Simultaneous configuration preparation of master cell group and secondary cell group for lower-layer triggered mobility

Abstract

A method is provided that includes providing a radio network service from a primary cell (PCell) of a master node to an user equipment in dual connectivity with a secondary primary cell (PSCell) of a secondary node. The method includes generating a lower-layer triggered mobility (LTM) candidate cell configuration associated with a master cell group (MCG) including at least one candidate target PCell. The method includes preparing a message including the LTM candidate configuration for the MCG, and an indication for the secondary node to generate multiple LTM candidate configurations associated with a secondary cell group (SCG) including at least one candidate target PSCell based on the LTM candidate configuration for the MCG. The method includes sending the message to the secondary node for generation of the multiple LTM candidate configurations, and sending a second message including the LTM candidate configuration for the MCG towards the user equipment.

Description

SIMULTANEOUS CONFIGURATION PREPARATION OF MASTER CELL GROUP AND SECONDARY CELL GROUP FOR LOWER-LAYER TRIGGERED MOBILITYTECHNOLOGICAL FIELD

[0001] The present disclosure relates generally to telecommunications and, in particular, simultaneous configuration preparation of a master cell group and a secondary cell group for lower-layer triggered mobility.BACKGROUND

[0002] A telecommunications system can be seen as a facility that enables communication sessions between two or more entities such as user terminals, base stations and / or other nodes by providing carriers between the various entities involved in the communications path. A telecommunications system can be provided for example by means of a communication network and one or more compatible communication devices. The communication sessions may comprise, for example, communication of data for carrying communications such as voice, video, electronic mail (email), text message, multimedia and / or content data and so on. Non-limiting examples of services provided comprise two-way or multi-way calls, data communication or multimedia services and access to a data network system, such as the Internet.

[0003] In a wireless telecommunications system at least a part of a communication session between at least two stations occurs over a wireless link. Examples of wireless systems comprise public land mobile networks (PLMN), satellite based communication systems and different wireless local networks, for example wireless local area networks (WLAN). Some wireless systems can be divided into cells, and are therefore often referred to as cellular systems.

[0004] A user can access the telecommunications system by means of an appropriate communication device or terminal. A communication device of a user may be referred to as user equipment (UE) or user device. A communication device is provided with an appropriate signal receiving and transmitting apparatus for enabling communications, for example enabling access to a communication network or communications directly with other users. The communication device may access a carrier provided by a station, for example a base station of a cell, and transmit and / or receive communications on the carrier.

[0005] The telecommunications system and associated devices typically operate in accordance with a given standard or specification which sets out what the various entities associated with the system are permitted to do and how that should be achieved. Communication protocols and / or parameters which shall be used for the connection are also typically defined. One example of a telecommunications system is the Universal Mobile Telecommunications System (UMTS). Other examples of telecommunications systems are Long-Term Evolution (LTE), LTE Advanced and the so-called 5G or New Radio (NR) networks. NR is being standardized by the 3rd Generation Partnership Project (3 GPP).BRIEF SUMMARY

[0006] Example implementations of the present disclosure are directed generally to telecommunications and, in particular, to simultaneous configuration preparation of a master cell group and a secondary cell group for lower-layer triggered mobility. According to some aspects, there is provided the subject matter of the independent claims. Some further aspects are defined in the dependent claims.

[0007] These and other features, aspects, and advantages of the present disclosure will be apparent from a reading of the following detailed description together with the accompanying figures, which are briefly described below. The present disclosure includes any combination of two, three, four or more features or elements set forth in this disclosure, regardless of whether such features or elements are expressly combined or otherwise recited in a specific example implementation described herein. This disclosure is intended to be read holistically such that any separable features or elements of the disclosure, in any of its aspects and example implementations, should be viewed as combinable unless the context of the disclosure clearly dictates otherwise.

[0008] It will therefore be appreciated that this Brief Summary is provided merely for purposes of summarizing some example implementations so as to provide a basic understanding of some aspects of the disclosure. Accordingly, it will be appreciated that the above described example implementations are merely examples and should not be construed to narrow the scope or spirit of the disclosure in any way. Other example implementations, aspects and advantages will become apparent from the following detailed description taken in conjunction with the accompanying figures which illustrate, by way of example, the principles of some described example implementations.BRIEF DESCRIPTION OF THE FIGURE(S)

[0009] Having thus described example implementations of the disclosure in general terms, reference will now be made to the accompanying figures, which are not necessarily drawn to scale, and wherein:

[0010] FIG. 1 illustrates a telecommunications system that includes one or more public land mobile networks (PLMNs) coupled to one or more external data networks, according to some example implementations of the present disclosure;

[0011] FIG. 2 illustrates a 5G deployment of a PLMN, according to some example implementations;

[0012] FIG. 3 illustrates an example of dual connectivity in a 5G deployment, according to some example implementations;

[0013] FIG. 4 illustrates a signaling chart for a lower-layer triggered mobility (LTM) procedure;

[0014] FIGS. 5 A and 5B illustrate a signaling chart for an LTM procedure in a CU-DU split architecture;

[0015] FIG. 6 illustrates an initial configuration of a primary cell (PCell) and a primary secondary cell (PSCell) for dual connectivity, according to some example implementations;

[0016] FIGS. 7A, 7B, 7C and 7D illustrate configurations of an LTM candidate cell (PSCell or PCell), or a reconfiguration of a PSCell, according to some example implementations;

[0017] FIG. 8 illustrates a first user equipment (UE) mobility scenario, according to some example implementations;

[0018] FIG. 9 illustrates a second UE mobility scenario, according to some example implementations ;

[0019] FIG. 10 is a flowchart of steps in a method of triggering simultaneous PCell and PSCell configurations under the first and second UE mobility scenarios, according to some example implementations;

[0020] FIGS. 11A, 11B and 11C illustrate a signaling chart for LTM preparation for simultaneous master cell group (MCG) and secondary cell group (SCG) in dual connectivity, according to some example implementations;

[0021] FIGS. 12A and 12B illustrate a signaling chart of LTM execution for the first mobility scenario, according to some example implementations;

[0022] FIGS. 13A and 13B illustrate a signaling chart of LTM execution for the second mobility scenario, according to some example implementations;

[0023] FIGS. 14, 15, 16, 17, 18 and 19 are flowcharts illustrating various steps in methods according to various example implementations; and

[0024] FIG. 20 illustrates an apparatus according to some example implementations.DETAILED DESCRIPTION

[0025] Some implementations of the present disclosure will now be described more fully hereinafter with reference to the accompanying figures, in which some, but not all implementations of the disclosure are shown. Indeed, various implementations of the disclosure may be embodied in many different forms and should not be construed as limited to the implementations set forth herein; rather, these example implementations are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art. Like reference numerals refer to like elements throughout.

[0026] Unless specified otherwise or clear from context, references to first, second or the like should not be construed to imply a particular order. A feature described as being above another feature (unless specified otherwise or clear from context) may instead be below, and vice versa;and similarly, features described as being to the left of another feature else may instead be to the right, and vice versa. Also, while reference may be made herein to quantitative measures, values, geometric relationships or the like, unless otherwise stated, any one or more if not all of these may be absolute or approximate to account for acceptable variations that may occur, such as those due to engineering tolerances or the like.

[0027] As used herein, unless specified otherwise or clear from context, the “or” of a set of operands is the “inclusive or” and thereby true if and only if one or more of the operands is true, as opposed to the “exclusive or” which is false when all of the operands are true. Thus, for example, “[A] or [B] ” is true if [A] is true, or if [B] is true, or if both [A] and [B] are true. Further, the articles “a” and “an” mean “one or more,” unless specified otherwise or clear from context to be directed to a singular form. Furthermore, it should be understood that unless otherwise specified, the terms “data,” “content,” “digital content,” “information,” and similar terms may be at times used interchangeably. The term “network” may refer to a group of interconnected computers including clients and servers; and within a network, these computers may be interconnected directly or indirectly by various means including via one or more switches, routers, gateways, access points or the like.

[0028] Reference may be made herein to terms specific to a particular system, architecture or the like, but it should be understood that example implementations of the present disclosure may be equally applicable to any of a number of systems, architectures and the like. For example, reference may be made to 3GPP technologies such as Global System for Mobile Communications (GSM), UMTS, LTE, LTE Advanced, 5G NR, 5G Advanced and 6G; however, it should be understood that example implementations of the present disclosure may be equally applicable to non-3GPP technologies such as IEEE 802, Bluetooth and Bluetooth Low Energy.

[0029] Further, as used in this application, the term “circuitry” may refer to one or more or all of the following: (a) hardware-only circuit implementations (such as implementations in only analog and / or digital circuitry); (b) combinations of hardware circuits and software, such as (as applicable): (i) a combination of analog and / or digital hardware circuit(s) with software / firmware and (ii) any portions of hardware processor(s) with software (including digital signal processor(s)), software, and memory(ies) that work together to cause an apparatus, such as a mobile phone or server, to perform various functions); or (c) hardware circuit(s) and / or processor(s), such as a microprocessor(s) or a portion of a microprocessor(s), that requires software (e.g., firmware) for operation, but the software may not be present when it is not needed for operation.

[0030] The above definition of circuitry applies to all uses of this 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 merely a hardware circuit or processor (or multiple processors) or portion of a hardware circuit or processor and its (or their) accompanying software and / orfirmware. The term circuitry also covers, for example and if applicable to the particular claim element, a baseband integrated circuit or processor integrated circuit for a mobile device or a similar integrated circuit in server, a cellular network device, or other computing or network device.

[0031] FIG. 1 illustrates a telecommunications system 100 according to various example implementations of the present disclosure. The telecommunications system generally includes one or more telecommunications networks. As shown, for example, the system includes one or more public land mobile networks (PLMNs) 102 coupled to one or more other external data networks 104 - notably including a wide area network (WAN) such as the Internet. Each of the PLMNs includes a core network (CN) 106 backbone such as the Evolved Packet Core (EPC) of LTE, the 5G core network (5GC) or the like; and each of the core networks and the Internet are coupled to one or more radio access networks (RANs) 108, air interfaces or the like that implement one or more radio access technologies (RATs). As used herein, a “network device” refers to any suitable device at a network side of a telecommunications network. Examples of suitable network devices are described in greater detail below.

[0032] In addition, the system includes one or more radio units that may be varyingly known as user equipment (UE) 110, terminal device, terminal equipment, mobile station or the like. The UE is generally a device configured to communicate with a network device or a further UE in a telecommunication network. The UE may be a portable computer (e.g., laptop, notebook, tablet computer), mobile phone (e.g., cell phone, smartphone), wearable computer (e.g., smartwatch), or the like. In other examples, the UE may be an Internet of things (loT) device, an industrial loT (IIoT device), a vehicle equipped with a vehicle-to-everything (V2X) communication technology, or the like. In operation, these UEs may be configured to connect to one or more of the RANs 108 according to their particular radio access technologies to thereby access a particular CN 106 of a PLMN 102, or to access one or more of the external data networks 104 (e.g., the Internet). The external data network may be configured to provide Internet access, operator services, 3rd party services, etc. For example, the International Telecommunication Union (ITU) has classified 5G mobile network services into three categories: enhanced mobile broadband (eMBB), ultra-reliable and low-latency communications (URLLC), and massive machine type communications (mMTC) or massive internet of things (MIoT).

[0033] Examples of radio access technologies include 3GPP radio access technologies such as GSM, UMTS, LTE, LTE Advanced, 5G NR, 5G Advanced, and 6G. Other examples of radio access technologies include IEEE 802 technologies such as IEEE 802.11 (Wi-Fi), IEEE 802.15 (including 802.15.1 (WPAN / Bluetooth), 802.15.4 (Zigbee) and 802.15.6 (WBAN)), Bluetooth, Bluetooth Low Energy (BLE), ultra wideband (UWB), and the like. Generally, a radio access technology may refer to any 2G, 3G, 4G, 5G, 6G or higher generation mobile communication technology and their different versions, as well as to any other wireless radio access technologythat may be arranged to interwork with such a mobile communication technology to provide access to the CN 106 of a mobile network operator (MNO).

[0034] In various examples, a RAN 108 may be configured as one or more macrocells, microcells, picocells, femtocells or the like. The RAN may generally include one or more radio access nodes that are configured to interact with UEs 110. In various examples, a radio access node may be referred to as a base station (BS), access point (AP), base transceiver station (BTS), Node B (NB), evolved NB (eNB), macro BS, NB (MNB) or eNB (MeNB), home BS, NB (HNB) or eNB (HeNB), next generation NB (gNB), enhanced gNB (en-gNB), next generation eNB (ng- eNB), or the like. The RAN may include some type of network controlling / goveming entity responsible for control of the radio access nodes. The network controlling / goveming entity and radio access node may be separate or integrated into a single apparatus. The network controlling / goveming entity may include processing circuity configured to carry out various management functions, etc. The processing circuity may be associated with a memory, computer- readable storage medium or database for maintaining information required in the management functions.

[0035] A RAN 108 may be centralized or distributed. In various examples, components of a RAN may be interconnected by Ethernet, Gigabit Ethernet, Asynchronous Transfer Mode (ATM), optical fiber, dark fiber, passive wavelength division multiplexing (WDM), WDM passive optical network (WDM-PON), optical transport network (OTN), time sensitive networking (TSN) and / or any other data link layer network, possibly including radio links. The RAN may be connected to a CN 106 through one or more gateways, network functions or the like.

[0036] As will be appreciated, a PLMN 102 may be deployed in a number of different manners. In a 4G LTE deployment, the EPC is the CN 106, and the evolved UMTS terrestrial radio access network (E-UTRAN) is the RAN 108; and the E-UTRAN includes one or more eNBs (radio access nodes) configured to connect UEs 110 to the E-UTRAN to thereby access the EPC. As shown in FIG. 2, in a 5G deployment 200, the 5GC 202 is the CN, and the next generation (NG) radio access network (NG-RAN) 204 is the RAN; and the NG-RAN includes one or more gNBs 206 (radio access nodes) configured to connect UEs 208 to the NG-RAN to thereby access the 5GC. The term ‘gNB’ in 5G may correspond to the eNB in 4G LTE.

[0037] Some deployments of 4G LTE and 5G in particular are considered standalone (SA) deployments. Other deployments combine 4G LTE and 5G technologies, and are referred to as non-standalone (NSA) deployments. In some deployments, the E-UTRAN includes one or more ng-eNBs that are configured to communicate with the 5GC, and that may also be configured to communicate with one or more gNBs. Similarly, in another deployment, the NG-RAN may include one or more en-gNBs that are configured to communicate with the EPC, and that may also be configured to communicate with one or more eNBs. In various instances, a single UE 110,208 a dual-mode or multimode UE, may support multiple (two or more) RANs — thereby being configured to connect to multiple RANs, such as 4G LTE and 5G.

[0038] In various instances, a single UE 110, 208 a dual-mode or multimode UE, may support multiple (two or more) RANs — thereby being configured to connect to multiple RANs. For example, a particular UE may support both LTE and 5G NR radio access technologies. In this regard, a number of deployments support dual connectivity (DC), and in some particular examples multi-radio dual connectivity (MR-DC), in which a UE may be configured to connect to two different radio access nodes connected via a non-ideal backhaul, one of the radio access nodes providing NR access and the other radio access node providing either E-UTRA or NR access. In these deployments, one radio access node may act as a master node (MN) and the other may act as a secondary node (SN).

[0039] In deployments such as the 5G deployment 200, node operations may be carried out, at least partly, in a central / centralized unit (CU) 210, such as a server, host or node, operationally coupled to a distributed unit (DU) 212, such as a radio head / node. It is also possible that node operations may be distributed among a plurality of servers, hosts or nodes. It should also be understood that the distribution of work between the 5GC 202 operations and gNB 204 operations may vary depending on implementation. Thus, a 5G network architecture may be based on a so- called CU-DU split. One gNB-CU (central node) may control one or more gNB-DUs. The gNB- CU may control a plurality of spatially separated gNB-DUs, acting at least as transmit / receive (Tx / Rx) nodes. In some example implementations, however, the gNB-DUs (also called DU) may include, for example, the radio link control (RLC), medium access control (MAC) and physical (PHY) layers, whereas the gNB-CU (also called a CU) may include the layers above RLC, such as packet data convergence protocol (PDCP), radio resource control (RRC), and an internet protocol (IP) layer. Other functional splits are also possible. It is considered that a skilled person is familiar with the open systems interconnection (OSI) model and the functionalities within each layer.

[0040] In some example implementations, the server or CU 210 may generate a virtual network through which the server communicates with the radio node. In general, virtual networking may involve a process of combining hardware and software network resources and network functionality into a single, software-based administrative entity, a virtual network. Such virtual network may provide flexible distribution of operations between the server and the radio head / node. In practice, any digital signal processing task may be performed in either the CU or the DU 212, and the boundary where the responsibility is shifted between the CU and the DU may be selected according to implementation.

[0041] Briefly returning to FIG. 1, in various instances, a single UE 110, a dual -mode or multimode UE, may support multiple (two or more) RANs — thereby being configured to connect to multiple RANs. For example, a particular UE may support both LTE and 5G NR radio accesstechnologies. In this regard, a number of deployments support dual connectivity (DC), and in some particular examples multi-radio dual connectivity (MR-DC), in which a UE may be configured to connect to two different radio access nodes connected via a non-ideal backhaul, one of the radio access nodes providing NR access and the other radio access node providing either E-UTRA or NR access. In these deployments, one radio access node may act as a master node (MN) and the other may act as a secondary node (SN). The MN functions as the controlling entity that provides control plane connection to the CN 106, and utilizes the SN for additional resources to the UE. Related to dual connectivity, a secondary cell group (SCG) refers to a group of serving cells associated with the SN, and the SCG includes primary cell referred to as the primary secondary cell (PSCell).

[0042] E -UTRAN supports dual connectivity via E-UTRA-NR dual connectivity (EN-DC), in which a UE 110 is connected to one eNB that acts as a MN and one en-gNB that acts as a SN. NG-RAN supports dual connectivity in a number of different manners. In NG-RAN E-UTRA- NR dual connectivity (NGEN-DC), a UE is connected to one ng-eNB that acts as a MN and one gNB that acts as a SN. In NR-E-UTRA dual connectivity (NE-DC), a UE is connected to one gNB that acts as a MN and one ng-eNB that acts as a SN. And in NR-NR dual connectivity (NR- DC), a UE is connected to one gNB that acts as a MN and another gNB that acts as a SN.

[0043] FIG. 3 illustrates an example of dual connectivity with the 5GC, according to some example implementations. More particularly, FIG. 3 illustrates a deployment 300 including a UE 208 connected to a MN 302 and a SN 304. The MN and SN may be implemented by gNBs that provide NR access, and which in some examples may include respective DUs 212 and CUs 210. The MN and SN are connected via a network interface 306, such as an Xn interface, and at least the MN is connected to the 5GC 202. As also shown, the MN may include a CU (also referred to as a MN-CU 306) operationally coupled to a DU (also referred to as a MN-DU 308). Likewise, the SN may include a CU (also referred to as a SN-CU 310) operationally coupled to a DU (also referred to as a SN-DU 312).

[0044] When a UE 208 registers to the 5GC 202, the UE can communicate with an external data network via one or more communication sessions, referred to in 5G NR as packet data unit (PDU) sessions, which are data paths established from the UE through the 5GC to the external data network. In the case of dual connectivity, these communication sessions may be served by the MN 302 and SN 304. In some examples, then, the MN may be referred to as a serving MN, and the SN may be referred to as a serving SN.

[0045] Based on several inputs taken into account such as measurements from the UE 208, a PSCell change can be triggered by the MN 302 or the SN 304. The former may be referred to as an MN-initiated PSCell change, whereas the latter may be referred to as an SN-initiated PSCell change. For example, an SN-initiated SN change procedure may be used to transfer a UE context from a source SN (S-SN) to a target SN (T-SN), and to change the SCG configuration in the UEfrom the S-SN to the T-SN. Similar to the S-SN, the MN and T-SN may be connected via a network interface 306 (e.g., Xn interface).

[0046] Currently in 3 GPP, mainstream mobility has been conducted using higher layer (layer 3, L3 or RRC controlled) mobility. In this regard, L3 handover based mobility is a well-known and proven method for ensuring a robust way of handing over the UE 208 from one serving cell (source cell) of a radio access node (e.g., gNB 206) to a new serving cell (target cell) of the same or another radio access node. The method has been used at least since GSM and is still in use in 5G NR. It is expected that L3 mobility (legacy handover) will also be commonly used in the future.

[0047] As the wireless generations evolve, however, so does the need for new and different solutions enabling more flexible, more efficient and sometimes faster procedures making the system seem more agile. One such enhancement includes moving the execution of the ‘handover’ from one cell to another from higher layers (L3), such as RRC, to lower layers. These lower layers may be either PHY (or layer 1, LI) or MAC (or layer 2, L2). This feature is currently referred to as L1 / L2 -triggered mobility, or lower-layer triggered mobility (LTM), which may reduce latency, overhead and interruption time when compared to L3 handover based mobility. In a CU-DU split architecture, LTM may support one or more of intra-DU mobility, intra-CU inter-DU mobility, or inter-CU inter-DU mobility.

[0048] LTM may be a cell switch procedure in which the network may switch a UE’s primary serving cell (PCell or PSCell) by sending a cell switch command, such as a MAC control element (MAC-CE). This LTM cell switch decision may be based on measurements (LI measurements) that are performed and reported (LI measurement report) by the UE. Measurements and reporting are based on LTM candidate cell configuration provided by the network for one or more LTM candidate cells. The LTM candidate cells may be neighboring cells or a UE’s current secondary serving cells (e.g., SCells). Relative to the PCell, the LTM candidate cells may be in a master cell group (MCG) including the PCell. Similarly, relative to the PSCell, the LTM candidate cells may be in a secondary cell group (SCG) inclulding the PSCell.

[0049] PIG. 4 illustrates a signaling chart 400 for an LTM procedure of a UE 208 in a RRC connected state with a gNB 206, which has been proposed. During LTM preparation, as shown at step 401, the UE sends a L3 measurement report to the gNB, which decides to use LTM and initiate LTM candidate preparation. The gNB at step 402 transmits a RRC reconfiguration message to the UE, including the configuration of one or more candidate target cells in the MCG / SCG. The RRC reconfiguration message may also include a configuration of LI measurement reporting for LTM execution. The UE stores the configurations, and the UE at step 403 transmits a RRC reconfiguration complete message to the gNB.

[0050] An early synchronization of the UE 208 with the candidate target cell(s) follows LTM preparation. As shown at step 404, the UE 208 performs downlink (DL) / uplink (UL)synchronization with the candidate target cell(s). During this procedure, the UE may acquire a timing advance (TA) of respective ones of the candidate target cell(s). This early synchronization may reduce interruption during LTM execution, as compared to L3 handover based mobility. In this regard, the TA may be used to control the timing of uplink transmissions of a UE toward the candidate target cell(s). The UE may likewise have an acquired TA of the cell of the gNB to control the timing of uplink transmissions toward the gNB.

[0051] During LTM execution, the UE 208 performs LI measurements on the configured candidate target cell(s), and the UE at step 405 transmits LI measurement reports to the gNB 206. The gNB decides to execute a cell switch, and selects one of the candidate target cell(s) as a target cell for the cell switch. The gNB then at step 406 transmits a cell switch command (e.g., MAC- CE), to trigger cell switch. The UE switches to the configuration of the target cell; and if the TA of the target cell (from step 404) is no longer available, the UE at step 407 initiates a random access channel (RACH) procedure with the target cell to acquire the TA of the target cell. The UE then at step 408 indicates successful completion of the cell switch.

[0052] FIGS. 5 A and 5B illustrate a signaling chart 500 for an LTM procedure in a CU-DU split architecture, including a CU 210, a source DU (S-DU) 212A for a serving cell, and a target DU (T-DU) 212B for a target cell. During preparation for LTM, as shown at steps 501 and 502, the UE 208 sends a L3 measurement report to the CU via the S-DU, and the CU at step 503 decides prepare one or more candidate target cells (DUs) for LTM. As shown at steps 504, 505, 506 and 507, the CU proceeds with the UE context setup / modification procedures. At step 508, the CU generates RRC reconfiguration(s) for the configured candidate target cell(s); and at steps 509 and 510, the CU provides the configurations to the UE 208 via the S-DU.

[0053] At steps 508, 509 and 510, the CU 210 also configures the UE 208 with LI measurement reporting for LTM execution. The CU provides the S-DU 212A with TA acquisition triggering criteria and configuration(s), as well as cell switch triggering criteria and configuration(s). The triggering criteria for TA acquisition and cell switch may be similar to measurement event report triggering conditions, e.g., A3, A4 or A5 event conditions or validity of acquired TA. The triggering conditions may include, for example, a filter configuration (for LI measurements), trigger offsets, cell individual offsets, or the like.

[0054] At steps 511 and 512, the UE 208 sends a RRC reconfiguration complete to the CU 210 via the S-DU 212A.

[0055] During execution, at step 513 onwards, the UE 208 performs LI measurements on the configured candidate target cell(s), and transmits LI measurement reports to the S-DU 212A. The S-DU at step 514 decides to trigger the TA acquisition of the candidate target cell(s) (including the cell of T-DU 212B), and the S-DU at step 515 transmits a TA acquisition command to the UE 208. The UE at step 516 transmits a random access preamble to the candidate target cell(s) (T-DU 212B / cell) to signal the candidate target cell(s) to estimate the TA between the UEand the candidate target cell(s). And at step 517, the S-DU 212A / cell receives a random access response (RAR) from respective ones of the candidate target cell(s) indirectly via the CU 210. Alternatively, the UE may receive the RAR of respective ones of the candidate target cell(s), indirectly via the CU and the S-DU.

[0056] The UE 208 at step 518 transmits LI measurements of the candidate target cell(s) to the S-DU 212A. The S-DU at steps 519 and 520 decides to initiate a cell change to the T-DU 212B / cell, and transmits a cell switch command (e.g., MAC-CE) to trigger the cell switch (also and at times interchangeably referred to as a cell change). In examples in which the RAR is received at the S-DU at step 517 (instead of the UE), the S-DU provides the TA of the T-DU / cell to the UE. If the TA of the T-DU / cell is still valid, the UE may skip the RACH procedure at step 521 when executing the cell switch. And at steps 522, 523, 524 and 525, the UE, S-DU, T-DU and CU proceed with completion of the LTM procedure.

[0057] In 3GPP, it has been agreed to support simultaneous configuration of MCG and SCG LTM, but this may require LTM preparation in which the MN 302 and SN 304 prepare multiple configurations of candidate PCells and PSCells ensuring that certain of their respective configuration parameters do not overlap. These configuration parameters include, for example data radio bearers (DRBs), and may be at times referred to as “deltas.” Configuring simultaneous MCG and SCG LTM during LTM preparation may also require configuration of a sequence on how the configurations of the candidate PCells and PSCells are triggered considering UE mobility. Based on UE mobility, several scenarios may emerge, including that the PCell has not changed but, based on L 1 measurements, the SN-DU 312 triggered SCG LTM for a PSCell switch. In another scenario, a PCell switch is triggered by the MN-DU 308, followed by PSCell change. In yet another scenario, the PCell changed but SN-DU has not triggered SCG LTM for a PSCell change.

[0058] For cases involving bearers’ re-alignment during PCell and PSCell change in dual connectivity, the bearer changes cannot be configured from two different RAN nodes (e.g., gNBs 206) as there will be non-zero overlap where the DRBs are configured at the MN-CU 306 and the SN-CU 310. It may therefore be important how and when the prepared configurations of the cell groups will be triggered in case of dual connectivity. Furthermore, storing a large number of configurations of candidate target PSCells and PCells may also be challenging.

[0059] To further illustrate, consider a simplistic scenario where four DRBs are mapped or re-mapped among the serving and candidate PCell and PSCell. Now, in case of PCell change, there may be different load in a first MN 302 providing a first PCell (PCell 1) and a second MN providing a second PCell (PCell 2). This may mean that different number of bearers are served by the RAN node that can cause a bearer re-mapping. FIG. 6 illustrates an initial configuration 600 (denoted config-0) of a PCell and a PSCell for dual connectivity. As shown, the serving PCell(PCell 1) may be configured with a first DRB (DRB1), and the serving PSCell (PSCell 1) may be configured with second, third and fourth DRBs (DRB2, DRB3 and DRB4).

[0060] FIGS. 7A, 7B, 7C and 7D illustrate configurations of an LTM candidate cell (PSCell or PCell), or a reconfiguration of a PSCell, according to some example implementations. In case if there is no PCell change, and based on SCG LTM if SN-DU 312 triggers a PSCell change, the new PSCell configuration of the target PSCell (PSCell 2) can retain same DRBs to that of the serving PSCell (PSCell 1). FIG. 7A illustrates this candidate target PSCell LTM configuration 702A (denoted config-1) when no PCell change is triggered. This PSCell configuration may be applied by a UE 208 during a PSCell change while no PCell change has been indicated (when the candidate target PSCell coverage area overlaps with the serving PCell coverage area), ensuring no overlapping DRBs (or other deltas) between the PCell and the PSCell.

[0061] Now, assume that a PCell change due to MCG LTM is triggered to the candidate target PCell (PCell 2), and that DRB-2 is allocated or re-mapped to this new candidate target PCell. This scenario becomes a strong possibility if two different MNs 302 configure two MCGs, and the candidate target PCell belongs to the MCG configured by a different MN. FIG. 7B illustrates this candidate target PCell LTM configuration 702B (denoted config-2) with re-mapped DRB.

[0062] In case no better candidate target PSCell exists, the same PSCell may be reconfigured with different DRBs. The SN 304 may update the current serving PSCell configuration (PSCell 1) ensuring there are no overlapping DRBs (or other deltas) with the PCell 2. FIG. 7C illustrates this reconfigured serving PSCell LTM configuration 702C (denoted config-4). This reconfigured PSCell configuration may be applied together with an updated PCell configuration concurrently or otherwise at the same time during a PCell change to prevent loss of PSCell connection in case if PCell is initiated with no previous instance of a PSCell change (when the coverage area of current PSCell associated with the serving PCell overlaps with the candidate target PCell coverage area).

[0063] If a PSCell change is triggered right after a PCell change, the new candidate target PSCell may overtake one or more of the DRBs that are not served by the MN 302. This may depend on the load the MN 302 can accept. The candidate target SN 304 may therefore remove or offload DRB2 since DRB2 is part of the initial serving PSCell, and now served by the new PCell (PCell 2). FIG. 7D illustrates this candidate target PSCell LTM configuration 702D with remapped DRB, which now contains DRB3 and DRB4 (denoted config-3).

[0064] The above PSCell configuration (config-3) may be applied by the UE 208 during a PSCell change right after a PCell switch instance (when the serving PSCell coverage area overlaps with the candidate target PCell coverage area). In other examples, PSCell configuration may be a reconfiguration of the current serving PSCell to be applied together with an updated PCell configuration at the same time during a PCell switch to prevent loss of PSCell connection in caseif PCell switch is initiated right after a PSCell change instance (when candidate target PSCell coverage area overlaps with the serving PCell coverage area). In either case, the PSCell configuration may be applied to ensure no no overlapping DRBs (or other deltas) between the PCell and PSCell.

[0065] FIG. 8 illustrates a first UE mobility scenario 800, according to some example implementations. In this first mobility scenario, the PCell has changed from the serving PCell (PCell 1) 802 to a candidate target PCell (PCell 2) 804, but the serving SN-DU 312 has not been able to find a better PSCell. During this duration, if the initial serving PSCell (PSCell 1) 806 does not reconfigure ensuring no-overlapping DRBs (or other deltas) with PCell 2, the secondary link will be lost. In this scenario, an LTM cell switch order may be configured as config-2, followed by config -4 and config-3 at the same time (concurrently). The sequence of triggering LTM cell switch execution by the MN-DU 308 and SN-DU 312 may therefore be summarized as follows: indicate to the SN-DU to trigger config-2 and config-4 at the same time if PCell change is indicated by the MN-CU 306 or the UE 208. The SN-DU may then trigger config-3 if a PSCell change is triggered based on LI measurements.

[0066] FIG. 9 illustrates a second UE mobility scenario 900, according to some example implementations. In this second mobility scenario, the UE 208 is initially in PCell 1 802 and PSCell 1 806. The PSCell 1 finds a better PSCell and makes an SCG LTM decision to change to PSCell 2 808. The PCell 1 then finds a better PCell and makes an MCG LTM decision to change to PCell 2 804. Once the PCell is changed, the PSCell re-maps its DRBs and update its configuration so that there are no overlapping DRBs with PCell 2. In this scenario, an LTM cell switch order may be configured as config- 1, followed by config -2 and config-3 at the same time (concurrently). The sequence of triggering LTM cell switch execution by the MN-DU 308 and SN-DU 312 may therefore be summarized as follows: indicate to the SN-DU to trigger config-1 if SN-DU finds a better PSCell and PCell change is not indicated by MN-CU 306. The MN-DU can then trigger config -2 and config-3 for a subsequent PCell and PSCell change at the same time.

[0067] Example implementations of the present disclosure therefore provide a strategy with signaling enhancements for dual connectivity to prepare multiple configurations of candidate target PCells and PSCells ensuring no over-lapping DRBs or other deltas between candidate target PCell(s) and PSCell(s). These multiple configurations may be simultaneously prepared and stored either in the MN 302, SN 304 or at the UE 208. Based on a trigger from one of the RAN nodes (SN-DU 312 or MN-DU 308) during a PSCell or PCell change, the UE may directly and concurrently apply these compatible PCell and PSCell configurations during LTM execution without having to wait to configure the candidate target cell for one cell group until LTM cell switch is successfully completed in the other cell group. This may reduce interruption time and significantly fasten LTM execution in dual connectivity mode.

[0068] Example implementations of the present disclosure address a number of problems. Some example implementations address the problem of overlapping deltas between candidate or current PCell and PSCell(s). For simultaneous PCell and PSCell change to work, necessary RRC configurations of the candidate target PCell and PSCells need to be prepared in advance during LTM preparation, and such that the candidate target or current PCell(s) and PSCell(s) do not include overlapping DRBs or other deltas.

[0069] Some example implementations also address the problem in which candidate target PSCell configurations may be outdated when a PCell change occurs. This problem may be illustrated by the first mobility scenario 800. In dual connectivity, the configuration of the SCG may depend on the MCG, and there may be cases in which a PCell change may necessitate a PSCell change or reconfiguration of the current serving PSCell.

[0070] Some example implementations address the problem of the UE applying an outdated SCG configuration stored in the candidate or reference configuration for cases where an earlier PSCell change is triggered, followed by the PCell change. This problem may be illustrated by the second mobility scenario 900. In dual connectivity, the complete LTM reference configuration constitutes the complete configuration of the MCG and SCG part. In scenarios where MCG LTM is configured, UE will be configured with reference configuration and candidate configuration. It is agreed that the combination of reference configuration and candidate configuration is a complete configuration. The understanding of which IES are considered as part of complete configuration is not clear. SCG configuration may be included to reference or candidate configuration to form a complete configuration. If PSCell change is triggered over SRB3 the SCG configuration may change and MN might be unaware of this. Thus, the SCG configuration in reference or candidate configuration would be the SCG configuration related to the previous PSCell before PSCell change. Thus, applying reference or candidate configuration may cause UE to apply an outdated SCG configuration stored in candidate or reference configuration. Therefore, if the MN 302 decides on a PCell switch based on MCG LTM after a PSCell change, the UE 208 may typically apply an outdated SCG configuration stored in the reference or candidate. The PSCell link may be impacted in that case.

[0071] Some example implementations address the problem of the SN-DU 312 being unaware of the sequence of executing PSCell configurations for LTM cell switch. If the network configures simultaneous PCell and PSCell configurations based on L1 / L2 triggered mobility (MCG and SCG LTM), the sequence of triggering the PCell and PSCell configurations may be important for UE mobility. There may be scenarios in which the PCell initially changes, followed by a PSCell change, or vice versa. If the sequence of triggering the cell change configurations is improperly executed by the SN-DU 312 during LTM execution, the UE 208 may end up losing either its primary link or secondary link.

[0072] Even further, some example implementations address the problem of storing multiple PCell and its corresponding PSCell configurations supporting MCG LTM based PCell change or multiple PCell configurations for SCG LTM based PSCell change. As described above, assume four DRBs configured for simultaneous PCell and PSCell change. These four DRBs or whole candidate target PSCell(s) delta configurations may be mapped and re-mapped among PCell and PSCell for a single RRC connection if dual connectivity is configured. Assume all four DRBs are used by the PCell and PSCell with no overlapping DRBs, Out of four DRBs, if the PCell has only one DRB configured, and remaining three are used by PSCell, there exist four possible combinations of configurations. This is the same if the PCell has three DRBs configured, and the remaining one DRB is used by the PSCell. If the PCell has two DRBs configured, and remaining two are used by PSCell, there exist six possible combinations of configurations.

[0073] Mathematically, there are therefore fourteen total possible combinations of the four DRBs mapped and remapped between the PCell and the PSCell. Upon generalization, the total number of possible configurations for a given PCell change followed by subsequent PSCell change generated based on non-overlapping DRBs (or other deltas) may be represented as: ssQ. where N is the number of DRBs. If generalized for M candidate target PSells and A DRBs mapped or remapped between the candidate target PCell and its corresponding candidate target PSCells, the total number of LTM configurations that exist for a given PCell change may be represented as:However, for a given PCell configuration at any given time a maximum of 8 candidate PSCells can be prepared at any given time and at max only 8 can be at different SNs.

[0074] Example implementations of the present disclosure provide enhancements that enables both the MN 302 and the SN 304 to prepare multiple candidate target PCell(s) and PSCell(s) at a given time during the LTM preparation ensuring that there are no overlapping DRBs or other deltas among candidate target PCell(s) and PSCell(s). As explained below, this may involve coordination between the MN and SN. Lor dual connectivity, some example implementations include preparation of multiple configurations for the candidate target PSCell(s) for PCell(s). The UE 208 may then simultaneously implement the prepared configurations based on the reception of a PCell change trigger from MN to SN, or a PSCell change trigger indication from SN to MN.

[0075] In some examples, then, LTM preparation may include the MN-CU 306 sharing its current serving PCell and candidate target PCell(s) configuration to the SN-CU 310 along with an indication denoted as PSCell preparation indication to prepare multiple candidate target PSCell configurations ensuring no overlapping deltas (that includes DRBs) with the serving andcandidate target PCell(s). The SN-CU 310 may prepare multiple configurations for candidate target PSCell(s) ensuring there are no overlapping DRBs or other deltas with the candidate target PCell(s) during the LTM preparation.

[0100] Notably, if cell switch is triggered to a candidate LTM cell that is not configured during the LTM preparation, the network may fall back on legacy behavior whereby the MCG LTM may be initially configured and executed, followed by configuration and execution of SCG LTM. Otherwise, the MN 302 may implement RRC reestablishment whereby all stored configurations are be released, and direct connectivity is de-configured before everything restarts again.

[0101] The SN-CU 310 may shares a PSCell change barring indication with the SN-DU 312 and the UE 208 to configure the SN-DU to prevent triggering SCG LTM (option-1) if it has received an indication from the UE that current serving PSCell configuration has changed due to a PCell change. Alternatively, upon receiving the PSCell change barring indication, the UE may be configured to suspend reporting LI measurement for candidate target PSCell(s) (option-2) if a PCell change is indicated by the MN-DU 308.

[0102] Similarly, in case a PSCell change is indicated before PCell change, a PCell change barring indication may be sent by the SN-CU 310 to MN-CU 306 which either configures the MN-DU 308 to prevent triggering MCG LTM, or configures the UE 208 to suspend reporting LI measurements for the candidate target PCell(s) while SCG LTM is ongoing.

[0103] In case option- 1 is implemented, the SN-CU 310 may share a PSCell change resumption indication that configures the SN-DU 312 to trigger SCG LTM upon reception of an MCG and SCG LTM reconfiguration complete message from the SN-CU.

[0104] Notably, the SN-CU 310 may be updated of success of the MCG and SCG configuration after PCell change, and current PSCell re-configuration, through an MCG and SCG LTM complete message, which may be applicable in both cases where candidate target PCell is located intra-MN or inter-MN. In the four DRBs re-mapping and bearer alignment example, config -2 and config -4 may be applied at the same time. Subsequently, based on LI measurements, SCG LTM may be be triggered to the candidate target PSCell (e.g., PSCell 2), such as by indicating to the UE 208 to apply the already stored config-3 and initiate random access for SCG LTM as described with respect to the first mobility scenario 800.

[0105] In case option-2 is selected, the SN-CU 310 may share a PSCell change resumption indication that configures the UE 208 to resume reporting LI measurements for the candidate target PSCell(s) after the UE has transmitted an RRC reconfiguration complete message to the MN-CU 306. Similarly, in case a PSCell change is indicated before PCell change, the MN-CU may share a PCell change resumption indication that configures the UE 208 to resume reporting LI measurements for the candidate target PCell(s) after the UE has transmitted an RRC reconfiguration complete message to the SN-CU.

[0106] In a number of examples, one or more of the features may be configured during LTM preparation for the MCG and SCG LTM. In other examples, the MN 302 may configure one or more of the features after the LTM preparation but before the start of LTM execution for a PCell change.

[0107] To handle a large number of possible RRC configurations for candidate target PSCell(s) during a given PCell change or vice-versa, SN-DU 312 may in some examples buffer or otherwise store the multiple configurations of candidate target PSCells corresponding to a PCell change. The SN-DU may then provide the suitable configuration at the time of the PCell switch to the UE 208 so that UE can apply the updated PSCell configuration. This same or a similar behavior may be extended for multiple candidate target PCell configurations which can be stored by the MN-DU 308 and shared at the time of PSCell switch.

[0108] In some examples, during MCG LTM configuration or after a PSCell change, the UE 208 may be indicated to update complete LTM reference configuration with a new SCG configuration. Alternatively, a separate complete LTM reference configuration for SCG, or a separate complete LTM reference configuration including current SCG configuration, may be indicated to the UE.

[0109] Also, in some examples where MN shares piggybacked updated SCG reference config to UE and asks UE to apply and update this in the reference config, the MN-CU 306 may send an override barring indication to the UE 208 (relayed through the MN-DU 308) to configure the UE to prevent overriding the complete LTM reference configuration that includes the MCG and the updated SCG part after the PSCell change with the previous complete LTM reference configuration. This may avoid the UE applying the old complete LTM reference configuration which result in the loss of the PSCell connection. Alternatively, if it is MN-CU which updates the SCG part of the reference configuration after PSCell change is indicated by the SN, the MN-CU prevents applying the outdated SCG part of the reference configuration when PCell change is triggered.

[0110] FIG. 10 is a flowchart of steps in a method 1000 of triggering simultaneous PCell and PSCell configurations under the first and second UE mobility scenarios, according to some example implementations. For purposes of these example implementations, it may be assumed that the UE 208 initially applies config-0. As shown, if a PCell change is indicated, the UE 208 may suspend LI measurement reporting to the SN-DU 312, as shown at blocks 1002, 1004. The UE may apply config -2 and config -4 together at the same time, and then resume LI measurement reporting to the SN-DU, as shown at blocks 1006, 1008. The UE may then apply config-3 if a PSCell change is triggered based on the LI measurements, as shown at block 1010.[oni] As also shown, if a PCell change is not indicated, and a PSCell change is also not indicated, the UE 208 may continue with its initial config-0, as shown at blocks 1002, 1012, 1014. On the other hand, if a PCell change is not indicated, but a PSCell change is indicated, the UEmay suspend LI measurement reporting to the MN-DU 308, as shown at blocks 1012, 1016. The UE may apply config- 1, and then resume LI measurement reporting to the MN-DU, as shown at blocks 1018, 1020. The UE may then apply config-2 and config-3 together at the same time if a PCell change is triggered based on the LI measurements, as shown at block 1022.

[0112] To further illustrate example implementations of the present disclosure, FIGS. 11 A, 11B and 11C illustrate a signaling chart 1100 for LTM preparation for simultaneous MCG and SCG in dual connectivity. As shown in FIG. 11 A, the UE at step 1101 is configured with SRB3, and the UE at steps 1102 and 1103 receives data with initial serving configuration of PCell and PSCell denoted as config-0.

[0113] The MN-CU 306 at step 1104 decides on a PCell change. The MN-CU at step 1105 prepares an RRC reconfiguration message with candidate target PCell configuration config -2. The MN-CU at the same time also prepares a PSCell preparation indication which configures the SN-CU 310 to prepare multiple configurations of the candidate target PSCell(s), including config- 1, config-3 and config -4 in the above examples ensuring no-overlapping DRBs with the candidate target PCell.

[0114] As shown in FIGS. 11A and 11B, the MN-CU 306 at steps 1106 and 1107 shares config-2 with the MN-DU 308 which in turn relays config-2 to the UE 208 along with a PCell change barring and resumption indication if a PSCell switch is triggered earlier than PCell switch. These indications are read by MN-DU 308.

[0115] The MN-CU 306 at step 1108 is configured to prevent over-riding the current complete LTM reference configuration (containing updated SCG part after PSCell switch) with the previous complete configuration with old SCG part in the complete LTM reference configuration.

[0116] The MN-CU 306 at step 1109 shares config -2 with the SN-DU 312 which in turn relays config-2 to the UE 208 along with the PSCell preparation indication. The MN-CU at step 1110 transmits PSCell preparation indication to the SN-CU 310. As shown in FIG. 11C, the SN- CU at step 1111 reads the PSCell preparation indication and prepares multiple candidate target PSCell configurations (config-1, config-3 and config-4). The SN-CU also configures the PSCell change barring indication and PSCell change resumption indication.

[0117] As shown at step 1112, the SN-CU 310 shares the multiple candidate target PSCell configurations (config- 1, config-3 and config -4), along with the PSCell change barring and resumption indication, with the SN-DU 312. The SN-DU at step 1113 reads the PSCell switch barring and resumption indication. The SN-DU at step 1114 relays RRC reconfiguration messages with config-1, config-3 and config-4 to the UE 208. The SN-DU may optionally at step 1115 store the PSCell configurations (config- 1, config-3 and config -4), and transmit the PSCell indications to the UE only upon receiving a PCell switch indication from the UE.

[0118] The UE 208 at step 1116 stores the multiple PSCell configurations (config- 1, config - 3 and config-4). And the UE at step 1117 reads the PSCell change barring indication.

[0119] FIGS. 12A and 12B illustrate a signaling chart 1200 of LTM execution for the first mobility scenario in which a PCell change is followed by a PSCell change, according to some example implementations. As shown in FIG. 12A, if a first option (option- 1) is selected, the MN 302 at step 1201 stops SCG LTM before MCG LTM is completed based on the PSCell change barring indication configured during the LTM preparation. The MN-DU 308 A at step 1202 sends LTM cell switch indication to UE with config -2 and config -4 (to be applied at the same time).

[0120] If a second option (option-2) is selected, the UE 208 at step 1203 stops LI candidate target PSCell(s) measurement reports as per the PSCell change barring indication configured during the LTM preparation. Alternatively, as per option- 1, the UE at step 1204 indicates to the SN-DU 312 through LI signaling that PSCell config changed due to PCell change. The SN-DU 312 at step 1205 does not trigger SCG LTM as per the PSCell change barring indication which was configured during the LTM preparation.

[0121] The UE 208 at step 1206 initiates random access to the candidate target PCell located either within the same MN 302 (MN-CU 306A or a different MN (including MN-CU2 306B). Upon success of the random access, the UE at step 1207 transmits an RRC reconfiguration complete message to the MN-CU2 as per the legacy behavior routed through the candidate target PCell’s MN-DU 308B.

[0122] As shown in FIG. 12B, if option-2 is selected, the UE 208 at step 1208 resumes reporting LI measurements of the candidate target PSCell(s) / DU(s) 312B to the SN-DU 312 after the UE transmits the RRC reconfiguration complete message. The UE at step 1209 transmits LI measurements to the SN-DU 312 indicating the new candidate target PSCell (PSCell 2) whose configuration is already stored in the UE (config-3).

[0123] The MN-CU2 306B at step 1210 indicates to the SN-CU 310 that MCG and SCG LTM is complete with config-2 and config-4. If option-1 is selected, the SN-CU at step 1211 transmits an MCG and SCG reconfiguration complete message to the SN-DU 312 indicating the successful PCell change, and that config-2 and config-4 have been successfully applied.

[0124] The SN-DU 312 at step 1212 triggers SCG LTM. The SN-DU then at step 1213 triggers the UE to apply config-3, which is the configuration of the selected candidate PSCell. Random access for the SCG LTM is initiated at step 1214. And the SN-DU at step 1215 informs the SN-CU 310 that SCG LTM cell switch has been triggered.

[0125] FIGS. 13A and 13B illustrate a signaling chart 1300 of LTM execution for the second mobility scenario in which a PSCell change is followed by a PCell change, according to some example implementations. As shown in FIG. 13 A, if a first option (option- 1) is selected, the MN 302 at step 1301 stops MCG LTM before SCG LTM is completed based on the PCell changebarring indication configured during LTM preparation. The SN-DU 312 at step 1302 sends LTM cell switch indication to the UE 208 with config- 1.

[0126] If a second option (option-2) is selected, the UE 208 at step 1303 stops LI candidate target PCell measurement reports as per the PCell change barring indication configured during the LTM preparation. Alternatively, as per option- 1, the UE at step 1304 indicates to the MN-DU 308 through LI signaling that a PSCell change has been triggered. The MN-DU 308 at step 1305 does not trigger MCG LTM as per the PCell change barring indication configured during LTM preparation.

[0127] The UE 208 at step 1306 initiates random access to the candidate target PSCell. Upon success of the random access, the UE 208 at step 1307 transmits an RRC reconfiguration complete message to the SN-CU 310 as per the legacy behavior routed through the candidate target PCell’s SN-DU 312B.

[0128] If option-2 is selected, the UE 208 at step 1308 resumes reporting LI measurements of the candidate target PCell(s) to the MN-DU 308 after the UE transmits the RRC reconfiguration complete message. The UE at step 1309 transmits LI measurements to the MN-DU 308 indicating the new candidate target PCell (PCell 2) whose configuration is already stored in the UE (config- 2).

[0129] The SN-CU 310 at step 1310 indicates to the MN-CU 306A that SCG LTM is complete with config- 1. Upon reception of the SCG LTM complete, the MN-CU at step 1311 transmits an SCG reconfiguration complete message to MN-DU 308 indicating the successful PSCell change, and that config- 1 has been successfully applied. The MN-CU also transmits the override barring indication.

[0130] The MN-DU 308 at step 1312 decides to trigger MCG LTM. The MN-DU at step 1313 triggers the UE 208 to concurrently (at the same time) apply the stored config-2 and config- 3, which is the configuration of the selected candidate target PCell and PSCell, along with the override barring indication.

[0131] The UE 208 at step 1314 prevents overriding the current complete LTM reference configuration with the previous complete LTM reference configuration upon initiating the PCell change. The UE at step 1315 concurrently applies config -2 and config-3. Random access for MCG LTM is initiated at step 1316. And at step 1317, MCG LTM cell switch has been triggered is informed by MN-DU 308 to the MN-CU 306A.

[0132] PIG. 14 is a flowchart illustrating various steps in a method 1400 according to various example implementations. The method includes providing a radio network service from a primary cell (PCell) of a master node to a user equipment in dual connectivity with a secondary primary cell (PSCell) of a secondary node, as shown at block 1402. The method includes generating a lower-layer triggered mobility (LTM) candidate cell configuration associated with a master cell group (MCG) including at least one candidate target PCell, as shown at block 1404. The methodincludes preparing a message including the LTM candidate configuration for the MCG, and an indication for the secondary node to generate multiple LTM candidate configurations associated with a secondary cell group (SCG) including at least one candidate target PSCell based on the LTM candidate configuration for the MCG, as shown at block 1406. The method includes sending the message to the secondary node for generation of the multiple LTM candidate configurations, as shown at block 1408. And the method includes sending a second message including the LTM candidate configuration for the MCG towards the user equipment, as shown at block 1410.

[0133] In some examples, the master node includes a central unit and a distributed unit, and the second message is sent at block 1410 from the central unit to the distributed unit for relaying to the user equipment. In some of these examples, the second message further includes an indication for the distributed unit to prevent triggering an LTM cell switch to a candidate target PSCell when an LTM cell switch from the PCell to a candidate PCell is indicated.

[0134] In some examples, the indication is a first indication, and the second message further includes a second indication for the distributed unit to enable triggering the LTM cell switch after the LTM cell switch to the candidate target PCell is complete.

[0135] In some examples, the second message sent to the user equipment at block 1410 further includes an indication for the user equipment to suspend measurements on the at least one candidate target PCell when an LTM cell switch to a candidate target PSCell is indicated.

[0136] In some examples, the indication is a first indication, and the second message further includes a second indication for the user equipment to resume the measurements on the at least one candidate target PCell when the LTM cell switch to the candidate target PSCell is complete.

[0137] In some examples, the second message sent to the user equipment at block 1410 further includes an indication for the user equipment to prevent the user equipment from applying an outdated configuration for the SCG stored in a candidate target PSCell or a complete LTM reference configuration, or when the master node has updated a configuration for the SCG after a PSCell change, prevent the user equipment from overriding the complete LTM reference configuration including the updated configuration for the SCG in the complete LTM reference configuration or LTM candidate configuration with the outdated configuration stored in the candidate target PSCell or the complete LTM reference configuration during an LTM cell switch to a candidate target PCell following LTM cell switch to a candidate target PSCell.

[0138] FIG. 15 is a flowchart illustrating various steps in a method 1500 according to various example implementations. The method includes providing a radio network service from a primary secondary cell (PSCell) of a secondary node to a user equipment in dual connectivity with a primary cell (PCell) of a master node, as shown at block 1502. The method includes receiving a message from the master node including a lower-layer triggered mobility (LTM) candidate cell configuration associated with a master cell group (MCG) including at least one candidate target PCell, as shown at block 1504. The method includes generating multiple LTM candidateconfigurations associated with a secondary cell group (SCG) including at least one candidate target PSCell based on the LTM candidate configuration for the MCG, as shown at block 1506. And the method includes sending a message including the multiple LTM candidate configurations for the SCG towards the user equipment, as shown at block 1508.

[0139] In some examples, the multiple LTM candidate configurations that are generated at block 1506 include a PSCell configuration to be applied by the user equipment during a PSCell change to a candidate target PSCell in which no PCell change has been indicated, and respective coverage areas of the PSCell and the candidate target PSCell overlap, such that bearers do not overlap between the PCell and the candidate target PSCell.

[0140] In some examples, the multiple LTM candidate configurations that are generated at block 1506 include a PSCell configuration to be applied by the user equipment during a PSCell change to a candidate target PSCell after a PCell change to a candidate target PCell in which coverage areas of the candidate target PSCell and the candidate target PCell overlap, such that bearers do not overlap between the candidate target PSCell and the candidate target PCell.

[0141] In some examples, the multiple LTM candidate configurations that are generated at block 1506 include a reconfiguration of a new serving PSCell to be applied by the user equipment concurrent with a configuration of a candidate target PCell during a PCell change to the candidate target PCell after a PSCell change in which coverage areas of the new serving PSCell and the candidate target PCell overlap, such that bearers do not overlap between the new serving PSCell and the candidate target PCell.

[0142] In some examples, the multiple LTM candidate configurations that are generated at block 1506 include a reconfiguration of the PSCell to be applied by the user equipment concurrent with a candidate target PCell during a PCell change to the candidate target PCell with no indication of a PSCell change in which coverage areas of the PSCell and the candidate target PCell overlap, such that bearers do not overlap between the PSCell and the candidate target PCell.

[0143] In some examples, the secondary node includes a central unit and a distributed unit, and the message is sent at block 1508 from the central unit to the distributed unit for relaying to the user equipment. In some of these examples, the message further includes an indication for the distributed unit to prevent triggering an LTM cell switch from the PSCell to a candidate target PSCell when an LTM cell switch to a candidate target PCell is indicated.

[0144] In some examples, the indication is a first indication, and the message further includes a second indication for the distributed unit to enable triggering the LTM cell switch after the LTM cell switch to the candidate target PCell is complete.

[0145] In some examples, the message sent to the user equipment at block 1508 further includes an indication for the user equipment to suspend measurements on the at least one candidate target PSCell when an LTM cell switch to a candidate target PCell is indicated.

[0146] In some examples, the indication is a first indication, and the second message further includes a second indication for the user equipment to resume the measurements on the at least one candidate target PSCell when the LTM cell switch to the candidate target PCell is complete.

[0147] In some examples, the secondary node includes a central unit and a distributed unit, and the message is sent at block 1508 from the central unit to the distributed unit for storing and selectively relaying one or more of the multiple LTM candidate configurations for the SCG to the user equipment.

[0148] FIG. 16 is a flowchart illustrating various steps in a method 1600 according to various example implementations. The method includes providing a radio network service from a primary secondary cell (PSCell) of a secondary node to a user equipment in dual connectivity with a primary cell (PCell) of a master node, as shown at block 1602. The method includes receiving signaling from the user equipment that indicates a lower-layer triggered mobility (LTM) cell switch from the PCell to a candidate target PCell in a master cell group (MCG), as shown at block 1604. The method includes preventing triggering an LTM cell switch from the PSCell to a candidate target PSCell during the LTM cell switch to the candidate target PCell, as shown at block 1606. The method includes receiving a message that indicates the LTM cell switch to the candidate target PCell is complete, as shown at block 1608. And the method includes sending a cell switch command to the user equipment to trigger the LTM cell switch from the PSCell to a candidate target PSCell, as shown at block 1610.

[0149] In some examples, signaling from the user equipment further indicates the LTM cell switch to the candidate target PCell includes a change in an LTM configuration associated with the MCG, and a concurrent change in a configuration associated with the SCG. In some of these examples, the cell switch command sent to the user equipment at block 1610 indicates another LTM candidate configuration associated with the SCG to be applied by the user equipment during the LTM cell switch from the PSCell to a candidate target PSCell.

[0150] FIG. 17 is a flowchart illustrating various steps in a method 1700 according to various example implementations. The method includes receiving a dual -connectivity radio network service from a primary cell (PCell) of a master node and a primary secondary cell (PSCell) of a secondary node, the PCell and the PSCell in respective ones of a master cell group (MCG) and a secondary cell group (SCG), as shown at block 1702. The method includes receiving a cell switch command to trigger a lower-layer triggered mobility (LTM) cell switch from the PCell to a candidate target PCell, as shown at block 1704. The method includes performing the LTM cell switch from the PCell to the candidate target PCell during which measurements on the at least one candidate target PSCell are suspended, as shown at block 1706. The method includes reporting measurements on the at least one candidate target PSCell after the LTM cell switch to the candidate target PCell is complete, as shown at block 1708. And the method includes receivinga second cell switch command to trigger an LTM cell switch from the PSCell to a candidate targetPSCell based on the measurements, as shown at block 1710.

[0151] In some examples, the cell switch command indicates an LTM candidate configuration associated with the MCG and an LTM candidate configuration associated with the SCG. In some of these examples, performing the LTM cell switch from the PCell to the candidate target PCell at block 1706 includes concurrently applying the LTM candidate configuration associated with the MCG and the LTM candidate configuration associated with the SCG.

[0152] In some examples, the second cell switch command indicates another LTM candidate configuration associated with the SCG to be applied during the LTM cell switch from the PSCell to a candidate target PSCell.

[0153] FIG. 18 is a flowchart illustrating various steps in a method 1800 according to various example implementations. The method includes providing a radio network service from a primary cell (PCell) of a master node to a user equipment in dual connectivity with a primary secondary cell (PSCell) of a secondary node, as shown at block 1802. The method includes receiving signaling from the user equipment that indicates a lower-layer triggered mobility (LTM) cell switch from the PSCell to a candidate target PSCell in a secondary cell group (MCG), as shown at block 1804. The method includes preventing triggering an LTM cell switch from the PCell to a candidate target PCell during the LTM cell switch to the candidate target PSCell, as shown at block 1806. The method includes receiving a message that indicates the LTM cell switch to the candidate target PSCell is complete, as shown at block 1808. And the method includes sending a cell switch command to the user equipment to trigger the LTM cell switch from the PCell to a candidate target PCell, as shown at block 1810.

[0154] In some examples, the message further indicates an LTM configuration associated with the SCG applied by the user equipment during the LTM cell switch to the candidate target PSCell. In some of these examples, the cell switch command sent to the user equipment at block 1810 indicates an LTM candidate configuration associated with the MCG and another LTM candidate configuration associated with the SCG to be concurrently applied by the user equipment during the LTM cell switch from the PCell to a candidate target PCell.

[0155] FIG. 19 is a flowchart illustrating various steps in a method 1900 according to various example implementations. The method includes receiving a dual -connectivity radio network service from a primary cell (PCell) of a master node and a primary secondary cell (PSCell) of a secondary node, the PCell and the PSCell in respective ones of a master cell group (MCG) and a secondary cell group (SCG), as shown at block 1902. The method includes receiving a cell switch command to trigger a lower-layer triggered mobility (LTM) cell switch from the PSCell to a candidate target PSCell, as shown at block 1904. The method includes performing the LTM cell switch from the PSCell to the candidate target PSCell during which measurements on the at least one candidate target PCell are suspended, as shown at block 1906. The method includes reportingmeasurements on the at least one candidate target PCell after the LTM cell switch to the candidate target PSCell is complete, as shown at block 1908. And the method includes receiving a second cell switch command to trigger an LTM cell switch from the PCell to a candidate target PCell based on the measurements, as shown at block 1910.

[0156] In some examples, the cell switch command indicates an LTM candidate configuration associated with the SCG. In some of these examples, performing the LTM cell switch from the PSCell to the candidate target PSCell at block 1906 includes applying the LTM candidate configuration associated with the SCG.

[0157] In some examples, the second cell switch command indicates an LTM candidate configuration associated with the MCG and another LTM candidate configuration associated with the SCG to be concurrently applied during the LTM cell switch from the PCell to a candidate target PCell.

[0158] According to example implementations of the present disclosure, a telecommunications system 100 or PLMN 102, and its components such as a UE 110, gNB 206, UE 208, CU 210, DU 212, S-DU 212A, T-DU 212B, MN 302, SN 304, MN-CU 306, MN-DU 308, SN-CU 310 and / or SN-DU 312 may be implemented by various means. Means for implementing the system and its components may include hardware, firmware, software, or combinations thereof. In some examples, one or more apparatuses may be configured to function as or otherwise implement the system and its components shown and described herein. In examples involving more than one apparatus, the respective apparatuses may be connected to or otherwise in communication with one another in a number of different manners, such as directly or indirectly via a wired or wireless network or the like.

[0159] According to some example implementations, at least some of the methods 1000, 1400, 1500, 1600, 1700, 1800 and 1900 described with respect to respective ones of FIGS. 10, 14, 15, 16, 17, 18 and 19 may be carried out by one or more apparatuses comprising means for performing functions corresponding steps of the methods. Examples of a suitable apparatus may include a gNB (e.g., gNB-CU, gNB-DU), ng-eNB, MN (e.g., MN-CU, MN-DU), SN (e.g., SN- CU, SN-DU) or any suitable apparatus, such as a server, host or node . Other examples of a suitable apparatus may include a user equipment, user device, user terminal or the like.

[0160] FIG. 20 illustrates an apparatus 2000 in which means for performing various functions includes hardware, alone or under direction of one or more computer programs from a computer-readable storage medium or other memory, such as computer memory, according to some example implementations of the present disclosure. Generally, an apparatus of example implementations of the present disclosure may comprise, include or be embodied in one or more fixed or portable electronic devices. Examples of suitable electronic devices include a wearable computer, mobile phone, portable computer, desktop computer, workstation computer, server (server computer) or the like. The apparatus may include one or more of each of a number ofcomponents such as, for example, processing circuitry 2002 connected to computer-readable storage medium or other memory 2004.

[0161] The processing circuitry 2002 may be composed of one or more processors alone or in combination with one or more computer-readable storage media. The processing circuitry is generally any piece of computer hardware that is capable of processing information such as, for example, data, computer programs and / or other suitable electronic information. The processing circuitry is composed of a collection of electronic circuits some of which may be packaged as an integrated circuit or multiple interconnected integrated circuits (an integrated circuit at times more commonly referred to as a “chip”). The processing circuitry may be configured to execute computer programs, which may be stored onboard the processing circuitry or otherwise stored in the memory 2004 (of the same or another apparatus).

[0162] The processing circuitry 2002 may be a number of processors, a multi-core processor or some other type of processor, depending on the particular implementation. Further, the processing circuitry may be implemented using a number of heterogeneous processor systems in which a main processor is present with one or more secondary processors on a single chip. As another illustrative example, the processing circuitry may be a symmetric multi-processor system containing multiple processors of the same type. In yet another example, the processing circuitry may be embodied as or otherwise include one or more ASICs, FPGAs or the like. Thus, although the processing circuitry may be capable of executing a computer program to perform one or more functions, the processing circuitry of various examples may be capable of performing one or more functions without the aid of a computer program. In either instance, the processing circuitry may be appropriately programmed to perform functions or operations according to example implementations of the present disclosure.

[0163] The memory 2004 is generally any piece of computer hardware that is capable of storing information such as, for example, data, computer programs, instructions 2006 (e.g., computer-readable program code) and / or other suitable information either on a temporary basis and / or a permanent basis. The memory may include volatile and / or non-volatile memory, and may be fixed or removable. Examples of suitable memory include recording media, random access memory (RAM), read-only memory (ROM), a hard drive, a flash memory, a thumb drive, a removable computer diskette, an optical disk or some combination thereof.

[0164] The memory 2004 is a non-transitory device capable of storing information. One example of a suitable memory is a computer-readable storage medium, which is distinguishable from a computer-readable transmission medium capable of carrying information from one location to another. Examples of suitable computer-readable transmission media comprise electronic carrier signals, telecommunications signals, software distribution packages, or some combination thereof. 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 persistency (e.g., RAMversus ROM). A computer-readable medium as described herein generally refers to a computer- readable storage medium or computer-readable transmission medium. A computer-readable medium is any entity or device capable in which information, such as one or more computer programs or portions thereof, may be stored and carried.

[0165] In addition to the memory 2004 (e.g., computer-readable storage medium), the processing circuitry 2002 may also be connected to one or more interfaces for displaying, transmitting and / or receiving information. The interfaces may include a communications interface 2008 and / or one or more user interfaces. The communications interface may be configured to transmit and / or receive information, such as to and / or from other apparatus(es), network(s) or the like. The communications interface may be configured to transmit and / or receive information by physical (wired) and / or wireless communications links. Examples of suitable communication interfaces include a network interface controller (NIC), wireless NIC (WNIC) or the like.

[0166] The user interfaces may include a display 2010 and / or one or more user input interfaces 2012. The display may be configured to present or otherwise display information to a user, suitable examples of which include a liquid crystal display (LCD), light-emitting diode (LED) display, organic LED (OLED) display, active-matrix OLED (AMOLED) or the like. The user input interfaces may be wired or wireless, and may be configured to receive information from a user into the apparatus, such as for processing, storage and / or display. Suitable examples of user input interfaces include a microphone, image or video capture device, keyboard or keypad, joystick, touch-sensitive surface (separate from or integrated into a touchscreen), biometric sensor or the like. The user interfaces may further include one or more interfaces for communicating with peripherals such as printers, scanners or the like.

[0167] Execution of the instructions 2006 by the processing circuitry 2002, or storage of the instructions in the memory 2004, supports combinations of operations for implementing example implementations of the present disclosure. In this manner, an apparatus 2000 may comprise at least one processing circuitry and at least one memory coupled to the at least one processing circuitry, where the at least one processing circuitry is configured to execute instructions stored in the at least one memory. It will also be understood that one or more functions, and combinations of functions, may be implemented by special purpose hardware -based computer systems and / or processing circuitry which perform the specified functions, or combinations of special purpose hardware and program code instructions.

[0168] Some example implementations of the present disclosure may also be carried out in the form of a computer process defined by one or more computer programs or portions thereof. Example implementations of the present disclosure may be carried out by executing at least one portion of a computer program comprising instructions. The computer program may be in source code form, object code form, or in some intermediate form. The computer program may be stored in a computer-readable medium that is readable by a computer, processing circuitry or othersuitable apparatus. As indicated above, for example, the computer program may be stored in a memory, such as a computer-readable storage medium. Additionally or alternatively, for example, the computer program may be stored in a computer-readable transmission medium. The coding of software for carrying out example implementations of the present disclosure is well within the scope of a person of ordinary skill in the art.

[0169] As will be appreciated, any suitable instructions may be loaded onto a computer, a processing circuitry or other programmable apparatus from a memory or a computer-readable medium (e.g., computer-readable storage medium, computer-readable transmission medium) to produce a particular machine, such that the particular machine becomes a means for implementing the functions specified herein. The instructions may also be stored in a computer-readable medium that can direct a computer, a processing circuitry or other programmable apparatus to function in a particular manner to thereby generate a particular machine or particular article of manufacture. In some examples, the instructions stored in the computer-readable medium may produce an article of manufacture, where the article of manufacture becomes a means for implementing functions described herein. The instructions may be retrieved from a computer-readable medium and loaded into a computer, processing circuitry or other programmable apparatus to configure the computer, processing circuitry or other programmable apparatus to execute operations to be performed on or by the computer, processing circuitry or other programmable apparatus.

[0170] Retrieval, loading and execution of instructions comprising program code instructions may be performed sequentially such that one instruction is retrieved, loaded and executed at a time. In some example implementations, retrieval, loading and / or execution may be performed in parallel such that multiple instructions are retrieved, loaded, and / or executed together. Execution of the program code instructions may produce a computer-implemented process such that the instructions executed by the computer, processing circuitry or other programmable apparatus provide operations for implementing functions described herein.

[0171] As explained above and reiterated below, the present disclosure includes, without limitation, the following example implementations.

[0172] Clause 1. An apparatus comprising: at least one memory configured to store instructions; and at least one processing circuitry configured to access the at least one memory, and execute the instructions to cause the apparatus to at least: provide a radio network service from a primary cell (PCell) of a master node to a user equipment in dual connectivity with a secondary primary cell (PSCell) of a secondary node; generate a lower-layer triggered mobility (LTM) candidate cell configuration associated with a master cell group (MCG) including at least one candidate target PCell; prepare a message including the LTM candidate configuration for the MCG, and an indication for the secondary node to generate multiple LTM candidate configurations associated with a secondary cell group (SCG) including at least one candidate target PSCell based on the LTM candidate configuration for the MCG; send the message to thesecondary node for generation of the multiple LTM candidate configurations; and send a second message including the LTM candidate configuration for the MCG towards the user equipment.

[0173] Clause 13. A method comprising: providing a radio network service from a primary cell (PCell) of a master node to a user equipment in dual connectivity with a secondary primary cell (PSCell) of a secondary node; generating a lower-layer triggered mobility (LTM) candidate cell configuration associated with a master cell group (MCG) including at least one candidate target PCell; preparing a message including the LTM candidate configuration for the MCG, and an indication for the secondary node to generate multiple LTM candidate configurations associated with a secondary cell group (SCG) including at least one candidate target PSCell based on the LTM candidate configuration for the MCG; sending the message to the secondary node for generation of the multiple LTM candidate configurations; and sending a second message including the LTM candidate configuration for the MCG towards the user equipment.

[0174] Clause 14. The method of clause 13, wherein the master node includes a central unit and a distributed unit, and the second message is sent from the central unit to the distributed unit for relaying to the user equipment, and wherein the second message further includes an indication for the distributed unit to prevent triggering an LTM cell switch to a candidate target PSCell when an LTM cell switch from the PCell to a candidate PCell is indicated.

[0175] Clause 15. The method of clause 14, wherein the indication is a first indication, and the second message further includes a second indication for the distributed unit to enable triggering the LTM cell switch after the LTM cell switch to the candidate target PCell is complete.

[0176] Clause 16. The method of any of clauses 13 to 15, wherein the second message sent to the user equipment further includes an indication for the user equipment to suspend measurements on the at least one candidate target PCell when an LTM cell switch to a candidate target PSCell is indicated.

[0177] Clause 17. The method of clause 16, wherein the indication is a first indication, and the second message further includes a second indication for the user equipment to resume the measurements on the at least one candidate target PCell when the LTM cell switch to the candidate target PSCell is complete.

[0178] Clause 18. The method of any of clauses 13 to 17, wherein the second message sent to the user equipment further includes an indication for the user equipment to prevent the user equipment from applying an outdated configuration for the SCG stored in a candidate target PSCell or a complete LTM reference configuration, or when the master node has updated a configuration for the SCG after a PSCell change, prevent the user equipment from overriding the complete LTM reference configuration including the updated configuration for the SCG in the complete LTM reference configuration or LTM candidate configuration with the outdated configuration stored in the candidate target PSCell or the complete LTM reference configurationduring an LTM cell switch to a candidate target PCell following LTM cell switch to a candidate target PSCell.

[0179] Clause 25. An apparatus comprising means for performing the method of any of clauses 13 to 18.

[0180] Clause 26. A computer-readable medium comprising instructions that, in response to execution by at least one processing circuitry, causes an apparatus to perform the method of any of clauses 13 to 18.

[0181] Clause 27. A computer-readable storage medium comprising instructions that, in response to execution by at least one processing circuitry, causes an apparatus to perform the method of any of clauses 13 to 18.

[0182] Clause 28. A computer program comprising instructions that, in response to execution by at least one processing circuitry, causes an apparatus to perform the method of any of clauses 13 to 18.

[0183] Clause 29. An apparatus comprising: at least one memory configured to store instructions; and at least one processing circuitry configured to access the at least one memory, and execute the instructions to cause the apparatus to at least: provide a radio network service from a primary secondary cell (PSCell) of a secondary node to a user equipment in dual connectivity with a primary cell (PCell) of a master node; receive a message from the master node including a lower-layer triggered mobility (LTM) candidate cell configuration associated with a master cell group (MCG) including at least one candidate target PCell; generate multiple LTM candidate configurations associated with a secondary cell group (SCG) including at least one candidate target PSCell based on the LTM candidate configuration for the MCG; and send a message including the multiple LTM candidate configurations for the SCG towards the user equipment.

[0184] Clause 30. The apparatus of clause 29, wherein the multiple LTM candidate configurations that are generated include a PSCell configuration to be applied by the user equipment during a PSCell change to a candidate target PSCell in which no PCell change has been indicated, and respective coverage areas of the PSCell and the candidate target PSCell overlap, such that bearers do not overlap between the PCell and the candidate target PSCell.

[0185] Clause 49. A method comprising: providing a radio network service from a primary secondary cell (PSCell) of a secondary node to a user equipment in dual connectivity with a primary cell (PCell) of a master node; receiving a message from the master node including a lower-layer triggered mobility (LTM) candidate cell configuration associated with a master cell group (MCG) including at least one candidate target PCell; generating multiple LTM candidate configurations associated with a secondary cell group (SCG) including at least one candidate target PSCell based on the LTM candidate configuration for the MCG; and sending a message including the multiple LTM candidate configurations for the SCG towards the user equipment.

[0186] Clause 50. The method of clause 49, wherein the multiple LTM candidate configurations that are generated include a PSCell configuration to be applied by the user equipment during a PSCell change to a candidate target PSCell in which no PCell change has been indicated, and respective coverage areas of the PSCell and the candidate target PSCell overlap, such that bearers do not overlap between the PCell and the candidate target PSCell.

[0187] Clause 51. The method of clause 49 or clause 50, wherein the multiple LTM candidate configurations that are generated include a PSCell configuration to be applied by the user equipment during a PSCell change to a candidate target PSCell after a PCell change to a candidate target PCell in which coverage areas of the candidate target PSCell and the candidate target PCell overlap, such that bearers do not overlap between the candidate target PSCell and the candidate target PCell.

[0188] Clause 52. The method of any of clauses 49 to 51, wherein the multiple LTM candidate configurations that are generated include a reconfiguration of a new serving PSCell to be applied by the user equipment concurrent with a configuration of a candidate target PCell during a PCell change to the candidate target PCell after a PSCell change in which coverage areas of the new serving PSCell and the candidate target PCell overlap, such that bearers do not overlap between the new serving PSCell and the candidate target PCell.

[0189] Clause 53. The method of any of clauses 49 to 52, wherein the multiple LTM candidate configurations that are generated include a reconfiguration of the PSCell to be applied by the user equipment concurrent with a candidate target PCell during a PCell change to the candidate target PCell with no indication of a PSCell change in which coverage areas of the PSCell and the candidate target PCell overlap, such that bearers do not overlap between the PSCell and the candidate target PCell.

[0190] Clause 54. The method of any of clauses 49 to 53, wherein the secondary node includes a central unit and a distributed unit, and the message is sent from the central unit to the distributed unit for relaying to the user equipment, and wherein the message further includes an indication for the distributed unit to prevent triggering an LTM cell switch from the PSCell to a candidate target PSCell when an LTM cell switch to a candidate target PCell is indicated.

[0191] Clause 55. The method of clause 54, wherein the indication is a first indication, and the message further includes a second indication for the distributed unit to enable triggering the LTM cell switch after the LTM cell switch to the candidate target PCell is complete.

[0192] Clause 56. The method of any of clauses 49 to 55, wherein the message sent to the user equipment further includes an indication for the user equipment to suspend measurements on the at least one candidate target PSCell when an LTM cell switch to a candidate target PCell is indicated.

[0193] Clause 57. The method of clause 56, wherein the indication is a first indication, and the second message further includes a second indication for the user equipment to resume themeasurements on the at least one candidate target PSCell when the LTM cell switch to the candidate target PCell is complete.

[0194] Clause 58. The method of any of clauses 49 to 57, wherein the secondary node includes a central unit and a distributed unit, and the message is sent from the central unit to the distributed unit for storing and selectively relaying one or more of the multiple LTM candidate configurations for the SCG to the user equipment.

[0195] Clause 69. An apparatus comprising means for performing the method of any of clauses 49 to 58.

[0196] Clause 70. A computer-readable medium comprising instructions that, in response to execution by at least one processing circuitry, causes an apparatus to perform the method of any of clauses 49 to 58.

[0197] Clause 71. A computer-readable storage medium comprising instructions that, in response to execution by at least one processing circuitry, causes an apparatus to perform the method of any of clauses 49 to 58.

[0198] Clause 72. A computer program comprising instructions that, in response to execution by at least one processing circuitry, causes an apparatus to perform the method of any of clauses 49 to 58.

[0199] Clause 73. An apparatus comprising: at least one memory configured to store instructions; and at least one processing circuitry configured to access the at least one memory, and execute the instructions to cause the apparatus to at least: provide a radio network service from a primary secondary cell (PSCell) of a secondary node to a user equipment in dual connectivity with a primary cell (PCell) of a master node; receive signaling from the user equipment that indicates a lower-layer triggered mobility (LTM) cell switch from the PCell to a candidate target PCell in a master cell group (MCG); prevent triggering an LTM cell switch from the PSCell to a candidate target PSCell during the LTM cell switch to the candidate target PCell; receive a message that indicates the LTM cell switch to the candidate target PCell is complete; and send a cell switch command to the user equipment to trigger the LTM cell switch from the PSCell to a candidate target PSCell.

[0200] Clause 77. A method comprising: providing a radio network service from a primary secondary cell (PSCell) of a secondary node to a user equipment in dual connectivity with a primary cell (PCell) of a master node; receiving signaling from the user equipment that indicates a lower-layer triggered mobility (LTM) cell switch from the PCell to a candidate target PCell in a master cell group (MCG); preventing triggering an LTM cell switch from the PSCell to a candidate target PSCell during the LTM cell switch to the candidate target PCell; receiving a message that indicates the LTM cell switch to the candidate target PCell is complete; and sending a cell switch command to the user equipment to trigger the LTM cell switch from the PSCell to a candidate target PSCell.

[0201] Clause 78. The method of clause 77, wherein signaling from the user equipment further indicates the LTM cell switch to the candidate target PCell includes a change in an LTM configuration associated with the MCG, and a concurrent change in a configuration associated with the SCG, and wherein the cell switch command sent to the user equipment indicates another LTM candidate configuration associated with the SCG to be applied by the user equipment during the LTM cell switch from the PSCell to a candidate target PSCell.

[0202] Clause 81. An apparatus comprising means for performing the method of clause 77 or clause 78.

[0203] Clause 82. A computer-readable medium comprising instructions that, in response to execution by at least one processing circuitry, causes an apparatus to perform the method of clause 77 or clause 78.

[0204] Clause 83. A computer-readable storage medium comprising instructions that, in response to execution by at least one processing circuitry, causes an apparatus to perform the method of clause 77 or clause 78.

[0205] Clause 84. A computer program comprising instructions that, in response to execution by at least one processing circuitry, causes an apparatus to perform the method of clause 77 or clause 78.

[0206] Clause 85. An apparatus comprising: at least one memory configured to store instructions; and at least one processing circuitry configured to access the at least one memory, and execute the instructions to cause the apparatus to at least: receive a dual-connectivity radio network service from a primary cell (PCell) of a master node and a primary secondary cell (PSCell) of a secondary node, the PCell and the PSCell in respective ones of a master cell group (MCG) and a secondary cell group (SCG); receive a cell switch command to trigger a lower-layer triggered mobility (LTM) cell switch from the PCell to a candidate target PCell; perform the LTM cell switch from the PCell to the candidate target PCell during which measurements on the at least one candidate target PSCell are suspended; report measurements on the at least one candidate target PSCell after the LTM cell switch to the candidate target PCell is complete; and receive a second cell switch command to trigger an LTM cell switch from the PSCell to a candidate target PSCell based on the measurements.

[0207] Clause 91. A method comprising: receiving a dual -connectivity radio network service from a primary cell (PCell) of a master node and a primary secondary cell (PSCell) of a secondary node, the PCell and the PSCell in respective ones of a master cell group (MCG) and a secondary cell group (SCG); receiving a cell switch command to trigger a lower-layer triggered mobility (LTM) cell switch from the PCell to a candidate target PCell; performing the LTM cell switch from the PCell to the candidate target PCell during which measurements on the at least one candidate target PSCell are suspended; reporting measurements on the at least one candidate target PSCell after the LTM cell switch to the candidate target PCell is complete; and receiving asecond cell switch command to trigger an LTM cell switch from the PSCell to a candidate targetPSCell based on the measurements.

[0208] Clause 92. The method of clause 91, wherein the cell switch command indicates an LTM candidate configuration associated with the MCG and an LTM candidate configuration associated with the SCG, and wherein performing the LTM cell switch from the PCell to the candidate target PCell includes concurrently applying the LTM candidate configuration associated with the MCG and the LTM candidate configuration associated with the SCG.

[0209] Clause 93. The method of clause 92, wherein the second cell switch command indicates another LTM candidate configuration associated with the SCG to be applied during the LTM cell switch from the PSCell to a candidate target PSCell.

[0210] Clause 97. An apparatus comprising means for performing the method of any of clauses 91 to 93.

[0211] Clause 98. A computer-readable medium comprising instructions that, in response to execution by at least one processing circuitry, causes an apparatus to perform the method of any of clauses 91 to 93.

[0212] Clause 99. A computer-readable storage medium comprising instructions that, in response to execution by at least one processing circuitry, causes an apparatus to perform the method of any of clauses 91 to 93.

[0213] Clause 100. A computer program comprising instructions that, in response to execution by at least one processing circuitry, causes an apparatus to perform the method of any of clauses 91 to 93.

[0214] Clause 101. An apparatus comprising: at least one memory configured to store instructions; and at least one processing circuitry configured to access the at least one memory, and execute the instructions to cause the apparatus to at least: provide a radio network service from a primary cell (PCell) of a master node to a user equipment in dual connectivity with a primary secondary cell (PSCell) of a secondary node; receive signaling from the user equipment that indicates a lower-layer triggered mobility (LTM) cell switch from the PSCell to a candidate target PSCell in a secondary cell group (MCG); prevent triggering an LTM cell switch from the PCell to a candidate target PCell during the LTM cell switch to the candidate target PSCell; receive a message that indicates the LTM cell switch to the candidate target PSCell is complete; and send a cell switch command to the user equipment to trigger the LTM cell switch from the PCell to a candidate target PCell.

[0215] Clause 105. A method comprising: providing a radio network service from a primary cell (PCell) of a master node to a user equipment in dual connectivity with a primary secondary cell (PSCell) of a secondary node; receiving signaling from the user equipment that indicates a lower-layer triggered mobility (LTM) cell switch from the PSCell to a candidate target PSCell in a secondary cell group (MCG); preventing triggering an LTM cell switch from the PCell to acandidate target PCell during the LTM cell switch to the candidate target PSCell; receiving a message that indicates the LTM cell switch to the candidate target PSCell is complete; and sending a cell switch command to the user equipment to trigger the LTM cell switch from the PCell to a candidate target PCell.

[0216] Clause 106. The method of clause 105, wherein the message further indicates an LTM configuration associated with the SCG applied by the user equipment during the LTM cell switch to the candidate target PSCell, and wherein the cell switch command sent to the user equipment indicates an LTM candidate configuration associated with the MCG and another LTM candidate configuration associated with the SCG to be concurrently applied by the user equipment during the LTM cell switch from the PCell to a candidate target PCell.

[0217] Clause 109. An apparatus comprising means for performing the method of clause 105 or clause 106.

[0218] Clause 110. A computer-readable medium comprising instructions that, in response to execution by at least one processing circuitry, causes an apparatus to perform the method of clause 105 or clause 106.

[0219] Clause 111. A computer-readable storage medium comprising instructions that, in response to execution by at least one processing circuitry, causes an apparatus to perform the method of clause 105 or clause 106.

[0220] Clause 112. A computer program comprising instructions that, in response to execution by at least one processing circuitry, causes an apparatus to perform the method of clause 105 or clause 106.

[0221] Clause 113. An apparatus comprising: at least one memory configured to store instructions; and at least one processing circuitry configured to access the at least one memory, and execute the instructions to cause the apparatus to at least: receive a dual-connectivity radio network service from a primary cell (PCell) of a master node and a primary secondary cell (PSCell) of a secondary node, the PCell and the PSCell in respective ones of a master cell group (MCG) and a secondary cell group (SCG); receive a cell switch command to trigger a lower-layer triggered mobility (LTM) cell switch from the PSCell to a candidate target PSCell; perform the LTM cell switch from the PSCell to the candidate target PSCell during which measurements on the at least one candidate target PCell are suspended; report measurements on the at least one candidate target PCell after the LTM cell switch to the candidate target PSCell is complete; and receive a second cell switch command to trigger an LTM cell switch from the PCell to a candidate target PCell based on the measurements.

[0222] Clause 119. A method comprising: receiving a dual-connectivity radio network service from a primary cell (PCell) of a master node and a primary secondary cell (PSCell) of a secondary node, the PCell and the PSCell in respective ones of a master cell group (MCG) and a secondary cell group (SCG); receiving a cell switch command to trigger a lower-layer triggeredmobility (LTM) cell switch from the PSCell to a candidate target PSCell; performing the LTM cell switch from the PSCell to the candidate target PSCell during which measurements on the at least one candidate target PCell are suspended; reporting measurements on the at least one candidate target PCell after the LTM cell switch to the candidate target PSCell is complete; and receiving a second cell switch command to trigger an LTM cell switch from the PCell to a candidate target PCell based on the measurements.

[0223] Clause 120. The method of clause 119, wherein the cell switch command indicates an LTM candidate configuration associated with the SCG, and performing the LTM cell switch from the PSCell to the candidate target PSCell includes applying the LTM candidate configuration associated with the SCG.

[0224] Clause 121. The method of clause 120, wherein the second cell switch command indicates an LTM candidate configuration associated with the MCG and another LTM candidate configuration associated with the SCG to be concurrently applied during the LTM cell switch from the PCell to a candidate target PCell.

[0225] Clause 125. An apparatus comprising means for performing the method of any of clauses 119 to 121.

[0226] Clause 126. A computer-readable medium comprising instructions that, in response to execution by at least one processing circuitry, causes an apparatus to perform the method of any of clauses 119 to 121.

[0227] Clause 127. A computer-readable storage medium comprising instructions that, in response to execution by at least one processing circuitry, causes an apparatus to perform the method of any of clauses 119 to 121.

[0228] Clause 128. A computer program comprising instructions that, in response to execution by at least one processing circuitry, causes an apparatus to perform the method of any of clauses 119 to 121.

[0229] Many modifications and other implementations of the disclosure set forth herein will come to mind to one skilled in the art to which the disclosure pertains having the benefit of the teachings presented in the foregoing description and the associated figures. Therefore, it is to be understood that the disclosure is not to be limited to the specific implementations disclosed and that modifications and other implementations are intended to be included within the scope of the appended claims. Moreover, although the foregoing description and the associated figures describe example implementations in the context of certain example combinations of elements and / or functions, it should be appreciated that different combinations of elements and / or functions may be provided by alternative implementations without departing from the scope of the appended claims. In this regard, for example, different combinations of elements and / or functions than those explicitly described above are also contemplated as may be set forth in some of theappended claims. Although specific terms are employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation.

Claims

WHAT IS CLAIMED IS:

1. An apparatus comprising: means for providing a radio network service from a primary cell (PCell) of a master node to an user equipment in dual connectivity with a secondary primary cell (PSCell) of a secondary node; means for generating a lower-layer triggered mobility (LTM) candidate cell configuration associated with a master cell group (MCG) including at least one candidate target PCell; means for preparing a message including the LTM candidate configuration for the MCG, and an indication for the secondary node to generate multiple LTM candidate configurations associated with a secondary cell group (SCG) including at least one candidate target PSCell based on the LTM candidate configuration for the MCG; means for sending the message to the secondary node for generation of the multiple LTM candidate configurations; and means for sending a second message including the LTM candidate configuration for the MCG towards the user equipment.

2. The apparatus of claim 1, wherein the master node includes a central unit and a distributed unit, and the second message is sent from the central unit to the distributed unit for relaying to the user equipment, and wherein the second message further includes an indication for the distributed unit to prevent triggering an LTM cell switch to a candidate target PSCell when an LTM cell switch from the PCell to a candidate PCell is indicated.

3. The apparatus of claim 2, wherein the indication is a first indication, and the second message further includes a second indication for the distributed unit to enable triggering the LTM cell switch after the LTM cell switch to the candidate target PCell is complete.

4. The apparatus of any of claims 1 to 3, wherein the second message sent to the user equipment further includes an indication for the user equipment to suspend measurements on the at least one candidate target PCell when an LTM cell switch to a candidate target PSCell is indicated.

5. The apparatus of claim 4, wherein the indication is a first indication, and the second message further includes a second indication for the user equipment to resume the measurements on the at least one candidate target PCell when the LTM cell switch to the candidate target PSCell is complete.

6. The apparatus of any of claims 1 to 5, wherein the second message sent to the user equipment further includes an indication for the user equipment to prevent the user equipment from applying an outdated configuration for the SCG stored in a candidate target PSCell or a complete LTM reference configuration, or when the master node has updated a configuration for the SCG after a PSCell change, prevent the user equipment from overriding the complete LTM reference configuration including the updated configuration for the SCG in the complete LTM reference configuration or LTM candidate configuration with the outdated configuration stored in the candidate target PSCell or the complete LTM reference configuration during an LTM cell switch to a candidate target PCell following LTM cell switch to a candidate target PSCell.

7. An apparatus comprising: means for providing a radio network service from a primary secondary cell (PSCell) of a secondary node to an user equipment in dual connectivity with a primary cell (PCell) of a master node; means for receiving a message from the master node including a lower-layer triggered mobility (LTM) candidate cell configuration associated with a master cell group (MCG) including at least one candidate target PCell; means for generating multiple LTM candidate configurations associated with a secondary cell group (SCG) including at least one candidate target PSCell based on the LTM candidate configuration for the MCG; and means for sending a message including the multiple LTM candidate configurations for the SCG towards the user equipment.

8. The apparatus of claim 7, wherein the multiple LTM candidate configurations that are generated include a PSCell configuration to be applied by the user equipment during a PSCell change to a candidate target PSCell in which no PCell change has been indicated, and respective coverage areas of the PSCell and the candidate target PSCell overlap, such that bearers do not overlap between the PCell and the candidate target PSCell.

9. The apparatus of claim 7 or claim 8, wherein the multiple LTM candidate configurations that are generated include a PSCell configuration to be applied by the user equipment during a PSCell change to a candidate target PSCell after a PCell change to a candidate target PCell in which coverage areas of the candidate target PSCell and the candidate target PCell overlap, such that bearers do not overlap between the candidate target PSCell and the candidate target PCell.

10. The apparatus of any of claims 7 to 9, wherein the multiple LTM candidate configurations that are generated include a reconfiguration of a new serving PSCell to be applied by the user equipment concurrent with a configuration of a candidate target PCell during a PCell change to the candidate target PCell after a PSCell change in which coverage areas of the new serving PSCell and the candidate target PCell overlap, such that bearers do not overlap between the new serving PSCell and the candidate target PCell.

11. The apparatus of claim 7 or claim 10, wherein the multiple LTM candidate configurations that are generated include a reconfiguration of the PSCell to be applied by the user equipment concurrent with a candidate target PCell during a PCell change to the candidate target PCell with no indication of a PSCell change in which coverage areas of the PSCell and the candidate target PCell overlap, such that bearers do not overlap between the PSCell and the candidate target PCell.

12. The apparatus of claim 7 or claim 11, wherein the secondary node includes a central unit and a distributed unit, and the message is sent from the central unit to the distributed unit for relaying to the user equipment, and wherein the message further includes an indication for the distributed unit to prevent triggering an LTM cell switch from the PSCell to a candidate target PSCell when an LTM cell switch to a candidate target PCell is indicated.

13. The apparatus of claim 12, wherein the indication is a first indication, and the message further includes a second indication for the distributed unit to enable triggering the LTM cell switch after the LTM cell switch to the candidate target PCell is complete.

14. The apparatus of any of claims 7 to 13, wherein the message sent to the user equipment further includes an indication for the user equipment to suspend measurements on the at least one candidate target PSCell when an LTM cell switch to a candidate target PCell is indicated.

15. The apparatus of claim 14, wherein the indication is a first indication, and the second message further includes a second indication for the user equipment to resume the measurements on the at least one candidate target PSCell when the LTM cell switch to the candidate target PCell is complete.

16. The apparatus of any of claims 7 to 15, wherein the secondary node includes a central unit and a distributed unit, and the message is sent from the central unit to the distributed unit for storing and selectively relaying one or more of the multiple LTM candidate configurations for the SCG to the user equipment.

17. An apparatus comprising: means for providing a radio network service from a primary secondary cell (PSCell) of a secondary node to an user equipment in dual connectivity with a primary cell (PCell) of a master node; means for receiving signaling from the user equipment that indicates a lower-layer triggered mobility (LTM) cell switch from the PCell to a candidate target PCell in a master cell group (MCG); means for preventing triggering an LTM cell switch from the PSCell to a candidate target PSCell during the LTM cell switch to the candidate target PCell; means for receiving a message that indicates the LTM cell switch to the candidate target PCell is complete; and means for sending a cell switch command to the user equipment to trigger the LTM cell switch from the PSCell to a candidate target PSCell.

18. The apparatus of claim 17, wherein signaling from the user equipment further indicates the LTM cell switch to the candidate target PCell includes a change in an LTM configuration associated with the MCG, and a concurrent change in a configuration associated with the SCG, and wherein the cell switch command sent to the user equipment indicates another LTM candidate configuration associated with the SCG to be applied by the user equipment during the LTM cell switch from the PSCell to a candidate target PSCell.

19. An apparatus comprising: means for receiving a dual-connectivity radio network service from a primary cell (PCell) of a master node and a primary secondary cell (PSCell) of a secondary node, the PCell and the PSCell in respective ones of a master cell group (MCG) and a secondary cell group (SCG); means for receiving a cell switch command to trigger a lower-layer triggered mobility (LTM) cell switch from the PCell to a candidate target PCell; means for performing the LTM cell switch from the PCell to the candidate target PCell during which measurements on the at least one candidate target PSCell are suspended;means for reporting measurements on the at least one candidate target PSCell after the LTM cell switch to the candidate target PCell is complete; and means for receiving a second cell switch command to trigger an LTM cell switch from the PSCell to a candidate target PSCell based on the measurements.

20. The apparatus of claim 19, wherein the cell switch command indicates an LTM candidate configuration associated with the MCG and an LTM candidate configuration associated with the SCG, and wherein the means for performing the LTM cell switch from the PCell to the candidate target PCell includes means for applying the LTM candidate configuration associated with the MCG and the LTM candidate configuration associated with the SCG.

21. The apparatus of claim 20, wherein the second cell switch command indicates another LTM candidate configuration associated with the SCG to be applied during the LTM cell switch from the PSCell to a candidate target PSCell.

22. An apparatus comprising: means for providing a radio network service from a primary cell (PCell) of a master node to an user equipment in dual connectivity with a primary secondary cell (PSCell) of a secondary node; means for receiving signaling from the user equipment that indicates a lower-layer triggered mobility (LTM) cell switch from the PSCell to a candidate target PSCell in a secondary cell group (MCG); means for preventing triggering an LTM cell switch from the PCell to a candidate target PCell during the LTM cell switch to the candidate target PSCell; means for receiving a message that indicates the LTM cell switch to the candidate target PSCell is complete; and means for sending a cell switch command to the user equipment to trigger the LTM cell switch from the PCell to a candidate target PCell.

23. The apparatus of claim 22, wherein the message further indicates an LTM configuration associated with the SCG applied by the user equipment during the LTM cell switch to the candidate target PSCell, and wherein the cell switch command sent to the user equipment indicates an LTM candidate configuration associated with the MCG and another LTM candidate configuration associated with the SCG to be concurrently applied by the user equipment during the LTM cell switch from the PCell to a candidate target PCell.

24. An apparatus comprising: providing means for receiving a dual -connectivity radio network service from a primary cell (PCell) of a master node and a primary secondary cell (PSCell) of a secondary node, the PCell and the PSCell in respective ones of a master cell group (MCG) and a secondary cell group (SCG); means for receiving a cell switch command to trigger a lower-layer triggered mobility (LTM) cell switch from the PSCell to a candidate target PSCell; means for performing the LTM cell switch from the PSCell to the candidate target PSCell during which measurements on the at least one candidate target PCell are suspended; means for reporting measurements on the at least one candidate target PCell after the LTM cell switch to the candidate target PSCell is complete; and means for receiving a second cell switch command to trigger an LTM cell switch from the PCell to a candidate target PCell based on the measurements.

25. The apparatus of claim 24, wherein the cell switch command indicates an LTM candidate configuration associated with the SCG, and the means for performing the LTM cell switch from the PSCell to the candidate target PSCell includes means for applying the LTM candidate configuration associated with the SCG.

26. The apparatus of claim 25, wherein the second cell switch command indicates an LTM candidate configuration associated with the MCG and another LTM candidate configuration associated with the SCG to be concurrently applied during the LTM cell switch from the PCell to a candidate target PCell.

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