Successful signaling in rach-less ltm completion

Abstract

A user equipment (UE) (201) is disclosed herein. The UE is configured to receive a layer 1 / layer 2 triggered mobility (LTM) cell handover command without random access channel (RACH) from a source gNB-DU (203). The UE is further configured to transmit a first UL data packet to a target gNB-DU (205) via one of a configured UL scheduling grant and a dynamic UL scheduling grant to indicate a successful LTM cell handover without RACH. The UE is configured to transmit a SR to the target gNB-DU to receive a dynamic grant to transmit a second UL data packet. The UE is configured to receive a second UL scheduling grant from the target gNB-DU in response to the transmitted scheduling request. The UE is configured to determine that the indication of the successful LTM cell handover without RACH to the target gNB-DU is successfully communicated in response to the received second UL scheduling grant.

Description

Cross-references to related applications

[0001] This application claims priority to Indian Provisional Application No. 202411016290, filed on 7 March 2024, and Indian Non-Provisional Application No. 202411016290, filed on 25 September 2024; the entire contents of the above applications are incorporated herein by reference. Technical Field

[0002] This invention relates to signaling for successful Layer 1 / Layer 2 triggered mobility (LTM) completion without a random access channel (RACH). Background Technology

[0003] The information disclosed in this background section is intended only to enhance the understanding of the general background of this disclosure and should not be construed as forming an affirmation of prior art known to those skilled in the art or any form of suggestion thereof.

[0004] Mobility or handover ensures seamless continuity of a UE’s ongoing communication sessions by transferring a UE’s session from one cell (i.e., a base station or gNodeB (gNB)) to another connected cell while the UE is moving.

[0005] According to the released 3GPP Release 17, cell change transmissions can be triggered by Layer 3 (L3) measurements and can be performed via Radio Resource Control (RRC) signaling. Furthermore, the released 3GPP Release 18 introduces Layer 1 / L2 triggered Mobility Measure (LTM), which improves handover latency and downtime compared to L3-based mobility.

[0006] Therefore, it is necessary to address the shortcomings or other deficiencies in the traditional solutions related to the LTM cell handover process. Summary of the Invention

[0007] The summary of this invention is provided to present a selection of concepts in a simplified form, which will be further elaborated in the detailed description of this disclosure. This summary is not intended to identify key or essential inventive concepts of this disclosure, nor is it intended to define the scope of this disclosure.

[0008] According to one embodiment of this disclosure, a user equipment (UE) is disclosed. The UE is configured to receive a Layer 1 / Layer 2 Mobility TM (LTM) cell handover command without a Random Access Channel (RACH) from a source gNodeB Distributed Unit (gNB-DU). The RACH-less LTM cell handover command is configured to trigger the UE to perform a cell handover to a target gNB-DU via L2 signaling. In response to the received RACH-less LTM cell handover command, the UE is configured to send a first UL data packet to the target gNB-DU via one of a configured uplink (UL) scheduling grant and a dynamic UL scheduling grant to indicate a successful RACH-less LTM cell handover. After sending the first UL data packet, the UE is configured to send a scheduling request (SR) to the target gNB-DU. The SR is sent to receive a second UL data packet in order to receive a dynamic grant. The UE is configured to receive a second UL scheduling grant from the target gNB-DU in response to the sent scheduling request. In response to the received second UL scheduling authorization, the UE is configured to determine that an indication of a successful RACH-free LTM cell handover to the target gNB-DU has been successfully delivered.

[0009] According to another embodiment of this disclosure, a method is disclosed. The method includes: a user equipment (UE) receiving a Layer 1 / Layer 2 triggered mobility (LTM) cell handover command without a random access channel (RACH) from a source gNodeB distributed unit (gNB-DU). The RACH-free LTM cell handover command is configured to trigger the UE to perform a cell handover to a target gNB-DU via L2 signaling. In response to receiving the RACH-free LTM cell handover command, the method includes sending a first UL data packet to the target gNB-DU via one of a configured uplink (UL) scheduling grant and a dynamic UL scheduling grant to indicate a successful RACH-free LTM cell handover. The first UL data packet is sent by the UE to the target gNB-DU. After sending the first UL data packet, the method includes sending a scheduling request (SR) to the target gNB-DU. The SR is sent by the UE to the target gNB-DU. The method also includes receiving a second UL scheduling grant in response to the sent scheduling request. In response to the received second dynamic grant, the method includes the UE determining that an indication of a successful RACH-free LTM cell handover to the target gNB-DU has been successfully transmitted.

[0010] According to another embodiment of this disclosure, an apparatus is disclosed. The apparatus is configured to receive uplink (UL) data packets via either a configured UL scheduling grant or a dynamic UL scheduling grant. The apparatus is configured to receive UL data packets from a user equipment (UE). The apparatus is configured to assign a dynamic UL grant with a predefined grant value to the UE. This predefined grant value is assigned to the dynamic UL grant to indicate reception of a Layer 1 / Layer 2 Mobility (LTM) cell handover indication without a Random Access Channel (RACH), or to signify successful reception of a UL data packet indicating a successful RACH-free LTM cell handover.

[0011] According to another embodiment of this disclosure, a method is disclosed. The method includes: receiving uplink (UL) data packets via one of a configured UL scheduling grant or a dynamic UL scheduling grant after a Layer 1 / Layer 2 mobility (LTM) cell handover without a random access channel (RACH). The UL data packets are received from the UE by a target gNB-DU. The method further includes: assigning a dynamic UL grant with a predefined grant value. The requested grant value is assigned as either reception indicating a successful RACH-less LTM cell handover indication, or successful reception of a UL data packet indicating a successful RACH-less LTM cell handover. The dynamic UL grant is assigned to the UE by the target gNB-DU.

[0012] According to another embodiment of this disclosure, a non-transitory computer-readable medium is disclosed. This non-transitory computer-readable medium stores instructions. These instructions include one or more instructions executed by a user equipment (UE). The UE includes one or more processors. The one or more instructions cause the one or more processors to receive a Layer 1 / Layer 2 Mobility TM (LTM) cell handover command without a Random Access Channel (RACH) from a source gNodeB Distributed Unit (gNB-DU). The RACH-less LTM cell handover command is configured to trigger the UE to perform a cell handover to a target gNB-DU via L2 signaling. In response to the received RACH-less LTM cell handover command, the one or more instructions cause the one or more processors to send a first UL data packet to the target gNB-DU via one of a configured uplink (UL) scheduling grant and a dynamic UL scheduling grant to indicate a successful RACH-less LTM cell handover. After sending the first UL data packet, the one or more instructions cause the one or more processors to send a scheduling request (SR) to the target gNB-DU to receive a dynamic grant to send a second UL data packet. One or more instructions cause one or more processors to receive a second UL scheduling grant from the target gNB-DU in response to a sent scheduling request. These one or more instructions also cause one or more processors to determine, in response to the received second uplink scheduling grant, that an indication of a successful LTM cell handover without a random access channel (RACH) to the target gNB-DU has been successfully delivered.

[0013] According to another embodiment of this disclosure, a non-transitory computer-readable medium is disclosed. This non-transitory computer-readable medium stores instructions. The instructions include one or more instructions executed by a target gNodeB Distributed Unit (gNB-DU) after a Layer 1 / Layer 2 mobility (LTM) cell handover without a random access channel (RACH). The target gNB-DU includes one or more processors. The one or more instructions cause the one or more processors to receive uplink (UL) data packets from a user equipment (UE). The one or more instructions cause the one or more processors to assign a dynamic UL grant with a predefined grant value to the user equipment (UE) to indicate the reception of a successful RACH-free LTM cell handover indication, or to indicate the successful reception of a UL data packet indicating a successful RACH-free LTM cell handover.

[0014] To further illustrate the advantages and features of this disclosure, a more specific description of the disclosure will be presented with reference to specific embodiments shown in the accompanying drawings. It should be understood that these drawings depict only typical embodiments of the disclosure and should therefore not be considered as limiting the scope of the disclosure. The disclosure will be described and explained in more detail in conjunction with the accompanying drawings. Attached Figure Description

[0015] Features, aspects, and advantages of certain exemplary embodiments of this disclosure will now be described with reference to the accompanying drawings, wherein like reference numerals denote like elements, and wherein: Figure 1 This illustrates a discrete gNB architecture based on existing technology; Figure 2A-2B The following is illustrated: a sequence of operations between a UE and a gNB-CU via gNB-DU1 and gNB-DU2 according to an embodiment of the present disclosure; Figures 3A-3B An operational sequence between a UE and a gNB-CU via gNB-DU1 and gNB-DU2 according to another embodiment of this disclosure is shown; Figure 4 A flowchart of an example method implemented by a UE according to an embodiment of the present disclosure is shown; Figure 5 A flowchart illustrating an example method implemented by a target gNB-DU according to an embodiment of this disclosure is shown; and Figure 6 An embodiment of an example device according to one embodiment of the present disclosure is shown. Detailed Implementation

[0016] The following detailed description of exemplary embodiments is provided with reference to the accompanying drawings. This disclosure provides illustration and description, but is not intended to be exhaustive or to limit implementations to the precise forms disclosed. Various modifications and variations are possible according to this disclosure, or may be obtained from the practice of implementation. 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). Additionally, the flowcharts and descriptions of operations provided below relate to at least one embodiment of this disclosure. It should be noted that other embodiments may be formulated that do not perfectly match the flowcharts and their descriptions. It will be understood that in other embodiments, one or more operations may be omitted, one or more operations may be added, or one or more operations may be performed (at least partially) simultaneously.

[0017] It should be apparent that the systems and / or methods described herein can be implemented in various forms of hardware, software, or combinations thereof. The actual dedicated control hardware or software code used to implement these systems and / or methods should not limit their implementation. Therefore, the operation and behavior of the systems and / or methods are described herein without reference to specific software code. It should be understood that software and hardware can be incorporated based on the descriptions herein to implement the systems and / or methods.

[0018] Although specific combinations of features are listed in the claims and / or disclosed in the specification, these specific combinations are not intended to limit the disclosure of implementation. In fact, many of these features can be combined in ways not specifically listed in the claims and / or not disclosed in the specification. Even if a dependent claim relies directly on only one claim, this disclosure may indicate that the dependent claim depends on other claims in the claim set.

[0019] Unless explicitly stated otherwise, no element, action, or instruction used herein should be construed as essential or necessary. Furthermore, as used herein, the articles “a” and “an” (in other words, nouns not mentioned in plural form) are intended to include one or more items and may be used interchangeably with “one or more”. Additionally, as used herein, the terms “having,” “having,” “containing,” “including,” “comprise,” etc., are intended to be open-ended terms. Furthermore, unless expressly stated otherwise, the phrase “based on” is intended to mean “at least partially based on.” Moreover, expressions such as “at least one of [A] and [B],” “[A] and / or [B],” or “at least one of [A] or [B]” should be understood to include only A, only B, or both A and B.

[0020] In Rel-18, the following protocol is reached in the context of a successful Layer 1 / Layer 2 triggered Mobility (LTM) cell handover. According to TS38.321: For LTM without a Radio Access Channel (RACH), Radio Access Network 2 (RAN2) assumes that the User Equipment (UE) is based on the access channel. Physical downlink control channel receiving the Cell Radio Network Temporary Identifier (C-RNTI) of the UE in the target cell The PDCCH (Programmable Continuous Channel Communication) determines the successful reception of its first uplink (UL) data. The target cell schedules new uplink data after the first UL data reception. The transmission (FFS) is used if specific content should be sent using this transmission, such as LTE Media Access Control - Control Element (LTE). MAC CE) .

[0021] After performing a RACH-free LTM cell handover, the source gNodeB Distributed Unit (gNB-DU) sends the RACH preamble, the selected Temporary Cell Identifier (TCI) status information, and the beam information passed to the UE in the LTM cell handover command (e.g., MAC CE). Based on this, the target gNB-DU can decide to perform pre-scheduling, schedule the new transmission to the UE, and provide UL scheduling authorization, i.e., dynamic authorization. The UE may have already initiated the transmission of UL data (real numbers, padding bits, or RRC messages) using the configuration authorization (i.e., UL scheduling authorization) allocated by the target gNB-DU during LTM candidate cell preparation to indicate a successful RACH-free LTM cell handover at time slot #N. The target gNB-DU may or may not receive UL data. If the target gNB-DU successfully receives UL data, the UL data will be received at time slot N+2.

[0022] As mentioned earlier, if the UE and gNB have no data to transmit in the UL and DL during a specific time period, the UE cannot know whether the first UL data was successfully received at the gNB (i.e., the target gNB-DU) (it was sent to indicate a successful RACH-free LTM cell handover), because there is no Hybrid Automatic Repeat Request (HARQ) acknowledgment from the gNB in ​​the DL, and it was sent using the CG before the DG was allocated. Therefore, informing the UE about the success / failure of UL data packet delivery is crucial.

[0023] Figure 1 A discrete architecture for the gNB 100 according to conventional technology is illustrated. A discrete architecture, defined in 3GPP, decomposes the gNB 100 into multiple logical entities. These multiple logical entities may include one or more first units 102, which can be represented by at least one distributed unit (gNB-DU); and one or more second units 104, which can be represented by a centralized unit (gNB-CU). The gNB-CU can be further subdivided into a CU control plane (CP) portion (also referred to as gNB-CU-CP) and a CU user plane (UP) portion (also referred to as gNB-CU-UP). Such a division enables the implementation of the CU-CP and CU-UP portions in different locations. For example, splitting the gNB 100 into multiple logical entities can enable flexibility, scalability, and efficiency in the deployment and operation of 5G networks. The discrete architecture of the gNB 100 may also include a radio unit (gNB-RU). Figure 1 Not shown in the image.

[0024] The gNB-RU is responsible for the wireless transmission and reception of signals. The gNB-RU may include physical radio frequency (RF) components such as antennas, power amplifiers, and analog-to-digital converters. The gNB-RU can be located at a cell site or on a radio tower near the antenna. Furthermore, the gNB-DU can perform baseband processing functions such as physical layer processing, channel coding, and modulation / demodulation. Specifically, the gNB-DU can carry the Radio Link Control (RLC) layer, Media Access Control (MAC) layer, and Physical (PHY) layer. The gNB-DU can also perform scheduling operations. Multiple gNB-RUs can be connected to a single gNB-DU, allowing centralized processing of multiple radio units. The gNB-CU can handle higher-level processing functions such as radio resource management, mobility management, and connection management. The gNB-CU can provide a centralized control point for multiple gNB-DUs, enabling network-wide coordination and optimization.

[0025] According to one configuration, a gNB-DU can host multiple cells (e.g., up to 512 according to current specifications). A gNB-CU-CP can host one or more gNB-DUs and one or more gNB-CU-UPs. Additionally, a gNB-CU-UP can host the Packet Data Convergence Protocol User Plane Part (PDCP-U) and the Service Data Adaptation Protocol (SDAP). More specifically, regarding the 3GPP RAN3 basic definition for 5G gNB 100: a gNB 100 can include only one gNB-CU-CP. There can be “n” gNB-DUs controlled by a gNB-CU-CP. Furthermore, there may be “m” gNB-CU-UPs controlled by a gNB-CU-CP within a gNB 100. Additionally, a gNB-DU can be served by multiple gNB-CU-UPs. Various entities and / or network functions within the gNB 100 can communicate via one or more interfaces, including the F1-C, F1-U, and E1 interfaces. The F1-C interface is the control plane interface between the gNB-CU and gNB-DU within the gNB 100. The F1-C interface is used for signaling and control messages related to radio resource management, mobility management, and configuration management. The F1-C interface facilitates coordination between the gNB-CU and gNB-DU, enabling efficient network operation and service delivery. The F1-U interface is the user plane interface between the gNB-CU and gNB-DU in the gNB 100 architecture. The F1-U interface is responsible for transmitting user data packets between the gNB-CU and gNB-DU. The F1-U interface handles user plane data processing, including packet forwarding, Quality of Service (QoS) management, and encryption / decryption functions. The E1 interface in the gNB 100 connects entities to the gNB-CU and / or gNB 100 core network elements, such as 5G core network (5GC) network functions.

[0026] In Rel-18, LTM is restricted to movement within the CU. Data scheduling operations typically occur at the gNB-DU. However, to support L1 / L2-centric inter-cell handover (i.e., handover of the serving cell) in the split gNB architecture 100, the HO preparation phase (i.e., providing the UE with candidate / target cell configuration) is performed by the gNB-CU-CP. This phase is performed autonomously by the gNB-DU without further interaction with the upper layers in the gNB-CU-CP.

[0027] Furthermore, according to current 5G technology, the UE does not receive any Hybrid Automatic Repeat Request (HARQ) acknowledgments from the network in the downlink (DL) for any uplink (UL) data sent by the UE. Such data reception acknowledgments can be indicated using the New Data Indicator (NDI) field. Further dynamic UL authorization allocation exists if the UE has more UL data in its buffer and sends a scheduling request to the gNB. The UE sends data packets to the gNB in ​​the UL to indicate a successful RACH-free LTM cell handover. If there is no UL data, the UE creates UL data packets using padding bits and sends them to indicate completion. Even RRC reconfiguration acknowledgment messages sent by the UE to indicate successful application of the target configuration can be considered UL data.

[0028] If the UE has UL data in its buffer, it will send a scheduling request and receive more UL dynamic grants. This ensures LTM completion when the UE receives grants from the target gNB-DU. However, if the UE has no data to send in the UL, it cannot know whether the UL data indicating LTM completion has been successfully received at the gNB because there is no HARQ acknowledgment from the gNB in ​​the DL. Therefore, if the UE is not notified that the gNB has successfully received UL data packets, the relevant timer may expire, and the UE can declare a Radio Link Failure (RLF).

[0029] Figure 2A-2B An operational sequence between a UE 201, gNB-DU1 203, gNB-DU2 205, and gNB control unit (gNB-CU) 207 according to one embodiment of the present disclosure is shown. The UE 201 is configured with LTM having one or more candidate / target cells. In the illustrated embodiment, gNB-DU1 203 may correspond to a source gNB-DU, while gNB-DU2 205 may correspond to a target gNB-DU.

[0030] refer to Figure 2AAt operation 202, UE 201 sends an L3 measurement report to gNB-CU 207. In response to the received L3 measurement report, at operation 204, gNB-CU 207 determines whether to add an inter-gNB-DU candidate cell. After determining to add an inter-gNB-DU candidate cell, gNB-CU 207 sends a UE context establishment request to gNB-DU2 205 (i.e., the candidate / target DU) at operation 206. This UE context establishment request corresponds to a request to perform LTM target cell preparation. At operation 208, gNB-DU2 205 sends a UE context establishment response to gNB-CU 207. This context establishment response may include LTM candidate / target cell configuration (i.e., cellGroupConfig). The LTM candidate cell configuration may include associated information and / or parameters with candidate / target cells prepared by the gNB. The LTM candidate cell configuration enables the UE to efficiently and effectively hand over to one of these candidate / target cells.

[0031] At operation 210, gNB-CU 207 sends a Radio Resource Control (RRC) reconfiguration message to UE 201. This RRC reconfiguration message includes the LTM candidate cell configuration received by gNB-CU 207 from gNB-DU2. At operation 212, UE 201 stores the LTM candidate cell configuration based on the received RRC reconfiguration message. Furthermore, at operation 214, UE 201 sends an L1 measurement report for the cell used for LTM configuration to gNB-DU1 203 (i.e., the source DU). At operation 216, gNB-DU1 203 decides to send a PDCCH command to the UE to obtain the timing advance (TA) of candidate cells among (multiple) gNB-DUs. At operation 218, gNB-DU1 sends a PDCCH command with a cell ID. This cell ID can correspond to the cell ID of the candidate LTM cell to be executed for its TA. At operation 220, UE 201 sends a RACH (preamble) to candidate / target gNB-DU2 205.

[0032] At operation 222, candidate / target gNB-DU2 205 sends a UE context modification request message to gNB-CU 207. This UE context modification request message may include the UE's TA and cell ID. At operation 224, gNB-CU 207 sends a UE context modification acknowledgment (Ack) to gNB-DU2 205. At operation 226, gNB-CU 207 decides to forward the received TA to the serving gNB-DU (i.e., gNB-DU1 203). Therefore, at operation 228, gNB-CU 207 sends a UE context modification request. The UE context modification request includes the TA destined for serving gNB-DU1 203 and the corresponding cell ID. In operation 230, gNB-DU1 203 sends a UE context modification response to gNB-CU 207. In addition, at operation 232, serving gNB-DU1 203 sends a MAC CE to UE 201, which includes the cell ID, RACH preamble, beam ID, and TA.

[0033] At operation 234, UE 201 performs a RACH-free LTM cell handover to the target gNB-DU 205 cell. Additionally, UE 201 can prepare for the transmission of UL data packets. If no UL data is available, UL data packets with padding bits are created. Alternatively, an RRC reconfiguration confirmation message sent by the UE can also be considered for the first UL data packet.

[0034] refer to Figure 2B At operation 236, gNB-DU1 203 sends the selected RACH preamble, the selected TCI state, the beam ID, and the cell ID to the target gNB-DU (i.e. gNB-DU2 205).

[0035] At operation 238, source gNB-DU1 203 sends a UE context modification request message to gNB-CU 207, which includes the RACH preamble, cell ID, and beam ID. At operation 240, gNB-CU 207 sends a UE context modification confirmation message to gNB-DU1 203.

[0036] At operation 242, gNB-CU 207 decides to forward the received RACH preamble, cell ID, and beam ID to the target gNB-DU2 205. At operation 244, gNB-CU2 207 sends a UE context modification request to gNB-DU 205, which includes the RACH preamble, cell ID, and beam ID. At operation 246, gNB-DU2 205 responds to the received UE context modification request by sending a UE context modification response to gNB-CU 207.

[0037] At operation 248, after receiving the information from operation 242 from source gNB-DU1 203, target gNB-DU2 205 may decide to perform pre-scheduling for the UE and allocate (multiple) dynamic grants on the PDCCH. At operation 250, UE 201 uses the Cell Radio Network Temporary Identifier (C-RNTI) to monitor the PDCCH to receive dynamic grants (i.e., UL dynamic grants). At operation 252, UE 201 sends a first UL data packet to gNB-DU2 205 to indicate that the UE has successfully completed a RACH-free LTM cell handover to the designated target cell. However, the UE may have already used a configured grant for the purpose of sending the first UL data, so there is no need to wait for operation 248 before initiating operation 252. Note that there is no dependency between operations 248 and 252, so 252 may be initiated earlier than 248 at the network and UE, or in parallel with 248.

[0038] At operation 254, gNB-DU2 205 receives the first UL data packet and is notified of a successful LTM cell handover. However, at operation 256, UE 201 is unaware of whether the UL data delivery was successful or unsuccessful because no HARQ was sent by gNB-DU2 205, and additionally, no other form of acknowledgment was provided. Furthermore, the dynamic grant allocation in this use case is based on pre-scheduling, not on the reception of the first UL data packet. Therefore, at operation 258, UE 201 sends another scheduling request (SR) (i.e., the second SR) to receive further UL dynamic grants.

[0039] At operation 260, gNB-DU2 205 allocates dynamic grants on the PDCCH corresponding to the new SR (second data packet). At operation 262, UE 201 uses C-RNTI to monitor the PDCCH to receive the newly allocated UL grant. For example, at operation 264, UE 201 receives the UL grant(s) corresponding to the transmitted new SR and determines that the first UL data has been successfully delivered because the second scheduling request has been serviced. Therefore, at operation 266, UE 201 sends the second padded user data packet to gNB-DU2 205. Furthermore, at operation 268, UE 201 sends an RRC reconfiguration confirmation to gNB-CU 207.

[0040] Therefore, in Figure 2A-2BIn the UE-based operation described above, the UE initiates a SR to send a second UL data packet / second pseudo UL data packet to the gNB. If a new UL grant corresponding to this SR (for the same HARQ procedure) is received, the UE can implicitly determine that the no-RACH success indication (i.e., the first UL data packet) has also been successfully delivered to the gNB. Otherwise, the UE can detect an LTM cell handover failure after the timer expires. This timer can be called an LTM failure timer, which defines the period of time the UE can wait before declaring an LTM cell handover failure. Meanwhile, if the LTM failure timer has not yet expired, the UE 201 can send another SR to request a UL grant for the same data.

[0041] Figures 3A-3B A series of operations between UE 201, gNB-DU1 203, gNB-DU2 205, and gNB-CU 207 according to another embodiment of this disclosure is illustrated. Operations 302-352 are related to those described in reference to... Figure 2A-2B Operations 202-252 are explained similarly. Therefore, for the sake of brevity, detailed descriptions of operations 302-352 have been omitted.

[0042] For example, at operation 302, UE 201 sends an L3 measurement report to gNB-CU 207. At operation 304, gNB-CU 207 determines whether to add candidate cells between gNB-DUs (multiple cells). At operation 306, gNB-CU 207 sends a UE context establishment request to gNB-DU2 205 (i.e., the candidate / target DU), requesting LTM target cell preparation. At operation 308, gNB-DU2 205 sends a UE context establishment response with LTM candidate / target cell configuration (cellGroupConfig) to gNB-CU 207. At operation 310, gNB-CU 207 sends an RRC reconfiguration message to UE 201. At operation 312, UE 201 stores LTM candidate cells based on the received RRC reconfiguration message. Furthermore, at operation 314, UE 201 sends an L1 measurement report for the cell used for LTM configuration to gNB-DU1 203 (the source DU). At operation 316, serving gNB-DU1 203 decides to send a PDCCH command to the UE to obtain the TA of the candidate cell between gNB-DUs. At operation 318, gNB-DU1 sends a PDCCH command with the cell ID. At operation 320, UE 201 sends a RACH (preamble) to candidate / target gNB-DU2 205.

[0043] At operation 322, candidate / target gNB-DU2 205 sends a UE context modification request message to gNB-CU 207. This UE context modification request message may include the UE's TA and cell ID. At operation 324, gNB-CU 207 sends a UE context modification confirmation message to gNB-DU2 205. At operation 326, gNB-CU 207 decides to forward the received TA to the serving gNB-DU. Therefore, at operation 328, gNB-CU 207 sends a UE context modification request to the serving gNB-DU1 203, which includes the received TA and the corresponding cell ID. At operation 330, gNB-DU1 203 sends a UE context modification response to gNB-CU 207. Furthermore, at operation 332, gNB-DU1 203 sends a MAC CE to UE 201, which includes the cell ID, RACH preamble, beam ID, and TA. At operation 334, UE 201 performs a RACH-free LTM cell handover to the target gNB-DU cell.

[0044] See Figure 3B At operation 336, gNB-DU1 203 sends the selected RACH preamble, beam ID, and cell ID to the target gNB-DU (i.e., gNB-DU2 205). At operation 338, gNB-DU1 203 sends a UE context modification request message to gNB-CU 207. At operation 340, gNB-CU 207 sends a UE context modification confirmation message to gNB-DU2 205. At operation 342, gNB-CU 207 decides to forward the received RACH preamble, cell ID, and beam ID to gNB-DU2 205. At operation 344, gNB-CU 207 sends a UE context modification request to gNB-DU 205, which includes the RACH preamble, cell ID, and beam ID. At operation 346, gNB-DU2 205 sends a UE context modification response to gNB-CU 207. At operation 348, gNB-DU2 205 decides to perform pre-scheduling and allocates (multiple) dynamic grants on the PDCCH. At operation 350, UE 201 uses C-RNTI to monitor the PDCCH to receive dynamic grants. At operation 352, UE 201 sends its first user data packet to gNB-DU2 205 using the CG allocated during candidate cell preparation. Note that there is no dependency between operations 350 and 352; therefore, 352 may be initiated earlier than 350 at the network and UE levels, or in parallel with 350.

[0045] Furthermore, at operation 354, gNB-DU2 205 receives data packets sent by UE 201. gNB-DU2 205 also detects a successful LTM handover. However, UE 201 still does not know whether the UL data delivery was successful. At operation 56, gNB-DU2 205 proactively allocates dynamic grant on the PDCCH (even without SR). In one embodiment, gNB-DU2 can allocate dynamic grant using a predefined grant value. The predefined grant value can be preconfigured and is known to UE 201 and gNB-DU2. In a non-limiting embodiment, the predefined grant value can be preconfigured by the network operator and stored at UE 201 and gNB-DU2. At operation 358, UE 201 uses C-RNTI to monitor the PDCCH to receive UL dynamic grant. It is possible for UE 201 to monitor the PDCCH for grant if it knows that gNB-DU will proactively allocate grant (upon receipt of filled UL data packets). Therefore, UE 201 can be pre-configured with the aforementioned actively allocated information. Thus, at operation 360, when UE 201 receives a new UL grant, UE 201 determines that the first UL data has been successfully transmitted. Furthermore, at operation 362, UE 201 sends an RRC reconfiguration confirmation to gNB-CU 207.

[0046] Therefore, in such Figures 3A-3B In the network-based operation described herein, if the gNB-DU receives the first UL data packet (an indication of a successful LTM cell handover without RACH) from the UE, the gNB-DU will proactively assign a minimum UL authorization without being requested by the UE, and schedule the PDCCH of the addressing UE's C-RNTI in the target cell to ensure that the UE is aware of the successful UL data transmission from the gNB.

[0047] Figure 4 A flowchart of an example method 400 according to another embodiment of this disclosure is shown. Method 400 can be performed by UE 201.

[0048] At step 402, UE 201 receives a RACH-free LTM cell handover command from gNB-DU (e.g., gNB-DU1 203). In one embodiment, the RACH-free LTM cell handover command can be configured to trigger the UE to hand over to the target gNB (e.g., gNB-DU2 205) cell via L1 / L2 signaling.

[0049] At step 404, UE 201 may send a first UL data packet to the target gNB-DU. The first UL data packet is sent via either a configured UL scheduling grant or a dynamic UL scheduling grant to indicate a successful RACH-free LTM cell handover. In one embodiment, the configured UL scheduling grant and / or the dynamic UL scheduling grant may be assigned to the UE accordingly during LTM candidate cell preparation and after LTM cell handover. The first UL data packet may include one or more real data bits, one or more padding data bits, or a UL signaling RRC message.

[0050] At step 406, UE 201 sends a scheduling request (SR) to the target gNB-DU (gNB-DU2 205). The SR is sent to request scheduling authorization to send a second UL data packet. The SR is sent after the first UL data packet. In one embodiment, the second UL data packet includes one or more real or padding data bits.

[0051] At step 408, UE 201 receives a second UL scheduling grant in response to the sent scheduling request. In one embodiment, the second UL scheduling grant may correspond to a dynamic UL scheduling grant with a predefined grant value.

[0052] In response to the received second UL scheduling authorization, at step 410, UE 201 determines that the indication of a successful RACH-free LTM cell handover to the target gNB-DU (gNB-DU2 205) (i.e., the first UL data packet) has been successfully delivered.

[0053] In one embodiment, after sending the SR, UE 201 may initiate an LTM failure timer. Furthermore, in response to the expiration of the LTM failure timer and the failure to receive the second UL scheduling authorization, UE 201 may determine that the successful RACH-less LTM cell handover indication to the target gNB-DU via L2 signaling has failed.

[0054] Figure 5 A flowchart of an example method 500 according to another embodiment of the present disclosure is shown. Method 500 can be performed by a target gNB-DU (gNB-DU2 205).

[0055] At step 502, gNB-DU2 205 receives UL data packets via either a configured UL scheduling grant or a dynamic UL scheduling grant from UE 201. These UL data packets are received after a Layer 1 / Layer 2 triggered mobility (LTM) cell handover without RACH triggering.

[0056] At step 504, gNB-DU2 205 assigns a dynamic UL grant with a predefined grant value to the UE from the target gNB, indicating successful reception of a RACH-free LTM cell handover indication, or meaning that the UL indicating a successful RACH-free LTM cell handover is the successful reception of data packets. In one embodiment, this dynamic UL grant corresponds to the Physical Downlink Control Channel (PDCCH) addressing the Cell Radio Network Temporary Identifier (C-RNTI) of the UE.

[0057] Figure 6 An embodiment of device / apparatus 600 is illustrated. As shown in FIG8, device 600 includes a processor 610, a memory 620, a storage component 630, an input component 640, an output component 650, a communication interface 660, and a bus 670. Device 600 may be associated with UE 201, gNB-DU1 203, gNB-DU2 205, and gNB-CU 207. In one embodiment, device 600 may correspond to UE 201. In one embodiment, device 600 may correspond to an apparatus implemented at a target gNB-DU (i.e., gNB-DU2 205). One or more components of device 600 may be configured to implement one or more operations / functions of this disclosure, as described above.

[0058] As used herein, processor 610 refers to any type of computing circuit that may include hardware and software components. Processor 610 may be embodied as a multi-core processor, a single-core processor, or a combination of one or more multi-core processors and / or one or more single-core processors, a distributed processing system, etc. Processor 610 may be a central processing unit (CPU), a graphics processing unit (GPU), an accelerated processor (APU), an application-specific integrated circuit (ASIC), or another type of processing component.

[0059] Memory 620 includes a non-transitory computer-readable medium. Memory 620 includes random access memory (RAM), read-only memory (ROM), and / or another type of dynamic or static storage device (e.g., flash memory, magnetic storage, and / or optical storage) that stores information and / or instructions for use by processor 610. Memory 620 includes machine-readable instructions executable by processor 610. When executed by processor 610, these machine-readable instructions cause processor 610 to perform one or more method steps of the above embodiments.

[0060] Storage component 630 stores information and / or software related to the operation and use of device 600. For example, storage component 630 may include a hard disk (e.g., a magnetic disk, optical disk, magneto-optical disk, and / or solid-state drive), an optical disk (CD), a digital versatile optical disk (DVD), a floppy disk, a magnetic tape cassette, a magnetic tape, and / or another type of non-transitory computer-readable medium, and a corresponding drive.

[0061] Input component 640 is configured to receive information, such as user input. For example, input component 640 may include, but is not limited to, a touchscreen display, keyboard, keypad, mouse, button, switch, and / or microphone. Alternatively, input component 640 may include sensors for sensing information (e.g., Global Positioning System (GPS), accelerometer, gyroscope, and / or actuator).

[0062] Output component 650 is configured to provide output information from device 600. For example, output component 650 may be, but is not limited to, a display, a speaker, a command device to an external device, and / or one or more light-emitting diodes (LEDs).

[0063] Communication interface 660 is an interface that provides communication connectivity with other devices, such as external and internal devices. The connection via communication interface 660 can be wired, wireless, or a combination of wired and wireless connections, and can be a direct connection or an indirect connection via a communication network existing between device 600 and other devices. In other words, the standard of communication interface 660 is unrestricted.

[0064] Bus 670 is used as an interconnect between the processor 610, memory 620, storage component 630, input component 640, output component 650, and communication interface 660 of device 600. Bus 670 may include wired interconnection or wireless interconnection.

[0065] Figure 6 The number and arrangement of components shown are given by way of example only. In practice, device 600 may include additional, fewer, different, or differently arranged components than those shown in FIG. 8. Alternatively or additionally, a set of components of device 600 (e.g., one or more components) may perform one or more functions described therein, performed by another set of components of device 600. Furthermore, one or more method steps described in any embodiment may be performed using multiple communicating devices 600.

[0066] Examples of the technologies and apparatus described herein include, but are not limited to, the following listed embodiments: [1] A user equipment (UE) is configured to: Receives a Layer 1 / Layer 2 triggered Mobility (LTM) cell handover command without RACH from the source gNodeB Distributed Unit (gNB-DU). This RACH-free LTM cell handover command is configured to trigger the UE to perform a cell handover to the target gNB-DU via L2 signaling. The first UL data packet is sent to the target gNB-DU via one of the configured uplink (UL) scheduling authorization and dynamic UL scheduling authorization to indicate a successful RACH-free LTM cell handover; After sending the first UL data packet, a scheduling request (SR) is sent to the target gNB-DU to receive dynamic authorization to send the second UL data packet; In response to the sent scheduling request, receive a second UL scheduling authorization from the target gNB-DU; and In response to the received second UL scheduling authorization, an indication that a successful RACH-free LTM cell handover to the target gNB-DU has been successfully transmitted. [2] As in [1], the UE is further configured after the transmission of the SR to: Initiate an LTM failure timer; and In response to the failure to receive the target gNB-DU and the second UL scheduling authorization, it is determined that the successful RACH-less LTM cell handover indication to the target gNB-DU was not successfully delivered. [3] For any of the UEs in [1]-[2], the first UL data packet includes one or more real data bits, or one or more padding data bits, or a UL signaling RRC message. [4] The UE of any one of claims [1]-[3], wherein the second UL data packet includes one or more real or padding data bits. [5] The UE of any one of claims [1]-[4], wherein the source gNB-DU and the target gNB-DU correspond to different gNBs. [6] A method comprising: The user equipment (UE) receives a Layer 1 / Layer 2 triggered mobility (LTM) cell handover command without RACH from the source gNodeB distributed unit (gNB-DU). This RACH-free LTM cell handover command is configured to trigger the UE to perform a cell handover to the target gNB-DU via Layer 2 signaling. The UE sends a first UL data packet to the target gNB-DU via one of the configured uplink (UL) scheduling authorization and dynamic UL scheduling authorization to indicate a successful RACH-free LTM cell handover; After sending the first UL data packet, the UE sends a scheduling request (SR) to the target gNB-DU to receive dynamic authorization to send the second UL data packet; In response to the sent scheduling request, the UE receives a second UL scheduling authorization from the target gNB-DU; and In response to the received second UL scheduling authorization, the UE determines that an indication of a successful RACH-free LTM cell handover to the target gNB-DU has been successfully delivered. [7] The method as in [6], wherein after the transmission of the SR, the method further includes: The LTM failure timer is initiated by the UE; and In response to the expiration of the LTM failure timer and the failure to receive the second UL scheduling authorization, the UE determines that the successful RACH-less LTM cell handover indication to the target gNB-DU via L2 signaling was unsuccessful. [8] The method of any of [6]-[7], wherein the first UL data packet includes one or more real data bits, or one or more padding data bits, or a UL signaling RRC message. [9] The method of any one of claims [6]-[8], wherein the second UL data packet comprises one or more real or padding data bits.

[10] The method of any one of claims [6]-[9], wherein the source gNB-DU and the target gNB-DU correspond to different gNBs.

[11] An apparatus configured to: Receive uplink (UL) data packets from the user equipment (UE) via either a configured UL scheduling grant or a dynamic UL scheduling grant; and Assign a dynamic UL grant with a predefined grant value to the UE to indicate the reception of a Layer 1 / Layer 2 Mobility (LTM) cell handover indication without a Random Access Channel (RACH), or to indicate the successful reception of a UL data packet indicating a successful RACH-free LTM cell handover.

[12] The apparatus as in

[11] , wherein the dynamic UL grant corresponds to the physical downlink control channel (PDCCH) of the cell radio network temporary identifier (C-RNTI) addressing the UE.

[13] The device of any of

[11] -

[12] , wherein the device is the target gNodeB (gNB-DU) after a RACH-less LTM cell handover.

[14] A method comprising: The target gNodeB-DU (gNB-DU) receives uplink (UL) data packets from the User Equipment (UE) via either a configured UL scheduling grant or a dynamic UL scheduling grant; and The target gNodeB-DU assigns a dynamic UL grant with a predefined grant value to the UE to indicate the reception of an LTM cell handover indication without RACH, or to indicate the successful reception of a UL data packet indicating a successful LTM cell handover without RACH.

[15] The method of claim

[14] , wherein the dynamic UL grant corresponds to the physical downlink control channel (PDCCH) of the cell radio network temporary identifier (C-RNTI) addressing the UE.

[16] A non-transitory computer-readable medium stores instructions comprising: one or more instructions, which, when executed by a user equipment (UE), include one or more processors, such that the one or more processors: Receives a Layer 1 / Layer 2 triggered Mobility (LTM) cell handover command without RACH from the source gNodeB Distributed Unit (gNB-DU). This RACH-free LTM cell handover command is configured to trigger the UE to perform a cell handover to the target gNB-DU via Layer 2 signaling. The first UL data packet is sent to the target gNB-DU via one of the configured uplink (UL) scheduling authorization and dynamic UL scheduling authorization to indicate a successful RACH-free LTM cell handover; After sending the first UL data packet, a scheduling request (SR) is sent to the target gNB-DU to receive dynamic authorization to send the second UL data packet; In response to the sent scheduling request, receive a second UL scheduling authorization from the target gNB-DU; and In response to the received second UL scheduling authorization, an indication that a successful RACH-free LTM cell handover to the target gNB-DU has been successfully transmitted.

[17] A non-transitory computer-readable medium storing instructions comprising: one or more instructions that, when executed by a target gNodeB distributed unit (gNB-DU) after a Layer 1 / Layer 2 mobility (LTM) cell handover without a random access channel (RACH), the target gNB-DU comprising one or more processors, such that the one or more processors: Receive uplink (UL) data packets from the user equipment (UE) via either a configured UL scheduling grant or a dynamic UL scheduling grant; and Assign a dynamic UL grant with a predefined grant value to the UE to indicate successful reception of a RACH-less LTM cell handover indication, or to indicate successful reception of a UL data packet indicating a successful RACH-less LTM cell handover.

[0067] Therefore, this disclosure allows for an indication of a successful LTM cell handover to the gNB, and this information is also sent to the UE. Furthermore, RLF / RRC reconstruction is avoided.

[0068] The embodiments disclosed herein can be implemented by at least one software program that runs on at least one hardware device and performs network management functions to control elements. These elements can be at least one of a hardware device or a combination of a hardware device and a software module. The UE and gNB may include a corresponding processor, a communication unit, and a storage unit (e.g., a memory). The communication unit can perform functions for transmitting and receiving signals. The storage unit may include executable instructions that, when executed by the corresponding processor, cause the corresponding UE and gNB to perform the functions described above. Figure 2A-5 The functions described above.

[0069] While specific language has been used to describe this disclosure, it is not intended to create any limitation. It will be apparent to those skilled in the art that various modifications can be made to the method in order to achieve the inventive concept as taught herein.

[0070] The accompanying drawings and the foregoing description provide examples of embodiments. Those skilled in the art will understand that the one or more elements can be well combined into a single functional element. Alternatively, certain elements may be separated into multiple functional elements. Elements from one embodiment may be added to another embodiment. For example, the order of the processes described herein may be changed, and the methods are not limited to those described herein.

[0071] Furthermore, actions in any flowchart need not be implemented in the order shown; nor are all actions required to be performed. Additionally, actions that do not depend on other actions can be performed in parallel with other actions. The scope of the embodiments is by no means limited to these specific examples. Many variations are possible, such as differences in structure, size, and the use of materials, regardless of whether they are explicitly stated in the specification. The scope of the embodiments is at least as broad as given by the following claims.

[0072] Advantages, other benefits, and solutions to the problem have been described above with respect to specific embodiments. However, the advantages, benefits, and solutions to the problem, as well as any components(s) that may cause any advantages, benefits, and solutions to the problem to appear or become more significant, should not be construed as key, essential, or fundamental features or components of any or all claims.

[0073] The above description of the specific embodiments will fully reveal the general nature of the embodiments herein, enabling others to easily modify and / or adapt these specific embodiments for various applications by applying existing knowledge without departing from the general concepts. Therefore, such modifications and adaptations should and are intended to be understood as being within the equivalent meaning and scope of the disclosed embodiments. It should be understood that the wording or terminology herein is for description only and not for limitation. Therefore, although embodiments herein have been described in terms of at least one embodiment, those skilled in the art will recognize that the embodiments herein can be practiced with modifications within the spirit and scope of the embodiments as described herein.

Claims

1. A user equipment (UE) (201) configured to: The UE (201) receives a Layer 1 / Layer 2 triggered Mobility (LTM) cell handover command without Random Access Channel (RACH) from the source gNodeB Distributed Unit (gNB-DU) (203), the RACH-free LTM cell handover command being configured to trigger the UE (201) to perform a cell handover to the target gNB-DU (205) via L2 signaling; In response to the received RACH-free LTM cell handover command, a first UL data packet is sent to the target gNB-DU (205) via one of the configured uplink (UL) scheduling authorization and dynamic UL scheduling authorization to indicate a successful RACH-free LTM cell handover; After sending the first UL data packet, a scheduling request (SR) is sent to the target gNB-DU (205) to receive dynamic authorization to send the second UL data packet; In response to the sent scheduling request, a second UL scheduling authorization is received from the target gNB-DU (205); and In response to the received second UL scheduling authorization, it is determined that the indication of a successful RACH-free LTM cell handover to the target gNB-DU (205) has been successfully delivered.

2. The UE (201) according to claim 1, wherein after the transmission of the SR, the UE 201 is further configured to: Initiate an LTM failure timer; and In response to the failure to receive the target gNB-DU (205) and the second UL scheduling authorization, it is determined that the successful RACH-free LTM cell handover indication to the target gNB-DU (205) was not successfully transmitted.

3. The UE (201) according to claim 1, wherein the first UL data packet includes one or more real data bits, or one or more padding data bits, or a UL signaling RRC message.

4. The UE (201) of claim 1, wherein the second UL data packet comprises one or more real or padding data bits.

5. The UE (201) according to claim 1, wherein the source gNB-DU and the target gNB-DU 203 correspond to different gNBs.

6. A method (400) comprising: The user equipment (UE) (201) receives (402) a Layer 1 / Layer 2 mobility (LTM) cell handover command without random access channel (RACH) from the source gNodeB distributed unit (gNB-DU) (203), the RACH-free LTM cell handover command being configured to trigger the UE (201) to perform a cell handover to the target gNB-DU (205) via L2 signaling; In response to receiving the RACH-free LTM cell handover command, the UE (201) sends a (404) first uplink (UL) data packet to the target gNB-DU (205) via one of the configured UL scheduling authorization and dynamic UL scheduling authorization to indicate a successful RACH-free LTM cell handover; After sending the first UL data packet, the UE (201) sends a (406) scheduling request (SR) to the target gNB-DU (205) to receive dynamic authorization to send the second UL data packet; In response to the sent scheduling request, the UE (201) receives (408) a second UL scheduling authorization from the target gNB-DU (205); and In response to the received second UL scheduling authorization, the UE (201) determines (410) that the indication of a successful RACH-free LTM cell handover to the target gNB-DU (205) has been successfully delivered.

7. The method (400) according to claim 6, wherein after the transmission of the SR, the method (400) further comprises: The LTM failure timer is initiated by the UE (201); In response to the expiration of the LTM failure timer and the failure to receive the second UL scheduling authorization, the UE (201) determines that the successful RACH-free LTM cell handover indication to the target gNB-DU (205) via the L2 signaling was unsuccessful.

8. The method (400) of claim 6, wherein the first UL data packet comprises one or more real data bits, or one or more padding data bits, or a UL signaling RRC message.

9. The method (400) of claim 6, wherein the second UL data packet comprises one or more real or padding data bits.

10. The method (400) according to claim 6, wherein the source gNB-DU (203) and the target gNB-DU (205) correspond to different gNBs.

11. An apparatus (600) configured to: Receive UL data packets from the User Equipment (UE) (201) via either a configured uplink (UL) scheduling grant or a dynamic UL scheduling grant; and Assign a dynamic UL grant with a predefined grant value to the UE (201) to indicate the reception of a Layer 1 / Layer 2 Mobility (LTM) cell handover indication without a Random Access Channel (RACH), or to indicate the successful reception of the UL data packet indicating a successful RACH-free LTM cell handover.

12. The apparatus (600) of claim 11, wherein the dynamic UL authorization corresponds to the physical downlink control channel (PDCCH) addressing the cell radio network temporary identifier (C-RNTI) of the UE.

13. The apparatus (600) according to claim 11, wherein the apparatus (600) is the target gNodeB distributed unit (gNB-DU) (205) after the RACH-free LTM cell handover.

14. A method (500) comprising: Following a Layer 1 / Layer 2 mobility (LTM) cell handover triggered by the target gNodeB distributed unit (gNB-DU) (205) without a random access channel (RACH), the user equipment (UE) (502) receives UL data packets from the user equipment (UE) (201) via one of the configured uplink (UL) scheduling grants or dynamic UL scheduling grants; and The target gNB-DU (205) assigns (504) a dynamic UL authorization with a predefined authorization value to indicate the reception of a successful RACH-free LTM cell handover indication, or to indicate the successful reception of a UL data packet indicating a successful RACH-free LTM cell handover.

15. The method (500) of claim 14, wherein the dynamic UL authorization corresponds to the physical downlink control channel (PDCCH) addressing the cell radio network temporary identifier (C-RNTI) of the UE.

16. A non-transitory computer-readable medium storing instructions, the instructions comprising: One or more instructions, which, when executed by a user equipment (UE), include one or more processors, such that the one or more processors: Receives a Layer 1 / Layer 2 triggered Mobility (LTM) cell handover command without Random Access Channel (RACH) from the source gNodeB Distributed Unit (gNB-DU), the RACH-free LTM cell handover command being configured to trigger the UE (201) to perform a cell handover to the target gNB-DU via L2 signaling; In response to the received RACH-free LTM cell handover command, a first UL data packet is sent to the target gNB-DU via one of the configured uplink (UL) scheduling authorization and dynamic UL scheduling authorization to indicate a successful RACH-free LTM cell handover. After sending the first UL data packet, a scheduling request (SR) is sent to the target gNB-DU to receive dynamic authorization to send the second UL data packet; In response to the sent scheduling request, a second UL scheduling authorization is received from the target gNB-DU; and In response to the received second UL scheduling authorization, it is determined that the indication of a successful RACHLTM cell handover to the target gNB-DU has been successfully delivered.

17. A non-transitory computer-readable medium storing instructions, the instructions comprising: One or more instructions, which, when executed by a target gNodeB distributed unit (gNB-DU) (205) after a Layer 1 / Layer 2 mobility (LTM) cell handover without a random access channel (RACH), the target gNB-DU (205) comprising one or more processors, such that the one or more processors: Receive UL data packets from the User Equipment (UE) (201) via either a configured uplink (UL) scheduling grant or a dynamic UL scheduling grant; and A dynamic UL grant with a predefined grant value is assigned to the UE (201) to indicate successful reception of a RACH LTM cell handover indication, or to indicate successful reception of a UL data packet indicating a successful RACH LTM cell handover.

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