 106A may be an EN-DC gNB (en-gNB) having an S1 interface to EPC 111, an en-gNB not connected to EPC 111, a gNB supporting an NR radio interface and an NG interface to 5GC 160, or an ng-eNB supporting an EUTRA radio interface and an NG interface to 5GC 160. To directly exchange messages with each other during the various scenarios discussed below, base stations 104A, 104B, 106A, 106B may support an X2 or Xn interface.

[0053] Among other components, the EPC 111 may include a Serving Gateway (S-GW) 112 and a Mobility Management Entity (MME) 114. The S-GW 112 is typically configured to transport user plane packets related to audio calls, video calls, Internet traffic, etc., and the MME 114 is typically configured to manage authentication, registration, paging, and other related functions. The 5GC 160 includes a User Plane Function (UPF) 162, an Access and Mobility Management Function (AMF) 164, and / or a Session Management Function (SMF) 166. The UPF 162 is typically configured to transport user plane packets related to audio calls, video calls, Internet traffic, etc., the AMF 164 is typically configured to manage authentication, registration, paging, and other related functions, and the SMF 166 is typically configured to manage PDU sessions.

[0054] Generally, the wireless communication system 100 may include any suitable number of base stations that support NR cells and / or EUTRA cells. More specifically, the EPC 111 or the 5GC 160 may be connected to any suitable number of base stations that support NR cells and / or EUTRA cells. For example, in the immediate and conditional handover scenarios discussed below with reference to Figure 1 additional base stations are considered. Although the following examples specifically relate to particular CN types (EPC, 5GC) and RAT types (5G NR and EUTRA), generally, the techniques of the present disclosure may also be applied to other suitable radio access and / or core network technologies, such as, for example, sixth generation (6G) radio access and / or 6G core network or 5G NR-6G DC.

[0055] As described above, the wireless communication system 100 may support various procedures (e.g., handover, SN addition, etc.) and operation modes (e.g., SC or DC). Example operations of various procedures that may be implemented in the wireless communication system 100 will now be described.

[0056] In some implementations, the wireless communication system 100 supports immediate handover between cells. In one scenario, for example, the UE 102 is initially connected to the base station 104A, and the base station 104A later performs the preparation for an immediate handover with the base station 106A via an interface (e.g., X2 or Xn). In this scenario, the base stations 104A and 106A operate as the source base station and the target base station, respectively. In the handover preparation, the source base station 104A sends a Handover Request message to the target base station 106A. In response, the target base station 106A includes an immediate handover command message in the Handover Request Acknowledge message and sends the handover request acknowledge message to the source base station 104A. Then, in response to receiving the handover request acknowledge message, the source base station 104A transmits a handover command message to the UE 102.

[0057] Upon receiving the immediate handover command message, the UE 102 immediately reacts to the immediate handover command by attempting to connect to the target base station 106A. To connect to the target base station 106A, the UE 102 may perform a random access procedure with the target base station 106A and then (after obtaining access to the control channel) transmit a handover complete message (i.e., in response to the immediate handover command) to the target base station 106A via the cell of the base station 106A.

[0058] In some implementations, the wireless communication system 100 also supports conditional handover. For example, in one scenario, the UE 102 is initially connected to the base station 104A, and the base station 104A later performs a first conditional handover preparation procedure with the base station 106A via an interface (e.g., X2 or Xn) to prepare for a potential handover of the UE 102 to the base station 106A. In this scenario, the base stations 104A and 106A operate as the source base station and the candidate base station, respectively. In the first conditional handover preparation procedure, the source base station 104A sends a handover request message to the candidate base station 106A. In response, the candidate base station 106A includes a first conditional handover command message in the handover request acknowledge message and sends the handover request acknowledge message to the source base station 104A. Then, in response to receiving the handover request acknowledge message, the source base station 104A transmits a first conditional handover command message to the UE 102.

[0059] Upon receiving the first conditional handover command message, the UE 102 does not immediately react to the first conditional handover command message by attempting to connect to the candidate base station 106A. Instead, the UE 102 connects to the candidate base station 106A according to the first conditional handover command message only if the UE 102 determines that the first condition for switching to the candidate cell 126A of the candidate base station 106A is satisfied. The base station 106A provides the configuration of the candidate cell 126A in the first conditional handover command message (i.e., the configuration that the UE 102 can use to connect to the base station 106A via the candidate cell 126A).

[0060] Before the first condition is satisfied, the UE 102 is not connected to the candidate base station 106A. In other words, the candidate base station 106A has not been connected to and serving the UE 102. In some implementations, the first condition may be that the signal strength / quality measured by the UE 102 on the candidate cell 126A of the candidate base station 106A is sufficiently "good". For example, if one or more measurement results obtained by the UE 102 (when performing measurements on the candidate cell 126A) are higher than the threshold configured by the source base station 104A or higher than a predetermined or pre-configured threshold, the first condition may be satisfied. If the UE 102 determines that the first condition is satisfied, the candidate base station 106A becomes the target base station 106A of the UE 102, and the UE 102 attempts to connect to the target base station 106A. To connect to the target base station 106A, the UE 102 may perform a random access procedure with the target base station 106A and then (after obtaining access to the control channel) transmit a first handover completion message to the target base station 106A via the candidate cell 126A. After the UE 102 successfully completes the random access procedure and / or transmits the first handover completion message, the target base station 106A becomes the serving base station 106A of the UE 102, and the UE 102 starts data communication with the serving base station 106A.

[0061] In some implementations and / or scenarios, conditional handover may occur with more than one candidate cell supported by the candidate base station 106A (e.g., cell 126A and Figure 1 another cell of the base station 106A not shown in the figure). In one such scenario, in addition to the configuration of the candidate cell 126A, the base station 106A may also provide the configuration of the additional candidate cell of the base station 106A in the first conditional handover command message. Then, the UE 102 may monitor whether the additional candidate cell of the candidate base station 106A satisfies a second condition while also monitoring whether the candidate cell 126A satisfies the first condition. The second condition may be the same as or different from the first condition.

[0062] In another scenario, the base station 104A also performs a second conditional handover preparation process with the base station 106A via an interface (e.g., X2 or Xn) to prepare for a potential handover of the UE 102 to the base station 106A in a process similar to the above. However, in this scenario, the base station 104A also transmits to the UE 102 a second conditional handover command message received by the base station 104A from the candidate base station 106A for the potential handover in the second conditional handover preparation. The base station 106A may provide the configuration of an additional candidate cell ( Figure 1 not shown in the figure) in the second handover command message. The UE 102 may monitor whether the additional candidate cell of the candidate base station 106A meets the second condition. The second condition may be the same as or different from the first condition.

[0063] The base station 104A may also perform a third conditional handover preparation process with the base station 106B via an interface (e.g., X2 or Xn) to prepare for a potential handover of the UE 102 to the base station 106B in a process similar to the above. In this scenario, the base station 104A transmits to the UE 102 a third conditional handover command message received by the base station 104A from the candidate base station 106B for the potential handover in the third conditional handover preparation. The base station 106A may provide the configuration of the candidate cell 126B in the third handover command message. The UE 102 may monitor whether the candidate cell 126B of the candidate base station 106B meets the third condition. The third condition may be the same as or different from the first condition and / or the second condition. The above conditional handover command message may be an RRC reconfiguration message or may be replaced by a conditional handover configuration as an information element (IE).

[0064] In some implementations, the wireless communication system 100 supports DC operation, including the SN addition and SN change processes. In one scenario, for example, after the UE 102 is connected to the base station 104A, the base station 104A may perform an immediate SN addition process to add the base station 106A as a secondary node, thereby configuring the UE 102 to operate in DC with the base stations 104A and 106A. At this time, the base stations 104A and 106A operate as the MN and SN respectively. Later, when the UE 102 is still in DC with the MN 104A and the SN 106A, the MN 104A may perform an immediate SN change process to change the SN of the UE 102 from the base station 106A (which may be referred to as the source SN or S-SN) to the base station 106B (which may be referred to as the target SN or T-SN).

[0065] In other scenarios, when the UE 102 is in single connectivity (SC) with the base station 104A, or when the UE 102 is in dual connectivity (DC) with the base stations 104A and 106B, and before the UE 102 has connected to the candidate secondary node (C-SN) 106A, the base station 104A may perform a conditional SN addition procedure to configure the base station 106A as the C-SN of the UE 102. In this case, the base stations 104A and 106A operate as the MN and C-SN of the UE 102, respectively. When the UE 102 receives the configuration for the C-SN 106A, the UE 102 does not connect to the C-SN 106A unless and until the UE 102 detects that the corresponding condition is met or the base station 104A performs an immediate SN addition procedure to add the base station 106A as a secondary node. If the UE 102 determines that the condition is met, the UE 102 connects to the C-SN 106A, such that the C-SN 106A becomes the SN 106A of the UE 102.

[0066] In some implementations, the condition may be that the signal strength / quality measured by the UE 102 on the candidate primary secondary cell (C-PSCell) of the C-SN 106A is "good" enough. For example, if one or more measurement results obtained by the UE 102 (when performing measurements on the C-PSCell) are higher than a threshold configured by the MN 104A or higher than a predetermined or pre-configured threshold, the first condition may be satisfied. If the UE 102 determines that the first condition is met, the UE 102 may perform a random access procedure with the C-SN 106A to connect to the C-SN 106A. Once the UE 102 successfully completes the random access procedure, the base station 106A becomes the SN of the UE 102, and the C-PSCell (e.g., cell 126A) becomes the PSCell of the UE 102. Then, the SN 106A may start data communication with the UE 102.

[0067] Another scenario involves conditional PSCell change. In this scenario, the UE 102 is initially in connection with the MN 104 (via the primary cell (PCell)) and the SN 106A (via a PSCell different from cell 126A, Figure 1DC (not shown in the figure). SN 106A may provide the configuration of C-PSCell 126A for UE 102. If UE 102 is configured with a signaling radio bearer (SRB) (e.g., SRB3) that allows exchanging RRC messages with SN106A, then SN 106A may directly transmit the configuration of C-PSCell 126A to UE 102 via the SRB or via MN 104. For example, SN 106A may transmit the configuration in response to one or more measurement results received from UE 102 via the SRB, or in response to one or more measurement results obtained by SN 106A from measuring the signals received from UE 102.

[0068] Contrary to the immediate PSCell change scenario discussed above, after receiving the configuration of C-PSCell 126A, UE102 does not immediately disconnect from the PSCell and attempt to connect to C-PSCell 126A. Instead, UE 102 does not connect to C-PSCell126A until UE 102 determines that a specific condition is met. When UE 102 determines that the condition has been satisfied, UE 102 connects to C-PSCell 126A, such that C-PSCell 126A starts operating as the PSCell 126A of UE 102. In some implementations, UE 102 disconnects from the PSCell in order to connect to C-PSCell 126A.

[0069] In some scenarios, the condition associated with conditional SN addition or conditional PSCell change may be that the signal strength / quality measured by UE102 on the C-PSCell of C-SN 106A exceeds a specific threshold or otherwise corresponds to an acceptable measurement. For example, when one or more measurement results obtained by UE 102 on C-PSCell 126A are higher than the threshold configured by MN 104 or C-SN 106A or higher than a predetermined or pre-configured threshold, UE 102 may determine that the condition is met. When UE102 determines that such a condition is satisfied, UE 102 may perform a random access procedure on C-PSCell 126A and with C-SN 106A to connect to C-SN 106A. Once UE 102 successfully completes the random access procedure on C-PSCell 126A, C-PSCell 126A becomes the PSCell 126A of UE 102. Then, C-SN 106A may start communicating data (user plane data and / or control plane data) with UE102 via PSCell 126A.

[0070] In different configurations or scenarios of the wireless communication system 100, the base station 104A can operate as a master eNB (MeNB) or a master gNB (MgNB), and the base stations 106A or 106B can be implemented as secondary gNBs (SgNBs) or candidate SgNBs (C-SgNBs). The UE 102 can communicate with the base station 104A and the base stations 106A or 106B via the same radio access technology (RAT) such as EUTRA or NR or via different RATs. If the base station 104A is a MeNB and the base station 106A is an SgNB, the UE 102 can be in EUTRA-NR DC (EN-DC) with the MeNB and the SgNB. In this scenario, the MeNB 104A may or may not configure the base station 106B as a C-SgNB for the UE 102. When the base station 104A is a MeNB and the base station 106A is a C-SgNB of the UE 102, the UE 102 can be in SC with the MeNB. In this scenario, the MeNB 104 may or may not configure the base station 106B as another C-SgNB for the UE 102.

[0071] In some cases, the MeNB, SeNB, or C-SgNB can be implemented as an ng-eNB instead of an eNB. When the base station 104A is a master ng-eNB (Mng-eNB) and the base station 106A is an SgNB, the UE 102 can be in next-generation (NG) EUTRA-NR DC (NGEN-DC) with the Mng-eNB and the SgNB. In this scenario, the MeNB 104A may or may not configure the base station 106B as a C-SgNB for the UE 102. When the base station 104A is an Mng-NB and the base station 106A is a C-SgNB of the UE 102, the UE 102 can be in SC with the Mng-NB. In this scenario, the Mng-eNB 104A may or may not configure the base station 106B as another C-SgNB for the UE 102.

[0072] When base station 104A is a MgNB and base station 106A is an SgNB, UE 102 can be in NR-NR DC (NR-DC) with the MgNB and the SgNB. In this scenario, MeNB 104A may or may not configure base station 106B as a C-SgNB for UE 102. When base station 104A is a MgNB and base station 106A is a C-SgNB of UE 102, UE 102 can be in SC with the MgNB. In this scenario, MgNB 104A may or may not configure base station 106B as another C-SgNB for UE 102.

[0073] When base station 104A is a MgNB and base station 106A is a secondary ng-eNB (Sng-eNB), UE 102 can be in NR-EUTRA DC (NE-DC) with the MgNB and the Sng-eNB. In this scenario, MgNB 104A may or may not configure base station 106B as a C-Sng-eNB for UE 102. When base station 104A is a MgNB and base station 106A is a candidate Sng-eNB (C-Sng-eNB) of UE 102, UE 102 can be in SC with the MgNB. In this scenario, MgNB 104A may or may not configure base station 106B as another C-Sng-eNB for UE 102.

[0074] Next, FIG. 2 illustrates in a simplified manner a radio protocol stack according to which UE 102 can communicate with an eNB / ng-eNB or a gNB. Each of base stations 104, 106A, or 106B can be an eNB / ng-eNB or a gNB.

[0075] The physical layer (PHY) 202A of EUTRA provides transport channels to the EUTRA Medium Access Control (MAC) sublayer 204A. The EUTRA MAC sublayer 204A in turn provides logical channels to the EUTRA Radio Link Control (RLC) sublayer 206A, and the EUTRA RLC sublayer in turn provides RLC channels to the EUTRA PDCP sublayer 208 and in some cases to the NR PDCP sublayer 210. Similarly, the PHY 202B of NR provides transport channels to the NR MAC sublayer 204B. The NR MAC sublayer 204B in turn provides logical channels to the NR RLC sublayer 206B, and the NR RLC sublayer 206B in turn provides RLC channels to the NR PDCP sublayer 210. In some implementations, the UE 102 supports both the EUTRA and NR stacks to support handover between EUTRA and NR base stations and / or DC via EUTRA and NR interfaces. Further, as shown in FIG. 2, the UE 102 may support layering of NR PDCP 210 on EUTRA RLC 206A.

[0076] The EUTRA PDCP sublayer 208 and the NR PDCP sublayer 210 receive packets that may be referred to as service data units (SDUs) (e.g., from the Internet Protocol (IP) layer, directly or indirectly layered on the PDCP layer 208 or 210), and output packets that may be referred to as protocol data units (PDUs) (e.g., to the RLC layer 206A or 206B). Except where differences between SDUs and PDUs are relevant, for simplicity, this disclosure refers to both SDUs and PDUs as "packets".

[0077] For example, on the control plane, the EUTRA PDCP sublayer 208 and the NR PDCP sublayer 210 provide SRBs to exchange Radio Resource Control (RRC) messages. On the user plane, the EUTRA PDCP sublayer 208 and the NR PDCP sublayer 210 provide DRBs to support data exchange.

[0078] When the UE 102 operates in EUTRA / NR DC (EN-DC) with the BS 104A operating as a MeNB and the BS 106A operating as an SgNB, the network may provide the UE 102 with a bearer terminated at the MN using EUTRA PDCP 208 or a bearer terminated at the MN using NR PDCP 210. The network in various scenarios may also provide the UE 102 with a bearer terminated at the SN using only NR PDCP 210. The bearer terminated at the MN may be an MCG bearer or a split bearer. The bearer terminated at the SN may be an SCG bearer or a split bearer. The bearer terminated at the MN may be an SRB (e.g., SRB1 or SRB2) or a DRB. The bearer terminated at the SN may be an SRB (e.g., SRB) or a DRB.

[0079] Next, several known techniques related to conditional configuration are briefly discussed with reference to FIGS. 3 to 6.

[0080] Referring first to FIG. 3, the base station 104A in scenario 300 operates as an MN, and the base station 106A operates as a C-SN. Initially, the UE 102 communicates 302 with the MN 104A. In one scenario, the UE 102 that is in SC with the MN 104A communicates data (e.g., UL data PDU and / or DL data PDU) with the MN 104A. In another scenario, the UE 102 that is in DC with the MN 104A and the SN 106B communicates data (e.g., UL data PDU and / or DL data PDU) with the MN 104A and / or the SN 106B (not shown in FIG. 3). In yet another scenario, the UE 102 that is in DC with the MN 104A and the SN 106A communicates data (e.g., UL data PDU and / or DL data PDU) with the MN 104A and / or the SN 106B. The MN 104A may determine that it should initiate a conditional SN addition procedure 304 to configure the base station 106A as the C-SN for the UE 102 or configure the cell of the base station 106A (which can be a C-SN or an SN) as the C-PSCell for the UE 102. The MN 104A may make this determination based on, for example, one or more measurement results received from the UE 102 or another suitable event. In response to this determination, the MN 104A sends 306 an SN addition request message to the C-SN 106A to initiate a conditional SN addition procedure. In response to receiving 306 the SN addition request message, the C-SN 106A includes the C-SN configuration in an SN addition request acknowledge message for the UE 102. Then, in response to the SN addition request message, the SN 106A sends 308 an SN addition request acknowledge message to the MN 104A. The C-SN configuration included in this message may include one or more configuration parameters of the C-PSCell.

[0081] For convenience, the following discussion refers to the configuration in the singular form, but it will be understood that the C-SN 106A may provide multiple C-SN configurations, where each C-SN configuration includes one or more configuration parameters of a specific C-PSCell.

[0082] In some implementations, the MN 104A may include a request for the base station 106A to operate as the C-SN for the UE 102 in the SN addition request message. In other implementations, a specific request message other than the SN addition request message may be defined and sent by the MN 104A to the base station 106A to request the base station 106A to operate as the C-SN for the UE 102. The C-SN 106 may send a specific request acknowledge message that includes the C-SN configuration instead of the SN addition request acknowledge message.

[0083] In some implementations, MN 104A may include the C-SN configuration in a first RRC message, and in some cases, may include one or more conditions for connecting to C-SN 106A via the C-PSCell. The information in the first RRC message may include one or more indicators or parameters, such as field names, dedicated information elements (IEs), and / or indications of the one or more conditions associated with the C-SN configuration.

[0084] In some implementations, the C-SN configuration may include a CellGroupConfig IE that configures the C-PSCell. In one implementation, SN 106A may include an RRCReconfiguration message containing the CellGroupConfig IE in the SN addition request confirmation message. The CellGroupConfig IE may comply with 3GPP TS 38.331.

[0085] In other implementations, the C-SN configuration may be a SCG-ConfigPartSCG-r12 IE that configures the C-PSCell. In one implementation, SN 106A may include an RRCConnectionReconfiguration message containing the ConfigPartSCG-r12 IE in the SN addition request confirmation message. In other implementations, the C-SN configuration may be an RRCConnectionReconfiguration message that includes the SCG-ConfigPartSCG-r12 IE. The SCG-ConfigPartSCG-r12 IE may comply with 3GPP TS 36.331.

[0086] Continuing to refer to FIG. 3, in response to receiving the 308 SN addition request confirmation message, MN 104A includes the C-SN configuration and at least one condition in the first RRC message and transmits the 310 first RRC message to UE 102. In some implementations, in response to the first RRC message, UE 102 transmits a first RRC response message to MN 104. In one example, the first RRC message may be an RRC connection reconfiguration (e.g., RRCConnectionReconfiguration) message, and the first RRC response message may be an RRC connection reconfiguration complete (e.g., RRCConnectionReconfigurationComplete) message. In another example, the first RRC message may be an RRC reconfiguration (e.g., RRCReconfiguration) message, and the first RRC response message may be an RRC reconfiguration complete (e.g., RRCReconfigurationComplete) message.

[0087] Events 306, 308, and 310 together may be considered to define a conditional configuration process 304.

[0088] UE 102 applies the at least one received condition (hereinafter discussed in the singular for convenience) to determine whether to connect to C-SN 106A via the C-PSCell. If UE 102 determines that the condition is satisfied, UE 102 connects to C-SN 106A via the C-PSCell according to the C-SN configuration. If UE 102 does not determine that the condition is satisfied, UE 102 does not connect to C-SN 106A via the C-PSCell according to the C-SN configuration.

[0089] Depending on the implementation, if one but must be all of the multiple conditions are satisfied, UE 102 may connect to C-SN 106 via the C-PSCell, or UE 102 may connect to C-SN 106 only if each condition is satisfied.

[0090] When UE 102 determines 380 that the condition for connecting to the C-PSCell is satisfied, in response to this detection, UE 102 initiates 382 a random access procedure via the C-PSCell with C-SN 106A. UE 102 performs 382 the random access procedure with C-SN 106A via the C-PSCell. If UE successfully completes the random access procedure, C-SN 106A starts operating as an SN to transmit data to and / or receive data from UE 102.

[0091] If base station 106A is the SN of UE 102, instead of the SN addition request message, MN 104 may use the SN Modification Request message, and instead of the SN addition request acknowledgement message, SN 106A may use the SN Modification Request Acknowledge message.

[0092] In scenario 400 of FIG. 4, base station 104A operates as the MN and base station 106A operates as the SN. Initially, UE 102 communicates with MN 104A and SN 106A in DC 403. Then, SN 106A determines 405 the conditional connection information of the C-PSCell. The conditional connection information may include configuration data related to SN 106A (more specifically, the C-PSCell of SN 106A) and one or more conditions for connecting to SN 106A. Thus, SN 106A determines that UE 102 can operate in DC with MN 104 and a cell of SN 106A that is subject to one or more conditions and is different from the cell to which UE 102 is currently connected (event 403). In another implementation, event 405 occurs at MN 104A.

[0093] In this scenario, SN 106A provides 406 the conditional connection information to MN 104A, which in turn provides 408 the conditional connection information to UE 102 via an RRC Reconfiguration message. UE 120 may respond 410 with an RRC Reconfiguration Complete message, and MN 104A optionally sends 412 a reconfiguration complete message to SN 106. Events 405, 406, 408, 410, and 412 together define the conditional SN reconfiguration process 404.

[0094] When UE 102 determines 480 that the conditions for connecting to the C-PSCell are met, in response to this detection, UE 102 initiates 482 a random access procedure with C-SN 106A via the C-PSCell. UE 102 performs 382 a random access procedure with C-SN 106A via the C-PSCell. If UE successfully completes the random access procedure, C-SN 106A operates 484 as the SN to transmit data to and / or receive data from UE 102.

[0095] Figure 5 illustrates a scenario 500 that is generally similar to scenario 400 of Figure 4, but here SN 106A directly sends conditional connection information 507 to UE 102 in an RRC reconfiguration message via a radio connection that already exists between UE 102 and SN 106. Optionally, UE 102 may respond 509 with an RRC reconfiguration complete message. Thus, events 505, 507, and 509 define another conditional SN reconfiguration process 504. Events 580, 582, and 584 are similar to events 480, 482, and 484 discussed above.

[0096] Next, Figure 6 illustrates a scenario 600 in which UE 102 initially communicates 602 with MN 104A. MN 104A may determine that it should initiate a conditional handover process 604 to hand over UE 102 to target MN 104B, and more specifically, to the C-PCell of MN 104B. MN 104A may make this determination based on, for example, one or more measurement results received from UE 102 or another suitable event. In response to this determination, MN 104A sends 606 a Conditional Handover Request message to T-MN 104B.

[0097] In response to receiving 606 the Conditional Handover Request message, T-MN 104B generates conditional connection information, which in this case includes a conditional handover configuration. T-MN 104B sends 608 a Conditional Handover Request Acknowledge message to S-MN 104A, and S-MN 104A sends 610 the conditional connection information to UE 102 in an RRC message. Similar to the above example, the conditional connection information may include configuration data and one or more conditions for handing over to T-MN 104B. Thus, events 606, 608, and 610 define the conditional handover process 604.

[0098] When UE 102 determines 680 that the conditions for handing over to T-MN 104B are met, in response to this detection, UE 102 initiates 682 a random access process via the C-PCell of T-MN 104B. When this process is successfully completed, UE 102 communicates 684 with T-MN 104B via the C-PCell according to the conditional handover configuration.

[0099] Next, refer to Figures 7 to 15 Discuss several techniques of the present disclosure for managing conditional configurations.

[0100] Figure 7Exemplary scenario 700, where base station 104A operates as an MN, and base station 106A operates as a C-SN or SN ((C-)SN), or base station 104B operates as a T-MN. When scenario 700 involves base station 104B, UE 102 can operate with base station 104B in SC mode, or in DC mode with base station 104B or another base station. For convenience, this disclosure refers to base station 104B as "MN" in both cases.

[0101] Initially, UE 102 communicates 702 with the MN (e.g., in the RRC_CONNECTED state). The MN 104 performs 704 a conditional configuration process, which can be a C-SN configuration process with the (C-)SN 106A similar to process 304, 404, or 504, or a conditional handover process with the T-MN 104B similar to process 604.

[0102] Then, the MN 104A determines 720 that UE 102 should suspend the radio connection (e.g., RRC connection) with the MN 104A. To this end, the MN 104A can determine that UE 102 should transition to the inactive state, or to the idle state with a suspended RRC connection. In response to this determination, the MN 104A transmits 722 an RRC release message (e.g., RRCRelease or RRCConnectionRelease) to UE 102 that includes an inactive field (e.g., suspendConfig, rrc-Suspend, or rrc-InactiveConfig).

[0103] The MN 104 in this implementation also transmits 724 a Conditional SN Release Request and / or an SN Release Request ((Conditional)SN Release Request) message to the (C-)SN 106A. In various implementations, the MN 104 transmits 724 the (Conditional)SN Release Request before or after transmitting 722 the RRC release message. In response to receiving 724 the (Conditional)SN Release Request from the MN 104, the (C-)SN 106A can transmit a (Conditional)SN Release Request acknowledgment (not shown) to the MN 104. In response to the (Conditional)SN Release Request acknowledgment, the MN 104 can transmit a UEContext Release (not shown) to the (C-)SN 106A; and in response to receiving the SN Release Request or the UEContext Release, the (C-)SN 106A releases 770 the C-SN or the conditional handover configuration.

[0104] When the UE 102 is in DC with the MN 104A and the SN 106B, in some implementations, the MN 104A transmits a SN Release Request to the SN 106B. In response to receiving the SN Release Request from the MN 104A, the SN 106B may transmit a SN Release Request Acknowledge to the MN 104A. In response to the SN Release Request Acknowledge, the MN 104 may transmit a UE context release to the SN 106B. In response to receiving the SN Release Request or the UE context release, the SN 106B releases the SCG configuration. In response to the RRC release message, the UE 102 stores the UE Inactive AS context and releases the C-SN configuration.

[0105] When the UE 102 is in DC with the MN 104A and the SN 106B or in SC with the MN 104A, in some implementations, the MN 104A transmits a CHO Release Request message to the T-MN 104B. In response to the CHO Release Request message, the T-MN 104B releases the conditional handover configuration. Additionally, in response to the RRC release message, the UE 102 stores the UE Inactive AS context and releases the conditional handover configuration.

[0106] Figure 8 Illustrative scenario 800, where the base station 104A operates as the MN, and the base station 106A operates as the C-SN or SN ((C-)SN), or the base station 104B operates as the T-MN. Events 802, 804, and 822 are similar to the above events 702, 704, and 722.

[0107] However, in response to receiving the 822 RRC Release message, the UE 102 stores the 830 UE Inactive AS context and retains the 842 C-SN or conditional handover configuration. In some implementations, the UE 102 stops or pauses detecting the conditions associated with the C-SN or conditional handover configuration.

[0108] After a certain period of time, UE 102 may determine 844 to perform an RRC resume procedure. In response to this determination, UE 102 transmits an 850 RRC resume request message to MN 104A and receives an 852 RRC resume message as a response. In response to the RRC resume message, UE 102 enters the connected state and transmits an 854 RRC resume complete message to MN 104A. The connected UE 102 continues or resumes detecting the (multiple) conditions associated with the C-SN or conditional configuration or conditional handover configuration, and performs a process 890 similar to processes 382, (482, 484), (582, 584), or (682, 684).

[0109] In some implementations, MN 104A may include an SK-counter value in the RRC resume message. As specified in 3GPP TS or TS 33.501, UE 102 derives or updates a secondary key (S-K gNB or S-K gNB or S-K eNB ) based on the K RRCenc key and uses the received sk-Counter value, derives encryption keys (e.g., K UPenc and K RRCint keys) and derives integrity keys (e.g., K UPint and K UPint keys). If UE 102 is not configured for integrity protection of the data radio bearer (DRB), UE 102 cannot derive the K

[0110] key. At events (482, 484), (582, 584), or (682, 684), UE uses the encryption key and integrity key to communicate data with (C-)SN 106A or T-MN 104B via the C-PSCell.

[0111] Now referring to Figure 9 , in scenario 900, base station 104A operates as the MN, and base station 106A operates as the C-SN or SN ((C-)SN), or base station 104B operates as the T-MN. In Figure 8 and Figure 9904, 920, 922, and 942 are similar to events 804, 820, 822, and 842, and the differences between the two scenarios are discussed below. UE 102 later determines 944 that the radio connection should be restored, and initiates an RRC recovery procedure with MN 104. UE transmits 950 an RRC resume request to MN 104A.

[0112] After receiving 950 the RRC resume request message from the UE 102, the MN 104A decides 951 to release the C-SN configuration or the conditional handover configuration. In response to the decision, the MN 104A transmits 956 an RRC resume message including an indication of releasing the conditional connection information (e.g., a C-SN release indication or a conditional handover release indication) to the UE 102, and / or transmits 924 a conditional SN release request or a conditional handover release to the C-SN 106A. In response to receiving 956 the RRC resume message with the C-SN release indication, the UE 102 releases the C-SN configuration or the conditional handover configuration. In response to receiving 924 the conditional SN release request message, the C-SN 106A releases 970 the C-SN configuration or the conditional handover configuration. In response to receiving 924 the conditional handover release message, the T-MN 104B releases 970 the conditional handover configuration.

[0113] In one scenario, MN 104A decides to release the C-SN configuration or the conditional handover configuration in response to configuring UE 102 to transition to the inactive state, and transmits 924 a conditional SN release request or a conditional handover release to C-SN 106A or T-MN 104B. Before receiving 950 the RRC resume message from UE 102, MN 104A transmits 924 the conditional SN release request or the conditional handover release to C-SN 106A or T-MN 104B.

[0114] In one example, MN 104A decides to retain the C-SN configuration or conditional handover configuration. In response to the decision, MN 104A does not include an indication of releasing the conditional connection information in the RRC resume message, and does not transmit 1310 a conditional SN release request or conditional handover release.

[0115] In one implementation, MN 104A decides to retain the conditional SN or handover configuration. In response to this decision, at event 956, MN 104A includes a retain or "keep" indication in the RRC resume message instead of a release indication, and does not transmit the conditional SN release request or conditional handover release 924. After receiving the RRC resume message including the "keep" indication at 956, UE 102 does not release the conditional SN or handover configuration.

[0116] In another scenario, MN 104A decides to release the C-SN or handover configuration. In response to this decision, MN 104A does not include a keep indication. Instead, it includes a release indication in the RRC resume message (event 956) and transmits the conditional SN release request or conditional handover release 924. After receiving the RRC resume message with the release indication at 956, UE 102 releases the conditional SN or handover configuration.

[0117] In one scenario, since the same C-SN configuration (e.g., SR configuration or random access configuration) has been allocated to another UE, MN 104A decides at 951 to release the C-SN configuration. In another scenario, MN 104 decides at 951 to release the C-PSCell configuration because it cannot exchange messages with C-SN 106A (e.g., C-SN 106A has powered off). For similar reasons, MN 104A may decide at 951 to release the conditional handover configuration.

[0118] In one embodiment, in response to the release configuration decision at event 951, MN 102 transmits a 956 RRC establishment message (e.g., RRCSetup or RRCConnectionSetup) or RRC release message to UE 102, and transmits a conditional SN release request or conditional handover request 924 to C-SN 106A or T-MN 104B. In response to receiving the 956 RRC establishment message or RRC release message, UE 102 releases the conditional SN or handover configuration 948.

[0119] Figure 10 Illustrative scenario 1000, where base station 104A operates as an MN, and base station 106A operates as a C-SN or SN ((C-)SN), or base station 104B operates as a T-MN. In Figure 9 and Figure 10 , similar reference numerals are used to label similar events, and events 1002, 1004, 1020, and 1022 are similar to events 902, 9004, 920, and 922 discussed above.

[0120] In this case, the UE 102 moves 1045 to the second MN 104B and determines to perform an RRC resume procedure with the MN 104B. In response to this decision, the UE 102 transmits 1051 an RRC resume request message to the MN 104B.

[0121] After receiving 1051 the RRC resume request message from the UE 102, the MN 104B transmits 1060 a UE context retrieve message to the MN 104A to obtain the UE context. In response to this request, the MN 104A decides 1052 to release the C-SN configuration or the conditional handover configuration. In response to this decision, the MN 104A transmits 1024 a conditional SN release request or a conditional handover release message to the C-SN 106A and transmits 1062 a UE context retrieve response including a C-SN release indication to the MN 104B.

[0122] After receiving 1024 the conditional SN release request message, the C-SN 106A releases 1070 the C-SN configuration or the conditional handover configuration. After receiving 1062 the UE context retrieve response including the release indication, the MN 104B transmits 1053 an RRC resume message including the release indication to the UE 102. In response, the UE 102 releases 1048 the C-SN configuration.

[0123] In one implementation, the UE context retrieve response (event 1062) does not include an SN release or a conditional handover indication, but includes the UE inactive AS context of the UE 102 and / or the C-SN configuration of the UE 102. If the MN 104B decides to release the C-SN or the conditional handover configuration, the MN includes an SN release or a conditional handover release indication in the RRC resume message (event 1053). If the MN 104B decides to retain the C-SN configuration, the MN 104B does not include a release indication in the RRC resume message (event 1053).

[0124] In some implementations, the MN 104B and the MN 104A are the same MN. In this case, in response to the RRC resume decision and procedure, the UE 102 and the MN 104A may decide to retain the C-SN configuration.

[0125] Figure 11 An example generally similar to reference Figure 8 the scenario 800 discussed, in Figure 8 and 11Similar reference numerals are used to label similar events in the following. However, in this case, MN 104A receives in the RRC Resume Complete message the measurement results related to C-SN 104A or T-MN 104B at 1155 and determines at 1151 that the conditional connection should be released. MN 104A accordingly releases the conditional connection information at 1158, 1124. Specifically, MN 104A transmits to UE 102 at 1158 an RRC reconfiguration message including a release indication, and in response, receives at 1159 an RRC reconfiguration complete message.

[0126] Figure 12 Illustrates scenario 1200 which is generally similar to scenario 700. In Figure 7 and 12 similar reference numerals are used to label similar events. However, in this scenario, MN 104A sends at 1222 an RRC release message and omits the indication that the conditional connection information should be retained. Accordingly, UE 102 releases the conditional connection information at 1249.

[0127] Now refer to Figure 13 and Figures 7 to 12 similar events to those in

[0128] Figure 14 are labeled with similar reference numerals. In scenario 1300, MN 104A sends at 1322 an RRC release message and includes an explicit indication that the conditional connection information should be released. Accordingly, UE 102 releases the conditional connection information at 1349. Figures 7 to 13 Illustrates another scenario 1400, and similar events to those in

[0129] are labeled with similar reference numerals. According to scenario 1400, in response to receiving at 1450 a request to resume a radio connection from UE 102, rather than earlier as in scenario 1300 for example, MN 104A sends at 1424 a conditional release request or a conditional handover release. Figure 15 In Figures 7 to 14 similar events to those in

[0130] Figure 16 is a flowchart of an example method 1600 for managing conditional connection information according to an indication received from an MN or S-MN, the method being applicable in Figure 1It is implemented in the UE 102 or another suitable device. For clarity, the method 1600 is described with an example reference to the UE 102.

[0131] At block 1602, the UE 102 receives an RRC message indicating that the UE 102 should suspend the radio connection (see Figure 7 event 722 of Figure 8 event 822 of Figure 9 event 922 of Figure 10 event 1022 of Figure 11 event 1122 of Figure 12 event 1222 of Figure 13 event 1322 of Figure 14 event 1422 of Figure 15 event 1522 of ). Next, at block 1604, the UE 102 determines whether the message includes an indication that the UE 102 should release the conditional connection information. When the message includes such an indication (see Figure 13 event 1342 of ), the process proceeds to block 1606, where the UE 102 releases the conditional connection information (see Figure 13 event 1349 of ). Otherwise, when the message does not include such an indication (see Figure 8 event 822 of Figure 9 event 922 of Figure 10 event 1022 of Figure 11 event 1122 of Figure 14 event 1422 of Figure 15 event 1522 of ), the process proceeds to block 1608, where the UE 102 retains the conditional connection information (see Figure 8 event 842 of Figure 9 event 942 of Figure 10 event 1042 of Figure 11 event 1142 of Figure 15 event 1542 of ).

[0132] Figure 17 is a flowchart of an example method 1700 for managing conditional connection information at the UE using an indication of whether the UE should retain the conditional connection information. This method can be implemented in a base station operating as an MN or S-MN Figure 1 At block 1702, the base station determines that the UE should suspend the radio connection with the base station (see Figure 7 event 720 of Figure 8 event 820 of Figure 9 event 920 of Figure 10 event 1020 of Figure 11 event 1120 of Figure 12Event 1220, Figure 13 Event 1320, Figure 14 Event 1420, Figure 15 Event 1520). Next, at block 1704, the base station determines whether the base station should release the conditional connection information configured for the UE and proceeds to block 1706 (yes) or block 1708 (no). At block 1706, the base station includes an indication in the RRC message that the UE should release the conditional connection information (see Figure 13 Event 1342). On the other hand, at block 1708, the base station generates an RRC message and omits the indication in the RRC message that the UE should release the conditional connection information (see Figure 8 Event 822, Figure 9 Event 922, Figure 10 Event 1022, Figure 11 Event 1122, Figure 14 Event 1422, Figure 15 Event 1522).

[0133] Figure 18 is a flowchart of an example method 1800 for managing conditional connection information based on whether the MN or S-MN has resumed a previously suspended radio connection, which can be implemented in a Figure 1 UE. At block 1802, the UE transmits a request to the MN to resume the suspended radio connection. At block 1804, the UE receives an RRC message as a response. If the UE determines at block 1806 that the RRC message is an instruction to resume the radio connection, the process proceeds to block 1808. Otherwise, if the UE determines at block 1806 that the RRC message is not an instruction to resume the radio connection, the process proceeds to block 1810. At block 1808, the UE retains the conditional connection information. At block 1810, the UE releases the conditional information.

[0134] Figure 19 is a flowchart of an example method 1900 for managing conditional connection information at the UE when the UE requests to resume a previously suspended radio connection, which can be implemented in a device operating as an MN or S-MN Figure 1Is implemented in the base station. At block 1902, the base station receives a request to resume a suspended radio connection from the UE (e.g., an RRC Resume Request message). If the base station determines at block 1904 that the base station should release the conditional connection information, the process proceeds to block 1906, where the base station transmits an RRC Setup message or an RRC Release message to the UE. Otherwise, if the base station determines at block 1904 that the base station should not release the conditional connection information, the process proceeds to block 1910, where the base station transmits an RRC Resume message to the UE.

[0135] Figure 20 Is a flowchart of an example method 2000 for managing conditional connection information at the UE based on measurement results regarding the C-SN or C-MN, which can be implemented in a Figure 1 Base station operating as an MN or S-MN. At block 2002, the base station receives an RRC Resume Request message or an RRC Reconfiguration Complete message from the UE. If the base station determines at block 2004 that the message does not include measurement results above a threshold related to another base station, the process proceeds to block 2006, where the base station releases the conditional connection information. Otherwise, if the base station determines at block 2004 that the message includes measurement results above the threshold, the process proceeds to block 2010, where the base station retains the conditional connection information.

[0136] Figure 21 Is a flowchart of an example method 2100 for managing conditional connection information based on whether the conditional connection information is still valid when the UE has resumed a previously suspended radio connection, which can be implemented in a Figure 1 MN. At block 2102, the base station receives an RRC Resume Request message or an RRC Reconfiguration Complete message from the UE. If the base station determines at block 2104 that the conditional connection information is invalid, the process proceeds to block 2106, where the base station releases the conditional connection information. Otherwise, if the base station determines at block 2104 that the conditional connection information is still valid, the process proceeds to block 2110, where the base station retains the conditional connection information.

[0137] Figure 22 Is a flowchart of an example method 2200 for managing conditional operations related to the UE, which can be implemented in a Figure 1Implemented in the base station. At block 2202, the (first) base station sends conditional connection information to the UE (see Figure 7 Process 704). The conditional connection information may include: configuration data related to another (second) base station such that the UE can communicate with the first base station and the second base station in DC; and / or one or more conditions for connecting to the second base station.

[0138] At block 2204, the first base station determines that the UE should suspend the radio connection with the first base station (see Figure 7 Event 720, Figure 9 Event 920, Figure 10 Event 1020, Figure 11 Event 1120, Figure 12 Event 1220, Figure 13 Event 1320, Figure 14 Event 1420, Figure 15 Event 1520). Next, at block 2206, the first base station causes the UE to suspend the radio connection (see Figure 7 Event 722, Figure 9 Event 922, Figure 10 Event 1022, Figure 11 Event 1122, Figure 12 Event 1222, Figure 13 Event 1322, Figure 14 Event 1422, Figure 15 Event 1522). At block 2208, the first base station causes the second base station to release the conditional connection information (see Figure 7 Event 724, Figure 9 Event 924, Figure 10 Event 1024, Figure 11 Event 1124, Figure 12 Event 1224, Figure 13 Event 1324, Figure 14 Event 1424, Figure 15 Event 1524).

[0139] Figure 23 Is a flowchart of an example method 2300 for managing conditional operations related to a second base station, which can be implemented in the Figure 1 UE. At block 2302, the UE receives conditional connection information from the first base station (see Figure 7 Process 704, Figure 12procedure 1204). The conditional connection information may include configuration data related to the second base station, such that the UE can communicate with the first and second base stations in DC. The conditional connection information may also include one or more conditions for connecting to the second base station. At block 2304, the UE suspends the radio connection in response to a trigger event such as a command from the first base station (see Figure 7 event 722, Figure 12 event 1222). At block 2306, the UE releases the conditional connection information in response to the trigger event (see Figure 7 event 748, Figure 12 event 1249).

[0140] Figure 24 is a flowchart of another exemplary method 2400 for managing conditional operations related to a second base station, which may be implemented in a Figure 1 UE. At block 2402, the UE receives conditional connection information from the first base station (see Figure 9 procedure 904, Figure 10 procedure 1004, Figure 11 procedure 1104, Figure 12 procedure 1204, Figure 13 procedure 1304). The conditional connection information may include configuration data related to the second base station, such that the UE can communicate with the first and second base stations in DC. The conditional connection information may also include one or more conditions for connecting to the second base station.

[0141] Next, at block 2404, the UE receives a suspension indicating that the UE is to suspend the radio connection (see Figure 9 event 922, Figure 10 event 1022, Figure 11 event 1122, Figure 12 event 1222, Figure 13 event 1322). At block 2406, the UE receives a conditional connection indication indicating whether the UE should release the conditional connection information (see Figure 9 event 956, Figure 10 event 1053, Figure 11 event 1158, Figure 12 event 1222, Figure 13 event 1322). At block 2406, the UE releases or retains the conditional connection information according to the indication (see Figure 9 event 948, Figure 10 event 1048, Figure 11 event 1148, Figure 12 event 1249, Figure 13 event 1349).

[0142] Additional Considerations

[0143] A user equipment (e.g., UE 102) capable of implementing the technology of the present disclosure may be any suitable device capable of wireless communication, such as a smart phone, a tablet computer, a laptop computer, a mobile gaming console, a point-of-sale (POS) terminal, a health monitoring device, a drone, a camera, a media streaming dongle or other personal media device, a wearable device such as a smart watch, a wireless hotspot, a femtocell or a broadband router. Additionally, in some cases, the user equipment may be embedded in an electronic system such as a head unit of a vehicle or an advanced driver assistance system (ADAS). Further, the user equipment may operate as an internet-of-things (IoT) device or a mobile-internet device (MID). Depending on the type, the user equipment may include one or more general-purpose processors, computer-readable memory, a user interface, one or more network interfaces, one or more sensors, etc.

[0144] In the present disclosure, certain embodiments are described as including logic or multiple components or modules. A module may be a software module (e.g., code or machine-readable instructions stored on a non-transitory machine-readable medium) or a hardware module. A hardware module is a tangible unit capable of performing certain operations and may be configured or arranged in a particular manner. A hardware module may include dedicated circuitry or logic that is permanently configured (e.g., as a dedicated processor such as a field programmable gate array (FPGA) or an application-specific integrated circuit (ASIC), a digital signal processor (DSP), etc.) to perform certain operations. A hardware module may also include programmable logic or circuitry (e.g., included in a general-purpose processor or other programmable processor) that is temporarily configured by software to perform certain operations. The decision to implement a hardware module in dedicated and permanently configured circuitry or in temporarily configured circuitry (e.g., configured by software) may be driven by cost and time considerations.

[0145] When implemented in software, these technologies may be provided as part of an operating system, a library used by multiple applications, a particular software application, etc. The software may be executed by one or more general-purpose processors or one or more dedicated processors.

[0146] Aspect 1, a method for managing conditional operations related to a user equipment (UE) in a first base station, the method comprising: sending conditional connection information to the UE via processing hardware, the conditional connection information including at least one of the following: (i) configuration data related to a second base station or (ii) one or more conditions for connecting to the second base station; and in response to determining via the processing hardware that the UE is to suspend a radio connection with the first base station: causing the UE to suspend the radio connection with the first base station, and causing the second base station to release the conditional connection information.

[0147] Aspect 2, the method according to aspect 1, wherein the conditional connection information is for connecting the UE to the second base station so that the UE operates in dual connection with the first base station and the second base station.

[0148] Aspect 3, the method according to aspect 2, wherein causing the second base station to release the conditional connection information includes: sending a request to release the conditional secondary node (SN) configuration at the second base station to the second base station.

[0149] Aspect 4, the method according to aspect 1, wherein the conditional connection information is related to a handover from the first base station to the second base station.

[0150] Aspect 5, the method according to aspect 4, wherein causing the second base station to release the conditional connection information includes: sending a request to release the conditional handover configuration at the second base station to the second base station.

[0151] Aspect 6, the method according to any one of aspects 1 to 5, further comprising: sending a message to the UE via a radio interface indicating that the UE is to release the conditional connection information.

[0152] Aspect 7, the method according to aspect 6, wherein the message includes a field indicating that the UE is to release the conditional connection information.

[0153] Aspect 8, the method according to aspect 6, wherein the message omits a field indicating that the UE is to retain the conditional connection information.

[0154] Aspect 9, the method according to any one of aspects 1 to 5, wherein causing the UE to suspend the radio connection includes: sending a message associated with a protocol for controlling radio resources to the UE, the message indicating that the UE is to transition to (i) an inactive mode associated with the protocol or (ii) an idle mode associated with the protocol in the case of a suspended radio connection.

[0155] Aspect 10. The method according to aspect 9, wherein the message is a first message; the method further comprises: receiving, from a UE, a request to resume a suspended radio connection; and in response to the request, sending, to the UE, a second message associated with a protocol for controlling radio resources, the second message instructing the UE to (i) resume the radio connection and (ii) release conditional connection information.

[0156] Aspect 11. The method according to any one of aspects 1 to 9, wherein causing the second base station to release conditional connection information comprises: sending, via an inter-base-station interface, an indication to the second base station that the second base station is to release conditional connection information.

[0157] Aspect 12. The method according to aspect 11, comprising: sending an indication in response to receiving, from a UE, a request to resume a radio connection.

[0158] Aspect 13. The method according to aspect 11, comprising: sending an indication shortly before or shortly after causing the UE to suspend the radio connection.

[0159] Aspect 14. The method according to aspect 11, comprising: sending an indication in response to receiving, from a third base station, a request to retrieve the context of the UE.

[0160] Aspect 15. A base station comprising processing hardware and configured to implement the method according to any one of aspects 1 to 14.

[0161] Aspect 16. A method for managing conditional operations related to a second base station in a user equipment (UE) having a radio connection to a first base station, the method comprising: receiving, by processing hardware, from the first base station conditional connection information comprising at least one of the following: (i) configuration data related to the second base station and (ii) one or more conditions for connecting to the second base station; suspending, by processing hardware, the radio connection in response to a trigger event; and retaining, by processing hardware, the conditional connection information in response to determining that the UE should resume the radio connection.

[0162] Aspect 17. The method according to aspect 16, further comprising: resuming, by processing hardware, the suspended radio connection; and connecting, using the configuration data, to the second base station in response to determining that one or more conditions for connecting to the second base station are met.

[0163] Aspect 18. The method according to aspect 17, wherein resuming the suspended radio connection comprises: sending, by processing hardware, a request to resume the suspended radio connection to the first base station; and receiving, by processing hardware, from the first base station a message instructing the UE to resume the radio connection.

[0164] Aspect 19. The method according to aspect 16 further includes: in response to determining, by processing hardware, to resume a suspended radio connection: sending, by the processing hardware, a request to resume the suspended radio connection to a first base station; and releasing, by the processing hardware, conditional connection information.

[0165] Aspect 20. The method according to aspect 16 further includes: sending, by the processing hardware, a request to resume the suspended radio connection to a first base station; receiving, by the processing hardware, a message indicating that the UE is to resume the suspended radio connection, the message including a conditional connection indication indicating whether the UE is to release the conditional connection information; and releasing or retaining the conditional connection information according to the conditional connection indication.

[0166] Aspect 21. The method according to aspect 16 further includes: determining, by the processing hardware, to resume a radio connection with a third base station; releasing, by the processing hardware, the conditional connection information; and resuming, by the processing hardware, the suspended radio connection with the third base station.

[0167] Aspect 22. The method according to aspect 21, wherein releasing the conditional connection information is in response to determining to resume the radio connection with the third base station.

[0168] Aspect 23. The method according to aspect 21, wherein releasing the conditional connection information is in response to receiving, from the third base station, a message indicating that the radio connection with the third base station has been resumed.

[0169] Aspect 24. The method according to any one of aspects 16 to 23, wherein the conditional connection information relates to connecting the UE to a second base station so that the UE operates in dual connection with the first base station and the second base station.

[0170] Aspect 25. The method according to any one of aspects 16 to 23, wherein the conditional connection information relates to a handover from the first base station to the second base station.

[0171] Aspect 26. The method according to aspect 20, wherein the triggering event includes receiving a message having a field indicating that the UE is to retain the conditional connection information.

[0172] Aspect 27. The method according to aspect 16, wherein the triggering event includes receiving a message in which a field indicating that the UE is to release the conditional connection information is omitted.

[0173] Aspect 28. The method according to aspect 16, wherein the triggering event includes receiving a message associated with a protocol for controlling radio resources, the message indicating that the UE is to transition to (i) an inactive mode associated with the protocol or (ii) an idle mode associated with the protocol in the case of a suspended radio connection.

[0174] Aspect 29, a method for managing conditional operations related to a second base station in a user equipment (UE) having a radio connection to a first base station, the method comprising: receiving, by processing hardware, conditional connection information from the first base station, the conditional connection information including at least one of the following: (i) configuration data related to the second base station and (ii) one or more conditions for connecting to the second base station; receiving, by processing hardware, a suspension indication from the base station indicating that the UE is to suspend the radio connection; receiving, by processing hardware, a conditional connection indication indicating whether the UE is to release the conditional connection information; and releasing or retaining the conditional connection information according to the conditional connection indication.

[0175] Aspect 30, the method according to aspect 29, wherein receiving the suspension indication comprises: receiving a message including the conditional connection indication.

[0176] Aspect 31, the method according to aspect 29, further comprising: receiving, by processing hardware, a resume message from the first base station indicating that the UE is to resume the suspended radio connection with the first base station, the resume message including the conditional connection indication.

[0177] Aspect 32, the method according to aspect 29, further comprising: receiving, by processing hardware, a resume message from a third base station indicating that the UE is to resume the suspended radio connection with the third base station, the resume message including the conditional connection indication.

[0178] Aspect 33, a user equipment (UE) comprising processing hardware and configured to implement the method according to any one of aspects 16 to 32.

Claims

1. A method for managing conditional operations related to a user equipment (UE) in a first base station, the method comprising: sending, by the first base station, conditional connection information to the UE, the conditional connection information including (i) configuration data related to a second base station for the UE to operate in dual connection with the first base station and the second base station, and (ii) one or more conditions for connecting to the second base station; and in response to the first base station determining that the UE is to suspend the radio connection with the first base station: causing the UE to suspend the radio connection with the first base station, and causing the second base station to release the conditional connection information.

2. The method according to claim 1, wherein, Causing the second base station to release the conditional connection information includes: sending a request to release the conditional secondary node (SN) configuration at the second base station to the second base station.

3. The method according to claim 1, wherein The conditional connection information is related to conditional secondary node (SN) addition.

4. The method according to claim 1, wherein The conditional connection information is related to conditional primary secondary cell (PSCell) change.

5. The method according to any one of claims 1 to 4, wherein Causing the UE to suspend the radio connection includes: sending, to the UE, a message associated with a protocol for controlling radio resources, the message indicating that the UE is to switch to (i) an inactive mode associated with the protocol or (ii) an idle mode associated with the protocol in the case of suspension of the radio connection.

6. The method according to any one of claims 1 to 4, wherein Causing the second base station to release the conditional connection information includes: sending an indication to the second base station via an inter-base-station interface that the second base station is to release the conditional connection information.

7. The method according to claim 6, comprising sending the indication in response to receiving one of the following: (i) a request from the UE to resume the radio connection, or (ii) a request from a third base station to retrieve the UE's context.

8. A base station, comprising processing hardware and configured to implement the method according to any one of claims 1 to 7.

9. A method for managing conditional operations related to a second base station in a user equipment (UE) having a radio connection to a first base station, the method comprising: receiving, by the UE from the first base station, conditional connection information, the conditional connection information including (i) configuration data related to a second base station for the UE to operate in dual connection with the first base station and the second base station, and (ii) one or more conditions for connecting to the second base station; suspending, by the UE, the radio connection in response to a trigger event; and releasing, by the UE, the conditional connection information in response to the trigger event.

10. The method according to claim 9, wherein, The conditional connection information is related to conditional secondary node (SN) addition.

11. The method according to claim 9, wherein, The conditional connection information is related to conditional primary secondary cell (PSCell) change.

12. The method according to claim 9, further comprising: determining, by the UE, to resume the radio connection with a third base station; releasing, by the UE, the conditional connection information; and resuming, by the UE, the suspended radio connection with the third base station.

13. The method according to claim 9, wherein The trigger event includes: receiving a message omitting a field indicating that the UE is to release the conditional connection information.

14. The method according to claim 9, wherein The trigger event includes: receiving a message associated with a protocol for controlling radio resources, the message indicating that the UE is to switch to (i) an inactive mode associated with the protocol or (ii) an idle mode associated with the protocol in the case of suspension of the radio connection.

15. A user equipment UE, comprising processing hardware and configured to implement the method according to any one of claims 9 to 14.

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