Method and apparatus for satellite handover in wireless communication system

Abstract

Techniques for satellite handover in a wireless communication system are provided. A method performed by a terminal comprises the steps of: acquiring target satellite-related information from a source satellite; executing satellite switching from the source satellite to the target satellite based on the target satellite related information; and after executing the satellite switching, communicating with the target satellite based on the target satellite related information.

Description

Technical Field

[0001] This disclosure relates to satellite handover technology in wireless communication systems, and more specifically, to satellite handover technology in wireless communication systems that allows satellite handover without changing the Physical Cell Identifier (PCI). Background Technology

[0002] With the development of information and communication technologies, various wireless communication technologies are being developed. Representative wireless communication technologies include Long Term Evolution (LTE) and New Radio (NR), which are defined as standards under the 3rd Generation Partnership Project (3GPP). LTE can be one of the fourth-generation (4G) wireless communication technologies, and NR can be one of the fifth-generation (5G) wireless communication technologies.

[0003] To handle the rapidly increasing wireless data following the commercialization of 4G communication systems (e.g., LTE-enabled systems), 5G communication systems (e.g., NR-enabled systems) are being considered, utilizing frequency bands higher than those of 4G systems (e.g., below 6 GHz) and also the frequency bands of 4G systems. 5G communication systems can support enhanced mobile broadband (eMBB), ultra-reliable low-latency communication (URLLC), and massive machine-type communication (mMTC) scenarios.

[0004] Such wireless communication systems can be designed considering various scenarios, service requirements, potential system compatibility, and similar factors. In particular, there is active discussion regarding 5G NR systems and subsequent terrestrial network (TN) and non-terrestrial network (NTN) based communications. Communication based on these foundations is anticipated.

[0005] Traditional wireless communication systems (such as LTE) are TN-based wireless communication systems, where base stations (e.g., eNB, gNB, etc.) and terminals (e.g., user equipment (UE)) are both located on the ground. NTN, on the other hand, refers to a network where at least one of the base stations or terminals is not located on the ground. For example, TN-based communications may experience service disruptions during disasters and emergencies such as fires, earthquakes, and tsunamis. Furthermore, in low-demand-density suburbs, rural areas, remote areas, isolated areas, and at sea, there may be limitations in providing service due to higher capital expenditures (CAPEX) and operating expenditures (OPEX) relative to operator revenue. NTN can be a technology applied to overcome these limitations of TN. In such NTN-based systems, a technology is needed that allows satellite handover without changing the Physical Cell Identifier (PCI). Summary of the Invention

[0006] Technical issues This disclosure aims to solve the above-mentioned problems by providing a method and apparatus for satellite switching in a wireless communication system, which allows satellite switching without changing the PCI.

[0007] Technical solution A satellite handover method according to a first exemplary embodiment of the present disclosure for achieving the above objectives may include: obtaining target satellite-related information from a source satellite; performing a satellite handover from the source satellite to the target satellite based on the target satellite-related information; and, after performing the satellite handover, performing communication with the target satellite based on the target satellite-related information.

[0008] The steps of communicating with the target satellite may include: connecting to the target satellite without a random access procedure based on information related to the target satellite; and communicating with the target satellite based on information related to the target satellite.

[0009] The source satellite and the target satellite can be connected to the same base station. The source satellite can form a first quasi-Earth fixed cell, and the target satellite can form a second quasi-Earth fixed cell. The Physical Cell Identifier (PCI) of the first quasi-Earth fixed cell can be the same as the PCI of the second quasi-Earth fixed cell, and the frequency of the first synchronization signal block (SSB) transmitted by the source satellite can be the same as the frequency of the second SSB transmitted by the target satellite.

[0010] The steps of communicating with the target satellite may include: stopping communication services with the source satellite based on the satellite switching; connecting to the target satellite based on the target satellite's relevant information; and communicating with the target satellite through the target satellite's service link based on the target satellite's relevant information.

[0011] The steps of communicating with the target satellite may include: connecting to the target satellite based on target satellite-related information; stopping communication on the service link of the source satellite after connecting to the target satellite; and communicating with the target satellite through the service link of the target satellite based on the target satellite-related information.

[0012] The terminal can determine the uplink timing advance (TA) for the target satellite based on the relevant information of the target satellite, and can apply the determined uplink TA to communication with the target satellite.

[0013] The target satellite-related information may include at least one of the following in the non-terrestrial network configuration information for the target satellite: epoch time, uplink TA information, ephemeris information, uplink synchronization effective duration, cell-specific scheduling offset, network scheduling offset, TA report information, downlink polarization information, or uplink polarization information.

[0014] The target satellite information may include the time when the provision of communication services by the source satellite was stopped. When the provision of communication services was stopped at the time, the terminal may maintain the uplink Hybrid Automatic Repeat Request (HARQ) buffer without refreshing the uplink HARQ buffer, and when communication with the target satellite begins, the terminal may resume uplink HARQ operation with the target satellite.

[0015] The target satellite information may be included in the System Information Block (SIB) obtained by the terminal from the source satellite.

[0016] The terminal may perform the satellite handover when the target satellite information is included in a non-terrestrial network-related SIB, and may not perform the satellite handover when the target satellite information is not included in a non-terrestrial network-related SIB.

[0017] A satellite handover method according to a second exemplary embodiment of the present disclosure for achieving the above objectives, as a base station, may include: providing a terminal with target satellite-related information via a source satellite connected to the base station; performing a satellite handover from the source satellite to the target satellite when the provision of communication services by the source satellite is suspended; and providing communication services to the terminal via the target satellite after performing the satellite handover, wherein the base station provides the communication services to the terminal via the target satellite without performing a random access procedure between the target satellite and the terminal.

[0018] The target satellite information can be included in the System Information Block (SIB) sent to the terminal.

[0019] The target satellite-related information may include at least one of the following in the non-terrestrial network configuration information for the target satellite: epoch time, uplink TA information, ephemeris information, uplink synchronization effective duration, cell-specific scheduling offset, network scheduling offset, TA report information, downlink polarization information, or uplink polarization information.

[0020] The base station may include the target satellite information in the non-terrestrial network-related SIB to instruct the terminal to perform the satellite handover, and the base station may not include the target satellite information in the non-terrestrial network-related SIB to instruct the terminal not to perform the satellite handover.

[0021] According to a third exemplary embodiment of the present disclosure for achieving the above objectives, a satellite switching device as a terminal may include a processor, and the processor causes the terminal to perform the following operations: obtaining target satellite-related information from a source satellite; performing a satellite switch from the source satellite to the target satellite based on the target satellite-related information; and, after performing the satellite switch, performing communication with the target satellite based on the target satellite-related information.

[0022] When communicating with the target satellite, the processor can cause the terminal to perform the following operations: connect to the target satellite without a random access procedure based on the target satellite-related information; and perform communication with the target satellite based on the target satellite-related information.

[0023] When performing communication with the target satellite, the processor causes the terminal to perform the following operations: stop communication service with the source satellite based on the satellite switching; connect to the target satellite based on the target satellite's relevant information; and perform communication with the target satellite through the target satellite's service link based on the target satellite's relevant information.

[0024] The target satellite information may include the time when the provision of communication services by the source satellite was stopped. When the provision of communication services was stopped at the time, the processor may enable the terminal to maintain the uplink Hybrid Automatic Repeat Request (HARQ) buffer without refreshing the uplink HARQ buffer. When communication with the target satellite begins, the processor may enable the terminal to resume uplink HARQ operation with the target satellite.

[0025] The target satellite information may be included in the System Information Block (SIB) obtained by the terminal from the source satellite.

[0026] When the target satellite information is included in a non-terrestrial network-related SIB, the processor can cause the terminal to perform the satellite handover; when the target satellite information is not included in the non-terrestrial network-related SIB, the processor can cause the terminal not to perform the satellite handover.

[0027] Beneficial effects According to this disclosure, the terminal does not need to perform a separate random access procedure when performing a satellite handover from a source satellite to a target satellite, thereby solving the random access channel (RACH) congestion problem caused by the random access procedure. Furthermore, according to this disclosure, even if the terminal does not immediately perform a random access procedure after the satellite handover, if the terminal identifies a pre-compensated timing advance (TA) associated with the target satellite, the terminal can still perform uplink transmission to the base station. Additionally, according to this disclosure, the terminal can adjust the TA based on TA adjustment information received from the base station, enabling smooth communication via the target satellite. Attached Figure Description

[0028] Figure 1 This is a conceptual diagram illustrating an exemplary embodiment of a communication system.

[0029] Figure 2 This is a block diagram illustrating an exemplary embodiment of a communication node constituting a communication system.

[0030] Figure 3 This is a conceptual diagram illustrating an exemplary embodiment of a radio interface protocol structure in a communication system.

[0031] Figure 4 This is a conceptual diagram illustrating an exemplary embodiment of time resources for transmitting radio signals in a communication system.

[0032] Figure 5 This is a conceptual diagram illustrating the time difference between the reception timing of the i-th downlink frame and the transmission timing of the i-th uplink frame in an exemplary embodiment of a communication system.

[0033] Figure 6 This is a conceptual diagram illustrating an exemplary embodiment of a time / frequency resource grid for a communication system.

[0034] Figure 7 This is a conceptual diagram illustrating an exemplary embodiment of a communication system's synchronization signal and physical broadcast channel (SS / PBCH) block or synchronization signal block (SSB).

[0035] Figure 8 This is a conceptual diagram illustrating a first exemplary embodiment of a non-terrestrial network.

[0036] Figure 9 This is a conceptual diagram illustrating a second exemplary embodiment of a non-terrestrial network.

[0037] Figure 10 This is a conceptual diagram illustrating an exemplary embodiment of a satellite handover method in a quasi-Earth fixed cell.

[0038] Figure 11 This is a conceptual diagram illustrating an exemplary embodiment of a hard satellite handover method in a quasi-Earth fixed cell.

[0039] Figure 12 This is a conceptual diagram illustrating an exemplary embodiment of a soft satellite handover method in a quasi-Earth fixed cell.

[0040] Figure 13 This is a conceptual diagram illustrating a first exemplary embodiment of a satellite handover method without altering the PCI.

[0041] Figure 14 This is a conceptual diagram illustrating a first exemplary embodiment of a reference point, a public TA, and a UE-specific TA.

[0042] Figure 15 This is a conceptual diagram illustrating SSB and beam scanning operations in a wireless communication system.

[0043] Figure 16 This is a conceptual diagram illustrating a first exemplary embodiment of a method for indicating necessary system information using indicators included in the SIB.

[0044] Figure 17 This is a conceptual diagram illustrating a second exemplary embodiment of a method for indicating necessary system information using indicators included in the SIB.

[0045] Figure 18 This is a conceptual diagram illustrating a first exemplary embodiment of a method for independently providing system information needed immediately after a switchover within the SIB.

[0046] Figure 19 This is a conceptual diagram illustrating a first exemplary embodiment of satellite handover time based on hard satellite handover.

[0047] Figure 20 This is a flowchart illustrating a first exemplary embodiment of terminal operation in a satellite handover method in a wireless communication system. Detailed Implementation

[0048] While this disclosure is capable of various modifications and alternatives, specific embodiments thereof are illustrated by way of example in the accompanying drawings and will be described in detail herein. However, it should be understood that this disclosure is not intended to be limited to the specific forms disclosed, but rather, this disclosure is intended to cover all modifications, equivalents, and alternatives falling within the spirit and scope of this disclosure. Throughout the description of the accompanying drawings, the same reference numerals denote the same elements.

[0049] It should be understood that although the terms first, second, etc., may be used herein to describe various elements, these elements should not be limited by these terms. These terms are used only to distinguish one element from another. For example, without departing from the scope of this disclosure, a first element may be referred to as a second element, and similarly, a second element may be referred to as a first element. As used herein, the term "and / or" includes any and all combinations of one or more of the associated listed items.

[0050] In exemplary embodiments of this disclosure, "at least one of A and B" may refer to "at least one A or B" or "at least one of one or more combinations of A and B". Furthermore, "one or more of A and B" may refer to "one or more of A or B" or "one or more of one or more combinations of A and B".

[0051] It should be understood that when an element is described as "connected" or "coupled" to another element, it can be directly connected or coupled to the other element, or there may be intermediate elements. Conversely, when an element is described as "directly connected" or "directly coupled" to another element, there are no intermediate elements. Other terms used to describe the relationship between elements should be interpreted in a similar manner (i.e., "between" and "directly between", "adjacent" and "directly adjacent", etc.).

[0052] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit this disclosure. As used herein, the singular forms “a,” “an,” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprising,” “including,” “containing,” and / or “comprising” as used herein specify the presence of the stated features, integers, steps, operations, elements, and / or components, but do not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof.

[0053] Unless otherwise defined, all terms used herein (including technical and scientific terms) shall have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure pertains. It will be further understood that terms such as those defined in common dictionaries shall be interpreted as having a meaning consistent with their meaning in the context of the relevant field and shall not be interpreted in an idealized or overly formal sense unless expressly defined herein.

[0054] A communication system based on exemplary embodiments of the present disclosure will be described. The communication system based on exemplary embodiments of the present disclosure is not limited to what is described below, and can be applied to various communication systems. Here, "communication system" can have the same meaning as "communication network".

[0055] Throughout this disclosure, networks may include, for example, wireless internet such as Wi-Fi, mobile internet such as WiBro or WiMax, 2G mobile communication networks such as GSM or CDMA, 3G mobile communication networks such as WCDMA or CDMA2000, 3.5G mobile communication networks such as HSDPA or HSUPA, 4G mobile communication networks such as LTE or LTE-Advanced networks, 5G mobile communication networks, etc.

[0056] Throughout this disclosure, "terminal" may refer to a mobile station, mobile terminal, subscriber station, portable subscriber station, user equipment, access terminal, etc., and may include all or part of the functions of a terminal, mobile station, mobile terminal, subscriber station, mobile subscriber station, user equipment, access terminal, etc.

[0057] Here, desktop computers, laptops, tablet PCs, cordless phones, mobile phones, smartphones, smartwatches, smart glasses, e-book readers, portable multimedia players (PMPs), portable game consoles, navigation devices, digital cameras, digital multimedia broadcast (DMB) players, digital audio recorders, digital audio players, digital image recorders, digital image players, digital video recorders, and digital video players with communication capabilities can be used as terminals.

[0058] Throughout this specification, "base station" may refer to an access point, radio access station, Node B (NB), evolved Node B (eNB), base transceiver station, mobile multi-hop relay (MMR)-BS, etc., and may include all or part of the functions of base stations, access points, radio access stations, NBs, eNBs, base transceiver stations, MMR-BS, etc.

[0059] In the following description, preferred exemplary embodiments of the present disclosure will be described in more detail with reference to the accompanying drawings. In describing the present disclosure, the same reference numerals are used for the same elements in the drawings for ease of overall understanding, and repeated descriptions of the same elements are omitted.

[0060] Figure 1 This is a conceptual diagram illustrating an exemplary embodiment of a communication system.

[0061] Reference Figure 1The communication system 100 may include multiple communication nodes 110-1, 110-2, 110-3, 120-1, 120-2, 130-1, 130-2, 130-3, 130-4, 130-5, and 130-6. These multiple communication nodes can support 4G communication (e.g., Long Term Evolution (LTE), LTE-A Advanced)) and 5G communication (e.g., New Radio (NR)) as specified in the 3GPP standards. 4G communication can be performed in frequency bands below 6 GHz, and 5G communication can be performed in frequency bands above and below 6 GHz.

[0062] For example, to perform 4G, 5G, and 6G communications, multiple communication nodes can support communication protocols based on Code Division Multiple Access (CDMA), Wideband CDMA (WCDMA), Time Division Multiple Access (TDMA), Frequency Division Multiple Access (FDMA), Orthogonal Frequency Division Multiplexing (OFDM), Filtered OFDM, Cyclic Prefix OFDM (CP-OFDM), Discrete Fourier Transform Extended OFDM (DFT-s-OFDM), Orthogonal Frequency Division Multiple Access (OFDMA), Single Carrier FDMA (SC-FDMA), Non-Orthogonal Multiple Access (NOMA), Generalized Frequency Division Multiplexing (GFDM), Filter Bank Multicarrier (FBMC), Universal Filtered Multicarrier (UFMC), and Space Division Multiple Access (SDMA), etc.

[0063] In addition, the communication system 100 may also include a core network. When the communication system 100 supports 4G communication, the core network may include a Serving Gateway (S-GW), a Packet Data Network (PDN) Gateway (P-GW), a Mobility Management Entity (MME), etc. When the communication system 100 supports 5G or 6G communication, the core network may include User Plane Function (UPF), Session Management Function (SMF), Access and Mobility Management Function (AMF), etc.

[0064] In addition, each of the plurality of communication nodes 110-1, 110-2, 110-3, 120-1, 120-2, 130-1, 130-2, 130-3, 130-4, 130-5 and 130-6 constituting the communication system 100 may have the following structure.

[0065] Figure 2 This is a block diagram illustrating an exemplary embodiment of a communication node constituting a communication system.

[0066] Reference Figure 2The communication node 200 may include at least one processor 210, a memory 220, and a transceiver 230 connected to a network to perform communication. Furthermore, the communication node 200 may also include an input interface device 240, an output interface device 250, a storage device 260, etc. Each component included in the communication node 200 can communicate with each other when connected via a bus 270.

[0067] However, each component included in communication node 200 may not be connected to the common bus 270, but may be connected to processor 210 via a separate interface or a separate bus. For example, processor 210 may be connected to at least one of memory 220, transceiver 230, input interface device 240, output interface device 250 and storage device 260 via a dedicated interface.

[0068] Processor 210 can execute a program stored in at least one of memory 220 and storage device 260. Processor 210 may refer to a central processing unit (CPU), a graphics processing unit (GPU), or a dedicated processor that executes methods according to embodiments of the present disclosure thereon. Each of memory 220 and storage device 260 may be constituted by at least one of volatile storage medium and non-volatile storage medium. For example, memory 220 may include at least one of read-only memory (ROM) and random access memory (RAM).

[0069] Refer again Figure 1 The communication system 100 may include multiple base stations 110-1, 110-2, 110-3, 120-1, and 120-2, and multiple terminals 130-1, 130-2, 130-3, 130-4, 130-5, and 130-6. Each of the first base station 110-1, the second base station 110-2, and the third base station 110-3 may form a macro cell, and each of the fourth base station 120-1 and the fifth base station 120-2 may form a small cell. The fourth base station 120-1, the third terminal 130-3, and the fourth terminal 130-4 may be within the cell coverage area of ​​the first base station 110-1. Furthermore, the second terminal 130-2, the fourth terminal 130-4, and the fifth terminal 130-5 may be within the cell coverage area of ​​the second base station 110-2. Furthermore, the fifth base station 120-2, the fourth terminal 130-4, the fifth terminal 130-5, and the sixth terminal 130-6 can all fall within the cell coverage area of ​​the third base station 110-3. Additionally, the first terminal 130-1 can fall within the cell coverage area of ​​the fourth base station 120-1, and the sixth terminal 130-6 can fall within the cell coverage area of ​​the fifth base station 120-2.

[0070] Here, each of the multiple base stations 110-1, 110-2, 110-3, 120-1, and 120-2 can refer to a Node B (NB), an evolved Node B (eNB), a gNB, a Base Transceiver Station (BTS), a radio base station, a radio transceiver, an access point, an access node, a Roadside Unit (RSU), a Remote Radio Header (RRH), a Transmitter Point (TP), a Transmitter and Receiver Point (TRP), an eNB, a gNB, etc.

[0071] Each of the multiple terminals 130-1, 130-2, 130-3, 130-4, 130-5 and 130-6 can refer to a user equipment (UE), terminal, access terminal, mobile terminal, station, subscriber station, mobile station, portable subscriber station, node, device, Internet of Things (IoT) device, installed module / device / terminal, vehicle-mounted device / terminal, etc.

[0072] Furthermore, each of the multiple base stations 110-1, 110-2, 110-3, 120-1, and 120-2 can operate in the same or different frequency bands. The multiple base stations 110-1, 110-2, 110-3, 120-1, and 120-2 can be interconnected via ideal or non-ideal backhaul, and exchange information with each other via ideal or non-ideal backhaul. In addition, each of the multiple base stations 110-1, 110-2, 110-3, 120-1, and 120-2 can be connected to the core network via ideal or non-ideal backhaul. Each of the multiple base stations 110-1, 110-2, 110-3, 120-1, and 120-2 can transmit signals received from the core network to the corresponding terminals 130-1, 130-2, 130-3, 130-4, 130-5, or 130-6, and transmit signals received from the corresponding terminals 130-1, 130-2, 130-3, 130-4, 130-5, or 130-6 to the core network.

[0073] Furthermore, each of the multiple base stations 110-1, 110-2, 110-3, 120-1, and 120-2 can support multiple-input multiple-output (MIMO) transmission (e.g., single-user MIMO (SU-MIMO), multi-user MIMO (MU-MIMO), massive MIMO, etc.), cooperative multipoint (CoMP) transmission, carrier aggregation (CA) transmission, transmission in unlicensed frequency bands, device-to-device (D2D) communication (or neighbor service (ProSe)), etc. Here, each of the multiple terminals 130-1, 130-2, 130-3, 130-4, 130-5, and 130-6 can perform operations corresponding to the operations of the multiple base stations 110-1, 110-2, 110-3, 120-1, and 120-2, as well as operations supported by the multiple base stations 110-1, 110-2, 110-3, 120-1, and 120-2. For example, the second base station 110-2 can transmit signals to the fourth terminal 130-4 in SU-MIMO mode, and the fourth terminal 130-4 can receive signals from the second base station 110-2 in SU-MIMO mode. Optionally, the second base station 110-2 can transmit signals to the fourth terminal 130-4 and the fifth terminal 130-5 in MU-MIMO mode, and the fourth terminal 130-4 and the fifth terminal 130-5 can receive signals from the second base station 110-2 in MU-MIMO mode.

[0074] The first base station 110-1, the second base station 110-2, and the third base station 110-3 can transmit signals to the fourth terminal 130-4 using the CoMP transmission method, and the fourth terminal 130-4 can receive signals from the first base station 110-1, the second base station 110-2, and the third base station 110-3 using the CoMP method. Furthermore, each of the multiple base stations 110-1, 110-2, 110-3, 120-1, and 120-2 can exchange signals with the corresponding terminals 130-1, 130-2, 130-3, 130-4, 130-5, or 130-6 within its cell coverage area using the CA method. Each of base stations 110-1, 110-2, and 110-3 can control the D2D communication between the fourth terminal 130-4 and the fifth terminal 130-5. Therefore, the fourth terminal 130-4 and the fifth terminal 130-5 can perform D2D communication under the control of the second base station 110-2 and the third base station 110-3.

[0075] The following describes a method for configuring and managing a radio interface in a communication system. Even when a method (e.g., transmitting or receiving a signal) performed at a first communication node is described, a corresponding second communication node can also perform a method (e.g., receiving or transmitting a signal) corresponding to the method performed at the first communication node. That is, when the operation of a terminal is described, the corresponding base station can perform an operation corresponding to the terminal's operation. Conversely, when the operation of a base station is described, the corresponding terminal can perform an operation corresponding to the base station's operation.

[0076] Figure 3 This is a conceptual diagram illustrating an exemplary embodiment of a radio interface protocol structure in a communication system.

[0077] Reference Figure 3 An exemplary embodiment of the radio interface protocol structure 300 of the communication system can be configured to include a radio resource control (RRC) layer 310, a media access control (MAC) layer 320, a physical (PHY) layer 330, etc. Figure 3 The exemplary embodiment of the radio interface protocol structure 300 shown can correspond to various exemplary embodiments of the interface, such as the interface between a terminal and a base station, the interface between an IAB node distributed unit (IAB-DU) and an IAB node mobile terminal (IAB-MT) in an integrated access backhaul (IAB) network, the interface between an IAB-DU and a lower-layer node, the interface between an IAB-MT and an upper-layer node, the interface between multiple terminals, etc.

[0078] Near the PHY layer 330, the RRC layer 310 and MAC layer 320 can be positioned above the PHY layer 330. For example, the MAC layer 320 can be positioned above the PHY layer 330, and the RRC layer 310 can be positioned above the MAC layer 320.

[0079] MAC layer 320 can be connected to higher layers (e.g., RRC layer 310) via logical channel 315. PHY layer 330 can be connected to the higher MAC layer 320 via transport channel 325. PHY layer 330 can send control information or measurement information 350 to RRC layer 310 and receive control information or measurement information 350 from RRC layer 310.

[0080] PHY layer 330 can be referred to as "Layer 1" or "L1". MAC layer 320 can be referred to as "Layer 2" or "L2". RRC layer 310 can be referred to as "Layer 3" or "L3". RRC layer 310 and MAC layer 320 can be collectively referred to as "higher layers".

[0081] In this disclosure, "L1 signaling" refers to signaling such as downlink control information (DCI) transmitted on the physical downlink control channel (PDCCH), uplink control information (UCI) transmitted on the physical uplink control channel (PUCCH), and sidelink control information (SCI) transmitted on the physical sidelink control channel (PSCCH), which are channels of PHY layer 330. Similarly, in this disclosure, "higher layer signaling" may include L2 signaling transmitted via MAC control elements (CE), L3 signaling transmitted via RRC signaling, etc. Although for ease of description... Figure 3 The information transmitted via signals through interfaces between base stations or between base station components (such as distributed units (DU) and central units (CU)) (e.g., F1, next-generation (NG) interfaces, etc.) can also be collectively referred to as higher-layer signaling along with L2 signaling or L3 signaling.

[0082] In communication systems that utilize 5G communication technologies, one or more parameter sets from the parameter set in Table 1 can be used for various purposes, such as reducing inter-carrier interference (ICI) based on frequency band characteristics, reducing latency based on service characteristics, etc.

[0083] [Table 1]

[0084] Table 1 is merely an example for ease of description, and exemplary embodiments of parameter sets used in a communication system are not limited to this. Each parameter set This can correspond to the subcarrier spacing (SCS). And information about the cyclic prefix (CP). The terminal can identify the parameter set applied to the downlink bandwidth portion (BWP) or the uplink BWP based on higher-layer parameters such as subcarrier spacing and cyclic prefix. And CP value.

[0085] Figure 4 This is a conceptual diagram illustrating an exemplary embodiment of time resources for transmitting radio signals in a communication system.

[0086] Reference Figure 4 It can include one or more ( Frame 430, comprising one or more subframes Subframe 420 with 14 time slots and including 14 ( The time slot 410 of the OFDM symbol is used to represent the time resource for transmitting radio signals in the communication system 400. In this case, according to the configured parameter set, the values ​​according to Table 2 below can be used in the case of conventional CP. , and The value can be used as the value according to Table 3 below in the case of extended CP. , and The value. OFDM symbols included in a time slot can be classified as "downlink", "flexible" or "uplink" by a combination of higher-layer signaling and L1 signaling or by higher-layer signaling alone.

[0087] [Table 2]

[0088] [Table 3]

[0089] In a 5G NR communication system (e.g., a 5G communication system), frame 430 can have a length of 10 ms, and subframe 420 can have a length of 1 ms. Each frame 430 can be divided into two half-frames of equal length, and the first half-frame (i.e., half-frame 0) can consist of subframes #0 to #4, and the second half-frame (i.e., half-frame 1) can consist of subframes #5 to #9. A carrier can include a set of frames for the uplink (i.e., uplink frames) and a set of frames for the downlink (i.e., downlink frames).

[0090] Figure 5 This is a conceptual diagram illustrating the time difference between the reception timing of the i-th downlink frame and the transmission timing of the i-th uplink frame in an exemplary embodiment of a communication system.

[0091] Reference Figure 5 The time difference between the reception timing of the i-th downlink frame 500 and the transmission timing of the i-th uplink frame 510 can be T. TA 520. Therefore, the terminal can receive the i-th downlink frame 500 earlier by T. TA The transmission of the i-th uplink frame 510 begins at time T. TA This can be referred to as timing advance or timing adjustment of TA. The base station can instruct the terminal to change the TA via higher-layer signaling or L1 signaling. TA The value of T. For example, T can be used in base stations and / or terminals. TA Configured as defined This approach is applied. In the case of 5G NR communication systems, It can be defined as , It can be defined as , It can be defined as , It can be a value set by L3 signaling, and It can be based on the value indicated by L2 signaling. The value is determined by Equation 1 below.

[0092] [Equation 1]

[0093] Here, about and The description may be an example for a specific situation, and various other options may exist, but in order not to obscure the key points of the description, not all possible situations may be listed in this disclosure.

[0094] Figure 6 This is a conceptual diagram illustrating an exemplary embodiment of a time / frequency resource grid for a communication system.

[0095] Reference Figure 6 The time / frequency resource grid 600 of the communication system can have Subcarriers and One OFDM. A resource grid can be defined for each parameter set and each carrier. In this case, It can refer to the location of a Common Resource Block (CRB) indicated by higher-level signaling. This can refer to the number of resource blocks (RBs) starting from the CRB. In other words, This can refer to carrier bandwidth. For each link direction (e.g., uplink, downlink, or sidelink) or for each parameter set μ, and / or They can have different values. Here, the parameter set μ can be referred to by other terms such as SCS configuration if needed.

[0096] Each element in the resource grid used for antenna port p and SCS configuration μ can be referred to as a resource element (RE) 620. This can be configured for each location. RE 620 is uniquely defined. In this case, It can be a frequency axis index, and It can indicate the position of a symbol on the timeline. This can correspond to the complex values ​​used to transmit physical channels or signals. Physical resources. An RB610 can be defined as a continuous frequency axis. Subcarriers.

[0097] Compared to 3G / 4G communication systems, 5G NR communication systems can utilize wider carrier bandwidth. The concept of a Bandwidth Part (BWP) can be introduced to reduce the high implementation complexity and power consumption of terminals caused by the increased carrier bandwidth. A BWP can consist of consecutive CRBs, with the starting RB position of the BWP... and the number of RBs that make up BWP It can satisfy equations 2 and 3.

[0098] [Equation 2]

[0099] [Equation 3]

[0100] Up to four downlink BWPs within a single component carrier (CC) can be configured for a terminal. Only one downlink BWP configured for the terminal can be activated at a time. The terminal can receive Physical Downlink Shared Channel (PDSCH), Physical Downlink Control Channel (PDCCH), Channel State Information Reference Signal (CSI-RS), etc., without using the activated BWPs.

[0101] Up to four uplink BWPs can be configured within a single CC for a terminal. Only one uplink BWP configured for the terminal can be activated at a time. The terminal can transmit Physical Uplink Shared Channel (PUSCH), Physical Uplink Control Channel (PUCCH), Sound Reference Signal (SRS), etc., without using the activated BWPs.

[0102] Figure 7 This is a conceptual diagram illustrating an exemplary embodiment of a communication system's synchronization signal and physical broadcast channel (SS / PBCH) block or synchronization signal block (SSB).

[0103] Reference Figure 7The SS / PBCH block 700 of the communication system can be configured with a primary synchronization signal (PSS) transmitted in the middle 127 subcarriers of the first OFDM symbol, a secondary synchronization signal (SSS) transmitted in the middle 127 subcarriers of the third OFDM symbol, and physical broadcast channels (PBCH) transmitted in the second, third, and fourth OFDM symbols. The PBCH, occupying the widest bandwidth, can be transmitted over 20 RBs, which can be 3.6 MHz based on a 15 kHz SCS. A base station can transmit one SSB by applying the same beam. When the number of base station antennas increases or multiple beams need to be operated (such as applying one or more analog beams for high-frequency support), the base station can support multi-beam operation by transmitting multiple SSBs. The term "beam" can be referred to using various terms such as transmission precoding or spatial transmission filters. However, to avoid obscuring the key points of the description, "beam" is used as a uniform term below.

[0104] For example, a base station can transmit multiple SSBs 730, 740, 750, and 760 to represent multiple beams (e.g., beam #1, beam #2, beam #3, beam #4). In this case, one or more SSBs can be transmitted in a time slot according to a pattern predetermined based on each parameter set. SSBs 730, 740, 750, and 760 with different beams can be included in an SS burst 720. In other words, SSBs 730, 740, 750, and 760 with different beams can be configured as a group. The terminal can assume a half-frame window of 5ms length when monitoring SSBs. The SS burst set 715 configured by higher-layer signaling within the half-frame window can include one or more SS bursts 720. During initial access (IA) procedures, the terminal may not know one or more RRC configuration values ​​or may not be able to use one or more RRC configuration values. In this case, the terminal can assume that the period of the SS burst set 710 is 20ms to receive or measure SSBs.

[0105] Figure 8 This is a conceptual diagram illustrating a first exemplary embodiment of a non-terrestrial network.

[0106] Reference Figure 8 Non-terrestrial networks (NTNs) may include satellites 810, communication nodes 820, gateways 830, data networks 840, etc. Figure 8The NTN shown can be an NTN based on a transparent payload. Satellite 810 can be a low Earth orbit (LEO) satellite (at an altitude of 300 km to 1500 km), a medium Earth orbit (MEO) satellite (at an altitude of 7000 km to 25000 km), a geostationary Earth orbit (GEO) satellite (at an altitude of approximately 35786 km), a highly elliptical orbit (HEO) satellite, or an unmanned aerial vehicle system (UAS) platform. The UAS platform can include a high-altitude platform station (HAPS).

[0107] Communication node 820 may include communication nodes located at ground stations (e.g., user equipment (UE) or terminals) and communication nodes located in non-terrestrial space (e.g., aircraft, drones). A service link may be established between satellite 810 and communication node 820, and the service link may be a radio link. Satellite 810 may use one or more beams to provide communication services to communication node 820. The coverage area of ​​satellite 810's beams may be elliptical in shape.

[0108] Communication node 820 can use LTE and / or NR technologies to perform communication with satellite 810 (e.g., downlink and uplink communication). Communication between satellite 810 and communication node 820 can be performed using the NR-Uu interface. When dual connectivity (DC) is supported, communication node 820 can connect to other base stations (e.g., base stations supporting LTE and / or NR) as well as satellite 810, and perform DC operation based on the technologies defined in the LTE and / or NR specifications.

[0109] Gateway 830 can be located at a ground station and can establish a feeder link between satellite 810 and gateway 830. The feeder link can be a radio link. Gateway 830 can be referred to as a "Non-Terrestrial Network (NTN) Gateway." Communication between satellite 810 and gateway 830 can be performed based on the NR-Uu interface or the Satellite Radio Interface (SRI). Gateway 830 can connect to data network 840. A "core network" can exist between gateway 830 and data network 840. In this case, gateway 830 can connect to the core network, and the core network can connect to data network 840. The core network can support NR technology. For example, the core network may include Access and Mobility Management Functions (AMF), User Plane Functions (UPF), Session Management Functions (SMF), etc. Communication between gateway 830 and the core network can be performed based on the NG-C / U interface.

[0110] Optionally, a base station and a core network may exist between the gateway 830 and the data network 840. In this case, the gateway 830 can be connected to the base station, the base station can be connected to the core network, and the core network can be connected to the data network 840. The base station and the core network can support NR technology. Communication between the gateway 830 and the base station can be performed based on the NR-Uu interface, and communication between the base station and the core network (e.g., AMF, UPF, SMF, etc.) can be performed based on the NG-C / U interface.

[0111] Figure 9 This is a conceptual diagram illustrating a second exemplary embodiment of a non-terrestrial network.

[0112] Reference Figure 9 The non-terrestrial network may include the first satellite 911, the second satellite 912, the communication node 920, the gateway 930, the data network 940, etc. Figure 9 The NTN shown can be an NTN based on a regenerated payload. For example, each of satellites 911 and 912 can perform regeneration operations (e.g., demodulation, decoding, recoding, remodulation, and / or filtering operations) on a payload received from another entity (e.g., communication node 920 or gateway 930) and transmit the regenerated payload.

[0113] Each of satellites 911 and 912 can be a LEO satellite, MEO satellite, GEO satellite, HEO satellite, or UAS platform. The UAS platform may include HAPS. Satellite 911 can connect to satellite 912, and an inter-satellite link (ISL) can be established between satellites 911 and 912. The ISL can operate in the RF band or optical band. An ISL can be optionally established. Communication node 920 may include terrestrial communication nodes (e.g., UEs or terminals) and non-terrestrial communication nodes (e.g., aircraft or drones). A service link (e.g., a radio link) can be established between satellite 911 and communication node 920. Satellite 911 can provide communication services to communication node 920 using one or more beams.

[0114] Communication node 920 can use LTE and / or NR technologies to perform communication with satellite 911 (e.g., downlink (DL) communication or uplink (UL) communication). Communication between satellite 911 and communication node 920 can be performed using the NR-Uu interface. When DC is supported, communication node 920 can connect to other base stations (e.g., base stations supporting LTE and / or NR) as well as satellite 911, and can perform DC operation based on the technologies defined in the LTE and / or NR specifications.

[0115] Gateway 930 can be located at a ground station and can establish a feeder link between satellite 911 and gateway 930, and can also establish a feeder link between satellite 912 and gateway 930. The feeder link can be a radio link. When an ISL is not established between satellite 911 and satellite 912, a feeder link between satellite 911 and gateway 930 can be forced to be established.

[0116] Communication between each of satellites 911 and 912 and gateway 930 can be performed via the NR-Uu interface or SRI. Gateway 930 can connect to data network 940. A core network can exist between gateway 930 and data network 940. In this case, gateway 930 can connect to the core network, and the core network can connect to data network 940. The core network can support NR technology. For example, the core network may include AMF, UPF, SMF, etc. Communication between gateway 930 and core network can be performed via the NG-C / U interface.

[0117] Optionally, a base station and a core network may exist between the gateway 930 and the data network 940. In this case, the gateway 930 can be connected to the base station, the base station can be connected to the core network, and the core network can be connected to the data network 940. The base station and the core network can support NR technology. Communication between the gateway 930 and the base station can be performed based on the NR-Uu interface, and communication between the base station and the core network (e.g., AMF, UPF, SMF, etc.) can be performed based on the NG-C / U interface.

[0118] In addition, constituting Figure 8 and Figure 9 Each entity of the non-terrestrial network shown (e.g., satellite, communication node, gateway, etc.) may include at least one processor, memory, and a transceiver connected to the network to perform communication. Furthermore, the entity may also include input interface devices, output interface devices, storage devices, etc. Components included in an entity may be connected to each other via a bus for communication. However, each component included in an entity may be connected to the processor via a separate interface or a separate bus instead of a common bus. For example, the processor may be connected to at least one of the memory, transceiver, input interface device, output interface device, and storage device via a dedicated interface. The processor may execute at least one instruction stored in at least one of the memory and storage device. The processor may refer to a central processing unit (CPU), a graphics processing unit (GPU), or a dedicated processor that executes methods according to exemplary embodiments of the present disclosure thereon. Each of the memory and storage device may be configured as at least one of volatile storage media and non-volatile storage media. For example, the memory may be configured with at least one of read-only memory (ROM) and random access memory (RAM).

[0119] Furthermore, scenarios in NTN can be defined as shown in Table 4 below.

[0120] [Table 4]

[0121] when Figure 8 When satellite 810 in the NTN shown is a GEO satellite (e.g., a GEO satellite with transparency capabilities), this can be referred to as "Scenario A". When Figure 9 When satellites 911 and 912 in the NTN shown are GEO satellites (e.g., GEOs that support regeneration), this can be referred to as "Scenario B".

[0122] when Figure 8 When satellite 810 in the NTN shown is a LEO satellite with a steerable beam, this can be referred to as "Scenario C1". Figure 8 When satellite 810 in the NTN shown is a LEO satellite with a beam that moves with the satellite, this can be referred to as "Scene C2". When Figure 9 When satellites 911 and 912 in the NTN shown are LEO satellites with steerable beams, this can be referred to as "Scene D1". Figure 9 When satellites 911 and 912 in the NTN shown are LEO satellites with beams that move with the satellite, this can be referred to as "Scenario D2". Parameters for the scenarios defined in Table 4 can be defined as shown in Table 5 below.

[0123] [Table 5]

[0124] In addition, in the scenarios defined in Table 4, delay constraints can be defined as shown in Table 6 below.

[0125] [Table 6]

[0126] Furthermore, the terminal can support the calculation of specific timing advances (TAs) based on ephemeris information of position and service satellites obtained from the Global Navigation Satellite System (GNSS). As an example, for the Physical Random Access Channel (PRACH), It can be defined as 0. It can be updated based on the TA command field of Msg2 / MsgB and the Media Access Control (MAC) Control Element (CE) TA command. . The TA can be estimated by the terminal itself to pre-compensate for service link latency, and It can be a common TA for network control, and can include timing offsets that are deemed necessary in the network. It can support the value 0.

[0127] This can be a fixed offset used to calculate the TA. The terminal can assume that the round-trip time (RTT) between the terminal and the base station (gNB) is not equal to the TA calculated for Msg1 / MsgA. The effective duration configured for satellite ephemeris data in the network can indicate the maximum time the terminal can apply the satellite ephemeris without obtaining new satellite ephemeris data. The TA command field based on Msg2 / MsgB and the MAC CE TA command pair... The update can be used to modify the uplink TA as follows. When a timing advance command (TAC) is received via Msg2 / MsgB, the terminal can receive the first adjustment value, and It can be updated as shown in Equation 4 below.

[0128] [Equation 4]

[0129] here, This can be a value from the TAC field of Msg2 / MsgB. When a TAC provided by MAC CE is received, it can be updated as shown in Equation 5 below. In other words, the terminal can be powered by... The previous one Updated to .

[0130] [Equation 5]

[0131] here, This can be a value from the TAC field of the MAC CE. The common TA can include parameters indicating timing drift. The terminal can apply the common TA based on parameters provided by the network (if any), and when defining uplink timing error requirements, the offset between the common TA based on the parameters provided by the network and the actual feeder RTT can be disregarded.

[0132] To improve timing relationships, the terminal can introduce a scheduling offset. The scheduling offset can be set via system information. And scheduling offsets can be used during the initial access process. In this scenario, cell-specific support for all beams used in at least one cell can be achieved. In addition, besides In addition, the scheduling offset for MAC CE can be defined as .

[0133] Downlink and uplink frame timings can be aligned at the base station. In this case, the terminal's operation and / or assumptions regarding the downlink and uplink configurations indicated by the MAC CE command transmitted on the PDSCH may not be required. On the other hand, downlink frame timing and uplink frame timing may not be aligned at the base station. In this case, the terminal's operation and / or assumptions regarding the downlink configuration indicated by the MAC CE command transmitted on the PDSCH may need to be adjusted. .about Information can be included in system information. In other words, the base station can send information to the terminal including... The terminal can receive system information from the base station and obtain the information included in the system information. .

[0134] Support can be provided after the initial access process. Updated. By introducing features for TA command reception. This can supplement uplink transmission timing adjustments (e.g., alignment, modification, control). For the period after the initial access process... For updates, the network (e.g., base stations) can use MAC CE to provide and / or update UE-specific updates. For cell-specific settings configured by system information You can choose one of the following two options (for example, option 1 and option 2).

[0135] Option 1 could be a scheme of transmitting an offset value via signaling. For example, the value transmitted via signaling according to Option 1 could include the RTT of the serving link and the RTT between the serving satellite (e.g., the satellite providing the service) and the reference point. Option 2 could be a scheme of transmitting two offset values ​​via signaling. The two offset values ​​could include a first offset value and a second offset value. It can be the sum of two offset values. For example, the first offset value could be the RTT between the serving satellite and the reference point (or a value determined based on a common TA). The second offset value could be the RTT of the serving link.

[0136] If other than the value indicated by system information (e.g.) There are no others besides ) Provided to the terminal, the terminal can then apply the values ​​indicated by the system information (e.g., This improves all timing relationships. The network (e.g., a base station) can provide the terminal with information for MAC CE. , Is it except Additional scheduling offsets. If the network does not provide this to the terminal. Then the terminal can assume =0.

[0137] The estimated terminal-to-base station RTT can be equal to the terminal's TA and The sum. 'Terminal-to-base station RTT' can refer to the RTT between the terminal and the base station. It can be based on... To determine the terminal's TA. The base station-to-satellite RTT estimate can be equal to and The sum. Base station-satellite RTT can refer to the RTT in the link between the base station and the satellite. If the network does not provide this to the terminal... Then the terminal can assume =0.

[0138] NTN ephemeris (e.g., ephemeris information) can be divided into the ephemeris of the serving cell and the ephemeris of one or more neighboring cells. At least in quasi-earth fixed NTN scenarios, information about when a cell ceases local service and / or timing information (e.g., timers and / or absolute time) for new cells can be supported. When both types of ephemeris information (e.g., ephemeris information of the serving cell and ephemeris information of one or more neighboring cells) are required, both types of ephemeris information can be obtained based on system information and / or ephemeris information. At least for uplink scheduling adaptation, the terminal can report information about UE-specific TA pre-compensation. When performing the RA procedure, the terminal can use the MAC CE to report UE-specific TA pre-compensation to the base station.

[0139] If the reporting operation is activated by the network, the terminal can use MAC CE (e.g., the transmission procedure of MsgA, the transmission procedure of Msg3, and / or the transmission procedure of Msg5) to report information about UE-specific TA pre-compensation to the base station (e.g., the network) during the RA process. The information about UE-specific TA pre-compensation reported using MAC CE during the RA process can be UE-specific TA. The operation of reporting UE-specific TA (e.g., reporting UE-specific TA pre-compensation) during the RA process can be activated / deactivated via System Information (SI). The operation of reporting UE-specific TA (e.g., reporting information about UE-specific TA) can be supported in connected modes (e.g., RRC connected mode). Event-triggered schemes can be supported to report information about UE-specific TA in connected mode. If a trigger event is configured, the terminal can report information about UE-specific TA pre-compensation to the target cell during the RA process.

[0140] If the terminal cannot report UE location information in connected mode, the UE-specific TA reported to the base station in connected mode can be information about UE-specific TA pre-compensation. If the UE-specific TA information reported to the base station is the terminal's UE location information in connected mode, RRC signaling can be used to report the terminal's UE location information. If the terminal can report its UE location information to the base station in connected mode, the network (e.g., the base station) can configure the terminal to report UE-specific TA pre-compensation and / or UE location information in order to perform TA reporting in connected mode (e.g., reporting UE-specific TA information, reporting UE location information). If the UE-specific TA information reported to the network is the value of TA pre-compensation (e.g., UE-specific TA pre-compensation) in connected mode, the terminal can use MAC CE to report the UE-specific TA information.

[0141] The operation of reporting the UE location can be performed based on an event-triggered scheme. The base station can be configured to report the UE location based on an event-triggered scheme to obtain updated information on the UE location of the terminal in connected mode (e.g., RRC connected mode).

[0142] To configure the terminal to report information about a UE-specific TA during handover, a new instruction in the synchronized RRC reconfiguration may not be necessary. The SI (Indicator for Activating or Deactivating TA Reporting in the target cell (e.g., reporting information about a UE-specific TA) can be sent via the handover command.

[0143] In an RA process triggered by a request to another SI, information about UE-specific TA pre-compensation may not be reported. Event triggering for reporting information about UE-specific TA (e.g., UE-specific TA pre-compensation) may be based on the TA value. A TA offset threshold may be used during the event-triggered reporting process. The TA offset threshold may be at least a value between the current UE-specific TA value and the last successfully reported UE-specific TA value.

[0144] In quasi-fixed or fixed-earth scenarios, timing information about when a cell ceases service to its corresponding area may be needed to support cell reselection operations (e.g., NTN cell reselection operations). Base stations (e.g., cells, networks) can send system information to terminals including timing information about when a cell ceases service to its corresponding area. This system information can be broadcast. The time when a cell ceases service to its corresponding area may be referred to as the "cell stop time." Broadcasting information about the cell stop time using SIBs can be applied to quasi-fixed cells. In other words, broadcasting information about the cell stop time using SIBs may not be applicable to mobile cells. In quasi-fixed scenarios, timing information about when a cell ceases service (e.g., the cell stop time) can be used to determine when to perform measurements on neighboring cells. In quasi-fixed scenarios (e.g., quasi-fixed cells), system information including information about the reference location of a cell (e.g., the serving cell and / or neighboring cells) can be broadcast. The reference location may be the center of the cell.

[0145] In a quasi-earth fixed scenario, a terminal can begin measuring neighboring cells before the serving cell ceases to serve the current area. In this scenario, broadcast information about the cell's stop time (e.g., timing information) can indicate the time when the cell no longer covers the current area. "Cell no longer covers the current area" can mean that the cell does not provide service to the current area. In a quasi-earth fixed scenario, a terminal can be configured to perform measurements on neighboring cells (e.g., adjacent cells) before the broadcast stop time of the serving cell (e.g., cell stop time, time when the cell stops covering the current area). The exact time when the terminal performs measurements on neighboring cells can be determined based on the terminal's implementation.

[0146] In addition, non-terrestrial networks can support the following three types of service links.

[0147] 1) Fixed Earth Service Link: A fixed earth service link can be a service link provided by a beam that always covers the same geographical area. For example, a service link provided by a geostationary orbit (GSO) satellite can be a fixed earth service link.

[0148] 2) Quasi-Earth Fixed Service Link: A quasi-earth fixed service link can be a service link provided by one or more beams that cover one geographic area during a limited time period and another geographic area during a different time period. For example, a service link provided by a non-geostationary orbit (NGSO) satellite that generates a steerable beam can be a quasi-earth fixed service link.

[0149] 3) Earth Mobility Service Link: An Earth mobility service link can be a service link that corresponds to a situation where the coverage area provided by a service link from a satellite moves across the Earth's surface. For example, a service link provided by an NGSO satellite using a fixed beam or an unmanipulated beam can be an Earth mobility service link.

[0150] NTN can provide quasi-Earth fixed service links or Earth mobile service links via NGSO satellites. Additionally, NTN can provide Earth fixed service links via GSO satellites. Depending on the type of service link, NTN can support the following three types of cells.

[0151] 1) Fixed Earth Cell: A fixed earth cell can be a cell that uses a fixed earth service link.

[0152] 2) Quasi-Earth Fixed Cell: A quasi-earth fixed cell can be a cell that uses a quasi-earth fixed service link.

[0153] 3) Earth-mobile cell: Earth-mobile cell can be a cell that uses Earth-mobile service links.

[0154] Terminal mobility can be supported in NTN. Specifically, NTN can support mobility for terminals in idle or inactive modes through cell reselection. For example, to support the mobility of terminals in idle or inactive modes in TN, the terminal can measure neighboring cells and reselect the cell to camp on based on the measurement results. NTN can also use the same mechanism as TN to support the mobility of terminals in idle or inactive modes through cell reselection. NTN can support the mobility of terminals in idle or inactive modes through cell reselection.

[0155] On the other hand, connected-mode terminals can perform handovers, and mobility can be supported through handovers. For example, in a TN (Total Connected Network), to support the mobility of a terminal in connected mode, the terminal can measure neighboring cells around the currently connected cell (i.e., the source cell) and perform a handover to a cell selected based on the measurement results (i.e., the target cell). Even in an NTN (Network-to-Near Network), the mobility of connected-mode terminals can be supported through handovers using essentially the same mechanism as in a TN.

[0156] Figure 10 This is a conceptual diagram illustrating an exemplary embodiment of a satellite handover method in a quasi-Earth fixed cell.

[0157] Reference Figure 10The first satellite 1010 and the second satellite 1020 can be NGSO satellites moving along their orbits. Cell coverage 1030 can be served by the first satellite 1010. As the first satellite 1010 moves, the satellite serving cell coverage 1030 can switch from the first satellite 1010 to the second satellite 1020. In other words, Figure 10 A satellite handover scenario for a quasi-Earth fixed cell is illustrated, but the invention is not limited to this scenario. In the following text, during the satellite handover process, the satellite before the handover may be referred to as the source satellite, and the satellite after the handover may be referred to as the target satellite. However, this is merely for ease of description, and the exemplary embodiments of this disclosure are not limited to these terms.

[0158] Satellite handover methods for quasi-Earth fixed cells can be classified into hard satellite handover and soft satellite handover based on whether a service link is provided simultaneously during the handover process. The terms hard satellite handover and soft satellite handover are merely for descriptive purposes, and exemplary embodiments of this disclosure are not limited to these terms.

[0159] Figure 11 This is a conceptual diagram illustrating an exemplary embodiment of a hard satellite handover method in a quasi-Earth fixed cell.

[0160] Reference Figure 11 In the hard satellite handover method, the first satellite 1110 can provide a service link to the terminal using a quasi-Earth fixed cell 1130 before the handover. After the handover, the second satellite 1120 can provide a service link to the terminal using a quasi-Earth fixed cell 1140. However, during the handover, the first satellite 1110 and the second satellite 1120 may not simultaneously provide communication services to the terminal. Therefore, during the handover, the terminal may be located in a geographical area 1150 where no communication service is provided.

[0161] Figure 12 This is a conceptual diagram illustrating an exemplary embodiment of a soft satellite handover method in a quasi-Earth fixed cell.

[0162] Reference Figure 12 In the soft satellite handover method, the first satellite 1210 can provide communication services to the terminal using a quasi-Earth fixed cell 1230 before the handover. After the handover, the second satellite 1220 can provide communication services to the terminal using a quasi-Earth fixed cell 1240. During the handover, the first satellite 1210 and the second satellite 1220 can simultaneously provide communication services to the terminal. Therefore, during the handover, the terminal can be located in a geographical area providing two service links.

[0163] In the case of the aforementioned soft satellite handover, communication services for the target satellite can be provided before the communication services of the source satellite are stopped. The communication services of the source satellite can then be stopped. In other words, communication services for both satellites can be maintained during the handover period. For example, when the first satellite 1210 is providing communication services within the cell coverage area and is handed over to the second satellite 1220 via satellite handover, the communication services of the second satellite 1220 can be provided before the communication services of the first satellite 1210 are stopped, and the communication services of the first satellite 1210 can be stopped after the communication services of the second satellite 1220 are provided.

[0164] This disclosure considers satellite handover scenarios where the Physical Cell Identifier (PCI) remains unchanged, relating to the aforementioned satellite handover scenarios. The satellite handover method without changing the PCI can be a hard satellite handover method or a soft satellite handover method used in quasi-earth fixed cell scenarios. Furthermore, in the satellite handover method without changing the PCI, the satellites before and after the handover can connect to the same base station. Additionally, in the satellite handover method without changing the PCI, the same PCI can be used before and after the handover. Moreover, in the handover method without changing the PCI, the same frequency for transmitting the Synchronization Signal Block (SSB) can be used before and after the handover. Here, the PCI can be a cell identifier that allows differentiation between different cells. Furthermore, the SSB can include the Primary Synchronization Signal (PSS), the Secondary Synchronization Signal (SSS), and the Physical Broadcast Channel (PBCH).

[0165] The following description is based on a satellite handover scenario without changing the PCI, but exemplary embodiments are not limited to this and can be applied to other scenarios. Furthermore, a satellite handover scenario without changing the PCI can correspond to a satellite handover scenario with resynchronization. For example, a satellite handover scenario without changing the PCI can correspond to a satellite handover scenario with resynchronization because in satellite handover of quasi-Earth fixed cells, the same PCI and the same SSB transmission frequency are used for the same or similar areas. Additionally, a satellite handover scenario without changing the PCI is not limited to a specific name for the scenario under the above conditions, and different names can be used to refer to a satellite handover scenario without changing the PCI. In other words, a satellite handover scenario without changing the PCI is not limited to a specific name, can be applied to various scenarios operating based on the above description, and is not limited to a specific form. Hereinafter, for ease of description, the term "satellite handover scenario without changing the PCI" will be used.

[0166] Figure 13 This is a conceptual diagram illustrating a first exemplary embodiment of a satellite handover method without altering the PCI.

[0167] Reference Figure 13The first satellite 1310 and the second satellite 1320 can be orbiting satellites. In this case, the second satellite 1320 can be connected to the same gateway 1350 and / or base station 1360 to which the first satellite 1310 is connected. Satellite handover from the first satellite 1310 as the source satellite to the second satellite 1320 as the target satellite can be performed.

[0168] For example, the first satellite 1310 can provide service to the terminal 1370 using a quasi-fixed cell 1330. The first satellite 1310 can cease providing service to the terminal 1370 using the quasi-fixed cell 1330 when the first satellite 1310 moves. Then, the second satellite 1320 can use the quasi-fixed cell 1340 to provide service to the terminal 1370 instead. As described above, the first satellite 1310 and the second satellite 1320 can perform a hard satellite handover. At this time, the second satellite 1320 can connect to the gateway 1350 or base station 1360 that the first satellite 1310 has already connected to, or is in the process of connecting to the gateway 1350 or base station 1360 that the first satellite 1310 has already connected to. Therefore, the second satellite 1320 can provide service to the same service coverage area previously served by the first satellite 1310 by using the quasi-fixed cell 1340.

[0169] Therefore, the satellite serving terminal 1370 can be switched from the first satellite 1310 (hard satellite) to the second satellite 1320. Thus, after the satellite serving terminal 1370 is switched from the first satellite 1310 to the second satellite 1320, the PCI, frequency, etc., do not need to be changed.

[0170] As another example, the first satellite 1310 can provide communication services to the terminal 1370 using a quasi-Earth fixed cell 1330. After handover, the second satellite 1320 can provide communication services to the terminal 1370 using a quasi-Earth fixed cell 1340. During the handover, the first satellite 1310 and the second satellite 1320 can simultaneously provide communication services to the terminal 1370. Therefore, during the handover, the terminal 1370 can be located in two geographical areas where communication services are available.

[0171] In the case of soft satellite handover as described above, communication services for the target satellite can be provided before the communication services of the source satellite are stopped. The communication services of the source satellite can then be stopped. In other words, communication services for both satellites can be maintained during the handover period. For example, when the first satellite 1310 is providing communication services within the cell coverage area and handover is performed to the second satellite 1320, the communication services of the second satellite 1320 can be provided before the communication services of the first satellite 1310 are stopped. After the communication services of the second satellite 1320 are provided, the communication services of the first satellite 1310 can be stopped. Satellite handover scenarios without changing the PCI can be described as shown in Table 7.

[0172] [Table 7]

[0173] The satellite handover method without changing the PCI does not have to be a Layer 3 (L3) handover (HO) method or an L3 conditional handover (CHO) method involving the network. In the following text, for ease of description, the handover (or conditional handover) may be referred to as "(C)HO". Furthermore, the cell to which the terminal connects before the (C)HO is referred to as the "source cell", and the cell to which the terminal wishes to connect after the (C)HO is referred to as the "target cell", but exemplary embodiments are not limited to these names.

[0174] As an example, when providing services to a terminal via a quasi-Earth fixed cell using NGSO satellites, the satellite responsible for a specific ground area can be continuously changed. Terminals in connected mode belonging to a quasi-Earth fixed cell can typically perform L3 handover or L3 conditional handover when the satellite changes. However, in a method without changing the PCI, terminals in connected mode can avoid performing L3 handover or L3 conditional handover. As an example, in a satellite handover scenario without changing the PCI, terminals operating in connected mode do not perform (C)HO, thus overcoming the disadvantages of (C)HO. In other words, in a satellite handover method without changing the PCI, terminals operating in connected mode do not need the Radio Resource Control (RRC) signaling required for handover or conditional handover, thereby reducing signaling overhead. As a concrete example, in the case of handover in a quasi-Earth fixed cell, all terminals in the cell can perform handover almost simultaneously. As a result, RRC signaling may surge instantaneously. In other words, a handover storm may occur. Furthermore, in a quasi-Earth fixed cell, the time interval between satellite handovers may be very short. Therefore, the probability of handover failure may increase. However, the satellite handover method without changing the PCI can avoid such handover failures in terminals. Satellite handover methods without altering the PCI can avoid Random Access Channel (RACH) congestion. Terminals can pre-compensate for uplink TA with the target satellite.

[0175] In this scenario, the terminal can omit the random access (RA) procedure immediately following the handover or conditional handover to the target cell. The reason for omitting the RA procedure is that even without adjusting the touchpoint (TA) through the RA procedure, normal communication can still occur if the TA falls within the base station's acceptable range, although optimal uplink communication performance may not be achieved. By omitting the RA procedure, the terminal can adjust the TA while performing normal communication after the handover.

[0176] In handover scenarios within quasi-fixed Earth cells, all terminals in the cell perform the handover almost simultaneously, potentially leading to simultaneous random access procedures immediately after the handover. As a result, RACH capacity may become insufficient. This problem can be termed the RACH congestion problem. In satellite handover methods without changing the PCI, the random access procedure can be omitted, thus avoiding the RACH congestion problem. If the random access procedure can be omitted in satellite handover methods without changing the PCI, terminals in quasi-fixed Earth cells can save power. This is because, due to satellite movement within the quasi-fixed Earth cell, terminals can avoid performing L3 (conditional) handover or random access procedures, thereby saving power.

[0177] As an example, the method without changing the PCI allows NTN operators to configure quasi-terrestrial fixed cells using NGSO satellites. In this case, NTN operators can use the same base stations to serve a specific area on the ground, thus providing advantages such as the flexibility and lower cost of NTN configuration.

[0178] In the following description, this disclosure considers system information (SI). System information can be information required for a terminal to connect to a base station and communicate with the connected base station. System information can be broadly classified into main information blocks (MIBs) and system information blocks (SIBs). The terminal can receive MIBs from the base station via a physical broadcast channel (PBCH). Alternatively, the terminal can receive SIBs from the base station via a physical downlink shared channel (PDSCH), which serves as a common downlink channel. The base station can periodically broadcast SIBs. The terminal can then receive the periodically broadcast SIBs from the base station. Additionally and / or alternatively, the terminal can request one or more necessary SIBs from the base station. The base station can then receive the request for one or more SIBs from the terminal. The base station can then send the requested one or more SIBs to the terminal. Thus, the terminal can receive one or more requested SIBs from the base station. This method can be referred to as an "on-demand method."

[0179] SIBs can be divided into "SIBx" based on broadcast cycle, importance, or relevance. Here, x can be an integer of 1 or greater. Unlike TN cells, SIB19s can exist in NTN cells. Terminals can also distinguish whether the current cell is a TN or NTN cell by the presence or absence of SIB19s. Table 8 can represent SIB19 information. As an example, Table 8 below can be based on SIB19s presented in 3GPP Release 17, but is not limited to Release 17 and can be applied to other releases.

[0180] [Table 8]

[0181] In a 3GPP NTN cell, the terminal can receive SIB19 from the satellite as described above. Descriptions of the various fields in Table 8 are as described in Table 9.

[0182] [Table 9]

[0183] As an example, referring to Table 9, NTN-related SIBs may include NTN-config As NTN configuration information, and NTN- config It can be an information element (IE) configured as shown in Table 10 below, and its various fields can be as shown in Table 11.

[0184] [Table 10]

[0185] The descriptions of each field in Table 10 are shown in Table 11 below.

[0186] [Table 11]

[0187] Referring to Table 11, NTN auxiliary information can refer to information related to the ephemeris of serving and / or neighboring satellites, uplink TA information, etc. NTN auxiliary information can be... NTN-Config Or include NTN-Config Information from SIB19. In other words, epoch time can be provided via SIB or dedicated signaling. NTN-Config The epoch time is the information about the time. Therefore, the epoch time can change each time the terminal receives NTN auxiliary information. However, the value label of SIB1 can remain unchanged despite the change in epoch time.

[0188] Referring to Table 11, the uplink synchronization effective duration can refer to the maximum duration starting from the following epoch: during which the terminal can apply auxiliary information without acquiring new auxiliary information. The uplink synchronization effective duration can be updated only when one or more of the epoch time, uplink TA, or satellite ephemeris are updated. However, the SIB1 value label may not change with changes in the uplink synchronization effective duration. Satellite ephemeris information can be represented as... ephemerisInfo Additionally, uplink TA information can be represented as... ta-Info .

[0189] Referring to Table 11, the common TA can be a value determined by Equation 6 below. Here, t can be a real number.

[0190] [Equation 6] Common TA = {ta-Common-r17 / 2 + ta-CommonDrift-r17 / 2 × (t – epoch time) + ta-CommonDriftVariant × (t – epoch time)} 2} / 2 Additionally, as an example, as NTN-config The orbital information included ephemerisInfo Satellite ephemeris information, which may include position and velocity state vector format or orbital parameter format, is shown in Table 12.

[0191] [Table 12]

[0192] Figure 14 This is a conceptual diagram illustrating a first exemplary embodiment of a reference point, a public TA, and a UE-specific TA.

[0193] Reference Figure 14 The common TA can be a TA related to the time delay between the reference point and satellite 1410, and can be common to all terminals within the cell. The UE-specific TA can be a TA related to the time delay between satellite 1410 and terminal 1420, and can be a different value for each terminal within the cell. Here, the reference point can be the point where downlink and uplink frames are aligned.

[0194] The aforementioned pre-compensation may mean that the terminal derives a portion of the uplink TA using an open-loop scheme and the terminal can determine the uplink TA as shown in Equation 7 below.

[0195] [Equation 7] Uplink TA = (N TA + N TA, offset) × Tc + (public TA + UE-specific TA) Here, N TA The TA is obtained in a closed-loop scheme and can be updated via the TA command MAC CE. TA,offset The values ​​can be determined by the frequency and duplex scheme used. The remaining common TA and UE-specific TA can be values ​​derived from the following information: auxiliary information in the system information received by the terminal through an open-loop scheme, as well as the location and time information possessed by the terminal. The derivation of the common TA and UE-specific TA by the terminal can be referred to as pre-compensation.

[0196] Figure 15 This is a conceptual diagram illustrating SSB and beam scanning operations in a wireless communication system.

[0197] Reference Figure 15 One approach to selecting the downlink beam when a terminal communicates with a base station could be considered. For example, the terminal and the base station could determine the downlink beam used for communication. Here, the initial selection of the downlink beam could be performed during a random access procedure for the terminal to perform initial access to the base station. The terminal could then select the downlink beam during this random access procedure.

[0198] A base station (e.g., a gNB) can transmit one or more SSBs 1510 to a terminal via beams scanned within a synchronization signal burst (i.e., an SSB burst). The terminal can select the beam for downlink transmission based on the one or more SSBs 1510 transmitted by the base station. Specifically, an SSB can be a resource element used to transmit a synchronization signal for obtaining downlink synchronization. Here, the beam directions for synchronization transmission in the various SSBs within an SSB burst can be different.

[0199] Each beam scanned by the base station can be assigned to each SSB within an SSB burst. The terminal can select the optimal SSB (e.g., the SSB with the maximum reference signal received power (RSRP) estimated from the synchronization signal of the SSB) within the SSB burst. The terminal can then send a random access message (e.g., Msg1) to the base station using the random access resources associated with the selected SSB (e.g., random access channel timing (RACH timing)).

[0200] The base station can receive Msg1, and it can identify the resources (e.g., RACH timing) in which Msg1 is received. Specifically, the base station can identify which frequency-time resources are used for the transmission of Msg1 by the terminal, and thereby identify the beam selected by the terminal. Here, a random access resource (e.g., RACH timing) is associated with a specific beam, and the base station can identify the associated beam by identifying the resources (e.g., RACH timing) in which Msg1 is received.

[0201] The base station can transmit Msg2 to the terminal in response to Msg1. Here, the base station can use a downlink beam identified by the resources in which Msg1 is received (e.g., RACH timing) to transmit Msg2 to the terminal. Alternatively, the base station can use the downlink beam selected as described above to transmit a downlink signal sent to the terminal after Msg2.

[0202] The wireless communication system operating as described above may have limitations in NTN regarding terminal support for satellite handover scenarios without altering the PCI. Specifically, due to terminal operation based on existing 3GPP NTN specifications, terminals may have difficulty supporting satellite handover scenarios without altering the PCI.

[0203] Refer again Figure 10 In existing wireless communication systems, the satellite providing service to a terminal in connected mode can switch from a first satellite to a second satellite. When a satellite handover occurs from the first satellite to the second satellite, the uplink TA can be changed. For example, in L3 handover or L3 conditional handover, the terminal can pre-compensate for the uplink TA of the neighboring cell targeted for handover. This pre-compensation is possible because the terminal receives the configuration IE (i.e., NTN-NeighCellConfigIE) of the neighboring cell in the NTN neighboring cell configuration list within the SIB19 of the cell to which the terminal is connected.

[0204] On the other hand, satellite handover methods without changing the PCI may not be L3 handover or conditional handover. Therefore, in existing wireless communication systems, even if the communication service of the first satellite is stopped in a satellite handover scenario without changing the PCI, the terminal may not perform any procedures related to L3 handover or L3 conditional handover. In other words, this means that the pre-compensation in the terminal should use the value received from the first satellite, which is the source base station, before the handover, until the terminal receives SIB19 again from the second satellite after switching from the first satellite to the second satellite.

[0205] In the above scenario, the terminal can perform pre-compensation based on NTN-related information received from the source satellite. Therefore, before receiving new NTN-related system information from the target satellite (i.e., the second satellite) after satellite handover, the terminal can operate based on existing public TA and UE-specific TA that do not match those of the target satellite (i.e., the second satellite). Furthermore, since the terminal uses cell-specific information obtained from the source satellite... , Because of other NTN-related field values, the terminal may use values ​​that do not match the target satellite until new NTN-related system information is obtained from the second satellite. In other words, if a terminal operating on an existing wireless communication system switches satellites based on a satellite handover scenario without changing the PCI, uplink transmission performance may be significantly degraded or uplink transmission may fail due to incorrect TA-related values.

[0206] The following description considers the aforementioned issues to illustrate the operational method in a satellite handover scenario where the PCI remains unchanged. As an example, in a satellite handover scenario where the PCI remains unchanged, the terminal can obtain system information from the source satellite before the handover, which is used to communicate with the base station immediately after the handover via the target satellite. As an example, the system information required for the terminal to communicate with the base station via the target satellite can be referred to as "system information immediately needed by the terminal after the handover (post-handover necessary SI)". As another example, the system information required for the terminal to communicate with the base station via the target satellite can be referred to as "satellite handover related application information".

[0207] Here, Post-Switch Essential SI can refer to the system information required when a terminal switches to a target satellite based on satellite handover and subsequently communicates with the base station via the target satellite, and is not limited to a specific name. Different names can also be used. However, for ease of description, the aforementioned system information can be referred to as "system information immediately required by the terminal after handover (or "Post-Switch Essential SI")".

[0208] The necessary SI after handover can be information required for TA pre-compensation related to the target satellite. The terminal can receive the necessary SI after handover via the service link provided by the source satellite before handover. Specifically, since the terminal needs to communicate with the base station immediately after satellite handover via the service link provided by the target satellite, it can obtain the necessary SI after handover via the service link provided by the source satellite before the handover. Here, the necessary SI after handover can include the aforementioned TA pre-compensation information.

[0209] As an example, a base station can periodically broadcast a System Information Block (SIB) including system information. The terminal can receive the SIB from the base station and obtain the necessary SI after handover. As another example, the terminal can request necessary system information from the base station. The base station can receive the request for system information from the terminal and send the necessary SI after handover. The terminal can receive the necessary SI after handover from the base station. The terminal can obtain the necessary SI after handover based on at least one of the methods described above, and is not limited to a specific form.

[0210] As an example, a necessary SI after handover can be included in a single SIB. As an example, a necessary SI after handover can be sent to the terminal in a manner consistent with being included in an NTN-related SIB (e.g., SIB19). As another example, a necessary SI after handover can be divided into multiple SIBs, without being limited to a specific form.

[0211] Post-handover necessary SIs can be information included in one or more SIBs. Alternatively, post-handover necessary SIs can be information configured separately from one or more SIBs. As an example, post-handover necessary SIs can be indicated by an indicator in a specific SIB. Here, the indicator in the specific SIB can indicate which cell information in the neighboring cell list includes the post-handover necessary SI. As an example, the indicator indicating which cell information in the neighboring cell list includes the post-handover necessary SI can be a field or IE in the specific SIB. As a specific example, the indicator can indicate the PCI of a neighboring cell in the neighboring cell list. As an example, the PCI can be... physCellId .

[0212] As another example, the indicator can indicate neighboring cells based on the neighboring cell index in the neighboring cell list. Here, the index can be an integer value such as 1, 2, etc. maxCellNTN One of them. As an example, the list of neighboring cells could be... NTN- NeighCellConfigList or NTN-NeighCellConfigListExt However, it is not limited to this.

[0213] In other words, an indicator in a specific SIB can indicate a specific neighboring cell in the neighboring cell list. Here, the entire information about a neighboring cell indicated by an indicator in a specific SIB can be a handover-necessary SIB. As another example, some information about a neighboring cell indicated by an indicator in a specific SIB can be a handover-necessary SIB, and is not limited to a specific form.

[0214] Additionally, as an example, the aforementioned indicator may only be included in the SIB for satellite handover scenarios where the PCI remains unchanged. Therefore, the terminal can identify operations in the NTN system based on satellite handover scenarios where the PCI remains unchanged based on whether the indicator is included in a specific SIB. As an example, the SIB may be an NTN-related SIB. More specifically, the SIB may be SIB 19. In other words, if the NTN-related SIB includes the corresponding indicator, the terminal can identify that the NTN system is operating based on satellite handover scenarios where the PCI remains unchanged. On the other hand, if the NTN-related SIB does not include the corresponding indicator, the terminal can identify that the NTN system is operating based on scenarios other than satellite handover scenarios where the PCI remains unchanged. In other words, whether the NTN system is operating based on satellite handover scenarios where the PCI remains unchanged can be implicitly indicated based on whether the corresponding indicator is included in the NTN-related SIB.

[0215] As another example, necessary post-handover SIs can be configured independently within a specific SIB. As an example, the specific SIB could be an NTN-related SIB. More specifically, the specific SIB could be SIB19, but is not limited to this. Here, the terminal can identify whether the NTN system is operating under a satellite handover scenario without PCI changes based on whether the necessary post-handover SIs are included in the NTN-related SIBs. As an example, the specific SIB could be an NTN-related SIB. More specifically, the specific SIB could be SIB19. In other words, if the NTN-related SIBs include independently configured necessary post-handover SIs, the terminal can identify that the NTN system is operating under a satellite handover scenario without PCI changes. On the other hand, if the necessary post-handover SIs are not included in independently configured NTN-related SIBs, the terminal can identify that the NTN system is operating under a scenario other than a satellite handover scenario without PCI changes. In other words, whether the corresponding indicator is included in the NTN-related SIBs can implicitly indicate whether the NTN system is operating under a satellite handover scenario without PCI changes.

[0216] As an example, a necessary SI after handover can be indicated using an indicator included in the SIB. The indicator can specify that the necessary SI after handover is included in the cell information within the neighbor cell list of the corresponding SIB.

[0217] Figure 16 This is a conceptual diagram illustrating a first exemplary embodiment of a method for indicating necessary system information using indicators included in the SIB.

[0218] Reference Figure 16SIB 1610 may include an indicator 1611 indicating a necessary SI after handover. Specifically, indicator 1611 may indicate that the necessary SI after handover is included in cell information 1612, 1613, etc., in the neighbor cell list within SIB 1610. As an example, n in "SIBn" may be an integer representing the index of the SIB.

[0219] The indicator can specify which cell information in the neighboring cell list within the same SIB includes the necessary SI after handover. As a specific example, in Figure 16 In this context, SIBn 1610 can be SIB 19. In other words, a terminal can identify a cell included in the neighboring cell list by indicators included in the same SIB, including necessary SI information after handover.

[0220] Here, the terminal can receive SIBn 1610 before handover via the service link of the source satellite. In other words, the terminal can receive the necessary SI after handover via the service link of the source satellite before handover. Specifically, the terminal can receive SIBn before handover. The terminal can identify the indicators in the SIBn and identify the specific neighboring cell information indicated by the indicators from the neighboring cell list. The terminal can determine that all or part of the identified specific neighboring cell information is the necessary SI after handover. As another example, the necessary SI after handover can be indicated by indicators included in the SIB.

[0221] The indicator can indicate that, after a handover, the necessary SI is included in the list of neighboring cells in another SIB that is different from the corresponding SIB.

[0222] Figure 17 This is a conceptual diagram illustrating a second exemplary embodiment of a method for indicating necessary system information using indicators included in the SIB.

[0223] Reference Figure 17 The indicator 1711, indicating the necessary SI after handover, can be included in the first SIB (SIBk) 1710. Here, the second SIB (SIBn) 1720 may include information about a list of neighboring cells, and the indicator 1711 included in the first SIB 1710 can indicate that the necessary SI after handover is included in one cell of the neighboring cell list (a list of cells 1721, 1722, ..., etc.) included in the second SIB 1720. For example, n and k in "SIBn" and "SIBk" can be integers representing SIB indices and can be different values. In other words, the indicator can indicate whether the necessary SI after handover is included in one cell of the neighboring cell list in an SIB other than the SIB that includes the indicator.

[0224] Specifically, the terminal can receive SIBk and SIBn before handover. In other words, the terminal can receive SIBk and SIBn via the service link of the source satellite before handover. Here, SIBk can be an SIB associated with SIBn, which includes a list of the nearest neighboring cells. The terminal can identify the indicator in SIBk and can identify the specific neighboring cell information indicated by the indicator from the list of neighboring cells in SIBn. The terminal can obtain all or part of the identified specific neighboring cell information as the necessary SI after handover. As another example, the necessary SI after handover can be configured independently within the SIB. In other words, the necessary SI after handover can be configured independently without using the aforementioned indicator.

[0225] Figure 18 This is a conceptual diagram illustrating a first exemplary embodiment of a method for independently providing system information needed immediately after a switchover within the SIB.

[0226] Reference Figure 18 SIBn 1810 may include post-handover necessary SI 1811. In the figure, 'n' in 'SIBn' can be an integer representing the index of the SIB. In other words, post-handover necessary SIs may not be indicated by an indicator, and they can be configured individually within the corresponding SIB. For example, post-handover necessary SI 1811 may be information required for TA pre-compensation for the target satellite. Therefore, post-handover necessary SI 1811 may consist of one or more fields within SIBn. Optionally, post-handover necessary SI 1811 may be an information element (IE) within SIBn, and is not limited to a specific exemplary embodiment.

[0227] The terminal can receive SIBn via the service link of the source satellite before handover. Then, the terminal can identify the necessary post-handover SI 1811 within SIBn and apply the identified necessary post-handover SI 1811. Furthermore, as an example, the necessary post-handover SI can be included in the SIBs of the aforementioned satellite handover scenario without PCI changes. Here, the SIB can be an NTN-related SIB. In other words, the terminal can identify whether the NTN system is operating based on a satellite handover scenario without PCI changes based on the presence of a necessary post-handover SI in the NTN-related SIB. Specifically, if a necessary post-handover SI exists in the NTN-related SIB, the terminal can identify that the NTN system is operating based on a satellite handover scenario without PCI changes. On the other hand, if a necessary post-handover SI does not exist in the NTN-related SIB, the terminal can identify that the NTN system is operating based on other scenarios.

[0228] As an example, the necessary SI after the switchover can be NTN configuration information consisting of values ​​for the target satellite (e.g., NTN-config As another example, the necessary SI after the switchover can be NTN configuration information (e.g., NTN-config Some fields, or those configured by NTN (e.g., NTN-config The IE consists of some fields. Here, some of the fields mentioned above can be values ​​used for the target satellite. As a specific example, NTN configuration information (e.g., NTN-config Some fields of the NTN configuration information may include those illustrated in Table 13, as information required for TA pre-compensation for the target satellite. Specifically, the NTN configuration information (e.g., NTN-config Some fields include those that provide information about epoch time. epochTime Fields that provide TA-related information ta-info Fields, and those providing ephemeris-related information ephemerisInfo Field.

[0229] [Table 13]

[0230] Additionally, NTN configuration information (e.g., NTN-config Some fields may include the fields illustrated in Table 14, as part of NTN configuration information (e.g., NTN-config The fields within the NTN configuration information include one or more pieces of information. Specifically, NTN configuration information (e.g., NTN-config Some fields may include information on the effective duration of uplink synchronization in NTN. ntn-UlSyncValidityDuration Fields, providing cell-specific of cellSpecificKoffset Fields, Provided Information kmac Fields that provide TA report information ta-Report Fields that provide NTN polarization information ntn-PolarizationDL field or ntn-PolarizationUL Fields, etc.

[0231] [Table 14]

[0232] In other words, the necessary SI after the switchover may include at least one of Table 13 or Table 14 as NTN configuration information related to the target satellite (e.g., NTN-config ) or NTN configuration information (e.g., NTN-config The SI may include, but is not limited to, certain fields. Here, the necessary SI after the switchover may also include information from Table 15 related to at least one of Tables 13 or 14, as NTN configuration information related to the target satellite (e.g., NTN-config ) or NTN configuration information (e.g., NTN-config Some fields of the table. For example, Table 15 could be information about the start time or duration of the satellite handover. In other words, the post-handover required SI could further include time information related to the satellite handover.

[0233] [Table 15]

[0234] As an example, the terminal can apply the necessary post-handover SI immediately after switching to the target satellite, and perform operations and updates based on the necessary post-handover SI. Here, the necessary post-handover SI can include those shown in Table 14 above. ntn- UlSyncValidityDuration And when communication services for the target satellite begin immediately after switching to the target satellite, ntn-UlSyncValidityDuration It can also be applied to terminals. As an example, ntn- UlSyncValidityDuration It can indicate the period during which uplink synchronization is valid in the NTN system, and the timer can operate based on this period. Therefore, when starting communication services with the target satellite immediately after switching to the target satellite, the terminal can... ntn-UlSyncValidityDuration Start a timer, not limited to a specific exemplary embodiment.

[0235] As described above, the terminal can operate in an NTN system based on a satellite handover scenario without changing the PCI. Here, satellite handover without changing the PCI can be performed based on either hard or soft satellite handover in a quasi-Earth fixed cell satellite handover scenario. A satellite handover scenario without changing the PCI can be one where, before and after the handover, the source and target satellites use the same PCI to connect to the same base station and use the same SSB frequency, as shown in Table 7 above. The terminal may need to identify whether the system is operating in a satellite handover scenario without changing the PCI in order to support system operation based on this scenario.

[0236] Specifically, the terminal can identify satellite handover scenarios where the PCI has not changed by the presence or absence of an indicator that indicates the necessary SI after the handover. In other words, when based on Figure 16 When using an indicator included in the same SIB to indicate that the necessary SI after handover is included in the cell information of a neighboring cell list, or when based on Figure 17 When an indicator included in another SIB indicates that the necessary SI after the handover is included in the cell information of a neighboring cell list, the terminal can recognize the presence of the indicator and recognize that the NTN system is operating based on a satellite handover scenario without changing the PCI.

[0237] As another example, based on the above Figure 18 When a necessary SI for handover is configured independently within the SIB, the terminal can identify that the NTN system is operating in a satellite handover scenario without changing the PCI. In other words, the terminal can identify that the NTN system is operating in a satellite handover scenario without changing the PCI based on the presence of a necessary SI for handover within the SIB.

[0238] As another example, the terminal can be based on the start time of the communication service with the target satellite. t- Gap Fields are used to identify NTN system operations based on satellite handover scenarios where the PCI remains unchanged. As another example, the terminal can use fields related to the start time of communication services with the target satellite. t-Start The field is used to identify NTN system operations based on satellite handover scenarios without changes to the PCI.

[0239] As an example, identifying that the NTN system operates based on a satellite handover scenario without changing the PCI may mean that the terminal pre-identifies whether a satellite handover is to be performed based on hard or soft satellite handover, and the terminal can perform the operation corresponding to this identification.

[0240] For example, during a hard satellite handover, the terminal can stop the communication service provided by the source satellite and then connect to the service link of the target satellite. In other words, the terminal may not connect to two satellites simultaneously. Here, since the TA (Transmission Aspect) may have different values ​​before and after the satellite handover, smooth communication may not be possible if the TA is not identified. Therefore, when the communication service provided by the source satellite ends, the terminal may need to stop uplink transmission; for this purpose, the terminal may need to identify the end time of the communication service provided by the source satellite.

[0241] Specifically, the terminal can identify the occurrence of satellite handover based on the above content, according to a satellite handover scenario without PCI changes. However, the method by which the terminal identifies a satellite handover scenario without PCI changes is not limited to the above content. Then, the terminal can receive information from the source satellite regarding the time when the provision of communication services by the source satellite was stopped. As an example, the end time of the communication services of the source satellite could be determined by... t-service The specified time, but not limited to this. The terminal can identify the end time of the source satellite's communication service as described above.

[0242] As another example, the terminal can identify the occurrence of a satellite handover under a satellite handover scenario without a changed PCI based on the above content; however, the method by which the terminal identifies a satellite handover scenario without a changed PCI is not limited to the above content. Then, the terminal can receive information about the time at which it obtained the ephemeris and other auxiliary information of the source satellite via the source satellite. Here, the time at which the ephemeris and other auxiliary information of the source satellite are obtained can be determined by… epochTime The specified time, but not limited to this. The terminal can receive information about the length of the effective duration via the source satellite's service link, based on the time at which the source satellite's ephemeris and other ancillary information are obtained. As an example, the length of the effective duration can be determined by... ntn-UlSyncValidityDuration The indicated time, but not limited to this. When a valid duration has elapsed since the time the source satellite's ephemeris and other ancillary information were obtained, the terminal can recognize that the source satellite's communication service has ceased. In other words, the terminal can recognize the end time of the source satellite's communication service. As a specific example, the terminal can base its decision on (the time indicated by...). epochTime Specified time + by ntn-UlSyncValidityDuration The specified duration is used to identify the end time of the communication service of the source satellite, and is not limited to the exemplary embodiments.

[0243] As mentioned above, satellite handover scenarios based on unchanged PCI can be considered hard satellite handover. Therefore, there may be a period of time during which the terminal cannot use either the service link of the source satellite or the service link of the target satellite, and this period can be the time required for satellite handover. However, the name is for ease of description only and is not limited to a specific name. In the following text, for ease of description, this period will be referred to as the "satellite handover time".

[0244] Figure 19 This is a conceptual diagram illustrating a first exemplary embodiment of satellite handover time based on hard satellite handover.

[0245] Reference Figure 19 During satellite handover time 1910, the terminal may be unable to communicate with the base station. Additionally, when communication services are provided by the target satellite, the terminal can apply pre-compensation to the TA associated with the target satellite during uplink transmission. Considering the above, the terminal may need to identify the start and end times of satellite handover time 1910. In other words, the terminal may need to identify the end time of the communication service of the source satellite and the start time of the communication service of the target satellite. Here, the terminal can identify the start time of satellite handover time 1910 (i.e., the end time of the communication service of the source satellite) by identifying the end time of the communication service of the source satellite, but this is not limited to the specific exemplary embodiment.

[0246] In addition, the terminal may also need to identify the end time of satellite handover time 1910 (i.e., the start time of the target satellite's communication service). Specifically, based on the above, the terminal can identify that the NTN system is operating under a satellite handover scenario without changing the PCI, and identify the end time of the source satellite's communication service.

[0247] Here, the terminal can receive information about the satellite handover time via a service link provided by the source satellite. G-Gap The terminal can transmit (the end time of the source satellite's communication service + ...) information. t-Gap This is identified as the satellite handover time. In other words, the terminal can identify the start time of the communication service of the target satellite. As another example, the terminal can identify when the NTN system operates based on a satellite handover scenario without changing the PCI. Here, the terminal can receive information about the start time of the communication service defined as the target satellite through the service link of the source satellite. t-Start Information, and can be based on about t- Start The information identifies the start time of the communication service for the target satellite.

[0248] As another example, the terminal can recognize that the NTN system operates based on a satellite handover scenario without changing the PCI. Here, if the system information obtained by the terminal from the service link provided by the source satellite does not contain information about... t-Gap or t- Start If the terminal obtains information about the start time of the target satellite's communication service from the base station, it can identify the end time of the source satellite's communication service as the start time of the target satellite's communication service. In other words, if no information indicating the start time of the target satellite's communication service exists, the terminal can identify the end time of the source satellite's communication service as the start time of the target satellite's communication service. Here, the terminal can obtain information about the start time of the target satellite's communication service from the base station. t-Gap or t-Start Information. As an example, regarding... t-Gap or t-Start Information can be included in the necessary post-switching SI, as shown in Table 15. As an example, the terminal can receive the necessary post-switching SI via the service link of the source satellite before satellite handover, and can also receive information about... t-Gap or t-Start Information.

[0249] When a satellite handover occurs under a satellite handover scenario without changing the PCI, after the communication service of the source satellite ends, the terminal can be provided with a service link to the target satellite, and the terminal can communicate with the base station, as described above. Here, the terminal can receive the necessary SI after handover through the service link of the source satellite before the communication service of the source satellite ends. As described above, the terminal can identify whether the satellite handover scenario without changing the PCI is applied by receiving the necessary SI after handover.

[0250] The terminal can update system information related to the target satellite using the necessary post-switching SI received before the satellite handover, starting from the start time of the target satellite's communication service. Specifically, after the satellite handover, the terminal can use the necessary post-switching SI to update some or all of the information in Table 16. In other words, after the commencement of the target satellite's communication service, the terminal can update information related to the target satellite obtained through the service link of the source satellite.

[0251] [Table 16]

[0252] Specifically, the terminal can use the necessary SI after handover to determine the pre-compensated TA associated with the target satellite and apply the pre-compensated TA to communication with the base station from the start of the target satellite's communication service provision. Therefore, the terminal can communicate with the base station from the start time of the target satellite's communication service without performing a separate random access procedure. For example, the random access procedure could be a procedure performed by the terminal after the start of the target satellite's communication service to align the uplink TA for communication with the base station, but it is not limited to this.

[0253] In other words, the terminal can avoid performing a separate random access procedure when handing over from the source satellite to the target satellite, thus resolving the RACH congestion problem caused by the RA procedure. More specifically, if the terminal identifies a pre-compensated TA associated with the target satellite, it can perform uplink transmission to the base station, even if it does not immediately perform a random access procedure after the satellite handover. Therefore, the terminal can perform the TA alignment process without relying on random access.

[0254] A random access procedure can be used to identify the optimal uplink TA and apply it to uplink transmissions. However, if TA pre-compensation is possible, uplink transmissions to the target satellite can be performed without a random access procedure. The terminal can then align the TA within the TA error range through communication with the base station. Specifically, the terminal can send an uplink signal (e.g., a sounding reference signal (SRS)) to the base station, and the base station can correct the TA based on the received signal and indicate the corrected TA to the terminal. As an example, a TA command (TAC) MAC CE can be used to indicate the corrected TA. The terminal can correct the TA based on information from the base station regarding the corrected TA, and through this operation, smooth communication with the target satellite can be performed.

[0255] As another example, a terminal can cause a timer indicating the validity of system information to expire during a satellite handover. Here, if the timer indicating the validity of system information expires (or stops), the terminal can recognize a loss of uplink synchronization. For example, if the terminal switches to the target satellite, existing system information may no longer be used, so the timer indicating the validity of system information may expire when the terminal switches to the target satellite. In other words, the terminal can stop the timer indicating the validity of system information during a satellite handover. As a specific example, the timer can be the T430 timer defined in the 3GPP specification, but is not limited to it. For example, the time at which the terminal causes the timer indicating the validity of system information to expire (or stops) based on the satellite handover could be the end time of the provision of communication services on the source satellite. As another example, the time at which the terminal causes the timer indicating the validity of system information to expire (or stops) based on the satellite handover could be the start time of the communication services on the target satellite, but is not limited to it.

[0256] As an example, if a timer indicating the validity of system information expires (or stops), the terminal can suspend ongoing uplink transmissions at the end time of the source satellite's communication service. The terminal can then resume the suspended uplink transmissions at the start time of the target satellite's communication service. As a specific example, if uplink data exists in the terminal's uplink HARQ buffer, the terminal can maintain the HARQ buffer without refreshing it. The terminal can then resume transmitting the uplink data in the uplink HARQ buffer at the start time of the target satellite's communication service. This operation maintains uplink transmissions even during satellite handover.

[0257] As described above, when a terminal performs a satellite handover based on a satellite handover scenario without changing the PCI, since the terminal performs pre-compensation on the uplink TA for communication with the base station based on the system information immediately required after the start of communication service provision for the target satellite, a random access procedure can be omitted to align the uplink TA. However, as mentioned above, the terminal can select the downlink beam used by the base station during the random access procedure for initial access, but since a random access procedure is not performed in a satellite handover scenario without changing the PCI, this operation may be necessary.

[0258] As an example, a terminal may need to change the transmission beam used by the downlink of the service link provided by the target satellite immediately after a satellite handover. Here, since the terminal does not perform a random access procedure after the satellite handover, a method may be needed for immediately selecting a new transmission beam for the downlink used for the service link after the satellite handover.

[0259] Specifically, a terminal can use a mapping between the beam used immediately before satellite handover and the downlink transmission beam used immediately after handover to select the downlink transmission beam used for the serving link immediately after handover. As an example, a base station can identify the mapping between the transmission beams for a specific terminal in the source satellite and the transmission beams for a specific terminal in the target satellite before satellite handover. Then, during satellite handover, the base station can use this mapping to change the downlink transmission beam for the serving link for each terminal.

[0260] As a more specific example, communication services can be provided from the source satellite to the terminal via the downlink transmission beam with beam index 1. Later, when communication services from the target satellite to the terminal can be provided based on satellite handover, communication services can be provided from the target satellite via the downlink transmission beam with beam index 2. This can be considered the optimal beam selection. Here, beam index 1 in the source satellite and beam index 2 in the target satellite can have a mapping relationship. When the provision of communication services from the source satellite ends and the provision of communication services from the target satellite begins, the base station can select (change) the downlink transmission beam based on the aforementioned mapping relationship. In other words, when selecting the downlink transmission beam for the service link of a specific terminal, the base station can consider the mapping relationship of the downlink transmission beams of the service link of the source satellite for the specific terminal and select the downlink transmission beam of the service link of the target satellite for the specific terminal.

[0261] As an example, the above mapping relationship can be predetermined. As a specific example, the mapping relationship can be determined when planning a quasi-earth fixed cell for a satellite handover scenario where the PCI remains unchanged, but is not limited to this. The base station or network can select the downlink transmission beam based on a mapping relationship based on the terminal's location information obtained from the terminal immediately before the satellite handover. As another example, the base station or network can select the downlink transmission beam based on a mapping relationship between the terminal's location information obtained from the terminal immediately before the satellite handover and the terminal's location information obtained from the target satellite immediately after the satellite handover.

[0262] As another example, the mapping relationship can be obtained from the operational information acquired by the base station or network when serving a corresponding quasi-Earth fixed cell, but is not limited to this. Additionally, as an example, in a satellite handover scenario without changing the PCI, the terminal can receive the SSB of the serving link provided by the target satellite after the satellite handover. The terminal can obtain downlink synchronization through the received SSB and estimate the downlink received signal strength (e.g., RSRP). If the estimated downlink received signal strength is equal to or less than a preset threshold, the terminal can perform an RRC connection reconstruction procedure, but is not limited to this. Here, the preset threshold can be a parameter configured by the base station and can be broadcast through system information, but is not limited to this. As an example, the base station can configure different thresholds for each of multiple terminals. Specifically, the base station can configure the threshold for each individual terminal through parameters included in the RRC dedicated signaling for threshold configuration, and is not limited to a specific form.

[0263] As another example, a radio link failure (RLF) may occur after a terminal performs a satellite handover. In other words, if, after performing a satellite handover based on a scenario where the PCI has not been changed, the terminal identifies an RLF that prevents it from communicating with the base station while using the service link provided by the target satellite, the terminal can execute an RRC connection reconstruction procedure.

[0264] As another example, a terminal can perform operations in a satellite handover scenario where the PCI remains unchanged by considering a Time Alignment Timer (TAT). The TAT can be a timer provided by the base station to the terminal for managing uplink synchronization (e.g., uplink TA). Here, while the timer is running, the terminal can be in an uplink timing aligned state. The TAT can be a timer for the uplink synchronization validity period. The TAT can be set to a different value for each terminal (i.e., a UE-specific value) by a signal dedicated to each terminal. As another example, the TAT can be set by an SIB broadcast by the base station, so that all terminals in the cell have the same value (i.e., a cell-specific value), but is not limited to this. Here, the TAT can operate independently of satellite handover. As an example, the TAT can operate independently of timers indicating the validity of system information (e.g., the T430 timer). In other words, the TAT can be unaffected by satellite handover scenarios where the PCI remains unchanged and can operate in the same manner as before.

[0265] As another example, a terminal that supports satellite handover without changing the PCI can report to the base station that it supports satellite handover without changing the PCI. As a specific example, the terminal can report to the base station that it supports satellite handover without changing the PCI based on UE capability information. As an example, the terminal can generate a UE capability information message indicating that it supports satellite handover without changing the PCI. More specifically, the base station can send a UE capability query message to the terminal, and in response, the terminal can report this information to the base station by including information indicating whether it supports satellite handover without changing the PCI in the UE capability information message, but is not limited to this.

[0266] As an example, if the SIB obtained via the service link of the source satellite includes the Post-Switch Necessary SI, the terminal can identify a satellite handover scenario that supports the unchanged PCI. In other words, the terminal can identify a satellite handover scenario with resynchronization, as described above. In this document, the Post-Switch Necessary SI can be the first field (or first parameter) in the SIB. As a specific example, the first field (or first parameter) can be a parameter used for satellite handover with resynchronization (e.g., SatSwitchWithReSync(This is not limited to the above.) Here, when the terminal receives an SIB including the first field (or first parameter) through the service link of the source satellite, the terminal can identify a satellite handover scenario that supports the unchanged PCI. Furthermore, the SIB may also include other parameters related to the NTN system. As an example, the SIB may also include one or more parameters included in Table 9, but is not limited to this. Here, the terminal can identify a satellite handover scenario that supports the unchanged PCI based on the aforementioned first field (or first parameter) and other parameters related to the NTN system. As a specific example, the terminal can identify a satellite handover scenario that supports the unchanged PCI based on the aforementioned first field (or first parameter) included in the SIB and other parameters included in Table 9. t-service Fields (or parameters) are used to identify satellite handover scenarios where the PCI remains unchanged, and t-service The field indicates, but is not limited to, the end time of the satellite's communication service.

[0267] As another example, if the first field (or first parameter) is included in the SIB as a necessary SI after handover, the terminal can recognize that the PCI in the corresponding cell has not changed. As a specific example, in the satellite handover scenario where the PCI has not changed, a hard satellite handover can be performed if the PCI in the corresponding cell remains unchanged, but this is not a limitation. In other words, if the first field (or first parameter) is included in the SIB as a necessary SI after handover, the PCI in the corresponding cell can remain unchanged, and a soft satellite handover can be performed. As an example, the above description is based on performing a hard satellite handover in a satellite handover scenario where the PCI has not changed, but the same applies even when performing a soft satellite handover without changing the PCI.

[0268] In other words, in an NTN system, even when performing a soft satellite handover without changing the PCI, the same operation can be applied when the terminal obtains the necessary SI after handover via the service link of the source satellite, without being limited to a specific form. As another example, when the terminal receives the necessary SI after handover via the service link of the source satellite, the terminal can perform uplink TA pre-compensation on the service link of the target satellite without performing a random access procedure, and when the service link of the target satellite is established, the operation can be performed based on the pre-compensated TA and its updates. As an example, if the terminal obtains random access indication information after receiving the necessary SI after handover via the service link of the source satellite, the terminal can perform a random access procedure for the target satellite. In other words, if the terminal receives the necessary SI after handover via the service link of the source satellite, the terminal may not perform a random access procedure. However, if the base station indicates that a random access procedure is required, the terminal can perform a random access procedure based on that indication, without being limited to the corresponding exemplary embodiments.

[0269] Figure 20This is a flowchart illustrating a first exemplary embodiment of terminal operation in a satellite handover method in a wireless communication system.

[0270] Reference Figure 20 In the NTN system, the terminal can connect to the base station via the service link of the source satellite (S2010). Here, the terminal can obtain target satellite information via the service link of the source satellite (S2020). As an example, the target satellite information can be the necessary SI after handover as described above, but is not limited to this. Then, a satellite handover from the source satellite to the target satellite can be performed (S2030), and after the satellite handover to the target satellite is performed, the terminal can perform communication with the target satellite based on the target satellite information (S2040).

[0271] Here, as an example, if the terminal does not receive a random access instruction, it can connect to the target satellite's service link based on satellite handover without performing a random access procedure. In other words, when the terminal receives the necessary SI after handover through the source satellite's service link, it can connect to the target satellite without performing a random access procedure and perform communication through the target satellite's service link.

[0272] Here, the above operations can be performed based on a satellite handover scenario where the PCI remains unchanged. As an example, in the method without changing the PCI, the terminal can connect to the base station based on a first cell provided by the source satellite. After the satellite handover, the terminal can connect to the same base station based on a second cell provided by the target satellite. Both the first and second cells can be quasi-Earth fixed cells. Here, the PCI provided by the source satellite of the first cell and the PCI provided by the target satellite of the second cell can be the same. Furthermore, the frequency of the SSB received by the terminal from the source satellite based on the first cell and the frequency of the SSB received by the terminal from the target satellite based on the second cell can be the same.

[0273] Furthermore, when a terminal connects to the service link of a target satellite after the communication service of the source satellite is stopped due to satellite handover, the terminal can perform communication with the target satellite based on the target satellite's relevant information after switching to the target satellite based on satellite handover. As another example, the terminal can connect to the service link of the target satellite before the communication service of the source satellite is stopped, and if the communication service of the source satellite is stopped after connecting to the service link of the target satellite, the terminal can perform communication with the target satellite based on the target satellite's relevant information after switching to the target satellite based on satellite handover. Additionally, the target satellite's relevant information obtained by the terminal may include the target satellite's post-handover application information. The terminal can determine the target satellite's uplink TA based on the target satellite's post-handover application information and apply the determined uplink TA to communication with the target satellite. Here, the target satellite's post-handover application information may be... NTN-config It can also include itself. NTN- config Some fields in the [database name], as described above. For example, the post-switching application information for the target satellite may include [specific fields]. NTN- config In epochTime , TA-info , ephemerisInfo , ntn-UlSyncValidityDuration , cellSpecificK_offset , Kmac , TA-Report , ntn-PolarizationDL or ntn-PolarizationUL At least one of them. As another example, the post-switching application information for the target satellite may include t-Service , t-Start or t- Gap At least one of them, as described above.

[0274] Furthermore, the post-handover application information for the target satellite can consist of at least one field or IE from the SIB obtained by the terminal through the service link of the source satellite. In other words, as described above, the post-handover application information for the target satellite can be configured independently within the SIB. Additionally, the terminal can receive an NTN-related SIB, and the target satellite-related information can be included in the NTN-related SIB. As an example, if the first field exists in the NTN-related SIB, the terminal can determine that a satellite handover should be performed based on a scenario involving a satellite handover with resynchronization. As another example, when both the first and second fields exist in the NTN-related SIB, the terminal can determine that a satellite handover should be performed based on a scenario involving a satellite handover with resynchronization. Here, the first field can be... SatSwitchWithReSync And the second field can be t-service Fields, but not limited to these. Furthermore, if the first field exists in the NTN-related SIB, and the cell from which the terminal receives service is a quasi-earth fixed cell, the terminal can determine to perform a satellite handover based on a scenario with resynchronization. As an example, in a satellite handover scenario with resynchronization, the source satellite and the target satellite are connected to the same base station, the PCI of the cell is the same for both the source and target satellites, and the frequencies of one or more SSBs received by the terminal based on the cell may be the same. Furthermore, if uplink data exists in the uplink HARQ buffer based on the service link of the source satellite, the terminal can maintain the uplink data in the HARQ buffer during the satellite handover process and resume transmitting the uplink data in the uplink HARQ buffer after handover to the target satellite.

[0275] The operation of the method according to exemplary embodiments of this disclosure can be implemented as a computer-readable program or code in a computer-readable recording medium. The computer-readable recording medium can include all kinds of recording devices for storing data that can be read by a computer system. Furthermore, the computer-readable recording medium can store and execute programs or code, wherein the programs or code can be distributed across computer systems connected via a network and read in a distributed manner by a computer.

[0276] Computer-readable recording media can include hardware devices specifically configured to store and execute program commands, such as ROM, RAM, or flash memory. Program commands can include not only machine language code created by a compiler, but also high-level language code that can be executed by a computer using an interpreter.

[0277] Although some aspects of this disclosure have been described in the context of a device, these aspects may indicate corresponding descriptions according to the method, and blocks or devices may correspond to steps or features of the method. Similarly, aspects described in the context of a method may be represented as corresponding blocks or items or features of the corresponding device. Some or all of the steps of the method may be performed by (or using) hardware devices such as microprocessors, programmable computers, or electronic circuits. In some embodiments, one or more of the most important steps of the method may be performed by such devices.

[0278] In some exemplary embodiments, a programmable logic device, such as a field-programmable gate array (FPGA), can be used to perform some or all of the functions of the methods described herein. In some exemplary embodiments, a microprocessor can operate the FPGA to perform one of the methods described herein. Typically, the methods are preferably performed by a hardware device.

[0279] The description in this disclosure is merely exemplary in nature, and therefore, any changes that do not depart from the spirit and scope of this disclosure are intended to fall within its scope. These changes should not be considered as departing from the spirit and scope of this disclosure. Therefore, those skilled in the art will understand that various changes in form and detail may be made without departing from the spirit and scope defined by the appended claims.

Claims

1. A method for using a terminal, comprising: Obtain relevant information about the target satellite from the source satellite; Based on the target satellite's relevant information, a satellite handover is performed from the source satellite to the target satellite; as well as After the satellite handover is performed, communication with the target satellite is performed based on the target satellite's relevant information.

2. The method according to claim 1, wherein, The steps for performing communication with the target satellite include: Based on the target satellite's relevant information, connect to the target satellite without performing a random access procedure; and Communication with the target satellite is performed based on the target satellite's relevant information.

3. The method according to claim 1, wherein, The source satellite and the target satellite are connected to the same base station. The source satellite forms a first quasi-Earth fixed cell, and the target satellite forms a second quasi-Earth fixed cell. The physical cell identifier (PCI) of the first quasi-Earth fixed cell is the same as the PCI of the second quasi-Earth fixed cell, and the frequency of the first synchronization signal block (SSB) transmitted by the source satellite is the same as the frequency of the second SSB transmitted by the target satellite.

4. The method according to claim 1, wherein, The steps for performing communication with the target satellite include: Based on the satellite switching, communication services with the source satellite are terminated; Connect to the target satellite based on the target satellite's relevant information; and Based on the target satellite's relevant information, communication with the target satellite is performed through the target satellite's service link.

5. The method according to claim 1, wherein, The steps for performing communication with the target satellite include: Connect to the target satellite based on the relevant information of the target satellite; After connecting to the target satellite, communication on the service link of the source satellite is stopped; and Based on the target satellite's relevant information, communication with the target satellite is performed through the target satellite's service link.

6. The method according to claim 1, wherein, The terminal determines the uplink timing advance (TA) for the target satellite based on the relevant information of the target satellite, and applies the determined uplink TA to communication with the target satellite.

7. The method according to claim 1, wherein, The target satellite-related information includes at least one of the following: epoch time, uplink TA information, ephemeris information, uplink synchronization effective duration, cell-specific scheduling offset, network scheduling offset, TA report information, downlink polarization information, or uplink polarization information in the non-terrestrial network configuration information of the target satellite.

8. The method according to claim 1, in, The target satellite-related information includes the time when the communication service of the source satellite was interrupted, and Specifically, when the communication service is stopped at the specified time, the terminal maintains the uplink Hybrid Automatic Repeat Request (HARQ) buffer without refreshing the uplink HARQ buffer, and when communication with the target satellite begins, the terminal resumes uplink HARQ operation with the target satellite.

9. The method according to claim 1, wherein, The target satellite information is included in the System Information Block (SIB) obtained by the terminal from the source satellite.

10. The method according to claim 1, wherein, When the target satellite information is included in a non-terrestrial network-related SIB, the terminal performs the satellite handover, and When the target satellite information is not included in the non-terrestrial network related SIB, the terminal does not perform the satellite handover.

11. A method for establishing a base station, comprising: The target satellite information is provided to the terminal via a source satellite connected to the base station; When the communication service provided by the source satellite is stopped, a satellite handover is performed from the source satellite to the target satellite; as well as After the satellite handover is performed, communication services are provided to the terminal via the target satellite; In this scenario, without performing a random access procedure between the target satellite and the terminal, the base station provides communication services to the terminal via the target satellite.

12. The method according to claim 11, wherein, The target satellite information is included in the System Information Block (SIB) sent to the terminal.

13. The method according to claim 11, wherein, The target satellite-related information includes at least one of the following: epoch time, uplink TA information, ephemeris information, uplink synchronization effective duration, cell-specific scheduling offset, network scheduling offset, TA report information, downlink polarization information, or uplink polarization information in the non-terrestrial network configuration information of the target satellite.

14. The method according to claim 11, wherein, The base station includes the target satellite information in a non-terrestrial network-related SIB to instruct the terminal to perform the satellite handover, and The base station does not include the target satellite information in the non-terrestrial network related SIB to instruct the terminal not to perform the satellite handover.

15. A terminal, comprising a processor, wherein, The processor causes the terminal to perform the following operations: Obtain relevant information about the target satellite from the source satellite; Based on the target satellite's relevant information, a satellite handover is performed from the source satellite to the target satellite; as well as After the satellite handover is performed, communication with the target satellite is performed based on the target satellite's relevant information.

16. The terminal according to claim 15, wherein, When communicating with the target satellite, the processor causes the terminal to perform the following operations: Based on the target satellite's relevant information, connect to the target satellite without performing a random access procedure; and Communication with the target satellite is performed based on the target satellite's relevant information.

17. The terminal according to claim 15, wherein, When communicating with the target satellite, the processor causes the terminal to perform the following operations: Based on the satellite switching, communication services with the source satellite are terminated; Connect to the target satellite based on the relevant information of the target satellite; as well as Based on the target satellite's relevant information, communication with the target satellite is performed through the target satellite's service link.

18. The terminal according to claim 15, in, The target satellite-related information includes the time when the communication service of the source satellite was interrupted, and Specifically, when the communication service is stopped at the specified time, the processor causes the terminal to maintain the uplink Hybrid Automatic Repeat Request (HARQ) buffer without refreshing the uplink HARQ buffer, and when communication with the target satellite begins, the processor causes the terminal to resume uplink HARQ operation with the target satellite.

19. The terminal according to claim 15, wherein, The target satellite information is included in the System Information Block (SIB) obtained by the terminal from the source satellite.

20. The terminal according to claim 15, wherein, When the target satellite information is included in a non-terrestrial network-related SIB, the processor causes the terminal to perform the satellite handover, and When the target satellite information is not included in the non-terrestrial network related SIB, the processor causes the terminal not to perform the satellite handover.

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