Method and apparatus for managing system information in non-terrestrial network system

Abstract

The present disclosure relates to a 5G or 6G communication system for supporting a data transmission rate higher than that of a 4G communication system such as LTE. A method performed by user equipment in a wireless communication system using a non-terrestrial network (NTN), according to the present disclosure, may comprise the steps of: receiving, from a first NTN base station, a first SI message including a first system information block (SIB) and a first physical cell identity (PCI) regarding a first cell; storing the first SIB and the first PCI; receiving, from a second NTN base station, a second SI message including a second SIB and a second PCI; identifying whether the second SIB has been received at the same frequency as the first SIB; identifying whether the second PCI is different from the first PCI if the second SIB has been received at the same frequency as the first SIB; and determining whether the second SIB is identified as the first SIB if the second PCI is different from the first PCI. Various other embodiments understood through the specification are also possible.

Description

Method and device for managing system information in a non-terrestrial network system

[0001] The present disclosure relates to a wireless communication system, and more specifically, to a method and apparatus for managing system information in a non-terrestrial network (NTN) system.

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

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

[0004] To achieve such high data transmission speeds and ultra-low latency, 6G communication systems are being considered for implementation in the terahertz (THz) band (e.g., the 95 gigahertz (GHz) to 3 terahertz (3THz) band). Due to more severe path loss and atmospheric absorption phenomena compared to the millimeter wave (mmWave) band introduced in 5G, the importance of technologies capable of guaranteeing signal reach, or coverage, is expected to increase in the terahertz band. As key technologies to ensure coverage, new waveforms, beamforming, and multi-antenna transmission technologies such as massive Multiple-Input and Multiple-Output (MIMO), Full Dimensional MIMO (FD-MIMO), array antennas, and large-scale antennas, which are superior in terms of coverage compared to RF (Radio Frequency) devices, antennas, and OFDM (Orthogonal Frequency Division Multiplexing), must be developed. In addition, new technologies such as metamaterial-based lenses and antennas, high-dimensional spatial multiplexing technology using Orbital Angular Momentum (OAM), and Reconfigurable Intelligent Surface (RIS) are being discussed to improve the coverage of terahertz band signals.

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

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

[0007] The various embodiments disclosed in this document propose a method and apparatus for managing system information in a non-terrestrial network system.

[0008] A method performed by a user equipment in a wireless communication system using a non-terrestrial network (NTN) according to various embodiments disclosed in this document may include: receiving a first SI message from a first NTN base station comprising a first SIB (system information block) and a first PCI (physical cell identity) for a first cell; storing the first SIB and the first PCI; receiving a second SI message from a second NTN base station comprising a second SIB and a second PCI; identifying whether the second SIB is received at the same frequency as the first SIB; identifying whether the second PCI is different from the first PCI when the second SIB is received at the same frequency as the first SIB; and determining whether the second SIB is identified as the first SIB when the second PCI is different from the first PCI.

[0009] In a wireless communication system using a non-terrestrial network (NTN) according to various embodiments disclosed in this document, a terminal (user equipment) includes a transceiver and a controller coupled to the transceiver, and the controller may be configured to receive a first SI message including a first SIB (system information block) and a first PCI (physical cell identity) for a first cell from a first NTN base station, store the first SIB and the first PCI, receive a second SI message including a second SIB and a second PCI from a second NTN base station, identify whether the second SIB is received at the same frequency as the first SIB, identify whether the second PCI is different from the first PCI if the second SIB is received at the same frequency as the first SIB, and determine whether the second SIB is identified as the first SIB if the second PCI is different from the first PCI.

[0010] FIG. 1 illustrates an example in which the physical cell ID (PCI) of a satellite cell changes in a non-terrestrial network system according to one embodiment of the present disclosure.

[0011] FIG. 2 illustrates an operation in which a terminal determines the validity of a stored SIB in a non-terrestrial network system according to one embodiment of the present disclosure.

[0012] FIG. 3 illustrates a scenario in which the PCI of a satellite cell changes in a non-terrestrial network system according to one embodiment of the present disclosure.

[0013] FIG. 4 illustrates an operation in which a terminal determines the validity of a stored SIB in a non-terrestrial network system according to one embodiment of the present disclosure.

[0014] FIG. 5 illustrates an operation in which a non-ground network terminal determines the validity of a stored SIB according to one embodiment of the present disclosure.

[0015] FIG. 6 illustrates an operation in which a terminal determines the validity of a stored SIB in a non-terrestrial network system according to one embodiment of the present disclosure.

[0016] FIG. 7 illustrates an operation in which a terminal determines the validity of a stored SIB in a non-terrestrial network system according to one embodiment of the present disclosure.

[0017] FIG. 8 is a flowchart illustrating the operation of determining the validity of a stored SIB by a terminal in a non-terrestrial network system according to one embodiment of the present disclosure.

[0018] FIG. 9 is a flowchart illustrating the operation of determining the validity of a stored SIB by a terminal in a non-terrestrial network system according to one embodiment of the present disclosure.

[0019] FIG. 10 is a flowchart illustrating the operation of determining the validity of a stored SIB by a terminal in a non-terrestrial network system according to one embodiment of the present disclosure.

[0020] FIG. 11 is a flowchart illustrating the operation of determining the validity of a stored SIB by a terminal in a non-terrestrial network system according to one embodiment of the present disclosure.

[0021] FIG. 12 illustrates the operation of a terminal in a non-terrestrial network system according to one embodiment of the present disclosure.

[0022] FIG. 13 illustrates the structure of a terminal according to one embodiment of the present disclosure.

[0023] FIG. 14 illustrates the structure of a base station according to one embodiment of the present disclosure.

[0024] FIG. 15 illustrates the structure of a network entity according to one embodiment of the present disclosure.

[0025] In relation to the description of the drawings, the same or similar reference numerals may be used for identical or similar components.

[0026] Various aspects of the claimed subject matter are described with reference to the drawings, in which similar reference numerals are used to denote similar elements. In the following description, for the purpose of explanation, a number of specific details are described to provide a sufficient understanding of one or more embodiments. However, it may be apparent that the embodiments can be practiced without these specific details.

[0027] The terms used in this disclosure are used merely to describe specific embodiments and are not intended to limit the scope of other embodiments. A singular expression may include a plural expression unless the context clearly indicates otherwise. Terms used herein, including technical or scientific terms, may have the same meaning as generally understood by those skilled in the art described in this disclosure. Terms used in this disclosure that are defined in a general dictionary may be interpreted as having the same or similar meaning as they have in the context of the relevant technology, and are not to be interpreted in an ideal or overly formal sense unless explicitly defined in this disclosure. In some cases, even terms defined in this disclosure are not to be interpreted to exclude the embodiments of this disclosure.

[0028] Terms referring to signals used in the following description (e.g., message, signal, signaling, sequence, stream), terms referring to resources (e.g., symbol, slot, subframe, radio frame, subcarrier, RE (resource element), RB (resource block), BWP (bandwidth part), occurrence), terms for operations (e.g., step, method, process, procedure), terms referring to data (e.g., information, parameter, variable, value, bit, symbol, codeword), terms referring to channels, terms referring to control information (e.g., DCI (downlink control information), MAC CE (medium access control codeword element), RRC (radio resource control) signaling), terms referring to network entities, terms referring to device components, etc., are used for the convenience of explanation This is an example. Accordingly, the present disclosure is not limited to the terms described below, and other terms having equivalent technical meanings may be used.

[0029] Various embodiments of the present disclosure are described herein in relation to wireless terminals and / or base stations. A wireless terminal may refer to a device that provides voice and / or data access to a user. A wireless terminal may be connected to a computing device, such as a laptop computer or a desktop computer, or may be a self-contained device, such as a personal digital assistant (PDA). A wireless terminal may also be referred to as a system, subscriber unit, subscriber station, mobile station, mobile, mobile device, remote station, remote terminal, access terminal, user terminal, terminal, wireless communication device, user agent, user device, or user equipment. A wireless terminal may be a subscriber station, wireless device, cellular phone, PCS phone, wireless phone, Session Initiation Protocol (SIP) phone, wireless local loop (WLL) station, personal digital assistant (PDA), portable device with wireless access capability, or other processing device connected to a wireless modem. A base station (e.g., an access point) may refer to a device within an access network that communicates with wireless terminals at a wireless interface through one or more sectors. The base station can include an Internet Protocol (IP) network by converting received wireless interface frames into IP packets and can act as a router between the wireless terminal and the rest of the access network. The base station can also coordinate the management of attributes for the wireless interface.

[0030] Recently, active research has been conducted on non-terrestrial network (NTN) communication technology. NTN communication technology utilizes satellites as repeaters to establish communication coverage in areas where the installation of mobile communication base stations is physically or economically impossible (e.g., oceans, polar regions, remote areas, and the air). NTN communication technology refers to a technology that can be utilized not only in NTN using the LTE (Long Term Evolution) standard used in existing terrestrial networks and NR (New Radio) standards that include functions for NTN performance enhancement, but also in 6G communication systems expected to be commercialized by 2030.

[0031] In NTN, since satellites act as base stations or base station antennas, terminals must perform NTN communication by considering various phenomena caused by satellite mobility that do not occur in terrestrial networks. In non-terrestrial systems, terminals connected to NTN cells must communicate with satellites located at very long distances compared to terrestrial systems. Consequently, high transmission power may be essential to deliver radio waves to distant base stations. Furthermore, due to signal attenuation caused by long distances, terminals experience frequent disconnections and retransmissions; this can lead to higher power consumption for terminals connected to NTN cells compared to those connected to terrestrial cells.

[0032] Terrestrial networks (TN) and non-terrestrial networks (NTN) using mobile communication standards based on the 3GPP (3rd Generation Partnership Project) define a Physical Cell ID (PCI) to distinguish cell areas where a terminal can communicate. In terrestrial networks, network entities set different PCIs for each cell to distinguish them. The PCI set by the network entity can remain the same until the terminal changes the connected cell to another cell. PCIs can be set in various ways. For example, two different PCIs can be set sequentially, assigned dynamically depending on the status of the satellite cell, or a PCI can be set fixedly for each satellite.

[0033] Hereinafter, the NTN cell described in this disclosure may be a quasi-earth fixed cell. A quasi-earth fixed cell refers to a satellite cell formed in a specific area of ​​the Earth's surface. Since the satellites described in this disclosure (e.g., LE0 satellites and MEO satellites) move relative to the Earth's surface, they cannot continuously form a cell in a specific area. This disclosure illustrates a case where a quasi-earth fixed cell is formed in a specific area even if the satellite moves relative to the ground by rotating the antenna of the beam forming the satellite cell. For example, the NTN cell of FIG. 1 may represent a quasi-earth fixed cell in which the satellite maintains a constant position by rotating the beam antenna. Therefore, the PCI in the NTN cell described in this disclosure may allow the satellite forming the NTN cell to change continuously over time. That is, the PCI in the NTN cell may not be in a fixed form but may change dynamically by the network entity. If the satellite forming the NTN cell currently connected to the terminal changes, the PCI may change to the PCI set by the network entity for the satellite to be changed. However, this is not limited to this, and it may also be applied to the case of an Earth moving cell, an operation method in which the satellite cell moves along with the movement of the satellite when the antenna forming the cell of the MEO / LEO satellite cannot rotate.

[0034] Satellites forming cells in non-ground networks can be classified into GEO (geostationary earth orbit), ME0 (medium earth orbit), and LEO (low earth orbit) satellites depending on their altitude. LE0 satellites located at low altitudes have the advantage of low latency due to short radio round-trip times; however, because their movement speed is much faster than other satellites, the time available to form a cell on the ground is limited when an LEO satellite forms a cell. Consequently, terminals connected to satellite cells (or NTN cells) formed on the ground may not be able to maintain a constant PCI. When the satellite forming the cell changes, the terminal receives a PCI different from the existing PCI, and the terminal can detect the change in satellite by recognizing the change in PCI.

[0035] Meanwhile, a terminal connected to an NTN cell can receive system information (system information block, SI) from the satellite forming the NTN cell (or the NTN base station relaying between the satellite and the terminal). The system information is divided into a master information block (MIB) and multiple system information blocks (SIBs). The MIB is always transmitted over the BCH with an 80ms period and repeats within 80ms, and may include parameters necessary to obtain SIB1 (system information block type 1) from the cell. In this case, SIB1 includes information regarding the availability and scheduling (e.g., periodicity, SI-window size) of other SIBs. It also indicates whether these (i.e., other SIBs) are provided on a periodic broadcast basis or on demand. If other SIBs are provided on demand, SIB1 includes information for the terminal to perform an SI request. SIBs other than SIB1 are carried in system information messages transmitted over the DL-SCH.

[0036] To reduce the overhead of decoding whenever a SIB is received, the terminal may have the function of storing the SIB within the terminal and reusing the stored SIB. When reusing the SIB without modifying the system information, the amount of data transmitted for on-demand system information is reduced, and the power consumption required to decode the SIB at the terminal can be reduced.

[0037] As a method for determining whether a stored SIB can be reused, LTE systems can check for changes in system information by verifying the systemInfoValueTag value within SIB1. For example, a base station may notify a terminal of a change in system information by sending a systemModification notification within a paging message during the modification period, or by sending a systemInfoValueTag value different from the SIB stored within SIB1. The systemInfoValueTag value may be indicated as a value between 1 and 32, increasing by 1 each time the system information changes. However, while the base station can notify the terminal that the system information has changed, it cannot notify which specific SIB or which information element (IE) within the SIB has changed.

[0038] In the case of LTE systems, system information is information operated at the cell level, whereas in the case of NR systems, system information can be operated at the cell or area level. In an NR system, to verify the validity of a stored SIB, a terminal can determine whether the stored SIB can be reused by checking whether the PLMN (public land mobile network)-Identity, cellIdentity, and systemInformationAreaID values ​​within SIB1 are identical. Additionally, if a valueTag value is indicated within the SIB, the terminal can check whether the valueTag value is also identical to verify whether there has been a change in system information.

[0039] However, the question arises whether the aforementioned method can be used to verify whether the stored SIB can be reused even when the PCI of a terminal connected to the same NTN cell changes due to a change in satellite. This will be described later in Fig. 1.

[0040] The 3GPP standard document defines the validity period of system information stored in a terminal, and for example, system information stored in a terminal may be considered valid for about 3 hours from the last time it was determined to be valid. Additionally, in the case of Bluetooth terminals, NB-IoT (narrowband internet-of-Thing) terminals, etc., the stored system information may be considered valid for 24 hours. However, in addition to the validity period of the SIB defined in the standard document, if the PCI changes due to a satellite change in the same NTN cell, it may be necessary to set a separate timer (e.g., a SIB reuse timer) to determine whether the stored SIB is valid.

[0041] Hereinafter, the present disclosure proposes a method for determining whether a terminal connected to an NTN cell at the same location in a non-terrestrial network system can reuse stored system information (i.e., whether the system information is valid) when the PCI changes as the satellite changes.

[0042] Meanwhile, a terminal connected to an NTN cell described in the present disclosure may refer to a terminal connected to an NTN cell in an RRC CONNECTED state or in a camping state in an RRC IDLE state.

[0043] The base station in a non-terrestrial network (or, NTN base station) described in this disclosure may represent a satellite that performs the role of a base station relative to a satellite cell formed by a satellite through a beam to the Earth.

[0044] FIG. 1 illustrates an example in which the physical cell ID (PCI) of a satellite cell changes in a non-terrestrial network system according to one embodiment of the present disclosure.

[0045] Because satellites (e.g., LEO satellites) forming cells (e.g., NTN cells) in non-terrestrial networks move at high speeds unlike terrestrial base stations, the time available for a satellite to form a cell on the ground may be limited. Consequently, a terminal connected to an NTN cell may not be able to maintain a consistent PCI. If the satellite forming the cell changes, the terminal may receive a PCI different from the one previously stored by the terminal, and the terminal can detect the change in the satellite by receiving a PCI different from the one previously stored.

[0046] In one example, since the angle of the antenna forming the NTN cell in an Earth-moving cell is fixed, the angle of the beam formed by the satellite and the structure of the NTN cell formed by the beam can remain fixed regardless of the satellite's movement. Therefore, the beam or set of beams formed by the satellite constitutes a cell, and the cell will continue to use the same PCI until a change occurs by the NTN manager. From the perspective of the terminal, since the cell continuously moves over time, it can experience handovers or cell selections similar to those experienced by terminals moving at high speeds in a terrestrial network. Accordingly, the terminal can experience changes in the PCI corresponding to the direction of cell movement based on the satellite's orbit.

[0047] In a quasi-earth fixed cell, the location of the NTN cell formed on the ground is fixed, but the satellite forming the NTN cell and the beam from the satellite may change depending on the satellite's movement. If the satellite forming the cell currently connected to the terminal changes, the PCI may change to the PCI associated with the changed satellite.

[0048] In other words, the PCI can continuously change as the satellite changes within the same NTN cell. When the PCI changes, the terminal can synchronize with the network by performing random access.

[0049] If the PCI changes within an NTN cell at the same location, the System Information Block (SIB) prior to the PCI change cannot be reused after the PCI is modified. In one example, when an LTE-based NTN cell is in operation, the information elements of the systemInfoValueTag can be applied in an environment where the PCI is not modified; therefore, it may be difficult to determine whether the SIB can be reused using the systemInfoValueTag. Furthermore, when the PCI changes, the terminal perceives that the satellite has changed, so it cannot verify whether the SIB associated with the previously stored PCI is identical to the new SIB associated with the modified PCI. Consequently, when the PCI changes, the terminal needs to decode the SIB included in the newly received SI message.

[0050] Referring to FIG. 1, a terminal connected to an NTN cell (130) at the same location receives a SIB associated with PCI=7 (hereinafter referred to as the first SIB) from a first satellite (110) and can store the first SIB. Subsequently, when the satellite forming the NTN cell (130) changes from the first satellite (110) to the second satellite (120), the terminal can receive a SIB associated with the changed PCI=13 (hereinafter referred to as the second SIB). At this time, since the terminal has no way to determine whether to use the stored first SIB instead of the second SIB, it may have to decode the second SIB. That is, the terminal may have to perform decoding of the newly received SIB whenever the PCI changes as the satellite changes.

[0051] If the terminal fails to determine whether a SIB can be reused whenever the PCI changes (i.e., whenever the satellite changes) and continues to decode newly received SIBs, the power consumption of the terminal due to SIB decoding may increase. Furthermore, since the terminal may perform unnecessary SIB decoding operations even when a newly received SIB could reuse an existing stored SIB, there is a concern that overhead may occur due to the terminal's repetitive SIB decoding.

[0052] Hereinafter, the present disclosure proposes a method for determining whether a stored SIB can be reused when a terminal connected to an NTN cell recognizes a PCI change caused by a change in the satellite. FIGS. 2 to 12 described below explain operations for determining whether the terminal can reuse an already stored SIB (or whether the stored SIB is valid).

[0053] FIG. 2 illustrates an operation in which a terminal determines the validity of a stored SIB in a non-terrestrial network system according to one embodiment of the present disclosure.

[0054] According to one embodiment of the present disclosure, an information element (IE) capable of determining the validity of an SIB is added to the information defined in the current 3GPP standard document, so that the terminal can determine whether the stored SIB can be reused based on the information.

[0055] Figure 2 (A) illustrates an example in which an IE indicating the previous PCI and next PCI is added to a system information message received by a terminal.

[0056] According to one embodiment of the present disclosure, an IE (e.g., oldPCI and nextPCI) indicating a previous PCI or next PCI may be added to SIB 1 or SIB 19 and transmitted from a satellite (or NTN base station) to a terminal. In this case, since the range of PCI values ​​is from 0 to 503, the IE indicating the previous PCI or next PCI may require 9 bits. For example, as shown in [Table 1] below, an IE indicating the previous PCI or next PCI may be added to an information block related to a non-terrestrial network in SIB 1.

[0057]

[0058] In one example, when a terminal connected to an NTN cell receives a system information message in which the PCI has changed due to a change in the satellite, the terminal can verify information indicating the previous PCI or next PCI included in the system information message. At this time, the terminal can verify information indicating the previous PCI or next PCI included in the SIB by decoding the SIB included in the received system information message. For example, referring to (A) in FIG. 2, a terminal connected to an NTN cell receives a system information message from a first satellite (210) in which the value of PCI is PCI=5, and can verify information that the value of the next PCI is 13 (e.g., nextPCI=13) by decoding SIB1 or SIB19 in the system information message. When storing the SIB in the received system information message, the terminal displays the verified previous PCI value and next PCI value, and can use the displayed previous PCI value or next PCI value when determining whether the SIB is valid when the satellite and PCI change. When the satellite forming the same NTN cell changes from the first satellite (210) to the second satellite (220), the terminal can check whether the value of PCI displayed in the system information message received from the second satellite (220) (or the second NTN base station) is the same as the value of the next PCI (e.g., nextPCI=13 in (A) of FIG. 2) confirmed in the system information received from the first satellite (210). Additionally, by checking the previous PCI or the next PCI displayed in the system information message received from the second satellite (220), the terminal can check whether the value of PCI displayed in the previous PCI (e.g., oldPCI=5 in (A) of FIG. 2) is the same as the PCI value (PCI=5) for the first satellite (210).

[0059] Through this, the terminal can determine that the SIB received from the first satellite is valid if it compares the current PCI and the previous PCI displayed in the system information message received from the changed satellite with the next PCI and the current PCI displayed in the system information message received from the satellite before the change, respectively, and if they match. For example, if the PCI value of the second satellite (220) and the next PCI value displayed in the system information message of the first satellite (210) are the same at 13, the terminal can determine that the SIB stored when connected to the first satellite (210) can be reused. Additionally, if the previous PCI value displayed in the system information message of the second satellite (220) and the PCI value of the first satellite (210) are the same at 5, the terminal can determine that the SIB stored when connected to the first satellite (210) can be reused.

[0060] The operation of determining whether the PCI value of the changed satellite matches the information indicating the next PCI included in the SIB within the system information message received from the satellite prior to the change may not require decoding the SIB within the system information message received from the changed satellite.

[0061] However, the operation of determining whether the information indicating the previous PCI included in the SIB within the system information message received by the terminal from the changed satellite matches the PCI value of the satellite prior to the change may require decoding the SIB within the system information message received by the terminal from the changed satellite.

[0062] Meanwhile, there may be a limitation that the operation of determining the validity of the SIB by adding information indicating the previous PCI or next PCI included in the SIB as described above can only be verified when receiving consecutive satellite system information messages.

[0063] Figure 2 (B) illustrates an example of determining whether a stored SIB is valid by checking whether the terminal is located in the same cell in the same area.

[0064] According to one embodiment of the present disclosure, an IE (e.g., systemInformationAreaID or cell-Index) representing local information for a cell may be added to SIB 1 and transmitted from a satellite (or NTN base station) to a terminal. In this case, SIB 1 is information that is always decoded and verified upon reception, and if a SIB different from the SIB stored in the terminal arrives, or if a SIB 1 with a different version value arrives, other SIBs other than SIB 1 may be decoded.

[0065] In one example, a regionally unique ID (identity) is assigned to a cell, allowing the terminal to verify whether it is receiving system information from a cell at the same location. For instance, in the case of an NR system, the terminal can verify whether system information for the same area is being received by checking the systemInformationAreaID value within SIB 1 in the system information message received from the satellite, as shown in [Table 2] below. If the systemInformationAreaID value is the same, the terminal can determine that the previously stored SIB remains valid even if the PCI changes. In other words, if the terminal receives a SIB with the same systemInformationAreaID value, it can determine that the previously stored SIB can be reused. Meanwhile, not only terminals in NR systems but also terminals in NB-IoT systems can verify whether a SIB can be reused using the systemInformationAreaID value.

[0066]

[0067] In another example, SIB1 may be provided with a TAC (tracking area code) value and an IE representing a unique ID for a cell by assigning a number to the cell within the TAC for each TAC. A TAC refers to a code uniquely assigned to the TA (tracking area) of the cells. When the terminal is in an idle state, the terminal's location can be determined at the TA level, which represents a set of multiple cells, rather than at the cell level.

[0068] The terminal can determine whether a previously stored SIB can be reused by checking the combination of the TAC and the cell number within the TAC. A locally unique ID for a cell can be represented through the combination of the TAC and the cell number within the TAC. For example, as shown in [Table 3] below, a cell number within the same TAC value can be assigned by adding a cell-Index value representing the cell number to SIB1. Meanwhile, the TAC value is a value already represented in the SIB in the current NR standard. Even if the satellite changes, if the TAC value and cell-Index value included in SIB1 received from the changed satellite are the same as the TAC value and cell-Index value included in SIB1 received from the satellite before the change, the terminal can determine that the stored SIB can be reused by additionally checking whether the systemInformationAreaID value is the same.

[0069]

[0070] For example, referring to (B) of Fig. 2, for example, after checking the TAC and value TAC=17 and cell-Index value 1 in SIB1 within the SIB that the terminal initially received and stored, the terminal checks SIB1 within the newly received SIB to check whether the TAC and value and cell-Index value are the same, and if TAC=17 and cell-Index value 1 are the same, the systemInfoValueTag value is checked to check whether the stored SIB is reused.

[0071] FIG. 3 illustrates a scenario in which the PCI of a satellite cell changes in a non-terrestrial network system according to one embodiment of the present disclosure.

[0072] As shown in Fig. 2, a method may be required for the terminal to determine the validity of the SIB even without adding an IE capable of determining the validity of the SIB defined in the 3GPP standard document. Fig. 3 illustrates scenarios in which the PCI is changed so that the terminal can determine whether the stored SIB can be reused even without adding an IE to the SIB defined in the 3GPP standard document.

[0073] Referring to Fig. 3, scenarios in which PCI changes in a non-terrestrial network system are illustrated.

[0074] The first scenario involves a change in the satellite. If the satellite changes while the terminal is connected to the same NTN cell, the PCI may change. For example, in Figure 3, the terminal connected to the NTN cell recognized PCI=13 from the previous satellite, but subsequently recognized a changed PCI of PCI=7 due to a change in the satellite forming the NTN cell.

[0075] The second scenario involves a case where the terminal hands over to a neighbor cell, and the PCI of the SIB stored in the terminal is identified in the neighbor cell. In one example, a terminal connected to an NTN cell may be located at the edge of that NTN cell and hands over to another adjacent neighbor cell. For instance, in FIG. 3, if a terminal connected to an NTN cell with PCI=7 is located at the edge of the cell and hands over to another neighbor NTN cell, the PCI in the neighbor NTN cell may change to 19. At this time, the PCI for the NTN cell that the terminal was connected to prior to the handover may be identified in the neighbor NTN cell where the terminal hands over.

[0076] Finally, the third scenario involves a change in the connected cell due to the movement of the terminal. The third scenario is not a case where the terminal handovers to an adjacent neighboring NTN cell that is close to the existing connected NTN cell, but rather a case where the PCI for the existing NTN cell stored in the terminal is not confirmed in the handover NTN cell due to the terminal's movement. In other words, it may be a case where the terminal handovers to a non-adjacent NTN cell due to long-distance movement. For example, if the terminal is inside a vehicle, the terminal moves due to the vehicle's movement, and this may result in a change in the connected cell. For instance, a terminal connected to an NTN cell with PCI=7 in Fig. 3 may move via a vehicle to another cell with PCI=5 where the NTN cells do not overlap, causing the PCI to change.

[0077] Hereinafter, when determining whether the SIB stored by the terminal proposed in this disclosure can be reused, it is assumed that the PCI changes due to satellite movement. In order to limit the scope to cases where the PCI changes due to satellite movement, it is necessary to prevent the second and third scenarios among the aforementioned scenarios where the PCI changes. That is, the operation of the terminal proposed in this disclosure to verify the validity of the SIB must check whether the PCI changes due to a change in the satellite, and to determine whether the SIB can be reused by considering cases where the terminal hands over to an adjacent NTN cell and the PCI for the previous NTN cell is confirmed in the handover NTN cell, or where the terminal hands over to a non-adjacent NTN cell due to long-distance movement and the PCI for the previous NTN cell is not confirmed in the handover NTN cell. To this end, a procedure to check whether it corresponds to the first to third scenarios mentioned above may be required.

[0078] According to one embodiment of the present disclosure, in order to determine whether the PCI changes due to a change in the satellite, the terminal can check whether the SIB in which the basic IE is stored in SIB1 within the system information message received by the terminal from the satellite (or from the NTN base station) matches the newly received SIB. Specific details will be described below in FIG. 4.

[0079] According to one embodiment of the present disclosure, a terminal can determine whether to hand over to a neighboring cell by using the PCI information of a stored SIB to determine whether the terminal has handed over to a neighboring cell and whether the PCI stored in the neighboring cell to which the terminal handed over has been confirmed. Specific details will be described below in FIG. 5.

[0080] According to one embodiment of the present disclosure, a terminal may additionally set an SIB reuse timer of a length insufficient for the terminal to visit another cell in order to determine whether the PCI for the previous NTN cell is not confirmed in the NTN cell to which the terminal has moved a long distance and handed over to a non-adjacent NTN cell. Specific details will be described below in FIG. 6.

[0081] FIG. 4 illustrates an operation in which a terminal determines the validity of a stored SIB in a non-terrestrial network system according to an embodiment of the present disclosure. Specifically, FIG. 4 illustrates an example for determining whether the PCI changes due to a change in satellite, considering the first scenario described in FIG. 3. At this time, FIG. 4 assumes a situation in which the terminal first receives an SIB and then receives a new SIB along with a change in PCI.

[0082] First, the terminal can check whether the cell it is connected to is an NTN cell. Only when the cell it is connected to is an NTN cell can the terminal check whether the SIB can be reused, assuming a PCI case due to a satellite change. For example, in the case of an LTE terminal, it can check whether the cell it is connected to is an NTN cell by checking the PLMN ID within SIB1. In the case of an NR terminal, the terminal can check through cellAccessRelatedInfo-NTN in SIB1 within the SIB received by the terminal, or if the frequency at which the SIB was received is a frequency allocated only by the NTN system, the terminal can confirm that the cell it is connected to is an NTN cell.

[0083] According to one embodiment of the present disclosure, a terminal connected to an NTN cell in an NTN system stores a SIB within a system information message received from a satellite (or an NTN base station), and subsequently, when a new system information message is received, can determine whether some information within SIB1 matches the information within the stored SIB1. In one example, the information used by the terminal to determine whether the stored SIB matches the newly received system information message may be frequency, first-PLMN (public land mobile network) identity, TAC (tracking area code), and systemInfoValueTag. For example, the terminal can determine whether the newly received system information message was received at the same frequency as the stored SIB. Additionally, the terminal can determine whether the carriers match by checking whether the first-PLMN identity indicated by the newly received system information message is the same as the first-PLMN identity of the stored SIB. Additionally, the terminal can determine whether the area information of the SIB of the newly received system information message matches the area information of the stored SIB by checking the TAC. Finally, the terminal can determine whether the SIB version information matches by checking the systemInfoValueTag value indicated by a value from 1 to 32 in the newly received SIB and the stored SIB.

[0084] Referring to (A) of Fig. 4, the terminal stores a SIB having the value of TAC #1, and if the TAC value of a newly received SIB is subsequently confirmed to be TAC #2, it determines that the change in PCI is not due to a change in satellite and identifies the stored SIB as invalid. That is, if the TAC values ​​are not identical, it may not be determined that the change in PCI is due to a change in satellite.

[0085] Additionally, if the terminal stores a SIB with a systemInfoValueTag value of systemInfoValueTag=23 and subsequently confirms that the systemInfoValueTag value of a newly received SIB is systemInfoValueTag=7, it determines that the stored SIB is not system information of the same cell and identifies it as invalid. In other words, if the systemInfoValueTag value in the previously received SIB is not identical to the systemInfoValueTag value in the newly received SIB, it may not be determined that there is a change in PCI due to satellite variation.

[0086] Referring to (B) of Fig. 4, if the terminal receives a newly received SIB at a different frequency than the stored SIB, it can determine that the change in PCI is not due to satellite variation and identify that the stored SIB is invalid. That is, if the newly received SIB is not received at the same frequency as the SIB stored by the terminal, it may not be determined that the change in PCI is due to satellite variation.

[0087] As described above, the terminal can determine whether the PCI has changed due to a change in the satellite by checking whether some information within the SIB matches the stored SIB and the newly received SIB.

[0088] FIG. 5 illustrates an operation in which a non-ground network terminal determines the validity of a stored SIB according to one embodiment of the present disclosure. Specifically, FIG. 5 illustrates an operation in which the terminal determines whether the PCI has changed by handing over to an adjacent neighbor cell, taking into account the second scenario described in FIG. 3.

[0089] According to one embodiment of the present disclosure, the terminal can determine whether a handover has been performed by checking whether the newly changed PCI or the PCI of the stored SIB is found in a neighboring cell.

[0090] In one example, if the terminal has a neighbor cell list within the SIB stored before the PCI is changed, the terminal can determine whether the terminal has handed over by determining whether the changed PCI is found in the neighbor cell list. FIG. 5 (A) illustrates an example where a terminal connected to an NTN cell with PCI=9 changes the PCI to PCI=7 after storing a SIB indicating PCI=9. In this case, if there is a neighbor cell list within the stored SIB, the terminal can determine whether the newly changed PCI is found in the neighbor cell list. If the changed PCI is found in the neighbor cell list included in the SIB for PCI=9 stored by the terminal, it can be determined that the terminal has handed over to a neighbor cell. When it is determined that the terminal has handed over, it can be determined that the PCI was changed due to a handover rather than a change in the satellite.

[0091] In one example, if the terminal does not have a list of neighboring cells within the SIB stored before the PCI is changed, the terminal can determine whether the terminal has undergone a handover by scanning neighboring cells after the PCI is changed to check whether the PCI of the stored SIB is found. Figure 5 (B) illustrates an example where a terminal connected to an NTN cell with PCI=9 stores a SIB indicating PCI=9, and then the PCI is changed to PCI=7. In this case, if there is no list of neighboring cells within the SIB stored in the terminal, the terminal can scan neighboring cells to check whether the PCI of the stored SIB is found among the PCIs of the neighboring cells. For example, if the terminal scans neighboring cells after the PCI is changed to PCI=7 and finds a PCI among the neighboring cells that is identical to PCI=9, which is the PCI of the stored SIB, it can determine that the terminal has undergone a handover. When it is determined that the terminal has undergone a handover, it can be determined that the PCI was changed due to a handover rather than a change in the satellite.

[0092] FIG. 6 illustrates an operation in which a terminal determines the validity of a stored SIB in a non-terrestrial network system according to one embodiment of the present disclosure. Specifically, FIG. 6 illustrates an operation in which a PCI is determined whether it has changed due to the movement of the terminal, taking into account the third scenario described in FIG. 3.

[0093] According to one embodiment of the present disclosure, the terminal may additionally set a SIB reuse timer with a time length that is not sufficient for the terminal to visit another cell in order to determine whether the PCI has changed when the terminal moves to a cell where the PCI of the stored SIB is not found.

[0094] The SIB reuse timer of the present disclosure may refer to a timer that defines the validity period of a stored SIB to determine whether a terminal can reuse an existing stored SIB. In this case, the SIB reuse timer described in the present disclosure may be operated independently of the validity period of the SIB defined in the 3GPP LTE standard (for example, the validity period of the SIB that an LTE terminal can store is 3 hours, and the validity period of the SIB that an NB-IoT or Bluetooth terminal can store is 24 hours).

[0095] The duration of the SIB reuse timer can be set to a length that is insufficient for the terminal to visit another cell to determine whether the PCI has changed, such as when the terminal moves to a cell where the PCI of the stored SIB is not found. For example, the duration of the SIB reuse timer can be set considering the average size of an NTN cell, which is approximately 50 km (kilometers), while taking into account terminal movement by vehicle rather than walking. Additionally, the duration of the SIB reuse timer can be set based on the frequency reuse factor (FRF). The FRF is a parameter used to represent frequency efficiency, indicating how many cells the entire frequency band is divided into. For example, if the FRF value is FRF=1, all cells use the same frequency, and if the FRF value is FRF=3, the entire frequency band is divided into three cells.

[0096] For example, in FIG. 6 (A), when the FRF value for the NTN cell formed by the satellite is FRF=1 (610), the time length of the SIB reuse timer may be short because the terminal can move to a nearby cell with the same frequency over a short distance from the cell edge. When the vehicle speed is 100 km / hr, the time length of the SIB reuse timer when FRF=1 may be 1 to 3 minutes. As another example, in FIG. 6 (A), when the FRF value for the NTN cell formed by the satellite is FRF=3 (620), the time length of the SIB reuse timer may be longer than when FRF=1 because the terminal may have to move by the size of the cell to move to a nearby cell with the same frequency as the first NTN cell. When the vehicle speed is 100 km / hr, the time length of the SIB reuse timer when FRF=3 may be less than 10 minutes.

[0097] The start time of the SIB reuse timer can be set to the last time the terminal first connected to the NTN cell or checked the validity (or reusability) of the SIB.

[0098] According to one embodiment of the present disclosure, if the PCI changes while the SIB reuse timer is running, the terminal can determine that it has not moved from the previously connected NTN cell to another cell via a vehicle, etc. by detecting the change in PCI while the SIB reuse timer is running. For example, when the first SIB reuse timer is running in (B) of FIG. 6, the start time of the first SIB reuse timer may be the most recent time when the terminal confirmed the validity of the SIB by checking the systemInfoValueTag value in SIB 1 due to the non-change in PCI. If the terminal detects a change in PCI within the time length (630) during which the first SIB reuse timer is running, the terminal can determine that it has not moved from the previously connected NTN cell to another cell via a vehicle, etc. Through this, the terminal may determine that it can reuse the previously stored SIB.

[0099] According to one embodiment of the present disclosure, if the PCI changes after the SIB reuse timer expires, the terminal can determine that the terminal has moved from the previously connected NTN cell to another cell via a vehicle, etc. by detecting the change in PCI after the SIB reuse timer expires. In this case, the terminal can determine that the PCI changed due to the terminal's movement, rather than the change in PCI due to satellite movement. For example, when the second SIB reuse timer is activated in (B) of FIG. 6, the start time of the second SIB reuse timer may be the most recent time when the terminal confirmed the validity of the SIB by checking the systemInfoValueTag value in SIB 1 due to the non-change in PCI. If the terminal detects a change in PCI after the second SIB reuse timer expires after the time length (640) during which the second SIB reuse timer is activated has elapsed, the terminal can determine that it has moved from the previously connected NTN cell to another cell via a vehicle, etc. Through this, the terminal may determine that the previously stored SIB cannot be reused.

[0100] FIG. 7 illustrates an operation in which a terminal determines the validity of a stored SIB in a non-terrestrial network system according to one embodiment of the present disclosure. Specifically, FIG. 7 illustrates an operation in which a PCI is determined whether it has changed due to the movement of the terminal.

[0101] According to one embodiment of the present disclosure, the terminal can determine whether the distance traveled by the terminal is shorter than a reference distance in order to determine whether the PCI has been changed by moving the terminal.

[0102] The travel distance of the terminal can be calculated by subtracting the terminal's reference position from the terminal's current position. In one example, the terminal's current position can be determined using a Global Positioning System (GPS). The terminal's reference position can be calculated as the average of the positions of multiple spots within the NTN cell to which the terminal is connected. In this case, the multiple spots may represent points where the validity of the SIB has been verified. That is, the multiple spots may be points where it has been determined that the SIB can be reused.

[0103] For example, the reference position (x, y) illustrated in FIG. 7 is the average of the positions of multiple spots ((x1, y1), (x2, y2), (x3, y3)). It can be calculated as ).

[0104] Reference distance (d th ) can be calculated as the cell diameter subtracted from the distance between cells of the same frequency as the NTN cell (710) to which the terminal is connected. For example, the reference distance (or reference value of travel distance) (d) illustrated in FIG. 7 th ) can be calculated as the value obtained by subtracting the cell diameter (725) from the distance (720) between cells of the same frequency.

[0105] According to one embodiment of the present disclosure, if the calculated travel distance of the terminal is less than a reference distance, the terminal may determine that it has not moved from its previously connected NTN cell to another cell via a vehicle, etc. Through this, the terminal may determine that it can reuse a previously stored SIB.

[0106] According to one embodiment of the present disclosure, if the calculated movement distance of the terminal is greater than the reference distance, the terminal may determine that the PCI has changed due to the movement of the terminal, rather than being changed by satellite movement. Through this, the terminal may determine that the previously stored SIB cannot be reused.

[0107] FIG. 8 is a flowchart illustrating the operation of a terminal determining the validity of a stored SIB in a non-terrestrial network system according to one embodiment of the present disclosure. Specifically, FIG. 8 illustrates the operations of a terminal connected to an NTN cell determining the validity of a SIB, including the operation of the terminal described in FIG. 4 to 6 above.

[0108] In step 805, the terminal can connect to an NTN cell. In one example, for an LTE terminal, the terminal can check whether the cell it connected to is an NTN cell by checking the PLMN ID within SIB1. For an NR terminal, the terminal can check via cellAccessRelatedInfo-NTN in SIB1 within the SIB received by the terminal, or if the frequency at which the SIB was received is a frequency allocated only by the NTN system, the terminal can confirm that the cell it connected to is an NTN cell.

[0109] In step 810, the terminal can receive a system information message from a satellite (or NTN base station) in the connected NTN cell. The terminal can decode the SIB included in the received system information message and verify the PCI indicated in the system information message.

[0110] The terminal can check the information within the decrypted SIB and store the SIB and PCI in the terminal. Hereinafter, the SIB stored by the terminal is referred to as the first SIB, and the PCI stored by the terminal is referred to as the first PCI.

[0111] In step 815, the terminal may start a SIB reuse timer for the stored first SIB. At this time, if there is already a SIB reuse timer in operation, the timer may be initialized.

[0112] The SIB reuse timer of the present disclosure may mean a timer that defines the validity period of a stored SIB in order to determine whether a terminal can reuse an existing stored SIB.

[0113] The duration of the SIB reuse timer can be set to a length that is insufficient for the terminal to visit another cell to determine whether the PCI has changed, such as when the terminal moves to a cell where the PCI of the stored SIB is not found. For example, the duration of the SIB reuse timer can be set considering the average size of an NTN cell, which is approximately 50 km (kilometers), while taking into account terminal movement by vehicle rather than walking. Additionally, the duration of the SIB reuse timer can be set based on the frequency reuse factor (FRF). The FRF is a parameter used to represent frequency efficiency, indicating how many cells the entire frequency band is divided into. For example, if the FRF value is FRF=1, all cells use the same frequency, and if the FRF value is FRF=3, the entire frequency band is divided into three cells.

[0114] The start time of the SIB reuse timer can be set to the last time when the terminal first connected to the NTN cell or checked the validity (or reusability) of the SIB. For example, when the first SIB reuse timer is activated in (B) of FIG. 6, the start time of the first SIB reuse timer may be the most recent time when the terminal checked the validity of the SIB by checking the systemInfoValueTag value in SIB 1 due to no change in PCI.

[0115] At this time, the SIB reuse timer described in the present disclosure may be operated independently of the validity period of the SIB defined in the 3GPP LTE standard (for example, the validity period of the SIB that can be stored by an LTE terminal is 3 hours, and the validity period of the SIB that can be stored by an NB-IoT or Bluetooth terminal is 24 hours). However, the validity period of the SIB defined in the standard document may also start at the same time as the start time of the SIB reuse timer.

[0116] In step 820, while the SIB reuse timer is running, the terminal can determine whether a new SIB of the same frequency as the first SIB stored in step 810 has arrived.

[0117] If it is determined that a new SIB with the same frequency as the first SIB has arrived, step 825 can be performed.

[0118] However, if a new SIB of a different frequency from the first SIB arrives, the validity of the SIB is no longer determined, and the process returns to step 810 to decode (or decode) the newly received SIB and, if the PCI is changed, the changed PCI can be stored.

[0119] Hereinafter, a new SIB received by the terminal at the same frequency as the first SIB is referred to as the second SIB, and a PCI within the second SIB is referred to as the second PCI.

[0120] In step 825, the terminal can determine whether the first PCI in the stored first SIB and the second PCI in the received second SIB are different. At this time, if the first PCI and the second PCI are different, the terminal can recognize that a change in PCI has occurred, and the terminal can perform steps 835 to 845 to determine whether the cause of the change in PCI is due to a satellite switch or another cause (e.g., the second scenario (scenario 2) and third scenario (scenario 3) of FIG. 3).

[0121] However, if the first PCI and the second PCI are identical, the terminal may perform step 830.

[0122] In step 830, the terminal can additionally determine whether the systemInfoValueTag value defined in the 3GPP LTE standard document is the same as the first SIB and the second SIB.

[0123] In one example, if the systemInfoValueTag value of the first SIB and the systemInfoValueTag value of the second SIB are the same, it may be determined that the first SIB stored by the terminal can be reused based on LTE standards. In this case, the terminal can return to step 815 to reuse the stored first SIB, initialize the SIB reuse timer that was run, and run it again.

[0124] On the other hand, if the systemInfoValueTag value of the first SIB and the systemInfoValueTag value of the second SIB are different, the terminal determines that the system information is not of the same cell and returns to step 810 to decode the newly received second SIB and store it in the terminal.

[0125] In step 835, the terminal can determine whether the frequency, first-PLMN identity, TAC, and systemInfoValueTag of each SIB1 are all the same in the stored first SIB and the received second SIB. In one example, the terminal can determine whether the carriers match by checking whether the first-PLMN identity indicated by the newly received system information message is the same as the first-PLMN identity of the stored SIB. Additionally, by checking the TAC, the terminal can determine whether the region information of the SIB in the newly received system information message matches that of the stored SIB. Finally, the terminal can determine whether the SIB version information matches by checking the systemInfoValueTag value indicated by a value from 1 to 32 in the newly received SIB and the stored SIB.

[0126] In step 835, the operation of the terminal determining whether the frequency, first-PLMN identity, TAC, and systemInfoValueTag of each SIB1 within the first SIB and the second SIB are all the same is the same as the operation described above in FIG. 4. That is, the terminal can determine whether the PCI has changed due to a change in satellite by checking whether some information within the SIB matches the stored SIB and the newly received SIB.

[0127] If the frequency, first-PLMN identity, TAC, and systemInfoValueTag of each SIB1 in the first SIB and the second SIB are all the same, step 840 can be performed.

[0128] If any of the frequency, first-PLMN identity, TAC, and systemInfoValueTag of each SIB1 in the first SIB and the second SIB are not the same, the terminal may determine that the previously stored SIB cannot be reused. Accordingly, the terminal may return to step 810 to decode (or decode) the second SIB and store the modified second PCI.

[0129] In step 840, the terminal can determine whether the changed second PCI is found in the neighbor cell list if the neighbor cell list is included in the first SIB, or if the neighbor cell list is not included in the first SIB, it can scan the PCI of the neighbor cell to determine whether the first PCI is found in the PCI of the neighbor cell.

[0130] In one example, if a list of neighboring cells is included in the first SIB and a changed second PCI is found in the list of neighboring cells, the terminal may determine that it has handed over from an NTN cell to a neighboring NTN cell. If the terminal determines that it has handed over, it may determine that the PCI was changed due to the handover rather than a change in the satellite. In this case, the terminal may return to step 810 to decode (or decode) the second SIB and store the changed second PCI.

[0131] In another example, even if the first SIB does not contain a list of neighboring cells and the first PCI is found among the PCIs of the scanned neighboring cells, the terminal may determine that it has handed over from the NTN cell to the neighboring NTN cell. When the terminal determines that it has handed over, it may determine that the PCI has changed due to the handover rather than a change in the satellite. In this case, the terminal may return to step 810 to decode (or decode) the second SIB and store the changed second PCI.

[0132] On the other hand, if the neighbor cell list is included in the first SIB and the second PCI that was changed is not found in the neighbor cell list, or if the neighbor cell list is not included in the first SIB and the first PCI is not found among the PCIs of the scanned neighbor cells, it may be determined that no change in PCI due to the terminal's handover has occurred. In this case, the terminal may continue to perform step 845.

[0133] Meanwhile, the operation of the terminal at step 840 is the same as the operation described above in FIG. 5. That is, the terminal can determine whether a handover has been performed by checking whether the newly changed PCI or the PCI of the stored SIB is found in a neighboring cell.

[0134] In step 845, the terminal can check whether the SIB reuse timer started in step 815 is still running.

[0135] In one example, if the SIB reuse timer is still running, it may be determined that the terminal has not moved to another cell via a vehicle, etc. Accordingly, the terminal can continue to perform step 850.

[0136] On the other hand, if the SIB reuse timer has already expired, the terminal may determine that the PCI was changed due to the terminal's movement rather than the PCI being changed by satellite movement. Through this, the terminal may determine that the previously stored SIB cannot be reused. Accordingly, the terminal may return to step 810 to decode (or decode) the second SIB and store the changed second PCI.

[0137] The operation of the terminal in step 845 is the same as the operation of the terminal described in FIG. 6. That is, the terminal moves to a cell where the PCI of the stored SIB is not found, and in order to determine whether the PCI has changed, the terminal runs a SIB reuse timer with a time length that is not sufficient for the terminal to visit another cell, and can determine whether a change in the PCI has been detected while the SIB reuse timer is running.

[0138] In step 850, the terminal can determine that it can reuse the stored first SIB instead of the newly received second SIB. That is, the terminal can identify the SIB of the NTN cell to which the terminal is connected as the first SIB.

[0139] Additionally, the terminal can update the PCI. For example, the terminal can change the PCI from the stored first PCI to the second PCI.

[0140] Although omitted in this drawing, the terminal can then initialize the SIB reuse timer that was operated in step 815 and operate the SIB reuse timer again.

[0141] By reusing existing stored SIBs instead of decoding newly received SIBs, the terminal can effectively reduce the processing time and power waste associated with unnecessarily decoding SIBs. Furthermore, the probability of overhead occurring when decoding is performed every time a SIB is received can also be significantly reduced.

[0142] FIG. 9 is a flowchart illustrating an operation in which a terminal determines the validity of a stored SIB in a non-terrestrial network system according to one embodiment of the present disclosure. Specifically, FIG. 9 illustrates operations in which a terminal connected to an NTN cell optionally performs the operations of FIG. 4 to FIG. 6 described above to determine the validity of the SIB.

[0143] Since the operations of steps 905 to 950 illustrated in FIG. 9 are identical to the operations of steps 805 to 850 illustrated in FIG. 8, the specific description of the terminal's operation will be omitted.

[0144] According to one embodiment of the present disclosure, operations considering three scenarios in which the PCI described in FIG. 4 is changed (the first scenario is when the satellite is changed, the second scenario is when the terminal handovers to a neighbor cell and the PCI of the SIB stored in the terminal is confirmed in the neighbor cell, and when there is a change in the connected cell due to the movement of the terminal) may be performed optionally. For example, when the terminal determines whether the existing stored SIB can be reused, at least one of the terminal's operations considering the scenario in which the PCI is changed, such as steps 935, 940, and 945, may be omitted.

[0145] In one example, the terminal can determine whether the SIB can be reused without determining whether the first-PLMN identity, TAC, and systemInfoValueTag represented in SIB 1 within the stored first SIB and the newly received second SIB are all the same. For example, the terminal can determine whether the stored SIB can be reused by performing the remaining operations without performing step 935 of FIG. 9.

[0146] In another example, the terminal can determine whether the SIB can be reused without determining whether a handover has been performed based on whether the second PCI or the first PCI of the stored first SIB is found in a neighboring cell. For example, the terminal can determine whether the stored SIB can be reused by performing the remaining operations without performing step 940 of FIG. 9.

[0147] In another example, the terminal can determine whether the SIB can be reused without driving the SIB reuse timer. For example, the terminal can determine whether the stored SIB can be reused by performing the remaining operations without performing step 945 of FIG. 9. In this case, the terminal may also omit step 915, which drives the SIB reuse timer.

[0148] In addition, the terminal may perform only one of the terminal operations, steps 935, 940, and 945, which are considered scenarios in which the PCI is changed.

[0149] When selectively performing steps 915, 935, 940, or 945 as described above, the processing time for the terminal to determine whether the SIB can be reused can be reduced. However, in this case, the PCI change factor may be less clearly identified than when all steps are performed as shown in FIG. 8.

[0150] FIG. 10 is a flowchart illustrating operations in which a terminal determines the validity of a stored SIB in a non-terrestrial network system according to one embodiment of the present disclosure. Specifically, FIG. 10 illustrates operations in which a terminal determines whether to reuse a SIB without driving a SIB reuse timer.

[0151] Since the operations of steps 1005 and 1010 illustrated in FIG. 10 are identical to the operations of steps 805 and 810 illustrated in FIG. 8, and the operations of steps 1015 to 1035 are identical to the operations of steps 820 to 840 illustrated in FIG. 8, the description of the specific operations of the terminal is omitted.

[0152] According to one embodiment of the present disclosure, in addition to the method of determining whether the PCI has changed due to the movement of the terminal by driving the SIB reuse timer described in FIG. 8, the terminal can determine whether the PCI has changed due to the movement of the terminal by comparing the distance the terminal has moved with a reference distance.

[0153] A terminal that has performed the operations of steps 1010 to 1020 and steps 1030 to 1035 can perform step 1040.

[0154] In step 1040, the terminal can determine whether the terminal's travel distance is shorter than the reference distance.

[0155] The travel distance of the terminal can be calculated by subtracting the terminal's reference position from the terminal's current position. The terminal's reference position can be calculated as the average of the positions of multiple spots in the NTN cell to which the terminal is connected. In this case, the multiple spots may represent points where the validity of the SIB has been verified.

[0156] Also, reference distance (d th ) can be calculated as the value obtained by subtracting the cell diameter from the distance between cells of the same frequency as the NTN cell to which the terminal is connected.

[0157] According to one embodiment of the present disclosure, if the calculated travel distance of the terminal is less than the reference distance, the terminal may determine that it has not moved from its previously connected NTN cell to another cell via a vehicle, etc. Through this, the terminal may determine that it can reuse the previously stored SIB. In this case, the terminal may continue to perform step 1045.

[0158] According to one embodiment of the present disclosure, if the calculated movement distance of the terminal is greater than the reference distance, the terminal may determine that the PCI has been changed due to the movement of the terminal, rather than the change in the PCI due to satellite movement. Through this, the terminal may determine that the previously stored SIB cannot be reused. In this case, the terminal may return to step 1010 to decode (or decode) the second SIB and store the changed second PCI.

[0159] The operation of the terminal in step 1040 is the same as the operation of the terminal described in FIG. 7. That is, the terminal can determine whether the distance traveled by the terminal is shorter than the reference distance in order to determine whether the PCI has been changed by moving the terminal.

[0160] In step 1045, the terminal may determine that it can reuse the stored first SIB instead of the newly received second SIB. That is, the terminal may identify the SIB of the NTN cell to which the terminal is connected as the first SIB. Additionally, the terminal may update the PCI. For example, the terminal may change the PCI from the stored first PCI to the second PCI.

[0161] Although omitted in this drawing, the terminal can return to step 1015 to determine again whether a new SIB of the same frequency as the stored first SIB has arrived.

[0162] As described above, the terminal can effectively reduce the processing time and power waste associated with unnecessarily decoding SIBs by reusing existing stored SIBs instead of decoding newly received SIBs. Furthermore, the probability of overhead occurring when decoding is performed every time a SIB is received can also be significantly reduced.

[0163] FIG. 11 is a flowchart illustrating the operation of a terminal determining the validity of a stored SIB in a non-terrestrial network system according to one embodiment of the present disclosure. Specifically, FIG. 11 illustrates the operations of a terminal connected to an NTN cell to optionally perform the operations of FIG. 4, FIG. 5, and FIG. 7 described above to determine the validity of the SIB.

[0164] Since the operations of steps 1105 to 1145 illustrated in FIG. 11 are identical to the operations of steps 1005 to 1045 illustrated in FIG. 10, the description of the specific operation of the terminal is omitted.

[0165] According to one embodiment of the present disclosure, operations considering three scenarios in which the PCI described in FIG. 4 is changed (the first scenario is when the satellite is changed, the second scenario is when the terminal handovers to a neighbor cell and the PCI of the SIB stored in the terminal is confirmed in the neighbor cell, and when there is a change in the connected cell due to the movement of the terminal) may be performed optionally. For example, when the terminal determines whether the existing stored SIB can be reused, at least one of the terminal operations considering the scenario in which the PCI is changed, such as steps 1130, 1135, and 1140, may be omitted.

[0166] In one example, the terminal can determine whether the SIB can be reused without determining whether the first-PLMN identity, TAC, and systemInfoValueTag represented in SIB 1 within the stored first SIB and the newly received second SIB are all the same. For example, the terminal can determine whether the stored SIB can be reused by performing the remaining operations without performing step 1130 of FIG. 11.

[0167] In another example, the terminal may determine whether the SIB can be reused without determining whether a handover has been performed based on whether the second PCI or the first PCI of the stored first SIB is found in a neighboring cell. For example, the terminal may determine whether the stored SIB can be reused by performing the remaining operations without performing step 1135 of FIG. 11.

[0168] In another example, the terminal can determine whether the SIB can be reused without determining whether the terminal's travel distance is shorter than a reference distance. For example, the terminal can determine whether the stored SIB can be reused by performing the remaining operations without performing step 1140 of FIG. 11.

[0169] In addition, the terminal may perform only one of the terminal operations, steps 1130, 1135, and 1140, which are terminal operations considering a scenario in which the PCI is changed.

[0170] When steps 1130, 1135, and 1140 are performed selectively as described above, the processing time for the terminal to determine whether the SIB can be reused can be reduced. However, in this case, the PCI change factor may be less clearly identified than when all steps are performed as shown in FIG. 10.

[0171] FIG. 12 illustrates the operation of a terminal in a non-terrestrial network system according to one embodiment of the present disclosure. FIG. 12 assumes a situation in which a terminal connected to a first cell, which is an NTN cell, receives a second SIB, which is a new SIB, after receiving a first SIB from a satellite (or an NTN base station connected to the satellite). At this time, the terminal may receive the first SIB from the first NTN base station and receive the second SIB from the second NTN base station.

[0172] Referring to FIG. 12, in step 1210, the terminal may receive a first system information (SI) message from the first NTN base station, which includes a first SIB and a first PCI for the first cell. The first PCI may represent characteristics of the first cell formed by the first NTN base station.

[0173] In step 1220, the terminal can store the first SIB and the first PCI. At this time, the terminal can decode the first SIB to identify the information contained within the first SIB and then store the first SIB in the terminal.

[0174] In step 1230, the terminal can receive a second SI message including a second SIB and a second PCI from a second NTN base station.

[0175] At this time, whether the second SIB and the second PCI relate to the first cell can be determined through the operation of steps 1240 to 1260.

[0176] In step 1240, the terminal can determine whether the second SIB received from the second NTN base station is received at the same frequency as the first SIB stored in the terminal in step 1220.

[0177] If the second SIB is received at the same frequency as the first SIB stored therein, the terminal may continue to perform step 1250.

[0178] According to one embodiment of the present disclosure, if a newly received SIB is received at a frequency different from that of a stored SIB, the terminal can determine that the stored SIB is not a change in PCI due to satellite variation and identify that the stored SIB is invalid. That is, if a newly received SIB is not received at the same frequency as the SIB stored by the terminal, it may not be determined that the PCI is a change due to satellite variation. Meanwhile, the operation of the terminal in step 1240 illustrated in FIG. 12 is the same as the operation in step 820 of FIG. 8.

[0179] In step 1255, if it is determined that the second SIB is not received at the same frequency as the first SIB, the terminal can decode (or decode) the second SIB without further determining the validity of the SIB or identifying the second SIB as the first SIB. Additionally, if the first PCI and the second PCI are different, the changed second PCI can be updated as the PCI for the first NTN cell.

[0180] In step 1250, the terminal can determine whether the second PCI and the first PCI are different. Since this is a case where the satellite is changed in the same NTN cell proposed in the present disclosure, it can determine whether the PCI is changed due to the change in the satellite. At this time, if the first PCI and the second PCI are different, the terminal can recognize that a change in PCI has occurred, and the terminal can perform step 1260 to determine whether the cause of the change in PCI is due to a change in the satellite (switch) or another cause (e.g., the second scenario (scenario 2) and third scenario (scenario 3) of FIG. 3).

[0181] According to one embodiment of the present disclosure, when the first PCI and the first PCI are identical, it does not correspond to a case where the satellite changes when the PCI does not change; therefore, it is determined that the change in PCI is not due to a change in the satellite, and thus the stored SIB can be identified as invalid. That is, if a newly received SIB is not received on the same frequency as the SIB stored by the terminal, it may not be determined that the change in PCI is due to a change in the satellite. In this case, the aforementioned step 1255 may be performed so that the second SIB is not identified as the first SIB. That is, the terminal may not reuse the existing stored first SIB.

[0182] According to one embodiment of the present disclosure, an LTE-based terminal may additionally determine whether the systemInfoValueTag value defined in the 3GPP LTE standard document is the same as the first SIB and the second SIB when the first PCI and the first PCI are the same (e.g., step 830 of FIG. 8). In one example, if the systemInfoValueTag value of the first SIB and the systemInfoValueTag value of the second SIB are the same, it may be determined that the first SIB stored by the terminal can be reused based on the LTE standard. In this case, the terminal may reuse the first SIB, initialize the SIB reuse timer that was activated, and activate it again. On the other hand, if the systemInfoValueTag value of the first SIB and the systemInfoValueTag value of the second SIB are different, the terminal may determine that they are not system information of the same cell, decode the newly received second SIB, and store it in the terminal.

[0183] Meanwhile, the operation of the terminal at step 1240 shown in FIG. 12 is the same as the operation at step 820 in FIG. 8.

[0184] In step 1260, the terminal can determine whether the second SIB is identified as the first SIB. That is, the terminal can determine whether the first SIB can be reused as the SIB for the NTN cell to which it is connected even after receiving the second SIB.

[0185] According to one embodiment of the present disclosure, a terminal can determine whether the first SIB can be reused by using a SIB reuse timer for the stored first SIB. The SIB reuse timer may refer to a timer that defines the validity period of the stored SIB in order for the terminal to determine whether the existing stored SIB can be reused.

[0186] The SIB reuse timer may be activated to prevent the PCI from changing as the terminal moves to another cell via a vehicle, etc., rather than the satellite changing within the same NTN cell. In one example, the terminal may activate the SIB reuse timer after storing the first SIB and before receiving the second SIB. Steps 1230 through 1250 may be performed while the SIB reuse timer is activated, and if the second SIB is received at the same frequency as the second SIB while the SIB reuse timer is activated and the second PCI is different from the second PCI, it may be determined that the terminal has not moved to another cell via a vehicle, etc. Accordingly, the terminal may determine that the stored first SIB can be reused and identify the second SIB as the first SIB.

[0187] On the other hand, if the SIB reuse timer has already expired, the terminal may determine that the PCI was changed due to the terminal's movement, rather than the PCI being changed by satellite movement. Through this, the terminal may determine that the previously stored SIB cannot be reused. Accordingly, the terminal may not identify the second SIB as the first SIB. That is, the terminal may not reuse the previously stored first SIB. The terminal may decode the second SIB and update the first PCI to the second PCI.

[0188] The SIB reuse timer can start from the time when the first cell is first connected or from the last time when the reuse of the first SIB is determined.

[0189] The time length of the SIB reuse timer may be set to a length that is insufficient for the terminal to visit another cell to determine whether the PCI has changed, such that the terminal moves to a cell where the PCI of the stored SIB is not found. For example, the time length of the SIB reuse timer may be set considering the average size of an NTN cell, which is approximately 50 km (kilometers), but taking into account the movement of the terminal by vehicle rather than walking. Additionally, the time length of the SIB reuse timer may be set based on the frequency reuse factor (FRF).

[0190] The operation of the terminal that determines whether the second SIB is identified as the first SIB using the SIB reuse timer is the same as the operation of the terminal described above in FIG. 6. That is, the terminal moves to a cell where the PCI of the stored SIB is not found, and in order to determine whether the PCI has changed, the terminal drives the SIB reuse timer with a time length that is not sufficient for the terminal to visit another cell, and can determine whether a change in the PCI has been detected while the SIB reuse timer is running.

[0191] According to one embodiment of the present disclosure, a terminal can determine whether the first-PLMN identity, TAC, and systemInfoValueTag of each SIB1 are all the same in the stored first SIB and the received second SIB. In one example, the terminal can determine whether the carriers match by checking whether the first-PLMN identity indicated by the newly received system information message is the same as the first-PLMN identity of the stored SIB. Additionally, by checking the TAC, the terminal can determine whether the region information of the SIB of the newly received system information message matches that of the stored SIB. Finally, the terminal can determine whether the SIB version information matches by checking the systemInfoValueTag value indicated by a value of 1 to 32 in the newly received SIB and the stored SIB.

[0192] The operation of determining whether the first-PLMN identity, TAC, and systemInfoValueTag of the first SIB and the second SIB are all the same is the same as the operation described above in FIG. 4. That is, the terminal can determine whether the PCI has changed due to a change in satellite by checking whether some information within the SIB matches the stored SIB and the newly received SIB.

[0193] If the first-PLMN identity, TAC, and systemInfoValueTag of the first SIB and the second SIB are all the same, the second SIB can be identified as the first SIB.

[0194] If any of the frequency, first-PLMN identity, TAC, and systemInfoValueTag of each SIB1 within the first SIB and the second SIB are not identical, the terminal may determine that the previously stored first SIB cannot be reused. Accordingly, the terminal may not identify the second SIB as the first SIB. That is, the terminal may not reuse the previously stored first SIB. The terminal may decode (or decode) the second SIB and update the first PCI to the second PCI.

[0195] According to one embodiment of the present disclosure, the terminal may determine whether a changed second PCI is found in a neighbor cell list when a neighbor cell list is included in a first SIB, or, when a neighbor cell list is not included in a first SIB, scan the PCI of a neighbor cell to determine whether the first PCI is found in the PCI of a neighbor cell.

[0196] In one example, if a list of neighboring cells is included within the first SIB and a changed second PCI is found in the list of neighboring cells, the terminal may determine that it has handed over from an NTN cell to a neighboring NTN cell. When the terminal determines that it has handed over, it may determine that the PCI was changed due to the handover rather than a change in the satellite. In this case, the terminal may not identify the second SIB as the first SIB. That is, the terminal may not reuse the existing stored first SIB. The terminal may decode the second SIB and update the first PCI to the second PCI.

[0197] In another example, even if the first SIB does not contain a list of neighboring cells and the first PCI is found among the PCIs of the scanned neighboring cells, the terminal may determine that it has handed over from an NTN cell to a neighboring NTN cell. If the terminal determines that a handover has occurred, it may determine that the PCI has changed due to the handover rather than a change in satellite. In this case, the terminal may not identify the second SIB as the first SIB. The terminal may decode the second SIB and update the first PCI to the second PCI.

[0198] On the other hand, if the neighbor cell list is included within the first SIB and the second PCI that has been changed is not found in the neighbor cell list, or if the neighbor cell list is not included within the first SIB and the first PCI is not found among the PCIs of the scanned neighbor cells, it may be determined that no change in PCI due to the terminal's handover has occurred. In this case, the terminal may determine that the stored first SIB can be reused and identify the second SIB as the first SIB.

[0199] Meanwhile, this operation of the terminal is the same as the operation described above in FIG. 5. That is, the terminal can determine whether a handover has been performed by checking whether the newly changed PCI or the PCI of the stored SIB is found in a neighboring cell.

[0200] According to one embodiment of the present disclosure, the terminal may determine that it can reuse the stored first SIB instead of the newly received second SIB. That is, the terminal may identify the SIB of the NTN cell to which the terminal is connected as the first SIB. Additionally, the terminal may update the PCI. For example, the terminal may change the PCI from the stored first PCI to the second PCI.

[0201] The exemplary operations for determining whether such a terminal can identify the second SIB as the first SIB are optional operations that may be performed individually or sequentially. For example, as illustrated in FIG. 8 or FIG. 10, the terminal may determine whether the first SIB can be reused by sequentially performing steps 835 through 845 of FIG. 8 and steps 1030 through 1040 of FIG. 10.

[0202] As described above, when the terminal receives a new SIB in addition to the previously stored SIB, it can effectively reduce the processing time and power waste associated with unnecessarily decoding SIBs by additionally determining whether the stored SIB can be reused without decoding all SIBs. Furthermore, the probability of overhead occurring when decoding is performed every time a SIB is received can also be significantly reduced.

[0203] FIG. 13 illustrates the structure of a terminal (1300) according to various embodiments of the present disclosure.

[0204] The configuration exemplified in FIG. 13 can be understood as a configuration of a terminal (1300). Terms such as '...part', '...unit' used below refer to a unit that processes at least one function or operation, and this can be implemented as hardware or software, or a combination of hardware and software.

[0205] Referring to FIG. 13, the terminal (1300) includes a communication unit (1310), a storage unit (1320), and a control unit (1330).

[0206] The communication unit (1310) performs functions for transmitting and receiving signals through a wireless channel. For example, the communication unit (1310) performs a conversion function between a baseband signal and a bit sequence according to the physical layer specifications of the system. For example, when transmitting data, the communication unit (1310) generates complex symbols by encoding and modulating the transmitted bit sequence. Also, when receiving data, the communication unit (1310) restores the received bit sequence by demodulating and decoding the baseband signal. Additionally, the communication unit (1310) upconverts the baseband signal into an RF band signal and transmits it through an antenna, and downconverts the RF band signal received through the antenna into a baseband signal. For example, the communication unit (1310) may include a transmission filter, a reception filter, an amplifier, a mixer, an oscillator, a DAC, an ADC, etc.

[0207] Additionally, the communication unit (1310) may include a plurality of transmission and reception paths. Furthermore, the communication unit (1310) may include an antenna unit. The communication unit (1310) may include at least one antenna array composed of a plurality of antenna elements. In terms of hardware, the communication unit (1310) may be composed of a digital circuit and an analog circuit (e.g., a radio frequency integrated circuit (RFIC)). Here, the digital circuit and the analog circuit may be implemented as a single package. Additionally, the communication unit (1310) may include a plurality of RF chains. The communication unit (1310) may perform beamforming. The communication unit (1310) may apply beamforming weights to a signal to impart directionality according to the settings of the control unit (1330) to the signal to be transmitted or received. According to one embodiment, the communication unit (1310) may include a radio frequency (RF) block (or RF unit). The RF block may include a first RF circuitry associated with the antenna and a second RF circuitry associated with baseband processing. The first RF circuitry may be referred to as RF-A (antenna). The second RF circuitry may be referred to as RF-B (baseband).

[0208] Additionally, the communication unit (1310) can transmit and receive signals. To this end, the communication unit (1310) may include at least one transceiver. The communication unit (1310) can receive downlink signals. The downlink signal may include a synchronization signal (SS), a reference signal (RS) (e.g., DM (demodulation)-RS, PTRS (phase tracking reference signal)), system information (e.g., MIB, SIB, RMSI (remaining system information), OSI (other system information)), a configuration message, control information, or downlink data. Additionally, the communication unit (1110) may transmit an uplink signal. The uplink signal may include a random access related signal (e.g., random access preamble (RAP) (or Msg1 (message 1)), Msg3 (message 3)), a reference signal (e.g., SRS (sounding reference signal), DMRS, PTRS), or a power headroom report (PHR).

[0209] Additionally, the communication unit (1310) may include different communication modules to process signals of different frequency bands. Furthermore, the communication unit (1310) may include multiple communication modules to support multiple different wireless access technologies. For example, different wireless access technologies may include Bluetooth Low Energy (BLE), Wi-Fi (Wireless Fidelity), WiGig (WiFi Gigabyte), cellular networks (e.g., LTE (Long Term Evolution), NR (new radio), etc. Additionally, different frequency bands may include super high frequency (SHF) bands (e.g., 2.5 GHz, 5 GHz) and millimeter wave bands (e.g., 38 GHz, 60 GHz, etc.). Additionally, the communication unit (1310) may use the same type of wireless access technology on different frequency bands (e.g., unlicensed band for LAA (licensed Assisted Access), CBRS (citizens broadband radio service) (e.g., 3.5 GHz)).

[0210] The communication unit (1310) transmits and receives signals as described above. Accordingly, all or part of the communication unit (1310) may be referred to as a 'transmitter', a 'receiver', or a 'transmitter / receiver'. Furthermore, in the following description, transmission and reception performed via a wireless channel are used to mean that processing as described above is performed by the communication unit (1310).

[0211] The storage unit (1320) stores data such as basic programs, application programs, and setting information for the operation of the terminal (1300). The storage unit (1320) may be composed of volatile memory, non-volatile memory, or a combination of volatile memory and non-volatile memory. Additionally, the storage unit (1320) provides the stored data upon the request of the control unit (1330).

[0212] The control unit (1330) controls the overall operations of the terminal (1300). For example, the control unit (1330) transmits and receives signals through the communication unit (1310). Additionally, the control unit (1330) writes and reads data to and from the storage unit (1320). Furthermore, the control unit (1330) can perform the functions of the protocol stack required by the communication standard. To this end, the control unit (1330) may include at least one processor. The control unit (1330) may include at least one processor or microprocessor, or may be part of a processor. Additionally, part of the communication unit (1310) and the control unit (1330) may be referred to as CP. The control unit (1330) may include various modules for performing communication. According to various embodiments, the control unit (1330) may control the terminal to perform operations according to various embodiments.

[0213] FIG. 14 illustrates the structure of a base station (1400) according to various embodiments of the present disclosure.

[0214] Referring to FIG. 14, the base station (1400) includes a communication unit (1410), a storage unit (1420), and a control unit (1430).

[0215] The communication unit (1410) performs functions for transmitting and receiving signals through a wireless channel. For example, the communication unit (1410) performs a conversion function between a baseband signal and a bit sequence according to the physical layer specifications of the system. For example, when transmitting data, the communication unit (1410) generates complex symbols by encoding and modulating the transmitted bit sequence. Also, when receiving data, the communication unit (1410) restores the received bit sequence by demodulating and decoding the baseband signal. Additionally, the communication unit (1410) upconverts the baseband signal into an RF (radio frequency) band signal and transmits it through an antenna, and downconverts the RF band signal received through the antenna into a baseband signal.

[0216] To this end, the communication unit (1410) may include a transmission filter, a reception filter, an amplifier, a mixer, an oscillator, a digital-to-analog converter (DAC), an analog-to-digital converter (ADC), etc. Additionally, the communication unit (1410) may include a plurality of transmission and reception paths. Furthermore, the communication unit (1410) may include at least one antenna array composed of a plurality of antenna elements. In terms of hardware, the communication unit (1410) may be composed of a digital unit and an analog unit, and the analog unit may be composed of a plurality of sub-units according to operating power, operating frequency, etc.

[0217] The communication unit (1410) can transmit and receive signals. To this end, the communication unit (1410) may include at least one transceiver. For example, the communication unit (1410) can transmit a synchronization signal, a reference signal, system information, a message, control information, or data. Additionally, the communication unit (1410) can perform beamforming.

[0218] The communication unit (1410) transmits and receives signals as described above. In particular, the communication unit (1410) receives information or messages from a satellite and can transmit the received information or messages to a terminal.

[0219] All or part of the communication unit (1410) may be referred to as a 'transmitter', 'receiver', or 'transmit / receiver'. Additionally, in the following description, transmission and reception performed via a wireless channel are used to mean that processing as described above is performed by the communication unit (1410).

[0220] The storage unit (1420) stores data such as basic programs, application programs, and configuration information for the operation of the base station. The storage unit (1420) may include memory. The storage unit (1420) may be composed of volatile memory, non-volatile memory, or a combination of volatile memory and non-volatile memory. Additionally, the storage unit (1420) provides the stored data upon the request of the control unit (1430).

[0221] The control unit (1430) controls the overall operations of the base station (1400). For example, the control unit (1430) transmits and receives signals through the communication unit (1410). In addition, the control unit (1430) writes and reads data to and from the storage unit (1420). Furthermore, the control unit (1430) can perform the functions of a protocol stack required by the communication standard. To this end, the control unit (1430) may include at least one processor.

[0222] The configuration of the base station (1400) shown in FIG. 14 is merely one example of a base station, and the examples of base stations for performing various embodiments of the present disclosure are not limited to the configuration shown in FIG. 14. That is, depending on various embodiments, some configurations may be added, deleted, or changed.

[0223] In FIG. 14, the base station (1400) is described as a single entity, but the present disclosure is not limited thereto. According to various embodiments of the present disclosure, the base station (1400) may be implemented to form an access network having a distributed deployment as well as an integrated deployment. According to one embodiment, the base station may be distinguished into a central unit (CU) and a digital unit (DU), wherein the CU may be implemented to perform upper layer functions (e.g., packet data convergence protocol, RRC) and the DU may be implemented to perform lower layer functions (e.g., medium access control (MAC), physical (PHY)). The DU of the base station may form beam coverage on a wireless channel.

[0224] FIG. 15 illustrates the structure of a network entity (1500) according to an embodiment of the present disclosure.

[0225] A network entity according to one embodiment of the present disclosure may include a control unit (1530) that controls the overall operation of the network entity, a communication unit (1510) including a transmitting unit and a receiving unit, and a memory (1510). Of course, it is not limited to the above examples, and the network entity may include more or fewer configurations than the configuration shown in FIG. 15.

[0226] According to one embodiment of the present disclosure, a communication unit (1510) can transmit and receive signals with at least one of other network entities (such as base stations) or terminals. The signals transmitted and received with at least one of other network entities or terminals may include control information and data.

[0227] According to one embodiment of the present disclosure, the control unit (1530) can control a network entity to perform any one of the above-described embodiments. Meanwhile, the control unit (1530), the storage unit (1520), and the communication unit (1510) do not necessarily have to be implemented as separate modules, and can be implemented as a single component in the form of a single chip. Also, the control unit (1530) and the communication unit (1510) can be electrically connected. Furthermore, the control unit (1530) may be an Application Processor (AP), a Communication Processor (CP), a circuit, an application-specific circuit, or at least one processor.

[0228] According to one embodiment of the present disclosure, the storage unit (1520) may store data such as a basic program, an application program, and configuration information for the operation of a network entity. In particular, the storage unit (1520) provides the stored data upon a request from the control unit (1530). The storage unit (1520) may be composed of a storage medium or a combination of storage media such as ROM, RAM, a hard disk, a CD-ROM, and a DVD. Additionally, the storage unit (1520) may be a plurality of units. Furthermore, the control unit (1530) may perform the aforementioned embodiments based on a program for performing the aforementioned embodiments of the present disclosure stored in the storage unit (1520).

[0229] Meanwhile, the embodiments of the present invention disclosed in this specification and drawings are merely specific examples provided to facilitate the explanation of the technical content of the present invention and to aid in understanding the invention, and are not intended to limit the scope of the invention. That is, it is obvious to those skilled in the art that other variations based on the technical concept of the present invention are possible. Furthermore, each of the above embodiments may be combined and operated together as needed.

[0230] As described above, a method performed by a user equipment in a wireless communication system using a non-terrestrial network (NTN) according to various embodiments disclosed in this document may include: receiving a first SI message from a first NTN base station comprising a first SIB (system information block) and a first PCI (physical cell identity) for a first cell; storing the first SIB and the first PCI; receiving a second SI message from a second NTN base station comprising a second SIB and a second PCI; identifying whether the second SIB is received at the same frequency as the first SIB; identifying whether the second PCI is different from the first PCI when the second SIB is received at the same frequency as the first SIB; and determining whether the second SIB is identified as the first SIB when the second PCI is different from the first PCI.

[0231] According to various embodiments disclosed in this document, the step of determining whether a second SIB is identified as the first SIB further includes the step of driving a SIB reuse timer for the first SIB and the step of determining whether a second SI message is received before the SIB reuse timer expires, and if a second SI message is received before the SIB reuse timer expires, the second SIB is identified as the first SIB, and the second PCI may be different from the first PCI.

[0232] According to various embodiments disclosed in this document, the step of determining whether a second SIB is identified as a first SIB further includes the step of determining whether the values ​​of a PLMN ID (public land mobile network identity), a TAC (tracking area code), and a systemInfoValueTag indicated by the first SIB match the values ​​of a PLMN ID, a TAC, and a systemInfoValueTag indicated by the second SIB, and if the values ​​of a PLMN ID, a TAC, and a systemInfoValueTag indicated by the first SIB are all identical to the values ​​of a PLMN ID, a TAC, and a systemInfoValueTag indicated by the second SIB, the second SIB may be identified as the first SIB.

[0233] According to various embodiments disclosed in this document, the step of determining whether a second SIB is identified as a first SIB further includes, if the first SIB contains a list of second cells adjacent to a first cell, a step of identifying whether the list of second cells contains a second PCI, or if the first SIB does not contain a list of second cells, a step of identifying whether the PCI of the second cell is the same as the first PCI, and if the list of second cells contains a second PCI, or if the PCI of the second cell is the same as the first PCI, the second SIB may be identified as the first SIB.

[0234] According to various embodiments disclosed in this document, the step of determining whether a second SIB is identified as a first SIB further includes the step of calculating the travel distance of a terminal, and if the travel distance of the terminal is shorter than a reference distance, the second SIB is identified as a first SIB, and if the travel distance of the terminal is longer than a reference distance, the second SIB may not be identified as a first SIB.

[0235] According to various embodiments disclosed in this document, the SIB reuse timer is started from the timepoint when the terminal is connected to the first cell or from the last time when the terminal previously identified the SIB of the first cell, and the length of the SIB reuse timer can be set based on the frequency reuse factor (FRF).

[0236] According to various embodiments disclosed in this document, if the second SI message is not received at the same frequency as the first SI message, the second SIB may not be identified as the first SIB. That is, the terminal may not reuse the existing stored first SIB.

[0237] According to various embodiments disclosed in this document, when the second SIB is identified as the first SIB, the first PCI stored in the terminal is updated to the second PCI, and the second SIB may not be decoded.

[0238] According to various embodiments disclosed in this document, if the second SIB is not identified as the first SIB, the first PCI stored in the terminal may be updated to the second PCI, the second SIB may be decoded, and the first SIB stored in the terminal may be updated to the second SIB. That is, the terminal may decode the newly received second SIB without reusing the existing stored first SIB.

[0239] According to various embodiments disclosed in this document, the travel distance of the terminal is calculated by subtracting the reference position of the terminal from the position of the terminal, the reference distance is calculated by subtracting the diameter of the first cell from the distance between cells of the same frequency as the first cell, and the reference position of the terminal can be calculated as the average of the positions of a plurality of spots within the first cell.

[0240] As described above, in a wireless communication system using a non-terrestrial network (NTN) according to various embodiments disclosed in this document, a terminal (user equipment) includes a transceiver and a controller coupled to the transceiver, and the controller may be configured to receive a first SI message including a first SIB (system information block) and a first PCI (physical cell identity) for a first cell from a first NTN base station, store the first SIB and the first PCI, receive a second SI message including a second SIB and a second PCI from a second NTN base station, identify whether the second SIB is received at the same frequency as the first SIB, identify whether the second PCI is different from the first PCI if the second SIB is received at the same frequency as the first SIB, and determine whether the second SIB is identified as the first SIB if the second PCI is different from the first PCI.

[0241] According to various embodiments disclosed in this document, the controller is further configured to drive a SIB reuse timer for a first SIB and to identify whether a second SI message is received before the SIB reuse timer expires, and if a second SI message is received before the SIB reuse timer expires, the second SIB is identified as the first SIB, and the second PCI may be different from the first PCI.

[0242] According to various embodiments disclosed in this document, the controller is further configured to identify whether the values ​​of the public land mobile network identity (PLMN ID), tracking area code (TAC), and systemInfoValueTag indicated by the first SIB match the values ​​of the PLMN ID, TAC, and systemInfoValueTag indicated by the second SIB, and if the values ​​of the PLMN ID, TAC, and systemInfoValueTag indicated by the first SIB are all identical to the values ​​of the PLMN ID, TAC, and systemInfoValueTag indicated by the second SIB, the second SIB can be identified as the first SIB. That is, the terminal can reuse the existing stored first SIB.

[0243] According to various embodiments disclosed in this document, the controller is further configured to identify whether a second PCI is included in the list of second cells adjacent to a first cell when the first SIB contains a list of second cells, or to identify whether the PCI of the second cell is the same as the first PCI when the first SIB does not contain a list of second cells, and if the list of second cells contains a second PCI or the PCI of the second cell is the same as the first PCI, the second SIB can be identified as the first SIB. That is, the terminal can reuse the existing stored first SIB.

[0244] According to various embodiments disclosed in this document, the controller is further configured to calculate the travel distance of the terminal, and if the travel distance of the terminal is shorter than the reference distance, the second SIB is identified as the first SIB, and if the travel distance of the terminal is longer than the reference distance, the second SIB may not be identified as the first SIB. That is, the terminal may not reuse the existing stored first SIB.

[0245] According to various embodiments disclosed in this document, the SIB reuse timer is started from the timepoint when the terminal is connected to the first cell or from the last time when the terminal previously identified the SIB of the first cell, and the length of the SIB reuse timer can be set based on the frequency reuse factor (FRF).

[0246] According to various embodiments disclosed in this document, if the second SI message is not received at the same frequency as the first SI message, the second SIB may not be identified as the first SIB. That is, the terminal may not reuse the existing stored first SIB.

[0247] According to various embodiments disclosed in this document, when the second SIB is identified as the first SIB, the first PCI stored in the terminal is updated to the second PCI, and the second SIB may not be decoded.

[0248] According to various embodiments disclosed in this document, if the second SIB is not identified as the first SIB, the first PCI stored in the terminal may be updated to the second PCI, the second SIB may be decoded, and the first SIB stored in the terminal may be updated to the second SIB.

[0249] According to various embodiments disclosed in this document, the travel distance of the terminal is calculated by subtracting the reference position of the terminal from the position of the terminal, the reference distance is calculated by subtracting the diameter of the first cell from the distance between cells of the same frequency as the first cell, and the reference position of the terminal can be calculated as the average of the positions of a plurality of spots within the first cell.

Claims

1. A method performed by a terminal (user equipment) in a wireless communication system using a non-terrestrial network (NTN), A step of receiving a first SI message from a first NTN base station, the message including a first SIB (system information block) and a first PCI (physical cell identity) for a first cell; A step of storing the first SIB and the first PCI; A step of receiving a second SI message including a second SIB and a second PCI from a second NTN base station; A step of identifying whether the second SIB is received at the same frequency as the first SIB; A step of identifying whether the second PCI is different from the first PCI when the second SIB is received at the same frequency as the first SIB; and A method comprising the step of determining whether the second SIB is identified as the first SIB when the second PCI is different from the first PCI.

2. In claim 1, the step of determining whether the second SIB is identified as the first SIB is: Step of driving a SIB reuse timer for the first SIB; and The method further includes a step of identifying whether the second SI message was received before the above SIB reuse timer expires, and If the second SI message is received before the SIB reuse timer expires, the second SIB is identified as the first SIB, and The above second PCI is a method different from the above first PCI.

3. In claim 1, the step of determining whether the second SIB is identified as the first SIB is: The method further includes a step of identifying whether the values ​​of the PLMN ID (public land mobile network identity), TAC (tracking area code), and systemInfoValueTag indicated by the first SIB match the values ​​of the PLMN ID, TAC, and systemInfoValueTag indicated by the second SIB. A method in which the values ​​of PLMN ID, TAC, and systemInfoValueTag indicated by the first SIB are all the same as the values ​​of PLMN ID, TAC, and systemInfoValueTag indicated by the second SIB, wherein the second SIB is identified as the first SIB.

4. In claim 1, the step of determining whether the second SIB is identified as the first SIB is: If the first SIB contains a list of second cells adjacent to the first cell, a step of identifying whether the second PCI is included in the list of second cells; or If the first SIB does not include a list for the second cell, the method further includes a step of identifying whether the PCI of the second cell is the same as the first PCI. A method in which the second PCI is included in the list for the second cell, or the second SIB is identified as the first SIB when the PCI of the second cell is the same as the first PCI.

5. In claim 1, the step of determining whether the second SIB is identified as the first SIB is: The method further includes the step of calculating the movement distance of the above terminal, If the travel distance of the above terminal is shorter than the reference distance, the second SIB is identified as the first SIB, and A method in which, when the travel distance of the above terminal is longer than the reference distance, the second SIB is not identified as the first SIB.

6. In a wireless communication system using a non-terrestrial network (NTN), regarding a terminal (user equipment), At least one transceiver; At least one processor communicatively coupled to the above at least one transceiver; and It includes at least one memory that is communicationally coupled to the above at least one processor and stores instructions, and The above instructions are executed individually or in any combination by the above at least one processor, so that the terminal: A first SI message including a first SIB (system information block) and a first PCI (physical cell identity) for a first cell is received from a first NTN base station, and Storing the first SIB and the first PCI, Receive a second SI message including a second SIB and a second PCI from a second NTN base station, and Identify whether the second SIB is received at the same frequency as the first SIB, and If the second SIB is received at the same frequency as the first SIB, determine whether the second PCI is different from the first PCI, and A terminal configured to determine whether the second SIB is identified as the first SIB when the second PCI is different from the first PCI.

7. In claim 6, the above commands are the terminal: Driving the SIB reuse timer for the first SIB above, and It is further configured to identify whether the second SI message was received before the above SIB reuse timer expires, and If the second SI message is received before the above SIB reuse timer expires, the second SIB is identified as the first SIB, and The above second PCI is a terminal different from the above first PCI.

8. In claim 6, the above commands are the terminal: It is further configured to identify whether the values ​​of PLMN ID (public land mobile network identity), TAC (tracking area code), and systemInfoValueTag indicated by the first SIB match the values ​​of PLMN ID, TAC, and systemInfoValueTag indicated by the second SIB, and A terminal in which the values ​​of PLMN ID, TAC, and systemInfoValueTag indicated by the first SIB are all identical to the values ​​of PLMN ID, TAC, and systemInfoValueTag indicated by the second SIB.

9. In claim 6, the above commands are the terminal: If the first SIB contains a list of second cells adjacent to the first cell, identify whether the second PCI is included in the list of second cells, or If the first SIB above does not include a list for the second cell, it is further configured to identify whether the PCI of the second cell is the same as the first PCI, and A terminal in which the second PCI is included in the list for the second cell, or the second SIB is identified as the first SIB when the PCI of the second cell is the same as the first PCI.

10. In claim 6, the above commands are the terminal: It is further configured to calculate the movement distance of the above terminal, and If the travel distance of the above terminal is shorter than the reference distance, the second SIB is identified as the first SIB, and A terminal in which the travel distance of the above terminal is longer than the reference distance, the second SIB is not identified as the second SIB.

11. In Claim 7, The above SIB reuse timer is activated from the timepoint when the terminal is connected to the first cell or from the last time when the terminal previously identified the SIB of the first cell, and A terminal whose length of the above SIB reuse timer is set based on the frequency reuse factor (FRF).

12. In Claim 6, A terminal in which, if the second SI message is not received at the same frequency as the first SI message, the second SIB is not identified as the first SIB.

13. In Claim 6, When the above second SIB is identified as the above first SIB: The first PCI stored in the terminal is updated to the second PCI, and The above second SIB is a terminal that is not decoded.

14. In Claim 6, If the above second SIB is not identified as the above first SIB: The first PCI stored in the terminal is updated to the second PCI, and The above second SIB is decoded, and A terminal in which the first SIB stored in the terminal is updated to the second SIB.

15. In Claim 10, The movement distance of the above terminal is calculated as the value obtained by subtracting the reference position of the terminal from the position of the above terminal, and The above reference distance is calculated by subtracting the diameter of the first cell from the distance between cells of the same frequency as the first cell, and A terminal whose reference position is calculated as the average of the positions of a plurality of spots within the first cell.

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