Method and device for enhanced early ta information transmission in wireless communication system

Abstract

The present disclosure relates to a 5G or 6G communication system for supporting a data transmission rate higher than that of a 4G communication system such as LTE. The disclosure relates to a method performed by a terminal in a wireless communication system, and a device for performing same, the method comprising the steps of: receiving a physical downlink control channel (PDCCH) order from a source distributed unit (DU) entity; transmitting a physical random access channel (PRACH) to a candidate DU entity; receiving, from the candidate DU entity, a first message including timing advance (TA) information for L1 / L2 triggered mobility (LTM); and transmitting, to the source DU entity, a second message including information about whether the TA information acquisition is successful.

Description

Method and apparatus for enhanced early TA information transmission in a wireless communication system

[0001] The present disclosure relates to the operation of a terminal and a base station in a wireless communication or mobile communication system. Specifically, it relates to a method and apparatus for a candidate gNB-DU (ground node B-distributed unit) to transmit a pre-acquired TA (timing advance) value to a terminal.

[0002] Looking back at the evolution of wireless communication through successive generations, technologies have been developed primarily for human-oriented services, such as voice, multimedia, and data. Following the commercialization of 5G (5th-generation) communication systems, connected devices, which have been increasing explosively, are expected to be connected to communication networks. Examples of networked objects include vehicles, robots, drones, home appliances, displays, smart sensors installed in various infrastructures, construction machinery, and factory equipment. Mobile devices are expected to evolve into various form factors, such as augmented reality glasses, virtual reality headsets, and holographic devices. In the 6G (6th-generation) era, efforts are underway to develop improved 6G communication systems to connect hundreds of billions of devices and objects to provide diverse services. For this reason, 6G communication systems are referred to as "Beyond 5G" systems.

[0003] In the 6G communication system predicted to be realized around 2030, the maximum transmission speed is tera (i.e., 1,000 gigabit) bps, and the wireless latency is 100 microseconds (μsec). In other words, compared to the 5G communication system, the transmission speed in the 6G communication system is 50 times faster, and the wireless latency is reduced to one-tenth.

[0004] To achieve such high data transmission speeds and ultra-low latency, 6G communication systems are being considered for implementation in the terahertz band (e.g., the 95 GHz to 3 terahertz (3 THz) band). In the terahertz band, due to more severe path loss and atmospheric absorption compared to the millimeter wave (mmWave) band introduced in 5G, the importance of technology capable of guaranteeing signal reach, or coverage, is expected to increase. As key technologies to ensure coverage, radio frequency (RF) devices, antennas, new waveforms that offer better coverage than orthogonal frequency division multiplexing (OFDM), beamforming, and multi-antenna transmission technologies such as massive multiple-input and multiple-output (MIMO), full-dimensional MIMO (FD-MIMO), array antennas, and large-scale antennas must be developed. In addition, new technologies such as metamaterial-based lenses and antennas, high-dimensional spatial multiplexing technology using orbital angular momentum (OAM), and reconfigurable intelligent surface (RIS) are being discussed to improve coverage of terahertz band signals.

[0005] In addition, to improve frequency efficiency and system network, development is underway in 6G communication systems for full duplex technology, in which uplink and downlink simultaneously utilize the same frequency resources at the same time; network technology that integrates satellites and HAPS (high-altitude platform stations); network structure innovation technology that supports mobile base stations and enables network operation optimization and automation; dynamic spectrum sharing technology through collision avoidance based on spectrum usage prediction; AI-based communication technology that utilizes AI (artificial intelligence) from the design stage and internalizes end-to-end AI support functions to realize system optimization; and next-generation distributed computing technology that realizes services of complexity exceeding the limits of terminal computing capabilities by utilizing ultra-high performance communication and computing resources (mobile edge computing (MEC), cloud, etc.). In addition, attempts are continuing to further strengthen connectivity between devices, further optimize networks, promote the softwareization of network entities, and increase the openness of wireless communication through the design of new protocols to be used in 6G communication systems, the implementation of hardware-based security environments, the development of mechanisms for the safe utilization of data, and the development of technologies regarding privacy maintenance methods.

[0006] Due to the research and development of such 6G communication systems, it is expected that a new dimension of hyper-connected experience will become possible through the hyper-connectivity of 6G communication systems, which encompasses not only connections between objects but also connections between people and objects. Specifically, it is projected that 6G communication systems will enable the provision of services such as truly immersive extended reality (XR), high-fidelity mobile holograms, and digital replicas. Furthermore, services such as remote surgery, industrial automation, and emergency response, which are provided through 6G communication systems with enhanced security and reliability, will be applied in various fields including industry, healthcare, automotive, and home appliances.

[0007] The purpose of the present disclosure is to provide a method and apparatus for reducing signaling overhead and improving communication efficiency by providing a method for efficiently transmitting a TA value to a terminal where an LTM is set.

[0008] To solve the above problems, a method of a terminal in a wireless communication system is provided by the present disclosure. The method of the terminal is characterized by comprising the steps of: receiving a PDCCH (physical downlink control channel) order from a source DU (distributed unit) entity; transmitting a PRACH (physical random access channel) to a candidate DU entity; receiving a first message containing TA (timing advance) information for LTM (L1 / L2 triggered mobility) from the candidate DU entity; and transmitting a second message to the source DU entity containing information on whether the acquisition of the TA information was successful.

[0009] To solve the above problems, a terminal in a wireless communication system is provided according to the present disclosure. The terminal is characterized by comprising: a transceiver; and a control unit that receives a PDCCH order from a source DU (distributed unit) entity, transmits a PRACH (physical random access channel) to a candidate DU entity, receives a first message containing TA (timing advance) information for LTM (L1 / L2 triggered mobility) from the candidate DU entity, and transmits a second message containing information on whether the acquisition of the TA information was successful from the source DU entity.

[0010] To solve the above problems, the present disclosure provides a method performed by a source DU (distributed unit) entity in a wireless communication system. The method of the source DU entity comprises the steps of: transmitting an RRC (radio resource control) message containing LTM (L1 / L2 triggered mobility) related configuration information to a terminal; transmitting a PDCCH (physical downlink control channel) order to the terminal; and receiving a second message from the terminal, wherein the second message includes information regarding whether the terminal has successfully received TA (timing advance) information for LTM from the candidate DU entity in response to a PRACH (physical random access channel) transmitted by the terminal to the candidate DU entity based on the PDCCH order.

[0011] In addition, to solve the above-mentioned problem, a source DU (distributed unit) entity is provided in a wireless communication system according to the present disclosure. The source DU entity comprises: a transceiver; a radio resource control (RRC) message containing LTM (L1 / L2 triggered mobility) related configuration information to a terminal and a physical downlink control channel (PDCCH) order to the terminal; and a control unit that controls the reception of a second message from the terminal, wherein the second message is characterized by including information regarding whether the terminal has successfully received TA (timing advance) information for LTM from the candidate DU entity in response to a PRACH (physical random access channel) transmitted by the terminal to the candidate DU entity based on the PDCCH order.

[0012] The various embodiments of the present disclosure described above are merely some of the preferred embodiments of the present disclosure, and various embodiments reflecting the technical features of the various embodiments of the present disclosure can be derived and understood by those skilled in the art based on the detailed description to be described below.

[0013] According to the present disclosure, when an LTM is set for a terminal, the random access channel (RACH) process is skipped during the cell switch process, thereby minimizing the handover interruption / stalling / delay.

[0014] In addition, according to the present disclosure, congestion that may occur during the transfer of TA information between candidate DU and CU (centralized unit) and / or source DU can be resolved, and limited preamble resources can be efficiently allocated.

[0015] The effects obtainable from the present disclosure are not limited to those mentioned above, and other unmentioned effects will be clearly understood by those skilled in the art to which the present disclosure belongs from the description below.

[0016] Figure 1 is a diagram illustrating the basic structure of the time-frequency domain, which is a wireless resource domain where data or control channels are transmitted in a 5G system.

[0017] FIG. 2 is a drawing illustrating a frame, subframe, and slot structure in a wireless communication system according to one embodiment of the present disclosure.

[0018] FIG. 3 is a drawing illustrating an example of a bandwidth portion setting in a wireless communication system according to an embodiment of the present disclosure.

[0019] Figure 4 is a diagram illustrating an example of a control resource set (CORESET) in which a downlink control channel is transmitted in a 5G wireless communication system.

[0020] Figure 5 is a diagram showing an example of a basic unit of time and frequency resources that constitute a downlink control channel that can be used in 5G.

[0021] Figure 6 is a diagram illustrating the interrupt time or delay time of a handover process that may generally occur.

[0022] Figure 7 is a diagram showing the procedure for L3 (layer 3) handover.

[0023] Figure 8 is a diagram showing the procedure of the LTM proposed to reduce interruption time.

[0024] Figure 9 is a diagram illustrating the early TA acquisition procedure for early synchronization in the LTM procedure.

[0025] FIG. 10 is a diagram specifically illustrating a method for performing an early TA acquisition operation proposed in the present disclosure.

[0026] FIG. 11a is a diagram illustrating an example of a resource grid for downlink transmission.

[0027] FIG. 11b is a diagram illustrating an example of a downlink resource grid for transmitting TA information proposed in the present disclosure.

[0028] FIG. 12 is a diagram illustrating different types of CORESET areas for a terminal to monitor a PDCCH transmitted from a candidate DU.

[0029] FIG. 13 is a diagram illustrating an example of the structure or hierarchy of an RRC message when a source DU transmits configuration information related to a control channel area for a candidate DU that is configured for the terminal before connecting to the candidate DU via an RRC message to the terminal.

[0030] FIG. 14a is a diagram illustrating the F1AP procedure for determining configuration information related to CORESET for a candidate DU to transmit TA information to a terminal.

[0031] FIG. 14b is a diagram illustrating the F1AP procedure for determining configuration information related to CORESET for a candidate DU to transmit TA information to a terminal.

[0032] FIG. 15 is a diagram illustrating an example of the format of the MAC payload proposed in the present disclosure when a candidate DU transmits TA information to a terminal including it in the MAC payload.

[0033] FIG. 16 is a diagram illustrating a method for allocating a PDSCH resource area for transmitting TA information proposed in the present disclosure through a MAC payload.

[0034] FIG. 17 is a diagram illustrating information that may be included when a terminal transmits a message containing information about the success or failure of obtaining TA information in the form of MAC CE.

[0035] FIG. 18 is a diagram illustrating the structure or hierarchy of an RRC message for transmitting uplink grant-related configuration information proposed in the present disclosure.

[0036] FIG. 19 is a diagram schematically illustrating the TA information transmission method proposed in the present disclosure.

[0037] FIG. 20 is a diagram briefly illustrating a flowchart of a method for a terminal to perform an early TA acquisition operation proposed in the present disclosure.

[0038] FIG. 21 is a diagram illustrating, in its entirety, a flowchart of a method for a terminal to perform an early TA acquisition operation proposed in the present disclosure.

[0039] FIG. 22 is a drawing illustrating the structure of a terminal according to one embodiment of the present disclosure.

[0040] FIG. 23 is a drawing illustrating the structure of a base station according to one embodiment of the present disclosure.

[0041] Embodiments of the present disclosure will be described in detail below with reference to the attached drawings.

[0042] In describing the embodiments, descriptions of technical details that are well known in the technical field to which this disclosure belongs and are not directly related to this disclosure are omitted.

[0043] This is intended to convey the gist of the present disclosure more clearly without obscuring it by omitting unnecessary explanations.

[0044] For the same reason, some components in the attached drawings have been exaggerated, omitted, or schematically depicted. Additionally, the dimensions of each component do not entirely reflect their actual dimensions. Identical or corresponding components in each drawing have been assigned the same reference number.

[0045] The advantages and features of the present disclosure and the methods for achieving them will become clear by referring to the embodiments described below in detail together with the accompanying drawings.

[0046] However, the present disclosure is not limited to the embodiments disclosed below but may be implemented in various different forms. These embodiments are provided merely to complete the configuration of the present disclosure and to fully inform those skilled in the art of the scope of the disclosure, and the present disclosure is defined only by the scope of the claims. Throughout the specification, like reference numerals refer to like components.

[0047] At this time, it will be understood that each block of the process flow diagrams and combinations of the flow diagrams can be executed by computer program instructions. Since these computer program instructions can be loaded into the processor of a general-purpose computer, a special-purpose computer, or other programmable data processing equipment, the instructions executed through the processor of the computer or other programmable data processing equipment create means to perform the functions described in the flow diagram block(s). Since these computer program instructions can also be stored in computer-available or computer-readable memory oriented toward the computer or other programmable data processing equipment to be implemented in a specific manner, the instructions stored in such computer-available or computer-readable memory can also produce a manufactured item containing means of instruction to perform the functions described in the flow diagram block(s). Since computer program instructions can be loaded onto a computer or other programmable data processing equipment, instructions that perform a series of operation steps on the computer or other programmable data processing equipment to create a process executed by the computer can also provide steps for executing the functions described in the flowchart block(s).

[0048] Additionally, each block may represent a module, segment, or part of code containing one or more executable instructions for executing a specified logical function(s). It should also be noted that in some alternative execution examples, the functions mentioned in the blocks may occur out of order. For instance, two blocks described in succession may actually be executed substantially simultaneously, or the blocks may be executed in reverse order according to their corresponding functions.

[0049] In this embodiment, the term "part" refers to a software or hardware component such as a field programmable gate array (FPGA) or an application-specific integrated circuit (ASIC), and the "part" performs certain roles. However, the meaning of "part" is not limited to software or hardware. The "part" may be configured to reside in an addressable storage medium and may be configured to run one or more processors. Accordingly, as an example, the "part" includes components such as software components, object-oriented software components, class components, and task components, as well as processes, functions, attributes, procedures, subroutines, segments of program code, drivers, firmware, microcode, circuits, data, databases, data structures, tables, arrays, and variables. The functions provided within the components and "parts" may be combined into a smaller number of components and "parts" or further separated into additional components and "parts." In addition, the components and '~parts' may be implemented to play one or more CPUs (central processing units) within the device or secure multimedia card.

[0050] For the convenience of the following description, some terms and names defined in 3GPP (3rd generation partnership project) standards (specifications for 5G, NR, LTE, or similar systems) may be used. Additionally, terms and names newly defined in next-generation communication systems to which this disclosure applies (e.g., 6G, Beyond 5G systems) or used in existing communication systems may be used. The use of such terms is not limited to the terms and names of this disclosure and may be applied equally to systems conforming to other standards, and may be modified in other forms within the scope of the technical spirit of this disclosure. Embodiments of this disclosure can be easily modified and applied to other communication systems.

[0051] Additionally, it will be understood that singular expressions such as “one” and “the above” in one embodiment of the present disclosure, unless otherwise explicitly indicated, include plural expressions.

[0052] Additionally, in one embodiment of the present disclosure, terms including ordinal numbers, such as first, second, etc., may be used to describe various components, but said components are not limited by said terms. Such terms are used solely for the purpose of distinguishing one component from another. For example, without departing from the scope of the present disclosure, the first component may be named the second component, and similarly, the second component may be named the first component.

[0053] Additionally, in one embodiment of the present disclosure, the term “and / or” includes a combination of a plurality of related described items or any of a plurality of related described items.

[0054] Furthermore, the terms used in the embodiments of the present disclosure are used merely to describe specific embodiments and are not intended to limit the present disclosure. The singular expression includes the plural expression unless the context clearly indicates otherwise. In this specification, terms such as “comprising” or “having” are intended to indicate the existence of the features, numbers, steps, actions, components, parts, or combinations thereof described in the specification, and should be understood as not precluding the existence or addition of one or more other features, numbers, steps, actions, components, parts, or combinations thereof.

[0055] Additionally, the terms “associated with” and “associated therewith” and their derivatives used in one embodiment of the present disclosure may mean things such as include, be included within, interconnect with, contain, be contained within, connect to or with, couple to or with, be communicated with, cooperate with, interleave, juxtapose, be proximate to, be bound to or with, have, have a property of, etc.

[0056] Additionally, in this disclosure, expressions such as "greater than" or "less than" have been used to determine whether specific conditions are satisfied or fulfilled; however, this is merely for illustrative purposes and does not exclude descriptions of "greater than" or "less than." Conditions described as "greater than" may be replaced with "greater than," conditions described as "less than" with "less than," and conditions described as "greater than and less than" with "greater than and less than."

[0057] Additionally, in this disclosure, embodiments are described using terms used in some communication standards (e.g., LTE (long term evolution), NR (new radio) as defined by 3GPP (3rd generation partnership project)), but this is merely for illustrative purposes. The embodiments of this disclosure can be easily modified and applied to other communication systems.

[0058] Prior to a detailed description of the present disclosure, examples of possible meanings for some terms used in this specification are provided. However, it should be noted that the interpretations provided below are not limited to these examples.

[0059] In the present disclosure, a terminal (or communication terminal) is a subject that communicates with a base station or another terminal, and may be referred to as a node, UE (user equipment), NG UE (next generation UE), MS (mobile station), device, or terminal. Additionally, the terminal may include at least one of a smartphone, tablet PC, mobile phone, video phone, e-book reader, desktop PC, laptop PC, netbook computer, PDA, PMP (portable multimedia player), MP3 player, medical device, camera, or wearable device. Additionally, the terminal may include at least one of a television, DVD (digital video disk) player, audio, refrigerator, air conditioner, vacuum cleaner, oven, microwave, washing machine, air purifier, set-top box, home automation control panel, security control panel, media box, game console, electronic dictionary, electronic key, camcorder, or electronic photo frame.In addition, the terminal may include at least one of various medical devices (e.g., various portable medical measuring devices (blood glucose meter, heart rate monitor, blood pressure monitor, or body temperature monitor, etc.), MRA (magnetic resonance angiography), MRI (magnetic resonance imaging), CT (computed tomography), imaging device, or ultrasound device, etc.), navigation device, satellite navigation system (GNSS (global navigation satellite system)), EDR (event data recorder), FDR (flight data recorder), automotive infotainment device, marine electronic equipment (e.g., marine navigation device, gyrocompass, etc.), avionics, security device, vehicle head unit, industrial or household robot, drone, ATM of a financial institution, POS (point of sales) of a store, or Internet of Things device (e.g., light bulb, various sensor, sprinkler device, fire alarm, thermostat, street light, toaster, exercise equipment, hot water tank, heater, boiler, etc.). In addition, the terminal may include various types of multimedia systems capable of performing communication functions. Meanwhile, the present disclosure is not limited to what has been described above, and the terminal may be referred to by terms having the same or similar meaning.

[0060] In addition, in the present disclosure, the base station is an entity that communicates with a terminal and performs resource allocation for the terminal, and may take various forms and may be referred to as a BS (base station), NodeB (NB), NG RAN (next generation radio access network), AP (access point), TRP (transmission reception point), radio access unit, base station controller, or node on a network. Alternatively, depending on the separation of functions, it may be referred to as a CU (centralized unit) or a DU (distributed unit). Meanwhile, the present disclosure is not limited thereto, and the base station may be referred to by a term having the same or similar meaning.

[0061] Additionally, in this disclosure, a radio resource control (RRC) message may be referred to as high-level information, high-level message, high-level signal, high-level signaling, high-layer signaling, or high-level signaling, and the disclosure is not limited thereto, but may be referred to by terms having the same or similar meaning.

[0062] Additionally, in the present disclosure, data may be referred to as user data, UP (user plane) data, or application data, or may be referred to by a term having the same or similar meaning as a signal transmitted or received through a DRB (data radio bearer).

[0063] Additionally, in the present disclosure, the direction of data transmitted from a terminal may be referred to as an uplink (UL), and the direction of data transmitted to a terminal may be referred to as a downlink (DL). Accordingly, in the case of uplink transmission, the transmitter may refer to a terminal, and the receiver may refer to a specific network entity of a base station or communication system. Alternatively, in the case of downlink transmission, the transmitter may refer to a specific network entity of a base station or communication system, and the receiver may refer to a terminal.

[0064] Wireless communication systems support various mobility management methods, including L3 handover, to support terminal mobility. However, interrupt time may occur during the handover process designed to support terminal mobility.

[0065] The frame structure of the 5G system will be explained in more detail below with reference to the drawings.

[0066] Figure 1 is a diagram illustrating the basic structure of the time-frequency domain, which is a wireless resource domain where data or control channels are transmitted in a 5G system.

[0067] The horizontal axis of FIG. 1 represents the time domain, and the vertical axis represents the frequency domain. In the time and frequency domains, the basic unit of a resource is a resource element (RE, 101), which can be defined as one OFDM (orthogonal frequency division multiplexing) symbol (102) on the time axis and one subcarrier (103) on the frequency axis. In the frequency domain (For example, 12) consecutive REs can form a resource block (RB, 104). In the time axis, a subframe (110) can contain multiple OFDM symbols (102). For example, the length of one subframe can be 1 ms.

[0068] FIG. 2 is a drawing illustrating a frame, subframe, and slot structure in a wireless communication system according to one embodiment of the present disclosure.

[0069] FIG. 2 illustrates an example of a frame (200), subframe (201), and slot (202) structure. One frame (200) can be defined as 10ms. One subframe (201) can be defined as 1ms, and thus one frame (200) can be composed of a total of 10 subframes (201). One slot (202, 203) can be defined as 14 OFDM symbols (i.e., the number of symbols per slot ( )=14). One subframe (201) may be composed of one or more slots (202, 203), and the number of slots (202, 203) per one subframe (201) may vary depending on the setting value μ (204, 205) for the subcarrier spacing. In one example of FIG. 2, cases where μ=0 (204) and μ=1 (205) are set as the subcarrier spacing value are illustrated. When μ=0 (204), one subframe (201) may be composed of one slot (202), and when μ=1 (205), one subframe (201) may be composed of two slots (203). That is, the number of slots per one subframe ( ) may vary, and accordingly, the number of slots per frame ( ) may vary. Depending on each subcarrier spacing setting μ and It can be defined by [Table 1] below.

[0070]

[0071] Next, the configuration of the bandwidth part (BWP) in a 5G communication system will be explained in detail with reference to the drawing.

[0072] FIG. 3 is a drawing illustrating an example of a bandwidth portion setting in a wireless communication system according to an embodiment of the present disclosure.

[0073] FIG. 3 shows an example in which the terminal bandwidth (UE bandwidth) (300) is configured into two bandwidth portions, namely bandwidth portion #1 (BWP#1) (301) and bandwidth portion #2 (BWP#2) (302). The base station may configure one or more bandwidth portions for the terminal and may configure information such as [Table 2] below for each bandwidth portion.

[0074]

[0075] Of course, the above examples are not limited, and various parameters related to bandwidth portions may be configured for the terminal in addition to the above configuration information. The above information may be transmitted by the base station to the terminal via higher-layer signaling, for example, RRC (radio resource control) signaling. Among the one or more configured bandwidth portions, at least one bandwidth portion may be activated. Whether a configured bandwidth portion is activated may be transmitted quasi-statically from the base station to the terminal via RRC signaling or dynamically via DCI (downlink control information).

[0076] According to some embodiments, prior to the radio resource control (RRC) connection, the terminal may receive an initial bandwidth portion (initial BWP) for initial connection from the base station via a master information block (MIB). More specifically, during the initial connection phase, the terminal may receive configuration information for a control resource set (CORESET) and a search space via the MIB, through which a physical downlink control channel (PDCCH) can be transmitted to receive system information required for initial connection (which may correspond to remaining system information (RMSI) or system information block 1 (SIB1)). The control resource set and the search space configured via the MIB may each be considered as Identifier (ID) 0. The base station may notify the terminal via the MIB of configuration information, such as frequency allocation information, time allocation information, and numerology, for control resource set #0. In addition, the base station may notify the terminal via the MIB of configuration information regarding the monitoring period and occasion for control area #0, i.e., configuration information for search area #0. The terminal may regard the frequency area set as control area #0 obtained from the MIB as the initial bandwidth portion for initial access. At this time, the identifier (ID) of the initial bandwidth portion may be considered as 0.

[0077] The settings for the bandwidth portion supported by the above 5G can be used for various purposes.

[0078] According to some embodiments, if the bandwidth supported by the terminal is smaller than the system bandwidth, this can be supported through the bandwidth portion setting. For example, by setting the frequency position of the bandwidth portion (setting information 2) to the terminal, the terminal can transmit and receive data at a specific frequency position within the system bandwidth.

[0079] In addition, according to some embodiments, a base station may set multiple bandwidth portions for a terminal for the purpose of supporting different numerologies. For example, to support data transmission and reception using both a 15 kHz subcarrier interval and a 30 kHz subcarrier interval for a terminal, two bandwidth portions may be set to subcarrier intervals of 15 kHz and 30 kHz, respectively. Different bandwidth portions may be frequency division multiplexed, and when data transmission and reception is to be performed with a specific subcarrier interval, the bandwidth portion set to that subcarrier interval may be activated.

[0080] In addition, according to some embodiments, a base station may set bandwidth portions with different bandwidth sizes for the purpose of reducing the power consumption of the terminal. For example, if the terminal supports a very large bandwidth, such as 100 MHz, and always transmits and receives data using that bandwidth, very large power consumption may occur. In particular, in a situation where there is no traffic, monitoring an unnecessary downlink control channel using a large bandwidth of 100 MHz may be very inefficient in terms of power consumption. To reduce the power consumption of the terminal, the base station may set a bandwidth portion with a relatively small bandwidth, such as 20 MHz, for the terminal. In a situation where there is no traffic, the terminal can perform monitoring operations in the 20 MHz bandwidth portion, and when data is generated, it can transmit and receive data using the 100 MHz bandwidth portion according to the instructions of the base station.

[0081] In the method for setting the above bandwidth part, terminals prior to RRC connection can receive setting information for the initial bandwidth part through the master information block (MIB) during the initial connection phase. More specifically, the terminal can receive a control resource set (CORESET) for a downlink control channel through which downlink control information (DCI) scheduling system information blocks (SIB) can be transmitted from the MIB of the physical broadcast channel (PBCH). The bandwidth of the control resource set by the MIB can be considered as the initial bandwidth part, and through the set initial bandwidth part, the terminal can receive the physical downlink shared channel (PDSCH) through which SIBs are transmitted. In addition to receiving SIBs, the initial bandwidth part may also be utilized for other system information (OSI), paging, and random access.

[0082] When one or more bandwidth parts are set for a terminal, the base station may instruct the terminal to change (or switch, transition) the bandwidth part using the bandwidth part indicator field in the DCI. For example, in FIG. 3, if the currently active bandwidth part of the terminal is bandwidth part #1 (301), the base station may instruct the terminal to bandwidth part #2 (302) using the bandwidth part indicator in the DCI, and the terminal may perform a bandwidth part change to bandwidth part #2 (302) indicated by the received bandwidth part indicator in the DCI.

[0083] As mentioned above, since DCI-based bandwidth portion changes can be directed by the DCI scheduling PDSCH or PUSCH, when a terminal receives a bandwidth portion change request, it must be able to receive or transmit the PDSCH or PUSCH scheduled by the corresponding DCI in the changed bandwidth portion without difficulty. To this end, the standard specifies the delay time (T) required when changing the bandwidth portion. BWP The requirements for ) have been defined, and can be defined as, for example, [Table 3].

[0084]

[0085] The requirements for bandwidth portion change delay time support Type 1 or Type 2 depending on the terminal's capability. The terminal can report the supported bandwidth portion delay time type to the base station.

[0086] In accordance with the aforementioned requirements for bandwidth portion change delay time, if the terminal receives a DCI containing a bandwidth portion change indicator in slot n, the terminal performs a change to the new bandwidth portion indicated by the bandwidth portion change indicator in slot n+T BWP Completion can be performed at a time no later than the new bandwidth portion, and transmission and reception for the data channel scheduled by the corresponding DCI can be performed in the changed new bandwidth portion. If the base station intends to schedule a data channel in the new bandwidth portion, the terminal's bandwidth portion change delay time (T BWP By considering ), time-domain resource allocation for a data channel can be determined. That is, when a base station schedules a data channel with a new bandwidth portion, in the method for determining time-domain resource allocation for a data channel, the data channel can be scheduled after the bandwidth portion change delay time. Accordingly, the terminal [is notified] that the DCI instructing the bandwidth portion change is the bandwidth portion change delay time (T BWPYou may not expect to indicate a slot offset (K0 or K2) value smaller than )

[0087] If a terminal receives a DCI (e.g., DCI format 1_1 or 0_1) indicating a change in the bandwidth portion, the terminal may not perform any transmission or reception during a time interval corresponding to the time interval from the third symbol of the slot in which the PDCCH containing the said DCI was received to the beginning of the slot indicated by the slot offset value (K0 or K2) indicated by the time domain resource allocation indicator field within the said DCI. For example, if a terminal receives a DCI indicating a change in the bandwidth portion in slot n, and the slot offset value indicated by the said DCI is K, the terminal may not perform any transmission or reception from the third symbol of slot n to the previous symbol of slot n+K (i.e., the last symbol of slot n+K-1).

[0088] Next, we will explain the SS (synchronization signal) / PBCH block in 5G.

[0089] An SS / PBCH block may refer to a physical layer channel block composed of PSS (primary SS), SSS (secondary SS), and PBCH. Specifically, it is as follows.

[0090] - PSS: A signal that serves as the reference for downlink time / frequency synchronization and provides some information about the cell ID.

[0091] - SSS: Serves as the reference for downlink time / frequency synchronization and provides the remaining cell ID information not provided by PSS. Additionally, it can serve as a reference signal for PBCH demodulation.

[0092] - PBCH: Provides essential system information required for transmitting and receiving data channels and control channels of the terminal. The essential system information may include search space-related control information representing wireless resource mapping information of the control channel, scheduling control information for a separate data channel that transmits system information, etc.

[0093] - SS / PBCH block: An SS / PBCH block is composed of a combination of PSS, SSS, and PBCH. One or more SS / PBCH blocks may be transmitted within a time of 5ms, and each transmitted SS / PBCH block may be distinguished by an index.

[0094] The terminal can detect PSS and SSS during the initial connection phase and can decode PBCH. It can obtain MIB from PBCH and receive a control resource set (CORESET) #0 from it (which may correspond to a control resource set with a control resource set index of 0). The terminal can perform monitoring of control resource set #0 by assuming that the selected SS / PBCH block and the demodulation reference signal (DMRS) transmitted from control resource set #0 are quasi-co-located (QCL). The terminal can receive system information using downlink control information transmitted from control resource set #0. The terminal can obtain configuration information related to the random access channel (RACH) required for initial connection from the received system information. The terminal can transmit a physical RACH (PRACH) to the base station considering the selected SS / PBCH index, and the base station receiving the PRACH can obtain information regarding the SS / PBCH block index selected by the terminal. The base station can know that the terminal has selected a block among the respective SS / PBCH blocks and is monitoring the associated control area #0.

[0095] Next, downlink control information (DCI) in 5G systems will be explained in detail.

[0096] In a 5G system, scheduling information for uplink data (or physical uplink shared channel (PUSCH)) or downlink data (or physical downlink shared channel (PDSCH)) is included in the DCI and transmitted from the base station to the terminal. The terminal can monitor the fallback DCI format and the non-fallback DCI format for PUSCH or PDSCH. The fallback DCI format may consist of fixed fields selected between the base station and the terminal, and the non-fallback DCI format may include configurable fields.

[0097] DCI can be transmitted through the physical downlink control channel (PDCCH) after undergoing channel coding and modulation processes. A cyclic redundancy check (CRC) is attached to the DCI message payload, and the CRC can be scrambled into a radio network temporary identifier (RNTI) corresponding to the terminal's identity. Different RNTIs may be used depending on the purpose of the DCI message, such as UE-specific data transmission, power control commands, or random access responses. In other words, the RNTI is not transmitted explicitly but is included in the CRC calculation process. Upon receiving a DCI message transmitted over the PDCCH, the terminal checks the CRC using the assigned RNTI; if the CRC check result is correct, the terminal knows that the message has been transmitted to it.

[0098] For example, a DCI scheduling a PDSCH for system information (SI) can be scrambled to SI-RNTI. A DCI scheduling a PDSCH for a random access response (RAR) message can be scrambled to RA-RNTI. A DCI scheduling a PDSCH for a paging message can be scrambled to P-RNTI. A DCI notifying a slot format indicator (SFI) can be scrambled to SFI-RNTI. A DCI notifying a transmit power control (TPC) can be scrambled to TPC-RNTI. A DCI scheduling a terminal-specific PDSCH or PUSCH can be scrambled to C-RNTI (cell RNTI).

[0099] DCI format 0_0 can be used as a countermeasure DCI for scheduling PUSCH, in which case the CRC can be scrambled with C-RNTI. DCI format 0_0 with the CRC scrambled with C-RNTI can include, for example, the information in [Table 4].

[0100]

[0101] DCI format 0_1 ​​can be used as a non-defense DCI for scheduling PUSCH, in which case the CRC can be scrambled with C-RNTI. DCI format 0_1 ​​with the CRC scrambled with C-RNTI can include, for example, the information in [Table 5].

[0102]

[0103]

[0104] DCI format 1_0 can be used as a countermeasure DCI for scheduling PDSCH, in which case the CRC can be scrambled with C-RNTI. DCI format 1_0 with the CRC scrambled with C-RNTI can include, for example, the information in [Table 6].

[0105]

[0106] DCI format 1_1 can be used as a non-defense DCI for scheduling PDSCH, in which case the CRC can be scrambled with C-RNTI. DCI format 1_1 with the CRC scrambled with C-RNTI can include, for example, the information in [Table 7].

[0107]

[0108] In the following, the downlink control channel in a 5G communication system will be explained in more detail with reference to the drawings.

[0109] FIG. 4 illustrates an example of a control resource set (CORESET) in which a downlink control channel is transmitted in a 5G wireless communication system. FIG. 4 illustrates an example in which two control resources (control resource #1 (401), control resource #2 (402)) are set within a terminal bandwidth part (UE bandwidth part) (410) on the frequency axis and one slot (420) on the time axis. The control resources (401, 402) can be set in a specific frequency resource (403) within the entire terminal bandwidth part (410) on the frequency axis. On the time axis, they can be set with one or more OFDM symbols and can be defined as the control resource set duration (404). Referring to the example illustrated in FIG. 4, control resource #1 (401) is set with a control resource length of 2 symbols, and control resource #2 (402) is set with a control resource length of 1 symbol.

[0110] The control domain in the aforementioned 5G can be configured by a base station to a terminal through upper-layer signaling (e.g., system information, MIB (master information block), RRC (radio resource control) signaling). Configuring a control domain to a terminal means providing information such as a control domain identifier, the frequency location of the control domain, and the symbol length of the control domain. For example, it may include the information in [Table 8].

[0111]

[0112] In [Table 8], the tci-StatesPDCCH (simply named TCI (transmission configuration indication) state) configuration information may include information on one or more SS (synchronization signal) / PBCH (physical broadcast channel) block indices or CSI-RS (channel state information reference signal) indices that are in a quasi-co-located relationship with the DMRS transmitted in the corresponding control area.

[0113] FIG. 5 is a diagram showing an example of a basic unit of time and frequency resources that constitute a downlink control channel that can be used in 5G. According to FIG. 5, the basic unit of time and frequency resources that constitute a control channel can be called a REG (resource element group, 503), and the REG (503) can be defined as 1 OFDM symbol (501) on the time axis and 1 PRB (physical resource block, 502) on the frequency axis, that is, 12 subcarriers. A base station can concatenate REGs (503) to form a downlink control channel allocation unit.

[0114] As illustrated in FIG. 5, if the basic unit to which a downlink control channel is allocated in 5G is called a CCE (control channel element, 504), then 1 CCE (504) can be composed of multiple REGs (503). For example, if the REG (503) illustrated in FIG. 5 is described, the REG (503) can be composed of 12 REs, and if 1 CCE (504) is composed of 6 REGs (503), then 1 CCE (504) can be composed of 72 REs. When a downlink control area is established, the area can be composed of multiple CCEs (504), and a specific downlink control channel can be mapped to one or multiple CCEs (504) and transmitted according to the aggregation level (AL) within the control area. The CCEs (504) within the control area are distinguished by numbers, and the numbers of the CCEs (504) can be assigned according to a logical mapping method.

[0115] The basic unit of the downlink control channel, namely the REG (503) shown in FIG. 5, may include both the REs to which the DCI is mapped and the DMRS (505), which is a reference signal for decoding, to which the area is mapped. As shown in FIG. 5, three DMRS (505) may be transmitted within one REG (503). The number of CCEs required to transmit the PDCCH may be 1, 2, 4, 8, or 16 depending on the aggregation level (AL), and different numbers of CCEs may be used to implement link adaptation of the downlink control channel. For example, when AL=L, one downlink control channel may be transmitted through L CCEs. The terminal must detect the signal without knowing information about the downlink control channel, and a search space representing a set of CCEs is defined for blind decoding. A search space is a set of downlink control channel candidates consisting of CCEs that a terminal must attempt to decode on a given aggregation level, and since there are various aggregation levels that form a group of 1, 2, 4, 8, or 16 CCEs, a terminal may have multiple search spaces. A search space set can be defined as a set of search spaces on all configured aggregation levels.

[0116] Search spaces can be classified into common search spaces and UE-specific search spaces. A certain group of terminals or all terminals may examine the common search space of the PDCCH to receive cell-common control information, such as dynamic scheduling or paging messages regarding system information. For example, PDSCH scheduling allocation information for the transmission of SIBs containing cell operator information can be received by examining the common search space of the PDCCH. In the case of the common search space, since a certain group of terminals or all terminals must receive the PDCCH, it can be defined as a pre-arranged set of CCEs. Scheduling allocation information for a UE-specific PDSCH or PUSCH can be received by examining the UE-specific search space of the PDCCH. The UE-specific search space can be defined specifically as a function of the terminal's identifier and various system parameters.

[0117] In 5G, parameters for the search space for a PDCCH can be configured from the base station to the terminal via upper layer signaling (e.g., SIB, MIB, RRC signaling). For example, the base station may configure the terminal the number of PDCCH candidates at each aggregation level L, the monitoring period for the search space, the occasion for monitoring in slot-symbol units for the search space, the search space type (common search space or terminal-specific search space), the combination of DCI format and RNTI to be monitored in the search space, and the control domain index to be monitored in the search space. For example, the information in [Table 9] may be included.

[0118]

[0119]

[0120] According to the configuration information, the base station may set one or multiple sets of search spaces for the terminal. According to some embodiments, the base station may set search space set 1 and search space set 2 for the terminal, and may set DCI format A scrambled with X-RNTI in search space set 1 to be monitored in a common search space, and may set DCI format B scrambled with Y-RNTI in search space set 2 to be monitored in a terminal-specific search space.

[0121] According to the configuration information, one or more sets of search spaces may exist in a common search space or a terminal-specific search space. For example, Search Space Set #1 and Search Space Set #2 may be configured as a common search space, and Search Space Set #3 and Search Space Set #4 may be configured as a terminal-specific search space.

[0122] In the common search space, the following combinations of DCI formats and RNTI can be monitored. Of course, they are not limited to the examples below.

[0123] DCI format 0_0 / 1_0 with CRC scrambled by C-RNTI, CS-RNTI, SP-CSI-RNTI, RA-RNTI, TC-RNTI, P-RNTI, SI-RNTI

[0124] DCI format 2_0 with CRC scrambled by SFI-RNTI

[0125] DCI format 2_1 with CRC scrambled by INT-RNTI

[0126] DCI format 2_2 with CRC scrambled by TPC-PUSCH-RNTI, TPC-PUCCH-RNTI

[0127] DCI format 2_3 with CRC scrambled by TPC-SRS-RNTI

[0128] In terminal-specific search spaces, the following combinations of DCI formats and RNTI can be monitored. Of course, they are not limited to the examples below.

[0129] DCI format 0_0 / 1_0 with CRC scrambled by C-RNTI, CS-RNTI, TC-RNTI

[0130] DCI format 1_0 / 1_1 with CRC scrambled by C-RNTI, CS-RNTI, TC-RNTI

[0131] The specified RNTIs may follow the definitions and uses below.

[0132] C-RNTI (cell RNTI): Used for terminal-specific PDSCH scheduling

[0133] TC-RNTI (Temporary Cell RNTI): Used for terminal-specific PDSCH scheduling

[0134] CS-RNTI (Configured Scheduling RNTI): Used for semi-statically configured terminal-specific PDSCH scheduling.

[0135] RA-RNTI (Random Access RNTI): Used for PDSCH scheduling during the random access phase

[0136] P-RNTI (paging RNTI): Used for PDSCH scheduling where paging is transmitted.

[0137] SI-RNTI (System Information RNTI): Used for PDSCH scheduling where system information is transmitted.

[0138] INT-RNTI (Interruption RNTI): Used to indicate whether PDSCH is pucturing.

[0139] TPC-PUSCH-RNTI (transmit power control for PUSCH RNTI): Used to instruct power control commands to the PUSCH

[0140] TPC-PUCCH-RNTI (transmit power control for PUCCH RNTI): Used to instruct power control commands to the PUCCH

[0141] TPC-SRS-RNTI (transmit power control for SRS RNTI): Used to instruct power control commands to the SRS

[0142] The aforementioned specified DCI formats may follow definitions such as the example in [Table 10].

[0143]

[0144] In 5G, the search space of aggregation level L in the control domain p and search space set s can be expressed as [Equation 1] below.

[0145]

[0146] The value may be 0 for the common search space.

[0147] In the case of a terminal-specific search space, the value may correspond to a value that changes according to the terminal's identity (C-RNTI or ID set by the base station for the terminal) and the time index.

[0148] In 5G, as multiple sets of search spaces can be configured with different parameters (e.g., the parameters in [Table 9]), the set of search space sets monitored by the terminal at each point in time may vary. For example, if search space set #1 is configured with an X-slot period and search space set #2 is configured with a Y-slot period and X and Y are different, the terminal may monitor both search space set #1 and search space set #2 in a specific slot, and monitor either search space set #1 or search space set #2 in a specific slot.

[0149] FIG. 6 illustrates the interruption time or delay time of a handover process that may generally occur. For example, FIG. 6 shows the interruption time during a handover (HO) process that a terminal may experience. The interruption time may be defined as the time from when the terminal receives a handover command message from a base station until when the terminal first transmits uplink (UL) data to a target cell. In this case, the interruption time may include terminal reconfiguration (UE reconfiguration), downlink (DL) synchronization, and uplink synchronization (e.g., RACH procedure), as illustrated in FIG. 1.

[0150] In wireless communication systems, mobility management methods including handover are supported, and measures have been proposed to reduce the interruption time that may occur during this process. For example, there is a method such as conditional handover (CHO). However, since DL synchronization and UL synchronization account for a large proportion of the interruption time, the effectiveness of methods proposed to reduce interruption time, such as CHO, may be minimal.

[0151] Accordingly, L1 / L2 (layer1 / layer2) triggered mobility (LTM) was devised to reduce interruption time.

[0152] Figure 7 is a diagram showing the procedure for L3 (layer 3) handover.

[0153] As illustrated in FIG. 7, an L3 handover procedure according to one embodiment is described such that a terminal (701) in a radio resource control (RRC) connected state at 700 can transmit an L3 measurement report to a source distributed unit (702) at 710. For example, the terminal (701) can perform a measurement on at least one neighboring cell and report the measurement results.

[0154] In step 720, the L3 measurement report can be transmitted from the source DU (702) to the CU (centralized unit) (704).

[0155] In step 730, if an L3 handover is determined by the CU (704) based on the L3 measurement report, in step 740, the CU (704) can send an L3 HO request to the target DU (703). And in step 745, the target DU (703) can send an L3 handover acknowledgment (L3 HO acknowledge) to the CU (704).

[0156] In step 750, the CU (704) sends a UE context modification request to the source DU (702), and in step 755, the source DU (702) can send a UE context modification acknowledge to the CU (704).

[0157] Then, if the source DU (702) transmits an RRC reconfiguration message to the terminal (701) in step 760 and the terminal (701) transmits an RRC reconfiguration complete message to the source DU (702) in step 765, a RACH procedure may be performed in step 770. The RACH procedure of 770 may include steps such as the terminal (701) transmitting a PRACH (physical random access channel) preamble to the target DU (703), the terminal (701) receiving a message 2 (MSG 2) from the target DU (703), and the terminal (701) transmitting a message 3 (MSG 3) to the target DU (703).

[0158] In the L3 HO of Fig. 7 as described above, an interruption time may occur during the process of performing downlink synchronization (DL synchronization) and uplink synchronization (UL synchronization) with the target DU after the terminal receives a handover command (HO command) based on the RRC reset message.

[0159] Figure 8 is a diagram showing the procedure of the LTM proposed to reduce interruption time.

[0160] Based on FIG. 8, the LTM procedure is summarized and described. A terminal (801) in an RRC connected state at 800 can transmit a measurement report to a base station (802) at 805. The base station (802) may be an NR base station, such as a gNB. Or the base station (802) may be a base station of a next-generation communication system. According to one embodiment, the base station (802) may be composed of one CU and a plurality of DUs (e.g., a source DU and a target DU). Or the base station (802) may be composed of one CU and a plurality of cells (a source cell and a target cell). The terminal may be a terminal with LTM set.

[0161] In step 810, the base station (802) can perform an LTM candidate preparation procedure.

[0162] In step 815, the base station (802) can transmit information about an LTM candidate configuration through an RRC reset message. For example, the base station (802) can generate information about the LTM candidate configuration through the LTM candidate preparation procedure and transmit the information about the generated LTM candidate configuration to the terminal (801).

[0163] In step 820, the terminal (801) that receives the RRC reset message may transmit an RRC reset completion message to the base station (802). At this time, steps 805 to 820 may be LTM preparation procedures.

[0164] Step 825 is an early synchronization procedure, in which the terminal (801) can perform downlink / uplink synchronization with at least one candidate cell. For example, the terminal (801) can identify at least one candidate cell based on information regarding LTM candidate settings received from the base station (802) in step 815, and perform downlink / uplink synchronization with said at least one candidate cell.

[0165] In step 830, the terminal (801) can transmit an L1 measurement report to the base station (802).

[0166] In step 835, based on the measurement report transmitted from the terminal (801) in step 830, the base station (802) can make an LTM decision.

[0167] When an LTM decision is made by the base station (802) in step 840, the base station (802) can transmit a cell switch command to the terminal (801) using a MAC (medium access control) CE (control element).

[0168] In step 845, the terminal (801) that receives the MAC CE from the base station (802) may be detached from the source cell. Alternatively, the terminal (801) that receives the MAC CE from the base station (802) may be detached from the source cell and apply target configurations. The MAC CE may include a cell switch command.

[0169] In step 850, the terminal (801) can perform a connection to the target cell. Alternatively, the terminal (801) can cell switch to the target cell. Alternatively, the terminal (801) can perform a RACH procedure to the target cell.

[0170] The above 830 to 850 may be LTM execution procedures.

[0171] In step 855, the LTM can be completed as a completion procedure.

[0172] As illustrated in FIG. 8, in LTM, the terminal (801) can be synchronized in advance before receiving the cell switch command through an early synchronization procedure, so the interruption time can be reduced.

[0173] Furthermore, LTM has the advantage of not requiring processing at L3 compared to L3 handover, as such cell switch commands are transmitted via MAC CE based on L1 measurement reports (for example, by generating command messages at the MAC layer).

[0174] LTM is a new mobility-related technology introduced in Release 18 and is receiving attention as a baseline mobility technology for future 5G-Advanced and 6G. LTM determines handovers, or cell switches in LTM technology, based on L1 measurement reports rather than conventional L3 measurement reports; consequently, handovers are determined at the DU rather than the CU. This minimizes the impact of additional latency caused by the wired distance between the CU and the DU.

[0175] As another advantage, the RACH process for downlink synchronization and / or uplink synchronization during handover can be omitted through the early synchronization process. The uplink synchronization operation can be called early TA acquisition because it acquires the TA (timing advance) in advance.

[0176] Figure 9 is a diagram illustrating the early TA acquisition procedure for early synchronization in the LTM procedure.

[0177] In the LTM procedure, a base station may be composed of one CU and at least one DU (source DU and / or target DU). The area served by the source DU may be defined as the source cell, and the area served by the target DU may be defined as the target cell. The operation of the source DU may be understood as the operation of the source cell, and the operation of the target DU may be understood as the operation of the target cell. The source cell may be used interchangeably with the serving cell. The candidate cell and / or target cell may be used interchangeably with the non-serving cell.

[0178] In the LTM procedure, CU and / or DU may each mean gNB-CU and / or gNB-DU. Alternatively, in the LTM procedure, CU and / or DU may be base station entities of a 5G-advanced, 6G, or next-generation system. Embodiments of the present disclosure may be applied without being limited to these terms.

[0179] According to the present disclosure, in step 910, the terminal (900) may report a measurement to the source DU (901). The measurement report may be an L1 (layer 1) measurement report. Upon receiving the measurement report from the terminal (900), the source DU (901) may determine whether to perform a cell switch based on the received information. The source DU (901) may determine whether to perform an early TA acquisition operation to acquire a TA to be used in the cell switch. The early TA acquisition operation may be a procedure for early synchronization. The terminal (900) may be a terminal with an LTM set.

[0180] In step 920, the source DU (901) may perform a preliminary operation for a cell switch operation based on a measurement report received from the terminal (900). Alternatively, the source DU (901) may decide to perform an early TA acquisition operation based on a measurement report received from the terminal (900). The early TA acquisition operation may be a procedure for early synchronization.

[0181] In step 930, if the source DU (901) decides to perform an early TA acquisition operation, it may order the terminal (900) to perform an early synchronization operation with the candidate DU (902). For example, the source DU (901) may order the terminal (900) to send a PRACH to the candidate DU (902) to which it intends to acquire the TA in advance. The order may be to send or trigger a PDCCH (physical downlink control channel) order.

[0182] In step 940, the terminal (900) that receives a command from the source DU (901) can instruct the candidate DU (902) to measure TA. The terminal (900) can transmit PRACH to the candidate DU (902) based on the PDCCH order. The candidate DU (902) that receives the PRACH can measure TA. Although FIG. 9 is illustrated as the terminal (900) transmitting PRACH to one candidate DU (902), if it is instructed by the source DU (901) to transmit PRACH to multiple candidate DUs, it can perform the PRACH transmission operation to multiple candidate DUs.

[0183] Steps 920 to 940 may refer to an early TA acquisition operation. Accordingly, TA information including the measured TA value may be TA information for LTM.

[0184] In step 950, the candidate DU (902) can transmit or send the measured TA information to the CU (or serving CU) (903). The candidate DU (902) can send a message containing the measured TA information to the CU (903). The message may be an F1AP (F1 application protocol) message. The message may be a DU-CU TA INFORMATION TRANSFER message, which is an F1AP message.

[0185] In step 960, the CU (903) may transmit or forward the received TA information to the source DU (901). To do this, the CU (903) may send a message containing the TA information to the source DU (901). The message may be an F1AP message. The message may be a CU-DU TA INFORMATION TRANSFER message, which is an F1AP message. The operation of steps 950 and 960 may also be defined as an early TA acquisition operation.

[0186] In step 970, the source DU (901) can determine the cell switch. The determination may be to determine the LTM cell switch.

[0187] When the source DU (901) determines an LTM cell switch in step 980, it may issue a cell switch command to the terminal (900). The cell switch command may be a cell switch command to a candidate cell (902), and the terminal (900) that receives the cell switch command performs a cell switch operation to the designated candidate cell (902). At this time, the terminal (900) may skip the RACH procedure for the candidate cell (902). The cell switch command may include the TA information received by the source DU (901) from the CU (903). If the cell switch command includes TA information, the terminal may determine that the RACH procedure for the candidate cell (902) is unnecessary and perform a cell switch operation without the RACH procedure. The terminal may use the TA information included in the cell switch command to adjust uplink synchronization for the candidate cell (902) and perform an uplink transmission operation.

[0188] The message that transmits the TA information measured by the candidate DU (902) to the CU (903) in step 950 above may be an F1AP message or a DU-CU TA INFORMATION TRANSFER message. The message format of the DU-CU TA INFORMATION TRANSFER message is as shown in [Table 11] below.

[0189]

[0190] The message transmitted by the CU (903), which receives the TA information measured by the candidate DU (902) in step 960 above, to the source DU (901) may be an F1AP message or a CU-DU TA INFORMATION TRANSFER message. The message format of the CU-DU TA INFORMATION TRANSFER message is as shown in [Table 12] below.

[0191]

[0192] The DU-CU TA INFORMATION TRANSFER message, which is the message transmitted by the candidate DU (902) to the CU (903) in step 950, is a non-UE message. The CU-DU TA INFORMATION TRANSFER message, which is the message transmitted by the CU (903) to the source DU (901) in step 960, is a non-UE message. Additionally, since the DU-CU TA INFORMATION TRANSFER message or the CU-DU TA INFORMATION TRANSFER message does not contain a terminal identification factor, it may be difficult to determine which terminal it is for. Consequently, a specific preamble may need to be occupied at the terminal (900) for a certain period of time until the TA information is delivered to the terminal (900) for the purpose of obtaining an early TA in the LTM. In addition, due to the preamble resource allocation method in the F1AP protocol, preamble resources may be allocated to a specific DU rather than a specific terminal. This constraint may lead to the following problems.

[0193] 1. When multiple terminals simultaneously request an early TA acquisition operation, there may be cases where the early TA acquisition operation cannot be performed due to a shortage of available preamble resources caused by preamble resources being occupied for a longer period than in conventional contention-free based handover. For example, this problem may occur when multiple terminals on a subway or train attempt the LTM procedure.

[0194] 2. The above CU-DU TA INFORMATION TRANSFER message or DU-CU TA INFORMATION TRANSFER message contains an RA (random access)-RNTI (radio network temporary identifier) ​​value as a parameter to distinguish terminals. Generally, as it is possible for a terminal to transmit PRACH at regular intervals (e.g., 10ms) according to the PRACH settings, if multiple terminals use the same PRACH resource within the same PRACH transmission period, the RA-RNTI value may be calculated identically. If the RA-RNTI of all terminals connected to the cell is calculated identically, the cell cannot distinguish terminals. If the cell cannot distinguish terminals, it may not be possible to determine which terminal the TA information belongs to, and therefore, the preamble resource may need to be occupied by the cell for a certain period of time.

[0195] Accordingly, the present disclosure proposes a method for transmitting pre-acquired TA information from a candidate DU to a terminal when performing an early TA acquisition procedure. The method may be a method of transmitting the information via a wireless interface (air interface) between the candidate DU and the terminal. The method of transmitting TA information from the candidate DU to the terminal via a wireless interface can reduce network overhead and efficiently manage resources compared to the existing method in which TA information is shared via an F1AP interface between the candidate DU, CU, and source DU, and then transmitted by the source DU to the terminal. Furthermore, the method may propose a device and method to resolve problems that may arise because the cell transmitting TA information to the terminal is a non-serving cell (candidate cell or target cell). Alternatively, the method may propose a device and method to resolve problems that may arise because the DU transmitting TA information to the terminal is a non-serving DU (candidate DU or target DU).

[0196] The method proposed in this disclosure can reduce signaling between the source DU and / or candidate DU and the CU when transmitting TA information, and can resolve the problem of preamble resources becoming insufficient due to the preamble allocated for early TA acquisition in the LTM being occupied for a long time. In addition, the method can resolve congestion that may occur during the transmission of TA information between the candidate DU and the CU, or between the CU and the source DU, and can efficiently allocate limited preamble resources. In this disclosure, the term candidate DU may be used interchangeably with candidate cell and target cell. Additionally, the term source DU may be used interchangeably with source cell.

[0197] FIG. 10 is a diagram specifically illustrating a method for performing an early TA acquisition operation proposed in the present disclosure.

[0198] In step 1010, the terminal (1000) transmits a measurement report to the source DU (1001). The measurement report may be an L1 measurement report. The terminal (1000) may be a terminal with an LTM set.

[0199] In step 1020, the source DU (1001) that receives the measurement report from the terminal (1000) may decide to perform an early TA acquisition operation. The decision on whether to perform the early TA acquisition operation may be a decision based on the measurement report received by the source DU (1001).

[0200] In step 1030, the source DU (1001) may transmit an order to the terminal (1000) for acquiring TA information. The order may be based on the decision made by the source DU (1001) in step 1020 to perform an early TA acquisition operation. For example, in step S1002, the source DU (1001) decides to perform an early TA acquisition operation, and the source DU (1001) may transmit the order to the terminal (1000). The order may be a PDCCH order.

[0201] In step 1040, the terminal (1000) that receives the command can transmit PRACH to the candidate DU (1002). The terminal (1000) that receives the PDCCH order can transmit PRACH to the candidate DU (1002) indicated in the PDCCH order.

[0202] The candidate DU (1002) that receives the PRACH can measure the TA based on the PRACH. The measured TA value may be TA information that the terminal (1000) will use for uplink synchronization.

[0203] In step 1050, the candidate DU (1002) can transmit TA information including the measured TA value to the terminal (1000). The TA information may be included in a first message. The first message may be a message transmitted via PDCCH or a message transmitted via PDSCH. If the first message is a message transmitted via PDCCH, the format of the first message may be DCI (downlink control information). If the first message is a message transmitted via PDSCH, the first message may correspond to a random access MSG2 (random access response), and the random access MSG2 may be a MAC (medium access control) message. Specifically, the MAC message may be in the format of a MAC payload.

[0204] In step 1060, the terminal (1000) can determine whether the acquisition of the TA information was successful. Subsequently, the terminal (1000) can transmit information regarding the success of the acquisition of the TA information to the source DU (1001). If the terminal (1000) succeeds in acquiring the TA information, the information regarding the success of the acquisition of the TA information indicates success in acquiring the TA information, and if the terminal (1000) fails to acquire the TA information, the information regarding the success of the acquisition of the TA information indicates failure in acquiring the TA information. Determining whether the acquisition of the TA information was successful may involve determining whether PRACH retransmission is required. The determination of whether the acquisition of the TA information was successful may be the result of determining whether the terminal (1000) successfully received the TA information from the candidate DU (1002). The terminal (1000) can transmit a second message containing information regarding the success of the acquisition of the TA information to the source DU (1001). The second message may be message 3 of the random access procedure, but is not limited thereto. The format of the second message may be UCI (uplink control information) or MAC message. Specifically, the MAC message may be in the format of MACE CE (control element).

[0205] If the terminal (1000) determines whether the acquisition of the TA information was successful and the acquisition of the TA information failed, the terminal (1000) may retransmit PRACH to the candidate DU (1002). Alternatively, the terminal (1000) may repeat the early TA acquisition procedure. The early TA acquisition procedure repeated at this time may be steps 1040 to 1060. Although FIG. 10 illustrates a procedure for acquiring an Early TA for a single candidate cell, when the Early TA acquisition procedure is triggered for multiple candidate cells, the terminal (1000) may perform the operations of steps 1020 to 1060 for multiple candidate cells indicated by the source cell (1001).

[0206] In step 1070, the source cell (1001) can determine whether the terminal (1000) has successfully acquired the TA information based on information regarding the success or failure of acquiring the TA information included in the second message. If the terminal (1000) has successfully acquired the TA information, the source cell (1001) can determine whether to perform a cell switch operation (LTM cell switch operation).

[0207] In step 1080, if the source DU (1001) determines an LTM cell switch, the source DU (1001) may transmit a cell switch command to the terminal (1000). The terminal (1000) may perform a cell switch operation to a candidate cell (1002) based on the cell switch command. Since the terminal (1000) has successfully obtained TA information, after receiving the cell switch command, it may perform the cell switch procedure without performing an additional random access procedure for the candidate cell (1002).

[0208] When operating as in the procedure of Fig. 10, compared to the operation of Fig. 9, network overhead can be reduced because message exchange between the CU and DU can be omitted during the early TA acquisition process. In addition, when a candidate cell that has received PRACH from a terminal directly provides TA information to the terminal through a first message, and the terminal that has succeeded in acquiring TA information notifies the source cell of the success in acquiring TA information through a second message, the preamble resource previously allocated to the terminal that has succeeded in acquiring TA can be released, thereby allowing for efficient management of random access resources.

[0209] Hereinafter, a method for transmitting the first message for early TA acquisition according to the method proposed in the present disclosure will be described in detail. The first message transmitted by the candidate DU (1002) to the terminal (1000) may include TA information measured by the candidate DU (1002).

[0210] The format of the first message transmitted by the candidate DU (1002) to the terminal (1000) may be a DCI or MAC message. Specific details regarding the transmission method of the first message according to the format of the first message are as follows.

[0211] First, a method for a candidate DU (1002) proposed in the present disclosure to transmit the first message to a terminal (1000) in the form of a DCI is described. When the first message is transmitted in the form of a DCI, the terminal (1000) may decode two or more DCIs (or PDCCH) simultaneously to receive the first message.

[0212] When the first message for transmitting the above TA information is transmitted in the format of DCI, the DCI format of the first message may be devised by referring to the conventional DCI format 1_0. The conventional DCI format 1_0 may be a DCI for a RAR (random access response) (or message 2) in a RACH procedure. Whether the information included in the conventional DCI format 1_0 for transmitting the RAR in the RACH procedure is information that may be necessary for the first message proposed in this disclosure may be as shown in [Table 13] below. However, even if the information included in the conventional DCI format 1_0 is deemed unnecessary for the transmission of the first message based on [Table 13], it is not required to be excluded from the first message and may be included in the first message.

[0213]

[0214] Based on [Table 13], the DCI format of the first message proposed in this disclosure or the information that may be included in the first message may be as shown in [Table 14] below. For the DCI format of the first message, a new format may be defined, or the existing format may be maintained and new information added. In the first message, the cyclic redundancy check (CRC) may be scrambled by RA-RNTI.

[0215]

[0216] The first message above may include at least one of the information or parameters listed in [Table 14]. The information that may be included in the first message is not limited to the parameters of [Table 14]. The first message may further include a candidate cell identifier. This may be identifier information capable of distinguishing a candidate DU or candidate cell that measured the TA.

[0217] Hereinafter, a downlink resource allocation method for transmitting TA information from a candidate DU to a terminal proposed in the present disclosure is described.

[0218] FIG. 11a is a diagram illustrating an example of a resource grid for downlink transmission.

[0219] FIG. 11a illustrates resources for downlink transmission. FIG. 11a illustrates 1 RB (1100).

[0220] Resources for PDCCH (1110) and PDSCH (1120) may be separated in the downlink RB (1100). Additionally, resources (1130, 1140) for DMRS may be allocated in the downlink RB (1110).

[0221] FIG. 11b is a diagram illustrating an example of a downlink resource grid for transmitting TA information proposed in the present disclosure.

[0222] In the present disclosure, in order for a terminal to receive a downlink message containing TA information from a candidate DU (e.g., the message of step 1050 of FIG. 10 or the first message transmitted in the form of a DCI), the terminal performs a monitoring operation to receive a PDCCH (or DCI from a PDCCH) from the candidate DU. Additionally, since the serving cell servicing the terminal is a source DU, the terminal must perform a monitoring operation to receive a PDCCH or DCI from the source DU. Accordingly, the terminal may need to simultaneously monitor a first control channel area for monitoring a downlink control channel transmitted from the candidate DU and a second control channel area for monitoring a downlink control channel transmitted from the source DU. In this case, a problem of collision / overlap between the first control channel and the second control channel may occur. The first control channel area may be used with the same meaning as the CORESET area for the candidate DU and the PDCCH area for the candidate DU. The second control channel area can be used with the same meaning as the CORESET area for the source DU and the PDCCH area for the source DU.

[0223] To resolve the problem of overlap between the first control channel region for the candidate DU and the second control channel region for the source DU, as illustrated in FIG. 11b, the first control channel region (1150) for the candidate DU and the second control channel region (1160) for the source DU may be configured not to overlap each other. This may be equivalent to separating the CORESET region for the candidate DU and the CORESET region for the source DU. The first control channel region (1150) and the second control channel region (1160) may be configured not to overlap at least in the frequency region. The above configuration of not overlapping may include the first control channel region (1150) and the second control channel region (1160) not overlapping in the time resource region and / or not overlapping in the frequency resource region.

[0224] Alternatively, as illustrated in FIG. 11b, the first control channel region (1150) for the candidate cell (or target cell or non-serving cell) and the second control channel region (1160) for the source cell (or serving cell) may be configured so as not to overlap each other. This may mean that the CORESET region for the candidate cell and the CORESET region for the source cell are separated.

[0225] The following describes a method for setting a CORESET area for a candidate DU monitored by a terminal and a CORESER area for a source DU that is a serving cell, in order for the terminal to receive a downlink message containing TA information from the candidate DU. The CORESET area for the candidate DU and the CORESET area for the source DU can be set so as not to overlap each other.

[0226] FIG. 12 is a diagram illustrating different types of CORESET areas for a terminal to monitor a PDCCH transmitted from a candidate DU.

[0227] According to the present disclosure, different types of CORESET regions may be established for monitoring PDCCH transmitted from a candidate DUU. Hereinafter, the CORESET region may be used interchangeably with the PDCCH region or the control channel region. CORESET #0 (1200) may be a CORESET region for monitoring PDCCH transmitted from a target cell after the terminal connects to a target cell (or candidate cell or candidate DU). When the terminal connects to the target cell, it may have connected to the target cell via an LTM cell switch. Since the terminal is connected to the target cell, the target cell may be a serving cell that services the terminal. CORESET #1 (1250) may be a CORESET region for monitoring PDCCH transmitted by the target cell while the terminal is connected to a source cell. In this case, since the terminal is connected to the source cell, the target cell may be a non-serving cell to the terminal.

[0228] CORESET #1 (1250) may be a CORESET area for a candidate DU to transmit TA information to a terminal in order to perform the LTM procedure proposed in this disclosure. Specifically, CORESET #1 (1250) may be a CORESET area for transmitting the first message from the candidate DU to the terminal in step 1050 of FIG. 10. Thus, CORESET #0 (1200) may be a CORESET area for a target cell or a serving cell after connecting to a target cell, and CORESET #1 (1250) may be a CORESET area for a target cell or a non-serving cell to connect to a target cell. Thus, CORESET #0 (1200) and CORESET #1 (1250) may be different areas.

[0229] For example, CORESET #0 (1200) and CORESET #1 (1250) are different control channel areas and can be configured by separate configuration information. Accordingly, CORESET #0 (1200) and CORESET #1 (1250) can be assigned to different resources and their RB indices may overlap. For example, for CORESET #0 (1200), RB indices 0 to 273 can be used. In contrast, for CORESET #1 (1250), the target cell can be configured to use a resource area of ​​RB indices 180 to 273 to transmit TA information to a terminal connected to the source cell. At this time, to avoid conflict with the resource area configured for CORESET #1, RB indices 0 to 179 can be configured as a CORESET area for monitoring PDCCH transmitted from the source cell to the terminal. Alternatively, the source cell cannot use CORESET #1 (1250) (or the resource area of ​​RB index 180 to 273) when the first message is transmitted from the candidate cell to the terminal, but when the first message is not transmitted from the candidate cell to the terminal, the source cell can transmit PDCCH even in the resource area of ​​CORESET #1 (1250). When the first message is not transmitted from the candidate cell to the terminal, the source cell can use the resource area of ​​RB index 0 to 273. In the case of CORESET #0 (1200) allocated for transmission to the terminal connected to the target cell, a wider frequency band can be utilized than CORESET #1 (1250) allocated for transmission to the terminal connected to the source cell.

[0230] The present disclosure describes configuration information for transmitting TA information from a candidate DU to a terminal. In order for the candidate DU to transmit TA information in the form of DCI to a terminal connected to a source DU, it may be necessary to set a new control channel area for the candidate DU. Unlike the configuration information related to the control channel area for the candidate DU that is set for the terminal after connecting to the existing candidate DU, it may be necessary to set configuration information related to the control channel area for the candidate DU that is set for the terminal before connecting to the candidate DU. The control channel area for the candidate DU that is set for the terminal after connecting to the existing candidate DU may correspond to CORESET #0 (1200) of FIG. 12. The control channel area for the candidate DU that is set for the terminal before connecting to the candidate DU may correspond to CORESET #1 (1250) of FIG. 12.

[0231] Configuration information related to the control channel area for the candidate DU, which is configured for the terminal before connecting to the candidate DU, can be transmitted from the source DU to the terminal. Configuration information related to the control channel area for the candidate DU, which is configured for the terminal before connecting to the candidate DU, can be transmitted by being included in an RRC message or by being included in a SIB (system information block). Alternatively, it can be transmitted in another message format.

[0232] FIG. 13 is a diagram illustrating an example of the structure or hierarchy of an RRC message when a source DU transmits configuration information related to a control channel area for a candidate DU that is configured for the terminal before connecting to the candidate DU via an RRC message to the terminal.

[0233] As described in FIG. 12, there are different CORESET areas for monitoring PDCCH transmitted from the candidate DU. After performing the Cell switching procedure and connecting to the candidate DU, configuration information regarding the CORESET area for the candidate DU is included in an RRC message and transmitted from the source DU to the terminal. Configuration information regarding the CORESET area for monitoring PDCCH transmitted from the candidate DU to the terminal connected to the source DU to convey the TA information proposed in this disclosure may also be included in an RRC message and transmitted from the source DU to the terminal. After performing the Cell switching procedure and connecting to the candidate DU, the CORESET area for the candidate DU may correspond to CORESET #0 (1200) in FIG. 12. To convey the TA information proposed in this disclosure, the CORESET area for monitoring PDCCH transmitted from the candidate DU to the terminal connected to the source DU may correspond to CORESET #1 (1250) in FIG. 12. The CORESET area for monitoring the PDCCH transmitted from the candidate DU to the terminal connected to the source DU to transmit the TA information proposed in the present disclosure may be a control channel area for transmitting the first message transmitted by the candidate DU to the terminal in step 1050 of FIG. 10.

[0234] After connecting to the above candidate DU, configuration information regarding the CORESET area for the candidate DU may be included in an LTM-related configuration IE (information element) within the RRC message and transmitted from the source DU to the terminal. The LTM-related configuration IE within the RRC message may be an LTM-Config-r18 (1300) IE. The second configuration information may be included in configuration information related to the candidate cell or DU and transmitted from the source DU to the terminal. The configuration information IE related to the candidate cell or DU may be an ltm-CandidateConfig-r18 (1310).

[0235] Configuration information regarding the CORESET area for monitoring the PDCCH transmitted from the candidate DU to the terminal connected to the source DU (or configuration information regarding the CORESET area for the candidate DU before connecting to the candidate DU) may be information related to resource area allocation for LTM. Configuration information regarding the CORESET area for the candidate DU before connecting to the candidate DU may be included in an RRC message or an RRC reset message and transmitted from the source DU to the terminal. Configuration information regarding the CORESET area for the candidate DU before connecting to the candidate DU may be included in the LTM-related configuration IE within the RRC message and transmitted. The LTM-related configuration IE within the RRC message may be LTM-Config-r18 (1300). Configuration information regarding the CORESET area for the candidate DU before connecting to the candidate DU may be included in configuration information for performing an early synchronization operation. The configuration information for performing the above early synchronization operation may correspond to ltm-EarlyUL-SyncConfig-r18 (1330) IE. In this case, since the configuration information regarding the CORESET area for the candidate DU before connecting to the candidate DU is not a previously defined configuration information, the configuration information regarding the CORESET area for the candidate DU before connecting to the candidate DU may be included in the configuration information for performing the above early synchronization operation as a new IE. In this case, the new IE may correspond to ltm-EarlyUL-pdcch-Config (1340).The new IE for the first configuration information, ltm-EarlyUL-pdcch-Config (1340), may be included as a subordinate IE of the existing configuration IE for performing early synchronization operations, ltm-EarlyUL-SyncConfig-r18 (1330).

[0236] Configuration information regarding the CORESET area for the candidate DU before connecting to the above candidate DU may have the same format as the existing pdcch-Config IE. An example of configuration information regarding the CORESET area for the candidate DU before connecting to the above candidate DU may be as shown in [Table 15] below. The configuration information in [Table 15] below is exemplary, and other configuration information may be added or excluded. For example, the configuration information regarding the CORESET area for the candidate DU before connecting to the above candidate DU may include at least one of CORESET-related configuration information or TCI-related information.

[0237]

[0238] Among the configuration information regarding the CORESET area for the candidate DU prior to connecting to the candidate DU in [Table 15], the CORESET-related configuration information may include configuration information regarding the PDCCH area for transmitting TA information from the candidate DU to the terminal. Based on the configuration information regarding the PDCCH area for transmitting TA information from the candidate DU to the terminal, the PDCCH for TA information transmitted from the candidate DU to the terminal may not conflict with the PDCCH transmitted from the source DU to the terminal. The CORESET-related configuration information may be included in the controlResourceSet of [Table 15]. Specifically, the CORESET-related configuration information may be frequencyDomainResources information. In this case, 1 bit of information included in frequencyDomainResources may represent 6RB. This may mean that information regarding the PDCCH RBs available to the source DU is configured as a bitmap in units of 6RB or CCE. For example, when the first message is transmitted from the candidate DU to the terminal via DCI, the FDRA can be represented in a bitmap format, and each bit can represent 6 RBs to which the PDCCH can be transmitted.

[0239] The PDCCH resource area for a candidate DU to transmit TA information to a terminal is not always occupied by the candidate DU, but may be occupied only when necessary (or only when necessary for the transmission of said TA information). In this case, if the candidate DU does not occupy the PDCCH resource area for transmitting TA to the terminal, the PDCCH resource area may be allocated from the source DU.

[0240] When PDCCH resources are occupied for a candidate DU to transmit TA information from the candidate DU to the terminal, they may be occupied for a certain period of time. The time during which PDCCH resources are occupied for a candidate DU can be defined as follows. However, the above-mentioned occupied time (or occupancy time) is not limited to the alternatives below, and the alternatives below are proposed as examples.

[0241] - Alternative 1. The occupancy time may be from the time the source DU transmits the PDCCH order to the terminal (PDCCH order transmission time) until a specific window period expires. The specific window time may be set by configuration information. In this case, the specific window time may be set by TAAcquisitionWindow information.

[0242] - Alternative 2. The occupancy time may be from the time when the terminal that received the PDCCH order transmits PRACH to the candidate DU (PRACH transmission time) until a specific window period expires. The specific window time may be set by configuration information. In this case, the specific window time may be set by TAAcquisitionWindow information.

[0243] Configuration information related to the above occupancy time may be transmitted via an RRC message. Configuration information related to the above occupancy time may include information regarding TAAcquisitionWindow. The information regarding TAAcquisitionWindow may correspond to at least one of several configuration values. Specifically, the information regarding TAAcquisitionWindow may be expressed as ENUMERATED {sl1, sl2, sl4, sl8, sl10, sl20, sl40, sl80}.

[0244] To give an example based on Alternative 2, if the time at which PRACH is transmitted is x ms and the window time is set to 20 ms by TAAcquisitionWindow, the first CORESET area set by the first setting information from x ms to x+20 ms may be occupied to transmit the first message from the candidate DU to the terminal. At this time, the source DU cannot use the PDCCH resources at the corresponding CORESET location for the terminal connected to it or for its serving terminals (serving UEs). However, from the time after x+20 ms, the source DU can use the PDCCH resources for its serving terminals.

[0245] Hereinafter, a method for setting or determining configuration information regarding resource allocation for transmitting TA information from a candidate DU to a terminal as proposed in the present disclosure is described. The entity determining the configuration information regarding resource allocation for transmitting TA information from the candidate DU to the terminal may be a candidate DU or a CU. The configuration information regarding resource allocation for transmitting TA information from the candidate DU to the terminal may be configuration information regarding available downlink resource allocation. Specifically, the configuration information regarding resource allocation for transmitting TA information from the candidate DU to the terminal may be configuration information regarding FDRA (frequency domain resource allocation) for the transmission of the first message transmitted in step 1050 of FIG. 10.

[0246] When a candidate DU transmits TA information to a terminal via DCI, the configuration information for the candidate DU to transmit TA information to the terminal may include configuration information regarding a control channel area for transmitting the TA information. When a candidate DU transmits TA information to a terminal via a MAC message, the configuration information for the candidate DU to transmit TA information to the terminal may further include configuration information regarding a PDSCH resource area for transmitting the TA information. The configuration information for transmitting TA information from the candidate DU to the terminal may be included in an RRC message and transmitted from the source DU to the terminal, and a detailed explanation may be provided by referring to FIG. 12. When a candidate DU transmits TA information to a terminal via DCI, the configuration information of the new IE, ltm-EarlyUL-pdcch-Config, for the configuration information for transmitting TA information from the candidate DU to the terminal may be determined by the candidate DU or the CU.

[0247] When the CU or candidate DU determines the configuration information for transmitting TA information from the above candidate DU to the terminal, it can be determined using an F1AP message. If the CU determines the configuration information for transmitting TA information from the above candidate DU to the terminal, the following F1AP message may be used.

[0248] - UE CONTEXT SETUP REQUEST message sent from CU to candidate DU

[0249] - UE CONTEXT MODIFICATION REQUEST message sent from CU to candidate DU

[0250] Alternatively, if the candidate DU determines the configuration information for transmitting TA information to the terminal, the following F1AP message may be utilized. In order for the candidate DU to determine the configuration information for transmitting TA information to the terminal, a configuration may be required that allows a request for lower layer configuration in relation to the candidate DU. Specifically, a prerequisite may be required that "request for lower layer configuration IE" in relation to the candidate DU be set to true.

[0251] - UE CONTEXT SETUP RESPONSE message sent from candidate DU to CU

[0252] - UE CONTEXT MODIFICATION RESPONSE message transmitted from candidate DU to CU

[0253] Subsequently, configuration information for transmitting TA information from the candidate DU to the terminal, determined by the candidate DU or CU, may be transmitted from the CU to the source DU. At this time, the configuration information for transmitting TA information from the candidate DU to the terminal, determined at this time, may be transmitted from the CU to the source DU via an F1AP message. At this time, the F1AP message may be a UE CONTEXT MODIFICATION REQUEST message transmitted from the CU to the source DU.

[0254] FIG. 14a is a diagram illustrating the F1AP procedure for determining configuration information related to CORESET for a candidate DU to transmit TA information to a terminal.

[0255] The terminal can perform a measurement and report the measurement result to the source DU. The measurement result may be an L3 measurement result. The source DU that receives the measurement result may transmit the measurement result to the CU. The CU that receives the measurement result from the terminal may determine that an LTM operation is required and may determine configuration information for the LTM. The following describes a method for determining configuration information for transmitting TA information from the candidate DU to the terminal among the configuration information for the LTM.

[0256] In step 1410, the CU can determine configuration information for the candidate DU to transmit TA information to the terminal. The configuration information for the candidate DU to transmit TA information to the terminal may be available downlink resources. The CU can determine the configuration information for the candidate DU to transmit TA information to the terminal by utilizing the UE CONTEXT SETUP REQUEST message that the CU transmits to the candidate DU.

[0257] Alternatively, at step 1420, the candidate DU may determine configuration information for the candidate DU to transmit TA information to the terminal. The configuration information for the candidate DU to transmit TA information to the terminal may be an available downlink resource. The candidate DU may determine the configuration information for the candidate DU to transmit TA information to the terminal by utilizing the UE CONTEXT SETUP RESPONSE message that the candidate DU transmits to the CU.

[0258] In step 1430, the CU may transmit configuration information to the source DU for the candidate DU to transmit TA information to the terminal. The F1AP message used at this time may be a UE CONTEXT MODIFICATION REQUEST message transmitted by the CU to the source DU.

[0259] FIG. 14b is a diagram illustrating the F1AP procedure for determining configuration information related to CORESET for a candidate DU to transmit TA information to a terminal.

[0260] The terminal can perform a measurement and report the measurement result to the source DU. Refer to FIG. 14a for details regarding this.

[0261] In step 1440, the CU can determine configuration information for the candidate DU to transmit TA information to the terminal. The configuration information for the candidate DU to transmit TA information to the terminal may be available downlink resources. The CU can determine the configuration information for the candidate DU to transmit TA information to the terminal by utilizing the UE CONTEXT MODIFICATION REQUEST message that the CU transmits to the candidate DU.

[0262] Alternatively, at step 1420, the candidate DU may determine configuration information for the candidate DU to transmit TA information to the terminal. The configuration information for the candidate DU to transmit TA information to the terminal may be available downlink resources. The candidate DU may determine the configuration information for the candidate DU to transmit TA information to the terminal by utilizing the UE CONTEXT MODIFICATION RESPONSE message that the candidate DU transmits to the CU.

[0263] In step 1460, the CU may transmit configuration information to the source DU for the candidate DU to transmit TA information to the terminal. The F1AP message used at this time may be a UE CONTEXT MODIFICATION REQUEST message transmitted by the CU to the source DU.

[0264] Hereinafter, a method for the candidate DU to notify the terminal of TA information via PDSCH for the early TA acquisition proposed in the present disclosure is described. Specifically, a method for the candidate DU to transmit TA information to the terminal via a MAC message in the PDSCH is described. The TA information may be transmitted by being included in a MAC payload. The MAC payload containing the TA information may correspond to the first message transmitted in step 1050 of FIG. 10. The terminal may be required to have the capability to simultaneously decode PDCCHs transmitted from the source DU (or serving cell) and the candidate DU (or candidate cell). Alternatively, the terminal may be required to have the capability to indicate the number of PDCCHs that it can simultaneously decode (for example, the PDCCH may refer to a PDCCH transmitted from the candidate cell).

[0265] When a candidate DU transmits TA information to a terminal via a MAC message (e.g., MAC payload), it may need to be transmitted along with a MAC subheader in accordance with the legacy specifications. In this case, the information or parameters included in the legacy MAC subheader are as shown in [Table 16] below.

[0266]

[0267] [Table 16] shows parameters that may be necessary among the information included in a conventional MAC subheader when a candidate DU transmits TA information to a terminal via a MAC payload. In this case, the BI (backoff indicator) information included in the conventional MAC subheader may be excluded from the MAC subheader proposed in this disclosure. This is because BI was not considered in Release-18 when performing the Early TA acquisition operation. The MAC subheader proposed in this disclosure may exclude parameters included in the conventional MAC subheader and may include other parameters. The MAC subheader may include information indicating that the candidate DU is a message containing TA information to the terminal.

[0268] Additionally, when transmitting TA information included in a MAC payload, the MAC payload may include information from a conventional RAR (random access response) (e.g., conventional message 2). This means that when the candidate DU transmits TA information to the terminal including it in a MAC payload, the information included in the MAC payload may be identical to the conventional RAR information. Alternatively, when the candidate DU transmits TA information to the terminal including it in a MAC payload, the MAC payload may include at least one of the information included in the conventional RAR, and unnecessary information among the information included in the conventional RAR may be excluded. In this case, whether the information included in the conventional RAR needs to be included in the MAC payload may be as shown in [Table 17] below. However, even if the information included in the conventional RAR is deemed unnecessary based on [Table 17], it is not required to be excluded from the MAC payload, and it may be included.

[0269]

[0270] The TA command in [Table 17] may be TA information containing a TA value. Additionally, information regarding the uplink grant (UL grant) included in the conventional RAR may be included when the candidate DU transmits the TA information to the terminal via the MAC payload, or the source DU may transmit the configuration information related to the uplink grant by including the configuration information related to the LTM in the configuration information related to the LTM. The form included in the first message is described in detail in the alternative of Fig. 15 below. In the case of a temporary C-RNTI, it may be excluded from the first message because it can be configured by the configuration information transmitted by the source DU (e.g., it may be an RRC message) before transmitting the first message.

[0271] FIG. 15 is a diagram illustrating an example of the format of the MAC payload proposed in the present disclosure when a candidate DU transmits TA information to a terminal including it in the MAC payload.

[0272] The MAC payload proposed in this disclosure may be transmitted together with a MAC subheader according to specifications. In this case, Oct1 (1510) and Oct2 (1520) contain information that is included in a conventional MAC subheader. BI information (1515) and RAPID information (random access preamble identifier) ​​(1525) are information that is included in a conventional MAC subheader, and BI information (1515) may be excluded from the MAC subheader proposed in this disclosure.

[0273] In the present disclosure, when a candidate DU transmits TA information to a terminal, the TA information may be transmitted by including it in a MAC payload. At this time, the format of the MAC payload containing the TA information may be one of the following three alternatives. However, the following three alternatives are exemplary and are not limited thereto. The format of the MAC payload proposed in the present disclosure may be at least one of the following three alternatives and may be composed of a combination of the following three alternatives.

[0274] - Alternative 1. The MAC payload proposed in this disclosure may include only TA information or TA command information (1535, 1545). Thus, the MAC payload proposed in this disclosure may consist of Oct 3 (1530) and Oct 4 (1540).

[0275] - Alternative 2. The MAC payload proposed in this disclosure may include TA command information (1535, 1545) and uplink grant (UL grant) (1555, 1565, 1575) information for transmitting information regarding whether the terminal has successfully obtained TA information from the source DU (e.g., message 3 transmitted in step 1060 of FIG. 10). The uplink grant information (1555, 1565, 1575) may be in the same form as the information included in legacy message 3. Accordingly, the MAC payload proposed in this disclosure may be composed of Oct 3 (1530), Oct 4 (1540), Oct 5 (1550), Oct 6 (1560), and Oct 7 (1570). At this time, Oct 3 (1530) and Oct 4 (1540) may include TA command information (1535, 1545). At this time, Oct 5 (1550) to Oct 7 (1570) may include uplink grant information (1555, 1565, 1575).

[0276] - Alternative 3. The MAC payload proposed in the present disclosure may include TA command information (1535, 1545) and uplink grant (1555) information for transmitting information regarding whether the terminal has successfully acquired TA information from the source DU. Accordingly, the MAC payload proposed in the present disclosure may be composed of Oct 3 (1530) to Oct 5 (1550). In this case, Oct 3 (1530) and Oct 4 (1540) may include TA command information (1535, 1545). In this case, Oct 5 (1550) may include uplink grant information (1555). Specifically, Oct 5 (1550) may include index information for a list of uplink resources available for transmitting information regarding whether the terminal proposed in the present disclosure has successfully acquired TA information from the source DU. The above index information may include a field indicating the index of the pusch-TimeDomainAllocationList and a field indicating the index of the pusch-frequencyDomainAllocationList existing in the novel IE ltm-EarlyUL-PUSCHAllocation IE proposed in the present disclosure to be described below. The field indicating the index of the pusch-TimeDomainAllocationList and the field indicating the index of the pusch-frequencyDomainAllocationList may each be 3 bits.

[0277] The uplink grant information (1555, 1565, 1575) transmitted in Alternatives 2 and 3 may include configuration information regarding uplink resources available to transmit information regarding whether the terminal proposed in this disclosure has successfully acquired TA information to the source DU. In contrast, in the situation of Alternative 1, the source DU may allocate an uplink grant based on a conventional method to transmit information regarding whether the terminal has successfully acquired TA information to the source DU. Alternatives 2 and / or 3, which transmit uplink grant information from the candidate DU, may be applied in a centralized scheduler architecture.

[0278] Below, a method for allocating downlink resources when transmitting the TA information proposed in this disclosure via PDSCH is described.

[0279] First, when transmitting the TA information proposed in this disclosure from a candidate DU to a terminal via PDSCH, it can be transmitted via a MAC message (e.g., MAC payload). In order to transmit TA information from a candidate DU to a terminal via a MAC payload, resources may be allocated in the resource area for PDSCH transmission. The resource allocation in the PDCCH resource area used to be allocated in the PDSCH resource area may be subject to the provisions described in the resource allocation in the PDCCH resource area when transmitting TA information from a candidate DU to a terminal via DCI. Specifically, the CORESET area for the candidate DU (e.g., the first control channel area in FIG. 11b) may be separated from the CORESET area for the source DU (e.g., the second control channel area in FIG. 11b).

[0280] Next, a PDSCH resource allocation method for transmitting TA information from the candidate DU to the terminal via the MAC payload is described.

[0281] FIG. 16 is a diagram illustrating a method for allocating a PDSCH resource area for transmitting TA information proposed in the present disclosure through a MAC payload.

[0282] In the case of situation (a) (1600), the PDCCH resource area (1610) allocated for the candidate DU (or candidate cell) and the PDCCH resource area (1620) allocated for the source DU (or source cell) do not overlap. Since the PDCCH resource area (1610) allocated for the candidate DU and the PDCCH resource area (1620) allocated for the source DU do not overlap, no problem may occur. The PDCCH resource area may refer to a CORESET area or a control channel area for monitoring the PDCCH received from the candidate DU or source DU.

[0283] In addition, the PDSCH resource area (1630) allocated from the PDCCH transmitted from the candidate DU and the PDSCH resource area (1640) allocated from the PDCCH transmitted from the source DU do not overlap. In this case, interference due to collisions between PDSCH resources may not occur, and normal PDSCH decoding may be possible. Therefore, a resource allocation method such as in situation (a) (1600) may be valid. The PDSCH resource area may refer to a data channel area for monitoring the PDSCH received from the candidate DU or the source DU.

[0284] In the case of situation (b) (1650), the PDCCH resource area (1660) allocated for the candidate DU (or candidate cell) and the PDCCH resource area (1670) allocated for the source DU (or source cell) do not overlap. First, since the PDCCH resource area (1660) allocated for the candidate DU and the PDCCH resource area (1670) allocated for the source DU do not overlap, no problem may occur.

[0285] However, there exists a frequency domain (1685) where the PDSCH resource domain (1680) allocated from the PDCCH transmitted from the candidate DU and the PDSCH resource domain (1690) allocated from the PDCCH transmitted from the source DU overlap. When frequency domains overlap in this way, interference may occur due to collisions between PDSCH resources, making normal PDSCH decoding impossible. Therefore, a resource allocation method such as in situation (b) (1650) may not be valid.

[0286] The problem of overlap between the PDSCH from the source DU and the PDSCH from the candidate DU may occur because the source DU and the candidate DU do not share information for resource area allocation. Specifically, this may be because the schedulers of the source DU and the candidate DU allocate resource areas independently of each other. Consequently, the scheduler of the source DU and the scheduler of the candidate DU may not know which resource area or frequency area each scheduler allocates the PDSCH to.

[0287] Therefore, the resource schedulers of the source DU and the candidate DU may need to share the PDSCH resource area allocated for the transmission of TA information from the candidate DU. To this end, configuration information regarding the downlink resources available for the candidate DU to transmit TA information to the terminal may be shared between the source DU and the candidate DU. Based on the configuration information regarding the resource area for the candidate DU to transmit TA information to the terminal, the PDSCH for the candidate DU and the PDSCH for the source DU may not conflict.

[0288] To this end, the source DU can receive configuration information related to resource area allocation for the LTM from the CU. Specifically, the configuration information related to resource area allocation for the LTM may be configuration information related to a resource area for transmitting TA information for the LTM. Subsequently, the source DU can transmit the configuration information related to PDSCH resource area allocation for the LTM to the terminal.

[0289] In order for the candidate DU and the source DU to share configuration information regarding downlink resources for the candidate DU to transmit TA information to the terminal, the candidate DU or the CU may determine configuration information regarding downlink resources for the candidate DU to transmit TA information to the terminal, and the CU may notify the source DU of the determined configuration information. Subsequently, the determined configuration information may be transmitted to the terminal through the source DU. An F1AP message may be utilized in the procedure for the candidate DU or the CU to determine configuration information regarding downlink resources for the candidate DU to transmit TA information to the terminal. The procedure for determining configuration information regarding downlink resources for the candidate DU to transmit TA information to the terminal using the F1AP message may refer to the contents of FIG. 14a and / or FIG. 14b.

[0290] When the above candidate DU transmits TA information to a terminal via PDSCH, the configuration information regarding available downlink resources determined by the CU or candidate DU may include configuration information regarding the RB of the available PDSCH. The RB of the available PDSCH may be determined as follows. The following alternative is exemplary, and the RB of the available PDSCH may be determined in other ways.

[0291] - Alternative 1. The RBs of the PDSCH available for the transmission of the first message above may be indicated in a bitmap format by a candidate DU or CU. In this case, each bit may represent the number of RBs to be transmitted. Specifically, each bit may indicate the available PDSCH resource area through a bitmap of CCE or 6 RB units. For this to be possible, there may be a condition on the resource allocation method. In this case, the condition may be that the NR resource allocation type must be NR RA Type 0.

[0292] - Alternative 2. The RBs of the PDSCH available for the transmission of the first message above may be indicated by a candidate DU or CU as a combination of a start RB and the number of RBs. The information consisting of the combination of the start RB and the number of RBs may be a resource indicator value (RIV). For this, there may be a condition on the resource allocation method. In this case, the condition may be that the NR resource allocation type must be NR RA Type 1.

[0293] The above-determined configuration information may be included in an RRC message or an RRC reset message and transmitted from the source DU to the terminal. Configuration information related to the resource area for transmitting TA information from the candidate DU to the terminal may be included in the LTM-related configuration IE within the RRC message and transmitted. The LTM-related configuration IE within the RRC message may be LTM-Config-r18 (e.g., 1300 in FIG. 13). Configuration information related to the resource area for transmitting TA information from the candidate DU to the terminal may be included in configuration information for performing an early synchronization operation. Configuration information for performing an early synchronization operation may correspond to ltm-EarlyUL-SyncConfig-r18 (e.g., 1330 in FIG. 13) IE.

[0294] The information included in the configuration information regarding the resource area for transmitting TA information from the above candidate DU to the terminal may include the information included in the configuration information regarding the resource area when transmitting TA information via PDCCH. The information included in the above configuration information may include configuration information regarding the occupancy time.

[0295] The following describes a method for transmitting information to a source DU indicating whether the terminal has successfully acquired TA information. In this case, the TA information may be TA information for LTM. In this case, the information indicating whether the terminal has successfully acquired TA information may be information indicating whether the terminal requires PRACH retransmission. Or it may be information indicating whether there is a need to re-receive the said TA information. Or it may be information including the result of determining whether the terminal has successfully acquired TA information. The message containing the information indicating whether the terminal has successfully acquired TA information may be the second message transmitted from the terminal to the source DU in step 1060 of FIG. 10. Additionally, the terminal may transmit information indicating whether the terminal has successfully acquired TA information to the candidate DU that transmitted the TA information, and the candidate DU may transmit information indicating whether the terminal has successfully acquired TA information to the source DU.

[0296] First, we will explain the criteria for determining whether the terminal has successfully acquired TA information.

[0297] To determine whether the terminal has successfully acquired TA information, the terminal may determine whether it has received TA information within a period for receiving TA information. The time for receiving TA information may be a period for occupying an available downlink resource area for receiving TA information or the said occupancy time. The said occupancy time may be set by configuration information related to the occupancy time described above. The configuration information related to the said occupancy time may be TAAcquisitionWindow information. In this case, the information regarding the TAAcquisitionWindow may correspond to at least one of several configuration values ​​and may be set by an RRC message. Specifically, the information regarding the TAAcquisitionWindow may be expressed as ENUMERATED {sl1, sl2, sl4, sl8, sl10, sl20, sl40, sl80}.

[0298] Specifically, the criteria for determining whether the terminal has successfully acquired TA information are as follows.

[0299] - If the terminal successfully receives TA information from a candidate DU within the period for receiving the above TA information, the terminal determines that the result of acquiring the TA information is successful. When the terminal determines that the result of acquiring the information is successful, information indicating whether the terminal has successfully acquired TA information is transmitted from the terminal to the source DU, including information indicating successful acquisition of TA information.

[0300] - If the terminal does not successfully receive TA information from the candidate DU within the period for receiving the above TA information, the terminal determines that the result of acquiring TA information is a failure. When the terminal determines that the result of acquiring information is a failure, information indicating whether the terminal successfully acquired TA information is transmitted from the terminal to the source DU, including information indicating failure to acquire TA information.

[0301] If the terminal determines whether the acquisition of the TA information was successful and the terminal fails to acquire the TA information, the terminal may transmit information indicating the failure to acquire the TA information to the source DU. The source DU may retransmit a PDCCH order to the terminal for TA remeasurement. The terminal may retransmit PRACH to the candidate DU. Alternatively, the terminal may repeat the early TA acquisition procedure. The terminal may repeat the above procedure by receiving a PDCCH order from the source DU, or may repeat the procedure without receiving one. The number of times or the duration of repeating the above procedure may be set by the source DU.

[0302] If the terminal succeeds in acquiring the above TA information, the terminal may transmit information indicating the success of TA information acquisition to the source DU. The source DU may determine whether to perform an LTM cell switch. If it is decided to perform an LTM cell switch, the source DU may transmit a cell switch command to the terminal. Subsequently, the early TA acquisition procedure may be terminated.

[0303] The following describes a method for transmitting a message containing information indicating whether a terminal has successfully acquired TA information. The message containing information indicating whether the terminal has successfully acquired TA information from a candidate DU may be transmitted in the form of UCI (uplink control information) or MAC message. The MAC message may be in the form of MAC CE. When the terminal transmits a message containing information indicating whether it has successfully acquired TA information from a candidate DU in the form of a UCI or MAC message, the message may include information regarding the ID of the candidate DU or candidate cell that transmitted the TA information and information regarding the result indicating whether the terminal succeeded in acquiring the TA information.

[0304] When the above terminal transmits information regarding whether it has successfully obtained TA information from a candidate DU to a source DU in the form of a UCI, the UCI may be an event-driven UCI. Although general methods for transmitting event-driven UCIs are still under standardization, the method proposed in this disclosure for the terminal to transmit information including the result of determining whether it has successfully obtained TA information to a source DU in the form of a UCI may also follow the method determined in standardization.

[0305] When a terminal transmits a message in the form of a UCI containing information on whether it has successfully obtained TA information from a candidate DU, the message may include information regarding the ID of the candidate DU or candidate cell that transmitted the TA information and information regarding the result of the terminal determining whether the TA information acquisition was successful. In this case, the information indicating whether the TA information acquisition was successful may be in the form of the following alternatives.

[0306] - Alternative 1. When reporting the result of obtaining a TA for a single candidate DU or candidate cell (e.g., single result report), the message containing information regarding the result of determining whether the TA information acquisition was successful may include information regarding the success or failure of the TA information acquisition. The message may further include information regarding the candidate cell ID. The information regarding the candidate cell ID may be 3 bits of information. The information regarding the candidate cell ID may be set by configuration information included in the RRC message. The configuration information included in the RRC message may be ltm-CandidateIdList. The information regarding the success or failure of obtaining the TA information may be 1 bit of information indicating 'failure' or 'success'. The case of reporting the result of obtaining a TA for a single candidate DU or candidate cell may correspond to the case where a TA value is measured in a single candidate cell or the case where TA information is obtained from a candidate cell that received the most recent PRACH from the terminal.

[0307] - Alternative 2. When reporting the TA acquisition results for multiple candidate DUs or candidate cells (e.g., multiple results report), the message containing information regarding the success or failure of the TA acquisition may include information regarding each candidate cell ID and information regarding the result of determining the success or failure of the TA acquisition for each candidate cell. In this case, the information regarding each candidate cell ID may be 3 bits. The information regarding each candidate cell ID may be set by the configuration information included in the RRC message. The configuration information included in the RRC message may be ltm-CandidateIdList. The information regarding the result of determining the success or failure of the TA acquisition for each candidate cell may be 1 bit information indicating 'failure' or 'success'. The information regarding each candidate cell may be 4 bits, and thus, if a total of m results are reported, the total information may be 4m bits. The number of candidate cells reporting TA results may be set by the RRC message. The number of candidate cells reporting TA results can be set by the numTAAcquisitionReports setting information, which is an RRC parameter.

[0308] The terminal may transmit information regarding the success or failure of obtaining TA information to the source DU in a MAC message. The MAC message may be a MAC CE.

[0309] When the above terminal transmits information regarding the success or failure of obtaining TA information by including it in MAC CE, it may include a MAC subheader and MAC CE.

[0310] The MAC subheader may include information indicating that the terminal is a message containing information regarding whether the acquisition of TA information was successful. Additionally, the MAC subheader may include a logical channel identifier (LCID) and / or an extended LCID (eLCID). In this case, based on the Release-18 standard, the LCID may be set to reserved indices 37 through 42, and the eLCID may be set to reserved indices 64 through 282.

[0311] FIG. 17 is a diagram illustrating information that may be included when a terminal transmits a message containing information about the success or failure of obtaining TA information in the form of MAC CE.

[0312] FIG. 17 is a diagram illustrating information included in a message containing information regarding whether a terminal succeeded in obtaining TA information, and such information is exemplary. Accordingly, the information illustrated in FIG. 17 may be included in the message or excluded. Additionally, information other than that illustrated in FIG. 17 may be added to the message.

[0313] A message containing information regarding the success or failure of the terminal in acquiring TA information may include a field called Results (1730, 1750, 1770) which represents information regarding the result of determining whether the terminal has successfully acquired TA information transmitted from each candidate cell. Additionally, it may further include a field called Candidate cell ID (1720, 1740, 1760) which represents information regarding the ID of the candidate DU or candidate cell that measured the TA information. If there are multiple candidate cells that measured the TA information and transmitted it to the terminal, the Candidate cell ID (1720, 1740, 1760) may be indicated by multiple fields. It may also include information regarding reserved bits or the number of results determining the success or failure of acquiring TA information.

[0314] R (1700) contains information about reserved bits.

[0315] num (1710) may be information indicating the number of results of determining whether TA information acquisition was successful. This may be the number of result reports and may be up to 3 bits. Therefore, the number of result reports transmitted via MAC CE may be up to 8.

[0316] Candidate cell ID (1720, 1740, 1760) may include information about the ID of a candidate DU or candidate cell that measured TA information. The candidate cell ID may be set by configuration information included in an RRC message. The configuration information included in the RRC message may be ltm-CandidateIdList.

[0317] Results (1730, 1750, 1770) is information regarding the result of determining whether the terminal has successfully obtained TA information transmitted from each candidate cell. The information in Results (1730, 1750, 1770) can be matched for each candidate cell ID. The result may include information indicating success or failure and may be 1 bit. In this case, if the value included in Results (1730, 1750, 1770) is 0, it may be information indicating 'failure', and if it is 1, it may be information indicating 'success'.

[0318] The following describes a resource allocation method for transmitting to a source DU or source cell the result of determining whether a terminal has successfully acquired TA information transmitted from a candidate DU or candidate cell. When information regarding whether the terminal has successfully acquired TA information transmitted from a candidate DU or candidate cell is transmitted to the source DU in the form of a MAC CE, the message may be transmitted in the PUSCH resource area. Therefore, the following describes a method for allocating the PUSCH resource area for transmitting the message.

[0319] First, the PUSCH resource allocation method for transmitting information to the source DU regarding whether the terminal has successfully acquired TA information transmitted from the candidate DU or candidate cell may be the same as the existing uplink resource allocation method. For example, in the existing uplink resource allocation method, the terminal transmits a scheduling request (SR) to the base station, and the base station receiving it may allocate an uplink grant to transmit information regarding whether it has successfully acquired TA information transmitted from the candidate DU or candidate cell. The base station allocating the uplink grant may be the source DU.

[0320] Alternatively, a PUSCH resource allocation method for transmitting information to a source DU regarding whether the terminal has successfully acquired TA information transmitted from a candidate DU or a candidate cell may direct an uplink grant through a message containing TA information received by the terminal from the candidate DU. (e.g., Alternative 2 and / or Alternative 3 of FIG. 15)

[0321] Hereinafter, an uplink grant allocation method proposed in this disclosure is described to transmit information to a source DU regarding whether a terminal has successfully acquired TA information transmitted from a candidate DU or a candidate cell. The uplink grant allocation method may be a method of setting uplink grants in the time and frequency domains in the form of a list.

[0322] FIG. 18 is a diagram illustrating the structure or hierarchy of an RRC message for transmitting uplink grant-related configuration information proposed in the present disclosure.

[0323] The uplink grant-related configuration information proposed in the present disclosure may be resource allocation-related configuration information for transmitting information to a source DU or source cell regarding whether the terminal has successfully acquired TA information transmitted from a candidate DU or candidate cell. The resource allocation-related configuration information may be a method for allocating a PUSCH resource area. To this end, the present disclosure may set up an uplink grant list in the time and frequency domains through configuration information included in an RRC message and transmit it from the source DU to the terminal.

[0324] At this time, the configuration information included in the RRC message may be included in the configuration information for LTM. The configuration information for LTM may be LTM-Config-r18 (1810) IE. At this time, the configuration information included in the RRC message may be included in the configuration information for early synchronization. At this time, the configuration information for performing the early synchronization operation may correspond to ltm-EarlyUL-SyncConfig-r18 (1830) IE within ltm-CandidateToAddModList-r18.

[0325] In addition, since the above configuration information is not a previously defined configuration information, the above configuration information may be included in EarlyUL-PUSCHAllocation (1850) as a new IE. EarlyUL-PUSCHAllocation (1850), which is a new IE for the above configuration information, may be included as a sub-IE of ltm-EarlyUL-SyncConfig-r18 (1830) IE, which is a configuration IE for performing the existing early synchronization operation.

[0326] Examples of configuration information included in the new IE EarlyUL-PUSCHAllocation (1850) for the above configuration information may be as shown in [Table 18] below. The configuration information in [Table 18] below is exemplary, and other configuration information may be added or excluded.

[0327]

[0328] The description of the configuration information in [Table 18] above is as follows. First, pusch-TimeDomainAllocationList can contain the same information as IE for time-domain resource allocation defined in the existing RRC standard specifications.

[0329] - k2 configuration information may correspond to the L1 parameter 'K2' and may include information regarding the slot offset for PUSCH transmission. In this case, if the k2 field is empty (absent), the k2 value may be set as follows: if the PUSCH SCS (subcarrier spacing) is 15 or 30 kHz, the terminal may set or apply the value of the corresponding parameter to 1; if the PUSCH SCS is 60 kHz, the terminal may set the value of the corresponding parameter to 2; and if the PUSCH SCS is 120 kHz, the terminal may set the value of the corresponding parameter to 3. The description of the configuration information may follow the definition in Section 6.1.2.1 of the standard document TS 38.214.

[0330] - The mappingType setting information can set the PUSCH mapping type to be applied for PUSCH transmission. The description of the mappingType setting information may follow the definition in Section 6.1.2.1 of the standard document TS 38.214.

[0331] - The startSymbolAndLength configuration information can set the location of the PUSCH resource when the terminal transmits information about whether it has successfully obtained TA information from the candidate DU through the PUSCH resource.

[0332] pusch-FrequencyDomainAllocationList is a newly proposed IE that can represent configuration information regarding FDRA. This IE may include a RIV (resource indication value) defined in Uplink Resource Allocation Type 1 of Section 6.1.2.2.2 of the standard document TS 38.214. The RIV value is a starting virtual resource block, ) and the length of contiguously allocated resource blocks ( It can correspond to ). RIV can be defined as shown in [Table 19] below.

[0333]

[0334] Hereinafter, a method for obtaining TA information of a terminal proposed in the present disclosure will be described.

[0335] FIG. 19 is a diagram schematically illustrating the TA information transmission method proposed in the present disclosure.

[0336] In the present disclosure, the source DU (1901) may be a source gNB-DU (1901). Herein, the source DU (1901) may mean a source cell or a serving cell. In the present disclosure, the candidate DU (1902) may be a candidate gNB-DU (1902). Herein, the candidate DU (1902) may mean a candidate cell or a target cell. The candidate cell may be a non-serving cell before the terminal (1900) connects to the candidate DU (1902). In the present disclosure, the CU (1903) may be a gNB-CU (1903).

[0337] The terminal (1900) transmits a measurement report to the source DU (1001). The measurement report of the terminal may be an L3 measurement report. The CU (1903) may select a terminal (1900) to perform an LTM operation based on the measurement report of the terminal (1900) connected to the CU (1903). (LTM UE selection) (1910)

[0338] The CU (1903) may determine configuration information for performing an LTM procedure. Alternatively, the candidate DU (1902) may determine configuration information for performing an LTM procedure. (LTM configuration decision) (1930) Configuration information for performing an LTM procedure may be configuration information for performing an early synchronization operation. Configuration information for performing an early synchronization operation may be configuration information for performing an early TA acquisition operation. Specifically, configuration information for performing the LTM procedure may include configuration information for a resource area for transmitting TA information from the candidate DU (1902) to the terminal (1900). Alternatively, configuration information for performing the LTM procedure may include configuration information for a resource area for transmitting information to the source DU (1901) regarding whether the terminal (1900) has successfully acquired TA information from the candidate DU (1902).

[0339] When CU (1903) or candidate DU (1902) determines configuration information to perform the LTM procedure, it can be determined by utilizing F1AP messages.

[0340] If, at step 1931, the CU (1903) determines configuration information to perform the LTM procedure, the CU (1903) may send it to the candidate DU (1902) via the UE CONTEXT SETUP REQUEST message, or at step 1935, the CU (1903) may send it to the candidate DU (1902) via the UE CONTEXT MODIFICATION REQUEST message.

[0341] Alternatively, if the candidate DU (1902) determines configuration information to perform the LTM procedure in step 1932, the candidate DU (1902) may transmit it to the CU (1903) via the UE CONTEXT SETUP RESPONSE message, or in step 1936, the candidate DU (1902) may transmit it to the CU (1903) via the UE CONTEXT MODIFICATION RESPONSE message.

[0342] In step 1933, the CU (1903) may transmit configuration information for performing the LTM procedure, determined by the CU (1903) or the candidate DU (1902), to the source DU (1901). If the configuration information for performing the LTM procedure is determined through a UE CONTEXT SETUP REQUEST message transmitted by the CU (1903) to the candidate DU (1902) or a UE CONTEXT SETUP RESPONSE message transmitted by the candidate DU (1902) to the CU (1903), the CU (1903) may transmit the configuration information for performing the LTM procedure to the source DU (1901) through a UE CONTEXT MODIFICATION REQUEST message. Alternatively, if the CU (1903) determines the configuration information for performing the LTM procedure through the UE CONTEXT MODIFICATION REQUEST message sent by the CU (1903) to the candidate DU (1902) or the UE CONTEXT MODIFICATION RESPONSE message sent by the candidate DU (1902) to the CU (1903) in step 1937, the CU (1903) may send the configuration information for performing the LTM procedure to the source DU (1901) through the UE CONTEXT MODIFICATION REQUEST message.

[0343] A source DU (1901) that has received configuration information for performing an LTM procedure determined by a CU (1903) or a candidate DU (1902) may transmit configuration information for performing an LTM procedure to a terminal (1900). Configuration information for performing an LTM procedure may include configuration information for the candidate DU (1902) to allocate a resource area for transmitting TA information to the terminal (1900). Specifically, configuration information for the candidate DU (1902) to allocate a resource area for transmitting TA information to the terminal (1900) may be configuration information for a PDCCH resource area (or a CORESET resource area for PDCCH) or a PDSCH resource area for transmitting TA information to the terminal (1900). Based on the configuration information for allocating a resource area for transmitting TA information to the terminal (1900) by the above candidate DU (1902), the PDCCH or PDSCH transmitted by the candidate DU (1902) can be allocated to the terminal (1900) connected to the source DU (1901) so that the PDCCH or PDSCH transmitted by the candidate DU (1902) does not conflict with the PDCCH or PDSCH transmitted by the source DU (1901). Accordingly, the configuration information for allocating a resource area for transmitting TA information to the terminal (1900) by the above candidate DU (1902) may be configuration information for allocating a resource area for transmitting the first message to the terminal connected to the serving cell from the non-serving cell.

[0344] Additionally, the configuration information for performing the LTM procedure may include configuration information regarding a resource area for reporting whether the terminal (1900) has succeeded in obtaining TA information from the candidate DU (1902). The configuration information regarding the resource area may be configuration information for PUSCH resource allocation.

[0345] At step 1939, the source DU (1901) may transmit an RRC message (e.g., an RRC reset message) containing configuration information for performing an early TA acquisition operation to the terminal (1900). The RRC message may include configuration information for allocating a resource area for transmitting TA information and configuration information for allocating a resource area for reporting whether the terminal (1900) has succeeded in acquiring TA information from the candidate DU (1902). In this case, the configuration information may be included in the ltm-CandidateToAddModList-r18 IE within the RRC message. In this case, the configuration information may be included in the ltm-EarlyUL-SyncConfig-r18 IE within the RRC message. In this case, the configuration information for allocating a resource area for transmitting TA information may be included in the ltm-EarlyUL-pdcch-Config as a new IE within the RRC message proposed in this disclosure. Additionally, configuration information for allocating a resource area to report the result of determining whether TA information acquisition from candidate DU (1902) was successful may be included in EarlyUL-PUSCHAllocation as a new IE within the RRC message proposed in this disclosure. At this time, uplink grants can be allocated in the frequency and time domains based on the configuration information included in the EarlyUL-PUSCHAllocation IE.

[0346] Subsequently, the terminal (1900), source DU (1901), and / or candidate DU (1902) may perform an early TA acquisition procedure (1940). To do this, the terminal (1900) may transmit a measurement report to the source DU (1901). The measurement report may be an L1 measurement report (1942). This may be an L1 measurement report (1942) for performing an LTM operation.

[0347] At step 1943, the source DU (1901) that receives the measurement report (1942) from the terminal (1900) may decide to perform an early TA acquisition procedure (early TA acquisition decision).

[0348] The source DU (1901) that decides to perform the early TA acquisition procedure in step 1944 may command the terminal (1900) to perform the early TA acquisition operation. At this time, the source DU (1901) may send a PDCCH order to the terminal (1900).

[0349] In step 1946, the terminal (1900) that receives a PDCCH order from the source DU (1901) can send a signal to the candidate DU (1902) to measure the TA value. At this time, the terminal (1900) can send a PRACH to the candidate DU (1902). The candidate DU (1902) that receives the PRACH from the terminal (1900) can measure the TA value.

[0350] In step 1948, the candidate DU (1902) that measured the TA value may transmit TA information containing the measured TA value to the terminal (1900). At this time, the candidate DU (1902) may transmit TA information to the terminal (1900) through a first message containing TA information. At this time, the first message may be transmitted in the form of a DCI or MAC message. The MAC message may be transmitted in the form of a MAC payload.

[0351] Subsequently, the terminal (1900) may report to the source DU (1901) the result of determining whether the TA information acquisition was successful. The terminal (1900) determining whether the TA information acquisition was successful may be for determining whether PRACH retransmission is required for re-receiving the TA information. To this end, the terminal (1900) may determine whether the TA information acquisition was successful. Determining whether the TA information acquisition was successful may be determining whether the reception of the first message in step 1948 was successful. At this time, the terminal (1900) may determine whether the reception of the first message was successful within the occupancy time.

[0352] At step 1950, the terminal (1900) may report to the source DU (1901) the result of determining whether the TA information acquisition was successful. The terminal (1900) may transmit a second message to the source DU (1901) containing information regarding whether the TA information acquisition was successful.

[0353] If the terminal (1900) succeeds in obtaining TA information from the candidate DU (1902), the second message may include information indicating that the result of successfully obtaining TA information has been achieved.

[0354] The source DU (1901), having received information indicating that TA information was successfully acquired in step 1960, can decide whether to perform a cell switch. The decision to perform the cell switch may be an LTM cell switch decision.

[0355] The source DU (1901) that decided to perform an LTM cell switch in step 1970 may transmit a cell switch command to the terminal (1900). The cell switch command may be a cell switch command.

[0356] If the terminal (1900) fails to acquire TA information from the candidate DU (1902), the second message may include information indicating the result that the TA information was not acquired. If the terminal (1900) fails to acquire TA information from the candidate DU (1902), the early TA acquisition procedure (1940) may be repeated. The source DU (1901) that receives the information indicating the result that the TA information was not acquired may instruct the terminal (1900) to re-receive the TA information. To do this, the source DU (1901) may retransmit a PDCCH order to the terminal (1900). The terminal (1900) that receives the PDCCH order (1944) may retransmit PRACH to the candidate DU (1902).

[0357] FIG. 20 is a diagram briefly illustrating a flowchart of a method for a terminal to perform an early TA acquisition operation proposed in the present disclosure.

[0358] In step 2010, the terminal may receive a command from the source DU to perform an LTM procedure. To perform the LTM procedure, the candidate DU may be made to measure TA information. The TA information may be TA information for performing the LTM procedure. The LTM procedure may be a procedure for performing an early TA acquisition operation. The command to perform the LTM procedure received by the terminal from the source DU may be a PDCCH order.

[0359] In step 2030, the terminal may have the candidate DU measure the TA value. To do this, the terminal may transmit a signal to the candidate DU. The signal transmitted may be PRACH. The candidate DU that receives PRACH may measure the TA value.

[0360] In step 2050, the terminal may receive TA information including a measured TA value from the candidate DU. At this time, the terminal may receive a message containing TA information from the candidate DU. The message may be the first message transmitted by the candidate DU to the terminal in step 1948 of FIG. 19. At this time, the first message may be transmitted in the form of a DCI or MAC message. The MAC message may be transmitted in the form of a MAC payload.

[0361] In step 2070, the terminal may report to the source DU the result of whether the TA information acquisition was successful. The terminal determining to the source DU whether the TA information acquisition was successful may be for the purpose of determining whether a PRACH retransmission is necessary for re-receiving the TA information. The terminal may transmit a message to the source DU containing information regarding the success or failure of the TA information acquisition. In this case, the message containing information regarding the result of the success or failure of the TA information acquisition may be the second message transmitted by the terminal to the source DU in step 1950 of FIG. 19. If the terminal succeeds in acquiring the TA information, the second message may include information indicating the success of TA information acquisition, and if the source DU that receives the second message decides to perform a cell switch procedure, it may transmit a cell switch command to the terminal. If the terminal fails to acquire the TA information, the second message may include information indicating the failure of TA information acquisition, and the source DU that receives the second message may instruct the terminal to re-receive the TA information.

[0362] FIG. 21 is a diagram illustrating, in its entirety, a flowchart of a method for a terminal to perform an early TA acquisition operation proposed in the present disclosure.

[0363] In step 2100, the terminal may receive configuration information from the source DU to perform an LTM procedure. The configuration information to perform the LTM procedure may be configuration information to perform an early TA acquisition operation. The configuration information to perform the LTM procedure may include configuration information for allocating a resource area for the candidate DU to transmit TA information to the terminal. The configuration information for allocating a resource area for the candidate DU to transmit TA information to the terminal may be configuration information for a PDCCH resource area (or a CORESET resource area for PDCCH) or a PDSCH resource area for the candidate DU to transmit TA information to the terminal. Based on the configuration information for allocating a resource area for the candidate DU to transmit TA information to the terminal, the PDCCH or PDSCH transmitted by the candidate DU may be allocated to the terminal connected to the source DU so that the PDCCH or PDSCH transmitted by the source DU does not conflict.

[0364] Additionally, the configuration information for performing the LTM procedure may include configuration information for allocating a resource area to report the result of the terminal determining whether it succeeded in obtaining TA information from the candidate DU. The configuration information for allocating a resource area to report the result of the terminal determining whether it succeeded in obtaining TA information from the candidate DU may be configuration information for PUSCH resource allocation.

[0365] At this time, the source DU may transmit an RRC message (e.g., an RRC reset message) containing configuration information for performing the LTM procedure to the terminal. The RRC message may include configuration information for allocating a resource area for transmitting TA information and configuration information for allocating a resource area for reporting the result of the terminal's determination regarding whether the acquisition of TA information from the candidate DU was successful. The configuration information may be included in the ltm-CandidateToAddModList-r18 IE within the RRC reset message. The configuration information may be included in the ltm-EarlyUL-SyncConfig-r18 IE within the RRC message. The configuration information for allocating a resource area for transmitting TA information may be included in ltm-EarlyUL-pdcch-Config as a novel IE within the RRC message proposed in this disclosure. In addition, configuration information for allocating a resource area to report the result of determining whether TA information acquisition from the above candidate DU was successful may be included in EarlyUL-PUSCHAllocation as a new IE within the RRC message proposed in this disclosure. Uplink grants can be allocated in the frequency and time domains based on the configuration information included in the EarlyUL-PUSCHAllocation IE.

[0366] In step 2110, the terminal may transmit a measurement report to the source DU to perform an early TA acquisition procedure. The measurement report may be an L1 measurement report.

[0367] At step 2120, the source DU that receives the measurement report from the terminal may decide to perform an early TA acquisition procedure. The terminal may receive a command from the source DU to perform the early TA acquisition procedure. The command may be a PDCCH order.

[0368] In step 2130, the terminal may transmit a signal to the candidate DU to measure the TA value. The terminal may transmit PRACH to the candidate DU. The candidate DU that receives PRACH from the terminal may measure the TA value.

[0369] In step 2140, the terminal may receive TA information from the candidate DU. The TA information may include the measured TA value. The message containing the TA information may be the first message in step 1948 of FIG. 19. The first message may be transmitted in the form of a DCI or MAC message. The MAC message may be in the form of a MAC payload.

[0370] At step 2150, the terminal can determine whether the acquisition of TA information was successful. The terminal determining whether the acquisition of TA information was successful may be for determining whether PRACH retransmission is required for re-receiving TA information. The terminal determining whether the acquisition of TA information was successful may be for determining whether the reception of the first message was successful. The terminal can determine whether the reception of the first message was successful within the occupancy time.

[0371] In step 2160, the terminal may report to the source DU the result of determining whether the TA information acquisition was successful. The terminal may transmit a message to the source DU containing information regarding whether the TA information acquisition was successful. The message may be the second message transmitted in step 1950 of FIG. 19. If the terminal succeeds in acquiring TA information from the candidate DU, the second message may include information indicating the result that the TA information acquisition was successful.

[0372] At step 2165, the terminal may receive a cell switch command from the source DU that has decided to perform the cell switch procedure. The cell switch command received from the source DU may be a cell switch command for the LTM.

[0373] In step 2170, if the terminal fails to obtain TA information from the candidate DU, the second message may include information indicating the result that TA information was not obtained.

[0374] At step 2175, the terminal can repeat the early TA acquisition procedure. To do this, it can receive a PDCCH order from the source DU. At this time, the terminal can retransmit PRACH to the candidate DU. Through this, it can re-receive TA information from the candidate DU.

[0375] FIG. 22 is a drawing illustrating the structure of a terminal according to one embodiment of the present disclosure.

[0376] Referring to FIG. 22, the terminal may include a transceiver (2210), a control unit (2220), and a storage unit (2230). In the present disclosure, the control unit may be defined as a circuit or an application-specific integrated circuit or at least one processor.

[0377] The transceiver (2210) can transmit and receive signals with other network entities. The transceiver (2210) can, for example, transmit measurement reports to a base station and transmit and receive RRC messages. Additionally, the transceiver (2210) can, for example, receive a message containing TA information from a base station and transmit a message containing information on the successful acquisition result.

[0378] The control unit (2220) can control the overall operation of the terminal according to the embodiment proposed in the present disclosure. For example, the control unit (2220) can control the signal flow between each block to perform operations according to the flowchart described above. According to one embodiment, the control unit (2220) can determine whether the acquisition of TA information from the base station was successful and control the transmission of information including the result to the base station.

[0379] The storage unit (2230) can store at least one of the information transmitted and received through the transmission and reception unit (2210) and the information generated through the control unit (2220).

[0380] FIG. 23 is a drawing illustrating the structure of a base station according to one embodiment of the present disclosure. Meanwhile, according to one embodiment, FIG. 23 may be a CU entity or a DU entity.

[0381] Referring to FIG. 23, the base station may include a transceiver (2310), a control unit (2320), and a storage unit (2330). In the present disclosure, the control unit may be defined as a circuit or an application-specific integrated circuit or at least one processor.

[0382] The transmitting and receiving unit (2310) can transmit and receive signals with other network entities. The transmitting and receiving unit (2310) can, for example, transmit an RRC message to a terminal. The transmitting and receiving unit (2310) can, for example, transmit TA information to a terminal.

[0383] The control unit (2320) can control the overall operation of the base station according to the embodiment proposed in the present disclosure. For example, the control unit (2320) can control the signal flow between each block to perform operations according to the flowchart described above. Specifically, in the case of a CU entity, the control unit (2320) can control the generation of configuration information for allocating resources to transmit TA information to a terminal according to the embodiment of the present disclosure and transmit it to the source DU. In addition, in the case of a candidate DU entity, the control unit (2320) can control the generation of a message containing TA information to the terminal according to the embodiment of the present disclosure and transmit it. In addition, in the case of a source DU entity, the control unit (2320) can control the transmission of an RRC message containing configuration information related to LTM to the terminal according to the embodiment of the present disclosure.

[0384] The storage unit (2330) can store at least one of the information transmitted and received through the transmission and reception unit (2310) and the information generated through the control unit (2320).

[0385] In the specific embodiments of the present disclosure described above, the components included in the disclosure are expressed in a singular or plural form according to the specific embodiments presented. However, the singular or plural expression is selected to suit the situation presented for convenience of explanation, and the present disclosure is not limited to singular or plural components; even if a component is expressed in the plural form, it may be composed of a singular form, and even if a component is expressed in the singular form, it may be composed of a plural form.

[0386] Methods according to the embodiments described in the claims or specification of the present disclosure may be implemented in the form of hardware, software, or a combination of hardware and software.

[0387] When implemented in software, a computer-readable storage medium may be provided for storing one or more programs (software modules). One or more programs stored in the computer-readable storage medium are configured for execution by one or more processors within an electronic device. One or more programs include instructions that cause the electronic device to execute methods according to the embodiments described in the claims or specification of this disclosure.

[0388] Such programs (software modules, software) may be stored in random access memory, non-volatile memory including flash memory, ROM (Read Only Memory), Electrically Erasable Programmable Read Only Memory (EEPROM), magnetic disc storage devices, Compact Disc-ROM (CD-ROM), Digital Versatile Discs (DVDs), or other forms of optical storage devices, magnetic cassettes. Alternatively, they may be stored in memory composed of some or all of these. Additionally, each constituent memory may include multiple units.

[0389] Additionally, the program may be stored on an attachable storage device that can be accessed via a communication network such as the Internet, Intranet, Local Area Network (LAN), Wide LAN (WLAN), or Storage Area Network (SAN), or a combination thereof. Such a storage device may be connected to a device performing an embodiment of the present disclosure through an external port.

[0390] In addition, a separate storage device on a communication network may be connected to the device performing the embodiment of the present disclosure.

[0391] In the specific embodiments of the present disclosure described above, the components included in the present disclosure are expressed in a singular or plural form according to the specific embodiments presented. However, the singular or plural expression is selected to suit the situation presented for convenience of explanation, and the present disclosure is not limited to singular or plural components; even if a component is expressed in the plural, it may be composed of a singular form, and even if a component is expressed in the singular form, it may be composed of a plural form.

[0392] Meanwhile, the embodiments of the present disclosure disclosed in this specification and drawings are merely specific examples provided to facilitate the explanation of the technical content of the present disclosure and to aid in understanding the present disclosure, and are not intended to limit the scope of the present disclosure. That is, it is obvious to those skilled in the art that other variations based on the technical concept of the present disclosure are possible.

[0393] In addition, each of the above embodiments can be combined and operated as needed.

[0394] Meanwhile, the order of description in the drawings illustrating the method of the present disclosure does not necessarily correspond to the order of execution, and the order of execution may be changed or executed in parallel.

[0395] Alternatively, drawings describing the method of the present disclosure may omit some components and include only some components to the extent that the essence of the present disclosure is not impaired.

[0396] In addition, the method of the present disclosure may be practiced by combining some or all of the contents included in each embodiment to the extent that it does not impair the essence of the present disclosure.

[0397] Meanwhile, the embodiments of the present disclosure disclosed in this specification and drawings are merely specific examples provided to facilitate the explanation of the technical content of the present disclosure and to aid in understanding the present disclosure, and are not intended to limit the scope of the present disclosure. That is, it is obvious to those skilled in the art that other variations based on the technical concept of the present disclosure are possible. Furthermore, each of the above embodiments may be combined and operated together as needed. For example, parts of all embodiments of the present disclosure may be combined and operated together.

Claims

1. A method performed by a terminal of a wireless communication system, A step of receiving a PDCCH (physical downlink control channel) order from a source DU (distributed unit) entity; A step of transmitting PRACH (physical random access channel) to a candidate DU entity; A step of receiving a first message containing TA (timing advance) information for LTM (L1 / L2 triggered mobility) from the above candidate DU entity; and A method comprising the step of transmitting a second message to the source DU entity, the second message including information regarding the success or failure of obtaining the TA information.

2. In Paragraph 1, If the acquisition of the TA information from the candidate DU entity is successful, the step of receiving a cell switch command from the source DU entity; and A method further comprising the step of transmitting the PRACH to the candidate DU entity when the acquisition of the TA information from the candidate DU entity fails.

3. In Paragraph 1, The above first message corresponds to a DCI (downlink control information) or MAC (medium access control) message, and The above second message is a method corresponding to UCI (uplink control information) or MAC messages.

4. In Paragraph 1, The method further includes the step of receiving a radio resource control (RRC) message containing LTM-related configuration information from the source DU entity, and A method in which the above LTM-related configuration information includes configuration information for a control channel area for receiving the above first message from the above candidate DU entity via PDCCH.

5. In Paragraph 4, The above LTM-related configuration information includes at least one of configuration information for a resource area for receiving the first message from the candidate DU entity via a PDSCH (physical downlink shared channel) or configuration information for a resource area for transmitting the second message to the source DU entity via a PUSCH (physical uplink shared channel). The configuration information for a control channel area for receiving the first message from the candidate DU entity via PDCCH sets a first control channel area for receiving PDCCH from the candidate DU entity, and the second control channel area for receiving PDCCH from the source DU entity and the first control channel area do not overlap, and A method in which the configuration information for a resource area for receiving the first message from the candidate DU entity via PDSCH sets a first data channel area for receiving PDSCH from the candidate DU entity, and the first data channel area does not overlap with the second data channel area for receiving PDSCH from the source DU entity.

6. In Paragraph 4, The above LTM-related configuration information includes information regarding the acquisition window for occupying downlink resources to receive the first message, and A method for determining the success or failure of acquiring the TA information based on the time spent occupying the downlink resource.

7. In Paragraph 1, The uplink transmission resource for transmitting the above second message is, If the above first message does not include information regarding the uplink transmission resource area, it is allocated from the source DU entity, or Based on the above LTM-related configuration information, a list of uplink transmission resource areas available to the terminal is configured, and an index for the list of uplink transmission resource areas available to the terminal is indicated in a field within the first message, or A method indicated by configuration information regarding uplink transmission resources included in the first message above.

8. In Paragraph 1, A method in which, when the terminal receives the TA information from a plurality of candidate DU entities, the second message includes identifier (ID) information for each of the plurality of candidate DU entities and information regarding whether the terminal succeeded in obtaining the TA information for each of the plurality of candidate DU entities.

9. A method performed by a source DU (distributed unit) entity of a wireless communication system, A step of transmitting an RRC (radio resource control) message containing LTM (L1 / L2 triggered mobility) related configuration information to a terminal; A step of transmitting a PDCCH (physical downlink control channel) order to the above terminal; and The method includes the step of receiving a second message from the terminal, A method in which the second message above includes information on whether the terminal has successfully received TA (timing advance) information for LTM from the candidate DU entity in response to a PRACH (physical random access channel) transmitted by the terminal to the candidate DU entity based on the PDCCH command.

10. In Paragraph 9, The above LTM-related configuration information includes configuration information for a control channel area for receiving the first message from the candidate DU entity via PDCCH, and The configuration information for a control channel area for receiving the first message from the candidate DU entity via PDCCH comprises: the terminal setting a first control channel area for receiving PDCCH from the candidate DU entity; and the second control channel area for receiving PDCCH from the source DU entity and the first control channel area do not overlap. The above LTM-related configuration information includes at least one of configuration information for a resource area for receiving the first message from the candidate DU entity via a PDSCH (physical downlink shared channel) or configuration information for a resource area for transmitting the second message to the source DU entity via a PUSCH (physical uplink shared channel), and A method in which the configuration information for a resource area for receiving the first message from the candidate DU entity via PDSCH is configured such that the terminal sets a first data channel area for receiving PDSCH from the candidate DU entity, and the first data channel area does not overlap with the second data channel area for receiving PDSCH from the source DU entity.

11. In Paragraph 9, If the second message includes information indicating that the terminal succeeded in acquiring TA information, the step of transmitting a cell switch command to the terminal; and A method further comprising the step of transmitting the PDCCH command to the terminal when the second message contains information indicating that the terminal failed to acquire TA information.

12. In a terminal of a wireless communication system, At least one transceiver; At least one processor connected to the above at least one transceiver so as to be able to communicate; and The terminal is connected to communicate with at least one processor and is capable of executing individually or in any combination of the at least one processor, so that the terminal, Receives a PDCCH (physical downlink control channel) order from a source DU (distributed unit) entity, and Transmit PRACH (physical random access channel) to the candidate DU entity, and Receiving a first message containing TA (timing advance) information for LTM (L1 / L2 triggered mobility) from the above candidate DU entity, and A memory storing a command to transmit a second message containing information regarding the success or failure of acquiring the TA information from the source DU entity; A terminal including 13. In claim 12, the instruction executable by at least one processor individually or in any combination thereof is, said terminal, If the acquisition of the TA information from the source DU entity is successful, a cell switch command is received from the source DU entity, and A terminal characterized by further transmitting the PRACH to the candidate DU entity when the acquisition of the TA information from the source DU entity fails.

14. In a source DU (distributed unit) entity of a wireless communication system, At least one transceiver; At least one processor connected to the above at least one transceiver so as to be able to communicate; and The source DU entity is connected to communicate with at least one processor and is executable individually or in any combination of the at least one processor, so that the source DU entity Transmit a radio resource control (RRC) message containing LTM (L1 / L2 triggered mobility) related configuration information to the terminal, and Transmitting a PDCCH (physical downlink control channel) order to the above terminal; and A memory storing a command to receive a second message from the terminal; is included, The second message above is a source DU entity containing information on whether the terminal has successfully received TA (timing advance) information for LTM from the candidate DU entity in response to a PRACH (physical random access channel) transmitted by the terminal to the candidate DU entity based on the PDCCH command.

15. In Paragraph 14, The above LTM-related configuration information includes configuration information for a control channel area for receiving the first message from the candidate DU entity via PDCCH, and The configuration information for a control channel area for receiving the first message from the candidate DU entity via PDCCH comprises: the terminal setting a first control channel area for receiving PDCCH from the candidate DU entity; and the second control channel area for receiving PDCCH from the source DU entity and the first control channel area do not overlap. The above LTM-related configuration information includes at least one of configuration information for a resource area for receiving the first message from the candidate DU entity via a PDSCH (physical downlink shared channel) or configuration information for a resource area for transmitting the second message to the source DU entity via a PUSCH (physical uplink shared channel), and The configuration information for a resource area for receiving the first message from the candidate DU entity via PDSCH comprises a first data channel area for the terminal to receive PDSCH from the candidate DU entity, and a source DU entity for which the second data channel area for the terminal to receive PDSCH from the source DU entity and the first data channel area do not overlap.

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