Monitoring of early timing advance acquisition

Abstract

Example embodiments of the disclosure relate to, a method, apparatuses and a computer readable medium for early timing advance (TA) acquisition. In a method, a first apparatus determines measurement information about TA acquisition in early TA acquisition procedures with respect to a source- candidate target pair of cells for layer 1 / layer 2 (L1 / L2) triggered mobility (LTM), where the measurement information comprises a total number of TA acquisition requests for the source-candidate target pair of cells within a measurement period, and at least one of the following: a first number of successful TA acquisitions, or a second number of successful late TA acquisitions for the source-candidate target pair of cells within the measurement period. The first apparatus transmits the measurement information to a second apparatus for evaluation of the TA acquisition for the source-candidate target pair of cells.

Description

MONITORING OF EARLY TIMING ADVANCE ACQUISITIONFIELDS

[0001] Various example embodiments of the present disclosure generally relate to the field of telecommunication and in particular, to a method, apparatuses and a computer readable storage medium for early timing advance (TA) acquisition.BACKGROUND

[0002] The Layer 1 or Layer 2 (L1 / L2) triggered mobility (LTM) mechanism is provided for handover of a terminal device (e.g., UE) from a source cell to a target cell. The early TA acquisition for LTM is a mechanism that allows a terminal device to acquire TA information for the target cell in advance, e.g., before performing a handover or cell reselection. The monitoring of the early TA acquisition is important to optimize the LTM.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 at least to: determine measurement information about timing advance (TA) acquisition in early TA acquisition procedures with respect to a source-candidate target pair of cells for layer 1 / layer 2 (L1 / L2) triggered mobility (LTM), wherein the measurement information comprises a total number of TA acquisition requests for the source-candidate target pair of cells within a measurement period, and at least one of the following: a first number of successful TA acquisitions, or a second number of successful late TA acquisitions for the source-candidate target pair of cells within the measurement period; and transmit the measurement information to a second apparatus for evaluation of the TA acquisition for thesource-candidate target pair of cells.

[0004] In a second aspect of the present disclosure, there is provided a method. The method comprises: determining measurement information about timing advance (TA) acquisition in early TA acquisition procedures with respect to a source-candidate target pair of cells for layer 1 / layer 2 (L1 / L2) triggered mobility (LTM), wherein the measurement information comprises a total number of TA acquisition requests for the source-candidate target pair of cells within a measurement period, and at least one of the following: a first number of successful TA acquisitions, or a second number of successful late TA acquisitions for the source-candidate target pair of cells within the measurement period; and transmitting the measurement information to a second apparatus for evaluation of the TA acquisition for the source-candidate target pair of cells.

[0005] In a third aspect of the present disclosure, there is provided a first apparatus. The first apparatus comprises means for determining measurement information about timing advance (TA) acquisition in early TA acquisition procedures with respect to a source-candidate target pair of cells for layer 1 / layer 2 (L1 / L2) triggered mobility (LTM), wherein the measurement information comprises a total number of TA acquisition requests for the source-candidate target pair of cells within a measurement period, and at least one of the following: a first number of successful TA acquisitions, or a second number of successful late TA acquisitions for the source-candidate target pair of cells within the measurement period; and means for transmitting the measurement information to a second apparatus for evaluation of the TA acquisition for the source-candidate target pair of cells.

[0006] In a fourth 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 the second aspect.

[0007] 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

[0008] Some example embodiments will now be described with reference to the accompanying drawings, where:

[0009] FIG. 1 illustrates a contention free random access procedure without a network response;

[0010] FIG. 2 illustrates an example communication environment in which example embodiments of the present disclosure can be implemented;

[0011] FIG. 3 illustrates a procedure for a scenario where a UE moves within the same gNB-DU during an NR operation for LTM;

[0012] FIG. 4 illustrates a procedure for a scenario where user equipment (UE) moves from one gNB-DU to another gNB-DU within the same gNB-CU during an NR operation for LTM;

[0013] FIG. 5 illustrates a procedure for LTM with a change of gNB-CU-UP within a gNB;

[0014] FIG. 6 illustrates a signaling flow for early timing advance acquisition according to some example embodiments of the present disclosure;

[0015] FIG. 7 illustrates an example flowchart for determining a total number of TA acquisition requests according to some example embodiments of the present disclosure;

[0016] FIG. 8 illustrates an example flowchart for determining a first number of successful TA acquisitions according to some example embodiments of the present disclosure;

[0017] FIG. 9 illustrates an example flowchart for determining the second number of successful late TA acquisitions according to some example embodiments of the present disclosure;

[0018] FIG. 10 illustrates a flowchart of a method implemented at a first apparatus according to some example embodiments of the present disclosure;

[0019] FIG. 11 illustrates a simplified block diagram of a device that is suitable for implementing example embodiments of the present disclosure; and

[0020] FIG. 12 illustrates a block diagram of an example computer readable medium in accordance with some example embodiments of the present disclosure.

[0021] Throughout the drawings, the same or similar reference numerals represent the same or similar element.DETAILED DESCRIPTION

[0022] 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.

[0023] 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.

[0024] 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 notnecessarily 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.

[0025] 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.

[0026] As used herein, “at least one of the following: ” and “at least one of ” and similar wording, where the list of 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.

[0027] 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.

[0028] 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 componentsetc., but do not preclude the presence or addition of one or more other features, elements, components and / or combinations thereof.

[0029] 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.

[0030] This definition of circuitry applies to all uses of this term in this application, including in any claims. As a further example, as used in this application, the term circuitry also covers an implementation of merely a hardware circuit or processor (or multiple processors) or portion of a hardware circuit or processor and its (or their) accompanying software and / or firmware. The term circuitry also covers, for example and if applicable to the particular claim element, a baseband integrated circuit or processor integrated circuit for a mobile device or a similar integrated circuit in server, a cellular network device, or other computing or network device.

[0031] As used herein, the term “communication network” refers to anetwork 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), 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.

[0032] 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 behaves like a UE toward the parent node, and a DU part of an IAB node behaves like a basestation toward the next-hop IAB node.

[0033] 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, vehiclemounted 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.

[0034] 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 othercombination 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.

[0035] Mobility enhancements regarding the LTM is introduced in the following. When a UE moves from the coverage area of one cell to another cell, a serving cell change needs to be performed at some point. Currently, the serving cell change is triggered by Layer 3 (L3) measurements (for example, an RRC measurement report from a terminal device) and is done by downlink RRC signaling, i.e., RRC reconfiguration message with synchronization for change of Primary Cell (PCell) and Primary Secondary Cell (PSCell), as well as release and add for Secondary Cells (SCell)s when applicable. All cases involve complete L2 (and LI) resets, leading to longer latency, larger overhead, and longer interruption time than beam switch mobility. The goal of L1 / L2 mobility enhancements is to enable a serving cell change via L1 / L2 signaling, to reduce the latency, overhead, and interruption time.

[0036] LTM is a procedure in which a gNB receives LI measurement report(s) from a UE, and on their basis the gNB changes the serving cell of the UE by a cell switch command signaled via a Medium Access Control (MAC) Control Element (CE). The cell switch command indicates an LTM candidate cell configuration that the gNB previously prepared and provided to the UE through RRC signaling. Then, the UE switches to the target cell according to the cell switch command. The LTM procedure may be used to reduce mobility latency.

[0037] When configured by the network, it is possible to activate Transmission Configuration Indication (TCI) states of one or multiple cells that are different from the current serving cell. For instance, the TCI states ofthe LTM candidate cells may be activated in advance before any of those cells become the serving cell. This allows the UE to be downlink (DL) synchronized with those cells, thereby facilitating a faster cell switch to one of those cells when a cell switch is triggered.

[0038] When configured by the network, it is possible to initiate uplink (UL) TA acquisition procedure to one or multiple cells that are different from the current serving cell. For instance, the network may request the UE to perform early TA acquisition of a candidate cell before a cell switch. The early TA acquisition may be triggered by the Physical Downlink Control Channel (PDCCH) order or realized through a UE-based TA measurement. In the former case, the gNB to which the candidate cell belongs calculates the TA value and sends it to the gNB to which the serving cell belongs. The serving cell sends the TA value in the LTM cell switch command via MAC CE when triggering LTM cell switch. In the latter case, the UE applies the TA value measured by the UE and performs Random Access Channel (RACH)-less LTM upon receiving the cell switch command.

[0039] If the UE-based TA measurement is configured, the UE performs RACH-less LTM upon receiving the cell switch command. Otherwise, the UE determines whether to access the target cell with the Random Access (RA) procedure depending on whether a TA value is provided in the cell switch command. For RACH-less LTM, the UE accesses the target cell via a configured grant provided in the LTM candidate cell configuration and selects the configured grant occasion associated with the beam indicated in the cell switch command. If the LTM candidate cell configuration does not include a configured grant, the UE monitors PDCCH for dynamic scheduling from the target cell upon LTM cell switch. Before the completion of the RACH-less LTM procedure, the UE shall not trigger random access procedure if it does not have a valid Physical Uplink Control Channel (PUCCH) resource for triggered Scheduling Requests (SRs).

[0040] As mentioned, to facilitate a faster cell switch, it is possible to initiatean uplink TA acquisition procedure to one or multiple cells that are different from the current serving cell. For instance, the network may request the UE to perform early TA acquisition of a candidate cell before a cell switch.

[0041] For the random-access procedure towards a cell other than the current serving cell, for example, for early UL TA acquisition for an LTM candidate cell before LTM cell switch, Contention Free Random Access (CFRA) is triggered. FIG. 1 illustrates a contention free random access procedure without a network response. As shown in FIG. 1, a UE 102 sends a Message 1 (MSG1) towards a gNB of a candidate cell 104 without monitoring for a response from a gNB of a target cell.

[0042] Furthermore, the UE may not maintain a TA timer for the candidate cell and may rely on network implementation to guarantee the TA validity. The TA validity is fully hidden for the UE and thus cannot be reported via any UE report (nor in a RACH report) to the network. The monitoring of the early TA acquisition procedure is however an essential thing to optimize the LTM. It is to be noted that the UE has just one attempt to send the preamble and does not taking care of what happens afterwards. The target gNB DU either receives the preamble correctly and evaluates the TA, or receives the preamble but not able to evaluate the TA or does not receive the preamble at all. This behavior makes the monitoring of the early TA acquisition critical.

[0043] Example embodiments of the present disclosure propose a solution of early TA acquisition for LTM. With this scheme, measurement information about TA acquisition in early TA acquisition procedures with respect to a source-candidate target pair of cells for LTM is determined by a first apparatus (for example, a network device of a serving cell). The measurement information is transmitted by the first apparatus to a second apparatus for evaluation of the TA acquisition for the source-candidate target pair of cells.

[0044] In this way, the validity of the early TA acquisition procedure for LTM is obtained by evaluation of the TA acquisition for the source-candidatetarget pair of cells.

[0045] FIG. 2 illustrates an example communication environment 200 in which example embodiments of the present disclosure can be implemented. As shown in FIG. 2, the communication environment 200 comprises a first apparatus 210, a terminal device 220, and a third apparatus 230.

[0046] In some example embodiments, the first apparatus 210 may be a network device of a serving cell 240, for example, a gNB of the serving cell 240 for the terminal device 220. The third apparatus 230 may be a further network device of a candidate target cell 250, for example, a gNB of the candidate target cell 250. The candidate target cell 250 is a candidate for LTM of the terminal device 220. The terminal device 220, for example, may be a UE served by the serving cell 240. The candidate target cell 250 may be a potential candidate to become a new serving cell for the terminal device 220.

[0047] In the following, for the purpose of illustration, some example embodiments may be described with the first apparatus 210 or the third apparatus 230 operating as a network device. However, in some example embodiments, operations described in connection with a terminal device may be implemented at a network device or other device, and operations described in connection with a network device may be implemented at a terminal device or other device.

[0048] In some example embodiments, if the first apparatus 210 is a network device, a link from the first apparatus 210 to the terminal device 220 is referred to as a downlink (DL), and a link from the terminal device 220 to the first apparatus 210 is referred to as an uplink (UL). In DL, the first apparatus 210 is a transmitting (TX) device (or a transmitter) and the terminal device 220 is a receiving (RX) device (or a receiver). In UL, the terminal device 220 is a TX device (or a transmitter) and the first apparatus 210 is a RX device (or a receiver).

[0049] Communications in the communication environment 200 may beimplemented 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), 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.

[0050] In some example embodiments, a network device of a serving cell for a terminal device may include one or more DUs, e.g., one or more gNB-DUs, and one or more CUs, e.g., one or more gNB-CUs. A DU may be connected to the terminal device, and each DU may serve one or more cells. Depending on whether the serving cell and a candidate target cell is served by the same DU, the LTM procedure may include an intra-DU LTM procedure (e.g., intra-gNB- DU LTM procedure) where the candidate target cell and the serving cell are within the same DU, and an inter-DU LTM procedure (e.g., intra-gNB-DU LTM procedure) where the candidate target cell and the serving cell are within different DUs.

[0051] FIG. 3 illustrates a procedure for a scenario where a UE moves within the same gNB-DU during an NR operation for LTM, which demonstrates an intra-gNB-DU LTM procedure for intra-NR. The procedure of FIG. 3 involves a UE 350, a gNB-DU 360, and a gNB-CU 370.

[0052] As shown in FIG. 3, at 302, the UE 350 sends a measurement report message (represented as MeasurementReport message, which may include L3measurement results) to the gNB-DU 360 containing measurements of neighbouring cells. The gNB-DU 360 sends an uplink RRC message transfer message (represented as UL RRC MESSAGE TRANSFER message) conveying the received MeasurementReport message to the gNB-CU 370.

[0053] At 304, the gNB-CU 370 determines to initiate LTM configuration. At 306, the gNB-CU 370 sends a UE context modification request message (represented as UE CONTEXT MODIFICATION REQUEST message) to the gNB-DU 360 containing one target candidate cell ID, the LTM configuration ID of the candidate cell, and LTM configuration ID mapping list, the CSI resource configuration. The gNB-CU 370 requests Physical Random Access Channel (PRACH) resources from the gNB-DU 360. The gNB-CU 370 may request the gNB-DU 360 to provide the lower layer configuration for the purpose of generating the reference configuration.

[0054] At 308, if the gNB-DU 360 accepts the request of LTM configuration, it responds with a UE context modification response message (represented as UE CONTEXT MODIFICATION RESPONSE message) including the generated lower layer RRC configurations (for example, TCI state configuration, RACH configuration, and the CSI report configuration) for the accepted target candidate cell. It is to be noted that steps 306 and 308 may be initiated multiple times for LTM candidate cell preparation of multiple cells including the source cell.

[0055] At 310, the gNB-CU 370 sends a UE CONTEXT MODIFICATION REQUEST message to the source gNB-DU 360 including the collected TCI state configurations and the gNB-CU 370 may send the CSI report configuration for all the accepted target candidate cells.

[0056] At 312, the source gNB-DU 360 responds with a UE CONTEXT MODIFICATION RESPONSE message which includes an updated lower layer configuration, for example, containing the CSI report configuration of the source cell. It is to be noted that in case of subsequent LTM, the CU-initiatedUE Context Modification procedure may be invoked per each candidate cell to transfer to the candidate gNB-DU the CSI report configuration, TCI state information, RACH configuration, and the LTM configuration IDs of the candidate cells.

[0057] At 314, the gNB-CU 370 sends a downlink RRC message transfer message (represented as DL RRC MESSAGE TRANSFER message) to the gNB-DU 360, which includes the generated RRC reconfiguration message (represented as RRCReconfiguration message) with the LTM configuration. At 316, the gNB-DU 360 forwards the received RRCReconfiguration message to the UE 350.

[0058] At 318, the UE 350 responds to the gNB-DU 360 with an RRC reconfiguration complete message (represented as RRCReconfigurationComplete message). At 320, the gNB-DU 360 forwards the RRCReconfigurationComplete message to the gNB-CU 370 via an UL RRC MESSAGE TRANSFER message. At 322, Early synchronization may be performed. At 324, the UE 350 sends the LI measurement result to the gNB-DU 360. The gNB-DU 360 decides to execute LTM.

[0059] At 326, the gNB-DU 360 sends the Cell Switch command to the UE 350. At 328, the gNB-DU 360 sends a DU-CU cell change notification message (represented as DU-CU CELL CHANGE NOTIFICATION message) to the gNB-CU 370 to indicate the initiation of the Cell Switch command to the UE 350 including the target cell ID and the TCI state ID. At 330, the gNB- DU 360 detects the UE access. It is to be noted that, regarding the step 330, the UE 350 may still perform the random access procedure towards the target cell, if TA is not available or is not valid.

[0060] At 332, the target gNB-DU 360 sends the ACCESS SUCCESS message to the gNB-CU 370 with the target cell ID. At 334, the UE 350 sends an RRCReconfigurationComplete message to the gNB-DU 360. At 336, the gNB-DU 360 forwards the RRCReconfigurationComplete message to thegNB-CU 370 via an UL RRC MESSAGE TRANSFER message. At 338, the gNB-CU 370 may send the UE CONTEXT MODIFICATION REQUEST message to the gNB-DU 360 to release the resources of prepared cells. At 340, the gNB-DU 360 responds with a UE CONTEXT MODIFICATION RESPONSE message.

[0061] FIG. 4 illustrates a procedure for a scenario where a UE moves from one gNB-DU to another gNB-DU within the same gNB-CU during an NR operation for LTM, which demonstrates an inter-gNB-DU LTM procedure for intra-NR. The procedure of FIG. 4 involves a UE 402, a source gNB-DU 404, a candidate gNB-DU 406, and a gNB-CU 408.

[0062] As shown in FIG. 4, at 412, the UE 402 sends a MeasurementReport message (which may include L3 measurement results) to the source gNB-DU 404 containing measurements of neighbouring cells. The source gNB-DU 404 sends an UL RRC MESSAGE TRANSFER message conveying the received MeasurementReport message to the gNB-CU 408.

[0063] At 414, the gNB-CU 408 determines to initiate LTM configuration. At 416, the gNB-CU 408 sends a UE context setup request message (represented as UE CONTEXT SETUP REQUEST message) to the candidate gNB-DU(s) 406, containing one target candidate cell ID, the LTM configuration ID of the candidate cell, LTM configuration ID mapping list, and the CSI resource configuration. The gNB-CU 408 indicates the source gNB- DU ID, and requests PRACH resources from the candidate gNB-DU 406. The gNB-CU 408 may request the candidate gNB-DU 406 to provide the lower layer configuration for the purpose of generating the reference configuration.

[0064] At 418, if the candidate gNB-DU 406 accepts the request of LTM configuration, it responds with a UE context setup response message (represented as UE CONTEXT SETUP RESPONSE message) including the generated lower layer RRC configurations (e.g., TCI state configuration, RACH configuration, and the CSI report configuration) for the accepted targetcandidate cell. It is to be noted that the CU-initiated UE Context Modification procedure may be initiated for preparing candidate cells in the source gNB-DU 404 as specified in 416 and 308 of FIG. 3.

[0065] At 420, the gNB-CU 408 sends a UE CONTEXT MODIFICATION REQUEST message to the source gNB-DU 404 including the collected CSI report configuration, RACH configuration and the TCI state configuration for the accepted target candidate cell(s) in other gNB-DU(s). At 422, the source gNB-DU 404 responds with a UE CONTEXT MODIFICATION RESPONSE message which includes an updated lower layer configuration, e.g., containing the CSI report configuration.

[0066] At 424, the gNB-CU 408 sends a UE CONTEXT MODIFICATION REQUEST message to the candidate gNB-DU(s) 406 containing the CSI report configuration, TCI state information, RACH Configuration, and the LTM configuration IDs of the candidate cells in other candidate gNB-DU(s). The gNB-CU 408 may also provide the lower layer part of the reference configuration to the candidate gNB-DU(s) 406. The gNB-CU 408 may also provide an updated CSI resource configuration to the candidate gNB-DU(s) 406. It is to be noted that the candidate cell may be the same cell as source cell.

[0067] At 426, the candidate gNB-DU 406 responds with a UE CONTEXT MODIFICATION RESPONSE message including the updated lower layer configuration. The candidate gNB-DU 406 may also respond the updated CSI report configuration. At 428, the gNB-CU 408 sends a DL RRC MESSAGE TRANSFER message to the source gNB-DU 404, which includes the generated RRCReconfiguration message with the LTM configuration.

[0068] At 430, the source gNB-DU 404 forwards the received RRCReconfiguration message to the UE 402. At 432, the UE 402 responds to the source gNB-DU 404 with an RRCReconfigurationComplete message. At 434, the source gNB-DU 404 forwards the RRCReconfigurationCompletemessage to the gNB-CU 408 via an UL RRC MESSAGE TRANSFER message. At 436, early synchronization may be performed.

[0069] At 438 and 440, the candidate gNB-DU 406 sends the TA value, the associated CFRA resource information, the candidate cell ID and the source gNB-DU ID to the source gNB-DU 404 via a DU-CU TA information transfer message (represented as DU-CU TA INFORMATION TRANSFER message) and a CU-DU TA information transfer message (represented as CU-DU TA INFORMATION TRANSFER message), for which the source gNB-DU ID is omitted in the CU-DU TA INFORMATION TRANSFER message.

[0070] At 442, the UE 402 sends the LI measurement result to the source gNB-DU 404. At 444, the source gNB-DU 404 decides to execute LTM to a candidate target cell. At 446, the source gNB-DU 404 sends the Cell Switch command to the UE 402. At 448, the source gNB-DU 404 sends a DU-CU cell switch notification message (represented as DU-CU CELL SWITCH NOTIFICATION message) to the gNB-CU 408 to indicate the initiation of the Cell Switch command to the UE 402, for which the message includes the target cell ID and the TCI state ID.

[0071] At 450, the gNB-CU 408 forwards the target cell ID and the TCI state ID to the target gNB-DU in a CU-DU cell switch notification message (represented as CU-DU CELL SWITCH NOTIFICATION message). At 452, the target gNB-DU detects the UE access. It is to be noted that, regarding the step 452, the UE 402 may still perform the random access procedure towards the target cell, if TA is not available or is not valid.

[0072] At 454, the target gNB-DU sends the ACCESS SUCCESS message to the gNB-CU 408 with the target cell ID. At 456 the UE 402 sends an RRCReconfigurationComplete message to the target gNB-DU. At 458, the target gNB-DU forwards the RRCReconfigurationComplete message to the gNB-CU 408 via an UL RRC MESSAGE TRANSFER message. At 460, the gNB-CU 408 may send a UE context release command message (representedas UE CONTEXT RELEASE COMMAND message) to the source gNB-DU 404 to release the resources of prepared cells. At 462, the source gNB-DU 404 responds with a UE context release complete message (represented as UE CONTEXT RELEASE COMPLETE message).

[0073] FIG. 5 illustrates a procedure for LTM with a change of gNB-CU-UP within a gNB. As shown in FIG. 5, at 520, the source gNB-DU forwards the Measurement Report to the gNB-CU-CP. The procedure of FIG. 5 involves a source gNB-DU 502, a target gNB-DU 504, a gNB-CU-CP 506, a source gNB- CU-UP 508, and a target gNB-CU-UP 510.

[0074] At 522, the gNB-CU-CP 506 decides to initiate LTM configuration. At 524, the gNB-CU-CP 506 sends a bearer context setup request message (represented as BEARER CONTEXT SETUP REQUEST message) containing UL Transport Network Layer (TNL) address information for NG-U to setup the bearer context in the target gNB-CU-UP 510.

[0075] At 526, the target gNB-CU-UP 510 responds with a bearer context setup response message (represented as BEARER CONTEXT SETUP RESPONSE message) containing the UL TNL address information for Fl-U, DL TNL address information for NG-U, and the TNL address information for data forwarding to the target gNB-CU-UP 510.

[0076] At 528, LTM configuration procedures are performed between gNB- CU and candidate gNB-DUs, and between gNB-CU and the source gNB-DU 502 as specified from step 416 to step 426 of FIG. 4. At 530 and 532, the gNB- CU-CP 506 sends the RRC Reconfiguration message to the UE.

[0077] At 534, the UE sends the lower layer measurement result to the source gNB-DU 502, and the source gNB-DU 502 decides to execute LTM to a candidate target cell. At 536, the source gNB-DU 502 sends the DU-CU CELL SWITCH NOTIFICATION message to the gNB-CU-CP 506 with the selected target cell ID.

[0078] At 538 and 540, the gNB-CU-CP 506 performs the Bearer ContextModification procedure to retrieve the Packet Data Convergence Protocol (PDCP) UL / DL status and to exchange the TNL address information for data forwarding for the bearers. At 542 and 544, the gNB-CU-CP 506 performs the Bearer Context Modification procedure to send the DL TNL address information for Fl-U and the PDCP UP / DL status to the target gNB-CU-UP 510.

[0079] At 546, data forwarding may be performed from the source gNB-CU- UP 508 to the target gNB-CU-UP 510. At 548, the target gNB-DU 504 detects the UE in the target cell. It is to be noted that regarding the step 548, the UE may still perform random access procedure towards the target cell, if TA is not available or is not valid.

[0080] At 550, the target gNB-DU 504 sends an access success message (represented as ACCESS SUCCESS message) to the gNB-CU-CP 506. At 552 to 556, a path switch procedure is performed to update the DL TNL address information for the NG-U towards the core network. At 558 and 560, a Bearer Context Release procedure may be performed to release the UE context in the source gNB-DU 502.

[0081] Example embodiments will be discussed in detailed below with reference to the accompanying drawings.

[0082] FIG. 6 illustrates a signaling flow 600 for early timing advance acquisition according to some example embodiments of the present disclosure. For the purposes of discussion, the signaling flow 600 will be discussed with reference to FIG. 2. The signaling flow 600 may involve the first apparatus 210 and a second apparatus 606. The operations of the first apparatus 210 may be related to one or more terminal devices 220 and the third apparatus 230 in FIG. 2. It is to be understood that the signaling flow 600 may involves more apparatuses or less apparatuses, and the number of apparatuses illustrated in FIG. 6 is only for the purpose of illustration without suggesting any limitations.

[0083] As shown in FIG. 6, the first apparatus 210 determines (610)measurement information about TA acquisition in early TA acquisition procedures with respect to a source-candidate target pair of cells for LTM. The measurement information comprises a total number of TA acquisition requests for the source-candidate target pair of cells within a measurement period. In addition, depending on the timing of TA acquisitions, the measurement information further comprises a first number of successful TA acquisitions, a second number of successful late TA acquisitions for the source-candidate target pair of cells within the measurement period, or both of them.

[0084] The source-candidate target pair may include a serving cell for terminal devices and a candidate target cell for LTM of the terminal devices. The serving cell is provided by the first apparatus 210. The candidate target cell may be provided by the first apparatus 210 (in the case of intra-DU LTM procedure), or may be provided by a different apparatus, e.g., the third apparatus (in the case of inter-DU LTM procedure). The third apparatus 230 may be an apparatus different from the first apparatus 210. For example, if the first apparatus 210 is or is comprised in a distributed unit (DU) of a radio network device for a source cell in the LTM, and the third apparatus 230 may be or may be comprised in a further DU of the radio network device for the source cell in the LTM.

[0085] In some example embodiments, a counter with a first counter value may be used to determine the total number of TA acquisition requests. The first apparatus 210 may detect, within the measurement period, a successful transmission of a random access preamble intended for a candidate target cell 250 by the first apparatus 210 to the terminal device 220 connected to a source cell in an early TA acquisition procedure. Then, a first counter value is incremented by one, in accordance with the detection of the successful transmission of the random access preamble. The first apparatus 210 may determine, at an end of the measurement period, the total number of TA acquisition requests as the first counter value.

[0086] In some example embodiments, a counter with a second counter valuemay be used to determine the first number of successful TA acquisitions for an inter-network devices scenario. In some example embodiments where the LTM procedure for the source-candidate target pair is an inter-DU LTM procedure, the candidate target cell amongst the source-candidate target pair is provided by a different apparatus than the first apparatus 210. For example, the candidate target cell amongst the source-candidate target pair is the candidate target cell 250 provided by the third apparatus 230 which is different from the first apparatus 210. For the early TA acquisition during the inter-DU LTM procedure, the first apparatus 210 may receive TA information at the candidate target cell 250 from the third apparatus 230. Therefore, for the inter- DU LTM procedure, in accordance with a determination that the candidate target cell 250 is provided by the third apparatus 230, the first apparatus 210 may detect, within the measurement period, a successful reception of TA information at the candidate target cell 250 of the third apparatus 230 for the source-candidate target pair of cells from the third apparatus 230 before a cell switch command for the candidate target cell is sent to the terminal device 220 connected to a source cell of the first apparatus 210. In accordance with the detection of the successful reception of TA information before the cell switch command, a second counter value is incremented by one. The first apparatus 210 determines, at an end of the measurement period, the first number of successful TA acquisitions as the second counter value.

[0087] In some example embodiments, the TA information for the candidate target cell may comprise a TA value for the candidate target cell 250 within a TA information list information element (IE). For example, the TA information may be a centralized unit (CU)-DU TA INFORMATION TRANSFER message from a gNB-CU control plane (CP).

[0088] In some example embodiments, the counter with the second counter value may be further used to determine the first number of successful TA acquisitions for an intra-DU LTM scenario. In some example embodiments where the LTM procedure for the source-candidate target pair is an intra-DULTM procedure, the candidate target cell may be provided by the first apparatus 210. For the early TA acquisition during the intra-DU LTM procedure, the first apparatus 210 may receive TA information at the candidate target cell 250 from the first apparatus 210. Therefore, for the intra-DU LTM procedure, in accordance with a determination that the candidate target cell 250 for LTM is provided by the first apparatus 210, the first apparatus 210 may detect, within the measurement period, a successful TA acquisition at the candidate target cell for the source-candidate target pair of cells before the cell switch command for the candidate target cell is sent to a terminal device connected to a source cell. Then, the second counter may be incremented value by one, in accordance with the detection of the successful TA acquisition before the cell switch command. The first apparatus 210 may determine, at an end of the measurement period, the first number of successful TA acquisitions as the second counter value.

[0089] In some example embodiments, a counter with a third counter value may be used to determine the second number of successful late TA acquisitions for the inter-DU LTM scenario. For the inter-network devices procedure, in accordance with a determination that the candidate target cell 250 is provided by the third apparatus 230, the first apparatus 210 may detect, within the measurement period, a successful reception of TA information at the candidate target cell of the third apparatus 230 for the source-candidate target pair of cells from the third apparatus after a cell switch command for the candidate target cell is sent to a terminal device connected to a source cell of the first apparatus 210. Then, the third counter value may be incremented by one, in accordance with the detection of the successful reception of TA information after the cell switch command. The first apparatus 210 may determine, at an end of the measurement period, the second number of successful late TA acquisitions as the third counter value.

[0090] In some example embodiments, a counter with a third counter value may be used to determine the second number of successful late TA acquisitionsfor the intra-DU LTM scenario. For the intra-DU LTM procedure, in accordance with a determination that the candidate target cell 250 for LTM is provided by the first apparatus 210, the first apparatus 210 may detect, within the measurement period, a successful TA acquisition at the candidate target cell for the source-candidate target pair of cells after a cell switch command for the candidate target cell is sent to a terminal device connected to a source cell. Then, the third counter value may be incremented by one, in accordance with the detection of the successful TA acquisition after the cell switch command. The first apparatus 210 may determine, at an end of the measurement period, the second number of successful late TA acquisitions as the third counter value.

[0091] The first apparatus 210 transmits (620) the measurement information to a second apparatus 602 for evaluation of the TA acquisition for the sourcecandidate target pair of cells. The second apparatus 602 may be or may comprise any third-party tool for evaluation of the TA acquisition, for example, a core network function, an operations, administration, and maintenance (0AM) device, or a minimization of drive test (MDT) device.

[0092] In some example embodiments, the evaluation of the TA acquisition for the source-candidate target pair of cells may comprise a determination of a rate of successful TA acquisitions, and the rate of successful TA acquisitions may be determined by a ratio of the first number to the total number.

[0093] Alternatively, or in addition, the evaluation of the TA acquisition may comprise a determination of a rate of failure TA acquisitions, and the rate of failure TA acquisitions is determined by a ratio of a difference between the total number and the first number to the total number.

[0094] Alternatively, or in addition, the evaluation of the TA acquisition may comprise a determination of a rate of successful late TA acquisitions, and the rate of successful late TA acquisitions is determined by a ratio of the second number to the total number.

[0095] The results of the evaluation of the TA acquisition for the sourcecandidate target pair of cells may be utilized for various purposes, e.g., for network optimizations of the serving cell and / or the candidate target cell amongst the source-candidate target pair of cells.

[0096] In the following, some examples of measuring the total number of TA acquisition requests, the first number of successful TA acquisitions, and the second number of successful late TA acquisitions for the source-candidate target pair of cells are provided.

[0097] FIG. 7 illustrates an example flowchart 700 for determining the total number of TA acquisition requests according to some example embodiments of the present disclosure. The example flowchart 700 may be implemented by the first apparatus 210 of FIG. 2, for example, a source gNB-DU. The flowchart 700 may be considered as an example of measuring the total number of TA acquisition requests.

[0098] In the following, the measurement is based on the source gNB-DU for each source-candidate target pair of cells. The measurement is valid for the packet switched traffic and is applicable to a 5th Generation Mobile Communication System (5GS), while the measurement can further be applied in other systems. In addition, the measurement may be implemented for an intra gNB-DU LTM case or an inter gNB-DU LTM case. For the case of inter gNB-DU LTM case, the source gNB-DU and the candidate target gNB-DU are different devices. For the case of intra gNB-DU LTM, the source gNB-DU is also the candidate target gNB-DU.

[0099] The measurement of the flowchart 700 provides the total number of TA acquisition requests as part of the Early TA acquisition procedures for LTM.

[0100] At 702, a measurement period is started. At 704, an initial value of the total number of TA acquisition requests (i.e., the initial value of the first counter value, for example, MM.TAAckReqLTM=0).

[0101] At 706, during the measurement period, constantly detect the successful transmission of a random access preamble transmitted by the source gNB-DU to a UE for the early TA acquisition procedure. In some examples, NRCellDU and NRCellRelation are the measurement objects during the measurement period.

[0102] The random access preamble sending to the UE detected by the source gNB-DU may be related to the early TA acquisition procedure based on the procedures related to an LTM decision in a gNB-CU, which are followed by UE context modification for the impacted UE.

[0103] At 708, if a successful transmission of the random access preamble is detected, the first counter value is incremented by one. At 710, detect whether the measurement period is terminated. If the measurement period is not terminated, return to proceed 706 until the end of the measurement period.

[0104] At 712, if the measurement period is terminated, report the current first counter value (for example, the current value of MM.TAAckReqLTM) to a third party tool. The first counter value representing the measurement of the total number of TA acquisition requests should by an integer value.

[0105] FIG. 8 illustrates an example flowchart 800 for determining the first number of successful TA acquisitions according to some example embodiments of the present disclosure. The example flowchart 800 may be implemented by the first apparatus 210 of FIG. 2, for example, a source gNB- DU. The flowchart 800 may be considered as an example of measuring the first number of successful TA acquisitions.

[0106] The measurement of the flowchart 800 provides the first number of successful TA acquisitions as part of the early TA acquisition procedures for LTM, in the scenario where a possible Cell Switch Command has not been sent to the UE for a Candidate Cell ID of a candidate target cell.

[0107] At 802, a measurement period is started. At 804, an initial value of the first number of successful TA acquisitions (i.e., the initial value of thesecond counter value, for example, MM.TAAckSuccLTM=O) is predefined.

[0108] Then, an inter-gNB-DU LTM handover or an intra-gNB LTM handover is determined during the measurement period. At 806, for the inter- gNB LTM handover, determine whether a reception of a CU-DU TA INFORMATION TRANSFER message at the source gNB-DU from a gNB-CU CP with a TA Value within a TA Information List IE is successful, and a possible Cell Switch Command has not been yet sent to the UE for the Candidate Cell ID. If so, 810 is to be performed; otherwise, return to the step where the inter-gNB-DU LTM handover or the intra-gNB LTM handover is determined.

[0109] Furthermore, in case that the TA Information List IE contains the TA value for more than one Candidate Cell ID (i.e., the candidate target cell). The evaluation of the TA acquisition is done for each of the source-candidate target pair of cells, and the measurement is performed in the source gNB-DU per source and candidate target cell pair.

[0110] At 808, for the intra-gNB LTM handover, determine whether a reception of the TA acquisition per each Candidate Cell ID (i.e., the candidate target cell) is successful and a possible Cell Switch Command has not been yet sent to the UE for the Candidate Cell. The measurement is performed in the source gNB-DU per source and candidate target cell pair. If so, 810 is to be performed; otherwise, return to the step where the inter-gNB-DU LTM handover or the intra-gNB LTM handover is determined.[OHl] At 810, the second counter value is incremented by one. At 812, detect whether the measurement period is terminated. If the measurement period is not terminated, return to the step where the inter-gNB-DU LTM handover or the intra-gNB LTM handover is determined until the end of the measurement period.

[0112] In some examples, NRCellDU and NRCellRelation are the measurement objects during the measurement period.

[0113] At 812, if the measurement period is terminated, report the current second counter value (for example, the current value of MM.TAAckSuccLTM) to a third party tool. The second counter value representing the measurement of the first number of successful TA acquisitions should by an integer value.

[0114] FIG. 9 illustrates an example flowchart 900 for determining the second number of successful late TA acquisitions according to some example embodiments of the present disclosure. The example flowchart 900 may be implemented by the first apparatus 210 of FIG. 2, for example, a source gNB- DU. The flowchart 900 may be considered as an example of measuring the second number of successful late TA acquisitions.

[0115] The measurement of the flowchart 900 provides the second number of successful but late TA acquisitions as part of the early TA acquisition procedures for LTM, in the scenario where a possible Cell Switch Command has been sent to the UE for the Candidate Cell ID.

[0116] At 902, a measurement period is started. At 904, an initial value of the second number of successful TA late acquisitions (i.e., the initial value of the third counter value, for example, MM.TAAckSuccLateLTM=0) is predefined.

[0117] Then, an inter-gNB-DU LTM handover or an intra-gNB LTM handover is determined during the measurement period. At 906, for the inter- gNB LTM handover, determine whether a reception of a CU-DU TA INFORMATION TRANSFER message at the source gNB-DU from a gNB-CU CP with a TA Value within a TA Information List IE is successful, but a Cell Switch Command has been already sent to the UE for the Candidate Cell ID. If so, 910 is to be performed; otherwise, return to the step where the inter- gNB-DU LTM handover or the intra-gNB LTM handover is determined.

[0118] Furthermore, in case that the TA Information List IE contains the TA value for more than one Candidate Cell ID (i.e., the candidate target cell). The evaluation of the TA acquisition is done for each of the source-candidate targetpair of cells, and the measurement is performed in the source gNB-DU per source and candidate target cell pair.

[0119] At 908, for the intra-gNB LTM handover, determine whether a reception of the TA acquisition per each Candidate Cell ID (i.e., the candidate target cell) is successful, but a Cell Switch Command has been already sent to the UE for the Candidate Cell. The measurement is performed in the source gNB-DU per source and candidate target cell pair. If so, 910 is to be performed; otherwise, return to the step where the inter-gNB-DU LTM handover or the intra-gNB LTM handover is determined.

[0120] At 910, the third counter value is incremented by one. At 912, detect whether the measurement period is terminated. If the measurement period is not terminated, return to the step where the inter-gNB-DU LTM handover or the intra-gNB LTM handover is determined until the end of the measurement period.

[0121] In some examples, NRCellDU and NRCellRelation are the measurement objects during the measurement period.

[0122] At 912, if the measurement period is terminated, report the current third counter value (for example, the current value of MM.TAAckSuccLateLTM) to a third party tool. The third counter value representing the measurement of the second number of successful late TA acquisitions should by an integer value.

[0123] In some example embodiments, after the total number of TA acquisition requests is determined, and at least one of the first number of successful TA acquisitions, or the second number of successful late TA acquisitions is determined, the validity of the early TA acquisition procedure for LTM may be determined as a probability of the successful early TA acquisitions (or efficiency of the early TA acquisitions, also referred to as the rate of successful TA acquisitions), a probability of failure TA acquisitions (also referred to as the rate of failure TA acquisitions), or as a probability ofthe successful but late TA acquisitions (also referred to as the rate of successful late TA acquisitions).

[0124] For example, the rate of successful TA acquisitions may be evaluated as a ratio of the number of successful TA acquisitions for the candidate target LTM cell to the total number of TA acquisition requests for the candidate target LTM cell (i.e., a ratio of the first number to the total number). As for successful TA acquisitions for the candidate target LTM cell to distinguish between the so called “on time” and “late” cases, a measurement to monitor a type of failure (i.e., the late TA acquisition) is proposed. The rate of failure TA acquisitions may be evaluated as a ratio of the different between the total number of TA acquisition requests for the candidate target LTM cell and the number of successful TA acquisitions for the candidate target LTM cell to the total number of TA acquisition requests for the candidate target LTM cell (i.e., a ratio of a difference between the total number and the first number to the total number).

[0125] Similarly, the rate of successful late TA acquisitions may be evaluated as a ratio of the number of successful but late TA acquisitions for the candidate target LTM cell to the total number of TA acquisition requests for the candidate target LTM cell (i.e., a ratio of the second number to the total number).

[0126] Furthermore, LTM is a procedure where a gNB receives LI measurement report(s) from a UE and signals a cell switch command to the UE via a MAC CE to change its serving cell. This command indicates an LTM candidate cell configuration that the gNB previously prepared and it may be provided to the UE via RRC signaling. As a result, the UE may be switched to the candidate target cell according to the command. The LTM procedure can be used to reduce the mobility latency.

[0127] When configured by the network, it is possible to initiate UL TA acquisition procedure to one or multiple cells that are different from the currentserving cell. For instance, the network may request the UE to perform early TA acquisition of a candidate target cell before a cell switch. The early TA acquisition is triggered by the CFRA in such a way that the UE sends MSG1 towards the candidate target cell, without monitoring for a response from the candidate target cell. The TA validity may be fully hidden from the UE, and thus cannot be reported via any UE report (nor in Random Access Channel (RACH) report) to the network.

[0128] Therefore, the embodiments of the present disclosure present this scheme to monitor the validity of the early TA acquisition procedure for LTM with the “number of successful TA acquisitions for the candidate target LTM cell”, “number of successful late TA acquisitions for the candidate target LTM cell” and “total number of TA acquisition requests for the candidate target LTM cell”. In this way, the rate of the successful early TA acquisition, the rate of failure TA acquisitions, or the rate of successful late TA acquisitions may be evaluated so that some appropriate action may be taken to optimize the LTM configuration and RACH in the candidate target cells.

[0129] FIG. 10 shows a flowchart of an example method 1000 implemented at a first apparatus in accordance with some example embodiments of the present disclosure. For the purpose of discussion, the method 1000 will be described from the perspective of the first apparatus 210 in FIG. 2.

[0130] At block 1010, determining measurement information about timing advance (TA) acquisition in early TA acquisition procedures with respect to a source-candidate target pair of cells for layer 1 / layer 2 (L1 / L2) triggered mobility (LTM), the measurement information comprises a total number of TA acquisition requests for the source-candidate target pair of cells within a measurement period, and at least one of the following: a first number of successful TA acquisitions, or a second number of successful late TA acquisitions for the source-candidate target pair of cells within the measurement period.

[0131] At block 1020, transmitting the measurement information to a second apparatus for evaluation of the TA acquisition for the source-candidate target pair of cells.

[0132] In some example embodiments, the method 1000 further comprises: detecting, within the measurement period, a successful transmission of a random access preamble intended for a candidate target cell by the first apparatus to a terminal device connected to a source cell in an early TA acquisition procedure; in accordance with the detection of the successful transmission of the random access preamble, incrementing a first counter value by one; and determining, at an end of the measurement period, the total number of TA acquisition requests as the first counter value.

[0133] In some example embodiments, the method 1000 further comprises: in accordance with a determination that the candidate target cell is provided by a third apparatus different from the first apparatus, detecting, within the measurement period, a successful reception of TA information at the candidate target cell of the third apparatus for the source-candidate target pair of cells from the third apparatus before a cell switch command for the candidate target cell is sent to a terminal device connected to a source cell of the first apparatus; in accordance with the detection of the successful reception of TA information before the cell switch command, incrementing a second counter value by one; and determining, at an end of the measurement period, the first number of successful TA acquisitions as the second counter value.

[0134] In some example embodiments, the method 1000 further comprises: in accordance with a determination that the candidate target cell for the LTM is provided by the first apparatus, detecting, within the measurement period, a successful TA acquisition at the candidate target cell for the source-candidate target pair of cells before the cell switch command for the candidate target cell is sent to a terminal device connected to a source cell; in accordance with the detection of the successful TA acquisition before the cell switch command, incrementing the second counter value by one; and determining, at an end ofthe measurement period, the first number of successful TA acquisitions as the second counter value.

[0135] In some example embodiments, the method 1000 further comprises: in accordance with a determination that the candidate target cell is provided by a third apparatus different from the first apparatus, detecting, within the measurement period, a successful reception of TA information at the candidate target cell of the third apparatus for the source-candidate target pair of cells from the third apparatus after a cell switch command for the candidate target cell is sent to a terminal device connected to a source cell of the first apparatus; in accordance with the detection of the successful reception of TA information after the cell switch command, incrementing a third counter value by one; and determining, at an end of the measurement period, the second number of successful late TA acquisitions as the third counter value.

[0136] In some example embodiments, the method 1000 further comprises: in accordance with a determination that the candidate target cell for the LTM is provided by the first apparatus, detecting, within the measurement period, a successful TA acquisition at the candidate target cell for the source-candidate target pair of cells after a cell switch command for the candidate target cell is sent to a terminal device connected to a source cell; in accordance with the detection of the successful TA acquisition after the cell switch command, incrementing the third counter value by one; and determining, at an end of the measurement period, the second number of successful late TA acquisitions as the third counter value.

[0137] In some example embodiments, the evaluation of the TA acquisition for the source-candidate target pair of cells comprises a determination of at least one of the following: a rate of successful TA acquisitions, a rate of failure TA acquisitions, or a rate of successful late TA acquisitions, where the rate of successful TA acquisitions is determined by a ratio of the first number to the total number, the rate of failure TA acquisitions is determined by a ratio of a difference between the total number and the first number to the total number,and the rate of successful late TA acquisitions is determined by a ratio of the second number to the total number.

[0138] In some example embodiments, the TA information for the candidate target cell comprises a TA value for the candidate target cell within a TA information list information element.

[0139] In some example embodiments, the first apparatus comprises a distributed unit (DU) of a radio network device for a source cell in the LTM, where the second apparatus comprises a core network function, an operations, administration, and maintenance (0AM) device, or a minimization of drive test (MDT) device, and wherein the third apparatus comprises a further DU of the radio network device for the source cell in the LTM.

[0140] In some example embodiments, a first apparatus capable of performing any of the method 1000 (for example, the first apparatus 210 in FIG. 2 may comprise means for performing the respective operations of the method 1000. 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 210 in FIG. 2.

[0141] In some example embodiments, the first apparatus comprises means for determining measurement information about timing advance (TA) acquisition in early TA acquisition procedures with respect to a sourcecandidate target pair of cells for layer 1 / layer 2 (L1 / L2) triggered mobility (LTM), where the measurement information comprises a total number of TA acquisition requests for the source-candidate target pair of cells within a measurement period, and at least one of the following: a first number of successful TA acquisitions, or a second number of successful late TA acquisitions for the source-candidate target pair of cells within the measurement period; and means for transmitting the measurement information to a second apparatus for evaluation of the TA acquisition for the source-candidate target pair of cells.

[0142] In some example embodiments, the first apparatus further comprises: means for detecting, within the measurement period, a successful transmission of a random access preamble intended for a candidate target cell by the first apparatus to a terminal device connected to a source cell in an early TA acquisition procedure; means for, in accordance with the detection of the successful transmission of the random access preamble, incrementing a first counter value by one; and means for determining, at an end of the measurement period, the total number of TA acquisition requests as the first counter value.

[0143] In some example embodiments, the first apparatus further comprises: means for, in accordance with a determination that the candidate target cell is provided by a third apparatus different from the first apparatus, detecting, within the measurement period, a successful reception of TA information at the candidate target cell of the third apparatus for the source-candidate target pair of cells from the third apparatus before a cell switch command for the candidate target cell is sent to a terminal device connected to a source cell of the first apparatus; means for, in accordance with the detection of the successful reception of TA information before the cell switch command, incrementing a second counter value by one; and means for determining, at an end of the measurement period, the first number of successful TA acquisitions as the second counter value.

[0144] In some example embodiments, the first apparatus further comprises: means for, in accordance with a determination that the candidate target cell for the LTM is provided by the first apparatus, detecting, within the measurement period, a successful TA acquisition at the candidate target cell for the sourcecandidate target pair of cells before the cell switch command for the candidate target cell is sent to a terminal device connected to a source cell; means for, in accordance with the detection of the successful TA acquisition before the cell switch command, incrementing the second counter value by one; and means for determining, at an end of the measurement period, the first number ofsuccessful TA acquisitions as the second counter value.

[0145] In some example embodiments, the first apparatus further comprises: means for, in accordance with a determination that the candidate target cell is provided by a third apparatus different from the first apparatus, detecting, within the measurement period, a successful reception of TA information at the candidate target cell of the third apparatus for the source-candidate target pair of cells from the third apparatus after a cell switch command for the candidate target cell is sent to a terminal device connected to a source cell of the first apparatus; means for, in accordance with the detection of the successful reception of TA information after the cell switch command, incrementing a third counter value by one; and means for determining, at an end of the measurement period, the second number of successful late TA acquisitions as the third counter value.

[0146] In some example embodiments, the first apparatus further comprises: means for, in accordance with a determination that the candidate target cell for the LTM is provided by the first apparatus, detecting, within the measurement period, a successful TA acquisition at the candidate target cell for the sourcecandidate target pair of cells after a cell switch command for the candidate target cell is sent to a terminal device connected to a source cell; means for, in accordance with the detection of the successful TA acquisition after the cell switch command, incrementing the third counter value by one; and means for determining, at an end of the measurement period, the second number of successful late TA acquisitions as the third counter value.

[0147] In some example embodiments, the evaluation of the TA acquisition for the source-candidate target pair of cells comprises a determination of at least one of the following: a rate of successful TA acquisitions, a rate of failure TA acquisitions, or a rate of successful late TA acquisitions; where the rate of successful TA acquisitions is determined by a ratio of the first number to the total number, the rate of failure TA acquisitions is determined by a ratio of a difference between the total number and the first number to the total number,and the rate of successful late TA acquisitions is determined by a ratio of the second number to the total number.

[0148] In some example embodiments, the TA information for the candidate target cell comprises a TA value for the candidate target cell within a TA information list information element.

[0149] In some example embodiments, the first apparatus comprises a distributed unit (DU) of a radio network device for a source cell in the LTM, wherein the second apparatus comprises a core network function, an operations, administration, and maintenance (0AM) device, or a minimization of drive test (MDT) device, and wherein the third apparatus comprises a further DU of the radio network device for the source cell in the LTM.

[0150] In some example embodiments, the first apparatus further comprises means for performing other operations in some example embodiments of the method 1000 or the first apparatus 210. In some example embodiments, the means comprises at least one processor; and at least one memory storing instructions that, when executed by the at least one processor, cause the performance of the first apparatus.

[0151] FIG. 11 is a simplified block diagram of a device 1100 that is suitable for implementing example embodiments of the present disclosure. The device 1100 may be provided to implement a communication device, for example, the first apparatus 210, the terminal device 220, or the third apparatus 230 as shown in FIG. 2 or the second apparatus 602 in FIG. 6. As shown, the device 1100 includes one or more processors 1110, one or more memories 1120 coupled to the processor 1110, and one or more communication modules 1140 coupled to the processor 1110.

[0152] The communication module 1140 is for bidirectional communications. The communication module 1140 has one or more communication interfaces to facilitate communication with one or more other modules or devices. The communication interfaces may represent any interfacethat is necessary for communication with other network elements. In some example embodiments, the communication module 1140 may include at least one antenna.

[0153] The processor 1110 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 1100 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.

[0154] The memory 1120 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) 1124, 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) 1122 and other volatile memories that will not last in the power-down duration.

[0155] A computer program 1130 includes computer executable instructions that are executed by the associated processor 1110. The instructions of the program 1130 may include instructions for performing operations / acts of some example embodiments of the present disclosure. The program 1130 may be stored in the memory, e.g., the ROM 1124. The processor 1110 may perform any suitable actions and processing by loading the program 1130 into the RAM 1122.

[0156] The example embodiments of the present disclosure may be implemented by means of the program 1130 so that the device 1100 may perform any process of the disclosure as discussed with reference to FIG. 1 toFIG. 10. The example embodiments of the present disclosure may also be implemented by hardware or by a combination of software and hardware.

[0157] In some example embodiments, the program 1130 may be tangibly contained in a computer readable medium which may be included in the device 1100 (such as in the memory 1120) or other storage devices that are accessible by the device 1100. The device 1100 may load the program 1130 from the computer readable medium to the RAM 1122 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).

[0158] FIG. 12 shows an example of the computer readable medium 1200 which may be in form of CD, DVD or other optical storage disk. The computer readable medium 1200 has the program 1130 stored thereon.

[0159] 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.

[0160] 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 computerprogram product includes computer-executable 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.

[0161] 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.

[0162] 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.

[0163] 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 computerreadable 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.

[0164] 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 separately or in any suitable sub-combination.

[0165] 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

CLAIMS:

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 at least to: determine measurement information about timing advance (TA) acquisition in early TA acquisition procedures with respect to a sourcecandidate target pair of cells for layer 1 / layer 2 (L1 / L2) triggered mobility (LTM), wherein the measurement information comprises a total number of TA acquisition requests for the source-candidate target pair of cells within a measurement period, and at least one of the following: a first number of successful TA acquisitions, or a second number of successful late TA acquisitions for the source-candidate target pair of cells within the measurement period; and transmit the measurement information to a second apparatus for evaluation of the TA acquisition for the source-candidate target pair of cells.

2. The first apparatus of claim 1, wherein the first apparatus is caused to: detect, within the measurement period, a successful transmission of a random access preamble intended for a candidate target cell by the first apparatus to a terminal device connected to a source cell in an early TA acquisition procedure; in accordance with the detection of the successful transmission of the random access preamble, increment a first counter value by one; and determine, at an end of the measurement period, the total number of TA acquisition requests as the first counter value.

3. The first apparatus of claim 1 or 2, wherein the first apparatus is caused to: in accordance with a determination that the candidate target cell is providedby a third apparatus different from the first apparatus, detect, within the measurement period, a successful reception of TA information at the candidate target cell of the third apparatus for the source-candidate target pair of cells from the third apparatus before a cell switch command for the candidate target cell is sent to a terminal device connected to a source cell of the first apparatus; in accordance with the detection of the successful reception of TA information before the cell switch command, increment a second counter value by one; and determine, at an end of the measurement period, the first number of successful TA acquisitions as the second counter value.

4. The first apparatus of any of claims 1 to 3, wherein the first apparatus is caused to: in accordance with a determination that the candidate target cell for the LTM is provided by the first apparatus, detect, within the measurement period, a successful TA acquisition at the candidate target cell for the source-candidate target pair of cells before the cell switch command for the candidate target cell is sent to a terminal device connected to a source cell; in accordance with the detection of the successful TA acquisition before the cell switch command, increment the second counter value by one; and determine, at an end of the measurement period, the first number of successful TA acquisitions as the second counter value.

5. The first apparatus of any of claims 1 to 4, wherein the first apparatus is caused to: in accordance with a determination that the candidate target cell is provided by a third apparatus different from the first apparatus, detect, within the measurement period, a successful reception of TA information at the candidate target cell of the third apparatus for the source-candidate target pair of cells from the third apparatus after a cell switch command for the candidate target cell is sent to a terminal device connected to a source cell of the first apparatus;in accordance with the detection of the successful reception of TA information after the cell switch command, increment a third counter value by one; and determine, at an end of the measurement period, the second number of successful late TA acquisitions as the third counter value.

6. The first apparatus of any of claims 1 to 5, wherein the first apparatus is caused to: in accordance with a determination that the candidate target cell for the LTM is provided by the first apparatus, detect, within the measurement period, a successful TA acquisition at the candidate target cell for the source-candidate target pair of cells after a cell switch command for the candidate target cell is sent to a terminal device connected to a source cell; in accordance with the detection of the successful TA acquisition after the cell switch command, increment the third counter value by one; and determine, at an end of the measurement period, the second number of successful late TA acquisitions as the third counter value.

7. The first apparatus of any of claims 1 to 6, wherein the evaluation of the TA acquisition for the source-candidate target pair of cells comprises a determination of at least one of the following: a rate of successful TA acquisitions, a rate of failure TA acquisitions, or a rate of successful late TA acquisitions; wherein the rate of successful TA acquisitions is determined by a ratio of the first number to the total number, the rate of failure TA acquisitions is determined by a ratio of a difference between the total number and the first number to the total number, and the rate of successful late TA acquisitions is determined by a ratio of the second number to the total number.

8. The first apparatus of claim 3 or 5, wherein the TA information for the candidate target cell comprises a TA value for the candidate target cell within a TAinformation list information element.

9. The first apparatus of any of claims 1 to 8, wherein the first apparatus comprises a distributed unit (DU) of a radio network device for a source cell in the LTM, wherein the second apparatus comprises a core network function, an operations, administration, and maintenance (0AM) device, or a minimization of drive test (MDT) device, and wherein the third apparatus comprises a further DU of the radio network device for the source cell in the LTM.

10. A method comprising: determining measurement information about timing advance (TA) acquisition in early TA acquisition procedures with respect to a sourcecandidate target pair of cells for layer 1 / layer 2 (L1 / L2) triggered mobility (LTM), wherein the measurement information comprises a total number of TA acquisition requests for the source-candidate target pair of cells within a measurement period, and at least one of the following: a first number of successful TA acquisitions, or a second number of successful late TA acquisitions for the source-candidate target pair of cells within the measurement period; and transmitting the measurement information to a second apparatus for evaluation of the TA acquisition for the source-candidate target pair of cells.I L A first apparatus comprising: means for determining measurement information about timing advance(TA) acquisition in early TA acquisition procedures with respect to a source-candidate target pair of cells for layer 1 / layer 2 (L1 / L2) triggered mobility (LTM), wherein the measurement information comprises a total number of TA acquisition requests for the source-candidate target pair of cells within a measurement period, and at least one of the following: a first number of successful TA acquisitions, or a second number of successful late TA acquisitions for the source-candidate target pair of cells within the measurement period; and means for transmitting the measurement information to a second apparatus for evaluation of the TA acquisition for the source-candidate target pair of cells.

12. A computer readable medium comprising instructions stored thereon for causing an apparatus at least to perform the method of claim 10.

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