Electron device and method for selecting cell in non-terrestrial network

Abstract

To provide a satellite device and method for providing a non-terrestrial network (NTN) access.SOLUTION: A satellite 620 includes at least one processor 1303 and at least one transceiver 1301. The processor 1303 transmits, via the transceiver, a message containing handover related information to a terminal on a cell provided by the satellite 620. The handover related information includes information related to a group to which the satellite 620 belongs, information related to a target satellite of a target cell of a handover for the terminal, information related to a terminal group to which the terminal belongs, information related to a condition for a conditional handover of the terminal, and information related to at least one of a position, a speed, or an orbit of the target satellite.SELECTED DRAWING: Figure 13

Description

[Technical Field]

[0001] This disclosure relates generally to non-terrestrial networks (NTNs) that provide wireless communication services via earth-orbiting satellites or high-altitude aerial vehicles rather than via terrestrial base stations, and more particularly to an apparatus and method for cell selection in a non-terrestrial network. [Background technology]

[0002] Non-terrestrial networks (NTNs) have been introduced to supplement terrestrial networks that provide wireless communication systems. Non-terrestrial networks can provide communication services in areas where it is difficult to build terrestrial networks or in disaster situations. Furthermore, the recent reduction in satellite launch costs has made it possible to provide an efficient access network environment. Summary of the Invention [Means for solving the problem]

[0003] In an embodiment, a satellite device for providing non-terrestrial network (NTN) access is provided. The device may include at least one processor and at least one transceiver. The at least one processor may be configured to transmit, via the at least one transceiver, a message including handover-related information to a terminal on a cell provided by the satellite. The handover-related information may include information regarding a group to which the satellite belongs, information regarding a target satellite of a target cell of handover for the terminal, information regarding a terminal group to which the terminal belongs, information regarding a condition for conditional handover of the terminal, and information regarding at least one of a position, a velocity, or an orbit of the target satellite.

[0004] In an embodiment, a method performed by a satellite for providing non-terrestrial network (NTN) access is provided. The method can include an operation of transmitting a message including handover-related information to a terminal on a cell served by the satellite. The handover-related information can include information regarding a group to which the satellite belongs, information regarding a target satellite of a target cell of handover for the terminal, information regarding a terminal group to which the terminal belongs, information regarding a condition for conditional handover of the terminal, and information regarding at least one of a position, a velocity, or an orbit of the target satellite.

[0005] In an embodiment, a non-transitory recording medium is provided. The non-transitory recording medium may include a memory that stores instructions that, when executed by at least one processor, cause a satellite for providing non-terrestrial network (NTN) access to transmit a message including handover-related information to a terminal on a cell served by the satellite, the handover-related information including information about a group to which the satellite belongs, information about a target satellite of a target cell of handover for the terminal, information about a terminal group to which the terminal belongs, information about a condition for conditional handover of the terminal, and information about at least one of a position, a velocity, or an orbit of the target satellite. [Brief explanation of the drawings]

[0006] [Figure 1] 1 illustrates a wireless communication system. [Figure 2a] An example of a non-terrestrial network (NTN) is shown below. [Figure 2b] An example of a non-terrestrial network (NTN) is shown below. [Figure 3a] An example of a control plane (C-plane) is shown below. [Figure 3b] An example of a user plane (U-plane) is shown. [Figure 4] 1 illustrates an example of a time-frequency domain resource structure in a wireless communication system. [Figure 5] An example of a network structure for NTN is shown. [Figure 6a] 1 shows an example of a control plane for a regenerative satellite. [Figure 6b] 1 shows an example of a regenerative satellite user plane. [Figure 7a]1 shows an example of a group handover in satellite communications. [Figure 7b] 10 shows an example of a handover of a non-terrestrial base station. [Figure 8a] An example of system information for NTN is shown below. [Figure 8b] 1 shows an example of an RRC (radio resource control) message for NTN. [Figure 9a] 1 shows an example of signaling via the F1 interface in NTN. [Figure 9b] 1 shows an example of signaling via the F1 interface in NTN. [Figure 10] 1 shows an example of signaling via the XN interface in an NTN. [Figure 11a] An example of signaling via the NG interface in NTN is shown below. [Figure 11b] An example of signaling via the NG interface in NTN is shown below. [Figure 12a] An example of a handover procedure using a regenerative satellite is shown. [Figure 12b] An example of a handover procedure using a regenerative satellite is shown. [Figure 13] 1 shows examples of components of a satellite. [Figure 14] 1 shows an example of components of a terminal. DETAILED DESCRIPTION OF THE INVENTION

[0007] The terms used in this disclosure are merely used to describe specific embodiments and are not intended to limit the scope of other embodiments. A singular expression can include a plural expression unless otherwise specified in the context. Terms used herein, including technical or scientific terms, can have the same meaning as commonly understood by a person of ordinary skill in the art described in this disclosure. Among the terms used in this disclosure, terms defined in common dictionaries may be interpreted as having the same or similar meaning as in the context of the relevant art, and unless clearly defined in this disclosure, they should not be interpreted as having an ideal or overly formal meaning. In some cases, even terms defined in this disclosure cannot be interpreted to exclude embodiments of the present disclosure.

[0008] In the various embodiments of the present disclosure described below, a hardware approach is described as an example, however, the various embodiments of the present disclosure include techniques that use both hardware and software, and therefore the various embodiments of the present disclosure do not exclude a software-based approach.

[0009] In the following description, terms referring to signals (e.g., signal, information, message, signaling), terms referring to resources (e.g., symbol, slot, subframe, radio frame, subcarrier, resource element (RE), resource block (RB), bandwidth part (BWP), occasion), terms for operation states (e.g., step, operation, procedure), terms referring to data (e.g., packet, user stream, information, bit, symbol, codeword), terms referring to channels, terms referring to network entities, terms referring to device components, etc. are illustrated for convenience of explanation. Therefore, the present disclosure is not limited to the terms described below, and other terms having equivalent technical meanings may be used.

[0010] In the following description, the terms "physical channel" and "signal" may be used interchangeably with "data" or "control signal." For example, "physical downlink shared channel" (PDSCH) is a term referring to a physical channel over which data is transmitted, but "PDSCH" may also be used to refer to data. That is, in the present disclosure, the expression "transmitting a physical channel" may be interpreted as equivalent to the expression "transmitting data or a signal via a physical channel."

[0011] Hereinafter, in this disclosure, upper signaling refers to a signaling method transmitted from a base station to a terminal using a downlink data channel of a physical layer, or from a terminal to a base station using an uplink data channel of a physical layer. Upper signaling can be understood as RRC (radio resource control) signaling or MAC control element (hereinafter referred to as "CE").

[0012] Furthermore, in this disclosure, expressions such as "more than" or "less than" may be used to determine whether a particular condition is satisfied or fulfilled, but this is merely an explanation for illustrating an example and does not exclude descriptions such as "more than" or "less than." A condition described as "more than" can be replaced with "more than," a condition described as "less than," and a condition described as "more than and less than" can be replaced with "more than and less than." Furthermore, hereinafter, "A" to "B" refer to at least one element from A to B (including A). hereinafter, "C" and / or "D" refer to at least one of "C" or "D," i.e., {"C," "D," "C" and "D"}.

[0013] In the present disclosure, the signal quality may be, for example, at least one of RSRP (reference signal received power), BRSRP (beam reference signal received power), RSRQ (reference signal received quality), RSSI (received signal strength indicator), SINR (signal to interference and noise ratio), CINR (carrier to interference and noise ratio), SNR (signal to noise ratio), EVM (error vector magnitude), BER (bit error rate), and BLER (block error rate). In addition to the above examples, it goes without saying that other terms having equivalent technical meanings or other metrics representing channel quality may be used. Hereinafter, in the present disclosure, high signal quality refers to a large signal quality value related to signal size or a small signal quality value related to error rate. Higher signal quality may mean a more seamless wireless communication environment is guaranteed. An optimal beam may refer to a beam with the highest signal quality among beams.

[0014] Although the present disclosure describes various embodiments using terminology used in some communication standards (e.g., 3GPP (3rd Generation Partnership Project), ETSI (European Telecommunications Standards Institute)), this is for illustrative purposes only. Various embodiments of the present disclosure can be easily modified and applied to other communication systems.

[0015] FIG. 1 shows a wireless communication system. Referring to Figure 1, Figure 1 illustrates a terminal 110 and a base station 120 as part of a node utilizing a radio channel in a wireless communication system using New Radio (NR), which is an air interface of a Radio Access Technology (RAT). Although Figure 1 shows only one base station, the wireless communication system may further include other base stations that are the same as or similar to base station (e.g., NR gNB) 120.

[0016] The terminal 110 is a device used by a user and communicates with the base station 120 via a wireless channel. A link from the base station 120 to the terminal 110 is called a downlink (DL), and a link from the terminal 120 to the base station 120 is called an uplink (UL). Although not shown in FIG. 1 , the terminal 110 and other terminals can communicate with each other via wireless channels. In this case, a device-to-device link (D2D) between the terminal 110 and other terminals is called a sidelink, and the term sidelink may be used interchangeably with a PC5 interface. In some other embodiments, the terminal 110 can be operated without user involvement. According to one embodiment, the terminal 110 is a device for performing machine type communication (MTC) and may not be carried by the user. Furthermore, according to one embodiment, the terminal 110 may be a narrowband (NB)-Internet of Things (IoT) device.

[0017] For purposes of describing the systems and methods herein, terminal 110 may be an electronic device used to communicate voice and / or data to base station 120, which in turn may communicate with a network of devices (e.g., public switched telephone network (PSTN), the Internet, etc.).

[0018] In addition to a terminal, terminal 110 may also be referred to as a "user equipment (UE)," a "vehicle," a "customer premises equipment (CPE)," a "mobile station," a "subscriber station," a "remote terminal," a "wireless terminal," an electronic device, or a "user device," an access terminal, a "mobile terminal," a "remote station," a "user terminal," a "subscriber unit," a "mobile device," or other terms having equivalent technical meanings.

[0019] Examples of terminal 110 include a mobile phone, a smartphone, a personal digital assistant (PDA), a laptop computer, a netbook, an e-reader, a wireless modem, etc. In the 3GPP standard, terminal 110 is typically referred to as a UE. However, because the scope of the disclosure herein should not be limited to the 3GPP standard, the terms "UE" and "terminal" may be used interchangeably herein to refer to the more general term "wireless communication device." A UE may also be more generally referred to as a terminal device.

[0020] A base station 120 is a network infrastructure that provides wireless connectivity to terminals 110. Terminals 110 have coverage, which is defined based on the distance over which signals can be transmitted. In 3GPP standards, base station 120 may be generally referred to as a "Node B," an "evolved Node B (eNB)," a "5th generation node," a "next generation node B (gNB)," a "home enhanced or evolved Node B (HeNB)," an access point (AP), a "wireless point," a "transmission / reception point (TRP)," or other terms having equivalent technical meanings.

[0021] Since the scope of the content disclosed herein should not be limited to the 3GPP standard, the terms “base station,” “Node B,” “eNB,” and “HeNB” can be used interchangeably herein to refer to the more general term “base station.” Furthermore, the term “base station” can be used to refer to an access point. An access point may be an electronic device that provides access to a network (e.g., a local area network (LAN), the Internet, etc.) for wireless communication devices. The term “communication device” can be used to refer to both wireless communication devices and / or base stations. An eNB or gNB may also be more generally referred to as a base station device.

[0022] The base station 120 can communicate with an NR Core Network (NR CN) entity 130. For example, the core network entity 130 can include an Access and Mobility Management Function (AMF) responsible for a control plane such as connection and mobility control functions for the terminal 110, and a User Plane Function (UPF) responsible for control functions for user data.

[0023] The terminal 110 may perform beamforming with the base station 120. The terminal 110 and the base station 120 may transmit and receive radio signals in a relatively low frequency band (e.g., FR1 (frequency range 1) of NR). The terminal 110 and the base station 120 may also transmit and receive radio signals in a relatively high frequency band (e.g., FR2 (or FR2-1, FR2-2, FR2-3), or FR3 of NR) or a millimeter wave (mmWave) band (e.g., 28 GHz, 30 GHz, 38 GHz, or 60 GHz). To improve channel gain, the terminal 110 and the base station 120 may perform beamforming. Here, beamforming may include transmit beamforming and receive beamforming. The terminal 110 and the base station 120 may impart directionality to a transmit signal or a receive signal. To this end, the terminal 110 and the base station 120 can select a serving beam through a beam search or beam management procedure. After the serving beam is selected, communication can be performed via resources that have a Quasi Co-Location (QCL) relationship with the resources that transmit the serving beam.

[0024] A first antenna port and a second antenna port can be evaluated as having a QCL relationship if large-scale characteristics of the channel that carried symbols on the first antenna port can be inferred from the channel that carried symbols on the second antenna port. For example, the large-scale characteristics can include at least one of delay spread, Doppler spread, Doppler shift, average gain, average delay, and spatial receiver parameters.

[0025] Both terminal 110 and base station 120 may perform beamforming, although embodiments of the present disclosure are not necessarily limited thereto. In some embodiments, terminal 110 may or may not perform beamforming. Also, base station 120 may or may not perform beamforming. That is, only one of terminal 110 and base station 120 may perform beamforming, or neither terminal 110 nor base station 120 may perform beamforming.

[0026] In this disclosure, a beam refers to a spatial flow of a signal in a wireless channel and is formed by one or more antennas (or antenna elements), and such a forming process may be referred to as beamforming. Beamforming may include at least one of analog beamforming or digital beamforming (e.g., precoding). Reference signals transmitted based on beamforming may include, for example, a demodulation-reference signal (DM-RS), a channel state information-reference signal (CSI-RS), a synchronization signal / physical broadcast channel (SS / PBCH), and a sounding reference signal (SRS). Furthermore, information elements (IEs) such as CSI-RS resources or SRS resources may be used as the configuration of each reference signal, and such configuration may include information associated with the beam. The beam-related information may refer to whether the configuration (e.g., a CSI-RS resource) uses the same spatial domain filter as other configurations (e.g., other CSI-RS resources in the same CSI-RS resource set) or whether a different spatial domain filter is used, or which reference signal it is quasi-co-located with, and if so, what type it is (e.g., QCL type A, B, C, D).

[0027] Hereinafter, for purposes of describing the embodiment, the terminal may be referred to as UE 110 and the base station may be referred to as gNB 120.

[0028] 2a and 2b illustrate examples of non-terrestrial networks (NTNs). FIG. 2a illustrates an example of a non-terrestrial network (NTN) using transparent satellites. FIG. 2b illustrates an example of a non-terrestrial network NTN using regenerative satellites. NTN refers to an NG-RAN that provides non-terrestrial NR access to UEs (e.g., UE 110) via NTN payloads and NTN gateways on airborne or space-borne NTN vehicles. This NG-RAN may include one or more gNBs (e.g., gNB 120).

[0029] Referring to FIG. 2a, NTN 200 illustrates the transparent satellite network environment. NTN 200 can include an NTN payload 221 and an NTN gateway 223 as a gNB 120. The NTN payload 221 is a network node mounted on a satellite or a high altitude platform station (HAPS) that provides connectivity between a service link (described below) and a feeder link (described below). The NTN gateway 223 is an earth station located on the Earth's surface that provides connectivity to the NTN payload 221 using the feeder link. The NTN gateway 223 is a transport network layer (TNL) node. The NTN 200 can provide non-terrestrial NR access to the UE 110. The NTN 200 can provide non-terrestrial NR access to the UE 110 via the NTN payload 221 and the NTN gateway 223. The link between the NTN payload 221 and the UE 110 is sometimes referred to as a service link. The link between the NTN gateway 223 and the NTN payload 221 is sometimes called a feeder link, which may correspond to a wireless link.

[0030] The NTN payload 221 can receive radio protocol data from the UE 110 via a service link. The NTN payload 221 can transparently convey the radio protocol data to the NTN gateway 223 via a feeder link. Therefore, the NTN payload 221 and the NTN gateway 223 can appear as one gNB 120 from the perspective of the UE 110. The NTN payload 221 and the NTN gateway 223 can communicate with the UE 110 via a Uu interface, which is a common radio protocol. That is, the NTN payload 221 and the NTN gateway 223 can perform radio protocol communication with the UE 110 as if they were one gNB 120. The NTN gateway 223 can communicate with a core network entity 235 (AMF or UPF) via an NG interface.

[0031] According to one embodiment, the NTN payload 221 and the NTN gateway 223 can use a radio protocol stack in the control plane of Figure 3a, which is described below. Additionally, according to one embodiment, the NTN payload 221 and the NTN gateway 223 can use a radio protocol stack in the user plane of Figure 3b.

[0032] Although Figure 2a illustrates one NTN payload 221 and one NTN gateway 223 included in the gNB 120, embodiments of the present disclosure are not limited thereto. For example, a gNB may include multiple NTN payloads. Furthermore, for example, an NTN payload may be provided by multiple gNBs. In other words, the implementation scenario illustrated in Figure 2a is an example and does not limit embodiments of the present disclosure.

[0033] Referring to FIG. 2b, NTN 250 represents the regenerative satellite network environment. NTN 250 may include satellite 260 operating as gNB 120. Satellite 260 represents a space-borne vehicle carrying a regenerative payload communications transmitter located in low-earth orbit (LEO), medium-earth orbit (MEO), or geostationary earth orbit (GEO). Satellite 260 may be referred to as a regenerative payload or a regenerative satellite. Satellite 260 represents a payload configured to convert and amplify uplink RF signals before transmitting them to the downlink, where converting the signal may refer to digital processing that may include demodulation, decoding, re-encoding, re-modulation, and / or filtering. NTN 250 may include NTN gateway 265, a ground-based entity connected to satellite 260. The NTN gateway 265 is an earth station located on the surface of the Earth that provides connectivity to the satellite 260 using the feeder link. The NTN 250 can provide non-terrestrial NR access to the UE 110. The NTN 250 can provide non-terrestrial NR access to the UE 110 via the satellite 260 and the NTN gateway 265.

[0034] The satellite 260 may be configured to regenerate signals received from Earth. A Uu interface may be defined between the satellite 260 and the terminal 110. A satellite radio interface (SRI) on a feeder link may be defined between the satellite 260 and the NTN gateway 265. Although not shown in FIG. 2b, the satellite 260 may provide inter-satellite links (ISLs) between the satellites. The ISLs are transmission links between the satellites, and the ISLs may be 3GPP or non-3GPP defined radio interfaces (e.g., XN interfaces) or optical interfaces. The satellite 260 may communicate via the core network entity 235 (AMF or UPF) and the NG interface based on the NTN gateway 265. According to one embodiment, the satellite 260 may use the radio protocol stack in the control plane of FIG. 3a, which will be described later. Furthermore, according to one embodiment, the satellite 260 may use the radio protocol stack in the user plane of FIG. 3b.

[0035] Although FIG. 2b illustrates a satellite 260 operating as a gNB 120, embodiments of the present disclosure are not limited thereto. The gNB 120 according to the embodiment may be implemented in a distributed deployment using a centralized unit (CU) configured to perform functions of the upper layers of the access network (e.g., packet data convergence protocol (PDCP) and radio resource control (RRC)) and distributed units (DUs) configured to perform functions of the lower layers. The interface between the CU and the distributed units (DUs) may be referred to as an F1 interface. The centralized unit (CU) is connected to one or more DUs and may perform functions of higher layers than the DUs. For example, the CU may be responsible for functions of the radio resource control (RRC) and packet data convergence protocol (PDCP) layers, while the DU and radio unit (RU) may be responsible for functions of the lower layers. The DU may be responsible for functions of the radio link control (RLC), media access control (MAC), and physical layer (PHY). In this distributed configuration, satellites 260 can be used as CUs or DUs that make up gNB 120.

[0036] 3a shows an example of a control plane (C-plane). At least some of the following discussion of gNB 120 may be understood with respect to satellite 260.

[0037] 3a, in the C-plane, the UE 110 and the AMF 235 can perform non-access stratum (NAS) signaling. In the C-plane, the UE 110 and the gNB 120 can communicate according to protocols specified in the RRC layer, the PDCP layer, the RLC layer, the MAC layer, and the PHY layer.

[0038] In NTN access, the main functions of the RRC layer may include at least some of the following functions: - Broadcasting of AS (access stratum) and NAS related system information - Paging initiated by 5GC (5G Core) or NG-RAN (Next Generation-Radio Access network) - Establishing, maintaining and tearing down the RRC connection between the UE and the NG-RAN, more specifically including the control of RLC, MAC and PHY: - Adding, modifying, and removing carrier aggregation - Addition, modification, and removal of dual connectivity between NR or E-UTRA and NR - Security features including Key Management - Setting, configuring, maintaining and canceling SRB (Signaling Radio Bearer) and DRB (Data Radio Bearer) - Movement features including: - Handover and context transfer UE cell selection and reselection, and cell selection and reselection control - Inter-RAT mobility - QoS (quality of service) management function UE measurement reporting and reporting control - Radio link failure detection and recovery - Send messages from / to the UE, to / from the NAS, and to the NAS. In NTN access, the main functions of the PDCP layer include at least some of the following functions: - Header compression and decompression (ROHC only) - Transfer of user data - In-sequence delivery of upper layer PDUs - Out-of-sequence delivery of upper layer PDUs - Reordering function (PDCP PDU reordering for reception) - Duplicate detection of lower layer SDUs - Retransmission of PDCP SDUs - Ciphering and deciphering functions - Timer-based SDU discard in uplink. In NTN access, the main functions of the RLC layer may include at least some of the following functions: - Data transmission function (Transfer of upper layer PDUs) - In-sequence delivery of upper layer PDUs - Out-of-sequence delivery of upper layer PDUs - ARQ function (Error Correction through ARQ) - Concatenation, segmentation and reassembly of RLC SDUs - Re-segmentation of RLC data PDUs - Reordering of RLC data PDUs - Duplicate detection - Protocol error detection - RLC SDU deletion function (RLC SDU discard) - RLC re-establishment function. In NTN access, the MAC layer can connect with several RLC layer devices configured in one terminal, and the main functions of the MAC can include at least some of the following functions: - Mapping between logical channels and transport channels - Multiplexing / demultiplexing of MAC SDUs - Scheduling information reporting function - Error correction through HARQ - Priority handling between logical channels of one UE - Priority handling between UEs by means of dynamic scheduling - MBMS service identification function - Transport format selection - Padding function.

[0039] In NTN access, the physical layer can perform the operations of channel coding and modulating upper layer data, converting it into OFDM symbols, and transmitting them over a wireless channel, or demodulating and channel decoding OFDM symbols received over a wireless channel, and transmitting them to an upper layer.

[0040] 3b shows an example of a user plane (U-plane). At least some of the following discussion of the gNB 120 may be understood with respect to the satellite 260.

[0041] 3b, in the U-plane, the UE 110 and the gNB 120 can communicate according to protocols specified in the SDAP layer, the PDCP layer, the RLC layer, the MAC layer, and the PHY layer, respectively. Except for the SDAP layer, the PDCP layer, the RLC layer, the MAC layer, and the PHY layer can refer to the description in FIG. 3a.

[0042] In NTN access, the SDAP layer can provide 5GC QoS flows. A single SDAP protocol entity can be configured for each individual PDU session, and the SDAP layer functions can include at least some of the following functions: - Mapping between QoS flows and data radio bearers - Display QoS Flow Identifier (QFI) for both DL and UL packets.

[0043] 4 shows an example of a time-frequency domain resource structure supported by a wireless communication system to which the embodiments proposed in this specification can be applied. Fig. 4 illustrates a basic structure of a time-frequency domain, which is a radio resource region in which data or control channels are transmitted in downlink or uplink in a 5G NR system to which the embodiments can be applied.

[0044] 4, the horizontal axis represents the time domain, and the vertical axis represents the frequency domain. The minimum transmission unit in the time domain is an OFDM symbol, and Nsymb A group of OFDM symbols 402 constitute one slot 406. Referring to FIG. 4, a radio frame in a wireless communication system to which the present invention is applied can be defined as having a length of 10 ms and consisting of 10 subframes, each having the same length of 1 ms. A radio frame 414 can be divided into 5 ms half-frames, each including five subframes. In FIG. 4, the slot 406 is composed of 14 OFDM symbols, but the length of the slot can vary depending on the subcarrier spacing. For example, in the case of numerologies with 15 kHz subcarrier spacing, the slot is 1 ms long, the same length as the subframe. In contrast, in the case of numerologies with 30 kHz subcarrier spacing, the slot is composed of 14 OFDM symbols, but one subframe can be 0.5 ms long and include two slots.

[0045] In other words, a subframe and a frame are defined by a fixed time length, and a slot is defined by the number of symbols, and the time length may vary depending on the subcarrier spacing. Referring again to Figure 4, radio resources supported by a wireless communication system to which the invention proposed in this specification can be applied are composed of symbols, which are multiple time resources, and subcarriers, which are multiple frequency resources, and each time resource and frequency resource can be represented as a two-dimensional resource grid. In Figure 4, one rectangle, which is the smallest physical resource consisting of one subcarrier and one symbol in the resource grid, is called a resource element (RE) 412.

[0046] In a wireless communication system to which the invention proposed in this specification can be applied, the minimum transmission unit in the frequency domain is a subcarrier, and the carrier bandwidth constituting a resource grid is N BW It is composed of subcarriers 404.

[0047] The basic unit of a resource in the time-frequency domain is a resource element (hereinafter referred to as "RE") 412, which can be expressed as an OFDM symbol index and a subcarrier index. A resource block 408 can include multiple resource elements 412. In a wireless communication system to which the invention proposed in this specification can be applied, a resource block 408 (or a physical resource block (hereinafter referred to as "PRB")) is defined as N 128 s in the time domain. symb consecutive OFDM symbols and N SC RB In an NR system, a resource block (RB) 408 can be defined as N consecutive subcarriers in the frequency domain. SC RB One RB 408 can be defined as N consecutive subcarriers 410 on the frequency axis. SC RB Includes RE412.

[0048] Generally, the minimum transmission unit of data is RB, and the number of subcarriers is N SC RB= 12. The frequency domain can include common resource blocks (CRBs). Physical resource blocks (PRBs) can be defined in the bandwidth part (BWP) in the frequency domain. The CRB number and PRB number can be determined based on the subcarrier spacing. The data rate can increase in proportion to the number of RBs scheduled to the terminal.

[0049] In an NR system, in the case of an FDD (frequency division duplex) system in which the downlink and uplink are operated by dividing the frequency, the downlink transmission bandwidth and the uplink transmission bandwidth may differ. The channel bandwidth indicates the RF (radio frequency) bandwidth corresponding to the system transmission bandwidth. Table 1 shows a portion of the correspondence between the system transmission bandwidth, subcarrier spacing (SCS), and channel bandwidth defined in an NR system in a frequency band (e.g., FR1 (410 MHz to 7125 MHz)) lower than the upper limit (e.g., 7.125 GHz) defined in the standard. Table 2 shows a portion of the correspondence between the transmission bandwidth, subcarrier spacing, and channel bandwidth defined in an NR system in a frequency band (e.g., FR2 (24250 MHz to 52600 MHz) or FR2-2 (52600 MHz to 71000 MHz)) higher than the lower limit (e.g., 24.25 GHz) defined in the standard. For example, an NR system with a 100 MHz channel bandwidth at 30 kHz subcarrier spacing has a transmission bandwidth of 273 RBs. In Tables 1 and 2, N / A may be a bandwidth-subcarrier combination that is not supported by the NR system.

[0050] [Table 1]

[0051] [Table 2]

[0052] Figure 5 shows an example of a network structure for an NTN. Satellite 260 is mounted on a space vehicle or aerial vehicle and can provide structure, power, command, telemetry, attitude control for the satellite (corresponding HAPS), and appropriate thermal environment and radiation shielding. Figure 5 illustrates an example in which satellite 260 is a regenerative payload and operates as a complete base station (e.g., gNB 120).

[0053] Referring to FIG. 5, the satellite 260 can operate as the gNB 120. The gNB 120 can communicate with the terminal 110 or can communicate with the core network entity 130. In FIG. 5, a UPF 550 is illustrated as the core network entity 130. An NR Uu interface 502 can be used between the satellite 260 and the terminal 110. According to an embodiment, at least one radio bearer 520 can be created between the satellite 260 and the terminal 110. For example, the radio bearer 520 can include a data radio bearer (DRB). For example, the radio bearer 520 can include a signaling radio bearer (SRB). An NG interface 504 can be used between the satellite 260 and a core network entity (e.g., AMF, UPF). For example, an N3 interface can be used between the satellite 260 and the UPF. For example, an N2 interface can be used between the satellite 260 and the AMF. According to one embodiment, a traffic tunnel may be created between the satellite 260 and the core network entity 130. For example, an NG-U tunnel 530 may be created between the satellite 260 and the UPF 550.

[0054] A packet data unit (PDU) session 540 may be created between the UE 110 and the core network entity 130 (e.g., UPF 550). The PDU session 540 may be used to provide end-to-end user plane connectivity between the terminal 110 and the data network via the UPF 550. The PDU session 540 may support one or more quality of service (QoS) flows. For example, the PDU session 540 may support a first QoS flow 511 and a second QoS flow 512. In the user plane, the radio bearer 520 may be mapped to the QoS flows (e.g., the first QoS flow 511, the second QoS flow 512). According to one embodiment, the satellite 260, as the gNB 120, may perform the mapping between the DRBs and the QoS flows.

[0055] Although not shown in Figure 5, operation and maintenance (O&M) may be used to provide the radio access network via satellite 260. The O&M may provide one or more parameters related to the NTN 500 to the gNB 120 (e.g., satellite 260). For example, operation and maintenance (O&M) 510 may provide at least the following NTN-related parameters to the gNB 120 for operation:

[0056] a) Earth fixed beams: For each beam provided by a particular NTN payload: - Cell identifiers mapped to beams (NG and Uu) - Cell reference location (e.g. cell center and range). b) Quasi Earth fixed beams: For each beam provided by a particular NTN payload: - Cell identifiers (NG and Uu) and time windows mapped to the beam - Cell / beam reference position (e.g. cell center and extent) - Switch-over time window (feeder link, service link) - Identifiers and time windows of all satellites and NTN gateways providing the service. c) Earth Moving Beams: For each beam provided by a particular NTN payload: - Uu cell identifiers mapped to the beam and mapping information of fixed geographical areas reported to NG, information on the movement of the beam's footprint on the Earth - NTN payload elevation - NTN-Gateway / gNB continuous service schedule - Continuous switch-over schedule (feeder link, service link).

[0057] FIG. 6a illustrates an example control plane for a regenerative satellite (eg, satellite 260).

[0058] Referring to Figure 6a, the UE 610 may support protocols for the PHY layer, MAC layer, RLC layer, PDCP layer, and RRC layer. The satellite 620, as a gNB, may support protocols for the PHY layer, MAC layer, RLC layer, PDCP layer, and RRC layer. For the satellite 620, the description of the satellite 260 may be referred to. For the description of the protocols for each layer, the description of Figure 3a may be referred to. The interface between the UE 610 and the satellite 620 may be a Uu interface.

[0059] The satellite 620 can perform NG-RAN protocol functions as a gNB on board or as part of a gNB. The satellite 620 can communicate (e.g., IP communication) with a terrestrial NTN gateway 630 via SRI. The satellite 620 can connect to the 5GC via the NTN gateway 630. Examples of network entities for the 5GC include an AMF 640 (e.g., AMF 235) and an SMF 650. The satellite 620 can support NG-AP, SCTP (stream control transmission protocol), and IP layer protocols for communication with the 5GC. The NG-AP layer can be used between the 5GC entity AMF 640 and the satellite 620 via the NTN gateway over SCTP. NAS signaling between the UE 610 and the AMF 640 can be performed via the satellite 620 and the NTN gateway 630. The NAS signaling can include a NAS-MM (mobility management) interface for the AMF 640. The NAS signaling may include NAS-SM relay and / or NAS-SM (session management) for the SMF 650. The NAS signaling may be transmitted via the NTN gateway 630 between the 5GC entity AMF 640 and the satellite 620 via an NG-AP layer protocol.

[0060] While Figure 6a illustrates an example in which a satellite operates entirely as a gNB, embodiments of the present disclosure are not limited thereto. In a non-limiting example, the satellite may operate as a gNB-DU with functional separation. Thus, the satellite may be configured to support RLC layer, MAC layer, and PHY layer protocols.

[0061] FIG. 6b shows an example of a user plane for a regenerative satellite (eg, satellite 260).

[0062] Referring to Figure 6b, the UE 610 may support protocols for the PHY layer, MAC layer, RLC layer, PDCP layer, and SDAP layer. The satellite 620 is a gNB and may support protocols for the PHY layer, MAC layer, RLC layer, PDCP layer, and SDAP layer. For a description of the protocols for each layer, refer to the description of Figure 3b. The interface between the UE 610 and the satellite 620 may be a Uu interface.

[0063] The satellite 620 is a gNB mounted on board and can execute NG-RAN protocol functions. The satellite 620 can communicate (e.g., IP communication) with a terrestrial NTN gateway 630 via the SRI. The satellite 620 can connect to the 5GC via the NTN gateway 630. The UPF 680 is exemplified as a network entity for the 5GC. The satellite 620 can support protocols for the GTP-U (GPRS (General Packet Radio Service) tunneling protocol - user plane) layer, UDP (user datagram protocol) layer, and IP layer for communication with the 5GC. A PDU session (e.g., PDU session 540 in FIG. 5) between the UE 610 and the UPF 680 can be generated. The SRI protocol stack can be used to transmit the UE user plane between the satellite and the NTN gateway. Signals on the PDU session can be transmitted via a GTP-U tunnel between the UPF 680, which is a 5GC, and the satellite 620 via the NTN gateway 630.

[0064] Although Figure 6b illustrates an example in which a satellite operates entirely as a gNB, embodiments of the present disclosure are not limited thereto. In a non-limiting example, the satellite may operate as a gNB-DU with functional separation. Thus, the satellite may be configured to support RLC layer, MAC layer, and PHY layer protocols.

[0065] FIG. 7a shows an example of a group handover in satellite communications.

[0066] Referring to FIG. 7a, satellites moving on the same orbit 707 can serve a terminal. For example, the satellites can include a first satellite 721 and a second satellite 723. For the first satellite 721 and the second satellite 723, refer to the description of satellite 620. The satellites can move along orbit 707 in a left-to-right direction in FIG. 7a. The terminals (e.g., UE 610-1, UE 610-2, ..., UE 610-n) can be served through a cell provided by the first satellite 721. As the first satellite 721 repeatedly moves through a designated orbit, the terminals (e.g., UE 610-1, UE 610-2, ..., UE 610-n) served by the first satellite 721 inevitably need to handover to a new cell.

[0067] For example, assume that multiple terminals served by fixed terrestrial cells need to move to a new cell at a cell stop time, or that a satellite moves to a point where a gateway needs to be switched. In this case, all terminals are required to connect to the new cell. If the satellite providing the terminal with a serving cell is switched from a first satellite 721 to a second satellite 723, the terminal can change cells (e.g., PCells) without moving. In this case, providing individual handover commands to each UE results in large signaling overhead and is therefore inefficient in terms of resource utilization. Furthermore, from the perspective of system throughput, high signaling overhead may result in providing handover commands too quickly or cause radio link failure (RLF). Therefore, messages and information according to embodiments of the present disclosure may be used in handover commands to reduce signaling overhead between the terminal and the source cell (e.g., the cell of the first satellite 721). According to one embodiment, a time-based conditional handover can be configured to reduce signaling overhead. The network knows the time range in which the terminal should be handed over and can cause the terminal to initiate handover via specific trigger conditions (e.g., time range and RSRP-based events). Furthermore, messages and information according to embodiments of the present disclosure can be used to reduce congestion to the target cell. According to one embodiment, RACH-less handover can be used to reduce congestion in the target cell. According to one embodiment, a random backoff mechanism can be introduced to initiate transmission of a random access preamble to the target cell.

[0068] FIG. 7b illustrates an example of a handover for a non-terrestrial base station (eg, satellite 620).

[0069] Referring to FIG. 7b, handover aspects for the satellite 620 can be performed not only between satellites (e.g., between a first satellite 721 and a second satellite 723) but also between a satellite and a terrestrial base station (e.g., base station 720). For handovers between satellites, the interface between the satellites may be referred to as an inter-satellite link (ISL). For example, if each satellite operates as a gNB, the interface between the satellites may be referred to as an XN interface. Because satellites have geographical characteristics of orbiting in designated orbits, the network can provide more efficient mobility management (e.g., cell selection, handover) to the terminal (e.g., UE 610) based on the satellite's orbit. For handovers between satellites and terrestrial base stations as the satellite moves along its orbit and moves away from a particular area, the terrestrial base station can provide communication services to the area previously served by the satellite instead of the satellite.

[0070] FIG. 8a shows an example of system information for an NTN.

[0071] 8a, in operation 801, the satellite 620 may broadcast system information. The system information may include information about the satellite. The UE 610 may receive the system information. The UE 610 may receive the system information from the satellite 620. According to one embodiment, the system information is a system information block (SIB) 801, which may be a predefined SIB (e.g., SIB19, SIB1, SIB2) or a SIB defined separately for a regenerative satellite (e.g., SIB extend (SIBx)). For example, SIBx may include information such as the following table:

[0072] [Table 3-1] [Table 3-2]

[0073] "ntn-Config" indicates parameters for connecting to a wireless network via NTN access, and can refer to the following table (e.g., [Table 4]). "t-service" can indicate time information regarding when a cell provided via an NTN quasi-Earth fixed system will discontinue service for the area it currently serves. "referenceLocation" indicates the reference location of a serving cell provided via an NTN quasi-Earth fixed system. "distanceThresh" indicates the distance from the reference location of the serving cell and can be used for location-based measurements in the RRC IDLE or RRC INACITVE state. "ntn-NeighCellConfigList" can indicate information regarding neighboring cells for a cell provided via a satellite (e.g., satellite 620).

[0074] [Table 4-1] [Table 4-2]

[0075] "epochTime" indicates the epoch time of the NTN assistance information. When provided explicitly via the SIB or via dedicated signaling, the epoch time indicates the start time of the DL subframe and may indicate the system frame number (SFN) and the subframe number signaled together with the assistance information. As a non-limiting example, for higher granularity, "epochTime" may further include an information element (IE) indicating a symbol in addition to a subframe. The IE may indicate one of 0 to 13, indicating one of 14 symbols.

[0076] 'ntn-UlSyncValidityDuration' is the validity duration of the aiding information (e.g., celestial force information, common TA parameters) set by the network. In other words, this duration represents the maximum time that the aiding information can be applied without acquiring new NTN aiding information. This time period can start from the epoch time. 'cellSpecificKoffset' represents the scheduling offset used for timing relationships changed for NTN. 'kmac' represents the scheduling offset used when the downlink timing and the uplink timing do not match. 'ta-Info' can include information for TA (timing advance). The information for TA can include 'ta-Common', which is a common TA controlled by the network, 'ta-CommonDrift', which represents the drift rate of the common TA, and 'ta-CommonDriftVariant', which indicates the variation of the drift rate. "ntn-PolarizationDL" and "ntn-PolarizationUL" indicate polarization information in DL and UL, respectively. "ephemerisInfo" indicates celestial force information, and can be exemplified by the following table (e.g., [Table 5]). "ta-Report" indicates that TA reporting is activated during RRC connection establishment, RRC connection resume, and RRC connection re-establishment.

[0077] [Table 5-1] [Table 5-2]

[0078] "positionX", "positionY", and "positionZ" respectively indicate the position state vector of the ECEF (earth-centered, earth-fixed) in the xyz coordinate system. The unit is meters, and one step represents 1.3 m (meter). For example, the actual value may be the field value * 1.3. "velocityX", "velocityY", and "velocityZ" respectively indicate the velocity state vector of the ECEF in the xyz coordinate system. One step represents 0.06 m / s (meter / seconds). For example, the actual value may be the field value * 0.06. "semiMajorAxis" is the semi-major axis, "eccentricity" is the bicentricity, "periapsis" is the periapsis, "longitude" is the longitude, "inclination" is the inclination, and "meanAnomaly" indicates the fraction of the elliptical orbital period that has elapsed since an object orbiting at a mean anomaly passed periapsis.

[0079] The parameters transmitted through the system information may include various satellite-related information in addition to the IEs defined in Tables 3 to 5 above.

[0080] 1. Satellite Group and Identification Information The satellite 620 may transmit identification information of a group (hereinafter, a satellite group) including the satellite 620 to the UE 610. According to one embodiment, satellites orbiting the same orbit may be classified into the same satellite group. For example, satellites in the same satellite group may share the same orbit. As an example, satellites in the same satellite group may have the same orbital information (e.g., "Orbital-r19" IE) in the celestial force information. In a non-limiting example, the system information may include orbital information specific to the satellite group rather than orbital information for each satellite. According to another embodiment, satellites using the same NTN gateway (e.g., NTN gateway 630) may be classified into the same group. The NTN gateway may be used at a fixed location on the ground. Therefore, satellites connected to the NTN gateway may be understood to be located within a certain distance from the NTN gateway. Therefore, satellites densely located in a specific area may be commonly connected to the NTN gateway. As satellites operate as unique base stations, they may provide one or more cells. Therefore, satellites may also be required to specify a unique ID in addition to a physical cell ID. For example, a gNB ID may be used to identify the satellite. In another example, a gNB-DU ID can be used to identify the satellite. As another example, a separately defined ID can be used to identify the satellite. The satellite group can be identified via a satellite group ID. For example, a satellite can be identified by the satellite group ID and a satellite ID within the group. In another example, a satellite can be assigned an individual satellite ID separate from the group. The satellite 620 can broadcast information about itself and information about satellites included in the same group as the satellite 620 as system information. The UE 610 can recognize information about surrounding satellites via the identification information of the satellite 620 or the identification information of the satellite group to which the satellite 620 belongs.

[0081] 2. Class Information Referring to Table 5, approximately 26 bits of information are required for each axis (e.g., x-axis, y-axis, z-axis) to indicate the position of celestial force information. As the number of satellites increases, there is a possibility that many other satellites will be placed in Earth orbit in addition to the satellite providing the current serving cell. Therefore, requiring approximately 84 bits per satellite (26 bits per satellite) for an x-y-z coordinate system in three-dimensional space to indicate the position of each satellite may place a burden on satellites configured to perform operations according to a communication protocol. Therefore, to reduce the burden of satellite operation and signal processing, classes can be used instead of specific values. For example, the range of the position state vector "PositionStateVector-r19" is "(-33554432..33554431)", which can be divided into four classes as shown in Table 6 below.

[0082] [Table 6]

[0083] The satellite 620 can be configured to indicate one of the four classes to the UE 610. When the position information of the satellite 620 is specified in four classes as in Table 6, only two bits are sufficient to distinguish between the four classes, so the number of bits required to indicate the position state vector of the satellite 620 on each axis of the three-dimensional coordinate system is reduced from 26 bits to 2 bits (2 2 = 4). In the above example, four classes are used, but more classes can be used. For example, if 64 classes are used, the number of bits required to indicate the position state vector on each axis can be reduced from 26 bits to 6 bits. On the other hand, even if classes are set, it can be understood that the resolution of the value indicating the position is not reduced, but the method of indicating it is simplified. In other words, a satellite operator can set a fixed value for the position within the range of a class.

[0084] Referring to Table 5, approximately 18 bits of information are required for each axis (e.g., x-axis, y-axis, z-axis) to indicate the velocity of celestial force information. As the number of satellites increases, many other satellites are located in Earth orbit in addition to the satellite providing the serving cell for the current UE. Therefore, if approximately 54 bits are required for each satellite in the xyz coordinate system to indicate velocity, it may place a burden on satellites configured to perform operations according to the communication protocol. To reduce the burden on system operation and signal processing, classes can be used instead of specific values. For example, the range of the velocity state vector 'VelocityStateVector-r19' is '(-131072...131071)', which can be divided into four classes as shown in Table 7 below.

[0085] [Table 7]

[0086] The satellite 620 may be configured to indicate one of the four classes to the UE 610. Accordingly, the number of bits required to indicate a velocity state vector on each axis (x-axis, y-axis, z-axis) constituting a three-dimensional coordinate system may be reduced from 18 bits to 2 bits. While the above example illustrates an example in which four classes are used, more classes may be used. For example, if 64 classes are used, the number of bits required to indicate a velocity state vector on each axis may be reduced from 18 bits to 6 bits. However, the class configuration does not reduce the resolution of the value indicating the velocity, but simplifies the method of indicating the velocity. In other words, a satellite operator may set a fixed value for the velocity within the range of the class.

[0087] Referring to [Table 5], when indicating celestial force information, at least 20 bits and up to 33 bits are required to represent each of "semiMajorAxis," "eccentricity," "periapsis," "longitude," "inclination," and "meanAnomaly." As the number of satellites increases, many other satellites are deployed in addition to the satellite that provides the serving cell to the current UE in Earth orbit. In other words, to indicate celestial force information for one satellite, 100 bits or more of information are required. Classes for orbit information can be defined to include more simplified information. For example, orbit classes can be defined as shown in [Table 8] below.

[0088] [Table 8]

[0089] Each orbit class may represent a type of combination of predefined "semiMajorAxis," "eccentricity," "periapsis," "longitude," "inclination," and "meanAnomaly." In the above example, five predefined orbital information items operated by a satellite operator are designated as orbit classes, and a satellite operating as a gNB (e.g., satellite 620) may notify an in-cell terminal (e.g., UE 610) of one of the orbital classes. As a non-limiting example, a group of satellites, i.e., a satellite group, may be defined according to the orbital class. For example, satellites belonging to the same satellite group may have the same orbital class.

[0090] 3. Group handover information As shown in Figure 7a, satellites move along fixed satellite orbits, and therefore handovers of terminals can be expected on the network side. For example, in the case of a satellite located at an altitude of approximately 200 km above the Earth, it moves along its orbit at a ground speed of approximately 7.8 km / s (4.8 mi / s) (28,000 km / h (17,000 mph)). Therefore, it is expected that the current satellite (e.g., first satellite 721) serving a particular region (serving cell) will be changed to another satellite (e.g., second satellite 723). Furthermore, handover procedures for each terminal located in the particular region are expected. Because satellites provide a wider coverage area than general terrestrial base stations, a relatively larger number of handover procedures can be expected than handovers in general base stations. Therefore, in one embodiment of the present invention, in order to reduce excessive signaling and congestion that may occur instantaneously to a UE located within a terrestrial coverage area (serving cell) served by a satellite, a satellite providing the serving cell (e.g., the first satellite 721, the satellite 620) can provide various information to the UE. For example, the various information can be exemplified as shown in Table 9 below.

[0091] [Table 9]

[0092] The system information of FIG. 8a may include at least one of the information in Table 9. The UE groups in Table 9 can be used to identify UEs that will perform a group handover. A UE that identifies itself as belonging to the UE group can prepare for a group handover. For example, the UE can start a timer. According to an embodiment, if the UE does not belong to the UE group, it may ignore the related information. The satellite ID in Table 9 may indicate the ID of the satellite to which the current UE is connected. An operator entity (e.g., AMF 640, satellite 620) that operates the network can reduce the amount of information required for the handover procedure by configuring UE groups and operating timers for each UE group. UEs located in one service area can be divided into groups in time. For example, in a first time period, UEs in a first group can perform a handover, and in a second time period after the first time period, UEs in a second group can perform a handover. The service-related information in Table 9 may be provided for data forwarding (e.g., to prevent interruption of data forwarding that may occur during handover). The handover-related information in Table 9 may include information about a target satellite adjacent to the current source satellite. By notifying the terminal of information about the target satellite in advance, the terminal can perform handover. As a non-limiting example, in this example, the satellite ID is fixed, and only the physical satellite bearing the satellite ID can be changed. Therefore, the terminal can maintain continuous connection via the fixed satellite ID. A satellite that leaves a specific region (e.g., the first satellite 721) changes its satellite ID to a new ID, and a satellite that enters the specific region (e.g., the second satellite 723) can newly use the satellite ID used by the existing satellite.

[0093] [Table 10]

[0094] The system information in FIG. 8a may include at least one of the information in Table 10. The satellite group refers to the satellite group described above. For example, satellites having the same orbit may be defined as one satellite group. As another example, satellites connected to the same NTN gateway may be defined as one satellite group. A serving satellite (e.g., satellite 620) providing a current serving cell to the terminal 610 may provide related satellite information to the terminal 610 in advance while a radio link is connected. This allows the serving satellite (e.g., satellite 620) to provide seamless service to the UE 610 even if the serving satellite (e.g., satellite 620) leaves the current serving cell where the terminal 610 is located by notifying the terminal 610 in advance of information about the satellite (target satellite) that serves the corresponding serving cell.

[0095] The related satellite information in this specification may be determined by at least one of ephemeris data or constellation data of a predetermined satellite in the system. The terminal ID in Table 10 may represent terminal information mapped to a satellite group and may be omitted depending on the situation. The service-related information may be provided for data forwarding (e.g., to prevent interruption of data transmission that may occur during handover). The handover-related information in Table 10 may include information about a target satellite adjacent to the current source satellite. By notifying the information about the target satellite, the terminal can enable handover.

[0096] 4. Coverage Information Although the above example describes an example in which only information related to satellites is provided, neighboring cells may be provided by terrestrial base stations in addition to satellites. Therefore, information related to the coverage serviced by the terrestrial base stations can also be provided to the terminal (e.g., UE 610) by reference. For example, satellite information provided by a non-terrestrial base station (e.g., satellite 620) is as follows:

[0097] [Table 11]

[0098] In Table 11, "coverageID" indicates a coverage ID, "referenceLocation" indicates a reference location of a cell provided via a terrestrial base station, and "distanceThresh" indicates a distance from the reference location of the cell. As a non-limiting example, not only coverage information but also other information related to the geographical location of the terrestrial base station may be included in the system information.

[0099] Just as information about a terrestrial base station is provided via a non-terrestrial base station, information about a non-terrestrial base station may be provided via a terrestrial base station. According to an embodiment, the information provided through Tables 3 to 10 may be provided by a terrestrial base station (e.g., base station 720) in addition to the satellite 620. For example, the terrestrial base station may provide at least one of the pieces of information exemplified in Tables 3 to 10 to the UE 610 as information about neighboring cells. The parameters described in Tables 3 to 11 may be included in existing system information instead of separate system information (e.g., SIBx, SIB19). According to an embodiment, the IEs in Tables 3 to 5 may include scheduling information about other system information and may be included in SIB1, which includes configuration information for the serving cell. According to another embodiment, the IEs in Tables 3 to 5 may be included in SIB2, which includes random access parameters.

[0100] Figure 8b shows an example of an RRC (radio resource control) message for NTN. Figure 8a shows system information for transmitting cell-specific parameters to terminals in a cell. Figure 8b shows an RRC message 851 defined for transmitting UE-specific parameters to a specific UE in a cell.

[0101] 8b, the satellite 620 may transmit an RRC message 851 to the UE 610. The RRC message 851 may include information about the satellite. The UE 610 may receive the RRC message 851. According to one embodiment, the RRC message 851 may be an RRC setup message. According to one embodiment, the RRC message 851 may be an RRC resume message. According to one embodiment, the RRC message may be an RRC reestablishment message. According to one embodiment, the RRC message 851 may be an RRC reconfiguration message.

[0102] The RRC message 851 may include at least one of the information mentioned in FIG. 8a. According to one embodiment, the RRC message 851 may include at least one of 'ntn-Config', 't-service', 'referenceLocation', 'distanceThresh', or 'ntn-NeighCellConfigList'. According to one embodiment, the RRC message 851 may include at least one of 'epochTime', 'ntn-UlSyncValidityDuration', 'cellSpecificKoffset', 'kmac', 'ta-Info', 'ntn-PolarizationDL', 'ntn-PolarizationUL', 'ta-Report', and 'ephemerisInfo'. According to one embodiment, the RRC message 851 may include at least one of 'PositionVelocity' and / or 'Orbital'.

[0103] According to one embodiment, the RRC message 851 may include identification information related to a satellite group. The satellite 620 may transmit the RRC message 851 to the UE 610, including identification information of the group (hereinafter, the satellite group) that includes the satellite 620. According to one embodiment, satellites orbiting the same orbit may be classified into the same satellite group. For example, satellites in the same satellite group may share the same orbit. As an example, satellites in the same satellite group may have the same orbital information (e.g., the "Orbital-r19" IE) in the celestial force information. In a non-limiting example, the RRC message 851 may include orbital information specific to a satellite group, instead of including orbital information for each satellite.

[0104] According to another embodiment, satellites using the same NTN gateway (e.g., NTN gateway 630) may be grouped together. The NTN gateway may be located at a fixed position on the ground. Therefore, satellites connected to an NTN gateway may be understood to be located within a certain distance from the NTN gateway. Therefore, satellites densely packed in a particular area may be commonly connected to the NTN gateway. As a satellite operates as its own base station, it may provide one or more cells. Therefore, a satellite may be required to specify a unique ID in addition to a physical cell ID. For example, a gNB ID may be used to identify the satellite.

[0105] In another example, a gNB-DU ID can be used to identify the satellite. As yet another example, a separately defined ID can be used to identify the satellite. The satellite group can be identified via a satellite group ID. For example, a satellite can be identified by the satellite group ID and a satellite ID within the group. In another example, a satellite can be assigned an individual satellite ID separate from the group. The satellite 620 can transmit the RRC message including information about the satellite 620 or information about satellites included in the same group as the satellite 620. The UE 610 can recognize information about neighboring satellites via the identification information of the satellite 620 or the identification information of the satellite group to which the satellite 620 belongs.

[0106] According to one embodiment, the RRC message 851 may include class information. As illustrated by Tables 6 to 8, the class information may be used to represent the position state vector, the velocity state vector, and / or the celestial force information in a more simplified manner. For example, the satellite 620 may transmit an RRC message 851 to the UE 610 including information indicating a position class, as shown in Table 6. For example, the satellite 620 may transmit an RRC message 851 to the UE 610 including information indicating a velocity class, as shown in Table 7. For example, the satellite 620 may transmit an RRC message 851 to the UE 610 including information indicating an orbit class, as shown in Table 8.

[0107] According to one embodiment, the RRC message 851 may include information related to group handover. For example, the RRC message 851 may include at least one of the items shown in Table 9. Furthermore, for example, the RRC message 851 may include at least one of the items shown in Table 10.

[0108] According to one embodiment, the RRC message 851 may include coverage information. The coverage information may include information about the coverage of a terrestrial base station adjacent to a satellite that provides a serving cell. For example, the RRC message 851 may include information indicating a reference position of a cell provided via a terrestrial base station and / or information indicating a distance from the reference position of the cell.

[0109] 8b illustrates an example of an RRC message 851 provided by the satellite 620 to the terminal 610, but the embodiments of the present disclosure are not limited thereto. Providing the above information from the terminal 610 to the satellite 620 may also be understood as an embodiment of the present disclosure.

[0110] 8a and 8b illustrate examples of information that a satellite 620 can provide to a terminal 610. The information can be used to streamline handover procedures via satellites that repeatedly move in a specified orbit. The satellite of the target cell to be handovered can be predicted according to the movement of the satellite. The time of handover can be predicted according to the position and velocity of the satellite. Based on these factors, the terminal can prepare for handover in advance, and the handover procedure can be simplified within the NTN. Meanwhile, as the roles of satellites operating as base stations become more diverse, 3GPP messages can be used for each interface depending on the satellite deployment scenario, and the parameters / information described in FIGS. 8a and 8b can be included in existing 3GPP messages.

[0111] 9a-9b show an example of signaling over the F1 interface in an NTN.

[0112] 9a, in operation 901, the gNB-DU 910 may transmit a first message to the gNB-CU 920 via the F1 interface. The gNB-CU 920 may receive the first message from the gNB-DU 910.

[0113] In operation 903, the gNB-CU 920 may transmit a second message via the F1 interface to the gNB-DU 910. The gNB-DU 910 may receive the second message from the gNB-CU 920.

[0114] According to one embodiment, the first message may be an F1 setup request message, and the second message may be an F1 setup response message. The gNB-DU 910 may transmit the F1 setup request message to the gNB-CU 920 via the F1 interface. The gNB-CU 920 may transmit the F1 setup response message to the gNB-DU 910 via the F1 interface. The F1 setup request message may include at least one of the information in Tables 3 to 11. The F1 setup response message may include at least one of the information in Tables 3 to 11. For example, the first message may include the following IEs, as exemplified in Tables 12 to 14.

[0115] [Table 12-1] [Table 12-2] [Table 12-3]

[0116] [Table 13-1] [Table 13-2]

[0117] [Table 14]

[0118] According to one embodiment, the first message may be a GNB-DU Configuration Update message, and the second message may be a gNB-DU Configuration Update Confirm message. The gNB-DU 910 may send the GNB-DU Configuration Update message to the gNB-CU 920 via the F1 interface. The gNB-CU 920 may send the GNB-DU Configuration Update Confirm message to the gNB-DU 910 via the F1 interface. The GNB-DU Configuration Update message may include at least one of the information in Tables 3 to 11. The GNB-DU Configuration Update Confirm message may include at least one of the information in Tables 3 to 11. For example, the first message may include the following IEs, as exemplified in Table 15.

[0119] [Table 15-1] [Table 15-2] [Table 15-3] [Table 15-4] [Table 15-5]

[0120] For the IEs according to [Table 15] above, reference can be made to [Table 13] for "NTN-Config" and [Table 14] for "EphemerisInfo".

[0121] According to one embodiment, the first message may be a GNB-DU status indication message. If the first message is a GNB-DU status indication message, transmission of the second message may be omitted. The GNB-DU status indication message may include at least one of the information items in Tables 3 to 11. For example, the first message may include the following IEs shown in Table 16:

[0122] [Table 16-1] [Table 16-2]

[0123] For the IEs according to [Table 16] above, reference can be made to [Table 13] for "NTN-Config" and [Table 14] for "EphemerisInfo".

[0124] 9b, in operation 951, the gNB-CU 920 may transmit a first message to the gNB-DU 910 via the F1 interface. The gNB-DU 910 may receive the first message from the gNB-CU 920.

[0125] In operation 953, the gNB-DU 910 may transmit a second message via the F1 interface to the gNB-CU 920. The gNB-CU 920 may receive the second message from the gNB-DU 910.

[0126] According to one embodiment, the first message may be a GNB-CU Configuration Update message, and the second message may be a gNB-CU Configuration Update Confirm message. The gNB-CU 920 may send the gNB-CU Configuration Update message to the gNB-DU 910 via the F1 interface. The gNB-DU 910 may send the GNB-CU Configuration Update Confirm message to the gNB-CU 920 via the F1 interface. The GNB-CU Configuration Update message may include at least one of the information in Tables 3 to 11. The GNB-CU Configuration Update Confirm message may include at least one of the information in Tables 3 to 11. For example, the first message may include the following IEs shown in Table 17:

[0127] [Table 17-1] [Table 17-2] [Table 17-3] [Table 17-4] [Table 17-5] [Table 17-6] [Table 17-7] [Table 17-8] [Table 17-9] [Table 17-10]

[0128] For the IEs according to [Table 17] above, see Table 13 for "NTN-Config" and Table 14 for "EphemerisInfo".

[0129] According to one embodiment, the first message may be a GNB-DU resource adjustment request message, and the second message may be a gNB-DU resource adjustment response message. The gNB-CU 920 may transmit the GNB-DU resource adjustment request message to the gNB-DU 910 via the F1 interface. The gNB-DU 910 may transmit the GNB-DU resource adjustment response message to the gNB-CU 920 via the F1 interface. The GNB-DU resource adjustment request message may include at least one of the information in Tables 3 to 11. The GNB-DU resource adjustment response message may include at least one of the information in Tables 3 to 11. For example, the first message may include the following IEs shown in Table 18.

[0130] [Table 18-1] [Table 18-2] [Table 18-3]

[0131] For the IEs according to Table 18 above, see [Table 13] for "NTN-Config" and [Table 14] for "EphemerisInfo".

[0132] FIG. 10 illustrates an example of signaling over the XN interface in an NTN. Although FIG. 10 illustrates signaling between a non-terrestrial base station and a terrestrial base station, the embodiments of the present disclosure are not limited thereto. The messages over the XN interface illustrated in FIG. 10 may be transmitted not only between a non-terrestrial base station and a terrestrial base station, but also between a non-terrestrial base station and a non-terrestrial base station, or between a terrestrial base station and a terrestrial base station. Furthermore, although the messages illustrated in FIG. 10 are described as being transmitted first from a non-terrestrial base station to a terrestrial base station, this is not limiting. For example, a request message may be transmitted first from a terrestrial base station to a non-terrestrial base station, and then a response message may be transmitted from the non-terrestrial base station to the terrestrial base station. For example, the non-terrestrial base station may include a satellite 620. For example, the terrestrial base station may include a base station 1020.

[0133] 10 , in operation 1001, a satellite 620 may transmit a first message to a base station 1020 via an XN interface. The base station 1020 may receive the first message from the satellite 620.

[0134] In operation 1003, the base station 1020 may transmit a second message over the XN interface to the satellite 620. The satellite 620 may receive the second message from the base station 1020.

[0135] According to one embodiment, the first message may be a handover request message, and the second message may be a handover response message. The satellite 620 may transmit the handover request message to the base station 1020 via the XN interface. The base station 1020 may transmit the handover response message to the satellite 620 via the XN interface. The handover request message may include at least one of the information in Tables 3 to 11. The handover response message may include at least one of the information in Tables 3 to 11. For example, the first message may include the following IEs shown in Table 19.

[0136] [Table 19-1] [Table 19-2] [Table 19-3] [Table 19-4] [Table 19-5] [Table 19-6] [Table 19-7] [Table 19-8]

[0137] For the IEs according to [Table 19] above, reference can be made to the 3GPP TS 38.423 standard, [Table 13] for "NTN-Config" and [Table 14] for "EphemerisInfo".

[0138] According to one embodiment, the first message may be a cell activation request message, and the second message may be a cell activation response message. The satellite 620 may transmit the cell activation request message to the base station 1020 via the XN interface. The base station 1020 may transmit the cell activation response message to the satellite 620 via the XN interface. The cell activation request message may include at least one of the information in Tables 3 to 11. The cell activation response message may include at least one of the information in Tables 3 to 11. For example, the first message may include the following IEs shown in Table 20.

[0139] [Table 20-1] [Table 20-2] [Table 20-3]

[0140] For the IEs according to [Table 20] above, reference can be made to the 3GPP TS 38.423 standard, [Table 13] for "NTN-Config" and [Table 14] for "EphemerisInfo".

[0141] According to one embodiment, the first message may be an XN setup request message, and the second message may be an XN setup response message. The satellite 620 may transmit the XN setup request message to the base station 1020 via the XN interface. The base station 1020 may transmit the XN setup response message to the satellite 620 via the XN interface. The XN setup request message may include at least one of the information in Tables 3 to 11. The XN setup response message may include at least one of the information in Tables 3 to 11. For example, the first message may include the following IEs shown in Table 21.

[0142] [Table 21-1] [Table 21-2] [Table 21-3] [Table 21-4] [Table 21-5]

[0143] For the IEs according to [Table 21] above, reference can be made to the 3GPP TS 38.423 standard, [Table 13] for "NTN-Config" and [Table 14] for "EphemerisInfo".

[0144] According to one embodiment, the first message may be an NG-RAN node configuration update message, and the second message may be an NG-RAN node configuration update confirm message. The satellite 620 may transmit the NG-RAN node configuration update message to the base station 1020 via the XN interface. The base station 1020 may transmit the NG-RAN node configuration update confirm message to the satellite 620 via the XN interface. The NG-RAN node configuration update message may include at least one of the information in Tables 3 to 11. The NG-RAN node configuration update confirm message may include at least one of the information in Tables 3 to 11. For example, the first message may include the following IEs shown in Table 22.

[0145] [Table 22-1] [Table 22-2] [Table 22-3] [Table 22-4] [Table 22-5] [Table 22-6] [Table 22-7] [Table 22-8]

[0146] For the IEs according to [Table 22] above, reference can be made to the 3GPP TS 38.423 standard, [Table 13] for "NTN-Config" and [Table 14] for "EphemerisInfo".

[0147] According to one embodiment, the first message may be an S-node addition request message, and the second message may be an S-node addition response message. The satellite 620 may transmit the S-node addition request message to the base station 1020 via the XN interface. The base station 1020 may transmit the S-node addition response message to the satellite 620 via the XN interface. The S-node addition request message may include at least one of the information in Tables 3 to 11. The S-node addition response message may include at least one of the information in Tables 3 to 11. For example, the first message may include the following IEs shown in Table 23.

[0148] [Table 23-1] [Table 23-2] [Table 23-3] [Table 23-4] [Table 23-5] [Table 23-6] [Table 23-7] [Table 23-8] [Table 23-9]

[0149] For the IEs according to [Table 23] above, reference can be made to the 3GPP TS 38.423 standard, [Table 13] for "NTN-Config" and [Table 14] for "EphemerisInfo".

[0150] According to one embodiment, the first message may be an S-node modification request message, and the second message may be an S-node modification response message. The satellite 620 may transmit the S-node modification request message to the base station 1020 via the XN interface. The base station 1020 may transmit the S-node modification response message to the satellite 620 via the XN interface. The S-node modification request message may include at least one of the information in Tables 3 to 11. The S-node modification response message may include at least one of the information in Tables 3 to 11. For example, the first message may include the following IEs shown in Table 24.

[0151] [Table 24-1] [Table 24-2] [Table 24-3] [Table 24-4] [Table 24-5] [Table 24-6] [Table 24-7] [Table 24-8] [Table 24-9] [Table 24-10] [Table 24-11] [Table 24-12]

[0152] For the IEs according to [Table 24] above, reference can be made to the 3GPP TS 38.423 standard, "Table 13" for "NTN-Config" and "Table 14" for "EphemerisInfo".

[0153] According to one embodiment, the first message may be an S-node modification request message, and the second message may be an S-node modification confirmation message. The satellite 620 may transmit the S-node modification request message to the base station 1020 via the XN interface. The base station 1020 may transmit the S-node modification confirmation message to the satellite 620 via the XN interface. The S-node modification request message may include at least one of the information in Tables 3 to 11. The S-node modification confirmation message may include at least one of the information in Tables 3 to 11. For example, the first message may include the following IEs shown in Table 25.

[0154] [Table 25-1] [Table 25-2] [Table 25-3] [Table 25-4] [Table 25-5] [Table 25-6]

[0155] For the IEs according to [Table 25] above, reference can be made to 3GPP TS 38.423 standard, "Table 13" for "NTN-Config" and "Table 14" for "EphemerisInfo".

[0156] 11a to 11b show examples of signaling via the NG interface in an NTN. For the AMF for the NG interface, please refer to the descriptions of AMF 235 and AMF 640.

[0157] 11a, in operation 1101, the satellite 620 may transmit a first message to the AMF 1120 via an NG interface (e.g., an N2 interface). The AMF 1120 may receive the first message from the satellite 620.

[0158] In operation 1103, the AMF 1120 may transmit a second message to the satellite 620 via an NG interface (e.g., an N2 interface). The satellite 620 may receive the second message from the AMF 1120.

[0159] According to one embodiment, the first message may be a handover request message, and the second message may be a handover command message. The satellite 620 may transmit the handover request message to the AMF 1120 via an NG interface (e.g., an N2 interface). The AMF 1120 may transmit a handover command message to the satellite 620 via an NG interface (e.g., an N2 interface). The handover request message may include at least one of the information in Tables 3 to 11. The handover command message may include at least one of the information in Tables 3 to 11. For example, the first message may include the following IEs shown in Table 26:

[0160] [Table 26-1] [Table 26-2] [Table 26-3]

[0161] For the IEs according to [Table 26] above, reference can be made to the 3GPP TS 38.413 standard, [Table 13] for "NTN-Config" and [Table 14] for "EphemerisInfo".

[0162] According to one embodiment, the first message may be a path switch request message, and the second message may be a path switch response message. The satellite 620 may send the path switch request message to the AMF 1120 via an NG interface (e.g., an N2 interface). The AMF 1120 may send the path switch response message to the satellite 620 via an NG interface (e.g., an N2 interface). The path switch request message may include at least one of the information in Tables 3 to 11. The path switch response message may include at least one of the information in Tables 3 to 11. For example, the first message may include the following IEs shown in Table 27.

[0163] [Table 27-1] [Table 27-2] [Table 27-3]

[0164] For the IEs according to [Table 27] above, reference can be made to [Table 13] for "NTN-Config" and [Table 14] for "EphemerisInfo" in the 3GPP TS 38.413 standard.

[0165] 11b, in operation 1151, the AMF 1120 may transmit a first message to the satellite 620 via an NG interface (e.g., an N2 interface). The satellite 620 may receive the first message from the AMF 1120.

[0166] In operation 1153, the satellite 620 may transmit a second message to the AMF 1120 via an NG interface (e.g., an N2 interface). The AMF 1120 may receive the second message from the satellite 620.

[0167] According to one embodiment, the first message may be a handover request message, and the second message may be a handover response message. The AMF 1120 may transmit the handover request message to the satellite 620 via an NG interface (e.g., an N2 interface). The satellite 620 may transmit a handover response message to the AMF 1120 via an NG interface (e.g., an N2 interface). The handover request message may include at least one of the information in Tables 3 to 11. The handover response message may include at least one of the information in Tables 3 to 11. For example, the first message may include the following IEs shown in Table 28.

[0168] [Table 28-1] [Table 28-2] [Table 28-3] [Table 28-4] [Table 28-5] [Table 28-6]

[0169] For the IEs according to [Table 28] above, reference can be made to the 3GPP TS 38.413 standard, [Table 13] for "NTN-Config" and [Table 14] for "EphemerisInfo".

[0170] 11b illustrates an example of a handover request message and a handover response message, but the present disclosure is not limited thereto. In addition to a handover in which a cell is changed, a mobility order message and a mobility response message may be used as messages used to confirm the mobility of a terminal in one embodiment of the present disclosure.

[0171] 12a illustrates an example of a handover procedure using a regenerative satellite, such as satellite 620. The handover procedure may include a non-terrestrial base station to a terrestrial base station handover, a terrestrial base station to a non-terrestrial base station handover, and a non-terrestrial base station to a non-terrestrial base station handover.

[0172] 12a, in operation 1201, the satellite 620 may transmit an RRC configuration message to the UE 610. The RRC configuration message may include measurement configuration information. The RRC configuration message may include, for example, (i) measurement object information, (ii) reporting configuration information, (iii) measurement identity information, (iv) quantity configuration information, and (v) measurement gap information. The measurement object information may indicate objects on which the UE 610 will perform measurements.

[0173] Specifically, the measurement object information may indicate at least one of an intra-cell measurement object, an inter-cell measurement object, and an inter-RAT (radio access technology) measurement object. Some measurement object information may include identification information regarding a cell and / or a satellite served by a satellite. The reporting configuration information may indicate a report type or a reporting condition regarding when the UE 610 reports a measurement result. Specifically, the report type indicates a type of measurement result. The reporting condition may be information regarding an event or period that triggers the UE 610 to report a measurement result. The measurement identifier information may be information regarding a measurement identifier that associates a measurement object with a reporting configuration and indicates which measurement object the UE 610 reports, when, and in what type. The quantitative configuration information may be parameter information for a measurement unit, a reporting unit, and filtering measurement result values. The measurement gap information may be information regarding a measurement gap, which is a period that the UE 610 can use for measurement without considering data transmission with a serving cell.

[0174] In operation 1203, the UE 610 may perform measurements. The UE 610 may perform measurements on each cell of one or more cells. The one or more cells may include a serving cell and at least one neighboring cell. The one or more cells may include a cell provided by a satellite and / or a cell provided by a terrestrial base station. The UE 610 may perform measurements based on the measurement configuration information. For example, the UE 610 may measure cell quality based on a reference signal (e.g., CRS, CSI-RS) and / or a synchronization signal (e.g., SSB) received from a satellite 620. The UE 610 may measure the cell quality of a serving cell provided by the satellite 620. The UE 610 may measure the cell quality of a neighboring cell with respect to the cell of the satellite 620. For example, the cell quality may represent information about a signal associated with a cell. The signal associated with a cell may refer to a signal received via the cell. The cell quality may be information including a parameter associated with the signal. For example, the cell quality may be an indicator indicating the strength of the signal or an indicator indicating the quality of the signal. The parameter related to the signal may be a selected one of the parameters of each of a plurality of signals including the signal, for example, the parameter related to the signal may represent the maximum signal strength value of each of the signal strength values ​​of the plurality of signals.The cell quality may be, for example, at least one of RSRP (reference signal received power), BRSRP (beam reference signal received power), RSRQ (reference signal received quality), RSSI (received signal strength indicator), SINR (signal to interference and noise ratio), CINR (carrier to interference and noise ratio), SNR (signal to noise ratio), EVM (error vector magnitude), BER (bit error rate), and BLER (block error rate). In addition to the above examples, it goes without saying that other terms or metrics representing cell quality having equivalent technical meanings may be used. Hereinafter, in this disclosure, high cell quality means a large signal quality value related to signal size or a small cell quality value related to error rate. Higher cell quality may mean that a seamless wireless communication environment is guaranteed in the cell.

[0175] The UE 610 may generate a measurement report. The measurement report may include measurement results of the UE 610. The measurement results may include cell quality for each cell. The measurement results may include cell identification information and the cell quality of the cell. For example, the UE 610 may include in the measurement report information about neighboring cells that provide higher signal quality than the serving cell and measurement results including the cell quality of the neighboring cells. According to one embodiment, if the cell is served by a satellite, the UE 610 may further include information about the satellite (e.g., satellite ID, satellite group ID, location information, orbit ID) in the measurement report.

[0176] In operation 1205, the UE 610 may transmit a measurement report to the satellite 620. For example, the UE 610 may perform the measurement report periodically. For example, the UE 610 may perform the measurement report based on an event. The UE 610 may perform the measurement report when a trigger condition set in the measurement configuration information is met. As an example, when the channel quality of the serving cell provided by the satellite 620 is lower than the channel quality of a neighboring cell, the UE 610 may transmit a measurement report to the satellite 620.

[0177] In operation 1207, the satellite 620 may identify a target cell. The satellite 620 may identify a target cell for handover based on the measurement report and / or a policy. According to one embodiment, the satellite 620 may identify a target cell indicated through the measurement report. The target cell may be provided by another satellite or a terrestrial base station. While FIG. 12a illustrates the target cell being identified after receiving a measurement report, embodiments of the present disclosure are not limited thereto. Separately from the measurement report, the satellite 620 may identify a predetermined target cell based on a satellite moving along a specified orbit. The predetermined target cell may be provided by a satellite adjacent to the satellite 620. The satellite may be configured to serve an area served by the satellite 620 during a first time interval and then during a second time interval different from the first time interval. The second time interval may partially overlap with the first time interval. The satellite 620 can identify the target cell based on information about the satellite stored in a core network entity (eg, AMF 1120) or a value set in an internal memory.

[0178] In operation 1209, the satellite 620 may transmit a handover command to the UE 610. The satellite 620 may transmit the handover command to the UE 610, the handover command including information for indicating the target cell. For example, the satellite 620 may transmit an RRC reconfiguration message to the UE 610. The RRC reconfiguration message may be used to indicate a handover to a target cell. For example, the RRC reconfiguration message may include a "Reconfiguration with sync" IE. The RRC reconfiguration message may include information about the target cell. According to one embodiment, if the target cell is provided by a satellite, the RRC reconfiguration message may further include information related to a satellite providing the target cell. For example, the information related to the satellite may include NTN-related information (e.g., information in Table 3), NTN configuration information (e.g., NTN-Config IE), and / or celestial force information (e.g., EphemerisInfo IE).

[0179] 12b illustrates an example of cell selection using a regenerative satellite, such as satellite 620. The cell selection may include cell selection and / or cell reselection.

[0180] 12b, in operation 1251, the UE 610 may receive a downlink signal (e.g., CRS, SSB). The UE 610 may perform measurements based on the downlink signal. The UE 610 may perform measurements based on cell-specific downlink signals. The UE 610 may obtain cell quality for each cell. The cells to be measured may include cells served by a satellite and / or cells served by a terrestrial base station.

[0181] In operation 1253, the UE 610 may select a cell. The UE 610 may perform measurements based on the downlink signal. The UE 610 may select a cell based on the measurement results. For example, the UE 610 may camp on a cell when the cell quality of the cell exceeds a threshold. The UE 610 may receive system information (e.g., MIB, SIB1) from the cell. The UE 610 may initiate an attachment procedure to the cell based on the system information.

[0182] In operation 1255, the UE 610 may perform an initial connection procedure. The UE 610 may perform a cell connection procedure to connect to the cell. For example, the UE 610 may perform a RACH procedure (e.g., random access preamble transmission, random access response reception, Msg3 transmission (RRC Setup Request), Msg4 reception (Contention resolution) (RRC Setup)) based on the system information. If the cell to which the UE 610 is to connect is provided by a satellite, the UE 610 may omit at least a part of the RACH procedure.

[0183] The cell selection described with reference to FIGS. 12a and 12b may be determined by taking into consideration the inherent characteristics of a satellite (hereinafter, referred to as satellite characteristics) that is a non-terrestrial base station, in addition to signal quality such as RSRP. The satellite characteristics may include various factors. For example, the satellite characteristics may include at least one of satellite mobility, coverage characteristics that serve a relatively wide geographical area, and predictability of moving in a specified orbit. Satellite mobility or predictability can be quantified by defining satellites that move in the same orbit or serve the same region as one group. Therefore, cell selection may be based on at least one of information about the group to which the satellite belongs (e.g., a specific orbit, a specific NTN gateway), celestial force information about the satellite (e.g., EphemerisInfo IE), and / or information about the distance or communication time (e.g., TA) between the satellite and a terrestrial UE 610, in addition to signal quality such as RSRP. The cell quality used in the trigger conditions for measurement reporting in the standard (e.g., comparison of cell quality with a threshold, comparison of cell quality of the serving cell with cell quality of a neighboring cell) and in the trigger conditions for conditional handover (e.g., comparison of cell quality with a threshold, comparison of cell quality of the serving cell with cell quality of a neighboring cell) can be determined based on at least one of the above factors in addition to the signal quality.

[0184] 13 shows an example of components of a satellite (e.g., satellite 260, satellite 620). As used below, the terms "unit," "device," etc. refer to a unit that processes at least one function or operation, which can be implemented in hardware, software, or a combination of hardware and software.

[0185] 13, the satellite 620 may include a transceiver 1301, a processor 1303, and a memory 1305. The transceiver 1301 performs the function of transmitting and receiving signals via a wireless channel. For example, the transceiver 1301 upconverts a baseband signal to an RF band signal and then transmits the RF band signal via an antenna, and downconverts the RF band signal received via the antenna back to a baseband signal. For example, the transceiver 1301 may include a transmit filter, a receive filter, an amplifier, a mixer, an oscillator, a DAC, an ADC, etc.

[0186] The transceiver 1301 may include multiple transmission and reception paths. Furthermore, the transceiver 1301 may include an antenna unit. The transceiver 1301 may include at least one antenna array consisting of multiple antenna elements. From a hardware perspective, the transceiver 1301 may be configured with digital and analog circuits (e.g., RFIC (radio frequency integrated circuit)). Here, the digital and analog circuits may be implemented in a single package. Furthermore, the transceiver 1301 may include multiple RF chains. The transceiver 1301 may perform beamforming. The transceiver 1301 may apply beamforming weights to signals to be transmitted or received in order to impart directionality to the signals according to settings of the processor 1303. According to one embodiment, the transceiver 1301 may include an RF (radio frequency) block (or RF unit).

[0187] The transceiver 1301 can transmit and receive signals over a radio access network. For example, the transceiver 1301 can transmit downlink signals. The downlink signals can include synchronization signals (SS), reference signals (RS) (e.g., cell-specific reference signals (CRS), demodulation-RS), system information (e.g., MIB, SIB, remaining system information (RMSI), other system information (OSI)), configuration messages, control information, downlink data, etc. Additionally, for example, the transceiver 1301 can receive uplink signals. The uplink signals may include random access related signals (e.g., a random access preamble (RAP) (or Msg1 (message 1)), Msg3 (message 3)), reference signals (e.g., a sounding reference signal (SRS), DM-RS), or power headroom reports (PHRs). Although only transceiver 1301 is shown in FIG. 13, according to other embodiments, satellite 620 may include two or more RF transceivers.

[0188] The processor 1303 controls the overall operation of the satellite 620. The processor 1303 may be referred to as a control unit. For example, the processor 1303 transmits and receives signals via the transceiver 1301. The processor 1303 also writes and reads data to and from the memory 1305. The processor 1303 may execute protocol stack functions required by communication standards. While only the processor 1303 is shown in FIG. 13, in other embodiments, the satellite 620 may include two or more processors. The processor 1303 may be an instruction set or code stored in the memory 1305, instructions / code at least temporarily residing in the processor 1303, a memory space storing instructions / code, or part of a circuit constituting the processor 1303. The processor 1303 may further include various modules for performing communication. The processor 1303 may control the satellite 620 to perform operations according to the embodiments.

[0189] Memory 1305 stores data such as basic programs, application programs, and configuration information for the operation of satellite 620. Memory 1305 may be referred to as a storage unit. Memory 1305 may be configured as volatile memory, non-volatile memory, or a combination of volatile and non-volatile memory. Memory 1305 provides the stored data in response to requests from processor 1303. According to one embodiment, memory 1305 may include memory for conditions, instructions, or settings related to SRS transmission schemes.

[0190] 14 illustrates an example of components of a terminal (e.g., a UE 610). The terminal illustrates the UE 610. The UE 610 can perform connection to a gNB (e.g., the gNB 120) that provides NR access via an NTN.

[0191] 14, the UE 610 may include at least one processor 1401, at least one memory 1403, and at least one transceiver 1405. Hereinafter, components will be described in the singular, but implementation of multiple components or sub-components is not excluded.

[0192] The processor 1401 controls the overall operation of the UE 610. For example, the processor 1401 writes and reads data to the memory 1403. For example, the processor 1401 transmits and receives signals via the transceiver 1405. Although FIG. 14 shows one processor, embodiments of the present disclosure are not limited thereto. The UE 610 may include at least one processor to execute embodiments of the present disclosure. The processor 1401 may be referred to as a control unit or control means. According to embodiments, the processor 1401 can control the UE 610 to execute at least one operation or method according to embodiments of the present disclosure.

[0193] The memory 1403 can store data such as basic programs, application programs, and configuration information for the operation of the UE 610. The memory 1403 can store various data used by at least one component (e.g., the transceiver 1405, the processor 1401). The data can include, for example, software and input or output data for associated instructions. The memory 1403 can be configured as a volatile memory, a nonvolatile memory, or a combination of volatile and nonvolatile memory. The memory 1403 can provide the stored data according to a request from the processor 1401.

[0194] The transceiver 1405 performs functions to transmit and receive signals over a wireless channel. For example, the transceiver 1405 performs functions to convert between baseband signals and bit strings in accordance with the system's physical layer standard. For example, when transmitting data, the transceiver 1405 generates complex symbols by encoding and modulating a transmission bit string. When receiving data, the transceiver 1405 demodulates and decodes the baseband signal to restore the received bit string. The transceiver 1405 also upconverts the baseband signal to an RF (radio frequency) band signal and transmits it via an antenna, and downconverts the RF band signal received via the antenna back to a baseband signal.

[0195] For this purpose, the transceiver 1405 may include a transmit filter, a receive filter, an amplifier, a mixer, an oscillator, a digital-to-analog converter (DAC), an analog-to-digital converter (ADC), etc. Furthermore, the transceiver 1405 may include multiple transmit and receive paths. Furthermore, the transceiver 1405 may include at least one antenna array consisting of multiple antenna elements. In terms of hardware, the transceiver 1405 may be composed of a digital unit and an analog unit, and the analog unit may be composed of multiple sub-units depending on operating power, operating frequency, etc.

[0196] The transceiver 1405 transmits and receives signals as described above. Therefore, the transceiver 1405 may be referred to as a "transmitter," a "receiver," or a "transmitter / receiver." In the following description, transmission and reception via a wireless channel, a backhaul network, an optical cable, Ethernet, or other wired path are used to mean that the transceiver 1405 performs the processing described above. According to one embodiment, the transceiver 1405 can provide an interface for communicating with other nodes in the network. That is, the transceiver 1405 can convert bit strings to be transmitted from the UE 610 to other nodes, such as other access nodes, other base stations, upper nodes, and core networks, into physical signals, and can convert physical signals received from other nodes into bit strings.

[0197] In describing the embodiments of the present disclosure, terms and messages defined by 3GPP are used to describe messages between a satellite (e.g., satellite 620) and a terminal (e.g., UE 610). However, the embodiments of the present disclosure are not limited thereto. It goes without saying that terms and messages having equivalent technical meanings to the above terms and messages can be used interchangeably. Furthermore, not only the gNB, gNB-CU, and gNB-DU, but also the gNB-CU-CP (control plane) (e.g., the C-plane in FIG. 3a) and the gNB-CU-UP (user plane) (e.g., the U-plane in FIG. 3b) can be used as satellites. Furthermore, not only a satellite can be used as a base station (e.g., gNB) or a part of a base station (e.g., DU), but also a core network entity (e.g., AMF 235) connected to a base station can be realized as a satellite. For example, communication between a satellite operating as the AMF 235 and the satellite 620 can be defined. For example, a logical node including the AMF 235 and the gNB 120 can be implemented in one satellite. Through network virtualization, implemented in software, separate logical nodes can be placed within a single piece of hardware: the satellite.

[0198] In an embodiment, a satellite device for providing non-terrestrial network (NTN) access is provided. The device may include at least one processor and at least one transceiver. The at least one processor may be configured to transmit, via the at least one transceiver, a message including handover-related information to a terminal on a cell provided by the satellite. The handover-related information may include information regarding a group to which the satellite belongs, information regarding a target satellite of a target cell of handover for the terminal, information regarding a terminal group to which the terminal belongs, information regarding a condition for conditional handover of the terminal, and information regarding at least one of a position, a velocity, or an orbit of the target satellite.

[0199] According to one embodiment, the message may include at least one of position class information for indicating a position of the satellite or the target satellite, velocity class information for indicating a velocity of the satellite or the target satellite, or orbit class information for indicating an orbit of the satellite or the target satellite.

[0200] According to one embodiment, the device may be configured to receive a handover request message from an access and mobility management function (AMF) via the at least one transceiver, the handover request message including at least one of a satellite ID for the target satellite, a satellite group ID of a satellite group to which the target satellite belongs, orbital information of the target satellite, position information of the target satellite, velocity information of the target satellite, timing advance (TA) information of the target satellite, valid time information of the target satellite, polarization information of the target satellite, or scheduling offset information of the target satellite.

[0201] According to one embodiment, the message may include an event type for the conditional handover and at least one parameter for the event type. The message may include validity time information of a terminal group to which the terminal belongs. The validity time information may be used by terminals in the terminal group to indicate a time interval for the conditional handover.

[0202] According to one embodiment, the at least one processor may be configured to receive a handover command message from an access and mobility management function (AMF) via the at least one transceiver, the handover command message including at least one of a satellite ID for the target satellite, a satellite group ID of a satellite group to which the target satellite belongs, orbital information of the target satellite, position information of the target satellite, velocity information of the target satellite, timing advance (TA) information of the target satellite, valid time information of the target satellite, polarization information of the target satellite, or scheduling offset information of the target satellite.

[0203] According to one embodiment, the at least one processor may be configured to send a handover required message to an access and mobility management function (AMF) via the at least one transceiver, wherein the handover required message may include at least one of a satellite ID for the target satellite, a satellite group ID of a satellite group to which the target satellite belongs, orbital information of the target satellite, position information of the target satellite, velocity information of the target satellite, timing advance (TA) information of the target satellite, valid time information of the target satellite, polarization information of the target satellite, or scheduling offset information of the target satellite.

[0204] According to one embodiment, the at least one processor may be configured to determine a handover of the target satellite to a target cell, transmit a handover command message to the target satellite via the at least one transceiver, and receive a handover response message from the target satellite via the at least one transceiver.

[0205] According to one embodiment, the at least one processor may be configured to transmit a message including measurement configuration information to the terminal via the at least one transceiver, and to receive a measurement report message from the terminal via the at least one transceiver in accordance with the measurement configuration information. The measurement configuration information may include information related to measurements of each of one or more cells. The measurement report message may include a cell quality of a cell provided by a satellite. The cell quality may be determined based on at least one of signal quality, an orbit of the satellite, a satellite group to which the satellite belongs, a distance between the satellite and the terminal, or timing advance information for the satellite.

[0206] According to one embodiment, the at least one processor may be configured to transmit a gNB-DU (distributed unit) configuration update message to a gNB (next generation node base station)-CU (central unit) via the at least one transceiver over an F1 interface, and to receive a gNB-DU configuration update confirm message from the gNB-CU over the F1 interface via the at least one transceiver. The gNB-DU configuration update message may include at least one of information about one or more cells provided by the satellite and information about the satellite's orbit, information about a satellite group to which the satellite belongs, information about the satellite's speed, information about the satellite's service time, or information about the satellite's capabilities. The satellite may support a physical (PHY) layer protocol, a medium access control (MAC) layer protocol, and a radio link control (RLC) layer protocol, and the gNB-CU may support a radio resource control (RRC) layer protocol and a packet data convergence protocol (PDCP) layer protocol.

[0207] According to one embodiment, the at least one processor may be configured to broadcast system information over cells served by the satellites via the at least one transceiver, the system information including at least one of information about a satellite group to which the satellite belongs, information about the orbit of the satellite group, information about a cell of each satellite belonging to the satellite group, or information about an NTN gateway associated with the satellite group.

[0208] In an embodiment, a method performed by a satellite for providing NTN access is provided. The method can include an operation of transmitting a message including handover-related information to a terminal on a cell served by the satellite. The handover-related information can include information regarding a group to which the satellite belongs, information regarding a target satellite of a target cell of handover for the terminal, information regarding a terminal group to which the terminal belongs, information regarding a condition for conditional handover of the terminal, and information regarding at least one of a position, a velocity, or an orbit of the target satellite.

[0209] According to one embodiment, the message may include at least one of position class information for indicating a position of the satellite or the target satellite, velocity class information for indicating a velocity of the satellite or the target satellite, or orbit class information for indicating an orbit of the satellite or the target satellite.

[0210] According to one embodiment, the method may include receiving a handover request message from an access and mobility management function (AMF), wherein the handover request message may include at least one of a satellite ID for the target satellite, a satellite group ID of a satellite group to which the target satellite belongs, orbital information of the target satellite, position information of the target satellite, velocity information of the target satellite, timing advance (TA) information of the target satellite, valid time information of the target satellite, polarization information of the target satellite, or scheduling offset information of the target satellite.

[0211] According to one embodiment, the message may include an event type for the conditional handover and at least one parameter for the event type. The message may include validity time information of a terminal group to which the terminal belongs. The validity time information may be used by terminals in the terminal group to indicate a time interval for the conditional handover.

[0212] According to one embodiment, the method may include receiving a handover command message from an access and mobility management function (AMF), wherein the handover command message may include at least one of a satellite ID for the target satellite, a satellite group ID of a satellite group to which the target satellite belongs, orbital information of the target satellite, position information of the target satellite, velocity information of the target satellite, timing advance (TA) information of the target satellite, valid time information of the target satellite, polarization information of the target satellite, or scheduling offset information of the target satellite.

[0213] According to one embodiment, the method may include transmitting a handover required message to an access and mobility management function (AMF), wherein the handover required message may include at least one of a satellite ID for the target satellite, a satellite group ID of a satellite group to which the target satellite belongs, orbital information of the target satellite, position information of the target satellite, velocity information of the target satellite, timing advance (TA) information of the target satellite, valid time information of the target satellite, polarization information of the target satellite, or scheduling offset information of the target satellite.

[0214] According to one embodiment, the method may include operations of determining a handover of the target satellite to the target cell, sending a handover command message to the target satellite, and receiving a handover response message from the target satellite.

[0215] According to one embodiment, the method may include transmitting a message including measurement configuration information to the terminal, and receiving a measurement report message from the terminal according to the measurement configuration information. The measurement configuration information may include information related to measurements of each of one or more cells. The measurement report message may include cell quality of a cell provided by a satellite. The cell quality may be determined based on at least one of signal quality, an orbit of the satellite, a satellite group to which the satellite belongs, a distance between the satellite and the terminal, or timing advance (TA) information related to the satellite.

[0216] According to one embodiment, the method may include transmitting a gNB-DU (distributed unit) configuration update message to a gNB (next generation node base station)-CU (central unit) via an F1 interface, and receiving a gNB-DU configuration update confirm message from the gNB-CU via the F1 interface. The gNB-DU configuration update message may include at least one of information about one or more cells provided by the satellite and information about the satellite's orbit, information about a satellite group to which the satellite belongs, information about the satellite's speed, information about the satellite's service time, or information about the satellite's capabilities. The satellite may support a physical (PHY) layer protocol, a medium access control (MAC) layer protocol, and a radio link control (RLC) layer protocol, and the gNB-CU may support a radio resource control (RRC) layer protocol and a packet data convergence protocol (PDCP) layer protocol.

[0217] According to one embodiment, the system may include broadcasting system information on a cell served by the satellite, the system information including at least one of information about a satellite group to which the satellite belongs, information about the orbit of the satellite group, information about a cell of each satellite belonging to the satellite group, or information about an NTN gateway associated with the satellite group.

[0218] In an embodiment, a non-transitory recording medium is provided. The non-transitory recording medium may include a memory that stores instructions that, when executed by at least one processor, cause a satellite for providing NTN access to transmit a message including handover-related information to a terminal on a cell served by the satellite, the handover-related information including information on a group to which the satellite belongs, information on a target satellite of a target cell of handover for the terminal, information on a terminal group to which the terminal belongs, information on a conditional handover condition for the terminal, and information on at least one of a position, a velocity, or an orbit of the target satellite.

[0219] The methods according to the embodiments claimed or described in the specification of the present disclosure can be implemented in hardware, software, or a combination of hardware and software.

[0220] When implemented in software, a computer-readable storage medium storing one or more programs (software modules) can be provided. The one or more programs stored on the computer-readable storage medium are configured for execution by one or more processors in an electronic device. The one or more programs include instructions that cause the electronic device to perform a method according to an embodiment described in the claims or specification of the present disclosure.

[0221] Such programs (software modules, software) can be stored in random access memory, non-volatile memory including flash memory, read only memory (ROM), electrically erasable programmable read only memory (EEPROM), magnetic disc storage device, compact disc-ROM (CD-ROM), digital versatile disc (DVD) or other form of optical storage device, magnetic cassette, or in memory consisting of some or all of these. Also, each component memory may be included in plural.

[0222] In the specific embodiments of the present disclosure described above, elements included in the disclosure are expressed in singular or plural form according to the specific embodiments presented. However, the expressions singular or plural are selected to suit the presented circumstances for the convenience of explanation, and the present disclosure is not limited to singular or plural elements, and elements expressed in plural form may be composed of singular elements, or elements expressed in singular form may be composed of plural elements.

[0223] In the detailed description of the present disclosure, specific embodiments have been described, but it goes without saying that various modifications are possible without departing from the scope of the present disclosure.

Claims

1. A satellite device for providing non-terrestrial network (NTN) access, comprising: At least one processor; and at least one transceiver; The at least one processor configured to transmit, via said at least one transceiver, a message comprising handover related information to a terminal in a cell served by said satellite; The handover-related information includes at least one of information about a group to which the satellite belongs, information about a target satellite of a target cell of handover for the terminal, information about a terminal group to which the terminal belongs, information related to conditions of a conditional handover of the terminal, and information about at least one of a position, a velocity, or an orbit of the target satellite.

2. 2. The apparatus of claim 1, wherein the message includes at least one of position class information for indicating a position of the satellite or the target satellite, velocity class information for indicating a velocity of the satellite or the target satellite, or orbit class information for indicating an orbit of the satellite or the target satellite.

3. The at least one processor is configured to receive a handover request message from an access and mobility management function (AMF) via the at least one transceiver; 2. The apparatus of claim 1, wherein the handover request message includes at least one of a satellite ID for the target satellite, a satellite group ID of a satellite group to which the target satellite belongs, orbital information of the target satellite, position information of the target satellite, velocity information of the target satellite, timing advance information of the target satellite, effective time information of the target satellite, polarization information of the target satellite, or scheduling offset information of the target satellite.

4. the message includes an event type for the conditional handover and at least one parameter for the event type; The message includes validity time information of the terminal group to which the terminal belongs, The apparatus according to claim 1 , wherein the validity time information is used by terminals in the terminal group to indicate a time interval for the conditional handover.

5. The at least one processor configured to receive a handover command message from an access and mobility management function (AMF) via the at least one transceiver; 2. The apparatus of claim 1, wherein the handover command message includes at least one of a satellite ID for the target satellite, a satellite group ID of a satellite group to which the target satellite belongs, orbital information of the target satellite, position information of the target satellite, velocity information of the target satellite, timing advance information of the target satellite, effective time information of the target satellite, polarization information of the target satellite, or scheduling offset information of the target satellite.

6. The at least one processor configured to send a handover required message to an access and mobility management function (AMF) via the at least one transceiver; 2. The apparatus of claim 1, wherein the handover request message includes at least one of a satellite ID for the target satellite, a satellite group ID of a satellite group to which the target satellite belongs, orbital information of the target satellite, position information of the target satellite, velocity information of the target satellite, timing advance information of the target satellite, effective time information of the target satellite, polarization information of the target satellite, or scheduling offset information of the target satellite.

7. The at least one processor determining a handover of the target satellite to the target cell; transmitting a handover command message to the target satellite via the at least one transceiver; The apparatus of claim 1 , configured to receive a handover response message from the target satellite via the at least one transceiver.

8. The at least one processor transmitting a message including measurement configuration information to the terminal via the at least one transceiver; configured to receive, via the at least one transceiver, a measurement report message from the terminal according to the measurement configuration information; the measurement configuration information includes information regarding measurements of each of one or more cells; the measurement report message includes a cell quality of a cell served by the satellite; 2. The apparatus of claim 1, wherein the cell quality is determined based on at least one of a signal quality, an orbit of the satellite, a satellite group to which the satellite belongs, a distance between the satellite and the terminal, or timing advance information for the satellite.

9. The at least one processor Transmitting a gNB-DU (distributed unit) configuration update message via the at least one transceiver to a gNB (next generation node base station)-CU (central unit) via an F1 interface; configured to receive, via the at least one transceiver, a gNB-DU configuration update confirmation message from the gNB-CU via the F1 interface; The gNB-DU configuration update message includes at least one of information regarding one or more cells provided by the satellite and information regarding the orbit of the satellite, information regarding a satellite group to which the satellite belongs, or information regarding the speed of the satellite, information regarding the service time of the satellite, or information regarding the capability of the satellite; The device of claim 1, wherein the satellite supports a physical (PHY) layer protocol, a medium access control (MAC) layer protocol, and a radio link control (RLC) layer protocol, and the gNB-CU supports a radio resource control (RRC) layer protocol and a packet data convergence protocol (PDCP) layer protocol.

10. The at least one processor configured to broadcast, via the at least one transceiver, system information on a cell provided by the satellite; The apparatus of claim 1 , wherein the system information includes at least one of information about a satellite group to which the satellite belongs, information about an orbit of the satellite group, information about a cell of each satellite belonging to the satellite group, or information about an NTN gateway associated with the satellite group.

11. 1. A method performed by a satellite for providing non-terrestrial network (NTN) access, comprising: transmitting a message including handover related information to a terminal on a cell served by said satellite; The method, wherein the handover related information includes at least one of information about a group to which the satellite belongs, information about a target satellite of a target cell of handover for the terminal, information about a terminal group to which the terminal belongs, information related to conditions of a conditional handover of the terminal, and information about at least one of a position, a velocity, or an orbit of the target satellite.

12. 12. The method of claim 11, wherein the message includes at least one of position class information for indicating a position of the satellite or the target satellite, velocity class information for indicating a velocity of the satellite or the target satellite, or orbit class information for indicating an orbit of the satellite or the target satellite.

13. The method further includes an operation of receiving a handover request message from an access and mobility management function (AMF), 12. The method of claim 11, wherein the handover request message includes at least one of a satellite ID for the target satellite, a satellite group ID of a satellite group to which the target satellite belongs, orbital information of the target satellite, position information of the target satellite, velocity information of the target satellite, timing advance information of the target satellite, effective time information of the target satellite, polarization information of the target satellite, or scheduling offset information of the target satellite.

14. the message includes an event type for the conditional handover and at least one parameter for the event type; The message includes validity time information of the terminal group to which the terminal belongs, The method of claim 11 , wherein the validity time information is used by terminals in the terminal group to indicate a time interval for the conditional handover.

15. The method further includes an operation of receiving a handover command message from an access and mobility management function (AMF), 12. The method of claim 11, wherein the handover command message includes at least one of a satellite ID for the target satellite, a satellite group ID of a satellite group to which the target satellite belongs, orbital information of the target satellite, position information of the target satellite, velocity information of the target satellite, timing advance information of the target satellite, effective time information of the target satellite, polarization information of the target satellite, or scheduling offset information of the target satellite.

16. The method further includes an operation of sending a handover required message to an access and mobility management function (AMF), 12. The method of claim 11, wherein the handover request message includes at least one of a satellite ID for the target satellite, a satellite group ID of a satellite group to which the target satellite belongs, orbital information of the target satellite, position information of the target satellite, velocity information of the target satellite, timing advance information of the target satellite, effective time information of the target satellite, polarization information of the target satellite, or scheduling offset information of the target satellite.

17. determining a handover of the target satellite to the target cell; transmitting a handover command message to the target satellite; The method of claim 11 , further comprising an act of receiving a handover response message from the target satellite.

18. sending a message to the terminal, the message including measurement configuration information; The method further includes an operation of receiving a measurement report message from the terminal according to the measurement configuration information; the measurement configuration information includes information regarding measurements of each of one or more cells; the measurement report message includes a cell quality of a cell served by the satellite; 12. The method of claim 11, wherein the cell quality is determined based on at least one of a signal quality, an orbit of the satellite, a satellite group to which the satellite belongs, a distance between the satellite and the terminal, or timing advance information for the satellite.

19. An operation of transmitting a gNB-DU (distributed unit) configuration update message to a gNB (next generation node base station)-CU (central unit) via an F1 interface; and receiving a gNB-DU configuration update confirmation message from the gNB-CU via the F1 interface; The gNB-DU configuration update message includes at least one of information regarding one or more cells provided by the satellite and information regarding the orbit of the satellite, information regarding a satellite group to which the satellite belongs, or information regarding the speed of the satellite, information regarding the service time of the satellite, or information regarding the capability of the satellite; The method of claim 11, wherein the satellite supports a physical (PHY) layer protocol, a medium access control (MAC) layer protocol, and a radio link control (RLC) layer protocol, and the gNB-CU supports a radio resource control (RRC) layer protocol and a packet data convergence protocol (PDCP) layer protocol.

20. broadcasting system information on a cell served by said satellite; 12. The method of claim 11, wherein the system information includes at least one of information about a satellite group to which the satellite belongs, information about the orbit of the satellite group, information about a cell of each satellite belonging to the satellite group, or information about an NTN gateway associated with the satellite group.

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