Managing mobility in a network that supports dual connectivity

Abstract

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

Description

[Technical Field]

[0001] Various exemplary embodiments relate to facilitating handover between cells in new wireless networks for user equipment configured to support dual connectivity. [Background technology]

[0002] The new wireless 5G network may comprise network nodes formed in a distributed manner, such that there is a central node or unit that controls multiple distributed nodes or units, each supporting a distributed node providing radio coverage via one or more cells. These cells may be smaller than macrocells, and therefore movement between cells may occur more frequently. Summary of the Invention [Problem to be solved by the invention]

[0003] Lower layer mobility (LLM) is considered for networks in which handover decisions are made at distributed nodes based on lower layer signal measurements performed at the user equipment. Complications may arise for user equipment configured to support dual connectivity, where the user equipment is allowed to simultaneously connect to a primary distributed node providing access to a primary serving cell and to a secondary distributed node providing access to a secondary serving cell. Handover in the primary cell may affect the configuration of connections with secondary cells. [Means for solving the problem]

[0004] The scope of protection sought for various embodiments of the present disclosure is set forth in the independent claims. The embodiments and features described herein that do not fall within the scope of the independent claims, if any, are to be construed as examples useful for understanding various embodiments of the present invention.

[0005] In accordance with various, but not necessarily all, embodiments of the present disclosure, there is provided a user equipment for accessing a radio access network comprising a master central node and a plurality of master distributed nodes supporting providing radio coverage via a primary cell, the master central node controlling the plurality of master distributed nodes, a secondary central node and at least one secondary distributed node supporting providing radio coverage via at least one secondary cell, the secondary central node controlling the at least one secondary distributed node, and dual connectivity such that the user equipment is enabled to simultaneously connect to a primary distributed node providing access to a primary serving cell and a secondary distributed node providing access to a secondary serving cell. wherein the user equipment comprises: at least one processor; and at least one memory that stores instructions that, when executed by the at least one processor, cause the user equipment to at least: establish a dual connectivity connection to a primary serving cell and a secondary serving cell; receive from a master node a measurement configuration for performing measurements related to at least non-serving master cells and secondary cells to enable a serving master distributed node to perform lower layer mobility dual connectivity handover decisions; perform at least some of the configured measurements; and send measurement reports related to the performed measurements to the serving master distributed node via lower layer messages.

[0006] For user equipment configured to support dual connectivity, where lower layer mobility dual connectivity handover decisions are made at the serving master distributed node with respect to a primary cell change, it has been recognized that this may affect the configuration of the connection with the secondary cell both in situations where the serving secondary cell remains the same and in situations where the serving secondary cell changes. For example, if the serving secondary cell is located across a primary cell boundary, or if the secondary cell is itself changed, the assigned band in the secondary cell may change when the primary cell is changed, and therefore the measurements facilitating any handover decision may include measurements related to the secondary cell.

[0007] Thus, in order for the serving master distributed node to be able to make an informed lower layer dual connectivity handover decision, the user equipment may be provided with measurement configuration information relating to at least the non-serving master cells and the secondary cells, which enables the user equipment to perform at least some of the configured measurements and respond by sending reports relating to the measurements to the serving master distributed node, enabling the user equipment to make an informed dual connectivity handover decision, since the user equipment will have relevant information relating to both the updated secondary cell configuration and the updated primary cell that such a handover will trigger.

[0008] In some exemplary embodiments, the measurement reports relate to at least non-serving master cells and secondary cells.

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

[0010] SCG configuration 1 may be a configuration of secondary cells that matches a configuration of distributed nodes of one target primary cell, MCG configuration 1, while SCG configuration 2 may be a configuration of the same secondary cells that matches a configuration of distributed nodes of another one of the target primary cells, MCG configuration 2. The secondary cell may be the target secondary cell, or the secondary cell may be the current serving secondary cell.

[0011] In some exemplary embodiments, the MCG configuration 1 includes a PCellId of a first non-serving master distributed node, and the SCG configuration 1 includes at least one PS cellId (secondary cell identifier) of at least one secondary distributed node.

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

[0013] In some exemplary embodiments, the measurements include at least one of the following: Layer 1 signal strength or Layer 1 signal quality measurements.

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

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

[0016] In some exemplary embodiments, the Layer 2 message includes a MAC CE message that triggers the cell change.

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

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

[0019] In some exemplary 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 the secondary serving cell.

[0020] If the configuration has changed, rather than the secondary cell having changed, the connection will be suspended during this procedure.

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

[0022] In some exemplary embodiments, the received cell change indication includes a change of the secondary serving cell, and the user equipment responds to receiving the cell change indication to initiate connection procedures with the updated primary serving cell and the updated secondary serving cell.

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

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

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

[0026] In accordance with various, but not necessarily all, embodiments of the present disclosure, a master distributed node for supporting radio coverage via a primary cell and providing access to the primary cell for user equipment is provided according to further aspects, wherein the master distributed node is configured to support dual connectivity such that the user equipment is enabled to simultaneously connect to the master distributed node and to a secondary distributed node providing access to a secondary serving cell, the master distributed node becoming a serving master distributed node for the user equipment upon connection of the user equipment and providing access to the primary serving cell, the master distributed node comprising at least one processor and at least one memory storing instructions that, when executed by the at least one processor, cause the master distributed node to at least: receive measurement reports from the user equipment associated with at least non-serving master cells; and make a lower layer mobility dual connectivity handover decision in response to the measurement reports.

[0027] In some exemplary 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 exemplary embodiments, the received measurement reports relate to at least the non-serving primary cell and a secondary cell.

[0029] An exemplary embodiment provides measurement reports relating to at least the target master cell and the secondary cell from the user equipment to a serving master distributed node, enabling the master distributed node to make a lower layer mobility dual connectivity handover decision based on measurements for both the primary and secondary cells.

[0030] In some example embodiments, the distributed node is further configured, following making the handover decision, to generate a cell change indication indicating a change of primary serving cell, and to transmit the cell change indication to the user equipment as part of a Layer 2 message.

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

[0032] In some exemplary embodiments, the Layer 2 message is transmitted to the user equipment as part of a MAC CE message.

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

[0034] In some exemplary embodiments, the distributed node is further configured to forward a message to the user equipment including measurement configuration information relating to at least non-serving master cells and secondary cells, and to transmit the message to the user equipment as part of a radio resource control reconfiguration message.

[0035] In some exemplary embodiments, the configuration for performing measurements relating to at least the non-serving master cell and the secondary cell further includes configuration for connecting to at least the non-serving master cell and the secondary cell.

[0036] In some exemplary 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, rather than receiving and simply forwarding the measurement configuration information, the measurement configuration information may be received and processed at the distributed node, or the measurement configuration information may be generated at the distributed node prior to transmission to the user equipment.

[0038] In some exemplary embodiments, the distributed node is configured to receive, from a central node controlling the distributed node, a configuration of a target primary cell and an indication of at least one secondary cell for which measurements are requested, generate measurement configuration information for the indicated target primary cell and the at least one secondary cell, and transmit the measurement configuration information to the central node.

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

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

[0041] Target primary and secondary cells are cells prepared for lower layer mobility that are possible handover targets.

[0042] In accordance with various, but not necessarily all, embodiments of the present disclosure, there is provided according to still further aspects a central node for controlling a plurality of distributed nodes configured to support providing wireless coverage to a user equipment via a primary cell, the user equipment being configured to support dual connectivity by simultaneous connection to a serving master distributed node supporting providing wireless coverage via a primary serving cell and a serving secondary distributed node supporting providing wireless coverage via a secondary serving cell, the central node comprising: at least one processor; and at least one memory storing instructions that, when executed by the at least one processor, cause the central node to at least: determine at least one non-serving master cell to be prepared for lower layer mobility; generate and send information indicative of the at least one determined non-serving master cell to a secondary central node controlling a plurality of secondary distributed nodes configured to support providing wireless coverage to the user equipment via the secondary cell; and receive secondary cell configuration information for a secondary cell associated with the at least one non-serving master cell.

[0043] The multiple primary cells may be possible target cells for lower layer mobility handover.

[0044] In some exemplary embodiments, the central node is configured to generate and transmit the information as a secondary node modified signal.

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

[0046] In some exemplary embodiments, the central node is further configured to: generate a measurement and connection configuration request indicating a plurality of primary cells and at least one secondary cell for which measurement information is required, send the measurement and connection configuration request to the serving master distributed node, receive the measurement and connection configuration information from the serving master distributed node, generate reconfiguration information for the plurality of primary cells and the at least one secondary cell, and send the reconfiguration information to the serving master distributed node to enable a serving master distributed node to make lower layer mobility dual connectivity handover decisions with respect to the plurality of primary cells and at least one secondary cell.

[0047] In some exemplary embodiments, the central node is further configured to generate a measurement and connection configuration request to request measurement and connection configuration from a serving master distributed node, send the measurement and connection configuration request to the serving master distributed node, receive the measurement and connection configuration information from the serving master distributed node, generate measurement and connection configuration information for a plurality of primary cells and the at least one secondary cell, generate reconfiguration information for the plurality of primary cells and the at least one secondary cell, and send the reconfiguration information to the serving master distributed node.

[0048] In accordance with various, but not necessarily all, embodiments of the present disclosure, there is provided a system for providing a radio access network supporting lower layer mobility for user equipment configured for dual connectivity, the system comprising: a master central node according to still further aspects; and a plurality of master distributed nodes according to further aspects supporting providing radio coverage via a primary cell, the master central node controlling the plurality of master distributed nodes; and a secondary central node for controlling at least one secondary distributed node, the at least one secondary distributed node supporting providing radio coverage via at least one secondary cell.

[0049] In accordance with various, but not necessarily all, embodiments of the present disclosure, there is provided a method implemented in a user equipment for accessing a radio access network comprising a master central node and a plurality of master distributed nodes supporting providing radio coverage via a primary cell, wherein the master central node controls the plurality of master distributed nodes, and wherein a secondary central node and at least one secondary distributed node support providing radio coverage via one or more secondary cells, the secondary central node controls the at least one secondary distributed node, and wherein the user equipment is configured to support dual connectivity such that the user equipment is enabled to simultaneously connect to a primary distributed node providing access to a primary serving cell and to a secondary distributed node providing access to a secondary serving cell, the method including: establishing a dual connectivity connection to the primary serving cell and the secondary serving cell; receiving from the master node a measurement configuration for performing measurements related to at least non-serving master cells and secondary cells to enable the serving master distributed node to perform lower layer mobility dual connectivity handover decisions; performing at least some of the configured measurements; and transmitting a report related to the performed measurements to the serving master distributed node via a lower layer message.

[0050] In accordance with various, but not necessarily all, embodiments of the present disclosure, there is provided a computer program comprising instructions that, when executed by a user equipment, cause the user equipment to: establish a dual connectivity connection to a primary serving cell and a secondary serving cell; receive from a master node a measurement configuration for performing measurements related to at least non-serving master cells and secondary cells to enable a serving master distributed node to perform lower layer mobility dual connectivity handover decisions; perform at least some of the configured measurements; and send reports related to the performed measurements to the serving master distributed node via lower layer messages.

[0051] In accordance with various, but not necessarily all, embodiments of the present disclosure, a non-transitory computer-readable medium having stored thereon program instructions for performing at least the following: establishing a dual connectivity connection to a primary serving cell and a secondary serving cell; and in response to receiving from a master node a measurement configuration for performing measurements related to at least a non-serving master cell and a secondary cell, the measurements enabling a serving master distributed node to perform a lower layer mobility dual connectivity handover decision; and performing at least a portion of the configured measurements.

[0052] In accordance with various, but not necessarily all, embodiments of the present disclosure, there is provided a method implemented in a distributed node for supporting radio coverage via a primary cell and providing access to the primary cell for a user equipment configured to support dual connectivity such that the user equipment is enabled to simultaneously connect to the master distributed node and to a secondary distributed node providing access to a secondary serving cell, the master distributed node becoming a serving master distributed node for the user equipment and providing access to the primary serving cell, the method including: receiving measurement reports from the user equipment relating to at least a non-serving master cell; and making a lower layer mobility dual connectivity handover decision for the user equipment in response to the measurement reports.

[0053] In accordance with various, but not necessarily all, embodiments of the present disclosure, there is provided a computer program comprising instructions that, when executed by a distributed node, cause the distributed node to: receive measurement reports from the user equipment relating to at least a non-serving master cell; and, in response to the measurement reports, make a lower layer mobility dual connectivity handover decision for the user equipment.

[0054] In accordance with various, but not necessarily all, embodiments of the present disclosure, a non-transitory computer-readable medium is provided having stored thereon program instructions for performing at least the following: making a lower layer mobility dual connectivity handover decision for a user equipment in response to receiving from the user equipment a measurement report relating to at least a non-serving master cell.

[0055] In accordance with various, but not necessarily all, embodiments of the present disclosure, there is provided a method implemented in a central node for controlling a plurality of distributed nodes configured to support providing radio coverage via a primary cell to a user equipment configured to support dual connectivity by simultaneous connection to a serving master distributed node supporting providing radio coverage via a primary serving cell and a serving secondary distributed node supporting providing radio coverage via a secondary serving cell, the method including: determining at least one non-serving master cell prepared for lower layer mobility; generating and transmitting information indicative of the at least one determined non-serving master cell to a secondary central node controlling a plurality of secondary distributed nodes configured to support providing radio coverage via the secondary cell to the user equipment; and receiving secondary cell configuration information for a secondary cell associated with the at least one non-serving master cell.

[0056] According to various, but not necessarily all, embodiments of the present disclosure, there is provided a computer program comprising instructions that, when executed by a central node, cause the central node to: generate 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 master distributed node to make a lower layer mobility dual connectivity handover decision with respect to the plurality of primary cells and at least one secondary cell; and send the measurement and connection configuration request to the serving master distributed node.

[0057] In accordance with various, but not necessarily all, embodiments of the present disclosure, there is provided a user equipment for accessing a radio access network comprising a master central node and a plurality of master distributed nodes supporting providing radio coverage via a primary cell, wherein the master central node controls the plurality of master distributed nodes, and a secondary central node and at least one secondary distributed node supporting providing radio coverage via at least one secondary cell, wherein the secondary central node controls the at least one secondary distributed node, and wherein the user equipment is configured to support dual connectivity such that the user equipment is enabled to simultaneously connect to a primary distributed node providing access to a primary serving cell and a secondary distributed node providing access to a secondary serving cell, the user equipment including: means for establishing dual connectivity connections to the primary serving cell and the secondary serving cell; means for receiving from a master node a measurement configuration for performing measurements related to at least non-serving master cells and secondary cells to enable a serving master distributed node to perform lower layer mobility dual connectivity handover decisions; means for performing at least some of the configured measurements; and means for transmitting reports related to the performed measurements to the serving master distributed node via lower layer messages.

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

[0059] In some exemplary 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 the secondary serving cell.

[0060] In some exemplary embodiments, the received cell change indication includes a change of the secondary serving cell, and the means for establishing dual connectivity is responsive to receiving the cell change indication to initiate a connection procedure with the updated primary serving cell and the updated secondary serving cell.

[0061] In accordance with various, but not necessarily all, embodiments of the present disclosure, a master distributed node is provided for supporting radio coverage via a primary cell and for providing access to the primary cell for user equipment, the master distributed node being configured to support dual connectivity such that the user equipment is enabled to simultaneously connect to the master distributed node and to a secondary distributed node providing access to a secondary serving cell, the master distributed node becoming a serving master distributed node for the user equipment upon connection of the user equipment and providing access to the primary serving cell, the master distributed node including: means for receiving measurement reports from the user equipment relating to at least non-serving master cells and secondary cells; and means for determining a handover decision, the means for determining a handover decision responsive to the received measurement reports to make a lower layer mobility dual connectivity handover decision for the user equipment.

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

[0063] In some exemplary embodiments, the distributed node further includes means for forwarding a message to the user equipment, the message including measurement configuration information relating to at least a non-serving master cell and a secondary cell.

[0064] In some exemplary embodiments, the distributed node includes means for receiving, from a central node controlling the distributed node, an indication of the configuration of a target primary cell and at least one secondary cell for which measurements are required, means for generating measurement and connection configuration information for the indicated target primary cell and the at least one secondary cell, and means for transmitting the measurement and connection configuration information to the central node.

[0065] In accordance with various, but not necessarily all, embodiments of the present disclosure, there is provided according to still further aspects a central node for controlling a plurality of distributed nodes configured to support providing radio coverage to a user equipment via a primary cell, the user equipment being configured to support dual connectivity by simultaneous connection to a serving master distributed node supporting providing radio coverage via a primary serving cell and a serving secondary distributed node supporting providing radio coverage via a secondary serving cell, the central node including: means for determining at least one non-serving master cell prepared for lower layer mobility; means for transmitting information related to the at least one determined non-serving master cell to a secondary central node controlling a plurality of secondary distributed nodes configured to support providing radio coverage to the user equipment via the secondary cell; and means for receiving secondary cell configuration information for a secondary cell associated with the at least one non-serving master cell.

[0066] In some exemplary embodiments, the central node further includes: means 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 to enable a serving master distributed node to make a lower layer mobility dual connectivity handover decision with respect to the plurality of primary cells and at least one secondary cell; and means for generating reconfiguration information for the plurality of primary cells and the at least one secondary cell, wherein the means for transmitting is configured to transmit the measurement and connection configuration request to the serving master distributed node, the means for receiving is configured to trigger the means for generating reconfiguration information for the plurality of primary cells and the at least one secondary cell to generate the reconfiguration information in response to receiving the measurement and connection configuration information from the serving master distributed node, and the means for transmitting is configured to transmit the reconfiguration information to the serving master distributed node.

[0067] In accordance with various, though not necessarily all, embodiments of the present disclosure, there is provided according to still further aspects a central node for controlling a plurality of distributed nodes configured to support providing radio coverage via secondary cells to user equipment configured to support dual connectivity by simultaneous connection to a serving master distributed node supporting providing radio coverage via a primary serving cell and a serving secondary distributed node supporting providing radio coverage via a secondary serving cell, the central node comprising at least one processor and at least one memory storing instructions that, when executed by the at least one processor, cause the central node to at least: receive information regarding a master cell prepared for lower layer mobility; and generate a configuration for at least one secondary cell that matches the master cell prepared for lower layer mobility.

[0068] The central node controlling the secondary distributed nodes may respond to information about the master cell that is prepared for lower layer mobility, i.e., the target master cell, by generating configuration information about one or more secondary cells that are compatible with the target master cell so as to prevent user equipment capabilities from being exceeded when the central node connects to the target master cell and the secondary cell.

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

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

[0071] The central node may receive information about master cells prepared for lower layer mobility from a central node that controls the master distributed nodes.

[0072] Further particular and preferred aspects are set out in the accompanying independent and dependent claims. Features from the dependent claims may be combined with features of the independent claims as appropriate and may be combined with features other than those explicitly set out in the claims.

[0073] Some example embodiments will now be described with reference to the accompanying drawings. [Brief explanation of the drawings]

[0074] [Figure 1] FIG. 1 illustrates an example message exchange that may be used to enable lower layer mobility. [Figure 2A] FIG. 1 illustrates a schematic diagram of a user equipment handover with a change of master cell but no change of secondary serving cell. [Figure 2B]FIG. 1 illustrates a user equipment handover that changes both the master cell and the secondary cell. [Figure 3A] A diagram showing the steps of a method in which there is an intra-master node handover simultaneous with serving cell configuration modification and dual connectivity is set up before lower layer mobility. [Figure 3B] A diagram showing the steps of a method in which there is an intra-master node handover simultaneous with serving cell configuration modification and dual connectivity is set up before lower layer mobility. [Figure 3C] A diagram showing the steps of a method in which there is an intra-master node handover simultaneous with serving cell configuration modification and dual connectivity is set up before lower layer mobility. [Figure 4A] A diagram showing the steps of a method where there is simultaneous master node and secondary node handover and lower layer mobility is set up before dual connectivity. [Figure 4B] A diagram showing the steps of a method where there is simultaneous master node and secondary node handover and lower layer mobility is set up before dual connectivity. [Figure 4C] A diagram showing the steps of a method where there is simultaneous master node and secondary node handover and lower layer mobility is set up before dual connectivity. [Figure 5] FIG. 1 illustrates a network comprising a master central node, a master distributed node, a secondary central node, and a secondary distributed node, according to one embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0075] Before discussing exemplary embodiments in more detail, an overview will first be provided.

[0076] Lower Layer Mobility (LLM), also marked as L1 / 2 inter-cell mobility, is a future goal for enhancing mobility in new wireless networks. According to this paradigm, the decision regarding cell change is made at the L2 medium access control (MAC) layer in the distributed unit or node (DU) based on Layer 1 measurements (physical layer). Figure 1 shows a schematic of the message exchange for such an inter-DU LLM scenario. Briefly, the UE provides L3 measurements to the source DU, which are forwarded to the central unit control plane (CU-CP) (step 1). Based on these measurements, the CU-CP makes a cell preparation decision (HO decision) and proceeds to set up the context for the target DU (steps 4-5). The CU-CP then communicates with the central unit user plane (CU-UP) to perform bearer context setup (steps 6-7). In step 8, the CU-CP forwards the RRC reconfiguration message to the source DU using DL RRC message forwarding, and the source DU forwards the RRC reconfiguration message to the UE (step 9). The UE responds with an RRC reconfiguration end, which is then forwarded to the CU-CP (steps 10-11). The UE provides periodic L1 reports to the source DU based on its configuration (step 12). When the source DU determines that the UE should be handed over to another DU (i.e., target DU), the source DU triggers the handover using the MAC CE (step 13). By this time, the UE has received data from the serving DU. Then, the UE applies the RRC configuration for the target cell indicated by the MAC CE and performs Random Access (RA) to the target cell (steps 15-16). After the RA procedure, the UE sends an RRC reconfiguration end to the target cell, and the RRC reconfiguration end is forwarded to the CU-CP (steps 17-18). The CU-CP performs a bearer modification with the CU-UP (steps 19-20) to update the bearer setup and for the CU-UP to start forwarding data to the target DU (and stop forwarding data to the source DU). Once this is complete, the UE starts receiving data from the target DU (step 21). Finally, the CU-CP releases the UE context from the source DU using a UE context release request (steps 22-23).

[0077] The handover decision is then made at the DU using measurements from lower layers. If dual connectivity is supported, problems may arise because changes to the primary cell may change the configuration of the secondary cell and / or may also change the secondary cell. Therefore, the master distribution unit may need information about one or more secondary cells as well as information about the target master cell to facilitate making the decision. This may require some degree of coordination between the master node and the secondary nodes.

[0078] It should be understood that the master central node and secondary central node may be a single entity configured to control both the secondary distributed nodes and the master distributed node in a split architecture.

[0079] Problems that may arise with respect to handover in networks where dual connectivity is supported are shown schematically in Figures 2A and 2B. Figure 2A shows an intra-master node (MN) handover without secondary node or cell modification, while Figure 2B shows an intra-MN handover with secondary node modification.

[0080] FIG. 2A shows two primary cells 22 and 24 with respective master distributed nodes DU1 and DU2 and secondary cells 30, 32, and 34. Primary cell 22 is the current serving cell for user equipment 10, while secondary cell 34 is a secondary serving cell for user equipment 10 and spans the two primary cells 22 and 24. User equipment 10 is shown traveling between cells 30 and 32 and reaching cell 34. Handovers from cells 30 to 32 and from 32 to 34 are unproblematic and within master cell 22, and therefore only require secondary node modifications to be applied, without requiring coordination with the master node. However, upon reaching cell 34, user equipment 10 may request a handover from primary cell 22 to primary cell 24. Here, user equipment 10 does not change secondary cells, remaining within cell 34, but this change may require coordination between the master node and the secondary node. This is because there is a possibility of updating or changing the distributed node configuration DU2 compared to DU1, which may affect the secondary cells. These configuration changes may include frequency, band, carrier, security key, etc. Since the secondary cell group configuration is influenced by the master cell group configuration, preparing and running to use lower layer mobility is not feasible unless some degree of coordination between the master node and the secondary nodes is provided.

[0081] For example, if the allocation bands for the UE of master DU1 are B1 and B2, and master distribution unit DU2 needs to make the allocation B1, B4, B5, which changes the secondary component carrier part, any change in serving secondary cell will be entirely dependent on whether the primary cell secondary carrier component has been performed or not, therefore, in such a scenario, coordination between the master node and the secondary node is required.

[0082] 2B shows UE 10 moving from primary cell 22 to primary cell 24 and simultaneously from secondary cell 34 to secondary cell 36. Therefore, handover for both primary and secondary cells is required. Again, there is a possibility of updating / changing master distributed node (DU1 and DU2) configuration in frequency, band, carrier, security key, etc., so again, if master node unit DU1 assigns bands B1, B2, B3 to the UE, but master distributed unit 2 needs to change the assignment to B1, B4, B5, this will change the secondary cell group portion, and therefore coordination is also required.

[0083] Embodiments seek to provide coordination between the Master Node (MN) and the Secondary Node (SN) to enable LLM handover decisions to be made at the Serving Master distributed node for user equipment supporting dual connectivity, and these handovers will affect the secondary cell when there is a simultaneous handover to both the master cell and the secondary cell, or because the configuration of the serving secondary cell will change when the master cell changes.

[0084] Two scenarios are possible: first, DC (dual connectivity) is already set up and the MN (master node) may inform the SN (secondary node) about which cell the MN will configure, which may be sent in an SN modification request, and the SN will respond by providing a secondary cell group SCG configuration for the requested SN modification. The MN can then prepare LLM configurations for both the secondary and master cells and provide the LLM configurations to the UE.

[0085] Scenario 2: In this case, the LLM is set up in the MN before the DC. When the MN decides to set up a DC, it provides the SN with information about which cells it has configured using the LLM; in this case, an SN addition request is used. The SN will respond by providing the respective SCG configurations, and the MN will then prepare the LLM configurations for both the secondary and master cells and provide the LLM configurations to the UE.

[0086] The advantage of this cooperation is that it allows LLM with DC, which would not otherwise be possible in case of intraMN HO (handover) with different configurations.

[0087] The L1 / L2 based inter-cell mobility procedure covers the following scenarios, namely: Standalone, CA and NR-DC (Carrier Aggregation and New Radio Dual Connectivity) cases with serving cell change within one CG (configured grant) Intra-DU, intra-CU, and inter-DU cases (applicable for standalone and CA: no new RAN interfaces are expected) Both same frequency and different frequency Both FR1 (4.1GHz~7.125GHz) and FR2 (24.25GHz~52.6 GHz) The source and target cells may or may not be synchronized may be applicable to

[0088] As shown in Figures 2A and 2B, when having dual connectivity, two types of mobility can be distinguished: 1) intraSN (Secondary Node) modification - PS cell (primary cell or serving secondary group cell) changes within the same SN, 2) IntraMN (Master Node) Handover - The P-cell (Primary Cell) changes within the same MN.

[0089] When the MN (master node) initiates the procedure to configure the DC, it sends an SN Addition Request message to the SN (TS37.340). In this message, the MN can provide its configuration, including the frequency layers and measurement identities that can be used by the SN, to ensure that the UE capabilities are not exceeded. The SN must comply with this configuration. When the UE performs an intraMN handover, the configuration described above may change and new coordination may need to occur.

[0090] The embodiments seek to provide a framework for configuring and enabling LLM for UEs configured with dual connectivity.

[0091] Embodiments include: 1) Once the LLM is set up and the respective configurations are provided to the UE, the MN and SN attempt to cooperate. 2) Attempt to enable simultaneous intraMN HO and SN correction when needed a. Enables the UE to provide the SN's target PS cell (primary secondary cell or secondary serving cell) measurements to the MN's source DU b. Allow the source MN DU to decide on simultaneous intraMN HO and SN modifications based on available measurements.

[0092] The coordination across nodes during the preparation phase is: 1: The source MN indicates to the SN a list of P-cells (primary cells) that are prepared for lower layer mobility in the MN. 2: The SN generates an LLM SCG (Secondary Cell Group) configuration for the SN's prepared target PS cell that applies when lower layer mobility is performed. 3:SN is less than or equal to: o SCG configuration for SN-prepared target PS cells for lower layer mobility Measurement timing configuration of prepared target PS cells: SSB (synchronisation signal block) periodicity, SSB index location, SS / PBC power CSI resource configuration (Channel Status Information) and TCI (Transmission Configuration Indicator) status of the prepared target PS cell At least one of the above is provided to the MN. · 4: The CU of the MN communicates the CSI resource configuration and TCI state of the prepared PS cells in the SN to the serving DU of the MN. 5: The serving DU of the MN generates a CSI (channel status information) measurement configuration including configurations for reporting L1 beam measurements for the prepared target P-cell and PS-cell. It may include at least one of the following.

[0093] The method for associating the MCG and SCG configuration for LLM to the UE in RRC signaling is: · 6: The source MN generates DC lower layer mobility configurations consisting of MCG and SCG configurations for the LLM in the MCG and SCG. For example, for a given TCI state of an SCG, there may be two target configurations for the UE to choose from, depending on the serving cell of the MCG. 7: The UE reports the MN L1 beam measurement results for the target P cell and the target PS cell to the serving DU. In this embodiment, when the UE sends an L1 measurement report to one CG, it may also report the current TCI status of other CGs, based on which the DU can decide its switching action. 8: The serving DU determines the lower layer mobility using the L1 beam measurements received from the UE for the target P cell and the target PS cell. · 9: The UE receives a lower layer command from the serving DU to apply the stored DC configuration consisting of the MCG configuration and the SCG configuration. may include one or more of:

[0094] Two distinct cases can be distinguished in LLM and DC collaboration: Case 1: If DC is already set up, the source MN may inform the SN about which PCells it will configure prepared for LLM in the SN modification request, and the SN will provide the source MN with SCG configurations for the requested SN modification. The MN will then prepare the LLM configurations and provide them to the UE. Case 2: If an LLM is set up in the MN and the MN then decides to set up a DC, the MN will proceed with an SN addition request and provide which PCells the MN has configured using the LLM. The SN will provide the respective SCG configurations, and the MN will then prepare the LLM configurations and provide them to the UE.

[0095] Note: In a split architecture, the gNB-CU is common to both the MN and the SN. They are distinguished by the DU, where the MCG-DU (master configuration group-distributed unit) belongs to the MN and the SCG-DU belongs to the SN.

[0096] FIG. 3 shows an example message exchange for an inter-DU LLM scenario in which dual connectivity is set up prior to setting up lower layer mobility. The establishment of dual connectivity at the UE, which may be seen as step 0, involves the UE connecting to P Cell 1 of DU1 (of the MN) and PS Cell 1 of DU3 (of the SN). The DC establishment is described in section 10.2 of TS37.340. The SN addition procedure involves the MN deciding to provide resources from the SN to the UE based on L3 measurements. In particular, a UE context is established in the SN to provide resources from the SN to the UE. For bearers that require SCG (secondary cell group) radio resources, this procedure is used to add at least the initial SCG serving cell of the SCG.

[0097] Initially, in step 1: a UE is configured to operate in NR-DC with a serving MN (served by PCell1) and a serving SN (served by PSell1). DU1 supports providing radio coverage in PCell1, and DU2 supports providing radio coverage in cells 2 and 3. DU3 supports providing radio coverage for a secondary serving cell, sometimes referred to as the primary secondary cell PSell1. Within this cell group, cells 2 and 3, there is a further secondary cell, DU4, which supports providing radio coverage in cell 2 and DU5 in cell 3, and all of these secondary distributed nodes are controlled by the secondary central node CU2. In step 2: The UE provides the L3 measurements to the serving master or source DU, DU1, which forwards them to the CU-CP (central unit-control plane) master node CU1. In step 3: Based on the measurement report from the UE, CU1 decides to set up an LLM for the UE with possible target cell 2 and cell 3 of DU2. In step 4: CU1 (of the MN) sends an SN modification request (optional according to TS37.340), and CU1 provides CU2 (of the SN) with L3 measurement reports for the SN's serving and target cells, i.e., PS cell 1, DU4-cell 2, and DU5-cell 3, as well as a list of prepared cells for LLM in the MN (cells 2 and 3 of DU2) and the respective configurations for these cells. Thus, at this point, the CU of the MN sends information about the MN's cells to the SN. In step 5: CU2 decides to prepare a cell configuration (in the example, DU5-cell3) that is relevant for DU2-cell2 (SCG configuration 1 for DU5-cell3) and DU2-cell3 (SCG configuration 2 for DU5-cell3). That is, CU2 considers the target master cell and prepares a configuration for the secondary cell taking the target master cell into account. In this step, CU2 cooperates with DU5 to obtain measurement timing configuration including SSB periodicity and index location, SSB / PBCH power, CSI resource configuration, and TCI state of DU5-Cell3. In step 6: CU2 provides the following to CU1 of the MN: SCG configuration 1, SCG configuration 2, and measurement timing configuration, including SSB periodicity and index location, SSB / PBCH power, CSI resource configuration, and TCI state of DU5-Cell 3. This may be provided in the SN modified ACK. In steps 7-9: CU1 communicates with the (source or serving) DU (i.e., DU1) to generate a CSI measurement configuration. In this regard, CU1 provides the target P cell configuration and the target PS cell configuration to DU1. DU1 prepares CSI measurement configurations for the target P cell and for the serving secondary cell, the PS cell, and in some cases the target secondary cell, and provides them to CU1. Note: In an alternative implementation, the CU may provide the measurement configuration of the source DU and ask DU1 to generate the CSI measurement configuration in the CU. In step 10: 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 using DC. SCG configuration 1 is the configuration of cell 3 that matches the configuration of DU2 cell 2; SCG configuration 2 is the configuration of cell 3 that matches the configuration of DU2 cell 3; each SCG configuration is identified by a unique identifier, and among other things, each SCG configuration includes: SSB periodicity and index location, SSB / PBCH power, CSI resource configuration, and measurement timing configuration including TCI state of DU5-cell 3; each SCG configuration may also include the cell ID (e.g., PCI) of DU5-cell 3. Each SCG configuration may include the assigned frequency bands to be used / measured, the frequency carriers to be used / measured, and the security key to be used after HO. SCG configuration 1 and SCG configuration 2 are different because they must be compatible; MCG configuration 1 is the configuration for DU2 cell 2; MCG configuration 2 is the configuration for DU2 cell 3; like SCG configurations, MCG configurations are identified by a unique identifier and, among other things, MCG configurations include: SSB periodicity and index location, SSB / PBCH power, CSI resource configuration, and measurement timing configuration including TCI state for DU5-cell 3; MCG configurations may also include a cell ID (e.g., PCI). MCG configurations may also include the assigned frequency bands to be used / measured, the frequency carriers to be used / measured, and the security key to be used after HO. Steps 11-14: CU1 provides the UE with RRC configuration for LLM with DC, and the MN responds with RRC reconfiguration completed. Steps 15-18: The UE uses the measurement timing configuration, including the SSB periodicity and index location, SSB / PBCH power, CSI resource configuration, and TCI state of the target cell, to be able to perform measurements. Without this configuration, the UE cannot perform L1 measurements. The UE provides an L1 measurement report to the source DU based on these measurements. These include measurements on DU2-cell 2, DU2-cell 3, and optionally DU5-cell 3. The UE will report using the cell ID of the target cell, and therefore the following measurements: Measurements for serving cells DU2-Cell 2 Measurement DU2-Cell 3 Measurement DU5-Cell 3 Measurement Measurement of other target cells (if configured) This will provide a structure having at least a subset of: 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-Cell2 measurements and DU5-Cell3 measurements, it will select MCG configuration 1 and SCG configuration 1. DU1 then provides MAC to the UE to trigger a PCell change with PS cell configuration update / change, and information to CU1 that the UE has triggered LLM HO. Steps 19-23: The UE accesses the target cells (PCell and PS cell) and terminates the LLM HO by providing an RRC reconfiguration termination to CU1. Note: As FIG. 2A shows, it should be noted that the UE may remain in the same PS cell, but only needs to apply a new configuration for that same cell.

[0098] One point to note is that the TCI state is a "Transmission Configuration Indicator" state, enabling the UE to transmit and receive using one specific configuration. Each UE may be configured with multiple TCI states for serving and non-serving cells, and the multiple TCI states are used to enable transmission / reception. Based on measurements, the MN DU will trigger the application of a new configuration when it decides to switch HO and cells. The UE will use the TCI state in the indicated configuration to start transmission / reception. The MN may use a different TCI state in the serving cell taking into account UE beam measurements, which will not result in a handover. The use of TCI states occurs in other transmission / reception configuration updates (e.g., in inter-cell beam management).

[0099] Case 2: LLM is set up before DC (Figure 4) First, in step 1: The UE is configured to have LLM for the provisioned cells served by PCell1 of DU1, namely cell2 and cell3 from DU2. Step 2: The UE provides a measurement report to CU1, and CU1 decides to set up a DC. Step 3: CU1 sends an SN addition request to CU2 (of SN) in which CU1 provides the L3 measurement report and a list of prepared cells (cell 2 and cell 3 of DU2) for the LLM in the MN, as well as the respective configurations for these cells. Steps 4-6: CU2 decides to set up LLMs for some DUs that do not require interaction with the MN and for DU5's cell 3 that requires interaction with the MN. Then, CU2 sets up LLMs from DU3's PS cell to DU4's cell 2 with or without SRB3, while CU2 communicates with DU5 to obtain its cell's CSI measurement configuration, along with the measurement timing configuration including SSB periodicity and index location, SSB / PBCH power, CSI resource configuration, and TCI state for DU5-cell 3. Step 7: In the SN Addition ACK, CU2 provides the MN with the following: SCG configuration 1 (for DU2 cell 2), SCG configuration 2 (for DU2 cell 3), and measurement timing configuration including SSB periodicity and index location, SSB / PBCH power, CSI resource configuration, and TCI state of DU5-cell 3. Steps 8-10: CU1 communicates with the (source or serving) DU (i.e., DU1) to generate a CSI measurement configuration. In this regard, CU1 provides the target P-cell configuration and target PS-cell configuration to DU1. DU1 prepares CSI measurement configurations for the target P-cell and PS-cell and provides them to CU1. Note: In an alternative implementation, the CU may provide the measurement configuration of the source DU and ask DU1 to generate the CSI measurement configuration in the CU. 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 using DC. SCG configuration 1 is the configuration of cell 3 that matches the configuration of DU2 cell 2; SCG configuration 2 is the configuration of cell 3 that matches the configuration of DU2 cell 3; each SCG configuration is identified by a unique identifier, and among other things, each SCG configuration includes: SSB periodicity and index location, SSB / PBCH power, CSI resource configuration, and measurement timing configuration including TCI state of DU5-cell 3; each SCG configuration may also include the cell ID (e.g., PCI) of DU5-cell 3. Each SCG configuration may also include the assigned frequency bands to be used / measured, the frequency carriers to be used / measured, and the security key to be used after HO. SCG configuration 1 and SCG configuration 2 are different because they must be compatible; MCG configuration 1 is the configuration for DU2 cell 2; MCG configuration 2 is the configuration for DU2 cell 3; like SCG configurations, MCG configurations are identified by a unique identifier and, among other things, MCG configurations include: SSB periodicity and index location, SSB / PBCH power, CSI resource configuration, and measurement timing configuration including TCI state for DU5-cell 3; MCG configurations may also include a cell ID (e.g., PCI). MCG configurations may also include the assigned frequency bands to be used / measured, the frequency carriers to be used / measured, and the security key to be used after HO. Steps 12-15: CU1 provides RRC configuration for LLM with DC to UE, and MN responds with RRC reconfiguration completed. Steps 16-19: The UE uses the measurement timing configuration, including the SSB periodicity and index location, SSB / PBCH power, CSI resource configuration, and TCI state of the target cell, to be able to perform measurements. Without this configuration, the UE cannot perform L1 measurements. The UE provides an L1 measurement report to the source DU based on these measurements. These include measurements on DU2-cell 2, DU2-cell 3, and optionally DU5-cell 3. The UE will report using the cell ID of the target cell, and therefore the following measurements: Measurements for serving cells DU2-Cell 2 Measurement DU2-Cell 3 Measurement DU5-Cell 3 Measurement Measurement of other target cells (if configured) This will provide a structure having at least a subset of: 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-Cell2 measurements and DU5-Cell3 measurements, it will select MCG configuration 1 and SCG configuration 1. DU1 then provides MAC to the UE to trigger a PCell change with PS cell configuration update / change, and information to CU1 that the UE has triggered LLM HO.

[0100] Steps 20-24: The UE accesses the target cells (PCell and PS cell) and terminates the LLM HO by providing an RRC reconfiguration termination to CU1. Note: As FIG. 2A shows, it should be noted that the UE may remain in the same PS cell, but only needs to apply a new configuration for that same cell.

[0101] Embodiments provide the following advantages: Allows LLM with DC, which is not possible in the case of intraMN HO with different configurations Enables a serving DU in a MN to make lower layer mobility decisions based on L1 beam measurements for target P-cells and target PS-cells controlled by different SNs. · In case of simultaneous intraMN HO with SN modification, the configuration is provided to the UE by a single RCC reconfiguration message instead of two RCC reconfiguration messages leading to signaling gain. In the case of LLM in the SN, the SN will need to trigger cooperation with the MN before starting the process; this way the SN can do this proactively, which leads to signaling gains. One or more of the following may be provided:

[0102] 5 illustrates a schematic diagram of a 5G new wireless network according to one embodiment. The network comprises a plurality of primary cells 22, 24 and a plurality of secondary cells 32, 34. Radio coverage within primary cell 22 is supported by a master distributed node 21, while a master distributed node 26 supports providing radio coverage within primary cell 24. Both master distributed node 21 and master distributed node 26 are controlled by a master central node 41.

[0103] Secondary cells 32, 34 exist, and radio coverage in these cells is supported by secondary distributed nodes 31 and 33, respectively. Secondary distributed node 31 and secondary distributed node 33 are controlled by secondary central node 35. In this example, user equipment 10 is currently connected to secondary cell 34, which is supported by secondary distributed node 33, and primary cell 24, which is supported by distributed node 26. Thus, user equipment 10 is operating in dual connectivity mode. In this example, user equipment 10 moves from secondary cell 34 to secondary cell 32, and simultaneously moves from master cell 24 to master cell 22.

[0104] Embodiments allow handover decisions regarding such movements 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.

[0105] The user equipment 10 comprises a receiver 16 for receiving signals, which may be a means for receiving or a circuit configured to receive. The user equipment 10 further comprises a means for establishing dual connectivity 17, which may be a circuit configured to establish dual connectivity, and a means for performing measurements 18, which may also be a circuit configured to perform measurements, which may be L1 signal strength and / or quality measurements. The user equipment 10 also comprises a transmitter 19 or a means for transmitting. The receiver 16 may receive measurement configuration information from the distributed node 26 for performing measurements related to a non-serving master cell, in this case cell 22, and a secondary cell, in this case cell 32, which are the two cells for the target handover. The user equipment may respond to receiving this by performing measurements on these cells and sending a measurement report to the distributed node 26.

[0106] This is only an example, and in other embodiments there may be more cells for which measurement configuration information is received and for which measurements are performed, and in other embodiments the serving secondary cell may straddle two master cells, in which case measurements performed for the secondary cell may relate to the current serving secondary cell, but the measurements may be for a reconfigured frequency band for this cell, for example.

[0107] The serving master distributed node 26 comprises a receiver 51, which may be receiving means or circuitry configured to receive measurement reports, and makes a handover decision relating to the cell to hand over to in response using decision-making means 52 or circuitry configured to implement the handover decision. Following making the handover decision, the serving master distributed node 26 uses means for generating, or circuitry configured to generate, a cell change indication 53 to generate a cell change indication indicating any change of primary and secondary serving cell as determined in the handover decision. The serving master distributed node 26 then transmits this information to the user equipment as part of a Layer 2 message using means for transmitting 54.

[0108] Before the user equipment receives the measurement configuration information and the above steps are performed, there will be some degree of cooperation between the secondary node and the master central node.

[0109] The serving master central node 41, in cooperation with the serving secondary central node 35, will determine the configuration of the primary cell prepared for lower layer mobility and corresponding changes that may be required in the secondary cell configuration and / or the configuration of the secondary cell prepared for lower layer mobility.

[0110] The master central node 41 will use means for, or a circuit configured to determine 43, determining a primary cell to be prepared for lower layer mobility and will transmit this information to the secondary central node 35 using transmitting means 45 for, or a circuit configured to transmit, as a secondary node addition request or a secondary node modification request.

[0111] The secondary central node 35 may receive this information at a receiver 37 and, in response using a means for generating configuration information 36 or a circuit configured to generate configuration information, generate a configuration for at least one secondary cell that matches the master cell prepared for lower layer mobility and transmit this configuration information using a transmitter 38 in a secondary node addition or secondary node modification response.

[0112] The master central node 41, comprising means for receiving 47 or a circuit configured to receive, receives this secondary cell configuration information. The master central node 41 then exchanges information with the serving master distributed node to generate reconfiguration information for the primary cell and at least one reconfigured secondary cell using means for generating or a circuit configured to generate 42 a measurement configuration request, the configuration request indicating the primary cells and at least one secondary cell for which measurement information is required. This is transmitted to the serving master distributed node using transmitting means 45.

[0113] The serving master distributed node 26 receives this 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 measurements described above.

[0114] The following description may provide further details of alternatives, modifications, and variations: A gNB comprises a node that provides NR user plane and control plane protocol termination to the UE and is connected to the 5GC by an NG interface, for example, in accordance with 3GPP TS 38.300 V16.6.0 (2021-06) Section 3.2, which is incorporated by reference.

[0115] The following description may provide further details of alternatives, modifications, and variations: A gNB comprises a node that provides NR user plane and control plane protocol termination to the UE and is connected to the 5GC by an NG interface, for example, in accordance with 3GPP TS 38.300 V16.6.0 (2021-06) Section 3.2, which is incorporated by reference.

[0116] The gNB central unit (gNB-CU) comprises, for example, a logical node that controls the operation of one or more gNB-DUs, for example, hosting the gNB's radio resource control (RRC), service data adaptation protocol (SDAP), and packet data convergence protocol (PDCP) protocols, or the en-gNB's RRC and PDCP protocols. The gNB-CU terminates the F1 interface that connects with the gNB-DU.

[0117] The gNB distributed unit (gNB-DU) comprises, for example, a logical node that hosts, for example, the RLC (radio link control), MAC (medium access control), and PHY (physical) layers of a gNB or en-gNB, and its operation is partly controlled by the gNB-CU. One gNB-DU supports one or multiple cells. One cell is supported by only one gNB-DU. The gNB-DU terminates the F1 interface that connects to the gNB-CU.

[0118] 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 of the gNB-CU for the en-gNB and the user plane portion of the PDCP and SDAP protocols of the gNB-CU for the gNB. The gNB-CU-UP terminates the E1 interface connected to the gNB-CU-CP and the F1-U interface connected to the gNB-DU, for example, in accordance with 3GPP TS 38.401 V16.6.0(2021-07) Section 3.1, which is incorporated by reference.

[0119] Different divisions of functions between the central unit and the distributed units are possible, for example, called options: Option 1 (1A-like division): - The functional division in this option is similar to the 1A architecture in DC: RRC is in the central unit, PDCP, RLC, MAC, physical layer and RF are in the distributed units. Option 2 (3C-like division): - The functional division in this option is similar to the 3C architecture in DC: RRC and PDCP are in the central unit, and RLC, MAC, physical layer, and RF are in the distributed units. Option 3 (intraRLC splitting): - Low RLC (partial functions of RLC), MAC, physical layer, and RF are in the distributed units. PDCP and high RLC (other partial functions of RLC) are in the central unit. Option 4 (RLC-MAC Split): - MAC, physical layer and RF are in the distributed units. PDCP and RLC are in the central unit. Otherwise, follow, for example, 3GPP TR 38.801 V14.0.0(2017-03) Section 11, which is incorporated by reference. The gNB supports different protocol layers, for example, Layer 1 (L1) to the physical layer.

[0120] Layer 2 (L2) of NR consists of 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: - the physical layer provides transport channels to the MAC sublayer; - the MAC sublayer provides logical channels to the RLC sublayer; - the RLC sublayer provides an RLC channel to the PDCP sublayer; - the PDCP sublayer provides radio bearers to the SDAP sublayer; - The SDAP sublayer provides QoS flows for 5GC; - Comp. refers to header compression, Segm. refers to segmentation, - Control channels include (BCCH, PCCH).

[0121] Layer 3 (L3) includes, for example, Radio Resource Control (RRC), for example, according to 3GPP TS 38.300 V16.6.0(2021-06) Section 6, which is incorporated by reference.

[0122] A RAN (Radio Access Network) node or network node or central node or distributed node, etc., e.g., gNB, base station, gNB CU or gNB DU, or parts thereof, may be implemented using an apparatus having at least one processor and / or at least one memory (with computer readable instructions (computer programs)) configured to support and / or provide and / or process, e.g., CU and / or DU related functions and / or features, and / or at least one protocol (sub)layer of the RAN (Radio Access Network), e.g., Layer 2 and / or Layer 3. They may be executed using specific means configured to perform each specific task, e.g., Layer 3 means for performing Layer 3 operations, Layer 2 means for performing Layer 2 operations, etc.

[0123] The gNB CU and gNB DU portions may be, for example, co-located or physically separated. The gNB DU may be further divided into, for example, two portions, e.g., a portion including processing equipment and a portion including antennas. The central unit (CU) may be referred to as a BBU / REC / RCC / C-RAN / V-RAN, O-RAN, or portions thereof. The distributed unit (DU) may be referred to as an RRH / RRU / RE / RU, or portions thereof.

[0124] A gNB DU may support one or more cells and thus serve, for example, as a serving cell for a user equipment (UE).

[0125] A 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, an in-vehicle device, an IoT device, an M2M device, or others. Such a UE or device may comprise: at least one processor; and at least one memory containing computer program code, the at least one memory and the computer program code configured, with the at least one processor, to cause the device to perform at least certain operations, such as, for example, an RRC connection to the RAN. The UE may be configured, for example, to generate a message (e.g., including a cell ID) to be transmitted over the air to the RAN (e.g., to reach and communicate with a serving cell). The UE may generate, send, and receive RRC messages, including one or more RRC PDUs (Packet Data Units).

[0126] The UE may have different states (e.g., according to 3GPP TS 38.331 V16.5.0(2021-06) sections 42.1 and 4.4, which are incorporated by reference).

[0127] When an RRC connection is established, the UE is, for example, in an RRC_CONNECTED state or an RRC_INACTIVE state.

[0128] In RRC_CONNECTED state the UE: - may store AS context, - may forward unicast data to / from the UE, may monitor a control channel associated with the shared data to determine whether data is scheduled on the data channel; - May provide channel quality and feedback information; - Neighbor cell measurements and measurement reporting may be performed.

[0129] The RRC protocol includes, for example, the following main mechanisms: - RRC connection control, - Measurement configuration and reporting, - Establishment / modification / release of measurement configurations (e.g. intra-frequency, inter-frequency and inter-RAT measurements), - setting up and releasing the measurement gap, - Measurement reporting Includes:

[0130] Those skilled in the art will readily recognize that the steps of the various methods described above can be implemented by a programmed computer. Some embodiments are also intended herein to be directed to program storage devices, e.g., digital data storage media, which are machine- or computer-readable and encode a machine-executable or computer-executable program of instructions, which perform some or all of the steps of the methods described above. The program storage device may be, for example, a digital memory, a magnetic storage medium such as a magnetic disk or tape, a hard drive, or an optically readable digital data storage medium. Embodiments are also intended to be directed to computers programmed to implement the steps of the methods described above. As used herein, the term non-transitory is a limitation of the medium itself (i.e., tangible, not a signal), as opposed to a limitation on data storage permanence (e.g., RAM vs. ROM).

[0131] As used in this application, the term "circuitry" may refer to one or more or all of the following: (a) a hardware-only circuit implementation (e.g., an implementation using only analog and / or digital circuitry); and (b) Combinations of hardware circuitry and software, such as (where applicable): (i) a combination of analog and / or digital hardware circuitry with software / firmware, and (ii) any portion of a hardware processor (including a digital signal processor) with software, software, and memory that works together to cause a device, such as a mobile phone or server, to perform various functions; and (c) A hardware circuit and / or processor, such as a microprocessor or portion of a microprocessor, that requires software (e.g., firmware) to operate, but the software may not be present when not required for operation.

[0132] This definition of circuit applies to all uses of the term in this disclosure and any claims. As a further example, as used in this application, the term circuit also covers merely a hardware circuit or processor (or processors) or portions of a hardware circuit or processor and its (or their) accompanying software and / or firmware implementations. The term circuit also covers, for example, a baseband or processor integrated circuit for a mobile device, or similar integrated circuit in a server, cellular network device, or other computing or network device, if applicable to certain claim elements.

[0133] Although embodiments of the present invention have been described in the preceding paragraphs with reference to various examples, it should be recognized that modifications to the given examples can be made without departing from the scope of the invention as claimed.

[0134] Features described in the preceding description may be used in combinations other than those explicitly described.

[0135] Although functions have been described with reference to particular features, these functions may be implemented by other features, whether or not described.

[0136] Although features have been described with reference to particular embodiments, these features may be present in other embodiments whether or not they are described.

[0137] While the foregoing specification has attempted to draw attention to those features of the invention which are considered to be particularly important, it is to be understood that applicant seeks protection with respect to any patentable feature or combination of features described above with reference to and / or shown in the drawings, whether or not such feature is emphasized.

Claims

1. 1. A user equipment for accessing a radio access network comprising a master central node and a plurality of master distributed nodes supporting providing radio coverage via a primary cell, wherein the master central node controls the plurality of master distributed nodes, and a secondary central node and at least one secondary distributed node supporting providing radio coverage via at least one secondary cell, the secondary central node controls the at least one secondary distributed node, the user equipment being configured to support dual connectivity such that the user equipment is enabled to simultaneously connect to a primary distributed node providing access to a primary serving cell and a secondary distributed node providing access to a secondary serving cell, the user equipment comprising: at least one processor; and at least one memory that stores instructions that, when executed by the at least one processor, cause the user equipment to: establishing a dual connectivity connection to the primary serving cell and the secondary serving cell; receiving, from a serving master node, a configuration for performing measurements related to at least non-serving master cells and secondary cells to enable said serving master distributed node to perform lower layer mobility dual connectivity handover decisions; performing at least some of the configured measurements; sending a report related to the performed measurements to the serving master distributed node via a lower layer message; The user device.

2. The user equipment of claim 1 , wherein the measurement reports relate to at least a non-serving master cell and a secondary cell.

3. 3. The user equipment of claim 1, wherein the measurement configurations include a first configuration including a master cell group configuration MCG configuration 1 and an associated secondary cell group configuration SCG configuration 1, and a second configuration including a master cell group configuration MCG configuration 2 and an associated secondary cell group configuration SCG configuration 2.

4. A user equipment according to any one of claims 1 to 3, wherein said measurements include at least one of the following: Layer 1 signal strength or Layer 1 signal quality measurements.

5. 5. The user equipment of claim 1, further configured to receive a cell change indication indicating a change of a primary serving cell and a change of a configuration of a secondary cell, the cell change indication being received as part of a Layer 2 message.

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

7. the received cell change indication includes a change of the secondary serving cell; The user equipment of claim 6 , wherein the user equipment is responsive to receiving the cell change indication to initiate a connection procedure with the updated primary serving cell and the updated secondary serving cell.

8. The user equipment of any one of claims 1 to 7, wherein the measurement configuration is received from the serving master distributed node in a radio resource reconfiguration message.

9. A master distributed node for supporting radio coverage via a primary cell and providing access to the primary cell for user equipment, the master distributed node being configured to support dual connectivity such that the user equipment is allowed to simultaneously connect to the master distributed node and to a secondary distributed node providing access to a secondary serving cell, the master distributed node becoming a serving master distributed node for the user equipment upon connection of the user equipment and providing access to the primary serving cell, the master distributed node comprising at least one processor and at least one memory storing instructions that, when executed by the at least one processor, cause the master distributed node to provide at least: A master distributed node configured to receive measurement reports from the user equipment relating to at least non-serving master cells, and to make a lower layer mobility dual connectivity handover decision in response to the measurement reports.

10. The master distributed node of claim 9 , wherein the received measurement reports relate to at least the non-serving master cell and a secondary cell.

11. following said making the handover decision, generating a cell change indication indicating a change in the primary serving cell and a change in the configuration of the secondary cell; sending the cell change indication to the user equipment as part of a Layer 2 message; 11. The master distributed node of claim 9 or 10, further configured to:

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

13. forwarding a message to the user equipment, the message including a configuration for performing measurements related to at least non-serving master cells and secondary cells; transmitting said message to said user equipment as part of a radio resource control reconfiguration message; The master distributed node of any one of claims 9 to 12, further configured to:

14. 14. A master distributed node according to any one of claims 9 to 13, configured to receive from a central node controlling the master distributed node an indication of the configuration of a target primary cell and of at least one secondary cell for which measurements are requested, generate measurement and connection configuration information for the indicated target primary cell and the at least one secondary cell, and transmit the measurement and connection configuration information to the central node.

15. A central node for controlling a plurality of distributed nodes configured to support providing radio coverage to a user equipment via a primary serving cell, the user equipment being configured to support dual connectivity by simultaneous connection to a serving master distributed node supporting providing radio coverage via a primary serving cell and a serving secondary distributed node supporting providing radio coverage via a secondary serving cell, the central node comprising: at least one processor; and at least one memory that stores instructions that, when executed by the at least one processor, cause the central node to: determining at least one non-serving master cell prepared for lower layer mobility; generating and transmitting information indicative of the at least one determined non-serving master cell to a secondary central node that controls a plurality of secondary distributed nodes configured to support providing radio coverage to the user equipment via secondary cells; receiving secondary cell measurements and connection configurations for secondary nodes associated with the at least one non-serving master cell; Let the central node.

16. 16. The central node of claim 15, configured to generate and transmit said information as a secondary node correction signal.

17. 16. The central node of claim 15, configured to generate and transmit said information as a secondary node addition request signal.

18. 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 the serving master distributed node to make lower layer mobility dual connectivity handover decisions with respect to the plurality of primary cells and at least one secondary cell; sending the measurement and connection configuration request to the serving master distributed node; receiving the measurement and connection configuration information from the serving master distributed node; generating reconfiguration information for the plurality of primary cells and the at least one secondary cell; sending the reconfiguration information to the serving master distributed node; The central node according to any one of claims 15 to 17, further configured to:

19. generating a measurement and connection configuration request to request a measurement configuration from the serving master node; sending the measurement and connection configuration request to the serving 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; generating reconfiguration information for the plurality of primary cells and the at least one secondary cell; sending the reconfiguration information to the serving master distributed node; The central node according to any one of claims 15 to 17, further configured to:

20. 1. A system for providing a radio access network supporting lower layer mobility for user equipment configured for dual connectivity, 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, which support providing radio coverage via primary cells, wherein the master central node controls the plurality of master distributed nodes; a secondary central node for controlling at least one secondary distributed node; The at least one secondary distributed node supports providing radio coverage via at least one secondary cell.

21. 1. A method implemented in a user equipment for accessing a radio access network comprising a master central node and a plurality of master distributed nodes supporting providing radio coverage via a primary cell, wherein the master central node controls the plurality of master distributed nodes, a secondary central node and at least one secondary distributed node supporting providing radio coverage via at least one secondary cell, the secondary central node controls the at least one secondary distributed node, and the user equipment is configured to support dual connectivity such that the user equipment is enabled to simultaneously connect to a primary distributed node providing access to a primary serving cell and to a secondary distributed node providing access to a secondary serving cell, the method comprising: establishing a dual connectivity connection to the primary serving cell and the secondary serving cell; receiving, from a master node, a configuration for performing measurements and connections to at least non-serving master cells and secondary cells to enable the serving master distributed node to perform lower layer mobility dual connectivity handover decisions; performing at least some of the configured measurements; sending a report related to the performed measurements to the serving master distributed node via a lower layer message; A method comprising:

22. 1. A method implemented in a distributed node for supporting radio coverage via a primary cell and providing access to the primary cell for user equipment, the method being configured to support dual connectivity such that the user equipment is allowed to simultaneously connect to the master distributed node and to a secondary distributed node providing access to a secondary serving cell, the master distributed node becoming a serving master distributed node for the user equipment and providing access to the primary serving cell, the method comprising: receiving measurement reports from the user equipment relating to at least a non-serving master cell and a secondary cell; making a lower layer mobility dual connectivity handover decision in response to the measurement report; A method comprising:

23. 1. A method for controlling a plurality of distributed nodes configured to support providing radio coverage to a user equipment via a primary cell, the user equipment being configured to support dual connectivity by simultaneous connection to a serving master distributed node supporting providing radio coverage via at least one primary serving cell and a serving secondary distributed node supporting providing radio coverage via at least one secondary serving cell, the method comprising: determining at least one non-serving master cell prepared for lower layer mobility; generating and transmitting information indicative of the at least one determined non-serving master cell to a secondary central node that controls a plurality of secondary distributed nodes configured to support providing radio coverage to the user equipment via secondary cells; receiving secondary cell configuration information for a secondary cell associated with the at least one non-serving master cell; A method comprising:

Images