Mobility Support in Communication Networks

Abstract

[0006] Various exemplary aspects and embodiments relate to apparatus and methods for supporting mobility in a radio access network. One aspect provides a user equipment comprising: at least one processor; and at least one memory that stores instructions that, when executed by the at least one processor, cause the user equipment to: receive a radio configuration and a trigger condition for activating the radio configuration, the radio configuration associated with a cell of a radio access network, the radio configuration enabling a connection between the user equipment and the cell; receive an indication of which radio configuration associated with another cell is to be retained by the user equipment when the trigger condition for the cell is met; determine when the trigger condition is met and activate the radio configuration; assess which radio configuration associated with another target cell to retain based on the received indication; and communicate to the radio access network which configuration associated with the other cell is retained.

Description

[Technical Field]

[0001] Various exemplary embodiments relate to apparatus and methods for supporting mobility in a radio access network. [Background technology]

[0002] A radio access network provides radio coverage for user equipment (UE) for each geographic area. Network access nodes (e.g., base stations) are located in each geographic area to support one or more cells of radio coverage. User equipment within an area served or covered by a network access node communicates with the radio access network via one or more radio links with the network access node.

[0003] User equipment can move between cells of radio coverage within a radio access network. When in a connected state, user equipment can move between cells, and there may be a need to hand over ongoing communications with the user equipment between cells of the radio access network to maintain service continuity. In other words, nodes of the network need to be configured to support mobility events for user equipment within the network.

[0004] What is needed is a method and apparatus for supporting mobility events within a radio access network. Summary of the Invention

[0005] The scope of protection sought for various embodiments of the invention is set forth in the independent claims. To the extent that any configurations, examples, and features described herein do not fall within the scope of the independent claims, they are to be construed as examples useful for understanding various embodiments of the invention.

[0006] According to various (but not necessarily all) embodiments of the present invention, there is provided a user equipment comprising at least one processor and at least one memory that stores instructions that, when executed by the at least one processor, cause the user equipment to: receive a radio configuration and a trigger condition for activating the radio configuration, the radio configuration associated with a cell of a radio access network, the radio configuration enabling a connection between the user equipment and the cell; receive an indication of which radio configuration associated with another cell is to be retained by the user equipment if the trigger condition of the cell is met; determine when the trigger condition is met and activate the radio configuration; assess which radio configuration associated with another target cell to retain based on the received indication; and communicate to the radio access network which radio configuration associated with the other cell is retained.

[0007] In some exemplary embodiments, the cell comprises a target cell.

[0008] In some exemplary embodiments, the other cell includes a cell that served the user equipment prior to activation of the radio configuration.

[0009] In some demonstrative embodiments, the received indication includes an indication received from a serving central master node.

[0010] In some exemplary embodiments, the received indication includes a list of one or more other cells that have been selected to associate with the cell.

[0011] In some exemplary embodiments, the received indication includes a list of one or more other cells that are neighboring cells of the cell.

[0012] In some demonstrative embodiments, the received instruction includes a measurement configuration for performing measurements related to at least a subset of other cells when a trigger condition for the cell is met, and assessing includes performing the configured measurements.

[0013] In some exemplary embodiments, the measurement configuration includes a comparison of another cell's radio signal to a predetermined threshold.

[0014] In some exemplary embodiments, the measurement configuration includes a comparison of the radio signal of a cell to the radio signal of another cell.

[0015] In some exemplary embodiments, communicating includes transmitting to the network a list of other cells for which radio configurations are maintained.

[0016] In some exemplary embodiments, communicating includes transmitting to the network an indication of the cell for which the radio configuration is released.

[0017] In some exemplary embodiments, the radio configuration includes user equipment, cell, and another cell configuration for a conditional primary cell of a secondary cell group addition or change, CPAC, in a New Radio dual connectivity radio access network.

[0018] According to various (but not necessarily all) exemplary embodiments of the present invention, a user equipment method is provided that includes receiving a radio configuration, the radio configuration associated with a cell of a radio access network, the radio configuration enabling connection of the user equipment with the cell, and a trigger condition for activating the radio configuration; receiving an indication of which radio configuration associated with another cell is to be retained by the user equipment when the trigger condition for the cell is met; determining when the trigger condition is met and activating the radio configuration; assessing which radio configuration associated with the other cell to retain based on the received indication; and communicating which radio configuration associated with the other cell is retained to the radio access network.

[0019] In some exemplary embodiments, the cell comprises a target cell.

[0020] In some exemplary embodiments, the other cell includes a cell that served the user equipment prior to activation of the radio configuration.

[0021] In some demonstrative embodiments, the received indication includes an indication received from a serving central master node.

[0022] In some exemplary embodiments, the received indication includes a list of one or more other cells that have been selected to associate with the cell.

[0023] In some exemplary embodiments, the received indication includes a list of one or more other cells that are neighboring cells of the cell.

[0024] In some demonstrative embodiments, the received indication includes a measurement configuration for performing measurements related to at least a subset of the other cells when a trigger condition for the cell is met, and assessing includes performing the configured measurements.

[0025] In some exemplary embodiments, the measurement configuration includes a comparison of another cell's radio signal to a predetermined threshold.

[0026] In some exemplary embodiments, the measurement configuration includes a comparison of the radio signal of a cell to the radio signal of another cell.

[0027] In some exemplary embodiments, communicating includes transmitting to the network a list of other cells for which radio configurations are maintained.

[0028] In some exemplary embodiments, communicating includes transmitting to the network an indication of the cell for which the radio configuration is released.

[0029] In some exemplary embodiments, the radio configuration includes user equipment, cell, and another cell configuration for a conditional primary cell of a secondary cell group addition or change, CPAC, in a New Radio Dual Connectivity Radio Access Network.

[0030] According to various (but not necessarily all) exemplary embodiments of the present invention, there is provided a network node comprising at least one processor and at least one memory storing instructions that, when executed by the at least one processor, at least cause a user equipment to determine a radio configuration and a trigger condition for activating the radio configuration, the radio configuration being associated with a cell of a radio access network, the radio configuration enabling a connection of the user equipment with the cell; if the trigger condition of the cell is satisfied, evaluate which radio configuration associated with another cell is held by the user equipment; and transmit the radio configuration, the trigger condition, and the evaluation to the user equipment.

[0031] In some exemplary embodiments, the evaluating includes requesting neighbor cell information from the cell and selecting from the received neighbor cell information a list of other cells that maintain radio configuration information related to the cell.

[0032] In some exemplary embodiments, the evaluating includes requesting a mobility history from the cell and selecting, from the received mobility history, a list of other cells that maintain radio configuration information for the cell.

[0033] In some exemplary embodiments, the evaluating includes selecting a measurement configuration for transmission to the user equipment.

[0034] In some exemplary embodiments, the measurement configuration includes a predetermined threshold radio signal strength received from a cell.

[0035] In some exemplary embodiments, the measurement configuration includes a predetermined difference between the radio signal strength received from the cell compared to another cell.

[0036] In some exemplary embodiments, the network node comprises a master control network node.

[0037] According to various (but not necessarily all) exemplary embodiments of the present invention, there is provided a method performed by a network node, the method including determining a radio configuration and a trigger condition for activating the radio configuration, the radio configuration being associated with a cell of a radio access network, the radio configuration enabling a connection of a user equipment with the cell; evaluating which radio configuration associated with another cell is to be retained by the user equipment when the trigger condition of the cell is met; and transmitting the radio configuration, the trigger condition, and the evaluation to the user equipment.

[0038] In some exemplary embodiments, the evaluating includes requesting neighbor cell information from the cell and selecting from the received neighbor cell information a list of other cells that maintain radio configuration information related to the cell.

[0039] In some exemplary embodiments, the evaluating includes requesting a mobility history from the cell and selecting, from the received mobility history, a list of other cells that maintain radio configuration information for the cell.

[0040] In some exemplary embodiments, the evaluating includes selecting a measurement configuration for transmission to the user equipment.

[0041] In some exemplary embodiments, the measurement configuration includes a predetermined threshold radio signal strength received from a cell.

[0042] In some exemplary embodiments, the measurement configuration includes a predetermined difference between the radio signal strength received from the cell compared to another cell.

[0043] In some exemplary embodiments, the network node comprises a master control network node.

[0044] According to various (but not necessarily all) exemplary embodiments of the present invention, there is provided a network node supporting a cell of a radio access network, the network node comprising: at least one processor; and at least one memory storing instructions that, when executed by the at least one processor, cause a user equipment to receive a radio configuration associated with the cell, the radio configuration enabling a connection between the user equipment and the cell; receive a request for an indication of other cells associated with the cell; determine which other cells are associated with the cell; and, based on the determination, return a response to the request.

[0045] In some exemplary embodiments, determining which other cells are associated includes determining a set of neighboring cells of the cell.

[0046] In some exemplary embodiments, determining which other cells are relevant includes determining the mobility history of the cells.

[0047] In some exemplary embodiments, the network node comprises a secondary network node.

[0048] According to various (but not necessarily all) exemplary embodiments of the present invention, there is provided a method performed by a network node supporting a cell of a radio access network, the method including receiving a radio configuration associated with the cell, the radio configuration enabling a connection between user equipment and the cell; receiving a request for indication of other cells associated with the cell; determining which other cells are associated with the target cell; and returning a response to the request based on the determination.

[0049] In some exemplary embodiments, determining which other cells are associated includes determining a set of neighboring cells of the cell.

[0050] In some exemplary embodiments, determining which other cells are relevant includes determining the mobility history of the cells.

[0051] In some exemplary embodiments, the network node comprises a secondary network node.

[0052] According to various (but not necessarily all) exemplary embodiments of the present invention, a computer program product is provided that, when executed by a processor on an apparatus, is operable to control the apparatus to perform an embodiment or further embodiments.

[0053] According to various (but not necessarily all) exemplary embodiments of the present invention, there is provided a user equipment comprising: means configured to receive a radio configuration and a trigger condition for activating the radio configuration, the radio configuration being associated with a cell of a radio access network, the radio configuration enabling a connection between the user equipment and the cell; means configured to receive an indication of which radio configuration associated with another cell is to be retained by the user equipment when the trigger condition of the cell is satisfied; means configured to determine when the trigger condition is satisfied and to activate the radio configuration; means configured to assess which radio configuration associated with another target cell to retain based on the received indication; and means configured to communicate to the radio access network which radio configuration associated with the other cell is retained.

[0054] According to various (but not necessarily all) exemplary embodiments of the present invention, there is provided a network node comprising: means configured to determine a radio configuration and a trigger condition for activating the radio configuration, the radio configuration being associated with a cell of a radio access network, the radio configuration enabling a connection of a user equipment with the cell; means configured to evaluate which radio configuration associated with another cell is retained by the user equipment when the trigger condition of the cell is met; and means configured to transmit the radio configuration, the trigger condition, and the evaluation to the user equipment.

[0055] According to various (but not necessarily all) exemplary embodiments of the present invention, there is provided a network node supporting a cell of a radio access network, the network node comprising: means configured to receive a radio configuration associated with the cell, the radio configuration enabling a connection between user equipment and the cell; means configured to receive a request for an indication of other cells associated with the cell; and means configured to determine which other cells are associated with the cell and return a response to the request based on the determination.

[0056] According to various (but not necessarily all) exemplary embodiments of the present invention, a user equipment is provided that includes: circuitry configured to receive a radio configuration and a trigger condition for activating the radio configuration, the radio configuration being associated with a cell of a radio access network, the radio configuration enabling connection of the user equipment with the cell; circuitry configured to receive an indication of which radio configuration associated with another cell is to be retained by the user equipment when the trigger condition of the cell is satisfied; circuitry configured to determine when the trigger condition is satisfied and activate the radio configuration; circuitry configured to assess which radio configuration associated with another cell to retain based on the received indication; and circuitry configured to communicate to the radio access network which radio configuration associated with the other cell is retained.

[0057] According to various (but not necessarily all) exemplary embodiments of the present invention, there is provided a network node comprising: circuitry configured to determine a radio configuration and a trigger condition for activating the radio configuration, the radio configuration being associated with a cell of a radio access network, the radio configuration enabling a connection between a user equipment and the cell; circuitry configured to assess which radio configuration associated with another cell is retained by the user equipment when the trigger condition of the cell is met; and circuitry configured to transmit the radio configuration, the trigger condition, and the evaluation to the user equipment.

[0058] According to various (but not necessarily all) exemplary embodiments of the present invention, there is provided a network node supporting a cell of a radio access network, the network node comprising: circuitry configured to receive a radio configuration associated with the cell, the radio configuration enabling a connection between user equipment and the cell; circuitry configured to receive a request for an indication of other cells associated with the cell; and circuitry configured to determine which other cells are associated with the cell and return a response to the request based on the determination.

[0059] Further particular and preferred aspects are set out in the accompanying independent and dependent claims. Features from the dependent claims may be combined with features of the independent claims as appropriate and in combinations other than those explicitly set out in the claims.

[0060] Where features of a device are described as operable to provide a function, this will be understood to include features of a device that provide that function or that are adapted or configured to provide that function.

[0061] Some exemplary embodiments are described below with reference to the accompanying drawings. [Brief explanation of the drawings]

[0062] [Figure 1] FIG. 1 is a signaling diagram illustrating an exemplary embodiment of the subject matter described herein. [Figure 2] FIG. 1 illustrates an apparatus in a communication system according to an exemplary embodiment. [Figure 3] 3 is a flow diagram illustrating steps of a method performed in a network node according to the exemplary embodiment shown in FIG. 2. DETAILED DESCRIPTION OF THE INVENTION

[0063] Before describing exemplary embodiments in further detail, an overview will first be provided.

[0064] The main components of a radio access network include user equipment (UE), which can be located anywhere within the network. Some UEs can roam freely throughout the network. Network access nodes, e.g., base stations, are provided that support areas of radio coverage within cells within the radio access network. Many such network access nodes are provided, and are typically geographically dispersed to provide large areas of radio coverage for user equipment.

[0065] When a user equipment is within a cell supported by a network access node, communications may be established between the user equipment and the network using the associated radio link.

[0066] As user equipment roams within a radio access network, it may move between different cells of radio coverage. These cells may be supported by different network access nodes or may be supported by the same network access node. The radio access network operates to support user equipment mobility by handing over communication configurations as the radio environment experienced by the user equipment changes, in order to ensure continuity of service to the user equipment when the user equipment is actively in use.

[0067] As radio access networks continue to evolve, it is recognized that it may be useful to adapt or introduce procedures to support user equipment mobility. For example, support for user equipment mobility is also relevant when a user equipment operates in a Dual Connectivity (DC) wireless communication network. When operating in a DC, the UE is connected to a Master Node (MN) and a Secondary Node (SN). The MN is a network access node (base station) that controls a Master Cell Group (MCG). The MCG consists of a Primary Cell (PCell) and a set of one or more Secondary Cells (SCells) of the MCG. The SN is a network access node (base station) that controls a Secondary Cell Group (SCG). The SCG consists of a Primary Cell (PSCell) and a set of one or more Secondary Cells (SCells) of the SCG. As the radio conditions around a DC UE evolve, one or more cell groups may change to maintain continuity of service to the UE.

[0068] One way to improve mobility is to provide mechanisms and procedures that recognize that a handover may be necessary and take action before handover conditions are met. In such a scenario, known as a conditional handover, some action is initiated when a first set of conditions indicating that a handover may occur is met. Such action may include pre-configuring various nodes and cells in the network to support a handover if / when the handover conditions are met. Such conditional handover (CHO) configuration may require various nodes or cells in the network to use or keep resources available to support a handover if / when the handover conditions are met.

[0069] As an example, a conditional mobility event in an NR-DC wireless communication network will be described. A PSCell addition (or PSCell change) occurs when the network triggers a PSCell addition (or change) of an SN based on a measurement report sent by the UE. Upon receiving such a measurement report, which initiates the process, the network is configured to trigger the preparation of the target SN. If not operating according to a conditional handover technique, after sending the measurement report, the UE must wait until it receives a command from the network to add or change the PSCell. This delay can affect UE throughput because, in the case of an SN addition, the UE cannot take advantage of the high capacity associated with using the SN until it is added, and in the case of an SN change, the UE will be served for a longer time by an SN with poor radio quality. Conditional handover (e.g., conditional PSCell addition and conditional PSCell change (CPAC)) allows the UE to access the target SN without delay if the handover conditions are met.

[0070] When handover conditions are met at a particular candidate target network node, unused resources held in anticipation of a possible handover to another candidate network node are typically released. According to some conditional mobility functions, such as conditional PSCell addition and conditional PSCell change (CPAC) and conditional handover (CHO), any conditional configurations held at various nodes in the network are released after CHO / CPAC is performed. If the UE subsequently moves, for example, from the radio area best covered by the new serving cell to one of the other target cells that may have already been "prepared" as part of the original conditional configuration process, the entire set of CPAC or CHO preparations, along with the associated signaling overhead and RRC signaling, must be performed again. This allows the network node to be provided with the new conditional configuration needed for a possible subsequent cell change in a timely manner. Such an approach may be an inefficient use of resources and may delay support for UEs with fast mobility across cell groups due to the need to perform additional configuration steps.

[0071] Aspects and embodiments recognize that it may be possible to provide mechanisms and procedures that allow for conditional mobility signaling and configuration retention in order to support efficient overall resource usage within the network.

[0072] Although described in the context of a New Radio (NR) dual connectivity wireless communication system, it will be appreciated that the principles underlying the described aspects and embodiments may be applied to a variety of mobility issues within wireless communication networks where provisioning information is sent to one or more nodes within the network and the provisioning information may remain relevant to ongoing network operation.

[0073] It will be appreciated that maintaining and retaining all configuration information at one or more nodes, rather than releasing, can itself be an inefficient use of resources, and therefore some compromise is necessary to achieve a balance between release and retention. Aspects and embodiments may provide configurations for use with conditional mobility events. A conditional mobility event, for example, allows for the storage of multiple configurations at a UE to enable selective activation. Such multiple configurations may include, for example, configurations for multiple cell groups or a target cell configuration. With a conditional mobility event, a configuration change (selective activation) at a node can be completed with minimal disruption, preferably without or with minimal additional reconfiguration. Conditional handover is such that configuration selection occurs via RRC or lower layers based on measured or detected radio conditions or other similar criteria. With conditional activation between a set of cell groups or a set of configurations, there is typically a common measurement configuration for handover or activation criteria that is not affected by the cell change.

[0074] Aspects and embodiments recognize that while conditional mobility signaling and retention of configurations at nodes within the network, such as, for example, a UE or a network access node, can be helpful for subsequent possible configuration changes, it also results in resource reservation in all possible target cells for a longer period of time. Such continuous resource reservation can be detrimental to overall network operation, and aspects and embodiments recognize that the impact of such continuous resource reservation can be mitigated if one or more steps are taken to try and ensure that the configuration that is maintained or retained is one that is likely to be suitable for possible use after the initial cell change.

[0075] Since the handover target configuration may be maintained for a longer time than usual, the number of maintained target cells may be adjusted or reduced to avoid reserving resources for a long time in all target cells. By releasing some target cells, some resources are returned to the network for other uses.

[0076] Aspects and embodiments provide procedures and mechanisms that support the selection of conditional configurations to keep or maintain and those to release.

[0077] Further aspects and embodiments recognize that related problems may arise if the configuration is retained or maintained after the initial change. In particular, the potential target cell of the initial serving cell need not be the same as the target cell of the new serving cell to which the UE is transitioning. The configuration retained by the UE may take such differences into account.

[0078] Thus, in a general configuration, a user equipment may be provided that includes at least one processor and at least one memory that stores instructions that, when executed by the at least one processor, cause the user equipment to: receive a radio configuration and a trigger condition for activating the radio configuration, the radio configuration associated with a cell of a radio access network, the radio configuration enabling a connection between the user equipment and the cell; receive an indication of which radio configuration associated with another cell is to be retained by the user equipment if the trigger condition of the cell is met; determine when the trigger condition is met and activate the radio configuration; assess which radio configuration associated with another target cell to retain based on the received indication; and communicate to the radio access network which radio configuration associated with the other cell is retained.

[0079] The received radio configuration and trigger conditions for activating the radio configuration may include a handover condition associated with the target cell, or a radio configuration associated with the user equipment, the cell, and another cell configuration for a conditional primary cell of a secondary cell group addition or change, CPAC, in a New Radio Dual Connectivity Radio Access Network.

[0080] The radio configuration may be associated with a target cell, which may be a primary or secondary cell of a radio access network, and may include information that enables the establishment of a communication link between the user equipment and the cell.

[0081] The received indication as to which radio configuration associated with another cell will be retained by the user equipment when the trigger condition for that cell is met can take various forms: it may include, for each "target" cell, a list of other cells, including the original serving cell, whose radio configuration will be retained when communication with the new cell is activated.

[0082] The user equipment may be configured to determine when a trigger condition is met and activate the radio configuration of the cell for which the trigger condition is met, in other words, the cell may meet the conditional handover to cell addition trigger condition required to activate the radio configuration.

[0083] The user equipment may be configured to assess which radio reconfigurations to retain and which to release based on already available information. The information may be received from the master node, for example, or some assessment may be performed in the user equipment based on information from the master node and / or assessment criteria. As various reconfigurations are released or retained, the user equipment may be configured to communicate to the radio access network which radio configurations are being retained or, alternatively, released.

[0084] Having provided a general overview, some specific embodiments will now be described, e.g., relating to identifying functions and procedures in New Radio (NR) dual connectivity, where selective activation of cell groups, at least for secondary cell groups (SCGs), can occur via Layer 3 extensions.

[0085] In other words, specific embodiments and described implementations can be understood in relation to a user equipment (UE) for accessing a radio access network, a master central node, and possible target secondary nodes. The radio access network may include a master central node and multiple master distributed nodes that provide radio access coverage via a primary cell. The master central node is configured to control the multiple master distributed nodes. The radio access network may further include a secondary central node and multiple secondary distributed nodes that support radio access coverage via one or more secondary cells. The secondary central node is configured to control the secondary distributed nodes. The user equipment is configured to support dual connectivity, allowing the user equipment to simultaneously connect to a primary distributed node that provides access to a primary serving cell and a secondary distributed node that provides access to a secondary serving cell.

[0086] In particular, particularly described embodiments may relate to mechanisms and procedures that enable subsequent cell group changes after a first or initial cell group change. Configuration changes may be applied when transitioning from a single cell to a dual cell connectivity configuration (i.e., adding an SN), or may be applied when a secondary node is changed, for example. According to some described configurations, procedures and mechanisms enable subsequent changes, e.g., cell group changes, to be facilitated to occur without reconfiguration and reinitialization of conditional PSCell addition information or conditional PSCell change information.

[0087] It will be understood that the techniques and procedures of the specific embodiments described may be adapted appropriately, and similar approaches may be applied to radio access networks not operating in dual connectivity. In particular, it is envisioned that the principles described in relation to configuration may be applied to initial and "subsequent" mobility events in the context of a conditional handover (CHO) scenario. In this scenario, a UE may have conditional reconfiguration information related to handover from a serving node and associated cells to one or more potential target cell groups. Thus, reconfiguration information may be maintained in relation to a target Master Cell Group (MCG).

[0088] The following exemplary embodiment illustrates how it may be possible to determine the subset of initial CPAC conditional configurations that are maintained after an initial configuration change is performed.

[0089] Embodiment 1 As part of the CPAC preparation, the master node (MN) may be configured to request that each secondary node (SN) provide a list of other target cells in which it wishes the UE to maintain information related to that SN if the UE performs a change to that SN. In response to the request from the MN, the SN may be configured to return an indication of a preferred target cell to be maintained for selective activation (or an indication of a preferred target cell to be released) after performing an initial cell change. The information obtained by the MN can be used as assistance information in conditional mobility events where it is expected to retain or maintain some of the conditional handover reconfiguration information and resources after the initial handover has occurred.

[0090] Embodiment 2 Based on the assistance information received from the secondary node for selective activation described in relation to embodiment 1, the MN may be configured to generate a list of conditional configurations to be maintained after CPAC execution for each target cell configuration, and the information may be passed to the UE.

[0091] Alternatively or additionally, the MN may be configured to communicate additional metrics to the UE to enable it to select which conditional configurations to maintain after the CPAC execution. The additional metrics may include, for example, a condition regarding a comparison of the radio signal of the prepared target cell to a predetermined threshold and / or a condition regarding a comparison of the radio signal of the prepared target cell to one or more other prepared target cells. The conditions may be used as criteria to enable the UE to select and release one or more target cell conditional configuration information after the initial execution. The metrics may be selected to enable the release of conditional configurations that may no longer be relevant for selective activation.

[0092] The additional metric may be a new measurement configuration that facilitates the UE's comparison of the radio signals of two prepared target cells. While a measurement configuration typically allows the UE to compare measurements of the radio signal of a target cell with the radio signal of a serving cell, the new measurement configuration allows the UE to compare the radio signal of the target cell with the radio signal of another target cell. The evaluation of the new metric may be initiated by the UE when it is about to perform CPAC towards the selected target cell. This delayed initiation avoids the UE having to perform such a comparison across all target cells at each measurement evaluation.

[0093] As an example, consider a network operating in DC and configured with CPAC for target cells C2, C3, and C4 of a UE with a serving PSCell denoted by C1. The MN includes a new measurement ID with a new event (A3' or X3) that defines a condition to check whether the radio measurements of each prepared target cell are not more than X dB lower than the radio measurements of the serving cell. When the UE switches from C1 to C2, the measurement ID is evaluated based on the available measurements, considering C2 as the serving cell. Cells (C3, C4, etc.) that satisfy this X3 event are maintained as the selected active set. Other cells are released by the UE. An equivalent network release may occur in response to the UE indicating conditional release to the network.

[0094] Embodiment 3 According to this embodiment, during CPAC, the UE may be configured to maintain the configurations and conditions of a set of cells specifically instructed by the network to be maintained for further evaluation. In other words, the UE is configured to retain prepared target cells instructed by the network to be maintained / retained. The UE may report the list of maintained cells as part of RRC reconfiguration completion. This reporting allows the target node to recognize additional potential target cells for data forwarding and support updates to the selective activation configuration. Alternatively, if explicit metrics for candidate cell removal based on comparison thresholds / offsets are enabled or configured, the UE may instruct the removal of specific target configurations via RRC signaling when such conditions are met after the initial execution.

[0095] FIG. 1 is a signaling diagram illustrating signaling that may be implemented in accordance with some aspects and embodiments of the mechanisms and procedures described above.

[0096] Signaling occurs between the user equipment 10, the master node 20, and one or more potential target secondary nodes 30a, 30b. In the illustrated signaling diagram, two general signaling phases occur: one that generally occurs between the master node 20 and the potential target secondary nodes 30a, 30b, and one that occurs between the master node 20 and the user equipment 10.

[0097] When operating in a wireless communication network, the UE 10 is configured to send measurement reports to the network side. In this example, the measurement reports sent by the UE 10 to the master node 20 indicate that two other network access nodes are potential candidates for dual connectivity or potential candidates for secondary nodes when the UE 10 is already operating according to the DC technique.

[0098] In response to the measurement report from the UE 10 in step S1, the master node 20 initiates a conditional PSCell addition procedure (CPA) in step S2 according to one embodiment. The MN 20 supports conditional mobility events, which result in the continuation or retention of a conditional configuration for further mobility after the initial CPA execution. In steps S3 and S4, the master node 20 is configured to communicate with the target secondary nodes 30a, 30b and requests, from each potential target secondary node 30a, 30b, assistance information regarding cells to be maintained (or released) after the initial execution of the mobility event.

[0099] In steps S5 and S6, each target secondary node 30a, 30b provides an indication to the master node 20 of the list of cells to be kept (or released) after the initial CPAC. The indication is included in the SN addition request acknowledgement messaging. Each target secondary node 30a, 30b may also be configured to provide a list of cells to be kept or released after a normal SN addition request (without receiving a persistence indication).

[0100] After receiving the indication from the candidate secondary nodes 30a, 30b, the master node 20 may be configured to select, in step S7, a set of candidate cells in which the conditional configuration will be maintained after the mobility event.

[0101] In some configurations, the list of selected cells generated by the master node may be used directly by the UE and MN to determine which conditional configurations to maintain or retain after a mobility event.

[0102] In some configurations, the master node 20 may implement a procedure according to which the UE can take more active steps to determine which conditional configuration will be maintained after an initial mobility event. If operating according to such a configuration, in step S8 the master node 20 may generate a request to the user equipment 10 to perform additional measurement steps as part of relaying the conditional configuration signaling to the user equipment 10. In the illustrated configuration of FIG. 1, that additional measurement report request is called "measurement configuration selective activation."

[0103] The second phase of the illustrated configuration involves signaling between the master node 20 and the UE 10 to support the configuration of a conditional mobility event.

[0104] According to the configuration of Figure 1, in step S9 the master node is configured to send an RRC reconfiguration message to the UE 10 including a selected list of cells to be maintained after each run towards each of the target cells. The messaging also includes, in this configuration, metrics to be used by the UE to intelligently select a subset of cells for each given target secondary cell. As mentioned above, the metrics (measurement IDs) communicated to the UE are associated with an A3 type event, and the measurement comparisons performed by the UE are measurements against the selected target cell and other target cells (rather than comparisons against the master node).

[0105] After receiving the appropriate message from the master node 20, in the illustrated configuration, the UE is configured to perform various steps to support the retention of conditional configuration as part of a mobility event.

[0106] In step S10, the UE is configured to retain each of the conditional reconfigurations and measurement criteria set by the network side so that it can be used appropriately to evaluate both a primary (initial) mobility event that may be triggered by an appropriate measurement report, as well as what to do after the initial mobility event has been performed and which conditional configurations to retain.

[0107] In step S11, the UE can determine based on the measurements that the mobility event conditions—in this example, the addition of a secondary node to support DC communications—are met by one of the possible target secondary nodes 30 a, 30 b. The pre-configuration of the master node 20, the UE 10, and the secondary nodes 30 a, 30 b means that the addition of a secondary node that meets the mobility event conditions can occur quickly, without delay. In step S12, the UE can be configured to maintain an indication of the measurements instructed by the master node so that, if activation of a conditional mobility event is triggered, it can take appropriate action regarding the retention of other conditional configurations.

[0108] When the UE recognizes through measurements that the additional conditions for the secondary node are satisfied, execution of an initial mobility event is triggered in step S13. During execution of the initial mobility event, the UE 10 may be configured to check the suitability of other candidate (conditional) target cells based on assistance information provided by the master node 20 and / or measurement criteria provided to the UE 10 by the master node 20 in step S14. When using assistance information, the UE may be configured to retain conditional configuration information related to those cells selected by the master node 20 for a given target cell. According to some configurations, the UE may be configured to make measurements related to those selected cells for continued evaluation. The measurements made by the UE can be used for further filtering related to cells for which conditional configuration information is retained or maintained after the initial mobility event (CPAC in this example).

[0109] In step S15, the UE is configured to report to the master node that the mobility event is completed and to indicate those cells for which reconfiguration information is maintained (or released). According to some configurations, after each mobility event, e.g., CPAC execution and / or PSCell change, the UE 10 may be configured to autonomously release the CPAC configuration of some prepared target cells. In some configurations, the release may be based on an explicit list of PSCells provided to the UE by the master node 20 in step S9. The UE may be configured to confirm the release of the PSCell to the network side, e.g., to the master node 20 or to the selected new target PSCell / SN.

[0110] In step S16, the UE has some conditional configuration information and continues to monitor measurement events that may trigger the activation of such a reconfiguration and, if appropriate, may take steps to activate such a reconfiguration.

[0111] As shown in steps S17 and S18, the UE and the network are configured to release conditional configurations that are not maintained after the execution of an initial mobility event, such as a CPAC execution.

[0112] FIG. 2 illustrates devices in a communication system 1000 according to an exemplary embodiment. In particular, FIG. 2 illustrates a wireless communication network in which a core network 1100 includes a control node 20 capable of communicating with one or more base station nodes 30a, 30b supporting cells in the network. The cells are configurable to support communication with user equipment 10. In some examples, the base station nodes may include NR base stations. A master node 20 according to one exemplary embodiment may include circuitry 210 configured to determine a radio configuration and a trigger condition for activating the radio configuration, the radio configuration being associated with a cell supported by the base station 30a, 30b. The radio configuration may support a connection between the user equipment 10 and the cell supported by the base station 30a, 30b. The master node 20 may further include circuitry 220 configured to evaluate whether a radio configuration associated with another cell is retained by the user equipment when a trigger condition related to a first cell is satisfied. The master node may also include circuitry configured to transmit the radio configuration, the trigger condition, and the evaluation to the user equipment 10.

[0113] 2 further illustrates nodes 30a, 30b, each of which may be configured to support a cell and to support communication with user equipment 10. Each of nodes 30a, 30b includes circuitry 310 configured to receive a radio configuration associated with a cell from the network, the radio configuration enabling connectivity between user equipment 10 and the cell supported by network node 30a, 30b. The configuration may be received from node 20. Nodes 30a, 30b further include circuitry 320 configured to receive a request for an indication of other cells associated with the cell. The request may be received from node 20. Nodes 30a, 30b may further include circuitry 330 configured to determine which other cells are associated with the cell and return a response to the request based on the determination.

[0114] 2 further illustrates user equipment node 10 configured to operate within network 1000. According to an exemplary embodiment, user equipment node 10 may include circuitry 110 configured to receive a radio configuration and a trigger condition for activating the radio configuration. The radio configuration is typically associated with a cell of a radio access network. The radio configuration enables connectivity between user equipment 10 and the cell.

[0115] The user equipment 10 also includes circuitry 120 configured to receive an indication of which radio configurations associated with another cell are held by the user equipment when a trigger condition for the cell is met.

[0116] The user equipment also includes circuitry 130 configured to determine when a trigger condition is met and activate a radio configuration, and circuitry 140 configured to assess, based on the received instruction, which radio configuration associated with another cell to retain.

[0117] The user equipment may also include circuitry 150 configured to communicate to the radio access network 1100 which radio configurations associated with different cells are maintained.

[0118] FIG. 3 shows a flow diagram illustrating steps of a method performed in a network node according to the exemplary embodiment shown in FIG.

[0119] In particular, the network node 20 may be configured to perform the following steps: S210: Determine a radio configuration and a trigger condition for activating the radio configuration, where the radio configuration is associated with a cell of a radio access network, and the radio configuration enables a connection between the user equipment and the cell. S220: Evaluate which radio configuration associated with another cell is retained by the user equipment if a trigger condition for the cell is met. S230: Send the radio configuration, trigger conditions, and evaluation to the user equipment.

[0120] The network node 30 may be configured to perform the following steps. S310: Receive a radio configuration associated with a cell, the radio configuration enabling a connection between the user equipment and the cell. S320: A request to display another cell related to the cell is received. S330: Determine which other cells are associated with the target cell, and return a response to the request based on the determination.

[0121] The user equipment 10 may be configured to perform the following steps. S110: Receive a radio configuration and a trigger condition for activating the radio configuration, the radio configuration being associated with a cell of a radio access network, the radio configuration enabling a connection between the user equipment and the cell. S120: Receive an indication of which radio configuration associated with another cell is to be retained by the user equipment if a trigger condition for the cell is met. S130: Determine when a trigger condition is met and activate the wireless configuration. S140: Based on the received instruction, assess which radio configuration associated with the other cell to retain. S150: Communicate to the radio access network which radio configurations associated with other cells are maintained.

[0122] Those skilled in the art will readily recognize that the steps of the various methods described above can be performed by a programmed computer. It should be noted that some embodiments are also intended to cover a program storage device, e.g., a digital data storage medium, that is machine- or computer-readable and encodes a program of machine-executable or computer-executable instructions, the instructions performing some or all of the steps of the methods described above. The program storage device may be, for example, a digital memory, a magnetic storage medium such as a magnetic disk or magnetic tape, a hard drive, or an optically readable digital data storage medium. The embodiments are also intended to cover a computer programmed to perform the above steps of the methods described above. The term non-transitory, as used herein, refers to the medium itself (i.e., tangible, not a signal), as opposed to the data storage permanence (e.g., RAM vs. ROM).

[0123] As used herein, the term "circuitry" may refer to one or more or all of the following: (a) hardware-only circuit implementations (e.g., analog and / or digital-only circuit implementations); and (b) A combination of hardware circuitry and software (if applicable) that: (i) a combination of analog and / or digital hardware circuitry and software / firmware; and (ii) Software (including digital signal processors), software, and portions of hardware processors with memory that work together to cause devices such as mobile phones and servers to perform various functions. (c) A hardware circuit or processor, such as a microprocessor or part of a microprocessor, that requires software (e.g., firmware) to operate, but may be absent when the software is not required for operation.

[0124] This definition of circuit applies to all uses of the term in this application, including any claims. As a further example, as used herein, the term circuit also covers merely a hardware circuit or processor (or processors) or portion of a hardware circuit or processor and its (or their) accompanying software and / or firmware implementations. The term circuit also covers, for example, baseband or processor integrated circuits for mobile devices, or similar integrated circuits in servers, cellular network devices, or other computing or network devices, if applicable to particular claim elements.

[0125] While embodiments of the present invention have been described in the above paragraphs with reference to various examples, it should be understood that modifications of the illustrated examples are possible without departing from the scope of the invention as set forth in the claims.

[0126] The features set out in the foregoing description may also be used in combinations other than those expressly set out.

[0127] Although functions are described with reference to certain features, those functions can be performed by other features, whether or not described.

[0128] Although features are described with reference to particular embodiments, those features may also be present in other embodiments, whether or not described.

[0129] Although efforts have been made in the foregoing specification to draw attention to features of the invention which are considered to be particularly important, it is to be understood that the applicant claims protection in respect of any patentable feature or combination of features described hereinabove and / or shown in the drawings, whether or not specifically emphasized.

Claims

1. A user equipment, at least one processor; at least one memory for storing instructions; the instructions, when executed by the at least one processor, cause the user equipment to: receiving a radio configuration and a trigger condition for activating the radio configuration, the radio configuration being associated with a cell of a radio access network, the radio configuration enabling a connection between the user equipment and the cell; receiving an indication of which radio configuration associated with another cell is to be retained by the user equipment when the trigger condition for the cell is met; determining when the trigger condition is met and activating the wireless configuration; assessing which radio configuration associated with another cell to retain based on the received indication; communicating to the radio access network which radio configurations associated with other cells are maintained; The user device.

2. The user equipment of claim 1 , wherein the cell comprises a target cell.

3. The user equipment of claim 1 or 2, wherein the other cell comprises a cell that served the user equipment before activation of the radio configuration.

4. The user equipment of any of claims 1 to 3, wherein the received indication comprises an indication received from a serving central master node.

5. A user equipment according to any preceding claim, wherein the received indication comprises a list of one or more other cells selected to be associated with the cell.

6. A user equipment according to any preceding claim, wherein the received indication comprises a list of one or more other cells that are neighbouring cells of the cell.

7. 7. The user equipment of claim 1, wherein the received indication includes a measurement configuration for performing measurements related to at least a subset of other cells when the trigger condition for the cell is met, and wherein assessing includes performing the configured measurements.

8. The user equipment of claim 7 , wherein the measurement configuration includes a comparison of the radio signal of the other cell with a predetermined threshold.

9. 9. The user equipment of claim 7 or 8, wherein the measurement configuration comprises a comparison of a radio signal of the cell to a radio signal of the other cell.

10. 10. User equipment according to any of claims 1 to 9, wherein communicating comprises communicating to the network a list of the other cells for which the radio configuration is maintained.

11. 11. User equipment according to any preceding claim, wherein communicating comprises sending an indication to the network of a cell from which the radio configuration is released.

12. 12. The user equipment of claim 1, wherein the radio configuration includes a configuration of the user equipment, a cell, and another cell for a conditional primary cell of a secondary cell group addition or change, CPAC, in a New Radio dual connectivity radio access network.

13. 1. A user equipment method, comprising: receiving a radio configuration and a trigger condition for activating the radio configuration, the radio configuration being associated with a cell of a radio access network, the radio configuration enabling a connection between the user equipment and the cell; receiving an indication of which radio configuration associated with another cell is to be retained by the user equipment when the trigger condition for the cell is met; determining when the trigger condition is met and activating the wireless configuration; assessing which radio configuration associated with another cell to retain based on the received indication; communicating which radio configurations associated with other cells are held in said radio access network; A user equipment method comprising:

14. a network node, at least one processor; at least one memory for storing instructions; the instructions, when executed by the at least one processor, cause the user equipment to: determining a radio configuration and a trigger condition for activating the radio configuration, the radio configuration being associated with a cell of a radio access network, the radio configuration enabling a connection of a user equipment with the cell; evaluating which radio configuration associated with another cell is retained by the user equipment when the trigger condition for the cell is met; transmitting the radio configuration, trigger conditions, and evaluations to the user equipment; A network node.

15. 15. The network node of claim 14, wherein evaluating comprises requesting neighbor cell information from the cell and selecting from the received neighbor cell information a list of other cells that maintain radio configuration information related to the cell.

16. 15. The network node of claim 14, wherein evaluating comprises requesting a mobility history from the cell and selecting from the received mobility history a list of other cells that maintain radio configuration information of the cell.

17. A network node according to any one of claims 14 to 16, wherein evaluating comprises selecting a measurement configuration for transmission to the user equipment.

18. 18. The network node of claim 17, wherein the measurement configuration includes a predetermined threshold radio signal strength received from a cell.

19. 19. A network node according to claim 17 or 18, wherein the measurement configuration comprises a predetermined difference between radio signal strengths received from another cell compared to the cell.

20. 1. A method performed by a network node, comprising: determining a radio configuration and a trigger condition for activating the radio configuration, the radio configuration being associated with a cell of a radio access network, the radio configuration enabling a connection of a user equipment with the cell; evaluating which radio configuration associated with another cell is retained by the user equipment when the trigger condition for the cell is met; transmitting the radio configuration, trigger conditions, and evaluations to the user equipment; A method comprising:

21. 1. A network node supporting a cell of a radio access network, comprising: at least one processor; at least one memory for storing instructions; the instructions, when executed by the at least one processor, cause the user equipment to: receiving a radio configuration associated with the cell, the radio configuration enabling a connection between user equipment and the cell; receiving a request for an indication of other cells related to the cell; determining which other cells are associated with said cell; returning a response to the request based on the determination; A network node.

22. 22. The network node of claim 21, wherein determining which other cells are relevant comprises determining a set of neighbor cells of the cell.

23. 23. A network node according to claim 21 or 22, wherein determining which other cells are relevant comprises determining a mobility history of the cells.

24. 1. A method performed by a network node supporting a cell of a radio access network, comprising: receiving a radio configuration associated with the cell, the radio configuration enabling a connection between user equipment and the cell; receiving a request for an indication of other cells related to the cell; determining which other cells are associated with the target cell; returning a response to the request based on the determination; A method comprising:

25. A computer program product operable to perform the method of any one of claims 13, 20 or 24 when executed on a computer.

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