Method and device for updating reference location in wireless communication system

Abstract

A method by which a terminal updates a reference location on the basis of non-terrestrial networks (NTN) in a wireless communication system, may comprise the steps of: obtaining reference location-related information from a base station; determining whether the distance between the terminal and the reference location is less than a distance threshold on the basis of the reference location-related information, wherein if the distance between the terminal and the reference location is less than the distance threshold, measurement for cell reselection is not performed, and if the distance between the terminal and the reference location is greater than the distance threshold, the measurement for cell reselection is performed; and if the distance between the terminal and the reference location is less than the distance threshold, updating the reference location on the basis of a timer related to the reference location.

Description

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

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

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

[0003] To meet the requirements presented in "IMT for 2020 and beyond," the 3rd Generation Partnership Project (3GPP) NR (New Radio) system is being discussed to support various numerologies based on time-frequency resource units, taking into account various scenarios, service requirements, and potential system compatibility.

[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., vehicle / train / ship-type terminals / personally-carried smartphones) by utilizing non-terrestrial networks (NTNs) as well as terrestrial networks (TNs). Below, a method for measuring neighboring cells and performing cell reselection by considering the mobility of terminals between NTNs and TNs is described.

[0005] The present invention can provide a method and device for updating a reference position considered in a measurement for cell reselection in a wireless communication system.

[0006] The present invention can provide a method and device for updating a reference position by considering a moving cell in an NTN environment.

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

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

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

[0010] The present invention can provide a method and device for updating a reference location based on a reference location list in an NTN environment.

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

[0012] Additionally, according to one 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 validity time information, and absolute time information.

[0013] Additionally, according to one embodiment, a valid starting point for starting at least one of a reference position update timer and a timer for an uplink synchronization valid time based on absolute time information can be determined, and system information including reference position information can be acquired to perform reference position update.

[0014] Additionally, according to one embodiment, a valid starting point for starting a reference position update timer based on absolute time information can be determined, and a reference position update can be performed using satellite orbit information based on the reference position update timer.

[0015] Additionally, according to one embodiment, the reference position related information includes reference position list information, wherein the reference position list information is composed of an absolute time and a reference position corresponding to the absolute time, and the reference position update can be performed based on the reference position list information.

[0016] The features briefly summarized above regarding the present disclosure are merely exemplary aspects of the detailed description of the present disclosure that follows and do not limit the scope of the present disclosure.

[0017] According to the present disclosure, a method for updating a reference position considered in a measurement for cell reselection in a wireless communication system can be provided.

[0018] According to the present disclosure, a method for updating a reference position by considering a moving cell in an NTN environment can be provided.

[0019] According to the present disclosure, a method for setting a timer for a reference position update 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 orbit information (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 effects described above, and other effects not mentioned will be clearly understood by those skilled in the art to which the present disclosure pertains from the description below.

[0024] FIG. 1 is a drawing for explaining an NR frame structure to which the present disclosure can be applied.

[0025] FIG. 2 is a diagram showing an NR resource structure to which the present disclosure can be applied.

[0026] FIG. 3 is a diagram illustrating an NTN including a transparent satellite to which the present disclosure can be applied.

[0027] FIG. 4 is a diagram illustrating an NTN including a regenerative satellite without inter-satellite links (ISLs) to which the present disclosure may be applied.

[0028] FIG. 5 is a diagram illustrating an NTN including a regenerative satellite having an ISL to which the present disclosure can be applied.

[0029] 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.

[0030] 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.

[0031] FIG. 8 is a diagram illustrating a timing advance calculation method to which the present disclosure can be applied.

[0032] FIG. 9 is a diagram illustrating an earth fixed cell scenario to which the present disclosure can be applied.

[0033] FIG. 10 is a diagram illustrating an earth moving cell scenario to which the present disclosure can be applied.

[0034] FIG. 11 is a diagram illustrating a method for mapping PCI to satellite beams to which the present disclosure can be applied.

[0035] Figure 12 is a drawing showing a reference position to which the present disclosure can be applied.

[0036] Figure 13 is a diagram showing the received signal strength according to distance in TN and NTN to which the present disclosure can be applied.

[0037] FIG. 14 is a diagram illustrating a method for performing distance-based measurement for cell reselection to which the present disclosure can be applied.

[0038] Figure 15 is a diagram illustrating a reference position update method to which the present disclosure can be applied.

[0039] FIG. 16 is a diagram illustrating a method for performing a reference position update based on system information acquisition to which the present disclosure can be applied.

[0040] FIG. 17 is a diagram illustrating a method for performing a reference position update to which the present disclosure can be applied.

[0041] 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.

[0042] 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 can be applied.

[0043] FIG. 20 is a diagram illustrating a method for performing a reference position update based on system information acquisition to which the present disclosure can be applied.

[0044] Figure 21 is a diagram showing ECEF (Earth-Centered, Earth-Fixed) coordinates and Ellipsoid-Point to which the present disclosure can be applied.

[0045] Figure 22 is a diagram illustrating a reference position update method to which the present disclosure can be applied.

[0046] Figure 23 is a diagram illustrating a method for updating a reference position based on satellite orbit information to which the present disclosure can be applied.

[0047] 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.

[0048] Figure 25 is a diagram showing satellite movement and reference position change to which the present disclosure can be applied.

[0049] FIG. 26 is a diagram illustrating a reference position list-based signaling procedure and a reference position update procedure to which the present disclosure can be applied.

[0050] Figure 27 is a flowchart of a reference position update method to which the present disclosure can be applied.

[0051] Figure 28 is a flowchart of a reference position update method to which the present disclosure can be applied.

[0052] Figure 29 is a drawing showing a device configuration to which the present disclosure can be applied.

[0053] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the attached drawings so that those skilled in the art can easily implement the present disclosure. However, the present disclosure may be implemented in various different forms and is not limited to the embodiments described herein.

[0054] In describing embodiments of the present disclosure, detailed descriptions of known configurations or functions will be omitted if they are deemed to obscure the gist of the present disclosure. Furthermore, portions of the drawings that are irrelevant to the description of the present disclosure have been omitted, and similar portions are designated with similar reference numerals.

[0055] In the present disclosure, when a component is said to be "connected," "coupled," or "connected" to another component, this may include not only a direct connection, but also an indirect connection in which another component exists in between. Furthermore, when a component is said to "include" or "have" another component, unless otherwise specifically stated, this does not exclude the other component, but rather implies that the other component may be included.

[0056] In this disclosure, terms such as first, second, etc. are used solely to distinguish one component from another, and do not limit the order or importance of components unless specifically stated otherwise. Accordingly, 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.

[0057] In this disclosure, distinct components are used to clearly illustrate their respective characteristics, and do not necessarily imply that the components are separated. 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 specifically mentioned, such integrated or distributed embodiments are also included within the scope of this disclosure.

[0058] In the present disclosure, the components described in various embodiments are not necessarily essential components, and some may be optional components. Therefore, embodiments comprising a subset of the components described in one embodiment are also within the scope of the present disclosure. Furthermore, embodiments including other components in addition to the components described in various embodiments are also within the scope of the present disclosure.

[0059] 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 a signal in a system (e.g., a base station) that manages the wireless communication network, or in a process of transmitting or receiving a signal in a terminal connected to the wireless network.

[0060] It is self-evident that various operations performed for communication with terminals in a network consisting of multiple network nodes including a base station can be performed by the base station or other network nodes other than the base station. 'Base station (BS)' can be replaced by terms such as fixed station, Node B, eNodeB (eNB), ng-eNB, gNodeB (gNB), and access point (AP). In addition, 'terminal' can be replaced by terms such as UE (User Equipment), MS (Mobile Station), MSS (Mobile Subscriber Station), SS (Subscriber Station), and non-AP station (non-AP STA).

[0061] In the present disclosure, transmitting or receiving a channel means transmitting or receiving information or a signal through the channel. For example, transmitting a control channel means transmitting control information or a signal through the control channel. Similarly, transmitting a data channel means transmitting data information or a signal through the data channel.

[0062] In the following description, the term NR (New Radio) system is used for the purpose of distinguishing the system to which various examples of the present disclosure are applied from existing systems; however, the scope of the present disclosure is not limited by this term.

[0063] NR systems support a variety of subcarrier spacings (SCS) to accommodate diverse scenarios, service requirements, and potential system compatibility. Furthermore, NR systems can support the transmission of physical signals / channels across multiple beams to overcome challenging channel conditions, such as high path loss, phase noise, and frequency offsets that occur at high carrier frequencies. This enables NR systems 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).

[0064] Hereinafter, 5G mobile communication technology can be defined to include not only NR systems, but also existing LTE-A (Long Term Evolution-Advanced) systems and LTE (Long Term Evolution) systems. 5G mobile communication may include technologies that operate in consideration of backward compatibility with previous systems as well as the newly defined NR system. Therefore, the 5G mobile communication below may include technologies that operate based on NR systems and technologies that operate based on previous systems (e.g., LTE-A, LTE), and is not limited to a specific system.

[0065] First, we would like to briefly explain the physical resource structure of the NR system to which the present invention is applied.

[0066] FIG. 1 is a drawing for explaining an NR frame structure to which the present disclosure can be applied.

[0067] In NR, the basic unit of time domain is T c =1 / (Δf max ·N f ) can be, Δf max =480·10 3 and N f =4096. Meanwhile, in LTE, the basic unit of time domain is Ts=1 / (△f ref ·N f,ref ) can be, Δf ref =15·10 3 and N f,ref =2048. The constant for the multiple relationship between the NR time base unit and the LTE time base unit is =T s / T c = can be defined as 64.

[0068] Referring to Figure 1, the time structure of a frame for downlink / uplink (DL / UL) transmission is T f =(Δf max ·N f / 100)·T s =10ms. Here, one frame is T sf =(Δf max ·N f / 1000)·T s = It consists of 10 subframes corresponding to 1ms of time. The number of consecutive OFDM symbols in each subframe is N. subframe,u symb =N slot symb ·N subframe,u slot It can be. In addition, each frame is divided into two half frames of the same size, half frame 1 can be composed of sub frames 0-4, and half frame 2 can be composed of sub frames 5-9.

[0069] N TArepresents the timing advance (TA) between the downlink (DL) and uplink (UL). Here, the transmission timing of the uplink transmission frame i is determined based on the downlink reception timing at the terminal, based on the following mathematical expression 1.

[0070] [Mathematical Formula 1]

[0071]

[0072] Here, N TA,offset It may be a TA offset value that occurs due to differences in duplex mode, etc. In FDD (Frequency Division Duplex), N TA,offset has a value of 0, but in TDD (Time Division Duplex), N is used to consider the margin for DL-UL switching time. TA,offset can be defined as a fixed value. For example, in TDD (Time Division Duplex) of FR1 (Frequency Range 1), which is a frequency below 6 GHz, N TA,offset is 39936 or 25600 It could be 39936 is 20.327μs, and 25600 is 13.030μs. Also, at FR2 (Frequency Range 2), which is a millimeter wave (mmWave) frequency, N TA,offset is 13792 It could be. At this time, 13792 is 7.020 μs.

[0073] FIG. 2 is a diagram showing an NR resource structure to which the present disclosure can be applied.

[0074] Resource elements (REs) within a resource grid can be indexed according to each subcarrier spacing. Here, one resource grid can be created for each antenna port and each subcarrier spacing. Uplink and downlink transmission and reception can be performed based on the corresponding resource grid.

[0075] In the frequency domain, one resource block (RB) consists of 12 REs, and an index (nPRB) for one RB can be configured for each of the 12 REs. The index for the RB can be utilized within a specific frequency band or system bandwidth. The index for the RB can be defined as in the following mathematical expression 2. Here, N RB sc represents the number of subcarriers per RB, and k represents the subcarrier index.

[0076] [Equation 2]

[0077]

[0078] Different numerologies can be configured to meet the diverse services and requirements of NR systems. For example, while LTE / LTE-A systems can support a single subcarrier spacing (SCS), NR systems can support multiple SCSs.

[0079] A new numerology for NR systems supporting multiple SCSs can operate in frequency ranges or carriers such as below 3GHz, 3GHz-6GHz, 6GHZ-52.6GHz or above 52.6GHz to address the issue of not being able to use wide bandwidth in frequency ranges or carriers such as 700MHz or 2GHz.

[0080] Table 1 below shows examples of numerologies supported by the NR system.

[0081] uΔf=2 u ·15 [kHz]Cyclic prefix015Normal130Normal260Normal, Extended3120Normal4240Normal

[0082] Referring to Table 1 above, the numeral can be defined based on the subcarrier spacing (SCS), cyclic prefix (CP) length, and number of OFDM symbols per slot used in the Orthogonal Frequency Division Multiplexing (OFDM) system. The above values ​​can be provided to the terminal through the upper layer parameters DL-BWP-mu and DL-BWP-cp for the downlink, and through the upper layer parameters UL-BWP-mu and UL-BWP-cp for the uplink.

[0083] In Table 1 above, 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. For other numerology indices, only normal CP can be applied.

[0084] A normal slot can be defined as the basic time unit used to transmit a single piece of data and control information in an NR system. The length of a normal slot can be set to the number of OFDM symbols, which is 14 by default. Furthermore, unlike slots, a subframe has an absolute time length equivalent 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.

[0085] For example, in LTE, data can be transmitted based on a unit of time called a Transmission Time Interval (TTI), which can be set to one or more subframes. Here, one subframe can be set to 1ms and can contain 14 OFDM symbols (or 12 OFDM symbols).

[0086] In addition, a non-slot can be defined in NR. A non-slot can mean a slot having a number that is at least one symbol smaller than a normal slot. For example, in the case of providing low latency such as URLLC service, latency can be reduced through a non-slot having a number of symbols smaller than a normal slot. Here, the number of OFDM symbols included in a non-slot can be determined by considering the frequency range. For example, a non-slot with a length of 1 OFDM symbol can be considered in a frequency range of 6 GHz or higher. As an additional example, the number of OFDM symbols defining a non-slot can include at least 2 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 - 1). However, as a specification of a non-slot, the number of OFDM symbols may be limited to 2, 4, or 7 symbols, but is not limited thereto.

[0087] Additionally, for example, in unlicensed bands below 6 GHz, subcarrier spacing where u equals 1 and 2 may be used, and in unlicensed bands above 6 GHz, subcarrier spacing where u equals 3 and 4 may be used. For example, when u equals 4, it may be used for SSB (Synchronization Signal Block).

[0088] uN slot symb N frame,u slot Nsubframe,u slot 01410111420221440431480841416016

[0089] Table 2 shows the number of OFDM symbols per slot (N) for normal CP, by subcarrier spacing setting (u). slot symb ), number of slots per frame (N frame,u slot ), number of slots per subframe (N subframe,u slot ) is shown. Table 2 shows the above-described values ​​based on a normal slot having 14 OFDM symbols.

[0090] uN slot symb N frame,u slot N subframe,u slot 212404

[0091] Table 3 shows the number of slots per frame and the number of slots per subframe based on normal slots with 12 OFDM symbols per slot when extended CP is applied (i.e., when u is 2 and the subcarrier spacing is 60 kHz).

[0092] As mentioned above, one subframe may correspond to 1ms 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. Accordingly, the number of slots and symbols that can be considered within 10ms corresponding to one radio frame may be set differently. Table 4 may show the number of slots and symbols according to each SCS. In Table 4, the 480kHz SCS may not be considered, but the present invention is not limited to these examples.

[0093] SCS Number of slots in 10ms (14 symbols in 1 slot) Number of slots in 10ms (7 symbols in 1 slot) Number of symbols in 10ms 15kHz 1020 140 30kHz 2040 280 60kHz 4080 560 120kHz 80 160 1120 240kHz 160 320 2240 480kHz 320 640 4480

[0094]

[0095] Furthermore, for example, in existing wireless communication systems, communication could be performed based on a terrestrial network comprised of ground-based terminals and ground-based base stations. Terminals could access the network wirelessly. Here, when moving, the terminal could continuously receive the same service through other base stations within the terrestrial network. After connecting to the network, the terminal could access a specific service server through other wired or Internet networks. Furthermore, the terminal could receive services that connected it to other terminals through wired or wireless communication via the network.

[0096] However, new wireless communication systems can support terminal communication not only through terrestrial networks but also through non-terrestrial networks (NTN). Here, NTN can refer to a network or a part of a network that utilizes a mobile device floating in the air or space equipped with a base station or relay equipment. For example, NTN can support terminal-to-terminal communication services based on satellites equipped with communication capabilities in LEO (Low Earth Orbit) and GEO (Geostationary Earth orbit). As another example, NTN can support terminal-to-terminal communication services based on aircraft equipped with communication capabilities within Unmanned Aircraft Systems (UAS), but is not limited thereto.

[0097] Below, we distinguish between terrestrial networks (TN) and non-terrestrial networks (NTN). In existing communication systems, only terrestrial networks existed, so this distinction was not necessary. In contrast, below, we distinguish between NTN and TN as communication systems that enable terminal-to-terminal communication based on NTN, and describe methods for supporting terminal-to-terminal communication services based on these distinctions.

[0098] For example, wireless communication services between ground base stations and wireless terminals or between mobile base stations are described as mobile services, but are not limited thereto. Furthermore, communications between mobile ground base stations and at least one space base station may be considered mobile satellite services. Furthermore, wireless communication services between mobile ground base stations and space base stations, or between mobile ground base stations via at least one space base station, may also be considered mobile satellite services, but are not limited thereto.

[0099] The following describes a method for performing communication based on a wireless communication system that supports both mobile services and mobile satellite services. For example, while NTN technologies have been introduced specifically for satellite communications, NTN can also be introduced in TN communication systems (e.g., 5G systems) to operate alongside TN. Here, a terminal can support both NTN and TN simultaneously. For a terminal that supports both NTN and TN simultaneously, a wireless communication system may require specific NTN technologies in addition to long-term evolution (LTE) and new radio (NR) systems, which are radio access technologies (RATs). The following describes a method for achieving this. For example, the following may be definitions of each term related to NTN and TN.

[0100]

[0101] Non-terrestrial networks (NTN):

[0102] A network or part of a network that utilizes airborne or space-based mobile devices carrying base stations or relay equipment for communications.

[0103]

[0104] NTN Gateway (NTN-gateway):

[0105] A ground station or gateway located on the Earth's surface and equipped with sufficient wireless access equipment to connect to satellites. Typically, an NTN gateway may be a transport network layer node (TNL).

[0106]

[0107] Feeder link:

[0108] Wireless link between NTN gateway and satellite

[0109]

[0110] Geostationary Earth orbit (GEO):

[0111] A circular orbit 35,786 km above the Earth's equator, aligned with the direction of Earth's rotation. Objects or satellites in this orbit revolve with the same period as the Earth's rotation. Therefore, when observed from Earth, they appear to be stationary and motionless.

[0112]

[0113] Low Earth Orbit (LEO):

[0114] Orbits between 300 and 1500 km above the Earth

[0115]

[0116] Medium Earth Orbit (MEO):

[0117] Orbits that exist between LEO and GEO

[0118]

[0119] Unmanned Aircraft Systems (UAS):

[0120] Systems typically operate between 8 and 50 km above ground level and may include high-altitude platforms (HAPs). Unmanned aerial systems may include at least one of the following systems: Tethered UAS (TUA), Lighter Than Air UAS (LTA), and Heavier Than Air UAS (HTA).

[0121]

[0122] Minimum Elevation angle:

[0123] Minimum angle required for a ground terminal to face a satellite or UAS base station in the air

[0124]

[0125] Mobile Services:

[0126] Wireless communication services between ground base stations and wireless terminals or between mobile base stations

[0127]

[0128] Mobile Satellite Services:

[0129] It may be a wireless communication service between mobile ground base stations and one or more space base stations, or between mobile ground base stations and space base stations, or between mobile ground base stations via one or more space base stations.

[0130]

[0131] Non-Geostationary Satellites:

[0132] Satellites in LEO and MEO orbits may be satellites that orbit the Earth with a period of approximately 1.5 to 10 hours.

[0133]

[0134] On Board Processing:

[0135] Digital processing of uplink RF signals mounted on satellite or non-terrestrial equipment

[0136]

[0137] Transparent payload:

[0138] This may mean changing the carrier frequency of the uplink RF signal and filtering and amplifying it before transmitting it via the downlink.

[0139]

[0140] Regenerative payload:

[0141] Modification and amplification of an uplink RF signal before transmission via the downlink. The signal modification may include digital processing such as decoding, demodulation, re-modulation, re-encoding, and filtering.

[0142]

[0143] Onboard NTN gNB:

[0144] It may refer to an onboard satellite with a base station (gNB) implemented in a regenerative payload structure.

[0145]

[0146] On ground NTN gNB:

[0147] A ground base station (GNB) implemented in a transparent payload structure.

[0148]

[0149] One-way latency:

[0150] The time it takes for a wireless terminal to reach a public data network or from a public data network to a wireless terminal in a wireless communication system.

[0151]

[0152] Round Trip Delay (RTD):

[0153] The time it takes for any signal to reach a wireless terminal from an NTN gateway or from an NTN gateway to a wireless terminal and then return back. At this time, the returning signal may be a signal having a different form or message than the above-mentioned arbitrary signal.

[0154]

[0155] Satellite:

[0156] It can be a space vehicle equipped with a radio communication transceiver capable of supporting transparent payloads or regenerative payloads, and can typically be located in LEO, MEO, or GEO orbits.

[0157]

[0158] Satellite beam:

[0159] The beam generated by the antenna of the onboard satellite

[0160]

[0161] Service link:

[0162] Wireless link between satellite and terminal (UE)

[0163]

[0164] User Connectivity:

[0165] The ability to establish and maintain data / voice / video transmission between the network and the terminal.

[0166]

[0167] User Throughput:

[0168] Data transmission rate provided to the terminal

[0169]

[0170] FIG. 3 is a diagram illustrating an NTN including a transparent satellite to which the present disclosure can be applied.

[0171] Referring to FIG. 3, terminals included in the NTN may include terrestrial network terminals. For example, terminals in the NTN and TN may include manned or unmanned vehicles, such as ships, trains, buses, or airplanes, and may not be limited to a specific form. Referring to FIG. 3, a transparent satellite payload generated through a network including transparent satellites may be implemented in a manner corresponding to an RF repeater.

[0172] More specifically, a network including transparent satellites can perform frequency conversion and amplification for radio signals received in both uplink and downlink directions, and transmit the radio signals. Accordingly, the satellites can relay the NR-Uu radio interface, which includes both feeder links and service links, as described below.

[0173] As another example, referring to FIG. 3, a Satellite Radio Interface (SRI) over a feeder link may be included in the NR-Uu interface. That is, the satellite may not be the end point of the NR-Uu interface. Here, the NTN gateway may support all functions necessary to transmit signals defined in the NR-Uu interface. For example, other transparent satellites may be connected to the same base station on the ground. That is, a configuration in which multiple transparent satellites are connected to a single ground base station may also be possible. The base station may be an eNB or a gNB, but may not be limited to a specific form.

[0174] FIG. 4 is a diagram illustrating an NTN including a regenerative satellite without inter-satellite links (ISLs) to which the present disclosure may be applied.

[0175] Referring to Figure 4, the NTN may include a regenerative satellite. Here, a regenerative satellite may mean a satellite that includes a base station function. For example, a regenerative satellite payload generated through a network including a regenerative satellite may be implemented by regenerating a signal received from the ground.

[0176] More specifically, the regenerative 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 regenerative satellite can receive signals from the ground through the SRI (Satellite Radio Interface) on the feeder link between the NTN gateways. Here, the SRI (Satellite Radio Interface) can be defined in the transport layer between the satellite and the NTN gateway. The transport layer can mean the transport layer among the layers defined by the OSI 7 layer. That is, based on the regenerative satellite, the signal from the ground can be transformed based on digital processing such as decoding, demodulation, re-modulation, re-encoding, and filtering, but is not limited thereto.

[0177] FIG. 5 is a diagram illustrating an NTN including a regenerative satellite having an ISL to which the present disclosure can be applied.

[0178] Referring to Figure 5, ISL can be defined at the transport layer. Alternatively, ISL can be defined as a wireless 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 regeneration satellite can serve as a base station, and multiple regeneration satellites can be connected to the same 5G core network on the ground.

[0179] 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 may be applied. 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 may be applied.

[0180] The NR Uu interface may be an interface defined by protocols for wireless connection between a terminal and a base station in an NR system. At this time, the NR Uu interface may include a user plane defined by protocols for transmitting user data, including NTN. In addition, the NR Uu interface may include a control plane defined by protocols for transmitting signaling including radio resource control information, including NTN. For example, the Medium Access Control (MAC) layer is set based on Radio Link Control (RLC), Packet Data Convergence Protocol (PDCP), Service Data Adaptation Protocol (SDAP), and Radio Resource Control (RRC), and the protocols for each layer may be defined based on NR among 3GPP RAN-related standards, but may not be limited thereto.

[0181] For example, FIG. 6 may be a UP protocol stack structure based on a transparent satellite. That is, only frequency conversion and amplification of transparently received wireless signals may be performed and transmitted at the satellite and NTN gateway. Furthermore, FIG. 7 may be a CP protocol stack structure based on a transparent satellite. That is, only frequency conversion and amplification of transparently received wireless signals may be performed at the satellite and NTN gateway.

[0182] Based on the above, a wireless communication system supporting terminal-to-terminal communication using NTN and TN can be considered. For example, NTN may have a longer roundtrip time (RTT) between the terminal and the base station than conventional TN. Therefore, from a UP perspective, the terminal needs to buffer data to be transmitted via both uplink and downlink for a longer period of time due to the increased RTT. In other words, the terminal needs to store more data in the buffer. Consequently, the terminal may require a larger memory capacity than conventional systems, which will be discussed later.

[0183] Figure 8 is a diagram illustrating a timing advance calculation method applicable to the present disclosure. As described above, satellites included in NTNs are located in the sky, which can result in longer signal round-trip times (RTTs). For example, LEO satellites are located 300 to 1,200 km above the Earth's surface, while GEO satellites are located more than 36,000 km above the equator. Therefore, propagation delays in NTNs can be significantly greater than in TNs. On the other hand, because NTNs are located in the sky, they can offer greater cell coverage than terrestrial networks.

[0184] That is, since NTN may have different RTT and cell coverage compared to TN, there is a need to redefine the method for obtaining time synchronization for uplink transmission in NTN. As an example, FIG. 8 may be a method for calculating TA values ​​that occur depending on the satellite payload type.

[0185] More specifically, FIG. 8(a) may be a method for calculating a TA value when the satellite payload type is a playback payload. Additionally, FIG. 8(b) may be a method for calculating a TA value when the satellite payload type is a transparent payload.

[0186] Here, we consider a case where the terminal knows the satellite ephemeris and its position to ensure initial access and ongoing maintenance of the timing advance (TA) value. Here, the satellite ephemeris can refer to the distance between each satellite and the receiver and the position of each satellite. For example, the terminal can acquire the TA value on its own and then apply it (Option 1). Alternatively, the terminal can receive instructions for TA compensation and correction from the network (Option 2).

[0187] For example, referring to Fig. 8(a), if the satellite payload type is a replay payload, the satellite can directly perform the role of a base station. At this time, the terminal can calculate the TA value required for uplink transmission including the PRACH (physical random access channel). 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 a relatively long distance compared to the distance between terminals, a common TA value (Tcom) that takes into account the long round trip time (RTT) in cell coverage may be required. In addition, the terminal-specific TA value (TUEx) may be a value generated due to the different locations of each terminal within the cell coverage. If the terminal knows the position of the satellite at a specific time in advance through the satellite ephemeris stored in advance or received from NTN, and the position of the terminal is known through a function such as GNSS, the terminal can calculate the distance between the satellite and the terminal at a specific time, and can then obtain the TA value on its own and correct the TA value, thereby determining the TA value.

[0188] Through the above, the terminal can perform uplink timing alignment between terminals received from the base station with full TA compensation.

[0189] As another example, the terminal can perform downlink and uplink frame timing alignment on the network side. As shown in Fig. 8(b), if the satellite payload type is a transparent payload, the satellite can perform filtering and amplification of the radio signal and transmit the signal to the NTN gateway. In other words, the satellite can act as an RF repeater. At this time, there may be cases where the NTN gateway needs to be changed based on the continuous movement of the satellite. In Fig. 8(b), the common TA value (Tcom) can 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. At this time, the feeder link can be changed as the NTN gateway changes based on the movement of the satellite. In other words, the distance between the satellite and the NTN gateway can be changed based on the changed feeder link. Therefore, the common TA value that occurs may be changed, and there is a need to perform an update at the corresponding terminal. In addition, when setting an offset between the downlink frame timing and the uplink frame timing in the network, there is a need to additionally consider the case where the TA value generated by the feeder link is not compensated by the overall TA compensation method. In addition, when the terminal can only calculate a different TA value (TUEx) for each terminal, the terminal needs to confirm one reference point for each beam or cell and needs to transmit information about it to other terminals. When setting an offset between the downlink frame timing and the uplink frame timing in the network, the network needs to manage the offset information regardless of the satellite payload type. Here, as an example, the network may provide a value for TA compensation to each terminal, and is not limited to the above-described embodiment.

[0190] As another example, a method for directing TA compensation and correction in the network (Option 2) can be considered. In this case, a common TA value can be generated based on common factors for propagation delay shared by all terminals located within the coverage area of ​​a satellite beam or cell. The network can broadcast the common TA value to the terminals for each satellite beam or cell. 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 terminal-specific TA value (TUEx) can be determined based on the random access procedure defined in the existing communication system (e.g., Release 15 or Release 16 of the existing NR system). In this case, for example, when applying long TA values ​​and negative TA values, 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 this.

[0191] FIG. 9 is a diagram illustrating an earth fixed cell scenario to which the present disclosure can be applied.

[0192] Referring to FIG. 9, a fixed cell may be a cell with a fixed location from which a signal is transmitted from a satellite. For example, since a satellite moves over time, the antenna and beam must be varied so that the service coverage is fixed to a specific location in order to maintain a fixed cell. At this time, as an example, satellite 1 (910) in FIG. 9 can maintain a fixed cell by varying the antenna and beam during T1 to T3. Here, when a specific time (T4) elapses, satellite 1 can no longer service the corresponding location, so satellite 2 (920) provides service at the corresponding location to maintain service continuity. At this time, the beam or cell of satellite 2 (920), which services the same location as the location serviced by satellite 1 (910) in the previous time (T1 to T3) after time T4, may maintain the characteristics of the beam or cell of satellite 1 (910), and is not limited to the above-described embodiment.

[0193] For a more specific example, when a service is provided by satellite 1 (910) and satellite 2 (920), at least one of the physical cell ID (PCI) value and system information may remain the same. That is, as a cell with fixed service coverage, it may be generally set based on satellites in LEO and MEO orbits excluding GEO, which can vary the angles of their antennas and beams.

[0194] In contrast, FIG. 10 is a diagram illustrating an earth moving cell scenario to which the present disclosure may be applied. For example, a cell with a moving service coverage may be an earth moving cell.

[0195] For example, referring to FIG. 10, satellite 1 (1010), satellite 2 (1020), and satellite 3 (1030) can each provide services to cells having different PCIs. At this time, the antenna and beam through which the satellite transmits signals to the ground are fixed, and the type in which the service coverage moves as the satellite moves over time can be referred to as an Earth moving cell. The Earth moving cell can be established based on satellites in LEO and MEO orbits excluding GEO, among which the antenna and beam angles are fixed. Here, the satellites can have the advantages of being cheaper and having a lower failure rate compared to satellites that can adjust the angles of the antenna and beam.

[0196] Additionally, FIG. 11 is a diagram illustrating a method of mapping PCI to satellite beams to which the present disclosure can be applied.

[0197] For example, a PCI may refer to an index that can logically distinguish one 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. On the other hand, referring to FIG. 11(b), one PCI may be assigned to each satellite beam in one satellite. For example, a satellite beam may be composed of one or more SSB (Synchronization Signal Block, SS / PBCH block) beams. One cell (or PCI) may be composed of 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-described embodiment. That is, L may be similar to a terrestrial network (TN), which is an existing communication system (NR system), in which one or more SSB indices may be used for each PCI. Through this, SSBs transmitted through different beams can be distinguished, and SSB indices can be mapped to logically defined antenna ports or physically distinct beams.

[0198] For example, a terminal that can access NTN may be a terminal that supports GNSS (Global Navigation Satellite System) functionality. However, terminals that can access NTN may also include terminals that do not support GNSS. As another example, NTN may also support terminals that support GNSS functionality but are unable to obtain location information via GNSS, and the present invention is not limited to the above-described embodiment.

[0199] As described above, terminals can communicate via NTN. For example, terminals can receive non-terrestrial network-based services based on 5G / B5G NTN. This allows terminals to avoid the regional, environmental, spatial, and economic constraints of wireless access services (e.g., LTE, NR, WiFi, etc.) that rely on terrestrial network equipment. For example, based on the aforementioned approach, advanced wireless access technologies provided on terrestrial networks can be applied to non-terrestrial network platforms (e.g., satellites and UAVs). This allows for the provision of various wireless access service products and technologies alongside advanced network technologies.

[0200] NTN platforms can operate as a sort of mirror, relaying NR signals in space or at high altitudes, or by embedding base station (gNB, eNB) functionality. For example, NG-RAN-based NTN architectures can be implemented with "Transparent payload-based NTN" and "Regenerative payload-based NTN" structures, as previously mentioned.

[0201] Furthermore, as an example, NTN technology can be utilized as an extended network structure and technology for the 5G Integrated Access and Backhaul (IAB) architecture, enabling wider coverage and more wireless access services. The integration of NTN and terrestrial networks can ensure service continuity and scalability of 5G systems.

[0202] For example, integrated NTN and TN networks can offer significant benefits in terms of 5G target performance (e.g., user experience, data transmission rate, and reliability) in urban and suburban areas. Furthermore, integrated NTN and TN networks can ensure connectivity not only in highly dense areas (e.g., concert halls, sports stadiums, shopping centers, etc.), but also for fast-moving objects such as airplanes, high-speed trains, vehicles, and ships. Furthermore, integrated NTN and TN networks can utilize multi-connection capabilities to simultaneously access data transmission services from both NTN and TN networks. This allows for selective utilization of a better network depending on traffic characteristics and load levels, achieving both efficiency and cost-effectiveness for 5G wireless transmission services.

[0203] A terminal on a flat surface can simultaneously connect to both the NTN network and the TN network to utilize 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 access services for harsh environments or regions where the TN network is difficult to support. This allows the terminal to be utilized in conjunction with various services. In particular, the integrated NTN and TN networks can enhance the reliability of autonomous driving services and facilitate efficient network operation, and are not limited to the above-described embodiments.

[0204] Here, for example, V2X technology based on LTE mobile communication or standard technology based on the IEEE 802.11p standard may have similar limitations in the services that can be provided. The LTE V2X standard can be provided to meet the requirements defined in C-ITS (e.g., time delay of about 100ms, reliability of about 90%, and generation of messages of tens to hundreds of bytes 10 times per second, etc.). Therefore, new V2X services that require low latency, high reliability, high-capacity data traffic, and improved positioning may be needed. At this time, for example, the standardization of 5G wireless access technology (e.g., NR (New Radio)) is in progress based on the above-mentioned. In addition, for example, standardization of various numerologies, frame structures, and corresponding L2 / L3 protocol structures is in progress to be able to respond more flexibly to the requirements of new services than LTE. Based on the above, it may be possible to support enhanced V2X services such as autonomous driving and remote driving by introducing sidelink wireless access technology based on 5G mobile communication technology, and the NTN network may be utilized for this purpose.

[0205] As another example, NTN networks can be utilized to support IoT services in harsh environments and areas not covered by terrestrial networks. For example, IoT devices often require wireless communication with minimal power consumption in harsh channel environments (e.g., mountains, deserts, or oceans), depending on their intended use. Existing cellular-based technologies may primarily be targeted at mobile broadband (MBB) services. Therefore, they may be inefficient in providing IoT services in terms of wireless resource utilization and power control, and may not support flexible operation. Furthermore, existing non-cellular IoT technologies may have limitations in providing diverse IoT services due to limited mobility support and coverage. Considering the aforementioned issues, NTN networks can be applied, thereby improving services.

[0206] Furthermore, for example, if 5G mobile communication-based sidelink technology were applied to the NTN network, it could provide users with wider coverage and mobility through a more efficient wireless communication method than the current Bluetooth / Wi-Fi-based wearable devices. Furthermore, it could differentiate itself from existing communication standards in applications requiring high data rates and mobility support using wearable devices (e.g., wearable multimedia services).

[0207] Another example is that NTN networks can improve public safety communications networks and expand disaster communications coverage. For example, the high reliability and low latency of 5G mobile communication systems can be leveraged through NTN networks to provide public services such as disaster response. For example, mobile base stations, such as drones supporting 5G mobile communications, can be used to support mobile broadband services even in deserts and high mountainous areas. In other words, applying NTN networks to public services can expand disaster communications coverage by covering a wider range of areas.

[0208]

[0209] FIG. 12 is a diagram illustrating a reference location to which the present disclosure is applicable. Referring to FIG. 12, satellites (1210, 1220) having an earth-fixed beam can provide service for a fixed location for a specific period of time based on the fixed beam. In an NTN environment, the signal strength within a cell may be similar because the distance between the terminal and the satellite is large. Therefore, an RRC idle terminal may consider a reference location as a condition for performing adjacent cell measurement for cell reselection. That is, an RRC idle terminal may 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 (Sat 1, 1210) can obtain reference location information from the network through system information. The terminal can determine 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 its current location is outside the cell and can perform measurements on adjacent cells. In other words, the terminal can perform cell measurements for cell reselection by considering the distance between the terminal and the reference location.

[0210] Figure 13 is a diagram showing the received signal strength according to distance in TN and NTN. Referring to Figure 13(a), the signal strength of terminals (1321, 1322) located within the coverage of a base station (1310) in a TN environment may have a large difference based 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) on the ground may be greater than the received signal strength of a terminal (far-UE, 1322) located at the outskirts of the coverage, and the difference may be large enough to be distinguishable. On the other hand, referring to Figure 13(b), terminals (1331, 1332) located within the coverage of a satellite (1330) in an NTN environment may be considered. Here, since 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) located close to the coverage center and the received signal strength of a terminal (far-UE, 1332) located at the outskirts of the coverage may not be large. Therefore, in an NTN environment, there may be a limitation in the terminal performing cell reselection by considering only the received signal strength. Specifically, the terminal may not perform measurements for cell reselection because the difference in received signal strength within satellite coverage is not large. Accordingly, there may be insufficient time for neighboring cell SSB search, signal strength measurement, and camping. Considering the above, in an NTN environment, the terminal can perform measurements for cell reselection by considering the distance between the reference position and the terminal, as described above.

[0211] In addition, as an example, a terminal in the above-described fixed cell (earth fixed cell) or fixed beam can obtain information for time-based cell reselection through system information. For example, the terminal can obtain t-service for the time (or service time) during which satellite coverage is maintained through 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, so that when the terminal receives t-service information through system information, the cell can be regarded as a fixed cell. On the other hand, when the terminal does not receive t-service information through system information, the terminal can regard the cell as a moving cell (earth-moving cell). In other words, the terminal can implicitly obtain fixed cell and moving cell information through t-service information.

[0212] As another example, a terminal within a fixed cell can perform measurements for cell reselection when the distance between the reference position and the terminal becomes greater than a distance threshold, as described above. That is, when the terminal is located within the fixed cell coverage, the terminal can perform measurements for cell reselection using reference position information or t-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 according to the movement of the satellite, the reference position also needs to move. Therefore, when the terminal performs measurements for cell reselection based on the reference position of the mobile cell, if the measurement is performed using the existing reference position determination method, the problem of a terminal that does not need the measurement performing the measurement may arise. This will be described later in this regard. Meanwhile, in an NTN environment, the terminal can operate in a frequency band of 10 GHz or higher, and can communicate via satellite based on this. Additionally, for example, mobility, service continuity, emergency call, and public warning system considering high propagation delay and satellite movement can be provided in an NTN environment, but are not limited to specific embodiments.

[0213] FIG. 14 is a diagram illustrating a method for performing distance-based measurement for applicable cell reselection of the present disclosure. Referring to FIG. 14, a mobile cell may be provided based on a satellite (1410). Here, a case may be considered where a terminal performs measurement for cell reselection considering a reference position. Specifically, at time T1, terminal 1 (UE 1, 1421) may perform neighbor cell measurement for cell reselection because the distance between terminal 1 and the reference position is greater than a distance threshold. On the other hand, terminal 2 (UE 2, 1422) may not perform neighbor cell measurement for cell reselection because the distance between terminal 2 and the reference position is less than the distance threshold. Here, the reference position and distance threshold information may be provided to the terminal through system information. Specifically, the reference position and distance threshold information may be included in NTN-specific system information (e.g., SIB 19). Here, if the terminal switches to the RRC idle / inactive state, the above-described value may not change. Therefore, even at time T2, the terminal can operate based on the same information. For example, in FIG. 14, at time T2, terminal 2 (UE 2, 1422) needs to measure a neighboring cell outside the coverage area and attempt to camp on another cell. However, since the distance between the location of terminal 2 (UE 2, 1422) and the reference location is less than the distance threshold, the measurement for the neighboring cell may not be performed, and thus the cell reselection procedure may not be performed. In other words, in a mobile cell, there may be limitations in performing measurements for cell reselection by applying the reference location in the same way as in a fixed cell. Here, as an example, specific operations for cell reselection by the terminal may be as shown in Table 5 below.For example, the terminal may perform measurements based on at least one of frequency priority, signal strength of the serving cell, and distance threshold, as shown in Table 5 below. In addition, as an example, if the terminal receives system information (e.g., SIB19) including t-service information from the serving cell, the terminal may always perform Intra / Inter-frequency and Inter-RAT measurements before the t-service regardless of the conditions of Table 5. Here, the t-service information may mean an absolute time (epoch time) that services the coverage of a fixed cell. In addition, as an example, the terminal may always measure high-priority Intra / Inter-frequency and Inter-RAT frequencies regardless of Table 5, and may perform cell reselection through this.

[0214]

[0215] - If the priority of NR Inter-frequency or Inter-RAT frequency is higher than the current NR frequency: · The terminal always performs NR Inter-frequency or Inter-RAT frequency measurement. - If the priority of NR Inter-frequency or Inter-RAT frequency is equal to or lower than the current NR frequency: · If the signal strength (Srxlev) and signal quality (Squal) of the serving cell are greater than the signal strength threshold (s-NonIntraSearchP) and signal quality threshold (s-NonIntraSearchQ) within SIB2: · If the distance between the terminal and the reference location is less than the distance threshold within SIB19 provided by the serving cell, the terminal may not perform NR Inter-frequency or Inter-RAT frequency measurement. · If the distance between the terminal and the reference location is greater than the distance threshold within SIB19 provided by the serving cell, the terminal always performs NR Inter-frequency or Inter-RAT frequency measurement. · If there is no distance threshold within SIB19 provided by the serving cell, the terminal performs NR Inter-frequency or Inter-RAT frequency measurements may not be performed. · If the signal strength (Srxlev) and signal quality (Squal) of the serving cell are less than the signal strength threshold (s-IntraSearchP) and signal quality threshold (s-IntraSearchQ) within SIB2: · The terminal always performs NR Inter-frequency or Inter-RAT frequency measurements (for legacy NR mobility).

[0216]

[0217] In addition, FIG. 15 is a diagram illustrating a reference location update method applicable to the present disclosure. As described above, if the reference location in a mobile cell is applied in the same manner as the reference location of a fixed cell, problems may arise in the measurement conditions. Therefore, in the case of a mobile cell, an update of the reference location may be required. For example, in FIG. 15, the reference location may be updated based on a mobile cell moving according to the movement of a satellite (1510). Here, if the reference location update is not performed, the terminal cannot perform cell reselection, so there is a need to update the reference location at specific intervals.

[0218] In the following, considering the above-described points, a method for updating a reference location is described. For example, at time T2, terminal 2 (UE 2, 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 (UE 2, 1522) and the reference location (T2) at time T2 is greater than a distance threshold, measurement can be performed for cell reselection and camping can be attempted. In considering the above-described points, a method for updating a reference location is described below.

[0219]

[0220] Reference location update

[0221] A reference location can be newly defined or updated based on the movement of a satellite in a mobile cell. Here, the reference location can be updated based on parameters indicating a time interval (e.g., timer, epoch time, SFN, and subframe). As another example, the reference location can be indicated in a list format based on absolute time, which will be described later. As an example, a system frame number (SFN) can indicate the number of a specific system frame with a length of 10 ms. Additionally, a subframe can be a frame structure with a time length of 1 ms within a subframe. As another example, other time units can be considered and may not be limited to a specific time unit.

[0222] Here, as an example, the reference location update may be performed based on the reference location update time or when a timer expires. Here, the reference location update may be performed based on the acquisition of satellite orbit information (ephemeris) and system information. As another example, the reference location update may be performed through a reference location list. Here, the reference location list may refer to a reference location used at a specific location of a satellite by being associated with satellite orbit information (ephemeris) as a set of absolute time (epoch time) and reference locations, and this will be described later.

[0223] For example, satellite orbit information (ephemeris) can refer to satellite position information at a specific time or period. Satellite orbit information can be expressed as ECEF (Earth-Centered, Earth-Fixed) coordinate information, which is the coordinates (X, Y, Z) where the satellite is located from the center of the Earth in kilometers. As a specific example, satellite orbit information can be expressed in the form of "X= 19151.529 km, Y= -37578.251 km, Z= 17.622 km" at "2022-06-27 08:00:00.000" in absolute time (epoch time: day, hr, min, sec). As another example, the satellite orbit information can be expressed as "X= 19151.053 km, Y= -37578.556 km, Z= 17.359 km" at "2022-06-27 08:05:00.000" in absolute time (epoch time: day, hr, min, sec). Here, the velocity (km / s) along each of the X, Y, and Z axes can be expressed, and is not limited to a specific embodiment. In addition, as an example, the reference position can be provided in the form of an ellipsoid-point ellipse. The reference position can be indicated through bits indicating north / south directions and bits indicating latitude / longitude, and the ellipsoid-point can be as shown in Table 6 below, but may not be limited to a specific embodiment.

[0224] Ellipsoid-Point ::= SEQUENCE {latitudeSign ENUMERATED {north, south},degreesLatitude INTEGER (0..8388607), -- 23 bit fielddegreesLongitude INTEGER (-8388608..8388607) -- 24 bit field}

[0225]

[0226] Below, a method for updating a reference position based on a timer (hereinafter, method 1) and a method for updating a reference position based on a reference position list (hereinafter, method 2) are described.

[0227] For example, a terminal can update its reference position at specific time intervals set by the network. This specific time interval can be indicated by a timer. The terminal can update its reference position using satellite orbital information (ephemeris) at specific time intervals indicated by the network. In another example, the terminal can update its reference position by obtaining system information at specific time intervals indicated by the network.

[0228] For example, absolute time (epoch time) can be expressed as an integer value and can be a value expressed in a specific unit based on a specific point in time. As a specific example, absolute time (epoch time) can be a value expressed in units of 10ms from 00:00:00 on January 1, 1900 as "INTEGER (0..549755813887)", but may not be limited thereto. That is, a parameter indicating a specific point in time can be used and is not limited to a specific embodiment. Here, the reference location update can be performed through system information acquisition. For example, the terminal can update the reference location for each uplink synchronization validity period (e.g., UlSyncValidityDuration). As another example, the terminal can update the reference location based on a new timer using a reference location update timer. As another example, the reference location update can be performed based on satellite orbit information (ephemeris). The terminal can update the reference location based on a new timer using a reference location update timer.

[0229] FIG. 16 is a diagram illustrating a method for performing a reference position update based on system information acquisition applied to the present disclosure.

[0230] Referring to FIG. 16, in an NTN environment, a terminal can acquire system information for uplink synchronization. That is, the network can transmit feeder link delay and satellite coordinates to the terminal through system information, thereby performing uplink synchronization. Here, since the satellite continuously moves, the feeder link delay and satellite coordinates may continuously change. Therefore, when a delay change for uplink synchronization occurs, the network can modify parameters for uplink synchronization (e.g., Common TA, ephemeris) within the system information and transmit them to the terminal. In addition, the terminal can acquire system information at specific intervals (e.g., UlSyncValidityDuration) and update information for uplink synchronization. Here, the specific time may be the uplink synchronization validity time (UlSyncValidityDuration). For example, the specific time may be a type of timer that means the time during which uplink synchronization is valid. That is, a timer can operate as a time interval during which uplink synchronization is valid based on parameters for a specific time period (e.g., UlSyncValidityDuration) included in the system information. For convenience of explanation, the specific time period (e.g., UlSyncValidityDuration) included in the system information is referred to as the uplink synchronization valid time below. However, this is merely a configuration for convenience of explanation and is not limited to the above-described name.

[0231] Here, the uplink synchronization valid time may refer to the valid time of parameters for uplink synchronization (e.g., Common TA), satellite orbit information (ephemeris), and other parameters according to satellite movement. Here, the network may indicate to the terminal the start position of the valid time of the parameters for the uplink synchronization valid time based on the absolute time (epoch time) using the SFN and subframe. Before the uplink synchronization valid time expires, the terminal may obtain system information to update the parameters for uplink synchronization (e.g., Common TA), satellite orbit information (e.g., ephemeris), and other parameters related to the movement of the satellite, and restart the uplink synchronization valid time. For example, if the terminal does not update the parameters by the expiration of the uplink synchronization valid time, the terminal may determine that the parameters are invalid and stop uplink transmission.

[0232] As a specific example, referring to FIG. 16, the network can indicate a valid starting point for uplink synchronization parameters (e.g., Common TA), satellite orbit information (e.g., ephemeris), and other satellite movement-related parameters through system information, based on SFN and subframe, through parameters for absolute time (epoch time). In addition, the uplink synchronization validity time can be indicated in seconds. As a specific example, (s5, s10, s15, s20, s25, s30, s35, s40, s45, s50, s55, s60, s120, s180, s240) can be indicated as the uplink synchronization validity time, and is not limited to a specific embodiment.

[0233] In Fig. 16, the network can indicate SFN 0 and subframe 4 as a valid starting point through parameters for absolute time via system information. Therefore, the terminal can start the uplink synchronization valid time from subframe 4 within SFN 0. Here, when the uplink synchronization valid time is set to 5 seconds, the terminal can determine that the 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., SFN 500, subframe 3). Here, the terminal can acquire the system information before the uplink synchronization valid time expires, and update the parameters for uplink synchronization (e.g., Common TA), satellite orbit information (e.g., ephemeris), and other satellite movement-related parameters.

[0234] Here, for example, in a fixed cell environment, the reference position may remain constant for the t-service time or may change based on a long cycle. Therefore, the reference position may only be updated through an SI Modification procedure (i.e., a paging message). On the other hand, as described above, in a moving cell environment, the reference position needs to be continuously updated. Therefore, the existing position may be continuously updated based on the uplink synchronization validity time or timer.

[0235] 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 starting position of the reference position through system information. For example, the effective time of the reference position is the above-described uplink synchronization effective time, and the starting position can be indicated by the SFN and subframe through a parameter for absolute time (epoch time). In FIG. 17, if the parameter for absolute time indicates SFN 0 and subframe 4, the effective starting position of the reference position can be SFN 0 and subframe 4. The terminal can operate a timer in SFN 0 and subframe 4 as the starting position. For example, the timer can correspond to the above-described uplink synchronization effective time. If the timer is set to 5 seconds, the effective time of the reference position can be up to subframe 3 within SFN 500. Therefore, the terminal can obtain system information and update the reference position before the end of subframe 3 within SFN 500. Here, as an example, the system information may be NTN-specific system information such as SIB 19, but may not be limited thereto. The system information may be periodically scheduled and transmitted via a downlink shared channel. That is, the terminal may receive an SI message including SIB 19 within the SI window indicated by SIB 1, thereby performing a reference position update before the uplink synchronization effective time expires. In the case of updating the reference position through the uplink synchronization effective time based on the above, the uplink synchronization effective time may be indicated as (s5, s10, s15, s20, s25, s30, s35, s40, s45, s50, s55, s60, s120, s180, s240), and may be set from 5 seconds to 240 seconds accordingly.

[0236] However, unlike uplink synchronization, the reference position update may be information for performing measurements for cell reselection. Therefore, the reference position update needs to use a timer value other than the aforementioned validity 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, and this will be described in detail. 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 satellite orbits, and this will be described in detail later.

[0237] 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 starting point of the reference location can be indicated through an SFN and a subframe using a parameter for absolute time (epoch time). Here, the terminal can operate a new timer (referencelocationupdatetimer) at the starting point of the reference location. For example, the new timer can be a reference location update timer. However, this is only one name for the convenience of explanation and may not be limited to the name. That is, a new timer for updating the reference location can be used, and for the convenience of explanation, it is referred to as a reference location update timer below.

[0238] Specifically, in FIG. 18, the terminal may operate a reference position update timer at the position of subframe 4 within SFN 0. 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 SFN 0. The terminal may acquire system information up to subframe 4 within SFN 1 based on the reference position update timer and update the reference position. As a specific example, the reference position 1 may be changed to reference position 2 based on the reference position update. However, as an example, the reference position may not be changed within the timer, so reference positions 1 and 2 may be the same, and the present invention is not limited to a specific embodiment. As an example, the reference position may be changed when the next system information is acquired. That is, the reference position used in subframe 4 within SFN 0 to subframe 3 within SFN 1 may be the same as the reference position used in subframe 4 within SFN 1 to subframe 3 within SFN 2. After that, the reference position applied from subframe 4 within SFN 2 may be different, and is not limited to the above-described embodiment.

[0239] Here, for example, the reference position update can be performed even after the reference position update timer expires. If the terminal receives system information and updates the reference position after the reference position update timer expires, the terminal can re-establish the reference position valid starting point using the SFN and subframe through the parameter for absolute time (epoch time) in the system information and start the reference position update timer.

[0240] As another example, if the terminal does not perform a reference location update before the reference location update timer expires, the terminal may perform measurements for cell reselection based on the existing existing location. As another example, if the terminal does not perform a reference location update before the reference location update timer expires, the terminal may determine that the existing existing location is invalid and may not perform an operation for performing measurements using the reference location, but this is not limited to a specific embodiment.

[0241] FIG. 19 is a diagram illustrating a method for performing a reference position update based on a reference position update timer applicable to the present disclosure.

[0242] Referring to FIG. 19, parameters for the uplink synchronization valid time for updating uplink synchronization parameters and the reference position update timer parameters can operate separately. For example, the terminal can indicate the valid start time of parameters for uplink synchronization (e.g., Common TA), satellite orbit information (e.g., ephemeris), and other satellite movement-related parameters from the network as absolute time (epoch time) parameters through the SFN and subframe. Here, the terminal can operate the timer for the uplink synchronization valid time and the reference position update timer, respectively, at the valid start time. In addition, the terminal can receive the valid start points for the uplink synchronization valid time and the reference position update timer, respectively, as absolute time (epoch time) parameters through the SFN and subframe. For example, in FIG. 19, the terminal can operate the reference position update timer and the timer for the uplink synchronization valid time in subframe 4 within SFN 0. Here, as an example, the reference position update timer can be set to 1 second, and the timer for the uplink synchronization valid time can be set to 10 seconds. Here, SFN X can be a value from 0 to 1023, and if X + 1000 is greater than 1023, SFN can start over from 0.

[0243] The terminal can perform a reference position update by acquiring system information before or after the reference position update timer expires. For example, if the reference position update timer is set to 1 second, the terminal can update the reference position in subframe 4 within SFN X + {100, 200, 300, 400, 500, 600, 700, 800, 900} by starting the timer in subframe 4 within SFN X and by acquiring system information before or after the timer expires. On the other hand, the uplink synchronization parameter can be updated by acquiring system information before or after the timer for the uplink synchronization valid time expires. That is, if the timer for the uplink synchronization valid time is set to 10 seconds, the terminal can start the timer for the uplink synchronization valid time in subframe 4 within SFN X and by acquiring system information before or after the timer expires and by updating the uplink synchronization parameter in subframe 4 within SFN X + 1000.

[0244] Here, the reference position may not change for each reference position update timer, and the reference position within the system information may change at the next reference position update. That is, the reference position used in subframe 4 within SFN X to subframe 3 within SFN X + 100 may be the same as the reference position used in subframe 4 within SFN X + 100 to subframe 3 within SFN X + 200. On the other hand, the reference position applied from subframe 4 within SFN X + 200 may be different. That is, in the above-described manner, each timer may operate at the same effective time starting point, and is not limited to a specific embodiment.

[0245] FIG. 20 is a diagram illustrating a method for performing a reference position update based on system information acquisition applicable to the present disclosure.

[0246] Referring to FIG. 20, the terminal (2010) may acquire system information and update the reference position before or after the expiration of a timer (uplink synchronization valid interval timer and / or reference position update timer). The terminal (2010) may be in an RRC connection state with the network via NTN Cell A (NTN Cell A, 2020). As another example, the terminal (2010) may transition to an RRC idle state after previously being connected to the network. Referring to FIG. 20, the terminal (2010) can obtain at least one of a reference location update timer (reference location update timer), a reference location, an epoch time, and satellite orbit information (ephemeris) from an NTN cell A (2020) through an RRC message (e.g., system information, RRC Release). (S300) Here, the terminal (2010) in an RRC connection state can receive an RRC release message and transition to an RRC idle state. Here, the terminal (2010) in the RRC idle state can receive system information. In addition, the terminal (2010) in the RRC idle state may be camping on the NTN cell A (2020). (S310) Here, the terminal (2010) may use at least one of the uplink synchronization valid time timer and the reference position update timer as a timer for the reference position update. (S320) For example, the above-described timer may be started from a starting point set based on the SFN and subframe indicated through the absolute time (epoch time) parameter. The terminal (2010) may acquire system information and perform the reference position update before or after the expiration of at least one of the uplink synchronization valid time timer and the reference position update timer.

[0247] As a specific example, when the terminal (2010) updates the reference position based on the uplink synchronization valid time timer, the terminal (2010) can obtain parameter information to be updated through an RRC message (S330). Here, the newly updated parameters may be parameters for uplink synchronization required for uplink synchronization (e.g. Common TA), satellite orbit information (e.g. ephemeris), and reference position information for updating the reference position.

[0248] As another example, when the terminal (2010) updates the reference location based on the reference location update timer, the newly updated parameter may be reference location information required for the reference location update. Here, for example, if the timer expires but the reference location update is not performed, the terminal may determine that the reference location is invalid and may not check the distance condition until it acquires system information. Thereafter, when the terminal acquires system information and performs the reference location update, the terminal may check the distance condition from the start position (epoch time) at which the reference location is valid within the system information and determine whether to perform measurements for cell reselection.

[0249] As another example, the valid starting position (epoch time) of the reference position and the valid starting position (epoch time) of the uplink synchronization may be different. As a specific example, the starting position (epoch time) for applying the uplink synchronization may be Subframe Y within SFN X, and the starting position (epoch time) for applying the reference position may be Subframe M within SFN Z. As another example, the starting position (epoch time) for applying the uplink synchronization may be Subframe Y within SFN X, and the starting position (epoch time) for applying the reference position may be Subframe M within SFN X.

[0250] As another example, the terminal can determine the SFN and subframe for a valid starting point through the absolute time (epoch time) based on system information. Here, the terminal can operate both the uplink synchronization valid time timer and the reference position update timer based on the valid starting point. Thereafter, the terminal can obtain system information before or after the uplink synchronization valid time timer and the reference position update timer expire. Here, the system information can include reference position information for updating the reference position and information on the uplink synchronization valid period. Therefore, when the terminal receives the system information, it can update the reference position and determine that the synchronization is also valid. Accordingly, when the terminal receives the system information, it can 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 in the SFN and subframe indicated by the parameter for the absolute time (epoch time) included in the system information. That is, the terminal may reset both the uplink synchronization valid time timer and the reference position update timer to start from a new valid start point after acquiring system information, regardless of whether the reference position is updated or whether uplink synchronization is maintained, and may start from a new valid start point, without being limited to a specific embodiment.

[0251] As another example, the reference position update can be performed through satellite orbit information (ephemeris) rather than system information acquisition, and a method for this is described below.

[0252] FIG. 21 is a diagram showing ECEF (Earth-Centered, Earth-Fixed) coordinates and Ellipsoid-Point applicable to the present disclosure. For example, satellite orbit information (ephemeris) can be expressed based on ECEF coordinate information, and reference location information can be expressed by ellipsoid-point. Here, ECEF coordinate information can indicate x, y, z values ​​and movement speed in each axis with respect to the center of the Earth in km / s. Ellipsoid-point information can indicate latitude ( , longitude), longitude ( , latitude) and longitude can indicate whether the satellite is located in the northern or southern hemisphere based on the equator. For example, Tables 7 and 8 can be examples of satellite coordinates and velocities according to absolute time (epoch time). Referring to Table 8, the valid starting position of the satellite coordinates and velocities can be indicated through a specific SFN and subframe. For example, the network can transmit one absolute time (epoch time, SFN & Subframe) and the corresponding satellite coordinates and velocities to the terminal through system information (e.g. SIB19). Thereafter, the network can update the system information to modify the absolute time (epoch time) and the satellite coordinates and velocities.

[0253] As a specific example, the terminal can acquire system information. Here, the system information may include parameters for absolute time (epoch time), and the valid starting 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 can 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 can update the absolute time (epoch time) and the corresponding satellite coordinates and velocity.

[0254] For example, when updating the reference position based on satellite orbit information (ephemeris), the reference position expressed as an ellipsoid point can be derived using satellite coordinates and velocity. As a specific example, latitude and hardness can be expressed as . Here, the northern and southern hemispheres can be identified based on the longitude. Accordingly, the terminal can derive the ellipsoid point based on the satellite orbit information (ephemeris), ECEF coordinate information, and velocity of the serving cell.

[0255]

[0256] Epoch time(day, hr, min, sec)x [km]y [km]z [km]dx / dt [km / s]dy / dt [km / s]dz / dt [km / s]2030-11-10 11:00:00.00019151.529-37578.25117.682-0.00151-0.00102-0.001062030-11-10 11:05:00.00019151.073-37578.55617.359-0.00152-0.00101-0.001092030-11-10 11:10:00.00019150.614-37578.85517.029-0.00154-0.00099-0.001122030-11-10 11:15:00.00019150.150-37579.15116.690-0.00155-0.00098-0.00114

[0257]

[0258] Epoch time(SFN & Subframe) 219151.073-37578.55617.359-0.00152-0.00101-0.00109300 & 219150.614-37578.85517.029-0.00154-0.00099-0.00112400 & 319150.150-37579.15116.690-0.00155-0.00098-0.00114

[0259]

[0260] FIG. 22 is a diagram illustrating a reference location update method applicable to the present disclosure. For example, in an NTN mobile cell, the reference location must be updated by taking into account the movement of a satellite (2210) so that the terminal can perform accurate cell reselection.

[0261] As described above, the network can provide satellite orbit information (ephemeris) to the terminal. For example, referring to FIG. 22, specific satellite orbit information (ephemeris) can be provided, including satellite ECEF coordinates and velocity, at 2030-11-10 11:00:00.000 (SFN 2 & subframe 4). As another example, specific satellite orbit information (ephemeris) can be provided, including satellite ECEF coordinates and velocity, at 2030-11-10 11:05:00.000 (SFN 502 & subframe 4). Therefore, the terminal can derive the ECEF coordinates according to the satellite velocity between the time 2030-11-10 11:00:00.000 (SFN 2 & subframe 4) and the time 2030-11-10 11:05:00.000 (SFN 502 & subframe 4) and convert them to ellipsoid-points.

[0262] For example, the network can set a reference location update timer, and the terminal can update the reference location based on satellite orbit information (ephemeris) whenever the timer expires. For example, the terminal can determine the reference location based on the Unix time (epoch time, SFN, subframe) received through system information and then start the timer. Here, when the timer expires, the terminal can update the reference location based on satellite orbit information.

[0263] FIG. 23 is a diagram illustrating a method for updating a reference position based on satellite orbit information applicable to the present disclosure. For example, in FIG. 23, the expression 2030-11-10 11:00:00.000 represents year, month, day, hour, minute, and second, and coordinates and velocity information of a satellite may be transmitted through satellite orbit information (ephemeris). In addition, SFN X and subframe 0, which are points in time at which uplink synchronization parameters (e.g., Common TA, Ephemeris) are applied, may be indicated based on parameters for absolute time (epoch time) within system information. Here, a case in which the reference location update timer is set to 1 minute may be considered, but this is only one example for the convenience of description and is not limited to the above-described embodiment. Referring to FIG. 23, the reference location update timer may operate in subframe 0 within SFN X, which is an absolute time (epoch time). That is, the initial reference location may be a reference location between subframe 0 and 1 minute within SFN X. At this time, the terminal may update the reference location based on the effective start time and the initial reference location, and determine measurements for cell reselection.

[0264] More specifically, the terminal may check the initial reference position and the distance (d1) between subframes 0 and 1 minute within SFN X, and may not perform measurements for cell reselection if the distance is less than the distance threshold. In addition, the terminal may update the reference position between subframe 0 and 1 minute within SFN X at which the reference position update timer expires and restart the reference position update timer. In addition, the terminal may check the updated reference position and the distance (d2) between subframes "0+ 1 minute" within SFN X and "0+ 2 minutes" within SFN X, and may not perform measurements for cell reselection if the distance is less than the distance threshold. In addition, the terminal may update the reference position between subframes "0+ 2 minutes" within SFN X at which the reference position update timer expires and restart the reference position update timer. In addition, the terminal can check the distance (d3) from the updated reference location between subframe "0 + 2 minutes" within SFN X and subframe "0 + 3" within SFN X, and if it is greater than the distance threshold, can perform measurement for cell reselection. After that, after a certain period of time (e.g., 5 minutes), the terminal can obtain initial reference location information applied from subframe 0 within SFN Y, which is a new absolute time (epoch time), based on the movement of the satellite (2310). That is, the terminal can perform reference location update based on the reference location update timer until it obtains information about the newly acquired initial reference location based on the system information. Here, the reference location update timer is expressed in time units, but may not be limited thereto. As a specific example, the reference location update timer may instruct to update at a point where "SFN modulo X = 0".If you want to instruct the network to update the reference position every SFN (10ms), you can set X = 1, and if you want to instruct the network to update the reference position every two SFNs (20ms), you can set X = 2. As another example, you can indicate a specific absolute time. The absolute time (epoch time) is expressed as an integer value and can be 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 a value expressed in units of 10ms from 00:00:00 on January 1, 1900 as "INTEGER (0..549755813887)", but may not be limited thereto. At this time, the network can indicate a specific absolute time between the time intervals SFN X & subframe 0 and SFN Y & subframe 0, and the reference position update can be performed based on this. That is, the terminal can update the reference position when it reaches a specific absolute time after SFN X & subframe 0.

[0265] FIG. 24 is a diagram illustrating 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 (NTN Cell A, 2420). In addition, as an example, the terminal (2410) may have previously been connected to the network and may have transitioned to an RRC idle state. As an 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. As an example, the reference location update timer may be indicated based on at least one of a timer, Unix time, and SFN. In addition, the RRC message may further include at least one of an initial reference location, an epoch time, and ephemeris and instruct the terminal (2410). Here, the terminal (2410) in the RRC connected state may receive an RRC release message and transition to an RRC idle state. In addition, the terminal (2410) in the RRC idle state may receive system information. Here, the terminal (2410) in the RRC idle state may be camping on NTN cell A (2420). (S210) In addition, the terminal (2410) in the RRC idle state may determine the initial reference location based on the epoch time. The terminal (2410) may check the distance from the reference location of NTN cell A (2420) and perform measurements for cell reselection by comparing it with a distance threshold value.(S215) As a specific example, if the distance between the terminal (2410) and the reference location is greater than the distance threshold, the terminal (2410) may perform measurement for cell reselection. As another example, if the distance between the terminal (2410) and the reference location 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. In addition, 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.

[0266] As a specific example, a case may be considered where the timer in the reference location update timer configured by the terminal (2410) is set to 1 minute. That is, the timer may be a time that has elapsed 1 minute from the SFN and subframe indicated by the absolute time (epoch time) of NTN cell A (2420). As another example, the reference location update timer may be indicated by an SFN interval. As a specific example, when the SFN interval is configured as 3 and the absolute time (epoch time) indicated by the system information indicates SFN 0 and subframe 3, the reference location may be updated at SFN 3, SFN 6, ... SFN X. Here, SFN 3, SFN 6, ... SFN X may mean the time points at which SFN Modulo SFN interval = 0. After that, when the distance between the terminal (2410) and the reference location of NTN cell A (2420) becomes greater than the distance threshold, the signal strength of the adjacent cell can be measured for cell reselection. (S230) For example, the terminal (2410) can select NTN cell B (NTN Cell B, 2430) through a cell ranking procedure. Thereafter, the terminal (2410) in the RRC idle state can receive system information from NTN cell B (2430). (S240) Here, the system information can include a reference location update timer of NTN cell B (2430). At this time, the reference location update timer can be set based on at least one of a timer, Unix time, and SFN interval. In addition, the system information can indicate to the terminal (2410) an initial reference location. After that, the terminal (2410) can perform camping to NTN cell B (2430).(S250) After determining the reference position of NTN cell B (2430), the terminal (2410) can determine the measurement for cell reselection by checking the distance from the reference position. (S255) For example, if the distance between the terminal (2410) and the reference position is less than the distance threshold, the measurement 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 the measurement for cell reselection.

[0267]

[0268] As another example, a list of information on multiple absolute times (epoch times) and reference locations can be configured as an RRC message (system information, RRC release). The terminal can check the reference location 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 as coordinates in an ellipsoid format, such as the ellipsoid-point described above. As an example, the absolute time (epoch time) can be expressed as an integer value and can be 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 a value expressed in units of 10ms from 00:00:00 on January 1, 1900 as "INTEGER (0..549755813887)", but may not be limited thereto. As an example, Table 9 is a diagram showing a reference location list. Referring to Table 9, the absolute time (epoch time) is configured in 5-minute intervals, and the reference location to be used by the terminal every 5 minutes can be indicated by an ellipsoid-point in an elliptical coordinate format. Here, Table 9 below is only one example and may not be limited thereto. As another example, the absolute time (epoch time) interval may be set to 10 minutes, and the reference location may 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".

[0269] That is, the terminal can obtain information about absolute time (epoch time) set at preset intervals via RRC messages and corresponding reference location information, thereby confirming the reference location. As another example, the absolute time (epoch time) can be indicated by the SFN and subframe number, indicating at what point the terminal will use a specific reference location.

[0270]

[0271] Epoch timeReference location (Ellipsoid-point)2022-06-29 02:00:00.000Reference location 12022-06-29 02:05:00.000Reference location 22022-06-29 02:10:00.000Reference location 32022-06-29 02:15:00.000Reference location 42022-06-29 02:20:00.000Reference location 52022-06-29 02:25:00.000Reference location 62022-06-29 02:30:00.000Reference location 7

[0272]

[0273] FIG. 25 is a diagram illustrating satellite movement and reference position changes applicable to the present disclosure. Referring to FIG. 25, a satellite (2510) may have NGSO (Non-geo stationary orbit) non-steerable beams or fixed beams, and the service area may also change as it moves. Accordingly, the satellite moves every T1, T1 + 5 min, and T1 + 10 min, and the service area may also move accordingly. However, this is only one example and may not be limited to the above-described embodiment. Here, the network may indicate a reference position list at a preset interval of absolute time (epoch time). For example, the preset interval may be 5 minutes, but may not be limited thereto. The terminal may receive a 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.

[0274] As a more specific example, referring to FIG. 25, the terminal (2520) may be at a fixed position. At this time, the terminal (2520) can check the distance between the reference position 1 (2531) and the terminal (2520) between T1 and T1+5min (e.g., 2022-06-29 02:00:00.000 to 2022-06-29 02:05:00.000). In addition, the terminal (2520) can check the distance between the reference position 2 (2532) and the terminal (2520) between T1+5min and T1+10min (e.g., 2022-06-29 02:05:00.000 to 2022-06-29 02:10:00.000). Additionally, the terminal (2520) can check the distance between the reference location 3 (2533) and the terminal (2520) between T1+10min and T1+15min (e.g. 2022-06-29 02:10:00.000 to 2022-06-29 02:15:00.000). Here, the terminal can perform a measurement for cell reselection if the distance from the reference location is greater than a distance threshold.

[0275] As a specific example, a case where the distance threshold is set to a value greater than d1 and less than d2 can be considered. Here, the terminal (2520) can perform measurements for cell reselection at an absolute time (epoch time, 2022-06-29 02:05:00.000). That is, the terminal (2520) may not perform measurements for cell reselection because the distance (d1) between the reference location 1 (2531) and the terminal (2520) is less than the distance threshold between T1 and T1+5min. On the other hand, the terminal (2520) can perform measurements for cell reselection because the distance (d2) between the reference location 2 (2532) and the terminal (2520) is greater than the distance threshold between T1+5min and T1+10min.

[0276] As another example, in Table 10 below, the absolute time (epoch time) can be indicated by the SFN and subframe. Accordingly, the reference position update can be performed in a specific SFN and subframe. More specifically, referring to FIG. 25, the terminal (2520) can check the distance between the reference position 1 (2531) and the terminal (2520) in SFN 100, subframe 2, and if it is greater than the distance threshold, can perform measurement for cell reselection. Thereafter, the terminal (2520) can check the distance between the reference position 2 (2532) and the terminal (2520) in SFN 200, subframe 2, and if it is greater than the distance threshold, can perform measurement for cell reselection.

[0277] Epoch time (SFN & Subframe number)Reference location (Ellipsoid-point)100 & 2Reference location 1200 & 2Reference location 2300 & 2Reference location 3400 & 3Reference location 4500 & 3Reference location 5600 & 3Reference location 6700 & 9Reference location 7

[0278]

[0279] FIG. 26 is a diagram illustrating a signaling procedure based on a reference position list applicable to the present disclosure and a reference position update procedure.

[0280] The terminal (2610) may be in an RRC connection state with a network through NTN Cell A (NTN Cell A, 2620). In addition, the terminal (2610) may transition to an RRC idle state after performing a connection with 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 as 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. In addition, the terminal (2610) in the RRC idle state may receive system information. In addition, the terminal (2610) in the RRC idle state may be camping on NTN cell A (2620). (S110) Here, the terminal (2610) in the RRC idle state may check the distance between the reference location of NTN cell A (2620) and the terminal (2610) based on the reference location list, and may perform measurements for cell reselection by comparing the distance with a distance threshold. As a specific example, if the distance between the terminal (2610) and the reference location is greater than the distance threshold, the terminal (2610) may perform measurements for cell reselection. (S115) As another example, if the distance between the terminal (2610) and the reference location is less than the distance threshold, the terminal (2610) may not perform measurements for cell reselection. (S115) If the distance between the terminal (2610) and the reference location is less than the distance threshold, the reference location may be updated as a preset time elapses.Specifically, when the next absolute time (epoch time) in the reference position list is reached or the next SFN and subframe number is reached, the reference position of NTN cell A (2620) can be updated (S120). For example, when the terminal (2610) is configured with the reference position list of Table 9, the previous time and the reference position of NTN cell A (2620) can be "2022-06-29 02:00:00.000" and the reference position 1 (Ellipsoid-point) corresponding thereto. In addition, the reference position of NTN cell A (2620) for the next time can be "2022-06-29 02:05:00.000" and the reference position 2 (Ellipsoid-point) corresponding thereto.

[0281] On the other hand, if the terminal (2610) is configured with a reference position list as in Table 10, the reference position of the previous time and NTN cell A (2620) may be reference position 1 (Ellipsoid-point) corresponding to SFN 100, subframe 2. In addition, the reference position of the next time and NTN cell A (2620) may be reference position 2 (Ellipsoid-point) corresponding to SFN 200, subframe 2. The terminal (2610) updates the reference position based on the above, and can compare the distance between the reference position of NTN cell A (2620) and the terminal (2610) with a distance threshold value. (S130) Here, if the distance between the reference position of NTN cell A (2620) and the terminal (2610) is greater than the distance threshold value, the terminal (2610) may measure the signal strength of the adjacent cell for cell reselection. Here, the terminal (2610) can select NTN Cell B (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 perform camping to NTN Cell B (2630). (S150) Here, the terminal (2610) can determine measurement for cell reselection by checking the distance between the reference location of NTN Cell B (2630) and the terminal (2610). (S155) For example, if the distance between the reference location of NTN Cell B (2630) and the terminal (2610) is less than a distance threshold, the terminal (2610) may not perform measurement for cell reselection. On the other hand, if the distance between the reference position 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.

[0282] Fig. 27 is a flowchart illustrating a reference position update method to which the present disclosure can be applied. Referring to Fig. 27, a terminal may obtain reference position information (S2710). Here, the reference position information may be obtained through system information. In addition, the terminal may obtain at least one of timer information for an uplink synchronization valid time and a reference position update timer through the system information. In addition, the terminal may obtain absolute time (epoch time) information through the system information and determine an effective start time for the above-described timer based thereon. That is, at least one of the timer information for an uplink synchronization valid time and the reference position update timer may start from the effective start time (S2720). Here, as an example, if the distance between the terminal and the reference position 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 can perform measurements for cell reselection (S2740). That is, the terminal can perform measurements for cell reselection by comparing the distance between the terminal and the reference location with the distance threshold.

[0283] In addition, the terminal may perform a reference location update before or after the above-described timer expires. (S2750) Here, the reference location update may be performed based on acquisition of system information. That is, the terminal may acquire system information before or after the timer expires based on at least one of the timer information for the above-described valid 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 corresponding reference location information.

[0284] As another example, the terminal may perform a reference position update based on satellite orbit information (ephemeris). Here, the reference position update may be performed based on a reference position update timer. For example, the terminal may operate the reference position update timer at the aforementioned valid starting 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 reaches the ephemeris, the terminal may perform a reference position update based on satellite orbit information, as described above.

[0285]

[0286] Fig. 28 is a flowchart illustrating a reference position update method to which the present disclosure can be applied. Referring to Fig. 28, a terminal can obtain reference position list information (S2810). Here, the reference position list information can be obtained through system information. For example, the reference position list information can be composed of a specific absolute time and a reference position. Here, for example, if the distance between the terminal and the reference position is less than a distance threshold (S2820), the terminal may not perform measurements for cell reselection (S2830). That is, the terminal can maintain the current cell. On the other hand, if the distance between the terminal and the reference position is greater than the distance threshold (S2820), the terminal can perform measurements for cell reselection (S2830). That is, the terminal can perform specific cell reselection by comparing the distance between the terminal and the reference position with the distance threshold.

[0287] Additionally, the terminal can perform a reference position update based on the reference position list. (S2850) Here, the terminal can update the reference position to the corresponding reference position when a specific absolute time arrives based on the reference position list information. In other words, the terminal can apply a reference position corresponding to a specific point in time through the reference position list information, and perform measurement based on this.

[0288]

[0289] Figure 29 is a drawing showing a device configuration to which the present disclosure can be applied.

[0290] Referring to FIG. 29, a first device (2900) and a second device (2950) can 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.

[0291] For example, a case may be considered where a first device (2900) is a base station device and a second device (2950) is a terminal device. At this time, 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 a higher layer processing unit (2930) and a physical layer processing unit (2940). The higher layer processing unit (2930) may process operations of a MAC (Medium Access Control) layer, an RRC (Radio Resource Control) layer, or higher layers. The physical layer processing unit (2940) may process operations of a physical (PHY) layer (e.g., uplink reception signal processing, downlink transmission signal processing). In addition to performing baseband-related signal processing, the processor (2920) may also control the overall operation of the base station device (2900). The antenna unit (2912) may include one or more physical antennas, and when including multiple antennas, may support MIMO (Multiple Input Multiple Output) transmission and reception. In addition, beamforming may be supported. The memory (2916) may store information processed by the processor (2920), software related to the operation of the base station device (2900), an operating system, applications, etc., and may include components such as a buffer. The processor (2920) of the base station device (2900) may be configured to implement the operations of the base station in the embodiments described in the present invention.

[0292] The terminal device (2950) may include a processor (2970), an antenna unit (2962), a transceiver (2964), and a memory (2966). For example, the terminal device (2950) in the present invention may communicate with a base station device (2900). As another example, the terminal device (2950) in the present invention may perform sidelink communication with another terminal device. That is, the terminal device (2950) of the present invention refers to a device that can communicate 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 a higher layer processing unit (2980) and a physical layer processing unit (2990). The higher layer processing unit (2980) may process operations of a MAC layer, an RRC layer, or a higher layer. The physical layer processing unit (2990) can process the operation of the PHY layer (e.g., downlink reception signal processing, uplink transmission signal processing, sidelink signal processing). The processor (2970) can also control the overall operation of the terminal device (2950) in addition to performing baseband-related signal processing. The antenna unit (2962) can include one or more physical antennas, and when it includes multiple antennas, it can support MIMO transmission and reception. In addition, it can support beamforming. The memory (2966) can store information processed by the processor (2970), software related to the operation of the terminal device (2950), an operating system, applications, etc., and can also include components such as a buffer. The terminal device (2950) according to an example of the present invention can be associated with a vehicle. For example, the terminal device (2950) can be integrated into the vehicle, located in the vehicle, or located on the vehicle. Additionally, the terminal device (2950) according to the present invention may be the vehicle itself.In addition, the terminal device (2950) according to the present invention may be at least one of a wearable terminal, an AV / VR, an IoT terminal, a robot terminal, and a public safety terminal. The terminal device (2950) to which the present invention is applicable may include any type of communication device that supports interactive services utilizing sidelink for services such as Internet access, service execution, navigation, real-time information, autonomous driving, and safety and risk diagnosis. In addition, any type of communication device that is capable of sidelink operation or a sensor that performs relay operation may be included.

[0293] Here, the vehicles / terminals to which the present invention is applied may include autonomous vehicles / driving terminals, semi-autonomous vehicles / driving terminals, non-autonomous vehicles / driving terminals, 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 should not be construed as limiting the application of the present invention to 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 performing cooperation to support interactive services utilizing sidelink. In other words, the terminal device (2950) may not only directly support interactive services utilizing sidelink, but may also be utilized as a cooperation device to support interactive services utilizing sidelink.

[0294] The terminal device (2950) can obtain reference location information. Here, the reference location information can be obtained through system information. In addition, the terminal device (2950) can obtain at least one of timer information for the uplink synchronization valid time and the reference location update timer through the system information. In addition, the terminal device (2950) can obtain absolute time (epoch time) information through the system information and determine the valid start time for the above-described timer based on the absolute time (epoch time) information. That is, at least one of the timer information for the uplink synchronization valid time and the reference location update timer can be started at the valid start time. Here, as an example, the terminal device (2950) may not perform measurements for cell reselection if the distance between the terminal device (2950) and the reference location is less than a distance threshold. In other words, the terminal device (2950) can maintain the current cell. On the other hand, the terminal device (2950) can perform measurements for cell reselection if the distance between the terminal and the reference location is greater than the distance threshold. That is, the terminal device (2950) can perform specific cell reselection by comparing the distance between the terminal device (2950) and the reference location and the distance threshold value.

[0295] In addition, the terminal device (2950) can perform a reference location update before or after the above-described timer expires. 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 timer expires based on at least one of the timer information for the above-described valid time and the reference location update timer. Here, the system information can include reference location information, and the terminal device (2950) can perform a reference location update based on the corresponding reference location information.

[0296] As another example, the terminal device (2950) may perform a reference position update based on satellite orbit information (ephemeris). Here, the reference position update may be performed based on a reference position update timer. For example, the terminal device (2950) may operate the reference position update timer at the above-described valid starting point. Here, the reference position update timer may be set based on at least one of a timer, Unix time, and SFN. At this time, the terminal device (2950) may perform a reference position update based on satellite orbit information when the reference position update timer reaches, as described above. In addition, as an example, if the distance between the terminal and the reference position becomes greater than a threshold value based on the reference position or the updated reference position, the terminal device (2950) may perform a measurement for cell reselection and select an optimal cell.

[0297]

[0298] As another example, the terminal device (2950) can obtain reference location list information. Here, the reference location list information can be obtained through system information. As an example, the reference location list information can be composed of a specific absolute time and a reference location. Here, as an example, the terminal device (2950) may not perform measurements for cell reselection if the distance between the terminal device (2950) and the reference location is less than a distance threshold. That is, the terminal device (2950) may maintain the current cell. On the other hand, the terminal device (2950) may perform measurements for cell reselection if the distance between the terminal and the reference location is greater than the distance threshold. That is, the terminal device (2950) may perform specific measurements for cell reselection by comparing the distance between the terminal device (2950) and the reference location with the distance threshold.

[0299] In addition, the terminal device (2950) can perform a reference position update based on the reference position list. Here, the terminal device (2950) can update the reference position to the corresponding reference position when a specific absolute time arrives based on the reference position list information. That is, the terminal device (2950) can apply a reference position corresponding to a specific point in time through the reference position list information and perform measurement based thereon. In addition, as an example, when the distance between the terminal device (2950) and the reference position becomes larger than a threshold value based on the reference position or the updated reference position, the terminal device (2950) can perform measurement for cell reselection and select an optimal cell.

[0300] Additionally, various embodiments of the present disclosure may be implemented by hardware, firmware, software, or a combination thereof. In the case of hardware implementation, the embodiments may be implemented by 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.

[0301] The scope of the present disclosure includes software or machine-executable instructions (e.g., operating systems, applications, firmware, programs, etc.) that cause operations according to the methods of various embodiments to be executed on a device or a computer, and a non-transitory computer-readable medium having such software or instructions stored thereon and executable on the device or computer.

[0302] The various embodiments of the present disclosure are not intended to list all possible combinations but rather to illustrate 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.

[0303] The above may also apply to other systems.

Claims

1. In a method for a terminal to update its reference location based on non-terrestrial networks (NTN) in a wireless communication system, A step of obtaining reference location-related information from a base station; A step of determining whether the distance between the terminal and the reference location is less than a distance threshold based on the reference location-related information, wherein if the distance between the terminal and the reference location is less than the distance threshold, measurement for cell reselection is not performed, and if the distance between the terminal and the reference location is greater than the distance threshold, the measurement for cell reselection is performed; and A method for updating a reference position, comprising: a step of updating a reference position based on a timer related to the reference position.

2. In paragraph 1, A reference position update method, wherein the above reference position related information includes at least one of reference position information, satellite orbit information, reference position update timer information, uplink synchronization validity time information, and absolute time information.

3. In paragraph 2, Determine a valid starting point for starting at least one of the reference position update timer and the timer for the uplink synchronization valid time based on the above absolute time information, A reference location update method for performing the reference location update by obtaining system information including the reference location information.

4. In paragraph 2, Determine a valid starting point for starting the reference position update timer based on the above absolute time information, A reference position update method that performs the reference position update using satellite orbit information based on the reference position update timer.

5. In paragraph 1, The above reference location related information includes reference location list information, The above reference position list information is composed of an absolute time and a reference position corresponding to the absolute time, A reference position update method, wherein the above reference position update is performed based on the reference position list information.

Images