Event-triggered cell switch procedure for early timing advance acquisition using a dedicated preamble

Abstract

Example embodiments of the present disclosure are directed to an event-triggered cell switch procedure. A method comprises receiving, from a second apparatus, an event-triggered configuration indicating a list of candidate cells and a first condition for triggering a cell switch; prior to the first condition being met for a candidate cell of the list of candidate cells, transmitting a first preamble for obtaining a timing advance (TA) of the candidate cell, the first preamble being different from at least second preamble configured for a random access channel (RACH) procedure; receiving, from the second apparatus, a first message comprising the TA of the candidate cell; and in accordance with a determination that the first condition is met for the candidate cell, performing a transmission on the candidate cell based on the TA of the candidate cell.

Description

EVENT-TRIGGERED CELL SWITCH PROCEDUREFIELD

[0001] Various example embodiments of the present disclosure generally relate to the field of telecommunication and in particular, to methods, devices, apparatuses and computer readable storage medium for event-triggered cell switch procedure.BACKGROUND

[0002] With the continuous development of mobile networks, managing and optimizing user mobility between different network nodes has become crucial. Modern mobile communication systems require seamless connectivity between various network nodes to ensure efficient and reliable handovers. In order to ensure the communication continuousness in the wireless communication system, multiple technologies are proposed, such as cell switch. During the cell switch, the terminal device may switch among different cells. Further, technology of layer 1 / layer 2 (L1 / L2) triggered mobility (LTM) may be used for enabling the cell switch. LTM is a procedure in which the next generation node B (gNB) receives layer 1 (LI) and / or layer 3 (L3) measurement report(s) from a UE, and thus the gNB changes user equipment (UE) serving cell by a cell switch command signalled via a medium access control (MAC) control element (CE). The LTM procedure may be used to reduce the mobility latency.SUMMARY

[0003] In a first aspect of the present disclosure, there is provided a first apparatus. The first apparatus comprises at least one processor; and at least one memory storing instructions that, when executed by the at least one processor, cause the first apparatus to: receive, from a second apparatus, an event-triggered configuration indicating: a list of candidate cells, a first condition for triggering a cell switch, and a second condition for triggering a procedure for obtaining a timing advance (TA); and prior to the first condition being met for a candidate cell of the list of candidate cells, based on the second condition being met for the candidate cell, trigger a procedure for obtaining a TA of the candidate cell.

[0004] In a second aspect of the present disclosure, there is provided a second apparatus. iThe second apparatus comprises at least one processor; and at least one memory storing instructions that, when executed by the at least one processor, cause the second apparatus to: determine an event -triggered configuration for a first apparatus, the event -triggered configuration indicating: a list of candidate cells, a first condition for triggering a cell switch, and a second condition for triggering a procedure for obtaining a timing advance (TA); and transmit the event-triggered configuration to the first apparatus.

[0005] In a third aspect of the present disclosure, there is provided a first apparatus. The first apparatus comprises at least one processor; and at least one memory storing instructions that, when executed by the at least one processor, cause the first apparatus to: receive, from a second apparatus, an event-triggered configuration indicating a list of candidate cells and a first condition for triggering a cell switch; prior to the first condition being met for a candidate cell of the list of candidate cells, transmit a first preamble for obtaining a timing advance (TA) of the candidate cell, the first preamble being different from at least second preamble configured for a random access channel (RACH) procedure; receive, from the second apparatus, a first message comprising the TA of the candidate cell; and in accordance with a determination that the first condition is met for the candidate cell, perform a transmission on the candidate cell based on the TA of the candidate cell.

[0006] In a fourth aspect of the present disclosure, there is provided a second apparatus. The second apparatus comprises at least one processor; and at least one memory storing instructions that, when executed by the at least one processor, cause the second apparatus to: transmit, to a first apparatus, an event-triggered configuration indicating a list of candidate cells and a first condition for triggering a cell switch; receive, from the first apparatus, a first preamble for obtaining a timing advance (TA) of a candidate cell of the list of candidate cells, the first preamble is different from at least second preamble configured for a random access channel (RACH) procedure; and transmit, to the first apparatus, a first message comprising the TA of the candidate cell.

[0007] In a fifth aspect of the present disclosure, there is provided a first apparatus. The first apparatus comprises at least one processor; and at least one memory storing instructions that, when executed by the at least one processor, cause the first apparatus to: receive, from a second apparatus, an event-triggered configuration indicating a list of candidate cells and a first condition for triggering a cell switch; prior to the first condition being met for a candidate cell of the list of candidate cells, trigger a procedure for obtaining a timing advance (TA) of the candidate cell; and based at least in part on thefirst condition being met for the candidate cell and the procedure for obtaining the TA not being completed, start a TA acquisition timer to continue the procedure for obtaining the TA and / or delay the cell switch to the candidate cell.

[0008] In a sixth aspect of the present disclosure, there is provided a first apparatus. The first apparatus comprises at least one processor; and at least one memory storing instructions that, when executed by the at least one processor, cause the first apparatus to: receive, from a second apparatus, an event-triggered configuration indicating a list of candidate cells and a first condition for triggering a cell switch; prior to switching to a candidate cell of the list of candidate cells in response to the first condition being met for the candidate cell, determine a transmission configuration indicator (TCI) state to be applied on the candidate cell based on at least one of a first TCI state indicated by the second apparatus in a first message, or a second TCI state associated with a best measurement result of a reference signal (RS) resource; and in response to the first condition being met for the candidate cell, perform a transmission on the candidate cell based on the determined TCI state.

[0009] In a seventh aspect of the present disclosure, there is provided a second apparatus. The second apparatus comprises at least one processor; and at least one memory storing instructions that, when executed by the at least one processor, cause the second apparatus to: transmit, to a first apparatus, an event-triggered configuration indicating: a list of candidate cells and a first condition for triggering a cell switch; and determine a transmission configuration indicator (TCI) state to be applied on a candidate cell based on at least one of: a first TCI state indicated by the second apparatus in a first message, or a second TCI state associated with a best measurement result of a reference signal (RS) resource.

[0010] In an eight aspect of the present disclosure, there is provided a third apparatus. The third apparatus comprises at least one processor; and at least one memory storing instructions that, when executed by the at least one processor, cause the third apparatus to: receive, a context modification request comprising a transmission configuration indicator (TCI) state to be used for communication between a first apparatus and the third apparatus, wherein the first apparatus is to be switched to a candidate cell provided by the third apparatus; in accordance with a determination that the communication is configured grant, retain a configured grant of the TCI state comprised in the context modification message; and in accordance with a determination that the communication is dynamic grant,allocate a dynamic grant to the first apparatus based on the TCI state comprised in the context modification message.

[0011] In a ninth aspect of the present disclosure, there is provided a method. The method comprises: receiving, from a second apparatus, an event-triggered configuration indicating: a list of candidate cells, a first condition for triggering a cell switch, and a second condition for triggering a procedure for obtaining a timing advance (TA); and prior to the first condition being met for a candidate cell of the list of candidate cells, based on the second condition being met for the candidate cell, triggering a procedure for obtaining a TA of the candidate cell.

[0012] In a tenth aspect of the present disclosure, there is provided a method. The method comprises: determining an event-triggered configuration for a first apparatus, the event- triggered configuration indicating: a list of candidate cells, a first condition for triggering a cell switch, and a second condition for triggering a procedure for obtaining a timing advance (TA); and transmitting the event-triggered configuration to the first apparatus.

[0013] In an eleventh aspect of the present disclosure, there is provided a method. The method comprises: receiving, from a second apparatus, an event-triggered configuration indicating a list of candidate cells and a first condition for triggering a cell switch; prior to the first condition being met for a candidate cell of the list of candidate cells, transmit a first preamble for obtaining a timing advance (TA) of the candidate cell, the first preamble being different from at least second preamble configured for a random access channel (RACH) procedure; receiving, from the second apparatus, a first message comprising the TA of the candidate cell; and in accordance with a determination that the first condition is met for the candidate cell, performing a transmission on the candidate cell based on the TA of the candidate cell.

[0014] In a twelfth aspect of the present disclosure, there is provided a method. The method comprises: transmitting, to a first apparatus, an event-triggered configuration indicating a list of candidate cells and a first condition for triggering a cell switch; receiving, from the first apparatus, a first preamble for obtaining a timing advance (TA) of a candidate cell of the list of candidate cells, the first preamble is different from at least second preamble configured for a random access channel (RACH) procedure; and transmitting, to the first apparatus, a first message comprising the TA of the candidate cell.

[0015] In a thirteenth aspect of the present disclosure, there is provided a method. The method comprises: receiving, from a second apparatus, an event-triggered configuration indicating a list of candidate cells and a first condition for triggering a cell switch; prior to the first condition being met for a candidate cell of the list of candidate cells, triggering a procedure for obtaining a timing advance (TA) of the candidate cell; and based at least in part on the first condition being met for the candidate cell and the procedure for obtaining the TA not being completed, starting a TA acquisition timer to continue the procedure for obtaining the TA and / or delay the cell switch to the candidate cell.

[0016] In a fourteenth aspect of the present disclosure, there is provided a method. The method comprises: receiving, from a second apparatus, an event-triggered configuration indicating a list of candidate cells and a first condition for triggering a cell switch; prior to switching to a candidate cell of the list of candidate cells in response to the first condition being met for the candidate cell, determining a transmission configuration indicator (TCI) state to be applied on the candidate cell based on at least one of: a first TCI state indicated by the second apparatus in a first message, or a second TCI state associated with a best measurement result of a reference signal (RS) resource; and in response to the first condition being met for the candidate cell, performing a transmission on the candidate cell based on the determined TCI state.

[0017] In a fifteenth aspect of the present disclosure, there is provided a method. The method comprises: transmitting, to a first apparatus, an event-triggered configuration indicating: a list of candidate cells and a first condition for triggering a cell switch; and determining a transmission configuration indicator (TCI) state to be applied on a candidate cell based on at least one of: a first TCI state indicated by the second apparatus in a first message, or a second TCI state associated with a best measurement result of a reference signal (RS) resource.

[0018] In a sixteenth aspect of the present disclosure, there is provided a method. The method comprises: receiving, a context modification request comprising a transmission configuration indicator (TCI) state to be used for communication between a first apparatus and the third apparatus, wherein the first apparatus is to be switched to a candidate cell provided by the third apparatus; in accordance with a determination that the communication is configured grant, retaining a configured grant of the TCI state comprised in the context modification message; and in accordance with a determination that the communication is dynamic grant, allocating a dynamic grant to the first apparatusbased on the TCI state comprised in the context modification message.

[0019] In a seventeenth aspect of the present disclosure, there is provided a first apparatus. The first apparatus comprises means for receiving, from a second apparatus, an event-triggered configuration indicating: a list of candidate cells, a first condition for triggering a cell switch, and a second condition for triggering a procedure for obtaining a timing advance (TA); and means for prior to the first condition being met for a candidate cell of the list of candidate cells, based on the second condition being met for the candidate cell, triggering a procedure for obtaining a TA of the candidate cell.

[0020] In an eighteenth aspect of the present disclosure, there is provided a second apparatus. The second apparatus comprises means for determining an event-triggered configuration for a first apparatus, the event-triggered configuration indicating: a list of candidate cells, a first condition for triggering a cell switch, and a second condition for triggering a procedure for obtaining a timing advance (TA); and means for transmitting the event-triggered configuration to the first apparatus.

[0021] In a nineteenth aspect of the present disclosure, there is provided a first apparatus. The first apparatus comprises means for receiving, from a second apparatus, an event- triggered configuration indicating a list of candidate cells and a first condition for triggering a cell switch; means for prior to the first condition being met for a candidate cell of the list of candidate cells, transmit a first preamble for obtaining a timing advance (TA) of the candidate cell, the first preamble being different from at least second preamble configured for a random access channel (RACH) procedure; means for receiving, from the second apparatus, a first message comprising the TA of the candidate cell; and means for in accordance with a determination that the first condition is met for the candidate cell, performing a transmission on the candidate cell based on the TA of the candidate cell.

[0022] In a twentieth aspect of the present disclosure, there is provided a second apparatus. The second apparatus comprises means for transmitting, to a first apparatus, an event-triggered configuration indicating a list of candidate cells and a first condition for triggering a cell switch; means for receiving, from the first apparatus, a first preamble for obtaining a timing advance (TA) of a candidate cell of the list of candidate cells, the first preamble is different from at least second preamble configured for a random access channel (RACH) procedure; and means for transmitting, to the first apparatus, a first message comprising the TA of the candidate cell.

[0023] In a twenty-first aspect of the present disclosure, there is provided a first apparatus. The first apparatus comprises means for receiving, from a second apparatus, an event-triggered configuration indicating a list of candidate cells and a first condition for triggering a cell switch; means for prior to the first condition being met for a candidate cell of the list of candidate cells, triggering a procedure for obtaining a timing advance (TA) of the candidate cell; and means for based at least in part on the first condition being met for the candidate cell and the procedure for obtaining the TA not being completed, starting a TA acquisition timer to continue the procedure for obtaining the TA and / or delay the cell switch to the candidate cell.

[0024] In a twenty-second aspect of the present disclosure, there is provided a first apparatus. The first apparatus comprises means for receiving, from a second apparatus, an event-triggered configuration indicating a list of candidate cells and a first condition for triggering a cell switch; means for prior to switching to a candidate cell of the list of candidate cells in response to the first condition being met for the candidate cell, determining a transmission configuration indicator (TCI) state to be applied on the candidate cell based on at least one of a first TCI state indicated by the second apparatus in a first message, or a second TCI state associated with a best measurement result of a reference signal (RS) resource; and means for in response to the first condition being met for the candidate cell, performing a transmission on the candidate cell based on the determined TCI state.

[0025] In twenty-third aspect of the present disclosure, there is provided a second apparatus. The second apparatus comprises means for transmitting, to a first apparatus, an event-triggered configuration indicating: a list of candidate cells and a first condition for triggering a cell switch; and means for determining a transmission configuration indicator (TCI) state to be applied on a candidate cell based on at least one of a first TCI state indicated by the second apparatus in a first message, or a second TCI state associated with a best measurement result of a reference signal (RS) resource.

[0026] In a twenty-fourth aspect of the present disclosure, there is provided a third apparatus. The third apparatus comprises means for receiving, a context modification request comprising a transmission configuration indicator (TCI) state to be used for communication between a first apparatus and the third apparatus, wherein the first apparatus is to be switched to a candidate cell provided by the third apparatus; means for in accordance with a determination that the communication is configured grant, retaininga configured grant of the TCI state comprised in the context modification message; and means for in accordance with a determination that the communication is dynamic grant, allocating a dynamic grant to the first apparatus based on the TCI state comprised in the context modification message.

[0027] In a twenty-fifth aspect of the present disclosure, there is provided a computer readable medium. The computer readable medium comprises instructions stored thereon for causing an apparatus to perform at least the method according to any of the ninth to the sixteenth aspect.

[0028] It is to be understood that the Summary section is not intended to identify key or essential features of embodiments of the present disclosure, nor is it intended to be used to limit the scope of the present disclosure. Other features of the present disclosure will become easily comprehensible through the following description.BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Some example embodiments will now be described with reference to the accompanying drawings, where:

[0030] FIG. 1A and FIG. IB illustrate example communication environments in which example embodiments of the present disclosure can be implemented, respectively;

[0031] FIG. 2 illustrates a signaling flow for an event-triggered cell switch procedure in accordance with some example embodiments of the present disclosure;

[0032] FIG. 3 illustrates an example signaling flow for an event-triggered cell switch procedure in accordance with some example embodiments of the present disclosure;

[0033] FIG. 4 illustrates an example signaling flow for an event-triggered cell switch procedure in accordance with some example embodiments of the present disclosure;

[0034] FIG. 5 illustrates an example signaling flow for an event-triggered cell switch procedure in accordance with some example embodiments of the present disclosure;

[0035] FIG. 6A and FIG. 6B illustrate example signaling flows for an event-triggered intra-CU cell switch procedure in accordance with some example embodiments of the present disclosure;

[0036] FIG. 7 illustrates another example signaling flow for event-triggered intra-CU cell switch procedure in accordance with some example embodiments of the presentdisclosure;

[0037] FIG. 8A and FIG. 8B illustrate another example signaling flows for event- triggered intra-CU cell switch procedure in accordance with some example embodiments of the present disclosure;

[0038] FIG. 9A and FIG. 9B illustrate example signaling flows for early TCI state activation for cell switch in accordance with some example embodiments of the present disclosure;

[0039] FIG. 10A and FIG. 10B illustrate another example signaling flows for early TCI state activation for cell switch in accordance with some example embodiments of the present disclosure;

[0040] FIG. 11 illustrates a flowchart of a method implemented at a first apparatus in accordance with some example embodiments of the present disclosure;

[0041] FIG. 12 illustrates a flowchart of a method implemented at a second apparatus in accordance with some example embodiments of the present disclosure;

[0042] FIG. 13 illustrates another flowchart of a method implemented at a first apparatus in accordance with some example embodiments of the present disclosure;

[0043] FIG. 14 illustrates another flowchart of a method implemented at a second apparatus in accordance with some example embodiments of the present disclosure;

[0044] FIG. 15 illustrates another flowchart of a method implemented at a first apparatus in accordance with some example embodiments of the present disclosure;

[0045] FIG. 16 illustrates another flowchart of a method implemented at a first apparatus in accordance with some example embodiments of the present disclosure;

[0046] FIG. 17 illustrates another flowchart of a method implemented at a secpmd apparatus in accordance with some example embodiments of the present disclosure;

[0047] FIG. 18 illustrates a flowchart of a method implemented at a third apparatus in accordance with some example embodiments of the present disclosure;

[0048] FIG. 19 illustrates a simplified block diagram of a device that is suitable for implementing example embodiments of the present disclosure; and

[0049] FIG. 20 illustrates a block diagram of an example computer readable medium inaccordance with some example embodiments of the present disclosure.

[0050] Throughout the drawings, the same or similar reference numerals represent the same or similar element.DETAILED DESCRIPTION

[0051] Principle of the present disclosure will now be described with reference to some example embodiments. It is to be understood that these embodiments are described only for the purpose of illustration and help those skilled in the art to understand and implement the present disclosure, without suggesting any limitation as to the scope of the disclosure. Embodiments described herein can be implemented in various manners other than the ones described below.

[0052] In the following description and claims, unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skills in the art to which this disclosure belongs.

[0053] References in the present disclosure to “one embodiment,” “an embodiment,” “an example embodiment,” and the like indicate that the embodiment described may include a particular feature, structure, or characteristic, but it is not necessary that every embodiment includes the particular feature, structure, or characteristic. Moreover, such phrases are not necessarily referring to the same embodiment. Further, when a particular feature, structure, or characteristic is described in connection with an embodiment, it is submitted that it is within the knowledge of one skilled in the art to affect such feature, structure, or characteristic in connection with other embodiments whether or not explicitly described.

[0054] It shall be understood that although the terms “first,” “second,”..., etc. in front of noun(s) and the like may be used herein to describe various elements, these elements should not be limited by these terms. These terms are only used to distinguish one element from another and they do not limit the order of the noun(s). For example, a first element could be termed a second element, and similarly, a second element could be termed a first element, without departing from the scope of example embodiments. As used herein, the term “and / or” includes any and all combinations of one or more of the listed terms.

[0055] As used herein, “at least one of the following: ” and “at least one of ” and similar wording, where the listof two or more elements are joined by “and” or “or”, mean at least any one of the elements, or at least any two or more of the elements, or at least all the elements.

[0056] As used herein, unless stated explicitly, performing a step “in response to A” does not indicate that the step is performed immediately after “A” occurs and one or more intervening steps may be included.

[0057] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of example embodiments. As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises”, “comprising”, “has”, “having”, “includes” and / or “including”, when used herein, specify the presence of stated features, elements, and / or components etc., but do not preclude the presence or addition of one or more other features, elements, components and / or combinations thereof.

[0058] 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) and(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) and(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.

[0059] This definition of circuitry applies to all uses of this term in this application, including in any claims. As a further example, as used in this application, the termcircuitry 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.

[0060] As used herein, the term “communication network” refers to a network following any suitable communication standards, such as New Radio (NR), Long Term Evolution (LTE), LTE-Advanced (LTE-A), Wideband Code Division Multiple Access (WCDMA), High-Speed Packet Access (HSPA), Narrow Band Internet of Things (NB-IoT) and so on. Furthermore, the communications between a terminal device and a network device in the communication network may be performed according to any suitable generation communication protocols, including, but not limited to, the first generation (1G), the second generation (2G), 2.5G, 2.75G, the third generation (3G), the fourth generation (4G), 4.5G, the fifth generation (5G), 5.5G, the sixth generation (6G) communication protocols, and / or any other protocols either currently known or to be developed in the future. Embodiments of the present disclosure may be applied in various communication systems. Given the rapid development in communications, there will of course also be future type communication technologies and systems with which the present disclosure may be embodied. It should not be seen as limiting the scope of the present disclosure to only the aforementioned system.

[0061] As used herein, the term “network device” refers to a node in a communication network via which a terminal device accesses the network and receives services therefrom. The network device may refer to a base station (BS) or an access point (AP), for example, a node B (NodeB or NB), an evolved NodeB (eNodeB or eNB), an NR NB (also referred to as a gNB), a Remote Radio Unit (RRU), a radio header (RH), a remote radio head (RRH), a relay, an Integrated Access and Backhaul (IAB) node, a low power node such as a femto, a pico, a non-terrestrial network (NTN) or non-ground network device such as a satellite network device, a low earth orbit (LEO) satellite and a geosynchronous earth orbit (GEO) satellite, an aircraft network device, and so forth, depending on the applied terminology and technology. In some example embodiments, radio access network (RAN) split architecture comprises a Centralized Unit (CU) and a Distributed Unit (DU) at an IAB donor node. An IAB node comprises a Mobile Terminal (IAB-MT) part that behaveslike a UE toward the parent node, and a DU part of an IAB node behaves like a base station toward the next-hop IAB node.

[0062] The term “terminal device” refers to any end device that may be capable of wireless communication. By way of example rather than limitation, a terminal device may also be referred to as a communication device, user equipment (UE), a Subscriber Station (SS), a Portable Subscriber Station, a Mobile Station (MS), or an Access Terminal (AT). The terminal device may include, but not limited to, a mobile phone, a cellular phone, a smart phone, voice over IP (VoIP) phones, wireless local loop phones, a tablet, a wearable terminal device, a personal digital assistant (PDA), portable computers, desktop computer, image capture terminal devices such as digital cameras, gaming terminal devices, music storage and playback appliances, vehicle-mounted wireless terminal devices, wireless endpoints, mobile stations, laptop-embedded equipment (LEE), laptop-mounted equipment (LME), USB dongles, smart devices, wireless customer-premises equipment (CPE), an Internet of Things (loT) device, a watch or other wearable, a head-mounted display (HMD), a vehicle, a drone, a medical device and applications (e.g., remote surgery), an industrial device and applications (e.g., a robot and / or other wireless devices operating in an industrial and / or an automated processing chain contexts), a consumer electronics device, a device operating on commercial and / or industrial wireless networks, and the like. The terminal device may also correspond to a Mobile Termination (MT) part of an IAB node (e.g., a relay node). In the following description, the terms “terminal device”, “communication device”, “terminal”, “user equipment” and “UE” may be used interchangeably.

[0063] As used herein, the term “resource,” “transmission resource,” “resource block,” “physical resource block” (PRB), “uplink resource,” or “downlink resource” may refer to any resource for performing a communication, for example, a communication between a terminal device and a network device, such as a resource in time domain, a resource in frequency domain, a resource in space domain, a resource in code domain, or any other combination of the time, frequency, space and / or code domain resource enabling a communication, and the like. In the following, unless explicitly stated, a resource in both frequency domain and time domain will be used as an example of a transmission resource for describing some example embodiments of the present disclosure. It is noted that example embodiments of the present disclosure are equally applicable to other resources in other domains.

[0064] As used herein, “inter-centralized unit (CU)” may refer to the interactions and handovers occurring between different centralized units within a mobile communication network. CUs are network nodes responsible for handling higher-layer functions such as radio resource control and mobility management. The term “inter-CU” specifically pertains to the processes, procedures, and mechanisms involved when a user equipment (UE) transitions from one CU to another, ensuring continuous and seamless connectivity during the handover.

[0065] As used herein, “intra-CU” may refer to the interactions and handovers occurring among different distributed units (DUs) or different gNBs of a same CU within a mobile communication network. The term “intra-CU” specifically pertains to the processes, procedures, and mechanisms involved when a UE transitions from one DU / gNB to another DU / gNB of a same CU, ensuring continuous and seamless connectivity during the handover.

[0066] As mentioned above, technologies such as cell switch are proposed to ensure the communication continuousness in the wireless communication system. For example, LTM may be used for enabling the cell switch to reduce the mobility latency. In some mechanisms, a conditional LTM is supported. As used herein, a conditional LTM may be referred to as a UE triggered LTM or event -triggered LTM. For example, conditions for triggering LTM may be specified or configured. UE may evaluate the conditions for triggering the LTM. Conditional LTM may be supported including a subsequent LTM. In some cases, intra-CU LTM may be prioritized.

[0067] For release-19 (Rel-19) conditional LTM, procedures defined in release-18 (Rel- 18) LTM, which was based on network -triggered cell switch, may have to be enhanced to support UE-autonomous cell switch triggering. One of the procedures to be considered for enhancement is early TA acquisition. In Rel-18, since the cell switch is network triggered, the TA is provided to the UE with the cell switch command. For conditional LTM, this would result in the TA never reaching the UE in case of a UE-autonomous conditional LTM cell switch and, as a result LTM cell switch would always be random access channel (RACH)-based, which lack the benefit of reduced interruption time.

[0068] Therefore, for conditional LTM, a random access response (RAR) may be provided to the UE directly from the (candidate) target cell or TA information may be provided to the UE by the source cell (after being forwarded to it from the target DU viathe CU).

[0069] When conditional LTM is configured, UE is configured with a condition, if the condition is met for a candidate cell, UE selects the candidate cell as the target cell for cell switch and applies target configuration.

[0070] However, there is no existing mechanism to ensure TA is acquired before execution condition is met. If the execution condition for LTM is met before TA acquisition procedure is completed at UE, then extra signalling overhead related to RACH procedure causes delayed cell switch to target cell.

[0071] Current TCI state evaluation at the time of execution delays the cell switch due to the signalling of sending the target cell TCI state to the network and further processing at the network for grant allocation. There is no mechanism to ensure early TCI state information for target cell is available prior to execution condition being met. In order to have UE early sync to target cell for downlink and uplink, further coordination is needed with network prior to conditional LTM execution.

[0072] In order to solve at least part of the above problems or other potential problems, several solutions on event-triggered cell switch procedure such as an event-triggered LTM cell switch are proposed. In a solution, in addition to a first condition for triggering a cell switch, a second condition for triggering a procedure for obtaining a TA is configured. With the second condition, UE may initiate a procedure for obtaining a TA of a candidate cell prior to the first condition being met for the candidate cell. In this manner, early UL synchronization before the first condition being met may be initiated.

[0073] In another solution, prior to a condition for triggering a cell switch being met for a candidate cell, UE transmits a preamble for obtaining a TA of the candidate cell to the network. The network then transmits a message comprising the TA of the candidate cell to UE. In this way, the early TA acquisition may be achieved before the cell switch. Early UL synchronization may thus be initiated.

[0074] In a further solution, if a condition for triggering a cell switch is met for a candidate cell but a procedure for obtaining a TA of the candidate cell is not completed, UE starts a TA acquisition timer to continue the procedure for obtaining the TA and / or delay the cell switch to the candidate cell. Such TA acquisition timer may ensure that there will be no further delay in re-initiating RACH when the early TA acquisitionprocedure has already been triggered.

[0075] In a still further solution, prior to switching to a candidate cell in response to a condition for triggering a cell switch is met for the candidate cell, a TCI state to be applied on the candidate cell is determined based on at least one of: a first TCI state indicated by the network in a message, or a second TCI state associated with a best measurement result of a RS resource. In this manner, the TCI state to be applied to the target cell can be determined before the cell switch. Early TCI state activation can thus be achieved for conditional LTM.

[0076] Several solutions of the present disclosure has been briefly described. Principle and implementations of the present disclosure will be described in detail below with reference to FIGS. 1A-20.Example Environment

[0077] FIG. 1A shows an example communication environment 100A in which example embodiments of the present disclosure may be implemented. The network communication 100A includes a first apparatus 110, a second apparatus 120 and a third apparatuses 130.

[0078] In some example embodiments, the first apparatus 110 may be comprised in a terminal device / apparatus and the second apparatus 120 / third apparatus 130 may be comprised in a network device / apparatus. Additionally, the second apparatuses 120 and the third apparatus 130 may provide one or more coverage areas, also called as cells. As illustrated in FIG. 1A, the communication environment 100A includes a cell 150 provided by the second apparatus 120 and a cell 160 provided by the second apparatus 120 provided by the third apparatus 130.

[0079] Further, in some example embodiments, the radio access network (RAN) architecture may include a centralized part, or central unit (CU), and a distributed part, or distributed unit (DU). The CU and the DU may be connected to one another by a so-called Fl interface. In the example of FIG. 1A, the second apparatus 120 may refer to a base station (such as, the next generation node B, gNB), a gNB-CU and / or a gNB-DU. Similarly, the third apparatus 130 also may refer to a base station (such as, a gNB), a gNB CU and / or a gNB DU.

[0080] In the example of FIG. 1A, the first apparatus 110 may move over time. As illustrated in FIG. 1A, the first apparatus 110 locates at different positions at differenttime points (T1 and T2). As moving, the first apparatus 110 may switch among different cells, i.e., a cell switch procedure. In the example of FIG. 1A, the first apparatus 110 may switch from cell 150 to cell 160. For a better discussion, the cell 150 may be called as the source cell 150 or the serving cell 150, and the cell 160 may be called as the candidate cell 160. Further, in a case that the cell 160 is selected as a target cell, the cell 160 also may be called as the target cell 160.

[0081] Reference is now made to FIG. IB, which illustrates other example communication environments 100B in which example embodiments of the present disclosure may be implemented. In the example (A) of FIG. IB, the second apparatus 120 and the third apparatus 130 are gNB DUs, and both the second apparatus 120 and the third apparatus 130 are connected to a same gNB-CU. In the example (B) of FIG. IB, the second apparatus 120 and the third apparatus 130 are gNB DUs, while the second apparatus 120 the third apparatus 130 are connected to two different gNB-CUs.

[0082] It should be noted examples (A) and (B) of FIG. IB are two example communication environments of the present discourse which are illustrated only for the purpose of illustration without suggesting any limitations. In fact, the cell switch discussed herein may include at least one of the following: an intra-gNB cell switch, an inter-gNB cell switch, an intra-CU cell switch, or an inter-CU cell switch.

[0083] It is to be understood that the number of devices and their connections shown in FIG. 1A and FIG. IB are only for the purpose of illustration without suggesting any limitation. The communication environments 100 A and 100B may include any suitable number of devices configured to implementing example embodiments of the present disclosure. Although not shown, it would be appreciated that one or more additional devices may be located in the cell, and one or more additional cells may be deployed in the communication environments 100A and 100B. It is noted that although illustrated as a network device, the second apparatus 120 / the third apparatus 130 may be another device than a network device. Although illustrated as a terminal device, the first apparatus 110 may be another device than a terminal apparatus.

[0084] Communications in the communication environments 100 A and 100B may be implemented according to any proper communication protocol(s), comprising, but not limited to, cellular communication protocols of the first generation (1G), the second generation (2G), the third generation (3G), the fourth generation (4G), the fifth generation(5G), 5.5G, the sixth generation (6G), and the like, wireless local network communication protocols such as Institute for Electrical and Electronics Engineers (IEEE) 802.11 and the like, and / or any other protocols currently known or to be developed in the future. Moreover, the communication may utilize any proper wireless communication technology, comprising but not limited to: Code Division Multiple Access (CDMA), Frequency Division Multiple Access (FDMA), Time Division Multiple Access (TDMA), Frequency Division Duplex (FDD), Time Division Duplex (TDD), Multiple-Input Multiple-Output (MIMO), Orthogonal Frequency Division Multiple (OFDM), Discrete Fourier Transform spread OFDM (DFT-s-OFDM) and / or any other technologies currently known or to be developed in the future.Work Principle and Example Signalling for Communication

[0085] Example embodiments of the present disclosure will be described in detail below with reference to the accompanying drawings. It is noted the order acts shown in FIG. 2- 10B are only an example not limitation. Acts may be performed in any suitable manner. Example embodiments described with reference to FIG. 2 to FIG. 10B may be implemented separately or combined in any manner. For example, one or more example embodiments shown in a single drawing may be combined with one or more example embodiments shown in one or more other drawings.

[0086] In the following discussion, the cell switch may comprise at least one of the following: an intra-gNB cell switch, an inter-gNB cell switch, an intra-CU cell switch, or an inter-CU cell switch.

[0087] Further, in the following discussions, the first apparatus 110 may comprise a terminal apparatus, the second apparatus 120 may comprise one of the following: a next generation node B (gNB) serving the first apparatus 110, a distributed unit (DU) connecting with the first apparatus 110, or a centralized unit (CU) connecting with the DU, and the third apparatus 130 may comprises one of the following: a target next generation node B (gNB), or a target distributed unit (DU).

[0088] As briefly described, in a solution of the present disclosure, in addition to a first condition for triggering a cell switch, a second condition for triggering a procedure for obtaining a TA may be configured. With the second condition, UE may initiate a procedure for obtaining a TA of a candidate cell prior to the first condition being met for the candidate cell. FIG. 2 illustrates a signaling flow 200 for event-triggered cell switchprocedure with two conditions configured according to some example embodiments of the present disclosure. The signaling flow 200 involves the first apparatus 110 and the second apparatus 120 in FIG. 1 A and FIG. IB.

[0089] In operation, the second apparatus 120 determines (210) an event-triggered configuration for the first apparatus 110. The event-triggered configuration indicates a list of candidate cells (also referred to as a list of prepared (candidate) cells), a first condition for triggering a cell switch, and a second condition for triggering a procedure for obtaining a TA. As used herein, the first condition for triggering a cell switch may also be referred to as a “cell switch condition”, an “execution condition”, “the first condition” or the like. The second condition for triggering the procedure for obtaining TA may also be referred to as “early TA acquisition condition”, “early TA condition”, “the second condition” or the like.

[0090] The second apparatus 120 transmits (210-1) the determined event -triggered configuration to the first apparatus 110. The first apparatus 110 receives (210-2) the event- triggered configuration. By way of example, the event-triggered configuration may be comprised in a radio resource control (RRC) reconfiguration message or any other suitable message. For example, the event-triggered configuration may include an LTM-based configuration, and / or a layer 3 (L3) event-triggered configuration, or the like.

[0091] In some example embodiments, the first apparatus 110 may comprise a terminal apparatus and the second apparatus 120 may comprise a gNB serving the first apparatus 110, a DU connecting with the first apparatus 110, or a CU connecting with the DU.

[0092] If the second apparatus 120 is a CU connecting the DU, the transmission between the first apparatus 110 and the second apparatus 120 may be via the DU connecting with the first apparatus 110. For example, the second apparatus 120 transmitting (310-1) the event-triggered configuration to the first apparatus 110 means that the second apparatus 120 transmits the event -triggered configuration to the DU and then the DU forwards the event-triggered configuration to the first apparatus 110.

[0093] In embodiments where the second apparatus 120 comprises the DU connecting with the first apparatus 110, the second apparatus 120 may receive the event-triggered configuration from the CU connecting with the DU.

[0094] In embodiments where the second apparatus 120 comprises the CU, the secondapparatus 120 may transmit the event -triggered configuration to the DU serving the first apparatus 120. The DU may forward the event-triggered configuration to the first apparatus 110.

[0095] In some example embodiments, the first condition may be associated with a first set of criteria, and the second condition may be associated with a second set of criteria that is lower than the first set of criteria. By way of example, the first condition may include at least one first threshold corresponding to at least one event, and the second condition may include at least one second threshold corresponding to the at least one event, the second threshold being different from the first threshold.

[0096] As another example, the first condition may include at least one first threshold corresponding to at least one event, and the second condition may include at least one offset, the offset being a difference between a second threshold associated with the second condition and the first threshold.

[0097] As a further example, the second condition may include at least one second threshold corresponding to at least one event, and the first condition may include at least one offset, the offset being a difference between a first threshold associated with the first condition and the second threshold.

[0098] By configuring the first condition and the second condition with different criteria or thresholds, it may ensure that the second condition will be met before the first condition is met.

[0099] In some example embodiments, the first apparatus 110 may perform measurements on the list of candidate cells based on the event-triggered configuration. The first apparatus 110 may evaluate (230) the second condition based on results of the measurements.

[0100] If the second condition is met for a candidate cell (also referred to as a target cell hereinafter) of the list of candidate cells prior to the first condition being met for the candidate cell, the first apparatus 110 may trigger (240) a procedure for obtaining a TA of the candidate cell.

[0101] In some example embodiments, the first apparatus 110 may trigger (240) the procedure for obtaining the TA of the candidate cell by transmitting a first preamble to the second apparatus 120 for obtaining the TA. The first preamble (referred to as a TApreamble or a preamble for early TA) may be different from at least second preamble configured for a RACH procedure. Alternatively, in some example embodiments, the first apparatus 110 may trigger (240) the procedure for obtaining the TA of the candidate cell by initiating a RACH procedure for obtaining the TA by using the second preamble. It is to be understood that these example approaches for triggering the procedure of TA obtaining are only for the purpose of illustration, without suggesting any limitation. Any suitable approach may be used for triggering (240) the procedure for TA acquisition.

[0102] Alternatively, or in addition, in some example embodiments, the first apparatus 110 may trigger (240) the procedure for obtaining the TA of the candidate cell by initiating a UE-based TA evaluation procedure. With the UE-based TA evaluation, the TA estimation may be done at the UE without waiting for TA from network. Details regarding the UE-based TA evaluation procedure will be described with respect to FIG. 7 in the following descriptions.

[0103] The first apparatus 110 may evaluate (250) the first condition based on results of the measurements. If the first condition is met for the candidate cell, the first apparatus 110 may switch (260) to the candidate cell. For example, the first apparatus 110 may perform a transmission on the candidate cell based on the TA obtained from the procedure triggered by the first apparatus 110.

[0104] With the signaling flow 200, the TA acquisition of the target cell may be triggered before the cell switch or cell change is triggered. In this manner, early UL synchronization before the first condition being met may be initiated. Further details of the signaling flow 200 may be illustrated with respect to FIG. 6A to FIG. 8B in the following descriptions.

[0105] As briefly mentioned, in another solution of the present disclosure, prior to a condition for triggering a cell switch being met for a candidate cell, UE may transmit a preamble for obtaining a TA of the candidate cell to the network instead of initiating a RACH procedure. The network then transmits a message comprising the TA of the candidate cell to UE. FIG. 3 illustrates a signaling flow 300 for event-triggered cell switch procedure according to some example embodiments of the present disclosure. The signaling flow 300 involves the first apparatus 110 and the second apparatus 120 in FIG. 1A and FIG. IB.

[0106] In operation, the second apparatus 120 transmits (310-1), to the first apparatus 110, an event-triggered configuration indicating a list of candidate cells or preparedcandidate cells and a first condition for triggering a cell switch. The first apparatus 110 receives (310-2) the event-triggered configuration. In some example embodiments, the event-triggered configuration comprises at least one of an LTM-based configuration or an L3 event-triggered configuration. The event-triggered configuration may be comprised in an RRC reconfiguration message or any other suitable message.

[0107] In some example embodiments, the first apparatus 110 may include a terminal apparatus and the second apparatus 120 may include a gNB serving the first apparatus 110, a DU connecting with the first apparatus 110, or a CU connecting with the DU. If the second apparatus 120 is a CU connecting the DU, the transmission between the first apparatus 110 and the second apparatus 120 may be via the DU connecting with the first apparatus 110. For example, the second apparatus 120 transmitting (310-1) the event- triggered configuration to the first apparatus 110 means that the second apparatus 120 transmits the event-triggered configuration to the DU and then the DU forwards the event- triggered configuration to the first apparatus 110.

[0108] In embodiments wherein the second apparatus 120 is the DU connecting with the first apparatus 110, the second apparatus 120 may receive the event -triggered configuration from the CU connecting with the DU, and then forward the received event- triggered configuration to the first apparatus 110.

[0109] Prior to the first condition being met for a candidate cell of the list of candidate cells, the first apparatus 110 transmits (330-1) a first preamble for obtaining a TA of the candidate cell for example to the second apparatus 120. The first preamble is different from at least second preamble configured for a RACH procedure. The second apparatus 120 receives (330-2), from the first apparatus 110, the first preamble. As used herein, the first preamble may be referred to as a TA preamble or early TA preamble. The second preamble may be referred to as a RACH preamble.

[0110] In embodiments where the second apparatus 120 is the CU, the second apparatus 120 may determine whether a TA identity (ID) of a source cell of the first apparatus 110 is different from a TA identity of a target cell of the first apparatus 110. If the TA ID of the source cell is different from the TA ID of the target cell, the second apparatus 120 may comprise the first preamble in the event-triggered configuration. The second apparatus 120 may transmit the event -triggered configuration to DU. DU may forward the event-triggered configuration to the first apparatus 110. That is, the first preamble for TAacquisition may be configured by network.[OHl] The second apparatus 120 transmits (340-1), to the first apparatus 110, a first message comprising the TA of the candidate cell. The first apparatus 110 receives (340- 2), from the second apparatus 120, the first message comprising the TA of the candidate cell. By way of example, the first message may be a MAC CE or any other suitable message. As used herein, a message comprising the TA of the candidate cell may be referred to as a “first message”. If the first apparatus 110 determines (345) that the first condition is met for the candidate cell, the first apparatus 110 performs (350) a transmission on the candidate cell based on the TA of the candidate cell.

[0112] In embodiments where the first preamble is comprised in the event-triggered configuration, the first apparatus 120 may determine whether a second condition for triggering a procedure for obtaining the TA is met. The second condition may be indicated in the event-triggered configuration or a different message, or be specified. The first apparatus 110 may evaluate (320) whether the second condition is met. In some example embodiments, the first apparatus 110 may perform measurements on the list of candidate cells based on the event-triggered configuration. The first apparatus 110 may evaluate (320) the second condition based on results of the measurements.

[0113] If the second condition is met for the candidate cell, the first apparatus 110 may transmit (330-1) the first preamble for obtaining the TA of the candidate cell to the second apparatus 120. The first apparatus 110 then receives (340-2) the first message comprising the TA of the candidate cell from the second apparatus 120. Further embodiments regarding such approach will be described with respect to FIG. 6A and FIG. 6B.

[0114] Alternatively, or in addition, in some example embodiments, if the second condition for triggering a procedure for obtaining the TA is met, the first apparatus 110 may transmit a second message comprising an identity of the candidate cell to the second apparatus 120. The second apparatus 120 may receive the second message. For example the second message may be a MAC CE or any other suitable message. As used herein, the second message may refer to a message such as MAC CE comprising an identity of the candidate cell. The second apparatus 120 may transmit, to the first apparatus 110, a third message comprising the first preamble. The first apparatus 110 may receive the third message. The third message may be a physical downlink control channel (PDCCH) order or any other suitable message. As used herein, the third message may refer to a PDCCHorder comprising the first preamble. Further embodiments regarding such approach will be described with respect to FIG. 8 A and FIG. 8B.

[0115] In this way, UE triggers the network to initiate the early TA acquisition before the cell switch. Early UL synchronization may be initiated. The early TCI state activation ensures the cell switch to target happens sooner and successfully since the best beam evaluation is done prior to execution.

[0116] In some cases, a procedure for obtaining a TA of the candidate cell may be triggered first. In the following, if a condition for triggering a cell switch is met for a candidate cell but the trigged procedure for obtaining a TA of the candidate cell has not been completed, it is improper to trigger the cell switch immediately, because such operation would result the trigged procedure for obtaining the TA meaningless. According to some example embodiments of the present disclosure, the UE may start a TA acquisition timer to continue the procedure for obtaining the TA and / or delay the cell switch to the candidate cell. Such TA acquisition timer may ensure that there will be no further delay in re-initiating RACH when the early TA acquisition procedure has already been triggered. More example embodiments may be discussed with reference to FIG. 4, which illustrates a signaling flow 400 for event-triggered cell switch procedure according to some example embodiments of the present disclosure. The signaling flow 400 involves the first apparatus 110 and the second apparatus 120 in FIG. 1A and FIG. IB.

[0117] In operation, the second apparatus 120 trasnmits (410-1) an event -triggered configuration indicating a list of candidate cells and a first condition for triggering a cell switch to the first apparatus 110, and the first apparatus 110 receives (410-2) the event- triggered configuration accordingly.

[0118] Then, prior to the first condition being met for a candidate cell of the list of candidate cells, the first apparatus 110 triggers (420) a procedure for obtaining a TA of the candidate cell.

[0119] Next, based at least in part on the first condition being met for the candidate cell and the procedure for obtaining the TA not being completed, the first apparatus 110 starts a TA acquisition timer to continue the procedure for obtaining the TA and / or delay the cell switch to the candidate cell.

[0120] In some example embodiments, a duration of the TA acquisition timer may be apre-defined default value, configured by the second apparatus 120, or determined by the first apparatus 110 based on a capability of the first apparatus 110.

[0121] In some example embodiments, the first apparatus 110 may determine that the procedure for obtaining the TA has not been completed based on a determination that a first message comprising the TA of the candidate cell has not been received from the second apparatus 120. Accordingly, in some other example embodiments, the first apparatus 110 may determine that the procedure for obtaining the TA has been completed based on a determination that the first message comprising the TA of the candidate cell has been received from the second apparatus 120. In other words, in a case where the first apparatus 110 obtains the TA from the second apparatus 120 (rather than UE-initiated TA procedure), the first apparatus 110 may need to maintain the TA acquisition timer.

[0122] Further, whether to start the TA acquisition timer may depend on the signal strength of the second apparatus 120. Specifically, in some example embodiments, the first apparatus 110 may start the TA acquisition timer further based on a determination that a signal strength of the second apparatus 120 is above or equal to a threshold. Alternatively, in some embodiments, based on a determination that the procedure for obtaining the TA has not been completed and the first condition is met for the candidate cell, the first apparatus 110 may initiate a random access channel (RACH) procedure to obtain the TA of the candidate cell if a signal strength of the second apparatus 120 is below or equal to a threshold.

[0123] In the following, more example embodiments about the processes after the TA acquisition timer being started will be discussed.

[0124] In some example embodiments, if the procedure for obtaining the TA has been completed before expiry of the TA acquisition timer, the first apparatus 110 may perform a transmission on the candidate cell based on the TA of the candidate cell. Alternatively, or in addition, in some example embodiments, the first apparatus 110 may stop the TA acquisition timer in response to completion of the procedure for obtaining the TA.

[0125] In some example embodiments, if the procedure for obtaining the TA still has not been completed by the time the TA acquisition timer expires, the first apparatus 110 may initiate a random access channel (RACH) procedure to obtain the TA of the candidate cell.

[0126] In some example embodiments, during the TA acquisition timer is running, if thesignal strength of the second apparatus 120 is below or equal to a threshold, the first apparatus 110 may terminate the procedure. Specifically, in some example embodiments, in some example embodiments, the first apparatus 110 may stop the TA acquisition timer and / or initiate a RACH procedure to obtain the TA of the candidate cell in response to a signal strength of the second apparatus 120 being below or equal to a threshold.

[0127] As discussed above, the determination of the TCI state to be applied on the candidate cell also may introduce the delay and interruption during cell switch. According to some example embodiments of the present disclosure, prior to switching to a candidate cell in response to a condition for triggering a cell switch is met for the candidate cell, a TCI state to be applied on the candidate cell may be determined. In other words, the TCI state to be applied to the target cell can be determined before the cell switch. Early TCI state activation may thus be achieved for conditional LTM. More example embodiments may be discussed with reference to FIG. 5, which illustrates a signaling flow 500 for event-triggered cell switch procedure according to some example embodiments of the present disclosure. The signaling flow 500 involves the first apparatus 110, the second apparatus 120 and the third apparatus 130 in FIG. 1A and FIG. IB.

[0128] In operation, the second apparatus 120 (510-1) transmits an event -triggered configuration to a first apparatus 110, and the first apparatus 110 receives (510-2) the event-triggered configuration accordingly, where the event-triggered configuration indicates: a list of candidate cells and a first condition for triggering a cell switch.

[0129] In some example embodiments, the event-triggered configuration may comprise at least one of the following: a layer 1 / layer 2 (L1 / L2) triggered mobility (LTM)-based configuration, or a layer 3 (L3) event-triggered configuration. In some example embodiments, the event-triggered configuration is comprised in a radio resource control (RRC) reconfiguration message.

[0130] In some example embodiments, the cell switch may comprise at least one of the following: an intra-the next generation node B (gNB) cell switch, an inter-gNB cell switch, an intra-centralized unit (CU) cell switch, or an inter-CU cell switch.

[0131] Next, prior to switching to a candidate cell of the list of candidate cells in response to the first condition being met for the candidate cell, the first apparatus 110 determines (520-1) a TCI state to be applied on the candidate cell based on a first TCI state indicated by the second apparatus 120 in a first message. Alternatively, or in addition, the firstapparatus 110 determines (520-1) a TCI state to be applied on the candidate cell based on a second TCI state associated with a best measurement result of a reference signal (RS) resource. For example, the second TCI state may be a latest (best) TCI state applied on the candidate cell. The second TCI state may be determined by the first apparatus 110. As used herein, the first TCI state may be referred to as a NW indicated TCI state or an indicated TCI state. The second TCI state may be referred to as a best measured TCI state, a UE-derived TCI state or a latest (best) TCI state.

[0132] Accordingly, the second apparatus 120 also may determine the TCI accordingly. Specifically, the second apparatus 120 also determines (520-2) the TCI state to be applied on the candidate cell based on a first TCI state indicated by the second apparatus 120 in a first message and / or a second TCI state associated with a best measurement result of an RS resource. The second TCI state may be triggered and communicated from the first apparatus 110 to the second apparatus 120.

[0133] In some example embodiments, if the first apparatus 110 determines (520-1) the TCI state later than being indicated of the first TCI state from the second apparatus 120, the second TCI state may be applied on the candidate cell. Otherwise, if the first TCI state is indicated to the first apparatus 110 before the first apparatus 110 determines (520-1) the TCI state, the first TCI state may be applied on the candidate cell.

[0134] The determined TCI also needs be informed to the third apparatus 130. As illustrated in FIG. 5, the second apparatus 120 trasnmits (530-1) a context modification request to the third apparatus 130 and the third apparatus 130 receives (530-2) the context modification request accordingly, where the context modification request comprising the TCI state to be used for communication between a first apparatus 110 and the third apparatus 130. For example, the context modification request may be a UE context modification request.

[0135] In response to the TCI state, in a case that the communication is configured grant, the third apparatus 130 retains (540-1) a configured grant of the TCI state comprised in the context modification message. In addition, the configured grant for other beams (that is, beams corresponding to other TCI states different from the determined TCI state) may be released. Alternatively, in a case that the communication is dynamic grant, the third apparatus 130 allocates (540-2) a dynamic grant to the first apparatus 110 based on the TCI state comprised in the context modification message.

[0136] In some example embodiments, in a case that the second apparatus is a DU, the second apparatus 120 may transmit a context modification message comprising the determined TCI state to a further apparatus (such as, a CU), such that the determined TCI state is informed to the candidate cell. For example, the CU further inform the determined TCI to the candidate cell. The context modification message may be a UE context modification message.

[0137] In some example embodiments, the third apparatus 130 may transmit (550-1) a context modification response of the context modification request to the second apparatus 120, and the second apparatus 120 may receive (550-2) the context modification response accordingly.

[0138] According to the above procedure, the first apparatus 110 and the third apparatus 130 may know the TCI to the applied for communication between a first apparatus 110 and the third apparatus 130. As a result, in response to the first condition being met (560) for the candidate cell, the first apparatus may switch (570) to the candidate cell and perform a transmission on the candidate cell based on the determined TCI state.

[0139] In the following, more example embodiments about how to determine the TCI will be discussed.

[0140] As discussed, the TCI state may be determined based on the first TCI state. In one example embodiment, the first apparatus 110 may transmit a first preamble for obtaining a timing advance (TA) of the candidate cell to the second apparatus 120, where the first preamble is different from at least second preamble configured for a random access channel (RACH) procedure. Then, the first apparatus 110 may receive the first message comprising the TA of the candidate cell and the first TCI state from the second apparatus 120.

[0141] In some example embodiments, the first message is a medium access control (MAC) control element (CE).

[0142] As discussed, the TCI state may be determined based on the second TCI state such as the latest TCI state. In one example embodiment, the first apparatus 110 may determine the second TCI state associated with a best measurement result of an RS resource (i.e., a best beam), and may transmit a fourth message indicating the second TCI state to the second apparatus 120. Additionally, in some example embodiments, if the firstapparatus 110 determines that the first TCI state and the second TCI state are different TCI states, the first apparatus 110 may determine the second TCI state as the TCI state to be applied on the candidate cell, and then may transmit the fourth message indicating the second TCI state to the second apparatus 120.

[0143] In some example embodiments, the fourth message may be a medium access control (MAC) control element (CE).

[0144] Merely for a better understanding of the above processes, more example embodiments will be discussed with reference to FIG. 6A and FIG. 10B.

[0145] FIG. 6A illustrates a signaling flow 600A for a preparation of an intra-CU cell switch (also referred to as “cell change”) procedure in accordance with some example embodiments of the present disclosure. The signaling flow 600A involves a UE 601, a source DU 602, a target DU 603 and a CU 604. The UE 601 may be an example implementation of the first apparatus 110 in FIG. 1A and FIG. IB, the source DU 602 may be an example implementation of the gNB-DU of the second apparatus 120 in FIG. IB, the target DU 603 may be an example implementation of the gNB-DU of the third apparatus 130 in FIG. IB and the CU 604 may be an example implementation of the gNB- CU of the second apparatus 120 in (A) of FIG. IB.

[0146] In operation, a preparation for the cell switch may be performed. By way of example, the UE 601 may transmit (6010) a layer three (L3) measurement report to the source DU 602. In response to receiving the L3 measurement report, the source DU 602 may transmit (6020), to the CU 604, an UL RRC message transfer including the received L3 measurement report.

[0147] The CU 604 may analyze the L3 measurement report and trigger (6030) the LTM candidate preparation. For example, the CU 604 may determine the target DU 603 based on the L3 measurement report analysis. The CU 604 may transmit (6040) a UE context setup request to the target DU 603. The UE context setup request may indicate at least one candidate cell of the target DU 603. The target DU 603 may transmit (6050) a UE context setup response to the CU 604.

[0148] In some example embodiments, the CU 604 may transmit (6060) a UE context modification request to the source DU 602. In response to receiving the UE context modification request, the source DU 602 may transmit (6070) a UE context modificationresponse to the CU 604.

[0149] The CU 604 may generate (6080) a message such as a RRC message or RRCReonfiguration message to be transmitted to UE 601. The RRC message may include an event-triggered configuration. The event-triggered configuration may include a measurement configuration of LI cell change and a configuration of a list of candidate cells such as prepared cells.

[0150] The CU 604 may transmit (6090), to the source DU 602, a DL RRC (reconfiguration) message transfer including the event -triggered configuration such as the measurement configuration (MeasConfig). The RRC reconfiguration measurement configuration may include two conditions, that is, a first condition for triggering a cell switch and a second condition for triggering a procedure for obtaining a TA. The first condition may be an LTM execution condition. The second condition may be referred to as an early TA condition or early TA acquisition condition. The first and second conditions may be configured such that the second condition will be met first before the second condition is met. For example, the first condition may be associated with a first set of criteria, and the second condition is associated with a second set of criteria that may be lower than the first set of criteria. Taking the second condition as a base condition, then the first condition may be regarded as a sum of the first condition and an offset. In this way, it is ensured that in most cases, early TA acquisition condition will be met before the execution condition is met.

[0151] The RRC reconfiguration measurement configuration may further include a (dedicated) preamble for early TA and a preamble for contention free random access (CFRA). That is, the early TA may be along with a dedicated preamble. The network such as the CU 604 may ensure that the preamble for early TA (referred to as early TA preamble) and the preamble for CFRA are different.

[0152] In response to receiving the RRC reconfiguration message such as MeasConfig, the source DU 602 may transmit (6100) the RRC reconfiguration message to the UE 601. The RRC reconfiguration message includes the measurement configuration mentioned above. The UE 601 may transmit (6110) an RRC reconfiguration complete message to the source DU 602.

[0153] In response to receiving the RRC reconfiguration complete message, the source DU 602 may transmit (6120) an UL RRC message transfer including the RRCreconfiguration complete to the CU 604.

[0154] After the preparation of intra-CU cell switch shown in the signaling flow 600A, the inter-CU cell switch procedure is performed. FIG. 6B illustrates an example of a signaling flow 600B for the intra-CU cell switch procedure in accordance with some example embodiments of the present disclosure. The signaling flow 600B involves the UE 601, the source DU 602, the target DU 603 and the CU 604. The signaling flow 600B follows the signaling flow 600A.

[0155] In operation, UE 601 may start evaluating (6130) whether the second condition (that is, the given early TA acquisition condition) is met. In some example embodiments, a DL synchronization is done (6140) with the candidate Cells. If the early TA acquisition condition is met (6150) at UE 601, UE 601 may transmit (6160), to the target DU 603, a preamble for early TA acquisition. The preamble may be configured or indicated in the RRC reconfiguration including the MeasConfig.

[0156] In a first option (referred to as Option 1), the first condition for LTM execution may be met after the TA is received. In such option, TA or TA value may be derived at a candidate cell or a target cell of the target DU 603 for UE 601. The derived TA may be transmitted (6170) from the target DU 603 to CU 604 and then forwarded (6180) to the source DU 602. The source DU 602 may transmit (6190), to UE 601, a message such as a MAC CE to inform UE 601 the TA for the target cell. For example, the MAC CE may include the target cell and the TA for the target cell.

[0157] In some example embodiments, the first condition for LTM execution is met, a cell switch is triggered (6210) by UE 601 to the target cell of the target DU 603. The UE 601 may transmit (6220) an RRC reconfiguration complete message to the target DU 603 using the cell switched target cell. The target DU 603 may transmit (6230) an UL RRC message transfer including the RRC reconfiguration complete to the CU 604. The target DU 603 may also transmit (6240) an access notification to the CU 604.

[0158] Alternatively, or in addition, in a second option (referred to as Option 2), the first condition for LTM execution may be met before the TA is received. In such option, the first condition for LTM execution is met (6250). UE 601 may check (6260) the source cell signal strength and compare it with a configured threshold. If the source cell signal strength (e.g., reference signal received power (RSRP)) is below the configured threshold, then UE will not start TA acquisition timer, instead RACH will be triggered.

[0159] In some example embodiments, UE 601 may start (6270) a new TA acquisition timer and wait to receive the TA. In an example option (referred to as Option 2-1), the TA is received before expiry of the TA acquisition timer. For example, the TA may be derived at a candidate cell or a target cell of the target DU 603 for UE 601. The derived TA is communicated (6290) from the target DU 603 to CU 604. CU 604 may transmit (6300) the TA to the source DU 602.

[0160] The source DU 602 may inform (6310) UE 601 the TA for the target cell using a MAC CE. In response to receiving the MAC CE including the TA for the target cell, UE601 may stop (6320) the TA acquisition timer. A cell switch may be triggered (6330) by UE 601 to the target cell.

[0161] UE 601 may transmit (6340) an RRC Reconfiguration Complete to the target DU 603 using the cell switched target cell. The target DU 603 may transmit (6350) an UL RRC message transfer containing RRC Reconfiguration Complete to CU 604. In addition, the target DU 603 may transmit (6360) an access notification to CU 604.

[0162] In another option (referred to as Option 2.2), the TA acquisition timer is expired before receiving the TA for UE 601. For example, the TA acquisition timer is expired (6380). In a further embodiment, while the TA acquisition timer is running, UE 601 may also measure source cell reference signal strength (e.g., SSB RSRP) and if it is below a threshold, UE 601 may stop waiting for the TA and determine that a RACH-based LTM cell switch may be performed.

[0163] A random access process may be done (6390) towards the target Cell of target - DU 603. UE 601 may transmit (6400) an RRC Reconfiguration Complete to the target DU 603 using the cell switched target cell. The target DU 603 may transmit (6410) an UL RRC message transfer containing RRC Reconfiguration Complete to CU 604. The target DU 603 may transmit (6420) an access notification to CU 604. With the TA acquisition timer, it is ensured that there won’t be any further delay for again doing RACH when early TA acquisition procedure is already triggered.

[0164] In a completion of the cell switch procedure, CU 604 may transmit (6430) a UE context release command to the source DU 602 to release the UE Context. The source DU602 may transmit (6440) a UE context release complete to CU 604 after releasing the UE context. Then, a path switch procedure may be done (6450).

[0165] Embodiments regarding the intra-CU cell switch based on the event-triggered configuration have been described with respect to FIG. 6A and FIG. 6B. With these embodiments, two conditions are shared (i.e., one with an offset (such as a few dB) to other condition), such that always the early TA acquisition condition will be met first then the LTM execution condition. In case TA is not received (though the pre-assigned preamble is sent for TA after Early TA acquisition condition met) before the execution condition is met, then one new timer may be started to wait for TA to be received. So that there won’t be any further delay for again do the RACH where Early TA acquisition procedure is already triggered. Hence, UE-based early synchronization to the target cell for DL and UL prior to the conditional LTM may be achieved.

[0166] FIG. 7 illustrates a signaling flow 700 for another example procedure of intra-CU cell switch. Similar to the signaling flows 600A and 600B, the signaling flow 700 involves UE 601, source DU 602, target DU 603 and CU 604. It is to be understood that several signaling or operations involved in the signaling flow 700 are same or similar with those of the signaling flows 600A and 600B. Details of some same or similar signaling or operations will not be repeated here.

[0167] As shown, after generating (6080) the RRC configuration, CU 604 may check (7010) if TA identity of a target cell (referred to as target cell TA-ID) is same as the source cell TA-ID. If the target cell TA-ID is the same with the source cell TA-ID, the UE-based TA estimation may be configured. For UE-based TA estimation, UE may evaluate the TA, and thus no preamble is required for TA. Otherwise, if the target cell TA-ID is different from the source cell TA-ID, a dedicated preamble may be used for TA. For example, the event-triggered configuration such as the measurement configuration may include the dedicated preamble, as described with respect to FIG. 6A. In the description of FIG. 7, it is assumed that the target cell TA-ID is same as the source cell TA-ID, that is, no preamble is required for TA.

[0168] CU 604 may transmit (7020), to the source DU 602, a DL RRC message transfer including the RRC reconfiguration MeasConfig with the two conditions mentioned above. The source DU 602 may transmit (7030), to UE 601, the RRC reconfiguration MeasConfig with the two conditions. In response to receiving the RRC reconfiguration message, UE 601 may transmit (7040) an RRC reconfiguration complete to the source DU 602. The source DU 602 may transmit (7050), to CU 604, an UL RRC message transfer including the RRC reconfiguration complete.

[0169] In some example embodiments, the UE 601 may evaluate (7060) whether the second condition (that is, the early TA acquisition condition) is met. If the early TA acquisition condition is met (7070) at UE 601, UE 601 may evaluate (7080) TA for the target cell. A downlink synchronization may be performed (7090).

[0170] The UE 601 may evaluate (7100) whether the first condition for triggering the cell switch (that is, the execution condition) is met. If the first condition is met, UE 601 may trigger (7110) a change of serving cell serving UE 601. For example, UE 601 may transmit (7120) an RRC reconfiguration complete to the target DU 603. The target DU 603 may transmit (7130), to CU 604, an UL RRC message transfer including the RRC reconfiguration complete. In addition, the target DU 603 may transmit (7140) an access notification to CU 604.

[0171] In a completion of the cell switch procedure, CU 604 may transmit (7150) a UE context release command to the source DU 602 to release the UE context. The source DU 602 may transmit (7160) a UE context release complete to CU 604 after releasing the UE context. Then, a path switch procedure may be done (7170).

[0172] In this way, a UE-based early synchronization prior to the cell change such as the conditional LTM may be achieved with the UE-based TA. By using the UE-based TA, the TA estimation is done at the UE without waiting for TA from network.

[0173] FIG. 8A and FIG. 8B illustrate signaling flows 800A and 800B for another example procedure of intra-CU cell switch. Similar to the signaling flows 600A and 600B, the signaling flows 800 A and 800B involves UE 601, source DU 602, target DU 603 and CU 604. It is to be understood that several signaling or operations involved in the signaling flows 800A and 800B are same or similar with those of the signaling flows 600A and 600B. Details of some same or similar signaling or operations will not be repeated here.

[0174] As shown, a preparation for the cell switch may be performed. By way of example, the UE 601 may transmit (6010) a L3 measurement report to the source DU 602. In response to receiving the L3 measurement report, the source DU 602 may transmit (6020), to the CU 604, an UL RRC message transfer including the received L3 measurement report.

[0175] The CU 604 may analyze the L3 measurement report and trigger (6030) the LTM candidate preparation. For example, the CU 604 may determine the target DU 603 based on the L3 measurement report analysis. The CU 604 may transmit (6040) a UE contextsetup request to the target DU 603. The UE context setup request may indicate at least one candidate cell of the target DU 603. The target DU 603 may transmit (6050) a UE context setup response to the CU 604.

[0176] In some example embodiments, the CU 604 may transmit (6060) a UE context modification request to the source DU 602. In response to receiving the UE context modification request, the source DU 602 may transmit (6070) a UE context modification response to the CU 604.

[0177] The CU 604 may generate (6080) a message such as a RRC message or RRCReconfiguration message to be transmitted to UE 601. The RRC message may include an event-triggered configuration. The event-triggered configuration may include a measurement configuration of LI cell change and a configuration of a list of candidate cells such as prepared cells.

[0178] The CU 604 may transmit (8010), to the source DU 602, a DL RRC (reconfiguration) message transfer including the event-triggered configuration such as the measurement configuration (MeasConfig). The RRC reconfiguration measurement configuration may include two conditions, that is, a first condition for triggering a cell switch and a second condition for triggering a procedure for obtaining a TA. The first condition may be an LTM execution condition. The second condition may be referred to as an early TA condition or early TA acquisition condition. The first and second conditions may be configured such that the second condition will be met first before the first condition is met. For example, the first condition may be associated with a first set of criteria, and the second condition is associated with a second set of criteria that may be lower than the first set of criteria. Taking the second condition as a base condition, then the first condition may be regarded as a sum of the first condition and an offset. In this way, it is ensured that in most cases, early TA acquisition condition will be met before the execution condition is met. What is different from the signaling flow 600A is that, in the signaling flow 800A, the RRC reconfiguration measurement configuration may include a preamble for CFRA, without a dedicated preamble for early TA.

[0179] In response to receiving the RRC reconfiguration message such as MeasConfig, the source DU 602 may transmit (8020) the RRC reconfiguration message to the UE 601. The RRC reconfiguration message includes the measurement configuration mentioned above. The UE 601 may transmit (8030) an RRC reconfiguration complete message to thesource DU 602.

[0180] In response to receiving the RRC reconfiguration complete message, the source DU 602 may transmit (8040) an UL RRC message transfer including the RRC reconfiguration complete to the CU 604.

[0181] After the preparation of intra-CU cell switch shown in the signaling flow 800A, the intra-CU cell switch procedure is performed. FIG. 8B illustrates an example of a signaling flow 800B for the intra-CU cell switch procedure in accordance with some example embodiments of the present disclosure. The signaling flow 800B involves the UE 601, the source DU 602, the target DU 603 and the CU 604. The signaling flow 800B follows the signaling flow 800A.

[0182] In operation, UE 601 may start evaluating (8130) whether the second condition (that is, the given early TA acquisition condition) is met. In some example embodiments, the second condition is met (8140) at UE 601. A DL synchronization is done (8150) with the candidate Cells. UE 601 may transmit (8160), to the target DU 603, a new proposed message such as a MAC CE to the source DU 602 to indicate TA condition being met towards a target cell 603. The MAC CE may include candidate target cell information. In other words, if the initial TA acquisition condition is met, UE 601 may trigger the network using the MAC CE to initiate the early TA acquisition.

[0183] The source DU 602 may maintain a pool of preambles for all the target cells based on the allocation from those target cells. From the pool of preambles, one preamble may be retrieved for the target cell to be sent in a PDCCH order. The source DU 602 may transmit (8180) a PDCCH order to UE 601. The PDCCH order may include the target cell, the preamble for the target cell, and SSB information. The preamble for the target cell in the PDCCH order may be used as an early TA preamble for the target cell. The PDCCH order may be an existing PDCCH order. That is, an existing LTM functionality of PDCCH order may be reused. The network may ensure that the CFRA preamble sent in the RRC reconfiguration earlier and the early TA preamble are different. In response to receiving the PDCCH order, UE 601 may transmit (8190) the preamble for early TA (received in the PDCCH order) to the candidate cell (that is, the target cell) for early TA acquisition.

[0184] In a first option, the first condition (that is, the execution condition) is met after TA is received. The TA may be derived at the candidate cell of the target DU 603 for UE 601. The target DU 603 may communicate (8200) the derived TA (value) to CU 604. CU604 may transmit (8210) the TA (value) to the source DU 602. The source DU 602 may transmit (8220) a message such as MAC CE to UE 601 to inform the TA for the target cell. That is, the MAC CE includes the TA for target cell.

[0185] If UE 601 evaluates (8230) that the first condition is met, a cell switch may be triggered (8240) by UE 601 to the target cell. UE 601 may transmit (8250) an RRC reconfiguration complete to the target DU 603 using the cell switched target cell. The target DU 603 may transmit (8260) an UL RRC message transfer including the RRC reconfiguration complete to the CU 604. The target DU 603 may also transmit (8270) an access notification to the CU 604.

[0186] Alternatively, or in addition, in a second option, the first condition (that is, the execution condition) may be met before the TA is received. For example, UE 601 may evaluate (8280) that the first condition is met. UE 601 may start (8290) a TA acquisition timer and wait to receive the TA. In an example option 8300, the TA is received before expiry of the TA acquisition timer. For example, the TA may be derived at a candidate cell or a target cell of the target DU 603 for UE 601. The derived TA is communicated (8310) from the target DU 603 to CU 604. CU 604 may transmit (8320) the TA to the source DU 602.

[0187] The source DU 602 may inform (8330) UE 601 the TA for the target cell using a MAC CE. In response to receiving the MAC CE including the TA for the target cell, UE 601 may stop (8340) the TA acquisition timer. A cell switch may be triggered (8350) by UE 601 to the target cell.

[0188] UE 601 may transmit (8360) an RRC Reconfiguration Complete to the target DU 603 using the cell switched target cell. The target DU 603 may transmit (8370) an UL RRC message transfer containing RRC Reconfiguration Complete to CU 604. In addition, the target DU 603 may transmit (8380) an access notification to CU 604.

[0189] In another option 8390, the TA acquisition timer is expired before receiving the TA for UE 601. For example, the TA acquisition timer is expired (8400). A random access process may be done (8410) towards the target Cell of target-DU 603. UE 601 may transmit (8420) an RRC Reconfiguration Complete to the target DU 603 using the cell switched target cell. The target DU 603 may transmit (8430) an UL RRC message transfer containing RRC reconfiguration complete to CU 604. The target DU 603 may transmit (8440) an access notification to CU 604. With the TA acquisition timer, it is ensured thatthere won’t be any further delay for again doing RACH when early TA acquisition procedure is already triggered.

[0190] In a completion of the cell switch procedure, CU 604 may transmit (8450) a UE context release command to the source DU 602 to release the UE Context. The source DU 602 may transmit (8460) a UE context release complete to CU 604 after releasing the UE context. Then, a path switch procedure may be done (8470).

[0191] In this manner, a network -based UE-triggered early TA for conditional LTM can be achieved. UE-based early synchronization prior to the cell change such as the conditional LTM may thus be achieved. The early TA acquisition may be triggered by UE itself upon early TA condition is met without sending LI measurement report to network.

[0192] As mentioned, in some example embodiments, an early TCI state activation may be performed for an event-triggered cell switch such as a conditional LTM. FIG. 9A and FIG. 9B illustrate signaling flows 900A and 900B for the early TCI state activation for cell switch in accordance with some example embodiments of the present disclosure. The signaling flows 900 A and 900B involves UE 601, source DU 602, target DU 603 and CU 604. The signaling flow 900A follows the signaling flow 600A in FIG. 6A, and the signaling flows 900B follows the signaling flow 900A.

[0193] As mentioned, the signaling flow 900A follows the signaling flow 600A in FIG. 6A. That is, before the signaling flow 900A, an L3 measurement is sent from UE 601. The serving CU 604 identifies the potential targets based on the measurement report, and prepares the target cells and shares the target cell configurations with the UE 601. CU 604 transmits, to the source DU 602, the event -triggered configuration such as the RRC Reconfiguration with the first condition for triggering the cell switch and the second condition for triggering a procedure for obtaining TA (that is, the condition for early TA) as mentioned above. In addition, the second condition for early TA may be along with a dedicated preamble for early TA. The early TA preamble is different from the CFRA preamble. The first and second conditions are configured such that the second condition will be met first before the first condition being met. For example, the second condition may be a base condition, and the first condition may be the base condition with an offset. The threshold for the second condition may be lesser than the threshold for the first condition. The source DU 602 transmits the RRC reconfiguration with the first and second conditions to UE 601.

[0194] In the signaling flow 900 A, UE 601 may evaluate (9010) if the second condition (that is, the early TA condition) is met. If UE 601 determines (9020) that the second condition is met, UE 601 may do (9030) DL synchronization with target cells parallelly. Since the second condition is met, UE 601 may transmit (9040) a preamble to the target cell using the TA preamble received in the RRC reconfiguration from the source DU 602.

[0195] In an option, the first condition (that is, the execution condition) is met after TA is received. UE 601 may transmit (9050) an LI measurement report to the source DU 602. This measurement report may be used for deriving a TCI state for the target cell. The source DU 602 may get the TCI state of the target cell using this report.

[0196] Based on the preamble received from UE 601, TA information of the target cell may be derived at the target DU 603. The target DU 603 may transmit (9060) the derived TA to the CU 604. CU 604 may forward (9070) the TA to the source DU 602.

[0197] The source DU 602 may transmit (9080) a new message such as a new MAC CE to UE 601 once the TA of the target cell is available at the source DU 602. The MAC CE may include the TA of the target cell and a latest TCI state or SSB of the target cell.

[0198] The source DU 602 may transmit (9090), to the CU 604, a context modification message such as a UE context modification required message indicating the selected TCI state. CU 604 may respond (9100) a UE context modification confirm message to the source DU 602. The CU 604 may transmit (9110) a UE context modification request message for the selected TCI state (also referred to as determined TCI state) to the target DU 603. The selected TCI state is to be used for a communication between the UE 601 and the target DU 603. With these signaling, the selected TCI state may be sent to the target DU 603, such that the selected TCI state is informed to the candidate cell or target cell.

[0199] As an example, if the communication between the UE 601 and the target DU 603 is configured grant, the target DU 603 may retain (9120) a configured grant of the TCI state comprised in the UE context modification message. That is, the target DU 603 may retain the configured grant for the selected beam (corresponding to the selected TCI state) and release the grant(s) for remaining beam(s). As another example, if the communication between the UE 601 and the target DU 603 is dynamic grant, the target DU 603 may allocate (9130) a dynamic grant to the UE 601 based on the TCI state comprised in the UE context modification message. That is, the target DU 603 may allocate the dynamicgrant for the selected beam corresponding to the selected TCI state. Then, the target DU 603 may transmit (9140) a UE context modification response to the CU 604.

[0200] In some example embodiments, if UE 601 determines (9150) that the first condition (the execution condition) is met, UE 601 may trigger (9160) a cell switch to the target cell based on the selected TCI state or SSB. UE 601 may transmit (9170) an RRC reconfiguration complete to the target DU 603. The target DU 603 may transmit (9180) an UL RRC message transfer including the RRC reconfiguration complete to the CU 604 and transmit (9190) an access notification to the CU 604.

[0201] Alternatively, or in addition, there is another option for cases that the first condition is met before the early TA is received. Such option is shown in the signaling flow 900B in FIG. 9B. The signaling flow 900B may follow the signaling flow 900A. As illustrated, if UE 601 determines (9200) that the first condition (the execution condition) is met, UE 601 may start (9210) a TA acquisition timer to wait for TA acquisition.

[0202] If the TA is received before expiry of the TA Acquisition timer, UE 601 may transmit (9220) an LI measurement report to the source DU 602. The measurement report is used for deriving the TCI state for the target cell. The source DU 602 may derive the TCI state of the target cell based on the measurement report. Specifically, LI measurement will be sent from UE 601 periodically after receiving the RRCReconfiguration, so the source DU 602 may evaluate the TCI state of the target cell any time after the RRCReconfiguration procedure.

[0203] Based on the preamble transmitted (9040) by UE 601, TA information of the target cell may be derived at target DU 603 and sent (9230) to the CU 604 and then forwarded (9240) to the source DU 602. The source DU 602 may transmit (9250) a new message such as a new MAC CE to UE 601 once the TA of the target cell is available at the source DU 602. The MAC CE may include TA of the target cell and latest TCI state / SSB of the target cell. UE 601 may stop (9260) the TA Acquisition timer once TA of the target cell is available.

[0204] In some example embodiments, the source DU 602 may transmit (9270), to CU 604, a context modification message such as a UE context modification required message for the selected TCI state. CU 604 may transmit (9280) a UE context modification confirm to the source DU 602. CU 604 may transmit (9290) a UE context modification request message for the selected TCI state to the target DU 603.

[0205] In an option, if configured grant is to be used for the communication between UE601 and the target DU 603, the target DU 603 may retain (9300) configured grant of the selected TCI state and release the grants for the other SSBs or beams. In another option, is dynamic grant is to be used for the communication between UE 601 and the target DU 603, the target DU 603 may allocate (9310) dynamic grant to the UE 601 on the selected SSB or beam. The target DU 603 may then transmit (9320) a UE context modification response to CU 604.

[0206] A cell switch may be triggered (9330) by UE 601 to the target cell based on selected TCI state or SSB. UE 601 may transmit (9340) an RRC reconfiguration complete to the target DU 603. The target DU 603 may transmit (9350) an UL RRC message transfer including the RRC reconfiguration complete to the CU 604 and transmit (9360) an access notification to the CU 604.

[0207] Alternatively, in some cases, if the TA acquisition timer is expired (9370) without receiving TA, a random access process may be performed (9380) using the CFRA preamble. For example, the random access towards the target cell using CFRA preamble received in RRC Reconfiguration message is performed. UE 601 may trigger a cell switch to the target cell based on the selected TCI state or SSB. For example, UE 601 may transmit (9390) an RRC reconfiguration complete to the target DU 603. The target DU 603 may transmit (9400) an UL RRC message transfer including the RRC reconfiguration complete to the CU 604 and transmit (9410) an access notification to the CU 604.

[0208] In a completion of the cell switch procedure, CU 604 may transmit (9420) a UE context release command to the source DU 602 to release the UE Context. The source DU602 may transmit (9430) a UE context release complete to CU 604 after releasing the UE context. Then, a path switch procedure may be done (9440).

[0209] With the signaling flows 900A and 900B, early TCI state activation for conditional LTM may be achieved. For example, the network activates the early TCI state along with early UL synchronization procedure. A new message such as a single MAC CE may be used to inform target cell TA and activation of TCI state for target cell. The early TCI state activation ensures the cell switch to target happens sooner and successfully since the best beam evaluation is done prior to execution.

[0210] FIG. 10A and FIG. 10B illustrate signaling flows 1000A and 1000B for the early TCI state activation for cell switch in accordance with some example embodiments of thepresent disclosure. The signaling flows 1000A and 1000B involves UE 601, source DU 602, target DU 603 and CU 604. The signaling flow 1000A follows the signaling flow 600A in FIG. 6A, and the signaling flows 1000B follows the signaling flow 1000A. It is to be understood that several signaling or operations involved in the signaling flows 1000 A and 1000B are same or similar with those of the signaling flows 900 A and 900B. Details of some same or similar signaling or operations will not be repeated here.

[0211] In operation, in an option for the first condition being met after the TA is received, after the target DU 603 transmitting (9140) the UE context modification response to the CU 604, the following operations may be performed. By way of example, just prior to the first condition being met or at the time of the first condition being met, if the best beam or TCI state for the target cell is different from the TCI state given earlier such as the TCI state indicated by the MAC CE transmitted (9080) by the source DU, UE 601 may trigger (10150) a new MAC CE with a newly selected TCI state. The newly selected TCI state may be a best TCI sate or a TCI state corresponding to the best beam or any other suitable TCI state. It is to be understood that in some example embodiments, the transmitted (9080) MAC CE may not indicate a TCI state. In such cases, UE 601 may trigger (10150) a new MAC CE with the newly selected TCI state as well.

[0212] UE 601 may transmit (10160) the new MAC CE indicating the new selected TCI state to the source DU 602 to inform the selected TCI state, the candidate cell and / or SSB based on latest measurements. UE 601 may decide the right time to transmit the selected TCI state prior to execution for example when starting Time to trigger.

[0213] The source DU 602 may transmit (10170), to the CU 604, a context modification message such as a UE context modification required message indicating the selected TCI state. CU 604 may respond (10180) a UE context modification confirm message to the source DU 602. The CU 604 may transmit (10190) a UE context modification request message for the selected TCI state (also referred to as determined TCI state) to the target DU 603. The selected TCI state is to be used for a communication between the UE 601 and the target DU 603. With these signaling, the selected TCI state may be sent to the target DU 603, such that the selected TCI state is informed to the candidate cell or target cell.

[0214] As an example, if the communication between the UE 601 and the target DU 603 is configured grant, the target DU 603 may retain (10200) a configured grant of the TCIstate comprised in the UE context modification message. That is, the target DU 603 may retain the configured grant for the selected beam (corresponding to the selected TCI state) and release the grant(s) for remaining beam(s). As another example, if the communication between the UE 601 and the target DU 603 is dynamic grant, the target DU 603 may allocate (10210) a dynamic grant to the UE 601 based on the TCI state comprised in the UE context modification message. That is, the target DU 603 may allocate the dynamic grant for the selected beam corresponding to the selected TCI state. Then, the target DU 603 may transmit (10220) a UE context modification response to the CU 604.

[0215] In some example embodiments, if UE 601 determines (10230) that the first condition (the execution condition) is met, UE 601 may trigger (10240) a cell switch to the target cell based on the selected TCI state or SSB. UE 601 may transmit (10250) an RRC reconfiguration complete to the target DU 603. The target DU 603 may transmit (10260) an UL RRC message transfer including the RRC reconfiguration complete to the CU 604 and transmit (10270) an access notification to the CU 604.

[0216] Similar to the signaling flow 900B, there is another option for cases that the first condition is met before the early TA is received. Such option is shown in the signaling flow 1000B in FIG. 10B. The signaling flow 1000B may follow the signaling flow 1000 A. As illustrated, if UE 601 determines (9200) that the first condition (the execution condition) is met, UE 601 may start (9210) a TA acquisition timer to wait for TA acquisition.

[0217] If the TA is received before expiry of the TA Acquisition timer, UE 601 may transmit (9220) an LI measurement report to the source DU 602. The measurement report is used for deriving the TCI state for the target cell. The source DU 602 may derive the TCI state of the target cell based on the measurement report.

[0218] Based on the preamble transmitted (9040) by UE 601, TA information of the target cell may be derived at target DU 603 and sent (9230) to the CU 604 and then forwarded (9240) to the source DU 602. The source DU 602 may transmit (9250) a new message such as a new MAC CE to UE 601 once the TA of the target cell is available at the source DU 602. The MAC CE may include TA of the target cell and latest TCI state / SSB of the target cell. UE 601 may stop (9260) the TA Acquisition timer once TA of the target cell is available.

[0219] In some example embodiments, UE 601 may transmit (10360), to the source DU602, a MAC CE to inform the selected TCI state. That is, UE 602 informs the selected TCI state using MAC CE.

[0220] The source DU 602 may transmit (10370), to CU 604, a context modification message such as a UE context modification required message for the selected TCI state. CU 604 may transmit (10380) a UE context modification confirm to the source DU 602. CU 604 may transmit (10390) a UE context modification request message for the selected TCI state to the target DU 603.

[0221] In an option, if configured grant is to be used for the communication between UE601 and the target DU 603, the target DU 603 may retain (10400) configured grant of the selected TCI state and release the grants for the other SSBs or beams. In another option, is dynamic grant is to be used for the communication between UE 601 and the target DU603, the target DU 603 may allocate (10410) dynamic grant to the UE 601 on the selected SSB or beam. The target DU 603 may then transmit (10420) a UE context modification response to CU 604.

[0222] A cell switch may be triggered (10430) by UE 601 to the target cell based on selected TCI state or SSB. UE 601 may transmit (10440) an RRC reconfiguration complete to the target DU 603. The target DU 603 may transmit (10450) an UL RRC message transfer including the RRC reconfiguration complete to the CU 604 and transmit (10460) an access notification to the CU 604.

[0223] Alternatively, in some cases, if the TA acquisition timer is expired (10470) without receiving TA, a random access process may be performed (10480) using the CFRA preamble. For example, the random access towards the target cell using CFRA preamble received in RRC Reconfiguration message is performed. UE 601 may trigger a cell switch to the target cell based on the selected TCI state or SSB. For example, UE 601 may transmit (10490) an RRC reconfiguration complete to the target DU 603. The target DU 603 may transmit (10500) an UL RRC message transfer including the RRC reconfiguration complete to the CU 604 and transmit (10510) an access notification to the CU 604.

[0224] In a completion of the cell switch procedure, CU 604 may transmit (10520) a UE context release command to the source DU 602 to release the UE Context. The source DU602 may transmit (10530) a UE context release complete to CU 604 after releasing the UE context. Then, a path switch procedure may be done (10540).

[0225] With the signaling flows 1000A and 1000B, early TCI state activation for conditional LTM may be achieved. For example, UE informs the latest TCI state to the network, so that the network needs not to evaluate TCI state. Thus, the cell switch becomes faster and successful. The early TCI state activation ensures the cell switch to target happens sooner and successful since the best beam evaluation is done by UE till the cell switch is done.

[0226] It is to be understood that although the signaling flows 600A, 600B, 700, 800A, 800B, 900 A, 900B, 1000 A and 1000B are described with the intra-CU cell switch for LTM as an example, some embodiments described with respect to these signaling flows may also be applicable for any other suitable mobility or any other suitable cell switch. Scope of embodiments of the present disclosure is not limited here.

[0227] It would be appreciated that some example specifications, signaling flows and embodiments are provided above, and the detailed description may be varied. It is to be understood that these signaling flows 200, 300, 400, 500, 600A, 600B, 700, 800A, 800B, 900A, 900B, 1000A and / or 1000B may be used separately, or in any suitable combinations. In this way, the event -triggered cell switch procedure such as LTM intra-CU cell switch procedure can be enhanced.Example Method

[0228] FIG. 11 shows a flowchart of an example method 1100 implemented at a first apparatus in accordance with some example embodiments of the present disclosure. For the purpose of discussion, the method 1100 will be described from the perspective of the first apparatus 110 in FIG. 1A and FIG. IB.

[0229] At block 1110, the first apparatus receives, from a second apparatus, an event- triggered configuration indicating: a list of candidate cells, a first condition for triggering a cell switch, and a second condition for triggering a procedure for obtaining a timing advance (TA).

[0230] At block 1120, prior to the first condition being met for a candidate cell of the list of candidate cells, based on the second condition being met for the candidate cell, the first apparatus triggers a procedure for obtaining a TA of the candidate cell.

[0231] In some example embodiments, the first condition may be associated with a first set of criteria, and the second condition is associated with a second set of criteria that islower than the first set of criteria.

[0232] In some example embodiments, the first apparatus may perform measurements on the list of candidate cells based on the event-triggered configuration; and evaluate the second condition based on results of the measurements.

[0233] In some example embodiments, the first condition comprises at least one first threshold corresponding to at least one event, and the second condition comprises at least one second threshold corresponding to the at least one event, the second threshold being different from the first threshold.

[0234] In some example embodiments, the first condition comprises at least one first threshold corresponding to at least one event, and the second condition comprises at least one offset, where the offset is a difference between a second threshold associated with the second condition and the first threshold.

[0235] In some example embodiments, the second condition comprises at least one first threshold corresponding to at least one event, and the first condition comprises at least one offset, wherein the offset is a difference between a first threshold associated with the first condition and the second threshold.

[0236] In some example embodiments, the first apparatus may trigger the procedure for obtaining the TA of the candidate cell by one of the following: transmitting a first preamble to the second apparatus for obtaining the TA, the first preamble being different from at least second preamble configured for a random access channel (RACH) procedure; initiating a user equipment (UE)-based TA evaluation procedure; or initiating a RACH procedure for obtaining the TA by using the second preamble.

[0237] In some example embodiments, the event-triggered configuration comprises at least one of the following: a layer 1 / layer 2 (L1 / L2) triggered mobility (LTM)-based configuration, or a layer 3 (L3) event-triggered configuration.

[0238] In some example embodiments, the event-triggered configuration is comprised in a radio resource control (RRC) reconfiguration message.

[0239] In some example embodiments, the cell switch comprises at least one of the following: an intra-the next generation node B (gNB) cell switch, an inter-gNB cell switch, an intra-centralized unit (CU) cell switch, or an inter-CU cell switch.

[0240] In some example embodiments, the first apparatus comprises a terminal apparatus and the second apparatus comprises one of the following: a next generation node B (gNB) serving the first apparatus, or a distributed unit (DU) connecting with the first apparatus.

[0241] FIG. 12 shows a flowchart of an example method 1200 implemented at a second apparatus in accordance with some example embodiments of the present disclosure. For the purpose of discussion, the method 1200 will be described from the perspective of the second apparatus 120 in FIG. 1A and FIG. IB.

[0242] At block 1210, the second apparatus determines an event -triggered configuration for a first apparatus, the event-triggered configuration indicating: a list of candidate cells, , a first condition for triggering a cell switch, and a second condition for triggering a procedure for obtaining a timing advance (TA).

[0243] At block 1220, the second apparatus transmits the event -triggered configuration to the first apparatus.

[0244] In some example embodiments, the first apparatus comprises a terminal apparatus and the second apparatus comprises one of the following: a next generation node B (gNB) serving the first apparatus, a distributed unit (DU) connecting with the first apparatus, or a centralized unit (CU) connecting with the DU.

[0245] In some example embodiments, the second apparatus may receive the event- triggered configuration from the CU.

[0246] In some example embodiments, the first condition is associated with a first set of criteria, and the second condition is associated with a second set of criteria that is lower than the first set of criteria.

[0247] In some example embodiments, the first condition comprises at least one first threshold corresponding to at least one event, and the second condition comprises at least one second threshold corresponding to at least one event, the second threshold being different from the first threshold.

[0248] In some example embodiments, the first condition comprises at least one first threshold corresponding to at least one event, and the second condition comprises at least one offset, where the offset is a difference between a second threshold associated with the second condition and the first threshold.

[0249] In some example embodiments, the second condition comprises at least one first threshold corresponding to at least one event, and the first condition comprises at least one offset, wherein the offset is a difference between a first threshold associated with the first condition and the second threshold.

[0250] In some example embodiments, the event-triggered configuration comprises at least one of the following: a layer 1 / layer 2 (L1 / L2) triggered mobility (LTM)-based configuration, or a layer 3 (L3) event-triggered configuration.

[0251] In some example embodiments, the event-triggered configuration is comprised in a radio resource control (RRC) reconfiguration message.

[0252] In some example embodiments, the cell switch comprises at least one of the following: an intra-the next generation node B (gNB) cell switch, an inter-gNB cell switch, an intra-centralized unit (CU) cell switch, or an inter-CU cell switch.

[0253] FIG. 13 shows a flowchart of an example method 1300 implemented at a first apparatus in accordance with some example embodiments of the present disclosure. For the purpose of discussion, the method 1300 will be described from the perspective of the first apparatus 110 in FIG. 1A and FIG. IB.

[0254] At block 1310, the first apparatus receives, from a second apparatus, an event- triggered configuration indicating a list of candidate cells and a first condition for triggering a cell switch.

[0255] At block 1320, prior to the first condition being met for a candidate cell of the list of candidate cells, the first apparatus transmits a first preamble for obtaining a timing advance (TA) of the candidate cell, the first preamble being different from at least second preamble configured for a random access channel (RACH) procedure.

[0256] At block 1330, the first apparatus receives, from the second apparatus, a first message comprising the TA of the candidate cell.

[0257] At block 1340, in accordance with a determination that the first condition is met for the candidate cell, the first apparatus performs a transmission on the candidate cell based on the TA of the candidate cell.

[0258] In some example embodiments, the first message is a medium access control (MAC) control element (CE).

[0259] In some example embodiments, in accordance with a determination that a second condition for triggering a procedure for obtaining the TA is met for the candidate cell, the first apparatus may transmit the first preamble for obtaining the TA of the candidate cell to the second apparatus; and the first apparatus receive the first message comprising the TA of the candidate cell from the second apparatus.

[0260] In some example embodiments, in accordance with a determination that a second condition for triggering a procedure for obtaining the TA is met, the first apparatus transmit a second message comprising an identity of the candidate cell to the second apparatus; receive from the second apparatus a third message comprising the first preamble; transmit the first preamble for obtaining the TA of the candidate cell to the second apparatus; and receive the first message comprising the TA of the candidate cell from the second apparatus.

[0261] In some example embodiments, the second message is a medium access control (MAC) control element (CE) and the third message is a physical downlink control channel (PDCCH) order.

[0262] In some example embodiments, the event-triggered configuration further comprises a second condition for triggering a procedure for obtaining a TA.

[0263] In some example embodiments, the event-triggered configuration comprises at least one of the following: a layer 1 / layer 2 (L1 / L2) triggered mobility (LTM)-based configuration, or a layer 3 (L3) event-triggered configuration.

[0264] In some example embodiments, the event-triggered configuration is comprised in a radio resource control (RRC) reconfiguration message.

[0265] In some example embodiments, the cell switch comprises at least one of the following: an intra-the next generation node B (gNB) cell switch, an inter-gNB cell switch, an intra-centralized unit (CU) cell switch, or an inter-CU cell switch.

[0266] In some example embodiments, the first apparatus comprises a terminal apparatus and the second apparatus comprises one of the following: a next generation node B (gNB) serving the first apparatus, or a distributed unit (DU) connecting with the first apparatus.

[0267] FIG. 14 shows a flowchart of an example method 1400 implemented at a second apparatus in accordance with some example embodiments of the present disclosure. For the purpose of discussion, the method 1400 will be described from the perspective of thesecond apparatus 120 in FIG. 1A and FIG. IB.

[0268] At block 1410, the second apparatus transmits, to a first apparatus, an event- triggered configuration indicating a list of candidate cells and a first condition for triggering a cell switch.

[0269] At block 1420, the second apparatus receives, from the first apparatus, a first preamble for obtaining a timing advance (TA) of a candidate cell of the list of candidate cells, the first preamble is different from at least second preamble configured for a random access channel (RACH) procedure.

[0270] At block 1430, the second apparatus transmits, to the first apparatus, a first message comprising the TA of the candidate cell.

[0271] In some example embodiments, the first apparatus comprises a terminal apparatus and the second apparatus comprises one of the following: a next generation node B (gNB) serving the first apparatus, a distributed unit (DU) connecting with the first apparatus, or a centralized unit (CU) connecting with the DU.

[0272] In some example embodiments, the second apparatus may receive the event- triggered configuration from the CU connecting with the DU.

[0273] In some example embodiments, in accordance with a determination that a TA identity of a source cell of the first apparatus is different from a TA identity of a target cell of the first apparatus, the second apparatus may comprise the first preamble in the event-triggered configuration.

[0274] In some example embodiments, the first message is a medium access control (MAC) control element (CE).

[0275] In some example embodiments, the first preamble is comprised in the event- triggered configuration.

[0276] In some example embodiments, the second apparatus may receive, from the first apparatus, a second message comprising an identity of the candidate cell; transmit, to the first apparatus, a third message comprising the first preamble.

[0277] In some example embodiments, the second message is a medium access control (MAC) control element (CE) and the third message is a physical downlink control channel (PDCCH) order.

[0278] In some example embodiments, the event-triggered configuration further comprises a second condition for triggering a procedure for obtaining a TA.

[0279] In some example embodiments, the event-triggered configuration comprises at least one of the following: a layer 1 / layer 2 (L1 / L2) triggered mobility (LTM)-based configuration, or a layer 3 (L3) event-triggered configuration.

[0280] In some example embodiments, the event-triggered configuration is comprised in a radio resource control (RRC) reconfiguration message.

[0281] In some example embodiments, the cell switch comprises at least one of the following: an intra-the next generation node B (gNB) cell switch, an inter-gNB cell switch, an intra-centralized unit (CU) cell switch, or an inter-CU cell switch.

[0282] FIG. 15 shows a flowchart of an example method 1500 implemented at a first apparatus in accordance with some example embodiments of the present disclosure. For the purpose of discussion, the method 1500 will be described from the perspective of the first apparatus 110 in FIG. 1 A and FIG. IB.

[0283] At block 1510, the first apparatus receives, from a second apparatus, an event- triggered configuration indicating a list of candidate cells and a first condition for triggering a cell switch.

[0284] At block 1520, prior to the first condition being met for a candidate cell of the list of candidate cells, the first apparatus triggers a procedure for obtaining a timing advance (TA) of the candidate cell.

[0285] At block 1530, based at least in part on the first condition being met for the candidate cell and the procedure for obtaining the TA not being completed, the first apparatus starts a TA acquisition timer to continue the procedure for obtaining the TA and / or delay the cell switch to the candidate cell.

[0286] In some example embodiments, the first apparatus may determine that the procedure for obtaining the TA has not been completed based on a determination that a first message comprising the TA of the candidate cell has not been received from the second apparatus; and determine that the procedure for obtaining the TA has been completed based on a determination that the first message comprising the TA of the candidate cell has been received from the second apparatus.

[0287] In some example embodiments, the first apparatus may start the TA acquisition timer further based on a determination that a signal strength of the second apparatus is above or equal to a threshold.

[0288] In some example embodiments, based on a determination that the procedure for obtaining the TA has not been completed and the first condition is met for the candidate cell, the first apparatus may initiate a random access channel (RACH) procedure to obtain the TA of the candidate cell if a signal strength of the second apparatus is below or equal to a threshold.

[0289] In some example embodiments, the first apparatus may stop the TA acquisition timer in response to one of the following: completion of the procedure for obtaining the TA, or a signal strength of the second apparatus being below or equal to a threshold.

[0290] In some example embodiments, in accordance with a determination that the procedure for obtaining the TA has been completed before expiry of the TA acquisition timer, the first apparatus may perform a transmission on the candidate cell based on the TA of the candidate cell.

[0291] In some example embodiments, the method 1500 further comprises: before expiry of the TA acquisition timer, the first apparatus may initiate a random access channel (RACH) procedure to obtain the TA of the candidate cell in accordance with a determination that a signal strength of the second apparatus is below or equal to a threshold.

[0292] In some example embodiments, in accordance with a determination that the procedure for obtaining the TA has not been completed by the time the TA acquisition timer expires, the first apparatus may initiate a random access channel (RACH) procedure to obtain the TA of the candidate cell.

[0293] In some example embodiments, a duration of the TA acquisition timer is a predefined default value, configured by the second apparatus, or determined by the first apparatus based on a capability of the first apparatus.

[0294] In some example embodiments, the event-triggered configuration comprises at least one of the following: a layer 1 / layer 2 (L1 / L2) triggered mobility (LTM)-based configuration, or a layer 3 (L3) event-triggered configuration.

[0295] In some example embodiments, the event-triggered configuration is comprised ina radio resource control (RRC) reconfiguration message.

[0296] In some example embodiments, the cell switch comprises at least one of the following: an intra-the next generation node B (gNB) cell switch, an inter-gNB cell switch, an intra-centralized unit (CU) cell switch, or an inter-CU cell switch.

[0297] In some example embodiments, the first apparatus comprises a terminal apparatus and the second apparatus comprises one of the following: a next generation node B (gNB) serving the first apparatus, or a distributed unit (DU) serving the first apparatus.

[0298] FIG. 16 shows a flowchart of an example method 1600 implemented at a first apparatus in accordance with some example embodiments of the present disclosure. For the purpose of discussion, the method 1600 will be described from the perspective of the first apparatus 110 in FIG. 1A and FIG. IB.

[0299] At block 1610, the first apparatus receives, from a second apparatus, an event- triggered configuration indicating a list of candidate cells and a first condition for triggering a cell switch.

[0300] At block 1620, prior to switching to a candidate cell of the list of candidate cells in response to the first condition being met for the candidate cell, the first apparatus determines a transmission configuration indicator (TCI) state to be applied on the candidate cell based on at least one of: a first TCI state indicated by the second apparatus in a first message, or a second TCI state associated with a best measurement result of a reference signal (RS) resource.

[0301] At block 1630, in response to the first condition being met for the candidate cell, the first apparatus performs a transmission on the candidate cell based on the determined TCI state.

[0302] In some example embodiments, the first apparatus may transmit, to the second apparatus, a first preamble for obtaining a timing advance (TA) of the candidate cell, the first preamble being different from at least second preamble configured for a random access channel (RACH) procedure; and receive, from the second apparatus, the first message comprising the TA of the candidate cell and the first TCI state.

[0303] In some example embodiments, the first message is a medium access control (MAC) control element (CE).

[0304] In some example embodiments, in accordance with a determination that the first TCI state and the second TCI state are different TCI states, the first apparatus may determine the second TCI state as the TCI state to be applied on the candidate cell; and transmitting, to the second apparatus, a fourth message indicating the second TCI state.

[0305] In some example embodiments, the fourth message is a medium access control (MAC) control element (CE).

[0306] In some example embodiments, the event-triggered configuration further comprises a second condition for triggering a procedure for obtaining a timing advance (TA).

[0307] In some example embodiments, the event-triggered configuration comprises at least one of the following: a layer 1 / layer 2 (L1 / L2) triggered mobility (LTM)-based configuration, or a layer 3 (L3) event-triggered configuration.

[0308] In some example embodiments, the event-triggered configuration is comprised in a radio resource control (RRC) reconfiguration message.

[0309] In some example embodiments, the cell switch comprises at least one of the following: an intra-the next generation node B (gNB) cell switch, an inter-gNB cell switch, an intra-centralized unit (CU) cell switch, or an inter-CU cell switch.

[0310] In some example embodiments, the first apparatus comprises a terminal apparatus and the second apparatus comprises one of the following: a next generation node B (gNB) serving the first apparatus, or a distributed unit (DU) connecting with the first apparatus.

[0311] FIG. 17 shows a flowchart of an example method 1700 implemented at a second apparatus in accordance with some example embodiments of the present disclosure. For the purpose of discussion, the method 1700 will be described from the perspective of the second apparatus 120 in FIG. 1A and FIG. IB.

[0312] At block 1710, the second apparatus transmits, to a first apparatus, an event- triggered configuration indicating: a list of candidate cells and a first condition for triggering a cell switch.

[0313] At block 1720, the second apparatus determines a transmission configuration indicator (TCI) state to be applied on a candidate cell based on at least one of: a first TCI state indicated by the second apparatus in a first message, or a second TCI state associatedwith a best measurement result of a reference signal (RS) resource.

[0314] In some example embodiments, the second apparatus may receive, from the first apparatus, a first preamble for obtaining a timing advance (TA) of the candidate cell, the first preamble being different from configured at least second preamble for a random access channel (RACH) procedure; and transmitting, to the first apparatus, a first message comprising the TA of the candidate cell and the first TCI state.

[0315] In some example embodiments, the second apparatus may receive, from the first apparatus, a fourth message indicating the second TCI state; and determining the second TCI state as the TCI state to be applied on the candidate cell.

[0316] In some example embodiments, the second apparatus may transmit a context modification message comprising the determined TCI state to a further apparatus, such that the determined TCI state is informed to the candidate cell.

[0317] In some example embodiments, the event-triggered configuration further comprises a second condition for triggering a procedure for obtaining a timing advance (TA).

[0318] In some example embodiments, the event-triggered configuration comprises at least one of the following: a layer 1 / layer 2 (L1 / L2) triggered mobility (LTM)-based configuration, or a layer 3 (L3) event-triggered configuration.

[0319] In some example embodiments, the event-triggered configuration is comprised in a radio resource control (RRC) reconfiguration message.

[0320] In some example embodiments, the cell switch comprises at least one of the following: an intra-the next generation node B (gNB) cell switch, an inter-gNB cell switch, an intra-centralized unit (CU) cell switch, or an inter-CU cell switch.

[0321] In some example embodiments, the first apparatus comprises a terminal apparatus and the second apparatus comprises one of the following: a next generation node B (gNB) serving the first apparatus, a distributed unit (DU) connecting with the first apparatus, or a centralized unit (CU) connecting with the DU.

[0322] FIG. 18 shows a flowchart of an example method 1800 implemented at a third apparatus in accordance with some example embodiments of the present disclosure. For the purpose of discussion, the method 1800 will be described from the perspective of thethird apparatus 130 in FIG. 1A and FIG. IB.

[0323] At block 1810, the third apparatus receives, a context modification request comprising a transmission configuration indicator (TCI) state to be used for communication between a first apparatus and the third apparatus, wherein the first apparatus is to be switched to a candidate cell provided by the third apparatus.

[0324] At block 1820, in accordance with a determination that the communication is configured grant, the third apparatus retains a configured grant of the TCI state comprised in the context modification message.

[0325] At block 1830, in accordance with a determination that the communication is dynamic grant, the third apparatus allocates a dynamic grant to the first apparatus based on the TCI state comprised in the context modification message.

[0326] In some example embodiments, the third apparatus may transmit a context modification response of the context modification request.

[0327] In some example embodiments, the first apparatus comprises a terminal apparatus and the third apparatus comprises one of the following: a target next generation node B (gNB), or a target distributed unit (DU).Example Apparatus, Device and Medium

[0328] In some example embodiments, a first apparatus capable of performing any of the method 1100 (for example, the first apparatus 110 in FIG. 1 A and FIG. IB) may comprise means for performing the respective operations of the method 1100. The means may be implemented in any suitable form. For example, the means may be implemented in a circuitry or software module. The first apparatus may be implemented as or included in the first apparatus 110 in FIG. 1 A and FIG. IB.

[0329] In some example embodiments, the first apparatus comprises means for receiving, from a second apparatus, an event-triggered configuration indicating: a list of candidate cells, a first condition for triggering a cell switch, and a second condition for triggering a procedure for obtaining a timing advance (TA); and means for prior to the first condition being met for a candidate cell of the list of candidate cells, based on the second condition being met for the candidate cell, triggering a procedure for obtaining a TA of the candidate cell.

[0330] In some example embodiments, the first condition is associated with a first set of criteria, and the second condition is associated with a second set of criteria that is lower than the first set of criteria.

[0331] In some example embodiments, the first apparatus further comprises: means for performing measurements on the list of candidate cells based on the event-triggered configuration; and means for evaluating the second condition based on results of the measurements.

[0332] In some example embodiments, 4. The first apparatus of claim 1 or 2, wherein, the first condition comprises at least one first threshold corresponding to at least one event, and the second condition comprises at least one second threshold corresponding to the at least one event, the second threshold being different from the first threshold.

[0333] In some example embodiments, the first condition comprises at least one first threshold corresponding to at least one event, and the second condition comprises at least one offset, where the offset is a difference between a second threshold associated with the second condition and the first threshold.

[0334] In some example embodiments, the second condition comprises at least one first threshold corresponding to at least one event, and the first condition comprises at least one offset, wherein the offset is a difference between a first threshold associated with the first condition and the second threshold.

[0335] In some example embodiments, the first apparatus further comprises: trigger the procedure for obtaining the TA of the candidate cell by one of the following: means for transmitting a first preamble to the second apparatus for obtaining the TA, the first preamble being different from at least second preamble configured for a random access channel (RACH) procedure; means for initiating a user equipment (UE)-based TA evaluation procedure; or means for initiating a RACH procedure for obtaining the TA by using the second preamble.

[0336] In some example embodiments, the event-triggered configuration comprises at least one of the following: a layer 1 / layer 2 (L1 / L2) triggered mobility (LTM)-based configuration, or a layer 3 (L3) event-triggered configuration.

[0337] In some example embodiments, the event-triggered configuration is comprised in a radio resource control (RRC) reconfiguration message.

[0338] In some example embodiments, the cell switch comprises at least one of the following: an intra-the next generation node B (gNB) cell switch, an inter-gNB cell switch, an intra-centralized unit (CU) cell switch, or an inter-CU cell switch.

[0339] In some example embodiments, the first apparatus comprises a terminal apparatus and the second apparatus comprises one of the following: a next generation node B (gNB) serving the first apparatus, or a distributed unit (DU) connecting with the first apparatus.

[0340] In some example embodiments, a second apparatus capable of performing any of the method 1200 (for example, the second apparatus 120 in FIG. 1A and FIG. IB) may comprise means for performing the respective operations of the method 1200. The means may be implemented in any suitable form. For example, the means may be implemented in a circuitry or software module. The second apparatus may be implemented as or included in the second apparatus 120 in FIG. 1A and FIG. IB.

[0341] In some example embodiments, the second apparatus comprises means for determining an event-triggered configuration for a first apparatus, the event-triggered configuration indicating: a list of candidate cells, a first condition for triggering a cell switch, and a second condition for triggering a procedure for obtaining a timing advance (TA); and means for transmitting the event-triggered configuration to the first apparatus.

[0342] In some example embodiments, the first apparatus comprises a terminal apparatus and the second apparatus comprises one of the following: a next generation node B (gNB) serving the first apparatus, a distributed unit (DU) connecting with the first apparatus, or a centralized unit (CU) connecting with the DU.

[0343] In some example embodiments, the second apparatus further comprises: means for receiving the event-triggered configuration from the CU.

[0344] In some example embodiments, the first condition is associated with a first set of criteria, and the second condition is associated with a second set of criteria that is lower than the first set of criteria.

[0345] In some example embodiments, the first condition comprises at least one first threshold corresponding to at least one event, and the second condition comprises at least one second threshold corresponding to at least one event, the second threshold being different from the first threshold.

[0346] In some example embodiments, the first condition comprises at least one firstthreshold corresponding to at least one event, and the second condition comprises at least one offset, where the offset is a difference between a second threshold associated with the second condition and the first threshold.

[0347] In some example embodiments, the second condition comprises at least one first threshold corresponding to at least one event, and the first condition comprises at least one offset, wherein the offset is a difference between a first threshold associated with the first condition and the second threshold.

[0348] In some example embodiments, the event-triggered configuration comprises at least one of the following: a layer 1 / layer 2 (L1 / L2) triggered mobility (LTM)-based configuration, or a layer 3 (L3) event-triggered configuration.

[0349] In some example embodiments, the event-triggered configuration is comprised in a radio resource control (RRC) reconfiguration message.

[0350] In some example embodiments, the cell switch comprises at least one of the following: an intra-the next generation node B (gNB) cell switch, an inter-gNB cell switch, an intra-centralized unit (CU) cell switch, or an inter-CU cell switch.

[0351] In some example embodiments, a first apparatus capable of performing any of the method 1300 (for example, the first apparatus 110 in FIG. 1 A and FIG. IB) may comprise means for performing the respective operations of the method 1300. The means may be implemented in any suitable form. For example, the means may be implemented in a circuitry or software module. The first apparatus may be implemented as or included in the first apparatus 110 in FIG. 1 A and FIG. IB.

[0352] In some example embodiments, the first apparatus comprises means for receiving, from a second apparatus, an event-triggered configuration indicating a list of candidate cells and a first condition for triggering a cell switch; means for prior to the first condition being met for a candidate cell of the list of candidate cells, transmitting a first preamble for obtaining a timing advance (TA) of the candidate cell, the first preamble being different from at least second preamble configured for a random access channel (RACH) procedure; means for receiving, from the second apparatus, a first message comprising the TA of the candidate cell; and means for in accordance with a determination that the first condition is met for the candidate cell, performing a transmission on the candidate cell based on the TA of the candidate cell.

[0353] In some example embodiments, the first message is a medium access control (MAC) control element (CE).

[0354] In some example embodiments, the first apparatus further comprises: means for in accordance with a determination that a second condition for triggering a procedure for obtaining the TA is met for the candidate cell, transmitting the first preamble for obtaining the TA of the candidate cell to the second apparatus; and means for receiving the first message comprising the TA of the candidate cell from the second apparatus.

[0355] In some example embodiments, the first apparatus further comprises: means for in accordance with a determination that a second condition for triggering a procedure for obtaining the TA is met, transmitting a second message comprising an identity of the candidate cell to the second apparatus; means for receiving from the second apparatus a third message comprising the first preamble; means for transmitting the first preamble for obtaining the TA of the candidate cell to the second apparatus; and means for receiving the first message comprising the TA of the candidate cell from the second apparatus.

[0356] In some example embodiments, the second message is a medium access control (MAC) control element (CE) and the third message is a physical downlink control channel (PDCCH) order.

[0357] In some example embodiments, the event-triggered configuration further comprises a second condition for triggering a procedure for obtaining a TA.

[0358] In some example embodiments, the event-triggered configuration comprises at least one of the following: a layer 1 / layer 2 (L1 / L2) triggered mobility (LTM)-based configuration, or a layer 3 (L3) event-triggered configuration.

[0359] In some example embodiments, the event-triggered configuration is comprised in a radio resource control (RRC) reconfiguration message.

[0360] In some example embodiments, the cell switch comprises at least one of the following: an intra-the next generation node B (gNB) cell switch, an inter-gNB cell switch, an intra-centralized unit (CU) cell switch, or an inter-CU cell switch.

[0361] In some example embodiments, the first apparatus comprises a terminal apparatus and the second apparatus comprises one of the following: a next generation node B (gNB) serving the first apparatus, or a distributed unit (DU) connecting with the first apparatus.

[0362] In some example embodiments, a second apparatus capable of performing any of the method 1400 (for example, the second apparatus 120 in FIG. 1A and FIG. IB) may comprise means for performing the respective operations of the method 1400. The means may be implemented in any suitable form. For example, the means may be implemented in a circuitry or software module. The second apparatus may be implemented as or included in the second apparatus 120 in FIG. 1A and FIG. IB.

[0363] In some example embodiments, the second apparatus comprises means for transmitting, to a first apparatus, an event-triggered configuration indicating a list of candidate cells and a first condition for triggering a cell switch; means for receiving, from the first apparatus, a first preamble for obtaining a timing advance (TA) of a candidate cell of the list of candidate cells, the first preamble is different from at least second preamble configured for a random access channel (RACH) procedure; and means for transmitting, to the first apparatus, a first message comprising the TA of the candidate cell.

[0364] In some example embodiments, the first apparatus comprises a terminal apparatus and the second apparatus comprises one of the following: a next generation node B (gNB) serving the first apparatus, a distributed unit (DU) connecting with the first apparatus, or a centralized unit (CU) connecting with the DU.

[0365] In some example embodiments, the second apparatus further comprises: means for receiving the event-triggered configuration from the CU connecting with the DU.

[0366] In some example embodiments, the second apparatus further comprises: means for in accordance with a determination that a TA identity of a source cell of the first apparatus is different from a TA identity of a target cell of the first apparatus, comprising the first preamble in the event-triggered configuration.

[0367] In some example embodiments, the first message is a medium access control (MAC) control element (CE).

[0368] In some example embodiments, the first preamble is comprised in the event- triggered configuration.

[0369] In some example embodiments, the second apparatus further comprises: means for receiving, from the first apparatus, a second message comprising an identity of the candidate cell; means for transmitting, to the first apparatus, a third message comprisingthe first preamble.

[0370] In some example embodiments, the second message is a medium access control (MAC) control element (CE) and the third message is a physical downlink control channel (PDCCH) order.

[0371] In some example embodiments, the event-triggered configuration further comprises a second condition for triggering a procedure for obtaining a TA.

[0372] In some example embodiments, the event-triggered configuration comprises at least one of the following: a layer 1 / layer 2 (L1 / L2) triggered mobility (LTM)-based configuration, or a layer 3 (L3) event-triggered configuration.

[0373] In some example embodiments, the event-triggered configuration is comprised in a radio resource control (RRC) reconfiguration message.

[0374] In some example embodiments, the cell switch comprises at least one of the following: an intra-the next generation node B (gNB) cell switch, an inter-gNB cell switch, an intra-centralized unit (CU) cell switch, or an inter-CU cell switch.

[0375] In some example embodiments, a first apparatus capable of performing any of the method 1500 (for example, the first apparatus 110 in FIG. 1 A and FIG. IB) may comprise means for performing the respective operations of the method 1500. The means may be implemented in any suitable form. For example, the means may be implemented in a circuitry or software module. The first apparatus may be implemented as or included in the first apparatus 110 in FIG. 1 A and FIG. IB.

[0376] In some example embodiments, the first apparatus comprises means for receiving, from a second apparatus, an event-triggered configuration indicating a list of candidate cells and a first condition for triggering a cell switch; means for prior to the first condition being met for a candidate cell of the list of candidate cells, triggering a procedure for obtaining a timing advance (TA) of the candidate cell; and means for based at least in part on the first condition being met for the candidate cell and the procedure for obtaining the TA not being completed, starting a TA acquisition timer to continue the procedure for obtaining the TA and / or delay the cell switch to the candidate cell.

[0377] In some example embodiments, the first apparatus further comprises: means for determining that the procedure for obtaining the TA has not been completed based on a determination that a first message comprising the TA of the candidate cell has not beenreceived from the second apparatus; and means for determining that the procedure for obtaining the TA has been completed based on a determination that the first message comprising the TA of the candidate cell has been received from the second apparatus.

[0378] In some example embodiments, the first apparatus further comprises: means for starting the TA acquisition timer further based on a determination that a signal strength of the second apparatus is above or equal to a threshold.

[0379] In some example embodiments, the first apparatus further comprises: means for based on a determination that the procedure for obtaining the TA has not been completed and the first condition is met for the candidate cell, initiating a random access channel (RACH) procedure to obtain the TA of the candidate cell if a signal strength of the second apparatus is below or equal to a threshold.

[0380] In some example embodiments, the first apparatus further comprises: stop the TA acquisition timer in response to one of the following: completion of the procedure for obtaining the TA, or a signal strength of the second apparatus being below or equal to a threshold.

[0381] In some example embodiments, the first apparatus further comprises: means for in accordance with a determination that the procedure for obtaining the TA has been completed before expiry of the TA acquisition timer, performing a transmission on the candidate cell based on the TA of the candidate cell.

[0382] In some example embodiments, the first apparatus further comprises: means for before expiry of the TA acquisition timer, initiating a random access channel (RACH) procedure to obtain the TA of the candidate cell in accordance with a determination that a signal strength of the second apparatus is below or equal to a threshold.

[0383] In some example embodiments, the first apparatus further comprises: means for in accordance with a determination that the procedure for obtaining the TA has not been completed by the time the TA acquisition timer expires, initiating a random access channel (RACH) procedure to obtain the TA of the candidate cell.

[0384] In some example embodiments, a duration of the TA acquisition timer is a predefined default value, configured by the second apparatus, or determined by the first apparatus based on a capability of the first apparatus.

[0385] In some example embodiments, the event-triggered configuration comprises atleast one of the following: a layer 1 / layer 2 (L1 / L2) triggered mobility (LTM)-based configuration, or a layer 3 (L3) event-triggered configuration.

[0386] In some example embodiments, the event-triggered configuration is comprised in a radio resource control (RRC) reconfiguration message.

[0387] In some example embodiments, the cell switch comprises at least one of the following: an intra-the next generation node B (gNB) cell switch, an inter-gNB cell switch, an intra-centralized unit (CU) cell switch, or an inter-CU cell switch.

[0388] In some example embodiments, the first apparatus comprises a terminal apparatus and the second apparatus comprises one of the following: a next generation node B (gNB) serving the first apparatus, or a distributed unit (DU) serving the first apparatus.

[0389] In some example embodiments, a first apparatus capable of performing any of the method 1600 (for example, the first apparatus 110 in FIG. 1 A and FIG. IB) may comprise means for performing the respective operations of the method 1600. The means may be implemented in any suitable form. For example, the means may be implemented in a circuitry or software module. The first apparatus may be implemented as or included in the first apparatus 110 in FIG. 1 A and FIG. IB.

[0390] In some example embodiments, the first apparatus comprises means for receiving, from a second apparatus, an event-triggered configuration indicating a list of candidate cells and a first condition for triggering a cell switch; means for prior to switching to a candidate cell of the list of candidate cells in response to the first condition being met for the candidate cell, determining a transmission configuration indicator (TCI) state to be applied on the candidate cell based on at least one of: a first TCI state indicated by the second apparatus in a first message, or a second TCI state associated with a best measurement result of a reference signal (RS) resource; and means for in response to the first condition being met for the candidate cell, performing a transmission on the candidate cell based on the determined TCI state.

[0391] In some example embodiments, the first apparatus further comprises: means for transmitting, to the second apparatus, a first preamble for obtaining a timing advance (TA) of the candidate cell, the first preamble being different from at least second preamble configured for a random access channel (RACH) procedure; and means for receiving, from the second apparatus, the first message comprising the TA of the candidate cell and thefirst TCI state.

[0392] In some example embodiments, the first message is a medium access control (MAC) control element (CE).

[0393] In some example embodiments, the first apparatus further comprises: means for in accordance with a determination that the first TCI state and the second TCI state are different TCI states, determining the second TCI state as the TCI state to be applied on the candidate cell; and means for transmitting, to the second apparatus, a fourth message indicating the second TCI state.

[0394] In some example embodiments, the fourth message is a medium access control (MAC) control element (CE).

[0395] In some example embodiments, the event-triggered configuration further comprises a second condition for triggering a procedure for obtaining a timing advance (TA).

[0396] In some example embodiments, the event-triggered configuration comprises at least one of the following: a layer 1 / layer 2 (L1 / L2) triggered mobility (LTM)-based configuration, or a layer 3 (L3) event-triggered configuration.

[0397] In some example embodiments, the event-triggered configuration is comprised in a radio resource control (RRC) reconfiguration message.

[0398] In some example embodiments, the cell switch comprises at least one of the following: an intra-the next generation node B (gNB) cell switch, an inter-gNB cell switch, an intra-centralized unit (CU) cell switch, or an inter-CU cell switch.

[0399] In some example embodiments, the first apparatus comprises a terminal apparatus and the second apparatus comprises one of the following: a next generation node B (gNB) serving the first apparatus, or a distributed unit (DU) connecting with the first apparatus.

[0400] In some example embodiments, a second apparatus capable of performing any of the method 1700 (for example, the second apparatus 120 in FIG. 1A and FIG. IB) may comprise means for performing the respective operations of the method 1700. The means may be implemented in any suitable form. For example, the means may be implemented in a circuitry or software module. The second apparatus may be implemented as or included in the second apparatus 120 in FIG. 1A and FIG. IB.

[0401] In some example embodiments, the second apparatus comprises means for transmitting, to a first apparatus, an event-triggered configuration indicating: a list of candidate cells and a first condition for triggering a cell switch; and means for determining a transmission configuration indicator (TCI) state to be applied on a candidate cell based on at least one of a first TCI state indicated by the second apparatus in a first message, or a second TCI state associated with a best measurement result of a reference signal (RS) resource.

[0402] In some example embodiments, the second apparatus further comprises: means for receiving, from the first apparatus, a first preamble for obtaining a timing advance (TA) of the candidate cell, the first preamble being different from configured at least second preamble for a random access channel (RACH) procedure; and means for transmitting, to the first apparatus, a first message comprising the TA of the candidate cell and the first TCI state.

[0403] In some example embodiments, the second apparatus further comprises: means for receiving, from the first apparatus, a fourth message indicating the second TCI state; and means for determining the second TCI state as the TCI state to be applied on the candidate cell.

[0404] In some example embodiments, the second apparatus further comprises: means for transmitting a context modification message comprising the determined TCI state to a further apparatus, such that the determined TCI state is informed to the candidate cell.

[0405] In some example embodiments, the event-triggered configuration further comprises a second condition for triggering a procedure for obtaining a timing advance (TA).

[0406] In some example embodiments, the event-triggered configuration comprises at least one of the following: a layer 1 / layer 2 (L1 / L2) triggered mobility (LTM)-based configuration, or a layer 3 (L3) event-triggered configuration.

[0407] In some example embodiments, the event-triggered configuration is comprised in a radio resource control (RRC) reconfiguration message.

[0408] In some example embodiments, the cell switch comprises at least one of the following: an intra-the next generation node B (gNB) cell switch, an inter-gNB cell switch, an intra-centralized unit (CU) cell switch, or an inter-CU cell switch.

[0409] In some example embodiments, the first apparatus comprises a terminal apparatus and the second apparatus comprises one of the following: a next generation node B (gNB) serving the first apparatus, a distributed unit (DU) connecting with the first apparatus, or a centralized unit (CU) connecting with the DU.

[0410] In some example embodiments, a third apparatus capable of performing any of the method 1800 (for example, the third apparatus 130 in FIG. 1A and FIG. IB) may comprise means for performing the respective operations of the method 1800. The means may be implemented in any suitable form. For example, the means may be implemented in a circuitry or software module. The third apparatus may be implemented as or included in the third apparatus 110 in FIG. 1 A and FIG. IB.

[0411] In some example embodiments, the third apparatus comprises means for receiving, a context modification request comprising a transmission configuration indicator (TCI) state to be used for communication between a first apparatus and the third apparatus, wherein the first apparatus is to be switched to a candidate cell provided by the third apparatus; means for in accordance with a determination that the communication is configured grant, retaining a configured grant of the TCI state comprised in the context modification message; and means for in accordance with a determination that the communication is dynamic grant, allocating a dynamic grant to the first apparatus based on the TCI state comprised in the context modification message.

[0412] In some example embodiments, the third apparatus further comprises: means for transmitting a context modification response of the context modification request.

[0413] In some example embodiments, the first apparatus comprises a terminal apparatus and the third apparatus comprises one of the following: a target next generation node B (gNB), or a target distributed unit (DU).

[0414] FIG. 19 is a simplified block diagram of a device 1900 that is suitable for implementing example embodiments of the present disclosure. The device 1900 may be provided to implement a communication device, for example, the first apparatus 110, the second apparatus 120 or the third apparatus 130 as shown in FIG. 1A and FIG. IB. As shown, the device 1900 includes one or more processors 1910, one or more memories 1920 coupled to the processor 1910, and one or more communication modules 1940 coupled to the processor 1910.

[0415] The communication module 1940 is for bidirectional communications. The communication module 1940 has one or more communication interfaces to facilitate communication with one or more other modules or devices. The communication interfaces may represent any interface that is necessary for communication with other network elements. In some example embodiments, the communication module 1940 may include at least one antenna.

[0416] The processor 1910 may be of any type suitable to the local technical network and may include one or more of the following: general purpose computers, special purpose computers, microprocessors, digital signal processors (DSPs) and processors based on multicore processor architecture, as non-limiting examples. The device 1900 may have multiple processors, such as an application specific integrated circuit chip that is slaved in time to a clock which synchronizes the main processor.

[0417] The memory 1920 may include one or more non-volatile memories and one or more volatile memories. Examples of the non-volatile memories include, but are not limited to, a Read Only Memory (ROM) 1924, an electrically programmable read only memory (EPROM), a flash memory, a hard disk, a compact disc (CD), a digital video disk (DVD), an optical disk, a laser disk, and other magnetic storage and / or optical storage. Examples of the volatile memories include, but are not limited to, a random-access memory (RAM) 1922 and other volatile memories that will not last in the power-down duration.

[0418] A computer program 1930 includes computer executable instructions that are executed by the associated processor 1910. The instructions of the program 1930 may include instructions for performing operations / acts of some example embodiments of the present disclosure. The program 1930 may be stored in the memory, e.g., the ROM 1924. The processor 1910 may perform any suitable actions and processing by loading the program 1930 into the RAM 1922.

[0419] The example embodiments of the present disclosure may be implemented by means of the program 1930 so that the device 1900 may perform any process of the disclosure as discussed with reference to FIG. 2 to FIG. 18. The example embodiments of the present disclosure may also be implemented by hardware or by a combination of software and hardware.

[0420] In some example embodiments, the program 1930 may be tangibly contained in acomputer readable medium which may be included in the device 1900 (such as in the memory 1920) or other storage devices that are accessible by the device 1900. The device 1900 may load the program 1930 from the computer readable medium to the RAM 1922 for execution. In some example embodiments, the computer readable medium may include any types of non-transitory storage medium, such as ROM, EPROM, a flash memory, a hard disk, CD, DVD, and the like. The term “non-transitory,” as used herein, is a limitation of the medium itself (i.e., tangible, not a signal) as opposed to a limitation on data storage persistency (e.g., RAM vs. ROM).

[0421] FIG. 20 shows an example of the computer readable medium 2000 which may be in form of CD, DVD or other optical storage disk. The computer readable medium 2000 has the program 1930 stored thereon.

[0422] Generally, various embodiments of the present disclosure may be implemented in hardware or special purpose circuits, software, logic or any combination thereof. Some aspects may be implemented in hardware, and other aspects may be implemented in firmware or software which may be executed by a controller, microprocessor or other computing device. Although various aspects of embodiments of the present disclosure are illustrated and described as block diagrams, flowcharts, or using some other pictorial representations, it is to be understood that the block, apparatus, system, technique or method described herein may be implemented in, as non-limiting examples, hardware, software, firmware, special purpose circuits or logic, general purpose hardware or controller or other computing devices, or some combination thereof.

[0423] Some example embodiments of the present disclosure also provide at least one computer program product tangibly stored on a computer readable medium, such as a non- transitory computer readable medium. The computer program product includes computerexecutable instructions, such as those included in program modules, being executed in a device on a target physical or virtual processor, to carry out any of the methods as described above. Generally, program modules include routines, programs, libraries, objects, classes, components, data structures, or the like that perform particular tasks or implement particular abstract data types. The functionality of the program modules may be combined or split between program modules as desired in various embodiments. Machine-executable instructions for program modules may be executed within a local or distributed device. In a distributed device, program modules may be located in both local and remote storage media.

[0424] Program code for carrying out methods of the present disclosure may be written in any combination of one or more programming languages. The program code may be provided to a processor or controller of a general-purpose computer, special purpose computer, or other programmable data processing apparatus, such that the program code, when executed by the processor or controller, cause the functions / operations specified in the flowcharts and / or block diagrams to be implemented. The program code may execute entirely on a machine, partly on the machine, as a stand-alone software package, partly on the machine and partly on a remote machine or entirely on the remote machine or server.

[0425] In the context of the present disclosure, the computer program code or related data may be carried by any suitable carrier to enable the device, apparatus or processor to perform various processes and operations as described above. Examples of the carrier include a signal, computer readable medium, and the like.

[0426] The computer readable medium may be a computer readable signal medium or a computer readable storage medium. A computer readable medium may include but not limited to an electronic, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus, or device, or any suitable combination of the foregoing. More specific examples of the computer readable storage medium would include an electrical connection having one or more wires, a portable computer diskette, a hard disk, a random-access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or Flash memory), an optical fiber, a portable compact disc read-only memory (CD-ROM), an optical storage device, a magnetic storage device, or any suitable combination of the foregoing.

[0427] Further, although operations are depicted in a particular order, this should not be understood as requiring that such operations be performed in the particular order shown or in sequential order, or that all illustrated operations be performed, to achieve desirable results. In certain circumstances, multitasking and parallel processing may be advantageous. Likewise, although several specific implementation details are contained in the above discussions, these should not be construed as limitations on the scope of the present disclosure, but rather as descriptions of features that may be specific to particular embodiments. Unless explicitly stated, certain features that are described in the context of separate embodiments may also be implemented in combination in a single embodiment. Conversely, unless explicitly stated, various features that are described in the context of a single embodiment may also be implemented in a plurality of embodiments separatelyor in any suitable sub-combination.

[0428] Although the present disclosure has been described in languages specific to structural features and / or methodological acts, it is to be understood that the present disclosure defined in the appended claims is not necessarily limited to the specific features or acts described above. Rather, the specific features and acts described above are disclosed as example forms of implementing the claims.

Claims

I / We Claim:

1. A first apparatus comprising: at least one processor; and at least one memory storing instructions that, when executed by the at least one processor, cause the first apparatus to: receive, from a second apparatus, an event-triggered configuration indicating a list of candidate cells and a first condition for triggering a cell switch; prior to the first condition being met for a candidate cell of the list of candidate cells, transmit a first preamble for obtaining a timing advance (TA) of the candidate cell, the first preamble being different from at least second preamble configured for a random access channel (RACH) procedure; receive, from the second apparatus, a first message comprising the TA of the candidate cell; and in accordance with a determination that the first condition is met for the candidate cell, perform a transmission on the candidate cell based on the TA of the candidate cell.

2. The first apparatus of claim 1, wherein the first message is a medium access control (MAC) control element (CE).

3. The first apparatus of claim 1 or 2, wherein the first preamble is comprised in the event-triggered configuration and the first apparatus is further caused to: in accordance with a determination that a second condition for triggering a procedure for obtaining the TA is met for the candidate cell, transmit the first preamble for obtaining the TA of the candidate cell to the second apparatus; and receive the first message comprising the TA of the candidate cell from the second apparatus.

4. The first apparatus of claim 1 or 2, wherein the first apparatus is further caused to: in accordance with a determination that a second condition for triggering a procedure for obtaining the TA is met, transmit a second message comprising an identity of the candidate cell to the second apparatus;72receive from the second apparatus a third message comprising the first preamble; transmit the first preamble for obtaining the TA of the candidate cell to the second apparatus; and receive the first message comprising the TA of the candidate cell from the second apparatus.

5. The first apparatus of claim 4, wherein the second message is a medium access control (MAC) control element (CE) and the third message is a physical downlink control channel (PDCCH) order.

6. The first apparatus of any of claims 1 to 5, wherein the event-triggered configuration further comprises a second condition for triggering a procedure for obtaining a TA.

7. The first apparatus of any of claims 1 to 6, wherein the event-triggered configuration comprises at least one of the following: a layer 1 / layer 2 (L1 / L2) triggered mobility (LTM)-based configuration, or a layer 3 (L3) event-triggered configuration.

8. The first apparatus of any of claims 1 to 7, wherein the event-triggered configuration is comprised in a radio resource control (RRC) reconfiguration message.

9. The first apparatus of any of claims 1 to 8, wherein the cell switch comprises at least one of the following: an intra-the next generation node B (gNB) cell switch, an inter-gNB cell switch, an intra-centralized unit (CU) cell switch, or an inter-CU cell switch.

10. The first apparatus of any of claims 1 to 9, wherein the first apparatus comprises a terminal apparatus and the second apparatus comprises one of the following: a next generation node B (gNB) serving the first apparatus, or a distributed unit (DU) connecting with the first apparatus.

11. A second apparatus comprising: at least one processor; and at least one memory storing instructions that, when executed by the at least one processor, cause the second apparatus to:transmit, to a first apparatus, an event-triggered configuration indicating a list of candidate cells and a first condition for triggering a cell switch; receive, from the first apparatus, a first preamble for obtaining a timing advance (TA) of a candidate cell of the list of candidate cells, the first preamble is different from at least second preamble configured for a random access channel (RACH) procedure; and transmit, to the first apparatus, a first message comprising the TA of the candidate cell.

12. The second apparatus of claim 11, wherein the first apparatus comprises a terminal apparatus and the second apparatus comprises one of the following: a next generation node B (gNB) serving the first apparatus, a distributed unit (DU) connecting with the first apparatus, or a centralized unit (CU) connecting with the DU.

13. The second apparatus of claim 12, wherein the second apparatus is the DU connecting with the first apparatus and the second apparatus is further caused to: receive the event-triggered configuration from the CU connecting with the DU.

14. The second apparatus of claim 12, wherein the second apparatus is the CU and the second apparatus is further caused to: in accordance with a determination that a TA identity of a source cell of the first apparatus is different from a TA identity of a target cell of the first apparatus, comprise the first preamble in the event-triggered configuration.

15. The second apparatus of any of claims 11 to 14, wherein the first message is a medium access control (MAC) control element (CE).

16. The second apparatus of any of claims 12 to 15, wherein the first preamble is comprised in the event-triggered configuration.

17. The second apparatus of any of claims 12 to 16, wherein the second apparatus is further caused to: receive, from the first apparatus, a second message comprising an identity of the candidate cell;transmit, to the first apparatus, a third message comprising the first preamble.

18. The second apparatus of claim 17, wherein the second message is a medium access control (MAC) control element (CE) and the third message is a physical downlink control channel (PDCCH) order.

19. The second apparatus of any of claims 12 to 18, wherein the event-triggered configuration further comprises a second condition for triggering a procedure for obtaining a TA.

20. The second apparatus of any of claims 12 to 19, wherein the event-triggered configuration comprises at least one of the following: a layer 1 / layer 2 (L1 / L2) triggered mobility (LTM)-based configuration, or a layer 3 (L3) event-triggered configuration.

21. The second apparatus of any of claims 12 to 20, wherein the event-triggered configuration is comprised in a radio resource control (RRC) reconfiguration message.

22. The second apparatus of any of claims 12 to 21, wherein the cell switch comprises at least one of the following: an intra-the next generation node B (gNB) cell switch, an inter- gNB cell switch, an intra-centralized unit (CU) cell switch, or an inter-CU cell switch.

23. A method comprising: receiving, by a first apparatus from a second apparatus, an event-triggered configuration indicating a list of candidate cells and a first condition for triggering a cell switch; prior to the first condition being met for a candidate cell of the list of candidate cells, transmitting a first preamble for obtaining a timing advance (TA) of the candidate cell, the first preamble being different from at least second preamble configured for a random access channel (RACH) procedure; receiving, from the second apparatus, a first message comprising the TA of the candidate cell; and in accordance with a determination that the first condition is met for the candidate cell, performing a transmission on the candidate cell based on the TA of the candidate75cell.

24. The method of claim 23, wherein the first message is a medium access control (MAC) control element (CE).

25. The method of claim 23 or 24, wherein the first preamble is comprised in the event- triggered configuration and the first apparatus further performs the following: in accordance with a determination that a second condition for triggering a procedure for obtaining the TA is met for the candidate cell, transmitting the first preamble for obtaining the TA of the candidate cell to the second apparatus; and receiving the first message comprising the TA of the candidate cell from the second apparatus.

26. The method of claim 23 or 24, wherein the first apparatus further performs the following: in accordance with a determination that a second condition for triggering a procedure for obtaining the TA is met, transmitting a second message comprising an identity of the candidate cell to the second apparatus; receiving from the second apparatus a third message comprising the first preamble; transmitting the first preamble for obtaining the TA of the candidate cell to the second apparatus; and receiving the first message comprising the TA of the candidate cell from the second apparatus.

27. The method of claim 26, wherein the second message is a medium access control (MAC) control element (CE) and the third message is a physical downlink control channel (PDCCH) order.

28. The method of any of claims 23 to 27, wherein the event-triggered configuration further comprises a second condition for triggering a procedure for obtaining a TA.

29. The method of any of claims 23 to 28, wherein the event-triggered configuration comprises at least one of the following: a layer 1 / layer 2 (L1 / L2) triggered mobility (LTM)-based configuration, or76a layer 3 (L3) event-triggered configuration.

30. The method of any of claims 23 to 29, wherein the event-triggered configuration is comprised in a radio resource control (RRC) reconfiguration message.

31. The method of any of claims 23 to 30, wherein the cell switch comprises at least one of the following: an intra-the next generation node B (gNB) cell switch, an inter-gNB cell switch, an intra-centralized unit (CU) cell switch, or an inter-CU cell switch.

32. The method of any of claims 23 to 31, wherein the first apparatus comprises a terminal apparatus and the second apparatus comprises one of the following: a next generation node B (gNB) serving the first apparatus, or a distributed unit (DU) connecting with the first apparatus.

33. A method comprising: transmitting, to a first apparatus, an event-triggered configuration indicating a list of candidate cells and a first condition for triggering a cell switch; receiving, from the first apparatus, a first preamble for obtaining a timing advance (TA) of a candidate cell of the list of candidate cells, the first preamble is different from at least second preamble configured for a random access channel (RACH) procedure; and transmitting, to the first apparatus, a first message comprising the TA of the candidate cell.

34. A first apparatus comprising: means for receiving, from a second apparatus, an event-triggered configuration indicating a list of candidate cells and a first condition for triggering a cell switch; means for prior to the first condition being met for a candidate cell of the list of candidate cells, transmitting a first preamble for obtaining a timing advance (TA) of the candidate cell, the first preamble being different from at least second preamble configured for a random access channel (RACH) procedure; means for receiving, from the second apparatus, a first message comprising the TA of the candidate cell; and means for in accordance with a determination that the first condition is met for the77candidate cell, performing a transmission on the candidate cell based on the TA of the candidate cell.

35. A second apparatus comprising: means for transmitting, to a first apparatus, an event-triggered configuration indicating a list of candidate cells and a first condition for triggering a cell switch; means for receiving, from the first apparatus, a first preamble for obtaining a timing advance (TA) of a candidate cell of the list of candidate cells, the first preamble is different from at least second preamble configured for a random access channel (RACH) procedure; and means for transmitting, to the first apparatus, a first message comprising the TA of the candidate cell.

36. A computer readable medium comprising instructions stored thereon for causing an apparatus at least to perform the method of any of claims 23 to 33.

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