Managing mobility in network supporting dual connectivity

Abstract

A 5G new radio network supporting dual connectivity for a user equipment allows the user equipment to access the network simultaneously via a primary cell and a secondary cell. The radio coverage in the primary cell is supported by a primary distributed node controlled by a primary central node, while the radio coverage in the secondary cell is supported by a secondary distributed node controlled by a secondary central node. Embodiments seek to support low layer dual connectivity mobility of user equipment by providing cooperation between a primary cell and a secondary cell, such that handover decisions may be made at a primary distributed node based on low layer measurements.

Description

Technical Field

[0001] Various example embodiments are directed to facilitating handover between cells in a new radio network for user equipment configured to support dual connectivity. Background Art

[0002] The new radio 5G network may include network nodes formed in a distributed manner such that there is a central node or unit that controls multiple distributed nodes or units, each of which supports providing radio coverage via one or more cells. These cells may be smaller than macro cells, and therefore movement between cells may occur more frequently.

[0003] Low layer mobility LLM is being considered for such networks, where handover decisions are made in distributed nodes based on low layer signal measurements performed at the user equipment. Complexities may arise for user equipment configured to support dual connectivity, such that the user equipment is simultaneously connected to a primary distributed node, which provides access to a primary serving cell, and a secondary distributed node, which provides access to a secondary serving cell, and a handover in the primary cell may affect the connection configuration with the secondary cell. Summary of the invention

[0004] The scope of protection sought by various embodiments of the present disclosure is defined by the independent claims. Embodiments and features described in this specification that do not belong to the scope of the independent claims (if any) should be interpreted as examples that help understand various embodiments of the present invention.

[0005] According to various but not necessarily all embodiments of the present disclosure, a user equipment for accessing a radio access network is provided, the radio access network comprising: a primary central node and a plurality of primary distributed nodes, the plurality of primary distributed nodes supporting provision of radio coverage via a primary cell, the primary central node controlling the plurality of primary distributed nodes; and a secondary central node and at least one secondary distributed node, the at least one secondary distributed node supporting provision of radio coverage via at least one secondary cell, the secondary central node controlling the at least one secondary distributed node, wherein the user equipment is configured to support dual connectivity, so that the user equipment can be simultaneously connected to the primary distributed node and the secondary distributed node, the primary distributed node The user equipment comprises: at least one processor; and at least one memory storing instructions, which, when executed by the at least one processor, enables the user equipment to at least: establish a dual connectivity connection toward the primary service cell and the secondary service cell, receive a measurement configuration from the primary node, the measurement configuration being used to perform measurements at least related to the non-serving primary cell and the secondary cell so that the serving primary distributed node can perform a low-layer mobility dual connectivity switching decision, perform at least a portion of the configured measurements, and send a report related to the performed measurements to the serving primary distributed node via a low-layer message.

[0006] It should be appreciated that for a user equipment configured to support dual connectivity, when a low layer mobility dual connectivity handover decision is made at a serving primary distributed node for a primary cell change, this may affect the connection configuration with the secondary cell both when the serving secondary cell remains the same and when the serving secondary cell changes. For example, when the serving secondary cell is located across the primary cell boundary, or the secondary cell itself is changing, when the primary cell changes, the allocated frequency band at the secondary cell may change, and therefore, the measurements that facilitate any handover decision may include measurements related to the secondary cell.

[0007] Therefore, in order to enable the serving primary distributed node to make an informed low-layer dual connectivity handover decision, measurement configuration information at least related to the non-serving primary cell and the secondary cell may be provided to the user equipment. This allows the user equipment to respond by performing at least some configured measurements and sending a report related to the measurements to the serving primary distributed node, thereby allowing the serving primary distributed node to make an informed dual connectivity handover decision, because the serving primary distributed node will have relevant information related to both the updated secondary cell configuration that such a handover will trigger, and the updated primary cell.

[0008] In some example embodiments, the measurement report is related to at least a non-serving primary cell and a secondary cell.

[0009] In some example embodiments, the measurement configuration includes a first configuration and a second configuration, the first configuration including MCG configuration 1 and associated SCG configuration 1 , the second configuration including MCG configuration 2 and associated SCG configuration 2 .

[0010] SCG configuration 1 may be a configuration of a secondary cell, which is compatible with a configuration MCG configuration 1 of a distributed node of a target primary cell, and SCG configuration 2 may be a configuration of the same secondary cell, which is compatible with a configuration MCG configuration 2 of a distributed node of another target primary cell. The secondary cell may be a target secondary cell, or it may be a currently serving secondary cell.

[0011] In some example embodiments, MCG configuration 1 includes a PCell Id of a first non-serving primary distributed node, and SCG configuration 1 includes at least one PSCell Id (Secondary Cell Identifier) ​​of at least one secondary distributed node.

[0012] In some example embodiments, the measurement configuration is received from the serving master distributed node as a layer 2 message.

[0013] In some example embodiments, the measurement comprises at least one of: a layer one signal strength, or a layer one signal quality measurement.

[0014] The secondary serving cell may also be referred to as a secondary cell, and the serving node may be referred to as a source node.

[0015] In some example embodiments, the user equipment is further configured to receive a cell change indication indicating: a change in a primary serving cell and a change in configuration of the secondary cell, the cell change indication being received as part of a layer 2 message.

[0016] In some example embodiments, the layer 2 message comprises a MAC CE message triggering the cell change.

[0017] In some example embodiments, the indication is received from the serving master distributed node to which the measurement is sent.

[0018] In some example embodiments, the cell change indication may include a configuration ID, the configuration ID indicating: in the cell change, a configuration for the primary cell and for the secondary cell.

[0019] In some example embodiments, the user equipment is further configured to respond to receipt of the cell change indication by initiating a connection procedure with the updated primary serving cell and with the secondary serving cell.

[0020] When the secondary cell has not changed but the configuration has changed, then the connection will be suspended during the process.

[0021] In some example embodiments, the connection procedure may include a random access procedure.

[0022] In some example embodiments, the received cell change indication includes a change in the secondary serving cell; and the user equipment initiates a connection procedure with the updated primary serving cell and with the updated secondary serving cell in response to receiving the cell change indication.

[0023] In some example embodiments, the measurement configuration received from the serving master distributed node is received in a radio resource reconfiguration message.

[0024] In some example embodiments, the plurality of primary cells include a target cell, and the one or more secondary cells include at least one of the following: a target cell, or a serving cell.

[0025] In some example embodiments, the user equipment is configured to use the received radio resource configuration information when performing the connection procedure.

[0026] According to various but not necessarily all embodiments of the present disclosure, according to another aspect, a main distributed node is provided for supporting radio coverage via a main cell and for providing user equipment with access to the main cell, the user equipment being configured to support dual connectivity so that the user equipment can simultaneously connect to the main distributed node and a secondary distributed node, the secondary distributed node providing access to a serving secondary cell, the main distributed node becoming a serving main distributed node for the user equipment on the connection of the user equipment, and providing access to a primary serving cell, the main distributed node comprising: at least one processor; and at least one memory storing instructions, which, when executed by the at least one processor, causes the main distributed node to at least: receive a measurement report related to at least a non-serving main cell from the user equipment, and make a low-layer mobility dual connectivity switching decision in response to the measurement report.

[0027] In some example embodiments, the master distributed node is configured to make handover decisions for both the secondary cell and the primary cell based on measurements from at least one target primary cell.

[0028] In some example embodiments, the received measurement report is related to at least the non-serving primary cell and the secondary cell.

[0029] Example embodiments provide measurement reporting from user equipment to a serving master distributed node, the measurement reporting relating to the last target primary and secondary cells, allowing the master distributed node to make low layer mobility dual connectivity handover decisions based on measurements for both primary and secondary cells.

[0030] In some example embodiments, after making the handover decision, the distributed node is further configured to: generate a cell change indication indicating a change in a primary serving cell; and send the cell change indication to the user equipment as part of a layer 2 message.

[0031] In some example embodiments, the cell change indication may include a configuration ID indicating a configuration for the primary cell and the secondary cell in the cell change.

[0032] In some example embodiments, the layer 2 message is sent towards the user equipment as part of a MAC CE message.

[0033] In some example embodiments, the cell change indication further includes: an indication of a cell change for the secondary serving cell.

[0034] In some example embodiments, the distributed node is further configured to: forward a message to the user equipment, the message comprising measurement configuration information at least related to a non-serving primary cell and a secondary cell; and send the message towards the user equipment as part of a radio resource control reconfiguration message.

[0035] In some example embodiments, the configuration for performing measurements related to at least a non-serving primary cell and a secondary cell further comprises: a configuration for connecting to at least a non-serving primary cell and a secondary cell.

[0036] In some example embodiments, the measurement configuration information is received from the central master node as part of an L3 message and forwarded as an L2 message.

[0037] In other embodiments, the measurement configuration information may be received and processed at the distributed node in addition to being received and simply forwarded, or it may be generated at the distributed node before being transmitted towards the user equipment.

[0038] In some example embodiments, the distributed node is configured to: receive a configuration of a target primary cell and an indication of at least one secondary cell from a central node that controls the distributed node, and measurements need to be performed on the target primary cell and the at least one secondary cell; and generate measurement configuration information for the indicated target primary cell and the at least one secondary cell; and send the measurement configuration information to the central node.

[0039] In other example embodiments, the distributed node is configured to: receive a request for its measurement configuration from a central node that controls the distributed node, and in response to receiving the measurement configuration of the distributed node, the central node generates measurement and connection configuration information for the target primary cell and the at least one secondary cell.

[0040] In some example embodiments, the at least one secondary cell comprises a serving secondary cell, and in some example embodiments, the at least one secondary cell comprises at least one target secondary cell.

[0041] The target primary cell and the secondary cell are cells prepared for low-layer mobility and are potential handover targets.

[0042] According to various but not necessarily all embodiments of the present disclosure, according to another aspect, a central node for controlling multiple distributed nodes is provided, the multiple distributed nodes are configured to: support providing radio coverage to user equipment via a primary cell, the user equipment is configured to: support dual connectivity by simultaneously connecting to a serving primary distributed node and a serving secondary distributed node, the serving primary distributed node supports providing radio coverage via a primary serving cell, the serving secondary distributed node supports providing radio coverage via a secondary serving cell, the central node includes: at least one processor; and at least one memory storing instructions, which, when executed by the at least one processor, causes the central node to at least: determine at least one non-serving primary cell to be prepared for low-layer mobility; generate and send information indicating the at least one non-serving primary cell determined to a secondary central node, the secondary central node controls multiple secondary distributed nodes, the multiple secondary distributed nodes are configured to: support providing radio coverage to the user equipment via a secondary cell; and receive secondary cell configuration information for the secondary cell, the secondary cell being related to the at least one non-serving primary cell.

[0043] Multiple primary cells may be potential target cells for low layer mobility handover.

[0044] In some example embodiments, the central node is configured to generate and send the information as a secondary node modification signal.

[0045] In some example embodiments, the central node is configured to generate and send the information as a secondary node addition request signal.

[0046] In some example embodiments, the central node is further configured to: generate a measurement and connection configuration request, the measurement and connection configuration request indicating multiple primary cells and at least one secondary cell, for which measurement information is required so that the serving main distributed node can perform low-layer mobility dual connectivity switching decisions for the multiple primary cells and the at least one secondary cell; and send the measurement and connection configuration request to the serving main distributed node; receive the measurement and connection configuration information from the serving main distributed node; and generate reconfiguration information for the multiple primary cells and the at least one secondary cell; and send the reconfiguration information to the serving main distributed node.

[0047] In some example embodiments, the central node is further configured to: generate a measurement and connection configuration request requesting measurement and connection configuration of a serving main distributed node; and send the measurement and connection configuration request to the serving main distributed node; receive the measurement and connection configuration information from the serving main distributed node; generate measurement and connection configuration information for multiple main cells and the at least one secondary cell; and generate reconfiguration information for the multiple main cells and the at least one secondary cell; and send the reconfiguration information to the serving main distributed node.

[0048] According to various but not necessarily all embodiments of the present disclosure, a system for providing a radio access network is provided, the system supporting low-layer mobility for user equipment, the user equipment being configured for dual connectivity, the system comprising: a main central node according to another aspect; a plurality of main distributed nodes according to another aspect, the plurality of main distributed nodes supporting provision of radio coverage via a main cell, the main central node controlling the plurality of main distributed nodes; a secondary central node for controlling at least one secondary distributed node; and at least one secondary distributed node supporting provision of radio coverage via at least one secondary cell.

[0049] According to various but not necessarily all embodiments of the present disclosure, a method performed at a user equipment is provided, wherein the user equipment is used to access a radio access network, the radio access network comprising: a main central node and multiple main distributed nodes, the multiple main distributed nodes supporting provision of radio coverage via a main cell, the main central node controlling the multiple main distributed nodes; and a secondary central node and at least one secondary distributed node, the at least one secondary distributed node supporting provision of radio coverage via one or more secondary cells, the secondary central node controlling the at least one secondary distributed node, wherein the user equipment is configured to support dual connectivity so that the user equipment can be simultaneously connected to the main distributed node and the secondary distributed node, the main distributed node providing access to the main service cell, and the secondary distributed node providing access to the secondary service cell, wherein the method comprises: establishing a dual connectivity connection towards the main service cell and the secondary service cell; receiving a configuration from the main node, the configuration being used to perform measurements at least related to non-serving main cells and secondary cells so that the serving main distributed node can perform a low-layer mobility dual connectivity switching decision; performing at least a portion of the configured measurements; and sending a report to the serving main distributed node via a low-layer message, the report being related to the performed measurements.

[0050] According to various but not necessarily all embodiments of the present disclosure, a computer program is provided including instructions, which, when executed by a user equipment, causes the user equipment to: establish a dual connectivity connection toward a primary serving cell and a secondary serving cell; receive a measurement configuration from a primary node, the measurement configuration being used to perform measurements related at least to a non-serving primary cell and a secondary cell so that a serving primary distributed node can perform a low-layer mobility dual connectivity switching decision; perform at least a portion of the configured measurements; and send a report to the serving primary distributed node via a low-layer message, the report being related to the measurements performed.

[0051] According to various but not necessarily all embodiments of the present disclosure, a non-transitory computer-readable medium including program instructions stored thereon is provided, for performing at least the following items: establishing a dual connectivity connection toward a primary service cell and a secondary service cell; and in response to receiving a measurement configuration, the measurement configuration is used to perform measurements related to at least a non-serving primary cell and a secondary cell from a primary node, the measurements enabling a serving primary distributed node to perform a low-layer mobility dual connectivity switching decision; performing at least a portion of the configured measurements.

[0052] According to various but not necessarily all embodiments of the present disclosure, a method performed at a distributed node is provided, wherein the distributed node is used to support radio coverage via a primary cell and to provide user equipment with access to the primary cell, the user equipment being configured to support dual connectivity so that the user equipment can simultaneously connect to the primary distributed node and a secondary distributed node, the secondary distributed node providing access to a serving secondary cell, the primary distributed node becoming a serving primary distributed node for the user equipment over the connection of the user equipment and providing access to a primary serving cell, the method comprising: receiving a measurement report from the user equipment, the measurement report being related to at least a non-serving primary cell; and making a low-layer mobility dual connectivity switching decision for the user equipment in response to the measurement report.

[0053] According to various but not necessarily all embodiments of the present disclosure, a computer program is provided comprising instructions which, when executed by a distributed node, cause the distributed node to: receive a measurement report related at least to a non-serving primary cell from the user equipment; and make a low-layer mobility dual-connectivity switching decision for the user equipment in response to the measurement report.

[0054] According to various but not necessarily all embodiments of the present disclosure, a non-transitory computer-readable medium including program instructions stored thereon is provided for performing at least the following items: in response to reception of a measurement report from a user equipment at least related to a non-serving primary cell, making a low-layer mobility dual-connectivity switching decision for a user equipment.

[0055] According to various but not necessarily all embodiments of the present disclosure, a method for controlling multiple distributed nodes at a central node is provided, the multiple distributed nodes are configured to: support providing radio coverage to user equipment via a primary cell, the user equipment is configured to: support dual connectivity by simultaneously connecting to a serving primary distributed node and a serving secondary distributed node, the serving primary distributed node supports providing radio coverage via a primary serving cell, the serving secondary distributed node supports providing radio coverage via a secondary serving cell, the method includes: determining at least one non-serving primary cell to be prepared for low-layer mobility; generating and sending information indicating the at least one determined non-serving primary cell to a secondary central node, the secondary central node controlling multiple secondary distributed nodes, the multiple secondary distributed nodes being configured to: support providing radio coverage to the user equipment via a secondary cell; and receiving secondary cell configuration information for the secondary cell, the secondary cell being related to the at least one non-serving primary cell.

[0056] According to various but not necessarily all embodiments of the present disclosure, a computer program including instructions is provided, which, when executed by a central node, causes the central node to: generate a measurement and connection configuration request, the measurement and connection configuration request indicating multiple primary cells and at least one secondary cell for which measurement information is required, so that a serving primary distributed node can perform a low-layer mobility dual-connectivity switching decision for the multiple primary cells and the at least one secondary cell; and send the measurement and connection configuration request to the serving primary distributed node.

[0057] According to various but not necessarily all embodiments of the present disclosure, a user equipment for accessing a radio access network is provided, the radio access network comprising: a main central node and a plurality of main distributed nodes, the plurality of main distributed nodes supporting provision of radio coverage via a main cell, the main central node controlling the plurality of main distributed nodes; and a secondary central node and at least one secondary distributed node, the at least one secondary distributed node supporting provision of radio coverage via at least one secondary cell, the secondary central node controlling the at least one secondary distributed node, wherein the user equipment is configured to support dual connectivity so that the user equipment can be simultaneously connected to the main distributed node and the secondary distributed node, the main distributed node providing access to a main serving cell, the secondary distributed node providing access to a secondary serving cell, wherein the user equipment comprises: a component for establishing a dual connectivity connection towards the main serving cell and the secondary serving cell; a component for receiving a measurement configuration from the main node, the measurement configuration being used to perform measurements at least related to a non-serving main cell and a secondary cell so that a serving main distributed node can perform a low-layer mobility dual connectivity switching decision; a component for performing at least a portion of the configured measurements; and a component for sending a report to the serving main distributed node via a low-layer message, the report being related to the performed measurements.

[0058] In some example embodiments, the user equipment further comprises means for receiving a cell change indication indicating: a change in a primary serving cell and a change in configuration of the secondary cell, the cell change indication being received as part of a layer 2 message.

[0059] In some example embodiments, the means for establishing the dual connectivity connection is configured to respond to receipt of the cell change indication by initiating a connection procedure with the updated primary serving cell and with the secondary serving cell.

[0060] In some example embodiments, the received cell change indication includes a change in the secondary serving cell; and a component for initiating a connection process with the updated primary serving cell and with the updated secondary serving cell in response to receiving the cell change indication to establish dual connectivity.

[0061] According to various but not necessarily all embodiments of the present disclosure, a main distributed node is provided for supporting radio coverage via a main cell and for providing user equipment with access to the main cell, the user equipment being configured to support dual connectivity so that the user equipment can simultaneously connect to the main distributed node and a secondary distributed node, the secondary distributed node providing access to a serving secondary cell, the main distributed node becoming a serving main distributed node for the user equipment on the connection of the user equipment and providing access to the main serving cell, the main distributed node comprising: a component for receiving a measurement report related to at least a non-serving main cell and a secondary cell from the user equipment, and a component for determining a switching decision, the component for determining a switching decision making a low-layer mobility dual-connectivity switching decision for the user equipment in response to the measurement report.

[0062] In some example embodiments, the distributed node further comprises: means for generating a cell change indication message in response to the handover decision, the cell change indication indicating a change of a primary serving cell; and means for sending the cell change indication to the user equipment.

[0063] In some example embodiments, the distributed node further comprises: a component for forwarding a message to the user equipment, the message comprising: measurement configuration information at least related to a non-serving primary cell and a secondary cell.

[0064] In some example embodiments, the distributed node includes: a component for receiving an indication of the following items from a central node that controls the main distributed node: configuration of a target primary cell and at least one secondary cell, for which measurements need to be performed; and a component for generating measurement and connection configuration information for the indicated target primary cell and the at least one secondary cell; and a component for sending the measurement and connection configuration information to the central node.

[0065] According to various but not necessarily all embodiments of the present disclosure, according to another aspect, a central node for controlling multiple distributed nodes is provided, the multiple distributed nodes are configured to: support providing radio coverage to user equipment via a primary cell, the user equipment is configured to: support dual connectivity by simultaneously connecting to a serving primary distributed node and a serving secondary distributed node, the serving primary distributed node supports providing radio coverage via a primary serving cell, the serving secondary distributed node supports providing radio coverage via a secondary serving cell, the central node includes: a component for determining at least one non-serving primary cell to be prepared for low-layer mobility; a component for sending information related to the at least one non-serving primary cell determined to a secondary central node, the secondary central node controls multiple secondary distributed nodes, the multiple secondary distributed nodes are configured to: support providing radio coverage to the user equipment via a secondary cell; and a component for receiving secondary cell configuration information for a secondary cell, the secondary cell being related to the at least one non-serving primary cell.

[0066] In some example embodiments, the central node further comprises: a component for generating a measurement and connection configuration request indicating a plurality of primary cells and at least one secondary cell for which measurement information is required, so that a serving primary distributed node can perform a low-layer mobility dual-connectivity switching decision for the plurality of primary cells and the at least one secondary cell; and a component for generating reconfiguration information for the plurality of primary cells and the at least one secondary cell; wherein the component for sending is configured to: send the measurement and connection configuration request to the serving primary distributed node; and the component for receiving is configured to: in response to receiving the measurement and connection configuration information from the serving primary distributed node, trigger the component for generating reconfiguration information for the plurality of primary cells and the at least one secondary cell to generate the reconfiguration information; and the component for sending is configured to: send the reconfiguration information to the serving primary distributed node.

[0067] According to various but not necessarily all embodiments of the present disclosure, according to another aspect, a central node for controlling a plurality of distributed nodes is provided, the plurality of distributed nodes are configured to: support providing radio coverage to a user equipment via a secondary cell, the user equipment is configured to: support dual connectivity by simultaneously connecting to a serving primary distributed node and a serving secondary distributed node, the serving primary distributed node supports providing radio coverage via a primary serving cell. The serving secondary distributed node supports providing radio coverage via a secondary serving cell, the central node comprises: at least one processor; and at least one memory storing instructions, which, when executed by the at least one processor, causes the central node to at least: receive information about a primary cell prepared for low-layer mobility; and generate a configuration of at least one secondary cell compatible with the primary cell prepared for low-layer mobility.

[0068] The central node controlling the secondary distributed nodes can respond to information about the primary cell (i.e., the target primary cell) prepared for low-layer mobility, thereby suppressing the user equipment capabilities from being exceeded when it is connected to the target primary cell and the secondary cell by: generating configuration information for one or more secondary cells that are compatible with the target primary cell.

[0069] The generated configuration information may include: a frequency layer and a measurement identifier that may be used by the secondary cell.

[0070] The central node may transmit the configuration information in a secondary node addition or secondary node modification response.

[0071] The central node may receive information about the primary cell prepared for the low layer mobility from the central node controlling the primary distributed node.

[0072] Further particular and preferred aspects are set out in the accompanying independent and dependent claims. Features of 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. BRIEF DESCRIPTION OF THE DRAWINGS

[0073] Some example embodiments will now be described with reference to the accompanying drawings, in which:

[0074] Figure 1 shows an example message exchange that may be used to enable low layer mobility;

[0075] Figure 2A Schematically illustrating user equipment handover with a primary cell changed but a secondary serving cell unchanged;

[0076] Figure 2B User equipment switching is shown with both primary and secondary cell changes;

[0077] FIG3 shows steps in a method for simultaneous intra-primary node handover and serving cell configuration modification, before low layer mobility and with dual connectivity established;

[0078] FIG4 shows steps in a method for simultaneous primary and secondary node handovers where low layer mobility is established prior to dual connectivity; and

[0079] Figure 5 A network including a primary central node, a primary distributed node, a secondary central node, and secondary distributed nodes according to an embodiment is shown. DETAILED DESCRIPTION

[0080] Before discussing example embodiments in any greater detail, an overview will first be provided.

[0081] Low Layer Mobility (LLM), also known as L1 / L2 inter-cell mobility, is a future goal to enhance mobility in new radio networks. According to the paradigm, the decision on cell change is based on Layer 1 (physical layer) measurements and is made at the L2 MAC (medium access control) layer in a distributed unit or node (DU). Figure 1 The message exchanges for such an inter-DU LLM scenario are schematically shown. In short: The UE provides L3 measurements to the source DU, which are forwarded to the CU-CP (Central Unit Control Plane) (step 1). Based on these measurements, the CU-CP decides on cell preparation (HO decision) and proceeds with context establishment in the target DU (steps 4 to 5). The CU-CP then communicates with the CU-UP (Central Unit User Plane) to perform the bearer context establishment (steps 6 to 7).

[0082] In step 8, the CU-CP forwards the RRC Reconfiguration message to the source DU using DL RRC messaging, and the latter forwards the RRC Reconfiguration message to the UE (step 9). The UE responds with an RRC Reconfiguration Complete, which is then forwarded to the CU-CP (steps 10 to 11).

[0083] The UE provides periodic L1 reports to the source DU based on its configuration (step 12).

[0084] When the source DU decides that the UE should be handed over to another DU (ie, the target DU), it triggers the handover using the MAC CE (step 13). Up to now, the UE receives data from the serving DU.

[0085] The UE then applies the RRC configuration for the target cell indicated by the MAC CE and performs random access (RA) to the target cell (steps 15 to 16). After the RA procedure, the UE sends an RRC reconfiguration complete to the target cell, which is forwarded to the CU-CP (steps 17 to 18).

[0086] The CU-CP and CU-UP perform bearer modification (steps 19 to 20) to update the bearer establishment and start forwarding data to the target DU (and stop forwarding data to the source DU) for the latter. After completion, the UE starts receiving data from the target DU (step 21).

[0087] Finally, the CU-CP releases the UE context from the source DU using the UE context release request (step 22 to step 23).

[0088] Therefore, the handover decision is made at the DU using measurements from lower layers. When supporting dual connectivity, problems may arise because a change in the primary cell may change the configuration of the secondary cell, and / or the secondary cell may also change. Therefore, the primary distributed unit may need information about one or more secondary cells, as well as about the target primary cell, in order to make a decision. This may require some collaboration between the primary node and the secondary nodes.

[0089] It should be appreciated that in a decomposed architecture, the primary central node and the secondary central nodes may be a single entity configured to control both the secondary distributed nodes and the primary distributed nodes.

[0090] Problems that may arise when switching in a network that supports dual connectivity are Figure 2A and Figure 2B is schematically shown in FIG. Figure 2A shows a handover within a master node MN (master node) without secondary nodes or cell modification, while Figure 2A An intra-MN handover with secondary node modification is shown.

[0091] Figure 2A Two primary cells 22 and 24 are shown, which have primary distributed nodes DU1 and DU2, respectively, and secondary cells 30, 32, 34. The primary cell 22 is the current serving cell of the user equipment 10, while the secondary cell 34 is a secondary serving cell for the user equipment 10 and spans the two primary cells 22, 24. The user equipment 10 is shown moving between the cell 30 and the cell 32, and arriving at the cell 34. Within the primary cell 22, there is no problem with handover from the cell 30 to the cell 32, and from the cell 32 to the cell 34, so only the secondary node modifications need to be applied without any cooperation with the primary node. However, when the user equipment 10 arrives at the cell 34, it may seek to switch from the primary cell 22 to the primary cell 24. Now although it does not change the remaining secondary cells within the cell 34, this change may require cooperation between the primary node and the secondary node, because there are potential updates or changes in the distributed node configuration DU2 compared to DU1, which may affect the secondary cells. These configuration changes may include frequency, frequency band, carrier, security keys, etc. Since the secondary cell group configuration is affected by the primary cell group configuration, preparation and execution using low-layer mobility is not feasible unless some cooperation between the primary and secondary nodes is provided.

[0092] For example, if the frequency bands allocated to the UE by the main DU1 are B1 and B2, and the main distributed unit DU2 wants to change the allocation to B1, B4, B5, and change the secondary component carrier part, then any changes in the serving secondary cell are entirely dependent on whether the secondary carrier component of the main cell has been implemented. Therefore, in this case, collaboration between the main node and the secondary node is required.

[0093] Figure 2B The UE 10 is shown moving from the primary cell 22 to the primary cell 24, while moving from the secondary cell 34 to the secondary cell 36. Therefore, a handover is required for both the primary cell and the secondary cell. Likewise, there are updates / changes to the frequencies, bands, carriers, security keys etc. in the primary distributed node (DU1 and DU2) configuration, so similarly, if the primary node unit DU1 allocates the bands B1, B2, B3 to the UE, but the primary distributed unit 2 wants to change the allocation to B1, B4, B5, this will change the secondary cell group part, so again coordination is required.

[0094] Embodiments seek to provide collaboration between a master node (MN) and a secondary node (SN) to allow LLM switching decisions to be made at a serving master distributed node for user equipment supporting dual connectivity, where these switches will affect the secondary cell, there are simultaneous switches at both the primary cell and the secondary cell, or the configuration of the serving secondary cell will change with changes to the primary cell.

[0095] Consider two scenarios, in the first scenario: DC (dual connectivity) has been established, and the MN (primary node) can inform the SN (secondary node) about which cells it will configure, which can be sent in an SN modification request, and the SN will respond by providing the secondary cell group SCG configuration for the required SN modification. The MN can then prepare the LLM configuration for both the secondary cell and the primary cell and provide it to the UE.

[0096] Scenario 2: In this case, LLM is established in the MN before DC. When the MN decides to establish DC, it provides the SN with information about the cells that have been configured with LLM, in this case, SN Add Request is used. The SN will respond by providing the corresponding SCG configuration, and then the MN will prepare the LLM configuration for both the secondary cell and the primary cell and provide it to the UE.

[0097] The advantage of this cooperation is that it enables LLM with DC, which would otherwise not be possible in case of intra-MN HO (handover) with different configurations.

[0098] The L1 / L2-based inter-cell mobility process is applicable to the following scenarios:

[0099] Standalone, CA, and NR-DC (Carrier Aggregation and New Radio Dual Connectivity) cases with serving cell change within one CG (Configuration Grant);

[0100] Intra-DU case, and intra-CU inter-DU case (applicable to both standalone and CA: no new RAN interface is expected);

[0101] Both intra-frequency and inter-frequency

[0102] Both FR1 (4.1 GHz to 7.125 GHz) and FR2 (24.25 GHz to 52.6 GHz);

[0103] The source cell and the target cell can be synchronized or not.

[0104] like Figure 2A and Figure 2B As shown, when we have dual connectivity we can distinguish two types of mobility:

[0105] 1) Modification within the SN (Secondary Node), where the PSCell (primary cell or serving secondary group cell) is changed within the same SN,

[0106] 2) Intra-MN (Master Node) handover, where the PCell (primary cell) changes within the same MN.

[0107] When the MN (master node) initiates the process of configuring DC, it sends a SN add request message [TS37.340] to the SN. In this message, it provides its configuration, including the configuration of frequency layers and measurement identifiers that can be used by the SN to ensure that the UE capabilities are not exceeded. The SN has to comply with this configuration. When the UE performs intra-MN handover, the above configuration may change and new collaboration may be required.

[0108] Embodiments seek to provide a framework for configuring and enabling LLM for a UE configured with dual connectivity.

[0109] Embodiments seek to:

[0110] 1) When LLM is established, collaboration is performed between the MN and the SN, and the corresponding configuration is provided to the UE.

[0111] 2) Enable simultaneous intra-MN HO and SN modification if necessary.

[0112] a. Enable the UE to provide the target PSCell (primary secondary cell or secondary serving cell) measurement of the SN to the source DU of the MN;

[0113] b. Enable the source MN DU to decide on simultaneous intra-MN HO and SN modification based on available measurements.

[0114] The method for cross-node collaboration during the preparation phase may involve at least one of the following:

[0115] 1: The source MN indicates to the SN the PCell prepared for the lower layer mobility in the MN

[0116] (Primary cell) list.

[0117] ·2: The SN generates an LLM SCG (Secondary Cell Group) configuration for the prepared target PSCell of the SN to be applied when low layer mobility is performed.

[0118] 3: The SN provides the MN with at least one item in the IE:

[0119] o SCG configuration of the target PSCell of the SN for low-layer mobility preparation;

[0120] o Prepared measurement timing configuration of the target PSCell: SSB (Synchronization Signal Block)

[0121] Periodicity, SSB index position, SS / PBC power;

[0122] o Prepare the CSI (channel state information) resource configuration and TCI (transmission configuration indicator) status of the target PSCell.

[0123] ·4: The CU of the MN transmits the CSI resource configuration and TCI status of the PSCell prepared in the SN to the serving DU of the MN.

[0124] 5: The serving DU of the MN generates a CSI (channel state information) measurement configuration, which includes: reporting the configuration of L1 beam measurement for the prepared target PCell and PSCell.

[0125] Methods of associating MCG and SCG configurations for LLM towards a UE in RRC signaling may include one or more of the following:

[0126] 6: The source MN generates a DC low layer mobility configuration, which consists of the MCG and SCG configurations for the LLMs in the MCG and SCG.

[0127] o For example, for a given SCG TCI state, there may be two target configurations for the UE to select from depending on the serving cell of the MCG.

[0128] ·7: The UE reports the L1 beam measurement results for the target PCell and target PSCell to the serving DU of the MN.

[0129] o In this embodiment, when the UE sends an L1 measurement report to one CG, it can report the current TCI status of other CGs. Based on the TCI status of other CGs, the DU can decide its switching action.

[0130] 8: The serving DU uses the L1 beam measurements received from the UE for the target PCell and the target PSCell to determine the low layer mobility.

[0131] 9: The UE receives a low layer command from the serving DU to apply the stored DC configuration consisting of the MCG and SCG configurations.

[0132] Two distinct cases can be identified in LLM and DC collaboration:

[0133] Case 1: If DC has been established, the source MN can inform the SN in the SN Modification Request about which PCells it will configure for LLM, and the SN will provide the SCG configuration to the source MN for the required SN modification. The MN will then prepare the LLM configuration and provide it to the UE.

[0134] Case 2: If LLM is set up in the MN and then the MN decides to set up DC, it will go ahead and provide the PCell it has configured using LLM in the SN Add Request. The SN will provide the corresponding SCG configuration and then the MN will prepare the LLM configuration and provide it to the UE.

[0135] Note: In the decomposed architecture, the gNB-CU is common to both MN and SN. They are differentiated by DU, where MCG-DU (Master Configuration Group - Distributed Unit) belongs to MN and SCG-DU belongs to SN.

[0136] FIG3 shows an example message exchange for an inter-DU LLM scenario, where dual connectivity is established before establishing low-layer mobility.

[0137] The establishment of dual connectivity at the UE (which may be considered as step 0) involves the UE connecting to PCell1 of DU1 (MN), and PSCell1 of DU3 (SN).

[0138] DC establishment is described in Section 10.2 of TS37.340. The SN addition process involves: the MN determines to provide resources from the SN to the UE based on L3 measurements. Specifically, the UE context is established at the SN to provide resources from the SN to the UE. For bearers that require SCG (Secondary Cell Group) radio resources, this process is used to add at least the initial SCG serving cell of the SCG.

[0139] Initially in step 1, the UE is configured to operate in NR-DC with a serving MN (served by PCell1) and a serving SN (served by PSCell1). DU1 supports providing radio coverage in PCell1, and DU2 supports providing radio coverage in cell 2 and cell 3. DU3 supports providing radio coverage for a secondary serving cell (sometimes referred to as a primary secondary cell PSCell1). There are additional secondary cells within the cell group cell 2 and cell 3, DU4 supports providing radio coverage in cell 2, and DU5 supports providing radio coverage in cell 3, all of which are controlled by the secondary central node CU2.

[0140] In step 2, the UE provides L3 measurements to the serving master node or source DU, DU1, and DU1 forwards these measurements to the CU-CP (Central Unit - Control Plane) master node CU1.

[0141] At step 3: Based on the measurement report from the UE, CU1 decides to establish LLM for the UE using potential target cell 2 and cell 3 of DU2.

[0142] At step 4: CU1 (MN) sends a SN modification request (optionally according to TS37.340), in which it provides CU2 (SN) with L3 measurement reports for the serving cell and target cell of the SN (i.e. PSCell1, DU4 cell 2, and DU5 cell 3), and the LLM cell list prepared in the MN (cell 2 and cell 3 of DU2), and the corresponding configurations for these cells. Therefore, at this time, the CU of the MN sends information about the cells of the MN to the SN.

[0143] At step 5: CU2 decides to prepare cell configurations (DU5 cell 3 in the example) related to DU2 cell 2 (SCG configuration 1 for DU5 cell 3) and DU2 cell 3 (SCG configuration 2 for DU5 cell 3). That is, CU2 considers the target primary cell and prepares the configuration for the secondary cell according to the target primary cell.

[0144] In this step, CU2 cooperates with DU5 to obtain the measurement timing configuration, which includes: SSB periodicity and index position, SSB / PBCH power, CSI resource configuration, and TCI status of DU5 cell 3.

[0145] At step 6: CU2 provides the following items to CU1 of the MN: SCG configuration 1, SCG configuration 2, and measurement timing configuration, the measurement timing configuration including: SSB periodicity and index position, SSB / PBCH power, CSI resource configuration, and TCI status of DU5 cell 3. This can be provided in the SN modification ACK.

[0146] At steps 7 to 9: CU1 communicates with the (source or serving) DU (i.e., DU1) to generate a CSI measurement configuration. In the request, it provides the target PCell configuration and the target PSCells configuration to DU1. DU1 prepares the CSI measurement configuration for the target PCell, and for the serving secondary cell PSCell, and in some cases for the target secondary cell, and provides it to CU1.

[0147] Note: In an alternative implementation, the CU may ask DU1 to provide the measurement configuration of the source DU and generate the CSI measurement configuration in the CU.

[0148] Step 10: CU1 generates LLM RRC configurations for the target PCell with DC (i.e., MCG configuration 1 and SCG configuration 1, and MCG configuration 2 and SCG configuration 2). SCG configuration 1 is the configuration of cell 3, which is compatible with the configuration of DU2 cell 2; SCG configuration 2 is the configuration of cell 3, which is compatible with the configuration of DU2 cell 3; each SCG configuration is identified by a unique identifier, and each SCG configuration contains, among other items, a measurement timing configuration, which includes: SSB periodicity and index position of DU5 cell 3, SSB / PBCH power, CSI resource configuration, and TCI status; each SCG configuration may also include: cell ID of DU5 cell 3 (e.g., PCI). Each SCG configuration may also include: the allocated frequency band to be used / measured, the frequency carrier to be used / measured, and the security key to be used after HO.

[0149] SCG Configuration 1 and SCG Configuration 2 are different because they have to be compatible with:

[0150] MCG configuration 1 is the configuration of DU2 cell 2; MCG configuration 2 is the configuration of DU2 cell 3; Similar to the SCG configuration, the MCG configuration is identified by a unique identifier, and in addition to other items, the MCG configuration includes: measurement timing configuration, the measurement timing configuration includes: SSB periodicity and index position of DU5 cell 3, SSB / PBCH power, CSI resource configuration, and TCI status; The MCG configuration may also include: cell ID (e.g., PCI). The MCG configuration may also include: the allocated frequency band to be used / measured, the frequency carrier to be used / measured, and the security key to be used after HO.

[0151] Steps 11 to 14: CU1 provides the UE with RRC configuration for LLM with DC, and the MN responds with RRC Reconfiguration Complete.

[0152] Steps 15 to 18: The UE uses the measurement timing configuration (including the SSB periodicity and index position of the target cell, SSB / PBCH power, CSI resource configuration, and TCI status) to be able to perform measurements. Without this configuration, the UE cannot perform L1 measurements.

[0153] The UE provides an L1 measurement report to the source DU based on these measurements. These measurement reports include: measurements for DU2 cell 2, DU2 cell 3, and optionally DU5 cell 3. The UE will report using the cell ID of the target cell, so it will provide a structure with at least a subset of the following measurements:

[0154] Measurements for serving cells;

[0155] DU2 cell 2 measurement;

[0156] DU2 cell 3 measurement;

[0157] DU5 cell 3 measurement;

[0158] Measurements of other target cells [if configured].

[0159] DU1 decides that the UE should perform LLM HO with DC and decides to which target Pcell the UE should be handed over. If the MN's DU [step 16] receives measurements with high DU2 cell 2 measurements and DU5 cell 3 measurements, it will select MCG configuration 1 and SCG configuration 1. DU1 then provides MAC to the UE to trigger PCell change with PSCell configuration update / change and provides information to CU1 about the LLM HO it triggered.

[0160] Step 19 to step 23: The UE ends the LLM HO by accessing the target cell (PCell and PScell) and providing RRC reconfiguration completion to CU1.

[0161] Note: It should be noted that if Figure 2A As shown, the UE can remain in the same PSCell and only needs to apply the new configuration to the same cell.

[0162] One thing to note is that the TCI state is a "transmission configuration indicator" state and enables the UE to transmit and receive using one specific configuration. Each UE can be configured with multiple TCI states for serving cells and non-serving cells, and multiple TCI states are used to enable transmission / reception. Based on measurements when the MN DU decides to HO and switch cells, the measurements will trigger the application of the new configuration. The UE will start transmitting / receiving using the TCI state in the indicated configuration. Taking into account the UE beam measurements, the MN can use different TCI states in the serving cell, which will not cause a handover. The use of TCI states occurs in other transmission / reception configuration updates (for example, in inter-cell beam management).

[0163] Case 2: LLM is established before DC (Figure 4)

[0164] Initially at step 1: the UE is served with PCell1 of DU1 and is configured with LLM utilizing prepared cells (ie, cell2 and cell3 from DU2).

[0165] Step 2: The UE provides a measurement report to CU1, and CU1 decides to establish a DC.

[0166] Step 3: CU1 sends a SN Add Request, in which it provides CU2 (of the SN) with the L3 Measurement Report, and the list of cells for LLM prepared in the MN (cell 2 and cell 3 of DU2), and the corresponding configurations for these cells.

[0167] Step 4 to step 6: CU2 decides to establish LLM using some DUs that do not need to interact with the MN and cell 3 of DU5 that needs to interact with the MN. Then, CU2 establishes LLM from the PSCell of DU3 to cell 2 of DU4 (with or without SRB3), and CU2 communicates with DU5 to obtain the CSI measurement configuration of the cell and the measurement timing configuration, which includes: SSB periodicity and index position of DU5 cell 3, SSB / PBCH power, CSI resource configuration, and TCI state.

[0168] Step 7: In the SN additional ACK, CU2 provides the following items to the MN: SCG configuration 1 (for DU2 cell 2), SCG configuration 2 (for DU2 cell 3), and measurement timing configuration, the measurement timing configuration includes: SSB periodicity and index position of DU5 cell 3, SSB / PBCH power, CSI resource configuration, and TCI status.

[0169] Steps 8 to 10: CU1 communicates with the (source or serving) DU (i.e. DU1) to generate a CSI measurement configuration. In this request, it provides DU1 with the target PCell configuration, and the target PSCell configuration. DU1 prepares the CSI measurement configuration for the target PCell and PSCell and provides it to CU1.

[0170] Note: In an alternative implementation, the CU may request DU1 to provide the measurement configuration of the source DU and generate the CSI measurement configuration in the CU.

[0171] Step 11: CU1 generates LLM RRC configurations (i.e., MCG configuration 1 and SCG configuration 1, and MCG configuration 2 and SCG configuration 2) for the target PCell with DC. SCG configuration 1 is the configuration of cell 3, which is compatible with the configuration of DU2 cell 2; SCG configuration 2 is the configuration of cell 3, which is compatible with the configuration of DU2 cell 3; each SCG configuration is identified by a unique identifier, and each SCG configuration includes, among other items: measurement timing configuration, the measurement timing configuration includes: SSB periodicity and index position of DU5 cell 3, SSB / PBCH power, CSI resource configuration, and TCI status; each SCG configuration may also include: cell ID of DU5 cell 3 (e.g., PCI). Each SCG configuration may also include: the allocated frequency band to be used / measured, the frequency carrier to be used / measured, and the security key to be used after HO.

[0172] SCG Configuration 1 and SCG Configuration 2 are different because they have to be compatible with:

[0173] MCG configuration 1 is the configuration of DU2 cell 2; MCG configuration 2 is the configuration of DU2 cell 3; Similar to the SCG configuration, the MCG configuration is identified by a unique identifier, and in addition to other items, the MCG configuration also includes: measurement timing configuration, the measurement timing configuration includes: SSB periodicity and index position of DU5 cell 3, SSB / PBCH power, CSI resource configuration, and TCI status; MCG configuration may also include: cell ID (e.g., PCI). The MCG configuration may also include: the allocated frequency band to be used / measured, the frequency carrier to be used / measured, and the security key to be used after HO.

[0174] Steps 12 to 15: CU1 provides the RRC configuration for LLM with DC to the UE, and the MN responds with RRC Reconfiguration Complete.

[0175] Steps 16-19: The UE uses the measurement timing configuration (the measurement timing configuration includes: SSB periodicity and index position of the target cell, SSB / PBCH power, CSI resource configuration, and TCI status) to be able to perform measurements. Without this configuration, the UE cannot perform L1 measurements.

[0176] The UE provides an L1 measurement report to the source DU based on these measurements. These measurements include: measurements for DU2 cell 2, DU2 cell 3, and optionally DU5 cell 3. The UE will report using the cell ID of the target cell, so it will provide a structure with at least a subset of the following measurements:

[0177] Measurements for serving cells;

[0178] DU2 cell 2 measurement;

[0179] DU2 cell 3 measurement;

[0180] DU5 cell 3 measurement;

[0181] Measurements of other target cells [if configured].

[0182] DU1 decides that the UE should perform LLM HO with DC, and decides to which target Pcell the UE should be handed over. If the MN's DU [step 16] receives measurements with high DU2 cell 2 measurements, and DU5 cell 3 measurements, it will select MCG configuration 1 and SCG configuration 1. DU1 then provides MAC to the UE to trigger PCell change with PSCell configuration update / change, and provides information to CU1 about the LLM HO it triggered.

[0183] Step 20 to step 24: The UE ends the LLM HO by accessing the target cell (PCell and PScell) and providing RRC reconfiguration completion to CU1.

[0184] Note: It should be noted that if Figure 2A As shown, the UE can remain in the same PSCell and only needs to apply the new configuration to the same cell.

[0185] Embodiments may provide one or more of the following advantages:

[0186] • Enable LLM with DC, which is not possible in case of intra-MN HO with different configurations.

[0187] Allowing the serving DU in the MN to make low-layer mobility decisions based on L1 beam measurements of target PCell and target PSCell controlled by different SNs.

[0188] In case of simultaneous intra-MN HO and SN modification, the configuration is provided to the UE using a single RRC reconfiguration message instead of two RRC reconfiguration messages to obtain signaling gain.

[0189] In the case of LLM in the SN, the SN needs to trigger cooperation with the MN before initiating the process; with this method, the SN can proactively do so to obtain signaling gain.

[0190] Figure 5 A 5G new radio network according to an embodiment is schematically shown. The network comprises: a plurality of primary cells 22, 24, and a plurality of secondary cells 32, 34. Radio coverage within the primary cell 22 is supported by the primary distributed node 21, while the primary distributed node 26 supports providing radio coverage within the primary cell 24. Both the primary distributed node 21 and the primary distributed node 26 are controlled by a master central node 41.

[0191] There are secondary cells 32 and 34, and the radio coverage in these cells is supported by secondary distributed nodes 31 and 33 respectively. The secondary distributed node 31 and the secondary distributed node 33 are controlled by the secondary central node 35. In this example, the user equipment 10 is currently connected to the secondary cell 34 supported by the secondary distributed node 33, and the primary cell 24 supported by the distributed node 26. Therefore, the user equipment 10 operates in a dual connectivity mode. In this example, the user equipment 10 moves from the secondary cell 34 to the secondary cell 32, while it moves from the primary cell 24 to the primary cell 22.

[0192] Embodiments allow handover decisions regarding such movement to be made at the master distributed node 26 , which is currently the master serving distributed node, sometimes referred to as the source master distributed node for the user equipment 10 .

[0193] The user equipment 10 includes a receiver 16 for receiving a signal, and the receiver 16 may be a component for receiving, or a circuit system configured to receive. The user equipment 10 also includes a component 17 for establishing dual connectivity, which may be a circuit system configured to establish dual connectivity, and a component 18 for performing measurements, which may also be a circuit system configured to perform measurements, and the measurement may be L1 signal strength and / or quality measurement. The user equipment 10 also includes a transmitter 19, or a component for transmitting. The receiver 16 may receive measurement configuration information from the distributed node 26 for performing measurements related to a non-serving primary cell (cell 22 in this case) and a secondary cell (cell 32 in this case), which are two cells for target handover. The user equipment may respond to the measurement configuration information reception by performing measurements for these cells and sending the measurements to the distributed node 26.

[0194] This is merely an example, and in other embodiments, there may be multiple cells for which measurement configuration information is received and measurements are performed, and in other embodiments, the serving secondary cell may span two primary cells, in which case the measurements performed on the secondary cell may be related to the current serving secondary cell, but the measurements may be for a reconfigured frequency band, for example, for that cell.

[0195] The serving master distributed node 26 comprises a receiver 51, which may be a receiving component or a circuit system configured to receive, which receives the measurement report and, in response thereto, uses a decision making component 52 or a circuit system configured to perform a handover decision to make a handover decision related to the cell to be handed over to. After making the handover decision, the serving master distributed node 26 generates a cell change indication using a component for generating a cell change indication or a circuit system 53 configured to generate a cell change indication, which indicates any changes in the primary serving cell and the secondary cell determined in the handover decision. It then uses a component for sending 54 to send the information to the user equipment as part of a layer 2 message.

[0196] Before the user equipment receives the measurement configuration information and executes the above steps, some cooperation already exists between the secondary central node and the primary central node.

[0197] The serving primary central node 41 will collaborate with the serving secondary central node 35 to determine the configuration of the primary cell prepared for low layer mobility and corresponding changes that may be required in the secondary cell configuration and / or the configuration of the secondary cell prepared for low layer mobility.

[0198] The primary central node 41 uses a component for determining, or a circuit system 43 configured to determine, to determine the primary cell prepared for low-layer mobility, and uses a sending component 45, or a circuit system configured to send, to send the information as a secondary node addition request, or a secondary node modification request to the secondary central node 35.

[0199] The secondary central node 35 receives the information at a receiver 37 and, in response, generates a configuration for at least one secondary cell using a component 36 for generating configuration information, or a circuit system configured to generate configuration information, at least one secondary cell being compatible with a primary cell prepared for low-layer mobility, and may use a transmitter 38 to send the configuration information in a secondary node addition or secondary node modification response.

[0200] The master central node 41 includes a component 47 for receiving, or a circuit system configured to receive, and receives the secondary cell configuration information. The master central node 41 then contacts the serving master distributed node to generate reconfiguration information for the primary cell and at least one reconfigured secondary cell using a component for generating a measurement configuration request, or a circuit system 42 configured to generate a measurement configuration request, the configuration request indicating a plurality of primary cells and at least one secondary cell for which measurement information is required. The configuration request is sent to the serving master distributed node using a sending component 45.

[0201] The serving master distributed node 26 receives the configuration request at the receiver 51 and forwards the measurement configuration information to the user equipment 10 using the means for forwarding 55 so that the user equipment can perform the above-mentioned measurements.

[0202] The following description may provide additional details of alternatives, modifications, and differences: The gNB includes: for example, a node that provides NR user plane and control plane protocol terminals to the UE, and the node is connected to the 5GC via an NG interface, for example, according to Section 3.2 of 3GPP TS 38.300 V16.6.0 (2021-06) incorporated by reference.

[0203] The following description may provide additional details of alternatives, modifications, and differences: The gNB includes: for example, a node that provides NR user plane and control plane protocol terminals to the UE, and the node is connected to the 5GC via an NG interface, for example, according to Section 3.2 of 3GPP TS 38.300 V16.6.0 (2021-06) incorporated by reference.

[0204] The gNB Central Unit (gNB-CU) includes, for example, a logical node that hosts protocols such as RRC (Radio Resource Control), SDAP (Service Data Adaptation Protocol), and PDCP (Packet Data Convergence Protocol) for the gNB, or RRC and PDCP protocols for the en-gNB, and controls the operation of one or more gNB-DUs. The gNB-CU terminates at the F1 interface connected to the gNB-DU.

[0205] The gNB distributed unit (gNB-DU) includes, for example, a logical node that hosts the RLC (Radio Link Control), MAC (Media Access Control), and PHY (Physical) layers of a gNB or en-gNB, and whose operation is partially controlled by the gNB-CU. A gNB-DU supports one or more cells. A cell is supported by only one gNB-DU. The gNB-DU terminates at the F1 interface connected to the gNB-CU.

[0206] The gNB-CU-User Plane (gNB-CU-UP) comprises, for example, a logical node that hosts, for example, the user plane portion of the PDCP protocol for the gNB-CU of the en-gNB, and the user plane portions of the PDCP protocol and the SDAP protocol for the gNB-CU of the gNB. The gNB-CU-UP terminates at an E1 interface connected to the gNB-CU-CP and an F1-U interface connected to the gNB-DU, for example, according to Section 3.1 of 3GPP TS 38.401 V16.6.0 (2021-07) incorporated by reference.

[0207] Different functional divisions can be made between the central unit and the distributed units, which are called options, for example:

[0208] Option 1 (similar to 1A):

[0209] - The functional division in this option is similar to the 1A architecture in DC. RRC is located in the central unit. PDCP, RLC, MAC, physical layer, and RF are located in the distributed unit.

[0210] Option 2 (similar to the 3C division):

[0211] - The functional division in this option is similar to the 3C architecture in DC. RRC and PDCP are located in the central unit. RLC, MAC, physical layer, and RF are located in the distributed unit.

[0212] Option 3 (partitioning within RLC):

[0213] - Low RLC (partial functions of RLC), MAC, physical layer, and RF are located in the distributed unit. PDCP and High RLC (other partial functions of RLC) are located in the central unit.

[0214] Option 4 (RLC-MAC partition):

[0215] -MAC, physical layer, and RF are located in the distributed unit. PDCP and RLC are located in the central unit.

[0216] Or, for example according to section 11 of 3GPP TR 38.801 V14.0.0 (2017-03), incorporated by reference.

[0217] gNB supports different protocol layers, such as Layer 1 (L1) - physical layer.

[0218] Layer 2 (L2) of NR is divided into the following sublayers: Medium Access Control (MAC), Radio Link Control (RLC), Packet Data Convergence Protocol (PDCP), and Service Data Adaptation Protocol (SDAP), where for example:

[0219] -The physical layer provides transport channels to the MAC sublayer;

[0220] -The MAC sublayer provides logical channels to the RLC sublayer;

[0221] -The RLC sublayer provides RLC channels to the PDCP sublayer;

[0222] -The PDCP sublayer provides radio bearers to the SDAP sublayer;

[0223] -SDAP sublayer provides QoS flow to 5GC;

[0224] - Comp. refers to header compression, and Segm. refers to segmentation;

[0225] -Control channels include (BCCH, PCCH).

[0226] Layer 3 (L3) includes: for example, Radio Resource Control (RRC), for example according to Section 6 of 3GPP TS 38.300 V16.6.0 (2021-06) incorporated by reference.

[0227] RAN (Radio Access Network) nodes, or network nodes, or central nodes, or distributed nodes, such as: gNB, base station, gNB CU, or gNB DU or parts thereof, may be implemented using, for example, a device having at least one processor, and / or at least one memory (with computer-readable instructions (computer program)), at least one processor and / or at least one memory configured to support and / or provide and / or process CU and / or DU related functions and / or features; and / or at least one protocol (sub) layer of the RAN (Radio Access Network), such as layer 2 and / or layer 3. They may also be implemented using specific components configured to perform corresponding specific tasks (e.g., layer 3 components performing layer 3 operations, layer 2 components performing layer 2 operations, etc.). The central node may, for example, implement CU-CP and / or CP-UP functions.

[0228] The gNB CU and gNB DU parts may be, for example, co-located or physically separated. The gNB DU may be even further divided, for example into two parts, for example one part including processing equipment and the other part including antennas. The Central Unit (CU) may also be referred to as BBU / REC / RCC / C-RAN / V-RAN, O-RAN, or a part thereof. The Distributed Unit (DU) may also be referred to as RRH / RRU / RE / RU, or a part thereof.

[0229] The gNB-DU supports one or more cells and can therefore serve as a serving cell for a user equipment (UE).

[0230] User equipment (UE) may include: a wireless or mobile device, a device having a radio interface that interacts with a RAN (Radio Access Network), a smartphone, a vehicle-mounted device, an IoT device, an M2M device, etc. Such a UE or device may include: at least one processor; and at least one memory including a computer program code; wherein at least one memory and the computer program code are configured to, together with at least one processor, enable the device to perform at least certain operations, such as an RRC connection to the RAN. The UE is configured, for example, to generate a message (e.g., including a cell ID) to be sent to the RAN via radio (e.g., to arrive at a serving cell and communicate with the serving cell). The UE may generate, send, and receive an RRC message containing one or more RRC PDUs (packet data units).

[0231] The UE may have different states (e.g., according to Sections 42.1 and 4.4 of 3GPP TS 38.331 V16.5.0 (2021-06) incorporated by reference).

[0232] When the RRC connection has been established, the UE is in the RRC_CONNECTED state or the RRC_INACTIVE state.

[0233] In the RRC_CONNECTED state, the UE may:

[0234] -Store AS context;

[0235] -Transmission of unicast data to / from UE;

[0236] - monitoring a control channel associated with a shared data channel to determine whether data is scheduled for the data channel;

[0237] -Provide channel quality and feedback information;

[0238] -Perform neighboring cell measurements and measurement reporting;

[0239] The RRC protocol includes the following main functions:

[0240] -RRC connection control;

[0241] - Measurement configuration and reporting;

[0242] - Establishment / modification / release of measurement configurations (e.g. intra-frequency, inter-frequency, and inter-RAT measurements);

[0243] -Measurement of gap creation and release;

[0244] - Measurement report.

[0245] Those skilled in the art will readily recognize that the steps of the various methods described above can be performed by a programmed computer.Herein, some embodiments are also intended to encompass program storage devices, such as digital data storage media, which are machine or computer readable and are coded machine executable or computer executable instruction programs, wherein the instructions perform some or all of the steps of the above methods.The program storage device can be, for example, a digital memory, a magnetic storage medium (such as a disk and a tape), a hard drive, or an optically readable digital data storage medium.Embodiments are also intended to encompass computers programmed to perform the steps of the above methods.The term "non-transient" as used herein is a limitation of the medium itself (i.e., tangible, rather than a signal), rather than a limitation of data storage persistence (such as RAM and ROM).

[0246] As used in this application, the term "circuitry" may refer to one or more or all of the following:

[0247] (a) hardware circuitry implementation only (such as implementation in analog and / or digital circuitry only), (b) a combination of hardware circuitry and software, such as (as applicable):

[0248] (i) a combination of analog and / or digital hardware circuits and software / firmware, and

[0249] (ii) any portion of a hardware processor(s) with software (including digital signal processor(s), software, and memory(s) that work together to enable a device (such as a mobile phone or server) to perform various functions), and (c) hardware circuit(s) and / or processor(s), such as microprocessor(s) or portion(s) of microprocessor(s), that requires software (e.g., firmware) to operate, but where the software is not required for operation, the software may be absent.

[0250] This definition of circuitry applies to all uses of the term in this application, including in any claims. As a further example, as used in this application, the term circuitry also covers an implementation of only a hardware circuit or processor (or multiple processors) or a portion of a hardware circuit or processor and its accompanying software and / or firmware. For example, if applicable to a particular claim element, the term circuitry also covers a baseband integrated circuit or processor integrated circuit for a mobile device, or a similar integrated circuit in a server, cellular network device, or other computing or network device.

[0251] Although embodiments of the present invention have been described in the preceding paragraphs with reference to various examples, it should be appreciated that modifications to the examples given can be made without departing from the scope of the invention as claimed.

[0252] Features described in the preceding description may be used in combinations other than the combinations explicitly described.

[0253] Although functions have been described with reference to certain features, those functions may be performable by other features whether described or not.

[0254] Although features have been described with reference to certain embodiments, those features may also be present in other embodiments whether described or not.

[0255] While efforts have been made in the foregoing description to draw attention to features of the present invention regarded as particularly important, it should be understood that the applicant claims protection for any patentable feature or combination of features mentioned above and / or shown in the accompanying drawings, whether or not particular emphasis has been placed thereon.

Claims

1. A user equipment for accessing a radio access network, the radio access network comprising: a primary central node and a plurality of primary distributed nodes, the plurality of primary distributed nodes supporting provision of radio coverage via a primary cell, the primary central node controlling the plurality of primary distributed nodes; and a secondary central node and at least one secondary distributed node, the at least one secondary distributed node supporting provision of radio coverage via at least one secondary cell, the secondary central node controlling the at least one secondary distributed node, wherein the user equipment is configured to support dual connectivity, such that the user equipment can be simultaneously connected to the primary distributed node and the secondary distributed node, the primary distributed node providing access to a primary serving cell, the secondary distributed node providing access to a secondary serving cell, wherein the user equipment comprises: at least one processor; and at least one memory storing instructions that, when executed by the at least one processor, cause the user device to at least: establishing a dual connectivity connection towards the primary serving cell and the secondary serving cell, receiving a configuration from a serving primary node, the configuration being for performing measurements related to at least a non-serving primary cell and a secondary cell to enable the serving primary distributed node to perform a low layer mobility dual connectivity handover decision, performing at least a portion of the configured measurements, A report is sent to the serving master distributed node via a low layer message, the report relating to the measurements performed. 2 . The user equipment according to claim 1 , wherein the measurement report is at least related to a non-serving primary cell and a secondary cell.

3. The user equipment according to claim 1 or 2, wherein the measurement configuration includes a first configuration and a second configuration, the first configuration includes a main cell group configuration MCG configuration 1, and an associated secondary cell group configuration SCG configuration 1, and the second configuration includes a main cell group configuration MCG configuration 2, and an associated secondary cell group configuration SCG configuration 2.

4. The user equipment according to any one of the preceding claims, wherein the measurement comprises at least one of: a layer one signal strength, or a layer one signal quality measurement.

5. The user equipment according to any one of the preceding claims, the user equipment being further configured to receive a cell change indication, the cell change indication indicating: a change in a primary serving cell and a change in a configuration of a secondary cell, the cell change indication being received as part of a layer 2 message.

6. The user equipment according to claim 5, the user equipment is further configured to respond to the reception of the cell change indication by initiating a connection procedure with the updated primary serving cell and with the secondary serving cell.

7. The user equipment according to claim 6, wherein the received cell change indication comprises a change of the secondary serving cell; and In response to receiving the cell change indication, the user equipment initiates a connection process with the updated primary serving cell and with an updated secondary serving cell.

8. The user equipment according to any of the preceding claims, wherein the measurement configuration is received from the serving master distributed node in a radio resource reconfiguration message.

9. A primary distributed node, for supporting radio coverage via a primary cell, and for providing a user equipment with access to the primary cell, the user equipment being configured to support dual connectivity, so that the user equipment can be simultaneously connected to the primary distributed node and a secondary distributed node, the secondary distributed node providing access to a serving secondary cell, the primary distributed node becoming a serving primary distributed node for the user equipment on the connection of the user equipment, and providing access to a primary serving cell, the primary distributed node comprising: at least one processor; and at least one memory storing instructions, which, when executed by the at least one processor, cause the master distributed node to at least: receiving a measurement report at least related to a non-serving primary cell from the user equipment; and In response to the measurement report, a low layer mobility dual connectivity handover decision is made.

10. The master distributed node according to claim 9, wherein the received measurement report is at least related to the non-serving primary cell and the secondary cell.

11. The master distributed node according to claim 9 or 10, after making the switching decision, the master distributed node is further configured to: generating a cell change indication, the cell change indication indicating: a change in a primary serving cell and a change in a configuration of a secondary cell; and The cell change indication is sent to the user equipment as part of a layer 2 message.

12. The master distributed node according to claim 11, wherein the cell change indication further comprises: An indication of a cell change for the secondary serving cell.

13. The master distributed node according to any one of claims 9 to 12, the master distributed node is further configured to: forward a message including a configuration to the user equipment, the configuration being used to perform measurements related to at least a non-serving primary cell and a secondary cell; and The message is sent towards the user equipment as part of a radio resource control reconfiguration message.

14. The master distributed node according to any one of claims 9 to 13, wherein the master distributed node is configured as: receiving, from a central node controlling the primary distributed node, an indication of: configuration of a target primary cell and at least one secondary cell, for which measurements need to be performed; generating measurement and connection configuration information for the indicated target primary cell and the at least one secondary cell; as well as The measurement and connection configuration information is sent to the central node.

15. A central node for controlling a plurality of distributed nodes, the plurality of distributed nodes being configured to support provision of radio coverage to a user equipment via a primary cell, the user equipment being configured to support dual connectivity by being simultaneously connected to a serving primary distributed node and a serving secondary distributed node, the serving primary distributed node supporting provision of radio coverage via a primary serving cell, the serving secondary distributed node supporting provision of radio coverage via a secondary serving cell, the central node comprising: at least one processor; as well as at least one memory storing instructions that, when executed by the at least one processor, cause the central node to at least: determining at least one non-serving primary cell to be prepared for low layer mobility; generating and sending information indicating the determined at least one non-serving primary cell to a secondary central node, the secondary central node controlling a plurality of secondary distributed nodes, the plurality of secondary distributed nodes being configured to: support providing radio coverage to the user equipment via a secondary cell; and Secondary cell measurement and connection configuration information is received for a secondary cell, the secondary cell being related to the at least one non-serving primary cell.

16. The central node of claim 15, configured to generate and send the information as a secondary node modification signal.

17. The central node of claim 15, the central node being configured to generate and send the information as a secondary node addition request signal.

18. The central node according to any one of claims 15 to 17, the central node is further configured to: generating a measurement and connection configuration request indicating a plurality of primary cells and at least one secondary cell for which measurement information is required to enable a serving primary distributed node to perform a low layer mobility dual connectivity handover decision for the plurality of primary cells and the at least one secondary cell; as well as Sending the measurement and connection configuration request to the service master distributed node; receiving the measurement and connection configuration information from the serving master distributed node; as well as generating reconfiguration information for the multiple primary cells and the at least one secondary cell; as well as The reconfiguration information is sent to the service master distributed node.

19. The central node according to any one of claims 15 to 17, wherein the central node is further configured to: generating a measurement and connection configuration request for requesting measurement configuration of a service master node; as well as Sending the measurement and connection configuration request to the service master distributed node; receiving the measurement and connection configuration information from the serving master distributed node; generating measurement and connection configuration information for a plurality of primary cells and the at least one secondary cell; as well as generating reconfiguration information for the multiple primary cells and the at least one secondary cell; as well as The reconfiguration information is sent to the service master distributed node.

20. A system for providing a radio access network, the system supporting low layer mobility for a user equipment, the user equipment being configured for dual connectivity, the system comprising: A master central node according to any one of claims 15 to 19; A plurality of master distributed nodes according to any one of claims 9 to 14, the plurality of master distributed nodes supporting provision of radio coverage via a primary cell, the master central node controlling the plurality of master distributed nodes; a secondary central node, configured to control at least one secondary distributed node; and The at least one secondary distributed node supports providing radio coverage via at least one secondary cell.

21. A method performed at a user equipment, the user equipment being configured to access a radio access network, the radio access network comprising: A primary central node and a plurality of primary distributed nodes, the plurality of primary distributed nodes supporting provision of radio coverage via a primary cell, the primary central node controlling the plurality of primary distributed nodes; and a secondary central node and at least one secondary distributed node, the at least one secondary distributed node supporting provision of radio coverage via at least one secondary cell, the secondary central node controlling the at least one secondary distributed node, wherein the user equipment is configured to support dual connectivity such that the user equipment can be simultaneously connected to a primary distributed node and a secondary distributed node, the primary distributed node providing access to a primary serving cell, the secondary distributed node providing access to a secondary serving cell, wherein the method comprises: Establishing a dual connectivity connection towards the primary serving cell and the secondary serving cell; receiving a configuration from a primary node, the configuration being for performing measurements and connecting to at least a non-serving primary cell and a secondary cell to enable the serving primary distributed node to perform a low layer mobility dual connectivity handover decision; performing at least a portion of the configured measurements; A report is sent to the serving master distributed node via a low layer message, the report relating to the measurements performed.

22. A method performed at a distributed node, the distributed node being used to support radio coverage via a primary cell and to provide a user equipment with access to the primary cell, the user equipment being configured to support dual connectivity so that the user equipment can simultaneously connect to the primary distributed node and a secondary distributed node, the secondary distributed node providing access to a serving secondary cell, the primary distributed node becoming a serving primary distributed node for the user equipment on the primary distributed node and providing access to a primary serving cell, the method comprising: receiving a measurement report from the user equipment, the measurement report being related to at least a non-serving primary cell and a secondary cell; as well as In response to the measurement report, a low layer mobility dual connectivity handover decision is made.

23. A method for controlling a plurality of distributed nodes, the plurality of distributed nodes being configured to support provision of radio coverage to a user equipment via a primary cell, the user equipment being configured to support dual connectivity by simultaneously connecting to a serving primary distributed node and a serving secondary distributed node, the serving primary distributed node supporting provision of radio coverage via at least one primary serving cell, the serving secondary distributed node supporting provision of radio coverage via at least one secondary serving cell, the method comprising: determining at least one non-serving primary cell to be prepared for low layer mobility; generating and sending information indicating the at least one determined non-serving primary cell to a secondary central node, the secondary central node controlling a plurality of secondary distributed nodes, the plurality of secondary distributed nodes being configured to: support providing radio coverage to the user equipment via a secondary cell; and Secondary cell configuration information for a secondary cell is received, where the secondary cell is related to the at least one non-serving primary cell.

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