Method and apparatus for updating reference position in wireless communication system

Abstract

A method for updating a reference position based on a non-terrestrial network (NTN) by a user equipment (UE) in a wireless communication system may include: acquiring reference position related information from a base station; and determining whether a distance between the UE and a reference position is less than a distance threshold based on the reference position related information, if the distance between the UE and the reference position is less than the distance threshold, not performing a measurement for cell reselection, and if the distance between the UE and the reference position is greater than the distance threshold, not performing a measurement for cell reselection. If so, performing a measurement for cell reselection; and if the distance between the UE and the reference location is less than the distance threshold, performing a reference location update based on a reference location related timer.

Description

Technical Field

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

[0002] The International Telecommunication Union (ITU) has developed the International Mobile Telecommunications (IMT) framework and standards. Likewise, ongoing discussions on 5th generation (5G) communications are ongoing through a process called “IMT for 2020 and beyond”.

[0003] In order to meet the requirements requested by "IMT for 2020 and beyond", various proposals have been made to support various numerologies regarding time-frequency resource unit standards by considering various scenarios, service requirements, and potential system compatibility in the 3rd Generation Partnership Project (3GPP) New Radio (NR) system.

[0004] In addition, a method of supporting uninterrupted communication services of a user equipment (UE) having mobility (e.g., a vehicle / train / ship-type terminal / personal smart phone) using not only a terrestrial network (TN) but also a non-terrestrial network (NTN) in a new communication system is being discussed. Below, a method of measuring neighbor cells and performing cell reselection in consideration of the mobility of UE between NTN and TN is described. Summary of the invention Technical Topics

[0005] The present invention may provide a method and apparatus for updating a reference location considered in measurement for cell reselection in a wireless communication system.

[0006] The present invention may provide a method and apparatus for updating a reference location in consideration of a mobile cell in a non-terrestrial network (NTN) environment.

[0007] The present invention may provide a method and apparatus for setting a timer for reference location update 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 ephemeris information in an NTN environment.

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

[0011] According to an embodiment, a method for updating a reference location by a user equipment (UE) based on a non-terrestrial network (NTN) in a wireless communication system may include: obtaining reference location related information from a base station; based on the reference location related information, determining whether the distance between the UE and the reference location is less than a distance threshold, if the distance between the UE and the reference location is less than the distance threshold, not performing measurements for cell reselection, if the distance between the UE and the reference location is greater than the distance threshold, performing measurements for cell reselection; and if the distance between the UE and the reference location is less than the distance threshold, performing a reference location update based on a reference location related timer.

[0012] In addition, according to an embodiment, the reference position related information may include at least one of reference position information, satellite ephemeris information, reference position update timer information, uplink synchronization valid time information and epoch time information.

[0013] In addition, according to an embodiment, a validity start point for starting a reference location update timer and at least one of a timer for uplink synchronization validity time can be determined based on the epoch time information, and the reference location update can be performed by acquiring system information including reference location information.

[0014] Furthermore, according to an embodiment, a valid starting point for starting a reference position update timer may be determined based on epoch time information, and the reference position update may be performed through satellite ephemeris information based on the reference position update timer.

[0015] Furthermore, according to an embodiment, the reference position related information may include reference position list information, the reference position list information may be configured with the epoch time and the reference position corresponding to the epoch time, and the reference position update may be performed based on the reference position list information.

[0016] The features briefly summarized above with respect to the present disclosure are merely exemplary aspects of the detailed description of the present disclosure described below and are not to be construed as limiting the scope of the present disclosure. Beneficial Effects

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

[0018] According to the present disclosure, a method of updating a reference location considering a mobile cell in a non-terrestrial network (NTN) environment may be provided.

[0019] According to the present disclosure, a method of setting a timer for reference location update in an NTN environment may be provided.

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

[0021] According to the present invention, a method for updating a reference position based on satellite ephemeris information 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 may be provided.

[0023] The present invention is not limited to the above-mentioned effects, and other effects not described herein may be clearly understood by a person of ordinary skill in the art to which the present disclosure pertains from the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 An example of describing a New Radio (NR) frame structure to which the present disclosure is applicable is shown.

[0025] Figure 2 The NR resource structure to which the present disclosure is applicable is shown.

[0026] Figure 3 A non-terrestrial network (NTN) including transparent satellites to which the present disclosure can be applied is shown.

[0027] Figure 4 An NTN including a regenerative satellite without inter-satellite links (ISL) to which the present disclosure may be applied is shown.

[0028] Figure 5 An NTN including a regenerative satellite with an ISL to which the present disclosure may be applied is shown.

[0029] Figure 6 A User Plane (UP) protocol stack structure in an NTN including a transparent satellite to which the present disclosure may be applied is shown.

[0030] Figure 7 A control plane (CP) protocol stack structure in an NTN including a transparent satellite to which the present disclosure may be applied is shown.

[0031] Figure 8 A timing advance calculation method to which the present disclosure can be applied is shown.

[0032] Fig. 9 A geostationary cell scenario to which the present disclosure can be applied is shown.

[0033] Fig.10 An earth mobile cell scenario to which the present disclosure can be applied is shown.

[0034] Fig.11 A method of mapping a physical cell ID (PCI) to a satellite beam to which the present disclosure may be applied is shown.

[0035] Fig.12 Reference positions to which the present disclosure can be applied are shown.

[0036] Fig.13 Received signal strength according to distance in TN and NTN to which the present disclosure can be applied is shown.

[0037] Fig.14 A method of performing distance-based measurement for cell reselection to which the present disclosure may be applied is shown.

[0038] Fig.15 A reference position updating method to which the present disclosure can be applied is shown.

[0039] Fig.16 A method for performing reference location update based on system information acquisition to which the present disclosure can be applied is shown.

[0040] Fig.17 A method of performing reference position update to which the present disclosure can be applied is shown.

[0041] Fig.18 A method of updating a reference position based on a new timer to which the present disclosure can be applied is shown.

[0042] Fig.19 A method of performing a reference location update based on a reference location update timer to which the present disclosure may be applied is shown.

[0043] Fig. 20 A method for performing reference location update based on system information acquisition to which the present disclosure can be applied is shown.

[0044] Fig.21 Earth-Centered, Earth-Fixed (ECEF) coordinates and ellipsoid points (Ellipsoid-Point) to which the present disclosure can be applied are shown.

[0045] Fig. 22 A reference position updating method to which the present disclosure can be applied is shown.

[0046] Fig.23A method for updating a reference position based on satellite ephemeris information to which the present disclosure can be applied is shown.

[0047] Fig.24 A method for updating a reference position based on satellite ephemeris information to which the present disclosure can be applied is shown.

[0048] Fig.25 The changes in satellite motion and reference position to which the present disclosure may be applied are shown.

[0049] Fig.26 A reference location list-based signaling procedure and a reference location update procedure to which the present disclosure can be applied are shown.

[0050] Fig. 27 is a flow chart illustrating a reference position updating method to which the present disclosure may be applied.

[0051] Fig.28 is a flow chart illustrating a reference position updating method to which the present disclosure may be applied.

[0052] Fig.29 is a diagram showing a device configuration to which the present disclosure can be applied. DETAILED DESCRIPTION

[0053] Various examples of the present disclosure will be described more fully below with reference to the accompanying drawings so that those skilled in the art to which the present disclosure pertains can easily implement these examples. However, the present disclosure may be implemented in various forms and is not limited to the examples described herein.

[0054] When describing examples of the present disclosure, detailed descriptions of known configurations or functions may be omitted for clarity and conciseness. Throughout the drawings and detailed description, unless otherwise specified, the same reference numerals are understood to refer to the same elements, features, and structures.

[0055] It will be understood that when an element is referred to as being "connected to," "coupled to," or "accessed to" another element, it may be directly connected, coupled to, or accessed to the other element, or intervening elements may be present. Furthermore, it will be understood that when an element is described as "including / comprising" or "having" another element, it specifies the presence of the other element, but does not preclude the presence of the other element described in other ways.

[0056] In addition, terms such as first, second, etc. can be used to describe the elements in the description herein. These terms are used to distinguish an element from another element. Therefore, the terms do not limit the elements, arrangement order, or sequence, etc. Therefore, the first element in one example can be referred to as the second element in another example. Likewise, the second element in one example can be referred to as the first element in another example.

[0057] Here, providing distinguishing elements is only for the purpose of clearly explaining each feature, and does not mean that the elements must be separated from each other. That is, multiple elements can be integrated into a single hardware or software unit. Moreover, a single element can be distributed to multiple hardware or software units. Therefore, unless otherwise described, integrated or distributed examples are also included in the scope of this disclosure.

[0058] Here, the elements described in various examples may not necessarily be necessary and may be partially optional. Therefore, examples including a partial set of elements described in the examples are also included in the scope of this disclosure. In addition, examples including another element other than the elements described in various examples are also included in the scope of this disclosure.

[0059] The description described herein relates to a wireless communication network, and operations performed in the wireless communication network may be performed in a process in which a system (eg, base station) controlling the wireless network controls the network and transmits data, or may be performed in a user equipment.

[0060] Obviously, in a network including a base station and a plurality of network nodes, various operations performed for communicating with a UE may be performed by the base station or other network nodes other than the base station. Here, the term "base station (BS)" may be used interchangeably with other terms, such as a fixed station, a Node B, an eNodeB (eNB), a gNodeB (gNB), and an access point (AP). In addition, the term "terminal" may be used interchangeably with other terms, such as a user equipment (UE), a mobile station (MS), a mobile subscriber station (MSS), a subscriber station (SS), and a non-AP station (non-AP STA).

[0061] Here, sending or receiving a channel includes the meaning of sending or receiving information or signals through the corresponding channel. For example, sending a control channel means sending control information or signals through the control channel. Similarly, sending a data channel means sending data information or signals through the data channel.

[0062] In the following description, although the term “New Radio (NR) system” is used to distinguish a system according to various examples of the present disclosure from an existing system, the scope of the present disclosure is not limited thereto.

[0063] The New Radio (NR) system supports various subcarrier spacings (SCS) by considering various scenarios, service requirements, potential system compatibility, etc. In addition, in order to overcome the adverse channel environment such as high path loss, phase noise, and frequency offset that occur at high carrier frequencies, the NR system can support the transmission of physical signals / channels through multiple beams. In this way, the NR system can support a variety of applications, such as enhanced mobile broadband (eMBB), massive machine type communication (mMTC) / ultra machine type communication (uMTC), and ultra-reliable and low-latency communication (URLLC).

[0064] Here, 5G mobile communication technology can be defined by including the existing advanced long term evolution (LTE-A) system and the above-mentioned NR system. That is, 5G mobile communication technology can be operated by considering backward compatibility with previous systems and newly defined NR systems. Therefore, subsequent 5G mobile communication may include technologies based on NR system operation and technologies based on previous systems (e.g., LTE-A, LTE), but is not limited to a specific system.

[0065] First, the physical resource structure of the NR system to which the present disclosure is applied will be briefly described.

[0066] Figure 1 An example of an NR frame structure according to an example of the present invention is shown.

[0067] In NR, the basic unit of time domain can be T c =1 / (Δf max ·N f ). Here, Δf max =480·10 3 And N f =4096. In addition, κ = T s / T c =64 may be a constant related to the multiple relationship between the NR time unit and the LTE time unit. In LTE, T s =1 / (Δf ref ·N f,ref ),Δf ref =15·10 3 And N f,ref = 2048 can be defined as a reference time unit. The constant of the multiple relationship between the NR time basic unit and the LTE time basic unit can be defined as k = T s / T c =64.

[0068] Reference Figure 1 , which may include a time structure of a frame for downlink / uplink (DL / UL) transmission, which may include T f =(Δfmax N f / 100)·T s = 10 ms. Here, a single frame may include a time corresponding to T sf =(Δf max N f / 1000)·T s = 10 subframes of 1 ms. The number of consecutive OFDM symbols per subframe can be In addition, each frame may be divided into two half frames, and the half frame may include subframes 0 to 4 and subframes 5 to 9. Here, half frame 1 may include subframes 0 to 4, and half frame 2 may include subframes 5 to 9.

[0069] N TA Denotes the timing advance (TA) between downlink (DL) and uplink (UL). Here, according to the following equation 1, the transmission timing of the uplink transmission frame i is determined based on the downlink reception timing at the UE.

[0070] [Equation 1]

[0071] T TA =(N TA +N TA,offset )T c

[0072] N TA,offset Indicates the TA offset value due to duplex mode differences, etc. Basically, in frequency division duplex (FDD), N TA,offset = 0. In time division duplex (TDD), N can be defined by considering the margin of DL-UL switching time. TA,offset For example, in TDD (Time Division Duplex) of RF1 (Frequency Range 1) (which is a frequency below 6 GHz or lower), N TA,offset It can be 39936T C or 2600T C .39936T C =20.327μs and 25600T C =13.030μs. In addition, in FR2 (frequency range 2) of millimeter wave (mmWave), N TA,offset It can be 13792T C At this time, 39936T C =7.020μs.

[0073] Figure 2 An NR resource structure to which the present disclosure is applicable is shown.

[0074] Resource elements within a resource grid may be indexed based on each subcarrier spacing. Here, a single resource grid may be generated for each antenna port and each subcarrier spacing. Uplink / downlink transmission and reception may be performed based on the corresponding resource grid.

[0075] A resource block (RB) in the frequency domain is configured with 12 REs, and for every 12 REs, an RB index (n PRB ). The index of the RB may be used within a specific frequency band or system bandwidth. The index of the RB may be defined as shown in the following equation 2. Here, N RB sc represents the number of subcarriers in each RB, and k represents the subcarrier index.

[0076] [Equation 2]

[0077]

[0078] The digital parameter configuration can be configured differently to meet various services and requirements of the NR system. For example, one subcarrier spacing (SCS) can be supported in the LTE / LTE-A system, but multiple SCSs can also be supported in the NR system.

[0079] The new digital parameter configuration of the NR system supporting multiple SCSs can operate in a frequency range or carrier such as 3 GHz or less, 3 GHz-6 GHz, 6 GHz-52.6 GHz or more to solve the problem that a wide bandwidth cannot be obtained in a frequency range or carrier such as 700 MHz or 2 GHz.

[0080] Table 1 below shows an example of digital parameters supported by the NR system.

[0081] [Table 1]

[0082] Referring to Table 1 above, the digital parameter configuration may be defined based on the SCS used in the OFDM system, the cyclic prefix (CP) length, and the number of OFDM symbols per time slot. The above values ​​may be provided to the UE through higher layer parameters DL-BWP-mu and DL-BWP-cp for the downlink, and through higher layer parameters UL-BWP-mu and UL-BWP-cp for the uplink.

[0083] In the above Table 1, if μ=2 and SCS=60 kHz, normal CP and extended CP may be applied. In other frequency bands, only normal CP may be applied.

[0084] Here, a normal slot may be defined as a basic time unit for sending a single piece of data and control information in an NR system. The length of a normal slot may basically include 14 OFDM symbols. In addition, unlike a slot, a subframe may have an absolute time length corresponding to 1ms in an NR system and may be used as a reference time for the length of another time segment. Here, for the coexistence and backward compatibility of LTE and NR systems, the NR standard may require a time segment such as an LTE subframe.

[0085] For example, in LTE, data may be transmitted based on a transmission time interval (TTI) as a unit time. TTI may include at least one subframe unit. Here, even in LTE, a single subframe may be set to 1 ms and may include 14 OFDM symbols (or 12 OFDM symbols).

[0086] In addition, in the NR system, non-slots can be defined. Non-slots may refer to slots having at least one less symbol than the number of symbols of ordinary slots. For example, in the case of providing low latency such as ultra-reliable and low-latency communication (URLLC) services, latency can be reduced by non-slots having a smaller number of slots than the number of slots of ordinary slots. Here, the number of OFDM symbols included in the non-slots can be determined based on the frequency range. For example, non-slots having a length of 1 OFDM symbol in a frequency range of 6 GHz or higher can be considered. As another example, the number of symbols used to define a non-slot may include at least two OFDM symbols. Here, the number range of OFDM symbols included in the non-slots can be configured to have a micro-slot length of up to (ordinary slot length) -1. Here, although the number of OFDM symbols can be limited to 2, 4 or 7 as a non-slot standard, it is provided only as an example.

[0087] In addition, for example, SCS corresponding to μ = 1 and 2 can be used in unlicensed bands of 6 GHz or less, and SCS corresponding to μ = 3 and 4 can be used in unlicensed bands above 6 GHz. Here, for example, if μ = 4, it can be used for synchronization signal blocks (SSBs).

[0088] [Table 2]

[0089] Table 2 shows the number of OFDM symbols per time slot for a normal CP set by subcarrier spacing. The number of time slots per frame and the number of time slots per subframe In Table 2, the values ​​are based on a normal slot with 14 OFDM symbols.

[0090] [Table 3]

[0091] In Table 3, in the case where extended CP is applied (ie, μ=2 and SCS=60 kHz), the number of slots per frame and the number of slots per subframe based on normal slots where the number of OFDM symbols per slot is 12 are shown.

[0092] As described above, a single subframe may correspond to 1 ms on the time axis. Moreover, a single time slot may correspond to 14 symbols on the time axis. For example, a single time slot may correspond to 7 symbols on the time axis. Therefore, the number of time slots and the number of symbols that may be considered may be set differently within 10 ms corresponding to a single radio frame. Table 4 may show the number of time slots and the number of symbols according to each SCS. Although an SCS of 480 kHz may not be considered in Table 4, the present disclosure is not limited to such an example.

[0093] [Table 4] SCS Time slot within 10ms Time slot within 10ms Symbols within 10ms 15kHz 10 20 140 30kHz 20 40 280 60kHz 40 80 560 120kHz 80 N / A 1120 240kHz 160 N / A 2240 480kHz 320 N / A 4480

[0095] In addition, for example, in an existing wireless communication system, communication can be performed based on a terrestrial network including a UE existing on the ground and a base station existing on the ground. The UE can access the network wirelessly. Here, when the UE moves, the UE can continuously receive the same service through another base station in the terrestrial network. The UE can access the network and then access a specific service server through other wired or Internet networks. Moreover, the UE can receive a service connected to another UE by wired or wireless communication through the network.

[0096] However, the new wireless communication system can support the communication of UE not only through the terrestrial network but also through the non-terrestrial network (NTN). Here, NTN may refer to a network or some of these networks, each of which uses a mobile object floating in the air or space, which is equipped with a base station or a relay device. For example, NTN can support device-to-device communication services based on artificial satellites equipped with communication functions in low earth orbit (LEO) and geostationary earth orbit (GEO). As another example, NTN can support device-to-device communication services based on aircraft equipped with communication functions within an unmanned aircraft system (UAS), but is not limited thereto.

[0097] In the following, a terrestrial network (TN) is described distinguishably compared to a non-terrestrial network (NTN). That is, in the existing communication system, only the terrestrial network exists, so there is no need to distinguish them. On the other hand, in the following, NTN and TN are distinguished and described as a communication system capable of performing device-to-device communication based on NTN, and based on this, a method of supporting a device-to-device communication service is described.

[0098] For example, the wireless communication service between a land base station and a wireless terminal or between mobile base stations is described as a mobile service, but is not limited thereto. In addition, the communication between a mobile land base station and one or more space base stations may be a mobile satellite service. In addition, the wireless communication service between a mobile land base station and a space base station or between mobile land base stations via at least one space base station may be a mobile satellite service, but is not limited thereto.

[0099] Below, a method for performing communication based on a wireless communication system that supports all mobile services and mobile satellite services is described. For example, NTN technology has been introduced specifically for satellite communication, but NTN can be introduced into a communication system of TN (such as a 5G system) to operate with TN. Here, the UE can support NTN and TN at the same time. For UEs that support both NTN and TN, in addition to the long-term evolution (LTE) and new wireless (NR) systems as radio access technologies (RATs), the wireless communication system may require specific technologies for NTN, and the method for this purpose is described below. For example, the following may be a definition of each term related to NTN and TN.

[0101] Non-terrestrial network (NTN):

[0102] They are a network or a number of networks, each of which uses a mobile object floating in the air or space equipped with a base station or relay device for communication.

[0104] NTN Gateway:

[0105] It is a terrestrial base station or gateway that exists on the surface of the earth and is equipped with radio access equipment sufficient to access satellites. Typically, an NTN gateway can be a transport network layer node (TNL).

[0107] Feeder link:

[0108] It is the radio link between the NTN gateway and the satellite.

[0110] Geosynchronous Orbit (GEO):

[0111] It is a circular orbit at 35,786km above the Earth's equator, matching the direction of Earth's rotation. An object or satellite in orbit orbits with the same period as the Earth's rotation period. Therefore, when observed from Earth, it appears to exist in a fixed position and not move.

[0113] Low Earth Orbit (LEO):

[0114] It is an orbit between 300km and 1500km above the Earth.

[0116] Medium Earth Orbit (MEO):

[0117] It is an orbit between LEO and GEO.

[0119] Unmanned Aerial Systems (UAS):

[0120] A UAS is a system that typically operates at 8km to 50km above the ground, which may include a high altitude platform (HAP). A UAS may include at least one of a tethered UAS (TUA), a lighter-than-air UAS (LTA), and a heavier-than-air UAS (HTA) system.

[0122] Minimum elevation angle:

[0123] It is the minimum angle required for a land terminal to face a satellite or UAS base station in the sky.

[0125] Mobile Services:

[0126] They are wireless communication services between terrestrial base stations and wireless terminals or between mobile base stations.

[0128] Mobile Satellite Services:

[0129] They can be wireless communication services between a mobile land base station and one or more space base stations, between a mobile land base station and a space base station, or between mobile land base stations through at least one space base station.

[0131] Non-geosynchronous satellites:

[0132] They are satellites in LEO and MEO and may be satellites that orbit the Earth with a period of about 1.5 to 10 hours.

[0134] On board processing:

[0135] It is the digital processing of uplink radio frequency (RF) signals mounted on satellites or non-terrestrial equipment.

[0137] Transparent Payload :

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

[0140] Regeneration Payload:

[0141] It involves transforming and amplifying the uplink RF signal before sending it via the downlink, and the transformation of the signal may include digital processing such as decoding, demodulation, remodulation, recoding and filtering.

[0143] Airborne NTN base station (gNB):

[0144] It can mean an onboard satellite where the base station (gNB) is implemented in a regenerative payload structure.

[0146] NTN base station on the ground (gNB):

[0147] It is a terrestrial base station in which the base station (gNB) is implemented with a transparent payload structure.

[0149] One-way waiting time:

[0150] It is the amount of time it takes to reach a public data network from a wireless terminal or vice versa in a wireless communication system.

[0152] Round Trip Delay (RTD):

[0153] It may be the amount of time for an arbitrary signal to reach the NTN gateway from the wireless terminal or from the NTN gateway to the wireless terminal and then return. Here, the return signal may be a signal containing a form or message different from the arbitrary signal.

[0155] satellite:

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

[0158] Satellite beam:

[0159] It is a beam generated by the antenna onboard the satellite.

[0161] Service link:

[0162] It is the radio link between the satellite and the UE.

[0164] User Connectivity:

[0165] It is capable of configuring and maintaining data / voice / video transmission between the network and the UE.

[0167] User throughput:

[0168] It is the data transmission rate provided to the UE.

[0170] Figure 3 An NTN including transparent satellites to which the present disclosure can be applied is shown.

[0171] Reference Figure 3 , UEs included in the NTN may include land network terminals. For example, UEs of the NTN and TN may include manned or unmanned mobile objects such as ships, trains, buses, and airplanes, and may not be limited to a specific form. Figure 3 , a transparent satellite payload generated by a network including transparent satellites can be implemented in a manner equivalent to an RF repeater.

[0172] In more detail, the network including the transparent satellite can perform frequency conversion and amplification on the wireless signal received in the uplink and downlink directions, and can transmit the wireless signal. Therefore, the satellite can perform the function of relaying the NR-Uu wireless interface, which includes the feeder link and service link directions, and the NR-Uu wireless interface is described below.

[0173] As another example, refer to Figure 3 , the satellite radio interface (SRI) in the feeder link may be included in the NR-Uu interface. That is, the satellite may not be an endpoint of the NR-Uu interface. Here, the NTN gateway may support all functions required to send signals defined in the NR-Uu interface. For example, other transparent satellites may be connected to the same base station on land. That is, multiple transparent satellites may be configured to connect to a single land base station. The base station may be an eNB or a gNB, but may not be limited to a specific form.

[0174] Figure 4An NTN including regenerative satellites without inter-satellite links (ISLs) to which the present disclosure may be applied is shown.

[0175] refer to Figure 4 , the NTN may include a regenerative satellite. Here, the regenerative satellite may mean that the base station function is included in the satellite. For example, the regenerative satellite payload generated by the network including the regenerative satellite may be implemented in a manner that regenerates the signal received from the land.

[0176] In more detail, the regeneration satellite may receive a signal from the ground based on the NR-Uu radio interface between the UE and the satellite. As another example, the regeneration satellite may receive a signal from the ground through an SRI in a feeder link between NTN gateways. Here, the SRI may be defined in a transport layer between the satellite and the NTN gateway. The transport layer may refer to a transport layer in a layer defined as OSI 7 layers. That is, the signal from the ground may be transformed based on the regeneration satellite through digital processing such as decoding, demodulation, remodulation, recoding, and filtering, but is not limited thereto.

[0177] Figure 5 An NTN including a regenerative satellite with an ISL to which the present disclosure may be applied is shown.

[0178] Reference Figure 5 , ISL can be defined in the transport layer. As another example, ISL can be defined as a radio interface or a visible light interface, but is not limited to a specific embodiment. Here, the NTN gateway can support all functions of the transport protocol. In addition, each regenerated satellite can become a base station, and multiple regenerated satellites can be connected to the same 5G core network existing on the ground.

[0179] Figure 6 The user plane (UP) protocol stack structure in NTN including transparent satellites to which the present disclosure can be applied is shown. In addition, Figure 7 A control plane (CP) protocol stack structure in an NTN including a transparent satellite to which the present disclosure may be applied is shown.

[0180] The NR Uu interface may be an interface defined as a protocol for a wireless connection between a UE and a base station in an NR system. Here, the NR Uu interface may include a user plane defined as a protocol for user data transmission, including NTN. In addition, the NR Uu interface may include a control plane defined as a protocol for sending signaling containing radio resource control information, including NTN. For example, the media access control (MAC) layer may be configured based on radio link control (RLC), packet data convergence protocol (PDCP), service data adaptation protocol (SDAP), and radio resource control (RRC). The protocol of each layer may be defined based on NR in the 3GPP RAN-related standards, but is not limited thereto.

[0181] For example, Figure 6 It can be a UP protocol stack structure based on transparent satellite. That is, in the satellite and NTN gateway, only the frequency conversion and amplification of the transparently received wireless signal are performed, and then the signal can be transmitted. Moreover, Figure 7 It can be a transparent satellite-based CP protocol stack structure. That is, in the satellite and NTN gateway, only the frequency conversion and amplification of the transparently received wireless signal are performed.

[0182] Based on the above, a wireless communication system that supports communication between UEs with NTN and TN may be considered. Here, NTN may have a larger round trip time (RTT) between the UE and the base station compared to the existing TN. Therefore, from the perspective of UP, due to the increase in RTT, the UE may need to store data sent through each of the uplink and downlink in the buffer for a longer period of time. That is, the UE may need to store more data in the buffer. Therefore, the UE may need a larger storage capacity than before, which will be described below.

[0183] Figure 8 A timing advance calculation method to which the present disclosure can be applied is shown. As described above, since the satellites included in the NTN are located in the sky, the signal RTT may increase. For example, in the case of LEO, the satellites may exist at an altitude of 300km to 1200km, and in the case of GEO, the satellites may exist at an altitude of 36,000km or more above the equator. Therefore, the propagation delay in the NTN may be significantly greater than the propagation delay in the TN. On the other hand, since the NTN exists in the sky, the cell coverage may be greater than the coverage of the terrestrial network.

[0184] That is, since NTN may have different RTT and cell coverage compared with TN, a new method for obtaining time synchronization of uplink transmission in NTN needs to be newly defined. For example, Figure 8It can be a method of calculating the TA value generated according to the satellite payload type.

[0185] In more detail, Figure 8 (a) may be a method of calculating a timing advance (TA) value when the satellite payload type is a regenerative payload. In addition, Figure 8 (b) may be a method for calculating the TA value when the satellite payload type is a transparent payload.

[0186] Here, for initial access and continuous maintenance of a timing advance (TA) value, a case where the UE knows satellite ephemeris information and the location of the UE may be considered. Here, the satellite ephemeris information may indicate the distance between each satellite and the receiver and the location information of each satellite. For example, the UE may obtain a TA value by itself and then apply the TA value (hereinafter, option 1). As another example, the UE may receive instructions for TA compensation and correction from the network (hereinafter, option 2).

[0187] For example, refer to Figure 8 (a), when the satellite payload type is a regenerative payload, the satellite can be used directly as a base station. Here, the UE can calculate the TA value required for uplink transmission including the physical random access channel (PRACH). The UE can calculate the common TA value (T COM ) and UE-specific TA value (T UEx For example, the common TA value (T COM ) may be a TA value required for all UEs due to the large cell coverage and long RTT of NTT. That is, since NTT exists in the sky and has a relatively longer distance than the distance between UEs, a common TA value (T ) for long RTT in the cell coverage may need to be considered. COM In addition, the UE-specific TA value (T UEx ) may be a value generated due to the difference in the position of each UE within the cell coverage. If the UE pre-verifies the position of the satellite corresponding to a specific time through the satellite ephemeris pre-stored or received from the NTN, and knows the position of the UE, the UE can calculate the distance between the satellite and the corresponding UE at the specific time. Therefore, the UE can obtain the TA value by itself, and then correct the TA value, and by doing so, the TA value can be determined.

[0188] Through the above description, the UE may perform UE-to-UE uplink timing alignment received from the base station as full TA compensation.

[0189] As another example, the UE may perform downlink and uplink frame timing alignment on the network side. Figure 8When the transparent payload is shown in (b), the satellite can perform filtering and amplification of the wireless signal and can send the signal to the NTN gateway. That is, the satellite can work like an RF repeater. Here, in some cases, it may be necessary to change the NTN gateway based on the continuous movement of the satellite. Figure 8 (b), the common TA value (T COM ) can be based on the distance D between the reference position (reference point) and the satellite 01 and the distance D between the satellite and the NTN gateway 02 Here, the feeder link may change based on the movement of the satellite in response to a change in the NTN gateway. That is, the distance between the satellite and the NTN gateway may change based on the changed feeder link. Therefore, the common TA value may change and needs to be updated in the corresponding UE. In addition, in the case where an offset between the downlink frame timing and the uplink frame timing is set in the network, it may be necessary to additionally consider the case where the TA value generated due to the feeder link is not corrected using the full TA compensation method. In addition, when the UE is only able to calculate the UE-specific differential TA value (T UEx ), the UE needs to verify a single reference position (reference point) for each beam or each cell, and needs to send corresponding information to other UEs. In the case where the offset between the downlink frame timing and the uplink frame timing is set in the network, the network needs to manage the offset information regardless of the satellite payload type. Here, for example, the network may also provide a value for TA correction to each user equipment, without being limited to the above-mentioned embodiment.

[0190] As another example, a method of indicating TA compensation and correction in the network (Option 2) may be considered. Here, a common TA value may be generated based on a common element of propagation delay shared by all UEs present within the coverage of a beam or cell of a satellite. The network may send the common TA value to UEs for each cell or beam of each satellite based on a broadcast method. The common TA value may be calculated in the network, where it may be assumed that each cell or beam of each satellite has at least one reference position. In addition, a UE-specific TA value (TA) may be determined based on a random access procedure defined in an existing communication system (e.g., Release 15 or Release 16 of an existing NR system). UEx ). Here, for example, in the case of applying long TA values ​​and negative TA values, a new field may be required in the random access message. For example, when the network provides the UE with a timing change rate, the UE may support TA value correction based on the timing change rate.

[0191] Fig. 9 A geostationary cell scenario to which the present disclosure can be applied is shown.

[0192] Reference Fig. 9A fixed cell may be a cell where the location of the signal transmitted from the satellite is fixed. For example, since the satellite moves over time, the antenna and beam need to be changed to ensure that the service coverage is fixed at a specific location so that the fixed cell can be maintained. Here, for example, Fig. 9 In the embodiment, satellite 1 910 may maintain the fixed cell while changing the antenna and beam during T1 to T3. Here, if a specific time (T4) has passed, satellite 1 910 may no longer serve the corresponding location, and satellite 2 920 may provide service at the corresponding location, thereby maintaining service continuity. Here, after time T4, the cell or beam of satellite 2 920 serving the same location as the location provided by satellite 1 910 at the previous time (T1 to T3) may maintain the characteristics of the cell or beam of satellite 1 910, and is not limited to the above-mentioned embodiments.

[0193] As a more detailed example, in the case of providing services through satellite 1 910 and satellite 2 920, at least one of a physical cell id (PCI) value and system information may remain the same. That is, as a cell with a fixed service coverage, configuration may generally be performed based on a satellite capable of changing a beam and an antenna angle among satellites in LEO and MEO other than GEO.

[0194] on the other hand, Fig.10 The present disclosure is applicable to a scenario of an earth mobile cell. For example, a cell with mobile service coverage may be an earth mobile cell.

[0195] For example, refer to Fig.10 , each of satellite #1 1010, satellite #2 1020, and satellite #3 1030 can provide services to its own cell using different PCIs. Here, the earth moving cell may be in a form in which an antenna and a beam for the satellite to send a signal to the land are fixed, and the service coverage changes as the satellite moves over time. The earth moving cell may be configured based on a satellite having a fixed beam and antenna angle among satellites other than GEO in LEO and MEO. Here, the corresponding satellite may have advantages such as a low price and a low failure rate compared to a satellite capable of adjusting a beam and an antenna angle.

[0196] also, Fig.11 A method of mapping PCIs to satellite beams to which the present disclosure may be applied is shown.

[0197] For example, PCI may refer to an index that can logically identify a single cell. That is, beams with the same PCI value may be included in the same cell. Fig.11(a), a single PCI can be assigned to multiple satellite beams. Fig.11 (b), a single PCI can be assigned to each satellite beam from a single satellite. For example, a satellite beam may include one or more synchronization signal block (SSB) (SS / PBCH block) beams. A single cell (or PCI) may include up to L SSB beams. Here, depending on the size of the frequency band and / or subcarrier band, L may be 4, 8, 64, or 256, but is not limited to the above embodiments. That is, for L, similar to a terrestrial network (TN) corresponding to an existing communication system (NR system), one or more SBS indexes may be used for each PCI. In this way, SSBs transmitted through different beams may be distinguished, and SSB indexes may be mapped to logically defined antenna ports or physically separate formed beams.

[0198] For example, the UE accessible to the NTN may be a UE supporting a global navigation satellite system (GNSS) function. However, the UE accessible to the NTN may include a UE that does not support a GNSS function. As another embodiment, the NTN may support a UE that supports a GNSS function, but does not ensure location information through the GNSS, and is not limited to the above embodiments.

[0199] As described above, the UE can perform communication through the NTN. For example, the UE can receive non-terrestrial network-based services based on 5G / B5GNTN. In this way, the UE can avoid regional, environmental, spatial and economic constraints for radio access services (e.g., LTE, NR, WiFi, etc.) based on the installation of terrestrial network equipment. For example, based on the above, advanced radio access technologies provided from terrestrial networks can be applied to non-terrestrial network platforms (e.g., satellites and UAVs). In this way, advanced network technologies can be provided for various wireless access service products and technologies.

[0200] The NTN platform can be equipped with NR signal relay functions or base station (gNB, eNB) functions in space or at high altitudes, and can operate as a mirror. For example, as already mentioned, the functions of the NG-RAN-based NTN architecture can be implemented with the "NTN based on transparent payload" and "NTN based on regeneration payload" structures, which are described above.

[0201] Similarly, for example, NTN technology refers to the extended network structure and technology of the 5G integrated access and backhaul (IAB) architecture, and can be used for wider coverage and more radio access services. The integration of NTN and TN can guarantee the business continuity and scalability of the 5G system.

[0202] As a detailed example, the NTN and TN integrated network can provide significant gains in 5G target performance (e.g., user experience data rate and reliability) in urban and suburban areas. As another example, the NTN and TN integrated network can ensure connectivity not only in very dense areas (e.g., concert halls, stadiums, shopping malls, etc.), but also in fast-moving objects such as airplanes, high-speed trains and ships. As another example, the NTN and TN integrated network can use data transmission services from NTN and TN at the same time through the multi-connection function. Here, the efficiency and economic feasibility of 5G wireless transmission services can be achieved by selectively utilizing a better network according to business characteristics and business load degree.

[0203] Generally, a commonly existing UE can use wireless data services by connecting to NTN and TN at the same time. Moreover, the UE can provide wireless data access services for harsh environments or areas where it is difficult to simultaneously connect to one or more NTN platforms (e.g., two or more LEO / GEO satellites) and support the platforms in TN. In this way, the UE can be used in association with various services. Specifically, the NTN and TN integrated network can improve the reliability of autonomous driving services and perform efficient network operations, and is not limited to the above-mentioned embodiments.

[0204] Here, for example, the services provided by V2X technology based on LTE mobile communication or standard technology based on IEEE 802.11p standard may have similar limitations. LTE V2X standard can be provided to meet the requirements defined in C-ITS (e.g., about 100ms of latency, about 90% of reliability, and about 10 times per second of the generation of messages of tens to hundreds of bytes in size). Therefore, new V2X services requiring low latency, high reliability and high-capacity data services and improved positioning may be required. Here, for example, based on the above, standardization of 5G radio access technology (e.g., new radio (NR)) is underway. In addition, for example, in order to respond to the needs of new services more flexibly than LTE, various digital parameter configurations and frame structures and the standardization of L2 / L3 protocol structures corresponding thereto are being carried out. Based on the above, by introducing sidelink wireless access technology based on 5G mobile communication technology, improved V2X services such as autonomous driving or remote driving can be supported. To this end, NTN can be used.

[0205] As another example, NTN can be used to support IoT services in harsh environments and areas that are not covered by terrestrial networks. For example, depending on the purpose of use, IoT devices may need to frequently perform wireless communications with minimal power consumption in poor channel environments (e.g., mountains, deserts, or oceans). Previously proposed cellular-based technologies may be mainly targeted at mobile broadband (MBB) services. Therefore, the efficiency of providing IoT services may be low in terms of radio resource utilization and power control, and flexible operation may not be supported. In addition, for example, in the case of existing non-cellular-based IoT technologies, there may be limitations in providing various IoT services due to limited mobility support and coverage. Taking the above into account, NTN can be applied, and services can be improved through NTN.

[0206] In addition, for example, if the sidelink technology based on 5G mobile communication is applied through NTN, it can provide users with wider coverage and mobility through a more efficient wireless communication method than the current wearable devices based on Bluetooth / WiFi. In addition, in applications that require high data transmission rates and mobility support using wearable devices (e.g., wearable multimedia services), it can be distinguished from existing communication standards.

[0207] As another example, through NTN, public safety communication networks can be improved and disaster communication coverage can be expanded. For example, through NTN, the high reliability and low latency technology of 5G mobile communication systems can provide public services such as disaster response. For example, even in deserts or high mountains, mobile base stations such as drones supporting 5G mobile communications can be used to support mobile broadband services. That is, in the case of applying NTN to public services, disaster communication coverage can be expanded by covering various areas.

[0209] Fig.12 Reference locations to which the present disclosure can be applied are shown. Fig.12, satellites 1210 and 1220 with earth-fixed beams can provide services for a specific time period to a fixed location based on a fixed beam. In an NTN environment, the UE-satellite distance is large, so the signal strength within the cell may be similar. Therefore, a UE in an RRC idle state may regard a reference location as a condition for performing neighboring cell measurements for cell reselection. That is, a UE in an RRC idle state may perform cell measurements for cell reselection based on the distance between the UE and the reference location. In detail, a UE present in the coverage of satellite 1 (Sat 1) 1210 may obtain reference location information through system information from the network. The UE may verify the distance between the UE and the reference location based on the location of the UE. Here, if the distance between the UE and the reference location is greater than a distance threshold, the UE may identify the current location of the UE as a cell edge, and may perform measurements for neighboring cells. That is, the UE may perform cell measurements for cell reselection considering the distance between the reference location and the UE.

[0210] Fig.13 The received signal strength according to the distance in TN and NTN is shown. Fig.13 (a), in a TN environment, UEs 1321 and 1332 existing within the coverage of a base station (gNB) 1310 may have a large difference in signal strength based on the distance between the base station 1310 and the corresponding UE. In detail, for a transmission signal, the received signal strength of a UE (near UE) 1321 at the center of the coverage of the base station 1310 existing on the ground may be greater than the received signal strength of a UE (far UE) 1322 existing at the edge of the coverage, and the difference may be large enough to be distinguished. On the other hand, referring to Fig.13 (b), UEs 1331 and 1332 existing within the coverage of a satellite 1330 in an NTN environment may be considered. Here, since a transmission signal is generated from a satellite 1330 located at a high position, the received signal strength of a UE (near UE) 1331 close to the center of the coverage and the received signal strength of a UE (far UE) 1332 existing at the edge of the coverage may not be large. Therefore, in an NTN environment, there may be limitations in performing cell reselection considering only the received signal strength. In detail, since the difference in received signal strength within the satellite coverage is not large, the UE may not perform measurements for cell reselection. Therefore, the time for neighboring cell SSB search, signal strength measurement, and dwelling may not be sufficient. Taking this into account, as described above, the UE may perform measurements for cell reselection considering the distance between the reference position and the UE in the NTN environment.

[0211] In addition, for example, a UE in the above-mentioned fixed cell (earth fixed cell) or fixed beam can obtain information for time-based cell reselection through system information. For example, the UE can obtain a t-service (t-service) using a duration (or service time) for maintaining satellite coverage through system information. The UE can perform cell reselection based on the t-service time information. Here, the t-service time may be the time for providing services of a fixed cell. Therefore, if the UE receives t-service information through system information, the UE may regard the corresponding cell as a fixed cell. On the contrary, if the UE does not receive t-service information through system information, the UE may regard the corresponding cell as a mobile cell (earth mobile cell). That is, the UE can implicitly obtain fixed cell and mobile cell information through t-service information.

[0212] As another example, as described above, if the distance between the reference location and the UE in the fixed cell becomes greater than the distance threshold, the UE may perform measurements for cell reselection. That is, when the UE is present in the coverage of the fixed cell, the UE may use the reference location information or the t service information to perform measurements for cell reselection. Here, the reference location of the mobile cell and the reference location of the fixed cell may be different. In detail, since the mobile cell moves according to the movement of the satellite, the reference location also needs to move. Therefore, when the UE performs measurements for cell reselection based on the reference location of the mobile cell, there may be a problem that if the measurement is performed by the existing reference location determination method, the UE that does not need to measure may perform the measurement. This will be described below. At the same time, in the NTN environment, the UE can operate in a frequency band of 10 GHz or higher, and based on this, communication can be performed by satellite. In addition, for example, mobility, service continuity, emergency calls and public warning systems considering high propagation delay and satellite movement can be provided in the NTN environment, but not limited to a specific embodiment.

[0213] Fig.14 A method for performing distance-based measurement for cell reselection to which the present disclosure is applied is shown. Fig.14, a mobile cell may be provided based on satellite 1410. Here, a case may be considered where the UE performs measurements for cell reselection taking into account a reference position. In detail, at time T1, since the distance between UE1 1421 and the reference position is greater than the distance threshold, UE1 1421 may perform neighboring cell measurements for cell reselection. On the other hand, since the distance between UE2 1422 and the reference position is less than the distance threshold, UE 2 1422 may not perform neighboring cell measurements for cell reselection. Here, the reference position and distance threshold information may be provided to the UE via system information. In detail, the reference position and distance threshold information may be included in NTN specific system information (e.g., SIB 19). Here, if the UE moves to an RRC idle / inactive state, the above values ​​may not be changed. Therefore, even at time T2, the UE may operate based on the same information. For example, at Fig.14 , at time T2, UE2 1422 may need to perform measurements on neighboring cells at the edge of the coverage and try to camp on another cell. However, since the distance between the location of UE2 1422 and the reference location is less than the distance threshold, UE2 1422 may not perform measurements on neighboring cells, and therefore may not perform a cell reselection process. That is, in a mobile cell, by applying the reference location in the same manner as in a fixed cell, there may be limitations in performing measurements for cell reselection. Here, for example, a specific operation of cell reselection performed by the UE may be as shown in Table 5 below. For example, the UE may perform measurements based on at least one of a frequency priority, a signal strength of a serving cell, and a distance threshold, as shown in Table 5 below. In addition, for example, when the UE receives system information (e.g., SIB19) including t service information from a serving cell, the UE may need to perform intra / inter-frequency and inter-RAT measurements at all times before t service, regardless of the conditions shown in Table 5. Here, the t service information may represent an epoch time for the coverage of a serving fixed cell. In addition, for example, the UE may measure high priority intra-frequency / inter-frequency and inter-RAT frequencies at any time regardless of Table 5, and may thereby perform cell reselection.

[0215] [Table 5]

[0217] also, Fig.15The reference location update method applicable to the present disclosure is shown. As described above, if the reference location is applied in the mobile cell in the same manner as the reference location of the fixed cell, problems may occur in the measurement conditions. Therefore, in the case of the mobile cell, the reference location may need to be updated. For example, in Fig.15 In the present invention, the reference location may be updated based on a mobile cell that moves according to the movement of the satellite 1510. Here, when the reference location update is not performed, the UE may not perform cell reselection, and thus needs to update the reference location at every specific time.

[0218] Below, the method of updating the reference location is described by considering the above. For example, at time T2, UE2 1522 may perform cell reselection without using the reference location (T1) information configured at time T1 and using the updated reference location (T2) information. In detail, if the distance between the location of UE2 1522 and the reference location (T2) at time T2 is greater than the distance threshold, UE2 1522 may perform measurements for cell reselection and may attempt to stay. Taking the above into consideration, the reference location update method is described below.

[0220] Reference position update

[0221] The reference position may be newly defined or updated according to the movement of the satellite in the mobile cell. Here, the reference position may be updated based on a parameter indicating a time interval (e.g., a timer, an epoch time, a system frame number (SFN) & a subframe). As another example, the reference position may be indicated in a list format based on the epoch time. This is described below. For example, a system frame number (SFN) may refer to the number of a specific system frame having a length of 10 ms. In addition, a subframe may be a frame structure having a time length of 1 ms within a subframe. As another example, other time units may be considered and may not be limited to specific time units.

[0222] Here, for example, the reference position update may be performed based on the reference position update time or if the timer expires. Here, the reference position update may be performed based on satellite ephemeris information and system information acquisition. As another example, the reference position update may be performed by a reference position list. Here, the reference position list refers to a set of epoch times and reference positions, and may indicate a reference position used at a specific position of a satellite associated with satellite ephemeris information, which will be described below.

[0223] For example, the satellite ephemeris information may indicate the satellite position information at a specific time or time period. The satellite ephemeris information refers to geocentric earth fixed (ECEF) coordinate information, and may represent the coordinates (X, Y, Z) of the satellite relative to the center of the earth in km units. In detail, for example, the satellite ephemeris information may be expressed in the form of "X=19151.529km, Y=37578.251km, Z=17.622km" at "2022-06-2708:00:00.000" as the epoch time (day, hour, minute, second). As another example, the satellite ephemeris information may be expressed as "X=19151.053km, Y=-37578.556km, Z=17.359km" at "2022-06-2708:05:00.000" as the epoch time (day, hour, minute, second). Here, the speed (km / s) on each of the X, Y, and Z axes may be represented, and is not limited to a specific embodiment. In addition, for example, a reference position may be provided in the form of an ellipse point. The reference position may be indicated by a bit indicating the north / south direction and a bit indicating the latitude / longitude, and the ellipse point may be as shown in Table 6 below, but may not be limited to a specific embodiment.

[0224] [Table 6]

[0226] Hereinafter, a method of updating a reference location based on a timer (hereinafter, method 1) and a method of updating a reference location based on a reference location list (hereinafter, method 2) are described.

[0227] For example, the UE may update the reference position at a specific time interval set by the network. Here, a timer may be used to indicate the specific time interval. The UE may update the reference position through satellite ephemeris information at a specific time interval indicated by the network. As another example, the UE may obtain system information and may update the reference position at a specific time interval indicated by the network.

[0228] For example, the epoch time may be a value expressed as an integer value and expressed in a specific unit based on a specific point in time. In detail, for example, the epoch time may be expressed as "IINTEGER(0..549755813887)" in units of 10 ms from 00:00:00 on January 1, 1900, but may not be limited thereto. That is, a parameter indicating a specific point in time may be used, and is not limited to a specific embodiment. Here, the reference location update may be performed by system information acquisition. For example, the UE may update the reference location at each uplink synchronization valid duration (e.g., UlSyncValidiyDuration). As another example, the UE may update the reference location based on a new timer as a reference location update timer. As another example, the reference location update may be performed based on satellite ephemeris information. The UE may update the reference location based on a new timer as a reference location update timer.

[0229] Fig.16 A method for performing reference position update based on system information acquisition applied to the present disclosure is shown.

[0230] refer to Fig.16 In an NTN environment, the UE may acquire system information for uplink synchronization. That is, the network may send the feeder link delay and the satellite coordinates to the UE through the system information, and thus may perform uplink synchronization. Here, since the satellite is constantly moving, the feeder link delay and the satellite coordinates may change continuously. Therefore, when the delay of the uplink synchronization changes, the network may modify the parameters (e.g., common TA, ephemeris) used for uplink synchronization within the system information, and may send it to the UE. In addition, the UE may acquire the system information at each specific time (e.g., UlSyncValidiyDuration), and may update the information used for uplink synchronization. Here, the specific time may be the uplink synchronization valid time (UlSyncValidiyDuration). For example, the specific time refers to the duration during which the uplink synchronization is valid, and may be a type of timer. That is, at the specific time (e.g., UlSyncValidiyDuration) included in the system information, the timer may operate as a duration during which the uplink synchronization is valid based on the parameters. Hereinafter, for clarity of description, a specific time (eg, UlSyncValidityDuration) included in the system information is referred to as uplink synchronization validity time. However, this is merely a configuration for convenience of description and is not limited to the above name.

[0231] Here, the uplink synchronization effective time may indicate the effective time of parameters (e.g., common TA), satellite ephemeris information, and other parameters for uplink synchronization according to satellite movement. Here, the network may use SFN and subframe to indicate to the UE the starting position of the duration (as the uplink synchronization effective time) during which the parameters are effective based on the epoch time. The UE may acquire system information before the uplink synchronization effective time expires, may update parameters (e.g., common TA), satellite ephemeris information (e.g., ephemeris), and other parameters related to the movement of the satellite, and may restart the uplink synchronization effective time. For example, when the UE does not update the parameters until the uplink synchronization effective time expires, the UE may determine that the parameters are invalid and may suspend uplink transmission.

[0232] For details, for example, refer to Fig.16 , the network can indicate the starting point at which parameters for uplink synchronization (e.g., common TA), satellite ephemeris information (e.g., ephemeris), and parameters related to the movement of the satellite are valid through system information and through parameters of epoch time based on SFN and subframe. In addition, the uplink synchronization valid time can be indicated based on seconds. In detail, for example, (s5, s10, s15, s20, s25, s30, s35, s40, s45, s50, s55, s60, s120, s180, s240) can be indicated as the uplink synchronization valid time, and is not limited to a specific embodiment.

[0233] exist Fig.16 In the example, the network may indicate SFN 0 and subframe 4 as valid starting points through the parameters of the system information and the epoch time. Therefore, the UE may start the uplink synchronization valid time in subframe 4 within SFN 0. Here, if the uplink synchronization valid time is set to 5 seconds, the UE may determine that the parameters for uplink synchronization (e.g., common TA), satellite ephemeris information (e.g., ephemeris), and parameters related to the movement of the satellite acquired through the system information are valid within up to 5 seconds (i.e., SFN 500, subframe 3). Here, the UE may acquire the system information before the uplink synchronization valid time expires, and may update the parameters for uplink synchronization (e.g., common TA), satellite ephemeris information (e.g., ephemeris), and parameters related to the movement of the satellite.

[0234] Here, for example, in a fixed cell environment, the reference location may not change within the t service time, or may change based on a long period of time. Therefore, the reference location can be updated only through the SI modification process (i.e., paging message). On the other hand, as described above, in a mobile cell environment, the reference location needs to be continuously updated. Therefore, the existing location can be continuously updated based on the uplink synchronization effective time or timer.

[0235] In detail, for example, Fig.17 A method for performing reference position update applicable to the present disclosure is shown. 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 can be the above-mentioned uplink synchronization effective time, and the starting position can be indicated by using SFN and subframe through the parameters of the epoch time. Fig.17 , when the epoch time parameter indicates SFN 0 and subframe 4, the valid starting position of the reference position can be SFN 0 and subframe 4. The UE can operate a timer in SFN 0 and subframe 4 as the starting position. For example, the timer can correspond to the above-mentioned uplink synchronization validity time. If the timer is set to 5 seconds, the validity time of the reference position can be up to subframe 3 within SFN 500. Therefore, before the end of subframe 3 within SFN 500, the UE can obtain system information and can update the reference position. Here, for example, the system information can be NTN-specific system information in SIB 19, but is not limited to this. The system information can be scheduled periodically and sent through a downlink shared channel. That is, the UE can receive an SI message including SIB 19 indicating SIB 1 in the SIB window, and thereby can perform a reference position update before the uplink synchronization validity time expires. Based on the above, when the reference position is updated by the uplink synchronization valid time, the uplink synchronization valid time can be indicated as (s5, s10, s15, s20, s25, s30, s35, s40, s45, s50, s55, s60, s120, s180, s240) and can therefore be set to from 5 seconds to 240 seconds.

[0236] However, the reference location update may be information for performing measurements for cell reselection that is different from uplink synchronization. Therefore, the reference location update needs to use a timer value other than the above-mentioned effective time so that measurements for cell reselection can be performed in detail. That is, a new timer for reference location update may be used, and description is made in this regard. Here, for example, the reference location may be updated based on system information acquisition. As another example, the reference location may be updated based on satellite ephemeris, which will be described below.

[0237] In detail, for example, Fig.18 A method for updating a reference position based on a new timer applicable to the present disclosure is shown. Fig.18 , the starting point of the reference location can be indicated by the parameters for the epoch time using the SFN and the subframe. Here, the UE 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, for ease of description, it is only a name and may not be limited to the name. That is, the new timer can be used for reference location update, and for the sake of clarity of description, it will be referred to as the reference location update timer below.

[0238] In detail, Fig.18 In the embodiment of the present invention, the UE may operate a reference location update timer at a position of subframe 4 within SFN 0. The UE may update the reference location before the reference location update timer expires. For example, if the reference location update timer is set to 10 ms, the UE may operate a corresponding timer in subframe 4 within SFN 0. The UE may update the reference location by acquiring system information within subframe 4 within SFN 1 based on the reference location update timer. In detail, for example, the reference location may be changed from reference location 1 to reference location 2 based on the reference location update. However, for example, since the reference location may not change within the timer, reference location 1 and reference location 2 may be the same and are not limited to a specific embodiment. For example, when acquiring subsequent system information, the reference location may be changed. That is, the reference location used in a subframe from subframe 4 within SFN 0 to subframe 3 within SFN 1 and the reference location used in a subframe from subframe 4 within SFN 1 to subframe 3 within SFN 2 may be the same. Then, the reference location applied from subframe 4 within SFN 2 may be different and is not limited to the above-mentioned embodiment.

[0239] Here, for example, even after the reference location update timer expires, the reference location update may be performed. When the UE receives system information and updates the reference location after the reference location update timer expires, the UE may reset the reference location effective starting point using the SFN and subframe by the parameters of the epoch time in the system information, and may operate the reference location update timer.

[0240] As another example, when the UE does not perform the reference location update until the reference location update timer expires, the UE may perform measurements for cell reselection based on the existing location. As another example, when the UE does not perform the reference location update until the reference location update timer expires, the UE may determine that the existing reference location is invalid and may not perform an operation of performing measurements through the reference location, but is not limited to a specific embodiment.

[0241] Fig.19 A method of performing reference location update based on a reference location update timer applicable to the present disclosure is shown.

[0242] Reference Fig.19 , the parameters of the uplink synchronization valid time and the reference location update timer parameters for updating the uplink synchronization parameters can be operated separately. For example, the UE can indicate a starting point from the network by SFN and subframe as epoch time parameters, at which starting point the parameters for uplink synchronization (e.g., common TA), satellite ephemeris information (e.g., ephemeris), and other parameters related to the movement of the satellite are valid. Here, the UE can operate each of the timers for the uplink synchronization valid time and the reference location update timer at the valid starting point. In addition, the UE can configure the valid starting point of each of the uplink synchronization valid time and the reference location update timer as an epoch time parameter by SFN and subframe. For example, in Fig.19 In the present invention, the UE may operate the reference location update timer and the timer for uplink synchronization valid time in subframe 4 within SFN X. Here, for example, the reference location update timer may be set to 1 second, and the timer for uplink synchronization valid time may be set to 10 seconds. Here, SFN X may be a value from 0 to 1023, and if X+1000 becomes greater than 1023, SFN may start from 0 again.

[0243] The UE may acquire system information before or after the reference location update timer expires, and may perform a reference location update. For example, if the reference location update timer is set to 1 second, the UE may operate a corresponding timer in subframe 4 within SFN X, and may update the reference location in subframe 4 within SFN X+{100, 200, 300, 400, 500, 600, 700, 800, 900} by acquiring system information before or after the timer expires. On the other hand, the uplink synchronization parameter may 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 UE may operate a timer for the uplink synchronization valid time in subframe 4 within SFN X, and may update the uplink synchronization parameter in subframe 4 within SFN X+1000 by acquiring system information before or after the timer expires.

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

[0245] Fig. 20 A method for performing reference position update based on system information acquisition applicable to the present disclosure is shown.

[0246] Reference Fig. 20 , UE 2010 can update the reference location by acquiring system information before or after the timer (uplink synchronization valid duration timer and / or reference location update timer) expires. UE 2010 can be in an RRC connected state with the network through NTN cell A 2020. As another example, UE 2010 can switch to an RRC idle state after connecting to the network. Fig. 20 , UE 2010 may obtain at least one of a reference location update timer (ReferenceLocationUpdateTimer), a reference location, an epoch time, and satellite ephemeris information (ephemeris) through an RRC message (e.g., system information, RRC release) from NTN cell A 2020 (S300). Here, UE 2010 in an RRC connected state may receive an RRC release message and may switch to an RRC idle state. Here, UE 2010 in an RRC idle state may receive system information. In addition, UE 2010 in an RRC idle state may reside on NTN cell A 2020 (S310). Here, UE 2010 may use at least one of an uplink synchronization valid time timer and a reference location update timer as a timer for reference location update (S320). For example, the above timer may start at a starting point set based on the SFN and subframe indicated by the epoch time parameter. UE 2010 may perform a reference location update by acquiring system information before or after at least one of an uplink synchronization valid time timer and a reference location update timer.

[0247] In detail, for example, when UE 2010 updates the reference position based on the uplink synchronization valid time timer, UE 2010 can obtain parameter information to be updated through an RRC message (S330). Here, the parameters to be newly updated can be parameters for uplink synchronization (e.g., common TA), satellite ephemeris information (e.g., ephemeris), and reference position information for reference position update.

[0248] As another example, when UE 2010 updates the reference location based on the reference location update timer, the parameter to be newly updated may be the 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 UE may determine that the reference location is invalid and may not verify the distance condition until the system information is acquired. Then, when the UE acquires the system information and performs the reference location update, the UE may verify the distance condition from the starting position (epoch time) at which the reference location in the system information is valid, and may determine the measurement for cell reselection.

[0249] As another example, the effective starting position (epoch time) of the reference position and the effective starting position (epoch time) of the uplink synchronization may be different. In detail, for 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 UE can verify the SFN and subframe of the effective starting point through the epoch time based on the system information. Here, the UE can operate all uplink synchronization effective time timers and reference location update timers based on the effective starting point. Then, the UE can obtain system information before or after the uplink synchronization effective time timer and the reference location update timer expire. Here, the system information may include reference location information for reference location update and information about the effective duration of uplink synchronization. Therefore, if the system information is received, the UE can update the reference location and can determine that the synchronization is also valid. Therefore, if the system information is received, the UE can reset all uplink synchronization effective time timers and reference location update timers, and can reset all uplink synchronization effective time timers and reference location update timers in the SFN and subframe indicated by the parameters for the epoch time included in the system information. That is, if system information is acquired after starting the uplink synchronization valid time timer and the reference location update timer at the valid starting point regardless of the reference location update status and the uplink synchronization maintenance status, the UE can reset all the uplink synchronization valid time timers and the reference location update timers, and can start them at a new valid starting point, and is not limited to a specific embodiment.

[0251] As another example, the reference position update may be performed through satellite ephemeris information rather than system information acquisition, which will be described below.

[0252] Fig.21 The geocentric earth fixed (ECEF) coordinates and ellipsoid points applicable to the present disclosure are shown. For example, satellite ephemeris information (ephemeris) can be represented based on ECEF coordinate information, and reference position information can be represented by ellipsoid points. Here, the ECEF coordinate information can indicate the x, y, and z values ​​at the center of the earth and the moving speed on each axis in km / s. The ellipsoid point information can indicate longitude (λ), latitude (λ), and And whether the latitude is located in the northern hemisphere or the southern hemisphere relative to the equator. For example, Table 7 and Table 8 may be examples of satellite coordinates and velocities according to epoch time. Referring to Table 8, the starting position at which the satellite coordinates and velocities are valid may be indicated by a specific SFN and subframe. For example, the network may send an epoch time (SFN & subframe) and the satellite coordinates and velocities corresponding thereto to the UE through system information (e.g., SIB19). The network may then update the system information and may modify the epoch time and satellite coordinates and velocities.

[0253] In detail, for example, the UE may acquire system information. Here, the parameter of the epoch time may be included in the system information, and the valid starting point may be indicated by the SFN and the subframe. For example, when the UE verifies the epoch time corresponding to SFN 100 and subframe 2 and the satellite coordinates and speed corresponding thereto, the UE may determine that the satellite coordinates and speed are valid starting from the time corresponding to SFN 100 and subframe 2, and then, when the UE acquires system information and verifies the epoch time corresponding to SFN 200 and subframe 2 and the satellite coordinates and speed corresponding thereto, the UE may update the epoch time and satellite coordinates and speed corresponding thereto.

[0254] For example, in the case where the reference position is updated based on satellite ephemeris information (ephemeris), the reference position expressed as an ellipse point can be derived by the satellite coordinates and velocity. In detail, for example, it can be expressed as longitude and latitude Here, the northern hemisphere and the southern hemisphere can be verified according to the latitude, so the UE can derive the ellipse point according to the ephemeris ECEF coordinate information and speed of the serving cell.

[0256] [Table 7]

[0258] [Table 8]

[0260] Fig. 22 A reference location update method applicable to the present disclosure is shown. For example, when the reference location is updated in consideration of the movement of the satellite 2210 in the NTN mobile cell, the UE can perform accurate cell reselection.

[0261] As described above, the network can provide satellite ephemeris information to the UE. Fig. 22 , as specific satellite ephemeris information, the satellite ECEF coordinates and velocity may be provided at 2030-11-1011:00:00.000 (SFN 2 and subframe 4). As another example, as specific satellite ephemeris information, the satellite ECEF coordinates and velocity may be provided at 2030-11-1011:05:00.000 (SFN 502 and subframe 4). Therefore, the UE may derive the ECEF coordinates based on the satellite velocity between 2030-11-1011:00:00.000 (SFN 2 & subframe 4) and 2030-11-1011:05:00.000 (SFN 502 & subframe 4), and may convert them into ellipsoidal points.

[0262] For example, the network may indicate a reference location update timer, and the UE may update the reference location based on the satellite ephemeris information each time the timer expires. For example, the UE may determine the reference location based on the Unix time (epoch time, SFN, subframe) received through the system information, and then may operate the timer. Here, if the timer expires, the UE may update the reference location based on the satellite ephemeris information.

[0263] Fig.23 A method for updating a reference position based on satellite ephemeris information applicable to the present disclosure is shown. Fig.23 In the expression 2030-11-10 11:00:00.000, it refers to the time of year, month, day, hour, minute and second, and the satellite coordinates and speed information may be sent through the satellite ephemeris information. In addition, based on the epoch time parameter in the system information, SFN X and subframe 0 may be indicated as the starting point for applying uplink synchronization parameters (e.g., common TA, ephemeris). Here, the case where the reference location update timer is set to 1 minute may be considered. However, this is only an example for describing clarity and is not limited to the above embodiment. Reference Fig.23 , the reference location update timer may operate in subframe 0 in SFN X, which is the epoch time. That is, the initial reference location may be a reference location between subframe 0 and 1 minute within SFN X. Here, the UE may update the reference location based on the effective starting point and the initial reference location, and may determine measurements for cell reselection.

[0264] In more detail, the UE may verify the distance (d1) from the initial reference position between subframes 0 and 1 minute within SFN X, and if the distance is less than the distance threshold, measurements for cell reselection may not be performed. In addition, the UE may update the reference position at 1 minute from subframe 0 within SFN X (at which the reference location update timer expires), and may restart the reference location update timer. In addition, the UE may verify the distance (d2) from the reference position updated between subframes "0+1 minute" within SFN X and subframes "0+2 minutes" within SFN X, and if the distance is less than the distance threshold, measurements for cell reselection may not be performed. In addition, the UE may update the reference position at a time corresponding to the subframe "0+2 minutes" within SFN X at which the reference location update timer expires, and may restart the reference location update timer. In addition, the UE may verify the distance (d3) from the updated reference position between subframes "0+2 minutes" within SFN X and subframes "0+3 minutes" within SFN X, and if the distance is greater than the distance threshold, measurements for cell reselection may be performed. Then, after a predetermined time period (e.g., 5 minutes) has passed, the UE may acquire the initial reference location information applied from subframe 0 within SFN Y, which is a new epoch time based on the movement of satellite 2310. That is, the UE may perform a reference location update based on a reference location update timer until the information about the initial reference location newly acquired based on the system information is acquired. Here, the reference location update timer is expressed in time units, but may not be limited thereto. In detail, for example, the reference location update timer may indicate an update at a point of "SFN mode X = 0". When the network desires to indicate that the reference location is to be updated at each SFN (10ms), X = 1 may be set. When the network desires to indicate that the reference location is to be updated at every two SFNs (20ms), X = 2 may be set. As another example, a specific epoch time may be indicated. The epoch time may be a value expressed as an integer value and expressed in a specific unit based on a specific point in time. In detail, for example, the epoch time may be a value expressed in units of 10 ms from 00:00:00 on January 1, 1900, expressed as "INTEGER (0..549755813887)", but may not be limited thereto. Here, in the network, a specific epoch time may be indicated between the time intervals (SFN X & subframe 0 and SFN Y & subframe 0), and the reference position update may be performed based on this. That is, when a specific epoch time after SFN X & subframe 0 arrives, the UE may update the reference position.

[0265] Fig.24 A method for updating a reference position based on satellite ephemeris information is shown. Fig.24, the reference location update may be performed based on at least one of the reference location update timer, the Unix time, and the SFN interval. The UE 2410 may be in an RRC connection state with the network through the NTN cell A 2420. In addition, for example, the UE 2410 may be in a state where the UE 2410 was previously connected to the network and transitioned to the RRC idle state. For example, the UE 2410 may receive an RRC message (system information, RRC release) (S200) from the NTN cell A 2420. Here, the RRC message may include a reference location update timer. For example, the reference location update timer may be indicated based on at least one of the timer, the Unix time, and the SFN. In addition, by further including at least one of the initial reference location, the epoch time, and the satellite ephemeris information (ephemeris), the RRC message may be indicated to the UE 2410. Here, the UE 2410 in the RRC connection state may receive the RRC release message and may transition to the RRC idle state. In addition, the UE 2410 in the RRC idle state may receive system information. Here, the UE 2410 in the RRC idle state may camp on the NTN cell A 2420 (S210). In addition, the UE 2410 in the RRC idle state may determine an initial reference position based on the epoch time. The UE 2410 may verify the distance from the reference position of the NTN cell A 2420, may compare the verified distance with the distance threshold, and may perform measurements for cell reselection (S215). In detail, for example, if the distance between the UE 2410 and the reference position becomes greater than the distance threshold, the UE 2410 may perform measurements for cell reselection. As another example, if the distance between the UE 2410 and the reference position is less than the distance threshold, the UE 2410 may not perform measurements for cell reselection. Here, the UE may perform a reference location update (S220). For example, in the case where the distance between the UE 2410 and the reference position is less than the distance threshold, if the timer expires, the UE 2410 may perform a reference location update. In addition, for example, in a case where the distance between the UE 2410 and the reference location is less than a distance threshold, if a preset Unix time or a preset SFN interval is reached, the UE 2410 may update the reference location of the NTN cell A 2420 .

[0266] In detail, for example, a case where the timer is set to 1 minute in the reference location update timer configured in the UE 2410 may be considered. That is, the timer may be the time after 1 minute has passed from the SFN and subframe indicated by the epoch time of the NTN cell A 2420. As another example, the reference location update timer may be indicated as an SFN interval. In detail, for example, when the SFN interval is configured as 3 and the epoch time indicated by the system information indicates SFN 0 and subframe 3, the reference location may be updated in SFN 3, SFN 6, ..., SFN X. Here, SFN 3, SFN 6, ...SFN X may refer to a point where the SFN ModuloSFN interval = 0. Then, if the distance between the reference location of the UE 2410 and the NTN cell A 2420 becomes greater than the distance threshold, the signal strength of the neighboring cell may be measured for cell reselection (S230). For example, the UE 2410 may select the NTN cell B 2430 through a cell ranking process. Then, the UE 2410 in the RRC idle state may receive system information from the NTN cell B 2430 (S240). Here, the system information may include a reference location update timer of the NTN cell B 2430. Here, the reference location update timer may be set based on at least one of a timer, a Unix time, and a SFN interval. In addition, the system information may be indicated to the UE 2410 by including an initial reference location. Then, the UE 2410 may perform a camp on the NTN cell B 2430 (S250). The UE 2410 may determine the reference location of the NTN cell B 2430, then, the distance from the reference location may be verified, and measurements for cell reselection may be performed (S255). For example, if the distance between the UE 2410 and the reference location is less than a distance threshold, the UE 2410 may not perform measurements for cell reselection. On the contrary, if the distance between the UE 2410 and the reference location is greater than the distance threshold, the UE 2410 may perform measurements for cell reselection.

[0268] As another example, multiple epoch times and reference location information lists may be configured as an RRC message (system information, RRC release). The UE may verify the reference location used at a specific epoch time. Here, the epoch time may be provided in units of date, hour, minute, and second, and the reference location may be represented as an elliptical coordinate, such as the elliptical point described above. For example, the epoch time may be a value expressed as an integer value and expressed in a specific unit based on a specific point in time. In detail, for example, the epoch time may be a value expressed in units of 10 ms from 00:00:00 on January 1, 1900, which may be expressed as "INTEGER (0..549755813887)", but may not be limited thereto. For example, Table 9 shows a reference location list. Referring to Table 9, the epoch time may be configured at 5-minute intervals, and the reference location used by the UE every 5 minutes may be indicated as a coordinate ellipsoid point of an ellipsoid type. Here, Table 9 below is only an example and may not be limited thereto. As another example, the epoch time interval may be set to 10 minutes, and the reference position may be indicated as an ellipse point corresponding to “2022-06-29 02:00:00.000” and an ellipse point corresponding to “2022-06-29 02:10:00.000”.

[0269] That is, the UE can obtain information about the epoch time set at preset intervals and the reference location information corresponding thereto through the RRC message, and can verify the reference location through this information. As another example, the epoch time can be indicated using the SFN and the subframe number, and the epoch time can indicate at which point the UE uses a specific reference location.

[0271] [Table 9] Epoch time Reference position (ellipse point) 2022-06-29 02:00:00.000 Reference position 1 2022-06-29 02:05:00.000 Reference position 2 2022-06-29 02:10:00.000 Reference position 3 2022-06-29 02:15:00.000 Reference position 4 2022-06-29 02:20:00.000 Reference position 5 2022-06-29 02:25:00.000 Reference position 6 2022-06-29 02:30:00.000 Reference position 7

[0273] Fig.25 The satellite movement and reference position changes applicable to the present disclosure are shown. Fig.25 , satellite 2510 may have a non-geostationary orbit (NGSO) non-steerable beam or a fixed beam, and its service area may change according to its movement. Therefore, the satellite may move once every T1, T1+5min, and T1+10min, and the service area may also move. However, this is merely an example and may not be limited to the above embodiments. Here, the network may indicate a reference location list at preset intervals of epoch time. For example, the preset interval may be 5 minutes, but may not be limited thereto. The UE may receive a reference location list via an RRC message (system information, RRC release), and may perform measurements for cell reselection based on the distance between the UE and the reference location.

[0274] For details, for example, refer to Fig.25 , the UE 2520 may be preset at a fixed position. Here, the UE 2520 may verify the distance between the reference position 1 2531 and the UE 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 UE 2520 may verify the distance between the reference position 2 2532 and the UE 2520 between T1+5min and T1+10min (e.g., 2022-06-29 02:05:00.000 to 2022-06-29 02:10:00.000). In addition, the UE 2520 may verify the distance between the reference location 3 2533 and the UE 2520 between T1+10min and T1+15min (e.g., 2022-06-29 02:10:00.000-2022-06-29 02:15:00.000). Here, if the distance to the reference location is greater than the distance threshold, the UE may perform measurement for cell reselection.

[0275] In detail, for example, a case where the distance threshold is set to a value greater than d1 and less than d2 may be considered. Here, UE2520 may perform measurements for cell reselection at the epoch time (2022-06-29 02:05:00.000). That is, since the distance (d1) between reference position 1 2531 and UE 2520 is less than the distance threshold between T1 and T1+5min, UE 2520 may not perform measurements for cell reselection. On the contrary, since the distance (d2) between reference position 2 2532 and UE 2520 is greater than the distance threshold between T1+5min and T1+10min, UE 2520 may perform measurements for cell reselection.

[0276] As another example, in the following Table 10, SFN and subframe may be used to indicate the epoch time. Therefore, the reference location update may be performed in a specific SFN and subframe. Fig.25 , UE 2520 may verify the distance between reference position 1 2531 and UE 2520 in SFN 100 and subframe 2, and if the distance is greater than a distance threshold, measurements for cell reselection may be performed. Then, UE 2520 may verify the distance between reference position 2 2532 and UE 2520 in SFN 200 and subframe 2, and if the distance is greater than a distance threshold, measurements for cell reselection may be performed.

[0277] [Table 10]

[0279] Fig.26 A reference location list-based signaling process and a reference location update process applicable to the present disclosure are shown.

[0280] UE 2610 may be in an RRC connection state with a network through NTN cell A 2620. In addition, UE 2610 may perform a connection to the network and then may transition to an RRC idle state. Here, UE 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. Here, as described above, the reference location list may be represented as an epoch time and reference location information. Here, UE 2610 in an RRC connection state may receive an RRC release message and may transition to an RRC idle state. In addition, UE 2610 in an RRC idle state may receive system information. In addition, UE 2610 in an RRC idle state may reside on NTN cell A 2620 (S110). Here, the UE 2610 in the RRC idle state may verify the distance between the reference position of the NTN cell A 2620 and the UE 2610 based on the reference position list, may compare the distance with the distance threshold, and may perform measurements for cell reselection. In detail, for example, if the distance between the UE 2610 and the reference position becomes greater than the distance threshold, the UE 2610 may perform measurements for cell reselection (S115). As another example, if the distance between the UE 2610 and the reference position is less than the distance threshold, the UE 2610 may not perform measurements for cell reselection (S115). If the distance between the UE 2610 and the reference position is less than the distance threshold, the reference position may be updated as a preset time passes. In detail, when a subsequent epoch time in the reference position list is reached or when a subsequent SFN and subframe number is reached, the reference position of the NTN cell A 2620 may be updated (S120). For example, when the reference location list of Table 9 is configured in UE 2610, the reference location of the previous time and NTN cell A 2620 may be "2022-06-29 02:00:00.000" and the reference location 1 (ellipse point) corresponding thereto. In addition, the reference location of the subsequent time and NTN cell A 2620 may be "2022-06-29 02:05:00.000" and the reference location 2 (ellipse point) corresponding thereto.

[0281] On the contrary, when the reference position list as shown in Table 10 is configured in the UE 2610, the reference position of the previous time and the NTN cell A 2620 may be the reference position 1 (ellipse point) corresponding to SFN 100 and subframe 2. Similarly, the reference position of the subsequent time and the NTN cell A 2620 may be the reference position 2 (ellipse point) corresponding to SFN 200 and subframe 2. Based on the above, the UE 2610 may update the reference position, and may compare the distance between the reference position of the NTN cell A 2620 and the UE 2610 with the distance threshold (S130). Here, if the distance between the reference position of the NTN cell A 2620 and the UE 2610 is greater than the distance threshold, the UE 2610 may measure the signal strength of the neighboring cell for cell reselection. Here, the UE 2610 may select the NTN cell B 2630 through the cell ranking process. The UE 2610 in the RRC idle state may receive system information from the NTN cell B 2630, and may receive reference location list information of the NTN cell B 2630 (S140). In addition, the UE 2610 may perform camping on the NTN cell B 2630 (S150). Here, the UE 2610 may verify the distance between the reference location of the NTN cell B 2630 and the UE 2610, and may determine the measurement for cell reselection (S155). For example, if the distance between the reference location of the NTN cell B 2630 and the UE 2610 is less than the distance threshold, the UE 2610 may not perform the measurement for cell reselection. On the contrary, as described above, if the distance between the reference location of the NTN cell B 2630 and the UE 2610 is greater than the distance threshold, the UE 2610 may perform the measurement for cell reselection.

[0282] Fig. 27 is a flow chart showing a reference position updating method to which the present disclosure can be applied. Fig. 27, the UE may obtain reference location information (S2710). Here, the reference location information may be obtained through system information. In addition, the UE may obtain at least one of timer information about uplink synchronization validity time and reference location update timer through system information. In addition, the UE may obtain epoch time information through system information, and may determine the effective starting point of the above-mentioned timer based on this. That is, at least one of timer information about uplink synchronization validity time and reference location update timer may start at the effective starting point (S2720). Here, for example, if the distance between the UE and the reference location is less than the distance threshold (S2730), the UE may not perform measurements for cell reselection (S2740). That is, the UE may maintain the current cell. On the contrary, if the distance between the UE and the reference location is greater than the distance threshold (S2730), the UE may perform measurements for cell reselection (S2750). That is, the UE may perform measurements for cell reselection by comparing the distance between the UE and the reference location with the distance threshold.

[0283] In addition, the UE may perform a reference location update before or after the expiration of the above-mentioned timer (S2760). Here, the reference location update may be performed based on system information acquisition. That is, based on at least one of the above-mentioned timer information about the effective time and the reference location update timer, the UE may acquire system information before or after the timer expires. Here, the system information may include reference location information, and the UE may perform a reference location update based on the corresponding reference location information.

[0284] As another example, the UE may perform a reference location update based on satellite ephemeris information. Here, the reference location update may be performed based on a reference location update timer. For example, the UE may operate the reference location update timer at the above-mentioned valid starting point. Here, the reference location update timer may be set based on at least one of a timer, a Unix time, and a SFN. Here, as described above, in response to the arrival of the reference location update timer, the UE may perform a reference location update based on satellite ephemeris information.

[0286] Fig.28 is a flow chart showing a reference position updating method to which the present disclosure can be applied. Fig.28, the UE may obtain reference location list information (S2810). Here, the reference location list information may be obtained through system information. For example, the reference location list information may be configured with a specific epoch time and a reference location. Here, if the distance between the UE and the reference location is less than a distance threshold (S2820), the UE may not perform measurements for cell reselection (S2830). That is, the UE may maintain the current cell. On the contrary, if the distance between the UE and the reference location is greater than a distance threshold (S2820), the UE may perform measurements for cell reselection (S2840). That is, the UE may perform measurements for cell reselection by comparing the distance between the UE and the reference location with the distance threshold.

[0287] In addition, the UE may perform a reference location update based on the reference location list (S2850). Here, if a specific epoch time is reached based on the reference location list information, the UE may update the reference location with the corresponding reference location. That is, the UE may apply a reference location corresponding to a specific time point through the reference location list information, and may perform measurement based on the reference location.

[0289] Fig.29 is a diagram showing a first device and a second device that can be applied to the present disclosure.

[0290] Reference Fig.29 , the first device (2900) and the second device (2950) communicate with each other. At this time, as an example, the first device (2900) may be a base station, and the second device (2950) may be a user equipment (UE) device. As another example, both the first device (2900) and the second device (2950) may be UE devices. That is, the first device (2900) and the second device (2950) may be devices that perform communication with each other based on NR communication.

[0291] As an example, the case where the first device (2900) is a base station and the second device (2950) is a UE device can be considered. 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 processor 2930 and a physical layer processor 2940. The higher layer processor 2930 may process the operation of the media access control (MAC) layer, the radio resource control (RRC) layer, or its higher layer. The physical layer processor 2940 may process the operation of the physical (PHY) layer (e.g., uplink received signal processing, downlink transmission signal processing). In addition, in order to perform signal processing related to the baseband, the processor 2920 may also control the operation of the base station device 2900 as a whole. The antenna unit 2912 may include one or more physical antennas, and may support multiple input multiple output (MIMO) transmission and reception when multiple antennas are included. In addition, beamforming may be supported. The memory 2916 may store computing processing information related to the operation of the base station device 2900 of the processor 2920, software, operating system, applications, etc., and may include components such as a buffer. The processor 2920 of the base station 2900 may be configured to implement the operation of the base station in the examples described herein.

[0292] The UE device 2950 may include a processor 2970, an antenna unit 2962, a transceiver 2964, and a memory 2966. For example, in the present invention, the UE device 2950 may communicate with the base station device 2900. As another example, in the present invention, the UE device 2950 may perform SL communication with another UE device. That is, the UE device 2950 of the present invention refers to a device capable of communicating with at least one of the base station device 2900 and other UE devices, and is not limited to communicating with a specific device. The processor 2970 performs baseband-related signal processing and may include a higher layer processor 2980 and a physical layer processor 2990. The higher layer processor 2980 may process the operation of the MAC layer, the RRC layer, or the higher layer. The physical layer processor 2990 may process the operation of the PHY layer (e.g., downlink received signal processing, uplink transmission signal processing). In addition, in order to perform baseband-related signal processing, the processor 2970 may also control the operation of the UE device 2950 as a whole. The antenna unit 2962 may include one or more physical antennas, and may support MIMO transmission and reception in the case of including multiple antennas. In addition, beamforming may be supported. The memory 2966 may store computational processing information related to the operation of the UE device 2950 of the processor 2970, software, operating system, application, etc., and may include components such as a buffer. The UE device 2950 according to the example of the present invention may be associated with a vehicle. For example, the UE device 2950 may be integrated into a vehicle, may be located in a vehicle, or may be located on a vehicle. In addition, the UE device 2950 according to the present invention may be the vehicle itself. In addition, the UE device 2950 of 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 UE device 2950 to which the present invention may be applied may include any communication device of various types that supports interactive services using a side link for a service, such as Internet access, service performance, navigation, real-time information, autonomous driving, and safety and risk diagnosis. In addition, an AR / VR device capable of performing a side link operation or any type of communication device capable of performing a relay operation as a sensor may be included.

[0293] Here, the vehicles / terminals to which the present invention can be applied include autonomous vehicles / driving terminals, semi-autonomous vehicles / driving terminals, non-autonomous vehicles / terminals, etc. At the same time, although the UE device 2950 according to the example of the present invention is described as being associated with a vehicle, at least one UE 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 UE device 2950 according to the example of the present invention may include various types of communication devices that can perform collaboration to support interactive services using a side link. That is, in addition to the case where the UE device 2950 directly supports interactive services using a side link, it can be used as a collaborative device supporting interactive services using a side link.

[0294] The UE device 2950 may acquire reference location information. Here, the reference location information may be acquired through system information. In addition, the UE device 2950 may acquire at least one of the timer information about the uplink synchronization effective time and the reference location update timer through the system information. In addition, the UE device 2950 may acquire the epoch time information through the system information, and may determine the effective starting point of the aforementioned timer based on this. That is, at least one of the timer information about the uplink synchronization effective time and the reference location update timer may start at the effective starting point. Here, for example, if the distance between the UE device 2950 and the reference location is less than the distance threshold, the UE device 2950 may not perform measurements for cell reselection. That is, the UE device 2950 may maintain the current cell. On the contrary, if the distance between the UE and the reference location is greater than the distance threshold, the UE device 2950 may perform measurements for cell reselection. That is, the UE device 2950 may perform measurements for cell reselection by comparing the distance between the UE device 2950 and the reference location with the distance threshold.

[0295] In addition, the UE device 2950 may perform a reference location update before or after the above-mentioned timer expires. Here, the reference location update may be performed based on system information acquisition. That is, based on at least one of the timer information about the effective time and the reference location update timer, the UE device 2950 may acquire system information before or after the timer expires. Here, the system information may include reference location information, and the UE device 2950 may perform a reference location update based on the corresponding reference location information.

[0296] As another example, the UE device 2950 may perform a reference location update based on satellite ephemeris information. Here, the reference location update may be performed based on a reference location update timer. For example, the UE device 2950 may operate a reference location update timer at the above-mentioned valid starting point. Here, the reference location update timer may be set based on at least one of a timer, a Unix time, and a SFN. Here, as described above, in response to the arrival of the reference location update timer, the UE device 2950 may perform a reference location update based on satellite ephemeris information. In addition, for example, based on the reference location or the updated reference location, when the distance between the UE and the reference location becomes greater than a threshold, the UE device 2950 may perform measurements for cell reselection, and may select the best cell.

[0298] As another example, the UE device 2950 may obtain reference location list information. Here, the reference location list information may be obtained through system information. For example, the reference location list information may be configured with a specific epoch time and a reference location. Here, for example, if the distance between the UE device 2950 and the reference location is less than a distance threshold, the UE device 2950 may not perform measurements for cell reselection. That is, the UE device 2950 may maintain the current cell. On the contrary, if the distance between the UE and the reference location is greater than the distance threshold, the UE device 2950 may perform measurements for cell reselection. That is, the UE device 2950 may perform measurements for cell reselection by comparing the distance between the UE device 2950 and the reference location with the distance threshold.

[0299] In addition, the UE device 2950 may perform a reference location update based on the reference location list. Here, if a specific epoch time is reached based on the reference location list information, the UE device 2950 may update the reference location with the corresponding reference location. That is, the UE device 2950 may apply a reference location corresponding to a specific time point through the reference location list information, and may perform measurements based on the reference location. In addition, for example, based on the reference location or the updated reference location, when the distance between the UE device 2950 and the reference location becomes greater than a threshold, the UE device 2950 may perform measurements for cell reselection, and may select the best cell.

[0300] In addition, 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 purpose processors, controllers, microcontrollers, microprocessors, etc.

[0301] The scope of the present disclosure includes software or machine-executable instructions (e.g., OS, applications, firmware, programs, etc.) that enable operations according to the methods of various embodiments to be performed on a device or computer, and non-transitory computer-readable media that stores such software or instructions for execution on a device or computer.

[0302] The various embodiments of the present disclosure are used to explain representative aspects of the present disclosure rather than to list all possible combinations, and the contents described in the various embodiments may be applied alone or in combination of two or more embodiments. Industrial Applicability

[0303] The above content can also be applied to other systems.

Claims

1. A method for updating a reference location by a user equipment (UE) based on a non-terrestrial network (NTN) in a wireless communication system, the method comprising: Acquire reference location related information from a base station; Determine, based on the reference location related information, whether the distance between the UE and the reference location is less than a distance threshold, if the distance between the UE and the reference location is less than the distance threshold, not perform measurement for cell reselection, and if the distance between the UE and the reference location is greater than the distance threshold, perform the measurement for the cell reselection; as well as Based on a reference position related timer, a reference position update is performed.

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

3. The method according to claim 2, wherein: a valid starting point for starting at least one of a reference location update timer and a timer for uplink synchronization valid time is determined based on the epoch time information, and The reference location update is performed by acquiring system information including the reference location information.

4. The method according to claim 2, wherein: A valid starting point for starting a reference position update timer is determined based on the epoch time information, and The reference position update is performed through satellite ephemeris information based on the reference position update timer.

5. The method according to claim 1, wherein the reference location related information comprises reference location list information, The reference position list information is configured with an epoch time and a reference position corresponding to the epoch time, and The reference location update is performed based on the reference location list information.

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