Candidate cell channel state information acquisition in lower-layer triggered mobility

Abstract

A method is provided that includes receiving a channel state information (CSI) measurement configuration for performing one or more channel measurements, and an event-triggered layer 1 (L1) measurement reporting configuration including one or more reporting events associated with one or more candidate cells configured for handover. The method includes performing L1 measurements on the one or more candidate cells according to the event-triggered L1 measurement reporting configuration associated with candidate cells configured for handover. The method includes making a determination that a reporting event of the one or more reporting events is fulfilled based on the L1 measurements, and selecting at least one of the one or more candidate cells. And the method includes performing the one or more channel measurements according to the CSI measurement configuration to acquire CSI for the at least one of the candidate cells.

Description

CANDIDATE CELL CHANNEL STATE INFORMATIONACQUISITION IN LOWER-LAYER TRIGGERED MOBILITYTECHNOLOGICAL FIELD

[0001] The present disclosure relates generally to telecommunications and, in particular, to channel state information acquisition in a telecommunications system.BACKGROUND

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

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

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

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

[0006] Example implementations of the present disclosure are directed to telecommunications and, in particular, to channel state information acquisition in a telecommunications system. The present disclosure includes, without limitation, the following example implementations.

[0007] Some example implementations provide an apparatus comprising: at least one memory configured to store instructions; and at least one processing circuitry configured to access the at least one memory, and execute the instructions to cause the apparatus to at least: receive a channel state information (CSI) measurement configuration for performing one or more channel measurements, and an event- triggered layer 1 (LI) measurement reporting configuration including one or more reporting events associated with one or more candidate cells configured for handover; perform layer 1 measurements on the one or more candidate cells according to the event-triggered LI measurement reporting configuration associated with candidate cells configured for handover; make a determination that a reporting event of the one or more reporting events is fulfilled based on the LI measurements; select at least one of the one or more candidate cells; and perform the one or more channel measurements according to the CSI measurement configuration to acquire CSI for the at least one of the candidate cells.

[0008] Some example implementations provide a method comprising: receiving a channel state information (CSI) measurement configuration for performing one or more channel measurements, and an event-triggered layer 1 (LI) measurement reportingconfiguration including one or more reporting events associated with one or more candidate cells configured for handover; performing LI measurements on the one or more candidate cells according to the event-triggered LI measurement reporting configuration associated with candidate cells configured for handover; making a determination that a reporting event of the one or more reporting events is fulfilled based on the LI measurements; selecting at least one of the one or more candidate cells; and performing the one or more channel measurements according to the CSI measurement configuration to acquire CSI for the at least one of the candidate cells.

[0009] Some example implementations provide an apparatus comprising: at least one memory configured to store instructions; and at least one processing circuitry configured to access the at least one memory, and execute the instructions to cause the apparatus to at least: receive a channel state information (CSI) measurement configuration for performing one or more channel measurements, and a configuration including one or more handover conditions associated with one or more candidate cells configured for handover; perform layer 1 (LI) measurements according to the configuration including the one or more handover conditions; make a determination to begin an evaluation of the one or more handover conditions for at least one of the one or more candidate cells; perform the one or more channel measurements according to the CSI measurement configuration to acquire CSI for the at least one of the one or more candidate cells; and perform the evaluation of the one or more handover conditions for the at least one of the one or more candidate cells based on the LI measurements, and triggered by the determination.

[0010] Some example implementations provide a method comprising: receiving a channel state information (CSI) measurement configuration for performing one or more channel measurements, and a configuration including one or more handover conditions associated with one or more candidate cells configured for handover; performing layer 1 (LI) measurements according to the configuration including the one or more handover conditions; making a determination to begin an evaluation of the one or more handover conditions for at least one of the one or more candidate cells; performing the one or more channel measurements according to the CSI measurement configuration to acquire CSI for the at least one of the one or more candidate cells; and performing the evaluation ofthe one or more handover conditions for the at least one of the one or more candidate cells based on the LI measurements, and triggered by the determination.

[0011] These and other features, aspects, and advantages of the present disclosure will be apparent from a reading of the following detailed description together with the accompanying figures, which are briefly described below. The present disclosure includes any combination of two, three, four or more features or elements set forth in this disclosure, regardless of whether such features or elements are expressly combined or otherwise recited in a specific example implementation described herein. The present disclosure is intended to be read holistically such that any separable features or elements of the disclosure, in any of its aspects and example implementations, should be viewed as combinable unless the context of the disclosure clearly dictates otherwise.

[0012] It will therefore be appreciated that this Brief Summary is provided merely for purposes of summarizing some example implementations so as to provide a basic understanding of some aspects of the disclosure. Accordingly, it will be appreciated that the above described example implementations are merely examples and should not be construed to narrow the scope or spirit of the disclosure in any way. Other example implementations, aspects and advantages will become apparent from the following detailed description taken in conjunction with the accompanying figures which illustrate, by way of example, the principles of some described example implementations.BRIEF DESCRIPTION OF THE FIGURE(S)

[0013] Having thus described example implementations of the disclosure in general terms, reference will now be made to the accompanying figures, which are not necessarily drawn to scale, and wherein:

[0014] FIG. 1 illustrates a telecommunications system that includes one or more public land mobile networks (PLMNs) coupled to one or more external data networks, according to some example implementations of the present disclosure;

[0015] FIG. 2 illustrates a 5G deployment of a PLMN, according to some example implementations;

[0016] FIG. 3 is a signaling chart for a L1 / L2 -triggered mobility, also known as lower-layer triggered mobility (LTM) procedure;

[0017] FIG. 4 illustrates LTM-related configurations for a user equipment, according to some example implementations;

[0018] FIG. 5 illustrates beams on which a number of synchronization signal (SS) / physical broadcast channel (PBCH) blocks (SSBs) and channel state information reference signals (CSI-RSs) may be transmitted;

[0019] FIGS. 6Aand 6B illustrate a signaling chart for an LTM procedure including channel state information (CSI) acquisition, according to some example implementations;

[0020] FIG. 7 illustrates a signaling chart for a conditional LTM procedure including CSI acquisition, according to some example implementations;

[0021] FIGS. 8 A, 8B and 8C are flowcharts illustrating various steps in a method, according to various example implementations;

[0022] FIGS. 9A, 9B and 9C are flowcharts illustrating various steps in a method, according to various example implementations; and

[0023] FIG. 10 illustrates an apparatus according to some example implementations.DETAILED DESCRIPTION

[0024] Some implementations of the present disclosure will now be described more fully hereinafter with reference to the accompanying figures, in which some, but not all implementations of the disclosure are shown. Indeed, various implementations of the disclosure may be embodied in many different forms and should not be construed as limited to the implementations set forth herein; rather, these example implementations are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art. Like reference numerals refer to like elements throughout.

[0025] Unless specified otherwise or clear from context, references to first, second or the like should not be construed to imply a particular order. A feature described as being above another feature (unless specified otherwise or clear from context) may instead be below, and vice versa; and similarly, features described as being to the left of another feature else may instead be to the right, and vice versa. Also, while reference may be made herein to quantitative measures, values, geometric relationships or the like, unless otherwise stated, any one or more if not all of these may be absolute or approximate toaccount for acceptable variations that may occur, such as those due to engineering tolerances or the like.

[0026] As used herein, unless specified otherwise or clear from context, the “or” of a set of operands is the “inclusive or” and thereby true if and only if one or more of the operands is true, as opposed to the “exclusive or” which is false when all of the operands are true. Thus, for example, “[A] or [B]” is true if [A] is true, or if [B] is true, or if both [A] and [B] are true. Further, the articles “a” and “an” mean “one or more,” unless specified otherwise or clear from context to be directed to a singular form. Furthermore, it should be understood that unless otherwise specified, the terms “data,” “content,” “digital content,” “information,” and similar terms may be at times used interchangeably. The term “network” may refer to a group of interconnected computers including clients and servers; and within a network, these computers may be interconnected directly or indirectly by various means including via one or more switches, routers, gateways, access points or the like.

[0027] Reference may be made herein to terms specific to a particular system, architecture or the like, but it should be understood that example implementations of the present disclosure may be equally applicable to any of a number of systems, architectures and the like. For example, reference may be made to 3 GPP technologies such as Global System for Mobile Communications (GSM), UMTS, LTE, LTE Advanced, 5GNR, 5G Advanced and 6G; however, it should be understood that example implementations of the present disclosure may be equally applicable to non-3GPP technologies such as IEEE 802, Bluetooth and Bluetooth Low Energy.

[0028] Further, as used in this application, the term “circuitry” may refer to one or more or all of the following: (a) hardware-only circuit implementations (such as implementations in only analog and / or digital circuitry); (b) combinations of hardware circuits and software, such as (as applicable): (i) a combination of analog and / or digital hardware circuit(s) with software / firmware and (ii) any portions of hardware processor(s) with software (including digital signal processor(s)), software, and memory(ies) that work together to cause an apparatus, such as a mobile phone or server, to perform various functions); or (c) hardware circuit(s) and / or processor(s), such as a microprocessor(s) or aportion 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.

[0029] The above definition of circuitry applies to all uses of this term in this application, including in any claims. As a further example, as used in this application, the term circuitry also covers an implementation of merely a hardware circuit or processor (or multiple processors) or portion of a hardware circuit or processor and its (or their) accompanying software and / 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.

[0030] FIG. 1 illustrates a telecommunications system 100 according to various example implementations of the present disclosure. The telecommunications system generally includes one or more telecommunications networks. As shown, for example, the system includes one or more PLMNs 102 coupled to one or more other external data networks 104 - notably including a wide area network (WAN) such as the Internet. Each of the PLMNs includes a core network (CN) 106 backbone such as the Evolved Packet Core (EPC) of LTE, the 5G core network (5GC) or the like; and each of the core networks and the Internet are coupled to one or more RANs 108, air interfaces or the like that implement one or more radio access technologies (RATs). As used herein, a “network device” refers to any suitable device at a network side of a telecommunications network. Examples of suitable network devices are described in greater detail below.

[0031] In addition, the system includes one or more radio units that may be varyingly known as user equipment (UE) 110, terminal device, terminal equipment, mobile station or the like. The UE is generally a device configured to communicate with a network device or a further UE in a telecommunications network. The UE may be a portable computer (e.g., laptop, notebook, tablet computer), mobile phone (e.g., cell phone, smartphone), wearable computer (e.g., smartwatch), or the like. In other examples, the UE may be an Internet of things (loT) device, an industrial loT (IIoT device), a vehicle equipped with a vehicle-to-everything (V2X) communication technology, or the like. In some examples, as referenced by 3 GPP, the UE may be a narrowband loT (NB-IoT)device, an enhanced machine-type communication (eMTC) device, a reduced capability (RedCap) device, an ambient loT device, or the like.

[0032] In operation, these UEs 110 may be configured to connect to one or more of the RANs 108 according to their particular radio access technologies to thereby access a particular CN 106 of a PLMN 102, or to access one or more of the external data networks 104 (e.g., the Internet). The external data network may be configured to provide Internet access, operator services, 3rd party services, etc. For example, the International Telecommunication Union (ITU) has classified 5G mobile network services into three categories: enhanced mobile broadband (eMBB), ultra- reliable and low-latency communications (URLLC), and massive machine type communications (mMTC) or massive internet of things (MIoT).

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

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

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

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

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

[0038] In some deployments, operations of a gNB 206 or other radio access node may be distributed or functionally split into components including one or more remote radio head (RRHs) or radio units (RUs) 208, and a baseband unit (BBU); and in some architectures, the BBU may be split into a distributed unit (DU) 210 and a central / centralized unit (CU) 212, such as a server, host or node. In some architectures, the RRH / RU and DU may be co-located. It is also possible that node operations may be distributed among a plurality of servers, hosts or nodes. It should also be understood that the distribution of work between CN operations and radio access node operations may vary depending on implementation.

[0039] As shown and described, for example, some 5G deployments may be based on a so-called CU-DU split including one or more DUs 210 and a CU 212. One gNB-CU (central node) may control one or more gNB-DUs. The gNB-CU may control a plurality of spatially separated gNB-DUs, acting at least as transmit / receive (Tx / Rx) nodes. In some example implementations, however, the gNB-DUs (also called DU) may include, for example, a radio link control (RLC), medium access control (MAC) layer and a physical (PHY) layer, whereas the gNB-CU (also called a CU) may include the layers above the RLC layer, such as a packet data convergence protocol (PDCP) layer, a radio resource control (RRC), and an internet protocol (IP) layer. Other functional splits are also possible. It is considered that a skilled person is familiar with the open systems interconnection (OSI) model and the functionalities within each layer.

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

[0041] Currently in 3 GPP, mainstream mobility has been conducted using higher layer (L3 or RRC controlled) mobility. In this regard, L3 handover based mobility is awell-known and proven method for ensuring a robust way of handing over the UE 110 from one serving cell (source cell) of a radio access node 202 to a new serving cell (target cell) of the same or another radio access node. The method has been used at least since GSM and is still in use in 5GNR. It is expected that L3 mobility (legacy handover) will also be commonly used in the future.

[0042] L1 / L2 -triggered mobility, or lower-layer triggered mobility (LTM) moves the execution of the ‘handover’ from one cell to another from higher layers (L3), such as RRC, to lower layers. These lower layers may be either PHY (or LI) or MAC (or L2). LTM may reduce latency, overhead and interruption time when compared to L3 handover based mobility. In a CU-DU split architecture, LTM may support one or more of intra- DU mobility, intra-CU inter-DU mobility, or inter-CU inter-DU mobility.

[0043] FIG. 3 illustrates a signaling chart 300 for an LTM procedure of a UE 110 in a RRC connected state with a gNB 206, which has been proposed. During LTM preparation, as shown at step 301, the UE sends a L3 measurement report to the gNB, which decides to use LTM and initiate LTM candidate preparation. The gNB at step 302 transmits a RRC reconfiguration message to the UE, including the configuration of one or more candidate cells. The RRC reconfiguration message may also include a configuration of LI measurement reporting for LTM execution. The UE stores the configurations, and the UE at step 303 transmits a RRC reconfiguration complete message to the gNB.

[0044] An early synchronization of the UE 110 with the candidate cell(s) follows LTM preparation. As shown at step 304, the UE 110 performs downlink (DL) and may perform uplink (UL) synchronization with the candidate cell(s). For DL synchronization, the gNB 206 may perform an early activation of configured transmission configuration indicator (TCI) states for the candidate cell(s), such as via a MAC control element (MAC CE). The UE may receive this TCI state activation MAC CE, and begin monitoring configured DL reference signal (RS) resources associated with the activate TCI states to synchronize with the candidate cell(s).

[0045] During early UL synchronization, the UE 110 may acquire a timing advance (TA) of respective one or more of the candidate cell(s). In this regard, the gNB 206 may request that the UE to perform early TA acquisition for example via contention free random access (CFRA) triggered by a physical downlink control channel (PDCCH) order(using downlink control information (DCI) format 1 0) or other TA acquisition command, following which the UE 110 sends a random access channel (RACH) preamble on the physical random access channel (PRACH) towards an indicated candidate cell. In 3 GPP, the random access (RA) or RACH preamble is sent as a first message (msgl) as part of a RA or RACH procedure; and accordingly, the RA or RACH preamble may at times be referred to as msgl. In order to minimize the data interruption of the gNB due to CFRA towards the candidate cell(s), the UE may not receive a random access response (RAR) from the network (from the candidate cell) for the purpose of TA value acquisition, and the TA value to be used when accessing the candidate cell may be indicated in a subsequent cell switch command.

[0046] This early synchronization may reduce interruption during LTM execution, as compared to L3 handover based mobility. In this regard, the TA may be used to control the timing of uplink transmissions of a UE toward the candidate cell(s). The UE may likewise have an acquired TA of the cell of the gNB to control the timing of uplink transmissions toward the gNB.

[0047] During LTM execution, the UE 110 performs LI measurements on the configured candidate cell(s), and the UE at step 305 transmits LI measurement reports to the gNB 206. The gNB decides to execute a cell switch (more generally a handover), and selects one of the candidate cell(s) as a target cell for the cell switch. The gNB then at step 306 transmits a cell switch command, such as a MAC CE, to trigger cell switch. The UE switches to the configuration of the target cell; and if the TA of the target cell (from step 304) is no longer available (or otherwise not acquired), the UE at step 307 initiates a RACH procedure with the target cell to acquire the TA of the target cell. In some cases, the cell switch command may include CFRA RACH related parameters for the UE to perform the RACH procedure. The UE then at step 308 indicates successful completion of the cell switch.

[0048] In 3GPP, Release-18 LTM, information about measurement resources (SSBs) from candidate cells are provided to the UE 110 so that UE can make measurements. The UE may also be configured with LI measurement reporting configuration where the UE can report the measurements. For LTM, periodic and semi-persistent report on physicaluplink control channel (PUCCH), semi-persistent report on physical uplink shared channel (PUSCH), and aperiodic report on PUSCH are supported.

[0049] As shown in FIG. 4, a UE 110 can be configured with one or more LTM CSI reporting configurations (LTM-CSI-ReportConfig) where each reporting configuration includes a LTM CSI resource configuration (LTM-CSI-ResourceConfig) with the information of resources to be used for channel measurements (reference signal received power (RSRP) measurements). For each reporting configuration, the UE may be configured to report M beams from each of the L configured candidate cells. In this regard, each LTM CSI resource setting (LTM-CSI-ResourceConfig) may include configuration of an LTM -CSI -SSB-Re source Set which comprises of a list of Z > 1 synchronization signal (SS) / physical broadcast channel (PBCH) block (SSB) indices (given by Itm-CSI-SSB-ResourceList) and a list of Z LTM-Candidatelds (given by Itm- CandidatelDList) referring to candidate cells associated with the SSB indices. An SSB may also at times be more simply referred to as a synchronization signal block (SSB).

[0050] For each candidate cell, the UE 110 may determines the time domain behavior of a SSB resource from ssb-Periodicity and ssb-PositionsInBurst and the frequency domain behavior of a SSB resource is determined by the higher layer parameters subCarrierSpacing, ssbFrequency.

[0051] LTM CSI report configurations may be given for each cell under current serving cell’s configuration where each report configuration includes an indication of a LTM CSI resource configuration and other parameters related for reporting, e.g., timing and uplink resources to transmit reports. An LTM CSI resource configuration may include a set of SSB indices from multiple candidate cells. The LTM CSI resource configuration may be placed in a common LTM configuration, i.e., in LTM-Config.

[0052] The detailed configuration of each SSB of a candidate cell indicated in a LTM CSI resource configuration may be given in LTM-SSB-Config under LTM-Candidate IE. For each candidate cell, LTM-Candidate IE may include the configuration / information which may be needed by the UE before the cell switch, e.g., SSB information for LTM measurements. The LTM-Candidate IE also includes the list of NZP-CSLRS resources which are currently used to provide the information for activation of TCI states associated with tracking RS (a type of CSLRS). And even further, an LTM-Candidate IE alsoincludes RRC container (ServingCellConfig) which contains all the configuration details that will be needed by the UE after UE moves to this candidate cell after the cell switch from the current serving cell. In other words, ServingCellConfig given under LTM- Candidate IE contains the configuration details needed to perform regular serving cell operation within the candidate cell.

[0053] LTM was introduced in 3 GPP Release 18 and offers improvements in handover latency and interruption time compared to L3 mobility. But LTM as introduced also has a number of limitations relative to L3 mobility. A number of enhancements of LTM are currently under discussion to address these limitations. One of the objectives is to enable channel state information reference signal (CSI-RS) measurements for LTM procedures. In particular, enhancements are under discussion to support CSI-RS measurements for LTM procedures and enable CSI-RS beam based management.

[0054] Other measurement related enhancements for supporting LTM currently under discussion include event-triggered LI measurement reporting for LTM, CSI acquisition on candidate cell(s) based on CSI-RS before or during LTM cell switch. In context of CSI acquisition, CSI may include channel parameters, such as one or more of CSI-RS resource indicator (cri), channel quality indicator (CQI), precoding matrix indicator (PMI), layer indicator (LI), and / or rank indicator (RI), which may be used to set the appropriate modulation and coding rate, appropriate multiple- input multiple output (MIMO) configuration (e.g., number of layers, precoding matrix) of the channel.

[0055] Further enhancements under discussion include support for conditional LTM (C-LTM), and in particular conditional intra-CU LTM. The details of C-LTM are currently under discussion, but it has been agreed that at least the baseline of conditional handover CHO will be reused. In this regard, the UE 110 may be configured with one or more (LI or L3 based) conditions for one or more candidate cells or RSs associate with one or more candidate cells. The conditions can be provided in the common LTM configuration or can be candidate cell / RS specific. At the event of such condition becoming met, the UE may execute a C-LTM cell switch to a candidate cell for which the condition was met.

[0056] In order to trigger the cell change in step 306 of FIG. 3, the serving DU (in a CU-DU split architecture) may need to indicate a TCI state. As currently specified, thisTCI state includes QCL information for receiving on the PDCCH / physical downlink shared channel (PDSCH) from a candidate (target) cell (DL reception), and / or for transmitting on the PUCCH / PUSCH to a candidate (target) cell (UL transmission). The QCL information, in turn, includes the RS, QCL type, and the bandwidth part (bwp) where the RS is located. The QCL type may indicate a typeA (Doppler shift, Doppler spread, average delay, delay spread), typeB (Doppler shift, Doppler spread), typeC (Doppler shift, average delay), or typeD (spatial RX parameter).

[0057] The information element (IE) NZP-CSI-RS-Resource may be used to configure non-zero-power (NZP) CSLRS transmitted in the cell where the IE is included, which the UE may be configured to measure on. A change of configuration between periodic, semi-persistent or aperiodic for an NZP-CSI-RS-Resource may be supported with a release and add.

[0058] For a CSI-RS resource, there may be an SSB index that serves as a source RS for quasi co-location (QCL) information that may be configured by the NG-RAN 204. For periodic CSI-RSs, the QCL information may be given by an IE (qcl-InfoPeriodicC SIRS) that points to a TCI state, which further points to its QCL source RS. For other types of CSI-RSs, i.e., semi-persistent CSLRS, TCI state information can be provided by other means, i.e., dynamic signaling like MAC CE. For an aperiodic CSLRS, the TCI state information may be provided in the RRC configuration but can be also be updated dynamically based on the indicated TCI state(s) if the aperiodic CSLRS is configured to follow the unified TCI states. This connection between CSLRS and SSB can be done either direct or indirect QCL chain reference. In case of direct QCL reference, a SSB can be configured as the QCL source of the CSLRS. In case of indirect QCL reference, for example, a CSLRS can have another CSI-RS as the QCL reference where the reference CSI-RS has a SSB as its QCL reference. Given that an SSB is typically transmitted using a wider beam compared with a CSI-RS, multiple CSI-RS indices might be associated with the same source SSB-index.

[0059] FIG. 4 illustrates beams 400 on which a number of SSBs and CSI-RSs may be transmitted. Given that an SSB is typically transmitted using a wider beam compared with a CSI-RS, multiple CSI-RS indices may be associated with the same source SSB index. As shown in FIG. 5, for example, SSB1 serves as a source RS for QCLinformation of four CSI-RS indices, namely, CSI-RS1, CSI-RS2, CSI-RS3 and CSI-RS4. Likewise, SSB2 serves as a source RS for another four CSI-RS indices, namely, CSI- RS5, CSI-RS6, CSI-RS7 and CSI-RS8.

[0060]

[0061] In a number of cases, link adaptation is important for good spectral efficiency. Appropriate modulation and coding rate for data channels can be determined based on the link quality that may be indicated by CSI (CQI, PMI, RI, etc.) or other channel parameters. Likewise, an aggregation level for a control channel (e.g., PDCCH) can be determined based on CSI.

[0062] One of the motivations of LTM is to maintain high data transmission efficiency (or spectral efficiency) in the process of fast cell switch. To achieve this, CSI acquisition based on CSI-RS for the candidate cells has been agreed as one of the objectives for enhancement to LTM. With this, the UE 110 would be able to acquire and report the CSI parameters (e.g., CQI, PMI, RI, or / and LI) for a candidate cell, which then can be used for the transmission / reception in the target cell after the cell switch. This would reduce the need of additional measurements for CSI acquisition in the target cell for initial transmissions / receptions. The UE may still acquire CSI information for the target cell without absent early CSI acquisition, but this is typically done after the cell change. In this case, the target cell will receive the first CSI measurements only after some time that is needed for the UE perform these measurements (measurement delay); and during this time, the target cell will not be able to make optimal radio resource management (RRM) decisions.

[0063] Most UEs 110 are expected to have limited capability to perform measurements (in addition to SSB / CSLRS measurements for other purpose, e.g., cell switch, beam refinement) for CSI acquisition for all configured candidate cells, and it is currently not defined when the UE shall perform these measurements. Example implementations of the present provide a solution to reduce the UE measurements for CSI acquisition for multiple CSI-RSs configured for prepared candidate cells, by limiting the measurements to only candidate cells / RSs which are more potential to become the target cell. In this regard, example implementations of the present disclosure provide solutions for down-selection of CSI acquisition measurements for candidate cell(s).

[0064] Example implementations of the present disclosure may be applied in a number of different scenarios, including (1) event-triggered LI measurement reporting for handover, and (2) conditional handover. Example implementations are primarily descried in the context of LTM and C-LTM, but it should be understood that example implementations may equally apply to other types of handover.

[0065] In the case of event-triggered LI measurement reporting, a UE 110 may report channel strength (e.g., Ll-RSRP, Ll-SINR) of candidate RSs belonging to candidate cells. The channel strength may be expressed as LI RSRP (Ll-RSRP), LI signal-to- interference-plus-noise ratio (Ll-SINR), or the like. The purpose of event-triggered report for LTM is to reduce LI measurement reporting overhead on both the UE and the network side, and to enable network to configure early DL synchronization or cell switch based on the event-triggered reports. An event-triggered measurement report may therefore be considered a first step towards cell switch. Once the event is fulfilled, the UE is allowed an event-triggered reporting delay of one measurement period before it is required to send the report.

[0066] In the case of event-triggered LI measurement reporting, some example implementations provide a solution in which the UE 110 may select candidate cell(s) for CSI acquisition measurements based on the event-triggered LI measurement reporting. Likewise, in some examples, the UE may select CSLRS resources for the selected candidate cells for CSI acquisition measurements. The UE may prioritize a subset of cells / RSs for CSI acquisition measurements, such as when the UE capability does not allow the UE to perform CSI acquisition measurements for all of the selected cells / RSs based on the event- triggered LI measurement reporting. And in some examples, the UE may select cells / RSs for which to stop CSI acquisition measurements.

[0067] In the case of event-triggered LI measurement reporting, the UE 110 may be configured with LI measurements and event-triggered LI measurement reporting for one or more candidate cells. The UE may perform an evaluation based on measurements whether the condition for the event-triggered reporting becomes fulfilled for the configured event(s).

[0068] In some examples, the UE 110 may determine to perform CSI acquisition for one or more channel measurements (CSI measurements), such as CQI, CRI, PMI, RI,or / and LI, for a candidate cell based on a certain condition. In some of these examples, the condition may be an event / condition for an event-triggered LI measurement reporting (associated with the candidate cell) is fulfilled / met. Another example of a suitable condition is an event-triggered LI measurement report containing information (e.g., RS indicator or / and measurements) at least associated with the candidate cell is sent. And yet another example of a suitable condition is an acknowledgement received for an event- triggered measurement report including information (e.g., RS indicator or / and measurements) at least associated with the candidate cell.

[0069] In some examples, configuration of one or more CSLRSs associated with one or more candidate cell for CSI acquisition may be provided to the UE in the handover (e.g., LTM) configuration. The UE may select a subset of those configured CSLRSs for CSI acquisition. In some examples, upon determining that the UE 110 is configured to acquire CSI based on event-triggered LI measurement reporting, the UE may determine the one or more RSs (e.g., CSI-RS) or / and the QCL assumption (e.g., the QCL source of the RS) used for performing the channel measurements for CSI acquisition. The CSI acquisition may be based on the RS or RSs for which an event / condition for an event- triggered LI measurement reporting is met. Additionally or alternatively, the CSI acquisition may be based on the RS or RSs for which an event-triggered LI measurement reporting contains the information. Such RS / RSs may be a subset of RSs configured for CSI acquisition. As an example, if SSB ‘N’ of cell 1 is reported in the event-triggered LI measurement reporting, the UE may select the configured CSLRS ‘M’ for which the QCL source RS is SSB ‘N’, and perform the CSI acquisition measurements using the given configuration of CSLRS ‘M’.

[0070] In some examples, the UE 110 may further select a subset of cells / RSs from the cells / RSs for which one or more conditions are met, such as those described above (this selection may be useful when the UE has limited capability, and may not be able to perform CSI measurements for all the RSs satisfying the one or more of the above conditions). In some of these examples, the UE may select the subset of cells / RSs based on signal quality (L1-RSRP / L1-SINR). In this regard, the UE may select the RSs with the highest signal level. For a candidate cell, for example, the UE may select the RS with thehighest signal level satisfying the above conditions. The UE may do this for more than one candidate cells satisfying the above conditions, based on the UE capability.

[0071] Additionally or alternatively, the UE 110 may select the subset of cells / RSs based on the type of configured event, such as by prioritizing cells / RSs for which a certain event is met (e.g., LTM-3 or LTM-5), compared cells / RSs for which another event is met (e.g., LTM-4). Similarly, the UE may the subset of cells / RSs based on the order in which the events were triggered.

[0072] In some examples, the UE 110 may select the subset of cells / RSs based on the status of any already performed handover step(s). The UE may prioritize cells / RSs for which there is TCI state(s) associated with the cell / RS is on an active TCI list. Additionally or alternatively, the UE may prioritize cells / RSs for which the UE has performed the UE-based TA estimation. In another example, the UE may prioritize cells / RSs for which the UE has performed PRACH transmission triggered via a PDCCH order from the source cell. And in yet another example, the UE may prioritize cells for which the UE has performed early ASN.1 decoding or / and validity check.

[0073] In some examples, the UE 110 may determine to stop CSI acquisition for a candidate cell / RS based on at least one criterion. One example of a suitable criterion for stopping the CSI acquisition is an event / condition for an event-triggered LI measurement reporting, associated with a different candidate cell / RS is fulfilled / met. Another example of a suitable criterion is an event-triggered reporting not containing any information (e.g., RS indicator or / and measurements) associated with the candidate cell / RS is sent. In another example, a criterion for stopping the CSI acquisition may be an acknowledgement is received for an event-triggered reporting not containing any information (e.g., RS indicator or / and measurements) associated with the candidate cell / RS.

[0074] Other examples of criterion for stopping the CSI acquisition include the candidate cell is no longer detectable, the UE 110 receives a cell switch command or L3 handover command, an RRC reconfiguration is performed, a predefined or network indicated time has passed since the UE started the CSI acquisition measurements. And yet examples of a criterion for stopping the CSI acquisition is the reception of TCI state activation / deactivation MAC CE deactivating a TCI state associated with the candidateRS, and / or one or more TCI states have been activated for the candidate cell and network sends a TCI state activation / deactivation MAC-CE to deactivate all TCI states for the candidate cell.

[0075] For the RS associated with the candidate cell which is selected as the target cell, the UE 110 may determine to stop CSI acquisition for a candidate RS of that cell, after the cell switch, based on at least one criterion. These criteria / criterion may include, for example, when the UE performs first UL transmission to the target cell (becomes new serving cell), or when the UE receives first reception from the target cell. In other examples, the criterion may include when the UE receives a control message / signaling from the target cell triggering the reporting of the CSI acquisition measurements, or when the UE reports CSI acquisition measurements to the target cell.

[0076] In addition to event-triggered LI measurement reporting for LTM, another scenario in which example implementations of the present disclosure may be applied is C-LTM (conditional LTM). In this scenario, the UE 110 may be configured with one or more conditions for conditional cell switch for one or more candidate cells in a candidate cell configuration. In the event a condition is fulfilled for a candidate cell, the UE may perform a cell switch to the candidate cell without a network cell switch command. The condition may be based on serving and / or neighbor cell signal level / quality such as RSRP or SINR.

[0077] In the case of C-LTM, the UE 110 may be configured with one or more conditional LTM conditions for a set or subset of prepared candidate cells. In this scenario, some example implementations provide a solution in which the UE may select candidate cell(s) for CSI acquisition measurements based on the C-LTM condition evaluation. Likewise, in some examples, the UE may select CSI-RS resources for the selected candidate cells for CSI acquisition measurements. The UE may prioritize a subset of cells / RSs for CSI acquisition measurements, such as when the UE capability does not allow the UE to perform CSI acquisition measurements for all of the selected cells / RSs based on the C-LTM condition evaluation. And in some examples, the UE may select cells / RSs for which to stop CSI acquisition measurements.

[0078] When the UE 110 is configured with conditional LTM conditions for a set or subset of prepared candidate cells, the condition evaluation for C-LTM cell switch maybe restricted to a subset of configured candidate cells or a subset of RS configured for those candidate cells based on any configured or specified trigger.

[0079] In some examples, the UE 110 may determine to perform CSI acquisition for one or more channel measurements (CSI measurements), such as CQI, CRI, PMI, RI, or / and LI, for a candidate cell based on a certain condition. In some of these examples, the condition may be when the UE determines to start evaluating the C-LTM condition(s) for the candidate cell.

[0080] In some examples, configuration of one or more CSI-RSs associated with one or more candidate cell for CSI acquisition may be provided to the UE in the handover (e.g., LTM) configuration. The UE may select a subset of those configured CSI-RSs for CSI acquisition. In some examples, upon determining that the UE 110 is configured to acquire CSI based on C-LTM condition evaluation, the UE may determine the one or more RSs (e.g., CSI-RS) or / and the QCL assumption (e.g., the QCL source of the RS) used for performing the channel measurements for CSI acquisition. The CSI acquisition may be based on the RS or RSs for which a condition for C-LTM is being considered for evaluation. Such RS / RSs may be a subset of RSs configured for CSI acquisition.

[0081] In some examples, the UE 110 may further select a subset of cells / RSs to perform CSI measurements for CSI acquisition from the cells / RSs for which the UE determines to start evaluating the C-LTM condition(s). This selection may be useful when the UE has limited capability, and may not be able to perform CSI measurements for all the RSs satisfying the one or more of the above conditions. In some of these examples, the UE may select the subset of cells / RSs based on signal quality (L1-RSRP / L1-SINR). In this regard, the UE may select the RSs with the highest signal level for which the UE determines to start evaluating the C-LTM condition. The UE may do this for more than one candidate cells for which the UE determines to start evaluating the C-LTM condition, based on the UE capability.

[0082] In some examples, the UE 110 may select the subset of cells / RSs based on the status of any already performed handover step(s). The UE may prioritize cells / RSs for which there is TCI state(s) associated with the cell / RS is on an active TCI list. Additionally or alternatively, the UE may prioritize cells / RSs for which the UE has performed the UE-based TA estimation. In another example, the UE may prioritize1 cells / RSs for which the UE has performed PRACH transmission triggered via a PDCCH order from the source cell. And in yet another example, the UE may prioritize cells for which the UE has performed early ASN.1 decoding or / and validity check.

[0083] In some examples, the UE 110 may determine to stop CSI acquisition for a candidate cell / RS based on at least one criterion. One example of a suitable criterion for stopping the CSI acquisition is the UE tops C-LTM condition evaluation for that cell / RS. Another example of a suitable criterion is when the C-LTM condition is met and UE performs the cell switch. In another example, a criterion for stopping the CSI acquisition may be when UE receives LTM cell switch command. Yet another example of a suitable criterion is an RRC Reconfiguration is performed, And yet another example is when a predefined or network indicated time has passed since the UE started the CSI acquisition measurements.

[0084] For the RS associated with the candidate cell which is selected as the target cell, the UE 110 may determine to stop CSI acquisition for a candidate RS of that cell, after the cell switch, based on at least one criterion. These criteria / criterion may include, for example, when the UE performs first UL transmission to the target cell (becomes new serving cell), or when the UE receives first reception from the target cell. In other examples, the criterion may include when the UE receives a control message / signaling from the target cell triggering the reporting of the CSI acquisition measurements, or when the UE reports CSI acquisition measurements to the target cell.

[0085] FIGS. 6A and 6B illustrate a signaling chart 600 for an LTM procedure including CSI acquisition, according to some example implementations. The procedure is illustrated in a CU-DU split architecture, including a CU 212, a source DU (S-DU) 210A for a serving cell, and a target DU (T-DU) 210B for a target cell. The procedure is also shown for intra-CU LTM cell switch, although it should be understood that the procedure is likewise applicable to inter-CU LTM cell switch.

[0086] During preparation for LTM, as shown at steps 601 and 602, the UE 110 sends a L3 measurement report to the CU via the S-DU, and the CU at step 603 decides prepare one or more candidate target cells (DUs) for LTM.

[0087] The CU 212 may at step 604 prepare an LTM configuration including an LI measurement configuration, and an event-triggered LI measurement reportingconfiguration. The LI measurement configuration includes (in LTM-config) CSI-RSs from T-DU 210 / cell for CSI acquisition, and SSB / CSI-RSs for Ll-RSRP measurement. The event-triggered LI measurement reporting configuration includes (in each cell configuration) one or more reporting events to trigger reporting for Ll-RSRP measurements. As also shown, the LTM configuration may include an indication for the UE 110 to enable / disable CSI acquisition measurements based on the event-triggered measurement reporting (or the UE may otherwise have a pre-defined behavior to enable / disable CSI acquisition measurements). At steps 605, 606, the CU provides RRC reconfiguration(s) for the LTM configuration for the candidate target cell(s) (including T- DU 210B / cell) to the UE 110 (via the S-DU).

[0088] The UE 110 may at step 607 make the Ll-RSRP measurements and perform an evaluation according to the configured reporting events. Then, at step 608, a condition for an LI event-triggered reporting is fulfilled for an SSB2 of T-DU 210B / cell. The UE may at step 609 determine CSLRS(s) for which SSB2 is the QCL source RS, and start channel measurements using the configuration of selected CSI-RSs for CSI acquisition. Here, the CSI-RS may be selected, and the CSI acquisition measurements for the selected CSI-RS(s) triggered, when the condition for LI event-triggered reporting is fulfilled. The configuration of CSLRS(s) to perform CSI acquisition measurements may be provided in the LTM-config. The UE at step 610 sends an LI event-triggered measurement report to S-DU 210A / cell. The LI event-triggered measurement report includes the Ll-RSRP measurements of SSB2 of T-DU / cell.

[0089] The UE 110 may continue to make the Ll-RSRP measurements and perform an evaluation according to the configured reporting events. Then, at step 611, a condition for an LI event-triggered reporting is fulfilled for another SSB (SSB4) of T-DU 210B / cell. The UE 110 may at step 612 stop the CSI acquisition measurements for the CS- RS(s) associated with SSB2. That is, the UE may stop the CSI acquisition measurements when the condition for an LI event- triggered reporting is fulfilled for an RS associated with another CSLRS. The UE may also determine CSLRS(s) for which SSB4 is the QCL source RS, and start channel measurements using the configuration of selected CSI-RSs for CSI acquisition. Again, the CSLRS may be selected, and the CSI acquisition measurements for the selected CSLRS(s) triggered, when the condition for LI event-triggered reporting is fulfilled. The UE at step 613 sends an LI event- triggered measurement report to S-DU 210A / cell. This LI event-triggered measurement report includes the Ll-RSRP measurements of SSB4 of T-DU / cell.

[0090] The UE 110 may at step 614, before the cell switch, report the CSI acquisition measurements to the T-DU 210B / cell (via the S-DU 210A / cell). Alternatively, the UE may report the CSI acquisition measurements during or after the cell switch, as indicated below.

[0091] The S-DU 210A / cell may at steps 615 and 616 decide to initiate a cell change to the T-DU 210B / cell, and transmit a cell switch command (e.g., MAC-GE) to trigger the cell switch. The UE 110 may at step 617 stop the CSI acquisition measurements for the CS-RS(s) associated with SSB4 of T-DU 210B / cell. A cell switch of the UE to the T-DU / cell may be executed at step 618. If not earlier reported, the UE may at step 619 report CSI acquisition measurements to the T-DU 210B / cell (the new serving cell). And as shown at step 620, transmissions / receptions may be conducted between the UE and the T-DU / cell using the acquired CSI measurements.

[0092] FIG. 7 illustrates a signaling chart 700 for a conditional LTM (C-LTM) procedure including CSI acquisition, according to some example implementations. The procedure is illustrated in a CU-DU split architecture, including a CU 212, a source DU (S-DU) 210A for a serving cell, and a target DU (T-DU) 210B for a target cell. The procedure is also shown for intra-CU LTM cell switch, although it should be understood that the procedure is likewise applicable to inter-CU LTM cell switch.

[0093] During preparation for LTM, as shown at steps 701 and 702, the UE 110 sends a L3 measurement report to the CU via the S-DU, and the CU at step 703 decides prepare one or more candidate target cells (DUs) for LTM.

[0094] The CU 212 may at step 704 prepare an LTM configuration including an LI measurement configuration, and a C-LTM candidate cell configuration. The LI measurement configuration includes (in LTM-config) CSLRSs from T-DU 210 / cell for CSI acquisition, and SSB / CSI-RSs for Ll-RSRP measurement. The C-LTM candidate cell configuration includes one or more conditions to trigger an LTM cell switch, which may be candidate cell specific. As also shown, the LTM configuration may include an indication for the UE 110 to enable / disable CSI acquisition measurements based on theevent-triggered measurement reporting (or the UE may otherwise have a pre-defined behavior to enable / disable CSI acquisition measurements). At steps 705, 706, the CU provides RRC reconfiguration(s) for the LTM configuration for the candidate target cell(s) (including T-DU 210B / cell) to the UE 110 (via the S-DU).

[0095] As shown at step 707, the UE 110 may be triggered to start evaluation of the LTM cell switch conditions for an SSB2 of T-DU 210B / cell. The UE may at step 708 determine CSI-RS(s) for which SSB2 is the QCL source RS, and start channel measurements using the configuration of selected CSI-RSs for CSI acquisition. Here, the CSI-RS may be selected, and the CSI acquisition measurements for the selected CSI- RS(s) triggered, when the UE starts condition evaluation for C-LTM. The configuration of CSI-RS(s) to perform CSI acquisition measurements may be provided in the LTM- config.

[0096] The UE 110 may at step 709, before the cell switch, report the CSI acquisition measurements to the T-DU 210B / cell (via the S-DU 210A / cell). Alternatively, the UE may report the CSI acquisition measurements during or after the cell switch, as indicated below.

[0097] As shown at step 710, a condition to trigger an LTM cell switch of the UE 110 to T-DU 210B / cell is fulfilled. A cell switch of the UE to the T-DU / cell may be executed at step 711. The UE may then at step 712 stop the CSI acquisition measurements for the CS-RS(s) associated with the SSB of T-DU / cell (the new serving cell). If not earlier reported, the UE may at step 713 report CSI acquisition measurements to the T-DU / cell. And as shown at step 714, transmissions / receptions may be conducted between the UE and the T-DU / cell using the acquired CSI measurements.

[0098] FIGS. 8 A - 8C are flowcharts illustrating various steps in a method 800 according to various example implementations. The method includes receiving a channel state information (CSI) measurement configuration for performing one or more channel measurements, and an event- triggered layer 1 (LI) measurement reporting configuration including one or more reporting events associated with one or more candidate cells configured for handover, as shown at block 802 of FIG. 8A. The method includes performing LI measurements on the one or more candidate cells according to the event- triggered LI measurement reporting configuration associated with candidate cellsconfigured for handover, as shown at block 804. The method includes making a determination that a reporting event of the one or more reporting events is fulfilled based on the LI measurements, as shown at block 806. The method includes selecting at least one of the one or more candidate cells, as shown at block 808. And the method includes performing the one or more channel measurements according to the CSI measurement configuration to acquire CSI for the at least one of the candidate cells, as shown at block 810

[0099] In some examples, the CSI for the at least one of the candidate cells includes at least one of channel quality indicator (CQI), precoding matrix indicator (PMI), layer indicator (LI), or rank indicator (RI).

[0100] In some examples, selecting the at least one of the candidate cells for which to acquire the CSI at block 808 includes selecting at least one of the one or more of the candidate cells for which the reporting event is fulfilled, for which the measurement report includes LI measurements, or for which the measurement report includes LI measurements and an acknowledgement of the measurement report is received from the serving cell.

[0101] In some examples, the at least one of the candidate cells that is selected is a subset of the one or more candidate cells. In some of these examples, the method 800 further includes selecting the subset of the one or more candidate cells for which to acquire the CSI.

[0102] In some examples, the one or more channel measurements are performed on at least one reference signal associated with the at least one of the candidate cells. In some of these examples, the method 800 further includes determining the at least one reference signal, as shown at block 812 of FIG. 8D.

[0103] In some examples, the LI measurements are performed at block 804 on reference signals associated with the candidate cells. In some of these examples, the at least one reference signal on which the one or more channel measurements are performed is determined based on one or more of the reference signals associated with at least one of the one or more of the candidate cells for which the reporting event is fulfilled, or for which the measurement report includes LI measurements.

[0104] In some examples, the at least one reference signal on which the one or more channel measurements are performed at block 804 is determined based on a subset of the one or more of the reference signals. In some of these examples, the method 800 further includes selecting the subset of the one or more of the reference signals.

[0105] In some examples, the subset of the one or more of the reference signals is selected based on at least one of: signal quality of the one or more of the reference signals; a type of the reporting event; an order in which the reporting event among the one or more reporting events was determined to be fulfilled; at least one transmission configuration indication (TCI) state associated with the one of more of the reference signals is in a list of active TCI states; UE -based timing advance estimation associated with the one of more of the reference signals was performed; at least one random access channel preamble associated with the one of more of the reference signals was transmitted; or early ASN.1 decoding and / or validity check for the configuration of the cell associated with the one of more of the reference signals was performed.

[0106] In some examples, the one or more of the reference signals include a synchronization signal block (SSB) associated with a candidate cell of the at least one of the candidate cells. In some of these examples, determining the at least one reference signal at block 812 includes determining a CSI reference signal (CSI-RS) associated with the candidate cell based on the SSB, and the one or more channel measurements include at least one channel measurement performed on the CSI-RS associated with the candidate cell.

[0107] In some examples, determining the CSI-RS includes determining the CSI-RS for which the SSB is a quasi co-location (QCL) source.

[0108] In some examples, the method 800 further includes making determination that at least one criterion for stopping acquisition of the CSI for a reference signal of the at least one of the reference signals is satisfied, as at block 814 shown of FIG. 8C. In some of these examples, the method also includes stopping the one or more channel measurements for the reference signal triggered by the determination that the at least one criterion for stopping the acquisition of the CSI for the reference signal is satisfied, as shown at block 816.

[0109] In some examples, the at least one criterion for stopping the acquisition of the CSI includes at least one of at least one of the one or more reporting events is fulfilled for another of the reference signals; an event-triggered reporting not including any information associated with the reference signal is sent; an acknowledgement is received for an event-triggered reporting not containing any information associated with the reference signal; the candidate cell associated with the reference signal is no longer detectable; a control message is received to trigger the handover; a radio resource control (RRC) reconfiguration is performed; a predefined or network-indicated time has passed since the one or more channel measurements started; a TCI state activation or deactivation medium access control (MAC) control element (CE) is received to deactivate a TCI state associated with the reference signal; or one or more TCI states are activated for the candidate cell associated with the reference signal, and TCI state activation or deactivation MAC CE is received to deactivate the all the TCI states associated with the candidate cell.

[0110] In some examples, the at least one criterion for stopping the acquisition of the CSI includes, after the handover to the candidate cell as the target cell a first uplink transmission to the target cell as a new serving cell. The method 800 includes a first downlink reception from the new serving cell. The method includes a control message from the new serving cell triggering the reporting of channel measurements for CSI acquisition; or channel measurements for CSI acquisition reported to the new serving cell.

[0111] In some examples, the method 800 is performed by a user equipment (UE), and the method further includes sending UE capability information to a serving cell that includes an indication of a maximum or minimum number of cells or reference signals supported for channel measurements for CSI acquisition for the handover.

[0112] FIGS. 9A - 9C are flowcharts illustrating various steps in a method 900 according to various example implementations. The method includes receiving a channel state information (CSI) measurement configuration for performing one or more channel measurements, and a configuration including one or more handover conditions associated with one or more candidate cells configured for handover, as shown at block 902 of FIG. 9A. The method includes performing layer 1 (LI) measurements according to theconfiguration including the one or more handover conditions, as shown at block 904. The method includes making a determination to begin an evaluation of the one or more handover conditions for at least one of the one or more candidate cells, as shown at block 906. The method includes performing the one or more channel measurements according to the CSI measurement configuration to acquire CSI for the at least one of the one or more candidate cells, as shown at block 908. And the method includes performing the evaluation of the one or more handover conditions for the at least one of the one or more candidate cells based on the LI measurements, and triggered by the determination, as shown at block 910.

[0113] In some examples, the CSI for the at least one of the candidate cells includes at least one of channel quality indicator (CQI), precoding matrix indicator (PMI), layer indicator (LI), or rank indicator (RI).

[0114] In some examples, the one or more channel measurements are performed on at least one reference signal associated with the at least one of the one or more candidate cells. In some of these examples, the method 900 further includes determining the at least one reference signal, as shown at block 912 of FIG. 9B.

[0115] In some examples, the LI measurements are performed at block 904 on reference signals associated with the one or more candidate cells. In some of these examples, the at least one reference signal on which the one or more channel measurements are performed is determined based on one or more of the reference signals associated with the at least one of the one or more candidate cells considered for the evaluation.

[0116] In some examples, the at least one reference signal on which the one or more channel measurements are performed is determined based on a subset of the one or more of the reference signals associated with the at least one of the one or more candidate cells. In some of these examples, the method 900 further includes selecting the subset of the one or more of the reference signals.

[0117] In some examples, the subset of the one or more of the reference signals is selected based on at least one of signal quality of the one or more of the reference signals; at least one transmission configuration indication (TCI) state associated with the one of more of the reference signals is in a list of active TCI states; UE-based timing advanceestimation associated with the one of more of the reference signals was performed; at least one random access channel preamble associated with the one of more of the reference signals was transmitted; or early ASN.l decoding and / or validity check for the configuration of the cell associated with the one of more of the reference signals was performed.

[0118] In some examples, the one or more of the reference signals include a synchronization signal block (SSB) associated with a candidate cell of the at least one of the one or more candidate cells. In some of these examples, determining the at least one reference signal at block 912 includes determining a CSI reference signal (CSI-RS) associated with the candidate cell based on the SSB, and the one or more channel measurements include at least one channel measurement performed on the CSI-RS associated with the candidate cell, as shown at block 912 of FIG. 9D.

[0119] In some examples, determining the CSI-RS at block 912 includes determining the CSI-RS for which the SSB is a quasi co-location (QCL) source.

[0120] In some examples, the method 900 further includes making a determination that at least one criterion for stopping acquisition of the CSI for a reference signal of the at least one of the reference signals is satisfied, as shown at block 914 of FIG. 9C. In some of these examples, the method also includes stopping the one or more channel measurements for the reference signal triggered by the determination that the at least one criterion for stopping the acquisition of the CSI for the reference signal is satisfied, as shown at block 916.

[0121] In some examples, the at least one criterion for stopping the acquisition of the CSI includes at least one of the evaluation of the one or more handover conditions for the reference signal stops; a handover condition of the one or more handover conditions is fulfilled, and the handover is performed; a control message is received to trigger the handover; a radio resource control (RRC) reconfiguration is performed; or a predefined or network-indicated time has passed since the one or more channel measurements started.

[0122] In some examples, the at least one criterion for stopping the acquisition of the CSI includes, after the handover to the candidate cell as the target cell a first uplink transmission to the target cell as a new serving cell. The method includes a first downlinkreception from the new serving cell. The method includes a control message from the new serving cell triggering the reporting of channel measurements for CSI acquisition; or channel measurements for CSI acquisition reported to the new serving cell.

[0123] In some examples, the method 900 is performed by a user equipment (UE). In some of these examples, the method further includes sending UE capability information to a serving cell that includes an indication of a maximum or minimum number of cells or reference signals supported for channel measurements for CSI acquisition for the handover.

[0124] According to example implementations of the present disclosure, a telecommunications system 100 or PLMN 102, and its components such as a UE 110, gNB 206, CU 208, DU 210, S-DU 210A and / or T-DU 210B, may be implemented by various means. Means for implementing the system and its components may include hardware, firmware, software, or combinations thereof. In some examples, one or more apparatuses may be configured to function as or otherwise implement the system and its components shown and described herein. In examples involving more than one apparatus, the respective apparatuses may be connected to or otherwise in communication with one another in a number of different manners, such as directly or indirectly via a wired or wireless network or the like.

[0125] According to some example implementations, at least some of the method 800 described with respect to FIGS. 8A-8C may be carried out by an apparatus comprising means for performing functions corresponding steps of the method. Similarly, at least some of the method 900 described with respect to FIGS. 9A-9C may be carried out by an apparatus comprising means for performing functions corresponding steps of the method. Examples of a suitable apparatus may a user equipment, user device, user terminal or the like.

[0126] FIG. 10 illustrates an apparatus 1000 in which means for performing various functions includes hardware, alone or under direction of one or more computer programs from a computer-readable storage medium or other memory, such as computer memory, according to some example implementations of the present disclosure. Generally, an apparatus of example implementations of the present disclosure may compri se, include or be embodied in one or more fixed or portable electronic devices. Examples of suitableelectronic devices include a wearable computer, mobile phone, portable computer, desktop computer, workstation computer, server (server computer) or the like. The apparatus may include one or more of each of a number of components such as, for example, processing circuitry 1002 connected to computer-readable storage medium or other memory 1004.

[0127] The processing circuitry 1002 may be composed of one or more processors alone or in combination with one or more computer-readable storage media. The processing circuitry is generally any piece of computer hardware that is capable of processing information such as, for example, data, computer programs and / or other suitable electronic information. The processing circuitry is composed of a collection of electronic circuits some of which may be packaged as an integrated circuit or multiple interconnected integrated circuits (an integrated circuit at times more commonly referred to as a “chip”). The processing circuitry may be configured to execute computer programs, which may be stored onboard the processing circuitry or otherwise stored in the memory 1004 (of the same or another apparatus).

[0128] The processing circuitry 1002 may be a number of processors, a multi-core processor or some other type of processor, depending on the particular implementation. Further, the processing circuitry may be implemented using a number of heterogeneous processor systems in which a main processor is present with one or more secondary processors on a single chip. As another illustrative example, the processing circuitry may be a symmetric multi-processor system containing multiple processors of the same type. In yet another example, the processing circuitry may be embodied as or otherwise include one or more ASICs, FPGAs or the like. Thus, although the processing circuitry may be capable of executing a computer program to perform one or more functions, the processing circuitry of various examples may be capable of performing one or more functions without the aid of a computer program. In either instance, the processing circuitry may be appropriately programmed to perform functions or operations according to example implementations of the present disclosure.

[0129] The memory 1004 is generally any piece of computer hardware that is capable of storing information such as, for example, data, computer programs, instructions 1006 (e.g., computer-readable program code) and / or other suitable information either on atemporary basis and / or a permanent basis. The memory may include volatile and / or nonvolatile memory, and may be fixed or removable. Examples of suitable memory include recording media, random access memory (RAM), read-only memory (ROM), a hard drive, a flash memory, a thumb drive, a removable computer diskette, an optical disk or some combination thereof.

[0130] The memory 1004 is a non-transitory device capable of storing information. One example of a suitable memory is a computer-readable storage medium, which is distinguishable from a computer-readable transmission medium capable of carrying information from one location to another. Examples of suitable computer-readable transmission media comprise electronic carrier signals, telecommunications signals, or some combination thereof. As used herein, the term “non-transitory” is a limitation of the medium itself (i.e., tangible, not a signal) as opposed to a limitation on data storage persistency (e.g., RAM versus ROM). A computer-readable medium as described herein generally refers to a computer-readable storage medium or computer-readable transmission medium. A computer-readable medium is any entity or device capable in which information, such as one or more computer programs or portions thereof, may be stored and carried.

[0131] In addition to the memory 1004 (e.g., computer-readable storage medium), the processing circuitry 1002 may also be connected to one or more interfaces for displaying, transmitting and / or receiving information. The interfaces may include a communications interface 1008 and / or one or more user interfaces. The communications interface may be configured to transmit and / or receive information, such as to and / or from other apparatus(es), network(s) or the like. The communications interface may be configured to transmit and / or receive information by physical (wired) and / or wireless communications links. Examples of suitable communication interfaces include a network interface controller (NIC), wireless NIC (WNIC) or the like.

[0132] The user interfaces may include a display 1010 and / or one or more user input interfaces 1012. The display may be configured to present or otherwise display information to a user, suitable examples of which include a liquid crystal display (LCD), light-emitting diode (LED) display, organic LED (OLED) display, active-matrix OLED (AMOLED) or the like. The user input interfaces may be wired or wireless, and may beconfigured to receive information from a user into the apparatus, such as for processing, storage and / or display. Suitable examples of user input interfaces include a microphone, image or video capture device, keyboard or keypad, joystick, touch-sensitive surface (separate from or integrated into a touchscreen), biometric sensor or the like. The user interfaces may further include one or more interfaces for communicating with peripherals such as printers, scanners or the like.

[0133] Execution of the instructions 1006 by the processing circuitry 1002, or storage of the instructions in the memory 1004, supports combinations of operations for implementing example implementations of the present disclosure. In this manner, an apparatus 1000 may comprise at least one processing circuitry and at least one memory coupled to the at least one processing circuitry, where the at least one processing circuitry is configured to execute instructions stored in the at least one memory. It will also be understood that one or more functions, and combinations of functions, may be implemented by special purpose hardware-based computer systems and / or processing circuitry which perform the specified functions, or combinations of special purpose hardware and program code instructions.

[0134] Some example implementations of the present disclosure may also be carried out in the form of a computer process defined by one or more computer programs or portions thereof. Example implementations of the present disclosure may be carried out by executing at least one portion of a computer program comprising instructions. The computer program may be in source code form, object code form, or in some intermediate form. The computer program may be stored in a computer-readable medium that is readable by a computer, processing circuitry or other suitable apparatus. As indicated above, for example, the computer program may be stored in a memory, such as a computer-readable storage medium. Additionally or alternatively, for example, the computer program may be stored in a computer-readable transmission medium. The coding of software for carrying out example implementations of the present disclosure is well within the scope of a person of ordinary skill in the art.

[0135] As will be appreciated, any suitable instructions may be loaded onto a computer, a processing circuitry or other programmable apparatus from a memory or a computer-readable medium (e.g., computer-readable storage medium, computer-readabletransmission medium) to produce a particular machine, such that the particular machine becomes a means for implementing the functions specified herein. The instructions may also be stored in a computer-readable medium that can direct a computer, a processing circuitry or other programmable apparatus to function in a particular manner to thereby generate a particular machine or particular article of manufacture. In some examples, the instructions stored in the computer-readable medium may produce an article of manufacture, where the article of manufacture becomes a means for implementing functions described herein. The instructions may be retrieved from a computer-readable medium and loaded into a computer, processing circuitry or other programmable apparatus to configure the computer, processing circuitry or other programmable apparatus to execute operations to be performed on or by the computer, processing circuitry or other programmable apparatus.

[0136] Retrieval, loading and execution of instructions comprising program code instructions may be performed sequentially such that one instruction is retrieved, loaded and executed at a time. In some example implementations, retrieval, loading and / or execution may be performed in parallel such that multiple instructions are retrieved, loaded, and / or executed together. Execution of the program code instructions may produce a computer-implemented process such that the instructions executed by the computer, processing circuitry or other programmable apparatus provide operations for implementing functions described herein.

[0137] As explained above and reiterated below, the present disclosure includes, without limitation, the following example implementations.

[0138] Clause 1. A method comprising: receiving a channel state information (CSI) measurement configuration for performing one or more channel measurements, and an event-triggered layer 1 (LI) measurement reporting configuration including one or more reporting events associated with one or more candidate cells configured for handover; performing LI measurements on the one or more candidate cells according to the event- triggered LI measurement reporting configuration associated with candidate cells configured for handover; making a determination that a reporting event of the one or more reporting events is fulfilled based on the LI measurements; selecting at least one of the one or more candidate cells; and performing the one or more channel measurementsaccording to the CSI measurement configuration to acquire CSI for the at least one of the candidate cells.

[0139] Clause 2. The method of clause 1, wherein the CSI for the at least one of the candidate cells includes at least one of channel quality indicator (CQI), precoding matrix indicator (PMI), layer indicator (LI), or rank indicator (RI).

[0140] Clause 3. The method of clause 1 or clause 2, wherein selecting the at least one of the candidate cells for which to acquire the CSI includes selecting at least one of the one or more of the candidate cells for which the reporting event is fulfilled, for which the measurement report includes LI measurements, or for which the measurement report includes LI measurements and an acknowledgement of the measurement report is received from the serving cell.

[0141] Clause 4. The method of clause 3, wherein the at least one of the candidate cells that is selected is a subset of the one or more candidate cells, and the method further comprises sel ecting the subset of the one or more candidate cells for which to acquire the CSI.

[0142] Clause 5. The method of any of clauses 1 to 4, wherein the one or more channel measurements are performed on at least one reference signal associated with the at least one of the candidate cells, and the method further comprises determining the at least one reference signal.

[0143] Clause 6. The method of clause 5, wherein the LI measurements are performed on reference signals associated with the candidate cells, and wherein the at least one reference signal on which the one or more channel measurements are performed is determined based on one or more of the reference signals associated with at least one of the one or more of the candidate cells for which the reporting event is fulfilled, or for which the measurement report includes LI measurements.

[0144] Clause 7. The method of clause 6, wherein the at least one reference signal on which the one or more channel measurements are performed is determined based on a subset of the one or more of the reference signals, and the method further comprises selecting the subset of the one or more of the reference signals.

[0145] Clause 8. The method of clause 7, wherein the subset of the one or more of the reference signals is selected based on at least one of: signal quality of the one or more ofthe reference signals; a type of the reporting event; an order in which the reporting event among the one or more reporting events was determined to be fulfilled; at least one transmission configuration indication (TCI) state associated with the one of more of the reference signals is in a list of active TCI states; UE-based timing advance estimation associated with the one of more of the reference signals was performed; at least one random access channel preamble associated with the one of more of the reference signals was transmitted; or early ASN.1 decoding and / or validity check for the configuration of the cell associated with the one of more of the reference signals was performed.

[0146] Clause 9. The method of any of clauses 6 to 8, wherein the one or more of the reference signals include a synchronization signal block (SSB) associated with a candidate cell of the at least one of the candidate cells, and wherein determining the at least one reference signal includes determining a CSI reference signal (CSI-RS) associated with the candidate cell based on the SSB, and the one or more channel measurements include at least one channel measurement performed on the CSI-RS associated with the candidate cell.

[0147] Clause 10. The method of clause 9, wherein determining the CSI-RS includes determining the CSI-RS for which the SSB is a quasi co-location (QCL) source.

[0148] Clause 11. The method of any of clauses 5 to 10, wherein the method further comprises: making determination that at least one criterion for stopping acquisition of the CSI for a reference signal of the at least one of the reference signals is satisfied; and stopping the one or more channel measurements for the reference signal triggered by the determination that the at least one criterion for stopping the acquisition of the CSI for the reference signal is satisfied.

[0149] Clause 12. The method of clause 11, wherein the at least one criterion for stopping the acquisition of the CSI includes at least one of: at least one of the one or more reporting events is fulfilled for another of the reference signals; an event-triggered reporting not including any information associated with the reference signal is sent; an acknowledgement is received for an event-triggered reporting not containing any information associated with the reference signal; the candidate cell associated with the reference signal is no longer detectable; a control message is received to trigger the handover; a radio resource control (RRC) reconfiguration is performed; a predefined ornetwork-indicated time has passed since the one or more channel measurements started; a TCI state activation or deactivation medium access control (MAC) control element (CE) is received to deactivate a TCI state associated with the reference signal; or one or more TCI states are activated for the candidate cell associated with the reference signal, and TCI state activation or deactivation MAC CE is received to deactivate the all the TCI states associated with the candidate cell.

[0150] Clause 13. The method of clause 11 or clause 12, wherein the at least one criterion for stopping the acquisition of the CSI includes, after the handover to the candidate cell as the target cell: a first uplink transmission to the target cell as a new serving cell; a first downlink reception from the new serving cell; a control message from the new serving cell triggering the reporting of channel measurements for CSI acquisition; or channel measurements for CSI acquisition reported to the new serving cell.

[0151] Clause 14. The method of any of clauses 1 to 13, wherein the method is performed by a user equipment (UE), and the method further comprises sending UE capability information to a serving cell that includes an indication of a maximum or minimum number of cells or reference signals supported for channel measurements for CSI acquisition for the handover.

[0152] Clause 15. An apparatus comprising: at least one memory configured to store instructions; and at least one processing circuitry configured to access the at least one memory, and execute the instructions to cause the apparatus to perform the method of any of clauses 1 to 14.

[0153] Clause 16. An apparatus comprising means for performing the method of any of clauses 1 to 14.

[0154] Clause 17. A computer-readable medium comprising instructions that, in response to execution by at least one processing circuitry, causes an apparatus to perform the method of any of clauses 1 to 14.

[0155] Clause 18. A computer-readable storage medium comprising instructions that, in response to execution by at least one processing circuitry, causes an apparatus to perform the method of any of clauses 1 to 14.

[0156] Clause 19. A computer program comprising instructions that, in response to execution by at least one processing circuitry, causes an apparatus to perform the method of any of clauses 1 to 14.

[0157] Clause 20. A method comprising: receiving a channel state information (CSI) measurement configuration for performing one or more channel measurements, and a configuration including one or more handover conditions associated with one or more candidate cells configured for handover; performing layer 1 (LI) measurements according to the configuration including the one or more handover conditions; making a determination to begin an evaluation of the one or more handover conditi ons for at least one of the one or more candidate cells; performing the one or more channel measurements according to the CSI measurement configuration to acquire CSI for the at least one of the one or more candidate cells; and performing the evaluation of the one or more handover conditions for the at least one of the one or more candidate cells based on the LI measurements, and triggered by the determination.

[0158] Clause 21. The method of clause 20, wherein the CSI for the at least one of the candidate cells includes at least one of channel quality indicator (CQI), precoding matrix indicator (PMI), layer indicator (LI), or rank indicator (RI).

[0159] Clause 22. The method of clause 20 or clause 21, wherein the one or more channel measurements are performed on at least one reference signal associated with the at least one of the one or more candidate cells, and the method further comprises determining the at least one reference signal.

[0160] Clause 23. The method of clause 22, wherein the LI measurements are performed on reference signals associated with the one or more candidate cells, and wherein the at least one reference signal on which the one or more channel measurements are performed is determined based on one or more of the reference signals associated with the at least one of the one or more candidate cells considered for the evaluation.

[0161] Clause 24. The method of clause 23, wherein the at least one reference signal on which the one or more channel measurements are performed is determined based on a subset of the one or more of the reference signals associated with the at least one of the one or more candidate cells, and the method further comprises selecting the subset of the one or more of the reference signals.

[0162] Clause 25. The method of clause 24, wherein the subset of the one or more of the reference signals is selected based on at least one of: signal quality of the one or more of the reference signals; at least one transmission configuration indication (TCI) state associated with the one of more of the reference signals is in a list of active TCI states; UE-based timing advance estimation associated with the one of more of the reference signals was performed; at least one random access channel preamble associated with the one of more of the reference signals was transmitted; or early ASN.1 decoding and / or validity check for the configuration of the cell associated with the one of more of the reference signals was performed.

[0163] Clause 26. The method of any of clauses 23 to 25, wherein the one or more of the reference signals include a synchronization signal block (SSB) associated with a candidate cell of the at least one of the one or more candidate cells, and wherein determining the at least one reference signal includes determining a CSI reference signal (CSI-RS) associated with the candidate cell based on the SSB, and the one or more channel measurements include at least one channel measurement performed on the CSI- RS associated with the candidate cell.

[0164] Clause 27. The method of clause 26, wherein determining the CSI-RS includes determining the CSI-RS for which the SSB is a quasi co-location (QCL) source.

[0165] Clause 28. The method of any of clauses 22 to 27, wherein the method further comprises: making a determination that at least one criterion for stopping acquisition of the CSI for a reference signal of the at least one of the reference signals is satisfied; and stopping the one or more channel measurements for the reference signal triggered by the determination that the at least one criterion for stopping the acquisition of the CSI for the reference signal is satisfied.

[0166] Clause 29. The method of clause 28, wherein the at least one criterion for stopping the acquisition of the CSI includes at least one of: the evaluation of the one or more handover conditions for the reference signal stops; a handover condition of the one or more handover conditions is fulfilled, and the handover is performed; a control message is received to trigger the handover; a radio resource control (RRC) reconfiguration is performed; or a predefined or network-indicated time has passed since the one or more channel measurements started.

[0167] Clause 30. The method of clause 28 or clause 29, wherein the at least one criterion for stopping the acquisition of the CSI includes, after the handover to the candidate cell as the target cell: a first uplink transmission to the target cell as a new serving cell; a first downlink reception from the new serving cell; a control message from the new serving cell triggering the reporting of channel measurements for CSI acquisition; or channel measurements for CSI acquisition reported to the new serving cell.

[0168] Clause 31. The method of any of clauses 20 to 30, wherein the method is performed by a user equipment (UE), and the method further comprises sending UE capability information to a serving cell that includes an indication of a maximum or minimum number of cells or reference signals supported for channel measurements for CSI acquisition for the handover.

[0169] Clause 32. An apparatus comprising: at least one memory configured to store instructions; and at least one processing circuitry configured to access the at least one memory, and execute the instructions to cause the apparatus to perform the method of any of clauses 20 to 31.

[0170] Clause 33. An apparatus comprising means for performing the method of any of clauses 20 to 31.

[0171] Clause 34. A computer-readable medium comprising instructions that, in response to execution by at least one processing circuitry, causes an apparatus to perform the method of any of clauses 20 to 31.

[0172] Clause 35. A computer-readable storage medium comprising instructions that, in response to execution by at least one processing circuitry, causes an apparatus to perform the method of any of clauses 20 to 31.

[0173] Clause 36. A computer program comprising instructions that, in response to execution by at least one processing circuitry, causes an apparatus to perform the method of any of clauses 20 to 31.

[0174] Many modifications and other implementations of the disclosure set forth herein will come to mind to one skilled in the art to which the disclosure pertains having the benefit of the teachings presented in the foregoing description and the associated figures. Therefore, it is to be understood that the disclosure is not to be limited to thespecific implementations disclosed and that modifications and other implementations are intended to be included within the scope of the appended claims. Moreover, although the foregoing description and the associated figures describe example implementations in the context of certain example combinations of elements and / or functions, it should be appreciated that different combinations of elements and / or functions may be provided by alternative implementations without departing from the scope of the appended claims. In this regard, for example, different combinations of elements and / or functions than those explicitly described above are also contemplated as may be set forth in some of the appended claims. Although specific terms are employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation.

Claims

43WHAT IS CLAIMED IS:

1. An apparatus comprising: at least one memory configured to store instructions; and at least one processing circuitry configured to access the at least one memory, and execute the instructions to cause the apparatus to at least: receive a channel state information (CSI) measurement configuration for performing one or more channel measurements, and an event-triggered layer 1 (LI) measurement reporting configuration including one or more reporting events associated with one or more candidate cells configured for handover; perform layer 1 measurements on the one or more candidate cells according to the event-triggered LI measurement reporting configuration associated with candidate cells configured for handover; make a determination that a reporting event of the one or more reporting events is fulfilled based on the LI measurements; select at least one of the one or more candidate cells; and perform the one or more channel measurements according to the CSI measurement configuration to acquire CSI for the at least one of the candidate cells.

2. The apparatus of claim 1, wherein the CSI for the at least one of the candidate cells includes at least one of channel quality indicator (CQI), precoding matrix indicator (PMI), layer indicator (LI), or rank indicator (RI).

3. The apparatus of claim 1, wherein selecting the at least one of the candidate cells for which to acquire the CSI includes selecting at least one of the one or more of the candidate cells for which the reporting event is fulfilled, for which the measurement report includes LI measurements, or for which the measurement report includes LI measurements and an acknowledgement of the measurement report is received from the serving cell.

4. The apparatus of claim 3, wherein the at least one of the candidate cells that is selected is a subset of the one or more candidate cells, and the at least one44 processing circuitry is configured to execute the instructions to cause the apparatus to further select the subset of the one or more candidate cells for which to acquire the CSI.

5. The apparatus of claim 1, wherein the one or more channel measurements are performed on at least one reference signal associated with the at least one of the candidate cells, and the at least one processing circuitry is configured to execute the instructions to cause the apparatus to further determine the at least one reference signal.

6. The apparatus of claim 5, wherein the LI measurements are performed on reference signals associated with the candidate cells, and wherein the at least one reference signal on which the one or more channel measurements are performed is determined based on one or more of the reference signals associated with at least one of the one or more of the candidate cells for which the reporting event is fulfilled, or for which the measurement report includes LI measurements.

7. The apparatus of claim 6, wherein the at least one reference signal on which the one or more channel measurements are performed is determined based on a subset of the one or more of the reference signals, and the at least one processing circuitry is configured to execute the instructions to cause the apparatus to further select the subset of the one or more of the reference signals.

8. The apparatus of claim 7, wherein the subset of the one or more of the reference signals is selected based on at least one of: signal quality of the one or more of the reference signals; a type of the reporting event; an order in which the reporting event among the one or more reporting events was determined to be fulfilled; at least one transmission configuration indication (TCI) state associated with the one of more of the reference signals is in a list of active TCI states;45UE-based timing advance estimation associated with the one of more of the reference signals was performed; at least one random access channel preamble associated with the one of more of the reference signals was transmitted; or early ASN.1 decoding and / or validity check for the configuration of the cell associated with the one of more of the reference signals was performed.

9. The apparatus of claim 6, wherein the one or more of the reference signals include a synchronization signal block (SSB) associated with a candidate cell of the at least one of the candidate cells, and wherein the apparatus caused to determine the at least one reference signal includes the apparatus caused to determine a CSI reference signal (CSI-RS) associated with the candidate cell based on the SSB, and the one or more channel measurements include at least one channel measurement performed on the CSI-RS associated with the candidate cell.

10. The apparatus of claim 9, wherein determining the CSI-RS includes determining the CSI-RS for which the SSB is a quasi co-location (QCL) source.

11. The apparatus of claim 5, wherein the at least one processing circuitry is configured to execute the instructions to cause the apparatus to further at least: make a determination that at least one criterion for stopping acquisition of the CSI for a reference signal of the at least one of the reference signals is satisfied; and stop the one or more channel measurements for the reference signal triggered by the determination that the at least one criterion for stopping the acquisition of the CSI for the reference signal is satisfied.

12. The apparatus of claim 11, wherein the at least one criterion for stopping the acquisition of the CSI includes at least one of: at least one of the one or more reporting events is fulfilled for another of the reference signals;an event-triggered reporting not including any information associated with the reference signal is sent; an acknowledgement is received for an event-triggered reporting not containing any information associated with the reference signal; the candidate cell associated with the reference signal is no longer detectable; a control message is received to trigger the handover; a radio resource control (RRC) reconfiguration is performed; a predefined or network-indicated time has passed since the one or more channel measurements started; a TCI state activation or deactivation medium access control (MAC) control element (CE) is received to deactivate a TCI state associated with the reference signal; or one or more TCI states are activated for the candidate cell associated with the reference signal, and TCI state activation or deactivation MAC CE is received to deactivate the all the TCI states associated with the candidate cell.

13. The apparatus of claim 11, wherein the at least one criterion for stopping the acquisition of the CSI includes, after the handover to the candidate cell as the target cell: a first uplink transmission to the target cell as a new serving cell; a first downlink reception from the new serving cell; a control message from the new serving cell triggering the reporting of channel measurements for CSI acquisition; or channel measurements for CSI acquisition reported to the new serving cell.

14. The apparatus of claim 1, wherein the method is performed by a user equipment (UE), and the at least one processing circuitry is configured to execute the instructions to cause the apparatus to further send UE capability information to a serving cell that includes an indication of a maximum or minimum number of cells or reference signals supported for channel measurements for CSI acquisition for the handover.

15. A method comprising:receiving a channel state information (CSI) measurement configuration for performing one or more channel measurements, and an event-triggered layer 1 (LI) measurement reporting configuration including one or more reporting events associated with one or more candidate cells configured for handover; performing LI measurements on the one or more candidate cells according to the event-triggered LI measurement reporting configuration associated with candidate cells configured for handover; making a determination that a reporting event of the one or more reporting events is fulfilled based on the LI measurements; selecting at least one of the one or more candidate cells; and performing the one or more channel measurements according to the CSI measurement configuration to acquire CSI for the at least one of the candidate cells.

16. The method of claim 15, wherein the CSI for the at least one of the candidate cells includes at least one of channel quality indicator (CQI), precoding matrix indicator (PMI), layer indicator (LI), or rank indicator (RI).

17. The method of claim 15, wherein selecting the at least one of the candidate cells for which to acquire the CSI includes selecting at least one of the one or more of the candidate cells for which the reporting event is fulfilled, for which the measurement report includes LI measurements, or for which the measurement report includes LI measurements and an acknowledgement of the measurement report is received from the serving cell.

18. The method of claim 17, wherein the at least one of the candidate cells that is selected is a subset of the one or more candidate cells, and the method further comprises selecting the subset of the one or more candidate cells for which to acquire the CSI.

19. The method of claim 15, wherein the one or more channel measurements are performed on at least one reference signal associated with the at least one of the48 candidate cells, and the method further comprises determining the at least one reference signal.

20. The method of claim 19, wherein the LI measurements are performed on reference signals associated with the candidate cells, and wherein the at least one reference signal on which the one or more channel measurements are performed is determined based on one or more of the reference signals associated with at least one of the one or more of the candidate cells for which the reporting event is fulfilled, or for which the measurement report includes LI measurements.

21. The method of claim 20, wherein the at least one reference signal on which the one or more channel measurements are performed is determined based on a subset of the one or more of the reference signals, and the method further comprises selecting the subset of the one or more of the reference signals.

22. The method of claim 21, wherein the subset of the one or more of the reference signals is selected based on at least one of: signal quality of the one or more of the reference signals; a type of the reporting event; an order in which the reporting event among the one or more reporting events was determined to be fulfilled; at least one TCI state associated with the one of more of the reference signals is in a list of active TCI states;UE-based timing advance estimation associated with the one of more of the reference signals was performed; at least one random access channel preamble associated with the one of more of the reference signals was transmitted; or early ASN.1 decoding and / or validity check for the configuration of the cell associated with the one of more of the reference signals was performed..4923. The method of claim 20, wherein the one or more of the reference signals include a synchronization signal block (SSB) associated with a candidate cell of the at least one of the candidate cells, and wherein determining the at least one reference signal includes determining a CSI reference signal (CSI-RS) associated with the candidate cell based on the SSB, and the one or more channel measurements include at least one channel measurement performed on the CSI-RS associated with the candidate cell.

24. The method of claim 23, wherein determining the CSI-RS includes determining the CSI-RS for which the SSB is a quasi co-location (QCL) source.

25. The method of claim 19, wherein the method further comprises: making a determination that at least one criterion for stopping acquisition of the CSI for a reference signal of the at least one of the reference signals is satisfied; and stopping the one or more channel measurements for the reference signal triggered by the determination that the at least one criterion for stopping the acquisition of the CSI for the reference signal is satisfied.

26. The method of claim 25, wherein the at least one criterion for stopping the acquisition of the CSI includes at least one of: at least one of the one or more reporting events is fulfilled for another of the reference signals; an event-triggered reporting not including any information associated with the reference signalis sent; an acknowledgement is received for an event-triggered reporting not containing any information associated with the reference signal; the candidate cell associated with the reference signal is no longer detectable; a control message is received to trigger the handover; a RRC reconfiguration is performed; a predefined or network-indicated time has passed since the one or more channel measurements started;50 a TCI state activation or deactivation MAC CE is received to deactivate a TCI state associated with the reference signal; or one or more TCI states are activated for the candidate cell associated with the reference signal, and TCI state activation or deactivation MAC CE is received to deactivate the all the TCI states associated with the candidate cell.

27. The method of claim 25, wherein the at least one criterion for stopping the acquisition of the CSI includes, after the handover to the candidate cell as the target cell: a first uplink transmission to the target cell as a new serving cell; a first downlink reception from the new serving cell; a control message from the new serving cell triggering the reporting of channel measurements for CSI acquisition; or channel measurements for CSI acquisition reported to the new serving cell.

28. The method of claim 15, wherein the method is performed by a user equipment (UE), and the method further comprises sending UE capability information to a serving cell that includes an indication of a maximum or minimum number of cells or reference signals supported for channel measurements for CSI acquisition for the handover.

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