Method and apparatus for early ta acquisition in wireless communication system

Abstract

The disclosure relates to a 5th generation (5G) or 6th generation (6G) communication system for supporting a higher data transmission rate. A method performed by terminal in a wireless communication system is provided. The method includes receiving, from a base station, a radio resource control (RRC) message including low layer triggered mobility (LTM) candidate configuration information, wherein the LTM candidate configuration information includes random access (RA) configuration information for an early timing advance (TA) acquisition; and performing an RA for the early TA acquisition on a LTM candidate cell, based on the RA configuration information for the early TA acquisition.

Description

METHOD AND APPARATUS FOR EARLY TA ACQUISITION IN WIRELESS COMMUNICATION SYSTEM

[0001] The present disclosure relates to wireless communication systems, and more particularly, the disclosure relates to a method and an apparatus for early timing advance (TA) acquisition in a wireless communication system.

[0002] 5th generation (5G) mobile communication technologies define broad frequency bands such that high transmission rates and new services are possible, and can be implemented not only in "Sub 6GHz" bands such as 3.5GHz, but also in "Above 6GHz" bands referred to as mmWave including 28GHz and 39GHz. In addition, it has been considered to implement 6th generation (6G) mobile communication technologies (referred to as Beyond 5G systems) in terahertz bands (for example, 95GHz to 3THz bands) in order to accomplish transmission rates fifty times faster than 5G mobile communication technologies and ultra-low latencies one-tenth of 5G mobile communication technologies.

[0003] At the beginning of the development of 5G mobile communication technologies, in order to support services and to satisfy performance requirements in connection with enhanced mobile broadband (eMBB), ultra eliable low latency communications (URLLC), and massive machine-type communications (mMTC), there has been ongoing standardization regarding beamforming and massive multiple-input multiple output (MIMO) for mitigating radio-wave path loss and increasing radio-wave transmission distances in mmWave, supporting numerologies (for example, operating multiple subcarrier spacings) for efficiently utilizing mmWave resources and dynamic operation of slot formats, initial access technologies for supporting multi-beam transmission and broadbands, definition and operation of bandwidth part (BWP), new channel coding methods such as a low density parity check (LDPC) code for large amount of data transmission and a polar code for highly reliable transmission of control information, layer 2 (L2) pre-processing, and network slicing for providing a dedicated network specialized to a specific service.

[0004] Currently, there are ongoing discussions regarding improvement and performance enhancement of initial 5G mobile communication technologies in view of services to be supported by 5G mobile communication technologies, and there has been physical layer standardization regarding technologies such as vehicle-to-everything (V2X) for aiding driving determination by autonomous vehicles based on information regarding positions and states of vehicles transmitted by the vehicles and for enhancing user convenience, new radio unlicensed (NR-U) aimed at system operations conforming to various regulation-related requirements in unlicensed bands, new radio user equipment (NR UE) power saving, non-terrestrial network (NTN) which is UE-satellite direct communication for providing coverage in an area in which communication with terrestrial networks is unavailable, and positioning.

[0005] Moreover, there has been ongoing standardization in air interface architecture / protocol regarding technologies such as industrial internet of things (IIoT) for supporting new services through interworking and convergence with other industries, integrated access and backhaul (IAB) for providing a node for network service area expansion by supporting a wireless backhaul link and an access link in an integrated manner, mobility enhancement including conditional handover and dual active protocol stack (DAPS) handover, and two-step random access for simplifying random access procedures (2-step RACH for NR). There also has been ongoing standardization in system architecture / service regarding a 5G baseline architecture (for example, service based architecture or service based interface) for combining network functions virtualization (NFV) and software-defined networking (SDN) technologies, and mobile edge computing (MEC) for receiving services based on UE positions.

[0006] As 5G mobile communication systems are commercialized, connected devices, which have been exponentially increasing, will be connected to communication networks, and it is accordingly expected that enhanced functions and performances of 5G mobile communication systems and integrated operations of connected devices will be necessary. To this end, new research is scheduled in connection with extended reality (XR) for efficiently supporting augmented reality (AR), virtual reality (VR), mixed reality (MR) and the like, 5G performance improvement and complexity reduction by utilizing artificial intelligence (AI) and machine learning (ML), AI service support, metaverse service support, and drone communication.

[0007] Furthermore, such development of 5G mobile communication systems will serve as a basis for developing not only new waveforms for providing coverage in terahertz bands of 6G mobile communication technologies, multi-antenna transmission technologies such as full dimensional MIMO (FD-MIMO), array antennas and large-scale antennas, metamaterial-based lenses and antennas for improving coverage of terahertz band signals, high-dimensional space multiplexing technology using orbital angular momentum (OAM), and reconfigurable intelligent surface (RIS), but also full-duplex technology for increasing frequency efficiency of 6G mobile communication technologies and improving system networks, AI-based communication technology for implementing system optimization by utilizing satellites and AI from the design stage and internalizing end-to-end AI support functions, and next-generation distributed computing technology for implementing services at levels of complexity exceeding the limit of UE operation capability by utilizing ultra-high-performance communication and computing resources.

[0008] The above information is presented as background information only to assist with an understanding of the present disclosure. No determination has been made, and no assertion is made, as to whether any of the above might be applicable as prior art with regard to the disclosure.

[0009] The disclosure provides a method and an apparatus for early TA acquisition in a wireless communication system.

[0010] The embodiments disclosed herein are illustrated in the accompanying drawings, throughout which like reference letters indicate corresponding parts in the various figures. The embodiments herein will be better understood from the following description with reference to the drawings, in which:

[0011] FIG. 1 depicts the Next-Generation Radio Access Network (NG-RAN) architecture;

[0012] FIG. 2 depicts the New Radio (NR) protocol stack architecture for the user plane;

[0013] FIG. 3 depicts the NR radio protocol stack architecture for the control plane;

[0014] FIG. 4A depicts an example MAC structure;

[0015] FIG. 4B depicts a MAC structure overview with two MAC entities;

[0016] FIG. 5 depicts an example sequence for performing LTM;

[0017] FIG. 6 shows a block diagram of the wireless communication system, according to embodiments as disclosed herein;

[0018] FIG. 7 shows a flowchart for a method for performing early timing advance in a wireless communication network, according to embodiments as disclosed herein;

[0019] FIG. 8 depicts an example of a MAC Architecture for RACH control, according to embodiments disclosed herein;

[0020] FIG. 9 depicts a flowchart showing a method for LTM early synchronization indication for a self-organizing network (SON) and Minimisation of Drive Test (MDT), according to embodiments as disclosed herein;

[0021] FIG. 10 depicts the process of performing early TA synchronization, according to embodiments as disclosed herein;

[0022] FIG. 11 is a diagram illustrating a UE according to an embodiment of the present disclosure; and

[0023] FIG. 12 is a diagram illustrating a base station according to an embodiment of the present disclosure.

[0024] Throughout the present disclosure, the expression "at least one of a, b or c" indicates only a, only b, only c, both a and b, both a and c, both b and c, all of a, b, and c, or variations thereof. Throughout the specification, a layer (or a layer apparatus) may also be referred to as an entity. Hereinafter, operation principles of the disclosure will be described in detail with reference to accompanying drawings. In the following descriptions, well-known functions or configurations are not described in detail because they would obscure the disclosure with unnecessary details. The terms used in the specification are defined in consideration of functions used in the disclosure, and can be changed according to the intent or commonly used methods of users or operators. Accordingly, definitions of the terms are understood based on the entire descriptions of the present specification.

[0025] For the same reasons, in the drawings, some elements may be exaggerated, omitted, or roughly illustrated. Also, a size of each element does not exactly correspond to an actual size of each element. In each drawing, elements that are the same or are in correspondence are rendered the same reference numeral.

[0026] Advantages and features of the present disclosure and methods of accomplishing the same may be understood more readily by reference to the following detailed descriptions of embodiments and accompanying drawings of the disclosure. The disclosure may, however, be embodied in many different forms and should not be construed as being limited to the embodiments set forth herein; rather, these embodiments of the disclosure are provided so that this disclosure will be thorough and complete, and will fully convey the concept of the disclosure to one of ordinary skill in the art. Therefore, the scope of the present disclosure is defined by the appended claims. Throughout the specification, like reference numerals refer to like elements. It will be understood that blocks in flowcharts or combinations of the flowcharts may be performed by computer program instructions. Because these computer program instructions may be loaded into a processor of a general-purpose computer, a special-purpose computer, or another programmable data processing apparatus, the instructions, which are performed by a processor of a computer or another programmable data processing apparatus, create units for performing functions described in the flowchart block(s).

[0027] The computer program instructions may be stored in a computer-usable or computer-readable memory capable of directing a computer or another programmable data processing apparatus to implement a function in a particular manner, and thus the instructions stored in the computer-usable or computer-readable memory may also be capable of producing manufactured items containing instruction units for performing the functions described in the flowchart block(s). The computer program instructions may also be loaded into a computer or another programmable data processing apparatus, and thus, instructions for operating the computer or the other programmable data processing apparatus by generating a computer-executed process when a series of operations are performed in the computer or the other programmable data processing apparatus may provide operations for performing the functions described in the flowchart block(s).

[0028] In addition, each block may represent a portion of a module, segment, or code that includes one or more executable instructions for executing specified logical function(s). It is also noted that, in some alternative implementations, functions mentioned in blocks may occur out of order. For example, two consecutive blocks may also be executed simultaneously or in reverse order depending on functions corresponding thereto.

[0029] As used herein, the term "unit" denotes a software element or a hardware element such as a field-programmable gate array (FPGA) or an application-specific integrated circuit (ASIC), and performs a certain function. However, the term "unit" is not limited to software or hardware. The "unit" may be formed so as to be in an addressable storage medium, or may be formed so as to operate one or more processors. Thus, for example, the term "unit" may include elements (e.g., software elements, object-oriented software elements, class elements, and task elements), processes, functions, attributes, procedures, subroutines, segments of program code, drivers, firmware, micro-codes, circuits, data, a database, data structures, tables, arrays, or variables.

[0030] Functions provided by the elements and "units" may be combined into the smaller number of elements and "units," or may be divided into additional elements and "units." Furthermore, the elements and "units" may be embodied to reproduce one or more central processing units (CPUs) in a device or security multimedia card. Also, in an embodiment of the present disclosure, the "unit" may include at least one processor. In the following descriptions of the disclosure, well-known functions or configurations are not described in detail because they would obscure the disclosure with unnecessary details.

[0031] Hereinafter, for convenience of explanation, the present disclosure uses terms and names defined in the 3rd generation partnership project long term evolution (3GPP LTE) standards. However, the disclosure is not limited to the terms and names, and may also be applied to systems following other standards.

[0032] In the present disclosure, an evolved node B (eNB) may be interchangeably used with a next-generation node B (gNB) for convenience of explanation. That is, a base station (BS) described by an eNB may represent a gNB. In the following descriptions, the term "base station" refers to an entity for allocating resources to a user equipment (UE) and may be used interchangeably with at least one of a gNode B, an eNode B, a node B, a base station (BS), a radio access unit, a base station controller (BSC), or a node over a network. The term "terminal" may be used interchangeably with a UE, a mobile station (MS), a cellular phone, a smartphone, a computer, or a multimedia system capable of performing communication functions. However, the disclosure is not limited to the aforementioned examples. In particular, the disclosure is applicable to 3GPP new radio (NR) (or 5th generation (5G)) mobile communication standards. In the following description, the term eNB may be interchangeably used with the term gNB for convenience of explanation. That is, a base station explained as an eNB may also indicate a gNB. The term UE may also indicate a mobile phone, NB-IoT devices, sensors, and other wireless communication devices.

[0033] Embodiments disclosed herein relate to wireless communication networks, and more particularly to systems and methods for timing advance synchronization in wireless communication networks.

[0034] FIG. 1 depicts the Next-Generation Radio Access Network (NG-RAN) architecture. The NG-RAN comprises a set of 5G New Radio (NR) Node B (gNB(s)) connected to a 5G Core (5GC) through a Next-Generation (NG) interface. The gNB(s) may be interconnected through an Xn network interface. The gNB may include a 5G New Radio (NR) Node B centralized unit (gNB-CU) and a plurality of 5G New Radio (NR) Node B distributed units (gNB-DU(s)). The gNB-CU and the gNB-DU are connected through a point to point logical interface (F1) interface.

[0035] FIG. 2 depicts the New Radio (NR) protocol stack architecture for the user plane. The service data adaptation protocol (SDAP), packet data convergence protocol (PDCP) layer, radio link control (RLC) layer and medium access control (MAC) sublayers are terminated in the gNB on the network side and in a user equipment (UE).

[0036] FIG. 3 depicts the NR radio protocol stack architecture for the control plane. The protocol stack for the control plane, where PDCP, RLC and MAC sublayers (terminated in gNB on the network side) perform the functions listed in clause 6 of TS 38.401; RRC (terminated in the gNB on the network side) performs the functions listed in clause 7 of TS 38.401; and network access stratum (NAS) control protocol (terminated in the AMF on the network side) performs the functions listed for instance: authentication, mobility management, security control.

[0037] - The main services and functions of the MAC sublayer include, but are not limited to: Mapping between logical channels and transport channels;

[0038] - Multiplexing / demultiplexing of MAC service data units (SDUs) belonging to one or different logical channels into / from transport blocks (TB) delivered to / from the physical layer on transport channels;

[0039] - Scheduling information reporting;

[0040] - Error correction through hybrid automatic repeat request (HARQ) (one HARQ entity per cell in case of CA);

[0041] - Priority handling between UEs by means of dynamic scheduling;

[0042] - Priority handling between logical channels of one UE by means of logical channel prioritisation;

[0043] - Priority handling between overlapping resources of one UE; and

[0044] - Padding.

[0045] A single MAC entity may support multiple numerologies, transmission timings and cells. The mac entity may map the restrictions in logical channel prioritization control which numerology(ies), cell(s), and transmission timing(s) that may be used by a logical channel.

[0046] FIG. 4A depicts an example MAC structure. FIG. 4B depicts a MAC structure overview with two MAC entities. The MAC entity of the UE handles the transport channels. When the UE is configured with SCG, two MAC entities are configured to the UE. One MAC entity for the MCG and one MAC entity for the SCG. When the UE is configured with Dual Active Protocol Stack (DAPS) Handover, two MAC entities are used by the UE. One MAC entity for the source cell (source MAC entity) and one MAC entity for a target cell (target MAC entity). The functions of the different MAC entities in the UE operate independently of each other unless otherwise specified. The timers and parameters used in each MAC entity are configured independently unless otherwise specified. The serving Cells, Cell Radio Network Temporary Identifier (C-RNTI), radio bearers, logical channels, upper- and lower-layer entities, logical channel group (LCGs), and HARQ entities considered by each MAC entity refer to the HARQ entities mapped to the MAC entity unless otherwise specified. If the MAC entity is configured with one or more SCells, there are multiple downlink shared channels (DL-SCH) and there may be multiple uplink shared channel (UL-SCH) as well as multiple random-access channels (RACH) per MAC entity, one DL-SCH, one UL-SCH, and one RACH on the SpCell. If the MAC entity is configured with one or more SCells, there is one DL-SCH, zero or one UL-SCH and zero or one RACH for each SCell. If the MAC entity is not configured with any SCell, there is one DL-SCH, one UL-SCH, and one RACH per MAC entity.

[0047] In wireless technologies like 5G NR, devices can move across different cells. Mobility is performed using a procedure called cell reselection in RRC_IDLE mode. Till NR R17, mobility is performed using a procedure called handover in RRC_CONNECTED mode. Network controlled mobility applies to UEs in RRC_CONNECTED. The network-controlled mobility requires explicit RRC signalling to be triggered by the gNB in NR. The handover in NR usually consists of three steps: handover preparation, handover execution and handover completion. The gNB may configure the UE to report measurements. Based on the reported measurements or based on the network's understanding of the network topology, the gNB may send RRC Reconfiguration message to handover the UE to another cell called the target cell from the source cell. The UE accesses the target cell and then the UE sends RRC Reconfiguration complete message. In an alternative way introduced in 3gpp NR release 16, the gNB may configure the UE with the execution conditions for triggering handover. Once the execution conditions are satisfied, the UE may move to the target cell and send the RRC reconfiguration complete message. The 3gpp standards also introduced a new handover called DAPS handover in release 16. In the handover methods, the UE performs handover by sending layer 3 (RRC) messages causing considerable signalling overhead and latency issues. Referring to the handover, and conditional handover (CHO) as layer 3 mobility. In case of dual connectivity, UE may perform PSCellChange or Conditional PSCellChange. In the context of dual connectivity, one may refer to PSCellChange or Conditional PSCellChange also as layer 3 mobility. i.e. Handover, Conditional Handover, PSCellChange,Conditional PSCellChange etc. refers to L3 mobility. One may also refer to PSCellChange or Conditional PSCellChange as SCG layer 3 mobility and the handover and CHO as MCG layer 3 mobility in the context of dual connectivity.

[0048] Further, the UE may receive RRC configuration for updating some of the security parameters. The 3GPP specifications such as TS38.300, TS38.331, TS 38.321 V17.4.0 may be considered as relevant background.

[0049] 3GPP release 18 is considering Lower Layers (L1 / L2 layers) Triggered Mobility (also known as LTM) to solve the problem related to latency, signalling overhead etc. associated with layer 3 mobility. As per 3GPP, the goal of LTM is to enable a serving cell change via layer 1 and layer 2 (L1 / L2) signalling, in order to reduce the latency, overhead and interruption time. The network (i.e., gNB) may configure the UE with multiple candidate cells to allow fast application of configurations for candidate cells. The network may further send MAC CE or L1 signalling to dynamically switch the UE from a source cell to one of the configured candidate cells. Further, the LTM can be triggered based on the L1 measurements rather than the L3 measurements.

[0050] 3GPP proposes to perform LTM, without reset of lower layers like the MAC layer to avoid data loss and to reduce the additional delay of data recovery wherever possible. The gNB CU may provide LTM Candidate Configuration, i.e., configure LTM candidate cells through one RRC Reconfiguration message for a candidate target cell. The gNB may further release or modify the candidate configurations. The UE may store the LTM configuration of other candidate cells even after moving to a candidate cell through LTM. The gNB CU also may provide the UE with configuration(s) for performing LTM measurements for different candidate frequencies and candidate cells and reporting based on the performed LTM measurements. The UE performs the L1 measurements on the source cell and candidate cell and reports L1 measurements through channel state information (CSI) reports to the gNB DU of the source cell. The gNB DU may send a MAC CE (for e.g., an LTM MAC CE or an LTM cell switch MAC CE) asking the UE to perform a cell switch to another cell which is an LTM candidate cell. The UE may perform random access during the LTM cell switch, or the cell switch may be RACH less. The UE may receive a request to perform random access on a candidate cell before the cell switch. The network may calculate a timing advance (TA). The gNB may request the UE to perform random access towards one or more LTM candidate cells. The random access may be performed for receiving the timing advance (TA) before the cell switch is performed. The cell switch is performed through signalling such as PDCCH order. The TA may be referred to as an Early TA, Early synchronization (Sync) TA, or TA for Early Synchronization. Random access performed on the LTM candidate cells for the timing advance reception is known as random access for the early TA, random access for the early TA Synchronization, or random access for early TA acquisition. Embodiments herein also refer to random access performed on the LTM candidate cells for the timing advance reception as the early TA synchronization or early TA acquisition. A single random-access procedure may be used for performing the early TA synchronization after receiving the PDCCH order. Further early TA may be used for purposes other than for LTM.

[0051] The UE receives the PDCCH order from the primary cells such as a PCell and a PSCell for early TA synchronization. Upon reception of the PDCCH order, the UE initiates the RACH for the TA measurement for candidate cells on the one or more candidate cells as indicated by the network. The UE sends the RACH preamble to the candidate cells. The UE may receive the LTM Cell switch command including the timing advance. If the source DU indicates the UE to retransmit the RACH for early TA, the UE retransmits the same. The gNB may send PDCCH order requesting the UE to retransmit random access preamble for TA measurement to one or more candidate cells.

[0052] The UE Radio Resource Control (RRC) receives the configuration for the early TA from the gNB RRC. The UE RRC configures the UE MAC and / or the UE L1 with the RACH configuration for early TA.

[0053] 3GPP specifications such as TS38.300, TS38.331, TS 38.321 V17.4.0 can be considered as relevant background.

[0054] FIG. 5 depicts an example sequence for performing LTM. A 5G NR (new radio) radio access network also known as NG-RAN (Next Generation Radio Network) comprises a number of NR base stations known as gNBs. The gNBs can be connected to each other through an Xn interface, and may be connected to various core network elements like the AMF (Access and Mobility Management Function), the UPF (User Plane Function) etc. Further the gNBs can be divided into two physical entities; i.e., a CU (Centralized Unit) and a DU (Distributed Unit). The CU provides support for the higher layers of the protocol stack (such as SDAP (Session Data Application Protocol), PDCP (Packet Data Convergence Protocol) and RRC (Radio Resource Control)). The DU provides support for the lower layers of the protocol stack (such as RLC (Radio Link Control), MAC (Medium Access Control) and Physical layer). Each gNB can have multiple cells serving many UEs (User Equipment). The NG-RAN has to resort to manual techniques like drive tests to identify the parameters. However, manual parameter tuning is a costly operation since the testing depends on a lot of factors like the number of users, number of neighbours, maximum throughput in the cell, average throughput in the cell etc. Further, whenever a gNB is installed in the neighbourhood or a new service is introduced, many of these manual operations need to be repeated. To resolve the problem, 3GPP has introduced Self-Organizing Networks (SON) techniques in wireless technologies like NR. The SON was first introduced in 3GPP release 9, in LTE. SON solutions can be divided into three categories: Self-Configuration, Self-Optimization and Self-Healing. The SON architecture can be a centralized, distributed or a hybrid solution.

[0055] Self-optimization of RACH aims to minimize the number of attempts on the RACH. The UE may report the detailed information about RACH in the RACH Report to the network and the network will optimize various parameters associated with RACH using the information. The UE sends RACH reports to the network in RRC messages; for e.g., the UE Information Response. On receiving the RACH report, the gNB CU may send the RACH reports to the gNB DU or the operations and management (OAM) SON module or may directly use the RACH reports for optimizing various parameters related to random access. Examples of the parameters can be the number of preambles, configuration of group A and group B preambles, RACH prioritization information, contention resolution timer, number of RACH preambles for 2 step RACH, PUSCH related parameters for 2 step RACH, and so on.

[0056] The principal object of the embodiments herein is to disclose systems and methods for timing advance synchronization in wireless communication networks.

[0057] Another object of the embodiments herein is to disclose methods and systems for configuring and optimizing random access for early TA.

[0058] Another object of the embodiments herein is to disclose methods and systems for creating at least one random access channel (RACH) controller for a lower layer triggered mobility (LTM) candidate cell based on the LTM configuration.

[0059] Another object of the embodiments herein is to disclose methods and systems for configuring the created RACH controller with RACH parameters for the early TA synchronization.

[0060] Another object of the embodiments herein is to disclose methods and systems for maintaining the RACH specific UE variables for the LTM candidate cells through the RACH controller.

[0061] Another object of the embodiments herein is to disclose methods and systems for maintaining the RACH specific UE variables in a layer2 of the UE to handle the random access for synchronizing the early TA.

[0062] Another object of the embodiments herein is to disclose methods and systems for receiving a maximum number of preamble transmission and a random-access response window in the random-access configuration and ignoring the received maximum number of preamble transmissions and the random-access response window.

[0063] Another object of the embodiments herein is to disclose methods and systems for receiving a physical downlink control channel (PDCCH) order for the early TA synchronization from the network apparatus.

[0064] Another object of the embodiments herein is to disclose methods and systems for skipping incrementing of a preamble transmission counter for random access preamble transmission, if the random-access preamble transmission is for early TA synchronization.

[0065] Another object of the embodiments herein is to disclose methods and systems for transmitting the random access for early TA, irrespective of number of preamble transmissions already performed of early TA.

[0066] Another object of the embodiments herein is to disclose methods and systems for receiving a Contention Free RACH (CFRA) resource configuration and a request for a power ramping for the early TA synchronization, the maximum number of preamble transmission in the random-access configuration, and the random-access response window.

[0067] Another object of the embodiments herein is to disclose methods and systems for encoding the random-access configuration by the gNB DU and encoding the LTM configuration by a centralized unit (CU).

[0068] Another object of the embodiments herein is to disclose methods and systems for including the Contention Free RACH (CFRA) resource configuration and a request for a power ramping for the early TA synchronization in an RRC configuration message.

[0069] Another object of the embodiments herein is to disclose methods and systems for receiving an LTM command for triggering cell switch and storing an indication about TA presence in an RA information.

[0070] These and other aspects of the embodiments herein will be better appreciated and understood when considered in conjunction with the following description and the accompanying drawings. It should be understood, however, that the following descriptions, while indicating at least one embodiment and numerous specific details thereof, are given by way of illustration and not of limitation. Many changes and modifications may be made within the scope of the embodiments herein without departing from the spirit thereof, and the embodiments herein include all such modifications.

[0071] An embodiment herein relates to a method for timing advance (TA) synchronization in a wireless network. The method comprises receiving, by a User Equipment (UE), a lower-layer triggered mobility (LTM) configuration from a network apparatus. The LTM configuration comprises at least one of a random access configuration for an early timing advance (TA). The method further comprises creating by the UE, at least one random access channel (RACH) controller for an LTM candidate cell based on the LTM configuration. The method further comprises configuring by the UE, the created RACH controller with RACH parameters for the early TA synchronization.

[0072] An embodiment herein relates to user equipment (UE) in a wireless communication system, wherein the UE comprises a transceiver; and at least one controller coupled with the transceiver. The UE (102) is configured to receive a lower-layer triggered mobility (LTM) candidate configuration from a network apparatus. The LTM candidate configuration comprises at least one of a random access configuration for an early timing advance (TA). The UE (102) is configured to create at least one random access channel (RACH) controller for an LTM candidate cell based on the LTM candidate configuration. The UE (102) is configured to configure the LTM candidate cell specific to the created RACH controller with a RACH parameter for synchronizing the early TA.

[0073] An embodiment herein relates to network apparatus, comprising a processor; a transceiver; and a memory. The processor is coupled with the transceiver and the memory and configured to transmit a lower-layer triggered mobility (LTM) candidate configuration to a user equipment (UE). The LTM candidate configuration comprises at least one of a random access configuration for an early timing advance (TA). The processor is configured to receive at least one random access channel (RACH) controller for an LTM candidate cell from the UE based on the LTM candidate configuration. The processor is configured to receive a configuration of the LTM candidate cell specific to the RACH controller with a RACH parameter for synchronizing the early TA.

[0074] The embodiments herein and the various features and advantageous details thereof are explained more fully with reference to the non-limiting embodiments that are illustrated in the accompanying drawings and detailed in the following description. Descriptions of well-known components and processing techniques are omitted so as to not unnecessarily obscure the embodiments herein. The examples used herein are intended merely to facilitate an understanding of ways in which the embodiments herein may be practiced and to further enable those of skill in the art to practice the embodiments herein. Accordingly, the examples should not be construed as limiting the scope of the embodiments herein.

[0075] For the purposes of interpreting this specification, the definitions (as defined herein) will apply and whenever appropriate the terms used in singular will also include the plural and vice versa. It is to be understood that the terminology used herein is for the purposes of describing particular embodiments only and is not intended to be limiting. The terms "comprising", "having" and "including" are to be construed as open-ended terms unless otherwise noted.

[0076] The words / phrases "exemplary", "example", "illustration", "in an instance", "and the like", "and so on", "etc.", "etcetera", "e.g.," , "i.e.," are merely used herein to mean "serving as an example, instance, or illustration." Any embodiment or implementation of the present subject matter described herein using the words / phrases "exemplary", "example", "illustration", "in an instance", "and the like", "and so on", "etc.", "etcetera", "e.g.," , "i.e.," is not necessarily to be construed as preferred or advantageous over other embodiments.

[0077] Embodiments herein may be described and illustrated in terms of blocks which carry out a described function or functions.　These blocks, which may be referred to herein as managers, units, modules, hardware components or the like, are physically implemented by analog and / or digital circuits such as logic gates, integrated circuits, microprocessors, microcontrollers, memory circuits, passive electronic components, active electronic components, optical components, hardwired circuits and the like, and may optionally be driven by a firmware. The circuits may, for example, be embodied in one or more semiconductor chips, or on substrate supports such as printed circuit boards and the like.　The circuits constituting a block may be implemented by dedicated hardware, or by a processor (e.g., one or more programmed microprocessors and associated circuitry), or by a combination of dedicated hardware to perform some functions of the block and a processor to perform other functions of the block.　Each block of the embodiments may be physically separated into two or more interacting and discrete blocks without departing from the scope of the disclosure.　Likewise, the blocks of the embodiments may be physically combined into more complex blocks without departing from the scope of the disclosure.

[0078] It should be noted that elements in the drawings are illustrated for the purposes of this description and ease of understanding and may not have necessarily been drawn to scale. For example, the flowcharts / sequence diagrams illustrate the method in terms of the steps required for understanding of aspects of the embodiments as disclosed herein. Furthermore, in terms of the construction of the device, one or more components of the device may have been represented in the drawings by conventional symbols, and the drawings may show only those specific details that are pertinent to understanding the present embodiments so as not to obscure the drawings with details that will be readily apparent to those of ordinary skill in the art having the benefit of the description herein. Furthermore, in terms of the system, one or more components / modules which comprise the system may have been represented in the drawings by conventional symbols, and the drawings may show only those specific details that are pertinent to understanding the present embodiments so as not to obscure the drawings with details that will be readily apparent to those of ordinary skill in the art having the benefit of the description herein.

[0079] The accompanying drawings are used to help easily understand various technical features and it should be understood that the embodiments presented herein are not limited by the accompanying drawings. As such, the present disclosure should be construed to extend to any modifications, equivalents, and substitutes in addition to those which are particularly set out in the accompanying drawings and the corresponding description. Usage of words such as first, second, third etc., to describe components / elements / steps is for the purposes of this description and should not be construed as sequential ordering / placement / occurrence unless specified otherwise.

[0080] The embodiments herein achieve methods and systems for advance synchronization, wherein the MAC sublayer is operated in NR or any other wireless technology which supports LTM when the UE is configured for early TA Synchronization. Referring now to the drawings, and more particularly to FIG. 6 through 10, where similar reference characters denote corresponding features consistently throughout the figures, there are shown at least one embodiment.

[0081] FIG. 6 shows a block diagram of the wireless communication system, according to embodiments as disclosed herein. In an embodiment herein, the UE (602) comprises a controller (604) and a transceiver (606). The controller (604) communicates with a network apparatus (608) through the transceiver (606). The network apparatus (608) also may comprise a processor (612), memory (614) and a transceiver (610). The wireless network may include, but is not limited to, a plurality of network entities available in a network coverage area of the UE (602).

[0082] FIG. 7 shows a flowchart for a method for performing early timing advance in a wireless communication network, according to embodiments as disclosed herein. At step 702, a user equipment (UE) (602) may receive a lower-layer triggered mobility (LTM) candidate configuration comprising at least one of a random-access configuration for an early timing advance (TA). At step 704, the UE (602) may create at least one random access channel (RACH) controller for an LTM candidate cell. At step 706, the UE (602) may configure the LTM candidate cell specific to the RACH controller with a RACH parameter for the early TA synchronization.

[0083] In an embodiment herein, when a medium access control (MAC) entity in the UE (602) is configured with an LTM candidate cell, the UE (602) may create and maintain one RACH for each LTM candidate cell configured with random access for early TA synchronization. In an embodiment herein, when the MAC entity in the UE (602) is configured with the LTM candidate cells, the UE (602) creates and maintains one RACH Control module for each LTM candidate cell with random access for early TA synchronization. In an embodiment herein, the network apparatus (608) (for e.g., gNB) informs the UE (602) with the RACH parameters for early TA synchronization. The RACH parameters may include one or more New Radio (NR) parameters such as, but not limited to, contention free random access (CFRA). The RACH parameters also may include, but may not be limited to, CFRA parameters such as, but not limited to, prach-ConfigurationIndex, preambleReceivedTargetPower, and powerRampingStep. The RACH parameters also may include NR parameters such as, but not limited to, rach-ConfigGeneric or a subset of parameters in rach-ConfigGeneric such as, but not limited to, msg1-FDM, msg1-frequencyStart, zerorCorrelationZoneConfig, ra-responseWindow, and preambleTransMax.

[0084] In an embodiment herein, prach-ConfigurationIndex is the value Points to Table for prach-ConfigurationIndex in TS38.211. The value Points to table defines which PRACH format to use and when to send PRACH in time domain and number of RACH occasions available. In an embodiment herein, the msg1-FDM is the number of PRACH transmission occasions FDMed in a one-time instance. Up to eight RACH occasions can be used in one-time instance. In an embodiment herein, the msg1-FrequencyStart is the value that refers to the Offset of lowest PRACH transmission occasion in frequency domain with respect to PRB 0. The value is configured so that the corresponding RACH resource is entirely within the bandwidth of the UL BWP. In an embodiment herein, the preambleTransMax is the maximum number of RA preamble transmission performed before declaring a failure, that is the number of times a UE (602) can transmit MSG1 before declaring RACH failure. In an embodiment herein, the powerRampingStep is the power ramping steps for PRACH. The powerRampingStep value indicates the amount of power UE (602) needs to increase for RACH transmissions if the previous RACH attempt failed. In an embodiment herein, the ra-ResponseWindow is the Msg2 (RAR) window length in number of slots. The UE (602) scans for PDCCH looking for msg2 response from the gNB within the ra-ResponseWindow. If the UE did not receive msg2 within the window, the UE may consider RACH failure and start msg1 transmission again. In an embodiment herein, the totalNumberOfRA-Preambles is the total number of RA-Preambles indicating the total number of preambles available per PRACH occasion for both contention based and contention free RACH. This IE has a range of 0-63, If the IE is missing, then all 64 preambles are available. If the IE is present, then there are less than 64 preambles available to the UEs (602). In an embodiment herein, the ra-ContentionResolutionTimer is the initial value for the contention resolution timer. Value sf16 corresponds to 16 subframes, and so on. In an embodiment herein, the msg1-SubcarrierSpacing defines the Subcarrier spacing of PRACH. In an embodiment herein, the ssb-perRACH-OccasionAndCB-PreamblesPerSSB is a twofold: ssb-perRACH-Occasion conveys the information about the number of SSBs mapped per RACH occasion and CB-PreamblesPerSSB indicates the number of Contention Based preambles available per SSB

[0085] In an embodiment herein, the gNB may avoid configuring parameters related to a beam failure recovery, a 2 Step RACH, a MSG3 repetition related parameters, feature combination specific parameters, and synchronization signal block (SSB) selection based on reference signal received power (RSRP) thresholds for LTM candidate cells for the UE (602).

[0086] FIG. 8 depicts an example of a MAC Architecture for RACH control, according to embodiments disclosed herein. When the MAC entity is configured with the LTM candidate cells, the gNB creates and maintains one RACH for each LTM candidate cell with random access for early TA synchronization for each UE (602). In an embodiment herein, when the MAC entity is configured with the LTM candidate cells with the random access for early TA synchronization, the gNB creates and maintains one RACH Control module for each of the LTM candidate cell configured with random access for early TA synchronization for each UE (602).

[0087] In an embodiment herein, if the MAC entity is not configured with any SCell or the LTM candidate cell, there is one RACH (Random Access Control) per MAC entity.

[0088] In an embodiment herein, if the LTM candidate cell is a SCell, the UE (602) creates and maintains a single RACH (Random Access Control) to handle the random access for early TA Synchronization and the random-access operations for the same SCell. Maintaining the single RACH reduces the memory requirements and complexity in maintaining and operating random access in the UE.

[0089] In an embodiment herein, if the LTM candidate cell is a SCell, the UE (602) creates and maintains a separate RACH (Random Access Control) to handle the random access for early TA Synchronization and the random-access operations for the same SCell. Maintaining separate RACH increases the flexibility of random-access operations.

[0090] In an embodiment herein, the RACH control module for the LTM candidate cell maintains the RACH related variables such as, but not limited to, PREAMBLE_RECEIVED_TARGET_POWER, PCMAX PREAMBLE_TRANSMISSION_COUNTER, PREAMBLE_BACKOFF, and PREAMBLE_POWER_RAMPING_COUNTER. The preambleReceivedTargetPower can be used for 5G power control during the initial access process. The PREAMBLE_RECEIVED_TARGET_POWER specifies the target power level for the PRACH. The UE (602) adjusts the transmit power to adjust the preamble received by the base station (gNodeB) above a target power level. The adjustment is essential for the UE (602) to successfully initiate communication while managing power efficiently and minimizing interference. PCMAX PREAMBLE_TRANSMISSION_COUNTER is the counter for maximum power control in preamble transmission.

[0091] In an embodiment herein, when the MAC entity in the UE (602) is configured with LTM candidate cells with random access for early TA synchronization, the RACH (i.e., RACH control module) created for PCell or PSCell controls the random access for LTM candidate cell. In an embodiment herein, the network apparatus (608) (gNB) is configured with LTM candidate cells with random access for early TA synchronization, the RACH (i.e., RACH control module) created for PCell or PSCell controls the random access for LTM candidate cell.

[0092] In an embodiment herein, he RACH control module of Pcell or PSCell may maintain the configuration for each LTM candidate cell separately. Further, the PCell or PSCell RACH control module may maintain the RACH related variables such as, but not limited to, PREAMBLE_RECEIVED_TARGET_POWER, PCMAX PREAMBLE_TRANSMISSION_COUNTER, PREAMBLE_BACKOFF and PREAMBLE_POWER_RAMPING_COUNTER, separately for each LTM candidate cell Maintaining the configuration for each LTM candidate cell separately reduces the inter-module communications, and also reduces the resulting latency.

[0093] In an embodiment herein, a Layer1 entity in the UE (602) or the gNB may be configured with LTM candidate cells with random access for early TA synchronization. The RRC in the UE (602) or the gNB entity may avoid configuring the MAC with LTM candidate cells with random access for early TA synchronization.

[0094] In an embodiment herein, the Layer1 creates and maintains RACH (Random Access Control) to handle the random access for early TA Synchronization. In an embodiment herein, the RACH control module in L1 may maintain configuration for each LTM candidate cell separately.

[0095] Alternatively, a RACH control module may be created for PCell or PSCell in L1. The PCell or PSCell RACH control module in L1 may maintain the RACH related variables such as, but not limited to, PREAMBLE_RECEIVED_TARGET_POWER, PCMAX PREAMBLE_TRANSMISSION_COUNTER, PREAMBLE_BACKOFF and PREAMBLE_POWER_RAMPING_COUNTER separately for each LTM candidate cell.

[0096] In an embodiment herein, some of the above embodiments may be captured in NR TS 38.321 as below.

[0097] The MAC entity of the UE (602) handles the following transport channels:

[0098] - Broadcast Channel (BCH);

[0099] - Downlink Shared Channel(s) (DL-SCH);

[0100] - Paging Channel (PCH);

[0101] - Uplink Shared Channel(s) (UL-SCH); and

[0102] - Random Access Channel(s) (RACH).

[0103] In an embodiment herein, when the UE (602) is configured with a secondary cell group (SCG), two MAC entities are configured to the UE (602): a first MAC entity for a master cell group (MCG) and a second MAC entity for the SCG.

[0104] In an embodiment herein, when the UE (602) is configured with Dual Active Protocol Stack (DAPS) handover, two MAC entities are used by the UE (602); a first MAC entity for the source cell (source MAC entity), and a second MAC entity for the target cell (target MAC entity).

[0105] In an embodiment herein, the functions of the different MAC entities in the UE (602) operate independently unless otherwise specified. The timers and parameters used in each MAC entity are configured independently unless otherwise specified. The Serving Cells, C-RNTI, radio bearers, logical channels, upper- and lower-layer entities, LCGs, and HARQ entities considered by each MAC entity refer to those mapped to the MAC entity unless otherwise specified.

[0106] In an embodiment herein, if the MAC entity is configured with LTM candidate cells, there may be one RACH for each LTM candidate cell. If the MAC entity is configured with one or more SCells, there may be multiple DL-SCHs and there may be multiple UL-SCHs and multiple RACH per MAC entity; one DL-SCH, one UL-SCH, and one RACH on the SpCell, one DL-SCH, zero or one UL-SCH and zero or one RACH for each SCell and LTM candidate cell. If the MAC entity is not configured with any SCell, there is one DL-SCH, and one UL-SCH, per MAC entity. If the MAC entity is not configured with any SCell or LTM candidate cell, there is one RACH per MAC entity.

[0107] In an embodiment herein, the network apparatus (608) includes the preamble transmission counter to the UE (602) in the PDCCH order for early TA synchronization.

[0108] In an embodiment herein, if the random-access preamble transmission is for early TA synchronization, the UE (602) skips incrementing PREAMBLE_TRANSMISSION_COUNTER for random access preamble transmission. If the UE (602) receives a PDCCH order for retransmission of early TA synchronization, the UE (602) transmits the random access for early TA (or attempts to transmit the random access for early TA), irrespective of the number of preamble transmissions already performed of early TA.

[0109] In an embodiment herein, if the UE (602) receives a physical downlink control channel (PDCCH) order for early TA synchronization and the PREAMBLE_TRANSMISSION_COUNTER is greater than the preambleTransMax (for example, when PREAMBLE_TRANSMISSION_COUNTER is preambleTransMax+1 in NR), the UE (602) transmits the RACH preamble for early TA synchronization. The UE (602) ignores the received preambleTransMax value from the network apparatus (608) for early TA synchronization. PreambleTransMax is the maximum number of RA preamble transmissions performed before declaring a failure, i.e., the times a UE (602) can transmit MSG1 before declaring RACH failure.

[0110] In an embodiment herein, if the UE (602) receives a PDCCH order for early TA synchronization and the PREAMBLE_TRANSMISSION_COUNTER is greater than the preambleTransMax (for example, when the PREAMBLE_TRANSMISSION_COUNTER is preambleTransMax+1 in NR), the UE (602) skips transmitting the RACH preamble for the early TA synchronization. The UE (602) ignores the received instruction (i.e. PDCCH order) from the network apparatus (608) for early TA synchronization.

[0111] In an embodiment herein, if RACH preamble for early TA fails to be transmitted due to listen -before -talk (LBT) failure (for e.g., when the MAC receives LBT failure indication from lower layers), the UE (602) increases the power ramping counter (for e.g., PREAMBLE_POWER_RAMPING_COUNTER in NR).

[0112] In an embodiment herein, if the UE (602) receives a PDCCH order for retransmitting the early TA synchronization, the UE (602) retransmits the random-access preamble with ramped up power considering the PREAMBLE_POWER_RAMPING_COUNTER.

[0113] In an embodiment herein, if RACH preamble for the early TA may not be transmitted due to LBT failure (for e.g., when the MAC receives LBT failure indication from lower layers), the UE (602) increases PREAMBLE_TRANSMISSION_COUNTER. In an embodiment herein, if the RACH preamble for the early TA could not be transmitted due to LBT failure, and the PREAMBLE_TRANSMISSION_COUNTER is greater than preambleTransMax, the UE (602) stops transmitting the RACH preambles. The UE (602) may not transmit the random-access preamble for early TA Synchronization even when the UE (602) receives the PDCCH order for retransmitting the early TA synchronization. For example, when the MAC receives LBT failure indication from the lower layers (when PREAMBLE_TRANSMISSION_COUNTER is preambleTransMax+1 in NR), the UE (602) does not transmit the random-access preamble for early TA Synchronization even when the UE (602) receives the PDCCH order for retransmitting the early TA synchronization.

[0114] In an embodiment herein, if the RACH preamble for early TA could not be transmitted due to LBT failure (for example, when the MAC receives LBT failure indication from lower layers), the UE (602) skips increasing the power ramping counter (for example, PREAMBLE_POWER_RAMPING_COUNTER in NR). In an embodiment herein, if the PDCCH order is for retransmitting the early TA synchronization, the UE (602) transmits with the same power as the previous preamble transmission attempt where the LBT failure occurred.

[0115] In an embodiment herein, if the RACH preamble for early TA is not transmitted due to LBT failure, for example, when MAC receives LBT failure indication from lower layers the UE (602) MAC skips increasing the PREAMBLE_TRANSMISSION_COUNTER. In an embodiment herein, the UE (602) MAC may skip increasing the preamble transmission counter even when the LBT failure recovery configuration such as lbt-FailureRecoveryConfig is configured.

[0116] In an alternate embodiment herein, if the RACH preamble for early TA is not transmitted due to LBT failure, for example, when MAC receives LBT failure indication from lower layers, the UE (602) re-transmits the RACH preamble for early TA up on receiving a PDCCH order from the network apparatus (608) gNB irrespective of the number of transmissions and retransmissions performed for early TA.

[0117] In an embodiment herein, during an activated measurement gap, the UE MAC entity avoids performing the random access for early TA synchronization, on the LTM candidate cells in the corresponding frequency range of the measurement gap configured by measGapConfig (as specified in TS 38.331). The UE (602) prioritizes the measurement gap over early TA synchronization for LTM candidate cells. If the measurement gap is deactivated, the UE (602) performs the random access for early TA synchronization.

[0118] In an embodiment herein, during an activated measurement gap, the UE MAC entity performs the random access for early TA synchronization, on the LTM candidate cells in the corresponding frequency range of the measurement gap configured by measurement gap config (as specified in TS 38.331). The UE (602) prioritizes the early TA synchronization for LTM candidate cells over the measurement gap.

[0119] In an embodiment herein, during a MUSIM gap, the UE MAC entity avoids performing the random access for early TA synchronization, on the LTM candidate cells. The UE (602) prioritizes the early TA synchronization for MUSIM gap over the LTM candidate cell.

[0120] FIG. 9 depicts a flowchart showing a method for LTM early synchronization indication for a self-organizing network (SON) and Minimisation of Drive Test (MDT), according to embodiments as disclosed herein. At step 902, the UE (602) may perform the early TA synchronization. At step 904, the UE (602) may receive Timing Advance Information in the LTM Cell switch command from the network apparatus (608). At step 906, the UE (602) which has performed random access for early Timing Advance (TA) synchronization logs and reports to the network apparatus (608) whether the UE (602) has received Timing Advance Information in the LTM Cell switch command from the network apparatus (608). The UE (602) may log that the RACH-less LTM was not successful (not performed) though the UE (602)was configured for RACH-less LTM.

[0121] In an embodiment herein, the UE (602) logs and reports Timing Advance (TA) optimisation information to the network apparatus (608). In an embodiment herein, for a UE (602) which has performed random access for early Timing Advance (TA) synchronization and has received Timing Advance Information for performing random access for early TA synchronization in the LTM Cell switch command, logs and reports to the network apparatus (608) that early TA synchronization is successful as part of the TA optimisation information. In an embodiment herein, a UE (602) which has performed random access for early Timing Advance (TA) synchronization, but has not received Timing Advance Information in the LTM Cell switch command, the UE (602) logs and reports to the network apparatus (608) that early TA synchronization is unsuccessful as part of the TA optimisation information. In an embodiment herein, the timing advance optimisation information also means that UE (602) has fallen back from RACH-less LTM to RACH based LTM. In an embodiment herein, the Timing Advance optimisation information is logged and reported in RA-InformationCommon SEQUENCE in NR. In an embodiment herein, in NR, the Timing Advance information is logged and reported in a radio link failure (RLF) report, a Successful Handover Report (SHR), a Successful PSCell Change or Addition Report (SPR) and RA-Report. In an embodiment herein, the SON module understands whether RACH for early TA synchronization is successful based on the timing advance optimisation information. In an embodiment herein, the timing advance optimisation information is logged when there is early TA synchronization without RA Response.

[0122] In an embodiment herein, the UE (602) performs validation of the received LTM candidate configuration for the candidate cell before performing the early TA Synchronization.

[0123] In an embodiment herein, the network apparatus (608), for example, the gNB, informs the UE (602) of the power ramping step value to be used for early TA Synchronization in LTM candidate configuration.

[0124] FIG. 10 depicts the process of performing early TA synchronization, according to embodiments as disclosed herein. In an embodiment herein, at step 1002, the network apparatus (608) (for example, the gNB) informs the UE (602) about the Contention Free RACH (CFRA) resources for early TA Synchronization within LTM candidate Configuration (rather than the CellGroupConfig which is used for communicating CFRA resources for other scenarios). In an embodiment herein, at step 1004, these CFRA resources are encoded by the network apparatus (608) gNB CU, rather than the network apparatus (608) gNB DU.

[0125] An example of ASN.1 configuration according to 3gpp TS 38.331 is given below.

[0126] The RRC Reconfiguration message is the command to modify an RRC connection. The RRC reconfiguration message may convey information for measurement configuration, mobility control, radio resource configuration (including RBs, MAC main configuration and physical channel configuration) and AS security configuration.

[0127]

[0128]

[0129]

[0130]

[0131]

[0132]

[0133]

[0134] In an embodiment herein, if the network apparatus (608) gNB does not provide power ramping step in RACH configuration for early TA Synchronization, the UE (602) uses the value provided by RACH-Config Generic of the candidate cell (in an example, power ramping step in SIB1 in NR) as the powerRampingStep during power ramping for early TA synchronization.

[0135] In an embodiment herein, if the network apparatus (608) gNB fails to provide power ramping step in RACH configuration for early TA Synchronization, the UE (602) does not perform power ramping during early TA Synchronization, even if the network requests for performing power ramping for early TA synchronization through PDCCH order.

[0136] In an embodiment herein, if the network apparatus (608) gNB provides RACH configuration for early TA Synchronization (ltm-ra in the above example ASN.1 SEQUENCE) including power ramping step in one RRC Reconfiguration message and again provides RACH configuration for early TA Synchronization (ltm-ra in the above example ASN.1 SEQUENCE) excluding power ramping step for the same candidate cell, the UE (602) maintains the received power ramping step from the previous RRC Reconfiguration.

[0137] In an embodiment herein, the network apparatus (608) gNB CU receives the Contention Free RACH (CFRA) resources for early TA Synchronization from the network apparatus (608) gNB DU over F1AP interface and includes the resources in the LTM configuration. In an embodiment herein, the network apparatus (608) gNB CU receives the CFRA resources for early TA Synchronization from the network apparatus (608) gNB DU in an Inter Node RRC message (such as, but not limited to, CG-Config).

[0138] In an embodiment herein, the network apparatus (608) gNB CU receives power ramping for early TA Synchronization from the network apparatus (608) gNB DU over F1AP interface and includes the power ramping step in the LTM configuration. In an embodiment herein, the network apparatus (608) gNB CU receives power ramping for early TA Synchronization from the network apparatus (608) gNB DU in an Inter Node RRC message (such as, but not limited to, CG-Config).

[0139] In an embodiment herein, the UE (602) uses the power ramping step received from the RACH-config generic of the candidate cell for performing the power ramping for early TA Synchronization. In an embodiment herein, the UE (602) performs validation of the received LTM candidate configuration before performing the early TA Synchronization. In an embodiment herein, the UE (602) performs validation of the received LTM candidate configuration before power ramping of early TA Sync.

[0140] In an embodiment herein, the network apparatus (608) gNB CU receives preambleTransMax for early TA Synchronization from the network apparatus (608) gNB DU over F1AP interface and includes the received preambleTransMax in the LTM configuration. Application layer signalling protocol is referred to herein as F1 application protocol (F1AP). The F1AP provides the signalling service between a gNB-CU and a gNB-DU of a gNB within an NG-RAN, or between a gNB-CU and a gNB-DU of an en-gNB within an E-UTRAN. In an embodiment herein, the gNB CU receives preambleTransMax for early TA Synchronization from the gNB DU in Inter Node RRC message (such as, but not limited to, CG-Config).

[0141] In an embodiment herein, the UE (602) uses the preambleTransMax received from the RACH-ConfigGeneric of the candidate cell for performing the early TA Synchronization. In an embodiment herein, the UE (602) performs validation of received LTM candidate configuration for the candidate cell before performing the early TA Synchronization

[0142] In an embodiment herein, if the network apparatus (608) gNB does not provide preambleReceivedTargetPower in RACH configuration for early TA Synchronization, the UE (602) uses the value provided by RACH-ConfigGeneric of the candidate cell (in an example, preambleReceivedTargetPower in SIB1 in NR) as the preambleReceivedTargetPower during early TA synchronization. In an embodiment herein, the UE (602) uses the preambleReceivedTargetPower received from the RACH-ConfigGeneric of the candidate cell for performing the early TA Synchronization. In an embodiment herein, the UE (602) performs validation of received LTM candidate configuration for the candidate cell before performing the early TA Synchronization.

[0143] In an embodiment herein, if the network apparatus (608) gNB provides RACH configuration for early TA Synchronization (ltm-ra in the above example ASN.1 SEQUENCE) including preambleReceivedTargetPower in one RRC Reconfiguration message and again provides RACH configuration for early TA Synchronization (ltm-ra in the above example ASN.1 SEQUENCE) excluding preambleReceivedTargetPower for the same candidate cell, the UE (602) maintains the received power ramping step from the previous RRC Reconfiguration.

[0144] In an embodiment herein, the gNB CU includes RACH-ConfigGeneric in LTM candidate configuration. An example specification extract is given below (based on the previously mentioned RRC structure):

[0145]

[0146] In an embodiment herein, the network apparatus (608) gNB may include a subset of parameters in rach-ConfigGeneric such as msg1-FDM, msg1-frequencyStart, zerorCorrelationZoneConfig, ra-responseWindow, preambleTransMax etc.

[0147] In an embodiment herein, the network apparatus (608) gNB includes CFRA in RACH-CONFIGEARLYSYNC-r18.

[0148]

[0149] In an embodiment herein, if the UE (602) receives RACH-ConfigGeneric in the RACH-CONFIGEARLYSYNC-r18, the UE (602) may ignore the ra-responseWindow and the preambleTransMax. If the UE (602) receives the PDCCH order for retransmitting the random access for early TA, UE (602) retransmits the same irrespective of the value of preamble transmission counter. In an embodiment herein, if the UE (602) receives RACH-ConfigGeneric in the RACH-CONFIGEARLYSYNC-r18, the UE (602) ignores the ra-responseWindow and / or the preambleTransMax unless RAR reception is configured; i.e., if RAR reception is configured, the UE (602) does not ignore the ra-responseWindow and / or the preambleTransMax (on receiving the RACH-ConfigGeneric in the RACH-CONFIGEARLYSYNC-r18). When the RAR reception is configured for early sync, UE uses the preambleTransMax in RACH-ConfigGeneric and increases preamble transmission counter with each preamble transmission for early TA is performed. If the preamble transmission counter is preambleTransMax+1, UE considers that early sync is unsuccessful. The network apparatus (608) may send an information element (such as a flag or an enumerated) to the UE (602) to indicate whether the RAR reception is configured for early TA sync. The UE (602) waits for RA response and increments the preamble counter for early TA sync based on this information element. Alternatively, network apparatus (608) may use separate information elements to configure the RACH configuration for early TA sync with random access response and the early TA sync without random access response. Such distinction methods are needed since the UE (602) ignores the responseWindow even if it is configured for the early TA sync without RA response. In an embodiment, if there is a condition configured for early TA sync (such as the UE (602) performs early TA based on the conditions which are dependent on the measured RSRP or RSRQ of the serving cell or the candidate cells, the UE (603) performs early TA sync with random access response.

[0150] In an embodiment herein, if the network apparatus (608) gNB CU does not include RACH-ConfigGeneric in the LTM candidate configuration, the UE (602) applies the parameters from RACH-ConfigGeneric in the CellGroupConfig.

[0151] In accordance with an embodiment of the disclosure, a method for timing advance (TA) synchronization in a wireless network is provided. The method may comprise: receiving, by a User Equipment (UE) (602), a lower-layer triggered mobility (LTM) configuration from a network apparatus, wherein the LTM configuration comprises at least one of a random access configuration for an early timing advance (TA); creating by the UE (602), at least one random access channel (RACH) controller for an LTM candidate cell based on the LTM configuration; and configuring by the UE (602), the created RACH controller with RACH parameters for the early TA synchronization.

[0152] In an embodiment, the method comprises: maintaining, by the UE (602) through the RACH controller, the RACH specific UE variables for the LTM candidate cells; and wherein the RACH specific UE variables are maintained in a layer2 of the UE (602) to handle the random access for synchronizing the early TA.

[0153] In an embodiment, the method comprises: receiving by the UE (602), a maximum number of preamble transmission and a random access response window in the random access configuration and ignoring the received maximum number of preamble transmissions and the random access response window.

[0154] In an embodiment, the method comprises: receiving, by the UE (602), a physical downlink control channel (PDCCH) order for the early TA synchronization from the network apparatus; and skipping, by the UE (602), incrementing of a preamble transmission counter for random access preamble transmission, if the random access preamble transmission is for early TA synchronization and transmitting by the UE, the random access for early TA, irrespective of number of preamble transmissions already performed of early TA.

[0155] In an embodiment, the received random access configuration comprises of a Contention Free RACH (CFRA) resource configuration and a request for a power ramping for the early TA synchronization, the maximum number of preamble transmission in the random access configuration, and the random access response window; wherein the random access configuration is encoded by the gNB DU and the LTM configuration is encoded by a centralized unit (CU) and included in an RRC configuration message.

[0156] In an embodiment, the method comprises: performing, by the UE (602), a random access (RA) for early TA synchronization; receiving by the UE (602), an LTM command for triggering cell switch; and storing by the UE (602), an indication about TA presence in the LTM cell switch command in an RA information, wherein the RA information is included in at least one of a RA report, a radio link failure (RLF) report, a successful handover report (SHR) and a Successful PSCell Change or Addition Report (SPR).

[0157] In accordance with an embodiment of the disclosure, a user equipment (UE) (602) in a wireless communication system is provided. The UE (602) may comprise: a transceiver (606); and at least one controller (604) coupled with the transceiver (606) and the at least one controller (604) is configured to: receive a lower-layer triggered mobility (LTM) candidate configuration from a network apparatus (608), wherein the LTM candidate configuration comprises at least one of a random access configuration for an early timing advance (TA); create at least one random access channel (RACH) controller for an LTM candidate cell based on the LTM candidate configuration; and configure the LTM candidate cell specific to the created RACH controller with a RACH parameter for synchronizing the early TA.

[0158] In accordance with an embodiment of the disclosure, a network apparatus (608) is provided. The network apparatus (608) may comprise: a processor ; a transceiver ; and a memory (614). The processor is coupled with the transceiver and the memory (614) and the processor is configured to: transmit a lower-layer triggered mobility (LTM) candidate configuration to a user equipment (UE); wherein the LTM candidate configuration comprises at least one of a random access configuration for an early timing advance (TA); receive at least one random access channel (RACH) controller for an LTM candidate cell from the UE based on the LTM candidate configuration; and receive a configuration of the LTM candidate cell specific to the RACH controller with a RACH parameter for synchronizing the early TA.

[0159] In an embodiment, the network apparatus is configured to: receive at least one of a Contention Free RACH (CFRA) resource configuration and a request for a power ramping for synchronizing the early TA from a distributed unit (DU), in a configuration for LTM candidate cell from a CG-config message; and send the Contention Free RACH (CFRA) resource configuration and a request for a power ramping for synchronizing the early TA to a centralized unit (CU) in an RRC config message.

[0160] The embodiments disclosed herein can be implemented through at least one software program running on at least one hardware device and performing network management functions to control the elements. The elements can be at least one of a hardware device, or a combination of hardware device and software module.

[0161] In accordance with an embodiment of the disclosure, a method performed by a terminal in a wireless communication system is provided. The method may comprise: receiving, from a base station, a radio resource control (RRC) message including low layer triggered mobility (LTM) candidate configuration information, wherein the LTM candidate configuration information includes random access (RA) configuration information for an early timing advance (TA) acquisition; and performing an RA for the early TA acquisition on a LTM candidate cell, based on the RA configuration information for the early TA acquisition, wherein in case that the RA configuration information for the early TA acquisition includes RA channel (RACH) configuration generic information, a first parameter indicating a maximum number of RA preamble transmissions and a second parameter indicating a window length of an RA response (RAR) are ignored, the first parameter and the second parameter being included in the RACH configuration generic information.

[0162] In an embodiment, the RA configuration information for the early TA acquisition is related to information transmitted from 5G node B-distributed unit (gNB-DU) to gNB-central unit (CU).

[0163] In an embodiment, in case that a medium access control (MAC) entity of the terminal is configured with a first LTM candidate cell and a second LTM candidate cell, the terminal is configured with a first RACH for the first LTM candidate cell and a second RACH for the second LTM candidate cell.

[0164] In an embodiment, the method may further comprise: receiving, from the base station, a physical downlink control channel (PDCCH) order related to triggering the RA for the early TA acquisition.

[0165] In an embodiment, the performing of the RA for the early TA acquisition may comprise: transmitting, to the base station, a random access preamble.

[0166] In an embodiment, the RA for the early TA acquisition is related to a contention free random access (CFRA).

[0167] In an embodiment, the RA for the early TA acquisition is performed before receiving a cell switch command.

[0168] In accordance with an embodiment of the disclosure, a method performed by a base station in a wireless communication system is provided. The method may comprise: transmitting, to a terminal, a radio resource control (RRC) message including low layer triggered mobility (LTM) candidate configuration information, wherein the LTM candidate configuration information includes random access (RA) configuration information for an early uplink (UL) synchronization, wherein based on the RA configuration information for the early TA acquisition, an RA for the early TA acquisition is performed on a LTM candidate cell, and wherein in case that the RA configuration information for the early TA acquisition includes RA channel (RACH) configuration generic information, a first parameter indicating a maximum number of RA preamble transmissions and a second parameter indicating a window length of an RA response (RAR) are ignored, the first parameter and the second parameter being included in the RACH configuration generic information.

[0169] In an embodiment, the RA configuration information for the early TA acquisition is related to information transmitted from 5G node B-distributed unit (gNB-DU) to gNB-central unit (CU).

[0170] In an embodiment, in case that a medium access control (MAC) entity of the terminal is configured with a first LTM candidate cell and a second LTM candidate cell, the terminal is configured with a first RACH for the first LTM candidate cell and a second RACH for the second LTM candidate cell.

[0171] In an embodiment, the method may further comprise: transmitting, to the terminal, a physical downlink control channel (PDCCH) order related to triggering the RA for the early TA acquisition.

[0172] In an embodiment, the method may further comprise: receiving, from the terminal, a random access preamble.

[0173] In an embodiment, the RA for the early TA acquisition is related to a contention free random access (CFRA).

[0174] In accordance with an embodiment of the disclosure, a terminal in a wireless communication system is provided. The terminal may comprise: a transceiver; and at least one processor coupled with the transceiver and configured to: receive, from a base station via the transceiver, a radio resource control (RRC) message including low layer triggered mobility (LTM) candidate configuration information, wherein the LTM candidate configuration information includes random access (RA) configuration information for an early timing advance (TA) acquisition; and perform, via the transceiver, an RA for the early TA acquisition on a LTM candidate cell, based on the RA configuration information for the early TA acquisition, wherein in case that the RA configuration information for the early TA acquisition includes RA channel (RACH) configuration generic information, a first parameter indicating a maximum number of RA preamble transmissions and a second parameter indicating a window length of an RA response (RAR) are ignored, the first parameter and the second parameter being included in the RACH configuration generic information.

[0175] In accordance with an embodiment of the disclosure, a base station in a wireless communication system is provided. The base station may comprise: a transceiver; and at least one processor coupled with the transceiver and configured to: transmit, to a terminal via the transceiver, a radio resource control (RRC) message including low layer triggered mobility (LTM) candidate configuration information, wherein the LTM candidate configuration information includes random access (RA) configuration information for an early uplink (UL) synchronization, wherein based on the RA configuration information for the early TA acquisition, an RA for the early TA acquisition is performed on a LTM candidate cell, and wherein in case that the RA configuration information for the early TA acquisition includes RA channel (RACH) configuration generic information, a first parameter indicating a maximum number of RA preamble transmissions and a second parameter indicating a window length of an RA response (RAR) are ignored, the first parameter and the second parameter being included in the RACH configuration generic information.

[0176] Fig. 11 is a diagram illustrating a UE 1100 according to an embodiment of the present disclosure.

[0177] Referring to the Fig. 11, the UE 1100 may include a processor 1110, a transceiver 1120, and a memory 1130. However, all of the illustrated components are not essential. The UE 1100 may be implemented by more or less components than those illustrated in the Fig. 11. In addition, the processor 1110, and the transceiver 1120, and the memory 1130 may be implemented as a single chip according to another embodiment.

[0178] The aforementioned components will now be described in detail.

[0179] The processor 1110 may include one or more processors or other processing devices that control the proposed function, process, and / or method. Operation of the UE 1100 may be implemented by the processor 1110.

[0180] The transceiver 1120 may be connected to the processor 1110 and transmit and / or receive a signal. In addition, the transceiver 1120 may receive the signal through a wireless channel and output the signal to the processor 1110. The transceiver 1120 may transmit the signal output from the processor 1110 through the wireless channel.

[0181] The memory 1130 may store the control information or the data included in a signal obtained by the UE 1100. The memory 1130 may be connected to the processor 1110 and store at least one instruction, or a protocol, or a parameter for the proposed function, process, and / or method. The memory 1130 may include read-only memory (ROM) and / or random access memory (RAM) and / or hard disk and / or CD-ROM and / or DVD and / or other storage devices.

[0182] Fig. 12 is a diagram illustrating a base station 1200 according to an embodiment of the present disclosure.

[0183] Referring to the Fig. 12, the base station 1200 may include a processor 1210, a transceiver 1220 and a memory 1230. However, all of the illustrated components are not essential. The base station 1200 may be implemented by more or less components than those illustrated in Fig. 12. In addition, the processor 1210, and the transceiver 1220, and the memory 1230 may be implemented as a single chip according to another embodiment. The aforementioned components will now be described in detail.

[0184] The processor 1210 may include one or more processors or other processing devices that control the proposed function, process, and / or method. Operation of the base station 1200 may be implemented by the processor 1210.

[0185] The transceiver 1220 may be connected to the processor 1210 and transmit and / or receive a signal. The signal may include control information and data. In addition, the transceiver 1220 may receive the signal through a wireless channel and output the signal to the processor 1210. The transceiver 1220 may transmit a signal output from the processor 1210 through the wireless channel.

[0186] The memory 1230 may store the control information or the data included in a signal obtained by the base station 1200. The memory 1230 may be connected to the processor 1210 and store at least one instruction or a protocol or a parameter for the proposed function, process, and / or method. The memory 1230 may include read-only memory (ROM) and / or random access memory (RAM) and / or hard disk and / or CD-ROM and / or DVD and / or other storage devices.

[0187] Methods according to the claims of the disclosure or the various embodiments of the disclosure described in the specification may be implemented in hardware, software, or a combination of hardware and software.

[0188] When implemented in software, a computer-readable storage medium storing one or more programs (software modules) may be provided. One or more programs stored in the computer-readable storage medium are configured for execution by one or more processors in an electronic device. The one or more programs may include instructions that cause the electronic device to perform the methods in accordance with the claims of the disclosure or the various embodiments of the disclosure described in the specification.

[0189] The programs (software modules, software) may be stored in a random access memory (RAM), a non-volatile memory including a flash memory, a read only memory (ROM), an electrically erasable programmable ROM (EEPROM), a magnetic disc storage device, a compact disc-ROM (CD-ROM), a digital versatile disc (DVD) or other types of optical storage device, and / or a magnetic cassette. Alternatively, the programs may be stored in a memory including a combination of some or all of them. There may be a plurality of memories.

[0190] The program may also be stored in an attachable storage device that may be accessed over a communication network including the Internet, an intranet, a Local Area Network (LAN), a wide area network (WAN), or a storage area network (SAN), or a combination thereof. The storage device may be connected to an apparatus performing the various embodiments of the disclosure through an external port. In addition, a separate storage device in the communication network may be connected to the apparatus performing the various embodiments of the disclosure.

[0191] In the various embodiments of the present disclosure, a component is represented in a singular or plural form. It should be understood, however, that the singular or plural representations are selected appropriately according to the situations presented for convenience of explanation, and the disclosure is not limited to the singular or plural form of the component. Further, the component expressed in the plural form may also imply the singular form, and vice versa.

[0192] While the disclosure has been shown and described with reference to various embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the disclosure as defined by the appended claims and their equivalents.

[0193] The embodiments disclosed herein can be implemented through at least one software program running on at least one hardware device and performing network management functions to control the network elements. The network elements shown in FIG. 6 include blocks which can be at least one of a hardware device, or a combination of hardware device and software module.

[0194] The embodiment disclosed herein describes systems and methods for managing mobility in a wireless network. Therefore, it is understood that the scope of the protection is extended to such a program and in addition to a computer readable means having a message therein, such computer readable storage means contain program code means for implementation of one or more steps of the method, when the program runs on a server or mobile device or any suitable programmable device. The method is implemented in at least one embodiment through or together with a software program written in e.g., Very high-speed integrated circuit Hardware Description Language (VHDL) another programming language, or implemented by one or more VHDL or several software modules being executed on at least one hardware device. The hardware device can be any kind of portable device that can be programmed. The device may also include means which could be e.g., hardware means like e.g., an ASIC, or a combination of hardware and software means, e.g., an ASIC and an FPGA, or at least one microprocessor and at least one memory with software modules located therein. The method embodiments described herein could be implemented partly in hardware and partly in software. Alternatively, the invention may be implemented on different hardware devices, e.g., using a plurality of CPUs.

[0195] The foregoing description of the specific embodiments will so fully reveal the general nature of the embodiments herein that others can, by applying current knowledge, readily modify and / or adapt for various applications such specific embodiments without departing from the generic concept, and, therefore, such adaptations and modifications should and are intended to be comprehended within the meaning and range of equivalents of the disclosed embodiments. It is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation. Therefore, while the embodiments herein have been described in terms of embodiments and examples, those skilled in the art will recognize that the embodiments and examples disclosed herein can be practiced with modification within the scope of the embodiments as described herein.

Claims

1.A method performed by a terminal in a wireless communication system, the method comprising:receiving, from a base station, a radio resource control (RRC) message including low layer triggered mobility (LTM) candidate configuration information, wherein the LTM candidate configuration information includes random access (RA) configuration information for an early timing advance (TA) acquisition; andperforming an RA for the early TA acquisition on a LTM candidate cell, based on the RA configuration information for the early TA acquisition,wherein in case that the RA configuration information for the early TA acquisition includes RA channel (RACH) configuration generic information, a first parameter indicating a maximum number of RA preamble transmissions and a second parameter indicating a window length of an RA response (RAR) are ignored, the first parameter and the second parameter being included in the RACH configuration generic information.2.The method of claim 1, wherein the RA configuration information for the early TA acquisition is related to information transmitted from 5G node B-distributed unit (gNB-DU) to gNB-central unit (CU).3.The method of claim 1, wherein in case that a medium access control (MAC) entity of the terminal is configured with a first LTM candidate cell and a second LTM candidate cell, the terminal is configured with a first RACH for the first LTM candidate cell and a second RACH for the second LTM candidate cell.4.The method of claim 1, further comprising:receiving, from the base station, a physical downlink control channel (PDCCH) order related to triggering the RA for the early TA acquisition.5.The method of claim 1, wherein the performing of the RA for the early TA acquisition comprises:transmitting, to the base station, a random access preamble.6.The method of claim 1, wherein the RA for the early TA acquisition is related to a contention free random access (CFRA).7.The method of claim 1, wherein the RA for the early TA acquisition is performed before receiving a cell switch command.8.A method performed by a base station in a wireless communication system, the method comprising:transmitting, to a terminal, a radio resource control (RRC) message including low layer triggered mobility (LTM) candidate configuration information, wherein the LTM candidate configuration information includes random access (RA) configuration information for an early uplink (UL) synchronization,wherein based on the RA configuration information for the early TA acquisition, an RA for the early TA acquisition is performed on a LTM candidate cell, andwherein in case that the RA configuration information for the early TA acquisition includes RA channel (RACH) configuration generic information, a first parameter indicating a maximum number of RA preamble transmissions and a second parameter indicating a window length of an RA response (RAR) are ignored, the first parameter and the second parameter being included in the RACH configuration generic information.9.The method of claim 8, wherein the RA configuration information for the early TA acquisition is related to information transmitted from 5G node B-distributed unit (gNB-DU) to gNB-central unit (CU).10.The method of claim 8, wherein in case that a medium access control (MAC) entity of the terminal is configured with a first LTM candidate cell and a second LTM candidate cell, the terminal is configured with a first RACH for the first LTM candidate cell and a second RACH for the second LTM candidate cell.11.The method of claim 8, further comprising:transmitting, to the terminal, a physical downlink control channel (PDCCH) order related to triggering the RA for the early TA acquisition.12.The method of claim 8, further comprising:receiving, from the terminal, a random access preamble.13.The method of claim 8, wherein the RA for the early TA acquisition is related to a contention free random access (CFRA).14.A terminal in a wireless communication system, the terminal comprising:a transceiver; andat least one processor coupled with the transceiver and configured to:receive, from a base station via the transceiver, a radio resource control (RRC) message including low layer triggered mobility (LTM) candidate configuration information, wherein the LTM candidate configuration information includes random access (RA) configuration information for an early timing advance (TA) acquisition; andperform, via the transceiver, an RA for the early TA acquisition on a LTM candidate cell, based on the RA configuration information for the early TA acquisition,wherein in case that the RA configuration information for the early TA acquisition includes RA channel (RACH) configuration generic information, a first parameter indicating a maximum number of RA preamble transmissions and a second parameter indicating a window length of an RA response (RAR) are ignored, the first parameter and the second parameter being included in the RACH configuration generic information.15.A base station in a wireless communication system, the base station comprising:a transceiver; andat least one processor coupled with the transceiver and configured to:transmit, to a terminal via the transceiver, a radio resource control (RRC) message including low layer triggered mobility (LTM) candidate configuration information, wherein the LTM candidate configuration information includes random access (RA) configuration information for an early uplink (UL) synchronization,wherein based on the RA configuration information for the early TA acquisition, an RA for the early TA acquisition is performed on a LTM candidate cell, andwherein in case that the RA configuration information for the early TA acquisition includes RA channel (RACH) configuration generic information, a first parameter indicating a maximum number of RA preamble transmissions and a second parameter indicating a window length of an RA response (RAR) are ignored, the first parameter and the second parameter being included in the RACH configuration generic information.

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