Method and system for optimizing latency for L1 / L2 trigger mobility

Abstract

A method, system, and device for configuring an inter-cell change are provided. The method can be implemented by receiving, by a user equipment (UE), a downlink signal, where the downlink signal originates from a serving distribution unit (DU), and the downlink signal includes at least one of a scheduling gap duration value, a start time value, and a target cell index; and performing, by the UE, uplink synchronization with the target cell based on the downlink signal during the scheduling gap duration, where the uplink synchronization includes sending, by the UE, a preamble transmission to the target cell based on the downlink signal to acquire a timing advance of the target cell, where the target DU is one of a plurality of neighbor cells to the serving DU.

Description

Technical Field

[0001] Cross - reference to Related Applications This application claims priority from Indian Provisional Application No. 202241060061 filed with the Indian Patent Office on October 20, 2022, the entire disclosure of which is incorporated herein by reference for all purposes.

[0002] Systems and methods consistent with exemplary embodiments of the present disclosure relate to the optimization of latency in L1 / L2 trigger cell - to - cell changes in a decomposed telecommunications architecture.

Background Art

[0003] A radio access network (RAN) is an important component in a telecommunications system for connecting end - user devices (or user equipment (UE)) to other parts of the network. The RAN includes a combination of various network elements (NE) that connect end - user devices to the core network. Conventionally, the hardware and / or software of a particular RAN is vendor - specific.

[0004] In recent years, advancements in telecommunications technology have made it possible to virtually implement many telecommunications services in software form. For example, RANs such as the Open RAN (O-RAN) architecture decompose (deaggregate) a single network component into multiple functional elements. For instance, a baseband unit (BBU) or base station (i.e., eNB or gNB) can be decomposed into several functional elements, including a distributed unit (DU) and a centralized unit (CU), and the CU can be further decomposed into a Centralized Unit-Control Plane (CU-CP) and a Centralized Unit-User Plane (CU-UP). This decomposition of network elements makes it possible to define and provide telecommunications services and related functions in software-based forms or virtual network services, such as Virtualized Network Functions (VNFs), Cloud-native Network Functions (CNFs), or Software Defined Networking (SDNs).

[0005] Figure 1 shows the decomposed gNB architecture of related technologies in 3GPP®. A gNB is decomposed into multiple logical entities. Two gNB-DU nodes are shown, but it should be understood that multiple gNB-DU nodes may exist. Note that a single DU may host multiple cells. A gNB-DU node can communicate with a CU-CP via the F1-C interface and with a CU-UP via the F1-U interface. The CU-CP and CU-UP can communicate via the E1 interface. The gNB-CU-CP hosts the Packet Data Convergence Protocol (PDCP) layer and the Radio Resource Control (RRC) layer, while the gNB-DU hosts the Radio Link Control (RLC) layer, the Medium Access Control (MAC) layer, and the Physical (PHY) layer. Scheduling operations are performed by the gNB-DU.

[0006] To support L1 / L2-centric inter-cell changes, the RLC MAC and PHY layers are located in the gNB-DU; therefore, cell change configuration should be performed in the gNB-CU-CP, and serving cell changes should be performed autonomously by the gNB-DU without further interaction with higher layers. This operation may be referred to herein as L1 / L2 triggered mobility (LTM).

[0007] Specifically, LTM can be defined as a mobility procedure that enables the network to switch a UE from a source cell to a target cell without necessarily requiring synchronous reconfiguration. In particular, based on received L1 measurements, the network can indicate in L2 signaling (e.g., MAC CE) the beams belonging to LTM candidate cells on which the UE should perform the LTM cell switching procedure. Prior to performing the LTM cell switching procedure, the UE is provided with at least one (or more) LTM candidate cell configurations by the network.

[0008] In related technologies, the UE may periodically evaluate the link quality between the serving cell and its neighboring cells. To evaluate link quality, the UE may perform measurements on the serving cell and neighboring cells to the UE (e.g., reference signal received power (RSRP) and reference signal received quality (RSRQ) of the Synchronization Signal Block (SSB)). Such measurements may be processed (e.g., by L3 filtering) and reported to the serving cell based on a reporting configuration, and if one of the neighboring cells meets a predetermined handover criterion, the serving cell may indicate to the UE that it should hand over to that neighboring cell. The UE then uses a random access channel (RACH) in the new neighboring cell.

[0009] Figure 2 shows a call flow for a typical Layer 3 handover procedure involving a UE, a source gNB node, and a target gNB node (i.e., the gNB-DU node described above) using the relevant technology. In this example, explicit radio resource control (RRC) signaling needs to be triggered, which can result in a handover. In the first step, the source gNB node can initiate the handover by issuing a handover request (e.g., via the Xn interface). In the second step, the target gNB node can provide a new RRC configuration by performing admission control and acknowledging (ACKing) the handover request. In the third step, the source gNB node can provide the RRC configuration to the UE by forwarding the RRC reconfiguration message received with the handover request ACK. The RRC reconfiguration message may include at least the cell ID and any information necessary to access the target cell (which may include beam-specific information, if any) so that the UE can access the target cell without reading system information. In some cases, the RRC reconfiguration message may include information necessary for contention-based random access (CBRA) and contention-free random access (CFRA). In the fourth step, the UE can move the RRC connection to the target gNB node and then respond to the target gNB node with an RRC reconfiguration complete message.

[0010] In related technologies, another method of managing mobility may include inter-cell beam management (ICBM). Unlike the method shown above in Figure 2, ICBM does not require explicit RRC signaling to be triggered. Instead, in the case of ICBM, the UE may receive or transmit UE-dedicated channels / signals via transmission / reception points (TRPs) associated with physical cell IDs (PCIs) different from the serving cell's PCI, while non-UE-dedicated channels / signals may only be received via TRPs associated with the serving cell's PCI. Generally, in related technologies, a gNB node may provide the UE with a measurement configuration (via RRC signaling) that may include, for example, SSB and / or Channel State Information (CSI) resources and / or resource sets, reports, and configurations of trigger states for triggering channel and interference measurements and reports. In the case of ICBM, this may be a measurement configuration that includes SSB resources associated with a PCI different from the serving cell's PCI. Subsequently, beam-level mobility can be handled at lower layers by physical layer and MAC layer control signaling, and therefore the RRC (hosted at CU-CP) does not need to know which beam is being used by the UE at a given time. Other similar methods can include, for example, SSB-based beam-level mobility based on SSBs associated with the initial downlink bandwidth part (DL BWP) and can only be configured for DL ​​BWPs that include the initial DL BWP and the SSB associated with the initial DL BWP. For other DL BWPs, beam-level mobility can only be performed based on a channel state information reference signal (CSI-RS).

[0011] In related technologies, potential issues with LTM can arise when a UE must perform a Random Access Channel (RACH) when handing over to a new cell. In particular, delays caused by latency from the RACH procedure can increase. Specifically, during handover, the UE waits for a physical RACH (PRACH) opportunity to perform the RACH and synchronize with the target uplink, which is necessary because the timing advance of the UE in the target cell (configured for handover) may differ from the timing advance of the serving cell. Thus, the UE must wait for an available PRACH opportunity, send a preamble, and wait for a random access response (RAR). On average, this can cause a delay of 10-20 ms from the RACH procedure, which is suboptimal.

[0012] In addition, while methods and systems related to beam-based inter-cell mobility (such as the ICBMs mentioned above) are known in the relevant technologies, these technologies do not describe how to manage beam-based inter-cell mobility using handover. Therefore, it is necessary to optimize / reduce delays in the handover procedure while incorporating methods and systems for beam-based inter-cell mobility. [Overview of the Initiative]

[0013] Exemplary embodiments of this disclosure provide methods and systems for handling L1 / L2 trigger mobility (LTM) to reduce mobile latency. In particular, according to the embodiments, the scheduling gap duration in a serving cell may be indicated to the user equipment (UE) so that preamble transmission and uplink synchronization with the target cell (target DU) can be performed during the scheduling gap. The uplink synchronization and preamble transmission, which the UE uses to obtain the timing advance of the target cell, can be performed to the target cell, and these discoveries can be indicated back to the serving cell (serving DU). Thus, the exemplary embodiments can avoid performing random channel access (RACH) to perform a serving cell change (SCC) handover (HO) so as to reduce mobile latency. Furthermore, the exemplary embodiments can enable the UE to determine a suitable beam to be used by an adjacent target cell and indicate it to the serving cell / DU. Thus, embodiments of this disclosure provide a more optimal method for handling LTM with reduced latency and can enable beam-based inter-cell mobility.

[0014] According to one embodiment, a method may be provided for configuring inter-cell changes performed by at least one processor. The method may include receiving a downlink signal by a user device (UE), the downlink signal originating from a serving distribution unit (DU), the downlink signal including at least one of a scheduling gap duration value, a start time value, and a target cell index; and performing uplink synchronization with a target cell based on the downlink signal by the UE during the scheduling gap duration, the uplink synchronization including the UE sending a preamble transmission to the target cell to obtain the target cell's timing advance based on the downlink signal, the target DU being one of a plurality of neighboring cells to the serving DU.

[0015] The method may also include the UE obtaining a timing advance to use during transmission to or reception from the target cell, and the UE reporting the uplink synchronization results and the obtained timing advance to the Serving DU.

[0016] Preamble transmission and uplink synchronization may be performed while the UE is connected to the serving DU. Downlink signals may be either Physical Downlink Control Channel (PDCCH) or MAC Control Element (MAC CE) commands.

[0017] Performing a measurement based on a downlink signal further includes performing an L1 measurement of the target cell. The method may further include the UE sending the L1 measurement to the serving DU, which can then determine, based on the target cell timing advance reported by the UE, whether to perform an LTM handover without RACH based on the L1 measurement.

[0018] Sending a preamble transmission to a target DU based on a downlink signal means sending a random access preamble to the target DU during a scheduling gap duration determined based on a scheduling gap duration value, which may further include the target DU determining a timing advance value for the UE based on receiving the random access preamble.

[0019] The method may further include the UE performing uplink synchronization based on measurement and preamble transmission, and the UE sending a status signal to the serving DU.

[0020] L1 measurements are performed and reported on one or more target cells aperiodically or based on events, and the L1 measurements are sent aperiodically to the serving DU.

[0021] According to one embodiment, an apparatus for configuring inter-cell changes may be provided. The apparatus may include at least one memory storing computer executable instructions, and at least one processor configured to execute computer executable instructions: receive a downlink signal by a user device (UE), the downlink signal originating from a serving distribution unit (DU), the downlink signal comprising at least one of a scheduling gap duration value, a start time value, and a target cell index, and perform uplink synchronization with a target cell based on the downlink signal by the UE during the scheduling gap duration, the uplink synchronization comprising the UE sending a preamble transmission to the target cell to obtain a timing advance for the target cell based on the downlink signal, the target DU being one of a plurality of adjacent cells to the serving DU.

[0022] At least one processor may be further configured to execute computer executable instructions to obtain a timing advance for use by the UE during transmission to or reception from the target cell, and to report the results of uplink synchronization and the obtained timing advance to the serving DU.

[0023] At least one processor may be further configured to perform a measurement by executing a computer-executable instruction to perform an L1 measurement of a target cell based on a downlink signal, and at least one processor may be further configured to execute a computer-executable instruction to send the L1 measurement to the serving DU, which can then determine whether to perform an LTM handover without RACH based on the L1 measurement, based on the target cell timing advance reported by the UE.

[0024] At least one processor may be further configured to send a preamble transmission to the target DU based on a downlink signal by executing a computer executable instruction to send a random access preamble to the target DU during a scheduling gap duration determined based on a scheduling gap duration value, the target DU being able to determine a timing advance value for the UE based on receiving the random access preamble.

[0025] At least one processor may be further configured to execute computer executable instructions to enable the UE to perform uplink synchronization based on measurement and preamble transmission, and to enable the UE to send status signals to the serving DU.

[0026] Additional embodiments are partially described below, partially evident from the description, or may be realized by implementing the embodiments presented in this disclosure.

Brief Description of the Drawings

[0027] The features, aspects, and advantages of certain exemplary embodiments of the present disclosure are described below with reference to the accompanying drawings, in which like reference numerals indicate like elements.

[0028] [Figure 1] FIG. showing the decomposed gNB architecture according to the related art. [Figure 2] FIG. showing a call flow for a typical handover procedure for LTM involving a UE, a source gNB node, and a target gNB node according to the related art. [Figure 3] FIG. showing an inter-cell mobility scenario according to an embodiment. [Figure 4] FIG. showing a handover procedure according to an embodiment. [Figure 5] FIG. of an exemplary environment in which the systems and / or methods described herein can be implemented. [Figure 6] FIG. of exemplary components of a device according to an embodiment.

Modes for Carrying Out the Invention

[0029] The following detailed description of the exemplary embodiments refers to the accompanying drawings.

[0030] The foregoing disclosures provide examples and explanations, but are not intended to be exhaustive or to limit implementations to the exact forms disclosed. Modifications and variations are possible in light of the foregoing disclosures or can be derived from implementations. Furthermore, one or more features or components of one embodiment may be incorporated into or combined with another embodiment (or one or more features of another embodiment). Furthermore, it should be understood that in the flowcharts and operation descriptions provided below, one or more operations may be omitted, one or more operations may be added, one or more operations may be performed (at least partially) simultaneously, and the order of one or more operations may be changed.

[0031] It will be apparent that the systems and / or methods described herein may be implemented in different forms of hardware, firmware, or combinations of hardware and software. The actual dedicated control hardware or software code used to implement these systems and / or methods is not limited to any specific implementation. Therefore, the operation and behavior of the systems and / or methods are described herein without reference to any specific software code. It is understood that software and hardware may be designed to implement the systems and / or methods based on the descriptions herein.

[0032] Certain combinations of features are described in the claims and / or disclosed herein, but these combinations do not limit the disclosure of possible implementations. In fact, many of these features can be combined in ways not specifically described in the claims and / or disclosed herein. Each of the dependent claims listed below may directly depend on only one claim, but the disclosure of possible implementations includes each dependent claim in combination with all other claims in the set of claims.

[0033] Any element, action, or command used herein should not be construed as important or essential unless expressly stated otherwise. Furthermore, where used herein, the articles “a” and “an” are intended to include one or more items and may be used interchangeably with “one or more.” When only one item is intended, the term “one” or similar language should be used. Also, where used herein, terms such as “has,” “have,” “having,” “include,” and “including” are intended to be non-restrictive. Furthermore, the phrase “based on” should mean “at least partially based on” unless otherwise specified. Additionally, expressions such as “at least one of [A] and [B]” or “at least one of [A] or [B]” should be understood as including only A, only B, or both A and B.

[0034] Furthermore, the features, advantages, and characteristics described herein may be combined in any preferred manner in one or more embodiments. Those skilled in the art will recognize, in light of the description herein, that the disclosure may be practiced without one or more of the specific features or advantages of a particular embodiment. In other examples, additional features and advantages that may not be present in all embodiments of the disclosure may be recognized in a particular embodiment.

[0035] Exemplary embodiments of this disclosure provide methods and systems for handling L1 / L2 trigger mobility (LTM) to reduce mobile latency. In particular, according to the embodiments, the scheduling gap duration in a serving cell may be indicated to the user equipment (UE) so that preamble transmission and uplink synchronization with the target cell (target DU) can be performed during the scheduling gap. The uplink synchronization and preamble transmission, which the UE uses to obtain the timing advance of the target cell, can be performed to the target cell, and these discoveries can be indicated back to the serving cell (serving DU). Thus, the exemplary embodiments can avoid performing random channel access (RACH) to perform a serving cell change (SCC) handover (HO) so as to reduce mobile latency. Furthermore, the exemplary embodiments can enable the UE to determine a preferred beam to be used by an adjacent target cell and indicate it to the serving cell / DU.

[0036] Therefore, embodiments of the present disclosure can provide a more optimal method for processing LTM with reduced latency and enable beam-based inter-cell mobility.

[0037] Figure 3 shows an exemplary inter-cell mobility scenario according to one or more embodiments. A UE300, as well as cells-1 310-1, cell-2 310-2, and cell-3 310-3 are provided. As shown in Figure 3, the UE300 may be located in cell-1 310-1, which is a serving cell (i.e., a serving DU). Cells-2 310-2 and cell-3 310-3 may be considered adjacent cells to cell-1 310-1.

[0038] According to some embodiments, the UE300 may be configured with a measurement configuration that includes, for example, a configuration for measuring SSB and / or CSI-RS resources, physical cell ID, etc. The UE300 may also be configured with a measurement report configuration. For example, such a report configuration may include periodic and aperiodic reports to a serving cell (e.g., cell-1 310-1), but it should be recognized that other schemas and scheduling configurations for reporting may be configured by the UE300. The UE300 may be configured to measure the signal quality of one or more cells (i.e., serving cell cell-1 310-1 and adjacent cells cell-2 310-2 and cell-3 310-3).

[0039] The UE300 can perform cell measurements while connected to cell-1 310-1, and the UE300 can perform cell measurements during the scheduling gap indicated by cell-1 310-1 (the scheduling gap is described in more detail with reference to Figure 4 below). For inter-frequency measurements, the UE300 may be configured with a measurement gap. In other embodiments, the UE can dynamically indicate a set of time resources on which the UE can perform measurements. Signaling for such indications may take the form of physical downlink control channel (PDCCH) or MAC control element (MAC CE) commands.

[0040] According to one embodiment, UE300 can determine the preferred beam(s) to use while transmitting or receiving to or from an adjacent cell. UE300 can also report the preferred beam(s) to be used for its adjacent cell to serving cell-1 310-1 (e.g., via the uplink MAC CE).

[0041] According to one embodiment, the UE300 may be configured with a set of trigger states. In particular, each trigger state may include an offset value. For example, the offset value may be within a slot. Each trigger state may also include a gap length. The trigger states may be configured with RRC, and at least one trigger state may be activated or deactivated by MAC CE. The UE300 may indicate an index to a trigger state in Downlink Control Information (DCI). The offset value may indicate the time after a downlink signal (e.g., PDCCH) is received that the UE300 may begin performing a measurement, and the gap value may indicate the length of the gap over which the UE300 may continue performing a measurement. As an example, if a downlink signal is received in slot n and the trigger state value includes offset values ​​for L slots and gap values ​​for M slots, the UE300 may begin performing a measurement in slot n+L and end it in slot N+L+M-1. The UE300 may also indicate which cell(s) to measure as part of the trigger state. Alternatively, this may be indicated to the UE300 using another entry in the control information. In another embodiment, the offset value and / or gap value may be explicitly signaled in the DCI.

[0042] According to another embodiment, UE300 may be configured to receive a timing advance to be used for transmission to adjacent cell-2 310-2 and / or cell-3 310-3. This can be done proactively (i.e., before a handover request to an adjacent cell is received).

[0043] Figure 4 shows an exemplary timing diagram of an SCC / handover procedure according to one or more embodiments. A UE400, a serving DU410, a target DU420, and a CU-CP430 may be provided. It should be understood that, according to the embodiment, the UE400 may be similar to the UE300 described above, and the serving DU410 may be similar to the cell-1 310-1 described above. The target DU420 may be similar to either the cell-2 310-2 or cell-2 310-3 described above. The UE400 may be configured with lower layer (L1 / L2) trigger mobility (LTM) with one or more target cells in one or more DUs (e.g., target DU420). The CU-CP430 can send an RRC reconfiguration message to the UE400 to configure the LTM in the target cell (target DU420). The UE400 can then send an in-frequency L1 measurement report to the serving DU410.

[0044] Continuing to refer to Figure 4, in operation S440, the serving DU410 may detect that the target cell radio state exceeds a predefined threshold. For example, this may be based on an L1 measurement report indicating that the UE400 has an insufficient radio connection with the serving DU410. Thus, the serving DU410 may instruct the UE400 to perform a target cell measurement of the target DU420 and / or an uplink synchronization procedure with the target DU420 cell.

[0045] According to one embodiment, the instruction from the serving DU410 to the UE400 may be in the form of a downlink signal. The downlink signal may be in the form of a PDCCH or MAC CE command. The downlink signal may include a scheduling gap value, a start time value, and a target cell index. Specifically, the scheduling gap is a period of time during which no packets are scheduled downlink by the packet scheduler (MAC PS) located in the serving DU410 associated with the bearer. The scheduling gap may be in the form of a pre-configured index agreed upon by any well-known standard (e.g., 3GPP RAN2). Thus, different scheduling gap values ​​may be represented using different indices. Based on this information from the downlink signal, the UE400 can perform uplink measurement and / or uplink synchronization and / or preamble transmission during this scheduling gap. The downlink signal may include the physical cell ID (PCI) or index of the adjacent cell. PCI and / or indices can be used to determine the resource allocation for transmission (e.g., UE transmit beam, preamble index, random access time / frequency resources). Alternatively, the downlink signal may not include PCI or cell indices, but may include indices for preamble and / or random access resources.

[0046] In operation S441, after receiving a command in operation S440 to perform a target measurement, UE400 may perform uplink (UL) synchronization with target DU420. UL synchronization may include performing an L1 measurement (e.g., RSRP and / or RSRQ) of the adjacent target DU420, sending a preamble to target DU420, and obtaining the timing advance of UE400 in the target cell. Nevertheless, it should be noted that according to one embodiment, UL synchronization may be performed with one or more adjacent cells other than target DU420. According to another embodiment, the L1 measurement of the adjacent target DU cell 420, the timing advance obtained by UE400, and the results of the uplink synchronization may be signaled back to serving DU410 (e.g., via a MAC CE uplink). This report may be signaled to serving DU410 periodically or aperiodicly (i.e., on an event basis). Based on these measurements, the serving DU410 can instruct the UE (operation S443, as described in more detail below) to perform a non-RACH or RACH-based LTM handover / serving cell change (SCC) to the target DU420. The UE400 can also notify the serving DU410 (e.g., by sending a status signal) whether the UL synchronization and / or preamble transmission was successful. According to another embodiment, the UE400 may proactively send a random access preamble to the instructed target DU420 during the scheduling gap, so that the target DU420 can determine a timing advance. The serving DU410 can send the timing advance and the index of the cell corresponding to the timing advance to the UE400.Timing advance information from the UE400 can also be sent from the target DU420 to the serving DU410, for example, via the CU-CP430 (note that in this case, it is assumed that the serving DU410 and the target neighboring cell are associated with different gNB-DUs served by the same gNB-CU), or directly via the DU-DU interface if available.

[0047] According to one embodiment, UE400 can request a timing advance alignment applicable to the UE at target DU420 from serving DU410. The request can be sent to serving DU410 in MAC CE. The request may include the PCI and / or index of target DU420. Serving DU410 can send a timing advance value applicable to an adjacent cell to UE400, or (for example, if serving DU410 does not have a timing advance value or the value is outdated) can instruct UE400 to initiate the procedure disclosed above to obtain a timing advance value.

[0048] The UE400 may be configured with random access resources prior to this operation (for example, during target cell preparation), and these random access resources may be exclusively allocated to transmit the above random access preamble to the target DU420. The resource configuration may include, but is not limited to, preamble index, time / frequency resources (e.g., symbol / slot index, resource block (RB) index), transmit power, etc. The above measurements and preamble transmission may be performed while the UE400 maintains an RRC connection to the serving DU410.

[0049] In operation S443, serving DU410 may determine that the serving cell change radio condition is met (for example, based on the L1 measurement of target DU420). Therefore, serving DU410 can instruct UE400 to perform an SCC handover to target DU420. According to one embodiment, this instruction may be sent via a MAC CE command. It should be understood that the system information of target DU420 may already be available for use by UE400 (for example, from a previous configuration sent earlier before the procedure). Serving DU410 can also notify CU-CP430 of the change via an F1 message. Since UE400 has already obtained the timing advance of the target cell, it does not need to perform RACH and can directly send a scheduling request to target DU420. According to one embodiment, the scheduling request can utilize the previously obtained timing advance. The scheduling request configuration may also be available in UE400 from a previous configuration by serving DU410. Therefore, when UE400 moves to target DU420, target DU420 can use a suitable beam to transmit to the UE, since this information may have been shared by serving DU410. Similarly, UE400 can also use a suitable / optimal transmit / receive beam. In an alternative embodiment, it should be understood that UE400 may instead send an RRC configuration request to target DU420. In this alternative embodiment, the resource allocation for the RRC configuration message may already be available to UE400 from a previous configuration by serving DU410.

[0050] Therefore, the above embodiments can omit the execution of RACH in order to perform SCC / HO so that mobile latency is reduced. Furthermore, exemplary embodiments can enable the UE to determine a suitable beam to be used by an adjacent target cell and present it to the serving cell. Thus, embodiments of the present disclosure can provide a more optimal method for handling LTM with reduced latency and enable beam-based inter-cell mobility.

[0051] Figure 5 is a diagram of an exemplary environment 500 in which the system and / or method described herein may be implemented. As shown in Figure 5, the environment 500 may include a user device 510, a platform 520, and a network 530. The devices in environment 500 may be interconnected via wired connections, wireless connections, or a combination of wired and wireless connections. In embodiments, any of the functions and operations described above with reference to Figures 6-7 may be performed by any combination of the elements shown in Figure 5.

[0052] The user device 510 includes one or more devices capable of receiving, generating, storing, processing, and / or providing information related to the platform 520. For example, the user device 510 may include computing devices (e.g., desktop computers, laptop computers, tablet computers, handheld computers, smart speakers, servers, etc.), mobile phones (e.g., smartphones, wireless phones, etc.), wearable devices (e.g., smart glasses or smartwatches), or similar devices. In some implementations, the user device 510 can receive information from and / or transmit information to the platform 520.

[0053] Platform 520 includes one or more devices capable of receiving, generating, storing, processing, and / or providing information. In some implementations, Platform 520 may include a cloud server or a group of cloud servers. In some implementations, Platform 520 may be designed to be modular so that certain software components can be swapped in or swapped out as needed. Thus, Platform 520 can be easily and / or quickly reconfigured for different uses.

[0054] In some implementations, as shown, platform 520 may be hosted in a cloud computing environment 522. In particular, the implementations described herein describe platform 520 as being hosted within a cloud computing environment 522, but in some implementations, platform 520 may not be cloud-based (i.e., it may be implemented outside a cloud computing environment), or may be partially cloud-based.

[0055] The cloud computing environment 522 includes an environment that hosts platform 520. The cloud computing environment 522 may provide services such as computing, software, data access, and storage that do not require the end user's (e.g., user device 510) knowledge of the physical location and configuration of the system and / or device that hosts platform 520. As shown, the cloud computing environment 522 may include a group of computing resources 524 (collectively referred to as “computing resources 524” and individually referred to as “computing resources 524”).

[0056] The computing resource 524 includes one or more personal computers, a cluster of computing devices, a workstation computer, a server device, or other types of computing and / or communication devices. In some implementations, the computing resource 524 may host the platform 520. The cloud resource may include computing instances running within the computing resource 524, storage devices provided within the computing resource 524, data transfer devices provided by the computing resource 524, and so on. In some implementations, the computing resource 524 may communicate with other computing resources 524 via wired connections, wireless connections, or a combination of wired and wireless connections.

[0057] As further shown in Figure 5, the computing resource 524 includes a group of cloud resources such as one or more applications ("APP") 524-1, one or more virtual machines ("VM") 524-2, virtualized storage ("VS") 524-3, and one or more hypervisors ("HYP") 524-4.

[0058] Application 524-1 includes one or more software applications that may be provided to or accessed by the user device 510. Application 524-1 may eliminate the need to install and run software applications on the user device 510. For example, Application 524-1 may include software related to the platform 520 and / or any other software that may be provided via the cloud computing environment 522. In some implementations, one application 524-1 may send and receive information to and from one or more other applications 524-1 via a virtual machine 524-2.

[0059] A virtual machine 524-2 includes a machine (e.g., a computer) in the form of a software implementation that runs programs like a physical machine. Depending on its application and the degree to which the virtual machine 524-2 matches any actual machine, it may be either a system virtual machine or a process virtual machine. A system virtual machine may provide a complete system platform that supports the execution of a complete operating system ("OS"). A process virtual machine may run a single program and may support a single process. In some implementations, the virtual machine 524-2 may run on behalf of a user (e.g., a user device 510) and manage the infrastructure of a cloud computing environment 522, such as data management, synchronization, or long-term data transfer.

[0060] Virtualized storage 524-3 includes one or more storage systems and / or one or more devices that use virtualization technology within the storage system or device of the compute resource 524. In some implementations, the type of virtualization in the context of a storage system may include block virtualization and file virtualization. Block virtualization may refer to the extraction (or isolation) of logical storage from physical storage so that the storage system can be accessed regardless of whether it is physical storage or heterogeneous. Isolation may allow administrators flexibility in how the storage system manages storage for end users. File virtualization can eliminate the dependency between data accessed at the file level and where the file is physically stored. This may enable optimization of storage usage, server consolidation, and / or non-disruptive file movement.

[0061] Hypervisor 524-4 may provide hardware virtualization technology that enables multiple operating systems (e.g., "guest operating systems") to run simultaneously on a host computer such as computing resource 524. Hypervisor 524-4 may present a virtual operating platform to the guest operating system and manage the execution of the guest operating system. Multiple instances of various operating systems can share virtualized hardware resources.

[0062] Network 530 includes one or more wired and / or wireless networks. For example, Network 230 may include cellular networks (e.g., fifth-generation (5G) networks, long-term evolution (LTE) networks, third-generation (3G) networks, code division multiple access (CDMA) networks, etc.), public land mobile networks (PLMN), local area networks (LANs), wide area networks (WANs), metropolitan area networks (MANs), telephone networks (e.g., public switched telephone networks (PSTNs)), private networks, ad hoc networks, intranets, the Internet, fiber optic-based networks, etc., and / or combinations of these or other types of networks.

[0063] The number and arrangement of devices and networks shown in Figure 5 are provided as an example. In practice, there may be more or fewer devices and / or networks than those shown in Figure 5, or devices and / or networks that are different from those shown in Figure 5, or devices and / or networks that are arranged differently. Furthermore, two or more devices shown in Figure 5 may be implemented within a single device, or a single device shown in Figure 5 may be implemented as multiple distributed devices. Additionally or alternatively, a set of devices in environment 500 (e.g., one or more devices) may perform one or more functions that are described as being performed by another set of devices in environment 500.

[0064] Figure 6 shows an exemplary component of device 600. Device 600 may correspond to user device 510 and / or platform 520. As shown in Figure 6, device 600 may include a bus 610, a processor 620, memory 630, storage component 640, input component 650, output component 660, and communication interface 670.

[0065] Bus 610 includes components that enable communication between components of device 600. Processor 620 may be implemented in hardware, firmware, or a combination of hardware and software. Processor 620 may be a central processing unit (CPU), graphics processing unit (GPU), acceleration unit (APU), microprocessor, microcontroller, digital signal processor (DSP), field-programmable gate array (FPGA), application-specific integrated circuit (ASIC), or other types of processing components. In some implementations, processor 620 includes one or more processors that can be programmed to perform functions. Memory 630 includes random access memory (RAM), read-only memory (ROM), and / or other types of dynamic or static storage devices (e.g., flash memory, magnetic memory, and / or optical memory) that store information and / or instructions for use by processor 620.

[0066] The storage component 640 stores information and / or software related to the operation and use of device 600. For example, the storage component 640 may include, together with a corresponding drive, a hard disk (e.g., magnetic disk, optical disk, magneto-optical disk, and / or solid-state disk), a compact disk, a digital multipurpose disk, a floppy disk, a cartridge, a magnetic tape, and / or another type of non-temporary computer-readable medium. The input component 650 includes components that enable device 600 to receive information via user input (e.g., a touchscreen display, keyboard, keypad, mouse, buttons, switches, and / or microphone). Additionally or alternatively, the input component 650 may include sensors for sensing information (e.g., a Global Positioning System (GPS) component, an accelerometer, a gyroscope, and / or actuators). The output component 660 includes components that provide output information from device 600 (e.g., a display, a speaker, and / or one or more light-emitting diodes (LEDs)).

[0067] The communication interface 670 includes transceiver-like components (e.g., transceivers and / or separate receivers and transmitters) that enable device 600 to communicate with other devices via wired connections, wireless connections, or a combination of wired and wireless connections. The communication interface 670 may also enable device 600 to receive information from and / or provide information to other devices. For example, the communication interface 670 may include Ethernet interfaces, optical interfaces, coaxial interfaces, infrared interfaces, radio frequency (RF) interfaces, Universal Serial Bus (USB) interfaces, Wi-Fi interfaces, cellular network interfaces, and the like.

[0068] Device 600 may perform one or more processes described herein. Device 600 may perform these processes in response to the processor 620 executing software instructions stored in a non-temporary computer-readable medium such as memory 630 and / or storage component 640. A computer-readable medium is defined herein as a non-temporary memory device. A memory device includes a memory space within a single physical storage device or a memory space that extends across multiple physical storage devices.

[0069] Software instructions may be read into memory 630 and / or storage component 640 from another computer-readable medium or from another device via the communication interface 670. When executed, the software instructions stored in memory 630 and / or storage component 640 may cause the processor 620 to execute one or more processes described herein.

[0070] Additionally or alternatively, hardwired circuits may be used instead of, or in combination with, software instructions to perform one or more processes described herein. Therefore, the implementations described herein are not limited to any particular combination of hardware circuits and software.

[0071] The number and arrangement of components shown in Figure 6 are provided as an example. In practice, device 600 may include additional components, fewer components, different components, or components in different arrangements compared to the device shown in Figure 6. Additionally or alternatively, a set of components of device 600 (e.g., one or more components) may perform one or more functions that are described as being performed by another set of components of device 600.

[0072] In some embodiments, any one of the operations or processes shown in Figure 4 may be implemented by or using any one of the elements shown in Figures 5 and 6. Other embodiments are understood to be implemented in a variety of different architectures, but are not limited to them, such as bare metal architectures, Kubernetes, Docker, OpenStack, or any other cloud-based architecture or deployment architecture.

[0073] The foregoing disclosures provide examples and explanations, but are not intended to be exhaustive or to limit implementations to the exact forms disclosed. Modifications and variations are possible in light of the foregoing disclosures or may be derived from the practice of the implementations.

[0074] Some embodiments may relate to systems, methods, and / or computer-readable media in integration at any possible level of technical detail. Furthermore, one or more of the components described above may be implemented as instructions stored on a computer-readable medium and executable by at least one processor (and / or may include at least one processor). The computer-readable medium may include computer-readable non-temporary storage medium (or more mediums) having computer-readable program instructions for causing a processor to perform an operation.

[0075] A computer-readable storage medium can be a tangible device capable of holding and storing instructions for use by an instruction-executing device. A computer-readable storage medium may, but is not limited to, electronic storage devices, magnetic storage devices, optical storage devices, electromagnetic storage devices, semiconductor storage devices, or any suitable combination thereof. A non-exhaustive list of more specific examples of computer-readable storage mediums includes portable computer diskettes, hard disks, random-access memory (RAM), read-only memory (ROM), erasable programmable read-only memory (EPROM or flash memory), static random-access memory (SRAM), portable compact disk read-only memory (CD-ROM), digital multipurpose disks (DVDs), memory sticks, floppy disks, mechanically encoded devices such as punch cards or grooved raised structures on which instructions are recorded, and any suitable combination thereof. The computer-readable storage mediums used herein should not be construed as transient signals themselves, such as radio waves or other freely propagating electromagnetic waves, electromagnetic waves propagating through waveguides or other transmission media (e.g., optical pulses through optical fiber cables), or electrical signals transmitted through wires.

[0076] The computer-readable program instructions described herein may be downloaded from a computer-readable storage medium to each computing / processing device, or to an external computer or external storage device via a network, such as the Internet, a local area network, a wide area network, and / or a wireless network, or a combination thereof. The network may include copper transmission cables, optical transmission fibers, wireless transmissions, routers, firewalls, switches, gateway computers, and / or edge servers, or a combination thereof. A network adapter card or network interface within each computing / processing device receives computer-readable program instructions from the network and transfers the computer-readable program instructions for storage in a computer-readable storage medium within each computing / processing device.

[0077] The computer-readable program code / instructions for performing an operation may be either assembler instructions, instruction set architecture (ISA) instructions, machine instructions, machine-dependent instructions, microcode, firmware instructions, state setting data, integrated circuit configuration data, or source code or object code written in any combination of one or more programming languages, including object-oriented programming languages ​​such as Smalltalk and C++, and procedural programming languages ​​such as the "C" programming language or similar programming languages. The computer-readable program instructions may run entirely on the user's computer, partially on the user's computer, as a standalone software package, partially on the user's computer and partially on a remote computer, or entirely on a remote computer or server. In the latter scenario, the remote computer may be connected to the user's computer via any type of network, including a local area network (LAN) or wide area network (WAN), or it may be connected to an external computer (for example, via the Internet using an Internet service provider). In some embodiments, for example, an electronic circuit including a programmable logic circuit, a field-programmable gate array (FPGA), or a programmable logic array (PLA) can execute computer-readable program instructions by personalizing the electronic circuit using state information of computer-readable program instructions in order to perform an action or operation.

[0078] These computer-readable program instructions may be provided to a general-purpose computer, a dedicated computer, or a processor of another programmable data processing device to create a machine, such that instructions executed via the processor of a computer or other programmable data processing device create means for implementing functions / operations specified in one or more blocks of a flowchart and / or block diagram, or both. These computer-readable program instructions may also be stored in a computer-readable storage medium that can instruct a computer, a programmable data processing device, and / or other device to function in a particular way, such that the computer-readable storage medium storing the instructions internally contains a product containing instructions that implements a mode of function / operation specified in one or more blocks of a flowchart and / or block diagram.

[0079] Computer-readable program instructions may also be loaded into a computer, another programmable data processing device, or another device to generate a computer implementation process by causing the computer, another programmable device, or other device to execute a series of operational steps so that the instructions executed on the computer, another programmable device, or other device implement a function / action specified in one or more blocks of a flowchart and / or block diagram.

[0080] The flowcharts and block diagrams in the figures illustrate the architecture, functions, and operation of possible implementations of systems, methods, and computer-readable media in various embodiments. In this regard, each block in a flowchart or block diagram may represent a microservice(s), module, segment, or part of an instruction containing one or more executable instructions for implementing a specified logical function(s). Methods, computer systems, and computer-readable media may include additional blocks, fewer blocks, different blocks, or blocks arranged differently from those shown in the figures. In some alternative implementations, the functions described in the blocks may be performed in an order different from the order shown in the figures. For example, two consecutively shown blocks may actually be executed simultaneously or substantially simultaneously, or blocks may sometimes be executed in reverse order depending on the functions involved. It should also be noted that each block in a block diagram and / or flowchart, and combinations of blocks in a block diagram and / or flowchart, may be implemented by a dedicated hardware-based system that performs a specified function or operation, or a combination of dedicated hardware and computer instructions.

[0081] It will be apparent that the systems and / or methods described herein may be implemented in different forms of hardware, firmware, or combinations of hardware and software. The actual dedicated control hardware or software code used to implement these systems and / or methods is not limited to any specific implementation. Therefore, the operation and behavior of the systems and / or methods are described herein without reference to any specific software code, and it is understood that software and hardware may be designed to implement the systems and / or methods based on the descriptions herein.

[0082] Various embodiments

[0083] Various further embodiments and features of the embodiments of this disclosure can be defined by the following items. Item [1]: A method performed by at least one processor for configuring an inter-cell change, the method comprising: receiving a downlink signal by a user device (UE), the downlink signal originating from a serving distribution unit (DU), the downlink signal comprising at least one of a scheduling gap duration value, a start time value, and a target cell index; and performing an uplink synchronization with a target cell based on the downlink signal by the UE during the scheduling gap duration, the uplink synchronization comprising the UE sending a preamble transmission to the target cell to obtain a timing advance for the target cell based on the downlink signal, the target DU being one of a plurality of adjacent cells to the serving DU. Item [2]: The method according to Item [1], further comprising: the UE obtaining a timing advance to be used during transmission to or reception from a target cell; and the UE reporting the results of uplink synchronization and the obtained timing advance to the Serving DU. Item [3]: The method described in Item [1] or [2], wherein preamble transmission and uplink synchronization are performed while the UE is connected to the serving DU. Item [4]: ​​The method according to any one of items [1] to [3], wherein the downlink signal is one of either a physical downlink control channel (PDCCH) or a MAC control element (MAC CE) command. Item [5]: The method of any one of Items [1] to [4], further comprising the method of the UE sending the L1 measurement to a serving DU, the serving DU being able to determine, based on the target cell timing advance reported by the UE, whether to perform an LTM handover without RACH based on the L1 measurement. Item [6]. The method of Item [5], further comprising sending a preamble transmission to a target DU based on a downlink signal, during a scheduling gap duration determined based on a scheduling gap duration value, such that the target DU can determine a timing advance value for the UE based on receiving the random access preamble. Item [7]: A method according to any one of Items [1] to [6], further comprising: the UE performing uplink synchronization based on measurement and preamble transmission; and the UE sending a status signal to the serving DU. Item [8]: The method according to Item [5] or [6], wherein L1 measurements are performed and reported on one or more target cells aperiodicly or on an event basis, and the L1 measurements are sent aperiodicly to a serving DU. Item [9]: A device for configuring inter-cell changes, comprising at least one memory storing computer executable instructions, and at least one processor configured to execute computer executable instructions and receive a downlink signal by a user device (UE), the downlink signal originating from a serving distribution unit (DU) and comprising at least one of a scheduling gap duration value, a start time value, and a target cell index, and performing uplink synchronization with a target cell by the UE based on the downlink signal during the scheduling gap duration, wherein the uplink synchronization includes the UE sending a preamble transmission to a target cell to obtain a timing advance for the target cell based on the downlink signal, and the target DU is one of a plurality of adjacent cells to a serving DU. Item

[10] : The apparatus as described in Item [9], further configured to have at least one processor execute computer executable instructions to obtain a timing advance for use by the UE during transmission to or reception from a target cell, and to report the results of uplink synchronization and the obtained timing advance to the serving DU. Item

[11] : The apparatus described in Item [9] or

[10] , in which preamble transmission and uplink synchronization are performed while the UE is connected to the Serving DU. Item

[12] : A device described in any one of items [9] to

[11] , wherein the downlink signal is one of either a physical downlink control channel (PDCCH) or a MAC control element (MAC CE) command. Item

[13] : The apparatus described in any one of items [9] to

[12] , wherein at least one processor is further configured to perform a measurement by executing a computer executable instruction to perform an L1 measurement of a target cell based on a downlink signal, and at least one processor is further configured to perform sending an L1 measurement to a serving DU by the UE, the serving DU being able to determine whether to perform an LTM handover without RACH based on the L1 measurement, based on a target cell timing advance reported by the UE. Item

[14] : The apparatus described in Item

[13] , wherein at least one processor is further configured to send a preamble transmission to a target DU based on a downlink signal by sending a random access preamble to a target DU during a scheduling gap duration determined based on a scheduling gap duration value, the target DU can determine a timing advance value for the UE based on receiving the random access preamble. Item

[15] : The apparatus described in any one of items [9] to

[14] , wherein at least one processor is further configured to perform: by the UE, uplink synchronization based on measurement and preamble transmission, and by the UE, status signals to the serving DU. Item

[16] : The apparatus described in Item

[13] or

[14] , wherein L1 measurements are performed and reported on one or more target cells aperiodicly or on an event basis, and the L1 measurements are sent aperiodicly to a serving DU. Item

[17] : A non-temporary computer-readable recording medium on which instructions are recorded, wherein the instructions are executable by at least one processor, and the at least one processor: receives a downlink signal by a user device (UE), the downlink signal originating from a serving distribution unit (DU), the downlink signal comprising at least one of a scheduling gap duration value, a start time value, and a target cell index; and during the scheduling gap duration, the UE performs uplink synchronization with a target cell based on the downlink signal, the uplink synchronization comprising the UE sending a preamble transmission to the target cell to obtain a timing advance for the target cell based on the downlink signal, the target DU being one of a plurality of adjacent cells to the serving DU. Item

[18] : A non-temporary computer-readable recording medium as described in Item

[17] , further comprising: the UE obtaining a timing advance to use during transmission to or reception from a target cell; and the UE reporting the results of uplink synchronization and the obtained timing advance to the serving DU. Item

[19] : A non-temporary computer-readable recording medium as described in Item

[17] or

[18] , further comprising the method of performing a measurement based on a downlink signal, which in turn comprises sending the L1 measurement to a serving DU, the serving DU being able to determine, based on the target cell timing advance reported by the UE, whether to perform an LTM handover without RACH based on the L1 measurement. Item

[20] : A non-temporary computer-readable recording medium as described in Item

[19] , further comprising sending a preamble transmission to a target DU based on a downlink signal, during a scheduling gap duration determined based on a scheduling gap duration value, such that the target DU can determine a timing advance value for the UE based on receiving the random access preamble.

[0084] In light of the above teachings, it can be understood that many modifications and variations of this disclosure are possible. Within the scope of the attached clauses, it will be apparent that this disclosure may be implemented in ways other than those specifically described herein.

Claims

1. A method for configuring inter-cell changes, performed by at least one processor, Receiving a downlink signal by a user device (UE), wherein the downlink signal originates from a serving distribution unit (DU), and the downlink signal includes a scheduling gap duration value, a start time value indicating the time from the reception of the downlink signal until the start of the scheduling gap, and a target cell index. During the scheduling gap duration and before the UE receives a handover or serving cell change command, the UE performs uplink synchronization with the target cell of the target DU based on the downlink signal. Includes, The method includes the uplink synchronization by the UE sending a preamble transmission to the target cell to obtain a timing advance for the target cell based on the downlink signal, wherein the target cell is one of a plurality of adjacent cells to the serving DU.

2. The method described above is The UE obtains a timing advance to be used during transmission to or reception from the target cell, The UE reports the results of the uplink synchronization and the acquired timing advance to the Serving DU, The method according to claim 1, further comprising:

3. The method according to claim 1, wherein the preamble transmission and the uplink synchronization are performed while the UE is connected to the serving DU.

4. The method according to claim 1, wherein the downlink signal is one of a physical downlink control channel (PDCCH) or a MAC control element (MAC CE) command.

5. The method described above is The UE performs L1 measurement of the target cell based on the downlink signal, The UE sends the L1 measurement to the Serving DU, which can then determine, based on the target cell timing advance reported by the UE, whether to perform an LTM handover without RACH based on the L1 measurement. The method according to claim 1, further comprising:

6. Sending the preamble transmission to the target DU based on the downlink signal, Sending a random access preamble to the target DU during a scheduling gap duration determined based on the scheduling gap duration value, wherein the target DU can determine a timing advance value for the UE based on receiving the random access preamble. The method according to claim 5, further comprising:

7. The method described above is The aforementioned UE performs uplink synchronization based on the measurement and the preamble transmission, The UE sends a status signal to the Serving DU, The method according to claim 5, further comprising:

8. The method according to claim 5, wherein the L1 measurement is performed and reported on one or more target cells aperiodically or on an event basis, and the L1 measurement is sent aperiodically to the serving DU.

9. A device for configuring inter-cell changes, At least one memory location storing computer executable instructions, At least one processor, which executes the computer executable instructions, Receiving a downlink signal by a user device (UE), wherein the downlink signal originates from a serving distribution unit (DU), and the downlink signal includes a scheduling gap duration value, a start time value indicating the time from the reception of the downlink signal until the start of the scheduling gap, and a target cell index. During the scheduling gap duration and before the UE receives a handover or serving cell change command, the UE performs uplink synchronization with the target cell of the target DU based on the downlink signal. A processor configured to perform the following: Equipped with, The uplink synchronization includes the UE sending a preamble transmission to the target cell to obtain a timing advance for the target cell based on the downlink signal, wherein the target cell is one of a plurality of adjacent cells to the serving DU.

10. The at least one processor executes the computer executable instruction, The UE obtains a timing advance to be used during transmission to or reception from the target cell, The UE reports the results of the uplink synchronization and the acquired timing advance to the Serving DU, The apparatus according to claim 9, further configured to perform the following:

11. The apparatus according to claim 9, wherein the preamble transmission and the uplink synchronization are performed while the UE is connected to the serving DU.

12. The apparatus according to claim 9, wherein the downlink signal is one of a physical downlink control channel (PDCCH) or a MAC control element (MAC CE) command.

13. The at least one processor is further configured to execute the computer executable instructions to perform an L1 measurement of the target cell based on the downlink signal, and the at least one processor executes the computer executable instructions, The UE sends the L1 measurement to the Serving DU, which can then determine, based on the target cell timing advance reported by the UE, whether to perform an LTM handover without RACH based on the L1 measurement. The apparatus according to claim 9, further configured to perform the following:

14. The at least one processor executes the computer executable instruction, Sending a random access preamble to the target DU during a scheduling gap duration determined based on the scheduling gap duration value, wherein the target DU can determine a timing advance value for the UE based on receiving the random access preamble. The apparatus according to claim 13, further configured to send the preamble transmission to the target DU based on the downlink signal.

15. The at least one processor executes the computer executable instruction, The aforementioned UE performs uplink synchronization based on the measurement and the preamble transmission, The UE sends a status signal to the Serving DU, The apparatus according to claim 13, further configured to perform the following:

16. The apparatus according to claim 13, wherein the execution and reporting of the L1 measurement are performed aperiodically or on an event basis for one or more target cells, and the L1 measurement is sent aperiodicly to the serving DU.

17. A non-temporary computer-readable recording medium on which instructions are recorded, wherein the instructions are executable by at least one processor, and the at least one processor, Receiving a downlink signal by a user device (UE), wherein the downlink signal originates from a serving distribution unit (DU), and the downlink signal includes a scheduling gap duration value, a start time value indicating the time from the reception of the downlink signal until the start of the scheduling gap, and a target cell index. During the scheduling gap duration and before the UE receives a handover or serving cell change command, the UE performs uplink synchronization with the target cell of the target DU based on the downlink signal. Includes, The uplink synchronization includes the UE sending a preamble transmission to the target cell to obtain the timing advance of the target cell based on the downlink signal, wherein the target cell is one of a plurality of neighboring cells to the serving DU. A non-temporary computer-readable recording medium that enables the execution of a method.

18. The method described above is The UE obtains a timing advance to be used during transmission to or reception from the target cell, The UE reports the results of the uplink synchronization and the acquired timing advance to the Serving DU, A non-temporary computer-readable recording medium according to claim 17, further comprising:

19. The method described above is The UE performs L1 measurement of the target cell based on the downlink signal, The UE sends the L1 measurement to the Serving DU, which can then determine, based on the target cell timing advance reported by the UE, whether to perform an LTM handover without RACH based on the L1 measurement. A non-temporary computer-readable recording medium according to claim 18, further comprising:

20. Sending the preamble transmission to the target DU based on the downlink signal, The non-temporary computer-readable recording medium according to claim 19, further comprising sending a random access preamble to the target DU during a scheduling gap duration determined based on the scheduling gap duration value, so that the target DU can determine a timing advance value for the UE based on receiving the random access preamble.

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