Method and apparatus for performing carrier aggregation and dual connectivity in ntn system

Abstract

The present disclosure relates to a 5G or 6G communication system for supporting a higher data transmission rate. A method for processing control signals in a wireless communication system according to one embodiment disclosed herein is characterized by comprising the steps of: receiving a first control signal transmitted from a base station; processing the received first control signal; and transmitting a second control signal generated on the basis of the processing to the base station.

Description

Method and apparatus for performing carrier integration and multiple connections in an NTN system

[0001] The present disclosure relates to the operation of terminals and base stations in a mobile communication system. More specifically, the present disclosure relates to a method and apparatus for performing Carrier Aggregation (CA) and / or Dual Connectivity in a Non-Terrestrial Network (NTN) system.

[0002] 5G mobile communication technology defines a wide frequency band to enable fast transmission speeds and new services, and can be implemented not only in frequency bands below 6 GHz ('Sub 6 GHz'), such as 3.5 gigahertz (3.5 GHz), but also in ultra-high frequency bands called millimeter waves (mmWave), such as 28 GHz and 39 GHz ('Above 6 GHz'). In addition, for 6G mobile communication technology, which is referred to as a system beyond 5G, implementation in the terahertz band (e.g., the 3 terahertz (3 THz) band at 95 GHz) is being considered to achieve transmission speeds 50 times faster and ultra-low latency reduced to one-tenth compared to 5G mobile communication technology.

[0003] In the early stages of 5G mobile communication technology, aiming to satisfy service support and performance requirements for enhanced Mobile BroadBand (eMBB), Ultra-Reliable Low-Latency Communications (URLLC), and massive Machine-Type Communications (mMTC), technologies such as beamforming and Massive MIMO to mitigate path loss and increase transmission distance in ultra-high frequency bands, support for various numerologies (such as the operation of multiple subcarrier spacings) and dynamic operation of slot formats for the efficient utilization of ultra-high frequency resources, initial access techniques to support multi-beam transmission and broadband, definition and operation of Band-Width Parts (BWP), Low Density Parity Check (LDPC) codes for high-volume data transmission, new channel coding methods such as Polar Codes for the reliable transmission of control information, and L2 pre-processing (L2 Standardization has been carried out for pre-processing, network slicing which provides a dedicated network specialized for specific services, and other methods.

[0004] Currently, discussions are underway to improve and enhance the performance of the initial 5G mobile communication technology, taking into account the services that the 5G mobile communication technology was intended to support. Additionally, standardization of the physical layer is in progress for technologies such as V2X (Vehicle-to-Everything), which helps autonomous vehicles make driving decisions and enhance user convenience based on their own location and status information transmitted by the vehicle; NR-U (New Radio Unlicensed), which aims for system operation in unlicensed bands to comply with various regulatory requirements; NR terminal low power consumption technology (UE Power Saving); Non-Terrestrial Network (NTN), which is direct terminal-satellite communication for securing coverage in areas where communication with the terrestrial network is impossible; and positioning.

[0005] In addition, standardization is underway in the field of wireless interface architecture / protocols for technologies such as the Industrial Internet of Things (IoT) to support new services through linkage and convergence with other industries, Integrated Access and Backhaul (IAB) which provides nodes to expand network service areas by integrating wireless backhaul links and access links, Mobility Enhancement including Conditional Handover (CHO) and Dual Active Protocol Stack (DAPS) handover, and 2-step Random Access (2-step RACH for NR) which simplifies random access procedures. Standardization is also underway in the field of system architecture / services for 5G baseline architectures (e.g., Service based Architecture, Service based Interface) for the integration of Network Functions Virtualization (NFV) and Software-Defined Networking (SDN) technologies, and Mobile Edge Computing (MEC), which provides services based on the location of the terminal.

[0006] When such 5G mobile communication systems are commercialized, connected devices, which are increasing explosively, will be connected to communication networks. Accordingly, it is expected that there will be a need to enhance the functionality and performance of 5G mobile communication systems and to integrate the operation of connected devices. To this end, new research is planned to be conducted on 5G performance improvement and complexity reduction, support for AI services, support for metaverse services, and drone communication using eXtended Reality (XR), Artificial Intelligence (AI), and Machine Learning (ML) to efficiently support Augmented Reality (AR), Virtual Reality (VR), and Mixed Reality (MR).

[0007] Furthermore, the advancement of these 5G mobile communication systems encompasses multi-antenna transmission technologies such as new waveforms to guarantee coverage in the terahertz band of 6G mobile communication technology, Full Dimensional MIMO (FD-MIMO), array antennas, and large-scale antennas; metamaterial-based lenses and antennas to improve terahertz band signal coverage; high-dimensional spatial multiplexing technology using OAM (Orbital Angular Momentum); and Reconfigurable Intelligent Surface (RIS) technology; as well as Full Duplex technology for enhancing frequency efficiency and system networks in 6G mobile communication technology; AI-based communication technologies that realize system optimization by utilizing satellites and AI from the design stage and internalizing end-to-end AI support functions; and the realization of services of complexity exceeding the limits of terminal computing capabilities by utilizing ultra-high-performance communication and computing resources. It could serve as a foundation for the development of next-generation distributed computing technologies.

[0008] As a result of the aforementioned developments and advancements in mobile communication systems, it has become possible to provide a variety of services, and thus measures to effectively provide these services are required.

[0009] The present disclosure aims to provide an apparatus and a method capable of effectively providing a service for performing Carrier Aggregation (CA) and / or Dual Connectivity in a Non-Terrestrial Network (NTN) system.

[0010] The technical problems to be solved in the embodiments of the present disclosure are not limited to those mentioned above, and other technical problems not mentioned will be clearly understood by those skilled in the art to which the present disclosure belongs from the description below.

[0011] According to one embodiment of the present disclosure, a method is proposed to be performed by a terminal in a communication system to solve the aforementioned problems. More specifically, the method is characterized by comprising the steps of receiving configuration information for setting Carrier Aggregation (CA) or Dual Connectivity (DC) in a Non-Terrestrial Network (NTN) from a first satellite supporting a first cell, determining satellite reference time information (Epoch Time) of a second cell, determining propagation delay difference information for the second cell based on a reference serving cell based on the satellite reference time information of the second cell, and transmitting first control information including propagation delay difference information for the second cell to the first satellite supporting the first cell or the second satellite supporting the second cell.

[0012] According to another embodiment of the present disclosure, in order to solve the aforementioned problems, a method is proposed that is performed by a first satellite supporting a first cell in a communication system. More specifically, the method comprises the steps of: transmitting configuration information to a terminal for setting Carrier Aggregation (CA) or Dual Connectivity (DC) in a Non-Terrestrial Network (NTN); and receiving first control information from the terminal that includes propagation delay difference information for a second cell, wherein the propagation delay difference information for the second cell is determined based on the satellite reference time information (Epoch Time) of the second cell with respect to a reference serving cell.

[0013] In order to solve the aforementioned problems, according to another embodiment of the present disclosure, a terminal in a communication system is proposed. More specifically, the terminal comprises at least one transceiver; and at least one processor connected to the at least one transceiver so as to be able to communicate with the at least one transceiver. and a memory that is connected to communicate with at least one processor and is executable individually or in any combination of the at least one processor, wherein the terminal receives configuration information for setting Carrier Aggregation (CA) or Dual Connectivity (DC) in a Non-Terrestrial Network (NTN) from a first satellite supporting a first cell, determines satellite reference time information (Epoch Time) of a second cell, determines propagation delay difference information for the second cell based on a reference serving cell based on the satellite reference time information of the second cell, and stores a command to transmit first control information including propagation delay difference information for the second cell to the first satellite supporting the first cell or the second satellite supporting the second cell.

[0014] According to another embodiment of the present disclosure, in order to solve the aforementioned problems, a first satellite in a communication system is proposed. More specifically, the first satellite comprises: at least one transceiver; at least one processor connected to the at least one transceiver so as to be communicable; and a memory connected to the at least one processor so as to be communicable and capable of executing the at least one processor individually or in any combination thereof, wherein the first satellite transmits configuration information to a terminal for setting up Carrier Aggregation (CA) or Dual Connectivity (DC) in a Non-Terrestrial Network (NTN), and receives first control information including propagation delay difference information for a second cell from the terminal; wherein the propagation delay difference information for the second cell is determined based on the satellite reference time information (Epoch Time) of the second cell with respect to a reference serving cell.

[0015] According to one embodiment of the present disclosure, a service for performing Carrier Aggregation (CA) and / or Dual Connectivity in a Non-Terrestrial Network (NTN) system can be effectively performed.

[0016] The effects obtainable in the present disclosure are not limited to those mentioned in the various embodiments, and other unmentioned effects will be clearly understood by those skilled in the art to which the present disclosure pertains from the description below.

[0017] FIG. 1a is a drawing illustrating the structure of a next-generation mobile communication system according to one embodiment of the present disclosure.

[0018] FIG. 1b is a drawing for explaining a random access process according to one embodiment of the present disclosure.

[0019] FIG. 1c is a drawing for explaining a Non-Terrestrial Network (NTN) according to one embodiment of the present disclosure.

[0020] FIG. 1d is a drawing illustrating the format of a Timing Advance Report Medium Access Control (MAC) Control Element (CE) according to one embodiment of the present disclosure.

[0021] FIG. 1e is a flowchart of a process for performing a Random Access Channel (RACH)-less handover in a mobile communication system according to one embodiment of the present disclosure.

[0022] FIG. 1f is a diagram illustrating a scenario supporting Carier Aggregation (CA) and / or Dual Connectivity (DC) in a Non-Terrestrial Network (NTN) according to one embodiment of the present disclosure.

[0023] FIG. 1g is a flowchart of an operation for providing satellite switching configuration information in a Carrier Aggregation (CA) and / or Dual Connectivity (DC) scenario of a non-terrestrial network (NTN) according to one embodiment of the present disclosure.

[0024] FIG. 1h is a flowchart of a process for performing Carrier Aggregation (CA) and / or Dual Connectivity (DC) of a Non-Terrestrial Network (NTN) according to one embodiment of the present disclosure.

[0025] FIG. 1i is a drawing for illustrating the format of an extended Timing Advance Report Medium Access Control (MAC) Control Element (CE) according to one embodiment of the present disclosure.

[0026] FIG. 1j is a flowchart of a process for performing Early TA reporting to support Carrier Aggregation (CA) and / or Dual Connectivity (DC) of a Non-Terrestrial Network (NTN) according to one embodiment of the present disclosure.

[0027] FIG. 1k is a flowchart of a terminal operation performing Carrier Aggregation (CA) and / or Dual Connectivity (DC) of a Non-Terrestrial Network (NTN) according to one embodiment of the present disclosure.

[0028] FIG. 11 is a flowchart of base station operations for performing Carrier Aggregation (CA) and / or Dual Connectivity (DC) of a Non-Terrestrial Network (NTN) according to one embodiment of the present disclosure.

[0029] FIG. 1m is a flowchart of a process for performing a Non-Terrestrial Network (NTN) Random Access Channel (RACH)-less handover according to one embodiment of the present disclosure.

[0030] FIG. 1n is a diagram illustrating a method for deriving terminal location-based Timing Advance (TA) in a Non-Terrestrial Network (NTN) Random Access Channel (RACH)-less handover according to one embodiment of the present disclosure.

[0031] FIG. 10 is a flowchart of a terminal operation performing a Non-Terrestrial Network (NTN) Random Access Channel (RACH)-less handover according to one embodiment of the present disclosure.

[0032] FIG. 1p is a flowchart of base station operations performing a Non-Terrestrial Network (NTN) Random Access Channel (RACH)-less handover according to one embodiment of the present disclosure.

[0033] FIG. 1Q is a block diagram illustrating the internal structure of a terminal according to one embodiment of the present disclosure.

[0034] FIG. 1r is a block diagram illustrating the configuration of a base station according to one embodiment of the present disclosure.

[0035] In the following description of the present invention, if it is determined that a detailed description of related known functions or configurations may unnecessarily obscure the essence of the present invention, such detailed description will be omitted. Embodiments of the present invention will be described below with reference to the attached drawings. Although the present invention is based on an LTE system, it is also applicable to other mobile communication systems, such as NR, which is a next-generation mobile communication system. For example, in the present invention, the eNB in ​​LTE corresponds to the gNB in ​​NR, and the MME in LTE corresponds to the AMF in NR.

[0036] In describing the embodiments, 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. This is intended to convey the essence of this disclosure more clearly without obscuring it by omitting unnecessary explanations.

[0037] 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 numbers.

[0038] 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. 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 ensure that the disclosure is complete 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, the same reference numerals refer to the same components. Furthermore, in describing the present disclosure, if it is determined that a detailed description of related functions or configurations might unnecessarily obscure the essence of the present disclosure, such detailed description is omitted. Additionally, the terms described below are defined considering their functions in the present disclosure, and these may vary depending on the intentions or conventions of the user or operator. Therefore, their definitions should be based on the content throughout the specification.

[0039] Hereinafter, a base station is an entity that performs resource allocation for terminals and may be at least one of a gNode B, eNode B, Node B, BS (Base Station), wireless access unit, base station controller, or a node on a network. A terminal may include a UE (User Equipment), MS (Mobile Station), cellular phone, smartphone, computer, or a multimedia system capable of performing communication functions. In this disclosure, a downlink (DL) refers to a wireless transmission path for a signal transmitted by a base station to a terminal, and an uplink (UL) refers to a wireless transmission path for a signal transmitted by a terminal to a base station. Furthermore, while LTE (Long-Term Evolution), LTE-A (LTE-Advanced), or 5G systems may be described as examples below, embodiments of this disclosure may also be applied to other communication systems having similar technical backgrounds or channel types. For example, 5th generation mobile communication technologies (5G, new radio, NR) developed after LTE-A may be included, and the 5G below may be a concept that includes existing LTE, LTE-A, and other similar services. Furthermore, the present disclosure may be applied to other communication systems with some modifications made at the discretion of a person with skilled technical knowledge, without significantly departing from the scope of the present disclosure. The contents of the present disclosure are applicable to FDD and TDD systems.

[0040] At this point, 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 that can be directed toward the computer or other programmable data processing equipment to implement the function in a specific way, the instructions stored in computer-available or computer-readable memory can also produce a manufactured item containing instruction means to perform the function 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).

[0041] Additionally, each block may represent a module, segment, or part of code containing one or more executable instructions for executing a specific 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 example, two blocks described in succession may actually be executed substantially simultaneously, or the blocks may sometimes be executed in reverse order according to their corresponding functions.

[0042] In this embodiment, the term "part" refers to a software or hardware component such as an FPGA (Field Programmable Gate Array) or an ASIC (Application Specific Integrated Circuit), 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 or 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 utilize one or more CPUs (central processing units) within the device or secure multimedia card. Furthermore, in the embodiment, the 'part' may include one or more processors.

[0043] Wireless communication systems are evolving from providing early voice-oriented services to broadband wireless communication systems that provide high-speed, high-quality packet data services, such as communication standards like 3GPP’s HSPA (High Speed ​​Packet Access), LTE (Long Term Evolution or E-UTRA (Evolved Universal Terrestrial Radio Access)), LTE-Advanced (LTE-A), LTE-Pro, 3GPP2’s HRPD (High Rate Packet Data), UMB (Ultra Mobile Broadband), and IEEE’s 802.16e.

[0044] As a representative example of the above-mentioned broadband wireless communication system, the LTE system employs the Orthogonal Frequency Division Multiplexing (OFDM) method for the downlink (DL) and the Single Carrier Frequency Division Multiple Access (SC-FDMA) method for the uplink (UL). The uplink refers to a wireless link through which a terminal (User Equipment (UE) or Mobile Station (MS)) transmits data or control signals to a base station (eNode B, gNode B, or base station (BS)), and the downlink refers to a wireless link through which a base station transmits data or control signals to a terminal. The above-mentioned multiple access method can distinguish the data or control information of each user by allocating and operating time-frequency resources to be sent for each user so that they do not overlap, that is, so that orthogonality is established.

[0045] As a future communication system following LTE, that is, a 5G communication system, it must be able to freely reflect the diverse requirements of users and service providers, and therefore, services that satisfy various requirements simultaneously must be supported. Services being considered for the 5G communication system include enhanced Mobile Broadband (eMBB), massive Machine Type Communication (mMTC), and Ultra Reliability Low Latency Communication (URLLC).

[0046] eMBB aims to provide data transmission speeds that are superior to those supported by existing LTE, LTE-A, or LTE-Pro. For example, in a 5G communication system, eMBB must be able to provide a peak data rate of 20 Gbps in the downlink and 10 Gbps in the uplink from the perspective of a single base station. Furthermore, while providing these peak data rates, the 5G communication system must also provide an increased user-perceived data rate. To satisfy these requirements, it necessitates improvements in various transmission and reception technologies, including enhanced Multi-Input Multi-Output (MIMO) transmission technology. Additionally, while LTE transmits signals using a maximum bandwidth of 20 MHz in the 2 GHz band, the 5G communication system can meet the data transmission speeds required by using a frequency bandwidth wider than 20 MHz in frequency bands of 3–6 GHz or above 6 GHz.

[0047] Simultaneously, mMTC is being considered to support application services such as the Internet of Things (IoT) in 5G communication systems. To efficiently provide IoT, mMTC requires support for a large number of terminal connections within a cell, improved terminal coverage, enhanced battery life, and reduced terminal costs. Since IoT devices are attached to various sensors and equipment to provide communication functions, the system must be able to support a large number of terminals within a cell (e.g., 1,000,000 terminals / km²). Furthermore, due to the nature of the service, terminals supporting mMTC are likely to be located in dead zones not covered by cells, such as building basements; therefore, they may require wider coverage compared to other services provided by 5G communication systems. Terminals supporting mMTC must consist of low-cost devices, and since it is difficult to frequently replace terminal batteries, a very long battery life of 10 to 15 years may be required.

[0048] Finally, URLLC is a mission-critical cellular-based wireless communication service. Examples include services used for remote control of robots or machinery, industrial automation, unmanned aerial vehicles, remote health care, and emergency alerts. Therefore, the communication provided by URLLC must offer very low latency and very high reliability. For instance, services supporting URLLC must satisfy an air interface latency of less than 0.5 milliseconds and simultaneously require a packet error rate of 10^-5 or less. Consequently, for services supporting URLLC, 5G systems must provide a Transmission Time Interval (TTI) smaller than other services, and design considerations may be required to allocate wide resources within the frequency band to ensure the reliability of the communication link.

[0049] The three 5G services, namely eMBB, URLLC, and mMTC, can be multiplexed and transmitted within a single system. In this case, different transmission and reception techniques and parameters may be used between the services to satisfy the different requirements of each service. Of course, 5G is not limited to the three services mentioned above.

[0050] FIG. 1a is a drawing illustrating the structure of a next-generation mobile communication system according to one embodiment of the present disclosure.

[0051] Referring to FIG. 1a, as illustrated, the wireless access network of the next-generation mobile communication system (New Radio, NR) consists of a next-generation base station (New Radio Node B, hereinafter gNB) (1a-10) and an Access and Mobility Management Function (AMF) (1a-05, New Radio Core Network). A user terminal (New Radio User Equipment, hereinafter NR UE or terminal) (1a-15) can connect to an external network through the gNB (1a-10) and the AMF (1a-05).

[0052] In FIG. 1a, the gNB corresponds to the eNB (Evolved Node B) of the existing LTE system. The gNB is connected to the NR UE via a wireless channel and can provide superior service compared to the existing Node B (1a-20). In next-generation mobile communication systems, since all user traffic is serviced through a shared channel, a device is required to perform scheduling by collecting state information such as the buffer status, available transmission power status, and channel status of the UEs, and this is handled by the gNB (1a-10). A single gNB can typically control multiple cells. To achieve ultra-high-speed data transmission compared to existing LTE, it can have a maximum bandwidth greater than that of existing LTE, and beamforming technology can be additionally incorporated by using Orthogonal Frequency Division Multiplexing (hereinafter referred to as OFDM) as the wireless access technology. Additionally, an Adaptive Modulation & Coding (hereinafter referred to as AMC) method can be applied to determine the modulation scheme and channel coding rate according to the terminal's channel status.

[0053] The AMF (1a-05) performs functions such as mobility support, bearer configuration, and Quality of Service (QoS) configuration. The AMF is a device responsible for various control functions as well as mobility management functions for the terminal, and is connected to multiple base stations. In addition, the next-generation mobile communication system can be interconnected with the existing LTE system, and the AMF is connected to the MME (1a-25) via a network interface. The MME is connected to the existing base station, eNB (1a-30). A terminal supporting LTE-NR Dual Connectivity can transmit and receive data while maintaining a connection to both the gNB and the eNB (1a-35).

[0054] FIG. 1b is a drawing for explaining a random access process according to one embodiment of the present disclosure.

[0055] Random access can be performed when synchronizing the uplink or transmitting data over the network. More specifically, it can be performed when switching from standby mode to connected mode, when performing RRC re-establishment, when performing a handover, or when starting uplink and downlink data.

[0056] When the terminal (1b-05) receives a dedicated preamble from the base station (1b-10), it can apply the preamble and transmit the preamble. Otherwise, the terminal can select one of two preamble groups and select a preamble belonging to the selected group. The groups are referred to as group A and group B. If the channel quality condition is better than a specific threshold and the size of msg 3 is greater than the specific threshold, the preamble belonging to group B is selected, otherwise the preamble belonging to group A is selected.

[0057] In step 1b-15, if the terminal (1b-05) has transmitted the preamble in the n-th subframe, a Random Access Response (RAR) window is started from the n+3-th subframe, and in step 1b-20, whether a RAR is transmitted within the window time interval can be monitored. The scheduling information for the RAR is indicated by the Random Access - Radio Network Temporary Identifier (RA-RNTI) of the Physical Downlink Control Channel (PDCCH). The RA-RNTI is derived using the radio resource location in the time and frequency axes that was used to transmit the preamble. The RAR includes a Timing Advance, a UL grant, and a temporary C-RNTI. The Timing Advance information is used to determine the timing when the terminal transmits an uplink signal.

[0058] If the above RAR is successfully received in the above RAR window, in step 1b-25, the terminal (1b-05) can transmit msg3 using the UL grant information included in the RAR.

[0059] Msg3 contains other information depending on the purpose of the above random access. [Table 1] below is an example of information that may be included in msg 3.

[0060] [Table 1] Examples of information included in msg3

[0061]

[0062] Msg3 is transmitted in the (n+6)th subframe if a RAR is received in the nth subframe. Hybrid Automatic Repeat Request (HARQ) is applied starting from Msg3.

[0063] In step 1b-30, the terminal (1b-05) starts a specific timer after transmitting Msg3 and monitors Contention Resolution (CR) messages until the timer expires (1b-30). In addition to CR MAC CE, the CR messages may include RRC Connection Setup or RRC Connection Reestablishment messages, etc., depending on the purpose of random access.

[0064] A base station must receive signals transmitted from multiple terminals in time synchronization so that it can separate and decode each signal. Therefore, to adjust the synchronization of the uplink signal, the base station provides timing advance command information to each terminal through a random access process or by using the Timing Advance Command MAC CE. A terminal that receives the timing advance command information adjusts the timing for transmitting the uplink signal using the information.

[0065] Timing advance time, T_TA, is derived through the following and [Equation 1].

[0066] [Formula 1]

[0067] T_TA = (N_TA + N_TA,offset) x T_c

[0068] N_TA represents timing advance command information provided by RAR / MSGB or Timing Advance Command MAC CE, N_TA,offset represents the offset value, and T_c represents the sampling time. The N_TA value is set to 0 during the initial random access process.

[0069] FIG. 1c is a drawing for explaining a Non-Terrestrial Network (NTN) according to one embodiment of the present disclosure.

[0070] NTN is a technology that provides data services to terminals on the ground by utilizing artificial satellites or UAS (Unmanned Aerial System) located at high altitudes. The said artificial satellite (Satellite, 1c-05) acts as an independent base station, a base station DU in a CU-DU base station structure, or an RF repeater, and depending on the role of the said artificial satellite, a base station CU or a base station (1c-20) connected to the NTN-GW (Gateway, 1c-15) exists on the ground. The satellites considered in NTN are classified as follows according to the characteristics of the cells formed on the ground provided by the said satellite.

[0071] - Earth-fixed cell: An NTN cell fixed with respect to a certain geographic area on Earth. It can be provisioned by beam(s) continuously covering the same geographical area (eg the case of GSO satellites).

[0072] - Quasi-earth-fixed cell: An NTN cell fixed with respect to a certain geographic area on Earth during a certain time duration. It can be provisioned by beam(s) covering one geographic area for a limited period and a different geographic area during another period (eg the case of NGSO satellites generating steerable beams).

[0073] - Earth-moving cell: An NTN cell moving on the ground. It can be provisioned by beam(s) whose coverage area slides over the Earth's surface (eg the case of NGSO satellites generating fixed or non-steerable beams).

[0074] The wireless section between the above satellite and the ground NTN-GW is referred to as the Feeder link (1c-10), and the wireless section between the above satellite and the ground terminal (1c-30, 1c-35) is referred to as the Service link (1c-25).

[0075] Since the satellite moves at a high speed at a high altitude, very long propagation delay and Doppler distortion occur. Therefore, in order for the satellite and the terminal to communicate smoothly, these distortion phenomena must be compensated for in advance. To compensate for these Doppler distortion phenomena, specific information is required, and the satellite provides this information to the ground terminals through system information, SIB19 (1c-40). SIB19 may include position information regarding the satellite and adjacent satellites, speeds, and various information necessary to compensate for the propagation delay and Doppler distortion. The terminals utilize this information, along with their own position information, to compensate for the distortion phenomena.

[0076] A very long propagation delay occurs during communication with NTN. Therefore, time synchronization as described in Equation 1 above is insufficient to compensate for the delay. For example, if the delay time in the Feeder link and the delay time in the Service link resulting from the long distance between the satellite and the terminal are considered, the adjustment range through conventional time synchronization methods may be exceeded. Therefore, the Timing advance time, T_TA, in NTN uses [Equation 2] as follows.

[0077] [Equation 2]

[0078] T_TA = (N_TA + N_TA,common + N_TA,UE-specific + N_TA,offset) x T_c

[0079] N_TA,common is a value that compensates for the latency in the feeder link, and specific information (TA-Info IE) necessary to calculate this is provided in SIB19, and the terminal derives the value through the said specific information and a specific formula. The said TA-Info IE includes ta-Common, ta-CommonDrift, and ta-CommonDriftVariant, and the definitions of each field are as shown in [Table 2] below (excerpted from TS38.331).

[0080] [Table 2]

[0081]

[0082] N_TA,UE-specific is a value that compensates for latency in the service link, and satellite location information is provided through SIB19. The terminal calculates the distance between the satellite and the terminal by utilizing its own location information, and thereby derives the above value.

[0083] The above T_TA value is useful for the NTN cell to schedule the terminal. Therefore, the terminal can report a Timing Advance Report MAC CE (TAR MAC CE) including the above T_TA value to the NTN cell according to the base station settings. The conditions under which the terminal must report the above TAR MAC CE are as follows.

[0084] 1. RRC Setup, RRC Resume, RRC Re-establishment (RRE), Handover

[0085] 2. When receiving TAR-Config transmitted from the base station

[0086] 3. When the difference between the TA value stored in the recently reported TAR MAC CE and the current TA value exceeds a preset threshold

[0087] FIG. 1d is a drawing illustrating the format of a Timing Advance Report Medium Access Control (MAC) Control Element (CE) according to one embodiment of the present disclosure.

[0088] Referring to FIG. 1d, the Timing Advance Report MAC CE has a size of 2 Bytes and consists of 2 bits of Reserved fields (1d-05) and 14 bits of Timing Advance (TA) fields (1d-10). The Timing Advance fields may include the T_TA value of the serving NTN cell.

[0089] FIG. 1e is a flowchart of a process for performing a Random Access Channel (RACH)-less handover in a mobile communication system according to one embodiment of the present disclosure.

[0090] In LTE systems, RACH-less handover was introduced to perform handover without random access when the timing advance of the target cell is clearly identified.

[0091] In step 1e-20, the terminal (user equipment, UE, 1e-05) may report its capability information to the source base station (Source eNB, 1e-10). The capability information may include an indicator indicating whether it supports RACH-less handover. In LTE, the indicator corresponds to rach-Less-r14, which is extracted from the TS36.331 standard document in [Table 3] below.

[0092] [Table 3]

[0093]

[0094] In step 1e-25, if the source base station (1e-10) decides to perform a RACH-less handover for the terminal (1e-05), it exchanges configuration information necessary for performing the handover with a nearby target base station (Target eNB, 1e-15).

[0095] At this time, the target base station (1e-15) may provide the source base station (1e-10) with Timing Advance information (i.e., timing adjustment indication, e.g., N_TA value) to be applied when transmitting a signal to the target cell, and uplink scheduling information (ul-ConfigInfo). The uplink scheduling information may not be provided.

[0096] In step 1e-30, the source base station (1e-10) may transmit MobilityControlInfo IE containing a predetermined RACH-less configuration information to the terminal (1e-05). The predetermined RACH-less configuration information corresponds to RACH-Skip-r14 extracted from the TS36.331 standard document of [Table 4] below.

[0097] [Table 4]

[0098]

[0099] The targetTA information corresponds to the timing adjustment indication above, and if ta0 is indicated as the targetTA value, it means that N_TA is 0, and mcg-PTAG means N_TA applied to the PTAG belonging to MCG, scg-PTAG means N_TA applied to the PTAG belonging to SCG, mcg-STAG with STAG-Id means N_TA applied to the STAG corresponding to the STAG-Id belonging to MCG, and scg-STAG with STAG-Id means N_TA applied to the STAG corresponding to the STAG-Id belonging to SCG. The terminal uses the set N_TA value to derive the TA value applied when transmitting a signal to the target cell.

[0100] Therefore, the target cell for performing RACH-less handover is limited to a cell that can apply an N_TA value of 0, or a single serving cell in the existing CA / DC or a cell with the same TA. That is, it is limited to a cell that can apply an N_TA that the terminal already recognizes.

[0101] The numberOfConfUL-Processes information refers to the number of HARQ processes corresponding to the Uplink grant that the terminal will apply to the target cell.

[0102] ul-SchedInterval information refers to the period of uplink scheduling that the terminal will apply at the target cell (1e-50).

[0103] The ul-StartSubframe information indicates a subframe that the terminal can transmit uplink from the target cell (1e-45). A value of 0 indicates a subframe corresponding to subframe number 0, and a value of 1 indicates a subframe corresponding to subframe number 1.

[0104] ul-Grant information refers to wireless resource information that enables the terminal to perform uplink transmission in the target cell (1e-40).

[0105] The above target cell allocates wireless resources to the terminal at the scheduling time derived through the above RACH-less setting information.

[0106] In step 1e-35, the terminal (1e-05) that receives the RACH-less configuration information transmits a Physical Uplink Shared Channel (PUSCH) containing an RRCConnectionReconfigurationComplete message to the target cell at the transmission timing derived from the configuration information.

[0107] FIG. 1f is a diagram illustrating a scenario supporting Carrier Aggregation (CA) and / or Dual Connectivity (DC) in a Non-Terrestrial Network (NTN) according to one embodiment of the present disclosure.

[0108] NTN utilizes satellites located at high altitudes for data transmission and reception, and is classified into high-altitude geostationary satellites (GSO Satellite, 1f-05) and low-orbit satellites (NGSO Satellite, 1f-10) depending on the altitude.

[0109] Because geostationary satellites orbit the Earth at the same speed and in the same direction as the Earth's rotation, when viewed from the ground, they appear to be in a fixed position at a specific altitude.

[0110] On the other hand, low-orbit satellites, located at relatively low altitudes, are significantly affected by Earth's gravity; therefore, they must move at much faster speeds compared to geostationary satellites to maintain a constant altitude relative to the Earth. Consequently, since low-orbit satellites typically move faster than the Earth's rotation speed, they appear to be moving at a specific altitude when viewed from the ground.

[0111] NTN is discussing a method to provide data transmission and reception services to terminals by considering the aforementioned geostationary satellites and low-orbit satellites together. For example, geostationary satellites are advantageous for providing a wide service area because they are located at a relatively high altitude.

[0112] On the other hand, low-orbit satellites provide a narrower service area compared to geostationary satellites due to their low altitude, but they are more advantageous than geostationary satellites in terms of delay and signal strength because of their lower altitude relative to the ground. Therefore, geostationary satellites can be set as Master Nodes (MN) to support stable mobility, and low-orbit satellites can be set as Secondary Nodes (SN) to improve service quality, thereby providing Dual Connectivity (DC) to the terminal (1f-20).

[0113] Alternatively, geostationary satellites can be configured as PCells to support stable mobility, and low-orbit satellites as SCells to maximize data transmission rates, thereby providing Carrier Aggregation (CA) functionality to terminals. In a CA scenario, if each serving cell is provided through a different satellite, the serving cells belonging to that satellite can belong to different TAGs (Timing Advance Groups).

[0114] In one embodiment of the present disclosure, the DC involving the NTN is referred to as the NTN DC and the NTN CA involving the NTN. In this case, some serving cells may be provided by ground base stations or TNs rather than satellites. Satellite switching technology may be applied to the satellite responsible for the SCell or SCG in the CA or DC scenario.

[0115] The above Satellite Switching technology is an operation in which a satellite (1f-10) providing a quasi-earth-fixed cell transfers the cell it was providing to another satellite (1f-25) at a specific time. At this time, since only the satellite providing the service is replaced without changing the cell characteristics or settings, the terminal receiving the service does not need to reconfigure the cell. More specifically, the PCI (Physical Cell ID) of the cell is not changed. However, depending on the case, the terminal may perform a random access operation to the replacement satellite in order to re-determine the uplink timing with the new satellite.

[0116] The above Satellite Switching technology has the advantage of reducing signaling overhead and complexity by eliminating handover operations for multiple terminals that may occur when a satellite providing a quasi-earth-fixed cell leaves a specific area and hands over its service area to an adjacent satellite. In this embodiment, Satellite Switching for a satellite responsible for SCell or SCG is referred to as SN Satellite Switching or SCG Satellite Switching.

[0117] FIG. 1g is a flowchart of an operation for providing satellite switching configuration information in a Carrier Aggregation (CA) and / or Dual Connectivity (DC) scenario of a non-terrestrial network (NTN) according to one embodiment of the present disclosure.

[0118] In the NTN CA scenario, the satellite corresponding to STAG, or in the NTN DC scenario, the satellite corresponding to SCG, can be Satellite Switched.

[0119] The information required for the existing Satellite Switching operation is provided through the system information (SIB19) in [Table 5]. In SIB19, the t-Service field is used to indicate the time point when the current satellite (source satellite) stops service (during the Satellite Switching process). In the Satellite Switching procedure, information related to the replacement satellite (target satellite) is indicated in SatSwitchWithReSync IE. The said IE includes not only basic information (ntn-Config) about the satellite but also information on the time point to start service (t-ServiceStart). ssb-TimeOffset is the time offset value between the source satellite and the target satellite.

[0120] [Table 5]

[0121]

[0122] In an embodiment of the present disclosure, a method is proposed for providing Satellite Switching configuration information between source and / or target satellites corresponding to STAG or SCG in an NTN CA / DC scenario.

[0123] In step 1g-30, in a CA and / or DC scenario, a satellite or ground base station (TN) (1g-10) corresponding to a PTAG or MCG performs coordination with a source / target satellite (1g-15, 1g-25) corresponding to a STAG or SCG, ground base stations (1g-20) wirelessly connected to said satellite, and the source / target satellite corresponding to the STAG or SCG for satellite switching operations. The method of transmitting satellite switching configuration information derived through the coordination of said network entities to a terminal may be one of the following four options.

[0124] - Option 1 (1g-35): Satellite Switching configuration information between source / target satellites corresponding to STAG or SCG is provided through system information broadcast by a satellite or ground base station corresponding to PTAG or MCG in a CA / DC scenario.

[0125] Since the terminal can immediately receive system information broadcast by a satellite or ground base station corresponding to the PTAG or MCG, the procedure for acquiring said information is simple. In addition, the method of utilizing system information facilitates providing said configuration information to multiple terminals.

[0126] However, since NTN configuration information is time-critical, the latest configuration information of the source / target satellites corresponding to the STAG or SCG must be periodically provided to the satellites or ground base stations corresponding to the PTAG or MCG. This increases the complexity between network entities.

[0127] In terms of signaling, a new SatSwitchWithReSync IE (including target satellite information and a t-ServiceStart field) containing satellite switching configuration information between target satellites corresponding to STAG or SCG may be defined in the system information. Additionally, a t-Service field for the source satellite of STAG or SCG may be defined in the existing NTN-NeighCellConfigList IE or the new IE. At this time, a device capable of distinguishing that the information is for satellite switching between source / target satellites corresponding to STAG or SCG (new indicator information, introduction of a new IE distinct from the existing IE, etc.) is required.

[0128] - Option 2 (1g-40): In a CA / DC scenario, Satellite Switching configuration information between source (or target) satellites corresponding to STAG or SCG is provided through system information broadcast by the source (or target) satellite corresponding to STAG or SCG. The terminal is additionally required to perform a procedure to receive system information broadcast by the source (or target) satellite corresponding to STAG or SCG. However, there is no need to continuously transmit the latest configuration information of the source / target satellite corresponding to STAG or SCG to the satellite or ground base station corresponding to the PTAG or MCG.

[0129] - 3rd Option (1g-45): In a CA / DC scenario, Satellite Switching configuration information between source / target satellites corresponding to STAG or SCG is provided through dedicated signaling transmitted by a satellite or ground base station corresponding to PTAG or MCG. This is advantageous for configuring Satellite Switching operation only for a specific terminal.

[0130] - 4th Option (1g-50): Satellite Switching configuration information between source / target satellites corresponding to STAG or SCG is provided through system information broadcast by an adjacent ground base station. The adjacent ground base station may not be involved with the currently configured CA or DC. The adjacent ground base station has the advantage of ensuring low latency and high stability and being able to provide the information to the terminal.

[0131] In step 1g-55, the terminal (1g-05) can obtain DL synchronization by receiving a synchronization signal block (SSB) transmitted from the target satellite corresponding to the STAG or SCG at the time indicated by the t-ServiceStart. If necessary, the terminal can obtain UL synchronization through random access.

[0132] In step 1g-60, if the terminal (1g-05) fails to secure DL synchronization after a specific amount of time has passed since the time indicated by t-ServiceStart (if it failed to receive the SSB transmitted from the target satellite), the terminal (1g-05) may report the situation to the satellite or ground base station (1g-10) corresponding to the PTAG or MCG.

[0133] At the time indicated by the above t-Service, the terminal considers that UL synchronization with the source satellite corresponding to the STAG or SCG is invalid. This means that normal data services with the source satellite have been stopped.

[0134] FIG. 1h is a flowchart of a process for performing Carrier Aggregation (CA) and / or Dual Connectivity (DC) in a Non-Terrestrial Network (NTN) according to one embodiment of the present disclosure.

[0135] In step 1h-20, a terminal supporting NTN (UE, 1h-05) can transmit its capability information to a satellite base station (MN satellite, 1h-10).

[0136] The above capability information may include indicator information indicating whether the terminal supports NTN CA, DC, or SN (SCG) satellite switching.

[0137] In step 1h-25, the satellite base station (1h-10) can coordinate NTN CA, DC, or SN (SCG) satellite switching settings with an adjacent satellite base station (or a corresponding ground base station).

[0138] In step 1h-30, the satellite base station (1h-10) can transmit predetermined configuration information coordinated with the adjacent satellite base station to the terminal (1h-05).

[0139] The configuration information of the serving cell may include satellite information providing the serving cell. For example, the satellite information may be a satellite ID and NTN-Config. Alternatively, the system information including the NTN configuration information may include list information of cells supported by a specific satellite. The list may contain cell ID information indicating the cell, frequency information, etc.

[0140] The terminal (1h-05) that receives the above setting information performs the NTN CA, DC, or SN (SCG) satellite switching operation procedure indicated by the above setting information.

[0141] In step 1h-35, the terminal may report a new TAR MAC CE, including a Timing Advance value associated with the adjacent satellite, to the satellite or the adjacent satellite according to the prior settings.

[0142] The network may provide the terminal with separate configuration information regarding TAR MAC CE transmission for each MAC entity (i.e., per CG). The format of the new TAR MAC CE is to be described later in FIG. 1i. The existing TAR MAC CE may be reported to the network by the terminal when at least one of the following conditions is satisfied (excerpt from TS 38.321 V18.2.0).

[0143] - upon indication from upper layers to trigger a Timing Advance report; (i.e., when the ta-Report field in SIB19 is set to "enable" and setup, resume, re-establishment, or handover is performed, the RRC triggers a TA report to the MAC)

[0144] - upon configuration ofoffsetThresholdTAby upper layers, if the UE has not previously reported Timing Advance value to current Serving Cell;

[0145] - if the variation between the current estimate of the Timing Advance value and the last reported Timing Advance value is equal to or larger thanoffsetThresholdTA, if configured.

[0146] At this time, the above-mentioned setting parameter, offsetThresholdTA, is provided to the terminal via RRC signaling by the network.

[0147] The existing or the new TAR MAC CE may be reported to the network by the terminal when at least one of the following predetermined conditions, in addition to the existing conditions, is satisfied. For reference, an SCG TA reporting having the existing TAR MAC CE format may be transmitted to a satellite corresponding to the SCG.

[0148] - When PSCell addition or SCG change is performed

[0149] - When adding, enabling or deactivating, releasing, or changing SCell

[0150] The following configuration information for a satellite, NTN-Config (see excerpt from TS38.331 V18.2.0 below), includes epoch time information (epochTime field). This is a reference time for deriving the validity period of the received NTN-Config. For example, the satellite's coordinates or TA-Info information may change after a specific time. Therefore, the network informs the terminal of the validity period of the information, and when the validity period expires, the terminal is allowed to acquire it again.

[0151] In NTN-Config IE, the epochTime field is the reference point, and the ntn-UlSyncValidityDuration field is the valid time. After the reference point, if the valid time has elapsed, the terminal must re-receive the NTN-Config. The epochTime is indicated based on the SFN and sub-frame of the serving cell.

[0152]

[0153]

[0154]

[0155] If CA and / or DC are introduced in NTN, there may be multiple serving cells, and the epoch time must be indicated based on the SFN and sub-frame of a specific serving cell among the multiple serving cells (1h-40). The specific cell may be a SpCell (PCell in MCG, PSCell in SCG) or a pre-set serving cell.

[0156] In a CA / DC scenario, a specific serving cell may be provided by a SpCell and a different satellite. Accordingly, the epoch time of the satellite corresponding to the serving cell may be indicated based on the SFN and sub-frame of the pre-configured serving cell provided by the serving cell or the satellite.

[0157] To reduce signaling overhead, instead of providing epoch time information for the satellite corresponding to a given serving cell(s) through dedicated signaling or system information, the epoch time of a given serving cell may be applied. The following options may be considered.

[0158] - Option 1: If an epoch time is not set for a satellite corresponding to a given serving cell(s), the epoch time of said satellite follows the epoch time of the SpCell of the CG to which said serving cell belongs (i.e., PCell in MCG, PSCell in SCG) or the end time of the SI window in which the SIB19 broadcast from said CG (i.e., system information containing NTN configuration information) is scheduled.

[0159] - 2nd Option: If an epoch time is not set for a satellite corresponding to a specified serving cell(s), the epoch time of said satellite follows the epoch time of the specified serving cell of the TAG to which said serving cell belongs.

[0160] - 3rd Option: If an epoch time is not set for a satellite corresponding to a given serving cell(s), the epoch time of said satellite follows the epoch time of the serving cell set by the network.

[0161] - Option 4: If an epoch time is not set for a satellite corresponding to a given serving cell(s), the epoch time of said satellite follows a value to which a pre-set offset value is applied to the epoch time of the serving cell set by the network or a pre-specified serving cell.

[0162] - 5th Option: For a single satellite, epoch time information is always provided to the terminal via dedicated signaling or system information, and multiple serving cells provided by the satellite all follow the said epoch time.

[0163] The terminal can report propagationDelayDifference information to the network using UEAssistanceInformation messages (see excerpt from TS38.331 V18.2.0 below).

[0164] The propagationDelayDifference mentioned above refers to the difference between the service link propagation delay of the serving cell and the service link propagation delay of the adjacent cell. This information enables the network to identify the time difference in wireless propagation delay between the serving cell and the adjacent cell experienced by the terminal, and is used to appropriately configure specific functions such as SSB and measurement gap.

[0165]

[0166]

[0167] If CA / DC is introduced in NTN, the terminal may report propagationDelayDifference values ​​by TAG or by CG. The propagationDelayDifference value corresponding to a specific CG may be reported by the terminal only to the serving cells of that CG.

[0168] In CA / DC scenarios, since multiple serving cells exist, it is necessary to specify a reference serving cell to be applied when deriving propagationDelayDifference. Therefore, the propagationDelayDifference value may vary depending on the TAG to which the reference serving cell belongs.

[0169] PropDelayDiffReportConfig may include information on the ID of a reference serving cell or a TAG applied to derive the propagationDelayDifference value in IE.

[0170] In a CA scenario, at least one reference serving cell may be designated for each TAG in the network. In a DC scenario, at least one reference serving cell may be designated for each CG (Cell Group) in the network. To reduce complexity, the reference serving cell may always be fixed as a SpCell (i.e., PCell or PSCell). The ID information may be provided for each entry in the neighCellInfoList of the PropDelayDiffReportConfig IE. For example, each entry of the new IE containing the ID information may correspond sequentially to each entry in the neighCellInfoList of the PropDelayDiffReportConfig IE. At this time, the terminal uses the service link propagation delay of the designated reference serving cell or the service link propagation delay of one serving cell belonging to the designated TAG to derive the propagationDelayDifference value.

[0171] In another embodiment of the present disclosure, while the existing propagationDelayDifference values ​​only considered adjacent cells, since multiple serving cells exist in a CA / DC scenario, the terminal may derive propagationDelayDifference values ​​of serving cells other than the reference serving cell and report them to the network. Since serving cells belonging to the same TAG are considered to have the same TA value, propagationDelayDifference values ​​corresponding to each STAG based on the PTAG may be reported to the network. Since adjacent cells that are not serving cells do not belong to a specific TAG (TAG not set), propagationDelayDifference values ​​of each adjacent cell based on the PTAG may be reported to the network.

[0172] In step 1h-45, the network can be configured so that the terminal can report the propagationDelayDifference values ​​to an adjacent cell, another serving cell, or both.

[0173] In step 1h-50, the terminal (1h-05) may report propagationDelayDifference values ​​for the derived adjacent cell or serving cell to the network when at least one of the specified condition(s) is satisfied. For example, the specified condition is,

[0174] - When the terminal receives configuration information for the propagationDelayDifference report but has never reported the derived propagationDelayDifference value to the network

[0175] - When at least one propagationDelayDifference value derived for a pre-configured adjacent cell(s) or serving cell(s) is greater than a pre-configured predetermined threshold. In this case, the terminal may report only the propagationDelayDifference value satisfying the above condition and the corresponding predetermined information to the network, or may report both the latest derived propagationDelayDifference value and the corresponding predetermined information to the network.

[0176] - When at least one propagationDelayDifference value derived for a pre-configured adjacent cell(s) or serving cell(s) is greater than a previously reported propagationDelayDifference value and a pre-configured predetermined threshold. In this case, the terminal may report only the propagationDelayDifference value satisfying the above condition and the corresponding predetermined information to the network, or may report both the derived latest propagationDelayDifference value and the corresponding predetermined information to the network.

[0177] - When adjacent cells are additionally set

[0178] - When adding, enabling or deactivating, releasing, or changing SCell

[0179] - When PSCell addition or SCG change is performed

[0180] When the above terminal reports the propagationDelayDifference value, it may also report the following predetermined information. The propagationDelayDifference values ​​for adjacent cells and serving cells may be stored in different IEs.

[0181] - The ID of the adjacent cell or serving cell corresponding to the reported propagationDelayDifference value, e.g., CGI, PCI, serving cell / SCell index (for serving cells), etc.

[0182] - The ID of the reference serving cell used to derive the propagationDelayDifference value, e.g., CGI, PCI, serving cell / SCell index (in the case of a serving cell), etc.

[0183] - The ID of the TAG applied to derive the propagationDelayDifference value

[0184] In step 1h-55, the terminal (1h-05) may report the information to the network via a predetermined RRC message (e.g., UEAssistanceInformation) or a predetermined new MAC CE (1h-55).

[0185] FIG. 1i is a drawing for illustrating the format of an extended Timing Advance Report Medium Access Control (MAC) Control Element (CE) according to one embodiment of the present disclosure.

[0186] When NTN supports CA and / or DC, one or more TAGs (Timing Advance Groups) can be configured per CG (Cell Group). A TAG is a set of serving cells that have the same Timing Advance.

[0187] A TAG containing a PCell or PSCell is called a PTAG (Primary TAG), and a TAG consisting only of SCells is called a STAG (Secondary TAG). For example, up to 4 TAGs can be set per CG.

[0188] In one embodiment of the present disclosure, an improved TAR MAC CE is proposed to enable a terminal to report a Timing Advance for each TAG. There may be a form that stores a Timing Advance value for a single TAG and a form that stores Timing Advance values ​​for multiple TAGs.

[0189] The terminal may report its capability information, which includes an indicator indicating whether it supports the new TAR MAC CE, to the base station. Additionally, the base station may transmit configuration information to the terminal indicating that the new TAR MAC CE can be used. A corresponding LCID exists for the new TAR MAC CE, which can be distinguished from an LCID indicating an existing TAR MAC CE.

[0190] 1. Option 1 - Single TAR

[0191] The TAR MAC CE (Fig. 1i a) used to report the Timing Advance value for a single TAG consists of 2 bits (1i-05) indicating the TAG ID and 14 bits (1i-10) indicating the TA value. Here, TAG ID 0 means PCell or PSCell.

[0192] 2. Option 3 - Multiple TAR

[0193] A TAR MAC CE (Fig. 1i b) used to report Timing Advance values ​​for multiple TAGs can be configured with a set (1i-15, 1i-20) consisting of 2 bits indicating a TAG ID and 14 bits indicating a TA value, up to a maximum number of TAGs (e.g., 4). When configured with multiple sets, the TA field of the TAG corresponding to the TAG with the lowest TAG ID may be located at the top. Alternatively, the TA field corresponding to the PTAG may always be located at the top of the TAR MAC CE.

[0194] TA values ​​corresponding to four TAGs belonging to a single CG may always be included, in which case the TAG ID field is unnecessary. Therefore, the TAG ID field can be omitted, and the TA fields of the corresponding TAGs can be filled starting from the top in order of having the lowest TAG ID value.

[0195] If a specific TAG belonging to a CG is not set, the terminal sets an arbitrary value in the TA field corresponding to the TAG, and the base station that receives the TAR MAC CE will ignore the TA field.

[0196] 3. Option 3 - Multiple TAR for DC

[0197] A single TA value may be reported for each CG. In this case, the TA values ​​corresponding to each CG may be reported as a single TAR MAC CE (Fig. 1i-c). A set consisting of a CG ID (1i-25) indicating a CG and a TA value (1i-30) corresponding to said CG exists as many times as there are CGs and can be stored together in a single TAR MAC CE. If only MCG and SCG exist as CGs, the CG ID field may be omitted. The top set of the MAC CE corresponds to the TA value of the MCG, and the second set (1i-35) may correspond to the TA value of the SCG.

[0198] 4. Option 4 - Multiple TAR for multiple satellites

[0199] TA values ​​may be reported for each satellite. In this case, TA values ​​corresponding to each satellite may be reported as a single TAR MAC CE (Fig. 1i d). A set consisting of a satellite ID (1i-40) indicating a satellite and a TA value (1i-45) corresponding to said satellite exists as many times as there are satellites and can be stored together in a single TAR MAC CE.

[0200] The second set (1i-50) can correspond to the TA value of another satellite in CA and / or DC scenarios.

[0201] FIG. 1j is a flowchart of a process for performing Early TA reporting to support Carrier Aggregation (CA) and / or Dual Connectivity (DC) of a Non-Terrestrial Network (NTN) according to one embodiment of the present disclosure.

[0202] In the existing NTN, when the ta-Report field in SIB19 is set to “enable,” the terminal (1j-05) supporting the NTN triggers TA reporting for a serving NTN cell when performing setup, resume, re-establishment, or handover to a serving NTN cell. This is so that the network can obtain the reported TA information as early as possible, as the reported TA information is highly useful for efficient scheduling.

[0203] In an embodiment of the present disclosure, for rapid CA / DC setup, when performing TA reporting during setup or resume, the TA values ​​of pre-configured or pre-defined NTN cells (or target satellites) are additionally considered in addition to the currently serving NTN cell. At this time, the additionally considered NTN cells may be pre-configured and will be candidate serving cells for future CA or DC. If TA information regarding the candidate cells is reported to the network at an early stage, the network will be able to quickly utilize the candidate cells as serving cells through CA or DC procedures. It is assumed that a single target satellite can support one or more NTN cells. In an embodiment of the present disclosure, the proposed method is referred to as Early TA reporting.

[0204] In step 1j-15, the terminal (1j-05) may report its capability information to the base station (1j-10). The capability information may include an indicator of whether the terminal itself supports Early TA reporting operations.

[0205] In step 1j-20, the base station (1j-10) may transmit configuration information necessary to perform the Early TA reporting to the terminal (1j-05) through a predetermined radio resource control (RRC) message (e.g., RRCRelease message) or system information.

[0206] The above configuration information may include target satellite information that can be included in TA reporting. For example, the above target satellite information may be NTN-Config, carrier frequency (or freq list), PCI (or PCI list), etc.

[0207] In step 1j-25, the terminal (1j-05) that receives the RRCRelease message switches to standby mode or inactive mode.

[0208] In step 1j-30, the terminal (1j-05) derives the most recent TA value or propagation delay difference value for a pre-configured target satellite, and can report the information to the network during setup or resume.

[0209] In step 1j-35, the network (1j-10) may request the information through a predetermined RRC message or through system information.

[0210] In step 1j-40, the terminal (1j-05) may report the information to the network (1j-10), using a predetermined RRC message or the previously described TAR MAC CE format (e.g., FIG. 1i d) (1j-40).

[0211] In order for the above terminal to derive the above TA value, it must derive the N_TA value. Typically, the above N_TA value can be derived through random access. In the case of a serving satellite, the terminal can derive the N_TA value through random access performed in the setup or resume procedure. In the case of other satellites as well, the terminal can derive the N_TA value through a random access procedure.

[0212] However, when the terminal performs a random access procedure on a satellite other than the serving satellite during setup or resume, it may increase terminal complexity. Therefore, the terminal may report to the network an N_TA derived without a random access procedure for the target satellite, or a TA value to which N_TA = 0 is applied. A method for deriving N_TA without an access procedure will be described later.

[0213] If the terminal derives a TA value but a long time elapses before it is actually reported, the TA value may no longer be valid. Therefore, the terminal may run a predetermined timer when deriving the TA value and determine that the derived TA value is valid only until the timer expires.

[0214] Alternatively, if the change (rate) in signal strength experienced by the terminal or the distance traveled by the terminal is greater than a predetermined (pre-set) threshold value after deriving the TA value, the TA value may be considered no longer valid.

[0215] The terminal may always include the TA value of the serving NTN cell in the Early TA reporting. The terminal may not receive a reference signal from a target satellite pre-configured for Early TA reporting. In this case, the terminal may exclude the TA value of the target satellite from the Early TA reporting. Alternatively, it may report an indicator to the network indicating that the target satellite is not detected.

[0216] For reference, the above propagation delay difference is a delay difference of the service link, so it can be derived without a random access procedure as it is derived in satellite coordinates and terminal coordinates.

[0217] FIG. 1k is a flowchart of terminal operations for performing Carrier Aggregation (CA) and / or Dual Connectivity (DC) of a Non-Terrestrial Network (NTN) according to one embodiment of the present disclosure.

[0218] In step 1k-05, the terminal may report its capability information to the base station. The capability information may include an indicator indicating whether it supports NTN CA or DC functions. Additionally, the capability information may include an indicator indicating whether it supports Early TA reporting.

[0219] In step 1k-10, the terminal may receive an RRCRelease message from the base station, and the RRCRelease message may include configuration information related to Early TA reporting.

[0220] In step 1k-15, when the terminal receives the RRC message, it switches from connected mode to standby mode or inactive mode.

[0221] In the 1k-20 stage, the terminal can obtain satellite-related configuration information through system information broadcast from the base station. The system information may include configuration information related to Early TA reporting and may include an indicator that directs the execution of Early TA reporting.

[0222] In step 1k-25, the terminal switches to connection mode.

[0223] In step 1k-30, the terminal may report TA values ​​for serving and pre-configured satellites to the base station. The terminal operation for deriving the TA values ​​may be performed before or after switching the connection mode. The N_TA value required to derive the TA values ​​may be derived by directly performing random access to the target satellite, or a predetermined set value or a value of 0 may be applied.

[0224] In step 1k-35, the terminal can receive CA or DC-related configuration information from the base station.

[0225] In step 1k-40, the terminal determines and applies an epoch time corresponding to the configuration information of the satellite involved in the CA or DC according to the predetermined rule.

[0226] In step 1k-45, the terminal can receive configuration information necessary to perform propagation delay difference reporting from the base station.

[0227] In step 1k-50, the terminal may report a propagation delay difference value corresponding to adjacent cells or serving cells to the base station.

[0228] In step 1k-55, if DC is set, the terminal can receive setting information for SN satellite switching through system information or dedicated signaling from the base station.

[0229] In step 1k-60, the terminal can switch the satellite responsible for the SN in the DC to the target satellite at a predetermined time according to the setting information.

[0230] FIG. 11 is a flowchart of base station operations for performing Carrier Aggregation (CA) and / or Dual Connectivity (DC) of a Non-Terrestrial Network (NTN) according to one embodiment of the present disclosure.

[0231] In step 1l-05, the base station may receive capability information from the terminal. The capability information may include an indicator indicating whether it supports NTN CA or DC functions. Additionally, the capability information may include an indicator indicating whether it supports Early TA reporting.

[0232] In step 11-10, the base station may transmit an RRCRelease message containing Early TA reporting setting information to the terminal.

[0233] In step 11-15, the base station may receive an RRC Setup Request or RRC Resume Request message from the terminal.

[0234] In step 1l-20, the base station receives TA values ​​for the serving satellite and pre-configured adjacent satellites from the terminal. When the base station sets up CA or DC using multiple satellites for the terminal, it utilizes the TA values ​​to configure setting information such as SSB scheduling and measurement gap.

[0235] In step 11-25, the base station may transmit CA or DC-related configuration information to the terminal.

[0236] In step 1l-30, the base station may transmit configuration information necessary for performing propagation delay difference reporting to the terminal.

[0237] In step 1l-35, the base station can receive propagation delay difference information for adjacent and serving cells from the terminal.

[0238] In step 1l-40, the base station may transmit configuration information for SN satellite switching to the terminal through system information or dedicated signaling.

[0239] In step 1l-45, the base station can switch the satellite responsible for the SN in the DC to the target satellite at a predetermined time.

[0240] FIG. 1m is a flowchart of a process for performing a Non-Terrestrial Network (NTN) Random Access Channel (RACH)-less handover according to one embodiment of the present disclosure.

[0241] In step 1m-20, the terminal (UE, 1m-05) can transmit its capability information to the source NTN base station (Source NTN Cell, 1m-10). The capability information may include an indicator indicating whether it supports RACH-less in an NTN environment.

[0242] In step 1m-25, the source NTN base station (1m-10) can broadcast configuration information for itself and surrounding NTN cells through a predetermined system information.

[0243] The above-mentioned predetermined information may include at least one of the position coordinate information of the NTN satellite (ephemeris) and the information required to derive N_TA,common (ta-Common, ta-CommonDrift, ta-CommonDriftVariant).

[0244] In addition, in one embodiment of the present disclosure, the network may provide the terminal with TA setting information necessary to perform a RACH-less handover through the system information or dedicated signaling. In particular, the network may provide the terminal with an N_TA value necessary for uplink synchronization with a target satellite through the system information or dedicated signaling.

[0245] Typically, the above N_TA value can be derived by the terminal performing a random access procedure to the network, but the network or the terminal can apply a predicted value based on N_TA values ​​that were statistically applied in a specific location or area to the RACH-less handover.

[0246] If the network provides the N_TA values ​​to the terminal through system information, N_TA values ​​applicable to terminals located at a specific location or ground area for each target satellite, as shown in FIG. 1n, may be included (or stored) in the system information. The N_TA values ​​may be predicted values ​​based on N_TA values ​​that were statistically applied at the terminal's location or in that area. The information may be considered valid only for a specific period of time, and additional information may be stored in the system information so that the terminal can recognize the validity period.

[0247] In step 1m-30, the source NTN base station (1m-10) decides to perform a RACH-less handover for the terminal and can perform a coordination operation for the handover with a predetermined target NTN (Target NTN Cell, 1m-15) cell.

[0248] At this time, the source NTN base station transmits the HandoverPreparationInformation message to the target NTN cell (1m-15), including an indicator indicating that it is for a RACH-less handover and location information of the terminal. The target NTN cell (1m-15) provides handover setup information to the source NTN base station (1m-10).

[0249] In step 1m-35, the source NTN base station (1m-10) that received the above message can transmit an RRCReconfiguration message containing handover setting information to the terminal (1m-05).

[0250] The terminal (1m-05) that receives the above RACH-less handover setting information must derive a TA value to be applied in the target NTN cell. To do this, N_TA, T_TA,UE-specific, and T_TA,common values ​​are required. As described above, the T_TA,UE-specific value can be derived through location information between the terminal and the target NTN cell, and the T_TA,common value can be derived through related setting information.

[0251] However, the N_TA value may be applied by applying at least one of the following options (1m-40).

[0252] - Option 1: The terminal selects one of the N_TA values ​​provided from system information or dedicated signaling, taking into account the terminal's own location, and uses it to derive the TA value. The N_TA values ​​may be derived by utilizing Artificial Intellectual (AI) / Machine Learning (ML) based information in the network.

[0253] - Option 2: The terminal uses the N_TA value derived by utilizing its own AI / ML-based information to derive the TA value.

[0254] - 3rd Option: The terminal uses the N_TA value it previously applied to derive the TA value. This is a useful option when the terminal is an FWA with a fixed location.

[0255] The terminal that receives the above configuration information uses the information to derive the Timing Advance value (T_TA) to be applied when transmitting PUSCH to the target NTN cell.

[0256] Referring to 1m-45, the target NTN cell (1m-15) can periodically allocate wireless resources according to pre-set scheduling information, taking into account the derived TA value (1m-45). If the scheduling information is not provided, the terminal monitors the target cell's PDCCH.

[0257] In step 1m-50, the terminal (1m-05) may transmit a PUSCH at a predetermined time and wireless resource location based on (or derived from) the previously derived TA value and scheduling information in the target NTN cell. The PUSCH includes an RRCReconfigurationComplete message.

[0258] In step 1m-55, the target NTN cell (1m-15) that has successfully received the PUSCH may receive a TAR MAC CE or a TAC (Timing Advance Command) MAC CE from the terminal to match more accurate uplink timing (1m-55).

[0259] FIG. 1n is a diagram illustrating a method for deriving terminal location-based Timing Advance (TA) in a Non-Terrestrial Network (NTN) Random Access Channel (RACH)-less handover according to one embodiment of the present disclosure.

[0260] According to one embodiment of the present disclosure, a network can provide an N_TA value that can be applied to a specific satellite for each region where a terminal is located, using a predetermined SIB.

[0261] The distance from the satellite (1n-05) to the terminal on the ground is determined by the satellite's coordinates and the terminal's location. For example, the first terminal (1n-20) is located α (1n-10) away from the satellite. On the other hand, the second terminal (1n-25) is located α+β (1n-15) away from the satellite. Therefore, the second terminal will experience a propagation delay corresponding to a distance β relative to the first terminal. Due to the characteristics of OFMA transmission, signals with small, limited delays can be decoded together, so terminals within a certain range can have the same N_TA value applied.

[0262] For example, if terminals belonging to the first region (1n-30) apply the first N_TA value and terminals belonging to the second region (1n-35) apply the second N_TA value, the network receiving the OFDM signals of the terminals can decode them. At this time, the network must appropriately define the regions so that the uplink signals of the terminals can reach the satellite simultaneously within a predetermined allowable range. The N_TA value corresponding to each region can be derived based on an AI / ML technique utilizing predetermined TA information collected by the network.

[0263] Specific ground areas may be defined for each satellite based on the coordinates of each satellite, and the N_TA value to be applied by terminals belonging to each area is broadcast as system information. The information may be valid only for a specified period of time, and specific configuration information may be provided along with the system information so that the terminal can evaluate the validity. For example, the N_TA information may be valid only from the epoch time (reference time) until a pre-set validity period.

[0264] FIG. 10 is a flowchart of a terminal operation performing a Non-Terrestrial Network (NTN) Random Access Channel (RACH)-less handover according to one embodiment of the present disclosure.

[0265] In step 1o-05, the terminal may transmit its capability information to the base station. The capability information may include an indicator indicating whether it supports RACH-less in an NTN environment.

[0266] In step 10-10, the terminal can receive system information broadcast by the base station. The base station may be a TN (ground base station) or an NTN (satellite base station).

[0267] The above system information includes satellite-related configuration information for serving NTN cells and adjacent NTN cells. In addition, the above configuration information may include information necessary to derive N_TA or TA values ​​corresponding to the adjacent NTN cells.

[0268] In steps 10-15, the terminal can obtain information necessary to derive N_TA or TA values ​​corresponding to the adjacent NTN cells. This can be provided through the system information or through dedicated signaling transmitted from the serving NTN cell.

[0269] In step 10-20, the terminal can derive an N_TA or TA value for a predetermined adjacent NTN cell(s) based on the information.

[0270] In step 10-25, the terminal may receive configuration information related to a RACH-less handover to a specific NTN cell from the base station. Along with the configuration information, information necessary to derive an N_TA or TA value may be provided, and in this case, the terminal may derive an N_TA or TA value for the target NTN cell after receiving the information.

[0271] In step 10-30, the terminal can apply the derived TA value and transmit PUSCH to the target NTN cell. That is, it performs a RACH-less handover to the target cell.

[0272] In step 10-35, the terminal transmits the TAR MAC CE to the target cell.

[0273] FIG. 1p is a flowchart of base station operations for performing a Non-Terrestrial Network (NTN) Random Access Channel (RACH)-less handover according to one embodiment of the present disclosure.

[0274] In step 1p-05 of FIG. 1, the base station broadcasts system information. The base station may be a TN (ground base station) or an NTN (satellite base station). The system information may include satellite-related configuration information for a serving NTN cell and adjacent NTN cells. Additionally, the configuration information may include information necessary to derive N_TA or TA values ​​corresponding to the adjacent NTN cells.

[0275] In step 1p-10 of Fig. 1, the base station can receive capability information from the terminal.

[0276] In step 1p-15 of FIG. 1, the base station may transmit information necessary to derive N_TA or TA values ​​corresponding to adjacent NTN cells to the terminal using the system information or dedicated RRC signaling.

[0277] In step 1p-20 of FIG. 1, the base station may transmit a predetermined inter-node message, HandoverPreparationInformation message, to the target NTN cell to trigger a RACH-less handover.

[0278] In step 1p-25 of FIG. 1, the base station receives a HandoverCommand from the target NTN cell. At this time, configuration information necessary to perform a RACH-less handover is also provided.

[0279] In step 1p-30 of Fig. 1, the base station can transmit information received from the target NTN cell to the terminal.

[0280]

[0281] Figure 1q is a flowchart of base station operations for performing a Non-Terrestrial Network (NTN) Random Access Channel (RACH)-less handover according to one embodiment of the present disclosure. Figure 1q is a diagram illustrating the structure of a terminal according to one embodiment of the present disclosure.

[0282] Referring to the drawing above, the terminal includes an RF (Radio Frequency) processing unit (1q-10), a baseband processing unit (1q-20), a storage unit (1q-30), and a control unit (1q-40).

[0283] The RF processing unit (1q-10) performs functions for transmitting and receiving signals through a wireless channel, such as signal band conversion and amplification. That is, the RF processing unit (1q-10) up-converts the baseband signal provided by the baseband processing unit (1q-20) into an RF band signal and transmits it through an antenna, and down-converts the RF band signal received through the antenna into a baseband signal. For example, the RF processing unit (1q-10) may include a transmission filter, a reception filter, an amplifier, a mixer, an oscillator, a DAC (digital to analog converter), an ADC (analog to digital converter), etc. Although only one antenna is shown in the drawing, the terminal may be equipped with multiple antennas. In addition, the RF processing unit (1q-10) may include multiple RF chains. Furthermore, the RF processing unit (1q-10) may perform beamforming. For the above beamforming, the RF processing unit (1q-10) can adjust the phase and magnitude of each of the signals transmitted and received through a plurality of antennas or antenna elements. In addition, the RF processing unit can perform MIMO and can receive multiple layers when performing MIMO operation.

[0284] The baseband processing unit (1q-20) performs a conversion function between a baseband signal and a bit sequence according to the physical layer specifications of the system. For example, when transmitting data, the baseband processing unit (1q-20) generates complex symbols by encoding and modulating the transmitted bit sequence. Additionally, when receiving data, the baseband processing unit (1q-20) restores the received bit sequence by demodulating and decoding the baseband signal provided by the RF processing unit (1q-10). For example, in the case of following the OFDM (orthogonal frequency division multiplexing) method, when transmitting data, the baseband processing unit (1q-20) generates complex symbols by encoding and modulating the transmitted bit sequence, maps the complex symbols to subcarriers, and then constructs OFDM symbols through IFFT (inverse fast Fourier transform) operation and CP (cyclic prefix) insertion. Additionally, upon receiving data, the baseband processing unit (1q-20) divides the baseband signal provided by the RF processing unit (1q-10) into OFDM symbol units, restores the signals mapped to subcarriers through a fast Fourier transform (FFT) operation, and then restores the received bit sequence through demodulation and decoding.

[0285] The baseband processing unit (1q-20) and the RF processing unit (1q-10) transmit and receive signals as described above. Accordingly, the baseband processing unit (1q-20) and the RF processing unit (1q-10) may be referred to as a transmitting unit, a receiving unit, a transmitting and receiving unit, or a communication unit. Furthermore, at least one of the baseband processing unit (1q-20) and the RF processing unit (1q-10) may include a plurality of communication modules to support a plurality of different wireless access technologies. Additionally, at least one of the baseband processing unit (1q-20) and the RF processing unit (1q-10) may include different communication modules to process signals of different frequency bands. For example, the different wireless access technologies may include wireless LAN (e.g., IEEE 802.11), cellular network (e.g., LTE), etc. In addition, the above different frequency bands may include super high frequency (SHF) bands (e.g., 2 NRHz, NRHz) and millimeter wave (e.g., 60 GHz) bands.

[0286] The storage unit (1q-30) stores data such as basic programs, application programs, and setting information for the operation of the terminal. In particular, the storage unit (1q-30) can store information related to a second connection node that performs wireless communication using a second wireless connection technology. Additionally, the storage unit (1q-30) provides the stored data upon a request from the control unit (1q-40).

[0287] The control unit (1q-40) controls the overall operations of the terminal. For example, the control unit (1q-40) transmits and receives signals through the baseband processing unit (1q-20) and the RF processing unit (1q-10). Additionally, the control unit (1q-40) writes and reads data to and from the storage unit (1q-40). To this end, the control unit (1q-40) may include at least one processor. For example, the control unit (1q-40) may include a communication processor (CP) that performs control for communication and an application processor (AP) that controls upper layers such as applications.

[0288] FIG. 1r is a block diagram illustrating the configuration of a base station according to one embodiment of the present disclosure.

[0289] As illustrated in the drawing above, the base station is configured to include an RF processing unit (1r-10), a baseband processing unit (1r-20), a backhaul communication unit (1r-30), a storage unit (1r-40), and a control unit (1r-50).

[0290] The RF processing unit (1r-10) performs functions for transmitting and receiving signals through a wireless channel, such as signal band conversion and amplification. That is, the RF processing unit (1r-10) up-converts the baseband signal provided by the baseband processing unit (1r-20) into an RF band signal, transmits it through an antenna, and down-converts the RF band signal received through the antenna into a baseband signal. For example, the RF processing unit (1r-10) may include a transmit filter, a receive filter, an amplifier, a mixer, an oscillator, a DAC, an ADC, etc. Although only one antenna is shown in the drawing, the first connection node may be equipped with multiple antennas. Additionally, the RF processing unit (1r-10) may include multiple RF chains. Furthermore, the RF processing unit (1r-10) may perform beamforming. For the above beamforming, the RF processing unit (1r-10) can adjust the phase and magnitude of each of the signals transmitted and received through a plurality of antennas or antenna elements. The RF processing unit can perform down-to-down MIMO operation by transmitting one or more layers.

[0291] The baseband processing unit (1r-20) performs a conversion function between a baseband signal and a bit sequence according to the physical layer specifications of the first wireless access technology. For example, when transmitting data, the baseband processing unit (1r-20) generates complex symbols by encoding and modulating the transmitted bit sequence. Additionally, when receiving data, the baseband processing unit (1r-20) restores the received bit sequence by demodulating and decoding the baseband signal provided by the RF processing unit (1r-10). For example, in the case of following the OFDM method, when transmitting data, the baseband processing unit (1r-20) generates complex symbols by encoding and modulating the transmitted bit sequence, maps the complex symbols to subcarriers, and then constructs OFDM symbols through IFFT operation and CP insertion. Additionally, upon receiving data, the baseband processing unit (1r-20) divides the baseband signal provided by the RF processing unit (1r-10) into OFDM symbol units, restores the signals mapped to subcarriers through FFT operations, and then restores the received bit sequence through demodulation and decoding. The baseband processing unit (1r-20) and the RF processing unit (1r-10) transmit and receive signals as described above. Accordingly, the baseband processing unit (1r-20) and the RF processing unit (1r-10) may be referred to as a transmitting unit, a receiving unit, a transmitting and receiving unit, a communication unit, or a wireless communication unit.

[0292] The backhaul communication unit (1r-30) provides an interface for communicating with other nodes within the network. That is, the backhaul communication unit (1r-30) converts a bit sequence transmitted from the main base station to another node, e.g., an auxiliary base station, a core network, etc., into a physical signal, and converts a physical signal received from the other node into a bit sequence.

[0293] The storage unit (1r-40) stores data such as basic programs, application programs, and configuration information for the operation of the main station. In particular, the storage unit (1r-40) can store information regarding bearers assigned to connected terminals, measurement results reported from connected terminals, etc. Additionally, the storage unit (1r-40) can store information serving as a criterion for determining whether to provide or disconnect multiple connections to the terminals. Furthermore, the storage unit (1r-40) provides the stored data upon the request of the control unit (1r-50).

[0294] The control unit (1r-50) controls the overall operations of the main station. For example, the control unit (1r-50) transmits and receives signals through the baseband processing unit (1r-20) and the RF processing unit (1r-10) or through the backhaul communication unit (1r-30). Additionally, the control unit (1r-50) writes and reads data to and from the storage unit (1r-40). To this end, the control unit (1r-50) may include at least one processor.

[0295] 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.

[0296] 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.

[0297] 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.

[0298] Additionally, the program may be stored on an attachable storage device accessible 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 the device performing the embodiment of the present disclosure through an external port. Additionally, a separate storage device on the communication network may be connected to the device performing the embodiment of the present disclosure.

[0299] In the specific embodiments of the present disclosure described above, the components included in the invention 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, or even if a component is expressed in the singular form, it may be composed of a plural form.

[0300] 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 as needed. For example, parts of one embodiment of the present disclosure and parts of another embodiment may be combined to operate a base station and a terminal. For example, parts of the first embodiment and the second embodiment of the present disclosure may be combined to operate a base station and a terminal. In addition, although the above embodiments are presented based on an FDD LTE system, other variations based on the technical concept of the above embodiments may be implemented in other systems such as a TDD LTE system, 5G, or NR system.

[0301] Meanwhile, the order of description in the drawings illustrating the method of the present invention does not necessarily correspond to the order of execution, and the order of execution may be changed or executed in parallel.

[0302] Alternatively, drawings describing the method of the present invention may omit some components and include only some components to the extent that the essence of the present invention is not impaired.

[0303] In addition, the method of the present invention may be implemented by combining some or all of the contents included in each embodiment within a scope that does not impair the essence of the invention.

[0304] Various embodiments of the present disclosure have been described above. The foregoing description of the present disclosure is for illustrative purposes only and is not limited to the embodiments disclosed. Those skilled in the art will understand that other specific forms can be easily modified without altering the technical spirit or essential features of the present disclosure. The scope of the present disclosure is defined by the claims set forth below rather than by the foregoing detailed description, and all modifications or variations derived from the meaning and scope of the claims and equivalent concepts should be interpreted as being included within the scope of the present disclosure.

Claims

1. A method performed by a terminal in a communication system, A step of receiving configuration information for establishing Carrier Aggregation (CA) or Dual Connectivity (DC) in a Non-Terrestrial Network (NTN) from a first satellite supporting a first cell, Step of determining satellite reference time information (Epoch Time) of the second cell; A step of determining propagation delay difference information for the second cell based on the reference serving cell, based on the satellite reference time information of the second cell; and A method characterized by including the step of transmitting first control information, which includes propagation delay difference information for the second cell, to a first satellite supporting the first cell or a second satellite supporting the second cell.

2. In Paragraph 1, The satellite reference time information of the second cell is determined based on the Epoch Time of a Special Cell (SpCell) of a Cell Group (CG) containing the second cell, or based on the Epoch Time of a serving cell included in the same Timing Advance Group (TAG) as the second cell, or is determined by the Epoch Time of a serving cell set by the network, A method characterized in that the reference serving cell of the above-mentioned propagation delay difference information is set as SpCell, one reference serving cell is set per CG, is set per TAG, or is set by a network.

3. In Paragraph 1, A step of receiving a Radio Resource Control (RRC) Release message from a first satellite supporting the first cell, the message including Early Timing Advance (TA) Reporting related setting information, wherein the Early TA Reporting related setting information includes at least one target satellite information; A step of transitioning to RRC inactive mode or RRC idle mode based on the above RRC release message; A step of acquiring TA information regarding at least one target satellite based on the above Early TA Reporting related setting information; and The method is characterized by including the step of transmitting second control information, which includes TA information regarding at least one target satellite, to a first satellite supporting the first cell after transitioning to an RRC Connected state. A method characterized in that the above TA information is determined based on a timing control parameter (N_TA), and the above timing control parameter (N_TA) is determined based on a random access procedure, determined based on the location of the terminal, or determined based on information predicted based on an area containing the terminal.

4. In Paragraph 1, A step of obtaining satellite switch setting information, wherein the satellite switch setting information includes at least one of information related to the service stop time of a source satellite (t-service) or information related to the service start time of a target satellite (t-service start); and Based on the above satellite change setting information, the method further includes the step of changing the second cell to a third cell, and A method characterized by obtaining the above satellite change setting information through system information from a first satellite supporting the first cell, through system information from a second satellite supporting the second cell, through dedicated signaling from a first satellite supporting the first cell, or from an adjacent terrestrial network (TN) cell.

5. A method performed by a first satellite supporting a first cell in a communication system, A step of transmitting configuration information to a terminal for establishing Carrier Aggregation (CA) or Dual Connectivity (DC) in a Non-Terrestrial Network (NTN); and The method includes the step of receiving first control information including propagation delay difference information for a second cell from the above terminal, A method characterized in that the propagation delay difference information for the second cell is determined based on the satellite reference time information (Epoch Time) of the second cell, based on the reference serving cell.

6. In Paragraph 5, The satellite reference time information of the second cell is determined based on the Epoch Time of a Special Cell (SpCell) of a Cell Group (CG) containing the second cell, or based on the Epoch Time of a serving cell included in the same Timing Advance Group (TAG) as the second cell, or is determined by the Epoch Time of a serving cell set by the network, A method characterized in that the reference serving cell of the above-mentioned propagation delay difference information is set as SpCell, one reference serving cell is set per CG, is set per TAG, or is set by a network.

7. In Paragraph 5, The step of receiving a Radio Resource Control (RRC) Release message containing Early TA Reporting related configuration information to the terminal, wherein the Early TA Reporting related configuration information includes at least one target satellite information; The method includes the step of receiving second control information from the terminal, which includes TA information regarding at least one target satellite, after switching to an RRC Connected state with the terminal. The TA information regarding at least one target satellite is determined based on the Early TA Reporting related setting information in the RRC inactive mode or RRC idle mode of the terminal, and A method characterized in that the above TA information is determined based on a timing control parameter (N_TA), and the above timing control parameter (N_TA) is determined based on a random access procedure, determined based on the location of the terminal, or determined based on information predicted based on an area containing the terminal.

8. In Paragraph 5, The method includes the step of transmitting satellite switch setting information to the above terminal, The above satellite change setting information includes at least one of information related to the service stop time of the source satellite (t-service) or information related to the service start time of the target satellite (t-service start), and A method characterized in that the above satellite change setting information relates to a change from the second cell to the third cell.

9. In a terminal in a 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, Receive configuration information for establishing Carrier Aggregation (CA) or Dual Connectivity (DC) in a Non-Terrestrial Network (NTN) from a first satellite supporting a first cell, and Determining the satellite reference time information (Epoch Time) of the second cell, Based on the satellite reference time information of the second cell, propagation delay difference information for the second cell is determined based on the reference serving cell, and A memory storing a command to transmit first control information, including propagation delay difference information for the second cell, to a first satellite supporting the first cell or a second satellite supporting the second cell; A terminal including 10. In Paragraph 9, The satellite reference time information of the second cell is determined based on the Epoch Time of a Special Cell (SpCell) of a Cell Group (CG) containing the second cell, or based on the Epoch Time of a serving cell included in the same Timing Advance Group (TAG) as the second cell, or is determined by the Epoch Time of a serving cell set by the network, A terminal characterized in that the reference serving cell of the above-mentioned propagation delay difference information is set as an SpCell, one reference serving cell is set per CG, is set per TAG, or is set by a network.

11. In paragraph 9, the above command is that the terminal, A Radio Resource Control (RRC) Release message including Early Timing Advance (TA) Reporting related configuration information is received from a first satellite supporting the first cell, and the Early TA Reporting related configuration information includes at least one target satellite information. Based on the above RRC release message, transition to RRC inactive mode or RRC idle mode, and Based on the above Early TA Reporting related configuration information, TA information regarding at least one target satellite is obtained, and After transitioning to the RRC Connected state, second control information including TA information regarding at least one target satellite is transmitted to the first satellite supporting the first cell, and A terminal characterized in that the above TA information is determined based on a timing control parameter (N_TA), and the above timing control parameter (N_TA) is determined based on a random access procedure, determined based on the location of the terminal, or determined based on information predicted based on an area containing the terminal.

12. In paragraph 9, the above command is that the terminal, Satellite switch setting information is obtained, and said satellite switch setting information includes at least one of information related to the service stop time of a source satellite (t-service) or information related to the service start time of a target satellite (t-service start). Based on the above satellite change setting information, the above second cell is changed to a third cell, and A terminal characterized by obtaining the above satellite change setting information through system information from a first satellite supporting the first cell, through system information from a second satellite supporting the second cell, through dedicated signaling from a first satellite supporting the first cell, or from an adjacent terrestrial network (TN) cell.

13. In a first satellite supporting a first cell in a 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 first satellite is connected to communicate with the at least one processor and is capable of being executed individually or in any combination of the at least one processor, so that the first satellite, Transmit configuration information to a terminal to configure Carrier Aggregation (CA) or Dual Connectivity (DC) in a Non-Terrestrial Network (NTN), and A memory storing a command to receive first control information including propagation delay difference information for a second cell from the terminal; comprising, A first satellite characterized in that the propagation delay difference information for the second cell is determined based on the satellite reference time information (Epoch Time) of the second cell with respect to the reference serving cell.

14. In Paragraph 13, The above command causes the first satellite to transmit satellite switch setting information to the terminal, and The above satellite change setting information includes at least one of information related to the service stop time of the source satellite (t-service) or information related to the service start time of the target satellite (t-service start), and The above satellite change setting information relates to the change from the second cell to the third cell, and The satellite reference time information of the second cell is determined based on the Epoch Time of a Special Cell (SpCell) of a Cell Group (CG) containing the second cell, or based on the Epoch Time of a serving cell included in the same Timing Advance Group (TAG) as the second cell, or is determined by the Epoch Time of a serving cell set by the network, A first satellite characterized in that the reference serving cell of the above-mentioned propagation delay difference information is set as a SpCell, one reference serving cell is set per CG, is set per TAG, or is set by a network.

15. In Paragraph 13, the above command is that the above first satellite, The terminal receives a Radio Resource Control (RRC) Release message containing Early TA Reporting related configuration information, and the Early TA Reporting related configuration information includes at least one target satellite information. After switching to an RRC Connected state with the terminal, receive second control information including TA information regarding at least one target satellite from the terminal, and The TA information regarding at least one target satellite is determined based on the Early TA Reporting related setting information in the RRC inactive mode or RRC idle mode of the terminal, and The first satellite is characterized in that the above TA information is determined based on a timing control parameter (N_TA), and the above timing control parameter (N_TA) is determined based on a random access procedure, determined based on the location of the terminal, or determined based on information predicted based on an area containing the terminal.

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