Timing advance (TA) processing time information

Abstract

Example embodiments of the present disclosure are directed to timing advance (TA) processing time information. The method comprises initiating, a source distributed unit (DU), an early TA acquisition of a target cell associated with a target DU by requesting a user device, to send a random access (RA) preamble to the target DU; receiving, from a centralized unit (CU), along with TA information for the user device, a TA processing time information at least associated with a first TA processing time of the target DU and a second TA processing time of the CU; and determining, in case of a cell switch command, from the source DU to the user device, without the TA information or a case of a failed random access channel (RACH)-less cell switch, based on the TA processing time information, a latency of the early TA acquisition that is caused by processing at the target DU and the CU.

Description

TIMING ADVANCE (TA) PROCESSING TIME INFORMATIONFIELDS

[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 timing advance (TA) processing time information.BACKGROUND

[0002] L1 / L2 Triggered Mobility (LTM) is a procedure in which a network device receives LI measurement report(s) from a user device, and on their basis the network device changes a serving cell of the user device by a cell switch command signaled via a medium access control -control element (MAC CE). The cell switch command indicates an LTM candidate cell configuration that the network device previously prepared and provided to the user device through RRC signaling. Then the user device switches to the target cell according to the cell switch command. The LTM procedure can be used to reduce the mobility latency.SUMMARY

[0003] In a first aspect of the present disclosure, there is provided an 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 apparatus at least to: initiate an early TA acquisition of a target cell associated with a target distributed unit (DU) by requesting a user device, to send a random access (RA) preamble to the target DU; receive, from a centralized unit (CU), along with TA information for the user device, a TA processing time information at least associated with a first TA processing time of the target DU and a second TA processing time of the CU; and determine, in case of a cell switch command, from the apparatus to the user device, without the TA information or a case of a failed random access channel (RACH)-less cell switch, based on the TA processing time information, a latency of the early TA acquisition that is caused by processing at the target DU and the CU. i

[0004] In a second aspect of the present disclosure, there is provided an 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 apparatus at least to: during early TA acquisition of a target cell associated with a target DU , transmit, to a source DU, along with TA information for the user device, a TA processing time information at least associated with a first TA processing time of the target DU and a second TA processing time of the apparatus.

[0005] In a third aspect of the present disclosure, there is provided a method. The method comprises: initiating, by a source DU, an early TA acquisition of a target cell associated with a target DU by requesting a user device, to send a RA preamble to the target DU; receiving, from a CU, along with TA information for the user device, a TA processing time information at least associated with a first TA processing time of the target DU and a second TA processing time of the CU; and determining, in case of a cell switch command, from the source DU to the user device, without the TA information or a case of a failed RACH-less cell switch, based on the TA processing time information, a latency of the early TA acquisition that is caused by processing at the target DU and the CU.

[0006] In a fourth aspect of the present disclosure, there is provided a method. The method comprises: during early TA acquisition of a target cell associated with a target DU, transmitting, from a CU to a source DU, along with TA information for the user device, a TA processing time information at least associated with a first TA processing time of the target DU and a second TA processing time of the CU.

[0007] In a fifth aspect of the present disclosure, there is provided an apparatus. The apparatus comprises means for initiating an early TA acquisition of a target cell associated with a target DU by requesting a user device, to send a RA preamble to the target DU; means for receiving, from a CU, along with TA information for the user device, a TA processing time information at least associated with a first TA processing time of the target DU and a second TA processing time of the CU; and means for determining, in case of a cell switch command, from the apparatus to the user device, without the TA information or a case of a failed RACH-less cell switch, based on the TA processing time information, a latency of the early TA acquisition that is caused by processing at the target DU and the CU.

[0008] In a sixth aspect of the present disclosure, there is provided an apparatus. The apparatus comprises means for, during early TA acquisition of a target cell associated with a target DU , transmitting, to a source DU, along with TA information for the user device, a TA processing time information at least associated with a first TA processing time of the target DU and a second TA processing time of the apparatus.

[0009] In a seventh 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 third aspect.

[0010] In an eighth 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 fourth aspect.

[0011] 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

[0012] Some example embodiments will now be described with reference to the accompanying drawings, where:

[0013] FIG. 1 illustrates an example communication environment in which example embodiments of the present disclosure can be implemented;

[0014] FIG. 2 illustrates a signaling chart of communication according to some example embodiments of the present disclosure;

[0015] FIG. 3 illustrates a signaling chart of communication according to some example embodiments of the present disclosure;

[0016] FIG. 4 illustrates a flowchart of a method implemented at an apparatus in accordance with some example embodiments of the present disclosure;

[0017] FIG. 5 illustrates a flowchart of a method implemented at an apparatus in accordance with some example embodiments of the present disclosure;

[0018] FIG. 6 illustrates a simplified block diagram of a device that is suitable for implementing example embodiments of the present disclosure; and

[0019] FIG. 7 illustrates a block diagram of an example computer readable medium in accordance with some example embodiments of the present disclosure.

[0020] Throughout the drawings, the same or similar reference numerals represent the same or similar element.DETAILED DESCRIPTION

[0021] 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.

[0022] 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.

[0023] 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.

[0024] 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 firstelement, 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.

[0025] 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.

[0026] 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.

[0027] 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.

[0028] 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) foroperation, but the software may not be present when it is not needed for operation.

[0029] 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.

[0030] 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.

[0031] 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 earthorbit (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 base station toward the next-hop IAB node.

[0032] 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.

[0033] 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 bothfrequency 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.

[0034] FIG. 1 illustrates an example communication environment 100 in which example embodiments of the present disclosure can be implemented. The communication environment 100 comprises network nodes, such as a gNB CU 110, a first gNB DU 120 and a second gNB DU 130. In some cases, both the first gNB DU 120 and the second gNB DU 130 may be managed and controlled by the gNB CU 110. It is to be understood that the first gNB DU 120 and the second gNB DU 130 may also be managed by different gNB CUs. In the communication environment 100, the gNB CU 110 can communicate with the first gNB DU 120 and the second gNB DU 130.

[0035] The communication environment 100 further comprises a user device 140 (e.g., a UE). During a cell switch procedure, the user device 140 may switch from a first cell 102 associated with the first gNB DU 120 to a second cell 104 associated with the second gNB DU 120. In this scenario, the first cell 102 may be considered a source cell of the cell switch procedure and the first gNB DU 120 may be considered as the source gNB DU, while the second cell 104 may be considered a target cell of the cell switch procedure and the second gNB DU 130 may be considered as the target gNB DU.

[0036] It is to be understood that the number of devices and their connections shown in FIG. 1 are only for the purpose of illustration without suggesting any limitation. The communication environment 100 may include any suitable number of devices configured to implementing example embodiments of the present disclosure.

[0037] Although not shown, it would be appreciated that one or more additional devices may be located in the cell 102 or 104, and one or more additional cells may be deployed in the communication environment 100.

[0038] In some example embodiments, a link from the network node to the user device 140 is referred to as a downlink (DL), while a link from the user device 140 to the network node is referred to as an uplink (UL). In DL, the network node is a transmitting (TX) device (or a transmitter) and the user device 140 is a receiving (RX) device (or a receiver). In UL, the user device 140 is a TX device (or a transmitter) and the network node is a RX device (or a receiver).

[0039] Communications in the communication environment 100 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.

[0040] When a UE moves from the coverage area of a cell to another cell (e.g., from the cell 102 to the cell 104), a serving cell change needs to be performed at some point. Currently serving cell change may be triggered by Layer 3 (L3) measurements (i.e., a Radio Resource Control (RRC) measurement report from the UE) and may be done by downlink RRC signaling, i.e., an 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 Layer (L2) (and Layer (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.

[0041] 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 (CSC) signaled via a MAC CE. The cell switch command may indicate an LTM candidate cell configuration that the gNB previously prepared and provided to the UE through an RRC signaling. Then the user device 140 switches to the target cell (e.g., the cell 104) according to the cell switch command. The LTM procedure can be used to reduce the mobility latency.

[0042] When configured by the network, it is possible to activate TransmissionConfiguration Indicator (TCI) states of one or multiple cells that are different from the current serving cell (e.g., the cell 102). For instance, the TCI states of the LTM candidate cells can be activated in advance before any of those cells become the serving cell. This allows the UE to be DL synchronized with those cells, thereby facilitating a faster cell switch to one of those cells when cell switch is triggered.

[0043] When configured by the network, it is possible to initiate UL Timing Advance (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 is triggered by Physical Downlink Control Channel (PDCCH) order or realized through UE -based TA measurement. In the former case, the gNB to which the candidate cell belongs may calculate the TA value and send it to the gNB to which the serving cell belongs. The serving cell may send the TA value in the LTM cell switch command MAC CE when triggering LTM cell switch. In the latter case, the UE may apply the TA value measured by itself and perform RACH-less LTM upon receiving the cell switch command.

[0044] If UE-based TA measurement is configured, a UE may perform RACH-less LTM upon receiving the cell switch command. Otherwise, the UE may determine whether to access the target cell with the RA procedure depending on whether a TA value is provided in the cell switch command. For RACH-less LTM, the UE may access the target cell via a configured grant provided in the LTM candidate cell configuration and select 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 may monitor the PDCCH for dynamic scheduling from the target cell upon LTM cell switch. Before RACH-less LTM procedure completion, the UE may not trigger random access procedure if it does not have a valid Physical Uplink Control Channel (PUCCH) resource for triggered scheduling requests.

[0045] It is to be understood that the procedure of L1 / L2 based inter-cell mobility are applicable to standalone, carrier aggregation (CA) and new radio-dual connection (NR- DC) case with serving cell change within one Configured Grant (CG) scenario.

[0046] In nutshell, to facilitate a faster cell switch it is possible to initiate 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 acandidate cell before a cell switch for intra-gNB-DU LTM and inter-gNB-DU LTM, respectively. The same applies also for LTM with the change of gNB-CU-UP. The TA acquisition may be then successfully completed on transmission of the TA value of the candidate cell via a CU-DU TA INFORMATION TRANSFER message for inter gNB-DU LTM or on internal transmission within the gNB-DU which is acting as source and target for intra gNB-DU LTM scenario.

[0047] The LTM handover may be then triggered by sending a Cell Switch Command message to UE as outcome of the LTM decision done in source gNB-DU for inter gNB- DU LTM or within the same gNB-DU for intra gNB-DU LTM scenario.

[0048] Depending on the availability of a valid TA value, the UE may perform either a RACH-less LTM or RACH-based LTM cell switch. If the TA value is provided in the cell switch command, the UE may apply the TA value as instructed by the network. In the case where UE-based TA measurement is configured, but no TA value is provided in the cell switch command, the UE may apply the TA value by itself if available. Meanwhile, the UE may perform a RACH-less LTM cell switch upon receiving the cell switch command. If no valid TA value is available, the UE may perform a RACH-based LTM cell switch.

[0049] For the random-access procedure towards a cell other than the current serving cell, e.g. for an early UL TA acquisition for an LTM candidate cell before LTM cell switch, Contention Free Resource Allocation (CFRA) is triggered. The UE sends Message 1 (MSG1) towards the candidate cell without monitoring for a response from the target cell.

[0050] In the case where the network provides the TA value to the UE, the UE doesn’t maintain the TA timer for the candidate cell and relies completely on network implementation to guarantee the TA validity. The TA validity is fully hidden for UE and thus cannot be reported via any UE report (nor in RACH report) to the network. The monitoring of the early TA acquisition procedure is however essential to optimize the LTM. It is to be noted that UE has just one attempt to send the preamble for TA acquisition and since random access response (RAR) including TA information is sent back to source node, the UE is not taking care of what happens afterwards and has no opportunity to correct / update the TA value. The target gNB DU either receives the preamble correctly and evaluate the TA or receive the preamble but not able to evaluate the TA or does not receive the preamble at all.

[0051] As mentioned above, the most critical aspect of the LTM is that the UE has gotthe correct TA for the moment of the MAC-CE triggered cell switch, i.e. the right timing of the early TAA in relation to the CSC.

[0052] In case the TAA is not completed before the CSC, the UE may be forced to do a normal RACH towards the candidate cell, leading to delays in RACH succeeding and losing the advantage of the LTM mobility procedure. Similarly, the chances of RACH failing also increase. So, it is critical to have the correct value of the TA at the right time at the UE for the overall LTM mobility procedure to succeed.

[0053] Both events TAA and CSC are triggered by the serving gNB / DU, i.e., by a gNB / DU internal trigger criteria for those events, and this timing needs to be optimized.

[0054] The TAA needs to be triggered early enough that TA information has been arrived from target node before CSC is triggered. If the TA information did not arrive before CSC is triggered, it would be declared as “Too Late TAA”, and Self-Organized Network (SON) may after some statistical significance of this issue change TAA trigger criterion in the source gNB / DU.

[0055] The problem being addressed here is case that a delayed arrival of TA information at source node could be caused by (temporary) computational overload situation at target node, which would misdirect the SON algorithm, and therefore these failure cases where the delay was introduced by the network itself need to be detected and excluded from SON algorithm.

[0056] Hereinafter, “False identification of too late triggered Early TA acquisition” may be relevant to inter DU LTM scenario, which may be caused by processing and computing power in the involved network elements and not to the trigger criterion for the TAA to be optimized by SON. Therefore, such “False identification of too late triggered Early TA acquisition” needs to be identified and excluded from the SON method for TAA optimization.

[0057] In accordance with some example embodiments of the present disclosure, there is provided a solution for late triggered early TA acquisition identification. In this solution, a first gNB DU 120 (e.g., a source gNB DU) initiates an early TA acquisition of a target cell associated with a second gNB DU 130 (e.g., a target gNB DU), by requesting a user device 140, to send a RA preamble to the second gNB DU 130 associated with the target cell. The first gNB DU 120 receives, from a gNB CU 110, along with TA information forthe user device 140, a TA processing time information at least associated with a first TA processing time of the second gNB DU 130 and a second TA processing time of the gNB CU 110. The first gNB DU 120 determines, in case of a cell switch command, from the first gNB DU 120 to the user device 140, without the TA information or a case of a failed RACH-less cell switch, based on the TA processing time information, a latency of the early TA acquisition that is caused by processing at the second gNB DU 130 and the gNB CU 110.

[0058] Example embodiments of the present disclosure will be described in detail below with reference to the accompanying drawings.

[0059] The reference now is made to FIG. 2, which illustrates a signaling flow 200 of communication in accordance with some embodiments of the present disclosure. For the purposes of discussion, the signaling flow 200 will be discussed with reference to FIG. 1, for example, by using a gNB CU 110, a first gNB DU 120, a second gNB DU 130 and the user device 140.

[0060] At first, the first gNB DU 120 serves the user device 140, i.e., a cell 102 associated with the first gNB DU 120 acts a serving cell of the user device 140, which may be considered as a primary cell of the user device 140. The user device 140 is currently RRC connected to this primary cell.

[0061] In cell switch procedure, the cell 102 may be considered as a source cell and a cell associated with the second gNB DU 130 may be considered as a target cell. In this scenario, the first gNB DU 120 may be considered as a source gNB DU and the second gNB DU 130 may be considered as a target gNB DU.

[0062] The first gNB DU 120 initiates an early TA acquisition of the target cell associated with a second gNB DU 130. According to an embodiment, the early TA acquisition may be a part of LTM procedure. As shown in FIG. 2, the first gNB DU 120 may transmit (202) a RA preamble assignment to the user device 140. In this way, the first gNB DU 120 may request the user device 140, to send the assigned RA preamble to the second gNB DU 130.

[0063] That is, the first gNB DU 120 may initiate the early TA acquisition of the target cell by requesting the user device 140, to send the assigned RA preamble to the second gNB DU 130.

[0064] After the RA preamble is transmitted (204) from the user device 140 to the second gNB DU 130, the second gNB DU 130 may evaluate (206) TA information (i.e., TA value). During the determination of the TA information, the trigger condition for cell switch may be met.

[0065] For example, as shown in FIG. 2, the user device 140 may transmit (208) an LI measurement report to the first gNB DU 120. If the first gNB DU 120 determines, based on the LI measurement report, that the trigger condition for cell switch is met, the first gNB DU 120 may transmit (210) to the user device 140, a cell switch command indicating the user device 140 to be switched from the cell associated with the first gNB DU 120 to another cell associated with the second gNB DU 130. That is, the first gNB DU 120 may transmit a cell switch command without the TA information to the user device, because the evaluation of the TA value has not been completed.

[0066] If the TA value is successful evaluated by the second gNB DU 130 and the TA information has been generated, the second gNB DU 130 may transmit (212), to the gNB CU 110, a first TA processing time along with the TA information. The first TA processing time may indicate a time interval between a reception of a RA preamble at the second gNB DU 130 and a sending of the TA information from the second gNB DU 130 to the gNB CU 110.

[0067] For example, the sending of the first TA processing time may be via a Fl application (Fl-AP) message, and more specifically, via a DU-CU TA information transfer message.

[0068] Then the gNB CU 110 may transmit (214) the first TA processing time and a second TA processing time, along with the TA information, to the first gNB DU 120. The second TA processing time may indicate a time interval between the reception of the TA information at the gNB CU 110 and a sending of the TA information from the gNB CU 110 to the first gNB DU 120.

[0069] In this case, the first TA processing time and the second TA processing time together may be considered as the TA processing time information. That is, the TA processing time information, transmitted from the gNB CU 110 to the first gNB DU 120, may indicate a time interval that equals to a sum of the first TA processing time and the second TA processing time.

[0070] For example, the TA processing time information may be transmitted from the gNB CU 110 to the first gNB DU 120 via a Fl AP message, and more specifically, via a CU-DU TA information transfer message.

[0071] Based on the TA processing time information received from the gNB CU 110 along with the TA information, the first gNB DU 120 may determine (216) a latency of the early TA acquisition that is caused by processing at the second gNB DU 130 and the gNB CU 110. For example, the first gNB DU 120 may determine the latency as described in a case where a cell switch command, from the first gNB DU 120 to the user device 140, does not comprise(i.e., is without) the TA information or in case a RACH-less cell switch of the user device 140 fails. For example, cell switch command without TA information may mean that the cell switch command is transmitted, from the first gNB DU 120 to the user device 140, without TA value as shown, for example, in step 210 of Figure 2 and in step 310 of Figure 3.

[0072] The reference now is made to FIG. 3, which illustrates a signaling flow 300 of communication in accordance with some embodiments of the present disclosure. For the purposes of discussion, the signaling flow 300 will be discussed with reference to FIG. 1, for example, by using a gNB CU 110, a first gNB DU 120, a second gNB DU 130 and the user device 140. FIG. 3 shows another case where the first gNB DU 120 obtains the TA processing time information of processing and / or delivering the TA information by the second gNB DU 130 and the gNB CU 110.

[0073] As shown in FIG. 3, similarly, at first, the first gNB DU 120 serves the user device 140, i.e., a cell 102 associated with the first gNB DU 120 acts a serving cell of the user device 140, which may be considered as a primary cell of the user device 140. The user device 140 is currently RRC connected to this primary cell.

[0074] In cell switch procedure, the cell 102 may be considered as a source cell and a cell associated with the second gNB DU 130 may be considered as a target cell. In this scenario, the first gNB DU 120 may be considered as a source gNB DU and the second gNB DU 130 may be considered as a target gNB DU.

[0075] As shown in FIG. 3, the first gNB DU 120 may transmit (302) a RA preamble assignment to the user device 140. In this way, the first gNB DU 120 may request the user device 140, to send the assigned RA preamble to the second gNB DU 130.

[0076] That is, the first gNB DU 120 may initiate the early TA acquisition of the target cell by requesting the user device 140, to send the assigned RA preamble to the target cell associated with a second gNB DU 130.

[0077] After the RA preamble is transmitted (304) from the user device 140 to the second gNB DU 130, the second gNB DU 130 may evaluate (306) TA information (i.e., TA value). During the determination of the TA information, the trigger condition for cell switch may be met. For example, as shown in FIG. 3, the user device 140 may transmit (308) an LI measurement report to the first gNB DU 120. If the first gNB DU 120 determines, based on the LI measurement report, that the trigger condition for cell switch is met, the first gNB DU 120 may transmit (310) to the user device 140, a cell switch command without the TA information to the user device, because the evaluation of the TA value has not been completed.

[0078] After the TA value has been successful evaluated by the second gNB DU 130 and the TA information has been generated, the second gNB DU 130 may transmit (312), to the gNB CU 110 along with the TA information, a first TA processing time and a DU time stamp indicating a sending time of the TA information from the second gNB DU 130to the gNB CU 110.

[0079] The first TA processing time may indicate a time interval between a reception of a RA preamble at the second gNB DU 130 and a sending of the TA information from the second gNB DU 130 to the gNB CU 110.

[0080] Based on the time point on which the first TA processing time is received by the gNB CU 110 and the DU time stamp, the gNB CU 110 may determine (314) a delay between transmission and reception of the first TA processing time from the second gNB DU 130 to the gNB CU 110. This delay may be considered as a propagation delay from DU to CU.

[0081] For example, the sending of the first TA processing time (and also the DU time stamp) may be via a Fl application (Fl-AP) message from the second gNB DU 130 to the gNB CU 110, and more specifically, via a DU-CU TA information transfer message.

[0082] Then the gNB CU 110 may transmit (316) TA processing time information including the first TA processing time, the DU-CU delay and a second TA processing time to the first gNB DU 120 along with the TA information. That is, the TA processing timeinformation may indicate a time interval that equals to a sum of the first TA processing time, the second TA processing time and a delay between transmission and reception of the first TA processing time from the second gNB DU 130 to the gNB CU 110.

[0083] For example, the second TA processing time may indicate a time interval between the reception of the TA information at the gNB CU 110 and a sending of the TA information from the gNB CU 110 to the first gNB DU 120.

[0084] Additionally, the gNB CU 110 may transmit, along with the TA information and the TA processing time information, a CU time stamp indicates a sending time of the TA information from the gNB CU 110 to the first gNB DU 120.

[0085] For example, the TA processing time information (also the CU time stamp) may be transmitted from the gNB CU 110 to the first gNB DU 120 via an Fl AP message, and more specifically, via a CU-DU TA information transfer message.

[0086] Based on the CU time stamp and a time point on which the TA information is received at the first gNB DU 120, the first gNB DU 120 may determine a further delay between transmission and reception of the TA information from the gNB CU 110 to the first gNB DU 120. This delay may be considered as a propagation delay from CU to DU.

[0087] Then the first gNB DU 120 may determine (318) the latency of the early TA acquisition that is caused by processing at the second gNB DU 130 and the gNB CU 110 based on the TA processing time information and the further delay, for example, in a case where a cell switch command, from the first gNB DU 120 to the user device 140, is without the TA information or a RACH-less cell switch of the user device 140 fails.

[0088] The determined latency of the early TA acquisition, that is caused by processing at the second gNB DU 130 and the gNB CU 110, may be provided to a SON entity, for example, when the latency is retrieved by the SON entity.

[0089] For example, the SON entity may have a threshold - if the “TA processing time” is above the configured threshold, it may point out on “False identification of too late triggered Early TA acquisition” case and instead of triggering the TA acquisition earlier, the focus can be capacity optimization in target gNB DU and / or gNB CU to reduce the DU / CU TA processing time. This prevents the further degradation of the LTM procedure, as shown in the earlier sections.

[0090] As mentioned above, new IES such as the first processing time, the secondprocessing time, etc. may be added to F1AP messages, such as DU-CU TA INFORMATION TRANSFER message and / or CU-DU TA INFORMATION TRANSFER message. Examples of the possible new IES definition is proposed as below:Table 1 : An example of DU-CU TA INFORMATION TRANSFER

[0091] The IE “TA DU processing time” may indicate the time interval since reception of the RA preamble from UE related to Early TA acquisition procedure as defined in 3 GPP till the creation of the DU-CU TA INFORMATION TRANSFER message.Table 2: An example of CU-DU TA INFORMATION TRANSFER

[0092] In this case, this IE “TA CU processing time” may indicate the time interval since reception of the TA value of the candidate Cell id within the DU-CU TA INFORMATION TRANSFER in gNB-CU till the creation of the CU-DU TA INFORMATION TRANSFER message.

[0093] Based on the solution of the present disclosure, the overall time information can be retrieved and used by the SON entity dealing with mobility robustness optimization (MRO) for LTM during the SHR and Radio Line Failure (RLF) analysis to see whether the LTM procedure was spoiled by network-caused delay and excluded those issues from the “Too late TAA” classification, i.e. ensure avoiding false identification of too late triggered Early TA acquisition.

[0094] That is, instead of earlier triggering the Early TA acquisition procedure, an optimization in target gNB DU and / or gNB CU to reduce this processing time should be performed. That is, “False identification of too late triggered Early TA acquisition” may be identified according to this solution and excluded from the SON method for TAA optimization.

[0095] FIG. 4 shows a flowchart of an example method 400 implemented at an apparatus in accordance with some example embodiments of the present disclosure. For the purpose of discussion, the method 400 will be described from the perspective of a source DU (e.g., the first gNB DU 120 in FIG. 1).

[0096] At block 410, the source DU initiates an early TA acquisition of a target cellassociated with a target DU by requesting a user device, to send a RA preamble to the target DU.

[0097] At block 420, the source DU receives, from a CU, along with TA information for the user device, a TA processing time information at least associated with a first TA processing time of the target DU and a second TA processing time of the CU.

[0098] At block 430, the source DU determines, in case of a cell switch command, from the source DU to the user device, without the TA information or a case of a failed RACH- less cell switch, based on the TA processing time information, a latency of the early TA acquisition that is caused by processing at the target DU and the CU.

[0099] In some example embodiments, the TA processing time information indicates a time interval that equals to a sum of the first TA processing time and the second TA processing time, and wherein the latency of the early TA acquisition procedure equals to the time interval.

[0100] In some example embodiments, the TA processing time information indicates a time interval that equals to a sum of the first TA processing time, the second TA processing time and a delay between transmission and reception of the first TA processing time from the target DU to the CU, and the method 400 further comprises: obtaining, based on the TA processing time information, a CU time stamp indicating a sending time of the TA information from the CU to the source gNB DU; determining a further delay between transmission and reception of the TA information from CU to the source gNB DU based on the CU time stamp and a time point on which the TA information is received at source gNB DU; and determining the latency of the early TA acquisition procedure based on the time interval and the further delay.

[0101] In some example embodiments, the delay between the transmission and reception of the first TA processing time from the target DU to the CU is a time interval between a DU time stamp indicating a sending time of the TA information from the target DU to the CU and a time point at which the TA information is received by the CU.

[0102] In some example embodiments, the first TA processing time indicates a time interval between a reception of a random access preamble at the target DU and a sending of the TA information from the target DU to the CU.

[0103] In some example embodiments, the first TA processing time is transferred fromthe target DU to the CU along with the TA information via an Fl application, F1AP, message.

[0104] In some example embodiments, the second TA processing time indicates a time interval between the reception of the TA information at the CU and the sending of the TA information from the CU to the source gNB DU.

[0105] In some example embodiments, the method 400 further comprises: receiving the TA information plus the TA processing time information from the CU via an F1AP message.

[0106] In some example embodiments, the method 400 further comprises: in accordance with a determination that the latency of the early TA acquisition is retrieved by a selforganizing network, SON entity, providing the latency given by the TA processing time to the SON entity.

[0107] In some example embodiments, the latency given by the TA processing time is used for the SON entity for identifying a false identification of too late triggered TA acquisition.

[0108] FIG. 5 shows a flowchart of an example method 500 implemented at an apparatus in accordance with some example embodiments of the present disclosure. For the purpose of discussion, the method 500 will be described from the perspective of a CU (e.g., the gNB CU 110 in FIG. 1).

[0109] At block 510, during early TA acquisition of a target cell associated with a target DU , the CU transmits, to a source DU, along with TA information for the user device, a TA processing time information at least associated with a first TA processing time of the target DU and a second TA processing time of the CU.

[0110] In some example embodiments, the method 500 further comprises: receiving the first TA processing time from the target DU along with the TA information; and determining the TA processing time information based on the first TA processing time and the second TA processing time.

[0111] In some example embodiments, the TA processing time information indicates a time interval that equals to a sum of the first TA processing time and the second TA processing time.

[0112] In some example embodiments, the method 500 further comprises: receiving the first TA processing time and a DU time stamp indicating a sending time of the TA information from the target DU to the CU; determining a delay between transmission and reception of the first TA processing time from the target DU to the CU based on the DU time stamp and a time point on which the first TA processing time is received by the CU; and determining the TA processing time information based on the first TA processing time, the second TA processing time and the delay.

[0113] In some example embodiments, the TA processing time information indicates a time interval that equals to a sum of the first TA processing time, the second TA processing time and the delay.

[0114] In some example embodiments, the method 500 further comprises: transmitting, along with the TA information, a CU time stamp indicating a sending time of the TA information from the CU to the source DU.

[0115] In some example embodiments, the first TA processing time relates to a time interval from a reception of a random access preamble at the target DU which is related to previously triggered Early TA acquisition procedure by source DU and a sending of the first TA processing time from the target DU to the CU.

[0116] In some example embodiments, the method 500 further comprises: receiving the first TA processing time, along with the TA information, from the target DU via an Fl application, F1AP message.

[0117] In some example embodiments, the second TA processing time indicates a time interval between the reception of the first TA processing time at the CU and the sending of the TA information from the CU to the source DU.

[0118] In some example embodiments, the TA processing time information is transferred from the CU, along with the TA information, to the source DU via an F1AP message.

[0119] In some example embodiments, an apparatus capable of performing any of the method 400 (for example, the first gNB DU 120 in FIG. 1) may comprise means for performing the respective operations of the method 400. The means may be implemented in any suitable form. For example, the means may be implemented in a circuitry or software module. The apparatus may be implemented as or included in the first gNB DU120 in FIG. 1.

[0120] In some example embodiments, the apparatus comprises means for initiating an early TA acquisition of a target cell associated with a target DU by requesting a user device, to send a RA preamble to the target DU; means for receiving, from a CU, along with TA information for the user device, a TA processing time information at least associated with a first TA processing time of the target DU and a second TA processing time of the CU; and means for determining, in case of a cell switch command, from the apparatus to the user device, without the TA information or a case of a failed RACH-less cell switch, based on the TA processing time information, a latency of the early TA acquisition that is caused by processing at the target DU and the CU.

[0121] In some example embodiments, the TA processing time information indicates a time interval that equals to a sum of the first TA processing time and the second TA processing time, and wherein the latency of the early TA acquisition procedure equals to the time interval.

[0122] In some example embodiments, the TA processing time information indicates a time interval that equals to a sum of the first TA processing time, the second TA processing time and a delay between transmission and reception of the first TA processing time from the target DU to the CU, and wherein the apparatus comprises: means for obtaining, based on the TA processing time information, a CU time stamp indicating a sending time of the TA information from the CU to the apparatus; means for determining a further delay between transmission and reception of the TA information from CU to the apparatus based on the CU time stamp and a time point on which the TA information is received at apparatus; and means for determining the latency of the early TA acquisition procedure based on the time interval and the further delay.

[0123] In some example embodiments, the delay between the transmission and reception of the first TA processing time from the target DU to the CU is a time interval between a DU time stamp indicating a sending time of the TA information from the target DU to the CU and a time point at which the TA information is received by the CU.

[0124] In some example embodiments, the first TA processing time indicates a time interval between a reception of a random access preamble at the target DU and a sending of the TA information from the target DU to the CU.

[0125] In some example embodiments, the first TA processing time is transferred from the target DU to the CU along with the TA information via an Fl application, F1AP, message.

[0126] In some example embodiments, the second TA processing time indicates a time interval between the reception of the TA information at the CU and the sending of the TA information from the CU to the apparatus.

[0127] In some example embodiments, the apparatus comprises: means for receiving the TA information plus the TA processing time information from the CU via an F1AP message.

[0128] In some example embodiments, the apparatus comprises: means for in accordance with a determination that the latency of the early TA acquisition is retrieved by a self-organizing networks, SON entity, providing the latency given by the TA processing time to the SON entity.

[0129] In some example embodiments, the latency given by the TA processing time is used for the SON entity for identifying a false identification of too late triggered TA acquisition.

[0130] In some example embodiments, the apparatus comprises a source DU.

[0131] In some example embodiments, an apparatus capable of performing any of the method 500 (for example, the gNB CU 110 in FIG. 1) may comprise means for performing the respective operations of the method 500. The means may be implemented in any suitable form. For example, the means may be implemented in a circuitry or software module. The apparatus may be implemented as or included in the gNB CU 110 in FIG. 1.

[0132] In some example embodiments, the apparatus comprises means for, during early TA acquisition of a target cell associated with a target DU, transmitting, to a source DU, along with TA information for the user device, a TA processing time information at least associated with a first TA processing time of the target DU and a second TA processing time of the apparatus.

[0133] In some example embodiments, the apparatus comprises: means for receiving the first TA processing time from the target DU along with the TA information; and means for determining the TA processing time information based on the first TA processing time and the second TA processing time.

[0134] In some example embodiments, the TA processing time information indicates a time interval that equals to a sum of the first TA processing time and the second TA processing time.

[0135] In some example embodiments, the apparatus comprises: means for receiving the first TA processing time and a DU time stamp indicating a sending time of the TA information from the target DU to the apparatus; means for determining a delay between transmission and reception of the first TA processing time from the target DU to the apparatus based on the DU time stamp and a time point on which the first TA processing time is received by the apparatus; and means for determining the TA processing time information based on the first TA processing time, the second TA processing time and the delay.

[0136] In some example embodiments, the TA processing time information indicates a time interval that equals to a sum of the first TA processing time, the second TA processing time and the delay.

[0137] In some example embodiments, the apparatus comprises: means for transmitting, along with the TA information, a CU time stamp indicating a sending time of the TA information from the apparatus to the source DU.

[0138] In some example embodiments, the first TA processing time relates to a time interval from a reception of a random access preamble at the target DU which is related to previously triggered Early TA acquisition procedure by source DU and a sending of the first TA processing time from the target DU to the apparatus.

[0139] In some example embodiments, the apparatus comprises: means for receiving the first TA processing time, along with the TA information, from the target DU via an Fl application, F1AP message.

[0140] In some example embodiments, the second TA processing time indicates a time interval between the reception of the first TA processing time at the apparatus and the sending of the TA information from the apparatus to the source DU.

[0141] In some example embodiments, the TA processing time information is transferred from the apparatus, along with the TA information, to the source DU via an F1AP message.

[0142] FIG. 6 is a simplified block diagram of a device 600 that is suitable forimplementing example embodiments of the present disclosure. The device 600 may be provided to implement a communication device, for example, the first gNB DU 120 or the gNB CU 110 as shown in FIG. 1. As shown, the device 600 includes one or more processors 610, one or more memories 620 coupled to the processor 610, and one or more communication modules 640 coupled to the processor 610.

[0143] The communication module 640 is for bidirectional communications. The communication module 640 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 640 may include at least one antenna.

[0144] The processor 610 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 600 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.

[0145] The memory 620 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) 624, 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) 622 and other volatile memories that will not last in the power-down duration.

[0146] A computer program 630 includes computer executable instructions that are executed by the associated processor 610. The instructions of the program 630 may include instructions for performing operations / acts of some example embodiments of the present disclosure. The program 630 may be stored in the memory, e.g., the ROM 624. The processor 610 may perform any suitable actions and processing by loading the program 630 into the RAM 622.

[0147] The example embodiments of the present disclosure may be implemented bymeans of the program 630 so that the device 600 may perform any process of the disclosure as discussed with reference to FIG. 2 to FIG. 5. The example embodiments of the present disclosure may also be implemented by hardware or by a combination of software and hardware.

[0148] In some example embodiments, the program 630 may be tangibly contained in a computer readable medium which may be included in the device 600 (such as in the memory 620) or other storage devices that are accessible by the device 600. The device 600 may load the program 630 from the computer readable medium to the RAM 622 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).

[0149] FIG. 7 shows an example of the computer readable medium 700 which may be in form of CD, DVD or other optical storage disk. The computer readable medium 700 has the program 630 stored thereon.

[0150] 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.

[0151] 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.

[0152] 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.

[0153] 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.

[0154] 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.

[0155] 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 beadvantageous. 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.

[0156] 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

WHAT IS CLAIMED IS:

1. An apparatus comprising: at least one processor; and at least one memory storing instructions that, when executed by the at least one processor, cause the apparatus at least to: initiate an early timing advance, TA, acquisition of a target cell associated with a target distributed unit, DU, by requesting a user device, to send a random access, RA, preamble to the target DU; receive, from a centralized unit, CU, along with TA information for the user device, a TA processing time information at least associated with a first TA processing time of the target DU and a second TA processing time of the CU; and determine, in case of a cell switch command, from the apparatus to the user device, without the TA information or in case of a failed random access channel-less, RACH- less, cell switch, based on the TA processing time information, a latency of the early TA acquisition that is caused by processing at the target DU and the CU.

2. The apparatus of claim 1, wherein the TA processing time information indicates a time interval that equals to a sum of the first TA processing time and the second TA processing time, and wherein the latency of the early TA acquisition procedure equals to the time interval.

3. The apparatus of claim 1, wherein the TA processing time information indicates a time interval that equals to a sum of the first TA processing time, the second TA processing time and a delay between transmission and reception of the first TA processing time from the target DU to the CU, and wherein the apparatus is caused to: obtain, based on the TA processing time information, a CU time stamp indicating a sending time of the TA information from the CU to the apparatus; determine a further delay between transmission and reception of the TA informationfrom CU to the apparatus based on the CU time stamp and a time point on which the TA information is received at the apparatus; and determine the latency of the early TA acquisition procedure based on the time interval and the further delay.

4. The apparatus of claim 3, wherein the delay between the transmission and reception of the first TA processing time from the target DU to the CU is a time interval between a DU time stamp indicating a sending time of the TA information from the target DU to the CU and a time point at which the TA information is received by the CU.

5. The apparatus of any of claims 1-4, wherein the first TA processing time indicates a time interval between a reception of a random access preamble at the target DU and a sending of the TA information from the target DU to the CU.

6. The apparatus of claim 5, wherein the first TA processing time is transferred from the target DU to the CU along with the TA information via an Fl application, F1AP, message.

7. The apparatus of any of claims 1-6, wherein the second TA processing time indicates a time interval between the reception of the TA information at the CU and the sending of the TA information from the CU to the apparatus.

8. The apparatus of any of claims 1-6, wherein apparatus is caused to: receive the TA information plus the TA processing time information from the CU via an F1AP message.

9. The apparatus of any of claims 1-8, wherein the apparatus is caused to: in accordance with a determination that the latency of the early TA acquisition is retrieved by a self-organizing networks, SON, entity, provide the latency given by the TAprocessing time to the SON entity.

10. The apparatus of claim 9, wherein the latency given by the TA processing time is used for the SON entity for identifying a false identification of too late triggered TA acquisition.

11. The apparatus of any of claims 1-10, wherein the apparatus comprises a source DU.

12. An apparatus comprising: at least one processor; and at least one memory storing instructions that, when executed by the at least one processor, cause the apparatus at least to: during early timing advance, TA, acquisition of a target cell associated with a target distributed unit, DU, transmit, to a source DU, along with TA information for the user device, a TA processing time information at least associated with a first TA processing time of the target DU and a second TA processing time of the apparatus.

13. The apparatus of claim 12, wherein the apparatus is caused to: receive the first TA processing time from the target DU along with the TA information; and determine the TA processing time information based on the first TA processing time and the second TA processing time.

14. The apparatus of claim 13, wherein the TA processing time information indicates a time interval that equals to a sum of the first TA processing time and the second TA processing time.

15. The apparatus of claim 12, wherein the apparatus is caused to: receive the first TA processing time and a DU time stamp indicating a sending time of the TA information from the target DU to the apparatus; determine a delay between transmission and reception of the first TA processing time from the target DU to the apparatus based on the DU time stamp and a time point on which the first TA processing time is received by the apparatus; and determine the TA processing time information based on the first TA processing time, the second TA processing time and the delay.

16. The apparatus of claim 15, wherein the TA processing time information indicates a time interval that equals to a sum of the first TA processing time, the second TA processing time and the delay.

17. The apparatus of claim 15 or 16, wherein the apparatus is caused to: transmit, along with the TA information, a CU time stamp indicating a sending time of the TA information from the apparatus to the source DU.

18. The apparatus of claim any of claims 12-17, wherein the first TA processing time relates to a time interval from a reception of a random access preamble at the target DU which is related to previously triggered Early TA acquisition procedure by source DU and a sending of the first TA processing time from the target DU to the apparatus.

19. The apparatus of claim 18, wherein the apparatus is caused to: receive the first TA processing time, along with the TA information, from the target DU via an Fl application, F1AP message.

20. The apparatus of any of claims 12-19, wherein the second TA processing time indicates a time interval between the reception of the first TA processing time at the apparatus and the sending of the TA information from the apparatus to the source DU.

21. The apparatus of any of claims 12-20, wherein the TA processing time information is transferred from the apparatus, along with the TA information, to the source DU via an F1AP message.

22. The apparatus of any of claims 12-21, wherein the apparatus comprises a CU.

23. A method comprising: initiating, by a source DU, an early TA acquisition of a target cell associated with a target distributed unit, DU, by requesting a user device, to send a RA preamble to the target DU. receiving, from a centralized unit, CU, along with TA information for the user device, a TA processing time information at least associated with a first TA processing time of the target DU and a second TA processing time of the CU; and determining, in case of a cell switch command, from the source DU to the user device, without the TA information or case of a failed RACH-less cell switch, based on the TA processing time information, a latency of the early TA acquisition that is caused by processing at the target DU and the CU.

24. A method comprising: during early TA acquisition of a target cell associated with a target distributed unit, DU, transmitting, from a CU to a source DU, along with TA information for the user device, a TA processing time information at least associated with a first TA processing time of the target DU and a second TA processing time of the CU.

25. An apparatus comprising: means for initiating an early TA acquisition of a target cell associated with a target distributed unit, DU, by requesting a user device, to send a RA preamble to the target DU; means for receiving, from a centralized unit, CU, along with TA information for theuser device, a TA processing time information at least associated with a first TA processing time of the target DU and a second TA processing time of the CU; and means for determining, in case of a cell switch command, from the apparatus to the user device, without the TA information or in case of a failed RACH-less cell switch, based on the TA processing time information, a latency of the early TA acquisition that is caused by processing at the target DU and the CU.

26. An apparatus comprising: means for, during early TA acquisition of a target cell associated with a target distributed unit, DU, transmitting, to a source DU, along with TA information for the user device, a TA processing time information at least associated with a first TA processing time of the target DU and a second TA processing time of the apparatus.

27. A computer readable medium comprising instructions stored thereon for causing an apparatus at least to perform the method of claim 23 or the method of claim 24.

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