Enhancements for l1 measurements / reporting and beam switching for target cells with carrier aggregation

Abstract

The embodiments disclose a method for measurement and reporting enhancements for lower layer triggered mobility (LTM) scenarios with carrier aggregation. A user equipment (UE) receives configuration information from a source distributed unit (DU), based on which the UE is configured to perform layer 1(E1) measurement of a secondary cell (SCell) among one or more candidate cell groups. Based on the measurement of the SCell, the source DU transmits a LTM switching command to the UE so that the UE switches to the beams of the SCell. Prior to switching to the beams of the SCell, the UE receives a Medium Access Control (MAC) Control Element (CE) activating the transmission configuration indicator (TCI) state of the SCell.

Description

[0001] ENHANCEMENTS FOR LI MEASUREMENTS / REPORTING AND BEAM

[0002] SWITCHING FOR TARGET CELLS WITH CARRIER AGGREGATION

[0003] Technical Field:

[0004] Various example embodiments of the present disclosure relate to the field of telecommunication, and more particularly relate to enhancements for Layer 1 (LI) measurement / reporting and beam switching for target cells with carrier aggregation. Background:

[0005] Certain abbreviations that may be found in the description and / or in the figures are herewith defined as follows.

[0006] 5G NR 5thGeneration New Radio

[0007] CU Central Unit

[0008] DU Distributed Unit eNB Evolved Node B gNB Next Generation Node B

[0009] LIE Long Term Evolution

[0010] LIE -A Long Term Evolution Advanced

[0011] LTM Lower layer triggered switching or Layer 1 / Layer 2 triggered mobility

[0012] MAC Medium Access Control

[0013] MCG Master Cell Group

[0014] PCell Primary Cell

[0015] PDCCH Physical downlink control channel

[0016] PSCell Primary Secondary Cell

[0017] SCell Secondary Cell

[0018] SCG Secondary Cell Group SpCell Special Cell

[0019] SSB Synchronization Signal Block

[0020] TCI Transmission Configuration Indicator

[0021] UE User Equipment

[0022] In a wireless communication network, there may be regions of radio coverage (referred to as a “cell”). Each cell may be supported by a network node (e.g., a base station). A user equipment may have a source cell, wherein it is associated with a network node (i.e., source network node) serving the source cell. When the cell quality of the source cell drops below a threshold, when compared to the cell quality of a target cell, the UE may undergo a mobility procedure to the target cell. The ability for a UE to communicate effectively with the wireless communication system as it moves through cells, is typically referred to as mobility. 3 GPP (Third Generation Partnership Project) Release 18 (Rel-18) introduced Layer 1 (LI) or Layer 2 (L2) mobility, also referred to as lower- layer triggered mobility (LTM), for reducing the latency, overhead, and interruption time associated with a UE moving between the different cells. In Rel-18 LTM switching procedure, the UE sends an LI measurement report of the target cell(s) to its serving cell, and based on the LI measurement report, the serving cell transmits a LTM switching command to the UE, indicating which target cell should be used for cell change.

[0023] Carrier aggregation (CA) is a technique where cells can be combined to enable a user equipment to achieve higher data rates. In CA there may be one or more cell groups, wherein each cell group comprises a primary cell (PCell) (i.e., the cell operating on a primary frequency) and at least one secondary cell (SCell) (i.e., the cell operating on a secondary frequency). Even though Rel-18’s objectives include LTM for CA, it is currently restricted to (1) LI measurements of PCells and (2) indication of beam switching for PCell only. In other words, in Rel-18, LI measurement of SCells and indication of beam switching for SCells is not considered. Summary:

[0024] According to some aspects, there is provided the subject matter of independent claims. Some embodiments are defined in the dependent claims.

[0025] In a first aspect of the present disclosure, there is provided a method comprising: receiving, from a source network node serving a user equipment (UE), a higher layer message for a mobility procedure, the higher layer message comprising lower layer triggered mobility (LTM) configuration information, including an indication to differentiate at least one SCell in each candidate cell group, among one or more candidate cell groups, from each other, wherein each candidate cell group comprises a primary cell (PCell) and the at least one secondary cell (SCell); performing a LI measurement of the PCell in each candidate cell group based on the configuration information; sending, to the source network node, a first measurement report of the LI measurement of the PCell in each candidate cell group; receiving, from the source network node, a Medium Access Control (MAC) Control Element (CE) to activate layer 1 (LI) measurement of at least one SCell of a target cell group, among the one or more candidate cell groups, based on the first measurement report; performing the LI measurement of the at least one SCell of the target cell group based on the MAC CE and the configuration information; and sending, to the source network node, a second measurement report of the LI measurement of the at least one SCell.

[0026] In a second aspect of the present disclosure, there is provided a method comprising: receiving, from a source network node serving a user equipment, a higher layer message for a mobility procedure, the higher layer message comprising: lower layer triggered mobility (LTM) configuration information of one or more candidate cell groups, wherein each candidate cell group comprises a primary cell (PCell) and at least one secondary cell (SCell); and a selection criteria for the measurement of the at least one SCell associated with the PCell in each candidate cell group; performing a LI measurement of the PCell in each candidate cell group based on the configuration information; sending, to the source network node, a first measurement report of the LI measurement of the PCell in each candidate cell group; determining a subset of PCells comprising the PCell in each candidate cell group that meets the selection criteria, based on the first measurement report; performing a LI measurement of the at least one SCell associated with the subset of PCells; and sending, to the source network node, a second measurement report of the LI measurement of the at least one SCell associated with the subset of PCells.

[0027] In a third aspect of the present disclosure, there is provided a method comprising: receiving, from a source network node serving a user equipment, a higher layer message for a mobility procedure, the higher layer message comprising lower layer triggered mobility (LTM) configuration information of one or more candidate cell groups, wherein each candidate cell group comprises a primary cell (PCell) and at least one secondary cell (SCell); performing a LI measurement of the PCell in each candidate cell group based on the configuration information; sending, to the source network node, a first measurement report of the LI measurement of the PCell in each candidate cell group; determining that the PCell of a target cell group, among the one or more candidate cell groups, has the best beam among the PCell in each candidate cell group, based on the first measurement report; performing a LI measurement of the at least one SCell of the target cell group based on the configuration information; and sending, to the source network node, a second measurement report of the LI measurement of the at least one SCell of the target cell group.

[0028] In a fourth aspect of the present disclosure, there is provided a method comprising: receiving, from a source network node serving a user equipment, a higher layer message for a mobility procedure, the higher layer message comprising lower layer triggered mobility (LTM) configuration information of one or more candidate cell groups, wherein each candidate cell group comprises a primary cell (PCell) and at least one secondary cell (SCell) associated with the PCell; performing a LI measurement of the PCell and its associated at least one SCell from the one or more candidate cell groups, based on the configuration information; and sending, to the source network node, a first measurement report of the LI measurement of the PCell and its associated at least one SCell from the one or more candidate cell groups. In a fifth aspect of the present disclosure, there is provided a method comprising: receiving, from a source network node serving a user equipment, a higher layer message for a mobility procedure, the higher layer message comprising lower layer triggered mobility (LTM) configuration information of one or more candidate cell groups, wherein each candidate cell group comprises a primary cell (PCell) and at least one secondary cell (SCell) associated with the PCell; performing a LI measurement of the PCell from the each candidate cell group, based on the configuration information; sending, to the source network node, a first measurement report of the LI measurement of the PCell from each candidate cell group; performing a LI measurement of the at least one SCell from each candidate cell group, based on the configuration information; and sending, to the source network node, a second measurement report of the LI measurement of the at least one SCell from each candidate cell group. The method comprises sending the first measurement report as a MAC CE. In the method, the source network node includes a flag when preparing each candidate cell group for beam indication of its least one SCell. The method may comprise: receiving an LTM switching signal comprising a TCI state list comprising at least one TCI state that is mapped to the at least one SCell of a target cell group, among the one or more candidate cell groups; and applying the TCI state for the at least one SCell of the target cell group based on the mapping in the TCI state list. The method may comprise: receiving a MAC CE for activating the TCI state of the at least one SCell of the target cell group, wherein the MAC CE comprises the index of the at least one SCell; and receiving a LTM switching signal comprising the index of the at least one SCell whose TCI state is activated. The MAC CE comprises: an index of the target cell group; and a bitmap of the at least one SCell.

[0029] In a sixth aspect of the present disclosure, there is provided a user equipment comprising: at least one memory; and at least one processor operatively coupled to the at least one memory, wherein the at least one processor is configured to cause the apparatus to: receive, from a source network node serving the UE, a higher layer message for a mobility procedure, the higher layer message comprising lower layer triggered mobility (LTM) configuration information, including an indication to differentiate at least one secondary cell (SCell) of each candidate cell group, among one or more candidate cell groups, wherein each candidate cell group comprises a primary cell (PCell) and the at least SCell; perform a LI measurement of the PCell in each candidate cell group based on the configuration information; send, to the source network node, a first measurement report of the LI measurement of the PCell in each candidate cell group; receive, from the source network node, a Medium Access Control (MAC) Control Element (CE) to activate layer 1 (LI) measurement of at least one SCell of a target cell group among the one or more candidate cell groups, based on the first measurement report; perform the LI measurement of the at least one SCell of the target cell group based on the MAC CE and the configuration information; and send, to the source network node, a second measurement report of the LI measurement of the at least one SCell.

[0030] In a seventh aspect of the present disclosure, there is provided a user equipment comprising: at least one memory; and at least one processor operatively coupled to the at least one memory, wherein the at least one processor is configured to cause the apparatus to: receive, from a source network node serving the UE, a higher layer message for a mobility procedure, the higher layer message comprising: lower layer triggered mobility (LTM) configuration information of one or more candidate cell groups, wherein each candidate cell group comprises a primary cell (PCell) and at least one secondary cell (SCell); and a selection criteria for the measurement of the at least one SCell associated with the PCell in each candidate cell group; perform a LI measurement of the PCell in each candidate cell group based on the configuration information; send, to the source network node, a first measurement report of the LI measurement of the PCell in each candidate cell group; determine a subset of PCells comprising the PCell in each candidate cell group that meets the selection criteria, based on the first measurement report; perform a LI measurement of the at least one SCell associated with the subset of PCells; and send, to the source network node, a second measurement report of the LI measurement of the at least one SCell associated with the subset of PCells.

[0031] In an eight aspect of the present disclosure, there is provided a user equipment comprising: at least one memory; and at least one processor operatively coupled to the at least one memory, wherein the at least one processor is configured to cause the apparatus to: receive, from a source network node serving the UE, a higher layer message for a mobility procedure, the higher layer message comprising lower layer triggered mobility (LTM) configuration information of one or more candidate cell groups, wherein each candidate cell group comprises a primary cell (PCell) and at least one secondary cell (SCell); perform a LI measurement of the PCell in each candidate cell group based on the configuration information; send, to the source network node, a first measurement report of the LI measurement of the PCell in each candidate cell group; determine that the PCell of a target cell group, among the one or more candidate cell groups, has the best beam among the PCell in each candidate cell group, based on the first measurement report; perform a LI measurement of the at least one SCell of the target cell group based on the configuration information; and send, to the source network node, a second measurement report of the LI measurement of the at least one SCell of the target cell group.

[0032] In a ninth aspect of the present disclosure, there is provided a user equipment comprising: at least one memory; and at least one processor operatively coupled to the at least one memory, wherein the at least one processor is configured to cause the UE to: receive, from a source network node serving the UE, a higher layer message for a mobility procedure, the higher layer message comprising lower layer triggered mobility (LTM) configuration information of one or more candidate cell groups, wherein each candidate cell group comprises a primary cell (PCell) and at least one secondary cell (SCell) associated with the PCell; perform a LI measurement of the PCell and its associated at least one SCell from the one or more candidate cell groups, based on the configuration information; and send, to the source network node, a first measurement report of the LI measurement of the PCell and its associated at least one SCell from the one or more candidate cell groups.

[0033] In a tenth aspect of the present disclosure, there is provided a user equipment comprising: at least one memory; and at least one processor operatively coupled to the at least one memory, wherein the at least one processor is configured to cause the UE to: receive, from a source network node serving a user equipment, a higher layer message for a mobility procedure, the higher layer message comprising lower layer triggered mobility (LTM) configuration information of one or more candidate cell groups, wherein each candidate cell group comprises a primary cell (PCell) and at least one secondary cell (SCell) associated with the PCell; perform a LI measurement of the PCell from the each candidate cell group, based on the configuration information; send, to the source network node, a first measurement report of the LI measurement of the PCell from each candidate cell group; perform a LI measurement of the at least one SCell from each candidate cell group, based on the configuration information; and send, to the source network node, a second measurement report of the LI measurement of the at least one SCell from each candidate cell group. In the method, the UE sends the second measurement report as a MAC CE. In the tenth aspect, the source network node includes a flag when preparing each candidate cell group for beam indication of its least one SCell. In the tenth aspect, the at least one processor in the UE is configured to cause the UE to: receive an LTM switching signal comprising a TCI state list comprising at least one TCI state that is mapped to the at least one SCell of a target cell group, among the one or more candidate cell groups; and apply the TCI state for the at least one SCell of the target cell group based on the mapping in the TCI state list. In the tenth aspect, the at least one processor in the UE is configured to cause the UE to: receive a MAC CE for activating the TCI state of the at least one SCell of the target cell group, wherein the MAC CE comprises the index of the at least one SCell; and receive a LTM switching signal comprising the index of the at least one SCell whose TCI state is activated. In the tenth aspect, the MAC CE comprises: an index of the target cell group; and a bitmap of the at least one SCell.

[0034] Brief Description of Drawings:

[0035] In the following, various exemplary embodiments will be described in greater detail with reference to the accompanying drawings, in which:

[0036] FIG. 1 illustrates a message sequence chart for Rel-18 LTM procedure for a primary cell;

[0037] FIGs. 2A and 2B illustrate an LTM carrier aggregation scenario for different operating frequencies for a secondary cell; FIG. 3 illustrates a message sequence chart including measurement and reporting enhancements for a target secondary cell, according to an example embodiment of the present disclosure herein;

[0038] FIG. 4 illustrates a message sequence chart including transmission configuration indicator (TCI) state switching enhancements for a target secondary cell, according to an example embodiment of the disclosure herein;

[0039] FIGs. 5A to 5B illustrate a method for a first aspect of measurement enhancement of a target secondary cell, according to an example embodiment of the disclosure herein;

[0040] FIGs. 6A to 6B illustrate a method for a second aspect of measurement enhancement of a target secondary cell, according to an example embodiment of the disclosure herein;

[0041] FIGs. 7A to 7B illustrate a method for a third aspect of measurement enhancement of a target secondary cell, according to an example embodiment of the disclosure herein;

[0042] FIG. 8 illustrates a method for a fourth aspect of measurement enhancement of a target secondary cell, according to an example embodiment of the disclosure herein;

[0043] FIG. 9 illustrates a method for a fifth aspect of measurement enhancement of a target secondary cell, according to an example embodiment of the disclosure herein;

[0044] FIG. 10 illustrates a method for a preparation phase of TCI state switching enhancement of a target secondary cell, according to an example embodiment of the disclosure herein;

[0045] FIG. 11 illustrates a method for a execution phase of TCI state switching enhancement of a target secondary cell, according to an example embodiment of the disclosure herein; FIG. 12 illustrates a method for another execution phase of TCI state enhancement of a target secondary cell, according to an example embodiment of the disclosure herein; and

[0046] FIG. 13 illustrates a device that is suitable for implementing example embodiments of the disclosure herein.

[0047] Detailed Description

[0048] Example embodiments now will be described with reference to the accompanying drawings. The invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this invention will be thorough and complete, and will fully convey its scope to those skilled in the art. The terminology used in the detailed description of the example embodiments illustrated in the accompanying drawings is not intended to be limiting. In the drawings, like numbers refer to like elements.

[0049] The specification may refer to “an”, “one” or “some” embodiment(s) in several locations. This does not necessarily imply that each such reference is to the same embodiment(s), or that the feature only applies to a single embodiment. Single features of different embodiments may also be combined to provide other embodiments. As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless expressly stated otherwise. It will be further understood that the terms “includes”, “comprises”, “including” and / or “comprising” when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and / or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof. In other words, the terms “includes”, “comprises”, “including” and / or “comprising” is to be understood as being open-ended. As used herein, whenever the phrase “at least one of the following” precedes a list of elements, wherein the elements are joined by “and” or “or”, it means that at least any one of the elements or at least all the elements are present. As used herein, the term “and / or” includes any and all combinations and arrangements of one or more of the associated listed items.

[0050] Conditional language — such as “can” or “may” — among others, unless specifically stated otherwise, or otherwise understood within the context as used, is generally intended to convey that certain embodiments could include, while other embodiments may not include certain features, elements, and / or steps. Thus, such conditional language is not generally intended to imply that features, elements, and / or steps are in any way required for one or more embodiments. It will be understood that when an element is referred to as being “connected” or “coupled” to another element, it can be directly connected or coupled to the other element or intervening elements may be present. Furthermore, “connected” or “coupled” as used herein may include wirelessly connected or coupled.

[0051] Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.

[0052] The figures depict a simplified structure only showing some elements and functional entities, all being logical units whose implementation may differ from what is shown. The connections shown are logical connections; the actual physical connections may be different. In addition, all logical units described and depicted in the figures include the software and / or hardware components required for the unit to function. Further, each unit may comprise within itself one or more components, which are implicitly understood. These components may be operatively coupled to each other and be configured to communicate with each other to perform the function of the said unit. As used herein, the term “circuitry” may refer to at least one 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.

[0053] This 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 / or firmware. 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.

[0054] Before explaining in detail, the example embodiments of the present disclosure, certain general principles of a wireless communication system and mobile communication devices are briefly explained with reference to FIG. 1 to assist in understanding the technology underlying the described examples.

[0055] In the following, different exemplifying embodiments will be described using, as an example of a communication network to which examples of embodiments may be applied, a communication network architecture based on 3GPP standards for a communication network, such as 5G NR, without restricting the embodiments to such an architecture, however. It is apparent for a person skilled in the art that the embodiments may also be applied to other kinds of communication networks where mobile communication principles are integrated with a D2D (device-to-device) or V2X (vehicle to everything) configuration, such as SL (sidelink), e.g., Wi-Fi, worldwide interoperability for microwave access (WiMAX), Bluetooth, personal communications services, ZigBee, wideband code division multiple access (WCDMA), systems using ultra-wideband (UWB) technology, mobile ad-hoc networks (MANETs), wired access etc. Furthermore, without loss of generality, the description of some examples of embodiments is related to a mobile communication network, but principles of the disclosure can be extended and applied to any other type of communication network, such as a wired communication network.

[0056] A basic system architecture of a (tele)communication network including a mobile communication system where some examples embodiments are applicable may include an architecture of one or more communication networks including wireless access network subsystem(s) and core network(s). Such an architecture may include one or more communication network control elements or functions, access network elements, radio access network elements, access service network gateways or network nodes, such as a base station (BS), an access point (AP), a NodeB (NB), an eNB or a gNB, a distributed unit (DU) or a centralized / central unit (CU), which controls a respective coverage area or cell(s) and with which one or more communication stations such as communication elements or functions, like user devices or terminal devices, like a user equipment (UE), or another device having a similar function, such as a modern chipset, a chip, a module etc., which can also be part of a station, an element, a function or an application capable of conducting a communication, such as a UE, an element or function suable in a machine-to-machine communication architecture, or attached as a separate element to such an element, function or application capable of conducting a communication, or the like, are capable to communicate via one or more channels via one or more communication beams for transmitting several types of data in a plurality of access domains. Furthermore, core network elements or network functions, such as gateway network elements / functions, mobility management entities, a mobile switching center, servers, databases and the like, may be included. The UE can be any device that is capable of sending and receiving radio signals. Non-limiting examples of the UE comprise a mobile station (MS) or mobile device such as a mobile phone or what is known as a ’smart phone’, a computer provided with a wireless interface card or other wireless interface facility (e.g., USB dongle), personal data assistant (PDA) or a tablet provided with wireless communication capabilities, machine type devices or any combinations of these or the like.

[0057] The network node can comprise a processor and associated circuitry to execute or direct the execution of computer-readable instructions to perform operations such as those further described herein. Briefly, the network node can retrieve and execute software from storage, which can include a disk drive, a flash drive, memory circuitry, or some other memory device, and which can be local or remotely accessible. The software may comprise computer programs, firmware, or some other form of machine-readable instructions, and may include an operating system, utilities, drivers, network interfaces, applications, or some other type of software, including combinations thereof. Further, the network node can receive instructions and other input at a user interface.

[0058] A gNB Central Unit (gNB-CU) comprises e.g., a logical node hosting e.g., RRC (Radio Resource Layer), SDAP (Service Data Adaptation Protocol) and PDCP (Packet Data Convergence Protocol) protocols of the gNB or RRC and PDCP protocols of the en-GNB that controls the operation of one or more gNB-DUs (gNB Distributed Units). The gNB-CU terminates the Fl interface connected with the gNB-DU. For the sake of simplicity, and because the embodiments disclosed herein may be applicable to an evolution system subsequent to the 5G NR system, the gNB-CU may be referred to as CU.

[0059] A gNB Distributed Unit (gNB-DU) comprises e.g., a logical node hosting e.g., RLC (Radio Link Control), MAC (Medium Access Control) and PHY (Physical) layers of the gNB or en-gNB, and its operation is partly controlled by the gNB-CU. One gNB-DU supports one or multiple cells. One cell is supported by only one gNB-DU. The gNB-DU terminates the Fl interface connected with the gNB-CU. A gNB-DU may support one or multiple cells, and could thus serve as, for example, a serving cell for a UE. The gNB CU and gNB DU parts may, for example, be co-located or physically separated. For the sake of simplicity, and because the embodiments disclosed herein may be applicable to an evolution system subsequent to the 5G NR system, the gNB-DU may be referred to as source DU or target DU.

[0060] The technical scheme described in the embodiment of the application can be applied to a 5GNR system and also can be applied to a subsequent evolution system of the 5G NR system.

[0061] In this specification, a cell may refer to a component carrier having coverage of a signal transmitted from a transmission / reception point or a coverage of a signal transmitted from a transmission / reception point.

[0062] In this specification, a candidate cell may refer to the cell that the UE considers for undergoing lower layer triggered mobility (LTM). A target cell may refer to the cell that the UE switches to via a LTM switching command.

[0063] In this specification, a source cell and a serving cell may be used synonymously. Similarly, a source network node and a serving network node may be used synonymously.

[0064] FIG. 1 illustrates a message sequence chart for Rel-18 LTM procedure for a primary cell. At step 1, using the RRC (Radio Resource Control) configuration in the UE, the UE generates and transmits a layer 3 (L3) measurement report of at least one candidate cell to the source DU. The at least one candidate cell includes a target cell that the UE may be handed over to by the source DU.

[0065] At step 2, the source DU forwards the L3 measurement report to the CU via uplink RRC message transfer. At step 3, the CU prepares the at least one candidate cell for LTM, based on the L3 measurement report. At steps 4 and 5, the CU initiates the preparation procedure of the at least one candidate cell under the DU, where the target DU can also be the source DU (i.e., the source cell and the target cell belong to the same DU).

[0066] At steps 6 and 7, the CU and source DU proceed with the UE context modification procedure for further configuration details to be collected by the CU for LTM preparation procedure.

[0067] At step 8, the CU generates the RRC reconfiguration for the at least one candidate cell that has been prepared for LTM. The RRC configuration can include measurement and reporting configuration information of the at least one candidate cell as well as the RRC reconfiguration of the at least one candidate cell to be applied on the UE upon triggering cell change to the target cell.

[0068] At steps 9 to 12, the CU provides the UE with the RRC reconfiguration via the source DU for the at least one candidate cell that is prepared, and also receives an acknowledgement (by the UE) of the RRC reconfiguration reception.

[0069] At step 13, the UE starts reporting the layer 1 (LI) measurement of the at least one candidate cell based on the RRC reconfiguration. For the sake of simplicity, FIG. 1 illustrates only a single instance of LI measurement reporting taking place. However, when there are multiple candidate cells, there may be multiple instances LI measurement reporting occurring (e.g., periodic reporting).

[0070] At step 14, based on the LI measurement of the at least one candidate cell, the source DU determines the target cell that the UE is to be handed over to. As a result, the source DU triggers a timing advance (TA) acquisition of the target cell so that the UE can synchronize with the target cell.

[0071] At step 15, once the UE is triggered with the TA acquisition of the target cell, the UE may pause any transmission / reception (TX / RX) with the serving cell (source DU and CU), to send the PRACH (physical random access channel) preamble to the target cell. In case RF tuning is required (e.g., the target cell operates at a different carrier frequency), then the UE also tunes its RF before sending the PRACH preamble towards the target cell.

[0072] At step 16, the UE transmits the PRACH preamble to the target cell. At step 17, the UE tunes its RD back to the source cell (if needed) and resumes the TX / RX with the source cell.

[0073] At step 18, the UE continues with the LI measurement reporting as of step 13.

[0074] At step 19, the source DU decides to trigger the cell change to the target cell and sends the MAC (Medium Access Control) CE (Control Element) to trigger the UE to initiate the LTM towards the target cell. The MAC CE may include the TA of the target cell, which may have been obtained through the TA acquisition procedure.

[0075] At step 20 and 21, if the UE does not have the uplink timing synchronization of the target cell, the UE initiates the RACH procedure towards the target cell. At step 22, the UE and the network will proceed with the completion of the LTM procedure.

[0076] Broadly speaking, for Ll / L2-triggered mobility (LTM), the UE reports LI beam measurements to the source DU, and the source DU can decide when to trigger the mobility procedure to the target cell included in the LI measurement report. This LI measurement report may be based on previous L3 measurement values provided by the UE to indicate one or more candidate cells as being suitable to the UE for switching to.

[0077] FIGs. 2A and 2B illustrate an LTM carrier aggregation scenario for different operating frequencies for a secondary cell. In case of carrier aggregation in single connectivity, the UE may be served by a cell group (CG) which can comprise a primary cell (PCell) and at least one secondary cell (SCell). For the sake of simplicity, FIGs. 2A and 2B illustrate only a single SCell. FIG. 2A illustrates a carrier aggregation scenario where the target SCell (i.e., the SCell associated with the target PCell) and the source SCell are on the same operating frequency. The source PCell and the target PCell are also on the same operating frequency.

[0078] FIG. 2B illustrates a carrier aggregation scenario where the source PCell and the target PCell are on the same operating frequency. However, the source SCell and the target SCell are on different operating frequencies.

[0079] For the scenario illustrated in FIG. 2B, when it comes to LTM, there may be changes in the throughput during dynamic switching, for the which the embodiments disclosed herein seek to avoid.

[0080] Additionally, as can be seen from FIG. 1 Rel-18 LTM overview, the measurement and reporting of SCells are not considered. Nonetheless, even if measurement and reporting of SCells could take place, there are issues present in the current LTM framework, for which the example embodiments disclosed herein provide a solution for.

[0081] Issue#l : LI measurement of SCells

[0082] When UE operates with an SCell (in carrier aggregation), overall interruption may be improved when the beam-specific switching is used for SCells along with PCell. However, the UE may be having a capability that limits the number of beams that the UE can measure for LTM. With the inclusion of SCell beams for measurement, the UE capability may be exceeded. In other words, the UE may have a threshold number of beams that it can measure, and if the UE were to measure the SCell beams along with the PCell beams, the threshold number could be exceeded.

[0083] Moreover, as per current LI measurement framework, when the UE is to measure more candidate cell beams, the UE is to then be configured with additional beam locations for each candidate cell that is to be measured. Also, associated reporting configurations, where the UE reports these measurements using separate uplink PUCCH / PUSCH resources, may also need to be configured. This extension of existing mechanism for SCell measurements, along with PCell, and reporting them simultaneously via multiple reports may be resource inefficient in terms of reporting resources and UE measurement processing.

[0084] Issue#2: LTM beam switching indication for SCells

[0085] Currently, in the LTM framework, the LTM switching command only supports indication of beam switching of PCells. Inclusion of TCI states (beam indication) for SCells in an efficient manner with minimum signaling overhead is desirable.

[0086] An overarching solution for overcoming the problem outlined in Issue#l can be that beam-based switching is not needed for all SCells of all PCells. In other words, the UE may consider beambased switching for only those SCells that are associated with the candidate PCells (including the target PCell). Hence, LI measurements may be needed for only a subset of SCells dynamically depending on the traffic and radio-condition situations.

[0087] PIG. 3 illustrates a message sequence chart including measurement and reporting enhancements for a target secondary cell, according to some example embodiments of the present disclosure herein. The example embodiments illustrated in FIG. 3 provide multiple related solutions to the above-mentioned Issue#l with more specificity.

[0088] Moving onto the description of FIG. 3, at step 1, the UE may be in RRC CONNECTED mode with the serving cell at the source DU. At step 2, the UE may indicate its capability to store additional LI measurement resource (synchronization signal block (SSB)) configuration and / or support for dynamically performing / starting LI measurements for SCells (associated with the candidate PCells). Using the current RRC configuration, the UE may be able to perform an L3 measurement of the signals of the candidate cell groups. These signals can be reference signals (RS). At step 3, the UE may transmit the L3 measurement report to the CU, which receives it via the source DU.

[0089] At steps 4 to 6, based on the L3 measurement report, the CU may decide that the candidate cell groups are to be prepared for LTM. The CU may send a UE context setup request to the target DU(s). The CU may coordinate with the serving DU, using a UE context modification procedure to share the candidate cell groups configuration.

[0090] At step 7, the UE may receive from the CU via the source DU, RRC reconfiguration including LTM-RS configuration of the candidate cell groups (the PCell(s) and its associated SCell). This can also include the measurement and reporting configuration (for LI measurement) of the SCells. In an example embodiment, the measurement and reporting configuration can include a flag (or indication) to differentiate the SCells and its binding (i.e., its association) to the PCells. In other words, this flag (or indication) is included in the configuration for LTM LI measurement.

[0091] At step 8, which is related to informing the prepared LI -measurement configurations including PCells and SCells to the source DU, the CU may inform the prepared LI -measurement configuration (as part of the RRC reconfiguration) including reference signals of the PCell and SCells of each candidate cell group to the source DU. The source DU can use this information to process the received LI measurement reports including PCell and SCells of each candidate cell group.

[0092] At steps 9 to 13, which relate to a first aspect of measurement enhancement (i.e., a solution to Issue#l), the UE may transmit an LI measurement report of the candidate PCells (i.e., PCell of each candidate cell group) to the source DU. Based on the LI measurement report of the candidate PCells, the source DU may transmit a Medium Access Control (MAC) Control Element (CE) to activate the LI measurement of the SCells. The MAC CE may include a cell index (of the target PCell and its associated SCells). The UE may identify the SCells with the help of the flag / indication in the measurement and reporting configuration to differentiate between the SCells and its binding to the PCell. The MAC CE may also include specific reference signal configs to be activated for measurement of the target SCells (i.e., SCells of the target cell group). On activation of the target SCells measurement, the UE may start measuring the reference signals of the SCells that are associated with the cell index in the MAC CE. Accordingly, the UE transmits an LI measurement report of the SCells to the source DU.

[0093] At steps 14 to 17, which relate to a second aspect of measurement enhancement (i.e., a solution to Issue#l), the UE may decide to perform LI measurements of only those SCells that are associated with a PCell meeting a selection criteria. In other words, the UE may start SCell measurements for those SCells associated with a subset of candidate PCells. The selection criteria may be configured via RRC, such as valid timing advance (TA) and / or radio-condition or a TCI state activation. In some example embodiments, the activation of measurement resources may be commanded by the network prior to the UE actually starting to perform the measurements. In one example embodiment, the UE may be configured via RRC / MAC to initiate (additional) SCell measurements for SCells associated with a target PCell for which the TA acquisition procedure is performed (or for which the TA is acquired, for example, via uplink transmission / UE-based TA acquisition prior to ell switch). In another example embodiment, the radio condition may that the candidate PCell has been reported by the UE in the LI measurement report, or that the SCells that are measured are associated with those PCells that have a cell quality (measured in dB) within a threshold range of current serving PCell. In another example embodiment, for TCI state activation, if the UE receives activation of a TCI state for a target LTM PCell prior to the PCell switch, the UE may start the measurements of those SCells that are associated with the PCell whose TCI state is activated.

[0094] At steps 18-21, which relate to a third aspect of measurement reporting enhancement (i.e., a solution to Issue#l), the UE may perform SCell measurements of those SCells associated with the PCell having the highest reported beam. In other words, at step 19, on transmitting the LI measurement report of the candidate PCells, the UE, at step 20, may decide to perform an LI measurement of those SCells associated with the PCell listed in the measurement report as having the best beam. Accordingly, at step 21, the UE may transmit the LI measurement of those SCells to the UE.

[0095] At steps 22-23, which relate to a fourth aspect of measurement reporting enhancement (i.e., a solution to Issue#l), the UE may send a single measurement report that includes the LI measurements of the candidate PCells and its associated SCells. In others, the UE may send a single measurement report that combines the measurements of the candidate PCells and its associated SCells. In Rel-18, the primary report may include N candidate cells and M beams from each candidate cell, thereby resulting in a total of (N*M) beams that are reported in a reporting instance. The UE may be configured to replace of the N Cells (i.e., N PCells) with SCell-beams with corresponding M beams measurement values. In this case, a single measurement report can include the best PCell(s) and corresponding SCells. For example, one PCell with the strongest beam among all the candidate PCells and the remaining (N-l) SCells associated with the PCell may be considered for reporting. In another example, the top two PCells with the strongest beams among all the candidate PCells and then (N-l) / 2 SCells associated with each of the PCells may be considered for reporting.

[0096] At step 24, which relates to a fifth aspect of measurement reporting enhancement (i.e., a solution to Issue#l), the UE may perform the LI measurements of the SCells associated with the candidate PCells, and transmit the LI measurement report in the form of a MAC CE. This can help in avoiding LI reporting overhead. In an example embodiment, the reporting triggering condition may be configured, for example, based on the quality of the SCell and / or the PCell that it is associated with.

[0097] FIG. 4 illustrates a message sequence chart including transmission configuration indicator (TCI) state switching enhancements for a target secondary cell, according to an example embodiment of the disclosure herein. The example embodiments in FIG. 4 describe the solutions to Issue#2. For the sake of brevity, the description of steps 1 to 3 is omitted as it was previously disclosed herein.

[0098] At step 4, which can be considered as a preparation phase for the TCI state switching, the CU can include a flag ‘secondary-cell beam switch’ when preparing the candidate cells for beam indication for SCells. The target DU can indicate the TCI states which are common for a group of SCells. This may be done in the form of a list comprising a mapping of the SCells with its TCI state. The CU may inform the source DU of additional TCI states and its mapping to the list of SCells. In other words, for each target cell group, there may be a set of TCI states for the PCell that maps to each beam of the PCell. For the at SCells in the target cell group, multiple SCells may have same coverage, where there may be a single TCI state list for those SCells having the same coverage.

[0099] At step 5, the RRC reconfiguration message can include the list having the mapping of the TCI states to the SCells, for each candidate PCell.

[0100] At step 6, the UE may transmit the LI measurement report of the candidate PCells to the source DU. At step 7, the UE may transmit the LI measurement report of the SCell for a TCI group.

[0101] At step 8, which can be considered as a first execution phase for the TCI state switching enhancement, the UE may receive an LTM switching command (also referred to as “LTM switching signal”) from the source DU. The LTM switching command can include ‘additional TCI- list’ for SCells as a new MAC CE or as an extension of the LTM switching command. Based on the mapping in the TCI state list, the UE may be able to identify the SCell corresponding to the TCI state. It is to be noted that the UE may receive the LTM switching command (as a MAC level message carrying a set of bits) or the LTM switching signal (as a physical layer signal).

[0102] At step 9, the UE may apply the received TCI states for the SCells in the order of entry in the TCI state list. In a second execution phase, the UE may receive a command for TCI state activation prior to the LTM switching command. This prior activation can allow the UE to synchronize to target beams prior to actual switching. When LI measurements of the SCell are configured, the activation command and the subsequent LTM switching command can include the SCell beams and beamindex. The activation command may be sent to the UE as a MAC CE, and can include the TCI states of the SCells to be measured. In some example embodiments, the MAC CE can also include the target cell identifier (e.g., physical cell identifier) and also source cell identifier. In an example embodiment, the SCells associated with the target PCell may be listed in the form of bitmap, wherein the bitmap indicates which SCells are activated after cell switch.

[0103] It is to be noted that the steps pertaining to TCI state switching enhancements can be applicable to LI measurement and reporting of SCells with or without the abovementioned enhancements.

[0104] FIGs. 5A to 5B illustrate a method 500 for a first aspect of measurement enhancement of a target secondary cell, according to an example embodiment of the disclosure herein. The method 500 may be performed by the UE.

[0105] At step 502, the UE receives, from a source network node serving the UE, a higher layer message for a mobility procedure, wherein the higher layer message comprises LTM configuration information, including an indication (e.g., a flag) to differentiate at least one SCell in each candidate cell group, among one or more candidate cell groups, wherein each candidate cell group comprises a PCell and at least one SCell. The higher layer message can be a RRC message.

[0106] At step 504, the UE performs a LI measurement of the PCell in each candidate cell group based on the received configuration information in the higher layer message.

[0107] At step 506, the UE sends to the source network node a first measurement report of the LI measurement of the PCell in each candidate cell group. At step 508, the UE receives from the source network node, a MAC CE to activate the LI measurement of the at least one SCell in a target cell group, among the one or more candidate cell groups, based on the first measurement report. The MAC CE may activate the LI measurement of the at least one SCell in the target cell group based on a cell index of the target cell group. In another example embodiment, the MAC CE can include reference signal configurations to be activated for the LI measurement of the at least one SCell of the target cell group.

[0108] At step 510, the UE performs the LI measurement of the at least one SCell of the target cell group based on the MAC CE and the configuration information.

[0109] At step 512, the UE sends to the source network node a second measurement report of the LI measurement of the at least one SCell.

[0110] FIGs. 6A to 6B illustrate a method 600 for a second aspect of measurement enhancement of a target secondary cell, according to an example embodiment of the disclosure herein. The method 600 may be performed by a UE.

[0111] At step 602, the UE may receive from a source network node serving the UE, a higher layer message for a mobility procedure, wherein the higher layer message comprises: a) LTM configuration information of one or more candidate cell groups, wherein each candidate cell group comprises a PCell and at least one SCell; and b) A selection criteria for the measurement of the at least one SCell associated with the PCell of each candidate cell group.

[0112] At step 604, the UE may perform a LI measurement of the PCell of each candidate cell group, based on the configuration information. At step 606, the UE sends to the source network node a first measurement report of the LI measurement of the PCell in each candidate cell group.

[0113] At step 608, the UE determines a subset of PCells comprising the PCell in each candidate cell group that meets the selection criteria, based on the first measurement report.

[0114] At step 610, the UE performs a LI measurement of the at least one SCell associated with the subset of PCells.

[0115] At step 612, the UE sends to the source network node, a second measurement report of the LI measurement of the at least one SCell associated with the subset of PCells.

[0116] The subset of PCells can include those PCells that meet the following criteria: a) have acquired a timing advance; b) have a cell quality that is within a threshold range of a source cell served by the source network node; and c) have an activated TCI state.

[0117] FIGs. 7A to 7B illustrate a method 700 for a third aspect of measurement enhancement of a target secondary cell, according to an example embodiment of the disclosure herein. The method 700 may be performed by a UE.

[0118] At step 702, the UE receives from a source network node serving the UE, a higher layer message for a mobility procedure, wherein the higher layer message includes LTM configuration information of one or more candidate cell groups, wherein each candidate cell group comprises a PCell and at least one SCell.

[0119] At step 704, the UE performs a LI measurement of the PCell of each candidate cell group based on the configuration information. 1

[0120] At step 706, the UE sends to the source network node, a first measurement report of the LI measurement of the PCell in each candidate cell group.

[0121] At step 708, the UE determines that the PCell of a target cell group has the best beam among the PCell of each candidate cell group, based on the first measurement report. In other embodiments, the PCell of the target cell group may be chosen based on the cell quality, which may be determined based on the first measurement report including the highest reported beam among an average of N beams above a threshold.

[0122] At step 710, the UE performs a LI measurement of the at least one SCell in the target cell group, based on the configuration information.

[0123] At step 712, the UE sends to the source network node, a second measurement report of the LI measurement of the at least one SCell of the target cell group.

[0124] FIG. 8 illustrates a method 800 for a fourth aspect of measurement enhancement of a target secondary cell, according to an example embodiment of the disclosure herein. The method 800 may be performed by the UE.

[0125] At step 802, the UE receives from a source network node serving the UE, a higher layer message for a mobility procedure, the higher layer message including LTM configuration information of one or more candidate cell groups, wherein each candidate cell group comprises a PCell and at least one SCell.

[0126] At step 804, the UE performs a LI measurement of the PCell and its associated at least one SCell from the one or more candidate cell groups. At step 806, the UE sends to the source network node, a first measurement report of the LI measurement of the PCell and its associated at least one SCell. If the first measurement report has N candidate cells (including PCells and SCells) and M beams for each of the candidate cells, then for X number of PCells in the measurement report, there may be (N-X) SCells in the measurement report.

[0127] FIG. 9 illustrates a method 900 for a fifth aspect of measurement enhancement of a target secondary cell, according to an example embodiment of the disclosure herein. The method 900 may be performed by the UE.

[0128] At step 902, the UE receives from a source network node serving the UE, a higher layer message for a mobility procedure, the higher layer message including LTM configuration information of one or more candidate cell groups, wherein each candidate cell group comprises a PCell and at least one SCell.

[0129] At step 904, the UE performs a LI measurement of the PCell of each candidate cell group based on the configuration information.

[0130] At step 904, the UE sends to the source network node, a first measurement report of the LI measurement of the PCell in each candidate cell group.

[0131] At step 906, the UE performs a LI measurement of at least one SCell associated with one or more PCells in the first measurement report. In other words, the at least one SCell that is measured may, in some embodiments, only be associated with the PCell of some of the candidate cell groups.

[0132] At step 908, the UE sends to the source network node, a second measurement report of the LI measurement of the at least one SCell associated with the one or more PCells, as a MAC CE. FIGs. 10 to 12 illustrate various methods for TCI state switching enhancements. The TCI state switching enhancements can be applicable to LI measurement and reporting with enhancements (as described above) or without enhancements.

[0133] For example, the various steps in the methods illustrated in FIGs. 10 to 12 can take place after the following LI measurement and reporting. The UE receives from a source network node serving the user equipment, a higher layer message for a mobility procedure, the higher layer message comprising lower layer triggered mobility (LTM) configuration information of one or more candidate cell groups, wherein each candidate cell group comprises a primary cell (PCell) and at least one secondary cell (SCell) associated with the PCell. The UE performs a LI measurement of the PCell from each candidate cell group based on the configuration information. The UE sends to the source network node a first measurement report of the LI measurement of the PCell from each candidate cell group. The UE also performs a LI measurement of the at least one SCell from each candidate cell group, based on the configuration information. The UE then sends to the source network node a second measurement report of the LI measurement of the at least one SCell from each candidate cell group.

[0134] FIG. 10 illustrates a method 1000 for a preparation phase of TCI state switching enhancement of a target secondary cell, according to an example embodiment of the disclosure herein. The method 1000 can include steps performed by the CU or the target DU (i.e., target network node serving the target cell group).

[0135] At step 1002, the CU may include a flag ‘secondary-cell beam-switch’ when preparing the candidate cell group for beam indication for SCells.

[0136] At step 1004, the target DU may indicate TCI states that are common for a group of SCells, wherein the target DU provides a list with a mapping of the TCI states to the SCells in the group.

[0137] At step 1006, the CU informs the DU of additional TCI states and its mapping to list of SCells. At step 1008, the CU includes in the RRC reconfiguration message, a TCI-state list to SCell group mapping for each candidate primary cell (i.e., the PCell of each candidate cell group) for TCI state switch with SCells (i.e., SCells associated with the each candidate primary cell).

[0138] FIG. 11 illustrates a method 1100 for an execution phase of TCI state switching enhancement of a target secondary cell, according to an example embodiment of the disclosure herein.

[0139] At step 1102, the source DU includes in an LTM switching command (which is transmitted to the UE) an ‘additional TCI-list’ for SCells as new MAC CE or as an extension of the LTM switching command.

[0140] At step 1104, the UE identifies the SCell corresponding to the TCI state, based on the mapping in the TCI state list. This can allow the UE to apply the TCI state for the at SCell based on its mapping I the TCI state list.

[0141] FIG. 12 illustrates a method 1200 for another execution phase of TCI state enhancement of a target secondary cell, according to an example embodiment of the disclosure herein. The method 1200 may be performed by the source DU.

[0142] At step 1202, the source DU transmits to the UE, a MAC CE for activating the TCI state of one or more SCells, wherein the MAC CE includes the TCI state of the one or more SCells.

[0143] At step 1204, the source DU transmits to the UE an LTM switching command to switch to the one or more SCells whose TCI states are activated.

[0144] The methods depicted in FIGs. 5A to 5B, 6A to 6B, 7A to 7B. 8, 9, 10, 11, and 12 can comprise further steps not shown and / or may omit certain steps, therefore this should not be construed as limiting the scope of the present disclosure. Moreover, the steps in the aforementioned FIGS, may not necessarily occur in the same sequence as provided herein.

[0145] FIG. 13 is a simplified block diagram of a device 1300 for implementing the example embodiments of the present disclosure. The device 1300 is an example of a device that may be configured to implement the various methods and processes described herein. The device 1300 may be a network device (e.g., the source network node / source DU / CU / target DU) or a terminal device (e.g., the UE).

[0146] The device 1300 comprises a processor 1304 which can control the device’s operations. The processor 1304 may also be referred to as a central processing unit (CPU). The memory 1302, which may include both read-only memory (ROM) and random access memory (RAM), can provide instructions and data to the processor 1304. The memory 1302 and the processor 1304 may be operatively coupled. The memory 1302 may store computer readable instructions / computer program code. The computer readable instructions / computer program code may be pre-stored to the memory 1302 or, alternatively or additionally, they may be received, by the device 1300, via an electromagnetic carrier signal and / or may be copied from a physical entity such as a computer program product. Execution of the computer readable instructions by the processor 1304, can cause the device 1300 to carry out the example embodiments described herein.

[0147] In the context of this document, a “memory” (also referred to as “computer-readable media” or “computer-readable medium”) may be any non-transitory media or medium or means that can contain, store, communicate, propagate or transport the instructions for use by or in connection with an instruction execution system, apparatus, or device, such as a computer. The term “non- transitory,” as used herein, is a limitation of the medium itself (i.e., tangible, not a signal) as opposed to a limitation on data storage persistency (e.g., RAM vs. ROM).

[0148] The transmitter / receiver (TX / RX) circuitry 1306 may comprise a transmitter 1310 and a receiver 1312 that can enable the device 1300 to transmit or receive data. The device 1300 may comprise (not shown) multiple antennas, transmitters, and receivers. In some example embodiments, the device 1300 may comprise means that enable it to perform the steps / operations in FIGs. 5A to 5B, 6A to 6B, 7A to 7B. 8, 9, 10, 11, and 12. The means may be implemented in any suitable form. For example, the means may be implemented in a circuitry (e.g., the memory 1302 and processor 1304) or a software module.

[0149] Technical Effect:

[0150] The embodiments disclosed herein also result in improved throughput during dynamic switching and maximize the benefits of LI measurement beam-based switching for SCells, by preventing frequent changes in the throughput. The embodiments disclosed herein allow for LTM mobility scenarios to be applicable in carrier aggregation scenarios.

[0151] In the drawings and specification, there have been disclosed exemplary embodiments of the invention. Although specific terms are employed, they are used in a generic and descriptive sense only and not for purposes of limitation. It will be apparent to those having ordinary skill in this art that various modifications and variations may be made to the embodiments disclosed herein, consistent with the present invention, without departing from the spirit and scope of the present invention. Other embodiments consistent with the present invention will become apparent from consideration of the specification and the practice of the description disclosed herein.

Claims

We claim:

1. A method, comprising: receiving, from a source network node serving a user equipment (UE), a higher layer message for a mobility procedure, the higher layer message comprising lower layer triggered mobility (LTM) configuration information, including an indication to differentiate at least one SCell in each candidate cell group, among one or more candidate cell groups, from each other, wherein each candidate cell group comprises a primary cell (PCell) and the at least one secondary cell (SCell); performing an LI measurement of the PCell in each candidate cell group based on the configuration information; sending, to the source network node, a first measurement report of the LI measurement of the PCell in each candidate cell group; receiving, from the source network node, a Medium Access Control (MAC) Control Element (CE) to activate layer 1 (LI) measurement of at least one SCell of a target cell group, among the one or more candidate cell groups, based on the first measurement report; performing the LI measurement of the at least one SCell of the target cell group based on the MAC CE and the configuration information; and sending, to the source network node, a second measurement report of the LI measurement of the at least one SCell.

2. The method as claimed in claim 1, comprising: determining, for each candidate cell group, the at least one SCell’ s association to its corresponding PCell based on the received indication.

3. The method as claimed in claim 1, wherein based on the first measurement report, the MAC CE comprises a cell index for the target cell group.

4. The method as claimed in claim 3, wherein the MAC CE comprises reference signal configurations to be activated for the LI measurement of the at least one SCell of the target cell group.

5. The method as claimed in claim 1, wherein prior to receiving the higher layer message, the method comprises: indicating the UE’s capability for at least one of the following: storing the LTM configuration information for the at least one SCell in each candidate cell group; and performing the LI measurement of the at least one SCell based on an activation provided via the MAC CE.

6. The method as claimed in claim 1, wherein the UE sends the second measurement report as a MAC CE.

7. A method, comprising: receiving, from a source network node serving a user equipment, a higher layer message for a mobility procedure, the higher layer message comprising: lower layer triggered mobility (LTM) configuration information of one or more candidate cell groups, wherein each candidate cell group comprises a primary cell (PCell) and at least one secondary cell (SCell); and a selection criteria for the measurement of the at least one SCell associated with the PCell in each candidate cell group; performing an LI measurement of the PCell in each candidate cell group based on the configuration information; sending, to the source network node, a first measurement report of the LI measurement of the PCell in each candidate cell group;determining a subset of PCells comprising the PCell in each candidate cell group that meets the selection criteria, based on the first measurement report; performing an LI measurement of the at least one SCell associated with the subset of PCells; and sending, to the source network node, a second measurement report of the LI measurement of the at least one SCell associated with the subset of PCells.

8. The method as claimed in claim 7, wherein the selection criteria for the subset of PCells comprises at least one of the following: acquiring a timing advance; having a cell quality that is within a threshold range of a source cell served by the source network node; and having an activated TCI state.

9. The method as claimed in claim 7, wherein prior to receiving the higher layer message, the method comprises: indicating the UE’s capability for at least one of the following: storing the LTM configuration information for the at least one SCell in each candidate cell group; and performing the LI measurement of the at least one SCell based on an activation provided via a MAC CE.

10. The method as claimed in claim 7, wherein the UE sends the second measurement report of the at least one SCell associated with the subset of PCells as a MAC CE.I L A method, comprising: receiving, from a source network node serving a user equipment, a higher layer message for a mobility procedure, the higher layer message comprising lower layer triggered mobility(LTM) configuration information of one or more candidate cell groups, wherein each candidate cell group comprises a primary cell (PCell) and at least one secondary cell (SCell); performing an LI measurement of the PCell in each candidate cell group based on the configuration information; sending, to the source network node, a first measurement report of the LI measurement of the PCell in each candidate cell group; determining that the PCell of a target cell group, among the one or more candidate cell groups, has the best beam among the PCell in each candidate cell group, based on the first measurement report; performing an LI measurement of the at least one SCell of the target cell group based on the configuration information; and sending, to the source network node, a second measurement report of the LI measurement of the at least one SCell of the target cell group.

12. The method as claimed in claim 11, wherein prior to receiving the higher layer message, the method comprises: indicating the UE’s capability for at least one of the following: storing the LTM configuration information for the at least one SCell of each candidate cell group; and performing the LI measurement of the at least one SCell based on an activation provided via a MAC CE.

13. The method as claimed in claim 11, wherein the UE sends second measurement report of the at least one SCell associated with the subset of PCells as a MAC CE.

14. A method, comprising: receiving, from a source network node serving a user equipment, a higher layer message for a mobility procedure, the higher layer message comprising lower layer triggered mobility (LTM) configuration information of one or more candidate cell groups, wherein each candidatecell group comprises a primary cell (PCell) and at least one secondary cell (SCell) associated with the PCell; performing an LI measurement of the PCell and its associated at least one SCell from the one or more candidate cell groups, based on the configuration information; and sending, to the source network node, a first measurement report of the LI measurement of the PCell and its associated at least one SCell from the one or more candidate cell groups.

15. The method as claimed in claim 14, wherein the LI measurement report comprises: measurement details of a total number (N) of candidate cells; and measurement details of a total number (M) of beams for each of the candidate cells, wherein for a first number (X) of PCells as the candidate cells, there are a second number of (N- X) SCells as the candidate cells.

16. The method as claimed in claim 14, wherein prior to receiving the higher layer message, the method comprises: indicating the UE’s capability for at least one of the following: storing the LTM configuration information for the at least one SCell in each candidate cell group; and performing the LI measurement of the at least one SCell based on an activation provided via the MAC CE.

17. The method as claimed in claim 14, wherein the UE sends the first measurement report as a MAC CE.

18. A method, comprising: receiving, from a source network node serving a user equipment, a higher layer message for a mobility procedure, the higher layer message comprising lower layer triggered mobility (LTM) configuration information of one or more candidate cell groups, wherein each candidatecell group comprises a primary cell (PCell) and at least one secondary cell (SCell) associated with the PCell; performing an LI measurement of the PCell from the each candidate cell group, based on the configuration information; sending, to the source network node, a first measurement report of the LI measurement of the PCell from each candidate cell group; performing an LI measurement of the at least one SCell from each candidate cell group, based on the configuration information; and sending, to the source network node, a second measurement report of the LI measurement of the at least one SCell from each candidate cell group.

19. The method as claimed in claim 18, wherein the UE sends the second measurement report as a MAC CE.

20. The method as claimed in claim 18, wherein the source network node includes a flag when preparing each candidate cell group for beam indication of its least one SCell.

21. The method as claimed in claim 20, comprising: receiving an LTM switching signal comprising a TCI state list comprising at least one TCI state that is mapped to the at least one SCell of a target cell group, among the one or more candidate cell groups; and applying the TCI state for the at least one SCell of the target cell group based on the mapping in the TCI state list.

22. The method as claimed in claim 20, comprising: receiving a MAC CE for activating the TCI state of the at least one SCell of the target cell group, wherein the MAC CE comprises the index of the at least one SCell; and receiving a LTM switching signal comprising the index of the at least one SCell whoseTCI state is activated.

23. The method as claimed in claim 7, wherein the MAC CE comprises: an index of the target cell group; and a bitmap of the at least one SCell.

24. A user equipment (UE), comprising: at least one memory; and at least one processor operatively coupled to the at least one memory, wherein the at least one processor is configured to cause the apparatus to: receive, from a source network node serving the UE, a higher layer message for a mobility procedure, the higher layer message comprising lower layer triggered mobility (LTM) configuration information, including an indication to differentiate at least one secondary cell (SCell) of each candidate cell group, among one or more candidate cell groups, wherein each candidate cell group comprises a primary cell (PCell) and the at least SCell; perform an LI measurement of the PCell in each candidate cell group based on the configuration information; send, to the source network node, a first measurement report of the LI measurement of the PCell in each candidate cell group; receive, from the source network node, a Medium Access Control (MAC) Control Element (CE) to activate layer 1 (LI) measurement of at least one SCell of a target cell group among the one or more candidate cell groups, based on the first measurement report; perform the LI measurement of the at least one SCell of the target cell group based on the MAC CE and the configuration information; and send, to the source network node, a second measurement report of the LI measurement of the at least one SCell.

25. The UE as claimed in claim 24, wherein the at least one processor is configured to cause the UE to:determine, for each candidate cell group, the at least one SCell’s association to its corresponding PCell, based on the received indication.

26. The UE as claimed in claim 24, wherein based on the LI measurement result of first measurement report, the MAC CE comprises a cell index for the target cell group.

27. The UE as claimed in claim 26, wherein the MAC CE comprises reference signal configurations to be activated for the LI measurement of the at least one SCell of the target cell group.

28. The UE as claimed in claim 24, wherein prior to receiving the higher layer message, the at least one processor is configured to cause the UE to: indicate the UE’s capability for at least one of the following: storing the LTM configuration information for the at least one SCell in each candidate cell group; and performing the LI measurement of the at least one SCell based on an activation provided via the MAC CE.

29. The UE as claimed in claim 24, wherein the UE sends the second measurement report of the at least one SCell as a MAC CE.

30. A user equipment (UE), comprising: at least one memory; and at least one processor operatively coupled to the at least one memory, wherein the at least one processor is configured to cause the apparatus to: receive, from a source network node serving the UE, a higher layer message for a mobility procedure, the higher layer message comprising: lower layer triggered mobility (LTM) configuration information of one or more candidate cell groups, wherein each candidate cell group comprises a primary cell (PCell) and at least one secondary cell (SCell); anda selection criteria for the measurement of the at least one SCell associated with the PCell in each candidate cell group; perform an LI measurement of the PCell in each candidate cell group based on the configuration information; send, to the source network node, a first measurement report of the LI measurement of the PCell in each candidate cell group; determine a subset of PCells comprising the PCell in each candidate cell group that meets the selection criteria, based on the first measurement report; perform an LI measurement of the at least one SCell associated with the subset of PCells; and send, to the source network node, a second measurement report of the LI measurement of the at least one SCell associated with the subset of PCells.

31. The UE as claimed in claim 30, wherein the selection criteria for the subset of PCells comprises at least one of the following: acquiring a timing advance; having a cell quality that is within a threshold range of a source cell served by the source network node; and having an activated TCI state.

32. The UE as claimed in claim 30, wherein prior to receiving the higher layer message, the at least one processor is configured to cause the UE to: indicate the UE’s capability for at least one of the following: storing the LTM configuration information for the at least one SCell in each candidate cell group; and performing the LI measurement of the at least one SCell based on an activation provided via a MAC CE.

33. The UE as claimed in claim 30, wherein the UE sends the second measurement report of the at least one SCell associated with the subset of PCells as a MAC CE.

34. A user equipment (UE), comprising: at least one memory; and at least one processor operatively coupled to the at least one memory, wherein the at least one processor is configured to cause the apparatus to: receive, from a source network node serving the UE, a higher layer message for a mobility procedure, the higher layer message comprising lower layer triggered mobility (LTM) configuration information of one or more candidate cell groups, wherein each candidate cell group comprises a primary cell (PCell) and at least one secondary cell (SCell); perform an LI measurement of the PCell in each candidate cell group based on the configuration information; send, to the source network node, a first measurement report of the LI measurement of the PCell in each candidate cell group; determine that the PCell of a target cell group, among the one or more candidate cell groups, has the best beam among the PCell in each candidate cell group, based on the first measurement report; perform an LI measurement of the at least one SCell of the target cell group based on the configuration information; and send, to the source network node, a second measurement report of the LI measurement of the at least one SCell of the target cell group.

35. The UE as claimed in claim 34, wherein prior to receiving the higher layer message, the at least one processor is configured to cause the UE to: indicate the UE’s capability for at least one of the following: storing the LTM configuration information for the at least one SCell in each candidate cell group; andperforming the LI measurement of the at least one SCell based on an activation provided via the MAC CE.

36. The UE as claimed in claim 34, wherein the UE sends the second measurement report of the at least one SCell associated with the subset of PCells as a MAC CE.

37. A user equipment (UE), comprising: at least one memory; and at least one processor operatively coupled to the at least one memory, wherein the at least one processor is configured to cause the UE to: receive, from a source network node serving the UE, a higher layer message for a mobility procedure, the higher layer message comprising lower layer triggered mobility (LTM) configuration information of one or more candidate cell groups, wherein each candidate cell group comprises a primary cell (PCell) and at least one secondary cell (SCell) associated with the PCell; perform an LI measurement of the PCell and its associated at least one SCell from the one or more candidate cell groups, based on the configuration information; and send, to the source network node, a first measurement report of the LI measurement of the PCell and its associated at least one SCell from the one or more candidate cell groups.

38. The UE as claimed in claim 37, wherein the first measurement report comprises: measurement details of a total number (N) of candidate cells; and measurement details of a total number (M) of beams for each of the candidate cells, wherein for a first number (X) of PCells as the candidate cells, there are a second number of (N- X) SCells as the candidate cells.

39. The UE as claimed in claim 37, wherein prior to receiving the higher layer message, the method comprises: indicating the UE’s capability for at least one of the following:storing the LTM configuration information for the at least one SCell in each candidate cell group; and performing the LI measurement of the at least one SCell based on an activation provided via the MAC CE.

40. The UE as claimed in claim 37, wherein the UE sends the first measurement report as a MAC CE.

41. A user equipment (UE), comprising: at least one memory; and at least one processor operatively coupled to the at least one memory, wherein the at least one processor is configured to cause the UE to: receive, from a source network node serving a user equipment, a higher layer message for a mobility procedure, the higher layer message comprising lower layer triggered mobility (LTM) configuration information of one or more candidate cell groups, wherein each candidate cell group comprises a primary cell (PCell) and at least one secondary cell (SCell) associated with the PCell; perform an LI measurement of the PCell from the each candidate cell group, based on the configuration information; send, to the source network node, a first measurement report of the LI measurement of the PCell from each candidate cell group; perform an LI measurement of the at least one SCell from each candidate cell group, based on the configuration information; and send, to the source network node, a second measurement report of the LI measurement of the at least one SCell from each candidate cell group.

42. The UE as claimed in claim 41, wherein the UE sends the second measurement report as a MAC CE.

43. The UE as claimed in claim 41, wherein the source network node includes a flag when preparing each candidate cell group for beam indication of its least one SCell.

44. The UE as claimed in claim 43, comprising: receiving an LTM switching signal comprising a TCI state list comprising at least one TCI state that is mapped to the at least one SCell of a target cell group, among the one or more candidate cell groups; and applying the TCI state for the at least one SCell of the target cell group based on the mapping in the TCI state list.

45. The UE as claimed in claim 43, comprising: receiving a MAC CE for activating the TCI state of the at least one SCell of the target cell group, wherein the MAC CE comprises the index of the at least one SCell; and receiving a LTM switching signal comprising the index of the at least one SCell whose TCI state is activated.

46. The UE as claimed in claim 45, wherein the MAC CE comprises: an index of the target cell group; and a bitmap of the at least one SCell.

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