Method and apparatus for updating reference position in a wireless communication system

Abstract

A method for updating a reference position by a terminal based on non-terrestrial networks (NTN) in a wireless communication system, the method including the steps of: acquiring reference position-related information from a base station; determining whether a distance between the terminal and the reference position is smaller than a distance threshold based on the reference position-related information; not performing a measurement for cell reselection if the distance between the terminal and the reference position is smaller than the distance threshold; performing the measurement for cell reselection if the distance between the terminal and the reference position is larger than the distance threshold; and proceeding with a reference position update based on a reference position-related timer if the distance between the terminal and the reference position is smaller than the distance threshold.

Description

[Technical Field]

[0001] The present invention relates to a method and apparatus for updating a reference position in a wireless communication system.The present invention relates to a method for updating a reference position based on non-terrestrial networks (NTN). [Background technology]

[0002] The International Telecommunication Union (ITU) is developing the International Mobile Telecommunication (IMT) framework and standards, and has recently been discussing fifth-generation (5G) communications through a program called "IMT for 2020 and beyond."

[0003] To meet the requirements set out in "IMT for 2020 and beyond," the 3GPP (registered trademark) 3rd Generation Partnership Project (NR) New Radio (NR) system is currently discussing the support of various numerologies for time-frequency resource unit standards, taking into account various scenarios, service requirements, potential system compatibility, etc.

[0004] In addition, in new communication systems, discussions are underway on how to support seamless communication services at the service level for mobile terminals (e.g., vehicles / trains / ship-type terminals / personally owned smartphones) using not only terrestrial networks (TR) but also non-terrestrial networks (NON). Below, we will explain how to measure neighboring cells and perform cell reselection taking into account the mobility of terminals between NTN and TN. Summary of the Invention [Problem to be solved by the invention]

[0005] The present invention provides a method and apparatus for updating a reference position taken into account in measurements for cell reselection in a wireless communication system.

[0006] The present invention can provide a method and apparatus for updating a reference position taking into account moving cells in an NTN environment.

[0007] The present invention can provide a method and apparatus for setting a timer for updating a reference position in an NTN environment.

[0008] The present invention can provide a method and apparatus for updating a reference position based on system information in an NTN environment.

[0009] The present invention can provide a method and apparatus for updating a reference position based on satellite ephemeris in an NTN environment.

[0010] The present invention can provide a method and apparatus for updating a reference location based on a reference location list in an NTN environment. [Means for solving the problem]

[0011] According to one embodiment, a method for updating a reference position by a terminal based on non-terrestrial networks (NTN) in a wireless communication system may include the steps of: acquiring reference position-related information from a base station; determining whether a distance between the terminal and the reference position is smaller than a distance threshold based on the reference position-related information; not performing a measurement for cell reselection if the distance between the terminal and the reference position is smaller than the distance threshold; performing the measurement for cell reselection if the distance between the terminal and the reference position is larger than the distance threshold; and proceeding with a reference position update based on a reference position-related timer if the distance between the terminal and the reference position is smaller than the distance threshold.

[0012] According to an embodiment, the reference position related information may include at least one of reference position information, satellite orbit information, reference position update timer information, uplink synchronization valid time information, and absolute time information.

[0013] Furthermore, according to one embodiment, it is possible to determine an effective starting point for starting at least one of a reference position update timer and a timer for uplink synchronization effective time based on absolute time information, and obtain system information including reference position information to perform a reference position update.

[0014] In addition, according to one embodiment, an effective starting point for starting a reference position update timer can be determined based on absolute time information, and a reference position update can be performed through satellite orbit information based on the reference position update timer.

[0015] Further, according to one embodiment, the reference position related information includes reference position list information, which is composed of absolute times and reference positions corresponding to the absolute times, and the reference position update can be performed based on the reference position list information.

[0016] The above briefly summarized features of the present disclosure are merely exemplary embodiments of the following detailed description of the present disclosure and are not intended to limit the scope of the present disclosure. [Effects of the Invention]

[0017] According to the present disclosure, it is possible to provide a method for updating a reference position taken into account in measurements for cell reselection in a wireless communication system.

[0018] According to the present disclosure, a method for updating a reference position taking into account moving cells in an NTN environment can be provided.

[0019] According to the present disclosure, a method for setting a timer for updating a reference position in an NTN environment can be provided.

[0020] According to the present disclosure, a method for updating a reference position based on system information in an NTN environment can be provided.

[0021] According to the present disclosure, a method for updating a reference position based on satellite ephemeris in an NTN environment can be provided.

[0022] According to the present disclosure, a method for updating a reference location based on a reference location list in an NTN environment can be provided.

[0023] The present disclosure is not limited to the above-mentioned effects, and other effects not mentioned herein will be clearly understood by those skilled in the art to which the present disclosure pertains from the following description. [Brief explanation of the drawings]

[0024] [Figure 1] FIG. 1 is a diagram for explaining an NR frame structure to which the present disclosure can be applied. [Figure 2] FIG. 2 is a diagram illustrating an NR resource structure to which the present disclosure may be applied. [Figure 3] FIG. 3 is a diagram illustrating an NTN including transparent satellites to which the present disclosure may be applied. [Figure 4] FIG. 4 is a diagram illustrating an NTN including regenerative satellites without inter-satellite links (ISLs) to which the present disclosure may be applied. [Figure 5] FIG. 5 is a diagram illustrating an NTN including a regenerative satellite with an ISL to which the present disclosure can be applied. [Figure 6] FIG. 6 is a diagram illustrating a user plane (UP) protocol stack structure in an NTN including a transparent satellite to which the present disclosure can be applied. [Figure 7] FIG. 7 is a diagram illustrating a control plane (CP) protocol stack structure in an NTN including a transparent satellite to which the present disclosure can be applied. [Figure 8] FIG. 8 is a diagram illustrating a timing advance calculation method to which the present disclosure can be applied. [Figure 9] FIG. 9 is a diagram illustrating an earth fixed cell scenario to which the present disclosure may be applied. [Figure 10] FIG. 10 is a diagram illustrating an earth moving cell scenario to which the present disclosure may be applied. [Figure 11] FIG. 11 is a diagram illustrating a method for mapping PCI to satellite beams to which the present disclosure may be applied. [Figure 12] FIG. 12 is a diagram illustrating reference positions to which the present disclosure may be applied. [Figure 13] FIG. 13 is a diagram showing received signal strength as a function of distance in a TN and an NTN to which the present disclosure can be applied. [Figure 14] FIG. 14 illustrates a method for performing distance-based measurements for cell reselection to which the present disclosure may be applied. [Figure 15] FIG. 15 is a diagram illustrating a reference position update method to which the present disclosure can be applied. [Figure 16]FIG. 16 illustrates a method for performing a reference position update based on system information acquisition to which the present disclosure may be applied. [Figure 17] FIG. 17 is a diagram illustrating a method for performing a reference position update to which the present disclosure may be applied. [Figure 18] FIG. 18 is a diagram illustrating a method for updating a reference position based on a new timer to which the present disclosure can be applied. [Figure 19] FIG. 19 is a diagram illustrating a method for performing a reference position update based on a reference position update timer to which the present disclosure may be applied. [Figure 20] FIG. 20 illustrates a method for performing a reference position update based on system information acquisition to which the present disclosure may be applied. [Figure 21] FIG. 21 is a diagram showing ECEF (Earth-Centered, Earth-Fixed) coordinates and Ellipsoid-Point to which the present disclosure can be applied. [Figure 22] FIG. 22 is a diagram illustrating a reference position update method to which the present disclosure can be applied. [Figure 23] FIG. 23 is a diagram showing a method for updating a reference position based on satellite orbit information to which the present disclosure can be applied. [Figure 24] FIG. 24 is a diagram illustrating a method for updating a reference position based on satellite orbit information to which the present disclosure can be applied. [Figure 25] FIG. 25 is a diagram showing satellite movement and changes in reference position to which the present disclosure can be applied. [Figure 26] FIG. 26 is a diagram illustrating a reference location list-based signaling procedure and a reference location update procedure to which the present disclosure can be applied. [Figure 27] FIG. 27 is a flowchart illustrating a reference position update method to which the present disclosure can be applied. [Figure 28] FIG. 28 is a flowchart illustrating a reference position update method to which the present disclosure can be applied. [Figure 29] FIG. 29 is a diagram showing an apparatus configuration to which the present disclosure can be applied. DETAILED DESCRIPTION OF THE INVENTION

[0025] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0023] The present disclosure will be described in detail below with reference to the accompanying drawings, so that those skilled in the art can easily implement the present disclosure. However, the present disclosure may be embodied in various different forms and is not limited to the embodiments described herein.

[0026] In describing embodiments of the present disclosure, if it is determined that a detailed description of a known configuration or function would obscure the gist of the present disclosure, the detailed description will be omitted. In addition, in the drawings, parts that are not related to the description of the present disclosure will be omitted, and similar parts will be designated by similar reference numerals.

[0027] In this disclosure, when a component is said to be "coupled," "coupled," or "connected" to another component, this refers not only to a direct connection, but also to an indirect connection where there is another component between them. Furthermore, when a component is said to "include" or "have" another component, this does not exclude the other component, but means that the component may further include the other component, unless otherwise specified.

[0028] In this disclosure, terms such as first and second are used only to distinguish one component from another, and do not limit the order or importance of the components unless otherwise specified. Therefore, within the scope of this disclosure, a first component in one embodiment may be referred to as a second component in another embodiment, and similarly, a second component in one embodiment may be referred to as a first component in another embodiment.

[0029] In this disclosure, components that are distinguished from one another are used to clearly describe the characteristics of each component and do not necessarily mean that the components are separate. That is, multiple components may be integrated into a single hardware or software unit, or a single component may be distributed into multiple hardware or software units. Therefore, even if not otherwise specified, such integrated or distributed embodiments are also included within the scope of this disclosure.

[0030] In this disclosure, the components described in various embodiments are not necessarily essential components, and some may be optional components. Therefore, an embodiment consisting of a subset of the components described in one embodiment is also included in the scope of this disclosure. Note that an embodiment including other components in addition to the components described in various embodiments is also included in the scope of this disclosure.

[0031] The present disclosure describes a wireless communication network, and operations performed in the wireless communication network may be performed in a process of controlling the network and transmitting or receiving signals by a system (e.g., a base station) that manages the wireless communication network, or in a process of transmitting or receiving signals by a terminal coupled to the wireless network.

[0032] It is apparent that various operations performed for communication with a terminal in a network consisting of multiple network nodes including a base station may be performed by the base station or other network nodes other than the base station. The term "base station (BS)" may be replaced with terms such as fixed station, Node B, eNodeB (eNB), ng-eNB, gNodeB (gNB), access point (AP), etc. Furthermore, the term "terminal" may be replaced with terms such as user equipment (UE), mobile station (MS), mobile subscriber station (MSS), subscriber station (SS), non-AP station (non-AP STA), etc.

[0033] In this disclosure, transmitting or receiving a channel includes transmitting or receiving information or signals through the channel. For example, transmitting a control channel means transmitting control information or signals through the control channel. Similarly, transmitting a data channel means transmitting data information or signals through the data channel.

[0034] In the following description, the term NR (New Radio) system is used to distinguish the system to which various examples of the present disclosure are applied from existing systems, but the scope of the present disclosure is not limited by these terms.

[0035] The NR system supports various subcarrier spacings (SCS) taking into account various scenarios, service requirements, and potential system compatibility. The NR system can also support the transmission of physical signals / channels through multiple beams to overcome adverse channel conditions such as high path loss, phase noise, and frequency offset that occur at high carrier frequencies. This allows the NR system to support applications such as enhanced Mobile Broadband (eMBB), massive Machine Type Communications (mMTC) / ultra Machine Type Communications (uMTC), and Ultra Reliable and Low Latency Communications (URLLC).

[0036] Hereinafter, 5G mobile communication technology may be defined to include not only the NR system but also the existing LTE-A (Long Term Evolution-Advanced) and LTE (Long Term Evolution) systems. That is, 5G communication may include not only the newly defined NR system but also technologies that operate in consideration of backward compatibility with previous systems. Therefore, the 5G mobile communication described below may include technologies that operate based on the NR system and technologies that operate based on previous systems (e.g., LTE-A, LTE), and is not limited to a specific system.

[0037] First, a brief description will be given of the physical resource structure of the NR system to which the present invention is applied.

[0038] FIG. 1 is a diagram for explaining an NR frame structure to which the present disclosure can be applied.

[0039] The basic unit of time domain in NR is T c =1 / (Δf max N f ) and Δf max =480 10 3 and N f = 4096, whereas the time domain base unit in LTE is Ts = 1 / (Δf ref N f,ref ) and Δf ref =15 10 3 and N f,ref = 2048. The constant for the multiple relationship between the base unit of NR time and the base unit of LTE time is κ = T s / T c =64.

[0040] Referring to FIG. 1, the time structure of a frame for downlink / uplink (DL / UL) transmission is T f =(Δf max N f / 100)·T s= 10 ms, where one frame is T sf =(Δf max N f / 1000)·T s The number of consecutive OFDM symbols in each subframe is N subframe,u symb =N slot symb N subframe,u slot Alternatively, each frame may be divided into two half frames of the same size, with half frame 1 consisting of subframes 0-4 and half frame 2 consisting of subframes 5-9.

[0041] N TA denotes the timing advance (TA) between the downlink (DL) and the uplink (UL), where the transmission timing of the uplink transmission frame i is determined based on the downlink reception timing at the terminal according to the following Equation 1:

[0042]

number

[0043] where N TA,offset is the TA offset value that occurs due to differences in duplex modes. TA,offset has a value of 0, but in TDD (Time Division Duplex), N is set to N in consideration of the margin for DL-UL switching time. TA,offset For example, in TDD (Time Division Duplex) in FR1 (Frequency Range 1), which is a frequency below 6 GHz, N TA,offsetcan be 39936Tc or 25600Tc. 39936Tc is 20.327μs, and 25600Tc is 13.030μs. Also, in FR2 (Frequency Range 2), which is a millimeter wave (mmWave) frequency, N TA,offset can be 13792Tc, where 39936Tc is 7.020μs.

[0044] FIG. 2 is a diagram illustrating an NR resource structure to which the present disclosure may be applied.

[0045] The resource elements (REs) in the resource grid can be indexed by each subcarrier spacing, where one resource grid can be generated for each antenna port and each subcarrier spacing, and uplink and downlink transmission and reception can be performed based on the resource grid.

[0046] In the frequency domain, one resource block (RB) consists of 12 REs, and an index (n PRB ) can be configured. The index for the RB can be used within a specific frequency band or system bandwidth. The index for the RB can be defined as in Equation 2 below. Here, N RB sc denotes the number of subcarriers per RB, and k denotes the subcarrier index.

[0047]

number

[0048] Various neural networks can be configured to meet the various services and requirements of the NR system. For example, an LTE / LTE-A system can support one subcarrier spacing (SCS), while an NR system can support multiple SCSs.

[0049] New pneumatics for NR systems that support multiple SCSs can operate in frequency ranges or carriers such as below 3 GHz, 3 GHz-6 GHz, 6 GHz-52.6 GHz, or above 52.6 GHz, solving the problem of not being able to use wide bandwidths in frequency ranges or carriers such as 700 MHz or 2 GHz.

[0050] Table 1 below shows examples of pneumoradio supported by the NR system.

[0051] [Table 1]

[0052] Referring to Table 1, the neural network parameters can be defined based on the subcarrier spacing (SCS), cyclic prefix (CP) length, and number of OFDM symbols per slot used in an Orthogonal Frequency Division Multiplexing (OFDM) system. These values ​​can be provided to the UE through upper layer parameters DL-BWP-mu and DL-BWP-cp for the downlink and through upper layer parameters UL-BWP-mu and UL-BWP-cp for the uplink.

[0053] In Table 1, when the subcarrier spacing setting index (u) is 2, the subcarrier spacing (Δf) is 60 kHz, and normal CP and extended CP can be applied. In other cases, only normal CP can be applied.

[0054] A normal slot can be defined as a basic time unit used to transmit one piece of data and control information in an NR system. The length of a normal slot can be basically set to 14 OFDM symbols. Furthermore, unlike a slot, a subframe has an absolute time length corresponding to 1 ms in an NR system and can be used as a reference time for the length of other time intervals. Here, for coexistence or backward compatibility between LTE and NR systems, a time interval similar to an LTE subframe may be required in the NR standard.

[0055] For example, in LTE, data may be transmitted based on a transmission time interval (TTI), which is a unit of time, and the TTI may be set in units of one or more subframes. Here, in LTE, one subframe may be set to 1 ms and may include 14 OFDM symbols (or 12 OFDM symbols).

[0056] Furthermore, non-slots can be defined in NR. A non-slot may refer to a slot having a number of symbols at least one smaller than that of a normal slot. For example, when providing low latency, such as in a URLLC service, the latency can be reduced by using a non-slot having a number of symbols smaller than that of a normal slot. Here, the number of OFDM symbols included in a non-slot can be determined taking into account the frequency range. For example, in a frequency range of 6 GHz or higher, a non-slot having a length of one OFDM symbol can be considered. As a further example, the number of OFDM symbols defining a non-slot can include at least two OFDM symbols. Here, the range of the number of OFDM symbols included in a non-slot can be set as the length of a mini-slot up to a predetermined length (e.g., the normal slot length minus 1). However, as a non-slot standard, the number of OFDM symbols may be limited to, but not limited to, 2, 4, or 7 symbols.

[0057] For example, in unlicensed bands below 6 GHz, subcarrier spacing where u is 1 and 2 can be used, and in unlicensed bands above 6 GHz, subcarrier spacing where u is 3 and 4 can be used. For example, when u is 4, it can be used for SSB (Synchronization Signal Block).

[0058] [Table 2]

[0059] Table 2 shows the number of OFDM symbols per slot (N) for normal CP, depending on the subcarrier spacing setting (u). slot symb ), number of slots per frame (N frame,u slot ), the number of slots per subframe (N subframe,u slot ) Table 2 shows the above values ​​based on a normal slot having 14 OFDM symbols.

[0060] [Table 3]

[0061] Table 3 shows the number of slots per frame and the number of slots per subframe when extended CP is applied (i.e., when u is 2 and the subcarrier spacing is 60 kHz), based on a normal slot with 12 OFDM symbols per slot.

[0062] As mentioned above, one subframe may correspond to 1 ms on the time axis. Furthermore, one slot may correspond to 14 symbols on the time axis. For example, one slot may correspond to 7 symbols on the time axis. Therefore, the number of slots and symbols that can be considered within 10 ms, which corresponds to one radio frame, can be set differently. Table 4 shows the number of slots and symbols according to each SCS. In Table 4, the 480 kHz SCS may not be considered, but is not limited to these examples.

[0063] [Table 4]

[0064] For example, in an existing wireless communication system, communication can be performed based on a terrestrial network consisting of a terminal located on the ground and a base station located on the ground. The terminal can connect to the network wirelessly. Here, when the terminal moves, the terminal can continuously receive the same service through another base station in the terrestrial network. After connecting to the network, the terminal can connect to a specific service server through another wired or internet network. Furthermore, the terminal can receive a service that connects with another terminal via wired or wireless communication through the network.

[0065] However, new wireless communication systems can support terminal communications not only through terrestrial networks but also through non-terrestrial networks (NTNs). Here, NTNs can refer to networks or portions of networks that use airborne or spaceborne mobile objects equipped with base stations or relay devices. For example, NTNs can support terminal-to-terminal communications services based on satellites equipped with communications capabilities in low Earth orbit (LEO) and geostationary Earth orbit (GEO). For another example, NTNs can support terminal-to-terminal communications services based on aircraft equipped with communications capabilities within unmanned aerial systems (UAS), but this is not a limitation.

[0066] In the following description, terrestrial networks (TN) will be distinguished from non-terrestrial networks (NTN). That is, in existing communication systems, only terrestrial networks exist, so there is no need to distinguish between them. However, in the following description, NTN and TN will be distinguished as communication systems that enable terminal-to-terminal communication based on NTN, and a method for supporting terminal-to-terminal communication services based on NTN will also be described.

[0067] As an example, but not limited to, wireless communication services between terrestrial base stations and wireless terminals or between mobile base stations are described as mobile services. Furthermore, communication between mobile terrestrial base stations and at least one or more space base stations may be mobile satellite services. Furthermore, wireless communication services between mobile terrestrial base stations and space base stations, or between mobile terrestrial base stations via at least one or more space base stations, may also be mobile satellite services.

[0068] The following describes a method for performing communications based on a wireless communication system that supports both mobile services and mobile satellite services. For example, NTN-related technologies have been introduced specifically for satellite communications. However, NTN can also be introduced in TN communication systems (e.g., 5G systems) to operate like TN. Here, a terminal can simultaneously support NTN and TN. For terminals that simultaneously support NTN and TN, a wireless communication system may require specific technology for NTN in addition to the radio access technologies (RATs) LTE (long-term evolution) and NR (new radio). A method for achieving this is described below. For example, the following may be definitions of the terms related to NTN and TN.

[0069] Non-terrestrial networks (NTN): A network or part of a network using airborne or spaceborne mobile vehicles equipped with base stations or relay devices for communication

[0070] NTN Gateway: A terrestrial base station or gateway located on the ground and equipped with sufficient radio connectivity to connect to a satellite. In general, an NTN gateway can be a transport network layer node (TNL).

[0071] Feeder link: Radio link between the NTN Gateway and the satellite

[0072] Geostationary Earth orbit (GEO): A circular orbit 35,786 km above the Earth's equator that coincides with the Earth's rotation. An object or satellite in this orbit revolves around the Earth at the same period as the Earth's rotation. Therefore, when observed from Earth, it appears to be in a fixed, motionless position.

[0073] Low Earth Orbit (LEO): Orbits between 300km and 1500km above the ground

[0074] Medium Earth Orbit (MEO): Orbits between LEO and GEO

[0075] Unmanned Aircraft Systems (UAS): Generally, the system operates within a range of 8km to 50km above the ground and may include High Altitude Platforms (HAPs).Unmanned aerial systems may include at least one of Tethered UAS (TUA), Lighter Than Air UAS (LTA), and Heavier Than Air UAS (HTA) systems.

[0076] Minimum Elevation angle: The minimum angle required for a ground terminal to point towards an airborne satellite or UAS base station.

[0077] Mobile Services: Wireless communication services between terrestrial base stations and wireless terminals or between mobile base stations

[0078] Mobile Satellite Services: It may be a wireless communication service between a mobile terrestrial base station and one or more space base stations, or between a mobile terrestrial base station and a space base station, or between mobile terrestrial base stations through one or more space base stations.

[0079] Non-Geostationary Satellites: These may be satellites in LEO and MEO orbits, which orbit the Earth with a period between about 1.5 hours and 10 hours.

[0080] On Board Processing: Digital processing of uplink RF signals onboard satellites or non-terrestrial equipment

[0081] Transparent payload: This can mean changing the carrier frequency of an uplink RF signal, filtering and amplifying it before transmitting it over the downlink.

[0082] Regenerative payload: The uplink RF signal is modified and amplified before transmission over the downlink, and the signal modification may include digital processing such as decoding, demodulation, remodulation, re-encoding, and filtering.

[0083] Onboard NTN base station (On board NTN gNB): It can refer to an onboard satellite in which a base station (gNB) is implemented in a regenerative payload structure.

[0084] On-ground NTN base station (On ground NTN gNB): A terrestrial base station (gNB) realized with a transparent payload structure

[0085] One-way latency: The time it takes to travel from a wireless terminal to a shared data network or from the shared data network to a wireless terminal in a wireless communication system.

[0086] Round Trip Delay (RTD): This may be the time it takes for a signal to travel from a wireless terminal to an NTN gateway, or from an NTN gateway to a wireless terminal, and then return. At this time, the returning signal may have a different form or message than the signal.

[0087] Satellite: It may be a spaceborne vehicle equipped with a wireless communication transceiver capable of supporting a transparent payload or a regenerative payload, and may generally be located in a LEO, MEO, or GEO orbit.

[0088] Satellite beam: The beam generated by the onboard satellite antenna

[0089] Service link: Radio link between satellite and terminal (UE)

[0090] User Connectivity: Capability to set up and maintain data / voice / video transmission between the network and the terminal

[0091] User Throughput: Data transmission rate provided to the device

[0092] FIG. 3 is a diagram illustrating an NTN including transparent satellites to which the present disclosure may be applied.

[0093] Referring to Figure 3, the terminals included in the NTN may include terrestrial network terminals. For example, the NTN and TN terminals may include manned or unmanned vehicles such as ships, trains, buses, or airplanes, and are not limited to a specific form. Referring to Figure 3, transparent satellite payloads generated through a network including transparent satellites may be realized in a manner corresponding to an RF repeater.

[0094] More specifically, a network including transparent satellites can perform frequency switching and amplification on received radio signals in both uplink and downlink directions, and transmit the radio signals. Thus, the satellites can perform the function of relaying the NR-Uu radio interface, which includes both feeder links and service links, as described below.

[0095] As another example, referring to FIG. 3, a feeder link satellite radio interface (SRI) may be included in the NR-Uu interface. That is, the satellite may not be the end of the NR-Uu interface. Here, the NTN gateway may support all functions necessary to transmit signals defined in the NR-Uu interface. As an example, other transparent satellites may be connected to the same terrestrial base station. That is, a configuration in which multiple transparent satellites are connected to one terrestrial base station may also be possible. The base station may be an eNB or a gNB, but is not limited to a specific form.

[0096] FIG. 4 is a diagram illustrating an NTN including regenerative satellites without inter-satellite links (ISLs) to which the present disclosure may be applied.

[0097] Referring to FIG. 4, the NTN may include a regenerative satellite. Here, the regenerative satellite may mean that a base station function is included within the satellite. For example, a regenerative satellite payload generated through a network including the regenerative satellite may be realized in a manner that regenerates a signal received from the ground.

[0098] More specifically, the regenerating satellite can receive signals from the ground based on the NR-Uu radio interface on the service link between the terminal and the satellite. As another example, the regenerating satellite can receive signals from the ground through an SRI (Satellite Radio Interface) on the feeder link between the NTN gateway. Here, the SRI (Satellite Radio Interface) can be defined as the transport layer between the satellite and the NTN gateway. The transport layer can refer to the transport layer among the layers defined as the OSI 7 layer. That is, based on the regenerating satellite, the signals from the ground can be transformed based on digital processing such as, but not limited to, decoding, demodulation, remodulation, re-encoding, and filtering.

[0099] FIG. 5 is a diagram illustrating an NTN including a regenerative satellite with an ISL to which the present disclosure can be applied.

[0100] Referring to Figure 5, the ISL can be defined in the transport layer. As another example, the ISL can be defined as a radio interface or a visible light interface, and is not limited to a specific embodiment. Here, the NTN gateway can support all functions of the transport protocol. Furthermore, each regenerative satellite can be a base station, and multiple regenerative satellites can be connected to the same 5G core network on the ground.

[0101] Figure 6 is a diagram showing a user plane (UP) protocol stack structure in an NTN including a transparent satellite to which the present disclosure can be applied, and Figure 7 is a diagram showing a control plane (CP) protocol stack structure in an NTN including a transparent satellite to which the present disclosure can be applied.

[0102] The NR Uu interface may be an interface defined as a protocol for wireless connection between a terminal and a base station in an NR system. In this case, the NR Uu interface may include a user plane defined as a protocol for user data transmission, including the NTN. Furthermore, the NR Uu interface may include a control plane defined as a protocol for transmitting signaling including radio resource control information, including the NTN. For example, the medium access control (MAC) layer may be configured based on a radio link control (RLC), a packet data convergence protocol (PDCP), a service data adaptation protocol (SDAP), and a radio resource control (RAC), and protocols for each layer may be defined based on the NR among 3GPP RAN-related standards, but are not limited thereto.

[0103] As an example, Figure 6 shows a UP protocol stack structure based on a transparent satellite. That is, the satellite and NTN gateway can transmit only frequency switching and amplification of the received wireless signal. Furthermore, Figure 7 shows a CP protocol stack structure based on a transparent satellite. That is, the satellite and NTN gateway can transmit only frequency switching and amplification of the received wireless signal.

[0104] Based on the above, a wireless communication system supporting terminal-to-terminal communication in an NTN and a TN can be considered. Here, as an example, an NTN may have a longer round trip time (RTT) between a terminal and a base station than an existing TN. Therefore, from the perspective of UP, the terminal needs to store data transmitted through each of the uplink and downlink in a buffer for a longer period of time due to the increased RTT. That is, the terminal needs to store more data in a buffer. Therefore, the terminal may require a larger memory capacity than conventional terminals, which will be described later.

[0105] FIG. 8 illustrates a timing advance calculation method to which the present disclosure can be applied. As mentioned above, because satellites included in an NTN are located in the sky, the signal round trip time (RTT) can be long. For example, a LEO satellite can be located 300 km to 1,200 km above the sky, while a GEO satellite can be located 36,000 km or more above the equator. Therefore, propagation delays in an NTN can be significantly larger than in a TN. However, because an NTN is located in the sky, cell coverage can be greater than in a terrestrial network.

[0106] That is, since the RTT and cell coverage of an NTN may differ from those of a TN, it is necessary to newly define a method for obtaining time synchronization for uplink transmission in an NTN. As an example, Figure 8 shows a method for calculating the TA value generated depending on the satellite payload type.

[0107] More specifically, Figure 8(a) may be a method for calculating the TA value when the satellite payload type is a regenerated payload, and Figure 8(b) may be a method for calculating the TA value when the satellite payload type is a transparent payload.

[0108] Here, for initial connection and continuous maintenance of the timing advance (TA) value, it is possible to consider the case where the terminal knows the satellite's orbital force, i.e., orbital information (ephemeris), and the terminal's location. Here, satellite orbital information may refer to the distance between each satellite and the receiver and the location information of each satellite. As an example, the terminal may learn the TA value itself and then apply it (hereinafter referred to as option 1). As another example, the terminal may receive instructions for TA compensation and correction from the network (hereinafter referred to as option 2).

[0109] For example, referring to FIG. 8(a), if the satellite payload type is a regenerative payload, the satellite can directly function as a base station. In this case, the terminal can calculate a TA value required for uplink transmission including a physical random access channel (PRACH). The terminal can calculate a common TA value Tcom and a terminal-specific TA value TUEx. For example, the common TA value Tcom may be a TA value required for all terminals due to the large cell coverage and long round-trip time (RTT) of the NTN. That is, since the NTN is located in the sky and is relatively longer than the distance between terminals, a common TA value Tcom that takes into account the long round-trip time (RTT) in the cell coverage may be required. In addition, the terminal-specific TA value TUEx may be a value that occurs due to the different positions of each terminal within the cell coverage. If the terminal knows the satellite's position at a specific time in advance through satellite orbital information (ephemeris) that it has stored in advance or received from NTN, and if the terminal knows its position through a function such as GNSS, the terminal can calculate the distance between the satellite and the terminal at a specific time, so it can learn the TA value itself and then correct the TA value, thereby determining the TA value.

[0110] As described above, the terminal can perform uplink timing alignment between the terminals received from the base station with overall TA compensation.

[0111] As another example, the terminal may perform timing alignment of downlink and uplink frames on the network side. When the satellite payload type is a transparent payload, as shown in FIG. 8(b), the satellite may filter and amplify the radio signal and transmit it to the NTN gateway. That is, the satellite may operate like an RF repeater. In this case, the NTN gateway may need to be changed based on the satellite's continuous movement. The common TA value Tcom in FIG. 8(b) may be determined based on the sum of the distance D01 between the reference point and the satellite and the distance D02 between the satellite and the NTN gateway. The feeder link may change as the NTN gateway changes based on the satellite's movement. That is, the distance between the satellite and the NTN gateway may change based on the changed feeder link. Therefore, the generated common TA value may change, and the terminal may need to update it. Furthermore, when the network sets an offset between the downlink frame timing and the uplink frame timing, it is necessary to further consider the case where the TA value generated by the feeder link is not corrected in the overall TA compensation method. Furthermore, if a terminal can only calculate a different TA value TUEx for each terminal, the terminal needs to identify one reference point for each beam or cell and transmit information about this to other terminals. If the network sets an offset between downlink frame timing and uplink frame timing, the network needs to manage the offset information regardless of the satellite payload type. Here, as an example, the network can provide a value for TA correction to each terminal, and the present invention is not limited to the above-mentioned embodiment.

[0112] As another example, a method (Option 2) in which the network instructs TA compensation and correction can be considered. In this case, a common TA value can be generated based on a common element for propagation delay shared by all terminals located within the coverage of a satellite beam or cell. The network can transmit a common TA value to terminals for each satellite beam or cell based on a broadcast method. The common TA value can be calculated by the network assuming at least one reference position for each satellite beam or cell. In addition, the TA value TUEx for each terminal can be determined based on the random access procedure defined in an existing communication system (e.g., Release 15 or Release 16 in an existing NR system). In this case, for example, when a long TA value or a TA value in negative number form is applied, a new field may be required in the random access message. For example, if the network provides a timing change rate to the terminal, the terminal can support TA value correction based on the timing change rate.

[0113] FIG. 9 is a diagram illustrating an earth fixed cell scenario to which the present disclosure may be applied.

[0114] Referring to FIG. 9, a fixed cell may be a cell in which the position where a signal is transmitted by a satellite is fixed. For example, since a satellite moves over time, it is necessary to change its antenna and beam so that service coverage is fixed to a specific position in order to maintain the fixed cell. In this case, as an example, in FIG. 9, satellite 1 (910) can maintain the fixed cell by changing its antenna and beam between T1 and T3. Here, after a specific time T4 has passed, satellite 1 can no longer service the location, so satellite 2 (920) can provide service at the location to maintain service continuity. In this case, the beam or cell of satellite 2 (920), which serves the same location as satellite 1 (910) served at the previous time (T1 to T3) after time T4, can maintain the characteristics of the beam or cell of satellite 1 (910), and is not limited to the above-described embodiment.

[0115] As a more specific example, when a service is provided by satellite 1 (910) and satellite 2 (920), at least one of a physical cell ID (PCI) value and system information can be maintained to be the same. That is, as a cell with fixed service coverage, it can be set based on a satellite that can change the antenna and beam angle among satellites in LEO and MEO orbits, excluding GEO.

[0116] 10 is a diagram illustrating an earth moving cell scenario to which the present disclosure can be applied. As an example, a cell in which service coverage moves may be an earth moving cell.

[0117] For example, referring to Figure 10, satellite 1 (1010), satellite 2 (1020), and satellite 3 (1030) can each provide service to cells having different PCIs. In this case, the antenna and beam by which the satellite transmits signals to the ground are fixed, and the form in which the service coverage moves as the satellite moves over time can be called an Earth moving cell. Earth moving cells can be established based on satellites in LEO and MEO orbits, excluding GEO, that have fixed antenna and beam angles. Here, these satellites have the advantages of being cheaper and having a lower failure rate than satellites that can adjust the antenna and beam angles.

[0118] Additionally, FIG. 11 is a diagram illustrating a method for mapping PCI to satellite beams to which the present disclosure may be applied.

[0119] For example, a PCI may refer to an index that can logically distinguish a cell. That is, beams having the same PCI value may be included in the same cell. For example, referring to FIG. 11(a), a PCI may be assigned to multiple satellite beams. Conversely, referring to FIG. 11(b), one PCI may be assigned to each satellite beam in one satellite. For example, a satellite beam may be configured with one or more SSB (Synchronization Signal Block, SS / PBCH block) beams. One cell (or PCI) may be configured with up to L SSB beams. Here, L may be 4, 8, 64, or 256 depending on the size of the frequency band and / or subcarrier band, but is not limited to the above embodiment. That is, L may use one or more SSB indexes for each PCI, similar to a terrestrial network (TN), which is an existing communication system (NR system). This allows SSBs transmitted through different beams to be distinguished, and the SSB index may be mapped to a logically defined antenna port or a physically separated beam.

[0120] For example, a terminal connectable to an NTN may be a terminal that supports a Global Navigation Satellite System (GNSS) function. However, terminals connectable to an NTN may also include terminals that do not support GNSS. As another example, an NTN may support a terminal that supports a GNSS function but does not acquire location information through GNSS, and is not limited to the above-described embodiment.

[0121] As described above, a terminal can communicate through an NTN. For example, a terminal can receive services based on a 5G / B5G NTN-based non-terrestrial network. This allows the terminal to escape the regional, environmental, spatial, and economic constraints of wireless access services (e.g., LTE, NR, WiFi, etc.) based on the installation of terrestrial network equipment. For example, based on the above, advanced wireless access technologies provided on terrestrial networks may be applicable to non-terrestrial network platforms (e.g., satellites and UAVs). This allows various wireless access service products and technologies to be provided along with advanced network technologies.

[0122] The NTN platform can function as a kind of mirror, carrying the functions of relaying NR signals in space or at high altitudes, or as a base station (gNB, eNB). As an example, the NG-RAN-based NTN architecture can realize its functions using the "Transparent payload-based NTN" and "Regenerative payload-based NTN" structures, as mentioned above.

[0123] Furthermore, as an example, NTN technology can be utilized as an extended network structure and technology of the 5GIAB (Integrated Access and Backhaul) architecture to provide wider coverage and more wireless connectivity services. The integration of NTN with terrestrial networks can ensure service continuity and scalability of 5G systems.

[0124] As a specific example, an integrated NTN / TN network can provide significant benefits in terms of 5G target performance (e.g., user-experienced data transmission speed and reliability) in urban and suburban areas. As another example, an integrated NTN / TN network can ensure connectivity not only in highly dense areas (e.g., concert venues, sports stadiums, shopping centers, etc.) but also for fast-moving objects such as airplanes, high-speed trains, vehicles, and ships. As another example, an integrated NTN / TN network can use data transmission services simultaneously from the NTN network and the TN network through its multi-connection function. In this case, it is possible to selectively utilize better networks depending on the traffic characteristics and traffic load, thereby achieving both the efficiency and economy of 5G wireless transmission services.

[0125] A terminal on general flat ground can simultaneously connect to the NTN network and the TN network to use wireless data services. Furthermore, the terminal can simultaneously connect to one or more NTN platforms (e.g., two or more LEO / GEO satellites) to provide wireless data connection services for harsh environments or regions that are difficult to support with the TN network. This allows the terminal to be used in conjunction with various services. In particular, the integrated NTN network and TN network improves the reliability of autonomous driving services and enables efficient network operation, and is not limited to the above-mentioned embodiments.

[0126] For example, LTE mobile communication-based V2X technology or standard technology based on the IEEE 802.11p standard may have similar service limitations. LTE V2X standards can be provided to meet the requirements defined by C-ITS (e.g., a time delay of approximately 100 ms, reliability of approximately 90%, and generation of messages of tens to hundreds of bytes approximately 10 times per second). Therefore, new V2X services requiring low latency, high reliability, high data traffic capacity, and improved positioning may be required. Based on the above, standardization of 5G wireless access technology (e.g., New Radio (NR)) is currently underway. For example, various numerologies, frame structures, and corresponding L2 / L3 protocol structures are being standardized to more flexibly meet the requirements of new services than LTE. Based on the above, sidelink wireless access technology can be introduced based on 5G mobile communication technology to support improved V2X services such as autonomous driving and remote driving, and the NTN network can be utilized for this purpose.

[0127] As another example, NTN networks can be used to support IoT services in harsh environments and areas not covered by terrestrial networks. For example, IoT equipment may often need to perform wireless communication with minimal power consumption in harsh channel environments (e.g., mountains, deserts, or oceans) depending on its intended use. Previously proposed cellular-based technologies may primarily be intended to provide mobile broadband (MBB) services. Therefore, they may be less efficient in providing IoT services in terms of radio resource utilization and power control, and may not be able to support flexible operation. Furthermore, as an example, existing non-cellular-based IoT technologies may have limitations in providing various IoT services due to limited mobility support and coverage. Taking the above into consideration, NTN networks can be applied, thereby improving services.

[0128] Furthermore, for example, applying 5G mobile communication-based sidelink technology through the NTN network can provide users with wider coverage and mobility through a more efficient wireless communication method than current Bluetooth / Wi-Fi-based wearable devices. Furthermore, it can differentiate from existing communication standards in applications (e.g., wearable multimedia services) that require high data transmission speeds and mobility support using wearable devices.

[0129] As another example, the NTN network can improve public safety communication networks and expand disaster communication coverage. For example, the high reliability and low latency technology of 5G mobile communication systems can be used through the NTN network to provide public services such as disaster response. For example, by utilizing mobile base stations such as drones that support 5G mobile communications, mobile broadband services can be supported even in deserts and high mountain areas. In other words, when the NTN network is applied to public services, it can cover a variety of regions, thereby expanding disaster communication coverage.

[0130] FIG. 12 is a diagram illustrating a reference location to which the present disclosure can be applied. Referring to FIG. 12, satellites 1210 and 1220 having earth-fixed beams can provide service to a fixed location for a specific time based on the fixed beam. In an NTN environment, the distance between a terminal and a satellite is large, so signal strength within a cell may be similar. Therefore, a terminal in an RRC idle state can consider a reference location as a condition for performing neighbor cell measurement for cell reselection. That is, a terminal in an RRC idle state can perform cell measurement for cell reselection based on the distance between the terminal and the reference location. Specifically, a terminal located within the coverage of satellite 1 (Sat1, 1210) can obtain reference location information from the network through system information. The terminal can confirm the distance between the terminal and the reference location based on the terminal's location. Here, if the distance between the terminal and the reference location is greater than a distance threshold, the terminal recognizes that the terminal's current location is the cell boundary and can perform measurements on neighbor cells. That is, the terminal can perform cell measurements for cell reselection taking into account the distance between the reference position and the terminal.

[0131] FIG. 13 illustrates received signal strengths depending on distance in TN and NTN. Referring to FIG. 13(a), in a TN environment, the signal strengths of terminals 1321 and 1322 located within the coverage of a base station 1310 may differ significantly depending on the distance between the base station 1310 and the terminals. Specifically, the received signal strength of a terminal (near-UE) 1321 located at the center of the coverage of a base station 1310, whose transmission signal is on the ground, may be greater than the received signal strength of a terminal (far-UE) 1322 located at the outer edge of the coverage, and the difference may be noticeable. On the other hand, referring to FIG. 13(b), terminals 1331 and 1332 located within the coverage of a satellite 1330 may be considered in an NTN environment. Here, because the transmission signal is generated from a satellite 1330 located at a high altitude, the difference between the received signal strength of a terminal (near-UE) 1331 near the coverage center and that of a terminal (far-UE) 1332 located at the outer edge of the coverage may not be large. Therefore, in an NTN environment, there may be limitations to a terminal performing cell reselection considering only received signal strength. Specifically, the terminal does not need to perform measurements for cell reselection because the difference in received signal strength within the satellite coverage is not large. Therefore, there may be insufficient time for neighbor cell SSB search, signal strength measurement, and camping. In consideration of the above, in an NTN environment, a terminal can perform measurements for cell reselection considering the distance between the reference position and the terminal, as described above.

[0132] Further, as an example, a terminal in the above-mentioned earth fixed cell or fixed beam can acquire information for time-based cell reselection through system information. For example, the terminal can acquire t-service, which is the time during which satellite coverage is maintained (or serving time), through the system information. The terminal can perform cell reselection based on the t-service time information. Here, the t-service time may be the time during which service is provided for a fixed cell. Therefore, when the terminal receives t-service information through the system information, the terminal can consider the cell as a fixed cell. On the other hand, if the terminal does not receive t-service information through the system information, the terminal can consider the cell as a moving cell. That is, the terminal can implicitly acquire fixed cell and moving cell information through the t-service information.

[0133] As another example, a terminal in a fixed cell may perform measurements for cell reselection when the distance between the reference position and the terminal is greater than a distance threshold, as described above. That is, when the terminal is located within the fixed cell coverage, the terminal may perform measurements for cell reselection using reference position information or service information. Here, the reference position of the mobile cell may be different from the reference position of the fixed cell. Specifically, since the mobile cell moves due to the movement of the satellite, the reference position must also move. Therefore, when the terminal performs measurements for cell reselection based on the reference position of the mobile cell, performing measurements using an existing reference position determination method may result in a problem of the terminal performing measurements that do not require measurements. This will be described later. Meanwhile, in an NTN environment, a terminal may operate in a frequency band above 10 GHz and perform communications via satellites based thereon. Also, as an example, mobility, service continuity, emergency calls, and public warning systems that take into account high propagation delays and satellite movement may be provided in an NTN environment, but this is not limited to a specific embodiment.

[0134] FIG. 14 is a diagram illustrating a method for performing distance-based measurements for cell reselection to which the present disclosure is applied. Referring to FIG. 14, a moving cell may be provided based on a satellite 1410. Here, a case may be considered in which a terminal performs measurements for cell reselection taking into account a reference position. Specifically, at time T1, terminal 1 (UE1) 1421 may perform neighbor cell measurements for cell reselection because the distance between terminal 1 and the reference position is greater than the distance threshold. On the other hand, terminal 2 (UE2) 1422 may not perform neighbor cell measurements for cell reselection because the distance between terminal 2 and the reference position is less than the distance threshold. Here, information about the reference position and the distance threshold may be provided to the terminal through system information. Specifically, information about the reference position and the distance threshold may be included in NTN-specific system information (e.g., SIB19). Here, if the terminal switches to an RRC idle / inactive state, the above values ​​may not be changed. Therefore, the terminal may operate based on the same information even at time T2. For example, in FIG. 14, at time T2, UE 2 (UE2) 1422 needs to perform measurements on neighboring cells at the edge of coverage and attempt to camp on another cell. However, since the distance between the location of UE 2 (UE2) 1422 and the reference location is smaller than the distance threshold, measurements on neighboring cells may not be performed. Therefore, a cell reselection procedure may not be performed. That is, there may be limitations on applying the same reference location to a moving cell as to a fixed cell to perform measurements for cell reselection. Here, as an example, the measurement operation of the UE for cell reselection may be as shown in Table 5 below. For example, the UE may perform measurements based on at least one of frequency priority, signal strength of the serving cell, and a distance threshold, which may be as shown in Table 5 below. Also, for example, if the UE receives system information (e.g., SIB19) including t service information from the serving cell, the UE may always perform intra / inter-frequency and inter-RAT measurements before t service regardless of the conditions in Table 5.Here, the t service information may refer to the absolute time (epoch time) for serving the coverage of the fixed cell. Also, as an example, the UE can always measure high-priority Intra / Inter-frequency and Inter-RAT frequencies regardless of Table 5, thereby performing cell reselection.

[0135] [Table 5]

[0136] Also, Figure 15 is a diagram illustrating a reference location update method applicable to the present disclosure. As described above, if the reference location of a moving cell is applied to be the same as the reference location of a fixed cell, problems may occur in measurement conditions. Therefore, in the case of a moving cell, an update to the reference location may be necessary. As an example, in Figure 15, the reference location may be updated based on the moving cell that moves due to the movement of satellite 1510. Here, if the reference location update is not performed, the UE will not be able to perform cell reselection, so it is necessary to update the reference location at specific time intervals.

[0137] Taking the above into consideration, a method for updating the reference location will be described below. As an example, at time T2, terminal 2 (UE2) 1522 can perform cell reselection using updated reference location (T2) information rather than using the reference location (T1) information configured at time T1. Specifically, if the distance between the location of terminal 2 (UE2) 1522 and the reference location (T2) at time T2 is greater than a distance threshold, it can perform measurements and attempt camping for cell reselection. Taking the above into consideration, a method for updating the reference location will be described below.

[0138] Reference location update The reference location can be newly defined or updated in accordance with the movement of the satellite in the moving cell. Here, the reference location can be updated based on parameters indicating time intervals (e.g., timer, epoch time, SFN & subframe). As another example, the reference location can be indicated in list form based on absolute time, which will be described later. As an example, SFN (system frame number) can refer to the number of a specific system frame with a length of 10 ms. Also, a subframe can be a frame structure with a time length of 1 ms within the subframe. As another example, other time units can be considered, and the present invention is not limited to a specific time unit.

[0139] Here, as an example, the reference location update can be performed based on a reference location update time or when a timer expires. Here, the reference location update can be performed based on satellite ephemeris and system information acquisition. As another example, the reference location update can be performed through a reference location list. Here, the reference location list is a set of absolute time (epoch time) and reference locations, and can refer to reference locations associated with satellite ephemeris and used at specific positions of the satellite, as will be described later.

[0140] For example, satellite ephemeris may refer to satellite position information at a specific time or period. Satellite ephemeris is Earth-Centered, Earth-Fixed (ECEF) coordinate information, and may express the coordinates (X, Y, Z) of a satellite relative to the center of the Earth in kilometers. As a specific example, satellite ephemeris may be expressed as absolute time (epoch time: day, hour, minute, second) in the form of "X=19151.529km, Y=-37578.251km, Z=17.622km" for "2022-06-27 08:00:00.000." As another example, the satellite orbit information may be expressed as absolute time (epoch time: day, hour, minute, second) such as "2022-06-27 08:05:00.000" with "X=19151.053 km, Y=-37578.556 km, Z=17.359 km." Here, the speed (km / s) along each of the X, Y, and Z axes may be expressed, and this is not limited to a specific embodiment. Furthermore, as an example, the reference position may be provided in an elliptical format such as an ellipsoid point. The reference position may be indicated by bits indicating north / south direction and bits indicating latitude / longitude, and the ellipsoid point may be as shown in Table 6 below, but is not limited to a specific embodiment.

[0141] [Table 6]

[0142] A method for updating the reference position based on a timer (hereinafter referred to as Method 1) and a method for updating the reference position based on a reference position list (hereinafter referred to as Method 2) will be described below.

[0143] As one example, the terminal may update its reference position at specific time intervals set by the network. Here, the specific time intervals may be specified by a timer. The terminal may update its reference position through satellite ephemeris at specific time intervals specified by the network. As another example, the terminal may obtain system information and update its reference position at specific time intervals specified by the network.

[0144] For example, the absolute time (epoch time) may be expressed as an integer value, i.e., a value expressed in a specific unit based on a specific point in time. As a specific example, the absolute time (epoch time) may be expressed as "INTEGER(0..549755813887)" in 10 ms increments from 00:00:00 on January 1, 1900, but is not limited thereto. That is, a parameter indicating a specific point in time may be used, and is not limited to a specific embodiment. Here, the reference location update may be performed through system information acquisition. For example, the terminal may update the reference location for each uplink synchronization validity duration (e.g., UlSyncValidityDuration). As another example, the terminal may update the reference location based on a new timer, which is a reference location update timer. As another example, the reference location update may be performed based on satellite ephemeris information. The terminal may update the reference location based on a new timer, which is a reference location update timer.

[0145] FIG. 16 illustrates a method for performing a reference position update based on system information acquisition that is applicable to the present disclosure.

[0146] Referring to FIG. 16, in an NTN environment, a terminal can acquire system information for uplink synchronization. That is, the network can transmit the feeder link delay and satellite coordinates to the terminal through the system information, thereby performing uplink synchronization. Here, since satellites move continuously, the feeder link delay and satellite coordinates may change continuously. Therefore, if a change in the delay for uplink synchronization occurs, the network can modify the parameters for uplink synchronization (e.g., Common TA, ephemeris) in the system information and transmit it to the terminal. Also, the terminal can acquire system information at specific intervals (e.g., UlSyncValidityDuration) and update the information for uplink synchronization. Here, the specific time may be the uplink synchronization validity time (UlSyncValidityDuration). For example, the specific time may mean the time during which uplink synchronization is valid and may be a kind of timer. That is, a timer can operate for the time period during which uplink synchronization is valid based on the parameter for the specific time (e.g., UlSyncValidityDuration) included in the system information. Hereinafter, for convenience of explanation, a specific time (e.g., UlSyncValidityDuration) included in the system information will be referred to as an uplink synchronization validity time. However, this is a configuration for convenience of explanation and is not limited to the above-mentioned name.

[0147] Here, the uplink synchronization validity time may refer to the validity time of parameters for uplink synchronization (e.g., Common TA), satellite ephemeris, and other parameters depending on satellite movement. Here, the network may indicate to the terminal the start position of the time during which the parameters are valid as the uplink synchronization validity time using the SFN and subframe based on absolute time (epoch time). The terminal may acquire system information before the uplink synchronization validity time expires, update parameters for uplink synchronization (e.g., Common TA), satellite ephemeris, and other parameters related to satellite movement, and resume the uplink synchronization validity time. For example, if the terminal does not update parameters until the uplink synchronization validity time expires, the terminal may determine that the parameters are invalid and suspend uplink transmission.

[0148] As a specific example, referring to FIG. 16, the network may indicate, through the system information, a parameter for uplink synchronization (e.g., Common TA), satellite orbit information (e.g., epoch time), and a starting point at which other satellite movement-related parameters are valid based on the SFN and subframe through parameters related to absolute time (epoch time). In addition, the uplink synchronization valid time may be indicated in seconds. As a specific example, (s5, s10, s15, s20, s25, s30, s35, s40, s45, s50, s55, s60, s120, s180, s240) may be indicated as the uplink synchronization valid time, and this is not limited to a specific embodiment.

[0149] In FIG. 16, the network can indicate SFN0 and subframe 4 as valid starting points through parameters related to absolute time based on system information. Therefore, the terminal can start the uplink synchronization valid time from subframe 4 within SFN0. Here, if the uplink synchronization valid time is set to 5 seconds, the terminal can determine that parameters for uplink synchronization (e.g., Common TA), satellite orbit information (e.g., ephemeris), and other satellite movement-related parameters acquired through the system information are valid for up to 5 seconds (i.e., SFN500, subframe 3). Here, the terminal can acquire system information and update parameters for uplink synchronization (e.g., Common TA), satellite orbit information (e.g., ephemeris), and other satellite movement-related parameters before the uplink synchronization valid time expires.

[0150] Here, for example, in a fixed cell environment, the reference position may not change for t service time or may change based on a long period. Therefore, the reference position can only be updated through an SI Modification procedure (i.e., a paging message). On the other hand, as mentioned above, in a moving cell environment, the reference position needs to be continuously updated. Therefore, the existing position can be continuously updated based on an uplink synchronization valid time or a timer.

[0151] As a specific example, FIG. 17 is a diagram illustrating a method for performing a reference position update applicable to the present disclosure. Referring to FIG. 17, the network can indicate the effective time and start position of the reference position through system information. For example, the effective time of the reference position is the above-mentioned uplink synchronization effective time, and the start position can be indicated by SFN and subframe through parameters related to absolute time (epoch time). If the parameters related to absolute time (epoch time) indicate SFN 0 and subframe 4 in FIG. 17, the effective start position of the reference position can be SFN 0 and subframe 4. The terminal can operate a timer with SFN 0 and subframe 4 as the start position. For example, the timer can correspond to the above-mentioned uplink synchronization effective time. If the timer is set to 5 seconds, the effective time of the reference position can be until subframe 3 in SFN 500. Therefore, the terminal can obtain system information and update the reference position before the end of subframe 3 in SFN 500. Here, for example, the system information can be, but is not limited to, NTN-specific system information as SIB19. The system information can be periodically scheduled and transmitted through a downlink shared channel. That is, the terminal can receive an SI message including SIB19 within the SI window indicated by SIB1, thereby performing a reference position update before the uplink synchronization valid time expires. Based on the above, when updating the reference position through the uplink synchronization valid time, the uplink synchronization valid time can be indicated as (s5, s10, s15, s20, s25, s30, s35, s40, s45, s50, s55, s60, s120, s180, s240), and can be set from 5 seconds to 240 seconds.

[0152] However, unlike uplink synchronization, the reference position update may be information for performing measurements for cell reselection. Therefore, the reference position update may need to use a timer value other than the above-mentioned valid time so that measurements for cell reselection can be performed in detail. That is, a new timer for the reference position update may be used, which will be described below. Here, as an example, the reference position may be updated based on system information acquisition. As another example, the reference position may be updated based on a satellite orbit, which will be described later.

[0153] As a specific example, FIG. 18 is a diagram illustrating a method for updating a reference location based on a new timer applicable to the present disclosure. Referring to FIG. 18, the start point of the reference location can be indicated by an SFN and a subframe through parameters related to absolute time (epoch time). Here, the terminal can operate a new timer (referencelocationupdatetimer) at the start point of the reference location. As an example, the new timer can be a reference location update timer. However, this is merely one name for convenience of explanation and is not limited to this name. That is, a new timer for updating the reference location can be used, and will be referred to as a reference location update timer hereinafter for convenience of explanation.

[0154] Specifically, in FIG. 18, the terminal may operate a reference position update timer at the position of subframe 4 within SFN0. The terminal may update the reference position before the reference position update timer expires. For example, if the reference position update timer is set to 10 ms, the terminal may operate the timer at subframe 4 within SFN0. The terminal may acquire system information up to subframe 4 within SFN1 based on the reference position update timer and update the reference position. As a specific example, the reference position may be changed from reference position 1 to reference position 2 based on the reference position update. However, for example, the reference position may not be changed within the timer, and therefore reference position 1 and reference position 2 may be the same, and this is not limited to the specific embodiment. For example, the reference position may be changed when acquiring the next system information. That is, the reference position used from subframe 4 within SFN0 to subframe 3 within SFN1 may be the same as the reference position used from subframe 4 within SFN1 to subframe 3 within SFN2. Thereafter, the reference position applied from subframe 4 within SFN2 may be different, and this is not limited to the above-mentioned embodiment.

[0155] Here, for example, the reference position update may be performed even after the reference position update timer expires. When the UE receives system information and updates the reference position after the reference position update timer expires, the UE may reset the reference position validity start point in the SFN and subframe through a parameter related to absolute time (epoch time) in the system information, and operate the reference position update timer.

[0156] As another example, if the UE does not perform a reference position update until the reference position update timer expires, the UE may perform measurements for cell reselection based on the existing reference position. As another example, if the UE does not perform a reference position update until the reference position update timer expires, the UE may determine that the existing reference position is invalid and may not perform an operation of performing measurements through the reference position, but this is not limited to a specific embodiment.

[0157] FIG. 19 illustrates a method for performing a reference position update based on a reference position update timer applicable to the present disclosure.

[0158] Referring to FIG. 19, parameters related to the uplink synchronization effective time and reference position update timer parameters for updating the uplink synchronization parameters can be operated separately. For example, the UE can receive from the network an indication of the start point at which parameters for uplink synchronization (e.g., Common TA), satellite orbit information (e.g., ephemeris), and other satellite movement-related parameters are valid using an absolute time (epoch time) parameter via an SFN and a subframe. Here, the UE can operate the timer related to the uplink synchronization effective time and the reference position update timer at the valid start point. Furthermore, the UE can receive configuration of the valid start points for the uplink synchronization effective time and the reference position update timer using an absolute time (epoch time) parameter via an SFN and a subframe. For example, in FIG. 19, the UE can operate the timer related to the reference position update timer and the uplink synchronization effective time in subframe 4 within SFN 0. Here, for example, the reference position update timer can be set to 1 second, and the timer related to the uplink synchronization effective time can be set to 10 seconds. Here, SFNX can be a value between 0 and 1023, and if X+1000 is greater than 1023, SFN can restart from 0.

[0159] The terminal may acquire system information before or after the reference position update timer expires and perform a reference position update. For example, if the reference position update timer is set to 1 second, the terminal may operate the timer in subframe 4 within SFNX and update the reference position in subframe 4 within SFNX + {100, 200, 300, 400, 500, 600, 700, 800, 900} by acquiring system information before or after its expiration. On the other hand, the uplink synchronization parameters may be updated by acquiring system information before or after the expiration of the timer related to the uplink synchronization validity time. That is, if the timer related to the uplink synchronization validity time is set to 10 seconds, the terminal may operate the timer related to the uplink synchronization validity time in subframe 4 within SFNX and update the uplink synchronization parameters in subframe 4 within SFNX + 1000 by acquiring system information before or after its expiration.

[0160] Here, the reference position may not be changed for each reference position update timer, or the reference position may change in the system information when the next reference position is updated. That is, the reference position used from subframe 4 within SFNX to subframe 3 within SFNX+100 may be the same as the reference position used from subframe 4 within SFNX+100 to subframe 3 within SFNX+200. However, the reference positions applied from subframe 4 within SFNX+200 may be different. That is, in the above, each timer may operate at the same effective time start point, and is not limited to a specific embodiment.

[0161] FIG. 20 illustrates a method for performing a reference position update based on system information acquisition applicable to the present disclosure.

[0162] Referring to FIG. 20, a terminal 2010 may acquire system information and update its reference location before or after a timer (uplink synchronization validity interval timer and / or reference location update timer) expires. The terminal 2010 may be in an RRC connected state with the network through NTN cell A 2020. As another example, the terminal 2010 may transition to an RRC dormant state after previously connecting to the network. Referring to FIG. 20, the terminal 2010 may acquire at least one of a reference location update timer, a reference location, an epoch time, and satellite ephemeris through an RRC message (e.g., system information, RRC Release) from NTN cell A 2020 (S300). Here, the terminal 2010 in the RRC connected state may receive an RRC release message and transition to an RRC dormant state. Here, the terminal 2010 in the RRC dormant state may receive system information. Furthermore, the terminal 2010 in the RRC idle state may be camped on the NTN cell A 2020 (S310). Here, the terminal 2010 can use at least one of an uplink synchronization valid time timer and a reference position update timer as a timer for the reference position update (S320). As an example, the timers can be started at a starting point set based on the SFN and subframe indicated through an absolute time (epoch time) parameter. The terminal 2010 can acquire system information and perform a reference position update even before or after the expiration of at least one of the uplink synchronization valid time timer and the reference position update timer.

[0163] As a specific example, when the terminal 2010 updates the reference position based on the uplink synchronization validity time timer, the terminal 2010 may acquire parameter information to be updated through an RRC message (S330). Here, the newly updated parameters may be parameters for uplink synchronization (e.g., Common TA) required for uplink synchronization, satellite orbit information (e.g., ephemeris), and reference position information for updating the reference position.

[0164] As another example, when the UE 2010 updates the reference position based on the reference position update timer, the newly updated parameters may be reference position information required for the reference position update. Here, as an example, if the timer expires but the reference position update has not been performed, the UE may determine that the reference position is invalid and may not check the distance condition until acquiring system information. If the UE subsequently acquires system information and updates the reference position, the UE may check the distance condition from the start position (epoch time) for which the reference position in the system information is valid and determine measurement for cell reselection.

[0165] As another example, the valid start position (epoch time) of the reference position may be different from the valid start position (epoch time) of the uplink synchronization. As a specific example, the start position (epoch time) for applying uplink synchronization may be subframe Y within SFNX, and the start position (epoch time) for applying the reference position may be subframe M within SFN Z. As another example, the start position (epoch time) for applying uplink synchronization may be subframe Y within SFNX, and the start position (epoch time) for applying the reference position may be subframe M within SFNX.

[0166] As another example, the UE may check the SFN and subframe related to the valid start point through the absolute time (epoch time) based on the system information. Here, the UE may operate both the uplink synchronization valid time timer and the reference position update timer based on the valid start point. Then, the UE may acquire the system information before or after the uplink synchronization valid time timer and the reference position update timer expire. Here, the system information may include reference position information for the reference position update and information about the uplink synchronization valid interval. Therefore, upon receiving the system information, the UE may update the reference position and determine that synchronization is valid. Thus, upon receiving the system information, the UE may reset both the uplink synchronization valid time timer and the reference position update timer and restart both the uplink synchronization valid time timer and the reference position update timer at the SFN and subframe indicated by the parameter related to the absolute time (epoch time) included in the system information. That is, regardless of whether the reference position update is possible or not and whether uplink synchronization is maintained or not, when the terminal acquires system information after starting the uplink synchronization valid time timer and the reference position update timer from the valid start point, it can reset both the uplink synchronization valid time timer and the reference position update timer and start them at a new valid start point, and is not limited to a specific embodiment.

[0167] As another example, the reference position update can be performed through satellite ephemeris rather than through the acquisition of system information, and a method for this will be described below.

[0168] FIG. 21 illustrates ECEF (Earth-Centered, Earth-Fixed) coordinates and ellipsoid points applicable to the present disclosure. For example, satellite ephemeris information can be expressed based on ECEF coordinate information, and reference location information can be expressed using ellipsoid points. Here, the ECEF coordinate information can indicate x, y, and z values ​​and the speed of movement along each axis in km / s relative to the center of the Earth. The ellipsoid point information can indicate latitude (λ, longitude) and longitude (φ, latitude), and whether the longitude is located in the northern or southern hemisphere relative to the equator. For example, Tables 7 and 8 may be examples of satellite coordinates and velocities based on absolute time (epoch time). Referring to Table 8, the starting position at which the satellite coordinates and velocities are valid can be indicated by a specific SFN and subframe. For example, the network can transmit an absolute time (epoch time, SFN & subframe) and the corresponding satellite coordinates and velocities to a terminal via system information (e.g., SIB19). The network can then update the system information to change the epoch time and the satellite coordinates and velocities.

[0169] As a specific example, the terminal may acquire system information. Here, the system information may include parameters related to absolute time (epoch time), and the validity start point may be indicated through the SFN and subframe. For example, if the terminal confirms the absolute time (epoch time) corresponding to SFN 100 and subframe 2 and the corresponding satellite coordinates and velocity, the terminal may determine that the satellite coordinates and velocity are valid from the time of SFN 100 and subframe 2. Thereafter, if the terminal acquires system information and confirms the absolute time (epoch time) corresponding to SFN 200 and subframe 2 and the corresponding satellite coordinates and velocity, the terminal may update the absolute time (epoch time) and the corresponding satellite coordinates and velocity.

[0170] For example, when updating the reference position based on satellite ephemeris, the reference position expressed as an ellipsoid point can be derived from the satellite coordinates and velocity. JPEG2025533382000010.jpg1762 and longitude It can be expressed as JPEG2025533382000011.jpg1762. Here, the northern or southern hemisphere can be identified by longitude. Therefore, the terminal can derive the ellipsoid-point using the ECEF coordinate information, which is the satellite ephemeris of the serving cell, and the speed.

[0171] [Table 7]

[0172] [Table 8]

[0173] 22 is a diagram illustrating a reference location update method applicable to the present disclosure. As an example, in an NTN mobile cell, if the reference location is not updated taking into account the movement of a satellite 2210, the terminal cannot perform accurate cell reselection.

[0174] As described above, the network can provide satellite ephemeris to the terminal. For example, referring to FIG. 22, specific satellite ephemeris may be provided as satellite ECEF coordinates and velocity at 2030-11-10 11:00:00.000 (SFN2 & subframe 4). As another example, specific satellite ephemeris may be provided as satellite ECEF coordinates and velocity at 2030-11-10 11:05:00.000 (SFN502 & subframe 4). Therefore, the terminal can derive ECEF coordinates based on the satellite velocity between 2030-11-10 11:00:00.000 (SFN2 & subframe 4) and 2030-11-10 11:05:00.000 (SFN502 & subframe 4) and convert them into ellipsoid points.

[0175] For example, the network may instruct a reference location update timer, and the terminal may update the reference location based on satellite ephemeris information each time the timer expires. For example, the terminal may determine the reference location based on Unix time (epoch time, SFN, subframe) received through system information and then operate the timer. Here, when the timer expires, the terminal may update the reference location based on the satellite ephemeris information.

[0176] FIG. 23 is a diagram illustrating a method for updating a reference location based on satellite orbit information applicable to the present disclosure. For example, the expression 2030-11-10 11:00:00.000 in FIG. 23 represents the time in years, months, days, hours, minutes, and seconds, and the coordinates and velocity information of the satellite's location can be transmitted through the satellite orbit information (ephemeris). Furthermore, the SFNX and subframe 0, which are the time points at which uplink synchronization parameters (e.g., Common TA, Ephemeris) are applied, can be indicated based on parameters related to absolute time (epoch time) in the system information. Here, a case in which the reference location update timer is set to 1 minute can be considered, but this is merely an example for convenience of explanation and is not limited to the above-described embodiment. Referring to FIG. 23, the reference location update timer can operate at subframe 0 within SFNX, which is the absolute time (epoch time). That is, the initial reference location can be a reference location between subframe 0 and 1 minute within SFNX. At this time, the terminal can update the reference position based on the validity start time and the initial reference position and determine measurements for cell reselection.

[0177] More specifically, the UE checks the initial reference location and distance d1 between subframe 0 and 1 minute within SFNX, and if the distance is less than the distance threshold, it may not perform measurements for cell reselection. The UE may also update the reference location between subframe 0 and 1 minute within SFNX when the reference location update timer expires, and restart the reference location update timer. The UE may also check the updated reference location and distance d2 between subframe "0+1 minute" within SFNX and subframe "0+2 minute" within SFNX, and if the distance is less than the distance threshold, it may not perform measurements for cell reselection. The UE may also update the reference location between subframe "0+2 minute" within SFNX when the reference location update timer expires, and restart the reference location update timer. The UE may also check the distance d3 from the updated reference location between subframe "0+2 minute" within SFNX and subframe "0+3 minute" within SFNX, and perform measurements for cell reselection if the distance is greater than the distance threshold. Then, after a certain time has elapsed (e.g., 5 minutes), the terminal can acquire initial reference location information to be applied from subframe 0 within SFNY, which is a new absolute time (epoch time), based on the movement of the satellite 2310. That is, the terminal can perform a reference location update based on the reference location update timer until information on a new initial reference location is obtained based on the system information. Here, the reference location update timer is expressed in time units, but is not limited to this. As a specific example, the reference location update timer can be instructed to update at a point where 'SFN modulo X=0' is satisfied. If the network wants to instruct the reference location to be updated every SFN (10 ms), X can be set to 1, and if the network wants to instruct the reference location to be updated every two SFNs (20 ms), X can be set to 2. As another example, a specific absolute time can be specified. The absolute time (epoch time) may be expressed as an integer value and may be a value expressed in a specific unit based on a specific point in time.As a specific example, the absolute time (epoch time) may be expressed as "INTEGER(0..549755813887)" in 10 ms increments from 00:00:00 on January 1, 1900, but is not limited to this. In this case, the network may specify a specific absolute time between the time intervals SFNX&subframe 0 and SFNY&subframe 0, and perform a reference position update based on this. That is, the terminal may update its reference position when the specific absolute time is reached after SFNX&subframe 0.

[0178] FIG. 24 illustrates a method for updating a reference location based on satellite orbit information. Referring to FIG. 24, a reference location update may be performed based on at least one of a reference location update timer, Unix time, and SFN interval. A terminal 2410 may be in an RRC connection state with a network via NTN Cell A 2420. For example, the terminal 2410 may have previously connected to the network and transitioned to an RRC idle state. For example, the terminal 2410 may receive an RRC message (system information, RRC release) from NTN Cell A 2420 (S200). At this time, the RRC message may include a reference location update timer. For example, the reference location update timer may be indicated based on at least one of a timer, Unix time, and SFN. Furthermore, the RRC message may further include at least one of an initial reference location, an epoch time, and satellite orbit information (ephemeris), and indicate the information to the terminal 2410. Here, the terminal 2410 in the RRC connected state receives an RRC release message and can transition to an RRC idle state. Also, the terminal 2410 in the RRC idle state can receive system information. Here, the terminal 2410 in the RRC idle state may be camped on NTN cell A 2420 (S210). Also, the terminal 2410 in the RRC idle state can determine an initial reference position based on absolute time (epoch time). The terminal 2410 can check the distance from the reference position of NTN cell A 2420 and compare it with a distance threshold to perform measurement for cell reselection (S215). As a specific example, if the distance between the terminal 2410 and the reference position is greater than the distance threshold, the terminal 2410 can perform measurement for cell reselection. As another example, if the distance between the terminal 2410 and the reference position is less than the distance threshold, the terminal 2410 may not perform measurement for cell reselection.Here, the terminal may perform a reference location update (S220). As an example, if the distance between the terminal 2410 and the reference location is less than the distance threshold, the terminal 2410 may perform a reference location update when a timer expires. Further, as an example, if the distance between the terminal 2410 and the reference location is less than the distance threshold, the terminal 2410 may update the reference location of NTN cell A 2420 when a preset Unix time or a preset SFN interval is reached.

[0179] As a specific example, consider a case where the reference location update timer configured by the terminal 2410 is set to 1 minute. That is, the timer may be the time 1 minute has elapsed since the SFN and subframe indicated by the absolute time (epop time) of the NTN cell A 2420. As another example, the reference location update timer may be indicated by the SFN interval. As a specific example, if the SFN interval is configured as 3 and the absolute time (epop time) indicated by the system information indicates SFN 0 and subframe 3, the reference location may be updated as SFN 3, SFN 6, ..., SFNX. Here, SFN 3, SFN 6, ..., SFNX may refer to the time points at which the SFN modulo SFN interval = 0. Thereafter, if the distance between the terminal 2410 and the reference location of the NTN cell A 2420 becomes greater than the distance threshold, the signal strength of neighboring cells may be measured for cell reselection (S230). For example, the UE 2410 may select NTN cell B 2430 through a cell ranking procedure. Thereafter, the UE 2410 in an RRC idle state may receive system information from NTN cell B 2430 (S240). Here, the system information may include a reference location update timer of NTN cell B 2430. At this time, the reference location update timer may be set based on at least one of a timer, Unix time, and an SFN interval. Furthermore, the system information may include an initial reference location and instruct the UE 2410. Thereafter, the UE 2410 may camp on NTN cell B 2430 (S250). After determining the reference location of NTN cell B 2430, the UE 2410 may check the distance from the reference location and determine measurements for cell reselection (S255). For example, if the distance between the UE 2410 and the reference location is less than a distance threshold, measurements for cell reselection may not be performed.On the other hand, if the distance between the terminal 2410 and the reference position is greater than the distance threshold, the terminal 2410 can perform measurements for cell reselection.

[0180] As another example, a list of multiple absolute times (epoch times) and reference location information can be configured in an RRC message (system information, RRC release). The UE can confirm the reference location to be used at a specific absolute time (epoch time). Here, the absolute time (epoch time) can be provided in units of date, hour, minute, and second, and the reference location can be expressed in ellipsoid coordinates such as the above-mentioned ellipsoid-point. For example, the absolute time (epoch time) can be expressed as an integer value, i.e., a value expressed in a specific unit based on a specific point in time. As a specific example, the absolute time (epoch time) can be expressed as 'INTEGER(0..549755813887)' in 10 ms increments from 00:00:00 on January 1, 1900, but is not limited to this. As an example, Table 9 shows a reference location list. Referring to Table 9, absolute time (epoch time) is configured in 5-minute intervals, and the reference location used by the terminal every 5 minutes can be indicated by an ellipsoid-point, which is an elliptical coordinate. Here, Table 9 below is merely an example and is not limited thereto. As another example, absolute time (epoch time) intervals can be set to 10 minutes, and the reference location can be indicated by an ellipsoid-point corresponding to "2022-06-29 02:00:00.000" and an ellipsoid-point corresponding to "2022-06-29 02:10:00.000".

[0181] That is, the terminal can obtain information about the absolute time (epoch time) set at preset intervals and the corresponding reference position information through the RRC message, and thereby confirm the reference position. As another example, the absolute time (epop time) can be indicated by the SFN and subframe number, and can indicate at what point in time the terminal uses a specific reference position.

[0182] [Table 9]

[0183] FIG. 25 is a diagram illustrating satellite movement and changes in reference position applicable to the present disclosure. Referring to FIG. 25, a satellite 2510 may have non-geo stationary orbit (NGSO) non-steerable beams or fixed beams, and the service area may change as the satellite moves. Therefore, the satellite moves every T1, T1+5 min, and T1+10 min, and the service area may also move accordingly. However, this is merely an example and is not limited to the above embodiment. Here, the network may indicate the reference position list at a preset interval of absolute time (epoch time). For example, the preset interval may be, but is not limited to, 5 minutes. The terminal may receive the configuration of the reference position list through an RRC message (system information, RRC release) and perform measurements for cell reselection based on the distance between the terminal and the reference position.

[0184] 25, the terminal 2520 may be at a fixed location. In this case, the terminal 2520 may check the distance between reference position 1 (2531) and the terminal 2520 at a time between T1 and T1+5 min (e.g., 2022-06-29 02:00:00.000 to 2022-06-29 02:05:00.000). The terminal 2520 may also check the distance between reference position 2 (2532) and the terminal 2520 at a time between T1+5 min and T1+10 min (e.g., 2022-06-29 02:05:00.000 to 2022-06-29 02:10:00.000). Furthermore, the terminal 2520 can check the distance between reference location 3 (2533) and the terminal 2520 at a time between T1+10 min and T1+15 min (e.g., 2022-06-29 02:10:00.000 to 2022-06-29 02:15:00.000). Here, if the distance from the reference location is greater than a distance threshold, the terminal can perform measurements for cell reselection.

[0185] As a specific example, consider a case where the distance threshold is set to a value greater than d1 and less than d2. Here, the terminal 2520 can perform measurements for cell reselection at absolute time (epoch time, 2022-06-29 02:05:00.000). That is, the terminal 2520 does not need to perform measurements for cell reselection between T1 and T1+5 min because the distance d1 between the terminal 2520 and reference position 1 (2531) is less than the distance threshold. On the other hand, the terminal 2520 can perform measurements for cell reselection between T1+5 min and T1+10 min because the distance d2 between the terminal 2520 and reference position 2 (2532) is greater than the distance threshold.

[0186] As another example, absolute time (epoch time) can be indicated by SFN and subframe in Table 10 below. Therefore, reference position update can be performed at a specific SFN and subframe. More specifically, referring to FIG. 25, UE 2520 can check the distance between reference position 1 (2531) and UE 2520 in SFN 100, subframe 2, and perform measurement for cell reselection if the distance is greater than the distance threshold. Thereafter, UE 2520 can check the distance between reference position 2 (2532) and UE 2520 in SFN 200, subframe 2, and perform measurement for cell reselection if the distance is greater than the distance threshold.

[0187] [Table 10]

[0188] FIG. 26 illustrates a reference location list-based signaling procedure and a reference location update procedure applicable to the present disclosure.

[0189] The terminal 2610 may be in an RRC connected state with the network through NTN cell A 2620. Furthermore, the terminal 2610 may transition to an RRC idle state after connecting to the network. Here, the terminal 2610 may receive an RRC message (system information, RRC release) from NTN cell A 2620 (S100). Here, the RRC message may include a reference location list. At this time, the reference location list may be expressed by absolute time (epoch time) and reference location information, as described above. Here, the terminal 2610 in the RRC connected state may receive an RRC release message and transition to an RRC idle state. Furthermore, the terminal 2610 in the RRC idle state may receive system information. Furthermore, the terminal 2610 in the RRC idle state may be camped on NTN cell A 2620 (S110). Here, the UE 2610 in the RRC idle state can check the distance between the reference location of NTN cell A 2620 and the UE 2610 based on the reference location list, compare the distance with a distance threshold, and perform measurements for cell reselection. As a specific example, if the distance between the UE 2610 and the reference location is greater than the distance threshold, the UE 2610 can perform measurements for cell reselection (S115). As another example, if the distance between the UE 2610 and the reference location is less than the distance threshold, the UE 2610 may not perform measurements for cell reselection (S115). If the distance between the UE 2610 and the reference location is less than the distance threshold, the reference location may be updated as a preset time elapses. Specifically, if the next absolute time (epoch time) in the reference location list is reached or the next SFN and subframe number are reached, the reference location of NTN cell A 2620 can be updated (S120). As an example, if the terminal 2610 receives the configuration of the reference position list in Table 9, the previous time and reference position of NTN cell A2620 may be "2022-06-29 02:00:00.000" and the corresponding reference position 1 (Ellipsoid-point).Also, the next time and reference position of NTN cell A2620 can be "2022-06-2902:05:00.000" and the corresponding reference position 2 (Ellipsoid-point).

[0190] On the other hand, if the UE 2610 receives the configuration of the reference position list as shown in Table 10, the reference position of NTN cell A 2620 at the previous time may be reference position 1 (ellipsoid point) corresponding to SFN 100, subframe 2. Also, the reference position of NTN cell A 2620 at the next time may be reference position 2 (ellipsoid point) corresponding to SFN 200, subframe 2. The UE 2610 updates the reference position based on the above and compares the distance between the reference position of NTN cell A 2620 and the UE 2610 with the distance threshold (S130). Here, if the distance between the reference position of NTN cell A 2620 and the UE 2610 is greater than the distance threshold, the UE 2610 may measure the signal strength of neighboring cells for cell reselection. Here, the UE 2610 may select NTN cell B 2630 through a cell ranking procedure. The terminal 2610 in the RRC idle state can receive system information from NTN cell B 2630 and receive reference location list information of NTN cell B 2630 (S140). In addition, the terminal 2610 can camp on NTN cell B 2630 (S150). Here, the terminal 2610 can check the distance between the reference location of NTN cell B 2630 and the terminal 2610 and determine measurements for cell reselection (S155). As an example, if the distance between the reference location of NTN cell B 2630 and the terminal 2610 is smaller than the distance threshold, the terminal 2610 may not perform measurements for cell reselection. On the other hand, if the distance between the reference location of NTN cell B 2630 and the terminal 2610 is greater than the distance threshold, the terminal 2610 can perform measurements for cell reselection, as described above.

[0191] FIG. 27 is a flowchart illustrating a reference location update method to which the present disclosure can be applied. Referring to FIG. 27, a terminal may acquire reference location information (S2710). Here, the reference location information may be acquired through system information. Furthermore, the terminal may acquire at least one of timer information related to an uplink synchronization effective time and a reference location update timer through the system information. The terminal may also acquire absolute time (epoch time) information through the system information and determine the effective start time of the timers described above based on the epoch time information. That is, at least one of the timer information related to the uplink synchronization effective time and the reference location update timer may start from the effective start time (S2720). Here, as an example, if the distance between the terminal and the reference location is less than a distance threshold (S2730), the terminal may not perform measurement for cell reselection (S2740). That is, the terminal may maintain the current cell. On the other hand, if the distance between the terminal and the reference location is greater than the distance threshold (S2730), the terminal may perform measurement for cell reselection (S2740). That is, the terminal can perform measurements for cell reselection by comparing the distance between the terminal and the reference position with a distance threshold.

[0192] In addition, the terminal may perform a reference location update before or after the timer expires (S2760). Here, the reference location update may be performed based on system information acquisition. That is, the terminal may acquire system information before or after the timer expires based on at least one of the timer information regarding the validity time and the reference location update timer. Here, the system information may include reference location information, and the terminal may perform a reference location update based on the reference location information.

[0193] As another example, the terminal may perform a reference position update based on satellite ephemeris information. Here, the reference position update may be performed based on a reference position update timer. As an example, the terminal may operate a reference position update timer at the above-mentioned valid start point. Here, the reference position update timer may be set based on at least one of a timer, Unix time, and SFN. In this case, when the reference position update timer expires, the terminal may perform a reference position update based on satellite ephemeris information, as described above.

[0194] FIG. 28 is a flowchart illustrating a reference location update method to which the present disclosure can be applied. Referring to FIG. 28, a terminal may acquire reference location list information (S2810). Here, the reference location list information may be acquired through system information. As an example, the reference location list information may be configured with a specific absolute time and a reference location. Here, as an example, if the distance between the terminal and the reference location is smaller than a distance threshold (S2820), the terminal may not perform measurements for cell reselection (S2830). That is, the terminal may maintain the current cell. On the other hand, if the distance between the terminal and the reference location is greater than the distance threshold (S2820), the terminal may perform measurements for cell reselection (S2830). That is, the terminal may perform measurements for cell reselection by comparing the distance between the terminal and the reference location with the distance threshold.

[0195] The terminal may also perform a reference position update based on the reference position list (S2850). Here, when a specific absolute time arrives, the terminal may update the reference position to the corresponding reference position based on the reference position list information. That is, the terminal may apply a reference position corresponding to a specific time point through the reference position list information and perform measurements based on the reference position.

[0196] FIG. 29 is a diagram showing an apparatus configuration to which the present disclosure can be applied.

[0197] 29, a first device 2900 and a second device 2950 may communicate with each other. In this case, as an example, the first device 2900 may be a base station device, and the second device 2950 may be a terminal device. As another example, both the first device 2900 and the second device 2950 may be terminal devices. That is, the first device 2900 and the second device 2950 may be devices that communicate with each other based on NR-based communication.

[0198] As an example, consider a case where the first device 2900 is a base station device and the second device 2950 is a terminal device. In this case, the base station device 2900 may include a processor 2920, an antenna unit 2912, a transceiver 2914, and a memory 2916. The processor 2920 performs baseband-related signal processing and may include an upper layer processing unit 2930 and a physical layer processing unit 2940. The upper layer processing unit 2930 may process operations of a Medium Access Control (MAC) layer, a Radio Resource Control (RRC) layer, or higher layers. The physical layer processing unit 2940 may process operations of a physical (PHY) layer (e.g., uplink receive signal processing, downlink transmit signal processing). The processor 2920 may control the overall operation of the base station device 2900 in addition to performing baseband-related signal processing. The antenna unit 2912 may include one or more physical antennas, and if multiple antennas are included, it may support multiple input multiple output (MIMO) transmission and reception. The base station device 2900 may also support beamforming. The memory 2916 may store information processed by the processor 2920, software associated with the operation of the base station device 2900, an operating system, applications, etc., and may include components such as buffers. The processor 2920 of the base station device 2900 may be configured to implement the operation of a base station in the embodiments described herein.

[0199] The terminal device 2950 may include a processor 2970, an antenna unit 2962, a transceiver 2964, and a memory 2966. As an example, in the present invention, the terminal device 2950 may communicate with the base station device 2900. As another example, in the present invention, the terminal device 2950 may perform sidelink communication with another terminal device. That is, the terminal device 2950 of the present invention refers to a device capable of communicating with at least one of the base station device 2900 and another terminal device, and is not limited to communication with a specific device. The processor 2970 performs baseband-related signal processing and may include an upper layer processing unit 2980 and a physical layer processing unit 2990. The upper layer processing unit 2980 may process operations of the MAC layer, the RRC layer, or higher layers. The physical layer processing unit 2990 may process operations of the PHY layer (e.g., downlink receive signal processing, uplink transmit signal processing, sidelink signal processing). In addition to performing baseband-related signal processing, the processor 2970 may control the overall operation of the terminal device 2950. The antenna unit 2962 may include one or more physical antennas, and when multiple antennas are included, MIMO transmission and reception may be supported. Beamforming may also be supported. The memory 2966 may store information processed by the processor 2970, software associated with the operation of the terminal device 2950, ​​an operating system, applications, etc., and may include components such as a buffer. The terminal device 2950 according to an example of the present invention may be associated with a vehicle. For example, the terminal device 2950 may be incorporated into, located in, or located on the vehicle. The terminal device 2950 according to the present invention may also be the vehicle itself. The terminal device 2950 according to the present invention may be at least one of a wearable terminal, an AV / VR terminal, an IoT terminal, a robot terminal, and a public safety terminal.The terminal device 2950 to which the present invention can be applied may include any of various types of communication devices that support interactive services using a sidelink for services such as Internet connection, service execution, navigation, real-time information, autonomous driving, safety, and risk diagnosis, etc. It may also include any type of communication device that can perform a sidelink operation, such as an AR / VR device, or a sensor that performs a relay operation.

[0200] Here, the vehicle / terminal to which the present invention is applied may include an autonomous vehicle / terminal, a semi-autonomous vehicle / terminal, a non-autonomous vehicle / terminal, etc. Meanwhile, although the terminal device 2950 according to an example of the present invention is described as being associated with a vehicle, one or more of the UEs may not be associated with a vehicle. This is merely an example, and the application of the present invention should not be construed as being limited by the described example. In addition, the terminal device 2950 according to an example of the present invention may also include various types of communication devices capable of cooperating to support an interactive service using a sidelink. That is, the terminal device 2950 may be used not only to directly support an interactive service using a sidelink, but also as a cooperating device to support an interactive service using a sidelink.

[0201] The terminal device 2950 may acquire reference location information. Here, the reference location information may be acquired through system information. In addition, the terminal device 2950 may acquire at least one of timer information regarding an uplink synchronization effective time and a reference location update timer through the system information. In addition, the terminal device 2950 may acquire absolute time (epoch time) information through the system information and determine the effective start point for the above-mentioned timers based on the epoch time information. That is, at least one of the timer information regarding the uplink synchronization effective time and the reference location update timer may start at the effective start point. Here, as an example, if the distance between the terminal device 2950 and the reference location is smaller than a distance threshold, the terminal device 2950 may not perform measurement for cell reselection. That is, the terminal device 2950 may maintain the current cell. On the other hand, if the distance between the terminal device 2950 and the reference location is greater than the distance threshold, the terminal device 2950 may perform measurement for cell reselection. That is, the terminal device 2950 may perform measurement for cell reselection by comparing the distance between the terminal device 2950 and the reference location with the distance threshold.

[0202] Furthermore, the terminal device 2950 can perform a reference location update before or after the expiration of the above-mentioned timer. Here, the reference location update can be performed based on system information acquisition. That is, the terminal device 2950 can acquire system information before or after the expiration of a timer based on at least one of the timer information regarding the above-mentioned validity time and the reference location update timer. Here, the system information may include reference location information, and the terminal device 2950 can perform a reference location update based on the reference location information.

[0203] As another example, the terminal device 2950 may perform a reference position update based on satellite ephemeris information. Here, the reference position update may be performed based on a reference position update timer. As an example, the terminal device 2950 may operate a reference position update timer at the above-described valid start point. Here, the reference position update timer may be set based on at least one of a timer, Unix time, and SFN. In this case, when the reference position update timer expires, the terminal device 2950 may perform a reference position update based on satellite ephemeris information, as described above. Furthermore, as an example, if the distance between the terminal and the reference position based on the reference position or the updated reference position is greater than a threshold, the terminal device 2950 may perform measurements for cell reselection and select an optimal cell.

[0204] The terminal device 2950 can acquire reference location list information. Here, the reference location list information can be acquired through system information. As an example, the reference location list information may be configured with a specific absolute time and reference location. Here, as an example, if the distance between the terminal device 2950 and the reference location is smaller than a distance threshold, the terminal device 2950 may not perform measurement for cell reselection. That is, the terminal device 2950 can maintain the current cell. On the other hand, if the distance between the terminal device 2950 and the reference location is larger than the distance threshold, the terminal device 2950 can perform measurement for cell reselection. That is, the terminal device 2950 can perform measurement for cell reselection by comparing the distance between the terminal device 2950 and the reference location with the distance threshold.

[0205] Furthermore, the terminal device 2950 can perform a reference location update based on the reference location list. Here, when a specific absolute time arrives, the terminal device 2950 can update the reference location to the reference location based on the reference location list information. That is, the terminal device 2950 can apply a reference location corresponding to a specific time point through the reference location list information and perform measurements based thereon. Further, as an example, if the distance between the terminal device 2950 and the reference location based on the reference location or the updated reference location is greater than a threshold, the terminal device 2950 can perform measurements for cell reselection and select an optimal cell.

[0206] Furthermore, various embodiments of the present disclosure may be implemented using hardware, firmware, software, or a combination thereof, etc. In the case of a hardware implementation, the implementation may be using one or more Application Specific Integrated Circuits (ASICs), Digital Signal Processors (DSPs), Digital Signal Processing Devices (DSPDs), Programmable Logic Devices (PLDs), Field Programmable Gate Arrays (FPGAs), general processors, controllers, microcontrollers, microprocessors, etc.

[0207] The scope of the present disclosure includes software or machine-executable instructions (e.g., operating systems, applications, firmware, programs, etc.) that cause the operations of the methods of the various embodiments to be performed on a device or computer, as well as non-transitory computer-readable media on which such software or instructions are stored and which can be executed on a device or computer.

[0208] The various embodiments of the present disclosure do not enumerate all possible combinations, but are intended to describe representative aspects of the present disclosure, and the matters described in the various embodiments may be applied independently or in combination of two or more. [Industrial Applicability]

[0209] The above may also be applied to other systems.

Claims

1. A method for updating a reference position of a terminal based on non-terrestrial networks (NTN) in a wireless communication system, comprising: obtaining reference location-related information from a base station; determining whether a distance between the terminal and a reference position is smaller than a distance threshold based on the reference position related information, not performing measurements for cell reselection when the distance between the terminal and the reference position is smaller than the distance threshold, and performing the measurements for cell reselection when the distance between the terminal and the reference position is larger than the distance threshold; and progressing the reference position update based on a reference position related timer.

2. The reference position update method according to claim 1 , wherein the reference position related information includes at least one of reference position information, satellite orbit information, reference position update timer information, uplink synchronization valid time information, and absolute time information.

3. determining a validity start point for starting at least one of a reference position update timer and a timer related to an uplink synchronization validity time based on the absolute time information; The reference position update method according to claim 2 , further comprising: acquiring system information including the reference position information to perform the reference position update.

4. determining an effective starting point for starting a reference position update timer based on the absolute time information; The reference position update method according to claim 2 , further comprising: performing the reference position update through satellite orbit information based on the reference position update timer.

5. the reference position related information includes reference position list information, the reference position list information is composed of absolute times and reference positions corresponding to the absolute times, The reference position update method according to claim 1 , wherein the reference position update is performed based on the reference position list information.

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