Determining a measurement configuration to apply after cell selection or reselection

Abstract

A user equipment (UE) configured for early Timing Advance (TA) acquisition in a wireless communication network. The UE comprises a transceiver and one or more processors configured to receive, from a serving cell, a dedicated configuration comprising an identifier, priority information, and early TA acquisition parameters for one or more target cells. The processor selects a target cell based on signal quality and priority and initiates a contention-based random-access transmission including a preamble, the identifier, an early TA acquisition request, and an indication that a response is not required. These elements are transmitted in one or more message transmission, allowing the target cell to estimate and store the TA without replying to the UE. The UE refrains from monitoring for a response and stores the early TA attempt outcome, thereby enabling efficient, low-latency handovers without requiring reserved preambles or extended signaling procedures.

Description

DETERMINING A MEASUREMENT CONFIGURATION TO APPEY AFTER CEEE SEEECTION OR RESEEECTIONTechnical Field:

[0001] The present disclosure relates to the field of wireless communication, and more particularly relates to particularly to methods and apparatuses for early Timing Advance (TA) acquisition using Contention-Based Random Access (CBRA) procedures in User Equipment (UE) and network nodes.Background:

[0002] Certain abbreviations that may be found in the description and / or in the figures are herewith defined as follows.3 GPP 3rdGeneration Partnership Project5G NR 5thGeneration New RadioCA Carrier AggregationDC Dual ConnectivitygNB Next Generation Node BNR New Radio (5G)RAN Radio Access NetworkRNA RAN Notification AreaRRC Radio Resource ControlSIB System Information BlockTA Tracking AreaUE User Equipment

[0003] In wireless communication networks, ensuring seamless connectivity and minimizing service disruption during handover or initial access is crucial for maintaining high-quality user experience. Timing Advance (TA) acquisition plays a critical role in aligning uplink transmissions with network timing to avoid interference and optimize spectrum efficiency. Traditionally, TA acquisition is performed using Contention-Based Random Access (CBRA) or Contention-Free Random Access (CFRA) mechanisms.

[0004] In conventional CBRA-based TA acquisition, User Equipment (UE) initiates a Random-Access Channel (RACH) procedure by transmitting a preamble (Msgl) to the target cell, followed by receiving a Random- Access Response (RAR) message (Msg2) containing an initial TA value. The UE then transmits further messages (Msg3 and Msg4) to complete the process. However, this approach introduces significant Time of Outage (ToO), as the UE must wait for contention resolution in Msg4 to consider the TA value received in Msg2. Moreover, if multiple candidate cells are involved, the cumulative delay increases, leading to potential service degradation.

[0005] Existing solutions mitigate this issue by pre- reserving RACH preambles for early TA acquisition, but this reduces the availability of contention-based resources for legacy access. Additionally, preamble reservation adds complexity and signaling overhead.

[0006] To address these challenges, improved CBRA-based early TA acquisition techniques are needed that eliminate the requirement for preamble reservations while ensuring faster and more efficient uplink synchronization. The present invention introduces an enhanced CBRA-based early TA acquisition method that allows the UE to transmit early TA requests with unique identification, enabling the network to precompute and store estimated TA values, thereby minimizing Time of Outage (ToO) and improving handover performance.Summary:

[0007] Aspects pertaining to example embodiments disclosed herein are set forth below. It should be understood that these aspects are not intended to limit the scope of this disclosure. Indeed, this disclosure may encompass a variety of aspects that may not be set forth below.

[0008] In the first aspect a method, performed by User Equipment (UE) is provided. The method comprises receiving, via a dedicated message, a UE-specific configuration comprising: configuration information associated with early TA acquisition for one or more target cells, a priority associated with each of the target cells, a number of target cells suitable for the early TA attempt, and an identifier to be used by the UE in conjunction with an early TA acquisition request. The method further comprises selecting a target cell based on the priority and signal quality, transmitting, to the selected target cell at least one of: msgl, msg3, msgA and refraining from monitoring receipt of a response from the target cell.

[0009] In another aspect a User Equipment (UE) is provided. The user equipment (UE), comprises a transceiver and one or more processors configured to: receive, from a serving cell, a UE-specificconfiguration via a dedicated RRC message, the configuration including priority information, an identifier, and the number of target cells. The user equipment selects a target cell based on priority and signal strength, transmits to the selected target cell, at least one of: msgl, msg3, msgA, and refrains from monitoring receipt of a response from the target cell.

[0010] In yet another aspect a method performed by a network node is provided. The method comprises receiving, from a UE, at least one of: msgl, msg3, msgA, determining a TA value based on the timing of the received at least one of: msgl , msg3, msgA, storing the TA value in association with a UE identifier and using the stored TA value during handover to enable uplink synchronization without further contention.

[0011] In yet another aspect a network node in a wireless communication network is provided. A network node, comprises a transceiver and one or more processors configured to receive, from a UE, at least one of: msgl, msg3, msgA, determine a TA value based on the timing of the received at least one of: msgl, msg3, msgA, store the TA value linked to a UE identifier, and apply the TA value to synchronize uplink timing when the UE is handed over to the target cell.

[0012] The means for the said aspects may be implemented in hardware and / or software. They include for instance, at least one memory storing the computer program code / instructions, and at least one processor for executing computer program code / instructions for causing the user equipment or network node to perform the respective method as per the third and fourth aspects. The means could also include circuitry (as defined in the disclosure herein).

[0013] The details of the example embodiments are set forth in the accompanying drawings and the description below. Other features, objects, and advantages of the disclosure will be apparent from the description and drawings, and from the claims.Brief Description of Drawings:

[0014] The detailed description is described with reference to the accompanying figures. The same numbers are used throughout the drawings to reference features and components.

[0015] FIG. 1 illustrates an exemplary network environment, with a serving cell, neighboring cell, and User Equipment (UE), in which the present invention operates.

[0016] FIG. 2 illustrates an exemplary Contention-Based Random Access (CBRA) early Timing Advance (TA) acquisition.

[0017] FIGS. 3 A to 3D illustrate exemplary configurations and signaling approaches for Contention-Based Random Access (CBRA) early Timing Advance (TA) acquisition across multiple network cells.

[0018] FIG. 4 illustrates an exemplary architecture of User Equipment (UE) for CBRA-Based Early TA Acquisition.

[0019] FIG. 5 illustrates functional Architecture of Network Node for CBRA-Based Early TA Acquisition.Detailed Description

[0020] Example embodiments now will be described with reference to the accompanying drawings. The terminology used in the present disclosure of the example embodiments illustrated in the accompanying drawings is not intended to be limiting. In the drawings, like numbers refer to like elements.

[0021] It shall be understood that although the terms “first,” “second” and the like may be used herein to describe various elements, these elements should not be limited by these terms. These terms are only used to distinguish one element from another. For example, a first element could be termed a second element, and similarly, a second element could be termed a first element, without departing from the scope of example embodiments.

[0022] As used herein, the singular forms “a,” “an,” and “the,” are intended to include the plural forms as well, unless explicitly stated otherwise. It will be further understood that the terms “includes,” “comprises,” “including,” and / or “comprising,” when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and / or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof.

[0023] As used herein, whenever the phrase “at least one of’ or “one or more of’ precedes a list of elements, wherein the elements are joined by “and” or “or”, it means that at least any one of the elements or at least all the elements are present. As used herein, whenever the phrase “one of’ precedes a list of elements, wherein the elements are joined by “and” or “or”, it means that only one of the elements are present at a given instant, unless the context permits a meaning that allows the inclusion of more than one element. The usage of the term “or” is to be understood as “inclusive or” instead of “exclusive or”, unless indicated otherwise by the relevant context. Conditional language, such as among others, “can” or “may”, unless specifically stated otherwise,or otherwise understood within the context as used, is generally intended to convey that certain example embodiments could include, while other example embodiments may not include certain features, elements, and / or steps. Thus, such conditional language is not generally intended to imply that features, elements, and / or steps are in any way required for one or more example embodiments. It will be understood that when an element is referred to as being “connected” or “coupled” to another element, it may be directly connected or coupled to the other element or intervening elements may be present. Furthermore, “connected” or “coupled” as used herein may include wirelessly connected or coupled. As used herein, the term “and / or” includes any and all combinations and arrangements of one or more of the associated listed items.

[0024] As used herein, the terms “the at least one” and “the one or more” mean “any one of the at least one” and “any one of the one or more,” respectively.

[0025] Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure pertains. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.

[0026] The figures depict a simplified structure only showing some elements and functional entities, all being logical units whose implementation may differ from what is shown. The connections shown are logical connections; the actual physical connections may be different. In addition, all logical units described and depicted in the figures include the software and / or hardware components required for the unit to function. Further, each unit may comprise / include within itself one or more components, which are implicitly understood. These components may be operatively coupled to each other and be configured to communicate with each other to perform the function of the said unit.

[0027] As used herein, the term “circuitry” may refer to at least one of the following: a) hardware-only circuit implementations (such as implementations in analog, digital, and / or quantum circuitry); b) combinations of hardware circuit(s) and software, such as (as applicable): (i) a combination of analog, digital, and / or quantum hardware circuit(s) with software / firmware and (ii) any or all portions of hardware processor(s) (including digital and / or quantum processor(s)), with software, and memory(ies) that work together to cause an apparatus, such as a mobile device,computing device, or server, to perform various functions); c) any or all portions of hardware circuit(s), such as a microprocessor(s) and / or quantum processor(s), that requires software (e.g., firmware) for operation, but the software may not be present when it is not needed for operation.

[0028] This definition of circuitry applies to all uses of this term in this application, including in any claims. As a further example, as used in this application, the term circuitry also covers an implementation of merely a hardware circuit or processor (or multiple processors) or portion of a hardware circuit or processor and its (or their) accompanying software and / or firmware. The term circuitry also covers, for example, and if applicable to the particular claim element, a baseband integrated circuit or processor integrated circuit for a mobile device or a similar integrated circuit in server, a cellular network device, or other computing or network device.

[0029] In the following, different example embodiments will be described using, as an example of a communication network to which example embodiments may be applied, a communication network architecture based on 3 GPP standards for a communication network, such as 5G NR or 6G (sixth generation), without restricting the example embodiments to such an architecture, however.

[0030] FIG. 1 illustrates a wireless communication network environment supporting Contention-Based Random Access (CBRA)-based early Timing Advance (TA) acquisition. The network comprises multiple network nodes, including a serving cell (130) and a neighboring cell (140), interacting with User Equipment (UE) (120) to facilitate early TA acquisition and efficient handovers. In this architecture, the UE (120) is connected to the serving cell (130) while also measuring signal strength and evaluating the feasibility of early TA acquisition for neighboring cells (140). The network nodes (110A, HOB) represent various base stations, such as 5G New Radio (NR) base stations (gNBs), that provide network connectivity across different cells.

[0031] FIGS. 2 illustrates the Contention-Based Random Access (CBRA)-based early Timing Advance (TA) acquisition procedure, depicting how User Equipment (UE) (120) interacts with the Serving Cell (130) and the neighboring Cell (140) to obtain an estimated Timing Advance (TA) value before a handover. This method ensures seamless uplink synchronization, reducing Time of Outage (ToO) and improving the overall handover process in wireless communication networks.

[0032] The process begins when the UE (120) initiates an early TA request to a Neighboring Cell (140). This is done by transmitting Msgl: Preamble Request (201), which comprises of a randomaccess preamble used for initiating the CBRA procedure. This message is sent on a preconfiguredPRACH occasion defined in the CBRA configuration received from the Serving Cell (130). The Neighboring Cell (140) receives this request and processes it to determine the appropriate TA value for the UE.

[0033] After receiving Msgl (201), the neighboring Cell (140) responds with Msg2: Random Access Response (RAR) with TA (202). This message includes an initial TA value, which is determined based on the timing of the received preamble. The RAR message (202) is transmitted on a preconfigured PDSCH occasion. The UE (120) then extracts the TA value and prepares for the next phase of contention resolution.

[0034] In the next step, the UE (120) sends Msg3: Contention Resolution (203), which includes its UE identification (UE-ID) as instructed by the Serving Cell (130). The neighboring Cell (140) receives this message and verifies whether the preamble corresponds to a valid UE-ID. If contention is successfully resolved, the neighboring Cell (140) prepares to finalize the TA assignment.

[0035] The final step in the process is Msg4: Final TA Assignment (204). Neighboring Cell (140) transmits this message to confirm and finalize the TA value for the UE (120). This ensures that the UE (120) can establish uplink synchronization before executing a handover. By completing this CBRA-based early TA acquisition, the UE (120) stores the TA information from multiple Neighboring Cells (140).

[0036] This approach significantly reduces handover latency as the Serving Cell (130) does not need to initiate a new Random Access (RA) procedure after the handover. Instead, the Neighboring Cell (140) can immediately apply the pre-stored TA when the UE (120) transitions into its coverage area. This eliminates unnecessary RA attempts, minimizes contention-based delays, and ensures that the UE (120) achieves immediate uplink synchronization upon handover.

[0037] Overall, the CBRA-based early TA acquisition procedure enhances network efficiency, particularly in high-mobility scenarios where frequent handovers are required. By utilizing a proactive TA estimation approach, this method reduces network signaling overhead while maintaining seamless connectivity. Furthermore, by eliminating the need for dedicated preamble reservations, this solution ensures better resource utilization for both legacy and next-generation wireless networks.

[0038] Thus, Figure 2 demonstrates how CBRA-based early TA acquisition enables the UE (120) to preemptively obtain TA values from multiple Neighboring Cells (140). This allows for fastuplink synchronization and minimizes ToO during handover, ensuring a seamless transition between cells and improving overall network performance.

[0039] Figure 3A illustrates an exemplary Contention-Based Random Access (CBRA)-based early Timing Advance (TA) acquisition method using cell-specific configuration parameters provided by the Serving Cell (150). The figure depicts interactions between the User Equipment (UE) (120), the Serving Cell (150), and multiple Target Cells (160, 170) for acquiring an estimated Timing Advance (TA) value before initiating a handover. By preemptively obtaining a TA estimate, the UE (120) can achieve immediate uplink synchronization in the target cell, reducing handover latency and minimizing Time of Outage (ToO).

[0040] The UE (120) receives early TA acquisition configuration (301) from the Serving Cell (150) via System Information Block (SIB) messages or dedicated Radio Resource Control (RRC) signaling. The configuration parameters provide instructions on how, when, and where early TA acquisition should be performed.

[0041] The parameters included in the configuration (301) are: 1. CB-eTA-PRACHConfig (302) - This includes msgA-RO-FDM and msgA-RO -Frequency Start, defining the time-frequency resources allocated for CBRA-based early TA acquisition. These resources specify the PRACH occasions when the UE (120) should transmit an early TA request to a Target Cell (160, 170). 2. Cell-Specific eTA Threshold (303) - This defines the signal strength threshold that the UE (120) must meet before attempting early TA acquisition with a target cell. If the measured SSB signal strength exceeds this threshold, the UE (120) proceeds with early TA acquisition. Priority of Target Cells - The Serving Cell (150) ranks multiple neighboring cells (160, 170) in order of priority. The UE (120) attempts early TA acquisition with the highest-priority Target Cell (160, 170) first. Number of Target Cells for eTA - Specifies the number of neighboring cells where the UE (120) should attempt early TA acquisition. eTAReqReportTimer - Defines the time window within which the UE (120) must report early TA acquisition results to the Serving Cell (150). UE Identification Parameter - Specifies whether the UE (120) should use Temporary Mobile Subscriber Identity (TMSI), S-Temporary Mobile Subscriber Identity (S-TMSI), or Globally Unique Temporary Identifier (GUTI) for identification in the early TA request.

[0042] Upon receiving the early TA configuration (301), the UE (120) performs signal strength measurements for neighboring Target Cells (160, 170). If the measured signal strength exceeds the eTA threshold (303), the UE (120) selects the highest-priority target cell and initiates an early TArequest. The UE (120) determines whether the Target Cell (160, 170) supports the 2-Step CBRA procedure and selects the appropriate early TA request format accordingly.

[0043] For example, if the Target Cell (160, 170) supports the 2-Step CBRA procedure, the UE (120) transmits MsgA, which consolidates Msgl (CBRA RACH preamble) and Msg3 (Contention Resolution Message) into a single message.

[0044] The MsgA transmission contains: CBRA RACH Preamble (Msgl) (302) - This preamble is selected from the CBRA configuration received from the Serving Cell (150) and is used to initiate the early TA request. UE Identification (UE-ID) (303) - This uniquely identifies the UE (120) to the Target Cell (160, 170) and is included as per the Serving Cell’s (150) instructions. ResNotNeeded Flag - This flag instructs the Target Cell (160, 170) to store the estimated TA value without sending a response to the UE (120). This eliminates contention resolution delays and reduces unnecessary signaling overhead.

[0045] By utilizing MsgA, the UE (120) reduces the number of required message exchanges, minimizing network signaling overhead and optimizing handover latency. If the Target Cell (160, 170) does not support the 2-Step CBRA procedure, the UE (120) transmits an ETA-MsgA message using a traditional 4-step CBRA procedure with modifications for early TA acquisition.

[0046] The ETA-MsgA transmission consists of: Legacy Msg3 Format - The UE (120) sends Msg3 using a preconfigured RACH resource allocated for CBRA early TA acquisition.

[0047] Cause: eTA - This field within Msg3 indicates that the request is specifically for early TA acquisition rather than a standard contention-based random-access attempt. UE Identification (UE-ID) - The UE (120) includes its UE-ID (TMSI, S-TMSI, or GUTI) for recognition in the Target Cell (160, 170). ResNotNeeded Flag - This flag instructs the Target Cell (160, 170) to store the estimated TA value without responding to the UE (120). The ETA-MsgA approach ensures that early TA acquisition can still be performed even if the Target Cell (160, 170) does not support the 2-Step CBRA procedure.

[0048] Once the UE (120) successfully completes early TA acquisition, it reports the results to the Serving Cell (150) before the eTAReqReportTimer expires. During handover execution, the Serving Cell (150) transfers theUE’s stored TA value to the Target Cell (160, 170) in the Handover Request Message. Upon handover completion, the Target Cell (160, 170) applies the pre-stored TA value, enabling the UE (120) to achieve immediate uplink synchronization without requiring an additional contention-based random-access attempt.

[0049] Figure 3B presents an exemplary alternative approach to Contention-Based Random Access (CBRA)-based early Timing Advance (TA) acquisition where the User Equipment (UE) (120) receives a UE-specific configuration from the Serving Cell (150) instead of a cell-specific configuration. This method allows a more dynamic and tailored approach to early TA acquisition, improving handover efficiency and reducing Time of Outage (ToO) by leveraging individualized measurement configurations.

[0050] The Serving Cell (150) transmits a UE-specific early TA acquisition configuration (304) via RRC signaling to the UE (120). This configuration differs from the cell-specific configuration in Figure 3 A because it is uniquely designed for the specific UE (120) based on its mobility characteristics, network conditions, and neighboring cell availability.

[0051] The UE-specific configuration (304) includes the following parameters: Measurement Configuration (305) - Specifies how the UE (120) should perform measurements of neighboring Target Cells (160, 170) to determine their suitability for early TA acquisition. RRC Reconfiguration Message (306) - Includes the updated measurement configuration and parameters necessary for early TA acquisition, such as: msgA-RO-FDM and msgA-RO-FrequencyStart for PRACH resource allocation, eTA threshold to ensure early TA acquisition is performed only when the signal strength is sufficient, Target cell priority to rank neighboring cells (160, 170) for early TA acquisition, Number of target cells for early TA Random Access (RA) requests, Identification parameter (TMSI, S-TMSI, or GUTI) to be used in early TA requests. RRC Reconfiguration Completion (307) - Sent by the UE (120) to acknowledge the reception and application of the UE-specific configuration for early TA acquisition.

[0052] Upon receiving the UE-specific configuration (304), the UE (120) follows the measurement and transmission strategy provided by the Serving Cell (150). If the signal strength of a Target Cell (160, 170) meets the eTA threshold, the UE (120) proceeds with the early TA request process.

[0053] If the UE (120) determines that a Target Cell (160, 170) is suitable for early TA acquisition based on the configured measurement parameters (305), it proceeds with a 2-Step CBRA Procedure (if supported by the Target Cell). The UE (120) transmits MsgA, which combines: CBRA RACH Preamble (Msgl) (302) - Used for initial random access to the Target Cell (160, 170). UE Identification (UE-ID) (303) - Allows the Target Cell (160, 170) to recognize the requesting UE (120). ResNotNeeded Flag - Instructs the Target Cell (160, 170) to store theestimated TA without sending a response. Legacy CBRA Procedure (if the 2-Step CBRA procedure is not supported by the Target Cell).

[0054] The UE (120) transmits ETA-MsgA, containing: Legacy Msg3 Format - The UE (120) sends Msg3 using a preconfigured PRACH resource allocated for CBRA early TA acquisition. Cause: eTA - Indicates that the random-access attempt is specifically for early TA acquisition. UE Identification (UE-ID) - Ensures that the Target Cell (160, 170) correctly identifies the UE (120). ResNotNeeded Flag - Prevents the Target Cell (160, 170) from sending a response, ensuring that the TA value is stored for later use.

[0055] By using a UE-specific configuration (304), the Serving Cell (150) can optimize the early TA acquisition process based on the specific conditions of the UE (120), such as its speed, coverage area, and signal variations.

[0056] Once the UE (120) completes early TA acquisition, it reports the results to the Serving Cell (150) within the timeframe specified by the eTAReqReportTimer. During handover execution, the Serving Cell (150) transfers the pre-stored TA value to the Target Cell (160, 170) in the Handover Request Message. When the UE (120) enters the coverage of the Target Cell (160, 170), it applies the pre-stored TA value, ensuring immediate Uplink Synchronization - No additional Random Access (RA) attempts are required post-handover. The UE (120) can seamlessly switch to Target Cell (160, 170) without additional contention resolution delays.

[0057] This UE-specific early TA configuration allows the network to dynamically adapt early TA acquisition procedures based on real-time UE behavior, improving handover reliability and network efficiency.

[0058] Figure 3C illustrates an exemplary alternative approach to Contention-Based Random Access (CBRA)-based early Timing Advance (TA) acquisition using Layer 3 (L3) and Layer 2 (L2) based solutions. This figure depicts how the User Equipment (UE) (120) interacts with the Serving Cell (150) and multiple Target Cells (160, 170) for acquiring an estimated Timing Advance (TA) value before initiating a handover. The solutions outlined in this figure allow flexible early TA acquisition configurations based on network capabilities and resource availability.

[0059] The Serving Cell (150) provides the UE (120) with an early TA acquisition configuration via RRC signaling. This configuration may be delivered using Layer 3 (L3)-based signaling or Layer 2 (L2)-based signaling, each offering a different trade-off between control overhead andefficiency. L3-Based Configuration (308): The Serving Cell (150) transmits early TA configuration parameters via RRC signaling. These parameters include msgA-RO-FDM, msgA-RO-FrequencyStart, eTA threshold, and target cell priority. The UE (120) processes the configuration and determines the neighboring cells (160, 170) eligible for early TA acquisition.

[0060] L2 -Based Configuration (309): The Serving Cell (150) uses MAC-CE signaling to provide the UE (120) with early TA acquisition parameters. The MAC-CE message includes random access configurations tailored for early TA acquisition, reducing signaling overhead compared to L3-based signaling. Upon receiving the early TA configuration (308, 309), the UE (120) measures the signal strength of neighboring Target Cells (160, 170). If the measured signal strength exceeds the eTA threshold, the UE (120) selects the highest-priority Target Cell and initiates an early TA request.

[0061] Depending on Target Cell’s capabilities, the UE (120) selects one of the following methods to perform early TA acquisition. L3 -Based Early TA Request (310, 311): If the Target Cell (160, 170) supports L3-based signaling, the UE (120) transmits MsgA using an RRC-based message format. This includes: CBRA RACH Preamble (Msgl) (310) - The UE (120) transmits a preamble to initiate the early TA request.

[0062] RRC eTA Request (Msg3) (311) - The UE (120) includes the UE Identification (UE-ID) and the ResNotNeeded flag, instructing the Target Cell (160, 170) to store the estimated TA value without responding. By using L3 -based signaling, the UE (120) benefits from robust error handling and reliability, making it suitable for high-latency scenarios.

[0063] L2 -Based Early TA Request (312, 313): For networks that prioritize low-latency signaling, the UE (120) may use an L2-based early TA request. This includes: CBRA RACH Preamble (Msgl) (312) - The UE (120) transmits a preamble using PRACH resources allocated by the Serving Cell (150).

[0064] MAC-CE eTA Request (Msg3) (313) - The UE (120) sends an early TA request using MAC-CE instead of an RRC message. This approach significantly reduces signaling overhead while ensuring that the Target Cell (160, 170) correctly stores the estimated TA value. By using L2 -based signaling, the UE (120) achieves a faster response time and minimizes network congestion, making it suitable for high-speed mobility scenarios.

[0065] Hybrid Approach Using PDCCH-Based eTA Request (314, 315): In some scenarios, a Physical Downlink Control Channel (PDCCH)-based solution is used for early TA acquisition.The Serving Cell (150) may trigger the UE (120) to perform an early TA request by transmitting aPDCCH order (314).

[0066] Upon receiving this order, the UE (120) immediately transmits MsgA, which includes: CBRA RACH Preamble (Msgl) (315) - This is transmitted using the PRACH resources allocated for early TA acquisition. MAC-GE eTA Request (Msg3) - Similar to the L2 -based approach but triggered by a PDCCH order instead of preconfigured RRC signaling. The PDCCH-based early TA request (314, 315) provides a network-controlled mechanism to ensure timely execution of early TA acquisition, allowing the Serving Cell (150) to adapt dynamically based on real-time conditions.

[0067] After early TA acquisition, the UE (120) reports the estimated TA value to the Serving Cell (150). During handover execution: The Serving Cell (150) sends a Handover Request to the Target Cell (160, 170), including the UE Identification (UE-ID) and the pre-stored TA value. The Target Cell (160, 170) applies the TA value upon UE arrival, enabling immediate uplink synchronization. The UE (120) transitions to the Target Cell (160, 170) without requiring additional contentionbased random-access attempts.

[0068] By ensuring that TA values are stored before handover, the proposed solutions reduce handover latency, improve service continuity, and minimize network signaling overhead.

[0069] Figure 3D presents an exemplary enhanced handover procedure that integrates Contention-Based Random Access (CBRA)-based early Timing Advance (TA) acquisition to improve handover efficiency. The figure illustrates how the User Equipment (UE) (120) interacts with the Serving Cell (150) and the Target Cell (160, 170) to achieve seamless uplink synchronization during handover. By using pre-stored TA values, this method eliminates the need for additional contention-based random access attempts post-handover, thereby reducing Time of Outage (ToO) and improving network performance.

[0070] Handover Decision (316): The handover process begins when the Serving Cell (150) determines that the UE (120) should transition to a Target Cell (160, 170). The handover decision is based on multiple network conditions, such as: Degrading signal strength from the Serving Cell. Stronger received signal strength from a Target Cell. Load balancing requirements to optimize network resource distribution. Mobility patterns of the UE (120) indicating that it will soon move out of the Serving Cell’s coverage. Upon reaching a predefined handover threshold, the ServingCell (150) prepares to transfer the UE (120) to the Target Cell (160, 170) while ensuring that uplink synchronization is maintained.

[0071] eTAReqReportTimer Elapsed (317): Before executing the handover, the UE (120) reports its early TA acquisition results to the Serving Cell (150). The eTAReqReportTimer ensures that the UE (120) sends this report within a predefined window. The report contains: Estimated TA values obtained from multiple Target Cells (160, 170) during the early TA acquisition phase. Signal strength measurements to help prioritize the most suitable Target Cell for handover. The Serving Cell (150) uses this information to prepare an optimized handover request.

[0072] Handover Request Including UE Identification (318): The Serving Cell (150) sends a handover request to the Target Cell (160, 170). This request contains: UE Identification (UE-ID) - A unique identifier assigned to the UE (120) to ensure correct recognition in the Target Cell (160, 170). Estimated TA Value - The pre-stored TA value acquired during early TA acquisition, allowing the Target Cell (160, 170) to configure uplink parameters in advance. By including this information, the Target Cell (160, 170) can pre-configure uplink synchronization before the UE (120) arrives.

[0073] Target Cell Recognizes UE and Stores Estimated TA (319): Upon receiving the handover request, the Target Cell (160, 170):Verifies the UE-ID to ensure accurate mapping of the UE (120), Retrieves the pre-stored TA value associated with the UE from early TA acquisition, Configures uplink synchronization parameters based on the received TA value, allowing for immediate connectivity.

[0074] The Target Cell (160, 170) acknowledges the handover request and confirms the stored TA value that will be applied when the UE (120) transitions. Sends the Handover Command back to the Serving Cell (150), which will be relayed to the UE (120). By storing and transmitting this preconfigured TA value, the Target Cell (160, 170) eliminates the need for contention-based random access post-handover.

[0075] RRC Reconfiguration Message with Handover Command (321): The Serving Cell (150) forwards the handover command to the UE (120) via an RRC Reconfiguration Message. This message includes Handover instructions specifying the new Target Cell (160, 170). Pre-Stored TA Value allowing the UE (120) to apply uplink synchronization immediately upon arrival. By receiving this message before transitioning, the UE (120) is already prepared for a seamless handover. As the UE (120) moves to the Target Cell (160, 170), it performs contention detectionto check whether multiple UEs are attempting to access the cell simultaneously. If contention occurs, the Target Cell (160, 170) executes a resolution mechanism, which may include: Prioritization based on UE-ID to ensure the correct UE is recognized, Random backoff and retransmission if contention persists. By applying contention detection proactively, the UE (120) avoids unnecessary signaling delays. Upon reaching the Target Cell (160, 170), the UE (120): applies the pre-configured TA value, achieving immediate uplink synchronization. Avoids additional contention-based random access, minimizing handover latency.

[0076] RRC Reconfiguration Complete (324): This step involves the UE (120) sending an RRC Reconfiguration Complete message to confirm that: It has successfully transitioned to the Target Cell (160, 170). The pre-configured TA value has been successfully applied. No additional random-access attempts are needed. This message finalizes the handover, marking the successful completion of the process.

[0077] Advantages of Enhanced Handover with Early TA: Immediate Uplink Synchronization, he UE (120) applies a pre-stored TA value, ensuring no delays in establishing connectivity with the Target Cell (160, 170). Reduced Time of Outage (ToO) - Eliminating post-handover random access attempts significantly reduces service disruption. Optimized Network Signaling - The handover signaling is streamlined, preventing redundant messaging and reducing network overhead. Seamless Mobility Support - The method ensures uninterrupted connectivity for highspeed UEs, including those in moving vehicles and high-speed rail environments. Efficient Contention Handling - The proactive contention resolution mechanism prevents delays and ensures smooth handover execution.

[0078] Thus, Figure 3D demonstrates an optimized handover procedure leveraging CBRA-based early TA acquisition. By integrating pre-stored TA values into the handover signaling process, this approach eliminates unnecessary contention-based steps, significantly reducing handover latency while enhancing network performance. This method is particularly beneficial for high-mobility UEs, where minimizing Time of Outage (ToO) is crucial to ensuring seamless connectivity.

[0079] Thus, User Equipment (UE) (120) as a key component in the early Timing Advance (TA) acquisition process facilitates seamless handovers between the Serving Cell (150) and Target Cells (160, 170). The UE plays a crucial role in evaluating network conditions, selecting neighboring cells for early TA acquisition, and transmitting requests to store the estimated TA value for later use during handovers.

[0080] Referring to Figure 3A and Figure 3B, the UE (120) first receives a message from the Serving Cell (150) containing cell-specific configuration information (304). This configuration includes key parameters for Contention-Based Random Access (CBRA)-based early TA acquisition, such as: msgA-RO-FDM and msgA-RO-FrequencyStart, defining PRACH resource allocation. eTA threshold, which determines if the UE should initiate early TA acquisition. UE identification (UE-ID), allowing proper recognition in the Target Cell (160, 170).

[0081] Upon receiving this configuration, the UE (120) evaluates the eligibility of neighboring cells (305) based on: 1. Signal strength measurements from Synchronization Signal Blocks (SSBs).2. Configuration information received via System Information Block (SIB) or RRC signaling.

[0082] If a neighboring Target Cell (160, 170) satisfies the eTA threshold, the UE (120) generates an ETA-MsgA (310) containing: CBRA RACH preamble (Msgl) - A randomly selected preamble for contention-based access. UE-ID (311) - Used for unique UE identification within the Target Cell. ResNotNeeded flag - Instructs the Target Cell to store the TA value without sending a response.

[0083] As illustrated in Figure 3C, the UE (120) transmits the ETA-MsgA (312) using either: L3-based signaling (RRC message) (310, 311) or L2-based signaling (MAC-CE) (313, 314). After transmission, the UE (120) continues normal operation with the Serving Cell (150) without waiting for a response from the Target Cell (160, 170). If early TA acquisition is successful, the UE includes success / failure information in the measurement report (322, 323), helping the Serving Cell (150) make better handover decisions.

[0084] Correspondingly the Network Node in the Target Cell (160, 170) is responsible for receiving, processing, and storing the estimated TA values reported by the UE (120).

[0085] Referring to Figure 3D, the network node (160, 170) performs the following key functions: 1. Transmitting Early TA Configuration (318) The network node (160, 170) provides the Serving Cell (150) with early TA acquisition parameters, including: PRACH configurations for CBRA-based access. The expected UE-ID format (S-TMSI, TMSI, or GUTI). Predefined handover thresholds for seamless mobility support.

[0086] 2. Receiving Early TA Request (319, 320): Upon receiving the ETA-MsgA (319) from the UE (120), the network node (160, 170) extracts: The CBRA RACH preamble (Msgl).

[0087] The UE-ID. The ResNotNeeded flag, which prevents unnecessary contention resolution.

[0088] 3. Storing the Estimated TA (321): The network node (160, 170) stores the estimated TA value in an internal database. The TA value is linked to the UE-ID, ensuring accurate retrieval during handover execution.

[0089] 4. Providing TA Value During Handover (322-324): When the Serving Cell (150) initiates a handover request, the network node (160, 170) retrieves the pre-stored TA value and includes it in the handover command (323, 324). The UE (120) applies the TA value upon arrival in the Target Cell (160, 170), ensuring immediate uplink synchronization.

[0090] By following this process, the network node (160, 170) facilitates faster and more reliable handovers, reducing network signaling overhead and minimizing Time of Outage (ToO).

[0091] Thus, User Equipment (120) and the Network Node (160, 170) work together to implement an optimized CBRA-based early TA acquisition framework. The UE evaluates potential Target Cells, initiates early TA acquisition requests, and continues communication with the Serving Cell (150). Meanwhile, the Network Node (160, 170) processes the early TA request, stores the estimated TA value, and retrieves it during handover execution, ensuring seamless network transitions.

[0092] In an embodiment the UE receives UE-specific configuration is received via a MAC Control Element (MAC-CE) message or a Radio resource Control (RRC) message.

[0093] In an embodiment the msgl or msg2 comprises a contention-based random-access preamble, an identifier, an early TA acquisition request, an indication that a response is not required, and the identifier is selected from TMSI, S-TMSI, or GUTI.

[0094] In an embodiment the message is transmitted for target cells whose signal strength exceeds a configured threshold.

[0095] In an embodiment the UE stores results of early TA acquisition attempts for each target cell.

[0096] In an embodiment the UE transmits a report to the serving cell indicating early TA acquisition success or failure.

[0097] In an embodiment the indication that no response is required is a ResNotNeeded flag.

[0098] In an embodiment the number of target cells for early TA is dynamically configured by the serving cell.

[0099] In an embodiment the UE-specific configuration is received via a MAC Control Element (MAC-CE) message or a Radio resource Control (RRC) message.

[0100] In an embodiment the msgl or msg2 comprises a contention-based random-access preamble, an identifier, an early TA acquisition request, an indication that a response is not required, and the identifier is selected from TMSI, S-TMSI, or GUTI.

[0101] In an embodiment the UE stores the result of each early TA acquisition attempt.

[0102] In an embodiment the early TA request is transmitted if the received signal strength of a target cell exceeds a configured threshold.

[0103] In an embodiment the processor is configured to generate and send a measurement report to the serving cell.

[0104] In an embodiment the UE is configured to transmit the identifier and the ResNotNeeded flag as separate MAC-CE elements.

[0105] In an embodiment the early TA request is received via a MAC-CE message.

[0106] In an embodiment the msgl or msg2 comprises a contention-based random-access preamble, an identifier, an early TA acquisition request, an indication that a response is not required, and the identifier is selected from TMSI, S-TMSI, or GUTI.

[0107] In an embodiment the stored TA value is included in a handover command transmitted to the UE.

[0108] In an embodiment the network node maintains a table mapping UE identifier to TA values for early handover support.

[0109] In an embodiment the UE-specific early TA request is received via a MAC-CE message.

[0110] In an embodiment the msgl or msg2 comprises a contention-based random-access preamble, an identifier, an early TA acquisition request, an indication that a response is not required, and the identifier is selected from TMSI, S-TMSI, or GUTI.

[0111] In an embodiment the parameters comprise: PRACH occasions and time-frequency resources for PUSCH transmission in neighboring cells and an identification parameter specifying whether the UE should use a temporary mobile subscriber identity (TMSI) or a globally unique temporary identifier (GUTI) for early TA request.

[0112] In an embodiment the CBRA early TA acquisition request is part of a l-step CBRA RACH procedure including sending two messages from the UE towards the eligibleneighbor cell, wherein the first message is an msgl message, and the second message is an msg3 message or a MAC CE message.

[0113] In an embodiment the second message further includes an indication that the CBRA early TA acquisition request refers to a l-step CBRA RACH procedure or a “response not needed” flag.

[0114] In an embodiment the ETA-MsgA comprises: a combined msgl and msg3 transmission including a preamble for RACH transmission, a UE identification parameter (UE-ID) to uniquely identify the UE and a ResNotNeeded flag, instructing the neighboring cell to store the estimated TA without responding to the UE.

[0115] In an embodiment the identification parameter instructs the UE to use the S-TMSI or TMSI if the neighboring cell belongs to the same AMF group as the serving cell or The GUTI if the neighboring cell belongs to a different AMF group.

[0116] In an embodiment the UE determines eligibility of neighboring cells for early TA acquisition based on: Signal strength measurements from Synchronization Signal Blocks (SSBs), Configuration information received in the SIB or dedicated RRC signaling.

[0117] In an embodiment the CB-eTA-PRACHConfig parameters include neighboring cell(s), priority, and number of cells to perform early TA acquisition, Optionally, neighboring cells’ CBRA configuration including PRACH preamble, RACH occasions, and RACH frame details, UE ID flag (TMSI / GUTI or another ID) and PUSCH resources such as eTAmsgA-RO-FDM and eTAmsgA-RO -Frequency Start.

[0118] In an embodiment the UE transmits the ETA-MsgA using a layer 3-based solution, wherein the early TA request is embedded in an RRC signaling message.

[0119] In an embodiment the UE transmits the ETA-MsgA using a layer 2-based solution, wherein the early TA request is included in a MAC Control Element (MAC-CE).

[0120] In an embodiment the UE transmits to the serving cell at least one of the geographical locations of the UE, the UE mobility status (stationary or high-speed movement) or the type of service being used by the UE (e.g., critical services requiring low latency).

[0121] In an embodiment the UE receives, via the serving cell, a short UE identifier to be used for CBRA-based early TA acquisition; including the short UE identifier in the CBRA early TA acquisition request, transmits the CBRA early TA acquisition request towardsthe determined eligible neighbor cell and continues communication with the serving cell without waiting for a response from the neighboring cell.

[0122] In an embodiment the UE includes information in a measurement report to the serving cell indicating for which neighboring cells a CBRA early TA acquisition request has been transmitted.

[0123] In an embodiment the CBRA early TA acquisition request is part of a 1-step CBRA RACH procedure including sending two messages from the UE towards the eligible neighbor cell, wherein the first message is an msgl message, and the second message is an msg3 message or a MAC CE message.

[0124] In an embodiment the parameters comprise: PRACH occasions and time-frequency resources for PUSCH transmission in neighboring cells and an identification parameter specifying whether the UE should use a temporary mobile subscriber identity (TMSI) or a globally unique temporary identifier (GUTI) for early TA request to an eligible neighboring cell.

[0125] In an embodiment the network node determines whether the neighboring cell belongs to the same Access and Mobility Management Function (AMF) group as the serving cell, and based on this determination, instructs the UE to use: S-TMSI or TMSI for neighboring cells within the same AMF group or GUTI for neighboring cells in a different AMF group.

[0126] In an embodiment the transmitter of the UE is configured to transmit the CBRA early TA acquisition request without requiring dedicated preamble reservations, allowing contention-based access without reducing preamble availability for legacy access.

[0127] In an embodiment the transmitter of the UE is configured to indicate, in a measurement report to the serving cell, for which neighboring cells have successfully performed an early TA value, optimizing network-assisted handover decisions.

[0128] In an embodiment the neighboring cell identifies the UE using the UE-ID received in the ETA-MsgA and stores the estimated TA corresponding to the UE-ID for later retrieval during handover.

[0129] In an embodiment the network node is configured for storing the estimated Timing Advance (TA) value corresponding to a received UE identifier, maintaining the stored TA value for a predefined period to ensure availability during handover, transmittingthe stored TA value in response to a handover request from the serving cell and ensuring that the UE receives the stored TA value in the handover command for seamless transition.

[0130] In an embodiment the transmitter of the UE is configured to transmit the ETA-MsgA using a contention-based random-access method without requiring a response from the neighboring cell.

[0131] In an embodiment the receiver of the UE is configured to receive an RRC signaling message containing the identification parameter, instructing the UE to use a specific identifier for early TA acquisition.

[0132] In an embodiment the network node dynamically configures the identification parameter for each UE based on: The UE’s mobility status (stationary or high-speed movement), the UE’s geographical location or the type of service the UE is using (e.g., delaysensitive applications).

[0133] In an embodiment the processing unit of the UE is configured to prioritize early TA acquisition requests for delay-sensitive applications, such as ultra-reliable low-latency communications (URLLC).

[0134] In an embodiment of the neighboring cell stores the estimated TA in an internal handover preparation database, ensuring rapid retrieval during the handover procedure.

[0135] In an embodiment the serving cell determines the most suitable neighbouring cells for early TA acquisition based on historical UE movement patterns, signal strength measurements, and network load conditions.

[0136] In an embodiment the serving cell determines the most suitable neighboring cells for early TA acquisition based on historical UE movement patterns, signal strength measurements, and network load conditions.

[0137] In an embodiment the network node transmits the early TA acquisition configuration to the UE using: a broadcasted SIB message, applicable to all UEs in the serving cell or a dedicated RRC signaling message, applicable to a specific UE based on network conditions.

[0138] In an embodiment the serving cell receives measurement reports from the UE indicating which neighboring cells have successfully stored an early TA value, enabling optimized handover decision-making.

[0139] In an embodiment the network node prioritizes early TA acquisition requests from UEs engaged in delay-sensitive applications, ensuring lower latency for critical services such as voice calls or ultra-reliable low- latency communications (URLLC).

[0140] In an embodiment the serving cell broadcasts PRACH occasions and TA acquisition parameters to multiple UEs, allowing UE-specific early TA acquisition without dedicated preamble reservations.

[0141] In an embodiment the network node provides a short UE identifier for early TA acquisition, transmits, to the UE, the short identifier along with CBRA early TA acquisition parameters, receives, from the UE, a CBRA early TA acquisition request containing the short identifier, stores the estimated TA value corresponding to the short identifier; and provided the stored TA value in a handover command to the UE via the serving cell.

[0142] In an embodiment the neighboring cell - identifies the UE using the UE-ID received in the ETA-MsgA and ResNotNeeded flag and instructs the network to store the estimated TA corresponding to the UE-ID for later retrieval during handover.

[0143] In an embodiment of the network node the transmitter is configured to send an RRC signaling message to the UE containing an explicit handover preparation message including the stored TA, enabling an optimized handover process.

[0144] In an embodiment, the network enables UE early TA acquisition without requiring a dedicated RACH preamble allocation.

[0145] In an embodiment the transmitter of the network node is configured to send a handover request (HoRequest) to the target cell including the UE-ID used for early TA acquisition, allowing the target cell to retrieve the estimated TA and provide it in the handover command.

[0146] In the drawings and specification, there have been disclosed example embodiments of the present disclosure. Although specific terms are employed, they are used in a generic and descriptive sense only and not for purposes of limitation. It will be apparent to those having ordinary skill in this art that various modifications and variations may be made to the example embodiments disclosed herein, consistent with the present disclosure, without departing from the spirit and scope of the present disclosure. Other example embodiments consistent with the present disclosure willbecome apparent from consideration of the specification and the practice of the description disclosed herein.

Claims

CLAIMS1. A method performed by a user equipment (UE), the method comprising: receiving, via a dedicated message, a UE-specific configuration comprising: configuration information associated with early TA acquisition for one or more target cells, a priority associated with each of the target cells, a number of target cells suitable for the early TA attempt, and an identifier to be used by the UE in conjunction with an early TA acquisition request; selecting a target cell based on the priority and signal quality; transmitting, to the selected target cell: at least one of: msgl, msg3, msg A; and refraining from monitoring receipt of a response from the target cell.

2. The method of claim 1, wherein the UE-specific configuration is received via a MAC Control Element (MAC-CE) message or a Radio resource Control (RRC) message.

3. Thmethod of claim 1, wherein the at least one of: msgl, msg3, msgA comprises a contention-based random-access preamble, an identifier, an early TA acquisition request, an indication that a response is not required, and the identifier is selected from TMSI, S-TMSI, or GUTI.

4. The method of claim 1, wherein the message is transmitted for target cells whose signal strength exceeds a configured threshold.

5. The method of claim 1, wherein the UE stores results of early TA acquisition attempts for each target cell.

6. The method of claim 1, further comprising transmitting a report to the serving cell indicating early TA acquisition success or failure.

7. The method of claim 1, wherein the indication that no response is required is a ResNotNeeded flag.

248. The method of claim 1, wherein the number of target cells for early TA is dynamically configured by the serving cell.

9. A user equipment (UE), configured to perform the method steps of claim 1.

10. The UE of claim 9, wherein the UE is further configured to perform at least one of the method steps of claim 2 to 8.

11. A method performed by a network node, comprising: receiving, from a UE, at least one of: msgl, msg3, msgA; determining a TA value based on the timing of the received at least one of: msgl, msg3, msgA; storing the TA value in association with a UE identifier; and using the stored TA value during handover to enable uplink synchronization without further contention.

12. The method of claim 11, wherein the early TA request is received via a MAC-CE message.

13. The method of claim 11 wherein the at least one of: msgl, msg3, msgA comprises a contention-based random-access preamble, an identifier, an early TA acquisition request, an indication that a response is not required, and the identifier is selected from TMSI, S-TMSI, or GUTI.

14. The method of claim 11, wherein the stored TA value is included in a handover command transmitted to the UE.

15. The method of claim 11, wherein the network node maintains a table mapping UE identifier to TA values for early handover support.

16. A network node, configured to perform the method steps of claim 11.

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