Method and apparatus for enhancements in measurements / reporting

Abstract

The disclosure relates to fast activation of L1 measurement and beam switching of target- secondary-cells without early measurements performed while connected with the serving cell. The disclosure provides RACH-less L1 / L2 triggered mobility with preconfigured uplink grants or LTM Switching command to include MAC Control Element to activate a channel state information reference signal CSI-RS measurement and reporting for secondary cells immediately after switching, wherein a resource location is expected at a pre-configured time from the LTM command.

Description

METHOD AND APPARATUS FOR ENHANCEMENTS IN MEASUREMENTS / REPORTINGTechnical Field:

[0001] The present disclosure relates to the field of wireless communication systems, and more particularly to facilitating lower layer (L1 / L2) triggered mobility (LTM) within wireless communication systems.

[0002] Any discussion of the background art throughout the specification should in no way be considered as an admission that such art is widely known or forms part of common general knowledge in the field.

[0003] In a communication system such as a Long-Term Evolution (LTE) or a New Radio (NR or 5G), a user equipment’s movement occurs from one cell coverage to another cell coverage, with the cells being supported by more than one network node. The third Generation Partnership Project (3 GPP) Release 18 (Rel-18) which introduced LTM mobility for mobility enhancements provides that mobility is triggered by Layer 2 (L2) based on LI measurements. Lower layer triggered mobility enables changing a serving cell via L1 / L2 signaling while keeping configuration of the upper layers. LI encompasses the physical layer (PHY) and L2 encompasses the medium access control (MAC), radio link control (RLC) and packet data convergence protocol (PDCP) and Service Data Adaptation Protocol (SDAP) layers. A UE may be configured for lower layer mobility, to perform handover procedure to target cell.

[0004] In high-performing networks, carrier aggregation is deployed for aggregating several frequency bands for achieving higher data rates. In case of carrier aggregation in single connectivity, the UE may be served by a cell group comprising a primary cell (PCell) operating on a primary frequency and at least one secondary cell (SCell) operating on asecondary frequency. A cell group comprising a target PCell and at least one target SCell may be prepared for the UE for LTM switching. While the objectives of Rel-18 include LTM for CA, the work in Rel-18 is, however, currently restricted insofar that with limited capability of the UE for beam measurements, only PCell LI measurements take place. Optimizations for LTM switching with S cells and for LTM switching with beam level switching for Scells which are not co-located with the PCell, are, therefore, needed for configurations for improved throughput.

[0005] In accordance with an aspect of the present disclosure, there is provided an apparatus comprising at least one processor, and at least one memory coupled to the at least one processor, which is configured to cause the apparatus to receive, from a source network element, configuration information related to channel state information reference signal, CSI-RS, measurement and reporting configuration for a target cell for a cell change, the target cell comprising a primary cell, PCell, and at least one secondary cell, SCell, acquire a CSI-RS of the at least one Scell, wherein the at least one SCell is associated with the PCell, based on the received configuration information, perform a LI measurement of the acquired CSI-RS, and transmit, to the target network element, an LI measurement report including measurement information of the acquired CSI-RS, wherein data transmission to the at least one SCell is activated based on the LI measurement report of the acquired CSI-RS.

[0006] In accordance with another aspect of the present disclosure, there is provided an apparatus comprising at least one processor and at least one memory coupled to the at least one processor, configured to cause the apparatus to receive configuration information related to channel state information reference signal, CSI-RS, measurement and reporting configuration for a target cell for a cell change, the target cell comprising a primary cell, PCell, and at least one secondary cell, SCell, transmit, to a UE, the configuration information, and transmit, to the UE, an LTM switching command to switch to the target cell.

[0007] In accordance with yet another embodiment of the present disclosure, there is provided a method by a user equipment (UE) comprising: receiving, from a source network element, configuration information related to channel state information reference signal, CSI-RS, measurement and reporting configuration for a target cell, for a cell change, the target cell comprising a primary cell, PCell, and at least one secondary cell, SCell, acquiring a CSI-RS of the at least one Scell, wherein the at least one SCell is associated with the PCell based on the received configuration information, performing a LI measurement of the acquired CSI- RS; and transmitting, to the target network element, a LI measurement report including measurement information of the acquired CSI-RS, wherein data transmission to the at least one SCell is activated based on the LI measurement report of the acquired CSI-RS.

[0008] In accordance with yet another embodiment of the present disclosure, there is provided a method by a source network element comprising: receiving configuration information related to channel state information reference signal, CSI-RS, measurement and reporting configuration for the target cell for a cell change, the target cell comprising a primary cell, PCell, and at least one secondary cell, SCell, transmitting, to the UE, the configuration information, and transmitting, to the UE, an LTM switching command to switch to the target cell.

[0009] In accordance with a further aspect of the present disclosure, there is also provided an apparatus comprising at least one processor and at least one memory coupled to the at least one processor, configured to cause the apparatus to: receive, from a source network element, configuration information for a target cell for a cell change, the target cell comprising a primary cell, PCell, and at least one secondary cell, SCell, transmit, to the source network element, an LI measurement report of the PCell based on the configuration information, receive an LTM switching command to switch to the PCell based on the configuration information, wherein the LTM switching command includes information on channel state information reference signal, CSI-RS, measurement and reporting configuration of the at least one Scell associated with the Pcell, acquire a CSI-RS of the at least one Scell based on the information in the LTM switching command, perform a LI measurement of the acquiredCSI-RS, and transmit, to the target network element, an LI measurement report of the acquired CSI-RS, wherein data transmission to the at least one SCell is activated based on the LI measurement report of the acquired CSI-RS.

[0010] Furthermore, according to some example embodiments, there is provided an apparatus comprising: at least one processor: and at least one memory coupled to the at least one processor, configured to cause the apparatus at least to: receive configuration information related to a target cell for a cell change, the target cell comprising a primary cell, PCell, and at least one secondary cell, SCell, transmit, to a UE, the configuration information related to the target cell, receive, from the UE, an LI measurement report of the PCell based on the configuration information, and transmit, to the UE, an LTM switching command to switch to the PCell based on the configuration information, wherein the LTM switching command includes information on channel state information reference signal, CSI-RS, measurement and reporting configuration of the at least one Scell associated with the Pcell..

[0011] Moreover, according to some example embodiments, there is also provided a method by a user equipment (UE) comprising: receiving, from a source network element, configuration information for a target cell for a cell change, the target cell comprising a primary cell, PCell, and at least one secondary cell, SCell, transmitting, to the source network element, an LI measurement report of the PCell based on the configuration information, receiving an LTM switching command to switch to the PCell based on the configuration information, wherein the LTM switching command includes information on channel state information reference signal, CSI-RS, measurement and reporting configuration of the at least one Scell associated with the Pcell, acquiring a CSI-RS of the at least one Scell based on the information in the LTM switching command, performing a LI measurement of the acquired CSI-RS, and transmitting, to the target network element, an LI measurement report of the acquired CSI- RS, wherein data transmission to the at least one SCell is activated based on the LI measurement report of the acquired CSI-RS.

[0012] In addition, according to some other example embodiments, there is provided, for example, a method by a source network element comprising: receiving configuration information related to a target cell for a cell change, the target cell comprising a primary cell, PCell, and at least one secondary cell, SCell, transmitting, to a UE, the configuration information related to the target cell, and receiving from the UE, an LI measurement report of the PCell based on the configuration information, and transmitting, to the UE, an LTM switching command to switch to the PCell based on the configuration information, wherein the LTM switching command includes information on channel state information reference signal, CSI-RS, measurement and reporting configuration of the at least one Scell associated with the Pcell.

[0013] While some example embodiments will be described herein with particular reference to the above application, it will be appreciated that the present disclosure is not limited to such a field of use, and is applicable in broader contexts.

[0014] Notably, it is understood that methods according to the present disclosure relate to methods of operating the apparatuses (or systems) according to the above example embodiments and variations thereof, and that respective statements made with regard to the apparatuses (or systems) likewise apply to the corresponding methods, and vice versa, such that similar description may be omitted for the sake of conciseness. In addition, the above aspects may be combined in many ways, even if not explicitly disclosed. The skilled person will understand that these combinations of aspects and features / steps are possible unless it creates a contradiction which is explicitly excluded.

[0015] In the following, various exemplary embodiments will be described in greater detail with reference to the accompanying drawings, in which:

[0016] FIG. 1 illustrates a message sequence chart for L1 / L2 Triggered mobility (LTM) procedure for a primary cell.

[0017] FIG. 2 illustrates a message sequence chart including an issue with the existing LTM procedure for activation of target secondary cell (SCell).

[0018] FIG. 3 illustrates a message sequence chart for fast activation of the target SCell beam measurement and switching after LTM switching, in accordance with an embodiment of the present disclosure.

[0019] FIG. 4 illustrates a first method for fast activation of target SCell beam measurement and switching after LTM switching, in accordance with an exemplary embodiment of the present disclosure.

[0020] FIG. 5 illustrates a second method for fast activation of target SCell beam measurement and switching after LTM switching, in accordance with another exemplary embodiment of the present disclosure.

[0021] FIG. 6 illustrates a device that is suitable for implementing example embodiments of the disclosure herein.Description of Example Embodiments:

[0022] 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.

[0023] 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 ofdifferent 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. 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. The phrase “exemplary embodiment” is meant to be understood as an example embodiment, instead of a preferred embodiment.

[0024] 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.

[0025] 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.

[0026] 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.

[0027] Before discussing the example embodiments in detail, first, an overview is provided.

[0028] FIG.1 shows a message sequence chart for reference LTM procedure, described hereinbelow.

[0029] 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 3 GPP standards for a communication network, such as 5G NR, without restricting the embodiments to such an architecture, however.

[0030] A basic system architecture of a communication network including a mobile communication system where some examples of 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 respective coverage area or cell(s) and with which one or more communication stations such as communication elements orfunctions, 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 usable 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.

[0031] A gNB Central Unit (gNB-CU) comprises e.g., a logical node hosting e.g., RRC, SDAP and PDCP protocols of the gNB or RRC and PDCP protocols of the en-GNB that controls the operation of one or more gNB Distributed Units (gNB-Dus). The gNB-CU terminates the Fl interface connected with the gNB-DU.

[0032] A gNB-DU comprises e.g., a logical node hosting e.g., RLC, MAC and PHY 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. 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. Different functional splits between the central and distributed unit are possible.

[0033] A network node (also referred to as “network element”) may comprise at least one of the following or support functionality of at least one of the following: a base station, a 5G gNB, a Centralized Unit, a Distributed Unit, or a secondary node.

[0034] A gNB supports different protocol layers, e.g., Layer 1 (LI) - physical layer. The layer 2 (L2) of NR is split into the following sublayers: Medium Access Control (MAC), Radio Link Control (RLC), Packet Data Convergence Protocol (PDCP) and Service Data Adaptation Protocol (SDAP), where e.g.: the physical layer offers to the MAC sublayer transport channels; the MAC sublayer offers to the RLC sublayer logical channels; the RLC sublayer offers to the PDCP sublayer RLC channels; the PDCP sublayer offers to the SDAP sublayer radio bearers; the SDAP sublayer offers to 5GC QoS flows; Comp, refers to header compression and Segm. To segmentation; Control channels 5 include (BCCH, PCCH). Layer 3 (L3) includes e.g., Radio Resource Control (RRC), e.g., according to 3GPP TS 38.300 VI 6.6.0 (2021-06) section 6 incorporated by reference.

[0035] A RAN (Radio Access Network) node or network node like e.g. a gNB, base station, gNB CU or gNB DU or parts thereof may be implemented using e.g. an apparatus with at least one processor and / or at least one memory (with computer-readable instructions (computer program)) configured to support and / or provision and / or process CU and / or DU related functionality and / or features, and / or at least one protocol (sub-15) layer of a RAN (Radio Access Network), e.g. layer 2 and / or layer 3.

[0036] The gNB CU and gNB DU parts may e.g., be co-located or physically separated. The gNB DU may even be split further, e.g., into two parts, e.g., one including processing equipment and other including an antenna. A Central Unit (CU) may also be called BBU / REC / RCC / C-RAN / V-RAN, 0-RAN, or part thereof. A Distributed Unit (DU) may also be called RRH / RRU / RE / RU, or part thereof.

[0037] A gNB-DU supports one or multiple cells, and could thus serve as e.g., a serving cell for a user equipment (UE).

[0038] A user equipment (UE) may include a wireless or mobile device, an apparatus with a radio interface to interact with a RAN (Radio Access Network), a smartphone, an in-vehicle apparatus, an loT device, a M2M device, or else. Such UE or apparatus may comprise: atleast one processor; and at least one memory including computer program code; wherein the at least one memory and the computer program code are configured, with the at least one processor, to cause the apparatus at least to perform certain operations, like e.g. RRC connection to the RAN. A UE is e.g., configured to generate a message (e.g., including a cell ID) to be transmitted via radio towards a RAN (e.g., to reach and communicate with a serving cell). A UE may generate and transmit and receive RRC messages containing one or more RRC PDUs (Packet Data Units). The UE may have different states (e.g., according to 3GPP TS 38.331 V16.5.0 (2021-06) sections 4.2.1 and 4.4, incorporated by reference). A UE is e.g., either in RRC CONNECTED state or in RRC INACTIVE state when an RRC connection has been established.

[0039] The RRC protocol includes e.g. the following main functions: RRC connection control; measurement configuration and reporting; establishment / modification / release of measurement configuration (e.g. intra-frequency, inter-frequency and inter-RAT measurements); setup and release of measurement gaps; measurement reporting.

[0040] A person of skill in the art would readily recognize that steps of various described methods can be performed by programmed computers. Herein, some embodiments are also intended to cover program storage devices, e.g., digital data storage media, which are machine or computer readable and encode machine executable or computer-executable programs of instructions, wherein said instructions perform some or all of the steps of said above-described methods. The program storage devices may be, e.g., digital memories, magnetic storage media such as magnetic disks and magnetic tapes, hard drives, or optically readable digital data storage media. The embodiments are also intended to cover computers programmed to perform said steps of the above-described methods. 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).

[0041] In step 1 as shown in FIG. 1, the UE sends the L3 Measurement Report to the source DU that includes the signal measurements of the candidate target cells.

[0042] In step 2, the source DU forwards the received L3 measurements to the CU via Uplink Radio Resource Control UL RRC message transfer.

[0043] In step 3, the CU decides to prepare the candidate cells for LTM.

[0044] In step 4-5, the CU initiates the preparation procedure of those candidate cells that are under target DU where the target DU can also be source DU.

[0045] In steps 6-7, 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.

[0046] In step 8, the CU generates the RRC Reconfiguration for the candidate cells that are prepared for LTM, the configuration including the measurement, reporting configuration of the prepared cells as well as the RRC Reconfiguration of the prepared candidate cells to be applied on the UE upon triggering cell change to one of the prepared candidate cells.

[0047] In step 9-12, the CU provides the RRC Reconfiguration via source DU for the candidate cells that are prepared and receives the acknowledgement of the configuration reception.

[0048] In step 13, the UE starts reporting of the LI measurements after the RRC Reconfiguration. While FIG.1 shows only one LI measurement reporting, for simplicity, however, there could be several LI measurements reported by the UE, e.g. periodic reporting.

[0049] In step 14, once the source-DU decides, it triggers the timing advance (TA) acquisition of one of the prepared candidate cells.

[0050] In step 15, once the UE is triggered with the TA acquisition of a candidate cell, it pauses the transmission / reception (TX / RX) with the serving cell to send the Physical RandomAccess Channel Preamble (PRACH preamble) to the candidate cell. In case Radio Frequency (RF) tuning is required, e.g., the target cell operates at different carrier frequency, the UE also tunes its RF before sending the PRACH preamble towards the candidate cell.

[0051] In step 16, the UE sends the PRACH preamble towards the candidate cell.

[0052] In step 17, the UE tunes its RF back to the source cell (if needed) and resumes the TX / RX with the source cell.

[0053] In stepl8, the UE continues the LI measurement reporting as of step 13.

[0054] In step 19, the source DU decides to trigger the cell change towards the candidate cell or cell group (CG) and sends the MAC CE command to trigger UE to initiate the LTM towards that candidate cell or CG. This cell switch MAC CE command contains the beam indication (TCI state) of the target cell which is to be used by the UE to send / receive signals to / from the target cell. This cell switch MAC CE command may also contain the TA of the target cell acquired by early TA acquisition process. Before sending the cell switch MAC CE command, the source DU may send a separate MAC CE for TCI activation to enable the UE to acquire fine DL time / frequency synchronization with the target cell.

[0055] Step 20-21: In case that the UE does not have the UL timing synchronization of the candidate cell (e.g., a valid TA is not provided in the cell switch command), the UE may be triggered to initiate the RACH procedure towards the candidate cell.

[0056] Step 22: The UE and the network will proceed with the completion of the LTM procedure.

[0057] In case of carrier aggregation in single connectivity, the UE may be served by a cell group which consists of one PCell and one or more SCells. Similarly, the Central Unit (CU)may prepare a cell group for LTM where the cell group consists of one target PCell and one or multiple target SCells.

[0058] In a given situation, the SCells associated with target cells may operate on a frequency that is the same as the frequency of the source SCells, such that a source PCell and a target PCell operate on the same frequency and the Source SCells and the Target SCells operate on the same frequency. In another situation, the SCells associated with the target cells may operate on a frequency different from the frequency of the source SCells such that the source PCell and the target PCell operate on the same frequency but the Source SCells and the Target SCells operate on different frequencies. For such situations, for the LTM to avoid frequent changes in the throughput during dynamic switching and to maximize the benefits of LI measurements-based beam switching for secondary cells, there needs to be enhancements related to LI measurement configurations, measurements and reporting.

[0059] FIG. 2 illustrates another messaging sequence chart to depict a delay (i.e. an issue) in secondary cell activation using the existing LTM procedure for target cells with activated secondary cells.

[0060] For the sake of brevity, description of steps 1-6 of FIG. 2 are omitted as the same has been covered above in the description relating to FIG. 1.

[0061] At step 7, the UE applies the target configuration (prepared by the CU at step 3) to activate the SCells.

[0062] At step 8, the UE switches to the PCell downlink immediately.

[0063] At step 9, the UE monitors the CSI-RS of a SCell associated with the PCell.

[0064] At step 10, the UE transmits a measurement report of the CSI-RS of the SCell to the target DU.

[0065] At step 11, the UE then receives the PDCCH via the SCell.

[0066] Subsequently, at step 12, the data transmission between the UE and the SCell is activated.

[0067] As seen from FIG. 2, as per the existing LTM procedure, secondary cell data transmission is possible only after steps 9-10 without any enhancements to fast activate the secondary cells at the time of switching.

[0068] If the LI measurements for S Cells of the target cell from the current serving cell is not possible due to limitations of UE capability or due to network configurations, additional enhancements to activate dynamic LI measurements for RACH less LTM switching are needed for faster switching of data transmission to target secondary cells.

[0069] The example embodiments of the present disclosure enable fast activation of LI measurement and beam switching of target-secondary-cells, without early measurements performed while connected with the serving cell.

[0070] FIG. 3 is a message sequence chart illustrating a first and a second aspect of fast activation of target SCell beam measurement and switching after LTM switching, in accordance with example embodiments of the present disclosure.

[0071] At step 1, the UE’s RRC connection with the source DU is active.

[0072] At step 2, using the RRC configuration, the UE sends a L3 measurement report of a target cell group (supported by the target DU (target network element)) comprising a PCell and at least one SCell.

[0073] At steps 3 and 4, the CU prepares the target cell group, and also generates the RRC configuration information for CSLRS measurement and reporting configuration.

[0074] Steps 5-12 relate to the first aspect of fast activation of the target SCell. The first aspect relates to RACH-less LTM with preconfigured uplink grants. Broadly, according to the first aspect, the CSI-RS measurement configuration and reporting configurations (semi-static or aperiodic) linked to physical uplink shared channel (PUSCH) occasions of LTM switching (PUSCH occasions given for RRC reconfiguration complete message which is an uplink message indicating LTM switching complete) is included in the target candidate cell LTM configuration including for secondary cells marked for direct activation. In other words, the CSI-RS measurement and reporting configuration is linked to PUSCH configured for an LTM switching complete message from the UE. A new RRC configuration parameter is used in candidate LTM configuration. On LTM switching command reception, after successful transmission of PUSCH (containing RRC reconfiguration complete message indicating LTM switch complete) in target-cell, UE starts monitoring the CSLRSs and report LI measurements on the configured resources. This activates PDCCH transmission from secondary cells immediately.

[0075] Specifically, at step 5, the UE receives from the CU, via the source DU, the RRC reconfiguration including the target cell group configuration, CSI-RS measurement and reporting configuration for at least one SCell, and an uplink grant location that is linked to the CSI-RS location. The CSI-RS measurement and reporting configuration may be linked to PUSCH occasions of LTM switching, and may be included in the RRC reconfiguration.

[0076] At step 6, the UE transmits an LI measurement report of the PCell in the target cell to the source DU.

[0077] At step 7, based on the LI measurement report of the PCell in the target cell, the UE receives from the source DU an LTM switching command to switch to the PCell. On the LTM switching command reception, the UE starts to monitor the CSLRSs.

[0078] At step 8, the UE is triggered to switch to the target PCell (i.e., PCell of the target cell group).

[0079] At step 9, the target DU activates PUSCH reception on an uplink grant and also activate CSI-RS transmission as per the given configuration towards the UE.

[0080] At step 10, the UE completes switching to the PCell. The UE transmits an LTM complete message to the PCell.

[0081] At step 11, the UE acquires the CSI-RS of at least one SCell associated with the PCell in the target cell group using the CSI-RS location provided in the RRC reconfiguration and start performing associated measurement and reporting to the target PCell.

[0082] At step 12, data transmission between the UE and the SCell is resumed.

[0083] Steps 13-18 relate to a second aspect of fast activation of the target SCell. Broadly, the second aspect relates to activating target cell beam measurement and switching in LTM command wherein the LTM switching command includes a MAC Control Element (MAC CE) to activate the CSI-RS measurement and reporting for secondary cells immediately after switching. The resource location is expected at a pre-configured time from the LTM command.

[0084] Specifically, at step 14, the UE receives the LTM switching command to the PCell. The LTM switching command can include MAC CE to also activate CSI-RS measurement and reporting for the at least one SCell immediately after switching. The downlink control information (DCI), which schedules the LTM switching command, can configure aperiodic CSI-RS measurement and reporting in target cell group.

[0085] At step 15, an alternative activation of CSI-RS measurement and reporting is shown where if the UE receives a PDCCH containing a dynamic uplink grant for LTM complete message from the UE, the PDCCH can also contain the activation of CSI-RS measurement and reporting at the SCell. The CSI-RS measurement and reporting can be aperiodic or semistatic.

[0086] At step 16, the UE completes LTM switching to the PCell using an uplink grant.

[0087] At step 17, the UE acquires the CSI-RS of the SCell which includes performing CSI-RS measurement and reporting to the target PCell.

[0088] At step 18, the data transmission between the UE and the SCell is resumed.

[0089] FIG. 4 illustrates a first method 400 for fast activation of target SCell beam measurement and switching after LTM switching, in accordance with an exemplary embodiment of the present disclosure. The method may be performed by a UE.

[0090] At step 402, a user equipment receives from a source network element, configuration information related to channel state information reference signal, CSI-RS, measurement and reporting configuration for a target cell for a cell change. The target cell comprises a primary cell, PCell, and at least one secondary cell, SCell. A source cell associated with the source network element serves the user equipment and the target cell is supported by a target network element. The configuration information is included in a radio resource control (RRC) reconfiguration message. The CSI-RS measurement and reporting may be aperiodic or semi-static.

[0091] At step 404, the UE acquires a CSI-RS of the at least one Scell. The at least one SCell is associated with the PCell, based on the received configuration information. The UE acquires the CSI-RS based on an uplink grant location linked to a CSI-RS location provided in the configuration information. Further, prior to acquiring the CSI-RS of the at least one cell, the UE generates and transmits to the source network element an LI measurement report of the PCell based on the configuration information.

[0092] At step 406, the UE performs an LI measurement of the acquired CSI-RS.

[0093] At step 408, the UE transmits an LI measurement report including measurement information of the acquired CSI-RS to the target network element. The data transmission to the at least one SCell is activated based on the LI measurement report of the acquired CSI- RS.

[0094] The method 400 encompasses receiving an LTM switching command, from the source network element to switch to the target cell, sending an LTM complete message to the target cell on switching to the target cell, and starting the CSI-RS measurement and reporting for the target cell.

[0095] The method 400 further encompasses that the UE undergoes L1 / L2 Triggered Mobility (LTM) switching to the at least one SCell, and wherein the LTM switching command is based on the LI measurement report of the acquired CSLRS. The CSI-RS measurement and reporting configuration is linked to a physical uplink shared channel (PUSCH) configured for LTM switching complete message from the UE. The switching of the UE to the at least one SCell occurs RACHless.

[0096] The method 400 also encompasses receiving an LTM switching command to switch to the PCell based on the LI measurement report, and the switching of the UE to the PCell occurs RACHless.

[0097] FIG. 5 illustrates a second method 500 for fast activation of target SCell beam measurement and switching after LTM switching, in accordance with an exemplary embodiment of the present disclosure. The method may be performed by a UE.

[0098] At step 502, the UE receives configuration information, from a source network element, for a target cell for a cell change. The target cell comprises a primary cell, PCell, and at least one secondary cell, SCell. The UE is served by a source cell associated with the source network element and the target cell is supported by a target network element.

[0099] At step 504, the UE transmits, to the source network element, an LI measurement report of the PCell based on the configuration information.

[0100] At step 506, the UE receives an LTM switching command to switch to the PCell based on the configuration information. The LTM switching command includes information on channel state information reference signal, CSI-RS, measurement and reporting configuration of the at least one SCell associated with the PCell. The LTM switchingcommand includes a MAC CE for activating the measurement of the at least one SCell. The LTM switching command is scheduled by downlink control information that configures CSI-RS measurement and reporting in the target cell. The CSI-RS measurement and reporting is aperiodic or semi-static.

[0101] At step 508, the UE acquires a CSI-RS of the at least one SCell based on the information in the LTM switching command. The UE can acquire the CSI-RS via a Physical Downlink Control Channel (PDCCH). An alternative method to activate CSI-RS measurement and reporting encompasses the PDCCH, providing the dynamic Uplink UL grant (in case of configured UL grants are not configured for LTM switch complete message) for an LTM switching complete message, configures CSI-RS measurement and reporting in the target cell.

[0102] At step 510, the UE performs an LI measurement of the acquired CSI-RS.

[0103] At step 512, the UE transmits to the target network element, an LI measurement report of the acquired CSI-RS. The data transmission to the at least one SCell is activated based on the LI measurement report of the acquired CSI-RS. The UE can transmit data to the at least one SCell via a Physical Uplink Shared Channel (PUSCH) linked to the measurement and reporting configuration in the LTM switching command.

[0104] The methods depicted in PIGs. 4 and 5 (including the description thereof) 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, (including the description thereof) may not necessarily occur in the same sequence as provided herein.

[0105] FIG. 6 is a simplified block diagram of a device 600 for implementing the example embodiments of the present disclosure. The device 600 is an example of a device that may be configured to implement the various methods and processes described herein. The device 600 may be a network device (e.g., the source network element / source DU / CU / target DU) or a terminal device (e.g., the UE).

[0106] The device 600 comprises a processor 604 which can control the device’s operations. The processor 604 may also be referred to as a central processing unit (CPU). The memory 6602, which may include both read-only memory (ROM) and random access memory (RAM), can provide instructions and data to the processor 604. The memory 602 and the processor 604 may be operatively coupled. The memory 602 may store computer readable instructions / computer program code. The computer readable instructions / computer program code may be pre-stored to the memory 602 or, alternatively or additionally, they may be received, by the device 600, 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 604, can cause the device 600 to carry out the example embodiments described herein.

[0107] 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).

[0108] The transmitter / receiver (TX / RX) circuitry 606 may comprise a transmitter 610 and a receiver 612 that can enable the device 600 to transmit or receive data. The device 600 may comprise (not shown) multiple antennas, transmitters, and receivers.

[0109] In some example embodiments, the device 600 may comprise means that enable it to perform the steps / operations in above-described FIGs. 3, 4 and 5. The means may be implemented in any suitable form. For example, the means may be implemented in a circuitry (e.g., the memory 602 and processor 604) or a software module.

[0110] 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 anddescriptive 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 hereinabove.

[0111] Certain abbreviations that may be found in the description and / or in the figures are herewith defined as follows.CU Central UnitDU Distributed UnitLTM Lower layer triggered switching or Layer 1 / Layer 2 triggered mobilityTCI Transmission Configuration IndicatorSSB Synchronisation Signal BlockMAC Medium Access ControlMCG Master Cell GroupPCell Primary CellPDCCH Physical downlink control channelPSCell Primary Secondary CellSCell Secondary CellSCG Secondary Cell GroupSpCell Special CellUE User Equipment

Claims

CLAIMS:

1. An apparatus comprising: at least one processor; and at least one memory coupled to the at least one processor, configured to cause the apparatus to: receive, from a source network element, configuration information related to channel state information reference signal, CSLRS, measurement and reporting configuration for a target cell for a cell change, the target cell comprising a primary cell, PCell, and at least one secondary cell, SCell; acquire a CSLRS of the at least one Scell, wherein the at least one SCell is associated with the PCell, based on the received configuration information; perform a LI measurement of the acquired CSLRS; and transmit, to a target network element, an LI measurement report including measurement information of the acquired CSLRS, wherein data transmission to the at least one SCell is activated based on the LI measurement report of the acquired CSLRS.

2. The apparatus of claim 1, wherein the apparatus is served by a source cell associated with the source network element and the target cell is supported by the target network element.

3. The apparatus of claim 1, wherein the configuration information is included in a radio resource control (RRC) reconfiguration message.

4. The apparatus of claim 1, wherein the at least one processor is configured to cause the apparatus to: receive an L1 / L2 triggered mobility (LTM) switching command, from the source network element, to switch to the target cell; send an LTM switching complete message to the target cell on switching to the target cell; and start the CSLRS measurement and reporting for the target cell.

5. The apparatus of claim 1, wherein the at least one processor is configured to cause the apparatus to receive an LTM switching command, from the source network element, to switch to the at least one SCell, and wherein the LTM switching command is based on the LI measurement report of the acquired CS RS.

6. The apparatus of claim 1, wherein the CSI-RS measurement and reporting configuration is linked to a physical uplink shared channel (PUSCH) configured for an LTM switching complete message from the UE.

7. The apparatus of claim 1, wherein the apparatus acquires the CSI-RS based on an uplink grant location linked to a CSI-RS location provided in the configuration information.

8. The apparatus of claim 1, wherein prior to acquiring the CSI-RS of the at least one SCell, the at least one processor is configured to cause the apparatus to generate and transmit, to the source network element, an LI measurement report of the PCell based on the configuration information.

9. The apparatus of claim 8, wherein the at least one processor is configured to cause the apparatus to receive an L1 / L2 triggered mobility (LTM) switching command to switch to the PCell based on the LI measurement report of the PCell.

10. The apparatus of claim 9, wherein the switching of the apparatus to the PCell occurs RACHless.

11. The apparatus of claim 5, wherein the switching of the apparatus to the at least one Scell occurs RACHless.

12. The apparatus of claim 1, wherein the CSI-RS measurement and reporting is aperiodic or semi-static.

13. An apparatus comprising: at least one processor: and at least one memory coupled to the at least one processor, configured to cause the apparatus to: receive configuration information related to channel state information reference signal, CSI-RS, measurement and reporting configuration for a target cell for a cell change, the target cell comprising a primary cell, PCell, and at least one secondary cell, SCell; transmit, to a UE, the configuration information; and transmit, to the UE, an L1 / L2 triggered mobility (LTM) switching command to switch to the target cell.

14. The apparatus of claim 13, wherein the apparatus serves the UE, and the target cell is supported by a target network element.

15. The apparatus of claim 13, wherein the configuration information is included in a radio resource control (RRC) reconfiguration message.

16. The apparatus of claim 13, wherein the CSI-RS measurement and reporting configuration is linked to a physical uplink shared channel (PUSCH) on which data transmission to the PCell occurs after the apparatus transmits the LTM switching command to the UE.

17. The apparatus of claim 13, wherein based on the LTM switching command, the UE switches to the target cell, such that switching occurs RACHless.

18. The apparatus of claim 13, wherein the CSI-RS measurement and reporting is aperiodic or semi-static.

19. A method by a user equipment (UE) comprising: receiving, from a source network element, configuration information related to channel state information reference signal, CSI-RS, measurement and reporting configurationfor a target cell, for a cell change, the target cell comprising a primary cell, PCell, and at least one secondary cell, SCell; acquiring a CSI-RS of the at least one Scell, wherein the at least one SCell is associated with the PCell based on the received configuration information; performing a LI measurement of the acquired CSI-RS; and transmitting, to a target network element, a LI measurement report including measurement information of the acquired CSI-RS, wherein data transmission to the at least one SCell is activated based on the LI measurement report of the acquired CSI-RS.

20. The method of claim 19, wherein the UE is served by a source cell associated with the source network element and the target cell is supported by the target network element.

21. The method of claim 19, wherein the configuration information is included in a radio resource control (RRC) reconfiguration message.

22. The method of claim 19, further comprising: receiving an L1 / L2 triggered mobility (LTM) switching command, from the source network element, to switch to the target cell; sending an LTM switching complete message to the target cell on switching to the target cell; and starting the CSI-RS measurement and reporting for the target cell.

23. The method of claim 19, wherein the UE receives an LTM switching command to switch the at least one SCell, wherein the LTM switching command is based on the LI measurement report of the acquired CSI-RS.

24. The method of claim 23, wherein the CSI-RS measurement and reporting configuration is linked to a physical uplink shared channel (PUSCH) configured for an LTM switching complete message from the UE.

125. The method of claim 19, wherein the method comprises: the UE acquiring the CSI-RS based on an uplink grant location linked to a CSI-RS location provided in the configuration information.

26. The method of claim 25, wherein the method comprises: prior to acquiring the CSI-RS of the at least one SCell, generating and transmitting, to the source network element an LI measurement report of the PCell based on the configuration information.

27. The method of claim 19, further comprising receiving an LTM switching command to switch to the PCell based on the LI measurement report of the PCell.

28. The method of claim 27, wherein the switching of the UE to the PCell occurs RACHless.

29. The method of claim 23, wherein the switching of the UE to the at least one Scell occurs RACHless.

30. The method of claim 19, wherein the CSI-RS measurement and reporting is aperiodic or semi-static.

31. A method by a source network element comprising: receiving configuration information related to channel state information reference signal, CSI-RS, measurement and reporting configuration for the target cell for a cell change, the target cell comprising a primary cell, PCell, and at least one secondary cell, SCell; transmitting, to the UE, the configuration information; and transmitting, to the UE, an L1 / L2 triggered mobility (LTM) switching command to switch to the target cell.

32. The method of claim 31, wherein the source network element serves the UE, and the target cell is supported by a target network element.

33. The method of claim 31, wherein the configuration information is included in a radio resource control (RRC) reconfiguration message.

34. The method of claim 31, wherein the CSI-RS measurement and reporting configuration is linked to a physical uplink shared channel (PUSCH) on which the data transmission to PCell occurs after the source network element transmits an LTM switching command to the UE.

35. The method of claim 31, wherein based on the LTM switching command, the UE switches to the target Cell, such that the switching occurs RACHless.

36. The method of claim 31, wherein the CSI-RS measurement and reporting is aperiodic or semi-static.

37. An apparatus comprising: at least one processor; and at least one memory coupled to the at least one processor, configured to cause the apparatus to: receive, from a source network element, configuration information for a target cell for a cell change, the target cell comprising a primary cell, PCell, and at least one secondary cell, SCell; transmit, to the source network element, an LI measurement report of the PCell based on the configuration information; receive an L1 / L2 triggered mobility (LTM) switching command to switch to the PCell based on the configuration information, wherein the LTM switching command includes information on channel state information reference signal, CSI-RS, measurement and reporting configuration of the at least one Scell associated with the Pcell; acquire a CSI-RS of the at least one Scell based on the information in the LTM switching command; perform a LI measurement of the acquired CSI-RS; andtransmit, to a target network element, an LI measurement report of the acquired CSL RS, wherein data transmission to the at least one SCell is activated based on the LI measurement report of the acquired CS RS.

38. The apparatus of claim 37, wherein the apparatus is served by a source cell associated with the source network element and the target cell is supported by the target network element.

39. The apparatus of claim 37, wherein the configuration information is included in a radio resource control (RRC) reconfiguration message.

40. The apparatus of claim 37, wherein a Physical Downlink Control channel, PDCCH, providing an uplink UL grant for an LTM switching complete message, configures CSI-RS measurement and reporting in the target cell.

41. The apparatus of claim 37, wherein the least one processor is configured to cause the apparatus to transmit data to the at least one Scell on a Physical Uplink Shared Channel, PUS CH, linked to the measurement and reporting configuration in the LTM switching command.

42. The apparatus of claim 37, wherein the LTM switching command includes a MAC CE for activating the measurement of the at least one SCell.

43. The apparatus of claim 37, wherein the LTM switching command is scheduled by downlink control information that configures CSLRS measurement and reporting in the target cell.

44. The apparatus of claim 40, wherein the CSLRS measurement and reporting is aperiodic or semi-static.

45. An apparatus comprising: at least one processor: and at least one memory coupled to the at least one processor, configured to cause the apparatus at least to: receive configuration information related to a target cell for a cell change, the target cell comprising a primary cell, PCell, and at least one secondary cell, SCell; transmit, to a UE, the configuration information related to the target cell; receive, from the UE, an LI measurement report of the PCell based on the configuration information; and transmit, to the UE, an L1 / L2 triggered mobility (LTM) switching command to switch to the PCell based on the configuration information, wherein the LTM switching command includes information on channel state information reference signal, CSI-RS, measurement and reporting configuration of the at least one Scell associated with the Pcell.

46. The apparatus of claim 45, wherein the apparatus serves the UE, and the target cell is supported by a target network element.

47. The apparatus of claim 45, wherein the configuration information is included in a radio resource control (RRC) reconfiguration message.

48. The apparatus of claim 45, wherein the data transmission to the at least one SCell occurs on a PUS CH linked to the measurement and reporting configuration in the LTM switching command.

49. The apparatus of claim 45, wherein the apparatus includes a MAC CE, in the LTM switching command, for activating the measurement of the CSI-RS of the at least one Scell.

50. The apparatus of claim 45, wherein the least one processor is configured to cause apparatus to schedule the LTM switching command by downlink control information that configures CSI-RS measurement and reporting in the target cell.

51. The apparatus of claim 45, wherein the CSI-RS measurement and reporting is aperiodic or semi-static.

52. A method by a user equipment (UE) comprising: receiving, from a source network element, configuration information for a target cell for a cell change, the target cell comprising a primary cell, PCell, and at least one secondary cell, SCell; transmitting, to the source network element, an LI measurement report of the PCell based on the configuration information; receiving an L1 / L2 triggered mobility (LTM) switching command to switch to the PCell based on the configuration information, wherein the LTM switching command includes information on channel state information reference signal, CSI-RS, measurement and reporting configuration of the at least one Scell associated with the Pcell; acquiring a CSI-RS of the at least one Scell based on the information in the LTM switching command; performing a LI measurement of the acquired CSI-RS; and transmitting, to a target network element, an LI measurement report of the acquired CSI- RS, wherein data transmission to the at least one SCell is activated based on the LI measurement report of the acquired CSI-RS.

53. The method of claim 52, wherein the UE is served by a source cell associated with the source network element and the target cell is supported by the target network element.

54. The method of claim 52, wherein the configuration information is included in a radio resource control (RRC) reconfiguration message.

55. The method of claim 52, wherein a Physical Downlink Control channel, PDCCH, providing an uplink UL grant for an LTM switching complete message, configures CSI-RS measurement and reporting in the target cell.

56. The method of claim 52, wherein the data transmission to the at least one SCell occurs on a Physical Uplink Shared Channel, PUSCH, linked to the measurement and reporting configuration in the LTM switching command.

57. The method of claim 52, wherein the LTM switching command includes a MAC CE for activating the measurement of the at least one SCell.

58. The method of claim 52, wherein the LTM switching command is scheduled by downlink control information that configures CSLRS measurement and reporting in the target cell.

59. The method of claim 52, wherein the CSI-Rs measurement and reporting is aperiodic or semi-static.

60. A method by a source network element comprising: receiving configuration information related to a target cell for a cell change, the target cell comprising a primary cell, PCell, and at least one secondary cell, SCell; transmitting, to a UE, the configuration information related to the target cell; receiving from the UE, an LI measurement report of the PCell based on the configuration information; and transmitting, to the UE, an LTM switching command to switch to the PCell based on the configuration information, wherein the LTM switching command includes information on channel state information reference signal, CSI-RS, measurement and reporting configuration of the at least one Scell associated with the Pcell.

61. The method of claim 60, wherein the source network element serves the UE, and the target cell is supported by a target network element.

62. The method of claim 60, wherein the configuration information is included in a radio resource control (RRC) reconfiguration message.

63. The method of claim 60, wherein the data transmission to the at least one SCell occurs on a PUS CH linked to the measurement and reporting configuration in the LTM switching command.

64. The method of claim 60, wherein the LTM switching command includes a MAC CE for activating the measurement of the CSLRS of the at least one SCell.

65. The method of claim 60, wherein the LTM switching command is scheduled by downlink control information that configures CSLRS measurement and reporting in the target cell.

66. The method of claim 60, wherein the CSLRs measurement and reporting is aperiodic or semi-static.

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