Transmission configuration indicator (TCI) state activation for mobility

Abstract

A method performed by a user equipment (UE) is provided. The method includes receiving a configuration that includes candidate configurations for candidate cells. The method includes performing transmission configuration indicator (TCI) state activation of one or more activated TCI states for a first one or more of the candidate cells. The method includes receiving, from a serving cell, at least one message including timing advance (TA) information for a second one or more of the candidate cells. And the method includes keeping at least one of the one or more activated TCI states active, based on the at least one message including the TA information, for at least one candidate cell that is in both the first one or more of the candidate cells and the second one or more of the candidate cells.

Description

TRANSMISSION CONFIGURATION INDICATOR (TCI) STATE ACTIVATION FOR MOBILITY TECHNOLOGICAL FIELD

[0001] The present disclosure relates generally to telecommunications and, in particular, to mobility in a telecommunications system.BACKGROUND

[0002] Telecommunications systems can be seen as facilities that enable communications between two or more entities such as between two user equipment, between a user equipment and a base station, between two base stations, a user equipment and a network function of a communication network and / or a base station and other nodes. A telecommunications system can include a communication network and one or more user equipment. 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 telecommunications system that includes a wireless communication network, at least a part of a communication session between at least two stations occurs over a wireless link. Examples of wireless communication networks comprise public land mobile networks (PLMN), satellite-based communication networks and different wireless local networks, for example wireless local area networks (WLAN). Some wireless communication networks can be divided into cells, and are therefore often referred to as cellular networks.

[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, forexample enabling access to a communication network or communications directly with other users. The communication device may access a carrier provided by, for example, a base station of a cell, and transmit and / or receive communications on the carrier.

[0005] Telecommunications systems have evolved through multiple generations, each bringing advancements in speed, capacity, and functionality. The Evolved Packet System (EPS) represents the 4G architecture, which includes Long-Term Evolution (LTE) and LTE-Advanced (LTE-A) as its radio access technologies. The 5G System (5GS) builds upon EPS, introducing 5G New Radio (5GNR) for enhanced mobile broadband, massive machine-type communications, and ultra-reliable low-latency communications. The future 6G System (6GS) is expected to further revolutionize telecommunications with even more advanced capabilities. These systems are interconnected, with 5GS designed to interwork with EPS for seamless service continuity. The 3rd Generation Partnership Project (3 GPP) plays a crucial role in developing and maintaining standards for these telecommunications systems, ensuring global interoperability and evolution from Universal Mobile Telecommunications System (UMTS) (3G) through to the ongoing development of 6G technologies.BRIEF SUMMARY

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

[0007] Some example implementations provide an apparatus to implement a user equipment (UE), the 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 configuration that includes candidate configurations for candidate cells; perform transmission configuration indicator (TCI) state activation of one or more activated TCI states for a first one or more of the candidate cells; receive, from a serving cell, at least one message including timing advance (TA) information for a second one or more of the candidate cells; and keep at least one of the one or more activated TCI states active, based on the at least one message including the TA information, for at least one candidate cellthat is in both the first one or more of the candidate cells and the second one or more of the candidate cells.

[0008] Some example implementations provide a method performed by a user equipment (UE), the method comprising: receiving a configuration that includes candidate configurations for candidate cells; performing transmission configuration indicator (TCI) state activation of one or more activated TCI states for a first one or more of the candidate cells; receiving, from a serving cell, at least one message including timing advance (TA) information for a second one or more of the candidate cells; and keeping at least one of the one or more activated TCI states active, based on the at least one message including the TA information, for at least one candidate cell that is in both the first one or more of the candidate cells and the second one or more of the candidate cells.

[0009] Some example implementations provide an apparatus to implement a user equipment (UE), the 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 configuration that includes candidate configurations for candidate cells; perform transmission configuration indicator (TCI) state activation of one or more activated TCI states for a first one or more of the candidate cells; receive, from a serving cell, at least one message including timing advance (TA) information for a second one or more of the candidate cells; and deactivate at least one of the one or more activated TCI states, based on the at least one message including the TA information, for at least one candidate cell in the first one or more of the candidate cells.

[0010] Some example implementations provide a method performed by a user equipment (UE), the method comprising: receiving a configuration that includes candidate configurations for candidate cells; performing transmission configuration indicator (TCI) state activation of one or more activated TCI states for a first one or more of the candidate cells; receiving, from a serving cell, at least one message including timing advance (TA) information for a second one or more of the candidate cells; and deactivating at least one of the one or more activated TCI states, based on the at least onemessage including the TA information, for at least one candidate cell in the first one or more of the candidate cells.

[0011] Some example implementations provide an apparatus to implement a user equipment (UE), the 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 configuration that includes candidate configurations for candidate cell; receive, from a serving cell, at least one message including timing advance (TA) information for one or more of the candidate cells; and activate one or more transmission configuration indicator (TCI) states, based on the at least one message including the TA information, for at least one candidate cell that is in the one or more of the candidate cells.

[0012] Some example implementations provide a method performed by a user equipment (UE), the method comprising: receiving a configuration that includes candidate configurations for candidate cell; receiving, from a serving cell, at least one message including timing advance (TA) information for one or more of the candidate cells; and activating one or more transmission configuration indicator (TCI) states, based on the at least one message including the TA information, for at least one candidate cell that is in the one or more of the candidate cells.

[0013] 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.

[0014] 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 beconstrued 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)

[0015] 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:

[0016] 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;

[0017] FIG. 2 illustrates a PLMN, according to some example implementations;

[0018] FIG. 3 is a diagram of a procedure for L1 / L2- triggered mobility, also known as lower-layer triggered mobility (LTM);

[0019] FIG. 4 illustrates a control message for activation / deactivation of transmission configuration indicator (TCI) states;

[0020] FIGS. 5 A, 5B and 5C illustrate a diagram of a procedure for conditional LTM (CLTM), according to some example implementations;

[0021] FIGS. 6A, 6B, 6C, 6D and 6E are flowcharts illustrating various steps in a method performed by a user equipment (UE), according to various example implementations;

[0022] FIGS. 7A, 7B and 7C are flowcharts illustrating various steps in a method performed by a UE, according to various example implementations;

[0023] FIGS. 8 A, 8B and 8C are flowcharts illustrating various steps in a method performed by a UE, according to various example implementations; and

[0024] FIG. 9 illustrates an apparatus according to some example implementations.DETAILED DESCRIPTION

[0025] Some implementations of the present disclosure will now be described more fully hereinafter with reference to the accompanying figures, in which some, but not allimplementations 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. Unless specified otherwise or clear from context, references to first, second or the like should not be construed to imply a particular order but are merely utilized to distinguish one item or operation from another.

[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] The present disclosure discusses telecommunication systems and mobile or cellular networks and user equipment thereof, and while specific terms may be used, are broadly applicable across various technologies. For instance, while the present disclosure may reference radio access technologies such as 5G NR and 5G Advanced, the present disclosure is equally relevant to next generation radio access technologies, such as 6G. Example implementations of the present disclosure described herein also mention public land mobile networks (PLMNs) and mobile network operators (MNOs), but example implementations are similarly applicable to standalone non-public networks (SNPNs).

[0028] Although some examples and figures focus on radio access networks (RANs) and in particular radio access networks that operate in accordance with the 3 GPP standard for 5G NR (generally referred to as 3GPP access or 3GPP access networks), exampleimplementations are applicable to any type of access networks. The applicability to any type of access network includes not only 3GPP access networks but also non-3GPP access networks, such as wireline access, untrusted non-3GPP access network, and trusted non-3GPP access network using wireless access gateway function (W-AGF), non-3GPP interworking function (N3IWF), or trusted non-3GPP gateway function (TNGF) to connect to a core network (e.g., a 5G core network (5GC) or a 6G core network (6GC)) of a mobile or cellular network.

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

[0030] The above definition of circuitry applies to all uses of this term in this application, including in any claims. As a further example, as used in this application, the term circuitry also covers an implementation of merely a hardware circuit or processor (or multiple processors) or portion of a hardware circuit or processor and its (or their) accompanying software and / 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.

[0031] FIG. 1 illustrates a telecommunications system 100 according to various example implementations of the present disclosure. Examples of suitable telecommunications systems include UMTS, EPS and 5GS, as well as the future 6GS. The telecommunications system (otherwise referred to as a system) generally includes one or more mobile or cellular networks, and these mobile or cellular networks may interwork between telecommunications systems. As shown, for example, the systemincludes 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. As will be appreciated, a PLMN may be a standalone PLMN that includes a 5GC, or may be a non-standalone PLMN that includes both an Evolved Packet Core (EPC) and a 5GC connected to a RAN.

[0032] Each of the PLMNs 102 includes a core network (CN) 106, such as the EPC, the 5GC, or a 6GC; and each CN is coupled to one or more RANs 108 that implement one or more radio access technologies (RATs). Examples of these RANs include the evolved UMTS terrestrial radio access network (E-UTRAN) of 4G LTE, the next generation (NG) radio access network (NG-RAN) of 5GNR, and the 6GRAN. As used herein, a “network device” refers to any suitable device of a RAN or a core network of a telecommunications system. Examples of suitable network devices are described in greater detail below.

[0033] Examples of RATs include 3GPP radio access technologies such as GSM, CDMA2000 IxEV-DO (HRPD), CDMA2000 lx (IxRTT), UTRA, E-UTRA, 5GNR, 5G Advanced, and 6G. Other examples of RATs 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 RAT may refer to any 2G, 3G, 4G, 5G, 6G or higher generation RAT and their different versions, as well as to any other RAT that may be arranged to interwork with such a RAT to provide access to the CN 106 of a MNO.

[0034] The telecommunications system 100 also includes one or more communication devices 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 (e.g., an access node such as a RAN node of RAN 108) or a or a further UE in the telecommunications system. 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) communicationtechnology, 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.

[0035] In operation, these UEs 110 may connect to one or more RAN nodes of the RANs 108 according to their particular RATs 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) or services provided by the PLMN. The external data network may provide Internet access, or 3rd party services. For example, the International Telecommunication Union (ITU) has classified 5G mobile network services (e.g., services provided by a 5G mobile network) 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).

[0036] In various examples, a RAN 108 may be configured to provide one or more macrocells, microcells, picocells, femtocells or the like. The RAN may generally include one or more RAN nodes that interact with UEs 110. In various examples, a RAN node may be referred to as a base station (BS), access point (AP), base transceiver station (BTS). Examples of RAN nodes include a 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), 6G NB (6gNB), or the like. The term ‘gNB’ in 5G NR may correspond to the eNB in 4G LTE. Also, a NG-RAN node may refer to a gNB or a ng-eNB. And unless otherwise specified, a gNB in 5G NR or a 6gNB in 6G may at times be more generally referred to as a (6)gNB or more simply a gNB.

[0037] The RAN 108 may include some type of network controlling / governing entity responsible for control of the RAN nodes. The network controlling / governing entity and RAN node may be separate or integrated into a single apparatus. The network controlling / governing entity may include processing circuity configured to carry out various management functions for controlling RAN nodes of the RAN. The processing circuity may be associated with a memory, computer-readable storage medium or a data storage device comprising a database for maintaining information required in the various management functions.

[0038] FIG. 2 illustrates an example of a PLMN 102, such as 4G LTE, 5G NR or 6G PLMN that communicates with a UE 110 and an external data network 104 of the telecommunications system 100. As shown, the RAN 108 (e.g., E-UTRAN, NG-RAN, 6G RAN) includes one or more RAN nodes 202 configured to connect one or more UEs to the RAN to thereby access the CN 106 (e.g., EPC, 5GC, 6GC). In 4G LTE, the UE, E-UTRAN and EPC compose EPS. Similarly, in 5GNR, the UE, NG-RAN and 5GC compose the 5GS. And in 6G, the UE, 6GRAN and 6GC compose the 6GS.

[0039] In some implementations, operations of a gNB or other RAN node may be distributed or functionally split into components including one or more remote radio head (RRHs) or radio units (RUs), and a baseband unit (BBU); and in some implementations, the BBU may be split into a central / centralized unit (CU) (central node) and a distributed unit (DU) (distributed node). The CU may be, for example, a server, host or node. In some implementations, the RRH / RU and DU may be collocated at a network device. It is also possible that operations of a gNB or RAN node may be distributed among a plurality of servers, hosts or nodes.

[0040] It should also be understood that the distribution of work between core network operations and RAN node operations may vary depending on implementation. A 5G or 6G network architecture, for example, may be based on a so-called CU-DU split. One gNB-CU (a CU 204) may control one or more gNB-DUs (DUs 206). 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 may include, for example, a radio link control (RLC), medium access control (MAC) layer and a physical (PHY) layer, whereas the gNB-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 skilled person is familiar with the open systems interconnection (OSI) model and the functionalities within each layer.

[0041] In some example implementations, the server or CU 204 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, avirtual 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 206, and the boundary where the responsibility is shifted between the CU and the DU may be selected according to implementation.

[0042] 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 a well-known and proven method for ensuring a robust way of handing over the UE 110 from one serving cell (source cell) of a RAN node 202 to a new serving cell (target cell) of the same or another RAN 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.

[0043] 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 (layer 1 or LI) or MAC (layer 2 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.

[0044] FIG. 3 illustrates a diagram of a procedure for LTM procedure of a UE 110 in a RRC connected state with a RAN node 202, which has been proposed. During LTM preparation, as shown at step 301, the UE sends a L3 measurement report to the RAN node, which decides to use LTM and initiate LTM candidate preparation. The RAN node at step 302 sends a RRC reconfiguration message to the UE, including candidate configurations of one or more candidate cells (at times referred to as LTM candidate cells). In the context of LTM, a candidate cell is a cell configured by the RAN node for potential a cell switch, and that may be later selected by the RAN node (among one or more candidate cells) for the cell switch. The RRC reconfiguration message may also include a configuration of LI measurement reporting for LTM execution. The UE stores the candidate configurations, and the UE at step 303 sends a RRC reconfiguration complete message to the RAN node.

[0045] An optional early synchronization of the UE 110 with the candidate cell(s) follows LTM preparation. As shown at steps 304A and 304B, the UE 110 performs downlink (DL) and may perform uplink (UL) synchronization with the candidate cell(s). For DL synchronization, the RAN node 202 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) or other control message. The UE may receive this TCI state activation MAC CE, and start tracking configured DL reference signal (RS) resources associated with the activate TCI states to synchronize with the candidate cell(s). In this regard, an active TCI state is a configured TCI state that has been activated for use by the UE to determine information, typically quasi co-location (QCL) information, for DL reception or UL transmission. The tracking of RS may refer to making one or more measurements using the RS. With each measurement, one or more parameters such as, RS received power, delay spread, Doppler, spread, average delay, Dopier shift, spatial domain filter coefficient may be acquired or updated. The measurement may be performed with one or more consecutive / periodic occurrences of the RS. In various examples, the RS resources may include synchronization signal block (SSB), channel state information reference signal (CSLRS), tracking reference signal (TRS), or the like.

[0046] 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 RAN node 202 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 RAN node 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 thepurpose 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.

[0047] 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 110 may likewise have an acquired TA of the cell of the RAN node to control the timing of uplink transmissions toward the RAN node 202.

[0048] During LTM execution, the UE 110 may be configured to perform LI or L3 measurements on the configured candidate cell(s), and the UE at step 305 sends L1 / L3 measurement reports to the RAN node 202. The RAN node 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. L1 / L3 measurement reports may also be used by the RAN node to select candidate cells and corresponding TCI states for early DL synchronization or / and to select candidate cells and CFRA configuration, like SSB identifier (ID) to trigger RACH procedure by a PDCCH order.

[0049] The RAN node 202 at step 306 transmits a cell switch command, such as a MAC CE, to trigger cell switch. The cell switch command may indicate a target configuration identifier (ID) which indicates the index of the candidate configuration of the target cell. The cell switch command may also indicate a beam indicated with a TCI state, or beams indicated with DL and UL TCI states, and TA value for the target cell, if available. The UE switches to the candidate 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.

[0050] As indicated above, early DL synchronization with respect to a DL reference signal of a candidate cell, such as the SSB, CSI-RS or TRS, may be facilitated via early TCI state activation associated with the DL reference signal. In 5GNR, a TCI state represents a specific set of transmission parameters, including spatial relationships, that the UE 110 uses for receiving DL transmissions or sending UL transmissions. Asindicated above, a TCI state typically includes QCL information. This QCL information may include Doppler spread, Doppler shift, average delay, delay spread, spatial domain filter coefficient or beam information or spatial receive (Rx) parameters, and reference signal(s) information. The UE may derive the QCL parameters from measurements on the specified reference signals, which may then be applied to all transmissions and receptions associated with that TCI state.

[0051] Early TCI activation for candidate cell(s) may be supported to trigger the UE 110 to start fine time / frequency synchronization with the given joint or / and uplink TCI state(s) of the candidate cell(s). This may be used by the RAN 108 as a pre-DL-synchronization aiming to prepare the UE for cell switch and enable shorter interruption at cell switch, which does not necessarily involve time tracking for the target TCI state(s). The source cell may trigger the activation of specific TCI states for a candidate cell based on measurements reported by the UE. As the measurement reports from the UE include reference signal information, the source cell may determine the corresponding TCI states. Once the TCI state(s) are selected, the source cell may send a MAC control element (MAC CE) or other control message including the TCI state(s) and candidate cell information. In this regard, FIG. 4 illustrates a control message for activation / deactivation of TCI states.

[0052] Upon receiving the TCI state activation MAC CE, the UE 110 may be expected to start tracking the reference signals and acquire and maintain the associated QCL parameters. The RAN 108 may assumes a specific time (i.e., TCI state activation delay) before the RAN is considered that the UE has acquired all necessary parameters and is ready to use the activated TCI state for transmission and / or reception. In this regard, the TCI state activation delay is the time from when the UE receives the TCI state activation MAC CE (or another TCI state activation command) to the time UE has completed the activation, including fine DL synchronization (if needed). This process may be applied to multiple LTM TCI states for various candidate cells.

[0053] When a candidate cell is selected for the cell switch, the source cell may select one (or two in case of separate DL and UL TCI states) TCI states and include / indicate the selected TCI state(s) in the cell switch command MAC CE. If the indicated TCI state(s) was already activated, the UE 110 may be expected to have fine DL synchronization withthe TCI state; and accordingly, the UE is not given time (a cell switch delay) for DL synchronization during the cell switch under certain conditions, which may be defined in cell switch delay requirements in 3 GPP.

[0054] According to these 3 GPP cell switch delay requirements, in the case when the UE 110 is configured with LI measurements for a candidate cell, and a TCI state is activated before cell switch command for a candidate cell, the UE may be required to have fine DL synchronization based on early TCI state activation if the time from completing the TCI state activation, i.e., after the TCI activation is completed or after taking the TCI activation delay into account, is not more than 160 milliseconds (ms), or the measurement period for the SSB associated to the target TCI state is up to 160 ms. On the other hand, when the UE is not configured with LI measurements and LTM cell switch is triggered based on L3 measurements, the UE may be required to have fine DL synchronization based on early TCI state activation if the time from completing the TCI state activation is not more than 480 ms for intra- frequency candidate cell or 160 ms for inter-frequency candidate cell.

[0055] In the 3 GPP cell switch delay requirements, Tfirst-Rs is the time for fine time tracking and acquiring full timing information of a target cell, and TRs-Proo is the time for SSB processing. The UE 110 may not be given time for DL synchronization (i.e., Tfirst-Rs = 0 and TRs-proo = 0) under certain conditions for example when the UE already has DL synchronization for the indicated TCI state; otherwise, the UE may otherwise be given time for DL synchronization (i.e., Tfirst-Rs > 0 and TRs-Proo > 0) during the cell switch, which means that TCI state activation did not provide any reduction in the cell switch interruption.

[0056] 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 enhancements under discussion is support for conditional LTM (CLTM or C-LTM). The details of CLTM are currently under discussion, but it has been agreed that at least the baseline of conditional handover (CHO) will be reused (including the configuration of execution condition(s) for cell switch), and that agreed that RACH-less intra-CU LTM issupported. It has also been agreed that PDCCH-ordered early TA acquisition is supported for CLTM, and that early candidate TCI state activation / deactivation is supported for conditional intra-CU LTM.

[0057] From the current agreements, the early synchronization behavior for CLTM is primarily like that of conventional LTM. The MAC CE for activation / deactivation of TCI state(s) may be reused for the early activation / deactivation of TCI state(s) of a candidate configuration for CLTM. Early TA information may be signaled to the UE 110 from the source cell, but delivery of the early TA information may differ in CLTM. In case of conventional LTM, the TA value acquired during early synchronization is stored in the RAN node 202 that provides the serving cell. The TA value may be shared with the UE along with the MAC CE cell switch command during an execution phase based on measurements performed by the UE. In CLTM, however, there is no explicit cell change command from the RAN 108; and accordingly, the TA information needs to be shared with the UE in advance by the network. The RAN node may inform the UE of the TA information for the candidate cell(s) via a separate MAC CE. The TA information may include the TA value(s) for the LTM candidate cell(s). The TA value for a candidate cell may be maintained by a time alignment timer (TAT) for the candidate cell.

[0058] Again, according to the cell switch delay requirements for LTM, when the UE 110 is configured with LI measurements for an LTM candidate cell and a TCI state is activated before the cell switch command for that candidate cell, the UE may be required to have fine DL synchronization based on early TCI state activation (i.e., Tfirst-Rs = 0 and TRs-proo = 0) only if the time from completing the TCI state activation does not exceed 160 ms, or the measurement period for the SSB associated with the target TCI state is up to 160 ms. When the UE is not configured with LI measurements and the LTM cell switch is triggered based on L3 measurements, the UE may be required to have fine DL synchronization based on early TCI state activation only if the time from completing the TCI state activation does not exceed 480 ms for intra-frequency candidate cell or 160 ms for inter-frequency candidate cell. If these conditions are not met, the UE may be allowed to perform fine DL synchronization (Tfirst-Rs and TRs-Proo) during the cell switch, meaning that TCI state activation does not contribute to reducing the cell switch interruption.

[0059] For CLTM, the UE 110 may be configured to trigger a cell switch to a target cell when a configured execution condition (at times more simply referred to as a condition for cell switch) is satisfied for the target cell. If the execution condition is satisfied with a candidate beam (any beam from the candidate RS set), the UE may perform RACH-less CLTM using that beam for LI -based CLTM if it has a valid TA for the associated candidate cell. Otherwise, the UE may perform RACH-based CLTM.

[0060] The UE 110 may also be configured to perform early synchronization procedures similar to LTM, such as PDCCH-ordered RACH-based early TA acquisition and / or MAC CE-based candidate TCI state activation / deactivation with one or more candidate cells. For DL synchronization, the same cell switch requirements may apply. That is, if the candidate beam that meets the CLTM execution condition is not associated with the activated TCI state, the UE may be required to perform fine DL synchronization during the cell switch, leading to a longer cell switch delay.

[0061] In LTM, the timing of TCI state activation and the cell switch command is controlled by the RAN 108. But this is not the case in CLTM, as there is no explicit cell switch command from the RAN. In view of the foregoing, example implementations of the present disclosure provide solution(s) that enable the UE to perform the cell switch with an activated TCI state, and thereby avoid fine DL synchronization delays during the cell switch.

[0062] In the solution(s) of some example implementations, a UE 110 supporting early TCI activation for candidate cell(s) may be configured to keep active or deactivate at least one activated TCI state based on at least one message (e.g., MAC CE) including early TA information for the same or other candidate cell(s). This may include the UE continuing to track or stop tracking DL synchronization information for the activated TCI state(s). The solution(s) may include selection of the activated TCI state(s) to keep active or deactivate. The solution(s) may also include a defined endpoint for activation of TCI state(s), which may indicate for how long the UE tracks the DL synchronization information for the TCI state(s). And in some examples, the solution(s) include introduction of a UE capability for TCI state activation / deactivation based on receipt of TA information.

[0063] The solution(s) are primarily described herein in the context of CLTM, but may be equally applicable to various other mobility and beam management scenarios. In some cases, the solution(s) may be applicable to scenarios in which a cell is provided with TA information, and TCI state activation is performed for the cell. For instance, the solution(s) may be applicable to LTM, L3 -based mobility with early TCI state activation and early UL synchronization. Similarly, the solution(s) may be applied in serving cell-related procedures, such as beam management for current serving cell(s) including the primary and secondary cells.

[0064] The solution(s) are primarily described herein in the context of a DL message including the TA information. The message including TA information may refer to a DL command or a DL control message, such as MAC CE, DCI, or RRC, which either provides the TA value directly or includes information that enables the UE to determine the TA value. However, in some scenarios, the message may also serve as a trigger for TA acquisition, such as by instructing the UE 110 to initiate a PRACH transmission.Alternatively, in some scenarios, a UE may to configured to perform TA estimation using UE-based TA estimation for a candidate cell, and the UE estimating or triggering the TA estimation for a candidate cell may be used to trigger or apply or perform the procedures which are described as the procedures triggered or performed based on the reception of the DL message.

[0065] According to some example implementations, a UE 110 may receive a configuration receive a configuration (e.g., cell switch configuration or LTM configuration) that includes candidate configurations for candidate cells. The UE may perform TCI state activation of one or more activated TCI states for a first one or more of the candidate cells, which may be triggered by a MAC CE or other control message from the serving cell provided by a RAN node 202 (e.g., DU 206). The UE may receive, from the serving cell, at least one message (e.g., MAC CE) including TA information for a second one or more of the candidate cells. In some scenarios, a message including the TA information for a candidate cell may be received after the TCI state activation for a TCI state for the candidate cell. In some other scenarios, the message including the TA information may be received before the TCI state activation.

[0066] In various examples, an activated TCI state may refer to a TCI state in an active TCI state list, or a TCI state activated by MAC CE (e.g., as shown in FIG. 4) or other control message received from the serving cell (without subsequent deactivation). In another example, an activated TCI state may refer to a TCI state activated within a predefined duration (X) relative to receipt of the message(s) (e.g., MAC CE) including the TA information. This predefined duration may be predefined or configured, such as part of the configuration that includes the candidate configurations. The duration (X) may also be based on UE capability.

[0067] Upon receipt of the message(s) including the TA information, the UE 110 may in some examples keep at least one of the activated TCI state(s) active, based on the message(s) (e.g., MAC CE) including the TA information, for at least one candidate cell that is in both the first one or more of the candidate cells and the second one or more of the candidate cells. Additionally or alternatively, in some examples, the UE may deactivate at least one of the activated TCI state(s), based on the message(s) including the TA information, for at least one candidate cell in the first one or more of the candidate cells. And in some examples, the UE may activate one or more TCI states, based on the message(s) including the TA information, for at least one candidate cell that is in the candidate cell(s) for which the message(s) include the TA information.

[0068] In some examples, the configuration that includes the candidate configurations, or the message that includes the TA information, may include an indication whether the UE is allowed or not allowed to keep activated TCI state(s) active, deactivate TCI state(s) and / or activate TCI state(s) based on the message with TA information.

[0069] The TCI state activation for a TCI state may be performed to acquire or track DL synchronization information using at least one reference signal associated with the TCI state. For example, a TCI state can include one or more reference signal information as part of its QCL information configuration. In case of more than one reference signals, the synchronization information may be acquired with respect to the reference signal which is configured to acquire a particular type of QCL type, e.g., QCL type D or any other QCL type (e.g., type A, type B, type C). The UE 110 may therefore in some examples continue to track or stop tracking the DL synchronization information for atleast one of the activated TCI state(s), based on the message(s) (e.g., MAC CE) including the TA information.

[0070] As above, acquisition or tracking of DL synchronization information refers to performing and processing measurements, and acquiring or keeping track of the fine DL timing and frequency synchronization using a reference signal associated with the TCI state. This reference signal (e.g., SSB, CSI-RS) may be specified in QCL information of the TCI state, or the reference signal may be one quasi-collocated (QCLed) with the reference signal in the QCL information of the TCI state. The acquisition and keeping track of the fine DL timing and frequency synchronization (fine DL timing / synchronization) may refer to the acquisition of one or more parameters such as downlink timing (e.g., frame timing), frequency offset, Doppler spread, average delay, delay spread, Doppler shift, and / or spatial domain filter coefficients, which may then be used to adjust a configuration to receive and / or transmit a channel / signal.

[0071] In some more particular examples, upon receipt of a message (e.g., MAC CE) including TA information for a candidate cell of the candidate cell(s), the UE 110 may keep at least one of the activated TCI state(s) for the candidate cell active. Lor example, the UE may keep all of the activated TCI state(s) for the candidate cell active. The UE may additionally keep at least one of the activated TCI state(s) active for at least one candidate cell co-locating or belonging to a timing advance group (TAG) associated with at least one of the candidate cell(s) for which the TA information is received. In this regard, a co-located candidate cell refers to a cell physically located at the same site or very close to at least one of the candidate cell(s) for which the TA information is received. A TAG refers to a group of cells that share the same TA value, and the TAG may include candidate cells (including at least one candidate cell for which the TA information is received). These co-located candidate cell(s) and / or candidate cell(s) belonging to the same TAG may be candidate cell(s) part of the same candidate configuration as the candidate cell, e.g., a secondary cell, or part of another candidate configuration, e.g., a collocated candidate PCell. Additionally or alternatively, the UE may additionally keep at least one of the activated TCI state(s) active for at least one candidate cell co-locating or belonging to a simultaneous TCI update list (e.g.,simultaneousU-TCI-UpdateList) associated with at least one of the candidate cell(s) for which the TA information is received.

[0072] In some other examples, the upon receipt of the message (e.g., MAC CE) including TA information for a candidate cell of the candidate cell(s), the UE 110 may keep active one of the activated TCI state(s) that is associated with a reference signal or beam for which the TA information is provided. For example, if PDCCH-ordered early TA acquisition is performed, the RACH preamble may be transmitted based on a RACH occasion linked to a specific reference signal (e.g., SSB, CSI-RS) given in the PDCCH order. The TCI state associated with that reference signal, then, may be kept active upon receipt of the message including the TA information. This specific reference signal may be specified in QCL information of the TCI state, may be one QCLed with the reference signal in the QCL information of the TCI state.

[0073] In some examples, such as in the case of CLTM or any other conditional mobility procedure, the configuration that includes the candidate configurations also includes one or more cell switch conditions (e.g., measurement- based cell switch conditions) for a cell switch. In some of these examples, upon receipt of the message (e.g., MAC CE) including TA information for a candidate cell of the candidate cell(s), the UE 110 may keep active activated TCI state(s) associated with reference signal(s) or beam(s) for which at least one of the cell switch condition(s) is configured.

[0074] The UE 110 may keep an activated TCI state for a candidate cell active for a duration which may be set, configured or determined in a number of different manners. In some examples, the UE may keep the activated TCI state active until one or more conditions are satisfied. These condition(s) may include, for example, expiration of a TAT or other validity timer associated with the TA information for a cell, a reference signal or a beam associated with the activated TCI state. In another example, the condition(s) may include the end of a predefined or configured duration (Y) which may depend on UE capability. In some other examples, the condition(s) may include satisfaction of a cell switch condition for another TCI state of the candidate cell or another of the candidate cells, and / or performance of a cell switch using another TCI state of the candidate cell or another of the candidate cells.

[0075] In some other examples, the condition(s) may include deactivation of the activated TCI state (before or after a cell switch), activation of another TCI state for the candidate cell (a new serving cell) after a cell switch is performed using the activated TCI state, and / or receipt or application of a reconfiguration message. In yet some other examples, the condition(s) may include receipt of another message (e.g., MAC CE) including TA information for another TCI state of the candidate cell, and / or receipt of another message including TA information for another of the candidate cells. In yet some other examples, the condition(s) may include receipt of a TA acquisition command (e.g., PDCCH order) to request TA acquisition for a reference signal or beam associated with another TCI state of the candidate cell, and / or receipt of a TA acquisition command to request TA acquisition for of the another candidate cells. And in yet some other examples, the condition(s) may include acquisition of a TA for a reference signal or beam associated with another TCI state of the candidate cell or for another candidate cell using the UE-based TA estimation mechanism.

[0076] In some other examples, the upon receipt of the message (e.g., MAC CE) including TA information for (second) candidate cell(s), the UE 110 may deactivate at least one of the activated TCI state(s) for at least one of the (first) candidate cell(s) for which the TCI state activation is performed. The UE may deactivate all of the activated TCI state(s) for each of the candidate cell(s) in the first but not the second one or more of the candidate cells. In some examples, the UE may deactivate any activated TCI state that is not associated with a reference signal or beam for which the TA information is provided, such as in a most recent message in which TA information is provided.

[0077] In some further examples, the UE 110 may deactivate any activated TCI state that is not associated with the reference signal or beam for which the TA information is provided in a most recent message in which TA information is provided. In some further examples, the UE may deactivate any activated TCI state that is not associated with the reference signal or beam for which the TA information is provided in a most recent defined number (M) of a plurality of messages in which TA information is provided, where the defined number (M) may be predefined or configured (e.g., based on UE capability). In some even further examples, the UE may deactivate any activated TCI state that is not associated with the reference signal or beam for which the TA informationis provided in the most recent defined number of a plurality of messages in which TA information is provided for the candidate cell. In these and other of the above example(s), the UE may keep active another number (N) of TCI state(s) associated with more recently received messages including TA information, where the number (N) may be predefined or configured (e.g., based on UE capability).

[0078] In some examples, the upon receipt of the message (e.g., MAC CE) including TA information for a candidate cell of the candidate cell(s), the UE 110 may activate TCI state(s), based on the message(s) including the TA information, for at least one of the candidate cell(s) for which the TA information is received. In some of these examples, the TCI state(s) may be associated with reference signal(s) or beam(s) for which the TA information is provided. These TCI state(s) may be TCI state(s) not already activated by an earlier TCI state activation (e.g., for the first one or more of the candidate cells). In some of examples, the TCI state(s) may be activated if the TCI state(s) are associated with reference signal(s) or beam(s) for which at least one cell switch condition is configured. In these and other of the above examples, activating a TCI state may include adding the TCI state to an active TCI state list. Additionally or alternatively, as indicated above, activating the TCI state may include acquiring or tracking DL synchronization information using at least one reference signal associated with the TCI state.

[0079] In some examples, the UE 110 may send, to the serving cell, information that indicates a UE capability to support keeping activated TCI states active, deactivating activated TCI states, or activating TCI states, based on the message(s) (e.g., MAC CE) including the TA information. In some of these examples, the information may further indicate a maximum number of activated TCI states the UE supports keeping activated, and / or a maximum number for which the UE supports TCI state activation, based on the message(s) including the TA information. The maximum number(s) may indicated per candidate cell or across candidate cells. And in some examples, the UE capability may include supported values for a number of parameters, such as values of X, Y, M and / or N, as indicated above.

[0080] In some examples, the UE 110 may determine a cell switch condition for a cell switch is satisfied or a cell switch is performed for a target cell or a beam of the target cell that is among the candidate cell(s) or beam(s) of the candidate cell(s) for whichthe at least one of the activated(s) TCI states is kept active or activated. In some of these examples, the UE may then perform the cell switch to the target cell using the DL synchronization information for a TCI state of the activated TCI state(s) for the target cell.

[0081] In some other examples, the cell switch condition may be satisfied or cell switch performed for a target cell among the candidate cells but not in the candidate cell(s) or beam(s) of the candidate cell(s) for which the at least one of the activated(s) TCI states is kept active or activated. The target cell may be among the candidate cell(s) or beam(s) of the candidate cell(s) for which activated TCI state(s) are deactivated. In some of these other examples, the UE may perform the cell switch to the target cell, and the cell switch may include a cell switch delay during which DL synchronization information is acquired for a TCI state of the target cell that is used in the cell switch. The UE may therefore be allowed time during the cell switch to acquire the DL synchronization information for the TCI state used in the cell switch.

[0082] In some more general examples, the UE 110 may determine a cell switch condition for a cell switch is satisfied or a cell switch is performed for a target cell or a beam of the target cell that is among the candidate cells for which the TCI state activation is performed and TA information is received. In one or more conditions determined by the UE, the UE may perform the cell switch to the target cell without any cell switch delay to acquire DL synchronization information for a TCI state for the target cell used in the cell switch. These condition(s) may include, for example, the cell switch condition is satisfied or the cell switch is performed within a predefined duration from when the TA information is received, and / or within a predefined duration from when tracking of the DL synchronization information is stopped based on the received TA information.Another example of a suitable condition includes the cell switch condition is satisfied or the cell switch is performed within a predefined duration from when the TCI state activation is completed.

[0083] In some other examples, in one or more conditions determined by the UE 110, the UE may perform the cell switch to the target cell with a cell switch delay during which the UE may acquire DL synchronization information for a TCI state for the target cell used in the cell switch. These condition(s) may include, for example, the cell switchcondition is not satisfied or the cell switch is not performed within a predefined duration from when the TA information is received, and / or within a predefined duration from when tracking of the downlink synchronization information is stopped based on the received TA information. Another example of a suitable condition in these other examples includes the cell switch condition is not satisfied or the cell switch is not performed within a predefined duration from when the TCI state activation is completed. In some scenarios, a combination of one or more of these conditions may be applied. Another example of a suitable condition in these other examples may include the cell switch condition is not satisfied or the cell switch is not performed either within a predefined duration from when the TCI state activation is completed or within a predefined duration from when the TA information is received. Another example of a suitable condition in these other examples may include the cell switch condition is not satisfied or the cell switch is not performed either within a predefined duration from when the TCI state activation is completed or within a predefined duration from when tracking of the downlink synchronization information is stopped based on the received TA information.

[0084] To further illustrate some example implementations, FIGS. 5A, 5B and 5C illustrate a diagram of a procedure for CLTM in a CU-DU split architecture, including a CU 204, a source DU (S-DU) 206A for a serving cell, and a target DU (T-DU) 206B for a target cell. During preparation for CLTM, as shown in FIG. 5A, a UE 110 may at step 501 indicate, to the CU, its capability to support keeping activated TCI states active, deactivating activated TCI states, or activating TCI states, based on MAC CE including TA information (referred to at times as TA MAC-CE).

[0085] As shown at steps 502, 503, the UE 110 sends an L3 measurement report to the CU 204 via the S-DU 206A, and the CU decides to prepare T-DU 206B / cell(s) for LTM. The CU at step 504 proceeds with LTM preparation in which UE context setup / modification procedures are performed with the S-DU and T-DU. The CU at steps 505, 506 generates and sends an RRC reconfiguration message to the UE via the S-DU. The RRC reconfiguration message includes a CLTM configuration which may include a candidate configuration for each candidate cell, including a configured grant (CG) configuration for RACH-less access, and candidate TCI state configuration for eachcandidate for early TCI state activation. The CLTM configuration may also include a configuration of execution condition(s) (for initial and any subsequent cell switches). The UE stores the CLTM configuration, and the UE at step 507 sends a RRC reconfiguration complete message to the CU via the S-DU.

[0086] As shown in FIG. 5B, the UE 110 may at step 508 start evaluating the configured execution condition(s) for candidate cells for which CLTM is configured. The UE may be configured to perform LI or L3 measurements on the configured candidate cells, and the UE at step 509 sends L1 / L3 measurement reports to the S-DU 206A (for LI measurements) or CU 204 (for L3 measurements). Based on a received L1 / L3 measurement report, the S-DU / CU may at step 510 decide to trigger early synchronization of the UE to one or more of the candidate cells.

[0087] The S-DU 206A / cell at step 511 sends a TCI state activation MAC CE (or another TCI state activation command) for a candidate TCI state 1 (associated with SSB1) of a candidate cell 1 of T-DU 206B. The UE 110 receives the TCI state activation MAC CE and activates the candidate TCI state 1, acquiring DL synchronization information and starting to track SSB1 to thereby the DL synchronization information. The S-DU / CU at step 512 sends a PDCCH order or other TA acquisition command to trigger the UE 110 to send a RACH (preamble) transmission for candidate cell 1 (associated with SSB1), and the UE at step 513 sends the RACH transmission to the T-DU / candidate cell 1.

[0088] The T-DU 206B / candidate cell 1 at step 514 sends, to the CU 204, a TA information message (or RAR) including TA information for candidate cell 1. The CU sends the TA information to the S-DU 206A / cell, and the S-DU at step 515 sends a TA MAC-CE including the TA information to the UE 110. Upon reception of the TAMAC-CE, the UE at step 516 starts a TAT associated with the TA information (the TAT value may be given in the TA MAC-CE or in the CLTM configuration). Since the TA information and the activated TCI state are both associated with the SSB1, the UE continues to track SSB1 and thereby the DL synchronization information for candidate cell 1. In this example, the UE may keep tracking SSB1 for the duration of the TAT. Other condition(s) until which the UE may keep track of SSB1 are described above.

[0089] The UE 110 at step 517 starts or continues evaluating the configured execution condition(s) for candidate cells for which CLTM is configured.

[0090] As shown in FIG. 5C, in a first scenario, the UE 110 at steps 518, 519 determines that an execution condition is satisfied for candidate cell 1 (of T-DU 206B), using the SSB1. The UE determines that the TAT is not yet expired; and accordingly, the UE has kept tracking SSB1 and thereby the DL synchronization information for candidate cell 1. In this case, the UE performs a cell switch to candidate cell 1, and is not required to reacquire the DL synchronization information for the cell switch. In this case, Tfirst-Rs = 0 and TRs-Proo = 0; or in other words, UE is required to have (obtained) the fine (DL) timing (synch) information for the cell switch to candidate cell 1 using the candidate TCI state 1 associated with the SSB1.

[0091] In a second scenario, the TAT expires at step 520. After expiration of the TAT, the UE 110 at steps 521, 522 determines that an execution condition is satisfied for candidate cell 1 (of T-DU 206B), using the SSB1. The UE determines that the TAT has already expired; and accordingly, the UE has stopped tracking SSB1 and thereby the DL synchronization information for candidate cell 1. In this case, the UE performs a cell switch to candidate cell 1, and the cell switch includes a cell switch delay for the UE to reacquire the DL synchronization information for the cell switch. In this case, Tfirst-Rs > 0 and TRs-proo > 0; or in other words, UE is allowed time to acquire the fine (DL) timing (synch) information for the cell switch to candidate cell 1 using the candidate TCI state 1 associated with the SSB1.

[0092] The solution(s) of some example implementations may be captured in 3 GPP cell switch delay requirements in a number of different manners, such as in one or more conditions in which UE 110 is not given time for DL synchronization (e.g., Tfirst-Rs = 0 and Tas-proo = 0) during cell switch. In a first example, the UE is not given time for DL synchronization when the UE has received a TA MAC-GE (a message including TA information) for the target cell, and the associated TAT is running at the time the CLTM cell switch condition is satisfied (or fulfilled) for the target cell. In a second example, the UE is not given time for DL synchronization when the UE has received a TA MAC-CE for the target cell within Y ms before the CLTM cell switch condition has been satisfied. In a third example, the UE is not given time for DL synchronization when the target TCIstate is on the active TCI state list, the UE has received a TA MAC-GE for the target cell, and the associated TAT is running at the time the CLTM cell switch condition is satisfied.

[0093] In a fourth example, the UE 110 is not given time for DL synchronization when the UE has received a TA MAC-CE associated with SSB that is associated with the target TCI state, and the associated TAT is running at the time CLTM cell switch condition is satisfied. In a fifth example, the UE is not given time for DL synchronization when the target TCI state is on the active TCI state list, the UE has received a TA MAC-CE associated with SSB that is associated with the target TCI state, and the TAT is still running. In a sixth example, the UE is not given time for DL synchronization when the UE has received a TA MAC-CE with SSB that is associated to the target TCI state, where the TA MAC-CE is one of the last N TA MAC-CEs the UE has received before the condition for CLTM cell switch is satisfied. And in a seventh example, the UE is not given time for DL synchronization when the UE has received a TA MAC-CE for a cell that belongs to the same [candidate] TAG as / has the same TA as / is collocated with the target cell, and the associated TAT is running at the time of CLTM cell switch condition becoming fulfilled.

[0094] FIGS. 6A - 6E are flowcharts illustrating various steps in a method 600 performed by a user equipment (UE), according to various example implementations. The method includes receiving a configuration that includes candidate configurations for candidate cells, as shown at block 602 of FIG. 6A. The method includes performing transmission configuration indicator (TCI) state activation of one or more activated TCI states for a first one or more of the candidate cells, as shown at block 604. The method includes receiving, from a serving cell, at least one message including timing advance (TA) information for a second one or more of the candidate cells, as shown at block 606. And the method includes keeping at least one of the one or more activated TCI states active, based on the at least one message including the TA information, for at least one candidate cell that is in both the first one or more of the candidate cells and the second one or more of the candidate cells, as shown at block 608.

[0095] In some examples, for each of the at least one candidate cell, the at least one of the one or more activated TCI states that is kept active at block 608 includes all of the one or more activated TCI states.

[0096] In some examples, the method 600 further includes keeping at least one of the one or more activated TCI states active for at least one candidate cell co-locating or belonging to a timing advance group or a simultaneous TCI update list associated with at least one of the second one or more of the candidate cells for which the TA information is received.

[0097] In some examples, for each of the at least one candidate cell, the at least one of the one or more activated TCI states is kept active at block 608 for one of the one or more activated TCI states that is associated with a reference signal or beam for which the TA information is provided.

[0098] In some examples, the configuration includes one or more cell switch conditions for which a cell switch. In some of these examples, for each of the at least one candidate cell, the at least one of the one or more activated TCI states active is kept active at block 608 for the at least one of the one or more activated TCI states that is associated with at least one reference signal or beam for which at least one of the one or more cell switch conditions is configured.

[0099] In some examples, the one or more activated TCI states activated for each of the first one or more of the candidate cells includes at least one of: a TCI state in an active TCI state list, a TCI state activated by control message received from the serving cell, or a TCI state activated within a predefined duration relative to receipt of the at least one message including the TA information for the second one or more of the candidate cells.

[0100] In some examples, an activated TCI state of the at least one of the one or more activated TCI states for a candidate cell of the at least one candidate cell is kept active at block 608 until one or more conditions are satisfied. In some of these examples, the one or more conditions include at least one of an expiration of a validity timer associated with the TA information for a cell, a reference signal or a beam associated with the activated TCI state, an end of a predefined or configured duration, satisfaction of a cell switch condition for another TCI state of the candidate cell or another of the candidate cells, performance of a cell switch using another TCI state of the candidate cell or another of the candidate cells, deactivation of the activated TCI state, activation of another TCI state for the candidate cell after a cell switch is performed using the activated TCI state, receiptor application of a reconfiguration message, receipt of another message including TA information for another TCI state of the candidate cell, receipt of another message including TA information for another of the candidate cells, receipt of a TA acquisition command to request TA acquisition for a reference signal or beam associated with another TCI state of the candidate cell, or receipt of a TA acquisition command to request TA acquisition for of the another candidate cells.

[0101] In some examples, the method 600 further includes deactivating at least one of the one or more activated TCI states, based on the at least one message including the TA information, for at least one candidate cell in the first one or more of the candidate cells.

[0102] In some examples, the method 600 further includes sending, to the serving cell, information that indicates the UE supports keeping activated TCI states active based on the at least one message including the TA information.

[0103] In some examples, the information further indicates a maximum number of activated TCI states the UE supports keeping activated, the maximum number indicated per candidate cell or across candidate cells.

[0104] In some examples, the TCI state activation for a TCI state is performed at block 604 to acquire or track downlink synchronization information using at least one reference signal associated with the TCI state.

[0105] In some examples, the method 600 further includes determining a cell switch condition for a cell switch is satisfied or a cell switch is performed for a target cell or a beam of the target cell that is among the at least one candidate cell or at least one beam of the at least one candidate cell for which the at least one of the one or more activated TCI states is kept active, as shown at block 610 of FIG. 6B. In some of these examples, the method also includes performing the cell switch to the target cell using the downlink synchronization information for a TCI state of the at least one of the one or more activated TCI states for the target cell, as shown at block 612.

[0106] In some examples, the method 600 further includes determining a cell switch condition for a cell switch is satisfied or a cell switch is performed for a target cell or a beam of the target cell that is among the candidate cells but not in the at least one candidate cell or at least one beam of the at least one candidate cell for which the at least one of the one or more activated TCI states is kept active, as shown at block 614 of FIG.6C. In some of these examples, the method also includes performing the cell switch to the target cell, the cell switch including a cell switch delay during which downlink synchronization information is acquired for a TCI state of the target cell that is used in the cell switch, as shown at block 616.

[0107] In some examples, the method 600 further includes determining a cell switch condition for a cell switch is satisfied or a cell switch is performed for a target cell or a beam of the target cell that is among the candidate cells for which the TCI state activation is performed and TA information is received, as shown at block 618 of FIG. 6D. In some of these examples, the method also includes determining one or more of the cell switch condition is satisfied or the cell switch is performed within a predefined duration from when the TA information is received, the cell switch condition is satisfied or the cell switch is performed within a predefined duration from when tracking of the downlink synchronization information is stopped based on the received TA information, or the cell switch condition is satisfied or the cell switch is performed within a predefined duration from when the TCI state activation is completed, as shown at block 620. And the method includes performing the cell switch to the target cell using the downlink synchronization information for a TCI state of the one or more TCI states for the target cell, without any cell switch delay during which the downlink synchronization information is acquired for the TCI state, as shown at block 622.

[0108] In some examples, the method 600 further includes determining a cell switch condition for a cell switch is satisfied or a cell switch is performed for a target cell or a beam of the target cell that is among the candidate cells for which the TCI state activation is performed and TA information is received, as shown at block 624 of FIG. 6E. In some of these examples, the method also includes determining one or more of the cell switch condition is not satisfied or the cell switch is not performed within a predefined duration from when the TA information is received, the cell switch condition is not satisfied or the cell switch is not performed within a predefined duration from when tracking of the downlink synchronization information is stopped based on the received TA information, or the cell switch condition is not satisfied or the cell switch is not performed within a predefined duration from when the TCI state activation is completed, as shown at block 626. And the method includes performing the cell switch to the target cell using thedownlink synchronization information for a TCI state of the one or more TCI states for the target cell, and including a cell switch delay during which the downlink synchronization information is acquired for the TCI state, as shown at block 628.

[0109] FIGS. 7 A - 7C are flowcharts illustrating various steps in a method 700 performed by a user equipment (UE), according to various example implementations. The method includes receiving a configuration that includes candidate configurations for candidate cells, as shown at block 702 of FIG. 7A. The method includes performing transmission configuration indicator (TCI) state activation of one or more activated TCI states for a first one or more of the candidate cells, as shown at block 704. The method includes receiving, from a serving cell, at least one message including timing advance (TA) information for a second one or more of the candidate cells, as shown at block 706. And the method includes deactivating at least one of the one or more activated TCI states, based on the at least one message including the TA information, for at least one candidate cell in the first one or more of the candidate cells, as shown at block 708.

[0110] In some examples, deactivating the at least one of the one or more activated TCI states at block 708 includes deactivating all of the one or more activated TCI states for each of the at least one candidate cell that is in the first one or more of the candidate cells but not in the second one or more of the candidate cells.

[0111] In some examples, deactivating the at least one of the one or more activated TCI states at block 708 includes deactivating any activated TCI state that is not associated with a reference signal or beam for which the TA information is provided.

[0112] In some examples, receiving the at least one message at block 706 includes receiving a plurality of messages including TA information. In some of these examples, deactivating at block 708 the at least one of the one or more activated TCI states includes deactivating any activated TCI state that is not associated with the reference signal or beam for which the TA information is provided in a most recent defined number of the plurality of messages.

[0113] In some examples, deactivating the at least one of the one or more activated TCI states at block 708 includes deactivating any activated TCI state that is not associated with the reference signal or beam for which the TA information is provided inthe most recent defined number of the plurality of messages that includes TA information for the candidate cell.

[0114] In some examples, the method 700 further includes sending, to the serving cell, information that indicates the UE supports deactivating activated TCI states based on the at least one message including the TA information.

[0115] In some examples, the TCI state activation for a TCI state is performed at block 704 to acquire or track downlink synchronization information using at least one reference signal associated with the TCI state.

[0116] In some examples, the method 700 further includes determining a cell switch condition for a cell switch is satisfied or a cell switch is performed for a target cell or a beam of the target cell that is among the candidate cells or at least one beam of the candidate cells for which at least one of the one or more activated TCI states is kept active, as shown at block 710 of FIG. 7B. In some of these examples, the method also includes performing the cell switch to the target cell using the downlink synchronization information for a TCI state of the at least one of the one or more activated TCI states for the target cell, as shown at block 712.

[0117] In some examples, the method 700 further includes determining a cell switch condition for a cell switch is satisfied or a cell switch is performed for a target cell or beam of the target cell that is among the at least one candidate cell or at least one beam of the at least one candidate cell for which the at least one of the one or more activated TCI states is deactivated, as shown at block 714 of FIG. 7C. In some of these examples, the the method also includes performing the cell switch to the target cell, the cell switch including a cell switch delay during which downlink synchronization information is acquired for a TCI state of the target cell that is used in the cell switch, as shown at block 716.

[0118] FIGS. 8 A - 8C are flowcharts illustrating various steps in a method 800 performed by a user equipment (UE), according to various example implementations. The method includes receiving a configuration that includes candidate configurations for candidate cell, as shown at block 802 of FIG. 8 A. The method includes receiving, from a serving cell, at least one message including timing advance (TA) information for one or more of the candidate cells, as shown at block 804. And the method includes activatingone or more transmission configuration indicator (TCI) states, based on the at least one message including the TA information, for at least one candidate cell that is in the one or more of the candidate cells, as shown at block 806.

[0119] In some examples, the one or more TCI states are associated with one or more reference signals or beams for which the TA information is provided.

[0120] In some examples, the method 800 further includes sending, to the serving cell, information that indicates the UE supports TCI state activation based on the at least one message including the TA information.

[0121] In some examples, the information further indicates a maximum number of TCI states for which the UE supports the TCI state activation, the maximum number indicated per candidate cell or across candidate cells.

[0122] In some examples, activating the one or more TCI states for the at least one candidate cell at block 806 includes adding the one or more TCI states to an active TCI state list.

[0123] In some examples, each TCI state of the one or more TCI states is activated to acquire or track downlink synchronization information using at least one reference signal associated with the TCI state.

[0124] In some examples, the method 800 further includes determining a cell switch condition for a cell switch is satisfied or a cell switch is performed for a target cell or a beam of the target cell that is among the at least one candidate cell or at least one beam of the at least one candidate cell for which the one or more TCI states are activated, as shown at block 808 of FIG. 8B. In some of these examples, the method also includes performing the cell switch to the target cell using the downlink synchronization information for a TCI state of the one or more TCI states that are activated for the target cell, as shown at block 810.

[0125] In some examples, the method 800 further includes determining a cell switch condition for a cell switch is satisfied or a cell switch is performed for a target cell or a beam of the target cell that is not among the at least one candidate cell or at least one beam of the at least one candidate cell for which the one or more TCI states are activated, as shown at block 812 of FIG. 8C. In some of these examples, the method also includes performing the cell switch to the target cell, the cell switch including a cell switch delayduring which downlink synchronization information is acquired for a TCI state of the target cell that is used in the cell switch, as shown at block 814.

[0126] According to example implementations of the present disclosure, a telecommunications system 100 or PLMN 102, and components thereof such as UE 110, CN 106, RAN 108, RAN node 202, CU 204 and / or DU 206, 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.

[0127] According to some example implementations, at least some of the method 600 described with respect to FIGS. 6A, 6B, 6C, 6D and 6E may be carried out by an apparatus comprising means for performing functions corresponding steps of the method. Similarly, at least some of the method 700 described with respect to FIGS. 7A, 7B and 7C may be carried out by an apparatus comprising means for performing functions corresponding steps of the method. And at least some of the method 800 described with respect to FIGS. 8 A, 8B, 8C may be carried out by an apparatus comprising means for performing functions corresponding steps of the method. Examples of a suitable apparatus may include a user equipment, user device, user terminal or the like.

[0128] FIG. 9 illustrates an apparatus 900 in which means for performing various operations 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. The apparatus may include one or more of each of a number of components such as, for example, processing circuitry 902 connected to computer-readable storage medium or other memory 904.

[0129] The processing circuitry 902 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 ofprocessing information such as, for example, data, computer programs, computer code 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 904 (of the same or another apparatus).

[0130] The processing circuitry 902 may comprise a number of processors, a multicore processor or some other type of processor, such as a central processing unit, a graphics processing unit, a tensor processing, unit, or an accelerator, 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 application specific integrated circuits (ASICs), field programmable gate arrays (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.

[0131] The memory 904 is generally any piece of computer hardware that is capable of storing information such as, for example, data, computer programs, instructions 906 (e.g., computer-readable program code) and / or other suitable information either on a temporary basis and / or a permanent basis. The memory may include volatile and / or 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.

[0132] The memory 904 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.

[0133] In addition to the memory 904 (e.g., computer-readable storage medium), the processing circuitry 902 may also be connected to one or more interfaces for displaying, transmitting and / or receiving information. The interfaces may include a communications interface 908 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.

[0134] The user interfaces may include a display 910 and / or one or more user input interfaces 912. The display may be configured to present or otherwise display information to a user, suitable examples of which include a liquid crystal display (LCD), light-emitting diode (LED) display, organic LED (OLED) display, active-matrix OLED (AMOLED) or the like. The user input interfaces may be wired or wireless, and may be configured to receive information from a user into the apparatus, such as for processing, storage and / or display. Suitable examples of user input interfaces include a microphone, image or video capture device, keyboard or keypad, joystick, touch-sensitive surface (separate from or integrated into a touchscreen), biometric sensor or the like. The userinterfaces may further include one or more interfaces for communicating with peripherals such as printers, scanners or the like.

[0135] Execution of the instructions 906 by the processing circuitry 902, or storage of the instructions in the memory 904, supports combinations of operations for implementing example implementations of the present disclosure. In this manner, an apparatus 900 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.

[0136] 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.

[0137] As will be appreciated, any suitable instructions may be loaded onto a computer, a processor, a processing circuitry or other programmable apparatus from a memory or a computer-readable medium (e.g., computer-readable storage medium, computer-readable transmission medium) to produce a particular machine, such that the particular machine becomes a means for implementing the functions specified herein. The instructions may also be stored in a computer-readable medium that can direct a computer, a processor, a processing circuitry or other programmable apparatus tofunction 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, processor, processing circuitry or other programmable apparatus to configure the computer, processor, processing circuitry or other programmable apparatus to execute operations to be performed on or by the computer, processor, processing circuitry or other programmable apparatus.

[0138] 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, processor, processing circuitry or other programmable apparatus provide operations for implementing functions described herein.

[0139] Many modifications and other implementations of the disclosure set forth herein will come to mind to one skilled in the art to which the disclosure pertains having the benefit of the teachings presented in the foregoing description and the associated figures. Therefore, it is to be understood that the disclosure is not to be limited to the specific implementations disclosed and that modifications and other implementations are intended to be included within the scope of the appended claims. Moreover, although the foregoing description and the associated figures describe example implementations in the context of certain example combinations of elements and / or functions, it should be appreciated that different combinations of elements and / or functions may be provided by alternative implementations without departing from the scope of the appended claims. In this regard, for example, different combinations of elements and / or functions than those explicitly described above are also contemplated as may be set forth in some of 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

WHAT IS CLAIMED IS:

1. A method performed by a user equipment (UE), the method comprising: receiving a configuration that includes candidate configurations for candidate cells;performing transmission configuration indicator (TCI) state activation of one or more activated TCI states for a first one or more of the candidate cells;receiving, from a serving cell, at least one message including timing advance (TA) information for a second one or more of the candidate cells; andkeeping at least one of the one or more activated TCI states active, based on the at least one message including the TA information, for at least one candidate cell that is in both the first one or more of the candidate cells and the second one or more of the candidate cells.

2. The method of claim 1, wherein for each of the at least one candidate cell, the at least one of the one or more activated TCI states that is kept active includes all of the one or more activated TCI states.

3. The method of claim 1 or claim 2, wherein the method further comprises keeping at least one of the one or more activated TCI states active for at least one candidate cell co-locating or belonging to a timing advance group or a simultaneous TCI update list associated with at least one of the second one or more of the candidate cells for which the TA information is received.

4. The method of any of claims 1 to 3, wherein for each of the at least one candidate cell, the at least one of the one or more activated TCI states is kept active for one of the one or more activated TCI states that is associated with a reference signal or beam for which the TA information is provided.

5. The method of any of claims 1 to 4, wherein the configuration includes one or more cell switch conditions for which a cell switch, andwherein for each of the at least one candidate cell, the at least one of the one or more activated TCI states active is kept active for the at least one of the one or more activated TCI states that is associated with at least one reference signal or beam for which at least one of the one or more cell switch conditions is configured.

6. The method of any of claims 1 to 5, wherein the one or more activated TCI states activated for each of the first one or more of the candidate cells includes at least one of:a TCI state in an active TCI state list;a TCI state activated by control message received from the serving cell; or a TCI state activated within a predefined duration relative to receipt of the at least one message including the TA information for the second one or more of the candidate cells.

7. The method of any of claims 1 to 6, wherein an activated TCI state of the at least one of the one or more activated TCI states for a candidate cell of the at least one candidate cell is kept active until one or more conditions are satisfied, and the one or more conditions include at least one of:an expiration of a validity timer associated with the TA information for a cell, a reference signal or a beam associated with the activated TCI state;an end of a predefined or configured duration;satisfaction of a cell switch condition for another TCI state of the candidate cell or another of the candidate cells;performance of a cell switch using another TCI state of the candidate cell or another of the candidate cells;deactivation of the activated TCI state;activation of another TCI state for the candidate cell after a cell switch is performed using the activated TCI state;receipt or application of a reconfiguration message;receipt of another message including TA information for another TCI state of the candidate cell;receipt of another message including TA information for another of the candidate cells;receipt of a TA acquisition command to request TA acquisition for a reference signal or beam associated with another TCI state of the candidate cell; orreceipt of a TA acquisition command to request TA acquisition for of the another candidate cells.

8. The method of any of claims 1 to 7, wherein the method further comprises deactivating at least one of the one or more activated TCI states, based on the at least one message including the TA information, for at least one candidate cell in the first one or more of the candidate cells.

9. The method of any of claims 1 to 8, wherein the method further comprises sending, to the serving cell, information that indicates the UE supports keeping activated TCI states active based on the at least one message including the TA information.

10. The method of claim 9, wherein the information further indicates a maximum number of activated TCI states the UE supports keeping activated, the maximum number indicated per candidate cell or across candidate cells.

11. The method of any of claims 1 to 10, wherein the TCI state activation for a TCI state is performed to acquire or track downlink synchronization information using at least one reference signal associated with the TCI state.

12. The method of claim 11, wherein the method further comprises: determining a cell switch condition for a cell switch is satisfied or a cell switch is performed for a target cell or a beam of the target cell that is among the at least one candidate cell or at least one beam of the at least one candidate cell for which the at least one of the one or more activated TCI states is kept active; andperforming the cell switch to the target cell using the downlink synchronization information for a TCI state of the at least one of the one or more activated TCI states for the target cell.

13. The method of claim 11 or claim 12, wherein the method further comprises:determining a cell switch condition for a cell switch is satisfied or a cell switch is performed for a target cell or a beam of the target cell that is among the candidate cells but not in the at least one candidate cell or at least one beam of the at least one candidate cell for which the at least one of the one or more activated TCI states is kept active; and performing the cell switch to the target cell, the cell switch including a cell switch delay during which downlink synchronization information is acquired for a TCI state of the target cell that is used in the cell switch.

14. The method of any of claims 11 to 13, wherein the method further comprises:determining a cell switch condition for a cell switch is satisfied or a cell switch is performed for a target cell or a beam of the target cell that is among the candidate cells for which the TCI state activation is performed and TA information is received;determining one or more of:the cell switch condition is satisfied or the cell switch is performed within a predefined duration from when the TA information is received;the cell switch condition is satisfied or the cell switch is performed within a predefined duration from when tracking of the downlink synchronization information is stopped based on the received TA information; orthe cell switch condition is satisfied or the cell switch is performed within a predefined duration from when the TCI state activation is completed; and performing the cell switch to the target cell using the downlink synchronization information for a TCI state of the one or more TCI states for the target cell, without any cell switch delay during which the downlink synchronization information is acquired for the TCI state.

15. The method of any of claims 11 to 14, wherein the method further comprises:determining a cell switch condition for a cell switch is satisfied or a cell switch is performed for a target cell or a beam of the target cell that is among the candidate cells for which the TCI state activation is performed and TA information is received;determining one or more of:the cell switch condition is not satisfied or the cell switch is not performed within a predefined duration from when the TA information is received;the cell switch condition is not satisfied or the cell switch is not performed within a predefined duration from when tracking of the downlink synchronization information is stopped based on the received TA information; orthe cell switch condition is not satisfied or the cell switch is not performed within a predefined duration from when the TCI state activation is completed; and performing the cell switch to the target cell using the downlink synchronization information for a TCI state of the one or more TCI states for the target cell, and including a cell switch delay during which the downlink synchronization information is acquired for the TCI state.

16. An apparatus comprising:at least one memory configured to store instructions; andat 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 claims 1 to 15.

17. An apparatus comprising means for performing the method of any of claims 1 to 15.

18. 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 claims 1 to 15.

19. 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 claims 1 to 15.

20. 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 claims 1 to 15.

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